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J Claverie

Publications and source records attributed to J Claverie.

8 recordsLinked to original sources
PubMed2001

Radical polymerization of styrene controlled by half-sandwich Mo(III)/Mo(IV) couples: all basic mechanisms are possible.

Density functional calculations of bond dissociation energies (BDEs) have been used as a guide to the choice of metal system suitable for controlling styrene polymerization by either the stable free radical polymerization (SFRP) or the atom transfer radical polymerization (ATRP) mechanism. In accord with the theoretical prediction, CpMo(eta(4)-C(4)H(6))(CH(2)SiMe(3))(2), 2, is not capable of yielding SFRP of styrene. Still in accord with theoretical prediction, CpMo(eta(4)-C(4)H(6))Cl(2), 1, CpMo(PMe(3))(2)Cl(2), 3, and CpMo(dppe)Cl(2) (dppe = 1,2-bis(diphenylphosphino)ethane), 4, yield controlled styrene polymerization by the SFRP mechanism in the presence of 2,2'-azobisisobutyronitrile (AIBN). This arises from the generation of a putative Mo(IV) alkyl species from the AIBN-generated radical addition to the Mo(III) compound. The controlled nature of the polymerizations is indicated by linear M(n) progression with the conversion in all cases and moderate polydispersity indices (PDIs). Controlled polymerization of styrene is also given by compounds 3 and 4 in combination with alkyl bromides. These complexes then operate by the ATRP mechanism, again in accord with the theoretical predictions. Controlled character is revealed by linear increase of M(n) versus conversion, low PDIs, a stop-and-go experiment, and (1)H NMR and MALDI-TOF analyses of the polymer end groups. The same controlled polymerization is given by a "reverse" ATRP experiment, starting from AIBN and CpMo(PMe(3))(2)Cl(2)Br, 5. On the other hand, when compound 1 or 2 is used in combination with an alkyl bromide (as for an ATRP experiment), the isolated polystyrene shows by M(n), (1)H NMR, and MALDI-TOF analyses that catalytic chain transfer (CCT) radical polymerization takes place in this case. Kinetics simulations underscore the conditions regulating the radical polymerization mechanism and the living character of the polymerization. The complexes herein described are ineffective at controlling the polymerization of methyl methacrylate.

Journal Article↗
PubMed1999

Microcephaly and macrocephaly in autism.

Data from a series of 126 autistic children ages 2-16 years and referred to an Autism Diagnosis Unit in South-West France were examined. Macrocephaly (head circumference > 97th centile) was observed in 16.7% of the sample, a significantly higher proportion than that expected. Macrocephaly was more frequent among older subjects but was otherwise not associated with gender, developmental level, the presence of epilepsy or of medical disorders, or severity of autistic symptomatology. Microcephaly (head circumference < 3rd centile) was also significantly raised and found in 15.1% of the sample. Microcephaly was significantly associated with the presence of medical disorders. Results support those from recent studies suggesting a raised rate of macrocephaly in autism which, pooling published data, can be estimated to be 20%. It is argued that the raised incidence of microcephaly among low-functioning autistic subjects with medical disorders might have contributed to delay the recognition of an increased head circumference among a minority of subjects with idiopathic autism.

Adolescent↗
PubMed1994

[ORL surgery in Albucasis's treatise on surgery. A vision of cervicofacial surgical therapeutics in the year 1000].

The work of the famous Arab doctor, Albucasis, is not well known to head and neck surgeons. However, the thirtieth time of his treatise on medicine is essentially a surgical textbook and includes many. Facts concerning otorhinolaryngology. Albucasis's complete work is an exhaustive compilation of late tenth century medical knowhow which ensured the link between ancient medicine, essentially of Greek origin, and modern western medicine. The important work of Jewish and Arab physicians in the early and late Middle Ages was necessary for the transmission of knowledge from the ancient near last to the modern western world. Among Albucasis's descriptions of surgical techniques, tonsillectomy and trachestomy are particularly interesting. In order to accurately formulate indications for surgery, Albucasis endeavors to present the signs and symptoms of pathological conditions requiring surgical treatment. Finally, Albucasis reveals himself to be a humanist, as well as a physician and surgeon.

History, Medieval↗
PubMedDate not supplied

[The Stein-Leventhal syndrome. Clinical, biological and anatomic study of 6 cases in adolescent girls (author's transl)].

Clinical, biological and anatomic studies were performed in 6 adolescent girls with the Stein-Leventhal syndrome. The rare occurrence of this syndrome in pediatrics is emphasized. The main clinical signs consist of obesity, hirsutism and menstrual irregularities. Basic LH and plasma testosterone are useful diagnostic means, as well as -- in children -- the suppression-stimulation and LH-RH tests. However, coelioscopy is necessary to allow a correct diagnosis. Histological examination might not be absolutely necessary since a large biopsy could be responsible for untimely ovulation. Estrogens and anti-androgens are the only logical treatment at the time of puberty.

Adolescent↗