2,4,6-Tris(4-nitrophenoxy)-1,3,5-triazine: a hexagonal host framework stabilised by the NO2-trimer supramolecular synthon

The title molecule forms a honeycomb network of molecular and nitro-trimer synthons with guest species included in the hexagonal voids.     

Topological equivalences between organic and coordination polymer crystal structures: an organic ladder formed with three-connected molecular and supramolecular synthons

[structure: see text] Crystal engineering of an organic ladder can be achieved with a T-shaped molecule, 4,4-bis(4'-hydroxyphenyl)-1-cyclohexanol, having three hydroxyl functionalities that can form O-H...O hydrogen-bonded helices. The topology of this network structure finds a parallel in three-connected coordination polymers.     

Quiesent Crystallization Kinetics of Nucleated Metallocene and ZN Isotactic Polypropylenes

Crystallization kinetics and thermodynamic properties of nucleated isotactic polypropylene (PP) are analyzed using Hoffman—Lauritzen crystallization theory to determine the mechanistic effects of the nucleators. Calorimetric data provides quantitative comparisons between nucleating efficiences of the (Millad) and (NJSTAR) nucleator in Metallocene (M) and Ziegler—Natta (ZN) PP. The two types of PP without nucleators showed similar crystallization behavior though the T°_m for ZN-iPP was about 10°C higher than M-iPP. Both nucleators show significant improvement in crystallization rate in both types of PP. In addition, Millad outperforms NJSTAR. The magnitude of the kinetic response is,however, different and both the nucleators appear to function better in ZN than in Metallocene PP. nucleated PP shows predominantly the form. The amount of the form is thermal history dependent and changes with supercooling (T=T°_m–T_c). Similar equilibrium melting temperature (T°_m) in the nucleated and control PPs indicates the lack of any thermodynamic effect of the nucleator. All nucleated PPs show a much lower secondary nucleation rate constant, K_g.This revised version was published online in November 2005 with corrections to the Cover Date.     

Imaging the neural circuitry and chemical control of aggressive motivation

Background  

With the advent of functional magnetic resonance imaging (fMRI) in awake animals it is possible to resolve patterns of neuronal activity across the entire brain with high spatial and temporal resolution. Synchronized changes in neuronal activity across multiple brain areas can be viewed as functional neuroanatomical circuits coordinating the thoughts, memories and emotions for particular behaviors. To this end, fMRI in conscious rats combined with 3D computational analysis was used to identifying the putative distributed neural circuit involved in aggressive motivation and how this circuit is affected by drugs that block aggressive behavior.     

The Existence of Positive Solutions to Neutral Differential Equations

In this paper, we shall consider a class of neutral differential equations of the form

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where τ (0, ∞), σ [0, ∞), Q(t) C([t₀, ∞), R ⁺ ), r(t) C([t₀, ∞), (0, ∞)) with r(t) nondecreasing on [t₀ − τ, ∞). We shall show that all positive solutions of ( * ) can be classified into four types, A, B, C, and D, and we shall obtain sufficient and necessary conditions for the existence of A-type, B-type, and D-type positive solutions of ( * ), respectively. A sufficient condition for the existence of C-type positive solutions of ( * ) is also given. Finally, we shall offer a sharp oscillation result for all solutions of ( * ). Our results generalize and improve those established in B. Yang and B. G. Zhang (Funkcial. Ekvac.39 (1996), 347–362).     

Electrical conduction mechanism in a polycrystalline Sb35Se65 sample

Localized state conduction through a variable-range hopping mechanism in the low-temperature region (～180–270 K) and thermally activated phonon-assisted tunneling in the higher-temperature region (～270–320 K) has been observed in a polycrystalline Sb₃₅Se₆₅ sample.     

Contraction and approximate contraction with an application to multi-point boundary value problems

The paper deals with some general iterative methods in n-metric spaces. The obtained results are more explicit than those known in the literature and provides error estimates when the sequence obtained on a floating-point system starts oscillating. A stopping criteria and error estimates at that stage are provided. An application to multi-point boundary value problems is also given.     

On finite anti-plane shear for compressible elastic circular tube

Knowles' theorem for anti-plane shear of compressible, homogeneous, isotropic elastic materials in finite elastostatics is used to determine some restrictions on a strain-energy density function characterizing materials for which two anti-plane shear problems of a circular tube are then solved exactly.

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Resumé Le theorème de Knowles pour le cisaillement anti-plane de matériaux compressibles, homogénes, isotropes, élastiques en élastostatique finie est utilisé afin de déterminer certaines restrictions sur un fonction-densité d'énergie de déformation caractérisant des matériaux pour lesquels deux problèmes de cisaillement anti-plan d'un tube circulaire sont alors résolus exactement.