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1

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

E-print Network

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 (TOV) 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 \\gamma=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.

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

2013-09-17

2

Charged Polytropic Stars and Quasiblack Holes  

NASA Astrophysics Data System (ADS)

We present results concerning the existence of static electrically charged spheres made by a charged perfect fluid with polytropic equation of state that are arbitrarily close to a quasiblack hole configuration. The study is performed by solving the Tolman-Oppenheimer- Volkoff equation, by assuming that the charge distribution is proportional to the energy density. We search for compact equilibrium configurations and verify that the extremal limit for charged polytropic spheres, i.e., the quasiblack hole limit, is approached when considering high polytropic indexes and large charge densities.

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

2015-01-01

3

Gravito-electrostatic fluctuations of a polytropic charged dust cloud  

NASA Astrophysics Data System (ADS)

An analytical model to explore the weakly nonlinear gravito-electrostatic waves in a field-free polytropic dust molecular cloud on the astrophysical scales of space and time is proposed. The polytrope consists of the lighter electrons, ions and massive dust grains with full ionization. This is a nonthermalized situation due to the cold grains, and the mutually thermalized hot electrons and hot ions. A quasi-hydrostatic equilibrium in one-dimensional (1D, Cartesian) configuration is adopted with presumed global quasi-neutrality. The grain dynamics considered is such that exact gravito-electrostatic equilibrium is facilitated with their first-order perturbed self-gravitational potential. The analytical infrastructure is developed by a standard multi-scale analysis of stretched variables centered on the assumed initially ‘homogeneous’ equilibrium in accordance with the Jeans swindle. We derive a new gravito-electrostatically coupled pair of modified Korteweg–de Vries (m-KdV) equations having unique self-consistent nonlinear sources arising due to gravito-electrostatic intermixed coupling. A detailed numerical shape analysis of the fluctuations is carried out in order to see their parametric excitations as solitary spectral patterns. Interestingly, it is seen that the electrostatic fluctuations undergo bi-periodicity, while the self-gravitational counterparts retain uni-periodicity in phase space. Nontrivial aspects of the results relevant in space and astrophysical environments are summarily indicated.

Gohain, M.; Karmakar, P. K.

2014-12-01

4

Electrically charged compact stars  

E-print Network

We review here the classical argument used to justify the electrical neutrality of stars and show that if the pressure and density of the matter and gravitational field inside the star are large, then a charge and a strong electric field can be present. For a neutron star with high pressure (~ 10^{33} to 10^{35} dynes /cm^2) and strong gravitational field (~ 10^{14} cm/s^2), these conditions are satisfied. The hydrostatic equation which arises from general relativity, is modified considerably to meet the requirements of the inclusion of the charge. In order to see any appreciable effect on the phenomenology of the neutron stars, the charge and the electrical fields have to be huge (~ 10^{21} Volts/cm). These stars are not however stable from the viewpoint that each charged particle is unbound to the uncharged particles, and thus the system collapses one step further to a charged black hole

Subharthi Ray; Manuel Malheiro; Jose' P. S. Lemos; Vilson T. Zanchin

2006-04-17

5

Charged compact objects in the linear regime  

E-print Network

Astrophysical compact stars provide a natural laboratory for testing theoretical models which are otherwise difficult to prove from an experimental setup. In our present work we analyse an exact solution to the Einstein-Maxwell system for a charged anisotropic compact body in the linear regime. The charged parameter may be set to zero which gives us the case of neutral solutions. We have tuned the model parameters for the uncharged case so as to match with recent updated mass-radius estimates for five different compact objects. Then we make a systematic study of the effect of charge for the different parameter set that fits the observed stars. The effect of charge is clearly illustrated in the increase of mass. We show that the physical quantities for the objects PSR J1614-2230, PSR J1903+327, Vela X-1, SMC X-1, Cen X-3 are well behaved.

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

2014-12-28

6

Supersymmetric polytropic gas dynamics  

NASA Astrophysics Data System (ADS)

We construct the N=1 supersymmetric extension of the polytropic gas dynamics. We give both the Lagrangian as well as the Hamiltonian description of this system. We construct the infinite set of ‘‘ Eulerian" conserved charges associated with this system and show that they are in involution, thereby proving complete integrability of this system. We construct the SUSY-B extension of this system as well and comment on the similarities and differences between this system and an earlier construction of the supersymmetric Chaplygin gas. We also derive the N=1 supersymmetric extension of the elastic medium equations, which, however, do not appear to be integrable.

Das, Ashok; Popowicz, Ziemowit

2002-04-01

7

Model of singularity free charged compact stars  

NASA Astrophysics Data System (ADS)

We provide a new charged compact star model. New classes of exact solutions to the Einstein-Maxwell system is found in closed form by assuming that the hypersurface { t=constant} is spheroidal. The solution is found for all positive spheroidal parameter K with a specific form of electric field intensity. Here, we consider the equation of state of a fluid as `the barotropic equation of state'. The mass radius relation is consistent with the experimental and theoretical results describing compact stars. The model of star satisfies all the energy conditions. Some physical features are briefly discussed.

Islam, Safiqul; Rahaman, Farook; Sardar, Iftikar Hossain

2015-04-01

8

Polytropic inspired inflation  

E-print Network

We study the chaotic inflation in the context of a gravity theory where the Friedman equation is modified, inspired by the polytropic gas equation of state. It is seen that in the $n=1$ case for the polytropic index the inflaton field at the end of inflation $\\phi_e$, depends on the Planck mass, while for $n\

M. R. Setare; F. Darabi

2013-10-27

9

Spherical polytropic balls cannot mimic black holes  

E-print Network

The so-called black hole shadow is a dark region which is expected to appear in a fine image of optical observation of black holes. It is essentially an absorption cross section of black hole, and the boundary of shadow is determined by unstable circular orbits of photons (UCOP). If there exists a compact object possessing UCOP but no black hole horizon, it can provide us with the same shadow image with black holes, and a detection of shadow image cannot be a direct evidence of black hole existence. However, we show that a static spherical polytropic ball of perfect fluid cannot possess UCOP, if the sound speed at centre is subluminal (slower-than-light). This implies that, if the polytrope is a good model of stellar matter in compact objects, a detection of shadow image is regarded as a good evidence of black hole existence. As a by-product, we have found an upper bound of mass-to-radius radio of polytropic ball, $M/R sound speed condition.

Hiromi Saida; Atsuhito Fujisawa; Chul-Moon Yoo; Yasusada Nambu

2015-03-09

10

Spherical polytropic balls cannot mimic black holes  

E-print Network

The so-called black hole shadow is a dark region which is expected to appear in a fine image of optical observation of black holes. It is essentially an absorption cross section of black hole, and the boundary of shadow is determined by unstable circular orbits of photons (UCOP). If there exists a compact object possessing UCOP but no black hole horizon, it can provide us the same shadow image with black holes, and a detection of shadow image cannot be a direct evidence of black hole existence. However, we show that a static spherical polytropic ball of perfect fluid cannot possess UCOP, if the sound speed at centre is subluminal. This implies that, if the polytrope is a good model of stellar matter in compact objects, a detection of shadow image is regarded as a good evidence of black hole existence. As a by-product, we have found an upper bound of mass-to-radius radio of polytropic ball, $M/R < 0.281$.

Saida, Hiromi; Yoo, Chul-Moon; Nambu, Yasusada

2015-01-01

11

DNA compaction in a crowded environment with negatively charged proteins.  

PubMed

We studied the conformational properties of DNA in a salt solution of the strongly charged protein bovine serum albumin. DNA is compacted when a suitable amount of bovine serum albumin is added to the solution due to a crowding effect and strong electrostatic repulsion between DNA and bovine serum albumin, both of which carry negative charges. However, DNA undergoes an unfolding transition with an increase in the salt concentration. This observation contradicts the current understanding of polymer- and salt-induced condensation, ? condensation. We propose a simple theoretical model by taking into account the competition between the translational entropy of ions and electrostatic interaction. PMID:20867679

Krotova, M K; Vasilevskaya, V V; Makita, N; Yoshikawa, K; Khokhlov, A R

2010-09-17

12

DNA Compaction in a Crowded Environment with Negatively Charged Proteins  

NASA Astrophysics Data System (ADS)

We studied the conformational properties of DNA in a salt solution of the strongly charged protein bovine serum albumin. DNA is compacted when a suitable amount of bovine serum albumin is added to the solution due to a crowding effect and strong electrostatic repulsion between DNA and bovine serum albumin, both of which carry negative charges. However, DNA undergoes an unfolding transition with an increase in the salt concentration. This observation contradicts the current understanding of polymer- and salt-induced condensation, ? condensation. We propose a simple theoretical model by taking into account the competition between the translational entropy of ions and electrostatic interaction.

Krotova, M. K.; Vasilevskaya, V. V.; Makita, N.; Yoshikawa, K.; Khokhlov, A. R.

2010-09-01

13

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

14

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

2013-01-01

15

Low power, compact charge coupled device signal processing system  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

16

Equilibrium sequences of irrotational binary polytropic stars : The case of double polytropic stars  

E-print Network

Solutions to equilibrium sequences of irrotational binary polytropic stars in Newtonian gravity are expanded in a power of $\\epsilon=a_0/R$, where R and $a_0$ are the orbital separation of the binary system and the radius of each star for $R=\\infty$. For each order of $\\epsilon$, we should solve ordinary differential equations for arbitrary polytropic indices n. We show solutions for polytropic indices n= 0.5, 1, 1.5 and 2 up to $\\epsilon^6$ orders. Our semi-analytic solutions can be used to check the validity of numerical solutions.

Keisuke Taniguchi; Takashi Nakamura

2000-04-03

17

Dark energy with polytropic equation of state  

E-print Network

Equation of state parameter plays a significant role for guessing the real nature of dark energy. In the present paper polytropic equation of state $p=\\omega\\rho^n$ is chosen for some of the kinematical $\\Lambda$-models viz., $\\Lambda \\sim (\\dot a/a)^2$, $\\Lambda \\sim \\ddot a/a$ and $\\Lambda \\sim \\rho$. Although in dust cases ($\\omega=0$) closed form solutions show no dependency on the polytropic index $n$, but in non-dust situations some new possibilities are opened up including phantom energy with supernegative ($\\omega<-1$) equation of state parameter.

Utpal Mukhopadhyay; Saibal Ray

2005-10-19

18

Magnetic flux concentrations in a polytropic atmosphere  

NASA Astrophysics Data System (ADS)

Context. Strongly stratified hydromagnetic turbulence has recently been identified as a candidate for explaining the spontaneous formation of magnetic flux concentrations by the negative effective magnetic pressure instability (NEMPI). Much of this work has been done for isothermal layers, in which the density scale height is constant throughout. Aims: We now want to know whether earlier conclusions regarding the size of magnetic structures and their growth rates carry over to the case of polytropic layers, in which the scale height decreases sharply as one approaches the surface. Methods: To allow for a continuous transition from isothermal to polytropic layers, we employ a generalization of the exponential function known as the q-exponential. This implies that the top of the polytropic layer shifts with changing polytropic index such that the scale height is always the same at some reference height. We used both mean-field simulations (MFS) and direct numerical simulations (DNS) of forced stratified turbulence to determine the resulting flux concentrations in polytropic layers. Cases of both horizontal and vertical applied magnetic fields were considered. Results: Magnetic structures begin to form at a depth where the magnetic field strength is a small fraction of the local equipartition field strength with respect to the turbulent kinetic energy. Unlike the isothermal case where stronger fields can give rise to magnetic flux concentrations at larger depths, in the polytropic case the growth rate of NEMPI decreases for structures deeper down. Moreover, the structures that form higher up have a smaller horizontal scale of about four times their local depth. For vertical fields, magnetic structures of super-equipartition strengths are formed, because such fields survive downward advection that causes NEMPI with horizontal magnetic fields to reach premature nonlinear saturation by what is called the "potato-sack" effect. The horizontal cross-section of such structures found in DNS is approximately circular, which is reproduced with MFS of NEMPI using a vertical magnetic field. Conclusions: Results based on isothermal models can be applied locally to polytropic layers. For vertical fields, magnetic flux concentrations of super-equipartition strengths form, which supports suggestions that sunspot formation might be a shallow phenomenon.

Losada, I. R.; Brandenburg, A.; Kleeorin, N.; Rogachevskii, I.

2014-04-01

19

Non-compact Lattice QED with Two Charges: Phase Diagram and Renormalization Group Flow  

E-print Network

The phase diagram of non-compact lattice QED in four dimensions with staggered fermions of charges 1 and $-1/2$ is investigated. The renormalized charges are determined and found to be in agreement with perturbation theory. This is an indication that there is no continuum limit with non-vanishing renormalized gauge coupling, and that the theory has a validity bound for every finite value of the renormalized coupling. The renormalization group flow of the charges is investigated and an estimate for the validity bound as a function of the cut-off is obtained. Generalizing this estimate to all fermions in the Standard Model,it is found that a cut-off at the Planck scale implies that $\\alpha_R$ has to be less than $1/80$. Due to spontaneous chiral symmetry breaking, strongly bound fermion-antifermion composite states are generated. Their spectrum is discussed.

A. Ali Khan

1995-11-10

20

Effects of space charge in a compact superconducting energy recovery linac with a low energy  

NASA Astrophysics Data System (ADS)

The Energy Recovery Linac (ERL) is one of the candidates for the next generation light sources, which is based on the 1.3 GHz superconducting radio frequency (SRF) linear accelerator. The ERL can produce high brilliance synchrotron radiation and a short pulse beam. We investigated the beam dynamics in the compact-Energy Recovery Linac (c-ERL) with a beam energy of 35 MeV, which is a prototype of the 5 GeV ERL at KEK. One of the main goals of our studies on the c-ERL is the emittance compensation in the merger section to achieve an emittance smaller than 1.0 mm mrad. In the case of the early commissioning phase, the injector system produces electron bunches of 5 MeV with a repetition rate of 1.3 GHz. The compensation of the emittance growth due to the space charge effect was investigated in order to achieve a small emittance at the exit of the merger. We discuss the results of a method to compensate the emittance growth which is based on beam envelope matching between the betatron function and the linear dispersion induced by the space charge force. We investigated the space charge effect when the beam energy in the superconducting RF section was changed. The effect of space charge in the arc section was also investigated. It is shown that the space charge effect in the c-ERL is an important source of distortion of the optics function. In this paper, we show the results on the analysis of the effect of space charge in the compact-ERL at KEK which has a low-energy beam.

Hwang, Ji-Gwang; Kim, Eun-San; Miyajima, Tsukasa

2012-08-01

21

Development of compact rapid charging power supply for capacitive energy storage in pulsed power drivers.  

PubMed

High energy capacitor bank is used for primary electrical energy storage in pulsed power drivers. The capacitors used in these pulsed power drivers have low inductance, low internal resistance, and less dc life, so it has to be charged rapidly and immediately discharged into the load. A series resonant converter based 45 kV compact power supply is designed and developed for rapid charging of the capacitor bank with constant charging current up to 150 mA. It is short circuit proof, and zero current switching technique is used to commute the semiconductor switch. A high frequency resonant inverter switching at 10 kHz makes the overall size small and reduces the switching losses. The output current of the power supply is limited by constant on-time and variable frequency switching control technique. The power supply is tested by charging the 45 kV/1.67 ?F and 15 kV/356 ?F capacitor banks. It has charged the capacitor bank up to rated voltage with maximum charging current of 150 mA and the average charging rate of 3.4 kJ/s. The output current of the power supply is limited by reducing the switching frequency at 5 kHz, 3.3 kHz, and 1.7 kHz and tested with 45 kV/1.67 ?F capacitor bank. The protection circuit is included in the power supply for over current, under voltage, and over temperature. The design details and the experimental testing results of the power supply for resonant current, output current, and voltage traces of the power supply with capacitive, resistive, and short circuited load are presented and discussed. PMID:25725838

Sharma, Surender Kumar; Shyam, Anurag

2015-02-01

22

Development of compact rapid charging power supply for capacitive energy storage in pulsed power drivers  

NASA Astrophysics Data System (ADS)

High energy capacitor bank is used for primary electrical energy storage in pulsed power drivers. The capacitors used in these pulsed power drivers have low inductance, low internal resistance, and less dc life, so it has to be charged rapidly and immediately discharged into the load. A series resonant converter based 45 kV compact power supply is designed and developed for rapid charging of the capacitor bank with constant charging current up to 150 mA. It is short circuit proof, and zero current switching technique is used to commute the semiconductor switch. A high frequency resonant inverter switching at 10 kHz makes the overall size small and reduces the switching losses. The output current of the power supply is limited by constant on-time and variable frequency switching control technique. The power supply is tested by charging the 45 kV/1.67 ?F and 15 kV/356 ?F capacitor banks. It has charged the capacitor bank up to rated voltage with maximum charging current of 150 mA and the average charging rate of 3.4 kJ/s. The output current of the power supply is limited by reducing the switching frequency at 5 kHz, 3.3 kHz, and 1.7 kHz and tested with 45 kV/1.67 ?F capacitor bank. The protection circuit is included in the power supply for over current, under voltage, and over temperature. The design details and the experimental testing results of the power supply for resonant current, output current, and voltage traces of the power supply with capacitive, resistive, and short circuited load are presented and discussed.

Sharma, Surender Kumar; Shyam, Anurag

2015-02-01

23

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

PubMed

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

Elsayed, M; Kristiansen, M; Neuber, A

2008-12-01

24

Fast-charging compact seed source for magnetic flux compression generators  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

25

Compact stars with a small electric charge: the limiting radius to mass relation and the maximum mass for incompressible matter  

E-print Network

One of the stiffest equations of state for matter in a compact star is constant energy density and this generates the interior Schwarzschild radius to mass relation and the Misner maximum mass for relativistic compact stars. If dark matter populates the interior of stars, and this matter is supersymmetric or of some other type, some of it possessing a tiny electric charge, there is the possibility that highly compact stars can trap a small but non-negligible electric charge. In this case the radius to mass relation for such compact stars should get modifications. We use an analytical scheme to investigate the limiting radius to mass relation and the maximum mass of relativistic stars made of an incompressible fluid with a small electric charge. The investigation is carried out by using the hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff (TOV) equation, together with the other equations of structure, with the further hypothesis that the charge distribution is proportional to the energy density. The approach relies on Volkoff and Misner's method to solve the TOV equation. For zero charge one gets the interior Schwarzschild limit, and supposing incompressible boson or fermion matter with constituents with masses of the order of the neutron mass one gets that the maximum mass is the Misner mass. For a small electric charge, our analytical approximating scheme valid in first order in the star's electric charge, shows that the maximum mass increases relatively to the uncharged case, whereas the minimum possible radius decreases, an expected effect since the new field is repulsive aiding the pressure to sustain the star against gravitational collapse.

José P. S. Lemos; Francisco J. Lopes; Gonçalo Quinta; Vilson T. Zanchin

2015-01-09

26

Compact stars with a small electric charge: the limiting radius to mass relation and the maximum mass for incompressible matter  

NASA Astrophysics Data System (ADS)

One of the stiffest equations of state for matter in a compact star is constant energy density and this generates the interior Schwarzschild radius to mass relation and the Misner maximum mass for relativistic compact stars. If dark matter populates the interior of stars, and this matter is supersymmetric or of some other type, some of it possessing a tiny electric charge, there is the possibility that highly compact stars can trap a small but non-negligible electric charge. In this case the radius to mass relation for such compact stars should get modifications. We use an analytical scheme to investigate the limiting radius to mass relation and the maximum mass of relativistic stars made of an incompressible fluid with a small electric charge. The investigation is carried out by using the hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff (TOV) equation, together with the other equations of structure, with the further hypothesis that the charge distribution is proportional to the energy density. The approach relies on Volkoff and Misner's method to solve the TOV equation. For zero charge one gets the interior Schwarzschild limit, and supposing incompressible boson or fermion matter with constituents with masses of the order of the neutron mass one finds that the maximum mass is the Misner mass. For a small electric charge, our analytical approximating scheme, valid in first order in the star's electric charge, shows that the maximum mass increases relatively to the uncharged case, whereas the minimum possible radius decreases, an expected effect since the new field is repulsive, aiding the pressure to sustain the star against gravitational collapse.

Lemos, José P. S.; Lopes, Francisco J.; Quinta, Gonçalo; Zanchin, Vilson T.

2015-02-01

27

General polytropic Larson-Penston-type collapses  

NASA Astrophysics Data System (ADS)

We investigate self-similar hydrodynamics of a general polytropic (GP) gas with spherical symmetry under self-gravity and extend the conventional polytropic (CP) relation n = 2 - ? for the self-similar index n and the polytropic index ? to a general relation n = 2(q + ? - 2)/(3q - 2), where q is a real parameter by specific entropy conservation along streamlines. We derive GP Larson-Penston (LP)-type solutions for q > 2/3 and ? > 4/3; Larson-Penston-Hunter (LPH)-type solutions are also constructed in a GP gas by a time-reversal operation on a GP-LP-type solution and by connecting to a GP free-fall-type solution across t = 0. These GP-LPH solutions describe dynamic processes that a GP gas globule, static and dense initially, undergoes a runaway collapse under self-gravity, forms a central mass singularity, and keeps accreting during a free-fall stage. We apply such GP-LPH-type solutions with variable envelope mass infall rates (EMIRs) for the dynamic evolution of globules and dense cores in star-forming molecular clouds. In particular, a GP-LPH-type solution can sustain an EMIR as low as 10-8 ˜ 10-6 M? yr-1 or even lower - much lower than that of Shu's isothermal model for a cloud core in Class 0 and Class I phases. Such GP-LPH-type solutions with EMIRs as low as 10-9 ˜ 10-8 M? yr-1 offer a sensible viable mechanism of forming brown dwarfs during the accretion stage in a collapsed GP globules with 1.495 ? ? ? 1.50 and 0.99 ? n ? 1.0. The GP-LPH solutions with 0.94 < n < 0.99 and 1.47 < ? < 1.495 can even give extremely low EMIRs of 10-12 ˜ 10-9 M? yr-1 to form gaseous planet-type objects in mini gas globules.

Lou, Yu-Qing; Shi, Chun-Hui

2014-12-01

28

Polytropic models of filamentary interstellar clouds - I. Structure and stability  

NASA Astrophysics Data System (ADS)

The properties of filamentary interstellar clouds observed at submillimetre wavelengths, especially by the Herschel Space Observatory, are analysed with polytropic models in cylindrical symmetry. The observed radial density profiles are well reproduced by negative-index cylindrical polytropes with polytropic exponent 1/3 ? ?p ? 2/3 (polytropic index -3 ? n ? -3/2), indicating either external heating or non-thermal pressure components. However, the former possibility requires unrealistically high gas temperatures at the filament's surface and is therefore very unlikely. Non-thermal support, perhaps resulting from a superposition of small-amplitude Alfvén waves (corresponding to ?p = 1/2), is a more realistic possibility, at least for the most massive filaments. If the velocity dispersion scales as the square root of the density (or column density) on the filament's axis, as suggested by observations, then polytropic models are characterized by a uniform width. The mass per unit length of pressure-bounded cylindrical polytropes depends on the conditions at the boundary and is not limited as in the isothermal case. However, polytropic filaments can remain stable to radial collapse for values of the axis-to-surface density contrast as large as the values observed only if they are supported by a non-isentropic pressure component.

Toci, Claudia; Galli, Daniele

2015-01-01

29

Stationary spiral flow in polytropic stellar models  

PubMed Central

It is shown that, in addition to the static Emden solution, a self-gravitating polytropic gas has a dynamic option in which there is stationary flow along spiral trajectories wound around the surfaces of concentric tori. The motion is obtained as a solution of a partial differential equation which is satisfied by the meridional stream function, coupled with Poisson's equation and a Bernoulli-type equation for the pressure (density). The pressure is affected by the whole of the Bernoulli term rather than by the centrifugal part only, which acts for a rotating model, and it may be reduced down to zero at the center. The spiral type of flow is illustrated for an incompressible fluid (n = 0), for which an exact solution is obtained. The features of the dynamic constant-density model are discussed as a basis for future comparison with the solution for compressible models. PMID:16592825

Pekeris, C. L.

1980-01-01

30

Rapidly rotating polytropes in general relativity  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

31

Compact formulae, dynamics and radiation of charged particles under synchro-curvature losses  

NASA Astrophysics Data System (ADS)

We consider the fundamental problem of charged particles moving along and around a curved magnetic field line, revising the synchro-curvature radiation formulae introduced by Cheng & Zhang. We provide more compact expressions to evaluate the spectrum emitted by a single particle, identifying the key parameter that controls the transition between the curvature-dominated and the synchrotron-dominated regime. This parameter depends on the local radius of curvature of the magnetic field line, the gyration radius, and the pitch angle. We numerically solve the equations of motion for the emitting particle by considering self-consistently the radiative losses, and provide the radiated spectrum produced by a particle when an electric acceleration is balanced by its radiative losses, as it is assumed to happen in the outer gaps of pulsar's magnetospheres. We compute the average spectrum radiated throughout the particle trajectory finding that the slope of the spectrum before the peak depends on the location and size of the emission region. We show how this effect could then lead to a variety of synchro-curvature spectra. Our results reinforce the idea that the purely synchrotron or curvature losses are, in general, inadequate to describe the radiative reaction on the particle motion, and the spectrum of emitted photons. Finally, we discuss the applicability of these calculations to different astrophysical scenarios.

Viganò, Daniele; Torres, Diego F.; Hirotani, Kouichi; Pessah, Martín E.

2015-02-01

32

On the determination of the polytropic specific heat  

NASA Astrophysics Data System (ADS)

The polytropic specific heat (Cn) is analyzed mathematically and the expression for Cn is shown to represent a translated and clockwise-rotated equilateral hyperbola. Such a well-defined geometric figure admits of rapid determination of Cn as well as the prediction of effects of uncertainties in the polytropic exponent (N) for any gas whose specific heat ratio is known. Numerical examples are presented in which a reciprocating air compressor is considered, and they show that it is possible to map out the entire range of the Cn values, to discern by inspection the effects of small variations in N, and to determine if and where mean values are admissible.

Rute, L.

1980-06-01

33

Interacting polytropic gas model of phantom dark energy in non-flat universe  

E-print Network

By introducing the polytropic gas model of interacting dark energy, we obtain the equation of state for the polytropic gas energy density in a non-flat universe. We show that for even polytropic index by choosing $K>Ba^{\\frac{3}{n}}$, one can obtain $\\omega^{\\rm eff}_{\\Lambda}universe dominated by phantom dark energy.

K. Karami; S. Ghaffari; J. Fehri

2009-11-25

34

Fast-charging compact seed source for magnetic flux compression generators  

Microsoft Academic Search

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

M. Elsayed; M. Kristiansen; A. Neuber

2008-01-01

35

Polytropic spheres in Palatini f(R) gravity  

E-print Network

We examine static spherically symmetric polytropic spheres in Palatini f(R) gravity and show that no regular solutions to the field equations exist for physically relevant cases such as a monatomic isentropic gas or a degenerate electron gas, thus casting doubt on the validity of Palatini f(R) gravity as an alternative to General Relativity.

Enrico Barausse; Thomas P. Sotiriou; John C. Miller

2008-01-31

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

Polytropic models of filamentary interstellar clouds - II. Helical magnetic fields  

NASA Astrophysics Data System (ADS)

We study the properties of magnetized cylindrical polytropes as models for interstellar filamentary clouds, extending the analysis presented in a companion paper. We formulate the general problem of magnetostatic equilibrium in the presence of a helical magnetic field, with the aim of determining the degree of support or compression resulting from the magnetization of the cloud. We derive scale-free solutions appropriate to describe the properties of the envelopes of filaments at radii larger than the flat-density region. In these solutions, the polytropic exponent determines the radial profiles of the density and the magnetic field. The latter decreases with radius less steeply than the density, and field lines are helices twisted over cylindrical surfaces. A soft equation of state supports magnetic configurations that preferentially compress and confine the filament, whereas in the isothermal limit the field provides support. For each value of the polytropic exponent, the Lorentz force is directed outwards or inwards depending on whether the pitch angle is below or above some critical value which is a function of the polytropic exponent only.

Toci, Claudia; Galli, Daniele

2015-01-01

38

Non-linear effects on radiation propagation around a charged compact object  

E-print Network

The propagation of non-linear electromagnetic waves is carefully analyzed on a curved spacetime created by static spherically symmetric mass and charge distribution. We compute how the non-linear electrodynamics affects the geodesic deviation and the redshift of photons propagating near this massive charged object and, in the linear approximation, the effects of electromagnetic self-interaction can be disparted from the usual Reissner-Nordstr\\"om terms. In the particular case of Euler-Heisenberg effective Lagrangian, we find that these self-interaction effects might be important near charged white dwarfs.

Cuzinatto, R R; de Vasconcelos, K C; Medeiros, L G; Pompeia, P J

2015-01-01

39

A compact model for dielectric charging in RF MEMS capacitive switches  

Microsoft Academic Search

• It constitutes a generalization of the one-dimensional models reported in the literature to date; • Utilizes experimentally-obtained data to extract parameters used for the description of the elec- trical properties of the model; • Enables the calculation and monitoring of the temporal evolution of charge accumulation at the top and bottom surfaces of the insulating dielectric film; • Enables

Prasad S. Sumant; Andreas C. Cangellaris; Narayan R. Aluru

2009-01-01

40

Self-Similar Polytropic Champagne Flows in H II Regions  

E-print Network

We explore large-scale hydrodynamics of H II regions for various self-similar shock flows of a polytropic gas cloud under self-gravity and with quasi-spherical symmetry. We formulate cloud dynamics by invoking specific entropy conservation along streamlines and obtain global self-similar "champagne flows" for a conventional polytropic gas with shocks as a subclass. Molecular cloud cores are ionized and heated to high temperatures after the onset of nuclear burning of a central protostar. We model subsequent evolutionary processes in several ways and construct possible self-similar shock flow solutions. We may neglect the mass and gravity of the central protostar. The ionization and heating of the surrounding medium drive outflows in the inner cloud core and a shock travels outwards, leading to the so-called "champagne phase" with an expanding outer cloud envelope. Complementarily, we also consider the expansion of a central cavity around the centre. As the inner cloud expands plausibly due to powerful stellar winds, a cavity (i.e., `void' or `bubble') can be created around the centre, and when the cavity becomes sufficiently large, one may neglect the gravity of the central protostar. We thus present self-similar shock solutions for "champagne flows" with an expanding central void. We compare our solutions with isothermal solutions and find that the generalization to the polytropic regime brings about significant differences of the gas dynamics, especially for cases of n<1, where n is a key scaling index in the self-similar transformation. We also compare our global polytropic self-similar solutions with numerical simulations on the expansion of H II regions.

Ren-Yu Hu; Yu-Qing Lou

2008-08-15

41

The Study of Two-dimensional Polytropic Stars  

E-print Network

In this article we have studied the structure of hypothetical two-dimensional polytropic stars. Considering some academic interest, we have developed a formalism to investigate some of the gross properties of such stellar objects. However, we strongly believe that the formalism developed here may be prescribed as class problem for post-graduate level students in physics or a post-graduate dissertation project work in physics.

Sanchari De; Somenath Chakrabarty

2014-04-28

42

Polytropic equation of state and primordial quantum fluctuations  

NASA Astrophysics Data System (ADS)

We study the primordial Universe in a cosmological model where inflation is driven by a fluid with a polytropic equation of state . We calculate the dynamics of the scalar factor and build a Universe with constant density at the origin. We also find the equivalent scalar field that could create such an equation of state and calculate the corresponding slow-roll parameters. We calculate the scalar perturbations, the scalar power spectrum, and the spectral index.

Freitas, R. C.; Gonçalves, S. V. B.

2014-12-01

43

Analytical representations for simple and composite polytropes and their moments of inertia  

NASA Astrophysics Data System (ADS)

Polytropes are widely applied in astrophysics. To facilitate their use, we derive analytical formulae for the moment of inertia as a function of polytropic index. We also provide 1- and 3-parameter equations that replicate the density variations in polytropic bodies to varying degrees of accuracy, determined by numerical calculations and analytical results for polytropic indices between 0 and 5. As an example, we construct a composite polytrope, suitable for gas giants, exoplanets, or tiny sub-solar dwarfs, wherein an inner sphere is modeled by constant density, which represents the density jump associated with production of a relatively incompressible solid, and an outer envelope is modeled as having a polytropic index near 2.5, which corresponds to a diatomic gas. Envelope sizes are constrained by the moment of inertia.

Criss, Robert E.; Hofmeister, Anne M.

2015-04-01

44

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

45

Polytropic dark matter flows illuminate dark energy and accelerated expansion  

NASA Astrophysics Data System (ADS)

Currently, a large amount of data implies that the matter constituents of the cosmological dark sector might be collisional. An attractive feature of such a possibility is that, it can reconcile dark matter (DM) and dark energy (DE) in terms of a single component, accommodated in the context of a polytropic-DM fluid. In fact, polytropic processes in a DM fluid have been most successfully used in modeling dark galactic haloes, thus significantly improving the velocity dispersion profiles of galaxies. Motivated by such results, we explore the time evolution and the dynamical characteristics of a spatially-flat cosmological model, in which, in principle, there is no DE at all. Instead, in this model, the DM itself possesses some sort of fluidlike properties, i.e., the fundamental units of the Universe matter-energy content are the volume elements of a DM fluid, performing polytropic flows. In this case, together with all the other physical characteristics, we also take the energy of this fluid's internal motions into account as a source of the universal gravitational field. This form of energy can compensate for the extra energy, needed to compromise spatial flatness, namely, to justify that, today, the total energy density parameter is exactly unity. The polytropic cosmological model, depends on only one free parameter, the corresponding (polytropic) exponent, ?. We find this model particularly interesting, because for ? ? 0.541, without the need for either any exotic DE or the cosmological constant, the conventional pressure becomes negative enough so that the Universe accelerates its expansion at cosmological redshifts below a transition value. In fact, several physical reasons, e.g., the cosmological requirement for cold DM (CDM) and a positive velocity-of-sound square, impose further constraints on the value of ?, which is eventually settled down to the range -0.089 < ? ? 0. This cosmological model does not suffer either from the age problem or from the coincidence problem. At the same time, this model reproduces to high accuracy the distance measurements performed with the aid of the supernovae (SNe) Type Ia standard candles, and most naturally interprets, not only when, but also why the Universe transits from deceleration to acceleration, thus arising as a mighty contestant for a DE model.

Kleidis, K.; Spyrou, N. K.

2015-04-01

46

Self-similar dynamics of polytropic gaseous spheres  

NASA Technical Reports Server (NTRS)

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

1988-01-01

47

Can rigidly rotating polytropes be sources of the Kerr metric?  

E-print Network

We use a recent result by Cabezas et al. 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 global harmonic coordinate system. We prove that if the metric and their first derivatives are continuous on the matching surface up to this order of approximation, the multipole moments of this metric cannot be fitted to those of the Kerr metric.

J. Martin; A. Molina; E. Ruiz

2007-09-07

48

Implementation of polytropic method to study initial structures of gas giant protoplanets  

NASA Astrophysics Data System (ADS)

In this paper we have determined the initial structures of gas giant protoplanets, formed via disk instability, having a mass range of 0.3-10 Jupiter masses by the simple polytropic method. The polytropic protoplanets or polytropes have been assumed to be spheres of solar composition, each of which is in a steady state of quasi-static equilibrium, where the only source of energy is the gravitational contraction of the gas. The results of our calculations for the polytropes with polytropic indices n = 1 and n = 1.5 are found to be closer to reality and are in good agreement with the findings obtained by other investigations with more rigorous treatment of the problem.

Paul, Gour Chandra; Barman, Mrinal Chandra; Mohit, Abdul Al

2014-12-01

49

Cosmological implications of interacting polytropic gas dark energy model in non-flat universe  

E-print Network

The polytropic gas model is investigated as an interacting dark energy scenario. The cosmological implications of the model including the evolution of EoS parameter $w_{\\Lambda}$, energy density $\\Omega_{\\Lambda}$ and deceleration parameter $q$ are investigated. We show that, depending on the parameter of model, the interacting polytropic gas can behave as a quintessence or phantom dark energy. In this model, the phantom divide is crossed from below to up. The evolution of $q$ in the context of polytropic gas dark energy model represents the decelerated phase at the early time and accelerated phase later. The singularity of this model is also discussed. Eventually, we establish the correspondence between interacting polytropic gas model with tachyon, K-essence and dilaton scalar fields. The potential and the dynamics of these scalar field models are reconstructed according to the evolution of interacting polytropic gas.

M. Malekjani; A. Khodam-Mohammadi; M. Taji

2011-04-26

50

Shear instabilities in a fully compressible polytropic atmosphere  

E-print Network

Shear flows have an important impact on the dynamics in an assortment of different astrophysical objects including accreditation discs and stellar interiors. Investigating shear flow instabilities in a polytropic atmosphere provides a fundamental understanding of the motion in stellar interiors where turbulent motions, mixing processes, as well as magnetic field generation takes place. Here, a linear stability analysis for a fully compressible fluid in a two-dimensional Cartesian geometry is carried out. Our study focuses on determining the critical Richardson number for different Mach numbers and the destabilising effects of high thermal diffusion. We find that there is a deviation of the predicted stability threshold for moderate Mach number flows along with a significant effect on the growth rate of the linear instability for small P\\'eclet numbers. We show that in addition to a Kelvin-Helmholtz instability a Holmboe instability can appear and we discuss the implication of this in stellar interiors.

Witzke, V; Favier, B

2015-01-01

51

Coalescing neutron stars -- gravitational waves from polytropic models  

E-print Network

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. (1994), (b) ``Model III'' of Shibata et al. (1992), and (c) ``Model A64'' of Ruffert et al. (1996). 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. Comparison (a) confronts the results of our grid-based PPM scheme with those from an SPH code. We found that due to the lower numerical viscosity of the PPM code, the post-merging oscillations and pulsations could be followed for a longer time and lead to larger secondary and tertiary maxima of the gravitational wave luminosity. In case (b) two grid based codes with the same backreaction formalism but differing hydrodynamic integrators and different numerical resolution are compared. 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. In (c) we find that using a polytropic equation of state instead of the high-density equation of state of Lattimer & Swesty (1991) does not change the overall dynamical evolution of the merger and yields agreement of the gravitational wave signature to within 20% accuracy. However, differences of the structure and evolution of the outer layers of the neutron stars are present, which has important implications for questions like mass loss and disk formation during the merging of binary neutron stars.

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

1996-11-07

52

Density probability distribution in one-dimensional polytropic gas dynamics  

NASA Astrophysics Data System (ADS)

We discuss the generation and statistics of the density fluctuations in highly compressible polytropic turbulence, based on a simple model and one-dimensional numerical simulations. Observing that density structures tend to form in a hierarchical manner, we assume that density fluctuations follow a random multiplicative process. When the polytropic exponent ? is equal to unity, the local Mach number is independent of the density, and our assumption leads us to expect that the probability density function (PDF) of the density field is a log-normal. This isothermal case is found to be special, with a dispersion ?2s scaling as the square turbulent Mach number M~2, where s? ln ? and ? is the fluid density. Density fluctuations are stronger than expected on the sole basis of shock jumps. Extrapolating the model to the case ??1, we find that as the Mach number becomes large, the density PDF is expected to asymptotically approach a power-law regime at high densities when ?<1, and at low densities when ?>1. This effect can be traced back to the fact that the pressure term in the momentum equation varies exponentially with s, thus opposing the growth of fluctuations on one side of the PDF, while being negligible on the other side. This also causes the dispersion ?2s to grow more slowly than M~2 when ??1. In view of these results, we suggest that Burgers flow is a singular case not approached by the high-M~ limit, with a PDF that develops power laws on both sides.

Passot, Thierry; Vázquez-Semadeni, Enrique

1998-10-01

53

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

54

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

55

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

PubMed

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

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

2014-06-01

56

Bifurcation and Fission of Three Dimensional, Rigidly Rotating and Self-Gravitating Polytropes  

NASA Astrophysics Data System (ADS)

A new computational method for solving three dimensional hydrostatic equilibrium structures of rotating polytropes is formulated by using analytic continuation. An elliptic-type differential equation such as Poisson equation is transformed into a hyperbolic-type one. Therefore, when Cauchy data are given in the central region, we can integrate the equation directly outward from the center and obtain the structure. Using this method, bifurcation and fission of rapidly rotating polytropes are investigated in order to reexamine the prevailing bifurcation and fission theories. The polytropes with x-y, y-z and z-x planes symmetry and with small compressibilities, i.e., polytropic indexes N=0., 0.1, 0.2, 0.3, 0.4 and 0.5 have been calculated. The results show the following: 1) All of these polytropes bifurcate from a spheroid-like shape to an ellipsoid-like one at each bifurfcation point. These bifurcations occur at much the same angular momentum (j=J/(4 ? GM10/3 ?c-1/3)1/2 ? 0.07). 2) The ellipsoid-like sequences with N= 0.1 ˜ 0.5 terminate at each critical point where the mass sheds from the equator before the dumb-bell shape appears, though 3) the dumb-bell configuration bifurcates from the Jacobi sequence in the incompressible case (N=0.).

Hachisu, I.; Eriguchi, Y.

1982-07-01

57

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

58

Compact accelerator  

DOEpatents

A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Kirbie, Hugh C. (Los Alamos, NM)

2007-02-06

59

Statefinder diagnostic and $w-w^{\\prime}$ analysis for interacting polytropic gas dark energy model  

E-print Network

The interacting polytropic gas dark energy model is investigated from the viewpoint of statefinder diagnostic tool and $w-w^{\\prime}$ analysis. The dependency of the statefinder parameters on the parameter of the model as well as the interaction parameter between dark matter and dark energy is calculated. We show that different values of the parameters of model and different values of interaction parameter result different evolutionary trajectories in $s-r$ and $w-w^{\\prime}$ planes. The polytropic gas model of dark energy mimics the standard $\\Lambda$CDM model at the early time.

M. Malekjani; A. Khodam-Mohammadi

2012-04-29

60

set of polytropes to resemble the stellar evolution structure. Convection is  

E-print Network

set of polytropes to resemble the stellar evolution structure. Convection is driven by a constant-D run. The computational domain includes 11.4 pressure scale heights. He-shell flash convection is dominated by large convective cells that are centered in the lower half of the convection zone (Fig. 1

Herwig, Falk

61

Changes in the global parameters of polytropic stars induced by the appearance of the soft core  

E-print Network

The effect of a soft phase core appearance in the center of polytropic star is analyzed by means of linear response theory. Approximate formulae for the changes of radius, moment of inertia and mass-energy of non-rotating configuration with arbitrary adiabatic indices are presented, followed by an example evaluation of astrophysical observables.

M. Bejger

2005-05-20

62

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

63

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

64

The effective geometry of the $n=1$ uniformly rotating self-gravitating polytrope  

E-print Network

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

Donato Bini; Christian Cherubini; Simonetta Filippi; Andrea Geralico

2014-08-20

65

Polytropic thin-shell collapse in non-commutative d-dimensional Reissner-Nordström geometry  

NASA Astrophysics Data System (ADS)

We study thin-shell collapse in non-commutative d-dimensional Reissner-Nordström geometry with most general polytropic equation of state. We formulate equation of motion for the shell using Israel junction conditions and express it in terms of non-commutative factor through smeared Gaussian distribution. It is found that non-commutative collapsing thin-shell in the presence of extra dimensions leads to the formation of either a black hole or naked singularity.

Sharif, M.; Iftikhar, Sehrish

2015-04-01

66

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

67

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

SciTech Connect

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

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

2013-03-10

68

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

69

Radial pulsations of neutron stars: computing alternative polytropic models regarding density and adiabatic index  

E-print Network

We revisit the problem of radial pulsations of neutron stars by computing four general-relativistic polytropic models, in which "density" and "adiabatic index" are involved with their discrete meanings: (i) "rest-mass density" or (ii) "mass-energy density" regarding the density, and (i) "constant" or (ii) "variable" regarding the adiabatic index. Considering the resulting four discrete combinations, we construct corresponding models and compute for each model the frequencies of the lowest three radial modes. Comparisons with previous results are made. The deviations of respective frequencies of the resolved models seem to exhibit a systematic behavior, an issue discussed here in detail.

Vassilis Geroyannis; Georgios Kleftogiannis

2014-06-14

70

Oil shale compaction experimental results  

SciTech Connect

Oil shale compaction reduces the void volume available for gas flow in vertical modified in situ (VMIS) retorts. The mechanical forces caused by the weight of the overlying shale can equal 700 kPa near the bottom of commercial retorts. Clear evidence of shale compaction was revealed during postburn investigation of the Rio Blanco retorts at the C-a lease tract in Colorado. Western Research Institute conducted nine laboratory experiments to measure the compaction of Green River oil shale rubble during retorting. The objectives of these experiments were (1) to determine the effects of particle size, (2) to measure the compaction of different shale grades with 12 to 25 percent void volume and (3) to study the effects of heating rate on compaction. The compaction recorded in these experiments can be separated into the compaction that occurred during retorting and the compaction that occurred as the retort cooled down. The leaner oil shale charges compacted about 3 to 4 percent of the bed height at the end of retorting regardless of the void volume or heating rate. The richer shale charges compacted by 6.6 to 22.9 percent of the bed height depending on the shale grade and void volume used. Additional compaction of approximately 1.5 to 4.3 percent of the bed height was measured as the oil shale charges cooled down. Compaction increased with an increase in void volume for oil shale grades greater than 125 l/Mg. The particle size of the oil shale brick and the heating rate did not have a significant effect on the amount of compaction measured. Kerogen decomposition is a major factor in the compaction process. The compaction may be influenced by the bitumen intermediate acting as a lubricant, causing compaction to occur over a narrow temperature range between 315 and 430/sup 0/C. While the majority of the compaction occurs early in the retorting phase, mineral carbonate decomposition may also increase the amount of compaction. 14 refs., 12 figs., 4 tabs.

Fahy, L.J.

1985-11-01

71

Relativistic Self-similar Dynamic Collapses of Black Holes in General Polytropic Spherical Clouds  

E-print Network

We study the hydrodynamic self-similar mass collapses of general polytropic (GP) spherical clouds to central Schwarzschild black holes and void evolution with or without shocks. In order to grossly capture characteristic effects of general relativity (GR) outside yet close to the event horizon of a Schwarzschild black hole and to avoid mathematical complexity, we adopt the approximation of the Paczynski-Wiita gravity to replace the simple Newtonian gravity in our model formulation. A new dimensionless parameter s appears with the physical meaning of the square of the ratio of the sound speed to the speed of light $c$. Various self-similar dynamic solutions are constructed for a polytropic index $\\gamma>4/3$. Two (for small enough $s4/3$, representing the collapse of static singular GP spheres towards the central singularity of spacetime. Such GP spherical dynamic mass collapse is shown to be highly efficient for the rapid formation of supermassive black holes (SMBHs; mass range of $10^6-10^{10}M_{\\odot}$) in ...

Lian, Biao

2013-01-01

72

An exact solution for arbitrarily rotating gaseous polytropes with index unity  

NASA Astrophysics Data System (ADS)

Many gaseous planets and stars are rapidly rotating and can be approximately described by a polytropic equation of state with index unity. We present the first exact analytic solution, under the assumption of the oblate spheroidal shape, for an arbitrarily rotating gaseous polytrope with index unity in hydrostatic equilibrium, giving rise to its internal structure and gravitational field. The new exact solution is derived by constructing the non-spherical Green's function in terms of the oblate spheroidal wavefunction. We then apply the exact solution to a generic object whose parameter values are guided by the observations of the rapidly rotating star ? Eridani with its eccentricity E_{? }= 0.7454, the most oblate star known. The internal structure and gravitational field of the object are computed from its assumed rotation rate and size. We also compare the exact solution to the three-dimensional numerical solution based on a finite-element method taking full account of rotation-induced shape change and find excellent agreement between the exact solution and the finite-element solution with about 0.001 per cent discrepancy.

Kong, Dali; Zhang, Keke; Schubert, Gerald

2015-03-01

73

Acoustic oscillations of rapidly rotating polytropic stars. II. Effects of the Coriolis and centrifugal accelerations  

E-print Network

Context: With the launch of space missions devoted to asteroseismology (like COROT), the scientific community will soon have accurate measurements of pulsation frequencies in many rapidly rotating stars. Aims: The present work focuses on the effects of rotation on pulsations of rapidly rotating stars when both the Coriolis and centrifugal accelerations require a non-perturbative treatment. Method: We develop a 2-dimensional spectral numerical approach which allows us to compute acoustic modes in centrifugally distorted polytropes including the full influence of the Coriolis force. This method is validated through comparisons with previous studies, and the results are shown to be highly accurate. Results: In the frequency range considered and with COROT's accuracy, we establish a domain of validity for perturbative methods, thus showing the need for complete calculations beyond v.sin i = 50 km/s for a R = 2.3 R_\\odot, M = 1.9 M_\\odot polytropic star. Furthermore, it is shown that the main differences between complete and perturbative calculations come essentially from the centrifugal distortion.

D. Reese; F. Lignières; M. Rieutord

2006-09-26

74

Reissner-Nordstrom and charged gas spheres  

E-print Network

The main point of this paper is a suggestion about the proper treatment of the photon gas in a theory of stellar structure and other plasmas. This problem arises in the study of polytropic gas spheres, where we have already introduced some innovations. The main idea, already advanced in the contextof neutral, homogeneous, polytropic stellar models, is to base the theory firmly on a variational principle. Another essential novelty is to let mass distribution extend to infinity, the boundary between bulk and atmosphere being defined by an abrupt change in the polytropic index, triggered by the density. The logical next step in this program is to include the effect of radiation, which is a very significant complication since a full treatment would have to include an account of ionization, thus fieldsrepresenting electrons, ions, photons, gravitons and neutral atoms as well. In way of preparation, we consider models that are charged but homogeneous, involving only gravity, electromagnetism and a single scalar field that represents both the mass and the electric charge; in short, anon-neutral plasma. While this work only represents a stage in the development of a theory of stars, without direct application to physical systems, it does shed some light on the meaning of the Reissner-Nordstrom solution of the modified Einstein-Maxwell equations., with an application to a simple system.

Christian Fronsdal

2007-08-30

75

Initial data for high-compactness black hole-neutron star binaries  

E-print Network

For highly compact neutron stars, constructing numerical initial data for black hole-neutron star binary evolutions is very difficult. We describe improvements to an earlier method that enable it to handle these more challenging cases. We examine the case of a 6:1 mass ratio system in inspiral close to merger, where the star is governed by a polytropic $\\Gamma=2$, an SLy, or an LS220 equation of state. In particular, we are able to obtain a solution with a realistic LS220 equation of state for a star with compactness 0.26 and mass 1.98 $M_\\odot$, which is representative of the highest reliably determined neutron star masses. For the SLy equation of state, we can obtain solutions with a comparable compactness of 0.25, while for a family of polytropic equations of state, we obtain solutions with compactness up to 0.21, the largest compactness that is stable in this family. These compactness values are significantly higher than any previously published results. We find that improvements in adapting the computational domain to the neutron star surface and in accounting for the center of mass drift of the system are the key ingredients allowing us to obtain these solutions.

Katherine Henriksson; François Foucart; Lawrence E. Kidder; Saul A. Teukolsky

2014-09-25

76

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

77

Hydrodynamics of binary coalescence. 2: Polytropes with gamma = 5/3  

NASA Technical Reports Server (NTRS)

We present a new numerical study of the equilibrium and stability properties of close binary systems. We use the smoothed-particle hydrodynamics (SPH) technique both to construct accurate equilibrium configurations in three dimensions and to follow their hydrodynamic evolution. We adopt a simple polytropic equation of state p = K(sub rho)(exp gamma) with gamma = 5/3 and K = constant within each star, applicable to low-mass degenerate dwarfs as well as low-mass main-sequence stars. For degenerate configurations, we set the two polytropic constants equal, K = K prime, independent of the mass ratio. For main-sequence stars, we adjust K and K prime so as to obtain a simple mass-radius relation of the form R/R prime = M/M prime, where R prime and M prime are the radius and mass of the secondary. Along a sequence of binary equilibrium configurations for two identical stars, we demonstrate the existence of both secular and dynamical instabilities, confirming directly the results of recent analytic work. We use the SPH method to calculate the nonlinear development of the dynamical instability and to determine the final fate of the system. We find that the two stars merge together into a single, rapidly rotating object in just a few orbital periods. Equilibrium sequences are also constructed for systems containing two nonidentical stars. These sequences terminate at a Roche limit, which we can determine very accurately using SPH. For two low-mass main-sequence stars with mass ratio q approximately less than 0.4 we find that the (synchronized) Roche limit configuration is secularly unstable. We discuss the implications of our results for the evolution of double white-dwarf systems and W Ursae Majoris binaries.

Rasio, Frederic A.; Shapiro, Stuart L.

1995-01-01

78

The density structure and star formation rate of non-isothermal polytropic turbulence  

NASA Astrophysics Data System (ADS)

The interstellar medium of galaxies is governed by supersonic turbulence, which likely controls the star formation rate (SFR) and the initial mass function (IMF). Interstellar turbulence is non-universal, with a wide range of Mach numbers, magnetic fields strengths and driving mechanisms. Although some of these parameters were explored, most previous works assumed that the gas is isothermal. However, we know that cold molecular clouds form out of the warm atomic medium, with the gas passing through chemical and thermodynamic phases that are not isothermal. Here we determine the role of temperature variations by modelling non-isothermal turbulence with a polytropic equation of state (EOS), where pressure and temperature are functions of gas density, P˜ ? ^?, T ˜ ?? - 1. We use grid resolutions of 20483 cells and compare polytropic exponents ? = 0.7 (soft EOS), ? = 1 (isothermal EOS) and ? = 5/3 (stiff EOS). We find a complex network of non-isothermal filaments with more small-scale fragmentation occurring for ? < 1, while ? > 1 smoothes out density contrasts. The density probability distribution function (PDF) is significantly affected by temperature variations, with a power-law tail developing at low densities for ? > 1. In contrast, the PDF becomes closer to a lognormal distribution for ? ? 1. We derive and test a new density variance-Mach number relation that takes ? into account. This new relation is relevant for theoretical models of the SFR and IMF, because it determines the dense gas mass fraction of a cloud, from which stars form. We derive the SFR as a function of ? and find that it decreases by a factor of ˜5 from ? = 0.7 to 5/3.

Federrath, Christoph; Banerjee, Supratik

2015-04-01

79

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....

80

Compaction managed mirror bend achromat  

DOEpatents

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

Douglas, David (Yorktown, VA)

2005-10-18

81

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

82

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

83

Hydrodynamics of binary coalescence. 1: Polytropes with stiff equations of state  

NASA Technical Reports Server (NTRS)

We performed a series of three-dimensional hydrodynamic calculations of binary coalescence using the smoothed particle hydrodynamics (SPH) method. The initial conditions are exact polytropic equilibrium configurations on the verge of dynamical instability. We consider synchronized equilbria only and concentrate on stiff equations of state, with adiabatic Gamma greater than 5/3. We assume that the polytropic constants (K identically equal to P/(rho(exp Gamma)) are the same for both components. These conditions apply well to models of neutron star binaries. Accordingly, we discuss our results in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO) project, and we calculate the emission of gravitational radiation in the quadruple approximation. The fully nonlinear development of the instability is followed using SPH until a new equilibrium configuration is reached by the system. We find that the properties of this final configuration depend sensitively on both the compressibility and mass ratio. An axisymmetric merged configuration is always produced when the adiabatic exponent Gamma approximately less than 2.3. As a consequence, the emission of gravitational radiation shuts off abruptly right after the onset of dynamical instability. In contrast, triaxial merged configurations are obtained when Gamma approximately greater than 2.3, and the system continues to emit gravitational waves after the final coalescence. Systems with mass ratios q not equal to 1 typically become dynamically unstable before the onset of mass transfer. Stable mass transfer from one neutron star to another in a close binary is therefore probably ruled out. For a mass ratio q approximately less than 0.5, however, dynamical mass transfer can temporarily retard the coalescence by causing a rapid reexpansion of the binary into a new, slightly eccentric but dynamically stable orbit. The maximum amplitude h(sub max) and peak luminosity L(sub max) of the gravitational waves emitted during the final coalescence are nearly independent of Gamma, but depend sensitively on the mass ratio q. The approximate scalings we find are h(sub max) varies as q(exp 2) and L(sub max) varies as q(exp 6) for q close to unity.

Rasio, Frederic A.; Shapiro, Stuart L.

1994-01-01

84

MOSFET Electric-Charge Sensor  

NASA Technical Reports Server (NTRS)

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

Robinson, Paul A., Jr.

1988-01-01

85

Tensor nature of the gas pressure and measurements of the polytropic indices for magnetic clouds: A case study  

NASA Astrophysics Data System (ADS)

For the magnetic cloud observed on March 19-20, 1980 we discuss the applicability of a simple bipolytropic approximation in which P?,e?P?,e and T?,e and T?,e are both related to the electron density ne through power laws. We find that (a) the magnetic cloud most likely consists of two flux tubes, in each of which a polytropic relation holds for both components of the electron temperature; (b) these relations are different for the parallel and perpendicular components, but both ??,e and ??,e are < 1; (c) for the first tube, where the linear regression results are very accurate, we have ??,e=0.64, ??,e=0.50 for the second tube ??,e=0.47, ??,e=0.29 (d) the correlation coefficients in these relations (~ -0.96 and -0.85, respectively) are substantially higher than those obtained from the scalar values in the first tube, and comparable in the second; (e) changes in magnetic cloud topology coincide with changes in the polytropic relation. If these simple relations are confirmed by other examples, they would allow further theoretical studies of the dynamics and stability of the plasma in magnetic clouds. From a broader astrophysical context, our results are consistent with Scudder's (1) suggestion that non-Maxwellian plasmas may carry polytropic indices below unity.

Farrugia, C. J.; Osherovich, V. A.; Fainberg, J.

1999-06-01

86

Global Compact  

NSDL National Science Digital Library

The Global Compact is a joint project of the International Labor Organization (ILO), the United Nations Environmental Programme (UNEP), and the Office of the High Commissioner for Human Rights. The site outlines the nine principles drafted at the World Economic Forum on January 31, 1999 to serve as guidelines for world businesses. The principles address three basic areas of concern: human rights, labor standards, and environment. The Global Compact also provides means and methods for enacting these principles, including case studies and research from the ILO and the UNEP. The site's Country Information section is a searchable database of labor, human rights, and environmental information from Abkhyazia to Zimbabwe. The News and Reviews section contains current and archived news, as well as statements about the Global Compact from UN Secretary General Kofi Annan and Secretary General Amnesty International Pierre Sane among others. Here, users will also find an analytical overview of the research and debates over these topics.

87

Effects of Ti charge state, ion size and beam-induced compaction on the formation of Ag metal nanoparticles in fused silica  

NASA Astrophysics Data System (ADS)

Metal nanoparticles formed by ion implantation in fused silica exhibit linear and nonlinear optical properties that can be altered by co-doping the silica substrate with transition-metal ions. For example, implantation of scandium in fused silica creates a directional optical dichroism due to the different spatial distribution of silver nanoparticles subsequently formed by Ag ion implantation. In this paper, we show that implantation of titanium ions alters the short- and intermediate-range order in the silica and thereby alters the diffusion and nucleation processes that lead to formation of silver nanoparticles. In particular, the dichroic response observed for Ag nanoparticles in Sc-implanted silica is, with one exception, in Ti-implanted silica. Compaction of the silica due to the ion implantation process appears to be similar for both Sc and Ti implantations, based on the observed shift of the 1,124 cm-1 transverse-optical phonon mode in the infrared reflectance spectrum. However, differences in chemical reactivity, bond lengths and electronic structure of Sc and Ti produce changes in electronic structure and strain that are sensitively reflected in the reflectance spectra of the Ag nanoparticles. These differences lead to modifications in the size, shape and spatial distributions of the silver nanoparticles and offer a powerful means of controlling their optical properties.

Magruder, R. H.; Meldrum, A.; Haglund, R. F.

2015-02-01

88

Effects of Ti charge state, ion size and beam-induced compaction on the formation of Ag metal nanoparticles in fused silica  

NASA Astrophysics Data System (ADS)

Metal nanoparticles formed by ion implantation in fused silica exhibit linear and nonlinear optical properties that can be altered by co-doping the silica substrate with transition-metal ions. For example, implantation of scandium in fused silica creates a directional optical dichroism due to the different spatial distribution of silver nanoparticles subsequently formed by Ag ion implantation. In this paper, we show that implantation of titanium ions alters the short- and intermediate-range order in the silica and thereby alters the diffusion and nucleation processes that lead to formation of silver nanoparticles. In particular, the dichroic response observed for Ag nanoparticles in Sc-implanted silica is, with one exception, in Ti-implanted silica. Compaction of the silica due to the ion implantation process appears to be similar for both Sc and Ti implantations, based on the observed shift of the 1,124 cm-1 transverse-optical phonon mode in the infrared reflectance spectrum. However, differences in chemical reactivity, bond lengths and electronic structure of Sc and Ti produce changes in electronic structure and strain that are sensitively reflected in the reflectance spectra of the Ag nanoparticles. These differences lead to modifications in the size, shape and spatial distributions of the silver nanoparticles and offer a powerful means of controlling their optical properties.

Magruder, R. H.; Meldrum, A.; Haglund, R. F.

2015-04-01

89

The polytropic index for the solar wind at Earth's bow shock  

NASA Astrophysics Data System (ADS)

Analysis of spacecraft shock-crossing data on the magnetosheath thickness to determine the polytropic index ? of the solar wind is shown to overestimate the value for ? when the gasdynamic (GD) equations are used for the shock jump. This is done by comparing GD estimates for ? extrapolated from observed data points to values obtained when more appropriate MHD equations are used. As a result of this bias a shock-crossing data analysis carried out recently using the GD equations appears to have obtained a value for ? that is over 0.5 too large. This is in part associated with the breakdown of GD with respect to nonzero angle between the bow-shock normal and the magnetic field for finite Alfven Mach numbers. The magnetosonic phenomenological model (sonic Mach number replaced with the magnetosonic Mach number in the GD equations), which was also recently used to determine ?, is found to reduce this bias by 70-90%. This analysis also strongly suggests that the phenomenological model inadequately treats variations in the angle between the bow-shock normal and the magnetic field, which may also produce systematic errors in the experimental determination of ? using this model.

Grabbe, Crockett L.

1996-05-01

90

Acoustic oscillations in rapidly rotating polytropic stars I. Effects of the centrifugal distortion  

E-print Network

A new non-perturbative method to compute accurate oscillation modes in rapidly rotating stars is presented. In this paper, the effect of the centrifugal force is fully taken into account while the Coriolis force is neglected. This assumption is valid when the time scale of the oscillation is much shorter than the inverse of the rotation rate and is expected to be suitable for high radial order p-modes of $\\delta$ Scuti stars. Axisymmetric p-modes have been computed in uniformly rotating polytropic models of stars. In the frequency and rotation range considered, we found that as rotation increases (i) the asymptotic structure of the non-rotating frequency spectrum is first destroyed then replaced by a new form of organization (ii) the mode amplitude tends to concentrate near the equator (iii) differences with perturbative methods become significant as soon as the rotation rate exceeds about fifteen percent of the Keplerian limit. The implications for the seismology of rapidly rotating stars are then discussed.

F. Lignieres; M. Rieutord; D. Reese

2006-04-13

91

Increased compactibility of acetames after roll compaction.  

PubMed

A common technique for manufacturing granules in a continuous way is the combination of roll compaction and subsequent milling. Roll compaction can considerably impact tableting performance of a material. The purpose of this study was to investigate the influence of roll compaction/dry granulation on the compaction behavior of acetames, a class of active pharmaceutical substances, which are mainly used for the treatment of central nervous diseases. Some representatives of acetames were roll compacted and then compressed into tablets. Compactibility of granules was compared with the compaction behavior of the directly compressed drug powders. In contrast to many other materials, the roll compaction step induced an increase in compactibility for all investigated acetames. Specific surface areas of the untreated and the roll compacted drugs were determined by nitrogen adsorption. The raise in compactibility observed was accompanied by an increase in specific surface area during roll compaction. PMID:20932904

Kuntz, Theresia; Schubert, Martin A; Kleinebudde, Peter

2011-01-01

92

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

93

TECHNICAL DESIGN NOTE: Identification of the flow-rate characteristics of a pneumatic valve by the instantaneous polytropic exponent  

NASA Astrophysics Data System (ADS)

A novel method of the identification of the flow-rate characteristics of pneumatic valves using the instantaneous polytropic exponents during a discharge process is proposed. The method can determine the sonic conductance C, the critical pressure ratio b and the subsonic index ms of a pneumatic valve with a single discharge process. The method is based on a new hybrid natural and forced convection heat transfer criterion model. The procedure of the identification of the flow-rate characteristics of the pneumatic valve has been derived. Some examples of the calculation are given and the results are graphically illustrated. Experimental results show that the model has good accuracy and universality.

Qian, Ye; Xiang, Meng Guo

2008-05-01

94

Critical rotation of general-relativistic polytropic models simulating neutron stars: a post-Newtonian hybrid approximative scheme  

E-print Network

We develop a "hybrid approximative scheme" in the framework of the post-Newtonian approximation for computing general-relativistic polytropic models simulating neutron stars in critical rigid rotation. We treat the differential equations governing such a model as a "complex initial value problem", and we solve it by using the so-called "complex-plane strategy". We incorporate into the computations the complete solution for the relativistic effects, this issue representing a significant improvement with regard to the classical post-Newtonian approximation, as verified by extended comparisons of the numerical results.

Vassilis S. Geroyannis; Vasileios G. Karageorgopoulos

2014-09-30

95

Compact magnetograph  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

96

The evolution of highly compact binary stellar systems  

NASA Technical Reports Server (NTRS)

A new theoretical treatment of the evolution of highly compact binary systems is presented. The evolution is calculated until almost the entire mass of the secondary has been transferred to the primary or lost from the system. It is assumed that gravitational radiation from the system is the cause of mass transfer. It is found that the structure of the mass-losing star can be approximated by an n = 3/2 polytrope, and as a result a relatively large number of different cases can be explored and some general conclusions drawn. An explanation is found for the existence of a cutoff in the orbital period distribution among the cataclysmic variables and light is shed upon the possible generic relationships among cataclysmic variables, the low-mass X-ray binaries, and the spectrally soft transient X-ray sources.

Rappaport, S.; Joss, P. C.; Webbink, R. F.

1982-01-01

97

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

98

Viral RNAs Are Unusually Compact  

PubMed Central

A majority of viruses are composed of long single-stranded genomic RNA molecules encapsulated by protein shells with diameters of just a few tens of nanometers. We examine the extent to which these viral RNAs have evolved to be physically compact molecules to facilitate encapsulation. Measurements of equal-length viral, non-viral, coding and non-coding RNAs show viral RNAs to have among the smallest sizes in solution, i.e., the highest gel-electrophoretic mobilities and the smallest hydrodynamic radii. Using graph-theoretical analyses we demonstrate that their sizes correlate with the compactness of branching patterns in predicted secondary structure ensembles. The density of branching is determined by the number and relative positions of 3-helix junctions, and is highly sensitive to the presence of rare higher-order junctions with 4 or more helices. Compact branching arises from a preponderance of base pairing between nucleotides close to each other in the primary sequence. The density of branching represents a degree of freedom optimized by viral RNA genomes in response to the evolutionary pressure to be packaged reliably. Several families of viruses are analyzed to delineate the effects of capsid geometry, size and charge stabilization on the selective pressure for RNA compactness. Compact branching has important implications for RNA folding and viral assembly. PMID:25188030

Gopal, Ajaykumar; Egecioglu, Defne E.; Yoffe, Aron M.; Ben-Shaul, Avinoam; Rao, Ayala L. N.; Knobler, Charles M.; Gelbart, William M.

2014-01-01

99

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

100

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

SciTech Connect

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

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

2013-05-01

101

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

102

A THREE-DIMENSIONAL NUMERICAL SOLUTION FOR THE SHAPE OF A ROTATIONALLY DISTORTED POLYTROPE OF INDEX UNITY  

SciTech Connect

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

Kong, Dali; Zhang, Keke [Department of Mathematical Sciences, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom)] [Department of Mathematical Sciences, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom); Schubert, Gerald [Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095-1567 (United States)] [Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095-1567 (United States); Anderson, John, E-mail: D.Kong@exeter.ac.uk, E-mail: K.Zhang@exeter.ac.uk, E-mail: jdandy@earthlink.net [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)] [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2013-02-15

103

Characterization of a Polytropic Murine Leukemia Virus Proviral Sequence Associated with the Virus Resistance Gene Rmcf of DBA/2 Mice  

PubMed Central

The DBA/2 mouse Rmcf gene is responsible for in vivo and in vitro resistance to infection by the polytropic mink cell focus-forming (MCF) virus subgroup of murine leukemia viruses (MLVs). Previous studies suggested that Rmcf resistance is mediated by expression of an interfering MCF MLV envelope (Env) gene. To characterize this env gene, we examined resistance in crosses between Rmcfr DBA/2 mice and Mus castaneus, a species that lacks endogenous MCF env sequences. In backcross progeny, inheritance of Rmcf resistance correlated with inheritance of a specific endogenous MCF virus env-containing 4.6-kb EcoRI fragment. This fragment was present in the DBA/2N substrain with Rmcf-mediated resistance but not in virus-susceptible DBA/2J substrain mice. This fragment contains a provirus with a 5? long terminal repeat and the 5? half of env; the gag and pol genes have been partially deleted. The Env sequence is identical to that of a highly immunogenic viral glycoprotein expressed in the DBA/2 cell line L5178Y and closely resembles the env genes of modified polytropic proviruses. The coding sequence for the full-length Rmcf Env surface subunit was amplified from DNAs from virus-resistant backcross mice and was cloned into an expression vector. NIH 3T3 and BALB 3T3 cells stably transfected with this construct showed significant resistance to infection by MCF MLV but not by amphotropic MLV. This study identifies an Rmcf-linked MCF provirus and indicates that, like the ecotropic virus resistance gene Fv4, Rmcf may mediate resistance through an interference mechanism. PMID:12134027

Jung, Yong Tae; Lyu, Myung Soo; Buckler-White, Alicia; Kozak, Christine A.

2002-01-01

104

Ordinal Compactness Paolo Lipparini  

E-print Network

of [, ]-compact- ness. #12;Throughout, let be infinite ordinals. Definition 1 We say that a topological space- ness are the following: · [µ, ]-compactness is equivalent to [, ]-com- pactness, for every with µ · [cf, cf]-compactness implies [, ]-compact- ness. On the other hand, there are many more non- trivial

Lipparini, Paolo

105

18 CFR 420.23 - Exempt uses under the Compact.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

106

18 CFR 420.23 - Exempt uses under the Compact.  

Code of Federal Regulations, 2014 CFR

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

2014-04-01

107

18 CFR 420.23 - Exempt uses under the Compact.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

108

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

NASA Technical Reports Server (NTRS)

In this paper empirical evidence is presented that between 0.4 and 5 AU the thermal portion (but not all) of the solar wind electron population obeys a polytrope relation. It is also shown that this functional relationship is a member of a broader class of possible laws required of a steady state, fully ionized plasma whose proper frame electric field is dominated by the polarization electric field. The empirically determined, thermodynamically interesting value of the polytrope index (1.175) is virtually that predicted (1.16) by the theoretical considerations of Scudder and Olbert (1979). Strong, direct, empirical evidence for the nearly isothermal behavior of solar wind electrons as has been indirectly argued in the literature for some time is provided.

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

1980-01-01

109

Compact plasma accelerator  

NASA Technical Reports Server (NTRS)

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

Foster, John E. (Inventor)

2004-01-01

110

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

E-print Network

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

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

2011-01-01

111

Compaction Behavior of Isomalt after Roll Compaction  

PubMed Central

The suitability of the new isomalt grade galenIQ™ 801 for dry granulation and following tableting is evaluated in this study. Isomalt alone, as well as a blend of equal parts with dibasic calcium phosphate, is roll compacted and tableted. Particle size distribution and flowability of the granules and friability and disintegration time of the tablets are determined. Tensile strength of tablets is related to the specific compaction force during roll compaction and the tableting force. In all cases, the tensile strength increases with raising tableting forces. The specific compaction force has a different influence. For isomalt alone the tensile strength is highest for tablets made from granules prepared at 2 kN/cm and 6 kN/cm and decreases at higher values, i.e., >10 kN/cm. Tensile strength of the blend tablets is almost one third lower compared to the strongest tablets of pure isomalt. Friability of pure isomalt tablets is above the limit. Disintegration time is longest when the tensile strength is at its maximum and decreases with higher porosity and lower tensile strengths. Isomalt proves to be suitable for tableting after roll compaction. Even though the capacity as a binder might not be as high as of other excipients, it is a further alternative for the formulation scientist. PMID:24300366

Quodbach, Julian; Mosig, Johanna; Kleinebudde, Peter

2012-01-01

112

Compact Polarimetry Potentials  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

113

Compact Groups of Galaxies  

Microsoft Academic Search

Compact groups of galaxies have posed a number of challenging questions. Intensive observational and theoretical studies are now providing answers to many of these and, at the same time, are revealing unexpected new clues about the nature and role of these systems. Most compact groups contain a high fraction of galaxies having morphological or kinematical peculiarities, nuclear radio and infrared

Paul Hickson

1997-01-01

114

Compact Propositional Gödel Logics  

Microsoft Academic Search

Entailment in propositional Godel logics can be defined in a natural way. While all infinite sets of truth values yield the same sets of tautologies, the entailment relations diff er. It is shown that there is a rich structure of infinite-valued Godel logics, only one of which is compact. It is also shown that the compact infinite-valued Godel logic is

Matthias Baaz; Richard Zach

1998-01-01

115

Branching to maximal compact  

E-print Network

's thm and alg geometry Zuckerman's thm From K to G and back again Summary Branching to maximal compact classically Helgason's thm and alg geometry Zuckerman's thm From K to G and back again Summary Outline the branching law: Zuckerman's theorem Relating representations of K and G #12;Branching to maximal compact

Vogan, David

116

SOIL COMPACTION MANAGEMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

During temporary droughts that often limit agricultural production, soil compaction can hinder plant roots from reaching depths of soil where moisture is available. Many fields exhibit various degrees of soil compaction, resulting from variable soil types and past tillage and traffic practices. Va...

117

ACOUSTIC COMPACTION LAYER DETECTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

The depth and strength of compacted layers in fields have been determined traditionally using the ASAE standardized cone penetrometer method. However, an on-the-go method would be much faster and much less labor intensive. The soil measurement system described here attempts to locate the compacted...

118

Saloplastics: processing compact polyelectrolyte complexes.  

PubMed

Polyelectrolyte complexes (PECs) are prepared by mixing solutions of oppositely charged polyelectrolytes. These diffuse, amorphous precipitates may be compacted into dense materials, CoPECs, by ultracentrifugation (ucPECs) or extrusion (exPECs). The presence of salt water is essential in plasticizing PECs to allow them to be reformed and fused. When hydrated, CoPECs are versatile, rugged, biocompatible, elastic materials with applications including bioinspired materials, supports for enzymes and (nano)composites. In this review, various methods for making CoPECs are described, as well as fundamental responses of CoPEC mechanical properties to salt concentration. Possible applications as synthetic cartilage, enzymatically active biocomposites, self-healing materials, and magnetic nanocomposites are presented. PMID:25771881

Schaaf, Pierre; Schlenoff, Joseph B

2015-04-01

119

DNA compaction by azobenzene-containing surfactant  

SciTech Connect

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.

Zakrevskyy, Yuriy; Kopyshev, Alexey; Lomadze, Nino; Santer, Svetlana [Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam (Germany); Morozova, Elena; Lysyakova, Ludmila; Kasyanenko, Nina [Department of Molecular Biophysics, Faculty of Physics, St. Petersburg State University, Ulyanovskaya St. 1, Petrodvorets, St. Petersburg 198504 (Russian Federation)

2011-08-15

120

Multipolar universal relations between f -mode frequency and tidal deformability of compact stars  

NASA Astrophysics Data System (ADS)

Though individual stellar parameters of compact stars usually demonstrate obvious dependence on the equation of state (EOS), EOS-insensitive universal formulas relating these parameters remarkably exist. In the present paper, we explore the interrelationship between two such formulas, namely the f -I relation connecting the f -mode quadrupole oscillation frequency ?2 and the moment of inertia I , and the I -Love-Q relations relating I , the quadrupole tidal deformability ?2, and the quadrupole moment Q , which have been proposed by Lau, Leung, and Lin [Astrophys. J. 714, 1234 (2010)] and Yagi and Yunes [Science 341, 365 (2013)], respectively. A relativistic universal relation between ?l and ?l with the same angular momentum l =2 ,3 ,… , the so-called "diagonal f -Love relation" that holds for realistic compact stars and stiff polytropic stars, is unveiled here. An in-depth investigation in the Newtonian limit is further carried out to pinpoint its underlying physical mechanism and hence leads to a unified f -I -Love relation. We reach the conclusion that these EOS-insensitive formulas stem from a common physical origin—compact stars can be considered as quasiincompressible when they react to slow time variations introduced by f -mode oscillations, tidal forces and rotations.

Chan, T. K.; Sham, Y.-H.; Leung, P. T.; Lin, L.-M.

2014-12-01

121

Multipolar universal relations between f-mode frequency and tidal deformability of compact stars  

E-print Network

Though individual stellar parameters of compact stars usually demonstrate obvious dependence on the equation of state (EOS), EOS-insensitive universal formulas relating these parameters remarkably exist. In the present paper, we explore the interrelationship between two such formulas, namely the $f$-$I$ relation connecting the $f$-mode quadrupole oscillation frequency $\\omega_2$ and the moment of inertia $I$, and the $I$-Love-$Q$ relations relating $I$, the quadrupole tidal deformability $\\lambda_2$, and the quadrupole moment $Q$, which have been proposed by Lau, Leung, and Lin [Astrophys. J. {\\bf 714}, 1234 (2010)] and Yagi and Yunes [Science {\\bf 341}, 365 (2013)], respectively. A relativistic universal relation between $\\omega_l$ and $\\lambda_l$ with the same angular momentum $l=2,3,\\ldots$, the so-called "diagonal $f$-Love relation" that holds for realistic compact stars and stiff polytropic stars, is unveiled here. An in-depth investigation in the Newtonian limit is further carried out to pinpoint its underlying physical mechanism and hence leads to a unified $f$-$I$-Love relation. We reach the conclusion that these EOS-insensitive formulas stem from a common physical origin --- compact stars can be considered as quasiincompressible when they react to slow time variations introduced by $f$-mode oscillations, tidal forces and rotations.

T. K. Chan; Y. -H. Sham; P. T. Leung; L. -M. Lin

2015-01-13

122

Compact conformal manifolds  

NASA Astrophysics Data System (ADS)

In this note we begin a systematic study of compact conformal manifolds of SCFTs in four dimensions (our notion of compactness is with respect to the topology induced by the Zamolodchikov metric). Supersymmetry guarantees that such manifolds are Kähler, and so the simplest possible non-trivial compact conformal manifold in this set of geometries is a complex one-dimensional projective space. We show that such a manifold is indeed realized and give a general prescription for constructing complex N-dimensional projective space conformal manifolds as certain small breaking deformations of strongly interacting SCFTs. In many cases, our prescription reduces the construction of such spaces to a study of the chiral ring. We also give an algorithm for constructing more general compact spaces of SCFTs.

Buican, Matthew; Nishinaka, Takahiro

2015-01-01

123

Compact Conformal Manifolds  

E-print Network

In this note we begin a systematic study of compact conformal manifolds of SCFTs in four dimensions (our notion of compactness is with respect to the topology induced by the Zamolodchikov metric). Supersymmetry guarantees that such manifolds are Kahler, and so the simplest possible non-trivial compact conformal manifold in this set of geometries is a complex one-dimensional projective space. We show that such a manifold is indeed realized and give a general prescription for constructing complex N-dimensional projective space conformal manifolds as certain small N=2->N=1 breaking deformations of strongly interacting N=2 SCFTs. In many cases, our prescription reduces the construction of such spaces to a study of the N=2 chiral ring. We also give an algorithm for constructing more general compact spaces of SCFTs.

Matthew Buican; Takahiro Nishinaka

2014-11-14

124

Compact microchannel system  

DOEpatents

The present invention provides compact geometries for the layout of microchannel columns through the use of turns and straight channel segments. These compact geometries permit the use of long separation or reaction columns on a small microchannel substrate or, equivalently, permit columns of a fixed length to occupy a smaller substrate area. The new geometries are based in part on mathematical analyses that provide the minimum turn radius for which column performance in not degraded. In particular, we find that straight channel segments of sufficient length reduce the required minimum turn radius, enabling compact channel layout when turns and straight segments are combined. The compact geometries are obtained by using turns and straight segments in overlapped or nested arrangements to form pleated or coiled columns.

Griffiths, Stewart

2003-09-30

125

Compact turbidity meter  

NASA Technical Reports Server (NTRS)

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

Hirschberg, J. G.

1979-01-01

126

Semi Compactness in Multiset Topology  

E-print Network

In this paper, we introduce and study the concepts of semi open SOM) and semi closed (SCM) M-sets in multiset topological spaces.With this generalization of the notions of open and closed sets in M-topology, we generalize the concept of compactness in M-topology as semi compactness. Further semi compactness is generalized as semi whole compactness, semi partial whole compactness and semi full compactness. Some characterizations of these compact spaces are studied in the setting of multiset theory. In each step, several remarks with proper justifications are provided taking the well existing theories of general topology as the base of our study.

J. Mahanta; D. Das

2014-11-21

127

Physically detached 'compact groups'  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

128

New observations on the compact myelin proteome.  

PubMed

Myelin formation and maintenance depends on the establishment of two structurally and biochemically discernible domains: (a)compact myelin, that is multilamellar stacks of plasma membrane sheets; and (b) cytoplasmic channels that border the compact myelin domains, attach them to the cell body and anchor the myelin sheath to the axonal membrane. To identify proteins involved in the organization of these domains we took advantage of the high lipid content of compact myelin to separate it cleanly from other neural membranes and then used reverse-phase HPLC coupled to Electro-Spray Double Mass Spectrometry('MudPIT') to characterize the proteome of this sample. MudPIT allowed us to sidestep the bias of 2D-PAGE against either highly charged or transmembrane proteins. Thus, of 97 proteins that presented at least two, fully tryptic peptides (a stringent threshold), seven were well known myelin markers, including the mayor CNS myelin proteins: proteolipid protein and myelin basic protein, which are not resolvable by 2D-PAGE. Furthermore, we have confirmed and extended the known compact myelin proteome by 22 proteins and confirmed that CNS and PNS myelinated tracts present Sirtuin 2, a tubulin deacetylase, and Septin7, a small GTPase that is likely to be involved in membrane and cytoplasm partitioning. PMID:18634588

Roth, Alejandro D; Ivanova, Anna; Colman, David R

2006-02-01

129

Compact groups of galaxies  

E-print Network

Compact groups of galaxies have posed a number of challenging questions. Intensive observational and theoretical studies are now providing answers to many of these, and at the same time, are revealing unexpected new clues about the nature and role of these systems. Most compact groups contain a high fraction of galaxies having morphological or kinematical peculiarities, nuclear radio and infrared emission, and starburst or active galactic nuclei (AGN) activity. They contain large quantities of diffuse gas and are dynamically dominated by dark matter. They most likely form as subsystems within looser associations and evolve by gravitational processes. Strong galaxy interactions result and merging is expected to lead to the ultimate demise of the group. Compact groups are surprisingly numerous, and may play a significant role in galaxy evolution.

Paul Hickson

1997-10-25

130

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

131

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

2012-01-01

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

Compact Groups of Galaxies  

Microsoft Academic Search

Compact groups of galaxies typically contain fewer than ten galaxies, separated from one another on the plane of the sky by a galaxy diameter or less. A continuing question about these groups is why we see so many of them even though galaxy interactions should quickly destroy the individual galaxies and result in a single merger remnant. The presence of

Rachel Ann Pildis

1995-01-01

134

Limestone compaction: an enigma  

USGS Publications Warehouse

Compression of an undisturbed carbonate sediment core under a pressure of 556 kg/cm2 produced a “rock” with sedimentary structures similar to typical ancient fine-grained limestones. Surprisingly, shells, foraminifera, and other fossils were not noticeably crushed, which indicates that absence of crushed fossils in ancient limestones can no longer be considered evidence that limestones do not compact.

Shinn, Eugene A.; Halley, Robert B.; Hudson, J. Harold; Lidz, Barbara H.

1977-01-01

135

Ute Indian water compact  

Microsoft Academic Search

A potential addition to the Law of the River, the Ute Indian Water Compact (approved by the Utah Legislature in 1980), attempts to resolve conflicts between the State of Utah and the Ute Indian Tribe of the Uintah and Ouray Reservation regarding rights to surface and ground waters appurtenant to the reservation. This includes several tributaries of the Colorado River.

Fetzer

1982-01-01

136

Compact, Integrated Photoelectron Linacs  

NASA Astrophysics Data System (ADS)

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

Yu, David

2000-12-01

137

Compact tubing testing unit  

Microsoft Academic Search

A mobile unit is described for use in testing tubing joints as the tubing is being made up and run into an oil well. The mobile unit includes a framework compactly receiving an engine driving a hydraulic pump, a drawworks, high pressure hydraulically actuated pump for pressuring the tubing joint to be tested, and tubing tongs for use in making

Matherne

1974-01-01

138

Compact plasma accelerator device  

Microsoft Academic Search

A compact plasma accelerator concept based on plasma production at a magnetic cusp was designed and fabricated. Plume and discharge characteristics of the device were documented using a Faraday probe and a retarding potential analyzer. The discharge current variations with increasing discharge voltage were nonlinear with the discharge current increasing rapidly with voltage. The device demonstrated the capability of generating

John E. Foster

2002-01-01

139

COMPACT SCHOOL AND $$ SAVINGS.  

ERIC Educational Resources Information Center

A REVIEW OF THE CRITERIA FOR CONSIDERING THE USE OF A TOTAL ENERGY SYSTEM WITHIN A SCHOOL BUILDING STATES THE WINDOWLESS, COMPACT SCHOOL OFFERS MORE EFFICIENT SPACE UTILIZATION WITH LESS AREA REQUIRED FOR GIVEN STUDENT POPULATION AND LOWER OPERATION COSTS. THE AUTHOR RECOMMENDS THAT THESE BUILDINGS BE WINDOWLESS TO REDUCE HEAT COSTS, HOWEVER, AT…

BAIR, W.G.

140

SPICE implementation of a compact single electron tunneling transistor model  

Microsoft Academic Search

A novel compact single electron tunneling transistor (SETT) SPICE model is described in this paper. This SPICE implementation is based on an analytical model derived from a simplified full master equation model. Besides of being able to accurately capture the SETT behavior under various circuit and temperature conditions our proposal can also evaluate background charge effects in SETT circuits. This

Cheng Jia; Hu Chaohong; Sorin Dan COTOFANA; Jiang Jianfei

2004-01-01

141

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

142

CHARGE IMBALANCE  

SciTech Connect

The purpose of this article is to review the theory of charge imbalance, and to discuss its relevance to a number of experimental situations. We introduce the concepts of quasiparticle charge and charge imbalance, and discuss the generation and detection of charge imbalance by tunneling. We describe the relaxation of the injected charge imbalance by inelastic scattering processes, and show how the Boltzmann equation can be solved to obtain the steady state quasiparticle distribution and the charge relaxation rate. Details are given of experiments to measure charge imbalance and the charge relaxation rate when inelastic scattering is the predominant relaxation mechanism. Experiments on and theories of other charge relaxation mechanisms are discussed, namely relaxation via elastic scattering in the presence of energy gap anisotropy, or in the presence of a pair breaking mechanism such as magnetic impurities or an applied supercurrent or magnetic field. We describe three other situations in which charge imbalance occurs, namely the resistance of the NS interface, phase slip centers, and the flow of a supercurrent in the presence of a temperature gradient.

Clarke, John

1980-09-01

143

Internal Charging  

NASA Technical Reports Server (NTRS)

(1) High energy (>100keV) electrons penetrate spacecraft walls and accumulate in dielectrics or isolated conductors; (2) Threat environment is energetic electrons with sufficient flux to charge circuit boards, cable insulation, and ungrounded metal faster than charge can dissipate; (3) Accumulating charge density generates electric fields in excess of material breakdown strenght resulting in electrostatic discharge; and (4) System impact is material damage, discharge currents inside of spacecraft Faraday cage on or near critical circuitry, and RF noise.

Minow, Joseph I.

2014-01-01

144

Super-Compact Laser  

NASA Technical Reports Server (NTRS)

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

1997-01-01

145

Compact Spreader Schemes  

SciTech Connect

This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.

Placidi, M.; Jung, J. -Y.; Ratti, A.; Sun, C.

2014-07-25

146

Compact infrared detector  

NASA Technical Reports Server (NTRS)

Broadband IR detector integrated into compact package for pollution monitoring and weather prediction is small, highly responsive, and immune to high noise. Sensing material is transparent sheet metalized with reflecting coating and overcoated with black material on same side. Pulse produced by chopping of infrared source beam creates transient "thermal lens" that temporarily defocuses laser beam probe. Detector monitoring beam measures defocusing which parallels infrared intensity.

Gupta, A.; Hong, S.; Moacanin, J.

1981-01-01

147

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.

148

Hydraulic conductivity of compacted zeolites.  

PubMed

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

Oren, A Hakan; Ozdamar, Tu?çe

2013-06-01

149

Charge-pump voltage converter  

DOEpatents

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

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

2009-11-03

150

CHARGE syndrome  

PubMed Central

CHARGE syndrome was initially defined as a non-random association of anomalies (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies/deafness). In 1998, an expert group defined the major (the classical 4C's: Choanal atresia, Coloboma, Characteristic ears and Cranial nerve anomalies) and minor criteria of CHARGE syndrome. Individuals with all four major characteristics or three major and three minor characteristics are highly likely to have CHARGE syndrome. However, there have been individuals genetically identified with CHARGE syndrome without the classical choanal atresia and coloboma. The reported incidence of CHARGE syndrome ranges from 0.1–1.2/10,000 and depends on professional recognition. Coloboma mainly affects the retina. Major and minor congenital heart defects (the commonest cyanotic heart defect is tetralogy of Fallot) occur in 75–80% of patients. Choanal atresia may be membranous or bony; bilateral or unilateral. Mental retardation is variable with intelligence quotients (IQ) ranging from normal to profound retardation. Under-development of the external genitalia is a common finding in males but it is less apparent in females. Ear abnormalities include a classical finding of unusually shaped ears and hearing loss (conductive and/or nerve deafness that ranges from mild to severe deafness). Multiple cranial nerve dysfunctions are common. A behavioral phenotype for CHARGE syndrome is emerging. Mutations in the CHD7 gene (member of the chromodomain helicase DNA protein family) are detected in over 75% of patients with CHARGE syndrome. Children with CHARGE syndrome require intensive medical management as well as numerous surgical interventions. They also need multidisciplinary follow up. Some of the hidden issues of CHARGE syndrome are often forgotten, one being the feeding adaptation of these children, which needs an early aggressive approach from a feeding team. As the child develops, challenging behaviors become more common and require adaptation of educational and therapeutic services, including behavioral and pharmacological interventions. PMID:16959034

Blake, Kim D; Prasad, Chitra

2006-01-01

151

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

152

Charge transport  

NASA Astrophysics Data System (ADS)

We report results from theoretical studies of charge and energy dynamics in organic molecular and polymeric systems. The studies were performed by employing an extended three-dimensional version of the Su-Schrieffer-Heeger model. The equation of motion for the lattice as well as the time dependent Schrodinger equation were solved simultaneously. The dynamics of charge transport and charge separation in conjugated polymeric systems have been investigated as well as the time evolution following the injection of hot electrons and excitons. The results of such studies will contribute to the understanding and the development of organic electronic and photovoltaic devices as well as artificial photosynthesis.

Stafstrãm, Sven; Boman, Magnus; Hultell Andersson, Magnus

2004-03-01

153

Hadrons in compact stars  

E-print Network

We discuss $\\beta$-equilibrated and charge neutral matter involving hyperons and $\\bar K$ condensates within relativistic models. It is observed that populations of baryons are strongly affected by the presence of antikaon condensates. Also, the equation of state including $\\bar K$ condensates becomes softer resulting in a smaller maximum mass neutron star.

Debades Bandyopadhyay

2005-12-28

154

Compact electrostatic comb actuator  

DOEpatents

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

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

2000-01-01

155

Accretion in Compact Binaries  

E-print Network

Compact binaries have long been a paradigm for accretion theory. Much of our present view of how accretion occurs comes directly from the comparison of theory with observations of these sources. Since theory differs little for other objects such as active galaxies, increasing efforts have recently gone into searching for correspondences in observed behaviour. This chapter aims at giving a concise summary of the field, with particular emphasis on new developments since the previous edition of this book. These developments have been significant. Much of the earlier literature implicitly assumed that accreting binaries were fairly steady sources accreting most of the mass entering their vicinity, often with main-sequence companions, and radiating the resulting accretion luminosity in rough isotropy. We shall see that in reality these assumptions fail for the majority of systems. Most are transient; mass ejection in winds and jets is extremely common; a large (sometimes dominant) fraction of even short-period systems have evolved companions whose structure deviates significantly from the zero-age main sequence; and the radiation pattern of many objects is significantly anisotropic. It is now possible to give a complete characterization of the observed incidence of transient and persistent sources in terms of the disc instability model and formation constraints. X-ray populations in external galaxies, particularly the ultraluminous sources, are revealing important new insights into accretion processes and compact binary evolution.

Andrew R. King

2003-03-26

156

Compaction of Titanium Powders  

SciTech Connect

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

Gerdemann, Stephen,J; Jablonski, Paul, J

2011-05-01

157

Compact Infrasonic Windscreen  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

158

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.

2012-06-26

159

Compact, Pneumatically Actuated Filter Shuttle  

NASA Technical Reports Server (NTRS)

A compact, pneumatically actuated filter shuttle has been invented to enable alternating imaging of a wind-tunnel model in two different spectral bands characteristic of the pressure and temperature responses of a pressure and temperature-sensitive paint. This filter shuttle could also be used in other settings in which there are requirements for alternating imaging in two spectral bands. Pneumatic actuation was chosen because of a need to exert control remotely (that is, from outside the wind tunnel) and because the power leads that would be needed for electrical actuation would pose an unacceptable hazard in the wind tunnel. The entire shuttle mechanism and its housing can be built relatively inexpensively [<$500 (prices as of year 2000)] from off-the-shelf parts. The shuttle mechanism (see Figure 1) is contained in a housing that has dimensions of 4 by 6 by 2 in. (about 10 by 15 by 5 cm). Two 2-in. (=5-cm)-diameter standard scientific-grade band-pass filters are mounted on sliding panels in a dual-track frame. The mechanism is positioned and oriented so the panels slide sideways with respect to the optical axis of a charge-coupled-device camera used for viewing the wind-tunnel model. The mechanism includes a pneumatic actuator connected to a linkage. The linkage converts the actuator stroke to a scissor-like motion that places one filter in front of the camera and the other filter out of the way. Optoelectronic sensors detect tabs on the sliding panels for verification of the proper positioning of the filters.

Leighy, Bradley D.

2003-01-01

160

Compact acoustic refrigerator  

SciTech Connect

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

161

Compact vacuum insulation embodiments  

DOEpatents

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

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

1992-04-28

162

Compact vacuum insulation  

DOEpatents

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

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

1993-01-05

163

Multipurpose Compact Spectrometric Unit  

SciTech Connect

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

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

2009-11-09

164

Compact acoustic refrigerator  

DOEpatents

A compact acoustic refrigeration system 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. 18 figs.

Bennett, G.A.

1992-11-24

165

Compact acoustic refrigerator  

DOEpatents

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

Bennett, Gloria A. (Los Alamos, NM)

1992-01-01

166

Compact vacuum insulation embodiments  

DOEpatents

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

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

1992-01-01

167

Compact vacuum insulation  

DOEpatents

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

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

1993-01-01

168

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

169

Compact Groups in the SDSS  

Microsoft Academic Search

We identify compact groups in the Sloan Digital Sky Survey (SDSS) using an algorithm similar to that developed by Lee et al. (2003, astro-ph 0312553). Given that some authors claim compact groups to be chance alignments of galaxies or diffuse galaxy groups cores (Zandivarez et al. 2003, MNRAS, 340, 1400), our intention is to make a statistical study of the

E. Díaz; C. Ragone; H. Muriel; A. Zandivarez

2006-01-01

170

ON GO-COMPACT SPACES  

Microsoft Academic Search

The purpose of this paper is to oer some more properties of GO-compact spaces and to introduce and investigate some properties of g-continuous mul- tifunctions. We also investigate GO-compact spaces in the context of multi- functions.

M. Caldas; S. Jafari; S. P. Moshokoa; T. Noiri

2008-01-01

171

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...

172

Development of 13 GHz compact electron cyclotron resonance ion source  

Microsoft Academic Search

An extremely compact, all-permanent-magnet electron cyclotron resonance ion source was designed and manufactured mainly for materials development. The ion source was installed in a 400 kV ion implanter, and a heavy ion beam in the mega-electron-volt (MeV) energy region with high beam intensity was available using multiply charged ions from the ion source. The magnet measured 120 mm in length

Y. Saitoh; K. Ohkoshi; K. Arakawa

2004-01-01

173

A Compact Ring Design with Tunable Momentum Compaction  

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, Y.; /SLAC; ,

2012-05-17

174

7 CFR 51.582 - Fairly compact.  

Code of Federal Regulations, 2011 CFR

... 2011-01-01 2011-01-01 false Fairly compact. 51.582 Section 51.582 Agriculture ...Standards for Celery Definitions § 51.582 Fairly compact. Fairly compact means that the branches on the stalk are...

2011-01-01

175

7 CFR 51.582 - Fairly compact.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Fairly compact. 51.582 Section 51.582 Agriculture ...Standards for Celery Definitions § 51.582 Fairly compact. Fairly compact means that the branches on the stalk are...

2010-01-01

176

Holding Charge  

NSDL National Science Digital Library

In this trick, learners discover how to stick a straw to the palm of their hand, window door, or anywhere using static electricity. This activity introduces learners to negative and positive charges and shows how opposites attract. Note: this trick works best in low humidity (dry air).

Eric Muller

1995-01-01

177

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

178

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

179

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

180

Compact Dexterous Robotic Hand  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

181

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

182

Compact neutron generator  

DOEpatents

A compact neutron generator has at its outer circumference a toroidal shaped plasma chamber in which a tritium (or other) plasma is generated. A RF antenna is wrapped around the plasma chamber. A plurality of tritium ion beamlets are extracted through spaced extraction apertures of a plasma electrode on the inner surface of the toroidal plasma chamber and directed inwardly toward the center of neutron generator. The beamlets pass through spaced acceleration and focusing electrodes to a neutron generating target at the center of neutron generator. The target is typically made of titanium tubing. Water is flowed through the tubing for cooling. The beam can be pulsed rapidly to achieve ultrashort neutron bursts. The target may be moved rapidly up and down so that the average power deposited on the surface of the target may be kept at a reasonable level. The neutron generator can produce fast neutrons from a T-T reaction which can be used for luggage and cargo interrogation applications. A luggage or cargo inspection system has a pulsed T-T neutron generator or source at the center, surrounded by associated gamma detectors and other components for identifying explosives or other contraband.

Leung, Ka-Ngo; Lou, Tak Pui

2005-03-22

183

Measurements of oil shale compaction  

SciTech Connect

Oil shale compaction has been measured in a series of laboratory experiments at the Western Research Institute (WRI). In these experiments, the compaction measurements have corresponded to stacked beds of shale bricks at low void volumes of 12% and 25% bed porosity. Compaction of the shale bricks during retorting was measured by applying a constant mechanical force of 138 - 689 kPA to the top of the shale bed. This range of mechanical compression corresponds to the weight of overlying shale rubble in commercial modified in situ retorts.

Fahy, L.J.; Schreiber, J.D.; Sudduth, B.C.

1988-01-01

184

Gravitational Waves from Compact Sources  

E-print Network

We review sources of high-frequency gravitational waves, summarizing our current understanding of emission mechanisms, expected amplitudes and event rates. The most promising sources are gravitational collapse (formation of black holes or neutron stars) and subsequent ringing of the compact star, secular or dynamical rotational instabilities and high-mass compact objects formed through the merger of binary neutron stars. Significant and unique information for the various stages of the collapse, the structure of protoneutron stars and the high density equation of state of compact objects can be drawn from careful study of gravitational wave signals.

Kostas D. Kokkotas; Nikolaos Stergioulas

2005-07-06

185

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

186

Compact, Reliable EEPROM Controller  

NASA Technical Reports Server (NTRS)

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

Katz, Richard; Kleyner, Igor

2010-01-01

187

Mesoscale Simulations of Powder Compaction  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

188

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

189

New considerations for compact cyclotrons  

E-print Network

A compact cyclotron built with superconducting magnets could be a transformative solution to many scientific problems facing the defense, medical, and energy industries today. This thesis discusses three potential applications ...

Marshall, Eric S. (Eric Scott)

2012-01-01

190

Seyfert Galaxies in Compact Groups  

E-print Network

We present results concerning the occurrence of Seyfert galaxies in a new large sample of Compact Groups (Focardi & Kelm 2002). Seyfert galaxies turn out to be relatively rare (Compact Groups displaying relatively high velocity dispersion and a large number of neighbours. These characteristics,together with an excess of ellipticals among companions, suggest that Seyferts are to be found preferentially in rich-groups/poor-cluster like CGs.

P. Focardi; B. Kelm; V. Zitelli; G. Sarti

2002-09-20

191

Compact Ho:YLF Laser  

NASA Technical Reports Server (NTRS)

Longitudinal pumping by laser diodes increases efficiency. Improved holmium:yttrium lithium fluoride laser radiates as much as 56 mW of power at wavelength of 2.1 micrometer. New Ho:YLF laser more compact and efficient than older, more powerful devices of this type. Compact, efficient Ho:YLF laser based on recent successes in use of diode lasers to pump other types of solid-state lasers.

Hemmati, H.

1988-01-01

192

Photon and neutrino redshift in the field of braneworld compact stars  

SciTech Connect

We study gravitational redshift of photons and neutrinos radiated by the braneworld neutron or quark stars that are considered in the framework of the simple model of the internal spacetime with uniform distribution of energy density, and the external spacetime described by the Reissner-Nordström geometry characterized by the braneworld ''tidal'' charge b. For negative tidal charges, the external spacetime is of the black-hole type, while for positive tidal charges, the external spacetime can be of both black-hole and naked-singularity type. We consider also extremely compact stars allowing existence of trapped null geodesics in their interior. We assume radiation of photons from the surface at radius R, neutrinos from the whole compact star interior, and their motion along radial null geodesics of the spacetime. In dependency on the compact stars parameters b and R, the photon surface redshift is related to the range of the neutrino internal redshift and the signatures of the tidal charge and possible existence of extremely compact stars are discussed. When both surface (photon) and internal (neutrino) redshift are given by observations, both compact star parameters R and b can be determined in the framework of our simple model.

Hladík, Jan; Stuchlík, Zden?k, E-mail: jan.hladik@fpf.slu.cz, E-mail: zdenek.stuchlik@fpf.slu.cz [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezrucovo nám. 13, CZ-746 01 Opava (Czech Republic)

2011-07-01

193

Compact Optoelectronic Compass  

NASA Technical Reports Server (NTRS)

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

Christian, Carl

2004-01-01

194

Soil Compaction College of Agricultural Sciences  

E-print Network

Effects of Soil Compaction College of Agricultural Sciences Agricultural Research and Cooperative Extension #12;2 EFFECTS OF SOIL COMPACTION Effects of Soil Compaction INTRODUCTION Soil compaction is the reduction of soil volume due to external factors; this reduction lowers soil productivity and environmental

Kaye, Jason P.

195

Non-Compact Cardiomyopathy or Ventricular Non-Compact Syndrome?  

PubMed Central

Ventricular myocardial non-compaction has been recognized and defined as a genetic cardiomyopathy by American Heart Association since 2006. The argument on the nomenclature and pathogenesis of this kind of ventricular myocardial non-compaction characterized by regional ventricular wall thickening and deep trabecular recesses often complicated with chronic heart failure, arrhythmia and thromboembolism and usually overlap the genetics and phenotypes of other kind of genetic or mixed cardiomyopathy still exist. The proper classification and correct nomenclature of the non-compact ventricles will contribute to the precisely and completely understanding of etiology and its related patho-physiological mechanism for a better risk stratification and more personalized therapy of the disease individually. All of the genetic heterogeneity and phenotypical overlap and the variety in histopathological, electromechanical and clinical presentation indicates that some of the cardiomyopathies might just be the different consequence of myocardial development variations related to gene mutation and phenotype of one or group genes induced by the interacted and disturbed process of gene modulation at different links of gene function expression and some other etiologies. This review aims to establish a new concept of "ventricular non-compaction syndrome" based on the demonstration of the current findings of etiology, epidemiology, histopathology and echocardiography related to the disorder of ventricular myocardial compaction and myocardial electromechanical function development. PMID:25580189

2014-01-01

196

Directional Oscillations, Concentrations, and Compensated Compactness via Microlocal Compactness Forms  

NASA Astrophysics Data System (ADS)

This work introduces microlocal compactness forms (MCFs) as a new tool to study oscillations and concentrations in L p -bounded sequences of functions. Decisively, MCFs retain information about the location, value distribution, and direction of oscillations and concentrations, thus extending at the same time the theories of (generalized) Young measures and H-measures. In L p -spaces oscillations and concentrations precisely discriminate between weak and strong compactness, and thus MCFs allow one to quantify the difference in compactness. The definition of MCFs involves a Fourier variable, whereby differential constraints on the functions in the sequence can also be investigated easily—a distinct advantage over Young measure theory. Furthermore, pointwise restrictions are reflected in the MCF as well, paving the way for applications to Tartar's framework of compensated compactness; consequently, we establish a new weak-to-strong compactness theorem in a "geometric" way. After developing several aspects of the abstract theory, we consider three applications; for lamination microstructures, the hierarchy of oscillations is reflected in the MCF. The directional information retained in an MCF is harnessed in the relaxation theory for anisotropic integral functionals. Finally, we indicate how the theory pertains to the study of propagation of singularities in certain systems of PDEs. The proofs combine measure theory, Young measures, and harmonic analysis.

Rindler, Filip

2015-01-01

197

Charge Equilibrium  

NASA Astrophysics Data System (ADS)

The mean equililibrium charge of a penetrating ion can be estimated on the basis of Bohr's velocity criterion or Lamb's energy criterion. Qualitative and quantitative results are derived on the basis of the Thomas-Fermi model of the atom, which is discussed explicitly. This includes a brief introduction to the Thomas-Fermi-Dirac model. Special attention is paid to trial function approaches by Lenz and Jensen as well as Brandt and Kitagawa. The chapter also offers a preliminary discussion of the role of the stopping medium, gas-solid differences, and a survey of data compilations.

Sigmund, Peter

198

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.

2014-09-18

199

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

200

Modelling of compaction in planetesimals  

NASA Astrophysics Data System (ADS)

Aims: Compaction of initially porous material prior to melting is an important process that has influenced the interior structure and the thermal evolution of planetesimals in their early history. On the one hand, compaction decreases the porosity resulting in a reduction of the radius and on the other hand, the loss of porosity results in an increase of the thermal conductivity of the material and thus in a more efficient cooling. Porosity loss by hot pressing is the most efficient process of compaction in planetesimals and can be described by creep flow, which depends on temperature and stress. Hot pressing has been repeatedly modelled using a simplified approach, for which the porosity is gradually reduced in some fixed temperature interval between ?650 K and 700 K. This approach neglects the dependence of compaction on stress and other factors such as matrix grain size and creep activation energy. In the present study, we compare this parametrised method with a self-consistent calculation of porosity loss via a creep related approach. Methods: We use our thermal evolution model from previous studies to model compaction of an initially porous body and consider four basic packings of spherical dust grains (simple cubic, orthorhombic, rhombohedral, and body-centred cubic). Depending on the grain packing, we calculate the effective stress and the associated porosity change via the thermally activated creep flow. For comparison, compaction is also modelled by simply reducing the initial porosity linearly to zero between 650 K and 700 K. As we are interested in thermal metamorphism and not melting, we only consider bodies that experience a maximum temperature below the solidus temperature of the metal phase. Results: For the creep related approach, the temperature interval in which compaction takes place depends strongly on the size of the planetesimal and is not fixed as assumed in the parametrised approach. Depending on the radius, the initial grain size, the activation energy, and the initial porosity and specific packing of the dust grains, the temperature interval lies within 500-1000 K. This finding implies that the parametrised approach strongly overestimates compaction and underestimates the maximum temperature. For the cases considered, the post-compaction porous layer retained at the surface is a factor of 1.5 to 4 thicker for the creep related approach. The difference in the temperature evolution between the two approaches increases with decreasing radius and the maximum temperature can deviate by over 30% for small bodies. Appendix is available in electronic form at http://www.aanda.org

Neumann, Wladimir; Breuer, Doris; Spohn, Tilman

2014-07-01

201

Blue ellipticals in compact groups  

NASA Technical Reports Server (NTRS)

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

Zepf, Stephen E.; Whitmore, Bradley C.

1990-01-01

202

Scaling theory for percolative charge transport in disordered molecular semiconductors.  

PubMed

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. PMID:22026880

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

2011-09-23

203

Charged particle distributions in Jupiter's magnetosphere  

Microsoft Academic Search

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

Neil Divine; H. B. Garrett

1983-01-01

204

Experiments on charge transfer across Coulomb islands  

NASA Astrophysics Data System (ADS)

Preliminary experiments on controlled charge transfer across tunnel junctions of small aluminium islands have been performed. We fabricate samples by conventional e-beam lithography using a converted SEM and measurements are carried out in a compact plastic dilution refrigerator fitting inside a 2” necked transport dewar. Experiments to test the effect of a coherent electro-acoustic wave on the I-V curve are in progress.

Pekola, J. P.; Kira, G. M.; Ma¨kela¨, T.; Paalanen, M. A.

1994-02-01

205

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 {approx}10 MV/m gradients for 10s of nanoseconds pulses and to {approx}100 MV/m gradients for {approx}1 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 detail 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; Carazo, V; Falabella, S; Guethlein, G; Guse, S; Harris, J R; Hawkins, S; Holmes, C; Krogh, M; Nelson, S; Paul, A C; Pearson, D; Poole, B; Schmidt, R; Sanders, D; Selenes, K; Sitaraman, S; Sullivan, J; Wang, L; Watson, J

2009-06-11

206

The low-frequency compact source in the Crab Nebula  

NASA Astrophysics Data System (ADS)

The parameters of the low-frequency compact source in the Crab nebula are given. In the decameter-wavelength range its coordinates, ?(1950.0) = 5h31m31s, 62±0s.22 and ?(1950.0) = 21°58arcmin52arcsec, 8±3arcsec.9, coincide within the error limits with those of the pulsar PSR 0531+21. The apparent angular size of the compact source varies with the frequency ? as ?0 ? ?-1.95±0.25 from 3arcsec.3 at 12.6 MHz to 0arcsec.18 at 75 MHz. The flux density of the integral radio emission of the compact source and the pulsar S?(Jy) in function of the frequency ?(Hz) is approximated by the expression S? = 44(1+2y2)-1y-5/3 where y = ?/(1.6×108). The spectrum of the summary emission of the compact source and the pulsar is explained by coherent curvature radiation of charged clots with effective thickness 60 cm.

Bovkun, V. P.; Zhuk, I. N.; Sobolev, Ya. M.

1987-08-01

207

Compact bilinear operators and commutators  

E-print Network

. Then the following statements are equivalent: (c1) T is compact. (c2) T (B1, X×Y ) is precompact. (c3) For all r > 0, T (Br, X×Y ) is precompact. (c4) For all r1, r2 > 0, T (Br1,X ×Br2,Y ) is precompact. (c5) For all bounded B ? X × Y , T (B) is precompact. (c6.... (c2) ? (c3) We simply need to notice that T (Br,X×Y ) = r 2T (B1,X×Y ). (c3) ? (c4) Assuming 0 < r1 ? r2, T (Br1,X×Y ) ? T (Br1,X ×Br2,Y ) ? T (Br1+r2,X×Y ). Again, since any closed subset of a compact set is compact, the assertion follows. (c4), c(6...

Bé nyi, Á rpá d; Torres, Rodolfo H.

2013-07-01

208

Mass Distribution in Compact Groups  

E-print Network

New redshift surveys of galaxies in the field of compact groups have discovered a population of faint galaxies which act as satellites orbiting in the potential well of the bright group. Here we analyze the mass distribution of the groups by comparing the mass derived from the bright members and the mass obtained from the satellite galaxies. Our analysis indicates the presence of a dark halo around the main group with a mass roughly four times that measured for the dominant galaxies of the compact group. We found that heavier halos are ruled out by the observations when comparing the distribution of positions and redshifts of the satellite galaxies with the distribution of satellites surrounding isolated spiral galaxies. The results agree with a picture where compact groups may form a stable system with galaxies moving in a common dark halo.

J. Perea; A. del Olmo; L. Verdes-Montenegro; M. S. Yun; W. K. Huchtmeier; B. A. Williams

1999-10-18

209

Compact Q-balls and Q-shells in a scalar electrodynamics  

Microsoft Academic Search

We investigate spherically symmetric nontopological solitons in electrodynamics with a scalar field self-interaction U|psi| taken from the complex signum-Gordon model. We find Q-balls for small absolute values of the total electric charge Q, and Q-shells when |Q| is large enough. In both cases the charge density exactly vanishes outside certain compact regions in the three-dimensional space. The dependence of the

H. Arodz; J. Lis

2009-01-01

210

Compact Q-balls and Q-shells in a scalar electrodynamics  

Microsoft Academic Search

We investigate spherically symmetric nontopological solitons in electrodynamics with a scalar field self-interaction U|| taken from the complex signum-Gordon model. We find Q-balls for small absolute values of the total electric charge Q, and Q-shells when |Q| is large enough. In both cases the charge density exactly vanishes outside certain compact regions in the three-dimensional space. The dependence of the

H. Arodz; J. Lis

2009-01-01

211

Compact accelerator for medical therapy  

DOEpatents

A compact accelerator system having an integrated particle generator-linear accelerator with a compact, small-scale construction capable of producing an energetic (.about.70-250 MeV) proton beam or other nuclei and transporting the beam direction to a medical therapy patient without the need for bending magnets or other hardware often required for remote beam transport. The integrated particle generator-accelerator is actuable as a unitary body on a support structure to enable scanning of a particle beam by direction actuation of the particle generator-accelerator.

Caporaso, George J.; Chen, Yu-Jiuan; Hawkins, Steven A.; Sampayan, Stephen E.; Paul, Arthur C.

2010-05-04

212

An ultra-compact virtual source FET model for deeply-scaled devices: Parameter extraction and validation for standard cell libraries and digital circuits  

E-print Network

In this paper, we present the first validation of the virtual source (VS) charge-based compact model for standard cell libraries and large-scale digital circuits. With only a modest number of physically meaningful parameters, ...

Mysore, Omar

213

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

214

Mesoscale simulations of powder compaction  

NASA Astrophysics Data System (ADS)

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

Lomov, Ilya; Antoun, Tarabay; Liu, Benjamin

2009-06-01

215

G-compactness and groups  

Microsoft Academic Search

Lascar described EKP as a composition of EL and the topological closure of EL ((1)). We generalize this result to some other pairs of equivalence relations. Motivated by an attempt to construct a new example of a non-G-compact theory, we consider the following example. Assume G is a group definable in a structure M. We define a structure M0 consisting

Jakub Gismatullin; Ludomir Newelski

2008-01-01

216

Laser driven compact ion accelerator  

DOEpatents

A laser driven compact ion source including a light source that produces an energy pulse, a light source guide that guides the energy pulse to a target and produces an ion beam. The ion beam is transported to a desired destination.

Tajima, Toshiki

2005-03-15

217

Mesoscale Simulations of Power Compaction  

SciTech Connect

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

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

2009-08-06

218

Compact color schlieren optical system  

NASA Technical Reports Server (NTRS)

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

Buchele, Donald R.; Griffin, Devon W.

1993-01-01

219

The Compact Project: Final Report.  

ERIC Educational Resources Information Center

The National Alliance of Business (NAB) surveyed the 12 sites that participated in the Compact Project to develop and implement programs of business-education collaboration. NAB studied start-up activities, key players, conditions for collaboration, accomplishments, challenges, and future plans. Program outcomes indicated that building successful…

National Alliance of Business, Inc., Washington, DC.

220

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

221

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. PMID:19186143

Saito, Takuya; Iwaki, Takafumi; Yoshikawa, Kenichi

2009-01-01

222

Compact Q-balls and Q-shells in a scalar electrodynamics  

NASA Astrophysics Data System (ADS)

We investigate spherically symmetric nontopological solitons in electrodynamics with a scalar field self-interaction ?|?| taken from the complex signum-Gordon model. We find Q-balls for small absolute values of the total electric charge Q, and Q-shells when |Q| is large enough. In both cases the charge density exactly vanishes outside certain compact regions in the three-dimensional space. The dependence of the total energy E of small Q-balls on the total electric charge has the form ?|Q|5/6, while in the case of very large Q-shells, ?|Q|7/6.

Arod?, H.; Lis, J.

2009-02-01

223

Compact groups of galaxies and their environment  

Microsoft Academic Search

A review of the latest findings about compact groups of galaxies is given. It is shown that complete redshift information brings convincing evidence that Hickson's compact groups of galaxies are physical entities. VLA radio data and infrared data both suggest that merging is a common ongoing process in the groups. Recent numerical simulations suggest that compact groups may have existed

G. G. C. Palumbo

1992-01-01

224

7 CFR 51.572 - Compact.  

Code of Federal Regulations, 2011 CFR

...Agriculture 2 2011-01-01 2011-01-01 false Compact. 51.572 Section 51.572 Agriculture Regulations...States Standards for Celery Definitions § 51.572 Compact. Compact means that the branches on the stalk are fairly...

2011-01-01

225

7 CFR 51.572 - Compact.  

Code of Federal Regulations, 2010 CFR

...Agriculture 2 2010-01-01 2010-01-01 false Compact. 51.572 Section 51.572 Agriculture Regulations...States Standards for Celery Definitions § 51.572 Compact. Compact means that the branches on the stalk are fairly...

2010-01-01

226

A Computer Verified Theory of Compact Sets  

Microsoft Academic Search

Compact sets in constructive mathematics capture our intuition of what computable sub- sets of the plane (or any other complete metric space) ought to be. A good representation of compact sets provides an efficient means of creating and displaying images with a com- puter. In this paper, I build upon existing work about complete metric spaces to define compact sets

Russell O'connor

2008-01-01

227

COMPACT WELL-BOUNDED OPERATORS CHENG QINGPING  

E-print Network

COMPACT WELL-BOUNDED OPERATORS CHENG QINGPING School of Mathematical and Physical Sciences, Murdoch. Every compact well-bounded operator has a representation as a lin- ear combination of disjoint that the converse of this result holds, thus characterizing compact well-bounded operators. We also apply

Doust, Ian

228

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

229

Program Assessment:Program Assessment: Academic Learning CompactsAcademic Learning Compacts  

E-print Network

Compacts in Program Assessment 59/13/2005 Academic Learning Compacts Communication Critical Thinking 79/13/2005 Academic Learning Compacts Critical Thinking: outcome activities that require analysis Compacts Critical thinking involves: identifying problems in a situation or organization thinking about

Kaup, David J.

230

Compact noninvasive electron bunch-length monitor  

DOE PAGESBeta

A compact rf cavity was constructed that simultaneously resonates at many harmonic modes when excited by a repetitive bunched electron beam passing through its bore. The excitation of these modes provides a Fourier description of the temporal characteristics of the bunch train. The cavity was used to noninvasively characterize electron bunches produced from thin and thick GaAs photocathodes inside a DC high voltage photogun illuminated with 37 ps (full width half maximum, FWHM) laser pulses at repetition rates near 1500 MHz, at average beam current from 5 to 500????A , and at beam energy from 75 to 195 keV. The cavity bunch-length 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 under way to detect shorter bunches by designing cavities with increased bandwidth. 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.

Roberts, B.; Mammei, R. R.; Poelker, M.; McCarter, J. L.

2012-12-01

231

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

232

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.

Roberts, Brock; Poelker, Matt; Mammei, Russell R.; McCarter, James L.

2012-12-01

233

Neutrino trapping in braneworld extremely compact stars  

E-print Network

Extremely Compact Stars (ECS) contain trapped null geodesics. When such objects enter the evolution period admitting geodetical motion of neutrinos, certain part of neutrinos produced in their interior will be trapped influencing their neutrino luminosity and thermal evolution. We study neutrino trapping in the braneworld ECS, assuming uniform distribution of neutrino emissivity and massless neutrinos. We give the efficiency of the neutrino trapping effects in the framework of the simple model of the internal spacetime with uniform distribution of energy density, and external spacetime described by the Reissner-Nordstr\\"om geometry characterized by the braneworld "tidal" parameter $b$. For $b 0$ the external spacetime can be of both black-hole and naked-singularity type. Then the ECS surface radius $R$ can be located also above the unstable (outer) photon circular orbit. Such basically new types of the spacetimes strongly alter the trapping phenomena as compared to the standard case of $b = 0$. It is shown that the neutrino trapping effects are slightly lowered by the presence of physically more plausible case of $b 1$. However, potential astrophysical relevance of the trapping phenomena is strongly enhanced for negative tidal charges enabling a significant enlargement of the ECS surface radius to values coherent with recent observations.

Zdenek Stuchlik; Jan Hladik; Martin Urbanec

2011-08-29

234

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

235

Compact planar microwave blocking filters  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

236

Compact optical microfiber phase modulator.  

PubMed

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

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

2012-02-01

237

Compact portable diffraction moire interferometer  

DOEpatents

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

Deason, Vance A. (Shelley, ID); Ward, Michael B. (Idaho Falls, ID)

1989-01-01

238

Compact portable diffraction moire interferometer  

DOEpatents

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

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

1988-05-23

239

Compact magnetic energy storage module  

DOEpatents

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

Prueitt, Melvin L. (Los Alamos, NM)

1994-01-01

240

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

241

Closeup View of Compacted Soil  

NASA Technical Reports Server (NTRS)

Soil on Mars can be a bit clumpy, as shown in this image of soil after it was compacted by one of the wheels of NASA's Mars Exploration Rover Spirit. Scientists think the light-colored material may be a global layer of airfall dust. Spirit's microscopic imager took this picture, showing an area approximately 3 centimeters (1.2 inches) square, during the rover's 314th martian day, or sol (Nov. 19, 2004).

2004-01-01

242

Compact Color Schlieren Optical System  

NASA Technical Reports Server (NTRS)

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

Buchele, Donald R.; Griffin, Devon W.

1996-01-01

243

COMPACT WELL-BOUNDED OPERATORS Cheng Qingping and Ian Doust  

E-print Network

COMPACT WELL-BOUNDED OPERATORS Cheng Qingping and Ian Doust Abstract. Every compact well-bounded operator has a representation as a l* *inear compact well-bounded operators. We also apply this result * *to study compact well

Doust, Ian

244

Compaction Waves in Granular HMX  

SciTech Connect

Piston driven compaction waves in granular HMX are simulated with a two-dimensional continuum mechanics code in which individual grains are resolved. The constitutive properties of the grains are modeled with a hydrostatic pressure and a simple elastic-plastic model for the shear stress. Parameters are chosen to correspond to inert HMX. For a tightly packed random grain distribution (with initial porosity of 19%) we varied the piston velocity to obtain weak partly compacted waves and stronger fully compacted waves. The average stress and wave speed are compatible with the porous Hugoniot locus for uni- axial strain. However, the heterogeneities give rise to stress concentrations, which lead to localized plastic flow. For weak waves, plastic deformation is the dominant dissipative mechanism and leads to dispersed waves that spread out in time. In addition to dispersion, the granular heterogeneities give rise to subgrain spatial variation in the thermodynamic variables. The peaks in the temperature fluctuations, known as hot spots, are in the range such that they are the critical factor for initiation sensitivity.

E. Kober; R. Menikoff

1999-01-01

245

Gravitational collapse of charged scalar fields  

NASA Astrophysics Data System (ADS)

In order to study the gravitational collapse of charged matter we analyze the simple model of an self-gravitating massless scalar field coupled to the electromagnetic field in spherical symmetry. The evolution equations for the Maxwell-Klein-Gordon sector are derived in the 3+1 formalism, and coupled to gravity by means of the stress-energy tensor of these fields. To solve consistently the full system we employ a generalized Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of General Relativity that is adapted to spherical symmetry. We consider two sets of initial data that represent a time symmetric spherical thick shell of charged scalar field, and differ by the fact that one set has zero global electrical charge while the other has non-zero global charge. For compact enough initial shells we find that the configuration doesn't disperse and approaches a final state corresponding to a sub-extremal Reissner-N\\"ordstrom black hole with $|Q|charge of the scalar field $q$ we find that the final black hole tends to become more and more neutral. Our results support the cosmic censorship conjecture for the case of charged matter.

Torres, Jose M.; Alcubierre, Miguel

2014-09-01

246

Anisotropic charged analogue of Heintzmann's solution  

NASA Astrophysics Data System (ADS)

We present an anisotropic charged analogue of Heintzmann's (Z. Phys. 228:489, 1969) solution of the general relativistic field equations in curvature coordinates by using simple form of electric intensity E and pressure anisotropy factor ? that involve charge parameter K and anisotropy parameter ? respectively. Our solution is well behaved in all respects for all values of X lying in the range 0compactness parameter "u" lying in the range 0compact stars like quark stars and neutron stars. We present some models of super dense quark star and neutron stars corresponding to X=0.1, ?=1 and K=3. By assuming surface density of quark star, ? b =4.6888×1014 g cm-3 the mass and radius are 1.271M ?, 10.09 km respectively. For ? b =2.7×1014 g cm-3 the mass and radius of neutron star are 1.675M ?, 13.297 km respectively. The well behaved class of relativistic stellar models obtained in this work might have astrophysical significance in the study of more realistic internal structure of compact stars.

Pradhan, N.; Pant, Neeraj

2014-12-01

247

Anisotropic charged analogue of Heintzmann's solution  

NASA Astrophysics Data System (ADS)

We present an anisotropic charged analogue of Heintzmann's (Z. Phys. 228:489, 1969) solution of the general relativistic field equations in curvature coordinates by using simple form of electric intensity E and pressure anisotropy factor ? that involve charge parameter K and anisotropy parameter ? respectively. Our solution is well behaved in all respects for all values of X lying in the range 0< X?1.1, ? lying in the range 0? ??6.2, K lying in the range 0< K?9.7 and Schwarzschild compactness parameter " u" lying in the range 0< u?0.391. Since our solution is well behaved for a wide ranges of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We present some models of super dense quark star and neutron stars corresponding to X=0.1, ?=1 and K=3. By assuming surface density of quark star, ? b =4.6888×1014 g cm-3 the mass and radius are 1.271 M ?, 10.09 km respectively. For ? b =2.7×1014 g cm-3 the mass and radius of neutron star are 1.675 M ?, 13.297 km respectively. The well behaved class of relativistic stellar models obtained in this work might have astrophysical significance in the study of more realistic internal structure of compact stars.

Pradhan, N.; Pant, Neeraj

2015-03-01

248

77 FR 22805 - Meeting of the Compact Council for the National Crime Prevention and Privacy Compact; Correction  

Federal Register 2010, 2011, 2012, 2013, 2014

...the Compact Council for the National Crime Prevention and Privacy Compact; Correction...the date and location of the National Crime Prevention and Privacy Compact Council (Council) created by the National Crime Prevention and Privacy Compact Act...

2012-04-17

249

Compact Video Microscope Imaging System Implemented in Colloid Studies  

NASA Technical Reports Server (NTRS)

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

McDowell, Mark

2002-01-01

250

Spacecraft charging, an update  

Microsoft Academic Search

Twenty years after the landmark SCATHA program, spacecraft charging and its associated effects continue to be major issues for Earth-orbiting spacecraft. Since the time of SCATHA, spacecraft charging investigations were focused primarily on surface effects and spacecraft external surface design issues. Today, however, a significant proportion of spacecraft anomalies are believed to be caused by internal charging effects (charging and

Henry B. Garrett; Albert C. Whittlesey

2000-01-01

251

Charged Q-balls and boson stars and dynamics of charged test particles  

E-print Network

We construct electrically charged Q-balls and boson stars in a model with a scalar self-interaction potential resulting from gauge mediated supersymmetry breaking. We discuss the properties of these solutions in detail and emphasize the differences to the uncharged case. We observe that Q-balls can only be constructed up to a maximal value of the charge of the scalar field, while for boson stars the interplay between the attractive gravitational force and the repulsive electromagnetic force determines their behaviour. We find that the vacuum is stable with respect to pair production in the presence of our charged boson stars. We also study the motion of charged, massive test particles in the space-time of boson stars. We find that in contrast to charged black holes the motion of charged test particles in charged boson star space-times is planar, but that the presence of the scalar field plays a crucial role for the qualitative features of the trajectories. Applications of this test particle motion can be made in the study of extreme-mass ratio inspirals (EMRIs) as well as astrophysical plasmas relevant e.g. in the formation of accretion discs and polar jets of compact objects.

Yves Brihaye; Valeria Diemer; Betti Hartmann

2014-03-27

252

Compact pulse forming line using barium titanate ceramic material.  

PubMed

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

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

2011-11-01

253

Compact pulse forming line using barium titanate ceramic material  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

254

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.

2012-06-26

255

Compaction of Space Mission Wastes  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

256

Gravitational Waves from Compact Objects  

NASA Astrophysics Data System (ADS)

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

Owen, Benjamin James

257

Status of compact-toroid research using high energy particle beams  

SciTech Connect

A workshop on the use of high-energy particle beams to generate compact-toroid plasma geometries was held at the Department of Energy (Germantown) on June 26-27, 1980, for the purpose of assisting the Division of Applied Plasma Physics in formulating program plans for this work, and assessing its importance relative to the rest of the compact toroid (CT) program. The scope of the workshop is given in Appendix A, and the charge to the panel of advisors responsible for writing this report is given in Appendix B.

None

1980-10-01

258

Two Piece Compaction Die Design  

SciTech Connect

Compaction dies used to create europium oxide and tantalum control plates were modeled using ANSYS 11.0. Two-piece designs were considered in order to make the dies easier to assemble than the five-piece dies that were previously used. The two areas of concern were the stresses at the interior corner of the die cavity and the distortion of the cavity wall due to the interference fit between the two pieces and the pressure exerted on the die during the compaction process. A successful die design would have stresses less than the yield stress of the material and a maximum wall distortion on the order of 0.0001 in. Design factors that were investigated include the inner corner radius, the value of the interference fit, the compaction force, the size of the cavity, and the outer radius and geometry of the outer ring. The results show that for the europium oxide die, a 0.01 in. diameter wire can be used to create the cavity, leading to a 0.0055 in. radius corner, if the radial interference fit is 0.003 in. For the tantalum die, the same wire can be used with a radial interference fit of 0.001 in. Also, for the europium oxide die with a 0.003 in. interference fit, it is possible to use a wire with a diameter of 0.006 in. for the wire burning process. Adding a 10% safety factor to the compaction force tends to lead to conservative estimates of the stresses but not for the wall distortion. However, when the 10% safety factor is removed, the wall distortion is not affected enough to discard the design. Finally, regarding the europium oxide die, when the cavity walls are increased by 0.002 in. per side or the outer ring is made to the same geometry as the tantalum die, all the stresses and wall distortions are within the desired range. Thus, the recommendation is to use a 0.006 in. diameter wire and a 0.003 in. interference fit for the europium oxide die and a 0.01 in. diameter wire and a 0.001 in. interference fit for the tantalum die. The dies can also be made to have the same outer geometry if desired.

Coffey, Ethan N [ORNL

2010-03-01

259

Scalar Curvature and Projective Compactness  

E-print Network

Consider a manifold with boundary, and such that the interior is equipped with a pseudo-Riemannian metric. We prove that, under mild asymptotic non-vanishing conditions on the scalar curvature, if the Levi-Civita connection of the interior does not extend to the boundary (because for example the interior is complete) whereas its projective structure does, then the metric is projectively compact of order 2. This implies a host of results including that the metric satisfies asymptotic Einstein conditions, and induces a canonical conformal structure on the boundary.

Andreas Cap; A. Rod Gover

2015-02-24

260

Compact Radiometers Expand Climate Knowledge  

NASA Technical Reports Server (NTRS)

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

2010-01-01

261

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

262

Shock compaction of molybdenum powder  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

263

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

SciTech Connect

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

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

2008-02-15

264

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

NASA Astrophysics Data System (ADS)

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

Suzuki, Hiroyuki Y.

2008-02-01

265

Anisotropic charged stellar models in Generalized Tolman IV spacetime  

NASA Astrophysics Data System (ADS)

With the presence of electric charge and pressure anisotropy some anisotropic stellar models have been developed. An algorithm recently presented by Herrera et al. (Phys. Rev. D 77, 027502 (2008)) to generate static spherically symmetric anisotropic solutions of Einstein's equations has been used to derive relativistic anisotropic charged fluid spheres. In the absence of pressure anisotropy the fluid spheres reduce to some well-known Generalized Tolman IV exact metrics. The astrophysical significance of the resulting equations of state (EOS) for a particular case (Wyman-Leibovitz-Adler) for the anisotropic charged matter distribution has been discussed. Physical analysis shows that the relativistic stellar structure obtained in this work may reasonably model an electrically charged compact star, whose energy density associated with the electric fields is on the same order of magnitude as the energy density of fluid matter itself like electrically charged bare strange quark stars.

Murad, Mohammad Hassan; Fatema, Saba

2015-01-01

266

Structural properties of compact groups  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

267

Compact fiber pumped terahertz source  

NASA Astrophysics Data System (ADS)

Converting near infrared signals in a nonlinear medium is an attractive way to generate terahertz radiation due to the availability of near-IR lasers and nonlinear materials. However, these terahertz generation schemes are typically inefficient and are often cumbersome, which may limit their use in certain applications. We have developed and demonstrated a compact, fiber pumped optical terahertz source based difference frequency mixing (DFM) of nanosecond pulses in zinc germanium phosphide (ZGP). With this setup, we have successfully generated 2mW of average power terahertz radiation at 2.45THz. This has enabled us to perform active, real-time terahertz imaging experiments using an uncooled microbolometer array. In performing these experiments, we have also developed a theoretical model for terahertz generation based on DFM of IR pump signals. In this paper, we discuss our compact fiber pumped terahertz source technology, imaging system, model, and how we intend to overcome some of the common issues associated with optical terahertz generation.

Creeden, Daniel; McCarthy, John C.; Ketteridge, Peter A.; Southward, Timothy; Schunemann, Peter G.; Kmoiak, James J.; Dove, Webster; Chicklis, Evan P.

2007-04-01

268

Compact Microscope Imaging System Developed  

NASA Technical Reports Server (NTRS)

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

McDowell, Mark

2001-01-01

269

Compact submanifolds supporting singular interactions  

SciTech Connect

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

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

2013-12-15

270

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

271

Compacted carbon for electrochemical cells  

DOEpatents

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

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

1997-01-01

272

Gravitational collapse of charged scalar fields  

E-print Network

In order to study the gravitational collapse of charged matter we analyze the simple model of an self-gravitating massless scalar field coupled to the electromagnetic field in spherical symmetry. The evolution equations for the Maxwell-Klein-Gordon sector are derived in the 3+1 formalism, and coupled to gravity by means of the stress-energy tensor of these fields. To solve consistently the full system we employ a generalized Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of General Relativity that is adapted to spherical symmetry. We consider two sets of initial data that represent a time symmetric spherical thick shell of charged scalar field, and differ by the fact that one set has zero global electrical charge while the other has non-zero global charge. For compact enough initial shells we find that the configuration doesn't disperse and approaches a final state corresponding to a sub-extremal Reissner-N\\"ordstrom black hole with $|Q|scalar field $q$ we find that the final black hole tends to become more and more neutral. Our results support the cosmic censorship conjecture for the case of charged matter.

Jose M. Torres; Miguel Alcubierre

2014-07-29

273

Non-compact WZW conformal field theories  

Microsoft Academic Search

Non-compact WZW sigma models are considered, especially the ones with symmetric space H(sup C)\\/H as the target, for H in a compact Lie group. The author offers examples of non-rational conformal field theories. The author notes their relation to the compact WZW models, but stresses their distinctive features such as the continuous spectrum of conformal weights, diverging partition functions, and

Krzysztof Gawedzki

1991-01-01

274

Method for preparing porous metal hydride compacts  

DOEpatents

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

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

1981-01-01

275

Method for preparing porous metal hydride compacts  

DOEpatents

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

Ron, M.; Gruen, D.M.; Mendelsohn, M.H.; Sheft, I.

1980-01-21

276

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

277

Some new Wyman-Adler type static relativistic charged anisotropic fluid spheres compatible to \\emph{self-bound} stellar modeling  

E-print Network

In this work some families of relativistic anisotropic charged fluid spheres have been obtained by solving Einstein-Maxwell field equations with preferred form of one of the metric potentials, a suitable forms of electric charge distribution and pressure anisotropy functions. The resulting equation of state (EOS) of the matter distribution has been obtained. Physical analysis shows that the relativistic stellar structure for matter distribution obtained in this work may reasonably model an electrically charged compact star whose energy density associated with the electric fields is on the same order of magnitude as the energy density of fluid matter itself (e.g. electrically charged bare strange stars). These models permit a simple method of systematically fixing bounds on the maximum possible mass of cold compact electrically charged self-bound stars. It has been demonstrated numerically that the maximum compactness and mass increase in the presence of electric field and anisotropic pressures. Based on the a...

Murad, Mohammad Hassan

2014-01-01

278

Variational charge renormalization in charged systems.  

PubMed

We apply general variational techniques to the problem of the counterion distribution around highly charged objects where strong condensation of counterions takes place. Within a field-theoretic formulation using a fluctuating electrostatic potential, the concept of surface-charge renormalization is recovered within a simple one-parameter variational procedure. As a test, we reproduce the Poisson-Boltzmann surface potential for a single-charged planar surface both in the weak-charge and strong-charge regime. We then apply our techniques to non-planar geometries where closed-form solutions of the non-linear Poisson-Boltzmann equation are not available. In the cylindrical case, the Manning charge renormalization result is obtained in the limit of vanishing salt concentration. However, for intermediate salt concentrations a slow crossover to the non-charged-renormalized regime (at high salt) is found with a quasi-power-law behavior which helps to understand conflicting experimental and theoretical results for the electrostatic persistence length of polyelectrolytes. In the spherical geometry charge renormalization is only found at intermediate salt concentrations, in agreement with previous numerical results. PMID:15011050

Netz, R R; Orland, H

2003-07-01

279

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

280

Finding an Unknown Charge  

NSDL National Science Digital Library

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

Wolfgang Christian

281

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

282

Uncertainty Principles for Compact Groups  

E-print Network

We establish an operator-theoretic uncertainty principle over arbitrary compact groups, generalizing several previous results. As a consequence, we show that if f is in L^2(G), then the product of the measures of the supports of f and its Fourier transform ^f is at least 1; here, the dual measure is given by the sum, over all irreducible representations V, of d_V rank(^f(V)). For finite groups, our principle implies the following: if P and R are projection operators on the group algebra C[G] such that P commutes with projection onto each group element, and R commutes with left multiplication, then the squared operator norm of PR is at most rank(P)rank(R)/|G|.

Gorjan Alagic; Alexander Russell

2008-08-29

283

A Compact Wakefield Measurement Facility  

NASA Astrophysics Data System (ADS)

The conceptual design of a compact, photoinjector-based, facility for high precision measurements of wakefields is presented. This work is motivated by the need for a thorough understanding of beam induced wakefield effects for any future linear collider. We propose to use a high brightness photoinjector to generate (approximately) a 2 nC, 2 mm-mrad drive beam at 20 MeV to excite wakefields and a second photoinjector to generate a 5 MeV, variably delayed, trailing witness beam to probe both the longitudinal and transverse wakefields in the structure under test. Initial estimates show that we can detect a minimum measurable dipole transverse wake function of 0.1 V/pC/m/mm and a minimum measurable monopole longitudinal wake function of 2.5 V/pC/m. Simulations results for the high brightness photoinjector, calculations of the facility's wakefield measurement resolution, and the facility layout are presented.

Power, J. G.; Gai, W.

2015-10-01

284

Compact Microwave Fourier Spectrum Analyzer  

NASA Technical Reports Server (NTRS)

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

Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry

2009-01-01

285

Studies of accelerated compact toruses  

SciTech Connect

In an earlier publication we considered acceleration of plasma rings (Compact Torus). Several possible accelerator configurations were suggested and the possibility of focusing the accelerated rings was discussed. In this paper we consider one scheme, acceleration of a ring between coaxial electrodes by a B/sub theta/ field as in a coaxial rail-gun. If the electrodes are conical, a ring accelerated towards the apex of the cone undergoes self-similar compression (focusing) during acceleration. Because the allowable acceleration force, F/sub a/ = kappaU/sub m//R where (kappa < 1), increases as R/sup -2/, the accelerating distance for conical electrodes is considerably shortened over that required for coaxial electrodes. In either case, however, since the accelerating flux can expand as the ring moves, most of the accelerating field energy can be converted into kinetic energy of the ring leading to high efficiency.

Hartman, C.W.; Eddleman, J.; Hammer, J.H.

1983-01-04

286

Compact torus experiments and theory  

SciTech Connect

Two types of compact toroids have been studied: spheromaks and field-reversed configurations (FRC). Spheromaks, which contain both toroidal and poloidal fields, have been formed with a magnetized coaxial injector and trapped in both prolate and oblate flux conservers. As expected from theory, the prolate configuration always tilts, but the oblate configuration can be made stable even in the presence of a guide field. Observations include 150..mu..s lifetimes, approx. 10/sup 14/ cm/sup -3/, and a decrease of field fluctuations by a factor of 100 at the time of complete reconnection. Theoretical studies of the FRC (no toroidal field) have been compared with the results of two field-reversed theta-pinches, FRX-A and FRX-B.

Armstrong, W.T.; Barnes, D.C.; Bartsch, R.R.

1980-01-01

287

Compact submanifolds supporting singular interactions  

NASA Astrophysics Data System (ADS)

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

Kaynak, Burak Tevfik; Teoman Turgut, O.

2013-12-01

288

Compact laser Doppler choroidal flowmeter  

NASA Astrophysics Data System (ADS)

A compact instrument is described that allows the measurement of the laser Doppler flow parameters, i.e., the velocity, the volume, and flow of blood in the foveal region of the human choroidal vascular system. This new device uses the optical principle of confocality for the delivery of the laser light to the site of measurement and heterodyne detection of the Doppler frequency shifted scattered light. Power of the incident light (785 nm) at the cornea is 90 (mu) W. Measurements were obtained in both eyes of a group of 21 normal volunteers without pupil dilatation. We determined the intrasubject reproducibility and the minimum statistically significant detectable changes in the flow parameters for a group of 21 eyes (one in each subject). Linear correlations were also established between the flow parameters in the right and left eyes.

Geiser, Martial H.; Diermann, Ulrich; Riva, Charles E.

1999-10-01

289

Compact Quantum Cascade Laser Transmitter  

SciTech Connect

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

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

2009-04-01

290

Analytical Compact Model of Ballistic Cylindrical Nanowire Metal-Oxide-Semiconductor Field-Effect Transistor  

NASA Astrophysics Data System (ADS)

We propose a compact model of drain current in the ballistic mode in a cylindrical gate-all-around metal-oxide-semiconductor field-effect transistor (MOSFET). Wave functions of electrons in a channel are represented by a linear combination of wave functions in a cylindrical infinite quantum well. With these wave functions, the energy levels of electrons in a channel are analytically derived by approximately solving the Schrödinger equation. Drain current is obtained using a coupled equation of electron energy levels and a current equation for ballistic transport. Electron energy levels are compared with numerical simulation results. The electron energy levels obtained using our compact model demonstrate excellent agreement with numerical simulation results. With our compact model, surface potential, potential shape in the confinement plane, total charge density, electron energy level, and drain current are calculated self-consistently with only two fitting parameters and one transcendental equation.

Tatsuhiro Numata,; Shigeyasu Uno,; Kazuo Nakazato,; Yoshinari Kamakura,; Nobuya Mori,

2010-04-01

291

Spacecraft surface charging handbook  

Microsoft Academic Search

Spacecraft surface charging is the buildup of net electric charge - and therefore electrostatic potential - on the external surfaces of a spacecraft due to incident particles with energies in the kilo-electron volt to tens of kilo-electron volts range. Geosynchronous and low-altitude, polar-orbiting spacecraft encounter charging environments. Surface charging causes problems for operational spacecraft. A primary effect is the occurrence

V. A. Davis; L. W. Gordon

1992-01-01

292

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

293

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

294

Shaped charge perforating device  

Microsoft Academic Search

A shaped charge perforating apparatus is described which consists of: an elongated tubular housing member having recesses spirally spaced therealong; an elongated tubular carrier member having shaped charge mounting locations spirally spaced therealong; a plurality of shaped charge units positioned in the mounting locations of the carrier member; a length of detonator cord helically wound about the tubular carrier member

Ayers

1986-01-01

295

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.

William C. Robertson, Ph.D.

2005-01-01

296

Particle charge spectrometer  

NASA Technical Reports Server (NTRS)

An airflow through a tube is used to guide a charged particle through the tube. A detector may be used to detect charge passing through the tube on the particle. The movement of the particle through the tube may be used to both detect its charge and size.

Fuerstenau, Stephen D. (Inventor)

2004-01-01

297

Spacecraft Charging Technology, 1980  

NASA Technical Reports Server (NTRS)

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

1981-01-01

298

Neutral hydrogen in compact groups of galaxies  

Microsoft Academic Search

Integrated H I profiles were detected for 34 of 51 Hickson compact groups (HCGs) of galaxies, and sensitive upper limits to the H I flux density were measured for the other 17. About 60 percent of the galaxies within compact groups are spirals, and a significant tendency exists for the fraction of elliptical galaxies to increase with group surface brightness.

B. A. Williams; Herbert J. Rood

1987-01-01

299

Blue Blobs in Compact Groups of Galaxies  

Microsoft Academic Search

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.

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

2009-01-01

300

Are compact groups of galaxies physically dense?  

Microsoft Academic Search

The properties of the compact groups of galaxies cataloged by Hickson (1982) are compared to the output of over 1000 numerical simulations of small groups of galaxies. Rather than being dense physical systems or transient unbound cores of loose groups, it is argued that roughly half of the compact groups in Hickson's catalog are simply chance alignments of galaxies within

G. A. Mamon

1986-01-01

301

ROSAT observations of compact groups of galaxies  

Microsoft Academic Search

We have systematically analyzed a sample of 13 new and archival ROSAT Position Sensitive Proportional Counter (PSPC) observations of compact groups of galaxies: 12 Hickson compact groups plus the NCG 2300 group. We find that approximately two-thirds of the groups have extended X-ray emission and, in four of these, the emission is resolved into diffuse emission from gas at a

Rachel A. Pildis; Joel N. Bregman; August E. Evrard

1995-01-01

302

Lensing by compact groups of galaxies  

Microsoft Academic Search

The observations of diffuse X-ray emission attributed to a hot intragroup gas observed in some of the Hickson compact groups of galaxies suggest that a fraction of these objects are physical entities embedded in large potential wells. We analyze here the average efficiency of compact groups as gravitational lenses. Assuming the conservative hypothesis of an isothermal profile for the mass

C. Mendes de Oliveira; E. Giraud

1994-01-01

303

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

304

Compact formulations as a union of polyhedra  

Microsoft Academic Search

We explore one method for finding the convex hull of certain mixed integer sets. The approach is to break up the original set into a small number of subsets, find a compact polyhedral description of the convex hull of each subset, and then take the convex hull of the union of these polyhedra. The resulting extended formulation is then compact,

Michele Conforti; Laurence A. Wolsey

2008-01-01

305

Exploration of Compact Stellarators as Power Plants  

E-print Network

Exploration of Compact Stellarators as Power Plants: Initial Results from ARIES-CS Study Farrokh, see: http://aries.ucsd.edu/ #12;Exploration and Optimization of Compact Stellarators as Power Plants in the context of power plant studies, e.g., particle loss Divertor (location, particle and energy distribution

California at San Diego, University of

306

Cooling of Color Superconducting Compact Stars  

E-print Network

We review the status of research on the cooling of compact stars, with emphasis on the influence of color superconducting quark matter phases. Although a consistent microscopic approach is not yet available, severe constraints on the phase structure of matter at high densities come from recent mass and cooling observations of compact stars.

David Blaschke

2006-03-26

307

September 25, 2006 Experimental pressure solution compaction  

E-print Network

September 25, 2006 Experimental pressure solution compaction of synthetic halite/calcite aggregates by addition of hard particles. Sieved mixtures of calcite and halite grains are experimentally compacted in drained pressure cells in the presence of a saturated aqueous solution. The individual halite grains

Paris-Sud XI, Université de

308

Hydraulic conductivity tests on compacted clay  

Microsoft Academic Search

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

Stephen S. Boynton; David E. Daniel

1985-01-01

309

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

310

The Compressor: Concurrent, Incremental, and Parallel Compaction  

E-print Network

The Compressor: Concurrent, Incremental, and Parallel Compaction Haim Kermany Erez Petrank Dept non-intrusive compactor is still missing. In this paper we present the Compressor, a novel compaction, thereby allowing acceptable runs on large heaps. Furthermore, the Compressor is the first compactor

Petrank, Erez

311

Compact reactor\\/ORC power source  

Microsoft Academic Search

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

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

1986-01-01

312

Physics of compact ignition tokamak designs  

SciTech Connect

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

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

1986-03-01

313

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

314

X-rays emission from a compact diode energized by capacitor discharge  

NASA Astrophysics Data System (ADS)

X-ray emission from a compact diode consisting of a sharp edged cathode and flat anode of copper and lead, energized by simple capacitor discharge is reported. With a sewing machine needle cathode, and lead target, the generation efficiency upto 0.4% is obtained. The efficiency is expected to enhance further with the increase in discharge energy, charging voltage and reducing the parasitic inductance.

Zakaullah, M.; Ahmed, S.; Hussain, S.; Afzal, M.; Waheed, A.

2005-01-01

315

Neutrino Oscillations Induced by Chiral Phase Transition in a Compact Star  

E-print Network

Electric charge neutrality in a compact star provides an important relation- ship between the chiral dynamics and neutrino propagation in the star. Since the sudden drop of the electron density at the critical point of the first-order chiral phase transition, the oscillation for low energy neutrinos is significant and can be regarded as a signature of chiral symmetry restoration in the core of the star.

Chengfu Mu; Gaofeng Sun; Pengfei Zhuang

2006-11-04

316

A small cold cathode heavy ion source for a compact cyclotron  

Microsoft Academic Search

A small cold cathode PIG ion source for multiply charged heavy ions was developed for the compact cyclotron of Tohoku University, and the performance was examined with H2, CO2, CH4, O2, Ne and Ar gases. The beam currents of 12C4+,5+, 14N4+,5+,6+, 16O5+,6+ and 20Ne5+ ions were measured at the cyclotron extraction radius. Design considerations and characteristics of this ion source

T. Yamaya; T. Shinozuka; K. Kotajima; M. Fujioka; T. Onodera

1984-01-01

317

Development Of A Compact, High-energy Spark Gap Switch And Trigger Generator System  

Microsoft Academic Search

High-energy switches and trigger generators are required for a range of capacitor banks in electric gun applications. We have developed a compact, long-lived spark gap and a matched series-injection trigger generator. The switch is of a two-electrode design using high density graphite electrodes. The demonstrated peak current capability is near 300 kA, with a charge transfer of 700 Cb, and

D. Bhasavanich; S. S. Hitchcock; P. M. Creely; R. S. Shaw; H. G. Hammon; J. T. Naff

1991-01-01

318

Nanodots formation with slow highly charged ions  

NASA Astrophysics Data System (ADS)

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

Yamazaki, Yasunori

2007-06-01

319

Electric Charge Electric charge is a fundamental property  

E-print Network

Charges · Charged objects interact by exerting forces on one another · Law of Charges: Like charges repel and angular momentum #12;Conduction and Induction · An object can be given a charge by conduction or induction) or by grounding the object #12;Induction · An electrically neutral object can have an induced charge when some

Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University

320

Application of a compact microwave ion source to radiocarbon analysis  

SciTech Connect

The compact, high current, 2.45 GHz microwave-driven plasma ion source which was built for the Chalk River TASCC facility is presently being adapted for testing as a gas ion source for accelerator mass spectrometry, at the Woods Hole Oceanographic Institution accelerator mass spectrometer. The special requirements for producing carbon-ion beams from micromole quantities of carbon dioxide produced from environmental samples will be discussed. These samples will be introduced into the ion source by means of argon carrier gas and a silicon capillary injection system. Following the extraction of positive ions from the source, negative ion formation in a charge exchange vapor will effectively remove the argon from the carbon beam. Simultaneous injection of the three carbon isotopes into the accelerator is planned.

Schneider, R. J.; Reden, K. F. von; Hayes, J. M.; Wills, J. S. C. [NOSAMS Facility, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 (United States); AECL Chalk River Laboratories, Chalk River, Ontario, K0J 1J0 (Canada)

1999-04-26

321

Application of compact electron cyclotron resonance ion source  

SciTech Connect

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

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

2008-02-15

322

Compact Zwitterion-Coated Iron Oxide Nanoparticles for Biological Applications  

PubMed Central

The potential of superparamagnetic iron oxide nanoparticles (SPIONs) in various biomedical applications, including magnetic resonance imaging (MRI), sensing, and drug delivery, requires that their surface be derivatized to be hydrophilic and biocompatible. We report here the design and synthesis of a compact and water-soluble zwitterionic dopamine sulfonate (ZDS) ligand with strong binding affinity to SPIONs. After ligand exchange, the ZDS coated SPIONs exhibit small hydrodynamic diameters (HD), and stability with respect to time, pH, and salinity. Furthermore, small ZDS coated SPIONs were found to have a reduced non-specific affinity (compared to negatively charged SPIONs) towards serum proteins; streptavidin/dye functionalized SPIONs were bioactive and thus specifically targeted biotin receptors. PMID:22185195

Wei, He; Insin, Numpon; Lee, Jungmin; Han, Hee-Sun; Cordero, Jose M.; Liu, Wenhao; Bawendi, Moungi G.

2012-01-01

323

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

324

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

325

Surface site density, silicic acid retention and transport properties of compacted magnetite powder  

NASA Astrophysics Data System (ADS)

In France, within the framework of investigations of the feasibility of deep geological disposal of high-level radioactive waste, studies on corrosion products of steel over packs are ongoing. Such studies concern silica and radionuclide retention. The objective of the present work is to study sorption of silicic acid on compacted magnetite in percolation cells to attempt to simulate confined site conditions. Potentiometric titration of commercial magnetite was carried out with both dispersed and compacted magnetite. The titration of the magnetite suspension has been made with two different methods: a batch method (several suspensions) and a direct fast method (one suspension). The Gran’s function gave 1.7 (±0.4) and 2.4 (±0.5) sorption sites nm -2 with these respective methods but site densities as high as 20/nm 2 could be obtained by modelling. The titration of magnetite compacted at 120 bars showed that the evolution of charge density on magnetite surfaces is similar for compacted and dispersed magnetite. Silicic acid sorption onto dispersed and compacted magnetite was similar with sorption site densities ranging between 2.2 and 4.4/nm 2.

Mayant, C.; Grambow, B.; Abdelouas, A.; Ribet, S.; Leclercq, S.

326

Field performance of compacted clay liners  

SciTech Connect

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

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

1999-05-01

327

Thermodynamic analysis of compact formation; compaction, unloading, and ejection. I. Design and development of a compaction calorimeter and mechanical and thermal energy determinations of powder compaction.  

PubMed

The aim of this investigation was to determine and evaluate the thermodynamic properties, i.e. heat, work, and internal energy change, of the compaction process by developing a 'Compaction Calorimeter'. Compaction of common excipients and acetaminophen was performed by a double-ended, constant-strain tableting waveform utilizing an instrumented 'Compaction Simulator.' A constant-strain waveform provides a specific quantity of applied compaction work. A calorimeter, built around the dies, used a metal oxide thermistor to measure the temperature of the system. A resolution of 0.0001 degrees C with a sampling time of 5 s was used to monitor the temperature. An aluminum die within a plastic insulating die, in conjunction with fiberglass punches, comprised the calorimeter. Mechanical (work) and thermal (heat) calibrations of the elastic punch deformation were performed. An energy correction method was outlined to account for system heat effects and mechanical work of the punches. Compaction simulator transducers measured upper and lower punch forces and displacements. Measurements of the effective heat capacity of the samples were performed utilizing an electrical resistance heater. Specific heat capacities of the samples were determined by differential scanning calorimetry. The calibration techniques were utilized to determine heat, work, and the change in internal energies of powder compaction. Future publications will address the thermodynamic evaluation of the tablet sub-processes of unloading and ejection. PMID:10722955

DeCrosta, M T; Schwartz, J B; Wigent, R J; Marshall, K

2000-03-30

328

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. PMID:20858435

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

2010-01-01

329

Dynamic compaction of granular materials.  

PubMed

An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding 'intergranular stress' coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading-unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model. PMID:24353466

Favrie, N; Gavrilyuk, S

2013-12-01

330

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

331

A compact tritium AMS system  

NASA Astrophysics Data System (ADS)

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

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

2000-10-01

332

Compact drilling and sample system  

NASA Technical Reports Server (NTRS)

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

Gillis-Smith, Greg R.; Petercsak, Doug

1998-01-01

333

Dynamic compaction of granular materials  

PubMed Central

An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding ‘intergranular stress’ coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading–unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model. PMID:24353466

Favrie, N.; Gavrilyuk, S.

2013-01-01

334

Compaction of North-sea chalk  

NASA Astrophysics Data System (ADS)

The Ekofisk field is the largest petroleum field in the Norwegian North Sea territory where oil is produced from chalk formations. Early stage of oil production caused considerable changes in pore fluid pressure which led to a reservoir compaction. Pore collapse mechanism caused by the dramatic increase of effective stress, which in turn was caused by the pressure reduction by hydrocarbon depletion, was early identified as a principal reason for the reservoir compaction (Sulak et al. 1991). There have been several attempts to model this compaction. They performed with variable success on predicting the Ekofisk subsidence. However, the most of these models are based on empirical relations and do not investigate in detail the phenomena involved in the compaction. In sake of predicting the Ekofisk subsidence while using only independently measurable variables we used a chalk compaction model valid on geological time-scales (Japsen et al. 2011) assuming plastic pore-collapse mechanism at a threshold effective stress level. We identified the phenomena involved in the pore collapse. By putting them in a sequential order we created a simple statistical analytical model. We also investigated the time-dependence of the phenomena involved and by assuming that one of the phenomena is rate-limiting we could make estimations of the compaction rate at smaller length-scales. By carefully investigating the nature of pressure propagation we could upscale our model to reservoir scale. We found that the predicted compaction rates are close enough to the measured rates. We believe that we could further increase accuracy by refining our model. Sulak, R. M., Thomas, L. K., Boade R. R. (1991) 3D reservoir simulation of Ekofisk compaction drive. Journal of Petroleum Technology, 43(10):1272-1278, 1991. Japsen, P., Dysthe, D. K., Hartz, E. H., Stipp, S. L. S., Yarushina, V. M., Jamtveit. (2011) A compaction front in North Sea chalk. Journal of Geophysical Research: Solid Earth (1978-2012), 116(B11)

Keszthelyi, Dániel; Dysthe, Dag Kristian; Jamtveit, Bjørn

2014-05-01

335

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

336

Relativistic Hadrons in Cosmic Compact Objects  

NASA Astrophysics Data System (ADS)

The articles in this book deal with energetic hadron processes near astrophysical compact objects, including compact binary systems and active galactic nuclei. A variety of observational results suggest that relativistic hadrons can be produced in the vicinity of these objects. Among the topics treated in detail are the question whether a large fraction of the energy produced by active galactic nuclei is channeled into a population of relativistic protons and the problem of the origin of very high and ultra-high energy gamma rays from galactic compact sources.

Zdziarski, Andrzej A.; Sikora, Marek

337

PICOBIT: A Compact Scheme System for Microcontrollers  

NASA Astrophysics Data System (ADS)

Due to their tight memory constraints, small microcontroller based embedded systems have traditionally been implemented using low-level languages. This paper shows that the Scheme programming language can also be used for such applications, with less than 7 kB of total memory. We present PICOBIT, a very compact implementation of Scheme suitable for memory constrained embedded systems. To achieve a compact system we have tackled the space issue in three ways: the design of a Scheme compiler generating compact bytecode, a small virtual machine, and an optimizing C compiler suited to the compilation of the virtual machine.

St-Amour, Vincent; Feeley, Marc

338

Spacecraft Charging Interactive Handbook  

Microsoft Academic Search

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

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

1998-01-01

339

Charging of interplanetary grains  

NASA Technical Reports Server (NTRS)

The objective of this program is to quantify, by laboratory experiments, the charging of ices and other insulators subject to irradiation with electrons, ions and ultraviolet photons and to model special conditions based on the data. The system and conditions to be studied are those relevant for charging of dust in magnetospheric plasmas. The measurements are supplemented by computer simulations of charging or grains under a variety of conditions. Our work for this period involved experiments on water ice, improved models of charging of ice grains for Saturn's E-ring, and the construction of apparatus for electron impact studies and measurements of electron energy distributions.

Baragiola, R. A.; Johnson, R. E.; Newcomb, John L.

1995-01-01

340

Holographic Charged Renyi Entropies  

E-print Network

We construct a new class of entanglement measures by extending the usual definition of Renyi entropy to include a chemical potential. These charged Renyi entropies measure the degree of entanglement in different charge sectors of the theory and are given by Euclidean path integrals with the insertion of a Wilson line encircling the entangling surface. We compute these entropies for a spherical entangling surface in CFT's with holographic duals, where they are related to entropies of charged black holes with hyperbolic horizons. We also compute charged Renyi entropies in free field theories.

Alexandre Belin; Ling-Yan Hung; Alexander Maloney; Shunji Matsuura; Robert C. Myers; Todd Sierens

2015-01-20

341

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

342

Generation of powder compaction response diagrams  

SciTech Connect

The effect of elastic compliances in the testing system is shown to have a considerable influence on the compaction diagram generated via an automatic procedure. Proper accounting of this effect allows rapid and accurate diagrams to be made.

Matsumoto, R.L.K.

1986-10-01

343

Deep Compaction Control of Sandy Soils  

NASA Astrophysics Data System (ADS)

Vibroflotation, vibratory compaction, micro-blasting or heavy tamping are typical improvement methods for the cohesionless deposits of high thickness. The complex mechanism of deep soil compaction is related to void ratio decrease with grain rearrangements, lateral stress increase, prestressing effect of certain number of load cycles, water pressure dissipation, aging and other effects. Calibration chamber based interpretation of CPTU/DMT can be used to take into account vertical and horizontal stress and void ratio effects. Some examples of interpretation of soundings in pre-treated and compacted sands are given. Some acceptance criteria for compaction control are discussed. The improvement factors are analysed including the normalised approach based on the soil behaviour type index.

Ba?achowski, Lech; Kurek, Norbert

2015-02-01

344

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

345

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

346

A CMOS-compatible compact display  

E-print Network

Portable information devices demand displays with high resolution and high image quality that are increasingly compact and energy-efficient. Microdisplays consisting of a silicon CMOS backplane integrated with light ...

Chen, Andrew R. (Andrew Raymond)

2005-01-01

347

Pharmaceutical tablet compaction : product and process design  

E-print Network

This thesis explores how tablet performance is affected by microstructure, and how microstructure can be controlled by selection of excipients and compaction parameters. A systematic strategy for formulation and process ...

Pore, Mridula

2009-01-01

348

Structure of plastically compacting granular packings  

E-print Network

The developing structure in systems of compacting ductile grains were studied experimentally in two and three dimensions. In both dimensions, the peaks of the radial distribution function were reduced, broadened, and shifted compared with those observed in hard disk- and sphere systems. The geometrical three--grain configurations contributing to the second peak in the radial distribution function showed few but interesting differences between the initial and final stages of the two dimensional compaction. The evolution of the average coordination number as function of packing fraction is compared with other experimental and numerical results from the literature. We conclude that compaction history is important for the evolution of the structure of compacting granular systems.

Lina Uri; Thomas Walmann; Luc Alberts; Dag Kristian Dysthe; Jens Feder

2005-10-13

349

ACTIVELY CONTROLLED AFTERBURNER FOR COMPACT WASTE INCINERATION  

EPA Science Inventory

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

350

Survey of compact storage rings in Japan  

NASA Astrophysics Data System (ADS)

The present status of Japanese compact electron storage rings, used as synchrotron orbital radiation (SOR) sources is surveyed. Typical compact storage rings are UV sources and soft-X-ray sources below 1 GeV. The former have been used since the middle 1970s for scientific applications, and the latter are still under development, mainly for dedicated lithography sources for the electronics industry to use in producing ultralarge scale integrated (ULSI) circuits. Other types of compact storage rings now being planned generally have energies between 1 GeV and 2 GeV, and are intended for medical uses such as angiography. In this electron energy region, there is the possibility of making a free electron laser in the range from microwaves to X-rays. The definition of compact storage rings is discussed in terms of ring size, electron beam energy and insertion devices as well as configurations of the rings and their injection schemes.

Hirabayashi, Hiromi

1990-05-01

351

ROSAT Observations of Compact Groups of Galaxies  

Microsoft Academic Search

We have systematically analyzed a sample of 13 new and archival ROSAT PSPC\\u000aobservations of compact groups of galaxies: 12 Hickson Compact Groups plus the\\u000aNCG 2300 group. We find that approximately two-thirds of the groups have\\u000aextended X-ray emission and, in four of these, the emission is resolved into\\u000adiffuse emission from gas at a temperature of $k$T $\\\\sim

Rachel A. Pildis; Joel N. Bregman; August E. Evrard

1995-01-01

352

ROSAT observations of compact groups of galaxies  

Microsoft Academic Search

The detection of X-ray emission from Hickson's compact groups of galaxies (HCGs) and its origin are the subject of this work. A search for X-ray emission from compact groups revealed detection from 8 out of the 12 HCG images extracted from the ROSAT public archive. For two of them (HCG 16 and HCG 44), the X-ray emission originates from point-like

P. Saracco; P. Ciliegi

1995-01-01

353

Stellar Populations of Compact Group Galaxies  

Microsoft Academic Search

The study of the stellar populations of the elliptical galaxies in compact groups could give us important information on the\\u000a merging history of the elliptical galaxies in the groups and could elucidate some of the questions regarding group evolution.\\u000a We have initiated a program to study the stellar populations of the elliptical galaxies in compact groups. In the following,\\u000a we

Paula Coelho; Cláudia Mendes de Oliveira; Jesus J. González; N. Visvanathan; B. Barbuy

2005-01-01

354

Compact reflective imaging spectrometer utilizing immersed gratings  

DOEpatents

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

Chrisp, Michael P. (Danville, CA)

2006-05-09

355

Compaction Dynamics of Wet Granular Assemblies  

NASA Astrophysics Data System (ADS)

The extremely slow compaction dynamics of wet granular assemblies is studied experimentally. The cohesion, due to capillary bridges between neighboring grains, is tuned using different liquids having specific surface tension values. The compaction dynamics of a cohesive packing obeys an inverse logarithmic law, like most dry random packings. However, the characteristic relaxation time ? grows strongly with cohesion. A model, based on free volume kinetic equations and the presence of a capillary energy barrier, is able to reproduce quantitatively the experimental curves.

Fiscina, J. E.; Lumay, G.; Ludewig, F.; Vandewalle, N.

2010-07-01

356

Selected problems in astrophysics of compact objects  

E-print Network

I review three problems in astrophysics of compacts stars: (i) the phase diagram of warm pair-correlated nuclear matter a sub-saturation densities at finite isospin asymmtery; (ii) the Standard Model neutrino emission from superfluid phases in neutron stars within the Landau theory of Fermi (superfluid) liquids; (iii) the beyond Standard Model physics of axionic cooling of compact stars by the Cooper pair-breaking processes.

Armen Sedrakian

2012-12-01

357

High Quality Compact Delay Test Generation  

E-print Network

HIGH QUALITY COMPACT DELAY TEST GENERATION A Dissertation by ZHENG WANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY... May 2010 Major Subject: Computer Engineering HIGH QUALITY COMPACT DELAY TEST GENERATION A Dissertation by ZHENG WANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment...

Wang, Zheng

2011-08-08

358

Polynomially Compact-Like Strongly Continuous Semigroups  

Microsoft Academic Search

J. R. Cuthbert gave some results about the class of semigroups of operators (T(t))\\u000at0 on a Banach space X which have the property that for some t>0, T(t)–I is compact. Cuthbert's results were extended to various classes of operators generalizing the set of compact operators such as the ideal of Fredholm perturbations or the set of Riesz operators. The

Khalid Latrach; J. Martin Paoli

2004-01-01

359

Location independent compact routing for wireless networks  

Microsoft Academic Search

While reactive routing protocols such as AODV operate efficiently for small ad hoc wireless networks, their O(N) perflow control overhead limits deployment on larger-scale networks. Deployment of compact routing protocols such as geographic routing have met with challenges. In this paper, we present Table Attenuation Routing Protocol (TARP), a protocol that combines compact per-node routing state with scalability to large

Robert Gilbert; Kerby Johnson; Shaomei Wu; Ben Y. Zhao; Haitao Zheng

2006-01-01

360

Dynamic compaction of tungsten carbide powder.  

SciTech Connect

The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction.

Gluth, Jeffrey Weston; Hall, Clint Allen; Vogler, Tracy John; Grady, Dennis Edward

2005-04-01

361

Compaction bands simulated in Discrete Element Models  

NASA Astrophysics Data System (ADS)

Compaction bands, i.e. tabular zones that accommodate compaction but no shear, have recently been observed in high-porosity sandstone, where the dominant micromechanism is grain breakage and crushing. Such bands are extremely important for hydrocarbon extraction, forming barriers that might inhibit the flow. They have further been associated with borehole stability problems. However, compaction band initiation and propagation remain poorly understood, while the necessary material conditions for their formation require further investigation. Three-dimensional Discrete Element Method simulations of the stressing of a sandstone sample were conducted. These successfully reproduced a discrete compaction band; its initiation and propagation are shown. An investigation into the effects of the cementation bond strength and the post-fragmentation behaviour of the grains on the observed behaviour is also presented. Well-localised discrete bands were observed when both the bond strengths were high and the grains lost their load-bearing capacity after being broken. On the contrary, an advancing crushing front resembling a diffuse compaction band was observed in simulations where the broken grain could still carry force. The data presented here provide the micromechanical insight necessary for a better understanding of conditions leading to compaction band initiation and propagation, which might facilitate identification of rocks that might form them.

Marketos, G.; Bolton, M. D.

2009-05-01

362

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

Federal Register 2010, 2011, 2012, 2013, 2014

...exemption for indirect access to Criminal Justice Information. (2) Encryption Standards for Criminal Justice Information at Rest. (3...Barron, FBI Compact Officer, Criminal Justice Information Services...

2013-10-03

363

Scrapie infection activates the replication of ecotropic, xenotropic, and polytropic murine leukemia virus (MuLV) in brains and spinal cords of senescence-accelerated mice: implication of MuLV in progression of scrapie pathogenesis.  

PubMed

Senescence-accelerated mice (SAMP8) have a short life span, whereas SAMR1 mice are resistant to accelerated senescence. Previously it has been reported that the Akv strain of ecotropic murine leukemia virus (E-MuLV) was detected in brains of SAMP8 mice but not in brains of SAMR1 mice. In order to determine the change of MuLV levels following scrapie infection, we analyzed the E-MuLV titer and the RNA expression levels of E-MuLV, xenotropic MuLV, and polytropic MuLV in brains and spinal cords of scrapie-infected SAM mice. The expression levels of the 3 types of MuLV were increased in scrapie-infected mice compared to control mice; E-MuLV expression was detected in infected SAMR1 mice, but only in the terminal stage of scrapie disease. We also examined incubation periods and the levels of PrPSc in scrapie-infected SAMR1 (sR1) and SAMP8 (sP8) mice. We confirmed that the incubation period was shorter in sP8 (210+/-5 days) compared to sR1 (235+/-10 days) after intraperitoneal injection. The levels of PrPSc in sP8 were significantly greater than sR1 at 210+/-5 days, but levels of PrPSc at the terminal stage of scrapie in both SAM strains were virtually identical. These results show the activation of MuLV expression by scrapie infection and suggest acceleration of the progression of scrapie pathogenesis by MuLV. PMID:16930537

Lee, Kyung-Hee; Jeong, Byung-Hoon; Jin, Jae-Kwang; Meeker, Harry C; Kim, Jae-Il; Carp, Richard I; Kim, Yong-Sun

2006-10-13

364

A compact, all solid-state LC high voltage generator.  

PubMed

LC generator is widely applied in the field of high voltage generation technology. A compact and all solid-state LC high voltage generator based on saturable pulse transformer is proposed in this paper. First, working principle of the generator is presented. Theoretical analysis and circuit simulation are used to verify the design of the generator. Experimental studies of the proposed LC generator with two-stage main energy storage capacitors are carried out. And the results show that the proposed LC generator operates as expected. When the isolation inductance is 27 ?H, the output voltage is 1.9 times larger than the charging voltage on single capacitor. The multiplication of voltages is achieved. On the condition that the primary energy storage capacitor is charged to 857 V, the output voltage of the generator can reach to 59.5 kV. The step-up ratio is nearly 69. When self breakdown gas gap switch is used as main switch, the rise time of the voltage pulse on load resistor is 8.7 ns. It means that the series-wound inductance in the discharging circuit is very small in this system. This generator can be employed in two different applications. PMID:23822362

Fan, Xuliang; Liu, Jinliang

2013-06-01

365

A compact, all solid-state LC high voltage generator  

NASA Astrophysics Data System (ADS)

LC generator is widely applied in the field of high voltage generation technology. A compact and all solid-state LC high voltage generator based on saturable pulse transformer is proposed in this paper. First, working principle of the generator is presented. Theoretical analysis and circuit simulation are used to verify the design of the generator. Experimental studies of the proposed LC generator with two-stage main energy storage capacitors are carried out. And the results show that the proposed LC generator operates as expected. When the isolation inductance is 27 ?H, the output voltage is 1.9 times larger than the charging voltage on single capacitor. The multiplication of voltages is achieved. On the condition that the primary energy storage capacitor is charged to 857 V, the output voltage of the generator can reach to 59.5 kV. The step-up ratio is nearly 69. When self breakdown gas gap switch is used as main switch, the rise time of the voltage pulse on load resistor is 8.7 ns. It means that the series-wound inductance in the discharging circuit is very small in this system. This generator can be employed in two different applications.

Fan, Xuliang; Liu, Jinliang

2013-06-01

366

Space charge measurement techniques and space charge in polyethylene  

Microsoft Academic Search

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

T. Mizutani

1994-01-01

367

Increasing Photocathode Charge Output  

Microsoft Academic Search

A fundamental concern in the operation of electron accelerators is the generation of intense beams with high polarization. The time structure of the electron beam determines whether the limiting factor in emission is laser power or surface charge buildup. The presence of excess surface charge comes about due to the photon absorption that excites electrons from the valence to the

Mulhollan; Gregory A

1999-01-01

368

Surface charges on membranes  

Microsoft Academic Search

Summary The equations of membrane potential developed by Kobatake and coworkers have been applied to the literature data on the resting membrane potential of the crayfish andMyxicola axons to derive values for the surface charge density present on the axon membranes. Some shortcomings of the method are briefly discussed. The value for the surface charge density derived for the squid

N. Lakshminarayanaiah

1976-01-01

369

Space-charge electrets  

Microsoft Academic Search

A literature review on space-charge electrets, covering the time period 1987 to 1996, is presented. The review starts out with a discussion of new inorganic and organic electret materials which also includes silicon based single and double layers. This is followed by a review of recent work on methods for measuring charge distributions. New results obtained with these methods on

R. Kressmann; G. M. Sessler; P. Gunther

1996-01-01

370

Jupiter probe charging study  

NASA Technical Reports Server (NTRS)

A model to predict spacecraft charging effects in the Jovian magnetosphere was developed for the preliminary design of a Jupiter probe. Charging calculations made with this model are presented and discussed. Differential potentials between interior and exterior surfaces and between sunlit and dark exterior surfaces are predicted to be in the kilovolt range.

Purvis, C. K.

1979-01-01

371

Compaction enhancement of pharmaceutical solids by engineered plasticization  

Microsoft Academic Search

The objective of this research was two fold: to use near infrared (NIR) spectroscopy for real-time monitoring and control of key compact attributes: content uniformity, moisture content, relative density, tensile strength and Young's modulus, during roller compaction; and, to develop a model for predicting the improvement in compaction behavior, during roller compaction, due to the plasticization effect of ambient moisture.

Abhay Gupta

2004-01-01

372

Rain Drop Charge Sensor  

NASA Astrophysics Data System (ADS)

begin{center} Large Large Rain Drop Charge Sensor Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , S. Murali Das (2) *Atmospheric Sciences Division, Centre for Earth Science Studies, Thiruvananthapuram 695011 (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) Kavyam, Manacaud, Thiruvananthapuram 695009 begin{center} ABSTRACT To study the inter-relations with precipitation electricity and precipitation microphysical parameters a rain drop charge sensor was designed and developed at CESS Electronics & Instrumentation Laboratory. Simultaneous measurement of electric charge and fall speed of rain drops could be done using this charge sensor. A cylindrical metal tube (sensor tube) of 30 cm length is placed inside another thick metal cover opened at top and bottom for electromagnetic shielding. Mouth of the sensor tube is exposed and bottom part is covered with metal net in the shielding cover. The instrument is designed in such a way that rain drops can pass only through unhindered inside the sensor tube. When electrically charged rain drops pass through the sensor tube, it is charged to the same magnitude of drop charge but with opposite polarity. The sensor tube is electrically connected the inverted input of a current to voltage converter operational amplifier using op-amp AD549. Since the sensor is electrically connected to the virtual ground of the op-amp, the charge flows to the ground and the generated current is converted to amplified voltage. This output voltage is recorded using a high frequency (1kHz) voltage recorder. From the recorded pulse, charge magnitude, polarity and fall speed of rain drop are calculated. From the fall speed drop diameter also can be calculated. The prototype is now under test running at CESS campus. As the magnitude of charge in rain drops is an indication of accumulated charge in clouds in lightning, this instrument has potential application in the field of risk and disaster management. By knowing the charge magnitude of initial drops from a precipitation event, gross cloud charge can be estimated and necessary precautions can be taken during convective cloud events. Being a site of high lightning incidence in tropics, Kerala state is affected in India and calls for much attention in lightning hazards mitigation. Installing this charge sensor and atmospheric electric field mill, an attempt to a better warning system can be attempted.

S, Sreekanth T.

373

Charging Black Saturn?  

E-print Network

We construct new charged static solutions of the Einstein-Maxwell field equations in five dimensions via a solution generation technique utilizing the symmetries of the reduced Lagrangian. By applying our method on the multi-Reissner-Nordstrom solution in four dimensions, we generate the multi-Reissner-Nordstrom solution in five dimensions. We focus on the five-dimensional solution describing a pair of charged black objects with general masses and electric charges. This solution includes the double Reissner-Nordstrom solution as well as the charged version of the five-dimensional static black Saturn. However, all the black Saturn configurations that we could find present either a conical singularity or a naked singularity. We also obtain a non-extremal configuration of charged black strings that reduces in the extremal limit to a Majumdar-Papapetrou like solution in five dimensions.

Brenda Chng; Robert Mann; Eugen Radu; Cristian Stelea

2008-10-28

374

Compact Q-balls and Q-shells in a scalar electrodynamics  

SciTech Connect

We investigate spherically symmetric nontopological solitons in electrodynamics with a scalar field self-interaction U{approx}|{psi}| taken from the complex signum-Gordon model. We find Q-balls for small absolute values of the total electric charge Q, and Q-shells when |Q| is large enough. In both cases the charge density exactly vanishes outside certain compact regions in the three-dimensional space. The dependence of the total energy E of small Q-balls on the total electric charge has the form E{approx}|Q|{sup 5/6}, while in the case of very large Q-shells, E{approx}|Q|{sup 7/6}.

Arodz, H.; Lis, J. [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland)

2009-02-15

375

DNA Compaction Induced by a Cationic Polymer or Surfactant Impact Gene Expression and DNA Degradation  

PubMed Central

There is an increasing interest in achieving gene regulation in biotechnological and biomedical applications by using synthetic DNA-binding agents. Most studies have so far focused on synthetic sequence-specific DNA-binding agents. Such approaches are relatively complicated and cost intensive and their level of sophistication is not always required, in particular for biotechnological application. Our study is inspired by in vivo data that suggest that DNA compaction might contribute to gene regulation. This study exploits the potential of using synthetic DNA compacting agents that are not sequence-specific to achieve gene regulation for in vitro systems. The semi-synthetic in vitro system we use include common cationic DNA-compacting agents, poly(amido amine) (PAMAM) dendrimers and the surfactant hexadecyltrimethylammonium bromide (CTAB), which we apply to linearized plasmid DNA encoding for the luciferase reporter gene. We show that complexing the DNA with either of the cationic agents leads to gene expression inhibition in a manner that depends on the extent of compaction. This is demonstrated by using a coupled in vitro transcription-translation system. We show that compaction can also protect DNA against degradation in a dose-dependent manner. Furthermore, our study shows that these effects are reversible and DNA can be released from the complexes. Release of DNA leads to restoration of gene expression and makes the DNA susceptible to degradation by Dnase. A highly charged polyelectrolyte, heparin, is needed to release DNA from dendrimers, while DNA complexed with CTAB dissociates with the non-ionic surfactant C12E5. Our results demonstrate the relation between DNA compaction by non-specific DNA-binding agents and gene expression and gene regulation can be achieved in vitro systems in a reliable dose-dependent and reversible manner. PMID:24671109

Ainalem, Marie-Louise; Bartles, Andrew; Muck, Joscha; Dias, Rita S.; Carnerup, Anna M.; Zink, Daniele; Nylander, Tommy

2014-01-01

376

DNA compaction induced by a cationic polymer or surfactant impact gene expression and DNA degradation.  

PubMed

There is an increasing interest in achieving gene regulation in biotechnological and biomedical applications by using synthetic DNA-binding agents. Most studies have so far focused on synthetic sequence-specific DNA-binding agents. Such approaches are relatively complicated and cost intensive and their level of sophistication is not always required, in particular for biotechnological application. Our study is inspired by in vivo data that suggest that DNA compaction might contribute to gene regulation. This study exploits the potential of using synthetic DNA compacting agents that are not sequence-specific to achieve gene regulation for in vitro systems. The semi-synthetic in vitro system we use include common cationic DNA-compacting agents, poly(amido amine) (PAMAM) dendrimers and the surfactant hexadecyltrimethylammonium bromide (CTAB), which we apply to linearized plasmid DNA encoding for the luciferase reporter gene. We show that complexing the DNA with either of the cationic agents leads to gene expression inhibition in a manner that depends on the extent of compaction. This is demonstrated by using a coupled in vitro transcription-translation system. We show that compaction can also protect DNA against degradation in a dose-dependent manner. Furthermore, our study shows that these effects are reversible and DNA can be released from the complexes. Release of DNA leads to restoration of gene expression and makes the DNA susceptible to degradation by Dnase. A highly charged polyelectrolyte, heparin, is needed to release DNA from dendrimers, while DNA complexed with CTAB dissociates with the non-ionic surfactant C12E5. Our results demonstrate the relation between DNA compaction by non-specific DNA-binding agents and gene expression and gene regulation can be achieved in vitro systems in a reliable dose-dependent and reversible manner. PMID:24671109

Ainalem, Marie-Louise; Bartles, Andrew; Muck, Joscha; Dias, Rita S; Carnerup, Anna M; Zink, Daniele; Nylander, Tommy

2014-01-01

377

Charged anisotropic matter with linear or nonlinear equation of state  

SciTech Connect

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 (10{sup 19}C) and maximum electric field intensities are very large (10{sup 23}-10{sup 24} statvolt/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 [Institute of Mathematics, Kings College, University of Aberdeen, Aberdeen AB24 3UE (United Kingdom); Department of Mathematics, Jadavpur University, Kolkata 700 032, West Bengal (India); Department of Physics, Government College of Engineering and Ceramic Technology, Kolkata 700 010, West Bengal (India); Department of Physics, Government Training College, Hooghly 712103 (India)

2010-08-15

378

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

379

Classification of solar cells according to mechanisms of charge separation and charge collection.  

PubMed

In the last decade, photovoltaics (PV) has experienced an important transformation. Traditional solar cells formed by compact semiconductor layers have been joined by new kinds of cells that are constituted by a complex mixture of organic, inorganic and solid or liquid electrolyte materials, and rely on charge separation at the nanoscale. Recently, metal organic halide perovskites have appeared in the photovoltaic landscape showing large conversion efficiencies, and they may share characteristics of the two former types. In this paper we provide a general description of the photovoltaic mechanisms of the single absorber solar cell types, combining all-inorganic, hybrid and organic cells into a single framework. The operation of the solar cell relies on a number of internal processes that exploit internal charge separation and overall charge collection minimizing recombination. There are two main effects to achieve the required efficiency, first to exploit kinetics at interfaces, favouring the required forward process, and second to take advantage of internal electrical fields caused by a built-in voltage and by the distribution of photogenerated charges. These principles represented by selective contacts, interfaces and the main energy diagram, form a solid base for the discussion of the operation of future types of solar cells. Additional effects based on ferroelectric polarization and ionic drift provide interesting prospects for investigating new PV effects mainly in the perovskite materials. PMID:25586862

Kirchartz, Thomas; Bisquert, Juan; Mora-Sero, Ivan; Garcia-Belmonte, Germà

2015-01-28

380

Modulation of folding energy landscape by charge-charge interactions: linking experiments with computational modeling.  

PubMed

The kinetics of folding-unfolding of a structurally diverse set of four proteins optimized for thermodynamic stability by rational redesign of surface charge-charge interactions is characterized experimentally. The folding rates are faster for designed variants compared with their wild-type proteins, whereas the unfolding rates are largely unaffected. A simple structure-based computational model, which incorporates the Debye-Hückel formalism for the electrostatics, was used and found to qualitatively recapitulate the experimental results. Analysis of the energy landscapes of the designed versus wild-type proteins indicates the differences in refolding rates may be correlated with the degree of frustration of their respective energy landscapes. Our simulations indicate that naturally occurring wild-type proteins have frustrated folding landscapes due to the surface electrostatics. Optimization of the surface electrostatics seems to remove some of that frustration, leading to enhanced formation of native-like contacts in the transition-state ensembles (TSE) and providing a less frustrated energy landscape between the unfolded and TS ensembles. Macroscopically, this results in faster folding rates. Furthermore, analyses of pairwise distances and radii of gyration suggest that the less frustrated energy landscapes for optimized variants are a result of more compact unfolded and TS ensembles. These findings from our modeling demonstrates that this simple model may be used to: (i) gain a detailed understanding of charge-charge interactions and their effects on modulating the energy landscape of protein folding and (ii) qualitatively predict the kinetic behavior of protein surface electrostatic interactions. PMID:25564663

Tzul, Franco O; Schweiker, Katrina L; Makhatadze, George I

2015-01-20

381

Increasing Photocathode Charge Output  

SciTech Connect

A fundamental concern in the operation of electron accelerators is the generation of intense beams with high polarization. The time structure of the electron beam determines whether the limiting factor in emission is laser power or surface charge buildup. The presence of excess surface charge comes about due to the photon absorption that excites electrons from the valence to the conduction band. Some fraction of the electrons can be trapped near the surface which induces a rise in the electron affinity through the increased electrostatic potential. The higher affinity causes a lower emission probability and thus less emitted charge at later times. The electron affinity can recover to the zero charge limit after electron-hole recombination. As an example, the Next Linear Collider requires 95 micropulses having 2 x 10{sup 10} electrons per pulse in 0.7 ns with an interpulse spacing of 2.8 ns. Experience at SLAC has shown it is possible to generate 16 x 10{sup 10} electrons in 2 ns pulses with the requisite polarization. However, subsequent pulses may experience strong intensity damping. Several parameters can be varied to enhance the net charge output of the later pulses. Among these are increasing either the electric field at the photocathode surface or the surface charge dissipation rate by raising the carrier concentration or shunting the trapped charge. We present a series of measurements and a phenomenological model to characterize the range of these influences.

Mulhollan, Gregory A

1999-10-19

382

Folding without charges.  

PubMed

Surface charges of proteins have in several cases been found to function as "structural gatekeepers," which avoid unwanted interactions by negative design, for example, in the control of protein aggregation and binding. The question is then if side-chain charges, due to their desolvation penalties, play a corresponding role in protein folding by avoiding competing, misfolded traps? To find out, we removed all 32 side-chain charges from the 101-residue protein S6 from Thermus thermophilus. The results show that the charge-depleted S6 variant not only retains its native structure and cooperative folding transition, but folds also faster than the wild-type protein. In addition, charge removal unleashes pronounced aggregation on longer timescales. S6 provides thus an example where the bias toward native contacts of a naturally evolved protein sequence is independent of charges, and point at a fundamental difference in the codes for folding and intermolecular interaction: specificity in folding is governed primarily by hydrophobic packing and hydrogen bonding, whereas solubility and binding relies critically on the interplay of side-chain charges. PMID:22454493

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

2012-04-10

383

Diagnostics of soil compaction in steppe zone  

NASA Astrophysics Data System (ADS)

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

Sorokin, Alexey; Kust, German

2014-05-01

384

Modeling of planetesimal compaction by hot pressing  

NASA Astrophysics Data System (ADS)

Compaction of initially porous material prior to melting is an important process that has influenced the interior structure and the thermal evolution of planetesimals in their early history. On one hand, compaction decreases the porosity resulting in a reduction of the radius. On the other hand, the loss of porosity results in an increase of the thermal conductivity of the material and, thus, in a more efficient cooling. Porosity loss by hot pressing is the most efficient process of compaction in planetesimals and can be described by creep flow, which depends on temperature and stress. Hot pressing has been repeatedly modeled using a simplified approach, for which the porosity is gradually reduced in some fixed temperature interval between ~650 K and 700 K [see e.g. 1--3]. This approach neglects the dependence of compaction on stress. In the present study [see 4], we compare this ''parametrized'' method with a self-consistent calculation of porosity loss via a ''creep-related'' approach. We use our thermal evolution model from previous studies [5] to model compaction of an initially porous ordinary chondritic body and consider four basic packings of spherical dust grains (simple cubic, orthorhombic, rhombohedral, and body-centered cubic). Depending on the grain packing, we calculate the effective stress and the associated porosity change via the thermally activated creep flow. For comparison, compaction is also modeled by simply reducing the initial porosity linearly to zero between 650 and 700 K. Since we are interested in thermal metamorphism and not melting, we only consider bodies that experience a maximum temperature below the solidus temperature of the metal phase. For the creep related approach, the temperature interval in which compaction takes place depends strongly on the size of the planetesimal and is not fixed as assumed in the parametrized approach. Depending on the radius, the initial grain size, the activation energy, the initial porosity, and the specific packing of the dust grains, the temperature interval lies within 600--1200 K. This finding implies that the parametrized approach strongly overestimates compaction and underestimates the maximal temperature. For the cases considered, the post-compaction porous layer retained at the surface, is a factor of 2.5 to 4.5 thicker for the creep-related approach. The difference in the temperature evolution between the two approaches increases with decreasing radius, and the maximal temperature can deviate by about 40 % for small bodies.

Neumann, W.; Breuer, D.; Spohn, T.

2014-07-01

385

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

386

Infrared emission from compact groups of galaxies  

SciTech Connect

A search of the IRAS Point Source Catalog, Version 2 has revealed infrared sources within 1 arcmin of the optical centers of 54 galaxies in Hickson's catalog of compact groups of galaxies. The 60-micron luminosity function for these galaxies has the same shape as the luminosity function of the IRAS bright galaxy sample. The space density of IRAS galaxies in compact groups is 60 times smaller than the space density of IRAS bright galaxies, indicating that of order 1 percent of all bright IRAS galaxies are in compact groups. The infrared emission from these galaxies is compared with the emission from samples of isolated galaxies by Keel et al. (1985) and cluster galaxies studied by Bicay and Giovanelli (1987). The fractional distribution of the ratio of far-infrared to optical luminosity of compact group galaxies is significantly larger than that of the isolated galaxies and comparable to that of the cluster galaxies. These results indicate that infrared emission is enhanced in the compact group galaxies, probably because of interactions. 24 refs.

Hickson, P.; Menon, T.K.; Palumbo, G.G.C.; Persic, M. (British Columbia Univ., Vancouver (Canada); CNR, Istituto di Studio e Tecnologie sulle Radiazioni Estraterrestri (Italy); Osservatorio Astronomico, Trieste (Italy))

1989-06-01

387

Neutral hydrogen in compact groups of galaxies  

SciTech Connect

Integrated H I profiles were detected for 34 of 51 Hickson compact groups (HCGs) of galaxies, and sensitive upper limits to the H I flux density were measured for the other 17. About 60 percent of the galaxies within compact groups are spirals, and a significant tendency exists for the fraction of elliptical galaxies to increase with group surface brightness. The amount of dark matter within the compact group region is negligibly small. An HCG on average contains half as much neutral hydrogen as a loose group with a similar spectrum of galaxy luminosities and morphological types, implying that compact groups are independent dynamical entities and not transient or projected configurations of loose groups. The observed fraction of galaxies which are luminous enough to be possible merger products of compact groups is small compared with the fraction required by the theory of dynamical friction. A clear discrepancy thus exists between solid empirical evidence and a straightforward prediction of Newtonian dynamical theory in a setting which does not permit a dark matter explanation. 44 references.

Williams, B.A.; Rood, H.J.

1987-02-01

388

A cosmological context for compact massive galaxies  

E-print Network

To provide a quantitative cosmological context to ongoing observational work on the formation histories and location of compact massive galaxies, we locate and study a sample of exceptionally compact systems in the Bolshoi simulation, using the dark matter structural parameters from a real, compact massive galaxy (NGC1277) as a basis for our working criteria. We find that over 80% of objects in this nominal compact category are substructures of more massive groups or clusters, and that the probability of a given massive substructure being this compact increases significantly with the mass of the host structure; rising to ~30% for the most massive clusters in the simulation. Tracking the main progenitors of this subsample back to z=2, we find them all to be distinct structures with scale radii and densities representative of the population as a whole at this epoch. What does characterise their histories, in addition to mostly becoming substructures, is that they have almost all experienced below-average mass a...

Stringer, Martin; Vecchia, Claudio Dalla; Martinez-Valpuesta, Inma

2015-01-01

389

Strategy Guideline: Compact Air Distribution Systems  

SciTech Connect

This Strategy Guideline discusses the benefits and challenges of using a compact air distribution system to handle the reduced loads and reduced air volume needed to condition the space within an energy efficient home. Traditional systems sized by 'rule of thumb' (i.e., 1 ton of cooling per 400 ft2 of floor space) that 'wash' the exterior walls with conditioned air from floor registers cannot provide appropriate air mixing and moisture removal in low-load homes. A compact air distribution system locates the HVAC equipment centrally with shorter ducts run to interior walls, and ceiling supply outlets throw the air toward the exterior walls along the ceiling plane; alternatively, high sidewall supply outlets throw the air toward the exterior walls. Potential drawbacks include resistance from installing contractors or code officials who are unfamiliar with compact air distribution systems, as well as a lack of availability of low-cost high sidewall or ceiling supply outlets to meet the low air volumes with good throw characteristics. The decision criteria for a compact air distribution system must be determined early in the whole-house design process, considering both supply and return air design. However, careful installation of a compact air distribution system can result in lower material costs from smaller equipment, shorter duct runs, and fewer outlets; increased installation efficiencies, including ease of fitting the system into conditioned space; lower loads on a better balanced HVAC system, and overall improved energy efficiency of the home.

Burdick, A.

2013-06-01

390

taking charge : optimizing urban charging infrastructure for shared electric vehicles  

E-print Network

This thesis analyses the opportunities and constraints of deploying charging infrastructure for shared electric vehicles in urban environments. Existing electric vehicle charging infrastructure for privately owned vehicles ...

Subramani, Praveen

2012-01-01

391

Photon: history, mass, charge  

E-print Network

The talk consists of three parts. ``History'' briefly describes the emergence and evolution of the concept of photon during the first two decades of the 20th century. ``Mass'' gives a short review of the literature on the upper limit of the photon's mass. ``Charge'' is a critical discussion of the existing interpretation of searches for photon charge. Schemes, in which all photons are charged, are grossly inconsistent. A model with three kinds of photons (positive, negative and neutral) seems at first sight to be more consistent, but turns out to have its own serious problems.

L. B. Okun

2006-02-13

392

Compact groups in theory and practice - I. The spatial properties of compact groups  

E-print Network

We use a mock galaxy catalogue based upon the Millennium Run simulation to investigate the intrinsic spatial properties of compact groups of galaxies. We find that approximately 30% of galaxy associations identified in our mock catalogue are physically dense systems of four or more galaxies with no interlopers, approximately half are close associations of 2, 3 or 4 galaxies with one or more interlopers, and the remainder are not physically dense. Genuine compact groups are preferentially brighter and more isolated than those with interlopers; by increasing the required minimum surface brightness of a group from the canonical value of 26mags/arcsec^2 to 22mags/arcsec^2, we can increase the proportion of genuinely compact systems identified with no interlopers from 29% to 75%. Of the genuine compact groups identified, more than half consist of a single dark matter halo with all the member galaxies deeply embedded within it. In some cases, there are other galaxies which share the same halo (typically with mass ~ 10^13 h^{-1} M_\\odot) but which are not identified as being members of the compact group. This implies that compact groups are associated with group environments, some or all members of which are in the compact group. For those compact groups where all galaxies are in the same halo, the three-dimensional velocity dispersion of the compact group correlates broadly with the virial velocity of the dark matter halo. However, the scale-size of the group - and hence the fraction of the halo mass which the group samples - is completely uncorrelated with the properties of the dark matter halo. This means that masses derived under the simple assumption of virial equilibrium using the observed velocity dispersions and sizes of compact groups give incorrect estimates of the true mass of the underlying dark matter.

Alan W. McConnachie; Sara L. Ellison; David R. Patton

2008-04-18

393

Role of electric charge in shaping equilibrium configurations of fluid tori encircling black holes  

SciTech Connect

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-Nordstroem black holes and compare them with equivalent configurations of electrically neutral tori.

Kovar, Jiri; Slany, Petr; Stuchlik, Zdenek; Karas, Vladimir; Cremaschini, Claudio; Miller, John C. [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava Bezrucovo nam. 13, CZ-74601 Opava (Czech Republic); Astronomical Institute, Academy of Sciences, Bocni II, CZ-14131 Prague (Czech Republic); SISSA and INFN, Via Bonomea 265, I-34136 Trieste (Italy); SISSA and INFN, Via Bonomea 265, I-34136 Trieste, Italy and Department of Physics (Astrophysics), University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom)

2011-10-15

394

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

NASA Astrophysics Data System (ADS)

In this paper, the development of compact transmission soft x-ray microscopy (XM) with sub-50 nm spatial resolution for biomedical applications is described. The compact transmission soft x-ray microscope operates at ? = 2.88 nm (430 eV) and is based on a tabletop regenerative x-ray source in combination with a tandem ellipsoidal condenser mirror for sample illumination, an objective micro zone plate and a thinned back-illuminated charge coupled device to record an x-ray image. The new, compact x-ray microscope system requires the fabrication of proper x-ray optical devices in order to obtain high-quality images. For an application-oriented microscope, the alignment procedure is fully automated via computer control through a graphic user interface. In imaging studies using our compact XM system, a gold mesh image was obtained with 45 nm resolution at ×580 magnification and 1 min exposure. Images of a biological sample (Coscinodiscus oculoides) were recorded.

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

2006-03-01

395

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

PubMed

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

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

2006-03-21

396

Morphology of galaxies in compact groups  

NASA Technical Reports Server (NTRS)

Results of a study of galaxy morphology in a homogeneous sample of 98 compact groups of galaxies are reported. Of all the galaxies, 49 percent are of late morphological type (S + Irr), somewhat less than the corresponding fraction for field galaxies. Similarly, for first-ranked galaxies only, 48 percent are late type. Several strong correlations are found between galaxy type and the galaxy environment. Morphological concordance occurs between galaxies within a group. Galaxy morphological type correlates with group optical luminosity, and galaxy morphology correlates with velocity dispersion. The latter correlation is found to be the more fundamental of the two. No strong correlation between morphological type and galaxy space density is found in these compact groups, contrary to the situation in rich clusters and loose groups. These results indicate that the morphological types of galaxies in compact groups are strongly influenced by the environment, and that this influence occurs mostly at the time of galaxy formation.

Hickson, Paul; Huchra, John P.; Kindl, Enrico

1988-01-01

397

The birthplace of compact groups of galaxies  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

398

Morphology of galaxies in compact groups  

SciTech Connect

Results of a study of galaxy morphology in a homogeneous sample of 98 compact groups of galaxies are reported. Of all the galaxies, 49 percent are of late morphological type (S + Irr), somewhat less than the corresponding fraction for field galaxies. Similarly, for first-ranked galaxies only, 48 percent are late type. Several strong correlations are found between galaxy type and the galaxy environment. Morphological concordance occurs between galaxies within a group. Galaxy morphological type correlates with group optical luminosity, and galaxy morphology correlates with velocity dispersion. The latter correlation is found to be the more fundamental of the two. No strong correlation between morphological type and galaxy space density is found in these compact groups, contrary to the situation in rich clusters and loose groups. These results indicate that the morphological types of galaxies in compact groups are strongly influenced by the environment, and that this influence occurs mostly at the time of galaxy formation. 22 references.

Hickson, P.; Huchra, J.P.; Kindl, E.

1988-08-01

399

Plasmons in optical compact disks: sensing applications  

NASA Astrophysics Data System (ADS)

In this work, we explore the sensing applications of Surface Plasmon Resonance (SPR) enhanced transmission of light through 1-D metal gratings on commonly available compact discs (CDs). We show that SPR on CDs (CD-SPR) can be used to build a simple and compact angular displacement measurement system with submicro- radian resolution. In addition we show that by controlling the azimuthal angle of the grating vector with respect to incident k-vector, it is also possible to measure angular displacement in two planes which is not possible with thin film SPR. The major advantage of this method is the compact form factor which will enable CD-SPR based angular measurement systems to be integrated into other experimental setups with the least burden.

Kumawat, Nityanand; Venugopalan, Priyamvada; Nayak, Rohit; Varma, Manoj M.

2010-12-01

400

Plasmons in optical compact disks: sensing applications  

NASA Astrophysics Data System (ADS)

In this work, we explore the sensing applications of Surface Plasmon Resonance (SPR) enhanced transmission of light through 1-D metal gratings on commonly available compact discs (CDs). We show that SPR on CDs (CD-SPR) can be used to build a simple and compact angular displacement measurement system with submicro- radian resolution. In addition we show that by controlling the azimuthal angle of the grating vector with respect to incident k-vector, it is also possible to measure angular displacement in two planes which is not possible with thin film SPR. The major advantage of this method is the compact form factor which will enable CD-SPR based angular measurement systems to be integrated into other experimental setups with the least burden.

Kumawat, Nityanand; Venugopalan, Priyamvada; Nayak, Rohit; Varma, Manoj M.

2011-08-01

401

Anisotropic Compact stars with variable cosmological constant  

E-print Network

Recently the small value of the cosmological constant and its ability to accelerate the expansion of the Universe is of great interest. We discuss the possibility of forming of anisotropic compact stars from this cosmological constant as one of the competent candidates of dark energy. For this purpose we consider the analytical solution of Krori and Barua metric. We take the radial dependence of cosmological constant and check all the regularity conditions, TOV equations, stability and surface redshift of the compact stars. It has been shown as conclusion that this model is valid for any compact star and we have cited $4U 1820-30$ as a specific example of that kind of star.

Sk. Monowar Hossein; Farook Rahaman; Jayanta Naskar; Mehedi Kalam; Saibal Ray

2012-11-22

402

Cylindrically Symmetric Models of Anisotropic Compact Stars  

E-print Network

In this paper we have discussed the possibility of forming anisotropic compact stars from cosmological constant as one of the competent candidates of dark energy with cylindrical symmetry. For this purpose, we have applied the analytical solution of Krori and Barua metric to a particular cylindrically symmetric spacetime. The unknown constants in Krori and Barua metric have been determined by using masses and radii of class of compact stars like 4$U$1820-30, Her X-1, SAX J 1808-3658. The properties of these stars have been analyzed in detail. In this setting the cosmological constant has been taken as a variable which depends on the radial coordinates. We have checked all the regularity conditions, stability and surface redshift of the compact stars 4$U$1820-30, Her X-1, SAX J 1808-3658.

G. Abbas; Sumara Nazeer; M. A. Meraj

2014-12-16

403

Transmon qubits coupled to compact resonators  

NASA Astrophysics Data System (ADS)

Compact resonators comprising of a meander inductor and an interdigitated capacitor are desirable building blocks for a multi-qubit processor due to their small size. We present an experiment on a superconducting transmon qubit coupled capacitively to such a compact resonator. We have fabricated low-loss Nb based compact resonators with an area within 1 mm^2 on a sapphire substrate to operate between 5 and 8 GHz. The resonator geometry was optimized to achieve an intrinsic quality factor above 300,000 at single-photon microwave powers and temperatures below 100 mK. Transmon qubits were made using Al/AlOx/Al Josephson junctions shunted by an Al interdigitated capacitor with an identical width and gap as the resonator. We will present our experimental progress towards measuring relaxation times of these qubits.

Shankar, S.; Geerlings, K.; Edwards, E.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.

2011-03-01

404

Compact Binaries as Sources of Gravitational Radiation  

E-print Network

With current terrestrial gravitational wave detectors working at initial design sensitivities, and upgrades and space missions planned, it is likely that in the next five to ten years gravitational radiation will be detected directly from a variety of classes of objects. The most confidently expected of these classes is compact binaries, involving neutron stars or black holes. Detection of their coalescence, or their long-term orbits, has the potential to inform us about the evolutionary history of compact binaries and possibly even star formation over the past several billion years. We review what is currently known about compact binaries as sources of gravitational radiation, as well as the current uncertainties and what we expect to learn from future detections of gravitational waves from these systems.

M. Coleman Miller

2006-12-03

405

Compaction of batch for flat glass  

SciTech Connect

The quality of the batch for flat glass can be improved by granulating it, in particular, by compacting it in roller presses with a smooth surface, a method which makes it possible to compact glass batches with a wide range of chemical and grain compositions. It does not require the finished product to be dried. It is outstanding in the simplicity of the molding equipment and in its productivity, of considerable significance in multi-ton production of flat glass. The authors study here some properties of batches which must be taken into account when calculating and selecting compaction equipment. The experimental batch comprised aluminum borosilicate for glass fiber, M /SUB m/ = 0.31 with 10% B2O3; in a lead crystal batch, M /SUB m/ = 0.29 with 24% PbO.

Kalygin, V.G.; Chekov, O.S.; Kozlova, L.N.; Nazarov, V.I.; Pankova, N.A.

1985-11-01

406

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

407

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

408

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

E-print Network

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 dynamical gravity equations of motion. We assume that black hole spacetime contains an asymptotically flat spacelike hypersurface with compact interior and non-degenerate components of the event horizon.

Marek Rogatko

2013-07-31

409

Charged Schrodinger black holes  

E-print Network

We construct charged and rotating asymptotically Schrödinger black hole solutions of type IIB supergravity. We begin by obtaining a closed-form expression for the null Melvin twist of a broad class of type IIB backgrounds, ...

Adams, Allan

410

Charged Particle Flux Sensor  

NASA Technical Reports Server (NTRS)

Improved version of Faraday cup increases accuracy of measurements of flux density of charged particles incident along axis through collection aperture. Geometry of cone-and-sensing cup combination assures most particles are trapped.

Gregory, D. A.; Stocks, C. D.

1983-01-01

411

International aeronautical user charges  

E-print Network

Introduction: 1.1 BACKGROUND AND MOTIVATION Very few issues relating to the international air transportation industry are today as divisive as those pertaining to user charges imposed at international airports and enroute ...

Odoni, Amedeo R.

1985-01-01

412

Abstract adiabatic charge pumping  

E-print Network

This paper is devoted to the analysis of an abstract formula describing quantum adiabatic charge pumping in a general context. We consider closed systems characterized by a slowly varying time-dependent Hamiltonian depending on an external parameter $\\alpha$. The current operator, defined as the derivative of the Hamiltonian with respect to $\\alpha$, once integrated over some time interval, gives rise to a charge pumped through the system over that time span. We determine the first two leading terms in the adiabatic parameter of this pumped charge under the usual gap hypothesis. In particular, in case the Hamiltonian is time periodic and has discrete non-degenerate spectrum, the charge pumped over a period is given to leading order by the derivative with respect to $\\alpha$ of the corresponding dynamical and geometric phases.

A. Joye; V. Brosco; F. Hekking

2010-02-05

413

Primitive Virtual Negative Charge  

E-print Network

Physical fields, such as gravity and electromagnetic field, are interpreted as results from rearrangement of vacuum particles to get the equilibrium of net charge density and net mass density in 4-dimensional complex space. Then, both fields should interact to each other in that physical interaction is considered as a field-to-field interaction. Hence, Mass-Charge interaction is introduced with primitive-virtual negative charge defined for the mass. With the concept of Mass-Charge interaction electric equilibrium of the earth is discussed, especially about the electric field and magnetic field of the earth. For unsettled phenomena related with the earth's gravity, such as antigravity phenomenon, gravity anomalies during the solar eclipses, the connection between geomagnetic storms and earthquakes, etc., possible explanations are discussed.

Kiyoung Kim

2008-11-04

414

Primitive Virtual Negative Charge  

E-print Network

Physical fields, such as gravity and electromagnetic field, are interpreted as results from rearrangement of vacuum particles to get the equilibrium of net charge density and net mass density in 4-dimensional complex space. Then, both fields should interact to each other in that physical interaction is considered as a field-to-field interaction. Hence, Mass-Charge interaction is introduced with primitive-virtual negative charge defined for the mass. With the concept of Mass-Charge interaction electric equilibrium of the earth is discussed, especially about the electric field and magnetic field of the earth. For unsettled phenomena related with the earth's gravity, such as antigravity phenomenon, gravity anomalies during the solar eclipses, the connection between geomagnetic storms and earthquakes, etc., possible explanations are discussed.

Kim, Kiyoung

2008-01-01

415

Can Water Store Charge?  

PubMed Central

Previous work from this and other laboratories has demonstrated large pH gradients in water. Established by passing current between immersed electrodes, pH gradients between electrodes were found to disappear slowly, persisting for tens of minutes after the current had been turned off. We find here that these pH gradients reflect a genuine separation of charge: at times well after disconnection of the power supply, current could be drawn through a resistor placed between the charging electrodes or between pairs of electrodes positioned on either side of the midline between original electrodes. In some experiments, it was possible to recover the majority of charge that had been imparted to the water. It appears, then, that water has the capacity to store and release substantial amounts of charge. PMID:19053655

Ovchinnikova, Kate; Pollack, Gerald H.

2010-01-01

416

Explaining compact groups as change alignments  

NASA Technical Reports Server (NTRS)

The physical nature of the apparently densest groups of galaxies, known as compact groups is a topic of some recent controversy, despite the detailed observations of a well-defined catalog of 100 isolated compact groups compiled by Hickson (1982). Whereas many authors have espoused the view that compact groups are bound systems, typically as dense as they appear in projection on the sky (e.g., Williams & Rood 1987; Sulentic 1987; Hickson & Rood 1988), others see them as the result of chance configurations within larger systems, either in 1D (chance alignments: Mamon 1986; Walke & Mamon 1989), or in 3D (transient cores: Rose 1979). As outlined in the companion review to this contribution (Mamon, in these proceedings), the implication of Hickson's compact groups (HCGs) being dense bound systems is that they would then constitute the densest isolated systems of galaxies in the Universe and the privileged site for galaxy interactions. In a previous paper (Mamon 1986), the author reviewed the arguments given for the different theories of compact groups. Since then, a dozen papers have been published on the subject, including a thorough and perceptive review by White (1990), thus more than doubling the amount written on the subject. Here, the author first enumerates the arguments that he brought up in 1986 substantiating the chance alignment hypothesis, then he reviews the current status of the numerous recent arguments arguing against chance alignments and/or for the bound dense group hypothesis (both for the majority of HCGs but not all of them), and finally he reconsiders each one of these anti-chance alignment arguments and shows that, rather than being discredited, the chance alignment hypothesis remains a fully consistent explanation for the nature of compact groups.

Mamon, Gary A.

1990-01-01

417

Observational properties of compact groups of galaxies  

NASA Technical Reports Server (NTRS)

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

Hickson, Paul

1990-01-01

418

Electrically charged targets  

DOEpatents

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

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

1984-01-01

419

Particle-Charge Spectrometer  

NASA Technical Reports Server (NTRS)

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

Fuerstenau, Stephen; Wilson, Gregory R.

2008-01-01

420

Dwarf galaxies in Hickson Compact Groups  

E-print Network

We observed 5 Hickson Compact Groups with the ESO/MPI 2.2m telescope and WFI to investigate the dwarf galaxy content and distribution in these galaxy groups. Our deep imaging and careful selection of the candidate galaxies revealed a rich population of mainly passively evolving dwarf galaxies, which is spatially much more extended than the originally defined Hickson Compact groups. The composite luminosity function of the 5 groups shows a bimodal structure with a very steep rise in the low luminosity regime. The faint end slope is close to the predictions of CDM theory for the slope of the Dark Matter halo mass function.

Dominik Bomans; Elvira Krusch; Ralf-Juergen Dettmar; Volker Mueller; Chris Taylor

2006-08-07

421

Low Luminosity Activity in Hickson Compact Groups  

E-print Network

With the aim of studying the influence of environment on the nuclear activity of galaxies, we have selected a well defined sample of 65 Compact Groups of galaxies with concordant redshift in the Hickson Catalog. In this proceeding, we present the results of the classification of nuclear activity for 42 galaxies, based on newly obtained spectral observations. In this subsample, 71% of the galaxies turned out to have emission lines in their nuclei. 73% of these emission-line galaxies were found to have characteristics consistent with low luminosity AGN (LLAGN), which makes compact groups extremely rich in such objects.

M. A. Martinez; A. del Olmo; J. Perea; R. Coziol

2006-11-02

422

Compact Raman Spectrometers Would Detect Hydrogen  

NASA Technical Reports Server (NTRS)

Compact Raman spectrometers developed to measure concentrations of hydrogen as low as hundreds of parts per million in air, nitrogen, or other carrier gases. Advantages include speed, dynamic range, and ease of calibration. Design concept incorporates Raman-scattering apparatus into compact instrument of hydrogen leaking into stream of gas or into gas enclosed in small space. Should hydrogen-fueled cars and trucks come into widespread use, instruments used to detect leaks from vehicles and supply equipment, to help prevent explosions. Similar spectrometers developed to detect other gases emitting characteristic Raman spectra.

Helms, William R.; Adler-Golden, Steven

1993-01-01

423

Compact Radio Cores in Seyfert Galaxies  

E-print Network

We have observed a sample of 157 Seyfert galaxies with a 275 km baseline radio interferometer to search for compact, high brightness temperature radio emission from the active nucleus. We obtain the surprising result that compact radio cores are much more common in Seyfert 2 than in Seyfert 1 galaxies, which at first seems to be inconsistent with orientation unification schemes. We propose a model, involving optical depth effects in the narrow-line region, which can reconcile our result with the standard unified scheme. (Accepted for publication in ApJ 1994 Sep 10)

A. L. Roy; R. P. Norris; M. J. Kesteven; E. R. Troup; J. E. Reynolds

1994-04-30

424

Kepler Observations of Transiting Hot Compact Objects  

NASA Astrophysics Data System (ADS)

We present Kepler lightcurves of two A spectral class stars which show hot, compact transiting companions. Our analysis of 45 days of high duty cycle, ultra precise photometry show the companions have radii of 40% and 90% that of Jupiter based and effective temperatures greater than 10 000K based on the transit and eclipse lightcurve profiles. These objects have properties similar to white dwarfs as they are compact and hot. The lightcurves also suggest the companions have masses less than 10% of the Sun. Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA, Science Mission Directorate.

Rowe, Jason; Borucki, W. J.; Koch, D.; Kepler Team

2010-01-01

425

Compact, Robust Chips Integrate Optical Functions  

NASA Technical Reports Server (NTRS)

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

2010-01-01

426

Remote vacuum compaction of compressible hazardous waste  

DOEpatents

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

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

1998-10-06

427

Compact Focal Plane Assembly for Planetary Science  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

428

Massive Compact Stars as Quark Stars  

E-print Network

High massive compact stars have been reported recently in the literature, providing strong constraints on the properties of the ultradense matter beyond the saturation nuclear density. In view of these results, the calculations of quark star or hybrid star equilibrium structure must be compatible with the provided observational data. But, since the used equations of state describing quark matter are in general too soft, in comparison with the equation of states used to describe the hadronic or nuclear matter, the calculated quark star models presented in the literature are in general not suitable to explain the stability of high compact massive objects.

Hilario Rodrigues; Sergio B. Duarte; Jos Carlos T. de Oliveira

2014-07-17

429

Stellar Populations of Compact Group Galaxies  

NASA Astrophysics Data System (ADS)

The study of the stellar populations of the elliptical galaxies in compact groups could give us important information on the merging history of the elliptical galaxies in the groups and could elucidate some of the questions regarding group evolution. We have initiated a program to study the stellar populations of the elliptical galaxies in compact groups. In the following, we describe our results for a sample of 12 galaxies. The kinematical properties of the same sample were previously studied by Mendes de Oliveira et al. (1993).

Coelho, Paula; Mendes de Oliveira, Cláudia; González, Jesus J.; Visvanathan, N.; Barbuy, B.

430

Momentum compaction and phase slip factor  

SciTech Connect

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

Ng, K.Y.; /Fermilab

2010-10-01

431

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

432

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

SciTech Connect

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

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

2012-10-01

433

A Novel Spacecraft Charge Monitor for LEO  

NASA Technical Reports Server (NTRS)

Five years ago we introduced a new method for measuring spacecraft chassis floating potential relative to the space plasma (absolute spacecraft potential) in low Earth orbit. The method, based on a straightforward interpretation of photoelectron spectra, shows promise for numerous applications, but has not yet been tried. In the interest of testing the method, and ultimately supplying another tool for measuring absolute spacecraft charge, we are producing a flight prototype Spacecraft Charge Monitor (SCM) with support from NASA's Small Business Innovation Research (SBIR) program. Although insight into the technique came from data collected in space over two decades ago, very little data are available. The data indicate that it may be possible to determine spacecraft floating potential to within 0.1 volt each with the SCM second under certain conditions. It is debatable that spacecraft floating potential has ever been measured with such accuracy. The compact, easily deployed SCM also offers the advantage of long-term stability in calibration. Accurate floating potential determinations from the SCM could be used to correct biases in space plasma measurements and evaluate charge mitigation and/or sensing devices. Although this paper focuses on the device's use in low Earth orbit (LEO), the device may also be able to measure spacecraft charge at higher altitudes, in the solar wind, and in orbits around other planets. The flight prototype SCM we are producing for delivery to NASA in the third quarter of 2004 will measure floating potential from 0 to -150 volts with 0.1 volt precision, weigh approximately 600-700 grams, consume approximately 2 watts, and will measure approximately 8 x 10 x 17 cm.

Goembel, Luke

2004-01-01

434

A compact time-of-flight mass spectrometer for ion source characterization  

NASA Astrophysics Data System (ADS)

A compact time-of-flight mass spectrometer with overall dimension of about 413 × 250 × 414 mm based on orthogonal injection and angle reflection has been developed for ion source characterization. Configuration and principle of the time-of-flight mass spectrometer are introduced in this paper. The mass resolution is optimized to be about 1690 (FWHM), and the ion energy detection range is tested to be between about 3 and 163 eV with the help of electron impact ion source. High mass resolution and compact configuration make this spectrometer useful to provide a valuable diagnostic for ion spectra fundamental research and study the mass to charge composition of plasma with wide range of parameters.

Chen, L.; Wan, X.; Jin, D. Z.; Tan, X. H.; Huang, Z. X.; Tan, G. B.

2015-03-01

435

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

PubMed

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

Khomane, Kailas S; Bansal, Arvind K

2014-09-10

436

Charge Exchange Processes for Highly Charged Ion -Atom, Molecule  

E-print Network

for Fusion Science H.A.Sakaue #12;Charge Exchange Processes Highly charged ions (HCI's) exist as an impurity ion in high temperature plasma. Charge exchange cross sections of HCI's are very large (~10-14cm2) Charge Exchange Processes of HCI's are very important for understanding the edge plasma behavior

Princeton Plasma Physics Laboratory

437

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

438

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

439

Compact High Repetition Rate Pseudospark Pulse Generator  

Microsoft Academic Search

A pseudospark-based high repetition rate pulse generator, together with a resonant charging power supply is presented. The pulse generator was developed for research applications that include transient plasma ignition. The design incorporates a lumped element Blumlein pulse-forming network that is switched by a commercial pseudospark into an output pulse transformer with a METGLAS core. The Blumlein is charged up to

Fei Wang; András Kuthi; Martin A. Gundersen

2005-01-01

440

AGN populations in compact groups of galaxies  

NASA Astrophysics Data System (ADS)

Compact groups of galaxies (CGG) have revealed some interesting problems from their origin and lifetime to the evolution of their members in such dense configurations. Some authors suppose that CGG probably are the best location for AGNs in the local Universe. According to our preliminary data about 7-10% of member galaxies in Shahbazian compact groups (SHCGs) are emission-line galaxies including the broad-line AGN and the narrow emission-line galaxies. Shahbazian 355/4 is a classical Seyfert 1 galaxy at the same redshift as host group. Moreover Shahbazian 278/4 is also a broad-line AGN in an early-type galaxy. This is the first emission-line object in SHCGs. Meanwhile there is no Seyfert 1 galaxy among the spectroscopically investigated galaxies in the South compact groups, although more than 70% of the member galaxies in these groups probably have an active nucleus. The UZC- compact groups have an excess of Seyfert 2s (but not Seyfert 1s!). Further observational studies are necessary to understand such and many other questions related to the puzzle of CGG.

Amirkhanian, A. S.; del Olmo, A.; Egikian, A. G.; Tiersch, H.; Stoll, D.; Perea, J.

2014-07-01

441

Infrared emission from compact groups of galaxies  

Microsoft Academic Search

A search of the IRAS Point Source Catalog, Version 2 has revealed infrared sources within 1 arcmin of the optical centers of 54 galaxies in Hickson's catalog of compact groups of galaxies. The 60-micron luminosity function for these galaxies has the same shape as the luminosity function of the IRAS bright galaxy sample. The space density of IRAS galaxies in

Paul Hickson; T. K. Menon; G. G. C. Palumbo; M. Persic

1989-01-01

442

Systematic properties of compact groups of galaxies  

Microsoft Academic Search

An analysis of estimated galaxy magnitudes, morphology, and group angular size for the case of 100 compact groups of galaxies indicates that (1) there is no correlation between group density and magnitude difference between first- and second-ranked galaxies, (2) there is no preferred morphological type for the first-ranked galaxies, many of which are spiral, (3) the groups contain fewer spirals

P. Hickson

1982-01-01

443

Evolution of galaxies in compact groups  

Microsoft Academic Search

This thesis presents new observations of the complete sample of galaxies in Hickson Compact Groups and combines these observations with various previous works to attempt to answer some fundamental questions about the nature, history, and dynamical state of these groups. The new data consist of radial velocities and surface photometry of individual galaxies and velocity dispersions and complete membership information

Claudia Mendesdeoliveira

1992-01-01

444

Dynamics of Hickson Compact Groups of Galaxies  

Microsoft Academic Search

It is shown that compact groups of galaxies (HCGs, ShCGS) are stable formations, in which principal member galaxies together with faint galaxies in their environment rotate in elongated orbits around the common gravitational center of the group. Hence, the multitude of puzzles related to CGs: the very existence of CGs, absence of strong radio sources, absence of strong signs of

H. M. Tovmassian; V. H. Chavushyan; O. Martinez; O. Yam; H. Tiersch

2002-01-01

445

AGN Population in Compact Groups Galaxies  

Microsoft Academic Search

The aim of this study is to establish the frequency of nuclear activity (AGN and star formation) in galaxies belonging to Compact Groups (CGs) and to characterize the type of activity as a function of the properties of both host galaxies and their parent group. To do so, we have selected a statistically complete sample of 65 groups from the

M. A. Martínez; A. Del Olmo; R. Coziol; J. Perea

2008-01-01

446

Photometry of galaxies in compact groups  

SciTech Connect

The results are given of photographic photometry of galaxies in compact groups. The luminosity function of the galaxies in the investigated groups is similar to the luminosity function of field galaxies, open groups, and clusters. Of 54 groups, signs of merging of galaxies are observed in only one group.

Tikhonov, N.A.

1988-03-01

447

IUE Spectra for Selected Compact Group Galaxies  

Microsoft Academic Search

Hickson Compact Groups (HCGs) represent an environment where interactions, tidally triggered activity, and galaxy mergers are expected to be at their highest rate of occurrence. Studies of a number of interacting pairs, both in the infrared and ultraviolet, suggest that interactions can trigger an inflow of gas into the galactic nucleus resulting in either starburst or AGN activity. Evidence for

M. Rodrigue; P. Rogers; T. Colegrove; J. Thompson; A. Schultz; J. Sulentic; K. Borne; L. Spight

1994-01-01

448

Star Formation in Compact Groups of Galaxies  

Microsoft Academic Search

We propose to obtain NUV and FUV images of a sample of nearby compact groups and their neighborhoods with the GALEX imaging facility. The main goals for this proposal are: (1) explore whether a relationship between the total star formation rates and the evolutionary state of the group holds, and also to explore the existence of interaction induced nuclear starburst

Jorge Paramo

2004-01-01

449

Are compact groups hostile towards faint galaxies?  

E-print Network

The goal of this work is to understand whether the extreme environment of compact groups can affect the distribution and abundance of faint galaxies around them. We performed an analysis of the faint galaxy population in the vicinity of compact groups and normal groups. We built a light-cone mock galaxy catalogue constructed from the Millennium Run Simulation II plus a semi-analytical model of galaxy formation. We identified a sample of compact groups in the mock catalogue as well as a control sample of normal galaxy groups and computed the projected number density profiles of faint galaxies around the first- and the second-ranked galaxies. We also compared the profiles obtained from the semi-analytical galaxies in compact groups with those obtained from observational data. In addition, we investigated whether the ranking or the luminosity of a galaxy is the most important parameter in the determination of the centre around which the clustering of faint galaxies occurs. There is no particular influence of the...

Zandivarez, Ariel; de Oliveira, Claudia Mendes; Gubolin, Henrique

2014-01-01

450

Trust and compactness in social network groups.  

PubMed

Understanding the dynamics behind group formation and evolution in social networks is considered an instrumental milestone to better describe how individuals gather and form communities, how they enjoy and share the platform contents, how they are driven by their preferences/tastes, and how their behaviors are influenced by peers. In this context, the notion of compactness of a social group is particularly relevant. While the literature usually refers to compactness as a measure to merely determine how much members of a group are similar among each other, we argue that the mutual trustworthiness between the members should be considered as an important factor in defining such a term. In fact, trust has profound effects on the dynamics of group formation and their evolution: individuals are more likely to join with and stay in a group if they can trust other group members. In this paper, we propose a quantitative measure of group compactness that takes into account both the similarity and the trustworthiness among users, and we present an algorithm to optimize such a measure. We provide empirical results, obtained from the real social networks EPINIONS and CIAO, that compare our notion of compactness versus the traditional notion of user similarity, clearly proving the advantages of our approach. PMID:25099965

De Meo, Pasquale; Ferrara, Emilio; Rosaci, Domenico; Sarné, Giuseppe M L

2015-02-01

451

COMPACT COILED DENUDER FOR ATMOSPHERIC SAMPLING  

EPA Science Inventory

A compact coiled denuder has been designed and its performance evaluated both theoretically and experimentally. he design is based on special features of laminar flow in a curved tube, which significantly enhance the mass transfer Sherwood number governing gas collection at the w...

452

Compact imaging spectrometer utilizing immersed gratings  

DOEpatents

A compact imaging spectrometer comprising an entrance slit for directing light, lens means for receiving the light, refracting the light, and focusing the light; an immersed diffraction grating that receives the light from the lens means and defracts the light, the immersed diffraction grating directing the detracted light back to the lens means; and a detector that receives the light from the lens means.

Lerner, Scott A.

2005-12-20

453

Key Features: -Handheld portability, compact rugged design  

E-print Network

Key Features: - Handheld portability, compact rugged design - Single handed operation and one - Internal playback speaker - USB 2.0 connectivity to PC, for drag and drop file exchange - Power from two AA-and-drop via the USB 2.0 connectivity. #12;Specifications: www.dm-pro.eu/pmd620 Digital audio system System

454

ORBITAL PHASE IN INSPIRALLING COMPACT BINARIES  

Microsoft Academic Search

We derive the rate of change of the mean motion up to the second post-Newtonian order for inspiralling compact binaries with spin, mass quadrupole and magnetic dipole moments on eccentric orbits. We give this result in terms of orbital elements. We also present the related orbital phase for circular orbits. Observations by Earth-based gravitational wave observatories are under way aiming

AS VAS ´; BAL ´ AZS MIK

455

Compact, Lightweight Servo-Controllable Brakes  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

456

Ringing the eigenmodes from compact manifolds  

E-print Network

We present a method for finding the eigenmodes of the Laplace operator acting on any compact manifold. The procedure can be used to simulate cosmic microwave background fluctuations in multi-connected cosmological models. Other applications include studies of chaotic mixing and quantum chaos.

Neil J. Cornish; Neil G. Turok

1998-02-26

457

Why Python? 1) readable, compact, simple syntax  

E-print Network

Starting with Python #12;Why Python? 1) readable, compact, simple syntax 2) documented 3) memory -> your_file.py your_file.pyc Compiled to .pyc file 10/19/2010 3 #12;Basic syntax · No semicolon; · C-based syntax, less brackets · Control flow via indentation if danger : if smaller_than_you(): fight() else: run

Spang, Rainer

458

Compact Linear Fresnel Reflector solar thermal powerplants  

Microsoft Academic Search

This paper evaluates Compact Linear Fresnel Reflector (CLFR) concepts suitable for large scale solar thermal electricity generation plants. In the CLFR, it is assumed that there will be many parallel linear receivers elevated on tower structures that are close enough for individual mirror rows to have the option of directing reflected solar radiation to two alternative linear receivers on separate

David R. Mills; Graham L. Morrison

2000-01-01

459

Compaction and Wear Concerns on Sports Fields.  

ERIC Educational Resources Information Center

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

Gillan, John

1999-01-01

460

FAULT PREDICTIVE CONTROL OF COMPACT DISK PLAYERS  

E-print Network

FAULT PREDICTIVE CONTROL OF COMPACT DISK PLAYERS Peter Fogh Odgaard Mladen Victor Wickerhauser playing certain discs with surface faults like scratches and fingerprints. The problem is to be found in an other publications of the first author. This scheme is based on an assumption that the surface faults do

Wickerhauser, M. Victor

461

Avoiding Exponential Explosion: Generating Compact Verification Conditions  

E-print Network

algorithm that generates compact VCs whose size is worst-case quadratic in the size of the source fragment at statically detecting certain kinds of errors, for example, applying a function to an in- correct number-specified properties such as method preconditions, method postconditions, and object invariants. Performing this kind

Flanagan, Cormac

462

Geometric Models and Compactness of Composition Operators  

Microsoft Academic Search

This work explores some of the terrain between functional equations, geometric function theory, and operator theory. It is inspired by the fact that whenever a composition operator or one of its powers is compact on the Hardy space H2, then its eigenfunctions cannot grow too quickly on the unit disc. The goal is to show that under certain natural (and

Joel H. Shapiro; Wayne Smith; David A. Stegenga

1995-01-01

463

Simplicial volume of non-compact manifolds  

E-print Network

Simplicial volume of non-compact manifolds Clara L¨oh April 2008 Abstract. Degree theorems are statements bounding the mapping degree in terms of the volumes of the domain and target manifolds. A possible strategy to ob- tain such degree theorems is to compare the Riemannian volume with a suitable topological

Löh, Clara

464

Thermal optimization of compact solar water heaters  

Microsoft Academic Search

In an effort to reduce the effects of night-cooling on the efficiency of compact solar water heaters, a design is proposed which will optimize the storage volume to collector area ratio. An analytic model is presented comparing heater design parameters with expected environmental conditions. Under the proposed optimization scheme, early morning storage temperatures in excess of 40 C are theoretically

A. Bar-Cohen

1978-01-01

465

Development of a compact cold atom clock  

Microsoft Academic Search

HORACE is a compact cold atom clock where the atoms are cooled inside the microwave interrogation cavity. About 108 atoms can be cooled at kinetic temperatures as low as 2.5 ?K. We report, for the first time, a Ramsey pattern observed with a 14 Hz linewidth and fringe contrast better than 80%. Since this clock is designed for space applications,

S. Tremine; S. Guerandel; D. Holleville; A. Clairon; N. Dimarcq

2004-01-01

466

Compact microwave cavity for hydrogen atomic clock  

NASA Technical Reports Server (NTRS)

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 of several methods for discriminating the oscillating modes. Experimental data and respective calculated values are also presented.

Zhang, Dejun; Zhang, Yan; Fu, Yigen; Zhang, Yanjun

1992-01-01

467

Compact Hydraulic Excavator and Support Unit  

NASA Technical Reports Server (NTRS)

Continuous-coal-mining machine maneuverable. Hydraulic coal excavator combined with chock, or roof-support structure, in self-contained unit that moves itself forward as it removes coal from seam. Unlike previous such units, new machine compact enough to be easily maneuverable; even makes small-radius right-angle turns.

Lewis, E. V.

1985-01-01

468

Compact range for variable-zone measurements  

DOEpatents

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

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

1987-02-27

469

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

470

7, 1158711619, 2007 A compact and stable  

E-print Network

(IPCC, 2007) and currently 20% of the enhanced greenhouse effect is due to methane (IPCC, 2007 a Creative Commons License. Atmospheric Chemistry and Physics Discussions A compact and stable eddy Discussion EGU 1 Introduction Methane is considered to be the third most important greenhouse gas globally

Boyer, Edmond

471

Astrophysics of Accretion onto Compact Objects  

Microsoft Academic Search

The most energetic phenomena in the universe are systems powered by gravity through accretion. For compact stars such as white dwarfs, neutron stars, and especially black holes, the energy released per unit mass accreted can significantly exceed that released by nuclear reactions. Over the last half century a growing body of observations has revealed a plethora of environments in which

John Hawley

2008-01-01

472

Dynamics of Galaxies in Compact Groups II.  

NASA Astrophysics Data System (ADS)

We show partial results of a program based on Fabry-Perot H? velocity field data of compact groups taken at the ESO and the CFH 3.6m telescopes in order to analyze the kinematics of compact group galaxies. This project has three main goals: 1. determine the evolutionary stages of the groups; 2. search for tidal dwarf galaxies and 3. determine the Tully-Fisher relation for the group galaxies. We classify the compact groups studied so far into the following subclasses : (1) merging groups, (2) strongly interacting, (3) mildly interacting, (4) kinematically undisturbed and (5) false groups/single galaxy (details are given in the companion paper Mendes de Oliveira and Amram, 2000). We present examples of velocity fields of galaxies in compact groups that are in different evolutionary stages as classified from the kinematic disturbances. Spiral-only groups have often been considered chance alignments or groups in the very early stages of dynamical evolution. However, we find that the kinematics of the member galaxies for spiral-only groups in classes (1), (2) and (3) above display peculiarities which suggest that the galaxies know of the presence of their neighbors.

Amram, P.; Mendes de Oliveira, C.

473

Unified beaming models and compact radio sources  

NASA Astrophysics Data System (ADS)

The basics of relativistic beaming from compact radio sources are reviewed, and unified models to account for this beaming are discussed. The Scheuer-Redhead model, which proved to be incorrect, is reviewed, showing where it went wrong. The Orr-Browne and the Blandford-Rees models are compared and discussed.

Peacock, J. A.

474

Compact Ultradense Objects in the Solar System  

E-print Network

We describe properties and gravitational interactions of meteor-mass and greater compact ultra dense objects with nuclear density or greater (CUDO s). We discuss possible enclosure of CUDO s in comets, stability of these objects on impact with the Earth and Sun and show that the hypothesis of a CUDO core helps resolve issues challenging the understanding of a few selected cometary impacts.

J. Rafelski; Ch. Dietl; L. Labun

2013-03-19

475

Sintered Diamond Compacts with a Cobalt Binder  

Microsoft Academic Search

Diamond powder can be successfully cemented with cobalt. At 62 kilobars the sintering occurs over the temperature range from 1570 degrees to 1610 degrees C. The maximum microhardness of the compact (> 3000 kilograms per square millimeter on the Knoop scale) is obtained with a mixture of 20 percent cobalt (by volume) and a diamond particle size of 1 to

Howard Katzman; W. F. Libby

1971-01-01

476

Compact antenna structures for mobile handsets  

Microsoft Academic Search

In this paper, novel compact antenna structures for mobile handsets are studied. The antennas are based on non-resonant coupling elements, which are used to optimally couple to the characteristic wavemodes of the chassis. The resonances for the antenna structures are created with matching circuits. Two different antenna models are designed based on the novel antenna structure. From each model, single-band

Juha Villanen; Jani Ollikainen; Outi Kivekäs; Pertti Vainikainen

2003-01-01

477

Hi Image Synthesis of Southern Compact Groups  

NASA Astrophysics Data System (ADS)

Four southern compact groups, the Hickson Compact Groups HCG 22 and HCG 26 (Hickson 1982), and the groups AM 1238 - 396 and ESO 410-G(024 - 026) have been imaged in Hi, along with 12 cm continuum using the Australia Telescope Compact Array (ATCA). The initial findings for the latter two groups are presented here. While ESO 410-G is not in fact a physical group, due to the discordant redshifts amongst the members, it is however presented here. Overall for all the groups we find no other sources of Hi in the field that might indicate that these are part of a larger loose group structure. This is not always the case, as with HCG 23 (Williams 1995) and HCG 95 (Hutchmeier 1999), both of whom find additional Hi sources within the primary beam accordant with the compact group's velocity. The Hi is also clearly associated with each of the individual member galaxies in all cases, except for HCG 26, which envelopes the whole group as was also shown by Williams and van Gorkom (Williams 1995).

Babic, B.; Price, R. M.; Jones, K.