On the cycle class map for zero-cycles over local fields

We study the Chow group of zero-cycles of smooth projective varieties over local and strictly local fields. We prove in particular the injectivity of the cycle class map to integral l-adic cohomology for a large class of surfaces with positive geometric genus, over local fields of residue characteristic different from l. The same statement holds for semistable K3 surfaces defined over C((t)), but does not hold in general for surfaces over strictly local fields.Comment: 37 pages (with an appendix by Spencer Bloch); bibliography updated, final versio

A restriction isomorphism for cycles of relative dimension zero

We study the restriction map to the closed fiber of a regular projective scheme over an excellent henselian discrete valuation ring, for a cohomological version of the Chow group of relative zero-cycles. Our main result extends the work of Saito--Sato to general perfect residue fields.Comment: 34 pages; final versio

Index of varieties over Henselian fields and Euler characteristic of coherent sheaves

Let X be a smooth proper variety over the quotient field of a Henselian discrete valuation ring with algebraically closed residue field of characteristic p. We show that for any coherent sheaf E on X, the index of X divides the Euler-Poincar\'e characteristic \chi(X,E) if p=0 or p>dim(X)+1. If 0<p\leq dim(X)+1, the prime-to-p part of the index of X divides \chi(X,E). Combining this with the Hattori-Stong theorem yields an analogous result concerning the divisibility of the cobordism class of X by the index of X. As a corollary, rationally connected varieties over the maximal unramified extension of a p-adic field possess a zero-cycle of p-power degree (a zero-cycle of degree 1 if p>dim(X)+1). When p=0, such statements also have implications for the possible multiplicities of singular fibers in degenerations of complex projective varieties.Comment: 20 pages; final versio

Front block distraction in orthodontic treatment: case report

The contribution of segmental osteotomies in ortho-surgical treatment has been given new ways of treatment by combining them with bone distraction techniques. The Köle osteotomy was used to correct anterior crowding in patients with Class I malocclusion involving mandibular incisors and canines. With minimal orthodontic preparation, bilateral diastemas were created in 15 days, which allowed alignment of the incisor-canine section without stripping or extractions. In this clinical case instead of the treatment plane involving extraction of premolars and an orthognathic surgery, a more conservative and rapid option was selected. The orthodontic preparation lasted 3 months, the surgery was performed, the distraction lasted 15 days and the orthodontic treatment finishing 4 months. The mandibular crowding and the overjet were corrected in 8 months.A contribuição das osteotomias segmentares no tratamento ortodôntico-cirúrgico são novas formas de tratamento ao combinarem-se com técnicas de distração óssea. A osteotomia de Köle foi usada para corrigir o apinhamento anterior em pacientes com má oclusão de Classe I envolvendo incisivos e caninos inferiores. Com o mínimo preparo ortodôntico, os diastemas bilaterais foram obtidos em 15 dias, o que permitiu o alinhamento dos incisivos e caninos sem desgastes interproximais ou extrações. Neste caso clínico, em vez do tratamento ser efetuado com exodontia de pré-molares e cirurgia ortognática, optou-se por uma opção mais conservadora e rápida. O preparo ortodôntico durou 3 meses, a cirurgia foi realizada, a distração durou 15 dias e o tratamento ortodôntico finalizando em 4 meses. O apinhamento mandibular e o overjet foram corrigidos em 8 meses

Remarks on cycle classes of sections of the arithmetic fundamental group

Given a smooth and separated K(pi,1) variety X over a field k, we associate a "cycle class" in etale cohomology with compact supports to any continuous section of the natural map from the arithmetic fundamental group of X to the absolute Galois group of k. We discuss the algebraicity of this class in the case of curves over p-adic fields, and deduce in particular a new proof of Stix's theorem according to which the index of a curve X over a p-adic field k must be a power of p as soon as the natural map from the arithmetic fundamental group of X to the absolute Galois group of k admits a section. Finally, an etale adaptation of Beilinson's geometrization of the pronilpotent completion of the topological fundamental group allows us to lift this cycle class in suitable cohomology groups.Comment: 19 pages; final version (added MSC codes and keywords

On abelian birational sections

For a smooth and geometrically irreducible variety X over a field k, the quotient of the absolute Galois group G_{k(X)} by the commutator subgroup of G_{\bar k(X)} projects onto G_k. We investigate the sections of this projection. We show that such sections correspond to "infinite divisions" of the elementary obstruction of Colliot-Th\'el\`ene and Sansuc. If k is a number field and the Tate-Shafarevich group of the Picard variety of X is finite, then such sections exist if and only if the elementary obstruction vanishes. For curves this condition also amounts to the existence of divisors of degree 1. Finally we show that the vanishing of the elementary obstruction is not preserved by extensions of scalars.Comment: 12 pages; added Remark 3.6; final versio

Étude sur l'analyse de risque de la Fièvre Catarrhale Ovine (Bluetongue) dans le bassin ovin laitier de Roquefort : cas particulier des centres d'insémination artificielle

Trois voies d'émission et d'introduction de la bluetongue sont identifiées : une voie impliquant l'animal, une les vecteurs et une dernière les vaccins. Des mesures de restrictions aux importations, le suivi sur le territoire métropolitain et le contrôle dans les élevages sélectionneurs rendent le risque d'introduction d'animaux malades de négligeable à faible. Pour les vecteurs, le risque d'apparition d'un culicoïde infecté à proximité des centres est qualifié de négligeable à faible. Pour la voie vaccins, le risque est qualifié de nul. Au niveau de chaque centre, l'environnement géographique, les flux d'animaux sont étudiés et les schémas prophylactiques sont notés. L'imperméabilité des centres aux insectes est évaluée. Ils semblent pouvoir éviter l'apparition et l'expansion de la maladie. Le risque de dissémination par la semence est qualifié de faible. Un protocole de qualification indemne de FCO des centres est proposé, de même que la simulation de quelques scénarii économiques

Dual inhibitory effects of APOBEC family proteins on retrotransposition of mammalian endogenous retroviruses

We demonstrated previously that the cytosine deaminase APOBEC3G inhibits retrotransposition of two active murine endogenous retroviruses, namely intracisternal A-particles (IAP) and MusD, in an ex vivo assay where retrotransposition was monitored by selection of neo-marked elements. Sequencing of the transposed copies further disclosed extensive editing, resulting in a high load of G-to-A mutations. Here, we asked whether this G-to-A editing was associated with an impact of APOBEC3G on viral cDNA yields. To this end, we used a specially designed quantitative PCR method to selectively measure the copy number of transposed retroelements, in the absence of G418 selection. We show that human APOBEC3G severely reduces the number of MusD and IAP transposed cDNA copies, with no effect on the level of the intermediate RNA transcripts. The magnitude of the decrease closely parallels that observed when transposed copies are assayed by selection of G418-resistant cells. Moreover, sequencing of transposed elements recovered by PCR without prior selection of the cells reveals high-level editing. Using this direct method with a series of cytosine deaminases, we further demonstrate a similar dual effect of African green monkey APOBE3G, human APOBEC3F and murine APOBEC3 on MusD retrotransposition, with a distinct extent and site specificity for each editing activity. Altogether the data demonstrate that cytosine deaminases have a protective effect against endogenous retroviruses both by reducing viral cDNA levels and by introducing mutations in the transposed copies, thus inactivating them for subsequent rounds of retrotransposition. This dual, two-step effect likely participates in the efficient defense of the cell genome against invading endogenous retroelements