A Novel Alternative Method for Modeling the Effects of Air Temperature and Slice Thickness on Quality and Drying Kinetics of Tomato Slices: Superposition Technique

The effect of air temperature (AT) and slice thickness (ST) on the quality and drying kinetics of tomato slices were studied. The drying period of tomato slices to reach the moisture content of 15% (wb) ranged from 2.6 to 18.7 h. The water diffusivity, activation energy, and resistance to diffusion ranged from 1.4 × 10^?10 to 2.8 × 10^?9 m²/s, 21.25 to 23.4 kJ/mol, and from 939 to 4590 m² s/kg, respectively. Drying had a significant effect on ascorbic acid, soluble solid, acidity, and pH (P = 0.01). The ascorbic acid degradation was greatly influenced by ST. The results show that time-temperature superposition technique (TTST) was very efficient in the modeling of the drying process. The proposed TTST provides a novel alternative in curve-fitting exercise of drying data. Neural networks also showed favorable performance in estimating the drying functions.     

Novel composite nanofibers based on polyamide 66/graphene oxide- grafted aliphatic- aromatic polyamide: preparation and characterization

New polyamide 66/graphene oxide (GO)-grafted aliphatic-aromatic polyamide (polyamide-imide) (PAI) (PA66/GOF) composites nanofibers were successfully prepared via electrospinning method for the first time. An polyamide imide (PAI) was synthesized using polycondensation reaction from a dicarboxylic acid and a diamine based on 4,4′-(4,4′-isopropylidenediphenyl-1,1′-diyldioxy) dianiline, and characterized by ¹HNMR and FTIR. Morphological, structural, thermal and mechanical characteristics of the nanocomposite fibers were investigated by means of SEM, TEM, WAXD, DMTA and TGA techniques. Composites nanofibers of PA66/GO, PA66/PAI and PA66/GOF with smooth surface, uniform structure as well as with diameter ranging from 195 to 784 nm were obtained. The GO incorporation caused a reduction in the nanofibers diameters. The TEM images showed that the GO was well dispersed in the PA66 nanofibers without significant aggregation. An approximately 10 °C temperature increase in the glass transition temperature of PA66 was achieved by addition of 0.5 wt% of PAI, resulting from aliphatic-aromatic structure of PAI. By the TGA results, an increase about 40 °C was observed in the thermal stability of PA66/PAI composite nanofibers in comparison with that of pure PA66 nanofibers.     

Polyacrylamides revisited: flocculation of kaolin suspensions and mature fine tailings

A series of acrylamide‐based water‐soluble (co)polymers was synthesized and they were investigated as flocculants of model kaolin suspensions and mature fine tailings of oil sands. The effects of molar mass, charge density, and polymer concentration on flocculation efficiency were studied by monitoring the initial settling rate during sedimentation. Hydrolyzed polyacrylamide (HPAM) with high molar mass and intermediate acrylic acid contents (0.14–0.41 mol/mol (14–41 mol%)) performed better in flocculation tests on kaolin suspensions requiring lower dose for maximum initial settling rate than native polyacrylamide (PAM). Surface force measurements showed that at low polymer concentrations (1 ppm), the partially‐adsorbed polymer induced a bridging attraction between the mica surfaces. Increasing the polymer concentration to 10 and 50 ppm caused purely repulsive forces. The presence of anionic groups in HPAM led to stronger repulsion, which was also demonstrated by the higher viscosity and larger hydrodynamic radius of the charged polymer. The charge‐induced increase in the viscosity of polymer solutions was suppressed by the screening effect of salts in a buffer solution and reducing the viscosity is desirable in the injection of flocculants in the industrial process.     

Continuous Application of Polyglycerol‐Supported Salen in a Membrane Reactor: Asymmetric Epoxidation of 6‐Cyano‐2,2‐dimethylchromene

In the current work, suitability of hyperbranched polyglycerol as a high loading catalyst support is demonstrated. A polyglycerol‐supported manganese‐salen complex (chemzyme) is applied as a homogeneous catalyst in the epoxidation of 6‐cyano‐2,2‐dimethylchromene. The recyclability of the corresponding catalyst was investigated in repetitive batch experiments as well as a continuous operation of the reaction in an ultrafiltration membrane reactor. An enhanced stability of the catalyst in repetitive batches was observed as a result of immobilization whereby the total turnover number increased from 23 in a single batch to 80 in four repetitive batches. To enable continuous operation, a continuously operated, stirred tanked reactor (CSTR) was equipped with an ultrafiltration membrane (MPF‐50) and a retention of 98% was determined. The continuous chemzyme membrane reactor was operated over the course of 20 residence times. After approximately 12 residence times, the steady state was reached yielding 70% conversion as well as an enantiomeric excess up to 92%. A space‐time yield (sty) of 458 g L ⁻¹ d⁻¹ and a turnover frequency (TOF_reaction) of up to 18 h⁻¹ was reached in the steady state. It was determined that the total turnover number (TTN) was enhanced by a factor of 10 from 24 (batch) up to 240 for 20 residence times in CSTR operation.     

Discontinuous Double-shell Domes through Islamic eras in the Middle East and Central Asia: History, Morphology, Typologies, Geometry, and Construction

This paper presents a developed geometric approach for deriving the typologies and geometries of discontinuous double-shell domes in Islamic architecture. Common geometric attributes are created using a corpus of twenty one domes that were built in the Middle East and Central Asia, beginning from the early through to the late Islamic periods. An outline of the origin and development of the discontinuous double-shell domes and their morphological features are addressed. Using the al-Kashi geometrical essences, a four-centered profile as an initial shape is constructed based on new geometric parameters to deduce the geometric commonalities of the two aspects of formal language (typologies and geometries) of such domes. Common geometric prototypes for typical profiles shared by the study cases are generated and formulated according to a proposed system. The theoretical frame work for the formal language of discontinuous double-shell dome architecture is structured to indicate a moderate development of this sort of Islamic domes and highlight the specific geometric relationship between the Islamic domical configurations and practical mathematic rules for many decades. It can also be established a basic approach for considering the geometric compositional designs and the typological derivations of the other eastern domes.