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Internal Space (internal + space)

Distribution by Scientific Domains
Chemistry66%

Selected Abstracts

Analytical space and work in Russia: Some remarks on past and present,

THE INTERNATIONAL JOURNAL OF PSYCHOANALYSIS, Issue 2 2005
IGOR M. KADYROV
In this paper, the author outlines the historical-cultural picture in the former USSR and post-Soviet Russia. He looks at some facets of psychoanalysis in Russia in the years immediately before and after the October Revolution as well as in its recent history, exploring the implicit question of how the wider social context, and specifi cally totalitarian and post-totalitarian reality, has infl uenced psychoanalytic work and analytic space in this country. With the help of Sebek's concept of the totalitarian object and Britton's formulations about the triangular space, the author attempts to understand the interaction of external and internal space and to give an introduction to the problem of establishing the analytic setting as well as fi nding some new possibilities of enlarging the space for new psychoanalysts in Russia. [source]

Revision of pyrrhotite structures within a common superspace model

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2007
Zunbeltz Izaola
The structure of pyrrhotite (Fe1,,,xS with 0.05 ,x, 0.125) has been reinvestigated in the framework of the superspace formalism. A common model with a centrosymmetric superspace group is proposed for the whole family. The atomic domains in the internal space representing the Fe atoms are parametrized as crenel functions that fulfil the closeness condition. The proposed model explains the x -dependent space groups observed and the basic features of the structures reported up to now. Our model yields for any x value a well defined ordered distribution of Fe vacancies in contrast to some of the structural models proposed in the literature. A new (3,+,1)-dimensional refinement of Fe0.91S using the deposited dataset [Yamamoto & Nakazawa (1982). Acta Cryst. A38, 79,86] has been performed as a benchmark of the model. The consistency of the proposed superspace symmetry and its validity for other compositions has been further checked by means of ab initio calculations of both atomic forces and equilibrium atomic positions in non-relaxed and relaxed structures, respectively. [source]

Chiral Encapsulation by Directional Interactions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009
Agnieszka Szumna
Abstract The complexation of chiral guests in the cavity of dimeric self-assembled chiral capsule 12 was studied by using NMR spectroscopy and X-ray crystallography. Capsule 12 has walls composed of amino acid backbones forming numerous directional binding sites that are arranged in a chiral manner. The polar character of the interior dictates the encapsulation preferences towards hydrophilic guests and the ability of the capsule to extract guests from water into an organic phase. Chiral discrimination towards hydroxy acids was evaluated by using association constants and competition experiments, and moderate de values were observed (up to 59,%). Complexes with one or two guest molecules in the cavity were formed. For 1:1 complexes, solvent molecules are coencapsulated; this influences guest dynamics and makes the chiral recognition solvent dependent. Reversal of the preferences can be induced by coencapsulation of a nonchiral solvent in the chiral internal environment. For complexes with two guests, filling of the capsule's internal space can be very effective and packing coefficients of up to 70,% can be reached. The X-ray crystal structure of complex 12,((S) -6)2 with well-resolved guest molecules reveals a recognition motif that is based on an extensive system of hydrogen bonds. The optimal arrangement of interactions with the alternating positively and negatively charged groups of the capsule's walls is fulfilled by the guest carboxylic groups acting simultaneously as hydrogen-bond donors and acceptors. An additional guest molecule interacting externally with the capsule reveals a possible entrance mechanism involving a polar gate. In solution, the structural features and dynamic behavior of the D4 -symmetric homochiral capsule were analyzed by variable-temperature NMR spectroscopy and the results were compared with those for the S8 -symmetric heterochiral capsule. [source]

Ligand-Gated Synthetic Ion Channels

CHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2005
Pinaki Talukdar
Abstract Supramolecular ,-stack architecture is fundamental in DNA chemistry but absent in biological and synthetic ion channels and pores. Here, a novel rigid-rod ,-stack architecture is introduced to create synthetic ion channels with characteristics that are at the forefront of rational design, that is, ligand gating by a conformational change of the functional supramolecule. Namely, the intercalation of electron-rich aromatics is designed to untwist inactive electron-poor helical ,-stacks without internal space into open barrel-stave ion channels. Conductance experiments in planar lipid bilayers corroborate results from spherical bilayers and molecular modeling: Highly cooperative and highly selective ligand gating produces small, long-lived, weakly anion selective, ohmic ion channels. Structural studies conducted under conditions relevant for function provide experimental support for helix,barrel transition as origin of ligand gating. Control experiments demonstrate that minor structural changes leading to internal decrowding suffice to cleanly annihilate chiral self-organization and function. [source]

Hollow Boron Nitride (BN) Nanocages and BN-Nanocage-Encapsulated Nanocrystals

CHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004
Ying-Chun Zhu Dr.
Abstract Hollow boron nitride (BN) nanocages (nanospheres, image on the left) and BN-nanocage-encapsulated GaN nanocrystals (right) have been synthesized by using a homemade BNO precursors. The as-prepared BN hollow nanocages have typically spherical morphologies with diameters ranging from 30 to 200 nm. The nanocages have crystalline structures. Peanutlike nanocages with double walls have also been observed; their internal space is divided into seperated compartments by the internal walls. The method is extended to sheathe nanocrystals with BN nanocages; BN-shell/GaN-core nanostructures have been successfully fabriacted. The method may be generally applicable to the fabrication BN-sheathed nanocrystals. [source]

Bone differentiation of marrow-derived mesenchymal stem cells using ,-tricalcium phosphate,alginate,gelatin hybrid scaffolds

JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 6 2007
Mohamadreza Baghaban Eslaminejad
Abstract The aim of the present study was to establish a 3D culture system for bone differentiation of mesenchymal stem cells (MSCs), using a new hybrid sponge. To manufacture the scaffold, a composite of ,-tricalcium phosphate,alginate,gelatin was prepared and cast as pellets of 1 cm diameter. The sponge was then fabricated by drying in freeze-dryer for 12 h. The porosity, mean pore size, compressive modulus and strength of the composite sponge fabricated in this study were 89.7%, 325.3 µm, 1.82 and 0.196 MPa, respectively. To establish a 3D culture system, the rat bone marrow-derived MSCs were suspended in 500 µl diluted collagen gel, loaded into the porous sponge and provided with medium with or without osteogenic supplements for 3 weeks. The day after loading, the cells appeared in the scaffold's internal spaces, where later some of them from either culture survived by anchoring on the surfaces. At the end of cultivation period, individually adhered cells from both cultures were observed to be replaced by cell aggregates, in which mineralized matrix was detected by alizarin red staining. Furthermore, RT-PCR analysis indicated that the bone-specific gene osteocalcin was expressed in cultures in both the presence and absence of the osteogenic supplements. Taken together, it seems that the studied scaffolds are cell-compatible and, more importantly, possess some osteo-inductive properties. Copyright © 2007 John Wiley & Sons, Ltd. [source]