60,283 research outputs found
Biodiversity study of Southern Biscayne Bay and Card Sound 1968-1973
A multi-disciplinary investigation was conducted in southern Biscayne Bay and Card Sound from 1968 to 1973. The purpose of the investigation was to conduct an integrated study of the ecology of southern Biscayne Bay with special emphasis on the effects of the heated effluent from the Turkey Point fossil fuel power plant, and to predict the impact of additional effluent from the planned conversion of the plant to nuclear fuel. The results of this investigation have been discussed in numerous publications. This report contains the unpublished biology data that resulted from the investigation. (PDF contains 44 pages
Differentially Private Distributed Optimization
In distributed optimization and iterative consensus literature, a standard
problem is for agents to minimize a function over a subset of Euclidean
space, where the cost function is expressed as a sum . In this paper,
we study the private distributed optimization (PDOP) problem with the
additional requirement that the cost function of the individual agents should
remain differentially private. The adversary attempts to infer information
about the private cost functions from the messages that the agents exchange.
Achieving differential privacy requires that any change of an individual's cost
function only results in unsubstantial changes in the statistics of the
messages. We propose a class of iterative algorithms for solving PDOP, which
achieves differential privacy and convergence to the optimal value. Our
analysis reveals the dependence of the achieved accuracy and the privacy levels
on the the parameters of the algorithm. We observe that to achieve
-differential privacy the accuracy of the algorithm has the order of
Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems
Eastern Boundary Upwelling Systems (EBUS) are characterized by a high
productivity of plankton associated with large commercial fisheries, thus
playing key biological and socio-economical roles. The aim of this work is to
make a comparative study of these four upwelling systems focussing on their
surface stirring, using the Finite Size Lyapunov Exponents (FSLEs), and their
biological activity, based on satellite data. First, the spatial distribution
of horizontal mixing is analysed from time averages and from probability
density functions of FSLEs. Then we studied the temporal variability of surface
stirring focussing on the annual and seasonal cycle. There is a global negative
correlation between surface horizontal mixing and chlorophyll standing stocks
over the four areas. To try to better understand this inverse relationship, we
consider the vertical dimension by looking at the Ekman-transport and vertical
velocities. We suggest the possibility of a changing response of the
phytoplankton to sub/mesoscale turbulence, from a negative effect in the very
productive coastal areas to a positive one in the open ocean.Comment: 12 pages. NPG Special Issue on "Nonlinear processes in oceanic and
atmospheric flows". Open Access paper, available also at the publisher site:
http://www.nonlin-processes-geophys.net/16/557/2009
Validation Through Simulations of a Cn2 Profiler for the ESO/VLT Adaptive Optics Facility
The Adaptive Optics Facility (AOF) project envisages transforming one of the
VLT units into an adaptive telescope and providing its ESO (European Southern
Observatory) second generation instruments with turbulence corrected
wavefronts. For MUSE and HAWK-I this correction will be achieved through the
GALACSI and GRAAL AO modules working in conjunction with a 1170 actuators
Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility
(4LGSF). Multiple wavefront sensors will enable GLAO and LTAO capabilities,
whose performance can greatly benefit from a knowledge about the stratification
of the turbulence in the atmosphere. This work, totally based on end-to-end
simulations, describes the validation tests conducted on a Cn2 profiler adapted
for the AOF specifications. Because an absolute profile calibration is strongly
dependent on a reliable knowledge of turbulence parameters r0 and L0, the tests
presented here refer only to normalized output profiles. Uncertainties in the
input parameters inherent to the code are tested as well as the profiler
response to different turbulence distributions. It adopts a correction for the
unseen turbulence, critical for the GRAAL mode, and highlights the effects of
masking out parts of the corrected wavefront on the results. Simulations of
data with typical turbulence profiles from Paranal were input to the profiler,
showing that it is possible to identify reliably the input features for all the
AOF modes.Comment: 15 pages, 12 figures, accepted for publication in the MNRAS Accepted
2015 January 22. Received 2015 January 21; in original form 2014 December
Flat deformation of a spacetime admitting two Killing fields
It is shown that given an analytic Lorentzian metric on a 4-manifold, ,
which admits two Killing vector fields, then it exists a local deformation law
, where is a 2-dimensional projector, such that is
flat and admits the same Killing vectors. We also characterize the particular
case when the projector coincides with the quotient metric. We apply some
of our results to general stationary axisymmetric spacetime
On the abundance discrepancy problem in HII regions
The origin of the abundance discrepancy is one of the key problems in the
physics of photoionized nebula. In this work, we analize and discuss data for a
sample of Galactic and extragalactic HII regions where this abundance
discrepancy has been determined. We find that the abundance discrepancy factor
(ADF) is fairly constant and of the order of 2 in all the available sample of
HII regions. This is a rather different behaviour than that observed in
planetary nebulae, where the ADF shows a much wider range of values. We do not
find correlations between the ADF and the O/H, O++/H+ ratios, the ionization
degree, Te(High), Te(Low)/ Te(High), FWHM, and the effective temperature of the
main ionizing stars within the observational uncertainties. These results
indicate that whatever mechanism is producing the abundance discrepancy in HII
regions it does not substantially depend on those nebular parameters. On the
contrary, the ADF seems to be slightly dependent on the excitation energy, a
fact that is consistent with the predictions of the classical temperature
fluctuations paradigm. Finally, we obtain that Te values obtained from OII
recombination lines in HII regions are in agreement with those obtained from
collisionally excited line ratios, a behaviour that is again different from
that observed in planetary nebulae. These similar temperature determinations
are in contradiction with the predictions of the model based on the presence of
chemically inhomogeneous clumps but are consistent with the temperature
fluctuations paradigm. We conclude that all the indications suggest that the
physical mechanism responsible of the abundance discrepancy in HII regions and
planetary nebulae are different.Comment: 14 pages, 8 figures, 9 tables. Accepted for publication in the Ap
Application of Near Infrared Reflectance Spectroscopy (NIRS) to Forage Evaluation in Uruguay
Near infrared reflectance spectroscopy (NIRS) were used to assess the chemical composition of a wide range of forages. Nearly five hundred herbage samples covering a wide range of temperate pastures species and mixtures, previously analysed by conventional wet chemistry were scanned in reflectance with a NIRS 6500 (NIRSystems, Silver Spring, USA). The coefficients of determination in calibration (R2 ) and the errors in cross validation (SECV) were 0.98 (5.8), 0.94 (22.2), 0.97 (5.6), 0.94 (6.9) and 0.89 (19.7) for crude protein, in vitro organic matter digestibility, dry matter, ash and acid detergent fiber, in g kg â1 on a dry weight respectively. The high correlation between NIRS and chemical analysis found in this study showed the potential use of NIRS for prediction forage quality
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