The effect of pressure on the raman spectrum of ice at low temperature

Extensive experimental studies of the Raman spectra of H₂O and D₂O ice in the lattice translational and OH (OD) stretching regions are reported for the first time at 88 K and from 0→6 kbar. An unambiguous transformation from ice I_h to ice IX has been observed, although previous studies suggest that a transition to ice II would have occurred. The ice I_h data are analysed in terms of various coefficients.     

Formation of a tris-capsule and a tris-carceplex from a cyclic six-bowl assembly

A macrocycle composed of six cavitands was assembled into a tris-capsule and a tris-carceplex, each of which encapsulates three guest molecules.     

A window fourier domain search system

A search system is presented that utilizes Fourier domain data. This system removes dominating features from the infrared absorbance data, transforms the data into the Fourier domain and performs a complete library search. The actual matching algorithm is very simple and excellent search results were attained using 16 cm^–1 resolution infrared absorbance spectra before transformation. This method can be used to distinguish very similar spectra that cannot be distinguished by many other search methods.     

A structural and n.m.r. investigation of chlorodinitrosyl bis(triphenyl phosphine) osmium(1+) tetrafluoroborate, [OsCl(NO)2(PPh3)2]BF4

Summary [OsCl(NO)₂(PPh₃)₂]BF₄ has been synthesised from [OsCl(CO)(NO)(PPh₃)₂] and NOBF₄ and characterised in the solid state by a single crystal x-ray analysis determination and in solution by³¹P{¹H} and¹⁵N n.m.r. studies. The nitrosyl ligands in [OsCl(NO)₂(PPh₃)₂]⁺ are approximately linear, and 170(1)⁰, and the co-ordination geometry about the metal ion is close to trigonal bipyramidal. This contrasts with the occurrence of a linear and a bent nitrosyl ligand in [RuCl(NO)₂(PPh₃)₂]⁺ and a square-pyramidal metal geometry. In solution the¹⁵N n.m.r. spectrum of a 50%¹⁵N enriched sample of [OsCl(NO)₂(PPh₃)₂]⁺ shows an equilibrium isotope effect similar to that reported for [RuCl(NO)₂(PPh₃)₂]⁺ and suggests that both complexes exist in solution as rapidly equilibrating isomeric forms.     

THE INTERACTION OF WATER SOLUBLE MEAT PROTEINS WITH MONO-GLYCERIDE AND DIGLYCERIDE AT THE CORN OIL-WATER INTERFACE ANDITS EFFECTONTIME-DEPENDENT INTERFACIALTENSION REDUCTION.

The influence of water soluble meat protein (WSMP) /glyceryl monostearate/glyceryl distearate ratio on the time-dependent reduction of interfacial tension at the corn oil-water Interface has been investigated at pH's 2.5, 3.5 and 9.5.The total WSMP-glycerides content was kept constant at 1.0% wt/wt. Both variables had an effect, with maximum reduction in the steady state interfacial tension occurring when using 0.5% WSMP in conjunction with 0.5% glycerides (monoglyceride/diglyceride ratio 3/1) at pH 3.5.Under these conditions the WSMP and glycerides associate to form a complex at the interface. At other WSMP/glycerides ratios the interfacial film has a more heterogeneous composition,.     

Self-assembly of a thymine quartet and quadruplex via an organic template

The synthesis of two hydrophobic cavitands bearing four (1) and eight (2) thymidine residues covalently linked with triazole moieties is reported. Spectral evidence indicates the adoption of a hydrogen-bonded T-quartet assembly by 1 in chloroform at low temperature and a π-stacked quadruplex by 2 in DMSO under ambient conditions.     

Effects of Heterogeneous Fracture Aperture on Multiphase Production from Shale Reservoirs

Production simulation from fractured shale reservoirs is often performed by simplifying the hydraulic fractures as rectangular planes with homogeneous aperture. This study investigates the effects of heterogeneous fracture aperture and proppant distribution in realistic, non-rectangular fractures on the multi-phase production from shales. The heterogeneous hydraulic fractures are generated with the GEOS multiphysics simulator under realistic 3D stress field. These fractures are embedded into the TOUGH+ multi-phase flow simulator for production simulation. The results emphasize the importance of flow barriers within the hydraulic fractures, due both to low-aperture regions caused by the stress-shadow effect and the settling of proppant. The production rate is particularly sensitive to aperture heterogeneity if the flow barriers are close to the wellbore such that a great portion of fracture volume is isolated from the well. A stage-to-stage comparison reveals that production from different stages could vary significantly because the local stress field leads to different fracture area and aperture. The use of proppant prevents fracture closure, but if the propped regions are far from the well, they do not enhance production because flow barriers between these regions and the well act as bottlenecks. The present study highlights the importance of incorporating aperture heterogeneity into production simulation, provides insights on the relationship between flow barriers, proppant concentration, and well production, and proposes a practical method to mitigate numerical difficulties when modeling heterogeneous fractures.

     

Microtubule particle dispersion in liquid crystal hosts

Abstract

Microtubule particles and metal-coated microtubules were dispersed in various host liquid crystal mixtures. Dispersion effects were evaluated as a function of liquid crystal type, viscosity, dielectric anisotropy and surface interaction. Experimental results indicated that all the types of liquid crystals studied were aligned perpendicular to the microtubule surfaces, regardless of liquid crystal composition or various surface coatings used on the metal-coated microtubules. Low concentrations of the metal-coated microtubules in nematic liquid crystal hosts were aligned by flow or cell surface alignment conditions, and could be modulated by electric or magnetic fields. We observed better microtubules dispersion uniformity in high viscosity liquid crystal host mixtures and in liquid crystal-monomers than in isotropic fluids. Microtubules particles dispersed in ROTN-404 liquid crystal mixture had a much higher birefringence in the microwave region than dispersion in a paraffin oil.     

Large local deflections of a dynamic crack front induced by intrinsic dislocations in brittle single crystals

We show that intrinsic dislocations in brittle single crystals can be a source of strong local perturbations along the crack path. A theoretical model was developed which predicts substantial crack front deflections. Investigating the crack surfaces in Si crystals with induced dislocation density of 10(9)-10(10) cm(-2) revealed a significant amount of crack front perturbations in the form of V-shaped grooves, which were completely missing in dislocation-free Si specimens. The measured depths of the perturbations were in the range of 2-20 nm and in excellent agreement with the theoretical model.