13,675,072 research outputs found
M-theory backgrounds with 30 Killing spinors are maximally supersymmetric
We show that all M-theory backgrounds which admit more than 29 Killing
spinors are maximally supersymmetric. In particular, we find that the
supercovariant curvature of all backgrounds which preserve 30 supersymmetries,
subject to field equations and Bianchi identities, vanishes, and that there are
no such solutions which arise as discrete quotients of maximally supersymmetric
backgrounds.Comment: 37 pages, latex. Minor changes
Downscaling landsat land surface temperature over the urban area of Florence
A new downscaling algorithm for land surface temperature (LST) images retrieved from Landsat Thematic Mapper (TM) was developed over the city of Florence and the results assessed against a high-resolution aerial image. The Landsat TM thermal band has a spatial resolution of 120 m, resampled at 30 m by the US Geological Survey (USGS) agency, whilst the airborne ground spatial resolution was 1 m. Substantial differences between Landsat USGS and airborne thermal data were observed on a 30 m grid: therefore a new statistical downscaling method at 30 m was developed. The overall root mean square error with respect to aircraft data improved from 3.3 °C (USGS) to 3.0 °C with the new method, that also showed better results with respect to other regressive downscaling techniques frequently used in literature. Such improvements can be ascribed to the selection of independent variables capable of representing the heterogeneous urban landscape
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Harvesting condensed atmospheric vapour as dew water can be an alternative or
complementary potable water resource in specific arid or insular areas. Such
radiation-cooled condensing devices use already existing flat surfaces (roofs)
or innovative structures with more complex shapes to enhance the dew yield. The
Computational Fluid Dynamic - CFD - software PHOENICS has been programmed and
applied to such radiation cooled condensers. For this purpose, the sky
radiation is previously integrated and averaged for each structure. The
radiative balance is then included in the CFD simulation tool to compare the
efficiency of the different structures under various meteorological parameters,
for complex or simple shapes and at various scales. It has been used to precise
different structures before construction. (1) a 7.32 m^2 funnel shape was
studied; a 30 degree tilted angle (60 degree cone half-angle) was computed to
be the best compromise for funnel cooling. Compared to a 1 m^2 flat condenser,
the cooling efficiency was expected to be improved by 40%. Seventeen months
measurements in outdoor tests presented a 138 % increased dew yield as compared
to the 1 m^2 flat condenser. (2) The simulation results for 5 various condenser
shapes were also compared with experimental measurement on corresponding pilots
systems: 0.16 m^2 flat planar condenser, 1 m^2 and 30 degree tilted planar
condenser, 30 m^2 and 30 degree tilted planar condenser, 255 m^2 multi ridges,
a preliminary construction of a large scale dew plant being implemented in the
Kutch area (Gujarat, India)
Candidate carriers and synthetic spectra of the 21- and 30-mu protoplanetary nebular bands
Computational chemistry is used here to determine the vibrational line
spectrum of several candidate molecules. It is shown that the thiourea
functional group, associated with various carbonaceous structures (mainly
compact and linear aromatic clusters), is able to mimic the 21-m band
emitted by a number of proto-planetary nebulae. The combination of nitrogen and
sulphur in thiourea is the essential source of emission in this model: the band
disappears if these species are replaced by carbon.
The astronomical 21-m feature extends redward to merge with another
prominent band peaking between 25 and 30 m, also known as the 30-m
band. It is found that the latter can be modelled by the combined spectra of
aliphatic chains, made of CH groups, oxygen bridges and OH groups, which
provide the 30-m emission. The absence of oxygen all but extinguishes the
30-m emission. The emission between the 21- and 30-m bands is
provided mainly by thiourea attached to linear aromatic clusters.
The chemical software reveals that the essential role of the heteroatoms N, S
and O stems from their large electronic charge. It also allows to determine the
type of atomic vibration responsible for the different lines of each structure,
which helps selecting the most relevant structures.
A total of 22 structures have been selected here, but their list is far from
being exhaustive; they are only intended as examples of 3 generic classes. When
background dust emission is added, model spectra are obtained, which are able
to satisfactorily reproduce recent observations of proto-planetary nebulae.
The relative numbers of atomic species used in this model are typically
H:C:O:N:S=53:36:8:2:1.Comment: 9 pages, 14 figure
Faraday optical isolator in the 9.2 m range for QCL applications
We have fabricated and characterized a n-doped InSb Faraday isolator in the
mid-IR range (9.2 m). A high isolation ratio of 30 dB with a
transmission over 80% (polarizer losses not included) is obtained at room
temperature. Further possible improvements are discussed. A similar design can
be used to cover a wide wavelength range (lambda ~ 7.5-30 m)
Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)
The discovery of amino acids in meteorites and the detection of glycine in
samples returned from a comet to Earth suggest that the interstellar chemistry
is capable of producing such complex organic molecules. Our goal is to
investigate the degree of chemical complexity that can be reached in the ISM.
We performed an unbiased, spectral line survey toward Sgr B2(N) and (M) with
the IRAM 30m telescope in the 3mm window. The spectra were analyzed with a
simple radiative transfer model that assumes LTE but takes optical depth
effects into account. About 3675 and 945 spectral lines with a peak
signal-to-noise ratio higher than 4 are detected toward N and M, i.e. about 102
and 26 lines per GHz, respectively. This represents an increase by about a
factor of 2 over previous surveys of Sgr B2. About 70% and 47% of the lines
detected toward N and M are identified and assigned to 56 and 46 distinct
molecules as well as to 66 and 54 less abundant isotopologues of these
molecules, respectively. We also report the detection of transitions from 59
and 24 catalog entries corresponding to vibrationally or torsionally excited
states of some of these molecules, respectively. Excitation temperatures and
column densities were derived for each species but should be used with caution.
Among the detected molecules, aminoacetonitrile, n-propyl cyanide, and ethyl
formate were reported for the first time in space based on this survey, as were
5 rare isotopologues of vinyl cyanide, cyanoacetylene, and hydrogen cyanide. We
also report the detection of transitions from within 12 new vib. or tors.
excited states of known molecules. Although the large number of unidentified
lines may still allow future identification of new molecules, we expect most of
these lines to belong to vib. or tors. excited states or to rare isotopologues
of known molecules for which spectroscopic predictions are currently missing.
(abridged)Comment: Accepted for publication in A&A. 266 pages (39 pages of text), 111
tables, 8 figure
LHC discovery potential for supersymmetry with \sqrt{s}=7 TeV and 5-30 fb^{-1}
We extend our earlier results delineating the supersymmetry (SUSY) reach of
the CERN Large Hadron Collider operating at a centre-of-mass energy \sqrt{s}=7
TeV to integrated luminosities in the range 5 - 30 fb^{-1}. Our results are
presented within the paradigm minimal supergravity model (mSUGRA or CMSSM).
Using a 6-dimensional grid of cuts for the optimization of signal to background
ratio -- including missing E_T-- we find for m(gluino) \sim m(squark) an LHC
5\sigma SUSY discovery reach of m(gluino) \sim 1.3,\ 1.4,\ 1.5 and 1.6 TeV for
5, 10, 20 and 30 fb^{-1}, respectively. For m(squark)>> m(gluino), the
corresponding reach is instead m(gluino)\sim 0.8,\ 0.9,\ 1.0 and 1.05 TeV, for
the same integrated luminosities.Comment: 7 pages with 2 .eps figure. In version 2, a new figure has been added
along with associated discussio
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