10,728 research outputs found
Determination of the critical current density in the d-wave superconductor YBCO under applied magnetic fields by nodal tunneling
We have studied nodal tunneling into YBa2Cu3O7-x (YBCO) films under magnetic
fields. The films' orientation was such that the CuO2 planes were perpendicular
to the surface with the a and b axis at 450 form the normal. The magnetic field
was applied parallel to the surface and perpendicular to the CuO2 planes. The
Zero Bias Conductance Peak (ZBCP) characteristic of nodal tunneling splits
under the effect of surface currents produced by the applied fields. Measuring
this splitting under different field conditions, zero field cooled and field
cooled, reveals that these currents have different origins. By comparing the
field cooled ZBCP splitting to that taken in decreasing fields we deduce a
value of the Bean critical current superfluid velocity, and calculate a Bean
critical current density of up to 3*10^7 A/cm2 at low temperatures. This
tunneling method for the determination of critical currents under magnetic
fields has serious advantages over the conventional one, as it avoids having to
make high current contacts to the sample.Comment: 8 pages, 2 figure
GIS Modeling and Analysis of Ohio's CO2 Budget: Mitigating CO2 Emissions Through Reforestation
Author Institution: Department of Geology, Bowling Green State UniversityThe United States has agreed to join with the international community in reducing its greenhouse gas emissions to 7% below 1990 levels. To aid in this goal a Geographic Information System (GIS) based deterministic model was created to assess the potential impact of different land-use strategies for mitigating Ohio's carbon dioxide (CO2) emissions and lowering its total CO2 budget. CO2 was chosen as the greenhouse gas of focus for this study because it has been identified as a significant greenhouse gas impacting the climate and it is the only greenhouse gas capable of being anthropogenically sequestered from the atmosphere
Good Pond Fishing is No Accident
There are approximately 100,000 ponds (also called stock dams) in South Dakota; 48,000 contain fish. Most ponds are privately owned and are on ranches in western and central South Dakota. Ponds must be managed if they are to provide quality angling. And if properly managed, they can provide memorable fishing year after year. A common misconception is that a pond can have it all, that it can be stocked with any and all fish species and that the fishing will be good for all species. It is more likely that fishing may not be good for any species. In reality, you must decide what you want and choose that management option that best fits your needs. We present the following key and discussion to help you decide the best pond management strategy for you. Start with Number 1 in the key and follow the directions after the answer that best fits you and your pond
Is there Evidence for a Hubble bubble? The Nature of Type Ia Supernova Colors and Dust in External Galaxies
We examine recent evidence from the luminosity-redshift relation of Type Ia
Supernovae (SNe Ia) for the detection of a ``Hubble bubble'' --
a departure of the local value of the Hubble constant from its globally
averaged value \citep{Jha:07}. By comparing the MLCS2k2 fits used in that study
to the results from other light-curve fitters applied to the same data, we
demonstrate that this is related to the interpretation of SN color excesses
(after correction for a light-curve shape-color relation) and the presence of a
color gradient across the local sample. If the slope of the linear relation
() between SN color excess and luminosity is fit empirically, then the
bubble disappears. If, on the other hand, the color excess arises purely from
Milky Way-like dust, then SN data clearly favors a Hubble bubble. We
demonstrate that SN data give , instead of the
one would expect from purely Milky-Way-like dust. This suggests that either SN
intrinsic colors are more complicated than can be described with a single
light-curve shape parameter, or that dust around SN is unusual. Disentangling
these possibilities is both a challenge and an opportunity for large-survey SN
Ia cosmology.Comment: Further information and data at
http://qold.astro.utoronto.ca/conley/bubble/ Accepted for publication in ApJ
Limits on Lorentz Violation from the Highest Energy Cosmic Rays
We place several new limits on Lorentz violating effects, which can modify
particles' dispersion relations, by considering the highest energy cosmic rays
observed. Since these are hadrons, this involves considering the partonic
content of such cosmic rays. We get a number of bounds on differences in
maximum propagation speeds, which are typically bounded at the 10^{-21} level,
and on momentum dependent dispersion corrections of the form v = 1 +-
p^2/Lambda^2, which typically bound Lambda > 10^{21} GeV, well above the Planck
scale. For (CPT violating) dispersion correction of the form v = 1 + p/Lambda,
the bounds are up to 15 orders of magnitude beyond the Planck scale.Comment: 24 pages, no figures. Added references, very slight changes. Version
published in Physical Review
X-ray Spectral Analysis of the Steady States of GRS 1915+105
We report on the X-ray spectral behavior within the steady states of GRS
1915+105. Our work is based on the full data set on the source obtained using
the Proportional Counter Array on the Rossi X-ray Timing Explorer and 15 GHz
radio data obtained using the Ryle Telescope. The steady observations within
the X-ray data set naturally separated into two regions in the color-color
diagram and we refer to them as steady-soft and steady-hard. GRS 1915+105
displays significant curvature in the coronal component in both the soft and
hard data within the {\it RXTE}/PCA bandpass. A majority of the steady-soft
observations displays a roughly constant inner disk radius (R_in), while the
steady-hard observations display an evolving disk truncation which is
correlated to the mass accretion rate through the disk. The disk flux and
coronal flux are strongly correlated in steady-hard observations and very
weakly correlated in the steady-soft observations. Within the steady-hard
observations we observe two particular circumstances when there are
correlations between the coronal X-ray flux and the radio flux with log slopes
\eta~0.68 +/- 0.35 and \eta ~ 1.12 +/- 0.13. They are consistent with the upper
and lower tracks of Gallo et al. (2012), respectively. A comparison of model
parameters to the state definitions show that almost all steady-soft
observations match the criteria of either thermal or steep power law state,
while a large portion of the steady-hard observations match the hard state
criteria when the disk fraction constraint is neglected.Comment: 21 pages, 15 figures, 2 tables. Accepted for publication in Ap
Water Demand Management in England and Wales: constructions of the domestic water-user
YesMeasures to manage demand include implicit and explicit messages about domestic water-users which have important potential impacts on their perceptions and practices. Drawing on recent literature, this paper identifies three different ¿dimensions¿ along which demand management measures¿ constructions of the water-user may vary: these relate to whether the water user is passive or active, whether they are motivated by individual or common needs, and whether they perceive water as a right or a commodity. Demand management measures currently used in England and Wales are then discussed and analysed. The paper concludes by highlighting the importance of communications associated with demand management, and in particular, notes the need to consider the cumulative impact of messages and their interactions with people¿s existing understandings
Earnings distribution, corporate governance and CEO pay
We investigate the relationship between earnings differentials and the pay of CEOs of 190 British companies between 1970 and 1990. We find that (i) changes in the differential between the 90th and 50th weekly earnings percentiles for non-manual adult male workers [90:50] explain changes in the level of real CEO salary and bonus in our sample of companies; (ii) changes in this differential also account for changes in the elasticity of CEO pay to firm size; (iii) a broader measure of earnings inequality does far worse than 90:50 at explaining changes in both the level and the firm size elasticity of CEO pay; (iv) fitting the model on data for 1970-1983 and predicting pay levels for the period starting with the widespread adoption of executive share option schemes in 1984, we find a structural break in the relationship between lower management pay differentials and the pay of the CEO. We conclude first that top executive pay prior to 1984 was a stable function of both firm size and earnings differentials lower on the administrative ladder, consistent with a hypothesis advanced by Herbert Simon in 1957; and second that the use of share options from 1984 onward represents not simply a change in the mode of top executive compensation, but a de -linking of the pay of top executives and that of their subordinates
Photometry of supernovae in an image series : methods and application to the Supernova Legacy Survey (SNLS)
We present a technique to measure lightcurves of time-variable point sources
on a spatially structured background from imaging data. The technique was
developed to measure light curves of SNLS supernovae in order to infer their
distances. This photometry technique performs simultaneous PSF photometry at
the same sky position on an image series. We describe two implementations of
the method: one that resamples images before measuring fluxes, and one which
does not. In both instances, we sketch the key algorithms involved and present
the validation using semi-artificial sources introduced in real images in order
to assess the accuracy of the supernova flux measurements relative to that of
surrounding stars. We describe the methods required to anchor these PSF fluxes
to calibrated aperture catalogs, in order to derive SN magnitudes. We find a
marginally significant bias of 2 mmag of the after-resampling method, and no
bias at the mmag accuracy for the non-resampling method. Given surrounding star
magnitudes, we determine the systematic uncertainty of SN magnitudes to be less
than 1.5 mmag, which represents about one third of the current photometric
calibration uncertainty affecting SN measurements. The SN photometry delivers
several by-products: bright star PSF flux mea- surements which have a
repeatability of about 0.6%, as for aperture measurements; we measure relative
astrometric positions with a noise floor of 2.4 mas for a single-image bright
star measurement; we show that in all bands of the MegaCam instrument, stars
exhibit a profile linearly broadening with flux by about 0.5% over the whole
brightness range.Comment: Accepted for publication in A&A. 20 page
MF2294
The information in this document has been funded wholly or in part by the United States Environmental Protection Agency.Jennifer R. Weins, Christopher S. Guy & Charles D. Lee, Streambank revetment, Kansas State University, September 1997
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