Volume effects on the nuclear quadrupole resonance transition frequency

A suitable modification of a general thermodynamic procedure to correct experimental data, usually gathered at constant (room) pressure, to that which would be obtained had the volume been kept constant, the normal condition under which the theory is worked out. This allows therefore meaningful comparison of data with theory. This modification is applied to the pressure derivative at constant temperature of the Nuclear Quadrupole Resonance transition frequency as a function of the temperature. It is shown in p-dichlorobenzene and in p-chlorophenol that, by using very reasonable values for the various parameters appearing in the procedure, excellent agreement is found between theory and experimental data.     

Immobilization of bacteria in microgel grafted onto macroporous polyethylene

The development of “Green Chemistry” requires new materials to replace the conventional organic chemistry by biological catalysts, to produce fine chemicals in an environmentally friendly manner. Microbial whole cells can be directly used as biocatalysts, providing a simple and cheap methodology since enzyme isolation and purification are avoided.High-density polyethylene (HDPE) is a very stable polymer though it can be activated by gamma radiation to induce grafting. Glycidyl methacrylate was grafted onto macroporous HDPE and PP in the range of 1–6%, proportional to the initial monomer concentration. Grafted polymers were further chemically modified with ethylenediamine to generate a cationic hydrogel of micron-size thickness onto the internal polymer surfaces. Modified polymers were able to immobilize Gram-positive and Gram-negative bacteria that can catalyze a chemical reaction as efficient as free cells do.     

Studies aimed at elucidating factors involved in the control of chemoselectivity in single electron transfer promoted photoreactions of branched-polydonor substituted phthalimides

Factors that govern the chemical selectivities and efficiencies of SET-promoted photocyclization reactions of acceptor-polydonor substrates were explored by using systems comprised of phthalimide acceptors linked via polymethylene or polyethylenoxy chains to α-silylether and thioether donors. A number of linear and branched substrates of this type were prepared and their photochemical behavior was explored. The results of this effort have led to the identification of several key factors that govern the chemoselectivities and efficiencies of the competitive reaction pathways followed. The observations suggest that the length and nature of the chain linking the phthalimide acceptor and α-silyl donor sites are important factors in controlling the rates of formation of zwitterionic biradicals that serve as penultimate intermediates in routes for product formation. In addition, the rates of methanol promoted desilylation at cation radical centers in intermediate zwitterionic biradicals also play important roles especially in cases where chain length/type is not a factor. The results are discussed in terms of both their mechanistic and synthetic significance.     

Fluorescence Nanoscopy with Optical Sectioning by Two‐Photon Induced Molecular Switching using Continuous‐Wave Lasers

During the last decade far‐field fluorescence microscopy methods have evolved that have resolution far below the wavelength of light. To outperform the limiting role of diffraction, all these methods, in one way or another, switch the ability of a molecule to emit fluorescence. Here we present a novel rhodamine amide that can be photoswitched from a nonfluorescent to a fluorescent state by absorption of one or two photons from a continuous‐wave laser beam. This bright marker enables strict control of on/off switching and provides single‐molecule localization precision down to 15 nm in the focal plane. Two‐photon induced nonlinear photoswitching of this marker with continuous‐wave illumination offers optical sectioning with simple laser equipment. Future synthesis of similar compounds holds great promise for cost‐effective fluorescence nanoscopy with noninvasive optical sectioning.     

Spin field topological linear defects in quasicrystals with magnetic order

It is proven that magnetizable quasicrystals undergoing large deformations admit elastic ground states characterized by a net of linear topological defects for the magnetic spin field.     

Development and Application of a Two-Phase Clean-Up System in Food Samples Prior to Fluorescence Analysis of Aflatoxins

A new method based on the use of a two-phase separation system is proposed for the clean-up of aflatoxins after their extraction from food samples. After extraction from the sample with an appropriate solvent, aflatoxins contained in organic solvent diffuse to the aqueous phase. At that stage their relative concentration is measured fluorimetrically at 350 nm (λ_exc). Different organic solvents were tested, and the composition of the aqueous phase was varied. The data obtained showed that the best efficiencies were observed with toluene and PBS-65% methanol. The method was simpler and shorter, and capable of monitoring aflatoxins in samples with a LOD equal to 0.3 μg kg⁻¹ (AFB₁). However, the proposed method shows limited selectivity and could thus serve as a screening method for total aflatoxins or be combined with chromatographic techniques for individual aflatoxin determination.     

Conventional Matrices Loaded Onto a Graphene Layer Enhances MALDI-TOF/TOF Signal: Its Application to Improve Detection of Phosphorylated Peptides

This is the first study where graphene is used as a MALDI adjuvant in combination with the traditional matrix α-cyano-4-hydroxycinnamic acid (CHCA) to improve the signal intensity of peptide samples. Use of this amended matrix not only leads to increased signals but also to a higher number of peaks detected in complex samples. Additionally, the use of graphene has a stabilizing effect that can also be exploited to improve the detection of easily cleavable molecules.

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Stability of luminescent trivalent cerium in silica host glasses modified by boron and phosphorus

Ce-doped borosilicate (BSG), phosphosilicate (PSG), and borophosphosilicate (BPSG) glasses (B:P:Si molar ratios 8:0:92, 0:8:92, and 8:8:84; Ce:Si molar ratio 1 x 10(-)(4) to 1 x 10(-)(2)) were prepared by the sol-gel method. High-resolution transmission electron microscopy (HRTEM), (31)P, (29)Si, and (11)B magic angle spinning nuclear magnetic resonance (MAS NMR), electron paramagnetic resonance (EPR), and UV-vis absorption investigations demonstrated that, in PSG and BPSG, Ce(3+) ions interact with phosphoryl, [O=PO(3/2)], metaphosphate, [O=PO(2/ 2)O](-), and pyrophosphate, [O=PO(1/2)O(2)](2)(-), groups, linked to a silica network. This inhibits both CeO(2) segregation and oxidation of isolated Ce(3+) ions to Ce(4+), up to Ce:Si = 5 x 10(-)(3). In BSG, neither trigonal [BO(3/2)] nor tetrahedral [BO(4/2)](-) boron units coordinate cerium; thus, Ce(3+) oxidation occurs even at Ce:Si = 1 x 10(-)(4), as in pure silica glass (SG). The homogeneous rare-earth dispersion in the host matrix and the stabilization of the Ce(3+) oxidation state enhanced the intensity of the photoluminescence emission in PSG and BPSG with respect to BSG and SG. The energy of the Ce(3+) emission band in PSG and BPSG matrixes agrees with the phosphate environment of the rare earth.     

Viscosities for Binary Mixtures of 1-Decanol, Hexane, and Diethylamine at 10, 25, and 40°C

Experimental viscosities provide information on the structure of liquids and are required in the design of processes, which involve fluid flow, mass transfer, or heat transfer calculations. This work reports experimental viscosity data of the binary mixtures: 1-decanol + hexane, 1-decanol + diethylamine, and hexane + diethylamine at 10, 25, and 40°C and atmospheric pressure for the whole range of compositions. The viscosities of the pure liquids and their mixtures were determined using Cannon Fenske viscometers thermostated at ±0.01°C. The estimated error in the measured viscosities was less than ±0.005 mPa-s. The dynamic viscosity and the excess energy of activation for viscous flow were also calculated. The equation of Redlich–Kister was used for fitting the excess properties of the binary mixtures. The excess viscosity shows positive deviations from ideal behavior for the mixtures 1- decanol + hexane and 1-decanol + diethylamine and a small negative deviation for the binary system hexane + diethylamine. The experimental results have been also used to test some empirical and semiempirical equations adopted previously to correlate viscosity composition data.