A review of the fossil record of turtles of the clade Pan-Carettochelys

Turtles of the total clade Pan-Carettochelys have a relatively poor fossil record that extends from the Early Cretaceous. The clade is only found in Asia during the Cretaceous, but spreads to Europe and North America during the Eocene. Neogene finds are restricted to Europe, Africa and Australia, whereas the only surviving species, Carettochelys insculpta, lives in New Guinea and the Northern Territories of Australia. The ecology of fossil pan-carettochelyids appears similar to that of the extant C. insculpta, although more primitive representatives were likely less adapted to brackish water. Current phylogenies only recognize three internested clades: Pan- Carettochelys, Carettochelyidae and Carettochelyinae. A taxonomic review of the group concludes that of 25 named taxa, 13 are nomina valida, 7 are nomina invalida, 3 are nomina dubia, and 2 are nomina nuda

A tetragonal-to-monoclinic phase transition in a ferroelectric perovskite: the structure of PbZr(0.52)Ti(0.48)O3

The perovskite-like ferroelectric system PbZr(1-x)Ti(x)O3 (PZT) has a nearly vertical morphotropic phase boundary (MPB) around x=0.45-0.50. Recent synchrotron x-ray powder diffraction measurements by Noheda et al. [Appl. Phys. Lett. 74, 2059 (1999)] have revealed a new monoclinic phase between the previously-established tetragonal and rhombohedral regions. In the present work we describe a Rietveld analysis of the detailed structure of the tetragonal and monoclinic PZT phases on a sample with x= 0.48 for which the lattice parameters are respectively: at= 4.044 A, ct= 4.138 A, at 325 K, and am= 5.721 A, bm= 5.708 A, cm= 4.138 A, beta= 90.496 deg., at 20K. In the tetragonal phase the shifts of the atoms along the polar [001] direction are similar to those in PbTiO3 but the refinement indicates that there are, in addition, local disordered shifts of the Pb atoms of ~0.2 A perpendicular to the polar axis.. The monoclinic structure can be viewed as a condensation along one of the directions of the local displacements present in the tetragonal phase. It equally well corresponds to a freezing-out of the local displacements along one of the directions recently reported by Corker et al.[J. Phys. Condens. Matter 10, 6251 (1998)] for rhombohedral PZT. The monoclinic structure therefore provides a microscopic picture of the MPB region in which one of the "locally" monoclinic phases in the "average" rhombohedral or tetragonal structures freezes out, and thus represents a bridge between these two phases.Comment: REVTeX, 7 figures. Modifications after referee's suggestion: new figure (figure 5), comments in 2nd para. (Sect.III) and in 2nd & 3rd para. (Sect. IV-a), in the abstract: "...of ~0.2 A perpendicular to the polar axis.

Allaeochelys libyca, a new carettochelyine turtle from the middle miocene (Langhian) of Libya

Fossil carettochelyine turtles are well known from the Paleogene of Europe (Allaeochelys), North America and Asia (Anosteira); however, the previously known Neogene fossil record is highly fragmentary and was therefore unsuitable for taxonomic analysis. In this work, we present a new carettochelyine taxon, Allaeochelys libyca, from the Middle Miocene (Langhian) of Gebel Zelten (Libya) based on an incomplete skull and disarticulated postcranial elements. The new taxon is diagnosed relative to the extant Carettochelys insculpta based on the placement of the foramen posterius canalis carotici interni close to the fenestra postotica, the horizontal orientation of the tubercula basioccipitalis, the substantial contribution of the opisthotic to the base of the tubercula basioccipitalis, the presence of a triangular pterygoid fossa, the arrangement of the mandibular condyles along a plane and the presence of an extremely well-developed fossa at the base of the processus mandibularis. A phylogenetic analysis of pancarettochelyids confirms the monophyly of Carettochelyidae and Carettochelyinae but resulted in a paraphyletic taxon, Allaeochelys. For the sake of nomenclatural stability, we provisionally retain the genus Allaeochelys as paraphyletic relative to the extant Carettochelys insculpta

ОСНОВНЫЕ ПРИНЦИПЫ СОЗДАНИЯ АРХИТЕКТУРНОГО ПРОЕКТА ЖИЛОЙ ГРУППЫ "СОБОРНАЯ ПЛОЩАДЬ"

The article discusses residential groups of a new type, which represent a single territorial and compositional whole, analyzed according to typological and architectural criteria. The primary idea of the direction being studied in shaping the architecture of the residential group “Square of community” are the recommendations made by the President of the Russian Federation on the formation in Russia of “Environment of social harmony”. The Square of community is viewed as unity in the multitude based on love, meaning free spiritual unity of people, fellowship in brotherhood and love, having existed under this name for more than a thousand years.В статье рассматриваются жилые группы нового типа, которые представляют собой единое территориальное и композиционное целое, анализируемое по типологическим и архитектурным критериям. Первичной идеей исследуемого направления в формообразовании архитектуры жилой группы «СОБОРНАЯ1 ПЛОЩАДЬ», являются высказанные Президентом РФ рекомендаций по формированию в России «Среды социальной гармонии2». Соборная площадь рассматривается, как единство во множестве основанное на любви, означающее свободное духовное единство людей, общение в братстве и любви, существуя под этим именем более тысячи лет

87Rb and 85Rb NQR study of phase transitions in RbH 3(SeO3)2

The temperature dependence of the nuclear quadrupole resonance spectra of 85Rb and 87Rb in RbH3(SeO3) 2 has been measured by a proton-Rb double resonance technique in the laboratory frame. The increase in the number of chemically non-equivalent sites from one to four and the observed temperature dependence of the quadrupole coupling constants and the asymmetry parameters on going into the ferroelectric phase agrees with the proposed soft mode motion involving rotations of one type of SeO3 groups. The existence of an intermediate incommensurate phase between Tc and Tc + 4 K has been confirmed.Nous avons mesuré le spectre de résonance quadrupolaire de 85Rb et 87Rb dans le composé RbH3(SeO3) 2 par une technique de double résonance proton-Rb. L'accroissement de un à quatre du nombre de sites non équivalents et la variation avec la température des constantes de couplages quadrupolaires et des paramètres d'asymétrie dans la phase ferroélectrique sont en accord avec un modèle de mode mou où l'on prend en compte la rotation d'un type de groupe SeO3. Nous avons confirmé l'existence d'une phase incommensurable intermédiaire entre Tc et T c + 4 K