Influence of specific anions on the orientational ordering of thermotropic liquid crystals at aqueous interfaces

We report that specific anions (of sodium salts) added to aqueous phases at molar concentrations can trigger rapid, orientational ordering transitions in water-immiscible, thermotropic liquid crystals (LCs; e.g., nematic phase of 4'-pentyl-4-cyanobiphenyl, 5CB) contacting the aqueous phases. Anions classified as chaotropic, specifically iodide, perchlorate, and thiocyanate, cause 5CB to undergo continuous, concentration-dependent transitions from planar to homeotropic (perpendicular) orientations at LC-aqueous interfaces within 20 s of addition of the anions. In contrast, anions classified as relatively more kosmotropic in nature (fluoride, sulfate, phosphate, acetate, chloride, nitrate, bromide, and chlorate) do not perturb the LC orientation from that observed without added salts (i.e., planar orientation). Surface pressure-area isotherms of Langmuir films of 5CB supported on aqueous salt solutions reveal ion-specific effects ranking in a manner similar to the LC ordering transitions. Specifically, chaotropic salts stabilized monolayers of 5CB to higher surface pressures and areal densities (12.6 mN/m at 27 ?(2)/molecule for NaClO(4)) and thus smaller molecular tilt angles (30° from the surface normal for NaClO(4)) than kosmotropic salts (5.0 mN/m at 38 ?(2)/molecule with a corresponding tilt angle of 53° for NaCl). These results and others reported herein suggest that anion-specific interactions with 5CB monolayers lead to bulk LC ordering transitions. Support for the proposition that these ion-specific interactions involve the nitrile group was obtained by using a second LC with nitrile groups (E7; ion-specific effects similar to 5CB were observed) and a third LC with fluorine-substituted aromatic groups (TL205; weak dipole and no ion-specific effects were measured). Finally, we also establish that anion-induced orientational transitions in micrometer-thick LC films involve a change in the easy axis of the LC. Overall, these results provide new insights into ionic phenomena occurring at LC-aqueous interfaces, and reveal that the long-range ordering of LC oils can amplify ion-specific interactions at these interfaces into macroscopic ordering transitions.     

Quantum metrology: dynamics versus entanglement

A parameter whose coupling to a quantum probe of n constituents includes all two-body interactions between the constituents can be measured with an uncertainty that scales as 1/n3/2, even when the constituents are initially unentangled. We devise a protocol that achieves the 1/n3/2 scaling without generating any entanglement among the constituents, and we suggest that the protocol might be implemented in a two-component Bose-Einstein condensate.     

Gravitational radiation and the ultimate speed in Rosen's bimetric theory of gravity

In Rosen's “bimetric” theory of gravity the (local) speed of gravitational radiation υ_g is determined by the combined effects of cosmological boundary values and nearby concentrations of matter. It is possible for υ_g to be less than the speed of light. I show here that emission of gravitational radiation prevents particles of nonzero rest mass from exceeding the speed of gravitational radiation. Observations of relativistic particles place limits on υ_g and the cosmological boundary values today, and observations of synchrotron radiation from compact radio sources place limits on the cosmological boundary values in the past.     

Constituents of cannabis sativa L. An improved method for the synthesis of dl-cannabichromene

A new procedure was developed for the synthesis of cannabichromene (III) which involves reflux of equimolar amounts of olivetol (I), citral (II) and t-butylamine in toluene for 9 hours. The purification of III was best achieved by sodium borohydride reduction of unreacted II followed by column chromatography on 1% sodium hydroxide impregnated silica gel 60-PF. The yield of III (62.0%) was much higher than that reported in the literature.     

Determination of hexamethylene diisocyanate-based isocyanates in spray-painting operations. Part 2. Comparison of high performance liquid chromatography with capillary zone electrophoresis

A capillary zone electrophoresis (CZE) approach was developed for the determination of hexamethylene diisocyanate (HDI) monomer and HDI-based oligomers. A comparison of CZE with high performance liquid chromatography (HPLC) indicates that the CZE separation completely isolates isocyanates from excess solvent, derivatizing reagent and pigment while offering a fivefold increase in sensitivity. The CZE approach allows for the quantification of HDI monomer and oligomer within a 1 min time window under the run conditions selected. For the determination of HDI-based oligomer, provided that the relative response with respect to HDI monomer is calculated, there is no significant difference (p < 0.05, n = 10) in the isocyanate air concentration when using either HPLC or CZE. The results are significant because they indicate that CZE has advantages for the determination of both HDI-based oligomer and HDI monomer generated during spray-painting operations.     

Operators of fibered groups

Let (G, ) denote a finite groupG with fibration . The group Aut (G, ) of operators of (G, ) is closely related to the group of collineations of (G, ). In this paper we investigate the geometric properties imposed on (G, ) by requiring that Aut (G, )=AutG. We find that in many instances this algebraic property restricts the geometry to a very special form.Dedicated to Professor Helmut Karzel on the occasion of his 60th birthday.     

Use of virtual screening, flexible docking, and molecular interaction fields to design novel HMG-CoA reductase inhibitors for the treatment of hypercholesterolemia

Dietary changes associated with drug therapy can reduce high serum cholesterol levels and dramatically decrease the risk of coronary artery disease, stroke, and overall mortality. Statins are hypolipemic drugs that are effective in the reduction of cholesterol serum levels, attenuating cholesterol synthesis in liver by competitive inhibition regarding the substrate or molecular target HMG-CoA reductase. We have herewith used computer-aided molecular design tools, i.e., flexible docking, virtual screening in large data bases, molecular interaction fields to propose novel potential HMG-CoA reductase inhibitors that are promising for the treatment of hypercholesterolemia.     

Experimental observation of orthogonally polarized time-delayed optical soliton trapping in birefringent fibers

Propagation of two orthogonally polarized time-delayed optical solitons in low-birefringence optical fiber is studied experimentally. We demonstrate soliton trapping and collisions and also the ability to control the separation and shape of soliton pulses by varying the power at the input of the fiber.     

Near-rings associated with generalized translation structures

In this paper we study generalized translation spaces with operators, denoted by GTSO. We associate to each GTSO a near-ring, called the kernel of the GTSO. Focusing on the finite case we show that every near-ring with identity arises as the kernel of an appropriate GTSO. In terms of the geometric properties of the GTSO we obtain representation results for the classes of local near-rings and near-fields.     

Optical filters with panchromatic emulsion layers for image processing

Amplitude filters with non-linear adaptive performance in the Fourier plane of a mirror optical system are considered. Panchromatic silver bromide layers with a printout effect are employed. The processing of binary and grey-scale images with the aid of a passively adaptive mirror filtering block is investigated.