Biocidal nanofibers via electrospinning

To achieve biocidal properties, a cyclic N‐halamine precursor, 7,7,9,9‐tetramethyl‐1,3,8‐triazaspiro[4.5]‐decane‐2,4‐dione (TTDD), was synthesized and introduced into nanosized polyacrylonitrile fibrous mat by an electrospinning technique. It was rendered antimicrobial by exposure to dilute hypochlorite solution. Synthesis routes and characterization data are presented. Scanning electron microscopy (SEM) demonstrated that the ultrafine fiber possessed average diameter 414 nm (from 240 to 650 nm). The chlorinated nanofibrous composites provided about 4.9 log reductions of both Gram‐positive bacteria Staphylococcus aureus (ATCC 6538) and Gram‐negative bacteria Escherichia coli O157:H7 (ATCC 43895) within 5 min of contact time. This is indicative of promising possible applications in the filtration of water and air. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

自水解预处理对稻草化学成分及酶解性能的影响

研究了自水解处理对稻草秸秆主要化学成分及酶解糖化效率的影响。结果显示:在100～160℃下对稻草进行自水解预处理,酸溶木质素的脱除程度随着自水解温度的升高而增大,而Klason木质素含量几乎没有变化,几乎全部SiO2仍然保留在预处理后草片中;稻草高聚糖的降解程度随着自水解温度的升高而增加,但由于自水解液酸性较弱,大量高聚糖仍保留在草片中;自水解预处理有利于促进稻草的酶解糖化,随着自水解预处理温度的升高和酶用量的增大,酶解液中各种聚糖得率均有不同程度的提高,但自水解温度的影响显得更为重要;经160℃自水解预处理的稻草在40 FPU/g混合酶用量下,葡聚糖和木聚糖的总转化率约为68%和45%,总糖转化率近60%。     

Determination of economic upper limit of drying processes in coal-fired power plants

In this study, the economic assessment of coal drying prior to ga rinding mill process in coal-fired thermal power plants was carried out. In the literature, despite the fact that there are studies regarding drying systems, the advantages and disadvantages of these systems in comparison to each other and the benefits that drying will provide, and the economic factors that are the most important determinants in the practice of the drying system, were not adequately analyzed. In this study, on the other hand, a model was developed to determine the necessary critical cost point in order to identify the appropriate drying system. Through the use of this model, the benefits to be gained from the planned drying system and the financial upper limit required for this investment can be specified. As a model application, eight of the thermal power plants in Turkey were examined. The economic upper limit of a drying system to enable coal to be dried at a rate of 10% was determined through a model study carried out for Catalagzi Power Plant.     

Novel carboxyl functional spherical electromagnetic polypyrrole nanocomposite polymer particles with good magnetic and conducting properties

Magnetic conducting nanoparticles with reactive functional groups are attractive materials for applications in electromagnetic interference shielding, magneto‐optical storage, biomedical sensing, gas and humidity sensors, flexible electronics etc. The objective of this work was to prepare carboxyl functionalized polypyrrole (PPy) nanocomposite particles having good magnetic properties. Electromagnetic PPy nanostructures, abbreviated as PPy/γ‐Fe₂O₃, were first prepared by a chemical one‐step method. In this reaction process FeCl₃ is used as an oxidant for the polymerization of pyrrole and as a source of Fe³⁺ for the formation of γ‐Fe₂O₃. The formation of γ‐Fe₂O₃ is also aided by the initial presence of Fe²⁺, and p‐toluenesulfonic acid (p‐TSA) acted as a dopant. The effects of different stabilizers on the stability and morphology of PPy/γ‐Fe₂O₃ particles were evaluated. The presence of citric acid/sodium dodecyl sulfate during chemical oxidative polymerization produced a relatively stable PPy/γ‐Fe₂O₃ colloidal emulsion. PPy/γ‐Fe₂O₃/poly(methylmethacrylate‐methacrylic acid) (PPy/γ‐Fe₂O₃/P(MMA‐MAA)) nanocomposite polymer particles were then prepared by the seeded copolymerization of MMA and MAA in the presence of magnetic PPy/γ‐Fe₂O₃ nanocomposite seed particles. The structure and morphology of the prepared nanocomposites were confirmed by different instrumental techniques such as Fourier transform IR spectroscopy, UV?visible spectroscopy, electron micrographs, XRD and X‐ray photoelectron spectroscopy. The electrical and magnetic properties were also investigated. The carboxyl functional electromagnetic PPy nanocomposite polymer particles should be useful for the immobilization of drugs or biomolecules to design electrically stimulated drug delivery systems for modulating the activities of nerve, cardiac, skeletal muscle and bone cells. © 2016 Society of Chemical Industry     

Impact behavior of hybrid composite plates

This experimental study deals with the impact response of hybrid composite laminates. Two different hybrid composite laminates, aramid/glass and aramid/carbon, and two different stacking sequences, such as [0/0/90/90]_A+ [90/90/0/0]_G for AG1 and [0/90/±45]_A+ [±45/90/0]_G for AG2 and so on (see Table I ), were chosen for impact testing. The impact energy was gradually increased until complete perforation took place, and an energy profiling method (EPM) was used to identify the perforation thresholds of composites. The damaged samples were visually inspected. The images of the several samples subjected to various impact energies were registered and used for comparison and identifying damage mechanisms. The perforation thresholds for [0/90/±45]_s aramid/glass and aramid/carbon laminates were found to be approximately 5% higher than those for their counterparts with the [0/0/90/90]_s stacking sequence. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface analytical approach to TiCl3-based Ziegler-Natta catalysts combined with microstructure analysis of polymer

In the field of Ziegler-Natta catalysis (ZNC), most of the previous works have been focused on the characterization of either catalyst surface or polymer microstructure but the combined studies of these two aspects are still limited. A clearer understanding concerning the isospecific nature of active sites on the donor-free TiCl₃ - based catalyst has been presented in this work in terms of both surface characteristics of the catalyst and microstructure of polypropylene (PP) produced. Ti- and Al-species existing in the catalyst surface have been identified by high resolution X-ray photoelectron spectroscopic (XPS) and solid-state magic angle spinning nuclear magnetic resonance (²⁷Al MAS NMR) techniques, respectively. Moreover, grinding effect on catalyst performance has been carried out to investigate the nature of active sites by particle size distribution (PSD) method. Microstructures of PPs produced using the surface characterized catalysts have been investigated by temperature rising elution fractionation (TREF), ¹³C NMR and GPC methods. It can be demonstrated that the surface structure of catalyst is dominantly affected by the type of Al-alkyl cocatalyst used as well as the preparation method of catalyst whilst it precisely determine the nature of isospecificity of active sites and its distribution. Two different types of surface Ti⁺³-species have been identified on the catalyst surface depending on the different vacant coordination states of surface titanium species. On the other hand, ²⁷Al MAS NMR experiments have shown the presence of surface aluminum in four (Al^IV), five (Al^V) and six (Al^VI) coordination number of multiple environments. The states of surface Al-species are sensitive to coordination number and symmetry of the local environment around the aluminum nuclei. Higher isospecificity of active sites is seen to be related to the higher fulfilled coordinated states of surface Ti- and Al-species.     

One-step hydrothermal synthesis of yttria-stabilized tetragonal zirconia polycrystalline nanopowders for blue-colored zirconia-cobalt aluminate spinel composite ceramics

A novel approach for the preparation of blue-color giving zirconia nanopowders by doping of 3?mol% Y₂O₃ through simple one-step hydrothermal process is proposed. A blue-color giving yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) powders were prepared by urea-based solution, zirconium acetate, CoCl₂·6H₂O and AlCl₃ precursors in hydrothermal vessel at 24?h, 150?°C and 20 bars. Based on the results, the synthesized blue-color giving Y-TZP nanopowders have entirely tetragonal structure as mono phase with 3.8?±?0.2?nm average grain size and (Y, Co, Al)_xZrO₂; x?≤?0.03?at. with chemical composition. Thermal treatment was also applied to synthesized Y-TZP powders at 1200?°C and 1450?°C to observe the color evolution. Only sharp blue was obtained in Y-TZP powders resulting the development of zirconia-cobalt aluminate spinel (ZrO₂-CoAl₂O₄) composite ceramic structure for both temperatures after heat-treatment. Herein, not only formation of CoAl₂O₄ but also incorporation of cobalt (Co) and aluminum (Al) into the Y-TZP grains plays a critical role on evolving of blue color. This synthesized Y-TZP nanopowders can be a good candidate for one-step production of blue-color sintered ZrO₂-CoAl₂O₄ spinel composite ceramics in numerous ceramic applications due to their superior structural and functional properties.     

The effects of Escherichia coli sepsis and short-term ischemia on coronary vascular reactivity and myocardial function

A moderately stable protein with typical folding kinetics unfolds and refolds many times during its cellular lifetime. In monomeric lambda repressor this process is extremely rapid, with an average folded state lifetime of only 30 milliseconds. A thermostable variant of this protein (G46A/G48A) unfolds with the wild-type rate, but it folds in approximately 20 microseconds making it the fastest-folding protein yet observed. The effects of alanine to glycine substitutions on the folding and unfolding rate constants of the G46A/G48A variant, measured by dynamic NMR spectroscopy, indicate that the transition state is an ensemble comprised of a disperse range of conformations. This structural diversity in the transition state is consistent with the idea that folding chains are directed towards the native state by a smooth funnel-like conformational energy landscape. The kinetic data for the folding of monomeric lambda repressor can be understood by merging the new energy landscape view of folding with traditional models. This hybrid model incorporates the conformational diversity of denatured and transition state ensembles, a transition state activation energy, and the importance of intrinsic helical stabilities.     

Inkjet Process for Conductive Patterning on Textiles: Maintaining Inherent Stretchability and Breathability in Knit Structures

In this work, a novel technique of inkjet printing e‐textiles with particle free reactive silver inks on knit structures is developed. The inkjet‐printed e‐textiles are highly conductive, with a sheet resistance of 0.09 Ω sq^‐1, by means of controlling the number of print passes, annealing process, and textile structures. It is notable that the inkjet process allows textiles to maintain its inherent properties, including stretchability, flexibility, breathability, and fabric hand after printing process. This is achieved by formation of ultrathin silver layers surrounding individual fibers. The silver layers coated on fibers range from 250 nm to 2.5 µm, maintaining the size of interstices and flexibility of fibers. The annealing process, structure of fibers, and printed layers significantly influence the electrical conductivity of the patterned structures on textiles. Outstanding electrical conductivity and durability are demonstrated by optimizing print passes, controlling textile structures, and incorporating an in situ annealing process. The electrical resistance dependence on the strain rate of the textiles is examined, showing the ability to maintain electrical conductivity to retain light‐emitting diode use, stable more than 500 consecutive strain cycles. Most importantly, inkjet‐printed e‐textiles maintain their characteristic washability, breathability, and fabric hands for applications in wearable technology.