Optimization of the thermal mending process in epoxy/cyclic olefin copolymer blends

Cyclic olefin copolymer (COC) is utilized as thermoplastic healing agent in an epoxy resin and the effect of mending temperature on the healing of resulting materials is investigated. Blends are prepared by adding 20 and 30 wt% COC powder in the epoxy resin. They are thermo-mechanically characterized and fractured samples are thermally mended at various temperatures to evaluate the healing efficiency of the repaired samples. Optical microscopy reveals a homogenous dispersion of COC domains within epoxy matrix, while thermogravimetric analysis shows improved thermal stability of the samples. The immiscibility of the two phases in the blends lead to a decrease of the mechanical properties under flexural and tensile loading modes with respect to neat epoxy. The fracture toughness increases upon COC addition at elevated amounts. Healing efficiency values up to more than 80% are obtained at the lowest investigated temperature of 145°C for samples with 30 wt% of COC.     

Antimicrobial effect,frictional resistance,and surface roughness of stainless steel orthodontic brackets coated with nanofilms of silver and titanium oxide: a preliminary study

Nano‐silver and nano‐titanium oxide films can be coated over brackets in order to reduce bacterial aggregation and friction. However, their antimicrobial efficacy, surface roughness, and frictional resistance are not assessed before. Fifty‐five stainless‐steel brackets were divided into 5 groups of 11 brackets each: uncoated brackets, brackets coated with 60 µm silver, 100 µm silver, 60 µm titanium, and 100 µm titanium. Coating was performed using physical vapor deposition method. For friction test, three brackets from each group were randomly selected and tested. For scanning electron microscopy and atomic‐force microscopy assessments, one and one brackets were selected from each group. For antibacterial assessment, six brackets were selected from each group. Of them, three were immediately subjected to direct contact with S. mutans. Colonies were counted 3, 6, 24, and 48 h of contact. The other three were stored in water for 3 months. Then were subjected to a similar direct contact test. Results pertaining to both subgroups were combined. Groups were compared statistically. Mean (SD) friction values of the groups 'control, silver‐60, silver‐100, titanium‐60, and titanium‐100' were 0.55 ± 0.14, 0.77 ± 0.08, 0.82 ± 0.11, 1.52 ± 0.24, and 1.57 ± 0.41 N, respectively (p = .0004, Kruskal–Wallis). Titanium frictions were significantly greater than control (p < .05), but silver groups were not (p > .05, Dunn). In the uncoated group, colony count increased exponentially within 48 h. The coated groups showed significant reductions in colony count (p < .05, two‐way‐repeated‐measures ANOVA). In conclusions, all four explained coatings reduce surface roughness and bacterial growth. Nano‐titanium films are not suitable for friction reduction. Nano‐silver results were not conclusive and need future larger studies.     

Improvement of kiwifruit drying using computer vision system (CVS) and ALM clustering method

The objective of this work was to improve kiwifruit drying with respect to quality. The drying of kiwifruit slices was studied with hot air drying (HAD) and hybrid hot air-infrared drying (HID) at 50, 60, and 70°C, air velocity of 0.5, 1.0, and 1.5?m/s and thickness of 3, 5, and 7?mm using full factorial design. Shrinkage and color changes of kiwifruit slices were monitored in real time with a computer vision system (CVS). The drying treatments were ranked based on desirability function, using the combination of minimal color change, minimal shrinkage, and drying time as decision criteria. The proper conditions of kiwifruit drying were determined by average linkage method clustering as: temperature, 70°C; thickness, 3?mm; air velocity, 1.5?m/s (HAD) or 0.5?m/s (HID). Finally, a hybrid approach with HID at the first stage and HAD at the second stage of drying was proposed as a reasonable compromise between drying time and product quality.     

Oxaliplatin‐loaded crosslinked polymeric network of chondroitin sulfate‐co‐poly(methacrylic acid) for colorectal cancer: Its toxicological evaluation

The purpose of this study was to develop and characterize chemically crosslinked chondroitin sulfate‐co‐poly(methacrylic acid) (CSMA) hydrogels for colon targeting of oxaliplatin (OXP) to treat colorectal cancer. CSMA hydrogels were synthesized by free‐radical polymerization. Chondroitin sulfate was chemically crosslinked with methacrylic acid in an aqueous medium. Ammonium peroxodisulfate and N,N‐methylene bisacrylamide were used as the initiator and crosslinker, respectively. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy studies were performed to characterize the fabricated polymeric system. The pH‐sensitive characteristics of the hydrogels were evaluated by swelling dynamics and equilibrium swelling ratio measurements at pH 1.2 and 7.4. A toxicity study of the developed formulations was also conducted on rabbits to determine the toxicity of the drug‐carrier system to the biological system. The characterization studies confirmed the formation of a new polymeric network. A high OXP loading and higher drug release was observed at pH 7.4. The toxicity study confirmed that the developed formulations were nontoxic to the biological system. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45312.     

Effect of cross‐linking time on the thermal and mechanical properties and pervaporation performance of poly(vinyl alcohol) membrane cross‐linked with fumaric acid used for dehydration of isopropanol

Cross‐linked poly (vinyl alcohol) membranes were prepared using fumaric acid as the cross‐linking agent and were used for the pervaporation separation of water/isopropanol mixtures. Cross‐linking process was carried out at 150°C at three different times of 10, 30, and 60 min. The membranes were characterized by different known methods of FT‐IR, TGA, XRD as well as tensile test. The effects of cross‐linking time on the thermal and mechanical properties of the membranes and also their pervaporation performance were investigated. Formation of more ester groups by increasing the cross‐linking time was confirmed by the FT‐IR results. TGA analyses showed that thermal stability of the membranes is improved by prolonging the duration of cross‐linking process. This was due to the formation of more compact structure in the membranes. The XRD results revealed that the crystalline regions of the membranes were relatively diminished with an increase in the cross‐linking time. No specific trend was observed for the variation of tensile strength at break with the cross‐linking time. The PVA membrane cross‐linked for 60 min showed high selectivity of 1492 for water permeation for the feed mixture containing 10 wt % water. The temperature dependency of the permeation flux was investigated using Arrhenius relationship, and the activation energy values were calculated for total permeation (E_p), water (E_pw), and IPA (E_pIPA) fluxes. Lower value of E_pw in comparison with E_pIPA supported excellent dehydration performance of the cross‐linked membranes. Despite large increase in activation energy of water with prolonged cross‐linking time, the selectivity was improved. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2013     

Optimization Model for Allocating Water in a River Basin during a Drought

Optimization of water use is a complex problem in a large scale river basin. One of the most important approaches in optimizing water use in a river basin is to find the relationship between water demand and water supply. The parameters that affect demand, supply, and the methods of evaluation of such elements are discussed in this study. Also, a method is presented for providing objective and constraint functions from considering these effects. Fuzzy logic theory is used to modify the stochastic dynamic programming (SDP) method such that an optimization model is developed for allocating water and can be defined as the “stochastic fuzzy dynamic programming (SFDP)” method. This method is applied to optimize water use in the Kor and Seevand river basins, located in the Bakhtegan watershed, Fars, Iran. The primary water resources management consisted of the variability ranges of decision variables such as release from Doroodzan Dam and reservoir storage and was also used for allocating water in these river basins based on the SDP method. Therefore, in the present study, these variability ranges are obtained based on historical data, and divided into several record classes. Optimum class of release, a case of the record classes, was obtained from the optimization model for each month during the past 4 out of 25 years. Although, the SFDP method can be used in optimizing water allocation during each period, the method is structured and discussed only during the drought periods (4 years). Later, a comparison was made between optimum classes and record classes that were operated during the primary water resources management. During this period, the SFDP method reduced the difference between the release from the dam and the total water demand of the river basin. Therefore, approximately a 27% improvement in adaptation between release and demand could be attained. Finally, if the decision maker makes the decision for the release from the dam that is optimal according to our objective function, the reliability of reservoir operating can be increased by 51% during future droughts.     

A B7.1-antibody fusion protein retains antibody specificity and ability to activate via the T cell costimulatory pathway

We describe the construction and characterization of an Ab fusion protein specific for the tumor-associated Ag HER2/neu linked to sequences encoding the extracellular domain of the B7.1 T cell costimulatory ligand. The Ab domain of the fusion molecule will specifically target HER2/neu-expressing tumor cells, while the B7.1 domain is designed to activate a specific immune response. We show that the B7.1 fusion Ab retained ability to selectively bind to the HER2/neu Ag and to the CTLA4/CD28 counter-receptors for B7.1. Specific T cell activation was observed when the B7.1 Ab fusion protein was bound to HER2/neu-expressing cells. The use of the B7.1 Ab fusion protein may overcome limitations of gene transfer and/or standard Ab therapy and represents a novel approach to the eradication of minimal residual disease.     

Dust Streaming Effect on Dust Acoustic Solitary Wave in Magnetized Dust-Ion Plasmas

The dust acoustic solitary structures in the presence of dust streaming are obtained through Sagdeev's pseudopotential approach in magnetized dustion plasmas. It is found that dust streaming plays a destructive role in the formation of dust acoustic solitary structures. However, the wave amplitude increases with the increase in the Mach number and obliqueness of the wave in the presence of contant dust streaming along a uniform external magnetic field. The numerical results are applied to Saturn's F-rings for illustrative purposes.     

An Assessment of the Double-Notch Shear Test for Interlaminar Shear Characterization of a Unidirectional Graphite/Epoxy under Static and Fatigue Loading

This research explores a modified testing technique for measuring interlaminar shear properties of orthotropic composite materials. An existing test method (double-notched test method) is examined here to characterize the interlaminar shear properties (strength and fatigue life) of a unidirectional ply under both static and fatigue loading conditions. No complicated fixture is required for the testing method which is beneficial for fatigue testing of the materials. The testing method is verified by a finite element technique where an optimized geometry for the specimen is found. AS4/3501-6 graphite/epoxy material is used in this study. The experimental results show that final failure occurs in the gage area for both static and fatigue loading conditions. Moreover, a reasonable amount of scatter for both the static strength and fatigue life is achieved.     

Surface Characteristics of Some Roller Burnished Non-ferrous Components

Burnishing as a cold working process can be used to decrease the roughness of surfaces, and to increase the surface hardness as a result of work hardening. In the present work, a roller type burnishing tool was used to study the influence of the main burnishing parameters on the surface roughness and hardness of commercial aluminum and brass. It was found that roller-burnishing can be used successfully to improve surface roughness and to increase surface hardness. Also, it was found that burnishing force and number of burnishing tool passes are the predominant parameters, for control of surface roughness and hardness of rolled-burnished components.