Design and testing of varying magnetic field effect in a pulsatility blood flow of viscoelastic material: Flexibility analysis in a curved channel

This paper attempts to investigate the peristaltic mechanism of Williamson fluid in a pipe flow under the influence of variable radial magnetic field along with slip effects and compliant walls. Viscous dissipation and thermophoresis effects are also considered. The solutions of coupled nonlinear ordinary differential equations are obtained using the perturbation technique and results are graphically represented. The effects on heat, mass, velocity, and heat transfer coefficient are studied under various pertinent parameters. The outcomes of the present model can be applied in various fields of biomedical engineering where smart peristaltic pumps can be engineered to transport the biological fluids without any contamination. The scope of the present article is valuable in explaining the blood transport dynamics in small vessels while considering the important wall features with chemical reaction characteristics.     

Deciphering the Effect of Lysine Acetylation on the Misfolding and Aggregation of Human Tau Fragment 171IPAKTPPAPK180 Using Molecular Dynamic Simulation and the Markov State Model

The formation of neurofibrillary tangles (NFT) with β-sheet-rich structure caused by abnormal aggregation of misfolded microtubule-associated protein Tau is a hallmark of tauopathies, including Alzheimer’s Disease. It has been reported that acetylation, especially K174 located in the proline-rich region, can largely promote Tau aggregation. So far, the mechanism of the abnormal acetylation of Tau that affects its misfolding and aggregation is still unclear. Therefore, revealing the effect of acetylation on Tau aggregation could help elucidate the pathogenic mechanism of tauopathies. In this study, molecular dynamics simulation combined with multiple computational analytical methods were performed to reveal the effect of K174 acetylation on the spontaneous aggregation of Tau peptide ¹⁷¹IPAKTPPAPK¹⁸⁰, and the dimerization mechanism as an early stage of the spontaneous aggregation was further specifically analyzed by Markov state model (MSM) analysis. The results showed that both the actual acetylation and the mutation mimicking the acetylated state at K174 induced the aggregation of the studied Tau fragment; however, the effect of actual acetylation on the aggregation was more pronounced. In addition, acetylated K174 plays a major contributing role in forming and stabilizing the antiparallel β-sheet dimer by forming several hydrogen bonds and side chain van der Waals interactions with residues I171, P172, A173 and T175 of the corresponding chain. In brief, this study uncovered the underlying mechanism of Tau peptide aggregation in response to the lysine K174 acetylation, which can deepen our understanding on the pathogenesis of tauopathies.     

Degradation of methotrexate by UV/peroxymonosulfate: Kinetics,effect of operational parameters and mechanism

Methotrexate (MTX) is one of the most consumed anti-cancer drugs in the pharmaceutical market around the world. The widespread occurrence of MTX in aquatic environment through hospital effluent has attracted increasing concern due to its potential to induce water pollution. In the present study, the degradation of MTX in aqueous medium was investigated by UV-activated peroxymonosulfate (PMS). A significant improvement in degradation rate by increasing UV intensity and PMS concentration while the decrease in degradation efficiency with the increase of solution pH and initial concentration of MTX was observed. The proposed UV/PMS process could achieve more than 90% MTX degradation in 30 min with a good mineralization degree (65%). A pseudofirst order kinetic model was employed and successfully predicted the degradation of MTX. The effect of other operational parameters such as the initial concentration of the targeted compound, dosage of oxidant (PMS), solution pH and UV intensity on the degradation rate were investigated. At the last, the main transform intermediates were identified using LC-MS and possible degradation pathways were proposed. The results show that UV/ PMS can be used as an efficient technology to treat pharmaceuticals such as methotrexate containing water and wastewater.     

CuxNi1-xO nanostructures and their nanocomposites with reduced graphene oxide: Synthesis,characterization, and photocatalytic applications

NiO nanostructure was synthesized using a simple co-precipitation method and was embedded on reduced graphene oxide surface via ultrasonication. Structural investigations were made through X-ray diffraction (XRD) and functional groups were confirmed by Fourier transform infrared spectroscopy (FTIR). XRD analysis revealed the grain size reduction with doping. Fourier transform infrared spectroscopy confirmed the presence of metal-oxygen bond in pristine and doped NiO nanostructure as well as the presence of carbon containing groups. Scanning electron microscopy (SEM) indicated that the particle size decreased when NiO nanostructure was doped with copper. BET surface area was found to increase almost up to 43 m²/g for Cu doped NiO nanostructure/rGO composite. Current-voltage measurements were performed using two probe method. UV–Visible spectroscopic profiles showed the blue and red shift for Cu doped NiO nanostructure and Cu doped NiO Nanostructure/rGO composite respectively. Rate constant for Cu doped NiO nanostructure/rGO composite found to increase 4.4 times than pristine NiO nanostructure.     

Determining the mechanical properties of epoxy resin (DGEBA) composites by ultrasonic velocity measurement

In this study, the composites of diglycidyl ether of bisphenol A (DGEBA) epoxy resin that have been formed by mixing epoxy resin with allyl glycidyl ether (AGE) and 2,3‐epoxypropyl methacrylate [glycidyl methacrylate (GMA)] were prepared in weight % ratios of 90 : 10, 80 : 20, and 70 : 30. A computer controlled analyzer with 35 MHz and a digital oscilloscope with 60 MHz were used for measuring the velocities of ultrasonic wave. The measurement of ultrasonic velocity carried out by pulse echo method at frequencies of 2.25 and 3.5 MHz at room temperature. The values of acoustic impedance (Z), Poisson ratio (μ), and coefficients of elasticity (L, G, K, E) of composites were calculated by values of densities and velocities that obtained. Thus, the effect of modificating epoxy resin (DGEBA) by AGE and GMA on mechanical properties of DGEBA was investigated using the ultrasonic method. Atomic force microscopy has been used for determining the microstructure of composites. By the results obtained from the investigation, it have been established that the longitudinal and shear ultrasonic wave velocities, and the values of all the elasticity constants of DGEBA were increased by modification with AGE and GMA. Also the most suitable combination ratio for the compound of DGEBA : AGE and DGEBA : GMA has been found as 80 : 20. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Study of nanofiber scaffolds of PAA,PAA/CS,and PAA/ALG for its potential use in biotechnological applications

In recent times, electrospun nanofibers have been widely studied from several biotechnological approaches; in this work, poly(acrylic acid) (PAA) solutions mixed with chitosan and alginate were electrospun and characterized to determine the behavior of these fibers when used in combination with bacteria, different samples were incubated with the bacterial strains: Streptomyces spp., Micromonospora spp., and Escherichia coli and a OD600 test was performed. The formation of nanofibers via electrospinning and the physicochemical properties of the obtained fibers were evaluated. Results showed that the presence of chitosan enhanced the thermal stability of PAA, since PAA/alginate fibers lost 5% of their mass at 41°C, whereas PAA/chitosan lost this amount at around 125°C. The fibers demonstrated suitable characteristics to be used as a bacteria bioreactor.     

Effect of sparse long‐chain branching on the step‐strain behavior of a series of well‐defined polyethylenes

The effect of sparse long chain branching, LCB, on the shear step‐strain relaxation modulus is analyzed using a series of eight high‐density polyethylene (HDPE) resins. Strains of 1 to 1250% are imposed on materials with LCB content ranging from zero to 3.33 LCB per 10,000 carbon atoms. All materials are observed to obey time–strain separation beyond some characteristic time, τ_k. The presence of LCB is observed to increase the value of τ_k relative to the linear resin. The behavior of the relaxation modulus at times shorter than τ_k is investigated by an analysis of the enhancement seen in the linear relaxation modulus, G⁰(t), as a function of strain and LCB content. This enhancement is seen to (1) increase with increasing strain in all resins, (2) be significantly larger in the sparsely branched HDPE resins relative to the linear HDPE resin, and (3) increase in magnitude with increasing LCB content. The shape and smoothness of the damping function is also investigated. The finite rise time to impose the desired strain is compared to the Rouse relaxation time of linear HDPE resins studied. Sparse LCB is found to increase the magnitude of the relaxation modulus at short times relative to the linear resin. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Multiscale Modeling for Food Drying: State of the Art

Plant‐based food materials are mostly porous in nature and heterogeneous in structure with huge diversity in cellular orientation. Different cellular environments of plant‐based food materials, such as intercellular, intracellular, and cell wall environments, hold different proportions of water with different characteristics. Due to this structural heterogeneity, it is very difficult to understand the drying process and associated morphological changes during drying. Transport processes and morphological changes that take place during drying are mainly governed by the characteristics of and the changes in the cells. Therefore, to predict the actual heat and mass transfer process that occurs in the drying process and associated morphological changes, development of multiscale modeling is crucial. Multiscale modeling is a powerful approach with the ability to incorporate this cellular structural heterogeneity with microscale heat and mass transfer during drying. However, due to the huge complexity involved in developing such a model for plant‐based food materials, the studies regarding this issue are very limited. Therefore, we aim in this article to develop a critical conceptual understanding of multiscale modeling frameworks for heterogeneous food materials through an extensive literature review. We present a critical review on the multiscale model formulation and solution techniques with their spatial and temporal coupling options. Food structure, scale definition, and the current status of multiscale modeling are also presented, along with other key factors that are critical to understanding and developing an accurate multiscale framework. We conclude by presenting the main challenges for developing an accurate multiscale modeling framework for food drying.     

Comparison of electrothermal and hydride generation atomic absorption spectrometry for the determination of total arsenic in broiler chicken

The purpose of this study was to estimate total arsenic concentration in different tissues (leg, breast, liver and heart) of broiler chicken by hydride generation atomic absorption spectrometry (HGAAS) and graphite furnace atomic absorption spectrometry (GFAAS), prior to microwave assisted acid digestion. The accuracy of the techniques was evaluated by using certified reference material DORM-2. The percentage recoveries of total As were observed as 100.6% and 99.4% for HGAAS and GFAAS, respectively. The precision of the techniques, expressed as relative standard deviation, was observed as 1.71% and 4.18% for HGAAS and GFAAS measurements, respectively. The limits of detection for HGAAS and GFAAS were 0.025 μg/g and 0.052 μg/g, respectively. The concentrations of total arsenic in different tissues of broiler chicken were found in the range of 2.19–5.28, 2.15–5.22, 2.97–7.17 and 2.68–6.36 μg/g for leg, breast, liver and heart tissues, respectively. At a mean level of chicken consumption (60 g/person/day), people may ingest in the range of 72.0–85.1 μg arsenic/person/day from chicken alone.