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Sample records for additional reversible mechanism

  1. Nano-mechanical magnetization reversal

    OpenAIRE

    Kovalev, Alexey A.; Bauer, Gerrit E. W.; Brataas, Arne

    2004-01-01

    The dynamics of the ferromagnetic order parameter in thin magnetic films is strongly affected by the magnetomechanical coupling at certain resonance frequencies. By solving the equation of motion of the coupled mechanical and magnetic degrees of freedom we show that the magnetic-field induced magnetization switching can be strongly accelerated by the lattice and illustrate the possibility of magnetization reversal by mechanical actuation.

  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. Reversible addition-fragmentation chain transfer polymerization in microemulsion.

    Science.gov (United States)

    O'Donnell, Jennifer M

    2012-04-21

    This tutorial review first details the uncontrolled microemulsion polymerization mechanism, and the RAFT polymerization mechanism to provide the necessary background for examining the RAFT microemulsion polymerization mechanism. The effect of the chain transfer agent per micelle ratio and the chain transfer agent aqueous solubility on the RAFT microemulsion polymerization kinetics, polymer molecular weight and polydispersity, and polymer nanoparticle size are discussed with a focus on oil-in-water microemulsions. Modeling of RAFT microemulsion polymerization kinetics and the resulting final polymer molecular weight are presented to assist with the analysis of observed experimental trends. Lastly, the current significance of RAFT microemulsion polymerization and the future directions are discussed. PMID:22246214

  4. 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.

  5. 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.

  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. PMID:27612831

  7. Effects of small ionic amphiphilic additives on reverse microemulsion morphology

    OpenAIRE

    Hopkins Hatzopoulos, Marios T; James, Craig; Rogers, Sarah E.; Grillo, Isabelle; Dowding, Peter J; Eastoe, Julian

    2014-01-01

    HypothesisInitial studies (Hopkins Hatzopoulos et al. (2013)) have shown that ionic hydrotropic additives can drive a sphere-to-cylinder (ellipsoid) transition in water-in-oil (w/o) microemulsions stabilized by the anionic surfactant Aerosol-OT; however the origins of this behaviour remained unclear. Here systematic effects of chemical structure are explored with a new set of hydrotropes, in terms of an aromatic versus a saturated cyclic hydrophobic group, and linear chain length of alkyl car...

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. In Situ Transmission Electron Microscopy Studies of the Magnetization Reversal Mechanism in Information Storage Materials.

    Science.gov (United States)

    Petford-Long; Portier; Bayle-Guillemaud; Anthony; Brug

    1998-05-01

    : The Foucault and Fresnel modes of Lorentz microscopy, together with a quantitative magnetization mapping technique, summed image differential phase-contrast imaging, were used to study the magnetization reversal mechanism of the sense layer in spin-valve structures exhibiting the giant magnetoresistance effect. In addition to studies of sheet film, lithographically defined spin-valve elements were investigated. A current can be passed through the element during magnetizing so that the effect of the applied current on the giant magnetoresistance and magnetization reversal mechanism can be studied. Results are presented for a number of different spin-valve structures. PMID:9767670

  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. 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.

  15. 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.

  16. 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.

  17. On the incorporation mechanism of hydrophobic quantum dots in silica spheres by a reverse microemulsion method

    OpenAIRE

    Koole, R; van Schooneveld, M.M.; Hilhorst, J.; De Mello Donega, C.; 't Hart, D.C.; van Blaaderen, A.; Vanmaekelbergh, D.A.M.; Meijerink, A.

    2008-01-01

    In this work, we show strong experimental evidence in favor of a proposed incorporation mechanism of hydrophobic semiconductor nanocrystals (or quantum dots, QDs) in monodisperse silica spheres (diameter ∼35 nm) by a water-in-oil (W/O) reverse microemulsion synthesis. Fluorescence spectroscopy is used to investigate the rapid ligand exchange that takes place at the QD surface upon addition of the various synthesis reactants. It is found that hydrolyzed TEOS has a high affinity for the QD surf...

  18. Reversion of Hormone Treatment Resistance with the Addition of an mTOR Inhibitor in Endometrial Stromal Sarcoma

    Directory of Open Access Journals (Sweden)

    J. Martin-Liberal

    2014-01-01

    Full Text Available Background. Endometrial stromal sarcomas (ESS are a subtype of gynaecological sarcomas characterized by the overexpression of hormone receptors. Hormone treatment is widely used in ESS but primary or acquired resistance is common. The mammalian target of rapamycin (mTOR pathway has been suggested to play a key role in the mechanisms of hormone resistance. Recent studies in breast and prostate cancer demonstrate that this resistance can be reversed with the addition of an mTOR inhibitor. This phenomenon has never been reported in ESS. Methods. We report the outcome of one patient with pretreated, progressing low grade metastatic ESS treated with medroxyprogesterone acetate in combination with the mTOR inhibitor sirolimus. Results. Partial response was achieved following the addition of sirolimus to the hormone treatment. Response has been maintained for more than 2 years with minimal toxicity and treatment is ongoing. Conclusion. This case suggests that the resistance to the hormone manipulation in ESS can be reversed by the addition of an mTOR pathway inhibitor. This observation is highly encouraging and deserves further investigation.

  19. Additively homomorphic encryption with a double decryption mechanism, revisited

    NARCIS (Netherlands)

    Peter, A.; Kronberg, M.; Trei, W.; Katzenbeisser, S.

    2012-01-01

    We revisit the notion of additively homomorphic encryption with a double decryption mechanism (DD-PKE), which allows for additions in the encrypted domain while having a master decryption procedure that can decrypt all properly formed ciphertexts by using a special master secret. This type of encryp

  20. 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.

  1. 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...

  2. 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

    Additive manufacturing allows for close-to unrestrained geometrical freedom in part design. The ability to manufacture geometries of such complexity is however limited by the fact that it proves difficult to verify tolerances of these parts. Tolerancs of featuress that are inaccessible with tradi......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.......Additive manufacturing allows for close-to unrestrained geometrical freedom in part design. The ability to manufacture geometries of such complexity is however limited by the fact that it proves difficult to verify tolerances of these parts. Tolerancs of featuress that are inaccessible...... 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...

  3. 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.

  4. 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.

  5. 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).

  6. Synthesis of carboxylic block copolymers via reversible addition fragmentation transfer polymerization for tooth erosion prevention.

    Science.gov (United States)

    Lei, Y; Wang, T; Mitchell, J W; Qiu, J; Kilpatrick-Liverman, L

    2014-12-01

    Dental professionals are seeing a growing population of patients with visible signs of dental erosion. The approach currently being used to address the problem typically leverages the enamel protection benefits of fluoride. In this report, an alternative new block copolymer with a hydrophilic polyacrylic acid (PAA) block and a hydrophobic poly(methyl methacrylate) (PMMA) block was developed to similarly reduce the mineral loss from enamel under acidic conditions. This series of PMMA-b-PAA block copolymers was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. Their structures were characterized by gel permeation chromatography (GPC) and (1)H nuclear magnetic resonance (NMR) spectra. The molar fractions of acrylic acid (AA) in the final block copolymer were finely controlled from 0.25 to 0.94, and the molecular weight (Mn) of PMMA-b-PAA was controlled from 10 kDa to 90 kDa. The binding capability of the block copolymer with hydroxyapatite (HAP) was investigated by ultraviolet-visible spectroscopy (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy. FTIR spectra confirmed that the PMMA-b-PAA block copolymer could bind to HAP via bridging bidentate bonds. Both UV-Vis and FTIR spectra additionally indicated that a high polymer concentration and low solution pH favored the polymer binding to HAP. The erosion-preventing efficacy of the PMMA-b-PAA block copolymer in inhibiting HAP mineral loss was quantitatively evaluated by atomic absorption spectroscopy (AAS). Based on the results, polymer treatment reduced the amount of calcium released by 27% to 30% in comparison with the unprotected samples. Scanning electron microscope (SEM) observations indicated that PMMA-b-PAA polymer treatment protected enamel from acid erosion. This new amphiphilic block copolymer has significant potential to be integrated into dentifrices or mouthrinses as an alternative non-fluoride ingredient to reduce tooth erosion. PMID:25248611

  7. Reversible mechanism for spin crossover in transition-metal cyanides

    Science.gov (United States)

    Kabir, Mukul; van Vliet, Krystyn J.

    2011-03-01

    Spin transitions generally occur in compounds of octahedrally coordinated 3 d transition metal ions. These transitions can be induced by external perturbations such as light, heat, pressure, magnetic field, and chemical substitution. Transition metal cyanides are one such material, which exhibit reversible spin transition while perturbed with light at T distorted) lattice in the intermediate spin (S = 1) state. The calculated energy required for this transition is in agreement with experiments. We further predict that this spin transition in such materials can be induced, and further tuned, by external pressure to enable realization of such reversible transitions at ambient temperatures.

  8. Time reversal noninvariance in quantum mechanics and in nonlinear optics

    OpenAIRE

    Kuz'menko, V. A.

    2005-01-01

    The experimental proofs of strong time invariance violation in optics are discussed. Time noninvariance is the only real physical base for explanation the origin of the most phenomena in nonlinear optics. The experimental study of forward and reversed transitions in oriented in uniform electric field molecules is proposed.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. The paleomagnetic field and possible mechanisms for the formation of reversed rock magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Trukhin, Vladimir I. [Faculty of Physics, Moscow State University, 119992 Moscow (Russian Federation)]. E-mail: trukhin@phys.msu.ru; Bezaeva, Natalia [Faculty of Physics, Moscow State University, 119992 Moscow (Russian Federation); Kurochkina, Evgeniya [Faculty of Physics, Moscow State University, 119992 Moscow (Russian Federation)

    2006-05-15

    Investigations of ancient magnetized rocks show that their natural remanent magnetization (NRM) can be oriented in the direction of modern geomagnetic field (GMF) as well as in the opposite direction. It is supposed that reversed NRM is related to reversals of the GMF in the past geological periods. During reversals, the strength of the GMF is near zero and can cause the destruction of living organisms as a result of powerful space and solar radiation, which, in the absence of the GMF, can reach the Earth's surface. That is why the question of reality of the GMF reversals is of global ecological importance. There is also another natural mechanism for the formation of reversed NRM-the self-reversal of magnetization as a result of thermomagnetization of rocks. In the paper, both natural processes for the formation of reversed NRM in rocks are discussed, and the results of experimental research on the physical mechanism of self-reversal of magnetization in continental and oceanic rocks are presented. The results of computer modeling of the self-reversal phenomenon are also presented.

  14. 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.

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

    International Nuclear Information System (INIS)

    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

  16. 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.

  17. 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.

  18. Coercivity, microstructure and magnetization reversal mechanism in TiNi-doped L10 FePt thin films

    Science.gov (United States)

    Zhang, Yongmei; Li, Xiaohong; Jing, Jingjing; Zhang, Xiangyi; Zhao, Yuhong

    2016-06-01

    Controlling coercivity and understanding how it is affected by the microstructure are of essential importance for practical application of FePt thin films as a recording media. In this study, the small size of ordered domain, lower coercivity and weak intergranular exchange coupling interaction in TiNi-doped L10 FePt thin films are obtained. The TiNi additions maybe diffuse out of the FePt lattice into FePt grain boundaries, which separate FePt grains. The doping in grain boundary provides the nucleation center of reversed domain, which leads both nucleation-type and pinning-type mechanism to coexist in magnetization reversal processes for TiNi-doped FePt thin films. The decrease of anisotropy constant and nucleation field of reversed domain provides an explanation for the coercivity reduction of FePt thin films after TiNi doping.

  19. Additives That Prevent Or Reverse Cathode Aging In Drift Chambers With Helium-Isobutane Gas

    International Nuclear Information System (INIS)

    Noise and Malter breakdown have been studied at high rates in a test chamber having the same cell structure and gas as in the BaBar drift chamber. The chamber was first damaged by exposing it to a high source level at an elevated high voltage, until its operating current at normal voltages was below 0.5nA/cm. Additives such as water or alcohol allowed the damaged chamber to operate at 25 nA/cm, but when the additive was removed the operating point reverted to the original low value. However with 0.02% to 0.05% oxygen or 5% carbon dioxide the chamber could operate at more than 25 nA/cm, and continued to operate at this level even after the additive was removed. This shows for the first time that running with an O2 or CO2 additive at high ionization levels can cure a damaged chamber from breakdown problems

  20. 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.

  1. 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.

  2. Enhancement of mechanical properties of a TRIP-aided austenitic stainless steel by controlled reversion annealing

    International Nuclear Information System (INIS)

    Controlled martensitic reversion annealing was applied to a heavily cold-worked metastable austenitic low-Ni Cr–Mn austenitic stainless steel (Type 201) to obtain different ultrafine austenite grain sizes to enhance the mechanical properties, which were then compared with the conventional coarse-grained steel. Characterization of the deformed and reversion annealed microstructures was performed by electron back scattered diffraction (EBSD), X-ray diffraction (XRD) and light and transmission electron microscopy (TEM). The steel with a reverted grain size ~1.5 μm due to annealing at 800 °C for 10 s showed significant improvements in the mechanical properties with yield stress ~800 MPa and tensile strength ~1100 MPa, while the corresponding properties of its coarse grained counterpart were ~450 MPa and ~900 MPa, respectively. However, the fracture elongation of the reversion annealed steel was ~50% as compared to ~70% in the coarse grained steel. A further advantage is that the anisotropy of mechanical properties present in work-hardened steels also disappears during reversion annealing

  3. Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects

    Science.gov (United States)

    Zhang, Jie; Sheng, Lei; Liu, Jing

    2014-11-01

    Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.

  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. Geomagnetic polarity reversals as a mechanism for the punctuated equilibrium model of biological evolution

    International Nuclear Information System (INIS)

    In contrast to what is predicted by classical Darwinian theory (phyletic gradualism), the fossil record typically displays a pattern of relatively sudden, dramatic changes as detailed by Eldregde and Gould's model of punctuated equilibrium. Evolutionary biologists have been at a loss to explain the ultimate source of the new mutations that drive evolution. One hypothesis holds that the abrupt speciation seen in the punctuated equilibrium model is secondary to an increased mutation rate resulting from periodically increased levels of ionizing radiation on the Earth's surface. Sporadic geomagnetic pole reversals, occurring every few million years on the average, are accompanied by alterations in the strength of the Earth's magnetic field and magnetosphere. This diminution may allow charged cosmic radiation to bombard Earth with less attenuation, thereby resulting in increased mutation rates. This episodic fluctuation in the magnetosphere is an attractive mechanism for the observed fossil record. Selected periods and epochs of geologic history for which data was available were reviewed for both geomagnetic pole reversal history and fossil record. Anomalies in either were scrutinized in greater depth and correlations were made. A 35 million year span (118-83 Ma) was identified during the Early/Middle Cretaceous period that was devoid of geomagnetic polarity reversals(the Cretaceous normal superchron). Examination of the fossil record (including several invertebrate and vertebrate taxons) during the Cretaceous normal superchron does not reveal any significant gap or slowing of speciation. Although increased terrestrial radiation exposure due to a diminution of the Earth's magnetosphere caused by a reversal of geomagnetic polarity is an attractive explanation for the mechanism of punctuated equilibrium, our investigation suggests that such polarity reversals cannot fully provide the driving force behind biological evolution. Further research is required to determine if

  7. Probabilistic Reversal Learning in Schizophrenia: Stability of Deficits and Potential Causal Mechanisms.

    Science.gov (United States)

    Reddy, Lena Felice; Waltz, James A; Green, Michael F; Wynn, Jonathan K; Horan, William P

    2016-07-01

    Although individuals with schizophrenia show impaired feedback-driven learning on probabilistic reversal learning (PRL) tasks, the specific factors that contribute to these deficits remain unknown. Recent work has suggested several potential causes including neurocognitive impairments, clinical symptoms, and specific types of feedback-related errors. To examine this issue, we administered a PRL task to 126 stable schizophrenia outpatients and 72 matched controls, and patients were retested 4 weeks later. The task involved an initial probabilistic discrimination learning phase and subsequent reversal phases in which subjects had to adjust their responses to sudden shifts in the reinforcement contingencies. Patients showed poorer performance than controls for both the initial discrimination and reversal learning phases of the task, and performance overall showed good test-retest reliability among patients. A subgroup analysis of patients (n = 64) and controls (n = 49) with good initial discrimination learning revealed no between-group differences in reversal learning, indicating that the patients who were able to achieve all of the initial probabilistic discriminations were not impaired in reversal learning. Regarding potential contributors to impaired discrimination learning, several factors were associated with poor PRL, including higher levels of neurocognitive impairment, poor learning from both positive and negative feedback, and higher levels of indiscriminate response shifting. The results suggest that poor PRL performance in schizophrenia can be the product of multiple mechanisms. PMID:26884546

  8. Biophysical Insights into the Inhibitory Mechanism of Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitors

    Directory of Open Access Journals (Sweden)

    Nicolas Sluis-Cremer

    2013-11-01

    Full Text Available HIV-1 reverse transcriptase (RT plays a central role in HIV infection. Current United States Federal Drug Administration (USFDA-approved antiretroviral therapies can include one of five approved non-nucleoside RT inhibitors (NNRTIs, which are potent inhibitors of RT activity. Despite their crucial clinical role in treating and preventing HIV-1 infection, their mechanism of action remains elusive. In this review, we introduce RT and highlight major advances from experimental and computational biophysical experiments toward an understanding of RT function and the inhibitory mechanism(s of NNRTIs.

  9. 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.

  10. Nucleation controlled magnetization reversal mechanism in oriented L10 FeCoPt ternary alloys

    Science.gov (United States)

    Goyal, Rajan; Sehdev, Neeru; Lamba, S.; Annapoorni, S.

    2016-01-01

    The angular dependence of scaled coercivity is investigated within the framework of various theoretical models to gather an insight into the magnetization reversal mechanism in hard magnetic materials. FeCoPt ternary alloy thin films with low concentration of Co were successfully fabricated on an Si substrate with different working pressures in order to attain an optimum energy product. The structural and hysteresis curve analysis show an improvement in atomic ordering and orientation of easy axis with annealing temperature. The experimental data for angular dependence of coercivity along with the theoretical predications based on the nucleation model indicates that the dominant reversal mechanism is nucleation along with a slight contribution from pinning. The magnetic force microscopy (MFM) imaging also supports the above model. The evolution of morphology and microstructure characterized by atomic force microscopy (AFM) was directly linked to an increase in surface roughness.

  11. Modeling astrophysical outflows via the unified Dynamo-Reverse Dynamo mechanism

    CERN Document Server

    Lingam, Manasvi

    2015-01-01

    The unified Dynamo-Reverse Dynamo (Dy-RDy) mechanism, capable of simultaneously generating large scale outflows and magnetic fields from an ambient microscopic reservoir, is explored in a broad astrophysical context. The Dy-RDy mechanism is derived via Hall magnetohydrodynamics, which unifies the evolution of magnetic field and fluid vorticity. It also introduces an intrinsic length scale, the ion skin depth, allowing for the proper normalization and categorization of microscopic and macroscopic scales. The large scale Alfv\\'en Mach number $\\mathcal{M}_{A}$, defining the relative "abundance" of the flow field to the magnetic field is shown to be tied to a microscopic scale length that reflects the characteristics of the ambient short scale reservoir. The dynamo (Dy), preferentially producing the large scale magnetic field, is the dominant mode when the ambient turbulence is mostly kinetic, while the outflow producing reverse dynamo (RDy) is the principal manifestation of a magnetically dominated turbulent res...

  12. [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.

  13. 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).

  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. 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.

  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. PMID:26595367

  17. 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.

  18. Reverse micelle synthesis of oxide nanopowders: mechanisms of precipitate formation and agglomeration effects.

    Science.gov (United States)

    Graeve, Olivia A; Fathi, Hoorshad; Kelly, James P; Saterlie, Michael S; Sinha, Kaustav; Rojas-George, Gabriel; Kanakala, Raghunath; Brown, David R; Lopez, Enrique A

    2013-10-01

    We present an analysis of reverse micelle stability in four model systems. The first two systems, composed of unstable microemulsions of isooctane, water, and Na-AOT with additions of either iron sulfate or yttrium nitrate, were used for the synthesis of iron oxide or yttrium oxide powders. These oxide powders were of nanocrystalline character, but with some level of agglomeration that was dependent on calcination temperature and cleaning procedures. Results show that even though the reverse micellar solutions were unstable, nanocrystalline powders with very low levels of agglomeration could be obtained. This effect can be attributed to the protective action of the surfactant on the surfaces of the powders that prevents neck formation until after all the surfactant has volatilized. A striking feature of the IR spectra collected on the iron oxide powders is the absence of peaks in the ~1715 cm(-1) to 1750 cm(-1) region, where absorption due to the symmetric C=O (carbonyl) stretching occurs. The lack of such peaks strongly suggests the carbonyl group is no longer free, but is actively participating in the surfactant-precipitate interaction. The final two microemulsion systems, containing CTAB as the surfactant, showed that loss of control of the reverse micelle synthesis process can easily occur when the amount of salt in the water domains exceeds a critical concentration. Both model systems eventually resulted in agglomerated powders of broad size distributions or particles that were large compared to the sizes of the reverse micelles, consistent with the notion that the microemulsions were not stable and the powders were precipitated in an uncontrolled fashion. This has implications for the synthesis of nanopowders by reverse micelle synthesis and provides a benchmark for process control if powders of the highest quality are desired. PMID:23906861

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

    Science.gov (United States)

    Wang, Shanshan; Lei, Ting; Zhang, Man

    2016-01-01

    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 chemotherapy. PMID

  20. 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.

  1. Reversal-mechanism of perpendicular switching induced by an in-plane current

    Energy Technology Data Exchange (ETDEWEB)

    Bi, Chong, E-mail: cbi@email.arizona.edu; Liu, Ming, E-mail: liuming@ime.ac.cn

    2015-05-01

    We propose a magnetization reversal model to explain the perpendicular switching of a single ferromagnetic layer induced by an in-plane current. Contrary to previously proposed reversal mechanisms that such magnetic switching is directly from the Rashba or spin Hall effects, we suggest that this type of switching arises from the current-induced chirality dependent domain wall motion. By measuring the field dependent switching behaviors, we show that such switching can also be achieved between any two multidomain states, and all of these switching behaviors can be well explained by this model. This model indicates that the spin Hall angle in such structures may be overestimated and also predicts similar switching behaviors in other ferromagnetic structures with chiral domain walls or skyrmions. - Highlights: • A reversal model is proposed to explain current-induced perpendicular switching. • Chirality-dependent domain nucleation and expansion dominate switching behaviors. • The switching between any two multidomain states was observed. • Similar switching behaviors are predicted for chiral domain walls or skyrmions.

  2. 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

  3. 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.

  4. Effect of Cu addition on microstructure and mechanical properties of 15%Cr super martensitic stainless steel

    International Nuclear Information System (INIS)

    Highlights: ► Cu contributes to refine the grains. ► Cu solutes in matrix under quenching and precipitates as ε-Cu during tempering. ► Cu promotes the kinetics of reversed austenite formation. ► Mechanical properties are significantly influenced by austenite amount. ► Cu alloyed super martensitic stainless steel exhibits greatly improved mechanical properties. -- Abstract: The effect of adding different content of Cu (0 wt.%, 1.5 wt.% and 3 wt.%) to the 15%Cr super martensitic stainless steel (SMSS) was investigated using optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Its consequence on mechanical properties was examined to clarify the role of Cu in the tested steels. The experimental results indicate that the microstructures of three tested steels are tempered martensite, retained austenite and reversed austenite; two kinds of austenites are dispersedly distributed among martensite matrix. Cu can solute in matrix under quenching condition and can precipitate as Cu-rich nanometer phase (ε-Cu) during tempering. Cu is helpful for the grain refinement and to promote the formation of reversed austenite during tempering. The maximum volume fraction of austenite is 55.9% in the steel with 3 wt.% Cu, which is responsible for the improvement of ductility. The results of the mechanical properties tests reveal that the mechanical properties are significantly influenced by the volume fraction of austenite. Cu can cause solid solution strengthening, precipitation strengthening and grain refinement strengthening in SMSS. Cu alloyed super martensitic stainless steel exhibits greatly improved mechanical properties.

  5. 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.

  6. Influence of Polymer Addition on Performance and Mechanical Properties of Lightweight Aggregate Concrete

    Institute of Scientific and Technical Information of China (English)

    Jiang Cong-sheng; Wang Tao; Ding Qing-jun; Huang Shao-long; Wang Fa-zhou; Geng Jian; Hu Shu-guang

    2004-01-01

    The influence of polymer addition on microstructure, performance and mechanical properties of lightweight aggregate concrete was investigated. It was found that the addition of polymer improved the performance and mechanical properties of lightweight aggregate concrete. It was asccrtaincd thai the modification of microstructural uniformity and dcnsification with the addition of polymer is responsible for the enhancement of mechanical properties.With respect to compressive strength and bending strcngth, the lightweight aggregate concrete added with 13% ethylene-acetate ethylene interpolymer (EVA) exhibits preferred mechanical properties.

  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. Pulsations with reflected boundary waves: a hydrodynamic reverse transport mechanism for perivascular drainage in the brain.

    Science.gov (United States)

    Coloma, M; Schaffer, J D; Carare, R O; Chiarot, P R; Huang, P

    2016-08-01

    Beta-amyloid accumulation within arterial walls in cerebral amyloid angiopathy is associated with the onset of Alzheimer's disease. However, the mechanism of beta-amyloid clearance along peri-arterial pathways in the brain is not well understood. In this study, we investigate a transport mechanism in the arterial basement membrane consisting of forward-propagating waves and their reflections. The arterial basement membrane is modeled as a periodically deforming annulus filled with an incompressible single-phase Newtonian fluid. A reverse flow, which has been suggested in literature as a beta-amyloid clearance pathway, can be induced by the motion of reflected boundary waves along the annular walls. The wave amplitude and the volume of the annular region govern the flow magnitude and may have important implications for an aging brain. Magnitudes of transport obtained from control volume analysis and numerical solutions of the Navier-Stokes equations are presented. PMID:26729476

  9. Influence of boron addition on the grain refinement and mechanical properties of AZ91 Mg alloy

    International Nuclear Information System (INIS)

    This article reports the effect of boron addition on the grain refinement efficiency and mechanical properties of AZ91 magnesium alloy. The results show that the addition of boron in the form of Al-4B master alloy, significantly refines the grain size of AZ91 alloy. This refinement is due to the presence of AlB2 particles, which act as potential nucleants for Mg grains. Improved mechanical properties are obtained with the addition of boron due to the finer grains.

  10. Wildfire as a Mechanism to Reverse Ecohydrologic Thresholds in Juniper-Encroached Shrublands

    Science.gov (United States)

    Williams, C. J.; Pierson, F. B.; Al-Hamdan, O. Z.; Hardegree, S. P.; Clark, P. E.; Kormos, P. R.

    2012-12-01

    Woodland encroachment into Great Basin, USA, sagebrush steppe potentially educes a shift from biotic-controlled resource retention to abiotic-driven losses of critical soil resources. The biotic-to-abiotic shift occurs where encroachment propagates runoff connectivity and amplified cross-scale erosion, that in-turn, promote woodland ecohydrologic resilience. Our research objective was to evaluate wildfire as a threshold-reversal mechanism for restoration of sagebrush steppe ecohydrologic resilience. We examined vegetation, soils, and runoff and erosion from artificial rainfall and concentrated flow experiments across multiple scales on burned and unburned areas of a late succession woodland to address three research questions: 1) Are there key vegetation and soil indicators that a former sagebrush community has experienced the biotic-to-abiotic shift?, 2) Can fire decrease late-succession woodland ecohydrologic resilience by increasing vegetation and ground cover within the first two years post-fire?, and 3) Is the soil erosion feedback reversible by burning in the later stages of woodland encroachment? Our findings suggest encroachment-induced increases in bare ground beyond 60% and extensive bare ground gaps (> 100 cm) between plant bases amplify erosion across spatial scales, indicative of the biotic-to-abiotic shift. The primary trigger for increased cross-scale erosion is concentrated flow formation within bare intercanopy areas. Burning in this study decreased late-succession woodland ecohydrologic resilience through herbaceous recruitment two years post-fire. The increased plant productivity decreased the structural connectivity of bare ground, improved infiltration of moderate intensity rainfall, and reduced erosion from simulated concentrated flow. However, the research site remained vulnerable to runoff and erosion from high intensity rainfall. We therefore opine burning can reduce woodland ecohydrologic resilience via post-fire plant recruitment, and

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. A mechanical nanogate based on a carbon nanotube for reversible control of ion conduction.

    Science.gov (United States)

    He, Zhongjin; Corry, Ben; Lu, Xiaohua; Zhou, Jian

    2014-04-01

    Control of mass transport through nanochannels is of critical importance in many nanoscale devices and nanofiltration membranes. The gates in biological channels, which control the transport of substances across cell membranes, can provide inspiration for this purpose. Gates in many biological channels are formed by a constriction ringed with hydrophobic residues which can prevent ion conduction even when they are not completely physically occluded. In this work, we use molecular dynamics simulations to design a nanogate inspired by this hydrophobic gating mechanism. Deforming a carbon nanotube (12,12) with an external force can form a hydrophobic constriction in the centre of the tube that controls ion conduction. The simulation results show that increasing the magnitude of the applied force narrows the constriction and lowers the fluxes of K(+) and Cl(-) found under an electric field. With the exerted force larger than 5 nN, the constriction blocks the conduction of K(+) and Cl(-) due to partial dehydration while allowing for a noticeable water flux. Ion conduction can revert back to the unperturbed level upon force retraction, suggesting the reversibility of the nanogate. The force can be exerted by available experimental facilities, such as atomic force microscope (AFM) tips. It is found that partial dehydration in a continuous water-filled hydrophobic constriction is enough to close the channel, while full dewetting is not necessarily required. This mechanically deformed nanogate has many potential applications, such as a valve in nanofluidic systems to reversibly control ion conduction and a high-performance nanomachine for desalination and water treatment. PMID:24566473

  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. Mechanism of chirality reversal for planar interface domain walls in exchange-coupled hard/soft magnetic bilayers

    OpenAIRE

    McCord, J; Henry, Y; Hauet, Thomas; Montaigne, F.; Fullerton, Eric E.; Mangin, S.

    2008-01-01

    International audience The mechanism of chirality reversal for a planar interface domain wall in a hard/soft magnetic bilayer has been identified by combining magnetoresistance measurements, modeling, and direct magnetic domain observations. The reversal occurs through IDW nucleation and lateral domain wall propagation. Over an unpredicted wide range of applied magnetic fields, the chirality transition takes place by an unwinding followed by a rewinding of the IDW. The chirality transition...

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

    OpenAIRE

    Bogucki R.; Pytel S.M.

    2014-01-01

    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 ...

  20. 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.

  1. Effect of Yttrium and Cerium Addition on Microstructure and Mechanical Properties of AM50 Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To develop magnesium alloy with low cost, high strength and excellent elevated temperature properties, effect of Y and Ce addition on microstructure and mechanical properties of AM50 magnesium alloy was studied. Result showed that addition of small amount of Y and Ce to AM50 alloys resulted in refinement of microstructure. Owing to the improvement of microstructure, the mechanical properties of alloys at both ambient and elevated temperature were increased. AM50 alloy containing 0.6%Ce-0.3%Y (mass fraction) had good refinement effect and relatively ideal mechanical properties.

  2. Investigate The Effect of Additives on Mechanical Properties During Casting of 6351 Aluminium

    Directory of Open Access Journals (Sweden)

    Kumar Sanjeev

    2016-01-01

    Full Text Available Aluminum is one of the significant and widely used metals in the manufacturing industries. The effectiveness of casting processes depends upon various process parameters like type of sand, moulding process and additive used. However, the additive in the sand plays important roles to make a perfect casting. Hence, in this research work the experiment were performed to investigate the effect of additives like Tamarind Powder, Starch Powder and Coal dust on the Mechanical Properties namely during casting of aluminium alloys.

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

    OpenAIRE

    Fraś E.; Górny M.; Kawalec M.

    2007-01-01

    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.

  4. Enhancement of mechanical strength in Y-Ba-Cu-O bulk superconductor through liquid binder addition

    International Nuclear Information System (INIS)

    We studied the effects of the binder addition on the green compacts. We studied the superconducting properties of bulk Y-Ba-Cu-O superconductors. The mechanical properties of the green compacts with binder addition were characterized with the compression tests. We could produce bulk Y-Ba-Cu-O superconductors with binder additions. We have studied the effects of the liquid binder (polyvinyl alcohol) addition (0-10 wt%) on the mechanical properties of the green compacts and also on the superconducting properties of bulk Y-Ba-Cu-O superconductors of 20 mm diameter produced with the top-seeded melt growth (TSMG) process. The mechanical properties of the green compacts with binder addition were characterized with the compression tests, which revealed that mechanical strength increased dramatically with increasing the amount of the binder addition. The binder-added green compacts were then subjected to the TSMG process and oxygen annealing. The trapped field measurements showed that we could produce single-grain bulk Y-Ba-Cu-O samples with binder additions up to 8 wt% without any deterioration in the superconducting properties.

  5. 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.

  6. Chronic ethanol exposure produces tolerance to elevations in neuroactive steroids: Mechanisms and reversal by exogenous ACTH

    OpenAIRE

    Boyd, Kevin N.; Kumar, Sandeep; O'Buckley, Todd K.; Morrow, A. Leslie

    2010-01-01

    Acute ethanol administration increases potent GABAergic neuroactive steroids, specifically (3α,5α)-3-hydroxypregnan-20-one (3α,5α-THP) and (3α,5α)-3,21-dihydroxypregnan-20-one. In addition, neuroactive steroids contribute to ethanol actions. Chronic ethanol exposure results in tolerance to many effects of ethanol, including ethanol-induced increases in neuroactive steroid levels. To determine the mechanisms of tolerance to ethanol-induced increases in neuroactive steroids, we investigated cri...

  7. Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy

    International Nuclear Information System (INIS)

    The influence of niobium addition on the mechanical properties at high temperature of HP alloy has been investigated. Two HP alloys were centrifugally cast with a similar chemical composition differing only in the niobium content. Low strain rate high temperature tensile tests and creep-rupture tests were performed in the range of 900–1100 °C, and the results compared between the alloys. According to the results, the high temperature mechanical behavior of both alloys is controlled by several factors like solid solution, network of eutectic carbides, intradendritic precipitation and dendrite spacing. A significant increase in the mechanical properties for the HP alloy with niobium addition was found within the temperature range of 900–1050 °C. Beyond this temperature the mechanical behavior of both alloys is basically the same

  8. Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, A.R., E-mail: arandrade@gmail.com [Department of Materials Engineering, Federal University of São Carlos, Rod. Washington Luiz, km 235, São Carlos, SP (Brazil); Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Bolfarini, C. [Department of Materials Engineering, Federal University of São Carlos, Rod. Washington Luiz, km 235, São Carlos, SP (Brazil); Ferreira, L.A.M.; Vilar, A.A.A. [Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Souza Filho, C.D.; Bonazzi, L.H.C. [Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Department of Materials, Aeronautical and Automotive Engineering, University of São Paulo, Av. Trabalhador Sancarlense, 400, São Carlos, SP (Brazil)

    2015-03-25

    The influence of niobium addition on the mechanical properties at high temperature of HP alloy has been investigated. Two HP alloys were centrifugally cast with a similar chemical composition differing only in the niobium content. Low strain rate high temperature tensile tests and creep-rupture tests were performed in the range of 900–1100 °C, and the results compared between the alloys. According to the results, the high temperature mechanical behavior of both alloys is controlled by several factors like solid solution, network of eutectic carbides, intradendritic precipitation and dendrite spacing. A significant increase in the mechanical properties for the HP alloy with niobium addition was found within the temperature range of 900–1050 °C. Beyond this temperature the mechanical behavior of both alloys is basically the same.

  9. 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.

  10. 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.

  11. First order reversal curves analysis of the temperature effect on magnetic interactions in barium ferrite with La-Co addition

    International Nuclear Information System (INIS)

    First order reversal curves (FORCs) distributions are a powerful tool for investigating hysteresis and interactions in magnetic systems and have been widely applied. La-Co substitution in barium hexaferrites has also been extensively studied. The most effective substitution to improve the magnetic properties (coercive field and energy product) is given by x=y=0.2 in the formula Ba1-xLaxFe12-yCoyO19. In this work, this stoichiometry is initially used to obtain a state where more than one phase is present. The magnetic behavior as a function of temperature was studied in order to have an insight into the magnetic interactions that originate a decrease in the magnetic performance of Ba hexaferrite magnets. The sample was structurally characterized by X-ray diffraction (XRD) and magnetically studied in a SQUID magnetometer. FORC distributions were used to study the dependence of the magnetic interactions with the temperature. FORC diagrams performed on the sample at different temperatures exhibit similar characteristics, such as the spread in the hc-hu plane and a spread out of the hc-axes. These features are interpreted in terms of exchange-interacting particles and dipolar interactions, respectively. As the temperature decreases, stronger interactions are noticed among hard and soft phases.

  12. Evaluation of the mechanical properties of acetic-cure silicone with the addition of magnesium silicate

    OpenAIRE

    Ronald Vargas Orellana; Neide Pena Coto; Igor Studart Medeiros; Reinaldo Brito Dias

    2015-01-01

    Current study evaluates the mechanical properties (tensile and tear strength) of an acetic-cure silicone with the addition of 10 or 20% vol. magnesium silicate. Magnesium silicate was added to the silicone at concentrations of 10 (MS-10) and 20% (MS-20) volume, followed by the analysis of tensile strength, maximal elongation during tensile and tear strength. Results were compared to control group of silicone without additives (CG). Mean rates were determined and compared by analysis of v...

  13. 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.

  14. 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.

  15. The relation between the distribution behaviour of the hysteresis loss and magnetization reversal mechanism in CoCr films

    NARCIS (Netherlands)

    Li, Cheng-Zhang; Lodder, J.C.

    1988-01-01

    The distribution of the hysteresis loss as a function of the applied field has been successfully used to investigate the magnetization reversal mechanism in our CoCr films. For high Hc/Hk films, the distribution of the hysteresis loss vs. applied field exhibits a monotonically decreasing curve with

  16. Thickness dependence of structural,magnetic properties and reversal mechanism of Co Cr Ta/Cr longitudinal recording media

    NARCIS (Netherlands)

    Kim, P.L.; Lodder, J.C.

    2002-01-01

    In this paper,a series of five samples of X nm Co Cr Ta/100 nm Cr (X 10 2 100 nm) longitudinal recording media was studied.The relationships between structural, magnetic properties and the reversal mechanism were investigated and discussed.It was found that the maximums of coercivity and squarenesse

  17. 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

  18. Mechanisms of Mn(OAc)3-based oxidative free-radical additions and cyclizations

    OpenAIRE

    Snider, Barry B.

    2009-01-01

    The mechanistic details of Mn(OAc)3-based oxidative free-radical additions and cyclizations are reviewed. The mechanisms of electron transfer to generate radicals, electron transfer to convert the radicals to oxidized products, and further oxidation of the products are covered.

  19. 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…

  20. 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.

  1. Effects of recrystallization and Nb additions on texture and mechanical anisotropy of Zircaloy

    Energy Technology Data Exchange (ETDEWEB)

    Murty, K.L. (North Carolina State University, Raleigh, NC 27695-7909 (United States)); Jallepalli, Ravi (North Carolina State University, Raleigh, NC 27695-7909 (United States)); Mahmood, S.T. (North Carolina State University, Raleigh, NC 27695-7909 (United States))

    1994-06-01

    The effect of recrystallization on the crystallographic textures and anisotropic mechanical properties of Zircaloy-4 sheets was investigated. In addition, the influence of niobium additions on these properties was studied using three different alloys. The mechanical anisotropy parameters were determined by mechanical testing of gridded tensile samples. The textures were characterized by X-ray pole figure measurements and crystallite orientation distribution functions (CODFs). The CODFs were combined with a crystal plasticity model to predict the anisotropy parameters based on the dominance individually of basal, prism and pyramidal slip systems. Good agreement was noted between the experimental results and model predictions based on prism slip for the recrystallized materials, while the results on cold-worked sheets differed from model predictions for all the three slip systems. ((orig.))

  2. Effects of recrystallization and Nb additions on texture and mechanical anisotropy of Zircaloy

    International Nuclear Information System (INIS)

    The effect of recrystallization on the crystallographic textures and anisotropic mechanical properties of Zircaloy-4 sheets was investigated. In addition, the influence of niobium additions on these properties was studied using three different alloys. The mechanical anisotropy parameters were determined by mechanical testing of gridded tensile samples. The textures were characterized by X-ray pole figure measurements and crystallite orientation distribution functions (CODFs). The CODFs were combined with a crystal plasticity model to predict the anisotropy parameters based on the dominance individually of basal, prism and pyramidal slip systems. Good agreement was noted between the experimental results and model predictions based on prism slip for the recrystallized materials, while the results on cold-worked sheets differed from model predictions for all the three slip systems. ((orig.))

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Mechanism underlying the reversal of contractility dysfunction in experimental colitis by cyclooxygenase-2 inhibition.

    Science.gov (United States)

    Khan, I; Oriowo, M A

    2006-03-01

    Inflammatory bowel diseases are associated with reduced colonic contractility and induction of cyclooxygenase-2. In this study a possible role of cyclooxygenase-2 in and the underlying mechanism of the reduced contractility were investigated in experimental colitis. The effects of meloxicam, a cyclooxygenase-2 selective inhibitor were examined on colonic contractility and MAP kinase p38 and ERK(1/2) expression. Colitis was induced in Sprague-Dawley male rats by intra-colonic instillation of trinitrobenzenesulphonic acid (TNBS; 40 mg/rat in 50 ethanol). The animals were divided into three groups. Group 1 (n=9) received meloxicam (3 mg/kg-day) gavage 1 h before and 1 day (Group 2) after induction of colitis. Group 3 (n=9) received phosphate buffered saline (PBS) in a similar manner and served as colitic control. The non colitic control animals received meloxicam in a similar manner. The animals were sacrificed after 5 days of treatment, colon was cleaned with PBS and colonic smooth muscle was obtained which was used in this study. Meloxicam treatment given 1 h before or 1 day after administration of colitis restored the reduced colonic contractility without affecting the sensitivity to carbachol. The levels of colonic smooth muscle IL-1beta mRNA, PGE(2), ERK(1/2), p38, malondialdehyde, myeloperoxidase activity and colonic mass were increased, whereas the body weight was decreased due to TNBS. The changes except colonic muscle mass and p38 expression were reversed by meloxicam treatment. These findings indicate that restoration of reduced colonic contractility by meloxicam is mediated by ERK(1/2), and that ERK(1/2) may serve as an important anti inflammatory target for treatment of colitis. PMID:16835710

  8. 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.

  9. 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.

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

    Science.gov (United States)

    Hounslow, Mark W

    2016-01-01

    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. PMID:27572303

  11. 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.

  12. 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.

  13. Mechanisms of inhibition of HIV replication by nonnucleoside reverse transcriptase inhibitors

    OpenAIRE

    Sluis-Cremer, Nicolas; Tachedjian, Gilda

    2008-01-01

    The nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) are a therapeutic class of compounds that are routinely used, in combination with other antiretroviral drugs, to treat HIV-1 infection. NNRTIs primarily block HIV-1 replication by preventing RT from completing reverse transcription of the viral single-stranded RNA genome into DNA. However, some NNRTIs, such as efavirenz, have been shown to inhibit the late stages of HIV-1 replication by interfering with HIV-1 Gag-Pol polyprotein...

  14. 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.

  15. The effect of nanometric zirconia particle additives on microstructure and mechanical properties of dense alumina

    Directory of Open Access Journals (Sweden)

    Lukasz Zych

    2009-09-01

    Full Text Available Zirconia additives have favourable influence on mechanical properties of dense alumina polycrystals. It results from the martensitic transformation of tetragonal zirconia particles into monoclinic symmetry at the crack tip propagating through a material. Usually applied zirconia particles were of sub-micrometer or micrometer sizes. In the present work nanometric zirconia particles prepared by hydrothermal crystallization technique were introduced into the alumina matrix. Both, zirconia and alumina powders were homogenized in an aqueous suspension of pH selected on the basis of the zeta (ξ potential measurements. It was found that this factor influences greatly strength of the resulting powder agglomerates and hence mechanical properties of the sintered material.

  16. Resonant vortex-core reversal in magnetic nano-spheres as robust mechanism of efficient energy absorption and emission

    Science.gov (United States)

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Jae-Hyeok; Kim, Min-Kwan

    2016-01-01

    We report on novel vortex-core reversal dynamics in nano-spheres of single-vortex spin configuration as revealed by micromagnetic simulations combined with analytical derivations. When the frequency of an AC magnetic field is tuned to the frequency of the vortex-core precession around the direction of a given static field, oscillatory vortex-core reversals occur, and additionally, the frequency is found to change with both the strength of the applied AC field and the particle size. Such resonant vortex-core reversals in nano-spheres may provide a new and efficient means of energy absorption by, and emission from, magnetic nanoparticles, which system can be effectively implemented in bio-applications such as magnetic hyperthermia. PMID:27531408

  17. 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.

  18. Mechanism for the addition of carbenoid CH2ClLi to formaldehyde

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Ab initio HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2ClLi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2ClLi 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.

  19. The role of additives in the recombination luminescence mechanism of irradiated 2-methyltetrahydrofuran glasses

    International Nuclear Information System (INIS)

    The radiothermoluminescence (RTL) of γ-irradiated pure glassy 2-methyltetrahydrofuran (2-MTHF) and of 2-MTHF glasses containing additives was measured. For pure 2-MTHF a very weak luminescence peak at 93 K (heating rate 0,05 K/s) was found which in the presence of certain additives was enhanced by several orders of magnitude. Using data of radiothermoluminescence, absorption and phosphorescence measurements and bleaching experiments an attempt was made to derive a reaction mechanism. It was found to exist different possibilities for activation the ionic species to give recombination luminescence. (author)

  20. 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.

  1. 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.

  2. Microstructure and mechanical properties of the Al-Ti alloy with calcium addition

    OpenAIRE

    L.A. Dobrzański; K. Labisz; Olsen, A

    2008-01-01

    Purpose: In this paper there are presented the investigation results of mechanical properties and microstructure with intermetallic phases of the aluminium – titanium alloy with a defined content of Ca addition. The purpose of this work was also to determine the heat treatment conditions for solution heat treatment of the investigation alloys.Design/methodology/approach: The reason of this work was to determine the heat treatment influence, particularly solution heat treatment time to the cha...

  3. Additive manufacture of an aluminium alloy: processing, microstructure, and mechanical properties

    OpenAIRE

    Aboulkhair, Nesma T.

    2016-01-01

    Additive manufacturing of aluminium alloys using selective laser melting (SLM) is of research interest nowadays because of its potential benefits in industry sectors such as aerospace and automotive. However, in order to demonstrate the credibility of aluminium SLM for industrial needs, a comprehensive understanding of the interrelation between the process parameters, produced microstructure, and mechanical behaviour is still needed. This thesis aims at contributing to developing this compreh...

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

    OpenAIRE

    Tesař Václav

    2016-01-01

    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, oscillati...

  5. 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.

  6. 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)

  7. 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.

  8. 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.)

  9. Stabilisation of mechanical properties in silver alloys by addition of lanthanides

    Directory of Open Access Journals (Sweden)

    W. Głuchowski

    2008-10-01

    Full Text Available Purpose: Silver alloys intended for industrial application should characterise by high electrical conductivity (as pure silver as well as high mechanical and functional properties, stable also at elevated temperature. The objective of this work was to investigate the mechanical properties stability of Ag-La (0.5% and Ag-mishmetal (1 and 4% alloys caused by severe plastic deformation compared to the Ag+(7.5 wt %Cu alloy and pure Ag materials.Design/methodology/approach: Tests were made with the samples obtained by casting and further plastic working included KOBO® extrusion process and drawing. Wires were annealed in temperature range 50 - 500°C. The mechanical properties (at room temperature, elevated temperature and after annealing and microstructure were examined. The values of yield strength obtained in a tension tests have been compared to the values calculated theoretically.Findings: Additive of rare earth metals contributed to fine structure obtaining, particles formed in grain boundaries stabilized microstructure at elevated temperature. Increase of mechanical properties of investigated alloys was connected with presence of fine precipitations in silver matrix, which confirmed susceptibility to precipitation hardening of silver – mishmetal alloys.Research limitations/implications: Ability of new alloys to precipitation hardening should be confirmed by further investigations, including solution heat treatment and ageing, also for materials prepared in vacuum furnace.Practical implications: Stability of mechanical properties at elevated temperature, gives possibility to use of new silver allays for producing elements designed to operate at elevated temperatures or exposed to rapid temperature changes. Increased mechanical properties and good tarnish resistance indicates possibility of new applications of investigated alloys in jewellery and medicine, after additional and essential investigations.Originality/value: The wire made from

  10. Mechanism of strengthening of cube texture for high purity aluminum foils by additional-annealing

    Institute of Scientific and Technical Information of China (English)

    张新明; 刘胜胆; 唐建国; 周卓平

    2003-01-01

    The mechanism of strengthening of cube texture ({001}〈100〉) by additional-annealing of high purity aluminum foils was investigated by using orientation distribution functions (ODFs) and electron back scattered diffraction (EBSD). The results of ODFs and fiber show that the orientation densities of the S {123}〈634〉 and Cu {112}〈111〉 components increase in both the additional-annealed samples and the 0.11 mm final cold-rolled foils. And the EBSD results demonstrate that cube nuclei can be identified in the deformed matrix of those additional-annealed samples. It is suggested that the strengthening of cube texture can be brought out by the increasing of components of S and Cu and the formation of cube nuclei caused by additional-annealing. Moreover, it is found that the cube texture increases first and then decreases with increasing additional-annealing temperature, and it is the strongest at 180 ℃.The strengthening of cube texture by additional-annealing is proposed as the result of oriented growth of cube subgrains.

  11. 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.

  12. Influence of niobium additions on mechanical properties and corrosion of INCOLOY 800 H

    International Nuclear Information System (INIS)

    The studies were carried out with six model alloys of the type INCOLOY alloy 800 H (32 Ni/20 Cr), obtained by variation of the niobium additions with up to 1.55 wt. p.c. of Nb. The mechanical properties and structural characteristics of these samples are listed after treatments as follows: - Aging at 650, 800, and 9000C (Notch bending tests and tensile tests at room temperature). - Carbonisation at 800 and 9000C in PNP standard helium (C-analysis, long-term creep tests at 9000C). Alloys with Nb additions showed constant good strength and ductility after aging, values being better than those for material without Nb additions. The creep tests showed that tensile strengths is improved with increasing niobium content; carbonisation is less than in alloys without Nb. (orig./IHOE)

  13. 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...

  14. Magnetization reversal mechanisms in hybrid resin-bonded Nd-Fe-B magnets

    International Nuclear Information System (INIS)

    The magnetic properties of isotropic epoxy resin-bonded magnets prepared by mixing a hard magnetic powder made from melt quenched Nd-Fe-Co-B ribbons and a soft magnetic iron powder have been examined. The magnetization reversal processes and the magnetic parameters have been studied by the measurement of the virgin magnetization curves, the major and minor hysteresis loops and sets of recoil curves. From these recoil curves the field dependence of the reversible and irreversible magnetization components during the magnetization and demagnetization processes has been derived. The remanence relationship was used to study the nature of magnetic interaction between the grains. A study of interaction domains was conducted using optical microscopy. Groups of domains, each over several grains, were observed. It was found that the reversal process in the samples investigated involves the rotation of magnetization vectors in the iron powder grains and pinning of domain walls at the MQP-B grain boundaries

  15. Mechanical properties of open-cell metallic biomaterials manufactured using additive manufacturing

    International Nuclear Information System (INIS)

    Highlights: ► Finite element (FE) models were used to predict the mechanical properties of porous biomaterials. ► Porous materials were produced using additive manufacturing techniques. ► Manufacturing irregularities need to be implemented in FE models. ► FE models are more accurate than analytical models in predicting mechanical properties. - Abstract: An important practical problem in application of open-cell porous biomaterials is the prediction of the mechanical properties of the material given its micro-architecture and the properties of its matrix material. Although analytical methods can be used for this purpose, these models are often based on several simplifying assumptions with respect to the complex architecture and cannot provide accurate prediction results. The aim of the current study is to present finite element (FE) models that can predict the mechanical properties of porous titanium produced using selective laser melting or selective electron beam melting. The irregularities caused by the manufacturing process including structural variations of the architecture are implemented in the FE models using statistical models. The predictions of FE models are compared with those of analytical models and are tested against experimental data. It is shown that, as opposed to analytical models, the predictions of FE models are in agreement with experimental observations. It is concluded that manufacturing irregularities significantly affect the mechanical properties of porous biomaterials

  16. 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.

  17. The Effects and Mechanisms of Periplaneta americana Extract Reversal of Multi-Drug Resistance in BEL-7402/5-FU Cells

    Directory of Open Access Journals (Sweden)

    Falu Yuan

    2016-06-01

    Full Text Available The present study reports the reversing effects of extracts from P. americana on multidrug resistance of BEL-7402/5-FU cells, as well as a preliminary investigation on their mechanism of action. A methylthiazolyl tetrazolium (MTT method was applied to determine the multidrug resistance of BEL-7402/5-FU, while an intracellular drug accumulation assay was used to evaluate the effects of a column chromatography extract (PACC and defatted extract (PADF from P. americana on reversing multi-drug resistance. BEL-7402/5-FU reflected high resistance to 5-FU; PACC and PADF could promote drug accumulation in BEL-7402/5-FU cells, among which PADF was more effective than PACC. Moreover, results from the immunocytochemical method showed that PACC and PADF could downregulate the expression of drug resistance-associated proteins (P-gp, MRP, LRP; PACC and PADF had no effects on the expression of multidrug resistance-associated enzymes (GST-π, but PACC could increase the expression of multidrug resistance-associated enzymes (PKC. Results of real-time fluorescence quantitative PCR revealed that PACC and PADF were able to markedly inhibit the expression of multidrug resistance-associated genes (MDR1, LRP and MRP1; PACC presented a significant impact on the gene expression of multidrug resistance-associated enzymes, which increased the gene expression of GST-π and PKC. However, PADF had little impact on the expression of multidrug resistance-associated enzymes. These results demonstrated that PACC and PADF extracted from P. americana could effectively reverse MDR in BEL-7402/5-FU cells, whose mechanism was to inhibit the expression of P-gp, MRP, and LRP, and that PADF was more effective in the reversal of MDR than did PACC. In addition, some of extracts from P. americana altered (sometimes increasing the expression of multidrug resistance-associated enzymes.

  18. The Effects and Mechanisms of Periplaneta americana Extract Reversal of Multi-Drug Resistance in BEL-7402/5-FU Cells.

    Science.gov (United States)

    Yuan, Falu; Liu, Junyong; Qiao, Tingting; Li, Ting; Shen, Qi; Peng, Fang

    2016-01-01

    The present study reports the reversing effects of extracts from P. americana on multidrug resistance of BEL-7402/5-FU cells, as well as a preliminary investigation on their mechanism of action. A methylthiazolyl tetrazolium (MTT) method was applied to determine the multidrug resistance of BEL-7402/5-FU, while an intracellular drug accumulation assay was used to evaluate the effects of a column chromatography extract (PACC) and defatted extract (PADF) from P. americana on reversing multi-drug resistance. BEL-7402/5-FU reflected high resistance to 5-FU; PACC and PADF could promote drug accumulation in BEL-7402/5-FU cells, among which PADF was more effective than PACC. Moreover, results from the immunocytochemical method showed that PACC and PADF could downregulate the expression of drug resistance-associated proteins (P-gp, MRP, LRP); PACC and PADF had no effects on the expression of multidrug resistance-associated enzymes (GST-π), but PACC could increase the expression of multidrug resistance-associated enzymes (PKC). Results of real-time fluorescence quantitative PCR revealed that PACC and PADF were able to markedly inhibit the expression of multidrug resistance-associated genes (MDR1, LRP and MRP1); PACC presented a significant impact on the gene expression of multidrug resistance-associated enzymes, which increased the gene expression of GST-π and PKC. However, PADF had little impact on the expression of multidrug resistance-associated enzymes. These results demonstrated that PACC and PADF extracted from P. americana could effectively reverse MDR in BEL-7402/5-FU cells, whose mechanism was to inhibit the expression of P-gp, MRP, and LRP, and that PADF was more effective in the reversal of MDR than did PACC. In addition, some of extracts from P. americana altered (sometimes increasing) the expression of multidrug resistance-associated enzymes. PMID:27367657

  19. 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.

  20. Reversible and irreversible mechanical effects in real cable-in-conduit conductors

    NARCIS (Netherlands)

    Mitchell, N.; Devred, A.; Larbalestier, D.C.; Lee, P.J.; Sanabria, C.; Nijhuis, A.

    2013-01-01

    The strong strain sensitivity of the critical properties of Nb3Sn is well established. However, the roles played by both the reversible strain sensitivity and the susceptibility to brittle fracture of Nb3Sn filaments is still leading to unexpected results and resulting design modifications of conduc

  1. Mechanism of Fast Axially--Symmetric Reversal of Magnetic Vortex Core

    OpenAIRE

    Pylypovskyi, Oleksandr V.; Sheka, Denis D.; Kravchuk, Volodymyr P.; Gaididei, Yuri; Mertens, Franz G.

    2012-01-01

    The magnetic vortex core in a nanodot can be switched by an alternating transversal magnetic field. We propose a simple collective coordinate model which describes comprehensive vortex core dynamics, including resonant behavior, weakly nonlinear regimes, and reversal dynamics. A chaotic dynamics of the vortex polarity is predicted. All analytical results were confirmed by micromagnetic simulations.

  2. The effect of density and feature size on mechanical properties of isostructural metallic foams produced by additive manufacturing

    International Nuclear Information System (INIS)

    Simple models describing the relationship between basic mechanical properties and the relative density of various types of porous metals (such as foams, sponges and lattice structures) are well established. Carefully evaluating these relationships experimentally is challenging, however, because of the stochastic structure of foams and the fact that it is difficult to systematically isolate density changes from variations in other factors, such as pore size and pore distribution. Here a new method for producing systematic sets of stochastic foams is employed based on electron beam melting (EBM) additive manufacturing (AM). To create idealised structures, structural blueprints were reverse-engineered by inverting X-ray computed tomographs of a randomly packed bed of glass beads. This three-dimensional structure was then modified by computer to create five foams of different relative density ρr, but otherwise consistent structure. Yield strength and Young’s modulus have been evaluated in compression tests and compared to existing models for foams. A power of 3 rather than a squared dependence of stiffness on relative density is found, which agrees with a recent model derived for replicated foams. A similar power of 3 relation was found for yield strength. Further analysis of the strength of nominally fully dense rods of different diameters built by EBM AM suggest that surface defects mean that the minimum size of features that can be created by EBM with similar strengths to machined samples is ∼1 mm

  3. Effects of Mo and Al addition on the Mechanical Properties of 15Cr ODS steel

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Jaewon; Noh, Sanghoon; Kang, Sukhoon; Chun, Youngbum; Choi, Byoungkwon; Han, Changhee; Kim, Taekyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-05-15

    Oxide particle controls the strength of the ODS steel and the addition of Mo, W, and Al, which changes the microstructures and remarkably influences the strength of ODS steel. In this study, Fe-based ODS alloys with Mo, W, and Al additions were fabricated by HIP and hot rolling processes, and their microstructures and mechanical properties were investigated. Some Fe-based ODS alloys were fabricated by a HIP process, and their microstructures and mechanical properties were investigated. Mo, W, and Al are considered to be very effective alloying elements for high strength and formability in Fe-based ODS alloys. As a result of a microstructure observation, grain refinement occurred in the case of the addition of W and Mo. However, the grain size and oxide particles of Fe-15Cr-ODS alloy Al added became coarse. Therefore, the hardness and tensile strength were decreased. On the other hand, the elongation was increased owing to the coarser grain. These preliminary results will be useful for developing advanced Fe-15Cr ODS alloy. The structural components for nuclear systems need to have formability as well as strength.

  4. 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.

  5. 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.

  6. 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°. PMID:26143351

  7. 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.

  8. Fluid mechanics of additive manufacturing of metal objects by accretion of droplets - a survey

    Science.gov (United States)

    Tesař, Václav

    2016-03-01

    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.

  9. 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.

  10. 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

    2016-07-01

    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. PMID:27299858

  11. 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.

  12. Exploring the mechanical strength of additively manufactured metal structures with embedded electrical materials

    International Nuclear Information System (INIS)

    Ultrasonic Additive Manufacturing (UAM) enables the integration of a wide variety of components into solid metal matrices due to the process induced high degree of metal matrix plastic flow at low bulk temperatures. Exploitation of this phenomenon allows the fabrication of previously unobtainable novel engineered metal matrix components. The feasibility of directly embedding electrical materials within UAM metal matrices was investigated in this work. Three different dielectric materials were embedded into UAM fabricated aluminium metal-matrices with, research derived, optimal processing parameters. The effect of the dielectric material hardness on the final metal matrix mechanical strength after UAM processing was investigated systematically via mechanical peel testing and microscopy. It was found that when the Knoop hardness of the dielectric film was increased from 12.1 HK/0.01 kg to 27.3 HK/0.01 kg, the mechanical peel testing and linear weld density of the bond interface were enhanced by 15% and 16%, respectively, at UAM parameters of 1600 N weld force, 25 µm sonotrode amplitude, and 20 mm/s welding speed. This work uniquely identified that the mechanical strength of dielectric containing UAM metal matrices improved with increasing dielectric material hardness. It was therefore concluded that any UAM metal matrix mechanical strength degradation due to dielectric embedding could be restricted by employing a dielectric material with a suitable hardness (larger than 20 HK/0.01 kg). This result is of great interest and a vital step for realising electronic containing multifunctional smart metal composites for future industrial applications

  13. Reversible Adaptive Plasticity: A Mechanism for Neuroblastoma Cell Heterogeneity and Chemo-Resistance

    OpenAIRE

    AnthonyDSandler

    2012-01-01

    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 nest...

  14. 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.

  15. Divergent genetic mechanisms underlie reversals to radial floral symmetry from diverse zygomorphic flowered ancestors

    Directory of Open Access Journals (Sweden)

    Wenheng eZhang

    2013-08-01

    Full Text Available Malpighiaceae possess flowers with a unique bilateral symmetry (zygomorphy, which is a hypothesized adaptation associated with specialization on neotropical oil bee pollinators. Gene expression of two representatives of the CYC2 lineage of floral symmetry TCP genes, CYC2A and CYC2B, demarcate the adaxial (dorsal region of the flower in the characteristic zygomorphic flowers of most Malpighiaceae. Several clades within the family, however, have independently lost their specialized oil bee pollinators and reverted to radial flowers (actinomorphy like their ancestors. Here, we investigate CYC2 expression associated with four independent reversals to actinomorphy. We demonstrate that these reversals are always associated with alteration of the highly conserved CYC2 expression pattern observed in most New World Malpighiaceae. In New World Lasiocarpus and Old World Microsteria, the expression of CYC2-like genes has expanded to include the ventral region of the corolla. Thus, the pattern of gene expression in these species has become radialized, which is comparable to what has been reported in the radial flowered legume clade Cadia. In striking contrast, in New World Psychopterys and Old World Sphedamnocarpus, CYC2-like expression is entirely absent or at barely detectable levels. This is more similar to the pattern of CYC2 expression observed in radial flowered Arabidopsis. These results collectively indicate that, regardless of geographic distribution, reversals to similar floral phenotypes in this large tropical angiosperm clade have evolved via different genetic changes from an otherwise highly conserved developmental program.

  16. A theoretical study of the mechanism of the addition reaction between carbene and azacyclopropane

    Directory of Open Access Journals (Sweden)

    XIAOJUN TAN

    2010-05-01

    Full Text Available The mechanism of the addition reaction between carbene and azacyclopropane was investigated using the second-order Moller–Plesset perturbation theory (MP2. By using the 6-311+G* basis set, geometry optimization, vibrational analysis and the energy properties of the involved stationary points on the potential energy surface were calculated. From the surface energy profile, it can be predicted that there are two reaction mechanisms. The first one (1 is carbene attack at the N atom of azacyclopropane to form an intermediate, 1a (IM1a, which is a barrier-free exothermic reaction. Then, IM1a can isomerize to IM1b via a transition state 1a (TS1a, in which the potential barrier is 30.0 kJ/mol. Subsequently, IM1b isomerizes to a product (Pro1 via TS1b with a potential barrier of 39.3 kJ/mol. The other one (2 is carbene attack at the C atom of azacyclopropane, firstly to form IM2 via TS2a, the potential barrier is 35.4 kJ/mol. Then IM2 isomerizes to a product (Pro2 via TS2b with a potential barrier of 35.1 kJ/mol. Correspondingly, the reaction energy for the reactions (1 and (2 is –478.3 and –509.9 kJ/mol, respectively. Additionally, the orbital interactions are also discussed for the leading intermediate.

  17. 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.

  18. Possible Mechanism of ``Additional'' Production of H^- in a Glow Discharge

    Science.gov (United States)

    Belostotskiy, S.; Economou, D.; Lopaev, D.; Rakhimova, T.

    2006-10-01

    Based on measurements of H^- and H densities a DC glow discharge in H2 (P=0.1-3 Torr) the rate coefficient of H^- production as a function of E/N was determined. To analyze the mechanisms of H^- production, a simple model of H2 vibrational excitation was developed. Estimations of vibrational level densities (v=3-5) obtained from VUV absorption measurements were in reasonable agreement with the calculated data. The analysis revealed that standard mechanisms of H^- production (dissociative attachment to vibrationally excited molecules H2(v) and molecules in Rydberg states H2(Ry)) were not enough to explain the experimental results. In order to describe both the shape (vs E/N) and the magnitude of the measured H^- production rate coefficient, an ``additional'' source of H^-, having a strong resonant electron attachment CS in the range of ˜5-9 eV, should be invoked. Although H2 has no resonances in the 5-9 eV range, water is known to strongly dissociatively attach in this range. Thus, even small amounts (0.1-1%) of water vapor in the apparatus can explain the origin of the ``additional'' H^- production. This result is corroborated by the work of Cadez et. al. in Proc. of XXVII ICPIG, 2005. This work was supported by the RFBR (No.05-02-17649a), Scientific School - 171113.2003.2 and NATO Collaborative Linkage Grant (No.980097).

  19. 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.

  20. 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.

  1. Effect of additives for higher removal rate in lithium niobate chemical mechanical planarization

    International Nuclear Information System (INIS)

    High roughness and a greater number of defects were created by lithium niobate (LN; LiNbO3) processes such as traditional grinding and mechanical polishing (MP), should be decreased for manufacturing LN device. Therefore, an alternative process for gaining defect-free and smooth surface is needed. Chemical mechanical planarization (CMP) is suitable method in the LN process because it uses a combination approach consisting of chemical and mechanical effects. First of all, we investigated the LN CMP process using commercial slurry by changing various process conditions such as down pressure and relative velocity. However, the LN CMP process time using commercial slurry was long to gain a smooth surface because of lower material removal rate (MRR). So, to improve the material removal rate (MRR), the effects of additives such as oxidizer (hydrogen peroxide; H2O2) and complexing agent (citric acid; C6H8O7) in a potassium hydroxide (KOH) based slurry, were investigated. The manufactured slurry consisting of H2O2-citric acid in the KOH based slurry shows that the MRR of the H2O2 at 2 wt% and the citric acid at 0.06 M was higher than the MRR for other conditions.

  2. Design of a mechanical system in gait rehabilitation with progressive addition of weight

    Science.gov (United States)

    Braidot, Ariel A. A.; Aleman, Guillermo L.

    2011-12-01

    In this paper we designed and developed a mechanical device for gait rehabilitation based on the application of "partial body weight reduction therapy". An evaluation of the characteristics of devices based on this therapy currently available on the market was carried out obtaining information of the different mechanisms used in it. The device was designed to adapt to different height and weight of patients and to be used with additional equipment in gait rehabilitation, for example, treadmills, elliptical trainers and vertical scalers. It was envisaged to be used by patients with asymmetry in the lower extremities capabilities. We developed a stable structure in steel ASTM A36 which does not depend on the building conditions of the installation site. RamAdvanse software was used to calculate structural stability. A winch with automatic brake mechanism was used to raise/lower the patient, who was tied to a comfortable harness which provided safety to the patient and therapist. It was possible to quantify precisely, using counterweights, the weight borne by the patient during therapy. We obtained a small-sized and ergonomic low-cost prototype, with similar features to those currently considered cutting-edge devices.

  3. 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.

  4. 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.

  5. Effect of boron and carbon addition on microstructure and mechanical properties of metastable beta titanium alloys

    International Nuclear Information System (INIS)

    Highlights: • Effect of boron and carbon on properties of three beta titanium alloys studied. • Ti–15V–3Cr–3Mo–3Sn, Ti–10V–2Fe–3Al, and Ti–5V–5Mo–5Al–3Cr alloys studied. • Hardness and 0.2% YS increases and elongation to failure deteriorates with the B and C addition. • Ageing in comparison to solution treatment results in increase in strength and decrease in elongation. • Low ‘n′ values and multiple slopes are observed in log–log plots of true stress–true strain curves. - Abstract: Effect of boron and carbon on microstructure and mechanical properties of β titanium alloys Ti–15V–3Cr–3Mo–3Sn, Ti–10V–2Fe–3Al, and Ti–5V–5Mo–5Al–3Cr has been studied in detail. The addition of boron and carbon results in refinement of β grain size and α-precipitates during ageing. While the hardness and tensile strength increase with the addition of boron and carbon, the elongation to failure deteriorates. The increase in strength is attributed to a synergistic effect of grain refinement and load sharing by TiB and TiC particles; whereas decrease in elongation is due to the brittleness of these hard particles. Ageing results in increase in strength and decrease in elongation as compared to solution treatment condition. In this case, the effect of boron and carbon is marginal. Further enhancement in the properties can be achieved by fine tuning heat treatment parameters. Multiple slopes are observed in log–log plots of true stress–true strain thereby implying different deformation mechanisms over a large range of plastic deformation

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Mechanism of weld formation during very-high-power ultrasonic additive manufacturing of Al alloy 6061

    International Nuclear Information System (INIS)

    The microstructures of Al alloy 6061 subjected to very-high-power ultrasonic additive manufacturing were systematically examined to understand the underlying ultrasonic welding mechanism. The microstructure of the weld interface between the metal tapes consisted of fine, equiaxed grains resulting from recrystallization, which is driven by simple shear deformation along the ultrasonically vibrating direction of the tape surface. Void formation at the weld interface is attributed to surface asperities resulting from pressure induced by the sonotrode at the initial tape deposition. Transmission electron microscopy revealed that Al–Al metallic bonding without surface oxide layers was mainly achieved, although some oxide clusters were locally observed at the original interface. The results suggest that the oxide layers were broken up and then locally clustered on the interface by ultrasonic vibration

  11. 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.

  12. Additive effect of alcohol and nicotine on lipid peroxidation and antioxidant defence mechanism in rats.

    Science.gov (United States)

    Ashakumary, L; Vijayammal, P L

    1996-01-01

    Cigarette smoking has been established as a major risk factor for atherosclerosis and also for lung cancer. Nicotine is one of the major toxic components of cigarette smoke that is believed to be partly responsible for the deleterious effect of cigarette smoke. Alcohol intake is another major risk factor for the development of cardiovascular disease. Lipid peroxidation is a process associated with the pathogenesis of atherosclerosis. The concentration of lipid peroxides is found to be increased in alcohol-treated rats. On nicotine administration along with alcohol, an additive effect was observed in lipid peroxidation and the antioxidant defence mechanism. The activity of scavenging enzymes superoxide dismutase, catalase and glutathione reductase was found to be decreased, while the activity of glutathione peroxidase and the concentration of glutathione were increased. PMID:8854216

  13. 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.

  14. Mechanical properties of fine grained superalloy K4169 with addition of refiners

    Institute of Scientific and Technical Information of China (English)

    HUANG Tai-wen; LIU Lin; YANG Ai-min; XIONG Yu-hua; ZHANG Rong

    2005-01-01

    Grain refinement of superalloy K4169 was achieved by adding refiners into the alloy melt and their effects on the mechanical properties were investigated. The tensile properties at room temperature and 700 ℃ and low cycle fatigue properties at room temperature were compared for both conventional and fine grained test bars.The results indicate that the rupture strength, yield strength, elongation and reduction of area for refined grains are all much superior to those for coarse ones. Whereas the elongation and reduction of area of fine grained samples decrease at 700 ℃. Low cycle fatigue properties of samples with refined grains at room temperature are improved significantly. In addition, the degree of dispersion of low cycle fatigue data of samples with refined grains is diminished.

  15. Reverse α′ → γ transformation mechanisms of martensitic Fe–Mn and age-hardenable Fe–Mn–Pd alloys upon fast and slow continuous heating

    International Nuclear Information System (INIS)

    The mechanisms governing the reverse martensite (α′) to austenite (γ) transformation (α′ → γ) and the effect of prior precipitation on the austenite reversion are investigated for martensitic Fe–Mn alloys containing 5 and 10 wt.% Mn and their age-hardenable variants with the addition of 1 wt.% Pd, respectively. Dilatometric experiments employing heating rates between 0.5 and 200 K min−1, atom-probe tomography measurements on continuously heated specimens and thermo-kinetic simulations were performed. On fast heating (200 K min−1), the α′ → γ transformation appeared in a single stage and can be regarded as a partitionless and interface-controlled reaction. In comparison to the binary alloys, the transformation temperatures of the Pd-containing steels are considerably increased, due to precipitates which act as obstacles to migrating austenite/martensite interfaces. For low heating rates of 0.5 and 2 K min−1, splitting of the α′ → γ transformation into two consecutive stages is observed for both the binary and the ternary alloys. With the assistance of thermo-kinetic simulations, a consistent description of this phenomenon is obtained. The first transformation stage is associated with the decomposition of the martensite matrix into Mn-rich and Mn-deficient regions, and the austenite formation is dominated by long-range diffusion. In the second stage, the austenite reversion mechanism changes and the Mn-depleted regions transform in a predominantly interface-controlled mode. This is corroborated by the results for the ternary alloys. The precipitates mainly impede the austenite formation in the second stage, which occurs over a considerably wider temperature range compared to the binary alloys

  16. 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.

  17. 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.

  18. 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.

  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. Beyond Mutations: Additional Mechanisms and Implications of SWI/SNF Complex Inactivation

    Directory of Open Access Journals (Sweden)

    Stefanie eMarquez

    2015-02-01

    Full Text Available SWI/SNF is a major regulator of gene expression. Its role is to facilitate the shifting and exposure of DNA segments within the promoter and other key domains to transcription factors and other essential cellular proteins. This complex interacts with a wide range of proteins and does not function within a single, specific pathway; thus, it is involved in a multitude of cellular processes, including DNA repair, differentiation, development, cell adhesion, and growth control. Given SWI/SNF’s prominent role in these processes, many of which are important for blocking cancer development, it is not surprising that the SWI/SNF complex is targeted during cancer initiation and progression both by mutations and by nonmutational mechanisms. Currently, the understanding of the types of alterations, their frequency, and their impact on the SWI/SNF subunits is an area of intense research that has been bolstered by a recent cadre of NextGen sequencing studies. These studies have revealed mutations in SWI/SNF subunits, indicating that this complex is thus important for cancer development. The purpose of this review is to put into perspective the role of mutations versus other mechanisms in the silencing of SWI/SNF subunits, in particular, BRG1 and BRM. In addition, this review explores the recent development of synthetic lethality and how it applies to this complex, as well as how BRM polymorphisms are becoming recognized as potential clinical biomarkers for cancer risk.

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

    International Nuclear Information System (INIS)

    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 1H nuclear magnetic resonance spectrometry (1H 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

  2. 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.

  3. 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.

  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. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

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

    International Nuclear Information System (INIS)

    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

  11. 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 (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.

  12. Thermally conductive, electrically insulating and melt-processable polystyrene/boron nitride nanocomposites prepared by in situ reversible addition fragmentation chain transfer polymerization.

    Science.gov (United States)

    Huang, Xingyi; Wang, Shen; Zhu, Ming; Yang, Ke; Jiang, Pingkai; Bando, Yoshio; Golberg, Dmitri; Zhi, Chunyi

    2015-01-01

    Thermally conductive and electrically insulating polymer/boron nitride (BN) nanocomposites are highly attractive for various applications in many thermal management fields. However, so far most of the preparation methods for polymer/BN nanocomposites have usually caused difficulties in the material post processing. Here, an in situ grafting approach is designed to fabricate thermally conductive, electrically insulating and post-melt processable polystyrene (PS)/BN nanosphere (BNNS) nanocomposites by initiating styrene (St) on the surface functionalized BNNSs via reversible addition fragmentation chain transfer polymerization. The nanocomposites exhibit significantly enhanced thermal conductivity. For example, at a St/BN feeding ratio of 5:1, an enhancement ratio of 1375% is achieved in comparison with pure PS. Moreover, the dielectric properties of the nanocomposites show a desirable weak dependence on frequency, and the dielectric loss tangent of the nanocomposites remains at a very low level. More importantly, the nanocomposites can be subjected to multiple melt processing to form different shapes. Our method can become a universal approach to prepare thermally conductive, electrically insulating and melt-processable polymer nanocomposites with diverse monomers and nanofillers. PMID:25493655

  13. Thermally conductive, electrically insulating and melt-processable polystyrene/boron nitride nanocomposites prepared by in situ reversible addition fragmentation chain transfer polymerization

    Science.gov (United States)

    Huang, Xingyi; Wang, Shen; Zhu, Ming; Yang, Ke; Jiang, Pingkai; Bando, Yoshio; Golberg, Dmitri; Zhi, Chunyi

    2015-01-01

    Thermally conductive and electrically insulating polymer/boron nitride (BN) nanocomposites are highly attractive for various applications in many thermal management fields. However, so far most of the preparation methods for polymer/BN nanocomposites have usually caused difficulties in the material post processing. Here, an in situ grafting approach is designed to fabricate thermally conductive, electrically insulating and post-melt processable polystyrene (PS)/BN nanosphere (BNNS) nanocomposites by initiating styrene (St) on the surface functionalized BNNSs via reversible addition fragmentation chain transfer polymerization. The nanocomposites exhibit significantly enhanced thermal conductivity. For example, at a St/BN feeding ratio of 5:1, an enhancement ratio of 1375% is achieved in comparison with pure PS. Moreover, the dielectric properties of the nanocomposites show a desirable weak dependence on frequency, and the dielectric loss tangent of the nanocomposites remains at a very low level. More importantly, the nanocomposites can be subjected to multiple melt processing to form different shapes. Our method can become a universal approach to prepare thermally conductive, electrically insulating and melt-processable polymer nanocomposites with diverse monomers and nanofillers.

  14. Thermally conductive, electrically insulating and melt-processable polystyrene/boron nitride nanocomposites prepared by in situ reversible addition fragmentation chain transfer polymerization

    International Nuclear Information System (INIS)

    Thermally conductive and electrically insulating polymer/boron nitride (BN) nanocomposites are highly attractive for various applications in many thermal management fields. However, so far most of the preparation methods for polymer/BN nanocomposites have usually caused difficulties in the material post processing. Here, an in situ grafting approach is designed to fabricate thermally conductive, electrically insulating and post-melt processable polystyrene (PS)/BN nanosphere (BNNS) nanocomposites by initiating styrene (St) on the surface functionalized BNNSs via reversible addition fragmentation chain transfer polymerization. The nanocomposites exhibit significantly enhanced thermal conductivity. For example, at a St/BN feeding ratio of 5:1, an enhancement ratio of 1375% is achieved in comparison with pure PS. Moreover, the dielectric properties of the nanocomposites show a desirable weak dependence on frequency, and the dielectric loss tangent of the nanocomposites remains at a very low level. More importantly, the nanocomposites can be subjected to multiple melt processing to form different shapes. Our method can become a universal approach to prepare thermally conductive, electrically insulating and melt-processable polymer nanocomposites with diverse monomers and nanofillers. (paper)

  15. 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

  16. 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.

  17. 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.

  18. Modification mechanism of hypereutectic Al-Si alloy with P-Na addition

    Institute of Scientific and Technical Information of China (English)

    吴树森; 涂小林; 福田葉椰; 菅野利猛; 中江秀雄

    2003-01-01

    Effect of P-Na united modification on Al-22%Si-1.0%Cu-0.5%Mg-0.5%Mn alloy was studied.The results show that the refining effect of P-Na addition on primary silicon is superior to that of P and the former could modify eutectic silicon at the same time.Effects of P-Na modification on crystallization and microstructure of hypereutectic Al-Si alloys were studied with Electron-Scanning Microscope,Electron-Probe and X-ray diffractometer.The modification mechanism represents that on one hand,the primary silicon is refined by AlP as heterogeneous nucleus;on the other hand,when Na is added at the same time,P atoms are difficult to diffuse in the melt,and then enrichs on the growing faces of silicon phase.Moreover,a SiP compound was also discovered in Si crystals,which prevents the growth of silicon phase and refines the primary silicon.

  19. About a possible path towards the reverse engineering of quantum mechanics

    CERN Document Server

    Ottolenghi, Alberto

    2011-01-01

    An out of the box intellectual path exploring the foundations of quantum mechanics is discussed in some detail, in order to clarify why a possibly different way to look at the relevant fundamental questions can be identified and can support further research. Two key concepts arise. (1) Einstein critics to quantum mechanics could be taken seriously, but ironically, in order to really do so, one would have to take seriously also some of Lorentz critics to special relativity - both in a possibly more modern way; such interconnection possibly having been a blocking factor to openly discuss some of the cross implications of alternative views about quantum mechanics to date. (2) The probabilistic interpretation is a by-product of (a) quantum evolution equations, (b) conservation laws for the combination of measuring system and measured object and (c) persistency of calibration of the measuring system - as such there is no intellectual conflict whatsoever between hidden variables theories and probabilistic interpret...

  20. Compositional dependence of magnetization reversal mechanism, magnetic interaction and Curie temperature of Co1−xSrxFe2O4 spinel thin film

    International Nuclear Information System (INIS)

    Highlights: • Nanoparticles and thin films of Co1−xSrxFe2O4 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: Co1−xSrxFe2O4, (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

  1. 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...

  2. 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.

  3. Reverse Faulting as a Crucial Mechanism for Magma Ascent in Compressional Volcanic Arcs: Field Examples from the Central Andes

    Science.gov (United States)

    Aron, F. A.; Gonzalez, G.; Cembrano, J. M.; Veloso, E. E.

    2010-12-01

    The nature of crustal deformation in active arcs and the feedback mechanisms between tectonics and magma transport constitute fundamental problems in the understanding of volcanic systems. Additionally, for geothermal energy exploration, a better understanding of how crustal architecture and stress field controls fluid ascent and heat transfer from deep levels to the surface is crucial. The Central Andes volcanic belt is an excellent, modern example of such systems but, the scarcity of good outcrops has limited our ability to define the relations between structure and volcanism. In the Salar de Atacama Basin of northern Chile, there are good exposures of folded and faulted Neogene units (continental sediments, volcanic rocks and ignimbrites) and reverse faults spatially and temporally related to volcanic edifices. The subsurface of the study area has been interpreted by previous authors as a thin-skinned, 6-8 km-deep, east-vergent compressional belt. We carried out structural mapping, Digital Elevation Models (DEMs) analyses, strain tensor analyses and fault-related fold kinematic modelling to assess the causal relationship between compressional deformation and magmatism in this region. Field observations indicate that the structures deformed progressively Oligocene-Miocene continental sedimentary units, the upper sedimentary infill of the Salar de Atacama basin (Pliocene-Present), and Pliocene-Pleistocene Ignimbrites. The topographic expression of the compressional belt corresponds to a set of subparallel, asymmetric, fault-related-folds, which can be seen in the field as prominent NS-trending ridges with heights ranging between 50 and 400 m. Furthermore, we found evidence of a ~100 km-long structure along the active magmatic arc, so-called Miscanti Fault. This fault represents the easternmost expression of the above mentioned compressional belt. Pleistocene-Holocene monogenetic cones and strato-volcanoes are located either at the hinge zone of fault

  4. Proposed mechanisms for oligonucleotide IMT504 induced diabetes reversion in a mouse model of immunodependent diabetes.

    Science.gov (United States)

    Bianchi, María S; Bianchi, Stefanía; Hernado-Insúa, Andrés; Martinez, Leandro M; Lago, Néstor; Libertun, Carlos; Chasseing, Norma A; Montaner, Alejandro D; Lux-Lantos, Victoria A

    2016-08-01

    Type 1 diabetes (T1D) originates from autoimmune β-cell destruction. IMT504 is an immunomodulatory oligonucleotide that increases mesenchymal stem cell cloning capacity and reverts toxic diabetes in rats. Here, we evaluated long-term (20 doses) and short-term (2-6 doses) effects of IMT504 (20 mg·kg(-1)·day(-1) sc) in an immunodependent diabetes model: multiple low-dose streptozotocin-injected BALB/c mice (40 mg·kg(-1)·day(-1) ip for 5 consecutive days). We determined blood glucose, glucose tolerance, serum insulin, islet morphology, islet infiltration, serum cytokines, progenitor cell markers, immunomodulatory proteins, proliferation, apoptosis, and islet gene expression. IMT504 reduced glycemia, induced β-cell recovery, and impaired islet infiltration. IMT504 induced early blood glucose decrease and infiltration inhibition, increased β-cell proliferation and decreased apoptosis, increased islet indoleamine 2,3-dioxygenase (IDO) expression, and increased serum tumor necrosis factor and interleukin-6 (IL-6). IMT504 affected islet gene expression; preproinsulin-2, proglucagon, somatostatin, nestin, regenerating gene-1, and C-X-C motif ligand-1 cytokine (Cxcl1) increased in islets from diabetic mice and were decreased by IMT504. IMT504 downregulated platelet endothelial cell adhesion molecule-1 (Pecam1) in islets from control and diabetic mice, whereas it increased regenerating gene-2 (Reg2) in islets of diabetic mice. The IMT504-induced increase in IL-6 and islet IDO expression and decreased islet Pecam1 and Cxcl1 mRNA expression could participate in keeping leukocyte infiltration at bay, whereas upregulation of Reg2 may mediate β-cell regeneration. We conclude that IMT504 effectively reversed immunodependent diabetes in mice. Corroboration of these effects in a model of autoimmune diabetes more similar to human T1D could provide promising results for the treatment of this disease. PMID:27329801

  5. 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

  6. Microstructure and mechanical properties of the Al-Ti alloy with cerium addition

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2009-12-01

    Full Text Available Purpose: In this work there are presented the investigation results of mechanical properties and microstructure concerning mainly intermetallic phases of the aluminium – titanium alloy with a defined content of 2 and 4 % of cerium addition. The purpose of this work was also to determine the heat treatment conditions for solution heat treatment of the investigation alloys.Design/methodology/approach: The reason of this work was to determine the heat treatment influence, particularly solution heat treatment time to the changes of the microstructure, as well to determine which intermetallic phases occur after the heat treatment performed, and how is the morphology of these particles.Findings: After solution heat treatment for 4 hours the structure changes. The grains are larger and no more uniform as showed before. The most stable intermetallic in the Al-Ti system is the Al3Ti phase. The solution heat treatment time should be greater than 4 hours to ensure a proper solution of titanium and cerium in the Al-α solid solution.Research limitations/implications: The investigated aluminium samples were examined metallographically using optical microscope with different image techniques, scanning electron microscope and also analyzed using a Vickers micro-hardness tester, also EDS microanalysis was made.Practical implications: As an implication for the practice a new alloy can be developed, some other investigation should be performed in the future, but the knowledge found in this research shows an interesting investigation direction.Originality/value: The combination of light weight and high strength Ti-based alloys is very attractive for aerospace and automotive industries. Furthermore, the presence of calcium cerium into existence new unknown phases as well can enhance the thermal stability of ternary Al-Ti-Ce alloy because of its higher melting point then Al-Ti.

  7. Validation of a 3-D, Thermo-Mechanically Coupled Model for Multi-Pass Rolling in a Reversing Mill

    Energy Technology Data Exchange (ETDEWEB)

    Rhee, M; Wang, P; Li, M; Becker, R

    2004-01-30

    A three dimensional numerical model simulating multi-pass, hot rolling on a reversing mill has been developed to analyze deformation patterns and shape changes of a rolled ingot. Validation simulations through 15 passes with an 86% reduction have been performed using the thermo-mechanically coupled model to track the evolution of the deformed ingot geometry. The heat transfer coefficient for thermal conduction between the rolls and slab has been estimated in accordance with experimental data, and heat transfer to the air and coolant outside of the roll bite is included. A hyperbolic sine model using the Zener-Hollomon parameter is used to capture the temperature and strain rate dependence of the aluminum alloy. A Coulomb friction model with a flow strength dependent maximum limit on the interfacial shear stress was employed between the rolls and ingot. Results of validation simulations and comparisons with experiments focusing on the ingot shape evolution are discussed.

  8. Mesoporous silica nanoparticles loading doxorubicin reverse multidrug resistance: performance and mechanism

    Science.gov (United States)

    Shen, Jianan; He, Qianjun; Gao, Yu; Shi, Jianlin; Li, Yaping

    2011-10-01

    Multidrug resistance (MDR) is one of the major obstacles for successful chemotherapy in cancer. One of the effective approaches to overcome MDR is to use nanoparticle-mediated drug delivery to increase drug accumulation in drug resistant cancer cells. In this work, we first report that the performance and mechanism of an inorganic engineered delivery system based on mesoporous silica nanoparticles (MSNs) loading doxorubicin (DMNs) to overcome the MDR of MCF-7/ADR (a DOX-resistant and P-glycoprotein (P-gp) over-expression cancer cell line). The experimental results showed that DMNs could enhance the cellular uptake of doxorubicin (DOX) and increase the cell proliferation suppression effect of DOX against MCF-7/ADR cells. The IC50 of DMNs against MCF-7/ADR cells was 8-fold lower than that of free DOX. However, an improved effect of DOX in DMNs against MCF-7 cells (a DOX-sensitive cancer cell line) was not found. The increased cellular uptake and nuclear accumulation of DOX delivered by DMNs in MCF-7/ADR cells was confirmed by confocal laser scanning microscopy, and could result from the down-regulation of P-gp and bypassing the efflux action by MSNs themselves. The cellular uptake mechanism of DMNs indicated that the macropinocytosis was one of the pathways for the uptake of DMNs by MCF-7/ADR cells. The in vivo biodistribution showed that DMNs induced a higher accumulation of DOX in drug resistant tumors than free DOX. These results suggested that MSNs could be an effective delivery system to overcome multidrug resistance.

  9. 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...

  10. Impact of combined clenbuterol and metoprolol therapy on reverse remodelling during mechanical unloading.

    Directory of Open Access Journals (Sweden)

    Manoraj Navaratnarajah

    Full Text Available Clenbuterol (Cl, a β2 agonist, is associated with enhanced myocardial recovery during left ventricular assist device (LVAD support, and exerts beneficial remodelling effects during mechanical unloading (MU in rodent heart failure (HF. However, the specific effects of combined Cl+β1 blockade during MU are unknown.We studied the chronic effects (4 weeks of β2-adrenoceptor (AR stimulation via Cl (2 mg/kg/day alone, and in combination with β1-AR blockade using metoprolol ((Met, 250 mg/kg/day, on whole heart/cell structure, function and excitation-contraction (EC coupling in failing (induced by left coronary artery (LCA ligation, and unloaded (induced by heterotopic abdominal heart transplantation (HATx failing rat hearts. Combined Cl+Met therapy displayed favourable effects in HF: Met enhanced Cl's improvement in ejection fraction (EF whilst preventing Cl-induced hypertrophy and tachycardia. During MU combined therapy was less beneficial than either mono-therapy. Met, not Cl, prevented MU-induced myocardial atrophy, with increased atrophy occurring during combined therapy. MU-induced recovery of Ca2+ transient amplitude, speed of Ca2+ release and sarcoplasmic reticulum Ca2+ content was enhanced equally by Cl or Met mono-therapy, but these benefits, together with Cl's enhancement of sarcomeric contraction speed, and MU-induced recovery of Ca2+ spark frequency, disappeared during combined therapy.Combined Cl+Met therapy shows superior functional effects to mono-therapy in rodent HF, but appears inferior to either mono-therapy in enhancing MU-induced recovery of EC coupling. These results suggest that combined β2-AR simulation +β1-AR blockade therapy is likely to be a safe and beneficial therapeutic HF strategy, but is not as effective as mono-therapy in enhancing myocardial recovery during LVAD support.

  11. 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.

  12. 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.

  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

    2013-12-01

    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

  14. Influence of niobium addition on microstructure, mechanical properties and oxidation resistance of ZrN coatings

    International Nuclear Information System (INIS)

    In this study, Zr-Nb-N coatings with 0–3.8 at.% Nb addition were deposited by magnetron co-sputtering deposition. The results reveal that Nb atoms substitute Zr atoms in Zr-N lattice, forming the solid solution structure. All the Zr-Nb-N coatings illustrate a dense columnar structure with the preferred orientation of (200), showing independent of Nb addition. Nanoindentation result reveals a promoted hardness of the Zr-Nb-N coatings from 23.9 ± 0.7 GPa to 28.4 ± 0.5 GPa with enhanced Nb content from 0 to 2.8 at.% due to both the solid solution strengthening and Hall–Petch effect. Scratch tests show that adhesion between substrates and coatings can be improved by Nb addition. After oxidation in air at 600 °C for 2 h, microstructural studies indicate the oxide scales consist of monoclinic-ZrO2 outer layer and tetragonal-ZrO2 inner layer. Moreover, ZrO2 can be stabilized in the tetragonal phase by Nb doping. The Zr-Nb-N coating with 1.3 at.% Nb addition exhibits superior oxidation resistance, while excess Nb addition produces detrimental effects on oxidation resistance. - Highlights: • Moderate Nb addition improves the hardness and adhesion of Zr-Nb-N coatings. • Significant improvement of oxidation resistance is obtained by Nb addition. • GAXRD and TEM microstructural studies of the Zr-Nb-N coatings. • Phase stabilization of tetragonal-ZrO2 is achieved by Nb addition

  15. Thermo-mechanical analysis of wire and arc additive manufacturing process

    OpenAIRE

    Ding, J

    2012-01-01

    Conventional manufacturing processes often require a large amount of machining and cannot satisfy the continuously increasing requirements of a sustainable, low cost, and environmentally friendly modern industry. Thus, Additive Manufacturing (AM) has become an important industrial process for the manufacture of custom-made metal workpieces. Among the different AM processes, Wire and Arc Additive Manufacture (WAAM) has the ability to manufacture large, low volume metal work-p...

  16. Influence of niobium addition on microstructure, mechanical properties and oxidation resistance of ZrN coatings

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z.T. [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Qi, Z.B. [School of Materials Science and Engineering, Xiamen University of Technology, Xiamen 361005 (China); Jiang, W.F. [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Wang, Z.C., E-mail: zcwang@xmu.edu.cn [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Liu, B. [Xiamen Annaiwy New Material CO., LTD, Xiamen 361005 (China)

    2014-11-03

    In this study, Zr-Nb-N coatings with 0–3.8 at.% Nb addition were deposited by magnetron co-sputtering deposition. The results reveal that Nb atoms substitute Zr atoms in Zr-N lattice, forming the solid solution structure. All the Zr-Nb-N coatings illustrate a dense columnar structure with the preferred orientation of (200), showing independent of Nb addition. Nanoindentation result reveals a promoted hardness of the Zr-Nb-N coatings from 23.9 ± 0.7 GPa to 28.4 ± 0.5 GPa with enhanced Nb content from 0 to 2.8 at.% due to both the solid solution strengthening and Hall–Petch effect. Scratch tests show that adhesion between substrates and coatings can be improved by Nb addition. After oxidation in air at 600 °C for 2 h, microstructural studies indicate the oxide scales consist of monoclinic-ZrO{sub 2} outer layer and tetragonal-ZrO{sub 2} inner layer. Moreover, ZrO{sub 2} can be stabilized in the tetragonal phase by Nb doping. The Zr-Nb-N coating with 1.3 at.% Nb addition exhibits superior oxidation resistance, while excess Nb addition produces detrimental effects on oxidation resistance. - Highlights: • Moderate Nb addition improves the hardness and adhesion of Zr-Nb-N coatings. • Significant improvement of oxidation resistance is obtained by Nb addition. • GAXRD and TEM microstructural studies of the Zr-Nb-N coatings. • Phase stabilization of tetragonal-ZrO2 is achieved by Nb addition.

  17. 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

    NARCIS (Netherlands)

    van der Holt, B; Lowenberg, B; Burnett, AK; Knauf, WU; Shepherd, J; Piccaluga, PP; Ossenkoppele, GJ; Verhoef, GEG; Ferrant, A; Crump, M; Selleslag, D; Theobald, M; Fey, MF; Vellenga, E; Dugan, M; Sonneveld, P

    2005-01-01

    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

  18. rHDL administration increases reverse cholesterol transport in mice, but is not additive on top of ezetimibe or cholestyramine treatment

    NARCIS (Netherlands)

    Maugeais, Cyrille; Annema, Wijtske; Blum, Denise; Mary, Jean-Luc; Tietge, Uwe J. F.

    2013-01-01

    Objective: Promoting reverse cholesterol transport (RCT) is a major atheroprotective property of HDL. The present study explored the effect of stimulating the first step of RCT (cholesterol efflux from macrophages) alone or in combination with stimulating the last step of RCT (fecal sterol excretion

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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. PMID:22248297

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Effect of sulfonation and diethanolamine addition on the mechanical and physicochemical properties of SEPS copolymer

    Science.gov (United States)

    Patiño, D.; Correa, E.; Acevedo-Morantes, M.

    2016-02-01

    Modification techniques have been developed to achieve changes in the processing of polymers, and modification of their mechanical, thermal and morphological properties, as well as their hydrophobicity and conductivity. Sulfonation improves ion conductivity, antistatic behaviour, hydrophilicity and solubility of the polymers. These characteristics are related to the presence of sulfonic groups in the polymer matrix. This research project focuses on the evaluation of mechanical, physical and chemical properties of membranes that are based on a sulfonated Styrene-Ethylene-Propylene-Styrene (SEPS) copolymer. The membranes were functionalized with diethanolamine at 5, 15 and 30% w/w, to separate carbon dioxide. FTIR and XRD analyses were used to characterize the membranes. The sulfonated-loaded membrane with 15% of diethanolamine showed the best results in each characterization.

  9. 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.

  10. 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.

  11. 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.

  12. Reverse Engineering Applied to Red Human Hair Pheomelanin Reveals Redox-Buffering as a Pro-Oxidant Mechanism.

    Science.gov (United States)

    Kim, Eunkyoung; Panzella, Lucia; Micillo, Raffaella; Bentley, William E; Napolitano, Alessandra; Payne, Gregory F

    2015-01-01

    Pheomelanin has been implicated in the increased susceptibility to UV-induced melanoma for people with light skin and red hair. Recent studies identified a UV-independent pathway to melanoma carcinogenesis and implicated pheomelanin's pro-oxidant properties that act through the generation of reactive oxygen species and/or the depletion of cellular antioxidants. Here, we applied an electrochemically-based reverse engineering methodology to compare the redox properties of human hair pheomelanin with model synthetic pigments and natural eumelanin. This methodology exposes the insoluble melanin samples to complex potential (voltage) inputs and measures output response characteristics to assess redox activities. The results demonstrate that both eumelanin and pheomelanin are redox-active, they can rapidly (sec-min) and repeatedly redox-cycle between oxidized and reduced states, and pheomelanin possesses a more oxidative redox potential. This study suggests that pheomelanin's redox-based pro-oxidant activity may contribute to sustaining a chronic oxidative stress condition through a redox-buffering mechanism. PMID:26669666

  13. Reverse Engineering Applied to Red Human Hair Pheomelanin Reveals Redox-Buffering as a Pro-Oxidant Mechanism.

    Science.gov (United States)

    Kim, Eunkyoung; Panzella, Lucia; Micillo, Raffaella; Bentley, William E; Napolitano, Alessandra; Payne, Gregory F

    2015-01-01

    Pheomelanin has been implicated in the increased susceptibility to UV-induced melanoma for people with light skin and red hair. Recent studies identified a UV-independent pathway to melanoma carcinogenesis and implicated pheomelanin's pro-oxidant properties that act through the generation of reactive oxygen species and/or the depletion of cellular antioxidants. Here, we applied an electrochemically-based reverse engineering methodology to compare the redox properties of human hair pheomelanin with model synthetic pigments and natural eumelanin. This methodology exposes the insoluble melanin samples to complex potential (voltage) inputs and measures output response characteristics to assess redox activities. The results demonstrate that both eumelanin and pheomelanin are redox-active, they can rapidly (sec-min) and repeatedly redox-cycle between oxidized and reduced states, and pheomelanin possesses a more oxidative redox potential. This study suggests that pheomelanin's redox-based pro-oxidant activity may contribute to sustaining a chronic oxidative stress condition through a redox-buffering mechanism.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Effect of Clay Addition on Mechanical Properties of Unsaturated Polyester/Glass Fiber Composites

    Directory of Open Access Journals (Sweden)

    Kusmono

    2013-01-01

    Full Text Available Unsaturated polyester (UP/glass fiber/clay composites were prepared by hand layup method. The effect of clay loading on the morphological and mechanical properties of UP/glass fiber composites was investigated in this study. X-ray diffraction (XRD was used to characterize the structure of the composites. The mechanical properties of the composites were determined by tensile, flexural, unnotched Charpy impact and fracture toughness tests. XRD results indicated that the exfoliated structure was found in the composite containing 2 wt% of clay while the intercalated structure was obtained in the composite with 6 wt% of clay. The tensile strength, flexural strength, and flexural modulus of the composites were increased in the presence of clay. The optimum loading of clay in the UP/glass fiber composites was attained at 2 wt%, where the improvement in in tensile strength, flexural strength, and flexural modulus was approximately 13, 21, and 11%, respectively. On the other hand, the highest values in impact toughness and fracture toughness were observed in the composites with 4 wt% of clay.

  1. 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.

  2. 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.

  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. On the importance of steady-state isotopic techniques for the investigation of the mechanism of the reverse water-gas-shift reaction.

    Science.gov (United States)

    Tibiletti, Daniele; Goguet, Alexandre; Meunier, Frederic C; Breen, John P; Burch, Robbie

    2004-07-21

    The formation and reactivity of surface intermediates in the reverse water-gas-shift reaction on a Pt/CeO2 catalyst are critically dependent on the reaction conditions so that conclusions regarding the reaction mechanism cannot be inferred using ex operando conditions. PMID:15263955

  5. Histamine reverses IL-5-Afforded human eosinophil survival by inducing apoptosis: Pharmacological evidence for a novel mechanism of action of histamine

    OpenAIRE

    Hasala, Hannele; Giembycz, Mark A.; Janka-Junttila, Mirkka; Moilanen, Eeva; Kankaanranta, Hannu

    2008-01-01

    Histamine reverses IL-5-Afforded human eosinophil survival by inducing apoptosis: Pharmacological evidence for a novel mechanism of action of histamine correspondence: Corresponding author. Tel.: +358335517318; fax: +358335518082. (Kankaanranta, Hannu) (Kankaanranta, Hannu) The Immunopharmacology Research Group--> , Medical School--> , University of Tampere--> , Tampere--> - FINLAND (Hasala, H...

  6. 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.

  7. 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 in...

  8. 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。

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

    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。

  10. 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.

  11. Inhibition of survivin expression and mechanisms of reversing drug-resistance of human lung adenocarcinoma cells by siRNA

    Institute of Scientific and Technical Information of China (English)

    LIU Jing-lei; WANG Yan; JIANG Ji; KONG Rui; YANG Yan-mei; JI Hong-fei; SHI Yu-zhi

    2010-01-01

    Background Survivin, a member of the inhibitor of apoptosis protein (IAP) family, overexpresses in tumor cells and not expresses in terminally differentiated adult tissues. This study aimed to investigate the effects of survivin-specific siRNA on cell proliferation, apoptosis and chemosensitivity to cisplatin in vitro and in vivo and explore the mechanisms about decreasing expression of survivin in reversing cancer cells resistance to chemotherapeutic drug.Methods Survivin-specific siRNA was transfected into A549/DDP cells. The expression of survivin and lung resistance-related protein (LRP) mRNA levels were determined by RT-PCR, chemosensitivity of A549/DDP (cisplatin)cells to cisplatin was determined by MTT assay, and apoptosis and cell cycle were determined by flow cytometry (FCM).The protein expression levels of survivin, LRP, cyclin-D1, caspase-3 and bcl-2 were determined by Western blotting analyses. The effect of survivin siRNA inhibition on tumor growth was studied in athymic nude mice in vivo.Results Survivin-specific siRNA efficiently down-regulated survivin expression. The cell cycle was arrested at G2/M phase, and apoptosis was obviously found. Inhibition of survivin expression could make the IC50 and drug-resistant index of cisplatin decrease, and enhance the cancer cells sensitivity to cisplatin. After transfection by survivin-specific siRNA, expression of LRP and cyclin-D1 were downregulated, caspase-3 expression was upregulated, bcl-2 expression had no obvious change. The animal experiment confirmed knockdown of survivin could inhibit the tumor growth.Conclusions Survivin-specific siRNA can efficiently suppress the expression of survivin, increase apoptosis, inhibit cells proliferation and enhance the chemosensitivity to cisplatin in vitro and in vivo. Suppression of survivin expression helping to reverse drug-resistance may have relationship with downregulation of LRP and upregulation of caspase-3.Anti-tumor strategies based on the inhibition of

  12. Mechanical alloying process of vanadium powder with 1.7 wt.%Y addition

    International Nuclear Information System (INIS)

    Alloying process of vanadium-yttrium powders using mechanical alloying (MA) method was studied. Vanadium powder was compressed after 10 h MA, while yttrium powder was comminuted into small particles. Although yttrium powder was broken into small particles, yttrium scarcely dissolves into vanadium powder. Alloying of yttrium started after 20 h MA and finished after 40 h MA. Molybdenum particle, which came from milling vessels and balls, mixed into vanadium powder after 40 h MA and molybdenum started to dissolve into vanadium powder after 60 h MA. After 80 h MA, Y2O3 particles formed in vanadium powder. Oxygen required for the formation of Y2O3 particles was probably discharged from the vessel wall and balls after flaking of those surface layers. Since prolonged MA caused powder contamination, optimum MA time for making V-1.7Y alloy was 40 h.

  13. 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.

  14. Effect of Zr addition on the mechanical characteristics and wear resistance of Al grain refined by Ti after extrusion

    Science.gov (United States)

    Zaid, Adnan I. O.; Al-Qawabah, S. M. A.

    2016-08-01

    Aluminum and its alloys are normally grain refined by Ti or Ti+B to transfer their columnar structure during solidification into equiaxed one which improves their mechanical behavior and surface quality. In this paper, the effect of addition of Zr on the metallurgical, and mechanical aspects, hardness, ductility and wear resistance of commercially pure aluminum grain refined by Ti after extrusion is investigated. Zr was added at a level of 0.1% which corresponds to the peretectic limit at the Al-Zr phase diagram. The experimental work was carried out on the specimens after direct extrusion. It was found that addition of Ti resulted in decrease of Al grain size, whereas addition of Zr alone or in the presence of Ti, resulted in reduction of Al grain size. This led to increase of Al hardness. The effect of the addition of Ti or Zr alone resulted almost in the same enhancement of Al mechanical characteristics. As for the strain hardening index,n, increase was obtained when Zr was added alone or in the presence of Ti. Hence pronounced improvement of its formability. Regarding the effect of Zr addition on the wear resistance of aluminum; it was found that at small loads and speeds addition of Ti or Zr or both together resulted in deterioration of its wear resistance whereas at higher loads and speeds resulted in pronounced improvement of its wear resistance. Finally, the available Archard model and the other available models which consider only the mass loss failed to describe the wear mechanism of Al and its micro-alloys because they do not consider the mushrooming effect at the worn end.

  15. 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。

  16. Energy efficient reduced graphene oxide additives: Mechanism of effective lubrication and antiwear properties

    Science.gov (United States)

    Gupta, Bhavana; Kumar, N.; Panda, Kalpataru; Dash, S.; Tyagi, A. K.

    2016-01-01

    Optimized concentration of reduced graphene oxide (rGO) in the lube is one of the important factors for effective lubrication of solid body contacts. At sufficiently lower concentration, the lubrication is ineffective and friction/wear is dominated by base oil. In contrast, at sufficiently higher concentration, the rGO sheets aggregates in the oil and weak interlayer sliding characteristic of graphene sheets is no more active for providing lubrication. However, at optimized concentration, friction coefficient and wear is remarkably reduced to 70% and 50%, respectively, as compared to neat oil. Traditionally, such lubrication is described by graphene/graphite particle deposited in contact surfaces that provides lower shear strength of boundary tribofilm. In the present investigation, graphene/graphite tribofilm was absent and existing traditional lubrication mechanism for the reduction of friction and wear is ruled out. It is demonstrated that effective lubrication is possible, if rGO is chemically linked with PEG molecules through hydrogen bonding and PEG intercalated graphene sheets provide sufficiently lower shear strength of freely suspended composite tribofilm under the contact pressure. The work revealed that physical deposition and adsorption of the graphene sheets in the metallic contacts is not necessary for the lubrication.

  17. Influence of the montmorillonite clay addition on the mechanical properties and crystallinity of polyamide 6

    International Nuclear Information System (INIS)

    Polyamide 6 (PA6) and montmorillonite clay nano composites were prepared by twin-screw extruder using three different screw speeds: 150, 250 and 350 rpm. The processed samples were submitted to the characterization by x-ray diffraction (XRD) through thin films to analyze the clay dispersion in PA6. Despite the 250 rpm processed sample present better dispersion, the result could not be significant compared to the others. The 250 rpm processed sample were characterized by mechanical tests which presented increase of the apparent elastic modulus and tensile resistance while there was the decrease of the elongation at break and the impact resistance of the nanocomposite compared to the pure PA6. The evaluation of the crystallinity of nanocomposites was performed by XRD in the longitudinal and transversal direction to the flow injection of impact samples and shows that montmorillonite acts as nucleating agent and promotes an increase of crystallinity of PA6. The crystallinity obtained in the longitudinal direction of injection flow was higher due to the orientation of the chains imposed by the injection flow. (author)

  18. 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.

  19. Decrease of droplet size of the reverse microemulsion 1-butyl-3-methylimidazolium tetrafluoroborate/Triton X-100/cyclohexane by addition of water.

    Science.gov (United States)

    Gao, Yanan; Hilfert, Liane; Voigt, Andreas; Sundmacher, Kai

    2008-03-27

    In the present contribution, results concerning the role of small amounts of water in the 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4)-in-cyclohexane ionic liquid (IL) reverse microemulsions are reported. Dynamic light scattering (DLS) revealed that the size of microemulsion droplets decreased remarkably with increasing water content although water is often used as a polar component to swell reverse microemulsions. It was thus deduced that the number of microemulsion droplets was increased which was confirmed by conductivity measurements. The states of dissolved water were investigated by Fourier transform IR (FTIR) spectroscopic analysis showing that water molecules mainly act as bound water. 1H NMR along with two-dimensional rotating frame nuclear Overhauser effect (NOE) experiments (ROESY) further revealed that water molecules were mainly located in the periphery of the polar core of the microemulsion droplets and behave like a chock being inserted in the palisade layer of the droplet. This increased the curvature of the surfactant film at the IL/cyclohexane interface and thus led to the decrease of the microemulsion droplet size. The order of surfactant molecules arranged in the interface film was increased and thus induced a loss of entropy. Isothermal titration calorimetry (ITC) indicated that an enthalpy increase compensates for the loss of entropy during the process of microstructural transition. PMID:18318531

  20. 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)

  1. Effects of rare earth Er addition on microstructure and mechanical properties of hypereutectic Al–20% Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qinglin [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China); Xia, Tiandong, E-mail: liql301@mail.nwpu.edu.cn [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China); Lan, Yefeng [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China); Li, Pengfei; Fan, Lu [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China)

    2013-12-20

    The microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with Er addition were investigated in the article. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Microstructural analyses demonstrated that primary Si was significantly refined from coarse polygonal, platelet-like and star-like shape to fine blocky shape, and eutectic Si structure was modified from coarse platelet-like/needle-like structure to fine coral-like fibrous structure as the addition contents of Er is 0.5%. However, the primary and eutectic Si phases became coarser when the level of rare earth Er was up to 0.8%. The mechanical properties were investigated by tensile test with various concentration of Er. It was found that the ultimate tensile strength (UTS) and elongation (El) increased by 72.5% and 72%, respectively, due to decreasing of the size and changing of morphology on primary and eutectic Si crystals, and the change of mechanical properties corresponds to the evolution of microstructure. In addition, the modification mechanism of Er on Al–20%Si alloy was also discussed.

  2. Deciphering records of geomagnetic reversals

    Science.gov (United States)

    Valet, Jean-Pierre; Fournier, Alexandre

    2016-06-01

    Polarity reversals of the geomagnetic field are a major feature of the Earth's dynamo. Questions remain regarding the dynamical processes that give rise to reversals and the properties of the geomagnetic field during a polarity transition. A large number of paleomagnetic reversal records have been acquired during the past 50 years in order to better constrain the structure and geometry of the transitional field. In addition, over the past two decades, numerical dynamo simulations have also provided insights into the reversal mechanism. Yet despite the large paleomagnetic database, controversial interpretations of records of the transitional field persist; they result from two characteristics inherent to all reversals, both of which are detrimental to an ambiguous analysis. On the one hand, the reversal process is rapid and requires adequate temporal resolution. On the other hand, weak field intensities during a reversal can affect the fidelity of magnetic recording in sedimentary records. This paper is aimed at reviewing critically the main reversal features derived from paleomagnetic records and at analyzing some of these features in light of numerical simulations. We discuss in detail the fidelity of the signal extracted from paleomagnetic records and pay special attention to their resolution with respect to the timing and mechanisms involved in the magnetization process. Records from marine sediments dominate the database. They give rise to transitional field models that often lead to overinterpret the data. Consequently, we attempt to separate robust results (and their subsequent interpretations) from those that do not stand on a strong observational footing. Finally, we discuss new avenues that should favor progress to better characterize and understand transitional field behavior.

  3. Effects of Sn addition on the microstructure, mechanical properties and corrosion behavior of Ti–Nb–Sn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Moraes, Paulo E.L., E-mail: pauloeduardo.leitedemoraes@gmail.com [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil); Contieri, Rodrigo J., E-mail: contieri@fem.unicamp.br [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil); Lopes, Eder S.N., E-mail: ederlopes@fem.unicamp.br [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil); Robin, Alain, E-mail: alain@demar.eel.usp.br [University of São Paulo, School of Engineering of Lorena, Polo Urbo-Industrial Gleba AI-6, Lorena, SP 12600-00 (Brazil); Caram, Rubens, E-mail: caram@fem.unicamp.br [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil)

    2014-10-15

    Ti and Ti alloys are widely used in restorative surgery because of their good biocompatibility, enhanced mechanical behavior and high corrosion resistance in physiological media. The corrosion resistance of Ti-based materials is due to the spontaneous formation of the TiO{sub 2} oxide film on their surface, which exhibits elevated stability in biological fluids. Ti–Nb alloys, depending on the composition and the processing routes to which the alloys are subjected, have high mechanical strength combined with low elastic modulus. The addition of Sn to Ti–Nb alloys allows the phase transformations to be controlled, particularly the precipitation of ω phase. The aim of this study is to discuss the microstructure, mechanical properties and corrosion behavior of cast Ti–Nb alloys to which Sn has been added. Samples were centrifugally cast in a copper mold, and the microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffractometry. Mechanical behavior evaluation was performed using Berkovich nanoindentation, Vickers hardness and compression tests. The corrosion behavior was evaluated in Ringer's solution at room temperature using electrochemical techniques. The results obtained suggested that the physical, mechanical and chemical behaviors of the Ti–Nb–Sn alloys are directly dependent on the Sn content. - Graphical abstract: Effects of Sn addition to the Ti–30Nb alloy on the elastic modulus. - Highlights: • Sn addition causes reduction of the ω phase precipitation. • Minimum Vickers hardness and elastic modulus occurred for 6 wt.% Sn content. • Addition of 6 wt.% Sn resulted in maximum ductility and minimum compression strength. • All Ti–30Nb–XSn (X = 0, 2, 4, 6, 8 and 10%) alloys are passive in Ringer's solution. • Highest corrosion resistance was observed for 6 wt.% Sn content.

  4. Mechanism and Optimal Application of Chemical Additives for Accelerating Early Strength of Lime-flyash Stabilized Soils

    Institute of Scientific and Technical Information of China (English)

    JIANG Zengguo; ZHAO Yuan

    2005-01-01

    To accelerate the early strength of lime-flyash stabilized soil for extending its further uses in highway and shortening highway construction time, five kinds of chemical additives were chosen on the basis of mechanism analysis of accelerating early strength in highway as a semi-rigid base material, and a series of experiments about the effect of different kinds of additives and quantity on the early strength of the stabilized soil were tested. The results show that chemical additives can efficiently improve the early strength of lime-flyash stabilized soil both the 7 d and 28d, and the optimum quantity for above chemical additive is 1.5%-2.5% approximately.Some suggestions for the practical construction were also proposed.

  5. 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.

  6. Effect of molybdenum addition on the mechanical properties of sinter-forged Fe–Cu–C alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rathore, Sanjay S., E-mail: rathore.sanjaysingh@gmail.com; Salve, Milind M., E-mail: milindrowling@gmail.com; Dabhade, Vikram V., E-mail: vvdabfmt@iitr.ac.in

    2015-11-15

    Molybdenum provides solid solution strengthening, enhances hardenability and has thus been used to improve mechanical properties of ferrous alloys significantly. The present study reports the effect of molybdenum addition on the properties of sinter-forged Fe–Cu–C alloys prepared using elemental powders under various heat treatment conditions. The elemental powder mixtures were compacted at a pressure of 500 MPa followed by sintering at 1120 °C in N{sub 2}–20%H{sub 2} atmosphere. Further, the sintered compacts were immediately forged at the sintering temperature in a closed die. The sinter-forged compacts were further homogenized and then heat treated under different cooling rates. Enhancement of the mechanical properties (hardness and tensile strength) were observed with Mo addition and increase in severity of quench. Hardness of air cooled samples was slightly lower than that of the water quenched samples but comparable with oil quenched samples. However, no significant increase in hardness was observed beyond 1.5 wt% Mo addition for all cooling conditions. At higher molybdenum content ductility was retained due to stabilization of ferrite phase by molybdenum. The microstructural study showed mostly ferrite–pearlite structure in furnace cooled condition whereas a complex microstructure was observed in the faster cooling conditions. Grain refinement was also observed with molybdenum addition. - Highlights: • Mo (0.25–4.0 wt%) addition in sinter-forged Fe–2Cu–0.65C alloys was investigated. • Effect of heat treatment on mechanical properties and microstructure was discussed. • Hardness and strength increased with Mo addition at the expense of ductility. • Hardness in air cooled condition was comparable with oil/water cooled conditions.

  7. Effect of molybdenum addition on the mechanical properties of sinter-forged Fe–Cu–C alloys

    International Nuclear Information System (INIS)

    Molybdenum provides solid solution strengthening, enhances hardenability and has thus been used to improve mechanical properties of ferrous alloys significantly. The present study reports the effect of molybdenum addition on the properties of sinter-forged Fe–Cu–C alloys prepared using elemental powders under various heat treatment conditions. The elemental powder mixtures were compacted at a pressure of 500 MPa followed by sintering at 1120 °C in N2–20%H2 atmosphere. Further, the sintered compacts were immediately forged at the sintering temperature in a closed die. The sinter-forged compacts were further homogenized and then heat treated under different cooling rates. Enhancement of the mechanical properties (hardness and tensile strength) were observed with Mo addition and increase in severity of quench. Hardness of air cooled samples was slightly lower than that of the water quenched samples but comparable with oil quenched samples. However, no significant increase in hardness was observed beyond 1.5 wt% Mo addition for all cooling conditions. At higher molybdenum content ductility was retained due to stabilization of ferrite phase by molybdenum. The microstructural study showed mostly ferrite–pearlite structure in furnace cooled condition whereas a complex microstructure was observed in the faster cooling conditions. Grain refinement was also observed with molybdenum addition. - Highlights: • Mo (0.25–4.0 wt%) addition in sinter-forged Fe–2Cu–0.65C alloys was investigated. • Effect of heat treatment on mechanical properties and microstructure was discussed. • Hardness and strength increased with Mo addition at the expense of ductility. • Hardness in air cooled condition was comparable with oil/water cooled conditions

  8. Synthesis of nanoparticeles in ductile iron with small additions of vanadium and niobium and its mechanical properties

    OpenAIRE

    E Fraś; M. Górny; Blicharski, M.; Dymek, S.; E. Guzik

    2007-01-01

    It has been shown that the heat treatment of 1095oC/640 oC type of ferritic ductile iron with small addition of 0.08% vanadium permits to obtain of the rounded VC nanoparticles with an average size of 50 nm and 0.13 volume fraction. Results of investigations of influence of small vanadium up to 0.3%, niobium up to 0.16% and nitrogen up to 58 ppm additions and heat treatment of 1080oC-24h/640 oC and 1080oC-24h/600 oC type on structure and mechanical properties (tensile strength, yields strengt...

  9. Effect of nitrogen on structure and mechanical properties of ductile iron with small additions vanadium and niobium

    OpenAIRE

    Fraś E.; Górny M.; Kawalec M.

    2007-01-01

    Results of investigations of influence of small additions of vanadium (about 0,08 and 0,12 % V) and niobium (about 0,05 and 0,16% Nb) as well as nitrogen (32 - 58 ppm.) on mechanical properties and structure of ductile iron is presented. Effect of these additions on graphite diameter distribution, nodule count, and ferrite fraction is determined. It has been also shown that vanadium and niobium lead to formation of their complex carbides, while nitrogen – complex carbide-nitrides containing m...

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

    OpenAIRE

    Naeem, Haider T.; Mohammed, Kahtan S.; Ahmad, Khairel R.; Azmi Rahmat

    2014-01-01

    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 ...

  11. Effect of nitrogen on structure and mechanical properties of ductile iron with small additions vanadium and niobium

    Directory of Open Access Journals (Sweden)

    Fraś E.

    2007-01-01

    Full Text Available Results of investigations of influence of small additions of vanadium (about 0,08 and 0,12 % V and niobium (about 0,05 and 0,16% Nb as well as nitrogen (32 - 58 ppm. on mechanical properties and structure of ductile iron is presented. Effect of these additions on graphite diameter distribution, nodule count, and ferrite fraction is determined. It has been also shown that vanadium and niobium lead to formation of their complex carbides, while nitrogen – complex carbide-nitrides containing magnesium and silicon.

  12. The effect of nitrogen on the formation of phase reversion-induced nanograined/ultrafine-grained structure and mechanical behavior of a Cr-Ni-N steel

    International Nuclear Information System (INIS)

    Research highlights: → We describe here an electron microscopy study of microstructural evolution associated with martensitic shear phase reversion-induced nanograined/ultrafine-grained (NG/UFG) structure in an experimental Fe-17Cr-7Ni alloy with nitrogen. The primary objective is to understand and obtain fundamental insights on the influence of degree of austenite stability and interstitial elements (nitrogen) in terms of phase reversion process, microstructural evolution during reversion annealing. - Abstract: In the study described here, we have used the concept of phase reversion involving combination of cold working and annealing to examine the effect of nitrogen on the reversion transformation of strain-induced martensite to austenite and tensile behavior of a Cr-Ni-N steel. The behavior is compared with that of a Cr-Ni steel with extremely low levels of interstitial elements C and N. Consistent with the high metastability of the investigated Cr-Ni-N steel, only 40% cold rolling reduction was adequate to transform 100% austenite to martensite, while Cr-Ni steel required ∼73% reduction for the complete transformation. The cold deformed austenite was characterized by a combination of lath and dislocation cell-type martensite. On annealing in the temperature range of 800-900 deg. C for 1-100 s, the phase reversion of martensite to austenite occurred by shear mechanism involving the following steps: (a) transformation of strain-induced martensite to lath-type austenite grains with high dislocation density, (b) refinement of reverted austenite grains due to recovery, i.e., dislocation cell formation to produce defect-free austenite subgrains, and (c) finally recrystallization of austenite grains following coalescence of sub-grains to form NG/UFG structure with grain size in the range of ∼200-600 nm. Some nucleation of secondary precipitates also occurred. Interestingly, the phase reversion mechanism was similar to that of the Cr-Ni steel. In spite of the

  13. 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.

  14. 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).

  15. 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. PMID:27281165

  16. 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.

  17. 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.

  18. Thermo-mechanical analysis of Wire and Arc Additive Layer Manufacturing process on large multi-layer parts

    OpenAIRE

    Ding, J.; Colegrove, Paul A.; Mehnen, Jorn; Ganguly, Supriyo; Sequeira Almeida, P. M.; Wang, F.; Williams, Stewart W.

    2011-01-01

    Wire and Arc Additive Layer Manufacturing (WAALM) is gaining increasing popularity as the process allows the production of large custom-made metal workpieces with high deposition rates. The high power input of the welding process, causes significant residual stress and distortion of the workpiece. This paper describes the thermo-mechanical behaviour of the multi-layer wall structure made by the WAALM process. A 3D thermo-elastic–plastic transient model and a model based on a...

  19. Effect of ZrO2 addition on the mechanical properties of porous TiO2 bone scaffolds.

    Science.gov (United States)

    Tiainen, Hanna; Eder, Georg; Nilsen, Ola; Haugen, Håvard J

    2012-08-01

    This study aimed at the investigation of the effect of zirconium dioxide (ZrO2) addition on the mechanical properties of titanium dioxide (TiO2) bone scaffolds. The highly biocompatible TiO2 has been identified as a promising material for bone scaffolds, whereas the more bioinert ZrO2 is known for its excellent mechanical properties. Ultra-porous TiO2 scaffolds (>89% porosity) were produced using polymer sponge replication with 0-40 wt.% of the TiO2 raw material substituted with ZrO2. Microstructure, chemical composition, and pore architectural features of the prepared ceramic foams were characterised and related to their mechanical strength. Addition of 1 wt.% of ZrO2 led to 16% increase in the mean compressive strength without significant changes in the pore architectural parameters of TiO2 scaffolds. Further ZrO2 additions resulted in reduction of compressive strength in comparison to containing no ZrO2. The appearance of zirconium titanate (ZrTiO4) phase was found to hinder the densification of the ceramic material during sintering resulting in poor intergranular connections and thus significantly reducing the compressive strength of the highly porous ceramic foam scaffolds. PMID:24364936

  20. Influence of Al-Ti-B addition on the microstructure and mechanical properties of A356 alloys

    Institute of Scientific and Technical Information of China (English)

    ZHU Man; YANG Gencang; YAO Lijuan; CHENG Suling; ZHOU Yaohe

    2009-01-01

    The mechanical properties (σb, σ0.2, and δ) and fracture behavior of tensile specimens of the refined A356 alloys were investigated as a func-tion of the addition level of Al-Ti-B master alloy under both as-cast and T6 hot-treated conditions. The results show that as the addition level of Al-5Ti- 1B master alloy increases from 0.1 wt.% to 5.0 wt.%, the mechanical properties of refined A356 alloys improve steadily and then decrease slightly under both as-cast and T6 heat-treated conditions. Also, they display excellent mechanical properties with σb = 231.30-258.30 Mpa, σ0.2 = 134.00-155.50 Mpa, and δ= 8.5%-11.75% at T6 heat-treated state. The excellent mechanical properties of refined A356 alloys are ascribed to the formation of a-Al equiaxed dendrites, the improvement of eutectic structure from needle/plate-like to short-lathy/block-shaped, and the Mg2Si aging precipitation phase after T6 heat treatment. The fracture surface examined by SEM exhibits a mixed fracture mode of refined A356 alloys at as-cast state, while it reveals a ductile fracture mode after T6 heat treatment.

  1. 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.

  2. 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.

  3. Effect of Cd and Sn Addition on the Microstructure and Mechanical Properties of Al-Si-Cu-Mg Cast Alloy

    Institute of Scientific and Technical Information of China (English)

    LI Rong-de; LI Run-xia; YU Li; HU Zhuang-qi

    2004-01-01

    The present work has investigated the effect of trace elements Cd and Sn on the microstructure and mechanical properties of Al-Si-Cu-Mg cast alloy. With the increase of Cd addition the strength of alloy rises at first and then drops. The optimal amount of Cd and Sn addition for Al-Si-Cu-Mg alloy is about 0.27% and 0.1% respectively. Due to the formation of some coarse Cd-rich phases and pure Cd particles the mechanical properties of alloy decrease when Cd amount exceeds0.27%. When more than 0.1% Sn added, some Sn atoms form low-melting eutectic compound at grain boundary, and then cause over-burning in alloy when solution treated, which may deteriorate properties of alloy, especially ductility of alloy.On the other hand, the addition of Cd and Sn remarkably increases the peak hardness and reduces the time to reach aging peak in Al-Si-Cu-Mg alloy. The action of Cd/Sn in quaternary Al-Si-Cu-Mg alloy is effectively the same as that occur in binary Al-Cu alloy that the enhanced hardening associated with Cd / Sn addition is due to the promotion of the θ' phase.

  4. 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.

  5. 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.

  6. 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

  7. Effects of Mn addition on microstructures and mechanical properties of 10Cr ODS ferritic/martensitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Hyun Ju; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    Ferritic/martensitic (FM) steels are very attractive for the structural materials of fast fission reactors such as a sodium cooled fast reactor (SFR) owing to their excellent irradiation resistance to a void swelling, but are known to reveal an abrupt loss of their creep and tensile strengths at temperatures above 600 .deg. C. Accordingly, high temperature strength should be considerably improved for an application of the FM steel to the structural materials of SFR. Oxide dispersion strengthened (ODS) FM steels are considered to be promising candidate materials for high- temperature components operating in severe environments such as nuclear fusion and fission systems due to their excellent high temperature strength and radiation resistance stemming from the addition of extremely thermally stable oxide particles dispersed in the ferritic/martensitic matrix.. To develop an advanced ODS steel for core structural materials for next generation nuclear reactor system applications, it is important to optimize its compositions to improve the high temperature strength and radiation resistance. This study investigates effects of Mn addition on microstructures and mechanical properties of 10Cr ODS FM steel. For this, two 10 Cr ODS FM steels were prepared by mechanical alloying (MA), hot isostatic pressing (HIP), and hot rolling process. Tensile tests were carried out at room temperature and 700 .deg. C to evaluate the influences of the Mn element on the mechanical properties. The microstructures were observed using SEM, electron back-scatter diffraction (EBSD) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). In the present study, the effects of Mn addition on the microstructure and mechanical properties of ODS FM steels were investigated. The ODS FM steels were manufactured by the MA, HIP and hot-rolling processes.

  8. Effect of ZrO2 addition on the mechanical properties of porous TiO2 bone scaffolds

    International Nuclear Information System (INIS)

    This study aimed at the investigation of the effect of zirconium dioxide (ZrO2) addition on the mechanical properties of titanium dioxide (TiO2) bone scaffolds. The highly biocompatible TiO2 has been identified as a promising material for bone scaffolds, whereas the more bioinert ZrO2 is known for its excellent mechanical properties. Ultra-porous TiO2 scaffolds (> 89% porosity) were produced using polymer sponge replication with 0–40 wt.% of the TiO2 raw material substituted with ZrO2. Microstructure, chemical composition, and pore architectural features of the prepared ceramic foams were characterised and related to their mechanical strength. Addition of 1 wt.% of ZrO2 led to 16% increase in the mean compressive strength without significant changes in the pore architectural parameters of TiO2 scaffolds. Further ZrO2 additions resulted in reduction of compressive strength in comparison to containing no ZrO2. The appearance of zirconium titanate (ZrTiO4) phase was found to hinder the densification of the ceramic material during sintering resulting in poor intergranular connections and thus significantly reducing the compressive strength of the highly porous ceramic foam scaffolds. - Highlights: ► Open porous scaffold with porosity in the range of 89.0 to 92.8% produced. ► Adding 1 wt.% of ZrO2 led to 16% increase in strength without changing porosity. ► Further ZrO2 additions resulted in reduced compressive strength versus no ZrO2. ► Presence of zirconium titanate (ZrTiO4) phase found to hinder the densification. ► Appearance of ZrTiO4 resulted in poor intergranular connections.

  9. Synthesis and mechanical characterization of PZT/Sr based composite ceramics with addition of Si3N4

    International Nuclear Information System (INIS)

    In the Underwater Acoustics field, piezoelectric ceramics are the most usually employed materials for the conversion of mechanical energy (acoustic signal) into electric energy (electric signal) and vice-versa, in sensors (hydrophones) or hydroacoustic projectors. In the development of new compositions for these applications, piezoelectric performance is generally prioritized, to the expense of its mechanical properties. With this in mind, the object of this work was to study the effects of the addition of Si3N4 in the mechanical properties of PZT-Sr based electronic ceramics. Thus, a novel piezoelectric ceramic with the addition of small percentages in weight (0;0.1;1;3 and 5) of the structural ceramic Si3N4 was successfully processed by the oxide mixing route ; the compounds were sintered in a conventional at 1200 deg C for 2h. The densities of the compounds thus obtained for the different percentages of Si3N4 ranged from 55 to 97% and decreased with the increase of the content of Si3N4. Presence of equiaxial grains with normal growth was observed in all samples. MEV/EDS analysis of the micro-structures of the compositions detected the presence of a second phase rich in Zr, confirmed by DRX, which is a result of large quantities of volatilized PbO; the sintered pieces had their mechanical properties investigated by ultra-sonic inspection. It was observed that, among the sintered compositions, the PZT-Sr ceramic with 0.1% Si3N4 presented the smallest value for Young's Modulus E and Shear Modulus G, 75 Gpa and 28 Gpa, respectively. The Poisson's Coefficients ν tended to decrease with the increase of Si3N4 added to the PZT-Sr ceramic, indicating, thus, that the added compound may be used to adjust the mechanical properties of the material. (author)

  10. Design rules for rational control of polymer glass formation behavior and mechanical properties with small molecular additives

    Science.gov (United States)

    Mangalara, Jayachandra Hari; Simmons, David

    Small molecule additives have long been employed to tune polymers' glass formation, mechanical and transport properties. For example, plasticizers are commonly employed to suppress polymer Tg and soften the glassy state, while antiplasticizers, which stiffen the glassy state of a polymer while suppressing its Tg, are employed to enhance protein and tissue preservation in sugar glasses. Recent literature indicates that additives can have a wide range of possible effects, but all of these have not been clearly understood and well appreciated. Here we employ molecular dynamics simulations to establish design rules for the selection of small molecule additives with size, molecular stiffness, and interaction energy chosen to achieve targeted effects on polymer properties. We furthermore find that a given additive's effect on a polymer's Tg can be predicted from its Debye-Waller factor via a function previously found to describe nanoconfinement effects on the glass transition. These results emphasize the potential for a new generation of targeted molecular additives to contribute to more targeted rational design of polymers. We acknowledge the Keck Foundation and the Ohio Supercomputing Center for financial and computational support of this effort, respectively.

  11. Effect of silver addition on the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductors

    CERN Document Server

    Nariki, S; Matsui, M; Murakami, M

    2002-01-01

    The effect of Ag addition on the microstructure and the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductor has been investigated. The single grain Gd-Ba-Cu-O bulk superconductors 32 mm in diameter were fabricated with 0-30 mass%Ag/sub 2/O additions by the melt growth method under controlled oxygen partial pressure of 1.0%. From microscopic observations, it was found that the macro- cracks in the a-b plane decreased with Ag addition. The three-point bending test showed that the average strength of Ag-free bulk was 69 MPa at room temperature, while the strength was dramatically improved to 110-115 MPa with 10-30 mass%Ag/sub 2/O additions. The trapped magnetic field of Ag-free bulk sample was 1.3 T at 77 K. The trapped field of bulk Gd-Ba-Cu-O samples with 10-20 mass%Ag/sub 2/O exhibited high values of 1.8-2.0 T at 77 K. However, the trapped field of the sample with 30 mass%Ag/sub 2/O addition was lowered to 1.1 T with decreasing the critical current density. The trapped field of Ag- adde...

  12. 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.

  13. Effect of the Addition MgO Nano Particle to Mechanical Properties and Microstructure of ZTA Ceramic Composite

    International Nuclear Information System (INIS)

    The mechanical properties and microstructure of zirconia-toughened alumina ceramic composite doped with nano particle of MgO is investigated. The nano-MgO weight percent was varied from 0 wt% to 1.3 wt%. Each batch of composition was mixed using ultrasonic cleaning and mechanical stirrer, uniaxially pressed and sintered at 1600 degree Celsius for 4 h in pressureless conditions. Analysis of bulk density, Vickers hardness, fracture toughness and microstructural observation has been carried out. Results of Vickers hardness increased linearly with addition of more nano-MgO until a certain composition. Maximum Vickers hardness obtained was 1740HV with 1.1 wt % MgO. (author)

  14. 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.

  15. Mechanical degradation under hydrogen of yttrium doped barium zirconate electrolyte material prepared with NiO additive

    Science.gov (United States)

    Ciria, D.; Ben Hassine, M.; Jiménez-Melendo, M.; Iakovleva, A.; Haghi-Ashtiani, P.; Aubin, V.; Dezanneau, G.

    2016-07-01

    Recently, a novel process was presented to fabricate dense yttrium-doped barium zirconate electrolytes with high proton conductivity. This process was based on the use of a NiO additive during reactive sintering. We show here that materials made from this process present a fast degradation of mechanical properties when put in hydrogen-rich conditions, while material made from conventional sintering without NiO aid remains intact in the same conditions. The fast degradation of samples made from reactive sintering, leading to sample failure under highly compressive conditions, is due to the reduction of NiO nanoparticles at grain boundaries as shown from structural and chemical analyses using Transmission Electron Microscopy. By the present study, we alert about the potential risk of cell failure due to this mechanical degradation.

  16. Effect of Si addition on glass-forming ability and mechanical properties of Cu-Zr-Al bulk metallic glass

    International Nuclear Information System (INIS)

    Research highlights: The Cu50Zr43Al7 alloy has a surprising GFA, and the glassy rods with diameter of 10 mm have been produced in this research. It has not been reported that the Cu-based glassy rods (Cu ≥ 50 at.%) to be produced with the critical diameter greater than 10 mm. The novelty of this research is that the glass formation has been improved and the critical diameter increased to 12 mm for the alloy having x = 1 with the addition of Si. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. - Abstract: The effect of Si addition on the glass-forming ability (GFA) and mechanical properties of (Cu50Zr43Al7)100-xSix (x = 0, 0.5, 1, 1.5 and 2 at.%) alloys were investigated. The GFA of Cu50Zr43Al7 alloy is improved by addition of a small amount of Si, and the critical diameter for glass formation increases from 10 mm for the alloy with x = 0-12 mm for the alloy with x = 1 when prepared using copper mold casting. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. In the uniaxial compression, the bulk glassy alloys exhibit a limited plastic strain of less than 1%, but the compressive fracture strength and Young's modulus were obtained in high values of 1969-2129 MPa and 101-144 GPa, respectively. Fracture surface and shear bands of samples were studied by using scanning electron microscopy (SEM).

  17. Etching characteristic and mechanism of BST thin films using inductively coupled Cl2/Ar plasma with additive CF4 gas

    International Nuclear Information System (INIS)

    BST thin films were etched with inductively coupled CF4/(Cl2+Ar) plasmas. The maximum etch rate of the BST thin films was 53.6 nm/min for a 10% CF4 to the Cl2/Ar gas mixture at RF power of 700 W, DC bias of -150 V, and chamber pressure of 2 Pa. Small addition of CF4 to the Cl2/Ar mixture increased chemical effect. Consequently, the increased chemical effect caused the increase in the etch rate of the BST thin films. To clarify the etching mechanism, the surface reaction of the BST thin films was investigated by X-ray photoelectron spectroscopy

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Morin reverses neuropathological and cognitive impairments in APPswe/PS1dE9 mice by targeting multiple pathogenic mechanisms.

    Science.gov (United States)

    Du, Ying; Qu, Jie; Zhang, Wei; Bai, Miao; Zhou, Qiong; Zhang, Zhuo; Li, Zhuyi; Miao, Jianting

    2016-09-01

    Alzheimer's disease (AD) is the most common form of dementia worldwide, characterized by progressive cognitive impairment and multiple distinct neuropathological features. Currently, there are no available therapies to delay or block the disease progression. Thus, the disease-modifying therapies are urgent for this devastating disorder by simultaneously targeting multiple distinct pathological processes. Morin, a natural bioflavonoid, have been shown to be strongly neuroprotective in vitro and in vivo. In this study, we first investigated the disease-modifying effects of chronic morin administration on the neuropathological and cognitive impairments in APPswe/PS1dE9 double transgenic mice. Our results showed that chronic morin administration prevented spatial learning and memory deficits in the APPswe/PS1dE9 mice. Morin treatment in the APPswe/PS1dE9 mice markedly reduced cerebral Aβ production and Aβ plaque burden via promoting non-amyloidogenic APP processing pathway by increasing ADAM10 expression, inhibiting amyloidogenic APP processing pathway by decreased BACE1 and PS1 expression, and facilitating Aβ degradation by enhancing Aβ-degrading enzyme expression. In addition, we also found that morin treatment in the APPswe/PS1dE9 mice markedly decreased tau hyperphosphorylation via its inhibitory effect on CDK5 signal pathway. Furthermore, morin treatment in the APPswe/PS1dE9 mice markedly reduced the activated glial cells and increased the expression of synaptic markers. Collectively, our findings demonstrate that chronic morin treatment restores cognitive functions and reverses multiple distinct neuropathological AD-like hallmarks in the APPswe/PS1dE9 mice. This study provides novel insights into the neuroprotective actions and neurobiological mechanisms of morin against AD, suggesting that morin is a potently promising disease-modifying agent for treatment of AD. PMID:27067919

  3. 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.

  4. Effects of Ce addition on microstructure, mechanical properties and corrosion resistance of as-cast AZ80 magnesium alloy

    Directory of Open Access Journals (Sweden)

    Wang Wei

    2014-05-01

    Full Text Available In this study, Ce was introduced into the AZ80 alloy and the effects of Ce addition on the microstructure, mechanical properties and corrosion resistance of the as-cast AZ80 magnesium alloy were investigated. The results show that the addition of Ce into the AZ80 alloy can not only refine the microstructure, but also result in the formation of the needle-like Al4Ce phase. These tiny Al4Ce phases are homogeneously distributed at grain boundaries and within grains. An appropriate Ce addition can also change the β-Mg17Al12 phase at the grain boundaries from continuous network to small island-like. At the same time, with the increase of Ce content from 0 to 2.0wt.%, the macro-hardness of the as-cast alloy is enhanced linearly, while impact toughness, tensile strength and elongation all firstly increase and then decrease. The AZ80 alloy containing 1.0wt.% Ce exhibits the optimal properties. Its macro-hardness, impact toughness, tensile strength and elongation are 61.90 HB, 15.50 J·cm-2, 171.80 MPa and 3.35%, increase by 9.95%, 63%, 13.3% and 36.7%, respectively compared with the base alloy. In addition, Ce can enhance the corrosion resistance of the AZ80 magnesium alloy.

  5. Low temperature impact toughness and fracture mechanism of cast QT400-18L ductile iron with different Ni additions

    Directory of Open Access Journals (Sweden)

    Zhang Xinning

    2013-09-01

    Full Text Available Different contents of Ni (0.3wt.% to 1.2wt.% were added to the QT400-18L ductile iron to investigate the effect of Ni addition on the impact toughness of cast ductile irons at low temperatures. The impact toughnesses of the samples at room and low temperatures were tested. The microstructures and fractographs were observed. Results show that with the increase of Ni addition there is a general trend of refinement of the ferrite matrix while the nodule density shows no obvious change. When the Ni content is 0.7wt.%, the matrix structure is the refined ferrite with a very small fraction (about 2% of pearlite near the eutectic cell boundaries. When the Ni content is further increased, the fraction of pearlite increases significantly and reaches more than 5% when 1.2wt.% Ni is added. The impact toughness at room temperature increases as the content of Ni increases from 0.3 wt.% to 0.7 wt.%, but decreases as the Ni content further increases to 1.2wt.% due to the increase of pearlite fraction. The maximum value of the impact work is 18.5 J at room temperature with 0.7wt.% Ni addition. The average value of the impact work is still more than 13 J even at -30 ℃. In addition, the fracture mechanism changes from ductile manner to brittleness as the testing temperature decreases from 20 ℃ to -60 ℃.

  6. 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.

  7. 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.

  8. 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

  9. Rapid and reversible impairments of short- and long-term social recognition memory are caused by acute isolation of adult rats via distinct mechanisms.

    Directory of Open Access Journals (Sweden)

    Hadar Shahar-Gold

    Full Text Available Mammalian social organizations require the ability to recognize and remember individual conspecifics. This social recognition memory (SRM can be examined in rodents using their innate tendency to investigate novel conspecifics more persistently than familiar ones. Here we used the SRM paradigm to examine the influence of housing conditions on the social memory of adult rats. We found that acute social isolation caused within few days a significant impairment in acquisition of short-term SRM of male and female rats. Moreover, SRM consolidation into long-term memory was blocked following only one day of social isolation. Both impairments were reversible, but with different time courses. Furthermore, only the impairment in SRM consolidation was reversed by systemic administration of arginine-vasopressin (AVP. In contrast to SRM, object recognition memory was not affected by social isolation. We conclude that acute social isolation rapidly induces reversible changes in the brain neuronal and molecular mechanisms underlying SRM, which hamper its acquisition and completely block its consolidation. These changes occur via distinct, AVP sensitive and insensitive mechanisms. Thus, acute social isolation of rats swiftly causes changes in their brain and interferes with their normal social behavior.

  10. The effect of Si additions on the sintering and sintered microstructure and mechanical properties of Ti-3Ni alloy

    International Nuclear Information System (INIS)

    Highlights: → Silicon is a potent sintering aid for Ti-Ni alloys revealed by predictions and confirmed by experiments. → The addition of Si should be limited to ≤1% to avoid coarse Ti5Si3 phase and ensure good ductility. → Liquid forms during heating at ∼988 deg. C due to reactions between Si and Ni and Ni and Ti. → Silicon can be a unique addition to PM Ti alloys for significantly improved mechanical properties. - Abstract: Thermodynamic predictions suggest that silicon has the potential to be a potent sintering aid for Ti-Ni alloys because small additions of Si lower the solidus of Ti-Ni alloys appreciably (>200 deg. C by 1 wt.% Si). A systematic study has been made of the effect of Si on the sintering of a Ti-3Ni alloy at 1300 deg. C. The sintered density increased from 91.8% theoretical density (TD) to 99.2%TD with increasing Si from 0% to 2%. Microstructural examination reveals that coarse particles and/or continuous networks of Ti5Si3 form along grain boundaries when the addition of Si exceeds 1%. The grain boundary Ti5Si3 phase leads to predominantly intergranular fracture and therefore a sharp decrease in ductility concomitant with increased tensile strengths. The optimum addition of Si is proposed to be ≤1%. Dilatometry experiments reveal different shrinkage behaviours with respect to different Si contents. Interrupted differential scanning calorimetry (DSC) experiments and corresponding X-ray diffraction (XRD) analyses clarify the sequence of phase formation during heating. The results provide a useful basis for powder metallurgy (PM) Ti alloy design with Si.

  11. Electrochemical Mechanism for FeS2/C Composite in Lithium Ion Batteries with Enhanced Reversible Capacity

    Directory of Open Access Journals (Sweden)

    Shengping Wang

    2016-03-01

    Full Text Available Nanoscale FeS2 was synthesized via a simple hydrothermal method and was decorated by hydrothermal carbonization (FeS2@C. The structural properties of the synthesized materials detected by X-ray diffraction (XRD, together with the morphologies characterized by scanning electron microscopy (SEM and transmission electron microscopy (TEM indicated that the hydrothermal carbonization only had an impact on the morphology of pyrite. Additionally, the electrochemical performance of the coated pyrite in Li/FeS2 batteries was evaluated by galvanostatic discharge-charge tests and electrochemical impedance spectroscopy (EIS. The results showed that the initial capacity of FeS2@C was 799.2 mAh·g−1 (90% of theoretical capacity of FeS2 and that of uncoated FeS2 was only 574.6 mAh·g−1. XRD and ultraviolet (UV visible spectroscopy results at different depths of discharge-charge for FeS2 were discussed to clarify the electrochemical mechanism, which play an important part in Li/FeS2 batteries.

  12. 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.

  13. 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.

  14. 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.

  15. Synthesis of nanoparticeles in ductile iron with small additions of vanadium and niobium and its mechanical properties

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2007-12-01

    Full Text Available It has been shown that the heat treatment of 1095oC/640 oC type of ferritic ductile iron with small addition of 0.08% vanadium permits to obtain of the rounded VC nanoparticles with an average size of 50 nm and 0.13 volume fraction. Results of investigations of influence of small vanadium up to 0.3%, niobium up to 0.16% and nitrogen up to 58 ppm additions and heat treatment of 1080oC-24h/640 oC and 1080oC-24h/600 oC type on structure and mechanical properties (tensile strength, yields strength and elongation of ductile iron are also presented in this work. It has been demonstrated that heat treatment and small additions of vanadium, and niobium as well as nitrogen enable to obtain material, which can be classified a EN-GJS-450-18 to EN-GJS-700-2 grade ductile iron.

  16. 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

  17. 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.

  18. 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.

  19. Effect of Nb addition on the microstructure and mechanical properties of an 1800 MPa ultrahigh strength steel

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huibin [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China); Ju, Biao, E-mail: jubiao@aliyun.com [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China); Tang, Di; Hu, Rirong [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China); Guo, Aimin [CITIC-CBMM Microalloying Technology Center (MTC), CITIC Group, Beijing 100004 (China); Kang, Qiang; Wang, Di [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-01-12

    The microstructure–property relationship of Nb-free and Nb-bearing ultrahigh strength steels were studied in this work. Martensitic steels with 1800 MPa tensile strength were obtained by conducting reheated quenching and tempering after thermomechanical rolling. The microstructures of the steels were investigated by scanning electron microscopy, transmission electron microscopy electron backscattering diffraction technique. The results show that with the addition of Nb, the prior austenite grain growth was impeded, which leaded to the further refinement of final martensite microstructure. Randomly distributed Nb-rich (Nb,Ti)C in Nb bearing steel played an important role in the strengthening of the steel. As revealed by dilatometry and differential scanning calorimetry, with the increase of tempering temperature the decrease of mechanical properties mainly initiated by the decomposition of retained austenite during low temperature tempering, and the formation of harmful iron carbides was retarded when the steel microalloyed with 0.021% Nb.

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

    International Nuclear Information System (INIS)

    In this study, the effects of grain size and the addition of CaCO3 on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 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 CaCO3 densified the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics at 1075 °C. In the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO3 content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe2CaO4 was observed, together with the disappearance of the second phase CuO. The grain size of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO3 content increased from 0 to 5 wt%. Initially rising to 807 after CaCO3 addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO3 content increased. The bending strength grew linearly with the CaCO3 content and reached twice the value for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with an addition of 5.0 wt% CaCO3. The initial permeability of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic decreased substantially from 402 to 103 as the addition of CaCO3 in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic was maximized at 95 for 1.0 wt% CaCO3 addition. - Highlights: • Effects of grain size and CaCO3 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 ferrite with 5.0 wt% CaCO3 addition. • Initial permeability of the ferrite decreased markedly with the addition of CaCO3. • Quality factor of the ferrite was maximized at 95 for 1.0 wt% CaCO3 addition

  1. 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

  2. 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.

  3. 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.

  4. 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. PMID:27403964

  5. Effects of Nb addition on microstructure and mechanical properties of TiNiNb alloys fabricated by elemental powder sintering

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jing; Wang, Huifeng; Liu, Jue; Ruan, Jianming, E-mail: jianming@csu.edu.cn

    2014-07-15

    Porous TiNi binary and TiNiNb ternary alloys of four compositions (Ti{sub 50}Ni{sub 47.5}Nb{sub 2.5}, Ti{sub 50}Ni{sub 45}Nb{sub 5}, Ti{sub 50}Ni{sub 42.5}Nb{sub 7.5}, and Ti{sub 50}Ni{sub 40}Nb{sub 10}) were fabricated by the elemental powder sintering process. The effects of Nb addition on microstructure and mechanical properties of TiNi(Nb) alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and tensile tests, respectively. With the increase of Nb contents, the TiNi matrix as the main phase is always retained, while the intensity of its diffraction peak gradually became weak with the appearance of β-Nb and TiNb phases. Most Nb particles are well-distributed in the TiNi matrix and (Ti,Nb){sub 2}Ni phase is found in the binding domain between Nb phase and TiNi phase. The tensile strength and elastic modulus of TiNiNb alloys increase with the increase of Nb contents, due to the solid solution strengthening effect of Nb-rich particles, the enlarged sintering neck and the strengthened bond between particles. Consequently, Nb plays a crucial role in adjusting composition and improving microstructure and mechanical properties of TiNiNb alloys.

  6. 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

  7. Graded microstructure and mechanical properties of additive manufactured Ti–6Al–4V via electron beam melting

    International Nuclear Information System (INIS)

    Electron beam melting (EBM®)-built Ti–6Al–4V has increasingly shown great potential for orthopedic implant and aerospace applications in recent years. The microstructure and mechanical properties of EBM-built Ti–6Al–4V have been systematically investigated in this work. Its microstructure consists of columnar prior β grains delineated by wavy grain boundary α and transformed α/β structures with both cellular colony and basket-weave morphology as well as numerous singular α bulges within the prior β grains. The β phase is found to form as discrete flat rods embedded in continuous α phase and its volume fraction is determined to be ∼3.6%. Moreover, α′ martensite was not observed as it has decomposed into α and β phases. In particular, the α/β interface was studied in detail combined transmission electron microscopy with atom probe tomography. Of note is that graded Ti–6Al–4V microstructure i.e. both prior β grain width and β phase interspacing continuously increase with the build height, was observed, which mainly arises from the decreasing cooling rate. Furthermore, an increasingly pronounced strain hardening effect was also observed as the previously built layers undergo a longer annealing compared to the subsequent layers. As a result, graded mechanical properties of Ti–6Al–4V with degraded microhardness and tensile properties were found. A good agreement with the Hall–Petch relation indicates that the graded property takes place mainly due to the graded microstructure. In addition, this graded microstructure and mechanical properties were discussed based on a quantitative characterization

  8. 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.

  9. 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.

  10. Effect of boron addition on the microstructures and mechanical properties of thermomechanically processed and tempered low carbon bainitic steels

    Institute of Scientific and Technical Information of China (English)

    Liangyun LAN; Chunlin QIU; Ping ZHOU; Dewen ZHAO; Canming LI; Xiuhua GAO; Linxiu DU

    2011-01-01

    Thermomechanical process and tempering heat treatment were employed to produce the experimental steel plates.The effect of boron addition on the microstructure and mechanical properties of low carbon bainitic steels was studied in this paper.Microstructure observation and crystallographic features were conducted by using optical microscopy,SEM,TEM and electron back scattering diffraction (EBSD) analysis.The results showed that under the same rolling processes and heat treatment conditions,a substantial increase in strength is obtained by addition of boron into steel,but accompanied by an obvious drop in toughness.New martensite phase forms along the grain boundaries on tempering at 650 ℃ mainly due to boron segregation,which can further deteriorate impact toughness of the boron bearing steel.The EBSD analysis showed that high angle grain boundary,is not responsible for the deteriorated toughness of the boron bearing steel because it has relatively higher percentage of high angle grain boundary than the boron free steel.The low toughness of the boron bearing steel is mainly attributed to the coarse boride precipitated particles according to the results of fractograph observation.

  11. Effects of Cu and B addition on microstructure and mechanical properties of high-strength bainitic steels

    International Nuclear Information System (INIS)

    Effects of Cu and B addition on microstructure and mechanical properties of high-strength bainitic steels were investigated in this study. Six kinds of steels were fabricated by controlling the amount of Cu and B addition, and their microstructures and tensile and Charpy impact properties were investigated. Their effective grain sizes were also characterized by the electron back-scatter diffraction analysis. The tensile test results indicated that the B- or Cu-containing steels had the higher yield and tensile strengths than the B- or Cu-free steels because their volume fractions of acicular ferrite and martensite were quite high. The B- or Cu-free steels had the higher upper shelf energy than the B- or Cu-containing steels because of their lower volume fraction of martensite. In the steel containing 10 ppm B without Cu, the best combination of high strengths, high upper shelf energy, and low energy transition temperature could be obtained by the decrease in effective grain size due to the presence of acicular ferrite having fine effective grain size.

  12. Magnetic anisotropy and reversal in epitaxial Fe/MgO(001) films revisited

    OpenAIRE

    Zhan, Qing-feng; Vandezande, Stijn; Temst, Kristiaan; Van Haesendonck, Chris

    2008-01-01

    We investigate the magnetization reversal in Fe/MgO(001) films with fourfold in-plane magnetic anisotropy and an additional uniaxial anisotropy whose orientation and strength are tuned using different growth geometries and post growth treatments. The previously adopted mechanism of 180^{o} domain wall nucleation clearly fails to explain the observed 180^{o} magnetization reversal. A new reversal mechanism with two successive domain wall nucleations consistently predicts the switching fields f...

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

    International Nuclear Information System (INIS)

    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 Al3(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 orientations

  14. 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

  15. 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.

  16. 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.

  17. In operando X-ray diffraction study of Li7MnN4 upon electrochemical Li extraction-insertion: A reversible three-phase mechanism

    Science.gov (United States)

    Emery, N.; Panabière, E.; Crosnier, O.; Bach, S.; Brousse, T.; Willmann, P.; Pereira-Ramos, J.-P.

    2014-02-01

    The Li7MnN4 structural response upon the first Li extraction-insertion cycle is highlighted using in operando XRD experiments. A 3-phases mechanism involving two biphasic regions for 0.1 ≲ x ≲ 0.8 and 0.8 ≲ x ≲ 1.2 in Li7-xMnN4 and a solid solution behaviour (1.2 ≲ x ≲ 1.5) explains its electrochemical fingerprint. These successive structural transitions do not change the cubic symmetry of the cell and induce a limited cell contraction (∼7%) associated to a reversible mechanical strain. This finding partly explains the excellent cycle life of this promising negative electrode for Li-ion batteries.

  18. Reaction mechanism of the reverse water-gas shift reaction using first-row middle transition metal catalysts L'M (M = Fe, Mn, Co): a computational study.

    Science.gov (United States)

    Liu, Cong; Cundari, Thomas R; Wilson, Angela K

    2011-09-19

    The mechanism of the reverse water-gas shift reaction (CO(2) + H(2) → CO + H(2)O) was investigated using the 3d transition metal complexes L'M (M = Fe, Mn, and Co, L' = parent β-diketiminate). The thermodynamics and reaction barriers of the elementary reaction pathways were studied with the B3LYP density functional and two different basis sets: 6-311+G(d) and aug-cc-pVTZ. Plausible reactants, intermediates, transition states, and products were modeled, with different conformers and multiplicities for each identified. Different reaction pathways and side reactions were also considered. Reaction Gibbs free energies and activation energies for all steps were determined for each transition metal. Calculations indicate that the most desirable mechanism involves mostly monometallic complexes. Among the three catalysts modeled, the Mn complex shows the most favorable catalytic properties. Considering the individual reaction barriers, the Fe complex shows the lowest barrier for activation of CO(2). PMID:21838224

  19. Effects of water ageing on the mechanical properties of flax and glass fibre composites: Degradation and reversibility

    OpenAIRE

    Apolinario, Guilherme; Ienny, Patrick; Corn, Stéphane; Léger, Romain; Bergeret, Anne; Haudin, Jean-Marc

    2015-01-01

    Mechanical properties of flax-fibre reinforced composites (FFRC) are strongly affected by water ageing compared to glass-fibre reinforced composites (GFRC). This study highlights the influence of water absorption during immersion at 30°C on mechanical properties of unsaturated polyester reinforced composites. Flax-fibre composites showed a Fickian absorption behaviour and a water uptake 15 times higher than that of glass-fibre composites. GFRC's tensile modulus and maximum stress were slightl...

  20. Hemolysate-mediated platelet aggregation: an additional risk mechanism contributing to thrombosis of continuous flow ventricular assist devices.

    Science.gov (United States)

    Tran, Phat L; Pietropaolo, Maria-Grazia; Valerio, Lorenzo; Brengle, William; Wong, Raymond K; Kazui, Toshinobu; Khalpey, Zain I; Redaelli, Alberto; Sheriff, Jawaad; Bluestein, Danny; Slepian, Marvin J

    2016-07-01

    Despite the clinical success and growth in the utilization of continuous flow ventricular assist devices (cfVADs) for the treatment of advanced heart failure, hemolysis and thrombosis remain major limitations. Inadequate and/or ineffective anticoagulation regimens, combined with high pump speed and non-physiological flow patterns, can result in hemolysis which often is accompanied by pump thrombosis. An unexpected increase in cfVADs thrombosis was reported by multiple major VAD implanting centers in 2014, highlighting the association of hemolysis and a rise in lactate dehydrogenase (LDH) presaging thrombotic events. It is well established that thrombotic complications arise from the abnormal shear stresses generated by cfVADs. What remains unknown is the link between cfVAD-associated hemolysis and pump thrombosis. Can hemolysis of red blood cells (RBCs) contribute to platelet aggregation, thereby, facilitating prothrombotic complications in cfVADs? Herein, we examine the effect of RBC-hemolysate and selected major constituents, i.e., lactate dehydrogenase (LDH) and plasma free hemoglobin (pHb) on platelet aggregation, utilizing electrical resistance aggregometry. Our hypothesis is that elements of RBCs, released as a result of shear-mediated hemolysis, will contribute to platelet aggregation. We show that RBC hemolysate and pHb, but not LDH, are direct contributors to platelet aggregation, posing an additional risk mechanism for cfVAD thrombosis. PMID:26590166

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Reverse Engineering

    International Nuclear Information System (INIS)

    This book gives descriptions of reverse engineering with principle and structure of it, including what reverse engineering is, prospect and concerned laws, basic knowledge for reverse engineering like manual and back to user mode, using tool such as IDA installation, dependency walker and dump bin, network monitoring and universal extractor. It indicates analysis of malignant code, giving explanations of file virus, spy ware, an infection way of malignant code, anti debugging like Find window.

  6. In situ microscopy reveals reversible cell wall swelling in kelp sieve tubes: one mechanism for turgor generation and flow control?

    Science.gov (United States)

    Knoblauch, Jan; Tepler Drobnitch, Sarah; Peters, Winfried S; Knoblauch, Michael

    2016-08-01

    Kelps, brown algae (Phaeophyceae) of the order Laminariales, possess sieve tubes for the symplasmic long-distance transport of photoassimilates that are evolutionarily unrelated but structurally similar to the tubes in the phloem of vascular plants. We visualized sieve tube structure and wound responses in fully functional, intact Bull Kelp (Nereocystis luetkeana [K. Mertens] Postels & Ruprecht 1840). In injured tubes, apparent slime plugs formed but were unlikely to cause sieve tube occlusion as they assembled at the downstream side of sieve plates. Cell walls expanded massively in the radial direction, reducing the volume of the wounded sieve elements by up to 90%. Ultrastructural examination showed that a layer of the immediate cell wall characterized by circumferential cellulose fibrils was responsible for swelling and suggested that alginates, abundant gelatinous polymers of the cell wall matrix, were involved. Wall swelling was rapid, reversible and depended on intracellular pressure, as demonstrated by pressure-injection of silicon oil. Our results revive the concept of turgor generation and buffering by swelling cell walls, which had fallen into oblivion over the last century. Because sieve tube transport is pressure-driven and controlled physically by tube diameter, a regulatory role of wall swelling in photoassimilate distribution is implied in kelps. PMID:26991892

  7. 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.

  8. Effect of Fe addition on microstructure and mechanical properties of Ti-25V-15Cr-2Al-0.2C alloy

    Institute of Scientific and Technical Information of China (English)

    雷力明; 黄旭; 孙福生; 吴学仁; 曹春晓

    2003-01-01

    The effect of 2% Fe addition on the microstructure and mechanical properties of Ti-25V-15Cr-2Al-0.2C alloy(mass fraction)was studied.It is found that the addition of 2% Fe seems to have no obvious effect on the microstructure of the alloy,but results in a significant change in mechanical properties.Compared with the alloy without Fe addition,the alloy with 2% Fe addition exhibits remarkable higher tensile strength and creep resistance,whereas the ductility is relatively lower at room temperature.The significant changes in mechanical properties can be rationalized by the decrease of stacking fault energy caused by the addition of 2% Fe.

  9. Facile synthesis, growth mechanism and reversible superhydrophobic and superhydrophilic properties of non-flaking CuO nanowires grown from porous copper substrates

    Science.gov (United States)

    Zhang, Qiao bao; Xu, Daguo; Hung, Tak Fu; Zhang, Kaili

    2013-02-01

    Reversible superhydrophobic and superhydrophilic surfaces based on porous substrates covered with CuO nanowires are developed in this study. A facile thermal oxidation method is used to synthesize non-flaking bicrystalline CuO nanowires on porous copper substrates in static air. The effects of thermal oxidation temperature and duration are systemically studied. The growth mechanism of the obtained non-flaking CuO nanowires is presented and the compression stress is believed to be the key driving force. The wettability of the CuO nanowires after chemical modification with trichloro(1H,1H,2H,2H-perfluorooctyl)silane is systemically investigated. The porous substrates covered with CuO nanowires exhibit excellent superhydrophobic performance with almost no water adhesion and no apparent drag resistance, and a maximum static water contact angle of 162 ± 2° is observed. Moreover, a rapid reversibly switchable wettability between superhydrophobic and superhydrophilic states is realized by the alternation of air-plasma treatment and surface fluorination. The porous substrates covered with CuO nanowires will find promising applications in surface and corrosion protection, liquid transportation, oil-water separation, and self-cleaning surfaces.

  10. Facile synthesis, growth mechanism and reversible superhydrophobic and superhydrophilic properties of non-flaking CuO nanowires grown from porous copper substrates

    International Nuclear Information System (INIS)

    Reversible superhydrophobic and superhydrophilic surfaces based on porous substrates covered with CuO nanowires are developed in this study. A facile thermal oxidation method is used to synthesize non-flaking bicrystalline CuO nanowires on porous copper substrates in static air. The effects of thermal oxidation temperature and duration are systemically studied. The growth mechanism of the obtained non-flaking CuO nanowires is presented and the compression stress is believed to be the key driving force. The wettability of the CuO nanowires after chemical modification with trichloro(1H,1H,2H,2H-perfluorooctyl)silane is systemically investigated. The porous substrates covered with CuO nanowires exhibit excellent superhydrophobic performance with almost no water adhesion and no apparent drag resistance, and a maximum static water contact angle of 162 ± 2° is observed. Moreover, a rapid reversibly switchable wettability between superhydrophobic and superhydrophilic states is realized by the alternation of air–plasma treatment and surface fluorination. The porous substrates covered with CuO nanowires will find promising applications in surface and corrosion protection, liquid transportation, oil–water separation, and self-cleaning surfaces. (paper)

  11. 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

  12. 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).

  13. 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.

  14. Reversible Sterilization

    Science.gov (United States)

    Largey, Gale

    1977-01-01

    Notes that difficult questions arise concerning the use of sterilization for alleged eugenic and euthenic purposes. Thus, how reversible sterilization will be used with relation to the poor, mentally ill, mentally retarded, criminals, and minors, is questioned. (Author/AM)

  15. Vasectomy Reversal

    Medline Plus

    Full Text Available ... improving health. Hello, my name is Harris Nagler. I'm the Chairman of the Sol and Margaret ... Israel Medical Center in New York City. Today I'm going to perform a vasectomy reversal using ...

  16. Vasectomy Reversal

    Medline Plus

    Full Text Available ... Today we are going to go to the operating room and show you microsurgical vasectomy reversal. We ... vas and that will be examined under the operating- under the microscope to see if there’s sperm ...

  17. Vasectomy Reversal

    Medline Plus

    Full Text Available ... is a realistic option for many patients. Today we are going to go to the operating room and show you microsurgical vasectomy reversal. We start the procedure by localizing the site of ...

  18. Vasectomy Reversal

    Medline Plus

    Full Text Available Vasectomy Reversal Beth Israel Medical Center, New York, NY February 19, 2009 Welcome to this "OR Live" Webcast presentation premiering from Beth Israel Medical Center in New York City. ...

  19. 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

  20. 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.

  1. 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.

  2. Research on reversible effects and mechanism between the energy-absorbing and energy-reflecting states of chameleon-type building coatings

    Energy Technology Data Exchange (ETDEWEB)

    Yiping Ma; Xiong Zhang; Beirong Zhu; Keru Wu [Tongji Univ., Shanghai (China). State Key Lab. of Concrete Materials Research

    2002-06-01

    In the present paper, the reversible effects between energy-absorbing and energy-reflecting states of chameleon-type building coatings were studied through demonstration of the layers' properties using infrared thermal imaging of the layers when exposed to a sunlamp or temperature measurements of the layers during exposure to sunlight at different ambient temperatures. The reversible transforming mechanism between the energy-absorbing and energy-reflecting states of the chameleon-type building coatings was investigated with IR, Raman and {sup 1}H NMR spectroscopy. The infrared thermal image results showed that when reversibly thermochromic pigments were added to normal white building coatings, the chameleon-type building coatings could absorb energy from the sunlamp below a switching temperature of about 18{sup o}C. Absorption of energy from the sunlamp stopped automatically above the switching temperature. The results from exposure to solar radiation showed that when the temperature was below the switching temperature, the chameleon-type building coating could absorb almost the same amount of solar energy as an ordinary coloured coating, and when the temperature was above the switching temperature, the chameleon-type building coating could reflect more solar energy than the ordinary coloured coating. The above results showed that chameleon-type building coatings could contribute to a thermally comfortable building environment. The IR spectroscopy results showed that when the environmental temperature was below the switching temperature of 18{sup o}C, the lactone ring of the thermochromic pigment molecule would open and the band of C=O would almost disappear. Raman spectra indicated that the band of C-O in -C{sub -O}{sup =O} would move to the high wave number range. From {sup 1}H NMR spectra, it could be found that there was some action between the hydrogen of the hydroxyl and the structure of -C{sub -O}{sup =}O. During the lactone ring opening, the electron

  3. 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.

  4. 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

    six-membered "flat chair") was probed by quantum mechanical calculations, which underpinned the idea of using external chiral ligands to enhance the diastereoselectivity of otherwise moderately selective reactions. In this way, the diastereomeric ratio of the product 3a could be raised from (84 : 16...

  5. Low temperature impact toughness and fracture mechanism of cast QT400-18L ductile iron with different Ni additions

    OpenAIRE

    Zhang Xinning; Qu Yingdong; Yang Hongwang

    2013-01-01

    Different contents of Ni (0.3wt.% to 1.2wt.%) were added to the QT400-18L ductile iron to investigate the effect of Ni addition on the impact toughness of cast ductile irons at low temperatures. The impact toughnesses of the samples at room and low temperatures were tested. The microstructures and fractographs were observed. Results show that with the increase of Ni addition there is a general trend of refinement of the ferrite matrix while the nodule density shows no obvious change. When the...

  6. Investigation of microstructure and mechanical properties of aluminum hybrid nano-composites with the additions of solid lubricant

    International Nuclear Information System (INIS)

    Highlights: • Aluminium hybrid nano-composite was made by mechanical alloying successfully. • High energy ball milling resulted in homogeneous distribution of reinforcements. • MA combined with pressing allowed to produce nano-crystalline matrix composites. • Hybrid nano-composites exhibited the best mechanical properties. • Wear resistance of the aluminum hybrid nano-composites found increased with increased filler content. - Abstract: In this experimental study, the tribological behavior of Al 2024–5 wt.% SiC–X wt.% graphite (X = 5 and 10) hybrid nano-composites was produced using powder metallurgy (P/M) technique. All specimens were prepared by mechanical milling of Al 2024 and SiC–Gr nano-composite powders, followed by a blend–press–sinter methodology. Pin on disc type apparatus has been used for determining the wear loss. The sintered samples have been characterized by XRD. Wear mechanisms are discussed based on scanning electron microscopy observations of worn surface and wear debris morphology. The hardness and wear resistance of the hybrid nano-composites were increased considerably by increasing the reinforcement content. The nano-composite with 5 wt.% SiC and 10 wt.% Gr showed the greatest improvement in tribological performance. Primary wear mechanisms for hybrid nano-composites were determined to be formation of lubricating layer on the surface of samples. The overall results revealed that hybrid aluminium nano-composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, particularly structural applications in the aerospace, automotive and military industries

  7. 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.

  8. On crystallochemical mechanism of small alloying addition effect on dissolution process of corrosion-resistant steels in active state

    International Nuclear Information System (INIS)

    Regularities of component dissolution and the changes of the surface layer composition of the Fe-Cr and Fe-Cr-Mo steels are studied. The investigations have been carried out taking as an example high-purity ferrite steels of the FeCr18 and FeCr26 type with Mo content from O to 1.7 and from 0 to 1.2 at. % in 1n H2SO4 respectively at room temperature. The notions of dissolution character of energetically heterogeneous alloy surface are developed. A conclusion is made on the mechanism of inhibitting effect of molybdenum on the anode process of steel dissolution in the active state and on the mechanism of its effect on steel passivation capacity

  9. 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.

  10. 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.

  11. 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.

    2016-08-01

    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.

  12. The effect of Li, Ce and Ni additions on the microstructure and the mechanical properties in the AlFe intermetallic system

    Energy Technology Data Exchange (ETDEWEB)

    Salazar, M.; Perez, R. [Programa de Investigacion y Desarrollo de Ductos, Inst. Mexicano del Petroleo, Col. San Bartolo Atepehuacan, Mexico D. F. (Mexico); Rosas, G. [Inst. de Investigaciones Metalurgicas, UMSNH, Morelia, Mich. (Mexico)

    2003-07-01

    Microstructural and mechanical properties of the Fe{sub 3}Al intermetallic compound with additions of Li, Ni, Ce and combinations of (Ce,Li), (Ce,Ni) were obtained. These alloys were produced by a normal casting methods using SiC crucibles. Compression test were carried out and some insights on the alloys mechanical properties are withdrawn. The main effect of these elements on the Fe{sub 3}Al alloy is related with the improvements of compressive ductility. Also, in this investigation systematic changes in the microstructure and mechanical behavior with the presence of Fe{sub 3}AlC phase content have been observed. (orig.)

  13. Effect of additional element and heat treating temperature on micro-structure and mechanical behavior of Ag alloy thin film

    Institute of Scientific and Technical Information of China (English)

    JU Dong-ying; ISHIGURO S; ARIZONO T; HASEGAWA K

    2006-01-01

    For Ag alloy film used for the storage media,it is required to have heat-resistance,anti-constant temperature and anti-constant humidity characteristics,corrosion resistance,while high reflectivity over Al is maintained. An Ag alloy thin film (additive element Pd,Cu,P) was created on glass substrates,and various heat treatment was conducted. Then,fine structure was observed on this thin film using AFM,and fine structure evaluation of the inside was carried out by the in-plane diffractometry and X-ray diffractometry,and in addition,residual stress analysis was carried out. These results were compared and were examined,and fine structure and physical property in a metallic thin film were evaluated,and usefulness of evaluation method was verified.

  14. Additive manufacturing of Ti-6Al-4V components by shaped metal deposition: Microstructure and mechanical properties

    International Nuclear Information System (INIS)

    Shaped metal deposition (SMD) is a relatively new technology of additive manufacturing, which creates near-net shaped components by additive manufacture utilizing tungsten inert gas welding. Especially for Ti alloys, which are difficult to shape by traditional methods and for which the loss of material during machining is also very costly, SMD has great advantages. In the case of Ti-6Al-4V the dense SMD components exhibit large, columnar prior β grains, with a Widmanstaetten α/β microstructure. These prior β grains are slightly tilted in a direction following the temperature field resulting from the moving welding torch. The ultimate tensile strength is between 929 and 1014 MPa, depending on orientation and location of the tensile specimens. Tensile testing vertically to the deposition layers exhibits a strain at failure of 16 ± 3%, while testing parallel to the layers gives a lower value of about 9%.

  15. Ostwald ripening of Pb nanocrystalline phase in mechanically milled Al-Pb alloys and the influence of Cu additive

    International Nuclear Information System (INIS)

    The coarsening behavior of nanosized Pb phase in both Al-10%Pb and Al-10%Pb-4.5%Cu alloys has been studied by X-ray diffraction and transmission electron microscopy analysis. The coarsening of Pb nanophase in Al-Pb alloys still follows the classical ripening theory (the LSW theory) and the addition of Cu decreases the coarsening rate of Pb nanophase

  16. The effect of the addition of ground olive stones on the physical and mechanical properties of clay bricks

    OpenAIRE

    Arezki, S.; Chelouah, N.; Tahakourt, A.

    2016-01-01

    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 o...

  17. 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.

  18. Improvement of mechanical and biological properties of TiNi alloys by addition of Cu and Co to orthodontic archwires.

    Science.gov (United States)

    Phukaoluan, Aphinan; Khantachawana, Anak; Kaewtatip, Pongpan; Dechkunakorn, Surachai; Kajornchaiyakul, Julathep

    2016-09-01

    The purpose of this study was to investigate improved performances of TiNi in order to promote tooth movement. Special attention was paid to the effect on the clinical properties of TiNi of adding Cu and Co to this alloy. Ti49.4Ni50.6, Ti49Ni46Cu5 and Ti50Ni47Co3 (at %) alloys were prepared. Specimens were cold-rolled at 30% reduction and heat-treated at 400°C for 60min. Then, the test results were compared with two types of commercial archwires. The findings showed that superelasticity properties were confirmed in the manufactured commercial alloys at mouth temperature. The difference of stress plateau in TiNi, TiNiCo and commercial wires B at 25°C changed significantly at various testing temperatures due to the combination of martensite and austenite phases. At certain temperatures the alloys exhibited zero recovery stress at 2% strain and consequently produced zero activation force for moving teeth. The corrosion test showed that the addition of Cu and Co to TiNi alloys generates an increase in corrosion potential (Ecorr) and corrosion current densities (Icorr). Finally, we observed that addition of Cu and Co improved cell viability. We conclude that addition of an appropriate amount of a third alloying element can help enhance the performances of TiNi orthodontic archwires. PMID:27520713

  19. 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.

  20. Partial Reversible Gates(PRG) for Reversible BCD Arithmetic

    OpenAIRE

    Thapliyal, Himanshu; Arabnia, Hamid R; Bajpai, Rajnish; Sharma, Kamal K

    2007-01-01

    IEEE 754r is the ongoing revision to the IEEE 754 floating point standard and a major enhancement to the standard is the addition of decimal format. Furthermore, in the recent years reversible logic has emerged as a promising computing paradigm having its applications in low power CMOS, quantum computing, nanotechnology, and optical computing. The major goal in reversible logic is to minimize the number of reversible gates and garbage outputs. Thus, this paper proposes the novel concept of pa...

  1. Magnetic Reversal on Vicinal Surfaces

    OpenAIRE

    Hyman, R. A.; Zangwill, A.; Stiles, M. D.

    1998-01-01

    We present a theoretical study of in-plane magnetization reversal for vicinal ultrathin films using a one-dimensional micromagnetic model with nearest-neighbor exchange, four-fold anisotropy at all sites, and two-fold anisotropy at step edges. A detailed "phase diagram" is presented that catalogs the possible shapes of hysteresis loops and reversal mechanisms as a function of step anisotropy strength and vicinal terrace length. The steps generically nucleate magnetization reversal and pin the...

  2. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRAFINE WC/Co CEMENTED CARBIDES WITH CUBIC BORON NITRIDE AND Cr₃C₂ ADDITIONS

    OpenAIRE

    Genrong Zhang; Haiyan Chen; Dong Lihua; Yin,; Li Kun

    2016-01-01

    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 dec...

  3. Response of Mg Addition on the Dendritic Structures and Mechanical Properties of Hypoeutectic Al-10Si (Wt Pct) Alloys

    Science.gov (United States)

    Karaköse, Ercan; Yildiz, Mehmet; Keskin, Mustafa

    2016-08-01

    Rapidly solidified hypoeutectic Al-10Si- xMg ( x = 0, 5, 10 wt pct) alloys were produced by the melt-spinning method. The phase composition was identified by X-ray diffractometry, and the microstructures of the alloys were characterized by scanning electron microscopy. The melting characteristics were studied by differential scanning calorimetry and differential thermal analysis under an Ar atmosphere. The mechanical properties of the melt-spun and conventionally solidified alloys were tested by tensile-strength and Vickers microhardness tests. The results illustrate that the cooling rate and solidification time of 89 μm thick melt-spun ribbon were estimated to be 2.97 × 107 K s-1 and 9.31 × 10-6 s, respectively. Nanoscale Si spot particles were observed growing on the surface of the dendritic α-Al matrix and the average sizes of these spots ranged from 10 to 50 nm. The improvement in the tensile properties and microhardness was related to structural refinement and the supersaturated α-Al solid solution; the nanoscale-dispersed Si spot particles made a significant improvement to the mechanical properties of the melt-spun ribbon. Detailed electrical resistivity tests of the ribbons were carried out at temperatures of 300 K to 800 K (27 °C to 527 °C).

  4. 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

  5. The mechanism of alkene addition to a nickel bis(dithiolene) complex: the role of the reduced metal complex.

    Science.gov (United States)

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

    2012-03-14

    The binding of an alkene by Ni(tfd)(2) [tfd = S(2)C(2)(CF(3))(2)] is one of the most intriguing ligand-based reactions. In the presence of the anionic, reduced metal complex, the primary product is an interligand adduct, while in the absence of the anion, dihydrodithiins and metal complex decomposition products are preferred. New kinetic (global analysis) and computational (DFT) data explain the crucial role of the anion in suppressing decomposition and catalyzing the formation of the interligand product through a dimetallic complex that appears to catalyze alkene addition across the Ni-S bond, leading to a lower barrier for the interligand adduct. PMID:22364208

  6. Microstructure, Texture and Mechanical Property Evolution during Additive Manufacturing of Ti6Al4V Alloy for Aerospace Applications

    OpenAIRE

    Antonysamy, Alphons Anandaraj

    2012-01-01

    Additive Manufacturing (AM) is an innovative manufacturing process which offers near-net shape fabrication of complex components, directly from CAD models, without dies or substantial machining, resulting in a reduction in lead-time, waste, and cost. For example, the buy-to-fly ratio for a titanium component machined from forged billet is typically 10-20:1 compared to 5-7:1 when manufactured by AM. However, the production rates for most AM processes are relatively slow and AM is consequently ...

  7. 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.

  8. 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.

  9. Tunable in-plane uniaxial anisotropy and the magnetization reversal mechanism of patterned high-frequency soft magnetic FeTa strips

    International Nuclear Information System (INIS)

    FeTa films with thickness of 110 nm are fabricated on glass substrates by magnetron sputtering, and then a series of strips is designed on the FeTa films by conventional optical lithography and the ion beam etching method. Patterned FeTa strips show a tunable in-plane uniaxial magnetic anisotropy property in contrast with the magnetic isotropic property of as-deposited FeTa thin films. The magnetization reversal mechanism of the patterned FeTa strips is investigated via the in-plane angular dependences of magnetization and coercivity. The angular dependence of coercivity (ADC) is explained well in terms of the two-phase model, giving good quantitative agreement with the experimentally measured M-shaped ADC curve. The domain structure and spatial resolution magneto-optical Kerr effect measurement indicate that the smaller the strip width, the stronger will be the anisotropy field. Regarding the dynamic magnetic properties, a transformation from Debye dispersion spectrum for strips with weak anisotropy to natural resonance spectrum for strips with strong anisotropy is finally obtained. The tunable in-plane anisotropy fields of the FeTa strips result in tunable high-frequency soft magnetic properties by altering the strip width, indicating that patterned FeTa strips have great potential in high-frequency soft magnetic application fields. (paper)

  10. Efficient triplet application in exciplex delayed-fluorescence OLEDs using a reverse intersystem crossing mechanism based on a ΔES-T of around zero.

    Science.gov (United States)

    Zhang, Tianyou; Chu, Bei; Li, Wenlian; Su, Zisheng; Peng, Qi Ming; Zhao, Bo; Luo, Yongshi; Jin, Fangming; Yan, Xingwu; Gao, Yuan; Wu, Hairuo; Zhang, Feng; Fan, Di; Wang, Junbo

    2014-08-13

    We demonstrate highly efficient exciplex delayed-fluorescence organic light-emitting diodes (OLEDs) in which 4,4',4″-tris[3-methylphenyl(phenyl)aminotriphenylamine (m-MTDATA) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were selected as donor and acceptor components, respectively. Our m-MTDATA:Bphen exciplex electroluminescence (EL) mechanism is based on reverse intersystem crossing (RISC) from the triplet to singlet excited states. As a result, an external quantum efficiency (EQE) of 7.79% at 10 mA/cm(2) was observed, which increases by 3.2 and 1.5 times over that reported in Nat. Photonics 2012, 6, 253 and Appl. Phys. Lett. 2012, 101, 023306, respectively. The high EQE would be attributed to a very easy RISC process because the energy difference between the singlet and triplet excited states is almost around zero. The verdict was proven by photoluminescence (PL) rate analysis at different temperatures and time-resolved spectral analysis. Besides, the study of the transient PL process indicates that the presence of an unbalanced charge in exciplex EL devices is responsible for the low EQE and high-efficiency roll-off. When the exciplex devices were placed in a 100 mT magnetic field, the permanently positive magnetoelectroluminescence and magnetoconductivity were observed. The magnetic properties confirm that the efficient exciplex EL only originates from delayed fluorescence via RISC processes but is not related to the triplet-triplet annihilation process. PMID:24840782

  11. Kinematic Analysis of Incomplete Gear Automatic Reverse Mechanism%不完全齿轮自动换向机构的运动分析

    Institute of Scientific and Technical Information of China (English)

    王猛; 李长春

    2012-01-01

    利用不完全齿轮机构的特点,设计一种齿轮式自动换向装置,实现输入轴连续单向转动,输出轴连续正反向转动,且保持输入轴的转速和输出轴的转速之比为定值.分析了不完全齿轮首齿和末齿的啮合线长度,在保证重合度等于1时,运用齿顶高修形法,避免了不完全齿轮传动的干涉现象发生.%By the characteristics of the incomplete gear mechanism, a kind of gear automatic reversing device to realize the input shaft continuous unidirectional turns is designed to realize, the output shaft positive and negative rotary under the condition of the input shaft speed and output speed ratio is fixed value. The length of line of action with the teeth at the end and the first of incomplete gear is analyzed, on the premise of contact ratio equal to one, using repair form method of addendum ,the interference phenomenon of the incomplete gear transmission is avoided.

  12. 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.

  13. 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.

    2016-07-01

    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.

  14. 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.

  15. Modeling the mechanical and aging properties of silicone rubber and foam - stockpile-historical & additively manufactured materials

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Weisgraber, T. H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gee, R. H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    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).

  16. 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)

  17. Reversible focal splenial lesions

    Energy Technology Data Exchange (ETDEWEB)

    Gallucci, Massimo; Limbucci, Nicola [University of L' Aquila, Department of Radiology, S. Salvatore Hospital, L' Aquila (Italy); Paonessa, Amalia [Loreto Nuovo Hospital, Department of Neuroradiology, Napoli (Italy); Caranci, Ferdinando [Federico II University, Department of Neurological Sciences, Napoli (Italy)

    2007-07-15

    Reversible focal lesions in the splenium of the corpus callosum (SCC) have recently been reported.They are circumscribed and located in the median aspect of the SCC. On MRI, they are hyperintense on T2-W and iso-hypointense on T1-W sequences, with no contrast enhancement. On DWI, SCC lesions are hyperintense with low ADC values, reflecting restricted diffusion due to cytotoxic edema. The common element is the disappearance of imaging abnormalities with time, including normalization of DWI. Clinical improvement is often reported. The most established and frequent causes of reversible focal lesions of the SCC are viral encephalitis, antiepileptic drug toxicity/withdrawal and hypoglycemic encephalopathy. Many other causes have been reported, including traumatic axonal injury. The similar clinical and imaging features suggest a common mechanism induced by different pathological events leading to the same results. Edema and diffusion restriction in focal reversible lesions of the SCC have been attributed to excitotoxic mechanisms that can result from different mechanisms; no unifying relationship has been found to explain all the pathologies associated with SCC lesions. In our opinion, the similar imaging, clinical and prognostic aspects of these lesions depend on a high vulnerability of the SCC to excitotoxic edema and are less dependent on the underlying pathology. In this review, the relevant literature concerning reversible focal lesions in the SCC is analyzed and hypotheses about their pathogenesis are proposed. (orig.)

  18. Reversal Effect and Mechanisms of Recombinant Human Tumor Necrosis Factor-NC Against the Doxorubicin Resistance in Leukemia K562/Doxorubicin Cells

    Directory of Open Access Journals (Sweden)

    Jing-hong ZHOU

    2015-09-01

    Full Text Available 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 fluorescence intensity was determined by flow 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<0.01. FCM analysis displayed that intra-cellular accumulation of Dox was significantly increased when combing Dox with rhTNF-NC. After treatment with rhTNF-NC, the expression of MDR gene (MDR1, MDR-associated protein (MRP, glutathione S transferase π (GSTπ mRNA, P glycoprotein (P-gp and protein kinase Cα (PKCα protein was down-regulated, while topoisomerase II (TopoII mRNA expression was up-regulated. 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.

  19. 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

  20. 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.

  1. Mechanical Properties of DS NiAl/Cr(Mo) Alloys with Low Addition of Hf for High-temperature Applications

    Institute of Scientific and Technical Information of China (English)

    Xinghao DU; Jianting GUO

    2005-01-01

    A multiphase NiAl-28Cr-5.85Mo-0.15Hf alloy, which was directionally solidified (DS) in an Al2O3-SiO2 mold by standard Bridgman method and then underwent prolonged solution and aging treatment was prepared. The microstructure, tensile properties as well as tensile creep of the heat-treated alloy at different temperatures were studied. The alloy was composed of NiAl, Cr(Mo) and Hf-rich phase and small amount of fine Heusler phase (Ni2AlHf). Although the present alloy exhibited high tensile strength at Iow temperature, it was weaker than that of system with high content Hf but still stronger than that of many NiAl-based alloys at high temperatures. The fracture toughness is lower than that of DS NiAl-28Cr-6Mo alloy. Nevertheless, advantageous effects on the mechanical properties, i.e.the decrease in brittle-to-ductile transition temperature (BDTT) were obtained for the Iow content of Hf. The obtained creep curves exhibit conventional shape: a short primary creep and long accelerated creep stages. The rupture properties of the heat-treated alloy follow the Monkman-Grant relationship, which exhibits similar creep behavior to that of NiAl/Cr(Mo) system with high Hf content.

  2. 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.

  3. 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.

  4. Reversible dementias

    OpenAIRE

    Tripathi, Manjari; Vibha, Deepti

    2009-01-01

    In recent years, more attention has been given to the early diagnostic evaluation of patients with dementia which is essential to identify patients with cognitive symptoms who may have treatable conditions. Guidelines suggest that all patients presenting with dementia or cognitive symptoms should be evaluated with a range of laboratory tests, and with structural brain imaging with computed tomography (CT) or magnetic resonance imaging (MRI). While many of the disorders reported as ‘reversible...

  5. 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.

  6. 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.

  7. 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. PMID:26275484

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Adsorption mechanism and dispersion efficiency of three anionic additives [poly(acrylic acid), poly(styrene sulfonate) and HEDP] on zinc oxide.

    Science.gov (United States)

    Dange, C; Phan, T N T; André, V; Rieger, J; Persello, J; Foissy, A

    2007-11-01

    Adsorption on ZnO of sodium poly(acrylate) (PAA), sodium poly(styrene sulfonate) (PSS) and a monomer surfactant [hydroxyethylidene diphosphonate (HEDP)] was investigated in suspensions initially equilibrated at pH 7. Results demonstrate interplay in the adsorption mechanism between zinc complexation, salt precipitation, and ZnO dissolution. In the case of PAA, the adsorption isotherm exhibits a maximum attributed to the precipitation of zinc polyacrylate. PSS and HEDP formed high-affinity adsorption isotherms, but the plateau adsorption of HEDP was significantly lower than that of PSS. The adsorption isotherm of each additive is divided into two areas. At low additive concentration (high zinc/additive ratio), the total zinc concentration in the solution decreased and the pH increased upon addition. At a higher additive ratio, zinc concentration and pH increased with the organic concentration. The increase in pH is due to the displacement of hydroxyl ions from the surface and the increase in zinc concentration results from the dissolution of ZnO due to the complexation of zinc ions by the organics. The stability of the ZnO dispersions was investigated by measurement of the particle size distribution after addition of various amounts of polymers. The three additives stabilized the ZnO dispersions efficiently once full surface coverage was reached. PMID:17720181

  13. 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.

  14. Cognitive training with and without additional physical activity in healthy older adults: cognitive effects, neurobiological mechanisms, and prediction of training success

    OpenAIRE

    Julia eRahe; Jutta eBecker; Fink, Gereon R.; Josef eKessler; Juraj eKukolja; Andreas eRahn; Rosen, Jan B.; Florian eSzabados; Brunhilde eWirth; Elke eKalbe

    2015-01-01

    Data is inconsistent concerning the question whether cognitive-physical training (CPT) yields stronger cognitive gains than cognitive training (CT). Effects of additional counseling, neurobiological mechanisms, and predictors have scarcely been studied. Healthy older adults were trained with CT (n = 20), CPT (n = 25), or CPT with counseling (CPT+C; n = 23). Cognition, physical fitness, BDNF, IGF-1, and VEGF were assessed at pre- and post-test. No interaction effects were found except for one ...

  15. 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. PMID:27157725

  16. 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.

  17. Numerical investigation of the mechanical properties of the additive manufactured bone scaffolds fabricated by FDM: The effect of layer penetration and post-heating.

    Science.gov (United States)

    Naghieh, S; Karamooz Ravari, M R; Badrossamay, M; Foroozmehr, E; Kadkhodaei, M

    2016-06-01

    In recent years, thanks to additive manufacturing technology, researchers have gone towards the optimization of bone scaffolds for the bone reconstruction. Bone scaffolds should have appropriate biological as well as mechanical properties in order to play a decisive role in bone healing. Since the fabrication of scaffolds is time consuming and expensive, numerical methods are often utilized to simulate their mechanical properties in order to find a nearly optimum one. Finite element analysis is one of the most common numerical methods that is used in this regard. In this paper, a parametric finite element model is developed to assess the effects of layers penetration׳s effect on inter-layer adhesion, which is reflected on the mechanical properties of bone scaffolds. To be able to validate this model, some compression test specimens as well as bone scaffolds are fabricated with biocompatible and biodegradable poly lactic acid using fused deposition modeling. All these specimens are tested in compression and their elastic modulus is obtained. Using the material parameters of the compression test specimens, the finite element analysis of the bone scaffold is performed. The obtained elastic modulus is compared with experiment indicating a good agreement. Accordingly, the proposed finite element model is able to predict the mechanical behavior of fabricated bone scaffolds accurately. In addition, the effect of post-heating of bone scaffolds on their elastic modulus is investigated. The results demonstrate that the numerically predicted elastic modulus of scaffold is closer to experimental outcomes in comparison with as-built samples. PMID:26874065

  18. Effect of additive V2O5 on sintering mechanism and properties of inert anodes of NiFe2O4 spinel

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In order to improve the properties of inert anode of NiFe2O4 spinel, some additive V2O5 was added to raw materials-powders of NiO and Fe2O3. The powders of NiO, Fe2O3 were mixed with slight amount of V2O5, then they are moulded and sintered at 1200℃ for 6h. The sintering mechanism of powders of NiO and Fe2O3 with some additive V2 O5 was researched. The effect of V2O5 on density, electrical conductivity and corrosion resistance of inert anode of NiFe2O4 spinel was studied at the same time. The results show that the sintering mechanism for powders of NiO and Fe2O3 with some additive V2O5 is liquid-phase sintering. Additive V2O5 can increase the density of the samples, especially it improves the corrosion resistance of the samples remarkably. When the amount of V2 O5 is 1.5 %, the sample's corrosion rate is 1/80 of that of sample without V2 O5. But the electrical conductivity of the samples with V2O5 is lower than that of the sample without V2O5.

  19. 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.

  20. 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.

  1. 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.

  2. The effect of location on the microstructure and mechanical properties of titanium aluminides produced by additive layer manufacturing using in-situ alloying and gas tungsten arc welding

    International Nuclear Information System (INIS)

    An innovative and low cost additive layer manufacturing (ALM) process is used to produce γ-TiAl based alloy wall components. Gas tungsten arc welding (GTAW) provides the heat source for this new approach, combined with in-situ alloying through separate feeding of commercially pure Ti and Al wires into the weld pool. This paper investigates the morphology, microstructure and mechanical properties of the additively manufactured TiAl material, and how these are affected by the location within the manufactured component. The typical additively layer manufactured morphology exhibits epitaxial growth of columnar grains and several layer bands. The fabricated γ-TiAl based alloy consists of comparatively large α2 grains in the near-substrate region, fully lamellar colonies with various sizes and interdendritic γ structure in the intermediate layer bands, followed by fine dendrites and interdendritic γ phases in the top region. Microhardness measurements and tensile testing results indicated relatively homogeneous mechanical characteristics throughout the deposited material. The exception to this homogeneity occurs in the near-substrate region immediately adjacent to the pure Ti substrate used in these experiments, where the alloying process is not as well controlled as in the higher regions. The tensile properties are also different for the vertical (build) direction and horizontal (travel) direction because of the differing microstructure in each direction. The microstructure variation and strengthening mechanisms resulting from the new manufacturing approach are analysed in detail. The results demonstrate the potential to produce full density titanium aluminide components directly using the new additive layer manufacturing method

  3. Effect of ZrO{sub 2} addition on the mechanical properties of porous TiO{sub 2} bone scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Tiainen, Hanna [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, NO-0317 Oslo (Norway); Eder, Georg [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, NO-0317 Oslo (Norway); Institute of Medical and Polymer Engineering, Chair of Medical Engineering, Technische Universitaet Muenchen, Boltzmannstrasse 15, 85748 Garching (Germany); Nilsen, Ola [Department of Chemistry, University of Oslo, PO Box 1033 Blindern, NO-0315 Oslo (Norway); Haugen, Havard J., E-mail: h.j.haugen@odont.uio.no [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, NO-0317 Oslo (Norway)

    2012-08-01

    This study aimed at the investigation of the effect of zirconium dioxide (ZrO{sub 2}) addition on the mechanical properties of titanium dioxide (TiO{sub 2}) bone scaffolds. The highly biocompatible TiO{sub 2} has been identified as a promising material for bone scaffolds, whereas the more bioinert ZrO{sub 2} is known for its excellent mechanical properties. Ultra-porous TiO{sub 2} scaffolds (> 89% porosity) were produced using polymer sponge replication with 0-40 wt.% of the TiO{sub 2} raw material substituted with ZrO{sub 2}. Microstructure, chemical composition, and pore architectural features of the prepared ceramic foams were characterised and related to their mechanical strength. Addition of 1 wt.% of ZrO{sub 2} led to 16% increase in the mean compressive strength without significant changes in the pore architectural parameters of TiO{sub 2} scaffolds. Further ZrO{sub 2} additions resulted in reduction of compressive strength in comparison to containing no ZrO{sub 2}. The appearance of zirconium titanate (ZrTiO{sub 4}) phase was found to hinder the densification of the ceramic material during sintering resulting in poor intergranular connections and thus significantly reducing the compressive strength of the highly porous ceramic foam scaffolds. - Highlights: Black-Right-Pointing-Pointer Open porous scaffold with porosity in the range of 89.0 to 92.8% produced. Black-Right-Pointing-Pointer Adding 1 wt.% of ZrO{sub 2} led to 16% increase in strength without changing porosity. Black-Right-Pointing-Pointer Further ZrO{sub 2} additions resulted in reduced compressive strength versus no ZrO{sub 2}. Black-Right-Pointing-Pointer Presence of zirconium titanate (ZrTiO{sub 4}) phase found to hinder the densification. Black-Right-Pointing-Pointer Appearance of ZrTiO{sub 4} resulted in poor intergranular connections.

  4. 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.

  5. 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.

  6. 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...

  7. 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.

  8. A study on the effects of aging treatment and W addition on the mechanical properties and sensitization behaviors of Fe-Cr-Mn stainless steels

    International Nuclear Information System (INIS)

    The characteristics of the mechanical properties and sensitization behaviors in Fe-Cr-Mn stainless steels by W addition and aging treatment were studied. Yield strength, tensile strength, elongation and impact energy were decreased, and hardness was slightly increased by aging treatment. W-containing alloys showed especially a larger degree of brittle characteristics due to the hard chi(χ) phase formed from the decomposition of ferrite. Carbides precipitated in grain boundary had a bad effect on impact energy rather than strength and hardness. Ni addition suppressed the formation of ferrite and resulted in the some improvement of mechanical properties. Anodic polarization tests showed that the corrosion resistance of aged alloys was decreased by the formation of carbides and secondary austenites. It was observed that W addition made no improvement of the pitting potential and passive current density of aged alloys in the HCl solution. But Ni and W decreased critical current density in the sulfuric acid and made easier formation of passive film, contributing to corrosion resistance. From the results of EPR (Electrochemical Potentiokinetic Reactivation), DOS (Degree of Sensitization) was increased with aging time and carbides and ferrite was preferentially attacked. It was observed that Ni delayed the sensitization. It can be concluded from the previous results that the selective dissolution of ferrite is due to the ferrite decomposition to chi (χ) phase and secondary austenites. In the secondary austenite Cr and W which are known to improve the corrosion resistance were depleted. Therefore, it seems that ferrite phase became sensitive to corrosion

  9. Effects of Aging and W Addition on the Corrosion Resistance and Mechanical Properties of Fe-Cr-Mn-N Stainless Steels

    International Nuclear Information System (INIS)

    The characteristics of the mechanical properties and sensitization behaviors in Fe-Cr-Mn stainless steels by W addition and aging treatment were studied. Yield strength, tensile strength, elongation and impact energy decreased, and hardness increased slightly by aging treatment. W-containing alloys showed especially a larger degree of brittle characteristics due to the hard chi(χ) phase formed from the decomposition of ferrite. Carbides precipitated in grain boundary had a bad effect on impact energy rather than on strength and hardness. Ni addition suppressed the formation of ferrite and resulted in some improvement of mechanical properties. Anodic polarization tests showed that the corrosion resistance of aged alloys decreased by the formation of carbides and secondary austenite. It was observed that W addition made no improvement of the pitting potential and passive current density of aged alloys in the HCI solution. But Ni and W decreased critical current density in the sulfuric acid and made easier formation of passive film, contributing to corrosion resistance. From the results of EPR (Electrochemical Potentiokinetic Reactivation). DOS (Degree of Sensitization) increased with aging time and carbides and ferrite were preferentially attacked. It was observed that Ni delayed the sensitization. It can be concluded from the previous results that the selective dissolution of ferrite is due to the ferrite decomposition to chi (χ) phase and secondary austenite. In the secondary austenite. Cr and W which are known to improve the corrosion resistance were depleted. Therefore, it seems that ferrite phase became sensitive to corrosion

  10. Kinetic Line Voronoi Operations and Their Reversibility

    DEFF Research Database (Denmark)

    Mioc, Darka; Anton, François; Gold, Christopher;

    2010-01-01

    , as the basic algorithms for addition, deletion and moving of spatial objects. Having developed reversible map operations on the lowest level, we were able to maintain reversibility of the map updates at higher levels as well. The reversibility in GIS can be used for efficient implementation of rollback...

  11. The effects of small titanium additions on the mechanical properties and the microstructures of controlled rolled niobium-bearing HSLA plate steels

    Energy Technology Data Exchange (ETDEWEB)

    He Kejian (Univ. of Strathclyde, Glasgow (United Kingdom)); Baker, T.N. (Univ. of Strathclyde, Glasgow (United Kingdom))

    1993-09-15

    Effects of small Ti additions (0.010, 0.022%) on mechanical properties and microstructures of Nb-bearing HSLA plate steels under two different rolling schedules were investigated. For comparison, a Ti-free steel was controlled rolled to 814 C. A side effect of the Ti additions was observed on strength of Nb-bearing steels. The lower yield stress values and hardness levels for all Ti-Nb steels were reduced both in as-rolled and normalized conditions, depending on Ti/N ratio and details of thermomechanical process. However, the Ti-Nb steels with a lower finish rolling temperature (FRT), 800 C, showed better toughness than the Ti-free control steel. For Ti-Nb steels, toughness was improved significantly by lowering the FRT from 940 to 800 C, owing mainly to considerable refinement of ferrite grain sizes and fewer fine carbides available for dispersion hardening. No advantages were observed for over-stoichiometric Ti addition (Ti/N=4.4). The steel with under-stoichiometric Ti addition (Ti/N = 2) and a lower FRT (800 C) showed best overall mechanical and toughness properties among all processed Ti-Nb steels. Precipitation of Nb nitrides and carbides in the Nb steels was changed by Ti additions which led to formation of complex Ti-Nb nitrides and carbonitrides, i.e. Ti-rich plates and cuboids. Moreover, these plates and cuboids acted as nucleating cores on which pure carbides formed, i.e. Nb carbide in 0.01%Ti steels whereas Nb-rich Ti-Nb carbide in 0.022%Ti steels. In as-rolled samples, no Al was found in the complex particles or as individual AlN while in the normalized condition, fine AlN precipitates were detected frequently with understoichiometric titanium addition (0.01%Ti), whereas formation of AlN was suppressed by the over-stoichiometric Ti addition (in 0.022%Ti). The Ti/N ratio, therefore, has a strong influence on type of precipitation and size.

  12. Vasectomy Reversal

    Medline Plus

    Full Text Available ... of the vas. This installation process should not meet any resistance. When there is an additional point ... looks like a figure of 8 because they meet at the 6:00 position. I'm placing ...

  13. Vasectomy Reversal

    Medline Plus

    Full Text Available ... ability to do the procedure or the post-operative course. So careful, meticulous hemostasis is obtained. At ... additional issues in the scrotum in the post-operative period, making examination of understanding of what one ...

  14. Effect of Addition of Plants-Derived Polyamide 11 Elastomer on the Mechanical and Tribological Properties of Hemp Fiber Reinforced Polyamide 1010 Composites

    OpenAIRE

    Mukaida, Jun; Nishitani, Yosuke; Kitano, Takeshi

    2015-01-01

    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 t...

  15. 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.

  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. 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.

  18. 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

    2016-06-01

    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.

  19. 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.

  20. 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.

  1. Periodicity and Immortality in Reversible Computing

    OpenAIRE

    Kari, Jarkko; Ollinger, Nicolas

    2008-01-01

    Additional material available on the web at http://www.lif.univ-mrs.fr/~nollinge/rec/gnirut/ We investigate the decidability of the periodicity and the immortality problems in three models of reversible computation: reversible counter machines, reversible Turing machines and reversible one-dimensional cellular automata. Immortality and periodicity are properties that describe the behavior of the model starting from arbitrary initial configurations: immortality is the property of having at ...

  2. 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.

  3. The Influence of Sc and Zr Additions on the Microstructure and Mechanical Behavior of Ultrafine Grained Al-Mg Alloys Processed by Powder Metallurgy

    Science.gov (United States)

    Harrell, Tammy Jeanne

    Additions of Sc and Zr to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc and Zr significantly increase the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultra-fine-grained (UFG) microstructure (e.g., 100's nm). Accordingly, we investigate the microstructural evolution and mechanical behavior of four powder metallurgy UFG Al-Mg-Sc-(Zr) compositions and compared the results to those of equivalent fine-grained (FG) compositions - Al-5Mg-0.1Sc, Al-3Mg-0.5Sc, Al-5Mg-0.4Sc and Al-5Mg-0.2Sc-0.2Zr (wt.%). Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic (DMD) forging. Under identical processing conditions, UFG ternary Al-5Mg-0.4Sc materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 - 3 μm apart, while precipitates in the FG materials have an average diameter of 24 nm and are spaced 50 - 200 nm apart. The strengthening mechanisms are quantitatively evaluated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are dispersion strengthening due to the presence of Mg-rich oxides/nitrides and precipitate strengthening, respectively. Preliminary results suggest that replacing 0.2 wt% Sc with Zr results in higher strength, lower ductility and a change in precipitate distribution.

  4. 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.

  5. Effect of Ti additive on (Cr, Fe){sub 7}C{sub 3} carbide in arc surfacing layer and its refined mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Yefei; Yang Yulin; Yang Jian; Hao Feifei [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Li Da [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); School of Material Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Ren Xuejun [School of Engineering, Liverpool John Moores University, Liverpool L3 3AF (United Kingdom); Yang Qingxiang, E-mail: qxyang@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2012-06-15

    Arc surfacing layer of hypoeutectic high chromium cast iron (HCCI) expects refiner carbides in the microstructure to improve its mechanical properties. In this paper, Ti additive as a strong carbide forming element was added in the hypoeutectic HCCI arc surfacing layer. Microstructure of titaniferous hypoeutectic HCCI was studied by optical microscopy, X-ray diffraction and field emission scanning electronic microscopy with energy dispersive spectrometer. Furthermore, the M(M = Cr, Fe){sub 7}C{sub 3} carbide refinement mechanism was explained by the phase diagram calculation and lattice misfit theory. The results show that, the M{sub 7}C{sub 3} carbide in arc surfacing microstructure of hypoeutectic HCCI has been refined with 2 wt.% Ti additive, and TiC carbide can be observed in/around the M{sub 7}C{sub 3} carbide. With Ti addictive increasing, the micro-hardness along the depth in profile section of layer becomes more uniform, and the wear resistance has been improved. According to the phase diagram calculation, MC carbide precipitates prior to M{sub 7}C{sub 3} carbide in Fe-Cr-C-Ti alloy. In addition, the lattice misfit between (1 1 0){sub TiC} and (010){sub Cr{sub 7C{sub 3}}} is 9.257%, which indicates that the TiC as heterogeneous nuclei of the M{sub 7}C{sub 3} is medium effective. Therefore, the M{sub 7}C{sub 3} carbide can be refined.

  6. Effect of minor addition of vanadium on mechanical properties and microstructures of as-extruded near eutectic Al–Si–Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yuna; Liao, Hengcheng, E-mail: hengchengliao@seu.edu.cn; Zhou, Kexin

    2014-04-01

    Mechanical properties of near eutectic Al–12.5 wt%Si–0.6 wt%Mg alloys with and without addition of V were tested. Results show that addition of 0.1 wt% V only has a minor influence on the tensile properties of near eutectic Al–Si–Mg alloy in as-cast and as-homogenized conditions. However, it can significantly improve the tensile properties in as-extruded condition. The YS is enhanced nearly 50% and the elongation can reach 14%. Three factors that may contribute to the enhancement of YS were analyzed by EBSD, XRD and TEM investigation, i.e. Δσ{sub gb} (the strengthening from (sub-) grain boundaries), M (Taylor factor) and τ{sub tot} (critical resolved shear stress). Results show that the higher τ{sub tot} in the alloy with V addition is the main contributor to the higher YS. According to the TEM observation and EDX analysis, the fine precipitates contributed to the higher τ{sub tot} in 4{sup #} alloy are quaternary AlFeVSi phases.

  7. Effect of minor addition of vanadium on mechanical properties and microstructures of as-extruded near eutectic Al–Si–Mg alloy

    International Nuclear Information System (INIS)

    Mechanical properties of near eutectic Al–12.5 wt%Si–0.6 wt%Mg alloys with and without addition of V were tested. Results show that addition of 0.1 wt% V only has a minor influence on the tensile properties of near eutectic Al–Si–Mg alloy in as-cast and as-homogenized conditions. However, it can significantly improve the tensile properties in as-extruded condition. The YS is enhanced nearly 50% and the elongation can reach 14%. Three factors that may contribute to the enhancement of YS were analyzed by EBSD, XRD and TEM investigation, i.e. Δσgb (the strengthening from (sub-) grain boundaries), M (Taylor factor) and τtot (critical resolved shear stress). Results show that the higher τtot in the alloy with V addition is the main contributor to the higher YS. According to the TEM observation and EDX analysis, the fine precipitates contributed to the higher τtot in 4# alloy are quaternary AlFeVSi phases

  8. 有机可逆热致变色材料的变色机理及应用进展%Color-changing Mechanism and Application Development of Organic Reversible Thermochromic Materials

    Institute of Scientific and Technical Information of China (English)

    张凤; 管萍; 胡小玲

    2012-01-01

    The low temperature color-changing properties of organic reversible thermochromic materials are superior to traditional inorganic materials and have aroused wide concern. Recently, so many thermochromic materials have been developed, but they have different color-changing mechanism. The effects of molecular structural changes on color-changing mechanism of organic reversible thermochromic materials are introduced. Applications of organic reversible thermochromic materials are reviewed.%有机可逆热致变色材料低温变色性能优于传统的无机可逆变色材料,已受到广泛的关注.目前,研究与开发的有机可逆热致变色材料已不少,其变色机理不尽相同.重点介绍了分子结构的变化对有机可逆热致变色材料变色机理的影响,并概述了有机可逆热致变色材料的应用.

  9. 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

  10. Achieving high superplasticity of a traditional thermal–mechanical processed non-superplastic Al–Zn–Mg alloy sheet by low Sc additions

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Yulu [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Xu, GuoFu, E-mail: csuxgf66@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Nonferrous Materials Science and Engineering of Ministry of Education, Central South University, Changsha 410083 (China); Zhou, Liqi; Xiao, Dan [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Deng, Ying, E-mail: csudengying@163.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Yin, Zhimin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Peng, Bing [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Pan, Qinglin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Wang, Yingjun; Lu, Liying [Northeast Light Alloy Co. Ltd, Harbin 150060 (China)

    2015-07-25

    Highlights: • The superplastic of the Al–Zn–Mg–Sc–Zr alloy subjected to a traditional thermal–mechanical processing was investigated. • The boundary characteristics and thermal stability of the Al–Zn–Mg–Sc–Zr alloy were examined. • The deformation mechanism for Al–Zn–Mg–Sc–Zr alloy was analyzed. - Abstract: The non-superplastic Al–Zn–Mg alloy sheet produced by a simple traditional thermal–mechanical processing can achieve high superplasticity at the temperatures ranging from 450 to 500 °C and the strain rates ranging from 1 × 10{sup −3} to 1 × 10{sup −2} s{sup −1} by low scandium additions in the presence of 0.10% Sc (wt.%). An elongation of 1050% is obtained at 500 °C and 5 × 10{sup −3} s{sup −1}. Analyses on the superplastic data reveal that the average values of the strain rate sensitivity and the activation energy of the Al–Zn–Mg–Sc–Zr alloy are about 0.5 and 85 kJ/mol{sup −1}, respectively. The microstructural results show that the studied alloy consists of 3.14 μm grains characterized by a high fraction of low angle grain boundaries and strong β-fiber rolling textures. During superplastic deformation, low angle grain boundaries gradually transfer into high angle grain boundaries to sustain grain boundary sliding, and the texture intensity diminishes. Besides, β-fiber rolling textures weaken and cube and random textures are dominant in the superplastic deformed alloy. Superior superplastic ductility of the Al–Zn–Mg–Sc–Zr alloy is ascribed to the coherent 10–20 nm Al{sub 3}Sc{sub x}Zr{sub 1−x} particles that strongly retard recrystallization grain growth. Analyses of the superplastic data indicate that grain boundary sliding is the predominant deformation mechanism.

  11. Effects of SnO2, WO3, and ZrO2 addition on the magnetic and mechanical properties of NiCuZn ferrites

    International Nuclear Information System (INIS)

    In this study, the effects of SnO2, WO3 and ZrO2 addition at levels up to 5 wt% on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 ceramics were investigated. Only Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with a SnO2 addition of ≥3.5 wt% required a densification temperature of 1150 °C, while the others reached maximum densification at 1075 °C. All samples revealed a pure spinel phase and a uniform microstructure, except for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with the WO3 addition, which showed an exaggerated grain growth accompanied with a small amount of needle-shaped Cu0.85Zn0.15WO4 second phase. The fracture mode in the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic revealed a transgranular phase, as the CuO second phase increased the grain boundary strength; the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics sintered with 5 wt% additives showed an intergranular phase. The Vickers hardness and the bending strength of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic were 733.6 and 62.0 MPa, respectively. The Vickers hardness of the ferrite with added SnO2 or ZrO2 showed only a slight improvement, while an apparent change (832.7) was observed with the addition of 5.0 wt% WO3. The bending strength of the ferrite was optimized at 75.7 MPa with 2.0 wt% SnO2 and at 90.5 MPa with 3.5 wt% ZrO2, while that of the ferrite sintered with WO3 added dropped gradually from 62.0 to 47.7 MPa as the amount of WO3 was increased from 0 to 5.0 wt% due to the non-uniform microstructure. The pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic sintered at 1075 °C had an initial permeability of 356.9 and a quality factor of 71.2. The addition of ZrO2 led to a significant increase in the initial permeability (588.4 at 5.0 wt% ZrO2), but a slight decline in the quality factor (56.6 at 5.0 wt% ZrO2). - Highlights: • Effects of additives on the physical properties of NiCuZn ceramics were studied. • NiCuZn with WO3 addition showed an abnormal grain growth and Cu0.85Zn0.15WO4 phase. • Ferrite with 5.0 wt% WO3 addition showed nearly 15

  12. Organocatalytic conjugate-addition polymerization of linear and cyclic acrylic monomers by N-heterocyclic carbenes: mechanisms of chain initiation, propagation, and termination.

    Science.gov (United States)

    Zhang, Yuetao; Schmitt, Meghan; Falivene, Laura; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene Y-X

    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 (I(t)Bu), 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 I(t)Bu. 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, I(t)Bu 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 M(n) = 70-85 kg/mol, regardless of the [MMBL]/[I(t)Bu] ratio employed. The I(t)Bu-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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. Reversible brazing process

    Science.gov (United States)

    Pierce, Jim D.; Stephens, John J.; Walker, Charles A.

    1999-01-01

    A method of reversibly brazing surfaces together. An interface is affixed to each surface. The interfaces can be affixed by processes such as mechanical joining, welding, or brazing. The two interfaces are then brazed together using a brazing process that does not defeat the surface to interface joint. Interfaces of materials such as Ni-200 can be affixed to metallic surfaces by welding or by brazing with a first braze alloy. The Ni-200 interfaces can then be brazed together using a second braze alloy. The second braze alloy can be chosen so that it minimally alters the properties of the interfaces to allow multiple braze, heat and disassemble, rebraze cycles.

  18. 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.

  19. Simulation studies of nucleation of ferroelectric polarization reversal.

    Energy Technology Data Exchange (ETDEWEB)

    Brennecka, Geoffrey L.; Winchester, Benjamin Michael

    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.

  20. Effect of nano-ZrO2 addition on microstructure, mechanical property and thermal shock behaviour of dense chromic oxide refractory material

    International Nuclear Information System (INIS)

    To obtain a good performance hot-face lining material in gasifier, nano-ZrO2, up to 5 wt %, was added into chromic oxide powder with 3 wt % TiO2 followed by sintering at 1500°C for 2.5 h. The effect of nano-ZrO2 addition on microstructure, mechanical property and thermal shock behaviour was studied. ZrO2 promoted densification at contents higher than 1 wt %. Microcracks and phase transformation toughened the dense chromic oxide refractory material. The main reason for decrease of strength was the existence microcracks in specimens and weakening of intergranular fracture. Dense chromic oxide refractory material with 2∼3 wt % nano-ZrO2 possessed good densification, uniform microstructure, normal mechanical property and proper thermal shock resistance. The rupture strength retention ratio was nearly twice than that of chromic oxide material without ZrO2 after three cycles of quenching test from 950°C to cold water. (author)

  1. 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.

  2. 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.

  3. Reversible watermarking for images

    Science.gov (United States)

    van Leest, Arno J.; van der Veen, Michiel; Bruekers, Fons

    2004-06-01

    Reversible watermarking is a technique for embedding data in a digital host signal in such a manner that the original host signal can be restored in a bit-exact manner in the restoration process. In this paper, we present a general framework for reversible watermarking in multi-media signals. A mapping function, which is in general neither injective nor surjective, is used to map the input signal to a perceptually equivalent output signal. The resulting unused sample values of the output signal are used to encode additional (watermark) information and restoration data. At the 2003 SPIE conference, examples of this technique applied to digital audio were presented. In this paper we concentrate on color and gray-scale images. A particular challenge in this context is not only the optimization of rate-distortion, but also the measure of perceptual quality (i.e. the distortion). In literature distortion is often expressed in terms of PSNR, making comparison among different techniques relatively straightforward. We show that our general framework for reversible watermarking applies to digital images and that results can be presented in terms of PSNR rate-distortions. However, the framework allows for more subtle signal manipulations that are not easily expressed in terms of PSNR distortion. These changes involve manipulations of contrast and/or saturation.

  4. 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 %.

  5. Length-scale dependent microalloying effects on precipitation behaviors and mechanical properties of Al–Cu alloys with minor Sc addition

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, L.; Li, J.K. [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Liu, G., E-mail: lgsammer@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, R.H. [School of Materials Science and Engineering, Xi' an University of Technology, Xi' an 710048 (China); Chen, B.A.; Zhang, J.Y. [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Sun, J., E-mail: junsun@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Yang, M.X.; Yang, G. [Central Iron and Steel Research Institute, Beijing 100081 (China); Yang, J.; Cao, X.Z. [Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2015-06-18

    Heat-treatable Al alloys containing Al–2.5 wt% Cu (Al–Cu) and Al–2.5 wt% Cu–0.3 wt% Sc (Al–Cu–Sc) with different grain length scales, i.e., average grain size >10 μm ( defined coarse grained, CG), 1–2 μm (fine grained, FG), and <1 μm (ultrafine grained, UFG), were prepared by equal-channel angular pressing (ECAP). The length scale and Sc microalloying effects and their interplay on the precipitation behavior and mechanical properties of the Al–Cu alloys were systematically investigated. In the Al–Cu alloys, intergranular θ-Al{sub 2}Cu precipitation gradually dominated by sacrificing the intragranular θ′-Al{sub 2}Cu precipitation with reducing the length scale. Especially in the UFG regime, only intergranular θ-Al{sub 2}Cu particles were precipitated and intragranular θ′-Al{sub 2}Cu precipitation was completely disappeared. This led to a remarkable reduction in yield strength and ductility due to insufficient dislocation storage capacity. The minor Sc addition resulted in a microalloying effect in the Al–Cu alloy, which, however, is strongly dependent on the length scale. The smaller is the grain size, the more active is the microalloying effect that promotes the intragranular precipitation while reduces the intergranular precipitation. Correspondingly, compared with their Sc-free counterparts, the yield strength of post-aged CG, FG, and UFG Al–Cu alloys with Sc addition increased by ~36 MPa, ~56 MPa, and ~150 MPa, simultaneously in tensile elongation by ~20%, ~30%, and 280%, respectively. The grain size-induced evolutions in vacancy concentration/distribution and number density of vacancy-solute/solute–solute clusters and their influences on precipitation nucleation and kinetics have been comprehensively considered to rationalize the length scale-dependent Sc microalloying mechanisms using positron annihilation lifetime spectrum and three dimension atom probe. The increase in ductility was analyzed in the light of Sc microalloying

  6. Mechanism of Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase by a Stavudine Analogue, 4′-Ethynyl Stavudine Triphosphate▿

    OpenAIRE

    Yang, Guangwei; Wang, Jimin; Cheng, Yao; Dutschman, Ginger E.; Tanaka, Hiromichi; Baba, Masanori; Cheng, Yung-Chi

    2008-01-01

    2′,3′-Didehydro-3′-deoxy-4′-ethynylthymidine (4′-Ed4T), a recently discovered nucleoside reverse transcriptase (RT) inhibitor, exhibits 5- to 10-fold-higher activity against human immunodeficiency virus type 1 (HIV-1) and less cytotoxicity than does its parental compound d4T (stavudine). Using steady-state kinetic approaches, we have previously shown that (i) 4′-ethynyl-d4T triphosphate (4′-Ed4TTP) inhibits HIV-1 RT more efficiently than d4TTP does and (ii) its inhibition efficiency toward th...

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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...

  12. 基于全球利基市场的后发企业逆向创新机理%Reverse Innovation Mechanism of Latecomer Enterprise Based on Global Niche Market

    Institute of Scientific and Technical Information of China (English)

    徐娜娜; 徐雨森

    2015-01-01

    Based on the reverse innovation cases ,namely Haier ,Netac Mindray and Sunward Intelligent ,this paper explores the mechanism of reverse innovation of latecomer enterprises based on global niche market. The results prove that local innovation resources with comparative ad‐vantages is the important foundation for reverse innovation ,and diversified cooperation and the synergy between technological and non‐techno‐logical are effective way to obtain resources ,and reverse innovation is helpful to construct core technology capability ,and then ensure continued innovation .%以海尔、迈瑞和山河智能的逆向创新为案例,探究了全球利基市场导向下后发企业逆向创新的实现机理。研究发现:在全球利基市场导向的逆向创新中,后发企业需要注重利用本土比较优势资源,尤其是本土大规模、多层次的市场结构可使企业获得相对宽松的市场环境;后发企业可通过多元化的国际联接机制、技术与非技术的协同创新来弥补创新资源不足和提高创新效率。另外,全球利基市场导向的逆向创新有助于后发企业构建核心技术能力,从而利于持续创新。

  13. Effect of addition of organo clay on mechanical properties and dynamic-mechanical based TPV; Preparacao de termoplasticos vulcanizados dinamicamente (TPV) de NBR/PP com nanocargas de argila

    Energy Technology Data Exchange (ETDEWEB)

    Honorato, Luciana R.; Silva, Adriana A.; Soares, Bluma G. [Universidade Federal do Rio de Janeiro - UFRJ, Instituto de Macromoleculas Professora Eloisa Mano, Rio de Janeiro, RJ (Brazil); Soares, Ketly P. [Centro Universitario do Leste de Minas Gerais (UNILESTEMG) - Coronel Fabriciano, MG (Brazil)

    2011-07-01

    The effect of organophilic clay on the mechanical and dynamical-mechanical properties of thermoplastic elastomers based on polypropylene (PP) and nitrile rubber (NBR) was investigated. The addition of clay was performed from a master batch prepared by a solution intercalation of NBR inside the clay galleries. Since the PP/NBR blend is highly incompatible, PP functionalized with maleic anhydride (PP-g-MA) and carboxylated NBR (XNBR) were employed as compatibilizing system together with triethylene-tetramine (TETA) used as coupling agent. The addition of Clay inside the elastomeric phase of the TPV resulted in a significant decrease of the elongation at break without changes on the tensile strength. The presence of clay also promoted a slight increase of the storage modulus and the glass transition temperature. The small angle X ray scattering confirmed the high dispersion of clay inside the TPV. Analysis of light scattering small angle (SAXS) confirmed the high dispersion of clay in the matrix of the TPV. (author)

  14. 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

  15. Effect of boron additions and processing on microstructure and mechanical properties of a titanium alloy Ti–6.5Al–3.3Mo–0.3Si

    International Nuclear Information System (INIS)

    The effects of boron additions in an amount of 0.1–2 wt%, thermomechanical processing and heat treatment on microstructure and mechanical properties of a two-phase titanium alloy Ti–6.5Al–3.3Mo–0.3Si alloy have been investigated. Depending on the boron amount, the materials under study were divided into two groups: (1) boron modified alloys containing ~0.1 wt% of boron and (2) discontinuously reinforced metal matrix Ti–TiB based composites containing 1.5–2 wt% of boron. Boron additions led to formation of TiB whiskers, which were predominantly located along boundaries of prior β-grains and α-colonies resulting in refined as-cast microstructure. Multiple 3D forging at T=650–700 °C applied for the boron modified alloys resulted in formation of ultrafine-grained microstructure and intensive breaking of TiB whiskers. Tensile properties of the Ti–6.5Al–3.3Mo–0.3Si–0.2 wt% B alloy after multiple 3D forging followed by β-heat treatment were found to be appreciably higher than those of the alloy free of boron after the same processing route that was ascribed to better controlling the β-grain size during β heat treatment. The composite materials were subjected to multiple isothermal 2D forging at T=950 °C that provided effective alignment of TiB whiskers while retaining their high aspect ratio. The hot forged composites demonstrated appreciably higher strength, creep resistance in comparison with those of the base alloy without drastic reduction in ductility. The effect of TiB whiskers orientation and morphology on the tensile properties of the composite materials is discussed

  16. Shifting from hydrogen bond network to π-π stacking: a key mechanism for reversible thermochromic sulfonated poly(ether ether ketone).

    Science.gov (United States)

    Jarumaneeroj, Chatchai; Tashiro, Kohji; Chirachanchai, Suwabun

    2014-08-01

    Sulfonated poly(ether ether ketone) (SPEEK) thin film performs reversible thermochromic property by developing the color to be yellowish at the temperature above 190 °C. The detailed analyses based on temperature-dependent techniques suggest the thermal treatment inducing the shifting of the hydrogen bond network between the sulfonated group and the hydrated water molecules to the π-π stacking among aromatic rings in SPEEK chains. Although it is general that the polymer chain packing is unfavorable at high temperature, the present work shows a good example that when the polymer chains can form specific molecular interaction, such as π-π stacking, even in harsh thermal treatment, a rearrangement will effectively occur, which leads to an external stimuli-responsive property. PMID:24942891

  17. Influence of fluoride additions on biological and mechanical properties of Na2O–CaO–SiO2–P2O5 glass–ceramics

    International Nuclear Information System (INIS)

    Two series of Na2O–CaO–SiO2–P2O5 glass–ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol–gel method. The glass–ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass–ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass–ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass–ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass–ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass–ceramic surface, indicating that the glass–ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass–ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass–ceramics are safe to serve as implants. - Highlights: • The variations of additions account for the differences in internal structure. • The intensity ratio of Si-O-NBO/Si-O (s,sym) of G-NH4HF2 is higher than that of G-CaF2. • The bioactivity of G-NH4HF2 is better than that of G-CaF2. • The

  18. Effect of burnable poison addition on the thermo-mechanical properties of UO2-5wt5CeO2 pellets

    International Nuclear Information System (INIS)

    The microstructural characteristics and the thermo-mechanical properties of the pellets were evaluated and compared for UO2 and UO2-5wt%CeO2 pellets doped with burnable poisons (5wt% and 10wt% of Gd2O3, Sm2O3 and Dy2O3), sintered in reducing atmosphere for 4h. The sintered density and the grain size of UO2 and UO2-5wt%CeO2 pellets decreased by adding Gd2O3, Sm2O3 and Dy2O3 and the Vickers handness (Hv) of these pellets were found not affected with density and grain size variations. The fracture toughness (KIC) of the UO2 pellets increased with Gd2O3 and Dy2O3 adding and decreased with 10wt% Sm2O3 but that of UO2-5wt%CeO2 pellets were not changed. The fracture strength (of) of UO2 and UO2-5wt%CeO2 pellets were not affected by addition of burnable poison material and the critical thermal shock temperature difference (ΔTc) of the pellets increased for UO2 pellets doped with Gd2O3. Sm2O3 and Dy2O3 in the low temperature range (80 ∼ 200 .deg. C)

  19. 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.

  20. 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.

  1. The Influence of As-Built Surface Conditions on Mechanical Properties of Ti-6Al-4V Additively Manufactured by Selective Electron Beam Melting

    Science.gov (United States)

    Sun, Y. Y.; Gulizia, S.; Oh, C. H.; Fraser, D.; Leary, M.; Yang, Y. F.; Qian, M.

    2016-03-01

    Achieving a high surface finish is a major challenge for most current metal additive manufacturing processes. We report the first quantitative study of the influence of as-built surface conditions on the tensile properties of Ti-6Al-4V produced by selective electron beam melting (SEBM) in order to better understand the SEBM process. Tensile ductility was doubled along with noticeable improvements in tensile strengths after surface modification of the SEBM-fabricated Ti-6Al-4V by chemical etching. The fracture surfaces of tensile specimens with different surface conditions were characterised and correlated with the tensile properties obtained. The removal of a 650- μm-thick surface layer by chemical etching was shown to be necessary to eliminate the detrimental influence of surface defects on mechanical properties. The experimental results and analyses underline the necessity to modify the surfaces of SEBM-fabricated components for structural applications, particularly for those components which contain complex internal concave and convex surfaces and channels.

  2. Effects of Al and Fe additions on microstructure and mechanical properties of SnAgCu eutectic lead-free solders

    Energy Technology Data Exchange (ETDEWEB)

    Kantarcıoğlu, A.; Kalay, Y.E., E-mail: ekalay@metu.edu.tr

    2014-01-21

    In this study, Sn–3.5Ag–0.9Cu (wt%) lead-free solder was modified with minor additions of Al and Fe. The thermal, microstructural and mechanical behaviors after and before compositional modifications were investigated by a combined study of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and shear strength measurements. EDS results and Darken–Gurry predictions indicated a high concentration of Fe substitution within the Cu{sub 6}Sn{sub 5} at the solder/copper interface which induced desirable effects on undercooling and microstructure evolution. Eutectic SAC and SAC+0.05 wt% Al solder joints exhibit considerable number of brittle proeutectic phases (i.e., Ag{sub 3}Sn). Proeutectic Ag{sub 3}Sn formation was found to be suppressed after Fe modification. A new type of Al–Sn–Cu intermetallic compound was detected for Al added specimens. The rod-like morphology of this IMC appears to cause a sharp decrease in the shear strength of Al modified solder joints. The shear strength values for Fe modified solder joints were found to be higher in a wider composition range (0.01–0.1 wt% Fe) as compared to eutectic SAC and SAC+0.05 wt% Al.

  3. Effects of Al and Fe additions on microstructure and mechanical properties of SnAgCu eutectic lead-free solders

    International Nuclear Information System (INIS)

    In this study, Sn–3.5Ag–0.9Cu (wt%) lead-free solder was modified with minor additions of Al and Fe. The thermal, microstructural and mechanical behaviors after and before compositional modifications were investigated by a combined study of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and shear strength measurements. EDS results and Darken–Gurry predictions indicated a high concentration of Fe substitution within the Cu6Sn5 at the solder/copper interface which induced desirable effects on undercooling and microstructure evolution. Eutectic SAC and SAC+0.05 wt% Al solder joints exhibit considerable number of brittle proeutectic phases (i.e., Ag3Sn). Proeutectic Ag3Sn formation was found to be suppressed after Fe modification. A new type of Al–Sn–Cu intermetallic compound was detected for Al added specimens. The rod-like morphology of this IMC appears to cause a sharp decrease in the shear strength of Al modified solder joints. The shear strength values for Fe modified solder joints were found to be higher in a wider composition range (0.01–0.1 wt% Fe) as compared to eutectic SAC and SAC+0.05 wt% Al

  4. Effects of B and Cu Addition and Cooling Rate on Microstructure and Mechanical Properties in Low-Carbon, High-Strength Bainitic Steels

    Science.gov (United States)

    Sung, Hyo Kyung; Shin, Sang Yong; Hwang, Byoungchul; Lee, Chang Gil; Lee, Sunghak

    2012-10-01

    The effects of B and Cu addition and cooling rate on microstructure and mechanical properties of low-carbon, high-strength bainitic steels were investigated in this study. The steel specimens were composed mostly of bainitic ferrite, together with small amounts of acicular ferrite, granular bainite, and martensite. The yield and tensile strengths of all the specimens were higher than 1000 MPa and 1150 MPa, respectively, whereas the upper shelf energy was higher than 160 J and energy transition temperature was lower than 208 K (-65 °C) in most specimens. The slow-cooled specimens tended to have the lower strengths, higher elongation, and lower energy transition temperature than the fast-cooled specimens. The Charpy notch toughness was improved with increasing volume fraction of acicular ferrite because acicular ferrites favorably worked for Charpy notch toughness even when other low-toughness microstructures such as bainitic ferrite and martensite were mixed together. To develop high-strength bainitic steels with an excellent combination of strength and toughness, the formation of bainitic microstructures mixed with acicular ferrite was needed, and the formation of granular bainite was prevented.

  5. Reversible arithmetic logic unit

    OpenAIRE

    zhou, Rigui; Shi, Yang; Zhang, Manqun

    2011-01-01

    Quantum computer requires quantum arithmetic. The sophisticated design of a reversible arithmetic logic unit (reversible ALU) for quantum arithmetic has been investigated in this letter. We provide explicit construction of reversible ALU effecting basic arithmetic operations. By provided the corresponding control unit, the proposed reversible ALU can combine the classical arithmetic and logic operation in a reversible integrated system. This letter provides actual evidence to prove the possib...

  6. Mechanism study of PEGylated polyester and β-cyclodextrin integrated micelles on drug resistance reversal in MRP1-overexpressed HL60/ADR cells.

    Science.gov (United States)

    Ji, Qian; Qiu, Liyan

    2016-08-01

    Chemotherapy is one of the main strategies for cancer treatment, but its effective application is seriously limited by the development of drug resistance. In this study, we designed micellar vectors for doxorubicin based on amphiphilic copolymers sequentially linking β-cyclodextrin (β-CD), polylacticacid (PLA) or polycaprolactone (PCL) block, and polyethylene glycol (PEG) block to overcome drug resistance in human acute myeloid leukemia cells (HL60/ADR) overexpressing multidrug resistance protein 1 (MRP1). The significant enhancement in cytotoxicity and inhibited HL60/ADR tumor growth in mouse was achieved. More importantly, several analyses were performed to understand the interactions between various polymers and MRP1 at the cellular level. The results showed that the polymers did not show remarkable correlation of MRP1 gene and protein expression, but could decrease intracellular ATP, mitochondrial membrane potential and glutathione levels, which was greatly dependent on the molecular structure of polymers. In conclusion, these novel micelles can be considered as a kind of promising drug delivery system for tumor therapy to reverse drug resistance related to MRP1 overexpression. PMID:27088190

  7. 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.

  8. 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

  9. 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.

  10. 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.

  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. Study on the Premium and Penalty Mechanism of Reverse Supply Chain Based on Manufacturers’ Competition%制造商竞争环境下逆向供应链的政府奖惩机制研究

    Institute of Scientific and Technical Information of China (English)

    王文宾; 陈祥东; 达庆利; 聂锐; 陈伟达

    2014-01-01

    Mainly considering the premium and penalty mechanism of reverse supply chain under manufacturers ’ competition environment, using game theory, we build 5 models, which are centralized decision-making of reverse supply chain , the total profits decision-making based on the profits of reverse supply chain and the manu-facturer who does not collect waste products , decentralized decision-making with no premium and penalty mecha-nism, government ’ s premium and penalty mechanisms for the manufacturers and recyclers of reverse supply chain.The study presents several conclusions .Competition is beneficial to raising collection rate and the more intense the competition , the higher the collection rate;the retail price of new products offered by manufacturers actively recycling is lower , which brings about price-competitive advantage .The fourth and fifth scenarios play a part in increasing collection rate , and the greater premium and penalty , the higher collection rate , the lower retail price of new products .It is more efficient for the government to offer them premium mechanism rather than the premium and penalty mechanism , sine the former is valid for increasing both the manufacturer and the collec-tor’ s enthusiasm .The buyback price of the fourth scenario is higher than that of the fifth scenario .With premi-um and penalty mechanism the profit of manufacturer who collects waste products is higher than that of manufac -turer who does not collect waste products .The profit of manufacturer , who does not collect waste products , decreases with the increase of the degree of premium and penalty .%主要运用博弈论方法探讨制造商竞争环境下的逆向供应链奖惩机制,建立了5个决策模型,分别是逆向供应链集中式决策、以逆向供应链和不回收再制造的制造商的总利润为目标决策、逆向供应链分散式决策、政府对制造商实施奖惩机制以及政府对回收商实施奖惩机制下逆向供应链

  13. 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.

  14. Ice ages and geomagnetic reversals

    Science.gov (United States)

    Wu, Patrick

    1992-01-01

    There have been speculations on the relationship between climatic cooling and polarity reversals of the earth's magnetic field during the Pleistocene. Two of the common criticisms on this relationship have been the reality of these short duration geomagnetic events and the accuracy of their dates. Champion et al. (1988) have reviewed recent progress in this area. They identified a total of 10 short-duration polarity events in the last 1 Ma and 6 of these events have been found in volcanic rocks, which also have K-Ar dates. Supposing that the speculated relationship between climatic cooling and geomagnetic reversals actually exist, two mechanisms that assume climatic cooling causes short period magnetic reversals will be investigated. These two methods are core-mantle boundary topography and transfer of the rotational energy to the core.

  15. 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.

  16. Reverse Shoulder Arthroplasty

    Medline Plus

    Full Text Available ... you can use for reverse shoulder replacement. The standard delto-pectoral approach, or the superior approach, which ... that are different between a reverse and a standard total is, first of all, we don't ...

  17. 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...

  18. 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.

  19. 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.

  20. 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.