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Sample records for bond lengths based

  1. Non-destructive testing of full-length bonded rock bolts based on HHT signal analysis

    Science.gov (United States)

    Shi, Z. M.; Liu, L.; Peng, M.; Liu, C. C.; Tao, F. J.; Liu, C. S.

    2018-04-01

    Full-length bonded rock bolts are commonly used in mining, tunneling and slope engineering because of their simple design and resistance to corrosion. However, the length of a rock bolt and grouting quality do not often meet the required design standards in practice because of the concealment and complexity of bolt construction. Non-destructive testing is preferred when testing a rock bolt's quality because of the convenience, low cost and wide detection range. In this paper, a signal analysis method for the non-destructive sound wave testing of full-length bonded rock bolts is presented, which is based on the Hilbert-Huang transform (HHT). First, we introduce the HHT analysis method to calculate the bolt length and identify defect locations based on sound wave reflection test signals, which includes decomposing the test signal via empirical mode decomposition (EMD), selecting the intrinsic mode functions (IMF) using the Pearson Correlation Index (PCI) and calculating the instantaneous phase and frequency via the Hilbert transform (HT). Second, six model tests are conducted using different grouting defects and bolt protruding lengths to verify the effectiveness of the HHT analysis method. Lastly, the influence of the bolt protruding length on the test signal, identification of multiple reflections from defects, bolt end and protruding end, and mode mixing from EMD are discussed. The HHT analysis method can identify the bolt length and grouting defect locations from signals that contain noise at multiple reflected interfaces. The reflection from the long protruding end creates an irregular test signal with many frequency peaks on the spectrum. The reflections from defects barely change the original signal because they are low energy, which cannot be adequately resolved using existing methods. The HHT analysis method can identify reflections from the long protruding end of the bolt and multiple reflections from grouting defects based on mutations in the instantaneous

  2. A fluorescent sensor for Zn(2+) and NO2(-) based on the rational control of C[double bond, length as m-dash]N isomerization.

    Science.gov (United States)

    Liu, Zheng; Peng, Cuina; Wang, Ying; Pei, Meishan; Zhang, Guangyou

    2016-05-04

    A new strategy for the ultrasensitive sensing of cations and anions based on the control of C[double bond, length as m-dash]N isomerization has been developed. Imine-derived ligand is non-fluorescent due to the C[double bond, length as m-dash]N isomerization process, whereas its ternary complex with ZnCl2 is moderately fluorescent because of the partial inhibition of C[double bond, length as m-dash]N isomerization. Such a ternary complex can give a remarkable fluorescence increase when it interacts with nitrite because of the much more efficient suppression of C[double bond, length as m-dash]N isomerization. This modulation process of C[double bond, length as m-dash]N isomerization can thus be used for the highly selective detection of Zn(2+) and NO2(-) in an aqueous solution.

  3. Bond lengths in organic and metal-organic compounds revisited: X-H bond lengths from neutron diffraction data.

    Science.gov (United States)

    Allen, Frank H; Bruno, Ian J

    2010-06-01

    The number of structures in the Cambridge Structural Database (CSD) has increased by an order of magnitude since the preparation of two major compilations of standard bond lengths in mid-1985. It is now of interest to examine whether this huge increase in data availability has implications for the mean bond-length values published in the late 1980s. Those compilations reported mean X-H bond lengths derived from rather sparse information and for rather few chemical environments. During the intervening years, the number of neutron studies has also increased, although only by a factor of around 2.25, permitting a new analysis of X-H bond-length distributions for (a) organic X = C, N, O, B, and (b) a variety of terminal and homometallic bridging transition metal hydrides. New mean values are reported here and are compared with earlier results. These new overall means are also complemented by an analysis of X-H distances at lower temperatures (T chemical environments for which statistically acceptable mean X-H bond lengths can be obtained, although values from individual structures are also collated to further extend the chemical range of this compilation. Updated default 'neutron-normalization' distances for use in hydrogen-bond and deformation-density studies are also proposed for C-H, N-H and O-H, and the low-temperature analysis provides specific values for certain chemical environments and hybridization states of X.

  4. Extreme oxatriquinanes and a record C-O bond length

    Science.gov (United States)

    Gunbas, Gorkem; Hafezi, Nema; Sheppard, William L.; Olmstead, Marilyn M.; Stoyanova, Irini V.; Tham, Fook S.; Meyer, Matthew P.; Mascal, Mark

    2012-12-01

    Oxatriquinanes are fused, tricyclic oxonium ions that are known to have exceptional stability compared to simple alkyl oxonium salts. C-O bonds in ethers are generally ˜1.43 Å in length, but oxatriquinane has been found to have C-O bond lengths of 1.54 Å. A search of the Cambridge Structural Database turned up no bona fide C-O bond length exceeding this value. Computational modelling of oxatriquinane alongside other alkyl oxonium ions indicated that the electronic consequences of molecular strain were primarily responsible for the observed bond elongation. We also show that substitution of the oxatriquinane ring system with alkyl groups of increasing steric demand pushes the C-O bond to unheard of distances, culminating in a tert-butyl derivative at a predicted 1.60 Å. Chemical synthesis and an X-ray crystallographic study of these compounds validated the results of the modelling work and, finally, an extraordinary 1.622 Å C-O bond was observed in 1,4,7-tri-tert-butyloxatriquinane.

  5. Kernel density estimation applied to bond length, bond angle, and torsion angle distributions.

    Science.gov (United States)

    McCabe, Patrick; Korb, Oliver; Cole, Jason

    2014-05-27

    We describe the method of kernel density estimation (KDE) and apply it to molecular structure data. KDE is a quite general nonparametric statistical method suitable even for multimodal data. The method generates smooth probability density function (PDF) representations and finds application in diverse fields such as signal processing and econometrics. KDE appears to have been under-utilized as a method in molecular geometry analysis, chemo-informatics, and molecular structure optimization. The resulting probability densities have advantages over histograms and, importantly, are also suitable for gradient-based optimization. To illustrate KDE, we describe its application to chemical bond length, bond valence angle, and torsion angle distributions and show the ability of the method to model arbitrary torsion angle distributions.

  6. Bond length (Ti-O) dependence of nano ATO3-based (A = Pb, Ba, Sr) perovskite structures: Optical investigation in IR range

    Science.gov (United States)

    Ghasemifard, Mahdi; Ghamari, Misagh; Okay, Cengiz

    2018-01-01

    In the current study, ABO3 (A = Pb, Ba, Sr and B = Ti) perovskite structures are produced by the auto-combustion route by using citric acid (CA) and nitric acid (NA) as fuel and oxidizer. The X-ray diffraction (XRD) patterns confirmed the perovskite nanostructure with cubic, tetragonal, and rhombohedral for SrTiO3, PbTiO3, and BaTiO3, respectively. Using Scherrer’s equation and XRD pattern, the average crystallite size of the samples were acquired. The effect of Ti-O bond length on the structure of the samples was evaluated. The type of structures obtained depends on Ti-O bond length which is in turn influenced by A2+ substitutions. Microstructural studies of nanostructures calcined at 850∘C confirmed the formation of polyhedral particles with a narrow size distribution. The values of optical band gaps were measured and the impact of A2+ was discussed. The optical properties such as the complex refractive index and dielectric function were calculated by IR spectroscopy and Kramers-Kronig (K-K) relations. Lead, as the element with the highest density as compared to other elements, changes the optical constants, remarkably due to altering titanium and oxygen distance in TO6 groups.

  7. Anatomy of Bond Formation. Bond Length Dependence of the Extent of Electron Sharing in Chemical Bonds

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Cooper, D.

    2005-01-01

    Roč. 727, 1-3 (2005), s. 133-138 ISSN 0166-1280 R&D Projects: GA AV ČR(CZ) IAA4072403 Institutional research plan: CEZ:AV0Z40720504 Keywords : electron sharing * chemical bonds Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.045, year: 2005

  8. Isotopic fractionation in proteins as a measure of hydrogen bond length

    Energy Technology Data Exchange (ETDEWEB)

    McKenzie, Ross H., E-mail: r.mckenzie@uq.edu.au [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia); Athokpam, Bijyalaxmi; Ramesh, Sai G. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)

    2015-07-28

    If a deuterated molecule containing strong intramolecular hydrogen bonds is placed in a hydrogenated solvent, it may preferentially exchange deuterium for hydrogen. This preference is due to the difference between the vibrational zero-point energy for hydrogen and deuterium. It is found that the associated fractionation factor Φ is correlated with the strength of the intramolecular hydrogen bonds. This correlation has been used to determine the length of the H-bonds (donor-acceptor separation) in a diverse range of enzymes and has been argued to support the existence of short low-barrier H-bonds. Starting with a potential energy surface based on a simple diabatic state model for H-bonds, we calculate Φ as a function of the proton donor-acceptor distance R. For numerical results, we use a parameterization of the model for symmetric O–H⋯O bonds [R. H. McKenzie, Chem. Phys. Lett. 535, 196 (2012)]. We consider the relative contributions of the O–H stretch vibration, O–H bend vibrations (both in plane and out of plane), tunneling splitting effects at finite temperature, and the secondary geometric isotope effect. We compare our total Φ as a function of R with NMR experimental results for enzymes, and in particular with an earlier model parametrization Φ(R), used previously to determine bond lengths.

  9. Bond-length fluctuations in the copper oxide superconductors

    CERN Document Server

    Goodenough, J B

    2003-01-01

    Superconductivity in the copper oxides occurs at a crossover from localized to itinerant electronic behaviour, a transition that is first order. A spinodal phase segregation is normally accomplished by atomic diffusion; but where it occurs at too low a temperature for atomic diffusion, it may be realized by cooperative atomic displacements. Locally cooperative, fluctuating atomic displacements may stabilize a distinguishable phase lying between a localized-electron phase and a Fermi-liquid phase; this intermediate phase exhibits quantum-critical-point behaviour with strong electron-lattice interactions making charge transport vibronic. Ordering of the bond-length fluctuations at lower temperatures would normally stabilize a charge-density wave (CDW), which suppresses superconductivity. It is argued that in the copper oxide superconductors, crossover occurs at an optimal doping concentration for the formation of ordered two-electron/two-hole bosonic bags of spin S = 0 in a matrix of localized spins; the correl...

  10. The Influences of Overlap Length, Bond Line Thickness and Pretreatmant on the Mechanical Properties of Adhesives : Focussing on Bonding Glass

    NARCIS (Netherlands)

    Vervloed, J.; Kwakernaak, A.; Poulis, H.

    2008-01-01

    This paper focuses on the influences of overlap length, bond line thickness and pretreatment on the mechanical properties of adhesive bonds. In order to determine the bond strength, lap shear tests were performed. The researched adhesives are a 2 component epoxy and MS polymer. The smallest overlap

  11. Bond length deviation in CuZr metallic glasses

    Science.gov (United States)

    Peng, Chuan-Xiao; Şopu, Daniel; Song, Kai-Kai; Zhang, Zhen-Ting; Wang, Li; Eckert, Jürgen

    2017-11-01

    We define a structural parameter, called atomic bond length deviation (BL Di ), to characterize structural heterogeneity of CuZr melt and metallic glass (MG). Molecular dynamics simulations have been performed to explore the average BL Di of the system evolution with temperature during C u64Z r36 and C u50Z r50 MGs formation and the correlation between BL Di and thermal relaxation/local atomic shear strain upon compressive loading. The results indicate that BL Di contains both symmetrical characteristic and volumetric information of the short-range order clusters while symmetry seems to play a more important role in relaxation and deformation events; the fast decreasing of average BL Di near above the glass transition temperature Tg with decreasing temperature corresponds to the sharp increase of the number of full icosahedra while the shear transformation zones or single jump events have a high propensity to originate from those regions with the higher BL Di clusters. Additionally, the system average BL Di can also be accessed experimentally, through the radial distribution function.

  12. Bond lengths in Cd1-xZnxTe beyond linear laws revisited

    International Nuclear Information System (INIS)

    Koteski, V.; Haas, H.; Holub-Krappe, E.; Ivanovic, N.; Mahnke, H.-E.

    2004-01-01

    We have investigated the development of local bond lengths with composition in the Cd 1-x Zn x Te mixed system by measuring the fine structure in X-ray absorption (EXAFS) at all three constituent atoms. The bond strength is found to dominate over the averaging of the bulk so that the local bond length deviates only slightly from its natural value determined for the pure binary components ZnTe and CdTe, respectively. The deviations are significantly less than predicted by a simple radial force constant model for tetrahedrally co-ordinated binary systems, and the bond-length variation with concentration is significantly non-linear. For the second shell, bimodal anion-anion distances are found while the cation-cation distances can already be described by the virtual crystal approximation. In the diluted regime close to the end-point compounds, we have complemented our experimental work by ab initio calculations based on density functional theory with the WIEN97 program using the linearised augmented plane wave method. Equilibrium atomic lattice positions have been calculated for the substitutional isovalent metal atom in a 32-atom super cell, Zn in the CdTe lattice or Cd in the ZnTe lattice, respectively, yielding good agreement with the atomic distances as determined in our EXAFS experiments

  13. Bond Lengths and Bond Strengths in Weak and Strong Chemisorption: N2, CO, and CO/H on Nickel Surfaces

    OpenAIRE

    Sayago, David I.; Hoeft, Jon T.; Polcik, Martin; Kittel, Martin; Toomes, Rachel L.; Robinson, J.; Woodruff, David Phillip; Pascal, Mathieu; Lamont, Christine L.A.; Nisbet, Gareth

    2003-01-01

    New chemical-state-specific scanned-energy mode photoelectron diffraction experiments and density functional theory calculations, applied to CO, CO/H, and N2 adsorption on Ni(100), show that chemisorption bond length changes associated with large changes in bond strength are small, but those associated with changes in bond order are much larger, and are similar to those found in molecular systems. Specifically, halving the bond strength of atop CO to Ni increases the Ni-C distance by 0.06 Å...

  14. Analysis of surface bond lengths reported for chemisorption on metal surfaces

    Science.gov (United States)

    Mitchell, K. A. R.

    1985-01-01

    A review is given of bond length information available from the techniques of surface crystallography (particularly with LEED, SEXAFS and photoelectron diffraction) for chemisorption on well-defined surfaces of metals (M). For adsorbed main-group atoms (X), measured X-M interatomic distances for 38 combinations of X and M have been assessed with a bond order-bond length relation in combination with the Schomaker-Stevenson approach for determining single-bond lengths. When the surface bond orders are fixed primarily by the valency of X, this approach appears to provide a simple framework for predicing X-M surface bond lengths. Further, in cases where agreement has been reached from different surface crystallographic techniques, this framework has the potential for assessing refinements to the surface bonding model (e.g. in determining the roles of the effective surface valency of M, and of coordinate bonding and supplementary π bonding between X and M). Preliminary comparisons of structural data are also given for molecular adsorption (CO and ethylidyne) and for the chemisorption of other metal atoms.

  15. Change of bond length in free-energy simulations: Algorithmic improvements, but when is it necessary?

    Science.gov (United States)

    Wang, Lu; Hermans, Jan

    1994-06-01

    Various methods are compared for calculating the constraint free energy in simulations with change of bond lengths. Bond forces can be evaluated as restraint forces with the use of flexible bonds, and also, when bond lengths are held fixed, as constraint forces calculated either from SHAKE displacements, or else from Gauss' principle of least constraint, and these forces can then be used to calculate the potential of mean force or free energy for the bond length changes. An alternative is to use so-called mean-potential forces. Analysis of the equations derived from Gauss' principle shows that the constraint force (and also the restraint force) contain a ``dynamic'' term, that depends on the molecular motion and for simple molecules averages to 2 kT/r, where r is the bond length. Integration of this term, which is not present with use of the mean-potential force, or in a Monte Carlo simulation, gives a free energy that corresponds to the change in conformational entropy of two particles maintained at a certain distance, when this distance is changed. It is unnecessary to compute this free energy term by simulation, as was done in earlier work. The accuracy and precision of these methods, and of methods in which the bond lengths do not change, are tested in a series of model calculations of increasing complexity. First, the equivalence of these methods is tested in a model system with small molecules whose motion is maintained by Brownian dynamics, and which can be subjected to very simple external forces, in order to permit very long simulations. Second, a comparison is made of techniques for calculating free energy change with and without change of bond lengths, applied to the transformation of ethane into ethanol in water. A third test system is the conversion of an alanine residue into a serine residue in an α-helix in water. It is found that results are much improved if the ``vanishing'' atoms (in this case hydroxyl O and H) are coupled to a heat bath via

  16. Bond length contraction in Au nanocrystals formed by ion implantation into thin SiO2

    International Nuclear Information System (INIS)

    Kluth, P.; Johannessen, B.; Giraud, V.; Cheung, A.; Glover, C.J.; Azevedo, G. de M; Foran, G.J.; Ridgway, M.C.

    2004-01-01

    Au nanocrystals (NCs) fabricated by ion implantation into thin SiO 2 and annealing were investigated by means of extended x-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy. A bond length contraction was observed and can be explained by surface tension effects in a simple liquid-drop model. Such results are consistent with previous reports on nonembedded NCs implying a negligible influence of the SiO 2 matrix. Cumulant analysis of the EXAFS data suggests surface reconstruction or relaxation involving a further shortened bond length. A deviation from the octahedral closed shell structure is apparent for NCs of size 25 A

  17. Models for mean bonding length, melting point and lattice thermal expansion of nanoparticle materials

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.com [Department of Physics, College of Science, University of Salahaddin-Erbil, Arbil, Kurdistan (Iraq)

    2012-11-15

    Graphical abstract: Three models are derived to explain the nanoparticles size dependence of mean bonding length, melting temperature and lattice thermal expansion applied on Sn, Si and Au. The following figures are shown as an example for Sn nanoparticles indicates hilly applicable models for nanoparticles radius larger than 3 nm. Highlights: ► A model for a size dependent mean bonding length is derived. ► The size dependent melting point of nanoparticles is modified. ► The bulk model for lattice thermal expansion is successfully used on nanoparticles. -- Abstract: A model, based on the ratio number of surface atoms to that of its internal, is derived to calculate the size dependence of lattice volume of nanoscaled materials. The model is applied to Si, Sn and Au nanoparticles. For Si, that the lattice volume is increases from 20 Å{sup 3} for bulk to 57 Å{sup 3} for a 2 nm size nanocrystals. A model, for calculating melting point of nanoscaled materials, is modified by considering the effect of lattice volume. A good approach of calculating size-dependent melting point begins from the bulk state down to about 2 nm diameter nanoparticle. Both values of lattice volume and melting point obtained for nanosized materials are used to calculate lattice thermal expansion by using a formula applicable for tetrahedral semiconductors. Results for Si, change from 3.7 × 10{sup −6} K{sup −1} for a bulk crystal down to a minimum value of 0.1 × 10{sup −6} K{sup −1} for a 6 nm diameter nanoparticle.

  18. Models for mean bonding length, melting point and lattice thermal expansion of nanoparticle materials

    International Nuclear Information System (INIS)

    Omar, M.S.

    2012-01-01

    Graphical abstract: Three models are derived to explain the nanoparticles size dependence of mean bonding length, melting temperature and lattice thermal expansion applied on Sn, Si and Au. The following figures are shown as an example for Sn nanoparticles indicates hilly applicable models for nanoparticles radius larger than 3 nm. Highlights: ► A model for a size dependent mean bonding length is derived. ► The size dependent melting point of nanoparticles is modified. ► The bulk model for lattice thermal expansion is successfully used on nanoparticles. -- Abstract: A model, based on the ratio number of surface atoms to that of its internal, is derived to calculate the size dependence of lattice volume of nanoscaled materials. The model is applied to Si, Sn and Au nanoparticles. For Si, that the lattice volume is increases from 20 Å 3 for bulk to 57 Å 3 for a 2 nm size nanocrystals. A model, for calculating melting point of nanoscaled materials, is modified by considering the effect of lattice volume. A good approach of calculating size-dependent melting point begins from the bulk state down to about 2 nm diameter nanoparticle. Both values of lattice volume and melting point obtained for nanosized materials are used to calculate lattice thermal expansion by using a formula applicable for tetrahedral semiconductors. Results for Si, change from 3.7 × 10 −6 K −1 for a bulk crystal down to a minimum value of 0.1 × 10 −6 K −1 for a 6 nm diameter nanoparticle.

  19. Doping and bond length contributions to Mn K-edge shift in La1 ...

    Indian Academy of Sciences (India)

    ... corresponds to the shift in the center of gravity of the unoccupied Mn 4-band contributing to the Mn K-absorption edge region. This correspondence is then used to separate the doping and size contributions to the edge shift due to variation in the number of electrons in valence band and Mn-O bond lengths, respectively, ...

  20. Modulation of Zn-C Bond Lengths Induced by Ligand Architecture in Zinc Carbatrane Compounds.

    Science.gov (United States)

    Ruccolo, Serge; Sattler, Wesley; Rong, Yi; Parkin, Gerard

    2016-11-09

    Bond lengths between pairs of atoms in covalent molecules are generally predicted well by the sum of their respective covalent radii, such that there are usually only small variations in related compounds. It is, therefore, significant that we have demonstrated that the incorporation of appropriately sized linkers between carbon and a metal center provides a means to modulate the length and nature of a metal-carbon interaction. Specifically, X-ray diffraction studies on a series of tris(1-methylimidazol-2-ylthio)methyl zinc complexes, [Titm Me ]ZnX, demonstrate how the Zn-C bond lengths are highly variable (2.17-2.68 Å) and are up to 0.67 Å longer than the average value listed in the Cambridge Structural Database (2.01 Å). Furthermore, density functional theory calculations on [Titm Me ]ZnCl demonstrate that the interaction is very flexible, such that either increasing or decreasing the Zn-C length from that in the equilibrium structure is associated with little energy change in comparison to that for other compounds with Zn-C bonds.

  1. Comparative study on direct and indirect bracket bonding techniques regarding time length and bracket detachment

    Directory of Open Access Journals (Sweden)

    Jefferson Vinicius Bozelli

    2013-12-01

    Full Text Available OBJECTIVE: The aim of this study was to assess the time spent for direct (DBB - direct bracket bonding and indirect (IBB - indirect bracket bonding bracket bonding techniques. The time length of laboratorial (IBB and clinical steps (DBB and IBB as well as the prevalence of loose bracket after a 24-week follow-up were evaluated. METHODS: Seventeen patients (7 men and 10 women with a mean age of 21 years, requiring orthodontic treatment were selected for this study. A total of 304 brackets were used (151 DBB and 153 IBB. The same bracket type and bonding material were used in both groups. Data were submitted to statistical analysis by Wilcoxon non-parametric test at 5% level of significance. RESULTS: Considering the total time length, the IBB technique was more time-consuming than the DBB (p < 0.001. However, considering only the clinical phase, the IBB took less time than the DBB (p < 0.001. There was no significant difference (p = 0.910 for the time spent during laboratorial positioning of the brackets and clinical session for IBB in comparison to the clinical procedure for DBB. Additionally, no difference was found as for the prevalence of loose bracket between both groups. CONCLUSION: the IBB can be suggested as a valid clinical procedure since the clinical session was faster and the total time spent for laboratorial positioning of the brackets and clinical procedure was similar to that of DBB. In addition, both approaches resulted in similar frequency of loose bracket.

  2. Bond between smooth prestressing wires and concrete : finite element model and transfer length analysis for pretensioned concrete crossties.

    Science.gov (United States)

    2014-04-03

    Pretensioned concrete ties are increasingly employed in railroad high speed : and heavy haul applications. The bond between prestressing wires or strands and : concrete plays an important role in determining the transfer length of pretensioned : conc...

  3. Two states are not enough: quantitative evaluation of the valence-bond intramolecular charge-transfer model and its use in predicting bond length alternation effects.

    Science.gov (United States)

    Jarowski, Peter D; Mo, Yirong

    2014-12-15

    The structural weights of the canonical resonance contributors used in the Two-state valence-bond charge-transfer model, neutral (N, R1) and ionic (VB-CT, R2), to the ground states and excited states of a series of linear dipolar intramolecular charge-transfer chromophores containing a buta-1,3-dien-1,4-diyl bridge have been computed by using the block-localized wavefunction (BLW) method at the B3LYP/6-311+G(d) level to provide the first quantitative assessment of this simple model. Ground- and excited-state analysis reveals surprisingly low ground-state structural weights for the VB-CT resonance form using either this Two-state model or an expanded Ten-state model. The VB-CT state is found to be more prominent in the excited state. Individual resonance forms were structurally optimized to understand the origins of the bond length alternation (BLA) of the bridging unit. Using a Wheland energy-based weighting scheme, the weighted average of the optimized bond lengths with the Two-state model was unable to reproduce the BLA features with values 0.04 to 0.02 Å too large compared to the fully delocalized (FD) structure (BLW: ca. -0.13 to -0.07 Å, FD: ca. -0.09 to -0.05 Å). Instead, an expanded Ten-state model fit the BLA values of the FD structure to within only 0.001 Å of FD. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Relation between frequency and H bond length in heavy water: Towards the understanding of the unusual properties of H bond dynamics in nanoporous media

    Energy Technology Data Exchange (ETDEWEB)

    Pommeret, Stanislas [CEA/Saclay, DSM/DRECAM/SCM URA 331 CNRS, Laboratoire de Radiolyse, F-91191 Gif-sur-Yvette (France); Leicknam, Jean-Claude; Bratos, Savo [Laboratoire de Physique Theorique de la Matiere Condensee, Universite Pierre et Marie Curie-Paris 6, UMR 7600 (CNRS), Paris (France); Musat, Raluca; Renault, Jean Philippe, E-mail: stanislas.pommeret@cea.f

    2009-06-01

    The published work on H bond dynamics mainly refers to diluted solutions HDO/D{sub 2}O rather than to normal water. The reasons for this choice are both theoretical and experimental. Mechanical isolation of the OH vibrator eliminating the resonant energy transfer makes it a better probe of the local H bond network, while the dilution in heavy water reduces the infrared absorption, which permits the use of thicker experimental cells. The isotopic substitution does not alter crucially the nature of the problem. The length r of an OH . . . O group is statistically distributed over a large interval comprised between 2.7 and 3.2 A with a mean value r{sub 0} = 2.86 A. Liquid water may thus be viewed as a mixture of hydrogen bonds of different length. Two important characteristics of hydrogen bonding must be mentioned. (i) The OH stretching vibrations are strongly affected by this interaction. The shorter the length r of the hydrogen bond, the strongest the H bond link and the lower is its frequency omega: the covalent OH bond energy is lent to the OH. . .O bond and reinforces the latter. A number of useful relationships between omega and r were published to express this correlation. The one adopted in our previous work is the relationship due to Mikenda. (ii) Not only the OH vibrations, but also the HDO rotations are influenced noticeably by hydrogen bonding. This is due to steric forces that hinder the HDO rotations. As they are stronger in short than in long hydrogen bonds, rotations are slower in the first case than in the second. This effect was only recently discovered, but its existence is hardly to be contested. In the present contribution, we want to revisit the relationship between the frequency of the OH vibrator and the distance OH. . .O.

  5. Relation between frequency and H bond length in heavy water: Towards the understanding of the unusual properties of H bond dynamics in nanoporous media

    International Nuclear Information System (INIS)

    Pommeret, Stanislas; Leicknam, Jean-Claude; Bratos, Savo; Musat, Raluca; Renault, Jean Philippe

    2009-01-01

    The published work on H bond dynamics mainly refers to diluted solutions HDO/D 2 O rather than to normal water. The reasons for this choice are both theoretical and experimental. Mechanical isolation of the OH vibrator eliminating the resonant energy transfer makes it a better probe of the local H bond network, while the dilution in heavy water reduces the infrared absorption, which permits the use of thicker experimental cells. The isotopic substitution does not alter crucially the nature of the problem. The length r of an OH . . . O group is statistically distributed over a large interval comprised between 2.7 and 3.2 A with a mean value r 0 = 2.86 A. Liquid water may thus be viewed as a mixture of hydrogen bonds of different length. Two important characteristics of hydrogen bonding must be mentioned. (i) The OH stretching vibrations are strongly affected by this interaction. The shorter the length r of the hydrogen bond, the strongest the H bond link and the lower is its frequency ω: the covalent OH bond energy is lent to the OH. . .O bond and reinforces the latter. A number of useful relationships between ω and r were published to express this correlation. The one adopted in our previous work is the relationship due to Mikenda. (ii) Not only the OH vibrations, but also the HDO rotations are influenced noticeably by hydrogen bonding. This is due to steric forces that hinder the HDO rotations. As they are stronger in short than in long hydrogen bonds, rotations are slower in the first case than in the second. This effect was only recently discovered, but its existence is hardly to be contested. In the present contribution, we want to revisit the relationship between the frequency of the OH vibrator and the distance OH. . .O.

  6. Supramolecular structures for determination and identification of the bond lengths in novel uranyl complexes from their infrared spectra

    Science.gov (United States)

    El-Sonbati, A. Z.; Diab, M. A.; Morgan, Sh. M.; Seyam, H. A.

    2018-02-01

    Novel dioxouranium (VI) heterochelates with neutral bidentate compounds (Ln) have been synthesized. The ligands and the heterochelates [UO2(Ln)2(O2NO)2] were confirmed and characterized by elemental analysis, 1H NMR, UV.-Vis, IR, mass spectroscopy, X-ray diffraction and thermogravimetric analysis (TGA). IR spectral data suggest that the molecules of the Schiff base are coordinated to the central uranium atom (ON donor). The nitrato groups are coordinated as bidentate ligands. The thermodynamic parameters were calculated using Coats-Redfern and Horowitz-Metzger methods. The ligands (Ln) and their complexes (1-3) showed the υ3 frequency of UO22+ has been shown to be an excellent molecular probe for studying the coordinating power of the ligands. The values of υ3 of the prepared complexes containing UO22+ were successfully used to calculate the force constant, FUO (1n 10-8N/Å) and the bond length RUO (Å) of the Usbnd O bond. A strategy based upon both theoretical and experimental investigations has been adopted. The theoretical aspects are described in terms of the well-known theory of 5d-4f transitions. Wilson's, matrix method, Badger's formula, and Jones and El-Sonbati equations were used to calculate the Usbnd O bond distances from the values of the stretching and interaction force constants. The most probable correlation between Usbnd O force constant to Usbnd O bond distance were satisfactorily discussed in term of Badger's rule and the equations suggested by Jones and El-Sonbati. The effect of Hammett's constant is also discussed.

  7. Dependence of the length of the hydrogen bond on the covalent and cationic radii of hydrogen, and additivity of bonding distances

    Czech Academy of Sciences Publication Activity Database

    Heyrovská, Raji

    2006-01-01

    Roč. 432, č. 1-3 (2006), s. 348-351 ISSN 0009-2614 R&D Projects: GA MŠk(CZ) LC06035 Institutional research plan: CEZ:AV0Z50040507 Keywords : length of the hydrogen bond * ionic radius * Golden ratio Subject RIV: BO - Biophysics Impact factor: 2.462, year: 2006

  8. EFFECT OF END ANCHORAGE LENGTH AND STIRRUP RATIO ON BOND AND SHEAR CAPACITY OF CONCRETE BEAMS WITH NONMETALLIC REINFORCEMENT

    Directory of Open Access Journals (Sweden)

    RENDY THAMRIN

    2016-06-01

    Full Text Available This paper presents a study on the effect of end anchorage length and stirrup ratio on bond and shear capacity of concrete beams reinforced with Carbon Fiber Reinforced Polymer (CFRP bars. This study was carried out using test data on nine simply supported reinforced concrete beams with stirrups. The beams were subjected to two point monotonic loads and the test variables were the length of end anchorage and the stirrup ratio. Theoretical equations for calculating bond strength and shear capacity obtained from literature were applied and then compared with experimental values. Beams with inadequate end anchorage length showed premature bond failure even when there was sufficient stirrup ratio. Beams with adequate end anchorage length failed in shear or flexure modes depending on the stirrup ratio. A numerical model for bond stress and slip in response to pullout forces was also used to determine analytically the bond stress distributions along end anchorage. The behavior of tensile force acting on the stirrups was also examined. Finally, a simple model for predicting tension force acting on the stirrups was proposed.

  9. Determination of Hydrogen Bond Structure in Water versus Aprotic Environments To Test the Relationship Between Length and Stability.

    Science.gov (United States)

    Sigala, Paul A; Ruben, Eliza A; Liu, Corey W; Piccoli, Paula M B; Hohenstein, Edward G; Martínez, Todd J; Schultz, Arthur J; Herschlag, Daniel

    2015-05-06

    Hydrogen bonds profoundly influence the architecture and activity of biological macromolecules. Deep appreciation of hydrogen bond contributions to biomolecular function thus requires a detailed understanding of hydrogen bond structure and energetics and the relationship between these properties. Hydrogen bond formation energies (ΔGf) are enormously more favorable in aprotic solvents than in water, and two classes of contributing factors have been proposed to explain this energetic difference, focusing respectively on the isolated and hydrogen-bonded species: (I) water stabilizes the dissociated donor and acceptor groups much better than aprotic solvents, thereby reducing the driving force for hydrogen bond formation; and (II) water lengthens hydrogen bonds compared to aprotic environments, thereby decreasing the potential energy within the hydrogen bond. Each model has been proposed to provide a dominant contribution to ΔGf, but incisive tests that distinguish the importance of these contributions are lacking. Here we directly test the structural basis of model II. Neutron crystallography, NMR spectroscopy, and quantum mechanical calculations demonstrate that O-H···O hydrogen bonds in crystals, chloroform, acetone, and water have nearly identical lengths and very similar potential energy surfaces despite ΔGf differences >8 kcal/mol across these solvents. These results rule out a substantial contribution from solvent-dependent differences in hydrogen bond structure and potential energy after association (model II) and thus support the conclusion that differences in hydrogen bond ΔGf are predominantly determined by solvent interactions with the dissociated groups (model I). These findings advance our understanding of universal hydrogen-bonding interactions and have important implications for biology and engineering.

  10. ESTIMATION OF STATURE BASED ON FOOT LENGTH

    Directory of Open Access Journals (Sweden)

    Vidyullatha Shetty

    2015-01-01

    Full Text Available BACKGROUND : Stature is the height of the person in the upright posture. It is an important measure of physical identity. Estimation of body height from its segments or dismember parts has important considerations for identifications of living or dead human body or remains recovered from disasters or other similar conditions. OBJECTIVE : Stature is an important indicator for identification. There are numerous means to establish stature and their significance lies in the simplicity of measurement, applicability and accuracy in prediction. Our aim of the study was to review the relationship between foot length and body height. METHODS : The present study reviews various prospective studies which were done to estimate the stature. All the measurements were taken by using standard measuring devices and standard anthropometric techniques. RESULTS : This review shows there is a correlation between stature and foot dimensions it is found to be positive and statistically highly significant. Prediction of stature was found to be most accurate by multiple regression analysis. CONCLUSIONS : Stature and gender estimation can be done by using foot measurements and stud y will help in medico - legal cases in establishing identity of an individual and this would be useful for Anatomists and Anthropologists to calculate stature based on foot length

  11. Comparison of Shear Bond Strengths of three resin systems for a Base Metal Alloy bonded to

    Directory of Open Access Journals (Sweden)

    Jlali H

    1999-12-01

    Full Text Available Resin-bonded fixed partial dentures (F.P.D can be used for conservative treatment of partially edentulous"npatients. There are numerous studies regarding the strength of resin composite bond to base meta! alloys. Shear bond"nstrength of three resin systems were invistigated. In this study these systems consisted of: Panavia Ex, Mirage FLC and"nMarathon V. Thirty base metal specimens were prepared from rexillium III alloy and divided into three groups. Then each"ngroup was bonded to enamel of human extracted molar teeth with these systems. All of specimens were stored in water at"n37ac for 48 hours. A shear force was applied to each specimen by the instron universal testing machine. A statistical"nevaluation of the data using one-way analysis of variance showed that there was highly significant difference (P<0.01"nbetween the bond strengths of these three groups."nThe base metal specimens bonded with panavia Ex luting agent, exhibited the highest mean bond strength. Shear bond"nstrength of the specimens bonded to enamel with Mirage F1C showed lower bond strenght than panavia EX. However, the"nlowest bond strength was obtained by the specimens bonded with Marathon V.

  12. The Hydrogen Bonded Structures of Two 5-Bromobarbituric Acids and Analysis of Unequal C5–X and C5–X′ Bond Lengths (X = X′ = F, Cl, Br or Me in 5,5-Disubstituted Barbituric Acids

    Directory of Open Access Journals (Sweden)

    Thomas Gelbrich

    2016-04-01

    Full Text Available The crystal structure of the methanol hemisolvate of 5,5-dibromobarbituric acid (1MH displays an H-bonded layer structure which is based on N–H∙∙∙O=C, N–H∙∙∙O(MeOH and (MeOHO–H∙∙∙O interactions. The barbiturate molecules form an H-bonded substructure which has the fes topology. 5,5′-Methanediylbis(5-bromobarbituric acid 2, obtained from a solution of 5,5-dibromobarbituric acid in nitromethane, displays a N–H···O=C bonded framework of the sxd type. The conformation of the pyridmidine ring and the lengths of the ring substituent bonds C5–X and C5–X′ in crystal forms of 5,5-dibromobarbituric acid and three closely related analogues (X = X′ = Br, Cl, F, Me have been investigated. In each case, a conformation close to a C5-endo envelope is correlated with a significant lengthening of the axial C5–X′ in comparison to the equatorial C5–X bond. Isolated molecule geometry optimizations at different levels of theory confirm that the C5-endo envelope is the global conformational energy minimum of 5,5-dihalogenbarbituric acids. The relative lengthening of the axial bond is therefore interpreted as an inherent feature of the preferred envelope conformation of the pyrimidine ring, which minimizes repulsive interactions between the axial substituent and pyrimidine ring atoms.

  13. Bond length and electric current oscillation of long linear carbon chains: Density functional theory, MpB model, and quantum spin transport studies

    International Nuclear Information System (INIS)

    Oeiras, R. Y.; Silva, E. Z. da

    2014-01-01

    Carbon linear atomic chains attached to graphene have experimentally been produced. Motivated by these results, we study the nature of the carbon bonds in these nanowires and how it affects their electrical properties. In the present study we investigate chains with different numbers of atoms and we observe that nanowires with odd number of atoms present a distinct behavior than the ones with even numbers. Using graphene nanoribbons as leads, we identify differences in the quantum transport of the chains with the consequence that even and odd numbered chains have low and high electrical conduction, respectively. We also noted a dependence of current with the wire size. We study this unexpected behavior using a combination of first principles calculations and simple models based on chemical bond theory. From our studies, the electrons of carbon nanowires present a quasi-free electron behavior and this explains qualitatively the high electrical conduction and the bond lengths with unexpected values for the case of odd nanowires. Our study also allows the understanding of the electric conduction dependence with the number of atoms and their parity in the chain. In the case of odd number chains a proposed π-bond (MpB) model describes unsaturated carbons that introduce a mobile π-bond that changes dramatically the structure and transport properties of these wires. Our results indicate that the nature of bonds plays the main role in the oscillation of quantum electrical conduction for chains with even and odd number of atoms and also that nanowires bonded to graphene nanoribbons behave as a quasi-free electron system, suggesting that this behavior is general and it could also remain if the chains are bonded to other materials

  14. Dental plaque microcosm response to bonding agents containing quaternary ammonium methacrylates with different chain lengths and charge densities.

    Science.gov (United States)

    Zhou, Han; Li, Fang; Weir, Michael D; Xu, Hockin H K

    2013-11-01

    Antibacterial bonding agents are promising to combat bacteria and caries at tooth-restoration margins. The objectives of this study were to incorporate new quaternary ammonium methacrylates (QAMs) to bonding agent and determine the effects of alkyl chain length (CL) and quaternary amine charge density on dental plaque microcosm bacteria response for the first time. Six QAMs were synthesized with CL=3, 6, 9, 12, 16, 18. Each QAM was incorporated into Scotchbond multi-purpose (SBMP). To determine the charge density effect, dimethylaminododecyl methacrylate (DMAHDM, CL=16) was mixed into SBMP at mass fraction=0%, 2.5%, 5%, 7.5%, 10%. Charge density was measured using a fluorescein dye method. Dental plaque microcosm using saliva from ten donors was tested. Bacteria were inoculated on resins. Early-attachment was tested at 4h. Biofilm colony-forming units (CFU) were measured at 2 days. Incorporating QAMs into SBMP reduced bacteria early-attachment. Microcosm biofilm CFU for CL=16 was 4 log lower than SBMP control. Charge density of bonding agent increased with DMAHDM content. Bacteria early-attachment decreased with increasing charge density. Biofilm CFU at 10% DMAHDM was reduced by 4 log. The killing effect was similarly-strong against total microorganisms, total streptococci, and mutans streptococci. Increasing alkyl chain length and charge density of bonding agent was shown for the first time to decrease microcosm bacteria attachment and reduce biofilm CFU by 4 orders of magnitude. Novel antibacterial resins with tailored chain length and charge density are promising for wide applications in bonding, cements, sealants and composites to inhibit biofilms and caries. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Dental plaque microcosm response to bonding agents containing quaternary ammonium methacrylates with different chain lengths and charge densities

    Science.gov (United States)

    Zhou, Han; Li, Fang; Weir, Michael D.; Xu, Hockin H.K.

    2013-01-01

    Objectives Antibacterial bonding agents are promising to combat bacteria and caries at tooth-restoration margins. The objectives of this study were to incorporate new quaternary ammonium methacrylates (QAMs) to bonding agent and determine the effects of alkyl chain length (CL) and quaternary amine charge density on dental plaque microcosm bacteria response for the first time. Methods Six QAMs were synthesized with CL = 3, 6, 9, 12, 16, 18. Each QAM was incorporated into Scotchbond Multi-purpose (SBMP). To determine the charge density effect, dimethylaminododecyl methacrylate (DMAHDM, CL = 16) was mixed into SBMP at mass fraction = 0%, 2.5%, 5%, 7.5%, 10%. Charge density was measured using a fluorescein dye method. Dental plaque microcosm using saliva from ten donors was tested. Bacteria were inoculated on resins. Early-attachment was tested at 4 hours. Biofilm colony-forming units (CFU) were measured at 2 days. Results Incorporating QAMs into SBMP reduced bacteria early-attachment. Microcosm biofilm CFU for CL = 16 was 4 log lower than SBMP control. Charge density of bonding agent increased with DMAHDM content. Bacteria early-attachment decreased with increasing charge density. Biofilm CFU at 10% DMAHDM was reduced by 4 log. The killing effect was similarly-strong against total microorganisms, total streptococci, and mutans streptococci. Conclusions Increasing alkyl chain length and charge density of bonding agent was shown for the first time to decrease microcosm bacteria attachment and reduce biofilm CFU by 4 orders of magnitude. Novel antibacterial resins with tailored chain length and charge density are promising for wide applications in bonding, cements, sealants and composites to inhibit biofilms and caries. PMID:23948394

  16. The unexpected mechanism of carbonyl hydrosilylation catalyzed by (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)).

    Science.gov (United States)

    Shirobokov, Oleg G; Gorelsky, Serge I; Simionescu, Razvan; Kuzmina, Lyudmila G; Nikonov, Georgii I

    2010-11-07

    Complex (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)) (2, Ar = 2,6-diisopropylphenyl) catalyzes the hydrosilylation of carbonyls by an unexpected associative mechanism. Complex 2 also reacts with PhSiH(3) by a σ-bond metathesis mechanism to give the silyl derivative (Cp)(ArN[double bond, length as m-dash])Mo(SiH(2)Ph)(PMe(3)).

  17. Determination by vibrational spectra of the strength and the bond length of atoms U and O in uranyl complexes

    International Nuclear Information System (INIS)

    Rodriguez S, A.; Martinez Q, E.

    1996-01-01

    The vibrational spectra of different uranyl compounds were studied. The wave number was related to the harmonic oscillator model and to the mathematical expression of Badger as modified by Jones, to determine the strength and the bond length of atoms U and O in UO 2 2+ . A mathematical simplification develop by us is proposed and its results compared with values obtained by other methods. (Author)

  18. Distinguishing the Effects of Bond-Length Alternation versus Bond-Order Alternation on the Nonlinear Optical Properties of π-Conjugated Chromophores

    KAUST Repository

    Gieseking, Rebecca L.

    2015-06-18

    Understanding the relationships between the molecular nonlinear optical (NLO) properties and the bond-length alternation (BLA) or π-bond-order alternation (BOA) along the molecular backbone of linear π-conjugated systems has proven widely useful in the development of NLO organic chromophores and materials. Here, we examine model polymethines to elucidate the reliability of these relationships. While BLA is solely a measure of molecular geometric structure, BOA includes information pertaining to the electronic structure. As a result, BLA is found to be a good predictor of NLO properties only when optimized geometries are considered, whereas BOA is more broadly applicable. Proper understanding of the distinction between BLA and BOA is critical when designing computational studies of NLO properties, especially for molecules in complex environments or in nonequilibrium geometries. © 2015 American Chemical Society.

  19. Anatomy of Bond Formation. Bond Length Dependence on the Extent of Electron Sharing in Chemical Bonds from the Analysis of Domain-Averaged Fermi holes.

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Cooper, D.L.

    2007-01-01

    Roč. 135, č. 7, (2007) , s. 31-41 ISSN 0301-7249 R&D Projects: GA AV ČR(CZ) IAA4072006 Institutional research plan: CEZ:AV0Z40720504 Keywords : electron sharing * chemical bonds * domain averaged fermi holes Subject RIV: CF - Physical ; Theoretical Chemistry

  20. σ-Bond Electron Delocalization in Oligosilanes as Function of Substitution Pattern, Chain Length, and Spatial Orientation

    Directory of Open Access Journals (Sweden)

    Johann Hlina

    2016-08-01

    Full Text Available Polysilanes are known to exhibit the interesting property of σ-bond electron delocalization. By employing optical spectroscopy (UV-vis, it is possible to judge the degree of delocalization and also differentiate parts of the molecules which are conjugated or not. The current study compares oligosilanes of similar chain length but different substitution pattern. The size of the substituents determines the spatial orientation of the main chain and also controls the conformational flexibility. The chemical nature of the substituents affects the orbital energies of the molecules and thus the positions of the absorption bands.

  1. Bond-length strain in buried Ga1-xInxAs thin-alloy films grown coherently on InP(001)

    International Nuclear Information System (INIS)

    Woicik, J.C.; Gupta, J.A.; Watkins, S.P.; Crozier, E.D.

    1998-01-01

    The bond lengths in a series of strained, buried Ga 1-x In x As thin-alloy films grown coherently on InP(001) have been determined by high-resolution extended x-ray absorption fine-structure measurements. Comparison with a random-cluster calculation demonstrates that the external in-plane epitaxial strain imposed by pseudomorphic growth opposes the natural bond-length distortions due to alloying.copyright 1998 American Institute of Physics

  2. Competition of hydrogen bonds and halogen bonds in complexes of hypohalous acids with nitrogenated bases.

    Science.gov (United States)

    Alkorta, Ibon; Blanco, Fernando; Solimannejad, Mohammad; Elguero, Jose

    2008-10-30

    A theoretical study of the complexes formed by hypohalous acids (HOX, X = F, Cl, Br, I, and At) with three nitrogenated bases (NH 3, N 2, and NCH) has been carried out by means of ab initio methods, up to MP2/aug-cc-pVTZ computational method. In general, two minima complexes are found, one with an OH...N hydrogen bond and the other one with a X...N halogen bond. While the first one is more stable for the smallest halogen derivatives, the two complexes present similar stabilities for the iodine case and the halogen-bonded structure is the most stable one for the hypoastatous acid complexes.

  3. Bond graph model-based fault diagnosis of hybrid systems

    CERN Document Server

    Borutzky, Wolfgang

    2015-01-01

    This book presents a bond graph model-based approach to fault diagnosis in mechatronic systems appropriately represented by a hybrid model. The book begins by giving a survey of the fundamentals of fault diagnosis and failure prognosis, then recalls state-of-art developments referring to latest publications, and goes on to discuss various bond graph representations of hybrid system models, equations formulation for switched systems, and simulation of their dynamic behavior. The structured text: • focuses on bond graph model-based fault detection and isolation in hybrid systems; • addresses isolation of multiple parametric faults in hybrid systems; • considers system mode identification; • provides a number of elaborated case studies that consider fault scenarios for switched power electronic systems commonly used in a variety of applications; and • indicates that bond graph modelling can also be used for failure prognosis. In order to facilitate the understanding of fault diagnosis and the presented...

  4. Maximum length scale in density based topology optimization

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Wang, Fengwen

    2017-01-01

    The focus of this work is on two new techniques for imposing maximum length scale in topology optimization. Restrictions on the maximum length scale provide designers with full control over the optimized structure and open possibilities to tailor the optimized design for broader range...... of manufacturing processes by fulfilling the associated technological constraints. One of the proposed methods is based on combination of several filters and builds on top of the classical density filtering which can be viewed as a low pass filter applied to the design parametrization. The main idea...

  5. Comparative evaluation of effect of laser on shear bond strength of ceramic bonded with two base metal alloys: an in-vitro study.

    Science.gov (United States)

    Deepak, K; Ahila, S C; Muthukumar, B; Vasanthkumar, M

    2013-01-01

    The most common clinical failure in metal ceramic restoration is at the ceramo-metal interface. For the clinical longevity, metal-ceramic prostheses must have satisfactory bond strength between metal and ceramic. The aim of this study is to evaluate the effect of Laser etching on shear bond strength between base metal alloys and ceramic. A total of 60 specimens were made (Base 5 mm diameter and 1 mm thickness, step with 4 mm diameter and 4 mm in length). They were divided into three groups. Group A-control, Group B-sand blasting, and Group C-laser etching. The Surface morphology, surface roughness, and wettability of the specimens were observed under scanning electron microscope (SEM) Ceramic application was carried out layer by layer for an optimal height of 4 mm. The shear bond strength test was performed using a universal testing machine and the nature of the fracture was examined under SEM. The mean shear bond strength values for laser etched (Group C) Nickel-chromium (Ni-Cr) alloy bonded with ceramic was (49.12 ± 7.12 MPa) and ceramic bonded with Cobalt-chromium (Co-Cr) was (50.04 ± 4.27 MPa), sand blasted (Group B) Ni-Cr alloy bonded with ceramic was (26.00 ± 5.22 MPa), and ceramic bonded with Co-Cr was 24.54 ± 4.78 MPa. The SEM image after debonding showed 10% of adhesive failure and 70% cohesive failure and 20% of both adhesive and cohesive failure for Laser etching. However, there was no significant difference in the values of shear bond strength between the two base metal alloys in Group C. The s hear bond strength between ceramic bonded with Ni-Cr alloys using the Laser etching as surface treatment was 49.12 ± 7.12 MPa and for Co-Cr alloys 50.04 ± 4.27 MPa. Laser surface treatment produces an excellent surface roughness and achieved good shear bond strength values and aid in achieving a better bond strength between metals and ceramic.

  6. Comparative evaluation of effect of laser on shear bond strength of ceramic bonded with two base metal alloys: An in-vitro study

    Directory of Open Access Journals (Sweden)

    K Deepak

    2013-01-01

    Full Text Available The most common clinical failure in metal ceramic restoration is at the ceramo-metal interface. For the clinical longevity, metal-ceramic prostheses must have satisfactory bond strength between metal and ceramic. Aim and Objective: The aim of this study is to evaluate the effect of Laser etching on shear bond strength between base metal alloys and ceramic. Materials and Methods: A total of 60 specimens were made (Base 5 mm diameter and 1 mm thickness, step with 4 mm diameter and 4 mm in length. They were divided into three groups. Group A-control, Group B-sand blasting, and Group C-laser etching. The Surface morphology, surface roughness, and wettability of the specimens were observed under scanning electron microscope (SEM Ceramic application was carried out layer by layer for an optimal height of 4 mm. The shear bond strength test was performed using a universal testing machine and the nature of the fracture was examined under SEM. Results: The mean shear bond strength values for laser etched (Group C Nickel-chromium (Ni-Cr alloy bonded with ceramic was (49.12 ± 7.12 MPa and ceramic bonded with Cobalt-chromium (Co-Cr was (50.04 ± 4.27 MPa, sand blasted (Group B Ni-Cr alloy bonded with ceramic was (26.00 ± 5.22 MPa, and ceramic bonded with Co-Cr was 24.54 ± 4.78 MPa. The SEM image after debonding showed 10% of adhesive failure and 70% cohesive failure and 20% of both adhesive and cohesive failure for Laser etching. However, there was no significant difference in the values of shear bond strength between the two base metal alloys in Group C. Conclusion: The s hear bond strength between ceramic bonded with Ni-Cr alloys using the Laser etching as surface treatment was 49.12 ± 7.12 MPa and for Co-Cr alloys 50.04 ± 4.27 MPa. Laser surface treatment produces an excellent surface roughness and achieved good shear bond strength values and aid in achieving a better bond strength between metals and ceramic.

  7. Microshear bond strength of preheated silorane- and methacrylate-based composite resins to dentin.

    Science.gov (United States)

    Demirbuga, Sezer; Ucar, Faruk Izzet; Cayabatmaz, Muhammed; Zorba, Yahya Orcun; Cantekin, Kenan; Topçuoğlu, Hüseyin Sinan; Kilinc, Halil Ibrahim

    2016-01-01

    The aim of this study was to investigate the effect of preheating on microshear bond strength (MSBS) of silorane and methacrylate-based composite resins to human dentin. The teeth were randomly divided into three main groups: (1) composite resins were heated upto 68 °C; (2) cooled to 4 °C; and (3) control [room temperature (RT)]. Each group was then randomly subdivided into four subgroups according to adhesive system used [Solobond M (Voco), All Bond SE (Bisco), Clearfil SE Bond (CSE) (Kuraray), Silorane adhesive system (SAS) (3M ESPE)]. Resin composite cylinders were formed (0.9 mm diameter × 0.7 mm length) and MSBS of each specimen was tested. The preheated groups exhibited the highest MSBS (p composite resins may be an alternative way to increase the MSBS of composites on dentin. © Wiley Periodicals, Inc.

  8. Probing the nature of hydrogen bonds in DNA base pairs.

    Science.gov (United States)

    Mo, Yirong

    2006-07-01

    Energy decomposition analyses based on the block-localized wave-function (BLW-ED) method are conducted to explore the nature of the hydrogen bonds in DNA base pairs in terms of deformation, Heitler-London, polarization, electron-transfer and dispersion-energy terms, where the Heitler-London energy term is composed of electrostatic and Pauli-exchange interactions. A modest electron-transfer effect is found in the Watson-Crick adenine-thymine (AT), guanine-cytosine (GC) and Hoogsteen adenine-thymine (H-AT) pairs, confirming the weak covalence in the hydrogen bonds. The electrostatic attraction and polarization effects account for most of the binding energies, particularly in the GC pair. Both theoretical and experimental data show that the GC pair has a binding energy (-25.4 kcal mol(-1) at the MP2/6-31G** level) twice that of the AT (-12.4 kcal mol(-1)) and H-AT (-12.8 kcal mol(-1)) pairs, compared with three conventional N-H...O(N) hydrogen bonds in the GC pair and two in the AT or H-AT pair. Although the remarkably strong binding between the guanine and cytosine bases benefits from the opposite orientations of the dipole moments in these two bases assisted by the pi-electron delocalization from the amine groups to the carbonyl groups, model calculations demonstrate that pi-resonance has very limited influence on the covalence of the hydrogen bonds. Thus, the often adopted terminology "resonance-assisted hydrogen bonding (RHAB)" may be replaced with "resonance-assisted binding" which highlights the electrostatic rather than electron-transfer nature of the enhanced stabilization, as hydrogen bonds are usually regarded as weak covalent bonds.

  9. Inhibition of nuclear T3 binding by fatty acids: dependence on chain length, unsaturated bonds, cis-trans configuration and esterification

    NARCIS (Netherlands)

    Wiersinga, W. M.; Platvoet-ter Schiphorst, M.

    1990-01-01

    1. Fatty acids have the capacity for inhibition of nuclear T3 binding (INB). The present studies were undertaken to describe the INB-activity of fatty acids as a function of chain length, unsaturated bonds, cis-trans configuration, and esterification. 2. Isolated rat liver nuclei were incubated with

  10. Continuing Bonds in Bereavement: An Attachment Theory Based Perspective

    Science.gov (United States)

    Field, Nigel P.; Gao, Beryl; Paderna, Lisa

    2005-01-01

    An attachment theory based perspective on the continuing bond to the deceased (CB) is proposed. The value of attachment theory in specifying the normative course of CB expression and in identifying adaptive versus maladaptive variants of CB expression based on their deviation from this normative course is outlined. The role of individual…

  11. Evaluation of bond strength of various epoxy resin based sealers in oval shaped root canals.

    Science.gov (United States)

    Cakici, Fatih; Cakici, Elif Bahar; Ceyhanli, Kadir Tolga; Celik, Ersan; Kucukekenci, Funda Fundaoglu; Gunseren, Arif Onur

    2016-09-30

    The aim of this study was to evaluate the bond strength of AH plus, Acroseal, and Adseal to the root canal dentin. A total of 36 single-rooted, mandibular premolar teeth were used. Root canal shaping procedures were performed with ProTaper rotary instruments (Dentsply Maillefer) up to size F4. The prepared samples were then randomly assembled into 3 groups (n = 12). For each group, an ultrasonic tip (size 15, 0.02 taper) which was also coated with an epoxy resin based sealer and placed 2 mm shorter than the working length. The sealer was then activated for 10 s. A push-out test was used to measure the bond strength between the root canal dentine and the sealer. Kruskal-Wallis test to evaluate the push-out bond strength of epoxy based sealer (P = 0.05). The failure mode data were statistically analyzed using Pearson's chi square test (P = 0.05). Kruskal-Wallis test indicated that there were no statistically significant difference among the push out bond strength values of 3 mm (p = 0.123) and 6 mm (P = 0.057) for groups, there was statistically significant difference push out bond strength value of 9 mm (P = 0.032). Pearson's chi square test showed statistically significant differences for the failure types among the groups. Various epoxy resin based sealers activated ultrasonically showed similar bond strength in oval shaped root canals. Apical sections for all groups have higher push out bond strength values than middle and coronal sections.

  12. Study of chemical bond strength of methyl methacrylate (MMA based bonding agent on type I dentin collagen at various humidity

    Directory of Open Access Journals (Sweden)

    Adioro Soetojo

    2007-06-01

    Full Text Available One of the basic agents used in dentin bonding solution is methyl methacrylate (MMA. This bonding agent is widely used in dentistry. It have been proved that the adhesion between dentin bonding agent and collagen fibril is chemically bond; though the chemical bonding contribution is smaller than physical mechanical bond. The purpose of the research was to examined the chemical bonding strength of MMA based dentin bonding on type I dentin collagen at various humidity. Samples of treatment group were put into desiccator with 60%, 70%, 80%, and 90% humidity, while for control groups at room humidity (65%. Chemical bond of pure MMA and MMA mixed with collagen were measured by FTIR. The lower the value of MMA carbonyl, the higher absorbance band speak of chemical bond strength between MMA and collagen. Data was statistically analyzed with One-Way ANOVA at 95% confidence level continued with Tukey-HSD test. The result showed that the highest chemical bond strength was at 65% humidity (p ≤ 0.05. In conclusion, many esther carbonyl MMA molecules reacted with amino collagen at 65% humidity. This can be shown by the lowest peak's value of the MMA carbonyl absorbance at FTIR.

  13. SPEAKERS' IDENTIFICATION METHOD BASED ON COMPARISON OF PHONEME LENGTHS STATISTICS

    Directory of Open Access Journals (Sweden)

    E. V. Bulgakova

    2015-01-01

    Full Text Available Subject of research. The paper presents a semi-automatic method of speaker identification based on prosodic features comparison - statistics of phone lengths. Due to the development of speech technologies in recent times, there is an increased interest in searching of expert methods for speaker's voice identification, which supplement existing methods to increase identification reliability and also have low labour intensity. An efficient solution for this problem is necessary for making the reliable decision whether the voices of the speakers in the audio recordings are identical or different. Method description. We present a novel algorithm for calculating the difference of speakers’ voices based on comparing of statistics for phone and allophone lengths. Characteristic feature of the proposed method is the possibility of its application along with the other semi-automatic methods (acoustic, auditive and linguistic due to the lack of a strong correlation between analyzed features. The advantage of the method is the possibility to carry out rapid analysis of long-duration recordings because of preprocessing automation for data being analyzed. We describe the operation principles of an automatic speech segmentation module used for statistics calculation of sound lengths by acoustic-phonetic labeling. The software has been developed as an instrument of speech data preprocessing for expert analysis. Method approbation. This method was approved on the speech database of 130 speech records, including the Russian speech of the male speakers and female speakers, and showed reliability equal to 71.7% on the database containing female speech records, and 78.4% on the database containing male speech records. Also it was experimentally established that the most informative of all used features are statistics of phone lengths of vowels and sonorant sounds. Practical relevance. Experimental results have shown applicability of the proposed method for the

  14. Supramolecular materials based on hydrogen-bonded polymers

    NARCIS (Netherlands)

    ten Brinke, Gerrit; Ruokolainen, Janne; Ikkala, Olli; Binder, W

    2007-01-01

    Combining supramolecular principles with block copolymer self-assembly offers unique possibilities to create materials with responsive and/or tunable properties. The present chapter focuses on supramolecular materials based on hydrogen bonding and (block co-) polymers. Several cases will be

  15. Organic ferroelectrics based on hydrogen-bonded supermolecules

    International Nuclear Information System (INIS)

    Horiuchi, Sachio; Kumai, Reiji; Tokura, Yoshinori

    2007-01-01

    This article describes a new design strategy and prospective approaches to the fabrication of novel organic ferroelectrics. Ferroelectricity and a significant dielectric response as well as collective proton transfer are demonstrated in the hydrogen-bonded supramolecular chains composed of 2,5-dihydroxy-p-benzoquinone derivatives (acid) and nitrogen-containing aromatic bases. (author)

  16. Modelling of Ion Transport in Solids with a General Bond Valence Based Force-Field

    OpenAIRE

    S. Adams; R.P. Rao

    2010-01-01

    Empirical bond length - bond valence relations provide insight into the link between structure of and ion transport in solid electrolytes. Building on our earlier systematic adjustment of bond valence (BV) parameters to the bond softness, here we discuss how the squared BV mismatch can be linked to the absolute energy scale and used as a general Morse-type interaction potential for analyzing low-energy pathways in ion conducting solid or mixed conductors either by an energy landscape approach...

  17. Length scale and manufacturability in density-based topology optimization

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Wang, Fengwen; Sigmund, Ole

    2016-01-01

    Since its original introduction in structural design, density-based topology optimization has been applied to a number of other fields such as microelectromechanical systems, photonics, acoustics and fluid mechanics. The methodology has been well accepted in industrial design processes where it can...... performance and in many cases can completely destroy the optimality of the solution. Therefore, the goal of this paper is to review recent advancements in obtaining manufacturable topology-optimized designs. The focus is on methods for imposing minimum and maximum length scales, and ensuring manufacturable...

  18. Investigation of bonding properties of denture bases to silicone-based soft denture liner immersed in isobutyl methacrylate and 2-hydroxyethyl methacrylate

    OpenAIRE

    Akin, Hakan; Tugut, Faik; Mutaf, Burcu; Guney, Umit

    2014-01-01

    PURPOSE The purpose of this study was to investigate the bonding properties of denture bases to silicone-based soft denture liners immersed in isobutyl methacrylate (iBMA) and 2-hydroxyethyl methacrylate (HEMA) for various lengths of time. MATERIALS AND METHODS Polymethyl methacrylate (PMMA) test specimens were fabricated (75 mm in length, 12 mm in diameter at the thickest section, and 7 mm at the thinnest section) and then randomly assigned to five groups (n=15); untreated (Group 1), resilie...

  19. Compressive and bonding strength of fly ash based geopolymer mortar

    Science.gov (United States)

    Zailani, Warid Wazien Ahmad; Abdullah, Mohd Mustafa Al Bakri; Zainol, Mohd Remy Rozainy Mohd Arif; Razak, Rafiza Abd.; Tahir, Muhammad Faheem Mohd

    2017-09-01

    Geopolymer which is produced by synthesizing aluminosilicate source materials with an alkaline activator solution promotes sustainable and excellent properties of binder. The purpose of this paper is to determine the optimum binder to sand ratio of geopolymer mortars based on mechanical properties. In order to optimize the formulation of geopolymer mortar, various binder to sand ratios (0.25, 0.33, 0.5, 1.0, 2.0, 3.0, and 4.0) are prepared. The investigation on the effect of sand inclusion to the compressive and bonding strength of geopolymer mortar is approached. The experimental results show that the bonding strength performance of geopolymer is also depends on the various binder to sand ratio, where the optimum ratio 0.5 gives a highest strength of 12.73 MPa followed by 12.35 MPa, which corresponds the ratio 1.0 for geopolymer, while the compared value of OPC bonding strength is given by 9.3 MPa. The morphological structure at the interface zone is determined by Scanning Electron Microscope (SEM) and the homogenous bonding between geopolymer and substrate can be observed. Fly ash based geopolymers reveal a new category of mortar which has high potential to be used in the field of concrete repair and rehabilitation.

  20. Modelling of Ion Transport in Solids with a General Bond Valence Based Force-Field

    Directory of Open Access Journals (Sweden)

    S. Adams

    2010-12-01

    Full Text Available Empirical bond length - bond valence relations provide insight into the link between structure of and ion transport in solid electrolytes. Building on our earlier systematic adjustment of bond valence (BV parameters to the bond softness, here we discuss how the squared BV mismatch can be linked to the absolute energy scale and used as a general Morse-type interaction potential for analyzing low-energy pathways in ion conducting solid or mixed conductors either by an energy landscape approach or by molecular dynamics (MD simulations. For a wide range of Lithium oxides we could thus model ion transport revealing significant differences to an earlier geometric approach. Our novel BV-based force-field has also been applied to investigate a range of mixed conductors, focusing on cathode materials for lithium ion battery (LIB applications to promote a systematic design of LIB cathodes that combine high energy density with high power density. To demonstrate the versatility of the new BV-based force-field it is applied in exploring various strategies to enhance the power performance of safe low cost LIB materials (LiFePO4, LiVPO4F, LiFeSO4F, etc..

  1. Accurate Bond Lengths to Hydrogen Atoms from Single?Crystal X?ray Diffraction by Including Estimated Hydrogen ADPs and Comparison to Neutron and QM/MM Benchmarks

    OpenAIRE

    Dittrich, Birger; L?bben, Jens; Mebs, Stefan; Wagner, Armin; Luger, Peter; Flaig, Ralf

    2017-01-01

    Abstract Amino acid structures are an ideal test set for method?development studies in crystallography. High?resolution X?ray diffraction data for eight previously studied genetically encoding amino acids are provided, complemented by a non?standard amino acid. Structures were re?investigated to study a widely applicable treatment that permits accurate X?H bond lengths to hydrogen atoms to be obtained: this treatment combines refinement of positional hydrogen?atom parameters with aspherical s...

  2. PMMA to Polystyrene bonding for polymer based microfluidic systems

    KAUST Repository

    Fan, Yiqiang

    2013-03-29

    A thermal bonding technique for Poly (methylmethacrylate) (PMMA) to Polystyrene (PS) is presented in this paper. The PMMA to PS bonding was achieved using a thermocompression method, and the bonding strength was carefully characterized. The bonding temperature ranged from 110 to 125 C with a varying compression force, from 700 to 1,000 N (0.36-0.51 MPa). After the bonding process, two kinds of adhesion quantification methods were used to measure the bonding strength: the double cantilever beam method and the tensile stress method. The results show that the bonding strength increases with a rising bonding temperature and bonding force. The results also indicate that the bonding strength is independent of bonding time. A deep-UV surface treatment method was also provided in this paper to lower the bonding temperature and compression force. Finally, a PMMA to PS bonded microfluidic device was fabricated successfully. © 2013 Springer-Verlag Berlin Heidelberg.

  3. Bond strength test of acrylic artificial teeth with prosthetic base

    Directory of Open Access Journals (Sweden)

    Erna Kurnikasari

    2008-07-01

    Full Text Available Denture consists of acrylic artificial teeth and acrylic prothesis base bond chemically with a bond strength of 315 kgF/cm2. Most of the commercial acrylic artificial teeth do not specify their specifications and all of those acrylic artificial teeth do not include mechanical data (bond strength. The aim of this study is to discover which acrylic artificial teeth meet ADA specification no. 15. This study is a descriptive analytic study performed to 5 acrylic artificial teeth posterior brands commonly used by dentists and technicians. From each brand, 3 sample teeth were taken. The acrylic artificial teeth were prepared into a rectangular shape and were attached between acrylic prothesis base simulation and jigs. The sample was given tensile load using a Universal Testing Machine. The amount of force that causes the teeth to be fractured was recorded and the bond strength was calculated. The results of the study show that the average value for the five acrylic artificial teeth for the five brands were as followed: Brand A, 125.993 kgF/cm2; B, 188.457 kgF/cm2; C, 175.880 kgF/cm2; D, 153.373 kgF/cm2; E, 82.839 kgF/cm2. The data can be tested statistically by using One Way ANOVA test and Dunnett test (alpha = 0.05. From the study, it is concluded that the five acrylic artificial teeth have a bond strength below the ADA specification no. 15.

  4. Splitting rules for the electronic spectra of two-dimensional Fibonacci-class quasicrystals with one kind of atom and two bond lengths

    Science.gov (United States)

    Yang, Xiangbo; Xing, Da

    2002-04-01

    On the basis of the substitution rules for a one-dimensional Fibonacci-class chain, we construct two-dimensional Fibonacci-class quasicrystals with one kind of atom and two bond lengths. In the framework of the single-electron tight-binding nearest-interaction transfer model, we study the splitting rules of the electronic energy spectra for two-dimensional Fibonacci-class quasicrystals by means of a decomposition-decimation method based on a renormalization-group technique, and we also calculate the electronic energy spectra numerically. It is found that there exist only three kinds of clusters-n×n, n×(n+1), and (n+1)×(n+1)-for all classes of two-dimensional quasilattices, and that the electronic energy bands split as Ym-n-l. The general formula of the number for energy levels is obtained. We discover that there is a kind of so-called Fibonacci-class-number set for the parameters used to describe the energy-level number, and we obtain the set formulas. The experienced formula are sought out. The analytical results are confirmed by numerical simulations.

  5. Strengthening of Concrete Structures with cement based bonded composites

    DEFF Research Database (Denmark)

    Täljsten, Björn; Blanksvärd, Thomas

    2008-01-01

    Due to demands on higher loads, degradation, re-construction etc. there is a constant need for repair or strengthening of existing concrete structures. Many varying methods exist to strengthen concrete structures, one such commonly used technique utilizes surface epoxy bonded FRPs (Fibre Reinforced...... with improved working environment and better compatibility to the base concrete structure. This study gives an overview of different cement based systems, all with very promising results for structural upgrading. Studied parameters are structural retrofit for bending, shear and confinement. It is concluded...

  6. Continuing bonds in bereavement: an attachment theory based perspective.

    Science.gov (United States)

    Field, Nigel P; Gao, Beryl; Paderna, Lisa

    2005-05-01

    An attachment theory based perspective on the continuing bond to the deceased (CB) is proposed. The value of attachment theory in specifying the normative course of CB expression and in identifying adaptive versus maladaptive variants of CB expression based on their deviation from this normative course is outlined. The role of individual differences in attachment security on effective versus ineffective use of CB in coping with bereavement also is addressed. Finally, the moderating influence of type of loss (e.g., death of a spouse vs. child), culture, and religion on type of CB expression within an overarching attachment framework is discussed.

  7. Exact and efficient calculation of Lagrange multipliers in biological polymers with constrained bond lengths and bond angles: proteins and nucleic acids as example cases.

    Science.gov (United States)

    García-Risueño, Pablo; Echenique, Pablo; Alonso, J L

    2011-11-15

    To accelerate molecular dynamics simulations, it is common to impose holonomic constraints on the hardest degrees of freedom. In this way, the time step used to integrate the equations of motion can be increased, thereby allowing longer total simulation times. The imposition of such constraints results in an aditional set of N(c) equations (the equations of constraint) and unknowns (their associated Lagrange multipliers), whose solution is closely related to any algorithm implementing the constraints in Euclidean coordinates. In this work, it is shown that, due to the essentially linear structure of typical biological polymers the algebraic equations that need to be solved involve a matrix which is not only sparse, but also banded if the constraints are indexed in a skilful way. This allows the Lagrange multipliers to be obtained through a noniterative procedure, which can be considered exact up to machine precision, and which takes O(N(c)) operations, instead of the usual O(N c3) for generic molecular systems. We develop the formalism, and describe the appropriate indexing for a number of model molecules. Finally, we provide a numerical example of the technique in a series of polyalanine peptides of different lengths. Although a use of the Lagrange multipliers without any modification in the solution of the underlying ordinary differential equations yields unstable integration algorithms, the central role of these quantities makes their efficient calculation useful for the improvement of methods that correctly enforce the exact satisfaction of the constraints at each time step. We provide several examples of this. Copyright © 2011 Wiley Periodicals, Inc.

  8. Safe-by-Design CuO Nanoparticles via Fe-Doping, Cu-O Bond Length Variation, and Biological Assessment in Cells and Zebrafish Embryos.

    Science.gov (United States)

    Naatz, Hendrik; Lin, Sijie; Li, Ruibin; Jiang, Wen; Ji, Zhaoxia; Chang, Chong Hyun; Köser, Jan; Thöming, Jorg; Xia, Tian; Nel, Andre E; Mädler, Lutz; Pokhrel, Suman

    2017-01-24

    The safe implementation of nanotechnology requires nanomaterial hazard assessment in accordance with the material physicochemical properties that trigger the injury response at the nano/bio interface. Since CuO nanoparticles (NPs) are widely used industrially and their dissolution properties play a major role in hazard potential, we hypothesized that tighter bonding of Cu to Fe by particle doping could constitute a safer-by-design approach through decreased dissolution. Accordingly, we designed a combinatorial library in which CuO was doped with 1-10% Fe in a flame spray pyrolysis reactor. The morphology and structural properties were determined by XRD, BET, Raman spectroscopy, HRTEM, EFTEM, and EELS, which demonstrated a significant reduction in the apical Cu-O bond length while simultaneously increasing the planar bond length (Jahn-Teller distortion). Hazard screening was performed in tissue culture cell lines and zebrafish embryos to discern the change in the hazardous effects of doped vs nondoped particles. This demonstrated that with increased levels of doping there was a progressive decrease in cytotoxicity in BEAS-2B and THP-1 cells, as well as an incremental decrease in the rate of hatching interference in zebrafish embryos. The dissolution profiles were determined and the surface reactions taking place in Holtfreter's solution were validated using cyclic voltammetry measurements to demonstrate that the Cu + /Cu 2+ and Fe 2+ /Fe 3+ redox species play a major role in the dissolution process of pure and Fe-doped CuO. Altogether, a safe-by-design strategy was implemented for the toxic CuO particles via Fe doping and has been demonstrated for their safe use in the environment.

  9. Nucleophilicities of Lewis Bases B and Electrophilicities of Lewis Acids A Determined from the Dissociation Energies of Complexes B⋯A Involving Hydrogen Bonds, Tetrel Bonds, Pnictogen Bonds, Chalcogen Bonds and Halogen Bonds.

    Science.gov (United States)

    Alkorta, Ibon; Legon, Anthony C

    2017-10-23

    It is shown that the dissociation energy D e for the process B⋯A = B + A for 250 complexes B⋯A composed of 11 Lewis bases B (N₂, CO, HC≡CH, CH₂=CH₂, C₃H₆, PH₃, H₂S, HCN, H₂O, H₂CO and NH₃) and 23 Lewis acids (HF, HCl, HBr, HC≡CH, HCN, H₂O, F₂, Cl₂, Br₂, ClF, BrCl, H₃SiF, H₃GeF, F₂CO, CO₂, N₂O, NO₂F, PH₂F, AsH₂F, SO₂, SeO₂, SF₂, and SeF₂) can be represented to good approximation by means of the equation D e = c ' N B E A , in which N B is a numerical nucleophilicity assigned to B, E A is a numerical electrophilicity assigned to A, and c ' is a constant, conveniently chosen to have the value 1.00 kJ mol -1 here. The 250 complexes were chosen to cover a wide range of non-covalent interaction types, namely: (1) the hydrogen bond; (2) the halogen bond; (3) the tetrel bond; (4) the pnictogen bond; and (5) the chalcogen bond. Since there is no evidence that one group of non-covalent interaction was fitted any better than the others, it appears the equation is equally valid for all the interactions considered and that the values of N B and E A so determined define properties of the individual molecules. The values of N B and E A can be used to predict the dissociation energies of a wide range of binary complexes B⋯A with reasonable accuracy.

  10. Nucleophilicities of Lewis Bases B and Electrophilicities of Lewis Acids A Determined from the Dissociation Energies of Complexes B⋯A Involving Hydrogen Bonds, Tetrel Bonds, Pnictogen Bonds, Chalcogen Bonds and Halogen Bonds

    Directory of Open Access Journals (Sweden)

    Ibon Alkorta

    2017-10-01

    Full Text Available It is shown that the dissociation energy D e for the process B⋯A = B + A for 250 complexes B⋯A composed of 11 Lewis bases B (N2, CO, HC≡CH, CH2=CH2, C3H6, PH3, H2S, HCN, H2O, H2CO and NH3 and 23 Lewis acids (HF, HCl, HBr, HC≡CH, HCN, H2O, F2, Cl2, Br2, ClF, BrCl, H3SiF, H3GeF, F2CO, CO2, N2O, NO2F, PH2F, AsH2F, SO2, SeO2, SF2, and SeF2 can be represented to good approximation by means of the equation D e = c ′ N B E A , in which N B is a numerical nucleophilicity assigned to B, E A is a numerical electrophilicity assigned to A, and c ′ is a constant, conveniently chosen to have the value 1.00 kJ mol−1 here. The 250 complexes were chosen to cover a wide range of non-covalent interaction types, namely: (1 the hydrogen bond; (2 the halogen bond; (3 the tetrel bond; (4 the pnictogen bond; and (5 the chalcogen bond. Since there is no evidence that one group of non-covalent interaction was fitted any better than the others, it appears the equation is equally valid for all the interactions considered and that the values of N B and E A so determined define properties of the individual molecules. The values of N B and E A can be used to predict the dissociation energies of a wide range of binary complexes B⋯A with reasonable accuracy.

  11. Comparison of fish-community size spectra based on length ...

    African Journals Online (AJOL)

    Estimates of fish-community size spectra are promising indicators of the impact of fishing on fish assemblages. Size spectra consist of logarithmic graphs of abundance plotted against fish body size. Size spectra may either be constructed from length frequency data or estimated from the mean sizes and abundances of the ...

  12. Measuring Clearance Mechanics Based on Dynamic Leg Length

    Science.gov (United States)

    Khamis, Sam; Danino, Barry; Hayek, Shlomo; Carmeli, Eli

    2018-01-01

    The aim of this study was to quantify clearance mechanics during gait. Seventeen children diagnosed with hemiplegic cerebral palsy underwent a three-dimensional gait analysis evaluation. Dynamic leg lengths were measured from the hip joint center to the heel, to the ankle joint center and to the forefoot throughout the gait cycle. Significant…

  13. DNA origami-based nanoribbons: assembly, length distribution, and twist

    International Nuclear Information System (INIS)

    Jungmann, Ralf; Scheible, Max; Kuzyk, Anton; Pardatscher, Guenther; Simmel, Friedrich C; Castro, Carlos E

    2011-01-01

    A variety of polymerization methods for the assembly of elongated nanoribbons from rectangular DNA origami structures are investigated. The most efficient method utilizes single-stranded DNA oligonucleotides to bridge an intermolecular scaffold seam between origami monomers. This approach allows the fabrication of origami ribbons with lengths of several micrometers, which can be used for long-range ordered arrangement of proteins. It is quantitatively shown that the length distribution of origami ribbons obtained with this technique follows the theoretical prediction for a simple linear polymerization reaction. The design of flat single layer origami structures with constant crossover spacing inevitably results in local underwinding of the DNA helix, which leads to a global twist of the origami structures that also translates to the nanoribbons.

  14. DNA origami-based nanoribbons: assembly, length distribution, and twist

    Energy Technology Data Exchange (ETDEWEB)

    Jungmann, Ralf; Scheible, Max; Kuzyk, Anton; Pardatscher, Guenther; Simmel, Friedrich C [Lehrstuhl fuer Bioelektronik, Physik-Department and ZNN/WSI, Technische Universitaet Muenchen, Am Coulombwall 4a, 85748 Garching (Germany); Castro, Carlos E, E-mail: simmel@ph.tum.de [Labor fuer Biomolekulare Nanotechnologie, Physik-Department and ZNN/WSI, Technische Universitaet Muenchen, Am Coulombwall 4a, 85748 Garching (Germany)

    2011-07-08

    A variety of polymerization methods for the assembly of elongated nanoribbons from rectangular DNA origami structures are investigated. The most efficient method utilizes single-stranded DNA oligonucleotides to bridge an intermolecular scaffold seam between origami monomers. This approach allows the fabrication of origami ribbons with lengths of several micrometers, which can be used for long-range ordered arrangement of proteins. It is quantitatively shown that the length distribution of origami ribbons obtained with this technique follows the theoretical prediction for a simple linear polymerization reaction. The design of flat single layer origami structures with constant crossover spacing inevitably results in local underwinding of the DNA helix, which leads to a global twist of the origami structures that also translates to the nanoribbons.

  15. Towards a unified description of the hydrogen bond network of liquid water: A dynamics based approach

    International Nuclear Information System (INIS)

    Ozkanlar, Abdullah; Zhou, Tiecheng; Clark, Aurora E.

    2014-01-01

    The definition of a hydrogen bond (H-bond) is intimately related to the topological and dynamic properties of the hydrogen bond network within liquid water. The development of a universal H-bond definition for water is an active area of research as it would remove many ambiguities in the network properties that derive from the fixed definition employed to assign whether a water dimer is hydrogen bonded. This work investigates the impact that an electronic-structure based definition, an energetic, and a geometric definition of the H-bond has upon both topological and dynamic network behavior of simulated water. In each definition, the use of a cutoff (either geometric or energetic) to assign the presence of a H-bond leads to the formation of transiently bonded or broken dimers, which have been quantified within the simulation data. The relative concentration of transient species, and their duration, results in two of the three definitions sharing similarities in either topological or dynamic features (H-bond distribution, H-bond lifetime, etc.), however no two definitions exhibit similar behavior for both classes of network properties. In fact, two networks with similar local network topology (as indicated by similar average H-bonds) can have dramatically different global network topology (as indicated by the defect state distributions) and altered H-bond lifetimes. A dynamics based correction scheme is then used to remove artificially transient H-bonds and to repair artificially broken bonds within the network such that the corrected network exhibits the same structural and dynamic properties for two H-bond definitions (the properties of the third definition being significantly improved). The algorithm described represents a significant step forward in the development of a unified hydrogen bond network whose properties are independent of the original hydrogen bond definition that is employed

  16. New Statistical Randomness Tests Based on Length of Runs

    Directory of Open Access Journals (Sweden)

    Ali Doğanaksoy

    2015-01-01

    Full Text Available Random sequences and random numbers constitute a necessary part of cryptography. Many cryptographic protocols depend on random values. Randomness is measured by statistical tests and hence security evaluation of a cryptographic algorithm deeply depends on statistical randomness tests. In this work we focus on statistical distributions of runs of lengths one, two, and three. Using these distributions we state three new statistical randomness tests. New tests use χ2 distribution and, therefore, exact values of probabilities are needed. Probabilities associated runs of lengths one, two, and three are stated. Corresponding probabilities are divided into five subintervals of equal probabilities. Accordingly, three new statistical tests are defined and pseudocodes for these new statistical tests are given. New statistical tests are designed to detect the deviations in the number of runs of various lengths from a random sequence. Together with some other statistical tests, we analyse our tests’ results on outputs of well-known encryption algorithms and on binary expansions of e, π, and 2. Experimental results show the performance and sensitivity of our tests.

  17. Semiempirical search for oxide superconductors based on bond valence sums

    International Nuclear Information System (INIS)

    Tanaka, S.; Fukushima, N.; Niu, H.; Ando, K.

    1992-01-01

    Relationships between crystal structures and electronic states of layered transition-metal oxides are analyzed in the light of bond valence sums. Correlations between the superconducting transition temperature T c and the bond-valence-sum parameters are investigated for the high-T c cuprate compounds. Possibility of making nonsuperconducting oxides superconducting is discussed. (orig.)

  18. Factors affecting the bond strength of denture base and reline acrylic resins to base metal materials

    Directory of Open Access Journals (Sweden)

    Naomi Tanoue

    2013-07-01

    Full Text Available OBJECTIVE: The shear bond strengths of two hard chairside reline resin materials and an auto-polymerizing denture base resin material to cast Ti and a Co-Cr alloy treated using four conditioning methods were investigated. MATERIAL AND METHODS: Disk specimens (diameter 10 mm and thickness 2.5 mm were cast from pure Ti and Co-Cr alloy. The specimens were wet-ground to a final surface finish of 600 grit, air-dried, and treated with the following bonding systems: 1 air-abraded with 50-70-µm grain alumina (CON; 2 1 + conditioned with a primer, including an acidic phosphonoacetate monomer (MHPA; 3 1 + conditioned with a primer including a diphosphate monomer (MDP; 4 treated with a tribochemical system. Three resin materials were applied to each metal specimen. Shear bond strengths were determined before and after 10,000 thermocycles. RESULTS: The strengths decreased after thermocycling for all combinations. Among the resin materials assessed, the denture base material showed significantly (p<0.05 greater shear bond strengths than the two reline materials, except for the CON condition. After 10,000 thermocycles, the bond strengths of two reline materials decreased to less than 10 MPa for both metals. The bond strengths of the denture base material with MDP were sufficient: 34.56 MPa for cast Ti and 38.30 for Co-Cr alloy. CONCLUSION: Bonding of reline resin materials to metals assessed was clinically insufficient, regardless of metal type, surface treatment, and resin composition. For the relining of metal denture frameworks, a denture base material should be used.

  19. Absolute and relative-rate measurement of the rate coefficient for reaction of perfluoro ethyl vinyl ether (C2F5OCF[double bond, length as m-dash]CF2) with OH.

    Science.gov (United States)

    Srinivasulu, G; Bunkan, A J C; Amedro, D; Crowley, J N

    2018-01-31

    The rate coefficient (k 1 ) for the reaction of OH radicals with perfluoro ethyl vinyl ether (PEVE, C 2 F 5 OCF[double bond, length as m-dash]CF 2 ) has been measured as a function of temperature (T = 207-300 K) using the technique of pulsed laser photolysis with detection of OH by laser-induced fluorescence (PLP-LIF) at pressures of 50 or 100 Torr N 2 bath gas. In addition, the rate coefficient was measured at 298 K and in one atmosphere of air by the relative-rate technique with loss of PEVE and reference reactant monitored in situ by IR absorption spectroscopy. The rate coefficient has a negative temperature dependence which can be parameterized as: k 1 (T) = 6.0 × 10 -13  exp[(480 ± 38/T)] cm 3 molecule -1 s -1 and a room temperature value of k 1 (298 K) = (3.0 ± 0.3) × 10 -12 cm 3 molecule -1 s -1 . Highly accurate rate coefficients from the PLP-LIF experiments were achieved by optical on-line measurements of PEVE and by performing the measurements at two different apparatuses. The large rate coefficient and the temperature dependence indicate that the reaction proceeds via OH addition to the C[double bond, length as m-dash]C double bond, the high pressure limit already being reached at 50 Torr N 2 . Based on the rate coefficient and average OH levels, the atmospheric lifetime of PEVE was estimated to be a few days.

  20. Branch length similarity entropy-based descriptors for shape representation

    Science.gov (United States)

    Kwon, Ohsung; Lee, Sang-Hee

    2017-11-01

    In previous studies, we showed that the branch length similarity (BLS) entropy profile could be successfully used for the shape recognition such as battle tanks, facial expressions, and butterflies. In the present study, we proposed new descriptors, roundness, symmetry, and surface roughness, for the recognition, which are more accurate and fast in the computation than the previous descriptors. The roundness represents how closely a shape resembles to a circle, the symmetry characterizes how much one shape is similar with another when the shape is moved in flip, and the surface roughness quantifies the degree of vertical deviations of a shape boundary. To evaluate the performance of the descriptors, we used the database of leaf images with 12 species. Each species consisted of 10 - 20 leaf images and the total number of images were 160. The evaluation showed that the new descriptors successfully discriminated the leaf species. We believe that the descriptors can be a useful tool in the field of pattern recognition.

  1. Formation of a metal-to-nitrogen bond of normal length by a neutral sufonamide group within a tridentate ligand. A new approach to radiopharmaceutical bioconjugation.

    Science.gov (United States)

    Perera, Theshini; Abhayawardhana, Pramuditha; Marzilli, Patricia A; Fronczek, Frank R; Marzilli, Luigi G

    2013-03-04

    We demonstrate that a tertiary sulfonamide group, N(SO2R)R'2, can rehybridize to form a M-N bond of normal length even when the group is in a linear tridentate ligand, such as in the new tridentate N(SO2R)dpa ligands derived from di-(2-picolyl)amine (N(H)dpa). N(SO2R)dpa ligands were used to prepare fac-[Re(CO)3(N(SO2R)dpa)](PF6 or BF4) complexes. Structural characterization of the new complexes established that the tertiary sulfonamide nitrogen atom binds to Re with concomitant sp(2)-to-sp(3) rehybridization, facilitating facial coordination. The new fac-[Re(CO)3(N(SO2R)dpa)]X structures provide the only examples for any metal with the sulfonamide as part of a noncyclic linear tridentate ligand and with a normal metal-to-nitrogen(tertiary sulfonamide) bond length. Rare previous examples of such normal M-N bonds have been found only in more constrained situations, such as with tripodal tetradentate ligands. Our long-term objectives for the new tridentate N(SO2R)dpa ligands are to develop the fundamental chemistry relevant to the eventual use of the fac-[M(I)(CO)3](+) core (M = (99m)Tc, (186/188)Re) in imaging and therapy. The sulfonamide group uniquely contributes to two of our goals: expanding ways to conjugate the fac-[M(I)(CO)3](+) core to biological molecules and also developing new symmetrical tridentate ligands that can coordinate facially to this core. Tests of our conjugation method, conducted by linking the fac-[Re(I)(CO)3](+) core to a new tetraarylporphyrin (T(N(SO2C6H4)dpa)P) as well as to a dansyl (5-(dimethylamino)naphthalene-1-sulfonyl) group, demonstrate that large molecular fragments can be tethered via a coordinated tertiary sulfonamide linkage to this core.

  2. Analyses of Non-bonding Length, Partial Atomics Charge and Electrostatic Energy from Molecular Dynamics Simulation of Phospholipase A2 – Substrate

    Directory of Open Access Journals (Sweden)

    Nirwan Syarif

    2016-11-01

    Full Text Available This paper reports molecular dynamics simulation of phospholipase A2 (PLA2– substrate that has been done. Non-bonding length, partial atomic charge and electrostatic energy were used to evaluation the interaction between PLA2 and substrate. The research was subjected for three types of PLA2 of different sources, i.e, homo sapien, bovinus and porcinus, by using computer files of their molecular structures. The files with code 3elo, 1bp2, dan 1y6o were downloaded from protein data bank. Substrate structure can be found in 1y60 and was separated from its enzyme structure and docked into two other PLA2 structures for simulation purpose. Molecular dynamics simulations were done for 30000 steps with constant in number of molecules, volume and temperature (NVT. The results showed the existing of flip-flop mechanism as basic feature of PLA2 – substrate reactions. Interaction length analysis results indicated the presence of water molecules on the structures of 1bp2 and 3elo at the time of the simulation was completed. The existence of aspagine at the reaction site confirmed the theory that this amino acid is responsible for the survival of the reaction. the electrostatic energy increased substantially in the interaction after homo sapien PLA2 (3elo and Bovinus (1bp2 with the substrate. Inverse effect took place in the PLA porcinus (1y6o.

  3. sp3-Bonded silicon allotropes based on the Kelvin problem.

    Science.gov (United States)

    Zhao, Hui-Yan; Wang, Jing; Ma, Qing-Min; Liu, Ying

    2013-10-28

    The Kelvin problem, how to partition three-dimensional space into cells of equal volume with minimal area, is a fascinating one. Aggregations of bubbles are naturally physical illustrations of the Kelvin problem. And the superconductor Na8Si46 as an inspiration leads to an amazing discovery of the Weaire-Phelan (WP) structure of foam - the optimal solution to the Kelvin problem to date. Here based on the structural similarity between sp(3)-bonded silicon allotropes and the solutions to the Kelvin problem, a series of new sp(3)-hybridization silicon allotropes, named "Kelvin Silicons", are presented. Furthermore, the structural stability and electronic properties of these new silicon allotropes are investigated using density-functional theory (DFT) calculations. The results show that Kelvin Silicons are structurally stable semiconductors with indirect bandgaps in the range of 0.17-1.40 eV, and their bulk moduli are about 75.9-88.5% that of the diamond phase. The simulated X-ray diffraction spectra of the new silicon crystalline structures would provide more information for possible experimental observations and synthesis.

  4. [Carbon-carbon bond formation based on alkenylphosphonates].

    Science.gov (United States)

    Nagaoka, Y

    2001-11-01

    We have been engaged in the development of asymmetric conjugate addition reactions of lithium thiolates, organolithiums and organocopper reagents under the control of external chiral ligands and we have also developed an efficient asymmetric Horner-Wadsworth-Emmons (HWE) reaction using an external chiral Ligand. We attempted to synthesize axial chiral allenes by combination of these conjugate addition reaction and HWE reaction. In the course of this study, we found that Michael-aldol reaction of alkenylphosphonates 1 using LDA and aldehydes results in the direct formation of alpha,beta-unsaturated hydroxyphosphonate 4, which was efficiently converted to allene by treatment with KH or KH-18-crown-6. Furthermore, allenes were synthesized by sequential double HWE reaction in one-flask manner starting from methylenebisphosphonate 8. The key to success is a metal exchange of intermediate lithium alkoxide 4-Li to potassium alkoxide 4-K by the addition of t-BuOK. As our continuous study of carbon-carbon bond formation based on alkenylphosphonates, a cyclization reaction of bisalkenylphosphonate 6 was developed. Although the treatment of 6 with organolithium reagents afforded a mixture of addition-cyclization product 9 and deprotonation-cyclization product 10, the treatment of 6 with LDA gave 10 selectively. These cyclization methods were applied to the synthesis of efficient chiral phosphine ligands.

  5. Evaluation of thiouracil-based adhesive systems for bonding cast silver-palladium-copper-gold alloy.

    Science.gov (United States)

    Yamashita, Miyuki; Koizumi, Hiroyasu; Ishii, Takaya; Furuchi, Mika; Matsumura, Hideo

    2010-09-01

    This study aimed to evaluate the effect of adhesive systems based on a thiouracil monomer on bonding to silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell M.C.12). Disk specimens were cast from the alloy and then air-abraded with alumina. The disks were bonded using six bonding systems selected from four primers and three luting materials. Shear bond strengths were determined both before and after thermocycling. Bond strength varied from 2.7 MPa to 32.0 MPa. Three systems based on a thiouracil monomer (MTU-6) showed durable bonding to the alloy, with post-thermocycling bond strengths of 22.4 MPa for the Metaltite (MTU-6) primer and Super-Bond, a tri-n-butylborane (TBB) initiated resin, 9.0 MPa for the Multi-Bond II resin, and 8.1 MPa for the Metaltite and Bistite II system. It can be concluded that a combination of thiouracil-based primer and TBB initiated resin is effective for bonding Ag-Pd-Cu-Au alloy.

  6. Quantification of Hydrogen Bond Strength Based on Interaction Coordinates: A New Approach.

    Science.gov (United States)

    Pandey, Sarvesh Kumar; Manogaran, Dhivya; Manogaran, Sadasivam; Schaefer, Henry F

    2017-08-17

    A new approach to quantify hydrogen bond strengths based on interaction coordinates (HBSBIC) is proposed and is very promising. In this research, it is assumed that the projected force field of the fictitious three atoms fragment (DHA) where D is the proton donor and A is the proton acceptor from the full molecular force field of the H-bonded complex characterizes the hydrogen bond. The "interaction coordinate (IC)" derived from the internal compliance matrix elements of this three-atom fragment measures how the DH covalent bond (its electron density) responds to constrained optimization when the HA hydrogen bond is stretched by a known amount (its electron density is perturbed by a specified amount). This response of the DH bond, based on how the IC depends on the electron density along the HA bond, is a measure of the hydrogen bond strength. The inter- and intramolecular hydrogen bond strengths for a variety of chemical and biological systems are reported. When defined and evaluated using the IC approach, the HBSBIC index leads to satisfactory results. Because this involves only a three-atom fragment for each hydrogen bond, the approach should open up new directions in the study of "appropriate small fragments" in large biomolecules.

  7. Statistical length of DNA based on AFM image measured by a computer

    International Nuclear Information System (INIS)

    Chen Xinqing; Qiu Xijun; Zhang Yi; Hu Jun; Wu Shiying; Huang Yibo; Ai Xiaobai; Li Minqian

    2001-01-01

    Taking advantage of image processing technology, the contour length of DNA molecule was measured automatically by a computer. Based on the AFM image of DNA, the topography of DNA was simulated into a curve. Then the DNA length was measured automatically by inserting mode. It was shown that the experimental length of a naturally deposited DNA (180.4 +- 16.4 nm) was well consistent with the theoretical length (185.0 nm). Comparing to other methods, the present approach had advantages of precision and automatism. The stretched DNA was also measured. It present approach had advantages of precision and automatism. The stretched DNA was also measured. It was shown that the experimental length (343.6 +- 20.7 nm) was much longer than the theoretical length (307.0 nm). This result indicated that the stretching process had a distinct effect on the DNA length. However, the method provided here avoided the DNA-stretching effect

  8. Measurement and Theory of Hydrogen Bonding Contribution to Isosteric DNA Base Pairs

    OpenAIRE

    Khakshoor, Omid; Wheeler, Steven E.; Houk, K. N.; Kool, Eric T.

    2012-01-01

    We address the recent debate surrounding the ability of 2,4-difluorotoluene (F), a low-polarity mimic of thymine (T), to form a hydrogen-bonded complex with adenine in DNA. The hydrogen bonding ability of F has been characterized as small to zero in various experimental studies, and moderate to small in computational studies. However, recent X-ray crystallographic studies of difluorotoluene in DNA/RNA have indicated, based on interatomic distances, possible hydrogen bonding interactions betwe...

  9. Life cycle assessment of bio-based, waterborne PU adhesives for fast industrial bonding processes

    OpenAIRE

    Maga, Daniel; Melchiors, Martin; Henneken, Hartmut; Taden, Andreas

    2017-01-01

    Aqueous PU dispersion adhesives based on high molecular weight, semi-crystalline polyurethane polymers have long demonstrated their outstanding performance and are a well-established bonding technology in several industrial applications. Due to their thermal activation properties and sharp melting area, these adhesives allow for efficient bonding processes with short bond strength build-up times. State-of-the-art is the use of polyester building blocks from fossil raw material resources to sy...

  10. Longer leukocyte telomere length in Costa Rica's Nicoyan Peninsula: A population-based study

    Science.gov (United States)

    Rehkopf, David H; Dow, William H; Rosero-Bixby, Luis; Lin, Jue; Epel, Elissa S; Blackburn, Elizabeth H

    2013-01-01

    Studies in humans suggest that leukocyte telomere length may act as a marker of biological aging. We investigated whether individuals in the Nicoya region of Costa Rica, known for exceptional longevity, had longer telomere length than those in other parts of the country. After controlling for age, age squared, rurality, rainy season and gender, mean leukocyte telomere length in Nicoya was substantially longer (81 base pairs, pCosta Rica, providing evidence of a biological pathway to which this notable longevity may be related. This relationship remains unchanged (79 base pairs, p<0.05) after statistically controlling for nineteen potential biological, dietary and social and demographic mediators. Thus the difference in mean leukocyte telomere length that characterizes this unique region does not appear to be explainable by traditional behavioral and biological risk factors. More detailed examination of mean leukocyte telomere length by age shows that the regional telomere length difference declines at older ages. PMID:23988653

  11. Dem Generation with Short Base Length Pleiades Triplet

    Science.gov (United States)

    Jacobsen, K.; Topan, H.

    2015-03-01

    An image triplet of Pleiades images covering the area of Zonguldak, Turkey has been investigated. The height to base relation of the first to the last image is just 1:4.5 and for the first and the second image 1:9. This is quite below the usual height to base relation of 1:1.6 for a typical stereo pair of space images. The corresponding small angle of convergence influences the possible vertical accuracy, but images with such a small angle of convergence are more similar to each other as images with larger convergence angles. This enables a better image matching, improving the vertical accuracy and compensating partially the influence of poor intersection geometry. Even over forest areas no matching gaps occurred. Height models are generated with different base configurations and compared with a reference height model. Pleiades images are distributed with 50cm ground sampling distance instead of the physical size of 70cm, the image quality justifies this zooming and also the geometric results are in the range of other space images with originally 50cm GSD. The image orientation by bias corrected Rational Polynomial Coefficients (RPC) is leading with more as 160 ground control points (GCP) to root mean square (RMS) differences slightly below 1.0 GSD of the distributed images (0.5m GSD). Only negligible systematic errors have been identified. With the combination of the first and last image a standard deviation of the generated height model of 1.6m, respectively for flat terrain close to 1.0m has been reached in relation to a reference height model. The small angle of convergence is not as much influencing the height accuracy as according to simple geometric relation.

  12. Fabrication and bonding of thiol-ene-based microfluidic devices

    DEFF Research Database (Denmark)

    Sikanen, Tiina M; Lafleur, Josiane P.; Moilanen, Maria-Elisa

    2013-01-01

    In this work, the bonding strength of microchips fabricated by thiol-ene free-radical polymerization was characterized in detail by varying the monomeric thiol/allyl composition from the stoichiometric ratio (1:1) up to 100% excess of thiol (2:1) or allyl (1:2) functional groups. Four different...

  13. Investigation of bonding properties of denture bases to silicone-based soft denture liner immersed in isobutyl methacrylate and 2-hydroxyethyl methacrylate.

    Science.gov (United States)

    Akin, Hakan; Tugut, Faik; Mutaf, Burcu; Guney, Umit

    2014-04-01

    The purpose of this study was to investigate the bonding properties of denture bases to silicone-based soft denture liners immersed in isobutyl methacrylate (iBMA) and 2-hydroxyethyl methacrylate (HEMA) for various lengths of time. Polymethyl methacrylate (PMMA) test specimens were fabricated (75 mm in length, 12 mm in diameter at the thickest section, and 7 mm at the thinnest section) and then randomly assigned to five groups (n=15); untreated (Group 1), resilient liner immersed in iBMA for 1 minute (Group 2), resilient liner immersed in iBMA for 3 minutes (Group 3), resilient liner immersed in HEMA for 1 minute (Group 4), and resilient liner immersed in HEMA for 3 minutes (Group 5). The resilient liner specimens were processed between 2 PMMA blocks. Bonding strength of the liners to PMMA was compared by tensile test with a universal testing machine at a crosshead speed of 5 mm/min. Data were evaluated by 1-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (α=0.05). The highest mean value of force was observed in Group 3 specimens. The differences between groups were statistically significant (P<.05), except between Group 1 and Group 4 (P=.063). Immersion of silicone-based soft denture liners in iBMA for 3 minutes doubled the tensile bond strength between the silicone soft liner and PMMA denture base materials compared to the control group.

  14. Accurate Bond Lengths to Hydrogen Atoms from Single-Crystal X-ray Diffraction by Including Estimated Hydrogen ADPs and Comparison to Neutron and QM/MM Benchmarks.

    Science.gov (United States)

    Dittrich, Birger; Lübben, Jens; Mebs, Stefan; Wagner, Armin; Luger, Peter; Flaig, Ralf

    2017-04-03

    Amino acid structures are an ideal test set for method-development studies in crystallography. High-resolution X-ray diffraction data for eight previously studied genetically encoding amino acids are provided, complemented by a non-standard amino acid. Structures were re-investigated to study a widely applicable treatment that permits accurate X-H bond lengths to hydrogen atoms to be obtained: this treatment combines refinement of positional hydrogen-atom parameters with aspherical scattering factors with constrained "TLS+INV" estimated hydrogen anisotropic displacement parameters (H-ADPs). Tabulated invariom scattering factors allow rapid modeling without further computations, and unconstrained Hirshfeld atom refinement provides a computationally demanding alternative when database entries are missing. Both should incorporate estimated H-ADPs, as free refinement frequently leads to over-parameterization and non-positive definite H-ADPs irrespective of the aspherical scattering model used. Using estimated H-ADPs, both methods yield accurate and precise X-H distances in best quantitative agreement with neutron diffraction data (available for five of the test-set molecules). This work thus solves the last remaining problem to obtain such results more frequently. Density functional theoretical QM/MM computations are able to play the role of an alternative benchmark to neutron diffraction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Validity of plant fiber length measurement : a review of fiber length measurement based on kenaf as a model

    Science.gov (United States)

    James S. Han; Theodore. Mianowski; Yi-yu. Lin

    1999-01-01

    The efficacy of fiber length measurement techniques such as digitizing, the Kajaani procedure, and NIH Image are compared in order to determine the optimal tool. Kenaf bast fibers, aspen, and red pine fibers were collected from different anatomical parts, and the fiber lengths were compared using various analytical tools. A statistical analysis on the validity of the...

  16. Errors in Length-weight Parameters at FishBase.org

    OpenAIRE

    Michael Courtney; Simeon Cole-Fletcher; Lucas Marin-Salcedo; Ajaya Rana

    2011-01-01

    Background: FishBase.org is an on-line database of fish related data that has been cited over 1500 times in the fisheries literature. Length-weight relationships in fish traditionally employ the model, W(L) = aL^b^, where L is length and W is weight. Parameters a and b are catalogued by FishBase for a large number of sources and species. FishBase.org detects outliers in a plot of log(a) vs. b to identify dubious length-weight parameters.

  17. Bond strength of resin cements to noble and base metal alloys with different surface treatments.

    Directory of Open Access Journals (Sweden)

    Farkhondeh Raeisosadat

    2014-10-01

    Full Text Available The bond strength of resin cements to metal alloys depends on the type of the metal, conditioning methods and the adhesive resins used. The purpose of this study was to evaluate the bond strength of resin cements to base and noble metal alloys after sand blasting or application of silano-pen.Cylinders of light cured Z 250 composite were cemented to "Degubond 4" (Au Pd and "Verabond" (Ni Cr alloys by either RelyX Unicem or Panavia F2, after sandblasting or treating the alloys with Silano-Pen. The shear bond strengths were evaluated. Data were analyzed by three-way ANOVA and t tests at a significance level of P<0.05.When the alloys were treated by Silano-Pen, RelyX Unicem showed a higher bond strength for Degubond 4 (P=0.021 and Verabond (P< 0.001. No significant difference was observed in the bond strength of Panavia F2 to the alloys after either of surface treatments, Degubond 4 (P=0.291 and Verabond (P=0.899. Panavia F2 showed a higher bond strength to sandblasted Verabond compared to RelyX Unicem (P=0.003. The bond strength of RelyX Unicem was significantly higher to Silano-Pen treated Verabond (P=0.011. The bond strength of the cements to sandblasted Degubond 4 showed no significant difference (P=0.59. RelyX Unicem had a higher bond strength to Silano-Pen treated Degubond 4 (P=0.035.The bond strength of resin cements to Verabond alloy was significantly higher than Degubond 4. RelyX Unicem had a higher bond strength to Silano-Pen treated alloys. Surface treatments of the alloys did not affect the bond strength of Panavia F2.

  18. Intramolecular hydrogen bonding and tautomerism in Schiff bases ...

    Indian Academy of Sciences (India)

    N and keto-amine, O…H-N forms) in this series. The molecular structure of 8 has been determined crystallographically, and observed that the compound is in the form of phenol-imine, defined by the strong intramolecular [O-H…N = 1.72(3), 1.81(2) Å] hydrogen bonds. Compound 8 crystallizes in the monoclinic space group ...

  19. Enhanced photocatalytic degradation of Amaranth dye on mesoporous anatase TiO2: evidence of C-N, N[double bond, length as m-dash]N bond cleavage and identification of new intermediates.

    Science.gov (United States)

    Naik, Amarja P; Salkar, Akshay V; Majik, Mahesh S; Morajkar, Pranay P

    2017-07-01

    The photocatalytic degradation mechanism of Amaranth, a recalcitrant carcinogenic azo dye, was investigated using mesoporous anatase TiO 2 under sunlight. Mesoporous anatase TiO 2 of a high photocatalytic activity has been synthesized using a sol-gel method and its photocatalytic activity for the degradation of Amaranth dye has been evaluated with respect to Degussa P25. The effect of bi-dentate complexing agents like oxalic acid, ethylene glycol and urea on the surface properties of TiO 2 catalyst has been investigated using TG-DTA, FTIR, HR-TEM, SAED, PXRD, EDS, UV-DRS, PL, BET N 2 adsorption-desorption isotherm studies and BJH analysis. The influence of catalyst properties such as the mesoporous network, pore volume and surface area on the kinetics of degradation of Amaranth as a function of irradiation time under natural sunlight has been monitored using UV-Vis spectroscopy. The highest rate constant value of 0.069 min -1 was obtained for the photocatalytic degradation of Amaranth using TiO 2 synthesized via a urea assisted sol-gel synthesis method. The effect of the reaction conditions such as pH, TiO 2 concentration and Amaranth concentration on the photodegradation rate has been investigated. The enhanced photocatalytic activity of synthesized TiO 2 in comparison with P25 is attributed to the mesoporous nature of the catalyst leading to increased pore diameter, pore volume, surface area and enhanced charge carrier separation efficiency. New intermediates of photocatalytic degradation of Amaranth, namely, sodium-3-hydroxynaphthalene-2,7-disulphonate, 3-hydroxynaphthalene, sodium-4-aminonaphthalenesulphonate and sodium-4-aminobenzenesulphonate have been identified using LC-ESI-MS for the very first time, providing direct evidence for simultaneous bond cleavage pathways (-C-N-) and (-N[double bond, length as m-dash]N-). A new plausible mechanism of TiO 2 catalysed photodegradation of Amaranth along with the comparison of its toxicity to that of its degradation

  20. Bond-Slip Relationship for CFRP Sheets Externally Bonded to Concrete under Cyclic Loading.

    Science.gov (United States)

    Li, Ke; Cao, Shuangyin; Yang, Yue; Zhu, Juntao

    2018-02-26

    The objective of this paper was to explore the bond-slip relationship between carbon fiber-reinforced polymer (CFRP) sheets and concrete under cyclic loading through experimental and analytical approaches. Modified beam tests were performed in order to gain insight into the bond-slip relationship under static and cyclic loading. The test variables are the CFRP-to-concrete width ratio, and the bond length of the CFRP sheets. An analysis of the test results in this paper and existing test results indicated that the slope of the ascending segment of the bond-slip curve decreased with an increase in the number of load cycles, but the slip corresponding to the maximum shear stress was almost invariable as the number of load cycles increased. In addition, the rate of reduction in the slope of the ascending range of the bond-slip curve during cyclic loading decreased as the concrete strength increased, and increased as the load level or CFRP-to-concrete width ratio enhanced. However, these were not affected by variations in bond length if the residual bond length was longer than the effective bond length. A bilinear bond-slip model for CFRP sheets that are externally bonded to concrete under cyclic loading, which considered the effects of the cyclic load level, concrete strength, and CFRP-to-concrete ratio, was developed based on the existing static bond-slip model. The accuracy of this proposed model was verified by a comparison between this proposed model and test results.

  1. Estimating the minimum delay optimal cycle length based on a time-dependent delay formula

    Directory of Open Access Journals (Sweden)

    Ahmed Y. Zakariya

    2016-09-01

    Full Text Available For fixed time traffic signal control, the well-known Webster’s formula is widely used to estimate the minimum delay optimal cycle length. However, this formula overestimates the cycle length for high degrees of saturation. In this paper, we propose two regression formulas for estimating the minimum delay optimal cycle length based on a time-dependent delay formula as used in the Canadian Capacity Guide and the Highway Capacity Manual (HCM. For this purpose, we develop a search algorithm to determine the minimum delay optimal cycle length required for the regression analysis. Numerical results show that the proposed formulas give a better estimation for the optimal cycle length at high intersection flow ratios compared to Webster’s formula.

  2. A recency-based account of the list length effect in free recall.

    Science.gov (United States)

    Ward, Geoff

    2002-09-01

    Free recall was examined using the overt rehearsal methodology with lists of 10, 20, and 30 words. The standard list length effects were obtained: As list length increased, there was an increase in the number and a decrease in the proportion of words that were recalled. There were significant primacy and recency effects with all list lengths. However, when the data were replotted in terms of when the words were last rehearsed, recall was characterized by extended recency effects, and the data from the different list lengths were superimposed upon one another. These findings support a recency-based account of episodic memory. The list length effect reflects the facts that unrehearsed words are less recent with longer lists, and that with longer lists, a reduced proportion of primacy and middle items may be rehearsed to later positions.

  3. Different Strategies to Bond Bis-GMA-based Resin Cement to Zirconia.

    Science.gov (United States)

    Lopes, Guilherme Carpena; Spohr, Ana Maria; De Souza, Grace M

    To evaluate the effect of different bonding strategies on short- and long-term bis-GMA-based resin cement bond strengths to zirconia. One hundred twenty samples of fully-sintered zirconia (Prettau Zirconia) were sandblasted and randomly distributed into 5 groups (n = 24): UA: Scotchbond Universal Adhesive; SZP: Signum Zirconia Bond I + II; ZPP: Z-Prime Plus; EXP: MZ experimental primer; CO: no primer application (control). After performing these surface treatments, translucent tubes (0.8 mm diameter and 1.0 mm height) were placed on the zirconia specimens, and bis-GMA-based cement (Duo-Link) was injected into them and light cured. Specimens were tested for microshear bond strength either 24 h or 6 months (m) after water storage (37°C) and surfaces were characterized by SEM and EDX. Two-way ANOVA and Tukey's post-hoc test (p zirconia surface. In these groups, EDX demonstrated the presence of phosphorus. Group ZPP resulted in a nonhomogeneous layer, exposing the zirconia substrate underneath. EXP application resulted in an undetectable layer. Water storage did not affect resin cement bond strengths to zirconia irrespective of the surface treatment. Bis-GMA-based resin cement bond strengths to zirconia are affected by specific bonding strategies.

  4. Microfluidic magnetic switching valves based on aggregates of magnetic nanoparticles: Effects of aggregate length and nanoparticle sizes

    Energy Technology Data Exchange (ETDEWEB)

    Jiemsakul, Thanakorn [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Nueng, Amphoe Khlong Luang, Pathum Thani 12120 (Thailand); Manakasettharn, Supone, E-mail: supone@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Nueng, Amphoe Khlong Luang, Pathum Thani 12120 (Thailand); Kanharattanachai, Sivakorn; Wanna, Yongyuth [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Chalongkrung Road, Bangkok 10520 (Thailand); Wangsuya, Sujint [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Chalongkrung Road, Bangkok 10520 (Thailand); Faculty of Science, Mahidol University, 272 Rama VI Road, Ratchathewi District, Bangkok 10400 (Thailand); Pratontep, Sirapat [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Chalongkrung Road, Bangkok 10520 (Thailand)

    2017-01-15

    We demonstrate microfluidic switching valves using magnetic nanoparticles blended within the working fluid as an alternative microfluidic flow control in microchannels. Y-shaped microchannels have been fabricated by using a CO{sub 2} laser cutter to pattern microchannels on transparent poly(methyl methacrylate) (PMMA) sheets covered with thermally bonded transparent polyvinyl chloride (PVC) sheets. To examine the performance of the microfluidic magnetic switching valves, an aqueous magnetic nanoparticle suspension was injected into the microchannels by a syringe pump. Neodymium magnets were then employed to attract magnetic nanoparticles and form an aggregate that blocked the microchannels at a required position. We have found that the maximum volumetric flow rate of the syringe pump that the magnetic nanoparticle aggregate can withstand scales with the square of the external magnetic flux density. The viscosity of the fluid exhibits dependent on the aggregate length and the size of the magnetic nanoparticles. This microfluidic switching valve based on aggregates of magnetic nanoparticles has strong potentials as an on-demand flow control, which may help simplifying microfluidic channel designs. - Highlights: • We demonstrate microfluidic switching valves based on aggregates of magnetic particles. • Maximum flow rate that the aggregate can withstand scales with the square of the external magnetic flux density. • Aggregates with smaller magnetic nanoparticle size can withstand higher flow rate. • Aggregate length exhibits a linear dependence with flow resistance of a viscous fluid.

  5. Characterization of Binary Organogels Based on Some Azobenzene Compounds and Alkyloxybenzoic Acids with Different Chain Lengths

    Directory of Open Access Journals (Sweden)

    Yongmei Hu

    2014-01-01

    Full Text Available In this work the gelation behaviors of binary organogels composed of azobenzene amino derivatives and alkyloxybenzoic acids with different lengths of alkyl chains in various organic solvents were investigated and characterized. The corresponding gelation behaviors in 20 solvents were characterized and shown as new binary organic systems. It showed that the lengths of substituent alkyl chains in compounds have played an important role in the gelation formation of gelator mixtures in present tested organic solvents. Longer methylene chains in molecular skeletons in these gelators seem more suitable for the gelation of present solvents. Morphological characterization showed that these gelator molecules have the tendency to self-assemble into various aggregates from lamella, wrinkle, and belt to dot with change of solvents and gelator mixtures. Spectral characterization demonstrated different H-bond formation and hydrophobic force existing in gels, depending on different substituent chains in molecular skeletons. Meanwhile, these organogels can self-assemble to form monomolecular or multilayer nanostructures owing to the different lengths of due to alkyl substituent chains. Possible assembly modes for present xerogels were proposed. The present investigation is perspective to provide new clues for the design of new nanomaterials and functional textile materials with special microstructures.

  6. Microshear Bond Strength of Tri-Calcium Silicate-based Cements to Different Restorative Materials.

    Science.gov (United States)

    Cengiz, Esra; Ulusoy, Nuran

    To evaluate the microshear bond strength of tri-calcium silicate-based materials to different restorative materials. Thirty-five disks of TheraCal LC and Biodentine were fabricated using teflon molds according to manufacturers' instructions. Then the specimens were randomly divided into 7 groups according to the materials applied: Fuji IX, Fuji II, Equia Fil, Vertise Flow, Filtek Bulk Fill Posterior Restorative, Filtek Z250 with Prime&Bond NT and with Clearfil SE Bond. All restorative materials were placed onto the disks using tygon tubes. Following a storage period, the specimens underwent microshear bond strength testing in a universal testing machine, and fracture modes were analyzed. Data were analyzed using one-way ANOVA and Tukey's post-hoc test. For all restorative materials, TheraCal LC showed significantly higher μSBS values compared to Biodentine. GIC based materials showed the lowest μSBS for TheraCal and Biodentine. For Biodentine, Filtek Z250 applied with Prime&Bond NT and Filtek Bulk Fill Posterior Restorative applied with Scotchbond Universal Adhesive exhibited the highest μSBS, while Filtek Z250 applied with Clearfil SE Bond revealed the highest bond strength to TheraCal LC. For all restorative materials tested in this study, TheraCal LC showed higher μSBS compared to Biodentine. For both TheraCal LC and Biodentine, the placement of GIC-based materials prior to composite resin restorations might decrease the bond strength. Composite resins applied with self-etching adhesives increased the bond strength of TheraCal LC; however, for Biodentine, application of etch-and-rinse adhesives may improve the adhesion of composite resins.

  7. Comparative evaluation of shear bond strengths of veneering porcelain to base metal alloy and zirconia substructures before and after aging – An in vitro study

    Science.gov (United States)

    Sreekala, Laju; Narayanan, Mahesh; Eerali, Sunil M.; Eerali, Susil M.; Varghese, Joju; Zainaba Fathima, A. l.

    2015-01-01

    Objective: The aim of this study was to evaluate and compare the shear bond strength of veneering porcelain to base metal alloy and zirconia substructures before and after aging. Scanning electron microscopy (SEM) was used to determine the failure pattern. Materials and Methods: Twenty rectangular blocks (9 mm length × 4 mm height × 4 mm width) of base metal alloy (Bellabond plus, Bego, Germany) and zirconia (Will ceramZ zirconia K block) were fabricated for shear bond strength test. Surface of the base metal alloy block (4 mm × 4 mm area) was veneered with corresponding veneering porcelain (Ivoclar, IPS classic, vivadent). Similarly, surface of the zirconia rectangular block (4 mm × 4 mm) was veneered with corresponding veneering ceramic (Cercon ceram kiss, Degudent). Out of forty rectangular porcelain veneered core specimen, ten porcelain veneered base metal alloy specimen and ten porcelain veneered zirconia specimen were immersed in water at 37°C for one month to simulate the oral environment. Results: On comparison, the highest shear bond strength value was obtained in porcelain veneered base metal alloy before aging group followed by porcelain veneered base metal alloy after aging group, Porcelain veneered zirconia before aging group, porcelain veneered zirconia after aging group. SEM analysis revealed predominantly cohesive failure of veneering ceramic in all groups. Conclusion: Porcelain veneered base metal alloy samples showed highest shear bond strength than porcelain veneered zirconia samples. Study concluded that aging had an influence on shear bond strength. Shear bond strength was found to be decreasing after aging. SEM analysis revealed cohesive failure of veneering ceramic in all groups suggestive of higher bond strength of the interface than cohesive strength of ceramic. Hence, it was concluded that veneering ceramic was the weakest link. PMID:26942121

  8. Comparative evaluation of shear bond strengths of veneering porcelain to base metal alloy and zirconia substructures before and after aging - An in vitro study.

    Science.gov (United States)

    Sreekala, Laju; Narayanan, Mahesh; Eerali, Sunil M; Eerali, Susil M; Varghese, Joju; Zainaba Fathima, A L

    2015-12-01

    The aim of this study was to evaluate and compare the shear bond strength of veneering porcelain to base metal alloy and zirconia substructures before and after aging. Scanning electron microscopy (SEM) was used to determine the failure pattern. Twenty rectangular blocks (9 mm length × 4 mm height × 4 mm width) of base metal alloy (Bellabond plus, Bego, Germany) and zirconia (Will ceramZ zirconia K block) were fabricated for shear bond strength test. Surface of the base metal alloy block (4 mm × 4 mm area) was veneered with corresponding veneering porcelain (Ivoclar, IPS classic, vivadent). Similarly, surface of the zirconia rectangular block (4 mm × 4 mm) was veneered with corresponding veneering ceramic (Cercon ceram kiss, Degudent). Out of forty rectangular porcelain veneered core specimen, ten porcelain veneered base metal alloy specimen and ten porcelain veneered zirconia specimen were immersed in water at 37°C for one month to simulate the oral environment. On comparison, the highest shear bond strength value was obtained in porcelain veneered base metal alloy before aging group followed by porcelain veneered base metal alloy after aging group, Porcelain veneered zirconia before aging group, porcelain veneered zirconia after aging group. SEM analysis revealed predominantly cohesive failure of veneering ceramic in all groups. Porcelain veneered base metal alloy samples showed highest shear bond strength than porcelain veneered zirconia samples. Study concluded that aging had an influence on shear bond strength. Shear bond strength was found to be decreasing after aging. SEM analysis revealed cohesive failure of veneering ceramic in all groups suggestive of higher bond strength of the interface than cohesive strength of ceramic. Hence, it was concluded that veneering ceramic was the weakest link.

  9. Indirect Wafer Bonding and Epitaxial Transfer of GaSb-Based Materials

    Science.gov (United States)

    Grzesik, M.; Vangala, S. R.; Goodhue, W. D.

    2013-04-01

    Results from a study of indirect wafer bonding and epitaxial transfer of GaSb-based materials are presented. Benzocyclobutene (BCB) was used as a bonding agent to bond GaSb and epitaxial structures lattice matched to GaSb onto Si, GaAs, and sapphire carrier substrates. To better understand sources of stress during the bonding process, which can result in cracking and subsurface damage of the GaSb-based materials, BCB's hardness and reduced elastic modulus were measured at various stages during the curing process. Based on the results of curing experiments, a bonding and epitaxial transfer process for GaSb-based materials was then developed. Following bonding, using an experimentally determined low-stress cure cycle, GaSb substrates were removed from epitaxial layers of InAsSb using a combination of mechanical thinning and polishing followed by selective chemical etching using a hydrofluoric and chromic acid solution. Etch selectivity data are also presented where selectivity greater than 100:1 is achieved for GaSb:InAsSb.

  10. The acid-base resistant zone in three dentin bonding systems.

    Science.gov (United States)

    Inoue, Go; Nikaido, Toru; Foxton, Richard M; Tagami, Junji

    2009-11-01

    An acid-base resistant zone has been found to exist after acid-base challenge adjacent to the hybrid layer using SEM. The aim of this study was to examine the acid-base resistant zone using three different bonding systems. Dentin disks were applied with three different bonding systems, and then a resin composite was light-cured to make dentin disk sandwiches. After acid-base challenge, the polished surfaces were observed using SEM. For both one- and two-step self-etching primer systems, an acid-base resistant zone was clearly observed adjacent to the hybrid layer - but with differing appearances. For the wet bonding system, the presence of an acid-base resistant zone was unclear. This was because the self-etching primer systems etched the dentin surface mildly, such that the remaining mineral phase of dentin and the bonding agent yielded clear acid-base resistant zones. In conclusion, the acid-base resistant zone was clearly observed when self-etching primer systems were used, but not so for the wet bonding system.

  11. An Investigation of Bond Strength of Reinforcing Bars in Fly Ash and GGBS Based Geopolymer Concrete

    Directory of Open Access Journals (Sweden)

    Boopalan C.

    2017-01-01

    Full Text Available Geopolymers are amorphous aluminosilicate materials. Geopolymers are binders formed by alkali activation of Geopolymer Source Materials (GSM using an alkaline activator solution. Concretes made using Geopolymer binders are excellent alternative to the Ordinary Portland Cement concretes from strength, durability, and ecological considerations. Especially, usage of industrial waste materials such as Fly Ash and Slags as GSMs considerably lower the carbon footprint of concrete and mitigate the damage due to the unscientific dumping/disposal of these materials. To use the Geopolymer concrete (GPC for reinforced structural members, the composite action of reinforcing bars with Geopolymer concrete i.e. the bond behaviour should be well understood. This paper describes the bond behaviour of 12mm and 16mm dia. bars embedded in Fly ash and GGBS based Geopolymer concrete and conventional Portland Pozzolana cement concrete specimens investigated using the pull-out tests as per Indian Standard Code IS:2770(Part-I; the bond stresses and corresponding slips were found out. The bond stress increased with increase in compressive strength. The peak bond stress was found to be 4.3 times more than the design bond stress as per IS:456-2000. The Geopolymer concretes possess higher bond strength compared to the conventional cement concretes.

  12. Explicit consideration of spatial hydrogen bonding direction for activity coefficient prediction based on implicit solvation calculations.

    Science.gov (United States)

    Chen, Wei-Lin; Lin, Shiang-Tai

    2017-08-09

    The activity coefficient of a chemical in a mixture is important in understanding the thermodynamic properties and non-ideality of the mixture. The COSMO-SAC model based on the result of quantum mechanical implicit solvation calculations has been shown to provide reliable predictions of activity coefficients for mixed fluids. However, it is found that the prediction accuracy is in general inferior for associating fluids. Existing methods for describing the hydrogen-bonding interaction consider the strength of the interaction based only on the polarity of the screening charges, neglecting the fact that the formation of hydrogen bonds requires a specific orientation between the donor and acceptor pairs. In this work, we propose a new approach that takes into account the spatial orientational constraints in hydrogen bonds. Based on the Valence Shell Electron Pair Repulsion (VSEPR) theory, the molecular surfaces associated with the formation of hydrogen bonds are limited to those in the projection of the lone pair electrons of hydrogen bond acceptors, in addition to the polarity of the surface screening charges. Our results show that this new directional hydrogen bond approach, denoted as the COSMO-SAC(DHB) model, requires fewer universal parameters and is significantly more accurate and reliable compared to previous models for a variety of properties, including vapor-liquid equilibria (VLE), infinite dilution activity coefficient (IDAC) and water-octanol partition coefficient (K ow ).

  13. Bond strength evaluation of ceramic and stainless steel bracket bases subjected to cyclic tensile loading.

    Science.gov (United States)

    Soderquist, Scott A; Drummond, James L; Evans, Carla A

    2006-02-01

    The aim of this study was to evaluate the effects of loading, static and cyclic, on 1 stainless steel and 3 ceramic bracket bonding bases. The brackets were chosen because of the different characteristics of their bonding bases. The brackets in each group were bonded to bovine teeth by using the same adhesive and subjected to both static and cyclic tensile loading; the results were analyzed (ANOVA and Scheffé) for statistical differences among the groups. The analysis showed that ceramic brackets have unique characteristics compared with stainless steel; the most significant is higher bond strengths. The effects of cyclic loading were shown to be significant, in that fatigue testing caused a decrease in mean tensile bond strength for most groups. An additional factor on the bond strength might be the composition and design of the bracket base. Simulations of occlusal forces (a combination of tensile, shear, and compressive forces) to orthodontic materials during in-vitro studies in accordance with clinical use might adequately describe actual clinical performance.

  14. The effect of recasting on bond strength between porcelain and base-metal alloys.

    Science.gov (United States)

    Madani, Azam S; Rokni, Shahin Rezaii; Mohammadi, Abolghasem; Bahrami, Mehran

    2011-04-01

    Long-term success of metal ceramic restorations depends on metal ceramic bond strength. The purpose of this study was to determine whether recasting of base-metal alloys has any effect on metal ceramic bond strength. Super Cast and Verabond base-metal alloys were used to cast 260 wax patterns. The alloy specimens were equally divided into five groups and cast as: group A 0.0%, B 25%, C 50%, D 75%, and E 100% once-cast alloy. Each group was divided into two subgroups: the first group was cast with Super Cast and the second with Verabond. In each subgroup half of the cast alloys were veneered with Vita VMK 68 and the others with Ceramco 3. Recasting decreased bond strength (p alloy. Group E with 100% new Super Cast alloy veneered with Vita VMK 68 porcelain had the highest bond strength (30.75 ± 9.58 MPa), and group B including 25% new and 75% recast Super Cast alloy veneered with the same porcelain had the lowest bond strength (21.72 ± 5.19 MPa). By adding over 50% once-cast alloy in base-metal alloys, metal-ceramic bond strength decreases significantly. © 2011 by The American College of Prosthodontists.

  15. Ceramic bond durability and degradation mechanism of commercial gamma-methacryloxypropyl trimethoxysilane-based ceramic primers.

    Science.gov (United States)

    Aida, Masahiro; Tabei, Naoko; Kimoto, Suguru; Tanimura, Hideki; Takahashi, Haruyoshi; Yaguchi, Takehiro; Nishiyama, Norihiro

    2012-08-01

    To investigate the bond durability and degradation mechanism of various commercial ceramic primers that are based on gamma-methacryloxypropyl trimethoxysilane (gamma-MPTS) and contain various organic additives. The null hypotheses tested were that (1) the type of ceramic primer had no effect on the bond strength after thermocycling and (2) the type of ceramic primer had no effect on the water contact angle after rinsing with THF. The adherent was a silica-based ceramic block used for computer-aided design/computer-aided manufacturing (CAD-CAM). Four commercial ceramic primers, Clearfil Mega Bond Porcelain Bonding kit (CM), Tokuso ceramic primer (TC), GC ceramic primer (CP), and Porcelain Liner M (PL), were compared with a simplified experimental ceramic primer (EP) that comprised gamma-MPTS and an inorganic acid (hydrochloric acid) but no other organic additives. The specimens for the adhesion test were prepared after a dual-curing type resin cement (Link Max) had adhered to the ceramic surfaces treated with each ceramic primer. The bonded specimens were then stored in water at 37 degrees C for 1 day. Then, the bonded specimens were thermocycled between 5 degrees C and 55 degrees C in water baths for 5000 or 10,000 cycles. The dwell time in each water bath and the transfer time were 60 and 7 seconds, respectively. The shear bond strength of resin to the ceramic surface was measured under a crosshead speed of 1.0 mm/minute by a conventional testing machine. Thereafter, the fracture mode for each specimen was determined. In addition, the water contact angle on the treated ceramic surfaces was measured before and after THF using a cotton pellet. As a control, the contact angle on the ground ceramic surface was measured without any ceramic primer. For all samples, thermocycling led to an increase in the frequency of interfacial failure, reflecting reduced mean bond strength of the resin to the treated ceramic surfaces. However, the bond degradation behavior differed

  16. Effect of different bonding procedures on micro-tensile bond strength between a fiber post and resin-based luting agents.

    Science.gov (United States)

    Wang, Ying-jie; Raffaelli, Ornella; Zhang, Ling; Chen, Ji-hua; Ferrari, Marco

    2007-06-01

    The purpose of this study was to evaluate the effect of silanization and light-irradiation on bonding between a fiber post and different resin-based luting agents. Sixty silicium fiber posts (Easy Post) were divided into 10 groups according to the type of resin-based luting agent employed, whether the post surface was silanized, whether the adhesive was light-irradiated, and whether Calibra luting agent was used. The micro-tensile bond strength and bonded interface of specimens in each group were evaluated. Specimens luted with Calibra or FluoroCore 2 resin-based luting agent systems were superior to those treated with Multilink or Variolink II, in terms of both bond strength and interfacial integrity. Application of silane, light-irradiation of the adhesive, or light-irradiation of the Calibra resin-based luting agent did not significantly increase the bond strength further. It can be concluded that Calibra or FluoroCore 2 resin-based luting agent systems are more suitable for luting prefabricated Easy Post in a clinical situation, while pre-silanization of the post surface and light-irradiation of XP Bond/SCA adhesive or resin-based luting agent may not be as important as hitherto considered.

  17. Shear bond strength of an autopolymerizing repair resin to injection-molded thermoplastic denture base resins.

    Science.gov (United States)

    Hamanaka, Ippei; Shimizu, Hiroshi; Takahashi, Yutaka

    2013-09-01

    This study investigated the shear bond strength of an autopolymerizing repair resin to injection-molded thermoplastic denture base resins. Four injection-molded thermoplastic resins (two polyamides, a polyethylene terephthalate copolymer and a polycarbonate) were used in this study. The specimens were divided into eight groups according to the type of surface treatment given: (1) no treatment, (2) air abrasion with alumina, (3) dichloromethane, (4) ethyl acetate, (5) 4-META/MMA-TBB resin, (6) alumina and 4-META/MMA-TBB resin, (7) tribochemical silica coating or (8) tribochemical silica coating and 4-META/MMA-TBB resin. Half of the specimens in groups 1, 5, 6 and 8 were thermocycled for 10,000 cycles in water between 5-55°C with a dwell time of 1 min at each temperature. The shear bond strengths were determined. The shear bond strengths to the two polyamides treated with alumina, dichloromethane and ethyl acetate and no treatment were very low. The greatest post-thermocycling bond strengths to polyamides were recorded for the specimens treated with tribochemical silica coating and 4-META/MMA-TBB resin (PA12: 16.4 MPa, PACM12: 17.5 MPa). The greatest post-thermocycling bond strengths to polyethylene terephthalate copolymer and polycarbonate were recorded for the treatment with alumina and 4-META/MMA-TBB resin (22.7 MPa, 20.8 MPa). Polyamide was exceedingly difficult to bond to an autopolymerizing repair resin; the shear bond strength improved using tribochemical silica coating followed by the application of 4-META/MMA-TBB resin. Both polyethylene terephthalate copolymer and polycarbonate were originally easy to bond to an autopolymerizing repair resin. However, with 4-META/MMA-TBB resin, the bond was more secure.

  18. Complexes possessing rare "tertiary" sulfonamide nitrogen-to-metal bonds of normal length: fac-[Re(CO)3(N(SO2R)dien)]PF6 complexes with hydrophilic sulfonamide ligands.

    Science.gov (United States)

    Abhayawardhana, Pramuditha L; Marzilli, Patricia A; Fronczek, Frank R; Marzilli, Luigi G

    2014-01-21

    Tertiary sulfonamide nitrogen-to-metal bonds of normal length are very rare. We recently discovered such a bond in one class of fac-[Re(CO)3(N(SO2R)(CH2Z)2)](n) complexes (Z = 2-pyridyl) with N(SO2R)dpa ligands derived from di-(2-picolyl)amine (N(H)dpa). fac-[M(CO)3(N(SO2R)(CH2Z)2)](n) agents (M = (186/188)Re, (99m)Tc) could find use as radiopharmaceutical bioconjugates when R is a targeting moiety. However, the planar, electron-withdrawing 2-pyridyl groups of N(SO2R)dpa destabilize the ligand to base and create relatively rigid chelate rings, raising the possibility that the rare M-N(sulfonamide) bond is an artifact of a restricted geometry. Also, the hydrophobic 2-pyridyl groups could cause undesirable accumulation in the liver, limiting future use in radiopharmaceuticals. Our goal is to identify a robust, hydrophilic, and flexible N(CH2Z)2 chelate framework. New C2-symmetric ligands, N(SO2R)(CH2Z)2 with (Z = CH2NH2; R = Me, dmb, or tol), were prepared by treating N(H)dien(Boc)2, a protected diethylenetriamine (N(H)dien) derivative, with methanesulfonyl chloride (MeSO2Cl), 3,5-dimethylbenzenesulfonyl chloride (dmbSO2Cl), and 4-methylbenzenesulfonyl chloride (tolSO2Cl). Treatment of fac-[Re(CO)3(H2O)3](+) with these ligands, designated as N(SO2R)dien, afforded new fac-[Re(CO)3(N(SO2R)dien)]PF6 complexes. Comparing the fac-[Re(CO)3(N(SO2Me)dien)]PF6 and fac-[Re(CO)3(N(SO2Me)dpa)]PF6 complexes, we find that the Re(I)-N(sulfonamide) bonds are normal in length and statistically identical and that the methyl (13)C NMR signal has an unusually upfield shift compared to that in the free ligand. We attribute this unusual upfield shift to the fact that the sulfonamide N undergoes an sp(2)-to-sp(3) rehybridization upon coordination to Re(I) in both complexes. Thus, the sulfonamide N of N(SO2R)dien ligands is a good donor, even though the chelate rings are conformationally flexible. Addition of the strongly basic and potentially monodentate ligand, 4-dimethylaminopyridine

  19. Threshold Research on Highway Length under Typical Landscape Patterns Based on Drivers’ Physiological Performance

    Directory of Open Access Journals (Sweden)

    Xia Zhao

    2015-01-01

    Full Text Available The appropriately landscaped highway scenes may not only help improve road safety and comfort but also help protect ecological environment. Yet there is very little research data on highway length threshold with consideration of distinctive landscape patterns. Against this backdrop, the paper aims to quantitatively analyze highway landscape’s effect on driving behavior based on drivers’ physiological performance and quantify highway length thresholds under three typical landscape patterns, namely, “open,” “semiopen,” and “vertical” ones. The statistical analysis was based on data collected in a driving simulator and electrocardiograph. Specifically, vehicle-related data, ECG data, and supplemental subjective stress perception were collected. The study extracted two characteristic indices, lane deviation and LF/HF, and extrapolated the drivers’ U-shaped physiological response to landscape patterns. Models on highway length were built based on LF/HF’s variation trend with highway length. The results revealed that the theoretical highway length threshold tended to increase when the landscape pattern was switched to open, semiopen, and vertical ones. And the reliability and accuracy of the results were validated by questionnaires and field operational tests. Findings from this research will assist practitioners in taking active environmental countermeasures pertaining to different roadside landscape patterns.

  20. Dynamic Allan Variance Analysis Method with Time-Variant Window Length Based on Fuzzy Control

    Directory of Open Access Journals (Sweden)

    Shanshan Gu

    2015-01-01

    Full Text Available To solve the problem that dynamic Allan variance (DAVAR with fixed length of window cannot meet the identification accuracy requirement of fiber optic gyro (FOG signal over all time domains, a dynamic Allan variance analysis method with time-variant window length based on fuzzy control is proposed. According to the characteristic of FOG signal, a fuzzy controller with the inputs of the first and second derivatives of FOG signal is designed to estimate the window length of the DAVAR. Then the Allan variances of the signals during the time-variant window are simulated to obtain the DAVAR of the FOG signal to describe the dynamic characteristic of the time-varying FOG signal. Additionally, a performance evaluation index of the algorithm based on radar chart is proposed. Experiment results show that, compared with different fixed window lengths DAVAR methods, the change of FOG signal with time can be identified effectively and the evaluation index of performance can be enhanced by 30% at least by the DAVAR method with time-variant window length based on fuzzy control.

  1. Estimation of the flow resistances exerted in coronary arteries using a vessel length-based method.

    Science.gov (United States)

    Lee, Kyung Eun; Kwon, Soon-Sung; Ji, Yoon Cheol; Shin, Eun-Seok; Choi, Jin-Ho; Kim, Sung Joon; Shim, Eun Bo

    2016-08-01

    Flow resistances exerted in the coronary arteries are the key parameters for the image-based computer simulation of coronary hemodynamics. The resistances depend on the anatomical characteristics of the coronary system. A simple and reliable estimation of the resistances is a compulsory procedure to compute the fractional flow reserve (FFR) of stenosed coronary arteries, an important clinical index of coronary artery disease. The cardiac muscle volume reconstructed from computed tomography (CT) images has been used to assess the resistance of the feeding coronary artery (muscle volume-based method). In this study, we estimate the flow resistances exerted in coronary arteries by using a novel method. Based on a physiological observation that longer coronary arteries have more daughter branches feeding a larger mass of cardiac muscle, the method measures the vessel lengths from coronary angiogram or CT images (vessel length-based method) and predicts the coronary flow resistances. The underlying equations are derived from the physiological relation among flow rate, resistance, and vessel length. To validate the present estimation method, we calculate the coronary flow division over coronary major arteries for 50 patients using the vessel length-based method as well as the muscle volume-based one. These results are compared with the direct measurements in a clinical study. Further proving the usefulness of the present method, we compute the coronary FFR from the images of optical coherence tomography.

  2. Effect of Repeated Firings of Porcelain on Bond Strength of Two Base Metal Alloys

    Directory of Open Access Journals (Sweden)

    Gerami Panah F

    2001-05-01

    Full Text Available The formation of oxides on the surface of the metal are proven to contribute to the formation of strong bonding. However, The base metal alloys are expected to exhibit more oxidation than high gold alloys, increase in oxide layer thickness due to repeated firing in them can reduce the bond strength. The aim of this study was to compare the effect of repeated porcelain firing on the bond strength of two base metal alloys (Minalux and Verabond II. Sixteen metal plates (20x5x0.5 from each alloy were cast and prepared according to the manufacturers' instruction. Porcelain with uniform thickness (Imm was applied on the middle one third of metal plates. After this stage, each alloy group divided to three subgroups. Group I was fired for the second time to form the final glaze, group II and III were fired two and four more times respectively. Specimens were subjected to 3-point flexural test in a digital tritest machine. Results showed no significant differences between bond strength of two alloys. Also results showed repeated firing had no significant effect on bond strength. Due to these findings, this study support similarity of two alloys (Minalux and Verabond II in their bond strength with porcelain.

  3. New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

    Directory of Open Access Journals (Sweden)

    Pavel Nagorny

    2016-12-01

    Full Text Available Hydrogen bond donor catalysis represents a rapidly growing subfield of organocatalysis. While traditional hydrogen bond donors containing N–H and O–H moieties have been effectively used for electrophile activation, activation based on other types of non-covalent interactions is less common. This mini review highlights recent progress in developing and exploring new organic catalysts for electrophile activation through the formation of C–H hydrogen bonds and C–X halogen bonds.

  4. Shear bond strength of a ceromer to noble and base metal alloys

    Directory of Open Access Journals (Sweden)

    Dorriz H.

    2006-08-01

    Full Text Available Background and Aim: The improvement of the physical and chemical properties of resins as well as great advances achieved in the field of chemical bonding of resin to metal has changed the trend of restorative treatments. Today the second generation of laboratory resins have an important role in the restoration of teeth. The clinical bond strength should be reliable in order to gain successful results. In this study the shear bond strength (SBS between targis (a ceromer and two alloys (noble and base metal was studied and the effect of thermocycling on the bond investigated. Materials and Methods: In this experimental study, alloys samples were prepared according to the manufacturer. After sandblasting of bonding surfaces with 50µ AI2o3 Targis was bonded to the alloy using Targis I link. All of the samples were placed in 37°C water for a period of 24 hours. Then half of the samples were subjected to 1000 cycles of thermocycling at temperatures of 5°C and 55°C. Planear shear test was used to test the bond strength in the Instron machine with the speed rate of 0.5mm/min. Data were analyzed by SPSS software. Two-way analysis of variance was used to compare the bond strength among the groups. T test was used to compare the alloys. The influence of thermocycling and alloy type on bond strength was studied using Mann Whitney test. P<0.05 was considered as the limit of significance. Result: The studied alloys did not differ significantly, when the samples were not thermocycled (P=0.136 but after thermocycling a significant difference was observed in SBS of resin to different alloys (P=000.1. Thermal stress and alloy type had significant interaction, with regard to shear bond strength (P=0.003. There was a significant difference in SBS before and after thermocycling in noble alloys (P=0.009, but this was not true in base metals (P=0.29. Maximum SBS (19.09 Mpa belonged to Degubond 4, before thermocycling. Minimum SBS (8.21 Mpa was seen in Degubond 4

  5. A method for estimating age of Danish medieval sub-adults based on long bone length

    DEFF Research Database (Denmark)

    Primeau, C.; Lynnerup, Niels; Friis, Laila Saidane

    2012-01-01

    for aging archaeological Danish sub-adults from the medieval period based on diaphyseal lengths. The problem with using data on Danish samples, which have been derived from a different population, is the possibility of skewing age estimates. In this study 58 Danish archaeological sub-adults were examined...

  6. Effect of different surface treatments on tensile bond strength of silicone-based soft denture liner.

    Science.gov (United States)

    Akin, Hakan; Tugut, Faik; Mutaf, Burcu; Akin, Gulsah; Ozdemir, A Kemal

    2011-11-01

    Failure of the bond between the acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to investigate the effect of different surface treatments (sandblasting, Er:YAG, Nd:YAG, and KTP lasers) on tensile bond strength of silicone-based soft denture liner. Polymethyl methacrylate test specimens were fabricated and each received one of eight surface treatments: untreated (control), sandblasted, Er:YAG laser irradiated, sandblasted + Er:YAG laser irradiated, Nd:YAG laser irradiated, sandblasted + Nd:YAG laser irradiated, KTP laser irradiated, and sandblasted + KTP laser irradiated. The resilient liner specimens (n = 15) were processed between two polymethyl methacrylate (PMMA) blocks. Bonding strength of the liners to PMMA were compared by tensile test with the use of a universal testing machine at a crosshead speed of 5 mm/min. Kruskal-Wallis and Wilcoxon tests were used to analyze the data (α = 0.05). Altering the polymethyl methacrylate surface by Er:YAG laser significantly increased the bond strengths in polymethyl methacrylate/silicone specimens, however, sandblasting before applying a lining material had a weakening effect on the bond. In addition, Nd:YAG and KTP lasers were found to be ineffective for increasing the strength of the bond.

  7. A quality quantitative method of silicon direct bonding based on wavelet image analysis

    Science.gov (United States)

    Tan, Xiao; Tao, Zhi; Li, Haiwang; Xu, Tiantong; Yu, Mingxing

    2018-04-01

    The rapid development of MEMS (micro-electro-mechanical systems) has received significant attention from researchers in various fields and subjects. In particular, the MEMS fabrication process is elaborate and, as such, has been the focus of extensive research inquiries. However, in MEMS fabrication, component bonding is difficult to achieve and requires a complex approach. Thus, improvements in bonding quality are relatively important objectives. A higher quality bond can only be achieved with improved measurement and testing capabilities. In particular, the traditional testing methods mainly include infrared testing, tensile testing, and strength testing, despite the fact that using these methods to measure bond quality often results in low efficiency or destructive analysis. Therefore, this paper focuses on the development of a precise, nondestructive visual testing method based on wavelet image analysis that is shown to be highly effective in practice. The process of wavelet image analysis includes wavelet image denoising, wavelet image enhancement, and contrast enhancement, and as an end result, can display an image with low background noise. In addition, because the wavelet analysis software was developed with MATLAB, it can reveal the bonding boundaries and bonding rates to precisely indicate the bond quality at all locations on the wafer. This work also presents a set of orthogonal experiments that consist of three prebonding factors, the prebonding temperature, the positive pressure value and the prebonding time, which are used to analyze the prebonding quality. This method was used to quantify the quality of silicon-to-silicon wafer bonding, yielding standard treatment quantities that could be practical for large-scale use.

  8. The use of MDP-based materials for bonding to zirconia.

    Science.gov (United States)

    de Souza, Grace; Hennig, Diana; Aggarwal, Anuj; Tam, Laura E

    2014-10-01

    A strong and stable bond between the luting resin and overlying ceramic restoration is critical to longevity, but no technique has been established for how to provide such a bond when the core material is zirconia. The purpose of this study was to evaluate the effect of different materials containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) on the bond strength to yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic. Forty Y-TZP slices (Lava) were cemented to substrates (8 groups; n=5 in each) with or without the previous application of an experimental primer (0.5% MDP) or an MDP-based adhesive (Clearfil S3 Bond Plus or Scotchbond Universal) with either an MDP (Clearfil SA) or a non-MDP (RelyX Ultimate) luting resin. Specimens were cut, stored in distilled water, and microtensile tested (5 beams per specimen) at 48 hours and again at 6 months after luting procedures. The data were analyzed by 4-way ANOVA (α=.05) and the Tukey test (α=.05). The mode of failure was classified with a stereomicroscope, and the treated surfaces were analyzed with energy-dispersive x-ray spectroscopy. Both adhesive (PMDP-containing adhesive and the shorter storage time were associated with higher bond strengths. At 48 hours, an overall incidence of 50.5% of Type 1 mode of failure (adhesive at ceramic/resin interface) occurred, as opposed to 68% after 6 months of water storage. Energy-dispersive x-ray spectroscopy results showed peaks of carbon and phosphorus when MDP-based materials were used. The application of an MDP-based adhesive may improve bond strength to zirconia. However, microtensile bond strength results for all groups did not remain stable over 6 months. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  9. State of the science of maternal-infant bonding: a principle-based concept analysis.

    Science.gov (United States)

    Bicking Kinsey, Cara; Hupcey, Judith E

    2013-12-01

    to provide a principle-based analysis of the concept of maternal-infant bonding. principle-based method of concept analysis for which the data set included 44 articles published in the last decade from Pubmed, CINAHL, and PyschINFO/PsychARTICLES. literature inclusion criteria were English language, articles published in the last decade, peer-reviewed journal articles and commentary on published work, and human populations. after a brief review of the history of maternal-infant bonding, a principle-based concept analysis was completed to examine the state of the science with regard to this concept. The concept was critically examined according to the clarity of definition (epistemological principle), applicability of the concept (pragmatic principle), consistency in use and meaning (linguistic principle), and differentiation of the concept from related concepts (logical principle). Analysis of the concept revealed: (1) Maternal-infant bonding describes maternal feelings and emotions towards her infant. Evidence that the concept encompasses behavioural or biological components was limited. (2) The concept is clearly operationalised in the affective domain. (3) Maternal-infant bonding is linguistically confused with attachment, although the boundaries between the concepts are clearly delineated. despite widespread use of the concept, maternal-infant bonding is at times superficially developed and subject to confusion with related concepts. Concept clarification is warranted. A theoretical definition of the concept of maternal-infant bonding was developed to aid in the clarification, but more research is necessary to further clarify and advance the concept. nurse midwives and other practitioners should use the theoretical definition of maternal-infant bonding as a preliminary guide to identification and understanding of the concept in clinical practice. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Improved water resistance of bio-based adhesives for wood bonding

    Science.gov (United States)

    Charles R. Frihart; James M. Wescott

    2004-01-01

    Synthetic resins, such as phenol-formaldehyde (PF), are dominant in wood bonding for exterior and semi-exterior applications because of their excellent water resistance. Replacement of petroleum-based resins with ones having high biomass content would further enhance the environmental preferability of reconstituted wood-based materials. Past studies on using soybean...

  11. Bond strength of self-adhesive resin cement to base metal alloys having different surface treatments

    Directory of Open Access Journals (Sweden)

    Farhad Shafiei

    2018-01-01

    Conclusion: Based on the results, sandblasting improves the shear bond strength of self-etch and self-adhesive resin cement to base metal alloys. The best results can be achieved with a combination of sandblasting and metal primers. The performance of resin cement depends on to their chemical composition, not to the type of system.

  12. Shear bond strength of acrylic teeth to acrylic denture base after different surface conditioning methods.

    Science.gov (United States)

    Madhav, Gajula Venu; Raj, Soundar; Yadav, Naveen; Mudgal, Ishitha; Mehta, Nidhi; Tatwadiya, Riddhi

    2013-09-01

    Acrylic resin ruled the dental profession for 60 years, and this success is attributed to its aesthetics, handling properties, physical and biological compatibility, its stability in oral environment and its cost effectiveness. The objective of this study is to evaluate and compare the bond strength of acrylic resin teeth treated with various conditioning materials like monomer and silane coupling agent. METHDOLOGY: A study was carried out in which 96 samples were grouped into 3 groups with a sample size of 32 each (16 premolars, 16 molars). They were conditioned with different conditioning materials i,e monomer and silane coupling agent. Monomer, Silane coupling agent are coated on the ridge lap area before thermocycling and cured according to the manufacturer recommendations. The samples are retained from the fask; trimmed and polished. The samples are then subjected to shear bond strength using the Insteron Universal Testing Machine. In the present study it was found that application of monomer increased the bond strength between acrylic teeth and denture base, when compared to the conventionally processed samples. However it was found that application of silane coupling agent further increased the shear bond strength between acrylic teeth and denture base. Interprations and Within the confnes of this study it is found that there was a signifcant improvement in the bond strength between the acrylic teeth and denture base when silane coupling agent and monomer were used as surface conditioning material. The order of shear strength of samples is control > monomer > silane coupling agent.

  13. Pedestrian Stride Length Estimation from IMU Measurements and ANN Based Algorithm

    Directory of Open Access Journals (Sweden)

    Haifeng Xing

    2017-01-01

    Full Text Available Pedestrian dead reckoning (PDR can be used for continuous position estimation when satellite or other radio signals are not available, and the accuracy of the stride length measurement is important. Current stride length estimation algorithms, including linear and nonlinear models, consider a few variable factors, and some rely on high precision and high cost equipment. This paper puts forward a stride length estimation algorithm based on a back propagation artificial neural network (BP-ANN, using a consumer-grade inertial measurement unit (IMU; it then discusses various factors in the algorithm. The experimental results indicate that the error of the proposed algorithm in estimating the stride length is approximately 2%, which is smaller than that of the frequency and nonlinear models. Compared with the latter two models, the proposed algorithm does not need to determine individual parameters in advance if the trained neural net is effective. It can, thus, be concluded that this algorithm shows superior performance in estimating pedestrian stride length.

  14. Node Detection and Internode Length Estimation of Tomato Seedlings Based on Image Analysis and Machine Learning

    Directory of Open Access Journals (Sweden)

    Kyosuke Yamamoto

    2016-07-01

    Full Text Available Seedling vigor in tomatoes determines the quality and growth of fruits and total plant productivity. It is well known that the salient effects of environmental stresses appear on the internode length; the length between adjoining main stem node (henceforth called node. In this study, we develop a method for internode length estimation using image processing technology. The proposed method consists of three steps: node detection, node order estimation, and internode length estimation. This method has two main advantages: (i as it uses machine learning approaches for node detection, it does not require adjustment of threshold values even though seedlings are imaged under varying timings and lighting conditions with complex backgrounds; and (ii as it uses affinity propagation for node order estimation, it can be applied to seedlings with different numbers of nodes without prior provision of the node number as a parameter. Our node detection results show that the proposed method can detect 72% of the 358 nodes in time-series imaging of three seedlings (recall = 0.72, precision = 0.78. In particular, the application of a general object recognition approach, Bag of Visual Words (BoVWs, enabled the elimination of many false positives on leaves occurring in the image segmentation based on pixel color, significantly improving the precision. The internode length estimation results had a relative error of below 15.4%. These results demonstrate that our method has the ability to evaluate the vigor of tomato seedlings quickly and accurately.

  15. Node Detection and Internode Length Estimation of Tomato Seedlings Based on Image Analysis and Machine Learning.

    Science.gov (United States)

    Yamamoto, Kyosuke; Guo, Wei; Ninomiya, Seishi

    2016-07-07

    Seedling vigor in tomatoes determines the quality and growth of fruits and total plant productivity. It is well known that the salient effects of environmental stresses appear on the internode length; the length between adjoining main stem node (henceforth called node). In this study, we develop a method for internode length estimation using image processing technology. The proposed method consists of three steps: node detection, node order estimation, and internode length estimation. This method has two main advantages: (i) as it uses machine learning approaches for node detection, it does not require adjustment of threshold values even though seedlings are imaged under varying timings and lighting conditions with complex backgrounds; and (ii) as it uses affinity propagation for node order estimation, it can be applied to seedlings with different numbers of nodes without prior provision of the node number as a parameter. Our node detection results show that the proposed method can detect 72% of the 358 nodes in time-series imaging of three seedlings (recall = 0.72, precision = 0.78). In particular, the application of a general object recognition approach, Bag of Visual Words (BoVWs), enabled the elimination of many false positives on leaves occurring in the image segmentation based on pixel color, significantly improving the precision. The internode length estimation results had a relative error of below 15.4%. These results demonstrate that our method has the ability to evaluate the vigor of tomato seedlings quickly and accurately.

  16. Experimental investigation of halogen-bond hard-soft acid-base complementarity.

    Science.gov (United States)

    Riel, Asia Marie S; Jessop, Morly J; Decato, Daniel A; Massena, Casey J; Nascimento, Vinicius R; Berryman, Orion B

    2017-04-01

    The halogen bond (XB) is a topical noncovalent interaction of rapidly increasing importance. The XB employs a `soft' donor atom in comparison to the `hard' proton of the hydrogen bond (HB). This difference has led to the hypothesis that XBs can form more favorable interactions with `soft' bases than HBs. While computational studies have supported this suggestion, solution and solid-state data are lacking. Here, XB soft-soft complementarity is investigated with a bidentate receptor that shows similar associations with neutral carbonyls and heavy chalcogen analogs. The solution speciation and XB soft-soft complementarity is supported by four crystal structures containing neutral and anionic soft Lewis bases.

  17. Characterization of wood-based molding bonded with citric acid

    OpenAIRE

    Umemura, Kenji; Ueda, Tomohide; Kawai, Shuichi

    2012-01-01

    The wood-based moldings were fabricated by using only citric acid as an adhesive. The mechanical properties, water resistances, thermal properties and chemical structure were investigated. Wood powder obtained from Acacia mangium was mixed with citric acid under certain weight ratios (0-40 wt%), and each powder mixture was molded using two types of metal molds at 200 °C and 4MPa for 10 min. The modulus of rupture (MOR) and the modulus of elasticity (MOE) values of the wood-based molding conta...

  18. Influence of previous provisional cementation on the bond strength between two definitive resin-based luting and dentin bonding agents and human dentin.

    Science.gov (United States)

    Erkut, Selim; Küçükesmen, Hakki Cenker; Eminkahyagil, Neslihan; Imirzalioglu, Pervin; Karabulut, Erdem

    2007-01-01

    This study evaluated the effect of two different types of provisional luting agents (RelyX Temp E, eugenol-based; RelyX Temp NE, eugenol-free) on the shear bond strengths between human dentin and two different resin-based luting systems (RelyXARC-Single Bond and Duo Link-One Step) after cementation with two different techniques (dual bonding and conventional technique). One hundred human molars were trimmed parallel to the original long axis, to expose flat dentin surfaces, and were divided into three groups. After related surface treatments for each specimen, the resin-based luting agent was applied in a silicone cylindrical mold (3.5 x 4 mm), placed on the bonding-agent-treated dentin surfaces and polymerized. In the control group (n = 20), the specimens were further divided into two groups (n = 10), and two different resin-based luting systems were immediately applied following the manufacturer's protocols: RelyX ARC-Single Bond (Group I C) and Duo Link-One Step (Group II C). In the provisionalization group (n = 40), the specimens were further divided into four subgroups of 10 specimens each (Group I N, I E and Group II N, II E). In Groups I N and II N, eugenol-free (RelyX NE), and in groups I E and II E, eugenol-based (RelyX E) provisional luting agents (PLA), were applied on the dentin surface. The dentin surfaces were cleaned with a flour-free pumice, and the resin-based luting systems RelyX ARC (Group I N and E) and Duo Link (Group II N and E) were applied. In the Dual bonding groups (n = 40), the specimens were divided into four subgroups of 10 specimens each (Group I ND, ED and Group II ND, ED). The specimens were treated with Single Bond (Groups I ND and ED) or One Step (Groups II ND and ED). After the dentin bonding agent treatment, RelyX Temp NE was applied to Groups I ND and II ND, and RelyX Temp E was applied to Groups I ED and II ED. The dentin surfaces were then cleaned as described in the provisionalization group, and the resin-based luting systems

  19. Modal Analysis of In-Wheel Motor-Driven Electric Vehicle Based on Bond Graph Theory

    Directory of Open Access Journals (Sweden)

    Di Tan

    2017-01-01

    Full Text Available A half-car vibration model of an electric vehicle driven by rear in-wheel motors was developed using bond graph theory and the modular modeling method. Based on the bond graph model, modal analysis was carried out to study the vibration characteristics of the electric vehicle. To verify the effectiveness of the established model, the results were compared to ones computed on the ground of modal analysis and Newton equations. The comparison shows that the vibration model of the electric vehicle based on bond graph theory not only is able to better compute the natural frequency but also can easily determine the deformation mode, momentum mode, and other isomorphism modes and describe the dynamic characteristics of an electric vehicle driven by in-wheel motors more comprehensively than other modal analysis methods.

  20. Shear Bond Strength of Acrylic Denture Teeth to PMMA and Polyamide Denture Base Materials

    Directory of Open Access Journals (Sweden)

    Mohammadreza Nakhaei

    2018-03-01

    Full Text Available Introduction: Detachment of denture teeth from denture base is one of the most common reasons for costly denture repairs .This study aimed at evaluating the bond strength of an acrylic denture tooth to polyamide injection-molded thermoplastic denture base material compared with three conventional polymethylmethacrylate (PMMA denture base resins. Materials and Method: A total of 40 acrylic denture molar teeth were randomly allocated into four groups (n=10 of heat-polymerized (HP, Auto-polymerized (AP, Injection molded (IM and Polyamide thermoplastic (PT. All denture base/acrylic teeth combinations underwent 5000 thermal cycles (5-55◦C.Samples were subjected to shear bond strength test by a universal testing machine with a 1 mm/min crosshead speed .Data were analyzed using ANOVA and Tukey’s tests(α=0.05. Results: Mean ±SD of shear bond strength values were (MPa 4.82±1.21, 4.52±1.67, 3.7±0.84 and 4.13±2.21 for groups HP, AP, IM and PT respectively. No significant difference was found among the experimental groups (P=0.429. Conclusion: Polyamide thermoplastic denture base resin was similar to conventional PMMA denture base materials in terms of bond strength to artificial denture teeth.

  1. Intramolecular Hydrogen Bonding Involving Organic Fluorine: NMR Investigations Corroborated by DFT-Based Theoretical Calculations

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar Mishra

    2017-03-01

    Full Text Available The combined utility of many one and two dimensional NMR methodologies and DFT-based theoretical calculations have been exploited to detect the intramolecular hydrogen bond (HB in number of different organic fluorine-containing derivatives of molecules, viz. benzanilides, hydrazides, imides, benzamides, and diphenyloxamides. The existence of two and three centered hydrogen bonds has been convincingly established in the investigated molecules. The NMR spectral parameters, viz., coupling mediated through hydrogen bond, one-bond NH scalar couplings, physical parameter dependent variation of chemical shifts of NH protons have paved the way for understanding the presence of hydrogen bond involving organic fluorine in all the investigated molecules. The experimental NMR findings are further corroborated by DFT-based theoretical calculations including NCI, QTAIM, MD simulations and NBO analysis. The monitoring of H/D exchange with NMR spectroscopy established the effect of intramolecular HB and the influence of electronegativity of various substituents on the chemical kinetics in the number of organic building blocks. The utility of DQ-SQ technique in determining the information about HB in various fluorine substituted molecules has been convincingly established.

  2. Physicochemical Properties and Dentin Bond Strength of a Tricalcium Silicate-Based Retrograde Material.

    Science.gov (United States)

    Lucas, Camila de Paula Telles Pires; Viapiana, Raqueli; Bosso-Martelo, Roberta; Guerreiro-Tanomaru, Juliane Maria; Camilleri, Josette; Tanomaru-Filho, Mário

    2017-01-01

    The aim of this study was to evaluate the physicochemical properties and the apical dentin bond strength of the tricalcium silicate-based Biodentine in comparison to white MTA and zinc oxide eugenol-based cement (ZOE). Setting time and radiopacity were evaluated according to ISO 6876:2012 specification. Final setting time, compressive strength and pH were also assessed. Material's bond strength to the apical root canal dentin was measured by the push-out assay. Data were analyzed by ANOVA and Tukey-Krammer post-hoc test. Biodentine presented the shortest initial (16.2±1.48 min) and final setting time (35.4±5.55 min). Radiopacity of Biodentine (2.79±0.27 mmAl) does not agree with ISO 6876:2012 specifications. On the other hand, Biodentine showed higher compressive strength after 21 days (37.22±5.27 MPa) and higher dentin bond strength (11.2±2.16 MPa) in comparison to white MTA (27.68±3.56 MPa for compressive strength and 2.98±0.64 MPa for bond strength) (pBiodentine produced an alkaline environment (approximately pH 10) (p>0.05) compared to ZOE (pH 7). It may be concluded that Biodentine exhibited faster setting, higher long-term compressive strength and bond strength to the apical dentin than MTA and ZOE.

  3. Bond strength of a chairside autopolymerizing reline resin to injection-molded thermoplastic denture base resins.

    Science.gov (United States)

    Hamanaka, Ippei; Shimizu, Hiroshi; Takahashi, Yutaka

    2017-01-01

    This study evaluated the shear bond strength of a chairside autopolymerizing reline resin to injection-molded thermoplastic denture base resins. Four kinds of injection-molded thermoplastic resins (two polyamides, a polyethylene terephthalate copolymer and a polycarbonate) and PMMA, as a control, were tested. The eight types of surface treatment: ((1) no treatment, (2) air abrasion, (3) dichloromethane, (4) ethyl acetate, (5) 4-META/MMA-TBB resin, (6) air abrasion and 4-META/MMA-TBB resin, (7) tribochemical silica coating, and (8) tribochemical silica coating and 4-META/MMA-TBB resin) were applied to each specimen. The chairside autopolymerizing reline resins were bonded to disks of the injection-molded thermoplastic denture base resins. All of the specimens were immersed in water for 4 months and then thermocycled for 10,000 cycles in water between 5 and 55°C. The shear bond strengths were determined. The shear bond strengths of the two polyamides treated using air abrasion, dichloromethane and ethyl acetate and no treatment were exceedingly low. The greatest bond strength was recorded for the polyethylene terephthalate copolymer specimens treated with tribochemical silica coating and 4-META/MMA-TBB resin (22.5MPa). The bond strengths of the other injection-molded thermoplastic denture base resins increased using 4-META/MMA-TBB resin. Tribochemical silica coating and 4-META/MMA-TBB resin were the most effective surface treatments among all denture base resins tested. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  4. Spherical aberration compensation method for long focal-length measurement based on Talbot interferometry

    Science.gov (United States)

    Luo, Yupeng; Huang, Xiao; Bai, Jian; Du, Juan; Liu, Qun; Luo, Yujie; Luo, Jia

    2017-08-01

    Large-aperture and long focal-length lens is widely used in high energy laser system. The method based on Talbot interferometry is a reliable method to measure the focal length of such elements. By employing divergent beam and two gratings of different periods, this method could realize full-aperture measurement, higher accuracy and better repeatability. However, it does not take into account the spherical aberration of the measured lens resulting in the moiré fringes bending, which will introduce measurement error. Furthermore, in long-focal measurement with divergent beam, this error is an important factor affecting the measurement accuracy. In this paper, we propose a new spherical aberration compensation method, which could significantly reduce the measurement error. Characterized by central-symmetric scanning window, the proposed method is based on the relationship between spherical aberration and the lens aperture. Angle data of moiré fringes in each scanning window is retrieved by Fourier analysis and statistically fitted to estimate a globally optimum value for spherical-aberration-free focal length calculation. Simulation and experiment have been carried out. Compared to the previous work, the proposed method is able to reduce the relative measurement error by 50%. The effect of scanning window size and shift step length on the results is also discussed.

  5. Comparison of the Effects of Four Pre-Bonding Preparation Methods on the Bond Strength between a Multilithic Tooth and Denture Base Resin

    Directory of Open Access Journals (Sweden)

    Ramin Mosharraf

    2007-01-01

    Full Text Available Introduction: With introducing composite teeth, their wear resistance has been well investigated, but there are few papers about their bonding to acrylic denture base resins. The aim of this study was to compare the four pre-bonding preparation methods on the ridge lap surface of one multilithic denture tooth by determining its bond strength to denture base resin.Materials and Methods: In this experimental laboratory study, 84 maxillary anterior teeth were divided into four groups based on four different pre-bonding methods (untreated, grinding, 2 retention grooves and diatorics. The teeth were mounted on 2 sides of triangular shaped wax models. Then, the laboratory procedures (wax elimination and resin packing were done. Each of the specimens was tested by universal testing machine with cross head speed of 5 mm/min. The data were analyzed by Kruskal-Wallis and Mann- Whitney tests.Results: The mean bond strength in untreated group was 287.38 ± 51.82 N, in grinding group was 301.52 ± 113.65 N, in retention grooves group was 374.38 ± 88.22 N and in diatorics group was 415.19 ± 226.37 N. The highest mean bond strength was seen in diatorics group (P=0.009. The percentage of cohesive fractures in this group(90.5% was significantly more than that in other groups (P<0.001.Conclusion: The results of this study showed that creating retention hole in the ridge lap surface of the multilithic tooth can increase its bond strength with denture base resin.

  6. Are flowable resin-based composites a reliable material for metal orthodontic bracket bonding?

    Science.gov (United States)

    Pick, Bárbara; Rosa, Vinícius; Azeredo, Tatiana Rocha; Cruz Filho, Eduardo Augusto Mascarenhas; Miranda, Walter Gomes

    2010-07-01

    To compare the tensile bond strength (TBS) and adhesive remnant index (ARI) of three flowable resin-based composites and three orthodontic adhesive systems for metal bracket bonding. Sixty bovine incisors were randomly divided into six groups. Enamel surfaces were etched with 37 percent phosphoric acid for 30 seconds and stainless steel orthodontic brackets were bonded using either flowable resin-based composites (3M Flow, FL; Tetric Flow, TF; and Wave, WA) or orthodontic bonding systems (Transbond XT, TX; Concise Orthodontic, CO; Fill Magic Ortodôntico, FM). All specimens were thermal cycled and stored in distilled water at 37°C for 24 hours, after which they were subsequently tested for TBS using a universal testing machine. ARI scores were determined after the failure of brackets. TBS and ARI data were submitted to ANOVA, Tukey, and Kruskal-Wallis tests (p=0.05), respectively. Rankings of the resin-based composites based on TBS means (MPa) were TX (6.4 ± 2.1), followed by CO (4.5 ± 2.7), FM (3.7 ± 1.2), FL (3.6 ± 1.2), TF (3.3 ± 1.2), and WA (2.4 ± 0.6). CO exhibited the lowest ARI mean score (0.9 ± 1.2) which was significantly different from the other five materials: TX (2.8 ± 0.42), FM (2.8 ± 0.42), FL (2.9 ± 0.32), TF (2.9 ± 0.32), and WA (3.0 ± 0.01). However, there were no statistically significant differences among the other groups with mean scores of 2.8-3.0. A score of 3.0 indicated that all the resin remained bonded to the tooth surface. The flowable resin-based composites tested (Fl, TF, and WA) used to bond metal orthodontic brackets to bovine enamel had low mean TBS values but acceptable ARI mean scores. Flowable composites may not be appropriate for bracket bonding, unless the teeth to be bonded are not subjected to higher orthodontic stresses, such as those without an antagonist.

  7. Effect of root canal filling techniques on the bond strength of epoxy resin-based sealers.

    Science.gov (United States)

    Rached-Júnior, Fuad Jacob Abi; Souza, Angélica Moreira; Macedo, Luciana Martins Domingues; Raucci-Neto, Walter; Baratto-Filho, Flares; Silva, Bruno Marques; Silva-Sousa, Yara Teresinha Corrêa

    2016-01-01

    The aim of this study was to evaluate the effects of different root canal filling techniques on the bond strength of epoxy resin-based sealers. Sixty single-rooted canines were prepared using ProTaper (F5) and divided into the following groups based on the root filling technique: Lateral Compaction (LC), Single Cone (SC), and Tagger Hybrid Technique (THT). The following subgroups (n = 10) were also created based on sealer material used: AH Plus and Sealer 26. Two-millimeter-thick slices were cut from all the root thirds and subjected to push-out test. Data (MPa) was analyzed using ANOVA and Tukey's test (α = 0.05). The push-out values were significantly affected by the sealer, filling technique, and root third (p < 0.05). AH Plus (1.37 ± 1.04) exhibited higher values than Sealer 26 (0.92 ± 0.51), while LC (1.80 ± 0.98) showed greater bond strength than THT (1.16 ± 0.50) and SC (0.92 ± 0.25). The cervical (1.45 ± 1.14) third exhibited higher bond strength, followed by the middle (1.20 ± 0.72) and apical (0.78 ± 0.33) thirds. AH Plus/LC (2.26 ± 1.15) exhibited the highest bond strength values, followed by AH Plus/THT (1.32 ± 0.61), Sealer 26/LC (1.34 ± 0.42), and Sealer 26/THT (1.00 ± 0.27). The lowest values were obtained with AH Plus/SC and Sealer 26/SC. Thus, it can be concluded that the filling technique affects the bond strength of sealers. LC was associated with higher bond strength between the material and intra-radicular dentine than THT and SC techniques.

  8. Tensile Bond Strength between Soft Liners and Two Chemically Different Denture Base Materials: Effect of Thermocycling.

    Science.gov (United States)

    Tugut, Faik; Coskun, Mehmet Emre; Dogan, Derya Ozdemir; Kirmali, Omer; Akin, Hakan

    2016-06-01

    The bond strength of soft denture liner to a recently introduced denture base resin after thermocycling has not been compared to traditional denture base materials. The objective of this study was to investigate the effects of thermocycling on the tensile bond strength of soft denture liners to two chemically different denture base resins, polymethyl methacrylate (PMMA) and urethane dimethacrylate (UDMA). A total of 48 PMMA and UDMA tensile test specimens were fabricated by attaching two different soft denture liners (Molloplast-B, Permaflex) according to the manufacturers' instructions and assigned to two groups. Half of the specimens for each group were stored in water for 1 week, and the other half were thermocycled (5000 cycles) between baths of 5°C and 55°C. Specimens were mounted on a universal testing machine with a 5 mm/min crosshead speed. The data were analyzed with three-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (α = 0.05). The highest bond strength was measured in the specimens from the UDMA/Molloplast groups, and the lowest was seen in the PMMA/Permaflex group. No significant difference in bond strength was detected in PMMA/Permaflex groups after thermocycling (p = 0.082), whereas other groups exhibited significant differences after thermocycling (p < 0.05). Thermocycling decreased the bond strength values in both the PMMA and UDMA groups. Regardless of types of soft liners, PMMA specimens presented lower bond strength values than UDMA specimens, both before and after thermocycling. © 2015 by the American College of Prosthodontists.

  9. Mission-profile-based stress analysis of bond-wires in SiC power modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Iannuzzo, Francesco; Blaabjerg, Frede

    2016-01-01

    This paper proposes a novel mission-profile-based reliability analysis approach for stress on bond wires in Silicon Carbide (SiC) MOSFET power modules using statistics and thermo-mechanical FEM analysis. In the proposed approach, both the operational and environmental thermal stresses are taken...... and the mechanical stress on bond wires is consequently extracted by finite-element simulations. In the final step, the considered mission profile is translated in a stress sequence to be used for Rainflow counting calculation and lifetime estimation....

  10. Multiscale Analysis on the Pricing of Intensity-Based Defaultable Bonds

    Directory of Open Access Journals (Sweden)

    Sun-Hwa Cho

    2013-01-01

    Full Text Available This paper studies the pricing of intensity-based defaultable bonds where the volatility of default intensity is assumed to be random and driven by two different factors varying on fast and slow time scales. Corrections to the constant intensity of default are obtained and then how these corrections influence the term structure of interest rate derivatives is shown. The results indicate that the fast scale correction produces a more significant impact on the bond price than the slow scale correction and the impact tends to increase as time to maturity increases.

  11. Superfluorinated Ionic Liquid Crystals Based on Supramolecular, Halogen-Bonded Anions.

    Science.gov (United States)

    Cavallo, Gabriella; Terraneo, Giancarlo; Monfredini, Alessandro; Saccone, Marco; Priimagi, Arri; Pilati, Tullio; Resnati, Giuseppe; Metrangolo, Pierangelo; Bruce, Duncan W

    2016-05-17

    Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen-bonded supramolecular anions [Cn F2 n+1 -I⋅⋅⋅I⋅⋅⋅I-Cn F2 n+1 ](-) are reported. The material system is unique in many ways, demonstrating for the first time 1) ionic, halogen-bonded liquid crystals, and 2) imidazolium-based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  12. Interfacial shear bond strength between different base metal alloys and five low fusing feldspathic ceramic systems.

    Science.gov (United States)

    Sipahi, Cumhur; Ozcan, Mutlu

    2012-01-01

    This study compared the bond strength between metal alloys and 5 ceramic systems. Ceramic systems (Vita VMK68, Ivoclar IPSd. SIGN, Ceramco II, Matchmaker and Finesse) were fired onto either Ni-Cr or Co-Cr base metal alloy. Metal-ceramic interfaces were subjected to shear loading until failure. The ceramic type significantly affected the bond strength results (palloy, the results ranged between 15.4-25.3 MPa and for Co-Cr alloy between 13.3-19.0 MPa. The highest mean bond strength value was obtained with the combination of Ni-Cr alloy-Ceramco II (25.3 MPa), the lowest bond strength was received from the combination of Co-Cr alloy-Ivoclar IPS d.SIGN ceramic (13.3 MPa). Adhesive failures between metal and ceramic were significantly more frequent with Ni-Cr alloy (31 out of 50) than with Co-Cr (20 out of 50) (p<0.05). Ceramco II presented the highest bond strength with both Ni-Cr and Co-Cr being significantly different from one another.

  13. Bond Strength of Methacrylate-Based Composite to Dentin using a Silorane Adhesive

    Science.gov (United States)

    2013-06-06

    the CEJ in a custom cylindrical block. A diamond saw (Isomet, Buhler, Lake Bluff, IL) was used to section the crowns of the teeth horizontally in a...resin 3M/ESPE St. Paul, MN Bis-GMA, Bis-EMA, UDMA, TEGDMA Zirconia , silica LS System Adhesive 2-step self-etch methacrylate-based bonding

  14. Moisture diffusion coefficients determination of furan bonded sands and water based foundry coatings

    DEFF Research Database (Denmark)

    Di Muoio, Giovanni Luca; Tiedje, Niels Skat

    2016-01-01

    Moisture content in furan bonded sand and water based coatings can be one of the main causes for gas related defects in large cast iron parts. Moisture diffusion coefficients for these materials are needed to precisely predict the possible moisture levels in foundry moulds. In this study, we first...

  15. The bond between acrylic resin denture teeth and the denture base: recommendations for best practice.

    Science.gov (United States)

    Radford, D R; Juszczyk, A S; Clark, R K F

    2014-02-01

    Failure of the bond between denture teeth and base acrylic resin has been shown to be a cause of denture failure leading to inconvenience and costly repair. The optimal combination of acrylic resin denture tooth, denture base material, laboratory protocol and processing method has not yet been established. Extensive research enables the following recommendations for best practice to be made. Adopt practices that maximise the strength of the bond: select appropriate denture teeth; select base acrylic resin from the same manufacturer as the denture teeth; remove the glaze from ridgelaps of the denture teeth; apply monomer to the ridgelaps of the denture teeth before packing the base acrylic resin dough; use the manufacturers' recommended liquid/powder ratio; follow the manufacturers' recommended curing cycle; allow the flask to cool slowly and rest before deflasking. Adopt practices that avoid factors detrimental to bond strength: remove all traces of wax from the ridge laps of the denture teeth; remove all traces of mould seal from the ridgelaps of the denture teeth. It is evident that a number of factors are involved which may assist or prevent formation of an adequate bond, suggesting that attention to detail by the dental technician may be the most critical factor.

  16. Shear bond strength of a denture base acrylic resin and gingiva-colored indirect composite material to zirconia ceramics.

    Science.gov (United States)

    Kubochi, Kei; Komine, Futoshi; Fushiki, Ryosuke; Yagawa, Shogo; Mori, Serina; Matsumura, Hideo

    2017-04-01

    To evaluate the shear bond strengths of two gingiva-colored materials (an indirect composite material and a denture base acrylic resin) to zirconia ceramics and determine the effects of surface treatment with various priming agents. A gingiva-colored indirect composite material (CER) or denture base acrylic resin (PAL) was bonded to zirconia disks with unpriming (UP) or one of seven priming agents (n=11 each), namely, Alloy Primer (ALP), Clearfil Photo Bond (CPB), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB+Act), Metal Link (MEL), Meta Fast Bonding Liner (MFB), MR. bond (MRB), and V-Primer (VPR). Shear bond strength was determined before and after 5000 thermocycles. The data were analyzed with the Kruskal-Wallis test and Steel-Dwass test. The mean pre-/post-thermalcycling bond strengths were 1.0-14.1MPa/0.1-12.1MPa for the CER specimen and 0.9-30.2MPa/0.1-11.1MPa for the PAL specimen. For the CER specimen, the ALP, CPB, and CPB+Act groups had significantly higher bond strengths among the eight groups, at both 0 and 5000 thermocycles. For the PAL specimen, shear bond strength was significantly lower after thermalcycling in all groups tested. After 5000 thermocycles, bond strengths were significantly higher in the CPB and CPB+Act groups than in the other groups. For the PAL specimens, bond strengths were significantly lower after thermalcycling in all groups tested. The MDP functional monomer improved bonding of a gingiva-colored indirect composite material and denture base acrylic resin to zirconia ceramics. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  17. Microstructural developments in TLP bonds using thin interlayers based on Ni-B coatings

    Energy Technology Data Exchange (ETDEWEB)

    Saha, R.K. [Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4 (Canada); Khan, T.I., E-mail: tkhan@ucalgary.ca [Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4 (Canada)

    2009-09-15

    Oxide dispersion strengthened alloy MA 758 was transient liquid phase (TLP) bonded using thin interlayers based on Ni-B electrodeposited coatings and the microstructural developments across the joint region were studied. The bonding surfaces were electrodeposited with a coat thickness of 2-9 {mu}m and microstructural features were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The homogeneity of the joint was assessed performing micro-hardness test. The results showed that the coating thickness as well as the amount of melting point depressants (boron) in the coatings had a significant effect on the microstructural developments within the joint region. TLP bonds made using a 2 {mu}m thick coating interlayer produced a joint with no visible precipitate formation and parent metal dissolution, and the absence of precipitates was attributed to the lower volume concentration of boron in the 2 {mu}m thick coating interlayer.

  18. Microstructural developments in TLP bonds using thin interlayers based on Ni-B coatings

    International Nuclear Information System (INIS)

    Saha, R.K.; Khan, T.I.

    2009-01-01

    Oxide dispersion strengthened alloy MA 758 was transient liquid phase (TLP) bonded using thin interlayers based on Ni-B electrodeposited coatings and the microstructural developments across the joint region were studied. The bonding surfaces were electrodeposited with a coat thickness of 2-9 μm and microstructural features were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The homogeneity of the joint was assessed performing micro-hardness test. The results showed that the coating thickness as well as the amount of melting point depressants (boron) in the coatings had a significant effect on the microstructural developments within the joint region. TLP bonds made using a 2 μm thick coating interlayer produced a joint with no visible precipitate formation and parent metal dissolution, and the absence of precipitates was attributed to the lower volume concentration of boron in the 2 μm thick coating interlayer.

  19. Study on effective anchorage length of anchor cable based on Gauss's function

    Science.gov (United States)

    Ren, Feng; WuShuai; Liu, Yan; Liu, Jun-yan

    2017-11-01

    In the current relevant codes and technical standards, the design of anchor cables (bars) is based on the assumption that the shear stress is distributed uniformly along the anchor segment. However, according to this assumption, the super-deep pit need a large uplift bearing capacity, which will lead to the long anchor segment and has great hidden danger in the actual engineering design. Therefore, this paper, based on the previous derived shear stress function between τ and the anchor length, we get a research suitable model-Gauss curve distribution model through the analysis of saturated clay drawing data, and strata anchor shear stress distribution is more suitable for the Gauss function model in saturated clay; at the same time, through the FLAC numerical simulation of Jinan Government Affairs Center project, we obtained the optimal anchor effective anchor length is about 10~12m, the foundation pit anchor is optimized.

  20. Transient liquid phase bonding of titanium-, iron- and nickel-based alloys

    Science.gov (United States)

    Rahman, A. H. M. Esfakur

    The operating temperature of land-based gas turbines and jet engines are ever-increasing to increase the efficiency, decrease the emissions and minimize the cost. Within the engines, complex-shaped parts experience extreme temperature, fatigue and corrosion conditions. Ti-based, Ni-based and Fe-based alloys are commonly used in gas turbines and jet engines depending on the temperatures of different sections. Although those alloys have superior mechanical, high temperature and corrosion properties, severe operating conditions cause fast degradation and failure of the components. Repair of these components could reduce lifecycle costs. Unfortunately, conventional fusion welding is not very attractive, because Ti reacts very easily with oxygen and nitrogen at high temperatures, Ni-based superalloys show heat affected zone (HAZ) cracking, and stainless steels show intergranular corrosion and knife-line attack. On the other hand, transient liquid phase (TLP) bonding method has been considered as preferred joining method for those types of alloys. During the initial phase of the current work commercially pure Ti, Fe and Ni were diffusion bonded using commercially available interlayer materials. Commercially pure Ti (Ti-grade 2) has been diffusion bonded using silver and copper interlayers and without any interlayer. With a silver (Ag) interlayer, different intermetallics (AgTi, AgTi2) appeared in the joint centerline microstructure. While with a Cu interlayer eutectic mixtures and Ti-Cu solid solutions appeared in the joint centerline. The maximum tensile strengths achieved were 160 MPa, 502 MPa, and 382 MPa when Ag, Cu and no interlayers were used, respectively. Commercially pure Fe (cp-Fe) was diffusion bonded using Cu (25 m) and Au-12Ge eutectic interlayer (100 microm). Cu diffused predominantly along austenite grain boundaries in all bonding conditions. Residual interlayers appeared at lower bonding temperature and time, however, voids were observed in the joint

  1. Horizontal Directional Drilling-Length Detection Technology While Drilling Based on Bi-Electro-Magnetic Sensing.

    Science.gov (United States)

    Wang, Yudan; Wen, Guojun; Chen, Han

    2017-04-27

    The drilling length is an important parameter in the process of horizontal directional drilling (HDD) exploration and recovery, but there has been a lack of accurate, automatically obtained statistics regarding this parameter. Herein, a technique for real-time HDD length detection and a management system based on the electromagnetic detection method with a microprocessor and two magnetoresistive sensors employing the software LabVIEW are proposed. The basic principle is to detect the change in the magnetic-field strength near a current coil while the drill stem and drill-stem joint successively pass through the current coil forward or backward. The detection system consists of a hardware subsystem and a software subsystem. The hardware subsystem employs a single-chip microprocessor as the main controller. A current coil is installed in front of the clamping unit, and two magneto resistive sensors are installed on the sides of the coil symmetrically and perpendicular to the direction of movement of the drill pipe. Their responses are used to judge whether the drill-stem joint is passing through the clamping unit; then, the order of their responses is used to judge the movement direction. The software subsystem is composed of a visual software running on the host computer and a software running in the slave microprocessor. The host-computer software processes, displays, and saves the drilling-length data, whereas the slave microprocessor software operates the hardware system. A combined test demonstrated the feasibility of the entire drilling-length detection system.

  2. Engineering a disulfide bond in the lid hinge region of Rhizopus chinensis lipase: increased thermostability and altered acyl chain length specificity.

    Directory of Open Access Journals (Sweden)

    Xiao-Wei Yu

    Full Text Available The key to enzyme function is the maintenance of an appropriate balance between molecular stability and structural flexibility. The lid domain which is very important for "interfacial activation" is the most flexible part in the lipase structure. In this work, rational design was applied to explore the relationship between lid rigidity and lipase activity by introducing a disulfide bond in the hinge region of the lid, in the hope of improving the thermostability of R. chinensis lipase through stabilization of the lid domain without interfering with its catalytic performance. A disulfide bridge between F95C and F214C was introduced into the lipase from R. chinensis in the hinge region of the lid according to the prediction of the "Disulfide by Design" algorithm. The disulfide variant showed substantially improved thermostability with an eleven-fold increase in the t(1/2 value at 60°C and a 7°C increase of T(m compared with the parent enzyme, probably contributed by the stabilization of the geometric structure of the lid region. The additional disulfide bond did not interfere with the catalytic rate (k(cat and the catalytic efficiency towards the short-chain fatty acid substrate, however, the catalytic efficiency of the disulfide variant towards pNPP decreased by 1.5-fold probably due to the block of the hydrophobic substrate channel by the disulfide bond. Furthermore, in the synthesis of fatty acid methyl esters, the maximum conversion rate by RCLCYS reached 95% which was 9% higher than that by RCL. This is the first report on improving the thermostability of the lipase from R. chinensis by introduction of a disulfide bond in the lid hinge region without compromising the catalytic rate.

  3. Restoring Congenitally Missing Maxillary Lateral Incisors Using Zirconia-Based Resin Bonded Prostheses.

    Science.gov (United States)

    Stylianou, Antigoni; Liu, Perng-Ru; O'Neal, Sandra J; Essig, Milton E

    2016-01-01

    This clinical report describes an alternative treatment modality for the replacement of congenitally missing maxillary lateral incisors in a 17-year-old patient. Zirconia-based resin-bonded fixed partial dentures (RBFPDs) were selected as a viable and conservative treatment option in a young individual with highly aesthetic expectations. Fabrication of all-ceramic RBFPDs followed specific preparation design and features to accommodate two retainers. The zirconia frameworks with bilateral wings were digitally designed and then milled by a computer-aided design and computer-aided manufacturing (CAD/CAM)-controlled milling machine. Zirconia surface was treated with a two-step chairside tribochemical silica-coating/silane coupling surface treatment protocol, and adhesive resin luting cement was used to achieve micromechanical and chemical bonding. Completion of the treatment resulted in a functional and aesthetic successful outcome and a 17-month follow-up presented uneventful. Contemporary adhesive techniques involving resin-bonded zirconia-based prostheses can be utilized successfully and predictably in young patients with single missing teeth when implant therapy is currently not a treatment of choice and a less invasive approach is desired. The zirconia-based resin-bonded prosthesis constitutes a viable and conservative treatment modality for the replacement of missing teeth either congenitally or from another etiology in young patients in which implant therapy and a fixed partial denture are currently contraindicated. © 2015 Wiley Periodicals, Inc.

  4. Effect of adherend temperature on bond strengths of resin bonding systems to denture base resin and a semi-precious alloy.

    Science.gov (United States)

    Murahara, Sadaaki; Minami, Hiroyuki; Suzuki, Shiro; Sakoguchi, Kenji; Shiomuki, Daisaku; Minesaki, Yoshito; Tanaka, Takuo

    2013-01-01

    This study investigated the effect of adherend temperature on shear bond strengths of auto-polymerizing resin to denture base resin and 4-META/MMA-TBBO resin to silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy. Bonding procedure was carried out when adherend temperature was 10, 23, 37, or 55°C, and shear bond strengths (SBSs) were measured before and after thermocycling. Before thermocycling, there were no significant differences in bond strength among the four adherend temperatures for each adhesive resin: 31.59±6.11-32.89±2.12 MPa for auto-polymerizing resin; 35.43±2.2-38.38±0.61 MPa for 4-META/MMA-TBBO resin. After thermocycling, optimal adherend temperature to achieve the highest bond strength was 37°C for auto-polymerizing resin to denture base resin (30.02±2.29 MPa) and 10ºC for 4-META/MMA-TBBO resin to Ag-Pd-Cu-Au alloy (37.14±2.17 MPa).

  5. Hydrogen-bond-dynamics-based switching of conductivity and magnetism: a phase transition caused by deuterium and electron transfer in a hydrogen-bonded purely organic conductor crystal.

    Science.gov (United States)

    Ueda, Akira; Yamada, Shota; Isono, Takayuki; Kamo, Hiromichi; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Murakami, Youichi; Yamamoto, Kaoru; Nishio, Yutaka; Mori, Hatsumi

    2014-08-27

    A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O···D···O](-1)-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve.

  6. A new class of cuprous bromide cluster-based hybrid materials: direct observation of the stepwise replacement of hydrogen bonds by coordination bonds.

    Science.gov (United States)

    Zhang, Xian-Ming; Hou, Juan-Juan; Guo, Cai-Hong; Li, Chun-Fang

    2015-01-20

    Although a variety of functional metal-organic frameworks (MOFs) have been synthesized, post-modified, and applied in various areas, there is little knowledge about how molecular cluster building units are stepwise evolved into MOFs via intermediates. Coordination bonds are generally stronger than hydrogen bonds, and thus equivalent replacement of X-H···Y hydrogen bonds by X-M-Y coordination bonds can transform hydrogen bond networks into MOFs. In this work, solvothermal in situ reduction reactions of CuBr2 and 1,4-diazoniabicyclo[2,2,2]octane (DABCO) generated a myriad of tunable photoluminescent cuprous body-centered cubic bromide cluster-based networks with the general formula [Cu4+xH4-xBr6(DABCO)4](HCO2)2·S (x = 0, 0.56, 0.81, 1.27, 1.39, 2.56, 2.78, and 4 for compounds 1-8, respectively). All of these compounds crystallize in the cubic space group with the largest volume difference being only 5.2%, but they belong to three remarkably different kinds of crystals. Complex 1 is a molecular crystal and consists of tetrahedral [Cu4Br6(HDABCO)4](2+) clusters with monodentate HDABCO groups that are supported via N-H···Br synthons in the hydrogen bond network. Compound 8 is a [Cu8Br6](2+) cube cluster-based MOF with bridged DABCO ligands. Complexes 2-7 are seemingly impossible Cu/H-substituted solid solutions of 1 and 8. The CuBr framework components in 1-8 are Cu4Br6, Cu4.56Br6, Cu4.81Br6, Cu5.27Br6, Cu5.39Br6, Cu6.56Br6, Cu6.78Br6, and Cu8Br6, respectively. Crystallization kinetics studies revealed that the [Cu4Br6(HDABCO)4](2+) cluster-based hydrogen bond network (1) was initially formed such that N-H···Br hydrogen bonds could be stepwise replaced by N-Cu-Br coordination bonds to form the [Cu8Br6](2+) cube cluster-based MOF (8) via solid solutions. These observations directly reveal the equivalence and transformation between the N-H···Br hydrogen bond and the N-Cu-Br coordination bond and the evolutionary mechanism of a molecular crystal to a MOF via

  7. A hydrogen-bonded electron-tunneling circuit reads the base composition of unmodified DNA

    International Nuclear Information System (INIS)

    He Jin; Lin Lisha; Liu Hao; Zhang Peiming; Lindsay, S M; Lee, Myeong; Sankey, O F

    2009-01-01

    Using a tunnel junction in which one electrode is guanidinium-functionalized (to trap DNA via hydrogen bonding to the backbone phosphates) and a second electrode which is functionalized with a base (to capture its complementary target on the DNA), current versus distance curves are obtained which yield an accurate measure of the base composition of DNA oligomers. With this long tunneling path, resolution is limited to sequence blocks of about twenty bases or larger, because of the need to form a large-area tunnel junction. A shorter hydrogen-bonded path across bases will be required for DNA sequencing. Nonetheless, these measurements point the way to a new type of nanoscale sensor.

  8. Minimum length modulator design with a graphene-based plasmonic waveguide.

    Science.gov (United States)

    Ghahri, Muhammad Reza; Faez, Rahim

    2017-06-10

    In this study, we simulated and analyzed a plasmonic waveguide modulator based on a single layer of graphene. It includes a graphene sheet, which sandwiches between two layers of silicon dioxide. Then, some gates are arranged on either side of the waveguide on a periodic structure. When an electric field is applied perpendicular to the waveguide plate, the Fermi level of graphene under the gates changes. Detailed analysis is performed by the method of lines based on Maxwell's equations along the propagation direction of the waveguide. Computation of the multi-gate device starts by examining the effect of the Fermi level. The transmission coefficient of the magnetic-field norms of the modulator is calculated by varying the parameters, such as Fermi level, length, gates number, and distance between the gates to achieve optimized design of the modulator device with very small dimensions. The results show that at higher Fermi levels, where the imaginary part of the effective index of the waveguide is close to zero, the reflection is dominant and absorption is low. Therefore, the modulator length becomes so long that it is more than one hundred nanometers. At lower Fermi levels, where the amount of the imaginary part of the effective index is significant, the absorption is dominant. At this range, a one-gate device is sufficient for modulation. Consequently, the designed minimum device length becomes equal to six nanometers for the ten-micrometer wavelength. Furthermore, the design is carried out in other wavelengths.

  9. An Improved Endmember Selection Method Based on Vector Length for MODIS Reflectance Channels

    Directory of Open Access Journals (Sweden)

    Yuanliu Xu

    2015-05-01

    Full Text Available Endmember selection is the basis for sub-pixel land cover classifications using multiple endmember spectral mixture analysis (MESMA that adopts variant endmember matrices for each pixel to mitigate errors caused by endmember variability in SMA. A spectral library covering a large number of endmembers can account for endmember variability, but it also lowers the computational efficiency. Therefore, an efficient endmember selection scheme to optimize the library is crucial to implement MESMA. In this study, we present an endmember selection method based on vector length. The spectra of a land cover class were divided into subsets using vector length intervals of the spectra, and the representative endmembers were derived from these subsets. Compared with the available endmember average RMSE (EAR method, our approach improved the computational efficiency in endmember selection. The method accuracy was further evaluated using spectral libraries derived from the ground reference polygon and Moderate Resolution Imaging Spectroradiometer (MODIS imagery respectively. Results using the different spectral libraries indicated that MESMA combined with the new approach performed slightly better than EAR method, with Kappa coefficient improved from 0.75 to 0.78. A MODIS image was used to test the mapping fraction, and the representative spectra based on vector length successfully modeled more than 90% spectra of the MODIS pixels by 2-endmember models.

  10. Feedback Linearization Based Arc Length Control for Gas Metal Arc Welding

    DEFF Research Database (Denmark)

    Thomsen, Jesper Sandberg

    2005-01-01

    In this paper a feedback linearization based arc length controller for gas metal arc welding (GMAW) is described. A nonlinear model describing the dynamic arc length is transformed into a system where nonlinearities can be cancelled by a nonlinear state feedback control part, and thus, leaving only...... a linear system to be controlled by linear state feedback control. The advantage of using a nonlinear approach as feedback linearization is the ability of this method to cope with nonlinearities and different operating points. However, the model describing the GMAW process is not exact, and therefore......, the cancellation of nonlinear terms might give rise to problems with respect to robustness. Robustness of the closed loop system is therefore nvestigated by simulation....

  11. Comparative study of ceramometal tensile bonding strength in two base metal alloys

    Directory of Open Access Journals (Sweden)

    Comparative study of ceramometal tensile bonding strength in two base metal alloys

    2005-06-01

    Full Text Available Statement of Problem: One of the greatest problems in metal –ceramic restorations is debonding of porcelain from dental alloys. Production of dental alloys by Iranian companies necessitates the evaluation of physical and handling properties of these products. Purpose: In this study the bond strength between porcelain and two types of base metal alloys, Supercast (with beryllium and Minalux (without beryllium was investigated. Materials and Methods: In this experimental study 10 cylindric bars from each base metal alloy were prepared. The bars were degassed and porcelain was applied around them in a disc form (8 mm diameter and 2 mm thickness. The bond strength of porcelain to metal bars was tested with the shear strength test by Instron. Data were analyzed with student t-test and P<0.05 was considered as the limit of significance. Results: The mean failure load was 71.58±6.4 KgF for Supercast and 67.34±5.48 for Minalux alloy. The bond strength of Supercast and Minalux were 55.85±4.99 MPa and 52.54±4.27 MPa respectively. The difference was statistically significant (P0.001. Conclusions: This study showed that nickel-chromium-beryllium alloy (Supercast produced significantly better ceramometal bonding than nickel chromium alloy without beryllium (Minalux.

  12. 17 CFR 240.6h-2 - Security future based on note, bond, debenture, or evidence of indebtedness.

    Science.gov (United States)

    2010-04-01

    ..., bond, debenture, or evidence of indebtedness. 240.6h-2 Section 240.6h-2 Commodity and Securities... of Exchanges § 240.6h-2 Security future based on note, bond, debenture, or evidence of indebtedness... indebtedness or a narrow-based security index composed of such securities. ...

  13. Determination of Wind Turbine Near-Wake Length Based on Stability Analysis

    International Nuclear Information System (INIS)

    Sørensen, Jens N; Mikkelsen, Robert; Sarmast, Sasan; Ivanell, Stefan; Henningson, Dan

    2014-01-01

    A numerical study on the wake behind a wind turbine is carried out focusing on determining the length of the near-wake based on the instability onset of the trailing tip vortices shed from the turbine blades. The numerical model is based on large-eddy simulations (LES) of the Navier-Stokes equations using the actuator line (ACL) method. The wake is perturbed by applying stochastic or harmonic excitations in the neighborhood of the tips of the blades. The flow field is then analyzed to obtain the stability properties of the tip vortices in the wake of the wind turbine. As a main outcome of the study it is found that the amplification of specific waves (traveling structures) along the tip vortex spirals is responsible for triggering the instability leading to wake breakdown. The presence of unstable modes in the wake is related to the mutual inductance (vortex pairing) instability where there is an out-of-phase displacement of successive helix turns. Furthermore, using the non-dimensional growth rate, it is found that the pairing instability has a universal growth rate equal to π/2. Using this relationship, and the assumption that breakdown to turbulence occurs once a vortex has experienced sufficient growth, we provide an analytical relationship between the turbulence intensity and the stable wake length. The analysis leads to a simple expression for determining the length of the near wake. This expression shows that the near wake length is inversely proportional to thrust, tip speed ratio and the logarithmic of the turbulence intensity

  14. Erosive cola-based drinks affect the bonding to enamel surface: an in vitro study

    Directory of Open Access Journals (Sweden)

    Leslie Caroll CASAS-APAYCO

    2014-10-01

    Full Text Available Objective: This study aimed to assess the impact of in vitro erosion provoked by different cola-based drinks (Coke types, associated or not with toothbrushing, to bonding to enamel. Material and methods: Forty-six bovine enamel specimens were prepared and randomly assigned into seven groups (N=8: C- Control (neither eroded nor abraded, ERO-RC: 3x/1-minute immersion in Regular Coke (RC, ERO-LC: 3x/1-minute immersion in Light Coke (LC, ERO-ZC: 3x/1-minute immersion in Zero Coke (ZC and three other eroded groups, subsequently abraded for 1-minute toothbrushing (EROAB-RC, EROAB-LC and EROAB-ZC, respectively. After challenges, they were stored overnight in artificial saliva for a total of 24 hours and restored with Adper Single Bond 2/Filtek Z350. Buildup coronal surfaces were cut in 1 mm2 -specimens and subjected to a microtensile test. Data were statistically analyzed by two-way ANOVA/Bonferroni tests (α=0.05. Failure modes were assessed by optical microscopy (X40. The Interface of the restorations were observed using Confocal Laser Scanning Microscopy (CLSM. Results: All tested cola-based drinks significantly reduced the bond strength, which was also observed in the analyses of interfaces. Toothbrushing did not have any impact on the bond strength. CLSM showed that except for Zero Coke, all eroded specimens resulted in irregular hybrid layer formation. Conclusions: All cola-based drinks reduced the bond strength. Different patterns of hybrid layers were obtained revealing their impact, except for ZC.

  15. Directionality of Cation/Molecule Bonding in Lewis Bases Containing the Carbonyl Group.

    Science.gov (United States)

    Valadbeigi, Younes; Gal, Jean-François

    2017-09-14

    Relationship between the C═O-X + (X = H, Li, Na, K, Al, Cu) angle and covalent characteristic of the X + -M (M = CH 2 O, CH 3 CHO, acetone, imidazol-2-one (C 2 H 2 N 2 O), cytosine, γ-butyrolactone) was investigated, theoretically. The calculated electron densities ρ at the bond critical points revealed that the covalency of the M-X + interaction depended on the nature of the cation and varied as H + > Cu + > Al + > Li + > Na + > K + . The alkali cations tended to participate in electrostatic interactions and aligned with the direction of the molecule dipole or local dipole of C═O group to form linear C═O-X geometries. Because of overlapping with lone-pair electrons of the sp 2 carbonyl oxygen, the H + and Cu + formed a bent C═O-X angle. Al + displayed an intermediate behavior; the C═O-Al angle was 180° in [CH 2 O/Al] + (mainly electrostatic), but when the angle was bent (146°) under the effect of local dipole of an adjacent imine group in cytosine, the covalency of the CO-Al + interaction increased. The C═O-X angles in M/X + adduct ions were scanned in different O-X bond lengths. It was found that the most favorable C═O-X angle depended on the O-X bond length. This dependency was attributed to variation of covalent and electrostatic contributions with O-X distance. In addition, the structures of [CH 2 S/X] + and [CH 2 Se/X] + were studied, and only bent C═S-X and C═Se-X angles were obtained for all cations, although the dipole vectors of CH 2 S and CH 2 Se coincide with the C═S and C═Se bonds. The bending of the C═S-X and C═Se-X angles was attributed to the covalent characteristic of S-X and Se-X interactions due to high polarizability of S and Se atoms.

  16. [Preliminary study of bonding strength between diatomite-based dental ceramic and veneering porcelains].

    Science.gov (United States)

    Lu, Xiao-li; Gao, Mei-qin; Cheng, Yu-ye; Zhang, Fei-min

    2015-04-01

    In order to choose the best veneering porcelain for diatomite-based dental ceramic substrate, the bonding strength between diatomite-based dental ceramics and veneering porcelains was measured, and the microstructure and elements distribution of interface were analyzed. The coefficient of thermal expansion (CTE) of diatomite-based dental ceramics was detected by dilatometry. Three veneering porcelain materials were selected with the best CTE matching including alumina veneering porcelain (group A), titanium porcelain veneering porcelain (group B), and E-max veneering porcelain (group C). Shear bonding strength was detected. SEM and EDS were used to observe the interface microstructure and element distribution. Statistical analysis was performed using SPSS 17.0 software package. The CTE of diatomite-based dental ceramics at 25-500 degrees centigrade was 8.85×10-6K-1. The diatomite-based substrate ceramics combined best with group C. Shear bonding strength between group A and C and group B and C both showed significant differences(Pveneer.

  17. Work-related exhaustion and telomere length: a population-based study.

    Directory of Open Access Journals (Sweden)

    Kirsi Ahola

    Full Text Available Psychological stress is suggested to accelerate the rate of biological aging. We investigated whether work-related exhaustion, an indicator of prolonged work stress, is associated with accelerated biological aging, as indicated by shorter leukocyte telomeres, that is, the DNA-protein complexes that cap chromosomal ends in cells.We used data from a representative sample of the Finnish working-age population, the Health 2000 Study. Our sample consisted of 2911 men and women aged 30-64. Work-related exhaustion was assessed using the Maslach Burnout Inventory--General Survey. We determined relative leukocyte telomere length using a quantitative real-time polymerase chain reaction (PCR -based method.After adjustment for age and sex, individuals with severe exhaustion had leukocyte telomeres on average 0.043 relative units shorter (standard error of the mean 0.016 than those with no exhaustion (p = 0.009. The association between exhaustion and relative telomere length remained significant after additional adjustment for marital and socioeconomic status, smoking, body mass index, and morbidities (adjusted difference 0.044 relative units, standard error of the mean 0.017, p = 0.008.These data suggest that work-related exhaustion is related to the acceleration of the rate of biological aging. This hypothesis awaits confirmation in a prospective study measuring changes in relative telomere length over time.

  18. Work-related exhaustion and telomere length: a population-based study.

    Science.gov (United States)

    Ahola, Kirsi; Sirén, Ilari; Kivimäki, Mika; Ripatti, Samuli; Aromaa, Arpo; Lönnqvist, Jouko; Hovatta, Iiris

    2012-01-01

    Psychological stress is suggested to accelerate the rate of biological aging. We investigated whether work-related exhaustion, an indicator of prolonged work stress, is associated with accelerated biological aging, as indicated by shorter leukocyte telomeres, that is, the DNA-protein complexes that cap chromosomal ends in cells. We used data from a representative sample of the Finnish working-age population, the Health 2000 Study. Our sample consisted of 2911 men and women aged 30-64. Work-related exhaustion was assessed using the Maslach Burnout Inventory--General Survey. We determined relative leukocyte telomere length using a quantitative real-time polymerase chain reaction (PCR) -based method. After adjustment for age and sex, individuals with severe exhaustion had leukocyte telomeres on average 0.043 relative units shorter (standard error of the mean 0.016) than those with no exhaustion (p = 0.009). The association between exhaustion and relative telomere length remained significant after additional adjustment for marital and socioeconomic status, smoking, body mass index, and morbidities (adjusted difference 0.044 relative units, standard error of the mean 0.017, p = 0.008). These data suggest that work-related exhaustion is related to the acceleration of the rate of biological aging. This hypothesis awaits confirmation in a prospective study measuring changes in relative telomere length over time.

  19. A stochastic length-based assessment model for the Pandalus stock in Skagerrak and the Norwegian Deep

    DEFF Research Database (Denmark)

    Nielsen, Anders; Munch-Petersen, Sten; Eigaard, Ole Ritzau

    2013-01-01

    This working document describes a length based stochastic assessment model of Pandalus in ICES areas IIIA and IVA. The model describing stock development is age based, but the model also estimates the relation between age and length assuming a von Bertalany growth curve. The model presented...

  20. Effect of MDP-Based Silane and Different Surface Conditioner Methods on Bonding of Resin Cements to Zirconium Framework.

    Science.gov (United States)

    Özdemir, Hatice; Yanikoğlu, Nuran; Sağsöz, Nurdan

    2017-07-24

    To determine the shear bond strength (SBS) between zirconium framework and resin cements after different surface conditioner methods and after application of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) based silane and a bonding agent mix. 128 disc-shaped zirconium-oxide specimens were prepared. Specimens were placed in autopolymerizing acrylic resin. The bonding surface of specimens was smoothed consecutively with 600-, 800-, and 1200-grit silicon carbide papers under water cooling. Eight groups were prepared: CJ, Co-Jet; N, Nd-YAG laser; E, Er-YAG laser; NS, Nd-YAG laser + silane; ES, Er-YAG laser + silane; CJB, Co-Jet + bonding agent; NSB, Nd-YAG laser + silane + bonding agent; ESB, Er-YAG laser + silane + bonding agent. SEM analysis was performed under 2000× magnification. Dual- and self-cured resin cements were bonded to specimens, and shear force was applied. Data were analyzed with one-way ANOVA and Tukey's multiple comparison test (p MDP-based silane and bonding agent mix increased SBS values of each cement belonging to each group. SB values of dual-cure resin cement were higher than those of self-cure resin cements. Different surface conditioner methods exhibit an important effect on the SBS of resin cements to zirconium. The application of MDP-based silane and bonding agent mix enhanced SB values. © 2017 by the American College of Prosthodontists.

  1. Tensile bond strength of dual curing resin-based cements to commercially pure titanium.

    Science.gov (United States)

    Schneider, Rafael; de Goes, Mario Fernando; Henriques, Guilherme Elias Pessanha; Chan, Daniel C N

    2007-01-01

    The aim of this study was to evaluate the tensile bond strength of dual curing luting resin cements to commercially pure titanium at 10 min and 24h after removal of the oxide layer. One hundred and twenty titanium discs were obtained by casting and polishing with silicon carbide papers. The titanium discs were sandblasted with 50 microm aluminum oxide, ultrasonic cleaned and bonded in pairs with the resin-based cements Panavia F and Rely X ARC at 10 min and 24h after the sandblasting. The tensile test was performed with a crosshead speed of 0.5mm/min in an Instron Universal testing machine. The Rely X ARC reached the highest tensile strength value at 24h after sandblasting (18.27 MPa), but there was no statistically significant difference between the two dual curing resin cements for both times tested. All specimens showed a mixture of cohesive fracture in the resin cement and adhesive failure. However, the predominant failure mode for Panavia F was cohesive in resin cement, and the Rely X ARC exhibited a greater proportion of specimens with adhesive failure between the alloy and resin luting cement at 10 min and 24h. Both cements had, statistically, the same tensile bond strength. But in the fracture mode analysis, the adhesive predominant fracture mode of Rely X ARC cement indicates a premature clinical adhesive failure. On the other hand, the cohesive predominant fracture mode of Panavia F indicates a longer clinical adhesive bond with titanium.

  2. Study on the Bond-Slip Performance of CFSSTs Based on Push-Out Tests

    Directory of Open Access Journals (Sweden)

    Lai Wang

    2018-01-01

    Full Text Available To study the interfacial bond-slip performance of concrete-filled square steel tubes (CFSSTs, taking the core concrete strength, slenderness ratio, and width-to-thickness ratio as the influencing factors; 9 specimens were designed with 3 factors and 3 levels for the orthogonal test method. In addition, different from the above 9 specimens, one specimen without rust removal was designed for the purpose of comparison. Based on the bond stress distribution and deformation coordination relationships between the specimens during the push-out tests, a theoretical formula for calculating the relative slip of a CFSST was deduced. The results show that with the increase of load, the relative slip at the loading ends was earlier than that at the free ends of the specimens; the interfacial bond failure and relative slip gradually developed from the two ends towards the centre of the specimens; the increase of the bond stress in the middle part was faster than that at the ends of the specimens. The order of these factors from main to secondary is the presence of rust in the inner wall of the square steel tube, the slenderness ratio, the core concrete strength, and the width-to-thickness ratio.

  3. An Alternative Cu-Based Bond Layer for Electric Arc Coating Process

    Science.gov (United States)

    Fadragas, Carlos R.; Morales, E. V.; Muñoz, J. A.; Bott, I. S.; Lariot Sánchez, C. A.

    2011-12-01

    A Cu-Al alloy has been used as bond coat between a carbon steel substrate and a final coating deposit obtained by applying the twin wire electric arc spraying coating technique. The presence of a copper-based material in the composite system can change the overall temperature profile during deposition because copper exhibits a thermal conductivity several times higher than that of the normally recommended bond coat materials (such as nickel-aluminum alloys or nickel-chromium alloys). The microstructures of 420 and 304 stainless steels deposited by the electric arc spray process have been investigated, focusing attention on the deposit homogeneity, porosity, lamellar structure, and microhardness. The nature of the local temperature gradient during deposition can strongly influence the formation of the final coating deposit. This study presents a preliminary study, undertaken to investigate the changes in the temperature profile which occur when a Cu-Al alloy is used as bond coat, and the possible consequences of these changes on the microstructure and adhesion of the final coating deposit. The influence of the thickness of the bond layer on the top coating temperature has also been also evaluated.

  4. Development of dental resin luting agents based on Bis-EMA4: bond strength evaluation

    Directory of Open Access Journals (Sweden)

    2008-02-01

    Full Text Available The aim of this study was to investigate the influence of incorporating Bis-EMA4 monomer into experimental Bis-GMA/TEGDMA-based resin luting agents on the bond strength to dentin. Seven mixtures were prepared with the following ratios (wt% of Bis-GMA/TEGDMA/Bis-EMA4: 50/50/0, 50/30/20, 50/10/40, 50/0/50, 30/10/60, 10/10/80 and 0/0/100. Camphorquinone (0.4 wt%, N,N-dimethyl-p-toluidine (0.8 wt% and hydroquinone (0.2 wt% were dissolved in each mixture, which was loaded with silanated strontium glass fillers to a constant content of 60 wt%. Bond strength was evaluated by microshear testing (n = 10 on bovine dentin. Data were submitted to Analysis of Variance (p<0.05. Modes of failure were classified under magnification (200×. Bond strength means (MPa, respective to each agent, were: 19.4, 19.8, 20.0, 19.1, 16.8, 18.7 and 17.8. No significant differences were detected among groups. Mixed failures were generally predominant for all materials. In conclusion, the addition of Bis-EMA4 presented no significant influence on the bond strength of the experimental resin luting agents to dentin.

  5. Communication disruption of guava moth (Coscinoptycha improbana) using a pheromone analog based on chain length.

    Science.gov (United States)

    Suckling, D M; Dymock, J J; Park, K C; Wakelin, R H; Jamieson, L E

    2013-09-01

    The guava moth, Coscinoptycha improbana, an Australian species that infests fruit crops in commercial and home orchards, was first detected in New Zealand in 1997. A four-component pheromone blend was identified but is not yet commercially available. Using single sensillum recordings from male antennae, we established that the same olfactory receptor neurons responded to two guava moth sex pheromone components, (Z)-11-octadecen-8-one and (Z)-12-nonadecen-9-one, and to a chain length analog, (Z)-13-eicosen-10-one, the sex pheromone of the related peach fruit moth, Carposina sasakii. We then field tested whether this non-specificity of the olfactory neurons might enable disruption of sexual communication by the commercially available analog, using male catch to synthetic lures in traps in single-tree, nine-tree and 2-ha plots. A disruptive pheromone analog, based on chain length, is reported for the first time. Trap catches for guava moth were disrupted by three polyethylene tubing dispensers releasing the analog in single-tree plots (86% disruption of control catches) and in a plots of nine trees (99% disruption). Where peach fruit moth pheromone dispensers were deployed at a density of 1000/ha in two 2-ha areas, pheromone traps for guava moth were completely disrupted for an extended period (up to 470 days in peri-urban gardens in Mangonui and 422 days in macadamia nut orchards in Kerikeri). In contrast, traps in untreated areas over 100 m away caught 302.8 ± 128.1 moths/trap in Mangonui and 327.5 ± 78.5 moths/ trap in Kerikeri. The longer chain length in the pheromone analog has greater longevity than the natural pheromone due to its lower volatility. Chain length analogs may warrant further investigation for mating disruption in Lepidoptera, and screening using single-sensillum recording is recommended.

  6. Horizontal Directional Drilling-Length Detection Technology While Drilling Based on Bi-Electro-Magnetic Sensing

    Directory of Open Access Journals (Sweden)

    Yudan Wang

    2017-04-01

    Full Text Available The drilling length is an important parameter in the process of horizontal directional drilling (HDD exploration and recovery, but there has been a lack of accurate, automatically obtained statistics regarding this parameter. Herein, a technique for real-time HDD length detection and a management system based on the electromagnetic detection method with a microprocessor and two magnetoresistive sensors employing the software LabVIEW are proposed. The basic principle is to detect the change in the magnetic-field strength near a current coil while the drill stem and drill-stem joint successively pass through the current coil forward or backward. The detection system consists of a hardware subsystem and a software subsystem. The hardware subsystem employs a single-chip microprocessor as the main controller. A current coil is installed in front of the clamping unit, and two magneto resistive sensors are installed on the sides of the coil symmetrically and perpendicular to the direction of movement of the drill pipe. Their responses are used to judge whether the drill-stem joint is passing through the clamping unit; then, the order of their responses is used to judge the movement direction. The software subsystem is composed of a visual software running on the host computer and a software running in the slave microprocessor. The host-computer software processes, displays, and saves the drilling-length data, whereas the slave microprocessor software operates the hardware system. A combined test demonstrated the feasibility of the entire drilling-length detection system.

  7. Effects of different cavity disinfectants on shear bond strength of a silorane-based resin composite.

    Science.gov (United States)

    Arslan, Soley; Yazici, A Ruya; Gorucu, Jale; Ertan, Atilla; Pala, Kansad; Ustun, Yakup; Antonson, Sibel A; Antonson, Donald E

    2011-07-01

    This in vitro study evaluated the effect of different cavity disinfection agents on bond strength of a silorane-based resin composite. Thirty-six caries-free human third mandibular molars sectioned in mesio-distal direction were mounted in acrylic resin with their flat dentin surfaces exposed. After the dentin surfaces were wet ground with # 600 silicon carbide paper, the teeth were randomly divided into 6 groups of 12 each according to the cavity disinfection agents; chlorhexidine (CHX); sodium hypochlorite (NaOCl), propolis, ozone, Er,Cr:YSGG laser and no treatment (control). After treatment of dentin surfaces with one of these cavity disinfection agents, Filtek Silorane adhesive system was applied. The silorane-based resin composite, Filtek Silorane was condensed into a mold and polymerized. After storage at 37°C for 24 hours, the specimens were tested in shear mode at a crosshead speed of 1.0 mm/minute. The results were analyzed by one-way ANOVA. No statistically significant difference was observed between the groups (p>0.05). The use of the tested cavity disinfection agents, chlorhexidine, sodium hypochlorite, propolis, ozone and Er,Cr:YSGG laser did not significantly affect the dentin bond strength of a silorane-based resin composite, filtek supreme. Cavity disinfectant applications did not affect the dentin bond strength of a silorane-based resin composite.

  8. An ancient relation between units of length and volume based on a sphere.

    Directory of Open Access Journals (Sweden)

    Elena Zapassky

    Full Text Available The modern metric system defines units of volume based on the cube. We propose that the ancient Egyptian system of measuring capacity employed a similar concept, but used the sphere instead. When considered in ancient Egyptian units, the volume of a sphere, whose circumference is one royal cubit, equals half a hekat. Using the measurements of large sets of ancient containers as a database, the article demonstrates that this formula was characteristic of Egyptian and Egyptian-related pottery vessels but not of the ceramics of Mesopotamia, which had a different system of measuring length and volume units.

  9. Numerical modelling of two HMX-based plastic-bonded explosives at the mesoscale

    OpenAIRE

    Handley, Caroline A.

    2011-01-01

    Mesoscale models are needed to predict the effect of changes to the microstructure of plastic-bonded explosives on their shock initiation and detonation behaviour. This thesis describes the considerable progress that has been made towards a mesoscale model for two HMX-based explosives PBX9501 and EDC37. In common with previous work in the literature, the model is implemented in hydrocodes that have been designed for shock physics and detonation modelling. Two relevant physics effects, heat co...

  10. Shock induced shear strength in an HMX based plastic bonded explosive

    Science.gov (United States)

    Millett, J. C. F.; Taylor, P.; Appleby-Thomas, G.

    2017-01-01

    The shock induced mechanical response of an HMX based plastic bonded explosive (PBX) has been investigated in terms of the shear strength. Results show that shear strength increases with impact stress. However comparison with the calculated elastic response of both the PBX and pure HMX suggests that the overall mechanical response is controlled by the HMX crystals, with the near liquid like nature of the binder phase having a minimal contribution.

  11. Piezoelectric and bonding properties of a cement-based composite for dental application

    Science.gov (United States)

    Wang, Qi; Liu, Jinsong; Zhu, Jianguo; Ye, Yongmei; Li, Xiang; Chen, Zhiqing

    2008-11-01

    A cement-based piezoelectric composite was introduced as real-time health monitoring systems to dentin. Lithium sodium potassium niobate and zinc polycarboxylate cement were mixed and made piezoelectric under different poling conditions. X-ray diffraction and scanning electron microscope confirmed the component and microstructure of the cement. The bonding force of the composites was compared to that of pure cement by analysis of variance. The optimum poling method was determined and the influencing factors of piezoelectric coefficient were discussed.

  12. Piezoelectric and bonding properties of a cement-based composite for dental application

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qi [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, West China College of Stomatology, Sichuan University, Chengdu (China); Liu Jinsong [School and Hospital of Stomatology, Wenzhou Medical College, Wenzhou (China); Zhu Jianguo [College of Materials Science and Engineering, Sichuan University, Chengdu (China); Ye Yongmei [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, West China College of Stomatology, Sichuan University, Chengdu (China); Li Xiang [College of Materials Science and Engineering, Sichuan University, Chengdu (China); Chen Zhiqing [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, West China College of Stomatology, Sichuan University, Chengdu (China)], E-mail: liuy365@163.com

    2008-11-15

    A cement-based piezoelectric composite was introduced as real-time health monitoring systems to dentin. Lithium sodium potassium niobate and zinc polycarboxylate cement were mixed and made piezoelectric under different poling conditions. X-ray diffraction and scanning electron microscope confirmed the component and microstructure of the cement. The bonding force of the composites was compared to that of pure cement by analysis of variance. The optimum poling method was determined and the influencing factors of piezoelectric coefficient were discussed.

  13. Piezoelectric and bonding properties of a cement-based composite for dental application

    International Nuclear Information System (INIS)

    Wang Qi; Liu Jinsong; Zhu Jianguo; Ye Yongmei; Li Xiang; Chen Zhiqing

    2008-01-01

    A cement-based piezoelectric composite was introduced as real-time health monitoring systems to dentin. Lithium sodium potassium niobate and zinc polycarboxylate cement were mixed and made piezoelectric under different poling conditions. X-ray diffraction and scanning electron microscope confirmed the component and microstructure of the cement. The bonding force of the composites was compared to that of pure cement by analysis of variance. The optimum poling method was determined and the influencing factors of piezoelectric coefficient were discussed

  14. Biomaterial based novel polyurethane adhesives for wood to wood and metal to metal bonding

    OpenAIRE

    Patel,Mitesh Ramanlal; Shukla,Jignesh Markandray; Patel,Natvarbhai Khodidas; Patel,Ketan Haribhai

    2009-01-01

    Polyurethane adhesives made from synthetic chemicals are non-biodegradable, costly and difficult to find raw materials from local market. To avoid solid pollution problem, cost effectiveness and easy availability of raw materials, biomaterials based polyurethane adhesives are used in current industrial interest. Direct use of castor oil in polyurethane adhesive gives limited hardness. Modification on active sites of castor oil to utilize double bond of unsaturated fatty acid and carboxyl grou...

  15. Comparison between Conventional Blind Embryo Transfer and Embryo Transfer Based on Previously Measured Uterine Length

    Directory of Open Access Journals (Sweden)

    Nasrin Saharkhiz

    2014-11-01

    Full Text Available Background: Embryo transfer (ET is one of the most important steps in assisted reproductive technology (ART cycles and affected by many factors namely the depth of embryo deposition in uterus. In this study, the outcomes of intracytoplasmic sperm injection (ICSI cycles after blind embryo transfer and embryo transfer based on previously measured uterine length using vaginal ultrasound were compared. Materials and Methods: This prospective randomised clinical trial included one hundred and forty non-donor fresh embryo transfers during January 2010 to June 2011. In group I, ET was performed using conventional (blind method at 5-6cm from the external os, and in group II, ET was done at a depth of 1-1.5 cm from the uterine fundus based on previously measured uterine length using vaginal sonography. Appropriate statistical analysis was performed using Student’s t test and Chi-square or Fisher’s exact test. The software that we used was PASW statistics version 18. A p value <0.05 was considered statistically significant. Results: Chemical pregnancy rate was 28.7% in group I and 42.1% in group II, while the difference was not statistically significant (p=0.105. Clinical pregnancy, ongoing pregnancy and implantation rates for group I were 21.2%, 17.7%, and 12.8%, while for group II were 33.9%, 33.9%, and 22.1, respectively. In group I and group II, abortion rates were 34.7% and 0%, respectively, indicating a statistically significant difference (p<0.005. No ectopic pregnancy occurred in two groups. Conclusion: The use of uterine length measurement during treatment cycle in order to place embryos at depth of 1-1.5cm from fundus significantly increases clinical and ongoing pregnancy and implantation rates, while leads to a decrease in abortion rate (Registration Number: IRCT2014032512494N1.

  16. Chemically-bonded brick production based on burned clay by means of semidry pressing

    Science.gov (United States)

    Voroshilov, Ivan; Endzhievskaya, Irina; Vasilovskaya, Nina

    2016-01-01

    We presented a study on the possibility of using the burnt rocks of the Krasnoyarsk Territory for production of chemically-bonded materials in the form of bricks which are so widely used in multistory housing and private house construction. The radiographic analysis of the composition of burnt rock was conducted and a modifier to adjust the composition uniformity was identified. The mixing moisture content was identified and optimal amount at 13-15% was determined. The method of semidry pressing has been chosen. The process of obtaining moldings has been theoretically proved; the advantages of chemically-bonded wall materials compared to ceramic brick were shown. The production of efficient artificial stone based on material burnt rocks, which is comparable with conventionally effective ceramic materials or effective with cell tile was proved, the density of the burned clay-based cell tile makes up to 1630-1785 kg m3, with compressive strength of 13.6-20.0 MPa depending on the compression ratio and cement consumption, frost resistance index is F50, and the thermal conductivity in the masonry is λ = 0,459-0,546 W m * °C. The clear geometric dimensions of pressed products allow the use of the chemically-bonded brick based on burnt clay as a facing brick.

  17. 'Length'at Length

    Indian Academy of Sciences (India)

    Admin

    He was interested to know how `large' is the set of numbers x for which the series is convergent. Here large refers to its length. But his set is not in the class ♢. Here is another problem discussed by Borel. Consider .... have an infinite collection of pairs of new shoes and want to choose one shoe from each pair. We have an ...

  18. Comparison of shear bond strength of four types of orthodontic brackets with different base technologies

    Directory of Open Access Journals (Sweden)

    Gaurang H Chaudhary

    2017-01-01

    Full Text Available Objectives: The aim of this study was to compare the shear bond strength (SBS of brackets systems with four different base technologies. Materials and Methods: Maxillary first premolars were randomly divided into four groups of thirty specimens each: (1 Master Series™ conventional twin, (2 T3™ self-ligating, (3 Victory series™ conventional twin, and (4 H4™ self-ligating brackets. Maxillary first premolars were bracketed using an acid-etch composite system, and the SBS measured using an Instron Universal Testing Machine at a crosshead speed of 2 mm/min. The ANOVA and Tukey's multiple comparison tests were performed with significance predetermined at P ≤ 0.05. Results: The overall mean bond strengths were 8.49 ± 2.93, 10.85 ± 3.34, 9.42 ± 2.97, and 9.73 ± 2.62 for the Groups 1, 2, 3, and 4 brackets, respectively. One-way ANOVA test gave an F = 3.182 with a P = 0.026. The Group 1 and Group 2 were observed to have statistically significant difference with a P = 0.014. Conclusions: The T3 self-ligating one-piece design with microetched Quadra Grip™ base brackets had the highest bond strength. The SBS difference between Group 2, Group 3, and Group 4 was not significant, but the difference between Group 2 and Group 1 was statistically significant.

  19. Infant bone age estimation based on fibular shaft length: model development and clinical validation

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Andy; Stamoulis, Catherine; Bixby, Sarah D.; Breen, Micheal A.; Connolly, Susan A.; Kleinman, Paul K. [Boston Children' s Hospital, Harvard Medical School, Department of Radiology, Boston, MA (United States)

    2016-03-15

    Bone age in infants (<1 year old) is generally estimated using hand/wrist or knee radiographs, or by counting ossification centers. The accuracy and reproducibility of these techniques are largely unknown. To develop and validate an infant bone age estimation technique using fibular shaft length and compare it to conventional methods. We retrospectively reviewed negative skeletal surveys of 247 term-born low-risk-of-abuse infants (no persistent child protection team concerns) from July 2005 to February 2013, and randomized them into two datasets: (1) model development (n = 123) and (2) model testing (n = 124). Three pediatric radiologists measured all fibular shaft lengths. An ordinary linear regression model was fitted to dataset 1, and the model was evaluated using dataset 2. Readers also estimated infant bone ages in dataset 2 using (1) the hemiskeleton method of Sontag, (2) the hemiskeleton method of Elgenmark, (3) the hand/wrist atlas of Greulich and Pyle, and (4) the knee atlas of Pyle and Hoerr. For validation, we selected lower-extremity radiographs of 114 normal infants with no suspicion of abuse. Readers measured the fibulas and also estimated bone ages using the knee atlas. Bone age estimates from the proposed method were compared to the other methods. The proposed method outperformed all other methods in accuracy and reproducibility. Its accuracy was similar for the testing and validating datasets, with root-mean-square error of 36 days and 37 days; mean absolute error of 28 days and 31 days; and error variability of 22 days and 20 days, respectively. This study provides strong support for an infant bone age estimation technique based on fibular shaft length as a more accurate alternative to conventional methods. (orig.)

  20. Effect of priming agents on shear bond strengths of resin-based luting agents to a translucent zirconia material.

    Science.gov (United States)

    Yagawa, Shogo; Komine, Futoshi; Fushiki, Ryosuke; Kubochi, Kei; Kimura, Fumiaki; Matsumura, Hideo

    2017-09-19

    The purpose of the present study was to evaluate the effect of priming agents and artificial aging with thermocycling on shear bond strengths of two resin-based luting agents to a translucent zirconia material. A total of 308 pairs of translucent zirconia disk specimens were divided into seven treatment groups: Alloy Primer (ALP), Clearfil Ceramic Primer Plus (CCP), Meta Fast Bonding Liner (MFB), MR. bond (MRB), Super-Bond PZ Primer Liquid B (PZB), V-Primer (VPR), and an unprimed group (UP). The specimens in each group were bonded with Panavia V5 Universal (UNI) and Opaque shade (OPA). Shear bond strengths (n=11 each) were tested before and after 5000 thermocycles. The data were analyzed with the Kruskal-Wallis test and the Steel-Dwass test. For both 0 and 5000 thermocycles, the ALP (47.8 and 41.5MPa, respectively) and CCP (45.8 and 42.3MPa, respectively) groups showed significantly higher bond strengths than other groups in the UNI luting agent. For the OPA luting agent, CCP group (45.8MPa) exhibited the highest pre-thermocycling bond strength in all groups. The ALP (32.4MPa) and CCP (36.5MPa) groups had significantly higher post-thermocycling shear bond strengths than other groups. In several groups, the shear bond strengths of the UNI luting agent were significantly higher than those of the OPA luting agent before and after thermocycling. Application of priming agents containing hydrophobic phosphate monomer (MDP) yielded the durable bond strengths of resin-based luting agents to a translucent zirconia material. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  1. A Comparison of Shear Bond Strength of Ceramic and Resin Denture Teeth on Different Acrylic Resin Bases

    OpenAIRE

    Corsalini, Massimo; Venere, Daniela Di; Pettini, Francesco; Stefanachi, Gianluca; Catapano, Santo; Boccaccio, Antonio; Lamberti, Luciano; Pappalettere, Carmine; Carossa, Stefano

    2014-01-01

    The purpose of this study is to compare the shear bond strength of different resin bases and artificial teeth made of ceramic or acrylic resin materials and whether tooth-base interface may be treated with aluminium oxide sandblasting. Experimental measurements were carried on 80 specimens consisting of a cylinder of acrylic resin into which a single tooth is inserted. An ad hoc metallic frame was realized to measure the shear bond strength at the tooth-base interface. A complete factorial pl...

  2. DriverFinder: A Gene Length-Based Network Method to Identify Cancer Driver Genes

    Directory of Open Access Journals (Sweden)

    Pi-Jing Wei

    2017-01-01

    Full Text Available Integration of multi-omics data of cancer can help people to explore cancers comprehensively. However, with a large volume of different omics and functional data being generated, there is a major challenge to distinguish functional driver genes from a sea of inconsequential passenger genes that accrue stochastically but do not contribute to cancer development. In this paper, we present a gene length-based network method, named DriverFinder, to identify driver genes by integrating somatic mutations, copy number variations, gene-gene interaction network, tumor expression, and normal expression data. To illustrate the performance of DriverFinder, it is applied to four cancer types from The Cancer Genome Atlas including breast cancer, head and neck squamous cell carcinoma, thyroid carcinoma, and kidney renal clear cell carcinoma. Compared with some conventional methods, the results demonstrate that the proposed method is effective. Moreover, it can decrease the influence of gene length in identifying driver genes and identify some rare mutated driver genes.

  3. PCL-based Shape Memory Polymers with Variable PDMS Soft Segment Lengths

    Science.gov (United States)

    Zhang, Dawei; Giese, Melissa L.; Prukop, Stacy L.; Grunlan, Melissa A.

    2012-01-01

    Thermoresponsive shape memory polymers (SMPs) are stimuli-responsive materials that return to their permanent shape from a temporary shape in response to heating. The design of new SMPs which obtain a broader range of properties including mechanical behavior is critical to realize their potential in biomedical as well as industrial and aerospace applications. To tailor the properties of SMPs, “AB networks” comprised of two distinct polymer components have been investigated but are overwhelmingly limited to those in which both components are organic. In this present work, we prepared inorganic-organic SMPs comprised of inorganic polydimethyl-siloxane (PDMS) segments of varying lengths and organic poly(ε-caprolactone) (PCL) segments. PDMS has a particularly low Tg (−125 °C) which makes it a particularly effective soft segment to tailor the mechanical properties of PCL-based SMPs. The SMPs were prepared via the rapid photocure of solutions of diacrylated PCL40-block-PDMSm-block-PCL40 macromers (m = 20, 37, 66 and 130). The resulting inorganic-organic SMP networks exhibited excellent shape fixity and recovery. By changing the PDMS segment length, the thermal, mechanical, and surface properties were systematically altered. PMID:22904597

  4. Exploitation Status of Devis’Anchovy in Kei Island Waters: Based on Total Length Data

    Science.gov (United States)

    Supeni, E. A.; Dobo, J.

    2017-10-01

    Devis’ anchovy (Encrasicholina devisi) are a group of small pelagic fishes, which is thought to be one of the most abundant fishery resources in Indonesian waters. The high utilized of this resources will certainly affect to population status. This research aimed to know the exploitation status of anchovy in Kei Island waters. Sampling was carried out by using the data collected from lift net catches during April to July 2016 at Sathean, Selayar and Lebetawi, Kei Islands. A total of 3,524 anchovies were analyzed based on total length that ranged from 23 to 87 mm with a mean length of 55.4 ± 11.8 mm. The von Bertalanffy growth parameters estimated were L∞ = 89.25 mm and K = 0.74 year-1, with the growth models equation is Lt = 89.25 (1 ‑ e ‑0.74(t+0.161). The result of mortality analysis showed that Z = 2.97, M = 1.098, F= 1.87 year-1 and E = 0.63. This study reveals that exploitation status of anchovy in Kei Island is on fully exploited and leads to the over exploited condition.

  5. Wire bonding in microelectronics

    CERN Document Server

    Harman, George G

    2010-01-01

    Wire Bonding in Microelectronics, Third Edition, has been thoroughly revised to help you meet the challenges of today's small-scale and fine-pitch microelectronics. This authoritative guide covers every aspect of designing, manufacturing, and evaluating wire bonds engineered with cutting-edge techniques. In addition to gaining a full grasp of bonding technology, you'll learn how to create reliable bonds at exceedingly high yields, test wire bonds, solve common bonding problems, implement molecular cleaning methods, and much more. Coverage includes: Ultrasonic bonding systems and technologies, including high-frequency systems Bonding wire metallurgy and characteristics, including copper wire Wire bond testing Gold-aluminum intermetallic compounds and other interface reactions Gold and nickel-based bond pad plating materials and problems Cleaning to improve bondability and reliability Mechanical problems in wire bonding High-yield, fine-pitch, specialized-looping, soft-substrate, and extreme-temperature wire bo...

  6. Marginal microleakage of class V resin-based composite restorations bonded with six one-step self-etch systems

    Directory of Open Access Journals (Sweden)

    Alfonso Sánchez-Ayala

    2013-06-01

    Full Text Available This study compared the microleakage of class V restorations bonded with various one-step self-etching adhesives. Seventy class V resin-based composite restorations were prepared on the buccal and lingual surfaces of 35 premolars, by using: Clearfil S 3 Bond, G-Bond, iBond, One Coat 7.0, OptiBond All-In-One, or Xeno IV. The Adper Single Bond etch-and-rinse two-step adhesive was employed as a control. Specimens were thermocycled for 500 cycles in separate water baths at 5°C and 55°C and loaded under 40 to 70 N for 50,000 cycles. Marginal microleakage was measured based on the penetration of a tracer agent. Although the control showed no microleakage at the enamel margins, there were no differences between groups (p = 0.06. None of the adhesives avoided microleakage at the dentin margins, and they displayed similar performances (p = 0.76. When both margins were compared, iBond® presented higher microleakage (p < 0.05 at the enamel margins (median, 1.00; Q3–Q1, 1.25–0.00 compared to the dentin margins (median, 0.00; Q3–Q1, 0.25–0.00. The study adhesives showed similar abilities to seal the margins of class V restorations, except for iBond®, which presented lower performance at the enamel margin.

  7. Hydrogels Based on Dynamic Covalent and Non Covalent Bonds: A Chemistry Perspective

    Directory of Open Access Journals (Sweden)

    Francesco Picchioni

    2018-03-01

    Full Text Available Hydrogels based on reversible covalent bonds represent an attractive topic for research at both academic and industrial level. While the concept of reversible covalent bonds dates back a few decades, novel developments continue to appear in the general research area of gels and especially hydrogels. The reversible character of the bonds, when translated at the general level of the polymeric network, allows reversible interaction with substrates as well as responsiveness to variety of external stimuli (e.g., self-healing. These represent crucial characteristics in applications such as drug delivery and, more generally, in the biomedical world. Furthermore, the several possible choices that can be made in terms of reversible interactions generate an almost endless number of possibilities in terms of final product structure and properties. In the present work, we aim at reviewing the latest developments in this field (i.e., the last five years by focusing on the chemistry of the systems at hand. As such, this should allow molecular designers to develop a toolbox for the synthesis of new systems with tailored properties for a given application.

  8. PEG spacers of different length influence the biological profile of bombesin-based radiolabeled antagonists

    International Nuclear Information System (INIS)

    Jamous, Mazen; Tamma, Maria L.; Gourni, Eleni; Waser, Beatrice; Reubi, Jean C.; Maecke, Helmut R.; Mansi, Rosalba

    2014-01-01

    Introduction: The gastrin-releasing peptide receptor (GRPR) was shown to be expressed with high density on several types of cancers. Radiolabeled peptides for imaging and targeted radionuclide therapy have been developed. In this study, we evaluated the potential of statine-based bombesin antagonists, conjugated to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) through oligoethyleneglycol spacers, labeled with 177 Lu and we determined the effect of polyethyleneglycol (PEG) spacer length on in vitro and in vivo properties. Methods: The bombesin antagonists were synthesized on solid phase using Fmoc chemistry; the spacers Fmoc-dPEG x -OH (x = 2, 4, 6 and 12) and the DOTA(tBu) 3 were coupled using a standard procedure. The peptides were labeled with 177 Lu and evaluated in vitro (lipophilicity, serum stability, internalization and binding affinity assays). Biodistribution studies were performed in PC-3 tumor-bearing nude mice. Results: The solid-phase synthesis was straightforward with an overall yield ranging from 30% to 35% based on the first Fmoc cleavage. The hydrophilicity increased with spacer length (logD: − 1.95 vs − 2.22 of PEG 2 and PEG 12 analogs, respectively). There is a tendency of increased serum stability by increasing the spacer length (T 1/2 = 246 ± 4 and 584 ± 20 for PEG 2 and PEG 6 analogs, respectively) which seems to reverse with the PEG 12 analog. The IC 50 values are similar with the only significant difference of the PEG 12 analog. The 177 Lu-labeled PEG 4 and PEG 6 conjugates showed similar pharmacokinetic with high tumor uptake and excellent tumor-to-kidney ratios (7.8 and 9.7 at 4 h for the PEG 4 and PEG 6 derivatives, respectively). The pancreas uptake was relatively high at 1 h but it shows fast washout (0.46% ± 0.02% IA/g and 0.29% ± 0.08% IA/g already at 4 h). Conclusion: Among all the studied analogs the PEG 4 and PEG 6 showed significantly better properties. The very high tumor-to-non-target organ ratios, in

  9. Home-based detoxification for neonatal abstinence syndrome reduces length of hospital admission without prolonging treatment.

    Science.gov (United States)

    Smirk, Cameron L; Bowman, Ellen; Doyle, Lex W; Kamlin, Omar

    2014-06-01

    Neonatal abstinence syndrome (NAS) is a drug withdrawal syndrome, secondary to in utero chemical exposure and characterised by tremor, irritability and feed intolerance. It often requires prolonged hospital treatment and separation of families. Outpatient therapy may reduce this burden, but current literature is sparse. This review aimed to evaluate the safety and efficacy of our home-based detoxification programme and compare it with standard inpatient care. Infants requiring treatment for NAS between January 2004 and December 2010 were reviewed. Data on demographics, drug exposure, length of stay and type of therapy were compared between infants selected for home-based therapy and those treated conventionally. Of the 118 infants who were admitted for treatment of NAS, 38 (32%) were managed at home. Infants receiving home-based detoxification had shorter hospital stays (mean 19 days vs. 39 days), with no increase in total duration of treatment (mean 36 days vs. 41 days), and were more likely to be breastfeeding on discharge from hospital care (45% vs. 22%). In selected infants, home-based detoxification is associated with reduced hospital stays and increased rates of breastfeeding, without prolonging therapy. Safety of the infants remains paramount, which precludes many from entering such a programme. ©2014 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

  10. Inhibition of thermolysin by phosphonamidate transition-state analogues: measurement of 31P-15N bond lengths and chemical shifts in two enzyme-inhibitor complexes by solid-state nuclear magnetic resonance.

    Science.gov (United States)

    Copié, V; Kolbert, A C; Drewry, D H; Bartlett, P A; Oas, T G; Griffin, R G

    1990-10-02

    31P and 15N chemical shifts and 31P-15N bond lengths have been measured with solid-state NMR techniques in two inhibitors of thermolysin, carbobenzoxy-Glyp-L-Leu-L-Ala (ZGpLA) and carbobenzoxy-L-Phep-L-Leu-L-Ala (ZFpLA), both as free lithium salts and when bound to the enzyme. Binding of both inhibitors to thermolysin results in large changes in the 31P chemical shifts. These changes are more dramatic for the tighter binding inhibitor ZFpLA, where a approximately 20 ppm downfield movement of the 31P isotropic chemical shift (sigma iso) is observed. This shift is due to changes in the shift tensor elements sigma 11 and sigma 22, while sigma 33 remains essentially constant. We observed a similar pattern for ZGpLA, but only a approximately 5 ppm change occurs in sigma iso. The changes in the 15N chemical shifts for both inhibitors are small upon binding, amounting to downfield shifts of 2 and 4 ppm for ZGpLA and ZFpLA, respectively. This indicates that there are no changes in the protonation state of the 15N in either the ZFpLA- or the ZGpLA-thermolysin complex. NMR distance measurements yield a P-N bond length rP-N = 1.68 +/- 0.03 A for the tight binding inhibitor ZFpLA both in its free lithium salt form and in its thermolysin-ZFpLA complex, a distance that is much shorter than the 1.90-A distance reported by X-ray crystallography studies [Holden et al. (1987) Biochemistry 26, 8542-8553].(ABSTRACT TRUNCATED AT 250 WORDS)

  11. The origin of unequal bond lengths in the C̃ (1)B2 state of SO2: Signatures of high-lying potential energy surface crossings in the low-lying vibrational structure.

    Science.gov (United States)

    Park, G Barratt; Jiang, Jun; Field, Robert W

    2016-04-14

    The C̃ (1)B2 state of SO2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. The asymmetry in the potential energy surface is expressed as a staggering in the energy levels of the ν3(') progression. We have recently made the first observation of low-lying levels with odd quanta of v3('), which allows us-in the current work-to characterize the origins of the level staggering. Our work demonstrates the usefulness of low-lying vibrational level structure, where the character of the wavefunctions can be relatively easily understood, to extract information about dynamically important potential energy surface crossings that occur at much higher energy. The measured staggering pattern is consistent with a vibronic coupling model for the double-minimum, which involves direct coupling to the bound 2 (1)A1 state and indirect coupling with the repulsive 3 (1)A1 state. The degree of staggering in the ν3(') levels increases with quanta of bending excitation, which is consistent with the approach along the C̃ state potential energy surface to a conical intersection with the 2 (1)A1 surface at a bond angle of ∼145°.

  12. Umbilical cord length in singleton gestations: a Finnish population-based retrospective register study.

    Science.gov (United States)

    Georgiadis, L; Keski-Nisula, L; Harju, M; Räisänen, S; Georgiadis, S; Hannila, M-L; Heinonen, S

    2014-04-01

    Many complications of pregnancy and delivery are associated with umbilical cord length. It is important to examine the variation in length, in order to identify normal and abnormal conditions. Moreover, the factors influencing cord growth and development are not precisely known. The main objectives were to provide updated reference charts for umbilical cord length in singleton pregnancies and to evaluate potential factors affecting cord length. Birth register data of 47,284 singleton pregnant women delivering in Kuopio University Hospital, Finland was collected prospectively. Gender-specific centile charts for cord length from 22 to 44 gestational weeks were obtained using generalized additive models for location, scale, and shape (GAMLSS). Gestational, fetal, and maternal factors were studied for their potential influence on cord length with single variable analysis and stepwise multiple linear regression analysis. Cord length increased according to gestational age, while the growth decelerated post-term. Birth weight, placental weight, pregravid maternal body mass index, parity, and maternal age correlated to cord length. Gestational diabetes and previous miscarriages were associated with longer cords, while female gender and placental abruption were associated with shorter cords. Girls had shorter cords throughout gestation although there was substantial variation in length in both genders. Cord length associated significantly with birth weight, placental weight, and gestational age. Significantly shorter cords were found in women with placental abruption. This important finding requires further investigation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. The influence of size and structure of metal orthodontic bracket base on bond strength on tooth enamel

    Directory of Open Access Journals (Sweden)

    Mitić Vladimir

    2009-01-01

    Full Text Available Introduction. The factors which may influence the bond strength of the applied orthodontic brackets on the tooth surface are the size and structure of the bracket base. Objective. The aim of the paper was to investigate the influence of size and shape of different types of brackets on bond strength on the enamel and analyze the remaining quality of adhesive material on the tooth surface after debonding of orthodontic brackets (adhesive remnant index - ARI. Methods. In this study, three types of metal brackets of different sizes and shapes of Dentaurum manufacturer were used (Utratrimm, Equilibrium 2, Discovery, Dentaurum, Inspringen, Germany. The brackets were applied onto the middle part of the anatomic crowns of buccal surfaces of 30 premolars extracted for orthodontic reasons. In addition, the pre-treatment of teeth by 37% orthophosphoric acid and adhesive material System1+ (Dentaurum, Germany were used. Results. The mean value of the bonded brackets bond strength of Discovery type after debonding was 8.67±0.32 MPa, while the value of the bonded brackets bond strength of Equilibrium 2 type amounted to 8.62±0.22 MPa. The value of the bonded brackets bond strength of Ultratrimm type after debonding was 8.22±0.49 MPa. There were no statistical differences in the values of bond strength regarding all three groups of the investigated orthodontic brackets (F=4.56; p<0.05. Conclusion. The base size and design of metal orthodontic brackets did not play a significant role in bond strength, while the values of ARI index were identical in all three investigated groups.

  14. Biomaterial based novel polyurethane adhesives for wood to wood and metal to metal bonding

    Directory of Open Access Journals (Sweden)

    Mitesh Ramanlal Patel

    2009-01-01

    Full Text Available Polyurethane adhesives made from synthetic chemicals are non-biodegradable, costly and difficult to find raw materials from local market. To avoid solid pollution problem, cost effectiveness and easy availability of raw materials, biomaterials based polyurethane adhesives are used in current industrial interest. Direct use of castor oil in polyurethane adhesive gives limited hardness. Modification on active sites of castor oil to utilize double bond of unsaturated fatty acid and carboxyl group yields new modified or activated polyols, which can be utilized for polyurethane adhesive formulation. In view of this, we have synthesized polyurethane adhesives from polyester polyols, castor oil based polyols and epoxy based polyols with Isocyanate adducts based on castor oil and trimethylolpropane. To study the effects of polyurethane adhesive strength (i.e. lap shear strength on wood-to-wood and metal-to-metal bonding through various types of polyols, cross-linking density, isocyanate adducts and also to compare adhesive strength between wood to wood and metal to metal surface. These polyols and polyurethanes were characterized through GPC, NMR and IR-spectroscopy, gel and surface drying time. Thermal stability of PU adhesives was determined under the effect of cross-linking density (NCO/OH ratio. The NCO/OH ratio (1.5 was optimized for adhesives as the higher NCO/OH ratio (2.0 increasing cross-linking density and decreases adhesion. Lower NCO/OH ratio (1.0 provideslow cross-linking density and low strength of adhesives.

  15. Age determination by back length for African savanna elephants: extending age assessment techniques for aerial-based surveys.

    Science.gov (United States)

    Trimble, Morgan J; van Aarde, Rudi J; Ferreira, Sam M; Nørgaard, Camilla F; Fourie, Johan; Lee, Phyllis C; Moss, Cynthia J

    2011-01-01

    Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables.

  16. Age Determination by Back Length for African Savanna Elephants: Extending Age Assessment Techniques for Aerial-Based Surveys

    Science.gov (United States)

    Trimble, Morgan J.; van Aarde, Rudi J.; Ferreira, Sam M.; Nørgaard, Camilla F.; Fourie, Johan; Lee, Phyllis C.; Moss, Cynthia J.

    2011-01-01

    Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables. PMID:22028925

  17. Age determination by back length for African savanna elephants: extending age assessment techniques for aerial-based surveys.

    Directory of Open Access Journals (Sweden)

    Morgan J Trimble

    Full Text Available Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables.

  18. Effect of surface treatment methods on the shear bond strength of auto-polymerized resin to thermoplastic denture base polymer

    Science.gov (United States)

    Koodaryan, Roodabeh

    2016-01-01

    PURPOSE Polyamide polymers do not provide sufficient bond strength to auto-polymerized resins for repairing fractured denture or replacing dislodged denture teeth. Limited treatment methods have been developed to improve the bond strength between auto-polymerized reline resins and polyamide denture base materials. The objective of the present study was to evaluate the effect of surface modification by acetic acid on surface characteristics and bond strength of reline resin to polyamide denture base. MATERIALS AND METHODS 84 polyamide specimens were divided into three surface treatment groups (n=28): control (N), silica-coated (S), and acid-treated (A). Two different auto-polymerized reline resins GC and Triplex resins were bonded to the samples (subgroups T and G, respectively, n=14). The specimens were subjected to shear bond strength test after they were stored in distilled water for 1 week and thermo-cycled for 5000 cycles. Data were analyzed with independent t-test, two-way analysis of variance (ANOVA), and Tukey's post hoc multiple comparison test (α=.05). RESULTS The bond strength values of A and S were significantly higher than those of N (Pdenture base materials with acetic acid may be an efficient and cost-effective method for increasing the shear bond strength to auto-polymerized reline resin. PMID:28018569

  19. Dentin bonding performance and ability of four MMA-based adhesive resins to prevent demineralization along the hybrid layer.

    Science.gov (United States)

    Nurrohman, Hamid; Nikaido, Toru; Takagaki, Tomohiro; Sadr, Alireza; Waidyasekera, Kanchana; Kitayama, Shuzo; Ikeda, Masaomi; Tagami, Junji

    2012-08-01

    To evaluate the tensile bond durability and ability of four MMA-based adhesive resins to prevent demineralization along the hybrid layer when exposed to a demineralizing solution. A PMMA rod was bonded to human dentin using one of four MMA-based adhesive systems: Super-Bond C&B (SB), SBP-40TX (SBP, experimental), M-Bond (MB), and M-Bond II (MB II). Bonded specimens were sectioned into 0.9 mm x 0.9 mm beams and subjected to microtensile bond strength (µTBS) testing after water storage at 37°C for 24 h or 10,000 thermal cycles. Data were analyzed with two-way ANOVA and Bonferroni's t-test. Fracture mode analysis of the bonding interface was performed using a scanning electron microscope (SEM) and statistically analysed using the chi-square test. To disclose the demineralization inhibition potential through formation of an acid-base resistant zone (ABRZ), the bonded interface was exposed to a demineralizing solution (pH 4.5) for 90 min, and then 5% NaOCl for 20 min. After argon-ion etching, the interfacial ultrastructure was observed using an SEM. µTBS values without thermocycling were not significantly different (p > 0.05) among 4 adhesive resins. After thermocycling, a significant decrease in µTBS was found in MB and MB II (p 0.05). Failure modes were significantly different (p MMA-based adhesive resins. The ABRZ formation was only observed in the self-etching systems.

  20. Microtensile bond strength of different acrylic teeth to high-impact denture base resins.

    Science.gov (United States)

    Colebeck, Amanda C; Monaco, Edward A; Pusateri, Christopher R; Davis, Elaine L

    2015-01-01

    This study evaluated the effect of denture base acrylic, denture tooth composition, and ridge-lap surface treatment on the microtensile bond strength (μTBS) of three commercially available denture teeth and two injection denture processing systems. Sixteen experimental groups were formed (n = 3), according to denture tooth surface treatment (no treatment or surface treatment recommended by the manufacturer), denture base processing technique and acrylic (SR-Ivocap-Ivocap Plus or Success-Lucitone 199), and tooth type-composition at bonding interface (BlueLine DCL-PMMA, Portrait IPN-PMMA, Phonares II-PMMA, Phonares II-NHC). Rectangular bar specimens with a 1 mm(2) cross sectional area were fabricated and subsequently thermocycled at 10,000 cycles between 5°C and 55°C with a 15-second dwell time. Select specimens underwent μTBS testing in a universal testing machine with a 1 kN load cell at 0.5 mm/min crosshead speed. Data were analyzed statistically by two and three-way ANOVA and Tukey post hoc test (α = 0.05). Mean μTBS ranged between 56.2 ± 5.6 and 60.8 ± 5.0 N/mm(2) for the Ivocap Plus specimens and 13.3 ± 5.12 to 60.1 ± 6.0 N/mm(2) for the Lucitone 199 specimens. Among the Ivocap specimens, BlueLine DCL and Phonares II NHC had significantly higher μTBS than Portrait IPN to Ivocap Plus acrylic. There were no statistically significant differences among Blueline, Phonares II PMMA, and Phonares II NHC, or between Phonares II PMMA and Portrait IPN. Within the Luctione 199 specimens, there was a significantly higher μTBS for BlueLine DCL and Phonares II NHC denture teeth with the manufacturer-recommended surface treatment when compared to control surface. BlueLine, Portrait, and Phonares II PMMA groups achieved significantly higher mean μTBS than the Phonares II NHC group. There were no statistically significant differences among BlueLine, Portrait, and Phonares II PMMA groups. When evaluating the μTBS of PMMA and NHC denture teeth to base resins, a

  1. Intramolecular hydrogen bond in molecular and proton-transfer forms of Schiff bases

    Energy Technology Data Exchange (ETDEWEB)

    Filarowski, A.; Koll, A.; Karpfen, A.; Wolschann, P

    2004-02-16

    The force field and structural parameters modifications upon the formation of intramolecular hydrogen bond and proton transfer reaction in N-methyl-2-hydroxybenzylidene amine (HBZA) are determined on the basis of ab initio and DFT calculations. Reliability of the calculations is verified by comparing of the theoretical vibrational spectra with those experimentally determined in the gas phase. A model of resonance interactions is applied and the quantitative contribution of ortho-quinoid structure in the particular conformers is estimated. A comparison is also made to the systems without {pi}-electron coupling (Mannich bases)

  2. Prediction model for the diffusion length in silicon-based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Cheknane, A [Laboratoire d' Etude et Developpement des Materiaux Semiconducteurs et Dielectrques, Universite Amar Telidji de Laghouat, BP 37G, Laghouat 03000 (Algeria); Benouaz, T, E-mail: cheknanali@yahoo.co [Laboratoire de Modelisation, Universite Abou BakarBelkaid de Tlemcen Algerie (Algeria)

    2009-07-15

    A novel approach to compute diffusion lengths in solar cells is presented. Thus, a simulation is done; it aims to give computational support to the general development of a neural networks (NNs), which is a very powerful predictive modelling technique used to predict the diffusion length in mono-crystalline silicon solar cells. Furthermore, the computation of the diffusion length and the comparison with measurement data, using the infrared injection method, are presented and discussed.

  3. Comparison of bond strength of auto polymerizing, heat cure soft denture liners with denture base resin - An In Vitro study.

    Science.gov (United States)

    Mahajan, Neerja; Datta, Kusum

    2010-03-01

    Optimum bond strength between denture soft liner and denture base resin is very important for the success of any denture prosthesis. The tensile bond strength of two commercially available silicone-based heat cured (Molloplast B) and auto polymerizing (Mollosil) was compared with denture base material (trevalon). Molloplast B-trevalon bond in both un-polymerized (dough stage) and already polymerized forms were also compared. Lloyds Universal testing machine was used to test 60 samples. Molloplast B bond strength was greater than Mollosil soft denture liner; it was even greater when packed against trevalon in an un-polymerized form than an already polymerized trevalon using primo adhesive. Both the soft lining materials used are acceptable for clinical usage.

  4. The role of hydrogen bonds in the melting points of sulfonate-based protic organic salts

    DEFF Research Database (Denmark)

    Luo, Jiangshui

    2016-01-01

    there is evidence of bond formation [6]. Hydrogen bonds in the solid state fall into the classification of strong, moderate, and weak hydrogen bonds [7]. In molecular systems like H2O (vs. H2S) or NH3 (vs. PH3), strong hydrogen bonds lead to higher melting points. However, in organic salts, the situation may......There are three main types of interactions inside organic salts - electrostatic interaction, hydrogen bonding and van der Waals force [1-4]. While van der Waals force is relatively weak, it is hydrogen bonding and particularly electrostatic interaction that determine the lattice energies of ionic...

  5. Office-Based Tools and Primary Care Visit Communication, Length, and Preventive Service Delivery.

    Science.gov (United States)

    Lafata, Jennifer Elston; Shay, L Aubree; Brown, Richard; Street, Richard L

    2016-04-01

    The use of physician office-based tools such as electronic health records (EHRs), health risk appraisal (HRA) instruments, and written patient reminder lists is encouraged to support efficient, high-quality, patient-centered care. We evaluate the association of exam room use of EHRs, HRA instruments, and self-generated written patient reminder lists with patient-physician communication behaviors, recommended preventive health service delivery, and visit length. Observational study of 485 office visits with 64 primary care physicians practicing in a health system serving the Detroit metropolitan area. Study data were obtained from patient surveys, direct observation, office visit audio-recordings, and automated health system records. Outcome measures included visit length in minutes, patient use of active communication behaviors, physician use of supportive talk and partnership-building communication behaviors, and percentage of delivered guideline-recommended preventive health services for which patients are eligible and due. Simultaneous linear regression models were used to evaluate associations between tool use and outcomes. Adjusted models controlled for patient characteristics, physician characteristics, characteristics of the relationship between the patient and physician, and characteristics of the environment in which the visit took place. Prior to adjusting for other factors, visits in which the EHR was used on average were significantly (p communication behaviors facilitating patient involvement (2.1 vs. 2.6 occurrences), but more use of active patient communication behaviors (4.4 vs. 2.6). Likewise, HRA use was significantly associated with increased preventive services delivery (62.1 percent vs. 57.0 percent). All relationships remained significant (p > .05) in adjusted models with the exception of that between HRA use and preventive service delivery. Office-based tools intended to facilitate the implementation of desired primary care practice

  6. A Fracture-Based Criterion for Debonding Strength of Adhesive-Bonded Double-Strap Steel Joints

    Directory of Open Access Journals (Sweden)

    Prawit Santisukpotha

    2012-01-01

    Full Text Available This paper addresses the debonding strength of adhesive-bonded double-strap steel joints. A fracture-based criterion was formulated in terms of a stress singularity parameter, i.e., the stress intensity factor, which governs the magnitude of a singular stress field near the joint ends. No existing crack was assumed. A total of 24 steel joint specimens were tested under constant amplitude fatigue loadings at stress ratio of 0.2 and frequency of 2 Hz. The joint stiffness ratio was slightly less than one to control the maximum adhesive stresses at the joint ends. To detect the debonding, a simple and practical technique was developed. The test results showed that the interfacial failure near the steel/adhesive corner was a dominant failure mode. The failure was brittle and the debonding life was governed by the crack initiation stage. The finite element analysis was employed to calculate the stress intensity factors and investigate the effects of the adhesive layer thickness, lap length and joint stiffness ratio on the debonding strength.

  7. Application of PCR-based restriction fragment length polymorphism for the identification of mycobacterial isolates.

    Science.gov (United States)

    Deepa, P; Therese, K L; Madhavan, H N

    2005-05-01

    Conventional identification of mycobacteria is achieved by standard biochemical tests that are time consuming, laborious and is not always conclusive. This study was thus undertaken to standardize a simple, rapid and cost-effective polymerase chain reaction based restriction fragment length polymorphism (PCR-RFLP) using primers coding for the 16S - 23S rRNA spacer region to identify the mycobacterial isolates to the species level. The PCR with primers targeting the 16S-23S rRNA spacer region was standardized using the standard mycobacterial strains and applied on 51 clinical isolates. The PCR amplified products were subjected to RFLP using the restriction enzymes, Hae III, MspI and BstXI. The results obtained were compared with those of conventional biochemical tests. PCR was sensitive to detect 2.5 pg of H37Rv DNA (370 bp for slow grower mycobacteria) and 1.5 pg of M. fortuitum DNA (450 bp for rapid grower mycobacteria). Based on the PCRRFLP products obtained the 51 mycobacterial isolates were classified into 41 slow growers and 10 rapid growers. Among the 41 slow growers, 40 were identified as M. tuberculosis, one as M. xenopi and 10 rapid growers as M. fortuitum. PCR using primers targeting the 16S-23S rRNA spacer region was a reliable tool for rapid identification of mycobacterial isolates into slow and rapid growers within 4 h of isolation and further speciation by PCR-RFLP within 6-8 h.

  8. PMMA to SU-8 bonding for polymer based lab-on-a-chip systems with integrated optics

    DEFF Research Database (Denmark)

    Olsen, Brian Bilenberg; Nielsen, Theodor; Clausen, Bjarne Hans

    2004-01-01

    We present an adhesive bonding technique developed for SU-8 based "lab-on-a-chip"- systems with integrated optical components. Microfluidic channels and optical components (e.g. wave-guides) are defined in SU-8 photoresist on a Pyrex glass substrate. The microfluidic channels are sealed by a second...... Pyrex substrate, bonded on top of the cross-linked SU-8 structure using an inter- mediate layer of 950K molecular weight poly-methylmethacrylate (PMMA). Due to a lower refractive index of PMMA, this bonding technique offers optical waveguiding in the SU-8 structures in combination with good sealing...

  9. Analysis of the age of Panax ginseng based on telomere length and telomerase activity.

    Science.gov (United States)

    Liang, Jiabei; Jiang, Chao; Peng, Huasheng; Shi, Qinghua; Guo, Xiang; Yuan, Yuan; Huang, Luqi

    2015-01-23

    Ginseng, which is the root of Panax ginseng (Araliaceae), has been used in Oriental medicine as a stimulant and dietary supplement for more than 7,000 years. Older ginseng plants are substantially more medically potent, but ginseng age can be simulated using unscrupulous cultivation practices. Telomeres progressively shorten with each cell division until they reach a critical length, at which point cells enter replicative senescence. However, in some cells, telomerase maintains telomere length. In this study, to determine whether telomere length reflects ginseng age and which tissue is best for such an analysis, we examined telomerase activity in the main roots, leaves, stems, secondary roots and seeds of ginseng plants of known age. Telomere length in the main root (approximately 1 cm below the rhizome) was found to be the best indicator of age. Telomeric terminal restriction fragment (TRF) lengths, which are indicators of telomere length, were determined for the main roots of plants of different ages through Southern hybridization analysis. Telomere length was shown to be positively correlated with plant age, and a simple mathematical model was formulated to describe the relationship between telomere length and age for P. ginseng.

  10. THE NETWORK OF CITY PUBLIC TRANSPORT AS THE BASE FOR TRIP LENGTH DISTRIBUTION DETERMINING

    Directory of Open Access Journals (Sweden)

    P. Horbachov

    2015-07-01

    Full Text Available The up-to-date methods of modelling the demand for public transport services require an objective estimation and improvement. Such an improvement can be achieved by taking into account the trip length distribution during trip matrix calculation that requires determining the reasons of regularities occurance in city population trip lengths.

  11. Lengths of the maxillary central incisor, the nasal bone, and the anterior cranial base in different skeletal malocclusions

    DEFF Research Database (Denmark)

    Arntsen, Torill; Kjær, Inger; Sonnesen, Liselotte

    2009-01-01

    malocclusions. Material and methods . Incisor, nasal, and cranial base lengths were measured on lateral radiographs of adult patients with skeletal malocclusions, including open bite (n=35), mandibular overjet (n=56), maxillary overjet (n=31), deep bite (n=19), and compared with those of a control group...... with neutral occlusion and normal craniofacial morphology (n=39). Two-way ANOVA tests were used to evaluate differences in lengths between groups and gender. Results. Statistically shorter maxillary central incisor length was found in the open bite group (p....001), and in the deep bite group (p

  12. Bonding of resin-based luting cements to zirconia with and without the use of ceramic priming agents.

    Science.gov (United States)

    Koizumi, Hiroyasu; Nakayama, Daisuke; Komine, Futoshi; Blatz, Markus B; Matsumura, Hideo

    2012-08-01

    This study evaluated and compared bonding characteristics of resin-based luting agents and special ceramic primers to zirconia. Disk specimens (n = 242) were fabricated from zirconium dioxide ceramics (Katana) and bonded with four resin-based luting agents without priming. In addition, zirconia was bonded with 7 bondingsystem combinations of three priming agents and three resin-based luting agents. Two of the resin-based luting agents and two ceramic priming agents contain an identical adhesive monomer, 10-methacryloyloxydecyl dihydrogen phosphate (MDP), either in the material itself or in the priming agent. Shear bond strength was determined after 20,000 cycles of thermocycling. The Kruskal-Wallis test was performed for both pre- and post-thermocycling groups to evaluate the difference among primer and luting agent variations. On the basis of the Kruskal-Wallis test, Steel-Dwass multiple comparisons were further performed to compare the difference among four luting agents and seven conbinations of three primers and three luting agents for both pre- and post-thermocycling conditions. Within the four unprimed groups, Clearfil SA Cement (5.8 MPa) and Panavia F 2.0 (6.7 MPa) showed statistically higher post-thermocycling bond strength than the other materials (0.1 MPa) (p primed with Monobond Plus (4.0-4.6 MPa) (p priming agents containing the adhesive monomer MDP provide better bond strength to zirconia than do other systems.

  13. Microwave-assisted acid and base hydrolysis of intact proteins containing disulfide bonds for protein sequence analysis by mass spectrometry.

    Science.gov (United States)

    Reiz, Bela; Li, Liang

    2010-09-01

    Controlled hydrolysis of proteins to generate peptide ladders combined with mass spectrometric analysis of the resultant peptides can be used for protein sequencing. In this paper, two methods of improving the microwave-assisted protein hydrolysis process are described to enable rapid sequencing of proteins containing disulfide bonds and increase sequence coverage, respectively. It was demonstrated that proteins containing disulfide bonds could be sequenced by MS analysis by first performing hydrolysis for less than 2 min, followed by 1 h of reduction to release the peptides originally linked by disulfide bonds. It was shown that a strong base could be used as a catalyst for microwave-assisted protein hydrolysis, producing complementary sequence information to that generated by microwave-assisted acid hydrolysis. However, using either acid or base hydrolysis, amide bond breakages in small regions of the polypeptide chains of the model proteins (e.g., cytochrome c and lysozyme) were not detected. Dynamic light scattering measurement of the proteins solubilized in an acid or base indicated that protein-protein interaction or aggregation was not the cause of the failure to hydrolyze certain amide bonds. It was speculated that there were some unknown local structures that might play a role in preventing an acid or base from reacting with the peptide bonds therein. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

  14. Dentin bonding performance and interface observation of an MMA-based restorative material.

    Science.gov (United States)

    Shinagawa, Junichi; Inoue, Go; Nikaido, Toru; Ikeda, Masaomi; Sadr, Alireza; Tagami, Junji

    2016-07-30

    The purpose of this study was to evaluate bonding performance and dentin interface acid resistance using a 4-META/MMA-TBB based restorative material (BF) compared to a conventional 4-META/MMA-TBB resin cement (SB), and the effect of sodium fluoride (NaF) addition to the materials. Dentin surfaces were treated with 10% citric acid-3% ferric chloride (10-3) or 4-META containing self-etching primer (TP), followed by application of BF or SB polymer powders with or without NaF, to evaluate microtensile bond strength (µTBS) in six experimental groups; 10-3/SB, 10-3/BF, TP/SB, TP/BF, TP/SB/NaF and TP/BF/NaF. SEM observation of the resin-dentin interface was performed after acid-base challenge to evaluate interfacial dentin resistance to acid attack. TP/BF showed highest µTBS, while NaF polymers decreased µTBS. TP/BF showed funnel-shaped erosion at the interface, however, NaF polymers improved acid resistance of interface. In conclusion, BF demonstrated high µTBSs and low acid-resistance at the interface. NaF addition enhanced acid resistance but decreased µTBS.

  15. Hydrofluoric acid-assisted bonding of diatoms with SiO2-based substrates for microsystem application

    International Nuclear Information System (INIS)

    Zhang, Deyuan; Pan, Junfeng; Cai, Jun; Wang, Yu; Jiang, Yonggang; Jiang, Xinggang

    2012-01-01

    Diatom, with delicate three-dimensional porous structures and texture, has a promising application in micro-nanotechnology especially biosensing. In order to achieve a diatom-based compound substrate, a fabrication technique is developed for hydrofluoric acid (HF) bonding of diatom with SiO 2 -based substrate at a temperature as low as 80 °C. The bonding conditions are optimized with various HF concentrations and applied pressure. The optimized HF concentration is found to be in the range of 0.8% to 1.2% and applied pressure is from 0.4.0 MPa to 0.6.0 MPa. The morphological integrity and nano-microscale substructures of the diatoms after bonding are characterized. The bonding strength is approximately 0.435 MPa. (paper)

  16. The evaluation of microleakage and bond strength of a silicone-based resilient liner following denture base surface pretreatment.

    Science.gov (United States)

    Sarac, Duygu; Sarac, Y Sinasi; Basoglu, Tarik; Yapici, Oktay; Yuzbasioglu, Emir

    2006-02-01

    The failure of adhesion between a silicone-based resilient liner and a denture base is a significant clinical problem. The purpose of this study was to examine the effects of denture base resin surface pretreatments with different chemical etchants preceding the silicone-based resilient liner application on microleakage and bond strength. The initial effects of chemical etchants on the denture base resin in terms of microstructural changes and flexural strength were also examined. Forty-two polymethyl methacrylate (PMMA) denture base resin (Meliodent) specimens consisting of 2 plates measuring 30 x 30 x 2 mm were prepared and divided into 7 groups (n = 6). Specimen groups were treated by immersion in acetone for 30 (A30) or 45 (A45) seconds, methyl methacrylate monomer for 180 (M180) seconds, and methylene chloride for 5 (MC5), 15 (MC15) or 30 (MC30) seconds. Group C had no surface treatment and served as the control. Subsequently, an adhesive (Mollosil) and a silicone-based resilient denture liner (Mollosil) were applied to the treated surfaces, and all specimens were immersed in the radiotracer solution (thalium-201 chloride) for 24 hours. Tracer activity (x-ray counts), as a parameter of microleakage, was measured using a gamma camera. For bond-strength measurement, 84 rectangular PMMA specimens (10 x 10 x 40 mm) were surface-smoothed for bonding and treated with the different chemical etchants using the same previously described group configurations. The adhesive and the silicone-based denture liner were applied to the treated surfaces. Tensile bond-strength (MPa) was measured in a universal testing machine. Flexural strength measurement was performed with 49 PMMA specimens (65 x 10 x 3.3 mm according to ISO standard 1567) in 7 groups (n = 7), with 1 flat surface of each treated with 1 of the chemical etchants preceding adhesive application. The flexural strength (MPa) was measured using a 3-point bending test in a universal testing machine. The data were

  17. In vitro tensile bond strength of denture repair acrylic resins to primed base metal alloys using two different processing techniques.

    Science.gov (United States)

    Banerjee, Sarmistha; Engelmeier, Robert L; O'Keefe, Kathy L; Powers, John M

    2009-12-01

    Approximately 38% of removable partial denture (RPD) failures involve fracture at the alloy/acrylic interface. Autopolymerizing resin is commonly used to repair RPDs. Poor chemical bonding of repair acrylic to base metal alloys can lead to microleakage and failure of the bond. Therefore, ideal repair techniques should provide a strong, adhesive bond. This investigation compared the tensile bond strength between cobalt-chromium (Super Cast, Pentron Laboratory Technologies, Llc., Wallingford, CT) and nickel-chromium (Rexalloy, Pentron Laboratory Technologies, Llc.) alloys and autopolymerized acrylic resin (Dentsply Repair Material, Dentsply Int, Inc, York, Pa) using three primers containing different functional monomers [UBar (UB), Sun Medical Co., Ltd., Shiga, Japan: Alloy Primer (AP) Kuraray Medical Inc., Okayama, Japan; and MR Bond (MRB) Tokyuyama Dental Corp., Tokyo, Japan] and two processing techniques (bench cure and pressure-pot cure). One hundred and twenty eight base metal alloy ingots were polished, air abraded, and ultrasonically cleaned. The control group was not primed. Specimens in the test groups were primed with one of the three metal primers. Autopolymerized acrylic resin material was bonded to the metal surfaces. Half the specimens were bench cured, and the other half were cured in a pressure pot. All specimens were stored in distilled water for 24 hours at 37 degrees C. The specimens were debonded under tension at a crosshead speed of 0.05 cm/min. The forces at which the bond failed were noted. Data were analyzed using ANOVA. Fisher's PLSD post hoc test was used to determine significant differences (p alloys. Primed sandblasted specimens that were pressure-pot-cured had significantly higher bond strengths than primed sandblasted bench-cured specimens. The pressure-pot-curing method had a significant effect on bond strength of all specimens except Co-Cr alloy primed with UB. The highest bond strength was observed for both Co-Cr and Ni-Cr alloys that

  18. Mineral-Based Bonding of Carbon FRP to Strengthen Concrete Structures

    DEFF Research Database (Denmark)

    Täljsten, Björn; Blanksvärd, T.

    2007-01-01

    therefore be strengthened before it can be used. Different methods to retrofit with FRPs also exist, such as bonding of plates or sheets, with their use of epoxy as the bonding agent being the commonality. Epoxy provides very good bond to concrete and is durable and resistant to most environments...

  19. Memory-based robust adaptive control of a variable length stepping nanomanipulator

    Science.gov (United States)

    Saeidpourazar, Reza; Jalili, Nader

    2007-04-01

    This paper presents the modeling and memory-based robust adaptive control of a variable length stepping nanomanipulator. A three degree of freedom (3DOF) nanomanipulator with revolute revolute prismatic (RRP) actuator structure, namely here MM3A, is utilized for a variety of nanomanipulation tasks. Unlike widely used Cartesian-structure nanomanipulators, the MM3A is equipped with revolute-piezoelectric actuators which result in outstanding performance for controlling the nanomanipulator's tip alignment during the nanomanipulation process. However, the RRP structure of the nanomanipulator introduces complicity in kinematic and dynamic equations of the system which needs to be addressed in order to control the nanomanipulation process. Dissimilar to the ordinary piezoelectric actuators which provide only a couple of micrometers working range, the piezoelectric actuators utilized in MM3A, namely Nanomotors, provide wide range of action (120° in revolute actuators and 12mm in prismatic actuator) with sub-nano scale precision (0.1 μrad in revolute actuators and 0.25 nm in prismatic actuator). This wide range of action combined with sub-nano scale precision is achieved using a special stick/slip moving principle of the Nanomotors. However, such stick/slip motion results in stepping movement of the MM3A. Hence, due to the RRP structure and stepping movement principle of the MM3A nanomanipulator, controller design for the nanomanipulation process is not a trivial task. In this paper, a novel memory-based robust adaptive controller is proposed to overcome these shortfalls. Following the development of the memory-based robust adaptive controller, numerical simulations of the proposed controller are preformed to demonstrate the positioning performance capability of the controller in nanomanipulation tasks.

  20. Electronic energy spectrum structure of the two-dimensional Fibonacci quasilattices with three kinds of atoms and one kind of bond length

    Science.gov (United States)

    Xiang-bo, Yang; You-yan, Liu

    1995-07-01

    After establishing the method of constructing a class of two-dimensional Fibonacci quasilattices, by means of a decomposition-decimation method based on the renormalization-group technique, we have studied the rules of energy spectrum splitting for the two-dimensional Fibonacci quasilattices in the framework of single-electron tight-binding on-site model. Analytic results show that there are only six kinds of clusters and the electronic energy band consists of nine subbands. For the higher hierarchy of the spectrum, instead of the on-site model, the transfer model should be used, the electronic energy spectra split as type F. The analytic results are confirmed by numerical simulations.

  1. SPH with dynamical smoothing length adjustment based on the local flow kinematics

    Science.gov (United States)

    Olejnik, Michał; Szewc, Kamil; Pozorski, Jacek

    2017-11-01

    Due to the Lagrangian nature of Smoothed Particle Hydrodynamics (SPH), the adaptive resolution remains a challenging task. In this work, we first analyse the influence of the simulation parameters and the smoothing length on solution accuracy, in particular in high strain regions. Based on this analysis we develop a novel approach to dynamically adjust the kernel range for each SPH particle separately, accounting for the local flow kinematics. We use the Okubo-Weiss parameter that distinguishes the strain and vorticity dominated regions in the flow domain. The proposed development is relatively simple and implies only a moderate computational overhead. We validate the modified SPH algorithm for a selection of two-dimensional test cases: the Taylor-Green flow, the vortex spin-down, the lid-driven cavity and the dam-break flow against a sharp-edged obstacle. The simulation results show good agreement with the reference data and improvement of the long-term accuracy for unsteady flows. For the lid-driven cavity case, the proposed dynamical adjustment remedies the problem of tensile instability (particle clustering).

  2. An algorithm to manage variable-length records for highly portable clinical data base systems.

    Science.gov (United States)

    Okada, M; Okada, M

    1986-06-01

    An algorithm to archive patient data at free size in disk storage is presented. A record, assumed to be a character string such as an ASCII-coded text, is compressed and divided into fixed-length blocks. One block consists of a data field and a pointer field, and the blocks comprising a record are chained with pointers forwardly. A head pointer of each record is sequentially saved on a separate file. The data compression is performed as follows: if the same character code appears more than twice in succession, we count the number of the repetitions and save it with initial two characters. The algorithms for fetching, re-saving, and purging a record are also presented. These were implemented in FORTRAN77 and tested for performance using a practical patient data file. As the algorithm allows highly flexible record manipulation and can easily be implemented in conventional programming languages, it will make a useful tool for constructing a portable data base management system.

  3. Measurement and theory of hydrogen bonding contribution to isosteric DNA base pairs.

    Science.gov (United States)

    Khakshoor, Omid; Wheeler, Steven E; Houk, K N; Kool, Eric T

    2012-02-15

    We address the recent debate surrounding the ability of 2,4-difluorotoluene (F), a low-polarity mimic of thymine (T), to form a hydrogen-bonded complex with adenine in DNA. The hydrogen bonding ability of F has been characterized as small to zero in various experimental studies, and moderate to small in computational studies. However, recent X-ray crystallographic studies of difluorotoluene in DNA/RNA have indicated, based on interatomic distances, possible hydrogen bonding interactions between F and natural bases in nucleic acid duplexes and in a DNA polymerase active site. Since F is widely used to measure electrostatic contributions to pairing and replication, it is important to quantify the impact of this isostere on DNA stability. Here, we studied the pairing stability and selectivity of this compound and a closely related variant, dichlorotoluene deoxyriboside (L), in DNA, using both experimental and computational approaches. We measured the thermodynamics of duplex formation in three sequence contexts and with all possible pairing partners by thermal melting studies using the van't Hoff approach, and for selected cases by isothermal titration calorimetry (ITC). Experimental results showed that internal F-A pairing in DNA is destabilizing by 3.8 kcal/mol (van't Hoff, 37 °C) as compared with T-A pairing. At the end of a duplex, base-base interactions are considerably smaller; however, the net F-A interaction remains repulsive while T-A pairing is attractive. As for selectivity, F is found to be slightly selective for adenine over C, G, T by 0.5 kcal mol, as compared with thymine's selectivity of 2.4 kcal/mol. Interestingly, dichlorotoluene in DNA is slightly less destabilizing and slightly more selective than F, despite the lack of strongly electronegative fluorine atoms. Experimental data were complemented by computational results, evaluated at the M06-2X/6-31+G(d) and MP2/cc-pVTZ levels of theory. These computations suggest that the pairing energy of F to A

  4. Comparative study of freshwater crayfish, Cherax spp. (crustaceae: decapoda: parastacidae) from Papua, Indonesia based on length-weight analysis

    Science.gov (United States)

    Hamidah, H.; Abinawanto, Bowolaksono, A.

    2017-07-01

    The freshwater crayfish is one of the most important fish species as the protein resources. Lake and rivers are the habitat of crayfish in Papua. Morphological characters of crayfish, such as color, total body lengths (L) and body weight (W) were influenced by the habitat. The purpose of the study, therefore, was to compare the total body length and body weight as well as the unique color of crayfish from Uter lake (Atinjo district), Seremuk river (Haha village), Baliem river (Pike village; Hubukiak district, Jayawijaya), and Baliem river (Wesaput village; Wesaput district). Length-weight (body length; LB versus wet weight; WWT) relationships were determined for male and female crayfish (Cherax spp.) The length-weight relationships of total individuals was W = 0,022215.L3,159. This regression differed significantly (R2 = 97.5 %) between locations. Both males and females exhibited positive allometric growth as statistical difference was observed in the mean of the wet weight and body length between males and females. Besides, Canonical function was subjected to determine population distribution based on length-weight data.

  5. Resin-based luting agents and color stability of bonded ceramic veneers.

    Science.gov (United States)

    Almeida, Júlia R; Schmitt, Gabriela U; Kaizer, Marina R; Boscato, Noéli; Moraes, Rafael R

    2015-08-01

    The type of resin-based luting agent might influence the color stability of ceramic veneers. The purpose of this study was to investigate the effects of resin-based agents and aging on the color stability of ceramic veneers bonded to enamel. Ceramic disks were cemented to bovine enamel disks with 4 resin-based luting agents (n=10): dual-polymerizing cement (RelyX ARC), light-polymerizing cement (RelyX Veneer), flowable composite resin (Filtek Z350 Flow), or composite resin preheated for 30 minutes at 60°C (Filtek Z350 XT). CIE L*, a*, and b* color coordinates were measured 24 hours after cementation (baseline) with a color spectrophotometer and reevaluated after 10,000 and 20,000 thermal cycles. Color variation was calculated by using CIELab (ΔE*(ab)) and CIEDE2000 (ΔE00) methods. Then 95% confidence intervals were calculated for color variation means between baseline and 10,000 thermal cycles and between 10,000 and 20,000 thermal cycles. The 95% confidence intervals were also calculated for the means of individual color coordinates (L*, a*, and b*). The dual-polymerizing cement had the highest color variation among all luting agents. No significant differences were found in color variation among the light-polymerizing materials. All agents showed ΔE*(ab)>3.46 and ΔE00>2.25 after 20,000 thermal cycles. Variations in L*, a*, and b* coordinates were material dependent. The dual-polymerizing agent was yellowish and reddish after aging. The dual-polymerizing cement had higher color variation than the light-polymerized materials when used for bonding ceramic veneers to enamel. Flowable and preheated composite resins had similar color stability to that of light-polymerizing resin-based cement. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  6. Push-out bond strength of different tricalcium silicate-based filling materials to root dentin

    Directory of Open Access Journals (Sweden)

    Jorge Henrique Stefaneli Marques

    2018-03-01

    Full Text Available Abstract: The aim of this study was to evaluate the bond strength of different triccalcium silicate cements to retrograde cavity using a push out test. Thirty maxillary central incisors were shaped using #80 hand files and sectioned transversally. Root slices were obtained from the apical 4 mm after eliminating the apical extremity. The specimens were embedded in acrylic resin and positioned at 45° to the horizontal plane for preparation of root-end cavities with a diamond ultrasonic retrotip. The samples were divided into three groups according to the root-end filling material (n = 10: MTA Angelus, ProRoot MTA and Biodentine. A gutta-percha cone (#80 was tugged-back at the limit between the canal and the root-end cavity. The root-end cavity was filled and the gutta-percha cone was removed after complete setting of the materials. The specimens were placed in an Instron machine with the root-end filling turned downwards. The push-out shaft was inserted in the space previously occupied by the gutta-percha cone and push out testing was performed at a crosshead speed of 1.0 mm/min. There was no statistically significant difference in resistance to push out by the materials tested (p > 0.01. MTA Angelus and ProRoot MTA showed predominantly mixed failure while Biodentine exhibited mixed and cohesive failures. The tricalcium silicate-based root-end filling materials showed similar bond strength retrograde cavity.

  7. Research and design of documents compression algorithm based on variable length encoding

    Science.gov (United States)

    Yu, Jie; Wang, Fangxiu

    2015-12-01

    Considering there exists defects for Huffman coding to compress files, this paper presents a general algorithm to predict the vality of compressed files with variable-length coding. Through the pre-sentence of the prior estimate method of the average code length and the estimation method after file compressed, It implements a compressed file is no longer compressed. The algorithm includes character encoding and file encoding two stages, and it uses variable-length coding technique and compression rate information of the target file. First, it obtains the file code table from character probability statistics and the variable length encoding technique. Second, it uses the character probability and character code length to calculate the average code long. Finally, it determines whether the file is actually compressed according to the average code length of characters or the file compression ratio. Algorithm tests show: it can accurately pre-judge whether any type file can be compressed so that it only compresses the file that can be compressed.

  8. Comparative evaluation of orthodontic bracket base shapes on shear bond strength and adhesive remnant index: Anin vitrostudy.

    Science.gov (United States)

    Pham, Dennis; Bollu, Prashanti; Chaudhry, Kishore; Subramani, Karthikeyan

    2017-07-01

    The objective of this study was to evaluate the effect of orthodontic bracket base shape on shear bond strength and adhesive remnant index. In this in vitro study using 140 bovine incisors, shear bond strength (SBS) of brackets with different base shapes (rectangle, flower, round, heart, diamond, star, and football) were measured with an Instron testing machine and tested until bond failure. Adhesive Remnant Index (ARI) scoring was evaluated after debonding to evaluate the location of bond failure. Descriptive and one-way ANOVA post-hoc Tukey statistical analyses were performed with a statistical significance set at p ≤0.05. Statistically significant difference in mean SBS in Newtons was observed for multiple base shapes ( p football and flower base shapes (73.83 N ± 53.46; 65.82 N ± 37.89 respectively); the lowest mean was observed with diamond and heart shapes (30.51 N ± 11.73; 33.28 N ± 16.89 respectively). When reported in Megaspascals, statistically significant difference was observed for rectangle base shape (3.54 MPa ± 2.69) when compared to all other base shapes. Bracket base shape has an effect on SBS. Higher SBS (N) for rectangle, flower, and football base shape indicates even stress distributions throughout the bracket base. Base shape with a pronounced converging tip over the axial plane may contribute to the reduction in SBS due to increased peak stress concentration resulting in bond failure. Key words: Shaped brackets, Shear bond strength, Adhesive remnant index, WildSmiles®.

  9. Some considerations about bond indices in non-orthogonal bases and the MO calculation of valence and oxidation number

    International Nuclear Information System (INIS)

    Giambiagi, M.S. de; Giambiagi, M.; Jorge, F.E.

    1984-01-01

    In order to guarantee the desired invariance properties of bond indices, the importance of expliciting the tensor character of the matrices concerned, so as to deal with a contraction in the tensor sense between a covariant index and a contravariant one is shown. An MO valence definition using Wiberg's indices is generalized to non-orthogonal bases and a straightforward definition of oxidation numbers is proposed. IEH calculations of their magnitudes for some appropriate examples are performed: they emphasize the role of 'secondary' bonds in N and C-containing compounds; the hydrogen behaviour in half-bonds and strong H-bonds is satisfactorily accounted for; valence and oxidation number values are assigned to Fe, Co and Ni in a few complexes. (Author) [pt

  10. Extrafibrillar collagen demineralization-based chelate-and-rinse technique bridges the gap between wet and dry dentin bonding.

    Science.gov (United States)

    Mai, Sui; Wei, Chin-Chuan; Gu, Li-Sha; Tian, Fu-Cong; Arola, Dwayne D; Chen, Ji-Hua; Jiao, Yang; Pashley, David H; Niu, Li-Na; Tay, Franklin R

    2017-07-15

    Limitations associated with wet-bonding led to the recent development of a selective demineralization strategy in which dentin was etched with a reduced concentration of phosphoric acid to create exclusive extrafibrillar demineralization of the collagen matrix. However, the use of acidic conditioners removes calcium via diffusion of very small hydronium ions into the intrafibrillar collagen water compartments. This defeats the purpose of limiting the conditioner to the extrafibrillar space to create a collagen matrix containing only intrafibrillar minerals to prevent collapse of the collagen matrix. The present work examined the use of polymeric chelators (the sodium salt of polyacrylic acid) of different molecular weights to selectively demineralize extrafibrillar dentin. These polymeric chelators exhibit different affinities for calcium ions (isothermal titration calorimetry), penetrated intrafibrillar dentin collagen to different extents based on their molecular sizes (modified size-exclusion chromatography), and preserve the dynamic mechanical properties of mineralized dentin more favorably compared with completely demineralized phosphoric acid-etched dentin (nanoscopical dynamic mechanical analysis). Scanning and transmission electron microscopy provided evidence for retention of intrafibrillar minerals in dentin surfaces conditioned with polymeric chelators. Microtensile bond strengths to wet-bonded and dry-bonded dentin conditioned with these polymeric chelators showed that the use of sodium salts of polyacrylic acid for chelating dentin prior to bonding did not result in significant decline in resin-dentin bond strength. Taken together, the findings led to the conclusion that a chelate-and-rinse conditioning technique based on extrafibrillar collagen demineralization bridges the gap between wet and dry dentin bonding. The chelate-and-rinse dental adhesive bonding concept differentiates from previous research in that it is based on the size

  11. Effect of maleic anhydride pretreatment on tensile bond strength of a silicone soft liner to a denture base polymer.

    Science.gov (United States)

    Demir, Hakan; Soygun, Koray; Dogan, Arife; Keskin, Selda; Dogan, Orhan Murat; Bolayir, Giray

    2011-10-01

    To determine the effect of resin surface treatment with dissolved maleic anhydride in butanone added into primer on the tensile bond strength between an acrylic denture base resin and a silicone soft liner. To test tensile bond strength, standard dumbbell-shaped acrylic specimens were prepared. Five experimental groups, including the control, were tested (n = 5). Maleic anhydride solutions prepared in butanone at concentrations of 1%, 5%, 10% or 20% were then mixed with 1 ml of Primo adhesive and the mixtures were applied onto the resin bonding surfaces. Silicone liner material was applied to resin surfaces in the conventional manner. Tensile bond strength of the specimens was measured in a universal testing machine. Fractured surfaces were observed under the scanning electron microscope, and resulting chemical changes with the solutions used were analyzed spectroscopically. The highest bond strength value was obtained for the group treated with 5% maleic anhydride (2.53 ± 0.48 MPa); the lowest value was for the group treated with 20% maleic anhydride (1.59 ± 0.29 MPa). Mixed failure was the dominant type seen in the experimental groups. Spectroscopic analysis showed the interaction of the anhydride carbonyl groups with the Primo primer. The treatment of resin surfaces with maleic anhydride added to Primo adhesive effectively increased bond strength between silicone soft liner and denture base resin.

  12. Effect of thermocycling on the tensile and shear bond strengths of three soft liners to a denture base resin.

    Science.gov (United States)

    Elias, Carlos Nelson; Henriques, Flavio Queiroz

    2007-02-01

    In clinical practice, loss of adhesion between the silicone-based denture liner and the denture base resin is always an undesirable event that might cause loss of material softness, water sorption, bacterial colonization and functional failure of the prosthesis. This study evaluated the effect of thermocycling on tensile and shear bond strengths of three soft liner materials to a denture base acrylic resin. Three resilient liners (Mucopren-Soft, Mollosil-Plus and Dentusil) and a heat-polymerized acrylic resin (QC-20) were processed according to manufacturers' directions. Sixty specimens (14 x 14 mm cross-sectional area) per bond strength test (20 for each liner) were fabricated and either stored in water at 37 degrees C for 24 hours (control groups; n=10) or thermocycled 3,000 times in water between 5 degrees C and 55 degrees C (test groups; n=10). The specimens were tested in tensile and shear strength in a universal testing machine until fracture. Bond strength means were compared between water-stored and thermocycled groups for each material, as well as among materials for each treatment (water storage or thermocycling). Failure mode (adhesive, cohesive and mixed) after debonding was assessed. Data were analyzed statistically by paired Student's t-test and ANOVA at 5% significance level. The water-stored groups had statistically significant higher bond strengths than the thermocycled groups (p<0.05). Without thermocycling, Mucopren-Soft (2.83 +/- 0.48 MPa) had higher bond strength than Mollosil-Plus (1.04 +/- 0.26 MPa) and Dentusil (1.14 +/- 0.51 MPa). After thermocycling, Mucopren-Soft (1.63 +/- 0.48 MPa) had the highest bond strength (p<0.05). The bond strength of the three soft denture liners tested in this study changed with their chemical composition and all of them exhibited higher bond strengths than those usually reported as clinically acceptable. All soft lining materials tested in this study showed a significant decrease in the bond strength to an

  13. Effect of thermocycling on the tensile and shear bond strengths of three soft liners to a denture base resin

    Directory of Open Access Journals (Sweden)

    Carlos Nelson Elias

    2007-02-01

    Full Text Available STATEMENT OF PROBLEM: In clinical practice, loss of adhesion between the silicone-based denture liner and the denture base resin is always an undesirable event that might cause loss of material softness, water sorption, bacterial colonization and functional failure of the prosthesis. PURPOSE: This study evaluated the effect of thermocycling on tensile and shear bond strengths of three soft liner materials to a denture base acrylic resin. MATERIAL AND METHODS: Three resilient liners (Mucopren-Soft, Mollosil-Plus and Dentusil and a heat-polymerized acrylic resin (QC-20 were processed according to manufacturers' directions. Sixty specimens (14 x 14 mm cross-sectional area per bond strength test (20 for each liner were fabricated and either stored in water at 37ºC for 24 hours (control groups; n=10 or thermocycled 3,000 times in water between 5ºC and 55ºC (test groups; n=10. The specimens were tested in tensile and shear strength in a universal testing machine until fracture. Bond strength means were compared between water-stored and thermocycled groups for each material, as well as among materials for each treatment (water storage or thermocycling. Failure mode (adhesive, cohesive and mixed after debonding was assessed. Data were analyzed statistically by paired Student's t-test and ANOVA at 5% significance level. RESULTS: The water-stored groups had statistically significant higher bond strengths than the thermocycled groups (p<0.05. Without thermocycling, Mucopren-Soft (2.83 ± 0.48 MPa had higher bond strength than Mollosil-Plus (1.04 ± 0.26 MPa and Dentusil (1.14 ± 0.51 MPa. After thermocycling, Mucopren-Soft (1.63 ± 0.48 MPa had the highest bond strength (p<0.05. CONCLUSION: The bond strength of the three soft denture liners tested in this study changed with their chemical composition and all of them exhibited higher bond strengths than those usually reported as clinically acceptable. CLINICAL IMPLICATIONS: All soft lining materials

  14. Taylor-plasticity-based analysis of length scale effects in void growth

    KAUST Repository

    Liu, Junxian

    2014-09-25

    We have studied the void growth problem by employing the Taylor-based strain gradient plasticity theories, from which we have chosen the following three, namely, the mechanism-based strain gradient (MSG) plasticity (Gao et al 1999 J. Mech. Phys. Solids 47 1239, Huang et al 2000 J. Mech. Phys. Solids 48 99-128), the Taylor-based nonlocal theory (TNT; 2001 Gao and Huang 2001 Int. J. Solids Struct. 38 2615) and the conventional theory of MSG (CMSG; Huang et al 2004 Int. J. Plast. 20 753). We have addressed the following three issues which occur when plastic deformation at the void surface is unconstrained. (1) Effects of elastic deformation. Elasticity is essential for cavitation instability. It is therefore important to guarantee that the gradient term entering the Taylor model is the effective plastic strain gradient instead of the total strain gradient. We propose a simple elastic-plastic decomposition method. When the void size approaches the minimum allowable initial void size related to the maximum allowable geometrically necessary dislocation density, overestimation of the flow stress due to the negligence of the elastic strain gradient is on the order of lεY/R0 near the void surface, where l, εY and R0 are, respectively, the intrinsic material length scale, the yield strain and the initial void radius. (2) MSG intrinsic inconsistency, which was initially mentioned in Gao et al (1999 J. Mech. Phys. Solids 47 1239) but has not been the topic of follow-up studies. We realize that MSG higher-order stress arises due to the linear-strain-field approximation within the mesoscale cell with a nonzero size, lε. Simple analysis shows that within an MSG mesoscale cell near the void surface, the difference between microscale and mesoscale strains is on the order of (lε/R0)2, indicating that when lε/R0 ∼ 1.0, the higher-order stress effect can make the MSG result considerably different from the TNT or CMSG results. (3) Critical condition for cavitation instability

  15. Incorporation of guanosine gels into sieving matrices for length- and sequence-based separation of DNA in capillary electrophoresis.

    Science.gov (United States)

    Dong, Yingying; McGown, Linda B

    2011-05-01

    Sieving gels are used in capillary gel electrophoresis to resolve DNA strands of different lengths. For complex samples, however, such as those encountered in metagenomic analysis of microbial communities or biofilms, length-based separation may mask the true genetic diversity of the community since different organisms may contribute same-length DNA with different sequences. There is a need, therefore, for DNA separations based on both the length and sequence. Previous work has demonstrated the ability of guanosine gels (G-gels) to separate four single-stranded DNA 76-mers that differ by only a few A/G base substitutions. The goal of the present work is to determine whether G-gels could be combined with commercial sieving gels in order to simultaneously separate DNA based on both length and sequence. The results are given for the four 76-mers and for a standard dsDNA ladder. Commercial sieving gels were used alone and in combination with G-gels. For the 76-mers, the combined medium was less efficient than the G-gel alone but was able to achieve partial resolution. The combined medium was at least as effective as the sieving gel alone at resolving the denatured DNA ladder and showed indications of sequence-based resolution as well, as supported by MALDI-MS. The results show that the combined sieving gel/G-gel medium retains the selectivity of the individual media, providing a promising approach to simultaneous length- and sequence-based DNA separation for metagenomic analysis of complex systems. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Evaluation of tensile bond strength of heat cure and autopolymerizing silicone-based resilient denture liners before and after thermocycling.

    Science.gov (United States)

    Madan, Nishtha; Datta, Kusum

    2012-01-01

    To assess the effect of simulated mouth conditions reproduced with thermocycling on the tensile bond strength of two silicone based resilient denture liners with acrylic resin bases. Two silicone-based soft denture liners (Mollosil - Chairside autopolymerization and Molloplast B - Heat polymerization) were tested. For each liner, 30 specimens with a cross-sectional area of 10 Χ 10 mm and thickness 3 mm were processed between two acrylic blocks (Trevalon). Specimens were divided into a control group that was stored for 24 hours in water at 37°C and a test group that was thermocycled (2500 cycles) between baths of 5° and 55°C. Tensile bond strength (kg/cm²) was determined in a universal testing machine using crosshead speed of 5 mm/min. The student t-test was used to determine the significance of the difference in bond strength between the two liners. The mean tensile bond strength for control and thermocycled specimens of the two liners were: Mollosil (6.82 kg/cm² and 8.41 kg/cm²) and Molloplast-B (16.30 kg/cm² and 13.67 kg/cm²), respectively. Comparison of bond strength of control specimens with thermocycled specimens of the liners indicated a significant difference for both Mollosil (P=0.045) and Molloplast-B (P=0.027). Comparison between control specimens of both liners and thermocycled specimens of both liners indicated a highly significant difference (Ptensile bond strength than autopolymerizing liner Mollosil regardless of thermocycling. The bond strength of Mollosil increased after thermocycling while that of Molloplast-B decreased after thermocycling. Although heat-polymerized denture liners require more processing time than autopolymerizing liners, but they display much better adhesion properties to denture base resin and should thus be preferred when soft liner has to be used for a longer duration of time.

  17. Influence of Surface Modifications of Acrylic Resin Teeth on Shear Bond Strength with Denture Base Resin-An Invitro Study.

    Science.gov (United States)

    Mahadevan, Vallabh; Krishnan, Madhusudan; Krishnan, Chitra Shankar; Azhagarasan, N S; Sampathkumar, Jayakrishnakumar; Ramasubramanian, Hariharan

    2015-09-01

    Debonding of artificial teeth from the denture base is an important issue for edentulous patients rehabilitated with conventional or implant supported complete dentures. The purpose of this study was to evaluate shear bond strength between denture base resin and acrylic resin denture teeth subjected to three different surface modifications on the ridge lap area as compared to unmodified denture teeth. Forty acrylic resin central incisor denture teeth were selected and randomly divided into four test groups. The teeth in each group were subjected to one of the three different surface modifications, namely, chemical treatment, sandblasting and placement of retentive grooves on the ridge lap area respectively, prior to packing of the denture base resin. The group with unmodified teeth served as control. Forty acrylic resin test blocks thus obtained were tested for shear bond strength between acrylic resin teeth and denture base resin in Universal Testing Machine. Data obtained was statistically analysed using one-way ANOVA and Student- Newman- Keul's test (p< 0.05). Analysis of shear bond strength revealed that retentive grooves on the ridge lap area showed highest bond strength values followed by sandblasting and both were statistically significant compared to the control and chemically treated groups. Unmodified surface of the resin teeth showed the least bond strength. Within the limitations of this invitro study the placement of retentive grooves or sandblasting of the ridge lap area showed highly significant improvement in shear bond strength compared to the unmodified surface. Chemical treatment did not result in any significant improvement in the shear bond strength compared to the unmodified surface.

  18. Influence of Surface Modifications of Acrylic Resin Teeth on Shear Bond Strength with Denture Base Resin-An Invitro Study

    Science.gov (United States)

    Krishnan, Madhusudan; Krishnan, Chitra Shankar; Azhagarasan, N.S.; Sampathkumar, Jayakrishnakumar; Ramasubramanian, Hariharan

    2015-01-01

    Background Debonding of artificial teeth from the denture base is an important issue for edentulous patients rehabilitated with conventional or implant supported complete dentures. Aim The purpose of this study was to evaluate shear bond strength between denture base resin and acrylic resin denture teeth subjected to three different surface modifications on the ridge lap area as compared to unmodified denture teeth. Materials and Methods Forty acrylic resin central incisor denture teeth were selected and randomly divided into four test groups. The teeth in each group were subjected to one of the three different surface modifications, namely, chemical treatment, sandblasting and placement of retentive grooves on the ridge lap area respectively, prior to packing of the denture base resin. The group with unmodified teeth served as control. Forty acrylic resin test blocks thus obtained were tested for shear bond strength between acrylic resin teeth and denture base resin in Universal Testing Machine. Data obtained was statistically analysed using one-way ANOVA and Student- Newman- Keul’s test (p< 0.05). Results Analysis of shear bond strength revealed that retentive grooves on the ridge lap area showed highest bond strength values followed by sandblasting and both were statistically significant compared to the control and chemically treated groups. Unmodified surface of the resin teeth showed the least bond strength. Conclusion Within the limitations of this invitro study the placement of retentive grooves or sandblasting of the ridge lap area showed highly significant improvement in shear bond strength compared to the unmodified surface. Chemical treatment did not result in any significant improvement in the shear bond strength compared to the unmodified surface. PMID:26501005

  19. Variable length adjacent partitioning for PTS based PAPR reduction of OFDM signal

    International Nuclear Information System (INIS)

    Ibraheem, Zeyid T.; Rahman, Md. Mijanur; Yaakob, S. N.; Razalli, Mohammad Shahrazel; Kadhim, Rasim A.

    2015-01-01

    Peak-to-Average power ratio (PAPR) is a major drawback in OFDM communication. It leads the power amplifier into nonlinear region operation resulting into loss of data integrity. As such, there is a strong motivation to find techniques to reduce PAPR. Partial Transmit Sequence (PTS) is an attractive scheme for this purpose. Judicious partitioning the OFDM data frame into disjoint subsets is a pivotal component of any PTS scheme. Out of the existing partitioning techniques, adjacent partitioning is characterized by an attractive trade-off between cost and performance. With an aim of determining effects of length variability of adjacent partitions, we performed an investigation into the performances of a variable length adjacent partitioning (VL-AP) and fixed length adjacent partitioning in comparison with other partitioning schemes such as pseudorandom partitioning. Simulation results with different modulation and partitioning scenarios showed that fixed length adjacent partition had better performance compared to variable length adjacent partitioning. As expected, simulation results showed a slightly better performance of pseudorandom partitioning technique compared to fixed and variable adjacent partitioning schemes. However, as the pseudorandom technique incurs high computational complexities, adjacent partitioning schemes were still seen as favorable candidates for PAPR reduction

  20. Variable length adjacent partitioning for PTS based PAPR reduction of OFDM signal

    Energy Technology Data Exchange (ETDEWEB)

    Ibraheem, Zeyid T.; Rahman, Md. Mijanur; Yaakob, S. N.; Razalli, Mohammad Shahrazel; Kadhim, Rasim A. [School of Computer and Communication Engineering, Universiti Malaysia Perlis, 02600 Arau, Perlis (Malaysia)

    2015-05-15

    Peak-to-Average power ratio (PAPR) is a major drawback in OFDM communication. It leads the power amplifier into nonlinear region operation resulting into loss of data integrity. As such, there is a strong motivation to find techniques to reduce PAPR. Partial Transmit Sequence (PTS) is an attractive scheme for this purpose. Judicious partitioning the OFDM data frame into disjoint subsets is a pivotal component of any PTS scheme. Out of the existing partitioning techniques, adjacent partitioning is characterized by an attractive trade-off between cost and performance. With an aim of determining effects of length variability of adjacent partitions, we performed an investigation into the performances of a variable length adjacent partitioning (VL-AP) and fixed length adjacent partitioning in comparison with other partitioning schemes such as pseudorandom partitioning. Simulation results with different modulation and partitioning scenarios showed that fixed length adjacent partition had better performance compared to variable length adjacent partitioning. As expected, simulation results showed a slightly better performance of pseudorandom partitioning technique compared to fixed and variable adjacent partitioning schemes. However, as the pseudorandom technique incurs high computational complexities, adjacent partitioning schemes were still seen as favorable candidates for PAPR reduction.

  1. Modeling Wood Fibre Length in Black Spruce (Picea mariana (Mill. BSP Based on Ecological Land Classification

    Directory of Open Access Journals (Sweden)

    Elisha Townshend

    2015-09-01

    Full Text Available Effective planning to optimize the forest value chain requires accurate and detailed information about the resource; however, estimates of the distribution of fibre properties on the landscape are largely unavailable prior to harvest. Our objective was to fit a model of the tree-level average fibre length related to ecosite classification and other forest inventory variables depicted at the landscape scale. A series of black spruce increment cores were collected at breast height from trees in nine different ecosite groups within the boreal forest of northeastern Ontario, and processed using standard techniques for maceration and fibre length measurement. Regression tree analysis and random forests were used to fit hierarchical classification models and find the most important predictor variables for the response variable area-weighted mean stem-level fibre length. Ecosite group was the best predictor in the regression tree. Longer mean fibre-length was associated with more productive ecosites that supported faster growth. The explanatory power of the model of fitted data was good; however, random forests simulations indicated poor generalizability. These results suggest the potential to develop localized models linking wood fibre length in black spruce to landscape-level attributes, and improve the sustainability of forest management by identifying ideal locations to harvest wood that has desirable fibre characteristics.

  2. A continuum-based model capturing size effects in polymer bonds

    International Nuclear Information System (INIS)

    Diebels, S; Johlitz, M; Steeb, H; Chatzouridou, A; Batal, J; Possart, W

    2007-01-01

    It is known from applications that the mechanical behaviour of polymer bonds does not only depend on the properties of the polymer itself but also on the substrate. Therefore, the mechanical behaviour, i.e. the stiffness, of a polymer joint becomes thickness dependent. In the present work we describe experiments performed on polymer joints and we develop a continuum-based model which is able to describe the experimentally observed size effects without suggesting the microstructure in detail. The continuum mechanical model is enhanced by a scalar-valued structure parameter which describes all the effects taking place in the boundary layer which arises near the substrate. It is shown that the model parameters can be determined on the basis of simple shear experiments performed on polymer layers of different thickness

  3. Estimation of Length and Order of Polynomial-based Filter Implemented in the Form of Farrow Structure

    Directory of Open Access Journals (Sweden)

    S. Vukotic

    2016-08-01

    Full Text Available Digital polynomial-based interpolation filters implemented using the Farrow structure are used in Digital Signal Processing (DSP to calculate the signal between its discrete samples. The two basic design parameters for these filters are number of polynomial-segments defining the finite length of impulse response, and order of polynomials in each polynomial segment. The complexity of the implementation structure and the frequency domain performance depend on these two parameters. This contribution presents estimation formulae for length and polynomial order of polynomial-based filters for various types of requirements including attenuation in stopband, width of transitions band, deviation in passband, weighting in passband/stopband.

  4. Study on bisbenzocyclobutene bonding for the development of a Si-based miniaturized reformer of fuel cell systems

    International Nuclear Information System (INIS)

    Choi, Dae-Hyun; Yeo, Chan-Hyeok; Ok, Chi-Won; Im, Yeon-Ho; Kim, Jean-Tae; Kim, Jong-Seok; Kwon, Yongchai

    2009-01-01

    This paper reports the results of a systematic study of bisbenzocyclobutene (BCB) bonding for a Si-based miniaturized reformer system. The micro reformer system, which included microchannels with a depth and a width of 250 µm and 600 µm, respectively, was fabricated using conventional semiconductor processing and BCB bonding. The structural, thermo-mechanical and chemical stability of Pyrex to Si wafer bonding using BCB as an adhesive was examined at temperatures up to 350 °C. The BCB interfaces at the Pyrex to Si wafer bonding pairs were mechanically stable to withstand the typical pressure and temperature conditions of the reforming process (1 atm and 300 °C) with little outgassing during reforming at 1 atm and 300 °C. The thermo-mechanical and chemical stability during wafer bonding and during reforming was examined using an optical inspection, and pressure pop-up test, FTIR test and gas chromatograph (GC) test were performed. The results showed that Pyrex to Si wafer bonding using BCB is suitable for a miniaturized reformer in fuel systems

  5. Effect of Electroless Ni–P Plating on the Bonding Strength of Bi–Te-Based Thermoelectric Modules

    Directory of Open Access Journals (Sweden)

    Kim S.S.

    2017-06-01

    Full Text Available In the present study, electroless Ni–P plating was applied to Bi–Te-based thermoelectric materials as a barrier layer and the effect of the Ni–P plating on the bonding strength of the thermoelectric module was investigated. The bonding strength of the n- and p-type modules increased after being subjected to the electroless Ni–P plating treatment. In the case of the thermoelectric module that was not subjected to electroless Ni–P plating, Sn and Te were interdiffused and formed a brittle Sn–Te-based metallic compound. The shearing mostly occurred on the bonding interface where such an intermetallic compound was formed. On the other hands, it was found from the FE-EPMA analysis of the bonding interface of thermoelectric module subjected to electroless Ni-P plating that the electroless Ni-P plating acted as an anti-diffusion layer, preventing the interdiffusion of Sn and Te. Therefore, by forming such an anti-diffusion layer on the surface of the Bi–Te based thermoelectric element, the bonding strength of the thermoelectric module could be increased.

  6. The Influence of No-Primer Adhesives and Anchor Pylons Bracket Bases on Shear Bond Strength of Orthodontic Brackets

    Directory of Open Access Journals (Sweden)

    Andrea Scribante

    2013-01-01

    Full Text Available Objective. The aim of this study was to compare the shear bond strength (SBS and adhesive remnant index (ARI scores of no-primer adhesives tested with two different bracket bases. Materials and Methods. 120 bovine permanent mandibular incisors were divided into 6 groups of 20 specimens. Two brackets (ODP with different bracket bases (anchor pylons and 80-gauge mesh were bonded to the teeth using a conventional adhesive (Transbond XT and two different no-primer adhesive (Ortho Cem; Heliosit systems. Groups were tested using an instron universal testing machine. SBS values were recorded. ARI scores were measured. SEM microphotographs were taken to evaluate the pattern of bracket bases. Statistical analysis was performed. ANOVA and Tukey tests were carried out for SBS values, whereas a chi-squared test was applied for ARI scores. Results. Highest bond strength values were reported with Transbond XT (with both pad designs, Ortho Cem bonded on anchor pylons and Heliosit on 80-gauge mesh. A higher frequency of ARI score of “3” was reported for Transbond XT groups. Other groups showed a higher frequency of ARI score “2” and “1.” Conclusion. Transbond XT showed the highest shear bond strength values with both pad designs.

  7. ASSESSMENT OF GESTATIONAL AGE BASED ON ULTRASONIC FEMUR LENGTH OF FETUS

    Directory of Open Access Journals (Sweden)

    M. Honarvar

    1999-08-01

    Full Text Available The ultrasonic measurement of the fetal femur length is a sensitive and precise variable for estimation of fetal growth and development. Tlte objective of this study was to predict gestational age in fetuses older ttian twenty-four weeks of gestation by ultrasonic measurement of the femur length. In this study, pregnant mothers were identified by the criteria of normality, such as well-known LMP, regular menstrual cycles, no use of oral contraceptive pills for the prior 3 months, no smoking, no history of diabetes. The relation between gestational age and fetal femur length was determined by cross-sectional analysis of 900 normal fetuses (> 25 weeks using real -time ultrasonography. Mathematical modeling of the data demonstrated that the femur growth curve is always linear beyond 24 weeks of gestation. Tlte following regression equation was derived : GA (week = 5.2 FL (cm + 2, SD ±5 days (Honarvar's Formula 2. According to this data, the error in estimation of GA for given FL is less tlian 6 days. Tiiis equation appears to be clinically reliable and easy to use. Previous normal ultrasonic fetal femur length curves for otlicr populations may underestimate or overestimate normal fetal age for Iranian population.

  8. Comparison of shear bond strength and microleakage of Scotchbond multi-purpose (MP adhesive system and an experimental dentin bonding agent based on standard of ISOTR 11405

    Directory of Open Access Journals (Sweden)

    Jafarzadeh Kashi T.

    2009-12-01

    Full Text Available "nBackground and Aim: Evaluation of shear bond strength and microleakage of bonding agents is important as these properties play main roles in adhesion of composite to dental tissues. Microleakage results in bacterial penetration into dentin tubules and enamel surfaces and causes sensitivity and recurrent caries followed by destruction of composite filling. Insufficient shear bond strength results in early failure of filling in low masticatory forces. The main goal of this study was to compare the microleakage and shear bond strength of an experimental adhesive and Scotchbond multi-purpose (MP adhesive system."nMaterials and Methods: In this experimental study, sixty extracted caries free human molar teeth were randomly assigned into 4 groups of 15 each for shear bond strength. Variables were bonding agents, enamel and dentin. Twenty teeth assigned into 2 groups of 10 each were used for valuation of the microleakage. Microleakage and shear bond strength were performed according to ISO TR 11405. All data were analyzed with parametric and non-parametric tests according to their normality distribution. Also, Weibull distribution performed on data."nResults: Data obtained from both microleakage and shear bond strength tests showed no significant difference between the experimental bonding and Scotchbond MP bonding (P>0.05. Furthermore, there was no significant difference between the microleakage of occlusal and gingival parts of both bondings (P>0.05."nConclusion: Experimental adhesive bonding showed acceptable results regarding microleakage and shear bond strength. It may be concluded that the experimental dentin bonding had a comparable performance quality with that of commercial system.

  9. Shear Bond Strength of Porcelain to a Base-Metal Compared to Zirconia Core

    Directory of Open Access Journals (Sweden)

    Abrisham SM

    2017-03-01

    Full Text Available Statement of Problem: Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures. Objectives: The purpose of this study was to compare the shear bond strength (SBS of porcelain in the porcelain fused to metal and all-ceramic crowns with Zirconia core. Materials and Methods: Two groups were selected: porcelain fused to metal (PFM and porcelain fused to Zirconia (PFZ (n = 30.In the PFM group, a wax model (10 × 10 × 10mmwas used to cast metal base (Ni_Cr alloy. In the PFZ group, an acrylic cubic model (10 × 10 × 10mm was made as Zirconia model for scanning.15 cubic Zirconia samples were milled by CAD-CAM. The procedure of porcelain veneering was conducted by the conventional layering technique up to 2 mm thickness (2.5 × 2.5 × 2 mm. All specimens were stored in water for 48 hrs. Thermal cycling was conducted for 20000 cycles between 55°C and 5ºC alternatively for 30s.All samples were mounted in acrylic resin and the SBS test was performed, using a universal testing machine. The analysis of data was performed at a significance level of 0.05 using Kolmogorov-Smirnov and Mann-Whitney U-test. Results: Mean of SBS in PFM and PFZ was 24.57 and 20.88, respectively. The results of Mann-Whitney test showed that there was no statistically significant difference between the two groups of porcelain fused to metal and Zirconia in item shear bond strength (p = 0.455. Conclusions: There was no significant difference between the two groups of PFM and PFZ in the item SBS.

  10. Shear Bond Strength of Porcelain to a Base-Metal Compared to Zirconia Core.

    Science.gov (United States)

    Abrisham, S M; Fallah Tafti, A; Kheirkhah, S; Tavakkoli, M A

    2017-03-01

    Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures. The purpose of this study was to compare the shear bond strength (SBS) of porcelain in the porcelain fused to metal and all-ceramic crowns with Zirconia core. Two groups were selected: porcelain fused to metal (PFM) and porcelain fused to Zirconia (PFZ) (n = 30).In the PFM group, a wax model (10 × 10 × 10mm)was used to cast metal base (Ni_Cr alloy). In the PFZ group, an acrylic cubic model (10 × 10 × 10mm) was made as Zirconia model for scanning.15 cubic Zirconia samples were milled by CAD-CAM. The procedure of porcelain veneering was conducted by the conventional layering technique up to 2 mm thickness (2.5 × 2.5 × 2 mm). All specimens were stored in water for 48 hrs. Thermal cycling was conducted for 20000 cycles between 55°C and 5ºC alternatively for 30s.All samples were mounted in acrylic resin and the SBS test was performed, using a universal testing machine. The analysis of data was performed at a significance level of 0.05 using Kolmogorov-Smirnov and Mann-Whitney U-test. Mean of SBS in PFM and PFZ was 24.57 and 20.88, respectively. The results of Mann-Whitney test showed that there was no statistically significant difference between the two groups of porcelain fused to metal and Zirconia in item shear bond strength ( p = 0.455). There was no significant difference between the two groups of PFM and PFZ in the item SBS.

  11. Effect of amine counterion type on the retention of basic compounds on octadecyl silane bonded silica-based and polybutadiene-coated zirconia phases.

    Science.gov (United States)

    Yang, Xiqin; Dai, Jun; Carr, Peter W

    2003-07-01

    In a previous paper, we compared the mixed-mode retention characteristics of cationic solutes on octadecyl silane-bonded silica (ODS) and polybutadiene-coated zirconia (PBD-ZrO2) phases. It is well recognized that both reversed-phase and ion-exchange interactions contribute to the retention of cations on ODS phases. The reversed-phase interaction results from the bonded hydrocarbon chain; the ion-exchange interaction originates in the ionized residual silanol groups. These two types of interactions also exist on the PBD-ZrO2 phase. The polybutadiene contributes to the reversed-phase interaction and the ionized zirconol, but primarily, the adsorbed Lewis base anions, such as phosphate or fluoride, contribute to the ion-exchange interaction. We have shown that on ODS phases, reversed-phase interactions are much more important, whereas the opposite is true of PBD-ZrO2 phases. In this work, we investigate the effect of several amine mobile phase counterions on the retention of cationic solutes on ODS and PBD-ZrO2 phases. The effects of the chain length and the type of amine (1 degree, 2 degrees, 3 degrees) counterion on the retention of basic compounds were studied. In contrast to older studies of type A silica-based phases, the results show that the chain length and type of the amine blocker do not have a large effect on the retention of basic compounds with the newer type B silica-based materials. However, on the PBD-ZrO2 phase, very striking differences in retention were observed with different amine counterions. We show that the molecular geometry of the amine counterion has a significant effect on the retention of basic solutes on the PBD-ZrO2 phase.

  12. Is group singing special? Health, well-being and social bonds in community-based adult education classes.

    Science.gov (United States)

    Pearce, Eiluned; Launay, Jacques; Machin, Anna; Dunbar, Robin I M

    Evidence demonstrates that group singing improves health and well-being, but the precise mechanisms remain unknown. Given that cohesive social networks also positively influence health, we focus on the social aspects of singing, exploring whether improvements in health and well-being are mediated by stronger social bonds, both to the group as a whole (collective-bonding) and to individual classmates (relational-bonding). To do so, seven newly-formed community-based adult education classes (four singing, N =84, and three comparison classes studying creative writing or crafts, N =51) were followed over seven months. Self-report questionnaire data on mental and physical health, well-being, and social bonding were collected at Months 1, 3 and 7. We demonstrate that physical and mental health and satisfaction with life significantly improved over time in both conditions. Path analysis did not show any indirect effects via social bonding of Condition on health and well-being. However, higher collective-bonding at timepoint 3 significantly predicted increased flourishing, reduced anxiety and improved physical health independently of baseline levels. In contrast, relational-bonding showed no such effects, suggesting that it is feeling part of a group that particularly yields health and well-being benefits. Moreover, these results indicate that singing may not improve health and well-being more than other types of activities. Nonetheless, these findings encourage further work to refine our understanding of the social aspects of community-based adult education classes in promoting health, well-being and community cohesion.

  13. Sliding Mode Control of Cable-Driven Redundancy Parallel Robot with 6 DOF Based on Cable-Length Sensor Feedback

    Directory of Open Access Journals (Sweden)

    Wei Lv

    2017-01-01

    Full Text Available The sliding mode control of the cable-driven redundancy parallel robot with six degrees of freedom is studied based on the cable-length sensor feedback. Under the control scheme of task space coordinates, the cable length obtained by the cable-length sensor is used to solve the forward kinematics of the cable-driven redundancy parallel robot in real-time, which is treated as the feedback for the control system. First, the method of forward kinematics of the cable-driven redundancy parallel robot is proposed based on the tetrahedron method and Levenberg-Marquardt method. Then, an iterative initial value estimation method for the Levenberg-Marquardt method is proposed. Second, the sliding mode control method based on the exponential approach law is used to control the effector of the robot, and the influence of the sliding mode parameters on control performance is simulated. Finally, a six-degree-of-freedom position tracking experiment is carried out on the principle prototype of the cable-driven redundancy parallel robot. The experimental results show that the robot can accurately track the desired position in six directions, which indicates that the control method based on the cable-length sensor feedback for the cable-driven redundancy parallel robot is effective and feasible.

  14. Comparison of bond strength of auto polymerizing, heat cure soft denture liners with denture base resin — An In Vitro study

    OpenAIRE

    Mahajan, Neerja; Datta, Kusum

    2010-01-01

    Optimum bond strength between denture soft liner and denture base resin is very important for the success of any denture prosthesis. The tensile bond strength of two commercially available silicone-based heat cured (Molloplast B) and auto polymerizing (Mollosil) was compared with denture base material (trevalon). Molloplast B-trevalon bond in both un-polymerized (dough stage) and already polymerized forms were also compared. Lloyds Universal testing machine was used to test 60 samples. Mollop...

  15. Comparison of Micro-Shear Bond Strength between Silorane-Based Composite and Conventional Methacrylate-Based Composite to the Dentin of Primary Teeth

    Directory of Open Access Journals (Sweden)

    Maryam Sharifi

    2017-12-01

    Full Text Available Introduction: Bond strength between the restorative material and tooth structure is one of the major factors in the selection of restorative materials, which plays a key role in durable restoration and reducing microleakage. Considering the recent attention of researchers to low-shrinkage composites, the present study aimed to compare the micro-shear bond strength of silorane-based composite (P90 with the conventional methacrylate-based composite (Z250 to the dentin of primary teeth. Materials and Methods: In this experimental study, 24 intact primary canines were selected. Two disks (thickness: 2 mm were prepared from each tooth, and the samples were randomly divided into four groups (n=12. Composite resin cylinders (r=0.7 were adapted on each dentin surface, as follows: g1: (silorane bond system + P90, g2: (etch + silorane bond system + P90, g3: (single bond + Z250, g4: (etch + single bond + Z250. Afterwards, the samples were subjected to a micro-shear bond strength test until failure. Data analysis was performed using Tamhane’s T2 (P

  16. Effect of silica coating and silane surface treatment on the bond strength of soft denture liner to denture base material.

    Science.gov (United States)

    Atsü, Saadet; Keskın, Yasemin

    2013-01-01

    This study investigated the effects of different surface treatments on the tensile bond strength of an autopolymerizing silicone denture liner to a denture base material after thermocycling. Fifty rectangular heat-polymerized acrylic resin (QC-20) specimens consisting of a set of 2 acrylic blocks were used in the tensile test. Specimens were divided into 5 test groups (n=10) according to the bonding surface treatment as follows: Group A, adhesive treatment (Ufi Gel P adhesive) (control); Group S, sandblasting using 50-µm Al2O3; Group SCSIL, silica coating using 30-µm Al2O3 modified by silica and silanized with silane agent (CoJet System); Group SCA, silica coating and adhesive application; Group SCSILA, silica coating, silane and adhesive treatment. The 2 PMMA blocks were placed into molds and the soft lining materials (Ufi Gel P) were packed into the space and polymerized. All specimens were thermocycled (5,000 cycles) before the tensile test. Bond strength data were analyzed using 1-way ANOVA and Duncan tests. Fracture surfaces were observed by scanning electron microscopy. X-ray photoelectron spectrometer (XPS) and Fourier Transform Infrared spectrometer (FTIR) analysis were used for the chemical analysis and a profilometer was used for the roughness of the sample surfaces. The highest bond strength test value was observed for Group A (1.35±0.13); the lowest value was for Group S (0.28±0.07) and Group SCSIL (0.34±0.03). Mixed and cohesive type failures were seen in Group A, SCA and SCSILA. Group S and SCSIL showed the least silicone integrations and the roughest surfaces. Sandblasting, silica coating and silane surface treatments of the denture base resin did not increase the bond strength of the silicone based soft liner. However, in this study, the chemical analysis and surface profilometer provided interesting insights about the bonding mechanism between the denture base resin and silicone soft liner.

  17. Effect of Bracket Base Sandblasting on Bonding of Orthodontic Brackets on Enamel Surface

    Directory of Open Access Journals (Sweden)

    Mohammad Farahani

    2016-01-01

    Full Text Available Introduction: In evaluating bond failure, considerable attention has been paid to the various factors that affect bond strength. The bracket–resin interface is the site of usual bond failure. Therefore, many efforts have been accomplished on this interface. The aim of this study was to compare the effects of sandblasting on shear bond strength of three different metal brackets. Materials and Methods: For this experimental study, 180 human maxillary first and second premolars teeth were cleaned and stored in 0.1% thymol solution. The teeth were randomly assigned to either the control (n = 90 or experimental group (n = 90. Each group was subdivided into three equal groups (n = 30. In the control group, three different non-sandblasted metal brackets (American Orthodontics, Dentarum, and 3M Unitek were bonded with 3M (Unitek no-mix resin. In the next stage of the experiment, similar brackets were sandblasted and bonded. All samples were pumiced and etched with 37% phosphoric acid for 15 s. The teeth were embedded in blocks of autopolymerization polymethyl methacrylate, utilizing a special device to make their slots parallel to the horizontal. Samples were stored in distilled water for 24 h before testing. Shear bond testing was carried out with UTM Instron machine. Results: Mean shear bond strength of untreated groups was 15.51, 16.60, and 18.58 MPa for American Orthodontics, Dentarum, and 3M Unitek brackets, respectively. Mean shear bond strength of sandblasted brackets was 15.8, 19.36, and 18.66 for American Orthodontics, Dentarum, and 3M Unitek brackets, respectively. Conclusion: This study showed that there was a significant difference in the mean shear bond strength between untreated and sandblasted specimens only in the Dentarum bracket groups.

  18. ESTIMATION OF BURSTS LENGTH AND DESIGN OF A FIBER DELAY LINE BASED OBS ROUTER

    Directory of Open Access Journals (Sweden)

    RICHA AWASTHI

    2017-03-01

    Full Text Available The demand for higher bandwidth is increasing day by day and this ever growing demand cannot be catered to with current electronic technology. Thus new communication technology like optical communication needs to be used. In the similar context OBS (optical burst switching is considered as next generation data transfer technology. In OBS information is transmitted in forms of optical bursts of variable lengths. However, contention among the bursts is a major problem in OBS system, and for contention resolution defection routing is mostly preferred. However, deflection routing increases delay. In this paper, it is shown that the arrival of very large bursts is rare event, and for moderate burst length the buffering of contending burst can provide very effective solution. However, in case of arrival of large bursts deflection can be used.

  19. Length-based assessment of coral reef fish populations in the main and northwestern Hawaiian islands.

    Directory of Open Access Journals (Sweden)

    Marc O Nadon

    Full Text Available The coral reef fish community of Hawaii is composed of hundreds of species, supports a multimillion dollar fishing and tourism industry, and is of great cultural importance to the local population. However, a major stock assessment of Hawaiian coral reef fish populations has not yet been conducted. Here we used the robust indicator variable "average length in the exploited phase of the population ([Formula: see text]", estimated from size composition data from commercial fisheries trip reports and fishery-independent diver surveys, to evaluate exploitation rates for 19 Hawaiian reef fishes. By and large, the average lengths obtained from diver surveys agreed well with those from commercial data. We used the estimated exploitation rates coupled with life history parameters synthesized from the literature to parameterize a numerical population model and generate stock sustainability metrics such as spawning potential ratios (SPR. We found good agreement between predicted average lengths in an unfished population (from our population model and those observed from diver surveys in the largely unexploited Northwestern Hawaiian Islands. Of 19 exploited reef fish species assessed in the main Hawaiian Islands, 9 had SPRs close to or below the 30% overfishing threshold. In general, longer-lived species such as surgeonfishes, the redlip parrotfish (Scarus rubroviolaceus, and the gray snapper (Aprion virescens had the lowest SPRs, while short-lived species such as goatfishes and jacks, as well as two invasive species (Lutjanus kasmira and Cephalopholis argus, had SPRs above the 30% threshold.

  20. Length-based assessment of coral reef fish populations in the main and northwestern Hawaiian islands.

    Science.gov (United States)

    Nadon, Marc O; Ault, Jerald S; Williams, Ivor D; Smith, Steven G; DiNardo, Gerard T

    2015-01-01

    The coral reef fish community of Hawaii is composed of hundreds of species, supports a multimillion dollar fishing and tourism industry, and is of great cultural importance to the local population. However, a major stock assessment of Hawaiian coral reef fish populations has not yet been conducted. Here we used the robust indicator variable "average length in the exploited phase of the population ([Formula: see text])", estimated from size composition data from commercial fisheries trip reports and fishery-independent diver surveys, to evaluate exploitation rates for 19 Hawaiian reef fishes. By and large, the average lengths obtained from diver surveys agreed well with those from commercial data. We used the estimated exploitation rates coupled with life history parameters synthesized from the literature to parameterize a numerical population model and generate stock sustainability metrics such as spawning potential ratios (SPR). We found good agreement between predicted average lengths in an unfished population (from our population model) and those observed from diver surveys in the largely unexploited Northwestern Hawaiian Islands. Of 19 exploited reef fish species assessed in the main Hawaiian Islands, 9 had SPRs close to or below the 30% overfishing threshold. In general, longer-lived species such as surgeonfishes, the redlip parrotfish (Scarus rubroviolaceus), and the gray snapper (Aprion virescens) had the lowest SPRs, while short-lived species such as goatfishes and jacks, as well as two invasive species (Lutjanus kasmira and Cephalopholis argus), had SPRs above the 30% threshold.

  1. System simulation method for fiber-based homodyne multiple target interferometers using short coherence length laser sources

    Science.gov (United States)

    Fox, Maik; Beuth, Thorsten; Streck, Andreas; Stork, Wilhelm

    2015-09-01

    Homodyne laser interferometers for velocimetry are well-known optical systems used in many applications. While the detector power output signal of such a system, using a long coherence length laser and a single target, is easily modelled using the Doppler shift, scenarios with a short coherence length source, e.g. an unstabilized semiconductor laser, and multiple weak targets demand a more elaborated approach for simulation. Especially when using fiber components, the actual setup is an important factor for system performance as effects like return losses and multiple way propagation have to be taken into account. If the power received from the targets is in the same region as stray light created in the fiber setup, a complete system simulation becomes a necessity. In previous work, a phasor based signal simulation approach for interferometers based on short coherence length laser sources has been evaluated. To facilitate the use of the signal simulation, a fiber component ray tracer has since been developed that allows the creation of input files for the signal simulation environment. The software uses object oriented MATLAB code, simplifying the entry of different fiber setups and the extension of the ray tracer. Thus, a seamless way from a system description based on arbitrarily interconnected fiber components to a signal simulation for different target scenarios has been established. The ray tracer and signal simulation are being used for the evaluation of interferometer concepts incorporating delay lines to compensate for short coherence length.

  2. Assessment Of Possible Cycle Lengths For Fully-Ceramic Micro-Encapsulated Fuel-Based Light Water Reactor Concepts

    International Nuclear Information System (INIS)

    Sen, R. Sonat; Pope, Michael A.; Ougouag, Abderrafi M.; Pasamehmetoglu, Kemal; Venneri, Francesco

    2012-01-01

    The use of TRISO-particle-based dispersion fuel within SiC matrix and cladding materials has the potential to allow the design of extremely safe LWRs with failure-proof fuel. This paper examines the feasibility of LWR-like cycle length for such a low enriched uranium fuel with the imposed constraint of strictly retaining the original geometry of the fuel pins and assemblies. The motivation for retaining the original geometry is to provide the ability to incorporate the fuel 'as-is' into existing LWRs while retaining their thermal-hydraulic characteristics. The feasibility of using this fuel is assessed by looking at cycle lengths and fuel failure rates. Other considerations (e.g., safety parameters, etc.) were not considered at this stage of the study. The study includes the examination of different TRISO kernel diameters without changing the coating layer thicknesses. The study shows that a naive use of UO 2 results in cycle lengths too short to be practical for existing LWR designs and operational demands. Increasing fissile inventory within the fuel compacts shows that acceptable cycle lengths can be achieved. In this study, starting with the recognized highest packing fraction practically achievable (44%), higher enrichment, larger fuel kernel sizes, and the use of higher density fuels have been evaluated. The models demonstrate cycle lengths comparable to those of ordinary LWRs. As expected, TRISO particles with extremely large kernels are shown to fail under all considered scenarios. In contrast, the designs that do not depart too drastically from those of the nominal NGNP HTR fuel TRISO particles are shown to perform satisfactorily and display a high rates of survival under all considered scenarios. Finally, it is recognized that relaxing the geometry constraint will result in satisfactory cycle lengths even using UO 2 -loaded TRISO particles-based fuel with enrichment at or below 20 w/o.

  3. Retention Strength of PMMA/UDMA-Based Crowns Bonded to Dentin: Impact of Different Coupling Agents for Pretreatment

    Directory of Open Access Journals (Sweden)

    Bogna Stawarczyk

    2015-11-01

    Full Text Available Computer aided design/computer aided manufacturing (CAD/CAM polymers for long-term dental restorations benefit from enhanced mechanical properties. However, the quantification of their bonding properties on teeth is lacking. Therefore, the aim of this study was to determine the retention strength (RS of differently pretreated new developed polymethylmethacrylate/ urethanedimethacrylate-based CAD/CAM polymer bonded on dentin. In summary, 120 human caries-free molars were prepared, and polymeric crowns were milled and pretreated (n = 20: visio.link (VL, Scotchbond Universal (SU, Monobond Plus/Heliobond (MH, Margin Bond (MB, Margin Bond mixed with acetone (1:1 (MBA or not pretreated (CG. Half of the specimens were cemented using Variolink II and the other half with RelyX Ultimate. Specimens were stored for 24 h in distilled water and thermal cycled (5000 ×, 5 °C/55 °C. The retention load was measured and failure types were defined. RS was calculated and analyzed using both two- and one-way ANOVA with a post-hoc Scheffé-test, unpaired t-test, Kaplan–Meier with Breslow–Gehan test and chi-squared test (p < 0.05. Crowns bonded using RelyX Ultimate showed higher RS than those bonded using Variolink II. The pretreatment showed no impact on the RS. However, survival analysis within Variolink II found an impact of pretreatment. The median RS for MH was the lowest and statistically different from MB, MBA and CG. For Variolink II MH had the poorest survival as the estimated cumulative failure function of the debonded crown increased very quickly with increasing TBS. Within the RelyX Ultimate groups, no significant differences were determined. The newly developed CAD/CAM polymer showed the highest bonding properties after cementation using RelyX Ultimate.

  4. Structural and medium effects on the reactions of the cumyloxyl radical with intramolecular hydrogen bonded phenols. The interplay between hydrogen-bonding and acid-base interactions on the hydrogen atom transfer reactivity and selectivity.

    Science.gov (United States)

    Salamone, Michela; Amorati, Riccardo; Menichetti, Stefano; Viglianisi, Caterina; Bietti, Massimo

    2014-07-03

    A time-resolved kinetic study on the reactions of the cumyloxyl radical (CumO(•)) with intramolecularly hydrogen bonded 2-(1-piperidinylmethyl)phenol (1) and 4-methoxy-2-(1-piperidinylmethyl)phenol (2) and with 4-methoxy-3-(1-piperidinylmethyl)phenol (3) has been carried out. In acetonitrile, intramolecular hydrogen bonding protects the phenolic O-H of 1 and 2 from attack by CumO(•) and hydrogen atom transfer (HAT) exclusively occurs from the C-H bonds that are α to the piperidine nitrogen (α-C-H bonds). With 3 HAT from both the phenolic O-H and the α-C-H bonds is observed. In the presence of TFA or Mg(ClO4)2, protonation or Mg(2+) complexation of the piperidine nitrogen removes the intramolecular hydrogen bond in 1 and 2 and strongly deactivates the α-C-H bonds of the three substrates. Under these conditions, HAT to CumO(•) exclusively occurs from the phenolic O-H group of 1-3. These results clearly show that in these systems the interplay between intramolecular hydrogen bonding and Brønsted and Lewis acid-base interactions can drastically influence both the HAT reactivity and selectivity. The possible implications of these findings are discussed in the framework of the important role played by tyrosyl radicals in biological systems.

  5. Comparative Evaluation of Tensile Bond Strength between Silicon Soft Liners and Processed Denture Base Resin Conditioned by Three Modes of Surface Treatment: An Invitro Study.

    Science.gov (United States)

    Surapaneni, Hemchand; Ariga, Padma; Haribabu, R; Ravi Shankar, Y; Kumar, V H C; Attili, Sirisha

    2013-09-01

    Soft denture liners act as a cushion for the denture bearing mucosa through even distribution of functional load, avoiding local stress concentrations and improving retention of dentures there by providing comfort to the patient. The objective of the present study was to compare and evaluate the tensile bond strengths of silicone-based soft lining materials (Ufi Gel P and GC Reline soft) with different surface pre treatments of heat cure PMMA denture base acrylic resin. Stainless steel dies measuring 40 mm in length; 10 mm in width and 10 mm in height (40 × 10 × 10) were machined to prepare standardized for the polymethyl methacrylate resin blocks. Stainless steel dies (spacer for resilient liner) measuring 3 mm thick; 10 mm long and 10 mm wide were prepared as spacers to ensure uniformity of the soft liner being tested. Two types of Addition silicone-based soft lining materials (room temperature polymerised soft lining materials (RTPSLM): Ufi Gel P and GC Reline soft) were selected. Ufi Gel P (VOCO, Germany), GC Reline soft (GC America) are resilient, chairside vinyl polysiloxane denture reliners of two different manufacturers. A total of 80 test samples were prepared of which 40 specimens were prepared for Group A (Ufi Gel P) and 40 specimens for Group B (GC Reline soft). In these groups, based on Pre-treatment of acrylic resin specimens each group was subdivided into four sub groups of 10 samples each. Sub-group I-without any surface treatment. Sub-group II-sand blasted Sub-group III-treated with Methyl Methacrylate monomer Sub-group IV-treated with chemical etchant Acetone. The results were statistically analysed by Kruscal Wallis test, Mann-Whitney U test, and Independent t test. The specimens treated with MMA monomer wetting showed superior and significant bond strength than those obtained by other surface treatments. The samples belonging to subgroups of GC Reline soft exhibit superior tensile bond strength than subgroups of Ufi Gel P. The modes

  6. Development of a thin film vitreous bond based composite ceramic coating for corrosion and abrasion services

    International Nuclear Information System (INIS)

    Franke, B.

    2003-01-01

    IPC has been involved with the Alberta Research Council in developing a vitreous bond (VB) - based composite ceramic fluoropolymer coating technology. Compared to the present state of the art which is based on a hard discontinuous phase (ceramic particles) suspended in a soft continuous matrix (fluoropolymer mix) the novelty of our approach consists of designing a composite system in which both the ceramic and the fluoropolymer phases are continuous. The ceramic matrix will provide the strength and the erosion resistance for the fluoropolymer matrix even at high temperatures. The ceramic formulation employed is not affected by temperatures up to 500 o F while the fluoropolymer matrix provides a corrosion protection seal for the ceramic matrix. The inherent flexibility of the polymer matrix will protect against brittle fractures that may develop by handling or impact. Therefore the composite coating is able to withstand the deformation of the substrate without chipping or disbanding. The fluoropolymer matrix also provides dry lubrication properties further enhancing the erosion resistance of the ceramic phase. The thickness of the coating is very thin, in the 25 to 100 micron range. In summary, the coating technology is able to provide the following features: Corrosion protection levels similar to those of fluoropolymer coatings; Erosion resistance similar to that of ceramic coatings; Price comparable to that of polymer coatings; Exceptional wear resistance properties; and Capability for coating complicated shapes internally or externally or both. This paper will discuss the theory and development of this new technology and the resultant coating and potential properties. (author)

  7. Chemical composition, crystal structure, and their relationships with the intrinsic properties of spinel-type crystals based on bond valences.

    Science.gov (United States)

    Liu, Xiao; Wang, Hao; Lavina, Barbara; Tu, Bingtian; Wang, Weimin; Fu, Zhengyi

    2014-06-16

    Spinel-type crystals may possess complex and versatile chemical composition and crystal structure, which leads to difficulty in constructing relationships among the chemical composition, crystal structure, and intrinsic properties. In this work, we develop new empirical methods based on bond valences to estimate the intrinsic properties, namely, compressibility and thermal expansion of complex spinel-type crystals. The composition-weighted average of bond force constants in tetrahedral and octahedral coordination polyhedra is derived as a function of the composition-weighted average of bond valences, which can be calculated according to the experimental chemical composition and crystal structural parameters. We discuss the coupled effects of tetrahedral and octahedral frameworks on the aforementioned intrinsic properties. The bulk modulus could be quantitatively calculated from the composition-weighted average of bond force constants in tetrahedral and octahedral coordination polyhedra. In contrast, a quantitative estimation of the thermal expansion coefficient could be obtained from the composition-weighted average of bond force constants in octahedral coordination polyhedra. These empirical methods have been validated by the results obtained for a new complex quaternary spinel-type oxynitride Mg0.268Al2.577O3.733N0.267 as well as MgAl2O4 and Al2.85O3.45N0.55 from the literature. Further, these empirical methods have the potential to be extensively applied in other types of complex crystals.

  8. Effect of fluoride-containing desensitizing agents on the bond strength of resin-based cements to dentin

    Directory of Open Access Journals (Sweden)

    Duygu Saraç

    2009-10-01

    Full Text Available OBJECTIVE: The objective of this study was to evaluate the effect of desensitizing agents containing different amounts of fluoride on the shear bond strength of a dual polymerized resin cement and a resin-modified glass ionomer cement (RMGIC to dentin. MATERIAL AND METHODS: One hundred human molars were mounted in acrylic resin blocks and prepared until the dentin surface was exposed. The specimens were treated with one of four desensitizing agents: Bifluorid 12, Fluoridin, Thermoline and PrepEze. The remaining 20 specimens served as untreated controls. All groups were further divided into 2 subgroups in which a dual polymerized resin cement (Bifix QM or a resin-modified glass ionomer cement (AVANTO was used. The shear bond strength (MPa was measured using a universal testing machine at a 0.5 mm/min crosshead speed. The data were analyzed statistically with a 2-way ANOVA, Tukey HSD test and regression analysis (α=0.05. The effect of the desensitizing agents on the dentin surface was examined by scanning electron microscopy. RESULTS: The fluoride-containing desensitizing agents affected the bond strength of the resin-based cements to dentin (p<0.001. PrepEze showed the highest bond strength values in all groups (p<0.001. CONCLUSION: Regression analysis showed a reverse relation between bond strength values of resin cements to dentin and the amount of fluoride in the desensitizing agent (p<0.05.

  9. COGNAC: a web server for searching and annotating hydrogen-bonded base interactions in RNA three-dimensional structures.

    Science.gov (United States)

    Firdaus-Raih, Mohd; Hamdani, Hazrina Yusof; Nadzirin, Nurul; Ramlan, Effirul Ikhwan; Willett, Peter; Artymiuk, Peter J

    2014-07-01

    Hydrogen bonds are crucial factors that stabilize a complex ribonucleic acid (RNA) molecule's three-dimensional (3D) structure. Minute conformational changes can result in variations in the hydrogen bond interactions in a particular structure. Furthermore, networks of hydrogen bonds, especially those found in tight clusters, may be important elements in structure stabilization or function and can therefore be regarded as potential tertiary motifs. In this paper, we describe a graph theoretical algorithm implemented as a web server that is able to search for unbroken networks of hydrogen-bonded base interactions and thus provide an accounting of such interactions in RNA 3D structures. This server, COGNAC (COnnection tables Graphs for Nucleic ACids), is also able to compare the hydrogen bond networks between two structures and from such annotations enable the mapping of atomic level differences that may have resulted from conformational changes due to mutations or binding events. The COGNAC server can be accessed at http://mfrlab.org/grafss/cognac. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

  10. Excited state intramolecular proton transfer in some tautomeric azo dyes and Schiff bases containing an intramolecular hydrogen bond

    NARCIS (Netherlands)

    Joshi, H.C.; Kamounah, F.S.; Gooijer, C.; van der Zwan, G.; Antonov, L.

    2002-01-01

    Photophysical properties of several basically important aromatic azodyes (1-phenylazo-2-naphthol and 2-phenylazo-1-naphthol) and Schiff bases (N-(2-hydroxy-1-naphthylmethylidene) aniline and N-(1-hydroxy-2-naphthylmethylidene) aniline) all containing an intramolecular hydrogen bond were studied by

  11. PMMA to SU-8 Bonding for Polymer Based Lab-on -a-chip Systems with Integrated Optics

    DEFF Research Database (Denmark)

    Clausen, Bjarne

    2003-01-01

    An adhesive bonding technique for wafer-level sealing of SU-8 based lab-on-a-chip microsystems with integrated optical components is presented. Microfluidic channels and optical components, e.g. waveguides, are fabricated in cross-linked SU-8 and sealed with a Pyrex glass substrate by means...

  12. Synthesis, characterization and single crystal structures of chiral Schiff base and its tetranuclear palladium complex with Pdsbnd Osbnd Pd bridging and Pdsbnd Pd bonds

    Science.gov (United States)

    Rajegowda, H. R.; Kumar, P. Raghavendra; Hosamani, Amar; Butcher, R. J.; Naveen, S.; Lokanath, N. K.

    2018-03-01

    A new chiral Schiff base ligand 2-{N-[(2S)-(1-hydroxy-3-phenylpropan-2-yl]ethanimidoyl} phenol ((S)sbnd H2L) was obtained by acid catalyzed condensation of (2S)-(-)-2-amino-3-phenyl-1-propanol with 2‧-hydroxyacetophenone. The palladium complex was prepared by treating a solution of (S)sbnd H2L in acetone with a solution of Na2PdCl4 in water in 1:1 M ratio. The new ligand and its complex were characterized by FT-IR, 1H, 13C{1H} NMR spectroscopy, polarimetry and elemental analysis and their molecular structures were determined by single crystal X-ray diffraction. Both the compounds crystallizes in monoclinic system in the space group P21. There exists an intra [Osbnd H ⋯N (1.62(5) Å)] and intermolecular [Osbnd H ⋯O (1.53(5) Å) and Csbnd H ⋯O (2.59 Å)] hydrogen bonding and secondary interactions in the crystal of (S)sbnd H2L. The structure of the palladium complex was found very interesting wherein the ligand coordinated to metal center as tridentate dianionic (O-, N, O-) fashion, (S)-L, resulting in a tetranuclear palladium cluster, [Pd4((S)-L)4]. In these supramolecular structures phenolate oxygen coordinated to Pd(II) ion as Pdsbnd O terminal bonds [1.934(12) - 1.977(11) Å] and the alkoxide oxygen coordinated as Pdsbnd Osbnd Pd bridging bonds [1.993(11) - 2.012(12) Å]. The Pdsbnd N bond lengths found were in the range of 1.949(13) to 1.919(12) Å. There exists two asymmetric tetranuclear complex molecules in its crystal lattice. There exists very strong metal-metal bond interaction, Pd(2)sbnd Pd(3) [3.0410(18) Å] and Pd(6)sbnd Pd(7) [3.0517(19) Å] respectively in the two asymmetric units.

  13. Tensile bond strength of silicone-based soft denture liner to two chemically different denture base resins after various surface treatments.

    Science.gov (United States)

    Akin, Hakan; Tugut, Faik; Guney, Umit; Kirmali, Omer; Akar, Turker

    2013-01-01

    This study evaluated the effect of various surface treatments on the tensile bond strength of a silicone-based soft denture liner to two chemically different denture base resins, heat-cured polymethyl methacrylate (PMMA), and light-activated urethane dimethacrylate or Eclipse denture base resin. PMMA test specimens were fabricated and relined with a silicone-based soft denture liner (group AC). Eclipse test specimens were prepared according to the manufacturer's recommendation. Before they were relined with a silicone-based soft denture liner, each received one of three surface treatments: untreated (control, group EC), Eclipse bonding agent applied (group EB), and laser-irradiated (group EL). Tensile bond strength tests (crosshead speed = 5 mm/min) were performed for all specimens, and the results were analyzed using the analysis of variance followed by Tukey's test (p = 0.05). Eclipse denture base and PMMA resins presented similar bond strengths to the silicone-based soft denture liner. The highest mean force was observed in group EL specimens, and the tensile bond strengths in group EL were significantly different (p < 0.05) from those in the other groups.

  14. Amide Proton Transfer Imaging of Diffuse Gliomas: Effect of Saturation Pulse Length in Parallel Transmission-Based Technique.

    Science.gov (United States)

    Togao, Osamu; Hiwatashi, Akio; Keupp, Jochen; Yamashita, Koji; Kikuchi, Kazufumi; Yoshiura, Takashi; Yoneyama, Masami; Kruiskamp, Marijn J; Sagiyama, Koji; Takahashi, Masaya; Honda, Hiroshi

    2016-01-01

    In this study, we evaluated the dependence of saturation pulse length on APT imaging of diffuse gliomas using a parallel transmission-based technique. Twenty-two patients with diffuse gliomas (9 low-grade gliomas, LGGs, and 13 high-grade gliomas, HGGs) were included in the study. APT imaging was conducted at 3T with a 2-channel parallel transmission scheme using three different saturation pulse lengths (0.5 s, 1.0 s, 2.0 s). The 2D fast spin-echo sequence was used for imaging. Z-spectrum was obtained at 25 frequency offsets from -6 to +6 ppm (step 0.5 ppm). A point-by-point B0 correction was performed with a B0 map. Magnetization transfer ratio (MTRasym) and ΔMTRasym (contrast between tumor and normal white matter) at 3.5 ppm were compared among different saturation lengths. A significant increase in MTRasym (3.5 ppm) of HGG was found when the length of saturation pulse became longer (3.09 ± 0.54% at 0.5 s, 3.83 ± 0.67% at 1 s, 4.12 ± 0.97% at 2 s), but MTRasym (3.5 ppm) was not different among the saturation lengths in LGG. ΔMTRasym (3.5 ppm) increased with the length of saturation pulse in both LGG (0.48 ± 0.56% at 0.5 s, 1.28 ± 0.56% at 1 s, 1.88 ± 0.56% at 2 s and HGG (1.72 ± 0.54% at 0.5 s, 2.90 ± 0.49% at 1 s, 3.83 ± 0.88% at 2 s). In both LGG and HGG, APT-weighted contrast was enhanced with the use of longer saturation pulses.

  15. Fabrication of capacitive micromachined ultrasonic transducers based on adhesive wafer bonding technique

    International Nuclear Information System (INIS)

    Li, Zhenhao; Wong, Lawrence L P; Chen, Albert I H; Na, Shuai; Yeow, John T W; Sun, Jame

    2016-01-01

    This paper reports the fabrication process of wafer bonded capacitive micromachined ultrasonic transducers (CMUTs) using photosensitive benzocyclobutene as a polymer adhesive. Compared with direct bonding and anodic bonding, polymer adhesive bonding provides good tolerance to wafer surface defects and contamination. In addition, the low process temperature of 250 °C is compatible with standard CMOS processes. Single-element CMUTs consisting of cells with a diameter of 46 µ m and a cavity depth of 323 nm were fabricated. In-air and immersion acoustic characterizations were performed on the fabricated CMUTs, demonstrating their capability for transmitting and receiving ultrasound signals. An in-air resonance frequency of 5.47 MHz was measured by a vibrometer under a bias voltage of 300 V. (paper)

  16. Bond Strength Mechanism of Fly Ash Based Geopolymer Mortars: A Review

    Science.gov (United States)

    Zailani, W. W. A.; Abdullah, M. M. A. B.; Razak, R. A.; Zainol, M. R. R. M. A.; Tahir, M. F. M.

    2017-11-01

    Geopolymer possess many excellent properties such as high compressive and bond strength, long term durability, better acid resistance and also known as a “Sustainable Material” due to its low carbon emission and low energy consumption. Thus, it is a good opportunity to develop and explore not only for cement and concrete but also as geopolymeric repair materials. This reviews showed that good bonding properties between geopolymeric repair material and concrete substrate is important in order to acquire an enhanced resistance against penetration of harmful substances and avoiding respalling of the repair material by understanding the bonding behaviour. Bond strength depends to the properties of the repair materials itself and also the surface preparations of concrete substrate.

  17. Retentive Shear Strengths of Various Bonding Attachment Bases: An in vitro Study

    Directory of Open Access Journals (Sweden)

    Abhishek Goyal

    2013-01-01

    Conclusion: Gemini brackets provided the best bond strengths clinically, followed by Mini Diagonali, Nu-Edge, Mini Twin, Mini Diamond and the Sapphire brackets in decreasing order as measured using the Weibull analysis.

  18. Effect of surface treatments on the bond strength of soft denture lining materials to an acrylic resin denture base.

    Science.gov (United States)

    Gundogdu, Mustafa; Yesil Duymus, Zeynep; Alkurt, Murat

    2014-10-01

    Adhesive failure between acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to evaluate the effect of different surface treatments on the bond strength of 2 different resilient lining materials to an acrylic resin denture base. Ninety-six dumbbell-shaped specimens were fabricated from heat-polymerized acrylic resin, and 3 mm of the material was cut from the thin midsection. The specimens were divided into 6 groups according to their surface treatments: no surface treatment (control group), 36% phosphoric acid etching (acid group), erbium:yttrium-aluminum-garnet (Er:YAG) laser (laser group), airborne-particle abrasion with 50-μm Al2O3 particles (abrasion group), an acid+laser group, and an abrasion+laser group. The specimens in each group were divided into 2 subgroups according to the resilient lining material used: heat-polymerized silicone based resilient liner (Molloplast B) and autopolymerized silicone-based resilient liner (Ufi Gel P). After all of the specimens had been polymerized, they were stored in distilled water at 37°C for 1 week. A tensile bond strength test was then performed. Data were analyzed with a 2-way ANOVA, and the Sidak multiple comparison test was used to identify significant differences (α=.05). The effects of the surface treatments and resilient lining materials on the surface of the denture base resin were examined with scanning electron microscopy. The tensile bond strength was significantly different between Molloplast B and Ufi Gel P (Presin. Molloplast B exhibited significantly higher bond strength than Ufi Gel P. Altering the surface of the acrylic resin denture base with 36% phosphoric acid etching increased bond strength. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  19. Comparative evaluation of tensile bond strength of silicone-based denture liners after thermocycling and surface treatment.

    Science.gov (United States)

    Kaur, Harsimran; Datta, Kusum

    2015-01-01

    To examine, evaluate, and compare the tensile bond strength of two silicone-based liners; one autopolymerizing and one heat cured, when treated with different chemical etchants to improve their adhesion with denture base resin. Hundred and sixty test specimens of heat-cured polymethyl methacrylate (PMMA) were fabricated; out of which 80 specimens were tested for tensile bond strength after bonding it to autopolymerizing resilient liner (Ufigel P) and rest 80 to heat-cured resilient liner (Molloplast B). Each main group was further divided into four subgroups of 20 specimens each, one to act as a control and three were subjected to surface treatment with different chemical etchants namely dichloromethane, MMA monomer, and chloroform. The two silicone-based denture liners were processed between 2 PMMA specimens (10 mm × 10 mm × 40 mm) in the space provided by a spacer of 3 mm, thermocycled (5-55°C) for 500 cycles, and then their tensile strength measurements were done in the universal testing machine. One-way ANOVA technique showed a highly significant difference in the mean tensile bond strength values for all the groups. The Student's t-test computed values of statistics for the compared groups were greater than the critical values both at 5% and at 1% levels. Surface treatment of denture base resin with chemical etchants prior to the application of silicone-based liner (Ufigel P and Molloplast-B) increased the tensile bond strength. The increase was the highest with specimens subjected to 180 s of MMA surface treatment and the lowest with control group specimens.

  20. Comparative evaluation of tensile bond strength of silicone-based denture liners after thermocycling and surface treatment

    Directory of Open Access Journals (Sweden)

    Harsimran Kaur

    2015-01-01

    Full Text Available Purpose: To examine, evaluate, and compare the tensile bond strength of two silicone-based liners; one autopolymerizing and one heat cured, when treated with different chemical etchants to improve their adhesion with denture base resin. Materials and Methods: Hundred and sixty test specimens of heat-cured polymethyl methacrylate (PMMA were fabricated; out of which 80 specimens were tested for tensile bond strength after bonding it to autopolymerizing resilient liner (Ufigel P and rest 80 to heat-cured resilient liner (Molloplast B. Each main group was further divided into four subgroups of 20 specimens each, one to act as a control and three were subjected to surface treatment with different chemical etchants namely dichloromethane, MMA monomer, and chloroform. The two silicone-based denture liners were processed between 2 PMMA specimens (10 mm × 10 mm × 40 mm in the space provided by a spacer of 3 mm, thermocycled (5-55°C for 500 cycles, and then their tensile strength measurements were done in the universal testing machine. Results: One-way ANOVA technique showed a highly significant difference in the mean tensile bond strength values for all the groups. The Student′s t-test computed values of statistics for the compared groups were greater than the critical values both at 5% and at 1% levels. Conclusion: Surface treatment of denture base resin with chemical etchants prior to the application of silicone-based liner (Ufigel P and Molloplast-B increased the tensile bond strength. The increase was the highest with specimens subjected to 180 s of MMA surface treatment and the lowest with control group specimens.

  1. Handover Management for VoWLAN Based on Estimation of AP Queue Length and Frame Retries

    Science.gov (United States)

    Niswar, Muhammad; Kashihara, Shigeru; Tsukamoto, Kazuya; Kadobayashi, Youki; Yamaguchi, Suguru

    Switching a communication path from one Access Point (AP) to another in inter-domain WLANs is a critical challenge for delay-sensitive applications such as Voice over IP (VoIP) because communication quality during handover (HO) is more likely to be deteriorated. To maintain VoIP quality during HO, we need to solve many problems. In particular, in bi-directional communication such as VoIP, an AP becomes a bottleneck with the increase of VoIP calls. As a result, packets queued in the AP buffer may experience a large queuing delay or packet losses due to increase in queue length or buffer overflow, thereby causing the degradation of VoIP quality for the Mobile Nodes (MNs) side. To avoid this degradation, MNs need to appropriately and autonomously execute HO in response to the change in wireless network condition, i.e., the deterioration of wireless link quality and the congestion state at the AP. In this paper, we propose an HO decision strategy considering frame retries, AP queue length, and transmission rate at an MN for maintaining VoIP quality during HO. Through simulation experiments, we then show that our proposed method can maintain VoIP quality during HO by properly detecting the wireless network condition.

  2. Bonding ability of three ethanol-based adhesives after thermal fatigue.

    Science.gov (United States)

    Perdigão, Jorge; Gomes, George; Sezinando, Ana

    2011-06-01

    To study the effect of thermal fatigue on the microTBS and interfacial morphology of three ethanol-based etch-&-rinse 2-bottle adhesives. microTBS - 24 third molars were randomly assigned to one of three adhesive systems: (1) Adper Single Bond Plus (SBP, 3M ESPE); (2) Ambar (AMB, FGM); (3) Excite (EXC, Ivoclar Vivadent), and restored with a hybrid resin composite. For each adhesive, half of the specimens were thermocycled (TC) for 20,000 cycles (5-55 degrees C) while the other half was kept in distilled water for 24 hours at 37 degreesC (control). Specimens were sectioned in X and Y directions and the resulting sticks were tested to failure in tension mode at a crosshead speed of 1 mm/minute. Statistical analysis was computed using ANOVA and Tukey's post hoc for the microTBS; and non-parametric cross-tabulation with Chi-Square for the pre-testing failures at P< 0.05. Interfacial morphology -The occlusal enamel was removed from 12 extracted molars perpendicular to the long axis of the tooth. Teeth were equally assigned to one of the three adhesives and restored with a 1 mm-thick layer of a hybrid composite resin. A 2 mm-thick disk was sectioned from each specimen and cross-sectioned in two identical halves. Half of the each specimen was TC for 20,000 cycles (5-55 degrees C) while the other half was kept in distilled water for 24 hours at 37 degrees C (control). Specimens were chemically challenged and prepared for FESEM observation to observe the integrity of the hybrid layer before and after thermal fatigue. Micrographs were recorded digitally at standard magnifications and measurements were taken with the microscope embedded image software. microTBS - SBP and AMB resulted in statistically similar mean microTBS regardless of thermal fatigue. EXC resulted in statistically lower mean microTBS than SBP and AMB for the control (P< 0.001) and for the TC specimens (P< 0.0001). Interfacial morphology - The hybrid layers of SBP and AMB were densely infiltrated without

  3. Carboxymethyl chitosan based nanocomposites containing chemically bonded quantum dots and magnetic nanoparticles

    Science.gov (United States)

    Ding, Yongling; Yin, Hong; Chen, Rui; Bai, Ru; Chen, Chunying; Hao, Xiaojuan; Shen, Shirley; Sun, Kangning; Liu, Futian

    2018-03-01

    A biocompatible nanocomposite consisting of fluorescent quantum dots (QDs) and magnetic nanoparticles (MNPs) has been constructed via carboxymethyl chitosan (CMCS), resulting in magnetic-fluorescent nanoparticles (MFNPs). In these MFNPs, QDs and MNPs are successfully conjugated via covalent bonds onto the surface of CMCS. The composite retains favorable magnetic and fluorescent properties and shows a good colloidal stability in physiological environments. Folate (FA) as a specific targeting ligand was further incorporated into the nanocomposites to form a delivery vehicle with a targeting function. The therapeutic activity was achieved by loading chemotherapeutic drug doxorubicin (DOX) through electrostatic and hydrophobic interactions. The cumulative DOX release profile shows pH-sensitive. Both flow cytometry analysis and confocal laser scanning microscopic observation suggested that these nanocomposites were uptaken by cancer cells via FA receptor-mediated endocytosis pathway. In summary, the CMCS based nanocomposites developed in this work have a great potential for effective cancer-targeting and drug delivery, as well as in situ cellular imaging.

  4. Push-out Bond Strength of Injectable Pozzolan-based Root Canal Sealer.

    Science.gov (United States)

    Silva, Emmanuel João Nogueira Leal; Carvalho, Nancy Kudsi; Prado, Marina C; Zanon, Mayara; Senna, Plinio Mendes; Souza, Erick M; De-Deus, Gustavo

    2016-11-01

    The present study aimed to rank the bond strength to root dentin of a new injectable pozzolan-based root canal sealer, EndoSeal MTA, as compared with MTA Fillapex and AH Plus. Eighteen dentinal slices (1 ± 0.1 mm) were obtained from the middle third of 6 maxillary incisors previously selected. Three canal-like holes with 0.8 mm diameter were drilled perpendicularly on the axial surface of each slice. Then, a standardized irrigation was applied for all holes that were subsequently filled with 1 of 3 test root canal sealers. After that, slices were stored in contact with phosphate-buffered saline solution (pH 7.2) for 7 days at 37°C before the push-out assay. Friedman test and Wilcoxon signed rank test with a Bonferroni correction were used to rank the results. Significance boundary was set at α = 5%. Friedman test confirmed a significant dissimilarity in push-out ranks among the tested cements (P root canal sealer, it is not able to improve adhesion compared with AH Plus. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  5. Differences in tensile adhesion strength between HEMA and nonHEMA-based dentin bonding applied on superficial and deep dentin surfaces

    Directory of Open Access Journals (Sweden)

    Eresha Melati Kusuma Wurdani

    2017-03-01

    Full Text Available Background: Improvement in dentistry shows some progresses, due to patients awareness on the importance of dental care. Cervical lesion is the most common phenomenon which oftenly found 46.36% in man and 38.13% in woman. Cervical lesions need composite restoration for treatment to stop the process of tissue damage. The process of adhesion of composite restoration material to the structure of the tooth is not easily separated and it needs optimal function in the oral cavity. Application of dentin bonding agents to attach the composite is needed. Selection of HEMA-based bonding material and Hema free-based bonding material which have a different solvent in their composition, as applied to the dentin superficial and deep dentin, affect the results of debonding test. Debonding test is done to measure the adhesion strength of a bonding material. Purpose: The purpose of this study was to analyze differences in tensile bond strength of dentine bonding HEMA-based and HEMA-free based after application in superficial and deep dentine surfaces. Method: The tooth of the bovine was as samples. A superficial dentine sample was taken from 0.5-1 mm of dentino enamel junction and a deep dentine sample was taken from 0.5 mm culmination of pulp horn. Dentine surface area was equal to p x r2 = (3.14 x 22 = 12.56 mm2. Six samples of HEMA-based bonding was applied to the dentine superficial. Six samples of HEMAfree based bonding was applied to the superficial dentine. Six samples of HEMA-based bonding was applied to the deep dentine. Six samples of HEMA-free based bonding was applied to the deep dentine. Tensile strength was measured using an Autograph AG-10TE. Result: There were differences tensile bond strength of dentine bonding HEMA-based and HEMA-free based after the application on superficial (p=0.000 and deep dentine surfaces (p=0.000. Conclusion: There were differences tensile bond strength of dentine bonding HEMA-based and HEMA-free based after the

  6. Nonorthogonal orbital based N-body reduced density matrices and their applications to valence bond theory. I. Hamiltonian matrix elements between internally contracted excited valence bond wave functions

    Science.gov (United States)

    Chen, Zhenhua; Chen, Xun; Wu, Wei

    2013-04-01

    In this series, the n-body reduced density matrix (n-RDM) approach for nonorthogonal orbitals and their applications to ab initio valence bond (VB) methods are presented. As the first paper of this series, Hamiltonian matrix elements between internally contracted VB wave functions are explicitly provided by means of nonorthogonal orbital based RDM approach. To this end, a more generalized Wick's theorem, called enhanced Wick's theorem, is presented both in arithmetical and in graphical forms, by which the deduction of expressions for the matrix elements between internally contracted VB wave functions is dramatically simplified, and the matrix elements are finally expressed in terms of tensor contractions of electronic integrals and n-RDMs of the reference VB self-consistent field wave function. A string-based algorithm is developed for the purpose of evaluating n-RDMs in an efficient way. Using the techniques presented in this paper, one is able to develop new methods and efficient algorithms for nonorthogonal orbital based many-electron theory much easier than by use of the first quantized formulism.

  7. EFFECT OF THERMOCYCLING ON THE TENSILE AND SHEAR BOND STRENGTHS OF THREE SOFT LINERS TO A DENTURE BASE RESIN

    Science.gov (United States)

    Elias, Carlos Nelson; Henriques, Flavio Queiroz

    2007-01-01

    Statement of problem In clinical practice, loss of adhesion between the silicone-based denture liner and the denture base resin is always an undesirable event that might cause loss of material softness, water sorption, bacterial colonization and functional failure of the prosthesis. Purpose This study evaluated the effect of thermocycling on tensile and shear bond strengths of three soft liner materials to a denture base acrylic resin. Material and methods Three resilient liners (Mucopren-Soft, Mollosil-Plus and Dentusil) and a heat-polymerized acrylic resin (QC-20) were processed according to manufacturers’ directions. Sixty specimens (14 x 14 mm cross-sectional area) per bond strength test (20 for each liner) were fabricated and either stored in water at 37°C for 24 hours (control groups; n=10) or thermocycled 3,000 times in water between 5°C and 55°C (test groups; n=10). The specimens were tested in tensile and shear strength in a universal testing machine until fracture. Bond strength means were compared between water-stored and thermocycled groups for each material, as well as among materials for each treatment (water storage or thermocycling). Failure mode (adhesive, cohesive and mixed) after debonding was assessed. Data were analyzed statistically by paired Student’s t-test and ANOVA at 5% significance level. Results The water-stored groups had statistically significant higher bond strengths than the thermocycled groups (presin after thermocycling. In spite of thermocycling, though, the silicone-based liners had satisfactory bond strengths for clinical application. PMID:19089094

  8. A micromechanical approach of suffusion based on a length scale analysis of the grain detachment and grain transport processes.

    Science.gov (United States)

    Wautier, Antoine; Bonelli, Stéphane; Nicot, François

    2017-06-01

    Suffusion is the selective erosion of the finest particles of a soil subjected to an internal flow. Among the four types of internal erosion and piping identified today, suffusion is the least understood. Indeed, there is a lack of micromechanical approaches for identifying the critical microstructural parameters responsible for this process. Based on a discrete element modeling of non cohesive granular assemblies, specific micromechanical tools are developed in a unified framework to account for the two first steps of suffusion, namely the grain detachment and the grain transport processes. Thanks to the use of an enhanced force chain definition and autocorrelation functions the typical lengths scales associated with grain detachment are characterized. From the definition of transport paths based on a graph description of the pore space the typical lengths scales associated with grain transport are recovered. For a uniform grain size distribution, a separation of scales between these two processes exists for the finest particles of a soil

  9. A micromechanical approach of suffusion based on a length scale analysis of the grain detachment and grain transport processes.

    Directory of Open Access Journals (Sweden)

    Wautier Antoine

    2017-01-01

    Full Text Available Suffusion is the selective erosion of the finest particles of a soil subjected to an internal flow. Among the four types of internal erosion and piping identified today, suffusion is the least understood. Indeed, there is a lack of micromechanical approaches for identifying the critical microstructural parameters responsible for this process. Based on a discrete element modeling of non cohesive granular assemblies, specific micromechanical tools are developed in a unified framework to account for the two first steps of suffusion, namely the grain detachment and the grain transport processes. Thanks to the use of an enhanced force chain definition and autocorrelation functions the typical lengths scales associated with grain detachment are characterized. From the definition of transport paths based on a graph description of the pore space the typical lengths scales associated with grain transport are recovered. For a uniform grain size distribution, a separation of scales between these two processes exists for the finest particles of a soil

  10. Chemical bond fundamental aspects of chemical bonding

    CERN Document Server

    Frenking, Gernot

    2014-01-01

    This is the perfect complement to ""Chemical Bonding - Across the Periodic Table"" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemica

  11. A computational approach for the annotation of hydrogen-bonded base interactions in crystallographic structures of the ribozymes

    Science.gov (United States)

    Hamdani, Hazrina Yusof; Artymiuk, Peter J.; Firdaus-Raih, Mohd

    2015-09-01

    A fundamental understanding of the atomic level interactions in ribonucleic acid (RNA) and how they contribute towards RNA architecture is an important knowledge platform to develop through the discovery of motifs from simple arrangements base pairs, to more complex arrangements such as triples and larger patterns involving non-standard interactions. The network of hydrogen bond interactions is important in connecting bases to form potential tertiary motifs. Therefore, there is an urgent need for the development of automated methods for annotating RNA 3D structures based on hydrogen bond interactions. COnnection tables Graphs for Nucleic ACids (COGNAC) is automated annotation system using graph theoretical approaches that has been developed for the identification of RNA 3D motifs. This program searches for patterns in the unbroken networks of hydrogen bonds for RNA structures and capable of annotating base pairs and higher-order base interactions, which ranges from triples to sextuples. COGNAC was able to discover 22 out of 32 quadruples occurrences of the Haloarcula marismortui large ribosomal subunit (PDB ID: 1FFK) and two out of three occurrences of quintuple interaction reported by the non-canonical interactions in RNA (NCIR) database. These and several other interactions of interest will be discussed in this paper. These examples demonstrate that the COGNAC program can serve as an automated annotation system that can be used to annotate conserved base-base interactions and could be added as additional information to established RNA secondary structure prediction methods.

  12. A computational approach for the annotation of hydrogen-bonded base interactions in crystallographic structures of the ribozymes

    International Nuclear Information System (INIS)

    Hamdani, Hazrina Yusof; Artymiuk, Peter J.; Firdaus-Raih, Mohd

    2015-01-01

    A fundamental understanding of the atomic level interactions in ribonucleic acid (RNA) and how they contribute towards RNA architecture is an important knowledge platform to develop through the discovery of motifs from simple arrangements base pairs, to more complex arrangements such as triples and larger patterns involving non-standard interactions. The network of hydrogen bond interactions is important in connecting bases to form potential tertiary motifs. Therefore, there is an urgent need for the development of automated methods for annotating RNA 3D structures based on hydrogen bond interactions. COnnection tables Graphs for Nucleic ACids (COGNAC) is automated annotation system using graph theoretical approaches that has been developed for the identification of RNA 3D motifs. This program searches for patterns in the unbroken networks of hydrogen bonds for RNA structures and capable of annotating base pairs and higher-order base interactions, which ranges from triples to sextuples. COGNAC was able to discover 22 out of 32 quadruples occurrences of the Haloarcula marismortui large ribosomal subunit (PDB ID: 1FFK) and two out of three occurrences of quintuple interaction reported by the non-canonical interactions in RNA (NCIR) database. These and several other interactions of interest will be discussed in this paper. These examples demonstrate that the COGNAC program can serve as an automated annotation system that can be used to annotate conserved base-base interactions and could be added as additional information to established RNA secondary structure prediction methods

  13. A computational approach for the annotation of hydrogen-bonded base interactions in crystallographic structures of the ribozymes

    Energy Technology Data Exchange (ETDEWEB)

    Hamdani, Hazrina Yusof, E-mail: hazrina@mfrlab.org [School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi (Malaysia); Advanced Medical and Dental Institute, Universiti Sains Malaysia, Bertam, Kepala Batas (Malaysia); Artymiuk, Peter J., E-mail: p.artymiuk@sheffield.ac.uk [Dept. of Molecular Biology and Biotechnology, Firth Court, University of Sheffield, S10 T2N Sheffield (United Kingdom); Firdaus-Raih, Mohd, E-mail: firdaus@mfrlab.org [School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi (Malaysia)

    2015-09-25

    A fundamental understanding of the atomic level interactions in ribonucleic acid (RNA) and how they contribute towards RNA architecture is an important knowledge platform to develop through the discovery of motifs from simple arrangements base pairs, to more complex arrangements such as triples and larger patterns involving non-standard interactions. The network of hydrogen bond interactions is important in connecting bases to form potential tertiary motifs. Therefore, there is an urgent need for the development of automated methods for annotating RNA 3D structures based on hydrogen bond interactions. COnnection tables Graphs for Nucleic ACids (COGNAC) is automated annotation system using graph theoretical approaches that has been developed for the identification of RNA 3D motifs. This program searches for patterns in the unbroken networks of hydrogen bonds for RNA structures and capable of annotating base pairs and higher-order base interactions, which ranges from triples to sextuples. COGNAC was able to discover 22 out of 32 quadruples occurrences of the Haloarcula marismortui large ribosomal subunit (PDB ID: 1FFK) and two out of three occurrences of quintuple interaction reported by the non-canonical interactions in RNA (NCIR) database. These and several other interactions of interest will be discussed in this paper. These examples demonstrate that the COGNAC program can serve as an automated annotation system that can be used to annotate conserved base-base interactions and could be added as additional information to established RNA secondary structure prediction methods.

  14. Variable RF capacitor based on a-Si:H (P-doped) multi-length cantilevers

    International Nuclear Information System (INIS)

    Fu, Y Q; Milne, S B; Luo, J K; Flewitt, A J; Wang, L; Miao, J M; Milne, W I

    2006-01-01

    A variable RF capacitor with a-Si:H (doped with phosphine) cantilevers as the top electrode were designed and fabricated. Because the top multi-cantilever electrodes have different lengths, increasing the applied voltage pulled down the cantilever beams sequentially, thus realizing a gradual increase of the capacitance with the applied voltage. A high-k material, H f O 2 , was used as an insulating layer to increase the tuning range of the capacitance. The measured capacitance from the fabricated capacitor was much lower and the pull-in voltage was much higher than those from theoretical analysis because of incomplete contact of the two electrodes, existence of film differential stresses and charge injection effect. Increase of sweeping voltage rate could significantly shift the pull-in voltage to higher values due to the charge injection mechanisms

  15. Push-Out Bond Strength and Surface Microhardness of Calcium Silicate-Based Biomaterials: An in vitro Study

    Science.gov (United States)

    Majeed, Abdul; AlShwaimi, Emad

    2017-01-01

    Objective This was an in vitro evaluation of push-out bond strength and surface microhardness of calcium silicate-based biomaterials in coronal and apical root dentin. Materials and Methods Ninety sections (2 mm thick) of coronal and apical root dentin were obtained from roots of 60 extracted teeth; the canals were enlarged to a standardized cavity diameter of 1.3 mm. Sections were randomly divided into 6 groups (n = 15 per group), and cavities were filled with Biodentine™, BioAggregate, or ProRoot mineral trioxide aggregate (MTA), according to the manufacturers' instructions. Push-out bond strength values were measured using a universal testing machine under a compressive load at a speed of 1 mm/min. Samples were analyzed under a light microscope to determine the nature of bond failure. Ten samples (2 mm thick) were prepared for all the materials, and Vickers microhardness was determined using a digital hardness tester. Data were analyzed using one-way analysis of variance and Tukey-Kramer multiple comparison tests at a significance level of p Biodentine (42.02; 39.35 MPa) and ProRoot MTA (21.86; 34.13 MPa) showed significantly higher bond strengths than BioAggregate (6.63; 10.09 MPa) in coronal and apical root dentin, respectively (p Biodentine also differed significantly from ProRoot MTA in coronal dentin. Bond failure was predominantly adhesive in Biodentine and ProRoot MTA, while BioAggregate showed predominantly mixed failure. ProRoot MTA (158.52 HV) showed significantly higher microhardness and BioAggregate (68.79 HV) showed the lowest hardness. Conclusion Biodentine and ProRoot MTA showed higher bond strength and microhardness compared to BioAggregate. PMID:27852076

  16. Effects of different surface treatments on the bond strength of acrylic denture teeth to polymethylmethacrylate denture base material.

    Science.gov (United States)

    Akin, Hakan; Kirmali, Omer; Tugut, Faik; Coskun, Mehmet Emre

    2014-09-01

    The purpose of this study was to investigate the effects of various surface pretreatments in the ridge lap area of acrylic resin denture teeth on the shear bond strength to heat-polymerized polymethylmethacrylate (PMMA) denture base resin. Tooth debonding of the denture is a major problem for patients with removable prostheses. A total of 84 central incisor denture teeth were used in this study. Seven test groups with 12 specimens for each group were prepared as follows: untreated (control, group C), ground, with a tungsten carbide bur (group H), airborne-particle abrasion (group AA), primed with methyl methacrylate (group M), treated with izobutyl methacrylate (group iBMA), Eclipse Bonding Agent applied (group E), and Er:YAG laser irradiated (group L). Test specimens were produced according to the manufacturers' instructions and mounted to a universal testing machine for shear testing with a crosshead speed of 1 mm/min. Data were evaluated by one way variance analysis (ANOVA) and Tukey's test (α=0.05). Similar bond strength values were found between groups L and M, and these were the highest shear bond strengths among the groups. The lowest one was observed in group E. All surface treatments, except group E, exhibited significant difference when compared with group C (pacrylic resin denture teeth to PMMA denture base resin might be an alternative to wetting with MMA monomer. To overcome tooth debonding, surface treatment of the ridge lap area should be performed as part of denture fabrication.

  17. Effects of surface treatments and bonding types on the interfacial behavior of fiber metal laminate based on magnesium alloy

    Science.gov (United States)

    Zhang, Xi; Ma, Quanyang; Dai, Yu; Hu, Faping; Liu, Gang; Xu, Zouyuan; Wei, Guobing; Xu, Tiancai; Zeng, Qingwen; Xie, Weidong

    2018-01-01

    Fiber metal laminates based on magnesium alloys (MgFML) with different surface treatments and different bonding types were tested and analyzed. By using dynamic contact angle measurement and scanning electron microscopy (SEM), it was found that phosphating treatment can significantly improve the surface energy and wettability of magnesium alloy, and the surface energy of phosphated magnesium alloy was approximately 50% higher than that of abraded-only magnesium alloy. The single cantilever beam (SCB) test showed that the interfacial fracture energies of directly bonded MgFMLs based on abraded-only magnesium and abraded + phosphated magnesium were 650 J/m2 and 1030 J/m2, respectively, whereas the interfacial fracture energies of indirectly bonded MgFMLs were 1650 J/m2 and 2260 J/m2, respectively. Phosphating treatment and modified polypropylene interleaf were observed to improve the tensile strength and interfacial fracture toughness of MgFML. In addition, the rougher surface was more conducive to enhance the bonding strength and interfacial fracture toughness of MgFML.

  18. Fundamental length and relativistic length

    International Nuclear Information System (INIS)

    Strel'tsov, V.N.

    1988-01-01

    It si noted that the introduction of fundamental length contradicts the conventional representations concerning the contraction of the longitudinal size of fast-moving objects. The use of the concept of relativistic length and the following ''elongation formula'' permits one to solve this problem

  19. Addition of ammonium-based methacrylates to an experimental dental adhesive for bonding metal brackets: Carious lesion development and bond strength after cariogenic challenge.

    Science.gov (United States)

    Nascimento, Patrícia Layane de Menezes Macedo; Meereis, Carine Tais Welter; Maske, Tamires Timm; Ogliari, Fabrício Aulo; Cenci, Maximiliano Sérgio; Pfeifer, Carmem Sílvia; Faria-E-Silva, André Luis

    2017-05-01

    In this study, we evaluated the caries inhibition and shear bond strength achieved with the addition of the antibacterial monomer [2-(Methacryloyloxy)ethyl] trimethylammonium chloride (MADQUAT) to an adhesive used to bond orthodontic brackets. Experimental adhesives were formulated with addition of 0% (control), 5%, or 10% MADQUAT followed by measurement of the degree of conversion. These adhesives were used to lute brackets to the enamel of premolars (n = 30). Biofilm from a microcosm model was cultivated in half of the specimens under cariogenic challenge for 5 days. The brackets were subjected to a shear bond strength test followed by measurement of the internal hardness of the enamel around the brackets to calculate the integrated mineral loss. The addition of MADQUAT slightly increased the degree of conversion. Adhesive containing 10% MADQUAT significantly reduced the integrated mineral loss around the bracket but also resulted in the lowest values of bond strength. No effects on bond strength and integrated mineral loss were observed with the addition of 5% MADQUAT to the adhesive. The cariogenic challenge did not affect the bond strength and the failure mode. MADQUAT was effective to reduce the integrated mineral loss only when added to the adhesive at a concentration of 10% despite the reduction of bond strength. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

  20. Flame Length

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Flame length was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  1. Irreversible bonding of polyimide and polydimethylsiloxane (PDMS) based on a thiol-epoxy click reaction

    International Nuclear Information System (INIS)

    Hoang, Michelle V; Chung, Hyun-Joong; Elias, Anastasia L

    2016-01-01

    Polyimide is one of the most popular substrate materials for the microfabrication of flexible electronics, while polydimethylsiloxane (PDMS) is the most widely used stretchable substrate/encapsulant material. These two polymers are essential in fabricating devices for microfluidics, bioelectronics, and the internet of things; bonding these materials together is a crucial challenge. In this work, we employ click chemistry at room temperature to irreversibly bond polyimide and PDMS through thiol-epoxy bonds using two different methods. In the first method, we functionalize the surfaces of the PDMS and polyimide substrates with mercaptosilanes and epoxysilanes, respectively, for the formation of a thiol-epoxy bond in the click reaction. In the second method, we functionalize one or both surfaces with mercaptosilane and introduce an epoxy adhesive layer between the two surfaces. When the surfaces are bonded using the epoxy adhesive without any surface functionalization, an extremely small peel strength (<0.01 N mm −1 ) is measured with a peel test, and adhesive failure occurs at the PDMS surface. With surface functionalization, however, remarkably higher peel strengths of ∼0.2 N mm −1 (method 1) and  >0.3 N mm −1 (method 2) are observed, and failure occurs by tearing of the PDMS layer. We envision that the novel processing route employing click chemistry can be utilized in various cases of stretchable and flexible device fabrication. (paper)

  2. Fault diagnosis of air conditioning systems based on qualitative bond graph

    International Nuclear Information System (INIS)

    Ghiaus, C.

    1999-01-01

    The bond graph method represents a unified approach for modeling engineering systems. The main idea is that power transfer bonds the components of a system. The bond graph model is the same for both quantitative representation, in which parameters have numerical values, and qualitative approach, in which they are classified qualitatively. To infer the cause of faults using a qualitative method, a system of qualitative equations must be solved. However, the characteristics of qualitative operators require specific methods for solving systems of equations having qualitative variables. This paper proposes both a method for recursively solving the qualitative system of equations derived from bond graph, and a bond graph model of a direct-expansion, mechanical vapor-compression air conditioning system. Results from diagnosing two faults in a real air conditioning system are presented and discussed. Occasionally, more than one fault candidate is inferred for the same set of qualitative values derived from measurements. In these cases, additional information is required to localize the fault. Fault diagnosis is initiated by a fault detection mechanism which also classifies the quantitative measurements into qualitative values; the fault detection is not presented here. (author)

  3. Relative Leukocyte Telomere Length, Hematological Parameters and Anemia - Data from the Berlin Aging Study II (BASE-II).

    Science.gov (United States)

    Meyer, Antje; Salewsky, Bastian; Buchmann, Nikolaus; Steinhagen-Thiessen, Elisabeth; Demuth, Ilja

    2016-01-01

    The length of the chromosome ends, telomeres, is widely accepted as a biomarker of aging. However, the dynamic of the relationship between telomere length and hematopoietic parameters in the normal aging process, which is of particular interest with respect to age-related anemia, is not well understood. We have analyzed the relationship between relative leukocyte telomere length (rLTL) and several hematological parameters in the older group of the Berlin Aging Study II (BASE-II) participants. This paper also compares rLTL between both BASE-II age groups (22-37 and 60-83 years). Genomic DNA was extracted from peripheral blood leukocytes of BASE-II participants and used to determine rLTL by a quantitative PCR protocol. Standard methods were used to determine blood parameters, and the WHO criteria were used to identify anemic participants. Telomere length data were available for 444 younger participants (28.4 ± 3.1 years old; 52% women) and 1,460 older participants (68.2 ± 3.7 years old; 49.4% women). rLTL was significantly shorter in BASE-II participants of the older group (p = 3.7 × 10-12) and in women (p = 4.2 × 10-31). rLTL of older men exhibited a statistically significant, positive partial correlation with mean corpuscular hemoglobin (MCH; p = 0.012) and MCH concentration (p = 0.002). While these correlations were only observed in men, the rLTL of older women was negatively correlated with the number of thrombocytes (p = 0.015) in the same type of analysis. Among all older participants, 6% met the criteria to be categorized as 'anemic'; however, there was no association between anemia and rLTL. In the present study, we have detected isolated correlations between rLTL and hematological parameters; however, in all cases, rLTL explained only a small part of the variation of the analyzed parameters. In disagreement with some other studies showing similar data, we interpret the association between rLTL and some of the hematological parameters studied here to be

  4. A Managerial Perspective on Common Identity-based and Common Bond-based Groups in Non-governmental Organizations. Patterns of Interaction, Attachment and Social Network Configuration

    Directory of Open Access Journals (Sweden)

    Elena - Mădălina VĂTĂMĂNESCU

    2014-10-01

    Full Text Available The paper approaches the common identity and common bond theories in analyzing the group patterns of interaction, their causes, processes and outcomes from a managerial perspective. The distinction between identity and bond referred to people’s different reasons for being in a group, stressing out whether they like the group as a whole — identity-based attachment, or they like individuals in the group — bond-based attachment.  While members of the common identity groups reported feeling more attached to their group as a whole than to their fellow group members and tended to perceive others in the group as interchangeable, in bond-based attachment, people felt connected to each other and less to the group as a whole, loyalty or attraction to the group stemming from their attraction primarily to certain members in the group. At this level, the main question concerned with the particularities of common identity-based or common bond-based groups regarding social interaction, the participatory architecture of the group, the levels of personal and work engagement in acting like a cohesive group. In order to address pertinently this issue, the current work was focused on a qualitative research which comprised in-depth (semi-structured interviews with several project coordinators from non-governmental organizations (NGOs. Also, to make the investigation more complex and clear, the research relied on the social network analysis which was indicative of the group dynamics and configuration, highlighting the differences between common identity-based and common bond-based groups.

  5. Improved Road-Network-Flow Control Strategy Based on Macroscopic Fundamental Diagrams and Queuing Length in Connected-Vehicle Network

    Directory of Open Access Journals (Sweden)

    Xiaohui Lin

    2017-01-01

    Full Text Available Connected-vehicles network provides opportunities and conditions for improving traffic signal control, and macroscopic fundamental diagrams (MFD can control the road network at the macrolevel effectively. This paper integrated proposed real-time access to the number of mobile vehicles and the maximum road queuing length in the Connected-vehicles network. Moreover, when implementing a simple control strategy to limit the boundary flow of a road network based on MFD, we determined whether the maximum queuing length of each boundary section exceeds the road-safety queuing length in real-time calculations and timely adjusted the road-network influx rate to avoid the overflow phenomenon in the boundary section. We established a road-network microtraffic simulation model in VISSIM software taking a district as the experimental area, determined MFD of the region based on the number of mobile vehicles, and weighted traffic volume of the road network. When the road network was tending to saturate, we implemented a simple control strategy and our algorithm limits the boundary flow. Finally, we compared the traffic signal control indicators with three strategies: (1 no control strategy, (2 boundary control, and (3 boundary control with limiting queue strategy. The results show that our proposed algorithm is better than the other two.

  6. Oligomers Based on a Weak Hydrogen Bond Network: the Rotational Spectrum of the Tetramer of Difluoromethane

    Science.gov (United States)

    Feng, Gang; Evangelisti, Luca; Caminati, Walther; Cacelli, Ivo; Carbonaro, Laura; Prampolini, Giacomo

    2013-06-01

    Following the investigation of the rotational spectra of three conformers (so-called ``book'', ``prism'' and ``cage'') of the water hexamer, and of some other water oligomers, we report here the rotational spectrum of the tetramer of a freon molecule. The pulse jet Fourier transform microwave (pj-FTMW) spectrum of an isomer of the difluoromethane tetramer has been assigned. This molecular system is made of units of a relatively heavy asymmetric rotor, held together by a network of weak hydrogen bonds. The search of the rotational spectrum has been based on a high-level reference method, the CCSD(T)/CBS protocol. It is interesting to outline that the rotational spectrum of the water tetramer was not observed, probably because the minimum energy structures of this oligomer is effectively nonpolar in its ground states, or because of high energy tunnelling splittings. The rotational spectra of the monomer, dimer, trimer and tetramer of difluoromethane have been assigned in 1952, 1999, 2007, and 2013 (present work), with a decreasing time spacing between the various steps, looking then promising for a continuous and rapid extension of the size limits of molecular systems accessible to MW spectroscopy. C. Pérez, M. T. Muckle, D. P. Zaleski, N. A. Seifert, B. Temelso, G. C. Shields, Z. Kisiel, B. H. Pate, Science {336} (2012) 897. D. R. Lide, Jr., J. Am. Chem. Soc. {74} (1952) 3548. W. Caminati, S. Melandri, P. Moreschini, P. G. Favero, Angew. Chem. Int. Ed. {38} (1999) 2924. S. Blanco, S. Melandri, P. Ottaviani, W. Caminati, J. Am. Chem. Soc. {129} (2007) 2700.

  7. A method for estimating age of medieval sub-adults from infancy to adulthood based on long bone length

    DEFF Research Database (Denmark)

    Primeau, Charlotte; Friis, Laila Saidane; Sejrsen, Birgitte

    2016-01-01

    AND METHODS: A total of 183 skeletal sub-adults from the Danish medieval period, were aged from radiographic images. Linear regression formulae were then produced for individual bones. Age was then estimated from the femur length using three different methods: equations developed in this study, data based...... as later than the medieval period, although this would require further testing. The quadratic equations are suggested to yield more accurate ages then using simply linear regression equations. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.......OBJECTIVES: To develop a series of regression equations for estimating age from length of long bones for archaeological sub-adults when aging from dental development cannot be performed. Further, to compare derived ages when using these regression equations, and two other methods. MATERIAL...

  8. Push-out bond strength of MTA HP, a new high-plasticity calcium silicate-based cement.

    Science.gov (United States)

    Silva, Emmanuel Jnl; Carvalho, Nancy Kudsi; Zanon, Mayara; Senna, Plínio Mendes; DE-Deus, Gustavo; Zuolo, Mário Luis; Zaia, Alexandre Augusto

    2016-06-14

    This study was designed to investigate the resistance to dislodgment provided by MTA HP, a new high-plasticity calcium silicate-based cement. Biodentine and White MTA Angelus were used as reference materials for comparison. Three discs 1 ± 0.1 mm thick were obtained from the middle third of the roots of 5 maxillary canines. Three 0.8-mm-wide holes were drilled on the axial surface of each root disc. Standardized irrigation was performed. Then the holes were dried with paper points and filled with one of the three tested cements. The filled dental slices were immersed in a phosphate-buffered saline (PBS) solution (pH 7.2) for 7 days before the push-out assessment. The Kruskal-Wallis test was applied to assess the effect of each endodontic cement on the push-out bond strength. Mann-Whitney with Bonferroni correction was used to isolate the differences. The alpha-type error was set at 0.05. All specimens had measurable push-out values and no premature failure occurred. There were significant differences among the materials (p <0.05). The Biodentine specimens had the highest push-out bond strength values (p < 0.05). MTA HP had significantly higher bond strength than White MTA (p < 0.05). MTA HP showed better push-out bond strength than its predecessor, White MTA; however, Biodentine had higher dislodgment resistance than both MTA formulations.

  9. Halogen bonding from a hard and soft acids and bases perspective: investigation by using density functional theory reactivity indices.

    Science.gov (United States)

    Pinter, Balazs; Nagels, Nick; Herrebout, Wouter A; De Proft, Frank

    2013-01-07

    Halogen bonds between the trifluoromethyl halides CF(3)Cl, CF(3)Br and CF(3)I, and dimethyl ether, dimethyl sulfide, trimethylamine and trimethyl phosphine were investigated using Pearson's hard and soft acids and bases (HSAB) concept with conceptual DFT reactivity indices, the Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework and the non-covalent interaction (NCI) index. It is found that the relative importance of electrostatic and orbital (charge transfer) interactions varies as a function of both the donor and acceptor molecules. Hard and soft interactions were distinguished and characterised by atomic charges, electrophilicity and local softness indices. Dual-descriptor plots indicate an orbital σ hole on the halogen similar to the electrostatic σ hole manifested in the molecular electrostatic potential. The predicted high halogen-bond-acceptor affinity of N-heterocyclic carbenes was evidenced in the highest complexation energy for the hitherto unknown CF(3) I·NHC complex. The dominant NOCV orbital represents an electron-density deformation according to a n→σ*-type interaction. The characteristic signal found in the reduced density gradient versus electron-density diagram corresponds to the non-covalent interaction between contact atoms in the NCI plots, which is the manifestation of halogen bonding within the NCI theory. The unexpected C-X bond strengthening observed in several cases was rationalised within the molecular orbital framework. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Complications and operative spine fusion construct length in Parkinson's disease: A nationwide population-based analysis.

    Science.gov (United States)

    McClelland, Shearwood; Baker, Joseph F; Smith, Justin S; Line, Breton G; Hart, Robert A; Ames, Christopher P; Bess, R Shay

    2017-09-01

    There remains a dearth of information regarding the surgical complications following multilevel spine surgery in Parkinson's disease (PD) patients. This retrospective cohort study was performed to address this issue on a nationwide level using the Nationwide Inpatient Sample from 2001 to 2012. More than 25 postoperative variables were analyzed to assess the impact of fusion construct length on each variable. Subsequently, the same analysis was performed on admissions without PD. 4301 PD patients with spine fusion were identified, of whom 934 (21.7%) underwent fusion of at least three levels; the remaining 3367 underwent fusion of 1-2 levels. Patients with 3+ level fusions were more likely to suffer paraplegia (P=.001; OR=3.0; 95%CI=1.5-6.1), hematoma/seroma (P=.009; OR=1.9; 95%CI=1.2-3.2), IVC filter placement (P=.018; OR=2.1; 95%CI=1.1-3.9), RBC transfusion (Panemia (P1week (P<.001; OR=2.1; 95%CI=1.8-2.5), and a nonroutine discharge (P=.005; OR=1.9; 95%CI=1.4-2.4). 692,173 non-PD patients with spine fusion were identified; 123,964 (17.9%) underwent 3+ level fusion. Differences between 3+ versus 1-2 level fusions were similar to those in PD patient, but unlike PD patients, postoperative infection was significant while in-hospital mortality, PE and VTE were not. Fusion of at least three levels increased morbidity, mortality, and adverse discharge disposition compared with 1-2 level fusions. Nearly 80% of all spine fusions performed in the United States are fewer than three levels. These findings are worth considering during operative decision-making in both PD and non-PD patients. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Effect of silica coating combined to a MDP-based primer on the resin bond to Y-TZP ceramic.

    Science.gov (United States)

    May, Liliana Gressler; Passos, Sheila Pestana; Capelli, Diana Barca; Ozcan, Mutlu; Bottino, Marco Antonio; Valandro, Luiz Felipe

    2010-10-01

    The aim of this study was to evaluate the influence of silica coating and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer applications upon the bonding durability of a MDP-based resin cement to a yttrium stabilized tetragonal zirconia (Y-TZP) ceramic. Ninety-six Y-TZP tabs were embedded in an acrylic resin (free surface for adhesion: 5 × 5 mm(2)), ground finished and randomly divided into four groups (N = 24) according to the ceramic surface conditioning: (1) cleaning with isopropanol (ALC); (2) ALC + phosphoric acid etching + MDP-based primer application (MDP-primer); (3) silica coating + 3-methacryloyloxypropyl trimethoxysilane (MPS)-based coupling agent application (SiO2 + MPS-Sil); and (4) SiO2 + MDP-primer. The MDP-based resin cement was applied on the treated surface using a cylindrical mold (diameter= 3 mm). Half of the specimens from each surface conditioning were stored in distilled water (37 °C, 24 h) before testing. Another half of the specimens were stored (90 days) and thermo-cycled (12,000 x) during this period (90 d/TC) before testing. A shear bond strength (SBS) test was performed at a crosshead speed of 0.5 mm/min. Two factors composed the experimental design: ceramic conditioning strategy (in four levels) and storage condition (in two levels), totaling eight groups. After 90 d/TC (Tukey; p MDP-primer (24.40 MPa) promoted the highest SBS. The ALC and MDP-primer groups debonded spontaneously during 90 d/TC. Bonding values were higher and more stable in the SiO2 groups. The use of MDP-primer after silica coating increased the bond strength.

  12. What is a hydrogen bond?

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. What is a hydrogen bond? Precise definition of a hydrogen bond is still elusive!1. Several criteria are listed usually for X-H•••Y, X and Y initially thought to be F, O and N only1. Structural: The X-Y bond length is less than the sum of their van der Waals radii. X-H•••Y is ...

  13. Effect of surface treatment on the bonding of an autopolymerizing soft denture liner to a denture base resin.

    Science.gov (United States)

    Minami, Hiroyuki; Suzuki, Shiro; Ohashi, Hirohumi; Kurashige, Hisanori; Tanaka, Takuo

    2004-01-01

    This in vitro study evaluated the effects of surface treatments and thermocycling on the bonding of autopolymerizing silicone soft denture liner (Sofreliner) to denture base resin. The bonding surfaces of denture base cylinders were polished with 600-grit silicon carbide paper and pretreated with applications of Sofreliner Primer, Sofreliner Primer after air abrasion, Reline Primer, or Reline Primer after air abrasion. Failure loads and elongation at failure were measured after subjecting specimens to 0, 10,000, 20,000, and 30,000 thermocycles. Failure modes were assessed for all specimens. Seven specimens were fabricated for each of 16 groups, including four pretreatments and four thermocycle groups. Failure loads of the Sofreliner Primer group were significantly higher than those of the air-abrasion group up to 20,000 thermocycles; both groups showed cohesive failures of the soft denture liner. Failure loads of the Reline Primer group were significantly higher than with Reline Primer after air abrasion up to 10,000 thermocycles. Failure mode after 10,000 thermocycles was cohesive for the Reline Primer group and mixed cohesive/adhesive for Reline Primer after air abrasion. Failure loads of the Sofreliner Primer group were significantly higher than those of the Reline Primer group at each thermocycling interval. Elongation values decreased after 10,000 thermocycles for all groups. Air abrasion on the denture base resin surface was not effective in enhancing failure load. Cyclic thermal stress is one factor degrading the bond between soft denture liner and acrylic resin denture base.

  14. Effect of silica coating and silane surface treatment on the bond strength of soft denture liner to denture base material

    Science.gov (United States)

    ATSÜ, Saadet; KESKİN, Yasemin

    2013-01-01

    Objective This study investigated the effects of different surface treatments on the tensile bond strength of an autopolymerizing silicone denture liner to a denture base material after thermocycling. Material and Methods Fifty rectangular heat-polymerized acrylic resin (QC-20) specimens consisting of a set of 2 acrylic blocks were used in the tensile test. Specimens were divided into 5 test groups (n=10) according to the bonding surface treatment as follows: Group A, adhesive treatment (Ufi Gel P adhesive) (control); Group S, sandblasting using 50-µm Al2O3; Group SCSIL, silica coating using 30-µm Al2O3 modified by silica and silanized with silane agent (CoJet System); Group SCA, silica coating and adhesive application; Group SCSILA, silica coating, silane and adhesive treatment. The 2 PMMA blocks were placed into molds and the soft lining materials (Ufi Gel P) were packed into the space and polymerized. All specimens were thermocycled (5,000 cycles) before the tensile test. Bond strength data were analyzed using 1-way ANOVA and Duncan tests. Fracture surfaces were observed by scanning electron microscopy. X-ray photoelectron spectrometer (XPS) and Fourier Transform Infrared spectrometer (FTIR) analysis were used for the chemical analysis and a profilometer was used for the roughness of the sample surfaces. Results The highest bond strength test value was observed for Group A (1.35±0.13); the lowest value was for Group S (0.28±0.07) and Group SCSIL (0.34±0.03). Mixed and cohesive type failures were seen in Group A, SCA and SCSILA. Group S and SCSIL showed the least silicone integrations and the roughest surfaces. Conclusion Sandblasting, silica coating and silane surface treatments of the denture base resin did not increase the bond strength of the silicone based soft liner. However, in this study, the chemical analysis and surface profilometer provided interesting insights about the bonding mechanism between the denture base resin and silicone soft liner

  15. Effect of silica coating and silane surface treatment on the bond strength of soft denture liner to denture base material

    Directory of Open Access Journals (Sweden)

    Saadet Atsu

    2013-07-01

    Full Text Available OBJECTIVE: This study investigated the effects of different surface treatments on the tensile bond strength of an autopolymerizing silicone denture liner to a denture base material after thermocycling. MATERIAL AND METHODS: Fifty rectangular heat-polymerized acrylic resin (QC-20 specimens consisting of a set of 2 acrylic blocks were used in the tensile test. Specimens were divided into 5 test groups (n=10 according to the bonding surface treatment as follows: Group A, adhesive treatment (Ufi Gel P adhesive (control; Group S, sandblasting using 50-µm Al2O3; Group SCSIL, silica coating using 30-µm Al2O3 modified by silica and silanized with silane agent (CoJet System; Group SCA, silica coating and adhesive application; Group SCSILA, silica coating, silane and adhesive treatment. The 2 PMMA blocks were placed into molds and the soft lining materials (Ufi Gel P were packed into the space and polymerized. All specimens were thermocycled (5,000 cycles before the tensile test. Bond strength data were analyzed using 1-way ANOVA and Duncan tests. Fracture surfaces were observed by scanning electron microscopy. X-ray photoelectron spectrometer (XPS and Fourier Transform Infrared spectrometer (FTIR analysis were used for the chemical analysis and a profilometer was used for the roughness of the sample surfaces. RESULTS: The highest bond strength test value was observed for Group A (1.35±0.13; the lowest value was for Group S (0.28±0.07 and Group SCSIL (0.34±0.03. Mixed and cohesive type failures were seen in Group A, SCA and SCSILA. Group S and SCSIL showed the least silicone integrations and the roughest surfaces. CONCLUSION: Sandblasting, silica coating and silane surface treatments of the denture base resin did not increase the bond strength of the silicone based soft liner. However, in this study, the chemical analysis and surface profilometer provided interesting insights about the bonding mechanism between the denture base resin and silicone

  16. Shear bond strength and failure types of polymethyl methacrylate denture base resin and titanium treated with surface conditioner.

    Science.gov (United States)

    Lim, Hyun-Pil; Kim, Su-Sung; Yang, Hong-So; Vang, Mong-Sook

    2010-01-01

    This study compared the shear bond strength and failure types of a polymethyl methacrylate (PMMA) denture base resin to commercially pure (CP) titanium, Ti-6Al-4V alloy, and cobalt-chromium alloy using a metal surface conditioner. The PMMA denture base resin (5 x 5 x 5 mm(3)) was cured onto disks, 10 mm in diameter and 2.5-mm thick. The shear bond strength of the PMMA resin with the surface conditioner was significantly higher than that without (P < .05). There was no significant difference between the types of metal. The conditioned specimens showed mixed failures, whereas the nonconditioned specimens exhibited only adhesive failure at the metal-resin interface.

  17. Bond-based linear indices in QSAR: computational discovery of novel anti-trichomonal compounds

    Science.gov (United States)

    Marrero-Ponce, Yovani; Meneses-Marcel, Alfredo; Rivera-Borroto, Oscar M.; García-Domenech, Ramón; De Julián-Ortiz, Jesus Vicente; Montero, Alina; Escario, José Antonio; Barrio, Alicia Gómez; Pereira, David Montero; Nogal, Juan José; Grau, Ricardo; Torrens, Francisco; Vogel, Christian; Arán, Vicente J.

    2008-08-01

    Trichomonas vaginalis ( Tv) is the causative agent of the most common, non-viral, sexually transmitted disease in women and men worldwide. Since 1959, metronidazole (MTZ) has been the drug of choice in the systemic treatment of trichomoniasis. However, resistance to MTZ in some patients and the great cost associated with the development of new trichomonacidals make necessary the development of computational methods that shorten the drug discovery pipeline. Toward this end, bond-based linear indices, new TOMOCOMD-CARDD molecular descriptors, and linear discriminant analysis were used to discover novel trichomonacidal chemicals. The obtained models, using non-stochastic and stochastic indices, are able to classify correctly 89.01% (87.50%) and 82.42% (84.38%) of the chemicals in the training (test) sets, respectively. These results validate the models for their use in the ligand-based virtual screening. In addition, they show large Matthews' correlation coefficients ( C) of 0.78 (0.71) and 0.65 (0.65) for the training (test) sets, correspondingly. The result of predictions on the 10% full-out cross-validation test also evidences the robustness of the obtained models. Later, both models are applied to the virtual screening of 12 compounds already proved against Tv. As a result, they correctly classify 10 out of 12 (83.33%) and 9 out of 12 (75.00%) of the chemicals, respectively; which is the most important criterion for validating the models. Besides, these classification functions are applied to a library of seven chemicals in order to find novel antitrichomonal agents. These compounds are synthesized and tested for in vitro activity against Tv. As a result, experimental observations approached to theoretical predictions, since it was obtained a correct classification of 85.71% (6 out of 7) of the chemicals. Moreover, out of the seven compounds that are screened, synthesized and biologically assayed, six compounds (VA7-34, VA7-35, VA7-37, VA7-38, VA7-68, VA7-70) show

  18. H-shaped supra-amphiphiles based on a dynamic covalent bond.

    Science.gov (United States)

    Wang, Guangtong; Wang, Chao; Wang, Zhiqiang; Zhang, Xi

    2012-10-16

    The imine bond, a kind of dynamic covalent bond, is used to bind two bolaform amphiphiles together with spacers, yielding H-shaped supra-amphiphiles. Micellar aggregates formed by the self-assembly of the H-shaped supra-amphiphiles are observed. When pH is tuned down from basic to slightly acidic, the benzoic imine bond can be hydrolyzed, leading to the dissociation of H-shaped supra-amphiphiles. Moreover, H-shaped supra-amphiphiles have a lower critical micelle concentration than their building blocks, which is very helpful in enhancing the stability of the benzoic imine bond being hydrolyzed by acid. The surface tension isotherms of the H-shaped supra-amphiphiles with different spacers indicate their twisty conformation at a gas-water interface. The study of H-shaped supra-amphiphiles can enrich the family of amphiphiles, and moreover, the pH-responsiveness may make them apply to controlled or targetable drug delivery in a biological environment.

  19. Parental bonding and suicidality in pregnant teenagers: a population-based study in southern Brazil.

    Science.gov (United States)

    Coelho, Fábio Monteiro da Cunha; Pinheiro, Ricardo Tavares; Silva, Ricardo Azevedo; de Ávila Quevedo, Luciana; de Mattos Souza, Luciano Dias; de Matos, Mariana Bonati; Castelli, Rochele Dias; Pinheiro, Karen Amaral Tavares

    2014-08-01

    To assess the associations of the perceived quality of parental bonding with suicidality in a sample of pregnant adolescents. A cross-sectional study with a sample size of 828 pregnant teenagers receiving prenatal medical assistance in the national public health system in the urban area of Pelotas, southern Brazil. Suicidality and psychiatric disorders were assessed using the Mini International Neuropsychiatric Interview (MINI), and the Parental Bonding Instrument (PBI) was employed to measure the perceived quality of parental bonding. A self-report questionnaire was used to collect sociodemographic, obstetric and other psychosocial data. Forty-three (4.94 %) teenagers from a consecutive sample of 871 refused to participate, resulting in 828 participants. Prevalence of suicidality was 13.3 %, lifetime suicide attempts were 7.4 % with 1.3 % reporting attempting suicide within the last month. Significant associations of suicidality with the 18-19-year-old subgroup, low education, prior abortion, physical abuse within the last 12 months were present, and most psychiatric disorders were associated with a higher suicidality prevalence. Additionally, after adjustment in the multivariate analysis, the style of parental bonding was independently associated with suicidality in the pregnant adolescent, with a PR of 2.53 (95 % CI 1.14-5.59) for the maternal 'affectionless control' and a PR of 2.91 (95 % CI 1.10-7.70) for the paternal 'neglectful parenting.' We found that maternal 'affectionless control' and paternal 'neglectful parenting' were independent predictors of suicidality in this sample of pregnant teenagers.

  20. A study of the impact properties of adhesively-bonded aluminum alloy based on impact velocity

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Teng; Cheon, Seong Sik; Cho, Jae Ung [Kongju National University, Cheonan (Korea, Republic of); Kinloch, Anthony J.; Blackman, Bamber R. K.; Sanchez, F. S. Rodriguez [Imperial College London, London (United Kingdom); Bang, Hye Jin; Lee, Sang Kyo; Cho, Chong Du [Inha University, Seoul (Korea, Republic of)

    2015-02-15

    In this study, an experiment and a simulation were carried out on colliding an adhesively-bonded tapered double cantilever beam (TDCB) at the impact velocities of 5 m/s, 7.5 m/s and 12.5 m/s. The analysis method of the corrected beam theory (CBT) was used to obtain the rate of energy release in the bonded area according to the crack progression, and a simulation was performed to determine the maximum strain energy during the impact analysis as a means to examine the mechanical properties of aluminium alloy. The experimental data were found to be higher than the simulation data. This is deemed to explicable by the fact that the adhesive strength was maintained even after the specimen separated in the experiment. Crack progression occurred, irrespective of the impact velocity, and high strain energy occurred at the end of the bonded region, thereby causing the strain energy to increase in the final stages. Also, the maximum load applied on the pin and the maximum strain energy in the bonded area were shown increase at higher impact velocities. The results of the experiment and simulation performed in this study are expected to serve as important data in developing a safety design for composite materials that can help prevent the progression of cracks caused by impact.

  1. The chemical bond in inorganic chemistry the bond valence model

    CERN Document Server

    Brown, I David

    2016-01-01

    The bond valence model is a version of the ionic model in which the chemical constraints are expressed in terms of localized chemical bonds formed by the valence charge of the atoms. Theorems derived from the properties of the electrostatic flux predict the rules obeyed by both ionic and covalent bonds. They make quantitative predictions of coordination number, crystal structure, bond lengths and bond angles. Bond stability depends on the matching of the bonding strengths of the atoms, while the conflicting requirements of chemistry and space lead to the structural instabilities responsible for the unusual physical properties displayed by some materials. The model has applications in many fields ranging from mineralogy to molecular biology.

  2. Bond strength of a dental leucite-based glass ceramic to a resin cement using different silane coupling agents.

    Science.gov (United States)

    Hooshmand, Tabassom; Matinlinna, Jukka P; Keshvad, Alireza; Eskandarion, Solmaz; Zamani, Fereshteh

    2013-01-01

    To evaluate the effect of different types of novel silane coupling agents with two concentrations on the micro-tensile bond strength of a dental glass ceramic with leucite crystals to a dual-cured resin cement using an optimized method of silane application. Leucite-reinforced feldspathic ceramic blocks were fabricated, wet ground and cleansed. The bonding ceramic surfaces were treated with different organosilane solutions as follows: Control silane: Monobond S; methacryloxypropyltrimethoxy silane and experimental silanes with two concentrations (1.0 and 2.5 vol%): amino, isocyanate, styryl, and acrylate silanes. The silane application method consisted of brush application, hot air drying followed by rinsing with hot water and drying. Then a thin layer of an unfilled resin and a dual-cured resin cement was light-cured on the ceramic surfaces. The resin-ceramic blocks were stored in distilled water at 37°C for 24 h and sectioned to produce beam specimens (n=17) with a 1.0 mm(2) cross-sectional area. Specimens were then subjected to thermocycling and tested in a micro-tensile tester device. Data were analyzed using analysis of variance and Tamhane post-hoc test. The mean micro-tensile bond strength value for the styryl silane was significantly higher (P0.05). The micro-tensile bond strength of the leucite-based dental glass ceramic to a resin cement was affected by the type of silane coupling agent and not by the concentration of silane solutions. The best bond strength overall was achieved by methacryloxypropyltrimethoxysilane and experimental styryl silane solutions. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Comparison of the bond strength of laser-sintered and cast base metal dental alloys to porcelain.

    Science.gov (United States)

    Akova, Tolga; Ucar, Yurdanur; Tukay, Alper; Balkaya, Mehmet Cudi; Brantley, William A

    2008-10-01

    The purpose of this study was to compare shear bond strengths of cast Ni-Cr and Co-Cr alloys and the laser-sintered Co-Cr alloy to dental porcelain. Dental porcelain was applied on two cast and one laser-sintered base metal alloy. Ten specimens were prepared for each group for bond strength comparison. ANOVA followed by Tukey HSD multiple comparison test (alpha=0.05) was used for statistical analysis. Fractured specimens were observed with a stereomicroscope to classify the type of failure after shear bond testing. While the mean shear bond strength was highest for the cast Ni-Cr metal-ceramic specimens (81.6+/-14.6 MPa), the bond strength was not significantly different (P>0.05) from that for the cast Co-Cr metal-ceramic specimens (72.9+/-14.3 MPa) and the laser-sintered Co-Cr metal-ceramic specimens (67.0+/-14.9 MPa). All metal-ceramic specimens prepared from cast Ni-Cr and Co-Cr alloys exhibit a mixed mode of cohesive and adhesive failure, whereas five of the metal-ceramic specimens prepared from the laser-sintered Co-Cr alloy exhibited the mixed failure mode and five specimens exhibited adhesive failure in the porcelain. The new laser-sintering technique for Co-Cr alloy appears promising for dental applications, but additional studies of properties of the laser-sintered alloy and fit of castings prepared by this new technique are needed before its acceptance into dental laboratory practice. Laser sintering of Co-Cr alloy seems to be an alternative technique to conventional casting of dental alloys for porcelain fused to metal restorations.

  4. Conjugation Length Effect on TPA-Based Optical Limiting Performance of a Series of Ladder-Type Chromophores

    Directory of Open Access Journals (Sweden)

    Yujin Zhang

    2017-01-01

    Full Text Available Nonlinear optical properties of a series of newly-synthesized ladder-type chromophores containing oligo-p-phenylene moiety with different π-conjugated lengths were theoretically studied by numerically solving the rate equations and the field intensity equation with an iterative predictor-corrector finite-difference time-domain technique. Ab initio calculation results show that the compounds can be described by the three-level model. Based on the two-photon absorption mechanism, highly efficient optical limiting performances are demonstrated in the chromophores, which strongly depend on the π-conjugated length of the molecule. Special attention has been paid to the dynamical two-photon absorption, indicating that the parameter of the medium can affect the dynamical two-photon absorption cross section. Our numerical results agree well with the experimental measurements. It reveals that the increase in the π-conjugated length of ladder-type oligo-p-phenylene for these chromophores leads to enhanced nonlinear optical absorption. The results also provide a method to modulate the optical limiting and dynamical two-photon absorption of the compounds by changing the molecular density and thickness of the absorber.

  5. Effects of ethanol concentrations of acrylate-based dental adhesives on microtensile composite-dentin bond strength and hybrid layer structure of a 10 wt% polyhedral oligomeric silsesquioxane (POSS)-incorporated bonding agent.

    Science.gov (United States)

    Mousavinasab, Seyed Mostafa; Atai, Mohammad; Barekatain, Mehrdad; Fattahi, Parisa; Fattahi, Amir; Rakhshan, Vahid

    2018-01-01

    The aim of this study was to assess for the first time the effects of different amounts of ethanol solvent on the microtensile bond strength of composite bonded to dentin using a polyhedral oligomeric silsesquioxane (POSS)-incorporated adhesive. This experimental study was performed on 120 specimens divided into six groups (in accordance with the ISO TR11405 standard requiring at least 15 specimens per group). Occlusal dentin of thirty human molar teeth was exposed by removing its enamel. Five teeth were assigned to each of six groups and were converted to 20 microtensile rods (with square cross-sections of 1 mm × 1 mm) per group. The "Prime and Bond NT" (as a common commercial adhesive) was used as the control group. Experimental acrylate-based bonding agents containing 10 wt% POSS were produced with five concentrations of ethanol as solvent (0, 20, 31, 39, and 46 wt%). After application of adhesives on dentin surface, composite cylinders (height = 6 mm) were bonded to dentin surface. The microtensile bond strength of composite to dentin was measured. The fractured surfaces of specimens were evaluated under a scanning electron microscope to assess the morphology of hybrid layer. Data were analyzed using one-sample t -test, one-way analysis of variance (ANOVA), and Tukey tests (α = 0.05). the mean bond strength in the groups: "control, ethanol-free, and 20%, 31%, 39%, and 46% ethanol" was, respectively, 46.5 ± 5.6, 29.4 ± 5.7, 33.6 ± 4.1, 59.0 ± 5.5, 41.9 ± 6.2, and 18.7 ± 4.6 MPa. Overall difference was significant (ANOVA, P composite to dentin and improve the quality and morphology of the hybrid layer. However, higher concentrations of the solvent might not improve the bond strength or quality of the hybrid layer.

  6. Fundamental length

    International Nuclear Information System (INIS)

    Pradhan, T.

    1975-01-01

    The concept of fundamental length was first put forward by Heisenberg from purely dimensional reasons. From a study of the observed masses of the elementary particles known at that time, it is sumrised that this length should be of the order of magnitude 1 approximately 10 -13 cm. It was Heisenberg's belief that introduction of such a fundamental length would eliminate the divergence difficulties from relativistic quantum field theory by cutting off the high energy regions of the 'proper fields'. Since the divergence difficulties arise primarily due to infinite number of degrees of freedom, one simple remedy would be the introduction of a principle that limits these degrees of freedom by removing the effectiveness of the waves with a frequency exceeding a certain limit without destroying the relativistic invariance of the theory. The principle can be stated as follows: It is in principle impossible to invent an experiment of any kind that will permit a distintion between the positions of two particles at rest, the distance between which is below a certain limit. A more elegant way of introducing fundamental length into quantum theory is through commutation relations between two position operators. In quantum field theory such as quantum electrodynamics, it can be introduced through the commutation relation between two interpolating photon fields (vector potentials). (K.B.)

  7. Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine®).

    Science.gov (United States)

    Cantekin, Kenan; Avci, Serap

    2014-01-01

    Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB) composites, silorane-based (SB) composites, and glass ionomer cement (GIC) to Biodentine® and mineral trioxide aggregate (MTA). Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole) were prepared. In 45 of the samples, the holes were fully filled with Biodentine® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS) test, each block was secured in a universal testing machine. The highest (17.7 ± 6.2 MPa) and the lowest (5.8 ± 3.2 MPa) bond strength values were recorded for the MB composite-Biodentine® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7 ± 6.2) than it did to MTA (8.9 ± 5.7) (p Biodentine® = 8.0 ± 3,6) and GIC (GIC and MTA = 5.8 ± 3.2; GIC and Biodentine = 6.7 ± 2.6) showed similar bond strength performance with MTA compared with Biodentine (p = 0.73 and p = 0.38, respectively). The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite.

  8. Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine®

    Directory of Open Access Journals (Sweden)

    Kenan CANTEK?N

    2014-07-01

    Full Text Available Objectives: Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA. It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB composites, silorane-based (SB composites, and glass ionomer cement (GIC to Biodentine® and mineral trioxide aggregate (MTA. Material and Methods: Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole were prepared. In 45 of the samples, the holes were fully filled with Biodentine® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS test, each block was secured in a universal testing machine. Results: The highest (17.7±6.2 MPa and the lowest (5.8±3.2 MPa bond strength values were recorded for the MB composite-Biodentine® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7±6.2 than it did to MTA (8.9±5.7 (p<0.001, the SB composite (SB and MTA=7.4±3.3; SB and Biodentine®=8.0±3,6 and GIC (GIC and MTA=5.8±3.2; GIC and Biodentine=6.7±2.6 showed similar bond strength performance with MTA compared with Biodentine (p=0.73 and p=0.38, respectively. Conclusions: The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite.

  9. Characterization of the Bonds Developed between Calcium Silicate Hydrate and Polycarboxylate-Based Superplasticizers with Silyl Functionalities

    KAUST Repository

    Orozco, Carlos A.

    2017-03-24

    Major developments in concrete technology have been achieved with the use of polycarboxylate-based superplasticizers (PCEs) to improve the concrete rheology without increasing the mix water content. Currently, it is possible to control the fluidity of the fresh concrete and obtain stronger and more durable structures. Therefore, there is a strong incentive to understand the interactions between PCEs and cement hydrates at the atomic scale to design new customized functional PCEs according to the ever-increasing requirements of the concrete industry. Here, the bonding types generated between a PCE with silyl functionalities (PCE-Sil) and a synthetic calcium silicate hydrate (C-S-H) are analyzed using XRD, 29Si NMR spectroscopy, and synchrotron-based techniques, such as NEXAFS and EXAFS. The results indicated that the carboxylic groups present in PCE-Sil interact by a ligand-type bond with calcium, which modified not only the symmetry and coordination number of the calcium located at the surface of C-S-H but also the neighboring silicon atoms of the C-S-H. In addition, the silyl functionalities of the PCE-Sil generated covalent bonds through siloxane bridges between the silanol groups of PCE-Sil and the nonbonding oxygen located at the dimeric sites in C-S-H, forming new bridging silicon sites and subsequently increasing the silicate polymerization.

  10. Evaluation of shear bond strength, penetration ability, microleakage and remineralisation capacity of glass ionomer-based fissure sealants.

    Science.gov (United States)

    Kucukyilmaz, E; Savas, S

    2016-03-01

    The aim of this study was to evaluate the bond strength, penetration ability, microleakage, and remineralisation capacity of glass ionomer-based fissure sealant materials. In this study, three glass ionomer-based fissure sealants were evaluated (Fuji Triage, Fuji VII EP, and GCP Glass Seal). A dye-penetration test was performed to evaluate microleakage under a stereomicroscope. The materials were applied to occlusal tooth surfaces, and bucco-lingual sections (1 mm width) were assessed to evaluate the penetration ability. Shear bond strength of tested materials was assessed using a universal testing machine. Finally, the remineralisation capacities of the materials were evaluated with EDS. The Fuji Triage exhibited the lowest microleakage and unfilled area proportion (p<0.05). The highest shear bond strength was calculated with Fuji VII EP (p<0.05). The fluoride content for all treatment groups was significantly different when remineralisation values were compared to demineralisation (p<0.05). Both the Fuji Triage and Fuji VII EP yielded compatible and satisfactory results and all fissure sealants used in this study are sufficient as anti-caries agents.

  11. Analysis of the physical properties of trehalose-water-lithium iodide based on the bond strength coordination number fluctuation model

    International Nuclear Information System (INIS)

    Sahara; Jean L Ndeugueu; Masaru Aniya

    2010-01-01

    The temperature dependence of the viscosity of trehalose-water-lithium iodide system has been investigated by the mean of the Bond Strength Coordination Number Fluctuation (BSCNF) model. The result indicates that by increasing the trehalose content, maintaining the content of LiI constant, the fragility decreases due to the increase of the connectivity between the structural units. Our analysis suggests also that the fragility of the system is controlled by the amount of water in the composition. By increasing the water content, the total bond strength decreases and its fluctuation increases, resulting in the increase of the fragility. Based on the analysis of the obtained parameters of the BSCNF model, a physical interpretation of the VFT parameters reported in a previous study has been given. (author)

  12. Selective bond cleavage in potassium collisions with pyrimidine bases of DNA.

    Science.gov (United States)

    Almeida, Diogo; Ferreira da Silva, Filipe; García, Gustavo; Limão-Vieira, Paulo

    2013-01-11

    Electron transfer in alkali-molecule collisions to gas phase thymine and uracil yielding H- formation is selectively controlled in the energy range between 5.3 and 66.1 eV. By tuning the collision energy, electron transfer from the alkali to partly deuterated thymine, methylated thymine at the N1 and methylated uracil at the N3 positions, H- loss proceeds not only through the breaking of the (C-H) against (N-H) bonds but also through N1 against N3 sites. Such selectivity, as far as bond and site are concerned, is here reported for the first time by electron transfer induced dissociation experiments in alkali-molecule collisions.

  13. Mapping Optimal Charge Density and Length of ROMP-Based PTDMs for siRNA Internalization.

    Science.gov (United States)

    Caffrey, Leah M; deRonde, Brittany M; Minter, Lisa M; Tew, Gregory N

    2016-10-10

    A fundamental understanding of how polymer structure impacts internalization and delivery of biologically relevant cargoes, particularly small interfering ribonucleic acid (siRNA), is of critical importance to the successful design of improved delivery reagents. Herein we report the use of ring-opening metathesis polymerization (ROMP) methods to synthesize two series of guanidinium-rich protein transduction domain mimics (PTDMs): one based on an imide scaffold that contains one guanidinium moiety per repeat unit, and another based on a diester scaffold that contains two guanidinium moieties per repeat unit. By varying both the degree of polymerization and, in effect, the relative number of cationic charges in each PTDM, the performances of the two ROMP backbones for siRNA internalization were evaluated and compared. Internalization of fluorescently labeled siRNA into Jurkat T cells demonstrated that fluorescein isothiocyanate (FITC)-siRNA internalization had a charge content dependence, with PTDMs containing approximately 40 to 60 cationic charges facilitating the most internalization. Despite this charge content dependence, the imide scaffold yielded much lower viabilities in Jurkat T cells than the corresponding diester PTDMs with similar numbers of cationic charges, suggesting that the diester scaffold is preferred for siRNA internalization and delivery applications. These developments will not only improve our understanding of the structural factors necessary for optimal siRNA internalization, but will also guide the future development of optimized PTDMs for siRNA internalization and delivery.

  14. Growth estimation of mangrove cockle Anadara tuberculosa (Mollusca: Bivalvia: application and evaluation of length-based methods

    Directory of Open Access Journals (Sweden)

    Luis A Flores

    2011-03-01

    Full Text Available Growth is one of the key processes in the dynamic of exploited resources, since it provides part of the information required for structured population models. Growth of mangrove cockle, Anadara tuberculosa was estimated through length-based methods (ELEFAN I y NSLCA and using diverse shell length intervals (SLI. The variability of L∞, k and phi prime (Φ` estimates and the effect of each sample were quantified by jackknife techniques. Results showed the same L∞ estimates from ELEFAN I and NSLCA across each SLI used, and all L∞ were within the expected range. On the contrary, k estimates differed between methods. Jackknife estimations uncovered the tendency of ELEFAN I to overestimate k with increases in SLI, and allowed the identification of differences in uncertainty (PE and CV between both methods. The average values of Φ`derived from NSCLA1.5 and length-age sources were similar and corresponded to ranges reported by other authors. Estimates of L∞, k and Φ` from NSCLA1.5 were 85.97mm, 0.124/year and 2.953 with jackknife and 86.36mm de L∞, 0.110/year de k and 2.914 de Φ` without jackknife, respectively. Based on the observed evidence and according to the biology of the species, NSCLA is suggested to be used with jackknife and a SLI of 1.5mm as an ad hoc approach to estimate the growth parameters of mangrove cockle. Rev. Biol. Trop. 59 (1: 159-170. Epub 2011 March 01.

  15. Stable Au-C bonds to the substrate for fullerene-based nanostructures

    Czech Academy of Sciences Publication Activity Database

    Chutora, Taras; López, Roso Redondo Jesús R.; De La Torre Cerdeño, Bruno; Švec, Martin; Jelínek, Pavel; Vázquez, Héctor

    2017-01-01

    Roč. 8, č. 1 (2017), s. 1073-1079 ISSN 2190-4286 R&D Projects: GA ČR GA15-19672S Institutional support: RVO:68378271 Keywords : Au-C bonds * density functional theory (DFT) * fullerenes * scanning tunneling microscopy (STM) * sputtering Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.127, year: 2016

  16. In situ metalation of free base phthalocyanine covalently bonded to silicon surfaces

    Directory of Open Access Journals (Sweden)

    Fabio Lupo

    2014-11-01

    Full Text Available Free 4-undecenoxyphthalocyanine molecules were covalently bonded to Si(100 and porous silicon through thermic hydrosilylation of the terminal double bonds of the undecenyl chains. The success of the anchoring strategy on both surfaces was demonstrated by the combination of X-ray photoelectron spectroscopy with control experiments performed adopting the commercially available 2,3,9,10,16,17,23,24-octakis(octyloxy-29H,31H-phthalocyanine, which is not suited for silicon anchoring. Moreover, the study of the shape of the XPS N 1s band gave relevant information on the interactions occurring between the anchored molecules and the substrates. The spectra suggest that the phthalocyanine ring interacts significantly with the flat Si surface, whilst ring–surface interactions are less relevant on porous Si. The surface-bonded molecules were then metalated in situ with Co by using wet chemistry. The efficiency of the metalation process was evaluated by XPS measurements and, in particular, on porous silicon, the complexation of cobalt was confirmed by the disappearance in the FTIR spectra of the band at 3290 cm−1 due to –NH stretches. Finally, XPS results revealed that the different surface–phthalocyanine interactions observed for flat and porous substrates affect the efficiency of the in situ metalation process.

  17. Cooperative Binding in a Phosphine Oxide-Based Halogen Bonded Dimer Drives Supramolecular Oligomerization.

    Science.gov (United States)

    Maugeri, Leonardo; Lébl, Tomáš; Cordes, David B; Slawin, Alexandra M Z; Philp, Douglas

    2017-02-17

    Triphenylphosphine oxide forms halogen-bonded (XB) complexes with pentafluoroiodobenzene and a 1,4-diaryl-5-iodotriazole. The stability of these complexes is assessed computationally and by 31 P NMR spectroscopy in toluene-d 8 solution, where both complexes are weakly associated. This knowledge is applied to the design and synthesis of two self-complementary phosphine oxide-iodotriazole hybrids that incorporate a phosphine oxide XB acceptor and a 1,4-diphenyl-5-iodotriazole XB donor within the same molecule. The self-complementary design of these modules facilitates their assembly in both toluene-d 8 and, surprisingly, DCM-d 2 into dimers, with significant stabilities, through the formation of halogen-bonded diads. The stability of these assemblies is a result of significant levels of cooperative binding that is present in both solvents. The connection of two of these hybrid units together, using a flexible spacer, facilitates the aggregation of these modules in DCM-d 2 solution, through halogen bonding, forming oligomeric assemblies.

  18. Experimental Assessment on the Flexural Bonding Performance of Concrete Beam with GFRP Reinforcing Bar under Repeated Loading

    Directory of Open Access Journals (Sweden)

    Minkwan Ju

    2015-01-01

    Full Text Available This study intends to investigate the flexural bond performance of glass fiber-reinforced polymer (GFRP reinforcing bar under repeated loading. The flexural bond tests reinforced with GFRP reinforcing bars were carried out according to the BS EN 12269-1 (2000 specification. The bond test consisted of three loading schemes: static, monotonic, and variable-amplitude loading to simulate ambient loading conditions. The empirical bond length based on the static test was 225 mm, whereas it was 317 mm according to ACI 440 1R-03. Each bond stress on the rib is released and bonding force is enhanced as the bond length is increased. Appropriate level of bond length may be recommended with this energy-based analysis. For the monotonic loading test, the bond strengths at pullout failure after 2,000,000 cycles were 10.4 MPa and 6.5 MPa, respectively: 63–70% of the values from the static loading test. The variable loading test indicated that the linear cumulative damage theory on GFRP bonding may not be appropriate for estimating the fatigue limit when subjected to variable-amplitude loading.

  19. A GRASP-Based Heuristic for the Sorting by Length-Weighted Inversions Problem.

    Science.gov (United States)

    Arruda, Thiago da Silva; Dias, Ulisses; Dias, Zanoni

    2018-01-01

    Genome Rearrangements are large-scale mutational events that affect genomes during the evolutionary process. Therefore, these mutations differ from punctual mutations. They can move genes from one place to the other, change the orientation of some genes, or even change the number of chromosomes. In this work, we deal with inversion events which occur when a segment of DNA sequence in the genome is reversed. In our model, each inversion costs the number of elements in the reversed segment. We present a new algorithm for this problem based on the metaheuristic called Greedy Randomized Adaptive Search Procedure (GRASP) that has been routinely used to find solutions for combinatorial optimization problems. In essence, we implemented an iterative process in which each iteration receives a feasible solution whose neighborhood is investigated. Our analysis shows that we outperform any other approach by significant margin. We also use our algorithm to build phylogenetic trees for a subset of species in the Yersinia genus and we compared our trees to other results in the literature.

  20. The effect of shape, length and diameter of implants on primary stability based on resonance frequency analysis

    Directory of Open Access Journals (Sweden)

    Hamidreza Barikani

    2014-01-01

    Full Text Available Background: The aim of this in vitro study was to evaluate the effect of shape, diameter and length of implants on their primary stability based on resonance frequency analysis. Materials and Methods: Replace select tapered and Branemark MK III implants were selected. Each of these two selected groups was divided into nine subgroups based on the implant length (IL (short, medium and long and the implant diameter (ID (narrow platform [NP], regular platform [RP] and wide platform [WP]. Five implants were assigned to each of the nine subgroups. Implants were placed in artificial bone blocks with bone quality similar to D3 bone. Immediately after the implant placement, its primary stability was measured using Osstell Mentor equipment. T-test and Tukey′s honest significant difference Post hoc were performed for data analysis. Statistical significance was defined at P < 0.05. Results: Replace select system showed significantly higher primary stability compared to the Branemark system, when using the short implants for all three diameters (P ≤ 0.004. However, in medium length implants there were no significant differences between the two implant systems (P ≥ 0.31. In long implants, only when the NP and RP implants were used, the Replace Select system showed significantly higher primary stability compared to the Branemark system (P = 0.000. In the replace select system, long implants had a significantly higher primary stability compared to medium and short length implants (P ≤ 0.003. In the NP and RP Branemark implants, short implants showed significantly lower primary stability compared to medium and long implants (P ≤ 0.002. However, in WP Branemark implants, primary stability increased significantly with increasing the IL from short to medium and from medium to long (P = 0.000. There were also significant differences between NP and the two other wider implants in both systems (P = 0.000. Conclusion: The use of tapered implants is

  1. The effect of shape, length and diameter of implants on primary stability based on resonance frequency analysis

    Science.gov (United States)

    Barikani, Hamidreza; Rashtak, Shadab; Akbari, Soolmaz; Fard, Mohammadjavad Kharrazi; Rokn, Amirreza

    2014-01-01

    Background: The aim of this in vitro study was to evaluate the effect of shape, diameter and length of implants on their primary stability based on resonance frequency analysis. Materials and Methods: Replace select tapered and Branemark MK III implants were selected. Each of these two selected groups was divided into nine subgroups based on the implant length (IL) (short, medium and long) and the implant diameter (ID) (narrow platform [NP], regular platform [RP] and wide platform [WP]). Five implants were assigned to each of the nine subgroups. Implants were placed in artificial bone blocks with bone quality similar to D3 bone. Immediately after the implant placement, its primary stability was measured using Osstell Mentor equipment. T-test and Tukey's honest significant difference Post hoc were performed for data analysis. Statistical significance was defined at P Branemark system, when using the short implants for all three diameters (P ≤ 0.004). However, in medium length implants there were no significant differences between the two implant systems (P ≥ 0.31). In long implants, only when the NP and RP implants were used, the Replace Select system showed significantly higher primary stability compared to the Branemark system (P = 0.000). In the replace select system, long implants had a significantly higher primary stability compared to medium and short length implants (P ≤ 0.003). In the NP and RP Branemark implants, short implants showed significantly lower primary stability compared to medium and long implants (P ≤ 0.002). However, in WP Branemark implants, primary stability increased significantly with increasing the IL from short to medium and from medium to long (P = 0.000). There were also significant differences between NP and the two other wider implants in both systems (P = 0.000). Conclusion: The use of tapered implants is recommended, especially, when the use of short implants is necessary. The use of RP implants is also preferred to WP

  2. Suppression of interfacial voids formation during silane (SiH4)-based silicon oxide bonding with a thin silicon nitride capping layer

    Science.gov (United States)

    Lee, Kwang Hong; Bao, Shuyu; Wang, Yue; Fitzgerald, Eugene A.; Seng Tan, Chuan

    2018-01-01

    The material properties and bonding behavior of silane-based silicon oxide layers deposited by plasma-enhanced chemical vapor deposition were investigated. Fourier transform infrared spectroscopy was employed to determine the chemical composition of the silicon oxide films. The incorporation of hydroxyl (-OH) groups and moisture absorption demonstrates a strong correlation with the storage duration for both as-deposited and annealed silicon oxide films. It is observed that moisture absorption is prevalent in the silane-based silicon oxide film due to its porous nature. The incorporation of -OH groups and moisture absorption in the silicon oxide films increase with the storage time (even in clean-room environments) for both as-deposited and annealed silicon oxide films. Due to silanol condensation and silicon oxidation reactions that take place at the bonding interface and in the bulk silicon, hydrogen (a byproduct of these reactions) is released and diffused towards the bonding interface. The trapped hydrogen forms voids over time. Additionally, the absorbed moisture could evaporate during the post-bond annealing of the bonded wafer pair. As a consequence, defects, such as voids, form at the bonding interface. To address the problem, a thin silicon nitride capping film was deposited on the silicon oxide layer before bonding to serve as a diffusion barrier to prevent moisture absorption and incorporation of -OH groups from the ambient. This process results in defect-free bonded wafers.

  3. A multivariate relationship for the impact sensitivities of energetic N-nitrocompounds based on bond dissociation energy.

    Science.gov (United States)

    Li, Jinshan

    2010-02-15

    The ZPE-corrected N-NO(2) bond dissociation energies (BDEs(ZPE)) of a series of model N-nitrocompounds and typical energetic N-nitrocompounds have been calculated using density functional theory methods. Computed results show that using the 6-31G** basis set the UB3LYP calculated BDE(ZPE) is similar to the B3PW91 but is less than the UB3P86 and that for both UB3P86 and UB3PW91 methods the 6-31G(**) calculated BDE(ZPE) is close to the 6-31++G(**). For the series of model N-nitrocompounds it is drawn from the NBO analysis that at the UB3LYP/6-31G(**) level the order of BDE(ZPE) is not only in line with that of bond order but also with that of the energy gap between N-NO(2) bond and antibond orbitals. For the typical energetic N-nitrocompounds the impact sensitivity is strongly related to the BDE(ZPE) indeed, and based on the BDEs(ZPE) calculated at different density functional theory levels this work has established a good multivariate correlation of impact sensitivity with molecular parameters, which provides a method to address the sensitivity problem.

  4. Parental Bonding

    Directory of Open Access Journals (Sweden)

    T. Paul de Cock

    2014-08-01

    Full Text Available Estimating the early parent–child bonding relationship can be valuable in research and practice. Retrospective dimensional measures of parental bonding provide a means for assessing the experience of the early parent–child relationship. However, combinations of dimensional scores may provide information that is not readily captured with a dimensional approach. This study was designed to assess the presence of homogeneous groups in the population with similar profiles on parental bonding dimensions. Using a short version of the Parental Bonding Instrument (PBI, three parental bonding dimensions (care, authoritarianism, and overprotection were used to assess the presence of unobserved groups in the population using latent profile analysis. The class solutions were regressed on 23 covariates (demographics, parental psychopathology, loss events, and childhood contextual factors to assess the validity of the class solution. The results indicated four distinct profiles of parental bonding for fathers as well as mothers. Parental bonding profiles were significantly associated with a broad range of covariates. This person-centered approach to parental bonding has broad utility in future research which takes into account the effect of parent–child bonding, especially with regard to “affectionless control” style parenting.

  5. Estimation of compressive strength based on Pull-Out bond test results for on-site concrete quality control

    Directory of Open Access Journals (Sweden)

    M. S. Lorrain

    Full Text Available Quality control of structural concrete has been conducted for several decades based mainly on the results of axial compression tests. This kind of test, although widely used, is not exempt from errors and has some considerable drawbacks that may affect its reliability, such as the need for appropriate and careful specimen conditioning and adoption of adequate capping techniques. For these reasons, it would be useful to have complementary or alternative ways to check compressive strength, in order to improve concrete quality control. The use of a bond test to monitor concrete strength is being proposed by an international group of researchers from France, Tunisia and Brazil as a potential means to this end. Given the fact that the link between bond resistance and concrete strength is already well established, this type of test seems to be a viable alternative to traditional methods. Nonetheless, to check if the underlying principle is sound when used in different circumstances, the group has been gathering data from several studies conducted by different researchers in various countries, with distinct concretes and rebar types. An analysis of the data collected shows that there is a clear and strong correlation between bond resistance and compressive strength, no matter the influence of other variables. This result validates the basic idea of using an Appropriate Pull-Out (APULOT bond test to assess concrete strength. If the general principle is valid for random data obtained from different studies, the definition of a clear and appropriate test will probably lead to the reduction of experimental noise and increase the precision of the strength estimates obtained using this method.

  6. Experimental study of the effects of exhaust plume and nozzle length on transonic and supersonic axisymmetric base flows : An experimental study

    NARCIS (Netherlands)

    van Gent, P.L.; Payanda (Student TUDelft), Qais; Brust (Student TUDelft), Steve; van Oudheusden, B.W.; Schrijer, F.F.J.

    2017-01-01

    PIV measurements have been carried out to study the effect of exhaust plume and nozzle length on the flow topology and mean pressure distribution of axisymmetric base flows at freestream Mach numbers 0.76 and 2.20. Four different nozzle lengths with and without exhaust plume have been tested. The

  7. PEGylation of Phytantriol-Based Lyotropic Liquid Crystalline Particles-The Effect of Lipid Composition, PEG Chain Length, and Temperature on the Internal Nanostructure

    DEFF Research Database (Denmark)

    Nilsson, Christa; Ostergaard, Jesper; Larsen, Susan Weng

    2014-01-01

    of these lipidic nonlamellar liquid crystalline particles by using DSPE-mPEGs with three different block lengths of the hydrophilic PEG segment. The effects of lipid composition, PEG chain length, and temperature on the morphology and internal nanostructure of these self-assembled lipidic aqueous dispersions based...

  8. Influence of increment thickness on dentin bond strength and light transmission of composite base materials.

    Science.gov (United States)

    Omran, Tarek A; Garoushi, Sufyan; Abdulmajeed, Aous A; Lassila, Lippo V; Vallittu, Pekka K

    2017-06-01

    Bulk-fill resin composites (BFCs) are gaining popularity in restorative dentistry due to the reduced chair time and ease of application. This study aimed to evaluate the influence of increment thickness on dentin bond strength and light transmission of different BFCs and a new discontinuous fiber-reinforced composite. One hundred eighty extracted sound human molars were prepared for a shear bond strength (SBS) test. The teeth were divided into four groups (n = 45) according to the resin composite used: regular particulate filler resin composite: (1) G-ænial Anterior [GA] (control); bulk-fill resin composites: (2) Tetric EvoCeram Bulk Fill [TEBF] and (3) SDR; and discontinuous fiber-reinforced composite: (4) everX Posterior [EXP]. Each group was subdivided according to increment thickness (2, 4, and 6 mm). The irradiance power through the material of all groups/subgroups was quantified (MARC® Resin Calibrator; BlueLight Analytics Inc.). Data were analyzed using two-way ANOVA followed by Tukey's post hoc test. SBS and light irradiance decreased as the increment's height increased (p composite used. EXP presented the highest SBS in 2- and 4-mm-thick increments when compared to other composites, although the differences were not statistically significant (p > 0.05). Light irradiance mean values arranged in descending order were (p composites. Discontinuous fiber-reinforced composite showed the highest value of curing light transmission, which was also seen in improved bonding strength to the underlying dentin surface. Discontinuous fiber-reinforced composite can be applied safely in bulks of 4-mm increments same as other bulk-fill composites, although, in 2-mm thickness, the investigated composites showed better performance.

  9. Fractal-Based Lightning Channel Length Estimation from Convex-Hull Flash Areas for DC3 Lightning Mapping Array Data

    Science.gov (United States)

    Bruning, Eric C.; Thomas, Ronald J.; Krehbiel, Paul R.; Rison, William; Carey, Larry D.; Koshak, William; Peterson, Harold; MacGorman, Donald R.

    2013-01-01

    We will use VHF Lightning Mapping Array data to estimate NOx per flash and per unit channel length, including the vertical distribution of channel length. What s the best way to find channel length from VHF sources? This paper presents the rationale for the fractal method, which is closely related to the box-covering method.

  10. One-dimensional thermal evolution calculation based on a mixing length theory: Application to Saturnian icy satellites

    Science.gov (United States)

    Kamata, S.

    2017-12-01

    Solid-state thermal convection plays a major role in the thermal evolution of solid planetary bodies. Solving the equation system for thermal evolution considering convection requires 2-D or 3-D modeling, resulting in large calculation costs. A 1-D calculation scheme based on mixing length theory (MLT) requires a much lower calculation cost and is suitable for parameter studies. A major concern for the MLT scheme is its accuracy due to a lack of detailed comparisons with higher dimensional schemes. In this study, I quantify its accuracy via comparisons of thermal profiles obtained by 1-D MLT and 3-D numerical schemes. To improve the accuracy, I propose a new definition of the mixing length (l), which is a parameter controlling the efficiency of heat transportation due to convection. Adopting this new definition of l, I investigate the thermal evolution of Dione and Enceladus under a wide variety of parameter conditions. Calculation results indicate that each satellite requires several tens of GW of heat to possess a 30-km-thick global subsurface ocean. Dynamical tides may be able to account for such an amount of heat, though their ices need to be highly viscous.

  11. Shear Bond Strength of Porcelain to a Base-Metal Compared to Zirconia Core

    OpenAIRE

    Abrisham, SM.; Fallah Tafti, A.; Kheirkhah, S.; Tavakkoli, MA.

    2017-01-01

    Statement of Problem: Recent clinical results for Zirconia all-ceramic restorations have revealed that the fracture rate 6-15% of the Zirconia framework is so low and the core of Zirconia has high stability. However, chipping-off fractures of porcelain are the most common reason for failures of Zirconia in the fixed partial dentures. Objectives: The purpose of this study was to compare the shear bond strength (SBS) of porcelain in the porcelain fused to metal and all-ceramic crowns with Z...

  12. Polyacrylonitrile based composite materials with extracting agents containing chemically bonded CMPO groups for separation of actinoids

    International Nuclear Information System (INIS)

    Jan Kamenik; Ferdinand Sebesta; Jan John

    2015-01-01

    Composite materials made from polyacrylonitrile binding polymer and solid extracting agents with functional groups of diphenyl-carbamoylmethylphosphine oxide bonded to a platform of calix[4]arenes and cobalt bis(dicarbollide) cluster anion were tested for application in column chromatography. They exhibited high affinity for americium, plutonium, uranium, and europium ions in nitric acid solutions. However, europium distribution isotherm in 3 M HNO 3 indicated low capacity and unsatisfactory employment of the functional groups. Similar material with octyl(phenyl)-N,N'-diisobutylcarbamoylmethylphosphine oxide extracting agent had both high affinity and uptake capacity. (author)

  13. Effect of retreatment on the push-out bond strength of MTA-based and epoxy resin-based endodontic sealers

    Directory of Open Access Journals (Sweden)

    Hamidreza Yavari

    2017-03-01

    Full Text Available Background. Further studies on the adhesion properties of MTA-based materials seem necessary due to their growing use in endodontic treatment. This research aimed to assess the effect of retreatment on the bond strength of MTA-based (MTA Fillapex and epoxy resin-based (AH Plus sealers. Methods. ProTaper rotary files were applied to prepare the root canals of 80 human mandibular premolars. Then, the roots were randomly divided intotwo groups of A (n=40 and B (n=40, which were obturated with gutta-percha and MTA Filla-pex and AH Plus sealer, respectively. In both groups, the teeth were randomly subdivided into 2 subgroups. No retreatment was carried out in subgroups A1 and B1, while subgroups A2 and B2 were retreated with rotary files and a solvent. Then, a push-out test was performed on four 2-mm slices of each tooth at a distance of 2 mm from the coronal surface after two weeks of incubation. Data were analyzed with two-way ANOVA and statistical significance was set at P<0.05. Results. Regardless of the procedure followed (P<0.001, significant differences were detected in the mean bond strength values between the two sealers. Irrespective of the sealer type (P=0.3, no significant differences were revealed by comparing the mean bond strength values of the study subgroups. Furthermore, no statistically significant interaction (P=0.5 was found between the treatment and sealer types. Conclusion. AH Plus sealer exhibited a higher bond strength compared to MTA Fillapex. Retreatment using rotary files and chloroform had no statistically significant effect on the bond strength of sealers evaluated in this study.

  14. Effects of triazine dithione and hydrophobic phosphate monomers on bonding to Ag-Pd-Cu-Au alloy and titanium with a methacrylic resin-based luting agent.

    Science.gov (United States)

    Koizumi, Hiroyasu; Ishii, Takaya; Naito, Koji; Yoneyama, Takayuki; Tanoue, Naomi; Matsumura, Hideo

    2010-06-01

    The purpose of the current study was to evaluate the effects of thione and phosphate functional monomers on bond strength and durability of a methacrylic resin luting agent joined to silver-palladium based alloy and titanium. Disk specimens of two different sizes (10 mm and 8 mm in diameter by 2.5 mm thickness) were prepared from silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy and titanium. The specimens were ground with abrasive paper, and divided into four groups based on the following conditions: 1) unprimed control; 2) priming with Alloy Primer (thione and phosphate); 3) priming with Estenia Opaque Primer (phosphate); and 4) priming with VPrimer (thione). The disks were bonded with tri-n-butylborane (TBB)-initiated resin, and shear bond strengths were determined both before and after thermocycling. The Alloy Primer and V-Primer agents containing a triazine dithione monomer (VTD) bonded the Ag-Pd-Cu-Au alloy, whereas the Alloy Primer and Estenia Opaque Primer agents containing a hydrophobic phosphate monomer (MDP) bonded titanium. The reduction in bond strength after 20,000 thermocycles was not remarkable for the two groups (Alloy Primer and Ag-Pd-Cu-Au alloy; V-Primer and Ag-Pd-Cu-Au alloy). The thione monomer was effective in bonding the Ag-Pd-Cu-Au alloy, whereas the phosphate monomer was useful for bonding titanium. The thione did not interfere with the bonding of MDP to titanium, and MDP did not negatively affect bonding of VTD to the Ag-Pd-Cu-Au alloy. The combinations of two thione primers and the Ag-Pd-Cu- Au alloy exhibited the best adhesive performance within the limitations of the current experiment.

  15. A survey on the effects of three surface treatment methods on bond strength between base-metal alloys and Ceromer material (Targis)

    OpenAIRE

    Rokni. Sh.; Mehdizade. Sh

    2004-01-01

    Statement of Problem: Ceramics and resins belong to the earliest tooth restorative materials. Nowadays new generations of these materials have provided a revolution in cosmetic dentistry. Ceramic Optimized polymer (Ceromer) is a newly made product that the bond between this material and base metal alloys, which are used widely today, is paid too much attention. Purpose: The aim of this study was to evaluate the bond strength of targis (Ceromer) to three types of base metal alloys through thre...

  16. Modulation of a Molecular π-Electron System in a Purely Organic Conductor that Shows Hydrogen-Bond-Dynamics-Based Switching of Conductivity and Magnetism.

    Science.gov (United States)

    Ueda, Akira; Hatakeyama, Akari; Enomoto, Masaya; Kumai, Reiji; Murakami, Youichi; Mori, Hatsumi

    2015-10-12

    New important aspects of the hydrogen-bond (H-bond)-dynamics-based switching of electrical conductivity and magnetism in an H-bonded, purely organic conductor crystal have been discovered by modulating its tetrathiafulvalene (TTF)-based molecular π-electron system by means of partial sulfur/selenium substitution. The prepared selenium analogue also showed a similar type of phase transition, induced by H-bonded deuterium transfer followed by electron transfer between the H-bonded TTF skeletons, and the resulting switching of the physical properties; however, subtle but critical differences due to sulfur/selenium substitution were detected in the electronic structure, phase transition nature, and switching function. A molecular-level discussion based on the crystal structures shows that this chemical modification of the TTF skeleton influences not only its own π-electronic structure and π-π interactions within the conducting layer, but also the H-bond dynamics between the TTF π skeletons in the neighboring layers, which enables modulation of the interplay between the H-bond and π electrons to cause such differences. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Self-healing polyurethane/attapulgite nanocomposites based on disulfide bonds and shape memory effect

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yurun; Chen, Dajun, E-mail: cdj@dhu.edu.cn

    2017-07-01

    Nanocomposites with remarkable enhanced mechanical properties have attracted great research efforts recently. In this work, a series of self-healing polyurethane/attapulgite nanocomposites were prepared by solution blending. Introducing self-healing ability and attapulgite (AT) reinforcement simultaneously led to prolonged material lifetime and enhanced mechanical properties. Scanning electron microscope (SEM) observation indicated that AT could achieve a uniform dispersion in polyurethane matrix when AT content was relatively low. The influences on mechanical properties were evaluated by tensile test. Results showed that incorporating an appropriate content of AT would lead to an enhanced tensile properties. The interactions between AT and polyurethane matrix were studied by effective cross-linking density calculation and Fourier transform infrared (FTIR) analysis. Results indicated that rich hydrogen bonds were formed between AT and polyurethane matrix. Displacement data was utilized to evaluate the influence on shape memory effect. With the incorporation of AT, deformation of the sample under external force was restrained. Meanwhile, closure of the scratches still can be accomplished during healing process. Results of healing test suggested that incorporating 1% of AT would also promote self-healing property. - Highlights: • Composites with both self-healing and enhanced mechanical property are prepared. • Healing mechanism relies on disulfide exchange reaction and shape memory effect. • Mechanical enhancement is caused by rich hydrogen bonds introduced by attapulgite.

  18. Chemical bonding in copper-based transparent conducting oxides: CuMO{sub 2} (M = In, Ga, Sc)

    Energy Technology Data Exchange (ETDEWEB)

    Godinho, K G; Morgan, B J; Allen, J P; Scanlon, D O; Watson, G W, E-mail: scanloda@tcd.ie, E-mail: watsong@tcd.ie [School of Chemistry and CRANN, Trinity College Dublin, Dublin 2 (Ireland)

    2011-08-24

    The geometry and electronic structure of copper-based p-type delafossite transparent conducting oxides, CuMO{sub 2} (M = In, Ga, Sc), are studied using the generalized gradient approximation (GGA) corrected for on-site Coulomb interactions (GGA + U). The bonding and valence band compositions of these materials are investigated, and the origins of changes in the valence band features between group 3 and group 13 cations are discussed. Analysis of the effective masses at the valence and conduction band edge explains the experimentally reported conductivity trends.

  19. Fitting the pieces of the puzzle: the δ bond.

    Science.gov (United States)

    Falvello, Larry R; Foxman, Bruce M; Murillo, Carlos A

    2014-09-15

    The development of our understanding of the δ bond and its role in quadruple metal-metal bonding is described in terms of the conceptual advances and experimental and theoretical results achieved through a 50-year period beginning with the seminal report by Cotton and co-workers in 1964. The work behind the original discovery is described, along with the qualitative orbital description of the components of the quadruple bond. The effect of torsion about the metal-metal axis on the metal-metal bond length is described, together with the conclusion that this accords with a progressive loss of the δ component of the metal-metal bond. The important role of photoelectron spectroscopy in characterizing the loss of electrons from the metal-metal bonding orbitals is reviewed, as are the electron paramagnetic resonance results that establish that unpaired electrons, when present, populate metal-based orbitals. Other important results are described: destabilization of the metal-metal bond to produce strong reducing agents, exceptions to the expected orbital ordering, and the use of chiroptical properties to reveal additional information about the electronic structure of the metal-metal bond.

  20. Bonding of acrylic denture teeth to MMA/PMMA and light-curing denture base materials: the role of conditioning liquids.

    Science.gov (United States)

    Palitsch, Anne; Hannig, Matthias; Ferger, Paul; Balkenhol, Markus

    2012-03-01

    The connection between resin denture teeth and the denture base is essential for the integrity of partial and full dentures. The aim of the present study was to analyse the bond strength of acrylic denture teeth to two light curing denture base materials compared to the gold-standard (MMA/PMMA) using different conditioning liquids. The ridge laps of 220 identical denture teeth were ground and pre-treated using different conditioning liquids (MMA, an experimental conditioning liquid as well as the two commercially available liquids Palabond and Versyo.bond). The denture base materials (PalaXpress, Versyo.com, Eclipse) were applied using a split mould to obtain tensile bond strength specimens of identical shape. Ten specimens per test group were either stored in water for 24h or thermocycled (5000×, 5-55°C) prior to tensile bond strength testing (cross-head speed 10mm/min). Data was subjected to parametric statistics (α=0.05). The three-way ANOVA revealed a significant influence of the material, pre-treatment as well as the storage. PalaXpress showed the highest bond strength (24.3MPa) of all materials tested after TC, whereas the use of MMA led to the most constant results. Lower values were recorded for Versyo.com (17.5MPa) and Eclipse (10.4MPa) bonded with Versyo.bond. The results indicate that MMA/PMMA based denture base resins provide reliable and durable bond strength to acrylic denture teeth. Using light-curing denture base materials requires the application of appropriate conditioning liquids to obtain acceptable bond strength. The use of MMA affects bond strength to light-curing denture base materials. The pre-treatment of denture teeth is critical regarding their bond-strength to denture base materials and in turn for the integrity of removable full and partial dentures. Light-curing denture base resins are more sensitive to the correct tooth pre-treatment compared to conventional MMA/PMMA materials, requiring specific conditioning liquids. Copyright

  1. A method for estimating age of medieval sub-adults from infancy to adulthood based on long bone length.

    Science.gov (United States)

    Primeau, Charlotte; Friis, Laila; Sejrsen, Birgitte; Lynnerup, Niels

    2016-01-01

    To develop a series of regression equations for estimating age from length of long bones for archaeological sub-adults when aging from dental development cannot be performed. Further, to compare derived ages when using these regression equations, and two other methods. A total of 183 skeletal sub-adults from the Danish medieval period, were aged from radiographic images. Linear regression formulae were then produced for individual bones. Age was then estimated from the femur length using three different methods: equations developed in this study, data based on a modern population (Maresh: Human growth and development (1970) pp 155-200), and, lastly, based on archeological data with known ages (Rissech et al.: Forensic Sci Int 180 (2008) 1-9). As growth of long bones is known to be non-linear it was tested if the regression model could be improved by applying a quadratic model. Comparison between estimated ages revealed that the modern data result in lower estimated ages when compared to the Danish regression equations. The estimated ages using the Danish regression equations and the regression equations developed by Rissech et al. (Forensic Sci Int 180 (2007) 1-9) were very similar, if not identical. This indicates that the growth between the two archaeological populations is not that dissimilar. This would suggest that the regression equations developed in this study may potentially be applied to archaeological material outside Denmark as well as later than the medieval period, although this would require further testing. The quadratic equations are suggested to yield more accurate ages then using simply linear regression equations. © 2015 Wiley Periodicals, Inc.

  2. Corporate Bonds in Denmark

    DEFF Research Database (Denmark)

    Tell, Michael

    2015-01-01

    Corporate financing is the choice between capital generated by the corporation and capital from external investors. However, since the financial crisis shook the markets in 2007–2008, financing opportunities through the classical means of financing have decreased. As a result, corporations have...... to think in alternative ways such as issuing corporate bonds. A market for corporate bonds exists in countries such as Norway, Germany, France, the United Kingdom and the United States, while Denmark is still behind in this trend. Some large Danish corporations have instead used foreign corporate bonds...... markets. However, NASDAQ OMX has introduced the First North Bond Market in December 2012 and new regulatory framework came into place in 2014, which may contribute to a Danish based corporate bond market. The purpose of this article is to present the regulatory changes in Denmark in relation to corporate...

  3. Corporate Bonds in Denmark

    DEFF Research Database (Denmark)

    Tell, Michael

    2015-01-01

    Corporate financing is the choice between capital generated by the corporation and capital from external investors. However, since the financial crisis shook the markets in 2007–2008, financing opportunities through the classical means of financing have decreased. As a result, corporations have...... markets. However, NASDAQ OMX has introduced the First North Bond Market in December 2012 and new regulatory framework came into place in 2014, which may contribute to a Danish based corporate bond market. The purpose of this article is to present the regulatory changes in Denmark in relation to corporate...... bonds. The purpose is further to analyse the tax consequences of issuing bonds in both a direct issue of bonds and through securitization....

  4. Comparison effect of artificial tooth type and cyclic loading on the bond strength to auto-polymerized acrylic denture base resins

    Directory of Open Access Journals (Sweden)

    Fateme Nematollahi

    2013-05-01

    Full Text Available   Background and Aims: Failure of bonding between artificial teeth and denture base material is a considerable problem for patients who wear dentures. According to the different impact of artificial teeth and different information about resistance force of mastication and also with deficiency in researchs, this study was designed to compare the bond strength of composite and acrylic artificial teeth to auto-polymerized denture base resins with and without cyclic loading.   Materials and Methods: In this experimental and in vitro study, an acrylic resin auto-polymerized (Rapid Repair, Dentsply and four artificial teeth (Acrylic Marjan new, Composite Glamour teeth and Ivoclar acrylic and composite teeth were used. Therefore, 8 groups of 10 specimens each were evaluated. All specimens were thermocycled for 5000 cycles, in water baths between 5 and 55 ◦ C. Half the specimens in each group were treated with cyclic loading at 50N for 14, 400 cycles at 1.2 Hz. The shear bond strengths were measured using a Universal Testing Machine. Data were analyzed using Two-way ANOVA test.   Results: Statistical analysis demonstrated no significant effect of cyclic loading on the shear bond strength, but the type of artificial tooth affected the shear bond strength (P=0.006. Also, the interaction between Cyclic loading and the type of artificial tooth showed no significant difference (P=0.98. Tukey test showed that acrylic teeth (Ivoclar had statistically higher bond strength values than that of other teeth (PGlamour=0.02, (PComposite ivoclar=0.01 and (PMarjan new=0.02.   Conclusion: Within the limitation of this study, the predominant type of fracture in all groups was cohesive, therefore the bond strength was adequate in all teeth and the type of artificial tooth may influence the bond strength of denture teeth to denture base resin. Cyclic loading had no significant effect on the bond strength of denture teeth to the auto-polymerized acrylic resin.

  5. Comparison of Bond Strength of Brackets with Foil Mesh and Laser Structure Base using Light Cure Composite Resin: An in vitro Study.

    Science.gov (United States)

    Rajesh, R N G; Girish, K S; Sanjay, N; Scindhia, Rajath D; Kumar, Sujay G; Rajesh, Suchitra

    2015-12-01

    The purpose of this in vitro study was to evaluate the bond strength of the laser-etched base bracket, site of bond failure, and evaluate for enamel remnants on the bracket base after debonding, when compared to foil mesh base bracket. Sixty noncarious, human premolar extracted for the orthodontic treatment were used for this study. The teeth were randomly divided into two groups containing 30 teeth each, which were bonded with laser-etched base bracket and mesh base bracket using light cure resin. The tensile and mechanical bond strength was tested after 24 hours using TIRA. The forces recorded during debonding were measured in Newton and final readings were tabulated in megapascals (MPa). After debonding, the amount of residual adhesive and enamel detachment on the bracket base were assessed according to adhesive remnant index (ARI) and enamel detachment index (EDI) using stereomicroscope and energy dispersive X-ray spectrometer. The laser-etched base bracket showed statistically significant higher results than mesh base bracket. Mann-Whitney test indicated that laser-etched base bracket had significantly higher tensile bond strength of 8.47 MPa (SD ± 0.84), fatigue strength of 7.75 MPa (SD ± 0.79) compared to mesh base bracket with tensile bond strength of 5.53 Mpa (SD ± 0.89) and fatigue strength of 5.17 MPa (SD ± 1.15). Adhesive remnant index score indicated that laser-etched base bracket had ARI score of 3 for most of the bracket, when compared to mesh base bracket. This was statistically significant. Enamel detachment index scores indicated that less than 10% of enamel detachment occurred in both the types of brackets, which was not statistically significant. Laser-etched base bracket showed superior bond strength, when compared to the foil mesh base bracket. The site of bond failure of these laser-etched base bracket was at the interface of enamel-adhesive and did not induce any significant enamel detachment. Thus, we can conclude that laser-etched base

  6. The earthing system of the PRIMA Neutral Beam Test Facility based on the Mesh Common Bonding Network topology

    International Nuclear Information System (INIS)

    Pomaro, Nicola; Boldrin, Marco; Lazzaro, Gabriele

    2015-01-01

    Highlights: • We designed a high performance earthing system for the ITER Neutral Beam Test Facility. • The system is based on the Mesh Common Bonded Network topology. • Careful bonding of all metallic structures allowed to obtain a well meshed system. • Special care was dedicated to improve EMC performance of critical areas like control rooms. • The facility experimental results will be representative also of the ITER situation. - Abstract: PRIMA is a large experimental facility under realization in Padova, aimed at developing and testing the Neutral Beam Injectors for ITER. The operation of these devices involves high RF power and voltage up to 1 MV. Frequent and high voltage electrical breakdowns inside the beam sources occur regularly. The presence of a distributed carefully optimized earthing system is of paramount importance to achieve a satisfying disturbances immunity for equipment and diagnostics. The paper describes the design and the realization of the earthing system of the PRIMA facility, which is based on the MESH-Common Bonding Network (MESH-CBN) topology, as recommended by IEC and IEEE standards for installations with high levels of Electromagnetic Interferences (EMI). The principles of the MESH-CBN approach were adapted to the PRIMA layout, which is composed by several buildings, that are independent for seismic and architectural reasons, but are linked by many electrical conduits and hydraulic pipelines. The availability of huge foundations, with a large number of poles and pillars, was taken into account; building parts dedicated to host control rooms and sensitive equipment were treated with particular care. Moreover, the lightning protection system was integrated and harmonized with the earthing system.

  7. Eutectic-based wafer-level-packaging technique for piezoresistive MEMS accelerometers and bond characterization using molecular dynamics simulations

    Science.gov (United States)

    Aono, T.; Kazama, A.; Okada, R.; Iwasaki, T.; Isono, Y.

    2018-03-01

    We developed a eutectic-based wafer-level-packaging (WLP) technique for piezoresistive micro-electromechanical systems (MEMS) accelerometers on the basis of molecular dynamics analyses and shear tests of WLP accelerometers. The bonding conditions were experimentally and analytically determined to realize a high shear strength without solder material atoms diffusing to adhesion layers. Molecular dynamics (MD) simulations and energy dispersive x-ray (EDX) spectrometry done after the shear tests clarified the eutectic reaction of the solder materials used in this research. Energy relaxation calculations in MD showed that the diffusion of solder material atoms into the adhesive layer was promoted at a higher temperature. Tensile creep MD simulations also suggested that the local potential energy in a solder material model determined the fracture points of the model. These numerical results were supported by the shear tests and EDX analyses for WLP accelerometers. Consequently, a bonding load of 9.8 kN and temperature of 300 °C were found to be rational conditions because the shear strength was sufficient to endure the polishing process after the WLP process and there was little diffusion of solder material atoms to the adhesion layer. Also, eutectic-bonding-based WLP was effective for controlling the attenuation of the accelerometers by determining the thickness of electroplated solder materials that played the role of a cavity between the accelerometers and lids. If the gap distance between the two was less than 6.2 µm, the signal gains for x- and z-axis acceleration were less than 20 dB even at the resonance frequency due to air-damping.

  8. Giant negative thermal expansion in bonded MnCoGe-based compounds with Ni2In-type hexagonal structure.

    Science.gov (United States)

    Zhao, Ying-Ying; Hu, Feng-Xia; Bao, Li-Fu; Wang, Jing; Wu, Hui; Huang, Qing-Zhen; Wu, Rong-Rong; Liu, Yao; Shen, Fei-Ran; Kuang, Hao; Zhang, Ming; Zuo, Wen-Liang; Zheng, Xin-Qi; Sun, Ji-Rong; Shen, Bao-Gen

    2015-02-11

    MnCoGe-based compounds undergo a giant negative thermal expansion (NTE) during the martensitic structural transition from Ni2In-type hexagonal to TiNiSi-type orthorhombic structure. High-resolution neutron diffraction experiments revealed that the expansion of unit cell volume can be as large as ΔV/V ∼ 3.9%. The optimized compositions with concurrent magnetic and structural transitions have been studied for magnetocaloric effect. However, these materials have not been considered as NTE materials partially due to the limited temperature window of phase transition. The as-prepared MnCoGe-based compounds are quite brittle and naturally collapse into powders. By using a few percents (3-4%) of epoxy to bond the powders, we introduced residual stress in the bonded samples and thus realized the broadening of structural transition by utilizing the specific characteristics of lattice softening enforced by the stress. As a result, giant NTE (not only the linear NTE coefficient α but also the operation-temperature window) has been achieved. For example, the average α̅ as much as -51.5 × 10(-6)/K with an operating temperature window as wide as 210 K from 122 to 332 K has been observed in a bonded MnCo0.98Cr0.02Ge compound. Moreover, in the region between 250 and 305 K near room temperature, the α value (-119 × 10(-6)/K) remains nearly independent of temperature. Such an excellent performance exceeds that of most other materials reported previously, suggesting it can potentially be used as a NTE material, particularly for compensating the materials with large positive thermal expansions.

  9. Laser-based surface patterning of composite plates for improved secondary adhesive bonding

    KAUST Repository

    Tao, Ran

    2018-03-01

    The effects of laser irradiation surface pretreatments on the mode I fracture toughness of adhesively bonded composite joints were evaluated. First, pulsed CO2 laser irradiation was uniformly deployed on carbon fiber reinforced polymer (CFRP) substrates. Next, double cantilever beam (DCB) tests were performed to assess the effects of surface pretreatments on the mode I fracture toughness of the adhesive joints. Then, a thoughtful combination of the proposed surface pretreatments was deployed to fabricate DCB specimens with patterned interfaces. A wide range of techniques, including X-ray photoelectron spectroscopy (XPS), contact profilometry, and optical and scanning electron microscopy (SEM) were used to ascertain the effects of all investigated surface pretreatments. It is shown that patterning promoted damage mechanisms that were not observed in the uniformly treated interfaces, resulting in an effective fracture toughness well above that predicted by a classical rule of mixture.

  10. Self-bonded composite films based on cellulose nanofibers and chitin nanocrystals as antifungal materials.

    Science.gov (United States)

    Robles, Eduardo; Salaberria, Asier M; Herrera, Rene; Fernandes, Susana C M; Labidi, Jalel

    2016-06-25

    Cellulose nanofibers and chitin nanocrystals, two main components of agricultural and aquacultural by-products, were obtained from blue agave and yellow squat lobster industrial residues. Cellulose nanofibers were obtained using high pressure homogenization, while chitin nanocrystals were obtained by hydrolysis in acid medium. Cellulose nanofibers and chitin nanocrystals were characterized by X-ray diffraction, Atomic Force Microscopy and Infrared spectroscopy. Self-bonded composite films with different composition were fabricated by hot pressing and their properties were evaluated. Antifungal activity of chitin nanocrystals was studied using a Cellometer(®) cell count device, mechanical properties at tension were measured with a universal testing machine, water vapor permeability was evaluated with a thermohygrometer and surface tension with sessile drop contact angle method. The addition of chitin nanocrystals reduced slightly the mechanical properties of the composite. Presence of chitin nanocrystals influenced the growth of Aspergillus sp fungus in the surface of the composites as expected. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Printable optical sensors based on H-bonded supramolecular cholesteric liquid crystal networks.

    Science.gov (United States)

    Herzer, Nicole; Guneysu, Hilal; Davies, Dylan J D; Yildirim, Derya; Vaccaro, Antonio R; Broer, Dirk J; Bastiaansen, Cees W M; Schenning, Albertus P H J

    2012-05-09

    A printable H-bonded cholesteric liquid crystal (CLC) polymer film has been fabricated that, after conversion to a hygroscopic polymer salt film, responds to temperature and humidity by changing its reflection color. Fast-responding humidity sensors have been made in which the reflection color changes between green and yellow depending on the relative humidity. The change in reflection band is a result of a change in helix pitch in the film due to absorption and desorption of water, resulting in swelling/deswelling of the film material. When the polymer salt was saturated with water, a red-reflecting film was obtained that can potentially act as a time/temperature integrator. Finally, the films were printed on a foil, showing the potential application of supramolecular CLC materials as low-cost, printable, battery-free optical sensors.

  12. The human-animal bond in veterinary medical education: accessing web-based information.

    Science.gov (United States)

    Hart, Lynette A; Wood, Mary W

    2008-01-01

    Various aspects of the field known as the human-animal bond (HAB), or human-animal interactions, have expanded within veterinary medical education over the past quarter of a century. Using a variety of databases and informed search strategies, relevant information can be accessed, including recent articles, databases, journals, academic centers, societies and associations, programs, and key references. In this paper, methods for accessing resources supporting veterinary education on the HAB are organized into four subject areas: the HAB in veterinary school curricula; social work and support services for veterinary clients; the benefits of the HAB for human well-being, with applications of animal-assisted therapies, activities, and education; and companion animal behavior and welfare concerns. A related Web site can be accessed at http://www.vetmed.ucdavis.edu/CCAB/humananimalinteractions.html.

  13. Versatile micropipette technology based on deep reactive ion etching and anodic bonding for biological applications

    International Nuclear Information System (INIS)

    Lopez-Martinez, M J; Campo, E M; Esteve, J; Plaza, J A; Caballero, D; Errachid, A; Fernandez, E

    2009-01-01

    A novel, versatile and robust technology to manufacture transparent micropipettes, suitable for biological applications, is presented here. Up to three deep reactive ion etchings have been included in the manufacturing process, providing highly controlled geometry of reservoirs, connection cavities and inlet ports. Etching processes have been used for the definition of chip and reservoir and for nozzle release. Additionally, special design considerations have been developed to facilitate micro-to-macro fluidic connections. Implementation of anodic bonding to seal a glass substrate to the fluidic structure etched on Si, allowed observation of the flow inside the reservoir. Flow tests have been conducted by filling channels with different fluids. Flow was observed under an optical microscope, both during capillary filling and also during pumping. Dispensing has been demonstrated by functionalizing the surface of an AFM cantilever. Mechanical tests performed by piercing live mouse cells with FIB-sharpened micropipettes suggest the design is sturdy for biological piercing applications

  14. Ovulation Prevalence in Women with Spontaneous Normal-Length Menstrual Cycles - A Population-Based Cohort from HUNT3, Norway.

    Directory of Open Access Journals (Sweden)

    Jerilynn C Prior

    Full Text Available Ovulatory menstrual cycles are essential for women's fertility and needed to prevent bone loss. There is a medical/cultural expectation that clinically normal menstrual cycles are inevitably ovulatory. Currently within the general population it is unknown the proportion of regular, normal-length menstrual cycles that are ovulatory. Thus, the objective of this study was to determine the population point prevalence of ovulation in premenopausal, normally menstruating women. The null hypothesis was that such cycles are ovulatory.This is a single-cycle, cross-sectional, population-based study-a sub-study of the HUNT3 health study in the semi-rural county (Nord Trøndelag in mid-Norway. Participants included >3,700 spontaneously (no hormonal contraception menstruating women, primarily Caucasian, ages 20-49.9 from that county. Participation rate was 51.9%. All reported the date previous flow started. A single, random serum progesterone level was considered ovulatory if ≥9.54 nmol/L on cycle days 14 to -3 days before usual cycle length (CL.Ovulation was assessed in 3,168 women mean age 41.7 (interquartile range, [IQR] 36.8 to 45.5, cycle length 28 days (d (IQR 28 to 28 and body mass index (BMI 26.3 kg/m2 (95% CI 26.1 to 26.4. Parity was 95.6%, 30% smoked, 61.3% exercised regularly and 18% were obese. 1,545 women with a serum progesterone level on cycle days 14 to -3 were presumed to be in the luteal phase. Of these, 63.3% of women had an ovulatory cycle (n = 978 and 37% (n = 567 were anovulatory. Women with/ without ovulation did not differ in age, BMI, cycle day, menarche age, cigarette use, physical activity, % obesity or self-reported health. There were minimal differences in parity (96.7% vs. 94.5%, P = 0.04 and major differences in progesterone level (24.5 vs. 3.8 nmol/L, P = 0.001.Anovulation in a random population occurs in over a third of clinically normal menstrual cycles.

  15. VLSI Design of a Variable-Length FFT/IFFT Processor for OFDM-Based Communication Systems

    Directory of Open Access Journals (Sweden)

    Jen-Chih Kuo

    2003-12-01

    Full Text Available The technique of {orthogonal frequency division multiplexing (OFDM} is famous for its robustness against frequency-selective fading channel. This technique has been widely used in many wired and wireless communication systems. In general, the {fast Fourier transform (FFT} and {inverse FFT (IFFT} operations are used as the modulation/demodulation kernel in the OFDM systems, and the sizes of FFT/IFFT operations are varied in different applications of OFDM systems. In this paper, we design and implement a variable-length prototype FFT/IFFT processor to cover different specifications of OFDM applications. The cached-memory FFT architecture is our suggested VLSI system architecture to design the prototype FFT/IFFT processor for the consideration of low-power consumption. We also implement the twiddle factor butterfly {processing element (PE} based on the {{coordinate} rotation digital computer (CORDIC} algorithm, which avoids the use of conventional multiplication-and-accumulation unit, but evaluates the trigonometric functions using only add-and-shift operations. Finally, we implement a variable-length prototype FFT/IFFT processor with TSMC 0.35 μm 1P4M CMOS technology. The simulations results show that the chip can perform (64-2048-point FFT/IFFT operations up to 80 MHz operating frequency which can meet the speed requirement of most OFDM standards such as WLAN, ADSL, VDSL (256∼2K, DAB, and 2K-mode DVB.

  16. A Knowledge-Based Step Length Estimation Method Based on Fuzzy Logic and Multi-Sensor Fusion Algorithms for a Pedestrian Dead Reckoning System

    Directory of Open Access Journals (Sweden)

    Ying-Chih Lai

    2016-05-01

    Full Text Available The demand for pedestrian navigation has increased along with the rapid progress in mobile and wearable devices. This study develops an accurate and usable Step Length Estimation (SLE method for a Pedestrian Dead Reckoning (PDR system with features including a wide range of step lengths, a self-contained system, and real-time computing, based on the multi-sensor fusion and Fuzzy Logic (FL algorithms. The wide-range SLE developed in this study was achieved by using a knowledge-based method to model the walking patterns of the user. The input variables of the FL are step strength and frequency, and the output is the estimated step length. Moreover, a waist-mounted sensor module has been developed using low-cost inertial sensors. Since low-cost sensors suffer from various errors, a calibration procedure has been utilized to improve accuracy. The proposed PDR scheme in this study demonstrates its ability to be implemented on waist-mounted devices in real time and is suitable for the indoor and outdoor environments considered in this study without the need for map information or any pre-installed infrastructure. The experiment results show that the maximum distance error was within 1.2% of 116.51 m in an indoor environment and was 1.78% of 385.2 m in an outdoor environment.

  17. Effect of Different Surface Treatments and Thermocycling on Bond Strength of a Silicone-based Denture Liner to a Denture Base Resin.

    Science.gov (United States)

    Nakhaei, Mohammadreza; Dashti, Hossein; Ahrari, Farzaneh; Vasigh, Samaneh; Mushtaq, Shazia; Shetty, Rohit Mohan

    2016-02-01

    The aim of this study is to evaluate the effects of three different surface treatments and thermocycling on the tensile strength of a silicone lining material to denture resin. A total of 96 cube-shaped specimens were fabricated using heat-cured polymethyl methacrylate (PMMA) denture base resin. Three millimeters of the material was cut from the midsection. The specimens were divided into four groups. The bonding surfaces of the specimens in each group received one of the following surface treatments: no surface treatment (control group), airborne particle abrasion with 110 pirn alumina particles (air abrasion group), Er:yttrium aluminum garnet laser irradiation (laser group), and air abrasion + laser. After the lining materials were processed between the two PMMA blocks, each group was divided into two subgroups (n = 12), either stored in distilled water at 37°C for 24 hours or thermocycled between 5 and 55°C for 5,000 cycles. The specimens were tested in tensile and shear strength in a universal testing machine. Data were analyzed with two-way analysis of variance and Tamhane's post hoc tests (α = 0.05). The mode of failure was determined, and one specimen in each group was examined by scanning electron microscopy. Surface-treated groups demonstrated significantly higher tensile strengths compared to the control group (p 0.05). The tensile strength was significantly different between thermocycled and water-stored specimens (p = 0.021). Altering the surface of the acrylic denture base resin with air abrasion, laser, and air abrasion + laser increased the tensile strength. Thermocycling resulted in decrease in bond strength of silicone-based liner to surface-treated acrylic resin. Pretreatment of denture base resins before applying the soft liner materials improves the bond strength. However, thermocycling results in decrease in bond strength of soft denture liner to surface-treated acrylic resin.

  18. Evaluation of bond strength between leucite-based and lithium disilicate-based ceramics to dentin after cementation with conventional and self-adhesive resin agents.

    Science.gov (United States)

    Rigolin, Fernando J; Miranda, Milton E; Flório, Flávia M; Basting, Roberta T

    2014-01-01

    The aim of this study was to compare the microtensile bond strength of two heat-pressed ceramics (leucite-based--IPS Empress Esthetic/Ivoclar Vivadent, and lithium disilicate-based --IPS e.max Press/Ivoclar Vivadent) to dentin with the use of conventional and self-adhesive resin cements. The occlusal surface of 60 intact human molars was removed and the dentin was exposed. Ceramic blocks were cemented randomly with regard to the cementation systems (n = 10): conventional dual resin cement (Variolink II/Ivoclar Vivadent), conventional self-polymerizing resin cement (Multilink/Ivoclar Vivadent), and dual self-adhesive resin cement (RelyX U100/3M ESPE). The dual cementation systems were photoactivated with a LED light device (Radii Cal, SDI) for 40 seconds. The specimens were sectioned to obtain sticks of approximately 1 mm2 for microtensile tests on a universal testing machine (EMIC). The type of fracture was analyzed under a scanning electron microscope. The Analysis of Variance (ANOVA) and the Tukey test (alpha = 0.05) showed that there was no difference between types of ceramic. Average microtensile bond strength was higher for the conventional dual resin cement (Variolink II) and the self-adhesive dual resin cement (RelyX U100), despite greater prevalence of premature loss of the sticks with the latter. Average bond strength was lower when the conventional self-polymerizing resin cement (Multilink) was used. Leucite-based and lithium disilicate-based cements present similar bond strength to the dentin with conventional dual resin cement (Variolink II) and a dual self-adhesive cement (RelyX U100).

  19. Investigating the effect of recruitment variability on length-based recruitment indices for antarctic krill using an individual-based population dynamics model.

    Directory of Open Access Journals (Sweden)

    Stéphane Thanassekos

    Full Text Available Antarctic krill (Euphausia superba; herein krill is monitored as part of an on-going fisheries observer program that collects length-frequency data. A krill feedback management programme is currently being developed, and as part of this development, the utility of data-derived indices describing population level processes is being assessed. To date, however, little work has been carried out on the selection of optimum recruitment indices and it has not been possible to assess the performance of length-based recruitment indices across a range of recruitment variability. Neither has there been an assessment of uncertainty in the relationship between an index and the actual level of recruitment. Thus, until now, it has not been possible to take into account recruitment index uncertainty in krill stock management or when investigating relationships between recruitment and environmental drivers. Using length-frequency samples from a simulated population - where recruitment is known - the performance of six potential length-based recruitment indices is assessed, by exploring the index-to-recruitment relationship under increasing levels of recruitment variability (from ±10% to ±100% around a mean annual recruitment. The annual minimum of the proportion of individuals smaller than 40 mm (F40 min, % was selected because it had the most robust index-to-recruitment relationship across differing levels of recruitment variability. The relationship was curvilinear and best described by a power law. Model uncertainty was described using the 95% prediction intervals, which were used to calculate coverage probabilities and assess model performance. Despite being the optimum recruitment index, the performance of F40 min degraded under high (>50% recruitment variability. Due to the persistence of cohorts in the population over several years, the inclusion of F40 min values from preceding years in the relationship used to estimate recruitment in a given year

  20. Comparison of shear bond strength of the stainless steel metallic brackets bonded by three bonding systems

    Directory of Open Access Journals (Sweden)

    Mehdi Ravadgar

    2013-09-01

    Full Text Available Introduction: In orthodontic treatment, it is essential to establish a satisfactory bond between enamel and bracket. After the self-etch primers (SEPs were introduced for the facilitation of bracket bonding in comparison to the conventional etch-and-bond system, multiple studies have been carried out on their shear bond strengths which have yielded different results. This study was aimed at comparing shear bond strengths of the stainless steel metallic brackets bonded by three bonding systems. Methods: In this experimental in vitro study, 60 extracted human maxillary premolar teeth were randomly divided into three equal groups: in the first group, Transbond XT (TBXT light cured composite was bonded with Transbond plus self-etching primer (TPSEP; in the second group, TBXT composite was bonded with the conventional method of acid etching; and in the third group, the self cured composite Unite TM bonding adhesive was bonded with the conventional method of acid etching. In all the groups, Standard edgewise-022 metallic brackets (American Orthodontics, Sheboygan, USA were used. Twenty-four hours after the completion of thermocycling, shear bond strength of brackets was measured by Universal Testing Machine (Zwick. In order to compare the shear bond strengths of the groups, the variance analysis test (ANOVA was adopted and p≤0.05 was considered as a significant level. Results: Based on megapascal, the average shear bond strength for the first, second, and third groups was 8.27±1.9, 9.78±2, and 8.92±2.5, respectively. There was no significant difference in the shear bond strength of the groups. Conclusions: Since TPSEP shear bond strength is approximately at the level of the conventional method of acid etching and within the desirable range for orthodontic brackets shear bond strength, applying TPSEP can serve as a substitute for the conventional method of etch and bond, particularly in orthodontic operations.

  1. Transversely Compressed Bonded Joints

    DEFF Research Database (Denmark)

    Hansen, Christian Skodborg; Schmidt, Jacob Wittrup; Stang, Henrik

    2012-01-01

    The load capacity of bonded joints can be increased if transverse pressure is applied at the interface. The transverse pressure is assumed to introduce a Coulomb-friction contribution to the cohesive law for the interface. Response and load capacity for a bonded single-lap joint was derived using...... non-linear fracture mechanics. The results indicated a good correlation between theory and tests. Furthermore, the model is suggested as theoretical base for determining load capacity of bonded anchorages with transverse pressure, in externally reinforced concrete structures....

  2. INCLUSION RATIO BASED ESTIMATOR FOR THE MEAN LENGTH OF THE BOOLEAN LINE SEGMENT MODEL WITH AN APPLICATION TO NANOCRYSTALLINE CELLULOSE

    Directory of Open Access Journals (Sweden)

    Mikko Niilo-Rämä

    2014-06-01

    Full Text Available A novel estimator for estimating the mean length of fibres is proposed for censored data observed in square shaped windows. Instead of observing the fibre lengths, we observe the ratio between the intensity estimates of minus-sampling and plus-sampling. It is well-known that both intensity estimators are biased. In the current work, we derive the ratio of these biases as a function of the mean length assuming a Boolean line segment model with exponentially distributed lengths and uniformly distributed directions. Having the observed ratio of the intensity estimators, the inverse of the derived function is suggested as a new estimator for the mean length. For this estimator, an approximation of its variance is derived. The accuracies of the approximations are evaluated by means of simulation experiments. The novel method is compared to other methods and applied to real-world industrial data from nanocellulose crystalline.

  3. 1 mil gold bond wire study.

    Energy Technology Data Exchange (ETDEWEB)

    Huff, Johnathon; McLean, Michael B.; Jenkins, Mark W.; Rutherford, Brian Milne

    2013-05-01

    In microcircuit fabrication, the diameter and length of a bond wire have been shown to both affect the current versus fusing time ratio of a bond wire as well as the gap length of the fused wire. This study investigated the impact of current level on the time-to-open and gap length of 1 mil by 60 mil gold bond wires. During the experiments, constant current was provided for a control set of bond wires for 250ms, 410ms and until the wire fused; non-destructively pull-tested wires for 250ms; and notched wires. The key findings were that as the current increases, the gap length increases and 73% of the bond wires will fuse at 1.8A, and 100% of the wires fuse at 1.9A within 60ms. Due to the limited scope of experiments and limited data analyzed, further investigation is encouraged to confirm these observations.

  4. On the importance of cavity-length and heat dissipation in GaN-based vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Liu, W. J.; Hu, X. L.; Ying, L. Y.; Chen, S. Q.; Zhang, J. Y.; Akiyama, H.; Cai, Z. P.; Zhang, B. P.

    2015-04-01

    Cavity-length dependence of the property of optically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs) with two dielectric distributed Bragg reflectors was investigated. The cavity lengths were well controlled by employing etching with inductively coupled plasma and chemical mechanical polishing. It was found that the lasing characteristics including threshold, slope efficiency and spontaneous emission coupling factor were substantially improved with reducing the cavity length. In comparison with the device pumped by a 400 nm pulsed laser, the lasing spectrum was featured by a red shift and simultaneous broadening with increasing the pumping energy of a 355 nm pulsed laser. Moreover, the lasing threshold was much higher when pumped by a 355 nm pulsed laser. These were explained by taking into account of the significant heating effect under 355 nm pumping. Our results demonstrate that a short cavity length and good heat-dissipation are essential to GaN-based VCSELs.

  5. Ligand Bridging-Angle-Driven Assembly of Molecular Architectures Based on Quadruply Bonded Mo-Mo Dimers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian-Rong; Yakovenko, Andrey A; Lu, Weigang; Timmons, Daren J; Zhuang, Wenjuan; Yuan, Daqiang; Zhou, Hong-Cai

    2010-12-15

    A systematic exploration of the assembly of Mo₂(O₂C-)₄-based metal–organic molecular architectures structurally controlled by the bridging angles of rigid organic linkers has been performed. Twelve bridging dicarboxylate ligands were designed to be of different sizes with bridging angles of 0, 60, 90, and 120° while incorporating a variety of nonbridging functional groups, and these ligands were used as linkers. These dicarboxylate linkers assemble with quadruply bonded Mo–Mo clusters acting as nodes to give 13 molecular architectures, termed metal–organic polygons/polyhedra with metal cluster node arrangements of a linear shape, triangle, octahedron, and cuboctahedron/anti-cuboctahedron. The syntheses of these complexes have been optimized and their structures determined by single-crystal X-ray diffraction. The results have shown that the shape and size of the resulting molecular architecture can be controlled by tuning the bridging angle and size of the linker, respectively. Functionalization of the linker can adjust the solubility of the ensuing molecular assembly but has little or no effect on the geometry of the product. Preliminary gas adsorption, spectroscopic, and electrochemical properties of selected members were also studied. The present work is trying to enrich metal-containing supramolecular chemistry through the inclusion of well-characterized quadruply bonded Mo–Mo units into the structures, which can widen the prospect of additional electronic functionality, thereby leading to novel properties.

  6. Ligand bridging-angle-driven assembly of molecular architectures based on quadruply bonded Mo-Mo dimers.

    Science.gov (United States)

    Li, Jian-Rong; Yakovenko, Andrey A; Lu, Weigang; Timmons, Daren J; Zhuang, Wenjuan; Yuan, Daqiang; Zhou, Hong-Cai

    2010-12-15

    A systematic exploration of the assembly of Mo2(O2C-)4-based metal-organic molecular architectures structurally controlled by the bridging angles of rigid organic linkers has been performed. Twelve bridging dicarboxylate ligands were designed to be of different sizes with bridging angles of 0, 60, 90, and 120° while incorporating a variety of nonbridging functional groups, and these ligands were used as linkers. These dicarboxylate linkers assemble with quadruply bonded Mo-Mo clusters acting as nodes to give 13 molecular architectures, termed metal-organic polygons/polyhedra with metal cluster node arrangements of a linear shape, triangle, octahedron, and cuboctahedron/anti-cuboctahedron. The syntheses of these complexes have been optimized and their structures determined by single-crystal X-ray diffraction. The results have shown that the shape and size of the resulting molecular architecture can be controlled by tuning the bridging angle and size of the linker, respectively. Functionalization of the linker can adjust the solubility of the ensuing molecular assembly but has little or no effect on the geometry of the product. Preliminary gas adsorption, spectroscopic, and electrochemical properties of selected members were also studied. The present work is trying to enrich metal-containing supramolecular chemistry through the inclusion of well-characterized quadruply bonded Mo-Mo units into the structures, which can widen the prospect of additional electronic functionality, thereby leading to novel properties.

  7. A WEB-BASED SURVEY OF MOTHER-INFANT BOND, ATTACHMENT EXPERIENCES, AND METACOGNITION IN POSTTRAUMATIC STRESS FOLLOWING CHILDBIRTH.

    Science.gov (United States)

    Williams, Charlotte; Patricia Taylor, Emily; Schwannauer, Matthias

    2016-05-01

    Postnatal depression is linked to adverse outcomes for parent and child, with metacognition and parenting experiences key variables in the development and maintenance of depression. The attachment between mother and infant is especially vulnerable to the effects of untreated postnatal depression. Despite high levels of reported postnatal stress symptoms, less attention has been given the relationship between attachment, metacognition, and postnatal traumatic symptoms in the context of birth trauma. This study tested several hypotheses regarding the relationships between recalled parenting experiences, metacognition, postnatal symptoms of posttraumatic stress disorder and depression and perceptions of the mother-infant bond, confirming and extending upon metacognitive and mentalization theories. A Web-based, cross-sectional, self-report questionnaire design was employed in an analog sample of new mothers. Participants were 502 women recruited via open-access Web sites associated with birth organizations. Structural equation modeling was employed for the principal analysis. Metacognition fully mediated the relationship between recalled parenting experiences and postnatal psychological outcomes. Posttraumatic stress was indirectly associated with maternal perceptions of the bond, with this relationship mediated by depression. Metacognition may have a key role in postnatal psychological distress. Where postnatal depression or traumatic birth experiences are identified, screening for posttraumatic stress is strongly indicated. © 2016 Michigan Association for Infant Mental Health.

  8. Whole-molecule calculation of log p based on molar volume, hydrogen bonds, and simulated 13C NMR spectra.

    Science.gov (United States)

    Schnackenberg, Laura K; Beger, Richard D

    2005-01-01

    The prediction of Log P is usually accomplished using either substructure or whole-molecule approaches. However, these methods are complicated, and previous whole-molecule approaches have not been successful for the prediction of Log P in very complex molecules. The observed chemical shifts in nuclear magnetic resonance (NMR) spectroscopy are related to the electrostatics at the nucleus, which are influenced by solute-solvent interactions. The different solvation effects on a molecule by either water or methanol have a strong effect on the NMR chemical shift value. Therefore, the chemical shift values observed in an aqueous and organic solvent should correlate to Log P. This paper develops a rapid, objective model of Log P based on molar volume, hydrogen bonds, and differences in calculated 13C NMR chemical shifts for a diverse set of compounds. A partial least squares (PLS) model of Log P built on the sum of carbon chemical shift differences in water and methanol, molar volume, number of hydrogen bond donors and acceptors in 162 diverse compounds gave an r2 value of 0.88. The average r2 for 10 training models of Log P made from 90% of the data was 0.87+/-0.01. The average q2 for 10 leave-10%-out cross-validation test sets was 0.87+/-0.05.

  9. Growth estimation of mangrove cockle Anadara tuberculosa (Mollusca: Bivalvia: application and evaluation of length-based methods

    Directory of Open Access Journals (Sweden)

    Luis A Flores

    2011-03-01

    Full Text Available Growth is one of the key processes in the dynamic of exploited resources, since it provides part of the information required for structured population models. Growth of mangrove cockle, Anadara tuberculosa was estimated through length-based methods (ELEFAN I y NSLCA and using diverse shell length intervals (SLI. The variability of L∞, k and phi prime (Φ` estimates and the effect of each sample were quantified by jackknife techniques. Results showed the same L∞ estimates from ELEFAN I and NSLCA across each SLI used, and all L∞ were within the expected range. On the contrary, k estimates differed between methods. Jackknife estimations uncovered the tendency of ELEFAN I to overestimate k with increases in SLI, and allowed the identification of differences in uncertainty (PE and CV between both methods. The average values of Φ`derived from NSCLA1.5 and length-age sources were similar and corresponded to ranges reported by other authors. Estimates of L∞, k and Φ` from NSCLA1.5 were 85.97mm, 0.124/year and 2.953 with jackknife and 86.36mm de L∞, 0.110/year de k and 2.914 de Φ` without jackknife, respectively. Based on the observed evidence and according to the biology of the species, NSCLA is suggested to be used with jackknife and a SLI of 1.5mm as an ad hoc approach to estimate the growth parameters of mangrove cockle. Rev. Biol. Trop. 59 (1: 159-170. Epub 2011 March 01.El crecimiento es uno de los procesos clave en la dinámica de los recursos explotados. En este estudio se estimó el crecimiento de la concha prieta Anadara tuberculosa por medio de métodos basados en tallas (ELEFAN I y NSLCA y usando distintos intervalos de clase de talla (ICT. La variabilidad de los estimadores para L∞y k, y el efecto de cada muestra e ICT fueron cuantificados por la técnica de jackknife. ELEFAN I y NSLCA producen una misma estimación de L∞para cada uno de los ICT. Por el contrario, para k ambos métodos estiman diferentes valores. Las

  10. Modeling the Footprint and Equivalent Radiance Transfer Path Length for Tower-Based Hemispherical Observations of Chlorophyll Fluorescence

    Directory of Open Access Journals (Sweden)

    Xinjie Liu

    2017-05-01

    Full Text Available The measurement of solar-induced chlorophyll fluorescence (SIF is a new tool for estimating gross primary production (GPP. Continuous tower-based spectral observations together with flux measurements are an efficient way of linking the SIF to the GPP. Compared to conical observations, hemispherical observations made with cosine-corrected foreoptic have a much larger field of view and can better match the footprint of the tower-based flux measurements. However, estimating the equivalent radiation transfer path length (ERTPL for hemispherical observations is more complex than for conical observations and this is a key problem that needs to be addressed before accurate retrieval of SIF can be made. In this paper, we first modeled the footprint of hemispherical spectral measurements and found that, under convective conditions with light winds, 90% of the total radiation came from an FOV of width 72°, which in turn covered 75.68% of the source area of the flux measurements. In contrast, conical spectral observations covered only 1.93% of the flux footprint. Secondly, using theoretical considerations, we modeled the ERTPL of the hemispherical spectral observations made with cosine-corrected foreoptic and found that the ERTPL was approximately equal to twice the sensor height above the canopy. Finally, the modeled ERTPL was evaluated using a simulated dataset. The ERTPL calculated using the simulated data was about 1.89 times the sensor’s height above the target surface, which was quite close to the results for the modeled ERTPL. Furthermore, the SIF retrieved from atmospherically corrected spectra using the modeled ERTPL fitted well with the reference values, giving a relative root mean square error of 18.22%. These results show that the modeled ERTPL was reasonable and that this method is applicable to tower-based hemispherical observations of SIF.

  11. Molecular heterogeneous catalysts derived from bipyridine-based organosilica nanotubes for C-H bond activation.

    Science.gov (United States)

    Zhang, Shengbo; Wang, Hua; Li, Mei; Han, Jinyu; Liu, Xiao; Gong, Jinlong

    2017-06-01

    Heterogeneous metal complex catalysts for direct C-H activation with high activity and durability have always been desired for transforming raw materials into feedstock chemicals. This study described the design and synthesis of one-dimensional organosilica nanotubes containing 2,2'-bipyridine (bpy) ligands in the framework (BPy-NT) and their post-synthetic metalation to provide highly active and robust molecular heterogeneous catalysts. By adjusting the ratios of organosilane precursors, very short BPy-NT with ∼50 nm length could be controllably obtained. The post-synthetic metalation of bipyridine-functionalized nanotubes with [IrCp*Cl(μ-Cl)] 2 (Cp* = η 5 -pentamethylcyclopentadienyl) and [Ir(cod)(OMe)] 2 (cod = 1,5-cyclooctadiene) afforded solid catalysts, IrCp*-BPy-NT and Ir(cod)-BPy-NT, which were utilized for C-H oxidation of heterocycles and cycloalkanes as well as C-H borylation of arenes. The cut-short nanotube catalysts displayed enhanced activities and durability as compared to the analogous homogeneous catalysts and other conventional heterogeneous catalysts, benefiting from the isolated active sites as well as the fast transport of substrates and products. After the reactions, a detailed characterization of Ir-immobilized BPy-NT via TEM, SEM, nitrogen adsorption, UV/vis, XPS, and 13 C CP MAS NMR indicated the molecular nature of the active species as well as stable structures of nanotube scaffolds. This study demonstrates the potential of BPy-NT with a short length as an integration platform for the construction of efficient heterogeneous catalytic systems for organic transformations.

  12. Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system

    International Nuclear Information System (INIS)

    Lee, Sang Youl; Choi, Kwang Ki; Jeong, Hwan-Hee; Choi, Hee Seok; Oh, Tchang-Hun; Song, June O; Seong, Tae-Yeon

    2009-01-01

    We first report on the fabrication of 2 inch wafer-level GaN-based vertical light-emitting diodes (LEDs) by using a multi-functional bonding material system, which is composed of a thick Cu diffusion barrier and a bonding layer. The bonding material system superbly absorbs laser-induced stress and also effectively serves as a barrier to the indiffusion of Sn to the active region. Fully packaged vertical LEDs fabricated with indium tin oxide (ITO)/AgCu contact and the bonding material system give an operating voltage of 3.35 V at 350 mA. After over 1800 h, the operating voltages remain stable, and the reverse currents are in the range 3–8 × 10 −7 A at −5 V. (rapid communication)

  13. Tensile and shear bond strength of hard and soft denture relining materials to the conventional heat cured acrylic denture base resin: An In-vitro study.

    Science.gov (United States)

    Lau, Mayank; Amarnath, G S; Muddugangadhar, B C; Swetha, M U; Das, Kopal Anshuraj Ashok Kumar

    2014-04-01

    The condition of the denture bearing tissues may be adversely affected by high stress concentration during function. Chairside Denture (Hard and Soft) reliners are used to distribute forces applied to soft tissues during function. Tensile and shear bond strength has been shown to be dependent on their chemical composition. A weak bond could harbor bacteria, promote staining and delamination of the lining material. To investigate tensile and shear bond strength of 4 different commercially available denture relining materials to conventional heat cured acrylic denture base resin. 4 mm sections in the middle of 160 Acrylic cylindrical specimens (20 mm x 8 mm) were removed, packed with test materials (Mollosil, G C Reline Soft, G C Reline Hard (Kooliner) and Ufi Gel Hard and polymerized. Specimens were divided into 8 groups of 20 each. Tensile and shear bond strength to the conventional heat cured acrylic denture base resin were examined by Instron Universal Tensile Testing Machine using the equation F=N/A (F-maximum force exerted on the specimen (Newton) and A-bonding area= 50.24 mm2). One-way ANOVA was used for multiple group comparisons followed by Bonferroni Test and Hsu's MCB for multiple pairwise comparisons to asses any significant differences between the groups. The highest mean Tensile bond strength value was obtained for Ufi Gel Hard (6.49+0.08 MPa) and lowest for G C Reline Soft (0.52+0.01 MPa). The highest mean Shear bond strength value was obtained for Ufi Gel Hard (16.19+0.1 MPa) and lowest for Mollosil (0.59+0.05 MPa). The Benferroni test showed a significant difference in the mean tensile bond strength and the mean shear bond strength when the two denture soft liners were compared as well as when the two denture hard liners were compared. Hsu's MCB implied that Ufi gel hard is better than its other closest competitors. The Tensile and Shear bond strength values of denture soft reliners were significantly lower than denture hard reliners. How to cite the

  14. Telomere length and depression

    DEFF Research Database (Denmark)

    Wium-Andersen, Marie Kim; Ørsted, David Dynnes; Rode, Line

    2017-01-01

    BACKGROUND: Depression has been cross-sectionally associated with short telomeres as a measure of biological age. However, the direction and nature of the association is currently unclear. AIMS: We examined whether short telomere length is associated with depression cross-sectionally as well...... as prospectively and genetically. METHOD: Telomere length and three polymorphisms, TERT, TERC and OBFC1, were measured in 67 306 individuals aged 20-100 years from the Danish general population and associated with register-based attendance at hospital for depression and purchase of antidepressant medication....... RESULTS: Attendance at hospital for depression was associated with short telomere length cross-sectionally, but not prospectively. Further, purchase of antidepressant medication was not associated with short telomere length cross-sectionally or prospectively. Mean follow-up was 7.6 years (range 0...

  15. Myofilament length dependent activation

    Energy Technology Data Exchange (ETDEWEB)

    de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

    2010-05-25

    The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

  16. A consistent molecular hydrogen isotope chemistry scheme based on an independent bond approximation

    Directory of Open Access Journals (Sweden)

    M. C. Krol

    2009-11-01

    Full Text Available The isotopic composition of molecular hydrogen (H2 produced by photochemical oxidation of methane (CH4 and Volatile Organic Compounds (VOCs is a key quantity in the global isotope budget of (H2. The many individual reaction steps involved complicate its investigation. Here we present a simplified structure-activity approach to assign isotope effects to the individual elementary reaction steps in the oxidation sequence of CH4 and some other VOCs. The approach builds on and extends the work by Gerst and Quay (2001 and Feilberg et al. (2007b. The description is generalized and allows the application, in principle, also to other compounds. The idea is that the C-H and C-D bonds – seen as reactive sites – have similar relative reaction probabilities in isotopically substituted, but otherwise identical molecules. The limitations of this approach are discussed for the reaction CH4+Cl. The same approach is applied to VOCs, which are important precursors of H2 that need to be included into models. Unfortunately, quantitative information on VOC isotope effects and source isotope signatures is very limited and the isotope scheme at this time is limited to a strongly parameterized statistical approach, which neglects kinetic isotope effects. Using these concepts we implement a full hydrogen isotope scheme in a chemical box model and carry out a sensitivity study to identify those reaction steps and conditions that are most critical for the isotope composition of the final H2 product. The reaction scheme is directly applicable in global chemistry models, which can thus include the isotope pathway of H2 produced from CH4 and VOCs in a consistent way.

  17. A Component-Based Study of the Effect of Diameter on Bond and Anchorage Characteristics of Blind-Bolted Connections.

    Directory of Open Access Journals (Sweden)

    Muhammad Nasir Amin

    Full Text Available Structural hollow sections are gaining worldwide importance due to their structural and architectural advantages over open steel sections. The only obstacle to their use is their connection with other structural members. To overcome the obstacle of tightening the bolt from one side has given birth to the concept of blind bolts. Blind bolts, being the practical solution to the connection hindrance for the use of hollow and concrete filled hollow sections play a vital role. Flowdrill, the Huck High Strength Blind Bolt and the Lindapter Hollobolt are the well-known commercially available blind bolts. Although the development of blind bolts has largely resolved this issue, the use of structural hollow sections remains limited to shear resistance. Therefore, a new modified version of the blind bolt, known as the "Extended Hollo-Bolt" (EHB due to its enhanced capacity for bonding with concrete, can overcome the issue of low moment resistance capacity associated with blind-bolted connections. The load transfer mechanism of this recently developed blind bolt remains unclear, however. This study uses a parametric approach to characterising the EHB, using diameter as the variable parameter. Stiffness and load-carrying capacity were evaluated at two different bolt sizes. To investigate the load transfer mechanism, a component-based study of the bond and anchorage characteristics was performed by breaking down the EHB into its components. The results of the study provide insight into the load transfer mechanism of the blind bolt in question. The proposed component-based model was validated by a spring model, through which the stiffness of the EHB was compared to that of its components combined. The combined stiffness of the components was found to be roughly equivalent to that of the EHB as a whole, validating the use of this component-based approach.

  18. Kondo length in bosonic lattices

    Science.gov (United States)

    Giuliano, Domenico; Sodano, Pasquale; Trombettoni, Andrea

    2017-09-01

    Motivated by the fact that the low-energy properties of the Kondo model can be effectively simulated in spin chains, we study the realization of the effect with bond impurities in ultracold bosonic lattices at half filling. After presenting a discussion of the effective theory and of the mapping of the bosonic chain onto a lattice spin Hamiltonian, we provide estimates for the Kondo length as a function of the parameters of the bosonic model. We point out that the Kondo length can be extracted from the integrated real-space correlation functions, which are experimentally accessible quantities in experiments with cold atoms.

  19. STRait Razor: a length-based forensic STR allele-calling tool for use with second generation sequencing data.

    Science.gov (United States)

    Warshauer, David H; Lin, David; Hari, Kumar; Jain, Ravi; Davis, Carey; Larue, Bobby; King, Jonathan L; Budowle, Bruce

    2013-07-01

    Recent studies have demonstrated the capability of second generation sequencing (SGS) to provide coverage of short tandem repeats (STRs) found within the human genome. However, there are relatively few bioinformatic software packages capable of detecting these markers in the raw sequence data. The extant STR-calling tools are sophisticated, but are not always applicable to the analysis of the STR loci commonly used in forensic analyses. STRait Razor is a newly developed Perl-based software tool that runs on the Linux/Unix operating system and is designed to detect forensically-relevant STR alleles in FASTQ sequence data, based on allelic length. It is capable of analyzing STR loci with repeat motifs ranging from simple to complex without the need for extensive allelic sequence data. STRait Razor is designed to interpret both single-end and paired-end data and relies on intelligent parallel processing to reduce analysis time. Users are presented with a number of customization options, including variable mismatch detection parameters, as well as the ability to easily allow for the detection of alleles at new loci. In its current state, the software detects alleles for 44 autosomal and Y-chromosome STR loci. The study described herein demonstrates that STRait Razor is capable of detecting STR alleles in data generated by multiple library preparation methods and two Illumina(®) sequencing instruments, with 100% concordance. The data also reveal noteworthy concepts related to the effect of different preparation chemistries and sequencing parameters on the bioinformatic detection of STR alleles. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  20. Depressive symptoms are not associated with leukocyte telomere length: findings from the Nova Scotia Health Survey (NSHS95, a population-based study.

    Directory of Open Access Journals (Sweden)

    Jonathan A Shaffer

    Full Text Available Premature shortening of leukocyte telomere length has been proposed as a novel mechanism by which depression may confer increased risk of adverse cardiovascular events. Prior studies demonstrating associations of depression and depressive symptoms with shorter leukocyte telomere length were small, included selected psychiatric outpatients, were based on convenience samples, and/or adjusted for a limited number of possible confounding factors.We examined the associations of depressive symptoms, probable depressive disorder, and specific depressive symptom clusters, as assessed by the Center for Epidemiological Studies--Depression (CES-D scale, with leukocyte telomere length, measured by using a real-time PCR method, in 2,225 apparently healthy participants from the 1995 Nova Scotia Health Survey population-based study. The mean age was 48.2 ± 18.9 years; 49.9% of participants were female; and the mean CES-D score was 7.4 ± 7.9. The mean telomere length was 5,301 ± 587 base pairs. In an unadjusted model, depressive symptoms were significantly associated with longer leukocyte telomere length (B = 27.6 base pairs per standard deviation increase in CES-D, 95% confidence interval [CI] = 3.1-52.1, p = 0.027. This association was no longer significant after adjustment for age and sex (B = 9.5, 95% CI = -14.6-33.6, p = 0.44 or after further adjustment for body mass index, Framingham risk score and previous history of ischemic heart disease (all p's ≥ 0.37. Neither probable depressive disorder nor specific depressive symptom clusters were independently associated with leukocyte telomere length.Concurrent depressive symptoms were not associated with leukocyte telomere length in a large, representative, population-based study.

  1. Shear bond strength evaluation of resin composite to resin-modified glass-ionomer cement using three different resin adhesives vs. glass-ionomer based adhesive

    Directory of Open Access Journals (Sweden)

    Mostafa Sadeghi

    2015-12-01

    Full Text Available Background: The clinical success of sandwich technique depends on the strength of resin-modified glass ionomer cement (RMGIC bonding to both dentin and resin composite. Therefore, the shear bond strength (SBS of resin composite bonded to RMGIC utilizing different resin adhesives versus a GIC-based adhesive was compared. Materials and methods: In this in vitro study, 84 holes (5×2 mm were prepared in acrylic blocks, randomly divided into seven groups (n=12 and filled with RMGIC (Light-Cured Universal Restorative, GC. In the Group I; no adhesive was applied on the RMGIC. In the Group II, non-etched and Group III was etched with phosphoric acid. In groups II and III, after rinsing, etch-and-rinse adhesive (OptiBond Solo Plus; in the Group IV; a two-step self-etch adhesive (OptiBond XTR and in Group V; a one-step self-etch (OptiBond All-in-One were applied on the cement surfaces. Group VI; a GIC-based adhesive (Fuji Bond LC was painted over the cement surface and cured. Group VII; the GIC-based adhesive was brushed over RMGIC followed by the placement of resin composite and co-cured. Afterward; resin composite (Point 4 cylinders were placed on the treated cement surfaces. The specimens were placed in 100% humidity at 37 ± 1°C and thermo cycled. The shear bond test was performed at a cross-head speed of 1 mm/min and calculated in MPa; the specimens were examined to determine mode of failure. The results were analyzed using one-way ANOVA and Tukey test. Results: The maximum (24.62±3.70 MPa and minimum (18.15±3.38 MPa SBS mean values were recorded for OptiBond XTR adhesive and the control group, respectively. The pairwise comparisons showed no significant differences between the groups that bonded with different adhesives. The adhesive failure was the most common failure mode observed. Conclusion: This study suggests that GIC-based adhesive could be applied over RMGIC as co-cure technique for sandwich restorations in lieu of employing the resin

  2. Can there be a multi-bond between noble gas and metal? A theoretical study of F2XeMoF2.

    Science.gov (United States)

    Gao, Kunqi; Sheng, Li

    2017-04-05

    A new noble gas compound containing a Xe-Mo double bond, F 2 XeMoF 2 , was theoretically constructed and studied based on DFT and ab initio calculations. The CCSD(T)-calculated Xe-Mo bond length of 2.518 Å was comparable to the standard value of 2.56 Å. The bonding energy (32.3 kcal mol -1 ) was even higher than that of the Xe-Au bond in the well-known XeAuF complex (24.1 kcal mol -1 ). The result of natural bond orbital (NBO) analysis indicates that there is a σ-bond and a π-bond between the Xe and Mo atoms in F 2 XeMoF 2 . The properties of the Xe-Mo double bond were also analyzed with the atoms in molecules (AIM) approach and natural resonance theory (NRT).

  3. The Comparative Studies of Binding Activity of Curcumin and Didemethylated Curcumin with Selenite: Hydrogen Bonding vs Acid-Base Interactions.

    Science.gov (United States)

    Liao, Jiahn-Haur; Wu, Tzu-Hua; Chen, Ming-Yi; Chen, Wei-Ting; Lu, Shou-Yun; Wang, Yi-Hsuan; Wang, Shao-Pin; Hsu, Yen-Min; Huang, Yi-Shiang; Huang, Zih-You; Lin, Yu-Ching; Chang, Ching-Ming; Huang, Fu-Yung; Wu, Shih-Hsiung

    2015-12-04

    In this report, the in vitro relative capabilities of curcumin (CCM) and didemethylated curcumin (DCCM) in preventing the selenite-induced crystallin aggregation were investigated by turbidity tests and isothermal titration calorimetry (ITC). DCCM showed better activity than CCM. The conformers of CCM/SeO3(2-) and DCCM/SeO3(2-) complexes were optimized by molecular orbital calculations. Results reveal that the selenite anion surrounded by CCM through the H-bonding between CCM and selenite, which is also observed via IR and NMR studied. For DCCM, the primary driving force is the formation of an acid-base adduct with selenite showing that the phenolic OH group of DCCM was responsible for forming major conformer of DCCM. The formation mechanisms of selenite complexes with CCM or DCCM explain why DCCM has greater activity than CCM in extenuating the toxicity of selenite as to prevent selenite-induced lens protein aggregation.

  4. The Comparative Studies of Binding Activity of Curcumin and Didemethylated Curcumin with Selenite: Hydrogen Bonding vs Acid-Base Interactions

    Science.gov (United States)

    Liao, Jiahn-Haur; Wu, Tzu-Hua; Chen, Ming-Yi; Chen, Wei-Ting; Lu, Shou-Yun; Wang, Yi-Hsuan; Wang, Shao-Pin; Hsu, Yen-Min; Huang, Yi-Shiang; Huang, Zih-You; Lin, Yu-Ching; Chang, Ching-Ming; Huang, Fu-Yung; Wu, Shih-Hsiung

    2015-12-01

    In this report, the in vitro relative capabilities of curcumin (CCM) and didemethylated curcumin (DCCM) in preventing the selenite-induced crystallin aggregation were investigated by turbidity tests and isothermal titration calorimetry (ITC). DCCM showed better activity than CCM. The conformers of CCM/SeO32- and DCCM/SeO32- complexes were optimized by molecular orbital calculations. Results reveal that the selenite anion surrounded by CCM through the H-bonding between CCM and selenite, which is also observed via IR and NMR studied. For DCCM, the primary driving force is the formation of an acid-base adduct with selenite showing that the phenolic OH group of DCCM was responsible for forming major conformer of DCCM. The formation mechanisms of selenite complexes with CCM or DCCM explain why DCCM has greater activity than CCM in extenuating the toxicity of selenite as to prevent selenite-induced lens protein aggregation.

  5. From Molecules to Surfaces: Radical-Based Mechanisms of Si-S and Si-Se Bond Formation on Silicon.

    Science.gov (United States)

    Buriak, Jillian M; Sikder, Md Delwar H

    2015-08-05

    The derivatization of silicon surfaces can have profound effects on the underlying electronic properties of the semiconductor. In this work, we investigate the radical surface chemistry of silicon with a range of organochalcogenide reagents (comprising S and Se) on a hydride-terminated silicon surface, to cleanly and efficiently produce surface Si-S and Si-Se bonds, at ambient temperature. Using a diazonium-based radical initiator, which induces formation of surface silicon radicals, a group of organochalcogenides were screened for reactivity at room temperature, including di-n-butyl disulfide, diphenyl disulfide, diphenyl diselenide, di-n-butyl sulfide, diphenyl selenide, diphenyl sulfide, 1-octadecanethiol, t-butyl disulfide, and t-butylthiol, which comprises the disulfide, diselenide, thiol, and thioether functionalities. The surface reactions were monitored by transmission mode Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ionization mass spectrometry. Calculation of Si-Hx consumption, a semiquantitative measure of yield of production of surface-bound Si-E bonds (E = S, Se), was carried out via FTIR spectroscopy. Control experiments, sans the BBD diazonium radical initiator, were all negative for any evident incorporation, as determined by FTIR spectroscopy. The functional groups that did react with surface silicon radicals included the dialkyl/diphenyl disulfides, diphenyl diselenide, and 1-octadecanethiol, but not t-butylthiol, diphenyl sulfide/selenide, and di-n-butyl sulfide. Through a comparison with the rich body of literature regarding molecular radicals, and in particular, silyl radicals, reaction mechanisms were proposed for each. Armed with an understanding of the reaction mechanisms, much of the known chemistry within the extensive body of radical-based reactivity has the potential to be harnessed on silicon and could be extended to a range of technologically relevant semiconductor

  6. Effect of experimental acid/base conditioner on microtensile bond strength of 4-META/MMA-TBB resin to dentin after long-term water immersion.

    Science.gov (United States)

    Soeno, Kohyoh; Taira, Yohsuke; Ito, Shuichi

    2012-01-01

    An experimental conditioner (Exp), which was an aqueous solution of 10% ascorbic acid and 5% ferric chloride, was prepared in this study. This study evaluated the effect of Exp on the microtensile bond strength between a self-curing resin and dentin after long-term water immersion. Flat human dentin surfaces were sequentially pretreated with 40% phosphoric acid, 10% sodium hypochlorite, and Exp. Surface pretreatment with an aqueous solution of 10% citric and 3% ferric chloride (10-3) was used as a control. Composite resin rods were bonded to pretreated dentin surfaces using 4-META/MMA-TBB resin. Microtensile bond strengths were evaluated after water immersion at 24 h, 12 months, 24 months, and 36 months. At each immersion period, the bond strength of Exp was significantly higher than that of 10-3. After 36 months, Exp showed no significant decrease in microtensile bond strength, but 10-3 showed significant reductions. Pretreatment with experimental acid/base conditioner markedly improved the bonding durability of 4-META/MMA-TBB resin to human dentin when compared against the conventional 10-3 treatment.

  7. The Effect of Titanium Tetrafluoride and Sodium Hypochlorite on the Shear Bond Strength of Methacrylate and Silorane Based Composite Resins: an In-Vitro Study.

    Science.gov (United States)

    Sharafeddin, Farahnaz; Koohpeima, Fatemeh; Razazan, Nader

    2017-06-01

    The bond strength of composites with different adhesive systems with dentin is an important factor in long term durability of composite restorations. The effect of titanium tetrafluoride (TiF 4 ) as anti caries agent and sodium hypochlorite (NaOCl) as disinfectant on the shear bond of nanofilled and silorane based composite resins have not been investigated in previous studies. This study was conducted to determine bond strength between dentin and two composite systems, by means of shear bond test using TiF 4 and NaOCl. Middle dentin of 60 intact extracted maxillary premolar teeth were exposed by sectioning the crowns at a depth of 2mm from central groove and parallel to the occlusal surface. Standardized smear layer was created using a 600-grit silicon carbide paper and then samples were embedded in acrylic resin blocks. Then the samples were randomly divided into 6 \\groups summarized as Group I: Z350, Group II: Z350+ NaOCl, Group III: Z350+ TiF 4 , Group IV: P90, Group V: P90+ NaOCl, Group VI: P90+ TiF 4 according to manufacturer's instruction. Then samples were subjected to shear bond strength (SBS) test using universal testing machine and data were analyzed using ANOVA and Tukey tests ( p composite resin ( p = 0.004), and also silorane based composite resin ( p = 0.006). Application of 4% TiF 4 caused a significant increase in SBS of silorane based composite resin ( p = 0.001). The effect of TiF 4 on nanofilled composite was not statistically significant. Using TiF 4 has a positive effect on increasing the shear bond while NaOCl has negative effect on bond strength.

  8. Effect of calcium hydroxide and double and triple antibiotic pastes on the bond strength of epoxy resin-based sealer to root canal dentin.

    Science.gov (United States)

    Akcay, Merve; Arslan, Hakan; Topcuoglu, Hüseyin Sinan; Tuncay, Oznur

    2014-10-01

    The aim of this study was to evaluate the effects of calcium hydroxide (CH) and triple (TAP) and double (DAP) antibiotic pastes on the bond strength of an epoxy resin-based sealer (AH Plus Jet; Dentsply DeTrey, Konstanz, Germany) to the root canal dentin. Sixty-four single-rooted human mandibular premolars were decoronated and prepared using the rotary system to size 40. The specimens were randomly divided into a control group (without intracanal dressing) and 3 experimental groups that received an intracanal dressing with either CH, DAP, or TAP (n = 16). The intracanal dressing was removed by rinsing with 10 mL 17% EDTA followed by 10 mL 2.5% sodium hypochlorite. The root canals were then obturated with gutta-percha and AH Plus Jet sealer. A push-out test was used to measure the bond strength between the root canal dentin and the sealer. The data were analyzed using 2-way analysis of variance and Tukey post hoc tests to detect the effect of the independent variables (intracanal medicaments and root canal thirds) and their interactions on the push-out bond strength of the root canal filling material to the root dentin (P = .05). The push-out bond strength values were significantly affected by the intracanal medicaments (P .05). In the middle and apical third, the bond strength of the TAP group was higher than those of the CH and DAP groups (P < .05). The DAP and CH did not affect the bond strength of the epoxy resin-based sealer. Additionally, the TAP improved the bond strength of the epoxy resin-based sealer in the middle and apical thirds. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  9. New sugar-based gelators with an amino group, the gelatin ability of which is remarkably reinforced by the hydrogen bond and the metal coordination

    NARCIS (Netherlands)

    Amanokura, Natsuki; Kanekiyo, Yasumasa; Shinkai, Seiji; Reinhoudt, David

    1999-01-01

    Three sugar-integrated gelators bearing a p-aminophenyl group which are expected to exert a hydrogen-bonding effect and a metal coordination effect on the gelation ability were synthesised. -D-Galactose-based 2b was only soluble or precipitated and -D-glucose-based 4b gelated only two of 15 solvents

  10. Comparative evaluation of tensile bond strength of a polyvinyl acetate-based resilient liner following various denture base surface pre-treatment methods and immersion in artificial salivary medium: An in vitro study

    OpenAIRE

    Philip, Jacob M.; Ganapathy, Dhanraj M.; Ariga, Padma

    2012-01-01

    Background and Aim: This study was formulated to evaluate and estimate the influence of various denture base resin surface pre-treatments (chemical and mechanical and combinations) upon tensile bond strength between a poly vinyl acetate-based denture liner and a denture base resin. Materials and Methods: A universal testing machine was used for determining the bond strength of the liner to surface pre-treated acrylic resin blocks. The data was analyzed by one-way analysis of variance and the ...

  11. Comparative evaluation of tensile bond strength of a polyvinyl acetate-based resilient liner following various denture base surface pre-treatment methods and immersion in artificial salivary medium: An in vitro study.

    Science.gov (United States)

    Philip, Jacob M; Ganapathy, Dhanraj M; Ariga, Padma

    2012-07-01

    This study was formulated to evaluate and estimate the influence of various denture base resin surface pre-treatments (chemical and mechanical and combinations) upon tensile bond strength between a poly vinyl acetate-based denture liner and a denture base resin. A universal testing machine was used for determining the bond strength of the liner to surface pre-treated acrylic resin blocks. The data was analyzed by one-way analysis of variance and the t-test (α =.05). This study infers that denture base surface pre-treatment can improve the adhesive tensile bond strength between the liner and denture base specimens. The results of this study infer that chemical, mechanical, and mechano-chemical pre-treatments will have different effects on the bond strength of the acrylic soft resilient liner to the denture base. Among the various methods of pre-treatment of denture base resins, it was inferred that the mechano-chemical pre-treatment method with air-borne particle abrasion followed by monomer application exhibited superior bond strength than other methods with the resilient liner. Hence, this method could be effectively used to improve bond strength between liner and denture base and thus could minimize delamination of liner from the denture base during function.

  12. Comparative evaluation of tensile bond strength of a polyvinyl acetate-based resilient liner following various denture base surface pre-treatment methods and immersion in artificial salivary medium: An in vitro study

    Directory of Open Access Journals (Sweden)

    Jacob M Philip

    2012-01-01

    Full Text Available Background and Aim: This study was formulated to evaluate and estimate the influence of various denture base resin surface pre-treatments (chemical and mechanical and combinations upon tensile bond strength between a poly vinyl acetate-based denture liner and a denture base resin. Materials and Methods: A universal testing machine was used for determining the bond strength of the liner to surface pre-treated acrylic resin blocks. The data was analyzed by one-way analysis of variance and the t-test (α =.05. Results: This study infers that denture base surface pre-treatment can improve the adhesive tensile bond strength between the liner and denture base specimens. The results of this study infer that chemical, mechanical, and mechano-chemical pre-treatments will have different effects on the bond strength of the acrylic soft resilient liner to the denture base. Conclusion: Among the various methods of pre-treatment of denture base resins, it was inferred that the mechano-chemical pre-treatment method with air-borne particle abrasion followed by monomer application exhibited superior bond strength than other methods with the resilient liner. Hence, this method could be effectively used to improve bond strength between liner and denture base and thus could minimize delamination of liner from the denture base during function.

  13. Bond-based linear indices of the non-stochastic and stochastic edge-adjacency matrix. 1. Theory and modeling of ChemPhys properties of organic molecules.

    Science.gov (United States)

    Marrero-Ponce, Yovani; Martínez-Albelo, Eugenio R; Casañola-Martín, Gerardo M; Castillo-Garit, Juan A; Echevería-Díaz, Yunaimy; Zaldivar, Vicente Romero; Tygat, Jan; Borges, José E Rodriguez; García-Domenech, Ramón; Torrens, Francisco; Pérez-Giménez, Facundo

    2010-11-01

    Novel bond-level molecular descriptors are proposed, based on linear maps similar to the ones defined in algebra theory. The kth edge-adjacency matrix (E(k)) denotes the matrix of bond linear indices (non-stochastic) with regard to canonical basis set. The kth stochastic edge-adjacency matrix, ES(k), is here proposed as a new molecular representation easily calculated from E(k). Then, the kth stochastic bond linear indices are calculated using ES(k) as operators of linear transformations. In both cases, the bond-type formalism is developed. The kth non-stochastic and stochastic total linear indices are calculated by adding the kth non-stochastic and stochastic bond linear indices, respectively, of all bonds in molecule. First, the new bond-based molecular descriptors (MDs) are tested for suitability, for the QSPRs, by analyzing regressions of novel indices for selected physicochemical properties of octane isomers (first round). General performance of the new descriptors in this QSPR studies is evaluated with regard to the well-known sets of 2D/3D MDs. From the analysis, we can conclude that the non-stochastic and stochastic bond-based linear indices have an overall good modeling capability proving their usefulness in QSPR studies. Later, the novel bond-level MDs are also used for the description and prediction of the boiling point of 28 alkyl-alcohols (second round), and to the modeling of the specific rate constant (log k), partition coefficient (log P), as well as the antibacterial activity of 34 derivatives of 2-furylethylenes (third round). The comparison with other approaches (edge- and vertices-based connectivity indices, total and local spectral moments, and quantum chemical descriptors as well as E-state/biomolecular encounter parameters) exposes a good behavior of our method in this QSPR studies. Finally, the approach described in this study appears to be a very promising structural invariant, useful not only for QSPR studies but also for similarity

  14. Increased hallux angle in children and its association with insufficient length of footwear: A community based cross-sectional study

    Directory of Open Access Journals (Sweden)

    Kundi Michael

    2009-12-01

    Full Text Available Abstract Background Wearing shoes of insufficient length during childhood has often been cited as leading to deformities of the foot, particularly to the development of hallux valgus disorders. Until now, these assumptions have not been confirmed through scientific research. This study aims to investigate whether this association can be statistically proven, and if children who wear shoes of insufficient length actually do have a higher risk of a more pronounced lateral deviation of the hallux. Methods 858 pre-school children were included in the study. The study sample was stratified by sex, urban/rural areas and Austrian province. The hallux angle and the length of the feet were recorded. The inside length of the children's footwear (indoor shoes worn in pre-school and outdoor shoes were assessed. Personal data and different anthropometric measurements were taken. The risk of hallux valgus deviation was statistically tested by a stepwise logistic regression analysis and the relative risk (odds ratio for a hallux angle ≥ 4 degrees was calculated. Results Exact examinations of the hallux angle could be conducted on a total of 1,579 individual feet. Only 23.9% out of 1,579 feet presented a straight position of the great toe. The others were characterized by lateral deviations (valgus position at different degrees, equalling 10 degrees or greater in 14.2% of the children's feet. 88.8% of 808 children examined wore indoor footwear that was of insufficient length, and 69.4% of 812 children wore outdoor shoes that were too short. A significant relationship was observed between the lengthwise fit of the shoes and the hallux angle: the shorter the shoe, the higher the value of the hallux angle. The relative risk (odds ratio of a lateral hallux deviation of ≥ 4 degrees in children wearing shoes of insufficient length was significantly increased. Conclusions There is a significant relationship between the hallux angle in children and footwear that is

  15. Increased hallux angle in children and its association with insufficient length of footwear: A community based cross-sectional study

    Science.gov (United States)

    2009-01-01

    Background Wearing shoes of insufficient length during childhood has often been cited as leading to deformities of the foot, particularly to the development of hallux valgus disorders. Until now, these assumptions have not been confirmed through scientific research. This study aims to investigate whether this association can be statistically proven, and if children who wear shoes of insufficient length actually do have a higher risk of a more pronounced lateral deviation of the hallux. Methods 858 pre-school children were included in the study. The study sample was stratified by sex, urban/rural areas and Austrian province. The hallux angle and the length of the feet were recorded. The inside length of the children's footwear (indoor shoes worn in pre-school and outdoor shoes) were assessed. Personal data and different anthropometric measurements were taken. The risk of hallux valgus deviation was statistically tested by a stepwise logistic regression analysis and the relative risk (odds ratio) for a hallux angle ≥ 4 degrees was calculated. Results Exact examinations of the hallux angle could be conducted on a total of 1,579 individual feet. Only 23.9% out of 1,579 feet presented a straight position of the great toe. The others were characterized by lateral deviations (valgus position) at different degrees, equalling 10 degrees or greater in 14.2% of the children's feet. 88.8% of 808 children examined wore indoor footwear that was of insufficient length, and 69.4% of 812 children wore outdoor shoes that were too short. A significant relationship was observed between the lengthwise fit of the shoes and the hallux angle: the shorter the shoe, the higher the value of the hallux angle. The relative risk (odds ratio) of a lateral hallux deviation of ≥ 4 degrees in children wearing shoes of insufficient length was significantly increased. Conclusions There is a significant relationship between the hallux angle in children and footwear that is too short in length. The

  16. Effect of retreatment on the push-out bond strength of MTA-based and epoxy resin-based endodontic sealers.

    Science.gov (United States)

    Yavari, Hamidreza; Shahi, Shahriar; Galledar, Saeedeh; Samiei, Mohammad; Janani, Maryam

    2017-01-01

    Background. Further studies on the adhesion properties of MTA-based materials seem necessary due to their growing use in endodontic treatment. This research aimed to assess the effect of retreatment on the bond strength of MTA-based (MTA Fillapex) and epoxy resin-based (AH Plus) sealers. Methods. ProTaper rotary files were applied to prepare the root canals of 80 human mandibular premolars. Then, the roots were randomly divided intotwo groups of A (n=40) and B (n=40), which were obturated with gutta-percha and MTA Filla-pex and AH Plus sealer, respectively. In both groups, the teeth were randomly subdivided into 2 subgroups. No retreatment was carried out in subgroups A 1 and B 1 , while subgroups A 2 and B 2 were retreated with rotary files and a solvent. Then, a push-out test was performed on four 2-mm slices of each tooth at a distance of 2 mm from the coronal surface after two weeks of incubation. Data were analyzed with two-way ANOVA and statistical significance was set at PRetreatment using rotary files and chloroform had no statistically significant effect on the bond strength of sealers evaluated in this study.

  17. Peel bond strength of two silicone soft liners to a heat-cured denture base resin.

    Science.gov (United States)

    Demir, Hakan; Dogan, Arife; Dogan, Orhan Murat; Keskin, Selda; Bolayir, Giray; Soygun, Koray

    2011-12-01

    This study investigated the peel strength of two different soft liners to a polymethylmethacrylate (PMMA) denture base resin before and after thermocycling. The silicone-based soft liner materials tested were Molloplast B and Permaflex; the denture base material was a heat-cured acrylic resin, Meliodent. A total of 40 specimens was prepared using rectangular molds with dimensions of 100 x 10 x 2 mm for PMMA and 150 x 10 x 2 mm for soft liners, as described in ASTM-D903-93. For each of the liner materials, 10 specimens were packed against a cured PMMA denture base surface as recommended by the manufacturers. The other 10 specimens were packed against PMMA denture base dough and processed together. In each group, 5 of the specimens were tested directly, while the other 5 were thermocycled in a water bath (5°C to 55°C; 3000 cycles) before testing. Peel testing was performed using an Instron testing machine. The results revealed that peel strength values of the Permaflex specimens prepared according to the manufacturer's recommendations were significantly higher than those of Molloplast B (p < 0.05). However, when packing was done against uncured PMMA dough, the difference between the specimens of two liners was not significant. Thermocycling led to significant decreases in the peel strength of both Permaflex liner specimens packed against cured/uncured PMMA resin surfaces (p < 0.05), whereas this process did not affect the strength of Molloplast B specimens. Results indicated that the material Molloplast B was superior to the material Permaflex in terms of peel strength when the specimens were simultaneously polymerized with PMMA and thermocycled.

  18. Evaluation of predicted Medfly (Ceratitis capitata quarantine length in the United States utilizing degree-day and agent-based models [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Travis Collier

    2017-10-01

    Full Text Available Invasions by pest insects pose a significant threat to agriculture worldwide. In the case of Ceratitis capitata incursions on the US mainland, where it is not officially established, repeated detections are followed by quarantines and treatments to eliminate the invading population. However, it is difficult to accurately set quarantine duration because non-detection may not mean the pest is eliminated. Most programs extend quarantine lengths past the last fly detection by calculating the amount of time required for 3 generations to elapse under a thermal unit accumulation development model (“degree day”. A newer approach is to use an Agent-Based Simulation (ABS to explicitly simulate population demographics and elimination. Here, predicted quarantine lengths for 11 sites in the continental United States are evaluated using both approaches. Results indicate a strong seasonality in quarantine length, with longer predictions in the second half of the year compared with the first; this pattern is more extreme in degree day predictions compared with ABS. Geographically, quarantine lengths increased with latitude, though this was less pronounced under the ABS. Variation in quarantine lengths for particular times and places was dramatically larger for degree day than ABS, generally spiking in the middle of the year for degree day and peaking in second half of the year for ABS. Analysis of 34 C. capitata quarantines from 1975 to 2017 in California shows that, for all but two, quarantines were started in the second half of the year, when degree day quarantine lengths are longest and have the highest uncertainty. For a set of hypothetical outbreaks based on these historical quarantines, the ABS produced significantly shorter quarantines than degree day calculations. Overall, ABS quarantine lengths were more consistent than degree day predictions, avoided unrealistically long values, and captured effects of rare events such as cold snaps.

  19. Evaluation of predicted Medfly (Ceratitis capitata) quarantine length in the United States utilizing degree-day and agent-based models.

    Science.gov (United States)

    Collier, Travis; Manoukis, Nicholas

    2017-01-01

    Invasions by pest insects pose a significant threat to agriculture worldwide. In the case of Ceratitis capitata incursions on the US mainland, where it is not officially established, repeated detections are followed by quarantines and treatments to eliminate the invading population. However, it is difficult to accurately set quarantine duration because non-detection may not mean the pest is eliminated. Most programs extend quarantine lengths past the last fly detection by calculating the amount of time required for 3 generations to elapse under a thermal unit accumulation development model ("degree day"). A newer approach is to use an Agent-Based Simulation (ABS) to explicitly simulate population demographics and elimination. Here, predicted quarantine lengths for 11 sites in the continental United States are evaluated using both approaches. Results indicate a strong seasonality in quarantine length, with longer predictions in the second half of the year compared with the first; this pattern is more extreme in degree day predictions compared with ABS. Geographically, quarantine lengths increased with latitude, though this was less pronounced under the ABS. Variation in quarantine lengths for particular times and places was dramatically larger for degree day than ABS, generally spiking in the middle of the year for degree day and peaking in second half of the year for ABS. Analysis of 34 C. capitata quarantines from 1975 to 2017 in California shows that, for all but two, quarantines were started in the second half of the year, when degree day quarantine lengths are longest and have the highest uncertainty. For a set of hypothetical outbreaks based on these historical quarantines, the ABS produced significantly shorter quarantines than degree day calculations. Overall, ABS quarantine lengths were more consistent than degree day predictions, avoided unrealistically long values, and captured effects of rare events such as cold snaps.

  20. Topology of electron charge density for chemical bonds from valence bond theory: a probe of bonding types.

    Science.gov (United States)

    Zhang, Lixian; Ying, Fuming; Wu, Wei; Hiberty, Philippe C; Shaik, Sason

    2009-01-01

    To characterize the nature of bonding we derive the topological properties of the electron charge density of a variety of bonds based on ab initio valence bond methods. The electron density and its associated Laplacian are partitioned into covalent, ionic, and resonance components in the valence bond spirit. The analysis provides a density-based signature of bonding types and reveals, along with the classical covalent and ionic bonds, the existence of two-electron bonds in which most of the bonding arises from the covalent-ionic resonance energy, so-called charge-shift bonds. As expected, the covalent component of the Laplacian at the bond critical point is found to be largely negative for classical covalent bonds. In contrast, for charge-shift bonds, the covalent part of the Laplacian is small or positive, in agreement with the weakly attractive or repulsive character of the covalent interaction in these bonds. On the other hand, the resonance component of the Laplacian is always negative or nearly zero, and it increases in absolute value with the charge-shift character of the bond, in agreement with the decrease of kinetic energy associated with covalent-ionic mixing. A new interpretation of the topology of the total density at the bond critical point is proposed to characterize covalent, ionic, and charge-shift bonding from the density point of view.

  1. Short and long term behaviour of externally bonded fibre reinforced polymer laminates with bio-based resins for flexural strengthening of concrete beams

    Science.gov (United States)

    McSwiggan, Ciaran

    The use of bio-based resins in composites for construction is emerging as a way to reduce of embodied energy produced by a structural system. In this study, two types of bio-based resins were explored: an epoxidized pine oil resin blend (EP) and a furfuryl alcohol resin (FA) derived from corn cobs and sugar cane. Nine large-scale reinforced concrete beams strengthened using externally bonded carbon and glass fibre reinforced bio-based polymer (CFRP and GFRP) sheets were tested. The EP resin resulted in a comparable bond strength to conventional epoxy (E) when used in wet layup, with a 7% higher strength for CFRP. The FA resin, on the other hand, resulted in a very weak bond, likely due to concrete alkalinity affecting curing. However, when FA resin was used to produce prefabricated cured CFRP plates which were then bonded to concrete using conventional epoxy paste, it showed an excellent bond strength. The beams achieved an increase in peak load ranging from 18-54% and a 9-46% increase in yielding load, depending on the number of FRP layers and type of fibres and resin. Additionally, 137 concrete prisms with a mid-span half-depth saw cut were used to test CFRP bond durability, and 195 CFRP coupons were used to examine tensile strength durability. Specimens were conditioned in a 3.5% saline solution at 23, 40 or 50°C, for up to 240 days. Reductions in bond strength did not exceed 15%. Bond failure of EP was adhesive with traces of cement paste on CFRP, whereas that of FA was cohesive with a thicker layer of concrete on CFRP, suggesting that the bond between FA and epoxy paste is excellent. EP tension coupons had similar strength and modulus to E resin, whereas FA coupons had a 9% lower strength and 14% higher modulus. After 240 days of exposure, maximum reductions in tensile strength were 8, 19 and 10% for EP, FA and E resins, respectively. Analysis of Variance (ANOVA) was also performed to assess the significance of the reductions observed. High degrees of

  2. Comparison of fluoridated apatites with pure hydroxyapatite as potential biomimetic alternatives to enamel for laboratory-based bond strength studies.

    Science.gov (United States)

    Jones, Steven P; Cheuk, Godwin C Y; Georgiou, George; Moles, David R

    2009-05-01

    To investigate whether fluoridated apatites have a shear bond strength which more closely equates to that of natural enamel than pure hydroxyapatite, making them potentially useful as biomimetic alternatives to natural enamel for ex vivo laboratory bonding studies. Discs of pure hydroxyapatite, pure fluorapatite and a 1:1 mixture of hydroxyapatite-fluorapatite were produced by cold uni-axial pressing. The discs were sintered at 1300 degrees C, embedded in epoxy resin, ground and polished. X-ray diffraction technique was used to analyse the purity of the apatites. Scanning electron microscopy was employed to investigate the etch patterns of the apatite specimens. Ninely-six upper left central incisor brackets were bonded to each of the three groups of discs. Shear bond strengths were determined by debonding the brackets using a loaded metal jig in an Instron Universal Testing Machine. The sites of bond failure were recorded using the Adhesive Remnant Index. One-way analysis of variance (ANOVA) and Bonferroni post-hoc comparisons were used to determine statistical differences between the mean shear bond strengths of the three specimen groups. The mean shear bond strength of pure hydroxyapatite (20.44 MPa; SD: 8.03; 95% CI: 18.81, 22.07) was significantly higher than those of fluorapatite (13.13 MPa; SD: 6.76; 95% CI: 11.76, 14.50) and hydroxyapatitefluorapatite (13.62 MPa; SD: 7.03; 95% CI: 12.19, 15.04) (p hydroxyapatite-fluorapatite (p > 0.99), and both were below the normal range ascribed to enamel (15-20 MPa). More than 90 per cent of the fluorapatite and the hydroxyapatite-fluorapatite specimens demonstrated bond failure at the substrate-adhesive interface, while only one-third of the hydroxyapatite specimens exhibited bond failure at that interface. Pure fluorapatite and hydroxyapatite-fluorapatite specimens offer no advantage over pure hydroxyapatite as a suitable artificial substrate for ex vivo bond strength testing.

  3. Coherence length determination of meso-meso linked porphyrin arrays based on forward-backward pair trajectory analysis.

    Science.gov (United States)

    Lee, Myeongwon; Kim, Heeyoung; Kim, Dongho; Sim, Eunji

    2008-06-12

    We investigated the excitation energy transfer process of meso-meso linked zinc(II) porphyrin arrays using the on-the-fly filtered propagator path integral method. Details of the dynamics such as coherence length of a porphyrin array are estimated by analysis of the characteristics of forward-backward pair trajectories. Upon examination of the convergence of the reduced density matrix with respect to the subset of Hilbert space trajectories, we determine the number of porphyrin units that form collective coherent states, that is, the coherence length. Simulation results show that the coherence length of zinc(II) porphyrin arrays is up to 4 units, which agrees excellently with experimental observations. On the other hand, the energy bias provided by the energy-accepting 5,15-bisphenylethynylated zinc(II) porphyrin reduces the degree of coherence which becomes negligible for an array with more than for porphyrin units. Considering conformational inhomogeneity, we found that the experimentally determined coherence length is the result of electronic and environmental influence rather than the structure disorder. Temperature dependence is also discussed.

  4. Shear force bond analysis between acrylic resin bases and retention framework (open- and mesh-type)

    Science.gov (United States)

    Royhan, A.; Indrasari, M.; Masulili, C.

    2017-08-01

    Occlusions between teeth and the activity of the muscles around an artificial tooth during mastication create a force on dentures. This force causes friction between acrylic resin bases and retention frameworks that can lead to the complete loss of the acrylic resin base from the framework. The purpose of this study was to analyze the design of retention frameworks and determine which ones have a better resistance to shear forces in order to prevent the loss of heat cured acrylic resin base (HCARB). Six samples each of open-and mesh-type retention frameworks, both types made of Co-Cr material, and HCARB, were shear tested by means of a universal testing machine. The average shear force required to release the HCARB for mesh-type retention frameworks was 28.84 kgf, and the average for the open-type was 26.52 kgf. There was no significant difference between the shear forces required to remove HCARB from open- and mesh-type retention frameworks.

  5. Wafer bonding applications and technology

    CERN Document Server

    Gösele, Ulrich

    2004-01-01

    During the past decade direct wafer bonding has developed into a mature materials integration technology. This book presents state-of-the-art reviews of the most important applications of wafer bonding written by experts from industry and academia. The topics include bonding-based fabrication methods of silicon-on-insulator, photonic crystals, VCSELs, SiGe-based FETs, MEMS together with hybrid integration and laser lift-off. The non-specialist will learn about the basics of wafer bonding and its various application areas, while the researcher in the field will find up-to-date information about this fast-moving area, including relevant patent information.

  6. Nanofiber-bonded cloth materials based on poly-3-hydroxybutyrate with antibacterial properties for medical purposes

    Science.gov (United States)

    Tyubaeva, P. M.; Olkhov, A. A.; Karpova, S. G.; Iordansky, A. L.; Popov, A. A.

    2017-12-01

    Different transdermal systems based on solid polymer matrices or gels containing functional substances with antiseptic (antibacterial) properties have application to the therapy of many infectious diseases and cancer. Today the most promising type of matrices with antiseptic characteristics are the nano- and microfiber nonwoven materials. Fibers on the biopolymer (poly(3-hydroxybutyrate)) basis were obtained using the electrospinning method. In the present work, the effects of iron (III) complex with tetraphenylporphyrin and its influence on bactericidal and antibacterial properties of the ultrathin PHB fibers were investigated.

  7. Diffusion bonding

    International Nuclear Information System (INIS)

    Anderson, R.C.

    1976-01-01

    A method is described for joining beryllium to beryllium by diffusion bonding. At least one surface portion of at least two beryllium pieces is coated with nickel. A coated surface portion is positioned in a contiguous relationship with another surface portion and subjected to an environment having an atmosphere at a pressure lower than ambient pressure. A force is applied on the beryllium pieces for causing the contiguous surface portions to abut against each other. The contiguous surface portions are heated to a maximum temperature less than the melting temperature of the beryllium, and the applied force is decreased while increasing the temperature after attaining a temperature substantially above room temperature. A portion of the applied force is maintained at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions

  8. Weight, length and head circumference standards based on a population of Danish newborn boys and girls in gestational weeks 25 to 43

    DEFF Research Database (Denmark)

    Ulrich, M; Høst, A; Kamper, J

    1997-01-01

    Growth standards of birth weight, birth length and birth head circumference were constructed based on a population of Danish newborn boys and girls in gestational weeks twenty-five to forty-three. Study populations were residents of the municipality of Odense for later gestational ages and reside...

  9. Low temperature anodic bonding to silicon nitride

    DEFF Research Database (Denmark)

    Weichel, Steen; Reus, Roger De; Bouaidat, Salim

    2000-01-01

    Low-temperature anodic bonding to stoichiometric silicon nitride surfaces has been performed in the temperature range from 3508C to 4008C. It is shown that the bonding is improved considerably if the nitride surfaces are either oxidized or exposed to an oxygen plasma prior to the bonding. Both bulk...... and thin-film glasses were used in the bonding experiments. Bond quality was evaluated using a tensile test on structured dies. The effect of oxygen-based pre-treatments of the nitride surface on the bond quality has been evaluated. Bond strengths up to 35 Nrmm2 and yields up to 100% were obtained....

  10. Area-based initiatives – and their work in bonding, bridging and linking social capital

    DEFF Research Database (Denmark)

    Agger, Annika; Jensen, Jesper Ole

    2015-01-01

    In this article, we provide a conceptual and argumentative framework for studying how Area-based Initiatives (ABIs) can facilitate contact between networks in deprived neighbourhoods and external forms of power (linking social capital). These relations provide the residents and other members...... of civil society with crucial access to leveraging resources, ideas and information. Although few studies on linking social capital have been carried out in relation to urban regeneration, there is empirical evidence that suggests that it can play a positive role in establishing trust and relations between...... civil society and a municipality. We set out with a review of how social capital literature has been applied in an urban context, and then demonstrate empirical examples from Denmark of how, in different contexts (village, town and city), ABIs have facilitated processes that generated different forms...

  11. Numerical Parameter Optimization of the Ignition and Growth Model for HMX Based Plastic Bonded Explosives

    Science.gov (United States)

    Gambino, James; Tarver, Craig; Springer, H. Keo; White, Bradley; Fried, Laurence

    2017-06-01

    We present a novel method for optimizing parameters of the Ignition and Growth reactive flow (I&G) model for high explosives. The I&G model can yield accurate predictions of experimental observations. However, calibrating the model is a time-consuming task especially with multiple experiments. In this study, we couple the differential evolution global optimization algorithm to simulations of shock initiation experiments in the multi-physics code ALE3D. We develop parameter sets for HMX based explosives LX-07 and LX-10. The optimization finds the I&G model parameters that globally minimize the difference between calculated and experimental shock time of arrival at embedded pressure gauges. This work was performed under the auspices of the U.S. DOE by LLNL under contract DE-AC52-07NA27344. LLNS, LLC LLNL-ABS- 724898.

  12. Rational design of BINOL-based diimidazolyl ligands: homochiral channel-like mono-component organic frameworks by hydrogen-bond-directed self-assembly.

    Science.gov (United States)

    Yang, Li; Yang, Fei; Lan, Jingbo; Gao, Ge; You, Jingsong; Su, Xiaoyu

    2011-04-21

    We have developed a synthetic strategy to selectively incorporate the imidazole ring into the 1,1'-bi-2-naphthol (BINOL) skeleton at the different position. The resulting conformationally rigid BINOL-based diimidazolyl ligands bearing both hydrogen-bond-acceptors and -donators can self-assemble into homochiral channel-like mono-component organic frameworks via intermolecular O-H···N hydrogen bonds between the phenolic hydroxyl group and the N2 or N4 atom of the imidazole ring.

  13. A field-programmable-gate-array-based high-speed transceiver for a quartz crystal microbalance induced bond-rupture sensor

    International Nuclear Information System (INIS)

    Yuan, Yong J; Van der Werff, Matthew J; Xu, W L

    2011-01-01

    There is a need for faster and more precise biosensors to identify a disease in medical diagnostics. Bond-rupture scanning is a new sensor technique by inducing antibody–antigen bonds to rupture from a transducer surface. A quartz crystal microbalance (QCM) oscillates horizontally, and can be used as a platform to measure the mass change on its surface. A high speed digital electronics system was demonstrated for the purposes of inducing and detecting bond rupture. A field-programmable-gate-array-based high speed transceiver board is controlled by a digital signal processor, as well as various graphical user interfaces for the end user interaction. Bond-rupture detection was carried out by rupturing modified beads as a biological element shaking off from the surface of a QCM. It took as little as 20 s in a scanning experiment. The advantages of the proof-of-concept QCM and bond-rupture detection are that it is quick, simple and capable of discriminating between specific and non-specific interactions

  14. Psychometric Validation of the Parental Bonding Instrument in a UK Population–Based Sample Role of Gender and Association With Mental Health in Mid-Late Life

    NARCIS (Netherlands)

    M.K. Xu (Kate); A. J. S. Morin (Alexandre); H. W. Marsh (Herbert); M. Richards (Martin); P. B. Jones (Peter)

    2016-01-01

    markdownabstractThe factorial structure of the Parental Bonding Instrument (PBI) has been frequently studied in diverse samples but no study has examined its psychometric properties from large, population-based samples. In particular, important questions have not been addressed such as the

  15. Exclusive Aromatic vs Aliphatic C-H Bond Functionalization by Carbene Insertion with Gold-based Catalysts

    OpenAIRE

    Rivilla de la Cruz, Iván; Gómez Emeterio, Bella Pilar; Romero Fructos-Vázquez, Manuel; Díaz Requejo, María Mar; Pérez Romero, Pedro José

    2011-01-01

    The direct functionalization of aromatic C-H bonds by carbene insertion from diazocompounds catalyzed by gold complexes with N-heterocyclic ligands is described. The reaction is completely selective toward the Csp2-H bonds, other Csp3-H bonds remaining unreacted. A study with a several NHC ligands in Au(I) and Au(III) complexes has been performed. A potential application in profen derivatives has also been developed DGI (CTQ2008-00042BQU and Consolider Ingenio 2010, Grant CSD2006-0003) and...

  16. Study of chemical bonding in the interhalogen complexes based on density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Poleshchuk, O. Kh., E-mail: poleshch@tspu.edu.ru [National Research Tomsk Polytechnic University (Russian Federation); Fateev, A. V.; Yarkova, A. G. [Tomsk State Pedagogical University (Russian Federation); Ermakhanov, M. N.; Saidakhmetov, P. A. [M. Auezov South Kazakhstan State University (Kazakhstan)

    2016-12-15

    The density functional theory analysis was used for a number XYL complexes (XY is a dihalogen molecule and L is a Lewis base), formed between molecules I{sub 2}, ICl, IBr and pyridine. The calculated geometrical parameters, IR spectra and nuclear quadrupole interaction constants of iodine are consistent with the data of microwave spectroscopy and nuclear quadrupole resonance. The good correlation between the experimental and calculated binding energies of the inner electrons of iodine, chlorine and nitrogen atoms were found with the calculation using both Gaussian and Slater functions. The comparison of experimental and calculated changes in the electron density on the atoms upon complex formation suggested the choice of scheme for calculating the effective charge on the atoms, which allow us to interpret the experimental spectra. It is shown that the use of both calculated schemes allows us to predict the enthalpy of complex formation in close agreement with the experimental values. The energy analysis shows that in the complexes the electrostatic binding energy dominates that of covalent binding.

  17. Calibration of Eringen's small length scale coefficient for initially stressed vibrating nonlocal Euler beams based on microstructured beam model

    International Nuclear Information System (INIS)

    Wang, C M; Zhang, Z; Challamel, N; Duan, W H

    2013-01-01

    In this paper, we calibrate Eringen's small length scale coefficient e 0 for an initially stressed vibrating nonlocal Euler beam via a microstructured beam modelled by some repetitive cells comprising finite rigid segments and elastic rotational springs. By adopting the pseudo-differential operator and Padé's approximation, an analytical solution for the vibration frequency in terms of initial stress may be developed for the microstructured beam model. When comparing this analytical solution with the established exact vibration solution from the nonlocal beam theory, one finds that the calibrated Eringen's small length scale coefficient e 0 is given by e 0 = √(1/6)-(1/12)(σ 0 /σ-breve m ) where σ 0 is the initial stress and σ-breve m is the mth mode buckling stress of the corresponding local Euler beam. It is shown that e 0 varies with respect to the initial axial stress, from 1/√(12)∼0.289 at the buckling compressive stress to 1/√6∼0.408 when the axial stress is zero and it monotonically increases with increasing initial tensile stress. The small length scale coefficient e 0 , however, does not depend on the vibration/buckling mode considered. (paper)

  18. Development of CPV solar receiver based on insulated metal substrate (IMS): Comparison with receiver based on the direct bonded copper substrate (DBC) - A reliability study

    Science.gov (United States)

    Mabille, Loïc; Mangeant, Christophe; Baudrit, Mathieu

    2012-10-01

    Most of the CPV solar receivers are based on III-V multijunction cells die-attached to a direct bonded copper (DBC) substrate. An alternative to DBC resides in the insulated metal substrate (IMS). This paper presents the behavior of IMS and DBC receivers when tested under accelerated aging conditions such as described in the IEC 62108. Characterization tools involved in the monitoring of potential degradation are electroluminescence (EL), dark-I (V) (DIV), spectral response (EQE), diode factor measurements (VIM), RX tomography (RX-T), and, of course, illuminated I (V) under various concentration factors. Based on EL, DIV and EQE first results, IMS and DBC age in a similar way. Study is ongoing.

  19. Microstructure of bonding zones in laser-clad Ni-alloy-based composite coatings reinforced with various ceramic powders

    International Nuclear Information System (INIS)

    Pei, Y.T.; Ouyang, J.H.; Lei, T.C.

    1996-01-01

    Microstructure of the bonding zones (BZs) between laser-clad Ni-alloy-based composite coatings and steel substrates was studied by means of scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. Observations indicate that for pure Ni-alloy coating the laser parameters selected for good interface fusion have no effect on the microstructure of the BZ except for its thickness. However, the addition of ceramic particles (TiN, SiC, or ZrO 2 ) to the Ni alloy varies the compositional or constitutional undercooling of the melt near the solid/liquid interface and consequently leads to the observed changes of microstructure of the BZs. For TiN/Ni-alloy coating the morphology of γ-Ni solid solution in the BZ changes from dendritic to planar form with increasing scanning speed. A colony structure of eutectic is found in the BZ of SiC/Ni-alloy coating in which complete dissolution of SiC particles takes place during laser cladding. The immiscible melting of ZrO 2 and Ni-alloy powders induces the stratification of ZrO 2 /Ni-alloy coating which consists of a pure ZrO 2 layer fin the upper region and a BZ composed mainly of γ-Ni dendrites adjacent to the substrate. All the BZs studied in this investigation have good metallurgical characteristics between the coatings and the substrates

  20. Flexible free-standing luminescent two-component fiber films with tunable hierarchical structures based on hydrogen-bonding architecture.

    Science.gov (United States)

    Yan, Dongpeng; Williams, Gareth R; Zhao, Min; Li, Changming; Fan, Guoling; Yang, Hejia

    2013-12-17

    Although the fabrication of hierarchical architectures with highly ordered functional units is of great importance for both fundamental science and practical application, the development of one-dimensional (1D) organic hierarchical micro/nanostructures based on low-molecular-weight (LMW) building blocks remains at an early stage. Herein, we report two types of micro/nanoscaled multicomponent fluorescent fiber systems with tunable hierarchical morphologies through a one-step coassembly process. With the aid of hydrogen-bonding motifs, LMW precursors (1,4-bis(5-phenyloxazol-2-yl)benzene (A) and two coassembled building blocks: 4-bromotetrafluorobenzene carboxylic acid (B) and 2,3,4,5,6-pentafluorophenol (C)) have been self-organized into fibers and flexible free-standing films, which show hierarchical micro/nanostructures as well as tunable one-/two-photon luminescence. The disassembly of the multicomponent A.B and A.C fibers occurs at high temperature, which further alters the luminescence properties of the multicomponent materials. Therefore, this work provides a facile wet chemical route for fabricating multicomponent LMW self-assembled fibers and free-standing film systems with tunable hierarchical structures and photoemission behaviors, and such self-organized systems may have potential applications in fields of two-photon luminescence and thermal sensors.

  1. Evaluation of the physicochemical properties and push-out bond strength of MTA-based root canal cement.

    Science.gov (United States)

    Chávez-Andrade, Gisselle Moraima; Kuga, Milton Carlos; Duarte, Marco Antonio Hungaro; Leonardo, Renato de Toledo; Keine, Katia Cristina; Sant'Anna-Junior, Arnaldo; Só, Marcus Vinicius Reis

    2013-11-01

    This study investigated the flowability, setting time, pH, calcium release and bond strength of a MTA-based cement (MTA Fillapex(®)) compared to AH Plus and Sealapex. For the flowability test, the ISO 6876:2001 specification was utilized and for the setting time test, the ASTM C266-03 specification was utilized. For the pH and calcium release measurements, 10 samples were prepared for each group and analyzed for several different periods. For the push-out test, dentin disks were distributed into three groups, according to the cement utilized and into three subgroups, according to the root third (n = 10). After obturation, the specimens underwent push-out testing. The data were compared statistically using a significance level of 5%. The flowability of all materials was found to be similar (p > 0.05). The setting times were different among the groups tested (MTA Fillapex pH values (p 0.05). AH Plus presented the lowest pH and calcium release values (p root canal cement, in order to use this scaler in root canal fillings. MTA Fillapex showed satisfactory properties for clinical use.

  2. Bond-based 2D quadratic fingerprints in QSAR studies: virtual and in vitro tyrosinase inhibitory activity elucidation.

    Science.gov (United States)

    Casañola-Martin, Gerardo M; Marrero-Ponce, Yovani; Khan, Mahmud T H; Khan, Sher B; Torrens, Francisco; Pérez-Jiménez, Facundo; Rescigno, Antonio; Abad, Concepción

    2010-12-01

    In this report, we show the results of quantitative structure-activity relationship (QSAR) studies of tyrosinase inhibitory activity, by using the bond-based quadratic indices as molecular descriptors (MDs) and linear discriminant analysis (LDA), to generate discriminant functions to predict the anti-tyrosinase activity. The best two models [Eqs (6) and (12)] out of the total 12 QSAR models developed here show accuracies of 93.51% and 91.21%, as well as high Matthews correlation coefficients (C) of 0.86 and 0.82, respectively, in the training set. The validation external series depicts values of 90.00% and 89.44% for these best two equations (6) and (12), respectively. Afterwards, a second external prediction data are used to perform a virtual screening of compounds reported in the literature as active (tyrosinase inhibitors). In a final step, a series of lignans is analysed using the in silico-developed models, and in vitro corroboration of the activity is carried out. An issue of great importance to remark here is that all compounds present greater inhibition values than Kojic acid (standard tyrosinase inhibitor: IC₅₀ = 16.67 μm). The current obtained results could be used as a framework to increase the speed, in the biosilico discovery of leads for the treatment of skin disorders. © 2010 John Wiley & Sons A/S.

  3. Apatite and sodalite based glass-bonded waste forms for immobilization of 129I and mixed halide radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Goel, Ashutosh [Rutgers Univ., New Brunswick, NJ (United States); McCloy, John S. [Washington State Univ., Pullman, WA (United States); Riley, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Matyas, Josef [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-12-30

    The goal of the project was to utilize the knowledge accumulated by the team, in working with minerals for chloride wastes and biological apatites, toward the development of advanced waste forms for immobilizing 129I and mixed-halide wastes. Based on our knowledge, experience, and thorough literature review, we had selected two minerals with different crystal structures and potential for high chemical durability, sodalite and CaP/PbV-apatite, to form the basis of this project. The focus of the proposed effort was towards: (i) low temperature synthesis of proposed minerals (iodine containing sodalite and apatite) leading to the development of monolithic waste forms, (ii) development of a fundamental understanding of the atomic-scale to meso-scale mechanisms of radionuclide incorporation in them, and (iii) understanding of the mechanism of their chemical corrosion, alteration mechanism, and rates. The proposed work was divided into four broad sections. deliverables. 1. Synthesis of materials 2. Materials structural and thermal characterization 3. Design of glass compositions and synthesis glass-bonded minerals, and 4. Chemical durability testing of materials.

  4. Thermal decomposition and kinetics of plastic bonded explosives based on mixture of HMX and TATB with polymer matrices

    Directory of Open Access Journals (Sweden)

    Arjun Singh

    2017-02-01

    Full Text Available This work describes thermal decomposition behaviour of plastic bonded explosives (PBXs based on mixture of l,3,5,7-tetranitro- 1,3,5,7-tetrazocane (HMX and 2,4,6- triamino-1,3,5-trinitrobenzene (TATB with Viton A as polymer binder. Thermal decomposition of PBXs was undertaken by applying simultaneous thermal analysis (STA and differential scanning calorimetry (DSC to investigate influence of the HMX amount on thermal behavior and its kinetics. Thermogravimetric analysis (TGA indicated that the thermal decomposition of PBXs based on mixture of HMX and TATB was occurred in a three-steps. The first step was mainly due to decomposition of HMX. The second step was ascribed due to decomposition of TATB, while the third step was occurred due to decomposition of the polymer matrices. The thermal decomposition % was increased with increasing HMX amount. The kinetics related to thermal decomposition were investigated under non-isothermal for a single heating rate measurement. The variation in the activation energy of PBXs based on mixture of HMX and TATB was observed with varying the HMX amount. The kinetics from the results of TGA data at various heating rates under non-isothermal conditions were also calculated by Flynn–Wall–Ozawa (FWO and Kissinger-Akahira-Sunose (KAS methods. The activation energies calculated by employing FWO method were very close to those obtained by KAS method. The mean activation energy calculated by FWO and KAS methods was also a good agreement with the activation energy obtained from single heating rate measurement in the first step decomposition.

  5. Better Bonded Ethernet Load Balancing

    Energy Technology Data Exchange (ETDEWEB)

    Gabler, Jason

    2006-09-29

    When a High Performance Storage System's mover shuttles large amounts of data to storage over a single Ethernet device that single channel can rapidly become saturated. Using Linux Ethernet channel bonding to address this and similar situations was not, until now, a viable solution. The various modes in which channel bonding could be configured always offered some benefit but only under strict conditions or at a system resource cost that was greater than the benefit gained by using channel bonding. Newer bonding modes designed by various networking hardware companies, helpful in such networking scenarios, were already present in their own switches. However, Linux-based systems were unable to take advantage of those new modes as they had not yet been implemented in the Linux kernel bonding driver. So, except for basic fault tolerance, Linux channel bonding could not positively combine separate Ethernet devices to provide the necessary bandwidth.

  6. A simplified indirect bonding technique

    Directory of Open Access Journals (Sweden)

    Radha Katiyar

    2014-01-01

    Full Text Available With the advent of lingual orthodontics, indirect bonding technique has become an integral part of practice. It involves placement of brackets initially on the models and then their transfer to teeth with the help of transfer trays. Problems encountered with current indirect bonding techniques used are (1 the possibility of adhesive flash remaining around the base of the brackets which requires removal (2 longer time required for the adhesive to gain enough bond strength for secure tray removal. The new simplified indirect bonding technique presented here overcomes both these problems.

  7. The effect of different final irrigant activation techniques on the bond strength of an epoxy resin-based endodontic sealer: a preliminary study.

    Science.gov (United States)

    Topçuoğlu, Hüseyin Sinan; Tuncay, Öznur; Demirbuga, Sezer; Dinçer, Asiye Nur; Arslan, Hakan

    2014-06-01

    The aim of this study was to evaluate whether or not different final irrigation activation techniques affect the bond strength of an epoxy resin-based endodontic sealer (AH Plus; Dentsply DeTrey, Konstanz, Germany) to the root canal walls of different root thirds. Eighty single-rooted human mandibular premolars were prepared by using the ProTaper system (Dentsply Maillefer, Ballaigues, Switzerland) to size F4, and a final irrigation regimen using 3% sodium hypochlorite and 17% EDTA was performed. The specimens were randomly divided into 4 groups (n = 20) according to the final irrigation activation technique used as follows: no activation (control), manual dynamic activation (MDA), CanalBrush (Coltene Whaledent, Altststten, Switzerland) activation, and ultrasonic activation. Five specimens from each group were prepared for scanning electron microscopic observation to assess the smear layer removal after the final irrigation procedures. All remaining roots were then obturated with gutta-percha and AH Plus sealer. A push-out test was used to measure the bond strength between the root canal dentin and AH Plus sealer. The data obtained from the push-out test were analyzed using 2-way analysis of variance and Tukey post hoc tests. The bond strength values mostly decreased in the coronoapical direction (P < .001). In the coronal and middle thirds, ultrasonic activiation showed a higher bond strength than other groups (P < .05). In the apical third, MDA displayed the highest bond strength to root dentin (P < .05). The majority of specimens exhibited cohesive failures. The bond strength of AH Plus sealer to root canal dentin may improve with ultrasonic activation in the coronal and middle thirds and MDA in the apical third. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  8. Density functional theory based-study of 5-fluorouracil adsorption on β-cristobalite (1 1 1) hydroxylated surface: The importance of H-bonding interactions

    Energy Technology Data Exchange (ETDEWEB)

    Simonetti, S., E-mail: ssimonet@uns.edu.ar [Universidad Nacional del Sur (UNS)—Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca (Argentina); Universidad Tecnológica Nacional (UTN), Bahía Blanca (Argentina); Compañy, A. Díaz [Comisión de Investigaciones Científicas (CIC), Buenos Aires (Argentina); Pronsato, E.; Juan, A.; Brizuela, G. [Universidad Nacional del Sur (UNS)—Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca (Argentina); Lam, A. [Instituto de Ciencia y Tecnología de Materiales (IMRE), Universidad de La Habana (Cuba)

    2015-12-30

    Graphical abstract: - Highlights: • Favorable energies results in optimum four adsorption geometries. • Silanols are partially weakening and establish H-bonds with polar groups of 5-FU drug. • Dispersion forces approach the 5-FU molecule toward the surface. • Electron exchange is presented after adsorption. • H-bonds stabilize the molecule playing significant role in the adsorption mechanism. - Abstract: Silica-based mesoporous materials have been recently proposed as an efficient support for the controlled release of a popular anticancer drug, 5-fluorouracil (5-FU). Although the relevance of this topic, the atomistic details about the specific surface-drug interactions and the energy of adsorption are almost unknown. In this work, theoretical calculations using the Vienna Ab-initio Simulation Package (VASP) applying Grimme's—D2 correction were performed to elucidate the drug–silica interactions and the host properties that control 5-FU drug adsorption on β-cristobalite (1 1 1) hydroxylated surface. This study shows that hydrogen bonding, electron exchange, and dispersion forces are mainly involved to perform the 5-FU adsorption onto silica. This phenomenon, revealed by favorable energies, results in optimum four adsorption geometries that can be adopted for 5-FU on the hydroxylated silica surface. Silanols are weakening in response to the molecule approach and establish H-bonds with polar groups of 5-FU drug. The final geometry of 5-FU adopted on hydroxylated silica surface is the results of H-bonding interactions which stabilize and fix the molecule to the surface and dispersion forces which approach it toward silica (1 1 1) plane. The level of hydroxylation of the SiO{sub 2} (1 1 1) surface is reflected by the elevated number of hydrogen bonds that play a significant role in the adsorption mechanisms.

  9. BiOBr@SiO2 flower-like nanospheres chemically-bonded on cement-based materials for photocatalysis

    Science.gov (United States)

    Wang, Dan; Hou, Pengkun; Yang, Ping; Cheng, Xin

    2018-02-01

    Endowment of photocatalytic property on the surface of concrete structure can contribute to the self-cleaning of the structure and purification of the polluted environment. We developed a nano-structured BiOBr@SiO2 photocatalyst and innovatively used for surface-treatment of cement-based materials with the hope of attaining the photocatalytic property in visible-light region and surface modification/densification performances. The SiO2 layer on the flower-like BiOBr@SiO2 helps to maintain a stable distribution of the photocatalyst, as well as achieving a chemical bonding between the coating and the cement matrix. Results showed that the color fading rate of during the degradation of Rhodamine B dye of the BiOBr-cem sample is 2 times higher compared with the commonly studied C, N-TiO2-cem sample. The photo-degradation rates of samples BiOBr-cem and BiOBr@SiO2-cem are 93 and 81% within 150 min, respectively, while sample BiOBr@SiO2-cem reveals a denser and smoother surface after curing for 28 days and pore-filling effect at size within 0.01-0.2 μm when compared with untreated samples. Moreover, additional C-S-H gel can be formed due to the pozzolanic reaction between BiOBr@SiO2 and the hardened cement matrix. Both advantages of the BiOBr@SiO2 favor its application for surface-treatment of hardened cement-based material to acquire an improved surface quality, as well as durable photocatalytic functionality.

  10. Breaking Rules – Making Bonds

    Indian Academy of Sciences (India)

    IAS Admin

    RESONANCE | January 2016. GENERAL | ARTICLE. Breaking Rules – Making Bonds. A G Samuelson. Boron-containing molecules discovered recently have new types of dative bonds between carbenes and borylenes. At the same time, they show that traditional thumb rules regarding acids and bases are no longer valid.

  11. O hydrogen bonds in alkaloids

    Indian Academy of Sciences (India)

    An overview of general classification scheme, medicinal importance and crystal structure analysis with emphasis on the role of hydrogen bonding in some alkaloids is presented in this paper. The article is based on a general kind of survey while crystallographic analysis and role of hydrogen bonding are limited to only ...

  12. Why are Hydrogen Bonds Directional?

    Indian Academy of Sciences (India)

    for an interaction to be characterized as a hydro- gen bond but does not provide any rationale for the same. This article reports a rationale for limiting the angle, based on the electron density topology using the quantum theory of atoms in molecules. Electron density topol- ogy for common hydrogen bond donors HF, HCl, ...

  13. Comparative evaluation of shear bond strength of three resin based dual-cure core build-up materials: An In-vitro study

    OpenAIRE

    Jain, Gaurav; Narad, Aditi; Boruah, Lalit C.; Rajkumar, Balakrishnan

    2015-01-01

    Aim: The in-vitro study compared the shear bond strength (SBS) of three recently introduced dual-cure resin based core build-up materials namely ParaCore, FluoroCore, and MultiCore. Materials and Methods: One hundred twenty extracted permanent human mandibular molar teeth were taken and sectioned horizontally beneath the dentinoenamel junction to expose the coronal dentin. The specimens obtained were divided into three main groups based on the materials used and then further divided into ...

  14. A chiral organic base catalyst with halogen-bonding-donor functionality: asymmetric Mannich reactions of malononitrile with N-Boc aldimines and ketimines.

    Science.gov (United States)

    Kuwano, Satoru; Suzuki, Takumi; Hosaka, Yusei; Arai, Takayoshi

    2018-03-29

    A chiral organic base catalyst with halogen-bonding-donor functionality has been developed. This quinidine-derived acid/base catalyst smoothly promoted the asymmetric Mannich reaction of malononitrile and various N-Boc imines with up to 98% ee. The cooperative interaction with both substrates was responsible for the high activity that allowed a reduction of the catalyst amount to 0.5 mol%.

  15. Probing electron density of H-bonding between cation-anion of imidazolium-based ionic liquids with different anions by vibrational spectroscopy.

    Science.gov (United States)

    Gao, Yan; Zhang, Liqun; Wang, Yong; Li, Haoran

    2010-03-04

    Attenuated total reflection infrared spectroscopy and density functional theory calculation have been employed to study the spectral properties of imidazolium-based ionic liquids (ILs) with different anions. ILs based on 1-butyl-3-methylimidazolium cation with different ani