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1

Clumpy cold dark matter  

NASA Technical Reports Server (NTRS)

A study is conducted of cold dark matter (CDM) models in which clumpiness will inhere, using cosmic strings and textures suited to galaxy formation. CDM clumps of 10 million solar mass/cu pc density are generated at about z(eq) redshift, with a sizable fraction surviving. Observable implications encompass dark matter cores in globular clusters and in galactic nuclei. Results from terrestrial dark matter detection experiments may be affected by clumpiness in the Galactic halo.

Silk, Joseph; Stebbins, Albert

1993-01-01

2

Clumpy Cold Dark Matter and Biological Extinctions  

E-print Network

Cosmological models with cosmic string and texture seeded universes predict a present abundance of very dense clumps of Cold Dark Matter particles. Their crossing through the solar system would induce a non-negligible amount of radiation damage to all living tissue; the severity of such an episode is assessed. The estimated frequency of these crossings agrees with the apparent periodicity of the paleontological record of biological extinctions. (Phys. Lett. B, in press)

J. I. Collar

1995-12-10

3

A Submillimeter Galaxy Illuminating its Circumgalactic Medium: Ly? Scattering in a Cold, Clumpy Outflow  

NASA Astrophysics Data System (ADS)

We report the detection at 850 ?m of the central source in SSA22-LAB1, the archetypal "Lyman-? Blob" (LAB), a 100 kpc scale radio-quiet emission-line nebula at z = 3.1. The flux density of the source, S 850 = 4.6 ± 1.1 mJy, implies the presence of a galaxy or group of galaxies with a total luminosity of L IR ? 1012 L ?. The position of an active source at the center of a ~50 kpc radius ring of linearly polarized Ly? emission detected by Hayes et al. suggests that the central source is leaking Ly? photons preferentially in the plane of the sky, which undergo scattering in H I clouds at a large galactocentric radius. The Ly? morphology around the submillimeter detection is reminiscent of a biconical outflow, and the average Ly? line profiles of the two "lobes" are dominated by a red peak, which is expected for a resonant line emerging from a medium with a bulk velocity gradient that is outflowing relative to the line center. Taken together, these observations provide compelling evidence that the central active galaxy (or galaxies) is responsible for a large fraction of the extended Ly? emission and morphology. Less clear is the history of the cold gas in the circumgalactic medium being traced by Ly?: is it mainly pristine material accreting into the halo that has not yet been processed through an interstellar medium (ISM), now being blown back as it encounters an outflow, or does it mainly comprise gas that has been swept-up within the ISM and expelled from the galaxy?

Geach, J. E.; Bower, R. G.; Alexander, D. M.; Blain, A. W.; Bremer, M. N.; Chapin, E. L.; Chapman, S. C.; Clements, D. L.; Coppin, K. E. K.; Dunlop, J. S.; Farrah, D.; Jenness, T.; Koprowski, M. P.; Micha?owski, M. J.; Robson, E. I.; Scott, D.; Smith, D. J. B.; Spaans, M.; Swinbank, A. M.; van der Werf, P.

2014-09-01

4

Radiative Transfer in Clumpy and Fractal Media  

E-print Network

A Monte Carlo model of radiative transfer in multi-phase dusty media is applied to the situation of stars and clumpy dust in a sphere or a disk. The distribution of escaping and absorbed photons are shown for various filling factors and densities. Analytical methods of approximating the escaping fraction of radiation, based on the Mega-Grains approach, are discussed. Comparison with the Monte Carlo results shows that the escape probability formulae provide a reasonable approximation of the escaping/absorbed fractions, for a wide range of parameters characterizing a clumpy dusty medium. A possibly more realistic model of the interstellar medium is one in which clouds have a self-similar hierarchical structure of denser and denser clumps within clumps, resulting in a fractal distribution of gas and dust. Monte Carlo simulations of radiative transfer in such multi-phase fractal media are compared with the two-phase clumpy case.

Frank Varosi; Eli Dwek

1999-05-21

5

Damped Lyman-Alpha and Lyman Limit Absorbers in the Cold Dark Matter Model  

Microsoft Academic Search

We study the formation of damped Ly alpha and Lyman-limit absorbers in a hierarchical clustering scenario using a gasdynamical simulation of an Omega = 1 cold dark matter universe. In the simulation, these high column density systems are associated with forming galaxies. Damped Ly alpha absorption, NH I >~ 1020.2 cm-2, arises along lines of sight that pass near the

Neal Katz; David H. Weinberg; Lars Hernquist; Jordi Miralda-Escude

1996-01-01

6

The COS Cold Absorber Puzzle: Understanding the Metallicity and Phase of the Circumgalactic Medium  

NASA Astrophysics Data System (ADS)

Grasping the way gas gets in and out of galaxies is fundamental to our understanding of galaxy formation and evolution, and COS observations are slowly providing a better picture of these gas flows. Recent COS observations of the circumgalactic medium {CGM} have revealed two puzzles: the bimodal metallicity distribution of Lyman Limit Systems {LLSs} proximate to galaxies {Lehner et al. 2013} and the low volume density for cold absorbers in the CGM {Werk et al. 2014}. We propose to address both of these issues through the execution and analysis of grid-based cosmological hydrodynamics simulations of unprecedented resolution. By modeling galaxies at very high resolution using a physically-motivated, momentum-based feedback method, we will perform the first grid-based studies of the CGM at this scale, allowing us to identify analogs to the observed cold absorber population responsible for these puzzles. We will trace the simulated cold absorbers through time to understand their origins, producing a full picture of how they acquire and expel their gas.

Hummels, Cameron

2014-10-01

7

The properties of the clumpy torus and BLR in the polar-scattered Seyfert 1 galaxy ESO 323-G77 through X-ray absorption variability  

NASA Astrophysics Data System (ADS)

We report results from multi-epoch (2006-2013) X-ray observations of the polar-scattered Seyfert 1 galaxy ESO 323-G77. The source exhibits remarkable spectral variability from months to years timescales. The observed spectral variability is entirely due to variations of the column density of a neutral absorber towards the intrinsic nuclear continuum. The column density is generally Compton-thin ranging from a few times 1022 cm-2 to a few times 1023 cm-2. However, one observation reveals a Compton-thick state with column density of the order of 1.5 × 1024 cm-2. The observed variability offers a rare opportunity to study the properties of the X-ray absorber(s) in an active galaxy. We identify variable X-ray absorption from two different components, namely (i) a clumpy torus whose individual clumps have a density of ?1.7 × 108 cm-3 and an average column density of ˜4 × 1022 cm-2, and (ii) the broad-line region (BLR), comprising individual clouds with density of 0.1-8 × 109 cm-3 and column density of 1023-1024 cm-2. The derived properties of the clumpy torus can also be used to estimate the torus half-opening angle, which is of the order of 47°. We also confirm the previously reported detection of two highly ionized warm absorbers with outflow velocities of 1000-4000 km s-1. The observed outflow velocities are consistent with the Keplerian/escape velocity at the BLR. Hence, the warm absorbers may be tentatively identified with the warm/hot intercloud medium which ensures that the BLR clouds are in pressure equilibrium with their surroundings. The BLR line-emitting clouds may well be the cold, dense clumps of this outflow, whose warm/hot phase is likely more homogeneous, as suggested by the lack of strong variability of the warm absorber(s) properties during our monitoring.

Miniutti, G.; Sanfrutos, M.; Beuchert, T.; Agís-González, B.; Longinotti, A. L.; Piconcelli, E.; Krongold, Y.; Guainazzi, M.; Bianchi, S.; Matt, G.; Jiménez-Bailón, E.

2014-01-01

8

Distribution of Damped Ly? Absorbers in a ? Cold Dark Matter Universe  

NASA Astrophysics Data System (ADS)

We present the results of a numerical study of a galactic wind model and its implications on the properties of damped Ly? absorbers (DLAs) using cosmological hydrodynamic simulations. We vary both the wind strength and the internal parameters of the wind model in a series of smoothed particle hydrodynamics (SPH) simulations that include radiative cooling and heating by a UV background, star formation, and feedback from supernovae and galactic winds. To test our simulations, we examine the DLA ``rate of incidence'' as a function of halo mass, galaxy apparent magnitude, and impact parameter. We find that the statistical distribution of DLAs does not depend on the exact values of internal numerical parameters that control the decoupling of hydrodynamic forces when the gas is ejected from star-forming regions, although the exact spatial distribution of neutral gas may vary for individual halos. The DLA rate of incidence in our simulations at z=3 is dominated (80%-90%) by the faint galaxies with apparent magnitude RAB<25.5. However, interestingly in a ``strong wind'' run, the differential distribution of DLA sight lines is peaked at Mhalo=1012 h-1 Msolar (RAB~=27), and the mean DLA halo mass is DLA>=1012.4 h-1 Msolar (RAB~=26). The DLAs in our simulations are more compact than the present-day disk galaxies, and the impact parameter distribution is very narrow unless we limit the search for the host galaxy to only bright Lyman break galaxies (LBGs). We discuss conflicts between current simulations and observations, and potential problems with hydrodynamic simulations based on the cold dark matter model.

Nagamine, Kentaro; Wolfe, Arthur M.; Hernquist, Lars; Springel, Volker

2007-05-01

9

New Measures of Clumpiness for Incidence Data Eric T. Bradlow  

E-print Network

media consumption to name just a few; but a well-defined and careful measurement of clumpiness has: Clumpiness, test statistics, media consumption #12;1 Introduction In recent years, data clumpiness has been consumption, which supports the lore of "bingeability" of online content believed to exist today. Keywords

Small, Dylan

10

Cold tests of HOM absorber material for the ARIEL eLINAC at TRIUMF  

NASA Astrophysics Data System (ADS)

At TRIUMF development of a 50 MeV electron accelerator is well under way. Five 1.3 GHz, superconducting 9-cell cavities will accelerate 10 mA electrons to a production target to produce rare isotopes. Each cavity will provide 10 MV accelerating voltage. Plans to upgrade the accelerator in the future to a small ring with ERL capabilities requires that the shunt impedance of the dipole higher order modes to be less than 10M? . The design of the accelerator incorporates beam line absorbers to reduce the shunt impedance of potentially dangerous dipole modes.

Kolb, P.; Laxdal, R. E.; Zvyagintsev, V.; Chao, Y. C.; Amini, B.

2014-01-01

11

Clumpy Outflows from Supercritical Accretion Flow  

NASA Astrophysics Data System (ADS)

A significant amount of matter in supercritical (or super-Eddington) accretion flow is blown away by radiation force, thus forming outflows; however, the properties of such radiation-driven outflows have been poorly understood. We have performed global two-dimensional radiaion-magnetohydrodynamic simulations of supercritical accretion flow onto a black hole with 10 or 108 M? in a large simulation box of 514 rS × 514 rS (with rS being the Schwarzschild radius). We confirm that uncollimated outflows with velocities of 10 percent of the speed of light emerge from the innermost part of the accretion flow at a wide angle of 10° -50° from the disk rotation axis. Importantly, the outflows exhibit clumpy structures above heights of ˜ 250 rS. The typical size of the clumps is ˜ 10 rS , which corresponds to one optical depth, and their shapes are slightly elongated along the outflow direction. Since clumps start to form in the layer above which the (upward) radiation is superior in force to the (downward) gravity, the Rayleigh-Taylor instability seems to be a primary cause. In addition, a radiation-hydrodynamic instability, which arises when radiation funnels through a radiation-pressure-supported atmosphere, may also help to form clumps of one optical depth. A magnetic photon bubble instability does not seem to be essential, since a similar clumpy outflow structure is obtained in nonmagnetic radiation-hydrodynamic simulations. Since the spatial covering factor of the clumps is estimated to be ˜ 0.3, and since they are marginally optically thick, they will explain at least some of the rapid light variations of active galactic nuclei. We further discuss a possibility of producing broad-line region clouds by the clumpy outflow.

Takeuchi, Shun; Ohsuga, Ken; Mineshige, Shin

2013-08-01

12

The Search for Diversities in Clumpy Galaxies  

NASA Astrophysics Data System (ADS)

We present an investigation utilizing the deepest ultraviolet data in the Hubble Ultra Deep Field (HUDF) taken with Wide Field Camera 3 UVIS detector (90 orbits taken with F225W, F275W and F336W filters) during 3 epochs. Preliminary studies using selected galaxies in epochs 1 + 2 (F275W) show disks with clumps indicative of star forming regions. Here we present the analysis of the new epoch 3 data with the F275W band comprised of about 230 galaxies, many of which have a variety of clumps - from single clumps to galaxies littered with clumps. We perform a morphological study of ultraviolet-detected sources at redshifts 0.5 < z < 1.5 in the optical rest-frame. We used a morphological classification scheme similar to that employed by the Hubble CANDELS survey team and find that most of the clumpy objects are disks, followed by irregulars. We calculated both clump sizes and luminosities in the rest-frame UV. We find that the majority of these UV bright clumpy galaxies are classified as Scd and starburst spectral types and have clump sizes between 0.7 to 1.9 kpc.

Soto, Emmaris; De Mello, D. F.; Bond, N. A.; Rafelski, M.; Gardner, J. P.; Teplitz, H. I.; UV UDF Team

2014-01-01

13

Clumpy shocks and the clump mass function  

E-print Network

In this paper, we examine whether clumpy, colliding, flows could be responsible for the clump mass functions that have been observed in several regions of embedded star formation, which have been shown to be described by a Salpeter type slope. The flows presented here, which comprise a population of initially identical clumps and the calculations are performed with and without the inclusion of self-gravity. When the shock region is at its densest, we find that the clump mass spectrum is always well modelled by a Salpeter type slope. This is true regardless of whether the self-gravity is included in the simulations or not. In the non-self-gravitating simulations, this slope is retained at lower Mach numbers (Mach 5 and 10) as the simulations progress past the densest phase. In the simulations which include self-gravity, we find that low Mach number runs yield a flatter mass function after the densest phase. This is simply a result of increased coagulation due to gravitational collapse of the flows. In the high Mach number runs (Mach 20) the Salpeter slope is always lost. The self gravitating calculations also show that the sub-group of gravitationally bound clumps in which star formation occurs, always contain the most massive clumps in the population. The mass function of these bound star forming clumps is not at all similar to the Salpeter type mass function observed for stars in the field. We conclude that the clump mass function may not only have nothing to do with gravity, but also nothing to do with the star formation process and the resulting mass distribution of stars. This raises doubt over the claims that the clump mass function is the origin of the stellar IMF, for regions such as rho Oph, Serpens and the Orion B cloud.

Paul C. Clark; Ian A. Bonnell

2006-03-21

14

Analytical Approximations for Calculating the Escape and Absorption of Radiation in Clumpy Dusty Environments  

E-print Network

We present analytical approximations for calculating the scattering, absorption and escape of nonionizing photons from a spherically symmetric two-phase clumpy medium, with either a central point source of isotropic radiation, a uniform distribution of isotropic emitters, or uniformly illuminated by external sources. The analytical approximations are based on the mega-grains model of two-phase clumpy media, as proposed by Hobson & Padman, combined with escape and absorption probability formulae for homogeneous media. The accuracy of the approximations is examined by comparison with 3D Monte Carlo simulations of radiative transfer, including multiple scattering. Our studies show that the combined mega-grains and escape/absorption probability formulae provide a good approximation of the escaping and absorbed radiation fractions for a wide range of parameters characterizing the medium. A realistic test is performed by modeling the absorption of a starlike source of radiation by interstellar dust in a clumpy medium, and by calculating the resulting equilibrium dust temperatures and infrared emission spectrum of both the clumps and the interclump medium. In particular, we find that the temperature of dust in clumps is lower than in the interclump medium if clumps are optically thick. Comparison with Monte Carlo simulations of radiative transfer in the same environment shows that the analytic model yields a good approximation of dust temperatures and the emerging UV to FIR spectrum of radiation for all three types of source distributions mentioned above. Our analytical model provides a numerically expedient way to estimate radiative transfer in a variety of interstellar conditions and can be applied to a wide range of astrophysical environments, from star forming regions to starburst galaxies.

Frank Varosi; Eli Dwek

1999-05-05

15

First Statistical Tests for Clumpy Tori Models: Constraints from RXTE monitoring of Seyfert AGN  

NASA Astrophysics Data System (ADS)

We present an analysis of multi-timescale variability in line-of-sight X-ray absorbing gas as a function of optical classification in a large sample of Seyfert AGN to derive the first X-ray statistical constraints for clumpy-torus models. We systematically search for discrete absorption events in the vast archive of RXTE monitoring of 55 nearby type Is and Compton-thin type IIs. We are sensitive to discrete absorption events due to clouds of full-covering, neutral/mildly ionized gas with columns >˜10^{22-25} cm^{-2} transiting the line of sight. Our results probe model parameter space complementary to that for eclipses observed with XMM-Newton, Suzaku, and Chandra. We detect 12 eclipse events in 8 objects, roughly tripling the number previously published from RXTE. Peak column densities span 4-26 × 10^{22} cm^{-2}. Event durations span hours to years. The column density profile for a cloud in NGC 3783 is doubly spiked, possibly indicating a cloud that is being tidally sheared. We infer clouds' distances from the black hole to span 0.3 - 140 × 10^4 R_{g}. Most clouds' distances are commensurate with the outer portions of the BLR, or the inner regions of infrared-emitting dusty tori. We discuss implications for cloud distributions in the context of clumpy-torus models.

Markowitz, A.; Krumpe, M.; Nikutta, R.

2014-07-01

16

MASSIVE BLACK HOLE PAIRS IN CLUMPY, SELF-GRAVITATING CIRCUMNUCLEAR DISKS: STOCHASTIC ORBITAL DECAY  

SciTech Connect

We study the dynamics of massive black hole pairs in clumpy gaseous circumnuclear disks. We track the orbital decay of the light, secondary black hole M {sub .2} orbiting around the more massive primary at the center of the disk, using N-body/smoothed particle hydrodynamic simulations. We find that the gravitational interaction of M {sub .2} with massive clumps M {sub cl} erratically perturbs the otherwise smooth orbital decay. In close encounters with massive clumps, gravitational slingshots can kick the secondary black hole out of the disk plane. The black hole moving on an inclined orbit then experiences the weaker dynamical friction of the stellar background, resulting in a longer orbital decay timescale. Interactions between clumps can also favor orbital decay when the black hole is captured by a massive clump that is segregating toward the center of the disk. The stochastic behavior of the black hole orbit emerges mainly when the ratio M {sub .2}/M {sub cl} falls below unity, with decay timescales ranging from ?1 to ?50 Myr. This suggests that describing the cold clumpy phase of the interstellar medium in self-consistent simulations of galaxy mergers, albeit so far neglected, is important to predict the black hole dynamics in galaxy merger remnants.

Fiacconi, Davide; Mayer, Lucio; Roškar, Rok [Institute for Theoretical Physics, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland)] [Institute for Theoretical Physics, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Colpi, Monica, E-mail: fiacconi@physik.uzh.ch [Dipartimento di Fisica 'G. Occhialini', Università di Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy)] [Dipartimento di Fisica 'G. Occhialini', Università di Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy)

2013-11-01

17

AGN Dusty Tori: I. Handling of Clumpy Media  

E-print Network

According to unified schemes of Active Galactic Nuclei (AGN), the central engine is surrounded by dusty, optically thick clouds in a toroidal structure. We have recently developed a formalism that for the first time takes proper account of the clumpy nature of the AGN torus. We now provide a detailed report of our findings in a two-paper series. Here we present our general formalism for radiative transfer in clumpy media and construct its building blocks for the AGN problem -- the source functions of individual dusty clouds heated by the AGN radiation field. We show that a fundamental difference from smooth density distributions is that in a clumpy medium, a large range of dust temperatures coexist at the same distance from the radiation central source. This distinct property explains the low dust temperatures found close to the nucleus of NGC1068 in 10 \\mic interferometric observations. We find that irrespective of the overall geometry, a clumpy dust distribution shows only moderate variation in its spectral energy distribution, and the 10\\mic\\ absorption feature is never deep. Furthermore, the X-ray attenuating column density is widely scattered around the column density that characterizes the IR emission. All of these properties are characteristic of AGN observations. The assembly of clouds into AGN tori and comparison with observations is presented in the companion paper.

Maia Nenkova; Matthew M. Sirocky; Zeljko Ivezic; Moshe Elitzur

2008-06-03

18

Competition Drives Clumpy Species Coexistence in Estuarine Phytoplankton  

PubMed Central

Understanding the mechanisms that maintain biodiversity is a fundamental problem in ecology. Competition is thought to reduce diversity, but hundreds of microbial aquatic primary producers species coexist and compete for a few essential resources (e.g., nutrients and light). Here, we show that resource competition is a plausible mechanism for explaining clumpy distribution on individual species volume (a proxy for the niche) of estuarine phytoplankton communities ranging from North America to South America and Europe, supporting the Emergent Neutrality hypothesis. Furthermore, such a clumpy distribution was also observed throughout the Holocene in diatoms from a sediment core. A Lotka-Volterra competition model predicted position in the niche axis and functional affiliation of dominant species within and among clumps. Results support the coexistence of functionally equivalent species in ecosystems and indicate that resource competition may be a key process to shape the size structure of estuarine phytoplankton, which in turn drives ecosystem functioning. PMID:23301158

Segura, A. M.; Kruk, C.; Calliari, D.; García-Rodriguez, F.; Conde, D.; Widdicombe, C. E.; Fort, H.

2013-01-01

19

Four years of IUE research on clumpy irregular galaxies  

NASA Technical Reports Server (NTRS)

During the first four years of IUE operations seven shifts were used to observe 4 clumpy irregular galaxies: Markarian 7, 8, 297, and 325. All spectra were obtained at low resolution in both short and long wavelength, with exposure time ranging from half to a full shift. The IUE spectra of clumpy irregular galaxies show that the clumps contain a very large number of early O and B type stars, with a large number of supergiants with respect to the main sequence stars. Possibly Wolf-Rayet stars and massive objects of the type of R 136a could also contribute to the clump luminosity. On the average, each clump radiates in the UV 100 times more than 30 Dor. On the other end the liner dimension of a clump is not much larger than the one of 30 Dor.

Benvenuti, P.; Casini, C.; Heidmann, J.

1982-01-01

20

Multiple Scattering in Clumpy Media. II. Galactic Environments  

E-print Network

We present and discuss the results of new multiple-scattering radiative transfer calculations for three representative types of galactic environments, filled with either homogeneous or two-phase clumpy dust distributions. Extinction and scattering properties for two types of interstellar dust, similar to those found in the average diffuse medium of the Milky Way Galaxy (MW) and the Bar of the Small Magellanic Cloud (SMC), are considered. The wavelength coverage extends from 1000 A to 30,000 A, with particular emphasis on the rest-frame UV. This makes these models especially applicable to starburst galaxies and Lyman-break galaxy samples. The examination of the models concentrates on the study of UV/visual/near-IR reddening effects, the wavelength dependence of attenuation, and on the changes that arise from the transition from homogeneous to clumpy dust distributions in different star/dust geometries. Embedded dust, especially when clumpy, leads to saturation at fairly low reddening values with correspondingly gray attenuation functions. This makes the assessment of the attenuation of the far-UV flux from starburst galaxies difficult, if only UV/visual/near-IR data are available. Existing data for UV-selected starburst galaxies indicate a range of UV attenuation factors of 0-150. Our models reproduce the "Calzetti Attenuation Law", provided one adopts SMC-type dust and a clumpy shell-type dust distribution surrounding the starbursts. The average far-UV attenuation factor for the Calzetti sample is found to be 7.4. The only relatively reliable measure for the UV attenuation factor for single galaxies was found in the ratio of the integrated far-IR flux to the far-UV flux, measured near 1600 A, requiring the measurement of the entire spectral energy distribution of galaxies.

Adolf N. Witt; Karl D. Gordon

1999-07-25

21

Kinematic imprint of clumpy disk formation on halo objects  

NASA Astrophysics Data System (ADS)

Context. Clumpy disk galaxies in the distant universe, at redshift of z ? 1, have been observed to host several giant clumps in their disks. They are thought to correspond to early formative stages of disk galaxies. On the other hand, halo objects, such as old globular clusters and halo stars, are likely to consist of the oldest stars in a galaxy (age ? 10 Gyr), clumpy disk formation can thus be presumed to take place in a pre-existing halo system. Aims: Giant clumps orbit in the same direction in a premature disk and are so massive that they may be expected to interact gravitationally with halo objects and exercise influence on the kinematic state of the halo. Accordingly, I scrutinize the possibility that the clumps leave a kinematic imprint of the clumpy disk formation on a halo system. Methods: I perform a restricted N-body calculation with a toy model to study the kinematic influence on a halo by orbital motions of clumps and the dependence of the results on masses (mass loss), number, and orbital radii of the clumps. Results: I show that halo objects can catch clump motions and acquire disky rotation in a dynamical friction time scale of the clumps, ~0.5 Gyr. The influence of clumps is limited within a region around the disk, while the halo system shows vertical gradients of net rotation velocity and orbital eccentricity. The significance of the kinematic influence strongly depends on the clump masses; the lower limit of postulated clump mass would be ~5 × 108 M?. The result also depends on whether the clumps are subjected to rapid mass loss or not, which is an open question under debate in recent studies. The existence of such massive clumps is not unrealistic. I therefore suggest that the imprints of past clumpy disk formation could remain in current galactic halos.

Inoue, Shigeki

2013-02-01

22

THE INFRARED NUCLEAR EMISSION OF SEYFERT GALAXIES ON PARSEC SCALES: TESTING THE CLUMPY TORUS MODELS  

SciTech Connect

We present subarcsecond resolution mid-infrared (mid-IR) photometry in the wavelength range from 8 to 20 {mu}m of 18 Seyfert galaxies, reporting high spatial resolution nuclear fluxes for the entire sample. We construct spectral energy distributions (SEDs) that the active galactic nucleus (AGN) dominates, relatively uncontaminated by starlight, adding near-IR measurements from the literature at similar angular resolution. We find that the IR SEDs of intermediate-type Seyferts are flatter and present higher 10 to 18 {mu}m ratios than those of Seyfert 2 galaxies. We fit the individual SEDs with clumpy dusty torus models using the in-house-developed BayesClumpy tool. We find that the clumpy models reproduce the high spatial resolution measurements. Regardless of the Seyfert type, even with high spatial resolution data, near- to mid-IR SED fitting poorly constrains the radial extent of the torus. For the Seyfert 2 galaxies, we find that edge-on geometries are more probable than face-on views, with a number of clouds along equatorial rays of N{sub 0} = 5-15. The 10 {mu}m silicate feature is generally modeled in shallow absorption. For the intermediate-type Seyferts, N{sub 0} and the inclination angle of the torus are lower than those of the Seyfert 2 nuclei, with the silicate feature appearing in weak emission or absent. The columns of material responsible for the X-ray absorption are larger than those inferred from the model fits for most of the galaxies, which is consistent with X-ray absorbing gas being located within the dust sublimation radius, whereas the mid-IR flux arises from an area farther from the accretion disk. The fits yield both the bolometric luminosity of the intrinsic AGN and the torus-integrated luminosity, from which we derive the reprocessing efficiency of the torus. In the models, the outer radial extent of the torus scales with the AGN luminosity, and we find the tori to be confined to scales less than 5 pc.

Ramos Almeida, C.; Rodriguez Espinosa, J. M.; Asensio Ramos, A. [Instituto de Astrofisica de Canarias (IAC), C/Via Lactea, s/n, E-38205, La Laguna, Tenerife (Spain); Levenson, N. A. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Alonso-Herrero, A. [Instituto de Estructura de la Materia, CSIC, E-28006 Madrid (Spain); Radomski, J. T. [Gemini South Observatory, Casilla 603, La Serena (Chile); Packham, C.; Telesco, C. M. [Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611-2055 (United States); Fisher, R. S. [Gemini Observatory, Northern Operations Center, 670 North Aohoku Place, Hilo, HI 96720 (United States)], E-mail: cra@iac.es

2009-09-10

23

CLUMPY GALAXIES IN GOODS AND GEMS: MASSIVE ANALOGS OF LOCAL DWARF IRREGULARS  

SciTech Connect

Clumpy galaxies in the Galaxy Evolution from Morphology and SEDs and Great Observatories Origins Deep Survey fields are examined for clues to their evolution into modern spirals. The magnitudes of the clumps and the surface brightnesses of the interclump regions are measured and fitted to models of stellar age and mass. There is an evolutionary trend from clump clusters with no evident interclump emission to clump clusters with faint red disks, to spiral galaxies of the flocculent or grand design types. Along this sequence, the interclump surface density increases and the mass surface density contrast between the clumps and the interclump regions decreases, suggesting a gradual dispersal of clumps to form disks. Also along this sequence, the bulge-to-clump mass ratios and age ratios increase, suggesting a gradual formation of bulges. All of these morphological types occur in the same redshift range, indicating that the clump cluster morphology is not the result of bandshifting. This redshift range also includes clear examples of interacting galaxies with tidal tails and other characteristic features, indicating that clump clusters, which do not have these features, are not generally interacting. Comparisons to local galaxies with the same rest wavelength and spatial resolution show that clump clusters are unlike local flocculent and spiral galaxies primarily because of the high clump/interclump contrasts in the clump clusters. They bear a striking resemblance to local dwarf irregulars, however. This resemblance is consistent with a model in which the clumpy morphology comes from gravitational instabilities in gas with a high turbulent speed compared to the rotation speed and a high mass fraction compared to the stars. The morphology does not depend on galaxy mass as much as it depends on evolutionary stage: clump clusters are 100 times more massive than local dwarfs. The apparent lack of star formation in damped Lyman alpha absorbers may result from fast turbulence.

Elmegreen, Debra Meloy; Marcus, Max T.; Yau, Andrew [Vassar College, Department of Physics and Astronomy, Box 745, Poughkeepsie, NY 12604 (United States); Elmegreen, Bruce G. [IBM Research Division, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States); Shahinyan, Karlen [Wesleyan University, Department of Astronomy, Middletown, CT 06459 (United States); Petersen, Michael [Colgate University, Department of Physics and Astronomy, Hamilton, NY 13346 (United States)], E-mail: elmegreen@vassar.edu, E-mail: mamarcus@vassar.edu, E-mail: anyau@vassar.edu, E-mail: bge@watson.ibm.com, E-mail: kshahinyan@wesleyan.edu, E-mail: mpetersen@students.colgate.edu

2009-08-10

24

A Chandra view of the clumpy reflector at the heart of the Circinus galaxy  

NASA Astrophysics Data System (ADS)

We present a spectral and imaging analysis of the X-ray reflecting structure at the heart of the Circinus galaxy, investigating the innermost regions surrounding the central black hole. By studying an archival 200 ks Chandra Advanced CCD Imaging Spectrometer-S observation, we are able to image the extended clumpy structure responsible for both cold reflection of the primary radiation and neutral iron K? line emission. We measure an excess of the equivalent width of the iron K? line which follows an axisymmetric geometry around the nucleus on a hundred pc scale. Spectra extracted from different regions confirm a scenario in which the dominant mechanism is the reflection of the nuclear radiation from Compton-thick gas. Significant differences in the equivalent width of the iron K? emission line (up to a factor of 2) are found. It is argued that these differences are due to different scattering angles with respect to the line of sight rather than to different iron abundances.

Marinucci, A.; Miniutti, G.; Bianchi, S.; Matt, G.; Risaliti, G.

2013-12-01

25

A Clumpy Model for Self-Enrichment in Globular Clusters  

NASA Astrophysics Data System (ADS)

Hubble observations have demonstrated that globular clusters {GCs} are not the simple stellar populations once believed, but have internal subpopulations with slightly different ages, metallicities, and detailed abundances. High-mass GCs also exhibit a mass-metallicity relation that indicates that they are at least partly self-enriched by heavy elements produced by their own massive stars. We propose to extend our previous model for GC self-enrichment, which has proven very effective at understanding the mass-metallicity relation but which assumes no internal subpopulations, to include the effects of clumpiness in the protocluster cloud. This will allow us to predict how internal variation in a GC depends on other GC properties, and determine how much of the internal variation is due to internal processes rather than inhomogeneities in the protocluster cloud.

Bailin, Jeremy

2014-10-01

26

Bayesclumpy: Bayesian Inference with Clumpy Dusty Torus Models  

NASA Astrophysics Data System (ADS)

Our aim is to present a fast and general Bayesian inference framework based on the synergy between machine learning techniques and standard sampling methods and apply it to infer the physical properties of clumpy dusty torus using infrared photometric high spatial resolution observations of active galactic nuclei. We make use of the Metropolis-Hastings Markov Chain Monte Carlo algorithm for sampling the posterior distribution function. Such distribution results from combining all a priori knowledge about the parameters of the model and the information introduced by the observations. The main difficulty resides in the fact that the model used to explain the observations is computationally demanding and the sampling is very time consuming. For this reason, we apply a set of artificial neural networks that are used to approximate and interpolate a database of models. As a consequence, models not present in the original database can be computed ensuring continuity. We focus on the application of this solution scheme to the recently developed public database of clumpy dusty torus models. The machine learning scheme used in this paper allows us to generate any model from the database using only a factor of 10-4 of the original size of the database and a factor of 10-3 in computing time. The posterior distribution obtained for each model parameter allows us to investigate how the observations constrain the parameters and which ones remain partially or completely undetermined, providing statistically relevant confidence intervals. As an example, the application to the nuclear region of Centaurus A shows that the optical depth of the clouds, the total number of clouds, and the radial extent of the cloud distribution zone are well constrained using only six filters. The code is freely available from the authors.

Asensio Ramos, A.; Ramos Almeida, C.

2009-05-01

27

Gas accretion in a clumpy disk with application to AGNs  

E-print Network

We analyze the collective gravitational interaction among gas clouds in the inner regions of galactic disks and find that it leads to accretion at a rate disk, $M_t$ is sum of the central plus any axisymmetrically distributed mass, and $\\Omega$ is the mean angular speed of clumps. We discuss applications of this result to the mega-maser galaxy NGC 4258, for which we have observational evidence that the maser spots are concentrated in a thin molecular disk which is clumpy, and find the accretion rate to be about $1.5\\times 10^{-3}$ solar mass per year. If the gravitational energy release of this inward falling gas were to be radiated away efficiently, then the resulting luminosity would greatly exceed the observed central luminosity of NGC 4258, indicating that most of the thermal energy of the gas is advected with the flow into the blackhole as proposed by Lasota et al. (1996). The gravitational interactions among molecular clouds lying within the inner kpc of our galaxy give an accretion rate of about $10^{-...

Kumar, P

1997-01-01

28

Gas accretion in a clumpy disk with application to AGNs  

E-print Network

We analyze the collective gravitational interaction among gas clouds in the inner regions of galactic disks and find that it leads to accretion at a rate $\\sim M_{mc}\\Omega (M_{mc}/M_t)^2$; where $M_{mc}$ is the molecular mass of the disk, $M_t$ is sum of the central plus any axisymmetrically distributed mass, and $\\Omega$ is the mean angular speed of clumps. We discuss applications of this result to the mega-maser galaxy NGC 4258, for which we have observational evidence that the maser spots are concentrated in a thin molecular disk which is clumpy, and find the accretion rate to be about $1.5\\times 10^{-3}$ solar mass per year. If the gravitational energy release of this inward falling gas were to be radiated away efficiently, then the resulting luminosity would greatly exceed the observed central luminosity of NGC 4258, indicating that most of the thermal energy of the gas is advected with the flow into the blackhole as proposed by Lasota et al. (1996). The gravitational interactions among molecular clouds lying within the inner kpc of our galaxy give an accretion rate of about $10^{-5}$ solar mass per year, which is consistent with the value obtained by Narayan et al. (1995) by fitting the spectrum of Sagitarrius A$^*$. We also discuss possible application of this work to quasar evolution.

Pawan Kumar

1997-06-06

29

The clumpy structure of the chemically active L1157 outflow  

E-print Network

We present high spatial resolution maps, obtained with the Plateau de Bure Interferometer, of the blue lobe of the L1157 outflow. We observed four lines at 3 mm, namely CH3OH (2_K-1_K), HC3N (11-10), HCN (1-0) and OCS (7-6). Moreover, the bright B1 clump has also been observed at better spatial resolution in CS (2-1), CH3OH (2_1-1_1)A-, and 34SO (3_2-2_1). These high spatial resolution observations show a very rich structure in all the tracers, revealing a clumpy structure of the gas superimposed to an extended emission. In fact, the three clumps detected by previous IRAM-30m single dish observations have been resolved into several sub-clumps and new clumps have been detected in the outflow. The clumps are associated with the two cavities created by two shock episodes driven by the precessing jet. In particular, the clumps nearest the protostar are located at the walls of the younger cavity with a clear arch-shape form while the farthest clumps have slightly different observational characteristics indicating ...

Benedettini, Milena; Codella, Claudio; Bachiller, Rafael; Gueth, Frederic; Beltràn, Maria T; Dutrey, Anne; Guilloteau, Stephane

2007-01-01

30

Asphericity and clumpiness in the winds of Luminous Blue Variables  

E-print Network

We present the first systematic spectropolarimetric study of Luminous Blue Variables (LBVs) in the Galaxy and the Magellanic Clouds, in order to investigate the geometries of their winds. We find that at least half of our sample show changes in polarization across the strong H$\\alpha$ emission line, indicating that the light from the stars is intrinsically polarized and therefore that asphericity already exists at the base of the wind. Multi-epoch spectropolarimetry on four targets reveals variability in their intrinsic polarization. Three of these, AG Car, HR Car and P Cyg, show a position angle (PA) of polarization which appears random with time. Such behaviour can be explained by the presence of strong wind-inhomogeneities, or `clumps' within the wind. Only one star, R 127, shows variability at a constant PA, and hence evidence for axi-symmetry as well as clumpiness. However, if viewed at low inclination, and at limited temporal sampling, such a wind would produce a seemingly random polarization of the type observed in the other three stars. Time-resolved spectropolarimetric monitoring of LBVs is therefore required to determine if LBV winds are axi-symmetric in general. The high fraction of LBVs ($>$ 50%) showing intrinsic polarization is to be compared with the lower $\\sim$ 20-25 % for similar studies of their evolutionary neighbours, O supergiants and Wolf-Rayet stars. We anticipate that this higher incidence is due to the lower effective gravities of the LBVs, coupled with their variable temperatures within the bi-stability jump regime. This is also consistent with the higher incidence of wind asphericity that we find in LBVs with strong H$\\alpha$ emission and recent (last $\\sim$ 10 years) strong variability.

Ben Davies; Rene D. Oudmaijer; Jorick S. Vink

2005-05-17

31

The clumpy structure of the chemically active L1157 outflow  

NASA Astrophysics Data System (ADS)

We present high spatial resolution maps, obtained with the Plateau de Bure Interferometer, of the blue lobe of the L1157 outflow. We observed four lines at 3 mm, namely CH3OH (2K-1K), HC3N (11-10), HCN (1-0) and OCS (7-6). Moreover, the bright B1 clump has also been observed at better spatial resolution in CS (2-1), CH3OH (21-11)A- and 34SO (32-21). These high spatial resolution observations show a very rich structure in all the tracers, revealing a clumpy structure of the gas superimposed to an extended emission. In fact, the three clumps detected by previous IRAM 30-m single-dish observations have been resolved into several subclumps and new clumps have been detected in the outflow. The clumps are associated with the two cavities created by two shock episodes driven by the precessing jet. In particular, the clumps nearest the protostar are located at the wall of the younger cavity with a clear arch shape form while the farthest clumps have slightly different observational characteristics indicating that they are associated with the older shock episode. The emission of the observed species peaks in different part of the lobe: the eastern clumps are brighter in HC3N (11-10), HCN (1-0) and CS (2-1) while the western clumps are brighter in CH3OH (2K-1K), OCS (7-6) and 34SO (32-21). This peak displacement in the line emission suggests a variation of the physical conditions and/or the chemical composition along the lobe of the outflow at small scale, likely related to the shock activity and the precession of the outflow. In particular, we observe the decoupling of the silicon monoxide and methanol emission, common shock tracers, in the B1 clump located at the apex of the bow shock produced by the second shock episode.

Benedettini, M.; Viti, S.; Codella, C.; Bachiller, R.; Gueth, F.; Beltrán, M. T.; Dutrey, A.; Guilloteau, S.

2007-11-01

32

3D Modelling of Clumpy PDRs: the Structure of the ISM in Star Forming Regions  

NASA Astrophysics Data System (ADS)

The interstellar medium (ISM) is permanently irradiated and heated by the UV contribution of massive stars to the interstellar radiation field. A photon dominated region (PDR) is a region in interstellar space where the interstellar farUV radiation (with photon energies 6 eV< h? <13.6 eV) dominates the energy balance and the chemistry of the ISM. It is under investigation whether the radiation field triggers star formation in the ISM. The KOSMA-? PDR model has been developed to simulate the line emission of spherical geometries, "clumps", in the ISM. Furthermore, it has been shown that an equivalent superposition of such clumps (clumpy ensemble) can be used to mimic the structure of the ISM. Here, by assembling a 3-dimensional compound from different clumpy ensembles, a 3-dimensional model has been set up, enabling us to simulate the emission of clumpy PDRs in arbitrary geometric setups. The model supports analysis of the spatial structure of star forming regions and can simulate the variation of parameters like the UV field strength or the local density for the different clumpy ensembles within one star forming region. Furthermore, opacities of the clumpy structures are discussed theoretically and the resulting line absorptions are included into the simulations. This step not only refines the fits of observational data, but also improves the simulation of line profiles which can be done with our model. For testing purposes the new model is used to simulate the main cooling lines and other diagnostics of a well known star forming region, namely the Orion Bar. Through the fit of observational maps and line profiles we are able to constrain the spatial variation of the PDR parameters such as the total mass, different density components and the ambient UV field strength. In addition we can test our understanding of the internal clumpy structure of the ISM and perform a major step towards a fully self-consistent model of typically highly inhomogeneous PDRs.

Andree-Labsch, Silke; Röllig, Markus; Ossenkopf, Volker

2013-07-01

33

The clumpy structure of the chemically active L1157 outflow  

E-print Network

We present high spatial resolution maps, obtained with the Plateau de Bure Interferometer, of the blue lobe of the L1157 outflow. We observed four lines at 3 mm, namely CH3OH (2_K-1_K), HC3N (11-10), HCN (1-0) and OCS (7-6). Moreover, the bright B1 clump has also been observed at better spatial resolution in CS (2-1), CH3OH (2_1-1_1)A-, and 34SO (3_2-2_1). These high spatial resolution observations show a very rich structure in all the tracers, revealing a clumpy structure of the gas superimposed to an extended emission. In fact, the three clumps detected by previous IRAM-30m single dish observations have been resolved into several sub-clumps and new clumps have been detected in the outflow. The clumps are associated with the two cavities created by two shock episodes driven by the precessing jet. In particular, the clumps nearest the protostar are located at the walls of the younger cavity with a clear arch-shape form while the farthest clumps have slightly different observational characteristics indicating that they are associated to the older shock episode. The emission of the observed species peaks in different part of the lobe: the east clumps are brighter in HC3N (11-10), HCN (1-0) and CS (2-1) while the west clumps are brighter in CH3OH(2_K-1_K), OCS (7-6) and 34SO (3_2-2_1). This peak displacement in the line emission suggests a variation of the physical conditions and/or the chemical composition along the lobe of the outflow at small scale, likely related to the shock activity and the precession of the outflow. In particular, we observe the decoupling of the silicon monoxide and methanol emission, common shock tracers, in the B1 clump located at the apex of the bow shock produced by the second shock episode.

Milena Benedettini; Serena Viti; Claudio Codella; Rafael Bachiller; Frederic Gueth; Maria T. Beltràn; Anne Dutrey; Stephane Guilloteau

2007-08-01

34

Jet Bow Shocks and Clumpy Shells of H 2 Emission in the Young  

E-print Network

Jet Bow Shocks and Clumpy Shells of H 2 Emission in the Young Stellar Outflow Cepheus A Patrick as a result of cooling instabilities behind the bow shocks. Subject headings: ISM: jets and outflows -- stars and produce visible shock waves in the flow, and sometimes as less collimated bipolar flows of molecular gas

Hartigan, Patrick

35

Sound Absorbers  

NASA Astrophysics Data System (ADS)

Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.

Fuchs, H. V.; Möser, M.

36

An X-Ray Spectral Model for Clumpy Tori in Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

We construct an X-ray spectral model for the clumpy torus in an active galactic nucleus (AGN) using Geant4, which includes the physical processes of the photoelectric effect, Compton scattering, Rayleigh scattering, ? conversion, fluorescence line, and Auger process. Since the electrons in the torus are expected to be bounded instead of free, the deviation of the scattering cross section from the Klein-Nishina cross section has also been included, which changes the X-ray spectra by up to 25% below 10 keV. We have investigated the effect of the clumpiness parameters on the reflection spectra and the strength of the fluorescent line Fe K?. The volume filling factor of the clouds in the clumpy torus only slightly influences the reflection spectra, however, the total column density and the number of clouds along the line of sight significantly change the shapes and amplitudes of the reflection spectra. The effect of column density is similar to the case of a smooth torus, while a small number of clouds along the line of sight will smooth out the anisotropy of the reflection spectra and the fluorescent line Fe K?. The smoothing effect is mild in the low column density case (N H = 1023 cm-2), whereas it is much more evident in the high column density case (N H = 1025 cm-2). Our model provides a quantitative tool for the spectral analysis of the clumpy torus. We suggest that the joint fits of the broad band spectral energy distributions of AGNs (from X-ray to infrared) should better constrain the structure of the torus.

Liu, Yuan; Li, Xiaobo

2014-05-01

37

Clumpy and fractal shocks, and the generation of a velocity dispersion in molecular clouds  

E-print Network

We present an alternative explanation for the nature of turbulence in molecular clouds. Often associated with classical models of turbulence, we instead interpret the observed gas dynamics as random motions, induced when clumpy gas is subject to a shock. From simulations of shocks, we show that a supersonic velocity dispersion occurs in the shocked gas provided the initial distribution of gas is sufficiently non-uniform. We investigate the velocity size-scale relation $\\sigma \\propto r^{\\alpha}$ for simulations of clumpy and fractal gas, and show that clumpy shocks can produce realistic velocity size-scale relations with mean $\\alpha \\thicksim 0.5$. For a fractal distribution, with a fractal dimension of 2.2 similar to what is observed in the ISM, we find $\\sigma \\propto r^{0.4}$. The form of the velocity size-scale relation can be understood as due to mass loading, i.e. the post-shock velocity of the gas is determined by the amount of mass encountered as the gas enters the shock. We support this hypothesis with analytical calculations of the velocity dispersion relation for different initial distributions. A prediction of this model is that the line-of sight velocity dispersion should depend on the angle at which the shocked gas is viewed.

Clare Dobbs; Ian Bonnell

2006-10-24

38

DYNAMO II: Coupled Stellar and Ionized Gas Kinematics in Two Low Redshift Clumpy Disks  

E-print Network

We study the spatially resolved stellar kinematics of two star-forming galaxies at z = 0.1 from the larger DYnamics of Newly Assembled Massive Objects (DYNAMO) sample. These galaxies, which have been characterized by high levels of star formation and large ionized gas velocity dispersions, are considered possible analogs to high-redshift clumpy disks. They were observed using the GMOS instrument in integral field spectroscopy (IFS) mode at the Gemini Observatory with high spectral resolution (R=5400, equivalent to 24 km/s at the observed wavelengths) and 6 hour exposure times in order to measure the resolved stellar kinematics via absorption lines. We also obtain higher-quality emission line kinematics than previous observations. The spatial resolution (1.2 kpc) is sufficient to show that the ionized gas in these galaxies (as traced by H-beta emission) is morphologically irregular, forming multiple giant clumps while stellar continuum light is smooth and well described by an exponential profile. Clumpy gas mo...

Bassett, Robert; Fisher, David B; Green, Andrew W; Wisnioski, Emily; Obreschkow, Danail; Cooper, Erin Mentuch; Abraham, Roberto G; Damjanov, Ivana; McGregor, Peter J

2014-01-01

39

Milliarcsecond imaging of clumpy dust clouds in the red giant L2 Pup with the Very Large Telescope Interferometer  

NASA Astrophysics Data System (ADS)

Despite its importance in mass loss, the dust formation in AGB stars is not yet understood well. There is growing evidence that the dust envelopes of AGB stars are much more complex--clumpy and/or bipolar--than spherically expanding shells. The non-spherical structures emerging in AGB stars may be the seed of asymmetry in planetary nebulae. However, direct observations of the clumpy dust cloud formation close to the star is difficult, because we need milliarcsecond spatial resolution. We present milliarcsecond resolution near-IR imaging of the bright, nearby M giant L2 Pup. The 2.2 micron image taken with VLT/NACO at a spatial resolution of 54 mas shows an asymmetric circumstellar envelope with 300 x 200 mas (12 x 8 stellar radii), elongated in East-West direction. Furthermore, we succeeded in aperture-synthesis imaging of L2 Pup by combining these single-dish VLT/NACO data with near-IR interferometric data taken with the AMBER instrument at the Very Large Telescope Interferometer. The reconstructed image with a spatial resolution of 12 mas shows two clumps at 20--30 mas away from the star, as well as another clump over the stellar. This is the first imaging of clumpy dust clouds toward L2 Pup, whose presence was only inferred from polarimetric and photometric observations. Our observations reveal the clumpy dust formation close to the star, at 1.5--2.5 stellar radii.

Ohnaka, K.; Schertl, D.; Hofmann, K. H.; Weigelt, G.

2014-04-01

40

Sub-millimeter Galaxies: Dusty, Clumpy and Messy Starbursts in the Distant Universe  

NASA Astrophysics Data System (ADS)

We present the first spatially-resolved observations of the H? emission in three z˜2 sub-millimeter selected galaxies (SMGs) using the Keck OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) with Laser Guide Star Adaptive Optics (LGS-AO). With the unprecedent kpc-scale resolution - up to ten times that achieved with previous seeing-limited studies - and the kinematic insight that these observations provide, we unveil a clumpy H? structure and reveal velocity offsets that suggest these systems are in an advanced merging phase. The spatially-resolved spectral information also allows us to disentangle the H? emission arising from an active galactic nucleus (AGN) from that associated with star formation.

Menéndez-Delmestre, K.; Blain, A. W.; Swinbank, M.; Smail, I.; Ivison, R.; Chapman, S. C.; Gonçalves, T. S.

2014-10-01

41

Innermost structure and near-infrared radiation of dusty clumpy tori in active galactic nuclei  

NASA Astrophysics Data System (ADS)

The dusty clumpy torus surrounds the central black hole (BH) and the accretion disk in active galactic nuclei, and governs the growth of super-massive BHs via gas fueling towards the central engine. Near-infrared (NIR) monitoring observations have revealed that the torus inner radius is determined by the dust sublimation process. However, the observed radii are systematically smaller than the theoretical predictions by a factor of three. We take into account the anisotropic illumination by the central accretion disk to the torus, and calculate the innermost structure of the torus and the NIR time variability. We then show that the anisotropy naturally solves the systematic discrepancy and that the viewing angle is the primary source to produce an object-to-object scatter of the NIR time delay. Dynamics of clumps at the innermost region of the torus will be unveiled via future high- resolution X-ray spectroscopy (e.g., Astro-H)

Kawaguchi, Toshihiro

2012-12-01

42

Perfect Metamaterial Absorber  

Microsoft Academic Search

We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional

N. I. Landy; S. Sajuyigbe; J. J. Mock; D. R. Smith; W. J. Padilla

2008-01-01

43

Common Cold  

NSDL National Science Digital Library

This Web site provides comprehensive information, selected by medical doctors, about the common cold. "The goal is to provide a framework for critical thinking which will allow informed decisions about medical care for the common cold." The section entitled Understanding Colds gives a detailed overview of how the cold virus invades the human body and how cold symptoms are caused. Information about preventing colds, and some of the complications that can occur are also included. The Special Features section includes one of the most interesting parts of the site -- Myths of the Common Cold. This site should be interesting to almost anyone, but perhaps more so for those of us who have recently had a cold.

1999-01-01

44

Common Cold  

MedlinePLUS

... nose, coughing - everyone knows the symptoms of the common cold. It is probably the most common illness. In the course of a year, people ... avoid colds. There is no cure for the common cold. For relief, try Getting plenty of rest ...

45

A smart radar absorber  

Microsoft Academic Search

This paper proposes a configuration for a smart radar absorber which is capable of both self-tuning and absorb while scan operation. The discussion is complemented by modelled and measured performance data.

Barry Chambers

1999-01-01

46

Magnification Probability Distribution Functions of Standard Candles in a Clumpy Universe  

E-print Network

Lensing effects on light rays from point light sources, such like Type Ia supernovae, are simulated in a clumpy universe model. In our universe model, it is assumed that all matter in the universe takes the form of randomly distributed objects each of which has finite size and is transparent for light rays. Monte-Carlo simulations are performed for several lens models, and we compute probability distribution functions of magnification. In the case of the lens models that have a smooth density profile or the same degree of density concentration as the spherical NFW (Navarro-Frenk-White) lens model at the center, the so-called gamma distributions fit well the magnification probability distribution functions if the size of lenses is sufficiently larger than the Einstein radius. In contrast, the gamma distributions do not fit the magnification probability distribution functions in the case of the SIS (Singular Isothermal Sphere) lens model. We find, by using the power law cusp model, that the magnification probability distribution function is fitted well using the gamma distribution only when the slope of the central density profile is not very steep. These results suggest that we may obtain information about the slope of the central density profiles of dark matter halo from the lensing effect of Type Ia supernovae.

Chul-Moon Yoo; Hideki Ishihara; Ken-ichi Nakao; Hideyuki Tagoshi

2007-11-17

47

Orbital Decay of Supermassive Black Hole Binaries in Clumpy Multiphase Merger Remnants  

E-print Network

We simulate an equal-mass merger of two Milky Way-size galaxy discs with moderate gas fractions at parsec-scale resolution including a new model for radiative cooling and heating in a multi-phase medium, as well as star formation and feedback from supernovae. The two discs initially have a $2.6\\times10^6\\mathrm{~M_{\\odot}}$ supermassive black hole (SMBH) embedded in their centers. As the merger completes and the two galactic cores merge, the SMBHs form a a pair with a separation of a few hundred pc that gradually decays. Due to the stochastic nature of the system immediately following the merger, the orbital plane of the binary is significantly perturbed. Furthermore, owing to the strong starburst the gas from the central region is completely evacuated, requiring $\\sim10$~Myr for a nuclear disc to rebuild. Most importantly, the clumpy nature of the interstellar medium has a major impact on the the dynamical evolution of the SMBH pair, which undergo gravitational encounters with massive gas clouds and stochast...

Roškar, R; Fiacconi, D; Kazantzidis, S; Quinn, T R; Wadsley, J

2014-01-01

48

Wing galaxies - A formation mechanism of the clumpy irregular galaxy Markarian 297  

SciTech Connect

Numerical N-body simulations are made to understand a formation mechanism for the clumpy irregular starburst galaxy Markarian 297. A coplanar radial penetration collision between two disk galaxies explains overall morphological properties of Markarian 297. The evolutionary phase corresponds to about 150 million yr after the impact. The morphology of the disturbed galaxy looks like a 'wing'. In the case that the colliding partner is deformed to a 'ring' galaxy, the projected image of the two galaxies is quite similar to the entire observed shape of Markarian 297, when the colliding system is observed from a nearly edge-on view. It is also shown that the observed velocity field is well reproduced by this model. Numerical simulations of the gas cloud system are also made to study the star-forming activity in the galaxy. The unusually high star-formation rate (SFR) of Markarian 297, indicated by FIR observations, is explained as a sum of SFRs of both the wing and the ring galaxies. 44 refs.

Taniguchi, Yoshiaki; Noguchi, Masafumi (Kiso Observatory, Nagano (Japan) Nobeyama Radio Observatory, Minamimaki (Japan) Cardiff, University College, Wales (England))

1991-05-01

49

Perfect metamaterial absorber.  

PubMed

We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional absorbers, our MM consists solely of metallic elements. The substrate can therefore be optimized for other parameters of interest. We experimentally demonstrate a peak A(omega) greater than 88% at 11.5 GHz. PMID:18518577

Landy, N I; Sajuyigbe, S; Mock, J J; Smith, D R; Padilla, W J

2008-05-23

50

Composition for absorbing hydrogen  

DOEpatents

A hydrogen absorbing composition. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

Heung, Leung K. (Aiken, SC); Wicks, George G. (Aiken, SC); Enz, Glenn L. (N. Augusta, SC)

1995-01-01

51

Fibrous absorber solar collector  

SciTech Connect

A lightweight and durable solar collector employing a fibrous absorber is described. Sufficient fiber mass may be used to blanket all radiation. The absorber is disposed between a transparent cover and a heat insulating shield behind which may be a rigid collector container. A reflector disposed between the absorber and the insulation is optional. Air enters the collector passes into a duct near bottom of the absorber and across the width of the absorber, flows parallel to and through the thinnest dimension of the absorber conducting heat from the fiber at the depths of greatest absorption and then exits through a similar duct located near the top of the absorber and out of the collector.

Novinger, H.E.

1981-12-08

52

Hot and Cold  

NSDL National Science Digital Library

In this activity, learners explore temperature changes from chemical reactions by mixing urea with water in one flask and mixing calcium chloride with water in another flask. They observe that the urea flask gets cold and the calcium chloride flask gets hot. The main idea is that some chemical processes release heat energy and are exothermic, while some chemical processes absorb heat energy and are endothermic. This activity is currently used in the Nature of Matter Unit in OMSI's Chemistry Lab. Cost estimates are per 100 learners.

Industry, Oregon M.

1997-01-01

53

MAPPING THE CLUMPY STRUCTURES WITHIN SUBMILLIMETER GALAXIES USING LASER-GUIDE STAR ADAPTIVE OPTICS SPECTROSCOPY  

SciTech Connect

We present the first integral-field spectroscopic observations of high-redshift submillimeter-selected galaxies (SMGs) using Laser-Guide Star Adaptive Optics. We target H{alpha} emission of three SMGs at redshifts z {approx} 1.4-2.4 with the OH-Suppressing Infrared Imaging Spectrograph on Keck. The spatially resolved spectroscopy of these galaxies reveals unresolved broad-H{alpha} line regions (FWHM >1000 km s{sup -1}) likely associated with an active galactic nucleus (AGN) and regions of diffuse star formation traced by narrow-line H{alpha} emission (FWHM {approx}< 500 km s{sup -1}) dominated by multiple H{alpha}-bright stellar clumps, each contributing 1%-30% of the total clump-integrated H{alpha} emission. We find that these SMGs host high star formation rate surface densities, similar to local extreme sources, such as circumnuclear starbursts and luminous infrared galaxies. However, in contrast to these local environments, SMGs appear to be undergoing such intense activity on significantly larger spatial scales as revealed by extended H{alpha} emission over 4-16 kpc. H{alpha} kinematics show no evidence of ordered global motion as would be found in a disk, but rather large velocity offsets ({approx}few Multiplication-Sign 100 km s{sup -1}) between the distinct stellar clumps. Together with the asymmetric distribution of the stellar clumps around the AGN in these objects, it is unlikely that we are unveiling a clumpy disk structure as has been suggested in other high-redshift populations of star-forming galaxies. The SMG clumps in this sample may correspond to remnants of originally independent gas-rich systems that are in the process of merging, hence triggering the ultraluminous SMG phase.

Menendez-Delmestre, Karin; Goncalves, Thiago S. [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Antonio 43, Saude, Rio de Janeiro, RJ 20080-090 (Brazil); Blain, Andrew W. [California Institute of Technology, MC 105-24, Pasadena, CA 91125 (United States); Swinbank, Mark; Smail, Ian [Institute for Computational Cosmology, Durham University, Durham DH1 3LE (United Kingdom); Ivison, Rob J. [UK Astronomy Technology Centre, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Chapman, Scott C., E-mail: kmd@astro.ufrj.br [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

2013-04-20

54

The star-formation histories within clumpy disks at z ~ 2.2  

NASA Astrophysics Data System (ADS)

We propose to obtain WFC3 F438W images, sampling the rest-frame FUV (~1400A), of 10 clumpy disk galaxies at z~2.2. These 10

Carollo, Marcella

2014-10-01

55

Wing galaxies: A formation mechanism of the clumpy irregular galaxy Markarian 297  

NASA Technical Reports Server (NTRS)

In order to contribute to an understanding of collision-induced starburst activities, the authors present a detailed case study on the starburst galaxy Markarian 297 (= NGC 6052 = Arp 209; hereafter Mrk 297). This galaxy is classified as a clumpy irregular galaxy (CIG) according to its morphological properties (cf. Heidmann, 1987). Two major clumps and many small clumps are observed in the entire region of Mrk 297 (Hecquet, Coupinot, and Maucherat 1987). The overall morphology of Mrk 297 is highly chaotic and thus it seems difficult to determine possible orbits of galaxy-galaxy collision. However, the authors have serendipitously found a possible orbit during a course of numerical simulations for a radial-penetration collision between galaxies. The radial-penetration collision means that an intruder penetrates a target galaxy radially passing by its nucleus. This kind of collision is known to explain a formation mechanism of ripples around disk galaxies (Wallin and Struck-Marcell 1988). Here, the authors show that the radial-penetration collision between galaxies successfully explains both overall morphological and kinematical properties of Mrk 297. The authors made two kinds of numerical simulations for Mrk 297. One is N-body (1x10(exp 4) particles) simulations in which effects of self gravity of the stellar disk are taken into account. These simulations are used to study detailed morphological feature of Mrk 297. The response of gas clouds are also investigated in order to estimate star formation rates in such collisions. The other is test-particle simulations, which are utilized to obtain a rough picture of Mrk 297 and to analyze the velocity field of Mrk 297. The techniques of the numerical simulations are the same as those in Noguchi (1988) and Noguchi and Ishibashi (1986). In the present model, an intruding galaxy with the same mass of a target galaxy moves on a rectilinear orbit which passes the center of the target.

Taniguchi, Yoshiaki; Noguchi, Masafumi

1990-01-01

56

Radiative transfer in a clumpy universe: The colors of high-redshift galaxies  

NASA Technical Reports Server (NTRS)

We assess the effects of the stochastic attenuation produced by intervening QSO absorption systems on the broadband colors of galaxies at cosmological distances. We compute the H I opacity of a clumpy universe as a function of redshift, including scattering in resonant lines, such as Lyman alpha, Lyman beta, Lyman gamma, and higher order members, and Lyman-continuum absorption. Both the numerous, optically thin Lyman-alpha forest clouds and the rarer, optically thick Lyman limit systems are found to contribute to the obscuration of background sources. We study the mean properties of primeval galaxies at high redshift in four broad optical passbands, U(sub n), B, G, and R. Even if young galaxies radiated a significant amount of ionizing photons, the attenuation due to the accumulated photoelectric opacity along the path is so severe that sources beyond z approximately 3 will drop out of the U(sub n) image together. We also show that the observed B-R color of distant galaxies can be much redder than expected from a stellar population. At z approximately 3.5, the blanketing by discrete absorption lines in the Lyman series is so effective that background galaxies appear, on average, 1 mag fainter in B. By z approximately 4, the observed B magnitude increment due to intergalactic absorption exceeds 2 mag. By modeling the intrinsic UV spectral energy distribution of star-forming galaxies with a stellar population synthesis code, we show that the (B-R)(sub AB) approximately 0 criterion for identifying 'flat-spectrum,' metal-producing galaxies is biased against objects at z greater than 3. The continuum blanketing from the Lyman series produces a characteristic staircase profile in the transmitted power. We suggest that this cosmic Lyman decrement might be used as a tool to identify high-z galaxies.

Madau, Piero

1995-01-01

57

Externally tuned vibration absorber  

DOEpatents

A vibration absorber unit or units are mounted on the exterior housing of a hydraulic drive system of the type that is powered from a pressure wave generated, e.g., by a Stirling engine. The hydraulic drive system employs a piston which is hydraulically driven to oscillate in a direction perpendicular to the axis of the hydraulic drive system. The vibration absorbers each include a spring or other resilient member having one side affixed to the housing and another side to which an absorber mass is affixed. In a preferred embodiment, a pair of vibration absorbers is employed, each absorber being formed of a pair of leaf spring assemblies, between which the absorber mass is suspended.

Vincent, Ronald J. (Latham, NY)

1987-09-22

58

Methods for absorbing neutrons  

DOEpatents

A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

Guillen, Donna P. (Idaho Falls, ID); Longhurst, Glen R. (Idaho Falls, ID); Porter, Douglas L. (Idaho Falls, ID); Parry, James R. (Idaho Falls, ID)

2012-07-24

59

Common cold  

MedlinePLUS

... and before eating and preparing food. Disinfect your environment. Clean commonly touched surfaces (such as sink handles, ... system work properly. Eat yogurt that contains "active cultures." These may help prevent colds. Probiotics may help ...

60

No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z ~ 2 in CANDELS/3D-HST  

NASA Astrophysics Data System (ADS)

We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3 < z < 2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that despite being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z ~ 2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z ~ 2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratios (in the mass-excitation method), but the spatially resolved line ratios indicate this is likely due to extended phenomena rather than nuclear AGNs. Meanwhile, the X-ray data show that clumpy, smooth, and intermediate galaxies have nearly indistinguishable AGN fractions derived from both individual detections and stacked non-detections. The data demonstrate that AGN fueling modes at z ~ 1.85—whether violent disk instabilities or secular processes—are as efficient in smooth galaxies as they are in clumpy galaxies. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc, under NASA contract NAS 5-26555.

Trump, Jonathan R.; Barro, Guillermo; Juneau, Stéphanie; Weiner, Benjamin J.; Luo, Bin; Brammer, Gabriel B.; Bell, Eric F.; Brandt, W. N.; Dekel, Avishai; Guo, Yicheng; Hopkins, Philip F.; Koo, David C.; Kocevski, Dale D.; McIntosh, Daniel H.; Momcheva, Ivelina; Faber, S. M.; Ferguson, Henry C.; Grogin, Norman A.; Kartaltepe, Jeyhan; Koekemoer, Anton M.; Lotz, Jennifer; Maseda, Michael; Mozena, Mark; Nandra, Kirpal; Rosario, David J.; Zeimann, Gregory R.

2014-10-01

61

Solar energy absorber panel  

Microsoft Academic Search

Disclosed is a solar energy absorber panel comprising a heat absorbing and conducting sheet and an array of fluid conduits in thermal contact with the sheet. For a given efficiency, the weight of the panel is minimized by providing a sheet thickness of between about 0.001 inch and about 0.006 inch and a conduit density of between about 3 and

Godrick

1976-01-01

62

Thin Wideband Radar Absorbers  

Microsoft Academic Search

A procedure for the optimal design of thin wideband radar absorbers is presented. The resulting absorbers are implemented by printing a frequency selective surface on a lossy perforated substrate. A binary hill climbing optimization scheme with random restart is used to find optimal solutions. The method of moments in conjunction with the transmission line method is used to calculate the

Arya Fallahi; Alireza Yahaghi; Hans-Rudolf Benedickter; Habibollah Abiri; Mahmoud Shahabadi; Christian Hafner

2010-01-01

63

The evidence for clumpy accretion in the Herbig Ae star HR 5999  

NASA Technical Reports Server (NTRS)

Analysis of IUE high- and low-dispersion spectra of the young Herbig Ae star HR 5999 (HD 144668) covering 1978-1992 revealed dramatic changes in the Mg II h and k (2795.5, 2802.7 A) emission profiles, changes in the column density and distribution in radial velocity of accreting gas, and flux in the Ly(alpha), O I, and C IV emission lines, which are correlated with the UV excess luminosity. Variability in the spectral type inferred from the UV spectral energy distribution, ranging from A5 IV-III in high state to A7 III in the low state, was also observed. The trend of earlier inferred spectral type with decreasing wavelength and with increasing UV continuum flux has previously been noted as a signature of accretion disks in lower mass pre-main sequence stars (PMS) and in systems undergoing FU Orionis-type outbursts. Our data represent the first detection of similar phenomena in an intermediate mass (M greater than or equal to 2 solar mass) PMS star. Recent IUE spectra show gas accreting toward the star with velocities as high as plus 300 km/s, much as is seen toward beta Pic, and suggest that we also view this system through the debris disk. The absence of UV lines with the rotational broadening expected given the optical data (A7 IV, V sini=180 plus or minus 20 km/s for this system) also suggests that most of the UV light originates in the disk, even in the low continuum state. The dramatic variability in the column density of accreting gas, is consistent with clumpy accretion, such as has been observed toward beta Pic, is a hallmark of accretion onto young stars, and is not restricted to the clearing phase, since detectable amounts of accretion are present for stars with 0.5 Myr less than t(sub age) less than 2.8 Myr. The implications for models of beta Pic and similar systems are briefly discussed.

Perez, M. R.; Grady, C. A.; The, P. S.

1993-01-01

64

SHOCKED SUPERWINDS FROM THE z {approx} 2 CLUMPY STAR-FORMING GALAXY, ZC406690  

SciTech Connect

We have obtained high-resolution data of the z {approx} 2 ring-like, clumpy star-forming galaxy (SFG) ZC406690 using the VLT/SINFONI with adaptive optics (in K band) and in seeing-limited mode (in H and J bands). Our data include all of the main strong optical emission lines: [O II], [O III], H{alpha}, H{beta}, [N II], and [S II]. We find broad, blueshifted H{alpha} and [O III] emission line wings in the spectra of the galaxy's massive, star-forming clumps ({sigma} {approx} 85 km s{sup -1}) and even broader wings (up to 70% of the total H{alpha} flux, with {sigma} {approx} 290 km s{sup -1}) in regions spatially offset from the clumps by {approx}2 kpc. The broad emission likely originates from large-scale outflows with mass outflow rates from individual clumps that are 1-8 Multiplication-Sign the star formation rate (SFR) of the clumps. Based on emission line ratio diagnostics ([N II]/H{alpha} and [S II]/H{alpha}) and photoionization and shock models, we find that the emission from the clumps is due to a combination of photoionization from the star-forming regions and shocks generated in the outflowing component, with 5%-30% of the emission deriving from shocks. In terms of the ionization parameter (6 Multiplication-Sign 10{sup 7} to 10{sup 8} cm s{sup -1}, based on both the SFR and the O{sub 32} ratio), density (local electron densities of 300-1800 cm{sup -3} in and around the clumps, and ionized gas column densities of 1200-8000 M{sub Sun }pc{sup -2}), and SFR (10-40 M{sub Sun} yr{sup -1}), these clumps more closely resemble nuclear starburst regions of local ultraluminous infrared galaxies and dwarf irregulars than H II regions in local galaxies. However, the star-forming clumps are not located in the nucleus as in local starburst galaxies but instead are situated in a ring several kpc from the center of their high-redshift host galaxy, and have an overall disk-like morphology. The two brightest clumps are quite different in terms of their internal properties, energetics, and relative ages, and thus we are given a glimpse at two different stages in the formation and evolution of rapidly star-forming giant clumps at high-z.

Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Shapiro Griffin, Kristen [Aerospace Research Laboratories, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Davies, Ric; Foerster-Schreiber, Natascha M.; Tacconi, Linda J.; Kurk, Jaron; Wuyts, Stijn; Genel, Shy; Buschkamp, Peter; Eisenhauer, Frank; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr.1, D-85748 Garching (Germany); Lilly, Simon J.; Carollo, C. Marcella [Institute of Astronomy, Department of Physics, Eidgenoessische Technische Hochschule, ETH Zuerich CH-8093 (Switzerland); Renzini, Alvio; Mancini, Chiara [Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, Padova I-35122 (Italy); Bouche, Nicolas [Department of Physics and Astronomy, University of California, Santa Barbara, Santa Barbara, CA 93106 (United States); Burkert, Andreas [Department fuer Physik, Universitaets-Sternwarte Ludwig-Maximilians-Universitaet (USM), Scheinerstr. 1, Muenchen, D-81679 (Germany); Cresci, Giovanni [Istituto Nazionale di AstrofisicaOsservatorio Astronomico di Arcetri, Largo Enrico Fermi 5, I 50125 Firenze (Italy); Hicks, Erin, E-mail: sfnewman@berkeley.edu [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); and others

2012-06-20

65

A total and polarized infrared flux view of the AGN clumpy torus  

NASA Astrophysics Data System (ADS)

Magnetohydrodynamical theories consider the torus of Active Galactic Nuclei (AGN) to be part of an outflow wind moving away from the central engine. In this framework, the torus is a particular region of the wind, where dusty and optically thick clouds are formed. The outflows are strongly related to the accretion rate and magnetic field strength, which play an important role in the creation, morphology and evolution of the torus. Through infrared (IR) imaging and polarimetry observations, this dissertation (1) searches for signatures of dusty tori in low-luminosity AGN (LLAGN); (2) explores the role and strength of magnetic field in the torus; and (3) investigates the nucleus of radio-loud AGN. Recent theoretical models predicted that LLAGN do not host a Seyfert-like torus, since low-luminosities (<1042 erg s-1 ) cannot sustain the required outflow rate. High-spatial resolution mid-IR (MIR) imaging and nuclear spectral energy distribution of 22 LLAGN reveals different IR characteristics by dividing the sample in terms of the Eddington ratio. These galaxies show a diversity of nuclear morphologies and have a high MIR/X-ray luminosity ratio compared to higher-luminosity AGN. Star formation, jets and/or truncated accretion disk can explain the MIR excess. Although several models have been made to account for the outflowing dusty winds from the central engine, the magnetic field strength at the position of the torus remains poorly characterized. Through a novel study using near-IR polarimetry, the magnetic field strength in the clumpy torus was estimated. Specifically, if paramagnetic alignment is assumed in the dusty clouds of the torus, the magnetic field strength of the torus of IC5063 is estimated to be in the range of 12--128 mG. Alternatively, Chandrasekhar-Fermi method suggests a lower-limit magnetic field strength of 13 mG. For the archetypical radio-loud AGN, Cygnus A, MIR polarimetry using CanariCam on the 10.4-m Gran Telescopio de Canarias revealed a high polarized, 11+/-3% and 12+/-3% (at Si2 and Si5 respectively) unresolved nucleus. Polarimetric modeling suggests that the MIR polarization arises from a synchrotron component. This result represents the most compelling MIR polarization detection of synchrotron radiation in Cygnus A.

Lopez Rodriguez, Enrique

66

Multispectral metamaterial absorber.  

PubMed

We present the simulation, implementation, and measurement of a multispectral metamaterial absorber (MSMMA) and show that we can realize a simple absorber structure that operates in the mid-IR and terahertz (THz) bands. By embedding an IR metamaterial absorber layer into a standard THz metamaterial absorber stack, a narrowband resonance is induced at a wavelength of 4.3 ?m. This resonance is in addition to the THz metamaterial absorption resonance at 109 ?m (2.75 THz). We demonstrate the inherent scalability and versatility of our MSMMA by describing a second device whereby the MM-induced IR absorption peak frequency is tuned by varying the IR absorber geometry. Such a MSMMA could be coupled with a suitable sensor and formed into a focal plane array, enabling multispectral imaging. PMID:24690713

Grant, J; McCrindle, I J H; Li, C; Cumming, D R S

2014-03-01

67

Evolution of the Fraction of Clumpy Galaxies at 0.2 < z < 1.0 in the COSMOS Field  

NASA Astrophysics Data System (ADS)

Using the Hubble Space Telescope/Advanced Camera for Surveys data in the COSMOS field, we systematically searched clumpy galaxies at 0.2 < z < 1.0 and investigated the fraction of clumpy galaxies and its evolution as a function of stellar mass, star formation rate (SFR), and specific SFR (SSFR). The fraction of clumpy galaxies in star-forming galaxies with M star > 109.5 M ? decreases with time from ~0.35 at 0.8 < z < 1.0 to ~0.05 at 0.2 < z < 0.4, irrespective of the stellar mass, although the fraction tends to be slightly lower for massive galaxies with M star > 1010.5 M ? at each redshift. On the other hand, the fraction of clumpy galaxies increases with increasing both SFR and SSFR in all the redshift ranges we investigated. In particular, we found that the SSFR dependences of the fractions are similar among galaxies with different stellar masses, and the fraction at a given SSFR does not depend on the stellar mass in each redshift bin. The evolution of the fraction of clumpy galaxies from z ~ 0.9 to z ~ 0.3 seems to be explained by such SSFR dependence of the fraction and the evolution of SSFRs of star-forming galaxies. The fraction at a given SSFR also appears to decrease with time, but this can be due to the effect of the morphological k correction. We suggest that these results are understood by the gravitational fragmentation model for the formation of giant clumps in disk galaxies, where the gas mass fraction is a crucial parameter. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. Also based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under cooperative agreement with the National Science Foundation; and the Canada-France-Hawaii Telescope with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the NRC and CADC of Canada, the CNRS of France, TERAPIX, and the University of Hawaii.

Murata, K. L.; Kajisawa, M.; Taniguchi, Y.; Kobayashi, M. A. R.; Shioya, Y.; Capak, P.; Ilbert, O.; Koekemoer, A. M.; Salvato, M.; Scoville, N. Z.

2014-05-01

68

Cold Water Vapor in the Barnard 5 Molecular Cloud  

E-print Network

After more than 30 years of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds, however, there is only one region where cold (~10 K) water vapor has been detected - L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work -- likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 1_10 - 1_01) at 556.9360 GHz toward two positions in the cold molecular cloud Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

Wirström, E S; Persson, C M; Buckle, J V; Cordiner, M A; Takakuwa, S

2014-01-01

69

Cold Water Vapor in the Barnard 5 Molecular Cloud  

NASA Astrophysics Data System (ADS)

After more than 30 yr of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds; however, there is only one region where cold (~10 K) water vapor has been detected—L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work—likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 110-101) at 556.9360 GHz toward two positions in the cold molecular cloud, Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

Wirström, E. S.; Charnley, S. B.; Persson, C. M.; Buckle, J. V.; Cordiner, M. A.; Takakuwa, S.

2014-06-01

70

Fast cold gas in hot AGN outflows  

E-print Network

Observations of the emission from spatially extended cold gas around bright high-redshift QSOs reveal surprisingly large velocity widths exceeding 2000 km s^(-1), out to projected distances as large as 30 kpc. The high velocity widths have been interpreted as the signature of powerful AGN-driven outflows. Naively, these findings appear in tension with hydrodynamic models in which AGN-driven outflows are energy-driven and thus very hot with typical temperatures T = 10^6-7 K. Using the moving-mesh code Arepo, we perform 'zoom-in' cosmological simulations of a z = 6 QSO and its environment, following black hole growth and feedback via energy-driven outflows. In the simulations, the QSO host galaxy is surrounded by a clumpy circum-galactic medium pre-enriched with metals due to supernovae-driven galactic outflows. As a result, part of the AGN-driven hot outflowing gas can cool radiatively, leading to large amounts (> 10^9 M_sun) of cold gas comoving with the hot bipolar outflow. This results in velocity widths of...

Costa, Tiago; Haehnelt, Martin

2014-01-01

71

Baltic Astronomy, vol. 20, 490494, 2011 AGN DUSTY TORI AS A CLUMPY TWO-PHASE MEDIUM  

E-print Network

surrounding the central engine of an active galactic nucleus (AGN), absorbs the incoming radiation, the radiative cooling and the heating due to supernovae. They found that such a turbulent medium would produce a three- dimensional radiative transfer code to obtain spectral energy distributions and images of tori

Baes, Maarten

72

Internal absorber solar collector  

DOEpatents

Thin solar collecting panels are described made from arrays of small rod collectors consisting of a refracting dielectric rod lens with an absorber imbedded within it and a reflecting mirror coated on the back side of the dielectric rod. Non-tracking collector panels on vertical walls or roof tops receive approximately 90% of solar radiation within an acceptance zone 60.degree. in elevation angle by 120.degree. or more in the azimuth sectors with a collector concentration ratio of approximately 3.0. Miniaturized construction of the circular dielectric rods with internal absorbers reduces the weight per area of glass, plastic and metal used in the collector panels. No external parts or insulation are needed as heat losses are low due to partial vacuum or low conductivity gas surrounding heated portions of the collector. The miniature internal absorbers are generally made of solid copper with black selective surface and the collected solar heat is extracted at the collector ends by thermal conductivity along the absorber rods. Heat is removed from end fittings by use of liquid circulants. Several alternate constructions are provided for simplifying collector panel fabrication and for preventing the thermal expansion and contraction of the heated absorber or circulant tubes from damaging vacuum seals. In a modified version of the internal absorber collector, oil with temperature dependent viscosity is pumped through a segmented absorber which is now composed of closely spaced insulated metal tubes. In this way the circulant is automatically diverted through heated portions of the absorber giving higher collector concentration ratios than theoretically possible for an unsegmented absorber.

Sletten, Carlyle J. (106 Nagog Hill Rd., Acton, MA 01720); Herskovitz, Sheldon B. (88 Hammond St., Acton, MA 01720); Holt, F. S. (46 Emerson Rd., Winchester, MA 01890); Sletten, E. J. (Chestnut Hill Rd. R.F.D. Rte. #4, Amherst, NH 03031)

1981-01-01

73

Electromagnetic power absorber  

NASA Technical Reports Server (NTRS)

A structure is presented with a surface portion of dielectric material which passes electromagnetic radiation and with a portion below the surface which includes material that absorbs the radiation, the face of the structure being formed with numerous steep ridges. The steepness of the dielectric material results in a high proportion of the electromagnetic energy passing through the surface for absorption by the absorbing material under the surface. A backing of aluminum or other highly heat-conductive and reflective material lies under the face and has very steep protuberances supporting the absorbing and dielectric materials.

Iwasaki, R. S. (inventor)

1979-01-01

74

Lipid-absorbing Polymers  

NASA Technical Reports Server (NTRS)

The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

Marsh, H. E., Jr.; Wallace, C. J.

1973-01-01

75

Multiband terahertz metamaterial absorber  

NASA Astrophysics Data System (ADS)

This paper reports the design of a multiband metamaterial (MM) absorber in the terahertz region. Theoretical and simulated results show that the absorber has four distinct and strong absorption points at 1.69, 2.76, 3.41 and 5.06 THz, which are consistent with ‘fingerprints’ of some explosive materials. The retrieved material parameters show that the impedance of MM could be tuned to match approximately the impedance of the free space to minimise the reflectance at absorption frequencies and large power loss exists at absorption frequencies. The distribution of the power loss indicates that the absorber is an excellent electromagnetic wave collector: the wave is first trapped and reinforced in certain specific locations and then consumed. This multiband absorber has applications in the detection of explosives and materials characterisation.

Gu, Chao; Qu, Shao-Bo; Pei, Zhi-Bin; Xu, Zhuo; Liu, Jia; Gu, Wei

2011-01-01

76

Absorbance modulation optical lithography  

E-print Network

In this thesis, the concept of absorbance-modulation optical lithography (AMOL) is described, and the feasibility experimentally verified. AMOL is an implementation of nodal lithography, which is not bounded by the diffraction ...

Tsai, Hsin-Yu Sidney

2007-01-01

77

Multiband terahertz metamaterial absorber  

Microsoft Academic Search

This paper reports the design of a multiband metamaterial (MM) absorber in the terahertz region. Theoretical and simulated results show that the absorber has four distinct and strong absorption points at 1.69, 2.76, 3.41 and 5.06 THz, which are consistent with `fingerprints' of some explosive materials. The retrieved material parameters show that the impedance of MM could be tuned to

Chao Gu; Shao-Bo Qu; Zhi-Bin Pei; Zhuo Xu; Jia Liu; Wei Gu

2011-01-01

78

Project COLD.  

ERIC Educational Resources Information Center

Describes Project COLD (Climate, Ocean, Land, Discovery) a scientific study of the Polar Regions, a collection of 35 modules used within the framework of existing subjects: oceanography, biology, geology, meterology, geography, social science. Includes a partial list of topics and one activity (geodesic dome) from a module. (Author/SK)

Kazanjian, Wendy C.

1982-01-01

79

Cold War  

NSDL National Science Digital Library

Cold War is a major, 24-part series directed by renowned documentary filmmaker Jeremy Isaacs that recently premiered on CNN and BBC2. Whether or not this series will become "the definitive account of the Cold War" remains to be seen, but the research that has made it possible is quite impressive. This feature-filled, comprehensive site complements the series by offering, among other things, video previews and multimedia recaps of each episode; video, audio, and text excerpts from nearly 100 interviews filmed for the series; text from archival documents and contemporaneous Time and Russian newspaper stories; in-depth sections on Cold War culture; and a Knowledge Bank section containing a glossary, "Cold Warrior" profiles, related links, and a chronology. Additional resources include a classroom guide to the series, online Shockwave quiz games, and an online discussion group. As large as it is now, the site will continue to expand and add new features as the series progresses over the next three months.

80

Hot, Cold, and Really Cold.  

ERIC Educational Resources Information Center

Describes a physics experiment investigating temperature prediction and the relationship between the physical properties of heat units, melting, dissolving, states of matter, and energy loss. Details the experimental setup, which requires hot and cold water, a thermometer, and ice. Notes that the experiment employs a deliberate counter-intuitive…

Leyden, Michael

1997-01-01

81

Mechanical energy absorber  

NASA Technical Reports Server (NTRS)

An energy absorbing system for controlling the force where a moving object engages a stationary stop and where the system utilized telescopic tubular members, energy absorbing diaphragm elements, force regulating disc springs, and a return spring to return the telescoping member to its start position after stroking is presented. The energy absorbing system has frusto-conical diaphragm elements frictionally engaging the shaft and are opposed by a force regulating set of disc springs. In principle, this force feedback mechanism serves to keep the stroking load at a reasonable level even if the friction coefficient increases greatly. This force feedback device also serves to desensitize the singular and combined effects of manufacturing tolerances, sliding surface wear, temperature changes, dynamic effects, and lubricity.

Wesselski, Clarence J. (inventor)

1993-01-01

82

HYPOTHERMIA Surviving the Cold  

E-print Network

weather, cold water, or an indoor freezer ­ is part of the job for many British Columbia workers. One with either artificial or natural cold is potentially at risk. Artificial cold is found in areas such as cold

Machel, Hans

83

Shock Absorbing System  

NASA Technical Reports Server (NTRS)

A lightweight, inexpensive shock-absorbing system, developed by Langley Research Center 20 years ago, is now in service as safety device for an automated railway at Duke University Medical Center. The transportation system travels at about 25 miles per hour, carrying patients, visitors, staff and cargo. At the end of each guideway of the system are "frangible," (breakable) tube "buffers." If a slowing car fails to make a complete stop at the terminal, it would bump and shatter the tubes, absorbing energy that might otherwise jolt the passengers or damage the vehicle.

1982-01-01

84

Damped Lyman-alpha Absorbers in Cosmological SPH Simulations: the  

Microsoft Academic Search

We study the distribution of star formation rate (SFR) and metallicity of damped Lyman-alpha absorbers (DLAs) using cosmological smoothed particle hydrodynamics (SPH) simulations of the Lambda cold dark matter (CDM) model. Our simulations include a phenomenological model for feedback by galactic winds which allows us to examine the effect of galactic outflows on the distribution of SFR and metallicity of

K. Nagamine; V. Springel; L. Hernquist

2005-01-01

85

Abundance of damped Lyman? absorbers in cosmological SPH simulations  

Microsoft Academic Search

We use cosmological smoothed-particle hydrodynamics (SPH) simulations of the ? cold dark matter (CDM) model to study the abundance of damped Lyman-? absorbers (DLAs) in the redshift range z = 0 4.5. We compute the cumulative DLA abun- dance by using the relation between DLA cross-section and the total halo mass inferred from the simulations. Our approach includes standard radiative

K. Nagamine; V. Springel; L. Hernquist

86

Cold soybean management decision system based on JSP  

Microsoft Academic Search

In accordance with the requirements management of cold soybean growth characters integrated climatic conditions, soil fertility status of region, the laws of cold soybean absorbing nutrients, the soil nutrient supplying capacity and other various factors to set up models and rules. The system based on the object-oriented technology of JSP VB VC had some trials on middle plant part (Hailun),

Song Yihong; Yang Yushu; Li Xiao

2010-01-01

87

Neutron Absorbing Alloys  

DOEpatents

The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

Mizia, Ronald E. (Idaho Falls, ID); Shaber, Eric L. (Idaho Falls, ID); DuPont, John N. (Whitehall, PA); Robino, Charles V. (Albuquerque, NM); Williams, David B. (Bethlehem, PA)

2004-05-04

88

Solar energy absorbing panel  

Microsoft Academic Search

A solar energy absorbing panel is provided which may be integrally incorporated into a conventional building structure so that it does not protrude from the normal contour of the building , and which utilizes components of the building structure as a part of the collecting apparatus to thereby minimize the cost thereof. The panel is composed of a plurality of

McArthur

1981-01-01

89

Ionized Absorbers in AGN  

NASA Technical Reports Server (NTRS)

As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".

Mathur, S.

1999-01-01

90

Corrosion resistant neutron absorbing coatings  

DOEpatents

A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

Choi, Jor-Shan (El Cerrito, CA); Farmer, Joseph C. (Tracy, CA); Lee, Chuck K. (Hayward, CA); Walker, Jeffrey (Gaithersburg, MD); Russell, Paige (Las Vegas, NV); Kirkwood, Jon (Saint Leonard, MD); Yang, Nancy (Lafayette, CA); Champagne, Victor (Oxford, PA)

2012-05-29

91

Corrosion resistant neutron absorbing coatings  

DOEpatents

A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

Choi, Jor-Shan; Farmer, Joseph C; Lee, Chuck K; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

2013-11-12

92

THE THICK DISKS OF SPIRAL GALAXIES AS RELICS FROM GAS-RICH, TURBULENT, CLUMPY DISKS AT HIGH REDSHIFT  

SciTech Connect

The formation of thick stellar disks in spiral galaxies is studied. Simulations of gas-rich young galaxies show formation of internal clumps by gravitational instabilities, clump coalescence into a bulge, and disk thickening by strong stellar scattering. The bulge and thick disks of modern galaxies may form this way. Simulations of minor mergers make thick disks too, but there is an important difference. Thick disks made by internal processes have a constant scale height with galactocentric radius, but thick disks made by mergers flare. The difference arises because in the first case, perpendicular forcing and disk-gravity resistance are both proportional to the disk column density, so the resulting scale height is independent of this density. In the case of mergers, perpendicular forcing is independent of the column density and the low-density regions get thicker; the resulting flaring is inconsistent with observations. Late-stage gas accretion and thin-disk growth are shown to preserve the constant scale heights of thick disks formed by internal evolution. These results reinforce the idea that disk galaxies accrete most of their mass smoothly and acquire their structure by internal processes, in particular through turbulent and clumpy phases at high redshift.

Bournaud, Frederic; Martig, Marie [CEA, IRFU, SAp, 91191 Gif-sur-Yvette (France); Elmegreen, Bruce G. [IBM Research Division, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States)

2009-12-10

93

Absorber for solar power.  

PubMed

A simple, economical absorber utilizing a new principle of operation to achieve very low reradiation losses while generating temperatures limited by material properties of quartz is described. Its performance is analyzed and indicates approximately 90% thermal efficiency and 73% conversion efficiency for an earth based unit with moderately concentrated (~tenfold) sunlight incident. It is consequently compatible with the most economic of concentrator mirrors (stamped) or mirrors deployable in space. Space applications are particularly attractive, as temperatures significantly below 300 K are possible and permit even higher conversion efficiency. PMID:20134700

Powell, W R

1974-10-01

94

Underwater acoustic omnidirectional absorber  

NASA Astrophysics Data System (ADS)

Gradient index media, which are designed by varying local element properties in given geometry, have been utilized to manipulate acoustic waves for a variety of devices. This study presents a cylindrical, two-dimensional acoustic "black hole" design that functions as an omnidirectional absorber for underwater applications. The design features a metamaterial shell that focuses acoustic energy into the shell's core. Multiple scattering theory was used to design layers of rubber cylinders with varying filling fractions to produce a linearly graded sound speed profile through the structure. Measured pressure intensity agreed with predicted results over a range of frequencies within the homogenization limit.

Naify, Christina J.; Martin, Theodore P.; Layman, Christopher N.; Nicholas, Michael; Thangawng, Abel L.; Calvo, David C.; Orris, Gregory J.

2014-02-01

95

Cold Atoms  

NASA Astrophysics Data System (ADS)

This chapter and the following one address collective effects of quantum particles, that is, the effects which are observed when we put together a large number of identical particles, for example, electrons, helium-4 or rubidium-85 atoms. We shall see that quantum particles can be classified into two categories, bosons and fermions, whose collective behavior is radically different. Bosons have a tendency to pile up in the same quantum state, while fermions have a tendency to avoid each other. We say that bosons and fermions obey two different quantum statistics, the Bose-Einstein and the Fermi-Dirac statistics, respectively. Temperature is a collective effect, and in Section 5.1 we shall explain the concept of absolute temperature and its relation to the average kinetic energy of molecules. We shall describe in Section 5.2 how we can cool atoms down thanks to the Doppler effect, and explain how cold atoms can be used to improve the accuracy of atomic clocks by a factor of about 100. The effects of quantum statistics are prominent at low temperatures, and atom cooling will be used to obtain Bose-Einstein condensates at low enough temperatures, when the atoms are bosons.

Bellac, Michel Le

2014-11-01

96

Metamaterial saturable absorber mirror.  

PubMed

We propose a metamaterial saturable absorber mirror at midinfrared wavelengths that can show a saturation of absorption with intensity of incident light and switch to a reflecting state. The design consists of an array of circular metallic disks separated by a thin film of vanadium dioxide (VO(2)) from a continuous metallic film. The heating due to the absorption in the absorptive state causes the VO(2) to transit to a metallic phase from the low temperature insulating phase. The metamaterial switches from an absorptive state (R?0.1%) to a reflective state (R>95%) for a specific threshold intensity of the incident radiation corresponding to the phase transition of VO(2), resulting in the saturation of absorption in the metamaterial. The computer simulations show over 99.9% peak absorbance, a resonant bandwidth of about 0.8 ?m at 10.22 ?m wavelengths, and saturation intensity of 140 mW cm(-2) for undoped VO(2) at room temperature. We also carried out numerical simulations to investigate the effects of localized heating and temperature distribution by solving the heat diffusion problem. PMID:23381408

Dayal, Govind; Ramakrishna, S Anantha

2013-02-01

97

Sensing with THz metamaterial absorbers  

E-print Network

Metamaterial perfect absorbers from microwaves to optical part of the electromagnetic spectrum has been intensely studied for its ability to absorb electromagnetic radiation. Perfect absorption of light by metamaterials have opened up new opportunities for application oriented functionalities such as efficient sensors and emitters. We present an absorber based sensing scheme at the terahertz frequencies and discuss optimized designs to achieve high frequency and amplitude sensitivities. The major advantage of a perfect metamaterial absorber as a sensor is the sensitive shift in the absorber resonance frequency along with the sharp change in the amplitude of the resonance due to strong interaction of the analyte with the electric and the magnetic fields at resonant perfect absorption frequency. We compare the sensing performance of the perfect metamaterial absorber with its complementary structural design and planar metasurface with identical structure. The best FoM values obtained for the absorber sensor here...

Cong, Longqing

2014-01-01

98

Metamaterial electromagnetic wave absorbers.  

PubMed

The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch-the metamaterial perfect absorber (MPA)-has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed. PMID:22627995

Watts, Claire M; Liu, Xianliang; Padilla, Willie J

2012-06-19

99

Absorber coatings' degradation  

SciTech Connect

This report is intended to document some of the Los Alamos efforts that have been carried out under the Department of Energy (DOE) Active Heating and Cooling Materials Reliability, Maintainability, and Exposure Testing program. Funding for these activities is obtained directly from DOE although they represent a variety of projects and coordination with other agencies. Major limitations to the use of solar energy are the uncertain reliability and lifetimes of solar systems. This program is aimed at determining material operating limitations, durabilities, and failure modes such that materials improvements can be made and lifetimes can be extended. Although many active and passive materials and systems are being studied at Los Alamos, this paper will concentrate on absorber coatings and degradation of these coatings.

Moore, S.W.

1984-01-01

100

Progress in smart radar absorbers  

NASA Astrophysics Data System (ADS)

Conventional (i.e. passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms but such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional 'smart' functionality such as monitoring damage, adaptive control of RCS or target appearance, Identification-Friend-or-Foe (IFF) and Absorb-While-Scan (AWS) This paper outlines the concept and basic properties of a novel type of active radar absorber, the so-called Phase-Switched Screen (PSS). The basic PSS topology is then modified so as to enable it to operate as a smart radar absorber when used together with an external sensor and feedback control loop. The theoretical predictions are confirmed using data measured on transmission-line analogues of the smart PSS structure.

Chambers, Barry; Tennant, Alan

2003-07-01

101

Damped Lyman-alpha Absorbers in Cosmological SPH Simulations: the \\  

Microsoft Academic Search

We study the distribution of star formation rate (SFR) and metallicity of\\u000adamped Lyman-alpha absorbers (DLAs) using cosmological smoothed particle\\u000ahydrodynamics (SPH) simulations of the Lambda cold dark matter model. Our\\u000asimulations include a phenomenological model for feedback by galactic winds\\u000awhich allows us to examine the effect of galactic outflows on the distribution\\u000aof SFR and metallicity of DLAs.

Kentaro Nagamine; Volker Springel; Lars Hernquist

2003-01-01

102

Progress in smart radar absorbers  

Microsoft Academic Search

Conventional (i.e. passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms but such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional 'smart' functionality such as monitoring damage, adaptive control of RCS or target appearance,

Barry Chambers; Alan Tennant

2003-01-01

103

Metal-shearing energy absorber  

NASA Technical Reports Server (NTRS)

Device, consisting of tongue of thin aluminum alloy strip, pull tab, slotted steel plate which serves as cutter, and steel buckle, absorbs mechanical energy when its ends are subjected to tensile loading. Device is applicable as auxiliary shock absorbing anchor for automobile and airplane safety belts.

Fay, R. J.; Wittrock, E. P.

1971-01-01

104

Leaf absorbance and photosynthesis  

NASA Technical Reports Server (NTRS)

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

Schurer, Kees

1994-01-01

105

Cold Stress and the Cold Pressor Test  

ERIC Educational Resources Information Center

Temperature and other environmental stressors are known to affect blood pressure and heart rate. In this activity, students perform the cold pressor test, demonstrating increased blood pressure during a 1- to 2-min immersion of one hand in ice water. The cold pressor test is used clinically to evaluate autonomic and left ventricular function. This…

Silverthorn, Dee U.; Michael, Joel

2013-01-01

106

Ultrasensitive cold-electron bolometer  

NASA Astrophysics Data System (ADS)

The Cold-Electron Bolometer (CEB) is an ultrasensitive device designed for the detection of cosmic microwave background radiation. The key to its sensitivity is the electron cooling of the absorber by the superconductor-insulator-normal metal (SIN) tunnel junction. At a voltage near and below the superconducting gap, the electrons in the absorber are cooled well below the phonon temperature of the normal metal. This translates to the enhanced sensitivity of the CEB. This thesis describes the work we have done on the optimization of electron cooling of the normal metal absorber, and our measurement of the sensitivity of the CEB. We have optimized the electron cooling of the absorber by SIN tunnel junctions. The best electron cooling was achieved when normal metal traps were added in proximity to the superconducting electrodes in addition to the advanced geometry of the superconducting electrodes. With these modifications, we have decreased the electron temperature by 198 mK. With just the advanced geometry, the electron temperature drop was 129 mK. With just a simple geometry, the drop in temperature was 56 mK. The noise equivalent power (NEP) of the CEB was also measured at 100 mK to be at the level of 10 -18 W/Hz 1/2 at 1 kHz. The NEP was obtained by measuring the noise of the CEB, and then dividing that by its power responsivity, dV/dP. The main limitation in our measurements was the noise component from the amplifier. Finally, we have made measurements on the temperature sensitivity of the SIN tunnel junctions. We have compared the sensitivity between single and ten SIN junctions in series and found that it increases proportionally to the number of junctions. The best temperature responsivity obtained for 10 junctions was approximately 15 mV/mK. Using such thermometer, we have been able to measure the temperature stability of the Oxford Instruments cryogenfree refrigerator to be ±250 mK for a period of 8 hours. The resolution of the thermometer was measured to be ±100 mK, limited by the noise due to the amplifier. The current and future works are also discussed. These include: a CEB array designed to distribute the total power load, improving further the sensitivity; a one-thousand SIN tunnel junction series thermometer in order to realize and understand the fundamental limitation of such a device; a superconducting cold- electron bolometer (SCEB) for high background power loads; and different read- out systems including an on-chip quasiparticle amplifier (QPA).

Agulo, Ian Jasper Ayagan

2007-08-01

107

thin films as absorber  

NASA Astrophysics Data System (ADS)

Photovoltaic structures were prepared using AgSb(S x Se1- x )2 as absorber and CdS as window layer at various conditions via a hybrid technique of chemical bath deposition and thermal evaporation followed by heat treatments. Silver antimony sulfo selenide thin films [AgSb(S x Se1- x )2] were prepared by heating multilayers of sequentially deposited Sb2S3/Ag dipped in Na2SeSO3 solution, glass/Sb2S3/Ag/Se. For this, Sb2S3 thin films were deposited from a chemical bath containing SbCl3 and Na2S2O3. Then, Ag thin films were thermally evaporated on glass/Sb2S3, followed by selenization by dipping in an acidic solution of Na2SeSO3. The duration of dipping was varied as 3, 4 and 5 h. Two different heat treatments, one at 350 °C for 20 min in vacuum followed by a post-heat treatment at 325 °C for 2 h in Ar, and the other at 350 °C for 1 h in Ar, were applied to the multilayers of different configurations. X-ray diffraction results showed the formation of AgSb(S x Se1- x )2 thin films as the primary phase and AgSb(S,Se)2 and Sb2S3 as secondary phases. Morphology and elemental detection were done by scanning electron microscopy and energy dispersive X-ray analysis. X-ray photoelectron spectroscopic studies showed the depthwise composition of the films. Optical properties were determined by UV-vis-IR transmittance and reflection spectral analysis. AgSb(S x Se1- x )2 formed at different conditions was incorporated in PV structures glass/FTO/CdS/AgSb(S x Se1- x )2/C/Ag. Chemically deposited post-annealed CdS thin films of various thicknesses were used as window layer. J- V characteristics of the cells were measured under dark and AM1.5 illumination. Analysis of the J- V characteristics resulted in the best solar cell parameters of V oc = 520 mV, J sc = 9.70 mA cm-2, FF = 0.50 and ? = 2.7 %.

González, J. O.; Shaji, S.; Avellaneda, D.; Castillo, G. A.; Das Roy, T. K.; Krishnan, B.

2014-09-01

108

Cold and Cough Medicines  

MedlinePLUS

... What can you do for your cold or cough symptoms? Besides drinking plenty of fluids and getting ... medicines. There are lots of different cold and cough medicines, and they do different things. Nasal decongestants - ...

109

Cold fusion: Alchemist's dream  

Microsoft Academic Search

In this report the following topics relating to cold fusion are discussed: muon catalyzed cold fusion; piezonuclear fusion; sundry explanations pertaining to cold fusion; cosmic ray muon catalyzed cold fusion; vibrational mechanisms in excited states of D2 molecules; barrier penetration probabilities within the hydrogenated metal lattice\\/piezonuclear fusion; branching ratios of D2 fusion at low energies; fusion of deuterons into He-4;

E. D. Clayton

1989-01-01

110

Exercising in Cold Weather  

MedlinePLUS

... www.nia.nih.gov/Go4Life Exercising in Cold Weather Exercise has benefits all year, even during winter. ... activities when it’s cold outside: l Check the weather forecast. If it’s very windy or cold, exercise ...

111

Cold Fronts in Cold Dark Matter Clusters  

NASA Astrophysics Data System (ADS)

Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters. These features, called cold fronts, are characterized by an increase in surface brightness by a factor >~2 over 10-50 kpc accompanied by a drop in temperature of a similar magnitude. The existence of such sharp gradients can be used to put interesting constraints on the physics of the intracluster medium (ICM) if their mechanism and longevity are well understood. Here, we present results of a search for cold fronts in high-resolution simulations of galaxy clusters in cold dark matter models. We show that sharp gradients with properties similar to those of observed cold fronts naturally arise in cluster mergers when the shocks heat gas surrounding the merging subcluster, while its dense core remains relatively cold. The compression induced by supersonic motions and shock heating during the merger enhance the amplitude of gas density and temperature gradients across the front. Our results indicate that cold fronts are nonequilibrium transient phenomena and can be observed for a period of less than a billion years. We show that the velocity and density fields of gas surrounding the cold front can be very irregular, which would complicate analyses aiming to put constraints on the physical conditions of the ICM in the vicinity of the front.

Nagai, Daisuke; Kravtsov, Andrey V.

2003-04-01

112

Ultrathin multiband gigahertz metamaterial absorbers  

NASA Astrophysics Data System (ADS)

We propose ultrathin multiband metamaterial absorbers in the microwave frequencies in which the design, analysis, fabrication, and measurement of the absorbers working in multiple bands are presented. The metamaterial absorbers consist of a periodic arrangement of different scales of electric-field-coupled-LC (ELC) resonators and a metallic background plane, separated by only 1 mm dielectric spacer. By tuning the scale factor of the ELC unit cells, we achieve independently multiple absorptions at different customized frequencies. Experiments demonstrate excellent absorption rates in the designed frequency bands over wide angles of incident waves for both transverse electric and magnetic polarizations. The explanation to the physical mechanism of the multiband metamaterial absorber is presented and verified.

Li, Hui; Yuan, Li Hua; Zhou, Bin; Shen, Xiao Peng; Cheng, Qiang; Cui, Tie Jun

2011-07-01

113

Facts about the Common Cold  

MedlinePLUS

... Disease > Influenza > In-Depth-Resources Facts About the Common Cold What is a Cold? Colds are minor ... are no antiviral medications available for treating the common cold. Antibiotics are not useful for treating a ...

114

Countercurrent flow absorber and desorber  

DOEpatents

Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system. 9 figs.

Wilkinson, W.H.

1984-10-16

115

Packed Alumina Absorbs Hypergolic Vapors  

NASA Technical Reports Server (NTRS)

Beds of activated alumina effective as filters to remove hypergolic vapors from gas streams. Beds absorb such substances as nitrogen oxides and hydrazines and may also absorb acetylene, ethylene, hydrogen sulfide, benzene, butadiene, butene, styrene, toluene, and xoylene. Bed has no moving parts such as pumps, blowers and mixers. Reliable and energy-conservative. Bed readily adapted to any size from small portable units for use where little vapor release is expected to large stationary units for extensive transfer operations.

Thomas, J. J.; Mauro, D. M.

1984-01-01

116

Countercurrent flow absorber and desorber  

DOEpatents

Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.

Wilkinson, William H. (Columbus, OH)

1984-01-01

117

Perfect selective metamaterial solar absorbers.  

PubMed

In this work, we numerically investigate the radiative properties of metamaterial nanostructures made of two-dimensional tungsten gratings on a thin dielectric spacer and an opaque tungsten film from UV to mid-infrared region as potential selective solar absorbers. The metamaterial absorber with single-sized tungsten patches exhibits high absorptance in the visible and near-infrared region due to several mechanisms such as surface plasmon polaritons, magnetic polaritons, and intrinsic bandgap absorption of tungsten. Geometric effects on the resonance wavelengths and the absorptance spectra are studied, and the physical mechanisms are elucidated in detail. The absorptance could be further enhanced in a broader spectral range with double-sized metamaterial absorbers. The total solar absorptance of the optimized metamaterial absorbers at normal incidence could be more than 88%, while the total emittance is less than 3% at 100°C, resulting in total photon-to-heat conversion efficiency of 86% without any optical concentration. Moreover, the metamaterial solar absorbers exhibit quasi-diffuse behaviors as well as polarization independence. The results here will facilitate the design of novel highly efficient solar absorbers to enhance the performance of various solar energy conversion systems. PMID:24514927

Wang, Hao; Wang, Liping

2013-11-01

118

What's Cooler Than Being Cool? UltraCold Neutrons  

E-print Network

absorb most of the neutron's remaining energy, converting it to "sound waves" (called "phonons"). #12)? At Absolute Zero, no more heat can be removed from a system Record Low: 0.45 nK (MIT, 2003) 0.00000000045 K and eventually come into equilibrium with material Next, into cold "heavy" ice (20 K or -253 C) At ~ 20 K, bring

Martin, Jeff

119

Cold fusion, Alchemist's dream  

SciTech Connect

In this report the following topics relating to cold fusion are discussed: muon catalysed cold fusion; piezonuclear fusion; sundry explanations pertaining to cold fusion; cosmic ray muon catalysed cold fusion; vibrational mechanisms in excited states of D{sub 2} molecules; barrier penetration probabilities within the hydrogenated metal lattice/piezonuclear fusion; branching ratios of D{sub 2} fusion at low energies; fusion of deuterons into {sup 4}He; secondary D+T fusion within the hydrogenated metal lattice; {sup 3}He to {sup 4}He ratio within the metal lattice; shock induced fusion; and anomalously high isotopic ratios of {sup 3}He/{sup 4}He.

Clayton, E.D.

1989-09-01

120

DUSTY STRUCTURE AROUND TYPE-I ACTIVE GALACTIC NUCLEI: CLUMPY TORUS NARROW-LINE REGION AND NEAR-NUCLEUS HOT DUST  

SciTech Connect

We fitted Spitzer/IRS approx 2-35 mum spectra of 26 luminous quasi-stellar objects in an attempt to define the main emission components. Our model has three major components: a clumpy torus, dusty narrow-line region (NLR) clouds, and a blackbody-like dust. The models utilize the clumpy torus of Nenkova et al. and are the first to allow its consistent check in type-I active galactic nuclei (AGNs). Single torus models and combined torus-NLR models fail to fit the spectra of most sources, but three-component models adequately fit the spectra of all sources. We present torus inclination, cloud distribution, covering factor, and torus mass for all sources and compare them with bolometric luminosity, black hole mass, and accretion rate. The torus mass is found to be correlated with the bolometric luminosity of the sources. Torus-covering factor may also be (anti-)correlated, if some possibly anomalous points are omitted. We find that a substantial amount of the approx2-7 mum radiation originates from a hot dust component, which is likely situated in the innermost part of the torus. The luminosity radiated by this component and its covering factor are comparable to those of the torus. We quantify the emission by the NLR clouds and estimate their distance from the center. The distances are approx700 times larger than the dust sublimation radius, and the NLR-covering factor is about 0.07. The total covering factor by all components is in good agreement with the known AGN type-I:type-II ratio.

Mor, Rivay; Netzer, Hagai [School of Physics and Astronomy and the Wise Observatory, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978 (Israel); Elitzur, Moshe [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States)

2009-11-01

121

Damage tolerant light absorbing material  

DOEpatents

A light absorbing article comprised of a composite of carbon-bonded carbon fibers, prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000.degree. C. to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm.sup.3.

Lauf, Robert J. (Oak Ridge, TN); Hamby, Jr., Clyde (Harriman, TN); Akerman, M. Alfred (Knoxville, TN); Seals, Roland D. (Oak Ridge, TN)

1993-01-01

122

Damage tolerant light absorbing material  

DOEpatents

A light absorbing article comprised of a composite of carbon-bonded carbon fibers, is prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000 C to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm[sup 3]. 9 figures.

Lauf, R.J.; Hamby, C. Jr.; Akerman, M.A.; Seals, R.D.

1993-09-07

123

Anomalous Diffusion with Absorbing Boundary  

E-print Network

In a very long Gaussian polymer on time scales shorter that the maximal relaxation time, the mean squared distance travelled by a tagged monomer grows as ~t^{1/2}. We analyze such sub-diffusive behavior in the presence of one or two absorbing boundaries and demonstrate the differences between this process and the sub-diffusion described by the fractional Fokker-Planck equation. In particular, we show that the mean absorption time of diffuser between two absorbing boundaries is finite. Our results restrict the form of the effective dispersion equation that may describe such sub-diffusive processes.

Yacov Kantor; Mehran Kardar

2007-10-31

124

Polarization insensitive terahertz metamaterial absorber.  

PubMed

We present the simulation, implementation, and measurement of a polarization insensitive resonant metamaterial absorber in the terahertz region. The device consists of a metal/dielectric-spacer/metal structure allowing us to maximize absorption by varying the dielectric material and thickness and, hence, the effective electrical permittivity and magnetic permeability. Experimental absorption of 77% and 65% at 2.12 THz (in the operating frequency range of terahertz quantum cascade lasers) is observed for a spacer of polyimide or silicon dioxide respectively. These metamaterials are promising candidates as absorbing elements for thermally based terahertz imaging. PMID:21499411

Grant, J; Ma, Y; Saha, S; Lok, L B; Khalid, A; Cumming, D R S

2011-04-15

125

The X-Ray Warm Absorber in NGC 3516  

NASA Technical Reports Server (NTRS)

The Seyfert 1 galaxy, NGC 3516 has been the subject of many absorption line studies at both ultra-violet and X-ray wavelengths. In the UV, strong, broad, variable associated metal line absorption with velocity width approximately 2000 km s(exp -1) is thought to originate in gas with N(sub H)greater than or approximately 10(exp 10)cm (exp -2) lying between 0.01 and 9 pc from the central active nucleus. The Ginga X-ray data are consistent with several possibilities: a warm absorber and a cold absorber combined either with partial covering or an unusually strong reflection spectrum. We present ROSAT observations of NGC 3516 which show a strong detection of a warm absorber dominated by a blend of 0 VII/O VIII edges at approximately 0.8 keV with N(sub H) approximately 7x10(exp 21)cm(exp -2), and U:8-12. We argue that NGC 3516 contains an outflowing 'XUV' absorber showing the presence of X-ray absorption edges which are consistent with the presence of broad absorption lines in the old IUE spectra and their disappearance in the new UV observations. Our dynamical model suggests that the O VII absorption edge will continue to weaken compared to the O VIII edge, an easily testable prediction with future missions like AXAF. Eventually the source would be transparent to the X-rays unless a new absorption system is produced.

Mathur, Smita; Wilkes, Belinda; Aldcroft, Thomas

1997-01-01

126

An omnidirectional electromagnetic absorber made of metamaterials  

Microsoft Academic Search

In a recent theoretical work by Narimanov and Kildishev (2009 Appl. Phys. Lett. 95 041106) an optical omnidirectional light absorber based on metamaterials was proposed, in which theoretical analysis and numerical simulations showed that all optical waves hitting the absorber are trapped and absorbed. Here we report the first experimental demonstration of an omnidirectional electromagnetic absorber in the microwave frequency.

Qiang Cheng; Tie Jun Cui; Wei Xiang Jiang; Ben Geng Cai

2010-01-01

127

An omnidirectional electromagnetic absorber made of metamaterials  

Microsoft Academic Search

In a recent theoretical work by Narimanov and Kildishev (2009 Appl. Phys. Lett.95 041106) an optical omnidirectional light absorber based on metamaterials was proposed, in which theoretical analysis and numerical simulations showed that all optical waves hitting the absorber are trapped and absorbed. Here we report the first experimental demonstration of an omnidirectional electromagnetic absorber in the microwave frequency. The

Qiang Cheng; Tie Jun Cui; Wei Xiang Jiang; Ben Geng Cai

2010-01-01

128

Analysis and design of multilayer Jaumann absorbers  

Microsoft Academic Search

In this paper, a transmission line model is constructed to analyze the performance of radar absorbing materials and the reflection characteristic of the resonance frequency. First, the paper introduces some kind of radar absorbing materials. Then, multilayer Jaumann absorbers are also analyzed using Smith Chart. Last, some multilayer Jaumann absorbers can be designed in the paper , which have good

Li Ke; Zhang Xin; Hou Xinyu; Zhang Peng

2011-01-01

129

Oil and fat absorbing polymers  

NASA Technical Reports Server (NTRS)

A method is described for forming a solid network polymer having a minimal amount of crosslinking for use in absorbing fats and oils. The polymer remains solid at a swelling ratio in oil or fat of at least ten and provides an oil absorption greater than 900 weight percent.

Marsh, H. E., Jr. (inventor)

1977-01-01

130

Abbe's law, 210 absorbing media  

E-print Network

Index Abbe's law, 210 absorbing media apparent lack of energy conservation, 197--198 exceptions to reciprocity, 194--199 non­reversibility of optical paths, 196--197 reciprocity principle for, 198 for refraction, 145--146 adjoint, 147--148 angular form, 172 modified, 152 reciprocity principle for, 180

Stanford University

131

Radar Absorbing Applications of Metamaterials  

Microsoft Academic Search

Radar absorbing materials (RAM) is used to camouflage or shield highly reflective surfaces such metallic surfaces from incident electromagnetic (EM) waves. In this paper, we explore the applications of metamaterials as conformal RAM coatings for controlling the reflection of EM waves from metal surfaces. Metamaterials are engineered materials with specially designed metallic resonant structures that are much smaller than the

Vasundara V. Varadan

2007-01-01

132

Reactive absorbers Absorption around resonance  

E-print Network

1 Reactive absorbers · Absorption around resonance = 2 m" (-res) +..... ( m"- c 2/l)=(-res) d d [ m silencers ­ Expansion chamber ­ Branch resonator #12;3 Silencers Source ZS Duct 1 Z1 Duct 2 Z2 Receiver ZR

Berlin,Technische Universität

133

Cold Air Damming  

NSDL National Science Digital Library

Cold Air Damming is part of the Mesoscale Meteorology Primer series. This module first presents a Navy forecast scenario prior to the development of a major cold air damming (CAD) event along the east slopes of the Appalachian Mountains. Then, from a conceptual standpoint, the classic CAD scenario is described in detail, both from an observational and modeling standpoint.

Comet

2001-06-18

134

Cold Sores (HSV-1)  

MedlinePLUS

... sunlight, cold weather, hormone changes in menstruation or pregnancy, tooth extractions, and certain foods and drugs. In a lot of people, the cause is unpredictable. Here's how a cold sore develops: The herpes simplex virus-1, which has been lying dormant in ...

135

Warm absorbers in X-rays (WAX), a comprehensive high resolution grating spectral study of a sample of Seyfert galaxies: I. A global view and frequency of occurrence of warm absorbers  

E-print Network

We present results from a homogeneous analysis of the broadband 0.3-10 keV CCD resolution as well as of soft X-ray high-resolution grating spectra of a hard X-ray flux-limited sample of 26 Seyfert galaxies observed with XMM-Newton. Our goal is to characterise the warm absorber (WA) properties along the line-of-sight to the active nucleus. We significantly detect WAs in $65\\%$ of the sample sources. Our results are consistent with WAs being present in at least half of the Seyfert galaxies in the nearby Universe, in agreement with previous estimates . We find a gap in the distribution of the ionisation parameter in the range $0.5warm absorber flow is probably constituted by a clumpy distribution of discrete clouds rather than a continuous medium. The distribution of the WA column densities for the sources with broad Fe K$\\alpha$ lines are similar to those sources which do not have broadened emission l...

Laha, Sibasish; Dewangan, Gulab C; Chakravorty, Susmita; Kembhavi, Ajit K

2014-01-01

136

Cold Sores (Orofacial Herpes)  

MedlinePLUS

... on the lips and chin are typical of herpes simplex infection. Overview Herpes simplex infection of the mouth and face, known as orofacial herpes simplex, herpes labialis, cold sores, or fever blisters, is ...

137

Cyanobacteria in Cold Ecosystems  

Microsoft Academic Search

Perennially cold environments in which temperatures remain below 5°C are common throughout the biosphere (Margesin and Häggblom\\u000a 2007). In these habitats, the persistent cold temperatures are often accompanied by freeze—thaw cycles, extreme fluctuations\\u000a in irradiance (including ultraviolet radiation), and large variations in nutrient supply and salinity. As a result of these\\u000a constraints, polar and alpine environments contain a reduced biodiversity,

Frédéric Zakhia; Anne-Dorothee Jungblut; Arnaud Taton; Warwick F. Vincent; Annick Wilmotte

138

RADIATIVE TRANSFER IN A CLUMPY UNIVERSE. IV. NEW SYNTHESIS MODELS OF THE COSMIC UV/X-RAY BACKGROUND  

SciTech Connect

We present improved synthesis models of the evolving spectrum of the UV/X-ray diffuse background, updating and extending our previous results. Five new main components are added to our radiative transfer code CUBA: (1) the sawtooth modulation of the background intensity from resonant line absorption in the Lyman series of cosmic hydrogen and helium; (2) the X-ray emission from the obscured and unobscured quasars that gives origin to the X-ray background; (3) a piecewise parameterization of the distribution in redshift and column density of intergalactic absorbers that fits recent measurements of the mean free path of 1 ryd photons; (4) an accurate treatment of the photoionization structure of absorbers, which enters in the calculation of the helium continuum opacity and recombination emissivity; and (5) the UV emission from star-forming galaxies at all redshifts. We provide tables of the predicted H I and He II photoionization and photoheating rates for use, e.g., in cosmological hydrodynamics simulations of the Ly{alpha} forest and a new metallicity-dependent calibration to the UV luminosity density-star formation rate density relation. A 'minimal cosmic reionization model' is also presented in which the galaxy UV emissivity traces recent determinations of the cosmic history of star formation, the luminosity-weighted escape fraction of hydrogen-ionizing radiation increases rapidly with look-back time, the clumping factor of the high-redshift intergalactic medium evolves following the results of hydrodynamic simulations, and Population III stars and miniquasars make a negligible contribution to the metagalactic flux. The model provides a good fit to the hydrogen-ionization rates inferred from flux decrement and proximity effect measurements, predicts that cosmological H II (He III) regions overlap at redshift 6.7 (2.8), and yields an optical depth to Thomson scattering, {tau}{sub es} = 0.084 that is in agreement with Wilkinson Microwave Anisotropy Probe results. Our new background intensities and spectra are sensitive to a number of poorly determined input parameters and suffer from various degeneracies. Their predictive power should be constantly tested against new observations. We are therefore making our redshift-dependent UV/X emissivities and CUBA outputs freely available for public use at http://www.ucolick.org/{approx}pmadau/CUBA.

Haardt, Francesco [Dipartimento di Scienza e alta Tecnologia, Universita dell'Insubria, via Valleggio 11, 22100 Como (Italy); Madau, Piero, E-mail: haardt@uninsubria.it, E-mail: pmadau@ucolick.org [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

2012-02-20

139

Radiative Transfer in a Clumpy Universe. IV. New Synthesis Models of the Cosmic UV/X-Ray Background  

NASA Astrophysics Data System (ADS)

We present improved synthesis models of the evolving spectrum of the UV/X-ray diffuse background, updating and extending our previous results. Five new main components are added to our radiative transfer code CUBA: (1) the sawtooth modulation of the background intensity from resonant line absorption in the Lyman series of cosmic hydrogen and helium; (2) the X-ray emission from the obscured and unobscured quasars that gives origin to the X-ray background; (3) a piecewise parameterization of the distribution in redshift and column density of intergalactic absorbers that fits recent measurements of the mean free path of 1 ryd photons; (4) an accurate treatment of the photoionization structure of absorbers, which enters in the calculation of the helium continuum opacity and recombination emissivity; and (5) the UV emission from star-forming galaxies at all redshifts. We provide tables of the predicted H I and He II photoionization and photoheating rates for use, e.g., in cosmological hydrodynamics simulations of the Ly? forest and a new metallicity-dependent calibration to the UV luminosity density-star formation rate density relation. A "minimal cosmic reionization model" is also presented in which the galaxy UV emissivity traces recent determinations of the cosmic history of star formation, the luminosity-weighted escape fraction of hydrogen-ionizing radiation increases rapidly with look-back time, the clumping factor of the high-redshift intergalactic medium evolves following the results of hydrodynamic simulations, and Population III stars and miniquasars make a negligible contribution to the metagalactic flux. The model provides a good fit to the hydrogen-ionization rates inferred from flux decrement and proximity effect measurements, predicts that cosmological H II (He III) regions overlap at redshift 6.7 (2.8), and yields an optical depth to Thomson scattering, ?es = 0.084 that is in agreement with Wilkinson Microwave Anisotropy Probe results. Our new background intensities and spectra are sensitive to a number of poorly determined input parameters and suffer from various degeneracies. Their predictive power should be constantly tested against new observations. We are therefore making our redshift-dependent UV/X emissivities and CUBA outputs freely available for public use at http://www.ucolick.org/~pmadau/CUBA.

Haardt, Francesco; Madau, Piero

2012-02-01

140

Multiband Metamaterial Absorber at Terahertz Frequencies  

NASA Astrophysics Data System (ADS)

We propose a multi-band metamaterial absorber operating at terahertz frequencies. The design, characterization, and theoretical calculation of the high performance metamaterial absorber are reported. The multi-band metamaterial absorber consists of two metallic layers separated by a dielectric spacer. Theoretical and simulated results show that the metamaterial absorber has four distinct absorption points at frequencies 0.57 THz, 1.03 THz, 1.44 THz and 1.89 THz, with the absorption rates of 99.9%, 90.3%, 83.0%, 96.1%, respectively. Two single band metamaterial absorbers and a dual band metamaterial absorber on the top layer are designed. Some multi-band absorbers can be designed by virtue of combining some single band absorbers. The multiple-reflection theory is used to explain the absorption mechanism of our investigated structures.

Xu, Zong-Cheng; Gao, Run-Mei; Ding, Chun-Feng; Zhang, Ya-Ting; Yao, Jian-Quan

2014-05-01

141

Resolving the Clumpy Structure of the Outflow Winds in the Gravitationally Lensed Quasar SDSS J1029+2623  

NASA Astrophysics Data System (ADS)

We study the geometry and the internal structure of the outflowing wind from the accretion disk of a quasar by observing multiple sightlines with the aid of strong gravitational lensing. Using Subaru/High Dispersion Spectrograph, we performed high-resolution (R ~ 36,000) spectroscopic observations of images A and B of the gravitationally lensed quasar SDSS J1029+2623 (at z em ~ 2.197) whose image separation angle, ? ~ 22.''5, is the largest among those discovered so far. We confirm that the difference in absorption profiles in images A and B discovered by Misawa et al. has remained unchanged since 2010, implying the difference is not due to time variability of the absorption profiles over the delay between the images, ?t ~ 744 days, but rather due to differences along the sightlines. We also discovered a time variation of C IV absorption strength in both images A and B due to a change in the ionization condition. If a typical absorber's size is smaller than its distance from the flux source by more than five orders of magnitude, it should be possible to detect sightline variations among images of other smaller separation, galaxy-scale gravitationally lensed quasars. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Misawa, Toru; Inada, Naohisa; Oguri, Masamune; Gandhi, Poshak; Horiuchi, Takashi; Koyamada, Suzuka; Okamoto, Rina

2014-10-01

142

Resolving the Clumpy Structure of the Outflow Winds in the Gravitationally Lensed Quasar SDSS J1029+2623  

E-print Network

We study the geometry and the internal structure of the outflowing wind from the accretion disk of a quasar by observing multiple sightlines with the aid of strong gravitational lensing. Using Subaru/HDS, we performed high-resolution ($R$ $\\sim$ 36,000) spectroscopic observations of images A and B of the gravitationally lensed quasar SDSS J1029+2623 (at $z_{em}$ $\\sim$ 2.197) whose image separation angle, $\\theta$ $\\sim$ 22$^{\\prime\\prime}\\!\\!$.5, is the largest among those discovered so far. We confirm that the difference in absorption profiles in the images A and B discovered by Misawa et al. (2013) remains unchanged since 2010, implying the difference is not due to time variability of the absorption profiles over the delay between the images, $\\Delta t$ $\\sim$ 744 days, but rather due to differences along the sightlines. We also discovered time variation of C IV absorption strength in both images A and B, due to change of ionization condition. If a typical absorber's size is smaller than its distance from ...

Misawa, Toru; Oguri, Masamune; Gandhi, Poshak; Horiuchi, Takashi; Koyamada, Suzuka; Okamoto, Rina

2014-01-01

143

Scattered and absorbed powers in receiving antennas  

Microsoft Academic Search

This paper discusses the amount of power, which is scattered and absorbed by a receiving antenna and in particular, whether an antenna can absorb the entire power incident upon it. The absorbed and scattered power from dipole arrays in either free space, or over ground plane is considered. By defining a suitable \\

David Pozar

2004-01-01

144

Embedded absorbers for helicopter rotor lag damping  

NASA Astrophysics Data System (ADS)

Radial and chordwise damped vibration absorbers embedded in the rotor blade are compared for rotor lag damping augmentation. Results show that the radial absorber is more effective in transferring damping to the rotor blade lag mode. The chordwise absorber needs to be at a more outboard location and have a larger mass to introduce levels of lag damping comparable to that introduced by the radial absorber. The 1/rev amplitude of a chordwise absorber at the blade tip, per degree of blade lead-lag motion in forward flight, is of the order of 35% of the blade chord, and such a stroke might be difficult to accommodate. The 1/rev amplitude of a radial absorber at 70% span (having significantly lower mass than the chordwise absorber and producing comparable lag damping) is of the order of 4% of the rotor blade span. The static displacement of the radial absorber under centrifugal load needs to be limited using a frequency-dependent (high static stiffness, low dynamic stiffness) or nonlinear spring. The chordwise absorber can also undergo a large static displacement under the chordwise component of the centrifugal load if there is an offset from the feather axis, and this would again have to be limited using a strategy such as a frequency-dependent spring. Significant advantages of the radial absorber are—higher lag damping, lower absorber mass, space for absorber mass travel, and no chordwise travel of blade center of gravity reducing susceptibility to aeroelastic instability and dynamic pitch-link loads.

Byers, Lynn; Gandhi, Farhan

2009-09-01

145

Synchrotron radiation absorber for high density loads  

NASA Astrophysics Data System (ADS)

A design of a special synchrotron radiation absorber for the storage ring VEPP-4M is presented. The density of the synchrotron radiation power on the absorber surface is up to 500 W/mm 2. The absorber is made from a beryllium plate, brazed inside to the copper vacuum chamber, which is intensively water-cooled from outside.

Anashin, V. V.; Kuzminych, V. S.; Trakhtenberg, E. M.; Zholents, A. A.

1991-10-01

146

Adaptive radar absorbing structures with active FSS  

Microsoft Academic Search

A brief description of the theory of passive and active absorbers is presented followed by details of an experimental study into a new design of adaptive absorber. The absorber is a single-layer planar structure based upon the topology of a Salisbury screen, but in which the conventional resistive layer is replaced by an active frequency selective surface (FSS) controlled by

Alan Tennant; Barry Chambers

2002-01-01

147

An introduction to Radar Absorbent Materials (RAM)  

Microsoft Academic Search

The electromagnetic principles of radar absorbent materials are summarized. The fundamental theory of electromagnetic wave propagation in media and at the interfaces between different media is reviewed, and approaches to absorber design are described. The types of materials required and the techniques for measuring their electromagnetic properties and the performance of the finished absorber are outlined. A means of designing

P. G. Lederer

1986-01-01

148

Waveguide characterization of flexible absorbing material  

Microsoft Academic Search

Among the materials with adequate performance to be used as radar absorbing material (RAM), the conducting polymers have been under intensive study due to their excellent potential for application in electromagnetic interference and microwave absorption areas, replacing conventional absorbing materials. The aim of this work is to present electromagnetic characterization of the flexible radar absorbing material at microwave frequency range

L. C. Folgueras; R. Faez; M. C. Rezende

2003-01-01

149

Optimization of ramified absorber networks doing desalination  

Microsoft Academic Search

An iterated function system is used to generate fractal-like ramified graph networks of absorbers, which are optimized for desalination performance. The diffusion equation is solved for the boundary case of constant pressure difference at the absorbers and a constant ambient salt concentration far from the absorbers, while constraining both the total length of the network and the total area of

Martin S. Singleton; Gregor Heiss; Alfred Hübler

2011-01-01

150

Teaching in a Cold Environment.  

ERIC Educational Resources Information Center

Instructors who teach outdoors in an environment so cold as to cause injury must satisfy program objectives while avoiding cold injury to themselves and students, help students focus on learning instead of discomfort, and alleviate some students' intense fear of the cold. Dealing with the cold successfully requires a thorough knowledge of:…

Ewert, Alan

151

Cold Fusion, A Journalistic Investigation  

Microsoft Academic Search

Author of the recent book, The Rebirth of Cold Fusion, and founder of New Energy Times, Steven B. Krivit presents a summary of cold fusion's, past, present and possible future. This talk will briefly review five highlights of the recent New Energy Times investigation into cold fusion research:1. Analysis of early studies that supposedly disproved cold fusion.2. Key early corroborations

Steven B. Krivit

2005-01-01

152

The physics inside the scaling relations for X-ray galaxy clusters: gas clumpiness, gas mass fraction and slope of the pressure profile  

E-print Network

In galaxy clusters, the relations between observables in X-ray and millimeter wave bands and the total mass have normalizations, slopes and redshift evolutions that are simple to estimate in a self-similar scenario. We study these scaling relations and show that they can be efficiently expressed, in a more coherent picture, by fixing the normalizations and slopes to the self-similar predictions, and advocating, as responsible of the observed deviations, only three physical mass-dependent quantities: the gas clumpiness $C$, the gas mass fraction $f_g$ and the logarithmic slope of the thermal pressure profile $\\beta_P$. We use samples of the observed gas masses, temperature, luminosities, and Compton parameters in local clusters to constrain normalization and mass dependence of these 3 physical quantities, and measure: $C^{0.5} f_g = 0.110 (\\pm 0.002 \\pm 0.002) \\left( E_z M / 5 \\times 10^{14} M_{\\odot} \\right)^{0.198 (\\pm 0.025 \\pm 0.04)}$ and $\\beta_P = -d \\ln P/d \\ln r = 3.14 (\\pm 0.04 \\pm 0.02) \\left( E_z M ...

Ettori, S

2014-01-01

153

The Double Absorbing Boundary method  

NASA Astrophysics Data System (ADS)

A new approach is devised for solving wave problems in unbounded domains. It has common features to each of two types of existing techniques: local high-order Absorbing Boundary Conditions (ABC) and Perfectly Matched Layers (PML). However, it is different from both and enjoys relative advantages with respect to both. The new method, called the Double Absorbing Boundary (DAB) method, is based on truncating the unbounded domain to produce a finite computational domain ?, and on applying a local high-order ABC on two parallel artificial boundaries, which are a small distance apart, and thus form a thin non-reflecting layer. Auxiliary variables are defined on the two boundaries and inside the layer bounded by them, and participate in the numerical scheme. The DAB method is first introduced in general terms, using the 2D scalar time-dependent wave equation as a model. Then it is applied to the 1D Klein-Gordon equation, using finite difference discretization in space and time, and to the 2D wave equation in a wave guide, using finite element discretization in space and dissipative time stepping. The computational aspects of the method are discussed, and numerical experiments demonstrate its performance.

Hagstrom, Thomas; Givoli, Dan; Rabinovich, Daniel; Bielak, Jacobo

2014-02-01

154

Cold Regions Bibliography  

NSDL National Science Digital Library

A joint endeavor of the Federal Research Division of the Library of Congress and the US Army Cold Regions Research and Engineering Laboratory (CRREL), this project disseminates information on Antarctica and cold regions science and technology "by maintaining and continually updating a database which is an accumulation of over 40 years of materials on the science and technology of the world's cold regions." This database currently contains over 208,000 records, with about 6,000 accessions annually. After entering a supplied user id and password, users can search the database by keyword, author, or year of publication. Search returns include title, source, and a link to more information, including pages, notes, series, and publisher information. A DOS version of the database is also available for limited periods to qualified researchers. More information is available at the site.

155

Liquid crystal tunable metamaterial absorber.  

PubMed

We present an experimental demonstration of electronically tunable metamaterial absorbers in the terahertz regime. By incorporation of active liquid crystal into strategic locations within the metamaterial unit cell, we are able to modify the absorption by 30% at 2.62 THz, as well as tune the resonant absorption over 4% in bandwidth. Numerical full-wave simulations match well to experiments and clarify the underlying mechanism, i.e., a simultaneous tuning of both the electric and magnetic response that allows for the preservation of the resonant absorption. These results show that fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications. PMID:23679774

Shrekenhamer, David; Chen, Wen-Chen; Padilla, Willie J

2013-04-26

156

Modeling the Absorbing Aerosol Index  

NASA Technical Reports Server (NTRS)

We propose a scheme to model the absorbing aerosol index and improve the biomass carbon inventories by optimizing the difference between TOMS aerosol index (AI) and modeled AI with an inverse model. Two absorbing aerosol types are considered, including biomass carbon and mineral dust. A priori biomass carbon source was generated by Liousse et al [1996]. Mineral dust emission is parameterized according to surface wind and soil moisture using the method developed by Ginoux [2000]. In this initial study, the coupled CCM1 and GRANTOUR model was used to determine the aerosol spatial and temporal distribution. With modeled aerosol concentrations and optical properties, we calculate the radiance at the top of the atmosphere at 340 nm and 380 nm with a radiative transfer model. The contrast of radiance at these two wavelengths will be used to calculate AI. Then we compare the modeled AI with TOMS AI. This paper reports our initial modeling for AI and its comparison with TOMS Nimbus 7 AI. For our follow-on project we will model the global AI with aerosol spatial and temporal distribution recomputed from the IMPACT model and DAO GEOS-1 meteorology fields. Then we will build an inverse model, which applies a Bayesian inverse technique to optimize the agreement of between model and observational data. The inverse model will tune the biomass burning source strength to reduce the difference between modelled AI and TOMS AI. Further simulations with a posteriori biomass carbon sources from the inverse model will be carried out. Results will be compared to available observations such as surface concentration and aerosol optical depth.

Penner, Joyce; Zhang, Sophia

2003-01-01

157

Antioxidant properties of cold-pressed black caraway, carrot, cranberry, and hemp seed oils  

Microsoft Academic Search

Cold-pressed black caraway, carrot, cranberry, and hemp seed oils were extracted with methanol and evaluated for radical-scavenging activities against ABTS+ and DPPH, chelating activity, oxygen radical absorbing capacity (ORAC), and total phenolic contents (TPC). All the oil extracts had significant antioxidant activities. The ORAC value ranged from 28 to 220 ?mol TE\\/g oil for the cold-pressed hemp, carrot, and black

Liangli Lucy Yu; Kequan Kevin Zhou; John Parry

2005-01-01

158

The possibilities for initiation of the cold fusion of the deuterons in the hydrogen storage materials  

Microsoft Academic Search

The results of the research and the calculation of this paper, indicates that the D–D cold fusion will be initiated in the hydrogen storage materials which probably absorbed deuterium. There are two possible mechanisms of the D–D cold fusion. The first is the estimated acceleration mechanism in the cracks with the D–D fusion cross sections of (0.04–30) mb. The second

J. Xiao; P. Li

1999-01-01

159

Ultra-strong Mg II absorbers as a signature of cool intragroup gas  

NASA Astrophysics Data System (ADS)

We present the results of a spectroscopic survey of galaxies in the vicinity of an ultra-strong Mg II ??2786, 2803 absorber of rest-frame absorption equivalent width Wr(2796) = 4.2 Å at z = 0.5624. This absorber was originally found at projected separation ? = 246 kpc of a luminous red galaxy (LRG) at z = 0.5604. Inamori-Magellan Areal Camera and Spectrograph (IMAC) spectroscopy has revealed two galaxies at ? < 60 kpc (z = 0.5623 and z = 0.5621) and a third one at ? = 209 kpc (z = 0.5623) near the redshift of the absorber. These findings indicate that the absorbing gas resides in a group environment. Combining Sloan Digital Sky Survey (SDSS) broad-band photometry with additional B-, Ks-band images and optical spectroscopy, we perform a stellar population synthesis analysis of the group members to characterize their star formation histories, on-going star formation rates (SFR), and stellar masses. We find that the two group members at ? < 60 kpc are best characterized by old stellar populations (>1 Gyr) and little on-going star formation activity (SFR < 2.9 M? yr-1), while the third object at ? = 209 kpc exhibits [O II]- and continuum-derived SFR consistent with SFR > 3.0 M? yr-1. Including the two ultra-strong Mg II absorbers analysed by Nestor et al., this is the third ultra-strong Mg II absorber for which a detailed study of the galactic environment is available. All three absorbers are found in galaxy groups. We examine different physical mechanisms giving rise to the absorbing gas including starburst-driven outflows, cold filaments, extended rotating discs and stripped gas. We argue that the large equivalent width observed in these absorbers is more likely due to the gas dynamics of the intragroup medium rather than driven by starburst outflows.

Gauthier, Jean-René

2013-06-01

160

Cold War Propaganda.  

ERIC Educational Resources Information Center

Briefly discusses the development of Cold War propaganda in the United States, Canada, and the USSR after 1947. Presents two movie reviews and a Canadian magazine advertisement of the period which illustrate the harshness of propaganda used by both sides in the immediate postwar years. (GEA)

Bennett, Paul W.

1988-01-01

161

Cold Spring Mount Washington  

E-print Network

Spring Mount Washington Light Rail McAuley Hall Falls@ Woodheights Falls@ 43rd Keswick North Bldg Keswick 83 JonesFallsExpy 83 JonesFallsExpy 83 FallsRd N S EW Homewood - Mt. Washington Shuttle NextBus textth Keswick North Building Falls at 42nd Falls at Cold Spring Mount Washington Light Rail McAuley Hall

Hattar, Samer

162

Teaching "In Cold Blood."  

ERIC Educational Resources Information Center

The Truman Capote nonfiction novel, "In Cold Blood," which reflects for adolescents the immediacy of the real world, illuminates (1) social issues--capital punishment, environmental influence, and the gap between the "haves" and "have-nots," (2) moral issues--the complexity of man's nature, the responsibility of one man for another, and the place…

Berbrich, Joan D.

1967-01-01

163

Baby, it's cold outside....  

PubMed

For officers and other employees stationed outdoors in parking areas or on perimeter patrol during cold weather the risks of hypothermia and frostbite may be very real. In this article, the author explains how these two serious medical conditions can be prevented and treated. PMID:22423532

Kissane, Rhonda

2012-01-01

164

Recent Cold War Studies  

ERIC Educational Resources Information Center

Cold War historiography has undergone major changes since the 1991 collapse of the Soviet Union. For two years (1992-1993) the principal Soviet archives fell open to scholars, and although some of the richest holdings are now once again closed, new information continues to find its way out. Moreover, critical documentary information has become…

Pineo, Ronn

2003-01-01

165

Controlling Nanoparticle Aggregation in Colloidal Microwave Absorbers via Interface Chemistry  

E-print Network

Microwave absorbing materials for military applications have been investigated since the advent of radar systems. The majority of these systems, including Salisbury screens, Jaumann absorbers, radar absorbing absorber that utilizes ferromagnetic particles in combination with a dielectric matrix material offers

Stowell, Michael

166

Electromagnetic scattering by pyramidal and wedge absorber  

NASA Technical Reports Server (NTRS)

Electromagnetic scattering from pyramidal and wedge absorbers used to line the walls of modern anechoic chambers is measured and compared with theoretically predicted values. The theoretical performance for various angles of incidence is studied. It is shown that a pyramidal absorber scatters electromagnetic energy more as a random rough surface does. The apparent reflection coefficient from an absorber wall illuminated by a plane wave can be much less than the normal absorber specifications quoted by the manufacturer. For angles near grazing incidence, pyramidal absorbers give a large backscattered field from the pyramid side-faces or edges. The wedge absorber was found to give small backscattered fields for near-grazing incidence. Based on this study, some new guidelines for the design of anechoic chambers are advocated because the specular scattering models used at present do not appear valid for pyramids that are large compared to the wavelength.

Dewitt, Brian T.; Burnside, Walter D.

1988-01-01

167

An omnidirectional electromagnetic absorber made of metamaterials  

NASA Astrophysics Data System (ADS)

In a recent theoretical work by Narimanov and Kildishev (2009 Appl. Phys. Lett. 95 041106) an optical omnidirectional light absorber based on metamaterials was proposed, in which theoretical analysis and numerical simulations showed that all optical waves hitting the absorber are trapped and absorbed. Here we report the first experimental demonstration of an omnidirectional electromagnetic absorber in the microwave frequency. The proposed device is composed of non-resonant and resonant metamaterial structures, which can trap and absorb electromagnetic waves coming from all directions spirally inwards without any reflections due to the local control of electromagnetic fields. It is shown that the absorption rate can reach 99 per cent in the microwave frequency. The all-directional full absorption property makes the device behave like an 'electromagnetic black body', and the wave trapping and absorbing properties simulate, to some extent, an 'electromagnetic black hole.' We expect that such a device could be used as a thermal emitting source and to harvest electromagnetic waves.

Cheng, Qiang; Cui, Tie Jun; Jiang, Wei Xiang; Cai, Ben Geng

2010-06-01

168

Magnetic field effects on microwave absorbing materials  

NASA Technical Reports Server (NTRS)

The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

1991-01-01

169

A planar polarization-insensitive metamaterial absorber  

NASA Astrophysics Data System (ADS)

The model of the polarization-insensitive metamaterial (MM) absorber composed of split cross-ring resonator (SCRR), cave-cross resonator (CCR) and dielectric substrate was proposed at microwave frequencies. Based on perfect impedance-matched ( z˜(?)=1) to the free space, the single unit cell could achieve near-unity absorbance by properly assembling the sandwich structure. We have simulated and measured the reflectivity and transmission properties of a planar MM absorber with the thickness of 0.6 mm. The absorptivity of a single layer MM absorber achieve greater than 96% around 10.07 GHz in experiments and 98% in simulations for incident electromagnetic (EM) wave with different polarizations.

Cheng, Yongzhi; Yang, Helin; Cheng, Zhengze; Xiao, Boxun

2011-02-01

170

Metamaterial Electromagnetic Absorbers and Plasmonic Structures.  

E-print Network

??In this thesis metamaterial radar absorbers and plasmonic structures have been investigated. Following a brief overview covering metamaterial structures, and their applications in various areas… (more)

Noor, Adnan

2010-01-01

171

Cold Weather and Cardiovascular Disease  

MedlinePLUS

Cold Weather and Cardiovascular Disease Updated:Oct 28,2014 Th is winter season will bring cooler temperatures and ice ... for some. It’s important to know how cold weather can affect your heart, especially if you have ...

172

The origin of cold gas in giant elliptical galaxies and its role in fuelling radio-mode AGN feedback  

NASA Astrophysics Data System (ADS)

The nature and origin of the cold interstellar medium (ISM) in early-type galaxies are still a matter of debate, and understanding the role of this component in galaxy evolution and in fuelling the central supermassive black holes requires more observational constraints. Here, we present a multiwavelength study of the ISM in eight nearby, X-ray and optically bright, giant elliptical galaxies, all central dominant members of relatively low-mass groups. Using far-infrared spectral imaging with the Herschel Photodetector Array Camera & Spectrometer, we map the emission of cold gas in the cooling lines of [C II]?157 ?m, [O I] ?63 ?m and [O Ib] ?145 ?m. Additionally, we present H?+[N II] imaging of warm ionized gas with the Southern Astrophysical Research (SOAR) telescope, and a study of the thermodynamic structure of the hot X-ray emitting plasma with Chandra. All systems with extended H? emission in our sample (6/8 galaxies) display significant [C II] line emission indicating the presence of reservoirs of cold gas. This emission is cospatial with the optical H?+[N II] emitting nebulae and the lowest entropy soft X-ray emitting plasma. The entropy profiles of the hot galactic atmospheres show a clear dichotomy, with the systems displaying extended emission-line nebulae having lower entropies beyond r ? 1 kpc than the cold-gas-poor systems. We show that while the hot atmospheres of the cold-gas-poor galaxies are thermally stable outside of their innermost cores, the atmospheres of the cold-gas-rich systems are prone to cooling instabilities. This provides considerable weight to the argument that cold gas in giant ellipticals is produced chiefly by cooling from the hot phase. We show that cooling instabilities may develop more easily in rotating systems and discuss an alternative condition for thermal instability for this case. The hot atmospheres of cold-gas-rich galaxies display disturbed morphologies indicating that the accretion of clumpy multiphase gas in these systems may result in variable power output of the AGN jets, potentially triggering sporadic, larger outbursts. In the two cold-gas-poor, X-ray morphologically relaxed galaxies of our sample, NGC 1399 and NGC 4472, powerful AGN outbursts may have destroyed or removed most of the cold gas from the cores, allowing the jets to propagate and deposit most of their energy further out, increasing the entropy of the hot galactic atmospheres and leaving their cores relatively undisturbed.

Werner, N.; Oonk, J. B. R.; Sun, M.; Nulsen, P. E. J.; Allen, S. W.; Canning, R. E. A.; Simionescu, A.; Hoffer, A.; Connor, T.; Donahue, M.; Edge, A. C.; Fabian, A. C.; von der Linden, A.; Reynolds, C. S.; Ruszkowski, M.

2014-04-01

173

Remedies for Common Cold Symptoms  

PubMed Central

Individuals suffering from intolerable symptoms of the common cold can now be advised of safe and effective products for symptomatic relief. This article describes and discusses four categories of drugs used to treat the common cold. To simplify the product selection process for family physicians, suggestions are included for possible ingredients for treatments of specific cold symptoms. PMID:21234087

Miller, Penny F.

1991-01-01

174

Skewed Frequency Selective Surface Absorber  

NASA Astrophysics Data System (ADS)

In this paper, a skewed Frequency Selective Surface (FSS) absorber based on cross-dipole elements is presented. The proposed FSS design provides good frequency stability for oblique incidences. It provides better absorption rate for 5-GHz WLAN frequency band and allow other communication bands to pass through it. Also, the absorption in the stop-band reduces multipath fading of additional WLAN signals which occurred due to the placement of conducting/reflecting FSS. The FSS design consists of two layers; first layer consists of conducting cross-dipole and second layer consists of resistive cross-dipole placed in-front of the first layer. The periodicity of both elements is same. Asymmetric property is applied to FSS elements by taking a reference of central element. This technique leads to achieve a maximum stability in the stop-band. Simulated results demonstrated that the proposed FSS design has a stable frequency response for 5-GHz frequency band for both horizontal (TE) and vertical (TM) polarizations when the incident wave angle varied from 0 0 to 45 0.

Rafique, Umair; Khan, M. Arif; Afzal, M. Tausif; Malik, Fahad; Qasim, Shahzaib

2012-12-01

175

Device for absorbing mechanical shock  

DOEpatents

This invention is a comparatively inexpensive but efficient shock-absorbing device having special application to the protection of shipping and storage cylinders. In a typical application, two of the devices are strapped to a cylinder to serve as saddle-type supports for the cylinder during storage and to protect the cylinder in the event it is dropped during lifting or lowering operations. In its preferred form, the invention includes a hardwood plank whose grain runs in the longitudinal direction. The basal portion of the plank is of solid cross-section, whereas the upper face of the plank is cut away to form a concave surface fittable against the sidewall of a storage cylinder. The concave surface is divided into a series of segments by transversely extending, throughgoing relief slots. A layer of elastomeric material is positioned on the concave face, the elastomer being extrudable into slots when pressed against the segments by a preselected pressure characteristic of a high-energy impact. The compressive, tensile, and shear properties of the hardwood and the elastomer are utilized in combination to provide a surprisingly high energy-absorption capability.

Newlon, Charles E. (Knoxville, TN)

1980-01-01

176

Radial cold trap  

DOEpatents

The radial cold trap comprises a housing having a plurality of mesh bands disposed therein. The mesh bands comprise concentrically arranged bands of mesh with the mesh specific surface area of each band increasing from the outermost mesh band to the innermost mesh band. An inlet nozzle is attached to the outside section of the housing while an outlet nozzle is attached to the inner portion of the housing so as to be concentrically connected to the innermost mesh band. An inlet baffle having orifices therein may be disposed around the outermost mesh band and within the housing for directing the flow of the fluid from the inlet nozzle to the outermost mesh band in a uniform manner. The flow of fluid passes through each consecutive mesh band and into the outlet nozzle. The circular pattern of the symmetrically arranged mesh packing allows for better utilization of the entire cold trap volume. 2 figs.

Grundy, B.R.

1981-09-29

177

Cold heteromolecular dipolar collisions.  

PubMed

Cold molecules promise to reveal a rich set of novel collision dynamics in the low-energy regime. By combining for the first time the techniques of Stark deceleration, magnetic trapping, and cryogenic buffer gas cooling, we present the first experimental observation of cold collisions between two different species of state-selected neutral polar molecules. This has enabled an absolute measurement of the total trap loss cross sections between OH and ND(3) at a mean collision energy of 3.6 cm(-1) (5 K). Due to the dipolar interaction, the total cross section increases upon application of an external polarizing electric field. Cross sections computed from ab initio potential energy surfaces are in agreement with the measured value at zero external electric field. The theory presented here represents the first such analysis of collisions between a (2)? radical and a closed-shell polyatomic molecule. PMID:21881670

Sawyer, Brian C; Stuhl, Benjamin K; Yeo, Mark; Tscherbul, Timur V; Hummon, Matthew T; Xia, Yong; K?os, Jacek; Patterson, David; Doyle, John M; Ye, Jun

2011-11-14

178

Hot and Cold  

NSDL National Science Digital Library

In this chemistry challenge, learners discover that many chemical reactions involve heat loss or gain. With this understanding, they try to find a combination of chemicals that could be used to make an instant cold pack. They are given baking soda, ammonium nitrate, calcium chloride, and potassium chloride, along with vinegar and water (3% hydrogen peroxide and yeast can also be used). Learners combine chemicals into calorimeters, then use thermometers to measure how the temperature changes. Calorimeters can be made by pushing a heated test tube into home insulation foam (instructions in PDF) or can be purchased (one source is Flinn Scientific). The water and ammonium nitrate, and vinegar and baking soda, are candidates for making a cold pack.

Sciencenter

2014-08-27

179

Cold nuclear fusion  

Microsoft Academic Search

The possibility that negative muons could catalyze nuclear fusion was suggested on theoretical grounds by F.C. Frank and A.D. Sakharov in the late 1940s; the first experimental observations of the process followed serendipitously a decade later, in experiments at Berkeley by L.W. Alvarez. The fastest mechanism for muon-catalyzed, or 'cold' fusion, was suggested by Vesman (1967); it depends on a

Johann Rafelski; Steven E. Jones

1987-01-01

180

Teachers Debate Cold Fusion  

NASA Astrophysics Data System (ADS)

What follows is a collection of messages about cold fusion from teachers. The messages were posted on the internet discussion list, Phys-L, or were sent to me in private. They illustrate a wide range of opinion. Phys-L is a list dedicated to learning and teaching physics with 700 subscribers from over 35 countries, the majority of whom are physics educators. <>.

Kowalski, Ludwik

2005-12-01

181

COLPEX - Cold Pool Experiment  

Microsoft Academic Search

Planning has started towards designing a new field campaign aimed at studying the behaviour of the boundary layer over complex terrain. Of specific interest is the formation of cold-pools in valleys during stable night-time conditions. The field campaign will run continuously until the end of the winter in 2009\\/10. The experiment will make use of a wide variety of ground-based

H. Wells; J. Price; V. Horlacher; P. F. Sheridan; S. B. Vosper; A. R. Brown; S. D. Mobbs; A. N. Ross

2009-01-01

182

Cold nuclear fusion  

SciTech Connect

Recent accelerator experiments on fusion of various elements have clearly demonstrated that the effective cross-sections of these reactions depend on what material the target particle is placed in. In these experiments, there was a significant increase in the probability of interaction when target nuclei are imbedded in a conducting crystal or are a part of it. These experiments open a new perspective on the problem of so-called cold nuclear fusion.

Tsyganov, E. N., E-mail: edward.tsyganov@utsouthwestern.edu [University of Texas Southwestern Medical Center at Dallas (United States)

2012-02-15

183

Cold fusion prospects  

Microsoft Academic Search

The requirements for cold fusion may include, but are not limited to the following: a nuclear mass-energy resonance with an excitation level in the compound nucleus or in two output nuclei; very high density; a large neutron capture cross-section isotope and a neutron-rich isotope; overlapping de Broglie interaction wavelengths; nuclear spin and polarizability compatibility; and\\/or catalytic action by a passing

1989-01-01

184

Gravitational wave detection by bounded cold electronic plasma in a long pipe  

E-print Network

We intend to propose an experimental sketch to detect gravitational waves (GW) directly, using an cold electronic plasma in a long pipe. By considering an cold electronic plasma in a long pipe, the Maxwell equations in 3+1 formalism will be invoked to relate gravitational waves to the perturbations of plasma particles. It will be shown that the impact of GW on cold electronic plasma causes disturbances on the paths of the electrons. Those electrons that absorb energy from GW will pass through the potential barrier at the end of the pipe. Therefore, crossing of some electrons over the barrier will imply the existence of the GW.

O. Jalili; S. Rouhani; M. V. Takook

2013-10-15

185

Cold Stowage Flight Systems  

NASA Technical Reports Server (NTRS)

The International Space Station (ISS) provides a test bed for researchers to perform science experiments in a variety of fields, including human research, life sciences, and space medicine. Many of the experiments being conducted today require science samples to be stored and transported in a temperature controlled environment. NASA provides several systems which aide researchers in preserving their science. On orbit systems provided by NASA include the Minus Eighty Laboratory freezer for ISS (MELFI), Microgravity Experiment Research Locker Incubator (MERLIN), and Glacier. These freezers use different technologies to provide rapid cooling and cold stowage at different temperature levels on board ISS. Systems available to researchers during transportation to and from ISS are MERLIN, Glacier, and Coldbag. Coldbag is a passive cold stowage system that uses phase change materials. Details of these current technologies will be provided along with operational experience gained to date. With shuttle retirement looming, NASA has protected the capability to provide a temperature controlled environment during transportation to and from the ISS with the use of Glacier and Coldbags, which are compatible with future commercial vehicles including SpaceX's Dragon Capsule, and Orbital s Cygnus vehicle. This paper will discuss the capability of the current cold stowage hardware and how it may continue to support NASA s mission on ISS and in future exploration missions.

Campana, Sharon

2010-01-01

186

Cold Stowage Flight Systems  

NASA Technical Reports Server (NTRS)

The International Space Station (ISS) provides a test bed for researchers to perform science experiments in a variety of fields, including human research, life sciences, and space medicine. Many of the experiments being conducted today require science samples to be stored and transported in a temperature controlled environment. NASA provides several systems which aid researchers in preserving their science. On orbit systems provided by NASA include the Minus Eighty Laboratory freezer for ISS (MELFI), Microgravity Experiment Research Locker Incubator (MERLIN), and Glacier. These freezers use different technologies to provide rapid cooling and cold stowage at different temperature levels on board ISS. Systems available to researchers during transportation to and from ISS are MERLIN, Glacier, and Coldbag. Coldbag is a passive cold stowage system that uses phase change materials to maintain temperature. Details of these current technologies are provided along with operational experience gained to date. This paper discusses the capability of the current cold stowage hardware and how it may continue to support NASA s mission on ISS and in future exploration missions.

Campana, Sharon E.; Melendez, David T.

2011-01-01

187

Mechanical testing of absorbable suture anchors  

Microsoft Academic Search

Purpose: Absorbable suture anchors offer great advantages but are made of mechanically weak material. The weakest link in the fixation of soft tissue to bone may therefore be the anchor itself. In this study, several commercially available anchors were mechanically tested in vitro. Type of study: Biomechanical bench study. Methods: Twelve absorbable suture anchor models were implanted into an artificial

Dominik C. Meyer; Sandro F. Fucentese; Kurt Ruffieux; Hilaire A. C. Jacob; Christian Gerber

2003-01-01

188

A reinterpretation of the metamaterial perfect absorber  

E-print Network

We analytically prove that the appearance of two almost, but not exactly out-of-phase currents inside a metamaterial is necessary for a perfect absorber. We further show that although evanescent waves do not contribute to far fields scattered by the perfect absorber, they however must consume the electromagnetic energy significantly.

Zeng, Yong; Dalvit, Diego A R

2012-01-01

189

Torsional vibration reduction using passive nonlinear absorbers  

Microsoft Academic Search

This paper considers the dynamic performance of systems of centrifugal pendulum vibration absorbers that are used to attenuate torsional vibrations in rotating systems. These absorbers, which can be found in certain IC engines and helicopter rotors, consist of movable masses whose centers of mass are kinematically restricted to move along prescribed paths relative to the rotor of interest. The most

Steven W. Shaw; Abdallah Alsuwaiyan

2000-01-01

190

Pyro-adaptive impact energy absorber  

Microsoft Academic Search

The paper contains a proposal of energy dissipation density controlling in lightweight thinwalled structures by reducing their crushing stiffness during an impact process. For small scale laboratory experiments, low-energy-dissipation absorber was developed. Prismatic absorber made of thin lead sheets can dissipate the impact energy at two energy density levels. Moving the concept to the real steel or aluminum structures can

Marian Ostrowski; Paulius Griskevicius; Jan Holnicki-Szulc

191

Solar energy absorber apparatus and method  

Microsoft Academic Search

An improved apparatus and method for absorbing solar energy, the apparatus providing a sealed envelope having a transparent upper panel with a solar energy absorbing panel thermally isolated against convective and conductive heat losses by a partial vacuum in the sealed envelope. The transparent panel has an upwardly extending curvilinear surface which increases its strength characteristics against the pressure differential

Johnson

1982-01-01

192

Solar energy absorber apparatus and method  

Microsoft Academic Search

An improved apparatus and method is presented for absorbing solar energy. The apparatus provides a sealed envelope having a transparent upper panel with a solar energy absorbing panel thermally isolated against convective and conductive heat losses by a partial vacuum in the sealed envelope. The transparent panel has an upwardly extending curvilinear surface which increases its strength characteristics against the

Johnson

1980-01-01

193

Diffraction can mimic saturation in multiphoton absorbers  

NASA Astrophysics Data System (ADS)

Many traditional investigations of saturation in multiphoton absorbers with the z-scan method use an approximate analytical formula that assumes a steady-state approximation. Using a numerical simulation for Maxwell's equations for laser propagation including diffraction and coupled electron population dynamics, we show that the commonly used analytical formula for determining saturation in multiphoton absorbers is often incorrect, even when the sample thickness is only one diffraction length. Using published experimental data on an organic chromophore, we show that saturation, in fact, does not occur at the laser intensity values predicted for these two and three photon absorbers. We numerically fit the published experimental z-scan data and obtain new absorption coefficients for multiphoton absorbers that accurately reflect their intrinsic values. The new values are from three to ten times larger than the published values. Because multiphoton absorbers are being used more extensively in many applications such as optical limiter, medical diagnostics and two photon microscopy, it is important to have accurate values for the two and three-photon absorption coefficients. Knowing the real value of the multiphoton absorber coefficients, even for a single diffraction length, is therefore of the utmost importance. In particular, the laser intensity at which the absorber saturates can determine which absorber is useful for a particular application.

Potasek, M.; Parilov, E.; Walker, M.

2014-03-01

194

Wideband thin resistive metamaterial radar absorbing screen  

Microsoft Academic Search

It has been demonstrated that two layer metamaterial Hilbert curve array constructed from low conductivity material can act as a thin wideband radar absorbing screen. The advantage of using Hilbert curve over traditional circuit analogue radar absorbing screen is the smaller unit cell size, resulting in reduced coupling to higher order Floquent modes and reduced diffraction effects, which in turn

A. Noor; Zhirun Hu; H. H. Ouslimani; A. Priou

2009-01-01

195

The design of broadband radar absorbing surfaces  

Microsoft Academic Search

There has been a growing and widespread interest in radar absorbing material technology. As the name implies, radar absorbing materials or RAM's are coatings whose electric and magnetic properties have been selected to allow the absorption of microwave energy at discrete or broadband frequencies. In military applications low radar cross section (RCS) of a vehicle may be required in order

Go H. Suk

1990-01-01

196

Electromagnetic analysis of active radar absorbers  

Microsoft Academic Search

The details of an experimental active radar absorber have been presented. The absorber is based on the topology of a Salisbury screen but uses an active impedance layer to provide reflectivity tuning. The active impedance layer is a FSS controlled by semiconductor pin diodes. Measured reflectivity characteristics have been presented and compared to predictions obtained from a simple equivalent circuit

P. N. Kaleeba; A. Tennant; B. Chambers; J. P. Idez

2003-01-01

197

Modelling of magnetic radar absorbing composites  

Microsoft Academic Search

This paper addresses the modelling of radar absorbing composite layers with ferromagnetic inclusions. The radar absorbing properties of these layers are strongly determined by the effective permeability of the composite material. The applicability of mixing formulas is discussed to determine the effective permeability. Furthermore, the RF-frequency behaviour of ferromagnetic inclusions is described. The mixing formulas and the RF-frequency behaviour of

Harmen Schippers; Tomas Lundin; Jaap Heijstek

2010-01-01

198

An Absorbing Boundary Condition Based on Anechoic Absorber For EM Scattering Computation  

Microsoft Academic Search

A novel absorbing boundary condition (ABC), to be used with finite difference and finite element electromagnetic radiation and scattering problems is described. It is based on anechoic chamber absorber foam geometry, with specified complex permittivity and permeability. The advantage of this absorbing boundary is that it prevents reflections from much wider incident angles than currently used lattice termination conditions. Since

C. M. Rappaport; L. J. Bahrmasel

1992-01-01

199

On-site wastewater treatment using unsaturated absorbent biofilters  

SciTech Connect

A new type of single-pass aerobic biofilter is being developed as an alternative to the conventional septic tile bed and for treatment of wastewater in general. The Waterloo Biofilter uses absorbent Inter media that combine long retention times, separate flowpaths for wastewater and air, and large surface areas, thereby enabling loading rates 10 times greater than that for solid particle filter media. Although absorbent sphagnum peat and coarse sand plug readily at loading rates of 50 to 80 cm d{sup -1}, absorbent plastic particles provide consistent treatment with no plugging problems. The latest field trial removes 97.8% BOD{sub 7}, 96.1% TSS, and 99.5% fecal conform bacteria with 12 to 16{degrees}C wastewater loaded at 49 cm d{sup -1}. Surge Bows up to 204 cm d{sup -1} over several days are handled with little effect on effluent quality. In laboratory column experiments, removal of fecal coliforms averages >99.99% at 80 cm d{sup -1} loading, and >99.999% at 10 cm d{sup -1} after a 10- to 14-d acclimatization period. Ammonium is thoroughly oxidized to NO{sub 3}{sup -} with typically <2.5 mg L{sup - 1} NH{sub 4}{sup +}-N in the effluent. Overall treatment improves with forced air flow compared with natural convection. Cold influent and plugging by freezing are the main causes of poor treatment. This biofilter could find general application in renovating polluted water, including water for domestic consumption in developing regions of the world. 29 refs., 7 figs., 6 tabs.

Jowett, E.C.; McMaster, M.L. [Univ. of Waterloo, Waterloo, Ontario (Canada)

1995-01-01

200

Solar sustained plasma/absorber conceptual design  

NASA Technical Reports Server (NTRS)

A space power system concept was evaluated which uses concentrated solar energy to heat a working fluid to temperatures as high as 4000 K. The high temperature working fluid could be used for efficient electric power production in advanced thermal or magnetohydrodynamic conversion cycles. Energy absorber configurations utilizing particles or cesium vapor absorber material were investigaed. Results of detailed radiant heat transfer calculations indicated approximately 86 percent of the incident solar energy could be absorbed within a 12-cm-dia flowing stream of gas borne carbon particles. Calculated total energy absorption in the cesium vapor seeded absorber configuration ranged from 34 percent to 64 percent of the incident solar energy. Solar flux concentration ratios of between approximately 3000 and 10,000 will be required to sustain absorber temperatures in the range from 3000 K to 4000 K.

Rodgers, R. J.; Krascella, N. L.; Kendall, J. S.

1979-01-01

201

Torsional vibration reduction using passive nonlinear absorbers  

NASA Astrophysics Data System (ADS)

This paper considers the dynamic performance of systems of centrifugal pendulum vibration absorbers that are used to attenuate torsional vibrations in rotating systems. These absorbers, which can be found in certain IC engines and helicopter rotors, consist of movable masses whose centers of mass are kinematically restricted to move along prescribed paths relative to the rotor of interest. The most common choice for absorber paths are simple circles that are slightly mistuned from the desired order, so that undesirable nonlinear behaviors are avoided when the absorbers undergo large amplitude motions. In this work we consider a range of different path types and tunings, with the goal of optimizing performance over a wide operating range. This analytical study relies on a mathematical model of a rotor fitted with N identical, general-path absorbers, and utilizes perturbation techniques to obtain analytical estimates for the response of the rotor and the absorbers. The results are used to select path parameters based on selected performance measures, and the results are verified via simulation studies. It is shown that slightly overtuned cycloidal paths provide excellent vibration reduction characteristics and prevent the occurrence of nonlinear instabilities and vibration localization in the response of the absorbers.

Shaw, Steven W.; Alsuwaiyan, Abdallah

2000-04-01

202

Some like it cold: response of microorganisms to cold shock  

Microsoft Academic Search

Bacteria respond to an abrupt decrease in temperature with a specific response, in which cold-induced proteins (CIPs) are\\u000a transiently expressed at a higher level. Employing two-dimensional gel electrophoresis, several CIPs have been identified.\\u000a In spite of this, the overall function of the cold shock response is unclear. Recently, the main attention has focused on\\u000a a group of conserved cold shock

Peter Graumann; Mohamed A. Marahiel

1996-01-01

203

Annihilating cold dark matter  

PubMed

Structure formation with cold dark matter (CDM) predicts halos with a central density cusp, which are observationally disfavored. If CDM particles have an annihilation cross section sigmav approximately 10(-29)(m/GeV) cm(2), then annihilations will soften the cusps. We discuss plausible scenarios for avoiding the early Universe annihilation catastrophe that could result from such a large cross section. The predicted scaling of core density with halo mass depends upon the velocity dependence of sigmav, and s-wave annihilation leads to a core density nearly independent of halo mass, which seems consistent with observations. PMID:11030890

Kaplinghat; Knox; Turner

2000-10-16

204

Peregrinations on cold fusion  

SciTech Connect

Attention is focused on the possibility of resonance-enhanced deuteron Coulomb barrier penetration. Because of the many-body nature of the interactions of room-temperature deuterons diffusing through a lattice possessing deuterons in many of the interstitial positions, the diffusing deuterons can resonate on the atomic scale in the potential wells bounded by the ascending walls of adjacent Coulomb barriers and thereby penetrate the Coulomb barriers in a fashion vastly underestimated by two-body calculations in which wells for possible resonance are absent. Indeed, perhaps the lack of robust reproducibility in cold fusion originates from the narrowness of such transmission resonances. 4 refs., 1 fig.

Turner, L.

1989-01-01

205

Customised broadband metamaterial absorbers for arbitrary polarisation  

E-print Network

This paper shows that customised broadband absorption of electromagnetic waves having arbitrary polarisation is possible by use of lossy cut-wire (CW) metamaterials. These useful features are confirmed by numerical simulations in which different lengths of CW pairs are combined as one periodic metamaterial unit and placed near to a perfect electric conductor (PEC). So far metamaterial absorbers have exhibited some interesting features, which are not available from conventional absorbers, e.g. straightforward adjustment of electromagnetic properties and size reduction. The paper shows how with proper design a broad range of absorber characteristics may be obtained.

Wakatsuchi, Hiroki; Christopoulos, Christos; Paul, John

2010-01-01

206

Microwave diode switchable metamaterial reflector/absorber  

NASA Astrophysics Data System (ADS)

We embed diodes as active circuit elements within a metamaterial to implement a switchable metamaterial reflector/absorber at microwave frequencies. Diodes are placed in series with the unit cells of the metamaterial array. This results in just a pair of control lines to actively tune all the diodes in a metamaterial. Diodes can be tuned on and off to switch the function of the metamaterial between a perfect absorber and a reflector. The design, simulation, and experimental results of a switchable reflector/absorber in 2-6 GHz range are presented.

Xu, Wangren; Sonkusale, Sameer

2013-07-01

207

Plasmonic and Metamaterial Structures as Electromagnetic Absorbers  

E-print Network

Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrow band absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, bio-sensing, etc. In other applications such as solar energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple resonances together, exciting phase resonances, slowing down light by anisotropic metamaterials, employing high loss materials and so on.

Cui, Yanxia; Jin, Yi; Ding, Fei; Yang, Liu; Ye, Yuqian; Zhong, Shoumin; Lin, Yinyue; He, Sailing

2014-01-01

208

Customised broadband metamaterial absorbers for arbitrary polarisation.  

PubMed

This paper shows that customised broadband absorption of electromagnetic waves having arbitrary polarisation is possible by use of lossy cut-wire (CW) metamaterials. These useful features are confirmed by numerical simulations in which different lengths of CW pairs are combined as one periodic metamaterial unit and placed near to a perfect electric conductor (PEC). So far metamaterial absorbers have exhibited some interesting features, which are not available from conventional absorbers, e.g. straightforward adjustment of electromagnetic properties and size reduction. The paper shows how with proper design a broad range of absorber characteristics may be obtained. PMID:20941120

Wakatsuchi, Hiroki; Greedy, Stephen; Christopoulos, Christos; Paul, John

2010-10-11

209

Conformal metamaterial absorber for curved surface.  

PubMed

In this paper, three different unit cells are designed on the basis split-ring-cross resonators, and each unit cell has an absorption rate greater than 90% at incident angles of 0°, 30°, and 45°, respectively. They are non-periodically placed in three different zones on the curved surface. Therefore, the proposed conformal metamaterial absorber can achieve a high absorption rate. The performance of the proposed absorber is compared with that of a metallic curved surface and a conformal metamaterial absorber with the same unit cells. PMID:24104326

Jang, Youngsoo; Yoo, Minyeong; Lim, Sungjoon

2013-10-01

210

Cold streams in early massive hot haloes as the main mode of galaxy formation.  

PubMed

Massive galaxies in the young Universe, ten billion years ago, formed stars at surprising intensities. Although this is commonly attributed to violent mergers, the properties of many of these galaxies are incompatible with such events, showing gas-rich, clumpy, extended rotating disks not dominated by spheroids. Cosmological simulations and clustering theory are used to explore how these galaxies acquired their gas. Here we report that they are 'stream-fed galaxies', formed from steady, narrow, cold gas streams that penetrate the shock-heated media of massive dark matter haloes. A comparison with the observed abundance of star-forming galaxies implies that most of the input gas must rapidly convert to stars. One-third of the stream mass is in gas clumps leading to mergers of mass ratio greater than 1:10, and the rest is in smoother flows. With a merger duty cycle of 0.1, three-quarters of the galaxies forming stars at a given rate are fed by smooth streams. The rarer, submillimetre galaxies that form stars even more intensely are largely merger-induced starbursts. Unlike destructive mergers, the streams are likely to keep the rotating disk configuration intact, although turbulent and broken into giant star-forming clumps that merge into a central spheroid. This stream-driven scenario for the formation of discs and spheroids is an alternative to the merger picture. PMID:19158792

Dekel, A; Birnboim, Y; Engel, G; Freundlich, J; Goerdt, T; Mumcuoglu, M; Neistein, E; Pichon, C; Teyssier, R; Zinger, E

2009-01-22

211

The X-ray warm absorber and nuclear obscuration in the Seyfert 1.8 galaxy ESO 113-G010  

NASA Astrophysics Data System (ADS)

We present the first analysis of the X-ray warm absorber and nuclear obscuration in the Seyfert 1.8 galaxy ESO 113-G010. We used archival data from a 100 ks XMM-Newtonobservation made in 2005. From high resolution spectroscopy analysis of the RGS data, we detect absorption lines originating from a warm absorber consisting of two distinct phases of ionisation, with log ? ? 3.2 and 2.3 respectively. The higher-ionised component has a larger column density and outflow velocity (NH ? 1.6 × 1022 cm-2, v ? - 1100 km s-1) than the lower-ionised component (NH ? 0.5 × 1022 cm-2, v ? -700 km s-1). The shape of the optical-UV continuum and the large Balmer decrement (H?/H? ~ 8) indicate significant amount of reddening is taking place in our line of sight in the host galaxy of the AGN; however, the X-ray spectrum is not absorbed by cold neutral gas intrinsic to the source. We discuss different explanations for this discrepancy between the reddening and the X-ray absorption, and suggest that the most likely solution is a dusty warm absorber. We show that dust can exist in the lower-ionised phase of the warm absorber, which causes the observed reddening of the optical-UV emission, whereas the X-rays remain unabsorbed due to lack of cold neutral gas in the ionised warm absorber. Furthermore, we have investigated the uncertainties in the construction of the spectral energy distribution (SED) of this object due to obscuration of the nuclear source and the effects this has on the photoionisation modelling of the warm absorber. We show how the assumed SEDs influence the thermal stability of each phase and whether or not the two absorber phases in ESO 113-G010can co-exist in pressure equilibrium.

Mehdipour, M.; Branduardi-Raymont, G.; Page, M. J.

2012-06-01

212

Efficient waveform recall in absorbing media  

Microsoft Academic Search

Summary form only given. We have shown that efficient recall of temporally structured optical pulses in absorbing media can be obtained via the photon echo process if the absorption length and pulse area of brief pulses are appropriately chosen

C. S. Cornish; M. Azadeh; W. R. Babbitt; L. Tsang

1998-01-01

213

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

2005-01-01

214

Energy absorber uses expanded coiled tube  

NASA Technical Reports Server (NTRS)

Mechanical shock mitigating device, based on working material to its failure point, absorbs mechanical energy by bending or twisting tubing. It functions under axial or tangential loading, has no rebound, is area independent, and is easy and inexpensive to build.

Johnson, E. F.

1972-01-01

215

Passive Earth Entry Vehicle Energy Absorbing Systems  

NASA Astrophysics Data System (ADS)

A critical element of a passive EEV performance is the energy absorbing system required to attenuate the dynamic landing loads. Two design approaches are described and the pros and cons based on particular mission requirements are discussed.

Kellas, S.; Maddock, R. W.

2014-06-01

216

Neutron absorbing coating for nuclear criticality control  

DOEpatents

A neutron absorbing coating for use on a substrate, and which provides nuclear criticality control is described and which includes a nickel, chromium, molybdenum, and gadolinium alloy having less than about 5% boron, by weight.

Mizia, Ronald E. (Idaho Falls, ID); Wright, Richard N. (Idaho Falls, ID); Swank, William D. (Idaho Falls, ID); Lister, Tedd E. (Idaho Falls, ID); Pinhero, Patrick J. (Idaho Falls, ID)

2007-10-23

217

An ultra-broadband multilayered graphene absorber.  

PubMed

An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon modes that destructively interfere with the dipolar mode and generate electromagnetically induced absorption. (ii) The patterned graphene layers biased at different gate voltages backed-up with dielectric substrates are stacked on top of each other. The resulting absorber is polarization dependent but has an ultra-broadband of operation. (iii) Graphene's damping factor is increased by lowering its electron mobility to 1000 cm²/Vs. Indeed, numerical experiments demonstrate that with only three layers, bandwidth of 90% absorption can be extended upto 7THz, which is drastically larger than only few THz of bandwidth that can be achieved with existing metallic/graphene absorbers. PMID:24514545

Amin, Muhammad; Farhat, Mohamed; Ba?c?, Hakan

2013-12-01

218

WARM GAS IN THE VIRGO CLUSTER. I. DISTRIBUTION OF Ly{alpha} ABSORBERS  

SciTech Connect

The first systematic study of the warm gas (T = 10{sup 4-5} K) distribution across a galaxy cluster is presented using multiple background QSOs in and around the Virgo Cluster. We detect 25 Ly{alpha} absorbers (N{sub HI} = 10{sup 13.1-15.4} cm{sup -2}) in the Virgo velocity range toward 9 of 12 QSO sightlines observed with the Cosmic Origin Spectrograph, with a cluster impact parameter range of 0.36-1.65 Mpc (0.23-1.05 R{sub vir}). Including 18 Ly{alpha} absorbers previously detected by STIS or GHRS toward 7 of 11 background QSOs in and around the Virgo Cluster, we establish a sample of 43 absorbers toward a total of 23 background probes for studying the incidence of Ly{alpha} absorbers in and around the Virgo Cluster. With these absorbers, we find (1) warm gas is predominantly in the outskirts of the cluster and avoids the X-ray-detected hot intracluster medium (ICM). Also, Ly{alpha} absorption strength increases with cluster impact parameter. (2) Ly{alpha}-absorbing warm gas traces cold H I-emitting gas in the substructures of the Virgo Cluster. (3) Including the absorbers associated with the surrounding substructures, the warm gas covering fraction (100% for N{sub HI} > 10{sup 13.1} cm{sup -2}) is in agreement with cosmological simulations. We speculate that the observed warm gas is part of large-scale gas flows feeding the cluster both in the ICM and galaxies.

Yoon, Joo Heon; Putman, Mary E.; Bryan, Greg L. [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Thom, Christopher [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21211 (United States); Chen, Hsiao-Wen, E-mail: jhyoon@astro.columbia.edu [Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States)

2012-08-01

219

Passive vibration absorber with dry friction  

Microsoft Academic Search

Summary  ?The properties of a passive vibration absorber with dry friction significantly differ from those of the classical linear\\u000a absorber. The exceptional phenomenon is the possibility of suppressing all excited modes. This effect is influenced to a small\\u000a extent by a special shape of the friction characteristic, but mainly by an appropriately adjusted threshold of the static\\u000a friction. The theoretical predictions

A. Hartung; H. Schmieg; P. Vielsack

2001-01-01

220

A planar polarization-insensitive metamaterial absorber  

Microsoft Academic Search

The model of the polarization-insensitive metamaterial (MM) absorber composed of split cross-ring resonator (SCRR), cave-cross resonator (CCR) and dielectric substrate was proposed at microwave frequencies. Based on perfect impedance-matched (z˜(?)=1) to the free space, the single unit cell could achieve near-unity absorbance by properly assembling the sandwich structure. We have simulated and measured the reflectivity and transmission properties of a

Yongzhi Cheng; Helin Yang; Zhengze Cheng; Boxun Xiao

2011-01-01

221

Terahertz backscattering behavior of various absorbing materials  

NASA Astrophysics Data System (ADS)

The Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has investigated the electromagnetic scattering behavior of various broadband absorbers. Several absorbing materials were tested in a compact radar range operating at a center frequency of 160 GHz. The polarimetric radar cross section was measured at elevation angles from 15° to 75°. In addition to the backscattering behavior, the normal incidence transmittance of the materials was evaluated.

Wu, C.; Gatesman, A. J.; DeRoeck, L.; Horgan, T.; Giles, R. H.; Nixon, W. E.

2009-05-01

222

Perfect terahertz absorber using fishnet based metafilm  

SciTech Connect

We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials with desired values. Although the initial idea of metamaterials was to obtain a negative index medium, however, the evolution of metamaterials (MMs) offers a variety of practically applicable devices for controlling electromagnetic wave such as tunable filters, modulators, phase shifters, compact antenna, absorbers, etc. Terahertz regime, a crucial domain of the electromagnetic wave, is suffering from the scarcity of the efficient devices and might take the advantage of metamaterials. Here, we demonstrate design, fabrication, and characterization of a terahertz absorber based on a simple fishnet metallic film separated from a ground mirror plane by a dielectric spacer. Such absorbers are in particular important for bolometric terahertz detectors, high sensitivity imaging, and terahertz anechoic chambers. Recently, split-ring-resonators (SRR) have been employed for metamaterial-based absorbers at microwave and THz frequencies. The experimental demonstration reveals that such absorbers have absorptivity close to unity at resonance frequencies. However, the downside of these designs is that they all employ resonators of rather complicated shape with many fine parts and so they are not easy to fabricate and are sensitive to distortions.

Azad, Abul Kalam [Los Alamos National Laboratory; Shchegolkov, Dmitry Yu [Los Alamos National Laboratory; Chen, Houtong [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; Smirnova, E I [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory

2009-01-01

223

Is It A Cold Or The Flu? Symptoms Cold Flu  

E-print Network

Is It A Cold Or The Flu? Symptoms Cold Flu Fever Rare Usual, high (100-102°) Headache be severe 5 STEPS TO TAKE IF YOU GET THE FLU: 1. Stay at home and rest. CDC recommends that you stay home a medical condition that puts you at higher risk of flu complications (like asthma...), call your doctor

O'Toole, Alice J.

224

21 CFR 868.5310 - Carbon dioxide absorber.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Carbon dioxide absorber. 868.5310 Section 868...Therapeutic Devices § 868.5310 Carbon dioxide absorber. (a) Identification. A carbon dioxide absorber is a device that is...

2012-04-01

225

21 CFR 868.5300 - Carbon dioxide absorbent.  

...2014-04-01 2014-04-01 false Carbon dioxide absorbent. 868.5300 Section 868...Therapeutic Devices § 868.5300 Carbon dioxide absorbent. (a) Identification. A carbon dioxide absorbent is a device intended for...

2014-04-01

226

21 CFR 868.5310 - Carbon dioxide absorber.  

...2014-04-01 2014-04-01 false Carbon dioxide absorber. 868.5310 Section 868...Therapeutic Devices § 868.5310 Carbon dioxide absorber. (a) Identification. A carbon dioxide absorber is a device that is...

2014-04-01

227

21 CFR 868.5300 - Carbon dioxide absorbent.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Carbon dioxide absorbent. 868.5300 Section 868...Therapeutic Devices § 868.5300 Carbon dioxide absorbent. (a) Identification. A carbon dioxide absorbent is a device intended for...

2013-04-01

228

21 CFR 868.5310 - Carbon dioxide absorber.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Carbon dioxide absorber. 868.5310 Section 868...Therapeutic Devices § 868.5310 Carbon dioxide absorber. (a) Identification. A carbon dioxide absorber is a device that is...

2011-04-01

229

21 CFR 868.5300 - Carbon dioxide absorbent.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Carbon dioxide absorbent. 868.5300 Section 868...Therapeutic Devices § 868.5300 Carbon dioxide absorbent. (a) Identification. A carbon dioxide absorbent is a device intended for...

2012-04-01

230

21 CFR 868.5300 - Carbon dioxide absorbent.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Carbon dioxide absorbent. 868.5300 Section 868...Therapeutic Devices § 868.5300 Carbon dioxide absorbent. (a) Identification. A carbon dioxide absorbent is a device intended for...

2011-04-01

231

21 CFR 868.5310 - Carbon dioxide absorber.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Carbon dioxide absorber. 868.5310 Section 868...Therapeutic Devices § 868.5310 Carbon dioxide absorber. (a) Identification. A carbon dioxide absorber is a device that is...

2013-04-01

232

Cold Dark Matter Resuscitated?  

E-print Network

The Cold Dark Matter (CDM) model has an elegant simplicitly which makes it very predictive, but when its parameters are fixed at their `canonical' values its predictions are in conflict with observational data. There is, however, much leeway in the initial conditions within the CDM framework. We advocate a re-examination of the CDM model, taking into account modest variation of parameters from their canonical values. We find that CDM models with $n=0.8$--0.9 and $h=0.45$--0.50 can fit the available data. Our ``best fit'' CDM model has $n=0.9$, $h=0.45$ and $C_2^{T}/C_2^{S}=0.7$. We discuss the current state of observations which could definitely rule out this model.

Martin White; Douglas Scott; Joe Silk; Marc Davis

1995-08-02

233

Hot Planet - Cold Comfort  

NSDL National Science Digital Library

This page features videos from the "Hot Planet- Cold Comfort" television episode, related website articles and a student activity. The videos explore how the Gulf Stream conveyor belt may shut down; how Arctic river runoff and Alaskan glacial melt are freshening the oceans; and how ocean sediments and ice cores are being studied to understand the Little Ice Age. The videos total approximately one hour in length. The website articles explore the Little Ice Age; how the Arctic functions as a global thermostat, affecting global weather patterns; and great moments in climate change. The student activity is about light absorbtion. The site also contains a challenge activity to find details in a painting that depict Little Ice Age living conditions.

234

Cold isopressing method  

DOEpatents

A cold isopressing method in which two or more layers of material are formed within an isopressing mold. One of the layers consists of a tape-cast film. The layers are isopressed within the isopressing mold, thereby to laminate the layers and to compact the tape-cast film. The isopressing mold can be of cylindrical configuration with the layers being coaxial cylindrical layers. The materials used in forming the layers can contain green ceramic materials and the resultant structure can be fired and sintered as necessary and in accordance with known methods to produce a finished composite, ceramic structure. Further, such green ceramic materials can be of the type that are capable of conducting hydrogen or oxygen ions at high temperature with the object of utilizing the finished composite ceramic structure as a ceramic membrane element.

Chen, Jack C. (Getzville, NY); Stawisuck, Valerie M. (North Tonawanda, NY); Prasad, Ravi (East Amherst, NY)

2003-01-01

235

Experiments in cold fusion  

SciTech Connect

The work of Steve Jones and others in muon-catalyzed cold fusion of deuterium and hydrogen suggests the possibility of such fusion catalyzed by ions, or combinations of atoms, or more-or-less free electrons in solid and liquid materials. A hint that this might occur naturally comes from the heat generated in volcanic action in subduction zones on the earth. It is questionable whether the potential energy of material raised to the height of a midocean ridge and falling to the depth of an ocean trench can produce the geothermal effects seen in the volcanoes of subduction zones. If the ridge, the trench, the plates, and the asthenosphere are merely visible effects of deeper density-gradient driven circulations, it is still uncertain that observed energy-concentration effects fit the models.

Palmer, E.P.

1986-03-28

236

Identification of tyrosine-phosphorylated peptides using cold ion spectroscopy.  

PubMed

The accurate and unambiguous detection of post-translational modifications in proteins and peptides remains a challenging task. We report here the use of cold ion spectroscopy for the identification of phosphorylated tyrosine residues in peptides. This approach employs the wavelength-specific UV fragmentation of cryogenically cooled protonated peptides in the gas phase. In addition to the appearance of specific photofragments, the phosphorylation of tyrosine induces large spectral shifts of the peptide electronic band origins. Quantum chemical calculations and experiments together suggest a certain generality of the use of such shifts in the spectroscopic identification of phosphotyrosines. The enhanced selectivity offered by the joint application of wavelength-specific fragmentation and mass spectrometry of cold molecules can also be used in the identifications of aromatic residues in protonated peptides and, potentially, of other UV-absorbing groups in a variety of large polyatomic ions. PMID:24949741

Kopysov, Vladimir; Nagornova, Natalia S; Boyarkin, Oleg V

2014-07-01

237

Physiological characteristics of cold acclimatization in man  

Microsoft Academic Search

Studies were conducted on 15 healthy young soldiers to evaluate the effect of a cold acclimatization schedule on the thermoregulatory and metabolic activity on exposure to acute cold stress. These men were exposed to cold (10‡C) for 4 h daily wearing only shorts for 21 days, in a cold chamber. They were subjected to a standard cold test at 10

Lazar Mathew; S. S. Purkayastha; A. Jayashankar; H. S. Nayar

1981-01-01

238

Cold Urticaria and Celiac Disease  

Microsoft Academic Search

? Abstract Cold urticaria can be associated with blood and thyroid disorders, drugs, or infections. Celiac disease is an autoimmune enteropathy caused by permanent gluten intolerance. It is often associated with other autoimmune diseases, such as chronic idiopathic urticaria. Nevertheless, association with cold urticaria has not yet been described. A boy aged 3 years 8 months presented local urticaria-angioedema when

M Pedrosa Delgado; F Martín Muñoz; I Polanco Allué; M Martín Esteban

239

COLD STORAGE DESIGN REFRIGERATION EQUIPMENT  

E-print Network

of each section-1 This leaflet is part one of a series of five to be prepared within the broader overallCOLD STORAGE DESIGN AND REFRIGERATION EQUIPMENT REFRIGERATION OF FISH - PART 1 \\ "..\\- ,,, T I Fishery Leaflet 427 Washington 25, D. C. June 1956 REFRIGERATION OF FISH - PART em; COlD STORAGE DESIGN

240

A strained silicon cold electron bolometer using Schottky contacts  

NASA Astrophysics Data System (ADS)

We describe optical characterisation of a strained silicon cold electron bolometer (CEB), operating on a 350 mK stage, designed for absorption of millimetre-wave radiation. The silicon cold electron bolometer utilises Schottky contacts between a superconductor and an n++ doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to 160 GHz and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of 50% for radiation coupled into the device by the planar antenna and an overall noise equivalent power, referred to absorbed optical power, of 1.1×10-16 W Hz-1/2 when the detector is observing a 300 K source through a 4 K throughput limiting aperture. Even though this optical system is not optimized, we measure a system noise equivalent temperature difference of 6 mK Hz-1/2. We measure the noise of the device using a cross-correlation of time stream data, measured simultaneously with two junction field-effect transistor amplifiers, with a base correlated noise level of 300 pV Hz-1/2 and find that the total noise is consistent with a combination of photon noise, current shot noise, and electron-phonon thermal noise.

Brien, T. L. R.; Ade, P. A. R.; Barry, P. S.; Dunscombe, C.; Leadley, D. R.; Morozov, D. V.; Myronov, M.; Parker, E. H. C.; Prest, M. J.; Prunnila, M.; Sudiwala, R. V.; Whall, T. E.; Mauskopf, P. D.

2014-07-01

241

Solar absorber material reflectivity measurements at temperature  

SciTech Connect

Assessment of absorber shell material properties at high operating temperatures is essential to the full understanding of the solar energy absorption process in a solar thermal rocket. A review of these properties, their application and a new experimental methodology to measure them at high temperatures is presented. The direct application for the research is absorber cavity development for a Solar Thermal Upper Stage (STUS). High temperature measurements, greater than 1,000 Kelvin, are difficult to obtain for incident radiation upon a solid surface that forms an absorber cavity in a solar thermal engine. The basic material properties determine the amount of solar energy that is absorbed, transmitted or reflected and are dependent upon the material's temperature. This investigation developed a new approach to evaluate the material properties (i.e., reflectivity, absorptive) of the absorber wall and experimentally determined them for rhenium and niobium sample coupons. The secular reflectivity was measured both at room temperature and at temperatures near 1,000 Kelvin over a range of angles from 0 to 90 degrees. The same experimental measurements were used to calculate the total reflectivity of the sample by integrating the recorded intensities over a hemisphere. The test methodology used the incident solar energy as the heating source while directly measuring the reflected light (an integrated value over all visible wavelengths). Temperature dependence on total reflectivity was found to follow an inverse power function of the material's temperature.

Bonometti, J.A.; Hawk, C.W.

1999-07-01

242

Ultraviolet radiation absorbing compounds in marine organisms  

SciTech Connect

Studies on the biological effects of solar ultraviolet radiations are becoming increasingly common, in part due to recent interest in the Antarctic ozone hole and in the perceived potential for global climate change. Marine organisms possess many strategies for ameliorating the potentially damaging effects of UV-B (280-320 nm) and the shorter wavelengths of UV-A (320-400nm). One mechanism is the synthesis of bioaccumulation of ultraviolet radiation absorbing compounds. Several investigators have noted the presence of absorbing compounds in spectrophotometer scans of extracts from a variety of marine organisms, particularly algae and coelenterates containing endosymbiotic algae. The absorbing compounds are often mycosporine-like amino acids. Thirteen mycosporine-like amino acids have already been described, and several others have recently been detected. Although, the mycosporine-like amino acids are widely distributed. these compounds are by no means the only type of UV-B absorbing compounds which has been identified. Coumarins from green algae, quinones from sponges, and indoles from a variety of sources are laternative examples which are documented in the natural products literature. When the biological impact of solar ultraviolet radiation is assessed, adequate attention must be devoted to the process of photoadaptation, including the accumulation of ultraviolet radiation absorbing compounds.

Chalker, B.E.; Dunlap, W.C. (Australian Inst. of Marine Science, Queensland (Australia))

1990-01-09

243

A Dynamic Absorber With Active Vibration Control  

NASA Astrophysics Data System (ADS)

The design and construction of a dynamic absorber incorporating active vibration control is described. The absorber is a two-degrees-of-freedom spring — lumped mass system sliding on a guide pillar, with two internal vibration disturbance sources. Both the main mass and the secondary absorber mass are acted on by DC servo motors, respectively, to suppress the vibration amplitude. The state variable technique is used to model this dynamic system and a decoupling PID control method is used. First, the discrete time state space model is identified by using the commercial software MATLAB. Then the decoupling controller of this multi-input/multi-output system is derived from the identified model. Finally the results of some experiments are presented. The experimental results show that the system is effective in suppressing vibration. Also, the performance of this control strategy for position tracking control is evaluated based on experimental data.

Huang, S.-J.; Lian, R.-J.

1994-12-01

244

Optical analysis of solar energy tubular absorbers  

NASA Astrophysics Data System (ADS)

The energy absorbed by a solar energy tubular receiver element for a single incident ray is derived. Two types of receiver elements were analyzed: (1) an inner tube with an absorbing coating surrounded by a semi-transparent cover tube, and (2) a semitransparent inner tube filled with an absorbing fluid surrounded by a semitransparent cover tide. The formation of ray cascades in the semitransparent tubes is considered. A numerical simulation to investigate the influence of the angle of incidence, sizing, thickness, and coefficient of extinction of the tubes was performed. A comparison was made between receiver elements with and without cover tubes. Ray tracing analyses in which rays were followed within the tubular receiver element as well as throughout the rest of the collector were performed for parabolic and circular trough concentrating collectors.

Saltiel, C.; Sokolov, M.

1982-11-01

245

A tunable metamaterial absorber using varactor diodes  

NASA Astrophysics Data System (ADS)

We present the design, analysis and measurements of a polarization-insensitive tunable metamaterial absorber with varactor diodes embedded between metamaterial units. The basic unit shows excellent absorptivity in the designed frequency band over a wide range of incident angles. By regulating the reverse bias voltage on the varactor diode, the absorption frequency of the designed unit can be controlled continuously. The absorption mechanism is interpreted using the electromagnetic-wave interference theory. When the metamaterial units are placed along two orthogonal directions, the absorber is insensitive to the polarization of incident waves. The tunability of the absorber has been verified by experimental results with the measured bandwidth of 1.5 GHz (or relative bandwidth of 30%).

Zhao, Jie; Cheng, Qiang; Chen, Jie; Qing Qi, Mei; Jiang, Wei Xiang; Cui, Tie Jun

2013-04-01

246

Design, simulation, and measurement of metamaterial absorber  

NASA Astrophysics Data System (ADS)

We present a design for metamaterial absorber which is resonant with strong absorbance in the microwave frequency range. Our fabricated design consists of two resonators and a metal wire that couple separately so as to absorb all incident electric and magnetic fields within a single planar layer which is only 0.9 mm thick. Experiments demonstrate that the transmission coefficients (S21) are lower than -10 dB across the entire measurement frequency range and the reflectance coefficients (S11) are about -20 dB around 10.4 GHz. The absorptivity which can be obtained through S parameters is greater than 98% around 10.4 GHz in experiments and 99.9% in simulations.

Cheng, Yongzhi; Yang, Helin

2010-08-01

247

Absorber Materials at Room and Cryogenic Temperatures  

SciTech Connect

We recently reported on investigations of RF absorber materials at cryogenic temperatures conducted at Jefferson Laboratory (JLab). The work was initiated to find a replacement material for the 2 Kelvin low power waveguide Higher Order Mode (HOM) absorbers employed within the original cavity cryomodules of the Continuous Electron Beam Accelerator Facility (CEBAF). This effort eventually led to suitable candidates as reported in this paper. Furthermore, though constrained by small funds for labor and resources, we have analyzed a variety of lossy ceramic materials, several of which could be usable as HOM absorbers for both normal conducting and superconducting RF structures, e.g. as loads in cavity waveguides and beam tubes either at room or cryogenic temperatures and, depending on cooling measures, low to high operational power levels.

F. Marhauser, T.S. Elliott, A.T. Wu, E.P. Chojnacki, E. Savrun

2011-09-01

248

View of cold water eddies in Falkland Current off southern Argentina  

NASA Technical Reports Server (NTRS)

A view of cold water eddies in the Falkland Current off the South Atlantic Coast of southern Argentina (47.5S, 64.0W) as seen from the Skylab space station in Earth orbit. This land area (left corner) extends south along the coast from Puerto Deseado (center left border) for about 50 miles. Within the ocean, several light blue areas are visible and represent the occurrence of plankton within the Falkland Current. Over the ocean, the cold water eddies are identified by the circular cloud-free areas within the cloud street pattern and bordered by cumulus cloud buildup (white). The cloud streets indicate the wind is from the southwest and do not form over eddies because energy from the atmosphere is absorbed by the cold ocean water. On the downwind side of the eddies, cumulus clouds tend to form as the cold moist air flows over the warmer water.

1973-01-01

249

Cold Fronts in CDM clusters  

E-print Network

Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters (Vikhlinin et. al., 2001). These features, called ``cold fronts'', are characterized by an increase in surface brightness by a factor >2 over 10-50 kpc, accompanied by a drop in temperature of a similar magnitude. The existence of such sharp gradients can be used to put interesting constraints on the physics of the intracluster medium (ICM), if their mechanism and longevity are well understood. Here, we present results of a search for cold fronts in high-resolution simulations of galaxy clusters in cold dark matter (CDM) models. We show that sharp gradients with properties similar to those of observed cold fronts naturally arise in cluster mergers when the shocks heat gas surrounding the merging sub-cluster, while its dense core remains relatively cold. The compression induced by supersonic motions and shock heating during the merger enhance the amplitude of gas density and temperature gradients across the front. Our results indicate that cold fronts are non-equilibrium transient phenomena and can be observed for a period of less than a billion years. We show that the velocity and density fields of gas surrounding the cold front can be very irregular which would complicate analyses aiming to put constraints on the physical conditions of the intracluster medium in the vicinity of the front.

Daisuke Nagai; Andrey V. Kravtsov

2002-06-26

250

OSCEE fan exhaust bulk absorber treatment evaluation  

NASA Technical Reports Server (NTRS)

The acoustic suppression capability of bulk absorber material designed for use in the fan exhaust duct walls of the quiet clean short haul experiment engine (OCSEE UTW) was evaluated. The acoustic suppression to the original design for the engine fan duct which consisted of phased single degree-of-freedom wall treatment was tested with a splitter and also with the splitter removed. Peak suppression was about as predicted with the bulk absorber configuration, however, the broadband characteristics were not attained. Post test inspection revealed surface oil contamination on the bulk material which could have caused the loss in bandwidth suppression.

Bloomer, H. E.; Samanich, N. E.

1980-01-01

251

Polarization insensitive, broadband terahertz metamaterial absorber.  

PubMed

We present the simulation, implementation, and measurement of a polarization insensitive broadband resonant terahertz metamaterial absorber. By stacking metal-insulator layers with differing structural dimensions, three closely positioned resonant peaks are merged into one broadband absorption spectrum. Greater than 60% absorption is obtained across a frequency range of 1.86?THz where the central resonance frequency is 5?THz. The FWHM of the device is 48%, which is two and half times greater than the FWHM of a single layer structure. Such metamaterials are promising candidates as absorbing elements for bolometric terahertz imaging. PMID:21886249

Grant, James; Ma, Yong; Saha, Shimul; Khalid, Ata; Cumming, David R S

2011-09-01

252

Wavelength-tunable microbolometers with metamaterial absorbers.  

PubMed

Microbolometers are modified by metallic resonant absorber elements, leading to an enhanced responsivity at selectable wavelengths. The dissipative energy absorption of tailored metamaterials allows for engineering the response of conventional bolometer microbridges. The absorption peak position and height are determined by the geometry of the metamaterial. Square-shaped metal/dielectric/metal stacks as absorber elements show spectral resonances at wavelengths between 4.8 and 7.0 microm in accordance with numerical simulations. Total peak absorptions of 0.8 are obtained. The metamaterial modified bolometers are suitable for multispectral thermal imaging systems in the mid-IR and terahertz regime. PMID:19794799

Maier, Thomas; Brückl, Hubert

2009-10-01

253

Design optimization of nanostrip metamaterial perfect absorbers  

NASA Astrophysics Data System (ADS)

Metamaterial perfect absorber (MPA) promises many applications due to its capability of complete suppression of transmission or/and reflection. The complete dissipation of the incident electromagnetic energy by the absorptive meta-atoms makes it a unique candidate in many photonic and optoelectronic devices. An ultrathin metamaterial absorber that consists of a periodic nanostrip metal on top of a planar dielectric slab backed by a conducting metal plate is presented. The spectral absorptivity of MPA is investigated by the finite difference time domain method from visible to near-infrared. The various geometrical and material parameters of MPA are optimized for maximum absorption.

El-Aasser, Mostafa A.

2014-01-01

254

Versatile cold atom target apparatus.  

PubMed

We report on a compact and transportable apparatus that consists of a cold atomic target at the center of a high resolution recoil ion momentum spectrometer. Cold rubidium atoms serve as a target which can be operated in three different modes: in continuous mode, consisting of a cold atom beam generated by a two-dimensional magneto-optical trap, in normal mode in which the atoms from the beam are trapped in a three-dimensional magneto-optical trap (3D MOT), and in high density mode in which the 3D MOT is operated in dark spontaneous optical trap configuration. The targets are characterized using photoionization. PMID:22852676

Götz, Simone; Höltkemeier, Bastian; Hofmann, Christoph S; Litsch, Dominic; DePaola, Brett D; Weidemüller, Matthias

2012-07-01

255

Nonfreezing cold-induced injuries.  

PubMed

Non-freezing cold injury (NFCI) is the Cinderella of thermal injuries and is a clinical syndrome that occurs when tissues are exposed to cold temperatures close to freezing point for sustained periods. NFCI is insidious in onset, often difficult to recognize and problematic to treat, and yet the condition accounts for significant morbidity in both military and civilians who work in cold conditions. Consequently recognition of those at risk, limiting their exposure and the appropriate and timely use of suitable protective equipment are essential steps in trying to reduce the impact of the condition. This review addresses the issues surrounding NFCI. PMID:21465916

Imray, C H E; Richards, P; Greeves, J; Castellani, J W

2011-03-01

256

Microscopic mechanism for cold denaturation  

E-print Network

We elucidate the mechanism of cold denaturation through constant-pressure simulations for a model of hydrophobic molecules in an explicit solvent. We find that the temperature dependence of the hydrophobic effect is the driving force/induces/facilitates cold denaturation. The physical mechanism underlying this phenomenon is identified as the destabilization of hydrophobic contact in favor of solvent separated configurations, the same mechanism seen in pressure induced denaturation. A phenomenological explanation proposed for the mechanism is suggested as being responsible for cold denaturation in real proteins.

Cristiano L. Dias; Tapio Ala-Nissila; Mikko Karttunen; Ilpo Vattulainen; Martin Grant

2007-04-20

257

Terahertz backscattering behavior of various absorbing materials , A. J. Gatesmana  

E-print Network

, absorbers, scattering, radar 1. INTRODUCTION Absorbing materials are commonly utilized in a wide variety the backscattering behavior of several absorbing materials in a compact radar range at terahertz frequencies. Several different types of structures were characterized including wedged, pyramidal, and bulk absorbers. The 160

Massachusetts at Lowell, University of

258

A shallow-depth sloshing absorber for structural control  

Microsoft Academic Search

Sloshing absorbers work on a similar principle to that of tuned vibration absorbers. A sloshing absorber consists of a tank, partially filled with liquid. The absorber is attached to the structure to be controlled, and relies on the structure's motion to excite the liquid. Consequently, a sloshing wave is produced at the liquid free surface possessing energy dissipative qualities. The

A. P. Marsh; M. Prakash; S. E. Semercigil; Ö. F. Turan

2010-01-01

259

Abundance of damped Lyman-alpha absorbers in cosmological SPH simulations  

Microsoft Academic Search

We use cosmological smoothed-particle hydrodynamics (SPH) simulations of the\\u000aLambda cold dark matter (CDM) model to study the abundance of damped\\u000aLyman-alpha absorbers (DLAs) in the redshift range z=0-4.5. We compute the\\u000acumulative DLA abundance by using the relation between DLA cross-section and\\u000athe total halo mass inferred from the simulations. Our approach includes a\\u000aphenomenological model of galactic wind.

Kentaro Nagamine; Volker Springel; Lars Hernquist

2003-01-01

260

Clearing up the clouds around NGC 4151: evidence of a highly ionized absorber  

NASA Astrophysics Data System (ADS)

The Seyfert 1 galaxy NGC 4151 is characterized by complex X-ray absorption, well described by a dual absorber, composed of a uniform mildly ionized gas and a cold system that partially covers the central source. However, in one of the 5 BeppoSAX observations, the spectrum shows two peculiar features. An absorption feature is detected around 8.5-9 keV with a statistical significance of 99.96%. This feature can be fitted either with an absorption edge at E=8.62+0.34-0.52 keV with optical depth ?=0.06±0.03 or with an absorption line with 9.5+1.3-0.6 keV, width ?=0.95+1.2-0.7 keV and EW= 200 eV. In the first case, we associate the feature to highly ionized iron at rest, like FeXXII-FeXXIII ({Erest}=8.4-8.5 keV). In the second case the feature could be identified with a blend of FeXXV and FeXXVI lines, with an outflow velocity v ? (0.09-0.26)c. This spectrum is also characterized by a substantial reduction of the absorption column density and the covering fraction of the dual absorber. In particular the column density of the mildly ionized and cold absorbers is ?3-5 times lower than observed in the other states, and the covering fraction is reduced by ?40 per cent. We propose a possible explanation linking the two properties in terms of a multi-phase ionized absorber.

Piro, L.; de Rosa, A.; Matt, G.; Perola, G. C.

2005-10-01

261

Trapping cold molecular hydrogen.  

PubMed

Translationally cold H(2) molecules excited to non-penetrating |M(J)| = 3 Rydberg states of principal quantum number in the range 21-37 have been decelerated and trapped using time-dependent inhomogeneous electric fields. The |M(J)| = 3 Rydberg states were prepared from the X (1)?(+)(u)(v = 0, J = 0) ground state using a resonant three-photon excitation sequence via the B (1)?(+)(u)(v = 3, J = 1) and I (1)?(g) (v = 0, J = 2) intermediate states and circularly polarized laser radiation. The circular polarization of the vacuum ultraviolet radiation used for the B ? X transition was generated by resonance-enhanced four-wave mixing in xenon and the degree of circular polarization was determined to be 96%. To analyse the deceleration and trapping experiments, the Stark effect in Rydberg states of molecular hydrogen was calculated using a matrix diagonalization procedure similar to that presented by Yamakita et al., J. Chem. Phys., 2004, 121, 1419. Particular attention was given to the prediction of zero-field positions of low-l states and of avoided crossings between Rydberg-Stark states with different values of |M(J)|. The calculated Stark maps and probabilities for diabatic traversal of the avoided crossings were used as input to Monte-Carlo particle-trajectory simulations. These simulations provide a quantitatively satisfactory description of the experimental data and demonstrate that particle loss caused by adiabatic traversals of avoided crossings between adjacent |M(J)| = 3 Stark states of H(2) is small at principal quantum numbers beyond n = 25. The main source of trap losses was found to be from collisional processes. Predissociation following the absorption of blackbody radiation is estimated to be the second most important trap-loss mechanism at room temperature, and trap loss by spontaneous emission is negligible under our experimental conditions. PMID:21818497

Seiler, Ch; Hogan, S D; Merkt, F

2011-11-14

262

Panchromatic absorbers for solar light-harvesting.  

PubMed

A set of panchromatic absorbers exhibiting long excited-state lifetimes in both polar and nonpolar media has been prepared. The architectures are based on a porphyrin strongly coupled electronically to 1-4 perylene-monoimides via ethyne linkers. The constructs should find utility in molecular solar-conversion systems. PMID:25308466

Alexy, Eric J; Yuen, Jonathan M; Chandrashaker, Vanampally; Diers, James R; Kirmaier, Christine; Bocian, David F; Holten, Dewey; Lindsey, Jonathan S

2014-10-28

263

CONTROLLABLE ABSORBING STRUCTURE OF METAMATERIAL AT MICROWAVE  

Microsoft Academic Search

Akind of controllable metamaterial absorbing structure is presented in this paper, both transmission coefficient and single radar cross section (RCS) are electrically controlled. This structure is composed from split ring resonators (SRRs) and metallic wire arrays including pin diodes, pin diodes are periodically inserted at these wire arrays discontinuous, and they can be either in an on state or in

Zhanxian Xu; Weigan Lin; Lidu Kong

2007-01-01

264

Perfect terahertz absorber using fishnet based metafilm  

Microsoft Academic Search

We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials

Abul Kalam Azad; Dmitry Yu Shchegolkov; Houtong Chen; Antoinette Taylor; E I Smirnova; John F O Hara

2009-01-01

265

Customised broadband metamaterial absorbers for arbitrary polarisation  

Microsoft Academic Search

This paper shows that customised broadband absorption of electromagnetic waves having arbitrary polarisation is possible by use of lossy cut-wire (CW) metamaterials. These useful features are confirmed by numerical simulations in which different lengths of CW pairs are combined as one periodic metamaterial unit and placed near to a perfect electric conductor (PEC). So far metamaterial absorbers have exhibited some

Hiroki Wakatsuchi; Stephen Greedy; Christos Christopoulos; John Paul

2010-01-01

266

Electromagnetic waves in absorbing uniaxial metamaterials  

Microsoft Academic Search

Features of the polarization, energy fluxes of proper inhomogeneous electromagnetic waves in a layer of absorbing uniaxial negative index metamaterial, and an exact solution of the corresponding boundary problem are investigated. A comparative analysis and modeling of optical properties of anisotropic conventional media and metamaterials is carried out. Conditions and possible advantages of a controlled transformation of the radiation characteristics

Evgenii Starodubtsev

2007-01-01

267

Skin interaction with absorbent hygiene products  

Microsoft Academic Search

Skin problems due to the use of absorbent hygiene products, such as diapers, incontinence pads, and feminine sanitary articles, are mostly due to climate or chafing discomfort. If these conditions are allowed to prevail, these may develop into an irritant contact dermatitis and eventually superficial skin infections. Skin humidity and aging skin are among the most significant predisposing and aggravating

Bo Runeman

2008-01-01

268

Shock absorber protects motive components against overloads  

NASA Technical Reports Server (NTRS)

Shock absorber with an output shaft, hollow gear, and a pair of springs forming a resilient driving connection between shaft and gear, operates when abnormally high torques are applied. This simple durable frictional device is valuable in rotating mechanisms subject to sudden overloads.

1965-01-01

269

Two views of absorbative photon exchange effects  

Microsoft Academic Search

The problem of photon-pair transmission through an absorbing medium is discussed using two different approaches, a perturbative Fermi's golden rule calculation and a calculation using photon wavefunction description. The two approaches produce identical results regarding the two-photon absorption characteristics, despite their conceptual differences

G. G. Lapaire; K. J. Resch; J. S. Lundeen; A. M. Steinberg; J. E. Sipe

2004-01-01

270

Novel shock absorber features varying yield strengths  

NASA Technical Reports Server (NTRS)

A shock absorbent webbing of partially drawn synthetic strands is arranged in sections of varying density related to the varying mass of the human body. This is contoured to protect the body at points of contact, when subjected to large acceleration or deceleration forces.

Geier, D. J.

1964-01-01

271

Moving core beam energy absorber and converter  

DOEpatents

A method and apparatus for the prevention of overheating of laser or particle beam impact zones through the use of a moving-in-the-coolant-flow arrangement for the energy absorbing core of the device. Moving of the core spreads the energy deposition in it in 1, 2, or 3 dimensions, thus increasing the effective cooling area of the device.

Degtiarenko, Pavel V.

2012-12-18

272

Influence of Absorbers on the Electromagnetic Radiation  

E-print Network

The phenomenon of the electromagnetic absorption by arbitrarily distributed discrete absorbers is analyzed from the photon point of view. It is shown that apart from the decrease in the intensity of the signal the net effect of absorption includes a relative increase in the photon bunching.

Neil V. Budko

2007-12-05

273

Aldehyde-containing urea-absorbing polysaccharides  

NASA Technical Reports Server (NTRS)

A novel aldehyde containing polymer (ACP) is prepared by reaction of a polysaccharide with periodate to introduce aldehyde groups onto the C2 - C3 carbon atoms. By introduction of ether and ester groups onto the pendant primary hydroxyl solubility characteristics are modified. The ACP is utilized to absorb nitrogen bases such as urea in vitro or in vivo.

Mueller, W. A.; Hsu, G. C.; Marsh, H. E., Jr. (inventors)

1977-01-01

274

Design of a wideband radar absorbing structure  

Microsoft Academic Search

In this paper, a thin planar electromagnetic absorber consisting of two lossy Frequency Selective Surface (FSS) layers is introduced. The layers are separated by foam material and they are backed by the ground plane. Square rings and crossed dipoles are used in the design of these lossy layers. A wideband absorption characteristic is achieved for zero degrees of incidence angle

Egemen Yildirim; Ozlem Aydin Civi

2011-01-01

275

Anisotropic Layered Absorbers on Cylindrical Structures  

Microsoft Academic Search

A curved structure consisting of an imperfectly conducting circular cylinder coated by any number of coaxial thin anisotropic layers separated by isotroplc regions of different materials is considered. Each thin anisotroplc layer is represented by a sheet with an anisotropic Jump Impedance. Thus, the structure is a generalization to the anisotropic case of Jaumann absorbers on curved surfaces. For a

R. D. Graglia; P. L. E. Uslenghi

1987-01-01

276

FDTD modelling of active radar absorbers  

Microsoft Academic Search

An active absorber, such as the phase-switched screen (PSS), achieves an apparent reduction in the level of the electromagnetic energy reflected from its surface by using binary phase modulation to redistribute it over a bandwidth which is much wider than that of the receiver [Chambers B. and Tennant A., 2004]. Previous analyses of the PSS have been based on either

B. Chambers; A. Tennant

2007-01-01

277

ABSORBING BOUNDARY CONDITIONS FOR ELECTROMAGNETIC WAVE PROPAGATION  

E-print Network

ABSORBING BOUNDARY CONDITIONS FOR ELECTROMAGNETIC WAVE PROPAGATION Xiaobing Feng y Abstract of the electromagnetic fields indi­ vidually. This boundary condition allows any wave motion generated within the domain, and the electromagnetic wave scattering related to antennas. Because of the limitations of both speed and memory

278

Integrated tuned vibration absorbers: a theoretical study.  

PubMed

This article presents a simulation study on two integrated tuned vibration absorbers (TVAs) designed to control the global flexural vibration of lightly damped thin structures subject to broad frequency band disturbances. The first one consists of a single axial switching TVA composed by a seismic mass mounted on variable axial spring and damper elements so that the characteristic damping and natural frequency of the absorber can be switched iteratively to control the resonant response of three flexural modes of the hosting structure. The second one consists of a single three-axes TVA composed by a seismic mass mounted on axial and rotational springs and dampers, which are arranged in such a way that the suspended mass is characterized by uncoupled heave and pitch-rolling vibrations. In this case the three damping and natural frequency parameters of the absorber are tuned separately to control three flexural modes of the hosting structure. The simulation study shows that the proposed single-unit absorbers produce, respectively, 5.3 and 8.7?dB reductions of the global flexural vibration of a rectangular plate between 20 and 120?Hz. PMID:24180774

Gardonio, Paolo; Zilletti, Michele

2013-11-01

279

Composition for absorbing hydrogen from gas mixtures  

DOEpatents

A hydrogen storage composition is provided which defines a physical sol-gel matrix having an average pore size of less than 3.5 angstroms which effectively excludes gaseous metal hydride poisons while permitting hydrogen gas to enter. The composition is useful for separating hydrogen gas from diverse gas streams which may have contaminants that would otherwise render the hydrogen absorbing material inactive.

Heung, Leung K. (Aiken, SC); Wicks, George G. (Aiken, SC); Lee, Myung W. (Aiken, SC)

1999-01-01

280

Prescription Drugs and Cold Medicines  

MedlinePLUS

... Cold Medicines Email Facebook Twitter What is Prescription Drug Abuse: Some medications have psychoactive (mind-altering) properties and, ... Treatment Locator or 1-800-662-HELP . Prescription Drug Abuse Learn what you can do to prevent medicine ...

281

Cold Gas at High Redshift  

E-print Network

We discuss the current observational and theoretical issues concerning cold gas at high redshift and present simulations showing how a number of observational issues can be resolved with planned future instrumentation.

Colin A. Norman; Robert Braun

1995-12-20

282

A tunable EBG absorber for radio-frequency power imaging  

Microsoft Academic Search

Absorption characteristics of a tunable electromagnetic band-gap (EBG) absorber are analyzed, which is designed to capture 2d radio-frequency (RF) power distributions incident on the absorber surface. The EBG absorber has lumped resistors interconnecting the mushroom-type surface patches to absorb the incident RF power at the resonance frequency where the EBG structure exhibits a high-impedance feature. The absorbed RF power distribution

Satoshi Yagitani; Keigo Katsuda; Ryo Tanaka; Masayuki Nojima; Yoshiyuki Yoshimura; Hirokazu Sugiura

2011-01-01

283

Absorbing properties and structural design of microwave absorbers based on carbonyl iron and barium ferrite  

NASA Astrophysics Data System (ADS)

Carbonyl iron and barium ferrite powder (BaZn 1.5Co 0.5Fe 16O 27) were prepared in this work. The complex permittivity and permeability spectra for rubber radar absorbing materials employing carbonyl iron and barium ferrite powders were measured. A database describing the frequency dependence of the permittivities and permeabilities of the carbonyl iron and barium ferrite microwave absorbers with various powder percentage compositions in 2-18 GHz was created. Based on the database, the single-layer and double-layer absorbers were designed and prepared, and their microwave absorption properties were investigated. The results indicate that the carbonyl iron powder prepared via thermal decomposition of iron pentacarbonyl is single cubic iron and of spherical shape. The barium ferrite powder is single W-type ferrite and a hexagonal flake. The absorption band of the double-layer microwave absorber is obviously more than that of the single-layer absorber. The double-layer microwave absorbers with reflection loss <-13 dB over the range of 6-18 GHz and reflection loss <-8 dB over the range of 2-18 GHz were prepared. The thicknesses of the absorbers are only 3.6 and 3.7 mm, respectively.

Feng, Y. B.; Qiu, T.; Shen, C. Y.

2007-11-01

284

Highly ionized absorbers at high redshift  

E-print Network

We investigate the existence of a metal-rich OVI population in 10 high spectral resolution quasar spectra and define observational criteria for this class of absorbers. The low temperatures of nearly half of all OVI absorbers (redshifts 2.0 to 2.6), implied by their line widths, are too low for collisional ionization to be a dominant process. We estimate the oxygen abundance under the assumption of photoionization; a striking result is the bimodal distribution of [O/H] with median values close to 0.01 (0.5) solar for the metal-poor (metal-rich) populations. We present the first estimate of the OVI column density distribution and fit a single power-law index of ~-1.7 and a normalization of f(N)= 2.3e(-13) at log N(OVI) ~ 13.5, both with a ~30% uncertainty. The value of the index is similar to that found for CIV surveys, whereas the normalization factor is about ten times higher. We use f(N) to derive dn/dz and the cosmic density, Omega_b(OVI), selecting a limited column density range not strongly affected by incompleteness or sample variance. We find some decline of dn/dz with z. The cosmic OVI density derived from f(N), Omega_b(OVI) ~ 3.5e(-7), is 2.3 times higher than the value estimated using the observed OVI sample (of which the metal-rich population contributes ~35%), easing the problem of missing metals at high z (~1/4 of the produced metals) but not solving it. We find that the majority of the metal-rich absorbers are located within ~450 km/s of strong Ly-a lines and show that, contrary to the metal-poor absorbers, this population cannot be in hydrostatic equilibrium. All of the OVI absorber properties imply that there are two distinct populations: metal-poor absorbers tracing the intergalactic medium and metal-rich absorbers associated with active sites of star formation.

Jacqueline Bergeron; Stéphane Herbert-Fort

2005-06-28

285

Antibiotic use for common cold  

Microsoft Academic Search

Antibiotics do not help patients with an uncomplicated common cold. Antibiotics can have side effects for the individual taking\\u000a them that range from unpleasant to serious, even lethal. Antibiotic use also contributes to communal harm by encouraging antibiotic\\u000a resistance. If there can be no benefit, but there can be harm, why is the common cold the commonest reason for doctors

Timothy W. Kenealy; Bruce Arroll

286

Template stripping using cold welding  

Microsoft Academic Search

A method for fabricating ultra-flat template-stripped (TS) metal surfaces on standard silicon\\/silicon-oxide wafers by means of gold cold-welding is presented, and cold-welded template-stripped (CWTS) platinum surfaces are demonstrated as an example. Due to the lack of any adhesives, the final TS metal ``sandwiches'' are fully compatible with all organic solvents, as well as ultra-high vacuum (UHV). The produced CWTS platinum

Jason J. Blackstock; Zhiyong Li; Gun-Young Jung

2004-01-01

287

Cold fusion—Engineering perspectives  

Microsoft Academic Search

Considerable heat was liberated from a palladium-deuterium (Pd-D) system and this was attributed to cold nuclear fusion of deuterium within the palladium lattice.1 The primary source of heat in cold fusion was proposed to be the work-of-fracture of cracks in the Pd electrodes, and the mechanism for crack initiation and propagation was identified as deuterium or hydrogen embrittlement.2 In this

Ali F. AbuTaha

1990-01-01

288

Cold fusion in condensed matter  

Microsoft Academic Search

A model for cold fusion in condensed matter is proposed (cold fusion of deuterons in palladium). It is assumed that the palladium-deuterium system forms an alloy, i.e., it is assumed that Pd ions as well as d\\/sup +\\/ ions are embedded in an uniform background of negative charge (conduction electrons). The model is based on an interaction potential for deuterons

W. Schommers; C. Politis

1989-01-01

289

Cold-electron bolometers for future mm and sub-mm sky surveys  

NASA Astrophysics Data System (ADS)

Future sky surveys in the mm/sub-mm range, like the forthcoming balloon-borne missions LSPE, OLIMPO, SPIDER etc., will need detectors insensitive to cosmic rays (CRs) and with a NEP of the order of 10-17 ¥ 10-18 W/sqrt(Hz). The Cold-Electron Bolometers (CEBs) technology is promising, having the required proper- ties, since the absorber volume is extremely small and the electron system of the absorber is thermally insulated from the phonon system. We have developed an experimental setup to test the optical performance and the CRs insensitivity of CEBs, with the target of integrating them in the OLIMPO and LSPE focal planes.

Salatino, Maria; de Bernardis, Paolo; Mahashabde, Sumedh; Kuzmin, Leonid S.; Masi, Silvia

2014-07-01

290

Absorbed fractions for electrons in ellipsoidal volumes.  

PubMed

We applied a Monte Carlo simulation in Geant4 in order to calculate the absorbed fractions for monoenergetic electrons in the energy interval between 10 keV and 2 MeV, uniformly distributed in ellipsoids made from soft tissue. For each volume, we simulated a spherical shape, four oblate and four prolate ellipsoids, and one scalene shape. For each energy and for every geometrical configuration, an analytical relationship between the absorbed fraction and a 'generalized radius' was found, and the dependence of the fit parameters from electron energy is discussed and fitted by proper parametric functions. With the proposed formulation, the absorbed fraction for electrons in the 10-2000 keV energy range can be calculated for all volumes and for every ellipsoidal shape of practical interest. This method can be directly applied to evaluation of the absorbed fraction from the radionuclide emission of monoenergetic electrons, such as Auger or conversion electrons. The average deposited energy per disintegration in the case of extended beta spectra can be evaluated through integration. Two examples of application to a pure beta emitter such as (90)Y and to (131)I, whose emission include monoenergetic and beta electrons plus gamma photons, are presented. This approach represent a generalization of our previous studies, allowing a comprehensive treatment of absorbed fractions from electron and photon sources uniformly distributed in ellipsoidal volumes of any ellipticity and volume, in the whole range of practical interest for internal dosimetry in nuclear medicine applications, as well as in radiological protection estimations of doses from an internal contamination. PMID:21160113

Amato, E; Lizio, D; Baldari, S

2011-01-21

291

A study of exposure to cold in cold stores.  

PubMed

Effects of exposure to cold on skin-temperature and thermal sensations of eight experienced men wearing protective clothing, who were working normally in a cold store at sub-zero temperatures of about -27 degrees C, were studied to assess the feasibility of deriving work recovery routines from experiments conducted in the actual working environment. Although the variations in the responses to cold were such that insistence on a rigid pattern of working and recovery times would be unwise, results indicated that exposures of about 40% of the total time available would not make the risk of discomfort unacceptable, under the usual working conditions provided clothing rated at 5 to 6 togs was worn. Whilst individual reactions are important and there was, for example, an inverse relation between the age of the operative and the time spent in the cold, the results showed that the reactions of the working group are equally important. It was evident that the operatives worked together as a group which appeared to arrange the work loads to suit individual members of the group. The dry-bulb temperature of the air was an adequate index of the thermal environment, which was relatively constant so that the stress upon the operatives was assessed by time spent in the cold. Considerable individual variations in response to cold were evident; the hands and feet were found to be particularly vulnerable areas, and in general a significant fall in skin-temperature occurred whilst the operatives worked inside the store. At some time during the study, all operatives experienced discomfort from cold and there appeared to be a definite association between percentage incidence of discomfort and the time spent in the store. The current practice for the setting of work/recovery routines was questioned and suggestions were made following the results of the investigation. PMID:15676498

Williamson, D K; Chrenko, F A; Hamley, E J

1984-03-01

292

Biomolecular Effects of Cold Plasma Exposure  

NASA Technical Reports Server (NTRS)

The effects of cold plasma exposure on Deinococcus radiodurans, plasmid DNA and model proteins were assessed using microbiological, spectrometric and biochemical techniques. Exposure of D. radiodurans, an extremely radiation resistant microbe, to O2 plasma (less than or equal to 25 W, approx. 45 mTorr, 90 min) yielded a approx. 99.999 % sterilization and the sterilization rate was increased approx. 10-fold at 100 W and 500 mTorr. AFM images shows that the exposed cells are significantly deformed and possess 50-70 nm concavities. IR analysis indicates the chemical degradation of lipids, proteins and carotenoids of the cell wall and membrane. Intracellular damage was indicated by major absorbance loss at 1245, 1651 and 1538/cm corresponding to degradation of DNA and proteins, respectively. Biochemical experiments demonstrate that plasmas induce strand scissions and crosslinking of plasmid DNA, and reduction of enzyme activity; the degradation is power dependent with total sample loss occurring in 60 s at 200 W and 500 mTorr. Emission spectroscopy shows that D. radiodurans is volatilized into CO2, CO, N2 and H2O confirming the removal of biological matter from contaminated surfaces. The O2 plasma impacts several cellular components predominantly through chemical degradation by atomic oxygen. A CO2, plasma, however, was not effective at degrading D. radiodurans, revealing the importance of plasma composition, which has implications for planetary protection and the contamination of Mars.

Mogul, Rakesh; Bolshakov, Alexander A.; Chan, Suzanne L.; Stevens, Ramsey D.; Khare, Bishun N.; Meyyappan, M.; Trent, Jonathan D.; DeVincenzi, D. (Technical Monitor)

2002-01-01

293

Cold valleys: cluster decay, cold fusion, cold fission-a unifying theory of related phenomena  

Microsoft Academic Search

A unified description of cluster decay as spontaneous emission of clusters like 14C, 24Ne, 28Mg and 32Si in which the residual nucleus is close to the spherical double magic 208Pb nucleus, of cold fusion as the inverse process for the synthesis of first superheavy elements with Z=107, 108 and 109 by colliding 208Pb-projectiles with different targets and of cold fission

W. Greiner; A. Sandulescu

1991-01-01

294

Design of a non-traditional dynamic vibration absorber.  

PubMed

A non-traditional dynamic vibration absorber is proposed for the minimization of maximum vibration velocity response of a vibrating structure. Unlike the traditional damped absorber configuration, the proposed absorber has a linear viscous damper connecting the absorber mass directly to the ground instead of the main mass. Optimum parameters of the proposed absorber are derived based on the fixed-point theory for minimizing the maximum vibration velocity response of a single-degree-of-freedom system under harmonic excitation. The extent of reduction in maximum vibration velocity response of the primary system when using the traditional dynamic absorber is compared with that using the proposed one. Under the optimum tuning condition of the absorbers, it is proved analytically that the proposed absorber provides a greater reduction in maximum vibration velocity response of the primary system than the traditional absorber. PMID:19640019

Cheung, Y L; Wong, W O

2009-08-01

295

Absorbing properties and structural design of microwave absorbers based on carbonyl iron and barium ferrite  

Microsoft Academic Search

Carbonyl iron and barium ferrite powder (BaZn1.5Co0.5Fe16O27) were prepared in this work. The complex permittivity and permeability spectra for rubber radar absorbing materials employing carbonyl iron and barium ferrite powders were measured. A database describing the frequency dependence of the permittivities and permeabilities of the carbonyl iron and barium ferrite microwave absorbers with various powder percentage compositions in 2 18

Y. B. Feng; T. Qiu; C. Y. Shen

2007-01-01

296

Absorbing properties and structural design of microwave absorbers based on carbonyl iron and barium ferrite  

Microsoft Academic Search

Carbonyl iron and barium ferrite powder (BaZn1.5Co0.5Fe16O27) were prepared in this work. The complex permittivity and permeability spectra for rubber radar absorbing materials employing carbonyl iron and barium ferrite powders were measured. A database describing the frequency dependence of the permittivities and permeabilities of the carbonyl iron and barium ferrite microwave absorbers with various powder percentage compositions in 2–18GHz was

Y. B. Feng; T. Qiu; C. Y. Shen

2007-01-01

297

HDPE/MWCNT composite as microwave absorber  

NASA Astrophysics Data System (ADS)

A HDPE/CNT composite has been fabricated based on a commercial polyethylene loaded with a high concentration of CVD grown multiwalled carbon nanotubes with a high aspect ratio. Exploiting the resulting high conductivity of this composite material, we tested the possibility to use it as absorber of electromagnetic waves at microwave frequencies up to 25 GHz. For this purpose the device under test was placed as substrate of a microstrip transmission line. Measurements of the scattering parameters, done with a vectorial network analyzer, have been used in order to obtain the power absorption at different frequencies. Special attention was paid to the optimization of the microstrip geometry. A comparison of the microwave power absorption spectrum with those of commercial cavity absorbers showed encouraging results, regarding the microwave absorption capability of the HDPE/CNT composite material.

Di Giacomo, R.; Neitzert, H. C.

2014-05-01

298

Impedance matched thin metamaterials make metals absorbing.  

PubMed

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others. PMID:24220284

Mattiucci, N; Bloemer, M J; Aközbek, N; D'Aguanno, G

2013-01-01

299

Impedance matched thin metamaterials make metals absorbing  

NASA Astrophysics Data System (ADS)

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others.

Mattiucci, N.; Bloemer, M. J.; Aközbek, N.; D'Aguanno, G.

2013-11-01

300

Impedance matched thin metamaterials make metals absorbing  

PubMed Central

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others. PMID:24220284

Mattiucci, N.; Bloemer, M. J.; Akozbek, N.; D'Aguanno, G.

2013-01-01

301

High-performance THz metamaterial absorber  

E-print Network

We demonstrated an ultra-broadband, polarization-insensitive and wide-angle metamaterial absorber for terahertz (THz) frequencies using arrays of truncated pyramid unit structure made of metal-dielectric multilayer composite. In our design each sub-layer behaving as an effective waveguide is gradually modified in their lateral width to realize a wideband response by effectively stitching together the resonance bands of different waveguide modes. Experimentally, our five layer sample with a total thickness 21um is capable of producing a large absorptivity above 80% from 0.7 to 2.3 THz up to the maximum measurement angle 40{\\deg}. The full absorption width at half maximum (FWHM) of our device is around 127%, greater than those previously reported for THz frequencies. Our absorber design has high practical feasibility and can be easily integrated with the semiconductor technology to make high efficient THz-oriented devices.

Zhu, Jianfei; Sun, Wujiong; Ding, Fei; He, Qiong; Zhou, Lei; Ma, Yungui

2014-01-01

302

Ultra-broadband terahertz metamaterial absorber  

NASA Astrophysics Data System (ADS)

We demonstrated an ultra-broadband, polarization-insensitive, and wide-angle metamaterial absorber for terahertz (THz) frequencies using arrays of truncated pyramid unit structure made of metal-dielectric multilayer composite. In our design, each sub-layer behaving as an effective waveguide is gradually modified in their lateral width to realize a wideband response by effectively stitching together the resonance bands of different waveguide modes. Experimentally, our five layer sample with a total thickness 21 ?m is capable of producing a large absorptivity above 80% from 0.7 to 2.3 THz up to the maximum measurement angle 40°. The full absorption width at half maximum of our device is around 127%, greater than those previously reported for THz frequencies. Our absorber design has high practical feasibility and can be easily integrated with the semiconductor technology to make high efficient THz-oriented devices.

Zhu, Jianfei; Ma, Zhaofeng; Sun, Wujiong; Ding, Fei; He, Qiong; Zhou, Lei; Ma, Yungui

2014-07-01

303

Shock wave absorber having apertured plate  

DOEpatents

The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

Shin, Yong W. (Western Springs, IL); Wiedermann, Arne H. (Chicago Heights, IL); Ockert, Carl E. (Vienna, VA)

1985-01-01

304

Investigations on Absorber Materials at Cryogenic Temperatures  

SciTech Connect

In the framework of the 12 GeV upgrade project for the Continuous Electron Beam Accelerator Facility (CEBAF) improvements are being made to refurbish cryomodules housing Thomas Jefferson National Accelerator Facility?s (JLab) original 5-cell cavities. Recently we have started to look into a possible simplification of the existing Higher Order Mode (HOM) absorber design combined with the aim to find alternative material candidates. The absorbers are implemented in two HOM-waveguides immersed in the helium bath and operate at 2 K temperature. We have built a cryogenic setup to perform measurements on sample load materials to investigate their lossy characteristics and variations from room temperature down to 2 K. Initial results are presented in this paper.

Frank Marhauser, Thomas Elliott, Robert Rimmer

2009-05-01

305

Wide band cryogenic ultra-high vacuum microwave absorber  

DOEpatents

An absorber wave guide assembly for absorbing higher order modes of microwave energy under cryogenic ultra-high vacuum conditions, that absorbs wide-band multi-mode energy. The absorber is of a special triangular shape, made from flat tiles of silicon carbide and aluminum nitride. The leading sharp end of the absorber is located in a corner of the wave guide and tapers to a larger cross-sectional area whose center is located approximately in the center of the wave guide. The absorber is relatively short, being of less height than the maximum width of the wave guide.

Campisi, Isidoro E. (Newport News, VA)

1992-01-01

306

Design of double negative metamaterial thin absorber  

Microsoft Academic Search

This paper presents a new type of thin absorber exhibiting double negative metamaterial (MTM) characteristics. A MTM unit cell was constructed by a multiple split ring resonator (MSRR) and a meander-line arrangement. A MSRR structure exhibits negative permeability and a meander-line structure exhibits negative permittivity. Each unit cell is printed on the two side of a FR-4 substrate (relative dielectric

J. W. Park; H. M. Lee

2011-01-01

307

BIOCHEMISTRY: An Absorbing Study of Cholesterol  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. We obtain sterols from the animal and plant food that we eat. How these plant and animal sterols are absorbed, transported around the body, and excreted has been the subject of much investigation. In a Perspective, Allayee and colleagues discuss a new study (Berge et al.) that implicates two new ABC transporter proteins in the efflux of plant and animal sterols from gut epithelial cells into the gut lumen.

Hooman Allayee (University of California, Los Angeles (UCLA) School of Medicine;Department of Medicine and the Department of Microbiology, Immunology and Molecular Genetics); Bryan A. Laffitte (University of California, Los Angeles (UCLA) School of Medicine;Howard Hughes Medical Institute); Aldons J. Lusis (University of California, Los Angeles (UCLA) School of Medicine;Department of Medicine and the Department of Microbiology, Immunology and Molecular Genetics)

2000-12-01

308

Dielectric studies of water absorbed in epoxies  

E-print Network

consisting of chains of water molecules. In this thesis, dielectric spectroscopy was used to investigate the behavior of water absorbed in a model epoxy/amine polymer system (diglycidyl ether of bisphenol A cured with amino ethyl piperazine). Dielectric... OF TABLES TABLE I Analysis of Purified DER-332 Epoxy Resin. II Analysis of DEH-3g Curing Agent . III Epoxy Film Thickness Measurements . IV Relative Humidity Comparison. V WLF Comparison. VI Comparison of Calculated Activation Energies. VII Glass...

Pham, Ha Quoc

2012-06-07

309

Tech Transfer Webinar: Energy Absorbing Materials  

ScienceCinema

A new material has been designed and manufactured at LLNL that can absorb mechanical energy--a cushion--while also providing protection against sheering. This ordered cellular material is 3D printed using direct ink writing techniques under development at LLNL. It is expected to find utility in application spaces that currently use unordered foams, such as sporting and consumer goods as well as defense and aerospace.

Duoss, Eric

2014-07-15

310

Microcellular ceramic foams for radar absorbing structures  

Microsoft Academic Search

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project is to develop a lightweight, semi-structural, radar-absorbing ceramic foam that can be incorporated into aircraft exhaust systems to replace many of the currently used dense ceramic parts and thereby improve the radar cross section.

J. Huling; D. Phillips

1996-01-01

311

Trends in radar absorbing materials technology  

Microsoft Academic Search

The research in the area of Radar Absorbing Materials (RAMs) has been actively pursued for at least four decades. Although\\u000a resonant RAMs were originally designed by transmission line approach, and the broad band RAMs were obtained by multilayering,\\u000a the quest for ultrawide band performance has led to novel approaches such as chirality and even exploring biochemical products.\\u000a It is observed

K J Vinoy; R M Jha

1995-01-01

312

Development of a crash energy absorber  

E-print Network

are illustrated in Figures 3 through 7. The terminal consist of a series of five (5) telescoping New Jersey safety-shaped CMB plate steel shells housing energy absorbing cartridges. As you move away from the end of the longitudinal barrier, the telescoping... Figure 7 Details of CMB terminal segment no. 5. 19 The terminal segments, as previously discussed, are constructed &om plate steel. The steel shells are given lateral stiffness by reinforcing them along their longitudinal length with thin plate steel...

Bullard, Delbert Lance

2012-06-07

313

Cold Fronts in CDM clusters  

E-print Network

Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters (Vikhlinin et. al., 2001). These features, called ``cold fronts'', are characterized by an increase in surface brightness by a factor >2 over 10-50 kpc, accompanied by a drop in temperature of a similar magnitude. The existence of such sharp gradients can be used to put interesting constraints on the physics of the intracluster medium (ICM), if their mechanism and longevity are well understood. Here, we present results of a search for cold fronts in high-resolution simulations of galaxy clusters in cold dark matter (CDM) models. We show that sharp gradients with properties similar to those of observed cold fronts naturally arise in cluster mergers when the shocks heat gas surrounding the merging sub-cluster, while its dense core remains relatively cold. The compression induced by supersonic motions and shock heating during the merger enhance the ...

Nagai, D; Nagai, Daisuke; Kravtsov, Andrey V.

2003-01-01

314

Cold air systems: Sleeping giant  

SciTech Connect

This article describes how cold air systems help owners increase the profits from their buildings by reducing electric costs and improving indoor air quality through lower relative humidity levels. Cold air distribution involves energy savings, cost savings, space savings, greater comfort, cleaner air, thermal storage, tighter ducting, coil redesign, lower relative humidities, retrofitting, and improved indoor air quality (IAQ). It opens a door for architects, engineers, owners, builders, environmentalists, retrofitters, designers, occupants, and manufacturers. Three things have held up cold air's usage: multiple fan-powered boxes that ate up the energy savings of primary fans. Cold air room diffusers that provided inadequate comfort. Condensation from ducts, boxes, and diffusers. Such problems have been largely eliminated through research and development by utilities and manufacturers. New cold air diffusers no longer need fan powered boxes. It has also been found that condensation is not a concern so long as the ducts are located in air conditioned space, such as drop ceilings or central risers, where relative humidity falls quickly during morning startup.

MacCracken, C.D. (Calmac Manufacturing Corp., Englewood, NJ (United States))

1994-04-01

315

Template stripping using cold welding  

NASA Astrophysics Data System (ADS)

A method for fabricating ultra-flat template-stripped (TS) metal surfaces on standard silicon/silicon-oxide wafers by means of gold cold-welding is presented, and cold-welded template-stripped (CWTS) platinum surfaces are demonstrated as an example. Due to the lack of any adhesives, the final TS metal ``sandwiches'' are fully compatible with all organic solvents, as well as ultra-high vacuum (UHV). The produced CWTS platinum surfaces are demonstrated to have the same surface properties-most importantly single-angstrom rms roughness-as previously studied TS platinum. The effectiveness of the cold-welding technique is shown to decrease as a function of time exposed to ambient laboratory conditions after removal from vacuum and prior to pressurized cold-welding. Contact angle measurements demonstrate this decrease to be due to a gradual increase in surface contamination of the evaporated gold layers prior to their being joined by cold-welding. The potential versatility and scalability of the CWTS fabrication process is briefly discussed. .

Blackstock, Jason J.; Li, Zhiyong; Jung, Gun-Young

2004-05-01

316

Mathematical modeling of cold cap  

SciTech Connect

The ultimate goal of studies of cold cap behavior in glass melters is to increase the rate of glass processing in an energy-efficient manner. Regrettably, mathematical models, which are ideal tools for assessing the responses of melters to process parameters, have not paid adequate attention to the cold cap. In this study, we consider a cold cap resting on a pool of molten glass from which it receives a steady heat flux while temperature, velocity, and extent of conversion are functions of the position along the vertical coordinate. A one-dimensional (1D) mathematical model simulates this process by solving the differential equations for mass and energy balances with appropriate boundary conditions and constitutive relationships for material properties. The sensitivity analyses on the effects of incoming heat fluxes to the cold cap through its lower and upper boundaries show that the cold cap thickness increases as the heat flux from above increases, and decreases as the total heat flux increases. We also discuss the effects of foam, originating from batch reactions and from redox reactions in molten glass and argue that models must represent the foam layer to achieve a reliable prediction of the melting rate as a function of feed properties and melter conditions.

Pokorny, Richard; Hrma, Pavel R.

2012-10-13

317

PT-symmetric laser-absorber  

E-print Network

In a recent work, Y.D. Chong et al. [Phys. Rev. Lett. {\\bf 105}, 053901 (2010)] proposed the idea of a coherent perfect absorber (CPA) as the time-reversed counterpart of a laser, in which a purely incoming radiation pattern is completely absorbed by a lossy medium. The optical medium that realizes CPA is obtained by reversing the gain with absorption, and thus it generally differs from the lasing medium. Here it is shown that a laser with an optical medium that satisfies the parity-time $(\\mathcal{PT})$ symmetry condition $\\epsilon(-\\mathbf{r})=\\epsilon^*(\\mathbf{r})$ for the dielectric constant behaves simultaneously as a laser oscillator (i.e. it can emit outgoing coherent waves) and as a CPA (i.e. it can fully absorb incoming coherent waves with appropriate amplitudes and phases). Such a device can be thus referred to as a $\\mathcal{PT}$-symmetric CPA-laser. The general amplification/absorption features of the $\\mathcal{PT}$ CPA-laser below lasing threshold driven by two fields are determined.

Stefano Longhi

2010-08-31

318

Cosmic Dust in Mg II Absorbers  

NASA Astrophysics Data System (ADS)

Mg II absorbers induce reddening on background quasars. We measure this effect and infer the cosmic density of dust residing in these systems to be ? ? 2 × 10-6, in units of the critical density of the universe, which is comparable to the amount of dust found in galactic disks or about half the amount inferred to exist outside galaxies. We also estimate the neutral hydrogen abundance in Mg II clouds to be ? ? 1.5 × 10-4, which is approximately 5% of hydrogen in stars in galaxies. This implies a dust-to-gas mass ratio for Mg II clouds of about 1/100, which is similar to the value for normal galaxies. This would support the hypothesis of the outflow origin of Mg II clouds, which are intrinsically devoid of stars and hence have no sources of dust. Considerations of the dust abundance imply that the presence of Mg II absorbers around galaxies lasts effectively for a few Gyr. High-redshift absorbers allow us to measure the rest-frame extinction curve to 900 Å, at which the absorption by the Lyman edge dominates over scattering by dust in the extinction opacity.

Ménard, Brice; Fukugita, Masataka

2012-08-01

319

COSMIC DUST IN Mg II ABSORBERS  

SciTech Connect

Mg II absorbers induce reddening on background quasars. We measure this effect and infer the cosmic density of dust residing in these systems to be {Omega} Almost-Equal-To 2 Multiplication-Sign 10{sup -6}, in units of the critical density of the universe, which is comparable to the amount of dust found in galactic disks or about half the amount inferred to exist outside galaxies. We also estimate the neutral hydrogen abundance in Mg II clouds to be {Omega} Almost-Equal-To 1.5 Multiplication-Sign 10{sup -4}, which is approximately 5% of hydrogen in stars in galaxies. This implies a dust-to-gas mass ratio for Mg II clouds of about 1/100, which is similar to the value for normal galaxies. This would support the hypothesis of the outflow origin of Mg II clouds, which are intrinsically devoid of stars and hence have no sources of dust. Considerations of the dust abundance imply that the presence of Mg II absorbers around galaxies lasts effectively for a few Gyr. High-redshift absorbers allow us to measure the rest-frame extinction curve to 900 A, at which the absorption by the Lyman edge dominates over scattering by dust in the extinction opacity.

Menard, Brice [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Fukugita, Masataka [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 277-8583 (Japan)

2012-08-01

320

COLD-SAT dynamic model  

NASA Technical Reports Server (NTRS)

This report discusses the development and underlying mathematics of a rigid-body computer model of a proposed cryogenic on-orbit liquid depot storage, acquisition, and transfer spacecraft (COLD-SAT). This model, referred to in this report as the COLD-SAT dynamic model, consists of both a trajectory model and an attitudinal model. All disturbance forces and torques expected to be significant for the actual COLD-SAT spacecraft are modeled to the required degree of accuracy. Control and experimental thrusters are modeled, as well as fluid slosh. The model also computes microgravity disturbance accelerations at any specified point in the spacecraft. The model was developed by using the Boeing EASY5 dynamic analysis package and will run on Apollo, Cray, and other computing platforms.

Adams, Neil S.; Bollenbacher, Gary

1992-01-01

321

Is it a Cold or the Flu? -Know the Difference Signs & Symptoms Cold Flu  

E-print Network

Is it a Cold or the Flu? - Know the Difference Signs & Symptoms Cold Flu Onset Gradual Sudden Fever.rochester.edu/uhs (Check Care for Colds & Flu in "Health Topics.") Centers for Disease Control www.cdc.gov/flu University

Mahon, Bradford Z.

322

Antihydrogen Formation using Cold Plasmas  

SciTech Connect

Antihydrogen, the antimatter counterpart of the hydrogen atom, can be formed by mixing cold samples of antiprotons and positrons. In 2002 the ATHENA collaboration succeeded in the first production of cold antihydrogen. By observing and imaging the annihilation products of the neutral, non-confined, antihydrogen atoms annihilating on the walls of the trap we can observe the production in quasi-real-time and study the dynamics of the formation mechanism. The formation mechanism strongly influences the final state of the formed antihydrogen atoms, important for future spectroscopic comparison with hydrogen. This paper briefly summarizes the current understanding of the antihydrogen formation in ATHENA.

Madsen, N.; Bowe, P.D.; Hangst, J.S. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Amoretti, M.; Carraro, C.; Macri, M.; Testera, G.; Variola, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Genova, I-16146 Genova (Italy); Amsler, C.; Johnson, I.; Pruys, H.; Regenfus, C. [Physik-Institut, Zuerich University, CH-8057 Zurich (Switzerland); Bonomi, G.; Bouchta, A.; Doser, M.; Kellerbauer, A.; Landua, R. [PH Department, CERN, Geneva (Switzerland); Cesar, C.L. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21945-970 (Brazil); Charlton, M.; Joergensen, L.V. [Department of Physics, University of Wales Swansea, Swansea SA2 8PP (United Kingdom)] [and others

2004-10-20

323

40 CFR 65.150 - Absorbers used as control devices.  

Code of Federal Regulations, 2010 CFR

...AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONSOLIDATED FEDERAL AIR RULE Closed Vent Systems, Control Devices, and Routing to a Fuel Gas System or a Process § 65.150 Absorbers used as control devices. (a) Absorber equipment and...

2010-07-01

324

Flexible metamaterial absorbers for stealth applications at terahertz frequencies  

E-print Network

, "A transparent metamaterial to manipulate electromagnetic wave polarizations," Opt. Lett. 36(6), 927Flexible metamaterial absorbers for stealth applications at terahertz frequencies Krzysztof: We have wrapped metallic cylinders with strongly absorbing metamaterials. These resonant structures

Zhang, Xin

325

Experiment research on MM wavelength radar absorbing materials  

Microsoft Academic Search

Experiments to obtain high quality millimeter wavelengths radar absorbing materials are discussed. In order to obtain the best mixing proportion of materials, a great number of materials had been investigated. Several absorbing coating materials achieving this aim are found

Chen ZhiPing; Zhu Qi; Xu Shan-Jia

1999-01-01

326

Inorganic UV absorbers for the photostabilisation of wood-clearcoating systems: Comparison with organic UV absorbers  

NASA Astrophysics Data System (ADS)

Inorganic UV absorbers which are widely used today were originally designed neither as a UV blocker in coatings applications, nor for wood protection. In recent years however, there has been extensive interest in these compounds, especially with regard to their properties as a UV blocker in coating applications. In this work, we carried out a comparative study to look into some inorganic and organic UV absorbers used in wood coating applications. The aim of this study is to determine the photostabilisation performances of each type of UV absorbers, to seek possible synergies and the influences of different wood species. We have also searched to find eventual correlation between these performances and the influence of UV absorbers on the film properties. Our study has compared the performances of the following UV absorbers: hombitec RM 300, hombitec RM 400 from the Sachtleben Company; transparent yellow and red iron oxides from Sayerlack as inorganic UV absorbers; organic UV absorbers Tinuvin 1130 and Tinuvin 5151 from Ciba Company. The study was carried out on three wood species: Abies grandis, tauari and European oak. The environmental constraints (in particular the limitation of the emission of volatile organic compounds VOCs) directed our choice towards aqueous formulations marketed by the Sayerlack Arch Coatings Company. The results obtained after 800 h of dry ageing showed that the Tinuvins and the hombitecs present better wood photostabilisations. On the other hand in wet ageing, with the hombitec, there are appearances of some cracks and an increase in the roughness of the surface. This phenomenon is absent when the Tinuvins are used. With regard to these results, the thermomechanical analyses relating to the follow-up of the change of the glass transition temperature ( Tg) of the various coating systems, show a different behaviour between the two types of absorbers. However, contrary to organic UV absorbers, inorganic ones tend to increase Tg during ageing, and, consequently decrease the flexibility of films. These phenomena can lead to the appearance of cracks found in the case of the wet weathering.

Aloui, F.; Ahajji, A.; Irmouli, Y.; George, B.; Charrier, B.; Merlin, A.

2007-02-01

327

Method for absorbing an ion from a fluid  

DOEpatents

A method for absorbing an ion from a fluid by using dispersing an organic acid into an anion surfactant solution, mixing in a divalent-metal containing compound and a trivalent-metal containing compound and calcining the resulting solid layered double hydroxide product to form an absorbent material and then contacting the absorbent material with an aqueous solution of cations or anions to be absorbed.

Gao, Huizhen (Carlsbad, NM); Wang, Yifeng (Albuquerque, NM); Bryan, Charles R. (Albuquerque, NM)

2007-07-03

328

An Energy Absorber for the International Space Station  

NASA Technical Reports Server (NTRS)

The energy absorber described herein is similar in size and shape to an automotive shock absorber, requiring a constant, high load to compress over the stroke, and self-resetting with a small load. The differences in these loads over the stroke represent the energy absorbed by the device, which is dissipated as friction. This paper describes the evolution of the energy absorber, presents the results of testing performed, and shows the sensitivity of this device to several key design variables.

Wilkes, Bob; Laurence, Lora

2000-01-01

329

A Single-Layer Meta-Atom Absorber  

E-print Network

We realized and experimentally tested a conceptually new kind of electrically thin absorbers of electromagnetic waves. The idea is to utilize a single layer of precisely designed meta-atoms. This allows one to design an absorber with unprecedentedly small thickness. The absorber implies absence of a ground plane. High efficiency of the realized structure in the S band is demonstrated. The conceptual idea of the proposed absorber can find many applications especially at optical frequencies.

Faniayeu, Ihar; Dzerzhauskaya, Tatyana; Semchenko, Igor; Khakhomov, Sergei

2014-01-01

330

Avionics Box Cold Plate Damage Prevention  

NASA Technical Reports Server (NTRS)

Problem Introduction: 1. Prevent Cold Plate Damage in Space Shuttle. 1a. The number of cold plate problems had increased from an average of 16.5 per/year between 1990 through 2000, to an average of 39.6 per year between 2001through 2005. 1b. Each complete set of 80 cold plates cost approximately $29 million, an average of $362,500 per cold plate. 1c It takes four months to produce a single cold plate. 2. Prevent Cold Plate Damage in Future Space Vehicles.

Stambolian, Damon B.; Larchar, Steven W.; Henderson, Gena; Tran, Donald; Barth, Tim

2012-01-01

331

High temperature layered absorber for thermo-solar systems  

NASA Astrophysics Data System (ADS)

We present a theoretical description of ideal absorber performances for solar thermodynamic systems as well as a numerical and experimental study of high temperature layered absorber. The structure designed can convert 85% of the incident light under a concentration factor of 1000 suns, that is to say almost the ultimate power that a perfect absorber can deliver.

Langlais, Mathieu; Prod?homme, Patricia; Bru, Hélène; Ben-Abdallah, Philippe

2014-12-01

332

40 CFR 65.150 - Absorbers used as control devices.  

...2014-07-01 false Absorbers used as control devices. 65.150 Section 65.150...FEDERAL AIR RULE Closed Vent Systems, Control Devices, and Routing to a Fuel Gas System...Process § 65.150 Absorbers used as control devices. (a) Absorber equipment...

2014-07-01

333

Incident angle insensitive double negative (DNG) metamaterial absorber  

Microsoft Academic Search

An incident angle insensitive double negative metamaterial absorber by using hexagonal shape is described. It can absorb any incident angle transverse electromagnetic (TEM) wave because of its hexagonal symmetry shape. In spite of its structure, the absorber achieved a 81.5% absorptivity at 10.52 GHz in numerical results.

Youngsoo Jang; Joungyoung Lee; Sungjoon Lim

2011-01-01

334

A resonant point absorber of ocean-wave power  

Microsoft Academic Search

A system for absorbing and utilizing the energy carried by ocean waves is discussed. The 'point absorber' considered is a system in which the horizontal extent is much smaller than one wavelength. The point absorber is optimized for efficient energy conversion. The resonant characteristic frequency of the system is at all times tuned to the characteristic frequency of the wave.

K. Budar; J. Falnes

1975-01-01

335

Thin Radar Absorber Using an Artificial Magnetic Ground Plane  

Microsoft Academic Search

This paper provides experimental and numerical simulation verification of the radar absorbing properties of an ultra-thin radar absorber. The absorber takes the form of an artificial magnetic conductor with surface mounted resistors. Electromagnetic simulations show the confinement of current distributed across the surface which results as a consequence of plane wave excitation. For the first time it was shown experimentally

S. W. Simms; V. F. Fusco

2006-01-01

336

The control of transpiration by absorbed radiation  

NASA Astrophysics Data System (ADS)

Transpiration plays a key role in the hydrological cycle and models of transpiration have been used in many applications. However, our understanding of mechanisms which control the rate of transpiration is still limited being a domain of two different disciplines. Meteorologists apply the top-down approach driven by physical descriptions and water vapour transport, stomatal conductance is regarded as a boundary condition. Plant physiologists focus on the bottom-up approach and emphasize the physiological control of transpiration by stomatal conductance. It is generally accepted that transpiration is strongly influenced by the boundary layer outside the leaf and that feedback mechanisms within this layer decrease the sensitivity of transpiration to changes in stomatal conductance. This feedback mechanism is thought to increase with increasing scale from single stoma to canopy and ecosystem. In contrast, we propose a mechanism that would place much of the control inside the leaf. Most of the solar radiation reaching the leaf penetrates the epidermis with little interaction and the largest part of the energy is absorbed by chloroplasts in mesophyll cells. Thus, evaporation occurs into the intercellular air spaces of a leaf at cell walls adjacent to the chloroplasts of the leaf mesophyll and it is directly coupled to absorbed solar radiation. We present data showing that variation in the rate of transpiration and stomatal conductance at constant humidity and CO2 is closely proportional to changes in fluxes of energy (W m-2) absorbed by the leaf. Computer simulations of energy exchange between the leaf mesophyll and the atmosphere with different regimes of heat and water exchange operating on the inner and outer sides of the epidermis realistically simulate transpiration, stomatal response to a range of environmental conditions and provide a basis to calculate carbon fluxes. This approach has the potential for an up-scaling of water and carbon fluxes in canopies and ecosystems.

Pieruschka, Roland; Berry, Joseph A.

2010-05-01

337

Images of the Cold War.  

ERIC Educational Resources Information Center

The conventional U.S. picture traces the Cold War to Soviet violation of wartime agreements, while the U.S.S.R. defends its actions as responses to American violations and foreign adventurism. An understanding of how ideology is shaped by national self-interest will help students see beyond propaganda and myth in interpreting past and current…

Chomsky, Noam

1989-01-01

338

Cold Cloud Cores in Chamaeleon  

NASA Astrophysics Data System (ADS)

The ISOPHOT Serendipity Survey (ISOSS) is a far-infrared survey at 170 mum, using the slewing time of the ISO telescope. It is a powerful tool to explore both, extragalactic sources and objects within the Milky Way. As a first example to investigate the cold interstellar medium in nearby star forming regions, the molecular cloud complexes in Chamaeleon have been studied. The ISOSS coverage of the Chamaeleon region is ~30 %. Combining ISOSS with IRAS data, we derived the density and temperature of the cold interstellar medium. Altogether, 9 very cold cloud cores (VCCs) with colour temperatures of T_dust <= 13 K have been found. Comparing our results with molecular line surveys of the region, and with visual extinction maps, based on NIR starcounts, it shows that: (i) all VCCs have high gas densities, (ii) approx. 80 % have low gas temperatures, (iii) all but one VCC are associated with A_v > 6 mag extinction peaks, and (iv) very cold dust contributes considerably to the total mass of star forming clouds.

Hotzel, S.; Lemke, D.; Stickel, M.; Tóth, L. V.

339

The Cold Blooded Killer: Hypothermia.  

ERIC Educational Resources Information Center

Part of a series of home literacy readers with conversational text and sketches, this booklet depicts the subarctic Alaskan environment where cold makes extreme demands on body metabolism. Body temperature must be maintained above 80F (26.7C). A condition of too little body-heat is termed hypo- ('deficit') thermia ('heat'). Hypothermia is the…

Keller, Rosanne

340

Interface Model of Cold Fusion  

Microsoft Academic Search

The interface theory of cold fusion is a variant of Ion Band State (IBS) Theory.1 It models Bloch symmetry deuterons in a 2-dimensional metal lattice instead of the 3-dimensional metal lattice first used. Both IBS variants recognize that the required lattice symmetry has limited extent, with the reactive deuterons being bound inside a closed volume like a box. The reactive

Talbot A. Chubb

341

Hot, Cold, Fresh and Salty  

NSDL National Science Digital Library

In this activity, learners observe the effects of the layering of warm and cold water and water that is more or less saline than regular water. They will discover how the effects of salinity and temperature are the root cause of thermohaline layering in the ocean.

Roth, Jerry; Service, Noaa O.

342

Cold fusion — The heat mechanism  

Microsoft Academic Search

The assumption that deuterium, and not palladium, is the fuel in the Pons-Fleischmann experiments led to high expectations of cold nuclear fusion. The conversion of mechanical energy to heat was neglected in studying the phenomenon. Considerable strain energy is stored in metals when processed from the ore. The initiation, growth, and propagation of cracks in the bulk disturb the energy

Ali F. AbuTaha

1990-01-01

343

Warming up to cold fusion  

Microsoft Academic Search

The idea that tabletop equipment at room temperature could produce nuclear fusion was widely rejected five years ago by the scientific community. Nevertheless, recent results from numerous labs show that a novel phenomena of some kind may indeed be occurring, though theorist are still groping for an explanation. Many aspects of the cold fusion effect are now reproducible if known

Storms

2009-01-01

344

The status of `cold fusion'  

Microsoft Academic Search

The questions raised by reports of nuclear reactions at low energies, so called `cold fusion', are not yet answered to the satisfaction of many scientists. Further experimental investigations of these and related questions seems desirable, at least for scientific if not practical reasons. Properly conducted, such investigations would be indistinguishable from normal research. They would yield information germane to accepted

David J. Nagel

1998-01-01

345

Bandwidth enhancement in disordered metamaterial absorbers  

NASA Astrophysics Data System (ADS)

In this letter, we show numerically and experimentally that a positional disorder of a collection of absorbing electromagnetic wave resonators operating in the long wavelength regime dramatically enhances the absorption bandwidth. The demonstration is performed by using single-size ring-shaped thin metal pieces periodically or randomly positioned onto a back-grounded dielectric layer. For periodic array, an optimum in the periodicity is pointed out with a narrow bandwidth, while the increasing influence of coupling effects for resonators in close vicinity explains a three-fold bandwidth enhancement in the case of positional disorder.

Hao, Jianping; Lheurette, Éric; Burgnies, Ludovic; Okada, Étienne; Lippens, Didier

2014-08-01

346

Acoustical model of a Shoddy fibre absorber  

NASA Astrophysics Data System (ADS)

Shoddy fibres or "Shoddies" are a mixture of post-consumer and post-industrial fibres diverted from textile waste streams and recycled into their raw fibre form. They have found widespread use as a raw material for manufacturing sound absorbers that include, but are not limited to: automotive, architectural and home appliance applications. The purpose of this project is to develop a simple acoustic model to describe the acoustic behaviour of sound absorbers composed primarily of Shoddy fibres. The model requires knowledge of the material's bulk density only. To date, these materials have not been the focus of much published research and acoustical designers must rely on models that were developed for other materials or are overly complex. For modelling purposes, an equivalent fluid approach is chosen to balance complexity and accuracy. In deriving the proposed model, several popular equivalent fluid models are selected and the required input parameters for each model identified. The models are: the model of Delaney and Bazley, two models by Miki, the model of Johnson in conjunction with the model of Champoux and Allard and the model of Johnson in conjunction with the model of Lafarge. Characterization testing is carried out on sets of Shoddy absorbers produced using three different manufacturing methods. The measured properties are open porosity, tortuosity, airflow resistivity, the viscous and thermal characteristic lengths and the static thermal permeability. Empirical relationships between model parameters and bulk density are then derived and used to populate the selected models. This yields several 'simplified' models with bulk density as the only parameter. The most accurate model is then selected by comparing each model's prediction to the results of normal incidence sound absorption tests. The model of Johnson-Lafarge populated with the empirical relations is the most accurate model over the range of frequencies considered (approx. 300 Hz - 4000 Hz) Characterization testing yields specific values for intrinsic material parameters that allow for comparison to other porous materials. Individual parameter relations allow users to substitute measured or theoretical values as needed. A new empirical acoustical model is proposed to describe the behaviour of Shoddy-based fibre absorbers. The model requires knowledge of the bulk density only. This parameter is easily measured making application of the model elementary. Mots-clés : Shoddy, porous, fibre, recycled, absorption, model, acoustic.

Manning, John Peter

347

A completely absorbed oral preparation of digoxin.  

PubMed

Digoxin absorption was studied in healthy volunteers by determination of peak plasma concentrations, areas under plasma concentration curves, and urinary excretion after single-dose administration. By comparison with an aqueous solution, increased rate and extent of absorption occurred from experimental soft gelatin formulations of digoxin in solution. Enhanced bioavailability of the capsules was not affected by altered volume of contained solvent. Digoxin was considerably better absorbed from capsules than from tablets of moderately high dissolution rate. Mean percentage intestinal absorption was 75% from tablet and 97% from capsules. Reduced between-subject variability accompanied the enhanced absorption from capsules. PMID:1269214

Johnson, B F; Bye, C; Jones, G; Sabey, G A

1976-06-01

348

FDTD simulation of an optical absorber based on CPML absorbing boundary condition  

NASA Astrophysics Data System (ADS)

High scattering in biological turbid media limits the applicability of optical imaging techniques, such as optical coherence tomography (OCT). Accurate and robust simulations are required due to the complexity of optical wave propagation in these tissues. Recent computational simulations make use of finite-difference time-domain (FDTD) method to exactly solve the scattered electromagnetic field distribution. We propose a method to isolate and selectively remove energy from portions of the scattered field in these simulations. This technique will involve placing an absorber in the medium that consists of convolutional perfectly matched layers (CPML). The performance of the absorber as an optical target is analyzed.

Cantero, Sergio; Huang, Yian; Tseng, Snow H.

2014-03-01

349

Properties of Propagation of Electromagnetic Wave in a Multilayer Radar-Absorbing Structure With Plasma and Radar-Absorbing Material  

Microsoft Academic Search

A multilayer radar-absorbing structure with plasma- and radar-absorbing material (RAM) is established to investigate the stealth mechanisms of the multilayer absorber. The method of impedance transformation with multiple dielectrics is used to analyze the propagation of electromagnetic (EM) waves in the multilayer structure. The dependences of EM waves attenuation on the parameters of the plasma and RAMs are provided. The

Cheng-Xun Yuan; Zhong-Xiang Zhou; Jingwen W. Zhang; Xiao-Li Xiang; Yue Feng; Hong-Guo Sun

2011-01-01

350

Formation and evolution of quasar absorbers  

NASA Astrophysics Data System (ADS)

The column density distribution of quasar absorbers is believed to evolve over time so that different classes of quasar absorbers dominate the neutral gas content in the Universe at various redshifts. At z<3.5, damped Lyman-alpha systems (DLAs) are the major component of the HI mass. But it has been suggested that at z>3.5, 45% of the HI lies in systems below the traditional DLA definition, in ``sub-DLAs'' with 1019 < N(HI) < 2 * 1020 cm-2. A new sample of UVES spectra composed of 18 z>4 quasars is used to search for and analyse high redshift sub-DLAs. These data, together with another 22 UVES spectra from the ESO archives, allow to directly establish the column density distribution function down to N(HI) = 1019 cm-2 at various redshifts. Its evolution combined with measurements of the total amount of neutral gas are used to probe the formation epoch of damped Lyman-alpha systems.

Péroux, Celine; D'Odorico, Sandro; Dessauges-Zavadsky, Miroslava; Kim, Tae Sun

2004-12-01

351

Wave energy extraction by coupled resonant absorbers.  

PubMed

In this article, a range of problems and theories will be introduced that will build towards a new wave energy converter (WEC) concept, with the acronym 'ROTA' standing for resonant over-topping absorber. First, classical results for wave power absorption for WECs constrained to operate in a single degree of freedom will be reviewed and the role of resonance in their operation highlighted. Emphasis will then be placed on how the introduction of further resonances can improve power take-off characteristics by extending the range of frequencies over which the efficiency is close to a theoretical maximum. Methods for doing this in different types of WECs will be demonstrated. Coupled resonant absorbers achieve this by connecting a WEC device equipped with its own resonance (determined from a hydrodynamic analysis) to a new system having separate mass/spring/damper characteristics. It is shown that a coupled resonant effect can be realized by inserting a water tank into a WEC, and this idea forms the basis of the ROTA device. In essence, the idea is to exploit the coupling between the natural sloshing frequencies of the water in the internal tank and the natural resonance of a submerged buoyant circular cylinder device that is tethered to the sea floor, allowing a rotary motion about its axis of attachment. PMID:22184664

Evans, D V; Porter, R

2012-01-28

352

Metamaterial perfect absorber based hot electron photodetection.  

PubMed

While the nonradiative decay of surface plasmons was once thought to be only a parasitic process that limits the performance of plasmonic devices, it has recently been shown that it can be harnessed in the form of hot electrons for use in photocatalysis, photovoltaics, and photodetectors. Unfortunately, the quantum efficiency of hot electron devices remains low due to poor electron injection and in some cases low optical absorption. Here, we demonstrate how metamaterial perfect absorbers can be used to achieve near-unity optical absorption using ultrathin plasmonic nanostructures with thicknesses of 15 nm, smaller than the hot electron diffusion length. By integrating the metamaterial with a silicon substrate, we experimentally demonstrate a broadband and omnidirectional hot electron photodetector with a photoresponsivity that is among the highest yet reported. We also show how the spectral bandwidth and polarization-sensitivity can be manipulated through engineering the geometry of the metamaterial unit cell. These perfect absorber photodetectors could open a pathway for enhancing hot electron based photovoltaic, sensing, and photocatalysis systems. PMID:24837991

Li, Wei; Valentine, Jason

2014-06-11

353

Erbium concentration dependent absorbance in tellurite glass  

NASA Astrophysics Data System (ADS)

Enhancing the optical absorption cross-section in topically important rare earth doped tellurite glasses is challenging for photonic devices. Controlled synthesis and detailed characterizations of the optical properties of these glasses are important for the optimization. The influence of varying concentration of Er3+ ions on the absorbance characteristics of lead tellurite glasses synthesized via melt-quenching technique are investigated. The UV-Vis absorption spectra exhibits six prominent peaks centered at 490, 526, 652, 800, 982 and 1520 nm ascribed to the transitions in erbium ion from the ground state to the excited states 4F7/2, 2H11/2, 4F9/2, 4I9/2, 2H11/2 and 4I13/2, respectively. The results are analyzed by means of optical band gap Eg and Urbach energy Eu. The values of the energy band gap are found decreased from 2.82 to 2.51 eV and the Urbach energy increased from 0.15 to 0.24 eV with the increase of the Er2O3 concentration from 0 to 1.5 mol%. The excellent absorbance of the prepared tellurite glasses makes them suitable for fabricating solid state lasers.

Sazali, E. S.; Rohani, M. S.; Sahar, M. R.; Arifin, R.; Ghoshal, S. K.; Hamzah, K.

2014-09-01

354

Configurable metamaterial absorber with pseudo wideband spectrum.  

PubMed

Metamaterials attain their behavior due to resonant interactions among their subwavelength components and thus show specific designer features only in a very narrow frequency band. There is no simple way to dynamically increase the operating bandwidth of a narrowband metamaterial, but it may be possible to change its central frequency, shifting the spectral response to a new frequency range. In this paper, we propose and experimentally demonstrate a metamaterial absorber that can shift its central operating frequency by using mechanical means. The shift is achieved by varying the gap between the metamaterial and an auxiliary dielectric slab parallel to its surface. We also show that it is possible to create multiple absorption peaks by adjusting the size and/or shape of the dielectric slab, and to shift them by moving the slab relative to the metamaterial. Specifically, using numerical simulations we design a microwave metamaterial absorber and experimentally demonstrate that its central frequency can be set anywhere in a 1.6 GHz frequency range. The proposed configuration is simple and easy to make, and may be readily extended to THz frequencies. PMID:22418545

Zhu, Weiren; Huang, Yongjun; Rukhlenko, Ivan D; Wen, Guangjun; Premaratne, Malin

2012-03-12

355

Cold Weather Guidelines Temperature check-in  

E-print Network

respiratory injury, including 'exercise induced' asthma and increased respiratory infection. For your. The temperature cut-off we have set is to minimize cold weather injuries both with frost bite and cold induced

Scheel, David

356

Cold-Weather Sports and Your Family  

MedlinePLUS

... the weather turns frosty. Beating the Cold-Weather Blahs Once a chill is in the air, our ... more sedentary can lead to the "cold-weather blahs." Kids might feel more tired, lethargic, or even ...

357

Helium Find Thaws the Cold Fusion Trail.  

ERIC Educational Resources Information Center

Reported is a study of cold fusion in which trace amounts of helium, possible evidence of an actual fusion reaction, were found. Research methodology is detailed. The controversy over the validity of experimental results with cold fusion are reviewed. (CW)

Pennisi, E.

1991-01-01

358

21 CFR 890.5700 - Cold pack.  

Code of Federal Regulations, 2010 CFR

...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. ...contour of the body and that provides cold therapy for body surfaces. (b)...

2010-04-01

359

21 CFR 890.5700 - Cold pack.  

Code of Federal Regulations, 2011 CFR

...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. ...contour of the body and that provides cold therapy for body surfaces. (b)...

2011-04-01

360

21 CFR 890.5700 - Cold pack.  

Code of Federal Regulations, 2012 CFR

...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. ...contour of the body and that provides cold therapy for body surfaces. (b)...

2012-04-01

361

21 CFR 890.5700 - Cold pack.  

Code of Federal Regulations, 2013 CFR

...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. ...contour of the body and that provides cold therapy for body surfaces. (b)...

2013-04-01

362

A simple absorbing layer implementation for transmission line matrix modeling  

NASA Astrophysics Data System (ADS)

An absorbing layer formulation for transmission line matrix modeling is proposed. The approach consists in attenuating the incident pulse propagating toward the absorbing layer only, using an attenuation factor which gradually decreases as the sound wave propagates along the absorbing medium. The formulation of the damping function followed by the attenuation factor along the absorbing layer is depicted and discussed. The efficiency of the present formulation is validated by comparison with another absorbing layer model and virtual boundary conditions proposed in the literature. Numerical simulations are also given in order to evaluate the effects of both the attenuation factor and the depth on the absorbing layer efficiency. As expected, results are consistent with absorbing layer implementation in other numerical methods; firstly, the attenuation at the entrance of the absorbing layer must be gentle, and secondly the efficiency increases with the layer depth. Lastly, it is shown that the unwanted reflection seems to vanish over the time when increasing the layer depth, meaning that reflections continuously occur within the absorbing layer and not on the geometrical limits of the absorbing layer. Although the approach is dedicated to outdoor sound propagation modeling (only an example on urban acoustics application is given), the proposed formulation of absorbing layers can be applied in other domains of acoustics. However, its application in shielded areas should be avoided because unwanted reflections due to an insufficient attenuation can be significant in comparison with the ambient noise in such quiet environments.

Guillaume, Gwenaël; Picaut, Judicaël

2013-09-01

363

Electrical tree initiation in polyethylene absorbing Penning gas  

SciTech Connect

Ac tree initiation voltage was examined in untreated LDPE, vacuum degassed LDPE and LDPE absorbing He gas (He gas was absorbed after vacuum degassing). The authors have already reported that vacuum degassed LDPE shows much higher tree initiation voltage than untreated one because of absence of oxygen. Therefore they expected that LDPE absorbing He shows the same property with vacuum degassed LDPE. However tree initiation voltage of LDPE absorbing He is as low as that of untreated LDPE. LDPE absorbing Ar gas shows the same tendency. He or Ar gas does not change so much impulse tree initiation voltage. LDPE absorbing He was not well dyed with methylene blue after ac voltage application, which indicates that active oxidation does not occur. Low ac tree initiation voltage in LDPE absorbing He or Ar may be caused by Penning ionization in free volume.

Shimizu, N.; Tohyama, N.; Sato, H. [Nagoya Univ. (Japan). Dept. of Electrical Engineering

1996-12-31

364

Container and method for absorbing and reducing hydrogen concentration  

DOEpatents

A method for absorbing hydrogen from an enclosed environment comprising providing a vessel; providing a hydrogen storage composition in communication with a vessel, the hydrogen storage composition further comprising a matrix defining a pore size which permits the passage of hydrogen gas while blocking the passage of gaseous poisons; placing a material within the vessel, the material evolving hydrogen gas; sealing the vessel; and absorbing the hydrogen gas released into the vessel by the hydrogen storage composition. A container for absorbing evolved hydrogen gas comprising: a vessel having an interior and adapted for receiving materials which release hydrogen gas; a hydrogen absorbing composition in communication with the interior, the composition defining a matrix surrounding a hydrogen absorber, the matrix permitting the passage of hydrogen gas while excluding gaseous poisons; wherein, when the vessel is sealed, hydrogen gas, which is released into the vessel interior, is absorbed by the hydrogen absorbing composition.

Wicks, George G. (Aiken, SC); Lee, Myung W. (North Augusta, SC); Heung, Leung K. (Aiken, SC)

2001-01-01

365

Cold Fusion Has Now Come Out of the Cold  

Microsoft Academic Search

The phenomenon called cold fusion or LENR (Low-Energy-Nuclear-Reaction) has now achieved a level of reproducibility and understanding that warrants re-examination of the claims. A summary of what is known and want is being done worldwide to obtain more knowledge will be given. Rather than disappearing as better data are obtained, the effects are becoming more reproducible and of greater magnitude.

Edmund Storms

2003-01-01

366

The cold equation of state of tantalum  

SciTech Connect

In high-pressure isentropic compression experiments (ICE), the pressure is dominated by the cold curve. In order to obtain an accurate semi-empirical cold curve for Ta, we calculate the thermal pressure from ab initio phonon and electronic excitation spectra. The cold curve is then inferred from ultrasonic and shock data. Our empirical cold pressure is compared to density functional calculations and found to be closer to GGA results at low pressure and to approach LDA at high pressure.

Greeff, Carl W [Los Alamos National Laboratory; Rudin, Sven P [Los Alamos National Laboratory; Corckett, Scott D [Los Alamos National Laboratory; Wills, John M [Los Alamos National Laboratory

2009-01-01

367

Genetic control of plant resistance to cold  

Microsoft Academic Search

Data on the main pathways of the effect of cold on plants and on the pathways of plant responses to cold stress are reviewed.\\u000a Genes involved in these processes are described. Special attention is given to transcription factors regulating expression\\u000a of cold resistance genes. In addition, the participation of hormones and metabolites in the protection of plants from cold-induced\\u000a damage

A. S. Kurbidaeva; M. G. Novokreshchenova

2011-01-01

368

Psychrophilic enzymes: hot topics in cold adaptation  

Microsoft Academic Search

More than three-quarters of the Earth's surface is occupied by cold ecosystems, including the ocean depths, and polar and alpine regions. These permanently cold environments have been successfully colonized by a class of extremophilic microorganisms that are known as psychrophiles (which literally means cold-loving). The ability to thrive at temperatures that are close to, or below, the freezing point of

Charles Gerday; Georges Feller

2003-01-01

369

Is there a deep, cold biosphere?  

Microsoft Academic Search

Earth's biosphere is cold, with 14% being polar and 90% (by volume) cold ocean; more than 70% of Earth's freshwater is present as ice. New discoveries of microbial life in cold and saline lakes, permanent lake ice and glacial ice are extending the bounds of our biosphere. The recent description of potential bacterial life in Lake Vostok, and the discovery

J. C. Priscu; B. C. Christner; C. M. Foreman; J. A. Mikucki; C. F. Wolf; M. A. Voytek; D. W. Mogk

2003-01-01

370

Cold vs. Flu Know the Difference  

E-print Network

Cold vs. Flu Know the Difference Symptoms Cold Flu Fever Rare Usual ­ can be 100 to 102or higher can help prevent the spread of colds or flu F � KEEP YOUR HANDS CLEAN ­ Wash with soap and water. � STAY HOME WHEN SICK � GET VACCINATED FOR FLU Getting a flu shot or the nasal spray every year

Burke, Peter

371

Enhancement of cold fusion reaction rates  

Microsoft Academic Search

Although major controversy still remains as to the source of the excess thermal power output reported from diverse successful cold fusion calorimetry experiments, considerable independent evidence does exist that low-level, deuterium fueled, cold fusion reactions can occur based upon reported neutron and tritium measurements. Because the specific fusion power output may be very low in present cold fusion experiments, there

Gary M. Sandquist; Vern C. Rogers

1990-01-01

372

Study on Physical Basis of Cold Fusion  

Microsoft Academic Search

In order to understand questions about the study on cold fusion in these years, we have studied physical basis of cold fusion. Results show that even though the cold fusion is feasible theoretically in the view of physics, but its reaction ratio is too small to be detected, so that it has no prospect for practical usage at present. However,

Jia-quan Li; Li-ru Shen; Guo-sheng Li; Jiong Li

2002-01-01

373

Integrating non-planar metamaterials with magnetic absorbing materials to yield ultra-broadband microwave hybrid absorbers  

NASA Astrophysics Data System (ADS)

Broadening the bandwidth of electromagnetic wave absorbers has greatly challenged material scientists. Here, we propose a two-layer hybrid absorber consisting of a non-planar metamaterial (MM) and a magnetic microwave absorbing material (MAM). The non-planar MM using magnetic MAMs instead of dielectric substrates shows good low frequency absorption and low reflection across a broad spectrum. Benefiting from this and the high frequency strong absorption of the MAM layer, the lightweight hybrid absorber exhibits 90% absorptivity over the whole 2-18 GHz range. Our result reveals a promising and flexible method to greatly extend or control the absorption bandwidth of absorbers.

Li, Wei; Wu, Tianlong; Wang, Wei; Guan, Jianguo; Zhai, Pengcheng

2014-01-01

374

Two-Photon Cooperative Absorption in Colliding Cold Na Atoms  

NASA Astrophysics Data System (ADS)

Two-photon cooperative absorption is common in solid-state physics. In a sample of trapped cold atoms, this effect may open up new possibilities for the study of nonlinear effects. The experiment described herein starts with two colliding Na atoms in the S hyperfine ground state. The pair absorb two photons, resulting in both a P1/2 and a P3/2 atom. This excitation is observed by ionization using an external light source. A simple model that considers only dipole-dipole interactions between the atoms allows us to understand the basic features observed in the experimental results. Both the pair of generated atoms and the photons originating from their decay are correlated and may have interesting applications that remain to be explored.

Pedrozo-Peñafiel, E.; Paiva, R. R.; Vivanco, F. J.; Bagnato, V. S.; Farias, K. M.

2012-06-01

375

Cold bosons in optical lattices  

NASA Astrophysics Data System (ADS)

Basic properties of cold Bose atoms in optical lattices are reviewed. The main principles of correct self-consistent description of arbitrary systems with Bose-Einstein condensate are formulated. Theoretical methods for describing regular periodic lattices are presented. A special attention is paid to the discussion of Bose-atom properties in the frame of the boson Hubbard model. Optical lattices with arbitrary strong disorder, induced by random potentials, are treated. Possible applications of cold atoms in optical lattices are discussed, with an emphasis of their usefulness for quantum information processing and quantum computing. An important feature of the present review article, distinguishing it from other review works, is that theoretical fundamentals here are not just mentioned in brief, but are thoroughly explained. This makes it easy for the reader to follow the principal points without the immediate necessity of resorting to numerous publications in the field.

Yukalov, V. I.

2009-01-01

376

Cold dark matter heats up.  

PubMed

A principal discovery in modern cosmology is that standard model particles comprise only 5 per cent of the mass-energy budget of the Universe. In the ?CDM paradigm, the remaining 95 per cent consists of dark energy (?) and cold dark matter. ?CDM is being challenged by its apparent inability to explain the low-density 'cores' of dark matter measured at the centre of galaxies, where centrally concentrated high-density 'cusps' were predicted. But before drawing conclusions, it is necessary to include the effect of gas and stars, historically seen as passive components of galaxies. We now understand that these can inject heat energy into the cold dark matter through a coupling based on rapid gravitational potential fluctuations, explaining the observed low central densities. PMID:24522596

Pontzen, Andrew; Governato, Fabio

2014-02-13

377

Acclimatization to cold in humans  

NASA Technical Reports Server (NTRS)

This review focuses on the responses and mechanisms of both natural and artificial acclimatization to a cold environment in mammals, with specific reference to human beings. The purpose is to provide basic information for designers of thermal protection systems for astronauts during intra- and extravehicular activities. Hibernation, heat production, heat loss, vascular responses, body insulation, shivering thermogenesis, water immersion, exercise responses, and clinical symptoms and hypothermia in the elderly are discussed.

Kaciuba-Uscilko, Hanna; Greenleaf, John E.

1989-01-01

378

Cold Atoms and Maxwell's Demon  

NASA Astrophysics Data System (ADS)

Recent experiments have focused on realizing and studying asymmetric potential barriers for ultracold atoms. Practically speaking, asymmetric barriers, or "atomtronic diodes", open up newmethods for controlling cold atoms, and possibly methods for laser cooling atoms and molecules that are not amenable to present laser-cooling techniques. More fundamentally, asymmetric barriers are interesting as realizations of the textbook statistical-mechanics scenario of Maxwell's demon. This chapter reviews experimental progress in this area, as well as some related practical and theoretical issues.

Steck, Daniel A.

2013-12-01

379

Tally of Cold Fusion Papers  

Microsoft Academic Search

This document contains a tally of cold fusion papers from two sources: the list maintained by Dieter Britz at Aarhus U., and the EndNote database used to generate the indexes at LENR-CANR.org. Various tallies such as the number of peer-reviewed experimental papers are presented. Purpose This report presents some background and a breakdown of the items in two databases of

Jed Rothwell

2009-01-01

380

Hot and Cold Ideal Gases  

NSDL National Science Digital Library

The EJS Hot and Cold Ideal Gases model simulates the mixing of hot and cold two-dimensional ideal gases in a square box. This simulation can be used as part of the activity described in "The Statistical Interpretation of Entropy: An Activity" by Todd Timberlake, to be published in The Physics Teacher. In the model, one gas is initially confined to the left side of the box while the other gas is confined to the right side. An animation window shows the motion of the particles in the box, while an optional graph window plots the temperature of each side of the box, which is determined by measuring the average KE of the particles on each side. The initial number of particles and temperature on each side of the square can be changed and a button allows the user to reverse the particle velocities at any time. The user can modify this simulation if EJS is installed locally by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item. EJS Hot and Cold Ideal Gases model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_entropy_HotAndColdIdealGases.jar file will run the program if Java is installed. EJS is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional EJS models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or EJS.

Timberlake, Todd

2010-07-01

381

Dismantling the Cold War economy  

Microsoft Academic Search

End-of-the-Cold-War economic realities include political jockeying over the future of weapons systems, a paucity of meaningful conversion efforts, and a suspicion that a weak economy will be unable to compensate for the loss of jobs and purchasing power as defense budgets are reduced. The authors of this book present three interrelated hypotheses: The first is that the existence of a

A. Markusen; J. Yudkin

1992-01-01

382

More searches for cold fusion  

Microsoft Academic Search

Following the announcement of cold nuclear fusion being observed in electrochemical cells by Fleischmann and Pons1 and by Jones,2 we have searched for the characteristic radiations of thed+d andp+d fusion reactions in cells similar to those described in Refs. 1 and 2. No fusion product neutrons or gamma rays have been observed from either palladium or titanium cathodes. From measured

R. A. Henderson; K. R. Czerwinski; H. L. Hall; K. T. Lesko; E. B. Norman; B. Sur; D. C. Hoffman

1990-01-01

383

Skin interaction with absorbent hygiene products.  

PubMed

Skin problems due to the use of absorbent hygiene products, such as diapers, incontinence pads, and feminine sanitary articles, are mostly due to climate or chafing discomfort. If these conditions are allowed to prevail, these may develop into an irritant contact dermatitis and eventually superficial skin infections. Skin humidity and aging skin are among the most significant predisposing and aggravating factors for dermatitis development. Improved product design features are believed to explain the decline in observed diaper dermatitis among infants. Where adult incontinence-related skin problems are concerned, it is very important to apply a holistic perspective to understand the influences due to the individual's incontinence level and skin condition, as well as the hygiene and skin care measures provided. Individuals with frail, sensitive skin or with skin diseases may preferably have to use high-quality products, equipped with superabsorbent polymers and water vapor-permeable back sheets, to minimize the risk of skin complications. PMID:18280904

Runeman, Bo

2008-01-01

384

Absorbing processes in Richardson diffusion: analytical results  

E-print Network

We consider the recently addressed problem of a passive particle (a predator), being the center of a ``sphere of interception'' of radius $R$ and able to absorb other passive particles (the preys) entering into the sphere. Assuming that all the particles are advected by a turbulent flow and that, in particular, the Richardson equation properly describes the relative dispersion, we calculate an analytical expression for the flux into the sphere as a function of time, assuming an initial constant density of preys outside the sphere. In the same framework, we show that the distribution of times of first passage into the sphere has a $t^{-5/2}$ power law tail, seen in contrast to the $t^{-3/2}$ appearing in standard 3D diffusion. We also discuss the correction due to the integral length scale on the results in the stationary case.

Simone Pigolotti; Mogens H. Jensen; Angelo Vulpiani

2006-02-07

385

Electromagnetic radiation absorbers and modulators comprising polyaniline  

DOEpatents

A composition for absorbing electromagnetic radiation, wherein said electromagnetic radiation possesses a wavelength generally in the range of from about 1000 Angstroms to about 50 meters, wherein said composition comprises a polyaniline composition of the formula ##STR1## where y can be equal to or greater than zero, and R.sup.1 and R.sup.2 are independently selected from the group containing of H, --OCH.sub.3, --CH.sub.3, --F, --Cl, --Br, --I, NR.sup.3 .sub.2, --NHCOR.sup.3, --OH, --O.sup.-, SR.sup.3, --OCOR.sup.3, --NO.sub.2, --COOH, --COOR.sup.3, --COR.sup.3, --CHO, and --CN, where R.sup.3 is a C.sub.1 to C.sub.8 alkyl, aryl or aralkyl group.

Epstein, Arthur J. (Bexley, OH); Ginder, John M. (Columbus, OH); Roe, Mitchell G. (Columbus, OH); Hajiseyedjavadi, Hamid (Columbus, OH)

1992-01-01

386

Microcellular ceramic foams for radar absorbing structures  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project is to develop a lightweight, semi-structural, radar-absorbing ceramic foam that can be incorporated into aircraft exhaust systems to replace many of the currently used dense ceramic parts and thereby improve the radar cross section. Although the conventional processes for producing ceramic foams have not been able to provide materials that meet the design specifications for high strength at low density, we have developed and demonstrated a novel sol-gel emulsion process for preparing microcellular ceramic foams in which compositional and microstructural control is expected to provide the requisite high-temperature radar-absorption, strength-to-weight ratio, and thermal insulative properties.

Huling, J.; Phillips, D.

1996-09-01

387

Bank erosion in cold regions  

SciTech Connect

River and lake bank erosion is caused by multiple processes and influenced by many conditions that interact in complex ways. Their importance will vary spatially and temporally due in large part to regional and seasonal differences in climate, hydrology and soils. In cold areas, these normally complex interactions are further complicated because the same process or condition may cause erosion at one time and prevent erosion at another. Bank sediments when frozen may be more resistant to erosion than when unfrozen. However, during the process of freezing, soil structure can be disrupted and sediment pore water can be drawn to the freezing zone within the soil; ice formation may make bank sediment more susceptible to erosion during spring thaw. Ice that has been forced onto and piled upon a shore by wind or thermal expansion can cause considerable localized damage and yet can also protect shores against winter waves and nearshore currents. Ice push can form sediment ramparts that protect the toe of a bank. Spray from winds and waves can freeze to banks, covering them with a protective layer of ice. When river or lake water levels are high enough, however, ice can erode banks by shoving, gouging and disrupting bank sediment. This paper reviews the state of knowledge regarding the importance of cold regions factors in determining the erodibility and erosion of bank sediments. Ongoing investigations to improve methods of erosion prediction in cold climates will also be detailed.

Gatto, L.W. (Army Cold Regions Research and Engineering Lab., Hanover, NH (United States). Geological Sciences Branch)

1993-03-01

388

Cold cathode vacuum gauging system  

DOEpatents

A vacuum gauging system of the cold cathode type is provided for measuring the pressure of a plurality of separate vacuum systems, such as in a gas centrifuge cascade. Each casing is fitted with a gauge tube assembly which communicates with the vacuum system in the centrifuge casing. Each gauge tube contains an anode which may be in the form of a slender rod or wire hoop and a cathode which may be formed by the wall of the gauge tube. The tube is provided with an insulated high voltage connector to the anode which has a terminal for external connection outside the vacuum casing. The tube extends from the casing so that a portable magnet assembly may be inserted about the tube to provide a magnetic field in the area between the anode and cathode necessary for pressure measurements in a cold cathode-type vacuum gauge arrangement. The portable magnetic assembly is provided with a connector which engages the external high voltage terminal for providing power to the anode within in the gauge tube. Measurement is made in the same manner as the prior cold cathode gauges in that the current through the anode to the cathode is measured as an indication of the pressure. By providing the portable magnetic assembly, a considerable savings in cost, installation, and maintenance of vacuum gauges for pressure measurement in a gas centrifuge cascade is realizable.

Denny, Edward C. (Knoxville, TN)

2004-03-09

389

Light Absorbing Aerosols in Mexico City  

NASA Astrophysics Data System (ADS)

The direct effects of aerosol radiative forcing has been identified by the IPCC as a major uncertainty in climate modeling. The DOE Megacity Aerosol Experiment-Mexico City (MAX-Mex), as part of the MILAGRO study in March of 2006, was undertaken to reduce these uncertainties by characterization of the optical, chemical, and physical properties of atmospheric aerosols emitted from this megacity environment. Aerosol samples collected during this study using quartz filters were characterized in the uv-visible-infrared by using surface spectroscopic techniques. These included the use of an integrating sphere approach combined with the use of Kubelka-Munk theory to obtain aerosol absorption spectra. In past work black carbon has been assumed to be the only major absorbing species in atmospheric aerosols with an broad band spectral profile that follows a simple inverse wavelength dependence. Recent work has also identified a number of other absorbing species that can also add to the overall aerosol absorption. These include primary organics from biomass and trash burning and secondary organic aerosols including nitrated PAHs and humic-like substances, or HULIS. By using surface diffuse reflection spectroscopy we have also obtained spectra in the infrared that indicate significant IR absorption in the atmospheric window-region. These data will be presented and compared to spectra of model compounds that allow for evaluation of the potential importance of these species in adding strength to the direct radiative forcing of atmospheric aerosols. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64327 as part of the Atmospheric Science Program.

Marley, N. A.; Kelley, K. L.; Kilaparty, P. S.; Gaffney, J. S.

2008-12-01

390

Physiological characteristics of cold acclimatization in man  

NASA Astrophysics Data System (ADS)

Studies were conducted on 15 healthy young soldiers to evaluate the effect of a cold acclimatization schedule on the thermoregulatory and metabolic activity on exposure to acute cold stress. These men were exposed to cold (10‡C) for 4 h daily wearing only shorts for 21 days, in a cold chamber. They were subjected to a standard cold test at 10 ± 1‡C the day 1, 6, 11 and 21. The subjects were made to relax in a thermoneutral room (26 28‡C) for 1 h and their heart rate, blood pressure, oxygen consumption, oral temperature, mean skin temperature, mean body temperature, peripheral temperatures, and shivering activity were recorded. Then they were exposed to 10‡C and measurements were repeated at 30 min intervals, for 2 h. The cold induced vasodilatation (CIVD), cold pressor response and thermoregulatory efficiency tests were measured initially and at the end of acclimatization schedule. The data show that the procedure resulted in elevated resting metabolism, less fall in body temperature during acute cold stress, reduction in shivering, improvement in CIVD and thermoregulatory efficiency and less rise in BP and HR during cold pressor response. The data suggest the possibility of cold acclimatization in man by repeated exposure to moderately severe cold stress.

Mathew, Lazar; Purkayastha, S. S.; Jayashankar, A.; Nayar, H. S.

1981-09-01

391

Why are cold molecules so hot?  

PubMed

Herein, we aim to show why the work on translationally (and otherwise) cold molecules has sparked so much inspiration--and anticipation--in both the physics and chemistry communities. We begin by discussing the basic features of cold molecules as implied by their de Broglie wavelengths, large compared with molecular dimensions. We juxtapose cold molecule and cold atom research and recount the challenges that had to be met if molecules were to be cooled and trapped. Subsequently, both the indirect and direct techniques of producing cold and slow molecules are described in some detail, and their applicability to various classes of molecules is discussed. Advanced techniques of manipulating cold or slow molecules are illustrated by the examples of DC and AC trapping and storage. Finally, ongoing and future work with cold and/or trapped molecules is outlined. This includes precision spectroscopy, chemical reaction dynamics, simulations of few- and many-body physics, quantum computing, and tests of fundamental physics. PMID:19229896

Friedrich, Bretislav; Doyle, John M

2009-03-01

392

Cold Pools in the Columbia Basin  

SciTech Connect

Persistent midwinter cold air pools produce multi-day periods of cold, dreary weather in valleys and basins. Persistent stable stratification leads to the buildup of pollutants and moisture in the pool. Because the pool sometimes has temperatures below freezing while the air above is warmer, freezing precipitation often occurs with consequent effects on transportation and safety. Forecasting the buildup and breakdown of these cold pools is difficult because the physical mechanisms leading to their formation, maintenance, and destruction have received little study. This paper provides a succinct meteorological definition of a cold pool, develops a climatology of Columbia Basin cold pools, and analyzes remote and in situ temperature and wind sounding data for two winter cold pool episodes that were accompanied by fog and stratus, illustrating many of the physical mechanisms affecting cold pool evolution.

Whiteman, Charles D.; Zhong, Shiyuan; Shaw, William J.; Hubbe, John M.; Bian, Xindi; Mittelstadt, J.

2001-01-01

393

Rotor blade lag damping using embedded chordwise absorbers  

NASA Astrophysics Data System (ADS)

The feasibility of helicopter blade lag damping using embedded chordwise absorbers is investigated. The basic feature of this approach is the use of tuned vibration absorbers along the blades. This concept, utilizing a portion of the leading edge weights that are already incorporated into the blade as a part of the mass of the absorbers, may have the potential to replace current blade lag dampers and reduce complexity, aerodynamic drag, and weight. The effectiveness of the embedded absorbers is evaluated by analyzing and testing blade lag damping and rotor system aeromechanical stability. An aeromechanical stability analysis of the rotor system with embedded chordwise absorbers is developed. The rotor blade is modeled as an elastic beam undergoing axial, flapwise, lagwise, and torsional deflections. The fuselage is modeled as a rigid body with roll and pitch rotations about its center of mass. Each embedded absorber is modeled as a mass-spring pair. The rotor-absorber-fuselage system equations of motion are formulated using Hamilton's Principle and spatially discretized using the finite element method. The modal frequencies and damping of the system are found using complex eigenvalue solutions of the linearized equations. A rigid blade-absorber model is developed to explore the dynamic response of the embedded absorbers, including the static and steady-state dynamic response, and to examine the effect of the embedded absorber on rotor blade aeroelastic stability, including flap-lag flutter, pitch-flap flutter, and pitch divergence. A small-scale model rotor system with embedded absorbers is designed and constructed. A set of experiments measuring blade lag frequency and damping is conducted. The effects of some key issues, including absorber mass, location, and tuning frequency, are examined experimentally. The analytical results are correlated with the experimental data. The theoretical lag frequencies and damping of the blade with embedded absorbers are in good agreement with the experimental data. The aeromechanical stability analysis of the rotor-fuselage system also shows a good agreement with the experimental data. The theoretical and experimental results both show promising blade lag damping augmentation using embedded chordwise absorbers. The blade damping augmentation using embedded chordwise absorber varies from 0.3% to 15% critical damping ratio, depending on blade and absorber parameters. The ground resonance stability analysis of the hingeless rotor system and articulated rotor system shows that the blade lag damping augmentation using embedded chordwise absorbers improves the ground resonance stability. (Abstract shortened by UMI.)

Kang, Hao

394

An acoustic absorber implemented by graded index phononic crystals  

NASA Astrophysics Data System (ADS)

In this paper, we proposed the implementation of a two-dimensional omnidirectional and broadband acoustic absorber using graded index phononic crystals as the shell with an inner absorbing core. The phononic crystal was consisted of circular steel rod arranged as square lattice in air background. The plane wave expansion method was used to obtain the band diagram of the phononic crystal from which the effective refractive index could be computed. The radially distributed refractive index of the acoustic absorber was achieved by placing steel rods with spatially varying radii. The finite element method was employed in order to confirm the acoustic properties of the designed device. Numerical simulations illustrated that the acoustic waves were bent toward the central area by the outer shell and absorbed by the inner core of the implemented acoustic absorber. Furthermore, it was demonstrated that the implemented acoustic absorber could operate independent of the incident wave directions for a relative wide range of frequencies.

Liang, Yu-Jui; Chen, Lien-Wen; Wang, Ching-Cheng; Chang, I.-Ling

2014-06-01

395

Cold Fusion Has Now Come Out of the Cold  

NASA Astrophysics Data System (ADS)

The phenomenon called cold fusion or LENR (Low-Energy-Nuclear-Reaction) has now achieved a level of reproducibility and understanding that warrants re-examination of the claims. A summary of what is known and want is being done worldwide to obtain more knowledge will be given. Rather than disappearing as better data are obtained, the effects are becoming more reproducible and of greater magnitude. Justification for this claim can be obtained at www.LENR-CANR.org. The phenomenon is too important to ignore any longer even though it conflicts with conventional theory.

Storms, Edmund

2003-10-01

396

Wide-angle and polarization-independent chiral metamaterial absorber  

NASA Astrophysics Data System (ADS)

We propose a resonant microwave absorber based on a chiral metamaterial. We show, with both numerical simulations and experimental measurements, that the absorber works well for a very wide range of incident angles for different polarizations. The proposed absorber has a compact size and the absorption is close to one for a wide range of incident angles and it is a good candidate for potential applications.

Wang, Bingnan; Koschny, Thomas; Soukoulis, Costas M.

2009-07-01

397

Isotropic Mie resonance-based metamaterial perfect absorber  

NASA Astrophysics Data System (ADS)

An isotropic Mie resonance-based metamaterial perfect absorber with near unity absorbance is experimentally and numerically demonstrated. The metamaterial is constructed with an array of dielectric cubes and a metallic ground plane. The absorption peak of the metamaterial perfect absorber is dependent on the permittivity and the side length of the dielectric cubes. A good agreement between experimental and simulated result at X band absorption is achieved.

Liu, Xiaoming; Zhao, Qian; Lan, Chuwen; Zhou, Ji

2013-07-01

398

A Broadband Dielectric Microwave Absorber With Periodic Metallizations  

Microsoft Academic Search

An efficient technique is proposed to absorb microwave. This new kind of microwave absorber consists of a 2D-periodic array of metallic patches and a lossy dielectric layer backed by a metallic plate. In this paper, we study configurations involving dielectric stacks and arrays of metallic patches which produce broadband absorbers. Combining lossy dielectric stacks and 2D-periodic array of metallic patches

F. Terracher; G. Berginc

1999-01-01

399

A simple measuring method of reflectivity for radar absorbing material  

Microsoft Academic Search

The basic principle of measuring reflectivity for radar absorbing material (RAM) is analyzed. And a simple method for measuring reflectivity of radar absorbing material using vector network analyzer HP8722ET and APC-7mm coaxial line is presented. The results indicate that the reflectivity of the radar absorbing material can be measured in 0.05-18 GHz using this method. Under the ordinary laboratory condition,

Feng Yongbao; Qiu Tai; Shen Chunying; Li Xiaoyun

2005-01-01

400

Graphene metamaterials based tunable terahertz absorber: effective surface conductivity approach.  

PubMed

In this paper we present the efficient design of functional thin-film metamaterial devices with the effective surface conductivity approach. As an example, we demonstrate a graphene based perfect absorber. After formulating the requirements to the perfect absorber in terms of surface conductivity we investigate the properties of graphene wire medium and graphene fishnet metamaterials and demonstrate both narrowband and broadband tunable absorbers. PMID:23572003

Andryieuski, Andrei; Lavrinenko, Andrei V

2013-04-01

401

Dual band terahertz metamaterial absorber: Design, fabrication, and characterization  

NASA Astrophysics Data System (ADS)

We report the design, simulation, and measurement of a dual-band metamaterial absorber in the terahertz region. Theoretical and experimental results show that the absorber has two distinct and strong absorption points near 0.45 and 0.92 THz, both which are related to the LC resonance of the metamaterial. The distributions of the power flow and the power loss indicate that the absorber is an excellent electromagnetic wave collector: the wave is first trapped and reinforced in certain specific locations and then completely consumed. This dual-band absorber has applications in many scientific and technological areas.

Wen, Qi-Ye; Zhang, Huai-Wu; Xie, Yun-Song; Yang, Qing-Hui; Liu, Ying-Li

2009-12-01

402

Decomposition-based recovery of absorbers in turbid media  

SciTech Connect

We suggest that the concept of the point-spread function traditionally used to predict the blurred image pattern of various light sources embedded inside turbid media can be generalized under certain conditions to predict also the presence and location of spatially localized absorbing inhomogeneities based on shadow point-spread functions associated with each localized absorber in the medium. The combined image obtained from several absorbers can then be decomposed approximately into the arithmetic sums of these individual shadow point-spread functions with suitable weights that can be obtained from multiple-regression analysis. This technique permits the reconstruction of the location of absorbers.

Campbell, S. D.; Goodin, I. L.; Grobe, S. D.; Su, Q.; Grobe, R. [Intense Laser Physics Theory Unit and Department of Physics, Illinois State University, Normal, Illinois 61790-4560 (United States)

2007-12-15

403

Optimal active vibration absorber: Design and experimental results  

NASA Technical Reports Server (NTRS)

An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

Lee-Glauser, Gina; Juang, Jer-Nan; Sulla, Jeffrey L.

1992-01-01

404

21 CFR 886.3300 - Absorbable implant (scleral buckling method).  

Code of Federal Regulations, 2010 CFR

...scleral buckling method). (a) Identification. An absorbable implant (scleral buckling method) is a device intended to be implanted on the sclera to aid retinal reattachment. (b) Classification. Class...

2010-04-01

405

Wideband Aural Acoustic Absorbance Predicts Conductive Hearing Loss in Children  

PubMed Central

Objective This study tested the hypothesis that wideband aural absorbance predicts conductive hearing loss (CHL) in children medically classified as having otitis media with effusion. Design Absorbance was measured in the ear canal over frequencies from 0.25 to 8 kHz at ambient pressure or as a swept tympanogram. CHL was defined using criterion air-bone gaps of 20, 25 and 30 dB at octaves from 0.25 to 4 kHz. A likelihood-ratio predictor of CHL was constructed across frequency for ambient absorbance and across frequency and pressure for absorbance tympanometry. Performance was evaluated at individual frequencies and for any frequency at which a CHL was present. Study Sample Absorbance and conventional 226-Hz tympanograms were measured in children of age 3 to 8 years with CHL and with normal hearing. Results Absorbance was smaller at frequencies above 0.7 kHz in the CHL group than the control group. Based on the area under the receiver operating characteristic curve, wideband absorbance in ambient and tympanometric tests were significantly better predictors of CHL than tympanometric width, the best 226-Hz predictor. Accuracies of ambient and tympanometric wideband absorbance did not differ. Conclusions Absorbance accurately predicted CHL in children and was more accurate than conventional 226-Hz tympanometry. PMID:23072655

Keefe, Douglas H.; Sanford, Chris A.; Ellison, John C.; Fitzpatrick, Denis F.; Gorga, Michael P.

2013-01-01

406

The Warm, Cold and Very Cold Dusty Universe  

E-print Network

We are living in a dusty universe: dust is ubiquitously seen in a wide variety of astrophysical environments, ranging from circumstellar envelopes around cool red giants to supernova ejecta, from diffuse and dense interstellar clouds and star-forming regions to debris disks around main-sequence stars, from comets to interplanetary space to distant galaxies and quasars. In this review I focus on interstellar grains, with particular emphasis on the extinction (absorption plus scattering) and emission properties of cold submicron-sized ``classical'' grains which, in thermal equilibrium with the ambient interstellar radiation field, obtain a steady-state temperature of \\~15--25K, warm nano-sized (or smaller) "ultrasmall" grains which are, upon absorption of an energetic photon, transiently heated to temperatures as high as a few hundred to over 1000K, and the possible existence of a population of very cold (< 10K) dust. Whether dust grains can really get down to "temperature" less than the 2.7K cosmic microwave background radiation temperature will also be discussed. The robustness of the silicate-graphite-PAHs interstellar dust model is demonstrated by showing that the infrared emission predicted from this model closely matches that observed for the Milky Way, the Small Magellanic Cloud, and the ringed Sb galaxy NGC7331.

Aigen Li

2005-03-25

407

The Warm, Cold and Very Cold Dusty Universe  

E-print Network

We are living in a dusty universe: dust is ubiquitously seen in a wide variety of astrophysical environments, ranging from circumstellar envelopes around cool red giants to supernova ejecta, from diffuse and dense interstellar clouds and star-forming regions to debris disks around main-sequence stars, from comets to interplanetary space to distant galaxies and quasars. In this review I focus on interstellar grains, with particular emphasis on the extinction (absorption plus scattering) and emission properties of cold submicron-sized ``classical'' grains which, in thermal equilibrium with the ambient interstellar radiation field, obtain a steady-state temperature of \\~15--25K, warm nano-sized (or smaller) "ultrasmall" grains which are, upon absorption of an energetic photon, transiently heated to temperatures as high as a few hundred to over 1000K, and the possible existence of a population of very cold (< 10K) dust. Whether dust grains can really get down to "temperature" less than the 2.7K cosmic microwav...

Li, A

2005-01-01

408

The Cold Mass Support System and the Helium Cooling System for theMICE Focusing Solenoid  

SciTech Connect

The heart of the absorber focus coil (AFC) module for the muon ionization cooling experiment (MICE) is the two-coil superconducting solenoid that surrounds the muon absorber. The superconducting magnet focuses the muons that are cooled using ionization cooling, in order to improve the efficiency of cooling. The coils of the magnet may either be run in the solenoid mode (both coils operate at the same polarity) or the gradient (the coils operate at opposite polarity). The AFC magnet cold mass support system is designed to carry a longitudinal force up to 700 kN. The AFC module will be cooled using three pulse tube coolers that produce 1.5 W of cooling at 4.2 K. One of the coolers will be used to cool the liquid (hydrogen or helium) absorber used for ionization cooling. The other two coolers will cool the superconducting solenoid. This report will describe the MICE AFC magnet. The cold mass supports will be discussed. The reasons for using a pulsed tube cooler to cool this superconducting magnet will also be discussed.

Yang, Stephanie Q.; Green, Michael A.; Lau, Wing W.; Senanayake,Rohan S.; Witte, Holger

2006-08-10

409

Multifunctional Space Evaporator-Absorber-Radiator (SEAR)  

NASA Technical Reports Server (NTRS)

A system for non-venting thermal control for spacesuits was built by integrating two previously developed technologies, namely NASA's Spacesuit Water Membrane Evaporator (SWME), and Creare's flexible version of the Lithium Chloride Absorber Radiator (LCAR). This SEAR system was tested in relevant thermal vacuum conditions. These tests show that a 1 sq m radiator having about three times as much absorption media as in the test article would be required to support a 7 hour spacewalk. The serial flow arrangement of the LCAR of the flexible version proved to be inefficient for venting non-condensable gas (NCG). A different LCAR packaging arrangement was conceived wherein the Portable Life Support System (PLSS) housing would be made with a high-strength carbon fiber composite honeycomb, the cells of which would be filled with the chemical absorption media. This new packaging reduce the mass and volume impact of the SEAR on the Portable Life Support System (PLSS) compared to the flexible design. A 0.2 sq m panel with flight-like honeycomb geometry is being constructed and will be tested in thermal and thermal vacuum conditions. Design analyses forecast improved system performance and improved NCG control. A flight-like regeneration system also is also being built and tested. Design analyses for the structurally integrated prototype as well as the earlier test data show that SEAR is not only practical for spacesuits but also has useful applications in spacecraft thermal control.

Bue, Grant C.; Hodgson, Ed; Izenson, Mike; Chen, Weibo

2013-01-01

410

Energy absorbing hybrid nano-composite materials  

NASA Astrophysics Data System (ADS)

Base Epon 862 resin was enhanced with two types of fillers, graphitized carbon nanofiber (CNF) and silicon dioxide (SiO2) particles. The effect of both filler type and filler loading were investigated with respect to the energy absorbing capacity as well as the thermal stability of the hybrid composite material, measured in terms of the coefficient of thermal expansion (CTE). As well the composites with combinations of the fillers were evaluated for both enhanced damping and thermal stability, making it suitable for structural materials that need multiple functions. The composites were evaluated with dynamic mechanical analysis (DMA) to evaluate viscoelastic response, and using strain gauges to measure thermal strain responses. It has been found that the addition of 3wt% SiO2 along with 3wt% CNF can improve damping loss factors by up to 26% while at the same time improving thermal stability with reductions in CTE of up to 16.5%. Furthermore, these fillers loadings were successfully dispersed as received by mechanical mixing technique, making fabrication more economically suited to engineering applications.

Jang, Jae-Soon; Varischetti, Joshua; Lee, Gyo Woo; Suhr, Jonghwan

2009-03-01

411

Cold stream stability during minor mergers  

E-print Network

We use high-resolution Eulerian simulations to study the stability of cold gas flows in a galaxy size dark matter halo (10^12 Msun) at redshift z=2. Our simulations show that a cold stream penetrating a hot gaseous halo is stable against thermal convection and Kelvin-Helmholtz instability. We then investigate the effect of a satellite orbiting the main halo in the plane of the stream. The satellite is able to perturb the stream and to inhibit cold gas accretion towards the center of the halo for 0.5 Gyr. However, if the supply of cold gas at large distances is kept constant, the cold stream is able to re-establish itself after 0.3 Gyr. We conclude that cold streams are very stable against a large variety of internal and external perturbations.

Wang, Liang; Feng, Longlong; Macciò, Andrea V; Chang, Jiang; Kang, Xi

2014-01-01

412

Cold thermoregulatory responses following exertional fatigue.  

PubMed

Participants in prolonged, physically demanding cold-weather activities are at risk for a condition called "thermoregulatory fatigue". During cold exposure, the increased gradient favoring body heat loss to the environment is opposed by physiological responses and clothing and behavioral strategies that conserve body heat stores to defend body temperature. The primary human physiological responses elicited by cold exposure are shivering and peripheral vasoconstriction. Shivering increases thermogenesis and replaces body heat losses, while peripheral vasoconstriction improves thermal insulation of the body and retards the rate of heat loss. A body of scientific literature supports the concept that prolonged and/or repeated cold exposure, fatigue induced by sustained physical exertion, or both together, can impair the shivering and vasoconstrictor responses to cold ("thermoregulatory fatigue"). The mechanisms accounting for this thermoregulatory impairment are not clear, but there is evidence to suggest that changes in central thermoregulatory control or peripheral sympathetic responsiveness to cold lead to thermoregulatory fatigue and increased susceptibility to hypothermia. PMID:20515829

Castellani, John W; Sawka, Michael N; DeGroot, David W; Young, Andrew J

2010-01-01

413

A comparison of absorbable and non-absorbable 10-0 sutures for the repair of a divided rat facial nerve.  

PubMed

The use of absorbable sutures to anastomose nerves is controversial. This paper reports on a controlled trial comparing absorbable and non-absorbable sutures for this purpose. No difference between the sutures was found. PMID:8174304

Murray, J A; Willins, M; Mountain, R E

1994-02-01

414

The cold resistance of Macaronesian Sempervivoideae  

Microsoft Academic Search

Cold resistance of twenty-seven species of Macaronesian Sempervivoideae uniformly cultivated under cool moderate but not hardening conditions was measured. The resistance limits of all the tested species ranged between-4 and-10°C. Cold stress response was principially different: Cold resistance of about half of the tested species was due to freezing point lowering. This response type, avoidance of freezing, in which any

R. Lösch; L. Kappen

1981-01-01

415

Avionics Box Cold Plate Damage Prevention  

NASA Technical Reports Server (NTRS)

Over the years there have been several occurrences of damage to Space Shuttle Orbiter cold plates during removal and replacement of avionics boxes. Thus a process improvement team was put together to determine ways to prevent these kinds of damage. From this effort there were many solutions including, protective covers, training, and improved operations instructions. The focus of this paper is to explain the cold plate damage problem and the corrective actions for preventing future damage to aerospace avionics cold plate designs.

Stambolian, Damon; Larcher, Steven; Henderson, Gena; Tran, Donald

2011-01-01

416

Coagulation monitor based on serum migration through absorbent materials  

Microsoft Academic Search

I describe a method to measure blood coagulation prop- erties, based on the hypothesis that the distance the serum component of a clotted plasma sample moves through a suitable absorbent material should be propor- tional to the blood's ability to clot. A simple apparatus was constructed to test this principle, in which an absorbent strip contacts clotted plasma samples. At

Paul E. Wilson

417

Ultra-black nickel-phosphorus alloy optical absorber  

Microsoft Academic Search

To develop an optical absorber for use in the measurement of optical power, the authors have investigated and evaluated ultrablack films of nickel-phosphorus alloy which were deposited on substrates using an electroless plating process and subsequently etched. Results of varying the plating and etching bath components and conditions were studied. The result was a superior optical absorber which has a

S. Kodama; M. Horiuchi; T. Kunii; K. Kuroda

1990-01-01

418

Sodium erosion of boron carbide from breached absorber pins  

Microsoft Academic Search

The purpose of the irradiation experiment was to provide an engineering demonstration of the irradiation behavior of breached boron carbide absorber pins. By building defects into the cladding of prototypic absorber pins, and performing the irradiation under typical FFTF operating conditions, a qualitative assessment of the consequences of a breach was achieved. Additionally, a direct comparison of pin behavior with

J. A. Basmajian; D. E. Baker

1981-01-01

419

Resveratrol Is Absorbed in the Small Intestine as Resveratrol Glucuronide  

Microsoft Academic Search

We have studied the absorption and metabolism of resveratrol in the jejunum in an isolated rat small intestine model. Only small amounts of resveratrol were absorbed across the enterocytes of the jejunum and ileum unmetabolised. The major compound detected on the serosal side was the glucuronide conjugate of resveratrol (96.5% ± 4.6 of the amount absorbed) indicating the susceptibility of

Gunter Kuhnle; Jeremy P. E. Spencer; George Chowrimootoo; Hagen Schroeter; Edward S. Debnam; S. Kaila S. Srai; Catherine Rice-Evans; Ulrich Hahn

2000-01-01

420

Manipulating polarization of electromagnetic waves through controllable metamaterial absorber  

Microsoft Academic Search

In this presentation, we demonstrate an approach to manipulate electromagnetic waves with different polarizations through a controllable metamaterial absorber. The metamaterial absorber designed at 3.3 GHz is proposed by properly integrating resonant unit cells with orthogonal polarization sensitivity onto a dielectric substrate and coupling the unit cells with microwave diodes. Simulation and measurement results show that through tuning the bias

Bo Zhu; Ci Huang; Junming Zhao; Tian Jiang; Yijun Feng

2010-01-01

421

Omnidirectional graded index sound absorber O. Umnova and B. Zajamsek  

E-print Network

acoustic lens and electromagnetic black holes, a graded index metamaterial layer is designed using an array as an absorbing core. The device is shown to provide a nearly total absorption of acoustic waves with wavelengthsOmnidirectional graded index sound absorber O. Umnova and B. Zajamsek University of Salford

Paris-Sud XI, Université de

422

ANALYSIS AND DESIGN OF AN ULTRA-THIN METAMATERIAL ABSORBER  

Microsoft Academic Search

This paper presents a class of ultra-thin metamaterial absorbers, which consists of periodic microstrip lines on top of a planar lossy substrate backed by a conducting metallic plate. A highly efficient full-wave analysis method was developed to solve the electromagnetic response of the absorbers. The influence of electromagnetic properties of the substrate and physical dimensions of the microstrip lines were

Ruifeng Huang; Zheng-Wen Li; Ling Bing Kong; Lie Liu; Serguei Matitsine

2009-01-01

423

Metamaterial absorber with wide angular and frequency bandwidth  

Microsoft Academic Search

The absorbers usually employed in everyday applications and the ultimate layouts recently proposed in the literature and based on unconventional material loading, are usually backed by a metallic plate. The metallic backing plays two main roles. On one hand, it is used to avoid power transmission on the other side of the absorber. On the other hand, it enables a

Alessandro Toscano; Lucio Vegni

2009-01-01

424

Should the exchange rate be a shock absorber?  

Microsoft Academic Search

This paper examines the welfare case for the exchange rate as a “shock absorber”, cushioning an economy in face of shocks to world demand for its good. We provide an example in which, although the exchange rate acts perfectly as a shock absorber, stabilizing output around the natural rate, and eliminating the impact of nominal rigidities, it may in fact

Michael B. Devereux

2004-01-01

425

Science on a Roll. Part One: Absorbing Inquiry.  

ERIC Educational Resources Information Center

Presents an activity that tests the absorbency of different brands of paper towels. Suggests making this activity into an open-ended inquiry type of activity. Includes sample questions to guide students, topics for class discussion, and sample methods of using the absorbency activity. (KHR)

Brendzel, Sharon

2002-01-01

426

14 CFR 27.475 - Tires and shock absorbers.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Tires and shock absorbers. 27.475 Section...Requirements Ground Loads § 27.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2011-01-01

427

14 CFR 29.475 - Tires and shock absorbers.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Tires and shock absorbers. 29.475 Section...Requirements Ground Loads § 29.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2013-01-01

428

14 CFR 27.475 - Tires and shock absorbers.  

...2014-01-01 2014-01-01 false Tires and shock absorbers. 27.475 Section...Requirements Ground Loads § 27.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2014-01-01

429

14 CFR 29.475 - Tires and shock absorbers.  

...2014-01-01 2014-01-01 false Tires and shock absorbers. 29.475 Section...Requirements Ground Loads § 29.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2014-01-01

430

14 CFR 27.475 - Tires and shock absorbers.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Tires and shock absorbers. 27.475 Section...Requirements Ground Loads § 27.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2013-01-01

431

14 CFR 27.475 - Tires and shock absorbers.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Tires and shock absorbers. 27.475 Section...Requirements Ground Loads § 27.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2010-01-01

432

14 CFR 29.475 - Tires and shock absorbers.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Tires and shock absorbers. 29.475 Section...Requirements Ground Loads § 29.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2011-01-01

433

14 CFR 27.475 - Tires and shock absorbers.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Tires and shock absorbers. 27.475 Section...Requirements Ground Loads § 27.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2012-01-01

434

14 CFR 29.475 - Tires and shock absorbers.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Tires and shock absorbers. 29.475 Section...Requirements Ground Loads § 29.475 Tires and shock absorbers. Unless otherwise...for each specified landing condition, the tires must be assumed to be in their static...

2012-01-01

435

Computational method for radar absorbing composite lattice grids  

Microsoft Academic Search

Composite lattice grids reinforced by glass fibers (GFRC) and carbon fibers (CFRC) filled with spongy materials can be designed as lightweight radar absorbing structures (RAS). In the present paper, a computational approach based on periodic moment method (PMM) has been developed to calculate reflection coefficients of radar absorbing composite lattice grids. Total reflection backing (TRB) is considered directly in our

Mingji Chen; Yongmao Pei; Daining Fang

2009-01-01

436

Comparison of two-dimensional periodic and finite absorber structures  

Microsoft Academic Search

The study of absorber structures and shielding screens remains an important topic in EMC. A general two-dimensional boundary integral equation (BIE) technique has been implemented to handle both finite and periodic absorber structures. The generality of the method is twofold: the geometry of the structure may be chosen arbitrary finite or one-dimensional periodic, and the materials being used are uniaxial

B. Baekelandt; F. Olyslager; D. De Zutter

1995-01-01

437

Design of Salisbury screen absorbers using dielectric lossy sheets  

Microsoft Academic Search

In this study, we present design and manufacturing technology for the Salisbury screen type radar absorbing structure (RAS) in Xband. The RAS is composed of a dielectric lossy sheet and an E-glass fabric\\/epoxy composite laminate as the spacer. This RAS has a broader absorbing bandwidth and much thinner spacer than those of the conventional one which uses a 377 ?\\/?

Jinbong Kim

2011-01-01

438

Thin and broadband Salisbury screen absorber using Minkowski fractal structure  

Microsoft Academic Search

Salisbury screen radar absorber with high resistive surface is unconstrained by the restriction of 1\\/4 wavelength thickness of medium. EBG structure is an effective approach to realize it. This paper present a new type of Salisbury screen absorber based on one order Minkowski fractal surface with several symmetric patched resistors. Simulation results show that the total thickness is reduced dramatically

Yang Luo; Yuan Zhuang; Shouzheng Zhu

2009-01-01

439

Electronically tunable liquid crystal based Salisbury screen microwave absorber  

Microsoft Academic Search

In this paper we describe the design, manufacture and performance of an electrically thin (0.15 ¿) dynamically adaptive Salisbury screen absorber. The structure is backed by a high impedance surface which is constructed on a 250 ¿m thick liquid crystal substrate. The shift in the resonant frequency of the radar absorber is obtained by exploiting the voltage dependent anisotropic property

F. Che Seman; R. Cahill; V. F. Fusco

2009-01-01

440

Hybrid multilayer structures for use as microwave absorbing material  

Microsoft Academic Search

The aim of this study is the in situ processing of flexible multilayer radar absorbing structures materials based on polymeric substrates impregnated with polyaniline conducting polymer. There is a growing interest in the development of low density flexible absorber material for applications that require the reduction of the reflectivity of targets with complex shapes and improvement of the ease of

Luiza de C. Folgueras; Mirabel C. Rezende

2007-01-01

441

Return loss enhancement of surface resistors loaded microwave radar absorber  

Microsoft Academic Search

In this paper, return loss enhancement of a compact ultra-thin microwave radar absorber is demonstrated, The absorber is designed using textured surface technology comprised of a high impedance surface (HIS) positioned directly behind the anisotropically resistive-elements interconnecting a textured surface of square patches. By the selection of appropriate choice of the required surface resistors based on elementary circuit principles the

Achmad Munir; Vincent Fusco; Chairunnisa

2009-01-01

442

Composite sandwich constructions for absorbing the electromagnetic waves  

Microsoft Academic Search

RAS (radar absorbing structures) is a key component for weapon systems such as aircrafts, warships, and missiles to achieve both the stealth performance by absorbing EM (Electromagnetic) waves incident on and load bearing capability. In this work, the RAS was fabricated as sandwich constructions composed of nanocomposite, carbon fabric\\/epoxy composite, and PVC foam. The nanocomposite composed of E-glass fabric, epoxy

Po Chul Kim; Dai Gil Lee

2009-01-01

443

Application of Impedance Loading to Geometric Transition Radar Absorbent Material  

Microsoft Academic Search

This paper describes a novel, lightweight technique for significantly improving the low-frequency reflectivity performance of conventional geometric transition radar absorbent materials as used typically in anechoic chamber facilities for electromagnetic compatibility testing. The improvement is achieved by the inclusion of impedance-loading elements within the base region of the absorber, and these are implemented in the form of one or more

Kenneth Lee Ford; Barry Chambers

2007-01-01

444

CFRP-based broad-band Radar Absorbing Materials  

Microsoft Academic Search

Strong interest in radar absorbing materials (RAMs) took place with years due to their extensive sectors of application. RAMs are coatings whose electric and magnetic properties allow the absorption of microwave energy over certain frequencies. In particular, RAMs are very effective means of Radar Cross Section (RCS) reduction in the context of stealth technology. RCS reduction requires absorbers with broad-band

C. Mitrano; A. Balzano; M. Bertacca; M. Flaccavento; R. Mancinelli

2008-01-01

445

Application of Ferrite to Electromagnetic Wave Absorber and its Characteristics  

Microsoft Academic Search

An electromagnetic wave absorber utilizing ferrite or rubber ferrite composed of ferrite powder and rubber is described. In our investigation, the existence of a matching frequency fm and a matching thickness tm has been found. The terms fm and tm mean that the ferrite which is backed with a conducting plate can be a perfect absorber only under the conditions

YOSHIYUKI NAITO; KUNIHIRO SUETAKE

1971-01-01

446

Coupling of an Absorber to a Polarization-Sensitive Antenna  

E-print Network

Coupling of an Absorber to a Polarization-Sensitive Antenna Amol Upadhye Department of Physics Princeton University Supervisor: Suzanne Staggs October 18, 2002 #12;Abstract The polarization-sensitive of designing a polarization-sensitive bolometric detector. A bolometer or other absorber located near

447

Absorbing Set Spectrum Approach for Practical Code Design  

E-print Network

as separable, circulant-based (SCB) codes. For a specified circulant matrix, SCB codes all share a common mother matrix, examples of which are array-based LDPC codes and many common quasi-cyclic codes. SCB codes) for each absorbing set of interest in an SCB LDPC code. For an absorbing set to be present in an SCB LDPC

Wesel, Richard

448

An Absorbing Look at Terry-Cloth Towels  

ERIC Educational Resources Information Center

This article describes a lesson where students explore the absorbency of several towels with different weaves and weights. The lesson follows the 5E learning-cycle model and incorporates engineering in the sense of product testing with a focus on the relationship between the weave of a towel and its absorbency. The National Science Education…

Moyer, Richard; Everett, Susan

2010-01-01

449

Cold vacuum drying facility design requirements  

SciTech Connect

This document provides the detailed design requirements for the Spent Nuclear Fuel Project Cold Vacuum Drying Facility. Process, safety, and quality assurance requirements and interfaces are specified.

IRWIN, J.J.

1999-07-01

450

Evaporative cooling enhanced cold storage system  

DOEpatents

The invention provides an evaporatively enhanced cold storage system wherein a warm air stream is cooled and the cooled air stream is thereafter passed into contact with a cold storage unit. Moisture is added to the cooled air stream prior to or during contact of the cooled air stream with the cold storage unit to effect enhanced cooling of the cold storage unit due to evaporation of all or a portion of the added moisture. Preferably at least a portion of the added moisture comprises water condensed during the cooling of the warm air stream.

Carr, Peter (Cary, NC)

1991-01-01

451

Evaporative cooling enhanced cold storage system  

DOEpatents

The invention provides an evaporatively enhanced cold storage system wherein a warm air stream is cooled and the cooled air stream is thereafter passed into contact with a cold storage unit. Moisture is added to the cooled air stream prior to or during contact of the cooled air stream with the cold storage unit to effect enhanced cooling of the cold storage unit due to evaporation of all or a portion of the added moisture. Preferably at least a portion of the added moisture comprises water condensed during the cooling of the warm air stream. 3 figures.

Carr, P.

1991-10-15

452

Review on Cold-Formed Steel Connections  

PubMed Central

The concept of cold-formed light steel framing construction has been widespread after understanding its structural characteristics with massive research works over the years. Connection serves as one of the important elements for light steel framing in order to achieve its structural stability. Compared to hot-rolled steel sections, cold-formed steel connections perform dissimilarity due to the thin-walled behaviour. This paper aims to review current researches on cold-formed steel connections, particularly for screw connections, storage rack connections, welded connections, and bolted connections. The performance of these connections in the design of cold-formed steel structures is discussed. PMID:24688448

Tan, Cher Siang; Mohammad, Shahrin; Md Tahir, Mahmood; Shek, Poi Ngian

2014-01-01

453

Evolutionary Models of Cold, Magnetized, Interstellar Clouds  

NASA Technical Reports Server (NTRS)

We modeled the long-term and small-scale evolution of molecular clouds using direct 2D and 3D magnetohydrodynamic (MHD) simulations. This work followed up on previous research by our group under auspices of the ATP in which we studied the energetics of turbulent, magnetized clouds and their internal structure on intermediate scales. Our new work focused on both global and smallscale aspects of the evolution of turbulent, magnetized clouds, and in particular studied the response of turbulent proto-cloud material to passage through the Galactic spiral potential, and the dynamical collapse of turbulent, magnetized (supercritical) clouds into fragments to initiate the formation of a stellar cluster. Technical advances under this program include developing an adaptive-mesh MHD code as a successor to ZEUS (ATHENA) in order to follow cloud fragmentation, developing a shearing-sheet MHD code which includes self-gravity and externally-imposed gravity to follow the evolution of clouds in the Galactic potential, and developing radiative transfer models to evaluate the internal ionization of clumpy clouds exposed to external photoionizing UV and CR radiation. Gammie's work at UIUC focused on the radiative transfer aspects of this program.

Gammie, Charles F.; Ostriker, Eve; Stone, James M.

2004-01-01

454

Why muscle is an efficient shock absorber.  

PubMed

Skeletal muscles power body movement by converting free energy of ATP hydrolysis into mechanical work. During the landing phase of running or jumping some activated skeletal muscles are subjected to stretch. Upon stretch they absorb body energy quickly and effectively thus protecting joints and bones from impact damage. This is achieved because during lengthening, skeletal muscle bears higher force and has higher instantaneous stiffness than during isometric contraction, and yet consumes very little ATP. We wish to understand how the actomyosin molecules change their structure and interaction to implement these physiologically useful mechanical and thermodynamical properties. We monitored changes in the low angle x-ray diffraction pattern of rabbit skeletal muscle fibers during ramp stretch compared to those during isometric contraction at physiological temperature using synchrotron radiation. The intensities of the off-meridional layer lines and fine interference structure of the meridional M3 myosin x-ray reflection were resolved. Mechanical and structural data show that upon stretch the fraction of actin-bound myosin heads is higher than during isometric contraction. On the other hand, the intensities of the actin layer lines are lower than during isometric contraction. Taken together, these results suggest that during stretch, a significant fraction of actin-bound heads is bound non-stereo-specifically, i.e. they are disordered azimuthally although stiff axially. As the strong or stereo-specific myosin binding to actin is necessary for actin activation of the myosin ATPase, this finding explains the low metabolic cost of energy absorption by muscle during the landing phase of locomotion. PMID:24465673

Ferenczi, Michael A; Bershitsky, Sergey Y; Koubassova, Natalia A; Kopylova, Galina V; Fernandez, Manuel; Narayanan, Theyencheri; Tsaturyan, Andrey K

2014-01-01

455

Design of a polarization insensitive multiband terahertz metamaterial absorber  

NASA Astrophysics Data System (ADS)

We design a terahertz (THz) metamaterial absorber having four narrowband high absorptivities of 98%, 97%, 98% and 97% at frequencies of 0.68 THz, 1.27 THz, 2.21 THz and 3.05 THz, respectively. The absorber consists of three metallic layers, which are separated by two dielectric spacers. The absorption performances are simulated using a commercialized full-wave electromagnetic simulation software, and the mechanism of absorption is theoretically investigated. The result shows that the absorber is insensitive to the polarization of THz wave and the position of every absorption peak can be effectively tuned by the geometries of the absorber. The potential applications of the absorber include spectrally selective detecting, THz sensing and thermal imaging.

Hu, Fangrong; Wang, Li; Quan, Baogang; Xu, Xinlong; Li, Zhi; Wu, Zhongan; Pan, Xuecong

2013-05-01

456

Multilayer metamaterial absorbers inspired by perfectly matched layers  

E-print Network

We derive periodic multilayer absorbers with effective uniaxial properties similar to perfectly matched layers (PML). This approximate representation of PML is based on the effective medium theory and we call it an effective medium PML (EM-PML). We compare the spatial reflection spectrum of the layered absorbers to that of a PML material and demonstrate that after neglecting gain and magnetic properties, the absorber remains functional. This opens a route to create electromagnetic absorbers for real and not only numerical applications and as an example we introduce a layered absorber for the wavelength of $8$~$\\mu$m made of SiO$_2$ and NaCl. We also show that similar cylindrical core-shell nanostructures derived from flat multilayers also exhibit very good absorptive and reflective properties despite the different geometry.

Pastuszczak, Anna; Antosiewicz, Tomasz J; Kotynski, Rafal

2014-01-01

457

Minimax design of vibration absorbers for linear damped systems  

NASA Astrophysics Data System (ADS)

This paper addresses the issue of design of a passive vibration absorber in the presence of uncertainties in the forcing frequency. A minimax problem is formulated to determine the parameters of a vibration absorber which minimize the maximum motion of the primary mass over the domain of the forcing frequency. The limiting solutions corresponding to the forcing frequency being unrestricted and to that where the forcing frequency is known exactly, are shown to match those available in the literature. The transition of the optimal vibration absorber parameters between the extreme two cases is presented and the solutions are generalized by permitting the mass ratio of the absorber mass and the primary mass to be design parameters. For the specific case where the primary system is undamped, detailed analysis is presented to determine the transition of the optimal vibration absorber parameters between three distinct domains of solutions.

Brown, Brandon; Singh, Tarunraj

2011-05-01

458

The Stellar Continuum Light from Damped Lyman-alpha Absorber Galaxies Detected with Integral Field Spectroscopy  

NASA Astrophysics Data System (ADS)

A new challenge in galaxy evolution studies is to understand how gas flows in and out of galaxies through their circumgalactic medium (CGM). The best way to tackle this is to bring together data on cold gas, metals and stellar content of the same galaxies. Galaxies selected via the absorption they produce in the spectra of background quasars are a powerful tool to study the cold gas play a crucial role in this respect, but characterising the stellar content of these absorbers has proved to be challenging until now. Our group has used 3D spectroscopy at near-infrared wavelengths made possible by the SINFONI instrument on VLT, aided with adaptive optics (AO), to successfully detect 5 galaxies responsible for DLAs/sub-DLAs. For this sample, we have retrieved and analyzed data from HST/STIS (for the neutral gas content), VLT/UVES, Keck/HIRES or Magellan/MIKE (for the metallicity and dust content of H I gas), VLT/SINFONI (for SFR and kinematics of H II gas) and VLT/X-Shooter (for metallicity of H II gas). However, none of the data currently in hand can probe the faint optical continuum of these objects. Here we propose to observe these DLA/sub-DLA galaxies at z~1-2 using WFC3/UVIS and IR channels, to characterize the stellar content (extinction, stellar mass, age) and environment. The proposed observations will allow us to better probe the flow of gas around these galaxies, directly testing models of cold gas accretion from filaments and thus current theories of galaxy formation and evolution.

Peroux, Celine

2014-10-01

459

Age and Ethnic Differences in Cold Weather and Contagion Theories of Colds and Flu  

ERIC Educational Resources Information Center

Age and ethnic group differences in cold weather and contagion or germ theories of infectious disease were explored in two studies. A cold weather theory was frequently invoked to explain colds and to a lesser extent flu but became less prominent with age as children gained command of a germ theory of disease. Explanations of how contact with…

Sigelman, Carol K.

2012-01-01

460

Cold dark matter heats up  

E-print Network

One of the principal discoveries in modern cosmology is that standard model particles (including baryons, leptons and photons) together comprise only 5% of the mass-energy budget of the Universe. The remaining 95% consists of dark energy and dark matter (DM). Consequently our picture of the universe is known as {\\Lambda}CDM, with {\\Lambda} denoting dark energy and CDM cold dark matter. {\\Lambda}CDM is being challenged by its apparent inability to explain the low density of DM measured at the centre of cosmological systems, ranging from faint dwarf galaxies to massive clusters containing tens of galaxies the size of the Milky Way. But before making conclusions one should carefully include the effect of gas and stars, which were historically seen as merely a passive component during the assembly of galaxies. We now understand that these can in fact significantly alter the DM component, through a coupling based on rapid gravitational potential fluctuations.

Pontzen, Andrew

2014-01-01

461

Atomic Platters: Cold War Music  

NSDL National Science Digital Library

Along with ushering in a new age of global unrest and high anxiety, the emergence of the atomic bomb had a curious and not totally unpredictable effect on the world of popular (and not-so-popular) music. This site brings together these various subgenres of "atomic" music in a way that's rather fun, intriguing, and at times, a bit scary. Visitors can look through such subgenres as "Atomic", "Cold War", "Flying Saucer", and so on. While most of the songs are not available in their full form, visitors can read all of the lyrics and interpretive essays. Of course, visitors can find plenty of audio joy at the "CONELRAD Audio Archives" area. Herein are contained such gems as the positively odd "The Complacent Americans" and the equally lovable novelty album "The Goldwaters Sing Folk Songs to Bug the Liberals".

462

Status of cold fusion (2010)  

NASA Astrophysics Data System (ADS)

The phenomenon called cold fusion has been studied for the last 21 years since its discovery by Profs. Fleischmann and Pons in 1989. The discovery was met with considerable skepticism, but supporting evidence has accumulated, plausible theories have been suggested, and research is continuing in at least eight countries. This paper provides a brief overview of the major discoveries and some of the attempts at an explanation. The evidence supports the claim that a nuclear reaction between deuterons to produce helium can occur in special materials without application of high energy. This reaction is found to produce clean energy at potentially useful levels without the harmful byproducts normally associated with a nuclear process. Various requirements of a model are examined.

Storms, Edmund

2010-10-01

463

Status of cold fusion (2010).  

PubMed

The phenomenon called cold fusion has been studied for the last 21 years since its discovery by Profs. Fleischmann and Pons in 1989. The discovery was met with considerable skepticism, but supporting evidence has accumulated, plausible theories have been suggested, and research is continuing in at least eight countries. This paper provides a brief overview of the major discoveries and some of the attempts at an explanation. The evidence supports the claim that a nuclear reaction between deuterons to produce helium can occur in special materials without application of high energy. This reaction is found to produce clean energy at potentially useful levels without the harmful byproducts normally associated with a nuclear process. Various requirements of a model are examined. PMID:20838756

Storms, Edmund

2010-10-01

464

The cold-fog test  

SciTech Connect

The electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination (C), ice (I), fog (F) and an ambient temperature that rises through 0 C (T{sub 0{degree}}). Failures at operating voltage on 115-kV, 230-kV and 500-kV systems occur with increasing probability under these conditions. A new CFT{sub 0{degree}} or cold-fog test method has been developed to reproduce the flashovers at all three voltage levels. Three options are identified for improving CFT{sub 0{degree}} performance: use of semi-conductive glazes, substitution of silicone for porcelain and use of silicone coatings on existing porcelain insulators.

Chisholm, W.A.; Ringler, K.G.; Erven, C.C. [Ontario Hydro Technologies, Toronto, Ontario (Canada)] [and others] [Ontario Hydro Technologies, Toronto, Ontario (Canada); and others

1996-10-01

465

Cold Chemical Oxidation of Proteins  

PubMed Central

Various methods of protein footprinting use hydrogen peroxide as oxidant. Its removal by various solid-phase desalting methods, catalase treatment, or freeze-drying after the footprinting is critical to insure no uncontrolled oxidation. Although catalase treatment removes hydrogen peroxide with little loss of protein or additional protein oxidation, we discovered that freeze-drying or freezing of the protein in peroxide solution does lead to protein oxidation. Interestingly, the oxidation is not a result of freeze or thaw processes but depends on the temperature and length of time for incubation. After 2 h, apomyoglobin undergoes nearly complete single oxidation at ?80 °C and double oxidation at ?15 °C. The oxidation extents are in addition to the number of methionine residues. Minimal oxidation is observed at 4 °C and 22 °C compared to oxidation at ?80 °C or ?20 °C. The concentration of hydrogen peroxide is critical; 75 mM (0.2%) is required to oxidize > 50% of the protein at ?15 °C and 100-mM (0.3%) at ?80 °C. In addition to Met, ~ 5% of the tryptophan and tyrosine residues are oxidized as well as lower amounts of His and Phe. Oxidation of Val 68 and Val 17 (a buried residue) also occurs, with the oxidation of Val 17 likely occurring by electron transfer from one of two of the oxidized aromatic residues contacting Val 17. We describe here the need to remove the hydrogen peroxide prior to cold storage of proteins, and we also report some preliminary results pertaining to the mechanism of cold, solid-state oxidation. PMID:19715356

Hambly, David M.; Gross, Michael L.

2010-01-01

466

Fluorescent lamp cold environment performance improvement  

Microsoft Academic Search

Three approaches to improving the efficacy and start-up time of commercially available cold cathode fluorescent lamps under cold ambient conditions are evaluated in this paper: heating the tube on one side; heating the tube on two sides; heating the circumference of the outer tube. The internal power density generated by ion bombardment of the cathode and collisions in the plasma

M. Graovac; F. P. Dawson; M. Fila; D. E. Cormack

1998-01-01

467

REDUCTION OF COLD WELDING BY GEOMETRIC PARAMETERS  

Microsoft Academic Search

Cold-welding and fretting are especially relevant regarding opening and closing of engineering mechanisms, either placed in vacuum or embarked on spacecrafts, because they condition the life of the mechanism and its proper functioning. Fretting may cause wear of materials and coatings which could lead to cold welding. To avoid this risk, the question has to be answered, whether to select

A. Merstallinger; E. Semerad; B. D. Dunn

468

Cold Spring Harbor Asia High Throughput Biology  

E-print Network

Cold Spring Harbor Asia High Throughput Biology Suzhou, China April 19 - 23, 2011 Arranged by: Edward Rubin, Lawrence Berkeley National Laboratory and DOE Joint Genome Institute Bing Ren, Ludwig to announce the inaugural Cold Spring Harbor Asia conference on High Throughput Biology which will be held

Smith, Adam D.

469

Cold Climates Heat Pump Design Optimization  

Microsoft Academic Search

Heat pumps provide an efficient heating method; however they suffer from sever capacity and performance degradation at low ambient conditions. This has deterred market penetration in cold climates. There is a continuing effort to find an efficient air source cold climate heat pump that maintains acceptable capacity and performance at low ambient conditions. Systematic optimization techniques provide a reliable approach

Omar Abdelaziz; Bo Shen

2012-01-01

470

Was the Cold War a Security Dilemma?  

Microsoft Academic Search

Under the security dilemma, tensions and conºicts can arise between states even when they do not intend them. Some analysts have argued that the Cold War was a classic example of a security dilemma. This article disputes that notion. Although the Cold War contained elements of a deep security dilemma, it was not purely a case in which tensions and

Robert Jervis

2001-01-01

471

Feasibility study of cold expansion processes modelling  

NASA Astrophysics Data System (ADS)

A comprehensive review is presented of the cold expansion techniques currently used for the improvement of fatigue strength of fastened joints. Two common practices of generating residual stress fields responsible for increasing fatigue life are cold working of the open hole before fastener installation and interference fit fastener systems. Most of the materials studied were aluminum, and experimental work has shown that the benefits of cold working on fatigue life enhancement were substantial in some cases, particularly in the high cycle fatigue region. The performance of cold working depends on several parameters, the most influential being the material characteristics, degree of cold working, and remote applied stress. Analytical work characterizing cold working in order to establish the residual stress distribution uses several simplified assumptions, and analytical results may sometimes be unrealistic compared to results from experiments or finite element methods. Life prediction methods for cold worked materials, relaxation of the compressive residual stress during cycling, and nondestructive examination methods applied to cold working problems are also summarized.

Bernard, Marie; Thang, Bui-Quoc; Julien, Denis; Forgues, Sylvain

1993-03-01

472

Cold fusion back from the dead  

Microsoft Academic Search

The US Energy Department has renewed its efforts to investigate the prospects for cold fusion, the supposed generation of thermonuclear energy using tabletop apparatus. While critics say that the extravagant claims behind cold fusion need to be backed with exceptionally strong evidence, there has been a small group of dedicated researches who have continued to conduct investigations. Over the years,

J. Mullins

2004-01-01

473

Fracto-fusion. Mechanism of cold fusion  

Microsoft Academic Search

As a cold fusion mechanism, a fracto-fusion was investigated by which reacting particles are accelerated by the electric field generated between the crack surfaces in a crystal and the beam fusion occurs. By assuming the possible magnitude of the potential difference the fusion rate and energy multiplication factor were calculated. These results are consistent with cold fusion experiments. On the

Tatsuoki Takeda; Tomonori Takizuka

1989-01-01

474

Cold fusion reaction products and their measurement  

Microsoft Academic Search

The major reaction products that have been possibly associated with cold fusion reactions are neutrons, protons, tritium, He-3, He-4, internal conversion electrons, and gamma radiation. The branching ratios and relative reaction rates for these products are examined for consistency with cold fusion experiments. Both theoretical calculations and experimental data are examined and presented. The He-4 plus internal conversion reaction has

Vern C. Rogers; Gary M. Sandquist

1990-01-01

475

Numerical Analysis of Ammonia-Water Bubble Absorber  

NASA Astrophysics Data System (ADS)

Thin film mode in ammonia-water absorption systems provides relatively high heat transfer coefficients and is stable during operation. However, thin film mode needs good liquid distributors. Bubble mode provides not only high heat transfer coefficients but also good mixing effect between the liquid and the vapor. The objective of this paper are to develop a design model for a bubble absorber with plate heat exchangers, to evaluate a simultaneous heat and mass transfer within both liquid and bubble and to clarify significant factors for a design of a ammonia-water bubble absorber. This analysis used experimental correlation from previous study of ammonia-water bubble absorption. It was clarified that heat transfer coefficient of wall in the absorber was a dominant factor in the heat transfer resistance of absorber, and a mass transfer enhancement depended on the inlet flow rate of vapor. The number of orifice in the absorber and inlet flow rate of liquid solution had influence on the height of absorber, but the orifice diameter had relatively a little influence. There were optimum conditions that the height of absorber reached at minimum, for the inlet flow rates of liquid solution

Hamamoto, Yoshimori; Nagano, Tatsuhiko; Yamada, Jun; Akisawa, Atsushi; Kashiwagi, Takao

476

Simulation, fabrication and characterization of THz metamaterial absorbers.  

PubMed

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical(1) and experimental demonstration(2) of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical(3), near IR(4), mid IR(5) , THz(6) , mm-wave(7) , microwave(8) and radio(9) bands. Applications include perfect lenses(10), sensors(11), telecommunications(12), invisibility cloaks(13) and filters(14,15). We have recently developed single band(16), dual band(17) and broadband(18) THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers(19). In our MM absorber the THz radiation is absorbed in a thickness of ~ ?/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems. PMID:23299442

Grant, James P; McCrindle, Iain J H; Cumming, David R S

2012-01-01

477

Experimental verification of metamaterial based subwavelength microwave absorbers  

NASA Astrophysics Data System (ADS)

We designed, implemented, and experimentally characterized electrically thin microwave absorbers by using the metamaterial concept. The absorbers consist of (i) a metal back plate and an artificial magnetic material layer; (ii) metamaterial back plate and a resistive sheet layer. We investigated absorber performance in terms of absorbance, fractional bandwidth, and electrical thickness, all of which depend on the dimensions of the metamaterial unit cell and the distance between the back plate and metamaterial layer. As a proof of concept, we demonstrated a ? /4.7 thick absorber of type I, with a 99.8% absorption peak along with a 8% fractional bandwidth. We have shown that as the electrical size of the metamaterial unit cell decreases, the absorber electrical thickness can further be reduced. We investigated this concept by using two different magnetic metamaterial inclusions: the split-ring resonator (SRR) and multiple SSR (MSRR). We have also demonstrated experimentally a ? /4.7 and a ? /4.2 thick absorbers of type II, based on SRR and MSRR magnetic metamaterial back plates, respectively. The absorption peak of the SRR layout is 97.4%, while for the MSRR one the absorption peak is 98.4%. The 10 dB bandwidths were 9.9% and 9.6% for the SRR and MSRR cases, respectively.

Alici, Kamil Boratay; Bilotti, Filiberto; Vegni, Lucio; Ozbay, Ekmel

2010-10-01

478

Correlations between O VI Absorbers and Galaxies at Low Redshift  

E-print Network

We investigate the relationship between galaxies and metal-line absorption systems in a large-scale cosmological simulation with galaxy formation. Our detailed treatment of metal enrichment and non-equilibrium calculation of oxygen species allow us, for the first time, to carry out quantitative calculations of the cross-correlations between galaxies and O VI absorbers. We find the following: (1) The cross-correlation strength depends weakly on the absorption strength but strongly on the luminosity of the galaxy. (2) The correlation distance increases monotonically with luminosity from ~0.5-1h^-1 Mpc for 0.1L* galaxies to ~3-5h^-1 Mpc for L* galaxies. (3) The correlation distance has a complicated dependence on absorber strength, with a luminosity-dependent peak. (4) Only 15% of O VI absorbers lie near >=Lz* galaxies. The remaining 85%, then, must arise ``near'' lower-luminosity galaxies, though, the positions of those galaxies is not well-correlated with the absorbers. This may point to pollution of intergalactic gas predominantly by smaller galaxies. (5) There is a subtle trend that for >~0.5Lz* galaxies, there is a positive correlation between absorber strength and galaxy luminosity in the sense that stronger absorbers have a slightly higher probability of finding such a large galaxy at a given projection distance. For less luminous galaxies, there seems to be a negative correlation between luminosity and absorber strength.

Rajib Ganguly; Renyue Cen; Taotao Fang; Kenneth Sembach

2008-03-28

479

Extreme warm absorber variability in the Seyfert galaxy Mrk 704  

NASA Astrophysics Data System (ADS)

Context. In about half of the Seyfert galaxies, the X-ray emission is absorbed by an optically thin, ionized medium, the so-called "warm absorber", whose origin and location is still a matter of debate. Aims: The aim of this paper is to constrain the warm absorber further by studying its variability. Methods: We analyzed the X-ray spectra of a Seyfert 1 galaxy, Mrk 704, which was observed twice, three years apart, by XMM-Newton. Results: The spectra were well fitted with a two-zones absorber, which possibly covers the source only partially. The parameters of the absorbing matter - column density, ionization state, covering factor - changed significantly between the two observations. Possible explanations for the more ionized absorber are a torus wind (the source is a polar scattering one) or, in the partial covering scenario, an accretion disk wind. The less ionized absorber is possibly composed of orbiting clouds in the surroundings of the nucleus, similarly to what was already found in other sources, most notably NGC 1365.

Matt, G.; Bianchi, S.; Guainazzi, M.; Longinotti, A. L.; Dadina, M.; Karas, V.; Malaguti, G.; Miniutti, G.; Petrucci, P. O.; Piconcelli, E.; Ponti, G.

2011-09-01

480

Uptake of dissolved free amino acids by four cold-water coral species from the Mediterranean Sea  

NASA Astrophysics Data System (ADS)

Dissolved organic matter, which contains many compounds such as lipids, sugars and amino acids, is an important source of carbon and nitrogen for several symbiotic and asymbiotic tropical coral species. However, there is still no information on its possible uptake by cold-water coral species. In this study, we demonstrated that dissolved organic matter, in the form of dissolved free amino acids (DFAA), is actively absorbed by four cold-water coral species from the Mediterranean Sea. Although the uptake rates observed with 3 ?M DFAA concentration were one order of magnitude lower than those observed in tropical species, they corresponded to 12-50% of the daily excreted-nitrogen, and 16-89% of the daily respired-carbon of the cold-water corals. Consequently, DFAA, even at in situ concentrations lower than those tested in this study, can supply a significant amount of carbon and nitrogen to the corals, especially during periods when particulate food is scarce.

Gori, Andrea; Grover, Renaud; Orejas, Covadonga; Sikorski, Séverine; Ferrier-Pagès, Christine