2,651 research outputs found
XSIL: Extensible Scientific Interchange Language
We motivate and define the XSIL language as a flexible, hierarchical, extensible transport language for scientific data objects. The entire object may be represented in the file, or there may be metadata in the XSIL file, with a powerful, fault-tolerant linking mechanism to external data. The language is based on XML, and is designed not only for parsing and processing by machines, but also for presentation to humans through web browsers and web-database technology. There is a natural mapping between the elements of the XSIL language and the object model into which they are translated by the parser. As well as common objects (Parameter, Array, Time, Table), we have extended XSIL to include the IGWDFrame, used by gravitational-wave observatories
The Polyakov action on the supertorus
A consistent method for obtaining a well-defined Polyakov action on the
supertorus is presented. This method uses the covariantization of derivative
operators and enables us to construct a Polyakov action which is globally
defined.Comment: 15 pages LaTe
A Virtual Data Grid for LIGO
GriPhyN (Grid Physics Network) is a large US collaboration to
build grid services for large physics experiments, one of which is LIGO, a
gravitational-wave observatory. This paper explains the physics and computing
challenges of LIGO, and the tools that GriPhyN will build to address
them. A key component needed to implement the data pipeline is a virtual
data service; a system to dynamically create data products requested during
the various stages. The data could possibly be already processed in a certain
way, it may be in a file on a storage system, it may be cached, or it may need
to be created through computation. The full elaboration of this system will al-low
complex data pipelines to be set up as virtual data objects, with existing
data being transformed in diverse ways
Induced Polyakov supergravity on Riemann surfaces of higher genus
An effective action is obtained for the , induced supergravity on a
compact super Riemann surface (without boundary) of genus ,
as the general solution of the corresponding superconformal Ward identity. This
is accomplished by defining a new super integration theory on
which includes a new formulation of the super Stokes theorem and residue
calculus in the superfield formalism. Another crucial ingredient is the notion
of polydromic fields. The resulting action is shown to be well-defined and free
of singularities on \sig. As a by-product, we point out a morphism between
the diffeomorphism symmetry and holomorphic properties.Comment: LPTB 93-10, Latex file 20 page
W-algebras from symplectomorphisms
It is shown how -algebras emerge from very peculiar canonical
transformations with respect to the canonical symplectic structure on a compact
Riemann surface. The action of smooth diffeomorphisms of the cotangent bundle
on suitable generating functions is written in the BRS framework while a
-symmetry is exhibited. Subsequently, the complex structure of the symmetry
spaces is studied and the related BRS properties are discussed. The specific
example of the so-called -algebra is treated in relation to some other
different approaches.Comment: LaTex, 25 pages, no figures, to appear in Journ. Math. Phy
Large Chiral Diffeomorphisms on Riemann Surfaces and W-algebras
The diffeomorphism action lifted on truncated (chiral) Taylor expansion of a
complex scalar field over a Riemann surface is presented in the paper under the
name of large diffeomorphisms. After an heuristic approach, we show how a
linear truncation in the Taylor expansion can generate an algebra of symmetry
characterized by some structure functions. Such a linear truncation is
explicitly realized by introducing the notion of Forsyth frame over the Riemann
surface with the help of a conformally covariant algebraic differential
equation. The large chiral diffeomorphism action is then implemented through a
B.R.S. formulation (for a given order of truncation) leading to a more
algebraic set up. In this context the ghost fields behave as holomorphically
covariant jets. Subsequently, the link with the so called W-algebras is made
explicit once the ghost parameters are turned from jets into tensorial ghost
ones. We give a general solution with the help of the structure functions
pertaining to all the possible truncations lower or equal to the given order.
This provides another contribution to the relationship between KdV flows and
W-diffeomorphimsComment: LaTeX file, 31 pages, no figure. Version to appear in J. Math. Phys.
Work partly supported by Region PACA and INF
Serum deprivation alters lipid profile in HN9.10e embryonic hippocampal cells
The understanding of the mechanism of apoptosis is important to improve the use of stem cells for the treatment of neurodegenerative disorders. Sphingolipids are bioactive molecules involved in the regulation of cell fate. In HN9.10e embryonic hippocampal cells, serum deprivation induces apoptosis preceded by sphingomyelinase activation and raise of ceramide levels. Increasing evidence indicates that individual ceramide species regulated by specific pathways in distinct subcellular compartments might carry out distinct cellular functions, but the ceramides species involved in embryonic hippocampal cell death induced by growth factor deprivation are unknown. In the present paper, by using the UFLC-MS/MS methodology, we have investigated the effect of serum deprivation on the lipid profile in HN9.10e cells. At 48h of serum deprivation, we detected a decrease in cholesterol and increase in sphingosine-1-phoshate 18:1, phosphatidylcholine 18:1 18:0, sphingomyelin 18:1 16:0 and in ceramides 18:1 16:0; we also found an increase in saturated/unsaturated fatty acid ratio in sphingomyelin. We hypothesize that the rearrangement of sphingo- and glycerolipids with increase of saturated fatty acids in serum-deprivated, neural cells might represent a cellular response aimed at holding cholesterol inside the cells
Characterization of multilayer stack parameters from X-ray reflectivity data using the PPM program: measurements and comparison with TEM results
Future hard (10 -100 keV) X-ray telescopes (SIMBOL-X, Con-X, HEXIT-SAT, XEUS)
will implement focusing optics with multilayer coatings: in view of the
production of these optics we are exploring several deposition techniques for
the reflective coatings. In order to evaluate the achievable optical
performance X-Ray Reflectivity (XRR) measurements are performed, which are
powerful tools for the in-depth characterization of multilayer properties
(roughness, thickness and density distribution). An exact extraction of the
stack parameters is however difficult because the XRR scans depend on them in a
complex way. The PPM code, developed at ERSF in the past years, is able to
derive the layer-by-layer properties of multilayer structures from
semi-automatic XRR scan fittings by means of a global minimization procedure in
the parameters space. In this work we will present the PPM modeling of some
multilayer stacks (Pt/C and Ni/C) deposited by simple e-beam evaporation.
Moreover, in order to verify the predictions of PPM, the obtained results are
compared with TEM profiles taken on the same set of samples. As we will show,
PPM results are in good agreement with the TEM findings. In addition, we show
that the accurate fitting returns a physically correct evaluation of the
variation of layers thickness through the stack, whereas the thickness trend
derived from TEM profiles can be altered by the superposition of roughness
profiles in the sample image
Induced quantum gravity on a Riemann Surface
Induced quantum gravity dynamics built over a Riemann surface is studied in
arbitrary dimension. Local coordinates on the target space are given by means
of the Laguerre-Forsyth construction. A simple model is proposed and
pertubatively quantized. In doing so, the classical W-symmetry turns out to be
preserved on-shell at any order of the perturbative expansion. As a
main result, due to quantum corrections, the target coordinates acquire a
non-trivial character.Comment: LaTex, 32 pages, no figures, submitted to Int. J. Mod. Phys.
Spectral Line Removal in the LIGO Data Analysis System (LDAS)
High power in narrow frequency bands, spectral lines, are a feature of an
interferometric gravitational wave detector's output. Some lines are coherent
between interferometers, in particular, the 2 km and 4 km LIGO Hanford
instruments. This is of concern to data analysis techniques, such as the
stochastic background search, that use correlations between instruments to
detect gravitational radiation. Several techniques of `line removal' have been
proposed. Where a line is attributable to a measurable environmental
disturbance, a simple linear model may be fitted to predict, and subsequently
subtract away, that line. This technique has been implemented (as the command
oelslr) in the LIGO Data Analysis System (LDAS). We demonstrate its application
to LIGO S1 data.Comment: 11 pages, 5 figures, to be published in CQG GWDAW02 proceeding
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