11,710 research outputs found
Exchange-correlation potential for Current Density Functional Theory of frequency dependent linear response
The dynamical, long-wavelength longitudinal and transverse
exchange-correlation potentials for a homogeneous electron gas are evaluated in
a microscopic model based on an approximate decoupling of the equation of
motion for the current-current response function. The transverse spectrum turns
out to be very similar to the longitudinal one. We obtain evidence for a strong
spectral structure near twice the plasma frequency due to a two-plasmon
threshold for two-pair excitations, which may be observable in inelastic
scattering experiments. Our results give the entire input needed to implement
the Time-Dependent Current Density Functional Theory scheme recently developed
by G. Vignale and W. Kohn [Phys. Rev. Lett. 77, 2037 (1996)] and are fitted to
analytic functions to facilitate such applications.Comment: 6 pages, 3 figure
Experimental measurement of photothermal effect in Fabry-Perot cavities
We report the experimental observation of the photothermal effect. The
measurements are performed by modulating the laser power absorbed by the
mirrors of two high-finesse Fabry-Perot cavities. The results are very well
described by a recently proposed theoretical model [M. Cerdonio, L. Conti, A.
Heidmann and M. Pinard, Phys. Rev. D 63 (2001) 082003], confirming the
correctness of such calculations. Our observations and quantitative
characterization of the photothermal effect demonstrate its critical importance
for high sensitivity interferometric displacement measurements, as those
necessary for gravitational wave detection.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Steam storage systems for flexible biomass CHP plants - Evaluation and initial model based calculation
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Within the present study a novel concept for the demand-oriented power generation of a solid-biomass fueled combined heat and power (CHP) plant is investigated. The integration of a steam storage system into the plants process enables a decoupling of the steam (boiler) and the power generation (steam turbine). By buffering the steam, the power output of the turbine can be adjusted without changing the rated thermal capacity of the plant. Various available storage systems are selected and comparatively evaluated applying the adapted analytic hierarchy process (AHP). The technology assessment revealed that the combination of a steam accumulator and solid concrete storage represents the best suiting option. An initial model based simulation study is performed to identify the fundamental behaviour of this system, integrated in a biomass CHP plant. The operation principle is has proved their technical feasibility and seems to be applicable at a commercial scale. According to the modelling results flexible short term power generation in a time range of up to fifteen minutes is applicable. A load-range of almost the plants rated capacity can be achieved
Continuum elasticity theory of edge excitations in a two-dimensional electron liquid with finite range interactions
We make use of continuum elasticity theory to investigate the collective
modes that propagate along the edge of a two-dimensional electron liquid or
crystal in a magnetic field. An exact solution of the equations of motion is
obtained with the following simplifying assumptions: (i) The system is {\it
macroscopically} homogeneous and isotropic in the half-plane delimited by the
edge (ii) The electron-electron interaction is of finite range due to screening
by external electrodes (iii) The system is nearly incompressible. At
sufficiently small wave vector we find a universal dispersion curve independent of the shear modulus. At larger wave vectors the dispersion
can change its form in a manner dependent on the comparison of various length
scales. We obtain analytical formulas for the dispersion and damping of the
modes in various physical regimes.Comment: 3 figure
Tridactyl tracks from the Lavini di Marco dinosaur ichnosite (Hettangian, Southern Alps, NE Italy). Ichnotaxonomical review and palaeobiogeography
Early Retirement and Public Disability Insurance Applications: Exploring the Impact of Depression
This paper investigates the impact of depression on labor force participation among older workers. Empirically, we use two analytic strategies and rely on a sample drawn from the Health and Retirement Survey. Depression directly and indirectly increases individuals%u2019 probability of retiring early and applying for DI benefits, after accounting for other predictors of labor force exit. Accounting for the independent effects of depression, disability associated with physical illness may be smaller than the official statistics suggest. There may be great economic gains in increasing depression treatment awareness and access to treatment for individuals, employers and society.
The use of aerial- and close-range photogrammetry for the mapping of the Lavini di Marco tracksite (Hettangian, Southern Alps, NE Italy)
(EXCERPT FROM ABSTRACT) Close-range photogrammetry was executed following the procedure proposed by Mallison & Wings (2014). More than seventy 3D models were obtained and interpreted by means of color-coded and contour line images, which allow to improve the ichno- logical knowledge of the tracksite. The 3D models of the best-preserved tracks were used for the osteological reconstruction of the trackmakers’ autopodia, supposing the arthral position of the phalangeal pads. Three indirect methods were used to correlate tracks and their trackmakers: (i) synapomorphy-based approach; (ii) phenetic correlation; (iii) coincidence correlation (see Carrano & Wilson, 2001)
The final map was produced with different level of knowledge due to the distribution of tracks and current state of site preservation. Furthermore, it represents a complete documentation that will be used for future work of enhancement, preservation and valorization of the tracksite.
The ichnotaxonomical review of the quadrupedal trackways led us to emend the diagnosis of Lavinipes cheminii Avanzini et al. (2003) and to assign several other sparse tracks and trackways to L. chemini. The skeletal reconstruction of fore and hind limbs points towards Gongxianosaurus sp. as the most suitable trackmaker of L. cheminii. The herein supposed Laurasian affinity of the Lavini di Marco dinosaur assemblage clashes with the previous hypotheses that always link the Southern Alps sector with the Gondwana mainland
H-Band Spectroscopic Classification of OB Stars
We present a new spectroscopic classification for OB stars based on H-band
(1.5 micron to 1.8 micron) observations of a sample of stars with optical
spectral types. Our initial sample of nine stars demonstrates that the
combination of He I 1.7002 micron and H Brackett series absorption can be used
to determine spectral types for stars between about O4 and B7 (to within about
+/- 2 sub-types). We find that the Brackett series exhibits luminosity effects
similar to the Balmer series for the B stars. This classification scheme will
be useful in studies of optically obscured high mass star forming regions. In
addition, we present spectra for the OB stars near 1.1 micron and 1.3 micron
which may be of use in analyzing their atmospheres and winds.Comment: Accepted by AJ, 16 pages Latex (aastex4.0) including 4 figures and 2
tables. A complete PostScript copy is available at
ftp://degobah.colorado.edu/pub/rblum/Hband
- …