Time-resolved ESR study of the lowest excited triplet states of para-quinones in glassy matrices at 77 k

The lowest excited nπ* triplet of 9.10-anthraquinone, 1.4-naphthoquinone and 1,4-benzoquinone were studied in glassy matrices at 77 K using a time-resolved ESR method. The D value of the triplet state of 9,10-anthraquinone varied from ?0.351 cm^?1 in a polar solvent to ?0.318 cm^?1 in a non-polar solvent. Both 1,4-naphthoquinone and 1,4-benzoquinone in polar solvents showed triplet state spectra with a D value of ?0.330 cm^?1. A computer simulation revealed the existence of widely distributed zero-field splitting parameters in the glassy condition. These data are compared with an analysis of CIDEP results of para-quinones.     

Multiscaling analysis of a slowly varying anaerobic digestion model

We construct the slowly varying limiting state solutions to a nonlinear dynamical system for anaerobic digestion with Monod-based kinetics involving slowly varying model parameters arising from slow environmental variation. The advantage of these approximate solutions over numerical solutions is their applicability to a wide range of parameter values. We use these limiting state solutions to develop analytic approximations to the full nonlinear system by applying a multiscaling technique. The approximate solutions are shown to compare favorably with numerical solutions.     

Recent developments in polyetherimide membrane for gas separation

Polyetherimide (PEI) is an extraordinary type of polyimide with excellent thermal and mechanical properties. The polymer is also gas permeable and is considered one of the best membranes for gas separation. Despite the high selectivity, PEI suffers from low permeability due to the trade‐off between phenomena in polymers. To overcome this limitation, fillers are added during the membrane preparation to create voids for better gas transport. In this paper, permeability and selectivity data of PEI membranes for the separation of oxygen, carbon dioxide, and helium are discussed. The paper also summarizes the reported studies for adding fillers to improve the membrane performance.     

Separation of organohalides from their microemulsions by the pervaporation technique: Application to the n-butyl bromide/SDS/n-butanol/water system

An n-butyl bromide/sodium dodecyl sulfate/n-butanol/water microemulsion system was chosen as a model of an organohalide-containing microemulsion. Two systems were prepared using the Bourayne method: a water-rich system and an n-butyl-bromide-rich system. The destabilization of this micro-organized system and the phase separation were investigated. This microemulsion, in which the oil phase in the feed is the lower layer, was successfully destabilized using the pervaporation technique with polydimethylsiloxane and poly(vinyl alcohol) membranes. In this way, different factors governing the separation process were investigated such as the mass transfer and the effect of time and operating temperature on the microemulsion destabilization.     

In situ palladium/N-heterocyclic carbene complex catalyzed carbonylative cross-coupling reactions of arylboronic acids with 2-bromopyridine under CO pressure: efficient synthesis of unsymmetrical arylpyridine ketones and their antimicrobial activities

Transition Metal Chemistry - The carbonylative Suzuki cross-coupling of 2-bromopyridine with various boronic acids to prepare unsymmetrical arylpyridine ketones has been carried out using...     

Assessment of Environmental Quantitative Variation of Diosgenin in Fenugreek Seeds via High-Performance Thin-Layer Chromatography Method

JPC – Journal of Planar Chromatography – Modern TLC - Fenugreek is one of the oldest medicinal plants known by mankind. The aim of this study is to evaluate the effect of environmental...     

Determination of the composition,encapsulation efficiency and loading capacity in protein drug delivery systems using circular dichroism spectroscopy

Peptides and proteins have become very promising drug candidates in recent decades due to their unique properties. However, the application of these drugs has been limited by their high enzymatic susceptibility, low membrane permeability and poor bioavailability when administered orally. Considerable efforts have been made to design and develop drug delivery systems that could transport peptides and proteins to targeted area. Although it is of great importance to determine the composition after loading a drug to the carrier, the ability to do so is significantly limited by current analytical methods. In this letter, five important proteins, α₁-antitrypsin, hemoglobin human, human serum albumin, human transferrin and r-globulin were chemically conjugated to two model drug carriers, namely carbon dots and polymer O-(2-carboxyethyl) polyethylene glycol. A simple yet convenient method based on circular dichroism spectroscopy was developed to determine the compositions of the various protein-carrier conjugates.     

Synchronization of the Glycolysis Reaction-Diffusion Model via Linear Control Law

The Selkov system, which is typically employed to model glycolysis phenomena, unveils some rich dynamics and some other complex formations in biochemical reactions. In the present work, the synchronization problem of the glycolysis reaction-diffusion model is handled and examined. In addition, a novel convenient control law is designed in a linear form and, on the other hand, the stability of the associated error system is demonstrated through utilizing a suitable Lyapunov function. To illustrate the applicability of the proposed schemes, several numerical simulations are performed in one- and two-spatial dimensions.     

Dynamics and control in an $$({\varvec{n}}+{\varvec{2}})$$ ( n + 2 ) -neuron BAM network with multiple delays

Nonlinear Dynamics - The issues of the stability and bifurcation for a delayed BAM network involving two neurons in the I-layer and arbitrary neurons in the J-layer are concerned in the present...     

Simultaneous Deconvolution of the Molecular Weight and Chemical Composition Distribution of Polyolefins Made with Ziegler-Natta Catalysts

Heterogeneous Ziegler-Natta catalysts produce polyolefins that have broad distributions of molecular weight (MWD) and chemical composition (CCD). For such broad distributions, mathematical models are useful to quantify the information provided by polyolefin analytical techniques such as high-temperature gel permeation chromatography (GPC), temperature rising elution fractionation (TREF), and crystallization analysis fractionation (CRYSTAF). In this paper, we developed a mathematical model to deconvolute the MWD and CCD of polyolefins simultaneously, using Flory's most probable distribution and the cumulative CCD component of Stockmayer's distribution. We have applied this procedure to “model” polyolefin resins and to one industrial linear low-density polyethylene (LLDPE) resin. The proposed methodology is able to deconvolute theoretical distributions even when random noise is added to the MWDs and CCDs, and it can be used to calculate the minimum number of active site types on heterogeneous Ziegler-Natta catalysts.