Surface Ordering in Molecular Clusters by Interactions of Well-Defined Parity Multipoles.

The spontaneous alignment of dipoles in patterns tangential or transversal to the interface of molecular clusters is studied by molecular dynamics simulations throughout the entire aggregation process. Tangential ordering (TANGO) is found to rely on dispersion forces driven by dipolar fluctuations. Transversal ordering (TRANSO) results from the interplay of two conditions: the broken translational invariance at the cluster interface and the interactions of multipoles of opposite parity.

High vacuum equipment for the measurement of the macroscopic dipole moment of polar molecular crystals.

Polar crystals placed into a charged plate capacitor may experience a mechanical torque. Mounting crystals on a spiral spring allows us to measure the momentum and thus the macroscopic dipole moment of a crystal object. To exclude the influence of ambient conditions (air, ions, electrons), experiments are performed in a high vacuum.

Iatrogenic Vessel Dissection in Endovascular Treatment of Acute Ischemic Stroke.

Purpose: Knowledge about the localization and outcome of iatrogenic dissection (ID) during endovascular treatment of acute ischemic stroke (AIS) is limited. We aimed to determine the frequency, clinical aspects and morphology of ID in endovascular AIS treatment and to identify predictors of this complication.

Methods: Digital subtraction angiography (DSA) of ID carried out during endovascular treatment between January 2000 and March 2012 have been re-evaluated.

Stochastic polarity formation in molecular crystals, composite materials and natural tissues.

This topical review summarizes the theoretical and experimental findings obtained over the last 20 years on the subject of growth-induced polarity formation driven by a Markov chain process. When entering the growing surface of a molecular crystal, an inorganic-organic composite or a natural tissue, the building blocks may undergo 180° orientational disorder. Driven by configurational entropy, faulted orientations can promote the conversion of a growing non-polar seed into an object showing polar domains.

Magnetic separation: its application in mining, waste purification, medicine, biochemistry and chemistry.

The use of strong magnetic field gradients and high magnetic fields generated by permanent magnets or superconducting coils has found applications in many fields such as mining, solid state chemistry, biochemistry and medical research. Lab scale or industrial implementations involve separation of macro- and nanoparticles, cells, proteins, and macromolecules down to small molecules and ions. Most promising are those attempts where the object to be separated is attached to a strong magnetic nanoparticle.

Polarity formation in crystals with long range molecular interactions: A Monte Carlo study.

Stochastic formation of a bi-polar state in three dimensional arrays of polar molecules with full Coulomb interactions is reproduced by Monte Carlo simulation. The size of the system is comparable to that of a real crystal seed. The spatial decay of the average order parameter is significantly slowed down by the long range interactions and the exact representation of correlation effects in terms of a single characteristic length becomes impossible.

Peculiar orientational disorder in 4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP) leading to bipolar crystals.

180° orientational disorder of molecular building blocks can lead to a peculiar spatial distribution of polar properties in molecular crystals. Here we present two examples [4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP)] which develop into a bipolar final growth state. This means orientational disorder taking place at the crystal/nutrient interface produces domains of opposite average polarity for as-grown crystals.

Crystal structure of 2,4,6-tris-(cyclo-hex-yloxy)-1,3,5-triazine.

The title compound, C21H33N3O3, is a tri-substituted cyclo-hex-yloxy triazine. In the crystal, the triazine rings form (C3i-PU) Piedfort units. The inter-centroid distance of the π-π inter-action involving the triazine rings is 3.

Polar Nature of Biomimetic Fluorapatite/Gelatin Composites: A Comparison of Bipolar Objects and the Polar State of Natural Tissue.

The correspondence of the state of alignment of macromolecules in biomimetic materials and natural tissues is demonstrated by investigating a mechanism of electrical polarity formation: An in vitro grown biomimetic FAp/gelatin composite is investigated for its polar properties by second harmonic (SHGM) and scanning pyroelectric microscopy (SPEM). Hexagonal prismatic seed crystals formed in gelatin gels represent a monodomain polar state, due to aligned mineralized gelatin molecules. Later growth stages, showing dumbbell morphologies, develop into a bipolar state because of surface recognition by gelatin functionality: A reversal of the polar alignment of macromolecules, thus, takes place close to that basal plane of the seed.

Dynamic changes of intramural hematoma in patients with acute spontaneous internal carotid artery dissection.

Background: We prospectively investigated temporal and spatial evolution of intramural hematomas in patients with acute spontaneous internal carotid artery dissection using repeated magnetic resonance imaging over six-months.

Aim: The aim of the present study was to assess dynamic changes of intramural hematoma in patients with acute spontaneous internal carotid artery dissection at multiple follow-up time-points with T1w, PD/T2w, and magnetic resonance angiography.

Methods: We performed serial multiparametric magnetic resonance imaging in 10 patients with spontaneous internal carotid artery dissection on admission, at days 1, 3, 7-14 and at months 1·5, 3, and 6.

Crystal structure of 4'-bromo-2,3,5,6-tetra-fluoro-biphenyl-4-carbo-nitrile.

The title compound, C13H4BrF4N, synthesized from 1,4'-bromo-iodo-benzene and 4-bromo-2,3,5,6-tetra-fluoro-benzo-nitrile in a coupling reaction was found to crystallize in the ortho-rhom-bic space group P212121. The two phenyl rings are rotated with respect to each other by 40.6 (6)°.

Scanning SQUID microscopy of local superconductivity in inhomogeneous combinatorial ceramics.

Although combinatorial solid-state chemistry promises to be an efficient way to search for new superconducting compounds, the problem of determining which compositions are strongly diamagnetic in a mixed-phase sample is challenging. By means of reactions in a system of randomly mixed starting components (Ca, Sr, Ba, La, Y, Pb, Bi, Tl, and Cu oxides), samples were produced that showed an onset of diamagnetic response above 115 K in bulk measurements. Imaging of this diamagnetic response in ceramic samples by scanning SQUID microscopy (SSM) revealed local superconducting areas with sizes down to as small as the spatial resolution of a few micrometers.

Barium hydrogen phosphate/gelatin composites versus gelatin-free barium hydrogen phosphate: synthesis and characterization of properties.

Recently, attention has been spent on crystal growth of phosphate compounds in gels for studying the mechanism of in vitro crystallization processes. Here, we present a gel-based approach for the synthesis of barium hydrogen phosphate (BHP) crystals using single and double diffusion techniques in gelatin. The composite crystals were compared with analytical grade BHP powder, single and polycrystalline BHP materials using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), scanning pyroelectric microscopy (SPEM), optical microscopy (OM), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD).

Synthesis of bone-like micro-porous calcium phosphate/iota-carrageenan composites by gel diffusion.

Brushite and octacalcium phosphate (OCP) crystals are well-known precursors of hydroxylapatite (HAp), the main mineral found in bone. In this report, we present a new method for biomimicking brushite and OCP using single and double diffusion techniques. Brushite and OCP crystals were grown in an iota-carrageenan gel.

Glutamic acid inducing kidney stone biomimicry by a brushite/gelatin composite.

Brushite is a well known precursor of calcium oxalate monohydrate, the main mineral found in kidney stones having a monoclinic crystal structure. Here, we present a new method for biomimicking brushite using a single tube diffusion technique for gel growth. Brushite crystals were grown by precipitation of calcium hydrogen phosphate hydrate in a gelatin/glutamic acid network.

The new insight into dynamic crossover in glass forming liquids from the apparent enthalpy analysis.

One of the most intriguing phenomena in glass forming systems is the dynamic crossover (T(B)), occurring well above the glass temperature (T(g)). So far, it was estimated mainly from the linearized derivative analysis of the primary relaxation time τ(T) or viscosity η(T) experimental data, originally proposed by Stickel et al. [J.

Molecular origin of piezo- and pyroelectric properties in collagen investigated by molecular dynamics simulations.

Molecular dynamics simulations were used to study the effect of mechanical and thermal stimuli on the electrostatic properties of collagen model helices. Our model sequences were based on glycine proline and hydroxyproline amino acids. We find that longitudinal mechanical strain induces significant variation of the polarization of the collagen fibril.

All organic host-guest crystals based on a dumb-bell-shaped conjugated host for light harvesting through resonant energy transfer.

Together we glow: Fully organic host-guest crystals with two dyes inserted in their parallel nanochannels display broad emission in the visible range thanks to resonant energy transfer. The conjugated host crystal provides light harvesting in the UV region.

1-Bromo-2,3,5,6-tetra-fluoro-4-nitro-benzene.

In the title compound, C(6)BrF(4)NO(2), the nitro group is twisted by 41.7 (3)° with reference to the arene ring mean plane. The main inter-actions stabilizing the crystal structure include O⋯Br contacts [3.

Organic fluorine compounds: a great opportunity for enhanced materials properties.

Interactions of "organic fluorine" have gained great interest not only in the context of crystal engineering, but also in the systematic design of functional materials. The first part of this tutorial review presents an overview on interactions known by organic fluorine. This involves π-π(F), C-F···H, F···F, C-F···π(F), C-F···π, C-F···M(+), C-F···C=O and anion-π(F) interactions, as well as other halogen bonds.

Identification of superconducting phases in ceramic particles by magnetic field induced forces using a magnetized wire.

A new equipment for minority phase analysis of superconducting (SC) phases within chemically inhomogeneous ceramic grains using a high gradient magnetic field or field induced effect of torque is presented. Single grains down to 20 microm are either captured by a magnetized iron wire or identified because of their torque movement in a pulsed magnetic field. An assembly of many hundreds of grains can be investigated for minor quantities of SC phases from 80 K up to room temperature.

Alignment and relaxation dynamics of dye molecules in host-guest inclusion compounds as probed by dielectric spectroscopy.

The alignment and relaxation dynamics of a polar dye molecule, N,N-dimethyl-4(4-nitrophenylazo)aniline (DNAA), in zeolite L and perhydrotriphenylene (PHTP) channels were investigated by means of a combination of optical, dielectric, and quantum-chemical methods. Both the zeolite L and PHTP channels enable the dye molecules to align along the channel axis. An amplified net dipole moment of DNAA in PHTP is observed and attributed to enhanced 1D close alignment of dye molecules.

Channel forming organic crystals: guest alignment and properties.

Purely organic solid state materials providing nanometre sized parallel channels are suited for physical property design. In this tutorial review, key materials in this field are reviewed along with new directions forming porous covalent and polymeric networks. Among many known host materials, perhydrotriphenylene (PHTP), tris-(o-phenylenedioxy)-cyclotriphosphazene (TPP) and members of the 2,4,6-tris-(4-halo-phenoxy)-1,3,5 triazine (4-X-POT) family are prime materials for hosting guest molecules featuring diverse physical functionality.