24 results match your criteria: "Institute for Space Sciences[Affiliation]"
Phys Rev Lett
April 2023
Institute for Space Sciences, Bucharest-Măgurele, R 077125, Romania.
Following the removal of axial confinement the momentum distribution of a Tonks-Girardeau gas approaches that of a system of noninteracting spinless fermions in the initial harmonic trap. This phenomenon, called dynamical fermionization, has been experimentally confirmed in the case of the Lieb-Liniger model and theoretically predicted in the case of multicomponent systems at zero temperature. We prove analytically that for all spinor gases with strong repulsive contact interactions at finite temperature the momentum distribution after release from the trap asymptotically approaches that of a system of spinless fermions at the same temperature but with a renormalized chemical potential which depends on the number of components of the spinor system.
View Article and Find Full Text PDFPhys Rev Lett
March 2022
Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA.
The persistent current in small isolated rings enclosing magnetic flux is the current circulating in equilibrium in the absence of an external excitation. While initially studied in superconducting and normal metals, recently, atomic persistent currents have been generated in ultracold gases spurring a new wave of theoretical investigations. Nevertheless, our understanding of the persistent currents in interacting systems is far from complete, especially at finite temperatures.
View Article and Find Full Text PDFGeophys Res Lett
October 2021
NASA Langley Research Center, Hampton, VA, USA.
The warm Gulf Stream sea surface temperatures strongly impact the evolution of winter clouds behind atmospheric cold fronts. Such cloud evolution remains challenging to model. The Gulf Stream is too wide within the ERA5 and MERRA2 reanalyses, affecting the turbulent surface fluxes.
View Article and Find Full Text PDFScience
March 2021
Dr. Karl Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 96049 Bamberg, Germany.
The evolution of massive stars is influenced by the mass lost to stellar winds over their lifetimes. These winds limit the masses of the stellar remnants (such as black holes) that the stars ultimately produce. We used radio astrometry to refine the distance to the black hole x-ray binary Cygnus X-1, which we found to be [Formula: see text] kiloparsecs.
View Article and Find Full Text PDFPowerful relativistic jets are one of the main ways in which accreting black holes provide kinetic feedback to their surroundings. Jets launched from or redirected by the accretion flow that powers them are expected to be affected by the dynamics of the flow, which for accreting stellar-mass black holes has shown evidence for precession due to frame-dragging effects that occur when the black-hole spin axis is misaligned with the orbital plane of its companion star. Recently, theoretical simulations have suggested that the jets can exert an additional torque on the accretion flow, although the interplay between the dynamics of the accretion flow and the launching of the jets is not yet understood.
View Article and Find Full Text PDFEarth Syst Sci Data
June 2018
Environmental Modeling Center, NCEP/NWS/NOAA, NCWCP, College Park MD, USA.
The Global Energy and Water cycle Exchanges (GEWEX) Data and Assessments Panel (GDAP) initiated the GEWEX Water Vapor Assessment (G-VAP), which has the main objectives to quantify the current state of art in water vapour products being constructed for climate applications and to support the selection process of suitable water vapour products by GDAP for its production of globally consistent water and energy cycle products. During the construction of the G-VAP data archive, freely available and mature satellite and reanalysis data records with a minimum temporal coverage of 10 years were considered. The archive contains total column water vapour (TCWV) as well as specific humidity and temperature at four pressure levels (1000, 700, 500, 300 hPa) from 22 different data records.
View Article and Find Full Text PDFPhys Rev Lett
June 2018
Instituto de Física da UFRGS, Avenida Bento Gonçalves 9500, Porto Alegre, Rio Grande do Sul, Brazil.
We investigate the universal thermodynamics of the two-component one-dimensional Bose gas with contact interactions in the vicinity of the quantum critical point separating the vacuum and the ferromagnetic liquid regime. We find that the quantum critical region belongs to the universality class of the spin-degenerate impenetrable particle gas which, surprisingly, is very different from the single-component case and identify its boundaries with the peaks of the specific heat. In addition, we show that the compressibility Wilson ratio, which quantifies the relative strength of thermal and quantum fluctuations, serves as a good discriminator of the quantum regimes near the quantum critical point.
View Article and Find Full Text PDFDust influences the Indian summer monsoon on seasonal timescales by perturbing atmospheric radiation. On weekly time scales, aerosol optical depth retrieved by satellite over the Arabian Sea is correlated with Indian monsoon precipitation. This has been interpreted to show the effect of dust radiative heating on Indian rainfall on synoptic (few-day) time scales.
View Article and Find Full Text PDFGlob Chang Biol
December 2015
Global Change Research Centre AS CR, Bělidla 986/4a, 603 00, Brno, Czech Republic.
Variations in photosynthesis still cause substantial uncertainties in predicting photosynthetic CO2 uptake rates and monitoring plant stress. Changes in actual photosynthesis that are not related to greenness of vegetation are difficult to measure by reflectance based optical remote sensing techniques. Several activities are underway to evaluate the sun-induced fluorescence signal on the ground and on a coarse spatial scale using space-borne imaging spectrometers.
View Article and Find Full Text PDFSci Rep
February 2015
Environment and Sustainability Institute, University of Exeter, Penryn, UK.
Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope, and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties.
View Article and Find Full Text PDFNature
November 2014
Institute for Space Sciences, Freie Universität Berlin, 12165 Berlin, Germany.
The atmospheric carbon dioxide (CO2) record displays a prominent seasonal cycle that arises mainly from changes in vegetation growth and the corresponding CO2 uptake during the boreal spring and summer growing seasons and CO2 release during the autumn and winter seasons. The CO2 seasonal amplitude has increased over the past five decades, suggesting an increase in Northern Hemisphere biospheric activity. It has been proposed that vegetation growth may have been stimulated by higher concentrations of CO2 as well as by warming in recent decades, but such mechanisms have been unable to explain the full range and magnitude of the observed increase in CO2 seasonal amplitude.
View Article and Find Full Text PDFNature
August 2014
LUPM, Université Montpellier 2, CNRS/IN2P3, CC 72, Place Eugène Bataillon, F-34095 Montpellier Cedex 5, France.
A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon-oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive (56)Ni (refs 1-3). After the explosion, the decay chain from (56)Ni to (56)Co to (56)Fe generates γ-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission.
View Article and Find Full Text PDFGlob Chang Biol
December 2014
Institute for Space Sciences, Free University of Berlin, Berlin, 12165, Germany.
Photosynthesis simulations by terrestrial biosphere models are usually based on the Farquhar's model, in which the maximum rate of carboxylation (Vcmax ) is a key control parameter of photosynthetic capacity. Even though Vcmax is known to vary substantially in space and time in response to environmental controls, it is typically parameterized in models with tabulated values associated to plant functional types. Remote sensing can be used to produce a spatially continuous and temporally resolved view on photosynthetic efficiency, but traditional vegetation observations based on spectral reflectance lack a direct link to plant photochemical processes.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
April 2014
Institute for Space Sciences, Freie Universität Berlin, 12165 Berlin, Germany.
Photosynthesis is the process by which plants harvest sunlight to produce sugars from carbon dioxide and water. It is the primary source of energy for all life on Earth; hence it is important to understand how this process responds to climate change and human impact. However, model-based estimates of gross primary production (GPP, output from photosynthesis) are highly uncertain, in particular over heavily managed agricultural areas.
View Article and Find Full Text PDFSensors (Basel)
September 2013
Institute for Space Sciences, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin 12165, Germany.
The stability of radiance measurements taken by the Sky Quality Meter (SQM)was tested under rapidly changing temperature conditions during exposure to a stable light field in the laboratory. The reported radiance was found to be negatively correlated with temperature, but remained within 7% of the initial reported radiance over a temperature range of -15 °C to 35 °C, and during temperature changes of -33 °C/h and +70 °C/h.This is smaller than the manufacturer's quoted unit-to-unit systematic uncertainty of 10%,indicating that the temperature compensation of the SQM is adequate under expected outdoor operating conditions.
View Article and Find Full Text PDFSci Rep
June 2014
Institute for Space Sciences, Freie Universität Berlin, Berlin, Germany.
The skyglow produced by artificial lights at night is one of the most dramatic anthropogenic modifications of Earth's biosphere. The GLOBE at Night citizen science project allows individual observers to quantify skyglow using star maps showing different levels of light pollution. We show that aggregated GLOBE at Night data depend strongly on artificial skyglow, and could be used to track lighting changes worldwide.
View Article and Find Full Text PDFAppl Opt
November 2012
Institute for Space Sciences, Free University Berlin Department of Earth Sciences, Carl-Heinrich-Becker-Weg 6-10, Berlin D-12165, Germany.
The effects of polarization, sea water salinity, and temperature on top of atmosphere radiances and water leaving radiances (WLRs) are discussed using radiative transfer simulations for MEdium resolution imaging spectrometer (MERIS) channels from 412 to 900 nm. A coupled system of an aerosol-free atmosphere and an ocean bulk containing chlorophyll and colored dissolved organic matter (CDOM) (case 1 waters) was simulated. A simple, but realistic, bio-optical model was set up to relate chlorophyll concentration and wavelength to scattering matrices and absorption coefficients for chlorophyll and colored CDOM.
View Article and Find Full Text PDFPLoS One
March 2011
Institute for Space Sciences, Freie Universität Berlin, Berlin, Germany.
The diurnal cycle of light and dark is one of the strongest environmental factors for life on Earth. Many species in both terrestrial and aquatic ecosystems use the level of ambient light to regulate their metabolism, growth, and behavior. The sky glow caused by artificial lighting from urban areas disrupts this natural cycle, and has been shown to impact the behavior of organisms, even many kilometers away from the light sources.
View Article and Find Full Text PDFRadiat Prot Dosimetry
November 2011
Institute for Space Sciences, Bucharest-Magurele, Romania.
In this paper, the relative sensitivity from different human tissues of the human body, at a ground level, from muon cosmic radiation has been studied. The aim of this paper was to provide information on the equivalent dose rates received from atmospheric muons to human body, at the ground level. The calculated value of the effective dose rate by atmospheric muons plus the radiation levels of the natural annual background radiation dose, at the ground level, in the momentum interval of cosmic ray muon (0.
View Article and Find Full Text PDFOpt Lett
September 2009
Institute for Space Sciences, Free University Berlin, Department of Earth Sciences, Carl-Heinrich-Becker-Weg, 6-10 D-12165 Berlin, Germany.
A robust method for the optical characterization of polarimeter optics for a complete, multispectral polarimeter is presented. The polarimeter optics consists of a waveplate, a polarizing filter, and a multispectral detector. The method employs a source of unpolarized light and a rotating polarizing filter and retrieves the retardance and the angle of the waveplate.
View Article and Find Full Text PDFAppl Opt
August 2009
Department of Earth Sciences, Institute for Space Sciences, Free University Berlin, Carl-Heinrich-Becker-Weg 6-10, D-12165 Berlin, Germany.
We optimize a general class of complete multispectral polarimeters with respect to signal-to-noise ratio, stability against alignment errors, and the minimization of errors regarding a given set of polarization states. The class of polarimeters that are dealt with consists of at least four polarization optics each with a multispectral detector. A polarization optic is made of an azimuthal oriented wave plate and a polarizing filter.
View Article and Find Full Text PDFAppl Opt
July 2008
Free University Berlin, Institute for Space Sciences, Berlin, Germany.
Motivated by several observations of the degree of linear polarization of skylight in the oxygen A (O(2)A) band that do not yet have a quantitative explanation, we analyze the influence of aerosol altitude, microphysics, and optical thickness on the degree of linear polarization of the zenith skylight in the spectral region of the O(2)A band, between 755 to 775 nm. It is shown that the degree of linear polarization inside the O(2)A band is particularly sensitive to aerosol altitude. The sensitivity is strongest for aerosols within the troposphere and depends also on their microphysical properties and optical thickness.
View Article and Find Full Text PDFAppl Opt
December 2007
Institute for Space Sciences, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6-10, D-12165 Berlin, Germany.
We have designed an airborne spectrometer system for the simultaneous measurement of the direct sun irradiance and the aureole radiance in two different solid angles. The high-resolution spectral radiation measurements are used to derive vertical profiles of aerosol optical properties. Combined measurements in two solid angles provide better information about the aerosol type without additional and elaborate measuring geometries.
View Article and Find Full Text PDFAppl Opt
December 2006
Institute for Space Sciences, Free University Berlin, Berlin, Germany.
We analyze the sensitivity of the degree of linear polarization in the Sun's principal plane as a function of aerosol microphysical parameters: the real and imaginary parts of the refractive index, the median radius and geometric standard deviation of the bimodal size distribution (both fine and coarse modes), and the relative number weight of the fine mode at a wavelength of 675 nm. We use Mie theory for single-scattering simulations and the doubling-adding method with the inclusion of polarization for multiple scattering. It is shown that the behavior of the degree of linear polarization is highly sensitive to both the small mode of the bimodal size distribution and the real part of the refractive index of aerosols, as well as to the aerosol optical thickness; whereas not all parameters influence the polarization equally.
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