Fluorimetric determination of alkaline phosphatase in solid and fluid dairy products

A new assay has been developed for measuring residual alkaline phosphatase (ALP) activity in a wide variety of dairy products. The method proposed is simple, rapid and directly applicable to solid and liquid dairy samples. ALP in the test sample hydrolyzes a non fluorescent substrate, trifluoromethyl-β-umbelliferone phosphate, to its highly fluorescent phenolate product. The assay is performed in a reverse micellar medium composed of mixed buffer (2-amino-2-methyl-1-propanol buffer pH 9.0 and borate buffer pH 9.0) in AOT/isooctane, at a temperature of 38 °C. Total test time is 450 s. Reaction rates are linear (except for butter) up to 8.5 and 11% (v/v) raw milk, for whole milk and chocolate milk, respectively. The detection limits are 0.04, 0.4 and 0.22% (v/v) raw milk, for whole milk, chocolate milk and butter, respectively. The precision of the fluorimetric method was assessed by repeated analysis of a pasteurized milk sample spiked with mixed herd raw milk. The accuracy of the method was evaluated by comparison with an official colorimetric assay using p-nitrophenylphosphate as ALP substrate.     

Silver(I) oxide mediated highly selective monotosylation of symmetrical diols. Application to the synthesis of polysubstituted cyclic ethers

[reaction: see text] The reaction of symmetrical diols and oligo(ethylene glycol)s with a stoichiometric amount of p-toluenesulfonyl chloride in the presence of silver(I) oxide and a catalytic amount of potassium iodide led selectively to the monotosylate derivatives in high yields. Polysubstituted cyclic ethers were obtained readily upon treatment of the corresponding diols with an excess of silver oxide. The high selectivity was explained on the basis of the difference in acidity between the two hydroxy groups, which undergo an intramolecular hydrogen bonding.     

New advances on the characterisation of polymer surfaces by HREELS

Self assembled monolayers (SAMs) of thiols functionalised with oligothiophene functions were used as models for polymer surfaces. Thienyl functionalisation simulates the surface region and demonstrates that the analysed depth is of the order of 10 Å. Spectra of polystyrene (PS) films were recorded and show that impact mechanism dominates, which corroborates the high sensitivity of HREELS applied to polymer surfaces. Different orientation of phenyl groups is unravel for PS films deposited on platinum and silicon substrates, which is here related to a different conformation of the PS chains in the surface region of the film. To illustrate the state of the art of HREELS applied to organic films, spectra were recorded with old and new generation spectrometers.     

Sets of conductivity and elasticity tensors stable under lamination

A complete characterization is obtained of any set of constitutive (conductivity or elasticity) tensors that is stable under lamination between any two of the elements of the set. The conditions are local and are expressed in terms of the curvature and tangent plane at points on the boundary of the set. They are checked to hold for several well-known examples of sets stable under a more general process of homogenization. A companion paper investigates the link between these conditions and quasiconvexity. © 1994 John Wiley & Sons, Inc.     

A New Highly Versatile Handle for Chemistry on a Solid Support: The Pipecolic Linker

The design, synthesis, and potential application of the pipecolic linker is presented. This new versatile handle can immobilize primary, secondary, and aromatic amines, as well as alcohols, phenols, and hydrazides, on a solid support. Compared with other linkers, the anchoring step is easy and efficient. The release of final products from the resin proceeds upon acidic treatment with high purities. The pipecolic linker offers the promise of being using in peptide chemistry to produce peptides modified at the N and C terminus, peptidomimetics, as well as small organic molecules.     

Convex analysis and non-trivial invariant subspaces

Positivity - We establish sufficient conditions for the existence of invariant subspaces for operators on real Banach spaces, and we investigate the behaviour of operators without such subspaces....     

Bidimensional near-field sampling spectrometry

We report on a concept of compact optical Fourier-transform spectrometer based on bidimensional (2D) spatial sampling of a confined interferogram. The spectrometer consists of a nanostructured glass surface on which two light beams interfere in total internal reflection. Subwavelength spatial sampling of the interferogram near field is achieved by introducing a tilt angle between a 2D array of optical nanoantennas and the interferogram pattern. The intensity distribution of the scattered light is recorded on a 2D CCD camera, and a one-dimensional Fourier transform of the interferogram is used to recover the input light spectrum. Experimental results show a wide spectral bandwidth in the visible range, down to 380 nm, with spectral resolution of 1.6 nm around 780 nm.