Phase transitions between single- and double-layered smectic structures in binary mixtures of cyano-mesogens

Binary mixtures of mesogens which exhibit respectively single-layered (A 1), double layered (A2) and partially double layered (A d) smectic phases show abrupt A2-A1 or A2-Ad transitions as a function of concentration. Double layered structures imply the formation of dimerized entities and the possibility of dimerization is discussed in terms of the amphiphilic nature of the molecules in the binary mixture (symmetrical and dissymmetrical polar mesogens). The results are analysed with respect to the thermal stability of the A 2 phase when defects are introduced in the polar interface by adding non-polar symmetrical mesogens.Des mélanges binaires de mésogènes présentant respectivement des phases smectiques monocouches (A1), bicouches (A2) et partiellement bicouches (Ad) permettent de mettre en évidence en fonction de la concentration des transitions brusques A2-A1 ou A 2-Ad. La structure bicouche implique un processus de dimérisation des entités mésogènes qui est discuté en fonction du caractère amphipathique des molécules (molécules polaires symétriques et dissymétriques). La stabilité de la phase bicouche est également analysée lorsque l'on introduit une perturbation au niveau de l'interface polaire par adjonction de molécules non polaires

Structure bicouche des mésophases SA et SB du 4-cyanobutoxybenzylidene-4-octylaniline

In order to analyze the mesomorphic behavior of molecules containing a highly dipolar endgroup mechanically decoupled from the rigid moiety, the 4-cyanobutoxybenzylidene-4-octylaniline was synthesized. The first observations made (polarizing microscopy, differential scanning calorimetry, and X-ray diffraction) suggest the présence of two smectic mesophases, of B and A type respectively. The structure of these would correspond to double layers : in each sub-layer, the molecular arrangement would be of the ferro-type, and the stacking of the sub-layers would be of the antiferro-type. However, it is impossible to definitely specify the spatial extension of the order described, on the basis of the experimental data obtained so far.Pour analyser le comportement mésomorphe de molécules contenant un groupe fortement dipolaire découplé mécaniquement du tronçon rigide, nous avons synthétisé le 4-cyanobutoxybenzylidène-4-octylaniline. Les premières observations (microscope polarisant, enthalpimétrie différentielle, diffraction des rayons X) indiquent la présence de deux mésophases smectiques, l'une de type B et l'autre de type A. Celles-ci auraient une structure bicouche : dans chaque sous-couche, les molécules seraient arrangées de manière ferro- et les sous-couches, elles-mêmes, seraient superposées de manière antiferro- . Cependant, les données expérimentales obtenues ne permettent pas encore de se prononcer définitivement sur l'étendue spatiale de ce type d'ordre

Whole genome duplication is an early event leading to aneuploidy in -wild type glioblastoma

Glioblastoma, the most frequent and lethal form of glioma, displays chromosome instability and recurrent somatic copy number alterations (SCNA). Chromothripsis and whole genome duplication (WGD) have been recently identified in cancer. In the present study, we analyzed SCNA and determine the ploidy pattern in 123 -wild-type glioblastomas, using SNP array data. WGD and chromothripsis events were validated using, respectively, FISH and CTLPScanner. WGD was detected in 11.4% glioblastomas (14/123) and was associated with mutation ( = 0.0068). It was an early event occurring after the recurrent SCNA observed in diffuse high-grade gliomas. Glioblastomas with WGD were more aneuploid compared to glioblastomas without WGD ( < 0.0001). Chromothripsis occurred in 29.3% glioblastomas (36/123) and mostly affected chromosomes 7, 9 and 12, with amplification of oncogenes (EGFR, /), and homozygous deletion of tumor suppressor genes (). There was a significant association between chromothripsis and gene rearrangement at a given locus. WGD is an early genetic event significantly associated to mutation and leading to chromosome instability and aneuploidy in -wild-type glioblastoma. Chromothripsis recurrently targets oncogenes and tumor suppressor genes that are key players in gliomagenesis and tumor progression. The occurrence of chromothripsis points to underlying gene rearrangements (including gene fusions), potential therapeutic targets in glioblastoma

Making sense of variety in place leadership: the case of England’s smart cities

Making sense of variety in place leadership: the case of England’s smart cities. Regional Studies. There is rising interest in cities becoming ‘smart’ knowledge-oriented economies by prioritizing more digitally enabled modes of production and service delivery. Whilst the prevalence of these new organizational forms is well understood, the way that leadership agency is exercised (i.e., the actors involved and their modalities of action) is not. Drawing on new empirical data and sense-making methodology, the paper reveals discursive patterns in how public agencies, private firms and communities ‘see’ and ‘do’ leadership within these place-based contexts, and concludes that success in exploiting the social and spatial dynamics of ‘smart’ development lies in understanding actors’ assumptions about commercial and social gain

Smectic a1 ↔ a2 transition of n_c-60.8 : a two-dimensional phase separation of the molecular endgroups

The smectic A1 ↔ A2 phase transition of a one-component liquid crystalline system was studied with X-ray diffraction. The smectogen used was a polar but symmetrical smectogen, namely the 4-cyanohexyloxybenzylidene-4'-octylaniline. The intensities of the Bragg reflections were measured as a function of temperature. The experimental data were analysed according to a structural model describing the location of the cyano and methyl endgroups of the molecules at the surface of the smectic layers. The A1 ↔ A2 transition was then interpreted in terms of a two-dimensional phase separation of the endgroups.On a étudié par diffraction des rayons X la transition de phase smectique A1 ↔ smectique A2 d'un système mésomorphe unaire. Le smectogène considéré, polaire mais symétrique, était le 4-cyanohexyloxybenzylidène-4'-octylaniline. Les intensités des réflexions de Bragg ont été mesurées en fonction de la température. Les données expérimentales ont été analysées selon un modèle structural précisant la localisation des groupes cyano et méthyle terminaux à la surface des couches smectiques. La transition A1 ↔ A 2 a été ensuite interprétée en termes d'une séparation de phases bidimensionnelle des groupes terminaux

Metal-n-InP Rectifying Properties Enhancement with Zn Based Metallizations and Diffusion at Moderate Annealing Temperatures

Rectifying contacts on n-InP using Zn based metallizations followed by moderate annealing temperature and time were studied. Diffusion of Zn atoms at the metal-semiconductor interface creates a thin p-InP layer. Pseudo-Schottky junctions were obtained with a significant barrier height enhancement, typically 0.2–0.25 eV. The metallization process involved throughout the present work leads to high quality Schottky diodes within a rather simple procedure similar to this generally used to obtain good ohmic contacts. It is shown in particular that the special requirements needed for a lot of electrical measurements ($e.g.$ $C{-}V$ characteristics or D.L.T.S.) can be matched without any extra complication. The behaviour of Schottky devices was throroughly analysed as a function of the annealing procedure. Best performances were obtained by applying cumulative annealing sequences, increasing the temperature while decreasing the time of exposure. The homogeneity of the structures was attested from a satisfactory agreement between barrier heights deduced either from current or from capacitance measurements. A good linearity of $C^{-2}{-}V{-}T$ curves and low values of the series resistances were also obtained

ELECTRICAL AND MAGNETIC PROPERTIES OF POLY p.AZOPHENYLENE

Nous présentons des résultats concernant la conductivité et les propriétés paramagnétiques du poly p.azophénylène (P.P.N.) dopé et non dopé. Le dopage à AsF5 ne conduit pas à un matériau conducteur alors que le P.P.N. dopé à l'iode atteint une conductivité de 10-5 (Ωcm)-l. Il est vraisemblable que les dopants très oxydants entraînent une rupture des liaisons -N=N-.Conductivity and paramagnetic properties of virgin and doped poly p.azophenylene (P.P.N.) are investigated. AsF5 doping does not lead to a conductive material while iodine doped P.P.N. reaches a conductivity of 10-5 (Ωcm )-1. Strong oxidizing dopants probably induce the break of the -N=N- links