Crystallization and enzymatic degradation of novel poly(ε-caprolactone-co-propylene succinate) copolymers

A series of novel poly(ε-caprolactone-co-propylene succinate) P(CL-co-PSu) copolymers having low propylene succinate content and high molecular weight were synthesized following a combinatory scheme of ring opening and polycondensation reactions, in an attempt to obtain copolymers of sufficient performance and increased biodegradation rates. Enzymatic hydrolysis of the copolymers was studied in the presence of mixture of Rhizopus delemar and Pseudomonas cepacia lipases. Much higher hydrolysis rates, comparing to neat PCL, were proved by both mass loss measurements and scanning electron microscopy (SEM) observations of the degraded film surfaces. Thermodynamics of cocrystallization and wide-angle X-ray diffraction (WAXD) patterns were investigated to estimate the extent of comonomer cocrystallization. Results of the study showed that comonomer inclusion may hold, though the molar fraction of the comonomer in the PCL crystals is lower than in the bulk. This means that not only the observed decrease of the degree of crystallinity from about 48% for PCL to about 29% for the P(CL-co-PSu) 75/25 favours enzymatic hydrolysis, but also the enrichment of the amorphous phase in the fast degrading propylene succinate units plays its role. The non-isothermal crystallization rates of the copolymers, like the melting points, decreased substantially when the propylene succinate content exceeded 8 mol%. The activation energy of crystallization was calculated using the isoconversional method of Friedman, over the whole range of crystallization temperatures. An increase was found in the activation energy with increasing the comonomer content in the copolymers also proving the reduced symmetry along the copolymer chains due to the presence of comonomer units.     

Berth allocation at indented berths for mega-containerships

This paper addresses the berth allocation problem at a multi-user container terminal with indented berths for fast handling of mega-containerships. In a previous research conducted by the authors, the berth allocation problem at a conventional form of the multi-user terminal was formulated as a nonlinear mathematical programming, where more than one ship are allowed to be moored at a specific berth if the berth and ship lengths restriction is satisfied. In this paper, we first construct a new integer linear programming formulation for easier calculation and then the formulation is extended to model the berth allocation problem at a terminal with indented berths, where both mega-containerships and feeder ships are to be served for higher berth productivity. The berth allocation problem at the indented berths is solved by genetic algorithms. A wide variety of numerical experiments were conducted and interesting findings were explored.     

A Review of the Health Protective Effects of Phenolic Acids against a Range of Severe Pathologic Conditions (Including Coronavirus-Based Infections)

Phenolic acids comprise a class of phytochemical compounds that can be extracted from various plant sources and are well known for their antioxidant and anti-inflammatory properties. A few of the most common naturally occurring phenolic acids (i.e., caffeic, carnosic, ferulic, gallic, p-coumaric, rosmarinic, vanillic) have been identified as ingredients of edible botanicals (thyme, oregano, rosemary, sage, mint, etc.). Over the last decade, clinical research has focused on a number of in vitro (in human cells) and in vivo (animal) studies aimed at exploring the health protective effects of phenolic acids against the most severe human diseases. In this review paper, the authors first report on the main structural features of phenolic acids, their most important natural sources and their extraction techniques. Subsequently, the main target of this analysis is to provide an overview of the most recent clinical studies on phenolic acids that investigate their health effects against a range of severe pathologic conditions (e.g., cancer, cardiovascular diseases, hepatotoxicity, neurotoxicity, and viral infections—including coronaviruses-based ones).     

Designing an all-optical packet filtering module for WDM broadcast-and-select star networks

An all-optical packet filtering module for WDM broadcast-and-select star networks is introduced. At each time instant, only one packet per wavelength is allowed to pass to the star coupler. Therefore, collisions are avoided and the network performance is improved. The proposed module is based on the use of optical logic circuits for controlling the passing of the transmitted packets to the star coupler, without the need of optical to electronic translation or electronic processing of the network feedback information. In this way, the processing time is drastically reduced, while the need for slowly tunable optical filters is eliminated. Furthermore, due to the all-optical nature of the network hub, the reliability of the system is improved.     

On recognizing integer polyhedra

We give a simple proof that, determining whether a convex polytope has a fractional vertex, is NP-complete.Research supported by the National Science Foundation.     

Flow injection manifold for the direct spectrophotometric determination of bismuth in pharmaceutical products using Methylthymol Blue as a chromogenic reagent

A new simple and rapid flow injection method is reported for the direct determination of bismuth in pharmaceutical products. Methylthymol Blue (MTB) was used as a chromogenic reagent and the absorbance of the colored Bi(III)-MTB complex produced was monitored at 548 nm. The various chemical and physical variables were optimized and a study of interfering ions was also carried out. Linear calibration graphs were obtained from 0 to 100 mg l-1 Bi(m) (120 injections per hour). The precision was very good (sr = 1.3%) and the limit of detection was cL = 0.150 mg l-1. The average accuracy was also very good (er = 0.75%) and was evaluated by comparison of the results obtained with those claimed by the manufacturers. The method was found to be adequately selective, considering the ions that the samples contain.     

A simple model for calculating the compressibility of the transition-metal carbides and nitrides alloys ZrxNb1?xC and ZrxNb1?xN

The 4d-transition-metals carbides (ZrC, NbC) and nitrides (ZrN, NbN) in the rocksalt structure, as well as their ternary alloys, have been recently studied by means of a first-principles full potential linearized augmented plane waves method within the local density approximation. These materials are important because of their interesting mechanical and physical properties, which make them suitable for many technological applications. Here, by using a simple theoretical model, we estimate the bulk moduli of their ternary alloys Zr_xNb_1−xC and Zr_xNb_1−xN in terms of the bulk moduli of the end members alone. The results are comparable to those deduced from the first-principles calculations.     

Using clathrate hydrates for gas storage and gas-mixture separations: experimental and computational studies at multiple length scales

ABSTRACT

Clathrate hydrates have characteristic properties that render them attractive for a number of industrial applications. Of particular interest are the following two cases: (i) the incorporation of large amounts of gas molecules into the solid structure has resulted in considering hydrates as possible material for the storage/transportation of energy or environmental gases, and (ii) the selective incorporation of guest molecules into the solid structure has resulted in considering hydrates for gas-mixture separations. For the proper design of such industrial applications, it is essential to know accurately a number of thermodynamic, structural and transport properties. Such properties can either be measured experimentally or calculated at different scales that span the molecular scale-up to the continuum scale. By using clathrate hydrates as a particular case study, we demonstrate that performing studies at multiple length scales can be utilised in order to obtain properties that are essential to process design.