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1

Polytropic spheres with electric charge: Compact stars, the Oppenheimer-Volkoff and Buchdahl limits, and quasiblack holes  

NASA Astrophysics Data System (ADS)

We explore a class of compact charged spheres made of a charged perfect fluid with a polytropic equation of state. The charge density is chosen to be proportional to the energy density. The study is performed by solving the Tolman-Oppenheimer-Volkoff equation, which describes the hydrostatic equilibrium. We show the dependence of the structure of the spheres for several characteristic values of the polytropic exponent and for different values of the charge densities. We also study other physical properties of the charged spheres, such as the total mass, total charge, radius and sound speed and their dependence on the polytropic exponent. We find that for the polytropic exponent ?=4/3 the Chandrasekhar mass limit coincides with the Oppenheimer-Volkoff mass limit. We test the Oppenheimer-Volkoff limit for such compact objects. We also analyze the Buchdahl limit for these charged polytropic spheres, which happens in the limit of very high polytropic exponents, i.e., for a stiff equation of state. It is found that this limit is extremal and it is a quasiblack hole.

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

2013-10-01

2

Some charged polytropic models  

NASA Astrophysics Data System (ADS)

The Einstein-Maxwell equations with anisotropic pressures and electromagnetic field are studied with a polytropic equation of state. New exact solutions to the field equations are generated in terms of elementary functions. Special cases of the uncharged solutions of Feroze and Siddiqui (Gen Relativ Gravit 43:1025, 2011) and Maharaj and Mafa Takisa (Gen Relativ Gravit 44:1419, 2012) are recovered. We also obtain exact solutions for a neutral anisotropic gravitating body for a polytrope from our general treatment. Graphical plots indicate that the energy density, tangential pressure and anisotropy profiles are consistent with earlier treatments which suggest relevance in describing relativistic compact stars.

Takisa, P. Mafa; Maharaj, S. D.

2013-10-01

3

Polytropic, differentially rotating cylinders  

NASA Astrophysics Data System (ADS)

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 results for polytropic index 1.5.

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

1981-07-01

4

Polytropic spheres in the bimetric theory of gravitation  

SciTech Connect

The gravitational field equations are solved numerically in the Rosen bimetric theory for spherically symmetric configurations whose matter is in a state described by the polytropic equation. The integrated properties and internal structure are calculated for configurations with a polytropic index n=1, 1.5, 2, 2.5, 3, for selected values of the relativistic parameter ..cap alpha... The configurations obtained in the bimetric theory are more compact than the corresponding configurations in general relativity.

Sarkisyan, A.V.

1980-01-01

5

Two Quantum Polytropic Cycles  

NASA Astrophysics Data System (ADS)

In this work we follow the Bender et al paper [1] to study the quantum analogues of the Stirling and Ericsson polytropic cycles. In the context of the classical thermodynamics, the Stirling and Ericsson cycles correspond to reversible heat engines with two isothermal processes joined by two polytropic branches which occur in a device called regenerator. If this device is an ideal one, the efficiency of these cycles is the Carnot efficiency. Here, we introduce the quantum analogues of the Stirling and Ericsson cycles, the first one based on a double square potential well with a finite potential barrier, since in this system the tunnel effect could be the analogue to the regeneration classical process, therefore the isochoric quantum branches would really correspond to an internal energy storage, and the last one with an unknown system where the isobaric quantum processes don't induce changes in its quantum state. With these systems the quantum engines have cycles consisting of polytropic and isothermal quantum processes analogues to the corresponding classical processes. We show that in both cases the quantum cycles have an efficiency given by ?CQM = 1 - EC/EH, which is the same expression for the quantum analogue of the Carnot cycle studied by Bender.

Arias-Hernández, L. A.; Morales-Serrano, A. F.

2002-11-01

6

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

7

Relativistic Solution for a Class of Static Compact Charged Star in Pseudo-Spheroidal Spacetime  

NASA Astrophysics Data System (ADS)

Considering Vaidya-Tikekar metric, we obtain a class of solutions of the Einstein-Maxwell equations for a charged static fluid sphere. The physical 3-space (t = const.) here is described by pseudo-spheroidal geometry. The relativistic solution for the theory is used to obtain models for charged compact objects; thereafter, a qualitative analysis of the physical aspects of compact objects are studied. The dependence of some of the properties of a superdense star on the parameters of the three geometry is explored. We note that the spheroidicity parameter a plays an important role for determining the properties of a compact object. A nonlinear equation of state (EOS) is required to describe a charged compact object with pseudo-spheroidal geometry, which we have shown for known masses of compact objects. We also note that the size of a static compact charged star is more than that of a static compact star without charge.

Chattopadhyay, Pradip Kumar; Deb, Rumi; Paul, Bikash Chandra

2012-08-01

8

Symmetries of fluid dynamics with polytropic exponent  

NASA Astrophysics Data System (ADS)

The symmetries of the general Euler equations of fluid dynamics with polytropic exponent are determined using the Kaluza-Klein type framework of Duval et al. In the standard polytropic case the recent results of O'Raifeartaigh and Sreedhar are confirmed. Similar results are proved for polytropic exponent /?=-1, which corresponds to the dimensional reduction of /d-branes. The relation between the duality transformation used in describing supernova explosion and cosmology is explained.

Hassaïne, M.; Horváthy, P. A.

2001-01-01

9

Perturbation analysis of a general polytropic homologously collapsing stellar core  

NASA Astrophysics Data System (ADS)

For dynamic background models of Goldreich & Weber and Lou & Cao, we examine three-dimensional perturbation properties of oscillations and instabilities in a general polytropic homologously collapsing stellar core of a relativistically hot medium with a polytropic index ? = 4/3. Perturbation behaviours, especially internal gravity g modes, depend on the variation of specific entropy in the collapsing core. Among possible perturbations, we identify acoustic p modes and surface f modes as well as internal gravity g+ and g- modes. As in stellar oscillations of a static star, we define g+ and g- modes by the sign of the Brunt-Väisälä buoyancy frequency squared for a collapsing stellar core. A new criterion for the onset of instabilities is established for a homologous stellar core collapse. We demonstrate that the global energy criterion of Chandrasekhar is insufficient to warrant the stability of general polytropic equilibria. We confirm the acoustic p-mode stability of Goldreich & Weber, even though their p-mode eigenvalues appear in systematic errors. Unstable modes include g- modes and sufficiently high-order g+ modes, corresponding to core instabilities. Such instabilities occur before the stellar core bounce, in contrast to instabilities in other models of supernova (SN) explosions. The breakdown of spherical symmetry happens earlier than expected in numerical simulations so far. The formation and motion of the central compact object are speculated to be much affected by such g-mode instabilities. By estimates of typical parameters, unstable low-order l = 1 g-modes may produce initial kicks of the central compact object. Other high-order and high-degree unstable g modes may shred the nascent neutron core into pieces without an eventual compact remnant (e.g. SN 1987A). Formation of binary pulsars and planets around neutron stars might originate from unstable l = 2 g-modes and high-order high-degree g modes, respectively.

Cao, Yi; Lou, Yu-Qing

2009-12-01

10

Explicit Solution for Polytrope Solar Wind Equations.  

National Technical Information Service (NTIS)

An explicit solution for polytrope solar winds is presented, in which both the distance and the flow velocity are expressed as simple functions of the mass density. The correspondence between the velocity and the distance is explicitly exhibited through t...

T. Yeh

1970-01-01

11

Visible transitions of highly charged tungsten ions observed with a compact electron beam ion trap  

NASA Astrophysics Data System (ADS)

We present visible spectra of highly charged tungsten ions observed with a compact electron beam ion trap (EBIT). Several transition lines previously observed with the Tokyo EBIT (Watanabe et al 2012 Can. J. Phys. 90 497) have been reproducibly observed. By observing the electron energy dependence in detail, the charge state of the ion responsible for those lines is identified.

Minoshima, Maki; Sakoda, Junpei; Komatsu, Akihiro; Sakaue, Hiroyuki A.; Ding, Xiao-Bin; Kato, Daiji; Murakami, Izumi; Dong, Chen-Zhong; Koike, Fumihiro; Watanabe, Hirofumi; Nakamura, Nobuyuki

2013-09-01

12

A Compact Wireless Charging System for Electric Vehicles  

SciTech Connect

In this paper, a compact high efficiency wireless power transfer system has been designed and developed. The detailed gate drive design, cooling system design, power stage development, and system assembling are presented. The successful tests verified the feasibility of wireless power transfer system to achieve over-all 90% efficiency.

Ning, Puqi [ORNL; Miller, John M [ORNL; Onar, Omer C [ORNL; White, Cliff P [ORNL

2013-01-01

13

New Compact CMOS Li-Ion Battery Charger Using Charge-Pump Technique for Portable Applications  

Microsoft Academic Search

This paper presents a new compact CMOS Li-Ion battery charger for portable applications that uses a charge-pump technique. The proposed charger features a small chip size and a simple circuit structure. Additionally, it provides basic functions with voltage\\/current detection, end-of-charge detection, and charging speed control. The charger operates in dual-mode and is supported in the trickle\\/large constant-current mode to constant-voltage

Yuh-Shyan Hwang; Shu-Chen Wang; Fong-Cheng Yang; Jiann-Jong Chen

2007-01-01

14

Compact high-resolution retarding field energy analyzer for space-charge-dominated electron beams  

Microsoft Academic Search

We have developed a compact high-resolution retarding field energy analyzer for measuring the energy spread of space-charge-dominated electron beams. This energy analyzer has a cylindrical electrode to overcome the defocusing effects due to space-charge forces, beam trajectories, aperture effect, etc. The device provides excellent spatial and temporal information on the beam energy spread. Single-particle simulation shows that this energy analyzer

Y. Zou; Y. Cui; V. Yun; A. Valfells; R. A. Kishek; S. Bernal; I. Haber; M. Reiser; P. G. O'Shea; J. G. Wang

2002-01-01

15

Wormholes supported by polytropic phantom energy  

Microsoft Academic Search

It is generally agreed that the acceleration of the Universe can best be explained by the presence of dark or phantom energy. The equation of state of the latter shows that the null energy condition is violated. Such a violation is the primary ingredient for sustaining traversable wormholes. This paper discusses wormholes supported by a more general form called polytropic

Mubasher Jamil; Peter K. F. Kuhfittig; Farook Rahaman; Sk. A. Rakib

2010-01-01

16

Low power, compact charge coupled device signal processing system  

NASA Astrophysics Data System (ADS)

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.

1980-02-01

17

Determination of the equilibrium charge distribution for polyampholytes of different compactness in a single computer experiment  

NASA Astrophysics Data System (ADS)

The conformational properties of charge-balanced polyampholytes described by the end-to-end distance or radius of gyration depend on parameters such as the temperature and pH as well as on the detailed charge distribution along the backbone. In this work we present a method to determine the charge distribution along a semi-stiff polyampholyte backbone which will result in a thermodynamically stable structure for the compactness of interest, from several loops to an uncoiled structure, performed in a single computer experiment.

Siretskiy, Alexey; Elvingson, Christer; Khan, Malek O.

2011-09-01

18

Wormholes supported by polytropic phantom energy  

Microsoft Academic Search

It is generally agreed that the acceleration of the Universe can best be explained by the presence of dark or phantom energy.\\u000a The equation of state of the latter shows that the null energy condition is violated. Such a violation is the primary ingredient\\u000a for sustaining traversable wormholes. This paper discusses wormholes supported by a more general form called polytropic

Mubasher JamilPeter; Peter K. F. Kuhfittig; Farook Rahaman; Sk. A. Rakib

2010-01-01

19

Tachyon-polytropic inflation on the brane  

NASA Astrophysics Data System (ADS)

We consider the tachyon-brane inflationary universe model in the context of a polytropic gas equation of state. In slow-roll approximation, we discuss general conditions of this model. For exponential potential, in high-energy limit the characteristics of the model are presented. By using the seven-year Wilkinson Microwave Anisotropy Probe (WMAP7) observational data, we constrain the cosmological parameters of the model.

Setare, Mohammad R.; Kamali, Vahid

2013-05-01

20

On The Way To Off-equatorial Charged Discs Near Compact Objects - Single Test Particles Approximation  

NASA Astrophysics Data System (ADS)

We present our recent studies of charged particles motion out of the equatorial plane in strong gravitational and electromagnetic fields. Within the general relativistic approach, we have demonstrated that the interplay between gravitational and electromagnetic action may allow for stable off-equatorial circular motion along the so-called halo orbits near compact objects, such as rotating magnetic compact stars and Kerr black holes immersed in an asymptotically uniform magnetic field of external origin. Locations of halo orbits correspond to minima of the two-dimensional effective potential, which exhibits several qualitativelly different kinds of behaviour, reflecting the charge of moving particles and orientation of the motion. Along with the study of the halo motion itself, we have discussed the general motion in the related off-equatorial potential lobes, demonstrating its chaoticness or regularity in terms of the Poincaré surfaces of sections and recurrence plots. A possible outlook of this study is to build a single test particles model of putative circumpulsar discs consisting of charged dust particles. Institute of Physics and Astronomical Institute have been operated under the projects MSM 4781305903 and AV 0Z10030501, and further supported by the Centre for Theoretical Astrophysics LC06014 in the Czech Republic. JK, VK and ZS thank the Czech Science Foundation (ref. P209/10/P190, 205/07/0052, 202/09/0772). OK acknowledges the doctoral student program of the Czech Science Foundation (205/09/H033).

Kovar, Jiri; Kopacek, O.; Karas, V.; Stuchlik, Z.

2010-02-01

21

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

22

The Schoenberg-Chandrasekhar limit: A polytropic approximation  

Microsoft Academic Search

The existence of a maximum isothermal core mass fraction (qmax), the Schoenberg-Chandrasekhar limit, is one of the ‘classic’ results from the theory of stellar structure. This limit can be demonstrated through a simplified composite polytrope model in which an isothermal core is surrounded by ann=1 polytrope envelope. While this model underestimatesqmas by ~25% in the homogeneous case, it is accurate

Martin Beech

1988-01-01

23

Interacting Holographic Polytropic Gas Model of Dark Energy  

NASA Astrophysics Data System (ADS)

In this work, we establish a correspondence between the holographic dark energy model and polytropic gas model of dark energy in the FRW universe. This correspondence allows us to reconstruct the potential and the dynamics for the scalar field of the polytropic model according to the evolution of holographic dark energy in the FRW universe.

Taji, M.; Malekjani, M.

2013-10-01

24

Rapidly rotating general relativistic stars. II - Differentially rotating polytropes  

NASA Astrophysics Data System (ADS)

A previous numerical method (Komatsu, 1989) has been applied to the study of general relativistic differentially rotating bodies, including ring-like structures. Nine sequences for polytropic index (N) = 1/2 polytropes and 10 sequences for N = 3/2 polytropes have been computed for various values of the rotation parameter and the strength of gravity. For both general-relativistic and weak-Newtonian gravities, models have been obtained for the limiting cases of nearly rigid rotation and strongly differential rotation. It is found that the increase in the gravitational mass by rotation is considerably suppressed in the strong-gravity limit.

Komatsu, Hidemi; Eriguchi, Yoshiharu; Hachisu, Izumi

1989-07-01

25

Wormholes supported by polytropic phantom energy  

NASA Astrophysics Data System (ADS)

It is generally agreed that the acceleration of the Universe can best be explained by the presence of dark or phantom energy. The equation of state of the latter shows that the null energy condition is violated. Such a violation is the primary ingredient for sustaining traversable wormholes. This paper discusses wormholes supported by a more general form called polytropic phantom energy. Its equation of state results in significant generalizations of the phantom-energy and, in some cases, the generalized Chaplygin-gas wormhole models, both of which continue to receive considerable attention from researchers. Several specific solutions are explored, namely, a constant redshift function, a particular choice of the shape function, and an isotropic-pressure model with various shape functions. Some of the wormhole spacetimes are asymptotically flat, but most are not.

Jamil, Mubasher; Kuhfittig, Peter K. F.; Rahaman, Farook; Rakib, Sk. A.

2010-06-01

26

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

27

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

28

Small Adiabatic Radial Oscillations of Adiabatic and Polytropic Models  

Microsoft Academic Search

The authors have used a set of new equations of an adiabatic wave for discussing small adiabatic radial oscillations of adiabatic and polytropic models and have shown that such oscillations are in general possible.

V. K. Gurtu; D. A. Umate

1984-01-01

29

( 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

30

Polytropic spherical accretion flows on Schwarzschild black holes  

NASA Astrophysics Data System (ADS)

We study the Michel flow on a spherically symmetric black hole background for a polytropic equation of state. Based on standard tools from the theory of dynamical systems, we prove that for a polytropic index ? lying between 1 < ? <= 5/3 there exists a unique accretion flow for a given particle density number at infinity. This number can be matched to the density of the interstellar medium.

Chaverra, Eliana; Sarbach, Olivier

2012-08-01

31

Class II polytropic murine leukemia viruses (MuLVs) of AKR/J mice: possible role in the generation of class I oncogenic polytropic MuLVs.  

PubMed Central

We examined the frequency of occurrence of polytropic murine leukemia viruses (MuLVs) in the spleens and thymuses of preleukemic AKR/J mice from 1 week to 6 months of age and analyzed the genomic RNAs of several polytropic isolates by RNase T1 oligonucleotide fingerprinting. Polytropic MuLVs were first detected in the spleens of 3-week-old mice and preceded the appearance of polytropic MuLVs in the thymus by over 1 month. At 4 months of age and older, nearly all mice expressed polytropic MuLVs in both organs. In contrast to previous studies which have identified class I polytropic MuLVs in AKR/J mice, fingerprint analysis of polytropic MuLVs from both young (3- to 4-week-old) and older (5- to 6-month-old) preleukemic mice indicated that a large proportion of viruses at both ages were class II polytropic MuLVs. All polytropic viruses (five isolates) analyzed from 3- to 4-week-old mice were recovered from spleen cells and were class II polytropic MuLVs. In older preleukemic mice, five of seven isolates were class II polytropic MuLVs and two were class I polytropic viruses. Class I and class II polytropic MuLVs were recovered from both the spleens and thymuses of older preleukemic mice. A detailed comparison of the class I and class II polytropic MuLVs from 5- to 6-month-old mice revealed that the nonecotropic gp70 sequences of most of the class I and class II MuLVs were identical, consistent with a common origin for these sequences. In contrast, the nonecotropic p15E sequences of class I MuLVs were clearly derived from different endogenous sequences than the nonecotropic p15E sequences of the class II MuLVs. The in vitro host ranges of class I and class II polytropic viruses were clearly distinguishable. Examination of the in vitro host range of several isolates suggested that the predominant polytropic viruses initially identified in the thymus (2 to 3 months of age) were class II polytropic viruses. The order of appearance of the class I and class II polytropic MuLVs and the identity of the gp70 oligonucleotides of these MuLVs suggested a model for the stepwise generation of class I polytropic MuLVs involving a class II polytropic MuLV intermediate. Images

Evans, L H; Malik, F G

1987-01-01

32

Autogravity waves in a polytropic layer  

SciTech Connect

This dissertation was inspired by the mystery of the spiral arms in galaxies. A theory due to C.C. Lin and F.H. Shu interprets the spiral arms as density waves. This theory has been partially supported by observations, however it has also generated some criticism. A major weakness of this theory is its dispersiveness. The remedy for this defect is to include the nonlinear term that balances the dispersive term. With this in mind, the author explores the nonlinear properties of a simple model of galactic slab. He considers 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. He then studies the development of gravitational instability. To get to the nonlinear regime he chooses mild instability; that is to say the control parameters are near the critical point. In the long-wavelength limit, he found that the waves obey the nonlinear evolution equations similar to the Bousinesq and K.d.V. equations if appropriate scalings are chosen. On the other hand, if scalings are chosen 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. The solitary and periodic solutions are discovered in a general form.

Qian, Zhongshan.

1991-01-01

33

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

34

Centred compression-wave in polytropic gas, and its disintegration  

NASA Astrophysics Data System (ADS)

The isentropic plane motion of a loaded half-space filled with a polytropic gas is examined. The problem of the one-dimensional motion is formulated assuming that the laws of conservation of mass and momentum are obeyed. A solution is given for the case of a centered cumulation of a straight wave of finite deformation. The isentropic and shock adiabatic properties are discussed and the wave-front configuration after cumulation of the compression wave is analyzed. It is shown that for the polytropic exponent less than or equal to 5/3, disintegration of arbitrary discontinuity generated by the centered compression wave in the polytropic gas can result in the formation of a single shock wave, followed by a contact discontinuity behind which a rarefaction wave moves.

Wlodarczyk, E.

35

Charge Density and Molecular Weight of Polyphosphoramidate Gene Carrier Are Key Parameters Influencing Its DNA Compaction Ability and Transfection Efficiency  

PubMed Central

A series of polyphosphoramidates (PPA) with different molecular weights (MWs) and charge densities were synthesized and examined for their DNA compaction ability and transfection efficiency. A strong correlation was observed between the transfection efficiency of PPA/DNA nanoparticles and the MW and net positive charge density of the PPA gene carriers in three different cell lines (HeLa, HEK293 and HepG2 cells). An increase in MW and/or net positive charge density of PPA carrier yielded higher DNA compaction capacity, smaller nanoparticles with higher surface charges and higher complex stability against challenges by salt and polyanions. These favorable physicochemical properties of nanoparticles led to enhanced transfection efficiency. PPA/DNA nanoparticles with the highest complex stability showed comparable transfection efficiency as PEI/DNA nanoparticles likely by compensating the low buffering capacity with higher cellular uptake and affording higher level of protection to DNA in endolysosomal compartment. The differences in transfection efficiency were not attributed by any difference in cytotoxicity among the carriers, as all nanoparticles showed minimal level of cytotoxicity under the transfection conditions. Using PPA as a model system, we demonstrated the structural dependence of transfection efficiency of polymer gene carrier. These results offer more insights into nanoparticle engineering for non-viral gene delivery.

Ren, Yong; Jiang, Xuan; Pan, Deng; Mao, Hai-Quan

2011-01-01

36

Can rigidly rotating polytropes be sources of the Kerr metric?  

Microsoft Academic Search

We use a recent result by Cabezas et al (2007 Gen. Rel. Grav. 39 707) to build up an approximate solution to the gravitational field created by a rigidly rotating polytrope. We solve the linearized Einstein equations inside and outside the surface of zero pressure including second-order corrections due to rotational motion to get an asymptotically flat metric in a

J. Martín; A. Molina; E. Ruiz

2008-01-01

37

Instability of Nonadiabatic Oscillations in a Magnetized Polytrope  

Microsoft Academic Search

We apply linear stability analysis to a stratified plane parallel perfectly conducting atmosphere with a vertical magnetic field and Newton's law of cooling. For the case of a polytropically stratified atmosphere we find that there are overstable modes. The instability is due to the background temperature gradient combined with the cooling. We show perturbation results for the case of the

A. C. Birch; A. G. Kosovichev; E. A. Spiegel; L. Tao

1999-01-01

38

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

39

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

40

Physical characteristics of a polytrope index 5 with finite radius  

NASA Astrophysics Data System (ADS)

In astrophysics the polytropic law with index n is commonly used as a means of imposing a simple and ordered physical structure on a gaseous (or smoothed discrete) system. It is pointed out that the three well known classical analytical E type solutions of the Lane-Emden equation for n = 0, 1, and 5 all have some constraining physical features. Matched composite analytical solutions provide a means of extending the range of available E type analytical solutions of the Lane-Emden equations which can be used in applications. As an illustration the physical characteristics of an alternative complete polytropic model for index n = 5 which has finite mass, radius, and central condensation have been established. Buchdahl (1978) has pointed out that the polytrope of index 5 with infinite radius has in fact finite, not infinite, potential energy. A result calculated for this finite radius model is clearly in accord with Buchdahl's conclusions which are based on an explicit expression that was derived for the gravitational potential energy of the model.

Murphy, J. O.

41

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

42

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

SciTech Connect

Preliminary test bench results to study the beam quality extracted from a compact multicusp He{sup +} ion source for He{sup -} 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{sup +} 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{sup +} beam.

Shinto, K.; Sugawara, H.; Takenaga, M.; Takeuchi, S.; Tanaka, N.; Okamoto, A.; Kitajima, S.; Sasao, M.; Nishiura, M.; Wada, M. [School of Engineering, Tohoku University, Sendai 980-8579 (Japan); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Department of Electronics, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)

2006-03-15

43

Compact sub-hertz OTA-C filter design with MOS interface-trap charge pump  

Microsoft Academic Search

Single-ended and differential OTA configurations are biased with MOSFET interface-trap charge-pumping current generators to achieve very low transconductances for tunable sub-hertz OTA-C filter implementation. The paper reviews the basic physics of the current generator, presents the transconductor circuits, and two OTA-C filter configurations based on these transconductors. One of the filters is a lowpass with an experimentally determined lowest cutoff

A. Becker-Gomez; U. Cilingiroglu; J. Silva-Martinez

2002-01-01

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

Self-similar dynamics of polytropic gaseous spheres  

SciTech Connect

The fundamental equations governing the self-similar dynamics of polytropic gaseous spheres are derived, and the asymptotic solutions are given. The solutions divide into cases with and without critical points in closed analogy with the solar wind solutions of Holzer and Axford (1970). Properties for solutions with critical points are discussed, and their behavior around the critical point is derived explicitly for n = 1. Numerical examples of self-similar solutions for n = 1 and n = 2 - gamma are presented, and the properties of the solutions are discussed. 11 references.

Suto, Y.; Silk, J.

1988-03-01

46

Self-similar dynamics of polytropic gaseous spheres  

NASA Astrophysics Data System (ADS)

The fundamental equations governing the self-similar dynamics of 'polytropic' gaseous spheres are derived, and the asymptotic solutions are given. The solutions divide into cases with and without 'critical points' in closed analogy with the solar wind solutions of Holzer and Axford (1970). Properties for solutions with critical points are discussed, and their behavior around the critical point is derived explicitly for n = 1. Numerical examples of self-similar solutions for n = 1 and n = 2 - gamma are presented, and the properties of the solutions are discussed.

Suto, Yasushi; Silk, Joseph

1988-03-01

47

Long-Term Variability of the Polytropic Index of Solar Wind Protons at 1 AU  

NASA Astrophysics Data System (ADS)

Spacecraft data from the OMNI database were used to calculate the value of the polytropic index of the solar wind by fitting the logarithms of proton density and temperature in selected time intervals from 1 January 1995 to 30 June 2012. Bernoulli's integral and the correlation coefficient were used to filter the results. An alternative method based on the maximization of the correlation coefficient was employed to confirm our results. The long-term behavior of the polytropic index we obtained is found to be virtually identical for both methods. We noticed a characteristic behavior of the estimated polytropic index values, particularly from 1995 to 2006, which tends to have a periodicity of about one year. The distribution of the polytropic index is best described by a ?-Gaussian distribution with mean ? 1.8 and standard deviation ? 2.4. We finally examined the possible correlation between the polytropic index values and solar activity.

Nicolaou, G.; Livadiotis, G.; Moussas, X.

2013-10-01

48

The thickness of the magnetosheath: Constraints on the polytropic index  

SciTech Connect

A statistical analysis of 351 independent bow shock crossings and 233 independent magnetopause crossings by the ISEE-1 spacecraft from 1977 to 1980 was performed to determine the average positions and shapes of the bow shock and magnetopause. The standoff distance between the magnetopause and the bow shock depends on the compressibility of the plasma which in the polytropic' approximation is related to the ratio of specific heats, {gamma}. Standoff distances for the bow shock and magnetopause were found to be 13.7 R{sub E} ({plus minus} 0.2 R{sub E}) and 10.3 R{sub E} ({plus minus} 0.3 R{sub E}), respectively. These distances are smaller than those observed during earlier epochs. The observed thickness of the magnetosheath is that expected for the compression of a gas whose polytropic index, {gamma}, is 1.76 {plus minus} 0.15. This value, representative of the entire magnetosheath, is consistent with the value of 1.67 deduced from the behavior of the plasma across individual shock transitions. A value of 1.67 is expected for an adiabatic process in a collisional, monatomic gas with three degrees of freedom with lower values for non-adiabatic processes and higher values for anisotropic heating at the shock. The observed value of 1.76 indicates that heat flux does not much affect the position of the shock while the downstream anisotropy may have a small effect.

Farris, M.H.; Petrinec, S.M.; Russell, C.T. (Univ. of California, Los Angeles (United States))

1991-10-01

49

A low-energy charged particle distribution imager with a compact sensor for space applications  

NASA Astrophysics Data System (ADS)

Low-energy plasmas having temperatures of order 1 eV or less are found commonly in the ionospheres and space environments of Earth and other planets. Measuring the density, temperature, drift velocities, phase-space anisotropies, and other properties of these plasmas presents numerous challenges. Examples are distortions of particle trajectories due to spacecraft wakes, spacecraft charging, and particle gyromotion in magnetized plasmas. Furthermore, these plasmas are known to organize into structures as small as tens of meters across, traversed by spacecraft in tens of milliseconds or less. The Suprathermal Plasma Imager (SPI) was developed to address these challenges. The SPI is optimized for measurements of particles with ~1 eV energies, and of the suprathermal extension of those populations up to several hundred eV. The SPI is sensitive to particle flux intensities of order 6×105 cm-2 s-1 sr-1 eV-1 and greater. It produces 3024-pixel images corresponding to two-dimensional (angle/energy) cuts through plasma velocity distribution functions, with an image frame rate of up to 100 s-1. The SPI has a cylindrical sensor head measuring 37.5 mm in diameter and 14 cm long, with a mass of 350 g. The relatively small size and mass of the sensor allow it to be deployed easily on a boom, outside of the spacecraft's electrical sheath and in a region where wake perturbations are reduced. The SPI sensor head contains no electronic circuitry, but instead creates a visible image of the particle distribution with a system of dc-biased grids, microchannel plates, and a phosphor screen. The phosphor image is transferred via an imaging fiber-optic cable to an instrument box in the main spacecraft body, where it is sampled with a charge-coupled device and support electronics. Inside the sensor, angle/energy images of incident particle distributions are formed by a pair of concentric hemispherical grids. The incident energies Ei accessible to the analyzer lie in the range 0<=Ei<=Emax where Emax~q?V/3, ?V being the potential difference between the hemispheres. For an ideal analyzer, energy resolution ?E/E is <=22% over most of the imaged energy range, degrading at energies below Emax/10. Angular resolution varies from 2° to 8° full width at half maximum between Emax and Emax/10. Energy and angular resolutions are degraded in the presence of a potential difference between the sensor and surrounding plasma. A 37.5-mm-diam version of the analyzer with a 0.86-mm-wide aperture has an ideal energy-dependent geometry factor of ~5×10-4 eV sr cm2 for a square detector pixel of width 0.28 mm. Laboratory testing shows degraded energy resolution compared to ideal values, due in part to particle scattering within the analyzer. The SPI was tested successfully in flight on the GEODESIC auroral sounding rocket on 26 February 2000.

Knudsen, D. J.; Burchill, J. K.; Berg, K.; Cameron, T.; Enno, G. A.; Marcellus, C. G.; King, E. P.; Wevers, I.; King, R. A.

2003-01-01

50

Coalescing neutron stars - gravitational waves from polytropic models.  

NASA Astrophysics Data System (ADS)

The dynamics, time evolution of the mass distribution, and gravitational wave signature of coalescing neutron stars described by polytropes are compared with three simulations published previously: (a) "Run 2" of Zhuge et al. (1994PhRvD..50.6247Z), (b) "Model III" of Shibata et al. (1992, Prog, Theor. Phys. 88, 1079), and (c) "Model A64" of Ruffert et al. (1996A&A...311..532R). We aim at studying the differences due to the use of different numerical methods, different implementations of the gravitational wave backreaction, and different equations of state. We integrate the three-dimensional Newtonian equations of hydrodynamics by the Riemann-solver based "Piecewise Parabolic Method" on an equidistant Cartesian grid. Comparison (a) confronts the results of our grid-based PPM scheme with those from an SPH code. We find that due to the lower numerical viscosity of the PPM code, the post-merging oscillations and pulsations can be followed for a longer time and lead to larger secondary and tertiary maxima of the gravitational wave luminosity and to a stronger peak of the gravitational wave spectrum at a frequency of about f=~1.8KHz when compared to the results of Zhuge et al. (1994PhRvD..50.6247Z). In case (b) two grid based codes with the same backreaction formalism but differing hydrodynamic integrators and slightly different initial conditions are compared. Instead of rotationally deformed initial neutron stars we use spherically shaped stars. Satisfactory agreement of the amplitude of the gravitational wave luminosity is established, although due to the different initial conditions a small time delay develops in the onset of the dynamical instability setting in when the two stars come very close. In (c) we find that using a polytropic equation of state instead of the high-density equation of state of Lattimer & Swesty (1991, Nucl. Phys. A535, 331) employed by Ruffert et al. (1996A&A...311..532R) does not change the overall dynamical evolution of the merger and yields agreement of the gravitational wave signature to within 20% accuracy. Whereas the polytropic law describes the dynamical behaviour of the bulk of the matter at and above nuclear density sufficiently well, we, however, find clear differences of the structure and evolution of the outer layers of the neutron stars where the stiffness of the equation of state is largely overestimated. This has important implications for questions like mass loss and disk formation during the merging of binary neutron stars.

Ruffert, M.; Rampp, M.; Janka, H.-T.

1997-05-01

51

POLYTROPIC MODEL FITS TO THE GLOBULAR CLUSTER NGC 2419 IN MODIFIED NEWTONIAN DYNAMICS  

SciTech Connect

We present an analysis of the globular cluster NGC 2419, using a polytropic model in modified Newtonian dynamics (MOND) to reproduce recently published high-quality data on the structure and kinematics of the system. We show that a specific MOND polytropic model of NGC 2419 suggested by a previous study can be completely ruled out by the data. Furthermore, the highest likelihood fit polytrope in MOND is a substantially worse model (by a factor of {approx}5000) than a Newtonian Michie model we studied previously. We conclude that the structure and dynamics of NGC 2419 favor Newtonian dynamics and do indeed challenge the MOND theory.

Ibata, R. [Observatoire Astronomique, Universite de Strasbourg, CNRS, 11 rue de l'Universite, F-67000 Strasbourg (France); Sollima, A. [INAF-Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, I-35122 Padova (Italy); Nipoti, C.; Dalessandro, E. [Dipartimento di Astronomia, Universita degli Studi di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Bellazzini, M. [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Chapman, S. C., E-mail: rodrigo.ibata@astro.unistra.fr [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

2011-12-10

52

Non-polytropic effect on shock-induced phase transitions in a hard-sphere system  

NASA Astrophysics Data System (ADS)

By adopting a simplified model of a non-polytropic hard-sphere system where heat capacity depends on the temperature, we demonstrate the importance of non-polytropic effect on the shock-induced phase transitions. We show explicitly that with the increase of the shock strength the perturbed temperature (the temperature after a shock) increases and the vibrational modes are gradually excited, and as a result, shock-induced phase transitions are qualitatively and quantitatively different from the phase transitions observed in a simple polytropic model. The effect on the admissibility (stability) of a shock wave is also analyzed.

Zheng, Yue; Zhao, Nanrong; Ruggeri, Tommaso; Sugiyama, Masaru; Taniguchi, Shigeru

2010-07-01

53

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

NASA Astrophysics Data System (ADS)

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 ~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 ~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 ~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.; Alcator C-Mod Team; Frenje, J. A.; Leiter, R.; McDuffee, S.; Petrasso, R. D.

2006-08-01

54

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

55

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

56

A global polytropic model for the solar system - Planetary distances and masses resulting from the complex Lane-Emden differential equation  

Microsoft Academic Search

A global polytropic nonrotating model is developed to study the planetary nebula in a state of pure hydrostatic equilibrium. Polytropic shells with negative Re are identified using mathematical methods.

V. S. Geroyannis

1993-01-01

57

Effect of pressure anisotropy and flow velocity on Kelvin-Helmholtz instability of anisotropic magnetized plasma using generalized polytrope laws  

Microsoft Academic Search

The effect of pressure anisotropy and flow velocity on the Kelvin-Helmholtz (KH) instability of two magnetized anisotropic pressure plasmas flowing relative to each other is investigated using generalized polytrope laws. The anisotropic pressure with the generalized polytrope laws is considered with three-dimensional perturbations in the description of plasma using relevant magnetohydrodynamic (MHD) set of equations. The magnetic field is assumed

R. P. Prajapati; R. K. Chhajlani

2010-01-01

58

Effect of pressure anisotropy and flow velocity on Kelvin–Helmholtz instability of anisotropic magnetized plasma using generalized polytrope laws  

Microsoft Academic Search

The effect of pressure anisotropy and flow velocity on the Kelvin–Helmholtz (KH) instability of two magnetized anisotropic pressure plasmas flowing relative to each other is investigated using generalized polytrope laws. The anisotropic pressure with the generalized polytrope laws is considered with three-dimensional perturbations in the description of plasma using relevant magnetohydrodynamic (MHD) set of equations. The magnetic field is assumed

R. P. Prajapati; R. K. Chhajlani

2010-01-01

59

Quasi-static and nonquasi-static compact MOSFET models based on symmetric linearization of the bulk and inversion charges  

Microsoft Academic Search

A particularly simple form of the charge-sheet model (CSM) is developed using symmetric linearization of the bulk charge as a function of the surface potential. The new formulation is verified by comparison with the original form of the CSM and is used to obtain a simple and accurate expressions for the quasi-static (QS) terminal charges based on the Ward-Dutton partition.

Hailing Wang; Ten-Lon Chen; Gennady Gildenblat

2003-01-01

60

General relativistic polytropes for anisotropic matter: The general formalism and applications  

NASA Astrophysics Data System (ADS)

We set up in detail the general formalism to model polytropic general relativistic stars with anisotropic pressure. We shall consider two different possible polytropic equations, all of which yield the same Lane-Emden equation in the Newtonian limit. 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 this context, the Tolman mass, which is a measure of the active gravitational mass, is invoked to explain some features of the models. Prospective extensions of the proposed approach are pointed out.

Herrera, L.; Barreto, W.

2013-10-01

61

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

62

On the determination of electron polytrope indices within coronal mass ejections in the solar wind  

SciTech Connect

Electron temperature and density often appear to be negatively correlated with one another as a coronal mass ejection, CME, in the solar wind passes over a spacecraft at 1 AU and beyond. It has been suggested that this negative correlation within magnetic clouds, which form a subset of all CMEs, implies that the electron polytropic index for the plasma within the clouds is significantly less than 1.0. We argue that single-point measurements of density and temperature within clouds do not speak to the issue of the coupled evolution of density and temperature that occurs as the clouds expand out into the heliosphere, and thus do not provide a measure of the polytropic index within them. Moreover, we show that observed electron temperatures within magnetic clouds and CMEs close to the Sun, at 1 AU, and at large heliocentric distances do not agree with predictions based upon electron polytropic indices significantly less than 1.0. We suggest that the negative correlation between electron temperature and density often observed within CMEs and magnetic clouds at 1 AU and beyond simply reflects the presence of structure within the CMEs and the plasma{close_quote}s tendency to achieve local pressure balance as it evolves outward from the Sun. Our results indicate that self-similar models that require the electron polytrope index to be less than 1.0 in order for a magnetic cloud to expand are physically unrealistic. {copyright} 1999 American Geophysical Union

Gosling, J.T. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

1999-09-01

63

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

SciTech Connect

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 Xe{sup 46+} 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.

Schmidt, M. [DREEBIT GmbH, Zur Wetterwarte 50, D-01109 Dresden (Germany); Peng, H. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Zschornack, G. [Institut fuer Angewandte Physik, Technische Universitaet Dresden, Mommsenstr. 13, D-01062 Dresden (Germany); Sykora, S. [Institut fuer Theoretische Physik, Technische Universitaet Dresden, Mommsenstr. 13, D-01062 Dresden (Germany)

2009-06-15

64

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

65

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

SciTech Connect

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 vertical bar v{sub parallel}/v vertical bar <0.25 and the pitch angle cosine value v{sub parallel}/v changes sign along the diagnostic sight line. The measurable energy range for H{sup 0} is 1-170 keV. Radially resolved data on local H{sup 0} 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.; Veshchev, E. A.; Sergeev, V. Yu.; Krasilnikov, A. V. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193 (Japan); St. Petersburg Polytechnical University, 195251 St. Petersburg (Russian Federation); Troitsk Institute for Innovation and Fusion Research, 142092 Troitsk (Russian Federation)

2006-10-15

66

Performance of a compact position-sensitive photon counting detector with image charge coupling to an air-side anode  

NASA Astrophysics Data System (ADS)

We discuss a novel micro-channel plate (MCP) photomultiplier with resistive screen (RS-PMT) as a detection device for space- and time-correlated single photon counting, illustrated by several applications. The photomultiplier tube resembles a standard image intensifier device. However, the rear phosphor screen is replaced by a ceramic "window" with resistive coating. The MCP output is transferred through the ceramic plate to the read-out electrode (on the air side) via capacity-coupling of the image charge. This design allows for an easy reconfiguration of the read-out electrode (e.g. pixel, charge-sharing, cross-strip, delay-line) without breaking the vacuum for optimizing the detector performance towards a certain task. It also eases the design and manufacturing process of such a multi-purpose photomultiplier tube. Temporal and spatial resolutions well below 100 ps and 100 microns, respectively, have been reported at event rates as high as 1 MHz, for up to 40 mm effective detection diameter. In this paper we will discuss several applications like wide-field fluorescence microscopy and dual ?/fast-neutron radiography for air cargo screening and conclude with an outlook on large-area detectors for thermal neutrons based on MCPs.

Jagutzki, O.; Czasch, A.; Schössler, S.

2013-05-01

67

The polytropic index and adiabatic limit: Another interpretation to the convection stability criterion  

NASA Astrophysics Data System (ADS)

In this paper, from the relationship between nonextensive parameter and polytropic index, we deduce the nonextensive density distribution and Du's equation (Du J. L., Europhys. Lett., 67 (2004) 893), in one self-gravitational system. We propose that the adiabatic process should be the limit state of the polytropic process in one stationary system, so one inequality which can be regarded as the convection stability criterion is constructed. By applying it into the atmospheric convection of the Earth, one can find that when the vertical temperature gradient is higher than 1°C per one hundred meters, which is called adiabatic lapse rate in aerography, convection or turbulence will take place. One important conclusion can also be drawn that a sunspot is a kind of turbulent temperature inversion phenomenon, just similar to the one in the aerography.

Zheng, Yahui; Luo, Wang; Li, Qinan; Li, Jianjun

2013-04-01

68

Determination of electron polytropic indices in the environment of Comet P/Halley  

NASA Astrophysics Data System (ADS)

We present a general experimental method to investigate the relations between the density variations and the pressure variations for one particle population of a hot collisionless plasma. A complete description is provided of the data analysis technique for an experimental case, from Giotto electron and magnetic field data measured in the environment of Comet P/Halley, used to verify the theory. The correlations between the electron characteristics, density and pressures, and the magnetic field strength are investigated. In this case, the method shows that the relation between the electron density and pressures can be satisfactorily represented by two polytropic laws. The values inferred for the polytropic indices strongly differ from those usually found in the literature but are nevertheless fully quantitatively explained from the theoretical analytical calculations.

Mazelle, C.; Belmont, G.

1993-01-01

69

Neurologic Disease Induced by Polytropic Murine Retroviruses: Neurovirulence Determined by Efficiency of Spread to Microglial Cells  

Microsoft Academic Search

Several murine leukemia viruses (MuLV) induce neurologic disease in susceptible mice. To identify features of central nervous system (CNS) infection that correlate with neurovirulence, we compared two neurovirulent MuLV, Fr98 and Fr98\\/SE, with a nonneurovirulent MuLV, Fr54. All three viruses utilize the polytropic receptor and are coisogenic, each containing a different envelope gene within a common genetic background. Both Fr98

SHELLY J. ROBERTSON; KIM J. HASENKRUG; BRUCE CHESEBRO; JOHN L. PORTIS

1997-01-01

70

Innate immunity in the pathogenesis of polytropic retrovirus infection in the central nervous system  

Microsoft Academic Search

Neuroinflammation, including astrogliosis, microgliosis, and the production of proinflammatory cytokines and chemokines is\\u000a a common response in the central nervous system (CNS) to virus infection, including retrovirus infection. However, the contribution\\u000a of this innate immune response in disease pathogenesis remains unresolved. Analysis of the neuroinflammatory response to polytropic\\u000a retrovirus infection in the mouse has provided insight into the potential contribution

Karin E. Peterson; Min Du

2009-01-01

71

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

72

Quasiequilibrium models for triaxially deformed rotating compact stars  

SciTech Connect

Quasiequilibrium models of rapidly rotating triaxially deformed stars are computed in general relativistic gravity, assuming a conformally flat spatial geometry (Isenberg-Wilson-Mathews formulation) and a polytropic equation of state. Highly deformed solutions are calculated on the initial slice covered by spherical coordinate grids, centered at the source, in all angular directions up to a large truncation radius. Constant rest mass sequences are calculated from nearly axisymmetric to maximally deformed triaxial configurations. Selected parameters are to model (proto-) neutron stars; the compactness is M/R=0.001, 0.1, 0.14, and 0.2 for polytropic index n=0.3 and M/R=0.001, 0.1, 0.12, and 0.14 for n=0.5, where M/R refers to that of a nonrotating spherical star having the same rest mass. We confirmed that the triaxial solutions exist for these parameters as in the case of Newtonian polytropes. However, it is also found that the triaxial sequences become shorter for higher compactness, and those disappear at a certain large compactness for the n=0.5 case. In the scenario of the contraction of proto-neutron stars being subject to strong viscosity and rapid cooling, it is plausible that, once the viscosity driven secular instability sets in during the contraction, the proto-neutron stars are always maximally deformed triaxial configurations, as long as the compactness and the equation of state parameters allow such triaxial sequences. Detection of gravitational waves from such sources may be used as another probe for the nuclear equation of state.

Huang Xing; Markakis, Charalampos; Sugiyama, Noriyuki [Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States); Uryu, Koji [Department of Physics, University of the Ryukyus, Senbaru, Nishihara, Okinawa 903-0213 (Japan)

2008-12-15

73

Ewald method for polytropic potentials in arbitrary dimensionality  

NASA Astrophysics Data System (ADS)

The Ewald summation technique is generalised to power-law 1/|r|^k potentials in three-, two- and one-dimensional geometries with explicit formulae for all the components of the sums. The cases of short-range, long-range and "marginal" interactions are treated separately. The jellium model, as a particular case of a charge-neutral system, is discussed and the explicit forms of the Ewald sums for such system are presented. A generalised form of the Ewald sums for a noncubic (nonsquare) simulation cell for three- (two-) dimensional geometry is obtained and its possible field of application is discussed. A procedure for the optimisation of the involved parameters in actual simulations is developed and an example of its application is presented.

Osychenko, O. N.; Astrakharchik, G. E.; Boronat, J.

2012-02-01

74

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

SciTech Connect

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(x-vector,t)(density) and u(x-vector,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(x-vector,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 {gamma}(x-vector,t) = (nDp/Dt)(pDn/Dt) = (n/p)(Dp/Dn), with D/Dt = {partial_derivative}/{partial_derivative}t+u-vector{center_dot}{partial_derivative}/{partial_derivative}x-vector, which amounts to the closure equation if {gamma}(x-vector,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 {gamma} 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.; Jelic, N. [Association EURATOM-OAeW, Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Kos, L. [LECAD Laboratory, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Tskhakaya, D. jr; Tskhakaya, D. D. sr [Association EURATOM-OAeW, Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Andronikashvili Institute of Physics, Georgian Academy of Sciences, Tbilisi 0177 (Georgia)

2010-12-14

75

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

76

Two separate envelope regions influence induction of brain disease by a polytropic murine retrovirus (FMCF98).  

PubMed

The major determinants involved in neurological disease induction by polytropic murine leukemia virus FMCF98 are encoded by the envelope gene. To map these determinants further, we produced four chimeras which contained neurovirulent FMCF98 envelope sequences combined with envelope sequences from the closely related nonneurovirulent polytropic virus FMCF54. Surprisingly, two chimeric viruses containing completely separate envelope regions from FMCF98 could both induce neurological disease. Clinical signs caused by both neurovirulent chimeras appeared to be indistinguishable from those caused by FMCF98, although the incubation periods were longer. One neurovirulence determinant mapped to the N-terminal portion of gp7O, which contains the VRA and VRB receptor-binding regions, while the other determinant mapped downstream of both of the variable regions. Western blot (immunoblot) analyses and immunohistochemical staining of tissue sections indicated that the variations in neurovirulence of these viruses could not be explained by differences in either the quantitative level or the location of virus expression in the brain. PMID:8676516

Hasenkrug, K J; Robertson, S J; Porti, J; McAtee, F; Nishio, J; Chesebro, B

1996-07-01

77

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

2013-10-01

78

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

79

Effect of pressure anisotropy and flow velocity on Kelvin-Helmholtz instability of anisotropic magnetized plasma using generalized polytrope laws  

SciTech Connect

The effect of pressure anisotropy and flow velocity on the Kelvin-Helmholtz (KH) instability of two magnetized anisotropic pressure plasmas flowing relative to each other is investigated using generalized polytrope laws. The anisotropic pressure with the generalized polytrope laws is considered with three-dimensional perturbations in the description of plasma using relevant magnetohydrodynamic (MHD) set of equations. The magnetic field is assumed in the x-direction and parallel to the direction of the flow of plasma streams. A complete polytrope model is given for the considered system in terms of pressure components, magnetic field, and density of the fluids to discuss the condition of KH instability, stability, and overstability. The problem is solved using the normal mode analysis and the general dispersion relation is obtained by applying the appropriate boundary conditions. The case of nonvanishing wavenumber transverse to the direction of the stream is obtained, which represents the stationery configuration without excitation of KH instability. The longitudinal mode of propagation is discussed with conditions of KH instability, stability, and overstability for collisionless (anisotropic) double-adiabatic Chew-Goldberger-Low (CGL) and collisional (isotropic) MHD media, depending on various values of polytrope indices. The effects of pressure anisotropy, different flow velocities, and magnetic field are also discussed on the growth rate of KH instability. We observe that the presence of flow velocity and pressure anisotropy of the plasmas has a destabilizing influence on the growth rate of the system. The growth rate is found larger for MHD set of equations in comparison to the CGL set of equations. The presence of magnetic field has a stabilizing role on the growth rate of the considered system.

Prajapati, R. P.; Chhajlani, R. K. [School of Studies in Physics, Vikram University, Ujjain, Madhya Pradesh 456010 (India)

2010-11-15

80

Compact Storage  

USGS Multimedia Gallery

After a detailed inventory is completed and published on the web, processed materials are stored in compact shelving in the Field Records Collection. Collections are organized by scientist and project....

2009-04-09

81

Exact relativistic stellar models with liquid surface: I. Generalizing Buchdahl's n = 1 polytrope  

NASA Astrophysics Data System (ADS)

A family of exact relativistic stellar models is described. The family generalizes Buchdahl's n = 1 polytropic solution. The matter content is a perfect fluid and, excluding Buchdahl's original model, it behaves as a liquid at low pressures in the sense that the energy density is non-zero in the zero-pressure limit. The equation of state has two free parameters, a scaling and a stiffness parameter. Depending on the value of the stiffness parameter the fluid behaviour can be divided into four different types. Physical quantities such as masses, radii and surface redshifts as well as density and pressure profiles are calculated and displayed graphically. Leaving the details to a later publication, it is noted that one of the equation of state types can quite accurately approximate the equation of state of real cold matter in the outer regions of neutron stars. Finally, it is observed that the given equation of state does not admit models with a conical singularity at the centre.

Rosquist, Kjell

1999-06-01

82

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

83

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

PubMed

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. PMID:1310758

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

1992-03-01

84

Gravitational Instability of Rotating, Pressure-confined, Polytropic Gas Disks with Vertical Stratification  

NASA Astrophysics Data System (ADS)

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 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 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; Seo, Young Min; Hong, Seung Soo

2012-12-01

85

Explosive-powder compaction system  

Microsoft Academic Search

Sandia National Laboratories has developed a pressure-control system and a test fixture to study the behavior of explosive materials during compaction. Both the pressure-control system and the test fixture are self-contained and portable. Explosive materials are compacted in a bridged header charge holder assembly by means of a test fixture and a pneumatic cylinder arrangement. Forces are measured with load

A. P. Montoya; M. L. Reichenbach

1981-01-01

86

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

87

Compact, Lightweight, Smart Battery Charger.  

National Technical Information Service (NTIS)

A rugged, level-3 smart battery charger was developed and delivered to the Army. This compact, lightweight charger weighs 22.5 ounces and has a volume of 55 cubic inches. The charger accepts either a universal AC input or a 19-28 VDC input and charges at ...

R. S. Beech

2005-01-01

88

Hydrodynamical calculations towards steady state structures in boundary layers in accretion disks. 1: 1-D polytropic boundary layers  

NASA Astrophysics Data System (ADS)

We apply the one dimensional version of the multi-dimensional robust solver developed by Hujeirat & Rannacher (1994) to follow the viscous evolution of various models of polytropic boundary layers in accretion disks around a non-magnetic white dwarf. In this paper, we present the results of 13 different time-dependent hydrodynamical calculations. The results indicate that (1) no steady structure of the flow in the boundary layer is encountered. The solutions show that a quasi-standing shock is always present for very small alpha and high stellar rotation, (2) the rate of accreted angular momentum into the central object is much less than the corresponding Keplerian one, (3) the radial extent of the boundary layer (delta RBL) is much smaller than the vertical one as well as the radial extent of classical viscous boundary layers, (4) delta RBL increases with the rotational speed of the star, (5) an instability of the shock position is detected as well as quasi-periodic oscillations which are viscosity-dependent, (6) the polytropic equation of state with gamma = 2 yields unstable and chaotic behavior of the flow in the disk region.

Hujeirat, A.

1995-03-01

89

An Empirical Polytrope Law for Solar Wind Thermal Electrons Between 0.45 and 4.76 AU: Voyager 2 and Mariner 10  

Microsoft Academic Search

Empirical evidence is presented that solar wind thermal electrons obey a polrope law of the form P -- n ß with polytrope index ¾ -- 1.175 _+ 0.03 (30). The Voyager 2 and Mariner 10 data used span the radial range from 0.45 to 4.76 AU and have a large dynamic range in density (four decades), and in temper- ature

E. C. Sittler; J. D. Scudder

1980-01-01

90

A global polytropic model for the solar system: planetary distances and masses resulting from the complex Lane-Emden differential equation  

Microsoft Academic Search

In this paper a global polytropic model is developed and applied to the study of the solar system. The theoretical input to this model is very simple, while its numerical output seems to be interesting for illustrating various aspects of our solar system.

V. S. Geroyannis

1993-01-01

91

On phenomenology of compact intracloud lightning discharges  

Microsoft Academic Search

We examined wideband electric fields, electric and magnetic field derivatives, and narrowband VHF (36 MHz) radiation bursts produced by 157 compact intracloud discharges (CIDs). These poorly understood lightning events appear to be the strongest natural producers of HF-VHF radiation. All the events transported negative charge upward (or lowered positive charge), 150 were located by the U.S. National Lightning Detection Network

Amitabh Nag; Vladimir A. Rakov; Dimitris Tsalikis; John A. Cramer

2010-01-01

92

Compact torus  

SciTech Connect

The objective of the compact torus approach is to provide toroidal magnetic-field configurations that are based primarily on plasma currents and can be freed from closely surrounding mechanical structures. Some familiar examples are the current-carrying plasma rings of reversed-field theta pinches and relativistic-electron smoke ring experiments. The spheromak concept adds an internal toroidal magnetic field component, in order to enhance MHD stability. In recent experiments, three different approaches have been used to generate spheromak plasmas: (1) the reversed-field theta pinch; (2) the coaxial plasma gun; (3) a new quasi-static method, based on the initial formation of a toroidal plasma sleeve around a mechanical ring that generates poloidal and toroidal fluxes, followed by field-line reconnection to form a detached spheromak plasma. The theoretical and experimental MHD stability results for the spheromak configuration are found to have common features.

Furth, H.P.

1980-10-01

93

Near- and Far-field Response to Compact Acoustic Sources in Stratified Convection Zones  

NASA Astrophysics Data System (ADS)

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.

2013-05-01

94

Xpr1 Is an Atypical G-Protein-Coupled Receptor That Mediates Xenotropic and Polytropic Murine Retrovirus Neurotoxicity  

PubMed Central

Xenotropic murine leukemia virus-related virus (XMRV) was first identified in human prostate cancer tissue and was later found in a high percentage of humans with chronic fatigue syndrome (CFS). While exploring potential disease mechanisms, we found that XMRV infection induced apoptosis in SY5Y human neuroblastoma cells, suggesting a mechanism for the neuromuscular pathology seen in CFS. Several lines of evidence show that the cell entry receptor for XMRV, Xpr1, mediates this effect, and chemical cross-linking studies show that Xpr1 is associated with the G? subunit of the G-protein heterotrimer. The activation of adenylate cyclase rescued the cells from XMRV toxicity, indicating that toxicity resulted from reduced G-protein-mediated cyclic AMP (cAMP) signaling. Some proteins with similarity to Xpr1 are involved in phosphate uptake into cells, but we found no role of Xpr1 in phosphate uptake or its regulation. Our results indicate that Xpr1 is a novel, atypical G-protein-coupled receptor (GPCR) and that xenotropic or polytropic retrovirus binding can disrupt the cAMP-mediated signaling function of Xpr1, leading to the apoptosis of infected cells. We show that this pathway is also responsible for the classic toxicity of the polytropic mink cell focus-forming (MCF) retrovirus in mink cells. Although it now seems clear that the detection of XMRV in humans was the result of sample contamination with a recombinant mouse virus, our findings may have relevance to neurologic disease induced by MCF retroviruses in mice.

Vaughan, Andrew E.; Mendoza, Ramon; Aranda, Ramona; Battini, Jean-Luc

2012-01-01

95

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

96

Decay of electric charge on corona charged polyethylene  

NASA Astrophysics Data System (ADS)

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. In addition, the pulsed-electro-acoustic (PEA) technique has been employed to monitor charge profiles in corona charged LDPE films. By using the PEA technique, we are able to monitor charge migration through the bulk. Charge profiles in corona charged multilayer sample are consistent with surface potential results. Of further significance, the charge profiles clearly demonstrate that double injection has taken place in corona charged LDPE films.

Xu, Zhiqiang; Zhang, Linwen; Chen, George

2007-11-01

97

Precise Identification of Endogenous Proviruses of NFS/N Mice Participating in Recombination with Moloney Ecotropic Murine Leukemia Virus (MuLV) To Generate Polytropic MuLVs  

PubMed Central

Polytropic murine leukemia viruses (MuLVs) are generated by recombination of ecotropic MuLVs with env genes of a family of endogenous proviruses in mice, resulting in viruses with an expanded host range and greater virulence. Inbred mouse strains contain numerous endogenous proviruses that are potential donors of the env gene sequences of polytropic MuLVs; however, the precise identification of those proviruses that participate in recombination has been elusive. Three different structural groups of proviruses in NFS/N mice have been described and different ecotropic MuLVs preferentially recombine with different groups of proviruses. In contrast to other ecotropic MuLVs such as Friend MuLV or Akv that recombine predominantly with a single group of proviruses, Moloney MuLV (M-MuLV) recombines with at least two distinct groups. In this study, we determined that only three endogenous proviruses, two of one group and one of another group, are major participants in recombination with M-MuLV. Furthermore, the distinction between the polytropic MuLVs generated by M-MuLV and other ecotropic MuLVs is the result of recombination with a single endogenous provirus. This provirus exhibits a frameshift mutation in the 3? region of the surface glycoprotein-encoding sequences that is excluded in recombinants with M-MuLV. The sites of recombination between the env genes of M-MuLV and endogenous proviruses were confined to a short region exhibiting maximum homology between the ecotropic and polytropic env sequences and maximum stability of predicted RNA secondary structure. These observations suggest a possible mechanism for the specificity of recombination observed for different ecotropic MuLVs.

Alamgir, A. S. M.; Owens, Nick; Lavignon, Marc; Malik, Frank; Evans, Leonard H.

2005-01-01

98

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

Microsoft Academic Search

Mouse xenotropic and polytropic leukemia viruses (XMVs and PMVs) are closely related gammaretrovi- ruses 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,

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

2007-01-01

99

Six host range variants of the xenotropic\\/polytropic gammaretroviruses define determinants for entry in the XPR1 cell surface receptor  

Microsoft Academic Search

BACKGROUND: The evolutionary interactions between retroviruses and their receptors result in adaptive selection of restriction variants that can allow natural populations to evade retrovirus infection. The mouse xenotropic\\/polytropic (X\\/PMV) gammaretroviruses rely on the XPR1 cell surface receptor for entry into host cells, and polymorphic variants of this receptor have been identified in different rodent species. RESULTS: We screened a panel

Yuhe Yan; Qingping Liu; Christine A Kozak

2009-01-01

100

Reissner–Nordström and Charged Gas Spheres  

Microsoft Academic Search

This paper studies polytropic gas spheres with some innovations. The main idea, already advanced in the context of neutral,\\u000a homogeneous, polytropic stellar models, is to base the theory firmly on a variational principle. Another essential novelty\\u000a is that the mass distribution extends to infinity, the boundary between bulk and atmosphere being defined by an abrupt change\\u000a in the polytropic index,

Christian Frønsdal

2007-01-01

101

Compact antenna range  

Microsoft Academic Search

The applications of compact antenna range systems for indoor measurements under far-field conditions are discussed. Compact range systems are used to collimate the radiation from a point or a line source by means of a lens or parabolic reflector. Some technical consideration of compact range design are discussed, including: optimal stray radiation levels; shapes and dimensions of the plane wave

V. J. Vokurka

1983-01-01

102

Neurovirulence of Polytropic Murine Retrovirus Is Influenced by Two Separate Regions on Opposite Sides of the Envelope Protein Receptor Binding Domain?  

PubMed Central

Changes in the envelope proteins of retroviruses can alter the ability of these viruses to infect the central nervous system (CNS) and induce neurological disease. In the present study, nine envelope residues were found to influence neurovirulence of the Friend murine polytropic retrovirus Fr98. When projected on a three-dimensional model, these residues were clustered in two spatially separated groups, one in variable region B of the receptor binding site and the other on the opposite side of the envelope. Further studies indicated a role for these residues in virus replication in the CNS, although the residues did not affect viral entry.

Peterson, Karin E.; Pourciau, Susan; Du, Min; LaCasse, Rachel; Pathmajeyan, Melissa; Poulsen, David; Agbandje-McKenna, Mavis; Wehrly, Kathy; Chesebro, Bruce

2008-01-01

103

Dynamics and transport in charged porous media  

Microsoft Academic Search

Charged porous media are filled at least by counterions and often water and occasionally coions. The dynamics of those counterions, water molecules and coions depends strongly on the water content of the medium. For very compact media the water content is low and water and ions are slowed down. For less compact media the dynamics of inserted water and counterions

V. Marry; J. F. Dufreche; M. Jardat; G. Meriguet; P. Turq; F. Grun

2003-01-01

104

Compact ultraviolet laser  

Microsoft Academic Search

This dissertation presents theoretical analysis and experimental investigation of a compact ultraviolet laser, comprising an unstable resonator semiconductor (URSL) laser-pumped potassium titanyl phosphate (KTP) periodically segmented waveguide (PSW) laser. A comprehensive survey of existing short wavelength visible and near ultraviolet laser technologies suitable for the development of compact ultraviolet lasers is presented. This survey establishes the suitability of a diode-pumped

Brian Walter Baird

1997-01-01

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

Nonconformally flat initial data for binary compact objects  

NASA Astrophysics Data System (ADS)

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 ˜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.

Ury?, K?ji; Limousin, François; Friedman, John L.; Gourgoulhon, Eric; Shibata, Masaru

2009-12-01

107

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

108

Stabilization of compactible waste  

SciTech Connect

This report summarizes the results of series of experiments performed to determine the feasibility of stabilizing compacted or compactible waste with polymers. The need for this work arose from problems encountered at disposal sites attributed to the instability of this waste in disposal. These studies are part of an experimental program conducted at Brookhaven National Laboratory (BNL) investigating methods for the improved solidification/stabilization of DOE low-level wastes. The approach taken in this study was to perform a series of survey type experiments using various polymerization systems to find the most economical and practical method for further in-depth studies. Compactible dry bulk waste was stabilized with two different monomer systems: styrene-trimethylolpropane trimethacrylate (TMPTMA) and polyester-styrene, in laboratory-scale experiments. Stabilization was accomplished by wetting or soaking compactible waste (before or after compaction) with monomers, which were subsequently polymerized. Three stabilization methods are described. One involves the in-situ treatment of compacted waste with monomers in which a vacuum technique is used to introduce the binder into the waste. The second method involves the alternate placement and compaction of waste and binder into a disposal container. In the third method, the waste is treated before compaction by wetting the waste with the binder using a spraying technique. A series of samples stabilized at various binder-to-waste ratios were evaluated through water immersion and compression testing. Full-scale studies were conducted by stabilizing two 55-gallon drums of real compacted waste. The results of this preliminary study indicate that the integrity of compacted waste forms can be readily improved to ensure their long-term durability in disposal environments. 9 refs., 10 figs., 2 tabs.

Franz, E.M.; Heiser, J.H. III; Colombo, P.

1990-09-01

109

A compact low temperature scanning tunneling microscope  

NASA Astrophysics Data System (ADS)

We describe the design and fabrication of a compact Low Temperature Scanning Tunneling Microscope (LT-STM) together with a dipper cryostat for cooling the STM down to liquid helium temperatures. The STM, based on the piezo-tube walker as coarse approach mechanism, is suspended inside a cryostat vacuum can using three soft helical springs. The can is dipped into a liquid helium storage container for cooling the STM. Its compact size makes it less susceptible to mechanical vibrations and so the STM works with atomic resolution with a simple spring suspension. We demonstrate the performance of this STM for atomic resolution imaging and tunneling spectroscopy by observing the 3 ×3 charge modulation and the energy gap in the Charge Density Wave (CDW) phase of 2H-NbSe2 at liquid helium temperatures.

Gupta, Anjan Kumar; Sinha, Jaivardhan; Choudhary, Shyam Kumar; Singh, Udai Raj

2009-02-01

110

Compact wide-aperture hyperbolic analyzers  

Microsoft Academic Search

Compact electrostatic analyzers that employ a new geometry are described. They accept collimated beams of ions through relatively wide (non-slit-like) inlet apertures and focus them at various locations, depending on the ion energy per charge, along rectangular position-sensing detectors. Each analyzer has a dynamic range of 10 or more for a fixed deflection voltage. The focal line width at a

C. C. Curtis; K. C. Hsieh

1988-01-01

111

DNA compaction by azobenzene-containing surfactant.  

PubMed

We report on the interaction of cationic azobenzene-containing surfactant with DNA investigated by absorption and fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy. The properties of the surfactant can be controlled with light by reversible switching of the azobenzene unit, incorporated into the surfactant tail, between a hydrophobic trans (visible irradiation) and a hydrophilic cis (UV irradiation) configuration. The influence of the trans-cis isomerization of the azobenzene on the compaction process of DNA molecules and the role of both isomers in the formation and colloidal stability of DNA-surfactant complexes is discussed. It is shown that the trans isomer plays a major role in the DNA compaction process. The influence of the cis isomer on the DNA coil configuration is rather small. The construction of a phase diagram of the DNA concentration versus surfactant/DNA charge ratio allows distancing between three major phases: colloidally stable and unstable compacted globules, and extended coil conformation. There is a critical concentration of DNA above which the compacted globules can be hindered from aggregation and precipitation by adding an appropriate amount of the surfactant in the trans configuration. This is because of the compensation of hydrophobicity of the globules with an increasing amount of the surfactant. Below the critical DNA concentration, the compacted globules are colloidally stable and can be reversibly transferred with light to an extended coil state. PMID:21929022

Zakrevskyy, Yuriy; Kopyshev, Alexey; Lomadze, Nino; Morozova, Elena; Lysyakova, Ludmila; Kasyanenko, Nina; Santer, Svetlana

2011-08-08

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

Compactly Generated Domain Theory  

Microsoft Academic Search

Received We propose compactly generated monotone convergence spaces as a well-behaved topological generalization of directed-complete partial orders (dcpos). The category of such spaces enjoys the usual properties of categories of \\\\predomains\\

Ingo Battenfeld; Matthias Schroder; Alex Simpsony

114

Super-Compact Laser.  

National Technical Information Service (NTIS)

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 ou...

1997-01-01

115

A multicenter blinded analysis indicates no association between chronic fatigue syndrome/myalgic encephalomyelitis and either xenotropic murine leukemia virus-related virus or polytropic murine leukemia virus.  

PubMed

The disabling disorder known as chronic fatigue syndrome or myalgic encephalomyelitis (CFS/ME) has been linked in two independent studies to infection with xenotropic murine leukemia virus-related virus (XMRV) and polytropic murine leukemia virus (pMLV). Although the associations were not confirmed in subsequent studies by other investigators, patients continue to question the consensus of the scientific community in rejecting the validity of the association. Here we report blinded analysis of peripheral blood from a rigorously characterized, geographically diverse population of 147 patients with CFS/ME and 146 healthy subjects by the investigators describing the original association. This analysis reveals no evidence of either XMRV or pMLV infection. IMPORTANCE Chronic fatigue syndrome/myalgic encephalomyelitis has an estimated prevalence of 42/10,000 in the United States, with annual direct medical costs of $7 billion. Here, the original investigators who found XMRV and pMLV (polytropic murine leukemia virus) in blood of subjects with this disorder report that this association is not confirmed in a blinded analysis of samples from rigorously characterized subjects. The increasing frequency with which molecular methods are used for pathogen discovery poses new challenges to public health and support of science. It is imperative that strategies be developed to rapidly and coherently address discoveries so that they can be carried forward for translation to clinical medicine or abandoned to focus resource investment more productively. Our study provides a paradigm for pathogen dediscovery that may be helpful to others working in this field. PMID:22991430

Alter, Harvey J; Mikovits, Judy A; Switzer, William M; Ruscetti, Francis W; Lo, Shyh-Ching; Klimas, Nancy; Komaroff, Anthony L; Montoya, Jose G; Bateman, Lucinda; Levine, Susan; Peterson, Daniel; Levin, Bruce; Hanson, Maureen R; Genfi, Afia; Bhat, Meera; Zheng, HaoQiang; Wang, Richard; Li, Bingjie; Hung, Guo-Chiuan; Lee, Li Ling; Sameroff, Stephen; Heneine, Walid; Coffin, John; Hornig, Mady; Lipkin, W Ian

2012-09-18

116

Radiating Charge  

NSDL National Science Digital Library

The electric field lines from a point charge evolve in time as the charge moves. Watch radiation propagate outward at the speed of light as you wiggle the charge. Stop a moving charge to see bremsstrahlung (braking) radiation. Explore the radiation patterns as the charge moves with sinusoidal, circular, or linear motion. You can move the charge any way you like, as long as you donât exceed the speed of light.

Simulations, Phet I.; Dubson, Michael; Paul, Ariel

2013-02-01

117

DNA compaction by a dendrimer.  

PubMed

At physiological pH, a PAMAM dendrimer is positively charged and can effectively bind negatively charged DNA. Currently, there has been great interest in understanding this complexation reaction both for fundamental (as a model for complex biological reactions) as well as for practical (as a gene delivery material and probe for sensing DNA sequence) reasons. Here, we have studied the complexation between double-stranded DNA (dsDNA) and various generations of PAMAM dendrimers (G3-G5) through atomistic molecular dynamics simulations in the presence of water and ions. We report the compaction of DNA on a nanosecond time scale. This is remarkable, given the fact that such a short DNA duplex with a length close to 13 nm is otherwise thought to be a rigid rod. Using several nanoseconds long MD simulations, we have observed various binding modes of dsDNA and dendrimers for various generations of PAMAM dendrimers at varying charge ratios, and it confirms some of the binding modes proposed earlier. The binding is driven by the electrostatic interaction, and the larger the dendrimer charge, the stronger the binding affinity. As DNA wraps/binds to the dendrimer, counterions originally condensed onto DNA (Na+) and the dendrimer (Cl(-)) get released. We calculate the entropy of counterions and show that there is gain in entropy due to counterion release during the complexation. MD simulations demonstrate that, when the charge ratio is greater than 1 (as in the case of the G5 dendrimer), the optimal wrapping of DNA is observed. Calculated binding energies of the complexation follow the trend G5 > G4 > G3, in accordance with the experimental data. For a lower-generation dendrimer, such as G3, and, to some extent, for G4 also, we see considerable deformation in the dendrimer structure due to their flexible nature. We have also calculated the various helicoidal parameters of DNA to study the effect of dendrimer binding on the structure of DNA. The B form of the DNA is well preserved in the complex, as is evident from various helical parameters, justifying the use of the PAMAM dendrimer as a suitable delivery vehicle. PMID:21171620

Nandy, Bidisha; Maiti, Prabal K

2010-12-20

118

Grain charging in protoplanetary discs  

NASA Astrophysics Data System (ADS)

Context. Recent work identified a growth barrier for dust coagulation that originates in the electric repulsion between colliding particles. Depending on its charge state, dust material may have the potential to control key processes towards planet formation such as magnetohydrodynamic (MHD) turbulence and grain growth, which are coupled in a two-way process. Aims: We quantify the grain charging at different stages of disc evolution and differentiate between two very extreme cases: compact spherical grains and aggregates with fractal dimension Df = 2. Methods: Applying a simple chemical network that accounts for collisional charging of grains, we provide a semi-analytical solution. This allowed us to calculate the equilibrium population of grain charges and the ionisation fraction efficiently. The grain charging was evaluated for different dynamical environments ranging from static to non-stationary disc configurations. Results: The results show that the adsorption/desorption of neutral gas-phase heavy metals, such as magnesium, effects the charging state of grains. The greater the difference between the thermal velocities of the metal and the dominant molecular ion, the greater the change in the mean grain charge. Agglomerates have more negative excess charge on average than compact spherical particles of the same mass. The rise in the mean grain charge is proportional to N1/6 in the ion-dust limit. We find that grain charging in a non-stationary disc environment is expected to lead to similar results. Conclusions: The results indicate that the dust growth and settling in regions where the dust growth is limited by the so-called "electro-static barrier" do not prevent the dust material from remaining the dominant charge carrier.

Ilgner, M.

2012-02-01

119

Augmented Compact Genetic Algorithm  

Microsoft Academic Search

\\u000a An augmented compact genetic algorithm (acGA) is presented in this paper. It exhibits all the desirable characteristics of compact genetic algorithm (cGA). While\\u000a the selection strategy of cGA is similar to (steady-state) tournament selection with replacement (TSR), the proposed algorithm\\u000a employs a strategy akin to tournament selection without replacement (TS\\/R). The latter is a common feature of genetic algorithms\\u000a (GAs)

Chang Wook Ahn; Rudrapatna S. Ramakrishna

2003-01-01

120

[Myocardium non-compaction].  

PubMed

The left ventricular non-compaction (spongy cardiomyopathy) is a rare, poorly known pathology. Disease according to WHO classification applies to unclassified cardiomyopathy. Clinical picture is nonspecific. Diagnosis is established by means of instrumental techniques such as echocardiography and magnetic resonance imaging. Spongy cardiomyopathy usually affects the left ventricle, right ventricular failure occurs much less frequently. We present a description of the disease in 18 years old girl with signs of myocardial infarction and non-compaction of both (left and right) ventricles. PMID:23098553

Stukalova, O V; Shiriaev, G A; Harusov, O N; Ternovo?, S K

2012-01-01

121

Compact Ultradense Matter Impactors  

NASA Astrophysics Data System (ADS)

We study interactions of meteorlike compact ultradense objects (CUDO), having nuclear or greater density, with Earth and other rocky bodies in the Solar System as a possible source of information about novel forms of matter. We study the energy loss in CUDO puncture of the body and discuss differences between regular matter and CUDO impacts.

Rafelski, Johann; Labun, Lance; Birrell, Jeremiah

2013-03-01

122

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

123

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

124

Threads in compact semigroups  

Microsoft Academic Search

In this note we show that if S is a compact connected topological semigroup with unit, in which each subgroup is totally disconnected, then S contains a standard thread which meets the minimal ideal K and contains the unit. This is an extension of a previous result of the author [5] in which threads are constructed in partially ordered semigroups

Robert J. Koch

1964-01-01

125

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

126

Compact cogeneration system  

Microsoft Academic Search

This patent describes a compact heat exchanger for heating water with, and cleaning, the exhaust gas of an internal combustion engine of a cogeneration system. It comprises an outer shell having gas inlet means for entry of exhaust gas from the engine, gas outlet means for outflow of exhaust gas, water inlet means for entry of water to be heated,

Cabral

1991-01-01

127

Compact gas liquid separator  

Microsoft Academic Search

Compact gas-liquid separator comprising a cylindrical separation chamber including an inlet head and a degasifying vessel. The inlet head comprises an inlet tube supporting a nozzle positioned adjacent to the inner wall of a cover situated within the axis of the separation chamber. The cover includes a cylindrical portion closed by a convex cap and extends toward the bottom by

J. Y. J. Deysson; A. P. L. Potiron

1984-01-01

128

Compact air purifier unit  

Microsoft Academic Search

A compact air purifier unit is described adapted to remove contaminating particles of varying sizes which fall within different classes in a range from fine to coarse from the atmosphere of a room. The unit consists of: A a flow tube having an inlet and an outlet; B a suction fan coupled to the outlet of the tube to draw

1986-01-01

129

Compact piezoelectric ultrasonic motors  

Microsoft Academic Search

This paper reviews recent developments of compact ultrasonic motors using piezoelectric resonant vibrations. Following the historical background, ultrasonic motors using the standing and traveling waves are introduced. Driving principles and motor characteristics are explained in comparison with the conventional electromagnetic motors.

Kenji Uchino; Burhanettin Koc

1999-01-01

130

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

131

Soil compaction in cropping systems  

Microsoft Academic Search

Soil compaction is one of the major problems facing modern agriculture. Overuse of machinery, intensive cropping, short crop rotations, intensive grazing and inappropriate soil management leads to compaction. Soil compaction occurs in a wide range of soils and climates. It is exacerbated by low soil organic matter content and use of tillage or grazing at high soil moisture content. Soil

M. A. Hamza; W. K. Anderson

2005-01-01

132

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

133

CHARGE BOTTLE FOR A MASS SEPARATOR  

DOEpatents

Improved mass separator charge bottles are described for containing a dense charge of a chemical compound of copper, nickel, lead or other useful substance which is to be vaporized, and to the method of utilizing such improvcd charge bottles so that the chemical compound is vaporized from the under surface of the charge and thus permits the non-volatile portion thereof to fall to the bottom of the charge bottle where it does not form an obstacle to further evaporation. The charge bottle comprises a vertically disposed cylindrical portion, an inner re-entrant cylindrical portion extending axially and downwardly into the same from the upper end thereof, and evaporative source material in the form of a chemical compound compacted within the upper annular pontion of the charge bottle formed by the re-entrant cylindrical portion, whereby vapor from the chemical compound will pass outwardly from the charge bottle through an apertured closure.

Davidson, P.H.

1959-07-01

134

Compact optical isolator.  

PubMed

This paper describes a compact Faraday rotation isolator using terbium aluminum garnet (TAG) as the Faraday rotation material and small high field permanent magnets made of copper-rare earth alloys. The nominal isolation is 26 dB with a 0.4-dB forward loss. The present isolator can be adjusted to provide effective isolation from 4880 A to 5145 A. Details of the design, fabrication, and performance of the isolator are presented. PMID:20111324

Sansalone, F J

1971-10-01

135

Compact optical temporal processors  

NASA Astrophysics Data System (ADS)

Optical signal processing can be done with time-lens devices. A temporal processor based on chirp-z transformers is suggested. This configuration is more compact than a conventional 4-f temporal processor. On the basis of implementation aspects of such a temporal processor, we did a performance analysis. This analysis leads to the conclusion that an ultrafast optical temporal processor can be implemented.

Mendlovic, David; Melamed, Oded; Ozaktas, Haldun M.

1995-07-01

136

Compact power reactor  

DOEpatents

There is disclosed a small compact nuclear reactor operating in the epithermal neutron energy range for supplying power at remote locations, as for a satellite. The core contains fuel moderator elements of Zr hydride with 7 w/o of 93% enriched uranium alloy. The core has a radial beryllium reflector and is cooled by liquid metal coolant such as NaK. The reactor is controlled and shut down by moving portions of the reflector.

Wetch, Joseph R. (Woodland Hills, CA); Dieckamp, Herman M. (Canoga Park, CA); Wilson, Lewis A. (Canoga Park, CA)

1978-01-01

137

Compressed Compact Suffix Arrays  

Microsoft Academic Search

\\u000a The compact suffix array (CSA) is a space-efficient full-text index, which is fast in practice to search for patterns in a static text. Compared to\\u000a other compressed suffix arrays (Grossi and Vitter, Sadakane, Ferragina and Manzini), the CSA is significantly larger (2.7 times the text size, as opposed\\u000a to 0.6–0.8 of compressed suffix arrays). The space of the CSA includes

Veli Mäkinen; Gonzalo Navarro

2004-01-01

138

Compact ultrasonic rotary motors  

Microsoft Academic Search

This paper reviews recent developments of compact ultrasonic rotary motors using piezoelectric resonant vibrations. Following the historical background, three ultrasonic motors recently developed are introduced; windmill, PZT tube and metal tube types. Driving principles and motor characteristics are described in comparison with the conventional ultrasonic motors. Motors with 1.5 mm in diameter and 0.1 mNm in torque have been actually

K. Uchino; B. Koc; S. Dong

2001-01-01

139

National Campus Compact  

NSDL National Science Digital Library

Founded in 1985 by the presidents of Brown, Georgetown and Stanford universities, the Campus Compact organization was designed to combat the popular image of college students as being wholly self-absorbed and uninterested in the broad range of social concerns outside the walls of their respective colleges and universities. Today, the organization remains committed to helping a wide variety of institutions create supportive academic environments for community service and to forming partnerships with a host of institutions, including those in the worlds of business and social-service providers. As might be expected, there is a wide range of free publications available on the site, including materials on starting campus-community partnerships, information on relevant legislation and policy, and materials on incorporating service-learning projects into the college-level curriculum. Of course, visitors will want to take a look at the current edition (and the archived issues) of their two fine in-house publications, the Campus Compact Reader (which highlights the best writing on civic education and service-learning from around the US), and the Compact Current, which is the organization's quarterly newsletter for organizations and institutions involved in public and community service.

140

Intensity limitations in compact H{sup minus} cyclotrons  

SciTech Connect

At TRIUMF, we have demonstrated 2.5 mA in a compact H{sup -} cyclotron. It is worthwhile to explore possibility of going to even higher intensity. In small cyclotrons, vertical focusing vanishes at the center. The space charge tune shift further reduces vertical focusing, thus determining an upper limit on instantaneous current. Limit on average current is of course also dependent upon phase acceptance, but this can be made quite large in an H{sup -} cyclotron. Longitudinal space charge on the first turn can reduce the phase acceptance as well. For finite ion source brightness, another limit comes from bunching efficiency in presence of space charge forces. We present methods of calculating and optimizing these limits. In particular, we show that it is possible to achieve 10mA in a 50 MeV compact H{sup -} cyclotron.

Baartman, R.A.

1995-12-31

141

Compact heat exchangers  

SciTech Connect

This report aims to increase the market penetration of compact heat exchangers (CHEs) in industry by detailing current experience of their use. CHEs are characterized by having a comparatively large amount of surface area in a given volume, compared to traditional heat exchangers, in particular the shell-and-tube type. The most basic CHEs have volumes of less than 50% of that of a comparable shell-and-tube heat exchanger, for a given duty. Some new designs can, under appropriate process conditions, have only 5% of the volume of traditional equivalents. An essential component of many of these compact concepts is heat (and mass) transfer enhancement. This report also details some of the main enhancement methods which are used in the implementation of compact systems. CHEs are of interest for a number of reasons. As well as being, in general, highly efficient, allowing greater amounts of energy to be recovered between process streams, they are more versatile in terms of the number of process streams that can be handled. Some CHEs can handle only two streams. Others can handle four or more with ease. That, coupled with the availability of units to cater for most operating temperatures and pressures, makes them of interest to operators of complex thermal processing plants. Of even greater long-term importance to the process industries is the ability to use CHE manufacturing technology to integrate effective heat transfer with other unit operations, such as reactors, in one unit. This radical approach to process plant design has fostered many exciting concepts for combined unit operations, some of which are discussed in this report. Topics covered are: types of CHE; (2) the role of heat transfer enhancement; (3) benefits and perceived limitations of CHEs; (4) costs; (5) fouling; (6) specification, installation and operating procedures; (7) the new opportunities; and (8) conclusions.

NONE

1999-11-01

142

Compact electron storage rings  

SciTech Connect

There have been many recent developments in the area of compact storage rings. Such rings would have critical wavelengths of typically 10 A, achieved with beam energies of several hundreds of MeV and superconducting dipole fields of around 5 Tesla. Although the primary motivation for progress in this area is that of commercial x-ray lithography, such sources might be an attractive source for college campuses to operate. They would be useful for many programs in materials science, solid state, x-ray microscopy and other biological areas. We discuss the properties of such sources and review developments around the world, primarily in the USA, japan and W. Germany.

Williams, G.P.

1987-01-01

143

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

144

Compact laser amplifier system  

DOEpatents

A compact laser amplifier system is described in which a plurality of face-pumped annular disks, aligned along a common axis, independently radially amplify a stimulating light pulse. Partially reflective or lasing means, coaxially positioned at the center of each annualar disk, radially deflects a stimulating light directed down the common axis uniformly into each disk for amplification, such that the light is amplified by the disks in a parallel manner. Circumferential reflecting means coaxially disposed around each disk directs amplified light emission, either toward a common point or in a common direction. (Official Gazette)

Carr, R.B.

1974-02-26

145

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 ?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.

Stephen J. Gerdemann; Paul D. Jablonski

2010-11-01

146

Eccentric compact object mergers  

NASA Astrophysics Data System (ADS)

Stellar mass compact object mergers are one of the primary sources of gravitational wave emission that the ground-based gravitational wave detection effort is targeting. Furthermore, if one or both of the compact objects are neutron stars there is promise for coincident electromagnetic emission. Detection, and more importantly extracting properties of the merging system from observations requires theoretical knowledge of the characteristics of the emission. An interesting though possibly rare class of merger events are binaries that merge with large eccentricity. They could occur in close encounters in dense cluster environments, or in a hierarchical triple system subject to Kozai resonance. The gravitational wave signals are markedly different from quasi-circular inspirals, and template-based analysis strategies may not be ideal for eccentric mergers. I will describe ongoing numerical simulations of eccentric binary black hole, black hole-neutron star and binary neutron star systems highlighting some of the interesting dynamics, as well as early results of the efficacy of a stacked, excess power search strategy.

Pretorius, Frans; East, William; Levin, Janna; McWilliams, Sean; Tai, Kai Sheng

2013-04-01

147

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

148

Compact continuous L-domains  

Microsoft Academic Search

The purpose of this paper is to study the structure of compact continuous L-domains. It is proved that FS-domains, continuous B-domains, and compact continuous dcpos are all equivalent for L-domains. A basic notion of property W is introduced and some characterizations of compact continuous L-domains and of continuous L-domains are given by means of the continuity of function spaces and

K. Keimel

1999-01-01

149

METHOD OF FORMING ELONGATED COMPACTS  

DOEpatents

A powder compacting procedure and apparatus which produces elongated compacts of Be is described. The powdered metal is placed in a thin metal tube which is chemically compatible to lubricant, powder, atmosphere, and die material and will undergo a high degree of plastic deformation and have intermediate hardness. The tube is capped and placed in the die, and punches are applied to the ends. During the compacting stroke the powder seizes the tube and a thickening and shortening of the tube occurs. The tube is easily removed from the die, split, and peeled from the compact. (T.R.H.)

Larson, H.F.

1959-05-01

150

Charging machine  

DOEpatents

A charging machine for loading fuel slugs into the process tubes of a nuclear reactor includes a tubular housing connected to the process tube, a charging trough connected to the other end of the tubular housing, a device for loading the charging trough with a group of fuel slugs, means for equalizing the coolant pressure in the charging trough with the pressure in the process tubes, means for pushing the group of fuel slugs into the process tube and a latch and a seal engaging the last object in the group of fuel slugs to prevent the fuel slugs from being ejected from the process tube when the pusher is removed and to prevent pressure liquid from entering the charging machine.

Medlin, John B. (Newark, DE)

1976-05-25

151

Multipurpose Compact Spectrometric Unit  

NASA Astrophysics Data System (ADS)

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.

Bo?arov, Viktor; ?ermák, Pavel; Mamedov, Fadahat; Štekl, Ivan

2009-11-01

152

Compact ultraviolet laser  

NASA Astrophysics Data System (ADS)

This dissertation presents theoretical analysis and experimental investigation of a compact ultraviolet laser, comprising an unstable resonator semiconductor (URSL) laser-pumped potassium titanyl phosphate (KTP) periodically segmented waveguide (PSW) laser. A comprehensive survey of existing short wavelength visible and near ultraviolet laser technologies suitable for the development of compact ultraviolet lasers is presented. This survey establishes the suitability of a diode-pumped KTP PSW laser as an attractive approach for developing a compact ultraviolet laser. Requirements for an efficient diode-pumped KTP PSW laser are given, leading to the selection of a frequency-stabilized URSL and hydrothermal KTP PSWs as the component technologies to be developed and integrated. Since the design requirements for the URSL and KTP PSW are critically dependent on a thorough understanding of the spatial mode properties of KTP PSWs, analyses and modeling of the spatial mode properties of these devices is presented using effective index method (EIM) and beam propagation method (BPM) models. In addition, a new expression for the normalized conversion efficiency is presented which explicitly incorporates the dependence of this important parameter on the lateral variation of the refractive index and d coefficient. To assess the theoretical performance of an URSL-pumped KTP PSW, the BPM model was extended to incorporate second harmonic generation. This represents an important contribution to the development of numerical methods for modeling nonlinear waveguides, in general, and provides important information on the cooperative effects of diffraction and spatial mode beating on the SHG output from KTP PSWs. Extensive optical characterization of NUV SHG in hydrothermal KTP PSWs using an argon-ion laser-pumped Ti:Sapphire laser as the infrared laser pump source is presented. Spectral characterization, spatial mode characterization, and the temperature dependence of the QPM wavelength are presented. This work includes results for the highest cw output powers reported for NUV SHG output from a laser-pumped KTP PSW. In an important step towards demonstration of an URSL- pumped KTP PSW laser, fabrication methods and test results ate reported for half-symmetric, low magnification SQW AlGaAs URSLs emitting at 770 nm and designed for use as diode pump sources for hydrothermal KTP PSWs. These devices utilize a 200 /mu m × 500 /mu m active region profile and were focused-ion- beam micromachined to achieve a total resonator magnification of 2.9. The first demonstration of high brightness, single-longitudinal mode operation from a core grating URSL is reported. This dissertation concludes with results for the first demonstration of an URSL-pumped KTP waveguide laser. This compact ultraviolet laser represents a pioneering effort to take advantage of the high cw output powers available from high brightness URSLs to increase the SH output powers obtainable from diode-pumped nonlinear waveguide lasers and to extend the useful spectral range from these sources into the near ultraviolet.

Baird, Brian Walter

1997-09-01

153

Compact Femtosecond Oscillators  

NASA Astrophysics Data System (ADS)

Configurations are described for compact femtosecond Cr:LiSAF laser oscillators that operate with low pump-power thresholds. By way of illustration of resonator simplification, a progression of low-loss cavity designs from dual-prism through single-prism to prismless schemes is reviewed. A complete femtosecond laser system is described including the laser diode pump system and drivers that has a footprint as small as 22 cm × 28 cm, and a total electrical drive power of less than 1W! Examples of efficient and rugged femtosecond Yb:tungstate and Cr:YAG lasers are also described together with a brief outline of a demonstration in optical datacomms at rates above 1Tb/s for a scheme incorporating the latter laser.

Sibbett, W.; Agate, B.; Brown, C. T. A.; Lagatsky, A. A.; Leburn, C. G.; Stormont, B.; Rafailov, E. U.

154

CIM - compact intensity modulation.  

SciTech Connect

Compact intensity modulation (CIM), a new method to modulate the intensity of a neutron beam is demonstrated. CIM allows the production of arbitrary signals where the focus point can be chosen and changed without any constraints. A novel feature in this technique compared to spin echo techniques is that the neutron polarization is kept parallel or anti-parallel to the static fields during the passage through the magnetic fields and the beating pattern at the detector is produced by an amplitude modulation (AM) of the adiabatic RF-spin flippers rather than Larmor precession like in neutron spin echo (NSE) instruments; thus, the achievable contrast is very high and the instrument resolution can be changed very quickly. This gives the fascinating possibility at pulsed neutron sources to sweep the modulation frequency of the flippers in order to increase dynamic resolution range during the same neutron pulse.

Bleuel, M.; Lang, E.; Gahler, G.; Lal, J.; Intense Pulsed Neutron Source; Inst. Lau Langevin

2008-07-21

155

Compact acoustic refrigerator  

DOEpatents

This invention is comprised of a compact acoustic refrigeration system that actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment.

Bennett, G.A.

1991-12-31

156

Laboratory Evaluation of the Briaud Compaction Device  

Microsoft Academic Search

Soil compaction quality control pays an important role in earthwork construction. Compacted dry density is only loosely related to the actual deformation of the compacted soil. Rather than using dry density as the controlling factor for compacted fills, it would be better to measure properties more closely related to soil compressibility. The Briaud Compaction Device (BCD) is a simple, small-strain,

David M. Weidinger; Louis Ge

2009-01-01

157

POLYCRYSTALLINE DIAMOND COMPACT BIT HYDRAULICS  

Microsoft Academic Search

It is well understood and documented that bottomhole hydraulics plays an important role in conventional diamond bit performance. Recent industry experience has shown a similar importance with the new synthetic diamond compact bits. Certain types of polycrystalline diamond compact bits have cutters arranged in a reverse spiral mode. For optimum performance bit hydraulic design should be tailored to that reverse

R. H. Knowlton; Hsin Huang; B. Iversen

1982-01-01

158

SOIL COMPACTION SENSING AND MANAGEMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

As agricultural machinery has become larger and tillage practices have changed in recent decades, compaction as a result of mechanically applied forces such as traction or tillage has caused increasing concern. Amelioration of compaction generally requires some form of deep tillage, increasing costs...

159

Engineering Prototype for a Compact Medical Dielectric Wall Accelerator  

SciTech Connect

A compact accelerator system architecture based on the dielectric wall accelerator (DWA) for medical proton beam therapy has been developed by the Compact Particle Acceleration Corporation (CPAC). The major subsystems are a Radio Frequency Quadrupole (RFQ) injector linac, a pulsed kicker to select the desired proton bunches, and a DWA linear accelerator incorporating a high gradient insulator (HGI) with stacked Blumleins to produce the required acceleration energy. The Blumleins are switched with solid state laser-driven optical switches integrated into the Blumlein assemblies. Other subsystems include a high power pulsed laser, fiber optic distribution system, electrical charging system, and beam diagnostics. An engineering prototype has been constructed and characterized, and these results will be used within the next three years to develop an extremely compact 150 MeV system capable of modulating energy, beam current, and spot size on a shot-to-shot basis. This paper presents the details the engineering prototype, experimental results, and commercialization plans.

Zografos, Anthony; Hening, Andy; Joshkin, Vladimir; Leung, Kevin; Pearson, Dave; Pearce-Percy, Henry; Rougieri, Mario; Parker, Yoko; Weir, John [CPAC, Livermore, CA (United States); Blackfield, Donald; Chen, Yu-Jiuan; Falabella, Steven; Guethlein, Gary; Poole, Brian [Lawrence Livermore National Laboratory, Livermore, CA (United States); Hamm, Robert W. [R and M Technical Enterprises, Pleasanton, CA (United States); Becker, Reinard [Scientific Software Service, Gelnhausen (Germany)

2011-12-13

160

Engineering Prototype for a Compact Medical Dielectric Wall Accelerator  

NASA Astrophysics Data System (ADS)

A compact accelerator system architecture based on the dielectric wall accelerator (DWA) for medical proton beam therapy has been developed by the Compact Particle Acceleration Corporation (CPAC). The major subsystems are a Radio Frequency Quadrupole (RFQ) injector linac, a pulsed kicker to select the desired proton bunches, and a DWA linear accelerator incorporating a high gradient insulator (HGI) with stacked Blumleins to produce the required acceleration energy. The Blumleins are switched with solid state laser-driven optical switches integrated into the Blumlein assemblies. Other subsystems include a high power pulsed laser, fiber optic distribution system, electrical charging system, and beam diagnostics. An engineering prototype has been constructed and characterized, and these results will be used within the next three years to develop an extremely compact 150 MeV system capable of modulating energy, beam current, and spot size on a shot-to-shot basis. This paper presents the details the engineering prototype, experimental results, and commercialization plans.

Zografos, Anthony; Hening, Andy; Joshkin, Vladimir; Leung, Kevin; Pearson, Dave; Pearce-Percy, Henry; Rougieri, Mario; Parker, Yoko; Weir, John; Blackfield, Donald; Chen, Yu-Jiuan; Falabella, Steven; Guethlein, Gary; Poole, Brian; Hamm, Robert W.; Becker, Reinard

2011-12-01

161

Charge Challenge  

NSDL National Science Digital Library

In this activity, learners explore how objects can have positive, negative, or neutral charges, which attract, repel and move between objects. Learners charge various materials and observe their interactions. Winter is an ideal time to perform these experiments (because there is less water vapor in the air); if it is humid, use a hair dryer to dry the objects, surfaces, and air around the work area.

Kansas, University O.

2006-01-01

162

Six host range variants of the xenotropic/polytropic gammaretroviruses define determinants for entry in the XPR1 cell surface receptor  

PubMed Central

Background The evolutionary interactions between retroviruses and their receptors result in adaptive selection of restriction variants that can allow natural populations to evade retrovirus infection. The mouse xenotropic/polytropic (X/PMV) gammaretroviruses rely on the XPR1 cell surface receptor for entry into host cells, and polymorphic variants of this receptor have been identified in different rodent species. Results We screened a panel of X/PMVs for infectivity on rodent cells carrying 6 different XPR1 receptor variants. The X/PMVs included 5 well-characterized laboratory and wild mouse virus isolates as well as a novel cytopathic XMV-related virus, termed Cz524, isolated from an Eastern European wild mouse-derived strain, and XMRV, a xenotropic-like virus isolated from human prostate cancer. The 7 viruses define 6 distinct tropisms. Cz524 and another wild mouse isolate, CasE#1, have unique species tropisms. Among the PMVs, one Friend isolate is restricted by rat cells. Among the XMVs, two isolates, XMRV and AKR6, differ from other XMVs in their PMV-like restriction in hamster cells. We generated a set of Xpr1 mutants and chimeras, and identified critical amino acids in two extracellular loops (ECLs) that mediate entry of these different viruses, including 3 residues in ECL3 that are involved in PMV entry (E500, T507, and V508) and can also influence infectivity by AKR6 and Cz524. Conclusion We used a set of natural variants and mutants of Xpr1 to define 6 distinct host range variants among naturally occurring X/PMVs (2 XMV variants, 2 PMVs, 2 different wild mouse variants). We identified critical amino acids in XPR1 that mediate entry of these viruses. These gammaretroviruses and their XPR1 receptor are thus highly functionally polymorphic, a consequence of the evolutionary pressures that favor both host resistance and virus escape mutants. This variation accounts for multiple naturally occurring virus resistance phenotypes and perhaps contributes to the widespread distribution of these viruses in rodent and non-rodent species.

Yan, Yuhe; Liu, Qingping; Kozak, Christine A

2009-01-01

163

Wild mouse variants of envelope genes of xenotropic/polytropic mouse gammaretroviruses and their XPR1 receptors elucidate receptor determinants of virus entry.  

PubMed

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. PMID:17634227

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

2007-07-18

164

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

165

A compact single-stage converter for emergency lighting applications  

Microsoft Academic Search

This paper presents a compact single-stage converter for emergency lighting applications. The converter is derived by integrating a bi-directional flyback converter and a half-bridge series-resonant parallel-loaded inverter, which can fulfill the functions of battery charging, discharging and lamp ballasting. Unlike conventional approaches, the rectified and filtered input voltage is directly added on the battery voltage in the proposed system, which

Y.-C. Wu; T.-F. Wu; Y.-K. Chen

2002-01-01

166

Fractional statistics in three dimensions: Compact Maxwell-Higgs system  

SciTech Connect

We show that a (3+1)-dimensional system composed of an open magnetic vortex and an electrical point charge exhibits the phenomenon of Fermi-Bose transmutation. In order to provide the physical realization of this system we focus on the lattice compact scalar electrodynamics SQED{sub {ital c}} whose topological excitations are open Nielsen-Olesen strings with magnetic monopoles attached at their ends. {copyright} {ital 1996 The American Physical Society.}

Fort, H.; Gambini, R. [Instituto de Fisica, Facultad de Ciencias, Tristan Narvaja 1674, 11200 Montevideo (Uruguay)

1996-07-01

167

Compact heat exchanger  

SciTech Connect

A compact heat exchanger apparatus is described which consists of: a cluster of hollow shells, the shell having an outer surface and an inner surface, the shells being clustered to connect portions of their outer surfaces with portions of the outer surfaces of adjacent the shells to form a substantially contiguous interstitial space between the unconnected portions of the outer surfaces, the inner surfaces forming cavities which are interconnected by inner passages through the connecting portions of the shells' outer furfaces to cavaties in adjacent shells, at least some of the cavities and inner passages comprising a contiguous inner space within the inner surfaces of the cluster, fluid communication between the interstitial space and the inner space being prevented by the shells; a first side of the cluster bonded to a first bonding layer which seals the interstitial space on the first side of the cluster, the first side of the cluster being open to the exterior side of the first bonding layer to make the inner space accessible to a first manifold connected to the exterior side of the first bonding layer; a second side of the cluster bonded to a second bonding layer which seals the interstitial space on the second side of the cluster, the second side of the cluster being open to the exterior side of the second bonding layer.

Wood, C.D. III; Benson, H.S.

1986-07-15

168

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

169

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

170

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

171

Compact, low jitter, triggered spark gap  

SciTech Connect

High energy particle accelerators using compact, high gradient cavities will require small, highly reliable, triggered spark gaps. This paper will discuss the design and development of V/N triggered spark gaps operating from 520 kV to 1280 kV. Spark gap jitter of <3 ns has been obtained with trigger voltages of 60 kV. Capacitively balancing the trigger blade electrode, coupled with a trigger voltage rise time of 10 ns, produces three or more arcs across the main electrode gaps. A 2.3 ..cap omega.. injector using 12 parallel spark gaps operating at 1280 kV has been successfully tested. The total number of shots on this injector exceeds 700 without having to refurbish the gaps. A 0.44 ..cap omega.. accelerating cavity with 24 parallel spark gaps and operating at 520 kV charge voltage has also been tested.

Tucker, W.K.; Jones, E.E.; Franklin, T.L.; Bennett, L.F.; Weber, G.

1985-01-01

172

Collective Deceleration: Toward a Compact Beam Dump  

SciTech Connect

With the increasing development of laser accelerators, the electron energy is already beyond GeV and even higher in near future. Conventional beam dump based on ionization or radiation loss mechanism is cumbersome and costly, also has radiological hazards. We revisit the stopping power of high-energy charged particles in matter and discuss the associated problem of beam dump from the point of view of collective deceleration. The collective stopping length in an ionized gas can be several orders of magnitude shorter than the Bethe-Bloch and multiple electromagnetic cascades stopping length in solid. At the mean time, the tenuous density of the gas makes the radioactivation negligible. Such a compact and non-radioactivating beam dump works well for short and dense bunches, which is typically generated from laser wakefield accelerator.

Wu, H.-C.; /Munich, Max Planck Inst. Quantenopt.; Tajima, T.; Habs, D.; /Munich, Max Planck Inst. Quantenopt. /Munich U.; Chao, A.W.; /SLAC; Meyer-ter-Vehn, J.; /Munich, Max Planck Inst. Quantenopt.

2011-11-28

173

Simulation of roller compaction using a laboratory scale compaction simulator.  

PubMed

A method for simulation of the roller compaction process using a laboratory scale compaction simulator was developed. The simulation was evaluated using microcrystalline cellulose as model material and ribbon solid fraction and tensile strength as key ribbon properties. When compacted to the same solid fractions, real and simulated ribbons exhibited similar compression behavior and equivalent mechanical properties (tensile strengths). Thus, simulated and real ribbons are expected to result in equivalent granulations. Although the simulation cannot account for some roller compaction aspects (non-homogeneous ribbon density and material bypass) it enables prediction of the effects that critical parameters such as roll speed, pressure and radius have on the properties of ribbons using a fraction of material required by conventional roller compaction equipment. Furthermore, constant ribbon solid fraction and/or tensile strength may be utilized as scale up and transfer factors for the roller compaction process. The improved material efficiency and product transfer methods could enable formulation of tablet dosage forms earlier in drug product development. PMID:14706252

Zinchuk, Andrey V; Mullarney, Matthew P; Hancock, Bruno C

2004-01-28

174

Minimum mass radius ratio for charged gravitational objects  

NASA Astrophysics Data System (ADS)

We rigorously prove that for compact charged general relativistic objects there is a lower bound for the mass radius ratio. This result follows from the same Buchdahl type inequality for charged objects, which has been extensively used for the proof of the existence of an upper bound for the mass radius ratio. The effect of the vacuum energy (a cosmological constant) on the minimum mass is also taken into account. Several bounds on the total charge, mass and the vacuum energy for compact charged objects are obtained from the study of the Ricci scalar invariants. The total energy (including the gravitational one) and the stability of the objects with minimum mass radius ratio is also considered, leading to a representation of the mass and radius of the charged objects with minimum mass radius ratio in terms of the charge and vacuum energy only.

Böhmer, C. G.; Harko, T.

2007-06-01

175

Compact fission counter for DANCE  

SciTech Connect

The Detector for Advanced Neutron Capture Experiments (DANCE) consists of 160 BF{sub 2} crystals with equal solid-angle coverage. DANCE is a 4{pi} {gamma}-ray calorimeter and designed to study the neutron-capture reactions on small quantities of radioactive and rare stable nuclei. These reactions are important for the radiochemistry applications and modeling the element production in stars. The recognition of capture event is made by the summed {gamma}-ray energy which is equivalent of the reaction Q-value and unique for a given capture reaction. For a selective group of actinides, where the neutron-induced fission reaction competes favorably with the neutron capture reaction, additional signature is needed to distinguish between fission and capture {gamma} rays for the DANCE measurement. This can be accomplished by introducing a detector system to tag fission fragments and thus establish a unique signature for the fission event. Once this system is implemented, one has the opportunity to study not only the capture but also fission reactions. A parallel-plate avalanche counter (PPAC) has many advantages for the detection of heavy charged particles such as fission fragments. These include fast timing, resistance to radiation damage, and tolerance of high counting rate. A PPAC also can be tuned to be insensitive to {alpha} particles, which is important for experiments with {alpha}-emitting actinides. Therefore, a PPAC is an ideal detector for experiments requiring a fast and clean trigger for fission. A PPAC with an ingenious design was fabricated in 2006 by integrating amplifiers into the target assembly. However, this counter was proved to be unsuitable for this application because of issues related to the stability of amplifiers and the ability to separate fission fragments from {alpha}'s. Therefore, a new design is needed. A LLNL proposal to develop a new PPAC for DANCE was funded by NA22 in FY09. The design goal is to minimize the mass for the proposed counter and still be able to maintain a stable operation under extreme radioactivity and the ability to separate fission fragments from {alpha}'s. In the following sections, the description is given for the design and performance of this new compact PPAC, for studying the neutron-induced reactions on actinides using DANCE at LANL.

Wu, C Y; Chyzh, A; Kwan, E; Henderson, R; Gostic, J; Carter, D; Bredeweg, T; Couture, A; Jandel, M; Ullmann, J

2010-11-06

176

Mechanical compaction of Diemelstadt sandstone : from compacting shear bands to pure compaction bands  

NASA Astrophysics Data System (ADS)

Field observations and laboratory experiments have recently documented in porous sandstones the development of compaction bands sub-perpendicular to the direction of maximum principal stress. These compaction bands have been preferentially observed in relatively homogeneous sandstones of high porosity, such as Bentheim sandstone studied by Wong et al. [2001] and Baud et al. [2003]. The aim of this work is to study how the mineralogical composition could influence the development and the geometry of compaction bands, and if compaction bands could develop in a heterogeneous porous sandstones. We choose Dielmelstadt sandstone of 24% average porosity. This sandstone from Germany is made of 68% quartz, 26 % of feldspars and of 6% oxides and micas. Hydrostatic and conventional triaxial compression experiments were conducted at room temperature on saturated samples under drained conditions, with a constant pore pressure of 10 MPa. The samples were deformed in the range of effective pressure from 80 to 160 MPa with acoustic emission continuously recorded during the experiments. The samples were unloaded and retrieved from the pressure vessel to prepare petrographic thin-sections. At 160 MPa of effective pressure, microstructural characterization of spatial distribution of damage in failed sample confirms that compaction bands are present. For sample deformed at 80 MPa effective pressure, microstructural observation of damage in failed sample shows bands that are not perpendicular to maximum compressive stress. Indeed these bands are oriented with an angle of 30-40° with the horizontal axis. We interpret these bands as compacting shear bands. The failure of very porous rock can be associated with three types of strain localization: extension bands, shear bands, and compaction band. Besuelle [2001] has shown, that there is a continuous transition between pure extension bands and pure compaction bands, via dilating shear bands and compacting shear bands. We have used this theoretical analysis based on bifurcation to interpret our results.

Fortin, J.; Baud, P.; Wong, T.-F.

2003-04-01

177

Physics of compact stars  

NASA Astrophysics Data System (ADS)

This thesis starts with a pedagogical introduction to the study of white dwarfs and neutron stars. We will present a step-by-step study of compact stars in hydrostatic equilibrium leading to the equations of stellar structure. Through the use of a simple finite-difference algorithm, solutions to the equations for stellar structure both for white dwarfs and neutron stars are presented. While doing so, we will also introduce the physics of the equation of state and insights on dealing with units and rescaling the equations. The next project consists of the development of a "semi-classical" model to describe the equation of state of neutron-rich matter in the "Coulomb frustrated" phase known as nuclear pasta. In recent simulations we have resorted to a classical model that, while simple, captures the essential physics of the nuclear pasta, which consists of the interplay between long range Coulomb repulsion and short range nuclear attraction. However, for the nuclear pasta the de Broglie wavelength is comparable to the average inter- particle separation. Therefore, fermionic correlations are expected to become important. In an effort to address this challenge, a fictitious "Pauli potential" is introduced to mimic the fermionic correlations. In this thesis we will examine two issues. First, we will address some of the inherent difficulties in a widely used version of the Pauli potential. Second, we will refine the potential in a manner consistent with the most basic properties of a degenerate free Fermi gas, such as its momentum distribution and its two-body correlation function. With the newly refined potential, we study various physical observables, such as the two-body correlation function via Metropolis Monte-Carlo simulations.

Taruna, Jutri

2008-10-01

178

CIT (Compact Ignition Tokamak) Fueling.  

National Technical Information Service (NTIS)

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...

W. A. Houlberg

1988-01-01

179

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

180

Plutonium Diffusivity in Compacted Bentonite.  

National Technical Information Service (NTIS)

Measurement on plutonium diffusivity in water-saturated compacted bentonite was carried out. Representative specimens of sodium bentonite were taken from Tsukinuno and Kuroishi mines situated in northeast Japan. Tsukinuno bentonite was divided into three ...

K. Idemitsu K. Ishiguro Y. Yusa N. Sasaki N. Tsunoda

1989-01-01

181

Dynamic compaction of aluminum nanocrystals  

SciTech Connect

The authors investigated shock-compaction behavior of nanocrystalline aluminum (n-Al) powder with an average particle size of about 50--70 nm. The starting powders were analyzed using various analytical tools, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The initial Al particles were found to be coated naturally by a uniform, thin ({approximately}5 nm) near-stoichiometric, amorphous oxide layer. Shock compaction was carried out at 2--3 GPa (20--30 kbars) to obtain high-density disks. The microstructure of samples prior to and after consolidation were both examined. Despite substantial deformation during dynamic compaction, the surface oxide remained intact at the pressures employed and prevented a metallurgical bond between the nano-sized particles. Theoretical simulations of the dynamic compaction of n-Al were also carried out using an Eulerian hydrocode. The results were in good agreement with experimental observations.

Nieh, T.G.; Luo, P.; Nellis, W.; Lesuer, D. [Lawrence Livermore National Lab., CA (United States); Benson, D. [Univ. of California, San Diego, La Jolla, CA (United States). Dept. of Applied Mechanics and Engineering Sciences

1996-09-01

182

Compaction properties of granular bentonites  

Microsoft Academic Search

Bentonites have been examined recently in some countries as candidates for buffer materials for use in high-level nuclear waste repositories. Granular bentonites are anticipated as the raw materials for constructing bentonite-based buffer materials by in-situ compaction methods. For that reason, it is important to understand the influence of grain size distribution and physicochemical properties of bentonite ore on compaction properties

Hiroshi Ito

2006-01-01

183

Noise Analysis Compact Genetic Algorithm  

Microsoft Academic Search

\\u000a This paper proposes the Noise Analysis compact Genetic Algorithm (NAcGA). This algorithm integrates a noise analysis component\\u000a within a compact structure. This fact makes the proposed algorithm appealing for those real-world applications characterized\\u000a by the necessity of a high performance optimizer despite severe hardware limitations. The noise analysis component adaptively\\u000a assigns the amount of fitness evaluations to be performed in

Ferrante Neri; Ernesto Mininno; Tommi Kärkkäinen

2010-01-01

184

SPARC EBIT — a charge breeder for the HITRAP project  

NASA Astrophysics Data System (ADS)

Charge breeding of externally injected, singly-charged ions in an electron beam ion source/trap (EBIS/T) extends the range of elements from which highly-charged ions can be produced with these machines, which is important for numerous atomic and nuclear physics experiments. Existing EBIS/T charge breeders feature electron guns producing intense beams and superconducting magnets generating strong fields to achieve high efficiencies and high ion charge states. We show an alternative possibility to inject, capture, charge-breed and extract ions using a compact room-temperature EBIT based on permanent magnet technology. Singly-charged potassium and rubidium ions injected over the barrier were charge bred and extracted as bare and neon-like ions, respectively. Simulations of injection and capture of singly-charged ions in this EBIT show the challenges and help understanding the results.

Sokolov, A.; Herfurth, F.; Kester, O.; Stoehlker, Th; Thorn, A.; Vorobjev, G.; Zschornack, G.

2010-11-01

185

Microstructure studies of dynamically compacted material  

Microsoft Academic Search

Dynamic compaction has been used successfully to compact aluminum and titanium powder. A light gas (helium) gun was used for these studies. Fine oxide powders were added to the metal powders to identify the interparticle boundaries in the compacted material. The as-compacted and heat treated microstructures, particularly the interparticle boundary region, were examined by TEM and optical microscopy. These results

D. J. Miller; D. G. Konitzer; H. L. Fraser

2008-01-01

186

Charging characteristics of a solid insulator in vacuum under AC voltage excitation  

Microsoft Academic Search

We have investigated charging and flashover characteristics of a polymeric or glass insulator exposed to AC voltage in vacuum in order to develop compact and reliable high voltage VCBs (vacuum circuit breakers). This paper focuses on charging characteristics of a cylindrical model insulator. The charging of an insulator is investigated using an electrostatic probe that measures the electric field near

O. Yamamoto; S. Hamada; T. Fukuda; H. Omura

2006-01-01

187

Imaging compaction of single supercoiled DNA molecules by atomic force microscopy.  

PubMed

Supercoiled pGEMEX DNA, 3993 bp in length, was immobilized on different substrates (freshly cleaved mica, standard amino mica and modified amino mica with increased hydrophobicity and surface charge density compared with standard amino mica) and was visualized by atomic force microscopy (AFM) in air. Plectonemically supercoiled DNA (scDNA) molecules, as well as extremely compacted single molecules, were visualized on amino-modified mica, characterized by increased hydrophobicity and surface charge density. We show four-fold increase in DNA folding on the mica surface with high positive charge density. This result is consistent with a strongly enhanced molecular flexibility facilitated by shielding of the DNA phosphate charges. The formation of minitoroids with about a 50 nm diameter and molecules in spherical conformation was the final stage of single molecule compaction. A possible model of conformational transitions for scDNA in vitro in the absence of protein is proposed based on AFM image analysis. Compaction of the single scDNA molecules, up to minitoroids and spheroids, appears to be caused by screening of the negatively charged DNA phosphate groups. The high surface charge density from positively charged amino groups on mica, on which DNA molecules were immobilized, is an obvious candidate for the screening effect. PMID:19202207

Limanskaya, Olga Y; Limanskii, Alex P

2008-12-01

188

Compaction Stress in Fine Powders  

SciTech Connect

A vexing feature in granular materials compaction is density extrema interior to a compacted shape. Such inhomogeneities can lead to weaknesses and loss of dimensional control in ceramic parts, unpredictable dissolution of pharmaceuticals, and undesirable stress concentration in load-bearing soil. As an example, the centerline density in a cylindrical compact often does not decrease monotonically from the pressure source but exhibits local maxima and minima. Two lines of thought in the literature predict, respectively, diffusive and wavelike propagation of stress. Here, a general memory function approach has been formulated that unifies these previous treatments as special cases; by analyzing a convenient intermediate case, the telegrapher's equation, one sees that local density maxima arise via semidiffusive stress waves reflecting from the die walls and adding constructively at the centerline.

Hurd, A.J.; Kenkre, V.M.; Pease, E.A.; Scott, J.E.

1999-04-01

189

Compact orthogonal NMR field sensor  

SciTech Connect

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

190

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

191

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

192

Get Charged!  

NSDL National Science Digital Library

Students are introduced to the idea of electrical energy. They learn about the relationships between charge, voltage, current and resistance. They discover that electrical energy is the form of energy that powers most of their household appliances and toys. In the associated activities, students learn how a circuit works and test materials to see if they conduct electricity. Building upon a general understanding of electrical energy, they design their own potato power experiment. In two literacy activities, students learn about the electrical power grid and blackouts.

Integrated Teaching And Learning Program

193

Harmonics from compact fluorescent lamps  

Microsoft Academic Search

The measured performance of compact fluorescent lamps (CFLs) and some rectified incandescent lamps, which can cause considerable harmonic distortion of the input power, is discussed. These include both the electronically and magnetically ballasted CFLs with poor power factors and\\/or high harmonics. Using the model of a building's electrical load, it is shown that there is little cause for concern for

R. R. Verderber; O. C. Morse; W. R. Alling

1993-01-01

194

Compact integrated dynamic wavelength equalizer  

Microsoft Academic Search

An integrated dynamic wavelength equalizer that can control attenuation at 22 points across 35 nm of spectrum in a smooth manner is presented. It achieves low loss and compactness because it consists of a Michelson interferometer with a waveguide grating router in only one arm

C. R. Doerr; P. Schiffer; L. W. Stulz; M. Cappuzzo; E. Laskowski; A. Paunescu; L. Gomez; J. Gates

1999-01-01

195

Shock Compaction of Molybdenum Powder.  

National Technical Information Service (NTIS)

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 a...

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

1983-01-01

196

Compact Triaxial Accelerometer Systems (CTAS)  

Microsoft Academic Search

As the opportunities for microgravity experiment on drop towers, aircraft and spacecraft such as the Space Shuttle have increased, it has become profitable to develop systems able to detect acceleration precisely. The compact triaxial accelerometer system (CTAS) developed to do this has 12-bit precision and 10-micro-G resolution. It weighs 4 kg, and is small and light enough to fit in

Naoyuki Matsumoto; Masahiro Takayanagi; Fumio Takei; Naoto Kawase; Yutaka Zaiki; Shin-Ichi Kitamura; Masafumi Tanaka

1990-01-01

197

Explosive-Powder Compaction System.  

National Technical Information Service (NTIS)

Sandia National Laboratories has developed a pressure-control system and a test fixture to study the behavior of explosive materials during compaction. Both the pressure-control system and the test fixture are self-contained and portable. Explosive materi...

A. P. Montoya M. L. Reichenbach

1981-01-01

198

Globular Clusters in Compact Groups  

Microsoft Academic Search

We have studied globular cluster systems (GCSs) around elliptical galaxies in Hickson compact groups using multi-band deep, high quality images from Keck, VLT and CFHT. Analyzing the luminosity functions, specific frequencies, color and spatial distributions, we could determine the properties of the GCSs of those galaxies and trace their star formation histories. We have found poor populations, concentrated toward the

Cristiano Da Rocha; Claudia Mendes de Oliveira; Michael Bolte; Bodo L. Ziegler; Thomas H. Puzia

2003-01-01

199

Powder compaction with ultrasonic assistance  

Microsoft Academic Search

The compaction behaviour of a ceramic powder can be improved by ultrasonic assistance, only when ultrasounds are used at pressures lower than a critical value,PC. This critical pressure is connected with the limit of mobility of the powder grains under ultrasonic vibrations. Its value depends on the characteristics of the powder, as well as those of the ultrasounds: frequency, amplitude,

E. Emeruwa; J. Jarrige; J. Mexmain; M. Billy; K. Bouzouita

1990-01-01

200

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

201

Galaxy Evolution in Compact Groups  

NASA Astrophysics Data System (ADS)

The processes by which galaxies formed is one of the most important open questions in astrophysics. Most generally, it is now thought that galaxies formed through “hierarchical formation,” where galaxies grow by merging with similarly-sized galaxies and accreting smaller galaxies. Subsequently, clusters formed when galaxies would accumulate in gravitational potential wells. However, the detailed astrophysical processes involved are poorly constrained. Progress has been largely limited due to the lack of suitably high sensitivity and resolution data sets of these high redshift systems. In the absence of detailed observations of these environments in the earlier universe, the best current path forward is through relatively nearby analogs. Compact groups of galaxies provide a nearby environment with conditions similar to those in the earlier universe when galaxies were assembled. In particular, these groups give us the opportunity to witness hierarchical formation in progress. Our studies of compact groups aim to determine how this intense environment - one of high galaxy density and constant interactions - affects the evolution of member galaxies. We compare the mid-infrared (MIR) colorspace distribution of compact group galaxies to several other environments, and find that the compact group galaxies occupy MIR colorspace in a unique way; there is a statistically significant canyon between quiescent galaxies and active galaxies not seen in a field sample, interacting pairs, or the center of Coma. However, the infall region of Coma shows a similar colorspace distribution, indicating similar environments; both have high densities and still contain neutral gas. An analysis of compact group galaxies' SEDs reveals that galaxies in different regions of MIR colorspace contain dust with varying properties. We compare MIR and optical colors of compact group galaxies and find that the MIR 'canyon' galaxies do not occupy the optical 'green valley' as expected, rather they fall on the optical 'red sequence', indicating that the MIR properties transition on a different timescale than the optical properties. We have also obtained HI masses of compact groups for comparison with MIR and optical properties of member galaxies.

Walker, Lisa May; Johnson, K. E.

2013-01-01

202

Charge instabilities due to local charge conjugation symmetry in /2+1 dimensions  

NASA Astrophysics Data System (ADS)

Alice electrodynamics (AED) is a theory of electrodynamics in which charge conjugation is a local gauge symmetry. In this paper we investigate a charge instability in alice electrodynamics in /2+1 dimensions due to this local charge conjugation. The instability manifests itself through the creation of a pair of alice fluxes. The final state is one in which the charge is completely delocalized, i.e., it is carried as cheshire charge by the flux pair that gets infinitely separated. We determine the decay rate in terms of the parameters of the model. The relation of this phenomenon with other salient features of 2-dimensional compact QED, such as linear confinement due to instantons/monopoles, is discussed.

Bais, F. A.; Striet, J.

2003-08-01

203

Scaling Theory for Percolative Charge Transport in Disordered Molecular Semiconductors  

NASA Astrophysics Data System (ADS)

We present a scaling theory for charge transport in disordered molecular semiconductors that extends percolation theory by including bonds with conductances close to the percolating one in the random-resistor network representing charge hopping. A general and compact expression is given for the charge mobility for Miller-Abrahams and Marcus hopping on different lattices with Gaussian energy disorder, with parameters determined from numerically exact results. The charge-concentration dependence is universal. The model-specific temperature dependence can be used to distinguish between the hopping models.

Cottaar, J.; Koster, L. J. A.; Coehoorn, R.; Bobbert, P. A.

2011-09-01

204

Resonant charging  

NASA Astrophysics Data System (ADS)

It has been shown (Athas et al., 1994) that adiabatic switching can significantly reduce the dynamic power dissipation in an integrated circuit. Due to the overhead in the realization of adiabatic logic blocks (Saas et al., 2000) the best results are achieved when it is used only for charging dominant loads in an integrated circuit (Voss and Glessner, 2001). It has been demonstrated (Saas et al., 2001) that a multi stage driver is needed for minimal power dissipation. In this article a complete three stage driver including the generation of oscillating supply is described. To obtain a minimal power dissipation during synchronization the resonant frequency has to be constant. Therefore the waveforms for the logic states of the signal and the realization of a single stage differ from those presented in (Saas et al., 2001). In the H-SPICE simulations losses of the inductor are taken into account. This allows to estimate the power reduction that is achievable in a real system.

Saas, C.; Nossek, J. A.

2003-05-01

205

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

206

CHARGE Association  

PubMed Central

We present here a case of 17-year-old boy from Kolkata presenting with obesity, bilateral gynecomastia, mental retardation, and hypogonadotrophic hypogonadism. The patient weighed 70 kg and was of 153 cm height. Facial asymmetry (unilateral facial palsy), gynecomastia, decreased pubic and axillary hair, small penis, decreased right testicular volume, non-palpable left testis, and right-sided congenital inguinal hernia was present. The patient also had disc coloboma, convergent squint, microcornea, microphthalmia, pseudohypertelorism, low set ears, short neck, and choanalatresia. He had h/o VSD repaired with patch. Laboratory examination revealed haemoglobin 9.9 mg/dl, urea 24 mg/dl, creatinine 0.68 mg/dl. IGF1 77.80 ng/ml (decreased for age), GH <0.05 ng/ml, testosterone 0.25 ng/ml, FSH-0.95 ?IU/ml, LH 0.60 ?IU/ml. ACTH, 8:00 A.M cortisol, FT3, FT4, TSH, estradiol, DHEA-S, lipid profile, and LFT was within normal limits. Prolactin was elevated at 38.50 ng/ml. The patient's karyotype was 46XY. Echocardiography revealed ventricularseptal defect closed with patch, grade 1 aortic regurgitation, and ejection fraction 67%. Ultrasound testis showed small right testis within scrotal sac and undescended left testis within left inguinal canal. CT scan paranasal sinuses revealed choanalatresia and deviation of nasal septum to the right. Sonomammography revealed bilateral proliferation of fibroglandular elements predominantly in subareoalar region of breasts. MRI of brain and pituitary region revealed markedly atrophic pituitary gland parenchyma with preserved infundibulum and hypothalamus and widened suprasellar cistern. The CHARGE association is an increasingly recognized non-random pattern of congenital anomalies comprising of coloboma, heart defect, choanal atresia, retarded growth and development, genital hypoplasia, ear abnormalities, and/or deafness.[1] These anomalies have a higher probability of occurring together. In this report, we have described a boy with CHARGE association.

Chakraborty, Semanti; Chakraborty, Jayanta

2012-01-01

207

7 CFR 51.608 - Fairly compact.  

Code of Federal Regulations, 2013 CFR

...INSPECTION ACT FRESH FRUITS, VEGETABLES AND OTHER PRODUCTS 1,2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Definitions § 51.608 Fairly compact. Fairly compact means that the...

2013-01-01

208

Compact Sobolev Imbeddings for Pepper Sets.  

National Technical Information Service (NTIS)

The problem of compactness of imbeddings between Sobolev spaces of functions defined on unbounded domains has been investigated in several recent papers. Such compactness theorems are useful for studying existence and spectral theory for partial different...

R. A. Adams

1969-01-01

209

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.

Hetzer, D.C.

1997-08-01

210

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

211

Strength of Field Compacted Clayey Embankments.  

National Technical Information Service (NTIS)

The shearing behavior of a plastic Indiana clay (St. Croix) was studied for both laboratory and field compaction. This interim report deals with the field compacted phase. The strength tests were performed by unconsolidated-undrained (UU) and saturated co...

Y. Liang C. W. Lovell

1982-01-01

212

Modified valley fill high power factor electronic ballast for compact fluorescent lamps  

Microsoft Academic Search

A simple, lost cost, high power factor ballast, referred to as the modified valley fill circuit, for compact fluorescent lamps is introduced. This circuit peak charges the valley fill (electrolytic) capacitor from an auxiliary winding on the high frequency ballasting inductor to a fraction of the peak line voltage, where the input power factor is optimized at 0.95. A simple

Mustansir H. Kheraluwala; Sayed Amr El-Hamamsy

1995-01-01

213

LS-category of compact Hausdorff foliations  

Microsoft Academic Search

The transverse (saturated) Lusternik-Schnirelmann category of foliations, introduced by the first author in (5, 9), is an invariant of foliated homotopy type with values in {1, 2 ,..., ?} .A foliation with all leaves compact and Hausdorff leaf space M\\/F is called compact Hausdorff. The transverse saturated category cat? | M of a compact Hausdorff foliation is always finite. In

Hellen Colman; Steven Hurder

2003-01-01

214

THE UTTON CENTER MODEL COMPACTS PROJECT  

Microsoft Academic Search

Interstate compacts have been used since Colonial times to resolve conflicts between states. With regard to conflicts over interstate water resources, compacts have been used for multiple purposes including water supply, water allocation, pollution control, regional planning and flood control. Virtually all of the existing interstate compacts contain provisions that are now inconsistent with the requirements of federal and state

George William Sherk; Kathryn J. Hatcher

215

Analysis of compact antenna test range configurations  

Microsoft Academic Search

An antenna test center for antennas and payloads of large spacecraft was constructed. It consists of a near field and a compact test range. Results obtained during the analysis and definition phase of the compact range are described. Predicted co- and cross-polar contour plots of different compact range alternatives in the 5m x 7m quiet zone are presented. Compensation and

E. W. M. Dudok; D. Fasold

1986-01-01

216

Technology of compact fusion-reactor concepts  

SciTech Connect

An identification of future engineering needs of compact, high-power-density approaches to fusion power is presented. After describing a rationale for the compact approach and a number of compact fusion reactors, key technology needs are assessed relative to the similar needs of the conventional tokamak in order to emphasize differences in required technology with respect to the well-documented mainline approaches.

Krakowski, R.A.; Glancy, J.E.; Dabiri, A.E.

1982-01-01

217

Nondestructive evaluation of compacted clayey soils  

Microsoft Academic Search

Compacted clayey soils are analyzed using nondestructive testing methods. Ultrasonic testing and image analysis are used as nondestructive testing techniques. Tests were conducted on three clayey soils with low to high plasticities. The soils are compacted and then allowed to dry or subjected to wetting and drying cycles subsequent to compaction. Ultrasonic tests are performed to determine small strain elastic

Gokhan Inci

2001-01-01

218

Small Anion with Higher Valency Retards the Compaction of DNA in the Presence of Multivalent Cation  

PubMed Central

It has been established that, upon the addition of multivalent cations, long DNA chains in an aqueous solution exhibit a remarkable discrete transition from a coil state to a compact state at the level of a single chain. In this study, we investigated the polyelectrolyte nature of DNA with the experimental methodology of single-DNA observation, and provide a theoretical interpretation. We examined the effects of co-ions with different valencies (Cl?, SO42?, PO43?) on DNA compaction. As a result, we found that co-ions with a greater valency induce the coil state rather than the compact state. Based on a simple model with mean-field approximation that considered ion pairing, we show how the increase in entropy of small ions contributes to the stability of the compact state, by overcoming entropic penalties such as elastic confinement of the chain and a decrease in the translational freedom of counterions accompanied by charge neutralization.

Saito, Takuya; Iwaki, Takafumi; Yoshikawa, Kenichi

2009-01-01

219

On phenomenology of compact intracloud lightning discharges  

NASA Astrophysics Data System (ADS)

We examined wideband electric fields, electric and magnetic field derivatives, and narrowband VHF (36 MHz) radiation bursts produced by 157 compact intracloud discharges (CIDs). These poorly understood lightning events appear to be the strongest natural producers of HF-VHF radiation. All the events transported negative charge upward (or lowered positive charge), 150 were located by the U.S. National Lightning Detection Network (NLDN), and 149 of them were correctly identified as cloud discharges. NLDN-reported distances from the measurement station were 5-132 km. Three types of wideband electric field waveforms were observed. About 73% of CIDs occurred in isolation; 24% occurred prior to, during, or following cloud-to-ground or "normal" cloud lightning; and 4% occurred in pairs, separated by less than 200 ms ("multiple" CIDs). For a subset of 48 CIDs, the geometric mean of radiation source height was estimated to be 16 km. It appears that some CIDs actually occurred above cloud tops in clear air or in convective surges (plumes) overshooting the tropopause and penetrating deep into the stratosphere. For the same 48 CIDs, the geometric mean electric field peak normalized to 100 km (inclined distance) was as high as 20 V/m, and for 22 events within 10-30 km (horizontal distance), it was 15 V/m, both of which are higher than that for first strokes in negative cloud-to-ground lightning. The geometric means of total electric field pulse duration, width of initial half cycle, and ratio of initial peak to opposite polarity overshoot were 23 ?s, 5.6 ?s, and 5.7, respectively.

Nag, Amitabh; Rakov, Vladimir A.; Tsalikis, Dimitris; Cramer, John A.

2010-07-01

220

Measurement of compacted soil density in a compaction of thick finishing layer  

Microsoft Academic Search

The compaction of a soil is one of the important construction operations that influences the durability of soil structure. Therefore, the measurement of soil density, used to judge the degree of compaction, has to be performed exactly. Since a compaction of a thick finishing layer could be executed with the enlargement of compaction machinery and the improvement of productivity, new

Tadaomi Eguchi; Tatsuro Muro

2007-01-01

221

On Modeling Of Charged Structures Encircling Black Holes  

NASA Astrophysics Data System (ADS)

Results of our recent studies suggest a possibility of existence of halo (off-equatorial) clouds consisting of non-interacting charged test particles encircling compact objects (black holes, neutron stars) surrounded by magnetic fields. Here we upgrade the basic model of such diluted toroidal structures by adding internal properties of the matter like density and pressure, so that we have more feasible description for the real charged matter. We realize it by using the magnetohydrodynamic approach. Namely, we built a model of dielectric (zero conductivity) charged torus moving in strong gravitational and electromagnetic fields in the vicinity of black holes. This approach represents just the opposite one to that of widely used ideal magnetohydrodynamics, where the infinite conductivity is taken into account. However, the zero (or negligible) conductivity seems to be one of the assumptions for the existence of charged tori circling in strong gravitational and electromagnetic fields of compact objects.

Kovar, Jiri; Slany, P.; Stuchlik, Z.; Karas, V.; Cremaschini, C.; Miller, J.

2011-09-01

222

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

223

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

224

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

225

Rapid compaction during RNA folding  

NASA Astrophysics Data System (ADS)

We have used small angle x-ray scattering and computer simulations with a coarse-grained model to provide a time-resolved picture of the global folding process of the Tetrahymena group I RNA over a time window of more than five orders of magnitude. A substantial phase of compaction is observed on the low millisecond timescale, and the overall compaction and global shape changes are largely complete within one second, earlier than any known tertiary contacts are formed. This finding indicates that the RNA forms a nonspecifically collapsed intermediate and then searches for its tertiary contacts within a highly restricted subset of conformational space. The collapsed intermediate early in folding of this RNA is grossly akin to molten globule intermediates in protein folding.

Russell, Rick; Millett, Ian S.; Tate, Mark W.; Kwok, Lisa W.; Nakatani, Bradley; Gruner, Sol M.; Mochrie, Simon G. J.; Pande, Vijay; Doniach, Sebastian; Herschlag, Daniel; Pollack, Lois

2002-04-01

226

Charging apparatus  

SciTech Connect

A diode is disposed in the vicinity of a rechargeable battery. A current is applied to the diode from a current generating circuit. The current generating circuit comprises a thermistor which is responsive to the ambient temperature, so that a current associated with the ambient temperature is applied from the current generating circuit to the diode. The diode gives rise to a forward voltage drop, which is changeable as a function of the battery temperature. Accordingly, the forward voltage drop across the diode is changeable as a function of the ambient temperature and the battery temperature. The forward voltage drop across the diode is amplified to be used as a reference voltage. On the other hand, the rechargeable battery is supplied with a charging current from a power supply through a thyristor. The gate electrode of the thyristor is connected to receive the reference voltage and the cathode of the thyristor is connected to the battery. Accordingly, the thyristor is turned off if and when the difference between the reference voltage and the battery voltage becomes smaller than the switching voltage of the thyristor.

Furukawa, K.; Kakumoto, H.

1983-01-25

227

Multiprocessing Optimization for Compact Stellarators  

Microsoft Academic Search

Compact quasi-omnigeneous stellarator (QOS) and quasi-axisymmetric stellarator (QAS) configurations have been developed. These are designed to align flux surfaces with surfaces of constant J (QOS), or to obtain a symmetric |B| spectrum (QAS), using a Levenberg-Marquardt (LM) optimizer.(D. A. Spong, et al., Phys. Plasmas, 5), 1752 (1998). The VMEC code is used to evaluate 3D MHD equilibria needed for stability

S. P. Hirshman; A. S. Ware; M. C. Zarnstorff; S. Ethier

1999-01-01

228

A compact rotating gravitational instanton  

Microsoft Academic Search

A compact rotating gravitational instanton (a positive-definite metric solution of the Einstein equations with Lambda term) is presented. The manifold is the nontrivial S2 fibre bundle over S2 and has chi = 4, tau = 0, but no spinor structure. The metric can be obtained from a special limit of the positive-definite analytic extension of the Kerr-de Sitter metric or

Don Page

1978-01-01

229

Shock compaction of molybdenum powder  

Microsoft Academic Search

Shock recovery experiments carried out in the 9 to 12 GPa range on 1.4 distension Mo appear adequate to compact to full density (< 45 ..mu..m) powders. However, the stress levels 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 ..mu..m particles. The

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

1983-01-01

230

Dynamic compaction of aluminum nanocrystals  

Microsoft Academic Search

We investigated shock-compaction behavior of nanocrystalline aluminum (n-Al) powder with an average particle size of about 50–70 nm. The starting powders were analyzed using various analytical tools, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The initial Al particles were found to be coated naturally by a uniform, thin (? 5

T. G. Nieh; P. Luo; W. Nellis; D. Lesuer; D. Benson

1996-01-01

231

Nuclear Physics for Compact Stars  

SciTech Connect

A brief overview is given of the different lines of research developed under the INFN project 'Compact Stellar Objects and Dense Hadronic Matter' (acronym CT51). The emphasis of the project is on the structure of Neutron Stars (NS) and related objects. Starting from crust, the different Nuclear Physics problems are described which are encountered going inside a NS down to its inner core. The theoretical challenges and the observational inputs are discussed in some detail.

Baldo, M. [INFN, Sez. Catania, Via S. Sofia 64, 95123 Catania (Italy)

2009-05-04

232

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

233

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

234

Globular Clusters in Compact Groups  

Microsoft Academic Search

We have studied globular cluster systems (GCSs) around elliptical galaxies in Hickson compact groups using multi-band deep,\\u000a high quality images from Keck, VLT and CFHT. Analyzing the luminosity functions, specific frequencies, color and spatial distributions,\\u000a we could determine the properties of the GCSs of those galaxies and trace their star formation histories. We have found poor\\u000a populations, concentrated toward the

Cristiano Da Rocha; Claudia Mendes de Oliveira; Michael Bolte; Bodo L. Ziegler; Thomas H. Puzia

235

COMPACT HIGH TEMPERATURE REACTOR (CHTR)  

Microsoft Academic Search

Summary CHTR is a mainly 233U-Thorium fuelled, lead-bismuth cooled and beryllium oxide moderated reactor. This reactor, initially being developed to generate about 100 kWTh power, will have a core life of 15 years and will have several advanced passive safety features to enable its operation as compact power pack in remote areas not connected to the electrical grid. The reactor

I. V. Dulera; A. Basak; P. P. Kelkar; R. K. Sinha

236

Compact magnetic electron energy analyzer  

Microsoft Academic Search

A compact magnetic energy analyzer designed for the measurement of electron energies in the range from 20 keV through 1.5 MeV is described. The simple device, based on the semicircular focusing principle, is constructed from a high induction permanent magnet enclosed in a soft iron case. The design and operation of the analyzer in pulsed electron beam devices are discussed.

R. F. Schneider; C. M. Luo; M. J. Rhee; J. R. Smith

1985-01-01

237

Compact noninvasive electron bunch-length monitor  

SciTech Connect

A compact RF cavity was constructed that simultaneously resonates at many harmonic modes when excited by a bunched electron beam passing through its bore. The excitation of these modes provides a Fourier description of the temporal characteristics of the bunchtrain. The cavity was used to non-invasively characterize electron bunches produced from thin and thick GaAs photocathodes inside a DC high voltage photogun illuminated with 37 ps (FWHM) laser pulses at repetition rates near 500 and 1500 MHz, at average beam current from 5 uA to 500 uA and at beam energy from 75 keV to 195 keV. The cavity bunchlength monitor could detect electron bunches as short as 57 ps (FWHM) when connected directly to a sampling oscilloscope, and could clearly distinguish bunches with varying degrees of space-charge induced growth and with different tail signatures. Efforts are underway to detect shorter bunches, by designing cavities with increased bandwidth and improved coupling uniformity. This demonstration lends credibility to the idea that these cavities could also be used for other applications, including bunching and shaping, when driven with external RF.

Brock Roberts, Matt Poelker, Russell Mammei, James McCarter

2012-12-01

238

Collective deceleration: Toward a compact beam dump  

NASA Astrophysics Data System (ADS)

With the increasing development of laser electron accelerators, electron energies beyond a GeV have been reached and higher values are expected in the near future. A conventional beam dump based on ionization or radiation loss mechanisms is cumbersome and costly, not to mention the radiological hazards. We revisit the stopping power theory of high-energy charged particles in matter and discuss the associated problem of beam dumping from the point of view of collective deceleration. The collective stopping length in an ionized gas can be several orders of magnitude shorter than that described by the Bethe-Bloch formulas and associated with multiple electromagnetic cascades in solids. At the same time, the tenuous density of the gas makes the radioactivation negligible. Such a compact beam dump without radioactivation works well for short and dense bunches, as they are typically generated from a laser wakefield accelerator. In addition, the nonuniform transverse wakefield can induce microbunching of the electron bunch by betatron oscillation. The microstructure could serve as a prebunched source for coherent radiation or feeding a free electron laser.

Wu, H.-C.; Tajima, T.; Habs, D.; Chao, A. W.; Meyer-Ter-Vehn, J.

2010-10-01

239

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

240

Compact Stellarator Path to DEMO  

NASA Astrophysics Data System (ADS)

Issues for a DEMO reactor are sustaining an ignited/high-Q plasma in steady state, avoiding disruptions and large variations in power flux to the wall, adequate confinement of thermal plasma and alpha-particles, control of a burning plasma, particle and power handling, etc. Compact stellarators have key advantages -- steady-state high-plasma-density operation without external current drive or disruptions, stability without a close conducting wall or active feedback systems, and low recirculating power -- in addition to moderate plasma aspect ratio, good confinement, and high-beta potential. The ARIES-CS study established that compact stellarators can be competitive with tokamaks as reactors. Many of the issues for a compact stellarator DEMO can be answered using results from large tokamaks, ITER D-T experiments and fusion materials, technology and component development programs, in addition to stellarators in operation, under construction or in development. However, a large next-generation stellarator will be needed to address some physics issues: size scaling and confinement at higher parameters, burning plasma issues, and operation with a strongly radiative divertor. Technology issues include simpler coils, structure, and divertor fabrication, and better cost information.

Lyon, J. F.

2007-11-01

241

Thixoforming of Stellite Powder Compacts  

NASA Astrophysics Data System (ADS)

Thixoforming involves processing metallic alloys in the semi-solid state. The process requires the microstructure to be spheroidal when part-solid and part-liquid i.e. to consist of solid spheroids surrounded by liquid. The aim of this work was to investigate whether powder compacts can be used as feedstock for thixoforming and whether the consolidating pressure in the thixoformer can be used to remove porosity from the compact. The powder compacts were made from stellite 6 and stellite 21 alloys, cobalt-based alloys widely used for e.g. manufacturing prostheses. Isothermal heat treatments of small samples in the consolidated state showed the optimum thixoforming temperature to be in the range 1340°C-1350°C for both materials. The alloys were thixoformed into graphite dies and flowed easily to fill the die. Porosity in the thixoformed components was lower than in the starting material. Hardness values at various positions along the radius of the thixoformed demonstrator component were above the specification for both alloys.

Hogg, S. C.; Atkinson, H. V.; Kapranos, P.

2007-04-01

242

Thixoforming of Stellite Powder Compacts  

SciTech Connect

Thixoforming involves processing metallic alloys in the semi-solid state. The process requires the microstructure to be spheroidal when part-solid and part-liquid i.e. to consist of solid spheroids surrounded by liquid. The aim of this work was to investigate whether powder compacts can be used as feedstock for thixoforming and whether the consolidating pressure in the thixoformer can be used to remove porosity from the compact. The powder compacts were made from stellite 6 and stellite 21 alloys, cobalt-based alloys widely used for e.g. manufacturing prostheses. Isothermal heat treatments of small samples in the consolidated state showed the optimum thixoforming temperature to be in the range 1340 deg. C-1350 deg. C for both materials. The alloys were thixoformed into graphite dies and flowed easily to fill the die. Porosity in the thixoformed components was lower than in the starting material. Hardness values at various positions along the radius of the thixoformed demonstrator component were above the specification for both alloys.

Hogg, S. C. [Institute of PolymerTechnology and Materials Engineering, Loughborough University, Loughborough, LE11 3TU (United Kingdom); Atkinson, H. V. [Department of Engineering, University of Leicester, University Rd., Leicester LE1 7RH (United Kingdom); Kapranos, P. [Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

2007-04-07

243

Label transfer by measuring compactness.  

PubMed

This paper presents a new automatic image annotation algorithm. First, we introduce a new similarity measure between images: compactness. This uses low level visual descriptors for determining the similarity between two images. Compactness shows how close test image features lie to training image feature cluster centers. The measure provides the core for a k-nearest neighbor type image annotation method. Afterward, a formalism for defining different transfer techniques is devised and several label transfer techniques are provided. The method as whole is evaluated on four image annotation benchmarks. The results on these sets validate the accuracy of the approach, which outperforms many state-of-the-art annotation methods. The method presented here requires a simple training process, efficiently combines different feature types and performs better than complex learning algorithms, even in this incipient form. The main contributions of this paper are the usage of compactness as a similarity measure that enables efficient low level feature comparison and an annotation algorithm based on label transfer. PMID:23955754

Varga, Robert; Nedevschi, Sergiu

2013-08-08

244

Advanced radioactive waste compaction techniques: Final report  

SciTech Connect

The purpose of this test program is to provide definitive information on the volume reduction capabilities of conventional compactors used in the nuclear industry for the treatment of dry active waste and the effects of preshredding on compaction. The test program presents comprehensive data on compacted densities of dry active waste collected at five facilities generating this waste and using conventional compactors. Waste materials presently classified as ''non-compactable'' which would lend themselves to preshredding and compaction are identified. An ALARA evaluation of shredding operations and an economic evaluation of preshredding prior to compaction are also presented. 32 figs., 72 tabs.

Volodzko, M.; McGrath, R.N.; Kinsman, J.F.; Palo, W.J.

1988-08-01

245

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

246

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

247

The telomere binding protein TRF2 induces chromatin compaction.  

PubMed

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. PMID:21526145

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

2011-04-19

248

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

249

The compact liquid metal reactor  

SciTech Connect

As part of the Westinghouse Low Cost Plant Study, a compact 10 MWe sodium cooled reactor design has been developed for remote sites. Thus, design emphasis was placed on modular or factory fabrication and assembly, ease of operation and maintenance, and inherent safety. The reactor is a loop concept consisting of the reactor vessel, pump, evaporator and superheater. Containment is accomplished with a 15 meter cylindrical building 22 meters high. The turbine generator will operate at 480/sup 0/C and 105 kg/cm/sup 2/, while condenser cooling temperature is maintained by a water to air heat exchanger. Overall plant efficiency is expected to be approximately 24%.

Tupper, R.B.; Gallo, F.G.; Lowrie, R.R.; Sievers, R.K.

1984-08-01

250

Shock compaction of molybdenum powder  

SciTech Connect

Shock recovery experiments carried out in the 9 to 12 GPa range on 1.4 distension Mo appear adequate to compact to full density (< 45 ..mu..m) powders. However, the stress levels 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 ..mu..m particles. The present model predicts that for powders 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 ..mu..m range.

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

1983-09-01

251

Compact inline optical electron polarimeter  

NASA Astrophysics Data System (ADS)

A compact optical electron polarimeter using a helium target is described. It offers a maximum fluorescence detection efficiency of ~20 Hz/nA, which is an order of magnitude higher than that of earlier designs. With an argon target, this device is expected to have a polarimetric figure-of-merit of 270 Hz/nA. By relying on a magnetic field to guide a longitudinally spin-polarized electron beam, the present instrument employs fewer electrodes. It also uses a commercially available integrated photon counting module. These features allow it to occupy a smaller volume and make it easier to operate.

Pirbhai, M.; Ryan, D. M.; Richards, G.; Gay, T. J.

2013-05-01

252

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

253

EFFECTS OF MOULDING WATER CONTENT AND COMPACTION METHOD ON DEFORMATON AND STRENGHT CHARACTERISTICS OF COMPACTED SOIL  

NASA Astrophysics Data System (ADS)

In this paper, the effects of moulding water content and compaction method on strength and deformation properties were evaluated by means of consolidated undrained triaxial compression test and bender element test on a silty sand. The test results showed that the specimens compacted at water content being slightly dry side of the optimum water content exhibited the lowest compressibility and the highest peak deviator stress. Effects of compaction method were manifested in that the peak deviator stress of a statically compacted specimen was hi gher than the dynamically compacted specimen. These test results were interpreted by considering the soil structure of compacted soil by bender element test.

Kawajiri, Shunzo; Kawaguchi, Takayuki; Shibuya, Satoru; Takahashi, Masakazu

254

Low noise charge pump  

NASA Astrophysics Data System (ADS)

This paper presents a new architecture of a charge pump voltage converter. The charge pump implements novel parasitic capacitances precharge control loop. Output voltage ripples are significantly reduced.

Grodzicki, Andrzej; Pleskacz, Witold A.

2013-07-01

255

A solar battery charging module by means of Limit-Cycle MPPT control  

Microsoft Academic Search

The objective of this paper is to develop a power converter module that charges a battery with solar power, and the design technique at the product level is introduced to realize a compact size and light weight. The main circuit is a buck-boost chopper so that it can cover wide range of charging voltage. The MPPT control is realized by

Mikihiko Matsui; Kanghoon Koh; Byunggyu Yu; T. Kitano

2007-01-01

256

Thermally stimulated current spectra of binder resin powders for copiers: Correction for thermal shrinkage of the sample powder compactions  

NASA Astrophysics Data System (ADS)

Thermally stimulated current (TSC) spectra observed under open- circuit condition for styrene- acrylic binder resin powder compactions for toners are corrected for their thermal shrinkage during TSC observation. For this binder resin, extrinsic current from motion of powder compactions with charges due to their thermal shrinkage was found to be much more effective than the sensitivity coefficient of a TSC measuring apparatus used. Particle size dependence of charge retention power of the resin powders was also examined by using this correction method and found that it decreased with decreasing their particle size.

Ikezakt, K.; Murata, Y.

2008-12-01

257

Compact hybrid Si microring lasers  

NASA Astrophysics Data System (ADS)

In this paper we review the recent progress in developing compact microring lasers on the hybrid silicon platform. A simplified self-aligned process is used to fabricate devices as small as 15 ?m in diameter. The optically-pumped, continuous wave (cw) devices show low threshold carrier density, comparable to the carrier density to reach material transparency. In the electrically-pumped lasers, the short cavity length leads to the minimum laser threshold less than 5 mA in cw operation. The maximum cw lasing temperature is up to 65 °C. Detailed studies in threshold as a function of coupling coefficient and bus waveguide width are presented. Surface recombination at the dry-etched exposed interface is investigated qualitatively by studying the current-voltage characteristics. Ring resonator-based figures of merits including good spectral purity and large side-mode suppression ratio are demonstrated. Thermal impedance data is extracted from temperature-dependent spectral measurement, and buried oxide layer in silicon-on-insulator wafer is identified as the major thermal barrier to cause high thermal impedance for small-size devices. The demonstrated compact hybrid ring lasers have low power consumption, small footprint and dynamic performance. They are promising for Si-based optical interconnects and flip-flop applications.

Liang, Di; Bowers, John E.; Fiorentino, Marco; Beausoleil, Raymond G.

2010-02-01

258

Polycrystalline diamond compact bit hydraulics  

SciTech Connect

It is well understood and documented that bottomhole hydraulics plays an important role in conventional diamond bit performance. Recent industry experience has shown a similar importance with the new synthetic diamond compact bits. Certain types of polycrystalline diamond compact bits have cutters arranged in a reverse spiral mode. For optimum performance bit hydraulic design should be tailored to that reverse spiral mode. Theory reveals that a bit built with rectangular nozzles with a long axis in the tangential direction can give a fluid velocity envelope similar to the envelope of the reverse spiral. A rectangle can also reduce bit plugging by providing an increased perimeter in a non-concentric geometry. The introduction of rectangular nozzles into the bit renders the regular round nozzle pressure drop equation unsuitable for direct application. Extensive hydraulic tests were performed with different configurations of rectangular nozzles to establish more accurate pressure loss equations. The experiments included single nozzle studies and laboratory and field tests of bits. Field test results confirmed the reliability of the results obtained in the laboratory studies.

Knowlton, R.H.; Huang, H.; Iversen, B.

1982-09-01

259

High flux compact neutron generators  

SciTech Connect

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 the first tube design, the ion beam is formed using a multiple hole accelerator column. The beam is accelerated to energy of 80 keV by means of a three-electrode extraction system. The ion beam then impinges on a titanium target where either the 2.4 MeV D-D or 14 MeV D-T neutrons are generated. The MCNP computation code has predicted a neutron flux of {approximately}10{sup 11} n/s for the D-D reaction at beam intensity of 1.5 A at 150 kV. The neutron flux measurements of this tube design will be presented. Recently new compact high flux tubes are being developed which can be used for various applications. These tubes also utilize RF-discharge for plasma generation. The design of these tubes and the first measurements will be discussed in this presentation.

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

2001-06-15

260

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

261

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

262

Performance of compact hydrogen masers  

SciTech Connect

Compact hydrogen masers have been built and are under continuing development at several organizations. JPL maintains a special facility which is dedicated to testing, evaluating, improving and maintaining state of the art frequency standards. This paper presents the results of a series of tests that were performed at this facility on two different types of compact hydrogen masers. One of these masers is a prototype unit developed by Hughes Research Laboratories, Malibu, CA for the United States Naval Research Laboratory. This maser uses Q-enhancement to achieve cavity oscillation and is equipped with a cavity tuning servo system. The other is a prototype passive hydrogen maser also equipped with a cavity tuning servo system. The other is a prototype passive hydrogen maser also equipped with a cavity tuning servo system and was developed by the National Bureau of Standards, Boulder, CO. The data presented includes output frequency versus certain environmental parameters, Allan variance and drift. The work on the Hughes Research maser was sponsored by the United States Naval Research Laboratory (NRL). The NBS passive maser development was sponsored by the National Aeronautics and Space Administration (NASA) and NRL.

Kirk, A.

1983-01-01

263

Elitism-based compact genetic algorithms  

Microsoft Academic Search

This paper describes two elitism-based compact genetic algorithms (cGAs)-persistent elitist compact genetic algorithm (pe-cGA), and nonpersistent elitist compact genetic algorithm (ne-cGA). The aim is to design efficient cGAs by treating them as estimation of distribution algorithms (EDAs) for solving difficult optimization problems without compromising on memory and computation costs. The idea is to deal with issues connected with lack of

Chang Wook Ahn; Rudrapatna S. Ramakrishna

2003-01-01

264

Compact approach to fusion power reactors  

SciTech Connect

The potential of the Reversed-Field Pinch (RFP) for development into an efficient, compact, copper-coil fusion reactor has been quantified by comprehensive parametric tradeoff studies. These compact systems promise to be competitive in size, power density, and cost to alternative energy sources. Conceptual engineering designs that largely substantiate these promising results have since been completed. This 1000-MWe(net) design is described along with a detailed rationale and physics/technology assessment for the compact approach to fusion.

Hagenson, R.L.; Krakowski, R.A.; Bathke, C.G.; Miller, R.L.

1984-01-01

265

Soil Compaction in Conservation Tillage: Crop Impacts  

Microsoft Academic Search

Soil compaction effects on maize (Zea mays L.) plant population, height, and yield were studied from 2002-2005 in a no-tillage\\/in-row tillage study on a Hublersburg silt loam soil (Typic Hapludult) in Pennsylvania.Soilwascompactedannuallywithathree-axletruckwith 10-Mgaxleloadmountedwithroadtires(700kPainflationpressure)or flotationtires (250kPa).Inanothertreatment, soilwasonlycompacted with road tires in the first year without subsequent compaction. Re- mediation treatments were deep (40 cm) in-row tillage before or after compaction with

Dilraj Sidhu; Sjoerd W. Duiker

2006-01-01

266

Compact Solid State Cooling Systems: Compact MEMS Electrocaloric Module  

SciTech Connect

BEETIT Project: UCLA is developing a novel solid-state cooling technology to translate a recent scientific discovery of the so-called giant electrocaloric effect into commercially viable compact cooling systems. Traditional air conditioners use noisy, vapor compression systems that include a polluting liquid refrigerant to circulate within the air conditioner, absorb heat, and pump the heat out into the environment. Electrocaloric materials achieve the same result by heating up when placed within an electric field and cooling down when removed—effectively pumping heat out from a cooler to warmer environment. This electrocaloric-based solid state cooling system is quiet and does not use liquid refrigerants. The innovation includes developing nano-structured materials and reliable interfaces for heat exchange. With these innovations and advances in micro/nano-scale manufacturing technologies pioneered by semiconductor companies, UCLA is aiming to extend the performance/reliability of the cooling module.

None

2010-10-01

267

78 FR 61384 - Meeting of the Compact Council for the National Crime Prevention and Privacy Compact  

Federal Register 2010, 2011, 2012, 2013

...notify the Federal Bureau of Investigation (FBI) Compact Officer, Mr. Gary S. Barron...may be addressed to Mr. Gary S. Barron, FBI Compact Officer, Module D3, 1000 Custer...September 25, 2013. Gary S. Barron, FBI Compact Officer, Criminal Justice...

2013-10-03

268

The regular-locally compact coreflection of a stably locally compact locale  

Microsoft Academic Search

The Scott continuous nuclei form a subframe of the frame of all nuclei. We refer to this subframe as the patch frame. We show that the patch construction exhibits (i) the category of regular locally compact locales and perfect maps as a coreflective subcategory of the category of stably locally compact locales and perfect maps, (ii) the category of compact

Mart??n Hötzel Escardó

2001-01-01

269

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

270

Charge handling capacity in charge coupled devices  

Microsoft Academic Search

In analog signal processing applications, the charge handling capacity of a charge coupled device (CCD) is an important parameter that determines the dynamic range. In this paper, approximate expressions for the signal handling capacity for surface-channel and buried-channel CCD's are derived and compared. The upper limit for the buried-channel charge capacity is imposed by the onset of surface electron accumulation.

J. S. T. Huang

1977-01-01

271

Charge and Carry  

NSDL National Science Digital Library

In this activity about electricity, learners produce a spark that they can feel, see, and hear. Learners rub a Styrofoam plate with wool to give it an electric charge. Then, they use the charged Styrofoam to charge an aluminum pie pan. Essentially, learners build an electrophorus (Greek for "charge carrier"). This resource also contains instructions on how to build a large charge carrier called a "Leyden Jar" using a plastic film can.

Exploratorium, The

2012-06-26

272

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

273

Gravitational waves from compact objects  

NASA Astrophysics Data System (ADS)

Large ground-based laser beam interferometers are presently in operation both in the USA (LIGO) and in Europe (VIRGO) and potential sources that might be detected by these instruments are revisited. The present generation of detectors does not have a sensitivity high enough to probe a significant volume of the universe and, consequently, predicted event rates are very low. The planned advanced generation of interferometers will probably be able to detect, for the first time, a gravitational signal. Advanced LIGO and EGO instruments are expected to detect few (some): binary coalescences consisting of either two neutron stars, two black holes or a neutron star and a black hole. In space, the sensitivity of the planned LISA spacecraft constellation will allow the detection of the gravitational signals, even within a “pessimistic" range of possible signals, produced during the capture of compact objects by supermassive black holes, at a rate of a few tens per year.

de Freitas Pacheco, José Antonio

2010-11-01

274

Magnetohydodynamics stability of compact stellarators  

SciTech Connect

Recent stability results of external kink modes and vertical modes in compact stellarators are presented. The vertical mode is found to be stabilized by externally generated poloidal flux. A simple stability criterion is derived in the limit of large aspect ratio and constant current density. For a wall at infinite distance from the plasma, the amount of external flux needed for stabilization is given by Fi = (k2 {minus} k)=(k2 + 1), where k is the axisymmetric elongation and Fi is the fraction of the external rotational transform. A systematic parameter study shows that the external kink mode in QAS can be stabilized at high beta ({approximately} 5%) without a conducting wall by magnetic shear via 3D shaping. It is found that external kinks are driven by both parallel current and pressure gradient. The pressure contributes significantly to the overall drive through the curvature term and the Pfirsch-Schluter current.

Fu, G.Y.; Ku, L.P.; Cooper, W.A.; Hirshman, S.H. [and others

2000-01-03

275

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

276

Compact Triaxial Accelerometer Systems (CTAS)  

NASA Astrophysics Data System (ADS)

As the opportunities for microgravity experiment on drop towers, aircraft and spacecraft such as the Space Shuttle have increased, it has become profitable to develop systems able to detect acceleration precisely. The compact triaxial accelerometer system (CTAS) developed to do this has 12-bit precision and 10-micro-G resolution. It weighs 4 kg, and is small and light enough to fit in a floating rack with other instruments. Its low, 15-W, power consumption enables it to be powered by batteries, which also back up its nonvolatile semiconductor memory, used in data recording. Memory is housed in a cassette that can be replaced during operation. Raw analogue data is converted to digital and recorded in the cassette, to be processed afterward on the ground. Using the CTAS, accelerations on a parabolic flight aircraft and a roller coaster.

Matsumoto, Naoyuki; Takayanagi, Masahiro; Takei, Fumio; Kawase, Naoto; Zaiki, Yutaka; Kitamura, Shin-Ichi; Tanaka, Masafumi

277

A compact molecular beam machine  

SciTech Connect

We have developed a compact, low cost, modular, crossed molecular beam machine. The new apparatus utilizes several technological advancements in molecular beams valves, ion detection, and vacuum pumping to reduce the size, cost, and complexity of a molecular beam apparatus. We apply these simplifications to construct a linear molecular beam machine as well as a crossed-atomic and molecular beam machine. The new apparatus measures almost 50 cm in length, with a total laboratory footprint less than 0.25 m{sup 2} for the crossed-atomic and molecular beam machine. We demonstrate the performance of the apparatus by measuring the rotational temperature of nitric oxide from three common molecular beam valves and by observing collisional energy transfer in nitric oxide from a collision with argon.

Jansen, Paul [Vrije Universiteit, 1081 HV Amsterdam (Netherlands); Chandler, David W.; Strecker, Kevin E. [Sandia National Laboratories, Livermore, California 94551 (United States)

2009-08-15

278

Compact Sources of Ultrashort Pulses  

NASA Astrophysics Data System (ADS)

List of contributors; Acronyms and abbreviations; Preface; 1. Short pulse generation H. A. Haus; 2. Passive modelocking in solid state lasers Thomas Brabec, Stephen M. J. Kelly and Ferenc Krausz; 3. Compact modelocked solid state lasers pumped by laser diodes John R. M. Barr; 4. Modelocking of all-fiber lasers Irl N. Duling, III and Michael L. Dennis; 5. Nonlinear polarization evolution in passively modelocked fiber lasers Martin E. Fermann; 6. Ultrafast vertical cavity semiconductor lasers Wenbin Jiang and John Bowers; 7. High power ultrafast semiconductor for injection diode lasers Peter J. Delfyett; 8. The hybrid soliton pulse source Paul A. Morton; 9. Monolithic colliding pulse modelocked diode lasers Ming C. Wu and Young-Kai Chen; Index.

Duling, Irl N., III

1995-10-01

279

Compact Sources of Ultrashort Pulses  

NASA Astrophysics Data System (ADS)

List of contributors; Acronyms and abbreviations; Preface; 1. Short pulse generation H. A. Haus; 2. Passive modelocking in solid state lasers Thomas Brabec, Stephen M. J. Kelly and Ferenc Krausz; 3. Compact modelocked solid state lasers pumped by laser diodes John R. M. Barr; 4. Modelocking of all-fiber lasers Irl N. Duling, III and Michael L. Dennis; 5. Nonlinear polarization evolution in passively modelocked fiber lasers Martin E. Fermann; 6. Ultrafast vertical cavity semiconductor lasers Wenbin Jiang and John Bowers; 7. High power ultrafast semiconductor for injection diode lasers Peter J. Delfyett; 8. The hybrid soliton pulse source Paul A. Morton; 9. Monolithic colliding pulse modelocked diode lasers Ming C. Wu and Young-Kai Chen; Index.

Duling, Irl N., III

2006-11-01

280

Compact quantum cascade laser transmitter  

NASA Astrophysics Data System (ADS)

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 spectroscopy applications, where the 3 to 5 ?m and 8 to 12 ?m 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., Jr.; Hatchell, Brian K.; Gervais, Kevin L.; Wojcik, Michael D.; Krishnaswami, Kannan; Bernacki, Bruce E.

2009-05-01

281

General Relativity&Compact Stars  

SciTech Connect

Compact stars--broadly grouped as neutron stars and white dwarfs--are the ashes of luminous stars. One or the other is the fate that awaits the cores of most stars after a lifetime of tens to thousands of millions of years. Whichever of these objects is formed at the end of the life of a particular luminous star, the compact object will live in many respects unchanged from the state in which it was formed. Neutron stars themselves can take several forms--hyperon, hybrid, or strange quark star. Likewise white dwarfs take different forms though only in the dominant nuclear species. A black hole is probably the fate of the most massive stars, an inaccessible region of spacetime into which the entire star, ashes and all, falls at the end of the luminous phase. Neutron stars are the smallest, densest stars known. Like all stars, neutron stars rotate--some as many as a few hundred times a second. A star rotating at such a rate will experience an enormous centrifugal force that must be balanced by gravity or else it will be ripped apart. The balance of the two forces informs us of the lower limit on the stellar density. Neutron stars are 10{sup 14} times denser than Earth. Some neutron stars are in binary orbit with a companion. Application of orbital mechanics allows an assessment of masses in some cases. The mass of a neutron star is typically 1.5 solar masses. They can therefore infer their radii: about ten kilometers. Into such a small object, the entire mass of our sun and more, is compressed.

Glendenning, Norman K.

2005-08-16

282

Physics of Compact Advanced Stellarators  

SciTech Connect

Compact optimized stellarators offer novel solutions for confining high-beta plasmas and developing magnetic confinement fusion. The 3-D plasma shape can be designed to enhance the MHD stability without feedback or nearby conducting structures and provide drift-orbit confinement similar to tokamaks. These configurations offer the possibility of combining the steady-state low-recirculating power, external control, and disruption resilience of previous stellarators with the low-aspect ratio, high beta-limit, and good confinement of advanced tokamaks. Quasi-axisymmetric equilibria have been developed for the proposed National Compact Stellarator Experiment (NCSX) with average aspect ratio 4-4.4 and average elongation of approximately 1.8. Even with bootstrap-current consistent profiles, they are passively stable to the ballooning, kink, vertical, Mercier, and neoclassical-tearing modes for beta > 4%, without the need for external feedback or conducting walls. The bootstrap current generates only 1/4 of the magnetic rotational transform at beta = 4% (the rest is from the coils), thus the equilibrium is much less nonlinear and is more controllable than similar advanced tokamaks. The enhanced stability is a result of ''reversed'' global shear, the spatial distribution of local shear, and the large fraction of externally generated transform. Transport simulations show adequate fast-ion confinement and thermal neoclassical transport similar to equivalent tokamaks. Modular coils have been designed which reproduce the physics properties, provide good flux surfaces, and allow flexible variation of the plasma shape to control the predicted MHD stability and transport properties.

M.C. Zarnstorff; L.A. Berry; A. Brooks; E. Fredrickson; G.-Y. Fu; S. Hirshman; S. Hudson; L.-P. Ku; E. Lazarus; D. Mikkelsen; D. Monticello; G.H. Neilson; N. Pomphrey; A. Reiman; D. Spong; D. Strickler; A. Boozer; W.A. Cooper; R. Goldston; R. Hatcher; M. Isaev; C. Kessel; J. Lewandowski; J. Lyon; P. Merkel; H. Mynick; B.E. Nelson; C. Nuehrenberg; M. Redi; W. Reiersen; P. Rutherford; R. Sanchez; J. Schmidt; R.B. White

2001-08-14

283

New trends in lighting: compact lamps  

SciTech Connect

New trends in lighting systems are discussed. Compact fluorescent and metal halide lamps provide greater energy efficiency and better color renderings than their predecessors. An operating cost comparison is given for a 40W incandescent lamp and the new 7W compact fluorescent lamp.

Steffy, G.

1984-11-01

284

Explosive compaction of amorphous ferromagnetic metal powders  

Microsoft Academic Search

The magnetic properties of certain amorphous metals might be better exploited by the electrical industry if these metals, currently available as ribbon, could be consolidated into high density, principally amorphous, bulk shapes. This work attempted to produce such bodies using explosive compaction techniques. Toroidal specimens were successfully produced using a cylindrical explosive compaction technique. The key to this technique was

R. D. Caligiuri; D. R. Curran; P. S. DeCarli

2009-01-01

285

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

286

Compact antenna range at 36 GHz  

Microsoft Academic Search

The feasibility of operating a compact antenna test range at 35 GHz has been demonstrated. A compact range of simple construction has been shown to have a performance only slightly inferior to the performance at X-band. Diffracted rays from the edges of the source reflector can degrade the purity of the electric field. This has been investigated and successfully controlled

A. D. Olver; G. Tong

1977-01-01

287

The practical performance of compact antenna ranges  

Microsoft Academic Search

The principles of compact antenna test ranges are presented. The main factors which determine the performance are considered. These include diffraction from the reflector edge, reflector surface accuracy, the feed radiation pattern, and the focal length of the reflector. Practical performance was investigated with a compact range constructed using a three meter diameter paraboloidal reflector. The diffraction off the edge

A. D. Olver

1977-01-01

288

Evaluation of compaction rates for decompaction processes  

Microsoft Academic Search

Burial of sediment leads to mechanical compaction with diminution of both porosity and initial thickness. The compaction rate, tau = hâ\\/h, may be either directly measured in the sediment or estimated from variation of porosity. Examples of direct measures are given for different facies on the basis of: textural variations (density of grains, fossil debris, burrows, etc); deformation of fossils

B. Beaudoin; I. Cojan; G. Fries; B. Pinoteau

1987-01-01

289

Compact, Solid-State Femtosecond Source.  

National Technical Information Service (NTIS)

The goal of this program was to demonstrate that femtosecond laser sources (1 femtosecond = 10(sup -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 ...

P. Bado

1993-01-01

290

Energy release model of compaction band propagation  

Microsoft Academic Search

The elastic strain energy released per unit advance of a compaction band in an infinite layer of thickness h is used to identify and assess quantities relevant to propagation of isolated compaction bands observed in outcrop. If the elastic moduli of the band and the surrounding host material are similar and the band is much thinner than the layer, the

J. W. Rudnicki; K. R. Sternlof

2005-01-01

291

ISM Evolution in Compact Groups of Galaxies  

Microsoft Academic Search

Compact groups of galaxies provide unique environment to study the evolution of the ISM and mechanisms by which star formation occurs amid continuous gravitational encounters. We present Spitzer, 2MASS, and HI observations of a sample of 12 Hickson Compact Groups (HCGs) that include a total of 45 galaxies. The galaxies in this sample have observed infrared characteristics that are distinctly

Kelsey Johnson; J. Hibbard; S. Gallagher; J. Charlton; A. Hornschemeier; T. Jarrett; A. Reines

2007-01-01

292

Development of compact multipurpose ultrasonic technological device  

Microsoft Academic Search

In this work is described the potential range of applications of ultrasonic technologies in conditions of small-scale enterprises and the problems which limit such applications caused by the absence of low-cost compact multipurpose ultrasonic technological devices. The problems arising during compact ultrasonic device development are considered, and possible solutions given. The engineering solutions applied during the design of an oscillation

Vladimir N. Khmelev; Igor I. Savin; Roman V. Barsukov; Alexey N. Slivin; Sergey N. Tsyganok; Eugene V. Chipurin

2003-01-01

293

Magnetoelectric charge trap memory.  

PubMed

It is demonstrated that a charge-trapping layer placed in proximity to a ferromagnetic metal enables efficient electrical and optical control of the metal's magnetic properties. Retention of charge trapped inside the charge-trapping layer provides nonvolatility to the magnetoelectric effect and enhances its efficiency by an order of magnitude. As such, an engineered charge-trapping layer can be used to realize the magnetoelectric equivalent to today's pervasive charge trap flash memory technology. Moreover, by supplying trapped charges optically instead of electrically, a focused laser beam can be used to imprint the magnetic state into a continuous metal film. PMID:22300444

Bauer, Uwe; Przybylski, Marek; Kirschner, Jürgen; Beach, Geoffrey S D

2012-02-08

294

A compact high power pulsed modulator based on spiral Blumlein line  

NASA Astrophysics Data System (ADS)

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.

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

2007-10-01

295

MHD Stability in Compact Stellarators  

NASA Astrophysics Data System (ADS)

A key issue for current carrying compact stellarators(S.P. Hirshman et al., "Physics of compact stellarators", Phys. Plasmas 6, 1858 (1999).) is the stability of ideal MHD modes. We present recent stability results of external kink modes, ballooning mode, and vertical modes in Quasi-axisymmetric Stellarators (QAS)( A. Reiman et al, "Physics issue in the design of a high beta Quasi-Axisymmetric Stellarator" the 17th IAEA Fusion Energy conference, (Yokohama, Japan, October 1998), Paper ICP/06.) as well as Quasi-Omnigeneous Stellarators (QOS)^2. The 3D stability code Terpsichore(W. A. Cooper et al., Phys. Plasmas 3, 275 (1996)) is used in this study. The vertical stability in a current carrying stellarator is studied for the first time. The vertical mode is found to be stabilized by externally generated poloidal flux(G.Y. Fu et al., "Stability of vertical mode in a current carrying stellarator"., to be submitted). Physically, this is because the external poloidal flux enhances the field line bending energy relative to the current drive term in the MHD energy principle, ? W. A simple stability criteria is derived in the limit of large aspect ratio and constant current density. For wall at infinite distance from the plasma, the amount of external flux needed for stabilization is given by f=(?^2-?)/(?^2+1) where ? is the axisymmetric elongation and f is the fraction of the external rotational transform at the plasma edge. A systematic parameter study shows that the external kink in QAS can be stabilized at high beta ( ~ 5%) without a conducting wall by combination of edge magnetic shear and 3D shaping(G. Y. Fu et al., "MHD stability calculations of high-beta Quasi-Axisymmetric Stellarators", the 17th IAEA Fusion Energy conference, (Yokohama, Japan, October 1998), paper THP1/07.). The optimal shaping is obtained by using an optimizer with kink stability included in its objective function. The physics mechanism for the kink modes is studied by examining relative contributions of individual terms in ? W. It is found the external kinks are mainly driven by the parallel current. The pressure contributes significantly to the overall drive through the curvature term and the Pfirsch-Schluter current. These results demonstrate potential of QAS and QOS for disruption-free operations at high-beta without a close-fitting conducting wall and feedback stabilization.

Fu, Guoyong

1999-11-01

296

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

297

Compacting Plastic-Bonded Explosive Molding Powders to Dense Solids  

SciTech Connect

Dense solid high explosives are made by compacting plastic-bonded explosive molding powders with high pressures and temperatures for extended periods of time. The density is influenced by manufacturing processes of the powders, compaction temperature, the magnitude of compaction pressure, pressure duration, and number of repeated applications of pressure. The internal density variation of compacted explosives depends on method of compaction and the material being compacted.

B. Olinger

2005-04-15

298

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; Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States). Dept. of Civil Engineering; Boutwell, G.P. [Soil Testing Engineers, Inc., Baton Rouge, LA (United States)

1999-05-01

299

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

300

Focusing of He + beams using a compact electrostatic quadrupole lens system  

Microsoft Academic Search

A compact electrostatic quadrupole lens system has been developed, and experiments have been conducted to study transport and focusing of intense He+ beams with ?=v\\/c=0.0029 and generalized perveance (Theory and Design of Charged Particle Beams, Wiley, New York, 1994) K=0.0013. Such beams are transported without any loss of beam particles and focused at a distance of about 0.6m from the

S. K. Guharay; M. Nishiura; M. Sasao; M. Hamabe; M. Wada; T. Kuroda

2003-01-01

301

Fast Compaction of ?-Lactalbumin During Folding Studied by Stopped-flow X-ray Scattering  

Microsoft Academic Search

To monitor the fast compaction process during protein folding, we have used a stopped-flow small-angle X-ray scattering technique combined with a two-dimensional charge-coupled device-based X-ray detector that makes it possible to improve the signal-to-noise ratio of data dramatically, and measured the kinetic refolding reaction of ?-lactalbumin. The results clearly show that the radius of gyration and the overall shape of

Munehito Arai; Kazuki Ito; Tomonao Inobe; Masaharu Nakao; Kosuke Maki; Kiyoto Kamagata; Hiroshi Kihara; Yoshiyuki Amemiya; Kunihiro Kuwajima

2002-01-01

302

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

Microsoft Academic Search

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

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

2007-01-01

303

Fourth-order alternating direction implicit compact finite difference schemes for two-dimensional Schrödinger equations  

Microsoft Academic Search

In this paper, alternating direction implicit compact finite difference schemes are devised for the numerical solution of two-dimensional Schrödinger equations. The convergence rates of the present schemes are of order O(h4+?2). Numerical experiments show that these schemes preserve the conservation laws of charge and energy and achieve the expected convergence rates. Representative simulations show that the proposed schemes are applicable

Zhen Gao; Shusen Xie

2011-01-01

304

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

305

An improved compact model of cross-shaped horizontal CMOS-integrated Hall-effect sensor  

Microsoft Academic Search

A new compact model of a cross-shaped horizontal integrated Hall-effect sensor is presented in this paper. Compared to existing models, the model reliability is improved, especially for designs in which the bias and the measurement circuits are not independent. The Hall device model uses six subcomponents, each modeling the non-linear resistance due to the sensor space charge region modulation and

Morgan MADEC; Jean-Baptiste KAMMERER; Luc HEBRARD

2010-01-01

306

A compact race-track microtron as a free electron laser source  

Microsoft Academic Search

We investigate a compact, pulsed racetrack microtron as an energy amplifier and bunch compressor to produce bunch charges of ?100 pC in beams with a peak current of ?30 A or more having longitudinal emittance of 50 keV×deg and transverse emittance of 5–15? mm×mrad with energies from 5 to 35 MeV selectable in 2.5 MeV steps.

A. A. Alimov; O. V. Chubarov; E. A. Knapp; V. I. Shvedunov; W. P. Trower

1998-01-01

307

Compact pulsed gas transport laser  

SciTech Connect

A physically compact gas transport laser operable at high pulse rates (Greater than 1 khz) in a high vacuum (Greater than 10-5 torr) is achieved by flowing the active gas at high velocity (Greater than 50 m/sec) between two discharge electrodes in a hermetically sealed housing containing squirrel cage type blowers , a heat exchanger and the laser electrodes. A pulse forming network and blower motors are mounted externally of the housing as is the optical resonator assembly. A central partition divides the housing interior into upper and lower gas flow channels. The blowers are located in the lower channel at the housing end downstream from the electrodes and are rotatable in a plane parallel to the plane of the partition. The heat exchanger is located at the opposite end of the housing and both cools and stabalizes the flow of the circulating gas. The housing is a unitary structure having openings for installation of the blowers , heat exchanger and optical windows, which openings are closed by removable metal-to-metal sealing flanges for permitting access to the housing interior without compromising high vacuum integrity of the system.

Clark, D.J.; Fahlen, T.S.

1981-01-13

308

Color Superconductivity in Compact Stars  

NASA Astrophysics Data System (ADS)

After a brief review of the phenomena expected in cold dense quark matter, color superconductivity and color-flavor locking, we sketch some implications of recent developments in our understanding of cold dense quark matter for the physics of compact stars. We give a more detailed summary of our recent work on crystalline color superconductivity and the consequent realization that (some) pulsar glitches may originate in quark matter.We acknowledge helpful discussions with P. Bedaque, J. Berges, D. Blaschke, I. Bombaci, G. Carter, D. Chakrabarty, J. Madsen, C. Nayak, M. Prakash, D. Psaltis, S. Reddy, M. Ruderman, S.-J. Rey, T. Schäfer, A. Sedrakian, E. Shuryak, E. Shuster, D. Son, M. Stephanov, I. Wasserman, F. Weber and F. Wilczek. KR thanks the organizers of the ECT Workshop on Neutron Star Interiors for providing a stimulating environment within which many of the helpful discussions acknowledged above took place. This work is supported in part by the DOE under cooperative research agreement #DF-FC02-94ER40818. The work of JB was supported in part by an NDSEG Fellowship; that of KR was supported in part by a DOE OJI Award and by the A. P. Sloan Foundation.

Alford, Mark; Bowers, Jeffrey A.; Rajagopal, Krishna

309

A compact tritium AMS system  

SciTech Connect

Tritium ({sup 3}H) is a radioisotope that is extensively utilized in biological and environmental research. For biological research, {sup 3}H is generally quantified by liquid scintillation counting requiring gram-sized samples and counting times of several hours. For environmental research, {sup 3}H is usually quantified by {sup 3}He 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 {sup 3}H 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 in the biological and environmental research community. However in order to make the {sup 3}H 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 {sup 3}H AMS system has been designed and built based on a LLNL ion source/sample changer and an AccSys Technology, Inc. Radio Frequency Quadrupole (RFQ) linac. With the prototype system, {sup 3}/{sup 1}H ratios ranging from 1 x 10{sup -10} to 1 x 10{sup -13} have to 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 x 10{sup -15}.

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

1999-09-23

310

Fractional charge in perspective  

SciTech Connect

The concept of fractional charge has been recognized and developed in the past fifteen years. Under suitable circumstances an isolated object may display an eigenvalue of charge which is a fraction of the value carried by any elementary' excitation of the system. This phenomenon may be understood as due to vacuum polarization generated by couplings of the isolated object to elementary currents. One might expect that solitons or defects almost invariably would exhibit fractional charge, but this turns out to be the exception rather than the rule in 3+1 dimensions, both for quantum field theory and condensed matter systems. It is suggested that fractional charges are uncommon because some surprisingly weak general conditions are sufficient to assure integer charges. Thus the introduction of fractional charge has been far indeed from an opening of Pandora's box. Examples are reviewed where past proposals of fractional charge appear tenuous, or refer to an unconventional definition of charge.

Goldhaber, A.S. (Institute for Theoretical Physics, State University of New York, Stony Brook, New York 11794-3840 (United States))

1992-02-05

311

Compact laser radar and three-dimensional camera.  

PubMed

A novel three-dimensional (3D) camera is capable of providing high-precision 3D images in real time. The camera uses a diode laser to illuminate the scene, a shuttered solid-state charge-coupled device (CCD) sensor, and a simple phase detection technique based on the sensor shutter. The amplitude of the reflected signal carries the luminance information, while the phase of the signal carries range information. The system output is coded as a video signal. This camera offers significant advantages over existing technology. The precision in range is dependent only on phase shift and laser power and theoretically is far superior to existing time-of-flight laser radar systems. Other advantages are reduced size and simplicity and compact and inexpensive construction. We built a prototype that produced high-resolution images in range the (z) and x-y. PMID:16604759

Medina, Antonio; Gayá, Francisco; del Pozo, Francisco

2006-04-01

312

Compact laser radar and three-dimensional camera  

NASA Astrophysics Data System (ADS)

A novel three-dimensional (3D) camera is capable of providing high-precision 3D images in real time. The camera uses a diode laser to illuminate the scene, a shuttered solid-state charge-coupled device (CCD) sensor, and a simple phase detection technique based on the sensor shutter. The amplitude of the reflected signal carries the luminance information, while the phase of the signal carries range information. The system output is coded as a video signal. This camera offers significant advantages over existing technology. The precision in range is dependent only on phase shift and laser power and theoretically is far superior to existing time-of-flight laser radar systems. Other advantages are reduced size and simplicity and compact and inexpensive construction. We built a prototype that produced high-resolution images in range the (z) and x-y.

Medina, Antonio; Gayá, Francisco; Del Pozo, Francisco

2006-04-01

313

A Compact High-Voltage Pulse Generator for Plasma Applications  

NASA Astrophysics Data System (ADS)

The design and construction of a compact high-voltage pulse generator for providing input electron beam power for the LAP/INPE 32 GHz gyrotron and for treatment of metal and polymer materials by plasma immersion ion implantation (PIII) are described. The generator was built on a circuit category of Pulse Forming Network (PFN), consisting of nine LC sections with L = 270 muH and C = 2.5 nF. The instrument was designed to produce a flat 30 kV, several Amps pulse in 15 mus pulse length with pulse repetition frequency (PRF) of 8 to 100 Hz. By means of a resonant charging inductance it is possible to gain an output voltage with a factor of 1.8 higher than the voltage supplied by the pulse generator. The generator is fed with sine-wave, constant current source, and a 60 kV, 15 mA switching power supply.

Spassov, V. A.; Barroso, J.; Ueda, M.; Guerguiev, L.

314

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

315

Electret Charge Technique.  

National Technical Information Service (NTIS)

A dielectric tape of FEP (polyfluoroethylenepropylene) Teflon is electrostatically charged to a high level charge density using a motor driven capstan on which the tape is moved at a controlled velocity past a sponge assembly charged by a high DC voltage....

M. G. Garbett

1978-01-01

316

Charge exchange system  

DOEpatents

An improved charge exchange system for substantially reducing pumping requirements of excess gas in a controlled thermonuclear reactor high energy neutral beam injector. The charge exchange system utilizes a jet-type blanket which acts simultaneously as the charge exchange medium and as a shield for reflecting excess gas.

Anderson, Oscar A. (Berkeley, CA)

1978-01-01

317

A Compact Pulser for Magnetically Driven Isentropic-Compression Experiments  

NASA Astrophysics Data System (ADS)

The use of magnetic fields to isentropically compress materials for equation-of-state studies has been demonstrated on Sandia National Laboratories' Z machine. Sharing similarities with the GEPI pulser at the Centre de Etudes de Gramat in France, a compact pulser has been designed and built specifically for isentropic compression experiments. In order to be compact and low cost, the design uses a solid dielectric transmission line to couple current from eight low-inductance Haefely capacitors that are switched with ultra-low-inductance multi-channel gas switches. A peaking stage made of 72 General Atomics capacitors enhanced by a low-inductance, multi-channel peaking switch brings the fundamental rise time of the pulser down to 350 ns (10-90%). A varaible inductance in parallel with the peaking switch as well as using various gases in the switch allow us to control the details of the current wave shape. The pulser delivers a peak current of 4 MA at a charge voltage of 80 kV into a short circuit. The rise time can be lengthened to greater than 650 ns to deliver a current of 4.2 MA. The performance of this pulser will be described along with potential design changes that would provide decreases in current rise time and increases in current delivered to real world loads.

Spielman, R. B.; Bavay, M.; Mervini, J. A.; Avrillaud, G.

2007-06-01

318

Electrostatic Origin of Salt-Induced Nucleosome Array Compaction  

PubMed Central

The physical mechanism of the folding and unfolding of chromatin is fundamentally related to transcription but is incompletely characterized and not fully understood. We experimentally and theoretically studied chromatin compaction by investigating the salt-mediated folding of an array made of 12 positioning nucleosomes with 177 bp repeat length. Sedimentation velocity measurements were performed to monitor the folding provoked by addition of cations Na+, K+, Mg2+, Ca2+, spermidine3+, Co(NH3)63+, and spermine4+. We found typical polyelectrolyte behavior, with the critical concentration of cation needed to bring about maximal folding covering a range of almost five orders of magnitude (from 2 ?M for spermine4+ to 100 mM for Na+). A coarse-grained model of the nucleosome array based on a continuum dielectric description and including the explicit presence of mobile ions and charged flexible histone tails was used in computer simulations to investigate the cation-mediated compaction. The results of the simulations with explicit ions are in general agreement with the experimental data, whereas simple Debye-Hückel models are intrinsically incapable of describing chromatin array folding by multivalent cations. We conclude that the theoretical description of the salt-induced chromatin folding must incorporate explicit mobile ions that include ion correlation and ion competition effects.

Korolev, Nikolay; Allahverdi, Abdollah; Yang, Ye; Fan, Yanping; Lyubartsev, Alexander P.; Nordenskiold, Lars

2010-01-01

319

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

320

Charge regulation circuit  

SciTech Connect

This patent describes a charge regulation circuit. It comprises: an unregulated power supply having a first unregulated voltage value during a first charge cycle and a second unregulated voltage value during a second charge cycle, an inductor and capacitor connected in series with one another, wherein a charge voltage exists across the capacitor; a diode connected in parallel with the inductor and capacitor; a switch, and means for closing the switch at a first time for permitting the unregulated power supply to be connected to the capacitor through the inductor when the switch is in a closed position; means for opening the switch during the first charge cycle.

Ball, D.G.

1992-06-23

321

HU: promoting or counteracting DNA compaction?  

PubMed

The role of HU in Escherichia coli as both a protein involved in DNA compaction and as a protein with regulatory function seems to be firmly established. However, a critical look at the available data reveals that this is not true for each of the proposed roles of this protein. The role of HU as a regulatory or accessory protein in a number of systems has been thoroughly investigated and in many cases has been largely elucidated. However, almost 30 years after its discovery, convincing evidence for the proposed role of HU in DNA compaction is still lacking. Here we present an extensive literature survey of the available data which, in combination with novel microscopic insights, suggests that the role of HU could be the opposite as well. The protein is likely to play an architectural role, but instead of being responsible for DNA compaction it could be involved in antagonising compaction by other proteins such as H-NS. PMID:12372591

Dame, Remus Thei; Goosen, Nora

2002-10-01

322

Compaction of Amorphous Ferromagnetic Metal Powders.  

National Technical Information Service (NTIS)

The attractive magnetic properties of certain amorphous metal powders might be exploited in the electrical industry if the powders can be consolidated into relatively dense compacts. The production of integral bodies of an amorphous powder was attempted u...

R. D. Caligiuri

1982-01-01

323

Compaction Properties of L-Lysine Salts  

Microsoft Academic Search

Purpose. To examine the effects of salt form, i.e., different anions with a common cation (L-lysinium), on compaction properties and to identify the factors that determine the tensile strength of tablets.

Changquan Sun; David J. W. Grant

2001-01-01

324

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

325

Compact Acoustic Surface Wave Frequency Multiplexers.  

National Technical Information Service (NTIS)

The design of low cost, compact surface acoustic wave frequency multiplexers is described. The frequency selective properties of surface wave filters are used to achieve low inband (high-Q) loss and high outband rejection. Observations made on measured tr...

K. R. Laker A. J. Budreau P. H. Carr

1974-01-01

326

Massive parallelization of the compact genetic algorithm  

Microsoft Academic Search

This paper presents an architecture which is suitable for a massive parallelization of the compact genetic algorithm. The resulting scheme has three major advantages. First, it has low synchronization costs. Second, it is fault tolerant, and third, it is scalable.

Fernando G. Lobo; Claudio F. Lima; Hugo Mártires

327

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

328

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

329

Cosmic Ray Compaction of Porous Interstellar Ices  

NASA Astrophysics Data System (ADS)

We studied the compaction of microporous vapor-deposited ice films under irradiation with different ions in the 80-400 keV energy range. We found that porosity decreases exponentially with irradiation fluence, with a mean compaction area per ion that scales linearly with the stopping power of the projectile S above a threshold St=4 eV Å-1. The experiments roughly follow a universal dependence of ion-induced compaction with restricted dose (eV molecule-1). This behavior can be used to extrapolate our results to conditions of the interstellar medium. Relating our results to ionization rates of interstellar H2, we estimate that porous ice mantles on grains in dense molecular clouds are compacted by cosmic rays in ~10-50 million years.

Raut, U.; Famá, M.; Loeffler, M. J.; Baragiola, R. A.

2008-11-01

330

The Ultra Compact Imaging Spectrometer (UCIS)  

NASA Astrophysics Data System (ADS)

The Ultra Compact Imaging Spectrometer (UCIS) can be mounted on a rover or lander and address complex questions of geological evolution by mapping mineral composition. The instrument can be used on Mars, the Moon, comets, or asteroids.

Blaney, D. L.; Mouroulis, P.; Green, R. O.; Rodriquez, J.; Sellar, G.; Van Gorp, B.; Wilson, D.

2012-10-01

331

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

332

Development of an optimized compact test range  

Microsoft Academic Search

A method of measuring the electromagnetic far field characteristics of microwave antennas is introduced by means of compact test ranges. The performances of the front-fed Cassegrain system, which avoids the usually weak cross-polarization performance of the compact range geometries, are established. The chosen manufacturing process, milling of cast-iron reflectors, guaranteed highest achievable surface accuracies, even for very large reflectors. The

Evert Dudok; Dietmar Fasold; Hans-Juergen Steiner

1989-01-01

333

DLR-HR Compact Test Range facility  

Microsoft Academic Search

A compact test range (CTR) facility shall extend the measurement capabilities at the microwaves and Radar Institute of the German Aerospace Center (DLR) in Oberpfaffenhofen. Today's accuracy requirements in the RF-component characterization are decisive factors for the specification of a new measurement facility. Parts of a compact antenna test range (CATR) model 8074B, manufactured by March Microwave Systems B.V., have

M. Limbach; B. Gabler; R. Horn; A. Reigber

2009-01-01

334

Compact Genetic Algorithms Based on Mutation  

Microsoft Academic Search

(Abstract)Compact Genetic Algorithm(CGA) requires a small amount of memory, but it is apt to premature stagnate. This paper proposes a Mutation-Based Compact Genetic Algorithm(MBCGA) by introducing the mutation operator into CGA, thus MBCGA mimics all the main genetic operators in natural evolution, then local search is strengthened and premature stagnation can be avoided. Experimental results show that the MBCGA generally

LIN Tu-sheng; LIAO Liang

2008-01-01

335

A weight based compact genetic algorithm  

Microsoft Academic Search

In order to improve the performance of the compact Genetic Algorithm (cGA) to solve difficult optimization problems, an improved cGA which named as the weight based compact Genetic Algorithm (wcGA) is proposed. In the wcGA, S individuals are generated from the probability vector in each generation, when the winner competing with the other S-1 individuals to update the probability vector,

Qing-bin Zhang; Ti-hua Wu; Bo Liu

2009-01-01

336

Compact electron linacs for radiation technology systems  

Microsoft Academic Search

Compact, self-contained electron beam systems are used for sterilization of medical devices and materials, treatment of medical and infectious wastes, non-intrusive inspection of cargo containers, etc. These systems, having massive local radiation shielding, require compact accelerators. 5-MeV and 7-MeV electron linacs are presented in this paper. The accelerators use standing wave biperiodic structures fed by magnetron generators with 2.8 GHz

V. Belugin; A. Mischenko; V. Pirozhenko; N. Rozanov; A. Zavadtsev; A. Korolev; K. Simonov

2001-01-01

337

Compact zoom lens for stereoscopic television  

Microsoft Academic Search

This paper describes the on-going development of a compact zoom lens specifically for stereoscopic television in nuclear environments. Custom-designed optics in radiation-tolerant glass provide a focal length of 12.5 mm to 36 mm with a package length of less than 110 mm. A novel method of encoding the position of the lens elements allows for very compact motorization, and a

Peter M. Scheiwiller; S. P. Murphy; Andrew A. Dumbreck

1991-01-01

338

Compact capacitor/filter development. Final report  

SciTech Connect

This report presents the results of a program to develop compact capacitor banks and harmonic filters for transmission voltages with an installed cost equivalent to air insulated capacitor banks. The objective of this work was to develop, design, build, install, and field test such compact capacitor banks. For demonstration purposes, a single phase 362-kV shunt bank and a three phase 145-kV 11th harmonic filter were to be designed, constructed, and field tested.

Dodds, J.; Oswalt, N.; Johansson, A.; Danemar, A.

1984-04-01

339

COMPACTNESS AND INCOMPACTNESS PHENOMENA IN SET THEORY  

Microsoft Academic Search

Abstract. We prove two results with a common,theme: the tension between compactness and incompactness phenomena,in combinatorial set theory. The- orem 1 uses PCF theory to prove a sort of “compactness” for a version of Dzamonja and Shelah’s strong non-reflection principle. Theorem 2 investi- gates Jensen’s subcompact cardinals and their relationship with stationary set reflection and the failure of the square

James Cummings

340

Rotating compact star with superconducting quark matter  

SciTech Connect

A compact star with a superconducting quark core, a hadron crust, and a mixed phase between the two is considered. The quark-meson coupling model for hadron matter and the color-flavor-locked quark model for quark matter is used to construct the equation of state for the compact star. The effect of pairing of quarks in the color-flavor-locked phase and the mixed phase on the mass, radius, and period of the rotating star is studied.

Panda, P.K. [Indian Institute of Astrophysics, Koramangala, Bangalore-560034 (India); Institute of Physics, Bhubaneswar-751005 (India); Nataraj, H.S. [Indian Institute of Astrophysics, Koramangala, Bangalore-560034 (India)

2006-02-15

341

A compact, high-performance cryogenic stage  

Microsoft Academic Search

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

D. A. Fester; J. W. Robinson; B. A. Bicknell

1986-01-01

342

Compact waterjets for high-speed ships  

Microsoft Academic Search

The article describes the development and validation of a compact waterjet propulsion system for high-speed vessels. The development was conducted in four discrete phases over a period of 4 years: Phase 1 involved studies of pump-type options for compact units; Phase 2 used advanced Computational Fluid Dynamics (CFD) to design the preferred pump type for a high-speed ship design; Phase

D. R. Lavis; B. G. Forstell; J. G. Purnell

2007-01-01

343

Left ventricular non-compaction in pregnancy.  

PubMed

Left-ventricular non-compaction (LVNC) represents an arrest in the normal process of myocardial compaction, resulting in multiple, prominent, persistant trabeculations and deep inter-trabecular recesses communicating with the ventricular cavity. LVNC is a rarely encountered cardiomyopathy and few cases have been reported in pregnancy. In this case report we present a patient who referred to our clinic with symptoms of heart failure during pregnancy and whose echocardiographic examination revealed prominent trabeculations in the left ventricle. PMID:23728124

Kilic, Ismail Dogu; Tanriverdi, Halil; Evrengul, Harun; Uslu, Sukriye; Sungur, Mustafa Azmi

2013-04-23

344

Shedding light on the compact fluorescent  

Microsoft Academic Search

Through a series of in-depth surveys, EPRI researchers have learned that many U.S. consumers are dissatisfied with currently available compact fluorescent lamps (CFLs), a technology commonly promoted through utilities' efficient-lighting programs. Complaints include the high cost of CFLs and their inability to be used with dimmer switches. Despite such drawbacks, Japanese consumers have displayed a healthy appetite for compact fluorescents,

Lamarre

1993-01-01

345

Phased array compaction cell for measurement of the transversely isotropic elastic properties of compacting sediments  

Microsoft Academic Search

Sediments undergoing compaction typically exhibit transversely isotropic (TI) elastic properties. We present a new experimental apparatus, the phased array compaction cell, for measuring the TI elastic properties of clay-rich sediments during compaction. This apparatus uses matched sets of P- and S-wave ultrasonic transducers located along the sides of the sample and an ultrasonic P-wave phased array source, together with a

K. T. Nihei; S. Nakagawa; F. Reverdy; L. R. Meyer; L. Duranti; G. Ball

2010-01-01

346

Ceramic granule strength variability and compaction behavior  

SciTech Connect

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 behavior of granular assemblies. High variability in strength, represented by low Weibull modulus values (m<3) was observed for ceramic granules having a distribution of sizes and shapes, and for uniform-size glass spheres. Compaction pressure data were also analyzed using a Weibull distribution function, and the results were very similar to those obtained from the diametral compression strength tests for the same material. This similarity suggests that it may be possible to model granule compaction using a weakest link theory, whereby an assemblage of granules is viewed as the links of a chain, and failure of the weakest granule (i.e., the weakest link) leads to rearrangement and compaction. Additionally, with the use of Weibull statistics, it appears to be possible to infer the variability in strength of individual granules from a simple pressure compaction test, circumventing the tedious task of testing individual granules.

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

1995-08-01

347

D=4 extended Galilei superalgebras with central charges  

NASA Astrophysics Data System (ADS)

We perform a nonrelativistic contraction of N-extended Poincaré superalgebra with internal symmetry U(N) and general set of N(N-1) real central charges. We show that for even N=2k and particular choice of the dependence of Z on light velocity c one gets the N-extended Galilei superalgebra with unchanged number of central charges and compact internal symmetry algebra U(k;H)=USp(2k). The Hamiltonian positivity condition is modified only by one central charge. If we put all the central charges equal to zero one gets the 2k-extended Galilei superalgebra as the subalgebra of recently introduced extended Galilei conformal superalgebra (de Azcárraga, Lukierski (2009) [1] and Sakaguchi [2]).

Lukierski, Jerzy

2011-01-01

348

Nonrandom adsorption of polyelectrolyte chains on finite regularly charged surfaces.  

PubMed

Adsorption phenomena are relevant in a wide variety of subjects, from biophysics to technological applications. Different aspects, such as molecular recognition, multilayer deposition, and dynamics of polymer adsorption have been addressed. The methodologies used range from analytical and numerical methods to molecular dynamics or Monte Carlo simulations. In this work, a coarse-grained model is used to explore the adsorption of charged backbones to oppositely charged regions of a surface. These regions encompass those small enough to prevent complete adsorption, but extend to surfaces sufficiently large to promote adsorption with minimal effect on the three-dimensional conformation in bulk. Apart from the different surface areas explored, variations on the surface charge density, polyelectrolyte chain length, and chain stiffness were also considered. The degree of compaction of the polyelectrolyte, on adsorption, is different from that found in the bulk. Also, results indicate an nonuniform adsorption pattern on regularly charged surfaces. PMID:23386422

Nunes, Sandra C C; Pinto, P; Pais, A A C C

2013-02-05

349

COMPACT DIFFERENCES OF COMPOSITION OPERATORS ON BLOCH AND LIPSCHITZ SPACES  

Microsoft Academic Search

We consider the dierence T = C C of two analytic composition operators in the unit disc. We characterize the compactness and weak compact- ness of T on the standard Bloch space, improving an earlier result by Hosokawa and Ohno. We also characterize the compactness and weak compactness of T on analytic Lipschitz spaces. These characterizations are derived from a

PEKKA J. NIEMINEN

350

Compaction mechanism as the function of atomized powder particle size  

Microsoft Academic Search

The cold compaction process of spray dried powder for ceramic floor\\/wall tiles production was followed by compaction response and compaction rate diagrams. Seven fractions of defined size, as well as the industrial powder batch, were compacted at pressures up to 31.5 MPa. The effect of particle size, textural and morphological characteristics on the consolidation mechanism was investigated. Both plastic deformation

M. Radeka; J. Ranogajec; R. Marinkovi?-Nedu?in; B. Živanovi?

1995-01-01

351

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

352

COMPACT PROTON INJECTOR AND FIRST ACCELERATOR SYSTEM TEST FOR COMPACT PROTON DIELECTRIC WALL CANCER THERAPY ACCELERATOR  

SciTech Connect

A compact proton accelerator for cancer treatment is being developed by using the high-gradient dielectric insulator wall (DWA) technology [1-4]. We are testing all the essential DWA components, including a compact proton source, on the First Article System Test (FAST). The configuration and progress on the injector and FAST will be presented.

Chen, Y; Guethlein, G; Caporaso, G; Sampayan, S; Blackfield, D; Cook, E; Falabella, S; Harris, J; Hawkins, S; Nelson, S; Poole, B; Richardson, R; Watson, J; Weir, J; Pearson, D

2009-04-23

353

Mixing and compaction temperatures for Superpave mixes  

NASA Astrophysics Data System (ADS)

According to Superpave mixture design, gyratory specimens are mixed and compacted at equiviscous binder temperatures corresponding to viscosities of 0.17 and 0.28 Pa.s. respectively. These were the values previously used in the Marshal mix design method to determine optimal mixing and compaction temperatures. In order to estimate the appropriate mixing and compaction temperatures for Superpave mixture design, a temperature-viscosity relationship for the binder needs to be developed (ASTM D 2493, Calculation of Mixing and Compaction Temperatures). The current approach is simple and provides reasonable temperatures for unmodified binders. However, some modified binders have exhibited unreasonably high temperatures for mixing and compaction using this technique. These high temperatures can result in construction problems, damage of asphalt, and production of fumes. Heating asphalt binder to very high temperatures during construction oxidizes the binder and separates the polymer from asphalt binder. It is known that polymer modified asphalt binders have many benefits to the roads, such as; increasing rutting resistance, enhancing low temperature cracking resistance, improving traction, better adhesion and cohesion, elevating tensile strength which are directly related to the service life of the pavement. Therefore, oxidation and separation of the polymer from the asphalt binder results in reduction of the service life. ASTM D 2493 was established for unmodified asphalt binders which are Newtonian fluids at high temperatures. For these materials, viscosity does not depend on shear rate. However, most of the modified asphalt binders exhibit a phenomenon known as pseudoplasticity, where viscosity does depend on shear rate. Thus, at the high shear rates occurring during mixing and compaction, it is not necessary to go to very high temperatures. This research was undertaken to determine the shear rate during compaction such that the effect of this parameter could be included during viscosity measurements. The use of practical shear rates results in reasonable mixing and compaction temperatures for hot mix asphalt design and construction with modified asphalt binders. It was found that application of the shear rate concept, rather than the traditional approach used for unmodified binders, can reduce the mixing and compaction temperatures from between roughly 10 and 30°C, depending on the type and the amount of modifier.

Yildirim, Yetkin

354

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

355

CHARGE-2 rocket observations of vehicle charging and charge neutralization  

NASA Astrophysics Data System (ADS)

Observations of electrical charging and other phenomena have been made in the ionosphere with the CHARGE-2 tethered rocket system. In this experiment, two electrically connected payloads with a variety of plasma instruments measured effects associated with operation of a 1 keV, 40 mA electron gun and a 450-volt dc power supply. During electron beam operations, it was found that both mother and daughter payloads reached high positive potentials as a consequence of the restricted electron current collecting area of the payloads. During neutral gas thruster firings, the payload potentials were dramatically reduced, indicating that electrical discharges could effectively ground each payload to plasma potential. Other thruster-related effects were also seen, including substantial reductions of return current-associated electrical noise at HF and VLF and large increases in 3914 A light in the plasma sheath.

Banks, P. M.; Gilchrist, B. E.; Neubert, T.; Meyers, N.; Raitt, W. J.

356

Dynamic magnetic compaction of porous materials  

SciTech Connect

IAP Research began development of the Dynamic Magnetic Compaction (DMC) process three years before the CRADA was established. IAP Research had experimentally demonstrated the feasibility of the process, and conducted a basic market survey. IAP identified and opened discussions with industrial partners and established the basic commercial cost structure. The purpose of this CRADA project was to predict and verify optimum pressure vs. time history for the compaction of porous copper and tungsten. LLNL modeled the rapid compaction of powdered material from an initial density of about 30% theoretical maximum to more than 90% theoretical maximum. The compaction simulations were benchmarked against existing data and new data was acquired by IAP Research. The modeling was used to perform parameter studies on the pressure loading time history, initial porosity and temperature. LLNL ran simulations using codes CALE or NITO and compared the simulations with published compaction data and equation of state (EOS) data. This project did not involve the development or modification of software code. CALE and NITO were existing software programs at LLNL. No modification of these programs occurred within the scope of the CRADA effort.

NONE

1998-10-29

357

Counterintuitive compaction behavior of clopidogrel bisulfate polymorphs.  

PubMed

Being a density violator, clopidogrel bisulfate (CLP) polymorphic system (forms I and II) allows us to study individually the impact of molecular packing (true density) and thermodynamic properties such as heat of fusion on the compaction behavior. These two polymorphs of CLP were investigated for in-die and out-of-die compaction behavior using CTC profile, Heckel, and Walker equations. Compaction studies were performed on a fully instrumented rotary tabletting machine. Detailed examinations of the molecular packing of each form revealed that arrangement of the sulfate anion differs significantly in both crystal forms, thus conferring different compaction behavior to two forms. Close cluster packing of molecules in form I offers a rigid structure, which has poor compressibility and hence resists deformation under compaction pressure. This results into lower densification, higher yield strength, and mean yield pressure, as compared with form II at a given pressure. However, by virtue of higher bonding strength, form I showed superior tabletability, despite its poor compressibility and deformation behavior. Form I, having higher true density and lower heat of fusion showed higher bonding strength. Hence, true density and not heat of fusion can be considered predictor of bonding strength of the pharmaceutical powders. PMID:22488254

Khomane, Kailas S; More, Parth K; Bansal, Arvind K

2012-04-04

358

Phased array compaction cell for measurement of the transversely isotropic elastic properties of compacting sediments  

SciTech Connect

Sediments undergoing compaction typically exhibit transversely isotropic (TI) elastic properties. We present a new experimental apparatus, the phased array compaction cell, for measuring the TI elastic properties of clay-rich sediments during compaction. This apparatus uses matched sets of P- and S-wave ultrasonic transducers located along the sides of the sample and an ultrasonic P-wave phased array source, together with a miniature P-wave receiver on the top and bottom ends of the sample. The phased array measurements are used to form plane P-waves that provide estimates of the phase velocities over a range of angles. From these measurements, the five TI elastic constants can be recovered as the sediment is compacted, without the need for sample unloading, recoring, or reorienting. This paper provides descriptions of the apparatus, the data processing, and an application demonstrating recovery of the evolving TI properties of a compacting marine sediment sample.

Nihei, K.T.; Nakagawa, S.; Reverdy, F.; Meyer, L.R.; Duranti, L.; Ball, G.

2010-12-15

359

Multifunctional compact zwitterionic ligands for preparing robust biocompatible semiconductor quantum dots and gold nanoparticles.  

PubMed

We describe the synthesis of a series of four different ligands which are used to prepare hydrophilic, biocompatible luminescent quantum dots (QDs) and gold nanoparticles (AuNPs). Overall, the ligands are designed to be compact while still imparting a zwitterionic character to the NPs. Ligands are synthesized appended to a bidentate dihydrolipoic acid- (DHLA) anchor group, allowing for high-affinity NP attachment, and simultaneously incorporate tertiary amines along with carboxyl and/or hydroxyl groups. These are placed in close proximity within the ligand structure and their capacity for joint ionization imparts the requisite zwitterionic nature to the nanocrystal. QDs functionalized with the four different compact ligands were subjected to extensive physical characterization including surface charge, wettability, hydrodynamic size, and tolerance to a wide pH range or high salt concentration over time. The utility of the compact ligand coated QDs was further examined by testing of direct conjugation to polyhistidine-appended protein and peptides, aqueous covalent-coupling chemistry, and the ability to engage in Förster resonance energy transfer (FRET). Conjugating cell penetrating peptides to the compact ligand coated QD series facilitated their rapid and efficient cellular uptake, while subsequent cytotoxicity tests showed no apparent decreases in cell viability. In vivo biocompatibility was also demonstrated by microinjecting the compact ligand coated QDs into cells and monitoring their stability over time. Inherent benefits of the ligand design could be extended beyond QDs as AuNPs functionalized with the same compact ligand series showed similar colloidal properties. The strong potential of these ligands to expand NP capabilities in many biological applications is highlighted. PMID:21612225

Susumu, Kimihiro; Oh, Eunkeu; Delehanty, James B; Blanco-Canosa, Juan B; Johnson, Brandy J; Jain, Vaibhav; Hervey, William Judson; Algar, W Russ; Boeneman, Kelly; Dawson, Philip E; Medintz, Igor L

2011-05-25

360

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

361

Impacts by Compact Ultra Dense Objects  

NASA Astrophysics Data System (ADS)

We propose to search for nuclear density or greater compact ultra dense objects (CUDOs), which could constitute a significant fraction of the dark matter [1]. Considering their high density, the gravitational tidal forces are significant and atomic-density matter cannot stop an impacting CUDO, which punctures the surface of the target body, pulverizing, heating and entraining material near its trajectory through the target [2]. Because impact features endure over geologic timescales, the Earth, Moon, Mars, Mercury and large asteroids are well-suited to act as time-integrating CUDO detectors. There are several potential candidates for CUDO structure such as strangelet fragments or more generally dark matter if mechanisms exist for it to form compact objects. [4pt] [1] B. J. Carr, K. Kohri, Y. Sendouda, & J.'i. Yokoyama, Phys. Rev. D81, 104019 (2010). [0pt] [2] L. Labun, J. Birrell, J. Rafelski, Solar System Signatures of Impacts by Compact Ultra Dense Objects, arXiv:1104.4572.

Birrell, Jeremey; Labun, Lance; Rafelski, Johann

2012-03-01

362

Dense quark matter in compact stars  

NASA Astrophysics Data System (ADS)

The densest predicted state of matter is colour superconducting quark matter, in which quarks near the Fermi surface form a condensate of Cooper pairs. This form of matter may well exist in the core of compact stars, and the search for signatures of its presence is an ongoing enterprise. Using a bag model of quark matter, I will discuss the effects of colour superconductivity on the mass-radius relationship of compact stars, showing that colour superconducting quark matter will occur in compact stars at values of the bag constant where ordinary quark matter would not be allowed. The resultant 'hybrid' stars with colour superconducting quark matter interior and nuclear matter surface have masses in the range 1.3-1.6 Modot and radii 8-11 km.

Alford, M.

2004-01-01

363

Powder and compaction characteristics of pregelatinized starches.  

PubMed

Pregelatinized starch is widely used as a pharmaceutical aid, especially as a filler-binder. It is known that the tableting performance of excipients could be affected by their source. The aim of this study was to evaluate the powder and tableting properties of pregelatinized starches obtained from yucca, corn and rice and compare those properties with those of Starch 1500. This material had the lowest particle size, and porosity and largest density and best flow. However, yucca starch and corn starch showed an irregular granule morphology, better compactibility and compressibility than Starch 1500. Their onset of plastic deformation and their strain rate sensitivity was comparable to that of Starch 1500. These two materials showed compact disintegration slower that Starch 1500. Conversely, rice starch showed a high elasticity, and friability, low compactibility, which are undesirable for direct compression. This study demonstrated the potential use of pregelatinized starches, especially those obtained from yucca and corn as direct compression filler-binders. PMID:22822539

Rojas, J; Uribe, Y; Zuluaga, A

2012-06-01

364

Shock compaction of high- Tc superconductors  

SciTech Connect

We present the results of shock compaction experiments on high-{Tc} superconductors and describe the way in which shock consolidation addresses critical problems concerning the fabrication of high J{sub c} bulk superconductors. In particular, shock compaction experiments on YBa{sub 2}Cu{sub 3}O{sub 7} show that shock-induced defects can greatly increase intragranular critical current densities. The fabrication of crystallographically aligned Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} samples by shock-compaction is also described. These experiments demonstrate the potential of the shock consolidation method as a means for fabricating bulk high-{Tc} superconductors having high critical current densities.

Weir, S.T.; Nellis, W.J.; McCandless, P.C.; Brocious, W.F. (Lawrence Livermore National Lab., CA (USA)); Seaman, C.L.; Early, E.A.; Maple, M.B. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics); Kramer, M.J. (Ames Lab., IA (USA)); Syono, Y.; Kikuchi, M. (Tohoku Univ., Sendai (Japan))

1990-09-01

365

Hydraulic conductivity tests on compacted clay  

SciTech Connect

Permeability tests were performed in the laboratory on compacted clay to study the effects of type of permeameter, hydraulic anisotropy, diameter of test specimens, storage time, and desiccation cracking. Essentially identical hydraulic conductivities were measured with compaction-mold, consolidationcell, and flexible-wall permeameters. With good bonding between lifts, hydraulic conductivity was isotropic. Test specimens having a diameter of 15 cm were twice as permeable as specimens having a diameter of 4 cm, but this difference is too small to be of any consequence. There was no tendency for hydraulic conductivity to increase with increasing storage time. Desiccation cracks in compacted clay close only partially when the clay is moistened and permeated, unless substantial effective stresses are applied to aid in closing the cracks.

Boynton, S.S.; Daniel, D.E.

1985-04-01

366

Simulation of dynamic compaction of metal powders  

NASA Astrophysics Data System (ADS)

This article presents numerical studies on the deformation of particles during dynamic compaction of metal powders. The analysis of the process is based on a micromechanics approach using multiple particle configurations. The material considered is elastoviscoplastic with interparticle friction. Two-dimensional studies on particles in close packed arrangement were carried out using plane strain conditions for deformation and thermal response. The finite element method using an explicit dynamic analysis procedure was used for the simulations. The influence of speed of compaction, strain hardening, strain rate dependency, interparticle friction and size of the powder particles on the final shape and temperature variations within the particles were analyzed. The studies offer useful information on the shape and temperature variations within the particles. The results provide a better understanding of the dynamic compaction process at the micromechanics level.

Kumar, D. Roshan; Kumar, R. Krishna; Philip, P. K.

1999-01-01

367

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

368

Galactic center compact nonthermal radio source  

SciTech Connect

The current observational status of Sgr A*, the compact nonthermal radio source at the galactic center, is reviewed. It is a unique radio source at a unique position of the Galaxy. It is unlike any compact radio sources associated with known stellar objects, but it is similar to extragalactic nuclear compact radio sources. The positional offset between Sgr A* and IRS16 places little constraint on the nature of the underlying energy source, since the nature of IRS16 itself is not well understood and may not be the core of the central star cluster. With its unique properties in the Galaxy and being the only unsual object at the center with dimensions approaching the gravitational radius of a approx.10/sup 6/ M/sub sun/ black-hole, Sgr A* is still the best candidate for marking the location of a massive collapsed object.

Lo, K.Y.

1987-04-15

369

Hall MHD Equilibrium of Accelerated Compact Toroids  

NASA Astrophysics Data System (ADS)

We examine the structure and dynamics of the compact toroid's magnetic field. The compact toroid is dramatically accelerated by a large rail-gun Lorentz force density equal to j xB. We use magnetic data from the Compact Toroid Injection Experiment to answer the question of exactly where in the system j xB has nonzero values, and to what extent we can apply the standard model of force-free equilibrium. In particular we present a method of analysis of the magnetic field probe signals that allows direct comparison to the predictions of the Woltjer-Taylor force-free model and Turner's generalization of magnetic relaxation in the presence of a non-zero Hall term and fluid vorticity.

Howard, S. J.; Hwang, D. Q.; Horton, R. D.; Evans, R. W.; Brockington, S. J.

2007-11-01

370

Space charge stopband correction  

SciTech Connect

It is speculated that the space charge effect cause beam emittance growth through the resonant envelope oscillation. Based on this theory, we propose an approach, called space charge stopband correction, to reduce such emittance growth by compensation of the half-integer stopband width of the resonant oscillation. It is illustrated with the Fermilab Booster model.

Huang, Xiaobiao; /Fermilab /Indiana U.; Lee, S.Y.; /Indiana U.

2005-09-01

371

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

372

Scaling properties of maximally compact chains  

SciTech Connect

Scaling of the exact function for the number of intramolecular nonbonded contacts in a single maximally compact linear homopolymer on hypercubic lattices is determined as a function of number {ital N} of monomers and dimension {ital d}. A representative maximally compact structure is designed and an exact recursive expression for the maximum number m{sub max} of contacts is derived from that design. The equivalent nonrecursive expression yields the asymptotic scaling of m{sub max} as (d{minus}1)N{minus}dN{sup {Delta}}+1, with {Delta}=(d{minus}1)/d. Implications in polymer and protein studies are discussed. {copyright} {ital 1999} {ital The American Physical Society}

Foreman, K.W. [The Department of Pharmaceutical Chemistry, University of California, San Francisco, 3333 California Avenue, San Francisco, California 94118 (United States)

1999-05-01

373

Compact accelerator concept for proton therapy  

NASA Astrophysics Data System (ADS)

A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is being developed as a compact flash X-ray radiography source. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be presented.

Caporaso, G. J.; Sampayan, S.; Chen, Y.-J.; Harris, J.; Hawkins, S.; Holmes, C.; Krogh, M.; Nelson, S.; Nunnally, W.; Paul, A.; Poole, B.; Rhodes, M.; Sanders, D.; Selenes, K.; Sullivan, J.; Wang, L.; Watson, J.

2007-08-01

374

Operational experience with the compact prover  

SciTech Connect

A relatively new method of proving meters is discussed here. Operational experience with the compact prover provides a faster, more accurate and economical method in which to have accurate proving of custody transfer meters. Although there are several confirmed and accepted methods used by the industry to prove meters, namely prover tanks, master meters, uni-directional piston provers, and bi-directional ball type provers; it is difficult to say that one method is better than another. The paper suggests that technology has progressed to the point that we can now say that the compact prover is one of the best methods of proving P.D. and turbine meters.

Hinton, H.D.

1984-04-01

375

Compact cold atom gravimeter for field applications  

NASA Astrophysics Data System (ADS)

We present a cold atom gravimeter dedicated to field applications. Despite the compactness of our gravimeter, we obtain performances (sensitivity 42 ?Gal/Hz1/2, accuracy 25 ?Gal) close to the best gravimeters. We report gravity measurements in an elevator which led us to the determination of the Earth's gravity gradient with a precision of 4E. These measurements in a non-laboratory environment demonstrate that our technology of gravimeter is enough compact, reliable, and robust for field applications. Finally, we report gravity measurements in a moving elevator which open the way to absolute gravity measurements in an aircraft or a boat.

Bidel, Yannick; Carraz, Olivier; Charrière, Renée; Cadoret, Malo; Zahzam, Nassim; Bresson, Alexandre

2013-04-01

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

Dynamic compaction of particulate composite materials  

NASA Astrophysics Data System (ADS)

This paper describes the mechanical alloying + dynamic compaction flowchart for producing composites with particulate reinforcements. The combinations of components tested included aluminum silicon carbide, aluminum boron carbide, copper silicon carbide, and copper silica. Mechanical alloying produced granules of composite with reinforcements uniformly distributed in the matrix material. Dynamic compaction of mechanically alloyed granules was shown to produce high quality composite materials with crack-free structure. As the standard methods for explosive treatment lead to crack formation in bulk composites, this work included the development of a tool for treating composite materials.

Popov, V. A.; Staudhammer, K. P.; Goulbin, V. N.

2006-08-01

378

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.

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

1996-12-31

379

FODO-Supercell Based Compact Ring Design with Tunable Momentum Compaction and Optimized Dynamic Aperture  

SciTech Connect

A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and predamping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.

Sun, Yipeng; /SLAC

2012-05-03

380

FODO-Supercell Based Compact Ring Design with Tunable Momentum Compaction and Optimized Dynamic Aperture  

SciTech Connect

A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and pre-damping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.

Sun, Yipeng; /SLAC

2012-05-11

381

Charging car for coke ovens  

Microsoft Academic Search

A coal-charging apparatus includes a charging car with charging bins to discharge coal through filling tubes into charging holes in the roof of an oven chamber. A feed-screw conveys coal from the bottom of a charging bin to a trough communicating with a fixed filling tube. A peripheral trough on the bottom of this tube is filled with sand or

H. Kwasnik; H. Piduch

1982-01-01

382

Charged anisotropic matter with linear or nonlinear equation of state  

NASA Astrophysics Data System (ADS)

Ivanov pointed out substantial analytical difficulties associated with self-gravitating, static, isotropic fluid spheres when pressure explicitly depends on matter density. Simplifications achieved with the introduction of electric charge were noticed as well. We deal with self-gravitating, charged, anisotropic fluids and get even more flexibility in solving the Einstein-Maxwell equations. In order to discuss analytical solutions we extend Krori and Barua’s method to include pressure anisotropy and linear or nonlinear equations of state. The field equations are reduced to a system of three algebraic equations for the anisotropic pressures as well as matter and electrostatic energy densities. Attention is paid to compact sources characterized by positive matter density and positive radial pressure. Arising solutions satisfy the energy conditions of general relativity. Spheres with vanishing net charge contain fluid elements with unbounded proper charge density located at the fluid-vacuum interface. Notably the electric force acting on these fluid elements is finite, although the acting electric field is zero. Net charges can be huge (1019C) and maximum electric field intensities are very large (1023-1024statvolt/cm) even in the case of zero net charge. Inward-directed fluid forces caused by pressure anisotropy may allow equilibrium configurations with larger net charges and electric field intensities than those found in studies of charged isotropic fluids. Links of these results with charged strange quark stars as well as models of dark matter including massive charged particles are highlighted. The van der Waals equation of state leading to matter densities constrained by cubic polynomial equations is briefly considered. The fundamental question of stability is left open.

Varela, Victor; Rahaman, Farook; Ray, Saibal; Chakraborty, Koushik; Kalam, Mehedi

2010-08-01

383

A compact high performance thermal imager  

Microsoft Academic Search

A compact, low-cost, high-performance thermal imager based on a novel coaxial scanning technique is presented. Design requirements for this imager configuration encompass the avoidance of vignetting and pupil wander in the scanning elements and objective lenses, as well as the maximization of detector cold shielding. The requirements are met by the use of SPRITE IR detectors, and the use of

A. H. Lettington; W. T. Moore

1986-01-01

384

Technology Projection Using Simple Compact Models  

Microsoft Academic Search

We review recent efforts to capture the device nonidealities for circuit-level technology projection for Si CMOS. We also give some examples of simple compact model development for assessing the circuit-level performance of exploratory devices such as III-V FET, carbon nanotube transistor, and nanoelectromechanical (NEM) transistors and relays.

H.-S. P. Wong; Lan Wei; S. Oh; A. Lin; Jie Deng; Soogine Chong; K. Akarvardar

2009-01-01

385

Compact continuum brain model for human electroencephalogram  

NASA Astrophysics Data System (ADS)

A low-dimensional, compact brain model has recently been developed based on physiologically based mean-field continuum formulation of electric activity of the brain. The essential feature of the new compact model is a second order time-delayed differential equation that has physiologically plausible terms, such as rapid corticocortical feedback and delayed feedback via extracortical pathways. Due to its compact form, the model facilitates insight into complex brain dynamics via standard linear and nonlinear techniques. The model successfully reproduces many features of previous models and experiments. For example, experimentally observed typical rhythms of electroencephalogram (EEG) signals are reproduced in a physiologically plausible parameter region. In the nonlinear regime, onsets of seizures, which often develop into limit cycles, are illustrated by modulating model parameters. It is also shown that a hysteresis can occur when the system has multiple attractors. As a further illustration of this approach, power spectra of the model are fitted to those of sleep EEGs of two subjects (one with apnea, the other with narcolepsy). The model parameters obtained from the fittings show good matches with previous literature. Our results suggest that the compact model can provide a theoretical basis for analyzing complex EEG signals.

Kim, J. W.; Shin, H.-B.; Robinson, P. A.

2007-12-01

386

Thermal residual stress of polycrystalline diamond compacts  

Microsoft Academic Search

Thermal residual stresses in polycrystalline diamond compact (PDC) cutter arising from the difference in thermal expansion between the polycrystalline diamond (PCD) and the supporting tungsten carbide substrate after sintering at high pressure and high temperature were investigated using finite element simulation, laboratory tests and theoretical analysis. The obtained results show that although compressive residual stresses exist both in the interface

Feng CHEN; Gen XU; Chun-de MA; Guo-ping XU

2010-01-01

387

Acceleration radiation in a compact space  

NASA Astrophysics Data System (ADS)

A study is conducted of the response of a uniformly accelerated model particle detector in a spacetime with compact spatial sections. The basic thermal character of the response re-emerges, in spite of the fact that the spacetime does not possess event horizons. The model also permits a study of detector response to twisted field states.

Copeland, E. J.; Davies, P. C. W.; Hinton, K.

1984-03-01

388

Lens-type compact antenna range  

Microsoft Academic Search

A compact antenna range is described which uses a plastic foam lens to obtain a collimated beam within which the radiation pattern of a test antenna can be measured. A novel feature is the introduction of a controlled amount of loss into the lens so that a nearly uniform electric field is measured over a high proportion of the lens

A. D. Olver; A. A. Saleeb

1979-01-01

389

Compact ranges in antenna and RCS measurements  

Microsoft Academic Search

With the increased complexity and extended frequency range of operation model measurements and far field test ranges are no longer suitable to satisfy the demand of accurate testing. Moreover plane wave test conditions are required for Radar Cross Section (RCS) measurements which represent a key point in stealth technology. Compact ranges represent the best test facilities available presently since they

B. Audone

1989-01-01

390

Monoidal equivalence for locally compact quantum groups  

Microsoft Academic Search

In this article we investigate the notion of monoidal equivalence for locally compact quantum groups, using the notion of a (bi-)Galois object. If (M, ?) is the von Neumann algebraic realization of a locally comp act quantum group, a Galois object consists of a von Neumann algebra N together with an ergodic integrable coaction ? of M on N, such

Kenny De Commer

391

Topics in conformally compact Einstein metrics  

Microsoft Academic Search

We discuss a number of topics in the area of conformally compact Einstein\\u000ametrics, mostly centered around the global existence question of finding such\\u000ametrics with an arbitrarily prescribed conformal infinity. The paper is partly\\u000aa survey of this area but also presents new results and a number of open\\u000aproblems.

Michael T. Anderson

2005-01-01

392

A compact MMIC balun using spiral transformers  

Microsoft Academic Search

A MMIC balun has been realised using spiral transformers in a Marchand configuration. This arrangement results in a simple, compact design with good performance. Using standard foundry processing, amplitude balance of 0.2 dB and phase balance of 10° was achieved from 2 to 6 GHz

K. S. Ang; S. B. Economides; S. Nam; I. D. Robertson

1999-01-01

393

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

394

Materials needs for compact fusion reactors  

SciTech Connect

The economic prospects for magnetic fusion energy can be dramatically improved if for the same total power output the fusion neutron first-wall (FW) loading and the system power density can be increased by factors of 3 to 5 and 10 to 30, respectively. A number of compact fusion reactor embodiments have been proposed, all of which would operate with increased FW loadings, would use thin (0.5 to 0.6 m) blankets, and would confine quasi-steady-state plasma with resistive, water-cooled copper or aluminum coils. Increased system power density (5 to 15 MWt/m/sup 3/ versus 0.3 to 0.5 MW/m/sup 3/), considerably reduced physical size of the fusion power core (FPC), and appreciably reduced economic leverage exerted by the FPC and associated physics result. The unique materials requirements anticipated for these compact reactors are outlined against the well documented backdrop provided by similar needs for the mainline approaches. Surprisingly, no single materials need that is unique to the compact systems is identified; crucial uncertainties for the compact approaches must also be addressed by the mainline approaches, particularly for in-vacuum components (FWs, limiters, divertors, etc.).

Krakowski, R.A.

1983-01-01

395

ESTEC Mini Compact Antenna Test Range.  

National Technical Information Service (NTIS)

The ESTEC Mini Compact Antenna Test Range (Mini CATR) facility makes it possible to test full size antennas (up to 1.5 m) indoors in a relatively small space. A dual reflector system produces an incident plane wave so that the far field results are obtain...

1987-01-01

396

Hybrid Parallelization of a Compact Genetic Algorithm  

Microsoft Academic Search

Genetic algorithms (GAs) are stochastic optimization heuristics in which searches in solution space are carried out by imitating the population genetics stated in Darwin's theory of evolution. We have focused this work on compact genetic algorithms (cGAs), which unlike standard GAs do not manage a population of solutions but only mimics its existence. We study several approaches that can be

José Ignacio Hidalgo; Manuel Prieto; Juan Lanchares; Ranieri Baraglia; Francisco Tirado; Oscar Garnica

2003-01-01

397

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

398

Indoor radon detected by compact discs  

Microsoft Academic Search

An approach for a precise retrospective assessment of the indoor radon exposure using commercial compact discs (CDs) is proposed. It is based on the remarkable radon absorption and ? track-etch properties of polycarbonate — the basic material of the CDs. The experimental results indicate that the useful range of this approach is able to cover practically the entire range of

D. Pressyanov; J. Buysse; A. Van Deynse; A. Poffijn; G. Meesen

2001-01-01

399

28 CFR 2.107 - Interstate Compact.  

Code of Federal Regulations, 2013 CFR

...Compact Administrator with regard to the following...and carried out with the approval of...the Commission may issue a warrant pursuant...his designee may issue a temporary warrant...period of parole or mandatory release supervision pursuant to a sentence of imprisonment...

2013-07-01

400

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

401

Compact vs. Exponential-Size LP Relaxations.  

National Technical Information Service (NTIS)

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, Lova...

R. D. Carr G. Lancia

2000-01-01

402

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

403

Proposal to Produce Large Compact Toroids.  

National Technical Information Service (NTIS)

Relatively large, hot compact toroids might be produced in the annular space between two concentric one-turn coils. With currents in the two coils flowing in the same direction, the magnetic fields on each side of the plasma are in opposite directions. As...

J. A. Phillips

1981-01-01

404

Extension of a compact Lorentz manifold  

Microsoft Academic Search

For a certain geodesically incomplete, compact Lorentz manifold T, we construct an analytic non-Hausdorff extension in which no geodesic bifurcates. The extension is geodesically incomplete, but is a maximal analytic Lorentz manifold in the sense that any further analytic extension has bifurcating geodesics. We also obtain a maximal analytic Hausdorff extension of the universal covering space of T. The latter

J. G. Miller; M. D. Kruskal

1973-01-01

405

ISM Evolution in Compact Groups of Galaxies  

NASA Astrophysics Data System (ADS)

Compact groups of galaxies provide unique environment to study the evolution of the ISM and mechanisms by which star formation occurs amid continuous gravitational encounters. We present Spitzer, 2MASS, and HI observations of a sample of 12 Hickson Compact Groups (HCGs) that include a total of 45 galaxies. The galaxies in this sample have observed infrared characteristics that are distinctly different from the sample of galaxies in the Spitzer FLS or SINGS. Most notably, HCG galaxies exhibit a "gap" in infrared color space that is sparsely populated and which is not seen in either the FLS or SINGS. This gap may suggest a rapid evolution of galaxy properties in response to dynamical effects in HCGs. Moreover, there are striking trends seen between the ratio of HI mass to dynamical mass for an entire group and the infrared colors of the individual member galaxies. These trends suggest that the constituent galaxies in compact groups are related to the type of group in which they reside. This project provides insight into the build-up of galaxy clusters and fossil groups in the early Universe from structures like compact groups that were much more common. This work has been supported in part by funding from the National Science Foundation, the Spitzer Space Telescope, and the Spitzer Fellowship Program.

Johnson, Kelsey; Hibbard, J.; Gallagher, S.; Charlton, J.; Hornschemeier, A.; Jarrett, T.; Reines, A.

2007-12-01

406

Plowing: Interactive stretching and compaction in magic  

Microsoft Academic Search

The Magic layout editor provides a new operation called plowing, for stretching and compacting Manhattan VLSI layouts. Plowing works directly on the mask-level representation of a layout, allowing portions of it to be rearranged while preserving connectivity and layout-rule correctness. The layout and connectivity rules are read from a file, so plowing is technology independent. Plowing is fast enough to

Walter S. Scott; John K. Ousterhout

1984-01-01

407

Compact attic mounted solar heating pack assembly  

Microsoft Academic Search

A compact attic solar heating pack assembly for mounting within a building attic having south and north facing roof sections overlying a horizontal building attic floor forming the ceiling and defining an enclosed attic space above the occupied room space below the ceiling is described. The pack assembly comprises: a closed sheet metal plenum, means for fixedly mounting the plenum

1988-01-01

408

Refueling tokamaks by injection of compact toroids  

Microsoft Academic Search

It is shown that transverse injection of a hypervelocity high-density spheromak plasmoid into a tokamak plasma may be a viable fueling scheme. Three important processes occur and are discussed individually: establishment of equilibrium, slowing down, and disassembly of the compact toroid.

P. Parks

1988-01-01

409

SONIC AND ULTRASONIC COMPACTION OF UOâ  

Microsoft Academic Search

Two methods for packing nonsintered ceramic fuels by applied vibration ; are described. Vibrationally compacted UOâ is produced with frequencies in ; the sonic range and yr-eld densities of 89 to 94% of the theoretical density ; depending on the diameter of the cladding material. Characteristics of the ; powder and cladding, frequencies and accelerations, particle size distribution, ; and

J. Servais; Cl. Descamps

1961-01-01

410

Compact Linacs for Positron Emission Tomography.  

National Technical Information Service (NTIS)

Compact 14 MeV proton and 7 MeV deuteron linacs for use in positron emission tomography (PET) have been studied, and conceptual designs for low energy beam transports (LEBT), radio-frequency quadrupole (RFQ) and drift tube linacs (DTL) have been achieved....

D. Raparia S. Machida

1989-01-01

411

FABRICATION OF URANIUM OXYCARBIDE KERNELS AND COMPACTS FOR HTR FUEL  

SciTech Connect

As part of the program to demonstrate tristructural isotropic (TRISO)-coated fuel for the Next Generation Nuclear Plant (NGNP), Advanced Gas Reactor (AGR) fuel is being irradiation tested in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). This testing has led to improved kernel fabrication techniques, the formation of TRISO fuel particles, and upgrades to the overcoating, compaction, and heat treatment processes. Combined, these improvements provide a fuel manufacturing process that meets the stringent requirements associated with testing in the AGR experimentation program. Researchers at Idaho National Laboratory (INL) are working in conjunction with a team from Babcock and Wilcox (B&W) and Oak Ridge National Laboratory (ORNL) to (a) improve the quality of uranium oxycarbide (UCO) fuel kernels, (b) deposit TRISO layers to produce a fuel that meets or exceeds the standard developed by German researches in the 1980s, and (c) develop a process to overcoat TRISO particles with the same matrix material, but applies it with water using equipment previously and successfully employed in the pharmaceutical industry. A primary goal of this work is to simplify the process, making it more robust and repeatable while relying less on operator technique than prior overcoating efforts. A secondary goal is to improve first-pass yields to greater than 95% through the use of established technology and equipment. In the first test, called “AGR-1,” graphite compacts containing approximately 300,000 coated particles were irradiated from December 2006 to November 2009. The AGR-1 fuel was designed to closely replicate many of the properties of German TRISO-coated particles, thought to be important for good fuel performance. No release of gaseous fission product, indicative of particle coating failure, was detected in the nearly 3-year irradiation to a peak burn up of 19.6% at a time-average temperature of 1038–1121°C. Before fabricating AGR-2 fuel, each fabrication process was improved and changed. Changes to the kernel fabrication process included replacing the carbon black powder feed with a surface-modified carbon slurry and shortening the sintering schedule. AGR-2 TRISO particles were produced in a 6-inch diameter coater using a charge size about 21-times that of the 2-inch diameter coater used to coat AGR-1 particles. The compacting process was changed to increase matrix density and throughput by increasing the temperature and pressure of pressing and using a different type of press. AGR-2 fuel began irradiation in the ATR in late spring 2010.

Dr. Jeffrey A. Phillips; Eric L. Shaber; Scott G. Nagley

2012-10-01

412

CHARGE syndrome: an update.  

PubMed

CHARGE syndrome is a rare, usually sporadic autosomal dominant disorder due in 2/3 of cases to mutations within the CHD7 gene. The clinical definition has evolved with time. The 3C triad (Coloboma-Choanal atresia-abnormal semicircular Canals), arhinencephaly and rhombencephalic dysfunctions are now considered the most important and constant clues to the diagnosis. We will discuss here recent aspects of the phenotypic delineation of CHARGE syndrome and highlight the role of CHD7 in its pathogeny. We review available data on its molecular pathology as well as cytogenetic and molecular evidences for genetic heterogeneity within CHARGE syndrome. PMID:17299439

Sanlaville, Damien; Verloes, Alain

2007-02-14

413

Charged particle beams  

SciTech Connect

Theoretical and practical aspects of charged-particle beam devices are discussed in an introductory text and reference guide. Topics addressed include the phase-space description of charged-particle beams, beam emittance, beam-generated forces, electron and ion guns, high-power pulsed electron and ion diodes, paraxial beam transport with space charge, and high-current electron-beam transport under vacuum. Consideration is given to ion-beam neutralization, electron beams in plasmas, transverse instabilities, longitudinal instabilities, and the generation of radiation with electron beams. Extensive diagrams and graphs are provided. 111 refs.

Humphries, S. Jr.

1990-01-01

414

Baryon number conservation and enforced electric charge neutrality for bulk viscosity in quark matter  

SciTech Connect

General constraints on fluid velocity divergences for particles in quark matter are derived from baryon number conservation and enforced electric charge neutrality. A new oscillation pattern in three-flavor normal quark matter satisfying these conditions is found and its bulk viscosity is calculated. The result may have astrophysical implication for maximum rotation frequencies of compact stars.

Dong Hui; Wang Qun [Department of Modern Physics, University of Science and Technology of China, Anhui 230026 (China); Su Nan [Frankfurt Institute for Advanced Studies (FIAS), Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany)

2007-04-01

415

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

416

Space charge in proton linacs  

NASA Astrophysics Data System (ADS)

Space charge effects on beam dynamics in linear accelerators are discussed. Practical linac beam dynamics calculation methods which include space charge effects are discussed. Also, the status of beam performance experiments including space charge studies are summarized.

Wangler, T. P.; Merrill, F.; Rybarcyk, L.; Ryne, R.

1998-11-01

417

Nuclear Charge Distributions.  

National Technical Information Service (NTIS)

The Hartree-Fock (HF) and Single-Particle Potential (SPP) methods of calculating nuclear charge distributions are reviewed with particular reference to their value for understanding nuclear structure. The development of the SPP method is described in deta...

F. Malaguti A. Uguzzoni E. Verondini P. E. Hodgson

1981-01-01

418

New Charged Particle Detectors.  

National Technical Information Service (NTIS)

The objectives of the program were to perform experimental investigations directed toward the design and fabrication of new charged particle detectors. The particle detectors are to be used in satellite, rocket, and laboratory experiments to study the mag...

V. J. Belanger

1970-01-01

419

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

420

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

421

Compact Microscope Imaging System With Intelligent Controls Improved.  

National Technical Information Service (NTIS)

The Compact Microscope Imaging System (CMIS) with intelligent controls is a diagnostic microscope analysis tool with intelligent controls for use in space, industrial, medical, and security applications. This compact miniature microscope, which can perfor...

M. McDowell

2004-01-01

422

Off-equatorial orbits in strong gravitational fields near compact objects—II: halo motion around magnetic compact stars and magnetized black holes  

NASA Astrophysics Data System (ADS)

Off-equatorial circular orbits with constant latitudes (halo orbits) of electrically charged particles exist near compact objects. In the previous paper, we discussed this kind of motion and demonstrated the existence of minima of the two-dimensional effective potential which correspond to the stable halo orbits. Here, we relax previous assumptions of the pseudo-Newtonian approach for the gravitational field of the central body and study properties of the halo orbits in detail. Within the general relativistic approach, we carry out our calculations in two cases. Firstly, we examine the case of a rotating magnetic compact star. Assuming that the magnetic field axis and the rotation axis are aligned with each other, we study the orientation of motion along the stable halo orbits. In the poloidal plane, we also discuss shapes of the related effective potential halo lobes where the general off-equatorial motion can be bound. Then we focus on the halo orbits near a Kerr black hole immersed in an asymptotically uniform magnetic field of external origin. We demonstrate that, in both the cases considered, the lobes exhibit two different regimes, namely one where completely disjoint lobes occur symmetrically above and below the equatorial plane, and another where the lobes are joined across the plane. A possible application of the model concerns the structure of putative circumpulsar discs consisting of dust particles. We suggest that the particles can acquire a small (but non-zero) net electric charge, and this drives them to form the halo lobes.

Ková?, J.; Kopá?ek, O.; Karas, V.; Stuchlík, Z.

2010-07-01

423

Experimental simulations of beam propagation over large distances in a compact linear Paul trap  

NASA Astrophysics Data System (ADS)

The Paul Trap Simulator Experiment (PTSX) is a compact laboratory experiment that places the physicist in the frame of reference of a long, charged-particle bunch coasting through a kilometers-long magnetic alternating-gradient (AG) transport system. The transverse dynamics of particles in both systems are described by similar equations, including nonlinear space-charge effects. The time-dependent voltages applied to the PTSX quadrupole electrodes are equivalent to the axially oscillating magnetic fields applied in the AG system. Experiments concerning the quiescent propagation of intense beams over large distances can then be performed in a compact and flexible facility. An understanding and characterization of the conditions required for quiescent beam transport, minimum halo particle generation, and precise beam compression and manipulation techniques, are essential, as accelerators and transport systems demand that ever-increasing amounts of space charge be transported. Application areas include ion-beam-driven high energy density physics, high energy and nuclear physics accelerator systems, etc. One-component cesium plasmas have been trapped in PTSX that correspond to normalized beam intensities, ?=?p2(0)/2?q2, up to 80% of the space-charge limit where self-electric forces balance the applied focusing force. Here, ?p(0)=[nb(0)eb2/mb?0]1/2 is the on-axis plasma frequency, and ?q is the smooth-focusing frequency associated with the applied focusing field. Plasmas in PTSX with values of ? that are 20% of the limit have been trapped for times corresponding to equivalent beam propagation over 10 km. Results are presented for experiments in which the amplitude of the quadrupole focusing lattice is modified as a function of time. It is found that instantaneous changes in lattice amplitude can be detrimental to transverse confinement of the charge bunch.

Gilson, Erik P.; Chung, Moses; Davidson, Ronald C.; Dorf, Mikhail; Efthimion, Philip C.; Majeski, Richard

2006-05-01

424

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

425

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

2013-01-01

426

Study of Underwater Shock Compaction Device for Compaction of Titanium Diboride  

NASA Astrophysics Data System (ADS)

Shock compaction for powders has been used to study bulk consolidation of powder materials. Shock compaction has the advantage of processing at low temperatures and short duration to limit effects of high temperatures for long times, such as increased grain size and high energy cost. Many methods of shock loading of powders have been employed: direct contact with explosive, explosively driven flyer plates, and flyer plates launched with light gas or propellant gun. Another method, using explosives to create a shockwave in water that is then contact with a powder container, has been used extensively at Kumamoto University. This work presents a study of the development of the underwater shockwave device and investigates the water container geometry for control of parameters for shockwave peak pressure, duration, and distribution through the powder compaction process. Results of simulations for optimization of shock compaction properties are presented along with measurements from manganin gauge pressure measurements obtained from underwater shock compaction of titanium diboride. The goal of this work is to develop a better understanding of the entire compaction process to utilize the in-situ data to modify numerical simulations to predict performance.

Kennedy, G. B.; Kim, Y. K.; Hokamoto, K.; Itoh, S.

2007-12-01

427

Study of Underwater Shock Compaction Device for Compaction of Titanium Diboride Powder  

NASA Astrophysics Data System (ADS)

Shock compaction for powders has been used to study bulk consolidation of powder materials. Shock compaction has the advantage of processing at low temperatures and short duration to limit effects of high temperatures for long times, such as increased grain size and high energy cost. Many methods of shock loading of powders have been employed: direct contact with explosive, explosively driven flyer plates, and flyer plates launched with light gas or propellant gun. Another method, using explosives to create a shockwave in water that is in contact with a powder container, has been used extensively at Kumamoto University. This work presents a study of the development of the underwater shockwave device and investigates the water container geometry for control of parameters for shockwave peak pressure, duration, and distribution through the powder compaction process. Results of simulations for optimization of shock compaction properties are presented along with measurements from input and propagated manganin gauge pressure measurements obtained from underwater shock compaction of titanium diboride. The hardness measurements throughout the bulk of the shock compacted titanium diboride are discussed.

Kennedy, G. B.; Kim, Y. K.; Hokamoto, K.; Itoh, S.

2007-06-01

428

Correlation between the charge of proteins in solution and in the gas phase investigated by protein charge ladders, capillary electrophoresis, and electrospray ionization mass spectrometry  

SciTech Connect

Charge ladders of bovine carbonic anhydrase II, hen egg-white lysozyme, and bovine pancreatic trypsin inhibitor, prepared by partial acetylation of primary amino groups on the surface of the protein, have been analyzed by capillary electrophoresis (CE) and on-line electrospray ionization mass spectrometry (ESIMS) using solution conditions that maintain the native structure of the protein. CE was used to separate the proteins that constitute the charge ladder into individual rungs-protein derivatives that have the same number of acetylated amino groups and approximately the same net charge in solution. ESI was used to produce ions i the gas phase of the proteins that constitute each rung of the charge ladder; the mass spectra of these ions were obtained and analyzed. The distributions in charge states observed in the gas phase for the groups of proteins comprising each rung of the charge ladders were narrow, consistent with the retention of a compact structure of the proteins in the gas phase, and substantially independent of the number of acetylated amino groups. The ions observed in the gas phase had surface charge densities in a relatively narrow range of {approximately}0.9--1.5 units of charge per 10{sup 3}{angstrom}{sup 2} of surface area (as estimated from crystallographic structures). These results demonstrate that the distribution of charge states for proteins produced in the gas phase by ESI do not necessarily reflect the net charge of the protein in solution or the number of amino groups on the protein.

Carbeck, J.D.; Gao, J.; Smith, R.D.; Whitesides, G.M. [Harvard Univ., Cambridge, MA (United States). Dept. of Chemistry and Chemical Biology; Severs, J.C.; Wu, Q. [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Science Lab.

1998-12-17

429

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

430

Pure and shear-enhanced compaction bands in Aztec Sandstone  

Microsoft Academic Search

We report on the occurrence of deformation bands in Jurassic eolian Aztec Sandstone at Valley of Fire, Nevada, that accommodated roughly equal amounts of shear and band-perpendicular compaction by grain rearrangement and porosity collapse. These bands, referred to as shear-enhanced compaction bands, differ in orientation, structural arrangement, and microtexture from pure compaction bands that form perpendicular to the shortening direction.

Peter Eichhubl; John N. Hooker; Stephen E. Laubach

2010-01-01

431

Compaction of deep sea siliciclastic sediments based on log data  

Microsoft Academic Search

Compaction models, describing variations of velocity, density and porosity with depth, are important in basic and applied studies of the Earth. Many so-called global compaction trends have been proposed for different types of sedimentary rocks, but there is very little agreement among these published compaction trends. These differences are likely due partly to type of data analyses (e.g., cores vs.

Olga Brusova

2011-01-01

432

Die compaction of copper powder designed for material parameter identification  

Microsoft Academic Search

This article presents uniaxial compaction experiments of a fine copper powder in a cylindrical die. The compaction process consists of monotonic loading and of loading paths with inserted unloading and reloading cycles. An experimental setup that has been developed for determining the axial and radial stresses during the compaction is described and the calibration of the new device using highly

W. Bier; M. P. Dariel; N. Frage; S. Hartmann; O. Michailov

2007-01-01

433

Compaction of amorphous ferromagnetic metal powders. Final report  

Microsoft Academic Search

The attractive magnetic properties of certain amorphous metal powders might be exploited in the electrical industry if the powders could be consolidated into relatively dense compacts. This work attempted to produce integral bodies of an amorphous powder using explosive compaction techniques. A disk-shaped compact 2.5 cm in diameter by 1 cm thick having a relative measured density of 91% was

Caligiuri

1982-01-01

434

Flow characteristics in dynamically compacted soft porous materials  

Microsoft Academic Search

The dynamic behavior of soft compressible porous media undergoing uniform axial compaction was investigated experimentally in our unique cylinder-piston apparatus that has been used successfully in our previous work with snow compaction. Several synthetic porous materials have been tested and characterized under compression time scales below 0.2 sec. Excess pore pressure has been generated during dynamic compaction which is due

Michel Al Chidiac; Yiannis Andreopoulos; Sheldon Weinbaum

2007-01-01

435

The Digital Correction Unit: A Data Correction\\/Compaction Chip  

Microsoft Academic Search

The Digital Correction Unit (DCU) is a semi-custom CMOS integrated circuit which corrects and compacts data for the SLD experiment. It performs a piece-wise linear correction to data, and implements two separate compaction algorithms. This paper describes the basic functionality of the DCU and its correction and compaction algorithms.

S. MacKenzie; B. Nielsen; L. Paffrath; J. Russell; D. Sherden

1987-01-01

436

The Social Compact of Higher Education and Its Public  

Microsoft Academic Search

compact is such a civilized idea. It evokes an atmosphere of amicability and trust—the community interest placed foremost, everyone honorable, no accountability needed. The idea of a compact creates a far different image from a treaty, or even a contract. Indeed, most of us like to think of the time when there was a social compact concerning higher education. The

Larry Faulkner

437

Fault diagnosis aware ATE assisted test response compaction  

Microsoft Academic Search

Recently a new method called ATE assisted compaction for achieving test response compaction has been proposed. The method relies on testers to achieve additional compaction, without compromising fault coverage, beyond what may already be achieved using on-chip response compactors. The method does not add additional logic or modify the circuit under test or require additional tests and thus can be

J. M. Howard; Sudhakar M. Reddy; Irith Pomeranz; Bernd Becker

2011-01-01

438

A Study of Effective Soil Compaction Control of Granular Soils  

Microsoft Academic Search

Although it is known that impact compaction tests are not appropriate for granular soils, these tests continue to be widely used. Excessive settlements frequently occur in granular soils where specified field compaction is based on Standard Proctor (ASTM D 698; AASHTO T 99) maximum dry unit weights. A laboratory test program evaluated alternative test methods for granular soil compaction control

Vincent P. Drnevich; Aaron C. Evans; Adam Buser Prochaska

2007-01-01

439

CRIGOS: a compact robot for image-guided orthopedic surgery  

Microsoft Academic Search

The CRIGOS (compact robot for image-guided orthopedic surgery) project was set up for the development of a compact surgical robot system for image-guided orthopedic surgery based on user requirements. The modular system comprises a compact parallel robot and a software system for planning of surgical interventions and for supervision of the robotic device. Because it is not sufficient to consider

Guido Brandt; Andreas Zimolong; Lionel Carrat; Philippe Merloz; Hans-Walter Staudte; Stéphane Lavallée; Klaus Radermacher; Günther Rau

1999-01-01

440

Agronomic consequences of tractor wheel compaction on a clay soil  

Microsoft Academic Search

In southern New South Wales, Australia, farming operations using tractors often occur when the soils are moist and prone to soil compaction. However, the extent of soil compaction and its relative impact on crop yield have not been quantified in the region. In this experiment, re-compaction due to tractor wheel traffic in a sodic brown clay (Vertisol) was monitored under

K. Y. Chan; A. Oates; A. D. Swan; R. C. Hayes; B. S. Dear; M. B. Peoples

2005-01-01

441

Compaction Conditions, States Variables and Engineering Properties of Compacted Clay (Condiciones de Compactacion y Propiedades Mecanicas de Suelos Compactados).  

National Technical Information Service (NTIS)

Soil compaction is a means to produce a construction material whose properties fit the mechanical-including hydraulic- requirements of intended structures. Hence compaction conditions are to be selected for each particular case taking into account the rel...

D. Resendiz

1980-01-01

442

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

443

Experimental test of the radial force balance equation in the compact helical system  

NASA Astrophysics Data System (ADS)

Experimental test of the radial force balance equation was done in the Compact Helical System Heliotron/Torsatron [S. Okamura et al. Nucl. Fusion 39, 1337 (1999)]. A radial electric field is measured with a heavy ion beam probe, while plasma rotation and drift velocity of fully ionized carbon are measured with charge exchange spectroscopy. The two measurements agree with each other to within 10% of the radial electric field in a wide range of electron densities of 0.3-2.0×1019 m-3.

Ida, K.; Fujisawa, A.; Iguchi, H.; Yoshimura, Y.; Minami, T.; Okamura, S.; Nishimura, S.; Isobe, M.; Kado, S.; Liang, Y.; Nomura, I.; Tanaka, K.; Osakabe, M.; Takahashi, C.; Matsuoka, K.

2001-01-01

444

Logarithmic triviality of compact QED coupled to a four-Fermi interaction  

SciTech Connect

This is the completion of an exploratory study of compact lattice quantum electrodynamics with a weak four-Fermi interaction and four species of massless fermions. In this formulation of quantum electrodynamics massless fermions can be simulated directly and finite size scaling analyses can be performed at the theory's chiral symmetry breaking critical point. High statistics simulations on lattices ranging from 8{sup 4} to 24{sup 4} yield the equation of state, critical indices, scaling functions and cumulants. The measurements are well fit with the orthodox hypothesis that the theory is logarithmically trivial and its continuum limit suffers from Landau's zero charge problem.

Kogut, John B. [Physics Department, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-30 (United States); Strouthos, Costas G. [Department of Physics, University of Cyprus, CY-1678 Nicosia (Cyprus)

2005-05-01

445

Color-spin locking phase in two-flavor quark matter for compact star phenomenology  

SciTech Connect

We study a spin-1 single-flavor color-superconducting phase which results from a color-spin locking (CSL) interaction in two-flavor quark matter. This phase is particularly interesting for compact star cooling applications since the CSL phase may survive under charge neutrality constraints implying a mismatch between up- and down-quark chemical potentials which can destroy the scalar diquark condensate. CSL gaps are evaluated within an NJL model and they are found to be consistent with cooling phenomenology if a density dependent coupling constant is used.

Aguilera, D. N. [Institut fuer Physik, Universitaet Rostock, Universitaetsplatz 3, 18051 Rostock (Germany); Blaschke, D. [Gesellschaft fuer Schwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt (Germany); Bogoliubov Laboratory of Theoretical Physics, JINR Dubna, Joliot-Curie Street 6, 141980 Dubna (Russian Federation); Buballa, M. [Institut fuer Kernphysik, TU Darmstadt, Schlossgartenstr. 9, 64289 Darmstadt (Germany); Yudichev, V.L. [Bogoliubov Laboratory of Theoretical Physics, JINR Dubna, Joliot-Curie Street 6, 141980 Dubna (Russian Federation)

2005-08-01

446

Influence of the shape factor on efficiency of the green compact ultrasonic compacting and properties of sintered zirconia ceramics  

Microsoft Academic Search

The properties of green compacts and ceramics from ZrO2-Y2O3 nanopowder compacted under ultrasonic action (power of 0.5; 1; 2; 3 kW) were studied. The shape factor of the green compacts (the ratio of height to diameter) was h\\/D=0.05 and 0.37. Phase constitution, grain structure, density and shrinkage, of ceramics sintered at 1650°C from the green compacts with different h\\/D, were

O. L. Khasanov; Jae-Shin Lee; Yu. P. Pokholkov; E. S. Dvilis; V. M. Sokolov; Byung-Gi An

2000-01-01

447

Thermally efficient compact fluorescent fixture systems  

SciTech Connect

Compact fluorescent lamps that can be inserted into conventional light fixtures are rapidly gaining acceptance as both a viable retrofit and new design approach to reducing lighting loads. Ideally, the compact fluorescent lamp should have the same light output as the incandescent lamp it replaces, but overheating inside typically small enclosed fixtures can reduce lumen output and hence lighting fixture efficiency by 15 to 20 percent. Fortunately, simple fixture modifications can erase this efficiency penalty, so that the full efficiency benefit of replacing incandescent lamps with fluorescent lamps can be realized. The paper describes such modifications and presents experimental data documenting the potential efficiency enhancement associated with thermal control systems. 4 refs., 7 figs.

Siminovitch, M.J.; Rubinstein, F.M.; Packer, M.

1991-04-01

448

Computer design of a compact cyclotron  

NASA Astrophysics Data System (ADS)

Here we present results of the computer design of the structural elements of a compact cyclotron by the example of HITFiL cyclotron selected as the driving accelerator that is under construction at the Institute of Modern Physics (Lanzhou, China). In the article a complex approach to modeling of the compact cyclotron, including calculation of electromagnetic fields of the structural elements and beam dynamics calculations, is described. The existing design data on the axial injection, magnetic, acceleration and extraction systems of the cyclotron are used as a starting point in the simulation. Some of the upgrades of the cyclotron structural elements were proposed, which led to substantial improvement of the beam quality and transmission.

Wang, Bing; Hao, Huanfeng; Vorozhtsov, S. B.; Smirnov, V. L.; Yao, Qinggao; Zhang, Jinquan; Song, Mingtao; Zhao, Hongwei

2012-05-01

449

Blue Blobs in Compact Groups of Galaxies  

NASA Astrophysics Data System (ADS)

We report the discovery of a population of young blue objects, similar to M81/M82 blue blobs (de Mello et al. 2008), outside galaxies in compact groups. These blue blobs were found using multiwavelength data (UV, HI, optical) for the compact groups of galaxies HCG 2, 7, 22, 23, 92, 100 and NGC 92 which are in different stages of interaction. We find that all three evolved groups, HCG92, HCG100 and NGC 92, contain a population of young blue objects consistent with having ages < 100 Myr. Moreover, they also show extended HI tails and peculiar velocity field. Our results indicate that the blue blobs are stellar clusters and/or dwarf galaxies formed in the intra-group HI clouds of groups in advanced stage of interaction .

De Mello, Duilia F.; Torres-Flores, S.; Mendes de Oliveira, C.

2009-01-01

450

Compact inductive energy storage pulse power system.  

PubMed

An inductive energy storage pulse power system is being developed in BARC, India. Simple, compact, and robust opening switches, capable of generating hundreds of kV, are key elements in the development of inductive energy storage pulsed power sources. It employs an inductive energy storage and opening switch power conditioning techniques with high energy density capacitors as the primary energy store. The energy stored in the capacitor bank is transferred to an air cored storage inductor in 5.5 ?s through wire fuses. By optimizing the exploding wire parameters, a compact, robust, high voltage pulse power system, capable of generating reproducibly 240 kV, is developed. This paper presents the full details of the system along with the experimental data. PMID:22667637

K, Senthil; Mitra, S; Roy, Amitava; Sharma, Archana; Chakravarthy, D P

2012-05-01

451

Compact ranges in antenna and RCS measurements  

NASA Astrophysics Data System (ADS)

With the increased complexity and extended frequency range of operation model measurements and far field test ranges are no longer suitable to satisfy the demand of accurate testing. Moreover plane wave test conditions are required for Radar Cross Section (RCS) measurements which represent a key point in stealth technology. Compact ranges represent the best test facilities available presently since they allow for indoor measurements under far field conditions in real time without any calculation effort. Several types of compact ranges are described and compared discussing their relevant advantages with regard to RCS and antenna measurements. In parallel to measuring systems sophisticated computer models were developed with such a high level of accuracy that it is questionable whether experiments give better results than theory. Tests performed on simple structures show the correlation between experimental results and theoretical ones derived on the basis of GTD computer codes.

Audone, B.

1989-09-01

452

[Oversupercoiling and compactization of supercoiled DNA].  

PubMed

Supercoiled DNA pGEMEX with length of 3993 nucleotides was immobilized on the different substrates (freshly cleaved mica, standard aminomica and modified aminomica) and visualized by atomic force microscopy. Plectonomically supercoiled DNA molecules as well as molecules with extremely high level of compactization (i.e. molecules with considerably higher supercoiled density values in comparing with experimentally measured and theoretically investigated ones) were visualized on modified aminomica. At the further increasing of the compactization level an axis length of oversupercoiled molecules was decreased from approximately 390 nm to approximately 140 nm and formation of minitoroids of approximately 50 nm diameter and molecules in sphere conformation were observed. Model of possible conformational transitions of supercoiled DNA was proposed basing on the analysis of captured AFM images at the increasing of supercoiling density. PMID:16161416

Lymans'ky?, O

453

Compact fast analyzer of rotary cuvette type  

DOEpatents

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 optical passageways for the absorbance and fluorescence measurement systems. The frame also serves as a mounting structure for various optical components as well as for the cuvette rotor mount and drive system. A single light source and photodetector are used in making both absorbance and fluorescence measurements. Rotor removal and insertion are facilitated by a swing-out drive motor and rotor mount. BACKGROUND OF THE INVENTION The invention relates generally to concentration measuring instruments and more specifically to a compact fast analyzer of the rotary cuvette type which is suitable for making either absorbance or fluorescence measurements. It was made in the course of, or under, a contract with the U.S. Atomic Energy Commission.

Thacker, Louis H. (Knoxville, TN)

1976-01-01

454

Compact disc serial number inspection system  

NASA Astrophysics Data System (ADS)

This paper presents a reliable neural network based system for compact disc serial number inspection. Four major steps are performed in this system, namely polar image conversion, segmentation, recognition, and verification. Polar image conversion straightens the circular stripe images containing the serial numbers to horizontally linear images, segmentation divides the images into separate character segments, recognition classifies the separate character segments by a trained neural network, and verification double checks the characters with their verification neural networks if the serial number is known. Special back-propagation training processes for recognition and verification neural networks are used to increase the system's performance. Excellent recognition results for this system implemented in the Sony SUPER vision system have been obtained. Moreover, this system can process more than 3 compact discs in one second.

Oki, Toru; Paolella, Philip; Chiu, Chinchuan

1993-09-01

455

Progress Toward Improved Compact Stellarator Designs  

NASA Astrophysics Data System (ADS)

Stellarators offer robust physics solutions for MFE challenges-- steady-state operation, disruption elimination, and high-density operation-- but require design improvements to overcome technical risks in the construction and maintenance of future large-scale stellarators. Using the ARIES-CS design (aspect ratio 4.56) as a starting point, compact stellarator designs with improved maintenance characteristics have been developed. By making the outboard legs of the main magnetic field coils nearly straight and parallel, a sector maintenance scheme compatible with high availability becomes possible. Approaches that can allow the main coil requirements to be relaxed in this way are: 1) increase aspect ratio at the expense of compactness, 2) add local removable coils in the maintenance ports for plasma shaping, and 3) use passive conducting tiles made of bulk high-temperature superconducting material to help shape the magnetic field. Such tiles would be arranged on a shaped, segmented internal support structure behind the shield.

Neilson, G. H.; Brown, T.; Gates, D.; Ku, L. P.; Lazerson, S.; Pomphrey, N.; Reiman, A.; Zarnstorff, M.; Bromberg, L.; Boozer, A.; Harris, J.

2010-11-01

456

Compact de-NOxer for automotive exhaust  

SciTech Connect

Our two year project concluded with mixed results. The basic idea of using ozone and hydroxyl radical in a two stage plasma chemical reactor to remove NO{sub x} from automotive exhaust proved to be correct. However we found the energy needed to operate the plasma chemical reactor is 30% of the engine`s output, which is three times larger than that of the conventional catalytic converter. Our project is a partial success. If compactness is dropped as a requirement for our plasma-chemical reactor so that it is applicable to stationary rather than mobile power generators, then the reactor needs only 5% of the engine`s power. The energy inefficient component of the reactor, the part which makes our reactor compact, would be unnecessary. Thus our reactor has the potential for being a practical device to remove the NO{sub x} from the emissions of power plants.

Chang, B.; Garcia, M.

1996-06-01

457

Compact inductive energy storage pulse power system  

NASA Astrophysics Data System (ADS)

An inductive energy storage pulse power system is being developed in BARC, India. Simple, compact, and robust opening switches, capable of generating hundreds of kV, are key elements in the development of inductive energy storage pulsed power sources. It employs an inductive energy storage and opening switch power conditioning techniques with high energy density capacitors as the primary energy store. The energy stored in the capacitor bank is transferred to an air cored storage inductor in 5.5 ?s through wire fuses. By optimizing the exploding wire parameters, a compact, robust, high voltage pulse power system, capable of generating reproducibly 240 kV, is developed. This paper presents the full details of the system along with the experimental data.

K, Senthil; Mitra, S.; Roy, Amitava; Sharma, Archana; Chakravarthy, D. P.

2012-05-01

458

Characteristics of oscillating compact hydrogen masers  

SciTech Connect

The design, fabrication and test of the oscillating compact maser, CHYMNS-I, has been previously described. The objective of CHYMNS-1 was to demonstrate that a cavity Q-enhancement technique can be used to obtain sustained maser oscillation in a compact cavity. The superior signal-to-noise ratio of an oscillator and the simplified electronics would facilitate the development of a frequency standard of excellent performance. Obviously, an effective electronic cavity stabilization servo system would be essential to overcome the susceptibility of an external feedback system to environmental perturbations. On the other hand, such a system would provide improved long term maser performance compared to conventional masers where cavity stabilization is based on thermal/mechanical considerations. The objective of CHYMNS-I was successfully accomplished.

Wang, H.T.M.

1982-01-01

459

Compact linacs for positron emission tomography  

SciTech Connect

Compact 14 MeV proton and 7 MeV deuteron linacs for use in positron emission tomography (PET) have been studied, and conceptual designs for low energy beam transports (LEBT), radio-frequency quadrupole (RFQ) and drift tube linacs (DTL) have been achieved. The machines are compact and simple enough to be operated in hospitals. The LEBT consist of two Einzel lenses and are about 25 cm long. The 425 MHz proton RFQ is designed for 50 mA peak current, and the 425 MHz deuteron RFQ is designed for 25 mA peak current. Both 850 MHz DTLs use permanent quadrupole magnets and have high acceleration field of 15 MV/m with a peak field of twice the Kilpatrick limit. 6 refs., 5 figs., 2 tabs.

Raparia, D.; Machida, S.

1989-01-01

460

Compact, narrow bandwidth, lumped element bandstop resonators  

Microsoft Academic Search

This letter describes the design and simulation of novel, highly compact, lumped element bandstop resonators. The resonators are fabricated using copper microstrip lines, with resonant frequencies around 5GHz but with areas of only 1.075mm × 1.275mm. Each resonator consists of 8 interdigital capacitive fingers in parallel with a straight line inductor. The new design offers at least a 40% size

Zaid Aboush; Adrian Porch

2005-01-01

461

How Massive are Massive Compact Galaxies?  

Microsoft Academic Search

Using a sample of nine massive compact galaxies at z ~ 2.3 with rest-frame\\u000aoptical spectroscopy and comprehensive U through 8um photometry we investigate\\u000ahow assumptions in SED modeling change the stellar mass estimates of these\\u000agalaxies, and how this affects our interpretation of their size evolution. The\\u000aSEDs are fit to Tau-models with a range of metallicities, dust laws,

Adam Muzzin; Pieter van Dokkum; Marijn Franx; Danilo Marchesini; Mariska Kriek; Ivo Labbé

2009-01-01

462

Shock compaction of Fe-Nd-B  

Microsoft Academic Search

Shock compaction was performed using the 6.5-m-long two-stage light gas gun facility at LLNL on powders of Fe74Nd20B6, 10–20 ?m in size which were prepared using conventional powder metallurgical techniques. The behavior of Fe-Nd-B powders and Fe-Nd-B powders blended with 10 vol. % Al was examined. X-ray-diffraction experiments detected no discernable difference in phase distribution or crystallinity when shock pressures

Mahesh Chandramouli; Gareth Thomas; W. J. Nellis

1993-01-01

463

Residual stresses in polycrystalline diamond compacts  

Microsoft Academic Search

The thermal residual macrostresses in a series of polycrystalline diamond compacts were studied using neutron diffraction. Measurements were made of (1) the average in-plane stress in the polycrystalline diamond table as a function of substrate-to-table thickness ratio; (2) the average in-plane residual stress gradient in both the WC–Co substrate and the diamond table; and, (3) the radial and hoop components

A. D. Krawitz; R. Andrew Winholtz; E. F. Drake; N. D. Griffin

1999-01-01

464

Compact Compton polarimeter utilizing silicon drift detectors  

Microsoft Academic Search

A compact 90 degree-Compton scatter polarimeter has been developed to be used for energy resolved linear polarization analysis of Parametric X-radiation (PXR) in the energy range below 10 keV. The polarimeter employs 4 thermoelectrically cooled silicon drift detectors of excellent noise performance directed at a conical beryllium scatterer under azimuths spaced by 45 degrees to measure the azimuthal modulation of

Jan They; Gerd Buschhorn; Rainer Kotthaus; V. L. Morokhovskii; Dmitry Pugachev

2000-01-01

465

Compact, low jitter, triggered spark gap  

Microsoft Academic Search

High energy particle accelerators using compact, high gradient cavities will require small, highly reliable, triggered spark gaps. This paper will discuss the design and development of V\\/N triggered spark gaps operating from 520 kV to 1280 kV. Spark gap jitter of <3 ns has been obtained with trigger voltages of 60 kV. Capacitively balancing the trigger blade electrode, coupled with

W. K. Tucker; E. E. Jones; T. L. Franklin; L. F. Bennett; G. Weber

1985-01-01

466

Completeness of bispectrum on compact groups  

Microsoft Academic Search

This paper derives completeness properties of the bispectrum for compact groups and their homogeneous spaces. The bispectrum is the Fourier transform of the triple correlation, just as the magnitude-squared spectrum is the Fourier transform of the autocorrelation. The bispectrum has been applied in time series analysis to measure non-Gaussianity and non-linearity. It has also been applied to provide orientation and

Ramakrishna Kakarala

2009-01-01

467

Superconducting compact sources for lithography (invited)  

SciTech Connect

The production of advanced microchips by x-ray lithography seems likely to become the first large-scale industrial application of synchrotron radiation. Of all the possible x-ray sources, only storage rings have sufficent power to achieve economic throughputs. For this reason, many rings have been and are being built worldwide for lithography. Superconducting rings are preferred because their higher magnetic fields make them more compact.

Wilson, M.N. (Oxford Instruments, Ltd., Osney Mead, Oxford OX2 ODX (United Kingdom))

1992-01-01

468

Electrolyte diffusion in compacted montmorillonite engineered barriers  

SciTech Connect

The bentonite-based engineered barrier or packing is a proposed component of several designs conceived to dispose of high-level nuclear waste in geologic repositories. Once radionuclides escape the waste package, they must first diffuse through the highly impermeable clay-rich barrier before they reach the host repository. To determine the effectiveness of the packing as a sorption barrier in the transient release period and as a mass-transfer barrier in the steady release period over the geologic time scales involved in nuclear waste disposal, a fundamental understanding of the diffusion of electrolytes in compacted clays is required. We present, and compare with laboratory data, a model quantifying the diffusion rates of cationic cesium and uncharged tritium in compacted montmorillonite clay. Neutral tritium characterizes the geometry (i.e., tortuosity) of the particulate gel. After accounting for cation exchange, we find that surface diffusion is the dominant mechanism of cation transport, with an approximate surface diffusion coefficient of 2 x 10 W cmS/s for cesium. This value increases slightly with increasing background ionic strength. The implications of this work for the packing as a migration barrier are twofold. During the transient release period, K/sub d/ values are of little importance in retarding ion migration. This is because sorption also gives rise to a surface diffusion path, and it is surface diffusion which controls the diffusion rate of highly sorbing cations in compacted montmorillonite. During the steady release period, the presence of surface diffusion leads to a flux through the packing which is greatly enhanced. In either case, if surface diffusion is neglected, the appropriate diffusion coefficient of ions in compacted packing will be in considerable error relative to current design recommendations. 11 refs., 4 figs., 1 tab.

Jahnke, F.M.; Radke, C.J.

1985-09-01

469

An ultra-compact Marx HV generator  

Microsoft Academic Search

Summary form only given, as follows. This paper discusses the development and testing of an ultracompact, Marx-type, high-voltage generator. This system incorporates high-performance components that are integrated into an extremely compact assembly. Custom, low-profile, annular ceramic capacitors with coplanar extended electrodes provide primary energy storage, and are operated at 60 kV\\/cm stress levels. Low-inductance, spark gap switches are used for

D. A. Goerz; T. J. Ferriera; D. H. Nelson; R. D. Speer; M. J. Wilson

2001-01-01

470

Compact middle infrared zoom lens design  

Microsoft Academic Search

A compact mid-wavelength infrared zoom camera with a zoom range of 15:1 and active athermalization has been developed. The moving groups for a wide zoom range are only two lens groups and moving machanisms of zoom are very simple, which allows easy access of opto-mechanical and electromechanical design. The final design adopts the configuration of reflective mirror fold, comprising of

Xuan-Zhi Zhang; Ming-Yin Jiao; Yadong Luan; Wei-Jun Chang; Ting Sun

2011-01-01

471

Growing Magnetic Fields in Central Compact Objects  

NASA Astrophysics Data System (ADS)

We study the effects of growth models of magnetic fields in Central Compact Objects (CCOs). Such a field evolution is not a new idea (Blandford, Applegate, & Hernquist 1983) but the evolutionary implications not have been followed up completely (Michel 1994). We discussed the new class of neutron stars which belong to five main types that have mainly been recognized in the last ten years. The possibility that a rapid weakly magnetized pulsar might have formed in SN1987A is commented.

Bernal, C. G.; Page, D.

2011-10-01

472

Compact upwind schemes on adaptive octrees  

Microsoft Academic Search

Compact high-order upwind schemes using reconstruction from cell-averages are derived for application with the compressible three-dimensional Navier–Stokes equations. An adaptive-octree mesh, combined with the Adams–Bashforth–Moulton family of predictor–corrector schemes, provides a conservative high-order time-integration platform supporting localized h-refinement and timestep sub-cycling. Numerical examples for smooth flows demonstrate the improvement over explicit upwind schemes and formal accuracy of the schemes, as

Scott M. Murman

2010-01-01

473

Compact upwind schemes on adaptive octrees  

Microsoft Academic Search

Compact high-order upwind schemes using reconstruction from cell-averages are derived for application with the compressible three-dimensional Navier-Stokes equations. An adaptive-octree mesh, combined with the Adams-Bashforth-Moulton family of predictor-corrector schemes, provides a conservative high-order time-integration platform supporting localized h-refinement and timestep sub-cycling. Numerical examples for smooth flows demonstrate the improvement over explicit upwind schemes and formal accuracy of the schemes, as

Scott M. Murman

2010-01-01

474

Compact supercontinuum sources and their biomedical applications  

NASA Astrophysics Data System (ADS)

Recent developments of compact white-light supercontinuum laser sources are reviewed. Basically these sources make use of a sub-nanosecond microchip laser and a photonic crystal fiber, leading to spectral broadening in the ultraviolet, visible and infrared ranges. The applicability of such supercontinuum sources to the biomedical field is introduced, with the demonstration of promising results in flow cytometry, CARS microscopy and optical coherence tomography. Their attractive benefits in terms of size, robustness, stability and cost are highlighted.

Labruyère, Alexis; Tonello, Alessandro; Couderc, Vincent; Huss, Guillaume; Leproux, Philippe

2012-09-01