Vibrational Analysis for an Axially Moving Microbeam with Two Temperatures

In this article, the effect of two temperatures on an axially moving microbeam subjected to ramp-type heating is studied. The generalized thermoelasticity theory with one relaxation time model is used. The governing equations are expressed in Laplace transform domain. Based on Fourier series expansion technique, the inversion of Laplace transform is done numerically. Some comparisons have been shown in figures to present the effect of the temperature discrepancy and the transport speed on all the studied field quantities. Additional results across the thickness of the microbeam are presented graphically.     

Bimetal cup hydroforming of Al/St and Cu/St composites: Adaptive finite element analysis and experimental study

Journal of Mechanical Science and Technology - An adaptive Finite element analysis (FEA) was proposed in this paper for the industrial design of bimetal conical-cylindrical cup hydroforming....     

New syntheses of pyrazolo[3,4-d]pyrimidine,pyrazolo[3,4-d]pyridazine,isoindolinedione and pyrazole derivatives

Phenacylmalononitriles 2 react with hydrazines, acetic-hydrochloric acid and with diazotised primary aromatic amines to afford phenacylpyrazole ( 5a,b ), aminofurans ( 6a,b ) and aminopyrazole derivatives ( 3a,d ) respectively. The synthesised derivatives ( 3d, 6a ) were the key materials for the synthesis of isoindolinedione, ( 7a – c ) pyrazolopyrimidine ( 9, 10 ), and pyrazolopyridazine derivatives ( 11 ). The structures of the newly synthesised heterocycles were established on the basis of elemental analyses and spectral data besides synthesis via other routes.     

Biofilm and Small Colony Variants—An Update on Staphylococcus aureus Strategies toward Drug Resistance

Recently, the drawbacks arising from the overuse of antibiotics have drawn growing public attention. Among them, drug-resistance (DR) and even multidrug-resistance (MDR) pose significant challenges in clinical practice. As a representative of a DR or MDR pathogen, Staphylococcus aureus can cause diversity of infections related to different organs, and can survive or adapt to the diverse hostile environments by switching into other phenotypes, including biofilm and small colony variants (SCVs), with altered physiologic or metabolic characteristics. In this review, we briefly describe the development of the DR/MDR as well as the classical mechanisms (accumulation of the resistant genes). Moreover, we use multidimensional scaling analysis to evaluate the MDR relevant hotspots in the recent published reports. Furthermore, we mainly focus on the possible non-classical resistance mechanisms triggered by the two important alternative phenotypes of the S. aureus, biofilm and SCVs, which are fundamentally caused by the different global regulation of the S. aureus population, such as the main quorum-sensing (QS) and agr system and its coordinated regulated factors, such as the SarA family proteins and the alternative sigma factor σB (SigB). Both the biofilm and the SCVs are able to escape from the host immune response, and resist the therapeutic effects of antibiotics through the physical or the biological barriers, and become less sensitive to some antibiotics by the dormant state with the limited metabolisms.     

pH Responsive Abelmoschus esculentus Mucilage and Administration of Methotrexate: In-Vitro Antitumor and In-Vivo Toxicity Evaluation

The rapid progression in biomaterial nanotechnology apprehends the potential of non-toxic and potent polysaccharide delivery modules to overcome oral chemotherapeutic challenges. The present study is aimed to design, fabricate and characterize polysaccharide nanoparticles for methotrexate (MTX) delivery. The nanoparticles (NPs) were prepared by Abelmoschus esculentus mucilage (AEM) and chitosan (CS) by the modified coacervation method, followed by ultra-sonification. The NPs showed much better pharmaceutical properties with a spherical shape and smooth surface of 213.4–254.2 nm with PDI ranging between 0.279–0.485 size with entrapment efficiency varying from 42.08 ± 1.2 to 72.23 ± 2.0. The results revealed NPs to possess positive zeta potential and a low polydispersity index (PDI). The in-vitro drug release showed a sustained release of the drug up to 32 h with pH-dependence. Blank AEM -CS NPs showed no in-vivo toxicity for a time duration of 14 days, accompanied by high cytotoxic effects of optimized MTX loaded NPs against MCF-7 and MD-MBA231 cells by MTT assay. In conclusion, the findings advocated the therapeutic potential of AEM/CS NPs as an efficacious tool, offering a new perspective for pH-responsive routing of anticancer drugs with tumor cells as a target.     

Tepary Bean Starch Part III: In vitro Digestibility

In vitro digestibility of starch from tepary bean, Phaseolus acutifolius var. latifolius, was determined in comparison with tepary bean flour and maize starch. The extent of sample hydrolysis by α-amylase was measured as mg reducing sugar (maltose) released per 100 mg substrate. After 2 h incubation at 37°C, values obtained for tepary starch, tepary flour and maize starch treated in various ways were as follows: raw 8.0, 8.6 and 25.6; freeze dried 2.6, 3.2 and 17.8; autoclaved 7.4, 5.7 and 27.7; cooked (15 min) 81.7, 23.1 and 87.8; resp. Raw tepary starch was more resistant to hydrolysis than maize starch due, perhaps, to differences in granule structure and amylose content. Freeze-drying and autoclaving slightly decreased digestibility of both tepary starch and flour. Cooking greatly increased susceptibility to hydrolysis for each substrate. The rate of increase was reduced after 15 min exposure to enzymes, and no appreciable difference was found between cooked tepary and maize starches.     

The effect of microencapsulation with nitrocellulose on thermal properties of sodium azide particles

Based on the coacervation principle a solvent/non-solvent method has been used for microencapsulation of sodium azide (NaN₃) with fibrous nitrocellulose (NC). Scanning electron microscopy (SEM) was employed to examine the coating morphology. The thermal behavior of solid samples has been studied by means of thermogravimetry (TG) and differential scanning calorimetry (DSC). The results of TG–DTA analysis revealed that the main thermal degradation for the pure NC and NaN₃ occurs in the temperature ranges of 192–220 and 415–420 °C, respectively. The effects of some parameters, such as NC to NaN₃ weight ratio and volume and addition time of non-solvent, on coating quality and thermal properties have been investigated by SEM and thermal methods. The results of these experiments showed that the decomposition temperature of most stabilized coated sodium azide is about 50 °C higher than that of the pure sample. The DSC experiments were conducted to study the influence of the heating rate (5, 10, 15 and 20 °C/min) on the thermal decomposition processes of the pure NC, coated and pure NaN₃ samples. The results revealed that, as the heating rate was increased, decomposition temperature of the compounds was increased. Also, the kinetic parameters such as activation energy and frequency factor of the decomposition processes were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Our finding showed that coated NaN₃ has lower decomposition rate with respect to the pure one.     

Flexible polymer composite electromagnetic crystals

The dielectric properties of a ceramic powder (BaTiO₃) filled thermoplastic elastomer (EPDM TPE) were investigated for use in a flexible electromagnetic crystal. Materials were produced that had a high dielectric constant (approximately 9) and low loss tangent (less than 0.01). Materials were extruded and injection molded so as to povide low‐cost processing. Mechanical and electromagnetic test results showed the effect of processing conditions on the final quality of the composite. The shear rate during processing and the number of mixing cycles were found to affect the final material characteristics significantly. An electromagnetic crystal woven from extruded rods showed good reflectivity in the 10–15 GHz region.     

Synthesis,properties, and applications of polylactic acid-based polymers

Polylactic acid (PLA) is known as one of the greatest promising bioabsorbable and compostable polyesters with the capability of high molecular weight synthesis. Lactic acid condensation, azeotropic dehydration, and condensation ring-open polymerize of lactide are three methods for PLA polymerization. Comprehension of material properties is critical for choosing the right processing method and adjusting PLA characteristics. A variety of mechanical properties of this material, from soft and elastic to stiff and high strength makes PLA suitable for a wide range of applications. Besides, PLA can be blended or copolymerized with other polymeric or non-polymeric substances. Thus, this polymer can achieve suitable chemical, mechanical, and rheological properties. Understanding the role of these properties and selecting a suitable processing technique is necessary for its intended consumer and various applications. This study elaborated a general summary of the polymerization, processing, and characteristics of PLA (i.e., structural diversities, rheological performances, mechanical properties, and permeability). Besides, this work presented some information regarding essential factors that can be used for modifying PLA properties to address the requirements for various applications such as biomedical, food packing, biocomposite, and additive manufacturing.     

Investigating the effect of zirconium-based and titanium-based metal–organic frameworks nanoparticles on the performance of polysulfone hollow fiber mixed matrix membrane for dialysis application

This study aims to investigate polysulfone (PSF) mixed matrix membranes (MMMs) properties containing zirconium-based and titanium-based metal–organic frameworks (MOFs). for hemodialysis application. The nanoparticles were synthesized, and the membranes were produced by the phase inversion method. Membrane characterization conducted by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), field emission Scanning electron microscope (FE-SEM), energy-dispersive x-ray analysis (EDX), transmission electron microscopy (TEM), x-ray diffraction (XRD), and atomic force microscopy (AFM) confirmed the presence of MOF nanoparticles. Also, the evaluation of the specific surface area of nanoparticles was done by BET. The water contact angle reduced from 64.4° to 51.2°, indicating the hydrophilicity improvement, enhancing the pure water flux from 46.8 L/m²h for the pristine membrane to 76.7 L/m2h for the pristine membrane M₄. The total fouling resistance decreased from 30% to 21%, and the bovine serum albumin (BSA) adsorption of modified membranes was lower than that of the pristine membrane. Urea and creatinine were cleared significantly for modified ones, up to 82.6% and 72.1%, respectively, and all membranes showed BSA retention of more than 93%. A comparison between MMMs that contained UIO-66-NH₂ and MIL-125-NH₂ showed that the former had a better effect on the performance. M₄ had better results, indicating high water flux, the lowest fouling resistance, high porosity, lower BSA adsorption, proper clearance for urea and creatinine, and 94.2% BSA retention.