Labeling of cysteine 231 in acetylcholinesterase from Torpedo nobiliana by the active-site directed reagent, 1-bromo-2-[14C] pinacolone. Effects of 2,2'-dipyridyl disulfide and other sulfhydryl reagents

Acetylcholinesterase (AcChE, EC 3.1.1.7) was isolated from the electric organ of T. nobiliana and treated with the active-site-directed alkylating agent 1-bromo-2-[14C]pinacolone ([14C]BrPin), or with BrPin, which acts initially as a competitive inhibitor, Ki = 0.18 mM, and then inactivates the enzyme, k2 = 1.8 x 10(-4) s-1. AcChE aliquots were digested with trypsin and fractionated by reversed phase high performance liquid chromatography. Inactivation caused a decrease in one absorption peak and an increase in another, identified as the peptide beginning at Ala-222 and extending to Arg-242. 5-Trimethylammonio-2-pentanone, a competitive inhibitor, isosteric with acetylcholine, retarded the inactivation and decreased the quantity of labeled peptide. On sequencing, the 14C label was found associated with Cys-231. This was confirmed by comparison with synthesized S-pinacolonylcysteine, by study of effects of blocking the sequencing by o-phthalaldehyde, and by inactivation by 2,2'-dipyridyl disulfide (2-PDS), a thiol-specific reagent that acts initially as a competitive inhibitor, Ki = 0.042 mM, and then inactivates the enzyme, k2 = 5.0 x 10(-4) s-1. This is retarded by 5-trimethylammonio-2-pentanone, and prior inactivation by 2-PDS prevents subsequent reaction of [14C]BrPin in the active site. BrPin inactivates AcChEs from Electrophorus electricus and from human erythrocyte, but 2-PDS does not. Neither reagent inactivates butyrylcholinesterases from human and horse serum.     

Experimental studies on the suitability of human mesothelial cells for seeding vascular prostheses: shear stress resistance in vitro

This investigation forms part of a study on the suitability of human omentum mesothelial cells (HOMES) as an alternative to endothelial cells (EC) for seeding vascular grafts. Isolated HOMES were grown in primary culture and characterized by their morphology (light microscopy and scanning electron microscopy (SEM)), as well as by fluorescence-activated cell sorting (FACS) and immunocytochemistry. The latter two methods showed cells which were positive for smooth muscle-type actin and cytokeratin, but negative for factor VIII-related antigen. HOMES were grown to confluence on glass with or without a fibronectin coating. Controlled shear stress was applied for up to 30 min using a plate and cone rheometer at 20 dynes/cm². These dynamic culture conditions led to loss of only occasional cells. The most marked alterations seen on SEM were some cell elongation, marked raising of the nucleus and loss of luminal cytoplasmic microvilli. Time-lapse video microscopy revealed that shear stress also increased the spreading capacity of some cells. Similar experiments with venous endothelial cells gave a shearing off of a confluent monolayer. This investigation shows the marked shear-stress resistance of HOMES, a pre-requisite for their use to seed vascular prostheses.     

Process synthesis using block superstructure with automated flowsheet generation and optimization

An alternative method for chemical process synthesis using a block‐based superstructure representation is proposed. The block‐based superstructure is a collection of blocks arranged in a two‐dimensional grid. The assignment of different equipment on blocks and the determination of their connectivity are performed using a mixed‐integer nonlinear formulation for automated flowsheet generation and optimization‐based process synthesis. Based on the special structure of the block representation, an efficient strategy is proposed to generate and successively refine feasible and optimized process flowsheets. Our approach is demonstrated using two process synthesis case studies adapted from the literature and one new process synthesis problem for methanol production from biogas © 2018 American Institute of Chemical Engineers AIChE J, 64: 3082–3100, 2018     

Analyzing lifetime of energy harvesting underwater wireless sensor nodes

Underwater Wireless Sensor Networks (UWSNs) are utilized to monitor underwater environments that pose many challenges to researchers. One of the key complications of UWSNs is the difficulty of changing node batteries after their energy is depleted. This study aims to diminish the issues related to battery replacement by improving node lifetime. For this goal, three energy harvesting devices (turbine harvester, piezoelectric harvester, and hydrophone harvester) are analyzed to quantitate their impacts on node lifetime. In addition, two different power management schemes (schedule‐driven and event‐driven power management schemes) are combined with energy harvesters for further lifetime improvement. Performance evaluations via simulations show that energy harvesting methods joined by power management schemes can improve node lifetime substantially when actual conditions of Istanbul Bosporus Strait are considered. In this respect, turbine harvester makes the biggest impact and provides lifetime beyond 2000 days for most cases, while piezoelectric harvester can perform the same only for low duty cycle or event arrival values at short transmission ranges.     

Effect of Core Electrons in Defining the Total Energy,Correlation Energy,and Binding Energy of Graphene,Graphite, and Diamond: a First-Principles Study

Effects of core electrons on total energy, correlation energy, and binding energy of graphene, graphite, and diamond have been investigated along with density functional theory (DFT) calculations at the PBE level of theory using all electron and frozen-core calculations. For these calculations, correlation-consistent basis sets cc-pVXZ and cc-pCVXZ have been used where X is the cardinal number that represents the maximum angular momentum number in the basis set. By taking the difference between all electron and frozen-core calculations, core-electron binding energy contribution for each basis set has been obtained. It has been shown that to reduce the effects of core electrons, large basis sets should be used.     

The physical and mechanical properties of polymer composites filled with Fe‐powder

In this study, the effect of Fe powder on the physical and mechanical properties of high density polyethylene (HDPE) was investigated experimentally. HDPE and HDPE containing 5, 10, and 15 vol % Fe metal–polymer composites were prepared with a twin screw extruder and injection molding. After this, fracture surface, the modulus of elasticity, yield and tensile strength, % elongation, Izod impact strength (notched), hardness (Shore D), Vicat softening point, heat deflection temperature (HDT), melt flow index (MFI), and melting temperature (T_m) were determined, for each sample. When the physical and mechanical properties of the composites were compared with the results of unfilled HDPE, it was found that the yield and tensile strength, % elongation, and Izod impact strength of HDPE decreased with the vol % of Fe. As compared with the tensile strength and % elongation of unfilled HDPE, tensile strength and % elongation of 15 vol % Fe filled HDPE were lower, about 17.40% and 94.75% respectively. On the other hand, addition of Fe into HDPE increased the modulus of elasticity, hardness, Vicat softening, MFI, and HDT values, such that 15 vol % Fe increased the modulus of elasticity to about 48%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Subsurface damage during dry sliding wear of Al-Al3Ni eutectic alloy

Cylindrical Al-Al₃Ni eutectic alloy wear pins (10 mm in diameter) were slid against a polished steel surface in a pin-on-disc rotating machine under unlubricated conditions with bearing pressures of 6–60 kPa and a constant sliding speed of 70 m min^?1. Metallographic changes in the subsurface region of contact were examined by optical microscopy and microhardness measurements. In the bearing pressure range investigated the alloy exhibited “mild” wear in two linear regions identified as pure “oxidative” wear at low bearing pressures and oxidative with superimposed “metallic” wear at higher bearing pressures. Plastic deformation and fragmentation of the Al₃Ni phase occurred under all bearing pressures. However, in composites prepared by unidirectional solidification containing large Al₃Ni particles fragmentation was insignificant. In all other specimens the size of the fragmented particles in the subsurface region of contact was about 5 μm irrespective of the bearing pressure.     

Technological properties of wingnut (Pterocarya fraxinifolia (LAM.) Spach.) wood and characteristics of plywood from wingnut wood

The objective of this study was to determine some physical and mechanical properties of solid wood of wingnut (Pterocarya fraxinifolia (Lam.) Spach.) in comparison with major hardwood species in Turkey. In the study, some properties of plywood specimens produced from wingnut wood were also determined. Results showed that the characteristics of solid wingnut wood were comparable with some major hardwood species used in Turkey. Based on physical and mechanical properties tested, the wood could be consumed in some usage areas where high strength is not expected. Plywood from wingnut wood can be also used in various applications based on the mechanical properties tested.     

Facile Synthesis of Cu2ZnSnS4 Photovoltaic Absorber Thin Films via Sulfurization of Cu2SnS3/ZnS Layers

Copper zinc tin sulfide (Cu₂ZnSnS₄) has been receiving a lot of attention in recent years as a new, alternative absorber for the production of cheap thin film solar cells owing to the high natural abundance of all the constituents, its tunable direct-band-gap energy, and its large optical absorption coefficient. In addition, to overcome the problem of expensive vacuum-based methods, solution-based approaches are being developed for Cu₂ZnSnS₄ deposition. In this study, Cu₂ZnSnS₄ thin films were grown on soda lime glass substrates via the sulfurization of solution grown Cu₂SnS₃/ZnS stacked sulfide layers. A new facile route to overcome the difficulty of depositing Cu₂ZnSnS₄ thin film with a desired stoichiometric composition in a single cation solution has been presented. The influences of deposition cycles of layers on the morphological, compositional, structural, and optical properties of the samples were investigated. It was observed from scanning electron microscopy (SEM) images that the films were continuous and composed of homogenously distributed large grains. Possible chemical formulations of the best samples were predicted to be Cu_1.99Zn_1.25Sn_1.00S_3.76 and Cu_1.97Zn_1.03Sn_1.29S_3.71 via energy-dispersive X-ray spectroscopy (EDXS) results. The X-ray diffraction (XRD) patterns of the samples matched very well with the reference values. The Raman-scattering analysis of the films proved the phase purity of the CZTS samples. The optical absorption coefficient of the films was found to be about 10⁴ cm^?1 based on absorbance spectroscopy. The optical band gaps of the films were estimated to be between 1.36 and 1.50 eV. From these we are able to conclude that CZTS thin films can be effectively obtained via the vacuum-atmosphere sulfurization of Cu₂SnS₃/ZnS stacked sulfide layers.     

IFRS: An Indexed Face Recognition System Based on Face Recognition and RFID Technologies

Access control systems are in contact with humans in everyday life, it is used in buildings, smartphones, cars, and IoT. Access control systems became an active research area. The performance of an access control system is specified by its speed and accuracy. Biometric systems are powerful access control systems which use humans’ biological or physiological properties to provide access to the restricted data or area. From all of the many biometric system types, the face recognition system is the only type that is delivering the automatic property. Moreover, it is the most acceptable type of biometric systems to the humans. The main challenges in the face recognition system are the degradation of the speed and accuracy when the system database grew bigger. This is because the face recognition system is an identification system that adopts a one to many (1:M) relationship. As a result, there is a need to develop a system with one to one (1:1) relationship, which is a challenging process. Motivated by such challenge, this paper proposes a system called Indexed Face Recognition System (IFRS) which is based on the combination of face recognition technology and Radio Frequency Identification technology. IFRS uses Local Binary Pattern Histogram as a feature vector and Haar-cascade classifier for the face detection. Moreover, the system is enhanced with three pre-processing methods namely: Bilateral filter, Histogram Equalization, and applying Tan and Triggs’ algorithm. In addition, IFRS performs an image normalization processes before and after Face Detection phase to enhance images quality, these process are: Color Conversion and Image Cropping and Resizing. Two experiments were done. The first experiment was done on 400 images with 40 subjects (10 images per subject). The second experiment was done on 210 collected images for 21 subjects (10 images per subject) from University students as a real-life case study. The practical results demonstrates that 4?×?4 image divisions gives better results than 8?×?8 image divisions as far as recognition time, database access time, and storage capacity are concerned. The practical results show that IFRS can reach an accuracy of 100% with a very little amount of time delay that is negligible.