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Sample records for additional reversible mechanism

  1. Reversible Oxidative Addition at Carbon.

    Science.gov (United States)

    Eichhorn, Antonius F; Fuchs, Sonja; Flock, Marco; Marder, Todd B; Radius, Udo

    2017-04-07

    The reactivity of N-heterocyclic carbenes (NHCs) and cyclic alkyl amino carbenes (cAACs) with arylboronate esters is reported. The reaction with NHCs leads to the reversible formation of thermally stable Lewis acid/base adducts Ar-B(OR)2 ⋅NHC (Add1-Add6). Addition of cAAC(Me) to the catecholboronate esters 4-R-C6 H4 -Bcat (R=Me, OMe) also afforded the adducts 4-R-C6 H4 Bcat⋅cAAC(Me) (Add7, R=Me and Add8, R=OMe), which react further at room temperature to give the cAAC(Me) ring-expanded products RER1 and RER2. The boronate esters Ar-B(OR)2 of pinacol, neopentylglycol, and ethyleneglycol react with cAAC at RT via reversible B-C oxidative addition to the carbene carbon atom to afford cAAC(Me) (B{OR}2 )(Ar) (BCA1-BCA6). NMR studies of cAAC(Me) (Bneop)(4-Me-C6 H4 ) (BCA4) demonstrate the reversible nature of this oxidative addition process.

  2. The retro Grignard addition reaction revisited: the reversible addition of benzyl reagents to ketones

    DEFF Research Database (Denmark)

    Christensen, Stig Holden; Holm, Torkil; Madsen, Robert

    2014-01-01

    The Grignard addition reaction is known to be a reversible process with allylic reagents, but so far the reversibility has not been demonstrated with other alkylmagnesium halides. By using crossover experiments it has been established that the benzyl addition reaction is also a reversible transfo...

  3. Mechanism of reverse-offset printing

    Science.gov (United States)

    Choi, Young-Man; Lee, Eonseok; Lee, Taik-Min

    2015-07-01

    We propose a mechanism for reverse-offset printing based on a mathematical model. In reverse-offset printing, high resolution is achieved by patterning a coated, thin ink film with an intaglio-patterned cliché. By using the relationships among the ink blanket adhesion strength, the ink cliché adhesion strength, and the ink cohesion strength, a criterion for successful patterning is derived. We found that there is a printing window in the ink blanket adhesion strength that depends on the shear strength of the ink film and the dimensions of the pattern. The printing window diminishes as the line width decreases, resulting in a minimum printable line width. The proposed mechanism was verified by printing patterns with various shapes and dimensions.

  4. 'Green' reversible addition-fragmentation chain-transfer (RAFT) polymerization

    Science.gov (United States)

    Semsarilar, Mona; Perrier, Sébastien

    2010-10-01

    Reversible addition-fragmentation chain-transfer (RAFT) polymerization has revolutionized the field of polymer synthesis as a versatile tool for the production of complex polymeric architectures. As for all chemical processes, research and development in RAFT have to focus on the design and application of chemical products and processes that have a minimum environmental impact, and follow the principles of 'green' chemistry. In this Review, we summarize some of the green features of the RAFT process, and review the recent advances in the production of degradable polymers obtained from RAFT polymerization. Its use to modify biodegradable and renewable inorganic and organic materials to yield more functional products with enhanced applications is also covered. RAFT is a promising candidate for answering both the increasing need of modern society to employ highly functional polymeric materials and the global requirements for developing sustainable chemicals and processes.

  5. Mechanical Properties of Additively Manufactured Thick Honeycombs

    Directory of Open Access Journals (Sweden)

    Reza Hedayati

    2016-07-01

    Full Text Available Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.

  6. Mechanical properties of additively manufactured octagonal honeycombs.

    Science.gov (United States)

    Hedayati, R; Sadighi, M; Mohammadi-Aghdam, M; Zadpoor, A A

    2016-12-01

    Honeycomb structures have found numerous applications as structural and biomedical materials due to their favourable properties such as low weight, high stiffness, and porosity. Application of additive manufacturing and 3D printing techniques allows for manufacturing of honeycombs with arbitrary shape and wall thickness, opening the way for optimizing the mechanical and physical properties for specific applications. In this study, the mechanical properties of honeycomb structures with a new geometry, called octagonal honeycomb, were investigated using analytical, numerical, and experimental approaches. An additive manufacturing technique, namely fused deposition modelling, was used to fabricate the honeycomb from polylactic acid (PLA). The honeycombs structures were then mechanically tested under compression and the mechanical properties of the structures were determined. In addition, the Euler-Bernoulli and Timoshenko beam theories were used for deriving analytical relationships for elastic modulus, yield stress, Poisson's ratio, and buckling stress of this new design of honeycomb structures. Finite element models were also created to analyse the mechanical behaviour of the honeycombs computationally. The analytical solutions obtained using Timoshenko beam theory were close to computational results in terms of elastic modulus, Poisson's ratio and yield stress, especially for relative densities smaller than 25%. The analytical solutions based on the Timoshenko analytical solution and the computational results were in good agreement with experimental observations. Finally, the elastic properties of the proposed honeycomb structure were compared to those of other honeycomb structures such as square, triangular, hexagonal, mixed, diamond, and Kagome. The octagonal honeycomb showed yield stress and elastic modulus values very close to those of regular hexagonal honeycombs and lower than the other considered honeycombs.

  7. Remanence Properties and Magnetization Reversal Mechanism of Fe Nanowire Arrays

    Institute of Scientific and Technical Information of China (English)

    WANG Jian-Bo; LIU Qing-Fang; XUE De-Sheng; LI Fa-Shen

    2004-01-01

    @@ Remanence properties and magnetization reversal mechanism of Fe nanowire arrays with diameters 16 nm and130nm are studied. Isothermal remanent magnetization curves show that the contribution of irreversible magnetization decreases when the diameter changes from 16nm to 130nm. The remanence coercivities of these nanowires obtained in dc-demagnetization curve are about 2400 Oe and 800 Oe, respectively. The magnetization reversal mechanism is different in these two samples. For the nanowire array with diameter 16nm, both the nucleation and the pinning have effects on magnetization reversal mechanism, and the pinning field (about 2500Oe) is larger than the nucleation field (about 2200 Oe). However, for the nanowire array with diameter 130nm,the magnetization reversal mechanism is dominated by the pinning effect of domain walls.

  8. Mechanisms of Cytochrome C Extraction by Reverse Micelles

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The extraction of cytochrome C was carried out by means of phase transfer technique with three different reverse micellar systems, i.e., a CTAB micellar solution in n-butyl alcohol-chloroform(volume ratio 4∶1), an AOT micellar solution in isooctane and a SDSS-D2EHPA micellar solution in isooctane. The extraction mechanisms were studied. The results show that the extraction mechanisms for the same proteins with different types of reverse micellar systems can be distinct. The extraction of cytochrome C with CTAB and SDSS-D2EHPA reverse micellar systems are carried out according to the mechanism of electrostatic interaction. However, in the extraction of cytochrome C with the AOT reverse micellar system, the electrostatic interaction between the protein and the surfactant is not important.

  9. Additive strengthening mechanisms in dispersion hardened polycrystals

    DEFF Research Database (Denmark)

    Hansen, Niels; Ralph, B.

    1986-01-01

    the addition of strength components from various elements of the microstructure and substructure might explain this behaviour are investigated. It is shown that a linear combination of a matrix friction stress, an Orowan bowing stress, a matrix mean stress from the particles and a combined dislocation...

  10. Reversal mechanism in perpendicular media with columnar structure

    NARCIS (Netherlands)

    Wielinga, T.; Lodder, J.C.

    1986-01-01

    A contribution is given to the discussion concerning the nature of the magnetization reversal process in sputtered CoCr recording media with columnar morphology. The paper is restricted to the additional effects on the total perpendicular anisotropy by studying the columnar shape anisotropy and the

  11. Contact mechanics of reverse engineered distal humeral hemiarthroplasty implants.

    Science.gov (United States)

    Willing, Ryan; King, Graham J W; Johnson, James A

    2015-11-26

    Erosion of articular cartilage is a concern following distal humeral hemiarthroplasty, because native cartilage surfaces are placed in contact with stiff metallic implant components, which causes decreases in contact area and increases in contact stresses. Recently, reverse engineered implants have been proposed which are intended to promote more natural contact mechanics by reproducing the native bone or cartilage shape. In this study, finite element modeling is used in order to calculate changes in cartilage contact areas and stresses following distal humeral hemiarthroplasty with commercially available and reverse engineered implant designs. At the ulna, decreases in contact area were -34±3% (p=0.002), -27±1% (pengineered and cartilage reverse engineered designs, respectively. Peak contact stresses increased by 461±57% (p=0.008), 387±127% (p=0.229) and 165±16% (p=0.003). At the radius, decreases in contact area were -21±3% (p=0.013), -13±2% (p0.999), 241±32% (p=0.010) and 61±10% (p=0.021). Between the three different implant designs, the cartilage reverse engineered design yielded the largest contact areas and lowest contact stresses, but was still unable to reproduce the contact mechanics of the native joint. These findings align with a growing body of evidence indicating that although reverse engineered hemiarthroplasty implants can provide small improvements in contact mechanics when compared with commercially available designs, further optimization of shape and material properties is required in order reproduce native joint contact mechanics.

  12. Mechanism and kinetics of addition polymerizations

    CERN Document Server

    Kucera, M

    1991-01-01

    This volume presents an up-to-date survey of knowledge concerning addition type polymerizations. It contains nine chapters, each of which covers a particular basic term. Whenever necessary, the phenomena are discussed from the viewpoint of both stationary and non-stationary state of radical, ionic (i.e. anionic and cationic) and coordination polymerization. Special attention has been paid to the propagation process. It provides not only a general overview but also information on important special cases (theoretical conditions of propagation, influence of external factors, controlled propagatio

  13. Additional Raman Scattering Mechanism due to Transverse Polar Modes

    Institute of Scientific and Technical Information of China (English)

    CHENG Ze

    2001-01-01

    Longitudinal polar modes generate a macroscopic electric field in piezoelectric crystals and cause an additional mechanism of Raman scattering. The classical theory holds that transverse polar modes cannot produce such an additional mechanism. Our quantum theory shows that there is an additional Raman scattering mechanism arising from the electro-optic effect of transverse polar modes.``

  14. Left Atrial Reverse Remodeling: Mechanisms, Evaluation, and Clinical Significance.

    Science.gov (United States)

    Thomas, Liza; Abhayaratna, Walter P

    2017-01-01

    The left atrium is considered a biomarker for adverse cardiovascular outcomes, particularly in patients with left ventricular diastolic dysfunction and atrial fibrillation in whom left atrial (LA) enlargement is of prognostic importance. LA enlargement with a consequent decrease in LA function represents maladaptive structural and functional "remodeling" that in turn promotes electrical remodeling and a milieu conducive for incident atrial fibrillation. Medical and nonmedical interventions may arrest this pathophysiologic process to the extent that subsequent reverse remodeling results in a reduction in LA size and improvement in LA function. This review examines cellular and basic mechanisms involved in LA remodeling, evaluates the noninvasive techniques that can assess these changes, and examines potential mechanisms that may initiate reverse remodeling.

  15. Harnessing reversible oxidative addition: application of diiodinated aromatic compounds in the carboiodination process.

    Science.gov (United States)

    Petrone, David A; Lischka, Matthias; Lautens, Mark

    2013-09-27

    An I for an I: Conditions for the intramolecular carboiodination and the simultaneous convergent intramolecular carboiodination/intermolecular Heck reaction of various diiodoarenes were developed. The ability of the Pd(0)/QPhos catalyst/ligand combination to undergo reversible oxidative addition allows these reactions to proceed well, thus increasing both the appeal and utility of this class of substrates in site-selective cross-coupling reactions.

  16. Reversible Guest Exchange Mechanisms in Supramolecular Host-GuestAssemblies

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, Michael D.; Raymond, Kenneth N.

    2006-09-01

    Synthetic chemists have provided a wide array of supramolecular assemblies able to encapsulate guest molecules. The scope of this tutorial review focuses on supramolecular host molecules capable of reversibly encapsulating polyatomic guests. Much work has been done to determine the mechanism of guest encapsulation and guest release. This review covers common methods of monitoring and characterizing guest exchange such as NMR, UV-VIS, mass spectroscopy, electrochemistry, and calorimetry and also presents representative examples of guest exchange mechanisms. The guest exchange mechanisms of hemicarcerands, cucurbiturils, hydrogen-bonded assemblies, and metal-ligand assemblies are discussed. Special attention is given to systems which exhibit constrictive binding, a motif common in supramolecular guest exchange systems.

  17. The reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization of vinyl acetate mediated by xanthate

    Institute of Scientific and Technical Information of China (English)

    Bo Jiang; Qing Hua Zhang; Xiao Li Zhan; Feng Qiu Chen

    2009-01-01

    The reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization of vinyl acetate (VAt) mediated by methyl (methoxycarbonothioyl) sulfanyl acetate (MMSA) was carried out. The results showed that polymerizations initiated by AIBN and KPS proceeded in a controlled way. The RAFT miniemulsion polymerization of VAc initiated by KPS showed the shorter inhibition period, higher propagation rate coefficient and final conversion than those in experiment initiated by AIBN. When the monomer conversion reached 25%, the polydispersity index (PDI) of polymer became broad, which was related to chain transfer reaction in RAFT miniemulsion of VAc.

  18. Evaluation of the clenbuterol imprinted monolithic column prepared by reversible addition-fragmentation chain transfer polymerization

    Institute of Scientific and Technical Information of China (English)

    Mamat Turson; Xiao Lei Zhuang; Hui Na Liu; Ping Jiang; Xiang Chao Dong

    2009-01-01

    To make more homogenous organic monolithic structure,reversible addition-fragmentation chain transfer(RAFT)process was employed in the synthesis of the clenbuterol imprinted polymer.In the synthesis,the influence of synthetic conditions on the polymer structure and separation efficiency was studied.The result demonstrated that the imprinted columns prepared with RAFT process have higher column efficiency and selectivity than the columns prepared with conventional polymerization in the present study,which may result from the higher surface area,smaller pore size and the narrower globule size distribution in their structures.The result indicated that RAFT polymerization provided better conditions for the clenbuterol imprinted monolithic polymer preparation.

  19. Rejection mechanisms for contaminants in polymeric reverse osmosis membranes

    CERN Document Server

    Shen, Meng; Lueptow, Richard M

    2016-01-01

    Despite the success of reverse osmosis (RO) for water purification, the molecular-level physico-chemical processes of contaminant rejection are not well understood. Here we carry out NEMD simulations on a model polyamide RO membrane to understand the mechanisms of transport and rejection of both ionic and neutral contaminants in water. We observe that the rejection changes non-monotonously with ion sizes. In particular, the rejection of urea, 2.4 A radius, is higher than ethanol, 2.6 A radius, and the rejections for organic solutes, 2.2-2.8 A radius, are lower than Na+, 1.4 A radius, or Cl-, 2.3 A radius. We show that this can be explained in terms of the solute accessible intermolecular volume in the membrane and the solute-water pair interaction energy. If the smallest open spaces in the membrane's molecular structure are all larger than the hydrated solute, then the solute-water pair interaction energy does not matter. However, when the open spaces in the polymeric structure are such that solutes have to s...

  20. Metal Additive Manufacturing: A Review of Mechanical Properties

    Science.gov (United States)

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.

  1. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    Science.gov (United States)

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

  2. Molecular Imprinting of Silica Nanoparticle Surfaces via Reversible Addition-Fragmentation Polymerization for Optical Biosensing Applications

    Science.gov (United States)

    Oluz, Zehra; Nayab, Sana; Kursun, Talya Tugana; Caykara, Tuncer; Yameen, Basit; Duran, Hatice

    Azo initiator modified surface of silica nanoparticles were coated via reversible addition-fragmentation polymerization (RAFT) of methacrylic acid and ethylene glycol dimethacrylate using 2-phenylprop 2-yl dithobenzoate as chain transfer agent. Using L-phenylalanine anilide as template during polymerization led molecularly imprinted nanoparticles. RAFT polymerization offers an efficient control of grafting process, while molecularly imprinted polymers shows enhanced capacity as sensor. L-phenylalanine anilide imprinted silica particles were characterized by X-Ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM). Performances of the particles were followed by surface plasmon resonance spectroscopy (SPR) after coating the final product on gold deposited glass substrate against four different analogous of analyte molecules: D-henylalanine anilide, L-tyrosine, L-tryptophan and L-phenylalanine. Characterizations indicated that silica particles coated with polymer layer do contain binding sites for L-phenylalanine anilide, and are highly selective for the molecule of interest. This project was supported by TUBITAK (Project No:112M804).

  3. Additional considerations about the role of ion size in charge reversal

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Molina, A; Hidalgo-Alvarez, R [Grupo de Fisica de Fluidos y Biocoloides, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Granada, Granada 18071 (Spain); Quesada-Perez, M, E-mail: almartin@ugr.e [Departamento de Fisica, Universidad de Jaen, Escuela Politecnica Superior de Linares, 23700 Linares, Jaen (Spain)

    2009-10-21

    The effect of the ion size on the charge reversal process is studied via canonical Monte Carlo simulation. To this end, a primitive model of electrolyte is used to analyze the electric double layer formed by an asymmetric electrolyte in the presence of a charged planar wall. Different values of ion diameters and surface charge densities are used so as to determine the conditions at which the charge reversal first occurs. For each case, the apparent surface charge density is calculated as a function of the distance from the charged wall for the different electrolyte concentrations in order to establish the minimal salt concentration required for the charge reversal. We will refer to this electrolyte concentration as the reversal concentration and will show how it depends on the surface charge density and on the ion size. From the apparent surface charge density profiles, the distance from the wall at which the charge reversal arises as well as its intensity can be also inferred.

  4. A Dynamic Pricing Reverse Auction-Based Resource Allocation Mechanism in Cloud Workflow Systems

    Directory of Open Access Journals (Sweden)

    Xuejun Li

    2016-01-01

    Full Text Available Market-oriented reverse auction is an efficient and cost-effective method for resource allocation in cloud workflow systems since it can dynamically allocate resources depending on the supply-demand relationship of the cloud market. However, during the auction the price of cloud resource is usually fixed, and the current resource allocation mechanisms cannot adapt to the changeable market properly which results in the low efficiency of resource utilization. To address such a problem, a dynamic pricing reverse auction-based resource allocation mechanism is proposed. During the auction, resource providers can change prices according to the trading situation so that our novel mechanism can increase the chances of making a deal and improve efficiency of resource utilization. In addition, resource providers can improve their competitiveness in the market by lowering prices, and thus users can obtain cheaper resources in shorter time which would decrease monetary cost and completion time for workflow execution. Experiments with different situations and problem sizes are conducted for dynamic pricing-based allocation mechanism (DPAM on resource utilization and the measurement of Time⁎Cost (TC. The results show that our DPAM can outperform its representative in resource utilization, monetary cost, and completion time and also obtain the optimal price reduction rates.

  5. Polymer-grafted lignin surfactants prepared via reversible addition-fragmentation chain-transfer polymerization.

    Science.gov (United States)

    Gupta, Chetali; Washburn, Newell R

    2014-08-12

    Kraft lignin grafted with hydrophilic polymers has been prepared using reversible addition-fragmentation chain-transfer (RAFT) polymerization and investigated for use as a surfactant. In this preliminary study, polyacrylamide and poly(acrylic acid) were grafted from a lignin RAFT macroinitiator at average initiator site densities estimated to be 2 per particle and 17 per particle. The target degrees of polymerization were 50 and 100, but analysis of cleaved polyacrylamide was consistent with a higher average molecular weight, suggesting not all sites were able to participate in the polymerization. All materials were readily soluble in water, and dynamic light scattering data indicate polymer-grafted lignin coexisted in isolated and aggregated forms in aqueous media. The characteristic size was 15-20 nm at low concentrations, and aggregation appeared to be a stronger function of degree of polymerization than graft density. These species were surface active, reducing the surface tension to as low as 60 dyn/cm at 1 mg/mL, and a greater decrease was observed than for polymer-grafted silica nanoparticles, suggesting that the lignin core was also surface active. While these lignin surfactants were soluble in water, they were not soluble in hexanes. Thus, it was unexpected that water-in-oil emulsions formed in all surfactant compositions and solvent ratios tested, with average droplet sizes of 10-20 μm. However, although polymer-grafted lignin has structural features similar to nanoparticles used in Pickering emulsions, its interfacial behavior was qualitatively different. While at air-water interfaces, the hydrophilic grafts promote effective reductions in surface tension, we hypothesize that the low grafting density in these lignin surfactants favors partitioning into the hexanes side of the oil-water interface because collapsed conformations of the polymer grafts improve interfacial coverage and reduce water-hexanes interactions. We propose that polymer-grafted lignin

  6. Early career: Templating of liquid crystal microstructures by reversible addition-fragmentation chain transfer polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Heinen, Jennifer M. (O' Donnell) [Iowa State Univ., Ames, IA (United States)

    2014-12-31

    This research has shown that the microstructure of self-assembled copolymers can be decoupled from the polymer chemistry. The simplest polymer architecture, linear block copolymers, is valuable for a broad range of applications, including adhesives and coatings, medical devices, electronics and energy storage, because these block copolymers reproducibly self-assemble into microphase separated nanoscale domains. Unfortunately, the self-assembled microstructure is tuned by polymer composition, thus limiting the potential to simultaneously optimize chemical, mechanical, and transport properties for desired applications. To this end, much work was been put into manipulating block copolymer self-assembly independently of polymer composition. These efforts have included the use of additives or solvents to alter polymer chain conformation, the addition of a third monomer to produce ABC triblock terpolymers, architectures with mixed blocks, such as tapered/gradient polymers, and the synthesis of other nonlinear molecular architectures. This work has shown that the microstructures formed by linear ABC terpolymers can be altered by controlling the architecture of the polymer molecules at a constant monomer composition, so that the microstructure is tuned independently from the chemical properties.

  7. Effect and mechanism of siderite on reverse flotation of hematite

    Institute of Scientific and Technical Information of China (English)

    Wan-zhong Yin; Dong Li; Xi-mei Luo; Jin Yao; Qian-yu Sun

    2016-01-01

    The effects of siderite on reverse flotation of hematite were investigated using micro flotation, adsorption tests, and Fourier trans-form infrared spectroscopy. The flotation results show that interactions between siderite and quartz are the main reasons that siderite signifi-cantly influences the floatability. The interactions are attributed to dissolved siderite species and fine siderite particles. The interaction due to the dissolved species is, however, dominant. Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical calculations reveal that adhesion on quartz increases when the siderite particle size decreases and that fine particles partly influence quartz floatability. Chemical solution calcula-tions indicate that the dissolved species of siderite might convert the surface of active quartz to CaCO3 precipitates that can be depressed by starch. The theoretical calculations are in good agreement with the results of adsorption tests and FTIR spectroscopy and explain the reasons why siderite significantly influences reverse flotation of hematite.

  8. In-line monitoring and reverse 3D model reconstruction in additive manufacturing

    DEFF Research Database (Denmark)

    Pedersen, David Bue; Hansen, Hans Nørgaard; Nielsen, Jakob Skov

    2010-01-01

    with traditional measuring equipment such as Coordinate Measurement Machines (CMM's) can not easily be verified. This paradox is addresses by the proposal of an in-line reverse engineering and 3D reconstruction method that alows for a true to scale reconstruction of a part that is being additivelymanufactures on 3......D printing (3DP), or Selective Laser Sintering (SLS) equipment. The system will be implemented and tested on a 3DP machine with modifications developed at the author's university....

  9. REVERSE DESIGN APPROACH FOR MECHANISM TRAJECTORY BASED ON CODE-CHAINS MATCHING

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shuyou; YI Guodong; XU Xiaofeng

    2007-01-01

    Aiming at the problem of reverse-design of mechanism, a method based on the matching of trajectory code-chains is presented. The motion trajectory of mechanism is described with code-chain,which is normalized to simplify the operation of geometric transformation. The geometric transformation formulas of scale, mirror and rotation for trajectory code-chain are defined, and the reverse design for mechanism trajectory is realized through the analysis and solution of similarity matching between the desired trajectory and the predefined trajectory. The algorithm program and prototype system of reverse design for mechanism trajectory are developed. Application samples show that the method can break the restriction of trajectory patterns in matching, meet the demand of partial matching, and overcome the influence of geometric transformation of trajectory on the reverse design for mechanism.

  10. Bioinspired Cellular Structures: Additive Manufacturing and Mechanical Properties

    Science.gov (United States)

    Stampfl, J.; Pettermann, H. E.; Liska, R.

    Biological materials (e.g., wood, trabecular bone, marine skeletons) rely heavily on the use of cellular architecture, which provides several advantages. (1) The resulting structures can bear the variety of "real life" load spectra using a minimum of a given bulk material, featuring engineering lightweight design principles. (2) The inside of the structures is accessible to body fluids which deliver the required nutrients. (3) Furthermore, cellular architectures can grow organically by adding or removing individual struts or by changing the shape of the constituting elements. All these facts make the use of cellular architectures a reasonable choice for nature. Using additive manufacturing technologies (AMT), it is now possible to fabricate such structures for applications in engineering and biomedicine. In this chapter, we present methods that allow the 3D computational analysis of the mechanical properties of cellular structures with open porosity. Various different cellular architectures including disorder are studied. In order to quantify the influence of architecture, the apparent density is always kept constant. Furthermore, it is shown that how new advanced photopolymers can be used to tailor the mechanical and functional properties of the fabricated structures.

  11. Reversible addition of the OH radical to p-cymene in the gas phase: multiple adduct formation. Part 2.

    Science.gov (United States)

    Alarcón, Paulo; Bohn, Birger; Zetzsch, Cornelius; Rayez, Marie-Thérèse; Rayez, Jean-Claude

    2014-08-28

    A flash photolysis-resonance fluorescence (FP-RF) system was used to study the p-cymene (PC) + OH reaction at temperatures between 299 and 349 K in helium. Triexponential functions were fitted to groups of observed OH decay curves according to a model considering a reversible addition to form two adducts as thermolabile reservoirs of OH. Compared to Part 1 of this paper, consideration of a second adduct strongly improved the fits to our measurements, and the rate constants for the major pathways were optimized between 299 and 349 K. The Arrhenius expression for the rate constant of the sum of OH addition and H-atom abstraction pathways was found to be kOH = 1.9 × 10(-12) exp[(610 ± 210) K/T] cm(3) s(-1). Rate constants of unimolecular decomposition reactions of the adducts were similar to other aromatic compounds with the following Arrhenius expressions: 1 × 10(12) exp[(-7600 ± 800) K/T] s(-1) for adduct 1 and 4 × 10(11) exp[(-8000 ± 300) K/T] s(-1) for adduct 2. Adduct yields increased and decreased with temperature for adduct 1 and 2, respectively, but were similar (∼0.4) around room temperature. Equilibrium constants yielded values for reaction enthalpies and entropies of adduct formations. While for one adduct reasonable agreement was obtained with theoretical predictions, there were significant deviations for the other adduct. This indicates the presence of more than two adduct isomers that were not accounted for in the reaction model. Quantum chemical calculations (DFT M06-2X/6-31G(d,p)) and RRKM kinetics were employed with the aim of clarifying the mechanism of the OH addition to PC. These calculations show that formation of adducts with OH in ortho positions to the isopropyl and methyl substituents is predominant (55% and 24%) to those with OH in ipso positions (21% and 3%). A large fraction (>90%) of the ipso-C3H7 adduct is predicted to react by dealkylation forming p-cresol (in the absence of oxygen) and isopropyl radicals. These theoretical

  12. Molecular simulation of the reversible mechanical unfolding of proteins.

    Science.gov (United States)

    Rathore, Nitin; Yan, Qiliang; de Pablo, Juan J

    2004-03-22

    In this work we have combined a Wang-Landau sampling scheme [F. Wang and D. Landau, Phys. Rev. Lett. 86, 2050 (2001)] with an expanded ensemble formalism to yield a simple and powerful method for computing potentials of mean force. The new method is implemented to investigate the mechanical deformation of proteins. Comparisons are made with analytical results for simple model systems such as harmonic springs and Rouse chains. The method is then illustrated on a model 15-residue alanine molecule in an implicit solvent. Results for mechanical unfolding of this oligopeptide are compared to those of steered molecular dynamics calculations.

  13. The criterion for time symmetry of probabilistic theories and the reversibility of quantum mechanics

    Science.gov (United States)

    Holster, A. T.

    2003-10-01

    Physicists routinely claim that the fundamental laws of physics are 'time symmetric' or 'time reversal invariant' or 'reversible'. In particular, it is claimed that the theory of quantum mechanics is time symmetric. But it is shown in this paper that the orthodox analysis suffers from a fatal conceptual error, because the logical criterion for judging the time symmetry of probabilistic theories has been incorrectly formulated. The correct criterion requires symmetry between future-directed laws and past-directed laws. This criterion is formulated and proved in detail. The orthodox claim that quantum mechanics is reversible is re-evaluated. The property demonstrated in the orthodox analysis is shown to be quite distinct from time reversal invariance. The view of Satosi Watanabe that quantum mechanics is time asymmetric is verified, as well as his view that this feature does not merely show a de facto or 'contingent' asymmetry, as commonly supposed, but implies a genuine failure of time reversal invariance of the laws of quantum mechanics. The laws of quantum mechanics would be incompatible with a time-reversed version of our universe.

  14. Reducing cholinergic constriction: the major reversible mechanism in COPD

    Directory of Open Access Journals (Sweden)

    V. Brusasco

    2006-12-01

    Full Text Available The airway narrowing in chronic obstructive pulmonary disease (COPD has often been misunderstood as being irreversible. However, a large proportion of patients with COPD do respond to bronchodilator agents with significant changes in lung function. Unlike in asthma, abnormalities in airway smooth muscle structure or function are not believed to play a key role in COPD airway narrowing. Although there are only limited data suggesting that cholinergic tone may be increased in COPD, the well-documented efficacy of antimuscarinic agents in increasing airway calibre suggests that cholinergic tone represents the major reversible component of airflow obstruction in these patients. Airway wall thickening and loss of airway-to-parenchyma interdependence are nonreversible components of airflow obstruction in COPD that may amplify the effect of changes in airway smooth muscle tone. Thus, keeping airway smooth muscle tone to a minimum might offer patients long-lasting airway patency and protection against breathlessness, which is the major complaint of patients with COPD. Receptor antagonism by anticholinergic agents can achieve effective relaxation of airway smooth muscle in COPD. According to a classical view of cholinergic receptor function and distribution, the ideal anticholinergic bronchodilator would be one that blocks both M1 and M3 receptors, which mediate airway smooth muscle contraction, but not the M2 receptor, stimulation of which reduces acetylcholine release from vagus nerve endings and prevents the airway smooth muscle from contracting by excessive increments. Agents with such pharmacodynamic selectivity are not available, but effective and prolonged inhibition of airway smooth muscle tone has been obtained with tiotropium, which binds to all three major muscarinic receptor subtypes, but for much longer to M3 than to M2 receptors. Recent data show that long-term treatment with tiotropium for 1 yr helps sustain 24-h airway patency. This

  15. Sequential Polarity-Reversing Circuit

    Science.gov (United States)

    Labaw, Clayton C.

    1994-01-01

    Proposed circuit reverses polarity of electric power supplied to bidirectional dc motor, reversible electro-mechanical actuator, or other device operating in direction depending on polarity. Circuit reverses polarity each time power turned on, without need for additional polarity-reversing or direction signals and circuitry to process them.

  16. Mass transfer mechanism in chiral reversed phase liquid chromatography.

    Science.gov (United States)

    Gritti, Fabrice; Guiochon, Georges

    2014-03-01

    The mechanism of mass transfer in chiral chromatography was investigated using an experimental protocol already applied in RPLC and HILIC chromatography. The different contributions to the reduced height equivalent to a theoretical plate (HETP) include the longitudinal diffusion HETP term, the solid-liquid mass transfer resistance HETP term, the short-range eddy dispersion HETP term, and the long-range eddy dispersion HETP term. Their accurate measurement permits the determination of the adsorption rate constant kads of trans-stilbene enantiomers on a column packed with Lux 5 μm Cellulose-1 particles. The experimental results demonstrate that the number of adsorption-desorption steps per unit time of chiral compounds on polysaccharide-based chiral stationary phases is four orders of magnitude smaller than that of achiral compounds.

  17. Spectroscopic studies of the mechanism of reversible photodegradation of 1-substituted aminoanthraquinone-doped polymers

    CERN Document Server

    Hung, Sheng-Ting; Schademan, Kyle; Steverlynck, Joost; McCluskey, Matthew D; Koeckelberghs, Guy; Clays, Koen; Kuzyk, Mark G

    2015-01-01

    The mechanism of reversible photodegradation of 1-substituted aminoanthraquinones doped into poly(methyl methacrylate) and polystyrene is investigated. Time-dependent density functional theory is employed to predict the transition energies and corresponding oscillator strengths of the proposed reversibly- and irreversibly-damaged dye species. Ultraviolet-visible and Fourier transform infrared (FTIR) spectroscopy are used to characterize which species are present. FTIR spectroscopy indicates that both dye and polymer undergo reversible photodegradation when irradiated with a visible laser. These findings suggest that photodegradation of 1-substituted aminoanthraquinones doped in polymers originates from interactions between dyes and photoinduced thermally-degraded polymers, and the metastable product may recover or further degrade irreversibly.

  18. Spectroscopic studies of the mechanism of reversible photodegradation of 1-substituted aminoanthraquinone-doped polymers

    Science.gov (United States)

    Hung, Sheng-Ting; Bhuyan, Ankita; Schademan, Kyle; Steverlynck, Joost; McCluskey, Matthew D.; Koeckelberghs, Guy; Clays, Koen; Kuzyk, Mark G.

    2016-03-01

    The mechanism of reversible photodegradation of 1-substituted aminoanthraquinones doped into poly(methyl methacrylate) and polystyrene is investigated. Time-dependent density functional theory is employed to predict the transition energies and corresponding oscillator strengths of the proposed reversibly and irreversibly damaged dye species. Ultraviolet-visible and Fourier transform infrared (FTIR) spectroscopy are used to characterize which species are present. FTIR spectroscopy indicates that both dye and polymer undergo reversible photodegradation when irradiated with a visible laser. These findings suggest that photodegradation of 1-substituted aminoanthraquinones doped in polymers originates from interactions between dyes and photoinduced thermally degraded polymers, and the metastable product may recover or further degrade irreversibly.

  19. Spectroscopic studies of the mechanism of reversible photodegradation of 1-substituted aminoanthraquinone-doped polymers

    OpenAIRE

    Hung, Sheng-Ting; Bhuyan, Ankita; Schademan, Kyle; Steverlynck, Joost; McCluskey, Matthew D.; Koeckelberghs, Guy; Clays, Koen; Kuzyk, Mark G.

    2015-01-01

    The mechanism of reversible photodegradation of 1-substituted aminoanthraquinones doped into poly(methyl methacrylate) and polystyrene is investigated. Time-dependent density functional theory is employed to predict the transition energies and corresponding oscillator strengths of the proposed reversibly- and irreversibly-damaged dye species. Ultraviolet-visible and Fourier transform infrared (FTIR) spectroscopy are used to characterize which species are present. FTIR spectroscopy indicates t...

  20. SIMULATION OF OPEN MECHANISMS FOR THE ADDITIVE PROCESS WELD PLASTICS

    Directory of Open Access Journals (Sweden)

    N. N. Hurski

    2016-01-01

    Full Text Available This article discusses: model of the two-link mechanism; generalized scheme of mechatronic simulation model of 3D-printer with the positioning units of electric DC; mathematical model of the actuator of the printer unit in the form of a system of differential equations; 3D-printer programming model implemented in the Matlab-Simulink environment using the c standard library blocks and SimMechanics library; virtual (animated 3D printer model on the basis of the library Simulink 3D Animation, supports the visualization of the movements of the designed mechanism of the basic units. We present the initial data and the results of simulation of 3D-printer type Scara as a waveform positioning actuator (extruder in the manufacture of test items by fusing plastic.

  1. Microstructural evolution and magnetization reversal mechanism of CoPt films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, K K M; Chen, J S; Chow, G M [Department of Materials Science and Engineering, National University of Singapore, Singapore 119260 (Singapore); Hu, J F [Data Storage Institute, Singapore 117608 (Singapore)], E-mail: msecgm@nus.edu.sg

    2009-01-07

    Microstructural evolution and magnetization reversal mechanisms of perpendicular magnetic anisotropic Co{sub 72}Pt{sub 28} films were investigated. Results showed that in the initial stage of film growth, the Co{sub 72}Pt{sub 28} film was continuous and followed a dome-shaped structure with increasing film thickness. When the film thickness further increased above a certain critical value, the film growth acquired an inverted frustum shape structure and increased the intergranular magnetic interaction. The magnetization reversal mechanism showed a strong dependence on microstructures. The magnetization reversal followed the domain wall motion behaviour when the film was continuous and deviated towards the Stoner-Wohlfarth (S-W) model in the dome-shaped regime. A further deviation away from the S-W model was observed, when the film acquired an inverted frustum shape structure in order to minimize the surface energy.

  2. The relationships between deformation mechanisms and mechanical properties of additively manufactured porous biomaterials.

    Science.gov (United States)

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Zargarian, A; Schmauder, S

    2016-09-16

    Modulating deformation mechanism through manipulating morphological parameters of scaffold internal pore architecture provides potential to tailor the overall mechanical properties under physiological loadings. Whereas cells sense local strains, cell differentiation is also impressed by the elastic deformations. In this paper, structure-property relations were developed for Ti6-Al-4V scaffolds designed based on triply periodic minimal surfaces. 10mm cubic scaffolds composed of 5×5×5 unit cells formed of F-RD (bending dominated) and I-WP (stretching dominated) architectures were additively manufactured at different volume fractions and subjected to compressive tests. The first stages of deformation for stretching dominated structure, was accompanied by bilateral layer-by-layer failure of unit cells owing to the buckling of micro-struts, while for bending dominated structure, namely F-RD, global shearing bands appeared since the shearing failure of struts in the internal architecture. Promoted mechanical properties were found for stretching dominated structure since the global orientation of struts were parallel to loading direction while inclination of struts diminished specific properties for bending dominated structure. Moreover, elastic-plastic deformation was computationally studied by applying Johnson-Cook damage model to the voxel-based models in FE analysis. Scaling analysis was performed for mechanical properties with respect to the relative density thereby failure mechanism was correlated to the constants of power law describing mechanical properties.

  3. Exploration of a Novel Persistent Reversal of Pathological Pain: Mechanisms and Mediators

    Science.gov (United States)

    2015-04-01

    cultured glial cells blocked TNF and but not IL-10 production , suggesting that while PKA and PKC may play a role in A2AR agonist effects, there are also...models of neuropathic pain and to elucidate the underlying mechanisms that result in the production of IL-10 and subsequent reversal of the allodynia. 15...translated to numerous animal models of neuropathic pain and to elucidate the underlying mechanisms that result in the production of IL-10 and

  4. Study on the performance of polycarboxylate-based superplasticizers synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization

    Science.gov (United States)

    Yu, Binbin; Zeng, Zhong; Ren, Qinyu; Chen, Yang; Liang, Mei; Zou, Huawei

    2016-09-01

    A series of block type polycarboxylate-based superplasticizers (PCs) with different molecular architectures were synthesized with macromonomer butenyl alkylene polyoxyethylene-polyoxypropylene ether (BAPP) and acrylic acid (AA) by reversible addition-fragmentation chain transfer (RAFT) polymerization. Fourier-Transformed Infrared (FTIR) Spectroscopy and dynamic light scattering (DLS) were applied to investigate the PCs' molecular structure. The dispersion capacity of the PCs in cement were also measured, and the results showed that the polycarboxylic dispersing agents prepared by this method were suitable for portlant cement. It was found that the PCs could affect the hydration process, which was performed through retarding the generation of ettringite in the hydrated product. Our studies with X-ray diffraction (XRD), scanning electron microscopy (SEM) and compressive strength measurement of hydrated production were all supporting this conclusion.

  5. Functionalization of vertically aligned carbon nanotubes with polystyrene via surface initiated reversible addition fragmentation chain transfer polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Macdonald, Thomas; Gibson, Christopher T.; Constantopoulos, Kristina; Shapter, Joseph G. [Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA, 5001 (Australia); Ellis, Amanda V., E-mail: amanda.ellis@flinders.edu.au [Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA, 5001 (Australia)

    2012-01-15

    Here we demonstrate the covalent attachment of vertically aligned (VA) acid treated single-walled carbon nanotubes (SWCNTs) onto a silicon substrate via dicyclohexylcarbodiimide (DCC) coupling chemistry. Subsequently, the pendant carboxyl moieties on the sidewalls of the VA-SWCNTs were derivatized to acyl chlorides, and then finally to bis(dithioester) moieties using a magnesium chloride dithiobenzoate salt. The bis(dithioester) moieties were then successfully shown to act as a chain transfer agent (CTA) in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in a surface initiated 'grafting-from' process from the VA-SWCNT surface. Atomic force microscopy (AFM) verified vertical alignment of the SWCNTs and the maintenance thereof throughout the synthesis process. Finally, Raman scattering spectroscopy and AFM confirmed polystyrene functionalization.

  6. Investigation of the magnetization reversal mechanism of electrolessly deposited Co-B nanotubes

    Directory of Open Access Journals (Sweden)

    David Richardson

    2016-05-01

    Full Text Available Co-B nanotubes were prepared via an electroless deposition method. The morphology, magnetic properties and the magnetization reversal mechanism of the nanotubes were investigated. Deposition was carried out in porous polycarbonate membranes leading to the formation of Co-B nanotubes with an average external diameter of 400 nm and lengths up to 6 μm. Electroless deposition resulted in the formation of alloys with composition Co70B30 and a specific magnetization of 65.6 J T−1kg−1, which is about 40 % of that of pure Co (161 J T−1kg−1. The transversal and vortex modes were identified as the mechanisms responsible for magnetization reversal in the nanotubes. A crossover between the two modes is observed at low angles and the results are in line with current models for switching mechanisms of nanotubes.

  7. Investigation of the magnetization reversal mechanism of electrolessly deposited Co-B nanotubes

    Science.gov (United States)

    Richardson, David; Kingston, Samuel; Rhen, Fernando M. F.

    2016-05-01

    Co-B nanotubes were prepared via an electroless deposition method. The morphology, magnetic properties and the magnetization reversal mechanism of the nanotubes were investigated. Deposition was carried out in porous polycarbonate membranes leading to the formation of Co-B nanotubes with an average external diameter of 400 nm and lengths up to 6 μm. Electroless deposition resulted in the formation of alloys with composition Co70B30 and a specific magnetization of 65.6 J T-1kg-1, which is about 40 % of that of pure Co (161 J T-1kg-1). The transversal and vortex modes were identified as the mechanisms responsible for magnetization reversal in the nanotubes. A crossover between the two modes is observed at low angles and the results are in line with current models for switching mechanisms of nanotubes.

  8. Effect of Zr Addition on the Magnetization Reversal Behavior for α-Fe/Pr2Fe14B Nanocomposite Alloys

    Science.gov (United States)

    Pan, Minxiang; Zhang, Pengyue; Ge, Hongliang; Hong, Zhanglian; Wu, Qiong; Jiao, Zhiwei; Yang, Hangfu

    2011-09-01

    The microstructure and magnetic properties of the Zr-doped α-Fe/Pr2Fe14B nanocomposite magnets prepared by melt-spinning method have been studied by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The magnetization reversal behavior during the recoil processes of nanocomposite alloys has been investigated by analyzing the hysteresis curves and recoil loops of demagnetization curves. An enhanced magnetic properties has been obtained by the addition of 1 at. % Zr in α-Fe/Pr2Fe14B alloys, where the coercivity Hc increases from 470.7 to 793.2 kA/m, the maximum energy product (BH)max from 66.8 to 90.8 kJ/m3, the remanence ratio Mr/Ms from 0.74 to 0.77. The recoil loop results show that the maximum value of the integrated recoil loop area for 1 at. % Zr doped sample is quietly low of 1.87×10-3, only 1/2 for the Zr-free and 1/3 for 5 at. % Zr doped samples respectively. This result indicates that the 1 at. % Zr doped sample has a lower energy loss, resulting from a low recoverable portion of the magnetization remaining as long as the applied reversal field is below the coercivity Hc. This study provides a promising guideline for the future fabrication of low-energy-loss nanocomposite magnets for electric machines and generators.

  9. [Determination of arsanilic acid and sulfanilic acid as adulterant in feed additives by reversed-phase high performance liquid chromatography].

    Science.gov (United States)

    Xu, Jinping; He, Heng; Xu, Mengyi; Qu, Yanhua

    2010-02-01

    A reversed-phase high performance liquid chromatographic (RP-HPLC) method was established for the determination of arsanilic acid and sulfanilic acid as adulterant in the feed additives. The separation was carried out on a Waters Bondapak C18 column, and methanol-water (pH 2.9 adjusted by 0.01 mol/L phosphoric acid) (1 : 4, v/v) was used as the mobile phase with a flow rate of 1.0 mL/min. A diode array detector was used at 244 nm as the detection wavelength. Arsanilic acid and sulfanilic acid were separated within 3 min. The linear ranges all were 5 - 200 mg/L and the detection limits (S/N = 3) were 0.20 and 0.15 mg/L for arsanilic acid and sulfanilic acid, respectively. This method is simple and rapid, and suitable for the simultaneous determination of arsanilic acid and sulfanilic acid in feed additives.

  10. Exterior beam-column joint study with non-conventional reinforcement detailing using mechanical anchorage under reversal loading

    Indian Academy of Sciences (India)

    S Rajagopal; S Prabavathy

    2014-10-01

    Reinforced concrete structures beam-column joints are the most critical regions in seismic prone areas. Proper reinforcement anchorage is essential to enhance the performance of the joints. An attempt has been made to appraise the performance of the anchorages and joints. The anchorages are detailed as per ACI-352 (mechanical anchorages), ACI-318 (conventional bent hooks) and IS-456 (conventional full anchorage). The joints are detailed without confinement in group-I and with additional X-cross bar in group-II. To assess the seismic performance, the specimens are assembled into two groups of three specimens each and were tested under reversal loading, The specimen with T-type mechanical anchorage (Headed bar) and T-type mechanical anchorage combination with X-cross bar exhibited significant improvement in seismic performance: load-displacement capacity, displacement ductility, stiffness degradation, controlled crack capacity in the joint shear panel and also reduced congestion of reinforcement in joint core.

  11. A Study on Efficient Mobile IPv6 Fast Handover Scheme Using Reverse Binding Mechanism

    Science.gov (United States)

    Tolentino, Randy S.; Lee, Kijeong; Kim, Sung-Gyu; Kim, Miso; Park, Byungjoo

    This paper proposes a solution for solving the packet handover issues of MIPv6. We propose an efficient scheme that can support fast handover effectively in standard Mobile IPv6 (MIPv6) by optimizing the associated data and the flow of signal during handover. A new signaling message Reverse Packet Binding Mechanism is defined and utilized to hasten the handover procedure by adding a buffer in access point (AP) and home agent (HA).

  12. Asymmetric effect of mechanical stress on the forward and reverse reaction catalyzed by an enzyme.

    Directory of Open Access Journals (Sweden)

    Collin Joseph

    Full Text Available The concept of modulating enzymatic activity by exerting a mechanical stress on the enzyme has been established in previous work. Mechanical perturbation is also a tool for probing conformational motion accompanying the enzymatic cycle. Here we report measurements of the forward and reverse kinetics of the enzyme Guanylate Kinase from yeast (Saccharomyces cerevisiae. The enzyme is held in a state of stress using the DNA spring method. The observation that mechanical stress has different effects on the forward and reverse reaction kinetics suggests that forward and reverse reactions follow different paths, on average, in the enzyme's conformational space. Comparing the kinetics of the stressed and unstressed enzyme we also show that the maximum speed of the enzyme is comparable to the predictions of the relaxation model of enzyme action, where we use the independently determined dissipation coefficient [Formula: see text] for the enzyme's conformational motion. The present experiments provide a mean to explore enzyme kinetics beyond the static energy landscape picture of transition state theory.

  13. Mechanical continuity and reversible chromosome disassembly within intact genomes removed from living cells

    Science.gov (United States)

    Maniotis, A. J.; Bojanowski, K.; Ingber, D. E.

    1997-01-01

    decondensation which could be reversed by addition of histone H1, but not histones H2b or H3. These data suggest that DNA, its associated protein scaffolds, and surrounding cytoskeletal networks function as a structurally-unified system. Mechanical coupling within the nucleoplasm may coordinate dynamic alterations in chromatin structure, guide chromosome movement, and ensure fidelity of mitosis.

  14. Scale-up of the Reversible Addition-Fragmentation Chain Transfer (RAFT Polymerization Using Continuous Flow Processing

    Directory of Open Access Journals (Sweden)

    Nenad Micic

    2014-01-01

    Full Text Available A controlled radical polymerization process using the Reversible Addition-Fragmentation Chain Transfer (RAFT approach was scaled up by a factor of 100 from a small laboratory scale of 5 mL to a preparative scale of 500 mL, using batch and continuous flow processing. The batch polymerizations were carried out in a series of different glass vessels, using either magnetic or overhead stirring, and different modes of heating: Microwave irradiation or conductive heating in an oil bath. The continuous process was conducted in a prototype tubular flow reactor, consisting of 6 mm ID stainless steel tubing, fitted with static mixers. Both reactor types were tested for polymerizations of the acid functional monomers acrylic acid and 2-acrylamido-2-methylpropane-1-sulfonic acid in water at 80 °C with reaction times of 30 to 40 min. By monitoring the temperature during the exothermic polymerization process, it was observed that the type and size of reactor had a significant influence on the temperature profile of the reaction.

  15. Improvement in enzyme activity and stability by addition of low molecular weight polyethylene glycol to sodium bis(2-ethyl-L-hexyl)sulfosuccinate/isooctane reverse micellar system.

    Science.gov (United States)

    Talukder, M M R; Takeyama, T; Hayashi, Y; Wu, J C; Kawanishi, T; Shimizu, N; Ogino, C

    2003-08-01

    The activity and stability of Chromobacterium viscosum lipase (glycerolester hydrolase, EC 3.1.1.3)-catalyzed olive oil hydrolysis in sodium bis (2-ethyl-l-hexyl)sulfosuccinate (AOT)/isooctane reverse micelles is increased appreciably when low molecular weight polyethylene glycol (PEG 400) is added to the reverse micelles. To understand the effect of PEG 400 on the phase behavior of the reverse micellar system, the phase diagram of AOT/ PEG 400/water/isooctane system was studied. The influences of relevant parameters on the catalytic activity in AOT/PEG 400 reverse micelles were investigated and compared with the results in the simple AOT reverse micelles. In the presence of PEG 400, the linear decreasing trend of the lipase activity with AOT concentration, which is observed in the simple AOT reverse micelles, disappeared. Enzyme entrapped in AOT/PEG reverse micelles was very stable, retaining >75% of its initial activity after 60 d, whereas the half-life in simple AOT reverse micelles was 38 d. The kinetics parameter maximum velocity (Vmax) exhibiting the temperature dependence and the activation energy obtained by Arrhenius plot was suppressed significantly by the addition of PEG 400.

  16. Complete reversal of muscle wasting in experimental cancer cachexia: Additive effects of activin type II receptor inhibition and β-2 agonist.

    Science.gov (United States)

    Toledo, Míriam; Busquets, Sílvia; Penna, Fabio; Zhou, Xiaolan; Marmonti, Enrica; Betancourt, Angelica; Massa, David; López-Soriano, Francisco J; Han, H Q; Argilés, Josep M

    2016-04-15

    Formoterol is a highly potent β2-adrenoceptor-selective agonist, which is a muscle growth promoter in many animal species. Myostatin/activin inhibition reverses skeletal muscle loss and prolongs survival of tumor-bearing animals. The aim of this investigation was to evaluate the effects of a combination of the soluble myostatin receptor ActRIIB (sActRIIB) and the β2-agonist formoterol in the cachectic Lewis lung carcinoma model. The combination of formoterol and sActRIIB was extremely effective in reversing muscle wasting associated with experimental cancer cachexia in mice. Muscle weights from tumor-bearing animals were completely recovered following treatment and this was also reflected in the measured grip strength. This combination increased food intake in both control and tumor-bearing animals. The double treatment also prolonged survival significantly without affecting the weight and growth of the primary tumor. In addition, it significantly reduced the number of metastasis. Concerning the mechanisms for the preservation of muscle mass during cachexia, the effects of formoterol and sActRIIB seemed to be additive, since formoterol reduced the rate of protein degradation (as measured in vitro as tyrosine release, using incubated isolated individual muscles) while sActRIIB only affected protein synthesis (as measured in vivo using tritiated phenylalanine). Formoterol also increased the rate of protein synthesis and this seemed to be favored by the presence of sActRIIB. Combining formoterol and sActRIIB seemed to be a very promising treatment for experimental cancer cachexia. Further studies in human patients are necessary and may lead to a highly effective treatment option for muscle wasting associated with cancer.

  17. Mechanism of Cyclically Polarity Reversing Solar Magnetic Cycle as a Cosmic Dynamo

    Indian Academy of Sciences (India)

    Hirokazu Yoshimura

    2000-09-01

    We briefly describe historical development of the concept of solar dynamo mechanism that generates electric current and magnetic field by plasma flows inside the solar convection zone. The dynamo is the driver of the cyclically polarity reversing solar magnetic cycle. The reversal process can easily and visually be understood in terms of magnetic field line stretching and twisting and folding in three-dimensional space by plasma flows of differential rotation and global convection under influence of Coriolis force. This process gives rise to formation of a series of huge magnetic flux tubes that propagate along iso-rotation surfaces inside the convection zone. Each of these flux tubes produces one solar cycle. We discuss general characteristics of any plasma flows that can generate magnetic field and reverse the polarity of the magnetic field in a rotating body in the Universe. We also mention a list of problems which are currently being disputed concerning the solar dynamo mechanism together with observational evidences that are to be constraints as well as verifications of any solar cycle dynamo theories of short and long term behaviors of the Sun, particularly time variations of its magnetic field, plasma flows, and luminosity.

  18. Mechanisms of reversible photodegradation in disperse orange 11 dye doped in PMMA polymer

    CERN Document Server

    Embaye, Natnael B; Kuzyk, Mark G

    2008-01-01

    We use amplified spontaneous emission (ASE) and linear absorption spectroscopy to study the mechanisms of reversible photodegradation of 1-amino-2-methylanthraquinone (disperse orange 11-DO11) in solid poly(methyl methacrylate). Measurements as a function of intensity, concentration, and time suggest that ASE originates in a state (be it a tautomer or a vibronic level) that can form a dimer or some other aggregate upon relaxation, which through fluorescence quenching leads to degradation of the ASE signal. Whatever the degradation route, a high concentration of DO11 is required and the polymer plays a key role in the process of opening a new reversible degradation pathway that is not available at lower concentrations or in liquid solutions. We construct an energy level diagram that describes all measured quantities in the decay and recovery processes and propose a hypothesis of the nature of the associated states.

  19. Preparation and formation mechanism of Al2O3 nanoparticles by reverse microemulsion

    Institute of Scientific and Technical Information of China (English)

    HUANG Ke-long; YIN Liang-guo; LIU Su-qin; LI Chao-jian

    2007-01-01

    Al2O3 nanoparticles were prepared by polyethylene glycol octylphenyl ether(Triton X-100)/n-butyl alcohol/cyclohexane/ water W/O reverse microemulsion. The proper calcination temperature was determined at 1 150 ℃ by thermal analysis of the precursor products. The structures and morphologies of Al2O3 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy and UV-Vis spectra. The influences of mole ratio of water to surfactant on the morphologies and the sizes of the Al2O3 nanoparticles were studied. With the increase of surfactant content, the particles size becomes larger. The agglomeration of nanoparticles was solved successfully. And the formation mechanisms of Al2O3 nanoparticles in the reverse microemulsion were also discussed.

  20. The Reversal Effect and Its Mechanisms of Tetramethylpyrazine on Multidrug Resistance in Human Bladder Cancer.

    Directory of Open Access Journals (Sweden)

    Shanshan Wang

    Full Text Available Chemotherapy is an important strategy for the treatment of bladder cancer. However, the main problem limiting the success of chemotherapy is the development of multidrug resistance (MDR. To improve the management of bladder cancer, it is an urgent matter to search for strategies to reverse MDR. We chose three kinds of herbal medicines including ginsenoside Rh2, (--Epigallocatechin gallate (EGCG and Tetramethylpyrazine (TMP to detect their effects on bladder cancer. Reversal effects of these three herbal medicines for drug resistance in adriamycin (ADM-resistant Pumc-91 cells (Pumc-91/ADM were assessed by Cell Counting Kit-8 (CCK-8 cell proliferation assay system. The mechanisms of reversal effect for TMP were explored in Pumc-91/ADM and T24/DDP cells. After Pumc-91/ADM and T24/DDP cells were treated with TMP, cell cycle distribution analysis was performed by flow cytometry. The expression of MRP1, GST, BCL-2, LRP and TOPO-II was evaluated using quantitative real-time polymerase chain reaction (qRT-PCR, immunefluorescence assay and western blot. It was observed that TMP was capable of enhancing the cytotoxicity of anticancer agents on Pumc-91/ADM cells in response to ADM, however Rh2 and EGCG were unable to. The reversal effect of TMP was also demonstrated in T24/DDP cells. Moreover, the treatment with TMP in Pumc-91/ADM and T24/DDP cells led to an increased of G1 phase accompanied with a concomitant decrease of cell numbers in S phase. Compared to the control group, an obvious decrease of MRP1, GST, BCL-2 and an increase of TOPO-II were shown in TMP groups with a dose-dependency in mRNA and protein levels. However, there was no difference on LRP expression between TMP groups and the control group. TMP could effectively reverse MDR of Pumc-91/ADM and T24/DDP cells and its mechanisms might be correlated with the alteration of MRP1, GST, BCL-2 and TOPO-II. TMP might be a potential candidate for reversing drug resistance in bladder cancer

  1. Effect of fluorapatite additive on the mechanical properties of tricalcium phosphate-zirconia composites

    Science.gov (United States)

    Sallemi, I.; Ben Ayed, F.; Bouaziz, J.

    2012-02-01

    The effect of fluorapatite addition on the mechanical properties of tricalcium phosphate - 50 wt% zirconia composites was investigated during the sintering process. The Brazilian test was used to measure the mechanical resistance of bioceramics. The mechanical properties of composites increase with the sintering temperature and with fluorapatite additive. At 1400°C, the fluorapatite additive ameliorates the densification and the mechanical resistance of tricalcium phosphate - 50 wt% zirconia composites. The 31P magic angle spinning nuclear magnetic resonance analysis of tricalcium phosphate - zirconia composites sintered with fluorapatite additives reveals the presence of tetrahedral P sites.

  2. Theoretical and Experimental Investigation of Thermodynamics and Kinetics of Thiol-Michael Addition Reactions: A Case Study of Reversible Fluorescent Probes for Glutathione Imaging in Single Cells.

    Science.gov (United States)

    Chen, Jianwei; Jiang, Xiqian; Carroll, Shaina L; Huang, Jia; Wang, Jin

    2015-12-18

    Density functional theory (DFT) was applied to study the thermodynamics and kinetics of reversible thiol-Michael addition reactions. M06-2X/6-31G(d) with the SMD solvation model can reliably predict the Gibbs free energy changes (ΔG) of thiol-Michael addition reactions with an error of less than 1 kcal·mol(-1) compared with the experimental benchmarks. Taking advantage of this computational model, the first reversible reaction-based fluorescent probe was developed that can monitor the changes in glutathione levels in single living cells.

  3. Isoflurane reversibly destabilizes hippocampal dendritic spines by an actin-dependent mechanism.

    Directory of Open Access Journals (Sweden)

    Jimcy Platholi

    Full Text Available General anesthetics produce a reversible coma-like state through modulation of excitatory and inhibitory synaptic transmission. Recent evidence suggests that anesthetic exposure can also lead to sustained cognitive dysfunction. However, the subcellular effects of anesthetics on the structure of established synapses are not known. We investigated effects of the widely used volatile anesthetic isoflurane on the structural stability of hippocampal dendritic spines, a postsynaptic structure critical to excitatory synaptic transmission in learning and memory. Exposure to clinical concentrations of isoflurane induced rapid and non-uniform shrinkage and loss of dendritic spines in mature cultured rat hippocampal neurons. Spine shrinkage was associated with a reduction in spine F-actin concentration. Spine loss was prevented by either jasplakinolide or cytochalasin D, drugs that prevent F-actin disassembly. Isoflurane-induced spine shrinkage and loss were reversible upon isoflurane elimination. Thus, isoflurane destabilizes spine F-actin, resulting in changes to dendritic spine morphology and number. These findings support an actin-based mechanism for isoflurane-induced alterations of synaptic structure in the hippocampus. These reversible alterations in dendritic spine structure have important implications for acute anesthetic effects on excitatory synaptic transmission and synaptic stability in the hippocampus, a locus for anesthetic-induced amnesia, and have important implications for anesthetic effects on synaptic plasticity.

  4. Reversal effect and mechanism of Ginkgo biloba exocarp extracts in multidrug resistance of mice S180 tumor cells

    Science.gov (United States)

    Hu, Bi-Yuan; Gu, Yun-Hao; Cao, Chen-Jie; Wang, Jun; Han, Dong-Dong; Tang, Ying-Chao; Chen, Hua-Sheng; Xu, Aihua

    2016-01-01

    The aim of the present study was to investigate the reversal effect and its related mechanism of Ginkgo biloba exocarp extracts (GBEEs) in obtained multidrug resistance (MDR) of mice S180 tumor cells in vitro and in vivo. In order to simulate the clinical PFC [cis-dichlorodiamineplatinum, cisplatin (DDP) + fluorouracil (FU), FU+cyclophosphamide and cyclophosphamide] scheme, a gradually increasing dose was administered in a phased induction in order to induce S180 cells in vivo and to make them obtain multidrug resistance. The results in vitro demonstrated that GBEE could significantly increase the IC50 of DDP on S180 MDR cells, increase the accumulation of Adriamycin (ADR) and rhodamine 123 (Rho 123), and reduce the efflux of Rho 123 of S180 MDR cells. The results from the in vivo treatment with a combination of GBEE and DDP to S180 MDR ascites tumor in mice demonstrated that each dose of GBEE could effectively reverse the drug-resistance of S180 MDR cells to DDP in order to extend the survival time of mice with ascite tumors and inhibit tumor growth in solid tumor mice. In addition, GBEE effectively inhibited the expression of MDR-1 mRNA and multidrug resistance-associated protein-1 mRNA in S180 MDR cells of ascites tumor in mice and improved the expression levels of cytokines, including interleukin (IL)-3, IL-18 and interferon-γ in the blood serum of S180 MDR tumor-bearing mice. The present study showed that the mechanism of GBEE reversal of MDR may be associated with the inhibition of the functional activity of P-glycoprotein, the downregulation of drug resistance related gene expression of S180 MDR cells and the improvement of the production of related serum cytokines of S180 MDR tumor mice. PMID:27698692

  5. Reversal effect and mechanism of Ginkgo biloba exocarp extracts in multidrug resistance of mice S180 tumor cells.

    Science.gov (United States)

    Hu, Bi-Yuan; Gu, Yun-Hao; Cao, Chen-Jie; Wang, Jun; Han, Dong-Dong; Tang, Ying-Chao; Chen, Hua-Sheng; Xu, Aihua

    2016-10-01

    The aim of the present study was to investigate the reversal effect and its related mechanism of Ginkgo biloba exocarp extracts (GBEEs) in obtained multidrug resistance (MDR) of mice S180 tumor cells in vitro and in vivo. In order to simulate the clinical PFC [cis-dichlorodiamineplatinum, cisplatin (DDP) + fluorouracil (FU), FU+cyclophosphamide and cyclophosphamide] scheme, a gradually increasing dose was administered in a phased induction in order to induce S180 cells in vivo and to make them obtain multidrug resistance. The results in vitro demonstrated that GBEE could significantly increase the IC50 of DDP on S180 MDR cells, increase the accumulation of Adriamycin (ADR) and rhodamine 123 (Rho 123), and reduce the efflux of Rho 123 of S180 MDR cells. The results from the in vivo treatment with a combination of GBEE and DDP to S180 MDR ascites tumor in mice demonstrated that each dose of GBEE could effectively reverse the drug-resistance of S180 MDR cells to DDP in order to extend the survival time of mice with ascite tumors and inhibit tumor growth in solid tumor mice. In addition, GBEE effectively inhibited the expression of MDR-1 mRNA and multidrug resistance-associated protein-1 mRNA in S180 MDR cells of ascites tumor in mice and improved the expression levels of cytokines, including interleukin (IL)-3, IL-18 and interferon-γ in the blood serum of S180 MDR tumor-bearing mice. The present study showed that the mechanism of GBEE reversal of MDR may be associated with the inhibition of the functional activity of P-glycoprotein, the downregulation of drug resistance related gene expression of S180 MDR cells and the improvement of the production of related serum cytokines of S180 MDR tumor mice.

  6. Molecular mechanism of carvedilol in attenuating the reversion to fetal energy metabolism during cardiac hypertrophy development

    Institute of Scientific and Technical Information of China (English)

    胡琴; 李隆贵

    2003-01-01

    Objective: To explore the molecular regulation mechanism of carvedilol in attenuating the reversion back towards fetal energy metabolism during the development of cardiac hypertrophy induced by coarctation of abdominal aorta (CAA) in male Wistar rats. Methods: Hemodynamic and ventricular remodeling parameters, free fatty acid content in the serum were measured in the experimental animals at 16 weeks after the surgical CAA, the rats receiving carvedilol intervention (CAR) after CAA, and those with sham operation (SH). The expressions of muscle carnitine palmitoyltransferaseⅠ (M-CPTⅠ) and medium chain acyl-CoA dehydrogenase (MCAD) mRNA in the cardiac myocytes from every group were studied with RT-PCR. Results: Significant left ventricular hypertrophy were observed in the rats 16 weeks after coarctation operation (P<0.05), together with significant free fatty acids accumulation and downregulation of M-CPTⅠ and MCAD mRNA (P<0.05) in CAA group. Carvedilol at a dose of 30 mg/kg/d for 12 weeks inhibited the left ventricular hypertrophy induced by pressure overload and enhanced the gene expressions of rate-limiting enzyme (M-CPTⅠ) and key enzyme of fatty acid (MCAD) in the CAR group compared with CAA group (P<0.05). Conclusion: Pressure overload-induced hypertrophy in CAA rats causes the reversion back towards fetal enery metabolism, that is, downregulates the expressions of rate-limiting enzyme and key enzyme of fatty acid oxidation. The intervention therapy with carvedilol, a vasodilating alpha- and beta-adrenoreceptor antagonist, attenuates the reversion of the metabolic gene expression to fetal type through upregulating M-CPTⅠ and MCAD mRNA expressions. Thus, carvedilol may exert cardioprotective effects on heart failure by the mechanism of preserving the adult metabolic gene regulation.

  7. Compact piezoelectric tripod manipulator based on a reverse bridge-type amplification mechanism

    Science.gov (United States)

    Na, Tae-Won; Choi, Jun-Ho; Jung, Jin-Young; Kim, Hyeong-Geon; Han, Jae-Hung; Park, Kwang-Chun; Oh, Il-Kwon

    2016-09-01

    We report a hierarchical piezoelectric tripod manipulator based on a reverse bridge-type displacement amplifier. The reverse bridge-type amplification mechanism is pre-strained by each piezo-stack actuator up to 60 μm and is cross-stacked in a series arrangement to make a compact and high-stroke manipulator having load-bearing characteristics. The designed manipulator with three degrees of freedom is compact with a height of 56.0 mm, a diameter of 48.6 mm and total weight of 115 g. It achieves a translational stroke of up to 880 μm in heaving motion and a tilting angle of up to 2.0° in rotational motion within the operating voltage and power range of the piezoelectric stack actuator. A key feature of the present design is built-in and pre-strained displacement amplification mechanisms integrated with piezoelectric stacked actuators, resulting in a compact tripod manipulator having exceptionally high stroke and load-bearing capacity.

  8. Reverse task of passive and active mechanical system in torsional vibrations

    Directory of Open Access Journals (Sweden)

    K. Białas

    2009-08-01

    Full Text Available Purpose: The main aim of this paper is to develop a method for finding structure and parameters, i.e. a structural and parameter synthesis, of an active model of a viscous damper mechanical system in vibrations. The aim is to perfect the synthesis seen as modification at the sub-assembly design level in relation to the required spectrum of vibration frequency of the system.Design/methodology/approach: With complex systems classic design is very time consuming and it does not always produce satisfactory results. Therefore, it is necessary to use other design methods, such as the inverse task, which is called synthesis. It is searching for a system structure, together with elements value, which realizes the required frequency characteristics.Findings: Using the active elements allows complete elimination of the oscillations. The conducted analysis show that it is not necessary to use both the active and passive elements, as using only active elements produces the same results.Research limitations/implications: The scope of discussion is reverse task of mechanical system in torsional vibrations including passive and active elements, but for this type of systems, such approach is sufficient.Practical implications: The methods of reverse task and analysis can be base of design and construct for this type of mechanic systems.Originality/value: Thank to the approach, introduced in this paper, can be conducted as early as during the designing of future functions of the system as well as during the construction of the system. Using method and obtained results can be value for designers of mechanical systems with elements reducing vibrations.

  9. Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I) --Action mechanism of additive and property of donating-accepting electron

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The combination energy and chemical adsorption energy of N-substituted perfluoropoly- alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (RfO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a p-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of RfO. and accept electron of RfO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III>II>I>IV>V.

  10. Apparent anti-Woodward-Hoffmann addition to a nickel bis(dithiolene) complex: the reaction mechanism involves reduced, dimetallic intermediates.

    Science.gov (United States)

    Dang, Li; Shibl, Mohamed F; Yang, Xinzheng; Harrison, Daniel J; Alak, Aiman; Lough, Alan J; Fekl, Ulrich; Brothers, Edward N; Hall, Michael B

    2013-04-01

    Nickel dithiolene complexes have been proposed as electrocatalysts for alkene purification. Recent studies of the ligand-based reactions of Ni(tfd)2 (tfd = S2C2(CF3)2) and its anion [Ni(tfd)2](-) with alkenes (ethylene and 1-hexene) showed that in the absence of the anion, the reaction proceeds most rapidly to form the intraligand adduct, which decomposes by releasing a substituted dihydrodithiin. However, the presence of the anion increases the rate of formation of the stable cis-interligand adduct, and decreases the rate of dihydrodithiin formation and decomposition. In spite of both computational and experimental studies, the mechanism, especially the role of the anion, remained somewhat elusive. We are now providing a combined experimental and computational study that addresses the mechanism and explains the role of the anion. A kinetic study (global analysis) for the reaction of 1-hexene is reported, which supports the following mechanism: (1) reversible intraligand addition, (2) oxidation of the intraligand addition product prior to decomposition, and (3) interligand adduct formation catalyzed by Ni(tfd)2(-). Density functional theory (DFT) calculations were performed on the Ni(tfd)2/Ni(tfd)2(-)/ethylene system to shed light on the selectivity of adduct formation in the absence of anion and on the mechanism in which Ni(tfd)2(-) shifts the reaction from intraligand addition to interligand addition. Computational results show that in the neutral system the free energy of activation for intraligand addition is lower than that for interligand addition, in agreement with the experimental results. The computations predict that the anion enhances the rate of the cis-interligand adduct formation by forming a dimetallic complex with the neutral complex. The [(Ni(tfd)2)2](-) dimetallic complex then coordinates ethylene and isomerizes to form a Ni,S-bound ethylene complex, which then rapidly isomerizes to the stable interligand adduct but not to the intraligand adduct

  11. Mechanically clamped PZT ceramics investigated by First-order reversal curves diagram

    Directory of Open Access Journals (Sweden)

    Laurentiu Stoleriu

    2010-09-01

    Full Text Available The First Order Reversal Curves (FORC diagrams method was developed for characterizing the switching properties of ferroelectrics. In the present paper, the FORC method was applied for hard Pb(Zr,TiO3 ceramics with symmetric and asymmetric clamping. An ideal high-oriented single-crystalline ferroelectric with rectangular P(E loop would be characterised by a delta-function FORC distribution, while real ferroelectrics and mostly the polycrystalline ceramics show dispersed FORC distributions. All the investigated ceramics show FORC distributions with non-Gaussian shape, slightly elongated along the coercitive axis, meaning a high dispersion of the energy barriers separating the two bi-stable polarizations ±P. The degree of dispersion is enhanced by clamping. The maximum FORC coercivity is located at ~ (1.9-2 MV/m for all the hard ceramics. The FORC cycling experiment causes the reversal of the initial poling and result in a positive/negative bias on the FORC diagrams. According to the observed features, it results that FORC coercivity is more related to the nature of the material, while the bias field is more sensitive to the electrical and mechanical boundary conditions in which the ferroelectric ceramics evolves while switching.

  12. Improvement of mechanical properties on metastable stainless steels by reversion heat treatments

    Science.gov (United States)

    Mateo, A.; Zapata, A.; Fargas, G.

    2013-12-01

    AISI 301LN is a metastable austenitic stainless steel that offers an excellent combination of high strength and ductility. This stainless grade is currently used in applications where severe forming operations are required, such as automotive bodies. When these metastable steels are plastically deformed at room temperature, for example by cold rolling, austenite transforms to martensite and, as a result, yield strength increases but ductility is reduced. Grain refinement is the only method that allows improving strength and ductility simultaneously. Several researchers have demonstrated that fine grain AISI 301LN can be obtained by heat treatment after cold rolling. This heat treatment is called reversion because it provokes the reversion of strain induced martensite to austenite. In the present work, sheets of AISI 301LN previously subjected to 20% of cold rolling reduction were treated and a refined grain austenitic microstructure was obtained. Mechanical properties, including fatigue limit, were determined and compared with those corresponding to the steel both before and after the cold rolling.

  13. Reverse engineering the mechanical and molecular pathways in stem cell morphogenesis.

    Science.gov (United States)

    Lu, Kai; Gordon, Richard; Cao, Tong

    2015-03-01

    The formation of relevant biological structures poses a challenge for regenerative medicine. During embryogenesis, embryonic cells differentiate into somatic tissues and undergo morphogenesis to produce three-dimensional organs. Using stem cells, we can recapitulate this process and create biological constructs for therapeutic transplantation. However, imperfect imitation of nature sometimes results in in vitro artifacts that fail to recapitulate the function of native organs. It has been hypothesized that developing cells may self-organize into tissue-specific structures given a correct in vitro environment. This proposition is supported by the generation of neo-organoids from stem cells. We suggest that morphogenesis may be reverse engineered to uncover its interacting mechanical pathway and molecular circuitry. By harnessing the latent architecture of stem cells, novel tissue-engineering strategies may be conceptualized for generating self-organizing transplants.

  14. Reversible and rapid transfer-RNA deactivation as a mechanism of translational repression in stress.

    Science.gov (United States)

    Czech, Andreas; Wende, Sandra; Mörl, Mario; Pan, Tao; Ignatova, Zoya

    2013-08-01

    Stress-induced changes of gene expression are crucial for survival of eukaryotic cells. Regulation at the level of translation provides the necessary plasticity for immediate changes of cellular activities and protein levels. In this study, we demonstrate that exposure to oxidative stress results in a quick repression of translation by deactivation of the aminoacyl-ends of all transfer-RNA (tRNA). An oxidative-stress activated nuclease, angiogenin, cleaves first within the conserved single-stranded 3'-CCA termini of all tRNAs, thereby blocking their use in translation. This CCA deactivation is reversible and quickly repairable by the CCA-adding enzyme [ATP(CTP):tRNA nucleotidyltransferase]. Through this mechanism the eukaryotic cell dynamically represses and reactivates translation at low metabolic costs.

  15. Reversible and rapid transfer-RNA deactivation as a mechanism of translational repression in stress.

    Directory of Open Access Journals (Sweden)

    Andreas Czech

    2013-08-01

    Full Text Available Stress-induced changes of gene expression are crucial for survival of eukaryotic cells. Regulation at the level of translation provides the necessary plasticity for immediate changes of cellular activities and protein levels. In this study, we demonstrate that exposure to oxidative stress results in a quick repression of translation by deactivation of the aminoacyl-ends of all transfer-RNA (tRNA. An oxidative-stress activated nuclease, angiogenin, cleaves first within the conserved single-stranded 3'-CCA termini of all tRNAs, thereby blocking their use in translation. This CCA deactivation is reversible and quickly repairable by the CCA-adding enzyme [ATP(CTP:tRNA nucleotidyltransferase]. Through this mechanism the eukaryotic cell dynamically represses and reactivates translation at low metabolic costs.

  16. Dehydrogenation kinetics and reversibility of LiAlH4-LiBH4 doped with Ti-based additives and MWCNT

    Science.gov (United States)

    Thaweelap, Natthaporn; Utke, Rapee

    2016-11-01

    Dehydrogenation kinetics and reversibility of LiAlH4-LiBH4 doped with Ti-based additives (TiCl3 and Ti-isopropoxide), multiwall carbon nanotubes (MWCNT), and MWCNT impregnated with Ti-based additives are proposed. Reduction of dehydrogenation temperature as well as improvements of kinetics and reversibility, especially decomposition of thermodynamically stable hydride (LiBH4) is obtained from the samples doped with Ti-isopropoxide and MWCNT. This can be due to the fact that the formations of LixAl(1-x)B2 and LiH-Al containing phase during dehydrogenation favor decomposition of LiH, leading to increment of hydrogen capacity, and stabilization of boron in solid state, resulting in improvement of reversibility. Besides, the curvatures and thermal conductivity of MWCNT benefit hydrogen diffusion and heat transfer during de/rehydrogenation. Nevertheless, deficient hydrogen content reversible is observed in all samples due to the irreversible of LiAlH4 and/or Li3AlH6 as well as the formation of stable phase (Li2B12H12) during de/rehydrogenation.

  17. Actuation Mechanism of Two-step Reverse Transformation Behavior in TiNi Alloys Deformed at Parent Phase

    Institute of Scientific and Technical Information of China (English)

    HUAILi-min; CUILi-shan; ZHANGLai-bin; ZHENGYan-jun

    2004-01-01

    The actuation mechanism of TiNi shape memory alloy wires, which were deformed at parentphase followed by a cooling process under constant strain constraint, was investigated. The experimental resuhsshow that the two-step reverse martensitic transformation behavior occurs during the heating process, and the tem-perature range of reverse transformation was olwiously widened with the increasing of prestrain,The recovery strainvs temperature curves exhibits an actuation eharaeteristic of linear output recovery strain in a wide temperaturerange.

  18. Effect of small additions of vanadium and niobium on structure and mechanical properties of ductile iron

    Directory of Open Access Journals (Sweden)

    Fraś E.

    2007-01-01

    Full Text Available Results of investigations of influence of small additions of vanadium (up to 0,15 % V and niobium (up to 0,04% Nb on structure of ductile iron is presented in this work. Effect of these additions on distribution of graphite nodule diameter, nodule count, fraction and carbide count have been determined. Investigations of effect of small additions of vanadium and niobium on mechanical properties taking into account tensile strength, yield strength and elongation have also been made.

  19. Structure and magnetization reversal mechanism in L1{sub 0} FePt films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.J. [Surface Physics State Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Zheng Jianguo [Laboratory for Electron and X-ray Instrumentation, Calit2, University of California-Irvine, Irvine, CA 92697 (United States); Shi, Z., E-mail: shizhong@tongji.edu.cn [Surface Physics State Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Department of Physics, Tongji University, Shanghai 200092 (China); Zhou, S.M. [Surface Physics State Laboratory and Department of Physics, Fudan University, Shanghai 200433 (China); Department of Physics, Tongji University, Shanghai 200092 (China); Sun, L. [Department of Mechanical Engineering and Texas Center for Superconductivity (TcSUH), University of Houston, Houston, Texas 77204 (United States); Du, J. [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2012-06-30

    A series of L1{sub 0} Fe{sub 63}Pt{sub 37} films with controlled thickness (t{sub FM}) were deposited on MgO(100) substrates for microstructure and magnetization reversal mechanism study. X-ray diffraction measurements show that face-centered tetragonal (200) peak also exists in addition to face-centered tetragonal (002) one, and becomes weak for thick films. High resolution electron microscopy study reveals the existence of periodic misfit dislocations at the FePt/MgO interface and other types of defects such as twins and antiphase boundary inside the film. Out-of-plane initial magnetization shows a slow increase responding to the external magnetic field and then follows a steep increase. The out-of-plane coercivity H{sub C} at room temperature decreases with increasing t{sub FM} and increases when the angle {theta}{sub H} between the external magnetic field and the film normal direction increases. H{sub C} at {theta}{sub H} = 0 changes as a linear function of temperature for individual samples and the slope decreases with increasing t{sub FM}. In addition, magnetic viscosity measurements show that the fluctuation field at room temperature decreases with increasing t{sub FM}. These phenomena indicate that the magnetization reversal in the L1{sub 0} FePt films should be realized by the motion of weakly pinned domain wall and thus governed by the thermal activation model. The magnetization reversal thermal activation volume and corresponding energy increase with increasing t{sub FM}, as a result of the interactions between domain walls and structural defects can be attributed to the sample microstructural characteristic evolution with t{sub FM}. - Highlights: Black-Right-Pointing-Pointer A series of L1{sub 0} Fe{sub 63}Pt{sub 37} films with controlled thickness (t{sub FM}) were prepared. Black-Right-Pointing-Pointer Periodic misfit dislocations are observed at the FePt/MgO interface. Black-Right-Pointing-Pointer The dependence of H{sub C} on t{sub FM} and T is

  20. Reversible, partial inactivation of plant betaine aldehyde dehydrogenase by betaine aldehyde: mechanism and possible physiological implications.

    Science.gov (United States)

    Zárate-Romero, Andrés; Murillo-Melo, Darío S; Mújica-Jiménez, Carlos; Montiel, Carmina; Muñoz-Clares, Rosario A

    2016-04-01

    In plants, the last step in the biosynthesis of the osmoprotectant glycine betaine (GB) is the NAD(+)-dependent oxidation of betaine aldehyde (BAL) catalysed by some aldehyde dehydrogenase (ALDH) 10 enzymes that exhibit betaine aldehyde dehydrogenase (BADH) activity. Given the irreversibility of the reaction, the short-term regulation of these enzymes is of great physiological relevance to avoid adverse decreases in the NAD(+):NADH ratio. In the present study, we report that the Spinacia oleracea BADH (SoBADH) is reversibly and partially inactivated by BAL in the absence of NAD(+)in a time- and concentration-dependent mode. Crystallographic evidence indicates that the non-essential Cys(450)(SoBADH numbering) forms a thiohemiacetal with BAL, totally blocking the productive binding of the aldehyde. It is of interest that, in contrast to Cys(450), the catalytic cysteine (Cys(291)) did not react with BAL in the absence of NAD(+) The trimethylammonium group of BAL binds in the same position in the inactivating or productive modes. Accordingly, BAL does not inactivate the C(450)SSoBADH mutant and the degree of inactivation of the A(441)I and A(441)C mutants corresponds to their very different abilities to bind the trimethylammonium group. Cys(450)and the neighbouring residues that participate in stabilizing the thiohemiacetal are strictly conserved in plant ALDH10 enzymes with proven or predicted BADH activity, suggesting that inactivation by BAL is their common feature. Under osmotic stress conditions, this novel partial and reversible covalent regulatory mechanism may contribute to preventing NAD(+)exhaustion, while still permitting the synthesis of high amounts of GB and avoiding the accumulation of the toxic BAL.

  1. Hydrogen radical additions to unsaturated hydrocarbons and the reverse beta-scission reactions: modeling of activation energies and pre-exponential factors.

    Science.gov (United States)

    Sabbe, Maarten K; Reyniers, Marie-Françoise; Waroquier, Michel; Marin, Guy B

    2010-01-18

    The group additivity method for Arrhenius parameters is applied to hydrogen addition to alkenes and alkynes and the reverse beta-scission reactions, an important family of reactions in thermal processes based on radical chemistry. A consistent set of group additive values for 33 groups is derived to calculate the activation energy and pre-exponential factor for a broad range of hydrogen addition reactions. The group additive values are determined from CBS-QB3 ab-initio-calculated rate coefficients. A mean factor of deviation of only two between CBS-QB3 and experimental rate coefficients for seven reactions in the range 300-1000 K is found. Tunneling coefficients for these reactions were found to be significant below 400 K and a correlation accounting for tunneling is presented. Application of the obtained group additive values to predict the kinetics for a set of 11 additions and beta-scissions yields rate coefficients within a factor of 3.5 of the CBS-QB3 results except for two beta-scissions with severe steric effects. The mean factor of deviation with respect to experimental rate coefficients of 2.0 shows that the group additive method with tunneling corrections can accurately predict the kinetics and is at least as accurate as the most commonly used density functional methods. The constructed group additive model can hence be applied to predict the kinetics of hydrogen radical additions for a broad range of unsaturated compounds.

  2. Effect of Zn addition on microstructure and mechanical properties of an Al–Mg–Si alloy

    Directory of Open Access Journals (Sweden)

    Lizhen Yan

    2014-04-01

    Full Text Available In the present work, an Al–0.66Mg–0.85Si–0.2Cu alloy with Zn addition was investigated by electron back scattering diffraction (EBSD, high resolution electron microscopy (HREM, tensile and Erichsen tests. The mechanical properties of the alloy after pre-aging met the standards of sheet forming. After paint baking, the yield strength of the alloy was improved apparently. GP(II zones and ηʹ phases were formed during aging process due to Zn addition. With the precipitation of GP zones, β″ phases, GP(II zones and ηʹ phases, the alloys displayed excellent mechanical properties.

  3. Effect of Zn addition on microstructure and mechanical properties of an Al-Mg-Si alloy

    Institute of Scientific and Technical Information of China (English)

    Lizhen Yan; Yongan Zhang; Xiwu Li; Zhihui Li; Feng Wang; Hongwei Liu; Baiqing Xiong

    2014-01-01

    In the present work, an Al-0.66Mg-0.85Si-0.2Cu alloy with Zn addition was investigated by electron back scattering diffraction (EBSD), high resolution electron microscopy (HREM), tensile and Erichsen tests. The mechanical properties of the alloy after pre-aging met the standards of sheet forming. After paint baking, the yield strength of the alloy was improved apparently. GP(II) zones andηʹphases were formed during aging process due to Zn addition. With the precipitation of GP zones,β″phases, GP(II) zones andηʹphases, the alloys displayed excellent mechanical properties.

  4. Retention mechanism for polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography with monomeric stationary phases.

    Science.gov (United States)

    Rafferty, Jake L; Siepmann, J Ilja; Schure, Mark R

    2011-12-23

    Reversed-phase liquid chromatography (RPLC) is the foremost technique for the separation of analytes that have very similar chemical functionalities, but differ only in their molecular shape. This ability is crucial in the analysis of various mixtures with environmental and biological importance including polycyclic aromatic hydrocarbons (PAHs) and steroids. A large amount of effort has been devoted to studying this phenomenon experimentally, but a detailed molecular-level description remains lacking. To provide some insight on the mechanism of shape selectivity in RPLC, particle-based simulations were carried out for stationary phases and chromatographic parameters that closely mimic those in an experimental study by Sentell and Dorsey [J. Chromatogr. 461 (1989) 193]. The retention of aromatic hydrocarbons ranging in size from benzene to the isomeric PAHs of the formula C(18)H(12) was examined for model RPLC systems consisting of monomeric dimethyl octadecylsilane (ODS) stationary phases with surface coverages ranging from 1.6 to 4.2 μmol/m(2) (i.e., stationary phases yielding low to intermediate shape selectivity) in contact with a 67/33 mol% acetonitrile/water mobile phase. The simulations show that the stationary phase acts as a very heterogeneous environment where analytes with different shapes prefer different spatial regions with specific local bonding environments of the ODS chains. However, these favorable retentive regions cannot be described as pre-existing cavities because the chain conformation in these local stationary phase regions adapts to accommodate the analytes.

  5. Reversible adaptive plasticity: A mechanism for neuroblastoma cell heterogeneity and chemo-resistance

    Directory of Open Access Journals (Sweden)

    Lina eChakrabarti

    2012-08-01

    Full Text Available We describe a novel form of tumor cell plasticity characterized by reversible adaptive plasticity in murine and human neuroblastoma. Two cellular phenotypes were defined by their ability to exhibit adhered, anchorage dependent (AD or sphere forming, anchorage independent (AI growth. The tumor cells could transition back and forth between the two phenotypes and the transition was dependent on the culture conditions. Both cell phenotypes exhibited stem-like features such as expression of nestin, self-renewal capacity and mesenchymal differentiation potential. The AI tumorspheres were found to be more resistant to chemotherapy and proliferated slower in vitro compared to the AD cells. Identification of specific molecular markers like MAP2, β-catenin and PDGFRβ enabled us to characterize and observe both phenotypes in established mouse tumors. Irrespective of the phenotype originally implanted in mice, tumors grown in vivo show phenotypic heterogeneity in molecular marker signatures and are indistinguishable in growth or histologic appearance. Similar molecular marker heterogeneity was demonstrated in primary human tumor specimens. Chemotherapy or growth factor receptor inhibition slowed tumor growth in mice and promoted initial loss of AD or AI heterogeneity, respectively. Simultaneous targeting of both phenotypes led to further tumor growth delay with emergence of new unique phenotypes. Our results demonstrate that neuroblastoma cells are plastic, dynamic and may optimize their ability to survive by changing their phenotype. Phenotypic switching appears to be an adaptive mechanism to unfavorable selection pressure and could explain the phenotypic and functional heterogeneity of neuroblastoma.

  6. Mechanism of formation of metal sulfide ultrafine particles in reverse micelles using a gas injection method

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Hiroshi; Tsubaki, Yoritaka; Hirai, Takayuki; Komasawa, Isao [Osaka Univ., Toyonaka, Osaka (Japan)

    1997-01-01

    The mechanism of formation of ultrafine CdS, ZnS, and their composite particles by the injection of H{sub 2}S into reverse micelles was studied. The particle formation process was followed by the change in UV-visible absorption spectra. The kinetics of the whole process including dissolution of H{sub 2}S, nucleation, particle growth, and coagulation was analyzed from time-course changes of the size and number of formed particles. The dissolution of H{sub 2}S was the principal rate-determining step, and most of the dissolved H{sub 2}S was consumed for particle growth. The particles formed in the present gas injection method were larger in size than those in the previous solution-mixing method in most cases. A kinetic scheme based on the distribution of the species among the micelles was then proposed, and this successfully explained the particle growth. Composite particles of CdS and ZnS having mixed crystal or core-shell structures were also prepared, and the application of these particles as photocatalysts for the cleavage of water to generate H{sub 2} was then investigated.

  7. Magnetization reversal mechanism in patterned (square to wave-like) Py antidot lattices

    Science.gov (United States)

    Tahir, N.; Zelent, M.; Gieniusz, R.; Krawczyk, M.; Maziewski, A.; Wojciechowski, T.; Ding, J.; Adeyeye, A. O.

    2017-01-01

    The effects of shape and geometry of antidot (square, bi-component, and wave-like) lattices (ADLs) on the magnetization reversal processes and magnetic anisotropy has been systematically investigated by magneto-optical Kerr effect based microscopy. Our experimental results were reproduced by micromagnetic simulations, which highlight the qualitative agreement with the experimental results. We have demonstrated that a small antidot in the center of a unit cell in the square ADL is sufficient to induce additional easy axes with large coercive fields. In wave-like patterns, narrow channels connecting smaller and larger antidots (bi-component ADL) further drastically change the anisotropy map, creating the high coercive fields along a wide angular range (90°) of directions parallel to the channels. In simulated results, we have observed formation of periodic domain structures in all ADLs, however, in the case of a wave-like pattern it is most regular and moreover two different periodic patterns are stabilized at different applied magnetic field values. The formation of 360° domain walls were also observed in wave-like ADL where these domains are formed along the lines connecting adjacent larger and smaller antidots, perpendicular to the channels. These findings point out the possibility of exploiting ADLs with complex unit cells in magnonic or spintronic applications.

  8. Kinetics and mechanism of the cutinase-catalyzed transesterification of oils in AOT reversed micellar system.

    Science.gov (United States)

    Badenes, Sara M; Lemos, Francisco; Cabral, Joaquim M S

    2011-11-01

    The kinetics of the enzymatic transesterification between a mixture of triglycerides (oils) and methanol for biodiesel production in a bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/isooctane reversed micellar system, using recombinant cutinase from Fusarium solani pisi as a catalyst, was investigated. In order to describe the results that were obtained, a mechanistic scheme was proposed, based on the literature and on the experimental data. This scheme includes the following reaction steps: the formation of the active enzyme-substrate complex, the addition of an alcohol molecule to the complex followed by the separation of a molecule of the fatty acid alkyl ester and a glycerol moiety, and release of the active enzyme. Enzyme inhibition and deactivation effects due to methanol and glycerol were incorporated in the model. This kinetic model was fitted to the concentration profiles of the fatty acid methyl esters (the components of biodiesel), tri-, di- and monoglycerides, obtained for a 24 h transesterification reaction performed in a stirred batch reactor under different reaction conditions of enzyme and initial substrates concentration.

  9. A Case of Reverse Palmaris Longus Muscle- An Additional Muscle in the Anterior Compartment of the Forearm

    Science.gov (United States)

    Bhat, Ashwini Lagadamane Sathynarayana; Gadahad, Mohandas Rao Kappettu

    2016-01-01

    It is uncommon to have additional muscles in the upper limb. Some of them may restrict the movements or compress the nerves and vessels, while others may go unnoticed. During the routine dissection for undergraduate medical students, we observed an additional muscle in the anterior compartment of the forearm in about 60-year-old male cadaver. The muscle had a prominent belly and a long tendon. Distally, it was attached to the flexor retinaculum by a short and thick tendon. Proximally, long tendon of the muscle passed between the flexor carpi ulnaris and palmaris longus and was attached to the common aponeurosis shared by the extensor carpi ulnaris and flexor digitorum profundus muscles. The additional muscle belly was supplied by a branch from the anterior interosseous nerve. The ulnar nerve and artery was passing deep to the fleshy belly of the muscle. The muscle reported here might compress the ulnar nerve and artery and may produce neurovascular symptoms. On the other hand, the tendon and fleshy belly of the muscle could be useful in muscle/tendon grafts. The observations made by us in the present case will supplement our knowledge of variations of the muscles in this region which could be useful for surgeons during the forearm and hand surgeries. PMID:27134851

  10. Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

    Energy Technology Data Exchange (ETDEWEB)

    Shirdel, M., E-mail: mshirdel1989@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Parsa, M.H., E-mail: mhparsa@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-05-15

    A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

  11. Improving Student Understanding of Addition of Angular Momentum in Quantum Mechanics

    Science.gov (United States)

    Zhu, Guangtian; Singh, Chandralekha

    2013-01-01

    We describe the difficulties advanced undergraduate and graduate students have with concepts related to addition of angular momentum in quantum mechanics. We also describe the development and implementation of a research-based learning tool, Quantum Interactive Learning Tutorial (QuILT), to reduce these difficulties. The preliminary evaluation…

  12. Effect of carbon nanofibre addition on the mechanical properties of different f carbon-epoxy composites

    Indian Academy of Sciences (India)

    I Srikanth; Suresh Kumar; Vajinder Singh; B Rangababu; Partha Ghosal; Ch Subrahmanyam

    2015-04-01

    Carbon-epoxy (C-epoxy) laminated composites having different fibre volume fractions (40, 50, 60 and 70) were fabricated with and without the addition of aminofunctionalized carbon nanofibres (A-CNF). Flexural strength, interlaminar shear strength (ILSS) and tensile strength of the composite laminates were determined. It was observed that, the ability of A-CNF to enhance the mechanical properties of C-epoxy diminished significantly as the fibre volume fraction (f) of the C-epoxy increased from 40 to 60. At 70f, the mechanical properties of the A-CNF reinforced C-epoxy were found to be lower compared to the C-epoxy composite made without the addition of A-CNF. In this paper suitable mechanisms for the observed trends are proposed on the basis of the fracture modes of the composite.

  13. Influence of Molybdenum Addition on Mechanical Properties of Low Carbon HSLA-100 Steel

    Directory of Open Access Journals (Sweden)

    Bogucki R.

    2014-10-01

    Full Text Available The results of mechanical properties and microstructure observation of low carbon copper bearing steel with high addition of molybdenum are presented in this paper. This steels were characterized by contents of molybdenum in the range from 1% to 3% wt. After the thermo -mechanical processing the steels were subsequently quenched and tempered at different temperatures (500-800 °C for 1h. The changes of mechanical properties as function of tempering temperature were typical for the steel with the copper addition. The sudden drop of impact resistance after tempering from 575 °C to 600 °C was caused probably by precipitates of Laves phase of type Fe2Mo.

  14. Rapid detection of the addition of soybean proteins to cheese and other dairy products by reversed-phase perfusion chromatography.

    Science.gov (United States)

    García, M C; Marina, M L

    2006-04-01

    The undeclared addition of soybean proteins to milk products is forbidden and a method is needed for food control and enforcement. This paper reports the development of a chromatographic method for routine analysis enabling the detection of the addition of soybean proteins to dairy products. A perfusion chromatography column and a linear binary gradient of acetonitrile-water-0.1% (v/v) trifluoroacetic acid at a temperature of 60 degrees C were used. A very simple sample treatment consisting of mixing the sample with a suitable solvent (Milli-Q water or bicarbonate buffer (pH=11)) and centrifuging was used. The method enabled the separation of soybean proteins from milk proteins in less than 4 min (at a flow-rate of 3 ml/min). The method has been successfully applied to the detection of soybean proteins in milk, cheese, yogurt, and enteral formula. The correct quantitation of these vegetable proteins has also been possible in milk adulterated at origin with known sources of soybean proteins. The application of the method to samples adulterated at origin also leads to interesting conclusions as to the effect of the processing conditions used for the preparation of each dairy product on the determination of soybean proteins.

  15. Effect of the addition of a nonaqueous polar solvent (glycerol) on enzymatic catalysis in reverse micelles. Hydrolysis of 2-naphthyl acetate by alpha-chymotrypsin.

    Science.gov (United States)

    Falcone, R Darío; Biasutti, M Alicia; Correa, N Mariano; Silber, Juana J; Lissi, Eduardo; Abuin, Elsa

    2004-07-06

    The kinetics of hydrolysis of 2-naphthyl acetate (2-NA) catalyzed by alpha-chymotrypsin (alpha-CT), in reverse micellar solutions formed by glycerol (GY)-water (38% v/v) mixture/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane has been determined by spectroscopic measurements. To compare the efficiency of this reaction with that observed in micelles with water in the core, as well as in the corresponding homogeneous media, the reaction was also studied in water/AOT/n-heptane reverse micellar solutions and in both homogeneous media (water and GY-water, 38% v/v mixture). In every media, alpha-CT was characterized by the absorption and emission spectra, the fluorescence lifetimes, and the fluorescence anisotropy of its tryptophan residues. The effect of AOT concentration on the kinetic parameters obtained in the micellar systems was determined, at a constant molar ratio of the inner polar solvent and surfactant. Moreover, the data obtained allowed the evaluation of the 2-NA partition constant between the organic and the micellar pseudophase. It is shown that the addition of GY to the micelle interior results in an increase in the catalytic properties of alpha-CT. The fluorescence anisotropy studies in the different media show that the addition of GY increases the viscosity as compared with the aqueous systems. It seems that the GY addition to the reverse micellar aggregates results in a decrease of the conformational mobility of alpha-CT, which leads to an increase of the enzyme stability and activity.

  16. PAH growth initiated by propargyl addition: Mechanism development and computational kinetics

    KAUST Repository

    Raj, Abhijeet Dhayal

    2014-04-24

    Polycyclic aromatic hydrocarbon (PAH) growth is known to be the principal pathway to soot formation during fuel combustion, as such, a physical understanding of the PAH growth mechanism is needed to effectively assess, predict, and control soot formation in flames. Although the hydrogen abstraction C2H2 addition (HACA) mechanism is believed to be the main contributor to PAH growth, it has been shown to under-predict some of the experimental data on PAHs and soot concentrations in flames. This article presents a submechanism of PAH growth that is initiated by propargyl (C 3H3) addition onto naphthalene (A2) and the naphthyl radical. C3H3 has been chosen since it is known to be a precursor of benzene in combustion and has appreciable concentrations in flames. This mechanism has been developed up to the formation of pyrene (A4), and the temperature-dependent kinetics of each elementary reaction has been determined using density functional theory (DFT) computations at the B3LYP/6-311++G(d,p) level of theory and transition state theory (TST). H-abstraction, H-addition, H-migration, β-scission, and intramolecular addition reactions have been taken into account. The energy barriers of the two main pathways (H-abstraction and H-addition) were found to be relatively small if not negative, whereas the energy barriers of the other pathways were in the range of (6-89 kcal·mol-1). The rates reported in this study may be extrapolated to larger PAH molecules that have a zigzag site similar to that in naphthalene, and the mechanism presented herein may be used as a complement to the HACA mechanism to improve prediction of PAH and soot formation. © 2014 American Chemical Society.

  17. Effect of niobium addition on magnetization reversal behavior for SmCo-based magnets with TbCu7-type structure

    Institute of Scientific and Technical Information of China (English)

    胡晨宇; 泮敏翔; 吴琼; 葛洪良; 王秀敏; 卢阳春; 张朋越

    2016-01-01

    The effect of Nb addition on the microstructure and magnetic properties of nanocrystalline Sm(CobalNbxZr0.02)7 permanent magnet were investigated. The magnetization reversal behavior for ball milled Sm(CobalNbxZr0.02)7 samples with high coercivity was investigated by analyzing hysteresis curves and recoil loops of demagnetization curves. Nb addition proved to result in relevant im-provement in the magnetic properties, especially in the coercivityHc. It was shown that the magnetic properties of Sm(CobalNbx-Zr0.02)7 nanocrystalline magnets were improved by an additional 0.06 at.% Nb. In particular, Hc was improved from 602 to 786 kA/m at room temperature. The maximum value of the integrated recoil loops area for 0.06 at.% Nb-doped samples of 1.81 kJ/m3 was much lower than that of the Nb-free sample, which could be explained by a smaller recoverable portion of the magnetization remaining in the Nb-doped sample when the applied field was below the coercivityHc. The nucleation fieldHn for irreversible magnetization re-versal of the magnetically hard phase were calculated by analyzed in terms of theΔMirev-Hcurve and the Kondorsky model.

  18. Dehydrogenation kinetics, reversibility, and reaction mechanisms of reversible hydrogen storage material based on nanoconfined MgH2-NaAlH4

    Science.gov (United States)

    Plerdsranoy, Praphatsorn; Meethom, Sukanya; Utke, Rapee

    2015-12-01

    Studies of dehydrogenation kinetics, reversibility, and reaction mechanisms during de/rehydrogenation of nanoconfined MgH2-NaAlH4 into carbon aerogel scaffold (CAS) for reversible hydrogen storage material are for the first time proposed. Two different MgH2:NaAlH4 molar ratios (1:1 and 2:1) of hydride composite are melt infiltrated into CAS under 1:1 (CAS:hydride composite) weight ratio. Successful nanoconfinement is confirmed by N2 adsorption-desorption. Multiple-step dehydrogenation of milled samples is reduced to two-step reaction due to nanoconfinement. Peak temperatures corresponding to main dehydrogenation of nanoconfined samples significantly reduce as compared with those of milled samples, i.e., ∆T=up to 50 and 34 °C for nanoconfined sample with 1:1 and 2:1 (MgH2:NaAlH4) molar ratios, respectively. Hydrogen content released (the 1st cycle) and reproduced (the 2nd, 3rd, and 4th cycles) of nanoconfined samples enhance up to 80% and 68% with respect to theoretical hydrogen storage capacity, respectively, while those of milled samples are 71% and 38%, respectively. Remarkable hydrogen content reproduced after nanoconfinement is due to the fact that metallic Al obtained after dehydrogenation (T=300 °C under vacuum) of nanoconfined samples prefer to react with MgH2 and produces Al12Mg17, favorable for reversibility of MgH2-NaAlH4 system, whereas that of milled samples stays in the form of unreacted Al under the same temperature and pressure condition.

  19. Mechanism of Ascorbic Acid-induced Reversion Against Malignant Phenotype in Human Gastric Cancer Cells

    Institute of Scientific and Technical Information of China (English)

    YA-XUAN SUN; QIU-SHENG ZHENG; GANG LI; DE-AN GUO; ZI-REN WANG

    2006-01-01

    Objective To find out the mechanisms of redifferentiation and reversion of malignant human gastric cancer cells induced by ascorbic acid. Methods Human gastric cancer cells grown in the laboratory were used. The Trypan blue dye exclusion method was used to determine the cell doubling time. The electrophoresis rate and colonogenic potential were the indices used to measure the rate of redifferentiation. The content of malondialdehyde (MDA) was measured using the thiobarbituric acid(TBA) method. The activities of superoxide dismutase (SOD), catalase (CAT) and the content of H2O2 were evaluated by spectrophotography. Results Six mmol/L ascorbic acid was used as a positive control. Human gastric cancer cells were treated with 75 μm hydrogen peroxide, which alleviated many of the malignant characteristics. For example, the cell surface charge obviously decreased and the electrophoresis rate dropped from 2.21 to 1.10 μm·s-1·V-1·cm-1. The colonogenic potential, a measure of cell differentiation, decreased 90.2%. After treatment with ascorbic acid, there was a concentration- and time-dependent increase in hydrogen peroxide (H2O2) and the activity of superoxide dismutase (SOD). However, the activity of catalase (CAT) resulted in a concentration- and time-dependent decrease. SOD and 3-amino-1,2,4-triazole (AT) exhibited some effects, but there were statistically significant differences between the SOD and AT group and the H2O2 group. Conclusions Ascorbic acid induces growth inhibition and redifferentiation of human gastric cancer cells through the production of hydrogen peroxide.

  20. EFFECT OF MONTMORILLONITE ADDITION ON MECHANICAL CHARACTERIZATIONS OF POLYIMIDE NANOCOMPOSITE FILMS

    Institute of Scientific and Technical Information of China (English)

    Wang Xishu; Zhang Yihe; Fu Shaoyun; Feng Xiqiao

    2005-01-01

    Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the mechanical properties of nanocomposites, such as the nanolayer, matrix and nanolayer/matrix interface. How to contribute to the mechanical properties of nanocomposite film is a very complex problem. In this paper, these factors are analyzed based on the addition amount and fracture mechanics. The results indicate that the specimen at 20 wt% MMT breaks prematurely with a fracture strength (σb=78 MPa) much lower than that (σb = 128 MPa) at the 1wt% MMT. However, the Young's modulus (3.2 GPa) of the former is higher than that (1.9 GPa) of the latter. Fractography also indicates that the brittle cracking formed in high content addition is the main cause of failure but microscopically ductile fracture morphology still exists locally. And for the trace element addition, the smaller threading slipping veins are evenly distributed on the entire fracture section of these films. Therefore, these characteristics would presumably be associated with both the concentration effects of size of nanocomposite sheets and the increasing deformation harmony in nanolayers.

  1. Influence of cementitious additions on rheological and mechanical properties of reactive powder concretes

    Science.gov (United States)

    Zenati, A.; Arroudj, K.; Lanez, M.; Oudjit, M. N.

    2009-11-01

    Following needs of concrete market and the economic and ecological needs, several researchers, all over the world, studied the beneficial effect which the incorporation of the mineral additions in Portland cement industry can bring. It was shown that the incorporation of local mineral additions can decrease the consumption of crushing energy of cements, and reduce the CO2 emission. Siliceous additions, moreover their physical role of filling, play a chemical role pozzolanic. They contribute to improving concrete performances and thus their durability. The abundance of dunes sand and blast furnace slag in Algeria led us to study their effect like cementitious additions. The objective of this paper is to study the effect of the incorporation of dunes sand and slag, finely ground on rheological and mechanical properties of reactive powder concretes containing ternary binders.

  2. Geomagnetic reversal rates following Palaeozoic superchrons have a fast restart mechanism.

    Science.gov (United States)

    Hounslow, Mark W

    2016-08-30

    Long intervals of single geomagnetic polarity (superchrons) reflect geodynamo processes, driven by core-mantle boundary interactions; however, it is not clear what initiates the start and end of superchrons, other than superchrons probably reflect lower heat flow across the core-mantle boundary compared with adjacent intervals. Here geomagnetic polarity timescales, with confidence intervals, are constructed before and following the reverse polarity Kiaman (Carboniferous-Permian) and Moyero (Ordovician) superchrons, providing a window into the geodynamo processes. Similar to the Cretaceous, asymmetry in reversal rates is seen in the Palaeozoic superchrons, but the higher reversal rates imply higher heatflow thresholds for entering the superchron state. Similar to the Cretaceous superchron, unusually long-duration chrons characterize the ∼10 Myr interval adjacent to the superchrons, indicating a transitional reversing state to the superchrons. This may relate to a weak pattern in the clustering of chron durations superimposed on the dominant random arrangement of chron durations.

  3. Addition of Fructooligosaccharides and Dried Plum to Soy-Based Diets Reverses Bone Loss in the Ovariectomized Rat

    Directory of Open Access Journals (Sweden)

    Catherine D. Johnson

    2011-01-01

    Full Text Available Dietary bioactive components that play a role in improving skeletal health have received considerable attention in complementary and alternative medicine practices as a result of their increased efficacy to combat chronic diseases. The objectives of this study were to evaluate the additive or synergistic effects of dried plum and fructooligosaccharides (FOS and to determine whether dried plum and FOS or their combination in a soy protein-based diet can restore bone mass in ovarian hormone deficient rats. For this purpose, 72 3-month-old female Sprague-Dawley rats were divided into six groups (n = 12 and either ovariectomized (Ovx, five groups or sham-operated (sham, one group. The rats were maintained on a semipurified standard diet for 45 days after surgery to establish bone loss. Thereafter, the rats were placed on one of the following dietary treatments for 60 days: casein-based diet (Sham and Ovx, soy-based diet (Ovx + soy or soy-based diet with dried plum (Ovx + soy + plum, FOS (Ovx + soy + FOS and combination of dried plum and FOS (Ovx + soy + plum + FOS. Soy protein in combination with the test compounds significantly improved whole-body bone mineral density (BMD. All test compounds in combination with soy protein significantly increased femoral BMD but the combination of soy protein, dried plum and FOS had the most pronounced effect in increasing lumbar BMD. Similarly, all of the test compounds increased ultimate load, indicating improved biomechanical properties. The positive effects of these test compounds on bone may be due to their ability to modulate bone resorption and formation, as shown by suppressed urinary deoxypyridinoline excretion and enhanced alkaline phosphatase activity.

  4. Investigation on mechanism of magnetization reversal for nanocrystalline Pr-Fe-B permanent magnets by micromagnetic finite element methods

    Institute of Scientific and Technical Information of China (English)

    ZHENG Bo; ZHAO Sufen

    2009-01-01

    Magnetization configurations were calculated under various magnetic fields for nanocrystalline Pr-Fe-B permanent magnets by micromagnetic finite element method. According to the configurations during demagnetization process, the mechanism of magnetization reversal was analyzed. For the Pr2Fe14B with 10 nm grains or its composite with 10vol.% α-Fe, the coercivity was determined by nucleation of reversed domain that took place at grain boundaries. However, for Pr2Fe14B with 30 nm grains, coercivity was controlled by pinning of the nucleated domain. For Pr2Fe14B/α-Fe with 30vol.% α-Fe, the demagnetization behavior was characterized by continuous reversal of α-Fe moment.

  5. Role of extracellular vesicles in de novo mineralization: an additional novel mechanism of cardiovascular calcification.

    Science.gov (United States)

    New, Sophie E P; Aikawa, Elena

    2013-08-01

    Extracellular vesicles are membrane micro/nanovesicles secreted by many cell types into the circulation and the extracellular milieu in physiological and pathological conditions. Evidence suggests that extracellular vesicles, known as matrix vesicles, play a role in the mineralization of skeletal tissue, but emerging ultrastructural and in vitro studies have demonstrated their contribution to cardiovascular calcification as well. Cells involved in the progression of cardiovascular calcification release active vesicles capable of nucleating hydroxyapatite on their membranes. This review discusses the role of extracellular vesicles in cardiovascular calcification and elaborates on this additional mechanism of calcification as an alternative pathway to the currently accepted mechanism of biomineralization via osteogenic differentiation.

  6. Mechanism, time-reversal symmetry, and topology of superconductivity in noncentrosymmetric systems

    Science.gov (United States)

    Scheurer, M. S.

    2016-05-01

    We analyze the possible interaction-induced superconducting instabilities in noncentrosymmetric systems based on symmetries of the normal state. It is proven that pure electron-phonon coupling will always lead to a fully gapped superconductor that does not break time-reversal symmetry and is topologically trivial. We show that topologically nontrivial behavior can be induced by magnetic doping without gapping out the resulting Kramers pair of Majorana edge modes. In the case of superconductivity arising from the particle-hole fluctuations associated with a competing instability, the properties of the condensate crucially depend on the time-reversal behavior of the order parameter of the competing instability. When the order parameter preserves time-reversal symmetry, we obtain exactly the same properties as in the case of phonons. If it is odd under time reversal, the Cooper channel of the interaction will be fully repulsive leading to sign changes of the gap and making spontaneous time-reversal-symmetry breaking possible. To discuss topological properties, we focus on fully gapped time-reversal-symmetric superconductors and derive constraints on possible pairing states that yield necessary conditions for the emergence of topologically nontrivial superconductivity. These conditions might serve as a tool in the search for topological superconductors. We also discuss implications for oxide heterostructures and single-layer FeSe.

  7. Mechanism for the addition of carbenoid CH2ClLi to formaldehyde

    Institute of Scientific and Technical Information of China (English)

    李吉海[1; 孙昌俊[2; 刘少杰[3; 冯圣玉[4; 冯大诚[5

    2000-01-01

    Ab initlo HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2CILi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2CILi is first formed with quite exothermic effect. Only a little activation energy of 14.6 kJ/mol is needed for the complex developing into the product through a transition state with coplanar bicyclic structure. In this process, the eletrophilic attack of carbonyl carbon of formaldehyde is more active than the nucleophilic attack of carbon of carbenoid. The exothermal effect of this addition process is up to 216.5 kJ/mol.

  8. Influence of polymeric additives on the cohesion and mechanical properties of calcium phosphate cements.

    Science.gov (United States)

    An, Jie; Wolke, Joop G C; Jansen, John A; Leeuwenburgh, Sander C G

    2016-03-01

    To expand the clinical applicability of calcium phosphate cements (CPCs) to load-bearing anatomical sites, the mechanical and setting properties of CPCs need to be improved. Specifically, organic additives need to be developed that can overcome the disintegration and brittleness of CPCs. Hence, we compared two conventional polymeric additives (i.e. carboxylmethylcellulose (CMC) and hyaluronan (HA)) with a novel organic additive that was designed to bind to calcium phosphate, i.e. hyaluronan-bisphosphonate (HABP). The unmodified cement used in this study consisted of a powder phase of α-tricalcium phosphate (α-TCP) and liquid phase of 4% NaH2PO4·2H2O, while the modified cements were fabricated by adding 0.75 or 1.5 wt% of the polymeric additive to the cement. The cohesion of α-TCP was improved considerably by the addition of CMC and HABP. None of the additives improved the compression and bending strength of the cements, but the addition of 0.75% HABP resulted into a significantly increased cement toughness as compared to the other experimental groups. The stimulatory effects of HABP on the cohesion and toughness of the cements is hypothesized to derive from the strong affinity between the polymer-grafted bisphosphonate ligands and the calcium ions in the cement matrix.

  9. EFFECTS OF PHENOL RESIN ADDITIVE ON DYNAMIC MECHANICAL PROPERTIES OF ACRYLATE RUBBER AND ITS BLENDS

    Institute of Scientific and Technical Information of China (English)

    Chi-fei Wu

    2003-01-01

    The dynamic mechanical properties of a new blend system consisting of phenol resin and polar polymer (acrylate rubber and/or chlorinated polypropylene) were investigated. It was found that the addition of phenol resin to acrylate rubber and its incompatible blend can cause a remarkable improvement in the temperature dependence of the loss tangent. As a result, the present blends are very good damping materials.

  10. Molecular mechanism of indirubin-3'-monoxime and Matrine in the reversal of paclitaxel resistance in NCI-H520/TAX25 cell line

    Institute of Scientific and Technical Information of China (English)

    LUO Su-xia; DENG Wen-ying; WANG Xin-feng; L(U) Hui-fang; HAN Li-li; CHEN Bei-bei; CHEN Xiao-bing

    2013-01-01

    Background Multidrug resistance (MDR) is a main reason for paclitaxel (TAX) treatment failure.Indirubin-3'-monoxime (IRO) and Matrine are traditional Chinese medicines,which may reverse the resistance of tumor cells to some chemotherapy drugs,but the relationship between paclitaxel resistance and Matrine is still unclear.The aim of this study was to explore the potential molecular mechanism of IRO and Matrine in reversal of TAX resistance.Methods In this study,MTT assay was used to measure the non-cytotoxic dosage of IRO and Matrine on NCI-H520/TAX25 cells and determine the reversal extent of TAX resistance under non-toxic doses.In addition,RT-PCR and Western blotting were used to evaluate the mRNA expression and the protein level of survivin,Oct-4,and Sox-2 in NCI-H520/FAX25 cells using semi-quantitative methods.Results There was no obvious inhibition on sensitive cell strains and drug-resistant strains,when the final concentration was at lest 4 μmol/L for IRO and 100 μmol/L for Matrine.So 4 μmol/L of IRO and 100 μmol/L of Matrine were considered as the reversal dosage.When 4 μmol/L of IRO or 100 μmol/L of Matrine were used together with TAX,the sensitivity to TAX increased evidently in NCI-H520/TAX2 cells; the reversal rate of IRO and Matrine was about 1.92 (43.56/22.6 nmol/L) and 1.74 (43.56/25.0 nmol/L),respectively.The mRNA expression and the protein level of survivin,Oct-4,and Sox-2 in NCI-H520/TAX25 decreased significantly (P <0.05) after addition of IRO or Matrine in TAX treatment,compared to that of TAX treatment alone.Conclusion The decrease in both mRNA expression and protein level of survivin,Oct-4,and Sox-2 might be the molecular mechanism,by which IRO and Matrine mediate the reversal of TAX resistance.

  11. Addition Mechanisms of Phenol toward Formaldehyde under Acidic Condition: a Theoretical Investigation

    Institute of Scientific and Technical Information of China (English)

    XU Wen-Feng; XIONG Shan-Shan; SHI Yu-Qing; LI Tao-Hong; DU Guan-Ben; XIE Xiao-Guang

    2012-01-01

    The reaction mechanisms of phenol with formaldehyde in the first and second addition at the ortho- and para-position in acid solution were theoretically investigated at the PW91/DNP level with solvent effects included. The reaction of phenol with protonated methanediol firstly forms an adduct intermediate, via a SN2 mechanism with a water molecule as the leaving group. From the adduct intermediate, there are two reaction channels involving a proton transfer to form the addition products. One is that a proton directly transfers via a four-membered ring transition state with a notable energy barrier (Four-member mechanism). Another mechanism involving a water molecule as catalyst to mediate the proton transfer (WCP mechanism), is a barrierless process, indicating that the formation of the adduct intermediate, the first reaction step, is rate-limiting. The reaction products are free hydroxymethyl phenols and/or hydroxybenzy carbocation (HOC6H4CH2+) which plays an important role in the following formation of methylene and methylene ether linkages. The second addition reactions between formaldehyde and hydroxymethyl phenol at all possible reaction sites of the phenol ring in acid solution were also investigated and discussed.

  12. Increased Mechanical Properties Through the Addition of Zr to GRCop-84

    Science.gov (United States)

    Ellis, David L.; Lerch, Bradley A.

    2011-01-01

    GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) has shown exceptional mechanical properties above 932 F (773 K). However, its properties below 932 F (773 K) are inferior to precipitation strengthened alloys such as Cu-Cr, Cu-Zr and Cu-Cr-Zr when they are in the fully aged, hard-drawn condition. It has been noted that the addition of small amounts of Zr, typically 0.1 wt.% to 0.5 wt.%, can greatly enhance the mechanical properties of copper-based alloys. Limited testing was conducted upon GRCop-84 with an addition of 0.4 wt.% Zr to determine its tensile, creep and low cycle fatigue (LCF) properties. Very large increases in strength (up to 68%) and ductility (up to 123%) were observed at both room temperature and 932 F (773 K). Creep properties at 932 F (773 K) demonstrated more than an order of magnitude decrease in the creep rate relative to unmodified GRCop-84 with a corresponding order of magnitude increase in creep life. Limited LCF testing showed that the modified alloy had a comparable LCF life at room temperature, but it was capable of sustaining a much higher load. While more testing and composition optimization are required, the addition of Zr to GRCop-84 has shown clear benefits to mechanical properties.

  13. Effect of reinforcement nanoparticles addition on mechanical properties of SBS/curaua fiber composites

    Energy Technology Data Exchange (ETDEWEB)

    Borba, Patricia M. [Servico Nacional de Aprendizagem Industrial (CETEPO/SENAI/RS), Sao Leopoldo, RS (Brazil). Centro Tecnologico de Polimeros; Tedesco, Adriana [Braskem S. A., III Polo Petroquimico, Triunfo, RS (Brazil); Lenz, Denise M., E-mail: denise.lenz@gmail.com [Universidade Luterana do Brasil (ULBRA), Canoas, RS (Brazil). Programa de Pos-graduacao em Engenharia de Materiais e Processos Sustentaveis

    2014-03-15

    Composites of styrene-butadiene-styrene triblock copolymer (SBS) matrix with curauá fiber and/or a nanoparticulated mineral (montmorillonite clay - MMT) used as reinforcing agents were prepared by melt-mixing. The influence of clay addition on properties like tensile and tear strength, rebound resilience, flex fatigue life, abrasion loss, hardness and water absorption of composites with 5, 10 and 20 wt% of curauá fiber was evaluated in presence of maleic anhydride grafted styrene-(ethylene-co-butylene)-styrene triblock copolymer (MA-g-SEBS) coupling agent. Furthermore, the effect of mineral plasticizer loading on tensile strength of selected composites was investigated. The hybrid SBS composite that showed the best overall mechanical performance was composed by 2 wt% of MMT and 5 wt% of curauá fiber. Increasing fiber content up to 20 wt% resulted in a general decrease in all mechanical properties as well as incorporation of 5 wt% MMT caused a decrease in the tensile strength in all fiber contents. The hybrid composites showed clay agglomerates (tactoids) poorly dispersed that could explain the poor mechanical performance of composites at higher concentrations of curauá fiber and MMT nanoparticles. The addition of plasticizer further decreased the tensile strength while the addition of MMT nanoparticles decreased water absorption for all SBS composites. (author)

  14. Effect of Mg as sintering additive on the consolidation of mechanically alloyed Al powder

    Energy Technology Data Exchange (ETDEWEB)

    Fuentes, J.J. [UNET, Dept. de Ingenieria Mecanica, San Cristobal (Venezuela); Rodriguez, J.A.; Herrera, E.J. [Grupo de Metalurgia e Ingenieria de los Materiales, Escuela Superior de Ingenieros, Univ. de Sevilla, Camino de los Descubrimientos, Sevilla (Spain)

    2003-07-01

    Mechanically alloyed aluminium, MA Al, powder particles are hard and covered by surface oxide layers. This gives problems in consolidation processing. Consolidation is often carried out by hot extrusion, as the main processing step. An alternative consolidation method consisting in a press-and-sinter process has been developed at the University of Seville. MA Al powder was prepared by attrition milling. To improve the sinterability of MA Al powder, small amounts of magnesium, ranging from 0.0 to 1.2 wt% Mg, were added after milling. The mixed powder was consolidated by cold pressing (1120 MPa) and vacuum sintering (650 C, 1 h). Different mechanical and structural studies have been carried out. It has been observed that the addition of magnesium improves the mechanical properties of sintered MA Al. This is attributed to the reducing action of Mg on the Al sesquioxide layer and to the formation of liquid phases during sintering. (orig.)

  15. Clean development mechanism and off-grid small-scale hydropower projects: evaluation of additionality

    Energy Technology Data Exchange (ETDEWEB)

    Tanwar, N. [Punjab Engineering College, Chandigarh (India). Department of Civil Engineering

    2007-01-15

    The global climate change mitigation policies and their stress on sustainable development have made electrification of rural mountainous villages, using small hydro, an attractive destination for potential clean development mechanism (CDM) projects. This invariably involves judging the additionality of such projects. The paper suggests a new approach to judge the additionality of such stand-alone small hydropower projects. This has been done by breaking up additionality into two components: external and local. The external additionality is project developer dependent. For determining the local additionality, the paper takes into account the probability of a village getting electrified over a period of time, which is kept equal to the possible crediting period. This is done by defining an electrification factor (EF) whose value depends on the degree of isolation, financial constraints and institutional constraints encountered while electrifying a mountainous village. Using this EF, the additionality of a CDM project can be judged in a much easier and accurate way. The paper is based on the data and inputs gathered during site visits to many isolated villages located in the eastern Indian Himalayas. (author)

  16. Post-emplacement melt-flow as a feasible mechanism for reversed differentiation in tholeiitic sills

    Science.gov (United States)

    Aarnes, I.; Podladchikov, Y. Y.; Neumann, E.-R.; Galerne, C.

    2009-04-01

    This study provides a new explanation model for differentiation in sills, using a combination of geochemical data and field observations, numerical modeling and dimensional analysis. Geochemical data from a saucer-shaped dolerite sill intruded into the Karoo basin, South Africa reveal a process which causes reversed differentiation. The differentiation process is identified by D-shaped geochemical profiles. The notation is based on the vertical expression of whole-rock Mg-number (Mg# = 100*Mg/(Mg+Fetotal)) with the most primitive composition (i.e. high Mg#) in its center, and progressively more evolved composition (i.e. low Mg#) towards the upper and lower margins. Normal differentiation by fractional crystallization is known to produce C-shaped profiles (in terms of Mg# variations), as for example in the Skaergaard Intrusion. From a detailed field study of a saucer-shaped sill complex in the Karoo Basin, South Africa, we observe several different shapes (e.g. S, D and I) occurring within one sill. However, the C-shape is practically absent and hence fractional crystallization with double layer diffusion cannot be the main mechanism for differentiation in sheet intrusions. Several models have been proposed for the formation of D-shaped profiles, such as crystal settling and convection, multiple injections, flow differentiation, compositional convection, or Soret fractionation in combination with in situ crystallization. There is however no general agreement of one particular model, as they pose difficulties explaining all occurrences of D-shaped profiles. Based on numerical modeling we introduce post-emplacement flow as a feasible mechanism to explain the D-shaped profiles. A melt-flow can cause magmatic differentiation in the sill by transporting incompatible and less compatible elements associated with the melt phase (e.g. Zr and Fe) in an advective process through a stationary crystal network. Crystal networks of considerable strength are known to form in the

  17. Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives

    Directory of Open Access Journals (Sweden)

    Carlos Macias

    2016-01-01

    Full Text Available We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores. The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

  18. Additional degrees of freedom associated with position measurements in non-commutative quantum mechanics

    CERN Document Server

    Rohwer, CM

    2012-01-01

    In this thesis we shall demonstrate that a measurement of position alone in non-commutative space cannot yield complete information about the quantum state of a particle. Indeed, the formalism used entails a description that is non-local in that it requires all orders of positional derivatives through the star product that is used ubiquitously to map operator multiplication onto function multiplication in non-commutative systems. It will be shown that there exist several equivalent local descriptions, which are arrived at via the introduction of additional degrees of freedom. Consequently non-commutative quantum mechanical position measurements necessarily confront us with some additional structure which is necessary to specify quantum states completely. The remainder of the thesis, will involve investigations into the physical interpretation of these additional degrees of freedom. For one particular local formulation, the corresponding classical theory will be used to demonstrate that the concept of extended...

  19. Physical and mechanical characterization of Portland cement mortars made with expanded polystyrene particles addition (EPS

    Directory of Open Access Journals (Sweden)

    Ferrándiz-Mas, V.

    2012-12-01

    Full Text Available On this work the influence of the addition of different types (commercial and recycled and contents of expanded polystyrene on the physical and mechanical properties of Portland cement mortars has been studied. Variables studied are: workability, air content, bulk density, mechanical strength, porosity, water absorption and sound absorption. Mixtures have been also characterized by scanning electron microscopy. Air-entraining agents, water retainer and superplasticizer additives have been used in order to improve the workability of mortars. The results show that the workability and mechanical strength decreases with increasing content of expanded polystyrene. Additives improve the workability and porosity, allowing manufacture mortars with high levels of recycled material that show mechanical properties suitable for use as masonry mortars, stucco and plaster.

    El objetivo de este estudio es evaluar la influencia de la adición de distintos tipos y dosificaciones de poliestireno expandido, tanto comerciales como procedentes de reciclado, sobre las características físicas y mecánicas de morteros de cemento portland. Las variables estudiadas fueron: consistencia, aire ocluido, densidad aparente, resistencias mecánicas, porosidad, absorción de agua y absorción acústica. Los morteros también se han caracterizado por microscopia electrónica de barrido. Con objeto de mejorar la trabajabilidad de los morteros se ha empleado aditivos aireante, retenedor de agua y fluidificante. Los resultados muestran que al aumentar la cantidad de poliestireno expandido la trabajabilidad y las resistencias mecánicas disminuyen. El empleo de aditivos mejora la trabajabilidad y la porosidad, permitiendo fabricar morteros con altos contenidos de residuo, con propiedades mecánicas adecuadas para su empleo como morteros de albañilería, revoco y enlucido.

  20. Physico-mechanical and dissolution behaviours of ibuprofen crystals crystallized in the presence of various additives

    Directory of Open Access Journals (Sweden)

    A Nokhodchi

    2010-06-01

    Full Text Available "n  "n Background and the purpose of the study: The success of any direct-tableting procedure is strongly affected by the quality of the crystals used in the process. Ibuprofen is a poorly compactible drug with a high tendency for capping. In order to use ibuprofen in direct compression formulations, physico-mechanical properties of ibuprofen should be improved considerably. The aim of the present investigation was to employ crystallization techniques in order to improve the physico-mechanical properties of ibuprofen for direct compression. "nMethods:The experimental methods involved the preparation of ibuprofen crystals by solvent change technique. Ibuprofen was dissolved in ethanol and crystallized out with water in the absence or presence of various hydrophilic additives (PEG 6000, 8000, Brij 98P and polyvinyl alcohol 22000, PVA 22000 with different concentrations. The physico-mechanical properties of the ibuprofen crystals were studied in terms of flow, density, tensile strength and dissolution behaviour. Morphology of ibuprofen crystals was studied by scanning electron microscopic (SEM. Solid state of the recrystallized particles was also investigated using differential scanning calorimeter (DSC and FT-IR. "nResults:Ibuprofen samples crystallized in the presence of PEG 6000 and 8000 and PVA showed remarkable increase in the tensile strengths of the directly compressed tablets, while some other additives, i.e. Brij 98P did not produce improved ibuprofen crystals. Ibuprofen powders made from particles obtained in the presence of PVA and Brij 98P showed similar dissolution profiles to the commercial ibuprofen particles. DSC and FT-IR results ruled out any significant interaction between ibuprofen and additives except for the samples crystallized in the presence of PEG 8000. Conclusion:The crystal habit of ibuprofen can be altered successfully by the crystallization technique which was developed in this study. The crystals developed in the

  1. Reversal effect and mechanism of Ginkgo biloba exocarp extracts in multidrug resistance of mice S180 tumor cells

    OpenAIRE

    Hu, Bi-Yuan; Gu, Yun-Hao; Cao, Chen-Jie; Wang, Jun; Han, Dong-Dong; Tang, Ying-Chao; Chen, Hua-Sheng; Xu, Aihua

    2016-01-01

    The aim of the present study was to investigate the reversal effect and its related mechanism of Ginkgo biloba exocarp extracts (GBEEs) in obtained multidrug resistance (MDR) of mice S180 tumor cells in vitro and in vivo. In order to simulate the clinical PFC [cis-dichlorodiamineplatinum, cisplatin (DDP) + fluorouracil (FU), FU+cyclophosphamide and cyclophosphamide] scheme, a gradually increasing dose was administered in a phased induction in order to induce S180 cells in vivo and to make the...

  2. Mirror reversal and visual rotation are learned and consolidated via separate mechanisms: recalibrating or learning de novo?

    Science.gov (United States)

    Telgen, Sebastian; Parvin, Darius; Diedrichsen, Jörn

    2014-10-01

    Motor learning tasks are often classified into adaptation tasks, which involve the recalibration of an existing control policy (the mapping that determines both feedforward and feedback commands), and skill-learning tasks, requiring the acquisition of new control policies. We show here that this distinction also applies to two different visuomotor transformations during reaching in humans: Mirror-reversal (left-right reversal over a mid-sagittal axis) of visual feedback versus rotation of visual feedback around the movement origin. During mirror-reversal learning, correct movement initiation (feedforward commands) and online corrections (feedback responses) were only generated at longer latencies. The earliest responses were directed into a nonmirrored direction, even after two training sessions. In contrast, for visual rotation learning, no dependency of directional error on reaction time emerged, and fast feedback responses to visual displacements of the cursor were immediately adapted. These results suggest that the motor system acquires a new control policy for mirror reversal, which initially requires extra processing time, while it recalibrates an existing control policy for visual rotations, exploiting established fast computational processes. Importantly, memory for visual rotation decayed between sessions, whereas memory for mirror reversals showed offline gains, leading to better performance at the beginning of the second session than in the end of the first. With shifts in time-accuracy tradeoff and offline gains, mirror-reversal learning shares common features with other skill-learning tasks. We suggest that different neuronal mechanisms underlie the recalibration of an existing versus acquisition of a new control policy and that offline gains between sessions are a characteristic of latter.

  3. Mechanical properties and microstructures of hot extruded AE42 alloy with addition of zinc

    Institute of Scientific and Technical Information of China (English)

    WANG Feng; LIU Zheng; CHEN Li-jia; YU Bao-yi; LIN Li

    2006-01-01

    Mechanical properties and microstructures of AE42 magnesium alloy with addition of Zn and subjected to hot extrusion at 370 ℃ and an extrusion ratio of 8-1 were investigated. The results show that for the AE42 alloy, the addition of Zn can obviously improve its elongation as well as the ultimate tensile and yield strengths below 150 ℃. The addition of Zn can refine the microstructure of the AE42 alloy, and result in the precipitation of Mg17Al12 and MgZn2 phases. Due to the addition of Zn to the AE42 alloy, the amount of Al11RE3 phase decreases, while the Al11RE3 phase becomes short rod-shaped from acicular and block, and distributes along the grain boundaries, which will have a stronger effect on the tensile properties of the alloy at elevated temperature. In addition, with the presence of MgZn2 precipitates, the sliding of grain boundaries is restrained and the strength of the alloy gets enhanced.

  4. Mechanical properties of potato starch modified by moisture content and addition of lubricant

    Science.gov (United States)

    Stasiak, Mateusz; Molenda, Marek; Horabik, Józef; Mueller, Peter; Opaliński, Ireneusz

    2014-10-01

    Laboratory testing was conducted to deliver a set of characteristics of structure and mechanical properties of pure starch and starch with an addition of a lubricant - magnesium stearate. Considerable influence of moisture content of potato starch was found in the case of density, parameters of internal friction, coefficients of wall friction and flowability. Elasticity was found to be strongly influenced by water content of the material. Addition of magnesium stearate affected density and parameters of flowability, internal friction and elasticity. Bulk density increased from 604 to 774 kg m-3 with decrease in moisture content of potato starch from 17 to for 6%. Addition of magnesium stearate resulted in approximately 10% decrease in bulk density. Angle of internal friction obtained for 10 kPa of consolidation stress decreased from 33 to 24º with increase in moisture content, and to approximately 22º with addition of the lubricant. With an increase of moisture content from 6 to 18% and with addition of the lubricant, the modulus of elasticity during loading decreased from approximately 1.0 to 0.1 MPa. Modulus of elasticity during unloading was found in the range from 19 to 42 MPa and increased with increase of moisture content and amount of lubricant.

  5. Influence of silicon addition on the mechanical properties and corrosion resistance of low-alloy steel

    Indian Academy of Sciences (India)

    M Hebda; H Dębecka; J Kazior

    2015-12-01

    The addition of silicon to low-alloy steel allows to modify the materials' microstructure and thus to improve their corrosion resistance and mechanical properties. The influence of adding different amounts of silicon on the properties (density, transverse rupture strength, microhardness and corrosion resistance) and microstructure of low-alloy steel was investigated. Samples were prepared via the mechanical alloying process, which is the most useful method to homogeneously introduce silicon to low-alloy steel. Sintering was performed by using the spark plasma sintering (SPS) technique. After the SPS process, half of each of the obtained samples was heat-treated in a vacuum furnace. The results show that high-density materials were achieved, and a homogeneous and fine microstructure was obtained. The investigated compositions containing 1 wt% of silicon had better corrosion resistance than samples with 3 wt% of silicon addition. Furthermore, corrosion resistance as well as the mechanical and plastic properties of the samples with 1 wt% of silicon can be further improved by applying heat treatment.

  6. Effect of neodymium, gadolinium addition on microstructure and mechanical properties of AZ80 magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    姜楠; 陈雷; 孟令刚; 房灿峰; 郝海; 张兴国

    2016-01-01

    The microstructure and mechanical properties of AZ80 magnesium alloys with varying Nd, Gd contents were investigated. The results revealed that the as-cast microstructure of AZ80 alloy was composed ofα-Mg matrix and divorced eutecticβ-Mg17Al12 phases. The fraction of Mg17Al12 phase was reduced when 0.6 wt.% Nd was added, and new rod-shaped Al11Nd3 phase and small block-shaped Al-Nd-Mn phase appeared. With Gd addition, the Gd elements mixed with Nd to form rare earth phases. New block-shaped Al2Gd and Al2Nd phases which were collectively called Al2RE phases were observed in the microstructure with more than 0.6 wt.% Gd addition. Moreover, the addition of Gd could promote the precipitation of block-shaped Al2RE phase, and inhibit the original rod-shaped Al11Nd3 phase. The AZ80-0.6Nd-0.6Gd alloy exhibited the optimal mechanical properties among all the ex-perimental alloys, in which the tensile strength, yield strength and elongation were 215, 145 MPa and 8.33%, respectively.

  7. Effect of carbon nanofiber addition in the mechanical properties and durability of cementitious materials

    Directory of Open Access Journals (Sweden)

    Galao, O.

    2012-09-01

    Full Text Available This paper reports on recent work that is directed at studying the changes in the mechanical properties of Portland cement based mortars due to the addition of carbon nanofiber (CNF. Both flexural and compression strength has been determined and related to the CNF addition to the mix, to the curing time and to the porosity and density of the matrix. Also, corrosion of embedded steel rebars in CNF cement pastes exposed to carbonation and chloride attacks has been investigated. The increase in CNF addition implies higher corrosion intensity and higher levels of mechanical properties.En este artículo se han estudiado los cambios en las propiedades mecánicas de los morteros de cemento Portland debido a la adición de nanofibras de carbono (NFC. Se han determinado las resistencias a flexotracción y a compresión de los morteros en relación a la cantidad de NFC añadidas a la mezcla, al tiempo de curado y a la porosidad y densidad de los mismos. Además se han investigado los niveles de corrosión de barras de acero embebidas en pastas de cemento con NFC expuestos al ataque por carbonatación y por ingreso de cloruros. El aumento en el porcentaje de NFC añadido se traduce en un aumento la intensidad de corrosión registrada y una mejora de las propiedades mecánicas.

  8. Gelation Behaviors and Mechanism of Silk Fibroin According to the Addition of Nitrate Salts.

    Science.gov (United States)

    Im, Dong Su; Kim, Min Hee; Yoon, Young Il; Park, Won Ho

    2016-10-10

    Silk fibroin (SF) is a typical fibrous protein that is secreted by silkworms and spiders. It has been used in a variety of areas, and especially for tissue-engineering scaffolds, due to its sound processability, mechanical properties, biodegradability, and biocompatibility. With respect to gelation, the SF gelation time is long in aqueous solutions, so a novel approach is needed to shorten this time. The solubility of regenerated SF is sound in formic acid (FA), which is a carboxylic acid of the simplest structure. In this study, SF was dissolved in formic acid, and the addition of salts then induced a rapid gelation that accompanied a solution-color change. Based on the gelation behaviors of the SF solution according to different SF and salt concentrations, the gelation mechanism was investigated.

  9. Failure mechanisms of additively manufactured porous biomaterials: Effects of porosity and type of unit cell.

    Science.gov (United States)

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Anaraki, A P; Ahmadi, S M; Zadpoor, A A; Schmauder, S

    2015-10-01

    Since the advent of additive manufacturing techniques, regular porous biomaterials have emerged as promising candidates for tissue engineering scaffolds owing to their controllable pore architecture and feasibility in producing scaffolds from a variety of biomaterials. The architecture of scaffolds could be designed to achieve similar mechanical properties as in the host bone tissue, thereby avoiding issues such as stress shielding in bone replacement procedure. In this paper, the deformation and failure mechanisms of porous titanium (Ti6Al4V) biomaterials manufactured by selective laser melting from two different types of repeating unit cells, namely cubic and diamond lattice structures, with four different porosities are studied. The mechanical behavior of the above-mentioned porous biomaterials was studied using finite element models. The computational results were compared with the experimental findings from a previous study of ours. The Johnson-Cook plasticity and damage model was implemented in the finite element models to simulate the failure of the additively manufactured scaffolds under compression. The computationally predicted stress-strain curves were compared with the experimental ones. The computational models incorporating the Johnson-Cook damage model could predict the plateau stress and maximum stress at the first peak with less than 18% error. Moreover, the computationally predicted deformation modes were in good agreement with the results of scaling law analysis. A layer-by-layer failure mechanism was found for the stretch-dominated structures, i.e. structures made from the cubic unit cell, while the failure of the bending-dominated structures, i.e. structures made from the diamond unit cells, was accompanied by the shearing bands of 45°.

  10. Fluid mechanics of additive manufacturing of metal objects by accretion of droplets – a survey

    Directory of Open Access Journals (Sweden)

    Tesař Václav

    2016-01-01

    Full Text Available Paper presents a survey of principles of additive manufacturing of metal objects by accretion of molten metal droplets, focusing on fluid-mechanical problems that deserve being investigated. The main problem is slowness of manufacturing due to necessarily small size of added droplets. Increase of droplet repetition rate calls for basic research of the phenomena that take place inside and around the droplets: ballistics of their flight, internal flowfield with heat and mass transfer, oscillation of surfaces, and the ways to elimination of satellite droplets.

  11. On Self-Recovery Mechanism and Additional Maneuverability of a Mini Mobile Robot

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Ordinary mobile robots have some kind of moving mechanisms attached to one rigid body. When working on rough terrain or in other hazard environments, there existed some possibilities that the robot will be turned up side down, thus causing losses to the robot's expedition. Multi-bodied mobile robots provide a solution to that problem. Using active joints between bodies, the robot can recover from turnover situation by itself. In this paper, the authors discuss the joint arrangements and the additional maneuverability resulted from joints between body segments.

  12. Reduction mechanisms of additives on Si anodes of Li-ion batteries.

    Science.gov (United States)

    Martínez de la Hoz, Julibeth M; Balbuena, Perla B

    2014-08-28

    Solid-electrolyte interphase (SEI) layers are films deposited on the surface of Li-ion battery electrodes during battery charge and discharge processes. They are due to electrochemical instability of the electrolyte which causes electron transfer from (to) the anode (cathode) surfaces. The films could have a protective passivating role and therefore understanding the detailed reduction (oxidation) processes is essential. Here density functional theory and ab initio molecular dynamics simulations are used to investigate the reduction mechanisms of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) on lithiated silicon surfaces. These species are frequently used as "additives" to improve the SEI properties. It is found that on lithiated Si anodes (with low to intermediate degrees of lithiation) VC may be reduced via a 2e(-) mechanism yielding an opened VC(2-) anion. At higher degrees of lithiation, such a species receives two extra electrons from the surface resulting in an adsorbed CO(2-)(ads) anion and a radical anion ˙OC2H2O(2-). Additionally, in agreement with experimental observations, it is shown that CO2 can be generated from reaction of VC with the CO3(2-)anion, a product of the reduction of the main solvent, ethylene carbonate (EC). On the other hand, FEC reduction on LixSiy surfaces is found to be independent of the degree of lithiation, and occurs through three mechanisms. One of them leads to an adsorbed VC(2-) anion upon release from the FEC molecule and adsorption on the surface of F(-) and one H atom. Thus in some cases, the reduction of FEC may lead to the exact same reduction products as that of VC, which explains similarities in SEI layers formed in the presence of these additives. However, FEC may be reduced via two other multi-electron transfer mechanisms that result in formation of either CO2(2-), F(-), and ˙CH2CHO(-) or CO(2-), F(-), and ˙OCH2CHO(-). These alternative reduction products may oligomerize and form SEI layers with

  13. Influence of WC addition on the microstructure and mechanical properties of NbC-Co cermets

    Energy Technology Data Exchange (ETDEWEB)

    Huang, S.G. [Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Belgium); Li, L. [School of Material Science and Engineering, Shanghai University, 149 Yanchang Road, Shanghai 200072 (China); Van der Biest, O. [Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Belgium); Vleugels, J. [Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Belgium)]. E-mail: Jozef.Vleugels@mtm.kuleuven.be

    2007-03-14

    NbC-24.5 wt.% Co cermets with up to 30 wt.% WC were obtained by solid state hot pressing at 1300 {sup o}C under a pressure of 45 MPa for 10 min and pressureless liquid phase sintering at 1360 {sup o}C for 60 min. The effect of WC addition on the microstructure and mechanical properties of NbC-Co based cermets was investigated. The hot pressed cermets exhibited interconnected and irregular niobium carbide (NbC) or (Nb,W)C grains, whereas the shape of the NbC grains changed from faceted with rounded corners to spherical, as the WC content increased in the pressureless sintered cermets. The undissolved WC increased with increasing WC addition. A clear core/rim structure was observed in the hot pressed cermets with 10-30 wt.% WC additions, whereas this structure was gradually eliminated when pressureless sintering. The hardness remains nearly constant whereas the fracture toughness slightly increases with increasing WC addition. The dissolution of WC in the Co binder and NbC grains, as well as the formation of a solid solution (Nb,W)C phase were supported by thermodynamic calculations.

  14. [Influences of ion-suppressors on retention behaviors of nine food additives in reversed-phase high performance liquid chromatographic separation].

    Science.gov (United States)

    Zhao, Yonggang; Chen, Xiaohong; Li, Xiaoping; Yao, Shanshan; Jin, Micong

    2011-10-01

    The influences of ion-suppressors on retention behaviors of nine food additives, i.e., acesulfame, saccharin, caffeine, aspartame, benzoic acid, sorbic acid, stevioside, dehydroacetic acid and neotame in reversed-phase high performance liquid chromatographic (RP-HPLC) separation were investigated. The organic modification effects of acids, i. e. , trifluoroacetic acid (TFA) and buffer salts, i. e. , TFA-ammonium acetate (AmAc) were studied emphatically. The relationships between retention factors of solutes and volume percentages of ion-suppressors in the mobile phase systems of acetonitrile-TFA aqueous solution and acetonitrile-TFA-AmAc aqueous solution were quantitatively established, separately. The separation of nine food additives was completed by a gradient elution with acetonitrile-TFA (0.01%, v/v)-AmAc (2. 5 mmol/L) aqueous solution as the mobile phases. An RP-HPLC method was established for the simultaneous determination of nine food additives in red wine. In the range of 10. 0 - 100. 0 mg/L, nine food additives showed good linearity with the correlation coefficients ( r2 ) larger than 0. 999 1. The limits of detection (LODs) were in the range of 0. 33 - 2. 36 mg/L and the limits of quantification (LOQs) were in the range of 1. 11 - 7. 80 mg/L. The spiked recoveries were between 87. 61% and 108. 4% with the relative standard deviations (RSDs) of 2. 2% -9. 4%. These results are of referential significance for the rapid establishment and accu- rate optimization of RP-HPLC separation for the simultaneous determination of food additives in other foods.

  15. Analysis of Reverse-Bias Leakage Current Mechanisms in Metal/GaN Schottky Diodes

    Directory of Open Access Journals (Sweden)

    P. Pipinys

    2010-01-01

    Full Text Available Temperature-dependent reverse-bias current-voltage characteristics obtained by other researchers for Schottky diodes fabricated on GaN are reinterpreted in terms of phonon-assisted tunneling (PhAT model. Temperature dependence of reverse-bias leakage current is shown could be caused by the temperature dependence of electron tunneling rate from traps in the metal-semiconductor interface to the conduction band of semiconductor. A good fit of experimental data with the theory is received in a wide temperature range (from 80 K to 500 K using for calculation the effective mass of 0.222 me. and for the phonon energy the value of 70 meV. The temperature and bias voltages dependences of an apparent barrier height (activation energy are also explicable in the framework of the PhAT model.

  16. Design Paradigm Utilizing Reversible Diels-Alder Reactions to Enhance the Mechanical Properties of 3D Printed Materials.

    Science.gov (United States)

    Davidson, Joshua R; Appuhamillage, Gayan A; Thompson, Christina M; Voit, Walter; Smaldone, Ronald A

    2016-07-06

    A design paradigm is demonstrated that enables new functional 3D printed materials made by fused filament fabrication (FFF) utilizing a thermally reversible dynamic covalent Diels-Alder reaction to dramatically improve both strength and toughness via self-healing mechanisms. To achieve this, we used as a mending agent a partially cross-linked terpolymer consisting of furan-maleimide Diels-Alder (fmDA) adducts that exhibit reversibility at temperatures typically used for FFF printing. When this mending agent is blended with commercially available polylactic acid (PLA) and printed, the resulting materials demonstrate an increase in the interfilament adhesion strength along the z-axis of up to 130%, with ultimate tensile strength increasing from 10 MPa in neat PLA to 24 MPa in fmDA-enhanced PLA. Toughness in the z-axis aligned prints increases by up to 460% from 0.05 MJ/m(3) for unmodified PLA to 0.28 MJ/m(3) for the remendable PLA. Importantly, it is demonstrated that a thermally reversible cross-linking paradigm based on the furan-maleimide Diels-Alder (fmDA) reaction can be more broadly applied to engineer property enhancements and remending abilities to a host of other 3D printable materials with superior mechanical properties.

  17. Electrocatalytic mechanism of reversible hydrogen cycling by enzymes and distinctions between the major classes of hydrogenases

    OpenAIRE

    Hexter, Suzannah V.; Grey, Felix; Happe, Thomas; Climent, Victor; Armstrong, Fraser A.

    2012-01-01

    The extraordinary ability of Fe- and Ni-containing enzymes to catalyze rapid and efficient H+/H2 interconversion—a property otherwise exclusive to platinum metals—has been investigated in a series of experiments combining variable-temperature protein film voltammetry with mathematical modeling. The results highlight important differences between the catalytic performance of [FeFe]-hydrogenases and [NiFe]-hydrogenases and justify a simple model for reversible catalytic electron flow in enzymes...

  18. Mechanisms and Processes Leading to Reverse Zoning in the Andong Granitoid Pluton, Andong Batholith, Korea

    Institute of Scientific and Technical Information of China (English)

    Sang Koo HWANG

    2002-01-01

    The Andong pluton consists of comagmatic granitoid rocks which constitute outstanding examples of reversely zoned granitoids. The pluton has three lithofacies: hornblende biotite tonalite, biotite granodiorite and porphyritic biotite granite. The zoned pattern forms by locating a tonalite core containing high-temperature mafic assemblages in central part,granodiorite rims in marginal part, and a porphyritic granite cap containing more felsic assemblages in topside of the pluton.Mineral abundances as well as bulk compositions of the granitoids indicate that the interior is enriched in mafic minerals and that it shows higher contents of oxides than the margin and topside. The compositional gradients change gradually with continuity between the lithofacies. The regular compositional variations within the pluton support the argument that the pluton behaved as an individual petrochemical system. Model abundances of the granitoids are in agreement with the bulk compositional gradients, suggesting that no significant interaction with country rocks occurred. Remobilization (resurgence) of deeper parts of the system into the more felsic magmas of the chamber explains the reverse zoning. Fractional crystallization was of importance and probably accounts for the selective removal of the settling phases. The Andong pluton is an example of reversely zoned plutons related by remobilization of more mafic but consanguineous magmas. Large-scale upwelling occurred in the pluton leading to the present arrangement of three lithofacies. It is conceivable that remnants of the reverse zoning become more difficult to discern as the plutonic rocks reach the latest stages of their evolution. In this case, the Andong pluton represents an earlier stage in the evolution of a felsic system that is usually represented by the final stages in normally zoned plutons.

  19. TDDFT Study on Different Sensing Mechanisms of Similar Cyanide Sensors Based on Michael Addition Reaction

    Institute of Scientific and Technical Information of China (English)

    Guang-yue Li; Ping Song; Guo-zhong He

    2011-01-01

    The solvents and substituents of two similar fluorescent sensors for cyanide, 7-diethylamino-3-formylcoumarin (sensor a) and 7-diethylamino-3-(2-nitrovinyl)coumarin (sensor b), are proposed to account for their distinct sensing mechanisms and experimental phenomena.The time-dependent density functional theory has been applied to investigate the ground states and the first singlet excited electronic states of the sensor as well as their possible Michael reaction products with cyanide, with a view to monitoring their geometries and photophysical properties. The theoretical study indicates that the protic water solvent could lead to final Michael addition product of sensor a in the ground state, while the aprotic acetonitrile solvent could lead to carbanion as the final product of sensor b. Furthermore,the Michael reaction product of sensor a has been proved to have a torsion structure in its first singlet excited state. Correspondingly, sensor b also has a torsion structure around the nitrovinyl moiety in its first singlet excited state, while not in its carbanion structure. This could explain the observed strong fluorescence for sensor a and the quenching fluorescencefor the sensor b upon the addition of the cyanide anions in the relevant sensing mechanisms.

  20. Mechanism of wear and tribofilm formation with ionic liquids and ashless antiwear additives

    Science.gov (United States)

    Sharma, Vibhu

    Increasingly stringent government regulation on emissions (EPA Emissions Standard Reference Guide and latest CAFE standards requiring an average fuel economy of 54.5 mpg (combined cars and trucks) by 2025) impose significant challenges to the automotive and lubricant industries calling for the development and implementation of lower viscosity ILSAC GF-5&6 and API-CJ4&5 oils which further limit the amount of SAPS and deposits in engines. Development of additives that result in lower ash content, volatility and anti-wear property plays a crucial role in being able to reach these standards. The current industrial additive technology i.e. zinc dialkyldithiophosphate (ZDDP) forms harmful deposits on catalytic convertor due to the volatility of Zn, S and P which, impairs its functionality and consequently results in higher emission from vehicles. In this research work, ionic liquids (IL's) that are non-volatile have been studied as new generation environment friendly antiwear additives along with other ashless anti-wear additives including boron based additives to overcome the current challenges of improving the fuel efficiency and reducing the amount of hazardous emissions. The goal of this thesis work is to study the tribological performance of selected IL's and develop a comprehensive understating of IL's chemistry and its consequences to their friction and wear outcomes. As first approach, various P, S and F based ionic liquids are studied for their tribological properties by analyzing the friction and wear results generated using standard tribological experiments. Following this, advanced surface characterization techniques such as X-ray absorption near edge structure (XANES) spectroscopy, SEM, Nano-indentation, SPM techniques are used to investigate the chemical-mechanical properties of the antiwear films. Results indicate that the tribological properties of ionic liquids depend on their solubility in base oil (BO) as well as their chemical interaction with the

  1. Mechanism of tension generation in muscle: an analysis of the forward and reverse rate constants.

    Science.gov (United States)

    Davis, Julien S; Epstein, Neal D

    2007-04-15

    Tension generation in muscle occurs during the attached phase of the ATP-powered cyclic interaction of myosin heads with thin filaments. The transient nature of tension-generating intermediates and the complexity of the mechanochemical cross-bridge cycle have impeded a quantitative description of tension generation. Recent experiments performed under special conditions yielded a sigmoidal dependence of fiber tension on temperature--a unique case that simplifies the system to a two-state transition. We have applied this two-state analysis to kinetic data obtained from biexponential laser temperature-jump tension transients. Here we present the forward and reverse rate constants for de novo tension generation derived from analysis of the kinetics of the fast laser temperature-jump phase tau(2) (equivalent of the length-jump phase 2(slow)). The slow phase tau(3) is temperature-independent indicating coupling to rather than a direct role in, de novo tension generation. Increasing temperature accelerates the forward, and slows the reverse, rate constant for the creation of the tension-generating state. Arrhenius behavior of the forward and anti-Arrhenius behavior of the reverse rate constant is a kinetic signature of multistate multipathway protein-folding reactions. We conclude that locally unfolded tertiary and/or secondary structure of the actomyosin cross-bridge mediates the power stroke.

  2. Mechanisms underlying the additive and redundant Qrr phenotypes in Vibrio harveyi and Vibrio cholerae.

    Science.gov (United States)

    Hunter, Geoffrey A M; Keener, James P

    2014-01-07

    Vibrio harveyi and Vibrio cholerae regulate their virulence factors according to the local cell-population density in a regulatory system called quorum sensing. Their quorum sensing systems contain a small RNA (sRNA) circuit to regulate expression of a master transcriptional regulator via multiple quorum regulated RNA (Qrr) and a protein chaperon Hfq. Experiments and genetic analysis show that their respective quorum sensing networks are topologically equivalent and have homologous components, yet they respond differently to the same experimental conditions. In particular, V. harveyi Qrr are additive because all of its Qrr are required to maintain wild-type-like repression of its master transcriptional regulator. Conversely, V. cholerae Qrr are redundant because any of its Qrr is sufficient to repress its master transcriptional regulator. Given the striking similarities between their quorum sensing systems, experimentalists have been unable to identify conclusively the mechanisms behind these phenotypic differences. Nevertheless, the current hypothesis in the literature is that dosage compensation is the mechanism underlying redundancy. In this work, we identify the mechanisms underlying Qrr redundancy using a detailed mathematical model of the V. harveyi and V. cholerae sRNA circuits. We show that there are exactly two different cases underlying Qrr redundancy and that dosage compensation is unnecessary and insufficient to explain Qrr redundancy. Although V. harveyi Qrr are additive when the perturbations in Qrr are large, we predict that V. harveyi and V. cholerae Qrr are redundant when the perturbations in Qrr are small. We argue that the additive and redundant Qrr phenotypes can emerge from parametric differences in the sRNA circuit. In particular, we find that the affinity of Qrr and its expression relative to the master transcriptional regulator determine the level of redundancy in V. harveyi and V. cholerae. Furthermore, the additive and redundant Qrr

  3. Translation of Time-Reversal Violation in the Neutral K-Meson System into a Table-Top Mechanical System

    CERN Document Server

    Reiser, Andreas; Stiewe, Juergen

    2012-01-01

    Weak interactions break time-reversal (T) symmetry in the two-state system of neutral K mesons. We present and discuss a two-state mechanical system, a Foucault-type pendulum on a rotating table, for a full representation of K0 K0bar transitions by the pendulum motions including T violation. The pendulum moves with two different oscillation frequencies and two different magnetic dampings. Its equation of motion is identical with the differential equation for the real part of the CPT-symmetric K-meson wave function. The pendulum is able to represent microscopic CP and T violation with CPT symmetry owing to the macroscopic Coriolis force which breaks the symmetry under reversal-of-motion. Video clips of the pendulum motions are shown as supplementary material.

  4. Translation of time-reversal violation in the neutral K-meson system into a table-top mechanical system

    Science.gov (United States)

    Reiser, Andreas; Schubert, Klaus R.; Stiewe, Jürgen

    2012-08-01

    Weak interactions break time-reversal (T) symmetry in the two-state system of neutral K-mesons. We present and discuss a two-state mechanical system, i.e. a Foucault-type pendulum on a rotating table, for a full representation of {K^0}{{\\overlineK}{}^0} transitions by the pendulum motions including T violation. The pendulum moves with two different oscillation frequencies and two different magnetic dampings. Its equation of motion is identical to the differential equation for the real part of the CPT-symmetric K-meson wavefunction. The pendulum is able to represent microscopic CP and T violation with CPT symmetry owing to the macroscopic Coriolis force, which breaks the symmetry under reversal-of-motion. Video clips of the pendulum motions are given as supplementary material.

  5. Modeling and additive manufacturing of bio-inspired composites with tunable fracture mechanical properties.

    Science.gov (United States)

    Dimas, Leon S; Buehler, Markus J

    2014-07-07

    Flaws, imperfections and cracks are ubiquitous in material systems and are commonly the catalysts of catastrophic material failure. As stresses and strains tend to concentrate around cracks and imperfections, structures tend to fail far before large regions of material have ever been subjected to significant loading. Therefore, a major challenge in material design is to engineer systems that perform on par with pristine structures despite the presence of imperfections. In this work we integrate knowledge of biological systems with computational modeling and state of the art additive manufacturing to synthesize advanced composites with tunable fracture mechanical properties. Supported by extensive mesoscale computer simulations, we demonstrate the design and manufacturing of composites that exhibit deformation mechanisms characteristic of pristine systems, featuring flaw-tolerant properties. We analyze the results by directly comparing strain fields for the synthesized composites, obtained through digital image correlation (DIC), and the computationally tested composites. Moreover, we plot Ashby diagrams for the range of simulated and experimental composites. Our findings show good agreement between simulation and experiment, confirming that the proposed mechanisms have a significant potential for vastly improving the fracture response of composite materials. We elucidate the role of stiffness ratio variations of composite constituents as an important feature in determining the composite properties. Moreover, our work validates the predictive ability of our models, presenting them as useful tools for guiding further material design. This work enables the tailored design and manufacturing of composites assembled from inferior building blocks, that obtain optimal combinations of stiffness and toughness.

  6. Effect of alloying addition and microstructural parameters on mechanical properties of 93% tungsten heavy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ravi Kiran, U., E-mail: uravikiran@gmail.com [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India); Panchal, A.; Sankaranarayana, M. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India); Nageswara Rao, G.V.S. [National Institute of Technology, Warangal 506004 (India); Nandy, T.K. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India)

    2015-07-29

    Liquid phase sintering, heat treatment and swaging studies on three tungsten heavy alloys, 93W–4.9Ni–2.1Fe (wt%), 93W–4.2Ni–1.2Fe–1.6Co (wt%) and 93W–4.9Ni–1.9Fe–0.2Re (wt%) were carried out in detail with respect to microstructure, tensile and impact properties. All the alloys were sintered and swaged to 40% deformation. The results indicate that Re addition reduces the grain size of the alloy compared to W–Ni–Fe and W-Ni-Fe-Co alloys. W–Ni–Fe–Re alloy shows superior tensile properties in heat treated condition as compared to W–Ni–Fe and W–Ni–Fe–Co alloys. SEM study of fractured specimens clearly indicates that the failure in case of W–Ni–Fe–Re was due to transgranular cleavage of tungsten grains and W–W de-cohesion. W–Ni–Fe and W–Ni–Fe–Co alloys also failed by mixed mode failure. However, in these cases, ductile dimples corresponding the failure of the matrix phase was rarely seen. Thermo-mechanical processing resulted in significant changes in mechanical properties. While W–Ni–Fe–Re alloy showed the highest tensile strength (1380 MPa), W–Ni–Fe–Co exhibited the highest elongation (12%) to failure. A detailed analysis involving microstructure, mechanical properties and failure behavior was undertaken in order to understand the property trends.

  7. Additively Manufactured Scaffolds for Bone Tissue Engineering and the Prediction of their Mechanical Behavior: A Review

    Directory of Open Access Journals (Sweden)

    Xiang-Yu Zhang

    2017-01-01

    Full Text Available Additive manufacturing (AM, nowadays commonly known as 3D printing, is a revolutionary materials processing technology, particularly suitable for the production of low-volume parts with high shape complexities and often with multiple functions. As such, it holds great promise for the fabrication of patient-specific implants. In recent years, remarkable progress has been made in implementing AM in the bio-fabrication field. This paper presents an overview on the state-of-the-art AM technology for bone tissue engineering (BTE scaffolds, with a particular focus on the AM scaffolds made of metallic biomaterials. It starts with a brief description of architecture design strategies to meet the biological and mechanical property requirements of scaffolds. Then, it summarizes the working principles, advantages and limitations of each of AM methods suitable for creating porous structures and manufacturing scaffolds from powdered materials. It elaborates on the finite-element (FE analysis applied to predict the mechanical behavior of AM scaffolds, as well as the effect of the architectural design of porous structure on its mechanical properties. The review ends up with the authors’ view on the current challenges and further research directions.

  8. Effect of Titania Additive on Structural and Mechanical Properties of Alumina-Fluorapatite Composites

    Institute of Scientific and Technical Information of China (English)

    Awatef Guidara; Kamel Chaari; Jamel Bouaziz

    2012-01-01

    Mechanical properties of alumina-fluorapatite composites with different titania additive amounts (0, 0.5, 1, 1.4, 2, 3, 4 and 5 wt%) have been investigated between 1200 and 1600℃. The optimum values of densification and mechanical properties of composites have been reached with 1.4 wt% of titania after the sintering process at 1500℃ for 1 h. Thus, the rupture strength of alumina-26.52 wt% Fap-1.4 wt% TiO2 reaches 75 MPa. At higher temperature and beyond 1.4 wt% TiO2 ,the densification and mechanical properties were hindered by the formation of both intergranular porosity and secondary phase. X-ray diffraction (XRD) analysis of alumina-Fap-TiO2 composites shows the formation of aluminium titanate (Al2O3-TiO2:Al2TiO5 ). The 27Al magic angle scanning nuclear magnetic resonance analysis of Al2O3-Fap-TiO2 composites reveals the presence of octahedral and pentahedral aluminium and novel environment relative to tetrahedral aluminium sites.

  9. The effects of tantalum addition on the microtexture and mechanical behaviour of tungsten for ITER applications

    Science.gov (United States)

    Tejado, E.; Carvalho, P. A.; Munoz, A.; Dias, M.; Correia, J. B.; Mardolcar, U. V.; Pastor, J. Y.

    2015-12-01

    Tungsten (W) and its alloys are very promising materials for producing plasma-facing components (PFCs) in the fusion power reactors of the near future, even as a structural part in them. However, whereas the properties of pure tungsten are suitable for a PFC, its structural applications are still limited due to its low toughness, ductile to brittle transition temperature and recrystallization behaviour. Therefore, many efforts have been made to improve its performance by alloying tungsten with other elements. Hence, in this investigation, the thermo-mechanical performance of two new tungsten-tantalum materials has been evaluated. Materials with W-5wt.%Ta and W-15wt.%Ta were processed by mechanical alloying (MA) and later consolidation by hot isostatic pressing (HIP), with distinct settings for each composition. Thus, it was possible to determine the relationship between the microstructure and the addition of Ta with the macroscopic mechanical properties. These were measured by means of hardness, flexural strength and fracture toughness, in the temperature range of 300-1473 K. The microstructure and the fracture surfaces features of the tested materials were analysed by Field Emission Scanning Electron Microscopy (FESEM).

  10. Permeability and mechanical properties of cement mortars colored by nano-mineral additives

    Directory of Open Access Journals (Sweden)

    Kamali Bernard S.

    2012-09-01

    Full Text Available This work concerns a preliminary study on issues that relate primarily to the permeability of cementitious materials under the influence of some specific inexpensive additions that can play an important role in preserving the environment. We studied the addition of dyes in the presence of TiO2 on the Portland cement mortar. The used dyes are a yellow powder containing iron oxyhydroxide (FeO (OH, a blue-based powder tellurate manganese (MnTe2O5 and red powder containing iron oxide (Fe2O3. We measure the setting time, permeability and mechanical properties of Portland cement mortars colored with nano-mineral oxides mentioned previously. Test results indicate that the addition of nano-particles has a little influence on the setting time, improves penetration resistance that is due the affinity of the pore structure of mortar and slightly improves the resistance to compression for low levels of nanoparticles of TiO2.

  11. Effect of Meltable Triazine-DOPO Additive on Rheological, Mechanical, and Flammability Properties of PA6

    Directory of Open Access Journals (Sweden)

    Irina Butnaru

    2015-08-01

    Full Text Available Through a straightforward approach, a new meltable, halogen-free, nitrogen-phosphorus-based flame retardant (FR, 6-(2-(4,6-diamino-1,3,5-triazin-2-ylethyl dibenzo[c,e][1,2]oxaphosphinine 6-oxide (DTE-DOPO was synthesized and incorporated in polyamide 6 (PA6. It was proved that a very low phosphorus content of 1.46 wt% for DTE-DOPO additive improved the flame retardancy of PA6, leading to a non-flammable material. The performance of the new additive was compared to that of the commercially-available Exolit® OP 1230. The PA6 formulations were evaluated by measuring the rheological, mechanical, and flammability behavior. Using compounding by melt extrusion, 17 wt% additives was introduced into PA6 matrix and the corresponding formulations were characterized. The results evidenced a higher homogeneity of DTE-DOPO with PA6, a high thermal stability with a catalyzing decomposition effect on PA6 caused by the presence of the new developed FR, enhanced elasticity for the PA6/DTE-DOPO formulation and a V0 rating for both formulations. Thermal and fire analysis indicated a primary gas-phase activity, combined with a complete suppression of the self-sustained burning for the PA6/DTE-DOPO formulation.

  12. Gaining insight in the behaviour of imidazolium-based ionic liquids as additives in reversed-phase liquid chromatography for the analysis of basic compounds.

    Science.gov (United States)

    Ubeda-Torres, M T; Ortiz-Bolsico, C; García-Alvarez-Coque, M C; Ruiz-Angel, M J

    2015-02-06

    In reversed-phase liquid chromatography in the absence of additives, cationic basic compounds give rise to broad and asymmetrical peaks as a result of ionic interactions with residual free silanols on silica-based stationary phases. Ionic liquids (ILs), added to the mobile phase, have been suggested as alternatives to amines to block the activity of silanols. However, the dual character of ILs should be considered: both cation and anion may be adsorbed on the stationary phase, thereby creating a double asymmetrical layer positively or negatively charged, depending on the relative adsorption of both ions. In this work, a study of the performance of six imidazolium-based ILs (the chlorides and tetrafluoroborates of 1-ethyl-, 1-butyl- and 1-hexyl-3-methylimidazolium) as modifiers of the chromatographic behaviour of a group of 10 β-blockers is performed, and compared with triethylamine and dimethyloctylamine. In order to gain more insight in the behaviour of ILs in RPLC, the changes in the nature of the chromatographic system, at increasing concentration of the additives, were followed based on retention and peak shape modelling. The multiple interactions that amines and ILs experience inside the chromatographic system suggest that the suppressing potency should be measured based on the shape of chromatographic peaks and not on the changes in retention. The ILs 1-hexyl-3-methyl-imidazolium chloride and tetrafluoroborate offered the most interesting features for the separation of the basic drugs.

  13. ADDITIONAL STRESS AND FRACTURE MECHANICS ANALYSES OF PRESSURIZED WATER REACTOR PRESSURE VESSEL NOZZLES

    Energy Technology Data Exchange (ETDEWEB)

    Walter, Matthew [Structural Integrity Associates, Inc.; Yin, Shengjun [ORNL; Stevens, Gary [U.S. Nuclear Regulatory Commission; Sommerville, Daniel [Structural Integrity Associates, Inc.; Palm, Nathan [Westinghouse Electric Company, Cranberry Township, PA; Heinecke, Carol [Westinghouse Electric Company, Cranberry Township, PA

    2012-01-01

    In past years, the authors have undertaken various studies of nozzles in both boiling water reactors (BWRs) and pressurized water reactors (PWRs) located in the reactor pressure vessel (RPV) adjacent to the core beltline region. Those studies described stress and fracture mechanics analyses performed to assess various RPV nozzle geometries, which were selected based on their proximity to the core beltline region, i.e., those nozzle configurations that are located close enough to the core region such that they may receive sufficient fluence prior to end-of-life (EOL) to require evaluation of embrittlement as part of the RPV analyses associated with pressure-temperature (P-T) limits. In this paper, additional stress and fracture analyses are summarized that were performed for additional PWR nozzles with the following objectives: To expand the population of PWR nozzle configurations evaluated, which was limited in the previous work to just two nozzles (one inlet and one outlet nozzle). To model and understand differences in stress results obtained for an internal pressure load case using a two-dimensional (2-D) axi-symmetric finite element model (FEM) vs. a three-dimensional (3-D) FEM for these PWR nozzles. In particular, the ovalization (stress concentration) effect of two intersecting cylinders, which is typical of RPV nozzle configurations, was investigated. To investigate the applicability of previously recommended linear elastic fracture mechanics (LEFM) hand solutions for calculating the Mode I stress intensity factor for a postulated nozzle corner crack for pressure loading for these PWR nozzles. These analyses were performed to further expand earlier work completed to support potential revision and refinement of Title 10 to the U.S. Code of Federal Regulations (CFR), Part 50, Appendix G, Fracture Toughness Requirements, and are intended to supplement similar evaluation of nozzles presented at the 2008, 2009, and 2011 Pressure Vessels and Piping (PVP

  14. Temperature dependence of magnetization reversal mechanism in CoNi/CoO bilayers%CoNi/CoO双层膜磁化反转机制与温度的依赖关系

    Institute of Scientific and Technical Information of China (English)

    宋金涛; 袁淑娟

    2007-01-01

    Exchange coupling and magnetization reversal mechanism in two series of Cox Ni1-x/CoO (30 nm) (x=0.2 and 0.4) bilayers are studied by vector magnetometer. Two components of magnetization are measured parallel and perpendicular to the applied field. At low temperatures, coercivity He ∝ (tFM)-n, n = 1.5 and 1.38 for x = 0.2 and 0.4, respectively, in agreement with the random field model. At room temperature, the coercivity is nearly proportional to the inverse FM layer thickness. In addition to the exchange field and the coercivity, the characteristic of the magnetization reversal mechanism was found to change with temperature. At temperatures below 180 K, magnetization reversal process along the unidirectional axis is accompanied only by nucleation and pinning of domain wall while magnetization rotation is also involved at high temperatures.

  15. Effect of yttrium addition on the microstructure and mechanical properties of ODS RAF steels

    Energy Technology Data Exchange (ETDEWEB)

    Auger, M.A., E-mail: maria.auger@materials.ox.ac.uk [Departamento de Física, Universidad Carlos III de Madrid, Av Universidad 30, 28911 Leganés (Spain); Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford (United Kingdom); Castro, V. de; Leguey, T.; Tarcísio-Costa, J.; Monge, M.A.; Muñoz, A.; Pareja, R. [Departamento de Física, Universidad Carlos III de Madrid, Av Universidad 30, 28911 Leganés (Spain)

    2014-12-15

    An oxide dispersion strengthened (ODS) alloy with nominal composition Fe–14Cr–2W–0.3Ti–0.24Y (wt.%) was produced by mechanical alloying using elemental powders, and subsequent hot isostatic pressing. The microstructure of the material and characteristics of the oxide particle dispersion were investigated by electron microscopy. The effect of heat treatments on the microhardness and tensile properties at room temperature was also studied. The results show that a fine dispersion of Y–O-rich nanoparticles is achieved, together with larger (Cr, Ti)-rich precipitates. The absence of Ti is apparent in the majority of these nanoparticles, in contrast with reported results for ODS Ti-modified steels processed with Y{sub 2}O{sub 3} addition.

  16. Effect of Sc addition on microstructure and mechanical properties of 1460 alloy

    Directory of Open Access Journals (Sweden)

    Juan Ma

    2014-02-01

    Full Text Available The effect of minor addition of Sc on microstructure, age hardening behavior, tensile properties and fracture morphology of 1460 alloy have been studied. It is found that Sc content increase from 0.11 wt% to 0.22 wt% is favorable for grain refinement in as-cast alloy but results in a coarsening of Cu-rich particles. The alloy with 0.11 wt% Sc exhibits enhanced mechanical properties and age hardening effect. Transmission electron microscopy (TEM investigations on the alloy with 0.11 wt% Sc have suggested that a large amount of Al3(Sc, Zr particles precipitated at the earlier aging may inhibit recrystallization effectively.

  17. Influence of Carbon Nanofiber Addition on Mechanical Properties and Crystallization Behavior of Polypropylene

    Institute of Scientific and Technical Information of China (English)

    Xin TONG; Yong CHEN; Huiming CHENG

    2005-01-01

    Carbon nanofiber (CNF)-reinforced polypropylene (CNF/PP) composites with different CNF contents were prepared by melt mixing, and the mechanical properties and crystallization behavior of the CNF/PP composites obtained were investigated. It was found that the tensile modulus of the composites was increased with the addition of CNFs, but their elongation at break and fracture strain energy were decreased, while the tensile strength of the composites was firstly increased and then decreased due to the agglomeration of CNFs at higher loading. Nonisothermal crystallization analysis showed that the CNFs played a role as nucleating agent in PP matrix, which led to increment in the crystallization rate and the degree of crystallinity of PP. Moreover, X-ray diffraction studies showed that the CNFs incorporated in the PP matrix favored the growth of (040)-oriented PP crystals. With the increase in the CNF content, the nucleating and orientation roles of the CNFs were obviously enhanced.

  18. Effects of organic additives on microstructure and mechanical properties of porous Si3N4 ceramics

    Indian Academy of Sciences (India)

    Yu Fangli; Wang Huanrui; Yang Jianfeng; Gao Jiqiang

    2010-06-01

    Green bodies of porous Si3N4 ceramics were shaped by extrusion technique using different organic additives as binder during extrusion molding. Different porosity, microstructures and mechanical properties after the extrusion, drying, debinding and sintering stages were investigated. The solid slurry content of 70–75% and extrusion pressure of 0.5–1.0 MPa had played a decisive role in the smooth realization of extrusion molding. The porous Si3N4 ceramics were obtained with excellent properties using 4% hydroxypropyl methyl cellulose (HPMC) as binder and polyethylene glycol (PEG) of molecular weight, 1000, as plasticizer with a density of 1.91 g cm-3, porosity of 41.70%, three-point bending strength of 166.53 ± 20 MPa, fracture toughness of 2.45 ± 0.2 MPa m1/2 and Weibull modulus (m) of 20.75.

  19. Novel Additive Manufacturing Pneumatic Actuators and Mechanisms for Food Handling Grippers

    Directory of Open Access Journals (Sweden)

    Carlos Blanes

    2014-07-01

    Full Text Available Conventional pneumatic grippers are widely used in industrial pick and place robot processes for rigid objects. They are simple, robust and fast, but their design, motion and features are limited, and they do not fulfil the final purpose. Food products have a wide variety of shapes and textures and are susceptible to damaged. Robot grippers for food handling should adapt to this wide range of dimensions and must be fast, cheap, reasonably reliable, and with cheap and reasonable maintenance costs. They should not damage the product and must meet hygienic conditions. The additive manufacturing (AM process is able to manufacture parts without significant restrictions, and is Polyamide approved as food contact material by FDA. This paper presents that, taking the best of plastic flexibility, AM allows the implementation of novel actuators, original compliant mechanisms and practical grippers that are cheap, light, fast, small and easily adaptable to specific food products. However, if they are not carefully designed, the results can present problems, such as permanent deformations, low deformation limits, and low operation speed. We present possible solutions for the use of AM to design proper robot grippers for food handling. Some successful results, such as AM actuators based on deformable air chambers, AM compliant mechanisms, and grippers developed in a single part will be introduced and discussed.

  20. Mechanically tunable aspheric lenses via additive manufacture of hanging elastomeric droplets for microscopic applications

    Science.gov (United States)

    Fuh, Yiin-Kuen; Chen, Pin-Wen; Lai, Zheng-Hong

    2016-07-01

    Mechanically deformable lenses with dynamically tunable focal lengths have been developed in this work. The fabricated five types of aspheric polydimethylsiloxane (PDMS) lenses presented here have an initial focal length of 7.0, 7.8, 9.0, 10.0 and 10.2 mm. Incorporating two modes of operation in biconvex and concave-convex configurations, the focal lengths can be tuned dynamically as 5.2-10.2, 5.5-9.9, 6.6-11.9, 6.1-13.5 and 6.6-13.5 mm respectively. Additive manufacturing was utilized to fabricate these five types of aspheric lenses (APLs) via sequential layering of PDMS materials. Complex structures with three-dimensional features and shorter focal lengths can be successfully produced by repeatedly depositing, inverting and curing controlled PDMS volume onto previously cured PDMS droplets. From our experiments, we empirically found a direct dependence of the focal length of the lenses with the amount (volume) of deposited PDMS droplets. This new mouldless, low-cost, and flexible lens fabrication method is able to transform an ordinary commercial smartphone camera into a low-cost portable microscope. A few microscopic features can be readily visualized, such as wrinkles of ladybird pupa and printed circuit board. The fabrication technique by successively applying hanging droplet and facile mechanical focal-length-tuning set-up can be easily adopted in the development of high-performance optical lenses.

  1. Mechanical Characterization of an Additively Manufactured Inconel 718 Theta-Shaped Specimen

    Science.gov (United States)

    Cakmak, Ercan; Watkins, Thomas R.; Bunn, Jeffrey R.; Cooper, Ryan C.; Cornwell, Paris A.; Wang, Yanli; Sochalski-Kolbus, Lindsay M.; Dehoff, Ryan R.; Babu, Sudarsanam S.

    2016-02-01

    Two sets of "theta"-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlation between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. The spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.

  2. Effect of zirconium addition on the microstructure and mechanical properties of ODS ferritic steels containing aluminum

    Science.gov (United States)

    Gao, R.; Zhang, T.; Wang, X. P.; Fang, Q. F.; Liu, C. S.

    2014-01-01

    The oxide dispersion strengthened (ODS) ferritic steels with nominal composition of Fe-16Cr-2W-0.5Ti-0.4Y2O3-4Al-1Zr (16Cr-4Al-Zr-ODS) were fabricated by a sol-gel method combining with mechanical alloying and spark plasma sintering (SPS) technique, and the 16Cr-ODS and 16Cr-4Al-ODS steels were prepared for comparison in the same way. Microstructure characterization reveals that in the 16Cr-4Al-ODS steel coarse Y-Al-O particles were formed while in the 16Cr-4Al-Zr-ODS steel finer Y-Zr-O particles were formed. The mean size and number density of the nano-oxide particles in the 16Cr-4Al-Zr-ODS steel are about 25 nm and 2.6 × 1021/m3, respectively. The ultimate tensile strength (UTS) of the 16Cr-ODS steel is about 1045 MPa, but UTS of the 16Cr-4Al-ODS steel decreases to 974 MPa. However, UTS of the 16Cr-4Al-Zr-ODS steel increases to 1180 MPa while keeping a large uniform elongation up to 23%, indicating the enhancement of mechanical properties by Zr addition.

  3. The Effect of Structural Design on Mechanical Properties and Cellular Response of Additive Manufactured Titanium Scaffolds

    Directory of Open Access Journals (Sweden)

    Jan Wieding

    2012-08-01

    Full Text Available Restoration of segmental defects in long bones remains a challenging task in orthopedic surgery. Although autologous bone is still the ‘Gold Standard’ because of its high biocompatibility, it has nevertheless been associated with several disadvantages. Consequently, artificial materials, such as calcium phosphate and titanium, have been considered for the treatment of bone defects. In the present study, the mechanical properties of three different scaffold designs were investigated. The scaffolds were made of titanium alloy (Ti6Al4V, fabricated by means of an additive manufacturing process with defined pore geometry and porosities of approximately 70%. Two scaffolds exhibited rectangular struts, orientated in the direction of loading. The struts for the third scaffold were orientated diagonal to the load direction, and featured a circular cross-section. Material properties were calculated from stress-strain relationships under axial compression testing. In vitro cell testing was undertaken with human osteoblasts on scaffolds fabricated using the same manufacturing process. Although the scaffolds exhibited different strut geometry, the mechanical properties of ultimate compressive strength were similar (145–164 MPa and in the range of human cortical bone. Test results for elastic modulus revealed values between 3.7 and 6.7 GPa. In vitro testing demonstrated proliferation and spreading of bone cells on the scaffold surface.

  4. An Investigation on Tribological Properties and Lubrication Mechanism of Graphite Nanoparticles as Vegetable Based Oil Additive

    Directory of Open Access Journals (Sweden)

    Yu Su

    2015-01-01

    Full Text Available This paper used graphite nanoparticles with the diameter of 35 and 80 nm and LB2000 vegetable based oil to prepare graphite oil-based nanofluids with different volume fractions by two-step method. The tribological properties of graphite nanoparticles as LB2000 vegetable based oil additive were investigated with a pin-on-disk friction and wear tester. Field emission scanning electron microscope (FE-SEM and energy dispersive spectroscopy (EDS were used to examine the morphology and the content of some typical elements of wear scar, respectively. Further, the lubrication mechanism of graphite nanoparticles was explored. It was found that graphite nanoparticles as vegetable based oil additive could remarkably improve friction-reducing and antiwear properties of pure oil. With the increase of volume fraction of graphite nanoparticles, the friction coefficient and the wear volume of disk decreased. At the same volume fraction, the smaller particles, the lower friction coefficient and wear volume. The main reason for the improvement in friction-reducing and antiwear properties of vegetable based oil using graphite nanoparticles was that graphite nanoparticles could form a physical deposition film on the friction surfaces.

  5. Thermal degradation mechanism of addition-cure liquid silicone rubber with urea-containing silane

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Weizhen; Zeng, Xingrong, E-mail: psxrzeng@gmail.com; Lai, Xuejun; Li, Hongqiang; Chen, Wanjuan; Zhang, Yajun

    2015-04-10

    Highlights: • The urea-containing silane was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. • The thermal stability of the ALSR was improved by DEUPAS both in nitrogen and air • The TG–FTIR of evolved gases during degradation was performed. • The possible degradation mechanism of the ALSR samples was proposed. - Abstract: The reactive urea-containing silane, (γ-diethylureidopropyl) allyloxyethoxysilane (DEUPAS), was synthesized by the trans-etherification reaction. The chemical structure was characterized by Fourier transform infrared spectrometry (FTIR) and {sup 1}H nuclear magnetic resonance spectrometry ({sup 1}H NMR). Subsequently, DEUPAS was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. The thermal stability of the ALSR samples was investigated by thermogravimetry (TG) and thermogravimetry–Fourier transform infrared spectrometry (TG–FTIR). When DEUPAS was incorporated, the temperature of 10% weight loss and 20% weight loss under air atmosphere were respectively increased by 31 °C and 60 °C compared with those of the ALSR without DEUPAS. Meanwhile, the residual weight at 800 °C increased from 33.5% to 58.7%. It was found that the striking enhancement in thermal stability of the ALSR samples was likely attributed to the decomposition of the urea groups to isocyanic acid, which reacted with hydroxyl groups to inhibit the unzipping depolymerization.

  6. Effects of nitrogen addition on microstructure and mechanical behavior of biomedical Co-Cr-Mo alloys.

    Science.gov (United States)

    Yamanaka, Kenta; Mori, Manami; Chiba, Akihiko

    2014-01-01

    In the present study, the microstructures and tensile deformation behaviors of biomedical Co-29Cr-6Mo (wt%) alloys containing different concentrations of nitrogen (0-0.24wt%) were systematically investigated. As the nitrogen concentration increased, the volume fraction of athermal ε martensite decreased, because nanoprecipitates hindered the formation of stacking faults (SFs) by acting as obstacles to Shockley partial dislocation formation, and athermal ε martensite usually forms through the regular overlapping of SFs. The formation of the athermal ε martensite was completely suppressed when the nitrogen concentration exceeded 0.10wt%, resulting in a simultaneous improvement in the strength and ductility of the alloys. It was found that the glide of the Shockley partial dislocations and the strain-induced γ (fcc)→ε (hcp) martensitic transformation (SIMT) operated as the primary deformation mechanisms. However, adding nitrogen reduced the work hardening by suppressing the formation of the SFs and preventing the SIMT from taking place. This resulted in an intrinsic decrease in the tensile ductility of the alloys. It is also shown that all the alloys exhibited premature fractures owing to the SIMT. The formation of annealing twins in the γ grains is found to be enhanced by nitrogen addition and to promote the SIMT, resulting in a reduction in the elongation-to-failure due to nitrogen addition. These results should aid in the design of alloys that contain nitrogen.

  7. Mussel-inspired reversible metal-coordinate bonds as a pathway towards temporal control over the mechanical hierarchy of soft materials

    Science.gov (United States)

    Grindy, Scott; Learsch, Robert; Holten-Andersen, Niels

    2015-03-01

    Dynamic, reversible crosslinks have been shown to specifically control the mechanical properties of a wide variety of mechanically tough and resilient biomaterials. Here, we show that reversible histidine-metal ion interactions, long thought to contribute to the strong mechanical properties and self-healing nature of mussel byssal threads, can be used to control and engineer the hierarchical mechanical properties of model polyethylene glycol hydrogels orthogonally from the spatial structure of the material. We delve into the physics underlying these types of materials to properly understand how to explicitly engineer the mechanical properties of tough soft materials by utilizing their temporal hierarchy.

  8. ABC transporters as multidrug resistance mechanisms and the development of chemosensitizers for their reversal

    Directory of Open Access Journals (Sweden)

    Choi Cheol-Hee

    2005-10-01

    Full Text Available Abstract One of the major problems related with anticancer chemotherapy is resistance against anticancer drugs. The ATP-binding cassette (ABC transporters are a family of transporter proteins that are responsible for drug resistance and a low bioavailability of drugs by pumping a variety of drugs out cells at the expense of ATP hydrolysis. One strategy for reversal of the resistance of tumor cells expressing ABC transporters is combined use of anticancer drugs with chemosensitizers. In this review, the physiological functions and structures of ABC transporters, and the development of chemosensitizers are described focusing on well-known proteins including P-glycoprotein, multidrug resistance associated protein, and breast cancer resistance protein.

  9. Reaction Mechanisms for the Limited Reversibility of Li-O2 Chemistry in Organic Carbonate Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wu; Xu, Kang; Viswanathan, Vilayanur V.; Towne, Silas A.; Hardy, John S.; Xiao, Jie; Nie, Zimin; Hu, Dehong; Wang, Deyu; Zhang, Jiguang

    2011-11-15

    The Li-O2 chemistry in nonaqueous carbonate electrolytes and the underneath reason of its limited reversibility was exhaustively investigated. The discharge products collected from the air cathode in a Li-O2 battery at different depth of discharge (DOD) were systematically analyzed with X-ray diffraction. It is revealed that, independent of the discharge depth, lithium alkylcarbonate (either lithium propylenedicarbonate - LPDC, or lithium ethylenedicarbonate - LEDC, with other related derivatives) and lithium carbonate (Li2CO3) are always the main products, obviously originated from the electrolyte solvents propylene carbonate (PC) and ethylene carbonate (EC). These lithium alkylcarbonates are obviously generated from the single-electron reductive decomposition of the corresponding carbonate solvents initiated by the attack of superoxide radical anions. On the other hand, neither lithium peroxide (Li2O2) nor lithium oxide (Li2O) is detected. More significantly, from in situ gas chromatography/mass spectroscopy it is found that Li2CO3 and Li2O cannot be oxidized even when charged up to 4.6 V vs. Li/Li+, while LPDC, LEDC and Li2O2 are readily able to, with CO2 and CO released with the re-oxidation of LPDC and LEDC. It is therefore concluded that the quasi-reversibility of Li-O2 chemistry observed hitherto in an organic carbonate-based electrolyte is actually reliant on the formation of lithium alkylcarbonates through the reductive decomposition of carbonate solvents during discharge process and the subsequent oxidation of these same alkylcarbonates during charge process. It is the poor oxidizability of these alkylcarbonate species that constitutes the obstruction to an ideal rechargeable Li-O2 battery.

  10. An Integrated Theory of Adsorption and Partition Mechanism and Eash Contribution to Solute Retention in Reversed Phase Liquid Chromatography

    Institute of Scientific and Technical Information of China (English)

    耿信笃; 弗莱德依瑞格涅尔

    2003-01-01

    With the combination of the the stoichiometric displacement model for retention (SDM-R) in reversed phase liquid chromatography (RPLC) and the stoichiometric displacement model for adsorption (SDM-A) in physical chemistry,the total number of moles of the re-solvated methanol of stationary phase side.nr,and that of solute side in the mobile phase,q,corresponding the one mole of the desorbing solute,were separately determined and referred as the characterization parameters of the contributions of the adsorption mechanism and partition mechanism to the solute retention,respectively.A chromatographic system of insulin,using mobile phase consisting of the pseudo-homologue of alcohols(methanol,ethanol and 2-propanol)-water and trifluoroacetic acid was employed.The maximum number of the methanol layers on the stationary phase surface was found to be 10.6,only 3 of which being valid in usual RPLC,traditionally referred as a volume process in partition mechanism.However,it still follows the SDM-R.Both of q and nr of insulin were found not to be zero,indicating that the retention mechanism of insulin is a mixed mode of partition mechanism and adsorption mechanism.When methanol is used as the organic modifier,the ratio of q/nr was 1.13,indicating the contribution to insulin retention due to partition mechanism being a bit greater than that due to adsorption mechanism.A linear relationship between q,or nr and the carbon number of the pseudo-homologue in the mobile phase was also found.As a methodology for investigating the retention mechanism retention and behavior of biopolymers.a homologue of organic solvents as the organic modifier in mobile phase has also been explored.

  11. Martensite phase reversion-induced nano/ ultrafine grained AISI 304L stainless steel with magnificent mechanical properties

    Directory of Open Access Journals (Sweden)

    Mohammad Shirdel

    2015-06-01

    Full Text Available Austenitic stainless steels are extensively used in various applications requiring good corrosion resistance and formability. In the current study, the formation of nano/ ultrafine grained austenitic microstructure in a microalloyed AISI 304L stainless steel was investigated by the advanced thermomechanical process of reversion of strain-induced martensite. For this purpose, samples were subjected to heavy cold rolling to produce a nearly complete martensitic structure. Subsequently, a wide range of annealing temperatures (600 to 800°C and times (1 to 240 min were employed to assess the reversion behavior and to find the best annealing condition for the production of the nano/ultrafine grained austenitic microstructure. Microstructural characterizations have been performed using X-ray diffraction (XRD, scanning electron microscopy (SEM, and magnetic measurement, whereas the mechanical properties were assessed by tensile and hardness tests. After thermomechanical treatment, a very fine austenitic structure was obtained, which was composed of nano sized grains of ~ 85 nm in an ultrafine grained matrix with an average grain size of 480 nm. This microstructure exhibited superior mechanical properties: high tensile strength of about 1280 MPa with a desirable elongation of about 41%, which can pave the way for the application of these sheets in the automotive industry.

  12. Additive manufacturing of Inconel 718 using electron beam melting: Processing, post-processing, & mechanical properties

    Science.gov (United States)

    Sames, William James, V.

    Additive Manufacturing (AM) process parameters were studied for production of the high temperature alloy Inconel 718 using Electron Beam Melting (EBM) to better understand the relationship between processing, microstructure, and mechanical properties. Processing parameters were analyzed for impact on process time, process temperature, and the amount of applied energy. The applied electron beam energy was shown to be integral to the formation of swelling defects. Standard features in the microstructure were identified, including previously unidentified solidification features such as shrinkage porosity and non-equilibrium phases. The as-solidified structure does not persist in the bulk of EBM parts due to a high process hold temperature (˜1000°C), which causes in situ homogenization. The most significant variability in as-fabricated microstructure is the formation of intragranular delta-phase needles, which can form in samples produced with lower process temperatures (Inconel 718. Traditional post-processing methods of hot isostatic pressing (HIP) and solution treatment and aging (STA) were found to result in variability in grain growth and phase solution. Recrystallization and grain structure are identified as possible mechanisms to promote grain growth. These results led to the conclusion that the first step in thermal post-processing of EBM Inconel 718 should be an optimized solution treatment to reset phase variation in the as-fabricated microstructure without incurring significant grain growth. Such an optimized solution treatment was developed (1120°C, 2hr) for application prior to aging or HIP. The majority of as-fabricated tensile properties met ASTM AM Inconel 718 standards for yield stress and ultimate tensile strength, and STA yield stress, ultimate tensile strength, and elongation exceeded the ASTM standards for AM Inconel 718.

  13. Achieving reversibility of ultra-high mechanical stress by hydrogen loading of thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hamm, M.; Burlaka, V.; Wagner, S.; Pundt, A., E-mail: apundt@ump.gwdg.de [Institut of Materials Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany)

    2015-06-15

    Nano-materials are commonly stabilized by supports to maintain their desired shape and size. When these nano-materials take up interstitial atoms, this attachment to the support induces mechanical stresses. These stresses can be high when the support is rigid. High stress in the nano-material is typically released by delamination from the support or by the generation of defects, e.g., dislocations. As high mechanical stress can be beneficial for tuning the nano-materials properties, it is of general interest to deduce how real high mechanical stress can be gained. Here, we show that below a threshold nano-material size, dislocation formation can be completely suppressed and, when delamination is inhibited, even the ultrahigh stress values of the linear elastic limit can be reached. Specifically, for hydrogen solved in epitaxial niobium films on sapphire substrate supports a threshold film thickness of 6 nm was found and mechanical stress of up to (−10 ± 1) GPa was reached. This finding is of basic interest for hydrogen energy applications, as the hydride stability in metals itself is affected by mechanical stress. Thus, tuning of the mechanical stress-state in nano-materials may lead to improved storage properties of nano-sized materials.

  14. Effect of sulfur aggregates on mechanical resistance and durability for SFRHPC with the addition of slag

    Directory of Open Access Journals (Sweden)

    Boutiba Aldjia

    2014-04-01

    Full Text Available The transformation of sulfides present in the aggregate to sulfates causes internal sulfate attack (ISA by formation of secondary ettringite in the hardened concrete. This pathological ettringite crystallizes, the generated pressure is greater than the tensile strength of the concrete. It generates internal swelling and causes disorders that can severely damage the structures. Favors to their structural and economic performance, high performance concrete steel fiber (SFRHPC are increasingly used in construction. Increase productivity and reduce construction time on site. They provide substantial weight savings, therefore it is possible to build with less formwork, less concrete to set up and fewer reinforcement than ordinary concrete. The purpose of this study is to determine the effect of sulfur present in the hornfels crushed aggregates, on the mechanical strength, durability, and the microstructure of SFRHPC with the addition of blast furnace slag. In ordinary concrete, the pyrite aggregates cause cracking by expansion when they are in wet land. In high performance concretes this phenomenon is greatly reduced or absent. This is the result of a very low porosity, reduced flow of moisture that cannot propagate to aggregate. And sulfide is stable and cannot be transformed into aggressive sulfate.

  15. Effect of Ag and Pb Addition on Microstructural and Mechanical Properties of SAC 105 Solders

    Science.gov (United States)

    Molnar, Aliz; Janovszky, Dora; Kardos, Ibolya; Molnar, Istvan; Gacsi, Zoltan

    2015-10-01

    Melting and crystallization processes of lead-free and lead-contaminated alloys in near-equilibrium state were investigated. In addition, the effect of silver content up to 4 wt.% on the microstructure of Sn-Ag-Cu alloys was studied. The volume fraction of β-Sn decreased by half owing to 4 wt.% Ag content. Furthermore, contamination by lead strongly influences the properties of the solidified microstructure. The Pb grains appear as a result of two processes when the Pb content is equal to 0.5 wt.% or higher: Pb phase solidifies in the quaternary eutectic at 176°C, and Pb grains precipitate from the primary β-Sn solid solution grain during a solid state reaction. The freezing range enlarges to 51°C due to 2 wt.% Pb content owing to quaternary eutectic. Above 1 wt.% Pb content, the mechanical properties also improve due to grains of quaternary eutectic Pb and precipitated Pb grains with a size <1 μm.

  16. Additional funding mechanisms for Public Hospitals in Greece: the case of Chania Mental Health Hospital

    Science.gov (United States)

    2010-01-01

    Objectives To investigate whether the long term lease of public hospital owned land could be an additional financing mechanism for Greek public (mental) health hospitals. Methods We performed a financial analysis of the official 2008 data of a case - study hospital (Mental Health Hospital of Chania). We used a capital budgeting approach to investigate whether value is created for the public hospital by engaging its assets in a project for the development of a private renal dialysis Unit. Results The development of the private unit in hospital owned land is a good investment decision, as it generates high project Net Present Value and Internal Rate of Return. When the project commences generating operating cash flows, nearly €400.000 will be paid annually to the Mental Health Hospital of Chania as rent, thereby gradually decreasing the annual deficit of the hospital. Conclusions Revenue generated from the long term lease of public hospital land is crucial to gradually eliminate hospital deficit. The Ministry of Health should encourage similar forms of Public Private Partnerships in order to ensure the sustainability of public (mental) hospitals. PMID:21067580

  17. Mechanical properties of SiB6 addition of carbon sintered body

    Science.gov (United States)

    Tanaka, Samon; Fukushima, Noriyuki; Matsushita, Jun-ichi; Akatsu, T.; Niihara, K.; Yasuda, E.

    2001-04-01

    Boride material is said as the useful material, which has high melting point and high strength. B4C in carbide is very hard at the next of the diamond and cubic-BN in the Mohs hardness and B4C has excellent chemical stability and high strength. B4C is being used as the polishing material from the hardness. However, it is difficult to make sintered body from high melting point (2623 K). Several silicon boride phases such as SiB4, SiB6, SiB6-x, SiB6+x, and Si11B31, were previously reported. Silicon hexaboride (SiB6) has proved to be a potentially useful material because of its high degree of hardness, moderate melting point (2123 K), and low specific gravity. We studied the preparation of SiB6-B4C-SiC sintered body in this report. We knew experientially that SiB6 reacts with carbon at the high temperature, and forms B4C or SiC. Carbon addition SiB6 sintered body produced by hot pressing and reaction sintering that sintering condition was 1973 K for 3.6 ks in vacuum under a pressure of 25 MPa. The relative density of sintered bodies (SiB6-0,5,10,15 wt%C) was approximately 100%. Characterization of mechanical properties was used indentation, Vickers hardness and thermal

  18. Additional funding mechanisms for Public Hospitals in Greece: the case of Chania Mental Health Hospital

    Directory of Open Access Journals (Sweden)

    Golna Christina

    2010-11-01

    Full Text Available Abstract Objectives To investigate whether the long term lease of public hospital owned land could be an additional financing mechanism for Greek public (mental health hospitals. Methods We performed a financial analysis of the official 2008 data of a case - study hospital (Mental Health Hospital of Chania. We used a capital budgeting approach to investigate whether value is created for the public hospital by engaging its assets in a project for the development of a private renal dialysis Unit. Results The development of the private unit in hospital owned land is a good investment decision, as it generates high project Net Present Value and Internal Rate of Return. When the project commences generating operating cash flows, nearly €400.000 will be paid annually to the Mental Health Hospital of Chania as rent, thereby gradually decreasing the annual deficit of the hospital. Conclusions Revenue generated from the long term lease of public hospital land is crucial to gradually eliminate hospital deficit. The Ministry of Health should encourage similar forms of Public Private Partnerships in order to ensure the sustainability of public (mental hospitals.

  19. Interaction of α-Hexylcinnamaldehyde with a Biomembrane Model: A Possible MDR Reversal Mechanism.

    Science.gov (United States)

    Sarpietro, Maria Grazia; Di Sotto, Antonella; Accolla, Maria Lorena; Castelli, Francesco

    2015-05-22

    The ability of the naturally derived compound α-hexylcinnamaldehyde (1) to interact with biomembranes and to modulate their permeability has been investigated as a strategy to reverse multidrug resistance (MDR) in cancer cells. Dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles (MLVs) were used as biomembrane models, and differential scanning calorimetry was applied to measure the effect of 1 on the thermotropic behavior of DMPC MLVs. The effect of an aqueous medium or a lipid carrier on the uptake of 1 by the biomembrane was also characterized. Furthermore, taking into account that MDR is strictly regulated by redox signaling, the pro-oxidant and/or antioxidant effects of 1 were evaluated by the crocin-bleaching assay, in both hydrophilic and lipophilic environments. Compound 1 was uniformly distributed in the phospholipid bilayers and deeply interacted with DMPC MLVs, intercalating among the phospholipid acyl chains and thus decreasing their cooperativity. The lipophilic medium allowed the absorption of 1 into the phospholipid membrane. In the crocin-bleaching assay, the substance produced no pro-oxidant effects in both hydrophilic and lipophilic environments; conversely, a significant inhibition of AAPH-induced oxidation was exerted in hydrophilic medium. These results suggest a possible role of 1 as a chemopreventive and chemosensitizing agent for fighting cancer.

  20. Pyrimethamine-induced alterations in human lymphocytes in vitro. Mechanisms and reversal of the effect

    DEFF Research Database (Denmark)

    Bygbjerg, Ib Christian

    1985-01-01

    . The effects of PYR were completely corrected by low concentrations of folinic acid and high concentrations of folic acid, indicating that the basic mechanism of action of PYR is competitive blocking of dihydrofolate reductase. However, the effect of PYR was poorly corrected by exogenous thymidine; therefore...

  1. Agmatine reversed mechanical allodynia in a rat model of neuropathic pain

    Institute of Scientific and Technical Information of China (English)

    YANGHong-Ju; ZhAONan; GONGZheng-Hua; YUANWei-Xiou; LIYunFeng; LI-Jin; LUOZhi-Pu

    2004-01-01

    AIM: Agmatine is an endogenous neuromodulator present in the brain and spinal cord, agmatine has both NMDA receptor antagonist and NOS inhibitor activities, which may participate the pathological process in the neuropathic pain. The effect of agmatine on the mechanical allodynia in a rat model of the neuropathic pain was investigated in this experiment.

  2. Formation and adaptation of memory : Neurobiological mechanisms underlying learning and reversal learning

    NARCIS (Netherlands)

    Havekes, Robbert

    2008-01-01

    The hippocampus is a brain region that plays a critical role in memory formation. In addition, it has been suggested that this brain region is important for ‘updating’ information that is incorrect or outdated. The main goal of this thesis project was to investigate which neurobiological processes u

  3. Effect of Hypoeutectic Boron Additions on the Grain Size and Mechanical Properties of Ti-6Al-4V Manufactured with Powder Bed Electron Beam Additive Manufacturing

    Science.gov (United States)

    Mahbooba, Zaynab; West, Harvey; Harrysson, Ola; Wojcieszynski, Andrzej; Dehoff, Ryan; Nandwana, Peeyush; Horn, Timothy

    2017-03-01

    In additive manufacturing, microstructural control is feasible via processing parameter alteration. However, the window for parameter variation for certain materials, such as Ti-6Al-4V, is limited, and alternative methods must be employed to customize microstructures. Grain refinement and homogenization in cast titanium alloys has been demonstrated through the addition of hypoeutectic concentrations of boron. This work explores the influence of 0.00 wt.%, 0.25 wt.%, 0.50 wt.%, and 1.0 wt.% boron additions on the microstructure and bulk mechanical properties of Ti-6Al-4V samples fabricated in an Arcam A2 electron beam melting (EBM) system with commercial processing parameters for Ti-6Al-4V. Analyses of EBM fabricated Ti-6Al-4V + B indicate that the addition of 0.25-1.0 wt.% boron progressively refines the grain structure, and it improves hardness and elastic modulus. Despite a reduction in size, the β grain structure remained columnar as a result of directional heat transfer during EBM fabrication.

  4. Effect of Hypoeutectic Boron Additions on the Grain Size and Mechanical Properties of Ti-6Al-4V Manufactured with Powder Bed Electron Beam Additive Manufacturing

    Science.gov (United States)

    Mahbooba, Zaynab; West, Harvey; Harrysson, Ola; Wojcieszynski, Andrzej; Dehoff, Ryan; Nandwana, Peeyush; Horn, Timothy

    2016-12-01

    In additive manufacturing, microstructural control is feasible via processing parameter alteration. However, the window for parameter variation for certain materials, such as Ti-6Al-4V, is limited, and alternative methods must be employed to customize microstructures. Grain refinement and homogenization in cast titanium alloys has been demonstrated through the addition of hypoeutectic concentrations of boron. This work explores the influence of 0.00 wt.%, 0.25 wt.%, 0.50 wt.%, and 1.0 wt.% boron additions on the microstructure and bulk mechanical properties of Ti-6Al-4V samples fabricated in an Arcam A2 electron beam melting (EBM) system with commercial processing parameters for Ti-6Al-4V. Analyses of EBM fabricated Ti-6Al-4V + B indicate that the addition of 0.25-1.0 wt.% boron progressively refines the grain structure, and it improves hardness and elastic modulus. Despite a reduction in size, the β grain structure remained columnar as a result of directional heat transfer during EBM fabrication.

  5. Microstructure and Mechanical Properties of WE43 Alloy Produced Via Additive Friction Stir Technology

    OpenAIRE

    Calvert, Jacob Rollie

    2015-01-01

    In an effort to save weight, transportation and aerospace industries have increasing investigated magnesium alloys because of their high strength-to-weight ratio. Further efforts to save on material use and machining time have focused on the use of additive manufacturing. However, anisotropic properties can be caused by both the HCP structure of magnesium alloys as well as by layered effects left by typical additive manufacturing processes. Additive Friction Stir (AFS) is a relatively new add...

  6. Effect of cerium/lanthanum addition on microstructure and mechanical properties of Al7075 alloyvia mechanical alloying and sintering

    Institute of Scientific and Technical Information of China (English)

    R Prez-Bustamante; A Reyna-Cruz; D C Acosta-Pea; C R Santilln-Rodrguez; J A Matutes-Aquino; F Prez-Bustamante; M C Maldonado-Orozco; J Aguilar-Santilln; R Martnez-Snchez

    2016-01-01

    The effect of the Al-6Ce-3La (ACL) on the microstructural behavior of the Al7075 was investigated. Materials were syn-thesized by mechanical alloying with variation in the ACL content and milling time. Products were characterized and studied in the as-milled condition and mechanically evaluated after sintering. The synergetic effect of milling time and ACL content in the modified materials led to a reduction in the particle size. Results from electron microscopy showed a homogeneous dispersion of Ce/La phases up to 20 wt.% of ACL content after 10 h of milling. Mechanical evaluation under compressive test showed an improved performance for those alloys reinforced with 0.2 wt.% and 0.5 wt.% of ACL.

  7. Structural mechanism of reverse α → γ transformation and strengthening of Fe-Ni alloys

    Science.gov (United States)

    Sagaradze, V. V.; Kataeva, N. V.; Kabanova, I. G.; Zavalishin, V. A.; Valiullin, A. I.; Klyukina, M. F.

    2014-07-01

    Fe-32% Ni alloy subjected to slow heating to a temperature below A s at a rate of 0.01 K/min demonstrates the untwinning and appearance of an intermediate ɛ phase with an hcp lattice and lattice parameters a = 2.535, c = 4.132 Å, and c/a = 1.63. Slow heating to 430-490°C leads to the formation of nanocrystalline austenite enriched in nickel, which substantially increases the hardness of martensite. The formation of austenite in the Fe-32% Ni alloy, which is a mixture of martensite with 20-30% nanocrystalline austenite, during its rapid heating to 600°C occurs via the bulk mechanism with short-range atomic diffusion. In this case, the diffusion does not eliminate the concentration micro-inhomogeneity of the alloy in nickel but leads to the reorientation of γ-phase nanocrystals, almost eliminates the dislocation structure, and removes the strengthening by phase hardening.

  8. PVC mixtures’ mechanical properties with the addition of modified calcite as filler

    OpenAIRE

    Vučinić Dušica R.; Jovanović Vladimir D.; Kolonja Božo M.; Sekulić Živko T.; Mihajlović Slavica R.

    2012-01-01

    In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler) such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaki...

  9. Mechanical properties of polyvinyl chloride mixtures with the addition of modified calcite as filler

    OpenAIRE

    Mihajlović, Slavica R.; Sekulić, Živko T.; Vučinić, Dušica R.; Jovanović, Vladimir D.; Kolonja, Božo M.

    2012-01-01

    In this study, mechanical properties of PVC mixtures (PVC, stabilizer, lubricant and filler) such as tensile strength, tensile elongation, breaking strength and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure had better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking s...

  10. Effect of Flyash Addition on Mechanical and Gamma Radiation Shielding Properties of Concrete

    Directory of Open Access Journals (Sweden)

    Kanwaldeep Singh

    2014-01-01

    Full Text Available Six concrete mixtures were prepared with 0%, 20%, 30%, 40%, 50%, and 60% of flyash replacing the cement content and having constant water to cement ratio. The testing specimens were casted and their mechanical parameters were tested experimentally in accordance with the Indian standards. Results of mechanical parameters show their improvement with age of the specimens and results of radiation parameters show no significant effect of flyash substitution on mass attenuation coefficient.

  11. The value of the MDR1 reversal agent PSC-833 in addition to daunorubicin and cytarabine in the treatment of elderly patients with previously untreated acute myeloid leukemia (AML), in relation to MDR1 status at diagnosis.

    Science.gov (United States)

    van der Holt, Bronno; Löwenberg, Bob; Burnett, Alan K; Knauf, Wolfgang U; Shepherd, John; Piccaluga, Pier Paolo; Ossenkoppele, Gert J; Verhoef, Gregor E G; Ferrant, Augustin; Crump, Michael; Selleslag, Dominik; Theobald, Matthias; Fey, Martin F; Vellenga, Edo; Dugan, Margaret; Sonneveld, Pieter

    2005-10-15

    To determine whether MDR1 reversal by the addition of the P-glycoprotein (P-gp) inhibitor PSC-833 to standard induction chemotherapy would improve event-free survival (EFS), 419 untreated patients with acute myeloid leukemia (AML) aged 60 years and older were randomized to receive 2 induction cycles of daunorubicin and cytarabine with or without PSC-833. Patients in complete remission were then given 1 consolidation cycle without PSC-833. Neither complete response (CR) rate (54% versus 48%; P = .22), 5-year EFS (7% versus 8%; P = .53), disease-free survival (DFS; 13% versus 17%; P = .06) nor overall survival (OS; 10% in both arms; P = .52) were significantly improved in the PSC-833 arm. An integrated P-gp score (IPS) was determined based on P-gp function and P-gp expression in AML cells obtained prior to treatment. A higher IPS was associated with a significantly lower CR rate and worse EFS and OS. There was no significant interaction between IPS and treatment arm with respect to CR rate and survival, indicating also a lack of benefit of PSC-833 in P-gp-positive patients. The role of strategies aimed at inhibitory P-gp and other drug-resistance mechanisms continues to be defined in the treatment of patients with AML.

  12. Diminished swelling of cross-linked aromatic oligoamide surfaces revealing a new fouling mechanism of reverse-osmosis membranes.

    Science.gov (United States)

    Ying, Wang; Kumar, Rajender; Herzberg, Moshe; Kasher, Roni

    2015-06-02

    Swelling of the active layer of reverse osmosis (RO) membranes has an important effect on permeate water flux. The effects of organic- and biofouling on the swelling of the RO membrane active layer and the consequent changes of permeate flux are examined here. A cross-linked aromatic oligoamide film that mimics the surface chemistry of an RO polyamide membrane was synthesized stepwise on gold-coated surfaces. Foulant adsorption to the oligoamide film and its swelling were measured with a quartz crystal microbalance, and the effects of fouling on the membrane's performance were evaluated. The foulants were extracellular polymeric substances (EPS) extracted from fouled RO membranes and organic compounds of ultrafiltration permeate (UFP) from a membrane bioreactor used to treat municipal wastewater. The adsorbed foulants affected the swelling of the cross-linked oligoamide film differently. EPS had little effect on the swelling of the oligoamide film, whereas UFP significantly impaired swelling. Permeate flux declined more rapidly under UFP fouling than it did under EPS. Foulant adsorption was shown to diminish swelling of the aromatic oligoamide surfaces. Among the already known RO membrane fouling mechanisms, a novel RO fouling mechanism is proposed, in which foulant-membrane interactions hinder membrane swelling and thus increase hydraulic resistance.

  13. A tumor-promoting mechanism mediated by retrotransposon-encoded reverse transcriptase is active in human transformed cell lines

    Science.gov (United States)

    Sciamanna, Ilaria; Gualtieri, Alberto; Cossetti, Cristina; Osimo, Emanuele Felice; Ferracin, Manuela; Macchia, Gianfranco; Aricò, Eleonora; Prosseda, Gianni; Vitullo, Patrizia; Misteli, Tom; Spadafora, Corrado

    2013-01-01

    LINE-1 elements make up the most abundant retrotransposon family in the human genome. Full-length LINE-1 elements encode a reverse transcriptase (RT) activity required for their own retrotranpsosition as well as that of non-autonomous Alu elements. LINE-1 are poorly expressed in normal cells and abundantly in cancer cells. Decreasing RT activity in cancer cells, by either LINE-1-specific RNA interference, or by RT inhibitory drugs, was previously found to reduce proliferation and promote differentiation and to antagonize tumor growth in animal models. Here we have investigated how RT exerts these global regulatory functions. We report that the RT inhibitor efavirenz (EFV) selectively downregulates proliferation of transformed cell lines, while exerting only mild effects on non-transformed cells; this differential sensitivity matches a differential RT abundance, which is high in the former and undetectable in the latter. Using CsCl density gradients, we selectively identify Alu and LINE-1 containing DNA:RNA hybrid molecules in cancer but not in normal cells. Remarkably, hybrid molecules fail to form in tumor cells treated with EFV under the same conditions that repress proliferation and induce the reprogramming of expression profiles of coding genes, microRNAs (miRNAs) and ultraconserved regions (UCRs). The RT-sensitive miRNAs and UCRs are significantly associated with Alu sequences. The results suggest that LINE-1-encoded RT governs the balance between single-stranded and double-stranded RNA production. In cancer cells the abundant RT reverse-transcribes retroelement-derived mRNAs forming RNA:DNA hybrids. We propose that this impairs the formation of double-stranded RNAs and the ensuing production of small regulatory RNAs, with a direct impact on gene expression. RT inhibition restores the ‘normal’ small RNA profile and the regulatory networks that depend on them. Thus, the retrotransposon-encoded RT drives a previously unrecognized mechanism crucial to the

  14. Facile Preparation and Formation Mechanism of Uniform Silver Nanoparticles Using OP-10 as Emulsifier in Reverse Microemulsion

    Institute of Scientific and Technical Information of China (English)

    WU Xia; WANG Ting; WU Hui

    2011-01-01

    Using the polymerizable hydrophobic styrene monomer as the dispersion medium and the traditional nonionic surfactant OP-10 as emulsifier, stable silver nanoparticles of narrow size distribution were prepared by a reverse (w/o) microemulsion method. The powder X-ray diffraction (XRD) pattern indicated that the obtained silver nanoparticles were of face-centered cubic structure.The results of the transmission electron microscopy (TEM) show that the final silver nanoparticles are of spherical structure with an average diameter of 15.2 nm and ofa Gaussian distribution. The internal high-ordered structure of silver nanoparticles was characterized by the field-emission high-resolution transmission electron microscopy (FEHRTEM), indicating that the silver is monocrystalline and it has only one nucleation site during the formation process of a nanoparticle. The time-resolved UV-visible absorption spectra was used to monitor the process of the reaction in situ. The results show that the concentration of silver nanoparticles increases but the size changes little and the morphology transforms from obvious ellipsoidal shape to nearly spherical shape during the process. The experimental results indicate that the droplets' dynamic exchange which is closely related to the nature of surfactant film is the control factor of the kinetics. The dynamic exchange mechanism of silver nanoparticle formation is proposed to involve continual encounter of two separate droplets forming transient fused dimer in which the chemical reaction occurs followed by re-separation without combination. Attributed to the dual role of surfactant in the nanoparticle formation, tailored nanoparticles can be successfully synthesized in control in the premise of a certain stability of reverse microemulsion.

  15. A tumor-promoting mechanism mediated by retrotransposon-encoded reverse transcriptase is active in human transformed cell lines.

    Science.gov (United States)

    Sciamanna, Ilaria; Gualtieri, Alberto; Cossetti, Cristina; Osimo, Emanuele Felice; Ferracin, Manuela; Macchia, Gianfranco; Aricò, Eleonora; Prosseda, Gianni; Vitullo, Patrizia; Misteli, Tom; Spadafora, Corrado

    2013-12-01

    LINE-1 elements make up the most abundant retrotransposon family in the human genome. Full-length LINE-1 elements encode a reverse transcriptase (RT) activity required for their own retrotranpsosition as well as that of non-autonomous Alu elements. LINE-1 are poorly expressed in normal cells and abundantly in cancer cells. Decreasing RT activity in cancer cells, by either LINE-1-specific RNA interference, or by RT inhibitory drugs, was previously found to reduce proliferation and promote differentiation and to antagonize tumor growth in animal models. Here we have investigated how RT exerts these global regulatory functions. We report that the RT inhibitor efavirenz (EFV) selectively downregulates proliferation of transformed cell lines, while exerting only mild effects on non-transformed cells; this differential sensitivity matches a differential RT abundance, which is high in the former and undetectable in the latter. Using CsCl density gradients, we selectively identify Alu and LINE-1 containing DNA:RNA hybrid molecules in cancer but not in normal cells. Remarkably, hybrid molecules fail to form in tumor cells treated with EFV under the same conditions that repress proliferation and induce the reprogramming of expression profiles of coding genes, microRNAs (miRNAs) and ultraconserved regions (UCRs). The RT-sensitive miRNAs and UCRs are significantly associated with Alu sequences. The results suggest that LINE-1-encoded RT governs the balance between single-stranded and double-stranded RNA production. In cancer cells the abundant RT reverse-transcribes retroelement-derived mRNAs forming RNA:DNA hybrids. We propose that this impairs the formation of double-stranded RNAs and the ensuing production of small regulatory RNAs, with a direct impact on gene expression. RT inhibition restores the 'normal' small RNA profile and the regulatory networks that depend on them. Thus, the retrotransposon-encoded RT drives a previously unrecognized mechanism crucial to the

  16. HIV-1 Reverse Transcriptase Still Remains a New Drug Target: Structure, Function, Classical Inhibitors, and New Inhibitors with Innovative Mechanisms of Actions

    Directory of Open Access Journals (Sweden)

    Francesca Esposito

    2012-01-01

    Full Text Available During the retrotranscription process, characteristic of all retroviruses, the viral ssRNA genome is converted into integration-competent dsDNA. This process is accomplished by the virus-coded reverse transcriptase (RT protein, which is a primary target in the current treatments for HIV-1 infection. In particular, in the approved therapeutic regimens two classes of drugs target RT, namely, nucleoside RT inhibitors (NRTIs and nonnucleoside RT inhibitors (NNRTIs. Both classes inhibit the RT-associated polymerase activity: the NRTIs compete with the natural dNTP substrate and act as chain terminators, while the NNRTIs bind to an allosteric pocket and inhibit polymerization noncompetitively. In addition to these two classes, other RT inhibitors (RTIs that target RT by distinct mechanisms have been identified and are currently under development. These include translocation-defective RTIs, delayed chain terminators RTIs, lethal mutagenesis RTIs, dinucleotide tetraphosphates, nucleotide-competing RTIs, pyrophosphate analogs, RT-associated RNase H function inhibitors, and dual activities inhibitors. This paper describes the HIV-1 RT function and molecular structure, illustrates the currently approved RTIs, and focuses on the mechanisms of action of the newer classes of RTIs.

  17. Mechanical properties of PLA/PCL blends crosslinked by electron beam and TAIC additive

    Science.gov (United States)

    Malinowski, Rafał

    2016-10-01

    Investigation of the effect of electron radiation on selected mechanical properties of polylactide/polycaprolactone blends containing triallyl isocyanurate was the objective of the present paper. It was found that triallyl isocyanurate is an effective agent that hinders phase separation and links macromolecules of both the same and the different polymers. As a consequence of this, strength and modulus of elasticity of studied blends rise, while elongation at break as well as impact strength decrease. Moreover, some mechanical properties of crosslinked polylactide/polycaprolactone blends may also result from the partial degradation of polylactide phase after irradiation.

  18. Upgrading offshore pipelines concrete coated by silica fume additive against aggressive mechanical laying

    Directory of Open Access Journals (Sweden)

    M.I. Abdou

    2016-06-01

    Full Text Available Studies have been carried out to investigate the possibility of utilizing a broad range of micro-silica partial additions with cement in the production of concrete coating. This study investigated the strength properties and permeability of micro-silica concrete to achieve resistance toward concrete cracking and damage during laying. The chemical composition of micro-silica (silica fume was determined, and has been conducted on concrete mixes with additions of 3 up to 25% by weight of cement in concrete. Properties of hardened concrete such as compressive strength, flexural strength, and permeability have been assessed and analyzed. Cubic specimens and beams were produced and cured in a curing tank for 7 and 28 days. Testing results have shown that additions of silica fume to cement between 5% and 7%, which acts as a filler and cementations material, developed high flexural and compressive strength with reduction of permeability.

  19. Mechanism of unusual polymorph transformations in calcium carbonate: Dissolution-recrystallization vs additive-mediated nucleation

    Indian Academy of Sciences (India)

    Arpita Sarkar; Samiran Mahapatra

    2012-11-01

    Unusual transformation of one CaCO3 phase to another has been reported by the process of dissolution-recrystallization and under the influence of additive. In one case, while metastable vaterite transforms to another metastable phase aragonite by simple refluxing in distilled water, it instead transforms thermodynamically stable phase calcite upon refluxing in its `mother-liquor’. This is explained by the process of dissolution-recrystallization. In another case, aragonite is preferentially synthesized over calcite in the presence of molten lauric acid as an additive.

  20. Effect of Particle Size of Additives on the Flammability and Mechanical Properties of Intumescent Flame Retarded Polypropylene Compounds

    Directory of Open Access Journals (Sweden)

    Katalin Bocz

    2015-01-01

    Full Text Available The effect of particle size reduction of the components of a common intumescent flame retardant system, consisting of pentaerythritol (PER and ammonium polyphosphate (APP in a weight ratio of 1 to 2, was investigated on the flammability and mechanical performance of flame retarded polypropylene (PP compounds. Additives of reduced particle size were obtained by ball milling. In the case of PER, the significant reduction of particle size resulted in inferior flame retardant and mechanical performance, while the systems containing milled APP noticeably outperformed the reference intumescent system containing as-received additives. The beneficial effect of the particle size reduction of APP is explained by the better distribution of the particles in the polymer matrix and by the modified degradation mechanism which results in the formation of an effectively protecting carbonaceous foam accompanied with improved mechanical resistance. Nevertheless, 10% higher tensile strength was measured for the flame retarded PP compound when as-received APP was substituted by milled APP.

  1. Antiwear performance and mechanism of an oil-miscible ionic liquid as a lubricant additive.

    Science.gov (United States)

    Qu, Jun; Bansal, Dinesh G; Yu, Bo; Howe, Jane Y; Luo, Huimin; Dai, Sheng; Li, Huaqing; Blau, Peter J; Bunting, Bruce G; Mordukhovich, Gregory; Smolenski, Donald J

    2012-02-01

    An ionic liquid (IL) trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate has been investigated as a potential antiwear lubricant additive. Unlike most other ILs that have very low solubility in nonpolar fluids, this IL is fully miscible with various hydrocarbon oils. In addition, it is thermally stable up to 347 °C, showed no corrosive attack to cast iron in an ambient environment, and has excellent wettability on solid surfaces (e.g., contact angle on cast iron lubricating oils. For example, a 5 wt % addition into a synthetic base oil eliminated the scuffing failure experienced in neat oil and, as a result, reduced the friction coefficient by 60% and the wear rate by 3 orders of magnitude. A synergistic effect on wear protection was observed with the current antiwear additive when added into a fully formulated engine oil. Nanostructure examination and composition analysis revealed a tribo-boundary film and subsurface plastic deformation zone for the metallic surface lubricated by the IL-containing lubricants. This protective boundary film is believed to be responsible for the IL's antiscuffing and antiwear functionality.

  2. Molecular Mechanism of the Additive Effects of Leukotriene Modifier in Asthmatic Patients Receiving Steroid Therapy

    Directory of Open Access Journals (Sweden)

    Kazuto Matsunaga

    2009-01-01

    Conclusions: LM caused a greater improvement in pulmonary function and airway inflammation in asthmatics with AR. The RANTES-mediated pathway may be involved in the improvement of the airflow limitation and airway lability by LM additive therapy in asthmatics receiving steroid therapy.

  3. Mechanical properties and microstructure of TiB2 ceramic influenced by ZrB2 additive

    Institute of Scientific and Technical Information of China (English)

    王皓; 傅正义; 辜萍; 王为民; 袁润章

    2002-01-01

    Since some transition metal diborides have the same crystal structure with TiB2, which can react with TiB2 to form solid solution by adequate technique. With ZrB2 used as additive, the TiB2-ZrB2 solid solution was prepared by hot pressing. The effects of additive content on mechanical properties of composite were investigated. The microstructure analyzing were employed by EPMA, SEM and TEM. It is shown that TiB2 can partly form solid solution with ZrB2 and redound to gain uniform grains, which h results in the increase of mechanical properties.

  4. Research on toughening mechanisms of alumina matrix ceramic composite materials improved by rare earth additive

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xihua; LIU Changxia; LI Musen; ZHANG Jianhua

    2008-01-01

    Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550℃ and 28 Mpa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.

  5. Effects of trace addition of vanadium and depression amount on recrystallization temperature and mechanical performance of 5182 belts

    Institute of Scientific and Technical Information of China (English)

    GAO Jia-cheng; CHEN Zhi-qiang; MING Wen-liang; WANG Yong; CUI Xian-you; YUAN Li-jun

    2006-01-01

    Because the mechanical performances of 5182 belts used for carbonated drinks cover decrease after baking, the effects of trace addition of V and depression amount in last step on microstructure and properties of 5182 belts were investigated. The microstructure, mechanical performances and recrystallization temperature of 5182 belts and 5182V belts in different steps were analyzed comparatively with metallographic microscope, micro-hardness tester, electron universal materials test machine and differential thermal analyzer. The results show that the mechanical performances of the belts are remarkably improved by the trace addition of V and the reduction of depression amount in last step. In addition, the recrystallization temperature of the belts is also increased but not obviously. As the precipitation of V is not full, there are not enough disseminatedly distributed particles, and the recrystallization temperature increases little. However the solution strengthening and the fine grain strengthening are enough to improve the mechanical performances to satisfy customer requirements. The effects of reduction of depression amount in last step on mechanical performance were explained in view of energy. Moreover, the strengthening mechanism of V-compound interlocking grain boundary was also discussed.

  6. Process for improving mechanical properties of epoxy resins by addition of cobalt ions

    Science.gov (United States)

    Stoakley, D. M.; St.clair, A. K. (Inventor)

    1984-01-01

    A resin product useful as an adhesive, composite or casting resin is described as well as the process used in its preparation to improve its flexural strength mechanical property characteristics. Improved flexural strength is attained with little or no change in density, thermal stability or moisture resistance by chemically incorporating 1.2% to 10.6% by weight Co(3) ions in an epoxidized resin system.

  7. Energy model of projected transfer with additional mechanical force in the welding process

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the theory of electrodynamics and other relational subjects,through introducing "Surface Evolver" as the means of FEM analysis, by computing and describing the energy (electromagnetic, gravity, and so on) in the droplet transfer system, an energy model was accomplished for studying the mechanism of projected transfer mode.Furthermore, the behavior of droplet transfer was studied by analyzing its menisci with FEM, and the theoretical results coincide well with the experiment results.

  8. Influence of polymer addition on the mechanical properties of a premixed calcium phosphate cement.

    Science.gov (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan

    2013-01-01

    Premixed calcium phosphate cements can reduce handling complications that are associated with the mixing of cements in the operating room. However, to extend the clinical indication of ceramic cements their mechanical properties need to be further improved. The incorporation of a polymeric material with intrinsically high tensile properties could possibly assist in increasing the mechanical properties of calcium phosphate cement. In this study polymer microparticles made from poly(lactid-co-glycolide) plasticised with poly(ethylene glycol) 400 (PLGA/PEG microparticles) were added in amounts of up to 5 wt% to a premixed acidic calcium phosphate cement. The PLGA/PEG microparticles added undergo a shape transformation at 37 °C, which could give a better integration between polymer microparticles and ceramic cement compared with polymer microparticles lacking this property. The results showed that the incorporation of 1.25 wt% PLGA/PEG microparticles increased the compressive strength by approximately 20% up to 15.1 MPa while the diametral tensile strength was kept constant. The incorporation of PLGA/PEG microparticles increased the brushite to monetite ratio after setting compared with pure ceramic cements. In conclusion, small amounts of PLGA/PEG microparticles can be incorporated into premixed acidic calcium phosphate cement and increase their mechanical properties, which could lead to increased future applications.

  9. Influence of polymer addition on the mechanical properties of a premixed calcium phosphate cement

    Science.gov (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan

    2013-01-01

    Premixed calcium phosphate cements can reduce handling complications that are associated with the mixing of cements in the operating room. However, to extend the clinical indication of ceramic cements their mechanical properties need to be further improved. The incorporation of a polymeric material with intrinsically high tensile properties could possibly assist in increasing the mechanical properties of calcium phosphate cement. In this study polymer microparticles made from poly(lactid-co-glycolide) plasticised with poly(ethylene glycol) 400 (PLGA/PEG microparticles) were added in amounts of up to 5 wt% to a premixed acidic calcium phosphate cement. The PLGA/PEG microparticles added undergo a shape transformation at 37 °C, which could give a better integration between polymer microparticles and ceramic cement compared with polymer microparticles lacking this property. The results showed that the incorporation of 1.25 wt% PLGA/PEG microparticles increased the compressive strength by approximately 20% up to 15.1 MPa while the diametral tensile strength was kept constant. The incorporation of PLGA/PEG microparticles increased the brushite to monetite ratio after setting compared with pure ceramic cements. In conclusion, small amounts of PLGA/PEG microparticles can be incorporated into premixed acidic calcium phosphate cement and increase their mechanical properties, which could lead to increased future applications. PMID:24270588

  10. Transport mechanism of reverse surface leakage current in AlGaN/GaN high-electron mobility transistor with SiN passivation

    Institute of Scientific and Technical Information of China (English)

    郑雪峰; 张进成; 郝跃; 范爽; 陈永和; 康迪; 张建坤; 王冲; 默江辉; 李亮; 马晓华

    2015-01-01

    The transport mechanism of reverse surface leakage current in AlGaN/GaN high-electron mobility transistor (HEMT) becomes one of the most important reliability issues with the downscaling of feature size. In this paper, the research results show that the reverse surface leakage current in AlGaN/GaN HEMT with SiN passivation increases with the enhancement of temperature in a range from 298 K to 423 K. Three possible transport mechanisms are proposed and examined to explain the generation of reverse surface leakage current. By comparing the experimental data with the numerical transport models, it is found that neither Fowler–Nordheim tunneling nor Frenkel–Poole emission can describe the transport of reverse surface leakage current. However, good agreement is found between the experimental data and the two-dimensional variable range hopping (2D-VRH) model. Therefore, it is concluded that the reverse surface leakage current is dominated by the electron hopping through the surface states at barrier layer. Moreover, the activation energy of surface leakage current is extracted, which is around 0.083 eV. Finally, the SiN passivated HEMT with high Al composition and thin AlGaN barrier layer is also studied. It is observed that 2D-VRH still dominates the reverse surface leakage current and the activation energy is around 0.10 eV, which demonstrates that the alteration of AlGaN barrier layer does not affect the transport mechanism of reverse surface leakage current in this paper.

  11. Mechanical and corrosion resistant properties of martensitic stainless steel plasma nitrocarburized with rare earths addition

    Institute of Scientific and Technical Information of China (English)

    LIU Ruiliang; QIAO Yingjie; YAN Mufu; FU Yudong

    2012-01-01

    In order to improve surface hardness and corrosion resistant property of 17-4PH martensitic stainless steel,the steel was plasma nitrocarburized at 560 ℃ for 2-24 h in a gas mixture of nitrogen,hydrogen and ethanol with rare earths (RE) addition.The experimental results showed that the modified layer was characterized by a compound layer containing two distinct zones (i.e.out ‘dark zone’ and inner ‘white zone’).The inner ‘white zone’ was almost a precipitation free zone and had high hardness as well as good corrosion resistance.Anodic polarization test results showed that the specimens plasma nitrocarburized with RE addition had good corrosion resistance resulted mainly from their higher corrosion potentials,lower corrosion current densities and larger passive regions as compared with those of the untreated one.

  12. EFFECT OF COPPER ADDITION ON MECHANICAL PROPERTIES OF 4Cr16Mo

    Institute of Scientific and Technical Information of China (English)

    H.M. Geng; X.C. Wu; Y.A. Min; H.B. Wang; H.K. Zhang

    2008-01-01

    Experiments conducted to determine the effect of copper addition on the machinability of plastic mold steel, 4Cr16Mo, were presented. The machinability of mold steel 4Cr16Mo was visibly improved by adding Cu. The top wear of 4Cr16Mo with copper was less than that without copper. The Cu-rich phase had the effect of a lubricant and the heat conductivity, which reduced cutting-tool wear, improved machinability, and increased the service life of the cutting-tool. Increasing of copper addition decreased the hot-working character of 4Cr16Mo. The optimal hot-working parameters for 4Cr16Mo with copper were determined by the tensile test and the compression test. The rate of deformation should be adopted as 0.6 s-1. The heating-up temperature, initial forging temperature, and terminal forging temperature were 1200℃, 1150℃, and 950℃, respectively.

  13. PVC mixtures’ mechanical properties with the addition of modified calcite as filler

    Directory of Open Access Journals (Sweden)

    Vučinić Dušica R.

    2012-01-01

    Full Text Available In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture containing calcite modified by dry process. The results showed that the bonding strength between calcite and the adsorbed organic component affected tensile strength, tensile elongation and breaking strength of the PVC mixtures. The best filler was obtained by wet modification using 1.5% stearic acid solution that provided the formation of a stearate monolayer chemisorbed on calcite. The PVC mixtures containing the calcite modified by wet process using 1.5% stearic acid solution exhibited the best mechanical properties. This calcite was completely hydrophobic with dominant chemically adsorbed surfactant, which means that stearate chemisorbed on calcite provided stronger interaction in the calcite-stearic acid-PVC system.

  14. Influence of nickel addition on magnetic and electro-mechanical behaviour of permalloys

    Indian Academy of Sciences (India)

    Kiran Gupta; K K Raina; S K Sinha

    2006-08-01

    Magnetic and electro-mechanical investigations have been carried out in two Ni–Fe permalloys under hydrogen atmosphere by varying annealing temperature. These alloys have been characterized for various magnetic parameters like peak permeability, coercivity and core loss under changed annealing profile conditions. The magnetic properties of Ni-rich (Ni ∼ 82%) alloy at 100 Hz were found to be better than the low Ni (Ni ∼ 47%) alloy. The alloys were tested for watch movement and found that the battery life of the watch movement improved by 38% using Ni-rich permalloy.

  15. Valence electron structure analysis of refining mecha-nism of Sc and Ti additions on aluminum

    Institute of Scientific and Technical Information of China (English)

    LI PieJie; YE YiCong; HE LiangJu

    2009-01-01

    The mechanism of the difference of refining effect between Sc and Ti adding to aluminum can not be explained substantially with traditional theory. Valence electron structures of AI-Ti and Al-Sc alloys have been studied by using the empirical electron theory of solids and molecules (EET). The covalent bond electron numbers and interfacial electron density differences are calculated. The conclusion is that, in the two alloys, different covalent bond electron numbers of nucleation particles, and different electron densities on the interface between the second phase particles and the matrix, fundamentally lead to the difference of refining effect between Sc and Ti adding to aluminum.

  16. Mechanisms associated with HIV-1 resistance to acyclovir by the V75I mutation in reverse transcriptase.

    Science.gov (United States)

    Tchesnokov, Egor P; Obikhod, Aleksandr; Massud, Ivana; Lisco, Andrea; Vanpouille, Christophe; Brichacek, Beda; Balzarini, Jan; McGuigan, Christopher; Derudas, Marco; Margolis, Leonid; Schinazi, Raymond F; Götte, Matthias

    2009-08-01

    It has recently been demonstrated that the anti-herpetic drug acyclovir (ACV) also displays antiviral activity against the human immunodeficiency virus type 1 (HIV-1). The triphosphate form of ACV is accepted by HIV-1 reverse transcriptase (RT), and subsequent incorporation leads to classical chain termination. Like all approved nucleoside analogue RT inhibitors (NRTIs), the selective pressure of ACV is associated with the emergence of resistance. The V75I mutation in HIV-1 RT appears to be dominant in this regard. By itself, this mutation is usually not associated with resistance to currently approved NRTIs. Here we studied the underlying biochemical mechanism. We demonstrate that V75I is also selected under the selective pressure of a monophosphorylated prodrug that was designed to bypass the bottleneck in drug activation to the triphosphate form (ACV-TP). Pre-steady-state kinetics reveal that V75I discriminates against the inhibitor at the level of catalysis, whereas binding of the inhibitor remains largely unaffected. The incorporated ACV-monophosphate (ACV-MP) is vulnerable to excision in the presence of the pyrophosphate donor ATP. V75I compromises binding of the next nucleotide that can otherwise provide a certain degree of protection from excision. Collectively, the results of this study suggest that ACV is sensitive to two different resistance pathways, which warrants further investigation regarding the detailed resistance profile of ACV. Such studies will be crucial in assessing the potential clinical utility of ACV and its derivatives in combination with established NRTIs.

  17. Flow mechanism of self-induced reversed limit-cycle wing rock for a chined forebody configuration

    Science.gov (United States)

    Shi, Wei; Deng, Xueying; Wang, Yankui; Li, Qian

    2015-11-01

    The wing rock phenomenon reduces the maneuverability and affects the flight safety of modern advanced fighters, such as the F-35, which have chined forebodies. Understanding the flow mechanism is critical to suppressing this phenomenon. In this study, experiments were conducted to reveal the motion and flow behavior over a chined forebody configuration. The tests were performed in a wind tunnel at an angle of attack of 50∘ with a Reynolds number of 1.87 × 105. Reversed limit-cycle oscillation was discovered in the free-to-roll tests. The unstable rolling moment around zero roll angle in the static case suggests that the model tends to be driven away from zero roll angle. Thus, the model cannot maintain its equilibrium at zero roll angle during free-to-roll motion. The unstable rolling moment is generated by the wing vortex structure above the upward wing, which is induced by the forebody asymmetric vortices. During wing rock, the wing vortex structure appears above the upward wing at a large roll angle after crossing zero roll angle owing to a time lag in the forebody vortex position, which is conducive to the motion. The forebody asymmetric vortices are thus the key to induce and maintain the motion.

  18. A template-dependent dislocation mechanism potentiates K65R reverse transcriptase mutation development in subtype C variants of HIV-1.

    Directory of Open Access Journals (Sweden)

    Dimitrios Coutsinos

    Full Text Available Numerous studies have suggested that the K65R reverse transcriptase (RT mutation develops more readily in subtype C than subtype B HIV-1. We recently showed that this discrepancy lies partly in the subtype C template coding sequence that predisposes RT to pause at the site of K65R mutagenesis. However, the mechanism underlying this observation and the elevated rates of K65R development remained unknown. Here, we report that DNA synthesis performed with subtype C templates consistently produced more K65R-containing transcripts than subtype B templates, regardless of the subtype-origin of the RT enzymes employed. These findings confirm that the mechanism involved is template-specific and RT-independent. In addition, a pattern of DNA synthesis characteristic of site-specific primer/template slippage and dislocation was only observed with the subtype C sequence. Analysis of RNA secondary structure suggested that the latter was unlikely to impact on K65R development between subtypes and that Streisinger strand slippage during DNA synthesis at the homopolymeric nucleotide stretch of the subtype C K65 region might occur, resulting in misalignment of the primer and template. Consequently, slippage would lead to a deletion of the middle adenine of codon K65 and the production of a -1 frameshift mutation, which upon dislocation and realignment of the primer and template, would lead to development of the K65R mutation. These findings provide additional mechanistic evidence for the facilitated development of the K65R mutation in subtype C HIV-1.

  19. Late Chondritic Additions and Planet and Planetesimal Growth: Evaluation of Physical and Chemical Mechanisms

    Science.gov (United States)

    Righter, Kevin

    2013-01-01

    Studies of terrestrial peridotite and martian and achondritic meteorites have led to the conclusion that addition of chondritic material to growing planets or planetesimals, after core formation, occurred on Earth, Mars, asteroid 4 Vesta, and the parent body of the angritic meteorites [1-4]. One study even proposed that this was a common process in the final stages of growth [5]. These conclusions are based almost entirely on the highly siderophile elements (HSE; Re, Au, Pt, Pd, Rh, Ru, Ir, Os). The HSE are a group of eight elements that have been used to argue for late accretion of chondritic material to the Earth after core formation was complete (e.g., [6]). This idea was originally proposed because the D(metal/silicate) values for the HSE are so high, yet their concentration in the mantle is too high to be consistent with such high Ds. The HSE also are present in chondritic relative abundances and hence require similar Ds if this is the result of core-mantle equilibration. Since the work of [6] there has been a realization that core formation at high PT conditions can explain the abundances of many siderophile elements in the mantle (e.g., [7]), but such detailed high PT partitioning data are lacking for many of the HSE to evaluate whether such ideas are viable for all four bodies. Consideration of other chemical parameters reveals larger problems that are difficult to overcome, but must be addressed in any scenario which calls on the addition of chondritic material to a reduced mantle. Yet these problems are rarely discussed or emphasized, making the late chondritic (or late veneer) addition hypothesis suspect.

  20. Mechanism of hydrofluoric acid formation in ethylene carbonate electrolytes with fluorine salt additives

    Science.gov (United States)

    Tebbe, Jonathon L.; Fuerst, Thomas F.; Musgrave, Charles B.

    2015-11-01

    We utilized density functional theory to examine HF generation in lithium-ion battery electrolytes from reactions between H2O and the decomposition products of three electrolyte additives: LiPF6, LiPOF4, and LiAsF6. Decomposition of these additives produces PF5, AsF5, and POF3 along with LiF precipitates. We found PF5 and AsF5 react with H2O in two sequential steps to form two HF molecules and POF3 and AsOF3, respectively. PF5 (or AsF5) complexes with H2O and undergoes ligand exchange to form HF and PF4OH (AsF4OH) with an activation barrier of 114.2 (30.5) kJ mol-1 and reaction enthalpy of 14.6 (-11.3) kJ mol-1. The ethylene carbonate (EC) electrolyte forms a Lewis acid-base complex with the PF4OH (AsF4OH) product, reducing the barrier to HF formation. Reactions of POF3 were examined and are not characterized by complexation of POF3 with H2O or EC, while PF5 and AsF5 complex favorably with H2O and EC. HF formation from POF3 occurs with a reaction enthalpy of -3.8 kJ mol-1 and a 157.7 kJ mol-1 barrier, 43.5 kJ mol-1 higher than forming HF from PF5. HF generation in electrolytes employing LiPOF4 should be significantly lower than those using LiPF6 or LiAsF6 and LiPOF4 should be further investigated as an alternative electrolyte additive.

  1. Effect of molybdenum addition on microstructure and mechanical properties of plain carbon steel weld

    Directory of Open Access Journals (Sweden)

    Jyoti Menghani

    2016-12-01

    Full Text Available The present investigation has two main objectives; first is optimization of welding process parameters of submerged arc welding (SAW using Taguchi philosophy and second is to improve the mechanical properties such as strength and microhardness of weld joint by alloying with varying amounts of molybdenum. For optimization of welding process, parameters Taguchi philosophy have been applied on a mild steel plate (AISI C- 1020 of 10 mm thickness with 60o groove angle with arc voltage and welding speed as variables and bead width as output variables. A mathematical relationship between bead width, arc voltage and welding speed has also been found using multiple regression analysis for the present base metal plate geometry. After optimizing welding parameters, molybdenum has been added individually to the welding area in varying percentages. The properties of alloyed and unalloyed weld metal bead are compared. The mechanical characterization of weld has been done in terms of microhardness, tensile strength, whereas microstructural characterization has been performed using optical microscopy, XRD and EDS. The presence of molybdenum resulted in bainite structure in weld bead having a refined grain structure, enhancement in tensile strength and microhardness. The XRD results showed the formation of molybdenum carbides justifying the increase in microhardness value.

  2. Improving Mechanical Properties of Thermoset Biocomposites by Fiber Coating or Organic Oil Addition

    Directory of Open Access Journals (Sweden)

    Truc T. Ngo

    2015-01-01

    Full Text Available Two different thermoset biocomposite systems are experimented in this study with the hope to improve their mechanical properties. Fiberglass and hemp, in form of fabrics, are used to reinforce the thermoset polymer matrix, which includes a traditional epoxy resin and a linseed oil-based bioresin (UVL. The fiber/polymer matrix interface is modified using two different approaches: adding a plant-based oil (pine or linseed to the polymer matrix or coating the fibers with 3-(aminopropyltriethoxysilane (APTES prior to integrating them into the polymer matrix. Epoxy resin is cured using an amine-based initiator, whereas UVL resin is cured under ultraviolet light. Results show that hemp fibers with APTES prime coat used in either epoxy or UVL matrix exhibit some potential improvements in the composite’s mechanical properties including tensile strength, modulus of elasticity, and ductility. It is also found that adding oil to the epoxy matrix reinforced with fiberglass mostly improves the material’s modulus of elasticity while maintaining its tensile strength and ductility. However, adding oil to the epoxy matrix reinforced with hemp doubles the material’s ductility while slightly reducing its tensile strength and modulus of elasticity.

  3. Investigation of gamma ray shielding efficiency and mechanical performances of concrete shields containing bismuth oxide as an environmentally friendly additive

    Science.gov (United States)

    Yao, Ya; Zhang, Xiaowen; Li, Mi; Yang, Rong; Jiang, Tianjiao; Lv, Junwen

    2016-10-01

    Concrete has a proven ability to attenuate gamma rays and neutrons without compromising structural property; therefore, it is widely used as the primary shielding material in many nuclear facilities. Recently, there is a tendency toward using various additives to enhance the shielding properties of these concrete mixtures. However, most of these additives being used either pose hygiene hazards or require special handling processes. It would be ideal if environmentally friendly additives were available for use. The bismuth oxide (Bi2O3) additive shows promise in various shielding applications due to its proven radiation attenuation ability and environmentally friendly nature. To the best of our knowledge, however, Bi2O3 has never been used in concrete mixtures. Therefore, for this research, we fabricated the Bi2O3-based concrete mixtures by adding Bi2O3 powder in the ordinary concrete mixture. Concrete mixtures with lead oxide (PbO) additives were used for comparison. Radiation shielding parameters like the linear attenuation coefficients (LAC) of all these concrete mixtures showing the effects of the Bi2O3 additions are presented. The mechanical performances of concrete mixtures incorporated with Bi2O3 additive were also investigated. It suggested that the concrete mixture containing 25% Bi2O3 powder (B5 in this study) provided the best shielding capacity and mechanical performance among other mixes. It has a significant potential for application as a structural concrete where radiological protection capability is required.

  4. Reversible resistance induced by FLT3 inhibition: a novel resistance mechanism in mutant FLT3-expressing cells.

    Directory of Open Access Journals (Sweden)

    Ellen Weisberg

    Full Text Available Clinical responses achieved with FLT3 kinase inhibitors in acute myeloid leukemia (AML are typically transient and partial. Thus, there is a need for identification of molecular mechanisms of clinical resistance to these drugs. In response, we characterized MOLM13 AML cell lines made resistant to two structurally-independent FLT3 inhibitors.MOLM13 cells were made drug resistant via prolonged exposure to midostaurin and HG-7-85-01, respectively. Cell proliferation was determined by Trypan blue exclusion. Protein expression was assessed by immunoblotting, immunoprecipitation, and flow cytometry. Cycloheximide was used to determine protein half-life. RT-PCR was performed to determine FLT3 mRNA levels, and FISH analysis was performed to determine FLT3 gene expression.We found that MOLM13 cells readily developed cross-resistance when exposed to either midostaurin or HG-7-85-01. Resistance in both lines was associated with dramatically elevated levels of cell surface FLT3 and elevated levels of phosphor-MAPK, but not phospho-STAT5. The increase in FLT3-ITD expression was at least in part due to reduced turnover of the receptor, with prolonged half-life. Importantly, the drug-resistant phenotype could be rapidly reversed upon withdrawal of either inhibitor. Consistent with this phenotype, no significant evidence of FLT3 gene amplification, kinase domain mutations, or elevated levels of mRNA was observed, suggesting that protein turnover may be part of an auto-regulatory pathway initiated by FLT3 kinase activity. Interestingly, FLT3 inhibitor resistance also correlated with resistance to cytosine arabinoside. Over-expression of FLT3 protein in response to kinase inhibitors may be part of a novel mechanism that could contribute to clinical resistance.

  5. Quantified Mechanical Properties of the Deltoid Muscle Using the Shear Wave Elastography: Potential Implications for Reverse Shoulder Arthroplasty.

    Directory of Open Access Journals (Sweden)

    Taku Hatta

    Full Text Available The deltoid muscle plays a critical role in the biomechanics of shoulders undergoing reverse shoulder arthroplasty (RSA. However, both pre- and postoperative assessment of the deltoid muscle quality still remains challenging. The purposes of this study were to establish a novel methodology of shear wave elastography (SWE to quantify the mechanical properties of the deltoid muscle, and to investigate the reliability of this technique using cadaveric shoulders for the purpose of RSA. Eight fresh-frozen cadaveric shoulders were obtained. The deltoid muscles were divided into 5 segments (A1, A2, M, P1 and P2 according to the muscle fiber orientation and SWE values were measured for each segment. Intra- and inter-observer reliability was evaluated using intraclass correlation coefficient (ICC. To measure the response of muscle tension during RSA, the humeral shaft was osteotomized and subsequently elongated by an external fixator (intact to 15 mm elongation. SWE of the deltoid muscle was measured under each stretch condition. Intra- and inter-observer reliability of SWE measurements for all regions showed 0.761-0.963 and 0.718-0.947 for ICC(2,1. Especially, SWE measurements for segments A2 and M presented satisfactory repeatability. Elongated deltoid muscles by the external fixator showed a progressive increase in passive stiffness for all muscular segments. Especially, SWE outcomes of segments A2 and M reliably showed an exponential growth upon stretching (R2 = 0.558 and 0.593. Segmental measurements using SWE could be reliably and feasibly used to quantitatively assess the mechanical properties of the deltoid muscle, especially in the anterior and middle portions. This novel technique based on the anatomical features may provide helpful information of the deltoid muscle properties during treatment of RSA.

  6. Miniaturization of cellulose fibers and effect of addition on the mechanical and barrier properties of hydroxypropyl methylcellulose

    Science.gov (United States)

    Cellulose fibers were miniaturized by microfluidics technology and incorporated in hydroxypropyl methylcellulose (HPMC) films to study the effect of the addition of such fibers on the mechanical and barrier properties of HPMC films suitable for food packaging applications. The particle size of the f...

  7. Influence of additives on microstructures, mechanical properties and shock-induced reaction characteristics of Al/Ni composites

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Wei; Zhang, Xianfeng, E-mail: lynx@mail.njust.edu.cn; Wu, Yang; He, Yong; Wang, Chuanting; Guo, Lei

    2015-11-05

    Granular composites containing aluminum (Al) and nickel (Ni) are typical structural energetic materials, which possess ideal combination of both mechanical properties and energy release capability. The influence of two additives, namely Teflon (PTFE) and copper (Cu), on mechanical properties and shock-induced chemical reaction (SICR) characteristics of Al/Ni material system has been investigated. Three composites, namely Al/Ni, Al/Ni/PTFE and Al/Ni/Cu with same volumetric ratio of Al powder to Ni powder, were processed by means of static pressing. Scanning electron microscopy was used to study the microstructure of the mentioned three composites. Quasi static compression tests were also conducted to determine the mechanical properties and fracture behavior of the mentioned three composites. It was shown that the additives affected both compressive strength and fracture mode of the three composites. Impact initiation experiments on the mentioned three composites were performed to determine their shock-induced chemical reaction characteristics by considering pressure histories measured in the test chamber. The experimental results showed that the additives had significant effects on critical initiation velocity, reaction rate, reaction efficiency and post-reaction behavior. - Highlights: • .Al/Ni, Al/Ni/PTFE and Al/Ni/Cu were processed by means of static pressing. • .Microstructures, mechanical properties and shock-induced reactions were studied. • .Microstructures affect both compressive strength and fracture mode. • .Impact velocity is an important factor in shock-induced chemical characteristics. • .Each additive has significant effects on energy release behavior.

  8. Effect of tungsten additions on the mechanical properties of Ti-6Al-4V

    Energy Technology Data Exchange (ETDEWEB)

    Choe, Heeman [Department of Materials Science and Engineering, Northwestern University, Cook Hall, 2220 Campus Drive, Evanston, IL 60208-3108 (United States); Abkowitz, Susan M. [Dynamet Technology Inc., Eight A Street, Burlington, MA 01803 (United States); Abkowitz, Stanley [Dynamet Technology Inc., Eight A Street, Burlington, MA 01803 (United States); Dunand, David C. [Department of Materials Science and Engineering, Northwestern University, Cook Hall, 2220 Campus Drive, Evanston, IL 60208-3108 (United States)]. E-mail: dunand@northwestern.edu

    2005-04-15

    The alloy Ti-6Al-4V was modified by addition of 10 wt.% tungsten through powder metallurgy. Depending on the initial W powder size, different materials were formed after powder densification: (i) 'alloys' for fine (0.7 and 2 {mu}m) W powders which were almost completely dissolved in the Ti-6Al-4V matrix; (ii) 'alloyed composites' for intermediate (12 and <45 {mu}m) W powders which were partially dissolved; (iii) and 'composites' for coarse (<250 {mu}m) W powders which were nearly un-dissolved. In all cases, tungsten strengthens Ti-6Al-4V, but much more so when dissolved in the matrix than as a second phase. Ductility was not affected by W additions for the fully-dissolved alloys, but was reduced in the case of composites with W particles, which exhibited fracture or pull-out from the matrix. Flaw sensitivity was apparent from strain hardening being much lower in tension than in compression, and from a much reduced ductility exhibited by one specimen with residual porosity.

  9. Mechanical behaviour of pressed and sintered titanium alloys obtained from master alloy addition powders.

    Science.gov (United States)

    Bolzoni, L; Esteban, P G; Ruiz-Navas, E M; Gordo, E

    2012-11-01

    The fabrication of the workhorse Ti-6Al-4V alloy and of the Ti-3Al-2.5V alloy was studied considering the master alloy addition variant of the blending elemental approach conventionally used for titanium powder metallurgy. The powders were characterised by means thermal analysis and X-ray diffraction and shaped by means of uniaxial pressing. The microstructural evolution with the sintering temperature (900-1400 °C) was evaluated by SEM and EDS was used to study the composition. XRD patterns as well as the density by Archimedes method were also obtained. The results indicate that master alloy addition is a suitable way to fabricate well developed titanium alloy but also to produce alloy with the desired composition, not available commercially. Density of 4.3 g/cm³ can be obtained where a temperature higher than 1200 °C is needed for the complete diffusion of the alloying elements. Flexural properties comparable to those specified for wrought Ti-6Al-4V medical devices are, generally, obtained.

  10. 市场倒逼机制对企业文化建设的影响%Effect of Mechanism of Market Reversed Pressure on Enterprise Culture Construction

    Institute of Scientific and Technical Information of China (English)

    刘军捷

    2015-01-01

    From the perspective of the effect of market reversed pressure mechanism on enterprises the following points are elaborated: firstly, the formation of the effect of market reversed pressure mechanism on enterprise culture;secondly, the design principle of enterprise culture transition forced by market mechanism;thirdly, the path of enterprise culture transition forced by market mechanism.%从市场倒逼机制对企业的影响视角思考:一、市场倒逼机制对企业文化影响的形成机理;二、市场机制倒逼企业文化转型设计的原则;三、市场倒逼企业文化转型的路径。

  11. Structure and mechanical properties of Ti-5Cr based alloy with Mo addition

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Wen-Fu [Department of Materials Science and Engineering, Da-Yeh University, Taiwan (China); Wu, Shih-Ching [Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, Taiwan (China); Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Taiwan (China); Chang, Hsiang-Hao [Department of Materials Science and Engineering, Da-Yeh University, Taiwan (China); Hsu, Hsueh-Chuan, E-mail: hchsu@ctust.edu.tw [Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, Taiwan (China); Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Taiwan (China)

    2010-07-20

    The effects of molybdenum (Mo) on the structure and mechanical properties of a Ti-5Cr-based alloy were studied with an emphasis on improving its strength/modulus ratio. Commercially pure titanium (c.p. Ti) was used as a control. As-cast Ti-5Cr and a series of Ti-5Cr-xMo (x = 1, 3, 5, 7, 9 and 11 wt.%) alloys were prepared by using a commercial arc-melting vacuum-pressure casting system, and investigated with X-ray diffraction (XRD) for phase analysis. Three-point bending tests were performed to evaluate the mechanical properties of all specimens and their fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that Ti-5Cr-7Mo, Ti-5Cr-9Mo and Ti-5Cr-11Mo alloys exhibited ductile properties, and the {beta}-phase Ti-5Cr-9Mo alloy exhibited the lowest bending modulus. However, the Ti-5Cr-3Mo and Ti-5Cr-5Mo alloys had much higher bending moduli due to the formation of the {omega} phase during quenching. It is noteworthy that the Ti-5Cr-9Mo alloy exhibited the highest bending strength/modulus ratios at 26.0, which is significantly higher than those of c.p. Ti (8.5) and Ti-5Cr (13.3). Furthermore, the elastically recoverable angle of the Ti-5Cr-9Mo alloy (30{sup o}) was greater than that of c.p. Ti (2.7{sup o}). The reasonably high strength (or high strength/modulus ratio) {beta}-phase Ti-5Cr-9Mo alloy exhibited a low modulus, ductile property, and excellent elastic recovery capability, which qualifies it as a novel implant materials.

  12. Physical-mechanical properties of Bis-EMA based root canal sealer with different fillers addition

    Directory of Open Access Journals (Sweden)

    Marcela Oliveira de Souza

    2015-01-01

    Full Text Available Aim: To evaluate influence of three different filler particles on an experimental Bisphenol A ethoxylated dimethacrylate (Bis-EMA based root filling material. Materials and Methods: Resin-based endodontic sealers were produced using Bis-EMA, camphorquinone, ethyl 4-dimethylaminobenzoate (EDAB, N, N-dihydroxyethyl-p-toluidine (DHEPT, butylated hydroxytoluene (BHT, and benzoyl peroxide. The experimental groups were formulated adding 10, 20, 30, 40, and 50% of calcium tungstate (CaWO 4 , ytterbium trifluoride(YbF 3 , and tantalum oxide(Ta 2 O 5 . Flow, thickness, and radiopacity tests were conducted in accordance with ISO 6876. Sorption and solubility (SL tests were conducted in accordance with ISO 4049, pH was measured with a pH meter, and degree of conversion (DC was evaluated with Fourier transform infrared spectroscopy (FTIR. For radiopacity, two-way analysis of variance (ANOVA and Tukey′s multiple comparison test was performed. For DC analysis, one-way ANOVA and Tukey′s multiple comparison test was performed. All statistical analyses were performed with a significance level of 5%. Results: All groups showed lower flow with increased filler concentration. All groups showed film thickness values lower than 50μm, as ISO recommends, except CaWO 4 50% group (76.7μm. pH values varied from 5.95 (± 0.07 in YbF 3 40% group to 6.90 (± 0.07 in Ta 2 O 5 40% group. In the radiopacity test, YbF 3 30%, Ta 2 O 5 40%, and Ta 2 O 5 50% groups showed no statistical significant difference to 3mmAl. Ta 2 O 5 and YbF 3 groups in 10, 20, and 30% concentrations presented sorption and SL values as ISOrecommendation. Addition ofTa 2 O 5 and CaWO 4 decreased DC after 14 days. YbF 3 addition showed no difference in DC from control group. Conclusion: YbF 3 filler addition promoted higher properties compared to CaWO 4 and Ta 2 O 5 on Bis-EMA based root canal sealer.

  13. Reverse logistics - a framework

    OpenAIRE

    Brito, Marisa; Dekker, Rommert

    2002-01-01

    textabstractIn this paper we define and compare Reverse Logistics definitions. We start by giving an understanding framework of Reverse Logistics: the why-what-how. By this means, we put in context the driving forces for Reverse Logistics, a typology of return reasons, a classification of products, processes and actors. In addition we provide a decision framework for Reverse Logistics and we present it according to long, medium and short term decisions, i.e. strategic-tactic-operational decis...

  14. Controlling photo-oxidation processes of a polyfluorene derivative: The effect of additives and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, G.R. [Laboratory of Polymers and Electronic Properties of Materials – UFOP, Ouro Preto, MG (Brazil); Nowacki, B. [Paulo Scarpa Polymer Laboratory – UFPR, Curitiba, PR (Brazil); Magalhães, A. [Instituto de Química, Universidade Estadual de Campinas – UNICAMP, Campinas, SP (Brazil); Azevedo, E.R. de [Instituto de Física de São Carlos, Universidade de São Paulo – USP, São Carlos, SP (Brazil); Sá, E.L. de [Chemistry Department, Federal University of Parana, Curitiba, PR (Brazil); Akcelrud, L.C. [Paulo Scarpa Polymer Laboratory – UFPR, Curitiba, PR (Brazil); Bianchi, R.F., E-mail: bianchi@iceb.ufop.br [Laboratory of Polymers and Electronic Properties of Materials – UFOP, Ouro Preto, MG (Brazil)

    2014-08-01

    The control of the photo degradation of a fluorene–vinylene–phenylene based-polymer, poly(9,9-di-hexylfluorenediylvinylene-alt-1,4-phenylenevinylene) (LaPPS16) was achieved by addition of a radical scavenger (RS) (enhancing photo resistance) or a radical initiator (RI) (reducing photo resistance). Photoluminescence, UV–Vis absorption, {sup 1}H NMR spectroscopies and gel permeation chromatography (GPC) revealed that the incorporating small amounts of RS or RI is an efficient way to control the rates of the photo-oxidation reactions, and thus to obtain the conjugated polymer with foreseeable degradation rates for applications in blue-light sensitive detectors for neonatal phototherapy. - Highlights: • Photo degradation control of a fluorene–vinylene–phenylene based polymer was achieved. • A radical scavenger enhanced photo resistance and radical initiator decreased it. • Color change rate with irradiation dose provided a basis for dosimeter construction.

  15. Unravelling the impact of hydrocarbon structure on the fumarate addition mechanism--a gas-phase ab initio study.

    Science.gov (United States)

    Bharadwaj, Vivek S; Vyas, Shubham; Villano, Stephanie M; Maupin, C Mark; Dean, Anthony M

    2015-02-14

    The fumarate addition reaction mechanism is central to the anaerobic biodegradation pathway of various hydrocarbons, both aromatic (e.g., toluene, ethyl benzene) and aliphatic (e.g., n-hexane, dodecane). Succinate synthase enzymes, which belong to the glycyl radical enzyme family, are the main facilitators of these biochemical reactions. The overall catalytic mechanism that converts hydrocarbons to a succinate molecule involves three steps: (1) initial H-abstraction from the hydrocarbon by the radical enzyme, (2) addition of the resulting hydrocarbon radical to fumarate, and (3) hydrogen abstraction by the addition product to regenerate the radical enzyme. Since the biodegradation of hydrocarbon fuels via the fumarate addition mechanism is linked to bio-corrosion, an improved understanding of this reaction is imperative to our efforts of predicting the susceptibility of proposed alternative fuels to biodegradation. An improved understanding of the fuel biodegradation process also has the potential to benefit bioremediation. In this study, we consider model aromatic (toluene) and aliphatic (butane) compounds to evaluate the impact of hydrocarbon structure on the energetics and kinetics of the fumarate addition mechanism by means of high level ab initio gas-phase calculations. We predict that the rate of toluene degradation is ∼100 times faster than butane at 298 K, and that the first abstraction step is kinetically significant for both hydrocarbons, which is consistent with deuterium isotope effect studies on toluene degradation. The detailed computations also show that the predicted stereo-chemical preference of the succinate products for both toluene and butane are due to the differences in the radical addition rate constants for the various isomers. The computational and kinetic modeling work presented here demonstrates the importance of considering pre-reaction and product complexes in order to accurately treat gas phase systems that involve intra and inter

  16. Nano-tribological properties and mechanisms of the liquid crystal as an additive

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Under conditions of low speed, small viscosity and molecularly smooth tribo-surfaces, the behavior of lubricant film in the nano scale is different from that in elasto-hydrodynamic lubrication (EHL) and boundary lubrication (BL). Due to the size effect, long-range ordered structure of liquid crystal (LC) has great effects on the tribological prop-erties and film-forming mechanism of thin film in the nano scale. The technique of relative optical interference intensity (ROII) was used to investigate nano-tribological properties when cholesteryl LCs are added to hexadecane. The results indicate that the practical film thickness of hexadecane with liquid crystal is 3-5 times as large as that expected from EHL theory in the low speed region. The film thickness in-creases with the enhancement in polarity and concentration of LC in hexadecane, and external DC voltage. The effective viscosity of lubricant is related to the film thickness and the voltage and it varies from bulk viscosity to several times or tens of times of bulk viscosity with reducing film thickness, and slowly rises with increasing external DC voltage and then trends to a constant. The higher ordered degree of mo-lecules close to solid surfaces gives rise to a thicker film.

  17. In situ polymerized wood polymer composite: effect of additives and nanoclay on the thermal, mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Devi, Rashmi R; Maji, Tarun K., E-mail: tkm@tezu.ernet.in [Department of Chemical Sciences, Tezpur University, Assam, (India)

    2013-11-01

    This study concerns the preparation and characterization of wood polymer nanocomposites based on impregnation of styrene acrylonitrile co-polymer-nanoclay intercalating system in presence of glycidyl methacrylate (GMA), a cross linking agent, and vinyl trichloro silane (VTCS) as additives into Simul (Bombex ceiba, L.), a soft wood. The effect of nanoclay and VTCS on the properties of the resultant wood polymer nanocomposites (WPNC) has been evaluated. FTIR spectroscopy shows the interaction among wood, polymers, GMA, nanoclay and VTCS. The penetration of polymer and nanoclay into the wood cell wall is supported by SEM study. The distribution of nanoclay in the SAN polymer matrix present within the wood cell wall has been evidenced by TEM study. TGA results show an improvement in the thermostability of the resultant composites. The inclusion of VTCS enhances the self extinguishing behaviour of the WPNC as revealed by limiting oxygen index (LOI) test. Due to treatment, the resultant WPNC exhibits an improvement in all the properties like water repellency, dimensional stability, hardness, flexural, tensile and thermal stability compared to untreated wood. (author)

  18. Involvement of suppressive B-lymphocytes in the mechanism of tolerogenic dendritic cell reversal of type 1 diabetes in NOD mice.

    Science.gov (United States)

    Di Caro, Valentina; Phillips, Brett; Engman, Carl; Harnaha, Jo; Trucco, Massimo; Giannoukakis, Nick

    2014-01-01

    The objective of the study was to identify immune cell populations, in addition to Foxp3+ T-regulatory cells, that participate in the mechanisms of action of tolerogenic dendritic cells shown to prevent and reverse type 1 diabetes in the Non-Obese Diabetic (NOD) mouse strain. Co-culture experiments using tolerogenic dendritic cells and B-cells from NOD as well as transgenic interleukin-10 promoter-reporter mice along with transfer of tolerogenic dendritic cells and CD19+ B-cells into NOD and transgenic mice, showed that these dendritic cells increased the frequency and numbers of interleukin-10-expressing B-cells in vitro and in vivo. The expansion of these cells was a consequence of both the proliferation of pre-existing interleukin-10-expressing B-lymphocytes and the conversion of CD19+ B-lymphcytes into interleukin-10-expressing cells. The tolerogenic dendritic cells did not affect the suppressive activity of these B-cells. Furthermore, we discovered that the suppressive murine B-lymphocytes expressed receptors for retinoic acid which is produced by the tolerogenic dendritic cells. These data assist in identifying the nature of the B-cell population increased in response to the tolerogenic dendritic cells in a clinical trial and also validate very recent findings demonstrating a mechanistic link between human tolerogenic dendritic cells and immunosuppressive regulatory B-cells.

  19. Involvement of suppressive B-lymphocytes in the mechanism of tolerogenic dendritic cell reversal of type 1 diabetes in NOD mice.

    Directory of Open Access Journals (Sweden)

    Valentina Di Caro

    Full Text Available The objective of the study was to identify immune cell populations, in addition to Foxp3+ T-regulatory cells, that participate in the mechanisms of action of tolerogenic dendritic cells shown to prevent and reverse type 1 diabetes in the Non-Obese Diabetic (NOD mouse strain. Co-culture experiments using tolerogenic dendritic cells and B-cells from NOD as well as transgenic interleukin-10 promoter-reporter mice along with transfer of tolerogenic dendritic cells and CD19+ B-cells into NOD and transgenic mice, showed that these dendritic cells increased the frequency and numbers of interleukin-10-expressing B-cells in vitro and in vivo. The expansion of these cells was a consequence of both the proliferation of pre-existing interleukin-10-expressing B-lymphocytes and the conversion of CD19+ B-lymphcytes into interleukin-10-expressing cells. The tolerogenic dendritic cells did not affect the suppressive activity of these B-cells. Furthermore, we discovered that the suppressive murine B-lymphocytes expressed receptors for retinoic acid which is produced by the tolerogenic dendritic cells. These data assist in identifying the nature of the B-cell population increased in response to the tolerogenic dendritic cells in a clinical trial and also validate very recent findings demonstrating a mechanistic link between human tolerogenic dendritic cells and immunosuppressive regulatory B-cells.

  20. Study on the Coordinated Operation Mechanism of Reverse Logistics Based on the Internet of Things%基于物联网技术的逆向物流协调运作机制研究

    Institute of Scientific and Technical Information of China (English)

    吴晓晨

    2012-01-01

      Reverse logistics operation has high uncertainty and complexity, the internet of things can solve the information barriers in the process of reverse logistics through the information sharing platform, improve the reverse logistics’ operation efficiency, and ruduce operation cost. In addition, the success of reverse logistics should also make full use of the information sharing platform based on the internet of things to for the mechanisms of decision-making, communication and cooperation.%  逆向物流运作具有更高的不确定性和复杂性,物联网技术通过信息共享平台的建立,能够有效破解逆向物流运作过程中的信息障碍,提高逆向物流的运作效率,降低逆向物流的运作成本。同时,逆向物流的成功运作还应当充分利用物联网信息共享平台建立决策机制、沟通机制和合作机制。

  1. Effect of boron addition on injection molded 316L stainless steel: mechanical, corrosion properties and in vitro bioactivity.

    Science.gov (United States)

    Bayraktaroglu, Esra; Gulsoy, H Ozkan; Gulsoy, Nagihan; Er, Ozay; Kilic, Hasan

    2012-01-01

    The research was investigated the effect of boron additions on sintering characteristics, mechanical, corrosion properties and biocompatibility of injection molded austenitic grade 316L stainless steel. Addition of boron is promoted to get high density of sintered 316L stainless steels. The amount of boron plays a role in determining the sintered microstructure and all properties. In this study, 316L stainless steel powders have been used with the elemental NiB powders. A feedstock containing 62.5 wt% powders loading was molded at different injection molded temperature. The binders were completely removed from molded components by solvent and thermal debinding at different temperature. The debinded samples were sintered at different temperature for 60 min. Mechanical property, microstructural characterization and electrochemical property of the sintered samples were performed using tensile testing, hardness, optical, scanning electron microscopy and electrochemical corrosion experiments. Sintered samples were immersed in a simulated body fluid (SBF) with elemental concentrations that were comparable to those of human blood plasma for a total period of 15 days. Both materials were implanted in fibroblast culture for biocompatibility evaluations were carried out. Results of study showed that sintered 316L and 316L with NiB addition samples exhibited high mechanical and corrosion properties in a physiological environment. Especially, 316L with NiB addition can be used in some bioapplications.

  2. Mechanics model of additional longitudinal force transmission between bridges and continuously welded rails with small resistance fasteners

    Institute of Scientific and Technical Information of China (English)

    徐庆元; 周小林; 曾志平; 杨小礼

    2004-01-01

    A new mechanics model, which reveals additional longitudinal force transmission between the continuously welded rails and the bridges, is established on the fact that the influence of the mutual relative displacement among the rail, the sleeper and the beam is taken into account. An example is presented and numerical results are compared. The results show that the additional longitudinal forces calculated with the new model are less than those of the previous, especially in the case of the flexible pier bridges. The new model is also suitable for the analysis of the additional longitudinal force transmission between rails and bridges of ballastless track with small resistance fasteners without taking the sleeper displacement into account, and compared with the ballast bridges, the ballastless bridges have a much stronger additional longitudinal force transmission between the continuously welded rails and the bridges.

  3. Constituent phases and mechanical properties of iron oxide-additioned phosphoaluminate cement

    Directory of Open Access Journals (Sweden)

    Yang, Shuai

    2015-06-01

    Full Text Available Iron oxide was added to phosphoaluminate clinker and its effects on cement constituents were determined using XRD, DSC, SEM-EDS and conduction calorimetry analysis. The variations in compressive strength were also studied. The results showed that in moderate amounts, iron oxide acts as a mineraliser during clinker sintering, furthering the conversion of CA1-Y(PY to LHss at a lower temperature than normally required for that reaction. The main constituents of iron oxide-rich phosphoaluminate clinker included LHss, CA1-Y(PY, CP1-Z(AZ and ferrite. The EDS findings showed that the composition of the ferrite phase was nonuniform. The conclusion drawn was that by modifying the dose of Fe2O3 , the composition of phosphoaluminate cement can be controlled to produce clinker and cement compliant with different mechanical strength requirements. The conduction calorimetry findings were consistent with those results.Este trabajo estudia, mediante DRX DSC, SEM-EDS y calorimetría de conducción, el efecto de la adición de óxido de hierro a un clinker de fosfoaluminato, así como las variaciones sufridas en su resistencia a compresión. Los resultados mostraron que en cantidades moderadas, el óxido de hierro actúa como mineralizador durante la sinterización del clinker, promoviendo la conversión de CA1-Y(PY a LHss a una temperatura más baja de la normalmente requerida. Los componentes principales del clínker de fosfoaluminato con óxido de hierrop son LHss, CA1-Y(PY, CP1-Z(AZ y fase ferritica. Los resultados de EDS mostraron que la composición de esta fase ferrítica no era uniforme. DE este estudio se ha podido concluir que variando la dosificación del Fe2O3 , se puede controlar la composición del fosfoaluminato para producir clinker y cemento compatibles con diferentes requisitos de resistencia mecánica. Los resultados de calorimetría de conducción fueron consistentes con los resultados.

  4. Effect of the additions of carbide-forming elements on the microstructure and mechanical properties of steel shot

    Science.gov (United States)

    Shchennikova, T. L.; Zalazinskii, G. G.; Leont'ev, L. I.; Rybalko, O. F.

    2009-02-01

    The effect of the additions of carbide-forming elements (vanadium, titanium, chromium, molybdenum) on the microstructure and mechanical properties of the steel shot produced by the atomization of an iron-carbon melt (0.8% C) by water at a low pressure (0.2 MPa) is studied. The introduction of alloying elements is shown to affect the sizes of the structural constituents that form during the solidification of shot particles and, hence, the mechanical properties (hardness, wear resistance) of the shot. The additions can decrease the grain size in the shot by a factor of 2.5-3. The formation of the MC ( M is a carbide-forming element), VC, TiC, or M 2C (e.g., Mo2C) carbide increases the hardness of the shot material. Chromium and molybdenum form solid solutions with iron and complex (Fe, M)3C carbides.

  5. The effect of boron addition on microstructure and mechanical properties of biomedical Ti35Nb6Ta alloy

    Energy Technology Data Exchange (ETDEWEB)

    Málek, Jaroslav, E-mail: malek@ujp.cz [UJP PRAHA a.s., Nad Kamínkou 1345, 156 10 Prague, Zbraslav (Czech Republic); CTU in Prague, Faculty of Mechanical Engineering, Department of Materials Engineering, Karlovo Namesti 13, 121 35 Praha 2 (Czech Republic); Hnilica, František, E-mail: hnilica@ujp.cz [UJP PRAHA a.s., Nad Kamínkou 1345, 156 10 Prague, Zbraslav (Czech Republic); Veselý, Jaroslav, E-mail: vesely@ujp.cz [UJP PRAHA a.s., Nad Kamínkou 1345, 156 10 Prague, Zbraslav (Czech Republic); Smola, Bohumil, E-mail: smola@met.mff.cuni.cz [Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16 Prague 2 (Czech Republic); Březina, Vítězslav, E-mail: brezinavita@gmail.com [Masaryk University, Faculty of Medicine, Department of Stomathology, Komenského Náměstí 220/2, 662 43 Brno (Czech Republic); Kolařík, Kamil, E-mail: kamil.kolarik@email.cz [Faculty of Mechanical Engineering, University of West Bohemia, Univerzitní 22, 306 14 Plzeň (Czech Republic)

    2014-10-15

    The beta-titanium alloys are promising materials for bioapplications but their processing via melting is difficult. Coarse grains have been observed in as-cast specimens. Subsequent thermo-mechanical processing seems to be necessary in order to obtain fine-grained microstructure with better mechanical properties. The grain size can be decreased significantly by addition of small boron amount. In this work Ti–35Nb–6Ta alloy with various B additions (0, 0.05, 0.1, 0.3 and 0.5 wt.%) has been studied. Even the smallest amount of B leads to significant grain refinement in Ti–35Nb–6Ta alloy (from 1300 to about 350 μm). Slight grain refinement has been observed also after hot forging and solution treatment. TiB particles emerged in specimens due to B addition. These particles contribute to changes in mechanical properties not only in hot forged and solution treated specimens (hardness increase from 140 to 180 HV10), but also in cold swaged specimens (hardness from 230 to 250 HV10, tensile strength from 800 to 920 MPa). The hardness values can be increased up to 370 HV10 during aging at 400 °C (specimen with 0.5 wt.% B). It has been observed that specimens with low boron addition 0.05 wt.% possess no cytotoxicity. On the other hand in specimens with 0.1 wt.% B or more slight adverse effect on cytotoxicity has been observed. - Highlights: • The influence of boron on microstructure and mechanical properties has been studied. • Beta-transus temperature has been determined. • Cytotoxicity depending on boron content has been evaluated. • Possibility of final heat treatment has been determined.

  6. Effect of pMDI isocyanate additive on mechanical and thermal properties of Kenaf fibre reinforced thermoplastic polyurethane composites

    Indian Academy of Sciences (India)

    Y A El-Shekeil; S M Sapuan; K Abdan; E S Zainudin; O M Al-Shuja’a

    2012-12-01

    The effect of polymeric methylene diphenyl diisocyanate (pMDI) on mechanical and thermal properties of Kenaf fibre (KF) reinforced thermoplastic polyurethane (TPU) composites was studied. Various percentages viz. 2%, 4% and 6%, were studied. The composites were characterized by using tensile testing, thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR). It was noticed that the addition of pMDI 2%, 4%and 6% did not induce a better tensile nor thermal properties.

  7. Additive manufacturing and mechanical characterization of graded porosity scaffolds designed based on triply periodic minimal surface architectures.

    Science.gov (United States)

    Afshar, M; Anaraki, A Pourkamali; Montazerian, H; Kadkhodapour, J

    2016-09-01

    Since the advent of additive manufacturing techniques, triply periodic minimal surfaces have emerged as a novel tool for designing porous scaffolds. Whereas scaffolds are expected to provide multifunctional performance, spatially changing pore patterns have been a promising approach to integrate mechanical characteristics of different architectures into a unique scaffold. Smooth morphological variations are also frequently seen in nature particularly in bone and cartilage structures and can be inspiring for designing of artificial tissues. In this study, we carried out experimental and numerical procedures to uncover the mechanical properties and deformation mechanisms of linearly graded porosity scaffolds for two different mathematically defined pore structures. Among TPMS-based scaffolds, P and D surfaces were subjected to gradient modeling to explore the mechanical responses for stretching and bending dominated deformations, respectively. Moreover, the results were compared to their corresponding uniform porosity structures. Mechanical properties were found to be by far greater for the stretching dominated structure (P-Surface). For bending dominated architecture (D-Surface), although there was no global fracture for uniform structures, graded structure showed a brittle fracture at 0.08 strain. A layer by layer deformation mechanism for stretching dominated structure was observed. For bending dominated scaffolds, deformation was accompanied by development of 45° shearing bands. Finite element simulations were also performed and the results showed a good agreement with the experimental observations.

  8. Reverse blocking characteristics and mechanisms in Schottky-drain AlGaN/GaN HEMT with a drain field plate and floating field plates

    Science.gov (United States)

    Wei, Mao; Wei-Bo, She; Cui, Yang; Jin-Feng, Zhang; Xue-Feng, Zheng; Chong, Wang; Yue, Hao

    2016-01-01

    In this paper, a novel AlGaN/GaN HEMT with a Schottky drain and a compound field plate (SD-CFP HEMT) is presented for the purpose of better reverse blocking capability. The compound field plate (CFP) consists of a drain field plate (DFP) and several floating field plates (FFPs). The physical mechanisms of the CFP to improve the reverse breakdown voltage and to modulate the distributions of channel electric field and potential are investigated by two-dimensional numerical simulations with Silvaco-ATLAS. Compared with the HEMT with a Schottky drain (SD HEMT) and the HEMT with a Schottky drain and a DFP (SD-FP HEMT), the superiorities of SD-CFP HEMT lie in the continuous improvement of the reverse breakdown voltage by increasing the number of FFPs and in the same fabrication procedure as the SD-FP HEMT. Two useful optimization laws for the SD-CFP HEMTs are found and extracted from simulation results. The relationship between the number of the FFPs and the reverse breakdown voltage as well as the FP efficiency in SD-CFP HEMTs are discussed. The results in this paper demonstrate a great potential of CFP for enhancing the reverse blocking ability in AlGaN/GaN HEMT and may be of great value and significance in the design and actual manufacture of SD-CFP HEMTs. Project supported by the National Natural Science Foundation of China (Grant Nos. 61204085, 61334002, 61306017, 61474091, 61574112, and 61574110).

  9. Influence of additional coupling agent on the mechanical properties of polyester-agave cantala roxb based composites

    Science.gov (United States)

    Ubaidillah, Raharjo, Wijang W.; Wibowo, A.; Harjana, Mazlan, S. A.

    2016-03-01

    The mechanical and morphological properties of the unsaturated polyester resins (UPRs)-agave cantala roxb based composite are investigated in this paper. The cantala fiber woven in 3D angle interlock was utilized as the composite reinforcement. Surface grafting of the cantala fiber through chemical treatment was performed by introducing silane coupling agent to improving the compatibility with the polymer matrix. The fabrication of the composite specimens was conducted using vacuum bagging technique. The effect of additional coupling agent to the morphological appearance of surface fracture was observed using scanning electron microscopy. Meanwhile, the influence of additional silane to the mechanical properties was examined using tensile, bending and impact test. The photograph of surface fracture on the treated specimens showed the residual matrix left on the fibers in which the phenomenon was not found in the untreated specimens. Based on mechanical tests, the treated specimens were successfully increased their mechanical properties by 55%, 9.67%, and 92.4% for tensile strength, flexural strength, and impact strength, respectively, at 1.5% silane coupling agent.

  10. Influence of cooling rate and antimony addition content on graphite morphology and mechanical properties of a ductile iron

    Directory of Open Access Journals (Sweden)

    Liu Zhe

    2012-05-01

    Full Text Available Cooling rate and inoculation practice can greatly affect the graphite morphology of ductile irons. In the present research, the effects of the cooling rate and antimony addition on the graphite morphology and mechanical properties of ductile irons have been studied. Three ductile iron castings were prepared through solidification under cooling conditions S (slow, M (medium and F (fast. The cooling rates around the equilibrium eutectic temperature (1,150 ℃ for these cooling conditions (S, M and F were set at 0.21 ℃·min-1, 0.32 ℃·min-1 and 0.37 ℃·min-1, respectively. In addition, four ductile iron castings were prepared by adding 0.01%, 0.02%, 0.03% and 0.04% (by weight antimony, respectively under the slow cooling condition. The results show that the nodularity index, tensile strength and hardness of the ductile iron castings without antimony addition are all improved with the increase of cooling rate, while the ductile iron casting solidified under the medium cooling rate possesses the largest number of graphite nodules. Furthermore, for the four antimony containing castings, the graphite morphology and tensile strength are also improved by the antimony additions, and the effect of antimony addition is intensified when the addition increases from 0.01% to 0.03%. Moreover, the rare earth elements (REE/antimony ratio of 2 appears to be the most effective for fine nodular graphite formation in ductile iron.

  11. Role of quaternary additions on dislocated martensite, retain austenite and mechanical properties of Fe/Cr/C structural steels

    Energy Technology Data Exchange (ETDEWEB)

    Rao, B.V.N.

    1978-02-01

    The influence of quaternary alloy additions of Mn and Ni to Fe/Cr/C steels which have been designed to provide superior mechanical properties has been investigated. Transmission electron microscopy and x-ray analysis revealed increasing amounts of retained austenite with Mn up to 2 w/o and with 5 w/o Ni additions after quenching from 1100/sup 0/C. This is accompanied by a corresponding improvement in toughness properties of the quaternary alloys. In addition, the generally attractive combinations of strength and toughness in these quaternary alloys is attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. Grain-refining resulted in a further increase in the amount of retained austenite.

  12. PARAMETER DETERMINATION FOR ADDITIONAL OPERATING FORCE MECHANISM IN DEVICE FOR PNEUMO-CENTRIFUGAL MACHINING OF BALL-SHAPED WORKPIECES

    Directory of Open Access Journals (Sweden)

    A. A. Sukhotsky

    2014-01-01

    Full Text Available The paper describes development of the methodology for optimization of parameters for an additional operating force mechanism in a device for pneumo-centrifugal machining of glass balls. Specific feature in manufacturing glass balls for micro-optics in accordance with technological process for obtaining ball-shaped workpieces is grinding and polishing of spherical surface in a free state. In this case component billets of future balls are made in the form of cubes and the billets are given preliminary a form of ball with the help of rough grinding. An advanced method for obtaining ball-shaped work-pieces from brittle materials is a pneumocentrifugal machining. This method presupposes an application of two conic rings with abrasive working surfaces which are set coaxially with large diameters to each other and the billets are rolled along these rings. Rotation of the billets is conveyed by means of pressure medium.The present devices for pneumo-centrifugal machining are suitable for obtaining balls up to 6 mm. Machining of the work-pieces with full spherical surfaces and large diameter is non-productive due to impossibility to ensure a sufficient force on the billet in the working zone. For this reason the paper proposes a modified device where an additional force on the machined billet is created by upper working disc that is making a reciprocating motion along an axis of abrasive conic rings. The motion is realized with the help of a cylindrical camshaft mechanism in the form of a ring with a profile working end face and the purpose of present paper is to optimize parameters of the proposed device.The paper presents expressions for calculation of constitutive parameters of the additional operating force mechanism including parameters of loading element motion, main dimensions of the additional operating force mechanism and parameters of a profile element in the additional operating force mechanism.Investigation method is a mathematical

  13. Effects of Minute Addition of Ni on Microstructure and Mechanical Properties of Sn-Zn Eutectic Alloy

    Science.gov (United States)

    Pandey, P.; Tiwary, C. S.; Chattopadhyay, K.

    2016-10-01

    The current work explores the effects of a small addition of Ni on the microstructure and mechanical properties of Sn-Zn eutectic solder alloy (Sn-14.9 at.%Zn). In two sets of experiments, Ni is either added to the eutectic alloy or Zn in the eutectic alloy is replaced by an increasing amount of Ni. The study indicates that small additions of Ni in eutectic Sn-Zn solder (˜0.017 at.%) refines the eutectic microstructure together with the appearance of the small amount of primary Zn plates. Increasing the Ni content to 0.142 at.% and beyond, then an intermetallic phase ϒ-Ni5Zn21 with dendritic morphology appears in the microstructure along with dendrites of primary Sn. The scale of eutectic microstructure shows a decreasing trend till 0.902 at.%Ni with eutectic spacing of 1.98 ± 0.32 μm for this alloy. Further addition of Ni coarsens the microstructure. The replacement of Zn with Ni in the eutectic composition follows a similar trend with a lesser refinement of the microstructure. In both the scenarios, the addition of a small amount of Ni increases the eutectic temperatures till a critical concentration is reached beyond which one can observe a decrease in the eutectic point. The trend is similar for the solid solubility of Zn in Sn while the trend is opposite for the measured eutectic composition, which decreases at the initial stages of Ni addition. Through a detailed measurement of mechanical properties, the study establishes significant improvement of the strength of Sn-Zn solder with small additions of Ni in the alloy with a maximum hardness of 26 ± 1 HV and 0.2% proof stress of 72 ± 3 MPa at room temperature for the eutectic alloy with 0.902 at.%Ni.

  14. Metal and pharmaceutical mixtures: Is ion loss the mechanism underlying acute toxicity and widespread additive toxicity in zebrafish?

    Energy Technology Data Exchange (ETDEWEB)

    Alsop, Derek, E-mail: alsopde@mcmaster.ca; Wood, Chris M.

    2013-09-15

    Highlights: •Zebrafish larvae were used to test the acute toxicity of contaminant mixtures. •Interactions were observed between metals, ammonia and pharmaceuticals. •Larval Na{sup +} loss was observed with exposure to all acutely toxic contaminants tested. •Water quality criteria should recognize the toxic interactions between contaminants. -- Abstract: The acute toxicities and mechanisms of action of a variety of environmental contaminants were examined using zebrafish larvae (Danio rerio; 4–8 days post fertilization). Toxic interactions were observed between metals. For example, the addition of a sublethal level of nickel (15% of the LC{sub 50}, one third of the LC{sub 01}) to all copper treatments decreased the copper 96 h LC{sub 50} by 58%, while sublethal copper exposure (6% of the copper LC{sub 50}, 13% of the LC{sub 01}) decreased the cadmium 96 h LC{sub 50} by 47%. Two predictive models were assessed, the concentration addition (CA) model, which assumes similar mechanisms of action, and the independent action (IA) model, which assumes different mechanisms of action. Quantitative comparisons indicated the CA model performed better than the IA model; the latter tended to underestimate combined toxicity to a greater extent. The effects of mixtures with nickel or ammonia were typically additive, while mixtures with copper or cadmium were typically greater than additive. Larvae exposed to cadmium, copper or nickel experienced whole body ion loss. Decreases were greatest for Na{sup +} followed by K{sup +} (as high as 19% and 9%, respectively, in 24 h). Additive toxicity between copper and other pharmaceutical compounds such as fluoxetine (Prozac™), β-naphthoflavone, estrogen and 17α-ethinylestradiol were also observed. Similar to metals, acutely toxic concentrations of fluoxetine, β-naphthoflavone and ammonia all decreased whole body Na{sup +} and K{sup +}. Overall, whole body Na{sup +} loss showed the greatest correlation with mortality across a

  15. Role of hydrogen abstraction acetylene addition mechanisms in the formation of chlorinated naphthalenes. 2. Kinetic modeling and the detailed mechanism of ring closure.

    Science.gov (United States)

    McIntosh, Grant J; Russell, Douglas K

    2014-12-26

    The dominant formation mechanisms of chlorinated phenylacetylenes, naphthalenes, and phenylvinylacetylenes in relatively low pressure and temperature (∼40 Torr and 1000 K) pyrolysis systems are explored. Mechanism elucidation is achieved through a combination of theoretical and experimental techniques, the former employing a novel simplification of kinetic modeling which utilizes rate constants in a probabilistic framework. Contemporary formation schemes of the compounds of interest generally require successive additions of acetylene to phenyl radicals. As such, infrared laser powered homogeneous pyrolyses of dichloro- or trichloroethylene were perturbed with 1,2,4- or 1,2,3-trichlorobenzene. The resulting changes in product identities were compared with the major products expected from conventional pathways, aided by the results of our previous computational work. This analysis suggests that a Bittner-Howard growth mechanism, with a novel amendment to the conventional scheme made just prior to ring closure, describes the major products well. Expected products from a number of other potentially operative channels are shown to be incongruent with experiment, further supporting the role of Bittner-Howard channels as the unique pathway to naphthalene growth. A simple quantitative analysis which performs very well is achieved by considering the reaction scheme as a probability tree, with relative rate constants being cast as branching probabilities. This analysis describes all chlorinated phenylacetylene, naphthalene, and phenylvinylacetylene congeners. The scheme is then tested in a more general system, i.e., not enforcing a hydrogen abstraction/acetylene addition mechanism, by pyrolyzing mixtures of di- and trichloroethylene without the addition of an aromatic precursor. The model indicates that these mechanisms are still likely to be operative.

  16. [Reversal of adriamycin resistance by digoxin in human breast cancer cell line MCF-7/adriamycin and its mechanism].

    Science.gov (United States)

    Li, Bai-He; Yuan, Lei; Shi, Ran-Ran; Wang, Jian-Guo

    2015-12-25

    The aim of this study was to investigate the effects of digoxin on the chemoresistance of human breast cancer cell line MCF-7/adriamycin (ADR) and its underlying mechanism. MCF-7 and MCF-7/ADR cells were designated as control and ADR groups, respectively. MCF-7/ADR cells in ADR + digoxin group received 48 h of digoxin (10 nmol/L) treatment; MCF-7/ADR cells transfected with pLKO.1-shHIF-1α and pLKO.1-shcontrol plasmids were named shHIF-1α and shcontrol groups, respectively. CCK-8 assay was employed to detect the cytotoxic effect of ADR on MCF-7/ADR cells, and IC50 value and resistance index were calculated according to CCK-8. RT-PCR was used to measure the mRNA levels of hypoxia inducible factor-1α (HIF-1α) and multidrug resistance-1 (MDR1). Western blot was used to analyze the protein levels of HIF-1α and MDR1. Flow cytometry was used to determine the apoptosis. The result showed that the resistance index of MCF-7/ADR cells was 115.6, and it was reduced to 47.2 under the action of digoxin (P Digoxin reduced the protein levels of HIF-1α and MDR1, as well as the mRNA level of MDR1, but did not affect the mRNA level of HIF-1α. After HIF-1α gene was silenced, the protein levels of HIF-1α and MDR1 were down-regulated (P digoxin promoted cell apoptosis in both shcontrol and shHIF-1α groups, the difference between the two groups was not significant. In conclusion, the results suggest that digoxin may partially reverse the ADR resistance in human breast cancer cell line MCF-7/ADR by means of down-regulating the expression levels of HIF-1α and MDR1 and promoting apoptosis via HIF-1α-independent pathway.

  17. The Analysi s of Incomplete Gear Reversing Mechanism Dynamics%不完全齿轮换向机构的动力学特性分析

    Institute of Scientific and Technical Information of China (English)

    王猛; 李长春; 田希杰

    2012-01-01

    在利用Pro/E4.0对不完全齿轮进行渐开线参数化建模的基础上,使用ADAMS软件对不完全齿轮自动换向机构进行动力学仿真分析,并研究了齿轮作用力和转矩的特性曲线。%In the use of Pro / E 4 on the incomplete gear involute parametric modeling based on ADAMS software, use of incomplete gear automatic reversing mechanism simulation analysis of dynamic is carried out, and the study of the gear force and torque characteristic curve. Base on the incomplete gear involute parametric modeling in the use of Pro/E 4.0, the incomplete gear automatic reversing mechanism simulation analysis of dynamic on ADAMS software is carried out, and the study of the gear force and torque characteristic curve.

  18. In situ morphology studies of the mechanism for solution additive effects on the formation of bulk heterojunction films

    KAUST Repository

    Richter, Lee J.

    2014-09-29

    The most successful active film morphology in organic photovoltaics is the bulk heterojunction (BHJ). The performance of a BHJ arises from a complex interplay of the spatial organization of the segregated donor and acceptor phases and the local order/quality of the respective phases. These critical morphological features develop dynamically during film formation, and it has become common practice to control them by the introduction of processing additives. Here, in situ grazing incidence X-ray diffraction (GIXD) and grazing incidence small angle X-ray scattering (GISAXS) studies of the development of order in BHJ films formed from the donor polymer poly(3-hexylthiophene) and acceptor phenyl-C61-butyric acid methyl ester under the influence of two common additives, 1,8-octanedithiol and 1-chloronaphthalene, are reported. By comparing optical aggregation to crystallization and using GISAXS to determine the number and nature of phases present during drying, two common mechanisms by which the additives increase P3HT crystallinity are identified. Additives accelerate the appearance of pre-crystalline nuclei by controlling solvent quality and allow for extended crystal growth by delaying the onset of PCBM-induced vitrification. The glass transition effects vary system-to-system and may be correlated to the number and composition of phases present during drying. Synchrotron X-ray scattering measurements of nanoscale structure evolution during the drying of polymer-fullerene photovoltaic films are described. Changes in the number and nature of phases, as well as the order within them, reveals the mechanisms by which formulation additives promote structural characteristics leading to higher power conversion efficiencies.

  19. Dynamic mechanical properties of a maxillofacial silicone elastomer incorporating a ZnO additive: the effect of artificial aging.

    Science.gov (United States)

    Mouzakis, Dionysios E; Papadopoulos, Triantafillos D; Polyzois, Gregory L; Griniari, Panagiota G

    2010-11-01

    The main objective of the current study was to investigate the dynamic mechanical properties of a room-temperature vulcanizing silicone incorporating different fractions of zinc oxide (ZnO) after indoor and outdoor photoaging. Forty-eight samples were produced by adding different amounts of ZnO into a commercial maxillofacial silicone (EPISIL-E). The samples were divided into 4 groups containing 0.0, 0.2, 0.5, and 1 wt% ZnO additive, respectively. Samples were exposed to sunlight (subgroup 2), ultraviolet (subgroup 3), and fluorescence (subgroup 4) aging, whereas nonaged samples comprised the control subgroup (subgroup 1). Dynamic mechanical analysis was used to determine the storage modulus (E'), loss modulus (E″), and damping capacity (tanδ). General linear statistic model was conducted to evaluate the effects of aging, testing frequency, and composition on the dynamic mechanical properties of the silicone with the ZnO additive. Post hoc analysis was performed using Tukey test. Statistical analysis revealed a significant impact of composition on tanδ (P < 0.05). Aging influenced E' and E″ (P < 0.01). The combination of aging and composition had a significant effect on all dynamic properties (P < 0.01).

  20. Improvement of mechanical properties of AA1070 aluminium by the addition of borax under different holding conditions

    Energy Technology Data Exchange (ETDEWEB)

    Oeztuerk, M. [University of Gaziantep, Faculty of Engineering, Department of Mechanical Engineering, 27310, Gaziantep (Turkey); Yilmaz, N.F.

    2012-12-15

    In this study, mechanical properties of Al-B alloys, prepared by the addition of different amounts of borax to 99.70% pure commercial aluminum, were improved. The main objective is to study the influence of borax addition and holding conditions on the mechanical properties of cast Al-B alloys. In this process, amount of borax, holding temperature and holding time were realized as affecting parameters. By considering these parameters three specimens were prepared for each condition and they were subjected to mechanical tests such as tensile, impact and hardness tests. As a result of tests, tensile strength of the alloy with the incorporation of borax was found 33% increase in comparison to pure aluminum while 21% increase in impact energy and 54% in hardness value. A substantial quantity of aluminum-boride flakes were observed in the microstructural investigation of the samples. Microscopic observations of alloyed samples reveal homogeneous distribution of aluminum boride particles and fewer porosity levels. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. The effect of aluminum additions on the thermal, microstructural, and mechanical behavior of NiTiHf shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Derek Hsen Dai [Department of Materials Science and Engineering, University of Florida, 152 Rhines Hall, P.O. Box 116400, Gainesville, FL 32611 (United States); Hornbuckle, Billy Chad [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487 (United States); Valderrama, Billy; Barrie, Fatmata; Henderson, Hunter B. [Department of Materials Science and Engineering, University of Florida, 152 Rhines Hall, P.O. Box 116400, Gainesville, FL 32611 (United States); Thompson, Gregory B. [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487 (United States); Manuel, Michele V., E-mail: mmanuel@mse.ufl.edu [Department of Materials Science and Engineering, University of Florida, 152 Rhines Hall, P.O. Box 116400, Gainesville, FL 32611 (United States)

    2015-07-25

    Highlights: • We investigate the effect of aluminum on the thermomechanical properties of NiTiHf alloys. • The nanoscale structure of the alloys are investigated by advanced analytical techniques. • The Al solubility limit in NiTiHf was near 3 at.%. • Precipitation of both Heusler and Han phases are identified. • Al additions significantly affect transformation temperatures. - Abstract: Ni{sub 50}Ti{sub 30−X}Hf{sub 20}Al{sub X} (X = 0, 1, 2, 3, 4, 5 at.%) alloys were investigated using thermal, microstructural, and mechanical analysis. It was found that Al additions to this system decreased the transformation temperatures and thermal cyclic stability of the quaternary alloys. Also, the lenticular Han phase was observed in the aged 3–5% Al alloys in accordance with previous studies in literature performed at a similar aging temperature. Though no transformation was detected after DSC cycling down to −60 °C for the aged 4% and 5% Al alloys, mechanical testing confirmed pseudoelasticity. Additionally, TEM and atom probe analysis confirmed that aging at 600 °C resulted in precipitation of the Ni{sub 2}TiAl Heusler phase and determined the Al solubility limit in the matrix as near 3 at.%. Lastly, precipitation strengthening by the Heusler phase was observed when comparing the solution-treated and aged 4% and 5% Al alloys. Microstructural evolution was further characterized using XRD, SEM and compression testing.

  2. Insight into the reaction mechanisms for oxidative addition of strong σ bonds to an Al(i) center.

    Science.gov (United States)

    Zhang, Xiangfei; Cao, Zexing

    2016-06-21

    The oxidation addition of a series of σ H-X bonds (X = H, B, C, Si, N, P, and O) to a single Al(i) supported by a (NacNac)(-) bidentate ligand ((NacNac)(-) = [ArNC(Me)CHC(Me)NAr](-) and Ar = 2,6-(i)Pr2C6H3) has been explored through extensive DFT calculations. The presented results show that activation and addition of these σ bonds follow various reaction mechanisms, in which hydride transfer, proton transfer, and Al-X bond coupling steps are involved. The predicted free energy barriers for these oxidative additions range from 8 to 32 kcal mol(-1), and all the reactions are remarkably favorable thermodynamically. However, sterically hindered ligands, for most reactants, make the formation of the initial reactant complex difficult and may reduce the efficiency of the reaction. Calculations reveal a strong dependence of the reaction mechanism and low-energy channel on the bonding features of X-H and the local structural environments.

  3. Influence of time dependent longitudinal magnetic fields on the cooling process, exchange bias and magnetization reversal mechanism in FM core/AFM shell nanoparticles: a Monte Carlo study

    Science.gov (United States)

    Yüksel, Yusuf; Akıncı, Ümit

    2016-12-01

    Using Monte Carlo simulations, we have investigated the dynamic phase transition properties of magnetic nanoparticles with ferromagnetic core coated by an antiferromagnetic shell structure. Effects of field amplitude and frequency on the thermal dependence of magnetizations, magnetization reversal mechanisms during hysteresis cycles, as well as on the exchange bias and coercive fields have been examined, and the feasibility of applying dynamic magnetic fields on the particle have been discussed for technological and biomedical purposes.

  4. Reverse Logistics

    OpenAIRE

    Kulikova, Olga

    2016-01-01

    This thesis was focused on the analysis of the concept of reverse logistics and actual reverse processes which are implemented in mining industry and finding solutions for the optimization of reverse logistics in this sphere. The objective of this paper was the assessment of the development of reverse logistics in mining industry on the example of potash production. The theoretical part was based on reverse logistics and mining waste related literature and provided foundations for further...

  5. New Mechanism on Synergistic Effect of Nitrite and Triethanolamine Addition on the Corrosion of Ductile Cast Iron

    Directory of Open Access Journals (Sweden)

    K. T. Kim

    2016-01-01

    Full Text Available In general, we compared the different inhibition mechanisms of organic inhibitor with that of anodic inhibitor. When triethanolamine or nitrite was added separately to tap water for inhibiting the corrosion of ductile cast iron, large amounts of inhibitor were needed. This is because the corrosion inhibitors had to overcome the galvanic corrosion that occurs between graphite and matrix. In this work, we investigated the corrosion of ductile cast iron in tap water with/without inhibitors. The corrosion rate was measured using chemical immersion test and electrochemical methods, including anodic polarization test. The inhibited surface was analyzed using EPMA and XPS. Test solutions were analyzed by performing FT-IR measurement. When triethanolamine and nitrite coexisted in tap water, synergistic effect built up, and the inhibition effect was ca. 30 times more effective than witnessed with single addition. This work focused on the synergistic effect brought about by nitrite and triethanolamine and its novel mechanism was also proposed.

  6. Unexpected Effect of Nb Addition as a Microalloying Element on Mechanical Properties ofδ-TRIP Steels

    Institute of Scientific and Technical Information of China (English)

    Sajad Gholami SHIRI; Seyed Ahmad Jenabali JAHROMI; Yahya PALIZDAR; Majid BELBASI

    2016-01-01

    The concept of microalloying was applied to theδ-TRIP (transformation-induced plasticity)steel to inves-tigate the feasibility of increasing the mechanical properties and understanding the effect of microalloying on the morphology and structure of the steel.A hot rolledδ-TRIP steel with three different contents of Nb (0,0.03, 0.07 mass%)was subjected to the microstructural and mechanical examination.The high Al and Si concentration in these steels guaranteed the presence of the considerableδ-ferrite phase in the microstructure after the casting and the subsequent hot rolling.The obtained results showed that Nb dramatically affects the microstructure,the dynamic re-covery and recrystallization behavior,as well as the grain shape and thus the stability of austenite after the thermo-mechanical process of hot rolling.The results also revealed an unexpected effect of Nb on the mechanical properties. The addition of Nb to theδ-TRIP steel led to a significant decrease in the ultimate strength (from 1 144 to 917 MPa) and an increase in ductility (from 24% to 28%).These unconventional results could be explained by the change in the steel microstructure.The work-hardening behaviors of all samples exhibit three stages of the work-hardening rate evolution.At the stage 2,the work-hardening rate of the studied steels increased,being attributed to the TRIP effect and the transformation of austenite to martensite.

  7. studies in the relationship between molecular structure and chromatographic behaviour-III Mechanism of the reversed-phase chromatography of some alkyl phenols.

    Science.gov (United States)

    Bark, L S; Graham, R J

    1966-09-01

    It can be shown that thin-layer chromatography by the reversed-phase technique gives results which are sufficiently reproducible for correlation of Chromatographie behaviour with chemical structure to be attempted. To a first approximation the Martin additivity principle is valid, but variations in the intermolecular forces between solute molecules and solvent molecules, caused by the easy transmission of electronic effects through an aromatic system, result in deviations from ideal conditions.

  8. Porous calcium polyphosphate bone substitutes: additive manufacturing versus conventional gravity sinter processing-effect on structure and mechanical properties.

    Science.gov (United States)

    Hu, Youxin; Shanjani, Yaser; Toyserkani, Ehsan; Grynpas, Marc; Wang, Rizhi; Pilliar, Robert

    2014-02-01

    Porous calcium polyphosphate (CPP) structures proposed as bone-substitute implants and made by sintering CPP powders to form bending test samples of approximately 35 vol % porosity were machined from preformed blocks made either by additive manufacturing (AM) or conventional gravity sintering (CS) methods and the structure and mechanical characteristics of samples so made were compared. AM-made samples displayed higher bending strengths (≈1.2-1.4 times greater than CS-made samples), whereas elastic constant (i.e., effective elastic modulus of the porous structures) that is determined by material elastic modulus and structural geometry of the samples was ≈1.9-2.3 times greater for AM-made samples. X-ray diffraction analysis showed that samples made by either method displayed the same crystal structure forming β-CPP after sinter annealing. The material elastic modulus, E, determined using nanoindentation tests also showed the same value for both sample types (i.e., E ≈ 64 GPa). Examination of the porous structures indicated that significantly larger sinter necks resulted in the AM-made samples which presumably resulted in the higher mechanical properties. The development of mechanical properties was attributed to the different sinter anneal procedures required to make 35 vol % porous samples by the two methods. A primary objective of the present study, in addition to reporting on bending strength and sample stiffness (elastic constant) characteristics, was to determine why the two processes resulted in the observed mechanical property differences for samples of equivalent volume percentage of porosity. An understanding of the fundamental reason(s) for the observed effect is considered important for developing improved processes for preparation of porous CPP implants as bone substitutes for use in high load-bearing skeletal sites.

  9. Mechanical Deformation Behavior of Sn-Ag-Cu Solders with Minor Addition of 0.05 wt.% Ni

    Science.gov (United States)

    Hammad, A. E.; El-Taher, A. M.

    2014-11-01

    The aim of the present work is to develop a comparative evaluation of the microstructural and mechanical deformation behavior of Sn-Ag-Cu (SAC) solders with the minor addition of 0.05 wt.% Ni. Test results showed that, by adding 0.05Ni element into SAC solders, generated mainly small rod-shaped (Cu,Ni)6Sn5 intermetallic compounds (IMCs) inside the β-Sn phase. Moreover, increasing the Ag content and adding Ni could result in the change of the shape and size of the IMC precipitate. Hence, a significant improvement is observed in the mechanical properties of SAC solders with increasing Ag content and Ni addition. On the other hand, the tensile results of Ni-doped SAC solders showed that both the yield stress and ultimate tensile strengths decrease with increasing temperature and with decreasing strain rate. This behavior was attributed to the competing effects of work hardening and dynamic recovery processes. The Sn-2.0Ag-0.5Cu-0.05Ni solder displayed the highest mechanical properties due to the formation of hard (Cu,Ni)6Sn5 IMCs. Based on the obtained stress exponents and activation energies, it is suggested that the dominant deformation mechanism in SAC (205)-, SAC (0505)- and SAC (0505)-0.05Ni solders is pipe diffusion, and lattice self-diffusion in SAC (205)-0.05Ni solder. In view of these results, the Sn-2.0Ag-0.5Cu-0.05Ni alloy is a more reliable solder alloy with improved properties compared with other solder alloys tested in the present work.

  10. Effect of Y2O3 and Total Oxide Addition on Mechanical Properties of Pressureless Sintered β-SiC

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The effect of Y2O3 and the total oxide volume fraction (Y2O3+Al2O3) on density and mechanical properties of lowtemperature (1770~1940℃) pressureless sintered β-SiC ceramics were presented. The optimum temperature forpressureless sintering of β-SiC was found to be ~1850℃ and the optimum content of Y2O3 in the oxides was foundto be between 40 and 57 wt pct. The highest sintered density was achieved by adding oxides at 14 vol. pct. Both ofthe highest strength and fracture toughness were achieved at ~14 vol. pct oxide addition and yttria concentrationsbetween 40 and 57 wt pct in the oxides. Hardness, on the other hand, was found to be the highest for samples with14 vol. pct oxide addition and ~64 wt pct Y2O3 in oxides.

  11. Mechanical Properties and Fracture Behaviors of GTA-Additive Manufactured 2219-Al After an Especial Heat Treatment

    Science.gov (United States)

    Bai, J. Y.; Fan, C. L.; Lin, S. B.; Yang, C. L.; Dong, B. L.

    2017-03-01

    2219-Al parts were produced by gas tungsten arc-additive manufacturing and sequentially processed by an especial heat treatment. In order to investigate the effects of heat treatment on its mechanical properties, multiple tests were conducted. Hardness tests were carried out on part scale and layer scale along with tensile tests which were performed on welding and building directions. Results show that compared to conventional casting + T6 2219-Al, the current deposit + T6 2219-Al exhibits satisfying properties with regard to strength but unsatisfying results in plasticity. Additionally, anisotropy is significant. Fractures were observed and the cracks' propagating paths in both directional specimens are described. The effects of heat treatment on the cracks' initiation and propagation were also investigated. Ultimately, a revised formula was developed to calculate the strength of the deposit + T6 2219-Al. The aforementioned formula, which takes into consideration the belt-like porosities-distributing feature, can scientifically describe the anisotropic properties in the material.

  12. Theoretical study on the reaction mechanism of ozone addition to the double bonds of keto-limonene

    Institute of Scientific and Technical Information of China (English)

    Lei Jiang; Yisheng Xu; Baohui Yin; Zhipeng Bai

    2012-01-01

    The reaction mechanism of ozone (O3) addition to the double bonds of gas phase keto-limonene was investigated using ab initio methods.Two different possibilities for O3 addition to the double bond were considered and two corresponding van der Waais complexes (Complex 1 and Complex 2) were found for 1-endo and 2-endo.The rate constants were calculated using the transition state theory at the CCSD(T)/6-31G(d) + CF//B3LYP/6-31G(d,p) level.The high-pressure limit of the total rate constant at 298 K was 3.51 × 10-16cm3/(molecule.sec),which was in a good agreement with the experimental data.

  13. Crystallization, microstructure and mechanical properties of silumins with micro-additions of Cr, Mo, W and V

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2010-01-01

    Full Text Available In this paper results of the crystallization, microstructure and mechanical properties studies of hypo-, hyper- and eutectic silumins with addition of: Cr, Mo, W and V in amount of about 0,05% are presented. The influence of Sb, Sr and P together with Ti + B on the silumins crystallization process has been given. Results of: the microstructure, Rm, Rp0,2, A5 and HB testing of silumins after precipitation hardening and heat treatment in temperature of 560°C/3min and water chilling are presented.

  14. Enhancement of the Thermal Stability and Mechanical Hardness of Zr-Al-Co Amorphous Alloys by Ag Addition

    Science.gov (United States)

    Wang, Yongyong; Dong, Xiao; Song, Xiaohui; Wang, Jinfeng; Li, Gong; Liu, Riping

    2016-05-01

    The thermal and mechanical properties of Zr57Al15Co28- X Ag X ( X = 0 and 8) amorphous alloys were investigated using differential scanning calorimetry, in situ high-pressure angle dispersive X-ray diffraction measurements with synchrotron radiation, and nanoindentation. Results show that Ag doping improves effective activation energy, nanohardness, elastic modulus, and bulk modulus. Ag addition enhances topological and chemical short-range orderings, which can improve local packing efficiency and restrain long-range atom diffusion. This approach has implications for the design of the microstructure- and property-controllable functional materials for various applications.

  15. The Influence of Co Addition on Phase Transformation Behavior and Mechanical Properties of TiNi Alloys

    Institute of Scientific and Technical Information of China (English)

    JING Rui-rui; LIU Fu-shun

    2007-01-01

    The influences of Co-addition on phase transformation behavior and mechanical properties of TiNi alloys were investigated. Results indicate that, as a substitute for Ni, Co added to TiNi alloys can dramatically decrease the martensite transformation temperature,and R phase transformation and martensite transformation are accordingly separated. When Co-content reach 10 at.%, the martensite transformation temperature is lower than that of liquid nitrogen. During deformation at room temperature, Ti50Ni48Co2 alloy exhibits good ductility with a lower stress plateau caused by stress-induced martensite and martensite reorientation.

  16. Influence of silver additions to type 316 stainless steels on bacterial inhibition, mechanical properties, and corrosion resistance

    DEFF Research Database (Denmark)

    Chiang, Wen-Chi; Tseng, I-Sheng; Møller, Per;

    2010-01-01

    techniques. The microstructure of these 316 stainless steels was examined, and the influences of silver additions to 316 stainless steels on bacterial inhibition, mechanical properties, and corrosion resistance were investigated. This study suggested that silver-bearing 316 stainless steels could be used......Bacterial contamination is a major concern in many areas. In this study, silver was added to type 316 stainless steels in order to obtain an expected bacteria inhibiting property to reduce the occurrence of bacterial contamination. Silver-bearing 316 stainless steels were prepared by vacuum melting...

  17. A novel P106L mutation in EPSPS and an unknown mechanism(s) act additively to confer resistance to glyphosate in a South African Lolium rigidum population.

    Science.gov (United States)

    Kaundun, Shiv S; Dale, Richard P; Zelaya, Ian A; Dinelli, Giovanni; Marotti, Ilaria; McIndoe, Eddie; Cairns, Andrew

    2011-04-13

    Glyphosate resistance evolution in weeds is a growing problem in world agriculture. Here, we have investigated the mechanism(s) of glyphosate resistance in a Lolium rigidum population (DAG1) from South Africa. Nucleotide sequencing revealed the existence of at least three EPSPS homologues in the L. rigidum genome and identified a novel proline 106 to leucine substitution (P106L) in 52% DAG1 individuals. This mutation conferred a 1.7-fold resistance increase to glyphosate at the whole plant level. Additionally, a 3.1-fold resistance increase, not linked to metabolism or translocation, was estimated between wild-type P106-DAG1 and P106-STDS sensitive plants. Point accepted mutation analysis suggested that other amino acid substitutions at EPSPS position 106 are likely to be found in nature besides the P106/S/A/T/L point mutations reported to date. This study highlights the importance of minor mechanisms acting additively to confer significant levels of resistance to commercial field rates of glyphosate in weed populations subjected to high selection pressure.

  18. The Influence of Nickel and Tin Additives on the Microstructural and Mechanical Properties of Al-Zn-Mg-Cu Alloys

    Directory of Open Access Journals (Sweden)

    Haider T. Naeem

    2014-01-01

    Full Text Available The effects of nickel and nickel combined tin additions on mechanical properties and microstructural evolutions of aluminum-zinc-magnesium-copper alloys were investigated. Aluminum alloys containing Ni and Sn additives were homogenized at different temperatures conditions and then aged at 120°C for 24 h (T6 and retrogressed at 180°C for 30 min and then reaged at 120°C for 24 h (RRA. Comparison of the ultimate tensile strength (UTS of as-quenched Al-Zn-Mg-Cu-Ni and Al-Zn-Mg-Cu-Ni-Sn alloys with that of similar alloys which underwent aging treatment at T6 temper showed that gains in tensile strengths by 385 MPa and 370 MPa were attained, respectively. These improvements are attributed to the precipitation hardening effects of the alloying element within the base alloy and the formation of nickel/tin-rich dispersoid compounds. These intermetallic compounds retard the grain growth, lead to grain refinement, and result in further strengthening effects. The outcomes of the retrogression and reaging processes which were carried on aluminum alloys indicate that the mechanical strength and Vickers hardness have been enhanced much better than under the aging at T6 temper.

  19. Effect of copper addition on mechanical properties, corrosion resistance and antibacterial property of 316L stainless steel.

    Science.gov (United States)

    Xi, Tong; Shahzad, M Babar; Xu, Dake; Sun, Ziqing; Zhao, Jinlong; Yang, Chunguang; Qi, Min; Yang, Ke

    2017-02-01

    The effects of addition of different Cu content (0, 2.5 and 3.5wt%) on mechanical properties, corrosion resistance and antibacterial performance of 316L austenitic stainless steel (SS) after solution and aging treatment were investigated by mechanical test, transmission electron microscope (TEM), X-ray diffraction (XRD), electrochemical corrosion, X-ray photoelectron spectroscopy (XPS) and antibacterial test. The results showed that the Cu addition and heat treatment had no obvious influence on the microstructure with complete austenite features. The yield strength (YS) after solution treatment was almost similar, whereas the aging treatment obviously increased the YS due to formation of tiny Cu-rich precipitates. The pitting and protective potential of the solution treated Cu-bearing 316L SS in 0.9wt% NaCl solution increased with increasing Cu content, while gradually declined after aging, owing to the high density Cu-rich precipitation. The antibacterial test proved that higher Cu content and aging were two compulsory processes to exert good antibacterial performance. The XPS results further indicated that aging enhanced the Cu enrichment in passive film, which could effectively stimulate the Cu ions release from the surface of passive film.

  20. Effect of Grain and Calcinations Kaolin Additives on Some Mechanical and Physical properties on Low DensityPolyethylene Composites

    Directory of Open Access Journals (Sweden)

    Zanaib Y. Shnean

    2008-01-01

    Full Text Available In this work, a composite material was prepared from Low-density polyethylene (LDPE with different weight percent of grain and calcinations kaolin at temperature of (850oC using single screw extruder and a mixing machine operated at a temperature between (190-200oC. Some of mechanical and physical properties such as tensile strength, tensile strength at break, Young modulus, and elongation at break, shore hardness and water absorption were determined at different weight fraction of filler (0, 2, 7, 10 and 15%. It was found that the addition of filler increases the modulus of elasticity, elongation at break, shore hardness and impact strength; on other hand, it decreases the tensile strength and tensile strength at a break. Absorption test was carried out in water at different immersion times and different composite .The results of absorption show that it obeys Fick’s law and after the addition of kaolin the amount of absorption decrease. Calcinations kaolin filler produces better mechanical properties , than grain kaolin fillers.

  1. Quantum mechanics/molecular mechanics modeling of covalent addition between EGFR-cysteine 797 and N-(4-anilinoquinazolin-6-yl) acrylamide.

    Science.gov (United States)

    Capoferri, Luigi; Lodola, Alessio; Rivara, Silvia; Mor, Marco

    2015-03-23

    Irreversible epidermal growth factor receptor (EGFR) inhibitors can circumvent resistance to first-generation ATP-competitive inhibitors in the treatment of nonsmall-cell lung cancer. They covalently bind a noncatalytic cysteine (Cys797) at the surface of EGFR active site by an acrylamide warhead. Herein, we used a hybrid quantum mechanics/molecular mechanics (QM/MM) potential in combination with umbrella sampling in the path-collective variable space to investigate the mechanism of alkylation of Cys797 by the prototypical covalent inhibitor N-(4-anilinoquinazolin-6-yl) acrylamide. Calculations show that Cys797 reacts with the acrylamide group of the inhibitor through a direct addition mechanism, with Asp800 acting as a general base/general acid in distinct steps of the reaction. The obtained reaction free energy is negative (ΔA = -12 kcal/mol) consistent with the spontaneous and irreversible alkylation of Cys797 by N-(4-anilinoquinazolin-6-yl) acrylamide. Our calculations identify desolvation of Cys797 thiolate anion as a key step of the alkylation process, indicating that changes in the intrinsic reactivity of the acrylamide would have only a minor impact on the inhibitor potency.

  2. Mechanical and Tribological Characterization of Al-Mg2Si Composites After Yttrium Addition and Heat Treatment

    Science.gov (United States)

    Jafari Nodooshan, H. R.; Liu, Wencai; Wu, Guohua; Bahrami, A.; Pech-Canul, M. I.; Emamy, M.

    2014-04-01

    In this study, the effect of heat treatment and yttrium additions on the microstructure, mechanical properties, and tribological behavior of Al-15% Mg2Si cast composites was investigated. The microstructural study revealed the presence of both primary and secondary Mg2Si phases in all composite specimens and also Y-containing intermetallics (Al2Y phases) at higher concentrations. It was also found that Y addition does not change the size and morphology of primary Mg2Si particles considerably, but the pseudo-eutectic Mg2Si changed from a flake-like morphology to fine fibrous or rod-like one. The results show that proper content of Y additions can reduce the amount of Mg2Si phase through dissolving it into the matrix, lead to the precipitation of Al2Y phase and improve the mechanical properties. Modified composites with 0.5% Y exhibited an ultimate tensile strength (UTS) of 290 MPa with an elongation of 4.3%. After exposing the composite to solution treatment at 520 °C for 4 h, the tensile strength of the composite continuously increased with the increase of Y content, and reached the maximum at 1% Y. The maximum UTS and elongation at room temperature for the heat-treated composites are 294 MPa and 7.4%, respectively. In the cast specimen, fracture surfaces are covered by packets with coarse steps, suggesting a brittle mode of failure. Modified composites with 0.5 wt.% Y contain several cracked particles together with a few decohered primary Mg2Si particles. In solution heat-treated state, dimples present at the fracture surface are rather coarse but homogenous, showing a semi-ductile mode of fracture. Wear test results showed that the wear resistance of all specimens increases with the addition of Y up to 0.3 wt.%. Scanning electron microscopic observations of the worn surfaces revealed that the dominant wear mechanism was abrasive wear accompanied by some delamination wear mode.

  3. Effect of additive particles on mechanical, thermal, and cell functioning properties of poly(methyl methacrylate cement

    Directory of Open Access Journals (Sweden)

    Khandaker M

    2014-05-01

    Full Text Available Morshed Khandaker,1 Melville B Vaughan,2 Tracy L Morris,3 Jeremiah J White,1 Zhaotong Meng1 1Department of Engineering and Physics, 2Department of Biology, 3Department of Mathematics and Statistics, University of Central Oklahoma, Edmond, OK, USA Abstract: The most common bone cement material used clinically today for orthopedic surgery is poly(methyl methacrylate (PMMA. Conventional PMMA bone cement has several mechanical, thermal, and biological disadvantages. To overcome these problems, researchers have investigated combinations of PMMA bone cement and several bioactive particles (micrometers to nanometers in size, such as magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica. A study comparing the effect of these individual additives on the mechanical, thermal, and cell functional properties of PMMA would be important to enable selection of suitable additives and design improved PMMA cement for orthopedic applications. Therefore, the goal of this study was to determine the effect of inclusion of magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica additives in PMMA on the mechanical, thermal, and cell functional performance of PMMA. American Society for Testing and Materials standard three-point bend flexural and fracture tests were conducted to determine the flexural strength, flexural modulus, and fracture toughness of the different PMMA samples. A custom-made temperature measurement system was used to determine maximum curing temperature and the time needed for each PMMA sample to reach its maximum curing temperature. Osteoblast adhesion and proliferation experiments were performed to determine cell viability using the different PMMA cements. We found that flexural strength and fracture toughness were significantly greater for PMMA specimens that incorporated silica than for the other specimens. All additives prolonged the time taken to reach maximum curing temperature and significantly improved cell

  4. Modeling probability and additive summation for detection across multiple mechanisms under the assumptions of signal detection theory.

    Science.gov (United States)

    Kingdom, Frederick A A; Baldwin, Alex S; Schmidtmann, Gunnar

    2015-01-01

    Many studies have investigated how multiple stimuli combine to reach threshold. There are broadly speaking two ways this can occur: additive summation (AS) where inputs from the different stimuli add together in a single mechanism, or probability summation (PS) where different stimuli are detected independently by separate mechanisms. PS is traditionally modeled under high threshold theory (HTT); however, tests have shown that HTT is incorrect and that signal detection theory (SDT) is the better framework for modeling summation. Modeling the equivalent of PS under SDT is, however, relatively complicated, leading many investigators to use Monte Carlo simulations for the predictions. We derive formulas that employ numerical integration to predict the proportion correct for detecting multiple stimuli assuming PS under SDT, for the situations in which stimuli are either equal or unequal in strength. Both formulas are general purpose, calculating performance for forced-choice tasks with M alternatives, n stimuli, in Q monitored mechanisms, each subject to a non-linear transducer with exponent τ. We show how the probability (and additive) summation formulas can be used to simulate psychometric functions, which when fitted with Weibull functions make signature predictions for how thresholds and psychometric function slopes vary as a function of τ, n, and Q. We also show how one can fit the formulas directly to real psychometric functions using data from a binocular summation experiment, and show how one can obtain estimates of τ and test whether binocular summation conforms more to PS or AS. The methods described here can be readily applied using software functions newly added to the Palamedes toolbox.

  5. Review of Mechanical Properties of Ti-6Al-4V Made by Laser-Based Additive Manufacturing Using Powder Feedstock

    Science.gov (United States)

    Beese, Allison M.; Carroll, Beth E.

    2016-03-01

    Laser-based additive manufacturing (AM) of metals using powder feedstock can be accomplished via two broadly defined technologies: directed energy deposition (DED) and powder bed fusion (PBF). In these processes, metallic powder is delivered to a location and locally melted with a laser heat source. Upon deposition, the material undergoes a rapid cooling and solidification, and as subsequent layers are added to the component, the material within the component is subjected to rapid thermal cycles. In order to adopt AM for the building of structural components, a thorough understanding of the relationships among the complex thermal cycles seen in AM, the unique heterogeneous and anisotropic microstructure, and the mechanical properties must be developed. Researchers have fabricated components by both DED and PBF from the widely used titanium alloy Ti-6Al-4V and studied the resultant microstructure and mechanical properties. This review article discusses the progress to date on investigating the as-deposited and heat-treated microstructures and mechanical properties of Ti-6Al-4V structures made by powder-based laser AM using DED and PBF.

  6. Investigation into the effect of some additives on the mechanical strength, quality and thermal conductivity of clay bricks

    Science.gov (United States)

    Zaid, Adnan I. O.; Qandil, A.; Qattous, M. A. A.

    2016-08-01

    It was repeatedly reported that the clay bricks industry in Jordan is facing both weak mechanical strength and poor quality which caused marketing problems where it is expected to serve the increasing demand of housing in the country especially after the political crises in the neighboring countries Iraq and Syria. It is therefore anticipated that improvement of the mechanical strength and quality of the produced clay evaluation of the brick industry in Jordan is worth investigating. In this paper, theoretical and experimental investigation obtained from field visits to the factories producing clay bricks were carried out. Furthermore, the effect of using some additives from locally available materials namely: Battn El-Ghoul Clay, Suweileh sand and Olive extracts on the mechanical strength, thermal conductivity and surface quality of the produced bricks is investigated and discussed. The experimental results indicated that thermal conductivity, color and durability were all enhanced and the ultimate compressive strength was reduced but remained higher than the acceptable value for brickwork.

  7. Magnetization arrangement of hard magnetic phases and mechanism of magnetization and reversal magnetization of nano-composite magnets

    Institute of Scientific and Technical Information of China (English)

    LIU Xin-cai; XIE Ren; PAN Jing

    2009-01-01

    During the process of directional solidification, laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets, or die-upsetting of nano-composites, the arrangements of the easy-magnetization-axes of the hard magnetic phases (Nd_2Fe_(14)B, SmCo_5 or Sm_2Co_(17) type) in their designed directions have been studied. In Fe-Pt nano-composite magnets, attempts have been taken to promote phase transformation from disordered, soft magnetic A1 to ordered, hard magnetic L_(10) FePt phase at reduced temperatures. The dependence of the magnetization and reversal magnetization processes on the microstructures, involving the morphology and three critical sizes of particles of the FePt nano-composite magnets, are summarized. With the decrease of the nominal thickness of the anisotropic FePt film epitaxially grown on the single crystal MgO (001) substrate, the reversal magnetization process firstly changes from full domain wall displacement to partial magnetic wall pinning related to the morphology change, where the coercive force increases abruptly. The reversal magnetization process secondly changes from magnetic wall pinning to incoherent magnetization rotation associated with the particles being below the first critical size at which multi-domain particles turn into single domain ones, where the coercive force is still increased. And the reversal magnetization mode thirdly changes from incoherent to coherent rotation referred to the second critical size, where the increase of the coercive force keeps on. However, when the particle size decreases to approach the third critical size where the particles turn into the supperparamagnetic state, the coercive force begins to decrease due to the interplay of the size effect and the incomplete ordering induced by the size effect. Meanwhile, due to the size effect, Curie temperature of the ultra-small FePt particles reduces.

  8. Mechanisms of Solidification Structure Improvement of Ultra Pure 17 wt% Cr Ferritic Stainless Steel by Ti, Nb Addition

    Institute of Scientific and Technical Information of China (English)

    Yating Shan; Xinghong Luo; Xiaoqiang Hu; Shi Liu

    2011-01-01

    The grain structures and the precipitates in the solidification microstructure of the ultra pure 17 wt% Cr ferritic stainless steels with different Ti and/or Nb micro-alloying were investigated both experimentally and theoretically. It was found by the grain structure observation that the addition of Ti or Nb to the steel reduced the grain size (D) and elongation factor (E), and improved the equiaxed grain proportion (P) and globularity factor (ε). Among the four steels studied, the minimum grain size and maximum equiaxed grain proportion were obtained by jointly adding both Ti and Nb to the steel. The SEM observation indicated that several kinds of precipitations, such as TiN, MC (rich in Nb), Laves phase (Fe2Nb) and so on, formed in the corresponding steels. In addition, the results calculated using the Thermo-Calc software illustrated that TiN precipitates in the liquid at proper Ti and N contents. Meanwhile, the solidification interval (△T) was enlarged by the addition of Ti or Nb, and the effectiveness of Nb was stronger than Ti. Based on the experimental and calculation results, the mechanisms of grain refinement and increment in equiaxed grain proportion were discussed.

  9. Microstructure and Mechanical Properties of Microwave Sintered ZrO2 Bioceramics with TiO2 Addition.

    Science.gov (United States)

    Kuo, Hsien-Nan; Chou, Jyh-Horng; Liu, Tung-Kuan

    2016-01-01

    The microwave sintered zirconia ceramics with 0, 1, 3, and 5 wt% TiO2 addition at a low sintering temperature of 1300°C and a short holding time of 1 hour were investigated. Effect of contents of TiO2 addition on microstructure and mechanical properties of microwave sintered zirconia bioceramics was reported. In the sintered samples, the main phase is monoclinic zirconia (m-ZrO2) phase and minor phase is tetragonal zirconia (t-ZrO2) phase. The grain sizes increased with increasing the TiO2 contents under the sintering temperature of 1300°C. Although the TiO2 phase was not detected in the XRD pattern, Ti and O elements were detected in the EDS analysis. The presence of TiO2 effectively improved grain growth of the ZrO2 ceramics. The Vickers hardness was in the range of 125 to 300 Hv and increased with the increase of TiO2 contents. Sintering temperature dependence on the Vickers hardness was also investigated from 1150°C to 1300°C, showing the increase of Vickers hardness with the increase of the sintering temperature as well as TiO2 addition.

  10. Microstructure and Mechanical Properties of Microwave Sintered ZrO2 Bioceramics with TiO2 Addition

    Directory of Open Access Journals (Sweden)

    Hsien-Nan Kuo

    2016-01-01

    Full Text Available The microwave sintered zirconia ceramics with 0, 1, 3, and 5 wt% TiO2 addition at a low sintering temperature of 1300°C and a short holding time of 1 hour were investigated. Effect of contents of TiO2 addition on microstructure and mechanical properties of microwave sintered zirconia bioceramics was reported. In the sintered samples, the main phase is monoclinic zirconia (m-ZrO2 phase and minor phase is tetragonal zirconia (t-ZrO2 phase. The grain sizes increased with increasing the TiO2 contents under the sintering temperature of 1300°C. Although the TiO2 phase was not detected in the XRD pattern, Ti and O elements were detected in the EDS analysis. The presence of TiO2 effectively improved grain growth of the ZrO2 ceramics. The Vickers hardness was in the range of 125 to 300 Hv and increased with the increase of TiO2 contents. Sintering temperature dependence on the Vickers hardness was also investigated from 1150°C to 1300°C, showing the increase of Vickers hardness with the increase of the sintering temperature as well as TiO2 addition.

  11. Part I: Reverse-docking studies of a squaramide-catalyzed conjugate addition of a diketone to a nitro-olefin Part II: The development of ChemSort: an education game for organic chemistry

    Science.gov (United States)

    Granger, Jenna Christine

    Part 1: Reverse-docking studies of a squaramide-catalyzed conjugate addition of a diketone to a nitro-olefin. Asymmetric organocatalysis, the catalysis of asymmetric reactions by small organic molecules, is a rapidly growing field within organic synthesis. The ability to rationally design organocatalysts is therefore of increasing interest to organic chemists. Computational chemistry is quickly proving to be an extremely successful method for understanding and predicting the roles of organocatalysts, and therefore is certain to be of use in the rational design of such catalysts. A methodology for reverse-docking flexible organocatalysts to rigid transition state models of asymmetric reactions has been previously developed by the Deslongchamps group. The investigation of Rawal's squaramide-based organocatalyst for the addition of a diketone to a nitro-olefin is described, and the results of the reverse docking of Rawal's catalyst to the geometry optimized transition state models of the uncatalyzed reaction for both the R and S-product enantiomers are presented. The results of this study indicate a preference for binding of the organocatalyst to the R-enantiomer transition state model with a predicted enantiomeric excess of 99%, which is consistent with the experimental results. A plausible geometric model of the transition state for the catalyzed reaction is also presented. The success of this study demonstrates the credibility of using reverse docking methods for the rational design of asymmetric organocatalysts. Part 2: The development of ChemSort: an educational game for organic chemistry. With the advent of the millennial learner, we need to rethink traditional classroom approaches to science learning in terms of goals, approaches, and assessments. Digital simulations and games hold much promise in support of this educational shift. Although the idea of using games for education is not a new one, well-designed computer-based "serious games" are only beginning to

  12. The Effect of the Kind of Sands and Additions on the Mechanical Behaviour of S.C.C

    Science.gov (United States)

    Zeghichi, L.; Benghazi, Z.; Baali, L.

    The sand is an inert element essential in the composition of concrete; its use ensures granular continuity between the cement and gravel for better cohesion of concrete. This paper presents the results of a study that investigated the influence of sand quality on the properties of fresh and hardened self-compacting concrete (SCC). The dune sands are very fine materials characterized by a high intergranular porosity, high surface area and low fineness modulus; on the other hand crushed (manufactured) sand has a high rate into thin and irregular shapes which are influencing the workability of concrete. The amount of dune sand varies from (0% 50%, to 100%) by weight of fine aggregates. The effect of additions is also treated (blast furnace slag and lime stone) The results show that the rheological properties favour the use of dune sands; however the mechanical properties support the use of crushed sand.

  13. The Influence of Transition Metals Addition on the Corrosion Resistance of Nanocrystalline Al Alloys Produced by Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    Asiful Hossain Seikh

    2016-06-01

    Full Text Available The corrosion resistance of nanocrystalline Al, Al-10 wt. % Fe and Al-10 wt. % Fe-5 wt. % Cr alloys was investigated in 3.5% NaCl solution using cyclic potentiodynamic polarization (CPP and electrochemical impedance spectroscopy (EIS techniques. The alloys were fabricated using mechanical alloying (MA and heat induction sintering. When compared with the corrosion resistance of pure Al, the experimental results indicated that the addition of 10 wt. % Fe and 10 wt. % Fe-5 wt. % Cr to pure Al has resulted in an enhancement in the corrosion resistance of these newly fabricated alloys. The resistance to corrosion is due to enhanced microstructural stability along with the formation of stable oxide layer.

  14. Undeniable Confirmation of the syn-Addition Mechanism for Metal-Free Diboration by Using the Crystalline Sponge Method.

    Science.gov (United States)

    Cuenca, Ana B; Zigon, Nicolas; Duplan, Vincent; Hoshino, Manabu; Fujita, Makoto; Fernández, Elena

    2016-03-24

    The stereochemical outcome of the recently developed metal-free 1,2-diboration of aliphatic alkenes has, until now, only been elucidated by indirect means (e.g. derivatization). This is because classical conformational analysis of the resulting 1,2-diboranes is not viable; in the (1)H NMR spectrum the relevant (1)H resonances are broadened by (11)B, and the occurrence of the products as oily compounds precludes X-ray crystallographic analysis. Herein, the crystalline sponge method is used to display the crystal structures of the diboronic esters formed from internal E and Z olefins, evidencing the stereospecific syn addition mechanism of the reaction, which is fully consistent with the prediction from DFT calculations.

  15. Psychological Mechanism Underlying Preference Reversals in Intertemporal Choice%跨期选择中偏好反转的心理机制

    Institute of Scientific and Technical Information of China (English)

    陈海贤; 何贵兵

    2012-01-01

    通过直接测量近期和远期选择中备选项激活的情绪、间隔的时间知觉及对备选项金额差异和时间间隔的重视程度,以探究跨期选择中偏好反转产生的心理机制。结果表明:(1)近期选择中,备选项激活的情绪强度差异显著,而远期选择中两者的差异不显著;(2)近期和远期选择中,情绪强度差异和时间知觉差异能够预测偏好反转的发生。研究结果支持了偏好反转的情绪激活差异假说和时间知觉差异假说。%Preference reversals in intertemporal choice refer to the tendency of a decision maker to prefer alternative SS(Sooner-Smaller) to LL(Larger-Later) when the outcomes are near but prefer alternative LL to SS when the outcomes are distant.Preference reversals cast doubts on the DU(Discounting Utility) model,which assumed stationary preferences across time. There are three main theories about psychological mechanism underlying preference reversals.The first theory hypothesized that choices between the immediate outcome and the distant outcome activated stronger impulsive affection than choices between distant outcomes. Different impulsive affection caused reversals(Loewenstein,1996;Metcalfe Mischel,1999).The second theory hypothesized that the subject interval perception was longer in near choices than in distant choices,even though the object interval between alternatives was the same(Takahashi,Oonob, Radfordb,2008;Zauberman,Kim,Malkoc, Bettman,2009).Different interval perception caused different value discounting,which caused reversals.The third theory hypothesized that the magnitude of money (high-level construal) were more weighted whereas interval(low-level construal) was less weighted as psychology distance increased, and the varing weight of money and interval in near and distant choices caused reversals(Trope Liberman,2003,2010). The purpose of this study was to test these theories.We hypothesized that the psychological variables underlying

  16. Effects of microstructure and CaO addition on the magnetic and mechanical properties of NiCuZn ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Sea-Fue, E-mail: sfwang@ntut.edu.tw; Hsu, Yung-Fu; Liu, Yi-Xin; Hsieh, Chung-Kai

    2015-11-15

    In this study, the effects of grain size and the addition of CaCO{sub 3} on the magnetic and mechanical properties of Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics were investigated. The bending strength of the ferrites increased from 66 to 84 MPa as the grain size of the sintered ceramics decreased from 10.25 μm to 7.53 μm, while the change in hardness was insignificant. The addition of various amounts of CaCO{sub 3} densified the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics at 1075 °C. In the pure Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO{sub 3} content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe{sub 2}CaO{sub 4} was observed, together with the disappearance of the second phase CuO. The grain size of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO{sub 3} content increased from 0 to 5 wt%. Initially rising to 807 after CaCO{sub 3} addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO{sub 3} content increased. The bending strength grew linearly with the CaCO{sub 3} content and reached twice the value for the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic with an addition of 5.0 wt% CaCO{sub 3}. The initial permeability of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic decreased substantially from 402 to 103 as the addition of CaCO{sub 3} in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic was maximized at 95 for 1.0 wt% CaCO{sub 3} addition. - Highlights: • Effects of grain size and CaCO{sub 3} on the properties of NiCuZn ferrite were studied. • Bending strength increased with grain size of the ferrite but not in the hardness. • Bending strength reached a twice value for

  17. Unraveling the Fundamental Mechanisms of Solvent-Additive-Induced Optimization of Power Conversion Efficiencies in Organic Photovoltaic Devices.

    Science.gov (United States)

    Herath, Nuradhika; Das, Sanjib; Zhu, Jiahua; Kumar, Rajeev; Chen, Jihua; Xiao, Kai; Gu, Gong; Browning, James F; Sumpter, Bobby G; Ivanov, Ilia N; Lauter, Valeria

    2016-08-10

    The realization of controllable morphologies of bulk heterojunctions (BHJ) in organic photovoltaics (OPVs) is one of the key factors enabling high-efficiency devices. We provide new insights into the fundamental mechanisms essential for the optimization of power conversion efficiencies (PCEs) with additive processing to PBDTTT-CF:PC71BM system. We have studied the underlying mechanisms by monitoring the 3D nanostructural modifications in BHJs and correlated the modifications with the optical analysis and theoretical modeling of charge transport. Our results demonstrate profound effects of diiodooctane (DIO) on morphology and charge transport in the active layers. For small amounts of DIO (3 vol %), DIO facilitates a loosely packed mixed morphology with large clusters of PC71BM, leading to deterioration in PCE. Theoretical modeling of charge transport reveals that DIO increases the mobility of electrons and holes (the charge carriers) by affecting the energetic disorder and electric field dependence of the mobility. Our findings show the implications of phase separation and carrier transport pathways to achieve optimal device performances.

  18. Effect of addition of Ag nano powder on mechanical properties of epoxy/polyaminoamide adduct coatings filled with conducting polymer

    Energy Technology Data Exchange (ETDEWEB)

    Samad, Ubair Abdus [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Khan, Rawaiz [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Alam, Mohammad Asif [Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Al-Othman, Othman Y. [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Deanship of Graduate Studies, The Saudi Electric University, P. O. Box 93499, Riyadh 11673 (Saudi Arabia); Al-Zahrani, Saeed M. [Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); SABIC Polymer Research Center (SPRC) and department of chemical engineering, college of engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia)

    2015-05-22

    In this study the effect of Ag Nano powder on mechanical properties of epoxy coatings filled with optimized ratio of conducting polymers (Polyaniline and Polyppyrole) was evaluated. Bisphenol A diglycidyl ether epoxy resin (DGEBA) along with polyaminoamide adduct (ARADUR 3282-1 BD) is used as curing agent under optimized stoichiometry values. Curing is performed at room temperature with different percentages of Nano filler. Glass and steel panels were used as coating substrate. Bird applicator was used to coat the samples in order to obtain thin film with wet film thickness (WFT) of about 70-90 µm. The samples were kept in dust free environment for about 7 days at room temperature for complete curing. The coated steel panels were used to evaluate the mechanical properties of coating such as hardness, scratch and impact tests whereas coated glass panels were used for measuring pendulum hardness of the coatings. To check the dispersion and morphology of Nano filler in epoxy matrix scanning electron microscopy (SEM) was used in addition Nano indentation was also performed to observe the effect of Nano filler on modulus of elasticity and hardness at Nano scale.

  19. Effect of addition of Ag nano powder on mechanical properties of epoxy/polyaminoamide adduct coatings filled with conducting polymer

    Science.gov (United States)

    Samad, Ubair Abdus; Khan, Rawaiz; Alam, Mohammad Asif; Al-Othman, Othman Y.; Al-Zahrani, Saeed M.

    2015-05-01

    In this study the effect of Ag Nano powder on mechanical properties of epoxy coatings filled with optimized ratio of conducting polymers (Polyaniline and Polyppyrole) was evaluated. Bisphenol A diglycidyl ether epoxy resin (DGEBA) along with polyaminoamide adduct (ARADUR 3282-1 BD) is used as curing agent under optimized stoichiometry values. Curing is performed at room temperature with different percentages of Nano filler. Glass and steel panels were used as coating substrate. Bird applicator was used to coat the samples in order to obtain thin film with wet film thickness (WFT) of about 70-90 µm. The samples were kept in dust free environment for about 7 days at room temperature for complete curing. The coated steel panels were used to evaluate the mechanical properties of coating such as hardness, scratch and impact tests whereas coated glass panels were used for measuring pendulum hardness of the coatings. To check the dispersion and morphology of Nano filler in epoxy matrix scanning electron microscopy (SEM) was used in addition Nano indentation was also performed to observe the effect of Nano filler on modulus of elasticity and hardness at Nano scale.

  20. Meta-analysis of high-latitude nitrogen-addition and warming studies imply ecological mechanisms overlooked by land models

    Directory of Open Access Journals (Sweden)

    N. J Bouskill

    2014-08-01

    Full Text Available Accurate representation of ecosystem processes in land models is crucial for reducing predictive uncertainty in energy and greenhouse gas feedbacks with the atmosphere. Here we describe an observational and modeling meta-analysis approach to benchmark land models, and apply the method to the land model CLM4.5 with two versions of belowground biogeochemistry. We focused our analysis on the above and belowground high-latitude ecosystem responses to warming and nitrogen addition, and identified mechanisms absent, or poorly parameterized in CLM4.5. While the two model versions predicted similar trajectories for soil carbon stocks following both types of perturbation, other variables (e.g., belowground respiration differed from the observations in both magnitude and direction, indicating the underlying mechanisms are inadequate for representing high-latitude ecosystems. The observational synthesis attribute these differences to missing representations of microbial dynamics, characterization of above and belowground functional processes, and nutrient competition. We use the observational meta-analyses to discuss potential approaches to improving the current models (e.g., the inclusion of dynamic vegetation or different microbial functional guilds, however, we also raise a cautionary note on the selection of data sets and experiments to be included in a meta-analysis. For example, the concentrations of nitrogen applied in the synthesized field experiments (average =72 kg ha−1 yr−1 are many times higher than projected soil nitrogen concentrations (from nitrogen deposition and release during mineralization, which preclude a rigorous evaluation of the model responses to nitrogen perturbation. Overall, we demonstrate here that elucidating ecological mechanisms via meta-analysis can identify deficiencies in both ecosystem models and empirical experiments.

  1. Mechanical properties of tungsten alloys with Y{sub 2}O{sub 3} and titanium additions

    Energy Technology Data Exchange (ETDEWEB)

    Aguirre, M.V., E-mail: mariavega.aguirre@upm.es [Departamento de Tecnologias Especiales Aplicadas a la Aeronautica, Universidad Politecnica de Madrid, E.U.I.T. Aeronautica, 28040 Madrid (Spain); Martin, A.; Pastor, J.Y. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politecnica de Madrid.E.T.S. Ingenieros de Caminos, 28040 Madrid (Spain); LLorca, J. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politecnica de Madrid.E.T.S. Ingenieros de Caminos, 28040 Madrid (Spain); Instituto Madrileno de Estudios Avanzados en Materiales (Instituto IMDEA-Materiales), Ingenieros de Caminos, 28040 Madrid (Spain); Monge, M.A.; Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

    2011-10-01

    In this research the mechanical behaviour of pure tungsten (W) and its alloys (2 wt.% Ti-0.47 wt.% Y{sub 2}O{sub 3} and 4 wt.% Ti-0.5 wt.% Y{sub 2}O{sub 3}) is compared. These tungsten alloys, have been obtained by powder metallurgy. The yield strength, fracture toughness and elastic modulus have been studied in the temperature interval of 25 deg. C to 1000 deg. C. The results have shown that the addition of Ti substantially improves the bending strength and toughness of W, but it also dramatically increases the DBTT. On the other hand, the addition of 0.5% Y{sub 2}O{sub 3}, is enough to improve noticeably the oxidation behaviour at the higher temperatures. The grain size, fractography and microstructure are studied in these materials. Titanium is a good grain growth inhibitor and effective precursor of liquid phase in HIP. The simultaneous presence of Y{sub 2}O{sub 3} and Ti permits to obtain materials with low pores presence.

  2. Effect of minor Sc and Zr addition on microstructures and mechanical properties of Al-Zn-Mg-Cu alloys

    Institute of Scientific and Technical Information of China (English)

    ZOU Liang; PAN Qing-lin; HE Yun-bin; WANG Chang-zhen; LIANG Wen-jie

    2007-01-01

    Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and scanning electron microscopy, the effects of microalloying elements of Sc, Zr on the microstructure of super-high-strength Al-Zn-Mg-Cu alloys related to mechanical properties were investigated. The tensile properties and microstructures of the studied alloys under different heat treatment conditions were studied. The addition of minor Sc, Zr results in the formation of Al3(Sc,Zr) particles. These particles are highly effective in refining the microstructures, retarding recrystallization, pinning dislocations and subboundaries. The strength of Al-Zn-Mg-Cu alloys was greatly improved by simultaneously adding minor Sc, Zr, meanwhile the ductility of the studied alloys remains at a higher level. The 0.36%(Sc+Zr) alloys gain the optimal properties after 465 ℃/h solution and 120 ℃/24 h aging. The increment of strength is mainly due to strengthening of fine grain and substructure and precipitation of Al3(Sc, Zr) particles.

  3. Effects of Sc and Zr microalloying additions on the recrystallization texture and mechanism of Al–Zn–Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Ying, E-mail: csudengying@163.com; Xu, Guofu, E-mail: csuxgf66@mail.csu.edu.cn; Yin, Zhimin; Lei, Xuefeng; Huang, Jiwu

    2013-12-15

    Highlights: •Investigate texture evolution of Al–Zn–Mg/Al–Zn–Mg–Sc–Zr alloys during annealing. •Discuss the recrystallization mechanisms of Al–Zn–Mg/Al–Zn–Mg–Sc–Zr alloys. •Establish a recrystallization nucleation model. •Calculate orientation-dependent stored energies. -- Abstract: Effects of Sc and Zr microalloying additions on the recrystallization texture and mechanism during annealing were investigated in detail by the methods of X-ray diffraction macrotexture measurements and electron backscattering diffraction local orientation observations in three kinds of Al–Zn–Mg cold rolled sheets (Al–Zn–Mg, Al–Zn–Mg–0.10 wt.%Sc–0.10 wt.%Zr and Al–Zn–Mg–0.25 wt.%Sc–0.10 wt.%Zr). The results show that the texture of the three cold rolled alloys all consists of cube and rolling orientations. During recrystallization annealing in the conventional Al–Zn–Mg alloy, rolling texture gradually weakens and finally disappears and cube texture is the dominant recrystallization texture. The nucleation mechanism of the Al–Zn–Mg alloy is cube nucleation. For Al–Zn–Mg–Sc–Zr alloys, with the increase of Sc and Zr contents and annealing temperatures, the intensity of rolling texture β-fiber increases. Rolling texture is dominant in the recrystallized Al–Zn–Mg–Sc–Zr alloy. The main microstructural features of the Al–Zn–Mg–Sc–Zr alloy during annealing are that lots of disperse, coherent and nano-scaled Al{sub 3}(Sc, Zr) particles strongly pin dislocations and grain/sub-grain boundaries, inhibiting the occurrence of recovery and recrystallization. The microstructural observation results show that S and Brass orientations are the preferred nucleation orientations in the Al–Zn–Mg–Sc–Zr alloy. To calculate the orientation-dependent stored energies, a recrystallization nucleation model was established, based on a standard Read–Schockley equation. The calculated results show that S and Brass

  4. Diazepam neuroprotection in excitotoxic and oxidative stress involves a mitochondrial mechanism additional to the GABAAR and hypothermic effects.

    Science.gov (United States)

    Sarnowska, Anna; Beresewicz, Małgorzata; Zabłocka, Barbara; Domańska-Janik, Krystyna

    2009-01-01

    The aim of the present investigation was to analyze the molecular mechanism(s) of diazepam neuroprotection in two models of selective neuronal death in CA1 sector of hippocampus: in vivo following transient gerbil brain ischemia and in vitro in rat hippocampal brain slices subjected to glutamatergic (100 microM NMDA) or oxidative (30 microM tertbutyl-hydroksyperoxide (TBH)) stress. In the in vivo model the diazepam treatment (two doses of 10mg/kg i.p. 30 and 90 min after the insult) resulted in more than 60% of CA1 hippocampal neurons surviving the insult comparing with 15% in untreated animals. To test whether the protective effect of diazepam was due to the postulated drug-induced hypothermia we followed the fluxes of body temperature during postischemic reperfusion: diazepam reduced temperature from 36.6+/-1 degrees C to 33.4+/-2 degrees C. Equivalent hypothermia induced and maintained in animals after ischemia did not prevent neuronal cell loss to the same extent as diazepam did (42.8+/-9.2% and 72.4+/-14.5% of live neurons, respectively). In vitro, under constant temperature conditions, diazepam exerted neuroprotective effects following a "U-shaped" dose-response curve, with concentration efficacy window of 0.5-10 microM. Five micro-molar diazepam showed significant protection by reducing over 50% the number of (dead) propidium iodide labeled cells even in the presence of GABA(A) receptor antagonist bicuculline. Next, we have shown that diazepam reduced the efflux of cytochrome c out of mitochondria both in compromised CA1 neurons in vitro and in isolated mitochondria treated with 30 microM THB. Our results suggest that the neuroprotective action of diazepam relies on additional mechanism(s) and not solely on its hypothermic effect. We suggest that diazepam evokes neuroprotection through its central receptors located on the GABA(A) receptor complex and, possibly, through its peripheral receptor, the translocator protein TSPO (previously called the peripheral

  5. Prolonged reversal of the phencyclidine-induced impairment in novel object recognition by a serotonin (5-HT)1A-dependent mechanism.

    Science.gov (United States)

    Horiguchi, Masakuni; Miyauchi, Masanori; Neugebauer, Nichole M; Oyamada, Yoshihiro; Meltzer, Herbert Y

    2016-03-15

    Many acute treatments transiently reverse the deficit in novel object recognition (NOR) produced by subchronic treatment with the N-methyl-d-aspartate receptor non-competitive antagonist, phencyclidine (PCP), in rodents. Treatments which restore NOR for prolonged periods after subchronic PCP treatment may have greater relevance for treating the cognitive impairment in schizophrenia than those which restore NOR transiently. We examined the ability of post-PCP subchronic lurasidone, an atypical APD with potent serotonin (5-HT)1A partial agonism and subchronic tandospirone, a selective 5-HT1A partial agonist, to enable prolonged reversal of the subchronic PCP-induced NOR deficit. Rats treated with subchronic PCP (2mg/kg, twice daily for 7 days) or vehicle, followed by a 7day washout period were subsequently administered lurasidone or tandospirone twice daily for 7 days (day 15-21), and tested for NOR weekly for up to two additional weeks. Subchronic lurasidone (1, but not 0.1mg/kg) or tandospirone (5, but not 0.6mg/kg) significantly reversed the PCP-induced NOR deficit at 24h and 7days after the last injection, respectively. The effect of lurasidone persisted for one more week (day 36, 14 days after the last lurasidone dose), while tandospirone-treated rats were able to perform NOR at 7, but not 14, days after the last tandospirone dose. Co-administration of WAY100635 (0.6mg/kg), a 5-HT1A antagonist, with lurasidone, blocked the ability of lurasidone to restore NOR, suggesting that 5-HT1A receptor stimulation is necessary for lurasidone to reverse the effects of PCP. The role of dopamine, GABA and the MAPK/ERK signalling pathway in the persistent, but not indefinite, restoration of NOR is discussed.

  6. Novel high-throughput screen identifies an HIV-1 reverse transcriptase inhibitor with a unique mechanism of action.

    Science.gov (United States)

    Sheen, Chih-Wei; Alptürk, Onur; Sluis-Cremer, Nicolas

    2014-09-15

    HIV-1 resistance to zidovudine [AZT (azidothymidine)] is associated with selection of the mutations M41L, D67N, K70R, L210W, T215F/Y and K219Q/E in RT (reverse transcriptase). These mutations decrease HIV-1 susceptibility to AZT by augmenting RT's ability to excise the chain-terminating AZT-MP (AZT-monophosphate) moiety from the chain-terminated DNA primer. Although AZT-MP excision occurs at the enzyme's polymerase active site, it is mechanistically distinct from the DNA polymerase reaction. Consequently, this activity represents a novel target for drug discovery, and inhibitors that target this activity may increase the efficacy of nucleoside/nucleotide analogues, and may help to delay the onset of drug resistance. In the present study, we have developed a FRET (Förster resonance energy transfer)-based high-throughput screening assay for the AZT-MP excision activity of RT. This assay is sensitive and robust, and demonstrates a signal-to-noise ratio of 3.3 and a Z' factor of 0.69. We screened three chemical libraries (7265 compounds) using this assay, and identified APEX57219 {3,3'-[(3-carboxy-4-oxo-2,5-cyclohexadien-1-ylidene)methylene]bis[6-hydroxybenzoic acid]} as the most promising hit. APEX57219 displays a unique activity profile against wild-type and drug-resistant HIV-1 RT, and was found to inhibit virus replication at the level of reverse transcription. Mechanistic analyses revealed that APEX57219 blocked the interaction between RT and the nucleic acid substrate.

  7. Delayed onset of tricuspid valve flow in repaired tetralogy of Fallot: an additional mechanism of diastolic dysfunction and interventricular dyssynchrony

    Directory of Open Access Journals (Sweden)

    Benson Lee N

    2011-08-01

    Full Text Available Abstract Background Diastolic dysfunction of the right ventricle (RV is common after repair of tetralogy of Fallot. While restrictive physiology in late diastole has been well known, dysfunction in early diastole has not been described. The present study sought to assess the prevalence and mechanism of early diastolic dysfunction of the RV defined as delayed onset of the tricuspid valve (TV flow after TOF repair. Methods The study population consisted of 31 children with repaired TOF (mean age ± SD, 12.3 ± 4.1 years who underwent postoperative cardiovascular magnetic resonance (CMR. The CMR protocol included simultaneous phase-contrast velocity mapping of the atrioventricular valves, which enabled direct comparison of the timing and patterns of tricuspid (TV and mitral (MV valve flow. The TV flow was defined to have delayed onset when its onset was > 20 ms later than the onset of the MV flow. The TV and MV flow from 14 normal children was used for comparison. The CMR results were correlated with the findings on echocardiography and electrocardiography. Result Delayed onset of the TV flow was observed in 16/31 patients and in none of the controls. The mean delay time was 64.81 ± 27.07 ms (8.7 ± 3.2% of R-R interval. The delay time correlated with the differences in duration of the TV and MV flow (55.94 ± 32.88 ms (r = 0.90, p Conclusions Early diastolic dysfunction with delayed onset of TV flow is common after TOF repair, and is associated with reduced RV ejection fraction. It is a further manifestation of interventricular dyssynchrony and represent an additional mechanism of ventricular diastolic dysfunction.

  8. Casein Films: The Effects of Formulation, Environmental Conditions and the Addition of Citric Pectin on the Structure and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Laetitia M. Bonnaillie

    2014-07-01

    Full Text Available Thin casein films for food packaging applications reportedly possess good strength and low oxygen permeability, but low elasticity and high sensitivity to moisture. Modifying the films to target specific behaviors depending on environmental conditions can enable a variety of commercial applications for casein-based films. The mechanical properties of solvent-cast (15% solids calcium-caseinate/glycerol films (CaCas:Gly ratio of 3:1 were characterized as a function of processing and environmental conditions, including film thickness, solution formulation and ambient humidity (from 22% to 70% relative humidity (RH at ~20 °C. At constant RH, the elongation at break (EAB had a strong positive dependence on the film thickness. When RH increased, the tensile strength (TS and modulus (E decreased approximately linearly, while EAB increased. From 0.05% to 1% (w/w of citric pectin (CP was then incorporated into CaCas/Gly films following seven different formulations (mixing sequences, to alter the protein network and to evaluate the effects of CP on the tensile properties of CaCas/Gly/CP films. At constant film thickness and ~60% RH, the addition of 0.1% or 1.0% CP to the films considerably increased or decreased EAB, TS and E in different directions and to different extents, depending on the formulation, while optical micrographs also showed vastly differing network configurations, suggesting complex formulation- and stoichiometry-dependent casein-pectin interactions within the dried films. Depending on the desired film properties and utilization conditions, pectin may be a useful addition to casein film formulations for food packaging applications.

  9. Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

    Science.gov (United States)

    Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

    2016-04-01

    A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

  10. Influence of Li2Sb Additions on Microstructure and Mechanical Properties of Al-20Mg2Si Alloy

    Directory of Open Access Journals (Sweden)

    Hong-Chen Yu

    2016-03-01

    Full Text Available It is found that Li2Sb compound can act as the nucleus of primary Mg2Si during solidification, by which the particle size of primary Mg2Si decreased from ~300 to ~15–25 μm. Owing to the synergistic effect of the Li2Sb nucleus and adsorption-poisoning of Li atoms, the effect of complex modification of Li-Sb on primary Mg2Si was better than that of single modification of Li or Sb. When Li-Sb content increased from 0 to 0.2 and further to 0.5 wt.%, coarse dendrite changed to defective truncated octahedron and finally to perfect truncated octahedral shape. With the addition of Li and Sb, ultimate compression strength (UCS of Al-20Mg2Si alloys increased from ~283 to ~341 MPa and the yield strength (YS at 0.2% offset increased from ~112 to ~179 MPa while almost no change was seen in the uniform elongation. Our study offers a simple method to control the morphology and size of primary Mg2Si, which will inspire developing new Al-Mg-Si alloys with improved mechanical properties.

  11. Influence of granular strontium chloride as additives on some electrical and mechanical properties for pure polyvinyl alcohol

    Indian Academy of Sciences (India)

    A B Elaydy; M Hafez

    2010-04-01

    A matrix composed of polyvinyl-alcohol (PVA) mixed with different concentration ratios of the granular strontium chloride (SrCl2.6H2O) were prepared by casting technique method at room temperature (about 30°C). The electric and dielectric properties such as a.c. electrical conductivity by a conventional method, using Keithly 616 digital electrometer, dielectric constant, and dielectric loss were measured. Calculated equilibrium properties such as lattice constant, bulk modulus and elastic constants are in good agreement with experimental results. The calculated activation energy values agree well with experiment only when the SrCO2 molecules are allowed to displace under strain, indicating the importance of inner strain relaxation. From the elastic constants, theoretical values of the Young’s modulus, shear modulus, Poisson’s ratio, of SrCl2 are obtained. In addition mechanical properties such as Young’s modulus, creep relaxation, and energy stored properties for these samples were also determined at room temperature.

  12. Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R.A.G., E-mail: galdino.ricardo@gmail.com [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Paganotti, A.; Gama, S. [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A. [Instituto de Quimica - UNESP, Araraquara-SP (Brazil)

    2013-01-15

    The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: Black-Right-Pointing-Pointer The microstructure of Cu-Al alloy is modified in the Ag presence. Black-Right-Pointing-Pointer ({alpha} + {gamma}) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. Black-Right-Pointing-Pointer Ag-rich phase modifies the magnetic characteristics of Cu-Al-Mn alloy.

  13. The Effect of SiC Particle Addition During FSW on Microstructure and Mechanical Properties of AZ31 Magnesium Alloy

    Science.gov (United States)

    Abbasi, M.; Abdollahzadeh, A.; Bagheri, B.; Omidvar, H.

    2015-12-01

    Welding and joining of magnesium alloys exert a profound effect on magnesium application expansion, especially in ground and air transportations where large-size, complex components are required. Due to specific physical properties of magnesium, its welding requires great control. In general, the solid-state nature of friction stir welding (FSW) process has been found to produce a low concentration of defects. In the current research, specimens from AZ31 magnesium alloy were welded together using the friction stir process with previously inserted SiC powder particles in the nugget zone. In other words, during the FSW process, the pre-placed SiC particles were stirred throughout the nugget zone of the weld. The results indicated that proper values of rotation and translation speeds led to good appearance of weld zone and suitable distribution of SiC particles producing increased weld strength. The comparison of the microstructures and mechanical properties of FS-welded AZ31 with those of FS-welded one using pre-placed SiC particles showed that the addition of SiC particles decreased the grain size and increased the strength and the formability index.

  14. Reverse logistics

    NARCIS (Netherlands)

    M.P. de Brito (Marisa); S.D.P. Flapper; R. Dekker (Rommert)

    2002-01-01

    textabstractThis paper gives an overview of scientific literature that describes and discusses cases of reverse logistics activities in practice. Over sixty case studies are considered. Based on these studies we are able to indicate critical factors for the practice of reverse logistics. In addi

  15. Compositional dependence of magnetization reversal mechanism, magnetic interaction and Curie temperature of Co{sub 1−x}Sr{sub x}Fe{sub 2}O{sub 4} spinel thin film

    Energy Technology Data Exchange (ETDEWEB)

    Ghasemi, Ali, E-mail: ali13912001@yahoo.com

    2015-10-05

    Highlights: • Nanoparticles and thin films of Co{sub 1−x}Sr{sub x}Fe{sub 2}O{sub 4} were successfully synthesized by a sol–gel process. • The value of strength of interaction was enhanced from −0.23 for x = 0 to −0.75 for x = 0.5. • The magnetization reversal process for x = 0, 0.1 was almost controlled by Kondorsky models. • The reversal mechanism for x = 0.2–0.5 obey the Stoner–Wohlfarth rule. - Abstract: Co{sub 1−x}Sr{sub x}Fe{sub 2}O{sub 4}, (x varies from 0 to 0.5 in a step of 0.1) nanoparticles were formed by means of sol–gel processing method. The morphological and structural features of nanoparticles were evaluated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FE-SEM) equipped by EDS analysis, Mössbauer spectroscopy and vibrating sample magnetometer. It was found that almost narrow size distribution of nanoparticles with cation distribution occupancy preference in octahedral site was synthesized. The nanoparticles were used for addition in subsequent solution for fabricating ferrite thin films with similar mentioned chemical composition. Several techniques including FE-SEM, atomic force microscopy and vibrating sample magnetometer were employed to find the role of strontium cation distribution on the structural and magnetic properties of films. The Curie temperature, coercivity and magnetic interaction which was evaluated by Henkel plot were reduced by an increase in substitution contents. Coercivity of thin films reduced from 0.65 MA/m to 0.39 MA/m and Curie temperature declined from 690 to 455 °C. The value of strength of interaction was enhanced from −0.23 for x = 0 to −0.75 for x = 0.5. Angular dependence of coercivity proved that the magnetization reversal process was accompanied by the combination of domain wall motion and Stoner–Wohlfarth rotation, however for thin film with x = 0.2–0.5, the reversal mechanism obey the Stoner–Wohlfarth rule.

  16. Analysis of nine food additives in red wine by ion-suppression reversed-phase high-performance liquid chromatography using trifluoroacetic acid and ammonium acetate as ion-suppressors.

    Science.gov (United States)

    Zhao, Yong-Gang; Chen, Xiao-Hong; Yao, Shan-Shan; Pan, Sheng-Dong; Li, Xiao-Ping; Jin, Mi-Cong

    2012-01-01

    A reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the simultaneous determination of nine food additives, i.e., acesulfame, saccharin, caffeine, aspartame, benzoic acid, sorbic acid, stevioside, dehydroacetic acid and neotame in red wine. The effects of ion-suppressors, i.e., trifluoroacetic acid (TFA) and ammonium acetate (AmAc) on retention behavior of nine food additives in RP-HPLC separation were discussed in detail. The relationships between retention factors of solutes and volume percent of ion-suppressors in the mobile-phase systems of acetonitrile-TFA aqueous solution and acetonitrile-TFA-AmAc aqueous solution were quantitatively established, respectively. The results showed that the ion suppressors had not only an ion suppression effect, but also an organic modification effect on the acidic analytes. The baseline separation of nine food additives was completed by a gradient elution with acetonitrile-TFA(0.01%, v/v)-AmAc(2.5 mmol L(-1)) aqueous solution as the mobile phase. The recoveries were between 80.2 - 99.5% for all analytes with RSDs in the range of 1.5 - 8.9%. The linearities were in the range of 0.2 - 100.0 mg L(-1) with determination coefficients (r(2)) higher than 0.9991 for all analytes. The limits of quantification (LOQs) were between 0.53 - 0.99 mg L(-1). The applicability of the proposed method to detect and quantify food additives has been demonstrated in the analysis of 30 real samples.

  17. Forward and reverse transduction at the limit of sensitivity studied by correlating electrical and mechanical fluctuations in frog saccular hair cells.

    Science.gov (United States)

    Denk, W; Webb, W W

    1992-06-01

    The spontaneous fluctuations of the intracellular voltage and the position of the sensory hairbundle were measured concurrently using intracellular microelectrodes and an optical differential micro interferometer. Magnitude and frequency distribution of the hair bundles' spontaneous motion suggest that it consists mostly of Brownian motion. The electrical noise, however, exceeds the value expected for thermal Johnson noise by several orders of magnitude, and its frequency distribution reflects the transduction tuning properties of the hair cells. Frequently, a strong correlation was observed between the fluctuations of the hair bundle position and the intracellular electrical noise. From the properties of the correlation and from experiments involving mechanical stimulation we conclude that in most cases mechano-electrical transduction of the bundles' Brownian motion causes this correlation. Small signal transduction sensitivities ranged from 18 to 500 microV/nm. Bundle motion that was observed in response to current injection in more than half of the cells suggests the existence of a fast reverse (electro-mechanical) transduction mechanism to be common in these cells. The sensitivities could be as high as 600 pm of bundle deflection per millivolt of membrane potential change. In a significant minority (4 in 44) of cells, all showing excess electrical noise, we found 'non-causal' components of the electro-mechanical correlation, and in two of those cells narrow-band bundle motion in excess of their thermal motion at frequencies coincident with peaks in the intracellular noise was observed.

  18. STUDY OF THE IMPACT OF PHOSPHOGYPSUM ADDITIVE AND FERROUS SULPHATE SOLUTION ON THE MECHANISM OF THE MAGNESIA-BISHOFIT COMPOSITION

    Directory of Open Access Journals (Sweden)

    DEREVIANKO V. N.

    2015-11-01

    Full Text Available Problem statement. Phosphogypsum is a very pure raw material [16] with a negative, from a technical point of view, elongated shape of calcium dihydrate crystals (due to the formation conditions, which remains the same after both dehydration in dry air and grinding, this makes technical difficulties relating to further processing of the product into a binder, consequently, water resistance and plasticity of magnesium solutions can be improved by adding primary and secondary phosphates without strength reduction. Famous experts on phosphogypsum Yu. P. Meshcheryakov and N. A. Kolev [8] found, that when adding phosphogypsum instead of natural gypsum during grinding of Portland cement, which is intended to control the setting time of the mixture, there occurred reduction in the initial setting time from 1 h 55 min up to 1 h 36 min (when adding 4 % agent, and the final setting time was decreased from 6 h 15 min up to 6 min. After grinding of phosphogypsum, there appeared a fresh surface, on which the electron emission phenomenon occurs, however, not the entire surface emits, but only the active centres, where field strength reaches 108 V/cm. The positively charged active centres have low CaSO4 2H2O concentration on their surface. Purpose. Specifying the optimal amount of phosphogypsum and ferrous sulphate solution added, studying their impact on the curing mechanism of the magnesia-bishofit composition. Conclusion. To increase the sulphate compound, required for the crystallinity [10] reduction and magnesia stone sealing [4], the ferrous sulphate solution have been added to the composition formulation, ferrous sulphate anions immediately polarize free calcium ions with the formation of CaSO4∙2H2O. P. P. Budkov's experiments [8] prove that the larger the magnesia cement-to-sulphate stone ratio, the lower the setting time of the composition, and the higher the tensile strength of the stone. Moreover, V. V. Shchelyaghin [15] recommended adding ferrous

  19. High-cycle fatigue of 10M Ni-Mn-Ga magnetic shape memory alloy in reversed mechanical loading

    Science.gov (United States)

    Aaltio, I.; Soroka, A.; Ge, Y.; Söderberg, O.; Hannula, S.-P.

    2010-07-01

    Application of Ni-Mn-Ga magnetic shape memory alloys in magnetic-field-induced actuation relies on their performance in long-term high-cycle fatigue. In this paper the performance and changes in the microstructure of a Ni-Mn-Ga 10M martensite single crystal material are reported in a long-term mechanically induced shape change cycling. The longest test was run for 2 × 109 cycles at a frequency of 250 Hz and a strain amplitude of ± 1%. After the test a clear increase of the dynamic stiffness of the material was detected. Three specimens out of ten were cycled until fracture occurred and their fracture mechanism was studied. It was observed that the macroscopic crack growth took place roughly at a 45° angle with respect to the loading direction that was along the lang100rang crystallographic direction of the sample. The macroscopic fracture plane seemed to correspond roughly to the {111} crystal planes. On a microscopic scale the fracture propagated in a step-like manner at least partly along crystallographic planes. The steps at the fracture plane correspond to the {101} twin planes, with the height of steps along the lang101rang direction. The final fracture of the samples occurred in a brittle manner after the critical stress was exceeded.

  20. Structural modifications of dicationic acetylcholinesterase reactivators studied under ion-pairing mechanism in reversed-phase liquid chromatography.

    Science.gov (United States)

    Radulescu, Medeea; Kuca, Kamil; Musilek, Kamil; David, Victor

    2014-11-01

    A study focused on the chromatographic behavior of several acetylcholinesterase reactivators under ion-pairing mechanism is reported. Among these reactivators, dicationic oximes and carbamoyl-based pyridinium congeners were studied, which form ion pairs with alkylsulfonate anions. This mechanism was studied for some major experimental parameters, such as the chain length of the ion-pairing agent added to the aqueous phase, its concentration, temperature, and nature of the organic modifier from mobile phase. Retention data showed one or two possibilities of forming ion pairs and the tautomerism of the studied reactivators, for different pH values of the aqueous component. Double sigmoid shapes were obtained for the studied compounds for the dependence between retention factor and pH, indicating the possibility of one or two tautomeric equilibria: at pH close to 7 these compounds are not stable as dicationic species and they participate in the retention process as nitroso forms, which are not able to form ion pairs with alkylsulfonates. The dependences of the retention factor on the organic modifier content from mobile phase were linear. Two complementary theoretical models were used to explain the functional dependences for the retention data on the experimental parameters.

  1. SISGR -- Domain Microstructures and Mechanisms for Large, Reversible and Anhysteretic Strain Behaviors in Phase Transforming Ferroelectric Materials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu U. [Michigan Technological Univ., Houghton, MI (United States)

    2013-12-06

    This four-year project (including one-year no-cost extension) aimed to advance fundamental understanding of field-induced strain behaviors of phase transforming ferroelectrics. We performed meso-scale phase field modeling and computer simulation to study domain evolutions, mechanisms and engineering techniques, and developed computational techniques for nanodomain diffraction analysis; to further support above originally planned tasks, we also carried out preliminary first-principles density functional theory calculations of point defects and domain walls to complement meso-scale computations as well as performed in-situ high-energy synchrotron X-ray single crystal diffraction experiments to guide theoretical development (both without extra cost to the project thanks to XSEDE supercomputers and DOE user facility Advanced Photon Source).

  2. Addition of Oils to Polylactide Casting Solutions as a Tool to Tune Film Morphology and Mechanical Properties

    NARCIS (Netherlands)

    Sawalha, H.I.M.; Schroën, C.G.P.H.; Boom, R.M.

    2010-01-01

    Poly(L-lactide) (PLLA) films exhibit toughening by the addition of oils to the polymer casting. This was investigated by casting films from solution and evaporation in air; the investigated oils were linear alkanes, cyclic alkanes, and two terpenes (limonene and eugenol). The addition of the oils gr

  3. Effect of Ce-rich misch metal addition on squeeze cast microstructure and mechanical properties of AZ81 alloy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effect of cerium-rich misch metal addition on the microstructure and properties of squeeze cast magnesium alloys AZ81 was empirically investigated. The results indicate that the addition of cerium-rich misch metal modifies the microstructure gradually. With the increase of the RE addition, the amount of Mg17Al12 decreases while that of Al11(RE)3 increases, accompanied by grain refinement. When the addition reaches 1.5%, the grain refinement becomes obvious. However, when the addition exceeds 2.0%,Al11(RE)3 phase coarsens into rod shape and the grain size increases. The tensile properties of the AZ81 at both room temperature and 150℃ increase with the addition, and reach their optimal values with the addition of 1.5%. Further increase of the addition to above 2.0% decreases the tensile properties considerably. The tensile fracture of the alloy is characterized by the cleavage of the brittle second phases and ductile dimples of the matrix.

  4. Effect of Zr, Nb and Ti addition on injection molded 316L stainless steel for bio-applications: Mechanical, electrochemical and biocompatibility properties.

    Science.gov (United States)

    Gulsoy, H Ozkan; Pazarlioglu, Serdar; Gulsoy, Nagihan; Gundede, Busra; Mutlu, Ozal

    2015-11-01

    The research investigated the effect of Zr, Nb and Ti additions on mechanical, electrochemical properties and biocompatibility of injection molded 316L stainless steel. Addition of elemental powder is promoted to get high performance of sintered 316L stainless steels. The amount of additive powder plays a role in determining the sintered microstructure and all properties. In this study, 316L stainless steel powders used with the elemental Zr, Nb and Ti powders. A feedstock containing 62.5 wt% powders loading was molded at different injection molded temperature. The binders were completely removed from molded components by solvent and thermal debinding at different temperatures. The debinded samples were sintered at 1350°C for 60 min. Mechanical, electrochemical property and biocompatibility of the sintered samples were performed mechanical, electrochemical, SBF immersion tests and cell culture experiments. Results of study showed that sintered 316L and 316L with additives samples exhibited high corrosion properties and biocompatibility in a physiological environment.

  5. Comparison between Prothrombin Complex Concentrate (PCC) and Fresh Frozen Plasma (FFP) for the Urgent Reversal of Warfarin in Patients with Mechanical Heart Valves in a Tertiary Care Cardiac Center.

    Science.gov (United States)

    Fariborz Farsad, Bahram; Golpira, Reza; Najafi, Hamideh; Totonchi, Ziae; Salajegheh, Shirin; Bakhshandeh, Hooman; Hashemian, Farshad

    2015-01-01

    Fresh frozen plasma (FFP) and prothrombin complex concentrate (PCC) reverse oral anticoagulants such as Warfarin. We compared the standard dosage of FFP and PCC in terms of efficacy and safety for patients with mechanical heart valves undergoing interventional procedures while receiving Warfarin. Fifty patients were randomized (25 for each group) with mechanical heart valves [international normalized ratio (INR) >2.5]. FFP dosage was administered based on body weight (10-15 mL/Kg), while PCC dosage was administered based on both body weight and target INR. INR measurements were obtained at different time after PCC and FFP infusion. The mean ± SD of INR pre treatment was not significantly different between the PCC and FFP groups. However, over a 48-hour period following the administration of PCC and FFP, 76% of the patients in the PCC group and only 20% of the patients in the FFP group reached the INR target. Five (20%) patients in the PCC group received an additional dose of PCC, whereas 17 (68%) patients in the FFP group received a further dose of FFP (P=0.001). There was no significant difference between the two groups in Hb and Hct before and during a 48-hour period after PCC and FFP infusion. As regards safety monitoring and adverse drug reaction screening in the FFP group, the INR was high (INR > 2.5) in 86% of the patients. There was no report of hemorrhage in both groups. PCC reverses anticoagulation both effectively and safely while having the advantage of obviating the need to extra doses.

  6. An ion-imprinted functionalized SBA-15 adsorbent synthesized by surface imprinting technique via reversible addition-fragmentation chain transfer polymerization for selective removal of Ce(III) from aqueous solution.

    Science.gov (United States)

    Meng, Minjia; Meng, Xiangguo; Liu, Yan; Liu, Zhanchao; Han, Juan; Wang, Yun; Luo, Min; Chen, Rui; Ni, Liang; Yan, Yongsheng

    2014-08-15

    A novel Ce(III) ion-imprinted polymer (Ce(III)-IIP) has been prepared by surface imprinting technique with reversible addition-fragmentation chain transfer (RAFT) polymerization based on support matrix of SBA-15. The prepared adsorbent is characterized by FT-IR, XRD, SEM, TEM, nitrogen adsorption-desorption, GPC, and TGA. The results suggest that the surface imprinted polymer synthesized by RAFT is a thin layer. For adsorption experiments, Ce(III)-IIP is investigated to remove Ce(III) by column study at different flow rates, initial metal ion concentrations, and adsorption temperature. The dynamic kinetics analyses reveal that the overall adsorption process is successfully fitted with the pseudo-first-order kinetic model and the equilibrium time was 60 min. Meanwhile, the experimental data is in good agreement with Thomas model. Ce(III)-IIP has the excellent selectivity and regenerate property. Meanwhile, the proposed method has been successfully applied in the removal of Ce(III) in natural water samples with satisfactory results. All the results suggest that Ce(III)-IIP could be used as an excellent adsorbent for efficient removal of Ce(III) from aqueous solution.

  7. The influence of the "cage effect" on the mechanism of reversible bimolecular multistage chemical reactions in solutions.

    Science.gov (United States)

    Doktorov, Alexander B

    2015-08-21

    Manifestations of the "cage effect" at the encounters of reactants are theoretically treated by the example of multistage reactions in liquid solutions including bimolecular exchange reactions as elementary stages. It is shown that consistent consideration of quasi-stationary kinetics of multistage reactions (possible only in the framework of the encounter theory) for reactions proceeding near reactants contact can be made on the basis of the concepts of a "cage complex." Though mathematically such a consideration is more complicated, it is more clear from the standpoint of chemical notions. It is established that the presence of the "cage effect" leads to some important effects not inherent in reactions in gases or those in solutions proceeding in the kinetic regime, such as the appearance of new transition channels of reactant transformation that cannot be caused by elementary event of chemical conversion for the given mechanism of reaction. This results in that, for example, rate constant values of multistage reaction defined by standard kinetic equations of formal chemical kinetics from experimentally measured kinetics can differ essentially from real values of these constants.

  8. Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi'an; DAI Haiyang; ZOU Yu

    2008-01-01

    TiC based steel bonded carbides with the addition of nano TiN were prepared by vicuum sintering techniques.The microstructure was investigated using scanning electron microscopy(SEM)and transmission electron microscopy (TEM),and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides.the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.

  9. Ceramic matrix composites based on Mg-PSZ with Cr-Ni-steel-additions with improved thermo-mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Wenzel, C., E-mail: claudia.wenzel@ikgb.tu-freiberg.de [Institute of Ceramic, Glass and Construction Materials, Technische Universitaet Bergakademie Freiberg, Agricolastr. 17, D-09599 Freiberg (Germany); Aneziris, C.G., E-mail: aneziris@ikgb.tu-freiberg.de [Institute of Ceramic, Glass and Construction Materials, Technische Universitaet Bergakademie Freiberg, Agricolastr. 17, D-09599 Freiberg (Germany)

    2011-01-15

    The application of ceramic materials is limited due to their inherent brittleness. In the past years attempts have been made to improve the fracture toughness of structural ceramics by adding a secondary phase. In the present paper the influence of metastable austenitic TRIP-steel powder on the thermo-mechanical properties of magnesia partially stabilised zirconia has been investigated. Ceramic matrix composites have been prepared using slip casting technology. The sintering was performed in different argon atmospheres. The incorporation of the metastable metallic phase led to the successful generation of composite materials with advanced mechanical properties, especially after thermal shock attack.

  10. Improvements in the mechanical properties of the 18R {r_reversible} 6R high-hysteresis martensitic transformation by nanoprecipitates in CuZnAl alloys

    Energy Technology Data Exchange (ETDEWEB)

    Castro Bubani, Franco de, E-mail: franco@cab.cnea.gov.ar [Centro Atomico Bariloche (CNEA), Av. E. Bustillo km. 9,5 (8400) S.C. de Bariloche (Argentina); CONICET (Argentina); Sade, Marcos, E-mail: sade@cab.cnea.gov.ar [Centro Atomico Bariloche (CNEA), Av. E. Bustillo km. 9,5 (8400) S.C. de Bariloche (Argentina); CONICET (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo (Argentina); Lovey, Francisco, E-mail: lovey@cab.cnea.gov.ar [Centro Atomico Bariloche (CNEA), Av. E. Bustillo km. 9,5 (8400) S.C. de Bariloche (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo (Argentina)

    2012-05-01

    Highlights: Black-Right-Pointing-Pointer Mechanical properties of 6R martensite in CuZnAl are improved by nanoprecipitates. Black-Right-Pointing-Pointer Plastic deformation of 6R martensite is suppressed during 18R-6R transition. Black-Right-Pointing-Pointer 20% recoverable strain is obtained in full {beta}-18R-6R transition in single crystals. Black-Right-Pointing-Pointer 10% recoverable strain is obtained in 18R-6R transition with 150 MPa hysteresis. Black-Right-Pointing-Pointer The material could be used in mechanical damping or other applications. - Abstract: The 18R {r_reversible} 6R martensite-martensite transformation in Cu-based alloys exhibits large hysteresis, large pseudoelastic strain and weak transformation stress dependence on temperature. However, concomitant plastic deformation taking place in the 6R phase inhibits the use of these properties for applications. A novel approach to minimizing or even suppressing 6R plastic deformation during the 18R-6R transformation in CuZnAl shape-memory alloy single crystals with electronic concentration e/a = 1.48 is presented. The method is based on a thermal treatment that introduces nanoprecipitates in the alloy. Results suggest that the role of CuZnAl shape-memory alloys in engineering should be reconsidered, as many energy damping applications could benefit from the huge hysteresis associated with the 18R-6R transformation, once the 6R plastic deformation is suppressed.

  11. Reversal Effect and Mechanisms of Recombinant Human Tumor Necrosis Factor-NC Against the Doxorubicin Resistance in Leukemia K562/Doxorubicin Cells

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jing-hong; CHEN Bo-hua

    2015-01-01

    Objective: To explore the reversal effect and mechanisms of recombinant human tumor necrosis factor-NC (rhTNF-NC) against the doxorubicin (Dox) resistance in chronic myelogenous leukemia (CML) K562/Dox cells. Methods: The chemo-sensitivity of tumor cells dealt with different concentrations of rhTNF-NC to Dox was detected by tetrazolium dye assay (MTT). The intra-cellular Dox accumulation represented by lfuorescence intensity was determined by lfow cytometry (FCM) at the excitation wave length of 488 nm and emission wave length of 550 nm. The expression of multidrug resistance (MDR)-related genes and proteins was analyzed by reverse transcription polymerase chain reaction (RT-PCR) and Western blot assays. Results:After being exposed to gradually increasing concentrations of Dox for 10 consecutive months, K562/Dox cells were more resistant to Dox (nearly 132 times) than Dox-sensitive K562 cells. The IC50 of Dox for K562 and K562/Dox cells were (0.04±0.01) and (5.55±0.08) μmol/L, respectively. When K562/Dox cells were treated with rhTNF-NC at 500, 2 500 or 5 000U/mL, the IC50 of Dox was decreased to (2.22±0.34), (1.41±0.13) and (1.04±0.09) μmol/L, respectively. The concentration-response curves were moved upward by the treatment of rhTNF-NC (P Conclusion: rhTNF-NC can effectively augment the drug accumulation in tumor cells. This is due to the up-regulation of TopoIIα and down-regulation of MDR1, MRP and GSTπ at mRNA expression as well as reduction of P-gp and PKCα expression.

  12. Selective laser melting additive manufactured Inconel 718 superalloy parts: High-temperature oxidation property and its mechanisms

    Science.gov (United States)

    Jia, Qingbo; Gu, Dongdong

    2014-10-01

    This work presented a comprehensive study of high-temperature oxidation behaviors and mechanisms of Selective laser melting (SLM) processed Inconel 718 superalloy parts using different methods including isothermal oxidation testing, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The experimental results revealed that the oxidation process of the tested parts processed at a lower volumetric laser energy density experienced the severe spallation. On reasonably increasing the applied volumetric laser energy density, the oxidation kinetics of the as-produced parts obeyed a parabolic law, exhibiting the significantly improved oxidation resistance performance. The constitutional phases within the oxidation film were identified and the corresponding formation mechanisms were elucidated in detail according to the thermodynamic principles. The cross-sectional morphologies of oxidized Inconel 718 parts indicated that the oxidation microstructure mainly consisted of an external oxidation layer and an internal oxidation zone. The oxidation process was controlled by the outward diffusion of oxide forming elements and inward penetration of oxygen, by which the interaction mechanisms between the microstructures and internal oxidation zones were clarified. On the basis of the experimental results and theoretical analyses, the physical oxidation mechanisms were accordingly established to illustrate the oxidation behaviors of SLM-processed Inconel 718 parts at elevated operative temperatures.

  13. 蛋白质的反胶团萃取机制及动力学模型研究进展%Advances in Mechanism of Reverse Micelles Extraction of Proteins and Its Dynamics Model

    Institute of Scientific and Technical Information of China (English)

    李宏; 王崇均

    2011-01-01

    Reverse micelles extraction is a new method recently developed which used in the separation and purification of biological active matters (proteins,enzymes). This paper has introduced the principle and mechanism of the reverse micelle extraction of protein,the factors affecting the stability of protein in reverse micelles, the improved technology of protein reverse extraction using reverse micelles,the dynamics research of enzyme in reverse micelles and the application and prospect of reverse micelles technology.%反胶团萃取是近年发展起来的分离和纯化生化物质的新方法,本文介绍了反胶团萃取蛋白质技术的原理和机制、影响反胶团中蛋白质稳定性的因素,改进的蛋白质反萃取工艺,反胶团的酶动力学研究以及反胶团萃取技术的研究展望.

  14. Anti-Wear Performance and Mechanism of an Oil-Miscible Ionic Liquid as a Lubricant Additive

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Jun [ORNL; Bansal, Dinesh G [ORNL; Yu, Bo [ORNL; Howe, Jane Y [ORNL; Luo, Huimin [ORNL; Dai, Sheng [ORNL; Li, Huaqing [ORNL; Blau, Peter Julian [ORNL; Bunting, Bruce G [ORNL; Mordukhovich, Gregory [GM R& D and Planning, Warren, Michigan; Smolenski, Donald [GM R& D and Planning, Warren, Michigan

    2012-01-01

    An ionic liquid (IL) trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate has been investigated as a potential anti-wear lubricant additive. Unlike most other ILs that have very low solubility in non-polar fluids, this IL is fully miscible with various hydrocarbon oils. In addition, it is thermally stable up to 347 oC, showed no corrosive attack to cast iron in ambient environment, and has excellent wettability on solid surfaces (e.g., contact angle on cast iron <8o). Most importantly, this phosphonium-based IL has demonstrated effective anti-scuffing and anti-wear characteristics when blended with lubricating oils. For example, a 5 wt.% addition into a synthetic base oil eliminated the scuffing failure experienced by the neat oil and, as a result, reduced the friction coefficient by 60% and the wear rate by three orders of magnitude. A synergistic effect on wear protection was observed with the current anti-wear additive when added into a fully-formulated engine oil. Nanostructure examination and composition analysis revealed a tribo-boundary film and subsurface plastic deformation zone for the metallic surface lubricated by the IL-containing lubricants. This protective boundary film is believed to be responsible for the IL s anti-scuffing and anti-wear functionality.

  15. The mechanism of deceleration of nucleation and crystal growth by the small addition of transition metals to lithium disilicate glasses

    Science.gov (United States)

    Thieme, Katrin; Avramov, Isak; Rüssel, Christian

    2016-05-01

    The addition of small amounts of niobium or tantalum oxide to lithium disilicate glass provokes a drastic decrease of the steady-state nucleation rates and the crystal growth velocities. The viscosity of the residual glassy matrix is considered as a function of the crystallization degree in the course of a non-isothermal crystallization. For simplification, a homogeneous distribution of the added oxides in the glass matrix is assumed. While the viscosity initially decreases, it significantly increases again for higher crystallization degrees hindering crystal growth. However, it was shown that the additives are enriched at the crystal interface. Several possible reasons for the inhibition of nucleation and growth kinetics such as viscosity, interfacial energy crystal/glassy phase, thermodynamic driving force or impingement rate are discussed. Since the crystallization front is blocked by the additives the impingement rate is decreased with increasing additive concentration. Since small concentrations of Nb2O5 and Ta2O5 have a drastic effect on the nucleation, these components should be enriched at the interface crystal/glass. This will only take place, if it leads to a decrease in the interfacial energy. Since this effect alone should result in an increase of the nucleation rate, it must be overcompensated by kinetic effects.

  16. Effect of niobium addition on mechanical properties of hot rolled TRIP-aided steel sheets for automotive application

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Shunichi [CBMM Asia Co., Ltd., Tokyo (Japan); Ikeda, Shushi [Kobe Steel Ltd. (Japan); Sugimoto, Koh-ichi [Shinshu Univ., Nagano (Japan); Miyake, Syugo [Kobelco Research Inst., Inc., Kakogawa (Japan)

    2005-07-01

    The application of advanced high strength steel sheets such as TRIP-aided steel and DP steel have been progressed to meet the automobile industry's need for weight reduction. Automobile makers have asked for formable high strength steel sheets of 780 MPa TS grade for suspensions and structural parts. TRIP-aided steel is one of the most promising candidates which contribute to both car weight reduction and the improvement of crash worthiness. Based on the above mentioned back ground, the development of high TS grade steel sheets was carried out by taking into account the addition of Nb and Mo to 0.2%C-1.5%Si-1.5%Mn steel and coiling conditions after hot rolling. In addition to hot rolling experiment, in order to understand the effect of alloying elements and bainite transformation condition exactly, cold rolled sheets were heat treated and tensile tested. The results reveal that the addition of 0.05%Nb can attain higher elongation with higher strength compared with Hb-free steel. The obtained tensile strength in this steel was higher than 780MPa. The same behavior was confirmed by the simulated heat treatment from austenite region annealing. The good ductility in 0.05%Nb containing steel was mainly obtained by large volume fraction and high carbon concentration of retained austenite. In addition, finely dispersed retained austenite made some contribution to the improvement of ductility. (orig.)

  17. The mechanism of deceleration of nucleation and crystal growth by the small addition of transition metals to lithium disilicate glasses.

    Science.gov (United States)

    Thieme, Katrin; Avramov, Isak; Rüssel, Christian

    2016-05-06

    The addition of small amounts of niobium or tantalum oxide to lithium disilicate glass provokes a drastic decrease of the steady-state nucleation rates and the crystal growth velocities. The viscosity of the residual glassy matrix is considered as a function of the crystallization degree in the course of a non-isothermal crystallization. For simplification, a homogeneous distribution of the added oxides in the glass matrix is assumed. While the viscosity initially decreases, it significantly increases again for higher crystallization degrees hindering crystal growth. However, it was shown that the additives are enriched at the crystal interface. Several possible reasons for the inhibition of nucleation and growth kinetics such as viscosity, interfacial energy crystal/glassy phase, thermodynamic driving force or impingement rate are discussed. Since the crystallization front is blocked by the additives the impingement rate is decreased with increasing additive concentration. Since small concentrations of Nb2O5 and Ta2O5 have a drastic effect on the nucleation, these components should be enriched at the interface crystal/glass. This will only take place, if it leads to a decrease in the interfacial energy. Since this effect alone should result in an increase of the nucleation rate, it must be overcompensated by kinetic effects.

  18. Diastereoselective Addition of α-Metalated Sulfoxides to Imines Revisited: Mechanism, Computational Studies, and the Effect of External Chiral Ligands

    DEFF Research Database (Denmark)

    Pedersen, Brian; Rein, Tobias; Søtofte, Inger;

    2003-01-01

    Some new results on asymmetric synthesis via the addition of a-metalated methyl tolyl sulfoxides to imines are presented. Good diastereoselectivity (up to > 98% d.e. for product 3g) can be obtained under conditions of kinetic control (short reaction time, low temperature). The transition state (a...

  19. Design for Additive Manufacturing Considerations for Self-Actuating Compliant Mechanisms Created via Multi-Material PolyJet 3D Printing

    OpenAIRE

    Meisel, Nicholas Alexander

    2015-01-01

    The work herein is, in part, motivated by the idea of creating optimized, actuating structures using additive manufacturing processes (AM). By developing a consistent, repeatable method for designing and manufacturing multi-material compliant mechanisms, significant performance improvements can be seen in application, such as increased mechanism deflection. There are three distinct categories of research that contribute to this overall motivating idea: 1) investigation of an appropriate mult...

  20. Effect of Dy addition on mechanical and magnetic properties of Mn-rich Ni-Mn-Ga ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gao, L., E-mail: lgao@shou.edu.cn [College of Engineering Science and Technology, Shanghai Ocean University, Shanghai 201306 (China); Dong, G.F. [Department of Physics, Dalian University, Dalian 116622 (China); Gao, Z.Y.; Cai, W. [School of Materials Science and Engineering, P.O. Box 405, Harbin Institute of Technology, Harbin, 150001 (China)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer The Dy addition significantly improves the compressive properties of Ni-Mn-Ga alloy. Black-Right-Pointing-Pointer The mechanism of the improved mechanical properties by adding Dy is discussed. Black-Right-Pointing-Pointer Dy doping results in a change of the fracture type of Ni-Mn-Ga alloy. Black-Right-Pointing-Pointer Curie temperature almost remained unchanged at low Dy content and then decreases. - Abstract: The effects of partial substitution of rare earth Dy for Ga on the mechanical and magnetic properties of Mn-rich Ni{sub 50}Mn{sub 29}Ga{sub 21-x}Dy{sub x} (0 {<=} x {<=} 5) ferromagnetic shape memory alloys were investigated in detail. The results show that an appropriate amount of Dy addition significantly improves the mechanical properties of Ni-Mn-Ga alloy. With an increase in Dy content, the compressive strength enhances rapidly at first and then becomes stable when the Dy content is more than 1 at.%. However, the compressive strain increases dramatically and reaches a maximum value with 1 at.% Dy addition. Further increase in Dy content makes the compressive strain of the alloys decrease gradually. The mechanism of the improved mechanical properties is also discussed. Moreover, Dy doping changes the fracture type from intergranular fracture of Ni-Mn-Ga alloy to transgranular cleavage fracture of Ni-Mn-Ga-Dy alloys. The Curie temperature remains almost unchanged at low Dy content and subsequently decreases.

  1. Processing, Mechanical and Optical Properties of Additive-Free ZrC Ceramics Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Clara Musa

    2016-06-01

    Full Text Available In the present study, nearly fully dense monolithic ZrC samples are produced and broadly characterized from microstructural, mechanical and optical points of view. Specifically, 98% dense products are obtained by Spark Plasma Sintering (SPS after 20 min dwell time at 1850 °C starting from powders preliminarily prepared by Self-propagating High-temperature Synthesis (SHS followed by 20 min ball milling. A prolonged mechanical treatment up to 2 h of SHS powders does not lead to appreciable benefits. Vickers hardness of the resulting samples (17.5 ± 0.4 GPa is reasonably good for monolithic ceramics, but the mechanical strength (about 250 MPa up to 1000 °C could be further improved by suitable optimization of the starting powder characteristics. The very smoothly polished ZrC specimen subjected to optical measurements displays high absorption in the visible-near infrared region and low thermal emittance at longer wavelengths. Moreover, the sample exhibits goodspectral selectivity (2.1–2.4 in the 1000–1400 K temperature range. These preliminary results suggest that ZrC ceramics produced through the two-step SHS/SPS processing route can be considered as attractive reference materials for the development of innovative solar energy absorbers.

  2. Reversible Computing

    Science.gov (United States)

    1980-02-01

    will have been introduced. 9. Reversible celular autemata We shall assume the reader to have some familiarity with the concept of cel- lular...10003 Mr. Kin B. Thcmpson 1 copy Technical Director Information Systems Divisia.i Naval Research Laboratory (OP-91T) Technical Information Division

  3. The Effects of Hydroxyapatite Addition on the Properties of the Mechanically Alloyed and Sintered Mg-RE-Zr Alloy

    Science.gov (United States)

    Kowalski, K.; Nowak, M.; Jakubowicz, J.; Jurczyk, M.

    2016-10-01

    This paper discusses the influence of the chemical composition on the microstructure, mechanical and corrosion properties of mechanically alloyed and sintered (Mg-4Y-5.5Dy-0.5Zr)- x wt.% HA composites. Mechanical alloying for 25 h of the Mg-4Y-5.5Dy-0.5Zr composition, followed by sintering under argon at 550 °C for 2 h, led to the formation of a bulk alloy with an ultrafine grained microstructure. With the increase of the hydroxyapatite content in the (Mg-4Y-5.5Dy-0.5Zr)- x wt.% HA composite, a reduction of the grain sizes of the bulk material was noticeable. In the case of the bulk (Mg-4Y-5.5Dy-0.5Zr)-10 wt.% HA composite, the grain sizes of approx. 60 nm have been recorded by atomic force microscopy. The final microstructure of the synthesized composites strongly influenced the mechanical and corrosion properties. The Mg-4Y-5.5Dy-0.5Zr alloy was characterized by higher average values of Young's modulus (36.6 GPa). In the case of the (Mg-4Y-5.5Dy-0.5Zr)-5 wt.% HA scaffolds with the porosity of 48%, the Young's modulus was equal to 7.1 GPa. The (Mg-4Y-5.5Dy-0.5Zr)-10 wt.% HA composite was more corrosion resistant ( I c = 5.849 × 10-5 A cm-2, E c = -1.565 V versus SCE) than Mg-4Y-5.5Dy-0.5Zr alloy ( I c = 4.838 × 10-4 A cm-2, E c = -1.555 V versus SCE). The influence of hydrofluoric acid treatment on the corrosion behavior of the (Mg-4Y-5.5Dy-0.5Zr)-5 wt.% HA composite was also investigated. The electrochemical test showed that the corrosion resistance of fluoride-treated specimens was higher, compared with the untreated samples in the Ringer's solution. In conclusion, fluoride-treated (Mg-4Y-5.5Dy-0.5Zr)-HA composites are biodegradable materials with adjustable mechanical and corrosive properties.

  4. Resistance of Escherichia coli to nourseothricin (streptothricin): reduced penetrability of the cell wall as an additional, possibly unspecific mechanism.

    Science.gov (United States)

    Seltmann, G

    1989-01-01

    The resistance of E. coli strains to the antibiotic nourseothricin is known to be caused by an acetyltransferase acetylating the beta-lysine chain of the antibiotic. In addition, most of the resistant strains exhibit reduced penetrability of the outer membrane, presumably caused by a reduced amount of available negative charges. This was shown using crystal violet, Congo red, or the hydrophobic antibiotic novobiocin as indicators.

  5. The Molecular Mechanism of the Supra-Additive Response of Prostate Cancer to Androgen Ablation and Radiotherapy

    Science.gov (United States)

    2001-02-01

    months, 6 months, 1 year and 2 years after completion of treatment. In addition, a more specific questionaire designed to assess radiotherapy sexual ... Health and Human Services; Grant numbers: CA 06294, CA 16672; Grant sponsor: DOD; Grant number: DAMD 17-98-1-8483; Grant sponsor: Prostate Cancer...16672 awarded construct (Ad5-p53). A key question was whether Ad5-p53 by the National Cancer Institute, United States Department of Health and Human

  6. Thermo-mechanic and sensory properties of wheat and rye breads produced with varying concentration of the additive

    Directory of Open Access Journals (Sweden)

    Demin Mirjana A.

    2013-01-01

    Full Text Available The effects of different concentrations of the complex additive containing emulsifiers, oxido-reductive substances and enzymes, on the rheological conditions of dough, and on the sensory properties of three groups of bread were investigated. The best initial quality and the lowest degree of protein network weakening had the dough obtained from mixed wheat and rye flours. The best expected baking properties were shown by the white wheat flour due to the least damage of its starch. The use of the additive has an effect on the absorption of water and on the majority of C-values of all sorts of flour. The amount of additive had a significant effect on the sensory properties of wheat bread crumb texture. Also, storage duration significantly affected (p <0.01 the sensory properties of integral wheat bread aroma-taste and the weighted mean score. The interaction of these two factors had no significant effect on any of sensory properties of the investigated groups of bread.

  7. The Effect and Mechanism of Nano-Cu Lubricating Additives on the Electroless Deposited Ni-W-P Coating

    Institute of Scientific and Technical Information of China (English)

    CHEN Min; JIANG Xiaomin; ZHAO Zuxin; HUANG Xiaobo

    2012-01-01

    The coating and deposition process with excellent anti wear and suitable for industrial application were developed,and the optimum bath composition and process were obtained by studying the influence of the bath composition,temperature and pH value on the deposition rate and the plating solution stability.Moreover,the tribological properties of nano-Cu lubricating additives and electroless deposited Ni-W-P coating as well as their synergistic effect are researched using ring-block abrasion testing machine and energy dispersive spectrometer.Research results show that Ni-W-P alloy coating and nano-Cu lubricating additive have excellent synergistic effect,e g,the wear resistance of Ni-W-P alloy coating (with heat treatment and the oil with nano-Cu additives) has increased hundreds times than 45 steel as the metal substrate with the basic oil,and zero wear is achieved,which breaks through the bottleneck of previous separate research of the above-mentioned two aspects.

  8. The Effect of Commercial Rice Husk Ash Additives on the Porosity, Mechanical Properties, and Microstructure of Alumina Ceramics

    OpenAIRE

    Mohammed Sabah Ali; M.A. Azmah Hanim; S. M. Tahir; C. N.A. Jaafar; Norkhairunnisa Mazlan; Khamirul Amin Matori

    2017-01-01

    A porous ceramic is made from composite materials which consist of alumina and commercial rice husk ash. This type of ceramics is obtained by mixing the commercial rice husk ash as a source of silica (SiO2) and a pore forming agent with alumina (Al2O3) powder. To obtain this type of ceramic, a solid-state technique is used with sintering at high temperature. This study also investigated the effects of the rice husk ash ratios on the mechanical properties, porosity, and microstructure. The res...

  9. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRAFINE WC/Co CEMENTED CARBIDES WITH CUBIC BORON NITRIDE AND Cr₃C₂ ADDITIONS

    Directory of Open Access Journals (Sweden)

    Genrong Zhang

    2016-03-01

    Full Text Available This study investigates the microstructure and mechanical properties of ultrafine tungsten carbide and cobalt (WC/Co cemented carbides with cubic boron nitride (CBN and chromium carbide (Cr₃C₂ fabricated by a hot pressing sintering process. This study uses samples with 8 wt% Co content and 7.5 vol% CBN content, and with different Cr₃C₂ content ranging from 0 to 0.30 wt%. Based on the experimental results, Cr₃C₂ content has a significant influence on inhibiting abnormal grain growth and decreasing grain size in cemented carbides. Near-full densification is possible when CBN-WC/Co with 0.25 wt% Cr₃C₂ is sintered at 1350°C and 20 MPa; the resulting material possesses optimal mechanical properties and density, with an acceptable Vickers hardness of 19.20 GPa, fracture toughness of 8.47 MPa.m1/2 and flexural strength of 564 MPa.u̇ Å k⃗

  10. Gene expression suggests double-segmental and single-segmental patterning mechanisms during posterior segment addition in the beetle Tribolium castaneum.

    Science.gov (United States)

    Janssen, Ralf

    2014-01-01

    In the model arthropod Drosophila, all segments are patterned simultaneously in the blastoderm. In most other arthropods, however, posterior segments are added sequentially from a posterior segment addition zone. Posterior addition of single segments likely represents the ancestral mode of arthropod segmentation, although in Drosophila, segments are patterned in pairs by the pair-rule genes. It has been shown that in the new model insect, the beetle Tribolium, a segmentation clock operates that apparently patterns all segments in pairs as well. Here, I report on the expression of the segment polarity gene H15/midline in Tribolium. In the anterior embryo, segmental stripes of H15 appear in pairs, but in the posterior of the embryo stripes appear in a single-segmental periodicity. This implies that either two completely different segmentation-mechanisms may act in the germ band of Tribolium, that the segmentation clock changes its periodicity during development, or that the speed in which posterior segments are patterned changes. In any case, the data suggest the presence of another (or modified), yet undiscovered, mechanism of posterior segment addition in one of the best-understood arthropod models. The finding of a hitherto unrecognized segmentation mechanism in Tribolium may have major implications for the understanding of the origin of segmentation mechanisms, including the origin of pair rule patterning. It also calls for (re)-investigation of posterior segment addition in Tribolium and other previously studied arthropod models.

  11. The influence of α-Al2O3 addition on microstructure, mechanical and formaldehyde adsorption properties of fly ash-based geopolymer products.

    Science.gov (United States)

    Huang, Yi; Han, Minfang

    2011-10-15

    Fly ash-based geopolymer with α-Al(2)O(3) addition were synthesized and used to remove formaldehyde from indoor air. The microstructure, mechanical and formaldehyde adsorption properties of the geopolymer products obtained were investigated. The results showed that α-Al(2)O(3) addition with appropriate amount (such as 5 wt%) increased the geopolymerization extent, resulting in the increase of surface area and compressive strength. In addition, the improvement of structural ordering level for geopolymer sample with 5 wt% α-Al(2)O(3) addition was found through FTIR analysis. By contrast, excessive addition (such as 10 wt%) had the opposite effect. The test of formaldehyde adsorption capacity confirmed that fly ash-based geopolymer product exhibited much better property of adsorbing indoor formaldehyde physically and chemically than fly ash itself. The surface area was an important but not unique factor influencing the adsorption capacity of geopolymers.

  12. Characterization of mechanics and cytocompatibility of fibrin-genipin annulus fibrosus sealant with the addition of cell adhesion molecules.

    Science.gov (United States)

    Guterl, Clare C; Torre, Olivia M; Purmessur, Devina; Dave, Khyati; Likhitpanichkul, Morakot; Hecht, Andrew C; Nicoll, Steven B; Iatridis, James C

    2014-09-01

    There is an unmet clinical need for a biomaterial sealant capable of repairing small annulus fibrosus (AF) defects. Causes of these defects include painful intervertebral disc herniations, microdiscectomy procedures, morbidity associated with needle puncture injury from discography, and future nucleus replacement procedures. This study describes the enhancements of a fibrin gel through genipin crosslinking (FibGen) and the addition of the cell adhesion molecules (CAMs), fibronectin and collagen. The gel's performance as a potential AF sealant is assessed using a series of in vitro tests. FibGen gels with CAMs had equivalent adhesive strength, gene expression, cytomorphology, and cell proliferation as fibrin alone. However, FibGen gels had enhanced material behaviors that were tunable to higher shear stiffness values and approximated human annulus tissue as compared with fibrin alone, were more dimensionally stable, and had a slower in vitro degradation rate. Cytomorphology of human AF cells cultured on FibGen gels exhibited increased elongation compared with fibrin alone, and the addition of CAMs to FibGen did not significantly affect elongation. This FibGen gel offers the promise of being used as a sealant material to repair small AF defects or to be used in combination with other biomaterials as an adhesive for larger defects.

  13. The improved mechanical properties of β-CaSiO3 bioceramics with Si3N4 addition.

    Science.gov (United States)

    Pan, Ying; Zuo, Kaihui; Yao, Dongxu; Yin, Jinwei; Xin, Yunchuan; Xia, Yongfeng; Liang, Hanqin; Zeng, Yuping

    2015-03-01

    The motivation of this study is to investigate the effect of Si3N4 addition on the sinterability of β-CaSiO3 ceramics. β-CaSiO3 ceramics with different content of Si3N4 were prepared at the sintering temperature ranging from 1000°C to 1150°C. The results showed that Si3N4 can be successfully used as sintering additive by being oxidized to form SiO2. The β-CaSiO3 ceramics with 3wt% Si3N4 sintered at 1100°C revealed flexural strength, hardness and fracture toughness of 157.2MPa, 4.4GPa and 2.3MPam(1/2) respectively, which was much higher than that of pure β-CaSiO3 ceramics (41.1MPa, 1.0GPa, 1.1MPam(1/2)). XRD analysis and SEM observation indicated that the main phase maintained to be β-phase after sintering.

  14. Effects of h-BN addition on microstructures and mechanical properties of β-CaSiO3 bioceramics.

    Science.gov (United States)

    Pan, Ying; Yao, Dongxu; Zuo, Kaihui; Xia, Yongfeng; Yin, Jinwei; Liang, Hanqin; Zeng, Yuping

    2016-09-01

    The main purpose of this study consists in investigating the effects of h-BN addition on the sinterability of β-CaSiO3 (β-CS) bioceramics. β-CS bioceramics with different contents of h-BN were prepared at the sintering temperature ranging from 800°C to 1100°C. The results showed that h-BN can be successfully used as sintering additive by being oxidized to form low melting point B2O3 related glassy phase and enhanced the flexural strength by the formation of rod-like β-CS grains. β-CS bioceramics with 1wt% h-BN sintered at 1000°C revealed flexural strength and fracture toughness of 182.2MPa and 2.4MPam(1/2) respectively, which were much higher than that of pure β-CS bioceramics (30.2MPa, 0.53MPam(1/2)) fabricated in the same processing condition.

  15. Influence of Tin Additions on the Phase-Transformation Characteristics of Mechanical Alloyed Cu-Al-Ni Shape-Memory Alloy

    Science.gov (United States)

    Saud, Safaa N.; Hamzah, E.; Abubakar, T.; Bakhsheshi-Rad, H. R.; Mohammed, M. N.

    2016-10-01

    The influence of the addition of Sn to Cu-Al-Ni alloy as a fourth element with different percentages of 0.5, 1.0, and 1.5 wt pct on the microstructure, phase-transformation temperatures, mechanical properties, and corrosion behaviors was investigated. The modified and unmodified alloys were fabricated by mechanical alloying followed by microwave sintering. The sintered and homogenized alloys of Cu-Al-Ni- xSn shape-memory alloys had a refined particle structure with an average particle size of 40 to 50 µm associated with an improvement in the mechanical properties and corrosion resistance. With the addition of Sn, the porosity density tends to decrease, which can also lead to improvements in the properties of the modified alloys. The minimum porosity percentage was observed in the Cu-Al-Ni-1.0 wt pct Sn alloy, which resulted in enhancing the ductility, strain recovery, and corrosion resistance. Further increasing the Sn addition to 1.5 wt pct, the strength of the alloy increased because the highest volume fraction of precipitates was formed. Regarding the corrosion behavior, addition of Sn up to 1 wt pct increased the corrosion resistance of the base SMA from 2.97 to 19.20 kΩ cm2 because of formation of a protective film that contains hydrated tin oxyhydroxide, aluminum dihydroxychloride, and copper chloride on the alloy. However, further addition of Sn reduced the corrosion resistance.

  16. Investigation on the effect of titanium (Ti) addition to the Mg- AZ31 alloy in the as cast and after extrusion conditions on its metallurgical and mechanical characteristics

    Science.gov (United States)

    Zaid, Adnan I. O.; Raghad; Hememat, S.

    2016-08-01

    Magnesium-aluminum alloys are versatile materials which are used in manufacturing a number of engineering and industrial parts in the automobile and aircraft industries due to their strength - to -weight -ratios. Against these preferable characteristics, magnesium is difficult to deform at room temperature; therefore it is alloyed with other elements mainly aluminum and zinc to add some required properties particularly to achieve high strength -to- weight ratio. Grain refinement is an important technology to improve the mechanical propertiesand the microstructure uniformity of the alloys. Most of the published work on grain refinement was directed toward grain refining aluminum and zinc alloys; however, the effect of the addition of rare earth material on the grain size or the mechanical behavior of Mg alloys is rare. In this paper the effect of Ti addition on the grain size, mechanical behavior, ductility, extrusion force and energy, of Mg-AZ31 alloy both in the as cast condition and after direct extrusion is investigated.

  17. Structural Mechanism Underpinning Cross-reactivity of a CD8+ T-cell Clone That Recognizes a Peptide Derived from Human Telomerase Reverse Transcriptase*

    Science.gov (United States)

    Cole, David K.; van den Berg, Hugo A.; Lloyd, Angharad; Crowther, Michael D.; Beck, Konrad; Ekeruche-Makinde, Julia; Miles, John J.; Bulek, Anna M.; Dolton, Garry; Schauenburg, Andrea J.; Wall, Aaron; Fuller, Anna; Clement, Mathew; Laugel, Bruno; Rizkallah, Pierre J.; Wooldridge, Linda; Sewell, Andrew K.

    2017-01-01

    T-cell cross-reactivity is essential for effective immune surveillance but has also been implicated as a pathway to autoimmunity. Previous studies have demonstrated that T-cell receptors (TCRs) that focus on a minimal motif within the peptide are able to facilitate a high level of T-cell cross-reactivity. However, the structural database shows that most TCRs exhibit less focused antigen binding involving contact with more peptide residues. To further explore the structural features that allow the clonally expressed TCR to functionally engage with multiple peptide-major histocompatibility complexes (pMHCs), we examined the ILA1 CD8+ T-cell clone that responds to a peptide sequence derived from human telomerase reverse transcriptase. The ILA1 TCR contacted its pMHC with a broad peptide binding footprint encompassing spatially distant peptide residues. Despite the lack of focused TCR-peptide binding, the ILA1 T-cell clone was still cross-reactive. Overall, the TCR-peptide contacts apparent in the structure correlated well with the level of degeneracy at different peptide positions. Thus, the ILA1 TCR was less tolerant of changes at peptide residues that were at, or adjacent to, key contact sites. This study provides new insights into the molecular mechanisms that control T-cell cross-reactivity with important implications for pathogen surveillance, autoimmunity, and transplant rejection. PMID:27903649

  18. A New-type of Cermets Cutter with Nano-TiN Addition: Microstructure, Mechanical and Cutting Properties

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The microstructure and mechanical properties of a new- type of cermets cutter ( tool A ) with nano- TiN modification and its cutting properties in cutting gray cast iron are investigated.SEM and TEM observations of the microstructure of the above material reveal that nano- TiN modified cermets possess a finer microstructure than conventional cermets .In the cutting tests, for comparison, cemented carbide cutter ( YG8 , tool B) was also utilized.The cutting results show that the cutting properties of tool A are superior to those of tool B.It is also found that the predominant failure mode of tool A is normal wear and micro-spalling under lower cutting quantities, and that chipping occurs under higher cutting quantities.SEM analysis reveals that cohesion, oxidation and diffusion wear become very apparent at a higher cutting speed.On the contrary, grain wear also exists but is not apparent.

  19. Modeling the mechanical and aging properties of silicone rubber and foam - stockpile-historical & additively manufactured materials

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, A; Weisgraber, T H; Gee, R H

    2014-09-30

    M97* and M9763 belong to the M97xx series of cellular silicone materials that have been deployed as stress cushions in some of the LLNL systems. Their purpose of these support foams is to distribute the stress between adjacent components, maintain relative positioning of various components, and mitigate the effects of component size variation due to manufacturing and temperature changes. In service these materials are subjected to a continuous compressive strain over long periods of time. In order to ensure their effectiveness, it is important to understand how their mechanical properties change over time. The properties we are primarily concerned about are: compression set, load retention, and stress-strain response (modulus).

  20. The Effect of Commercial Rice Husk Ash Additives on the Porosity, Mechanical Properties, and Microstructure of Alumina Ceramics

    Directory of Open Access Journals (Sweden)

    Mohammed Sabah Ali

    2017-01-01

    Full Text Available A porous ceramic is made from composite materials which consist of alumina and commercial rice husk ash. This type of ceramics is obtained by mixing the commercial rice husk ash as a source of silica (SiO2 and a pore forming agent with alumina (Al2O3 powder. To obtain this type of ceramic, a solid-state technique is used with sintering at high temperature. This study also investigated the effects of the rice husk ash ratios on the mechanical properties, porosity, and microstructure. The results showed that, by increasing the content of the rice husk ash from 10 to 50 wt%, there is an increase in the porosity from 42.92% to 49.04%, while the mechanical properties decreased initially followed by an increase at 30 wt% and 50 wt%; the hardness at 20 wt% of the ash content was recorded at 101.90 HV1. When the ash content was increased to 30 wt% and 50 wt%, the hardness was raised to 150.92 HV1 and 158.93 HV1, respectively. The findings also revealed that the tensile and compressive strengths experienced a decrease at 10 wt% of the ash content and after that increase at 30 wt% and 50 wt% of rice husk ash. XRD analysis found multiple phases of ceramic formation after sintering for the different rice husk ash content.

  1. CoCr F75 scaffolds produced by additive manufacturing: Influence of chemical etching on powder removal and mechanical performance.

    Science.gov (United States)

    Van Hooreweder, Brecht; Lietaert, Karel; Neirinck, Bram; Lippiatt, Nicholas; Wevers, Martine

    2017-04-01

    Additive manufacturing techniques such as Selective Laser Melting (SLM) allow carefully controlled production of complex porous structures such as scaffolds. These advanced structures can offer many interesting advantages over conventionally produced products in terms of biological response and patient specific design. The surface finish of AM parts is often poor because of the layer wise nature of the process and adhering particles. Loosening of these particles after implantation should be avoided, as this could put the patient's health at risk. In this study the use of hydrochloric acid and hydrogen peroxide mixtures for surface treatment of cobalt-chromium F75 scaffolds produced by SLM is investigated. A 27% HCl and 8% H2O2 etchant proved effective in removing adhering particles while retaining the quasi-static and fatigue performance of the scaffolds.

  2. Ancient Magnetic Reversals: Clues to the Geodynamo.

    Science.gov (United States)

    Hoffman, Kenneth A.

    1988-01-01

    Discusses the question posed by some that the earth's magnetic field may reverse. States that rocks magnetized by ancient fields may offer clues to the underlying reversal mechanism in the earth's core. (TW)

  3. K70Q adds high-level tenofovir resistance to "Q151M complex" HIV reverse transcriptase through the enhanced discrimination mechanism.

    Directory of Open Access Journals (Sweden)

    Atsuko Hachiya

    Full Text Available HIV-1 carrying the "Q151M complex" reverse transcriptase (RT mutations (A62V/V75I/F77L/F116Y/Q151M, or Q151Mc is resistant to many FDA-approved nucleoside RT inhibitors (NRTIs, but has been considered susceptible to tenofovir disoproxil fumarate (TFV-DF or TDF. We have isolated from a TFV-DF-treated HIV patient a Q151Mc-containing clinical isolate with high phenotypic resistance to TFV-DF. Analysis of the genotypic and phenotypic testing over the course of this patient's therapy lead us to hypothesize that TFV-DF resistance emerged upon appearance of the previously unreported K70Q mutation in the Q151Mc background. Virological analysis showed that HIV with only K70Q was not significantly resistant to TFV-DF. However, addition of K70Q to the Q151Mc background significantly enhanced resistance to several approved NRTIs, and also resulted in high-level (10-fold resistance to TFV-DF. Biochemical experiments established that the increased resistance to tenofovir is not the result of enhanced excision, as K70Q/Q151Mc RT exhibited diminished, rather than enhanced ATP-based primer unblocking activity. Pre-steady state kinetic analysis of the recombinant enzymes demonstrated that addition of the K70Q mutation selectively decreases the binding of tenofovir-diphosphate (TFV-DP, resulting in reduced incorporation of TFV into the nascent DNA chain. Molecular dynamics simulations suggest that changes in the hydrogen bonding pattern in the polymerase active site of K70Q/Q151Mc RT may contribute to the observed changes in binding and incorporation of TFV-DP. The novel pattern of TFV-resistance may help adjust therapeutic strategies for NRTI-experienced patients with multi-drug resistant (MDR mutations.

  4. Ion irradiation induced effects and magnetization reversal mechanism in (Ni{sub 80}Fe{sub 20}){sub 1−x}Co{sub x} nanowires and nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Naeem, E-mail: naeem.ahmad@iiu.edu.pk [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100090 (China); Spintronics Laboratory, Department of Physics, Faculty of Basic and Applied Sciences (FBAS), International Islamic University H-10, Islamabad 44000 (Pakistan); Iqbal, Javed [Laboratory of Nanoscience and Technology, Department of Physics, International Islamic University, H-10, Islamabad,Pakistan (Pakistan); Chen, J.Y. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100090 (China); Hussain, Asim [Spintronics Laboratory, Department of Physics, Faculty of Basic and Applied Sciences (FBAS), International Islamic University H-10, Islamabad 44000 (Pakistan); Shi, D.W.; Han, X.F. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100090 (China)

    2015-03-15

    The effect of Co on the ferromagnetic characteristics of the Ni{sub 80}Fe{sub 20} nanocylinders having zero magnetostriction and soft magnetic nature is an interesting field of research. The (Ni{sub 80}Fe{sub 20}){sub 1−x}Co{sub x} nanocylinders have been prepared by electrodeposition into commercially available anodized aluminum oxide (AAO) nanoporous templates. The analysis of magnetization reversal from the angular dependence of coercivity has been studied in detail. This angular dependence of coercivity has shown a transition from curling to nucleation mode as a function of field angle for all (Ni{sub 80}Fe{sub 20}){sub 1−x}Co{sub x} nanocylinders depending upon the critical angle. The shape anisotropy, dipole–dipole interactions, surface effects and magnetocrystalline anisotropy have been found to play an effective role for the spontaneous magnetization in nanowires and nanotubes. It has been interestingly observed that the magnetostatic interactions or dipole–dipole interactions are dominant in nanocylinders regardless of its geometry. Furthermore, the prepared samples have been irradiated with He{sup 2+} ions (energy E=2 MeV, fluence=10{sup 14} ions/cm{sup 2} and ion current=16 nA) at room temperature using a 5-UDH-2pelletron tandem accelerator. The irradiations have created defects and these defects have induced changes in magnetization as a result an increase in coercivity as function of the ion fluences is observed. Such kind of behavior in coercivity enhancement and magnetization reduction can also be attributed to the stress relaxation and percolation in nonuniform states of ferromagnetic alloys, respectively. - Highlights: • We have prepared the ferromagnetic NiFeCo nanowires and nanotubes into anodized aluminum oxide templates (AAO) by electrodeposition method. • We have studied the magnetization reversal mechanism from the angle dependent coercivity measured by a hysteresis loop. • The ion irradiation effects on these nanostructures

  5. Effect of Graphene Nanoplatelets addition on mechanical properties of pure aluminum using a semi-powder method

    Institute of Scientific and Technical Information of China (English)

    Muhammad Rashad; Fusheng Pan; Aitao Tang; Muhammad Asif

    2014-01-01

    In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites for streng+ enhancement. +is paper reports an Aluminum-Graphene Nanoplatelets (Al/GNPs) composite using a semi-powder me+od followed by hot extrusion. +e effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in +is paper. It is demonstrated +at 0.3 wt% Graphene Nanoplatelets distributed homogeneously in +e matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monoli+ic aluminum (in tension), Al-0.3 wt%GNPs composite exhibited higher 0.2%yield streng+ ( + 14.7%), ultimate tensile streng+ ( + 11.1%) and lower failure strain ( - 40.6%). Surprisingly, compared to monoli+ic Al (in compression), Al-0.3 wt%GNPs composite exhibited same 0.2%compressive yield streng+ and lower ultimate compression streng+ ( - 7.8%), and lower failure strain ( - 20.2%). +e Al-0.3 wt%GNPs composite exhibited higher Vickers hardness compared to monoli+ic aluminum ( + 11.8%). Scanning electron microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate +e surface morphology, elemental percentage composition, and phase analysis, respectively.

  6. High-throughput exploration of thermoelectric and mechanical properties of amorphous NbO2 with transition metal additions

    Science.gov (United States)

    Music, Denis; Geyer, Richard W.; Hans, Marcus

    2016-07-01

    To increase the thermoelectric efficiency and reduce the thermal fatigue upon cyclic heat loading, alloying of amorphous NbO2 with all 3d and 5d transition metals has systematically been investigated using density functional theory. It was found that Ta fulfills the key design criteria, namely, enhancement of the Seebeck coefficient and positive Cauchy pressure (ductility gauge). These quantum mechanical predictions were validated by assessing the thermoelectric and elastic properties on combinatorial thin films, which is a high-throughput approach. The maximum power factor is 2813 μW m-1 K-2 for the Ta/Nb ratio of 0.25, which is a hundredfold increment compared to pure NbO2 and exceeds many oxide thermoelectrics. Based on the elasticity measurements, the consistency between theory and experiment for the Cauchy pressure was attained within 2%. On the basis of the electronic structure analysis, these configurations can be perceived as metallic, which is consistent with low electrical resistivity and ductile behavior. Furthermore, a pronounced quantum confinement effect occurs, which is identified as the physical origin for the Seebeck coefficient enhancement.

  7. Effect of Graphene Nanoplatelets addition on mechanical properties of pure aluminum using a semi-powder method

    Directory of Open Access Journals (Sweden)

    Muhammad Rashad

    2014-04-01

    Full Text Available In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites for strength enhancement. This paper reports an Aluminum–Graphene Nanoplatelets (Al/GNPs composite using a semi-powder method followed by hot extrusion. The effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in this paper. It is demonstrated that 0.3 wt% Graphene Nanoplatelets distributed homogeneously in the matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monolithic aluminum (in tension, Al–0.3 wt% GNPs composite exhibited higher 0.2% yield strength (+14.7%, ultimate tensile strength (+11.1% and lower failure strain (−40.6%. Surprisingly, compared to monolithic Al (in compression, Al–0.3 wt% GNPs composite exhibited same 0.2% compressive yield strength and lower ultimate compression strength (−7.8%, and lower failure strain (−20.2%. The Al–0.3 wt% GNPs composite exhibited higher Vickers hardness compared to monolithic aluminum (+11.8%. Scanning electron microscopy (SEM, Energy-Dispersive X-ray Spectroscopy (EDS and X-ray diffraction (XRD were used to investigate the surface morphology, elemental percentage composition, and phase analysis, respectively.

  8. The effect of the addition of ground olive stones on the physical and mechanical properties of clay bricks

    Directory of Open Access Journals (Sweden)

    Arezki, S.

    2016-06-01

    Full Text Available This study deals with the effect of ground olive stones (GOS on the performance of fired clay bricks. Seven different clay-GOS mixes with 0, 1, 2, 3, 4, 5 and 10 wt % of GOS respectively were used for making fired brick samples. All samples were fired at 900 °C. The technological properties of the resultant material were then determined, including shrinkage, apparent density, pore size distribution, thermal conductivity, water absorption, and compressive and flexural strength. The addition of GOS to the mixture reduced the compressive strength of fired clay bricks. All clay brick pieces exhibited low firing shrinkage. It was apparent that as the percentage of GOS increased in the body, there was a noticeable increase in porosity. The water absorption coefficient decreased with increasing additions. The results indicated that thermal conductivity decreases with decrease in density and increase in porosity in fired clay bricks.En este trabajo se ha estudiado el efecto de la incorporación de huesos de aceituna triturados en las prestaciones de ladrillos de arcilla cocida. Se utilizaron siete proporciones de huesos de aceituna 0 %, 1 %, 2 %, 3 %, 4 %, 5 % y 10 % en peso. Todas las muestras se calcinaron a 900 °C y posteriormente se determinaron las propiedades resultantes, incluyendo la densidad aparente, retracción, distribución de tamaños de poro, conductividad térmica, absorción de agua y resistencias mecánicas. La adición de huesos de aceituna molidos a la mezcla redujo la resistencia a la compresión de los ladrillos de arcilla cocida. Además se observó que todas las piezas de ladrillo mostraron baja retracción tras exposición a altas temperaturas. Como era de esperar a medida que el porcentaje de huesos de aceituna molidos aumentó, la porosidad se incrementó de manera evidente. El coeficiente de absorción de agua disminuyó con el aumento del porcentaje de sustitución. Los resultados indicaron que la conductividad t

  9. Processing of AISI M2 HSS with addition of NbC by mechanical alloying using two different types of attritor mills

    Energy Technology Data Exchange (ETDEWEB)

    Araujo Filho, Oscar Olimpio de; Gonzalez, Cezar Henrique; Urtiga Filho, Severino Leopoldino, E-mail: oscaroaf98@hotmail.com, E-mail: gonzalez@ufpe.br, E-mail: urtiga@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Engenharia Mecanica; Neves, Mauricio David Martins das, E-mail: mdneves@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Ambrozio Filho, Francisco, E-mail: ambrozio@fei.edu.br [Centro Universitario da FEI, Sao Bernardo do Campo, SP (Brazil)

    2009-07-01

    The processing of a molybdenum AISI M2 high speed steel with the addition of NbC (6% in mass) by a Powder Metallurgy technique of Mechanical Alloying is the aim of this work. Mechanical Alloying (MA) has been used primarily for particle size reduction, to its present status as an important method for the preparation of either materials with enhanced physical and mechanical properties or, indeed, new phases, or new engineering materials. In this work, niobium carbide (NbC) was added to the AISI M2 HSS powders by Mechanical Alloying technique in two different types of attritor mills and the materials which resulted were characterized by means of SEM plus EDS. The powders were processed in a horizontal attritor Zoz mill and in a vertical attritor mill developed in our laboratory. The parameters of milling were distinct and the results of the processing were compared. (author)

  10. Effect of organic additives on mechanical properties of SiC ceramics prepared by a modified gelcasting method

    Directory of Open Access Journals (Sweden)

    Feng Wang

    2016-12-01

    Full Text Available A novel and simple gel system of isobutylene and maleic anhydride (PIBM was used to prepare SiC ceramics. The rheological behaviour of the SiC slurries was investigated as function of organic additives. The SiC slurries with 0.2 wt.% PIBM and 0.2 wt.% tetramethylammonium hydroxide (TMAH showed low viscosity, which was favourable for casting SiC green bodies. In order to obtain homogeneous green bodies, polyvinyl alcohol (PVA was used to assist the dispersion of carbon black in the slurries, and polyethylene glycol (PEG was added to inhibit the surface exfoliation of green bodies. The content of PVA was controlled carefully to avoid the warpage of green bodies during the drying process. Finally, homogeneous defect-free SiC green bodies were successfully fabricated via aqueous gelcasting. The SiC ceramics sintered at 2100 °C (prepared from slurries with solid content of 60 wt.% showed an average flexural strength of 305.7 MPa with porosity of 19.92%.

  11. Effects of the addition of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on mechanical properties of luting and lining glass ionomer cement

    Science.gov (United States)

    Heravi, Farzin; Bagheri, Hossein; Rangrazi, Abdolrasoul; Mojtaba Zebarjad, Seyed

    2016-07-01

    Recently, the addition of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into glass ionomer cements (GICs) has attracted interest due to its remineralization of teeth and its antibacterial effects. However, it should be investigated to ensure that the incorporation of CPP-ACP does not have significant adverse effects on its mechanical properties. The purpose of this study was to evaluate the effects of the addition of CPP-ACP on the mechanical properties of luting and lining GIC. The first step was to synthesize the CPP-ACP. Then the CPP-ACP at concentrations of 1%, 1.56% and 2% of CPP-ACP was added into a luting and lining GIC. GIC without CPP-ACP was used as a control group. The results revealed that the incorporation of CPP-ACP up to 1.56%(w/w) increased the flexural strength (29%), diametral tensile strength (36%) and microhardness (18%), followed by a reduction in these mechanical properties at 2%(w/w) CPP-ACP. The wear rate was significantly decreased (23%) in 1.56%(w/w) concentration of CPP-ACP and it was increased in 2%(w/w). Accordingly, the addition of 1.56%(w/w) CPP-ACP into luting and lining GIC had no adverse effect on the mechanical properties of luting and lining GIC and could be used in clinical practice.

  12. Effect of Cr addition on the structural, magnetic and mechanical properties of magnetron sputtered Ni-Mn-In ferromagnetic shape memory alloy thin films

    Science.gov (United States)

    Akkera, Harish Sharma; Kaur, Davinder

    2016-12-01

    The effect of Cr substitution for In on the structural, martensitic phase transformation and mechanical properties of Ni-Mn-In ferromagnetic shape memory alloy (FSMA) thin films was systematically investigated. X-ray diffraction results revealed that the Ni-Mn-In-Cr thin films possessed purely austenitic cubic L21 structure at lower content of Cr, whereas higher Cr content, the Ni-Mn-In-Cr thin films exhibited martensitic structure at room temperature. The temperature-dependent magnetization ( M- T) and resistance ( R- T) results confirmed that the monotonous increase in martensitic transformation temperatures ( T M) with the addition of Cr content. Further, the room temperature nanoindentation studies revealed the mechanical properties such as hardness ( H), elastic modulus ( E), plasticity index ( H/ E) and resistance to plastic deformation ( H 3/ E 2) of all the samples. The addition of Cr content significantly enhanced the hardness (28.2 ± 2.4 GPa) and resistance to plastic deformation H 3/ E 2 (0.261) of Ni50.4Mn34.96In13.56Cr1.08 film as compared with pure Ni-Mn-In film. As a result, the appropriate addition of Cr significantly improved the mechanical properties with a decrease in grain size, which could be further attributed to the grain boundary strengthening mechanism. These findings indicate that the Cr-doped Ni-Mn-In FSMA thin films are potential candidates for microelectromechanical systems applications.

  13. Effect of addition of plants-derived polyamide 11 elastomer on the mechanical and tribological properties of hemp fiber reinforced polyamide 1010 composites

    Science.gov (United States)

    Mukaida, Jun; Nishitani, Yosuke; Kitano, Takeshi

    2015-05-01

    For the purpose of developing the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the effect of the addition of plant-derived polyamide 11 Elastomer (PA11E) on the mechanical and tribological properties of hemp fiber(HF) reinforced polyamide 1010 (HF/PA1010) composites was investigated. PA1010 and PA11E (except the polyether groups used as soft segment) were made from plant-derived castor oil. Hemp fiber was surface-treated by two types of treatment: alkali treatment by NaOH solution and surface treatment by ureido silane coupling agent. HF/PA1010/PA11E ternary composites were extruded by a twin screw extruder and injection-molded. Their mechanical properties such as tensile, bending, Izod impact and tribological properties by ring-on-plate type sliding wear testing were evaluated. The effect of the addition of PA11E on the mechanical and tribological properties of HF/PA1010 composite differed for each property. Izod impact strength and specific wear rate improved with the addition of PA11E although tensile strength, modulus, and friction coefficient decreased with PA11E. It follows from these results that it may be possible to develop the new engineering materials with sufficient balance between mechanical and tribological properties.

  14. Enhancement of the Mechanical Properties of Basalt Fiber-Wood-Plastic Composites via Maleic Anhydride Grafted High-Density Polyethylene (MAPE Addition

    Directory of Open Access Journals (Sweden)

    Yun Lu

    2013-06-01

    Full Text Available This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs. The maximum values of the specific tensile and flexural strengths are achieved at a MAPE content of 5%–8%. The elongation increases rapidly at first and then continues slowly. The nearly complete integration of the wood fiber with the high-density polyethylene upon MAPE addition to WPC is examined, and two models of interfacial behavior are proposed. We examined the physical significance of both interfacial models and their ability to accurately describe the effects of MAPE addition. The mechanism of formation of the Model I interface and the integrated matrix is outlined based on the chemical reactions that may occur between the various components as a result of hydrogen bond formation or based on the principle of compatibility, resulting from similar polarity. The Model I fracture occurred on the outer surface of the interfacial layer, visually demonstrating the compatibilization effect of MAPE addition.

  15. Theoretical study of the mechanism for the Markovnikov addition of imidazole to vinyl acetate catalyzed by the ionic liquid [bmIm]OH.

    Science.gov (United States)

    Sun, Hui; Zhang, Dongju; Wang, Fang; Liu, Chengbu

    2007-05-24

    By performing density functional theory calculations, we have studied the Markovnikov addition of imidazole to vinyl acetate catalyzed by 1-butyl-3-methylimidazolium hydroxide, [bmIm]OH, a novel basic ionic liquid. The purpose is to show the detailed reaction mechanism, to rationalize the experimental observations, and in particular to better understand the role of [bmIm]OH played in the reaction as a catalyst. Two different reaction pathways (stepwise and concerted) have been characterized and analyzed in detail. It was found that both the cation and anion of [bmIm]OH play important roles in the Markovnikov addition, which decrease the barrier and increase the selectivity of Markovnikov addition. The present results rationalize the early experimental findings well and provide a prototype for theoretically understanding the Markovnikov addition catalyzed by room-temperature ionic liquids.

  16. Two additive mechanisms impair the differentiation of 'substrate-selective' p38 inhibitors from classical p38 inhibitors in vitro

    Directory of Open Access Journals (Sweden)

    Seidl Kelly M

    2010-03-01

    Full Text Available Abstract Background The success of anti-TNF biologics for the treatment of rheumatoid arthritis has highlighted the importance of understanding the intracellular pathways that regulate TNF production in the quest for an orally-available small molecule inhibitor. p38 is known to strongly regulate TNF production via MK2. The failure of several p38 inhibitors in the clinic suggests the importance of other downstream pathways in normal cell function. Recent work has described a 'substrate-selective' p38 inhibitor that is able to preferentially block the activity of p38 against one substrate (MK2 versus another (ATF2. Using a combined experimental and computational approach, we have examined this mechanism in greater detail for two p38 substrates, MK2 and ATF2. Results We found that in a dual (MK2 and ATF2 substrate assay, MK2-p38 interaction reduced the activity of p38 against ATF2. We further constructed a detailed kinetic mechanistic model of p38 phosphorylation in the presence of multiple substrates and successfully predicted the performance of classical and so-called 'substrate-selective' p38 inhibitors in the dual substrate assay. Importantly, it was found that excess MK2 results in a stoichiometric effect in which the formation of p38-MK2-inhibitor complex prevents the phosphorylation of ATF2, despite the preference of the compound for the p38-MK2 complex over the p38-ATF2 complex. MK2 and p38 protein expression levels were quantified in U937, Thp-1 and PBMCs and found that [MK2] > [p38]. Conclusion Our integrated mechanistic modeling and experimental validation provides an example of how systems biology approaches can be applied to drug discovery and provide a basis for decision-making with limited chemical matter. We find that, given our current understanding, it is unlikely that 'substrate-selective' inhibitors of p38 will work as originally intended when placed in the context of more complex cellular environments, largely due to a

  17. The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al–5%Si–Cu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Salleh, M.S., E-mail: shukor@utem.edu.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia); Department of Manufacturing Process, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka (Malaysia); Omar, M.Z., E-mail: zaidi@eng.ukm.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia); Syarif, J., E-mail: syarif@eng.ukm.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia)

    2015-02-05

    Highlights: • The average globule size of α-Al decreased when Mg amount is increased. • T6 heat treatment has increased the strength of the thixoformed alloys. • The elongation after T6 heat treatment is even significantly improved. • Thixoformed alloy with high Mg content shows a brittle type fracture. • Thixoformed alloy in T6 condition shows a ductile type fracture. - Abstract: In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al–5%Si–Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 °C for 8 h, quenching in warm water at 60 °C, followed by aging at 155 °C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al{sub 9}FeMg{sub 3}Si{sub 5} phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt%Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed.

  18. Effects of silica addition on the chemical, mechanical and biological properties of a new α-Tricalcium Phosphate/Tricalcium Silicate Cement

    Directory of Open Access Journals (Sweden)

    Loreley Morejón-Alonso

    2011-12-01

    Full Text Available The addition of tricalcium silicate (C3S to apatite cements results in an increase of bioactivity and improvement in the mechanical properties. However, adding large amounts raises the local pH at early stages, which retards the precipitation of hydroxyapatite and produces a loss of mechanical strength. The introduction of Pozzolanic materials in cement pastes could be an effective way to reduces basicity and enhance their mechanical resistance; thus, the effect of adding silica on the chemical, mechanical and biological properties of α-tricalcium phosphate/C3S cement was studied. Adding silica produces a reduction in the early pH and a decrease in setting times; nevertheless, the presence of more calcium silicate hydrate (C-S-H delays the growth of hydroxyapatite crystals and consequently, reduces early compressive strength. The new formulations show a good bioactivity, but higher cytotoxicity than traditional cements and additions higher than 2.5% of SiO2 cause a lack of mechanical strength and an elevated degradability.

  19. Reverse design of transplanting mechanism with spatial planetary gear train based on spherical curve%基于球面曲线的空间非匀速行星轮系分插机构逆向设计

    Institute of Scientific and Technical Information of China (English)

    孙良; 祝建彬; 陈建能; 赵匀; 武传宇

    2014-01-01

    established. The transmission ratio of every single gear pair and the pitch curve of every gear were resolved by attaching a noncircular gear and a noncircular bevel gear to the two bar mechanism with three degrees of freedom. The parameter inverse and design program for a wide-narrow distance transplanting mechanism with noncircular gears and noncircular bevel gears, based on the development platform of MATLAB, was compiled and the ideal spherical surface trajectory was obtained by modifying the data point of plane trajectory. In addition, a group of mechanism parameters was reversed by the method of human-computer conversation afterward. Finally, a model machining of the transplanting mechanism was processed and a testing trajectory, similar to the theoretical trajectory was gained, which verified the feasibility of this reverse design method and supplied a new method for the design of a wide-narrow distance transplanting mechanism.%针对目前非圆锥齿轮行星系分插机构运动轨迹、姿态设计中存在的对机构参数选择和参数对设计目标影响的不确定性问题,提出一种基于球面曲线的空间行星轮系机构逆向设计方法。在利用样条曲线描述光滑、连续、封闭理想平面插秧轨迹的基础上,采用保测地曲率投影方式将平面轨迹映射到给定球面获得目标球面轨迹;由二杆三自由度空间开式机构复演球面轨迹,并根据杆件的空间几何关系建立行星轮系机构的总传动比反求模型;通过在杆件上依附非圆锥齿轮、非圆齿轮,实现基于给定运动要求的各级传动比分配和齿轮节曲线再现;利用Matlab编写反求程序,并在高速水稻宽窄行分插机构的设计中,实现非圆齿轮-非圆锥齿轮行星轮系宽窄行分插机构的参数反求。最后,通过设计并加工机构实物进行台架试验,由高速摄像技术测试并得到了与给定球面轨迹一致的插秧轨迹,验证了方法的可行性

  20. Introducing Catastrophe-QSAR. Application on Modeling Molecular Mechanisms of Pyridinone Derivative-Type HIV Non-Nucleoside Reverse Transcriptase Inhibitors

    Science.gov (United States)

    Putz, Mihai V.; Lazea, Marius; Putz, Ana-Maria; Duda-Seiman, Corina

    2011-01-01

    The classical method of quantitative structure-activity relationships (QSAR) is enriched using non-linear models, as Thom’s polynomials allow either uni- or bi-variate structural parameters. In this context, catastrophe QSAR algorithms are applied to the anti-HIV-1 activity of pyridinone derivatives. This requires calculation of the so-called relative statistical power and of its minimum principle in various QSAR models. A new index, known as a statistical relative power, is constructed as an Euclidian measure for the combined ratio of the Pearson correlation to algebraic correlation, with normalized t-Student and the Fisher tests. First and second order inter-model paths are considered for mono-variate catastrophes, whereas for bi-variate catastrophes the direct minimum path is provided, allowing the QSAR models to be tested for predictive purposes. At this stage, the max-to-min hierarchies of the tested models allow the interaction mechanism to be identified using structural parameter succession and the typical catastrophes involved. Minimized differences between these catastrophe models in the common structurally influential domains that span both the trial and tested compounds identify the “optimal molecular structural domains” and the molecules with the best output with respect to the modeled activity, which in this case is human immunodeficiency virus type 1 HIV-1 inhibition. The best molecules are characterized by hydrophobic interactions with the HIV-1 p66 subunit protein, and they concur with those identified in other 3D-QSAR analyses. Moreover, the importance of aromatic ring stacking interactions for increasing the binding affinity of the inhibitor-reverse transcriptase ligand-substrate complex is highlighted. PMID:22272148

  1. Introducing Catastrophe-QSAR. Application on Modeling Molecular Mechanisms of Pyridinone Derivative-Type HIV Non-Nucleoside Reverse Transcriptase Inhibitors

    Directory of Open Access Journals (Sweden)

    Marius Lazea

    2011-12-01

    Full Text Available The classical method of quantitative structure-activity relationships (QSAR is enriched using non-linear models, as Thom’s polynomials allow either uni- or bi-variate structural parameters. In this context, catastrophe QSAR algorithms are applied to the anti-HIV-1 activity of pyridinone derivatives. This requires calculation of the so-called relative statistical power and of its minimum principle in various QSAR models. A new index, known as a statistical relative power, is constructed as an Euclidian measure for the combined ratio of the Pearson correlation to algebraic correlation, with normalized t-Student and the Fisher tests. First and second order inter-model paths are considered for mono-variate catastrophes, whereas for bi-variate catastrophes the direct minimum path is provided, allowing the QSAR models to be tested for predictive purposes. At this stage, the max-to-min hierarchies of the tested models allow the interaction mechanism to be identified using structural parameter succession and the typical catastrophes involved. Minimized differences between these catastrophe models in the common structurally influential domains that span both the trial and tested compounds identify the “optimal molecular structural domains” and the molecules with the best output with respect to the modeled activity, which in this case is human immunodeficiency virus type 1 HIV-1 inhibition. The best molecules are characterized by hydrophobic interactions with the HIV-1 p66 subunit protein, and they concur with those identified in other 3D-QSAR analyses. Moreover, the importance of aromatic ring stacking interactions for increasing the binding affinity of the inhibitor-reverse transcriptase ligand-substrate complex is highlighted.

  2. Preparation and characterization of new dental porcelains, using K-feldspar and quartz raw materials. Effect of B2O3 additions on sintering and mechanical properties.

    Science.gov (United States)

    Harabi, Abdelhamid; Guerfa, Fatiha; Harabi, Esma; Benhassine, Mohamed-Tayeb; Foughali, Lazhar; Zaiou, Soumia

    2016-08-01

    The aim of this work was to determine the effect of temperature and boric oxide (B2O3) addition on sintering and mechanical properties of a newly developed dental porcelain (DP) prepared from local Algerian raw materials. Based on a preliminary work, the new selected composition was 75wt.% feldspar, 20wt.% quartz and 5wt.% kaolin. It was prepared by sintering the mixture at different temperatures (1100-1250°C). The optimum sintering conditions gave a relatively higher density (2.47g/cm(3)) and excellent mechanical properties. The three point flexural strength (3PFS) and Martens micro-hardness of dental porcelains were 149MPa and 2600MPa, respectively. This obtained 3PFS value is more than four times greater than that of hydroxyapatite (HA) value (about 37MPa) sintered under the same conditions. However, the sintering temperature was lowered by about 25 and 50°C for 3 and 5wt.% B2O3 additions, respectively. But, it did not improve furthermore the samples density and their mechanical properties. It has also been found that B2O3 additions provoke a glass matrix composition variation which delays the leucite formation during sintering.

  3. Influence of Zr and nano-Y{sub 2}O{sub 3} additions on thermal stability and improved hardness in mechanically alloyed Fe base ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kotan, Hasan, E-mail: hkotan@konya.edu.tr [Department of Metallurgical Engineering and Materials Science, Necmettin Erbakan University, Dere Aşıklar Mah. Demet Sokak, Meram, Konya 42140 (Turkey); Darling, Kris A. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005-5069 (United States); Scattergood, Ronald O.; Koch, Carl C. [Department of Materials Science and Engineering, NC State University, 911 Partners Way, Room 3078, Raleigh, NC 27695-7907 (United States)

    2014-12-05

    The motivation of this work was driven to improve the thermal stability in systems where polymorphic transformations can result in an additional driving force, upsetting the expected thermodynamic stability. In this study, Fe{sub 92}Ni{sub 8} alloys with Zr and nano-Y{sub 2}O{sub 3} additions were produced by ball milling and then annealed at high temperatures. Emphasis was placed on understanding the effects of dispersed nano-Y{sub 2}O{sub 3} particle additions and their effect on microstructural stability at and above the bcc-to-fcc transformation occurring at 700 °C in Fe–Ni systems. Results reveal that microstructural stability and hardness can be promoted by a combination of Zr and Y{sub 2}O{sub 3} additions, that being mostly effective for stability before and after phase transition, respectively. The mechanical strength of these alloys is achieved by a unique microstructure comprised a ultra-fine grain Fe base matrix, which contains dispersions of both nano-scale in-situ formed Zr base intermetallics and ex-situ added Y{sub 2}O{sub 3} secondary oxide phases. Both of these were found to be essential for a combination of high thermal stability and high mechanical strength properties. - Highlights: • Polymorphic transformations can limit the processing of nanostructured powders. • It causes a rapid grain growth and impairs the improved mechanical properties. • We aim to improve the hardness and thermal stability above the phase transformation. • Thermal stability is achieved by a combination of Zr and Y{sub 2}O{sub 3} additions. • Hardness is promoted by in-situ formed and ex-situ added secondary nano phases.

  4. Reversibly assembled cellular composite materials.

    Science.gov (United States)

    Cheung, Kenneth C; Gershenfeld, Neil

    2013-09-13

    We introduce composite materials made by reversibly assembling a three-dimensional lattice of mass-produced carbon fiber-reinforced polymer composite parts with integrated mechanical interlocking connections. The resulting cellular composite materials can respond as an elastic solid with an extremely large measured modulus for an ultralight material (12.3 megapascals at a density of 7.2 milligrams per cubic centimeter). These materials offer a hierarchical decomposition in modeling, with bulk properties that can be predicted from component measurements and deformation modes that can be determined by the placement of part types. Because site locations are locally constrained, structures can be produced in a relative assembly process that merges desirable features of fiber composites, cellular materials, and additive manufacturing.

  5. Formation of novel flower-like silicon phases and evaluation of mechanical properties of hypereutectic melt-spun Al–20Si–5Fe alloys with addition of V

    Energy Technology Data Exchange (ETDEWEB)

    Uzun, Orhan [Department of Metallurgical and Material Science Engineering, Bülent Ecevit University, Zonguldak (Turkey); Kilicaslan, Muhammed Fatih, E-mail: fatihkilicaslan@yahoo.com [Department of Materials and Nanotechnology Engineering, Kastamonu University, Kastamonu (Turkey); Yılmaz, Fikret [Department of Physics, Gaziosmanpaşa University, Tokat (Turkey)

    2014-06-01

    In this work, rapidly solidified hypereutectic Al–20Si–5Fe–XV (X=0, 0.5 and 1) alloys were fabricated by melt spinning under vacuum. Microstructural and spectroscopic analyses were performed using SEM, TEM, TEM-MAPing, TEM-EDS and XRD measurements. Mechanical properties of the alloys were determined using DSI measurements. Experimental results indicated that addition of 0.5 wt% V to melt-spun Al–20Si–5Fe alloys induced formation of a novel flower-like Si phase. And addition of higher amount V (1 wt%), caused formation of refined Si phases and mostly hindered formation of Fe-bearing intermetallics. Observations along with manuscript strongly indicate that V modifies the Si phases by the impurity induced twinning (IIT). Changes in the dynamic microhardness of the samples were mainly determined by the size of Si phases. Addition of vanadium led to quite lower elastic modulus in the vanadium added alloys compared to base alloy.

  6. Enhanced properties of MgO-Al2O3 composite materials with Al powder addition under 1300 °C creep test and its mechanism analysis

    Science.gov (United States)

    Jiang, Peng; Ma, Jiajia; Li, Yong; Yue, Dandan; Tong, Shanghao; Xue, Wendong

    2017-04-01

    The Al-MgO-Al2O3 composite samples were prepared with alumina (fused corundum and sintered alumina), high purity sintered magnesia and aluminum powder. Creep test was carried out at 1300 °C and studied. The results show that the creep rate of sample without aluminum addition decreases gradually. The creep properties of the MgO-Al2O3 composite material are improved by aluminum powder addition, with the sample demonstrating an increase creep rate. The physical properties of the samples are enhanced by aluminum powder addition as well. The mechanism of the improvement on the sample is analyzed by different characterization methods and kinetics calculations. Our results indicates that the AlN and MgAl2O4 spinel phases which are formed during the creep test are acting as the reinforcing phases and therefore enhance the creep performance of the samples.

  7. Reversible Statistics

    DEFF Research Database (Denmark)

    Tryggestad, Kjell

    2004-01-01

    The study aims is to describe how the inclusion and exclusion of materials and calculative devices construct the boundaries and distinctions between statistical facts and artifacts in economics. My methodological approach is inspired by John Graunt's (1667) Political arithmetic and more recent work...... within constructivism and the field of Science and Technology Studies (STS). The result of this approach is here termed reversible statistics, reconstructing the findings of a statistical study within economics in three different ways. It is argued that all three accounts are quite normal, albeit...... in different ways. The presence and absence of diverse materials, both natural and political, is what distinguishes them from each other. Arguments are presented for a more symmetric relation between the scientific statistical text and the reader. I will argue that a more symmetric relation can be achieved...

  8. Role of enzymatic activity in muscle damage and cytotoxicity induced by Bothrops asper Asp49 phospholipase A2 myotoxins: are there additional effector mechanisms involved?

    Directory of Open Access Journals (Sweden)

    Diana Mora-Obando

    2014-09-01

    Full Text Available Viperid venoms often contain mixtures of Asp49 and Lys49 PLA2 myotoxin isoforms, relevant to development of myonecrosis. Given their difference in catalytic activity, mechanistic studies on each type require highly purified samples. Studies on Asp49 PLA2s have shown that enzyme inactivation using p-bromophenacyl bromide (p-BPB drastically affects toxicity. However, based on the variable levels of residual toxicity observed in some studies, it has been suggested that effector mechanisms independent of catalysis may additionally be involved in the toxicity of these enzymes, possibly resembling those of the enzymatically inactive Lys49 myotoxins. A possibility that Lys49 isoforms could be present in Asp49 PLA2 preparations exists and, if undetected in previous studies, could explain the variable residual toxicity. This question is here addressed by using an enzyme preparation ascertained to be free of Lys49 myotoxins. In agreement with previous reports, inactivation of the catalytic activity of an Asp49 myotoxin preparation led to major inhibition of toxic effects in vitro and in vivo. The very low residual levels of myotoxicity (7% and cytotoxicity (4% observed can be attributed to the low, although detectable, enzyme remaining active after p-BPB treatment (2.7%, and would be difficult to reconcile with the proposed existence of additional catalytic-independent toxic mechanisms. These findings favor the concept that the effector mechanism of toxicity of Asp49 PLA2 myotoxins from viperids fundamentally relies on their ability to hydrolyze phospholipids, arguing against the proposal that membrane disruption may also be caused by additional mechanisms that are independent of catalysis.

  9. Affects of Mechanical Milling and Metal Oxide Additives on Sorption Kinetics of 1:1 LiNH2/MgH2 Mixture

    Directory of Open Access Journals (Sweden)

    Donald L. Anton

    2011-05-01

    Full Text Available The destabilized complex hydride system composed of LiNH2:MgH2 (1:1 molar ratio is one of the leading candidates of hydrogen storage with a reversible hydrogen storage capacity of 8.1 wt%. A low sorption enthalpy of ~32 kJ/mole H2 was first predicted by Alapati et al. utilizing first principle density function theory (DFT calculations and has been subsequently confirmed empirically by Lu et al. through differential thermal analysis (DTA. This enthalpy suggests that favorable sorption kinetics should be obtainable at temperatures in the range of 160 °C to 200 °C. Preliminary experiments reported in the literature indicate that sorption kinetics are substantially lower than expected in this temperature range despite favorable thermodynamics. Systematic isothermal and isobaric sorption experiments were performed using a Sievert’s apparatus to form a baseline data set by which to compare kinetic results over the pressure and temperature range anticipated for use of this material as a hydrogen storage media. Various material preparation methods and compositional modifications were performed in attempts to increase the kinetics while lowering the sorption temperatures. This paper outlines the results of these systematic tests and describes a number of beneficial additions which influence kinetics as well as NH3 formation.

  10. AFFECTS OF MECHANICAL MILLING AND METAL OXIDE ADDITIVES ON SORPTION KINETICS OF 1:1 LiNH2/MgH2 MIXTURE

    Energy Technology Data Exchange (ETDEWEB)

    Erdy, C.; Anton, D.; Gray, J.

    2010-12-08

    The destabilized complex hydride system composed of LiNH{sub 2}:MgH{sub 2} (1:1 molar ratio) is one of the leading candidates of hydrogen storage with a reversible hydrogen storage capacity of 8.1 wt%. A low sorption enthalpy of {approx}32 kJ/mole H{sub 2} was first predicted by Alapati et al. utilizing first principle density function theory (DFT) calculations and has been subsequently confirmed empirically by Lu et al. through differential thermal analysis (DTA). This enthalpy suggests that favorable sorption kinetics should be obtainable at temperatures in the range of 160 C to 200 C. Preliminary experiments reported in the literature indicate that sorption kinetics are substantially lower than expected in this temperature range despite favorable thermodynamics. Systematic isothermal and isobaric sorption experiments were performed using a Sievert's apparatus to form a baseline data set by which to compare kinetic results over the pressure and temperature range anticipated for use of this material as a hydrogen storage media. Various material preparation methods and compositional modifications were performed in attempts to increase the kinetics while lowering the sorption temperatures. This paper outlines the results of these systematic tests and describes a number of beneficial additions which influence kinetics as well as NH{sub 3} formation.

  11. Investigating the addition of SiO₂-CaO-ZnO-Na₂O-TiO₂ bioactive glass to hydroxyapatite: Characterization, mechanical properties and bioactivity.

    Science.gov (United States)

    Yatongchai, Chokchai; Placek, Lana M; Curran, Declan J; Towler, Mark R; Wren, Anthony W

    2015-11-01

    Hydroxyapatite (Ca10(PO4)6(OH)2) is widely investigated as an implantable material for hard tissue restoration due to its osteoconductive properties. However, hydroxyapatite in bulk form is limited as its mechanical properties are insufficient for load-bearing orthopedic applications. Attempts have been made to improve the mechanical properties of hydroxyapatite, by incorporating ceramic fillers, but the resultant composite materials require high sintering temperatures to facilitate densification, leading to the decomposition of hydroxyapatite into tricalcium phosphate, tetra-calcium phosphate and CaO phases. One method of improving the properties of hydroxyapatite is to incorporate bioactive glass particles as a second phase. These typically have lower softening points which could possibly facilitate sintering at lower temperatures. In this work, a bioactive glass (SiO2-CaO-ZnO-Na2O-TiO2) is incorporated (10, 20 and 30 wt%) into hydroxyapatite as a reinforcing phase. X-ray diffraction confirmed that no additional phases (other than hydroxyapatite) were formed at a sintering temperature of 560 ℃ with up to 30 wt% glass addition. The addition of the glass phase increased the % crystallinity and the relative density of the composites. The biaxial flexural strength increased to 36 MPa with glass addition, and there was no significant change in hardness as a function of maturation. The pH of the incubation media increased to pH 10 or 11 through glass addition, and ion release profiles determined that Si, Na and P were released from the composites. Calcium phosphate precipitation was encouraged in simulated body fluid with the incorporation of the bioactive glass phase, and cell culture testing in MC-3T3 osteoblasts determined that the composite materials did not significantly reduce cell viability.

  12. A New Nitrogenase Mechanism Using a CFe8S9 Model: Does H2 Elimination Activate the Complex to N2 Addition to the Central Carbon Atom?

    Science.gov (United States)

    McKee, Michael L

    2016-02-11

    A truncated model of the FeMo cofactor is used to explore a new mechanism for the conversion of N2 to NH3 by the nitrogenase enzyme. After four initial protonation/reduction steps, the H4CFe8S9 cluster has two hydrogen atoms attached to sulfur, one hydrogen bridging two iron centers and one hydrogen bonded to carbon. The loss of the CH and FeHFe hydrogens as molecular hydrogen activates the cluster to addition of N2 to the carbon center. This unique step takes place at a nearly planar four-coordinate carbon center and leads to an intermediate with a significantly weakened N-N bond. A hydrogen attached to a sulfur atom is then transferred to the distal nitrogen atom. Additional prontonation/reduction steps are modeled by adding a hydrogen atom to sulfur and locating the transition states for transfer to nitrogen. The first NH3 is lost in a thermal neutral step, while the second step is endothermic. The loss of H2 activates the complex by reducing the barrier for N2 addition by 3.5 kcal/mol. Since this is the most difficult step in the mechanism, reducing the barrier for this step justifies the "extra expense" of H2 production.

  13. Effect of electron beam irradiation and poly(vinylpyrrolidone addition on mechanical properties of polycaprolactone with empty fruit bunch fibre (OPEFB composite

    Directory of Open Access Journals (Sweden)

    2009-04-01

    Full Text Available Biodegradable composites or green composites were prepared by melt blending technique using polycaprolactone and oil palm empty fruit bunch fibre (OPEFB. Since OPEFB is not compatible with PCL a binder, poly(vinyl pyrrolidone, (PVP was used to improve the interaction between PCL and OPEFB. The composites produced were irradiated using electron beam to improve the mechanical properties. The tensile, flexural and impact strengths of PCL/OPEFB composites were improved by addition of 1% by weight of PVP and irradiated with 10 kGy of electron beam. The FTIR spectra indicate a slight increase of frequencies at C=O peaks from 1730 to 1732 cm–1 after irradiation indicates some interaction between C=O and O–H. The surface morphology of the facture surface obtained from tensile test shows no fibre pull out indicating good adhesion between the OPEFB and PCL after addition of PVP.

  14. Effects of Ti and B Addition on Microstructures and Mechanical Properties of Hot-Rolled High-Strength Nb-Containing Steels

    Science.gov (United States)

    Meng, Xianna; Li, Cong; Chen, Wanglin

    2016-08-01

    Four microalloyed samples were designed to study the effects of Ti and B additions on microstructures and mechanical properties. Experimental results show that the samples without B addition mainly contain well-developed pearlite and polygonal ferrite, whereas the B-containing samples consist of degenerated pearlite, polygonal ferrite, and Widmanstätten ferrite (WF). The B addition promotes the precipitation of the complex (Ti,Al,Nb)N and (Ti,Al,Nb)2CS phases during the hot-rolling process. Grain sizes are significantly refined by the combinations of undissolved (Ti,Al)N, (Ti,Al,Nb)N complex, (Ti,Al,Nb)2CS, and fine inclusions, which act as the nucleation sites of intragranular ferrite. The core of complex (Ti,Al,Nb)N precipitate is undissolved Ti-N-rich (Ti,Al)N phase, and the cap is Nb-N-rich (Nb,Ti)N phase. The property measurements show that the B addition enhances comprehensive properties of tensile strength and elongation, but decreases fracture toughness due to higher contents of the WF and subgrains.

  15. Mechanisms of Vanadium Recovery from Stone Coal by Novel BaCO3/CaO Composite Additive Roasting and Acid Leaching Technology

    Directory of Open Access Journals (Sweden)

    Zhenlei Cai

    2016-03-01

    Full Text Available In this report, the vanadium recovery mechanisms by novel BaCO3/CaO composite additive roasting and acid leaching technology, including the phase transformations and the vanadium leaching kinetics, were studied. The purpose of this manuscript is to realize and improve the vanadium recovery from stone coal using BaCO3/CaO as the composite additive. The results indicated that during the composite additive BaCO3/CaO roasting process, the monoclinic crystalline structure of muscovite (K(Al,V2[Si3AlO10](OH2 was converted into the hexagonal crystalline structure of BaSi4O9 and the tetragonal crystalline structure of Gehlenite (Ca2Al2SiO7, which could, therefore, facilitate the release and extraction of vanadium. Vanadium in leaching residue was probably in the form of vanadate or pyrovanadate of barium and calcium, which were hardly extracted during the sulfuric acid leaching process. The vanadium leaching kinetic analysis indicated that the leaching process was controlled by the diffusion through a product layer. The apparent activation energy could be achieved as 46.51 kJ/mol. The reaction order with respect to the sulfuric acid concentration was 1.1059. The kinetic model of vanadium recovery from stone coal using novel composite additive BaCO3/CaO could be finally established.

  16. Microstructure and mechanical properties of surface layers of 30CrMnSiA steel plasma nitrocarburized with rare earth addition

    Institute of Scientific and Technical Information of China (English)

    TANG Lina; YAN Mufu

    2012-01-01

    The pulse plasma nitrocarburizing for 30CrMnSiA steel was conducted at 560 ℃ for 8 h in mixed gases of N2∶3H2 and different flow rates of rare earths (RE) addition.Effects of rare earths (RE) addition in the carrier gas on the surface morphology,phase structure and mechanical properties of the nitrocarburized layer were characterized by optical microscopy (OM),X-ray diffraction (XRD),scanning electron microscopy (SEM),microhardness testing and wear testing,respectively.The results showed that the surface phase structures changed from dual phases ε-Fe2-3N(C) and γ'-Fe4N(C) to phase Fe3C and incipient nitrides,and the nitrocarburized surface hardness value decreased slightly from 756 to 681 HV0.1 with the RE addition increasing in the carrier gas,and the corresponding morphology of the nitrocarburized surface was granular nitride group (diameter 0.8-1.5 μm) and compact-fine Fe3C stick and patch (mean size 100-300 nm),respectively.The wear resistance of the experimental steel could be improved remarkably by plasma RE nitrocarburizing.The nitrocarburized layer with Fe3C phase formed in the mixed gases of N2∶3H2 and flow rate of 0.5 L/min RE addition showed the lowest friction coefficient and the narrowest wear track.

  17. 中国跨国公司逆向知识转移组织机制的实证研究%Empirical study on the organization mechanism of reverse knowledge transfers in mncs of china

    Institute of Scientific and Technical Information of China (English)

    刘明霞; 于飞

    2013-01-01

    Base on knowledge management theory and the sample of MNCs of China,this paper studies the effect of organization mechanism on reverse knowledge transfers from subsidiaries to MNC parents in China by survey and interviews.It is found that cooperation mechanism,communication mechanism and control mechanism affect positively reverse knowledge transfer.But the effect of knowledge management mechanism on reverse knowledge transfer is not significant.This study goes beyond the traditional focus on knowledge characteristics in the past research of knowledge transfer about MNCs,and pay more attention to organization design and mechanism in MNCs' knowledge transfer.This paper enriches the perspectives for research on knowledge transfer in MNCs.%运用知识管理相关理论,以中国跨国公司为研究对象,通过问卷调查和企业访谈,探析了组织机制对中国跨国公司逆向知识转移的影响.研究发现合作式运作结构、沟通机制、控制机制(层级命令、子公司自主权)对逆向知识转移有显著的促进作用,而知识管理机制对逆向知识转移的作用与预期相反且不显著.本文突破了以往跨国公司知识转移研究中只关注知识特性的局限,侧重于知识转移的组织设计和组织机制,丰富了跨国公司知识转移领域的研究视角.

  18. Multi-walled carbon nanotube filled polypropylene nanocomposites based on masterbatch route: Improvement of dispersion and mechanical properties through PP-g-MA addition

    Directory of Open Access Journals (Sweden)

    2008-10-01

    Full Text Available Multi-wall carbon nanotubes (MWNTs filled polypropylene (PP nanocomposites were prepared through diluting a PP/MWNT masterbatch in a PP matrix by melt compounding with a twin screw extruder. Polypropylene grafted maleic anhydride (PP-g-MA was used to promote the carbon nanotubes dispersion. The effect of PP-g-MA addition on the rheological, mechanical and morphological properties of the nanocomposites was assessed for different MWNTs loadings. Scanning electron microscopy (SEM has shown that nanotubes are distributed reasonably uniformly. A better dispersion and good adhesion between the nanotubes and the PP matrix is caused by wrapping of PP-g-MA on MWNTs. When PP-g-MA is added, dynamic moduli and viscosity further increases compared to PP/MWNT nanocomposites. The rheological percolation threshold drops significantly. Tensile and flexural moduli and Charpy impact resistance of the nanocomposites also increases by the addition of PP-g-MA. The present study confirms that PP-g-MA is efficient to promote the dispersion of MWNTs in PP matrix and serves as an adhesive to increase their interfacial strength, hence greatly improving the rheological percolation threshold and mechanical properties of PP/MWNT nanocomposites.

  19. ON THE ANALYSIS OF IMPEDANCE-DRIVEN REVERSE FLOW DYNAMICS

    Directory of Open Access Journals (Sweden)

    LEE V. C.-C.

    2017-02-01

    Full Text Available Impedance pump is a simple valve-less pumping mechanism, where an elastic tube is joined to a more rigid tube, at both ends. By inducing a periodic asymmetrical compression on the elastic tube will produce a unidirectional flow within the system. This pumping concept offers a low energy, low noise alternative, which makes it an effective driving mechanism, especially for micro-fluidic systems. In addition, the wave-based mechanism through which pumping occurs infers many benefits in terms of simplicity of design and manufacturing. Adjustment of simple parameters such as the excitation frequencies or compression locations will reverse the direction of flow, providing a very versatile range of flow outputs. This paper describes the experimental analysis of such impedance-driven flow with emphasis on the dynamical study of the reverse flow in open-loop environment. In this study, tapered section with converging steps is introduced at both ends of the elastic tube to amplify the magnitude of reverse flow. Study conducted shows that the reverse peak flow is rather significant with estimate of 23% lower than the forward peak flow. The flow dynamics on the other hand has shown to exhibit different characteristics as per the forward peak flow. The flow characteristics is then studied and showed that the tapered sections altered the impedance within the system and hence induce a higher flow in the reverse direction.

  20. Mechanism Study of Gate Leakage Current for AlGaN/GaN High Electron Mobility Transistor Structure Under High Reverse Bias by Thin Surface Barrier Model and Technology Computer Aided Design Simulation

    Science.gov (United States)

    Hayashi, Kazuo; Yamaguchi, Yutaro; Oishi, Toshiyuki; Otsuka, Hiroshi; Yamanaka, Koji; Nakayama, Masatoshi; Miyamoto, Yasuyuki

    2013-04-01

    Gate leakage current mechanism in GaN high electron mobility transistors (HEMTs) has been studied using a two-dimensional thin surface barrier (TSB) model to represent two unintentional donor thin layers that exit under and outside the gate electrode due to the existence of surface defects. The donor thin layer outside the gate affects the reverse gate current at the high gate voltage above the pinch-off voltage. Higher donor concentration of thin layer outside the gate results in larger ratio of lateral to vertical components of the electric field at the gate edge. On the other hand, the electric field at the center of the gate has only the vertical electric field component. As a result, the two-dimensional effects are only important for the reverse gate current above the pinch-off voltage. We have confirmed in this paper that the simulation results provided by our model correlate very well with the experimental reverse gate current characteristics of the device for a very wide range of reverse gate voltage from 0.1 to 90 V.

  1. Early decrease in dietary protein:energy ratio by fat addition and ontogenetic changes in muscle growth mechanisms of rainbow trout: short- and long-term effects.

    Science.gov (United States)

    Alami-Durante, Hélène; Cluzeaud, Marianne; Duval, Carine; Maunas, Patrick; Girod-David, Virginia; Médale, Françoise

    2014-09-14

    As the understanding of the nutritional regulation of muscle growth mechanisms in fish is fragmentary, the present study aimed to (1) characterise ontogenetic changes in muscle growth-related genes in parallel to changes in muscle cellularity; (2) determine whether an early decrease in dietary protein:energy ratio by fat addition affects the muscle growth mechanisms of rainbow trout (Oncorhynchus mykiss) alevins; and (3) determine whether this early feeding of a high-fat (HF) diet to alevins had a long-term effect on muscle growth processes in juveniles fed a commercial diet. Developmental regulation of hyperplasia and hypertrophy was evidenced at the molecular (expression of myogenic regulatory factors, proliferating cell nuclear antigen and myosin heavy chains (MHC)) and cellular (number and diameter of white muscle fibres) levels. An early decrease in dietary protein:energy ratio by fat addition stimulated the body growth of alevins but led to a fatty phenotype, with accumulation of lipids in the anterior part, and less caudal muscle when compared at similar body weights, due to a decrease in both the white muscle hyperplasia and maximum hypertrophy of white muscle fibres. These HF diet-induced cellular changes were preceded by a very rapid down-regulation of the expression of fast-MHC. The present study also demonstrated that early dietary composition had a long-term effect on the subsequent muscle growth processes of juveniles fed a commercial diet for 3 months. When compared at similar body weights, initially HF diet-fed juveniles indeed had a lower mean diameter of white muscle fibres, a smaller number of large white muscle fibres, and lower expression levels of MyoD1 and myogenin. These findings demonstrated the strong effect of early feed composition on the muscle growth mechanisms of trout alevins and juveniles.

  2. Effect of silver and indium addition on mechanical properties and indentation creep behavior of rapidly solidified Bi-Sn based lead-free solder alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shalaby, Rizk Mostafa, E-mail: rizk1969@yahoo.co.uk [Mansoura University, Metal Physics Lab., Physics Department, Faculty of Science, Al-Gomhouria Street, Mansoura, P.O.Box 35516 (Egypt)

    2013-01-10

    Mechanical properties and indentation creep of the melt-spun process Bi-42 wt%Sn, Bi-40 wt%Sn-2 wt%In, Bi-40 wt%Sn-2 wt%Ag and Bi-38 wt%Sn-2 wt%In-2 wt%Ag were studied by dynamic resonance technique and Vickers indentation testing at room temperature and compared to that of the traditional Sn-37 wt%Pb eutectic alloy. The results show that the structure of Bi-42 wt%Sn alloy is characterized by the presence of rhombohedral Bi and body centered tetragonal {beta}-Sn. The two ternary alloys exhibit additional constituent phases of intermetallic compounds SnIn{sub 19} for Bi-40 wt%Sn-2 wt%In and {epsilon}-Ag{sub 3}Sn for Bi-40 wt%Sn-2 wt%Ag alloys. Attention has been paid to the role of intermetallic compounds on mechanical and creep behavior. The In and Ag containing solder alloy exhibited a good combination of higher creep resistance, good mechanical properties and lower melting temperature as compared with Pb-Sn eutectic solder alloy. This was attributed to the strengthening effect of Bi as a strong solid solution element in the Sn matrix and formation of intermetallic compounds {beta}-SnBi, {epsilon}-Ag{sub 3}Sn and InSn{sub 19} which act as both strengthening agent and grain refiner in the matrix of the material. Addition of In and Ag decreased the melting temperature of Bi-Sn lead-free solder from 143 Degree-Sign C to 133 Degree-Sign C which was possible mainly due to the existence of InSn{sub 19} and Ag{sub 3}Sn intermetallic compounds. Elastic constants, internal friction and thermal properties of Bi-Sn based alloys have been studied and analyzed.

  3. The Mechanical properties and microstructural relationships in iron--manganese--chromium alloys. [14 to 20% Mn, 13 to 18% Cr, Al and Ti additions

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, L.D.

    1977-01-01

    The relationships between microstructure and mechanical properties were studied for a series of Fe--Mn--Cr alloys. A combination of optical and scanning electron microscopy, EDAX analysis, and x-ray diffractometry was used to characterize the microstructures. Tensile testing and Charpy V-notch impact testing were utilized to study the mechanical properties. Triplex structures of gamma (fcc), alpha (bcc), and epsilon (hcp) were obtained in air-cool and quench-and-refrigeration heat treatments. Increasing volume fractions of metastable austenite and epsilon-martensite phases, which transform during testing, were found to have beneficial effects on the toughness and ductility properties, without significant losses in strength properties. A chromium concentration of 13 percent led to a better combination of strength and ductility than a concentration of 18 percent. The mechanical properties and preliminary corrosion results for the air-cooled 18Mn--13Cr and 16Mn--13Cr alloys are comparable to those of AISI 300 series austenitic stainless steels. These alloys show promise, therefore, as base systems for replacement austenitic stainless alloys. In addition, the 18Mn--13Cr air-cooled alloy exhibits excellent cryogenic properties, i.e., a yield strength of 360 MPa (53 ksi), an ultimate strength of 1110 MPa (161 ksi) an elongation of 60 percent, and a reduction in area of 17 percent at -196/sup 0/C. 62 figures, 9 tables.

  4. Bifunctional Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase: Mechanism and Proof-of-Concept as a Novel Therapeutic Design Strategy

    Science.gov (United States)

    Bailey, Christopher M.; Sullivan, Todd J.; Iyidogan, Pinar; Tirado-Rives, Julian; Chung, Raymond; Ruiz-Caro, Juliana; Mohamed, Ebrahim; Jorgensen, William; Hunter, Roger; Anderson, Karen S.

    2013-01-01

    Human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) is a major target for currently approved anti-HIV drugs. These drugs are divided into two classes: nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTIs and NNRTIs). This study illustrates the synthesis and biochemical evaluation of a novel bifunctional RT inhibitor utilizing d4T (NRTI) and a TMC-derivative (a diarylpyrimidine NNRTI) linked via a poly(ethylene glycol) (PEG) linker. HIV-1 RT successfully incorporates the triphosphate of d4T-4PEG-TMC bifunctional inhibitor in a base-specific manner. Moreover, this inhibitor demonstrates low nanomolar potency that has 4.3-fold and 4300-fold enhancement of polymerization inhibition in vitro relative to the parent TMC-derivative and d4T, respectively. This study serves as a proof-of-concept for the development and optimization of bifunctional RT inhibitors as potent inhibitors of HIV-1 viral replication. PMID:23659183

  5. Food additives

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002435.htm Food additives To use the sharing features on this page, please enable JavaScript. Food additives are substances that become part of a food ...

  6. Variation in mechanical behavior due to different build directions of Titanium6Aluminum4Vanadium fabricated by electron beam additive manufacturing technology

    Science.gov (United States)

    Roy, Lalit

    Titanium has always been a metal of great interest since its discovery especially for critical applications because of its excellent mechanical properties such as light weight (almost half of that of the steel), low density (4.4 gm/cc) and high strength (almost similar to steel). It creates a stable and adherent oxide layer on its surface upon exposure to air or water which gives it a great resistance to corrosion and has made it a great choice for structures in severe corrosive environment and sea water. Its non-allergic property has made it suitable for biomedical application for manufacturing implants. Having a very high melting temperature, it has a very good potential for high temperature applications. But high production and processing cost has limited its application. Ti6Al4V is the most used titanium alloy for which it has acquired the title as `workhouse' of the Ti family. Additive layer Manufacturing (ALM) has brought revolution in manufacturing industries. Today, this additive manufacturing has developed into several methods and formed a family. This method fabricates a product by adding layer after layer as per the geometry given as input into the system. Though the conception was developed to fabricate prototypes and making tools initially, but its highly economic aspect i.e., very little waste material for less machining and comparatively lower production lead time, obviation of machine tools have drawn attention for its further development towards mass production. Electron Beam Melting (EBM) is the latest addition to ALM family developed by Arcam, ABRTM located in Sweden. The electron beam that is used as heat source melts metal powder to form layers. For this thesis work, three different types of specimens have been fabricated using EBM system. These specimens differ in regard of direction of layer addition. Mechanical properties such as ultimate tensile strength, elastic modulus and yield strength, have been measured and compared with standard data

  7. Organocatalytic conjugate-addition polymerization of linear and cyclic acrylic monomers by N-heterocyclic carbenes: Mechanisms of chain initiation, propagation, and termination

    KAUST Repository

    Zhang, Yuetao

    2013-11-27

    This contribution presents a full account of experimental and theoretical/computational investigations into the mechanisms of chain initiation, propagation, and termination of the recently discovered N-heterocyclic carbene (NHC)-mediated organocatalytic conjugate-addition polymerization of acrylic monomers. The current study specifically focuses on three commonly used NHCs of vastly different nucleophilicity, 1,3-di-tert-butylimidazolin-2-ylidene (ItBu), 1,3- dimesitylimidazolin-2-ylidene (IMes), and 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4- triazol-5-ylidene (TPT), and two representative acrylic monomers, the linear methyl methacrylate (MMA) and its cyclic analog, biomass-derived renewable γ-methyl-α-methylene-γ-butyrolactone (MMBL). For MMA, there exhibits an exquisite selectivity of the NHC structure for the three types of reactions it promotes: enamine formation (single-monomer addition) by IMes, dimerization (tail-to-tail) by TPT, and polymerization by ItBu. For MMBL, all three NHCs promote no dimerization but polymerization, with the polymerization activity being highly sensitive to the NHC structure and the solvent polarity. Thus, ItBu is the most active catalyst of the series and converts quantitatively 1000-3000 equiv of MMBL in 1 min or 10 000 equiv in 5 min at room temperature to MMBL-based bioplastics with a narrow range of molecular weights of Mn = 70-85 kg/mol, regardless of the [MMBL]/[ItBu] ratio employed. The ItBu-catalyzed MMBL polymerization reaches an exceptionally high turnover frequency up to 122 s -1 and a high initiator efficiency value up to 1600%. Unique chain-termination mechanisms have been revealed, accounting for the production of relative high-molecular-weight linear polymers and the catalytic nature of this NHC-mediated conjugate-addition polymerization. Computational studies have provided mechanistic insights into reactivity and selectivity between two competing pathways for each NHC-monomer zwitterionic adduct, namely enamine

  8. 基于逆向工程技术圆柱凸轮机构的CAD/CAM%CAD/CAM of cylindrical cam mechanism based on re-verse engineering technology

    Institute of Scientific and Technical Information of China (English)

    蒋萌; 葛正浩; 屈毅; 李艳妮

    2011-01-01

    The papeer presents a new process and method of revere design and manufacturing of the cylindrical cam mechanism.By applying the Coordinate Measuring Machine (CMM) and the PRO/E software as the platform to carry out aided design, by taking Microsoft Visual C + + 6.0 as the development tool, and based on Windows platform, the cylindrical cam mechanism dealgn and manufacturing software is generated, allowing the design of cycle map and cam profile, checking the pressure angle and curvature radius rapidly, almulating the motion of cam. And the NC machining codes which can be directly used for numerical control machine were generated, achieviug the integration of design and manufacture of cylindrical cam mechanism. This CAD/CAM system can not only be applied in the reverse design of cylindrical cam mechanism, but alao used to achieve the forward de-sign of cylindrical ,cam mechanism quickly and easily. Finally, by taking reverse, design and manufacture of the cylindrical indexing cam as an example, the reverse design and manufacturing process and method of cylindrical cam mechanism based on reverse engineering technology has been explained in detail.%介绍了圆柱凸轮机构逆向设计与制造的流程和方法.利用三坐标测量机和Pro/E软件为平台实现辅助设计,以Microsolft Visual C++6.0为开发工具,基于Windows平台编制了圆柱凸轮机构设计与制造软件,实现了圆柱凸轮机构的循环图和轮廓设计,并可进行压力角及曲率半径的快速校核和凸轮的运动仿真,生成了直接用于数控机床的刀具NC加工代码,实现了圆柱凸轮机构设计制造一体化.此CAD/CAM系统不仅可用于圆柱凸轮机构的反求设计,亦可简单快捷地实现圆柱凸轮机构的正向设计.文中以圆柱分度凸轮的反求与制造为例详细说明了基于逆向工程技术圆柱凸轮机构的设计与制造方法和流程.

  9. The NMR solution structure of a mutant of the Max b/HLH/LZ free of DNA: insights into the specific and reversible DNA binding mechanism of dimeric transcription factors.

    Science.gov (United States)

    Sauvé, Simon; Tremblay, Luc; Lavigne, Pierre

    2004-09-17

    Basic region-helix1-loop-helix2-leucine zipper (b/H(1)LH(2)/LZ) transcription factors bind specific DNA sequence in their target gene promoters as dimers. Max, a b/H(1)LH(2)/LZ transcription factor, is the obligate heterodimeric partner of the related b/H(1)LH(2)/LZ proteins of the Myc and Mad families. These heterodimers specifically bind E-box DNA sequence (CACGTG) to activate (e.g. c-Myc/Max) and repress (e.g. Mad1/Max) transcription. Max can also homodimerize and bind E-box sequences in c-Myc target gene promoters. While the X-ray structure of the Max b/H(1)LH(2)/LZ/DNA complex and that of others have been reported, the precise sequence of events leading to the reversible and specific binding of these important transcription factors is still largely unknown. In order to provide insights into the DNA binding mechanism, we have solved the NMR solution structure of a covalently homodimerized version of a Max b/H(1)LH(2)/LZ protein with two stabilizing mutations in the LZ, and characterized its backbone dynamics from (15)N spin-relaxation measurements in the absence of DNA. Apart from minor differences in the pitch of the LZ, possibly resulting from the mutations in the construct, we observe that the packing of the helices in the H(1)LH(2) domain is almost identical to that of the two crystal structures, indicating that no important conformational change in these helices occurs upon DNA binding. Conversely to the crystal structures of the DNA complexes, the first 14 residues of the basic region are found to be mostly unfolded while the loop is observed to be flexible. This indicates that these domains undergo conformational changes upon DNA binding. On the other hand, we find the last four residues of the basic region form a persistent helical turn contiguous to H(1). In addition, we provide evidence of the existence of internal motions in the backbone of H(1) that are of larger amplitude and longer time-scale (nanoseconds) than the ones in the H(2) and LZ domain

  10. Mechanism and Model Construction of Compression Set Reversible Rrecovery of HIPS/HVPBR Thermoplastic Vulcanizate%HIPS/HVPBR热塑性硫化胶压缩永久变形可逆回复的模型及机制

    Institute of Scientific and Technical Information of China (English)

    赵静; 华静; 王兆波

    2014-01-01

    采用动态硫化法制备了高抗冲聚苯乙烯(HIPS)/高乙烯基聚丁二烯(HVPBR)热塑性硫化胶(TPV),研究了橡塑比和热处理温度对压缩永久变形可逆回复的影响,探讨了可逆回复机制并构建了数学模型。结果表明,提高橡塑比和热处理温度,压缩永久变形的可逆回复程度和回复速度明显提高;热处理温度接近基体Tg 时,体系的压缩永久变形几乎完全可逆;基于可逆回复过程,探讨压缩永久变形的可逆回复机制,并构建了其数学模型,进而探讨了橡塑比和热处理温度对可逆回复各阶段松弛时间的影响。%Thermoplastic vulcanizate (TPV)based on high impact polystyrene (HIPS)/high vinyl polybutadiene rubber (HVPBR)blends were prepared by dynamic vulcanization,and the influences of blending ratio and heat-treatment temperature on the reversible recovery of compression set,together with the mechanism and model construction of the reversible recovery of the TPV,were investigated systematically.The results showed that increasing the content of HVPBR in TPV and increasing heat-treatment temperature would lead to the fast recovery of compression set;moreover,the TPV had fully reversible deformation ability when the heat-treatment temperature was close to the Tg of HIPS. The reversible recovery mechanism was discussed based on the characteristics of the reversible recov-ery curves of compression set.A mathematical model to explain the reversible recovery of compression set was established via the fitting of the experimental data,and the influences of blending ratio and heat-treatment temperature on the relaxation time in each stage of the recovery course were discussed.

  11. Anti-oxidant activity of 6-gingerol as a hydroxyl radical scavenger by hydrogen atom transfer, radical addition and electron transfer mechanisms

    Indian Academy of Sciences (India)

    MANISH K TIWARI; P C MISHRA

    2016-08-01

    Mechanisms of anti-oxidant action of 6-gingerol as a hydroxyl radical scavenger have been investigated using the transition state theory within the framework of density functional theory. Hydrogen abstraction by a hydroxyl radical from the different sites of 6-gingerol and addition of the former to the different sites ofthe latter were studied. Electron transfer from 6-gingerol to a hydroxyl radical was also studied. Solvent effect in aqueous media was treated using the integral equation formalism of the polarizable continuum model (IEFPCM). Reaction rate constants in aqueous media were generally found to be larger than those in gas phase. The tunneling contributions to rate constants were found to be appreciable. Our results show that 6-gingerol is an excellent anti-oxidant and would scavenge hydroxyl radicals efficiently.

  12. Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate (MMDS) as electrolyte additive and its acting mechanism

    Institute of Scientific and Technical Information of China (English)

    Fengju Bian; Zhongru Zhang; Yong Yang

    2014-01-01

    The effects of methylene methanedisulfonate (MMDS) on the high-temperature (∼50◦C) cycle performance of LiMn2O4/graphite cells are investigated. By addition of 2 wt%MMDS into a routine electrolyte, the high-temperature cycling performance of LiMn2O4/graphite cells can be significantly improved. The analysis of differential capacity curves and energy-dispersive X-ray spectrometry (EDX) indicates that MMDS decomposed on both cathode and anode. The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells. It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn2O4 material, while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.

  13. Mechanical properties and histological evaluation of sintered beta-Ca2P2O7 with Na4P2O7.10H2O addition.

    Science.gov (United States)

    Lin, F H; Lin, C C; Lu, C M; Liu, H C; Sun, J S; Wang, C Y

    1995-07-01

    The ultimate goal of implantation of biomaterials in the skeleton is to reach full integration of the non-living implant with the living bone. The biomaterial can be used much as a bone graft, resorbing or dissolving as bone growth occurs, and the end result is a new remoulded bone. Calcium pyrophosphate, Ca2P2O7, is one of the intermediate products of bone mineralization. beta-Dicalcium pyrophosphate (beta-DCP) doped with certain amounts of Na4P2O7.10H2O was prepared as the developed material. Na4P2O7.10H2O was used as a liquid-phase additive to improve the sintering process and promote physiological bioresorbability. Compressive strength and four-point bending strength were measured by the Bionix test system 858. The mechanical strength of the sintered beta-DCP increased with the addition of Na4P2O7.10H2O up to 5 wt%, but thereafter decreased. The microstructure and crystal structure were analysed by the techniques of SEM, EPMA, TEM and XRD. The relationship between the mechanical strength of the sintered bioceramics and the Na4P2O7.10H2O dopant was examined in terms of the presence of NaCa(PO3)3, grain growth and abnormal grain coalescence while the dopant increased. Preliminary in vivo evaluation was studied by rabbit femur condyle implantation. There was no inflammation or any toxic sign during the experimental period. The histological section of intraosseous implantation revealed that the new bone deposited directly on the surface of the material in the fourth week after operation. The implant gradually decreased in volume and was replaced by the surrounding regenerated bone in the rabbit condyle in vivo environment. The results led us to conclude that the developed material has great potential as a biodegradable bone substitute.

  14. Insights into mechanisms governing forest carbon response to nitrogen deposition: a model–data comparison using observed responses to nitrogen addition

    Directory of Open Access Journals (Sweden)

    R. Q. Thomas

    2013-06-01

    Full Text Available In many forest ecosystems, nitrogen (N deposition enhances plant uptake of carbon dioxide, thus reducing climate warming from fossil fuel emissions. Therefore, accurately modeling how forest carbon (C sequestration responds to N deposition is critical for understanding how future changes in N availability will influence climate. Here, we use observations of forest C response to N inputs along N deposition gradients and at five temperate forest sites with fertilization experiments to test and improve a global biogeochemical model (CLM-CN 4.0. We show that the CLM-CN plant C growth response to N deposition was smaller than observed and the modeled response to N fertilization was larger than observed. A set of modifications to the CLM-CN improved the correspondence between model predictions and observational data (1 by increasing the aboveground C storage in response to historical N deposition (1850–2004 from 14 to 34 kg C per additional kg N added through deposition and (2 by decreasing the aboveground net primary productivity response to N fertilization experiments from 91 to 57 g C m−2 yr−1. Modeled growth response to N deposition was most sensitive to altering the processes that control plant N uptake and the pathways of N loss. The response to N deposition also increased with a more closed N cycle (reduced N fixation and N gas loss and decreased when prioritizing microbial over plant uptake of soil inorganic N. The net effect of all the modifications to the CLM-CN resulted in greater retention of N deposition and a greater role of synergy between N deposition and rising atmospheric CO2 as a mechanism governing increases in temperate forest primary production over the 20th century. Overall, testing models with both the response to gradual increases in N inputs over decades (N deposition and N pulse additions of N over multiple years (N fertilization allows for greater understanding of the mechanisms governing C–N coupling.

  15. Simulation studies of nucleation of ferroelectric polarization reversal.

    Energy Technology Data Exchange (ETDEWEB)

    Brennecka, Geoffrey L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Winchester, Benjamin Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-08-01

    Electric field-induced reversal of spontaneous polarization is the defining characteristic of a ferroelectric material, but the process(es) and mechanism(s) associated with the initial nucleation of reverse-polarity domains are poorly understood. This report describes studies carried out using phase field modeling of LiTaO3, a relatively simple prototype ferroelectric material, in order to explore the effects of either mechanical deformation or optically-induced free charges on nucleation and resulting domain configuration during field-induced polarization reversal. Conditions were selected to approximate as closely as feasible those of accompanying experimental work in order to provide not only support for the experimental work but also ensure that additional experimental validation of the simulations could be carried out in the future. Phase field simulations strongly support surface mechanical damage/deformation as effective for dramatically reducing the overall coercive field (Ec) via local field enhancements. Further, optically-nucleated polarization reversal appears to occur via stabilization of latent nuclei via the charge screening effects of free charges.

  16. Characteristics and fate of the spermatozoa of Inachus phalangium (Decapoda, Majidae): description of novel sperm structures and evidence for an additional mechanism of sperm competition in Brachyura.

    Science.gov (United States)

    Rorandelli, Rocco; Paoli, Francesco; Cannicci, Stefano; Mercati, David; Giusti, Fabiola

    2008-03-01

    Various aspects of the reproductive anatomy of the spider crab Inachus phalangium are investigated utilizing light and electron microscopy. Spermatozoal ultrastructure reveals the presence of a glycocalyx in the peripheral region of the periopercular rim, never recorded before in crustacean sperm cells. Sperm cell morphological traits such as semi-lunar acrosome shape, centrally perforate and flat operculum, and absence of a thickened ring, are shared only with Macropodia longirostris, confirming a close phylogenetic relationship of these species and their separation from the other members of the family Majidae. Spermatozoa are transferred to females inside spermatophores of different sizes, but during ejaculate transfer, larger spermatophores might be ruptured by tooth-like structures present on the ejaculatory canal of the male first gonopod, releasing free sperm cells. Such a mechanism could represent the first evidence of a second form of sperm competition in conflict with sperm displacement, the only mechanism of sperm competition known among Brachyura, enabling paternity for both dominant and smaller, non-dominant, males. In addition, we propose several hypotheses concerning the remote and proximal causes of the existence of large seminal receptacles in females of I. phalangium. Among these, genetically diverse progeny, reduction of sexual harassment and phylogenetic retention seem the most plausible, while acquisition of nutrients from seminal fluids, demonstrated in other arthropods, and suggested by previous studies, could be discarded on the basis of the presented data.

  17. Effect of various additives on microstructure, mechanical properties, and in vitro bioactivity of sodium oxide-calcium oxide-silica-phosphorus pentoxide glass-ceramics.

    Science.gov (United States)

    Li, H C; Wang, D G; Hu, J H; Chen, C Z

    2013-09-01

    The partial substitution of MgO, TiO2, or CaF2 for CaO in the Na2O-CaO-SiO2-P2O5 (45S5) system was conducted by the sol-gel method and a comparative study on structural, mechanical properties, and bioactivity of the glasses was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass-ceramic properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and so on, and the bioactivity of the glass-ceramic was evaluated by in vitro assays in simulated body fluid (SBF). Results indicate that with the partial substitution of MgO, TiO2, CaF2 for CaO in glass composition, the mechanical properties of the glass-ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization and the crystallization does not inhibit the glass-ceramic bioactivity. All samples possess bioactivity; however, the bioactivity of these glass-ceramics is quite different. Compared with 45S5, the introduction of MgO decreases the ability of apatite induction. The addition of TiO2 does not significantly improve the bioactivity, and the replacement of CaO by CaF2 shows a higher bioactivity.

  18. The effects of addition of La{sub 2}O{sub 3} on the microstructure and mechanical properties of carbon/carbon composites

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jinhua, E-mail: lujinhua@nwpu.edu.cn; Yang, Binke; Li, Hejun; Fu, Qiangang; Zhang, Weiben

    2014-07-29

    For the purpose of comparison, C/C composites were prepared with and without lanthanum oxide (La{sub 2}O{sub 3}) by thermal gradient chemical vapour infiltration (TCVI). Natural gas was used as the carbon source, and N{sub 2} was selected as the diluent gas and protected gas in the experiments. The effects of percentage composition of La{sub 2}O{sub 3} on the microstructure and mechanical properties were investigated. The microstructure was investigated via polarized light microscope (PLM) and scanning electron microscope (SEM). The mechanical properties were studied via three-point flexural testing. The results indicate that the addition of La{sub 2}O{sub 3} has a considerable effect on pyrocarbon texture, with the matrix of the pure C/C composite being composed of ISO and smooth laminar (SL) pyrocarbon, whereas the matrix of composites with La{sub 2}O{sub 3} was mainly dominated by SL pyrocarbon. The differences are the refinement of pyrocarbon texture and increase of the extinction angle with the increasing content of La{sub 2}O{sub 3}. Moreover, it was observed that the ultimate flexural strength of C/C composites with La{sub 2}O{sub 3} was significantly improved, from which it can be deduced that La{sub 2}O{sub 3} improves the interface roughness and interface bonding strength between carbon fibres and the pyrocarbon matrix by interfacial chemical reaction.

  19. Reversible Switching of Cooperating Replicators

    Science.gov (United States)

    Urtel, Georg C.; Rind, Thomas; Braun, Dieter

    2017-02-01

    How can molecules with short lifetimes preserve their information over millions of years? For evolution to occur, information-carrying molecules have to replicate before they degrade. Our experiments reveal a robust, reversible cooperation mechanism in oligonucleotide replication. Two inherently slow replicating hairpin molecules can transfer their information to fast crossbreed replicators that outgrow the hairpins. The reverse is also possible. When one replication initiation site is missing, single hairpins reemerge from the crossbreed. With this mechanism, interacting replicators can switch between the hairpin and crossbreed mode, revealing a flexible adaptation to different boundary conditions.

  20. The Effect of Ag Addition on the Enhancement of the Thermal and Mechanical Properties of CuZrAl Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Tsan-Man Chung

    2016-09-01

    Full Text Available In this study, the thermal and mechanical properties of Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6 bulk metallic glasses (BMGs are investigated by using an X-ray diffractometer (XRD, a differential scanning calorimeter (DSC, differential thermal analysis (DTA, a Vickers hardness tester, a material test system (MTS, scanning electron microscopy (SEM, and transmission electron microscopy (TEM. Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6 BMGs were made by arc-melting and an injection casting process. The results revealed that the glass transition temperature (Tg and the crystallization temperature (Tx of CuZrAl alloy decreased with the Ag addition. Hence, the supercooled liquid region and γ of Cu45Zr43Al7Ag5 alloy increased to 76 K and 0.42, respectively. The thermal stability and glass forming ability of CuZrAlAg BMG alloys were enhanced by the microalloyed Ag content. The room temperature compressive fracture strength and strain measured of Cu47Zr43Al7Ag3 were about 2200 MPa and 2.1%, respectively. The distribution of vein patterns and the formation of nanocrystalline phases on the fracture surface of Cu47Zr43Al7Ag3 alloy can be observed by SEM and TEM to be significant, indicating a typical ductile fracture behavior and an improved plasticity of alloys with the addition of microalloyed Ag from 0 to 6 atom %.

  1. Microstructural evolution and mechanical property of Ti-6Al-4V wall deposited by continuous plasma arc additive manufacturing without post heat treatment.

    Science.gov (United States)

    Lin, Jianjun; Lv, Yaohui; Liu, Yuxin; Sun, Zhe; Wang, Kaibo; Li, Zhuguo; Wu, Yixiong; Xu, Binshi

    2017-05-01

    Plasma arc additive manufacturing (PAM) is a novel additive manufacturing (AM) technology due to its big potential in improving efficiency, convenience and being cost-savings compared to other AM processes of high energy bea\\m. In this research, several Ti-6Al-4V thin walls were deposited by optimized weld wire-feed continuous PAM process (CPAM), in which the heat input was gradually decreased layer by layer. The deposited thin wall consisted of various morphologies, which includes epitaxial growth of prior β grains, horizontal layer bands, martensite and basket weave microstructure, that depends on the heat input, multiple thermal cycles and gradual cooling rate in the deposition process. By gradually reducing heat input of each bead and using continuous current in the PAM process, the average yield strength (YS), ultimate tensile strength (UTS) and elongation reach about 877MPa, 968MPa and 1.5%, respectively, which exceed the standard level of forging. The mechanical property was strengthened and toughened due to weakening the aspect ratio of prior β grains and separating nano-dispersoids among α lamellar. Furthermore, this research demonstrates that the CPAM process has a potential to manufacture or remanufacture in AM components of metallic biomaterials without post-processing heat treatment.

  2. Improvement on the microstructure stability, mechanical and wetting properties of Sn-Ag-Cu lead-free solder with the addition of rare earth elements

    Energy Technology Data Exchange (ETDEWEB)

    Yu, D.Q.; Zhao, J.; Wang, L

    2004-08-11

    Ternary lead-free solder alloys Sn-Ag-Cu were considered as the potential alternatives to lead-tin alloys comparing with other solders. In this paper, microstructure and mechanical properties of Sn-2.5Ag-0.7Cu, Sn-3.5Ag-0.7Cu, Sn-3.5Ag-0.7Cu-0.1RE, and Sn-3.5Ag-0.7Cu-0.25RE alloys were researched. Coarse {beta}-Sn grains were formed in Sn-2.5Ag-0.7Cu and Sn-3.5Ag-0.7Cu alloys and bulky Ag{sub 3}Sn intermetallics were found in Sn-3.5Ag-0.7Cu alloy. With the addition of trace rare earth (RE) elements the coarse {beta}-Sn grains were refrained, at the same time, Cu{sub 6}Sn{sub 5} and Ag{sub 3}Sn intermetallics were finer according to the adsorption affection of the active rare earth elements. Due to the fine and uniform microstructure, the tensile strength and elongation were improved. In addition, the wetting properties were also enhanced. All these results indicated that adding trace rare earth elements was an efficient way to develop new solders.

  3. Mechanical and Combustion Performance of Multi-Walled Carbon Nanotubes as an Additive to Paraffin-Based Solid Fuels for Hybrid Rockets

    Science.gov (United States)

    Larson, Daniel B.; Boyer, Eric; Wachs, Trevor; Kuo, Kenneth, K.; Koo, Joseph H.; Story, George

    2012-01-01

    Paraffin-based solid fuels for hybrid rocket motor applications are recognized as a fastburning alternative to other fuel binders such as HTPB, but efforts to further improve the burning rate and mechanical properties of paraffin are still necessary. One approach that is considered in this study is to use multi-walled carbon nanotubes (MWNT) as an additive to paraffin wax. Carbon nanotubes provide increased electrical and thermal conductivity to the solid-fuel grains to which they are added, which can improve the mass burning rate. Furthermore, the addition of ultra-fine aluminum particles to the paraffin/MWNT fuel grains can enhance regression rate of the solid fuel and the density impulse of the hybrid rocket. The multi-walled carbon nanotubes also present the possibility of greatly improving the mechanical properties (e.g., tensile strength) of the paraffin-based solid-fuel grains. For casting these solid-fuel grains, various percentages of MWNT and aluminum particles will be added to the paraffin wax. Previous work has been published about the dispersion and mixing of carbon nanotubes.1 Another manufacturing method has been used for mixing the MWNT with a phenolic resin for ablative applications, and the manufacturing and mixing processes are well-documented in the literature.2 The cost of MWNT is a small fraction of single-walled nanotubes. This is a scale-up advantage as future applications and projects will require low cost additives to maintain cost effectiveness. Testing of the solid-fuel grains will be conducted in several steps. Dog bone samples will be cast and prepared for tensile testing. The fuel samples will also be analyzed using thermogravimetric analysis and a high-resolution scanning electron microscope (SEM). The SEM will allow for examination of the solid fuel grain for uniformity and consistency. The paraffin-based fuel grains will also be tested using two hybrid rocket test motors located at the Pennsylvania State University s High Pressure

  4. Reversibly Bistable Flexible Electronics

    KAUST Repository

    Alfaraj, Nasir

    2015-05-01

    Introducing the notion of transformational silicon electronics has paved the way for integrating various applications with silicon-based, modern, high-performance electronic circuits that are mechanically flexible and optically semitransparent. While maintaining large-scale production and prototyping rapidity, this flexible and translucent scheme demonstrates the potential to transform conventionally stiff electronic devices into thin and foldable ones without compromising long-term performance and reliability. In this work, we report on the fabrication and characterization of reversibly bistable flexible electronic switches that utilize flexible n-channel metal-oxide-semiconductor field-effect transistors. The transistors are fabricated initially on rigid (100) silicon substrates before they are peeled off. They can be used to control flexible batches of light-emitting diodes, demonstrating both the relative ease of scaling at minimum cost and maximum reliability and the feasibility of integration. The peeled-off silicon fabric is about 25 µm thick. The fabricated devices are transferred to a reversibly bistable flexible platform through which, for example, a flexible smartphone can be wrapped around a user’s wrist and can also be set back to its original mechanical position. Buckling and cyclic bending of such host platforms brings a completely new dimension to the development of flexible electronics, especially rollable displays.

  5. Study of the Activity and Possible Mechanism of Action of a Reversible Inhibitor of Recombinant Human KAT-2: A Promising Lead in Neurodegenerative and Cognitive Disorders

    Directory of Open Access Journals (Sweden)

    Alireza Nematollahi

    2016-06-01

    Full Text Available Abnormal levels of kynurenic acid (KYNA in the human brain are believed to be connected to several central nervous system (CNS diseases, therefore compounds which affect the production of this crucial metabolite are of interest in CNS drug development. The majority of KYNA production is accounted for by kynurenine aminotransferase-2 (KAT-2 in the mammalian brain; hence this enzyme is one of the most interesting targets with which to modulate KYNA levels. Recently developed human KAT-2 inhibitors with high potencies are known to irreversibly bind to the enzyme cofactor, pyridoxal-5′-phosphate (PLP, which may lead to severe side effects due to the abundance of PLP-dependent enzymes. In this study, we report a reversible and competitive inhibitor of KAT-2. Its inhibitory activities were examined using HPLC and surface plasmon resonance (SPR and compare favorably with other recently reported KAT-2 inhibitors. Our inhibitor, NS-1502, demonstrates suitable inhibitory activity, almost 10 times more potent than the known reversible KAT-2, (S-ESBA.

  6. Reversal effect of sulpiride on rotational behaviour of rats with unilateral frontal cortex ablation: an alternative explanation for the pharmacological mechanism of its antidepressant effect.

    Science.gov (United States)

    Kaneno, S; Fukamauchi, F; Komatsu, H; Koyama, K; Ikawa, K

    2001-02-01

    The antidepressant effect of sulpiride has been generally explained as the result of its preferential blocking effect on self-inhibitory presynaptic dopamine autoreceptors at low doses. Low dose haloperidol has the same blocking effect. In rats with unilateral ablation of the frontal cortex, methamphetamine administration induced mild contralateral rotation 10 days after the operation. We examined whether low dose sulpiride and haloperidol would have the same effect on this rotational model. High dose sulpiride (100 mg/kg) or low dose haloperidol (0.05 mg/kg) prevented this methamphetamine-induced rotation. However, low dose (15 mg/kg) sulpiride clearly reversed the direction of rotation. This reversal effect of low dose sulpiride is not explained by the preferential blocking effect on dopamine autoreceptors. The results suggest that low dose sulpiride, unlike low dose haloperidol, has a prominent blocking effect on D2 receptors in the frontal cortex. This unique effect of sulpiride may be relevant to its clinical antidepressant and anxiolytic effects at low doses.

  7. Surface molecular imprinting onto fluorescein-coated magnetic nanoparticlesvia reversible addition fragmentation chain transfer polymerization: A facile three-in-one system for recognition and separation of endocrine disrupting chemicals

    Science.gov (United States)

    Li, Ying; Dong, Cunku; Chu, Jia; Qi, Jingyao; Li, Xin

    2011-01-01

    In this study, we present a general protocol for the making of surface-imprinted magnetic fluorescence beads viareversible addition-fragmentation chain transfer polymerization. The resulting composites were characterized by X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The as-synthesized beads exhibited homogeneous polymer films (thickness of about 5.7 nm), spherical shape, high fluorescence intensity and magnetic property (Magnetization (Ms) = 3.67 emu g-1). The hybrids bind the original template 17β-estradiol with an appreciable selectivity over structurally related compounds. In addition, the resulting hybrids performed without obvious deterioration after five repeated cycles. This study therefore demonstrates the potential of molecularly imprinted polymers for the recognition and separation of endocrine disrupting chemicals.In this study, we present a general protocol for the making of surface-imprinted magnetic fluorescence beads viareversible addition-fragmentation chain transfer polymerization. The resulting composites were characterized by X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The as-synthesized beads exhibited homogeneous polymer films (thickness of about 5.7 nm), spherical shape, high fluorescence intensity and magnetic property (Magnetization (Ms) = 3.67 emu g-1). The hybrids bind the original template 17β-estradiol with an appreciable selectivity over structurally related compounds. In addition, the resulting hybrids performed without obvious deterioration after five repeated cycles. This study therefore demonstrates the potential of molecularly imprinted polymers for the recognition and separation of endocrine disrupting chemicals. Electronic

  8. Effect of growth mechanisms on the deformation of a unit cell and polarization reversal in barium-strontium titanate heterostructures on magnesium oxide

    Science.gov (United States)

    Mukhortov, V. M.; Golovko, Yu. I.; Biryukov, S. V.; Anokhin, A.; Yuzyuk, Yu. I.

    2016-01-01

    The effect of a growth mechanism on the unit cell strain and the related change in the properties of single-crystal Ba0.8Sr0.2TiO3 films grown on MgO substrates according to the Frank-van der Merwe and Volmer-Weber growth mechanisms is studied. The unit cell strain is shown to depend substantially on the film thickness and the growth mechanism. It is found that the same film-substrate pair can be used to vary stresses in the film from two-dimensional tensile to compressive stresses due to a change in the growth mechanism and the film thickness.

  9. 机械蒸汽再压缩技术处理反渗透浓水的中试研究%Pilot Study on Mechanical Vapor Recompression Technology for Treatment of Concentrated Water from Reverse Osmosis Process

    Institute of Scientific and Technical Information of China (English)

    张金鸿; 侯霙; 李海芳; 唐运平

    2011-01-01

    近年来,反渗透(RO)在污水厂二级出水深度处理中的应用越来越多.然而,RO浓水的含盐量较高、有机物难于降解,采用常规方法处理时出水水质难于达到排放标准.采用机械蒸汽再压缩技术(MVR)对某污水厂的反渗透浓水进行了6倍浓缩的中试,其出水COD≤50 mg/L、NH-N≤10 mg/L,可以达到(GB/T 18920-2002)的要求;COD、TDS、Mg和色度等指标的浓缩倍数与体系的浓缩倍数基本一致,而浓缩水中的TP、SiO、TN、NH-N浓度却低于原水的,这主要是由于磷酸盐、硅酸盐的沉淀和氨气逸出所致.另外,钙盐等的沉淀作用还造成浓缩水中SS浓度的增加.由此可见,利用MVR处理反渗透浓水在技术上是可行的,但是需要增加沉淀物的预处理和排出气体的收集处理装置.%Recently, the application of reverse osmosis (RO) in advanced treatment of effluent form WWTP becomes very popular. However, due to high salinity and refractory organic compounds in concentrated water of RO, the effluent treated by traditional processes can not meet the discharge standard. A pilot experiment at a concentration factor of 6 was conducted to treat concentrated water from reverse osmosis (RO) process in a sewage treatment plant using mechanical vapor recompression (MVR)technology. COD and NH3 -N in the effluent from MVR process are equal to or less than 50 mg/L and 10 mg/L, meeting the Reuse of Urban Recycling Water-Water Quality Standard for Urban Miscellaneous Water Consumption (GB/T 18920 -2002). The concentration factors of COD, TDS, Mg2+ and color in concentrated water of MVR are similar to those in concentrated water of RO. However, the concentration factors of TP, SiO2, TN and NH3 - N are lower than those in concentrated water of RO due to escape of ammonia and precipitation of phosphate and silicate. In addition, precipitation of calcium salt causes increase of SS in concentrated water of MVR. The experiment shows that MVR technology is

  10. Effect of Rare-Earth (La, Ce, and Y) Additions on the Microstructure and Mechanical Behavior of Sn-3.9Ag-0.7Cu Solder Alloy

    Science.gov (United States)

    Dudek, M. A.; Chawla, N.

    2010-03-01

    In this article, we report on the microstructure and mechanical properties of Ce- and Y-containing Sn-3.9Ag-0.7Cu solders. The microstructures of both as-processed solder and solder joints containing rare-earth (RE) elements (up to 0.5 wt pct) are more refined compared to conventional Sn-3.9Ag-0.7Cu, with decreases in secondary Sn dendrite size and spacing and a thinner Cu6Sn5 intermetallic layer at the Cu/solder interface. These results agree well with similar observations seen in La-containing solders reported previously. The monotonic shear behavior of reflowed Sn-3.9Ag-0.7Cu- X(Ce, Y)/Cu lap shear joints was studied as well as the creep behavior at 368 K (95 °C). The data were compared with results obtained for Sn-3.9Ag-0.7Cu and Sn-3.9Ag-0.7Cu- XLa alloys. All RE-containing alloys exhibited creep behavior similar to Sn-3.9Ag-0.7Cu. Alloys with Ce additions exhibited a small decrease in ultimate shear strength but higher elongations compared with Sn-Ag-Cu. Similar observations were seen in La-containing solders. The influence of the RE-containing intermetallics (CeSn3 and YSn3) that form in these alloys on the microstructural refinement, solidification behavior, and mechanical performance of these novel materials is discussed.

  11. Tape-cast and sintered β-tricalcium phosphate laminates for biomedical applications: Effect of milled Al2O3 fiber additives on microstructural and mechanical properties.

    Science.gov (United States)

    Tanimoto, Yasuhiro; Teshima, Masahiro; Nishiyama, Norihiro; Yamaguchi, Masaru; Hirayama, Satoshi; Shibata, Yo; Miyazaki, Takashi

    2012-11-01

    The aim of this study was to develop the tape-cast, laminated, and sintered β-tricalcium phosphate (β-TCP) with milled Al(2)O(3) fibers for biomedical applications. Moreover, the effects of Al(2)O(3)-fiber content on the microstructural and mechanical properties of the sintered β-TCP laminates were investigated. The milled Al(2)O(3) fibers were added at four different contents, namely 0, 5, 10, or 15 mass%, to the initial β-TCP slurry. Next, β-TCP green sheets were fabricated from the β-TCP slurry containing the milled Al(2)O(3) fibers by a tape-casting method. Finally, six plies of β-TCP monolayer sheet were laminated and sintered at a maximum temperature of 1100°C in a furnace. The results showed that there were large differences between the apparent porosities, dynamic hardness, and flexural properties of the sintered β-TCP laminates with Al(2)O(3)-fiber contents of 0 and 5 mass%, but few differences among laminates with fiber contents of 5, 10, and 15 mass%. This indicates that the addition of only 5 mass% of Al(2)O(3) fibers strongly affects the degree of sintering, corresponding to crystallization of the β-TCP matrix phase. Furthermore, the flexural moduli of our materials ranged from 10.7 to 16.0 GPa when the Al(2)O(3)-fiber content changed from 5 to 15 mass% and were the almost same as those of human bones reported by other researchers. In conclusion, sintered β-TCP laminates with Al(2)O(3) fibers have potential uses in a wide range of biomedical applications because the microstructural and mechanical properties of the sintered β-TCP laminates can be controlled by adding Al(2)O(3) fibers to the β-TCP.

  12. Insights into mechanisms governing forest carbon response to nitrogen deposition: a model-data comparison using observed responses to nitrogen addition

    Directory of Open Access Journals (Sweden)

    R. Q. Thomas

    2013-01-01

    Full Text Available In many forest ecosystems, nitrogen (N deposition enhances plant uptake of carbon dioxide, thus reducing climate warming from fossil fuel emissions. Therefore, accurately modeling how forest carbon (C sequestration responds to N deposition is critical for understanding how future changes in N availability will influence climate. Here, we use observations of forest C response to N inputs along N deposition gradients and at five temperate forest sites with fertilization experiments to test and improve a~global biogeochemical model (CLM-CN 4.0. We show that the CLM-CN plant C growth response to N deposition was smaller than observed and the modeled response to N fertilization was larger than observed. A set of modifications to the CLM-CN improved the correspondence between model predictions and observational data (1 by increasing the aboveground C storage in response to historical N deposition (1850–2004 from 14 to 34 kg C per additional kg N added through deposition and (2 by decreasing the aboveground net primary productivity response to N fertilization experiments from 91 to 57 g C m−2 yr−1. Modeled growth response to N deposition was most sensitive to altering the processes that control plant N uptake and the pathways of N loss. The response to N deposition also increased with a more closed N cycle (reduced N fixation and N gas loss and decreased when prioritizing microbial over plant uptake of soil inorganic N. The net effect of all the modifications to the CLM-CN resulted in greater retention of N deposition and a greater role of synergy between N deposition and rising atmospheric CO2 as a mechanism governing increases in temperate forest primary production over the 20th century. Overall, testing models with both the response to gradual increases in N inputs over decades (N deposition and N pulse additions of N over multiple years (N fertilization allows for greater understanding of the mechanisms

  13. Mechanism of drug resistance and reversal with ligustra-zine and cyclosporin A in cisplatin-induced human epithelial ovarian cancer resistant cell line 3Ao/cDDP

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Objective: To investigate the mechanism of resistance and reversal effect of ligustrazine and cyclosporin A in cisplatin-induced multidrug resistance ovarian cancer cell line 3Ao/cDDP. Methods: Using the corresponding dose calculated from clinical chemotherapy at 30 mg cisplatin per cycle, we established 3Ao/cDDP with 3Ao exposed at regular intervals and repeatedly to high-level concentration of cisplatin at 10 m g/ml for 24 hours each time. Expressions of LRP, MRP, P-gp, GSTp and TopoII were quantitatively detected with FCM. For drug resistance reversal, cyclosporin A and ligustrazine were administered singly or in combination at the maximal dose without cytotoxicity. Inhibition rates were determined by MTT assay. Results: 3Ao/cDDP was established after 4.5 months, with resistance factor 1.6 which was similar to clinical resistance degree. Low expression levels of MRP and P-gp were found in both 3Ao and 3Ao/cDDP (P>0.05), and LRP and GSTp expression levels in 3Ao/cDDP were significantly higher than those in 3Ao (P0.05 vs cDDP), cDDP plus cyclosporin A 49.635± 0.021% (P<0.01 vs cDDP), and cDDP plus ligustrazine and cyclosporin A 58.861± 0.014% (P<0.01 vs cDDP). Conclusions: 3Ao/cDDP, induced by cisplatin and established by imitating the characteristics of clinical chemotherapy for epithelial ovarian cancer, was an ideal model for investigation of cisplatin resistance in vitro. Cisplatin resistance in 3Ao/cDDP could be accounted for by higher LRP, GSTp and lower TopoII expression and was not associated with MRP or P-gp. Ligustrazine had no significant reversal effect on cisplatin resistance, but cyclosporin A could reverse the resistance effectively.

  14. Effect of Energy Input on Microstructure and Mechanical Properties of Titanium Aluminide Alloy Fabricated by the Additive Manufacturing Process of Electron Beam Melting

    Directory of Open Access Journals (Sweden)

    Ashfaq Mohammad

    2017-02-01

    Full Text Available Titanium aluminides qualify adequately for advanced aero-engine applications in place of conventional nickel based superalloys. The combination of high temperature properties and lower density gives an edge to the titanium aluminide alloys. Nevertheless, challenges remain on how to process these essentially intermetallic alloys in to an actual product. Electron Beam Melting (EBM, an Additive Manufacturing Method, can build complex shaped solid parts from a given feedstock powder, thus overcoming the shortcomings of the conventional processing techniques such as machining and forging. The amount of energy supplied by the electron beam has considerable influence on the final build quality in the EBM process. Energy input is decided by the beam voltage, beam scan speed, beam current, and track offset distance. In the current work, beam current and track offset were varied to reflect three levels of energy input. Microstructural and mechanical properties were evaluated for these samples. The microstructure gradually coarsened from top to bottom along the build direction. Whereas higher energy favored lath microstructure, lower energy tended toward equiaxed grains. Computed tomography analysis revealed a greater amount of porosity in low energy samples. In addition, the lack of bonding defects led to premature failure in the tension test of low energy samples. Increase in energy to a medium level largely cancelled out the porosity, thereby increasing the strength. However, this trend did not continue with the high energy samples. Electron microscopy and X-ray diffraction investigations were carried out to understand this non-linear behavior of the strength in the three samples. Overall, the results of this work suggest that the input energy should be considered primarily whenever any new alloy system has to be processed through the EBM route.

  15. An integrated mechanical-enzymatic reverse osmosis treatment of dairy industry wastewater and milk protein recovery as a fat replacer: a closed loop approach

    Directory of Open Access Journals (Sweden)

    F. Sarghini

    2013-09-01

    Full Text Available The dairy industry can be classified among the most polluting of the food industries in volume in regard to its large water consumption, generating from 0.2 to 10 L of effluent per liter of processed milk. Dairy industry effluents usually include highly dissolved organic matter with varying characteristics, and a correct waste management project is required to handle. In a framework of natural water resource availability and cost increase, wastewater treatment for water reuse can lower the overall water consumption and the global effluent volume of industrial plants. Moreover, correct dismissal of dairy industry wastewater is sometimes neglected by the operators , increasing the environmental impact due to the chemical and biological characteristics of such effluents. On the other hand, in the case of whey effluents, several by-products are still present inside, such as lactose and milk proteins. Membrane technology has some advantages including a high degree of reliability in removing dissolved, colloidal and particulate matter, like the selectivity in size of pollutants to be removed and the possibility of very compact treatment plants. For example, Reverse Osmosis (RO technology has been successfully applied for the treatment of dairy wastes (1, and as a technology for concentration and fractionation of whey. In this work a membrane treatment approach using reverse osmosis technology is investigated and implemented: the permeate obtained can be reused as clean warm water for cleaning and sanitation of production plants, while concentrated milk proteins are modified by using transglutaminase enzyme obtaining a high temperature resistant fat replacer to be used in different low-fat products like for example mozzarella cheese.

  16. 间隙对双行星换向机构动态特性的影响%Influence of Backlash on Dynamic Characteristic of Dual - planetary Reversing Mechanism

    Institute of Scientific and Technical Information of China (English)

    薛殿伦; 马洪涛; 李新燕

    2012-01-01

    针对轿车无级变速器的双行星换向机构,综合考虑时变啮合刚度、齿侧间隙、激励频率、综合啮合误差等因素,建立了该行星传动系统的非线性动力学模型.采用自适应变步长Runge-Kutta数值算法,对系统运动方程求解.通过动载荷时域历程、相图、Poincare映射、FFT等途径,分析了某激励频率下系统响应随齿侧间隙的变化历程,以及不同齿侧间隙下系统响应幅值的频域历程.结果表明,随着齿侧间隙的增加,系统响应将逐渐由简谐状态进入混沌状态,但途中存在突变、分岔及周期响应与混沌响应交替出现等复杂的动力学表现;另外,系统响应幅值在频域历程内出现多次跳跃,且随着间隙的增加,振幅跳跃的次数及幅度随之增大,系统的非线性表现增强.%Aiming at the dynamic characteristic of the CVT transmission dual - planetary reversing mechanism, considering backlash, time - varying stiffness, excitation frequency, comprehensive meshing error, the multi - freedom nonlinear dynamics model of the planetary transmission system is established, Then, the differential equation of the system is solved with the Runge - Kutta numerical integration method. Through dynamic load time domain course, phase diagram, Poincare mapping and FFT, the change course of system response with backlash under a excitation frequency and the frequency domain course of system response amplitude under different backlash are analyzed. The result show that with the increase of backlash, the system response will go from harmonic to chaos, but the complex dynamics performance of mutation, bifurcation, period response and chaos response jumping happens is exist in the process. In addition , the system response amplitude jumps jumps repeatedly in the frequency domain course, and with the increase of clearance, the number and range of amplitude jump is increase, the nonlinear of system is enhancement.

  17. Managing Reverse Logistics or Reversing Logistics Management?

    OpenAIRE

    Brito, Marisa

    2004-01-01

    textabstractIn the past, supply chains were busy fine-tuning the logistics from raw material to the end customer. Today an increasing flow of products is going back in the chain. Thus, companies have to manage reverse logistics as well.This thesis contributes to a better understanding of reverse logistics. The thesis brings insights on reverse logistics decision-making and it lays down theoretical principles for reverse logistics as a research field.In particular it puts together a framework ...

  18. Application of acid-treated yeast cell wall (AYC) as a pharmaceutical additive. III. AYC aqueous coating onto granules and film formation mechanism of AYC.

    Science.gov (United States)

    Yuasa, Hiroshi; Kaneshige, Junichi; Ozeki, Tetsuya; Kasai, Takahide; Eguchi, Takahiro; Ishiwaki, Naomu

    2002-04-26

    From the viewpoint of effective utilization of natural resources and development of new pharmaceutical materials, acid-treated yeast cell wall (AYC) was prepared via a novel approach involving acidification of brewers' yeast cell wall. AYC aqueous dispersion containing 5% (w/v) AYC and 0.5% (w/v) glycerol was prepared. Subsequently, AYC was coated onto core granules containing acetaminophen (AAP). Spray mist size under various spray conditions and viscosity of the AYC aqueous dispersion at various AYC concentrations were measured. AYC spray mists were optically observed. The surface of AYC cast film and AYC-coated granules were observed with a confocal scanning laser microscope. We attempted to show the utility of AYC as a novel material for granule coating, following the tablet coating in our previous report. In addition, the film formation mechanism of AYC was investigated. A smooth surface of the AYC-coated granules was obtained at a coating ratio of only 5%, which generally requires approximately 15-30% coating against the core granule weight, with no aggregation. These results are attributable to the fact that the granules were coated with a large number of small mists of AYC and the coating progressed efficiently, and the thin film layer of AYC was formed on the granules by mutual tangling of the hydrogel layers of AYC polysaccharides. AAP release from AYC-coated granules was obviously rapid, suggesting the high utility of AYC as a coating material for the rapidly releasing granules.

  19. Improvement of the mechanical properties of an {alpha}-TCP cement by the addition of a polymeric drug containing salicylic acid

    Energy Technology Data Exchange (ETDEWEB)

    Ginebra, M.P.; Rilliard, A.; Fernandez, E.; Planell, J.A. [Universidad Politecnica de Cataluna, Barcelona (Spain). Dept. of Materials Science and Metallurgical Engineering; Elvira, C.; San Roman, J. [CSIC, Madrid (Spain). Inst. de Ciencia y Tecnologia de Polimeros

    2001-07-01

    The aim of this work is to study the possibility to improve the mechanical properties of a calcium phosphate cement by adding a polymeric acrylic system supporting a derivative of the aminosalicylic acid. It is shown that besides the analgesic and antiinflammatory properties, the salicylic group present a calcium complexation ability. This feature makes it reasonable to envisage a good bonding between the inorganic and the polymeric phase, which can act as a reinforcing component in the cement. The inorganic phase of the cement studied consisted in {alpha}- tricalcium phosphate ({alpha}-Ca{sub 3}(PO{sub 4}){sub 2}) and precipitated hydroxyapatite as a seed, and the liquid phase was an aqueous solution of Na{sub 2}HPO{sub 4}. The polymeric drug used (poly (4-HMA), where 4-HMA is a methacrylamide derived from 4-aminosalicylic acid) was added in a 5 wt% to the liquid phase. The hydrolysis of the {alpha}-TCP into hydroxyapatite was not prevented, but the polymer produced a delay in the reaction. As a consequence the cement hardening was slightly slower, although the final compressive strength was 25% higher. The bending strength increased noticeably, from 5 MPa to 9 MPa with the addition of the polymeric drug. The strengthening of the structure could be related by SEM observations with the formation of a polymeric network between the entangled crystals of hydroxyapatite. (orig.)

  20. Usage of ATND method to determination of mechanical properties of AlMg10 alloy with complex additive of SbNiCr

    Directory of Open Access Journals (Sweden)

    J. Pezda

    2009-07-01

    Full Text Available Aluminum alloys with magnesium are commonly used in foundry industry due to lower density and higher corrosion resistance, comparing with silumins. Complicated shapes of produced alloys, differences in wall thickness and operation under changing loads require performing quality control as early as in stage of their preparation (melting. To register crystallization processes and monitor a phenomena arisen in result of the crystallization, are implemented methods based on analysis of temperature change (ATD, DTA. In the paper is present an attempt of usage of the ATND method (Thermal-Voltage-Derivative Analysis to registration of crystallization process of the investigated alloy. Obtained results concern registration of the crystallization process, strength and fatigue tests of the material, and visual observation of morphology of alloy’s fracture after static tensile test. Performed regression analysis has enabled implementation of changeable values of characteristic points of the ATND method to estimation of mechanical properties of the AlMg10 alloy with SbNiCr additive.

  1. Mechanics

    CERN Document Server

    Chester, W

    1979-01-01

    When I began to write this book, I originally had in mind the needs of university students in their first year. May aim was to keep the mathematics simple. No advanced techniques are used and there are no complicated applications. The emphasis is on an understanding of the basic ideas and problems which require expertise but do not contribute to this understanding are not discussed. How­ ever, the presentation is more sophisticated than might be considered appropri­ ate for someone with no previous knowledge of the subject so that, although it is developed from the beginning, some previous acquaintance with the elements of the subject would be an advantage. In addition, some familiarity with element­ ary calculus is assumed but not with the elementary theory of differential equations, although knowledge of the latter would again be an advantage. It is my opinion that mechanics is best introduced through the motion of a particle, with rigid body problems left until the subject is more fully developed. Howev...

  2. 埋栅型电力静电感应晶闸管的Ⅰ-Ⅴ特性反向转折机理%Mechanism of Reverse Snapback on Ⅰ-Ⅴ Characteristics of Power SITHs with Buried Gate Structure

    Institute of Scientific and Technical Information of China (English)

    王永顺; 李海蓉; 吴蓉; 李思渊

    2008-01-01

    The reverse snapback phenomena (RSP) on Ⅰ-Ⅴ characteristics of static induction thyristors (SITH) are physi- cally researched. The Ⅰ-Ⅴ curves of the power SITH exhibit reverse snapback phenomena, and even turn to the conducting-state,when the anode voltage in the forward blocking-state is increased to a critical value. The RSP Ⅰ-Ⅴ characteristics of the power SITH are analyzed in terms of operating mechanism, double carrier injection effect, space charge effect, elec-tron-hole plasma in the channel, and the variation in carrier lifetime. The reverse snapback mechanism is theoretically pro-posed and the mathematical expressions to calculate the voltage and current values at the snapback point are presented.The computing results are compared with the experiment values.%研究了静电感应晶闸管的反向转折特性.当工作在正向阻断态的阳极电压增大到某一临界值时,静电感应晶闸管的Ⅰ-Ⅴ曲线呈现出反向转折特性,甚至转向导通态.在综合考虑了工作机理、双注入效应、空间电荷效应、沟道中的电子-空穴等离子体和载流子寿命变化的基础上分析了静电感应晶闸管的反向转折特性.首次给出了反向转折机理的理论解释,并给出了估算转折电压和电流的数学表达式,在常用工艺参数范围内,计算结果和实验测量值基本一致.

  3. Resolvin D1 reverses chronic pancreatitis-induced mechanical allodynia, phosphorylation of NMDA receptors, and cytokines expression in the thoracic spinal dorsal horn

    Directory of Open Access Journals (Sweden)

    Quan-Xin Feng

    2012-10-01

    Full Text Available Abstract Background We previously reported that immune activation in the spinal dorsal horn contributes to pain induced by chronic pancreatitis (CP. Targeting immune response in the CNS may provide effective treatments for CP-induced pain. Recent findings demonstrate that resolvin D1 (RvD1 can potently dampen inflammatory pain. We hypothesized that intrathecal injection of RvD1 may inhibit pain of CP. Methods Rat CP model was built through intrapancreatic infusion of trinitrobenzene sulfonic acid (TNBS. All the rats were divided into three groups: TNBS, sham, and naïve controls and were further divided for intrathecal RvD1 administration. Pain behavior of rats was tested with von Frey filaments. Anxiety-like behavior and free locomotor and exploration of rats were evaluated by open field test and elevated plus maze. Pancreatic histology was evaluated with hematoxylin and eosin staining. Phosphorylation of NMDA receptor and expression of inflammatory cytokines were examined with Western blot, real-time RT-PCR and ELISA. Results Behavioral study indicated that compared to the vehicle control, RvD1 (100 ng/kg significantly decreased TNBS-induced mechanical allodynia at 2 h after administration (response frequencies: 49.2 ± 3.7% vs 71.3 ± 6.1%, and this effect was dose-dependent. Neither CP nor RvD1 treatment could affect anxiety-like behavior. CP or RvD1 treatment could not affect free locomotor and exploration of rats. Western blot analysis showed that compared with that of naïve group, phosphorylated NR1 (pNR1 and pNR2B in TNBS rats were significantly increased in the spinal cord (pNR1: 3.87±0.31 folds of naïve control, pNR2B: 4.17 ± 0.24 folds of naïve control. Compared to vehicle control, 10 ng/kg of RvD1 could significantly block expressions of pNR1 (2.21 ± 0.26 folds of naïve and pNR2B (3.31 ± 0.34 folds of naïve. Real-time RT-PCR and ELISA data showed that RvD1 (10 ng/kg but not vehicle could significantly block expressions of

  4. Additivity dominance

    Directory of Open Access Journals (Sweden)

    Paul Rozin

    2009-10-01

    Full Text Available Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned. In support of this, skim milk (with major subtraction of fat is rated as more natural than whole milk with a small amount of natural vitamin D added. It is also noted that ``additives'' is a common word, with a synonym reported by a native speaker in 17 of 18 languages, whereas ``subtractive'' is lexicalized in only 1 of the 18 languages. We consider reasons for additivity dominance, relating it to omission bias, feature positive bias, and notions of purity.

  5. Managing Reverse Logistics or Reversing Logistics Management?

    NARCIS (Netherlands)

    M.P. de Brito (Marisa)

    2004-01-01

    textabstractIn the past, supply chains were busy fine-tuning the logistics from raw material to the end customer. Today an increasing flow of products is going back in the chain. Thus, companies have to manage reverse logistics as well.This thesis contributes to a better understanding of reverse log

  6. Effect of additional sample bias in Meshed Plasma Immersion Ion Deposition (MPIID) on microstructural, surface and mechanical properties of Si-DLC films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Mingzhong [State Key Laboratory of Advanced Welding & Joining, Harbin Institute of Technology, Harbin 150001 (China); School of Materials Science & Engineering, Jiamusi University, Jiamusi 154007 (China); Tian, Xiubo, E-mail: xiubotian@163.com [State Key Laboratory of Advanced Welding & Joining, Harbin Institute of Technology, Harbin 150001 (China); Li, Muqin [School of Materials Science & Engineering, Jiamusi University, Jiamusi 154007 (China); Gong, Chunzhi [State Key Laboratory of Advanced Welding & Joining, Harbin Institute of Technology, Harbin 150001 (China); Wei, Ronghua [Southwest Research Institute, San Antonio, TX 78238 (United States)

    2016-07-15

    Highlights: • A novel Meshed Plasma Immersion Ion Deposition is proposed. • The deposited Si-DLC films possess denser structures and high deposition rate. • It is attributed to ion bombardment of the deposited films. • The ion energy can be independently controlled by an additional bias (novel set up). - Abstract: Meshed Plasma Immersion Ion Deposition (MPIID) using cage-like hollow cathode discharge is a modified process of conventional PIID, but it allows the deposition of thick diamond-like carbon (DLC) films (up to 50 μm) at a high deposition rate (up to 6.5 μm/h). To further improve the DLC film properties, a new approach to the MPIID process is proposed, in which the energy of ions incident to the sample surface can be independently controlled by an additional voltage applied between the samples and the metal meshed cage. In this study, the meshed cage was biased with a pulsed DC power supply at −1350 V peak voltage for the plasma generation, while the samples inside the cage were biased with a DC voltage from 0 V to −500 V with respect to the cage to study its effect. Si-DLC films were synthesized with a mixture of Ar, C{sub 2}H{sub 2} and tetramethylsilane (TMS). After the depositions, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy and nanoindentation were used to study the morphology, surface roughness, chemical bonding and structure, and the surface hardness as well as the modulus of elasticity of the Si-DLC films. It was observed that the intense ion bombardment significantly densified the films, reduced the surface roughness, reduced the H and Si contents, and increased the nanohardness (H) and modulus of elasticity (E), whereas the deposition rate decreased slightly. Using the H and E data, high values of H{sup 3}/E{sup 2} and H/E were obtained on the biased films, indicating the potential excellent mechanical and tribological properties of the films. In this

  7. Collagen insulated from tensile damage by domains that unfold reversibly: in situ X-ray investigation of mechanical yield and damage repair in the mussel byssus.

    Science.gov (United States)

    Harrington, Matthew J; Gupta, Himadri S; Fratzl, Peter; Waite, J Herbert

    2009-07-01

    The byssal threads of the California mussel, Mytilus californianus, are highly hysteretic, elastomeric fibers that collectively perform a holdfast function in wave-swept rocky seashore habitats. Following cyclic loading past the mechanical yield point, threads exhibit a damage-dependent reduction in mechanical performance. However, the distal portion of the byssal thread is capable of recovering initial material properties through a time-dependent healing process in the absence of active cellular metabolism. Byssal threads are composed almost exclusively of multi-domain hybrid collagens known as preCols, which largely determine the mechanical properties of the thread. Here, the structure-property relationships that govern thread mechanical performance are further probed. The molecular rearrangements that occur during yield and damage repair were investigated using time-resolved in situ wide-angle X-ray diffraction (WAXD) coupled with cyclic tensile loading of threads and through thermally enhanced damage-repair studies. Results indicate that the collagen domains in byssal preCols are mechanically protected by the unfolding of sacrificial non-collagenous domains that refold on a slower time-scale. Time-dependent healing is primarily attributed to stochastic recoupling of broken histidine-metal coordination complexes.

  8. Mechanisms involved in the inhibition of glycolysis by cyanide and antimycin A in Candida albicans and its reversal by hydrogen peroxide. A common feature in Candida species.

    Science.gov (United States)

    Peña, Antonio; Sánchez, Norma Silvia; González-López, Omar; Calahorra, Martha

    2015-12-01

    In Candida albicans, cyanide and antimycin A inhibited K(+) transport, not only with ethanol-O2 as the substrate, but also with glucose. The reason for this was that they inhibited not only respiration, but also fermentation, decreasing ATP production. Measurements of oxygen levels in cell suspensions allowed identification of the electron pathways involved. NADH fluorescence levels increased in the presence of the inhibitors, indirectly indicating lower levels of NAD(+) and so pointing to glyceraldehyde-3-phosphate dehydrogenase as the limiting step responsible for the inhibition of glycolysis, which was confirmed by the levels of glycolytic intermediaries. The cyanide effect could be reversed by hydrogen peroxide, mainly due to an activity by which H2O2 can be reduced by electrons flowing from NADH through a pathway that can be inhibited by antimycin A, and appears to be a cytochrome c peroxidase. Therefore, the inhibition of glycolysis by the respiratory inhibitors seems to be due to the decreased availability of NAD(+), resulting in a decreased activity of glyceraldehyde-3-phosphate dehydrogenase. Compartmentalization of pyridine nucleotides in favor of the mitochondria can contribute to explaining the low fermentation capacity of C. albicans. Similar results were obtained with three C. albicans strains, Candida dubliniensis and, to a lower degree, Candida parapsilosis.

  9. Effect of additional sample bias in Meshed Plasma Immersion Ion Deposition (MPIID) on microstructural, surface and mechanical properties of Si-DLC films

    Science.gov (United States)

    Wu, Mingzhong; Tian, Xiubo; Li, Muqin; Gong, Chunzhi; Wei, Ronghua

    2016-07-01

    Meshed Plasma Immersion Ion Deposition (MPIID) using cage-like hollow cathode discharge is a modified process of conventional PIID, but it allows the deposition of thick diamond-like carbon (DLC) films (up to 50 μm) at a high deposition rate (up to 6.5 μm/h). To further improve the DLC film properties, a new approach to the MPIID process is proposed, in which the energy of ions incident to the sample surface can be independently controlled by an additional voltage applied between the samples and the metal meshed cage. In this study, the meshed cage was biased with a pulsed DC power supply at -1350 V peak voltage for the plasma generation, while the samples inside the cage were biased with a DC voltage from 0 V to -500 V with respect to the cage to study its effect. Si-DLC films were synthesized with a mixture of Ar, C2H2 and tetramethylsilane (TMS). After the depositions, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy and nanoindentation were used to study the morphology, surface roughness, chemical bonding and structure, and the surface hardness as well as the modulus of elasticity of the Si-DLC films. It was observed that the intense ion bombardment significantly densified the films, reduced the surface roughness, reduced the H and Si contents, and increased the nanohardness (H) and modulus of elasticity (E), whereas the deposition rate decreased slightly. Using the H and E data, high values of H3/E2 and H/E were obtained on the biased films, indicating the potential excellent mechanical and tribological properties of the films. In this paper, the effects of the sample bias voltage on the film properties are discussed in detail and the optimal bias voltage is presented.

  10. Reversible Thermoset Adhesives

    Science.gov (United States)

    Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)

    2016-01-01

    Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.

  11. Nonidentified Kikuchi lines with reverse contrast

    Science.gov (United States)

    Karakhanyan, K. R.

    2009-03-01

    Electron diffraction patterns of silicon in transmission with contrast reversal from bright to dark for an unidentified Kikuchi line along its length have been obtained. The contrast reversal of an unidentified line is explained within the elementary mechanism of Kikuchi pattern formation taking into account the Kikuchi electron double diffraction.

  12. Potlining Additives

    Energy Technology Data Exchange (ETDEWEB)

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  13. Additivity dominance

    OpenAIRE

    2009-01-01

    Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA) that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned....

  14. Study Of Mechanical And Thermal Behavior Of Pla Modified With Nucleating Additive And Impact Modifier [estudo Do Comportamento Térmico E Mecânico Do Pla Modificado Com Aditivo Nucleante E Modificador De Impacto

    OpenAIRE

    Pereira R.B.; Morales A.R.

    2014-01-01

    Poly(lactic acid) (PLA) is the biodegradable polymer with greatest potential to replace petroleum-based polymers for the packaging industry. However one of its major limitations is the poor thermal dimensional stability. This paper presents a study of the influence of two additives: thermal modifier (nucleating) and impact modifier on the Heat Distortion Temperature (HDT), Vicat Softening Temperature (Vicat) and mechanical properties of PLA. The mechanism of these additives was evaluated by a...

  15. (YIP-10) Enabling Dynamic Oxidation Mechanisms in Reverse Infiltrated Ultra-High Temperature Ceramic Coated C-C Composites for Application in Hypersonics

    Science.gov (United States)

    2013-08-09

    of Hf ,Zr oxychloride hydrates, triethyl borate, and phenolic resin to form precipitate free sols that turn into stable gels with no catalyst addition...200 m/s). The testing facility consists of a welding tip (1.8 mm orifice) connected to oxygen and acetylene supply tanks. Ratios of oxygen to

  16. Reverse cholesterol transport revisited

    Institute of Scientific and Technical Information of China (English)

    Astrid; E; van; der; Velde

    2010-01-01

    Reverse cholesterol transport was originally described as the high-density lipoprotein-mediated cholesterol flux from the periphery via the hepatobiliary tract to the intestinal lumen, leading to fecal excretion. Since the introduction of reverse cholesterol transport in the 1970s, this pathway has been intensively investigated. In this topic highlight, the classical reverse cholesterol transport concepts are discussed and the subject reverse cholesterol transport is revisited.

  17. Cylindrical air flow reversal barrier

    Energy Technology Data Exchange (ETDEWEB)

    Woznica, C.; Rodziewicz, M.

    1988-06-01

    Describes an innovative design introduced in the ZMP mine in Zory for quick reversal of ventilation air flow. Geologic mining conditions at the 705 m deep horizon, where the barrier was built, are described. According to the design used until now, a reversal system consisted of safety barriers, ventilation air locks, a ventilation bridge and stopping needed in case of a fire when air flow direction must be reversed. Nine air locks and an expensive concrete ventilation bridge were needed and the air locks had to be operated at 8 points of the region to effect reversal. The new design consists of a 2-storey cylindrical barrier which also fulfills the function of a ventilation bridge. It can be manually or remotely operated by a mechanical or pneumatic system. Tests showed that the new barrier permits immediate air flow reversal while retaining 60% of the original air, which is important in the case of fire and methane hazards. It permits improved seam panelling and splitting of pillars and brings an economy of about 40 million zlotys in construction cost. Design and operation of the barrier is illustrated and ventilation air circulation is explained. 7 figs.

  18. Reverse logistics - a framework

    NARCIS (Netherlands)

    M.P. de Brito (Marisa); R. Dekker (Rommert)

    2002-01-01

    textabstractIn this paper we define and compare Reverse Logistics definitions. We start by giving an understanding framework of Reverse Logistics: the why-what-how. By this means, we put in context the driving forces for Reverse Logistics, a typology of return reasons, a classification of product

  19. Reverse Engineering Adverse Outcome Pathways in Ecotoxicology

    Science.gov (United States)

    The toxicological effects of many stressors are mediated through unknown, or incompletely characterized, mechanisms of action. We describe the application of reverse engineering complex interaction networks from high dimensional omics data (gene, protein, meabolic, signaling) t...

  20. Magnetic reversals from planetary dynamo waves.

    Science.gov (United States)

    Sheyko, Andrey; Finlay, Christopher C; Jackson, Andrew

    2016-11-24

    A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth's magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes place in Earth's core, but the precise mechanism is debated. The majority of numerical geodynamo simulations that exhibit reversals operate in a regime in which the viscosity of the fluid remains important, and in which the dynamo mechanism primarily involves stretching and twisting of field lines by columnar convection. Here we present an example of another class of reversing-geodynamo model, which operates in a regime of comparatively low viscosity and high magnetic diffusivity. This class does not fit into the paradigm of reversal regimes that are dictated by the value of the local Rossby number (the ratio of advection to Coriolis force). Instead, stretching of the magnetic field by a strong shear in the east-west flow near the imaginary cylinder just touching the inner core and parallel to the axis of rotation is crucial to the reversal mechanism in our models, which involves a process akin to kinematic dynamo waves. Because our results are relevant in a regime of low viscosity and high magnetic diffusivity, and with geophysically appropriate boundary conditions, this form of dynamo wave may also be involved in geomagnetic reversals.

  1. Successful reversal of propionic acidaemia associated cardiomyopathy: evidence for low myocardial coenzyme Q10 status and secondary mitochondrial dysfunction as an underlying pathophysiological mechanism.

    Science.gov (United States)

    Baruteau, J; Hargreaves, I; Krywawych, S; Chalasani, A; Land, J M; Davison, J E; Kwok, M K; Christov, G; Karimova, A; Ashworth, M; Anderson, G; Prunty, H; Rahman, S; Grünewald, S

    2014-07-01

    Dilated cardiomyopathy is a rare complication in propionic acidaemia (PA). Underlying pathophysiological mechanisms are poorly understood. We present a child of Pakistani consanguineous parents, diagnosed with late-onset PA at 18months of age. He presented a mild phenotype, showed no severe further decompensations, normal growth and psychomotor development on a low protein diet and carnitine supplementation. At 15years, a mildly dilated left ventricle was noticed. At 17years he presented after a 2-3month history of lethargy and weight loss with severe decompensated dilated cardiomyopathy. He was stabilised on inotropic support and continuous haemofiltration; a Berlin Heart biventricular assist device was implanted. He received d,l-hydroxybutyrate 200mg/kg/day, riboflavin and thiamine 200mg/day each and coenzyme Q10 (CoQ10). Myocardial biopsy showed endocardial fibrosis, enlarged mitochondria, with atypical cristae and slightly low respiratory chain (RC) complex IV activity relative to citrate synthase (0.012, reference range 0.014-0.034). Myocardial CoQ10 was markedly decreased (224pmol/mg, reference range 942-2738), with a marginally decreased white blood cell level (34pmol/mg reference range 37-133). The dose of CoQ10 was increased from 1.5 to 25mg/kg/day. Cardiomyopathy slowly improved allowing removal of the external mechanical cardiac support after 67days. We demonstrate for the first time low myocardial CoQ10 in cardiomyopathy in PA, highlighting secondary mitochondrial impairment as a relevant causative mechanism. According to these findings, a high-dose CoQ10 supplementation could be a potential adjuvant therapeutic to be considered in PA-related cardiomyopathy.

  2. 物流行业对城市货运共享枢纽的需求%The Study on the Theoretical Foundation of Reverse Logistics and Its Safeguard Mechanism in the Context of Low-carbon Economy

    Institute of Scientific and Technical Information of China (English)

    艾美利亚·C·里根[美; 托马斯·F·格勒博

    2011-01-01

    城市货运共享枢纽的问题从20世纪70年代开始受到关注,当时的情况是,随着城市间货物运输活动的效率不断提高,城市地区内通过货车进行货物运输的成本却大幅增加。早期研究建议建立城市货运共享枢纽,使货车运输企业能够将零散的货物集中起来。过去几年,一方面为了满足承运商装卸货物的需求,另一方面为了给货车司机在市中心周边提供一个交通高峰期轮候的场所,“城市港”的概念开始受到越来越多的关注。本文采用最新获取的调查数据,运用需求的有序概率模型来考察货运公司对此类设施是否感兴趣。%Developing reverse logistics is an important means to achieve low-carbon economy, and stakeholder theory, game theory, sustainable development theory, recycling economy theory, externality theory and ecological economics are its solid theoretical foundation. At this stage the problems in the development of reverse logistics include inadequate laws and regulations, low level of technology, uncertainty of supply and demand and inadequate network, which seriously hindered the development of reverse logistics. Safeguard mechanisms including government, business and citizen participation, adequate laws and regulations, advanced technologies, and efficient incentive measures should be established to promote the healthy and orderly development of reverse logistics.

  3. Reversible colour change in Arthropoda.

    Science.gov (United States)

    Umbers, Kate D L; Fabricant, Scott A; Gawryszewski, Felipe M; Seago, Ainsley E; Herberstein, Marie E

    2014-11-01

    The mechanisms and functions of reversible colour change in arthropods are highly diverse despite, or perhaps due to, the presence of an exoskeleton. Physiological colour changes, which have been recorded in 90 arthropod species, are rapid and are the result of changes in the positioning of microstructures or pigments, or in the refractive index of layers in the integument. By contrast, morphological colour changes, documented in 31 species, involve the anabolism or catabolism of components (e.g. pigments) directly related to the observable colour. In this review we highlight the diversity of mechanisms by which reversible colour change occurs and the evolutionary context and diversity of arthropod taxa in which it has been observed. Further, we discuss the functions of reversible colour change so far proposed, review the limited behavioural and ecological data, and argue that the field requires phylogenetically controlled approaches to understanding the evolution of reversible colour change. Finally, we encourage biologists to explore new model systems for colour change and to engage scientists from other disciplines; continued cross-disciplinary collaboration is the most promising approach to this nexus of biology, physics, and chemistry.

  4. Conjugation-Driven "Reverse Mars-van Krevelen"-Type Radical Mechanism for Low-Temperature C-O Bond Activation.

    Science.gov (United States)

    Mironenko, Alexander V; Vlachos, Dionisios G

    2016-07-01

    C-O bond activation on monofunctional catalysts (metals, carbides, and oxides) is challenging due to activity constraints imposed by energy scaling relationships. Yet, contrary to predictions, recently discovered multifunctional metal/metal oxide catalysts (e.g., Rh/ReOx, Rh/MoOx, Ir/VOx) demonstrate unusually high C-O scission activity at moderate temperatures. Herein, we use extensive density functional theory calculations, first-principles microkinetic modeling, and electronic structure analysis to elucidate the metal/metal oxide synergy in the Ru/RuO2 catalyst, which enables up to 76% yield of the C-O scission product (2-methyl furan) in catalytic transfer hydrogenolysis of furfural at low temperatures. Our key mechanistic finding is a facile radical-mediated C-O bond activation on RuO2 oxygen vacancies, which directly leads to a weakly bound final product. This is the first time the radical reduction mechanism is reported in heterogeneous catalysis at temperatures Mo2C. Furthermore, we reveal the cooperativity of active sites in multifunctional catalysts. The mechanism is fully consistent with kinetic studies and isotopic labeling experiments, and the insights gained might prove useful more broadly in overcoming activity constraints induced by energy scaling relationships.

  5. Magnetic reversals from planetary dynamo waves

    DEFF Research Database (Denmark)

    Sheyko, Andrey; Finlay, Chris; Jackson, Andrew

    2016-01-01

    place in Earth's core, but the precise mechanism is debated. The majority of numerical geodynamo simulations that exhibit reversals operate in a regime in which the viscosity of the fluid remains important, and in which the dynamo mechanism primarily involves stretching and twisting of field lines...... by columnar convection. Here we present an example of another class of reversing-geodynamo model, which operates in a regime of comparatively low viscosity and high magnetic diffusivity. This class does not fit into the paradigm of reversal regimes that are dictated by the value of the local Rossby number...

  6. Mechanical parameters reverse estimation of lunar soil and experimental verification%月壤力学参数反求及试验验证

    Institute of Scientific and Technical Information of China (English)

    李萌; 高峰; 孙鹏; 崔莹

    2011-01-01

    为了预测月球车的牵引特性并进行牵引控制,提出了一种基于线性最小二乘法的月壤力学参数估计算法,对内聚力和内摩擦角这两个关键的月壤力学参数进行反求.针对反映车轮土壤交互作用过程中轮刺效应的力学模型进行简化,建立了内聚力和内摩擦角的求解模型.将车轮与模拟月壤交互作用试验中的测量数据输入利用该算法编制的Matlab程序中,反求出模拟月壤的内聚力和内摩擦角,反求值与模拟月壤的实测值较为接近.试验验证结果表明该算法准确有效,且具有较好的稳定性和较快的运算速度,可用于月球车进行月壤力学参数的就位估计.%In order to predict and control the traction trafficability of a lunar rover, an algorithm for mechanical parameters estimation of lunar soil based on linear-least squares method was presented to estimate two key mechanical parameters, i. e. , internal cohesion and internal friction angle. The improved wheel-soil interaction model for lugged rigid wheel which considering the effect of wheel lugs on stress distribution was simplified ; An algorithm was thus created to calculate internal cohesion and internal friction angle of the soil. Exper- imental data of wheel-soil interaction were imported into Matlab programs to estimate cohesion and internal friction angle of lunar soil simulant, and the estimated values are close to the measured values of lunar soil stimulant. The results of experimental verification indicate that the algorithm is accurate and effective, moreover, the algorithm also shows good stability and high arithmetic speed, which allows a lunar rover to estimate mechanical parameters of the lunar soil on site.

  7. Study of mechanical properties of calcium phosphate cement with addition of sodium alginate and dispersant; Estudo das propriedades mecanicas de cimento de fosfato de calcio com adicao de alginato de sodio e defloculante

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, J.M.; Coelho, W.T.; Thurmer, M.B.; Vieira, P.S.; Santos, L.A., E-mail: julianafernandes2@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), RS (Brazil)

    2011-07-01

    Several studies in literature have shown that the addition of polymer additives and deflocculant has a strong influence on the mechanical properties of cements in general.The low mechanical strength is the main impediment to wider use of bone cement of calcium phosphate (CFCs) as the implant material, since they have mechanical strength which equals the maximum of trabecular bone.In order to evaluate the strength of a CFC compound alpha-tricalcium phosphate, sodium alginate were added (1%, 2% and 3% by weight) and dispersant ammonium polyacrylate (3%) in aqueous solution.Specimens were made and evaluated for density, porosity, crystalline phases and mechanical strength.The results show the increase of the mechanical properties of cement when added sodium alginate and dispersant. (author)

  8. The influence of the "cage" effect on the mechanism of reversible bimolecular multistage chemical reactions proceeding from different sites in solutions.

    Science.gov (United States)

    Doktorov, Alexander B

    2016-08-28

    Manifestations of the "cage" effect at the encounters of reactants have been theoretically treated on the example of multistage reactions (including bimolecular exchange reactions as elementary stages) proceeding from different active sites in liquid solutions. It is shown that for reactions occurring near the contact of reactants, consistent consideration of quasi-stationary kinetics of such multistage reactions (possible in the framework of the encounter theory only) can be made on the basis of chemical concepts of the "cage complex," just as in the case of one-site model described in the literature. Exactly as in the one-site model, the presence of the "cage" effect gives rise to new channels of reactant transformation that cannot result from elementary event of chemical conversion for the given reaction mechanism. Besides, the multisite model demonstrates new (as compared to one-site model) features of multistage reaction course.

  9. Reverse Transcriptase and Cellular Factors: Regulators of HIV-1 Reverse Transcription

    Directory of Open Access Journals (Sweden)

    David Harrich

    2009-11-01

    Full Text Available There is ample evidence that synthesis of HIV-1 proviral DNA from the viral RNA genome during reverse transcription requires host factors. However, only a few cellular proteins have been described in detail that affect reverse transcription and interact with reverse transcriptase (RT. HIV-1 integrase is an RT binding protein and a number of IN-binding proteins including INI1, components of the Sin3a complex, and Gemin2 affect reverse transcription. In addition, recent studies implicate the cellular proteins HuR, AKAP149, and DNA topoisomerase I in reverse transcription through an interaction with RT. In this review we will consider interactions of reverse transcription complex with viral and cellular factors and how they affect the reverse transcription process.

  10. Magnetic reversal dynamics of a quantum system on a picosecond timescale.

    Science.gov (United States)

    Klenov, Nikolay V; Kuznetsov, Alexey V; Soloviev, Igor I; Bakurskiy, Sergey V; Tikhonova, Olga V

    2015-01-01

    We present our approach for a consistent, fully quantum mechanical description of the magnetization reversal process in natural and artificial atomic systems by means of short magnetic pulses. In terms of the simplest model of a two-level system with a magnetic moment, we analyze the possibility of a fast magnetization reversal on the picosecond timescale induced by oscillating or short unipolar magnetic pulses. We demonstrate the possibility of selective magnetization reversal of a superconducting flux qubit using a single flux quantum-based pulse and suggest a promising, rapid Λ-scheme for resonant implementation of this process. In addition, the magnetization reversal treatment is fulfilled within the framework of the macroscopic theory of the magnetic moment, which allows for the comparison and explanation of the quantum and classical behavior.

  11. Unveiling Magnetic Dipole Radiation in Phase-Reversal Leaky-Wave Antennas

    CERN Document Server

    Gupta, Shulabh; Caloz, Christophe

    2014-01-01

    The radiation principle of travelling-wave type phase-reversal antennas is explained in details, unveiling the presence of magnetic-dipole radiation in addition to well-known electric dipole radiation. It is point out that such magnetic dipole radiation is specific to the case of traveling-wave phase-reversal antennas whereas only electric-dipole radiation exists in resonant-type phase-reversal antennas. It is shown that a phase-reversal travelling-wave antenna alternately operates as an array of magnetic dipoles and an array of electric-dipoles during a time-harmonic period. This radiation mechanism is confirmed through both full-wave and experimental results.

  12. Subsidiary Roles and Reverse Knowledge Transfer

    DEFF Research Database (Denmark)

    Rabbiosi, Larissa

    2011-01-01

    coordination mechanisms and knowledge flows from the subsidiary to the parent company, known as reverse knowledge transfer. It is crucial to understand the interdependencies between subsidiary roles and key coordination mechanisms, such as subsidiary autonomy, personal and electronic-based coordination...... of reverse knowledge transfer. The first is the combination of a high degree of subsidiary autonomy and greater use of personal coordination mechanisms, and the second is the combination of low subsidiary autonomy and greater use of electronic-based coordination mechanisms. However, the relevance...

  13. Reversible Watermarking Using Statistical Information

    Directory of Open Access Journals (Sweden)

    Kurugollu Fatih

    2010-01-01

    Full Text Available In most reversible watermarking methods, a compressed location map is exploited in order to ensure reversibility. Besides, in some methods, a header containing critical information is appended to the payload for the extraction and recovery process. Such schemes have a highly fragile nature; that is, changing a single bit in watermarked data may prohibit recovery of the original host as well as the embedded watermark. In this paper, we propose a new scheme in which utilizing a compressed location map is completely removed. In addition, the amount of auxiliary data is decreased by employing the adjacent pixels information. Therefore, in addition to quality improvement, independent authentication of different regions of a watermarked image is possible.

  14. Reversal of benign prostate hyperplasia by selective occlusion of impaired venous drainage in the male reproductive system: novel mechanism, new treatment.

    Science.gov (United States)

    Gat, Y; Gornish, M; Heiblum, M; Joshua, S

    2008-10-01

    The prostate is an androgen-regulated exocrine gland producing over 30% of the noncellular components of the semen and promoting optimal conditions for survival and motility of sperm in the vagina. Benign prostate hyperplasia (BPH) is the most common benign neoplasm in men. Its aetiology is not clear, and therefore, current medical treatments are directed towards the symptoms. Though testosterone is known to be the promoter of prostate cell proliferation, no causal relation between serum testosterone levels and BPH has been found. In this study, we propose a novel and tested pathophysiological mechanism for the evolution of BPH and suggest a tested and effective treatment. We found that in all BPH patients, the one-way valves in the vertically oriented internal spermatic veins are destroyed (clinically manifested as varicocele), causing elevated hydrostatic pressure, some 6-fold greater than normal, in the venous drainage of the male reproductive system. The elevated pressure propagates to all interconnected vessels leading to a unique biological phenomenon: venous blood flows retrograde from the higher pressure in the testicular venous drainage system to the low pressure in the prostatic drainage system directly to the prostate (law of communicating vessels). We have found that free testosterone levels in this blood are markedly elevated, with a concentration of some 130-fold above serum level. Consequently, the prostate is exposed to: (i) increased venous pressure that causes hypertrophy; (ii) elevated concentration of free testosterone causing hyperplasia. We have treated 28 BPH patients using a technique that restores normal pressure in the venous drainage in the male reproductive system. The back-pressure and the back-flow of blood from the testicular to the prostate drainage system were eliminated and, consequently, a rapid reduction in prostate volume and a regression of prostate symptoms took place.

  15. Interference of kallikrein 1b26 (klk1b26 translation by microRNA specifically expressed in female mouse submandibular glands: an additional mechanism for sexual dimorphism of klk1b26 protein in the glands

    Directory of Open Access Journals (Sweden)

    Kurihara Kinji

    2011-11-01

    Full Text Available Abstract Background Mouse kallikrein 1b26 (klk1b26 protein is more abundant in male submandibular glands (SMGs than in female ones. This sexual dimorphism has been thought to be due to increased mRNA synthesis stimulated by androgen. However, the klk1b26 protein level in female SMG is far less than that expected from the mRNA level, suggesting an additional mechanism for down-regulation of klk1b26 expression in female SMGs. Methods We examined the effects of small non-coding RNAs in mouse SMGs on in vitro translation of klk1b26 using a reticulocyte lysate system and reverse transcription (RT-PCR for klk1b26 mRNA. Statistical analyses were performed with a computer package (Microsoft Excel. Results The microRNA (miRNA preparation from female SMGs, but not male SMGs, interfered with the in vitro translation of the klk1b26 protein and inhibited the RT-PCR for klk1b26 mRNA with forward primers targeting its 5'-terminal region (between the 15th and 40th nucleotide from the 5'-terminal. The miRNA preparation from castrated mouse SMGs showed the inhibitory effect on the klk1b26 translation, but that from a 5α-dihydrotestosterone-treated female mouse SMGs did not. Synthetic miRNAs (miR-325 and miR-1497a, which have partial complementarity with klk1b26 mRNA at its 5'-terminal region (15th to 40th nucleotide position from the 5'-terminal, also interfered with the in vitro klk1b26 translation. When the female miRNA preparation was incubated with a 30-nucleotide-long single-strand oligoDNA (named [15th-44th]ssDNA, whose sequence corresponded to the 15th to 44th position from the 5'-terminal of klk1b26 mRNA prior to the addition into the in vitro translation system, the inhibitory effect of the miRNA preparation on klk1b26 translation disappeared, while [15th-44th]ssDNA itself had no effect on the translation. Preincubation of the miRNA preparation with another single-strand DNA ([169th-198th]ssDNA, whose sequence corresponded with 169th to 198th position

  16. Action mechanism of antioxidation and anticorrosion andmolecular design for perfiuoropolyether fluid additives (Ⅱ)Synthesis and measurement of N-substituted perfluoropolyalkylether phenyla-mide

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Three kinds of the antioxidation and anticorrosion additives from the N-substituted per-fluoropolyalkylether phenylamide (PFPEA) were selected and synthesized. UV and IR spectralanalyses were carried out, and strong absorption peaks of UV from benzene ring are about 240.7,215.4 and 230.1 nm, respectively. The characteristic peaks of IR from the C==O are about 1713.9,1712.2 and 1710.8 cm-1, respectively. The antioxidant and anticorrosive property was tested forthe three synthesized additives. The results show that the weight loss of lubrication oil can de-crease by 1/7, 1/9 and 1/25 respectively after adding synthesized additives. The thermal decom-position temperature(TD) in the presence of Al2O3 can increase by 19-22℃. From theoretic andexperimental study it indicates that the PFPEAs with nitrogen heteroatom not only accepts electronfrom perfluoropolyalkylether oxygen radical (RfO.) to form a stable adduct and to prevent RfO. de-composing further, but also donates electron to form chemical adsorption film and to protect metalfrom corrosion. These additives have shown the better property of the antioxidation and anticorro-sion. An electron-releasing group, or phenyl group, introduced to the N-atom of this kind of com-pound can improve the antioxidant and anticorrosive efficiency of the additives.

  17. Design and Experiment of 1LFQ-325 Pneumatic Reversible Plough

    Institute of Scientific and Technical Information of China (English)

    Xuan; ZHENG; Xuefeng; CHEN; Chaomin; QIN; Li; JIAbo; JIA

    2013-01-01

    A pneumatic reversible plough is developed, which complements to the tractor of 25.7-36.8 kW.The plough adopts the cylinder as reversing mechanism between the right and left plough bodies, and the cylinder can substitute the mechanical reversing mechanism. The pneumatic turnover allows the plough to be operated easily and turned over flexibly. Field experiment results show that indicators of plough performance meet the requirements of the relevant national standards.

  18. Mechanics

    CERN Document Server

    Hartog, J P Den

    1961-01-01

    First published over 40 years ago, this work has achieved the status of a classic among introductory texts on mechanics. Den Hartog is known for his lively, discursive and often witty presentations of all the fundamental material of both statics and dynamics (and considerable more advanced material) in new, original ways that provide students with insights into mechanical relationships that other books do not always succeed in conveying. On the other hand, the work is so replete with engineering applications and actual design problems that it is as valuable as a reference to the practicing e

  19. Reversible cortical blindness: posterior reversible encephalopathy syndrome.

    Science.gov (United States)

    Bandyopadhyay, Sabyasachi; Mondal, Kanchan Kumar; Das, Somnath; Gupta, Anindya; Biswas, Jaya; Bhattacharyya, Subir Kumar; Biswas, Gautam

    2010-11-01

    Cortical blindness is defined as visual failure with preserved pupillary reflexes in structurally intact eyes due to bilateral lesions affecting occipital cortex. Bilateral oedema and infarction of the posterior and middle cerebral arterial territory, trauma, glioma and meningioma of the occipital cortex are the main causes of cortical blindness. Posterior reversible encephalopathy syndrome (PRES) refers to the reversible subtype of cortical blindness and is usually associated with hypertension, diabetes, immunosuppression, puerperium with or without eclampsia. Here, 3 cases of PRES with complete or partial visual recovery following treatment in 6-month follow-up are reported.

  20. Additive effects of estrogen and mechanical stress on nitric oxide and prostaglandin E2 production by bone cells from osteoporotic donors.

    NARCIS (Netherlands)

    Bakker, A.D.; Klein-Nulend, J.; Tanck, E.J.M.; Albers, G.H.; Lips, P.; Burger, E.H.

    2005-01-01

    Mechanical loading is thought to provoke a cellular response via loading-induced flow of interstitial fluid through the lacuno-canalicular network of osteocytes. This response supposedly leads to an adaptation of local bone mass and architecture. It has been suggested that loss of estrogen during me

  1. Additively Manufactured Open-Cell Porous Biomaterials Made from Six Different Space-Filling Unit Cells: The Mechanical and Morphological Properties

    NARCIS (Netherlands)

    Ahmadi, S.M.; Yavari, S.A.; Wauthle, R.; Pouran, B.; Schrooten, J.; Weinans, H.; Zadpoor, A.A.

    2015-01-01

    It is known that the mechanical properties of bone-mimicking porous biomaterials are a function of the morphological properties of the porous structure, including the configuration and size of the repeating unit cell from which they are made. However, the literature on this topic is limited, primari

  2. Introduction to reversible computing

    CERN Document Server

    Perumalla, Kalyan S

    2013-01-01

    Few books comprehensively cover the software and programming aspects of reversible computing. Filling this gap, Introduction to Reversible Computing offers an expanded view of the field that includes the traditional energy-motivated hardware viewpoint as well as the emerging application-motivated software approach. Collecting scattered knowledge into one coherent account, the book provides a compendium of both classical and recently developed results on reversible computing. It explores up-and-coming theories, techniques, and tools for the application of rever

  3. The Amazon River reversal explained by tectonic and surface processes

    Science.gov (United States)

    Sacek, V.

    2014-12-01

    The drainage pattern in Amazonia was expressively modified during the mountain building of central and northern Andes. In Early Miocene, the fluvial systems in western Amazonia flowed to the foreland basins and northward to the Caribbean. By Late Miocene the drainage reversal occurred and formed the transcontinental Amazon River, connecting the Andes and the equatorial Atlantic margin. This event is recorded in the stratigraphic evolution of the Foz do Amazonas Basin by the onset of Andean-derived sedimentation. Additionally, an abrupt increase in sedimentation rate after the reversal occurred in the Foz do Amazonas Basin. Based on three-dimensional numerical models that couple surface processes, flexural isostasy and crustal thickening due to orogeny, I concluded that the Miocene drainage reversal can be explained by the flexural and surface processes response to the Andes formation with no need to invoke dynamic topography induced by mantle convection, as previously proposed. I observed that the instant of drainage reversal is directly linked to the rate of crustal thickening in the orogeny, the rate of erosion and, mainly, the efficiency of sediment transport. Moreover, the numerical experiments were able to predict the increase in sedimentation rate in the Amazon fan after the drainage reversal of the Amazon River as observed in the Late Miocene-Pliocene sedimentary record. However, the present numerical model fails to fully reproduce the evolution of the Pebas system, a megawetland in western Amazonia that preceded the drainage reversal. Therefore, further investigation is necessary to evaluate the mechanisms that generated and sustained the Pebas system.

  4. Reversible Logic Circuit Synthesis

    CERN Document Server

    Shende, V V; Markov, I L; Prasad, A K; Hayes, John P.; Markov, Igor L.; Prasad, Aditya K.; Shende, Vivek V.

    2002-01-01

    Reversible, or information-lossless, circuits have applications in digital signal processing, communication, computer graphics and cryptography. They are also a fundamental requirement for quantum computation. We investigate the synthesis of reversible circuits that employ a minimum number of gates and contain no redundant input-output line-pairs (temporary storage channels). We propose new constructions for reversible circuits composed of NOT, Controlled-NOT, and TOFFOLI gates (the CNT gate library) based on permutation theory. A new algorithm is given to synthesize optimal reversible circuits using an arbitrary gate library. We also describe much faster heuristic algorithms. We also pursue applications of the proposed techniques to the synthesis of quantum circuits.

  5. 反式twin-block治疗安氏Ⅲ类错牙合作用机理的研究%Mechanisms of Reverse Twin-block Appliance Therapy on Angle class Ⅲ Malocclusion

    Institute of Scientific and Technical Information of China (English)

    朱丽亚; 黄岩; 杨睿

    2014-01-01

    目的:通过治疗前后X线头颅定位侧位片的头影测量分析,得到反式Twin-block对生长发育期安氏Ⅲ类错(牙合)的治疗原理。方法选择替牙期、恒牙早期安氏Ⅲ类错牙合患者20例(男10例,女10例),平均年龄10岁8个月,全天戴用反式Twin-block矫治器治疗4.5-11个月。分别对治疗前后头颅定位侧位片进行头影测量。结果①上牙弓位置前移,上颌向前发育;②下颌向下后方向旋转;③上下颌牙齿发生代偿性移动。结论反式Twin-block可以有效矫治生长发育期安氏Ⅲ类错牙合,在患者侧面Ⅲ类骨面形得到明显改善的同时,牙齿发生代偿性移动。%Objective To assess the effect and mechanism of ClassⅢ malocclusions treatment with reverse Twin -block appliance.Methods Twenty subjects of ClassⅢ malocclusions were included in this study(10male,10 female).All patients were treated for all the day and for total of 4.5-11 months.The cephalometric re-cords of these subjects were examined before and after the treatments.The acquired data were processed with SPSS 10.0.Results①the reverse Twin-block could accel-erate the development of the maxillary bone .② the Mandibular showed a rotation of after the downward direction .③mandible teeth occurring compensatory move on . Conclusion Reverse Twin-block appliance could treat effectively angle classⅢ malocclusions.Patients had a significant improve in side of the form ,while the occur-rence of compensatory tooths movement .

  6. Effect of Minor Zn Additions on the Mechanical and Corrosion Properties of Solution-Treated AM60-2%RE Magnesium Alloy

    Science.gov (United States)

    Liu, Z. L.; Liu, Y.; Liu, X. Q.; Wang, M. M.

    2016-07-01

    The microstructure, mechanical properties, and corrosion behaviors of solution-treated AM60-2%RE magnesium alloy containing 0.2-0.8% wt.% Zn were investigated. With the increase of Zn, the volume fraction of dispersed rod-like Al4RE and granular-like Al11RE3 phases of solution-treated AM60-2%RE + x%Zn increased, which improved the mechanical properties by dispersion strengthening. With increasing Zn content, the corrosion current density decreased, and the corrosion potential and electrochemical impedance of the alloys increased, and the corrosion resistance of solution-treated AM60-2%RE + x%Zn was improved. With the increase of Zn content, the leaf-like corrosion products of the alloy became smaller and more compact, and the content of Zn, Al, Ce, and La in corrosion products increased, which was beneficial to inhibit the corrosion progress.

  7. Minimising reversion, using seawater and magnesium chloride, caused by the dissolution of tricalcium aluminate hexahydrate.

    Science.gov (United States)

    Palmer, Sara J; Frost, Ray L; Smith, Matthew K

    2011-01-15

    The increase in pH and aluminium concentration after the neutralisation of bauxite refinery residues is commonly known as reversion. This investigation reports the extent of reversion in synthetic supernatant liquor and possible methods to reduce reversion. This work is based on bauxite refinery residues produced from alumina refineries, where reversion is a real life situation in neutralised refinery residues. Tricalcium aluminate hexahydrate, a common phase in bauxite refinery residues, has been found to cause reversion. It has been established that reductions in both pH and aluminium from the seawater neutralisation process are due to the formation of 'Bayer' hydrotalcite Mg(7)Al(2)(OH)(18)(CO(3)(2-),SO(4)(2-))·xH(2)O. This is the primary mechanism involved in the removal of aluminium from solution. Increasing the volume of seawater used for the neutralisation process minimises the extent of reversion for both synthetic supernatant liquor and red mud slurry. The addition of MgCl(2)·6H(2)O also showed a reduction in reversion and confirmed that the decrease in aluminium and hydroxyl ions is due to the formation of Bayer hydrotalcite and not simply a dilution effect.

  8. Thermostability of Cromobacterium viscosum lipase in AOT/isooctane reverse micelle.

    Science.gov (United States)

    Talukder, M M R; Zaman, M M; Hayashi, Y; Wu, J C; Kawanishi, T

    2007-04-01

    The thermostability of Cromobacterium viscosum lipase (EC 3.1.1.3) entrapped in AOT (sodium bis-[2-ethylhexyl] sulfosuccinate) reverse micelles was increased by the addition of short-chain polyethylene glycol (PEG 400). Two different approaches were considered: (1) the determination of half-life time and (2) the mechanistic analysis of deactivation kinetics. The half-life of lipase entrapped in AOT/isooctane reverse micelles with PEG 400 at 60 degrees C was 28 h, ninefold higher than that in reverse micelles without PEG 400. The lipase entrapped in both reverse micellar systems followed a series-type deactivation mechanism involving two first-order steps. The deactivation constant for the first step at 60 degrees C in PEG containing reverse micelles was 0.055 h!1, 11-fold lower than that in reverse micelles without PEG, whereas it remained almost constant for the second step. The inactivation energy of the lipase entrapped in reverse micelles with and without PEG 400 was 88.12 and 21.97 kJ/mol, respectively.

  9. Reverse Genetics Approaches for the Development of Influenza Vaccines

    Directory of Open Access Journals (Sweden)

    Aitor Nogales

    2016-12-01

    Full Text Available Influenza viruses cause annual seasonal epidemics and occasional pandemics of human respiratory disease. Influenza virus infections represent a serious public health and economic problem, which are most effectively prevented through vaccination. However, influenza viruses undergo continual antigenic variation, which requires either the annual reformulation of seasonal influenza vaccines or the rapid generation of vaccines against potential pandemic virus strains. The segmented nature of influenza virus allows for the reassortment between two or more viruses within a co-infected cell, and this characteristic has also been harnessed in the laboratory to generate reassortant viruses for their use as either inactivated or live-attenuated influenza vaccines. With the implementation of plasmid-based reverse genetics techniques, it is now possible to engineer recombinant influenza viruses entirely from full-length complementary DNA copies of the viral genome by transfection of susceptible cells. These reverse genetics systems have provided investigators with novel and powerful approaches to answer important questions about the biology of influenza viruses, including the function of viral proteins, their interaction with cellular host factors and the mechanisms of influenza virus transmission and pathogenesis. In addition, reverse genetics techniques have allowed the generation of recombinant influenza viruses, providing a powerful technology to develop both inactivated and live-attenuated influenza vaccines. In this review, we will summarize the current knowledge of state-of-the-art, plasmid-based, influenza reverse genetics approaches and t