A novel modular fretting wear test rig

A novel modular experimental apparatus was designed and developed to measure and visualize fretting wear and friction for Hertzian circular and elliptical contacts and flat on flat contacts. The experimental apparatus utilizes a magnetostrictive actuator to reciprocate a flat, ball, or cylinder between two fixed specimens. Two stationary flat or cylindrical specimens mounted on a rotary table clamp the reciprocating specimen from the top and bottom to generate the fretting contact. The two stationary test specimens installed on the rotary table perpendicular to the moving specimen form a crossed cylinder geometry which creates a well-defined circular contact. An elliptical contact with different aspect ratios can be obtained by varying the angle between the fixed and the moving specimens. Dead weights placed on top of the upper stationary specimen provide the normal load. A force sensor located in line between the actuator output shaft and the specimen is used to measure friction. The test rig's modular design allows it to be configured for Hertzian circular (ball-on-flat, crossed cylinder), elliptical (crossed cylinder), and conformal (flat-on-flat) contacts. In the ball on flat configuration a steel flat or sapphire window is used in contact with the reciprocating ball. When the sapphire window is used a microscope and high speed camera is employed for in situ visualization and recording of the contact.     

A Class of Quasi-Cuk DC/DC Converters: Steady-State Analysis and Design

In this paper, new topologies for quasi-Cuk converter are proposed. The proposed converters with different voltage and current transfer ratio and reduced voltage stress on capacitor can be employed in distributed generation (DG) systems. In this paper, steady-state analysis of two proposed quasi-Cuk converters in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is presented. Then, besides values designing of used elements, maximum and minimum values of their current and voltage are calculated. Moreover, critical inductances between CCM and DCM for the proposed converters are calculated. Unique features of the proposed converters are different transfer ratio without employing additional elements compared to the conventional Cuk converter. Comparison of the proposed converters with conventional converter in terms of voltage transfer ratio, voltage stress on capacitor, and voltage stress on switch demonstrates advantages of the proposed converters. Finally, experimental results to verify the accuracy of the proposed converters in different operating modes are presented.     

Synthesis and NMR studies of the polymer membranes based on poly(4-vinylbenzylboronic acid) and phosphoric acid

Proton conduction in novel anhydrous membranes based on host polymer, poly(4-vinylbenzylboronic acid), (P4VBBA) and phosphoric acid, (H₃PO₄) as proton solvent was studied. The materials were prepared by the insertion of the proton solvent into P4VBBA at different stoichiometric ratios to get P4VBBA·xH₃PO₄ composite electrolytes. Homopolymer and the composite materials were characterized by FT-IR, ¹¹B MAS NMR and ³¹P MAS NMR. ¹¹B MAS NMR results suggested that acid doping favors or leads to a four-coordinated boron arrangement. ³¹P MAS NMR results illustrated the immobilization of phosphoric acid to the polymer through condensation with boron functional groups (B-O-P and/or B-O-P-O-B). Thermogravimetric analysis (TGA) showed that the condensation of composite materials starts approximately at 140 °C. An exponential weight loss above this temperature was attributed to intermolecular condensation of acidic units forming cross-linked polymer. The insertion of phosphoric acid into the matrix softened the materials shifting T_g to lower temperatures. The temperature dependence of the proton conductivity was modeled with Arrhenius relation. P4VBBA·2H₃PO₄ has a maximum proton conductivity of 0.0013 S/cm at RT and 0.005 S/cm at 80 °C.     

Essential oil composition,total phenolic content,antioxidant and antibiofilm activities of four Origanum species from southeastern Turkey

This study reports a comparative screening of four species of Origanum in Turkey, based on their essential oil composition, total phenolic content, antioxidant and antibiofilm activities. The major components of essential oils were p-cymene, linalool, and thymol. The total phenolic contents differed from 3.81 to 47.54 mg of GAE/g of extract. The concentrations of flavonoids varied from 12.74 to 58.39 mg of Ru/g of extract. Antioxidant activity was determined in vitro using DPPH reagent and expressed as concentration of each extract required to inhibit radical by 50% (IC₅₀) values that ranged from 16.03 to 48.94 μg/ml. Our results indicated that chloroform extracts of species O. majorana and O. onites, with a total content of polyphenols (47.54 mg of GAE/g and 45.17 mg of GAE/g, respectively) and an IC₅₀ of 16.03 μg/ml and 16.89 μg/ml, respectively were more antioxidant. Among the essential oil concentrations tested, maximum antibiofilm activity was found as 92.24% against M. luteus NRRL-B 1013 by O. majorana essential oil at 50 mg/ml.     

Optimisation of electroplasmolysis application for increased juice yield in carrot juice production

Electroplasmolysis (EP) which is among electrical methods and helps to increase cell permeability was used in this study as a pretreatment on carrot juice production for improving yield. A voltage range of 20–60 V and an application time of 30–90 s were studied using the electroplasmolyzator. Response surface methodology (RSM) was used for determining the appropriate voltage gradient and time that are effective on breakage of vegetable tissues. After the conditions were optimised, carrot juice was produced and compared with untreated control juices on the aspect of yield and some quality characteristics. As a result, yield was increased 10.49% by EP application. Relative to control samples total pectin (14.78%) and total phenolic content (4.73%) have significant increase. In addition by the effect of electrical pretreatment there was an improvement in soluble solid, pulp content and acidity of juices. The results suggested that juice yield and functional properties were improved by EP application.     

利用FFV预测缓蚀剂在不同体系中的协同效应

目的 研究一种分析缓蚀组分间协同效应的新方法。方法 使用Material Studio 7.0软件中的Amorphous Cell模块进行对象构建,在不同体系中利用Discover模块进行优化和运算,以水分子为探针进行FFV值测试,模拟计算得到FFV,再利用其变化率,来预测缓蚀组分间的协同效应,并通过传统方法验证该方法的正确性。结果 FFV模拟结果表明,在CO2体系中,MTIAS与AB2N具有协同效应,当二者按照摩尔比3∶2复配时的FFV最小,FFV的变化值D值最大,协同效应最好,缓蚀效率最高,而MTIAS与CPQA没有明显协同效应。在CO2/H2S体系中,MTIAS与CPQA按照摩尔比4∶1复配时的FFV最小,D值最大,协同效应最好,缓蚀效率最高;而当按照摩尔比1:4复配时,却出现了明显的拮抗效应,此时MTIAS与AB2N没有明显协同效应。失重法、极化曲线的测试结果与上述结果吻合。结论 通过缓蚀剂膜层的FFV预测缓蚀组分间的协同效应,是一种快速有效的研究方法。     

Optimization of conditions for single-step purification of recombinant hepatitis B surface antigen produced in Pichia pastoris using ion exchange chromatography

ABSTRACT

The adsorption and release of rHBsAg extracted from the final dosage form on various ion exchange resins and under different pH conditions were investigated after its peptide map and isoelectric point (PI) determination. Efficient antigen adsorption to the anion exchange resins occurred when the pH value of the protein buffer was adjusted to 5.0. In purification of rHBsAg derived from the yeast crude extract using Q Sepharose FF column, with adjusting the pH value of the crude extract to 5.0 (i.e., near to the target protein PI) and using 2M NaCl, rHBsAg with high purity (up to >95%) was obtained.

Abbreviations: rHBsAg, recombinant hepatitis B surface antigen; Alhydrogel, aluminum hydroxide; IEF, isoelectric focusing; PI, isoelectric point; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; RP-HPLC, reversed-phase high-performance liquid chromatography; SE-HPLC, size-exclusion high-performance liquid chromatography; PBS, phosphate-buffered saline     

Grading of gliomas using transfer learning on MRI images

Magnetic Resonance Materials in Physics, Biology and Medicine - Despite the critical role of Magnetic Resonance Imaging (MRI) in the diagnosis of brain tumours, there are still many pitfalls in the...     

Radiomics-based machine-learning method to diagnose prostate cancer using mp-MRI: a comparison between conventional and fused models

Magnetic Resonance Materials in Physics, Biology and Medicine - Multiparametric MRI (mp-MRI) has been significantly used for detection, localization and staging of Prostate cancer (PCa). However,...     

Numerical simulation of cooling performance in microchannel heat sinks made of AlN ceramics

Microsystem Technologies - The problem of generating a high amount of heat in microelectronic equipment should be minimized properly. Allowing systems to run for long periods of time in high...