International Nuclear Information System (INIS)

We study the spectral evolution of pulsar wind nebulae (PWNe) taking into account the energy injected when they are young. We model the evolution of the magnetic field inside a uniformly expanding PWN. Considering time-dependent injection from the pulsar and coolings by radiative and adiabatic losses, we solve the evolution of the particle distribution function. The model is calibrated by fitting the calculated spectrum to the observations of the Crab Nebula at an age of a thousand years. The spectral evolution of the Crab Nebula in our model shows that the flux ratio of TeV #gamma#-rays to X-rays increases with time, which implies that old PWNe are faint in X-rays, but not in TeV #gamma#-rays. The increase of this ratio is because the magnetic field decreases with time and is not because the X-ray emitting particles are cooled more rapidly than the TeV ...

International Nuclear Information System (INIS)

We consider the spin-up of the white dwarf in non-magnetic cataclysmic variables (CVs) during secular evolution. If this is unresisted, CVs are quenched as boundary-layer emitters once the binary period has decreased by #approx# 1 hr. Angular momentum loss in nova explosions may, however, prevent the star reaching breakup. If the explosions remove (1 + #epsilon#) x the mass accreted between outbursts, values 0.5 < #approx# #epsilon# < #approx# 1 allow CVs to be modest boundary-layer emitters for most of their lifetimes. Spectral effects will limit their detection as soft X-ray sources. (author).

CERN Document Server

Laboratory characterization of Interplanetary Dust Particles (IDPs) collected in the lower stratosphere represents a concrete analysis of cosmic dust properties which played a fundamental role in the origin and evolution of Solar System. The IDPs were characterized by Field Emission Scanning Electron Microscope (FESEM) analyses and by InfraRed (IR) micro-spectroscopy. We present the FESEM images of six IDPs: three smooth grains, two porous and one a compact sphere. We also show the results of micro-IR transmission measurements on four IDPs that allowed us to identify their spectral class according to the criteria defined by Sandford and Walker. Only three of the analyzed particles show IR transmission spectra with a dominant "silicate absorption feature" so that they could be assigned to the three IR spectral classes: one has been classified as "amorphous olivine", one appears to be a mixture of "olivines" and "pyroxenes" ...

CERN Document Server

We study the spectral and temporal behavior of the High Mass X-ray Binary A 0535+26 during a `pre-outburst flare' which took place ~5 d before the peak of a normal (type I) outburst in August/September 2005. We compare the studied behavior with that observed during the outburst. We analyse RXTE observations that monitored A 0535+26 during the outburst. We complete spectral and timing analyses of the data. We study the evolution of the pulse period, present energy-dependent pulse profiles both at the initial pre-outburst flare and close to outburst maximum, and measure how the cyclotron resonance-scattering feature (hereafter CRSF) evolves. We present three main results: a constant period P=103.3960(5)s is measured until periastron passage, followed by a spin-up with a decreasing period derivative of Pdot=(-1.69+/-0.04)x10^(-8)s/s at MJD 53618, and P remains constant again at the end of the main outburst. The spin-up ...

CERN Document Server

Over the last decade {\\it ab initio} modeling of material properties has become widespread in diverse fields of research. It has proved to be a powerful tool for predicting various properties of matter under extreme conditions. We apply modern computational chemistry and materials science methods, including density functional theory (DFT), to solve lingering problems in the modeling of the dense atmospheres of cool white dwarfs ($T_{\\rm eff}\\rm <7000 \\, K$). Our work on the revision and improvements of the absorption mechanisms in the hydrogen and helium dominated atmospheres resulted in a new set of atmosphere models. By inclusion of the Ly-$\\rm \\alpha$ red wing opacity we successfully fitted the entire spectral energy distributions of known cool DA stars. In the subsequent work we fitted the majority of the coolest stars with hydrogen-rich models. This finding challenges our understanding of the spectral ...

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We follow the evolution of the curvaton on superhorizon scales and check that the spectral tilt of the curvaton perturbations is unchanged as the curvaton becomes non-relativistic. Both inflation and pre-big bang cosmology can be treated since the curvaton mechanism within the two scenarios works the same way. We also discuss the amplitude of the density perturbations, which leads to some interesting constrains on the pre-big bang scenario. It is shown that within a SL(3,R) non-linear sigma model one of the three axions has the right coupling to the dilaton and moduli to yield a flat spectrum with a high string scale, if a quadratic non-perturbative potential is generated and an intermediate string phase lasts long enough.

British Library Electronic Table of Contents (United Kingdom)

ABSTRACT We address the problem of angular momentum transport in stellar radiative interiors with a novel semi-analytic spectral technique, using an eigenfunction series expansion, that can be used to derive benchmark solutions in hydromagnetic regimes with very high Reynolds number (107-108). The error arising from the truncation of the series is evaluated analytically. The main simplifying assumptions are the neglect of meridional circulation and of non-axisymmetric magnetic fields. The advantages of our approach are shown by applying it to a spin-down model for a Formula Not Shown main-sequence star. The evolution of the coupling between core and envelope is investigated for different values of the viscosity and different geometries and values of the poloidal field. We confirm that a vi...

International Nuclear Information System (INIS)

We report on the first measurements of the z-dependent evolution of electron-beam microbunching as revealed through coherent transition radiation (CTR) measurements in a visible self-amplified spontaneous emission free-electron laser experiment. The increase in microbunching was detected by tracking the growth of the visible CTR signals as generated from insertable metal mirrors/foils after each of the last three undulators. The same optical imaging diagnostics that were used to track the z-dependent intensity of the undulator radiation (UR) were also used to track the electron beam/CTR information. Angular distribution, beam size, and intensity data were obtained after each of the last three undulators in the five-undulator series, and spectral information was obtained after the last undulator. The exponential growth rate of the CTR was found to be very similar to that of the UR and consistent with simulations using the code GENESIS.

International Nuclear Information System (INIS)

The advances in laser technology have made available very short and intense laser pulses which can be used to seed a high-gain single-pass free-electron laser (FEL) amplifier. With these seed pulses, a regime of the FEL interaction where the radiation evolution is simultaneously dominated by nonlinear effects (saturation) and time-dependent effects (slippage) can be explored. This regime is characterized by the propagation of a solitary wavelike pulse where the power of the optical wave grows quadratically with time, its pulse length decreases and the spectral bandwidth increases. We analyze the interplay between the field and particle dynamics of this propagation regime which was studied before and termed super-radiance. Furthermore we analyze the properties of the strong higher-order harmonic emission from this wave and its behavior when propagating in a cascade FEL. The super-radiant pulse is indeed capable of passing through the stages of a ...

Science.gov (United States)

We present observations of PSRs J0437-4715, J0738-4042, J0835-4510, J0908-4913, J1048-5832, J1622-4950, J1644-4559, J1721-3532 and J1740-3015 at 17 GHz using the Parkes radio telescope. All nine were detected at 17 GHz, additionally, we detected PSR J0835-4510 and J1622-4950 at 24 GHz. Polarization profiles of each pulsar and the variation with frequency are discussed. In general, we find that the highly polarized edge components of young pulsars continue to dominate their profiles at 17 GHz. Older pulsars (?105 yr) appear to be almost completely depolarized. Our detection of PSR J0437-4715 is the highest frequency observation of a millisecond pulsar to date, and implies a luminosity at 17 GHz of 14 ?Jy kpc2, and a mean spectral index of 2.2. We find that the spectral index of the magnetar PSR J1622-4950 is flat between 1.4 and 24 GHz, similar to the other known radio magnetars XTE J1810-197 and 1E 1547.0-5408. The profile is similar to that ...

Science.gov (United States)

The Ames autotracking airborne sun photometer was used to investigate the spectral depth between 380

Science.gov (United States)

Another difference lies in the speed of star evolution. 2. Computation of Stellar Structure and Their Evolution. The structure of stars at certain instants ...

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The evolution of massive stars through hydrogen and helium burning is addressed. A set of stellar

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UV dwarf star evolution, using central and gap star models emphasizing photoneutrino emission

CERN Document Server

We investigate the environmental dependence of stellar population properties of galaxies in the local universe. Physical quantities related to the stellar content of galaxies are derived from a spectral synthesis method applied to a volume-limited sample containing about 50 thousand galaxies (0.05 < z < 0.1; M_r < -20.5), extracted from the Data Release 2 of the SDSS. Mean stellar ages, mean stellar metallicities and stellar masses are obtained from this method and used to characterise the stellar populations of galaxies. The environment is defined by the projected local galaxy density estimated from a nearest neighbour approach. We recover the star formation--density relation in terms of the mean light-weighted stellar age, which is strongly correlated with star formation parameters derived from Halpha. We find that the age--density relation is distinct when we divide galaxies according to luminosity or stellar mass. The relation is remarkable for ...

CERN Document Server

We summarize results of recent studies of heavy quarkonia correlators and spectral functions at finite temperatures from lattice QCD and systematic T-matrix studies using QCD motivated finite-temperature potentials. We argue that heavy quarkonia dissociation shall occur in the temperature range $1.2 \\le T_d/T_c \\le 1.5$ by the interplay of both screening and absorption in the strongly correlated plasma medium. We discuss these effects on the quantum mechanical evolution of quarkonia states within a time-dependent harmonic oscillator model with complex oscillator strength and compare the results with data for $R_{\\rm AA}/R_{\\rm AA}^{\\rm CNM}$ from RHIC and SPS experiments. We speculate whether the suppression pattern of the rather precise NA60 data from In-In collisions may be related to the recently discovered X(3872) state. Theoretical support for this hypothesis comes from the cluster expansion of the plasma Hamiltonian for heavy ...

CERN Document Server

We develop and demonstrate the methodology of testing multi-dimensional supernova models against observations by studying the properties of one example of the detonation from failed deflagration (DFD) explosion model of thermonuclear supernovae. Using time-dependent multi-dimensional radiative transfer calculations, we generate the synthetic broadband optical light curves, near-infrared light curves, color evolution curves, full spectral time-series, and spectropolarization of the model, as seen from various viewing angles. All model observables are critically evaluated against examples of well-observed, standard Type Ia supernovae (SNe Ia). We explore the consequences of the intrinsic model asphericity by studying the dependence of the model emission on viewing angle, and by quantifying the resulting dispersion in (and internal correlations between) various model observables. These statistical properties of the model are also evaluated against ...

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verified via high-resolution spectral density measurements using the Hadamard Variance. .... spectral density measurements were made with the HF5390 ...

UK PubMed Central (United Kingdom)

An application that provides a flexible and easy to use interface to the GAMMA spectral simulation package is described that is targeted at investigations using in vivo MR spectroscopic methods....Full Text Available

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FIG. 4. Power Spectral Density of the MAP W11 radiometer. The red and black traces are the power spectral density measurements of the two detectors on the ...

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star evolution, globular cluster structure and evolution, massive stars, supernova remnants, reflection nebulae, interstellar dust, structure of the ISM, ...

Science.gov (United States)

These include, but are not limited to: stellar winds and outflows, post-main- sequence stellar evolution, binary/multiple star evolution, globular cluster structure ...

KoreaScience (Korea)

Full Text Available

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No abstract prepared.

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An ASTER (advanced spaceborne thermal emission and reflection radiometer) is one of the image sensors. It is to be installed in an earth survey polar orbit platform satellite, EOS-AM1, which is to be launched in 1998, and it is going to start its operation. Data observed by the thermal infrared remote sensing of ASTER include the spectral emissivity, and the spectral emission reflectivity which is expressed by the function of temperature. It is required to overcome technical problems how to extract the spectral emissivity from the observed data. The spectral emissivity extracted from the remote sensing data by the MMD method, measured for samples collected in Cuprite area, Nevada, and/or measured at sampled points were compared to each other and discussed. The hemisphere spectral reflectivity, which is indirect spectral emissivity, agreed well with the direct ...

CERN Document Server

The so-called spectral dimension is a scale-dependent number associated with both geometries and field theories that has recently attracted much attention, driven largely though not exclusively by investigations of causal dynamical triangulations (CDT) and Horava gravity as possible candidates for quantum gravity. We advocate the use of the spectral dimension as a probe for the kinematics of these (and other) systems in the region where spacetime curvature is small, and the manifold is flat to a good approximation. In particular, we show how to assign a spectral dimension (as a function of so-called diffusion time) to any arbitrarily specified dispersion relation. We also analyze the fundamental properties of spectral dimension using extensions of the usual Seeley-DeWitt and Feynman expansions, and by saddle point techniques. The spectral dimension turns out to be a useful, robust ...

International Nuclear Information System (INIS)

Realization of the scale of spectral responsivity of the detectors in the Directorate of Measures and Precious Metals (DMDM) is based on silicon detectors traceable to LNE-INM. In order to realize the unit of spectral irradiance in the laboratory for photometry and radiometry of the Bureau of Measures and Precious Metals, the new method based on the calibration of the spectroradiometer by comparison with standard detector has been established. The development of the method included realization of the System of Spectral Comparisons (SSC), together with the detector spectral responsivity calibrations by means of a primary spectrophotometric system. The linearity testing and stray light analysis were preformed to characterize the spectroradiometer. Measurement of aperture diameter and calibration of transimpedance amplifier were part of the overall experiment. In this paper, the developed method is ...

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A major factor for the achievement of the desirable performance, efficiency and lifetime of flexible organic electronic devices is the optimization of the encapsulation layers that protect the device active layers by atmospheric gas molecule permeation. The active layers consisted of small molecule and/or polymer organic semiconductors as well as the organic conductors need to be encapsulated into a transparent medium that will provide the necessary protection and maintain their charge generation and transport characteristics. The encapsulation layers are generally consisted of inorganic thin films (silicon oxide-SiO{sub x} and aluminium oxide-AlO{sub x}) deposited onto the polymeric substrates, such as PolyEthylene Terephthalate (PET). In this work, in situ and real-time Spectroscopic Ellipsometry in the ultraviolet spectral region has been implemented in order to investigate the growth of inorganic SiO{sub x} and AlO{sub x} nano-layers onto PET flexible polymeric ...

International Nuclear Information System (INIS)

Moderate-resolution, near-infrared spectra between 0.8 and 5.2 #mu#m were obtained for 12 late-type (K0-M3) disk-bearing members of the #approx#5 Myr old Upper Scorpius OB association using SpeX on the NASA Infrared Telescope Facility. For most sources, continuum excess emission first becomes apparent between #approx#2.2 and 4.5 #mu#m and is consistent with that produced by single-temperature blackbodies having characteristic temperatures ranging from #approx#500 to 1300 K. The near-infrared spectra for 5 of 12 Upper Scorpius sources exhibit Pa#gamma#, Pa#beta#, and Br#gamma# emission, indicators of disk accretion. Using a correlation between Pa#beta# and Br#gamma# emission line luminosity and accretion luminosity, mass accretion rates ( M-dot ) are derived for these sources that range from M-dot = 3.5x10"-"1"0 to 1.5 x 10"-"8 M_s_u_n yr"-"1. Merging the SpeX observations with Spitzer Space Telescope mid-infrared (5.4-37.0 #mu#m) spectroscopy and 24 and 70 #mu#m broadband photometry, ...

UK PubMed Central (United Kingdom)

The capability to image tissue motion such as blood flow through an endoscope could have many applications in medicine. Spectrally encoded endoscopy (SEE) is a recently introduced technique...Full Text Available

UK PubMed Central (United Kingdom)

The 3-D spectral-domain optical coherence tomography (SD-OCT) images of the retina often do not reflect the true shape of the retina and are distorted differently along the x and y...Full Text Available

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... Measuring Instruments ..... 7-18 7.4 Power Spectral Density Measurements of Random DaL. .... 7-19 7 ...

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... ENGINEERING. Personal Author(s) : Ogino,Koji ; Cadzow,James A. Report Date : 1980. Pagination or Media Count : 18. ...

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... measurement. Power spectral density measurements are made by the dynamic signal analyzer for each channel. A cross power ...

CERN Document Server

Ozsvath and Szabo show that there is a spectral sequence whose E^2 term is the reduced Khovanov homology of L, and which converges to the Heegaard Floer homology of the (orientation reversed) branched double cover of S^3 along L. We prove that the E^k term of this spectral sequence is an invariant of the link L when k>2. If L is a transverse link, then we show that Plamenevskaya's transverse invariant gives rise to a transverse invariant of L in each of these higher terms.

International Nuclear Information System (INIS)

A multi-spectral Schottky barrier infrared detector array in which individual pixels of radiation from a remote radiating object are detected by two or more Schottky barrier infrared radiation detectors each having a different spectral response so as to provide a ''color'' discrimination for the array.

UK PubMed Central (United Kingdom)

The specificity of the hemodynamic response function (HRF) is determined spatially by the vascular architecture and temporally by the evolution of hemodynamic changes. The stimulus duration...Full Text Available

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These include, but are not limited to: stellar winds and outflows, post-main- sequence stellar evolution, binary/multiple star evolution, globular cluster ...

UK PubMed Central (United Kingdom)

Our global impact is finally receiving the scientific attention it deserves. The outcome will largely determine the future course of evolution. Human-modified ecosystems are shaped by our activities...Full Text Available

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Binary Star Evolution. The evolution of close binary stars can be very different from that of wide binaries of isolated stars. If the stars are close enough ...

International Nuclear Information System (INIS)

The evolution of the study of extra-terrestrial neutrinos over the 45 years since their discovery.

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The research sponsored by this grant was conducted in two fields of high-energy astrophysics:

Energy Technology Data Exchange (ETDEWEB)

Stars and star evolution are discussed, including supernovae, nucleosynthesis, and mass-luminosity and Hertzsprung--Russell diagrams./aip/.

Science.gov (United States)

Because of its high price, the extra virgin olive oil is frequently target for adulteration with lower quality oils. This paper presents an innovative optical technique capable of quantifying the adulteration of extra virgin olive oil caused by lowergrade olive oils. It relies on spectral fingerprinting the test liquid by means of diffuse-light absorption spectroscopy carried out by optical fiber technology in the wide 400-1700 nm spectral range. Then, a smart multivariate processing of spectroscopic data is applied for immediate prediction of adulterant concentration.

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Secondary deuterium in the atmosphere are produced in interactions by primary cosmic rays. The shape of their energy spectrum depends on the primary cosmic ray spectrum incident at the top of the atmosphere. At high energies, the spectral shape depends on the primary spectrum of helium and heavy nuclei. However, at very low energies, specially below the geomagnetic cut-off, the spectral shape depends on the evaporation and recoil processes and hence almost independent of the spectral shape of the primary radiation. It is undertaken a calculation of the secondary deuterium spectrum at small atmospheric depths at various latitudes and the results will be presented.

Energy Technology Data Exchange (ETDEWEB)

A temperature gradient across a thick ({ge}.1mm) film selective emitter will produce a significant reduction in the spectral emittance from the no temperature gradient case. Thick film selective emitters of rare earth doped host materials such as yttrium-aluminum-garnet (YAG) are examples where temperature gradient effects are important. In this paper a model is developed for the spectral emittance assuming a linear temperature gradient across the film. Results of the model indicate that temperature gradients will result in reductions the order of 20{percent} or more in the spectral emittance. {copyright} {ital 1997 American Institute of Physics.}

Science.gov (United States)

... The lateral cross spectral density measurements are normalized on the autospectrum. Frequency is normalized on r3 , and we take Uc _" 0.7 U0 . ...

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... Although cytologic evaluation of urine specimens is a standard Cesar Angeletti, MD ... 3. Rodriguez-Alonso A, Pita-Fernandez S, Gonzalez-Carrero J, ...

International Nuclear Information System (INIS)

... californium 252 fftf reactor mockup power density reactor cores reactor noise

Science.gov (United States)

results of motion energy spectral density measurements in the upper atmosphere for the time interval of 5 minutes to 12 hours, in ...

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... Voltage noise power spectral density measurements as a function of temperature, frequency, current, and magnetic field on DyBa2Cu3O7.x (DBCO ...

Science.gov (United States)

structures made out of composite laminates and/or composite sandwich panels. A Spectral Finite Element Method (SFEM) [19, 20] is used for evaluating the ...

Energy Technology Data Exchange (ETDEWEB)

A tunable diode laser is used to obtain infrared spectra of carbon dioxide in biological materials. The spectral resolution is sufficient to readily distinguish differing isotopic species. The technique may prove useful in clinical tests.

Science.gov (United States)

... Coastal Monitoring and Assessment, the University of Hawaii, BAE Systems Spectral Solutions and Analytical Laboratories of Hawaii, LLC. ... ...

Energy Technology Data Exchange (ETDEWEB)

Short communication.

Science.gov (United States)

... 37 18 Power Spectral Density Measurements of Buffet Pressures for Two Different Microphone Positions Compared with PSD Values Inferred from ...

International Nuclear Information System (INIS)

It is shown that it is necessary to take into account locality of the analysis and to introduce additional corrections for partial capture of matrix and fluorescent subexcitation by matrix during quantitative X-ray spectral microanalysis of finely dispersed materials. Cast two-phase (#alpha#+#beta#) titanium alloy VT3-1 is chosen as an investigation object.

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The application of a Compact Airborne Spectrographic Imager to assessment and monitoring of lakes in a lignite open cast mining area in central Germany is described. The imager was used in combination with additional ground experiments, such as field spectroscopy and water sampling. The spectral characteristics of an instrument under development for monitoring geochemical and hydrological processes are presented. Summary form only.

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Comparative studies of flocculent and grand-design spirals suggest that density waves are not the predominant trigger of star formation in most galaxies. Implications for chemical evolution are profound. It may be possible to ignore the details of the spiral-wave phenomenon in research aimed at unifying the chemical properties of spiral disks. 16 references.

UK PubMed Central (United Kingdom)

The evolution of drug resistant bacteria is a severe public health problem, both in hospitals and in the community. Currently, some countries aim at concentrating highly specialized services in large...Full Text Available

Science.gov (United States)

Neutron Star Evolution with Internal Energy h'q/>a. Dissipation by Vortex Creep. N. Shibazaki and F. K. Lamb. University of Illinois at Urbana-Champaign ...

International Nuclear Information System (INIS)

A disk formation model during collapse of the protosolar nebula, yielding a low-mass protoplanetary disk is presented. The following subject areas are covered: (1) circumstellar disks; (2) conditions for the formation of stars with disks; (3) early evolution of the protoplanetary disk; and (4) temperature conditions and the convection in the protoplanetary disk.

UK PubMed Central (United Kingdom)

All eukaryotes require mitochondria for survival and growth. The origin of mitochondria can be traced down to a single endosymbiotic event between two probably prokaryotic organisms. Subsequent evolution...Full Text Available

UK PubMed Central (United Kingdom)

Several phenomena in animal learning seem to call for evolutionary explanations, such as patterns of what animals learn and do not learn. While several models consider how evolution should influence...Full Text Available

International Nuclear Information System (INIS)

Recent experimental and theoretical studies of two-dimensional (2D) turbulence reveal that spectrally condensed turbulence which is a system of coupled large-scale coherent flow and broadband turbulence, is similar to plasma turbulence near the L-H transition threshold. Large condensate vortices fed via the turbulent inverse energy cascade, can control both the level of the broadband turbulence by shear decorrelation, and the energy injected into turbulence at the forcing scale via sweeping of the forcing-scale vortices. The interaction between these ingredients of spectrally condensed fluid turbulence is in many aspects similar to the interactions in the zonal flow-GAMs-turbulence system in plasma. In this paper we overview recent results on condensed 2D turbulence and present evidence of interaction between its three components: condensate structures, turbulence and forcing-scale vortices. This is compared with the modifications in the ...

International Nuclear Information System (INIS)

White dwarf evolution, particularly in the early phases, is not very strongly constrained by observation. Fortunately, white dwarfs undergo nonradial pulsation in three distinct regions of the H-R diagram. These pulsations provide accurate masses, surface compositional structure and rotation velocities, and help constrain other important physical properties. We demonstrate the application of the tools of stellar seismology to white dwarf evolution using the hot white dwarf star PG 1159-035 and the cool DAV (or ZZ Ceti) stars as examples. From pulsation studies, significant challenges to the theory of white dwarf evolution emerge. 44 refs.

International Nuclear Information System (INIS)

After presenting a general account of the observed global properties of single stars of low, intermediate, and high mass, together with their theoretical Hertzsprung-Russell diagram evolution, attention is given to the observed properties of various evolved close binaries and to an assessment of the value of comparisons between observation and crude theory in characterizing the physics of mass transfer within interacting binary systems. Detailed consideration is then undertaken of such topics as stellar evolution in globular clusters, interior star changes due to nucleosynthesis and mixing, asymptotic giant branch stars of intermediate mass, the response of white dwarfs in binary systems to mass accretion, and scenarios for binary star evolution tending toward close white dwarf pairs.

Science.gov (United States)

This exciting new development in neutron star evolution was presented at the Winter 2004 AAS Meeting in Atlantia,Georgia. ...

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The thermal evolution predicted by current models of the superfluid-crust interaction is noted to differ substantially from the thermal evolution predicted by models without internal heating as well as previous models of heating. Heating rates approaching the maximum predicted by current models enhance the photon luminosity of the star in the neutrino cooling era, and dramatically alter the thermal evolution in the photon cooling era. Standard cooling models are consistent with current pulsar temperature estimates and upper limits, except those for the Vela pulsar, which are lower than predicted. 77 refs.

KoreaScience (Korea)

Full Text Available

Science.gov (United States)

... the cinder-like planets in orbit around pulsars, the remnants of massive star evolution) to worlds that are more reassuringly familiar. ...

International Nuclear Information System (INIS)

Recent developments in the knowledge of Delta Scuti stars in relation to stellar evolution are reviewed. The stability of periods and amplitudes is examined, and a working hypothesis suggested. Furthermore, the systematics of the observed long-term period changes are compared with the computed evolutionary tracks, suggesting a severe disagreement for the evolved stars if the period changes are caused by radius changes resulting from stellar evolution. 30 refs.

British Library Electronic Table of Contents (United Kingdom)

The role of adaptation in the divergence of lineages has long been a central question in evolutionary biology, and as multilocus sequence data sets have become available for a wide range of taxa, empirical estimates of levels of adaptive molecular evolution are increasingly common. Estimates vary widely among taxa, with high levels of adaptive evolution in Drosophila, bacteria, and viruses but very little evidence of widespread adaptive evolution in hominids. Although estimates in plants are more limited, some recent work has suggested that rates of adaptive evolution in a range of plant taxa are surprisingly low and that there is little association between adaptive evolution and effective population size in contrast to patterns seen in other taxa. Here, we analyze data from 35 loci for si...

Energy Technology Data Exchange (ETDEWEB)

As the ground state potential curve is strongly related to spectral line shapes, the minumum position of the ground state potential is obtained from the experiemental absorption profile k({delta}{nu}, T) at high density of the radiating atoms. The temperature dependence of the absorption processes of Hg and Cd lines 253.65 and 326.1 nm, respectively perturbed by inert gases (Xe, Kr, Ar and Ne) had been carefully studied over a wide spectral range. Using the point of the maximum temperature dependence {delta}{nu} {sub m} in each case, we are able to calculate the position of the ground state potential R {sub m} using a simple formula.

CERN Document Server

Cyclic spectral analysis is a signal processing technique designed to deal with stochastic signals whose statistics vary periodically with time. Pulsar radio emission is a textbook example of this signal class, known as cyclostationary signals. In this paper, we discuss the application of cyclic spectral analysis methods to pulsar data, and compare the results with the traditional filterbank approaches used for almost all pulsar observations to date. In contrast to standard methods, the cyclic spectrum preserves phase information of the radio signal. This feature allows us to determine the impulse response of the interstellar medium and the intrinsic, unscattered pulse profile directly from a single observation. We illustrate these new analysis techniques using real data from an observation of the millisecond pulsar B1937+21.

British Library Electronic Table of Contents (United Kingdom)

We have developed efficient spectrally selective infrared (IR) emitters that can be utilized for thermophotovoltaic (TPV) power generation by using stainless steel (SUS304) substrates coated with b- FeSi2 thin films. To develop spectrally selective emitters, we theoretically propose antireflection (AR) coatings consisting of a single layer of a dielectric material having a high refractive index (~5) and are appropriate for use with metals such as stainless steels in the IR region. This type of AR coating is fabricated by sputtering a b- FeSi2 thin film on a polished SUS304 substrate. The reflectance in the IR region is successfully reduced to less than 10%. In addition, the AR properties are stable even at 700 K in air. Therefore, metals with AR coatings of b- FeSi2 can be applied to IR em...

Energy Technology Data Exchange (ETDEWEB)

The wavenumber-frequency spectral densities of turbulent wall pressure fluctuations are investigated over a rigid flat plate. Nonlinear Reynolds stress terms of the inhomogeneous Orr-Sommerfeld equation are regarded as a known forcing function. The forcing function is modeled after Bark{close_quote}s hydrodynamic bursting formulation. The inhomogeneous Orr-Sommerfeld equation is solved by the method of Eckhaus in terms of discrete homogeneous solutions. The method of Eckhaus is then extended and proved for the continuous Orr-Sommerfeld eigenfunctions. Turbulent wall pressure fluctuations in terms of wavenumber-frequency spectral densities are numerically computed and compared to the experimental results of Martin as well as to his transformation of Blake{close_quote}s data fitted to a modified Corcos model. The wavenumber-frequency spectral densities numerically computed from the discrete eigenfunctions compared well with ...

CERN Document Server

We report on recent inter-calibration studies featuring Swift's Burst Alert Telescope (BAT) and Fermi's Gamma-ray Burst Monitor (GBM) based upon correlated observations of GRBs 080804 and 080810, via their resultant joint spectral analysis. Swift's intrinsic multi-wavelength instrumentation and dynamical response complement Fermi's superior energy range. The addition of BAT's spectral response will (i) facilitate in-orbit GBM detector response calibration, (ii) augment Fermi's low energy sensitivity, (iii) enable ground-based follow-up efforts of Fermi GRBs, and (iv) help identify a subset of GRBs discovered via off-line GBM data analysis, for an annual estimate of ~30 GRBs. The synergy of BAT and GBM augments previous successful joint spectral fit efforts by enabling the study of peak photon energies (Epeak), while leveraging the over eleven energy decades afforded by Fermi's Large Area Telescope (LAT), in conjunction with ...

UK PubMed Central (United Kingdom)

Microbes in nature frequently function as members of complex multitaxon communities, but the structural organization of these communities at the micrometer level is poorly understood because of limitations...Full Text Available

Science.gov (United States)

Identification of the Ranging System Reference Point (SRP) ... Daylight Filter Type : (SPECTRAL FILTER/FABRY-PEROT/etc) Dayl. Filt. ... INT/etc) Edit Criterion 1st Chain : (ITERATIVE n.n SIGMA/MANUAL/NONE/etc) Edit Criterion 2nd Chain ...

UK PubMed Central (United Kingdom)

The latest-generation cochlear implant devices provide many deaf patients with good speech recognition in quiet listening conditions. However, speech recognition deteriorates rapidly as the level of...Full Text Available

CERN Document Server

This is a brief overview of researches of Dmitry Petrovich Zhelobenko (1934--2006). He is the best known for his book "Compact Lie groups and their representations" and for the classification of all irreducible representations of complex semisimple Lie groups. We tell also on other his works, especially on the spectral analysis of representations.

International Nuclear Information System (INIS)

Laser frequency stabilization giving a 500-Hz Allan deviation for a 2-ms integration time with drift reduced to 7 kHz/min over several minutes was achieved at 1536 nm in the optical communication band. A continuously regenerated spectral hole in the inhomogeneously broadened "4I_1_5_/_2(1)#->#"4I_1_3_/_2(1) optical absorption of an Er"3"+:Y_2SiO_5 crystal was used as the short-term frequency reference, while a variation on the locking technique allowed simultaneous use of the inhomogeneously broadened absorption line as a long-term reference. The reported frequency stability was achieved without vibration isolation. Spectral hole burning frequency stabilization provides ideal laser sources for high-resolution spectroscopy, real-time optical signal processing, and a range of applications requiring ultra-narrow-band light sources or coherent detection; the time scale for stability and the compatibility with spectral hole ...

UK PubMed Central (United Kingdom)

An electroencephalogram (EEG) signal is extremely nonstationary, highly composite and very complex, all of which reflects the underlying integral neurodynamics. Understanding the EEG “grammar”,...Full Text Available

UK PubMed Central (United Kingdom)

AbstractX-ray diffraction analysis of pressure-induced structural changes in the Aequorea yellow fluorescent protein Citrine reveals the structural basis for the continuous...Full Text Available

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Colour television is examined as an attempt to imitate the human visual system in image formation, spectral sensitivities, adaptation, contrast effects, signal processing, signal modulation, signal...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

Cross section parameterizations for antiproton production in pp collisions are used to predict the antiproton/proton ratio resulting from a flux of cosmic protons with energy spectral index of 2.6 interacting with a 5 gm/cm/sup 2/ column density of H. (GHT)

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Computer assisted energy-spectral analyses were obtained on EEG recordings of unilateral non-dominant hemisphere ECT-induced seizures using the different pre-ECT anesthetic agents methohexital (Brevital), Innovar, and ketamine (Ketalar). The previously postulated predominance of electrical energy over the stimulated (right) hemisphere early in ECT-induced seizures is confirmed. There appears to be marked reduction in total seizure energy with methohexital anesthesia, whereas ketamine anesthesia appears to be associated with increased overall seizure energy. The greatest right to left energy transfer during the seizure occurred with Innovar anesthesia. PMID:7172456

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Localized corrosion has a stochastic character by nature. This character leads to an observed random behavior: fluctuations of the free potential, fluctuations of the current when a constant potential is maintained. This random signal, which is similar to an electric noise, can be analyzed either in the time domain by counting the events or in the frequency domain by measuring the power spectral density of the electrochemical noise. The experimental techniques developed for investigating the localized corrosion on the probabilistic point of view, i.e., statistical counting and power spectral density measurements, are discussed. Then the experimental results reported in the literature are reviewed in order to see what kind of parameters are accessible and how they can be related to the localized corrosion processes.

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A general space- and energy-dependent formalism is developed in order to analyze zero-power neutron noise experiments in fast reactor systems. A generalized dispersion equation is combined with theoretical expressions for the experimentally measured power spectral density and variance-to-mean ratio which makes it possible to express these quantities in terms of a double moment of the Laplace and Fourier transformed Green's function of a slowing-down operator rather than those of the full Boltzmann operator. Several spatial approximations are analyzed in the context of the general formalism. In each case, the power spectral density and variance-to-mean ratio are written in terms of an appropriate fast reactor dispersion law for the medium which can be calculated from the solution to a simple slowing-down equation. The resultant expression for the power spectral density are analyzed for various combinations of ...

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A low power polychromatic beam of microwaves is used to diagnose the behavior of turbulent fluctuations in the core of the JT-60U tokamak during the evolution of the internal transport barrier. A continuous reduction in the size of turbulent structures is observed concomitant with the reduction of the density scale length during the evolution of the internal transport barrier. The density correlation length decreases to the order of the ion gyroradius, in contrast to the much longer scale lengths observed earlier in the discharge, while the density fluctuation level remain similar to the level before transport barrier formation.

International Nuclear Information System (INIS)

The method of an effective potential is used to investigate the possible types of evolution of vacuum shells in the Friedmann-Schwarzschild world. Such shells are assumed to emerge during phase transitions in the early Universe. The possible global geometries are constructed for the Friedmann-Schwarzschild worlds. Approximate solutions to the equation of motion of a vacuum shell have been found. The conditions under which the end result of the evolution of the vacuum shells under consideration is the formation of black holes and wormholes with baby universes inside have been found. The interior of this world can be a closed, flat, or open Friedmann universe.

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BackgroundThe evolution of eukaryotic cells is widely agreed to have proceeded through a series of endosymbiotic events between larger cells and proteobacteria or cyanobacteria,...Full Text Available

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requirements) + f3(accuracy of analyses) + f4(accuracy of fabrication) + f5( design time) + .... Learning curves suggest an evolution in rocket engines& ...

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The Nobel lecture of Chandrasekhar is printed in which he describes the basic processes that determine the life history of a star with particular emphasis on the roles of stellar mass and radiation pressure. (AIP)

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A SCENARIO FOR CARBON STAR EVOLUTION WILLEMS, F., DE JONG, T. 213> 821111 INFRARED OBSERVATIONS OF OH/IR STARS WILLIAMS, D. M., BOYLE, ...

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Aug 21, 1995... F.D. Two Southern Supernova Remnants Shibazaki, N. Effect of a Superfluid- Crust Coupling on the Neutron Star Evolution Siddiqui, ...

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sive star evolution based on our new calculations of this pulsational instability, where the initial mass of SNe progenitors increases according to the ...

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Aug 26, 2011 ... The main article on the back of the poster explains star evolution in very simple terms (including the fate of our own Sun), and how a planetary ...

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terms of 11) numerical models, 2D SPH simulations, and analytic models. The 1D model was useful for determining the evolution over very long timescales. ...

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the revealed stage of T Tauri star evolution, is only a mere shadow of its former self. Once primary accretion starts, one has the (poorly quantified) ...

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The binding energy parameter #lambda# plays an important role in common envelope evolution. Previous works have already pointed out that #lambda# varies throughout the stellar evolution, though it has been adopted as a constant in most of the population synthesis calculations. We have systematically calculated the binding energy parameter #lambda# for both Population I and Population II stars of masses 1-20 M _s_u_n, taking into account the contribution from the internal energy of stellar matter. We present fitting formulae for #lambda# that can be incorporated into future population synthesis investigations. We also briefly discuss the possible applications of the results in binary evolutions.

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Evolution in Space Radio Telescopes Reveal Youngest Stellar Corpse Gas Clouds in Whirlpool Galaxy Yield Important Clues Supporting Theory on Spiral Arms Starbust-driven Winds...

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... follows draws on Wittwer (1980b & c), Zinn et al. (1966) and Hess (1968). ... for the Starfish event) and much larger distances along the geomagnetic ...

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Jun 28, 2010 ... Ultracompact binaries represent the end product of a binary star evolution, and are important test cases of theories of extreme gravity. Perhaps ...

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Hie synthesis of diverse biologically important compounds, under condi- tions which existed on the earth in the initial period of its evolution, ha; ...

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and the implications for massive star evolution. In recent years, the complex nature of the circumstellar regions of evolved massive stars has become apparent. ...

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BackgroundSenescence is integral to the flowering plant life-cycle. Senescence-like processes occur also in non-angiosperm land plants, algae and photosynthetic prokaryotes. Increasing...Full Text Available

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Specialized olfactory lobe glomeruli relating to sexual or caste differences have been observed in at least five orders of insects, suggesting an early appearance of this trait in insect evolution....Full Text Available

UK PubMed Central (United Kingdom)

The study of genetic variability within natural populations of pathogens may provide insight into their evolution and pathogenesis. We used a Mycobacterium tuberculosis high-density...Full Text Available

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gently constrain calculations of single-star evolution at high metallicity. Independent of SIM Lite observa- tions, we also propose to establish 4) how to ...

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... each star goes. The results of (1) are compared with predictions based on (2) and on single star evolution theory to discover the various stages which occur. ...

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Mar 6, 2009 ... remnants of massive star evolution) to worlds that are more reassuringly familiar. In the latter category, we now have excellent evidence ...

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Apr 23, 2009 ... Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. ...

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... than the age of the universe unless it is an unresolved double degenerate or a product of common-envelope binary star evolution (Fontaine et al. ...

International Nuclear Information System (INIS)

These proceedings represent papers presented at the Astrophysics Conference in Maryland, USA. The topic of the Conference was the evolution of x-ray binaries and the papers encompass a wide range of subjects on x-ray astronomy. There were one hundred eighteen papers presented at the Conference and out of these three have been abstracted for the Energy Science and Technology database.

International Nuclear Information System (INIS)

We have measured the redshift evolution of the density of Lyman limit systems (LLSs) in the intergalactic medium over the redshift range 0 < z < 6. We have used two new quasar samples to (1) improve coverage at z #approx# 1, with GALEX grism spectrograph observations of 50 quasars with 0.8 < z_e_m < 1.3, and (2) extend coverage to z #approx# 6, with Keck ESI spectra of 25 quasars with 4.17 < z_e_m < 5.99. Using these samples together with published data, we find that the number density of LLS per unit redshift, n(z), can be well fit by a simple evolution of the form n(z) = n_3_._5[(1 + z)/4.5]"#gamma# with n_3_._5 = 2.80 #+-# 0.33 and #gamma# = 1.94"+"0"."3"6_-_0_._3_2 for the entire range 0 < z < 6. We have also reanalyzed the evolution of damped Ly#alpha# systems (DLAs) in the redshift range 4 < z < 5 using our high-redshift quasar sample. We find a total of 17 DLAs and sub-DLAs, which we ...

CERN Document Server

The galaxies of the Local Group that are currently forming stars can serve as our laboratories for understanding star formation and the evolution of massive stars. In this talk I will summarize what I think we've learned about these topics over the past few decades of research, and briefly mention what I think needs to happen next.

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We use the method of Padg approximants and Fourier transform techniques to treat analytically the problem of transverse and longitudinal mode evolution in FELs. We obtain simple relations providing a transparent understanding of the dynamic of pulse propagation effects and of transverse mode guiding. We discuss the interplay with inhomogeneous broadening effects and derive gain formulae including longitudinal and transverse mode couplings.

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The hydrodynamics of gas evolution plays an important role in the pitting corrosion of metals. A new technique for the measurement of the local hydrodynamics caused by corrosion processes, using the atomic force microscope, has been presented in this work. The hydrodynamics of hydrogen evolution on Al surface due to pitting corrosion was studied. The characteristic features of the hydrodynamics are discussed. To the best of our knowledge this is the first local measurement of pitting corrosion hydrodynamics.

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Two general categories are discussed concerning the evolution of the solar system: the dualistic view, the planetesimal approach and the monistic view, the nebular hypothesis. The major points of each view are given and the models that are developed from these views are described. Possible applications of gamma ray astronomical observations to the question of the dynamic evolution of the solar system are discussed.

International Nuclear Information System (INIS)

The spontaneous evolution from ultracold Rydberg atoms to plasma is investigated in a caesium MOT by using the method of field ionization. The plasma transferred from atoms in different Rydberg states (n=22-32) are obtained experimentally. Dependence of the threshold time of evolving to plasma and the threshold number of initial Rydberg atoms on the principal quantum number of initial Rydberg states is studied. The experimental results are in agreement with hot-cold Rydberg-Rydberg atom collision ionization theory. (authors)

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The theoretical evolution of a horizontal branch star of Population II is followed through the helium burning in the core phase and is compared with the results given by other investigators. The m- fluence of different physics and interpolation schemes in the opacity tables is discussed. Some thoughts are given on the explanation of the erratic period variations observed in some of the RR Lyrae variables in the globular clusters. (auth)

International Nuclear Information System (INIS)

Spectral room temperature photoluminescence (pl) of polycrystalline Cu(In,Ga)Se2 films (CIGSe) is evaluated with respect to optoelectronic properties and in particular for the determination of the splitting of quasi-Fermi levels (EFn - EFp). For lateral resolution of ? 1 ?m a confocal pl-setup is used. The depth profile of the excess carrier densities determining the rates of radiative transitions strongly govern the spectral pl-shape which has been numerically modeled with a matrix transfer formalism. In this optical approach we discriminate for wave propagation and attenuation in a multilayer system between a plane-wave ansatz and a 3D-spherical formalism, depending on excitation area large or small/similar compared to the thickness of the absorber. In both cases re-absorption of photons in energetic regimes with absorption approaches unity, from which the splitting of the quasi-Fermi levels is preferentially deduced, substantially influence ...

CERN Document Server

We use direct N-body simulations to investigate the evolution of star clusters with large size-scales with the particular goal of understanding the so-called extended clusters observed in various Local Group galaxies, including M31 and NGC6822. The N-body models incorporate a stellar mass function, stellar evolution and the tidal field of a host galaxy. We find that extended clusters can arise naturally within a weak tidal field provided that the tidal radius is filled at the start of the evolution. Differences in the initial tidal filling-factor can produce marked differences in the subsequent evolution of clusters and the size-scales that would be observed. These differences are more marked than any produced by internal evolution processes linked to the properties of cluster binary stars or the action of an intermediate-mass black hole, based on models performed in this work and ...

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A procedure and software have been developed to transform the area distribution of the residual surface heights available from the measurement with the Micromap interferometric microscope into a two-dimensional (2D) power spectral density (PSD) distribution of the surface height. The procedure incorporates correction of one of the spectral distortions of the PSD measurement. The distortion appears as a shape difference between the tangential and sagittal PSD spectra deduced from the 2D PSD distribution for an isotropic surface. A detailed investigation of the origin of the anisotropy was performed, and a mathematical model was developed and used to correct the distortion. The correction employs a modulation transfer function (MTF) of the detector deduced analytically based on an experimentally confirmed assumption about the origin of the anisotropy due to the asymmetry of the read-out process of the instrument's CCD camera. The ...

CERN Document Server

With recent and archival Rossi X-Ray Timing Explorer (RXTE) X-ray measurements of the heavily obscured X-ray pulsar EXO 1722-363 (IGR J17252-3616), we carried out a pulse timing analysis to determine the orbital solution for the first time. The binary system is characterized by a_x sin(i) = 101 +/- 3 lt-s and P_orb = 9.7403 +/- 0.0004 days (90% confidence), with the precision of the orbital period being obtained by connecting datasets separated by more than 7 years (272 orbital cycles). The orbit is consistent with circular, and e 61 degrees at the 99% confidence level, the radius of the primary is between 21 R_sun and 37 R_sun, and its mass is less than about 22 M_sun. The acceptable range of radius and mass shows that the primary is probably a supergiant of spectral type B0I-B5I. Photometric measurements of its likely counterpart are consistent with the spectral type and luminosity if the distance to the system is between 5.3 kpc and 8.7 ...

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The spectral dependences of absorption photoinduced in a pure bismuth titanium oxide crystal by 532-nm laser pulses are studied. It is shown that optical absorption in the crystal in the range from 492 to 840 nm increases with increasing exposure. The photoinduced absorption relaxes in the dark for more than 60 hours. A model of photoinduced absorption is proposed which assumes the population of two trap centres with the normal energy distribution law for the concentrations of electrons photoexcited from donors to the conduction band. This model well describes the spectral dependences of photoinduced absorption by using the average ionisation energies of the traps E{sub 1} = 1.60 eV and E{sub 2} = 2.57 eV. The model is used to estimate the increase in the photorefractive sensitivity of a bismuth titanium oxide crystal in the near IR region, which was earlier observed after exposing the crystal to visible radiation. It is predicted that the ...

International Nuclear Information System (INIS)

The paper presents the investigations of plasma streams generated by pulsed plasma gun 'Prosvet' operated with different gases: krypton (m=84) and helium (m=4). Contour parameters of working gas spectral lines (full intensities and half-widths) are used for determination of spatial distributions of the electron density and temperature. Temporal distributions of the spectral lines intensities (both neutrals and ions of working gas), impurity spectral lines and continuum intensities are analyzed. Plasma stream velocity was estimated by time-of-flight method between two monochromators (MUM) connected with photo-multiplier. longitudinal distributions of the plasma pressure for different time moments and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerator. ...

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The aim of the present study focuses on experimentally demonstrating the efficacy of using angularly-variable fiber geometry to achieve the desired tissue-layer selection and probing depths with the further objective of enhancing the sensitivity and specificity of spectral diagnosis in stratified architectures that resemble human cervical epithelia. The morphological and biochemical features of epithelial tissue vary in accordance with tissue depths; consequently, the accuracy of spectroscopic diagnosis of epithelial dysplasia may be enhanced by probing the optical properties of this tissue. When correlated to cellular dysplasia, layer-specific changes in tissue optical properties may be deciphered by reflectance spectroscopy coupled with angularly-variable fiber geometry. This study addresses the utility of using such angularly-variable fiber geometry for resolving spatially-specific spectral signatures of tissue pathology. This is ...

CERN Document Server

Accretion processes in quasars and active galactic nuclei are still poorly understood, especially as far as the connection between observed spectral properties and physical parameters is concerned. Quasars show an additional degree of complexity compared to stars that is related to anisotropic emission/obscuration influencing the observed properties in most spectral ranges. This complicating factor has hampered efforts to define the equivalent of an Hertzsprung-Russel diagram for quasars. Even if it has recently become possible to estimate black hole mass and Eddington ratio for sources using optical and UV broad emission lines, the results are still plagued by large uncertainties. Nevertheless, robust trends are emerging from multivariate analysis of large spectral datasets of quasars. A firm observational basis is being laid out by accurate measurements of broad emission line properties especially when the source ...

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This dissertation deals with both the theoretical and the technological aspects of monolithic tunable lasers, and the experimental techniques for opto-electronic integration. In the theoretical part, the principles and limitations of wavelength tuning and spectral linewidth reduction in monolithic semiconductor lasers are described, with coupled distributed feedback-Fabry Perot (DFB-FP) lasers and long DFB lasers as examples. Stepwise tuning of wavelength over tens of nanometers and continuous tuning over the range of a mode spacing are shown to be possible. Spatial hole burning is found to affect the spectral linewidth of lasers involving strong active gratings. On the technological side, one of the major issues is the fabrication of flexible gratings. Direct-writing techniques, such as focused ion beam (FIB) implantation and e-beam lithography, provide the resolution, flexibility and accuracy that conventional holographic lithography lacks. ...

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The theory of a method of determination of the reactivity from power spectral density measurements with /sup 252/Cf and the results of experiments with a critical assembly mock-up of a liquid-metal fast breeder reactor and with uranium (93.2 wt % /sup 235/U) metal cylinders and a sphere are presented. This method of reactivity determination has an advantage over existing methods in that it determines the reactivity only from properties of the reactor at the subcritical state of interest and thus does not require a calibration near delayed criticality. In these experiments the reactivity was varied by changing the fissile loading or the amount of neutron absorber inserted; for the LMFBR mock-up, the reactivity varied to approximately 75 dollars subcritical, and for the uranium metal assemblies, to approximately 30 dollars subcritical.

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The experimental technique used for detection of subcooled boiling through analysis of the fluctuation contained in pressure transducer signals is presented. This work was partly conducted at the Institut fuer Kerntechnik und zertoerungsfreie Pruefverfahren von Hannover (IKPH, Germany) in a thermal-hydraulic circuit with one electrically heated rod with annular geometry test section. Piezo resistive pressure sensors are used for onset of nucleate boiling (ONB) and onset of fully developed boiling (OFDB) detection using spectral analysis/ signal correlation techniques. Experimental results are interpreted by phenomenological analysis of these two points and compared with existing correlation. The results allow to conclude that this technique is adequate for the detection and monitoring of the ONB and OFDB. (author)

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Protein motions on all timescales faster than molecular tumbling are encoded in the spectral density. The dissection of complex protein dynamics is typically performed using relaxation rates determined at high and ultra-high field. Here we expand this range of the spectral density to low fields through field cycling using the nucleocapsid protein of the SARS coronavirus as a model system. The field-cycling approach enables site-specific measurements of R{sub 1} at low fields with the sensitivity and resolution of a high-field magnet. These data, together with high-field relaxation and heteronuclear NOE, provide evidence for correlated rigid-body motions of the entire {beta}-hairpin, and corresponding motions of adjacent loops with a time constant of 0.8 ns (mesodynamics). MD simulations substantiate these findings and provide direct verification of the time scale and collective nature of these motions.

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The launch of the first spaceborne hyperspectral instrument, Hyperion, in 2000 has provoked further research into its capabilities with regard to mineral exploration. Our study in the remote, mountainous region of Pulang, China employed a two-step progressive approach, first to locate target areas characterized by hydrothermal mineral alteration, using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and secondly, to attempt detailed mineral mapping using Hyperion. The preliminary target detection involved principal components and broad-band spectral analysis and led to the detection of two target areas characterized by argillic alteration, iron-oxide- and sulphate-bearing minerals. A focused hyperspectral study followed using Spectral Angle Mapper (SAM) and Mixt...

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Electrostatic fields of the order of 1 V/Angst, as they occur at field emission tips, are comparable to those experienced by valence electrons in atoms and molecules. Such fields are strong enough to induce a significant redistribution of the valence charge in chemical bonds. In this work we investigate the effects on the electronic properties of a single adatom on a metal surface induced by the presence of an electrostatic field. In particular we present the results of a full ab initio DFT calculation, within the embedding method, of the CCV Auger spectra of Si and Mg atoms in and on a jellium-Ag host. Differently from impurities in bulk, Auger spectral profiles of adsorbates on metal surfaces can show notable modifications due to the applied electric field.

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Knowledge on environmental variability and how it is affected by disturbances is crucial for understanding patterns of biodiversity and determining adequate conservation strategies. The aim of this study is to assess environmental variability in patches undergoing post-fire vegetation recovery, identifying trends of change and their relevant drivers. We particularly evaluate: the value of three spectral indices derived from Landsat satellite data [Normalized Burn Ratio (NBR), Normalized Difference Vegetation Index (NDVI) and Wetness Component of the Tasseled Cap Transformation (TCW)] for describing secondary succession; the effectiveness of three metrics (diversity, evenness and richness) as indicators of patch variability; and how thematic resolution can affect the perception of environme...

British Library Electronic Table of Contents (United Kingdom)

The Formula Not Shown system of Formula Not Shown was first observed in auroral emissions by Meinel in 1950. Although the Formula Not Shown band system has been reinvestigated since this first spectral study, no laboratory spectrum of the (2,1) vibronic band has been obtained. We have recently built a continuous-wave cavity ringdown spectrometer, and as a first test of this spectrometer we observed the (2,1) band of Formula Not Shown in a positive column discharge cell. Many lines of the first positive band system of Formula Not Shown were also identified during the process of assigning this spectrum. The relative intensities of the Formula Not Shown and Formula Not Shown bands were found to change with discharge cell pressure, and so each spectral region was observed at two pressures to a...

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The Full Aperture Backscatter System (FABS) provides a measure of the spectral power, and integrated energy scattered by stimulated Brillouin (348-354 nm) and Raman (400 - 700 nm) scattering into the final focusing lens of the first four beams of the NIF laser. The system was designed to provide measurements at the highest expected fluences with: (1) spectral and temporal resolution, (2) beam aperture averaging, and (3) near-field imaging. This is accomplished with a strongly attenuating diffusive fiber coupler and streaked spectrometer and separate calibrated time integrated spectrometers, and imaging cameras. Measurement of the wavelength dependent sensitivity of the complete system is accomplished with a calibrated Xe lamp. Data from the calibration system is combined with experimental data to produce the power and energy measurements. Examples of measurements will be discussed.

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From aerosol spectral optical depths ({tau}{sub p{lambda}}) at wavelengths in the range 380 to 1025 nm estimated at different locations in the near and far coastal regions of the Arabian sea adjoining the western coast of central India, the spatial and spectral characteristics of coastal aerosols and the effect of the proximity to the (urban) continent are investigated. The Aangstroem parameters are deduced from {tau}{sub p{lambda}} values. A significant increase, both in aerosol optical depths at shorter (visible) wavelengths ({lambda} {<=} 600 nm) and the Aangstroem wavelength exponent are observed in the near coastal regions, suggesting an increase in the (relative) concentration of sub micron particles, apparently of anthropogenic origin. The Aangstroem turbidity coefficient remains nearly steady spatially, indicating a (spatially) uniform loading of large particles. 31 refs, 10 figs, 1 tab

International Nuclear Information System (INIS)

The rapid circularization and synchronization of the stellar components in an eccentric binary system at the onset of Roche lobe overflow is a fundamental assumption common to all binary stellar evolution and population synthesis codes, even though the validity of this assumption is questionable both theoretically and observationally. Here we calculate the evolution of the orbital elements of an eccentric binary through the direct three-body integration of a massive particle ejected through the inner Lagrangian point of the donor star at periastron. The trajectory of this particle leads to three possible outcomes: direct accretion onto the companion star within a single orbit, self-accretion back onto the donor star within a single orbit, or a quasi-periodic orbit around the companion star, possibly leading to the formation of a disk. We calculate the secular evolution of the binary orbit in the first two cases and conclude ...

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A large part of mechanical and durability characteristics of cement-based materials comes from the performances of the hydrated cement, cohesive matrix surrounding the granular skeleton. Experimental studies, in situ or in laboratory, associated to models, have notably enhanced knowledge on the cement material and led to adapted formulations to specific applications or particularly aggressive environments. Nevertheless, these models, developed for precise cases, do not permit to specifically conclude for other experimental conclusions. To extend its applicability domain, we propose a new evolutive approach, based on reactive transport expressed at the microstructure scale of the cement. In a general point of view, the evolution of the solid compounds of the cement matrix, by dissolutions or precipitations, during chemical aggressions can be related to the pore solution evolution, and this one relied to the ionic exchanges ...

International Nuclear Information System (INIS)

The evolution of intermediate and high mass stars is reviewed focusing on the interpretation of Pop I Cepheids. First, a summary is given of the classical results of stellar evolution theory for the main evolutionary phases (main sequence and core He-burning) all over the HR diagram, putting into evidence the various points of disagreement with current observational data. Second, models incorporating the effect of convective overshoot, are reviewed, and studies are presented on the rich, young clusters in the Large Magellanic Cloud, in which the models are compared with the observational data. Arguments are given to favor the adoption of models with convective overshoot instead of the classical ones. Third, new results are presented for pulsational models of the Cepheid stars, and the shape of the instability strip in the HR diagram, the number frequency-period distribution, and the mass discrepancy are discussed. 81 refs.

CERN Document Server

This is our response to a comment by Walter Eifler on our paper `A simple model for the short-time evolution of near-surface current and temperature profiles' (arXiv:physics/0503186, accepted for publication in Deep-Sea Research II). Although Eifler raises genuine issues regarding our model's validity and applicability, we are nevertheless of the opinion that it is of value for the short-term evolution of the upper-ocean profiles of current and temperature. The fact that the effective eddy viscosity tends to infinity for infinite time under a steady wind stress may not be surprising. It can be interpreted as a vertical shift of the eddy viscosity profile and an increase in the size of the dominant turbulent eddies under the assumed conditions of small stratification and infinite water depth.

CERN Document Server

The Fourier transform of cosmological density perturbations can be represented in terms of amplitudes and phases for each Fourier mode. We investigate the phase evolution of these modes using a mixture of analytical and numerical techniques. Using a toy model of one-dimensional perturbations evolving under the Zel'dovich approximation as an initial motivation, we develop a statistic that quantifies the information content of the distribution of phases. Using numerical simulations beginning with more realistic Gaussian random-phase initial conditions, we show that the information content of the phases grows from zero in the initial conditions, first slowly and then rapidly when structures become non-linear. This growth of phase information can be expressed in terms of an effective entropy: Gaussian initial conditions are a maximum entropy realisation of the initial power spectrum, gravitational evolution decreases the phase entropy. We show that ...

International Nuclear Information System (INIS)

The site characterization of Yucca Mountain, NV as a potential high level nuclear waste repository includes study of the surficial deposits as a record of the paleoenvironmental history of the Yucca Mountain region. An important aspect of this history is an understanding of the evolution of paleogeography leading to establishment of the present drainage pattern. Establishment of drainage basin evolution is needed before geomorphic response to paleoclimate and tectonics can be assessed, because a major change in drainage basin geometry can predominantly affect the sedimentary record. Because alluvial aquifers are significant to regional hydrology, a major change in surface drainage resulting in buried alluvium could have hydrogeologic significance. In this paper, we report on geologic evidence for a major modification in surface drainage pattern in the Yucca Mountain region, resulting in the probable establishment of the Fortymile Wash drainage ...

British Library Electronic Table of Contents (United Kingdom)

The formation of a through-gut was a key innovation in the evolution of metazoans. There is still controversy regarding the origin of the anus and how it may have been either gained or lost during evolution in different bilaterian taxa. Thus, the study of groups with a blind gut is of great importance for understanding the evolution of this organ system. Here, we describe the morphogenesis and molecular patterning of the blind gut in the sexual triclad Schmidtea polychroa. We identify and analyze the expression of goosecoid, commonly associated with the foregut, and the GATA, ParaHox and T-box genes, members of which commonly are associated with gut regionalization. We show that GATA456a is expressed in the blind gut of triclads, while GATA456b is localized in dorsal parenchymal cells. Goo...

Environmental Research Database

Objectives1. To create a strong, interdisciplinary evidence base about the relationships linking ecosystems, agrobiodiversity, wild biodiversity, and sustainable livelihoods, including the use of trade-off analysis (modeling the relationships between agricultural productivity, levels of biodiversity, and ecosystem resilience); crop evolutionary studies (wild relative/crop interactions) and socioeconomic, cultural, and nutritional studies of the contribution of biodiversity to different livelihoods asset [continued...]DescriptionAgriculture, ecosystems, and humans have co-evolved over millennia in the Andean-Amazonian region, creating the richest of all Vavilov centers of crop origin and diversity. The conservation of a wide range of domesticated crops and landraces (i.e., indigenous, ancestral varieties or cultivars that are distinct, uniform, and stable) and their co-evolution with crop wild relatives (CRW) has been essential for food security, adaptation to ...

British Library Electronic Table of Contents (United Kingdom)

The paper describes two schemes that follow the model of Lamarckian evolution and combine differential evolution (DE), which is a population-based stochastic global search method, with the local optimization algorithm of conjugate gradients (CG). In the first, each offspring is fine-tuned by CG before competing with their parents. In the other CG is used to improve both parents and offspring in a manner that is completely seamless for individuals that survive more than one generation. Experiments involved training weights of feed-forward neural networks to solve three synthetic and four real-life problems. In six out of seven cases the DE?CG hybrid, which preserves and uses information on each solution?s local optimization process, outperformed two recent variants of DE.

Energy Technology Data Exchange (ETDEWEB)

Power spectral analysis of cosmic ray intensity recorded by neutron monitors at Calgary and Deep River, Alberta, was carried out over a wide range of frequencies from 3 {times} 10{sup {minus}9} Hz to 6 {times} 10{sup {minus}6} Hz during the epoch 1965-1989 and revealed different behavior of the power spectral density for the three ranges of frequency domains. At low frequencies corresponding to the periodicity T {approx} 20 months the power spectrum shows an abrupt change in the level and profile of power spectral density (PSD). This indicates that the processes responsible for the long period variations are different from the one which causes short-period variations. At middle frequencies corresponding to periodicities between 6 and 18 months, the PSD indicates that the periodicities are not stable and show a transient character over the entire epochy of analysis. The PSD for periods T {approx} 27 days indicates an 11 year ...

International Nuclear Information System (INIS)

The defect-induced effect on superconducting transition temperature T_c of A-15 compounds is examined. T_c is found from the Eliashberg equations which take into account the defect-induced changes in the electron-phonon spectral function and electron density of states. The dependence of T_c on the defect type in the superconductor is obtained.

Science.gov (United States)

... 1.7997 0.0537 1.7728 1.7760 16 1.8016 1.8520 0.0504 1.8268 1.8280 17 1.8549 1.9005 0.0456 1.8777 1.8760 18 1.9053 1.9571 0.0518 1.9312 1.9360 19 1.9558 ...

International Nuclear Information System (INIS)

We study quasifinite highest weight modules over the supersymmetric extension of the W_1_+_#infinity# algebra on the basis of the analysis by Kac and Radul. We find that the quasifiniteness of the modules is again characterized by polynomials, and obtain the differential equations for highest weights. The spectral flow, free field realization over the (B, C)-system, and the embedding into gl(#infinity#vertical stroke #infinity#) are also presented. (orig.).

UK PubMed Central (United Kingdom)

In this work we study the temperature dependence of the Soret band lineshape of the carbonmonoxy derivatives of sperm whale myoglobin, human hemoglobin, and its isolated alpha and beta subunits. To...Full Text Available

CERN Document Server

Using spectral hole-burning-based ultraslow group velocity in a dilute solid medium, we report enhanced photon echo efficiency three orders of magnitude higher than that in a nonslow light regime. The enhancement is due to exponentially increased absorption of an optical data pulse owing to the enhanced photon-atom interaction in an ultraslow light regime, whereas echo reabsorption is negligibly small due to group-velocity dependent population depletion.

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The gauge-invariant correlation function for the Yang-Mills field strengths is shown to admit a symmetric decomposition into electric and magnetic components. The spectral weights are seen to obey a sum rule of the superconvergence type, owing to asymptotic freedom. The close relation between the dielectric function, electric-magnetic duality, and the algebra of generalized Chern-Simons charges is illustrated for the linearized Yang-Mills-Higgs system.

CERN Document Server

We construct the Generalized Monodromy matrix $\\mathcal{\\hat{M}}(\\omega)$ of two dimensional string effective action by introducing the T-duality group properties.The integrability conditions with general solutions depending on spectral parameter are given. This construction is investigated for the exactly solvable Wess, Zumino, Novikov and Witten (WZNW) model in pp-wave Limit when B=0.

CERN Document Server

The indirect detection of particle dark matter (DM) is based on the search for anomalous components in cosmic rays (CRs) due to the annihilation of DM pairs in the galactic halo, on the top of the standard astrophysical production. These additional exotic components are potentially detectable at Earth as spectral distortions for the various cosmic radiations: $\\chi + \\chi \\to q \\bar{q}, W^+ W^-, ... \\to \\bar{p}, \\bar{D}, e^+ \\gamma and \

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Previous experiments in fast critical assemblies demonstrated a method of determining reactivity from power spectral density measurements with /sup 252/Cf. This method determines reactivity from properties of the reactor only at the subcritical state of interest, thus it does not require a calibration near delayed criticality. The interpretation of the measured data to obtain reactivity does not require knowledge of the relative or absolute values of the source intensity, knowledge of the detection efficiencies, or knowledge of the detection instrumentation frequency responses. An experiment was performed at the Pool Critical Assembly to evaluate the possibility of /sup 252/Cf source driven neutron noise spectral density measurements in light water moderated reactors. This experiment showed that using commercially available detectors, such measurements can be performed in a reasonable time, that is, the measurement of the quantity of interest ...

Energy Technology Data Exchange (ETDEWEB)

This document describes measurements of the directional spectral emittance of four ceramic mold materials. The work was performed with the samples at {approximately} 900{degree}C in a vacuum vessel pumped to {approximately}3 {times} 10{sup {minus}6}Torr. Results conform to expectations derived from prior work done with similar samples.

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This paper investigates the spectral characteristics of three-dimensionally porous carbon dioxide indicators based on a porous silicate glass and phenolphthalein. The absorption spectra of the original solutions of phenolphthalein in alkaline and acid solutions are shown. The solutions were acidified by bubbling CO/sub 2/ through an alkaline phenolphthalein solution. The authors have succeeded in producing a reversible colorimetric adsorption indicator for carbon dioxide which after proper calibration enables the CO/sub 2/ content of an atmosphere to be estimated quantitatively.

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The theory of neutron moderation and spectroscopy are briefly reviewed, and moderators that are useful for Bonner sphere spectrometers are discussed. The choice of the neutron detector for a Bonner sphere spectrometer is examined. Spectral deconvolution methods are briefly reviewed, including derivative, parametric, quadrature, and Monte Carlo methods. Calibration is then discussed. (LEW)

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In the paper is studied the physics of a free electron laser (FEL) based on a two-frequency undulator (TFU) which induces large non linear effects, especially on the spectral dynamics. These effects are analyzed in an extended formalism where the spontaneous emission, the low-gain regime and the strong-field saturation regime are studied. Numerical simulations show that the optimized TFU generates a laser field having both a large extraction efficiency and a narrow spectrum.

Science.gov (United States)

Based on our cryogenic FT-IR spectroscopic studies of hydrogen bonds in cholic acid, the two-dimensional FT-IR spectroscopy was applied to enhance our understanding of the hydrogen bonds. Fine spectral structures were revealed by asynchronous 2D FT-IR spectra. The co-relationship among various bands was discussed according to the synchronous 2D FT-IR spectra. .

UK PubMed Central (United Kingdom)

Here we use published 16S rRNA gene sequences to compare the bacterial assemblages associated with humans, other mammals, other metazoa, and free-living microbial communities spanning a range...Full Text Available

Science.gov (United States)

Al2O3-based ceramic is one of the most widely used materials for tools employed in hardened steel turning applications due to its high hardness, wear resistance, heat resistance and chemical stability. The objective of this work is to predict the lives of Al2O3-(W, Ti)C ceramic tools in intermittent turning of hardened AISI 1045 steel by means of damage evolution model taking into account the mechanical loading and thermal effect in the cutting process. A damage evolution model analyzing the RVE with uniformly distributed interacting cracks is constructed based on micromechanics. The calculated results of the proposed damage evolution model are compared with the lives of two kinds of Al2O3-(W, Ti)C ceramic tools obtained through experiments. It is found that the proposed model can be used to predict the lives of the ceramic cutting tools in intermittent turning operation.

UK PubMed Central (United Kingdom)

Ceratogaulus, a member of the extinct fossorial rodent clade Mylagaulidae, is the only known rodent with horns and the smallest known horned mammal. The function of the large, dorsally...Full Text Available

CERN Document Server

We study the redshift evolution of galaxy pair fractions and merger rates for different types of galaxies using kinematic pairs selected from the DEEP2 Redshift Survey. Parameterizing the evolution of the pair fraction as (1+z)^{m}, we find that the companion rate increases mildly with redshift with m = 0.41+-0.20 for all galaxies with -21 < M_B^{e} < -19. Blue galaxies show slightly faster evolution in the blue companion rate with m = 1.27+-0.35 while red galaxies have had fewer red companions in the past as evidenced by the negative slope m = -0.92+-0.59. We find that at low redshift the pair fraction within the red sequence exceeds that of the blue cloud, indicating a higher merger probability among red galaxies compared to that among the blue galaxies. With further assumptions on the merger time scale and the fraction of pairs that will merge, the galaxy major merger rates for 0.1 < z <1.2 are estimated to ...

UK PubMed Central (United Kingdom)

How does complex social behavior evolve? What are the developmental building blocks of division of labor and specialization, the hallmarks of insect societies? Studies have revealed the developmental...Full Text Available

Wastenet

Buizer, Arizona State University, USA; Gernot Klepper, Kiel Institute of World Economics, ...der Leeuw School for Human Evolution and Social Change, Arizona State University, USA

UK PubMed Central (United Kingdom)

The evolution of the human mitochondrial genome is characterized by the emergence of ethnically distinct lineages or haplogroups. Nine European, seven Asian (including Native American), and three African...Full Text Available

UK PubMed Central (United Kingdom)

The fauna of ancient lakes frequently contains taxa with highly derived morphologies that resulted from in situ radiation of lacustrine lineages with high antiquity. We employed a molecular...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundWith the advent of increasingly efficient means to obtain genetic information, a great insurgence of data has resulted, leading to the need for methods for analyzing this...Full Text Available

UK PubMed Central (United Kingdom)

Adaptive radiation is the rapid origination of multiple species from a single ancestor as the result of concurrent adaptation to disparate environments. This fundamental evolutionary process is considered...Full Text Available

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This review covers research done at Lawrence Livermore National Laboratory under DOE contract. Areas of research are as follows: star evolution supernovae, and nucleosynthesis; stellar atmospheres and winds; galaxies and interstellar space; and high-energy astrophysics.

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First comprehensive data on the evolution of nucleon resonance photocouplings with photon virtuality Q{sup 2} are presented for excited proton states in the mass range from 1.4 to 2.0 GeV.

UK PubMed Central (United Kingdom)

Endosomal sorting complexes required for transport (ESCRTs) are heteromeric protein complexes required for multivesicular body (MVB) morphogenesis. ESCRTs I, II, III and III-associated are ubiquitous...Full Text Available

Wastenet

...The Political Evolution of the Landfill Tax in the UK wm-1996-03 Green Taxes, Waste Management and Political Economy 1995 ^ Top ...on civil engineering Lifecycle assessment - an overlooked opportunity Refereed Journal Articles: Green taxes, waste management and political economy Reports: Environmental cost benefit ...

UK PubMed Central (United Kingdom)

One selection pressure shaping sequence evolution is the requirement that a protein fold with sufficient stability to perform its biological functions. We present...Full Text Available

Science.gov (United States)

Various methods to analyse the effect of a non-isotherme water injection on the pressure evolution during a test on a double geothermal well are investigated. Then, several types of injection test are simulated with experimental data to examine the condit...

UK PubMed Central (United Kingdom)

Numerous studies have noted that the evolution of new enzymatic specificities is accompanied by loss of the protein's thermodynamic stability (ΔΔG), thus suggesting...Full Text Available

UK PubMed Central (United Kingdom)

In this review we attempt to reconstruct the evolutionary history of hominin life history from extant and fossil evidence. We utilize demographic life history theory and distinguish life history variables,...Full Text Available

UK PubMed Central (United Kingdom)

Mycobacterium ulcerans is the causative agent of Buruli ulcer, the third most common mycobacterial disease after tuberculosis and leprosy. It is an emerging infectious disease that...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

Main features of star evolution are recalled. Then the general structure of white dwarf stars is examined. From the equation of state of an electron gas completely degenerated are deduced: mechanical equilibrium, Viriel theorem, mass-radius relationship and Chandrasekhar limit. These results are applied to neutron stars.

UK PubMed Central (United Kingdom)

Extended-spectrum beta-lactamases (ESBL) constitute a key antibiotic-resistance mechanism affecting Gram-negative bacteria, and also an excellent model for studying evolution in real time. A shift in...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundCichlid fishes in Lake Tanganyika exhibit remarkable diversity in their feeding habits. Among them, seven species in the genus Perissodus are known for...Full Text Available

UK PubMed Central (United Kingdom)

Animals sense changes in ambient temperature irrespective of whether core body temperature is internally maintained (homeotherms) or subject to environmental variation (poikilotherms). Here we show...Full Text Available

UK PubMed Central (United Kingdom)

A prevailing theory proposes that the brain's two visual pathways, the ventral and dorsal, lead to differing visual processing and world representations for conscious perception than those for action....Full Text Available

UK PubMed Central (United Kingdom)

New forms of payment, growing competition, the continued evolution of multiunit hospital systems, and associated forces are redefining the fundamental relationship between hospitals and physicians....Full Text Available

CERN Document Server

We discuss the evolution of a disc galaxy due to the formation of a bar and, subsequently, a peanut. After the formation stage there is still considerable evolution, albeit slower. In purely stellar cases the pattern speed of the bar decreases with time, while its amplitude grows. However, if a considerable gaseous component is present in the disc, the pattern speed may increase with time, while the bar strength may decrease. In some cases the gas can be brought sufficiently close to the center to create a strong central concentration, which, in turn, may modify the properties of the bar. More violent evolution can take place during interactions, so that some disc substructures can be either formed or destroyed in a time scale which is small compared to a Hubble time. These include spirals, bars, bridges, tails, rings, thick discs and bulges. In some cases interactions may lead to mergings. We briefly review comparisons of ...

UK PubMed Central (United Kingdom)

BackgroundGene duplication is the primary force of new gene evolution. Deciphering whether a pair of duplicated genes has evolved divergent functions is often challenging. The zebrafish...Full Text Available

CERN Document Server

A dissipative particle swarm optimization is developed according to the self-organization of dissipative structure. The negative entropy is introduced to construct an opening dissipative system that is far-from-equilibrium so as to driving the irreversible evolution process with better fitness. The testing of two multimodal functions indicates it improves the performance effectively

UK PubMed Central (United Kingdom)

Metazoan life cycles can be complex in different ways. A number of diverse phenotypes and reproductive events can sequentially occur along the cycle, and at certain stages a variety of developmental...Full Text Available