Effects of processing on the structure of zein/oleic Acid films investigated by x-ray diffraction

Zein films plasticized with oleic acid were formed by solution casting, by the stretching of moldable resins, and by blown film extrusion. The effects of the forming process on film structure were investigated by X-ray diffraction. Wide-angle X-ray scattering (WAXS) patterns showed d-spacings at 4.5 and 10 A, which were attributed to the zein alpha-helix backbone and inter-helix packing, respectively. The 4.5 A d-spacing remained stable under processing while the 10 A d-spacing varied with processing treatment. Small-angle X-ray scattering (SAXS) detected a long-range periodicity for the formed films but not for unprocessed zein, which suggests that the forming process-promoted film structure development is possibly aided by oleic acid. The SAXS d-spacing varied among the samples (130-238 A) according to zein origin and film-forming method. X-ray scattering data suggest that the zein molecular structure resists processing but the zein supramolecular arrangements in the formed films are dependent on processing methods. Structural model for a zein molecular aggregate (based on Matsushima et al.10). Rectangular prisms of individual zein molecules are hexagonally aligned parallel to each other.     

Optimized separation of scopoletin and umbelliferone and cis-trans isomers of ferulic and p-coumaric acids by reverse-phase high-performance liquid chromatography

A systematic optimization strategy for reverse-phase h.p.l.c. is used to produce complete separation of all components of a mixture containing two coumarins, umbelliferone and scopoletin, and the cis-trans isomers of two cinnamic acids, p-coumaric and ferulic. A series of experiments gives retention time data for each of these substances in four citric acid-buffered mobile phases. A mathematical model fitted to this data gives model parameters that provide the basis for a window diagram of relative retentions vs. mobile phase pH. The window diagram gives an estimate of the mobile phase pH required for optimum separation.     

Catalysts for the living insertion polymerization of alkenes: access to new polyolefin architectures using Ziegler-Natta chemistry

Coordination-insertion polymerization systems have long been superior to their anionic, cationic, and radical polymerization counterparts with regard to stereochemical control. However, until five years ago, these metal-based insertion methods were inferior to ionic and radical mechanisms in the category of living polymerization, which is simply a polymerization that occurs with rapid initiation and negligible chain termination or transfer. In the last half decade, the living insertion polymerization of unactivated olefins has emerged as a powerful tool for the synthesis of new polymer architectures. Materials available today by this route range from simple homopolymers such as linear and branched polyethylene, to atactic or tactic poly(alpha-olefins), to end-functionalized polymers and block copolymers. This review article summarizes recent developments in this rapidly growing research area at the interface of synthetic and mechanistic organometallic chemistry, polymer chemistry, and materials science. While special emphasis is placed on polymer properties and novel polymeric architectures, most of which were inaccessible just a decade ago, important achievements with respect to ligand and catalyst design are also highlighted.     

Comparison of dynamical heterogeneity in hard-sphere and attractive glass formers

Using molecular dynamics simulations, we have determined that the nature of dynamical heterogeneity in jammed liquids is very sensitive to short-ranged attractions. Weakly attractive systems differ little from dense hard-sphere and Lennard-Jones fluids. Particle motion is punctuated and tends to proceed in steps of roughly a single particle diameter. Both of these basic features change in the presence of appreciable short-ranged attractions. Transient periods of particle mobility and immobility cannot be discerned at intermediate attraction strength, for which structural relaxation is greatly enhanced. Strong attractions, known to dramatically inhibit relaxation, restore bimodality of particle motion. But in this regime, transiently mobile particles move in steps that are significantly more biased toward large displacements than those in the case of weak attractions. This modified feature of dynamical heterogeneity, which cannot be captured by conventional mode coupling theory, verifies recent predictions from a model of spatially correlated facilitating defects.     

Fluorescence-dip infrared spectroscopy and predissociation dynamics of OH A 2Sigma+ (v = 4) radicals

Fluorescence-dip infrared spectroscopy, an UV-IR double-resonance technique, is employed to characterize the line positions, linewidths, and corresponding lifetimes of highly predissociative rovibrational levels of the excited A (2)Sigma(+) electronic state of the OH radical. Various lines of the 4 <--2 overtone transition in the excited A (2)Sigma(+) state are observed, from which the rotational, centrifugal distortion, and spin-rotation constants for the A (2)Sigma(+) (v = 4) state are determined, along with the vibrational frequency for the overtone transition. Homogeneous linewidths of 0.23-0.31 cm(-1) full width at half maximum are extracted from the line profiles, demonstrating that the N = 0 to 7 rotational levels of the OH A (2)Sigma(+) (v = 4) state undergo rapid predissociation with lifetimes of < or =23 ps. The experimental linewidths are in near quantitative agreement with first-principles theoretical predictions.     

The European Eco-Management and Audit Scheme Accreditation – an overview

 Environmental quality is still deteriorating in the EU and worldwide despite all the Directives and Regulations in this field over the past 20 years. The European Community has devised a new approach to this problem with the introduction of the Eco-Management and Audit Scheme Regulation. This Regulation provides industry with an opportunity to demonstrate that it can achieve continuous improvement in its environmental performance through a voluntary scheme which is not based on the traditional command and control mechanisms of Directives. This paper gives an overview of the steps involved in implementing the European Eco-Management and Audit Scheme and the role of accreditation in supporting the scheme.     

A high-resolution micro-gel system for analyzing small amounts of protein with a wide diversity of molecular weights

We have used a micro-gel system to analyze the proteins in extracts of amphibian neurulae. Maximum band separation and resolution was achieved by using a dissociating discontinuous buffer with gels made of a discontinuous gradient of acrylamide.