Porphyrin-based nanoporous network polymers

Network polymers exhibiting large surfaces areas (900-1000 m2g-1) are prepared by the highly efficient dibenzodioxane forming reaction between meso-tetrakis(pentafluorophenyl)porphyrin and a rigid bis(catechol) monomer.     

Detector technologies for comprehensive two-dimensional gas chromatography

The detector is an integral and important part of any chromatographic system. The chromatographic peak profiles (i.e. peak separation) should, ideally, be unaffected by the detector--it should only provide the sensing capacity required at the end of a column separation process. The relatively new technique of comprehensive 2-D GC (GC x GC) extends the performance of GC manyfold, but comes at a price--existing GC systems may not be adequately designed with the requirements of GC x GC in mind. This is primarily the need for precise measurement of very fast peaks entering the detector (e.g. as fast as 50 ms basewidth in some instances). The capacity of the detector to closely track a rapidly changing chromatographic peak profile depends on a number of factors, such as design of flow paths and make-up gas introduction, type of detector response mechanism, and the chemistry of the response. These factors are discussed here as a means to appreciate the technical demands of detection in GC x GC. The MS detector will not be included in this review.     

Analysis of organic compounds of water-in-crude oil emulsions separated by microwave heating using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry

In this work the higher peak capacity and resolution of comprehensive two-dimensional gas chromatography (GCxGC) has been successfully applied, for the first time, to tentatively identify several polar organic compounds of organic extracts of aqueous phases resulting from microwave demulsification process of water-in-crude oil emulsions. Results have shown that higher temperatures and longer exposure time to microwave irradiation produced water phases with a wider variety of polar organic compounds. The microwave process showed to be suitable for the extraction of several polar compounds classes of petroleum. The proposed microwave extraction method and GCxGC identification of polar compounds of petroleum samples are of practical interest for the petrochemical industry due to corrosion and related problems associated with these polar compounds in refinery equipments. The GCxGC/time-of-flight MS technique shows to be very important in the total separation of different classes of compounds and allows the identification of many compounds in these classes.     

Identification of the elastic properties of an artificial capsule membrane with the compression test: effect of thickness

The mechanical properties of a capsule membrane are evaluated by means of a compression experiment between two parallel plates. Since large deformations of the membrane are involved, the choice of the wall material constitutive law is essential. In this paper, we explore different classical laws to describe the behavior of the membrane and evaluate also the limit of application of the thin shell approximation. A numerical study of the compression process is performed using Abaqus software and an inverse method is used to identify the material constants of the constitutive laws. The comparison between the model predictions and experimental measurements on capsules with serum albumin-alginate membranes, indicates that the thin shell approximation is valid only for thickness to radius ratios up to 5% and that thick membranes obey non linear elastomer type constitutive laws. The Young modulus of the membrane material is found to increase non-linearly with membrane thickness, thus indicating that fabrication of thicker serum albumin-alginate walls results in capsules stiffer than expected.     

Mapping the intracellular fraction of water by varying the gradient pulse length in q-space diffusion MRI

Finite gradient pulse lengths are traditionally considered a nuisance in q-space diffusion NMR and MRI, since the simple Fourier relation between the acquired signal and the displacement probability is invalidated. Increasing the value of the pulse length leads to an apparently smaller value of the estimated compartment size. We propose that q-space data at different gradient pulse lengths, but with the same effective diffusion time, can be used to identify and quantify components with free or restricted diffusion from multiexponential echo decay curves obtained on cellular systems. The method is demonstrated with experiments on excised human brain white matter and a series of model systems with well-defined free, restricted, and combined free and restricted diffusion behavior. Time-resolved diffusion MRI experiments are used to map the spatial distribution of the intracellular fraction in a yeast cell suspension during sedimentation, and observe the disappearance of this fraction after a heat treatment.     

Palladium-catalyzed cross-coupling: a historical contextual perspective to the 2010 Nobel Prize

In 2010, Richard Heck, Ei-ichi Negishi, and Akira Suzuki joined the prestigious circle of Nobel Laureate chemists for their roles in discovering and developing highly practical methodologies for C-C bond construction. From their original contributions in the early 1970s the landscape of the strategies and methods of organic synthesis irreversibly changed for the modern chemist, both in academia and in industry. In this Review, we attempt to trace the historical origin of these powerful reactions, and outline the developments from the seminal discoveries leading to their eminent position as appreciated and applied today.