12,866 research outputs found

    Remote estimation of soil moisture

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    Two methods under consideration for making remote estimates of soil moisture involve measurements made in electromagnetic spectral region of 0.4 to 14.0 micrometers: (1) spectral reflectance, (2) soil temperature

    Use of visible, near-infrared, and thermal infrared remote sensing to study soil moisture

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    Two methods are described which are used to estimate soil moisture remotely using the 0.4- to 14.0 micron wavelength region: (1) measurement of spectral reflectance, and (2) measurement of soil temperature. The reflectance method is based on observations which show that directional reflectance decreases as soil moisture increases for a given material. The soil temperature method is based on observations which show that differences between daytime and nighttime soil temperatures decrease as moisture content increases for a given material. In some circumstances, separate reflectance or temperature measurements yield ambiguous data, in which case these two methods may be combined to obtain a valid soil moisture determination. In this combined approach, reflectance is used to estimate low moisture levels; and thermal inertia (or thermal diffusivity) is used to estimate higher levels. The reflectance method appears promising for surface estimates of soil moisture, whereas the temperature method appears promising for estimates of near-subsurface (0 to 10 cm)

    A New Local Temperature Distribution Function for X-ray Clusters: Cosmological Applications

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    (abridged) We present a new determination of the local temperature function of X-ray clusters. We use a new sample comprising fifty clusters for which temperature information is now available, making it the largest complete sample of its kind. It is therefore expected to significantly improve the estimation of the temperature distribution function of moderately hot clusters. We find that the resulting temperature function is higher than previous estimations, but agrees well with the temperature distribution function inferred from the BCS and RASS luminosity function. We have used this sample to constrain the amplitude of the matter fluctuations on cluster's scale of 8Ω031h18\sqrt[3]{\Omega_0}^{-1}h^{-1}Mpc, assuming a mass-temperature relation based on recent numerical simulations. We find σ8=0.6±0.02\sigma_8 = 0.6\pm 0.02 for an Ω0=1\Omega_0 = 1 model. Our sample provides an ideal reference at z0z \sim 0 to use in the application of the cosmological test based on the evolution of X-ray cluster abundance (Oukbir & Blanchard 1992, 1997). Using Henry's sample, we find that the abundance of clusters at z=0.33z = 0.33 is significantly smaller, by a factor larger than 2, which shows that the EMSS sample provides strong evidence for evolution of the cluster abundance. A likelihood analysis leads to a rather high value of the mean density parameter of the universe: Ω=0.92±0.22\Omega =0.92 \pm 0.22 (open case) and Ω=0.86±0.25\Omega =0.86 \pm 0.25 (flat case), which is consistent with a previous, independent estimation based on the full EMSS sample by Sadat et al.(1998). Some systematic uncertainties which could alter this result are briefly discussed.Comment: 31 pages, 12 figures, mathches the version published in Astronomy and Astrophysic

    A Way Out of the Quantum Trap

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    We review Event Enhanced Quantum Theory (EEQT). In Section 1 we address the question "Is Quantum Theory the Last Word". In particular we respond to some of recent challenging staments of H.P. Stapp. We also discuss a possible future of the quantum paradigm - see also Section 5. In Section 2 we give a short sketch of EEQT. Examples are given in Section 3. Section 3.3 discusses a completely new phenomenon - chaos and fractal-like phenomena caused by a simultaneous "measurement" of several non-commuting observables (we include picture of Barnsley's IFS on unit sphere of a Hilbert space). In Section 4 we answer "Frequently Asked Questions" concerning EEQT.Comment: Replacement. Corrected affiliation. Latex, one .jpg figure. To appear in Proc. Conf. Relativistic Quantum Measurements, Napoli 1998, Ed. F. Petruccion

    The development of a questionnaire to assess the attitudes of older people to end-of-life issues (AEOLI)

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    Objectives: To develop an end-of-life attitudes questionnaire for use in a large community-based sample of older people. Design: Nominal groups and standardization of questions. Participants: Eighteen older people, ten academics and five specialist palliative care health professionals were involved in nominal groups. Thirty older people took part in initial pilot work and a further 50 were involved in reliability testing. Results: A 27-item attitudes of older people to end-of-life issues (AEOLI) questionnaire. Discussion: In modern times, death and dying predominantly occurs among older people and yet we know very little about older people's attitudes to end-of-life care. The AEOLI questionnaire can be used in large scale surveys to elicit attitudes on end-of life issues considered important by older people and health care professionals

    Towards the origin of the radio emission in AR Sco, the first radio-pulsing white dwarf binary

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    The binary system AR Sco contains an M star and the only known radio-pulsing white dwarf. The system shows emission from radio to X-rays, likely dominated by synchrotron radiation. The mechanism that produces most of this emission remains unclear. Two competing scenarios have been proposed: Collimated outflows, and direct interaction between the magnetospheres of the white dwarf and the M star. The two proposed scenarios can be tested via very long baseline interferometric radio observations. We conducted a radio observation with the Australian Long Baseline Array (LBA) on 20 Oct 2016 at 8.5 GHz to study the compactness of the radio emission. Simultaneous data with the Australian Telescope Compact Array (ATCA) were also recorded for a direct comparison of the obtained flux densities. AR Sco shows radio emission compact on milliarcsecond angular scales (0.02 AU\lesssim 0.02\ \mathrm{AU}, or $4\ \mathrm{R_{\odot}}).Theemissionisorbitallymodulated,withanaveragefluxdensityof). The emission is orbitally modulated, with an average flux density of \approx 6.5\ \mathrm{mJy}$. A comparison with the simultaneous ATCA data shows that no flux is resolved out on mas scales, implying that the radio emission is produced in this compact region. Additionally, the obtained radio light curves on hour timescales are consistent with the optical light curve. The radio emission in AR Sco is likely produced in the magnetosphere of the M star or the white dwarf, and we see no evidence for a radio outflow or collimated jets significantly contributing to the radio emission.Comment: 4 pages, 2 figures, accepted for publication in A&

    Soil water content and evaporation determined by thermal parameters obtained from ground-based and remote measurements

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    A procedure is presented for calculating 24-hour totals of evaporation from wet and drying soils. Its application requires a knowledge of the daily solar radiation, the maximum and minimum, air temperatures, moist surface albedo, and maximum and minimum surface temperatures. Tests of the technique on a bare field of Avondale loam at Phoenix, Arizona showed it to be independent of season

    Strict Deformation Quantization for a Particle in a Magnetic Field

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    Recently, we introduced a mathematical framework for the quantization of a particle in a variable magnetic field. It consists in a modified form of the Weyl pseudodifferential calculus and a C*-algebraic setting, these two points of view being isomorphic in a suitable sense. In the present paper we leave Planck's constant vary, showing that one gets a strict deformation quantization in the sense of Rieffel. In the limit h --> 0 one recovers a Poisson algebra induced by a symplectic form defined in terms of the magnetic field.Comment: 23 page

    A Hydrogen-Poor Superluminous Supernova with Enhanced Iron-Group Absorption: A New Link Between SLSNe and Broad-Lined Type Ic SNe

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    We present optical observations of the Type I superluminous supernova (SLSN-I) SN2017dwh at z ⁣ ⁣0.13z\!\approx\!0.13, which reached Mi ⁣ ⁣21M_{i}\!\approx\!-21 mag at peak. Spectra taken a few days after peak show an unusual and strong absorption line centered near 3200\AA\ that we identify with Co II, suggesting a high fraction of synthesized 56^{56}Ni in the ejecta. By  ⁣1\sim\!1 month after peak, SN2017dwh became much redder than other SLSNe-I, instead strongly resembling broad-lined Type Ic supernovae (Ic-BL SNe) with clear suppression of the flux redward of  ⁣5000\sim\!5000 \AA, providing further evidence for a large mass of Fe-group elements. Late-time upper limits indicate a 56^{56}Ni mass of 0.6\lesssim 0.6 M_\odot, leaving open the possibility that SN2017dwh produced a 56^{56}Ni mass comparable to SN1998bw ( ⁣0.4\approx\!0.4 M_\odot). Fitting the light curve with a combined magnetar and 56^{56}Ni model using MOSFiT{\tt MOSFiT}, we find that the light curve can easily accommodate such masses without affecting the inferred magnetar parameters. We also find that SN2017dwh occurred in the least-luminous detected host galaxy to date for a SLSN-I, with MB=13.5M_{B} = -13.5 mag and an implied metallicity of Z ⁣ ⁣0.08Z\!\sim\!0.08 ZZ_\odot. The spectral properties of SN2017dwh provide new evidence linking SLSNe-I with Type Ic-BL SNe, and in particular the high Fe-group abundance may be due to enhanced 56^{56}Ni production or mixing due to asphericity. Finally, we find that SN2017dwh represents the most extreme end of a correlation between continuum shape and Co II absorption strength in the near-peak spectra of SLSNe-I, indicating that Fe-group abundance likely accounts for some of the variation in their spectral shapes.Comment: 16 pages, 7 figures, Submitted to Ap
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