A New Semidefinite Programming Bound for Indefinite Quadratic Forms Over a Simplex

The paper describes a method for computing a lower bound of the global minimum of an indefinite quadratic form over a simplex. The bound is derived by computing an underestimator of the convex envelope by solving a semidefinite program (SDP). This results in a convex quadratic program (QP). It is shown that the optimal value of the QP is a lower bound of the optimal value of the original problem. Since there exist fast (polynomial time) algorithms for solving SDP's and QP's the bound can be computed in reasonable time. Numerical experiments indicate that the relative error of the bound is about 10 percent for problems up to 20 variables, which is much better than a known SDP bound.     

Spherical MCM-41 as support material in enantioselective HPLC

Spherical MCM-41 particles covalently linked with (R)-naphthylethylamine as selector are reported as a new chiral stationary phase for HPLC and show excellent resolution and efficiency in combination with low inlet pressures.     

Thermodynamic studies of mixtures for topical anesthesia: Lidocaine–salol binary phase diagram

The lidocaine–salol binary system has been investigated by differential scanning calorimetry, direct visual observations, and X-ray powder diffraction, resulting in a temperature-composition phase diagram with a eutectic equilibrium. The eutectic mixture, found at 0.423 ± 0.007 lidocaine mole-fraction, melts at 18.2 ± 0.5 °C with an enthalpy of 17.3 ± 0.5 kJ mol^?1. This indicates that the liquid phase around the eutectic composition is stable at room temperature. Moreover, the undercooled liquid mixture does not easily crystallize. The present binary mixture exhibits eutectic behavior similar to the prilocaine–lidocaine mixture in the widely used EMLA^® topical anesthetic preparation.     

Advances in the preparation of porous polymer monoliths in capillaries and microfluidic chips with focus on morphological aspects

Porous polymer monoliths have emerged as unique materials for many applications, including liquid-chromatographic analyses at an unrivaled speed, solid-phase extraction, and enzyme immobilization in capillary and microfluidic chip format. This article reviews the state of the art in the preparation of monoliths in narrow-bore capillaries and microfluidic chips and their miniaturization under conditions of spatial confinement. New developments in their preparation mainly using free radical polymerization techniques with a focus on morphological aspects in view of homogeneous porous materials are described. The suitability of monoliths for analysis of both large and small molecules is also discussed.     

New Chemical Constituents from Borreria verticillata (Rubiaceae)

A phytochemical study on Borreria verticillata has led to the isolation of two novel simple indole alkaloids, 6‐methoxy‐4‐(3‐methylbut‐2‐en‐1‐yl)‐1H‐indole, named verticillatine A ( 1 ), and 1‐(1H‐indol‐6‐yl)‐3‐methylbutan‐1‐one, named verticillatine B ( 2 ), one new iridoid, 6′‐O‐(2‐glyceryl)scandoside methyl ester ( 3 ), with the glycerol unit linked to a glucose unit, and two known ones, asperuloside ( 4 ) and scandoside methyl ester ( 5 ). The structures of these compounds were elucidated on the basis of spectroscopic‐data analyses, mainly ¹H‐ and ¹³C‐NMR, including 2D experiments (¹H,¹H‐COSY, NOESY, HMBC, and HMQC), and HR‐ESI‐MS.     

Properties of ZnO nanocrystals prepared by radiation method

Zinc oxide nanoparticles were prepared by irradiation of aqueous solutions containing zinc(II) ions, propan-2-ol, polyvinyl alcohol, and hydrogen peroxide. Zinc oxide was found in solid phase either directly after irradiation, or after additional heat treatment. Various physicochemical parameters, including scintillation properties of prepared materials, were studied. After decomposition of impurities and annealing of oxygen vacancies, the samples showed intensive emission in visible spectral range and well-shaped exciton luminescence at 390–400 nm. The best scintillating properties had zinc oxide prepared from aqueous solutions containing zinc formate as initial precursor and hydrogen peroxide. Size of the crystalline particles ranged from tens to hundreds nm, depending on type of irradiated solution and post-irradiation thermal treatment.     

The Use of Second‐Harmonic Generation to Study Diffusion through Films under a Liquid Phase

Knowledge of the diffusion of chemicals through buried films is important for a wide variety of systems—from sensing to drug delivery. Herein, we show that second‐harmonic generation (SHG) can be used to follow the diffusion through a thin film buried under a liquid in situ. More specifically, the diffusion of 4‐(4‐diethylaminostyryl)‐1‐methylpyridinium iodide through zeolite precursor films of different thickness is followed. The diffusion coefficients are calculated according to Fick’s law.