On the Hydrides of B, C, N, O and F

This paper reports a productive discussion of bonding principles in the non-metallic 2nd row hydrides. It suggests the inversion of a bonding character, potentially from hydrides of B & C, which may display unsaturation and electronic deficiency accompanied by electronic delocalization in 1D or 2D or 3D. Contrasted with the opposite possibility, within the finite number of hydrides of N, O and F, that display apparently extensive H-bonding and subsequently proton delocalization in 1D and 2D (in HF & ice polymorphs, respectively), and now potentially in 3D in a corresponding hydride of N called Rice's blue material, or perhaps polyimidogen. Where polyimidogen is a crystalline NH lattice that is a polymorph of the ammonium azide structure-type thus

Chemical Physics of Phonons & Superconductivity: A Heuristic Approach

Several lines of thought are pursued in an attempt to further clarify the role played by phonons in the theory of superconductivity. The central results of BCS theory are examined in the context of anharmonicity in the phonon motion and the role that Badger's rule of spectroscopy can play in simplifying and making more chemically intuitive the nature of the mechanism of superconductivity

The carbon allotrope glitter as n-diamond and i-carbon nanocrystals

Diffraction data taken from nanocrystalline n-diamond and i-carbon forms is fit to a so-called glitter model, in which the geometry of the C lattice has been optimized by density functional theory (DFT). A calculated theoretical diffraction pattern for glitter is shown to be a close fit to the experimental data for these novel C forms

Isoglitter

Described herein is a novel crystalline pattern in space group Ammm, that is a model of a C allotrope. This so-called isoglitter structure-type is a model of a graphite-diamond hybrid. A DFT geometry optimization and band structure calculation indicates that the lattice is metallic in a C realization

Geometrical-topological correlation in structures

The topology of polyhedra, tessellations and networks is described as to their mapping in Schlaefli space. A description of the topological form index is given and it is applied to these structural classes in terms of their geometries

Chemical Topology of Crystalline Matter and the Transcendental Numbers ϕ, e and π

In this paper, we describe certain rational approximations to the transcendental mathematical constants φ, e and π, that arise out of considerations of both: (1) the Euler relation for the division of the sphere into vertices, V, faces, F, and edges, E, and: (2) its simple algebraic transformation into the so-called Schläfli relation, which is an equivalent mathematical statement for the polyhedra, in terms of parameters known as the polygonality, defined as n = 2E/F, and the connectivivty, defined as p = 2E/V. It is thus the transformation to the Schläfli relation from the Euler relation, in particular, that enables one to move from a simple heuristic mapping of the polyhedra in the space of V, F and E, into a corresponding heuristic mapping into Schläfli-space, the space circumscribed by the parameters of n and p. It is also true, that this latter transformation equation, the Schläfli relation, applies only directly to the polyhedra, again, with their corresponding Schläfli symbols (n, p), but as a bonus, there is a direct 1-to-1 mapping result for the polyhedra, that can be seen to also be extendable to the tessellations in 2- dimensions, and the networks in 3-dimensions, in terms of coordinates in a 2-dimensional Cartesian grid, represented as the Schläfli symbols (n, p), as discussed above, which do not involve rigorous solutions to the Schläfli relation. For while one could never identify the triplet set of integers (V, F, E) for the tessellations and networks, that would fit as a rational solution within the Euler relation, it is in fact possible for one to identify the corresponding values of the ordered pair (n, p) for any tessellation or network. The identification of the Schläfli symbol (n, p) for the tessellations and networks emerges from the formulation of its so-called Well’s point symbol, through the proper translation of that Well’s point symbol into an equivalent and unambiguous Schläfli symbol (n, p) for a given tessellation or network, as has been shown by Bucknum et al. previously. What we report in this communication, are the computations of some, certain Schläfli symbols (n, p) for the so-called Waserite (also called platinate, Pt3O4, a 3-,4-connected cubic pattern), Moravia (A3B8, a 3-,8-connected cubic pattern) and Kentuckia (ABC2, a 4-,6-,8-connected tetragonal pattern) networks, and some topological descriptors of other relevant structures. It is thus seen, that the computations of the polygonality and connectivity indexes, n and p, that are found as a consequence of identifying the Schläfli symbols for these relatively simple networks, lead to simple and direct connections to certain rational approximations to the transcendental mathematical constants φ, e and π, that, to the author’s knowledge, have not been identified previously. Such rational approximations lead to elementary and straightforward methods to estimate these mathematical constants to an accuracy of better than 99 parts in 100.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

CD28 Ligation Increases Macrophage Suppression of T Cell Proliferation

When compared to spleen or lymph node cells, resident peritoneal cavity cells respond poorly to T cell activation in vitro. The greater proportional representation of macrophages in this cell source has been shown to actively suppress the T cell response. Peritoneal macrophages exhibit an immature phenotype $(MHC Class II^{lo}, B7^{lo})$ that reduces their efficacy as antigen presenting cells. Furthermore, these cells readily express inducible nitric oxide synthase (iNOS), an enzyme that promotes T cell tolerance by catabolism of the limiting amino acid arginine. Here, we investigate the ability of exogenous T cell costimulation to recover the peritoneal T cell response. We show that CD28 ligation failed to recover the peritoneal T cell response and actually suppressed responses that had been recovered by inhibiting iNOS. As indicated by cytokine ELISpot and neutralizing mAb treatment, this “co-suppression” response was due to CD28 ligation increasing the number of IFNγ-secreting cells. Our results illustrate that cellular composition and cytokine milieu influence T cell costimulation biology

Hsichengia: A 4,6-connected trigonal structural pattern in space group P3m1

A novel 4,6-connected network, called Hsichengia, is described. The novel network lies in the trigonal space group P3m1 (no. 156), with a = b = 3.447 A and c = 12.948 A; these lattice parameters were derived assuming Fe-S composition. It implies a binary AB2 stoichiometry in which the 6-connected A (Fe) atoms have octahedral configuration, and the 4-connected B (S) atoms have tetrahedral configuration. The Hsichengia network seems to be very closely related to the layered MoS2 structure-type, in which puckered MoS2 layers composed of octahedral Mo centers and trigonal-pyramidal S centers are held together by weak van der Waals forces normal to the a and b directions where the MoS2 layers extend. Thus the Hsichengia network can be generated from the MoS2 lattice by the formation of disulfide (S-S) bridges between particular layers, thereby creating a 3-dimensional network from a 2-dimensional layered structure, so that the S atoms are transformed from 3-connected trigonal-pyramidal coordination into fully 4-connected tetrahedral coordination. The Wells point symbol for the Hsichengia network is given by (4666)(4363)2, and it is thus seen to have the translated Schlafli symbol given as (5, 42/3). The latter is identical to that intrinsic to the well-known mineral structure of the pyrite network, FeS2, with the corresponding Wells point symbol (512)(56)2. Therefore, the Hsichengia network may be regarded as a topological isomer of the pyrite network, where topological isomerism is defined as occurring between unique networks possessing the same Schlafli symbol. Phase transformation between the two topological isomers is possible.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada