The effect of 3D printing on the morphological and mechanical properties of polycaprolactone filament and scaffold

Three‐dimensional (3D) printing becomes an attractive technique to fabricate tissue engineering scaffolds through its high control on fabrication and repeatability using the printing parameters. This technique can be combined by the finite element method (FEM), and tissue‐specific scaffolds with desirable morphological and mechanical properties can be designed and manufactured. In this study, the influential 3D printing parameters on the morphological and mechanical properties of polycaprolactone (PCL) filament and scaffold were studied experimentally and numerically. First, the effects of printing parameters and process on the properties of extruded PCL filament were investigated. Then, using FEM, the effects of filament specifications on the overall characteristics of the scaffold were evaluated. Results showed that both the printing process in terms of resting time and remaining time and the printing parameters like pressure, printing speed, and printing path length have influenced the filament properties. In addition, both the filament diameter and elastic modulus had significant effects on the properties of scaffold especially, a 20% increase in the filament diameter caused the scaffold compressive elastic modulus to rise by around 72%. It is concluded that the printing parameters and process must be tuned very well in fabricating scaffolds with the desired morphology and mechanical property.     

Development of colorimetric sensor array for discrimination of herbal medicine

Today, traditional systems of medicines (such as herbal distillates) become important resources for providing healthcare benefits. The ability to discriminate among closely similar herbal products is critical to ensure their efficacy. This article proposes a pattern-based recognition approach for the rapid discrimination of herbal distillates using a low-cost and sensitive colorimetric sensor array composed of 25 indicators. The color changes of the sensor exposed to the vapor of the herbal distillates can be monitored easily with an ordinary flatbed scanner. The digital representation of the array response was analyzed with hierarchical clustering analysis (HCA) and principal component analysis (PCA). Using new variable selection strategy, 6 indicators among the 25 employed indicators were selected as discriminant elements of the array. So, a complete discrimination (with 100% accuracy) of 46 herbal distillates was achieved. The proposed sensor represented a better resolution when analytes were placed in an oven at 85 °C for 45 min. This colorimetric sensor array demonstrates excellent potential for quality assurance/control applications of herbal distillates.     

Chitosan‐Supported Ni particles: An Efficient Nanocatalyst for Direct Amination of Phenols

A practical method for the direct amination of phenols using 2,4,6‐trichloro‐1,3,5‐triazine (TCT) as an efficient promotor for the activation of phenols in the presence of an efficient and recyclable heterogeneous catalyst prepared by immobilization of nickel particles on triazole modified chitosan is described. This heterogeneous catalyst has demonstrated a promising activity for the conversion of phenolic compounds to their corresponding amine under mild conditions. Moreover, the obtained catalyst can be reused in five consecutive runs with consistent catalytic activity.     

The Effect of Asphalt Precipitation on Flow Behavior and Production of a Fractured Carbonate Oil Reservoir During Gas Injection

The first field data, collected over an 11 year period, are presented which indicate the possible effect of asphalt precipitation on the permeability and injectivity index of a fractured carbonate oil reservoir. The asphalt aggregates were formed during enhanced oil recovery by injection of a rich gas into the reservoir. The data indicate that, while at the initial stages of the operations the permeability and injectivity index decrease, at later times they appear to oscillate with the process time, with apparent oscillations' periods that depend on the heterogeneity of the reservoir. Two classes of plausible mechanisms that give rise to such oscillatory behavior are discussed. One relies on the changes in the structure of the reservoir's fractures, while the other one is based on asphalt precipitation in the reservoir. Computer simulations of flow and precipitation of asphalt aggregates in a pore network model of the reservoir are carried out. The results appear to support our proposition that asphalt formation and precipitation in the reservoir are the main mechanism for the observed behavior of the injectivity index. We also develop a stochastic continuum model that accurately predicts the time-dependence of the reservoir's permeability and injectivity index during the gas injection process.     

Iron‐catalyzed cross‐coupling reaction: Heterogeneous palladium and copper‐free Heck and Sonogashira cross‐coupling reactions catalyzed by a reusable Fe(III) complex

An interesting silica‐supported iron catalyst was successfully prepared and demonstrated as an efficient heterogeneous catalyst for cross‐coupling reactions of aryl halides. The as‐prepared nanocatalyst was well characterized and found to be highly efficient in Heck reaction under mild and sustainable conditions (water as solvent at 80 °C in short reaction time). Furthermore, the obtained catalyst was used as an efficient, inexpensive and green heterogeneous catalyst for Sonogashira cross‐coupling reactions of various aryl iodides and provided the corresponding products with moderate to good yields. This phosphine, copper and palladium‐free catalyst was simply recovered from the reaction mixture and recycled five times without substantial decrease in its catalytic activity.     

Simultaneous measurement of leucine and isoleucine by multivariate image analysis-thin layer chromatography (MIA-TLC)

This paper introduces a new application of multivariate image analysis-thin layer chromatography, as simple and inexpensive method, for semi-separation and simultaneous measurement of two isomeric amino acids leucine (Leu) and isoleucine (Ile). The images recorded by a digital camera were processed by home-made software and were converted to TLC chromatograms. Linear calibration graphs were obtained for individual analytes with detection limits of 0.60 and 0.48 μg for Leu and Ile, respectively. The mobile phase composition was optimized for maximum separation. However, complete separation of the spots of the analytes was not obtained. So, the chromatograms were processed by partial least square regression to resolve the overlapped chromatogram. This offered simultaneous determination of Leu and Ile in their binary mixtures. Suitable models were obtained with root mean square error of prediction of 0.008 and 0.009 μg for Leu and Ile, respectively. The prediction ability of the developed model was assessed by determination of the analytes in diluted serum plasma and the obtained percent of recoveries were in the range of 95–105 %.     

Stability of mixed additive-quadratic Jensen type functional equation in non-Archimedean \ell -fuzzy normed spaces

In this papers we prove the generalized Hyers–Ulam–Rassias stability of the following mixed additive-quadratic Jensen functional equation $$\begin{aligned} 2f\left( \frac{x+y}{2}\right) +f\left( \frac{x-y}{2}\right) +f\left( \frac{y-x}{2}\right) =f(x)+f(y) \end{aligned}$$ in non- Archimedean \(\ell \) -fuzzy normed spaces.     

Common fixed point theorems for three maps in discontinuous Gb metric spaces

In [Aghajani A, Abbas M, Roshan JR. Common fixed point of generalized weak contractive mappings in partially ordered G_b-metric spaces. Filomat, 2013, in press], using the concepts of G-metric and b-metric Aghajani et al. defined a new type of metric which is called generalized b-metric or G_b-metric. In this paper, we prove a common fixed point theorem for three mappings in G_b-metric space which is not continuous. An example is presented to verify the effectiveness and applicability of our main result.