98 research outputs found
Inversion formulas for the broken-ray Radon transform
We consider the inverse problem of the broken ray transform (sometimes also
referred to as the V-line transform). Explicit image reconstruction formulas
are derived and tested numerically. The obtained formulas are generalizations
of the filtered backprojection formula of the conventional Radon transform. The
advantages of the broken ray transform include the possibility to reconstruct
the absorption and the scattering coefficients of the medium simultaneously and
the possibility to utilize scattered radiation which, in the case of the
conventional X-ray tomography, is typically discarded.Comment: To be submitted to Inverse Problem
Niveau de l'acétylcholinestérase chez quatre espÚces de poissons de l'estuaire du Sebou
Les organophosphorĂ©s (OP) et les carbamates (C), insecticides dâorigine agricole, sont toxiques pour la plupart des organismes en raison de leur facultĂ© dâinhibition des cholinestĂ©rases et plus particuliĂšrement lâacĂ©tylcholinestĂ©rase (AChE). En effet, ils provoquent une accumulation des cholines au niveau des synapses, aboutissant Ă la paralysie puis Ă la mort. Afin de dĂ©tecter une contamination de lâestuaire de lâOued Sebou par ces insecticides, lâactivitĂ© acĂ©tylcholinestĂ©rasique (AchE) a Ă©tĂ© dosĂ©e dans le muscle, le cerveau, le foie et les branchies de quatre poissons : Solea vulgaris (sole), Dicentrachus labrax (loup), Diplodus sargus (sar) et Pleuronectes platessa (plie). Les Ă©chantillons prĂ©levĂ©s semestriellement dans lâestuaire de lâOued Sebou prĂ©sentent une plus faible activitĂ© AChE par rapport Ă celle des espĂšces du site tĂ©moin (large de Mehdya). Cette diffĂ©rence de lâactivitĂ© AChE entre les deux sites, attribuĂ©e aux effets neurotoxiques liĂ©s Ă la prĂ©sence dans le milieu dâOP ou de C, signifierait une contamination de lâestuaire de lâOued Sebou
L'hypersensibilité des récepteurs dopaminergiques induite par des injections chroniques unilatérales intracaudales de l'anticorps anti-idiotypique dopaminergique
La contribution des mĂ©canismes immunologiques dans la genĂšse de la maladie de Parkinson est trĂšs controversĂ©e. Des injections chroniques unilatĂ©rales dans le noyau caudĂ© (1 injection par semaine pendant 5 semaines) de lâanticorps anti-idiotypique de la dopamine conjuguĂ©e (AIDA) ou de lâhalopĂ©ridol semblent induire, une semaine aprĂšs la derniĂšre injection, une hypersensibilitĂ© des rĂ©cepteurs dopaminergiques rĂ©vĂ©lĂ©e par lâinjection de faibles doses dâapomorphine. Cette hypersensibilitĂ© se traduit par un comportement de rotation controlatĂ©rale au site dâinjection
Effet à long terme d'injections intracérébroventriculaires d'anticorps dopaminergiques sur l'hypersensibilité comportementale chez la souris
ln the present study the effect ofrepeated intracerebroventricular (ICV) of anti-conjugated dopamine antibodies (Acm anti-DAc) was investigated on behavioural supersensitivity and eating behavior. Mice were injected in ICV (with an ICV cannula) with either Acm anti-DAc or no immuns immunoglobulins (IgNI) twice a week for 5 weeks, their behavioural supersensitivity to apomorphine (0.05 mglkg) were measured. The results showed that Repeated intracerebroventricular injections of anti conjugated dopamine antibodies produced a behavioural supersensitivity to apomorphine. Immunohistochemical analysis showed that the behavioural supersensitivity is not due to DA celllosses in the substantia nigra or the ventral tegmentum area.
Key words: Dopaminergic antibodies, Intracerebroventricular injections, Behavioural supersensitivity, Mice
Des injections intracérébroventriculaires répétées de l'anticorps monoclonal anti-dopamine conjuguée (ACm antiDAc) chez des souris Balb/c entraßnent, pendant 8 semaines aprÚs la fin des injections, une hypersensibilité comportementale. L'analyse immunohistochimique montre que cette hypersensibilité ne semble pas liée directement à une perte des cellules DA dans la substance noire et dans l'aire tegmentale ventrale.
Mots clés: Anticorps dopaminergiques, Injections intracérébroventriculaires, Hypersensibilité comportementale, Souri
Inverse Transport Theory of Photoacoustics
We consider the reconstruction of optical parameters in a domain of interest
from photoacoustic data. Photoacoustic tomography (PAT) radiates high frequency
electromagnetic waves into the domain and measures acoustic signals emitted by
the resulting thermal expansion. Acoustic signals are then used to construct
the deposited thermal energy map. The latter depends on the constitutive
optical parameters in a nontrivial manner. In this paper, we develop and use an
inverse transport theory with internal measurements to extract information on
the optical coefficients from knowledge of the deposited thermal energy map. We
consider the multi-measurement setting in which many electromagnetic radiation
patterns are used to probe the domain of interest. By developing an expansion
of the measurement operator into singular components, we show that the spatial
variations of the intrinsic attenuation and the scattering coefficients may be
reconstructed. We also reconstruct coefficients describing anisotropic
scattering of photons, such as the anisotropy coefficient in a
Henyey-Greenstein phase function model. Finally, we derive stability estimates
for the reconstructions
A remark on an overdetermined problem in Riemannian Geometry
Let be a Riemannian manifold with a distinguished point and
assume that the geodesic distance from is an isoparametric function.
Let be a bounded domain, with , and consider
the problem in with on ,
where is the -Laplacian of . We prove that if the normal
derivative of along the boundary of is a
function of satisfying suitable conditions, then must be a
geodesic ball. In particular, our result applies to open balls of
equipped with a rotationally symmetric metric of the form
, where is the standard metric of the sphere.Comment: 8 pages. This paper has been written for possible publication in a
special volume dedicated to the conference "Geometric Properties for
Parabolic and Elliptic PDE's. 4th Italian-Japanese Workshop", organized in
Palinuro in May 201
Détection voltamétrique des catécholamines dans le bulbe olfactif du rat
La voltamétrie différentielle sur impulsions normales (D.N.P.V.) associée à une fibre de carbone traitée électrochimiquement a été conçue pour la détermination des catécholamines. Une étude in vitro a permis de mettre au point un traitement électrochimique pour la détection des catécholamines qui a amplement amélioré les performances de l'électrode en termes de sélectivité, de sensibilité et de stabilité de la réponse. In vivo, l'électrode ainsi traitée a servi pour l'évaluation de trÚs faibles concentrations (10.7 à 10.8 M) des catécholamines extracellulaires au niveau du bulbe olfactif du rat.Voltammetric detection of catecholamines in the rat olfactory bulbDifferential normal pulse voltammetry (DNPV) associated to electrochemically treated carbon fiber electrode has been used for catecholamines determination. In vitro, study has permittÚd to take out electrochemical treatment for catécholamines detection. This treatment has widely improved selectivity, sensibility and stability ofresponse. In vivo, treated electrode was used for determination of very low concentrations (10.7 to 10.8 M) of extracellular catecholamines in the rat olfactory bulb
On arbitrages arising from honest times
In the context of a general continuous financial market model, we study
whether the additional information associated with an honest time gives rise to
arbitrage profits. By relying on the theory of progressive enlargement of
filtrations, we explicitly show that no kind of arbitrage profit can ever be
realised strictly before an honest time, while classical arbitrage
opportunities can be realised exactly at an honest time as well as after an
honest time. Moreover, stronger arbitrages of the first kind can only be
obtained by trading as soon as an honest time occurs. We carefully study the
behavior of local martingale deflators and consider no-arbitrage-type
conditions weaker than NFLVR.Comment: 25 pages, revised versio
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