267 research outputs found
On the -spectrum for -bounded operator on von-Neumann algebra
Let be a von Neumann algebra and let be a nonzero positive
element of . By and we denote the
-spectrum and the -spectral radius of , respectively.
In this paper, we show that . Sufficient conditions for the equality to be true are presented. Also, we show that is
finite for any if and only if is in the socle of
. Next , we consider the relationship between elements and
that satisfy one of the following two conditions: (1)
for all , (2) for all . Finally, a Gleason-Kahane-\.Zelazko's
theorem for the -spectrum is derived.% Finally, we introduce and study the
notion of the -approximate point spectrum for element of
Accumulation of DOC in Low Phosphate Low Chlorophyll (LPLC) area: is it related to higher production under high N:P ratio?
The biogeochemistry of carbon and nutrients (N,P) in the surface layer of the ocean strongly depends on the complex interactions between primary producers (phytoplankton) and remineralizers (heterotrophic bacteria). To understand how these interactions impact the overall DOC dynamics in the surface layer of the Mediterranean Sea, we implemented, using Eco3M (Ecological Mechanistic Modular Modelling tool), a multi-element model with a mechanistic description of primary production. We studied the model steady state results under various nutrient conditions and fixed cell abundances. By doing so, we show how the bottom up control of osmotrophs growth can impact the overall DOC dynamics in the system. Based on our set of parameters, the biogeochemical characteristics displayed by the model appear realistic when compared to literature data for the Mediterranean basin. Differences in DOC dynamics between N and P limited systems in the model, lead to the conclusion that the unusually high N:P ratio of the Mediterranean Sea may favour the uncoupling between growth and carbon production leading to higher DOC accumulation compared to systems with lower N:P ratio
Pseudo-K\"ahler Lie algebras with abelian complex structures
We study Lie algebras endowed with an abelian complex structure which admit a
symplectic form compatible with the complex structure. We prove that each of
those Lie algebras is completely determined by a pair (U,H) where U is a
complex commutative associative algebra and H is a sesquilinear hermitian form
on U which verifies certain compatibility conditions with respect to the
associative product on U. The Riemannian and Ricci curvatures of the associated
pseudo-K\"ahler metric are studied and a characterization of those Lie algebras
which are Einstein but not Ricci flat is given. It is seen that all
pseudo-K\"ahler Lie algebras can be inductively described by a certain method
of double extensions applied to the associated complex asssociative commutative
algebras
Myasthenie - spondylarthropathies: association fortuite ? A propos d’un cas et revue de la littérature
Propos Nous rapportons le cas d’un patient atteint d’une myasthénie associée à une spondylarthropathie. Cette observation est originale de part sa rareté, six cas seulement on été rapportés dans la littérature et le problème que pose cette association : est ce qu’elle est fortuite ou impliquerait-elle d’autres facteurs génétiques qui restent à prouver ?Observation Monsieur J.H. âgé de 32 ans, aux antécédents de myasthénie depuis 2002, était hospitalisé en avril 2004 pour polyarthrite chronique bilatérale et asymétrique évoluant depuis un an, touchant le poignet gauche, les inter phalangiennes proximales des 3ème et 5ème doigts droits et le genou droit associées à des talalgiesbilatérales et une douleur des articulations sacro-iliaques. La biologie montrait un syndrome inflammatoire modéré, des facteurs rhumatoïdes faiblement positifs et un typage HLA B7 et B17. Le bilan radiologiquemontrait une arthrite des mains, une enthésite calcanéenne et permettait de suspecter une sacro-iliite bilatérale qui était confirmée par un scanner. L’évolution était bonne sous anti- inflammatoires nonstéroïdiens pendant 6 mois. Il consulte en janvier 2006 pour le même tableau associé à une sècheresse buccale et oculaire. Le bilan trouvait une VS à 20, des facteurs rhumatoïdes faiblement positifs mais desAAN positifs à un taux 1/160 homogènes avec des anti SSA. Les radiographies standard montraient une carpite stade II gauche. L’examen ophtalmologique a confirmé le syndrome sec oculaire. La biopsie des glandes salivaires accessoires a montré un syndrome de Gougerot Sjögren grade 2 de Shisholm
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A Missense Mutation (Q279R) in the Fumarylacetoacetate Hydrolase Gene, Responsible for Hereditary Tyrosinemia, Acts as a Splicing Mutation
Background: Tyrosinemia type I, the most severe disease of the tyrosine catabolic pathway is caused by a deficiency in fumarylacetoacetate hydrolase (FAH). A patient showing few of the symptoms associated with the disease, was found to be a compound heterozygote for a splice mutation, IVS6-1g->t, and a putative missense mutation, Q279R. Analysis of FAH expression in liver sections obtained after resection for hepatocellular carcinoma revealed a mosaic pattern of expression. No FAH was found in tumor regions while a healthy region contained enzymeexpressing nodules. Results: Analysis of DNA from a FAH expressing region showed that the expression of the protein was due to correction of the Q279R mutation. RT-PCR was used to assess if Q279R RNA was produced in the liver cells and in fibroblasts from the patient. Normal mRNA was found in the liver region where the mutation had reverted while splicing intermediates were found in nonexpressing regions suggesting that the Q279R mutation acted as a splicing mutation in vivo. Sequence of transcripts showed skipping of exon 8 alone or together with exon 9. Using minigenes in transfection assays, the Q279R mutation was shown to induce skipping of exon 9 when placed in a constitutive splicing environment. Conclusion: These data suggest that the putative missense mutation Q279R in the FAH gene acts as a splicing mutation in vivo. Moreover FAH expression can be partially restored in certain liver cells as a result of a reversion of the Q279R mutation and expansion of the corrected cells
Diazotrophy as the main driver of the oligotrophy gradient in the western tropical South Pacific Ocean: results from a one-dimensional biogeochemical–physical coupled model
The Oligotrophy to UlTra-oligotrophy PACific Experiment (OUTPACE) cruise took
place in the western tropical South Pacific (WTSP) during the austral summer
(March–April 2015). The aim of the OUTPACE project was to investigate a
longitudinal gradient of biological and biogeochemical features in the WTSP,
and especially the role of N2 fixation in the C, N, and P cycles. Two
contrasted regions were considered in this study: the Western Melanesian
Archipelago (WMA), characterized by high N2 fixation rates,
significant surface production and low dissolved inorganic phosphorus (DIP)
concentrations, and the South Pacific Gyre (WGY), characterized by very low
N2 fixation rates, surface production and high DIP concentrations.
Since physical forcings and mixed layer dynamics in both regions were
similar, it was considered that the gradient of oligotrophy observed in
situ between the WMA and WGY was not explained by differences in physical
processes, but rather by differences in biogeochemical processes. A
one-dimensional physical–biogeochemical coupled model was used to
investigate the role of N2 fixation in the WTSP by running two
identical simulations, only differing by the presence (simWMA) or
absence (simWGY) of diazotrophs. We showed that the nitracline
and the phosphacline had to be, respectively, deeper and shallower than the
mixed layer depth (MLD) to bring N-depleted and P-repleted waters to the
surface during winter mixing, thereby creating favorable conditions for the
development of diazotrophs. We also concluded that a preferential
regeneration of the detrital phosphorus (P) matter was necessary to obtain
this gap between the nitracline and phosphacline depths, as the nutricline
depths significantly depend on the regeneration of organic matter in the
water column. Moreover, the model enabled us to highlight the presence of
seasonal variations in primary production and P availability in the upper
surface waters in simWMA, where diazotrophs provided a new source of nitrogen
(N) to the ecosystem, whereas no seasonal variations were obtained in simWGY,
in the absence of diazotrophs. These main results emphasized the fact that
surface production dynamics in the WTSP is based on a complex and sensitive
system which depends on the one hand on physical processes (vertical mixing,
sinking of detrital particles), and on the other hand on biogeochemical
processes (N2 fixation, remineralization).</p
Shrinkage and mechanical performance of geopolymeric mortars based on calcined Tunisian clay
"Special Issue for International Congress on Materials & Structural Stability, Rabat, Morocco, 27-30 November 2013"Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. Since the majority of the existent infrastructures are Portland cement concrete based this means that concrete infrastructure rehabilitation is a hot issue to be dealt with. Geopolymers are novel inorganic binders with high potential to replace Portland cement based ones. Geopolymerization is a complex chemical process evolving various aluminosilicate oxides with silicates under highly alkaline conditions, yielding polymeric units, similar to those of an aluminosilicate glass. So far very few studies in the geopolymer field have addressed the rehabilitation of deteriorated concrete structures. This paper discloses some results of an investigation concerning the development geopolymeric repair mortars based on a calcined Tunisian clay. The results show that Tunisian calcined clay based mortars have hydration products with typical geopolymeric phases. Results also show that the geopolymeric mortar shows a high unrestrained shrinkage behavior and that its modulus of elasticity is below the threshold required for this repair mortar
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