8,801 research outputs found
Consistent truncation of d = 11 supergravity on AdS_4 x S^7
We study the system of equations derived twenty five years ago by B. de Wit
and the first author [Nucl. Phys. B281 (1987) 211] as conditions for the
consistent truncation of eleven-dimensional supergravity on AdS_4 x S^7 to
gauged N = 8 supergravity in four dimensions. By exploiting the E_7(7)
symmetry, we determine the most general solution to this system at each point
on the coset space E_7(7)/SU(8). We show that invariants of the general
solution are given by the fluxes in eleven-dimensional supergravity. This
allows us to both clarify the explicit non-linear ansatze for the fluxes given
previously and to fill a gap in the original proof of the consistent
truncation. These results are illustrated with several examples.Comment: 41 pages, typos corrected, published versio
Deception Island Volcanism (South Shetland Islands, Antarctica): Results from Thin-Section Invertigations
The general gaugings of maximal d=9 supergravity
We use the embedding tensor method to construct the most general maximal
gauged/massive supergravity in d=9 dimensions and to determine its extended
field content. Only the 8 independent deformation parameters (embedding tensor
components, mass parameters etc.) identified by Bergshoeff \textit{et al.} (an
SL(2,R) triplet, two doublets and a singlet can be consistently introduced in
the theory, but their simultaneous use is subject to a number of quadratic
constraints. These constraints have to be kept and enforced because they cannot
be used to solve some deformation parameters in terms of the rest. The
deformation parameters are associated to the possible 8-forms of the theory,
and the constraints are associated to the 9-forms, all of them transforming in
the conjugate representations. We also give the field strengths and the gauge
and supersymmetry transformations for the electric fields in the most general
case. We compare these results with the predictions of the E11 approach,
finding that the latter predicts one additional doublet of 9-forms, analogously
to what happens in N=2, d=4,5,6 theories.Comment: Latex file, 43 pages, reference adde
The Gaugings of Maximal D=6 Supergravity
We construct the most general gaugings of the maximal D=6 supergravity. The
theory is (2,2) supersymmetric, and possesses an on-shell SO(5,5) duality
symmetry which plays a key role in determining its couplings. The field content
includes 16 vector fields that carry a chiral spinor representation of the
duality group. We utilize the embedding tensor method which determines the
appropriate combinations of these vectors that participate in gauging of a
suitable subgroup of SO(5,5). The construction also introduces the magnetic
duals of the 5 two-form potentials and 16 vector fields.Comment: 34 pages, latex, reference added, typo's corrected and minor
improvements mad
Comparison of Generic and Proprietary Sodium Stibogluconate for the Treatment of Visceral Leishmaniasis in Kenya.
OBJECTIVE: To compare the use of generic and proprietary sodium stibogluconate for the treatment of visceral leishmaniasis (kala-azar). METHODS: A total of 102 patients with confirmed kala-azar were treated in a mission hospital in West Pokot region, Kenya, with sodium stibogluconate (20 mg/kg/day for 30 days)--either as Pentostam (PSM) or generic sodium stibogluconate (SSG); 51 patients were allocated alternately to each treatment group. FINDINGS: There were no significant differences in baseline demographic characteristics or disease severity, or in events during treatment. There were 3 deaths in the PSM group and 1 in the SSG group; 2 patients defaulted in each group. Only 1 out of 80 test-of-cure splenic aspirates was positive for Leishmania spp.; this patient was in the SSG group. Follow-up after > or = 6 months showed that 6 out of 58 patients had relapsed, 5 in the SSG group and 1 in the PSM group. No outcome variable was significantly different between the two groups. CONCLUSION: The availability of cheaper generic sodium stibogluconate, subject to rigid quality controls, now makes it possible for the health authorities in kala-azar endemic areas to provide treatment to many more patients in Africa
AMBER and CRIRES observations of the binary sgB[e] star HD 327083: evidence of a gaseous disc traced by CO bandhead emission
HD 327083 is a sgB[e] star that forms a binary system with an orbital
semi-major axis of ~1.7 AU. Our previous observations using the VLTI and AMBER
in the medium resolution K-band mode spatially resolved the environment of HD
327083. The continuum visibilities obtained indicate the presence of a
circumbinary disc. CO bandhead emission was also observed. However, due to the
limited spectral resolution of the previous observations, the kinematic
structure of the emitting material was not constrained. In this paper, we
address this and probe the source of the CO emission with high spectral
resolution and spatial precision. We have observed HD 327083 with high spectral
resolution (25 & 6 km/s) using AMBER and CRIRES. The observations are compared
to kinematical models to constrain the source of the emission. It is shown that
the CO bandhead emission can be reproduced using a model of a Keplerian disc
with an inclination and size consistent with our previous VLTI observations.
The model is compared to AMBER differential phase measurements, which have a
precision as high as 30-micro-arcseconds. A differential phase signal
corresponding to 0.15 milli-arcseconds (~5 sigma) is seen over the bandhead
emission, which is in excellent agreement with the model that fits the CRIRES
observations. In comparison, a model of an equatorial outflow, as envisaged in
the standard sgB[e] scenario, does not reproduce the observations well. The
excellent agreement between the disc model and observations in the spatial and
spectral domains is compelling evidence that the CO bandhead emission of HD
327083 originates in a circumbinary Keplerian disc. In contrast, the model of
an equatorial outflow cannot reproduce the observations well. This suggests
that the standard sgB[e] scenario is not applicable to HD 327083, which
supports the hypothesis that the B[e] behaviour of HD 327083 is due to binarity
(ABRIDGED).Comment: Accepted for publication in A&
M Theory As A Matrix Model: A Conjecture
We suggest and motivate a precise equivalence between uncompactified eleven
dimensional M-theory and the N = infinity limit of the supersymmetric matrix
quantum mechanics describing D0-branes. The evidence for the conjecture
consists of several correspondences between the two theories. As a consequence
of supersymmetry the simple matrix model is rich enough to describe the
properties of the entire Fock space of massless well separated particles of the
supergravity theory. In one particular kinematic situation the leading large
distance interaction of these particles is exactly described by supergravity .
The model appears to be a nonperturbative realization of the holographic
principle. The membrane states required by M-theory are contained as
excitations of the matrix model. The membrane world volume is a noncommutative
geometry embedded in a noncommutative spacetime.Comment: Typo and tex error corrected. 41 pages, harvma
Distribution of phytoplankton pigments in nine European estuaries and implications for an estuarine typology
Phytoplankton pigments were studied by LiquidChromatography (HPLC) in nine West Europeanestuaries. Three estuaries, i.e. the Rhine,Scheldt and the Gironde were sampled four timesto cover the different seasons, whereas theother six estuaries were sampled once. Pigmentdistributions in estuaries reflect bothriverine inputs as well as autochthonousblooms. Fucoxanthin was the most commonaccessory photosynthetic pigment showing thatDiatoms were the most common group in thestudied estuaries and were particularlydominant during autumn and winter. In the veryturbid Gironde estuary, degradation processeswere predominant between salinities 1 and 20,while Diatoms, Dinoflagellates and Cryptophytesbloomed above 20 salinity during spring andsummer. This contrasted with the highlyeutrophic but less turbid Scheldt, wherephytoplanktonic blooms occurred at lowsalinities close to the city of Antwerp. In theScheldt, we observed both a tenfold fluctuationof phytoplankton biomass and a fluctuatingpigment diversity index. In contrast,chlorophyll a was always low in theGironde, but we observed large variations ofpigment diversity among samplings duringdifferent seasons. Distribution of pheopigmentsshowed that the maximum turbidity zone (MTZ)was a highly reactive region for heterotrophicphytoplankton degradation. The Scheldt and theThames were the most anthropogenic influencedestuaries contrasting with the Gironde estuarythat has a less urbanised watershed. Anestuarine typology is proposed based on threeclusters emerging from a correspondenceanalysis of pigment variables and variablescharacterising the anthropogenic impact andphysical forcing
N=8 Counterterms and E7(7) Current Conservation
We examine conservation of the E7(7) Noether-Gaillard-Zumino current in the
presence of N=8 supergravity counterterms using the momentum space helicity
formalism, which significantly simplifies the calculations. The main result is
that the 4-point counterterms at any loop order L are forbidden by the E7(7)
current conservation identity. We also clarify the relation between linearized
and full non-linear superinvariants as candidate counterterms. This enables us
to show that all n-point counterterms at L=7, 8 are forbidden since they
provide a non-linear completions of the 4-point ones. This supports and
exemplifies our general proof in arXiv:1103.4115 of perturbative UV finiteness
of N=8 supergravity.Comment: 18 page
Pathogenic bacteria and indicator organisms for anti-microbial resistance in pork meat at retail level in The Netherlands.
Slaughter pigs and pork carcasses are often contaminated with pathogenic bacteria. Consequently raw meat on sale in retail stores may also contain these bacteria. In The Netherlands the calculated contribution by pigs to the relative occurrence of human salmonellosis in the period 1994-1998 was 25.2 % (van Pelt, 2001). Survey and monitoring data on the contamination of raw products with pathogens like Salmonella, Campylobacter, Listeria monocytogenes and Escherichia coli O157 are essential for making risk estimates, and the results of surveys carried out in 1990/2000 and 2002 are presented here. In 2002 also a surveillance of anti-microbial resistance among indicator bacteria (Escherichia coli, Enterococcus faecium/faecalis) isolated from pork meat was started. The results show that pork meat was contaminated with Salmonella in levels between 6.2 - 10.5 %, S. Typhimurium being the predominant serotype, and to a lesser extent with Campylobacter, Listeria and E. coli O157
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