Determinants of condom breakage among female sex workers in Karnataka, India.

Science.gov (United States)

Bradley, Janet; Rajaram, S; Alary, Michel; Isac, Shajy; Washington, Reynold; Moses, Stephen; Ramesh, B M

2011-12-29

Condoms are effective in preventing the transmission of HIV and other sexually transmitted infections, when properly used. However, recent data from surveys of female sex workers (FSWs) in Karnataka in south India, suggest that condom breakage rates may be quite high. It is important therefore to quantify condom breakage rates, and examine what factors might precipitate condom breakage, so that programmers can identify those at risk, and develop appropriate interventions. We explored determinants of reported condom breakage in the previous month among 1,928 female sex workers in four districts of Karnataka using data from cross-sectional surveys undertaken from July 2008 to February 2009. Using stepwise multivariate logistic regression, we examined the possible determinants of condom breakage, controlling for several independent variables including the district and client load. Overall, 11.4% of FSWs reported at least one condom break in the previous month. FSWs were much more likely to report breakage if under 20 years of age (AOR 3.43, p = 0.005); if divorced/ separated/widowed (AOR 1.52, p = 0.012); if they were regular alcohol users (AOR 1.63, p = 0.005); if they mostly entertained clients in lodges/rented rooms (AOR 2.99, p = 0.029) or brothels (AOR 4.77, p = 0.003), compared to street based sex workers; if they had ever had anal sex (AOR 2.03, p = 0.006); if the sex worker herself (as opposed to the client) applied the condom at last use (AOR 1.90, p < 0.001); if they were inconsistent condom users (AOR 2.77, p < 0.001); and if they had never seen a condom demonstration (AOR 2.37, p < 0.001). The reported incidence of condom breakage was high in this study, and this is a major concern for HIV/STI prevention programs, for which condom use is a key prevention tool. Younger and more marginalized female sex workers were most vulnerable to condom breakage. Special effort is therefore required to seek out such women and to provide information and skills on correct

Fiber breakage phenomena in long fiber reinforced plastic preparation

International Nuclear Information System (INIS)

Huang, Chao-Tsai; Tseng, Huan-Chang; Chang, Rong-Yeu; Vlcek, Jiri

2015-01-01

Due to the high demand of smart green, the lightweight technologies have become the driving force for the development of automotives and other industries in recent years. Among those technologies, using short and long fiber-reinforced plastics (FRP) to replace some metal components can reduce the weight of an automotive significantly. However, the microstructures of fibers inside plastic matrix are too complicated to manage and control during the injection molding through the screw, the runner, the gate, and then into the cavity. This study focuses on the fiber breakage phenomena during the screw plastification. Results show that fiber breakage is strongly dependent on screw design and operation. When the screw geometry changes, the fiber breakage could be larger even with lower compression ratio. (paper)

Visual characterization and quantitative measurement of artemisinin-induced DNA breakage

Energy Technology Data Exchange (ETDEWEB)

Cai Huaihong [Bionanotechnology Lab, and Department of Chemistry, Jinan University, Guangzhou 510632 (China); Yang Peihui [Bionanotechnology Lab, and Department of Chemistry, Jinan University, Guangzhou 510632 (China)], E-mail: typh@jnu.edu.cn; Chen Jianan [Bionanotechnology Lab, and Department of Chemistry, Jinan University, Guangzhou 510632 (China); Liang Zhihong [Experiment and Technology Center, Jinan University, Guangzhou 510632 (China); Chen Qiongyu [Institute of Genetic Engineering, Jinan University, Guangzhou 510632 (China); Cai Jiye [Bionanotechnology Lab, and Department of Chemistry, Jinan University, Guangzhou 510632 (China)], E-mail: tjycai@jnu.edu.cn

2009-05-01

DNA conformational change and breakage induced by artemisinin, a traditional Chinese herbal medicine, have been visually characterized and quantitatively measured by the multiple tools of electrochemistry, UV-vis absorption spectroscopy, atomic force microscopy (AFM), and DNA electrophoresis. Electrochemical and spectroscopic results confirm that artemisinin can intercalate into DNA double helix, which causes DNA conformational changes. AFM imaging vividly demonstrates uneven DNA strand breaking induced by QHS interaction. To assess these DNA breakages, quantitative analysis of the extent of DNA breakage has been performed by analyzing AFM images. Basing on the statistical analysis, the occurrence of DNA breaks is found to depend on the concentration of artemisinin. DNA electrophoresis further validates that the intact DNA molecules are unwound due to the breakages occur at the single strands. A reliable scheme is proposed to explain the process of artemisinin-induced DNA cleavage. These results can provide further information for better understanding the anticancer activity of artemisinin.

Two-pulse laser control of bond-selective fragmentation

DEFF Research Database (Denmark)

Amstrup, Bjarne; Henriksen, Niels Engholm

1996-01-01

We elaborate on a two-pulse (pump-pump) laser control scheme for selective bond-breaking in molecules [Amstrup and Henriksen, J. Chem. Phys. 97, 8285 (1992)]. We show, in particular, that with this scheme one can overcome the obstacle of intramolecular vibrational relaxation. As an example, we...... consider an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18. It is shown that asymmetric bond stretching can be created in simple (intense) laser fields. We predict that an alternating high selectivity between the channels O-16+(OO)-O-16-O-18 and (OO)-O-16-O-16+ O-18 can...

Theoretical Modeling of Rock Breakage by Hydraulic and Mechanical Tool

Directory of Open Access Journals (Sweden)

Hongxiang Jiang

2014-01-01

Full Text Available Rock breakage by coupled mechanical and hydraulic action has been developed over the past several decades, but theoretical study on rock fragmentation by mechanical tool with water pressure assistance was still lacking. The theoretical model of rock breakage by mechanical tool was developed based on the rock fracture mechanics and the solution of Boussinesq’s problem, and it could explain the process of rock fragmentation as well as predicating the peak reacting force. The theoretical model of rock breakage by coupled mechanical and hydraulic action was developed according to the superposition principle of intensity factors at the crack tip, and the reacting force of mechanical tool assisted by hydraulic action could be reduced obviously if the crack with a critical length could be produced by mechanical or hydraulic impact. The experimental results indicated that the peak reacting force could be reduced about 15% assisted by medium water pressure, and quick reduction of reacting force after peak value decreased the specific energy consumption of rock fragmentation by mechanical tool. The crack formation by mechanical or hydraulic impact was the prerequisite to improvement of the ability of combined breakage.

The shape, stability and breakage of pendant liquid bridges

Science.gov (United States)

Padday, J. F.; Pétré, G.; Rusu, C. G.; Gamero, J.; Wozniak, G.

1997-12-01

Pendant liquid bridges are defined as pendant drops supporting a solid axisymmetric endplate at their lower end. The stability and shape properties of such bridges are defined in terms of the capillary properties of the system and of the mass and radius of the lower free-floating endplate. The forces acting in the pendant liquid bridge are defined exactly and expressed in dimensionless form. Numerical analysis has been used to derive the properties of a given bridge and it is shown that as the bridge grows by adding more liquid to the system a maximum volume is reached. At this maximum volume, the pendant bridge becomes unstable with the length of the bridge increasing spontaneously and irreversibly at constant volume. Finally the bridge breaks with the formation of a satellite drop or an extended thread. The bifurcation and breakage processes have been recorded using a high-speed video camera with a digital recording rate of up to 6000 frames per second. The details of the shape of the bridge bifurcation and breakage for many pendant bridge systems have been recorded and it is shown that satellite drop formation after rupture is not always viscosity dependent. Bifurcation and breakage in simulated low gravity demonstrated that breakage was very nearly symmetrical about a plane through the middle of the pendant bridge.

Bond selective chemistry beyond the adiabatic approximation

Energy Technology Data Exchange (ETDEWEB)

Butler, L.J. [Univ. of Chicago, IL (United States)

1993-12-01

One of the most important challenges in chemistry is to develop predictive ability for the branching between energetically allowed chemical reaction pathways. Such predictive capability, coupled with a fundamental understanding of the important molecular interactions, is essential to the development and utilization of new fuels and the design of efficient combustion processes. Existing transition state and exact quantum theories successfully predict the branching between available product channels for systems in which each reaction coordinate can be adequately described by different paths along a single adiabatic potential energy surface. In particular, unimolecular dissociation following thermal, infrared multiphoton, or overtone excitation in the ground state yields a branching between energetically allowed product channels which can be successfully predicted by the application of statistical theories, i.e. the weakest bond breaks. (The predictions are particularly good for competing reactions in which when there is no saddle point along the reaction coordinates, as in simple bond fission reactions.) The predicted lack of bond selectivity results from the assumption of rapid internal vibrational energy redistribution and the implicit use of a single adiabatic Born-Oppenheimer potential energy surface for the reaction. However, the adiabatic approximation is not valid for the reaction of a wide variety of energetic materials and organic fuels; coupling between the electronic states of the reacting species play a a key role in determining the selectivity of the chemical reactions induced. The work described below investigated the central role played by coupling between electronic states in polyatomic molecules in determining the selective branching between energetically allowed fragmentation pathways in two key systems.

Breakage of cephalomedullary nailing in operative treatment of trochanteric and subtrochanteric femoral fractures.

Science.gov (United States)

von Rüden, Christian; Hungerer, Sven; Augat, Peter; Trapp, Oliver; Bühren, Volker; Hierholzer, Christian

2015-02-01

Mechanical breakage of cephalomedullary nail osteosynthesis is a rare complication attributed to delayed fracture union or nonunion. This study presents a series of cases of breakage and secondary lag screw dislocation after cephalomedullary nailing. The aim of this study was to identify factors that contribute to cephalomedullary nail breakage. In a retrospective case series review between 02/2005 and 12/2013, we analyzed 453 patients with trochanteric and subtrochanteric fracture who had been treated by cephalomedullary nailing. Fractures were classified according to AO/OTA classification. 13 patients with cephalomedullary nail breakage were included (failure rate 2.9 %). Seven patients were women, and six men with a mean age of 72 years (range 35-94). Implant breakage occurred 6 months postoperatively (range 1-19 months). In ten cases, breakage was secondary to delayed or nonunion, which was thought to be mainly due to insufficient reduction of the fracture, and in two cases due to loss of the lag screw because of missing set screw. In one case, breakage was apparent during elective metal removal following complete fracture healing. Short-term outcome was evaluated 6 months after operative revision using Harris hip score in 11 out of 13 patients showing a mean score of 84 %. Complete radiological fracture healing has been found in 11 patients available for follow-up within 6 months after revision surgery. Breakage of cephalomedullary nail osteosynthesis of trochanteric fractures is a severe complication. The results of our study demonstrate that revision surgery provides good clinical and radiological short-term results. Predominately, failures of trochanteric fractures are related to lack of surgeon performance. Therefore, application of the implant requires accurate preoperative planning, advanced surgical experience to evaluate the patient and the fracture classification, and precise surgical technique including attention to detail and anatomical

A General Catalyst for Site-Selective C(sp(3))-H Bond Amination of Activated Secondary over Tertiary Alkyl C(sp(3))-H Bonds.

Science.gov (United States)

Scamp, Ryan J; Jirak, James G; Dolan, Nicholas S; Guzei, Ilia A; Schomaker, Jennifer M

2016-06-17

The discovery of transition metal complexes capable of promoting general, catalyst-controlled and selective carbon-hydrogen (C-H) bond amination of activated secondary C-H bonds over tertiary alkyl C(sp(3))-H bonds is challenging, as substrate control often dominates when reactive nitrene intermediates are involved. In this letter, we report the design of a new silver complex, [(Py5Me2)AgOTf]2, that displays general and good-to-excellent selectivity for nitrene insertion into propargylic, benzylic, and allylic C-H bonds over tertiary alkyl C(sp(3))-H bonds.

Friedel-Crafts reaction of benzyl fluorides: selective activation of C-F bonds as enabled by hydrogen bonding.

Science.gov (United States)

Champagne, Pier Alexandre; Benhassine, Yasmine; Desroches, Justine; Paquin, Jean-François

2014-12-08

A Friedel-Crafts benzylation of arenes with benzyl fluorides has been developed. The reaction produces 1,1-diaryl alkanes in good yield under mild conditions without the need for a transition metal or a strong Lewis acid. A mechanism involving activation of the C-F bond through hydrogen bonding is proposed. This mode of activation enables the selective reaction of benzylic C-F bonds in the presence of other benzylic leaving groups. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coke breakage behaviour in relation to its structure

Energy Technology Data Exchange (ETDEWEB)

Peirce, T J; Horton, A E; Tucker, J

1980-06-14

The relationship between coke macrostructure and volumetric (coarse) breakage behaviour, and the manner in which both features are affected by the coal charge composition are discussed. Coke pieces which are extensively fissured fail spontaneously after only a few revolutions in the drum; coke pieces which are less fissured require an extended treatment in the drum and finally fail in a manner consistent with that of fatigue crack growth induced by repeated impact. This heterogeneity in breakage behaviour was demonstrated in terms of an abrupt change in gradient of the Weibull distribution function for the coke. Heterogeneity may be removed by fully stabilising the coke or by the use of a more energetic test method. The role of fatigue crack growth in coke breakage was studied by cutting fissures of defined depth in full stabilised coke and assessing the rate of crack growth as a function of fissure depth and fracture toughness. The form of the results was consistent with that given by the Paris-Erdogan law and the rate of crack growth (for a given stress intensity level) was shown to increase with reducing coke toughness. Explanations are suggested to account for the role of blend additives in modifying the fissured properties and fracture toughness of coke made from high-volatile coal.

Diagnosis of Fanconi Anemia: Chromosomal Breakage Analysis

Science.gov (United States)

Oostra, Anneke B.; Nieuwint, Aggie W. M.; Joenje, Hans; de Winter, Johan P.

2012-01-01

Fanconi anemia (FA) is a rare inherited syndrome with diverse clinical symptoms including developmental defects, short stature, bone marrow failure, and a high risk of malignancies. Fifteen genetic subtypes have been distinguished so far. The mode of inheritance for all subtypes is autosomal recessive, except for FA-B, which is X-linked. Cells derived from FA patients are—by definition—hypersensitive to DNA cross-linking agents, such as mitomycin C, diepoxybutane, or cisplatinum, which becomes manifest as excessive growth inhibition, cell cycle arrest, and chromosomal breakage upon cellular exposure to these drugs. Here we provide a detailed laboratory protocol for the accurate assessment of the FA diagnosis as based on mitomycin C-induced chromosomal breakage analysis in whole-blood cultures. The method also enables a quantitative estimate of the degree of mosaicism in the lymphocyte compartment of the patient. PMID:22693659

Impact of polymeric membrane breakage on drinking water quality and an online detection method of the breakage.

Science.gov (United States)

Wu, Qilong; Zhang, Zhenghua; Cao, Guodong; Zhang, Xihui

2017-10-15

Polymeric membrane has been widely used for the treatment of drinking water in China, and the total treating capacity has reached up to 3.8 million m 3 /d. However, the membrane breakage found in the membrane modules in many water treatment plants resulted in an increase in turbidity and bacterial amount in the membrane permeate. In this study, a membrane module running for 3 years in a full-scale application was examined in terms of the breaking positions and the numbers of the broken fibers. It was found that most of the breaking positions were mainly on the outlet side of the module and that the distance from these points to the outlet was about 1/10-2/10 length of the membrane module. The lab-scale tests showed that the increase of the numbers of the breaking fibers in the membrane module (the breaking fibers were from 1 to 4 of 75 fibers) resulted in the increase in turbidity, particle count and the amount of total bacteria and coliform bacteria. Meanwhile, the water quality after the filtration with broken membrane fibers was similar to the quality of the raw water, which indicated that once the membrane fiber breakage occurred in the membrane module, the quality of drinking water after membrane filtration was significantly affected. Furthermore, the breaking position closer to the outlet side of the membrane module exposed much higher microbiological risk than those in the middle or near the bottom side. A pilot scale test was conducted by using a membrane module with 6600 fibers, and the effect of the membrane breakage (1-4 broken fibers) on water quality was also investigated. The results indicated that periodical backwashing caused drastic fluctuation of turbidity, particle count and the bacterial amount in the permeate water, which might be due to the washing force and self-blocking action inside the hollow fibers. Moreover, there is a good quantitative relationship (R 2 = 0.945) between particle count and the bacterial amount, which indicated that an

The risk of capsular breakage from phacoemulsification needle contact with the lens capsule: a laboratory study.

Science.gov (United States)

Meyer, Jay J; Kuo, Annie F; Olson, Randall J

2010-06-01

To determine capsular breakage risk from contact by phacoemulsification needles by machine and tip type. Experimental laboratory investigation. Infiniti (Alcon, Inc.) with Intrepid cartridges and Signature (Abbott Medical Optics, Inc.) phacoemulsification machines were tested using 19- and 20-gauge sharp and rounded tips. Actual and unoccluded flow vacuum were determined at 550 mm Hg, bottle height of 75 cm, and machine-indicated flow rate of 60 mL/minute. Breakage from brief tip contact with a capsular surrogate and human cadaveric lenses was calculated. Nineteen-gauge tips had more flow and less unoccluded flow vacuum than 20-gauge tips for both machines, with highest unoccluded flow vacuum in the Infiniti. The 19-gauge sharp tip was more likely than the 20-gauge sharp tip to cause surrogate breakage for Signature with micropulse and Ellips (Abbott Medical Optics, Inc.) ultrasound at 100% power. For Infiniti using OZil (Alcon, Inc.) ultrasound, 20-gauge sharp tips were more likely than 19-gauge sharp tips to break the membrane. For cadaveric lenses, using rounded 20-gauge tips at 100% power, breakage rates were micropulse (2.3%), Ellips (2.3%), OZil (5.3%). Breakage rates for sharp 20-gauge Ellips tips were higher than for rounded tips. Factors influencing capsular breakage may include active vacuum at the tip, flow rate, needle gauge, and sharpness. Nineteen-gauge sharp tips were more likely than 20-gauge tips to cause breakage in lower vacuum methods. For higher-vacuum methods, breakage is more likely with 20-gauge than with 19-gauge tips. Rounded-edge tips are less likely than sharp-edged tips to cause breakage. Copyright 2010 Elsevier Inc. All rights reserved.

Cranial MRI in the Nijmegen breakage syndrome

International Nuclear Information System (INIS)

Bekiesinska-Figatowska, M.; Chrzanowska, K.H.; Krajewska-Walasek, M.; Sikorska, J.; Walecki, J.; Jozwiak, S.; Kleijer, W.J.

2000-01-01

We present the results of MRI examinations in ten patients with documented Nijmegen breakage syndrome (NBS), aged 1.75-19 years. T1-, Proton-Density- and T2-weighted spin-echo sequences were performed in three planes. All patients showed microcephaly with decreased size of the frontal lobes and narrow frontal horns. In four patients agenesis of the posterior part of the corpus callosum was found, with colpocephaly and temporal horns dilatation. In one patient callosal hypoplasia was accompanied by abnormal cerebrospinal fluid spaces and wide cerebral cortex, suspicious of pachygyria. Sinusitis was present in all ten patients, as a result of primary immunodeficiency. As in ataxia teleangiectasia and other breakage syndromes, patients with NBS show an inherited susceptibility to malignancy and hypersensitivity to X- and γ-radiation. CT is therefore contraindicated in these patients and MRI should be the method of choice for diagnostic imaging. (orig.)

How quantum entanglement in DNA synchronizes double-strand breakage by type II restriction endonucleases.

Science.gov (United States)

Kurian, P; Dunston, G; Lindesay, J

2016-02-21

Macroscopic quantum effects in living systems have been studied widely in pursuit of fundamental explanations for biological energy transport and sensing. While it is known that type II endonucleases, the largest class of restriction enzymes, induce DNA double-strand breaks by attacking phosphodiester bonds, the mechanism by which simultaneous cutting is coordinated between the catalytic centers remains unclear. We propose a quantum mechanical model for collective electronic behavior in the DNA helix, where dipole-dipole oscillations are quantized through boundary conditions imposed by the enzyme. Zero-point modes of coherent oscillations would provide the energy required for double-strand breakage. Such quanta may be preserved in the presence of thermal noise by the enzyme's displacement of water surrounding the DNA recognition sequence. The enzyme thus serves as a decoherence shield. Palindromic mirror symmetry of the enzyme-DNA complex should conserve parity, because symmetric bond-breaking ceases when the symmetry of the complex is violated or when physiological parameters are perturbed from optima. Persistent correlations in DNA across longer spatial separations-a possible signature of quantum entanglement-may be explained by such a mechanism. Copyright © 2015 Elsevier Ltd. All rights reserved.

Breakage of Agglomerates : Attrition, Abrasion and Compression

NARCIS (Netherlands)

Van Laarhoven, B.

2010-01-01

In many industries particulate solids are handled in different forms. When producing particles breakage is an important wanted, in the case of grinding, or unwanted phenomenon. Granules often consist of more than one component and multiple phases. This means that granules are strongly anisotropic

Energy and Rate Determinations to Activate the C-C σ-BOND of Acetone by Gaseous NI^+

Science.gov (United States)

Castleberry, Vanessa A.; Dee, S. Jason; Villarroel, Otsmar J.; Laboren, Ivanna E.; Frey, Sarah E.; Bellert, Darrin J.

2009-06-01

A unique application of a custom fabricated photodissociation spectrometer permits the determination of thermodynamic properties (activation energies), reaction rates, and mechanistic details of bare metal cation mediated C-C σ-bond activation in the gas phase. Specifically, the products and rates resulting from the unimolecular decomposition of the Ni^+Acetone (Ni^+Ac) adduct are monitored after absorption of a known amount of energy. The three dissociative products which are observed in high yield are Ni^+, Ni^+CO, and CH3CO^+. The latter two fragment ions result from the activation of a C-C σ-bond. It was found that minimally 14 000 cm^{-1} of energy must be deposited into the adduct ion to induce C-C bond breakage. Preliminary results for the Ni^+ activation of the C-C σ-bond of acetone indicate that there are (at least) two low energy reaction coordinates leading to C-C bond breakage. The lower energy pathway emerges from the doublet ground state with an upper limit to the activation energy of 14 000 cm^{-1} and reaction rate ≈0.14 molecules/μs. The higher energy path is assumed to be along the quartet reaction coordinate with a minimum activation energy of 18 800 cm^{-1} (relative to the ground state) and a slightly slower reaction rate.

Lack of spontaneous and radiation-induced chromosome breakage at interstitial telomeric sites in murine scid cells.

Science.gov (United States)

Wong, H-P; Mozdarani, H; Finnegan, C; McIlrath, J; Bryant, P E; Slijepcevic, P

2004-01-01

Interstitial telomeric sites (ITSs) in chromosomes from DNA repair-proficient mammalian cells are sensitive to both spontaneous and radiation-induced chromosome breakage. Exact mechanisms of this chromosome breakage sensitivity are not known. To investigate factors that predispose ITSs to chromosome breakage we used murine scid cells. These cells lack functional DNA-PKcs, an enzyme involved in the repair of DNA double-strand breaks. Interestingly, our results revealed lack of both spontaneous and radiation-induced chromosome breakage at ITSs found in scid chromosomes. Therefore, it is possible that increased sensitivity of ITSs to chromosome breakage is associated with the functional DNA double-strand break repair machinery. To investigate if this is the case we used scid cells in which DNA-PKcs deficiency was corrected. Our results revealed complete disappearance of ITSs in scid cells with functional DNA-PKcs, presumably through chromosome breakage at ITSs, but their unchanged frequency in positive and negative control cells. Therefore, our results indicate that the functional DNA double-strand break machinery is required for elevated sensitivity of ITSs to chromosome breakage. Interestingly, we observed significant differences in mitotic chromosome condensation between scid cells and their counterparts with restored DNA-PKcs activity suggesting that lack of functional DNA-PKcs may cause a defect in chromatin organization. Increased condensation of mitotic chromosomes in the scid background was also confirmed in vivo. Therefore, our results indicate a previously unanticipated role of DNA-PKcs in chromatin organisation, which could contribute to the lack of ITS sensitivity to chromosome breakage in murine scid cells. Copyright 2003 S. Karger AG, Basel

Metabolic Engineering to Develop a Pathway for the Selective Cleavage of Carbon-Nitrogen Bonds

Energy Technology Data Exchange (ETDEWEB)

John J. Kilbane II

2005-10-01

The objective of the project is to develop a biochemical pathway for the selective cleavage of C-N bonds in molecules found in petroleum. Specifically a novel biochemical pathway will be developed for the selective cleavage of C-N bonds in carbazole. The cleavage of the first C-N bond in carbazole is accomplished by the enzyme carbazole dioxygenase, that catalyzes the conversion of carbazole to 2-aminobiphenyl-2,3-diol. The genes encoding carbazole dioxygenase were cloned from Sphingomonas sp. GTIN11 and from Pseudomonas resinovorans CA10. The selective cleavage of the second C-N bond has been challenging, and efforts to overcome that challenge have been the focus of recent research in this project. Enrichment culture experiments succeeded in isolating bacterial cultures that can metabolize 2-aminobiphenyl, but no enzyme capable of selectively cleaving the C-N bond in 2-aminobiphenyl has been identified. Aniline is very similar to the structure of 2-aminobiphenyl and aniline dioxygenase catalyzes the conversion of aniline to catechol and ammonia. For the remainder of the project the emphasis of research will be to simultaneously express the genes for carbazole dioxygenase and for aniline dioxygenase in the same bacterial host and then to select for derivative cultures capable of using carbazole as the sole source of nitrogen.

Destabilized SMC5/6 complex leads to chromosome breakage syndrome with severe lung disease

NARCIS (Netherlands)

van der Crabben, Saskia N; Hennus, Marije P; McGregor, Grant A; Ritter, Deborah I; Nagamani, Sandesh C S; Wells, Owen S; Harakalova, Magdalena; Chinn, Ivan K; Alt, Aaron; Vondrova, Lucie; Hochstenbach, Ron; van Montfrans, Joris M; Terheggen-Lagro, Suzanne W; van Lieshout, Stef; van Roosmalen, Markus J; Renkens, Ivo; Duran, Karen; Nijman, Isaäc J.; Kloosterman, Wigard P; Hennekam, Eric; Orange, Jordan S; van Hasselt, Peter M; Wheeler, David A; Palecek, Jan J; Lehmann, Alan R; Oliver, Antony W; Pearl, Laurence H; Plon, Sharon E; Murray, Johanne M; van Haaften, Gijs

The structural maintenance of chromosomes (SMC) family of proteins supports mitotic proliferation, meiosis, and DNA repair to control genomic stability. Impairments in chromosome maintenance are linked to rare chromosome breakage disorders. Here, we have identified a chromosome breakage syndrome

Contributions to reversed-phase column selectivity: III. Column hydrogen-bond basicity.

Science.gov (United States)

Carr, P W; Dolan, J W; Dorsey, J G; Snyder, L R; Kirkland, J J

2015-05-22

Column selectivity in reversed-phase chromatography (RPC) can be described in terms of the hydrophobic-subtraction model, which recognizes five solute-column interactions that together determine solute retention and column selectivity: hydrophobic, steric, hydrogen bonding of an acceptor solute (i.e., a hydrogen-bond base) by a stationary-phase donor group (i.e., a silanol), hydrogen bonding of a donor solute (e.g., a carboxylic acid) by a stationary-phase acceptor group, and ionic. Of these five interactions, hydrogen bonding between donor solutes (acids) and stationary-phase acceptor groups is the least well understood; the present study aims at resolving this uncertainty, so far as possible. Previous work suggests that there are three distinct stationary-phase sites for hydrogen-bond interaction with carboxylic acids, which we will refer to as column basicity I, II, and III. All RPC columns exhibit a selective retention of carboxylic acids (column basicity I) in varying degree. This now appears to involve an interaction of the solute with a pair of vicinal silanols in the stationary phase. For some type-A columns, an additional basic site (column basicity II) is similar to that for column basicity I in primarily affecting the retention of carboxylic acids. The latter site appears to be associated with metal contamination of the silica. Finally, for embedded-polar-group (EPG) columns, the polar group can serve as a proton acceptor (column basicity III) for acids, phenols, and other donor solutes. Copyright © 2015 Elsevier B.V. All rights reserved.

Studies of IBL wire bonds operation in a ATLAS-like magnetic field.

CERN Document Server

Alvarez Feito, D; Mandelli, B

2015-01-01

At the Large Hadron Collider (LHC) experiments, most of silicon detectors use wire bonds to connect front-end chips and sensors to circuit boards for the data and service trans- missions. These wire bonds are operated in strong magnetic field environments and if time varying currents pass through them with frequencies close to their mechanical resonance frequency, strong resonant oscillations may occur. Under certain conditions, this effect can lead to fatigue stress and eventually breakage of wire bonds. During the first LHC Long Shutdown, the ATLAS Pixel Detector has been upgraded with the addition of a fourth innermost layer, the Insertable B-Layer (IBL), which has more than 50000 wire bonds operated in the ATLAS 2 T magnetic field. The results of systematic studies of operating wire bonds under IBL-like conditions are presented. Two different solutions have been investigated to minimize the oscillation amplitude of wire bonds.

Development of yarn breakage detection software system based on machine vision

Science.gov (United States)

Wang, Wenyuan; Zhou, Ping; Lin, Xiangyu

2017-10-01

For questions spinning mills and yarn breakage cannot be detected in a timely manner, and save the cost of textile enterprises. This paper presents a software system based on computer vision for real-time detection of yarn breakage. The system and Windows8.1 system Tablet PC, cloud server to complete the yarn breakage detection and management. Running on the Tablet PC software system is designed to collect yarn and location information for analysis and processing. And will be processed after the information through the Wi-Fi and http protocol sent to the cloud server to store in the Microsoft SQL2008 database. In order to follow up on the yarn break information query and management. Finally sent to the local display on time display, and remind the operator to deal with broken yarn. The experimental results show that the system of missed test rate not more than 5%o, and no error detection.

Perspectives on condom breakage: a qualitative study of female sex workers in Bangalore, India.

Science.gov (United States)

Gurav, Kaveri; Bradley, Janet; Chandrashekhar Gowda, G; Alary, Michel

2014-01-01

A qualitative study was conducted to obtain a detailed understanding of two key determinants of condom breakage - 'rough sex' and poor condom fit - identified in a recent telephone survey of female sex workers, in Bangalore, India. Transcripts from six focus-group discussions involving 35 female sex workers who reported condom breakage during the telephone survey were analysed. Rough sex in different forms, from over-exuberance to violence, was often described by sex workers as a result of clients' inebriation and use of sexual stimulants, which, they report, cause tumescence, excessive thrusting and sex that lasts longer than usual, thereby increasing the risk of condom breakage. Condom breakage in this setting is the result of a complex set of social situations involving client behaviours and power dynamics that has the potential to put the health and personal lives of sex workers at risk. These findings and their implications for programme development are discussed.

Breakage of a Third Generation Gamma Nail: A Case Report and Review of the Literature

Directory of Open Access Journals (Sweden)

Takashi Iwakura

2013-01-01

Full Text Available The use of intramedullary nails to treat trochanteric fractures of the femur has increased with the increasing size of the elderly population. The third generation Gamma nail is currently one of the most popular devices for the treatment of trochanteric fractures. Nail breakage is a rare complication, possibly resulting from fatigue fracture of the implant. We present the first reported case of breakage of a third generation Gamma nail that was not used to treat a pathological fracture. An 83-year-old woman with an unstable trochanteric fracture of the femur was treated using a third generation Gamma nail. She was referred to our hospital 14 months postoperatively with nail breakage at the opening for the lag screw. The breakage was secondary to nonunion, which was thought to be mainly due to insufficient reduction of the fracture. The broken nail was removed, and the patient underwent cemented bipolar hemiarthroplasty. At followup 18 months later, she was mobile with a walker and asymptomatic with no complications. This case shows that inadequate operation such as insufficient reduction of the trochanteric fracture may result in nonunion and implant breakage, even when using a high-strength, well-designed implant.

Empirical Formulae for Breakage of Dolosse and Tetrapods

DEFF Research Database (Denmark)

Burcharth, H. F.; d'Angremond, K.; Meer, W. van der

2000-01-01

The slender, complex types of armour units, such as Tetrapods and Dolosse are widely used for rubble mound breakwaters. Many failures of such breakwaters were caused by unforeseen early breakage of the units, thus revealing an inbalance between the strength (structural integrity) of the units...... and the hydraulic stability (resistance to displacements) of the armour layers. Breakage occurs when the stresses from the static, pulsating and impact loads exceeds the tensile strength of the concrete. While the hydraulic stability can be studied in Froude-scale hydraulic model tests, it is not possible to study...... armour unit stresses in small scale models. This is partly because the strain in model armour units are too small to be recorded, and partly because the scaling law for impact load generated stresses is nonlinear. The paper discusses the scaling laws related to type of stresses and presents a method...

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.

[Bond strengths of customized titanium brackets manufactured by selective laser melting].

Science.gov (United States)

Zou, Dao-xing; Wang, Ze-min; Guo, Hong-ming; Li, Song; Bai, Yu-xing

2013-07-01

To investigate the bond strengths of customized titanium bracket manufactured by selective laser melting. Eighty human premolars which had been extracted for orthodontic purpose were collected and divided randomly (by random table) into two groups (customized bracket group and 3M bracket group, 40 molars in each group). The 35% phosphoric acid was used for etching and the brackets were bonded with 3M Unitek bonding adhesive. All bonded specimens were placed in saline for 24 hours at room temperature and were tested on DWD3050 electronic testing machine to determine the shear bond strength and tensile bond strength. After debonding, the adhesive remnant indexes (ARI) were recorded. The shear bond strengths of customized brackets was 6.80 (6.20, 8.32) MPa, which was significantly lower than that of the 3M brackets [10.46 (9.72, 11.48) MPa] (Z = -3.463, P < 0.05). And the tensile bond strengths of customized brackets was (6.93 ± 1.21) MPa, which was significantly higher than that of the 3M brackets [(5.88 ± 1.23) MPa] (t = 2.81, P < 0.05). No significant difference was found in the ARI between two different kinds of the brackets. The shear bond strength and tensile bond strength of both kinds of brackets were enough for clinic application.

Bond selective photochemistry in CH2BrI through electronic excitation at 210 nm

International Nuclear Information System (INIS)

Butler, L.J.; Hintsa, E.J.; Lee, Y.T.

1986-01-01

To explore the possibility of bond selective photochemistry in an excited electronic state, we have studied the photolysis of CH 2 BrI in a molecular beam at 210 nm. Following the direct local excitation of a repulsive transition on the C--Br bond at 210 nm, the fragments were detected by time-of-flight mass spectrometry. The dominant channel was found to be C--Br fission (60%) releasing an average of 15 kcal/mol into translation with the remainder reacting to form CH 2 +IBr and CH 2 +I+Br. There was no evidence for the primary fission of the C--I bond, making this the first clear example of the selective cleavage of a stronger bond in a molecule over the weakest one

Visual Inspection for Breakage of Micro-milling Cutter

Directory of Open Access Journals (Sweden)

WANG Lei

2014-11-01

Full Text Available In order to realize visual inspection for breakage of micro-milling cutter, a developed image acquisition method of the surface of a micro-milling cutter was constructed and a classification method based on multilayer neural network was proposed in this article. While the milling cutter was rotating at a constant speed, a camera was triggered by a rotary encoder to capture a series of images. And the developed image of milling cutter was created by image mosaic algorithms. The moment of regional feature as well as the gray feature of the tooth edge was extracted as the input vector of neural network. The feature vector includes moment of inertia, geometric central moment, three-dimensional invariants moment and the gray value of the projection on two principal axis directions of the tooth region. By designing a proper neural network, breakage defects can be detected 100 %. And the false discovery rate is 0.5 %.

Replication stress-induced chromosome breakage is correlated with replication fork progression and is preceded by single-stranded DNA formation.

Science.gov (United States)

Feng, Wenyi; Di Rienzi, Sara C; Raghuraman, M K; Brewer, Bonita J

2011-10-01

Chromosome breakage as a result of replication stress has been hypothesized to be the direct consequence of defective replication fork progression, or "collapsed" replication forks. However, direct and genome-wide evidence that collapsed replication forks give rise to chromosome breakage is still lacking. Previously we showed that a yeast replication checkpoint mutant mec1-1, after transient exposure to replication impediment imposed by hydroxyurea (HU), failed to complete DNA replication, accumulated single-stranded DNA (ssDNA) at the replication forks, and fragmented its chromosomes. In this study, by following replication fork progression genome-wide via ssDNA detection and by direct mapping of chromosome breakage after HU exposure, we have tested the hypothesis that the chromosome breakage in mec1 cells occurs at collapsed replication forks. We demonstrate that sites of chromosome breakage indeed correlate with replication fork locations. Moreover, ssDNA can be detected prior to chromosome breakage, suggesting that ssDNA accumulation is the common precursor to double strand breaks at collapsed replication forks.

Selective C(sp2)-C(sp) bond cleavage: the nitrogenation of alkynes to amides.

Science.gov (United States)

Qin, Chong; Feng, Peng; Ou, Yang; Shen, Tao; Wang, Teng; Jiao, Ning

2013-07-22

Breakthrough: A novel catalyzed direct highly selective C(sp2)-C(sp) bond functionalization of alkynes to amides has been developed. Nitrogenation is achieved by the highly selective C(sp2)-C(sp) bond cleavage of aryl-substituted alkynes. The oxidant-free and mild conditions and wide substrate scope make this method very practical. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental Research on the Specific Energy Consumption of Rock Breakage Using Different Waterjet-Assisted Cutting Heads

Directory of Open Access Journals (Sweden)

Hongxiang Jiang

2018-01-01

Full Text Available To investigate the specific energy consumption (SE of rock breakage by cutting heads assisted by different types of waterjet and to identify optimal waterjet parameters and assistance types, rock cutting with and without waterjets was carried on a rock fragmentation test bed. SE is a comprehensive evaluation index and was developed according to the applied load on cutting head, and the SE under different cutting conditions was compared and analyzed. The results show that the SE of rock breakage without waterjet assistance increased with the increasing of rock compressive strength (RCS but that the limited drilling depth decreased. The effect of the waterjet pressure on the SE of rock breakage by the cutting head I was marked, and SE decreased by 30∼40% when the ratio between RCS and waterjet pressure was less than 1. However, the function of the waterjet assistance was poor; therefore, a ratio of 1 could be used to distinguish the rock breakage effect of cutting head I. For cutting head II, the rock damage from the waterjet impact was limited due to the large waterjet standoff distance; thus the rock breakage performance of cutting head II was also limited. The waterjet impacting at the tip of the conical pick using cutting head III could enter into the cracks caused by the mechanical pick and fracture the rock. Therefore, the rock breakage performance of cutting head III was better than that of cutting head II.

Using DNA origami nanostructures to determine absolute cross sections for UV photon-induced DNA strand breakage.

Science.gov (United States)

Vogel, Stefanie; Rackwitz, Jenny; Schürman, Robin; Prinz, Julia; Milosavljević, Aleksandar R; Réfrégiers, Matthieu; Giuliani, Alexandre; Bald, Ilko

2015-11-19

We have characterized ultraviolet (UV) photon-induced DNA strand break processes by determination of absolute cross sections for photoabsorption and for sequence-specific DNA single strand breakage induced by photons in an energy range from 6.50 to 8.94 eV. These represent the lowest-energy photons able to induce DNA strand breaks. Oligonucleotide targets are immobilized on a UV transparent substrate in controlled quantities through attachment to DNA origami templates. Photon-induced dissociation of single DNA strands is visualized and quantified using atomic force microscopy. The obtained quantum yields for strand breakage vary between 0.06 and 0.5, indicating highly efficient DNA strand breakage by UV photons, which is clearly dependent on the photon energy. Above the ionization threshold strand breakage becomes clearly the dominant form of DNA radiation damage, which is then also dependent on the nucleotide sequence.

Genetic ecotoxicology IV: survival and DNA strand breakage is dependent on genotype in radionuclide-exposed mosquitofish

Energy Technology Data Exchange (ETDEWEB)

Theodorakis, C.W. [Texas A and M University, Department of Wildlife and Fisheries Sciences, College Station, TX 77843-2258 (United States); Elbl, T. [University of Pennsylvania, Department of Cell and Molecular Biology, Philadelphia, PA 19102 (United States); Shugart, L.R. [L.R. Shugart and Associates, Oak Ridge, TN 37831 (United States)

1999-05-01

Western mosquitofish (Gambusia affinis) were caged in situ in a radioactively-contaminated pond in order to determine if survival and amount of DNA strand breakage were dependent on genotype. Genotypes of fish were determined using the randomly amplified polymorphic (RAPD) technique, and DNA strand breakage was determined using agarose gel electrophoresis. This study is a continuation of research undertaken at the Oak Ridge National Laboratory, which examined the effects of radionuclide contamination on the population genetic structure of mosquitofish. The previous research found 17 RAPD markers that were present at a higher frequency in contaminated than in reference populations ('contaminant-indicative bands'), and fish from contaminated sites which possessed these markers had higher fecundity and fewer strand breaks than fish which did not. One of the contaminated populations (Pond 3513) was colonized from one of the reference populations (Crystal Springs) in 1977. In the present study, fish were obtained from Crystal Springs and an additional reference site, and caged in Pond 3513. The percent survival and amount of DNA strand breakage were then determined for fish with and without the contaminant-indicative markers. When Crystal Springs fish were caged in Pond 3513, it was found that the genotypic distribution of the survivors was more similar to the native Pond 3513 population than to the Crystal Springs population. Furthermore, for nine of the contaminant-indicative markers, the percent survival was greater for fish which possessed these markers than for fish which did not. For five of these markers, fish which possessed them had higher DNA integrity (fewer strand breaks) than fish which did not. These data indicate that probability of survival and degree of DNA strand breakage in radionuclide-exposed mosquitofish are dependent on RAPD genotype, and are consistent with the hypothesis that the contaminant-indicative RAPD bands are markers of loci

Tool wear and breakage monitoring in machining

International Nuclear Information System (INIS)

Madl, J.

1992-01-01

Risk minimization of metal cutting operations is one of the main problems of metal cutting technology. This paper describes some aspects in monitoring and control of machining processes. Tool monitoring is the fokus of machining process monitoring. Tool breakage and tool life recognition are the main problems of tool monitoring. All problems of this type of monitoring have not yet been fully solved. (orig.)

Breakage of internal maxillary distractor: considerable complication of maxillary distraction osteogenesis.

Science.gov (United States)

Aikawa, Tomonao; Iida, Seiji; Isomura, Emiko T; Namikawa, Mari; Matsuoka, Yudai; Yamada, Chiaki; Yamamoto, Taku; Takigawa, Yoko

2008-07-01

Maxillary distraction osteogenesis using intraoral distractors is now one of the standard treatments of maxillary retrusion. This report shows 2 cases of breakage of this internal maxillary distractor in patients with cleft lip and palate; one was observed during the distraction period and the other was during the retention period. The first case required a rotational movement of the distraction segment, and this movement caused the laterally dislocation of the posterior part of the distractor, where the distractor suffered some mechanical forces by mouth opening. In the latter case, breakage of distractor was observed on the radiographs taken 3 months after distraction and this complication may have been caused by mechanical force by occlusion and mastication. Both breakages were found at the joint of the anchorage plate and the extension rod, which has some flexibility for adjusting the plate to the bone surface. Therefore, surgeons should pay special attention for this mechanical weak area in this distractor not only during the advancement period, but also during the retention period and should avoid unnecessary frequent bending for adopting the bone surface, which directly weakens the joint.

Influence of the potential well on the breakage rate of colloidal aggregates in simple shear and uniaxial extensional flows.

Science.gov (United States)

Ren, Zhiqiang; Harshe, Yogesh M; Lattuada, Marco

2015-06-02

In this work we build on our previous paper (Harshe, Y. M.; Lattuada, M. Langmuir 2012, 28, 283-292) and compute the breakage rate of colloidal aggregates under the effect of shear forces by means of Stokesian dynamics simulations. A library of clusters made of identical spherical particles covering a broad range of masses and fractal dimension values (from 1.8 to 3.0) was generated by means of a combination of several Monte Carlo methods. DLVO theory has been used to describe the interparticle interactions, and contact forces have been introduced by means of the discrete element method. The aggregate breakage process was investigated by exposing them to well-defined shear forces, generated under both simple shear and uniaxial extensional flow conditions, and by recording the time required to reach the first breakage event. It has been found that the breakage rate of clusters was controlled by the potential well between particles as described by DLVO theory. A semiempirical Arrhenius-type exponential equation that relates the potential well to the breakage rate has been used to fit the simulation results. The dependence of the breakage process on the radius of gyration, on the external shear strength, and on the fractal dimension has been obtained, providing a very general relationship for the breakage rate of clusters. It was also found that the fragment mass distribution is insensitive to the presence of electrostatic repulsive interactions. We also clarify the physical reason for the large difference in the breakage rate of clusters between simple shear and the uniaxial extensional flow using a criterion based on the energy dissipation rate. Finally, in order to answer the question of the minimum cluster size that can break under simple shear conditions, a critical rotation number has been introduced, expressing the maximum number of rotations that a cluster exposed to simple shear could sustain before breakage.

METABOLIC ENGINEERING TO DEVELOP A PATHWAY FOR THE SELECTIVE CLEAVAGE OF CARBON-NITROGEN BONDS

Energy Technology Data Exchange (ETDEWEB)

John J. Kilbane II

2004-10-01

The objective of the project is to develop biochemical pathways for the selective cleavage of C-N bonds in molecules found in petroleum. The initial phase of the project was focused on the isolation or development of an enzyme capable of cleaving the C-N bond in aromatic amides, specifically 2-aminobiphenyl. The objective of the second phase of the research will be to construct a biochemical pathway for the selective removal of nitrogen from carbazole by combining the carA genes from Sphingomonas sp. GTIN11 with the gene(s) encoding an appropriate deaminase. The objective of the final phase of the project will be to develop derivative C-N bond cleaving enzymes that have broader substrate ranges and to demonstrate the use of such strains to selectively remove nitrogen from petroleum. During the first year of the project (October, 2002-September, 2003) enrichment culture experiments resulted in the isolation of microbial cultures that utilize aromatic amides as sole nitrogen sources, several amidase genes were cloned and were included in directed evolution experiments to obtain derivatives that can cleave C-N bonds in aromatic amides, and the carA genes from Sphingomonas sp. GTIN11, and Pseudomonas resinovorans CA10 were cloned in vectors capable of replicating in Escherichia coli. During the second year of the project (October, 2003-September, 2004) enrichment culture experiments succeeded in isolating a mixed bacterial culture that can utilize 2-aminobiphenyl as a sole nitrogen source, directed evolution experiments were focused on the aniline dioxygenase enzyme that is capable of deaminating aniline, and expression vectors were constructed to enable the expression of genes encoding C-N bond cleaving enzymes in Rhodococcus hosts. The construction of a new metabolic pathway to selectively remove nitrogen from carbazole and other molecules typically found in petroleum should lead to the development of a process to improve oil refinery efficiency by reducing the

Protection of DNA strand breakage by radiation exposure

International Nuclear Information System (INIS)

Lee, Jeong Ho; Kim, In Gyu; Lee, Kang Suk; Kim, Kug Chan; Shim, Hae Won

1997-12-01

Human ceruloplasmin, the plasma copper containing protein, is thought to play an essential role in iron metabolism, but it also has antioxidant properties. Ceruloplasmin directly scavenged hydroxyl radicals (.OH) generated in dithiothreitol/FeCl 3 system besides inhibitory function of hydroxyl radical formation and lipid peroxidation. Polyamines, spermidine and spermine, significantly protected the supercoiled DNA strand breakage by hydroxyl radicals and DNA strand breakage by UV was highly protected by all four polyamines used in this study. In polyamine deficient mutant KL527. It was shown that cell survivability following UV irradiation was slightly increased by exogenous polyamines putrescine and spermidine supplement. However the cell survivability of wild type (MG 1655) was not influenced by polyamine supplement. In γ-irradiated cells, cell survivability of polyamine-deficient mutant strain KL527 was significantly increased by exogenous putrescine supplement and that of wild type strain MG1655 was similar irrespective of polyamine supplement. These results implicate the possibility that polyamines play a potent role in radioprotection of cell and DNA level. (author). 32 refs., 8 figs

Radiobiology of DNA strand breakage

International Nuclear Information System (INIS)

Johansen, I.

1975-01-01

The yield of single-strand breaks in lambda DNA within lysogenic host bacteria was measured after exposure to 4-MeV electrons (50 msec) and rapid transfer (45 msec) to alkaline detergent. In nitrogen anoxia the yield was 1.2 x 10 -12 DNA single-strand breaks per rad per dalton, and under full oxygenation the yield increased to 5 x 10 -12 breaks per rad per dalton. A search for the presence of fast repair mechanisms failed to demonstrate the presence of any mechanism for repair of strand breaks operating within a fraction of a second. Strand breaks produced in the presence of oxygen were repaired in 30--40 sec, while breaks produced under anoxia were rejoined even slower. A functional product from the polAl gene was needed for the rejoining of the broken molecules. Intermediate levels of DNA strand breakage seen at low concentrations of oxygen are dependent on the concentration of cellular sulfhydryl compounds, suggesting that in strand breakage oxygen and hydrogen donors compete for reactions with radiation-induced transients in the DNA. Intercomparisons of data on radiation-induced lethality of cells and single-strand breaks in episomal DNA allow the distinction between two classes of radiation-induced radicals, R 1 and R 2 , with different chemical properties; R 1 reacts readily with oxygen and N-oxyls under formation of potentially lethal products. The reactivity of oxygen in this reaction is 30--40 times higher than that of TMPN. R 2 reacts 16 times more readily than R 1 with oxygen under formation of single-strand breaks in the DNA. R 2 does not react with N-oxyls

Hydraulic breakage of tanks for the transport of uranium hexafluoride (UF6)

International Nuclear Information System (INIS)

Biaggio, A.L.; Lee Gonzales, H.M.; Lopez Vietri, J.R.; Novo, R.G.

1987-01-01

To begin with, the tank models that are proposed by the international norms for the transport and storage of hexafluoride of uranium (UF 6 ) are briefly described. The operations related to the transport in its different forms are also described, particularly those that can produce the hydraulic breakage of tanks during its course or in later stages, when incorrectly performed. With reference to those operations, the most important physicochemical properties of UF 6 as for safety are analyzed. A quantitative evaluation of the deviations of parameters that are controlled during the heating of tanks, comparing them with the normative nominal values, is performed. Adopting some simplifying hypothesis, a general study, applicable to all tank models proposed by norms, is carried out to determine the temperature at which the hydraulic breakage takes place when they are heated in closed-valve conditions. A curve is obtained by plotting the hydraulic breakage temperature against the filling degree. To conclude, the values obtained are compared with the results of other theoretical studies on this subject. (Author)

Eliminating a Major Cause of Wire Drawing Breakage in A-15 High-Field Superconductors

International Nuclear Information System (INIS)

Austen, Alfred R.

2003-01-01

Eliminating a Major Cause of Wire Drawing Breakage in A-15 High-Field Superconductors Phase 1 Summary Purpose of the research: The Phase 1 goal was to make a significant improvement in the wire drawing technology used for difficult to draw superconductor precursor composites. Many ductile Nb-Al and Nb-Sn precursor wire composites have experienced the onset of wire drawing breakage at about 1.5 mm diameter. Phase 1 focused on evaluating the role that precision rigid guidance of the wire into the drawing die and the hydrostatic stress state at the die entrance played in preventing wire breakage. Research carried out: The research performed depended upon the construction of both a mechanical wire guide and a hydrostatic pressure stiffened wire guidance system. Innovare constructed the two wire guidance systems and tested them for their ability to reduce wire drawing breakage. One set of hardware provided rigid alignment of the wires to their wire drawing die axes within 0.35 degrees using ''hydrostatic pressure stiffening'' to enable the precision guidance strategy to be implemented for these highly flexible small diameter wires. This apparatus was compared to a guide arrangement that used short span mechanical guide alignment with a misalignment limit of about 0.75 degrees. Four A-15 composite wires with breakage histories were drawn to evaluate the use of these wire guiding systems to reduce and/or eliminate wire breakage. Research findings and results: In Phase 1, a breakthrough in wire drawing technology for A-15 superconductor composites was achieved by dramatically limiting or eliminating breakage in four different A-15 composite precursor wire designs during the drawing of these very desirable composites that previously could not be drawn to near final size. Research results showed that the proposed Phase 1 mechanical wire guides were sufficiently effective and successful in eliminating breakage when used along with other advanced wire drawing technology to

Stem breakage of salt marsh vegetation under wave forcing: A field and model study

Science.gov (United States)

Vuik, Vincent; Suh Heo, Hannah Y.; Zhu, Zhenchang; Borsje, Bas W.; Jonkman, Sebastiaan N.

2018-01-01

One of the services provided by coastal ecosystems is wave attenuation by vegetation, and subsequent reduction of wave loads on flood defense structures. Therefore, stability of vegetation under wave forcing is an important factor to consider. This paper presents a model which determines the wave load that plant stems can withstand before they break or fold. This occurs when wave-induced bending stresses exceed the flexural strength of stems. Flexural strength was determined by means of three-point-bending tests, which were carried out for two common salt marsh species: Spartina anglica (common cord-grass) and Scirpus maritimus (sea club-rush), at different stages in the seasonal cycle. Plant stability is expressed in terms of a critical orbital velocity, which combines factors that contribute to stability: high flexural strength, large stem diameter, low vegetation height, high flexibility and a low drag coefficient. In order to include stem breakage in the computation of wave attenuation by vegetation, the stem breakage model was implemented in a wave energy balance. A model parameter was calibrated so that the predicted stem breakage corresponded with the wave-induced loss of biomass that occurred in the field. The stability of Spartina is significantly higher than that of Scirpus, because of its higher strength, shorter stems, and greater flexibility. The model is validated by applying wave flume tests of Elymus athericus (sea couch), which produced reasonable results with regards to the threshold of folding and overall stem breakage percentage, despite the high flexibility of this species. Application of the stem breakage model will lead to a more realistic assessment of the role of vegetation for coastal protection.

Parametric Study on Responses of a Self-Anchored Suspension Bridge to Sudden Breakage of a Hanger

Directory of Open Access Journals (Sweden)

Wenliang Qiu

2014-01-01

Full Text Available The girder of self-anchored suspension bridge is subjected to large compression force applied by main cables. So, serious damage of the girder due to breakage of hangers may cause the collapse of the whole bridge. With the time increasing, the hangers may break suddenly for their resistance capacities decrease due to corrosion. Using nonlinear static and dynamic analysis methods and adopting 3D finite element model, the responses of an actual self-anchored suspension bridge to sudden breakage of hangers are studied in this paper. The results show that the sudden breakage of a hanger causes violent vibration and large changes in internal forces of the bridge. In the process of the vibration, the maximum tension of hanger produced by breakage of a hanger exceeds 2.22 times its initial value, and the reaction forces of the bearings increase by more than 1.86 times the tension of the broken hanger. Based on the actual bridge, the influences of some factors including flexural stiffness of girder, torsion stiffness of girder, flexural stiffness of main cable, weight of girder, weight of main cable, span to sag ratio of main cable, distance of hangers, span length, and breakage time of hanger on the dynamic responses are studied in detail, and the influencing extent of the factors is presented.

Parametric study on responses of a self-anchored suspension bridge to sudden breakage of a hanger.

Science.gov (United States)

Qiu, Wenliang; Jiang, Meng; Huang, Cailiang

2014-01-01

The girder of self-anchored suspension bridge is subjected to large compression force applied by main cables. So, serious damage of the girder due to breakage of hangers may cause the collapse of the whole bridge. With the time increasing, the hangers may break suddenly for their resistance capacities decrease due to corrosion. Using nonlinear static and dynamic analysis methods and adopting 3D finite element model, the responses of an actual self-anchored suspension bridge to sudden breakage of hangers are studied in this paper. The results show that the sudden breakage of a hanger causes violent vibration and large changes in internal forces of the bridge. In the process of the vibration, the maximum tension of hanger produced by breakage of a hanger exceeds 2.22 times its initial value, and the reaction forces of the bearings increase by more than 1.86 times the tension of the broken hanger. Based on the actual bridge, the influences of some factors including flexural stiffness of girder, torsion stiffness of girder, flexural stiffness of main cable, weight of girder, weight of main cable, span to sag ratio of main cable, distance of hangers, span length, and breakage time of hanger on the dynamic responses are studied in detail, and the influencing extent of the factors is presented.

METABOLIC ENGINEERING TO DEVELOP A PATHWAY FOR THE SELECTIVE CLEAVAGE OF CARBON-NITROGEN BONDS

Energy Technology Data Exchange (ETDEWEB)

John J. Kilbane III

2003-12-01

The objective of the project is to develop biochemical pathways for the selective cleavage of C-N bonds in molecules found in petroleum. The initial phase of the project will focus on the isolation or development of an enzyme capable of cleaving the C-N bond in aromatic amides, specifically 2-aminobiphenyl. The objective of the second phase of the research will be to construct a biochemical pathway for the selective removal of nitrogen from carbazole by combining the carA genes from Sphingomonas sp. GTIN11 with the gene(s) encoding an appropriate amidase. The objective of the final phase of the project will be to develop derivative CN bond cleaving enzymes that have broader substrate ranges and to demonstrate the use of such strains to selectively remove nitrogen from petroleum. The project is on schedule and no major difficulties have been encountered. During the first year of the project (October, 2002-September, 2003) enrichment culture experiments have resulted in the isolation of promising cultures that may be capable of cleaving C-N bonds in aromatic amides, several amidase genes have been cloned and are currently undergoing directed evolution to obtain derivatives that can cleave C-N bonds in aromatic amides, and the carA genes from Sphingomonas sp. GTIN11, and Pseudomonas resinovorans CA10 were cloned in vectors capable of replicating in Escherichia coli. Future research will address expression of these genes in Rhodococcus erythropolis. Enrichment culture experiments and directed evolution experiments continue to be a main focus of research activity and further work is required to obtain an appropriate amidase that will selectively cleave C-N bonds in aromatic substrates. Once an appropriate amidase gene is obtained it must be combined with genes encoding an enzyme capable of converting carbazole to 2'aminobiphenyl-2,3-diol: specifically carA genes. The carA genes from two sources have been cloned and are ready for construction of C-N bond cleavage

Bond-selective control of a gas-surface reaction

Science.gov (United States)

Killelea, Daniel R.

The prospect of using light to selectively control chemical reactions has tantalized chemists since the development of the laser. Unfortunately, the realization of laser-directed chemistry is frequently thwarted by the randomization of energy within the molecule through intramolecular vibrational energy distribution (IVR). However, recent results showing vibrational mode-specific reactivity on metal surfaces suggest that IVR may not always be complete for gas-surface reactions. Here, we combine molecular beam techniques and direct laser excitation to characterize the bond-specific reactivity of trideuteromethane on a Ni(111) surface. Our results reveal important details about how vibrational energy is distributed in the reactive molecule. We use a molecular beam to direct state-selected trideuteromethane (CHD 3) molecules onto a nickel single crystal sample and use the results we obtain to describe the flow of vibrational energy in the methane-surface reaction complex. We show that CHD3 molecules initially excited to v=1, J=2, K=0 of the v 1 symmetric C-H stretching mode will dissociate exclusively via C-H cleavage on Ni(111). This result highlights the localization of vibrational energy in the reaction complex, despite the presence of many energy exchange channels with the high state-density surface. We demonstrate, for the first time, highly parallel bond-selective control of a heterogeneously catalyzed reaction. We place our results in the context of recent experiments investigating IVR for molecules in both the gas phase and liquid solutions. If IVR is fast on the reaction timescale, vibrational energy would be randomly distributed throughout the nascent methane-surface reaction complex and vibrational mode-specific behavior would not occur. The short timescale of a direct gas-surface collision may explain how the exchange of energy via IVR is limited to only a small subset of the energetic configurations available to the reaction complex. This framework

Adaptive responses on chromosome aberration and DNA breakage of peripheral lymphocytes from workers exposed to thorium and rare earth mixed dust in Baotou steel plant

International Nuclear Information System (INIS)

Liu Qingjie; Feng Jiangbing; Lu Xue; Chen Deqing; Lv Huimin; Su Xu; Liu Yufei; Jia Kejun

2008-01-01

Objective: To explore if the occupational exposure to low dose thorium could induce adaptive response in peripheral lymphocytes. Methods: 40 individuals, who exposed to thorium and rare earth mixed dust (exposure group) or control in Baotou Steel Plant, were selected, and chromosome aberrations were analyzed. Then the peripheral blood samples were irradiated in vitro with 2 Gy 60 Co γ-rays, and unstable chromosome aberration or DNA stand breakage analysis using single cell gel electrophoresis was performed. Results: The dicentrics before 2 Gy exposure in exposure group was higher than that in control (P>0.05). But the dicentrics after 2 Gy exposure in exposure group was lower than that in control, but not significantly (P >0.05). The tricentrics in exposure group was significantly lower than that in control (U=3.1622, 0.001< P<0.002). The DNA strand breakage in control group was significantly higher than that in exposure group (t=25, P<0.001). Conclusions: Occupational exposure to low dose thorium could induce the adaptive response on chromosome aberration and DNA strand breakage in peripheral lymphocytes. (authors)

Chromosome breakage in peripheral lymphocytes of thorium workers

International Nuclear Information System (INIS)

Hoegerman, S.F.; Cummins, H.T.

1979-01-01

Cytogenic analysis of 21 thorium workers and 3 controls has not shown a significant elevation in the level of chromosome breakage in the workers' peripheral lymphocytes. The observation of a single dicentric chromosome in 100-cell samples from each of two workers with relatively long periods of occupational exposure and relatively high body burdens suggests, however, that such exposure might result in increases in chromosome aberration frequency

Review on Parameters Influencing the Rice Breakage and Rubber Roll Wear in Sheller

Directory of Open Access Journals (Sweden)

Prabhakaran P.

2017-09-01

Full Text Available The present review deals with parameters influencing the rice breakage during rice milling operations and the effect of rubber roll Sheller in rice husk removal process. The main objective of rice milling system is to remove the husk and bran layer to produce the white rice. In this process, rubber roll sheller is used to remove husk from the grains by friction process. If the rubber material is too soft, there may not be sufficient shear force to husk the paddy. Wear will be minimum for rubber material with high hardness but indeed it pronounce the breakage of rice. Hence, for efficient husking the rubber roll material should possess the balance of physico-mechanical properties. Rice breakage depends on several other parameters like the type of harvest, drying temperature, drying methods, physical characteristics of paddy, husking characteristics, paddy moisture content, rubber roller speed, rubber roll pressure, paddy feed rate and fissures. Rubber roll wear depends on the type of rubber material attached to the roller, feed rate, roller speed, pressure etc.

Communication: Site-selective bond excision of adenine upon electron transfer

Science.gov (United States)

Cunha, T.; Mendes, M.; Ferreira da Silva, F.; Eden, S.; García, G.; Limão-Vieira, P.

2018-01-01

This work demonstrates that selective excision of hydrogen atoms at a particular site of the DNA base adenine can be achieved in collisions with electronegative atoms by controlling the impact energy. The result is based on analysing the time-of-flight mass spectra yields of potassium collisions with a series of labeled adenine derivatives. The production of dehydrogenated parent anions is consistent with neutral H loss either from selective breaking of C-H or N-H bonds. These unprecedented results open up a new methodology in charge transfer collisions that can initiate selective reactivity as a key process in chemical reactions that are dominant in different areas of science and technology.

Video-supported analysis of Beggiatoa filament growth, breakage, and movement

DEFF Research Database (Denmark)

Kamp, Anja; Røy, Hans; Schulz-Vogt, Heide N.

2008-01-01

A marine Beggiatoa sp. was cultured in semi-solid agar with opposing oxygen-sulfide gradients. Growth pattern, breakage of filaments for multiplication, and movement directions of Beggiatoa filaments in the transparent agar were investigated by time-lapse video recording. The initial doubling time...

Selective Nitrate Recognition by a Halogen‐Bonding Four‐Station [3]Rotaxane Molecular Shuttle

Science.gov (United States)

Barendt, Timothy A.; Docker, Andrew; Marques, Igor; Félix, Vítor

2016-01-01

Abstract The synthesis of the first halogen bonding [3]rotaxane host system containing a bis‐iodo triazolium‐bis‐naphthalene diimide four station axle component is reported. Proton NMR anion binding titration experiments revealed the halogen bonding rotaxane is selective for nitrate over the more basic acetate, hydrogen carbonate and dihydrogen phosphate oxoanions and chloride, and exhibits enhanced recognition of anions relative to a hydrogen bonding analogue. This elaborate interlocked anion receptor functions via a novel dynamic pincer mechanism where upon nitrate anion binding, both macrocycles shuttle from the naphthalene diimide stations at the periphery of the axle to the central halogen bonding iodo‐triazolium station anion recognition sites to form a unique 1:1 stoichiometric nitrate anion–rotaxane sandwich complex. Molecular dynamics simulations carried out on the nitrate and chloride halogen bonding [3]rotaxane complexes corroborate the 1H NMR anion binding results. PMID:27436297

Determination of critical breakage conditions for double glazing in fire

International Nuclear Information System (INIS)

Wang, Yu; Li, Ke; Su, Yanfei; Lu, Wei; Wang, Qingsong; Sun, Jinhua; He, Linghui; Liew, K.M.

2017-01-01

Highlights: • Critical heat fluxes of exposed and ambient panes are 6 kW/m"2 and 25 kW/m"2. • Critical temperature difference of fire side pane is around 60 °C. • The ambient pane survives three times longer due to radiation filter and air gap. • Heat transfer in double glazing is revealed by a heat flux based theoretical model. - Abstract: Double glazing unit normally demonstrates better fire resistance than single glazing, but the knowledge on its thermal behavior and heat transfer mechanism during fire is limited. In this work, nine double glazing units were heated by a 500 × 500 mm"2 pool fire. The incident heat flux, temperature on four surfaces, breakage time and cracking behavior were obtained. The critical breakage conditions for interior and exterior panes were determined through gradually decreasing the glass-burner distance from 750 mm to 450 mm. It is established that in double glazing the pane at ambient side can withstand significantly more time than the pane exposed to fire. The critical temperature difference for interior pane is 60 °C; the critical temperature of exterior pane breakage is much higher due to no frame-covered area. In addition, the heat flux at the time of crack initiation is 6 kW/m"2 for the pane at fire side, while more than 25 kW/m"2 for ambient side pane. To reveal the heat transfer mechanism in glazing-air-glazing, theoretical and numerical investigations are also performed, which agrees well with the experimental results.

Needle breakage during an inferior alveolar nerve block in a child with KBG syndrome: A case report.

Science.gov (United States)

Bagattoni, S; D'Alessandro, G; Marzo, G; Piana, G

2018-04-01

Needle breakage during the administration of dental analgesia is an extremely rare event. A case of needle breakage during the administration of an inferior alveolar nerve block occurred in a child with KBG syndrome. During the injection, a sudden movement of the child caused the breakage of the needle. The next day, the retrieval of the needle was performed surgically under general analgesia. Three months after the surgery the healing was good. Two years later the child underwent a dental extraction with the aid of nitrous oxide/oxygen analgesia/anxiolysis. Needle fracture is a possible event during the administration of dental analgesia in children.

Hydrogen-bond-driven electrophilic activation for selectivity control: scope and limitations of fluorous alcohol-promoted selective formation of 1,2-disubstituted benzimidazoles and mechanistic insight for rationale of selectivity.

Science.gov (United States)

Chebolu, Rajesh; Kommi, Damodara N; Kumar, Dinesh; Bollineni, Narendra; Chakraborti, Asit K

2012-11-16

Hydrogen-bond-driven electrophilic activation for selectivity control during competitive formation of 1,2-disubstituted and 2-substituted benzimidazoles from o-phenylenediamine and aldehydes is reported. The fluorous alcohols trifluoroethanol and hexafluoro-2-propanol efficiently promote the cyclocondensation of o-phenylenediamine with aldehydes to afford selectively the 1,2-disubstituted benzimidazoles at rt in short times. A mechanistic insight is invoked by NMR, mass spectrometry, and chemical studies to rationalize the selectivity. The ability of the fluorous alcohols in promoting the reaction and controlling the selectivity can be envisaged from their better hydrogen bond donor (HBD) abilities compared to that of the other organic solvents as well as of water. Due to the better HBD values, the fluorous alcohols efficiently promote the initial bisimine formation by electrophilic activation of the aldehyde carbonyl. Subsequently the hydrogen-bond-mediated activation of the in situ-formed bisimine triggers the rearrangement via 1,3-hydride shift to form the 1,2-disubstituted benzimidazoles.

Influence of the power law index on the fiber breakage during injection molding by numerical simulations

Science.gov (United States)

Desplentere, Frederik; Six, Wim; Bonte, Hilde; Debrabandere, Eric

2013-04-01

In predictive engineering for polymer processes, the proper prediction of material microstructure from known processing conditions and constituent material properties is a critical step forward properly predicting bulk properties in the finished composite. Operating within the context of long-fiber thermoplastics (LFT, length > 15mm) this investigation concentrates on the influence of the power law index on the final fiber length distribution within the injection molded part. To realize this, the Autodesk Simulation Moldflow Insight Scandium 2013 software has been used. In this software, a fiber breakage algorithm is available from this release on. Using virtual material data with realistic viscosity levels allows to separate the influence of the power law index on the fiber breakage from the other material and process parameters. Applying standard settings for the fiber breakage parameters results in an obvious influence on the fiber length distribution through the thickness of the part and also as function of position in the part. Finally, the influence of the shear rate constant within the fiber breakage model has been investigated illustrating the possibility to fit the virtual fiber length distribution to the possible experimentally available data.

Environmental and chemotherapeutic agents induce breakage at genes involved in leukemia-causing gene rearrangements in human hematopoietic stem/progenitor cells

Energy Technology Data Exchange (ETDEWEB)

Thys, Ryan G., E-mail: rthys@wakehealth.edu [Department of Cancer Biology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1016 (United States); Lehman, Christine E., E-mail: clehman@wakehealth.edu [Department of Cancer Biology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1016 (United States); Pierce, Levi C.T., E-mail: Levipierce@gmail.com [Human Longevity, Inc., San Diego, California 92121 (United States); Wang, Yuh-Hwa, E-mail: yw4b@virginia.edu [Department of Biochemistry and Molecular Genetics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0733 (United States)

2015-09-15

Highlights: • Environmental/chemotherapeutic agents cause DNA breakage in MLL and CBFB in HSPCs. • Diethylnitrosamine-induced DNA breakage at MLL and CBFB shown for the first time. • Chemical-induced DNA breakage occurs at topoisomerase II cleavage sites. • Chemical-induced DNA breaks display a pattern similar to those in leukemia patients. • Long-term exposures suggested to generate DNA breakage at leukemia-related genes. - Abstract: Hematopoietic stem and progenitor cells (HSPCs) give rise to all of the cells that make up the hematopoietic system in the human body, making their stability and resilience especially important. Damage to these cells can severely impact cell development and has the potential to cause diseases, such as leukemia. Leukemia-causing chromosomal rearrangements have largely been studied in the context of radiation exposure and are formed by a multi-step process, including an initial DNA breakage and fusion of the free DNA ends. However, the mechanism for DNA breakage in patients without previous radiation exposure is unclear. Here, we investigate the role of non-cytotoxic levels of environmental factors, benzene, and diethylnitrosamine (DEN), and chemotherapeutic agents, etoposide, and doxorubicin, in generating DNA breakage at the patient breakpoint hotspots of the MLL and CBFB genes in human HSPCs. These conditions represent exposure to chemicals encountered daily or residual doses from chemotherapeutic drugs. Exposure of HSPCs to non-cytotoxic levels of environmental chemicals or chemotherapeutic agents causes DNA breakage at preferential sites in the human genome, including the leukemia-related genes MLL and CBFB. Though benzene, etoposide, and doxorubicin have previously been linked to leukemia formation, this is the first study to demonstrate a role for DEN in the generation of DNA breakage at leukemia-specific sites. These chemical-induced DNA breakpoints coincide with sites of predicted topoisomerase II cleavage. The

Environmental and chemotherapeutic agents induce breakage at genes involved in leukemia-causing gene rearrangements in human hematopoietic stem/progenitor cells

International Nuclear Information System (INIS)

Thys, Ryan G.; Lehman, Christine E.; Pierce, Levi C.T.; Wang, Yuh-Hwa

2015-01-01

Highlights: • Environmental/chemotherapeutic agents cause DNA breakage in MLL and CBFB in HSPCs. • Diethylnitrosamine-induced DNA breakage at MLL and CBFB shown for the first time. • Chemical-induced DNA breakage occurs at topoisomerase II cleavage sites. • Chemical-induced DNA breaks display a pattern similar to those in leukemia patients. • Long-term exposures suggested to generate DNA breakage at leukemia-related genes. - Abstract: Hematopoietic stem and progenitor cells (HSPCs) give rise to all of the cells that make up the hematopoietic system in the human body, making their stability and resilience especially important. Damage to these cells can severely impact cell development and has the potential to cause diseases, such as leukemia. Leukemia-causing chromosomal rearrangements have largely been studied in the context of radiation exposure and are formed by a multi-step process, including an initial DNA breakage and fusion of the free DNA ends. However, the mechanism for DNA breakage in patients without previous radiation exposure is unclear. Here, we investigate the role of non-cytotoxic levels of environmental factors, benzene, and diethylnitrosamine (DEN), and chemotherapeutic agents, etoposide, and doxorubicin, in generating DNA breakage at the patient breakpoint hotspots of the MLL and CBFB genes in human HSPCs. These conditions represent exposure to chemicals encountered daily or residual doses from chemotherapeutic drugs. Exposure of HSPCs to non-cytotoxic levels of environmental chemicals or chemotherapeutic agents causes DNA breakage at preferential sites in the human genome, including the leukemia-related genes MLL and CBFB. Though benzene, etoposide, and doxorubicin have previously been linked to leukemia formation, this is the first study to demonstrate a role for DEN in the generation of DNA breakage at leukemia-specific sites. These chemical-induced DNA breakpoints coincide with sites of predicted topoisomerase II cleavage. The

Selective Nitrate Recognition by a Halogen-Bonding Four-Station [3]Rotaxane Molecular Shuttle.

Science.gov (United States)

Barendt, Timothy A; Docker, Andrew; Marques, Igor; Félix, Vítor; Beer, Paul D

2016-09-05

The synthesis of the first halogen bonding [3]rotaxane host system containing a bis-iodo triazolium-bis-naphthalene diimide four station axle component is reported. Proton NMR anion binding titration experiments revealed the halogen bonding rotaxane is selective for nitrate over the more basic acetate, hydrogen carbonate and dihydrogen phosphate oxoanions and chloride, and exhibits enhanced recognition of anions relative to a hydrogen bonding analogue. This elaborate interlocked anion receptor functions via a novel dynamic pincer mechanism where upon nitrate anion binding, both macrocycles shuttle from the naphthalene diimide stations at the periphery of the axle to the central halogen bonding iodo-triazolium station anion recognition sites to form a unique 1:1 stoichiometric nitrate anion-rotaxane sandwich complex. Molecular dynamics simulations carried out on the nitrate and chloride halogen bonding [3]rotaxane complexes corroborate the (1) H NMR anion binding results. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Selective breaking of bonds in water with intense, 2-cycle, infrared laser pulses

Energy Technology Data Exchange (ETDEWEB)

Mathur, D., E-mail: atmol1@tifr.res.in; Dharmadhikari, A. K. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); Dota, K. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); Dey, D.; Tiwari, A. K. [Indian Institute of Science Education and Research Kolkata, Mohanpur 741 246 (India); Dharmadhikari, J. A. [Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); De, S. [Saha Institute of Nuclear Physics, Bidhan Nagar, Kolkata 700 064 (India); Vasa, P. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

2015-12-28

One of the holy grails of contemporary science has been to establish the possibility of preferentially breaking one of several bonds in a molecule. For instance, the two O–H bonds in water are equivalent: given sufficient energy, either one of them is equally likely to break. We report bond-selective molecular fragmentation upon application of intense, 2-cycle pulses of 800 nm laser light: we demonstrate up to three-fold enhancement for preferential bond breaking in isotopically substituted water (HOD). Our experimental observations are rationalized by means of ab initio computations of the potential energy surfaces of HOD, HOD{sup +}, and HOD{sup 2+} and explorations of the dissociation limits resulting from either O–H or O–D bond rupture. The observations we report present a formidable theoretical challenge that need to be taken up in order to gain insights into molecular dynamics, strong field physics, chemical physics, non-adiabatic processes, mass spectrometry, and time-dependent quantum chemistry.

Effects of particle size and confining pressure on breakage factor of rockfill materials using medium triaxial test

Directory of Open Access Journals (Sweden)

Ashok Kumar Gupta

2016-06-01

Full Text Available Rockfill dams are mostly constructed using blasted rockfill materials obtained by blasting rocks or alluvial rockfill materials collected from the riverbeds. Behaviors of rockfill materials and their characterization significantly depend on breakage factor observed during triaxial loading. In this paper, two modeled rockfill materials are investigated by using medium triaxial cell. Drained triaxial tests are conducted on various sizes of modeled rockfill materials used in the two dams, and test data are analyzed accordingly. Breakage factor of rockfill material is studied and the effects of particle size and confining pressure on breakage factor are investigated using medium triaxial cell as many researchers have already conducted investigation using large triaxial cell.

Diagnostic Overlap between Fanconi Anemia and the Cohesinopathies: Roberts Syndrome and Warsaw Breakage Syndrome

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Petra van der Lelij

2010-01-01

Full Text Available Fanconi anemia (FA is a recessively inherited disease characterized by multiple symptoms including growth retardation, skeletal abnormalities, and bone marrow failure. The FA diagnosis is complicated due to the fact that the clinical manifestations are both diverse and variable. A chromosomal breakage test using a DNA cross-linking agent, in which cells from an FA patient typically exhibit an extraordinarily sensitive response, has been considered the gold standard for the ultimate diagnosis of FA. In the majority of FA patients the test results are unambiguous, although in some cases the presence of hematopoietic mosaicism may complicate interpretation of the data. However, some diagnostic overlap with other syndromes has previously been noted in cases with Nijmegen breakage syndrome. Here we present results showing that misdiagnosis may also occur with patients suffering from two of the three currently known cohesinopathies, that is, Roberts syndrome (RBS and Warsaw breakage syndrome (WABS. This complication may be avoided by scoring metaphase chromosomes—in addition to chromosomal breakage—for spontaneously occurring premature centromere division, which is characteristic for RBS and WABS, but not for FA.

Destabilized SMC5/6 complex leads to chromosome breakage syndrome with severe lung disease

Science.gov (United States)

van der Crabben, Saskia N.; Hennus, Marije P.; McGregor, Grant A.; Ritter, Deborah I.; Nagamani, Sandesh C.S.; Wells, Owen S.; Harakalova, Magdalena; Chinn, Ivan K.; Alt, Aaron; Vondrova, Lucie; Hochstenbach, Ron; van Montfrans, Joris M.; Terheggen-Lagro, Suzanne W.; van Lieshout, Stef; van Roosmalen, Markus J.; Renkens, Ivo; Duran, Karen; Nijman, Isaac J.; Kloosterman, Wigard P.; Hennekam, Eric; van Hasselt, Peter M.; Wheeler, David A.; Palecek, Jan J.; Lehmann, Alan R.; Oliver, Antony W.; Pearl, Laurence H.; Plon, Sharon E.; Murray, Johanne M.

2016-01-01

The structural maintenance of chromosomes (SMC) family of proteins supports mitotic proliferation, meiosis, and DNA repair to control genomic stability. Impairments in chromosome maintenance are linked to rare chromosome breakage disorders. Here, we have identified a chromosome breakage syndrome associated with severe lung disease in early childhood. Four children from two unrelated kindreds died of severe pulmonary disease during infancy following viral pneumonia with evidence of combined T and B cell immunodeficiency. Whole exome sequencing revealed biallelic missense mutations in the NSMCE3 (also known as NDNL2) gene, which encodes a subunit of the SMC5/6 complex that is essential for DNA damage response and chromosome segregation. The NSMCE3 mutations disrupted interactions within the SMC5/6 complex, leading to destabilization of the complex. Patient cells showed chromosome rearrangements, micronuclei, sensitivity to replication stress and DNA damage, and defective homologous recombination. This work associates missense mutations in NSMCE3 with an autosomal recessive chromosome breakage syndrome that leads to defective T and B cell function and acute respiratory distress syndrome in early childhood. PMID:27427983

A Critique of a Phenomenological Fiber Breakage Model for Stress Rupture of Composite Materials

Science.gov (United States)

Reeder, James R.

2010-01-01

Stress rupture is not a critical failure mode for most composite structures, but there are a few applications where it can be critical. One application where stress rupture can be a critical design issue is in Composite Overwrapped Pressure Vessels (COPV's), where the composite material is highly and uniformly loaded for long periods of time and where very high reliability is required. COPV's are normally required to be proof loaded before being put into service to insure strength, but it is feared that the proof load may cause damage that reduces the stress rupture reliability. Recently, a fiber breakage model was proposed specifically to estimate a reduced reliability due to proof loading. The fiber breakage model attempts to model physics believed to occur at the microscopic scale, but validation of the model has not occurred. In this paper, the fiber breakage model is re-derived while highlighting assumptions that were made during the derivation. Some of the assumptions are examined to assess their effect on the final predicted reliability.

Timely Endocytosis of Cytokinetic Enzymes Prevents Premature Spindle Breakage during Mitotic Exit.

Directory of Open Access Journals (Sweden)

Cheen Fei Chin

2016-07-01

Full Text Available Cytokinesis requires the spatio-temporal coordination of membrane deposition and primary septum (PS formation at the division site to drive acto-myosin ring (AMR constriction. It has been demonstrated that AMR constriction invariably occurs only after the mitotic spindle disassembly. It has also been established that Chitin Synthase II (Chs2p neck localization precedes mitotic spindle disassembly during mitotic exit. As AMR constriction depends upon PS formation, the question arises as to how chitin deposition is regulated so as to prevent premature AMR constriction and mitotic spindle breakage. In this study, we propose that cells regulate the coordination between spindle disassembly and AMR constriction via timely endocytosis of cytokinetic enzymes, Chs2p, Chs3p, and Fks1p. Inhibition of endocytosis leads to over accumulation of cytokinetic enzymes during mitotic exit, which accelerates the constriction of the AMR, and causes spindle breakage that eventually could contribute to monopolar spindle formation in the subsequent round of cell division. Intriguingly, the mitotic spindle breakage observed in endocytosis mutants can be rescued either by deleting or inhibiting the activities of, CHS2, CHS3 and FKS1, which are involved in septum formation. The findings from our study highlight the importance of timely endocytosis of cytokinetic enzymes at the division site in safeguarding mitotic spindle integrity during mitotic exit.

Sensitivity to chromosomal breakage as risk factor in young adults with oral squamous cell carcinoma.

Science.gov (United States)

Braakhuis, Boudewijn J M; Nieuwint, Aggie W M; Oostra, Anneke B; Joenje, Hans; Flach, Géke B; Graveland, A Peggy; Brakenhoff, Ruud H; Leemans, C René

2016-03-01

Oral squamous cell carcinoma (OSCC) may develop in young adults. In contrast to older patients, the well-known etiological factors, exposure to tobacco and alcohol, play a minor role in the carcinogenesis in this patient group. It has been suggested that an intrinsic susceptibility to environmental genotoxic exposures plays a role in the development of OSCC in these patients. The hypothesis was tested whether young OSCC patients have an increased sensitivity to induced chromosomal damage. Fourteen OSCC patients with an average age of 32 years (range 20-42) were selected. Peripheral blood lymphocytes and skin fibroblasts of patients and 14 healthy controls were subjected to the chromosome breakage test with Mitomycin C. This test is routinely used to identify Fanconi anemia patients, who are well-known for their inherited high sensitivity to this type of DNA damage, but also for the high risk to develop OSCC. Human papilloma virus status of the carcinomas was also determined. None of the 14 young patients with OSCC had an increased response in the MMC-chromosomal breakage test. All tumors tested negative for human papilloma virus. No evidence was obtained for the existence of a constitutional hypersensitivity to DNA chromosomal damage as a potential risk factor for OSCC in young adults. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Amifostine Protection Against Mitomycin-induced Chromosomal Breakage in Fanconi Anaemia Lymphocytes

Directory of Open Access Journals (Sweden)

Miriam T. P. Lopes

2008-08-01

Full Text Available Fanconi anaemia (FA is a rare genetic chromosomal instability syndrome caused by impairment of DNA repair and reactive oxygen species (ROS imbalance. This disease is also related to bone marrow failure and cancer. Treatment of these complications with radiation and alkylating agents may enhance chromosomal breakage. We have evaluated the effect of amifostine (AMF on basal and mitomycin C (MMC-induced chromosomal breakage in FA blood cells using the micronucleus assay. The basal micronuclei count was higher among FA patients than healthy subjects. Pre-treatment with AMF significantly inhibited micronucleation induced by MMC in healthy subjects (23.4 ± 4.0 – MMC vs 12.3 ± 2.9 – AMF →MMC MN/1000CB, p < 0.01, one way ANOVA as well as in FA patients (80.0 ± 5.8 – MMC vs 40.1 ± 5.8 – AMF →MMC MN/1000CB, p < 0.01, ANOVA. Release of ROS by peripheral blood mononuclear cells treated with AMF →MMC and measured by chemoluminometry showed that AMF-protection was statistically higher among FA patients than in healthy individuals. Based on these results we suggest that AMF prevents chromosomal breakage induced by MMC, probably by its antioxidant effect.

Bond strength of selected composite resin-cements to zirconium-oxide ceramic

Science.gov (United States)

Fons-Font, Antonio; Amigó-Borrás, Vicente; Granell-Ruiz, María; Busquets-Mataix, David; Panadero, Rubén A.; Solá-Ruiz, Maria F.

2013-01-01

Objectives: The aim of this study was to evaluate bond strengths of zirconium-oxide (zirconia) ceramic and a selection of different composite resin cements. Study Design: 130 Lava TM cylinders were fabricated. The cylinders were sandblasted with 80 µm aluminium oxide or silica coated with CoJet Sand. Silane, and bonding agent and/or Clearfil Ceramic Primer were applied. One hundred thirty composite cement cylinders, comprising two dual-polymerizing (Variolink II and Panavia F) and two autopolymerizing (Rely X and Multilink) resins were bonded to the ceramic samples. A shear test was conducted, followed by an optical microscopy study to identify the location and type of failure, an electron microscopy study (SEM and TEM) and statistical analysis using the Kruskal-Wallis test for more than two independent samples and Mann-Whitney for two independent samples. Given the large number of combinations, Bonferroni correction was applied (α=0.001). Results: Dual-polymerizing cements provided better adhesion values (11.7 MPa) than the autopolymerizing (7.47 MPa) (p-value M-Wzirconium-oxide ceramic, creating a more rough and retentive surface, thus providing an improved micromechanical interlocking between the cement and the ceramic. Key words:Shear bond strength, silica coating, surface treatment, zirconia ceramics, phosphate monomer. PMID:22926485

Tree species traits but not diversity mitigate stem breakage in a subtropical forest following a rare and extreme ice storm.

Directory of Open Access Journals (Sweden)

Karin Nadrowski

Full Text Available Future climates are likely to include extreme events, which in turn have great impacts on ecological systems. In this study, we investigated possible effects that could mitigate stem breakage caused by a rare and extreme ice storm in a Chinese subtropical forest across a gradient of forest diversity. We used Bayesian modeling to correct stem breakage for tree size and variance components analysis to quantify the influence of taxon, leaf and wood functional traits, and stand level properties on the probability of stem breakage. We show that the taxon explained four times more variance in individual stem breakage than did stand level properties; trees with higher specific leaf area (SLA were less susceptible to breakage. However, a large part of the variation at the taxon scale remained unexplained, implying that unmeasured or undefined traits could be used to predict damage caused by ice storms. When aggregated at the plot level, functional diversity and wood density increased after the ice storm. We suggest that for the adaption of forest management to climate change, much can still be learned from looking at functional traits at the taxon level.

Persistence of Breakage in Specific Chromosome Bands 6 Years after Acute Exposure to Oil.

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Alexandra Francés

251 breakpoints in exposed individuals were identified, showing a non-uniform distribution in the human ideogram. Ten chromosome bands were found to be especially prone to breakage through both statistical methods. By comparing these bands with those observed in certain exposed individuals who had already participated the previous study, it was found in both studies that four bands (2q21, 3q27, 5q31 and 17p11.2 are particularly sensitive to breakage. Additionally, the dysfunction in DNA repair mechanisms was not significantly higher in oil-exposed individuals than in non-exposed individuals.The sample size and the possibility of some kind of selection bias should be considered. Genotoxic results cannot be extrapolated to the high number of individuals who participated occasionally in clean-up tasks.Our findings show the existence of at least four target bands (2q21, 3q27, 5q31 and 17p11.2 with a greater propensity to break over time after an acute exposure to oil. The breaks in these bands, which are commonly involved in hematological cancer, may explain the increase of cancer risk reported in chronically benzene-exposed individuals. In addition, a more efficiency of the DNA repair mechanisms has been detected six years after in fishermen who were highly exposed to the oil spill. To date, only this study, performed by our group on the previous and present genotoxic effects, has analyzed the chromosomal regions affected by breakage after an acute oil exposure.

Telomere healing following DNA polymerase arrest-induced breakages is likely the main mechanism generating chromosome 4p terminal deletions.

Science.gov (United States)

Hannes, Femke; Van Houdt, Jeroen; Quarrell, Oliver W; Poot, Martin; Hochstenbach, Ron; Fryns, Jean-Pierre; Vermeesch, Joris R

2010-12-01

Constitutional developmental disorders are frequently caused by terminal chromosomal deletions. The mechanisms and/or architectural features that might underlie those chromosome breakages remain largely unexplored. Because telomeres are the vital DNA protein complexes stabilizing linear chromosomes against chromosome degradation, fusion, and incomplete replication, those terminal-deleted chromosomes acquired new telomeres either by telomere healing or by telomere capture. To unravel the mechanisms leading to chromosomal breakage and healing, we sequenced nine chromosome 4p terminal deletion boundaries. A computational analysis of the breakpoint flanking region, including 12 previously published pure terminal breakage sites, was performed in order to identify architectural features that might be involved in this process. All terminal 4p truncations were likely stabilized by telomerase-mediated telomere healing. In the majority of breakpoints multiple genetic elements have a potential to induce secondary structures and an enrichment in replication stalling site motifs were identified. These findings suggest DNA replication stalling-induced chromosome breakage during early development is the first mechanistic step leading toward terminal deletion syndromes. © 2010 Wiley-Liss, Inc.

Estimates of DNA strand breakage in bottlenose dolphin (Tursiops truncatus leukocytes measured with the Comet and DNA diffusion assays

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Adriana Díaz

2009-01-01

Full Text Available The analysis of DNA damage by mean of Comet or single cell gel electrophoresis (SCGE assay has been commonly used to assess genotoxic impact in aquatic animals being able to detect exposure to low concentrations of contaminants in a wide range of species. The aims of this work were 1 to evaluate the usefulness of the Comet to detect DNA strand breakage in dolphin leukocytes, 2 to use the DNA diffusion assay to determine the amount of DNA strand breakage associated with apoptosis or necrosis, and 3 to determine the proportion of DNA strand breakage that was unrelated to apoptosis and necrosis. Significant intra-individual variation was observed in all of the estimates of DNA damage. DNA strand breakage was overestimated because a considerable amount (~29% of the DNA damage was derived from apoptosis and necrosis. The remaining DNA damage in dolphin leukocytes was caused by factors unrelated to apoptosis and necrosis. These results indicate that the DNA diffusion assay is a complementary tool that can be used together with the Comet assay to assess DNA damage in bottlenose dolphins.

Chromosomal instability can be induced by the formation of breakage-prone chromosome rearrangement junctions

International Nuclear Information System (INIS)

Allen, R.N.; Ritter, L.; Moore, S.R.; Grosovsky, A.J.

2003-01-01

Full text: Studies in our lab have led to the hypothesis that chromosomal rearrangements can generate novel breakage-prone sites, resulting in chromosomal instability acting predominantly in cis. For example, specific breakage of large blocks of centromeric region heterochromatin on chromosome 16q by treatment with 2,6-diaminopurine (DAP) is associated with repeated rearrangement of chromosome 16q during outgrowth of DAP-treated clones, thereby establishing a link between the initial site of damage and the occurrence of persistent chromosomal instability. Similarly, karyotypic analysis of gamma ray induced instability demonstrated that chromosomal rearrangements in sub-clones were significantly clustered near the site of previously identified chromosomal rearrangement junctions in unstable parental clones. This study investigates the hypothesis that integration of transfected sequences into host chromosomes could create breakage-prone junction regions and persistent genomic instability without exposure to DNA-damage agents. These junctions may mimic the unstable chromosomal rearrangements induced by DAP or radiation, and thus provide a test of the broader hypothesis that instability can to some extent be attributed to the formation of novel chromosomal breakage hot spots. These experiments were performed using human-hamster hybrid AL cells containing a single human chromosome 11, which was used to monitor instability in a chromosomal painting assay. AL cells were transfected with a 2.5 Kb fragment containing multiple copies of the 180 bp human alpha heterochromatic repeat, which resulted in chromosomal instability in 41% of the transfected clones. Parallel exposure to gamma-radiation resulted in a similar level of chromosomal instability, although control transfections with plasmid alone did not lead to karyotypic instability. Chromosomal instability induced by integration of alpha heterochromatic repeats was also frequently associated with delayed reproductive

DNA strand breakage by 125I-decay in oligoDNA

International Nuclear Information System (INIS)

Lobachevsky, P.; Martin, R.F.

1996-01-01

Full text: A double-stranded oligodeoxynucleotide containing 125 I-dC in a defined location, with 5'- or 3'- 32 P-end-labelling of either strand, was used to investigate DNA strand breakage resulting from 125 I decay. Samples of the 32 P-end-labelled and 125 I-dC containing oligoDNA were incubated in 20 mM phosphate buffer (PB), or PB + 2 M dimethylsulphoxide (DMSO) at 4 deg during 18-20 days. The 32 P-end-labelled DNA fragments produced by 125 I decays were separated on denaturing polyacrylamide gels, and the 3P activity in each fragment was determined by scintillation counting after elution from the gel. The fragment size distribution was then converted to a distribution of single stranded break probabilities at each nucleotide position. The results indicate that each 125 I decay event produces at least one break in the 125 I-dC containing strand, and causes breakage of the opposite strand in 75-80% of events. Thus, the double stranded break is produced by 125 I decay with probability ∼0.8. Most of single stranded breaks (around 90%) occurred within 5-6 nucleotides of the 125 I-dC, however DNA breaks were detected up to 18-20 nucleotides from the decay site. The average numbers of single stranded breaks per decay are 3.7 (PB) and 3.3 (PB+DMSO) in 125 I-dC containing strand, and 1.5 (PB) and 1.3 (PB+DMSO) in the opposite strand. Deconvolution of strand break probabilities as a function of separation from the 125 I, in terms of both distance (to target deoxyribosyl carbon atoms, in B-DNA) and nucleotide number, show that the latter is an important parameter for the shorter-range damage. This could indicate a role for attenuation/dissipation of damage through the stacked bases. In summary, the results represent a much more extensive set of data than available from earlier experiments on DNA breakage from l25 I-decay, and may provide new mechanistic insights

Selective bond breakage within the HOD molecule using optimized femtosecond ultraviolet laser pulses

DEFF Research Database (Denmark)

Tiwari, Ashwani Kumar; Møller, Klaus Braagaard; Henriksen, Niels Engholm

2008-01-01

With the HOD molecule initially in its vibrational ground state, we theoretically analyze the laser-induced control of the OD/OH branching ratio D+OH H+OD in the first absorption band. In the weak-field limit, any form of UV-pulse shaping control leads to a branching ratio larger than similar to 2...

Tetrel Bonding as a Vehicle for Strong and Selective Anion Binding

Directory of Open Access Journals (Sweden)

Steve Scheiner

2018-05-01

Full Text Available Tetrel atoms T (T = Si, Ge, Sn, and Pb can engage in very strong noncovalent interactions with nucleophiles, which are commonly referred to as tetrel bonds. The ability of such bonds to bind various anions is assessed with a goal of designing an optimal receptor. The Sn atom seems to form the strongest bonds within the tetrel family. It is most effective in the context of a -SnF3 group and a further enhancement is observed when a positive charge is placed on the receptor. Connection of the -SnF3 group to either an imidazolium or triazolium provides a strong halide receptor, which can be improved if its point of attachment is changed from the C to an N atom of either ring. Aromaticity of the ring offers no advantage nor is a cyclic system superior to a simple alkyl amine of any chain length. Placing a pair of -SnF3 groups on a single molecule to form a bipodal dicationic receptor with two tetrel bonds enhances the binding, but falls short of a simple doubling. These two tetrel groups can be placed on opposite ends of an alkyl diamine chain of any length although SnF3+NH2(CH2nNH2SnF3+ with n between 2 and 4 seems to offer the strongest halide binding. Of the various anions tested, OH− binds most strongly: OH− > F− > Cl− > Br− > I−. The binding energy of the larger NO3− and HCO3− anions is more dependent upon the charge of the receptor. This pattern translates into very strong selectivity of binding one anion over another. The tetrel-bonding receptors bind far more strongly to each anion than an equivalent number of K+ counterions, which leads to equilibrium ratios in favor of the former of many orders of magnitude.

Reducing the anisotropy of a Brazilian disc generated in a bonded-particle model

Science.gov (United States)

Zhang, Q.; Zhang, X. P.; Ji, P. Q.

2018-03-01

The Brazilian test is a widely used method for determining the tensile strength of rocks and for calibrating parameters in bonded-particle models (BPMs). In previous studies, the Brazilian disc has typically been trimmed from a compacted rectangular specimen. The present study shows that different tensile strength values are obtained depending on the compressive loading direction. Several measures are proposed to reduce the anisotropy of the disc. The results reveal that the anisotropy of the disc is significantly influenced by the compactibility of the specimen from which it is trimmed. A new method is proposed in which the Brazilian disc is directly generated with a particle boundary, effectively reducing the anisotropy. The stiffness (particle and bond) and strength (bond) of the boundary are set at less than and greater than those of the disc assembly, respectively, which significantly decreases the stress concentration at the boundary contacts and prevents breakage of the boundary particle bonds. This leads to a significant reduction in the anisotropy of the disc and the discreteness of the tensile strength. This method is more suitable for carrying out a realistic Brazilian test for homogeneous rock-like material in the BPM.

Sequence dependence of electron-induced DNA strand breakage revealed by DNA nanoarrays

DEFF Research Database (Denmark)

Keller, Adrian; Rackwitz, Jenny; Cauët, Emilie

2014-01-01

The electronic structure of DNA is determined by its nucleotide sequence, which is for instance exploited in molecular electronics. Here we demonstrate that also the DNA strand breakage induced by low-energy electrons (18 eV) depends on the nucleotide sequence. To determine the absolute cross sec...

Hydrogen bonds in the vicinity of the special pair of the bacterial reaction center probed by hydrostatic high-pressure absorption spectroscopy.

Science.gov (United States)

Kangur, Liina; Jones, Michael R; Freiberg, Arvi

2017-12-01

Using the native bacteriochlorophyll a pigment cofactors as local probes, we investigated the response to external hydrostatic high pressure of reaction center membrane protein complexes from the photosynthetic bacterium Rhodobacter sphaeroides. Wild-type and engineered complexes were used with a varied number (0, 1 or 2) of hydrogen bonds that bind the reaction center primary donor bacteriochlorophyll cofactors to the surrounding protein scaffold. A pressure-induced breakage of hydrogen bonds was established for both detergent-purified and membrane-embedded reaction centers, but at rather different pressures: between 0.2 and 0.3GPa and at about 0.55GPa, respectively. The free energy change associated with the rupture of the single hydrogen bond present in wild-type reaction centers was estimated to be equal to 13-14kJ/mol. In the mutant with two symmetrical hydrogen bonds (FM197H) a single cooperative rupture of the two bonds was observed corresponding to an about twice stronger bond, rather than a sequential rupture of two individual bonds. Copyright © 2017 Elsevier B.V. All rights reserved.

Multireference theoretical investigation on selectivity of the bond fissions in photodissociation of acetyl cyanide

Science.gov (United States)

Xiao, Hong-Yan; Liu, Ya-Jun; Fang, Wei-Hai

2007-12-01

The selectivity of the C -CH3 and C-CN bond fissions upon excitation of acetyl cyanide at 193nm has been investigated at the theoretical level of multistate complete active space self-consistent field second order perturbation. The calculated results indicated that the initially excited S3 state relaxes to S2 via ultrafast internal conversion. The S2 state could dissociate via two pathways. One, adiabatically dissociates to CH3CO(X˜)+CN(Ã). The other one internally converts to S1 before S1 intersystem crossing to T1. The T1 state subsequently dissociates to two groups of products: CH3(X˜)+OCCN(X˜) and CH3CO(X˜)+CN(X˜). The experimentally observed preference branching of CN elimination over CH3 one and bond selectivity are the results of the competition between the adiabatic and nonadiabatic dynamics of the S2 state.

Selectivity of calixarene-bonded silica phases in HPLC: Description of special characteristics with a multiple term linear equation at different methanol concentrations.

Science.gov (United States)

Schneider, Christian; Jira, Thomas

2010-10-01

Retention and selectivity characteristics of different calixarene-, resorcinarene- and alkyl-bonded stationary phases are examined by analyzing a set of test solutes covering the main interactions (hydrophobic, steric, ionic, polar) that apply in HPLC. Therefore Dolan and Snyder's multiple term linear equation has been adapted to fit the properties of calixarene-bonded columns. The obtained parameters are used to describe retention and selectivity of the novel Caltrex(®) phases and to elucidate underlying mechanisms of retention. Here, differences of stationary phase characteristics at different methanol concentrations in the mobile phases are examined. Both selectivity and retention were found to depend on the methanol content. Differences of these dependencies were found for different stationary phases and interactions. The differences between common alkyl-bonded and novel calixarene-bonded phases increase with increasing methanol content.

Nijmegen breakage syndrome (NBS

Directory of Open Access Journals (Sweden)

Chrzanowska Krystyna H

2012-02-01

Full Text Available Abstract Nijmegen breakage syndrome (NBS is a rare autosomal recessive syndrome of chromosomal instability mainly characterized by microcephaly at birth, combined immunodeficiency and predisposition to malignancies. Due to a founder mutation in the underlying NBN gene (c.657_661del5 the disease is encountered most frequently among Slavic populations. The principal clinical manifestations of the syndrome are: microcephaly, present at birth and progressive with age, dysmorphic facial features, mild growth retardation, mild-to-moderate intellectual disability, and, in females, hypergonadotropic hypogonadism. Combined cellular and humoral immunodeficiency with recurrent sinopulmonary infections, a strong predisposition to develop malignancies (predominantly of lymphoid origin and radiosensitivity are other integral manifestations of the syndrome. The NBN gene codes for nibrin which, as part of a DNA repair complex, plays a critical nuclear role wherever double-stranded DNA ends occur, either physiologically or as a result of mutagenic exposure. Laboratory findings include: (1 spontaneous chromosomal breakage in peripheral T lymphocytes with rearrangements preferentially involving chromosomes 7 and 14, (2 sensitivity to ionizing radiation or radiomimetics as demonstrated in vitro by cytogenetic methods or by colony survival assay, (3 radioresistant DNA synthesis, (4 biallelic hypomorphic mutations in the NBN gene, and (5 absence of full-length nibrin protein. Microcephaly and immunodeficiency are common to DNA ligase IV deficiency (LIG4 syndrome and severe combined immunodeficiency with microcephaly, growth retardation, and sensitivity to ionizing radiation due to NHEJ1 deficiency (NHEJ1 syndrome. In fact, NBS was most commonly confused with Fanconi anaemia and LIG4 syndrome. Genetic counselling should inform parents of an affected child of the 25% risk for further children to be affected. Prenatal molecular genetic diagnosis is possible if disease

Effect of solvent on proton location and dynamic behavior in short intramolecular hydrogen bonds studied by molecular dynamics simulations and NMR experiments

International Nuclear Information System (INIS)

Mori, Yukie; Masuda, Yuichi

2015-01-01

Highlights: • MD simulations were performed to study dynamics of strong hydrogen bonds. • Nuclear magnetic relaxation times of proton were measured in solution. • The hydrogen bond of dibenzoylmethane enol is asymmetric in methanol solution. • Formation or breakage of intermolecular hydrogen bonds can trigger proton transfer. • Dimethylsulfoxide may form a bifurcated hydrogen bond with a hydrogen-bonded system. - Abstract: Hydrogen phthalate anion has a short strong O–H–O hydrogen bond (H-bond). According to previous experimental studies, the H-bond is asymmetric and two tautomers are interconverted in aqueous solutions. In the present study, the effects of polar solvents on the H-bond in a zwitterionic hydrogen phthalate derivative 1 were investigated by quantum mechanics/molecular mechanics molecular dynamics (MD) simulations. The analyses of the trajectories for the methanol solution showed that the H-bonding proton tends to be located closer to the carboxylate group that forms fewer intermolecular H-bonds, than to the other carboxylate group and that the intramolecular proton transfer in 1 is triggered by the breakage and/or formation of an intermolecular H-bond. The enol form of dibenzoylmethane (2) also has a short H-bond, and the OH bond is reported to be rather long (>1.1 Å) in the crystal. In the present study, the effects of the solvent on the H-bond in 2 were investigated by molecular orbital (MO) calculations, MD simulations and nuclear magnetic resonance (NMR) spectroscopy. Density functional theory (DFT) calculations for 2 in vacuum indicated that the barrier height for the intramolecular proton transfer is almost the same as the zero-point energy of the vibrational ground state, resulting in broad distribution of the proton density along the H-bond, owing to the nuclear quantum effect. The OH distances were determined in CCl 4 , acetonitrile, and dimethylsulfoxide solutions from the magnetic dipolar interactions between the 17 O and 1

Effect of solvent on proton location and dynamic behavior in short intramolecular hydrogen bonds studied by molecular dynamics simulations and NMR experiments

Energy Technology Data Exchange (ETDEWEB)

Mori, Yukie, E-mail: mori.yukie@ocha.ac.jp; Masuda, Yuichi

2015-09-08

Highlights: • MD simulations were performed to study dynamics of strong hydrogen bonds. • Nuclear magnetic relaxation times of proton were measured in solution. • The hydrogen bond of dibenzoylmethane enol is asymmetric in methanol solution. • Formation or breakage of intermolecular hydrogen bonds can trigger proton transfer. • Dimethylsulfoxide may form a bifurcated hydrogen bond with a hydrogen-bonded system. - Abstract: Hydrogen phthalate anion has a short strong O–H–O hydrogen bond (H-bond). According to previous experimental studies, the H-bond is asymmetric and two tautomers are interconverted in aqueous solutions. In the present study, the effects of polar solvents on the H-bond in a zwitterionic hydrogen phthalate derivative 1 were investigated by quantum mechanics/molecular mechanics molecular dynamics (MD) simulations. The analyses of the trajectories for the methanol solution showed that the H-bonding proton tends to be located closer to the carboxylate group that forms fewer intermolecular H-bonds, than to the other carboxylate group and that the intramolecular proton transfer in 1 is triggered by the breakage and/or formation of an intermolecular H-bond. The enol form of dibenzoylmethane (2) also has a short H-bond, and the OH bond is reported to be rather long (>1.1 Å) in the crystal. In the present study, the effects of the solvent on the H-bond in 2 were investigated by molecular orbital (MO) calculations, MD simulations and nuclear magnetic resonance (NMR) spectroscopy. Density functional theory (DFT) calculations for 2 in vacuum indicated that the barrier height for the intramolecular proton transfer is almost the same as the zero-point energy of the vibrational ground state, resulting in broad distribution of the proton density along the H-bond, owing to the nuclear quantum effect. The OH distances were determined in CCl{sub 4}, acetonitrile, and dimethylsulfoxide solutions from the magnetic dipolar interactions between the {sup 17

The consequences of granulate heterogeneity towards breakage and attrition upon fluid-bed drying

NARCIS (Netherlands)

Nieuwmeyer, Florentine; Maarschalk, Kees van der Voort; Vromans, Herman

High-shear granulated lactose granulates were dried in it fluid-bed dryer at various conditions. Granules were characterized by water content and size analysis. It is shown that the drying process is very dynamic in terms of growth and breakage phenomena. Granular size heterogeneity, composition and

Ionisation and dissociation of water induced by swift multicharged ions; Etude de l'ionisation et de la dissociation d'H{sub 2}O induites par collision avec des ions multicharges rapides

Energy Technology Data Exchange (ETDEWEB)

Legendre, S

2006-02-15

Ionization and dissociation of water molecules and water clusters induced by 11.7 MeV/A Ni{sup 25+} ions were carried out by imaging techniques. Branching ratios, ionisation cross sections and Kinetic Energy Released distributions have been measured together with fragmentation dynamics studies. Multiple ionization represents approximately 30% of the ionizing events. Double ionization produces in significant way atomic oxygen, considered as a possible precursor of the large production of HO{sub 2} radical in liquid water radiolysis by ions of high Linear Energy Transfer. We evidence a strong selectivity of bond breakage in the case of ion-induced HOD fragmentation. Once the molecule doubly ionized, the breakage of the O-H bond is found 6.5 times more probable than that of the O-D bond. A semi-classical calculation simulating the fragmentation dynamics on the potential energy surface of the ground-state of di-cation H{sub 2}O{sup 2+} makes possible to as well reproduce the preferential nature of the breakage of the O-H bond as the position and the shift of the kinetic energy distributions. First results concerning interaction with water clusters are also reported. Measurements in coincidence are carried out giving access to correlation, with the distributions in energy and angle of the emitted fragments. Mass spectrum points fast intra-cluster proton transfer, leading to the emission of protonated clusters. (author)

Ionisation and dissociation of water induced by swift multicharged ions

International Nuclear Information System (INIS)

Legendre, S.

2006-02-01

Ionization and dissociation of water molecules and water clusters induced by 11.7 MeV/A Ni 25+ ions were carried out by imaging techniques. Branching ratios, ionisation cross sections and Kinetic Energy Released distributions have been measured together with fragmentation dynamics studies. Multiple ionization represents approximately 30% of the ionizing events. Double ionization produces in significant way atomic oxygen, considered as a possible precursor of the large production of HO 2 radical in liquid water radiolysis by ions of high Linear Energy Transfer. We evidence a strong selectivity of bond breakage in the case of ion-induced HOD fragmentation. Once the molecule doubly ionized, the breakage of the O-H bond is found 6.5 times more probable than that of the O-D bond. A semi-classical calculation simulating the fragmentation dynamics on the potential energy surface of the ground-state of di-cation H 2 O 2+ makes possible to as well reproduce the preferential nature of the breakage of the O-H bond as the position and the shift of the kinetic energy distributions. First results concerning interaction with water clusters are also reported. Measurements in coincidence are carried out giving access to correlation, with the distributions in energy and angle of the emitted fragments. Mass spectrum points fast intra-cluster proton transfer, leading to the emission of protonated clusters. (author)

Controllable synthesis of silver and silver sulfide nanocrystals via selective cleavage of chemical bonds

International Nuclear Information System (INIS)

Tang Aiwei; Wang Yu; Ye Haihang; Zhou Chao; Yang Chunhe; Li Xu; Peng Hongshang; Zhang Fujun; Hou Yanbing; Teng Feng

2013-01-01

A one-step colloidal process has been adopted to prepare silver (Ag) and silver sulfide (Ag 2 S) nanocrystals, thus avoiding presynthesis of an organometallic precursor and the injection of a toxic phosphine agent. During the reaction, a layered intermediate compound is first formed, which then acts as a precursor, decomposing into the nanocrystals. The composition of the as-obtained products can be controlled by selective cleavage of S–C bonds or Ag–S bonds. Pure Ag 2 S nanocrystals can be obtained by directly heating silver acetate (Ag(OAc)) and n-dodecanethiol (DDT) at 200 ° C without any surfactant, and pure Ag nanocrystals can be synthesized successfully if the reaction temperature is reduced to 190 ° C and the amount of DDT is decreased to 1 ml in the presence of a non-coordinating organic solvent (1-octadecene, ODE). Otherwise, the mixture of Ag and Ag 2 S is obtained by directly heating Ag(OAc) in DDT by increasing the reaction temperature or in a mixture of DDT and ODE at 200 ° C. The formation mechanism has been discussed in detail in terms of selective S–C and Ag–S bond dissociation due to the nucleophilic attack of DDT and the lower bonding energy of Ag–S. Interestingly, some products can easily self-assemble into two- or three-dimensional (2D or 3D) highly ordered superlattice structures on a copper grid without any additional steps. The excess DDT plays a key role in the superlattice structure due to the bundling and interdigitation of the thiolate molecules adsorbed on the as-obtained nanocrystals. (paper)

Simulation on breakage of heterogeneous materials caused by detonative loading; Bakugo shogeki ni yoru fukinshitsu zairyo no hakai gensho no simulation

Energy Technology Data Exchange (ETDEWEB)

Sassa, K; Watanabe, T; Ashida, Y [Kyoto University, Kyoto (Japan). Faculty of Engineering

1996-05-01

Investigations were conducted by simulation of breakage of inhomogeneous materials (rock) attributable to detonative loading, which simulation used the Days-2 Code. During the simulation, one-free-face blastings were used for testing a homogeneous structure, horizontal 2-layer structure, and horizontal 3-layer structure. Property values were assigned to the rocks on the assumption that they were sedimentary rocks such as sandstone or mudstone or hard rocks such as granite. As the result, it was found that a detonative loading resulted in shear failure in a sphere near the focus that was followed by radially developed cracks due to tension breakage, that more area is damaged in a soft rock than in a hard rock, that cracks due to breakage are produced by the overlapping of waves directly from the focus and those reflected from the free face in case of one-free-face blastings, that such cracks propagated along the soft rock layer in case there is a soft rock layer in a hard rock, but that breakage does not extend beyond the soft rock layer. 6 refs., 6 figs., 1 tab.

Metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting.

Science.gov (United States)

Xiang, Nan; Xin, Xian-Zhen; Chen, Jie; Wei, Bin

2012-06-01

This study was to evaluated the metal-ceramic bond strength of a Co-Cr dental alloy prepared using a selective laser melting (SLM) technique. Two groups comprised of twenty Co-Cr metal bars each were prepared using either a SLM or traditional lost-wax casting method. Ten bars from each group were moulded into standard ISO 9693:1999 dimensions of 25 mm × 3 mm × 0.5 mm with 1.1 mm of porcelain fused onto an 8 mm × 3 mm rectangular area in the centre of each bar. Metal-ceramic bonding was assessed using a three-point bending test. Fracture mode analysis and area fraction of adherence porcelain (AFAP) were determined by measuring Si content of specimens by SEM/EDS. Student's t-test within the groups demonstrated no significant difference for the mean bond strength between the SLM and traditional cast sample groups. While SEM/EDS analysis indicated a mixed fracture mode on the debonding interface of both the SLM and the cast groups, the SLM group showed significantly more porcelain adherence than the control group (p<0.05). The SLM metal-ceramic system exhibited a bonding strength that exceeds the requirement of ISO 9691:1999(E) and it even showed a better behaviour in porcelain adherence test comparable to traditional cast methods. Copyright © 2012 Elsevier Ltd. All rights reserved.

Selective Hydrogen Atom Abstraction through Induced Bond Polarization: Direct α-Arylation of Alcohols through Photoredox, HAT, and Nickel Catalysis.

Science.gov (United States)

Twilton, Jack; Christensen, Melodie; DiRocco, Daniel A; Ruck, Rebecca T; Davies, Ian W; MacMillan, David W C

2018-05-04

The combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid activation mode, has led to the development of an arylation method for the selective functionalization of alcohol α-hydroxy C-H bonds. This approach employs zinc-mediated alcohol deprotonation to activate α-hydroxy C-H bonds while simultaneously suppressing C-O bond formation by inhibiting the formation of nickel alkoxide species. The use of Zn-based Lewis acids also deactivates other hydridic bonds such as α-amino and α-oxy C-H bonds. This approach facilitates rapid access to benzylic alcohols, an important motif in drug discovery. A 3-step synthesis of the drug Prozac exemplifies the utility of this new method. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wear and breakage monitoring of cutting tools by an optical method: theory

Science.gov (United States)

Li, Jianfeng; Zhang, Yongqing; Chen, Fangrong; Tian, Zhiren; Wang, Yao

1996-10-01

An essential part of a machining system in the unmanned flexible manufacturing system, is the ability to automatically change out tools that are worn or damaged. An optoelectronic method for in situ monitoring of the flank wear and breakage of cutting tools is presented. A flank wear estimation system is implemented in a laboratory environment, and its performance is evaluated through turning experiments. The flank wear model parameters that need to be known a priori are determined through several preliminary experiments, or from data available in the literature. The resulting cutting conditions are typical of those used in finishing cutting operations. Through time and amplitude domain analysis of the cutting tool wear states and breakage states, it is found that the original signal digital specificity (sigma) 2x and the self correlation coefficient (rho) (m) can reflect the change regularity of the cutting tool wear and break are determined, but which is not enough due to the complexity of the wear and break procedure of cutting tools. Time series analysis and frequency spectrum analysis will be carried out, which will be described in the later papers.

Use of orthogonal field alternational gel electrophoresis (OFAGE) for studying DNA double strand breakage and repair

International Nuclear Information System (INIS)

Contopoulou, C.R.; Cook, V.; Mortimer, R.K.

1987-01-01

The study of DNA double strand breakage and repair has normally been carried by using neutral sucrose gradient or neutral elution techniques. The authors have applied OFAGE procedures to study x-ray induced double strand breaks and repair. Breakage of chromosomes is seen by a decrease in intensity of individual chromosome bands; as expected, this decrease becomes more pronounced as chromosome size increases. The fragments of broken chromosomes appears as a broad smear in the size range 100 kb to 1000 kb. Following repair, these fragments partially disappear and the chromosomal bands increase in intensity. In four repair deficient mutants, rad51, rad52, rad54, rad55, no increase in chromosomal band intensity was seen. These results have been confirmed by blotting for a specific chromosome

Incorrect condom use and frequent breakage among female sex workers and their clients.

Science.gov (United States)

Mukenge-Tshibaka, Léonard; Alary, Michel; Geraldo, Nassirou; Lowndes, Catherine M

2005-05-01

Our objective was to assess if female sex workers (FSWs) and their potential male clients in Cotonou, Benin, know how to use male condoms correctly. From April to June 2000, 314 FSWs and 208 men were interviewed, and asked to demonstrate on a wooden penis how they usually use male condoms. In all, 27.6% of both women and men tore the condom envelope on the notch; 89.3% of the women versus 75.4% of the men easily found the correct side; 17.3% of the women versus 28.3% of the men held the top of the condom to avoid air entering; 91.4% of the women versus 75.6% of the men correctly unrolled the condom. Taking all the four criteria together, only approximately 11% of participants performed a correct condom use demonstration. FSWs frequently reported condom breakage, which was significantly associated with incorrect condom demonstration (P = 0.04). Correct condom use is suboptimal in these heavy consumers of male condoms in Benin. Condom breakage is frequent and is associated with incorrect use.

Molecular targets, DNA breakage, DNA repair: Their roles in mutation induction in mammalian germ cells

International Nuclear Information System (INIS)

Sega, G.A.

1989-01-01

Variability in genetic sensitivity among different germ-cell stages in the mammal to various mutagens could be the result of how much chemical reaches the different stages, what molecular targets may be affected in the different stages and whether or not repair of lesions occurs. Several chemicals have been found to bind very strongly to protamine in late-spermatid and early-spermatozoa stages in the mouse. The chemicals also produce their greatest genetic damage in these same germ-cell stages. While chemical binding to DNA has not been correlated with the level of induced genetic damage, DNA breakage in the sensitive stages has been shown to increase. This DNA breakage is believed to indirectly result from chemical binding to sulfhydryl groups in protamine which prevents normal chromatin condensation within the sperm nucleus. 22 refs., 5 figs

An increase in pectin methyl esterase activity accompanies dormancy breakage and germination of yellow cedar seeds.

Science.gov (United States)

Ren, C; Kermode, A R

2000-09-01

Pectin methyl esterase (PME) (EC 3.1.1.11) catalyzes the hydrolysis of methylester groups of cell wall pectins. We investigated the role of this enzyme in dormancy termination and germination of yellow cedar (Chamaecyparis nootkatensis [D. Don] Spach) seeds. PME activity was not detected in dormant seeds of yellow cedar but was induced and gradually increased during moist chilling; high activity coincided with dormancy breakage and germination. PME activity was positively correlated to the degree of dormancy breakage of yellow cedar seeds. The enzyme produced in different seed parts and in seeds at different times during moist chilling, germination, and early post-germinative growth consisted of two isoforms, both basic with isoelectric points of 8.7 and 8.9 and the same molecular mass of 62 kD. The pH optimum for the enzyme was between 7.4 and 8.4. In intact yellow cedar seeds, activities of the two basic isoforms of PME that were induced in embryos and in megagametophytes following dormancy breakage were significantly suppressed by abscisic acid. Gibberellic acid had a stimulatory effect on the activities of these isoforms in embryos and megagametophytes of intact seeds at the germinative stage. We hypothesize that PME plays a role in weakening of the megagametophyte, allowing radicle emergence and the completion of germination.

Fibre Length Reduction in Natural Fibre-Reinforced Polymers during Compounding and Injection Moulding—Experiments Versus Numerical Prediction of Fibre Breakage

Directory of Open Access Journals (Sweden)

Katharina Albrecht

2018-03-01

Full Text Available To establish injection-moulded, natural fibre-reinforced polymers in the automotive industry, numerical simulations are important. To include the breakage behaviour of natural fibres in simulations, a profound understanding is necessary. In this study, the length and width reduction of flax and sisal fibre bundles were analysed experimentally during compounding and injection moulding. Further an optical analysis of the fibre breakage behaviour was performed via scanning electron microscopy and during fibre tensile testing with an ultra-high-speed camera. The fibre breakage of flax and sisal during injection moulding was modelled using a micromechanical model. The experimental and simulative results consistently show that during injection moulding the fibre length is not reduced further; the fibre length was already significantly reduced during compounding. For the mechanical properties of a fibre-reinforced composite it is important to overachieve the critical fibre length in the injection moulded component. The micromechanical model could be used to predict the necessary fibre length in the granules.

Unveiling of novel regio-selective fatty acid double bond hydratases from Lactobacillus acidophilus involved in the selective oxyfunctionalization of mono- and di-hydroxy fatty acids.

Science.gov (United States)

Kim, Kyoung-Rok; Oh, Hye-Jin; Park, Chul-Soon; Hong, Seung-Hye; Park, Ji-Young; Oh, Deok-Kun

2015-11-01

The aim of this study is the first time demonstration of cis-12 regio-selective linoleate double-bond hydratase. Hydroxylation of fatty acids, abundant feedstock in nature, is an emerging alternative route for many petroleum replaceable products thorough hydroxy fatty acids, carboxylic acids, and lactones. However, chemical route for selective hydroxylation is still quite challenging owing to low selectivity and many environmental concerns. Hydroxylation of fatty acids by hydroxy fatty acid forming enzymes is an important route for selective biocatalytic oxyfunctionalization of fatty acids. Therefore, novel fatty acid hydroxylation enzymes should be discovered. The two hydratase genes of Lactobacillus acidophilus were identified by genomic analysis, and the expressed two recombinant hydratases were identified as cis-9 and cis-12 double-bond selective linoleate hydratases by in vitro functional validation, including the identification of products and the determination of regio-selectivity, substrate specificity, and kinetic parameters. The two different linoleate hydratases were the involved enzymes in the 10,13-dihydroxyoctadecanoic acid biosynthesis. Linoleate 13-hydratase (LHT-13) selectively converted 10 mM linoleic acid to 13S-hydroxy-9(Z)-octadecenoic acid with high titer (8.1 mM) and yield (81%). Our study will expand knowledge for microbial fatty acid-hydroxylation enzymes and facilitate the designed production of the regio-selective hydroxy fatty acids for useful chemicals from polyunsaturated fatty acid feedstocks. © 2015 Wiley Periodicals, Inc.

Chemical and structural composition of Atlantic Canadian moose (Alces alces) incisors with patterns of high breakage

Energy Technology Data Exchange (ETDEWEB)

MacKenzie, Cynthia S. Kendall; Clough, Michael J. [Biology Department, Saint Mary' s University, Halifax, Nova Scotia, Canada B3H 3C3 (Canada); Broders, Hugh G., E-mail: hugh.broders@smu.ca [Biology Department, Saint Mary' s University, Halifax, Nova Scotia, Canada B3H 3C3 (Canada); Tubrett, Mike [Inco Innovation Centre, ICP-MS Facility, Memorial University of Newfoundland, P.O. Box 4200, St. John' s, Newfoundland, Canada A1C 5S7 (Canada)

2011-11-15

Analysis of mammalian teeth can provide information regarding local environmental conditions. For example, a high incidence of breakage and wear within a population may indicate poor food quality. Individuals consuming a diet causing high mechanical stress on their teeth, and/or lacking the appropriate minerals for proper development, could experience degradation of tooth condition. Previously, we documented a high rate of incisor tooth breakage, with age, in two genetically distinct moose populations in Atlantic Canada. In this study, multi-element ({sup 11}B, {sup 63}Cu, {sup 64}Zn, {sup 75}As, {sup 85}Rb, {sup 88}Sr, {sup 111}Cd, {sup 118}Sn, {sup 137}Ba, {sup 208}Pb, {sup 232}Th, and {sup 238}U) analyses using laser ablation ICP-MS were performed on moose incisors from multiple North American regions. The purpose was to determine whether the elemental composition of moose incisors varies among regions, and whether that variation is related to tooth degradation among Atlantic Canadian populations. A principal components analysis revealed that nearly 50% of the elemental variation in the inner enamel matrix of moose teeth was explained by three groupings of elements. The element groupings revealed differences among geographic regions, but did not explain the variation between incisors that were broken and those that were not. Regression models indicate that the elemental group which includes Cu, Pb, and Zn is related to decreases in incisal integrity. It is likely that other environmental factors contribute to the occurrence of increased incisor breakage in affected populations. The relationship between food resource quantity and quality, as a function of moose density, is hypothesized to explain loss of tooth integrity. - Highlights: {yields} Multi-element analysis of 1300 moose incisors using laser ablation ICP-MS. {yields} Three element groupings explain 50% of tooth composition variation among regions. {yields} Regional differences in tooth composition

Investigations into the molecular mechanism of chromatid breakage in the G2-phase of mammalian cells

International Nuclear Information System (INIS)

Bryant, P.E.; Armstrong, G.N.; Gray, L.; Frankenberg, D.; Mozdarani, H.

2003-01-01

Chromatid breakage following irradiation of cells in the G2-phase of the cell cycle results from the induction of DNA double-strand breaks (dsb). The conversion of dsb into chromatid breaks (cb) has a genetic basis, seemingly different from that of dsb rejoining. The variation in extent of this conversion is exemplified by the stiking variation in frequency of cb in irradiated cycling T-lymphocytes between different normal individuals. Elevated cb frequency in lymphocytes of around 40% of breast cancer patients and their first-degree relatives suggests the presence of mutations in low penetrance cancer predisposing genes that also affect conversion of dsb to cb. Investigation of the mechanism of chromatid radiosensitivity using genetically engineered rodent cell lines containing unique dsb break sites indicate that a single isolated dsb is sufficient to cause a cb. The single-event nature of chromatid breakage is confirmed by the fact that cb are induced as a linear function of radiation dose. Moreover, we have recently shown that ultrasoft carbon-K X-rays also induce chromatid breakage. In this case the energy of the secondary electrons produced by carbon-K X-rays is too low to span more than one DNA double helix, thus further supporting our conclusion that a single dsb is responsible for the formation of a cb. Chromatid breakage is thought to involve a rearrangement between DNA strands at the crossover points of chromatin loop(s) triggered by the presence of a dsb within the loop structure. The occasional observation of 'looped-out' sections of chromatin at cb sites supports this hypothesis. The occurrence of 'colour-switches' between FPG stained chromatids at a proportion of break sites (e.g. about 16% in CHO cells) shows that a significant proportion of cb definitely result from chromatin rearrangements. Measurements of altered colour-switch ratio (csr) in mutant rodent and human cells (irs1 and AT cells respectively) also indicate a genetic basis for the

R&D on dental implants breakage

Science.gov (United States)

Croitoru, Sorin Mihai; Popovici, Ion Alexandru

2017-09-01

Most used dental implants for human dental prostheses are of two steps type: first step means implantation and, after several months healing and osseointegration, second step is prosthesis fixture. For sure, dental implants and prostheses are meant to last for a lifetime. Still, there are unfortunate cases when dental implants break. This paper studies two steps dental implants breakage and proposes a set of instruments for replacement and restoration of the broken implant. First part of the paper sets the input data of the study: structure of the studied two steps dental implants based on two Romanian patents and values of the loading forces found in practice and specialty papers. In the second part of the paper, using DEFORM 2D™ FEM simulation software, worst case scenarios of loading dental implants are studied in order to determine which zones and components of the dental implant set are affected (broken). Last part of the paper is dedicated to design and presentation of a set for extracting and cutting tools used to restore the broken implant set.

Electro-mechanical behaviors of composite superconducting strand with filament breakage

International Nuclear Information System (INIS)

Wang, Xu; Gao, Yuanwen; Zhou, Youhe

2016-01-01

Highlights: • The electromechanical behaviors of the superconducting (SC) strand are investigated. • A 3D FEM model for bending behaviors and electric properties of strand is developed. • The influence of breakage of filaments on the critical current of SC strand is calculated. • The impact of current transfer length on the electric properties of SC strand is discussed. - Abstract: The bending behaviors of superconducting strand with typical multi-filament twist configuration are investigated based on a three-dimensional finite element method (FEM) model, named as the Multi-filament twist model, of the strand. In this 3D FEM model, the impacts of initial thermal residual stress, filament-breakage and its evaluation are taken into accounts. The mechanical responses of the strand under bending load are studied with the factors taken into consideration one by one. The distribution of the damage of the filaments and its evolution and the movement of the neutral axis caused by it are studied and displayed in detail. Besides, taking the advantages of the Multi-filament twist model, the normalized critical current of the strand under bending load is also calculated based on the invariant temperature and field strain functions. In addition, the non-negligible influences of the pitch length of the filaments on both the mechanical behaviors and the normalized critical current are discussed. The stress-strain characteristics of the strand under tensile load and the normalized critical current of it under axial and bending loads resulting from the Multi-filament twist model show good agreement with the experimental data.

Electro-mechanical behaviors of composite superconducting strand with filament breakage

Energy Technology Data Exchange (ETDEWEB)

Wang, Xu [Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, Lanzhou, Gansu 730000 (China); Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China); Gao, Yuanwen, E-mail: ywgao@lzu.edu.cn [Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, Lanzhou, Gansu 730000 (China); Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China); Zhou, Youhe [Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, Lanzhou, Gansu 730000 (China); Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

2016-10-15

Highlights: • The electromechanical behaviors of the superconducting (SC) strand are investigated. • A 3D FEM model for bending behaviors and electric properties of strand is developed. • The influence of breakage of filaments on the critical current of SC strand is calculated. • The impact of current transfer length on the electric properties of SC strand is discussed. - Abstract: The bending behaviors of superconducting strand with typical multi-filament twist configuration are investigated based on a three-dimensional finite element method (FEM) model, named as the Multi-filament twist model, of the strand. In this 3D FEM model, the impacts of initial thermal residual stress, filament-breakage and its evaluation are taken into accounts. The mechanical responses of the strand under bending load are studied with the factors taken into consideration one by one. The distribution of the damage of the filaments and its evolution and the movement of the neutral axis caused by it are studied and displayed in detail. Besides, taking the advantages of the Multi-filament twist model, the normalized critical current of the strand under bending load is also calculated based on the invariant temperature and field strain functions. In addition, the non-negligible influences of the pitch length of the filaments on both the mechanical behaviors and the normalized critical current are discussed. The stress-strain characteristics of the strand under tensile load and the normalized critical current of it under axial and bending loads resulting from the Multi-filament twist model show good agreement with the experimental data.

Condom Use: Slippage, Breakage, and Steps for Proper Use among Adolescents in Alternative School Settings

Science.gov (United States)

Coyle, Karin K.; Franks, Heather M.; Glassman, Jill R.; Stanoff, Nicole M.

2012-01-01

Background: School-based human immunodeficiency virus (HIV)/sexually transmitted infection (STI), and pregnancy prevention programs often focus on consistent and correct condom use. Research on adolescents' experience using condoms, including condom slippage/breakage, is limited. This exploratory study examines proper condom use and the…

Force deficits and breakage rates after single lengthening contractions of single fast fibers from unconditioned and conditioned muscles of young and old rats.

Science.gov (United States)

Lynch, Gordon S; Faulkner, John A; Brooks, Susan V

2008-07-01

The deficit in force generation is a measure of the magnitude of damage to sarcomeres caused by lengthening contractions of either single fibers or whole muscles. In addition, permeabilized single fibers may suffer breakages. Our goal was to understand the interaction between breakages and force deficits in "young" and "old" permeabilized single fibers from control muscles of young and old rats and "conditioned" fibers from muscles that completed a 6-wk program of in vivo lengthening contractions. Following single lengthening contractions of old-control fibers compared with young-control fibers, the twofold greater force deficits at a 10% strain support the concept of an age-related increase in the susceptibility of fibers to mechanical damage. In addition, the much higher breakage rates for old fibers at all strains tested indicate an increase with aging in the number of fibers at risk of being severely injured during any given stretch. Following the 6-wk program of lengthening contractions, young-conditioned fibers and old-conditioned fibers were not different with respect to force deficit or the frequency of breakages. A potential mechanism for the increased resistance to stretch-induced damage of old-conditioned fibers is that, through intracellular damage and subsequent degeneration and regeneration, weaker sarcomeres were replaced by stronger sarcomeres. These data indicate that, despite the association of high fiber breakage rates and large force deficits with aging, the detrimental characteristics of old fibers were improved by a conditioning program that altered both sarcomeric characteristics as well as the overall structural integrity of the fibers.

Increased chromosomal breakage in Tourette syndrome predicts the possibility of variable multiple gene involvement in spectrum phenotypes: Preliminary findings and hypothesis

Energy Technology Data Exchange (ETDEWEB)

Gericke, G.S.; Simonic, I.; Cloete, E.; Buckle, C. [Univ. of Pretoria (South Africa)] [and others

1995-10-09

Increased chromosomal breakage was found in 12 patients with DSM-IV Tourette syndrome (TS) as compared with 10 non-TS control individuals with respect to untreated, modified RPM1-, and BrdU treated lymphocyte cultures (P < 0.001 in each category). A hypothesis is proposed that a major TS gene is probably connected to genetic instability, and associated chromosomal marker sites may be indicative of the localization of secondary genes whose altered expression could be responsible for associated comorbid conditions. This concept implies that genes influencing higher brain functions may be situated at or near highly recombigenic areas allowing enhanced amplification, duplication and recombination following chromosomal strand breakage. Further studies on a larger sample size are required to confirm the findings relating to chromosomal breakage and to analyze the possible implications for a paradigmatic shift in linkage strategy for complex disorders by focusing on areas at or near unstable chromosomal marker sites. 32 refs., 1 tab.

The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds.

Science.gov (United States)

Kelsen, Vinciane; Wendt, Bianca; Werkmeister, Svenja; Junge, Kathrin; Beller, Matthias; Chaudret, Bruno

2013-04-28

The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and C=X bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for C=O bond hydrogenation.

Glutamic Acid Selective Chemical Cleavage of Peptide Bonds.

Science.gov (United States)

Nalbone, Joseph M; Lahankar, Neelam; Buissereth, Lyssa; Raj, Monika

2016-03-04

Site-specific hydrolysis of peptide bonds at glutamic acid under neutral aqueous conditions is reported. The method relies on the activation of the backbone amide chain at glutamic acid by the formation of a pyroglutamyl (pGlu) imide moiety. This activation increases the susceptibility of a peptide bond toward hydrolysis. The method is highly specific and demonstrates broad substrate scope including cleavage of various bioactive peptides with unnatural amino acid residues, which are unsuitable substrates for enzymatic hydrolysis.

Hair breakage as a presenting sign of early or occult central centrifugal cicatricial alopecia: clinicopathologic findings in 9 patients.

Science.gov (United States)

Callender, Valerie D; Wright, Dakara Rucker; Davis, Erica C; Sperling, Leonard C

2012-09-01

Central centrifugal cicatricial alopecia is the most common form of cicatricial alopecia in African American women. Treatment options are limited and mostly aimed at halting further hair loss but rarely result in hair regrowth. Therefore, it is important to recognize early clinical signs, perform a confirmatory biopsy, and begin treatment promptly. We have observed that hair breakage may be a key sign of early central centrifugal cicatricial alopecia, and this association is not clearly described in the literature. Nine patients with hair breakage on the vertex with or without scalp symptoms underwent scalp biopsies as part of their evaluation. Of these, 8 had histologic samples adequate for complete interpretation: 5 specimens (63%) showed histologic changes typical of central centrifugal cicatricial alopecia, with 1 of these showing advanced end-stage changes of cicatricial alopecia. Two (25%) revealed premature desquamation of the inner root sheath as the sole finding suggestive of early central centrifugal cicatricial alopecia and 1 (13%) was normal. Although hair breakage can have multiple causes, early central centrifugal cicatricial alopecia must be considered in the differential diagnosis, particularly in women of African ancestry. Histologic evaluation may reveal early or late findings that can help establish the diagnosis.

Hydration dynamics of a lipid membrane: Hydrogen bond networks and lipid-lipid associations

Science.gov (United States)

Srivastava, Abhinav; Debnath, Ananya

2018-03-01

Dynamics of hydration layers of a dimyristoylphosphatidylcholine (DMPC) bilayer are investigated using an all atom molecular dynamics simulation. Based upon the geometric criteria, continuously residing interface water molecules which form hydrogen bonds solely among themselves and then concertedly hydrogen bonded to carbonyl, phosphate, and glycerol head groups of DMPC are identified. The interface water hydrogen bonded to lipids shows slower relaxation rates for translational and rotational dynamics compared to that of the bulk water and is found to follow sub-diffusive and non-diffusive behaviors, respectively. The mean square displacements and the reorientational auto-correlation functions are slowest for the interfacial waters hydrogen bonded to the carbonyl oxygen since these are buried deep in the hydrophobic core among all interfacial water studied. The intermittent hydrogen bond auto-correlation functions are calculated, which allows breaking and reformations of the hydrogen bonds. The auto-correlation functions for interfacial hydrogen bonded networks develop humps during a transition from cage-like motion to eventual power law behavior of t-3/2. The asymptotic t-3/2 behavior indicates translational diffusion dictated dynamics during hydrogen bond breaking and formation irrespective of the nature of the chemical confinement. Employing reactive flux correlation analysis, the forward rate constant of hydrogen bond breaking and formation is calculated which is used to obtain Gibbs energy of activation of the hydrogen bond breaking. The relaxation rates of the networks buried in the hydrophobic core are slower than the networks near the lipid-water interface which is again slower than bulk due to the higher Gibbs energy of activation. Since hydrogen bond breakage follows a translational diffusion dictated mechanism, chemically confined hydrogen bond networks need an activation energy to diffuse through water depleted hydrophobic environments. Our calculations

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.

Purification, crystallization and preliminary X-ray diffraction experiments on the breakage-reunion domain of the DNA gyrase from Mycobacterium tuberculosis

International Nuclear Information System (INIS)

Piton, Jérémie; Matrat, Stéphanie; Petrella, Stéphanie; Jarlier, Vincent; Aubry, Alexandra; Mayer, Claudine

2009-01-01

The breakage-reunion domain of M. tuberculosis DNA gyrase was crystallized using the hanging-drop vapour-diffusion method. One of the four crystal forms obtained belonged to space group C2 and diffraction data were collected to a resolution of 2.7 Å. Mycobacterium tuberculosis DNA gyrase, a nanomachine that is involved in the regulation of DNA topology, is the only type II topoisomerase present in this organism and hence is the sole target for fluoroquinolone action. The breakage-reunion domain of the A subunit plays an essential role in DNA binding during the catalytic cycle. Two constructs of 53 and 57 kDa (termed GA53BK and GA57BK) corresponding to this domain have been overproduced, purified and crystallized. Diffraction data were collected from four crystal forms. The resolution limits ranged from 4.6 to 2.7 Å depending on the crystal form. The best diffracting crystals belonged to space group C2, with a biological dimer in the asymmetric unit. This is the first report of the crystallization and preliminary X-ray diffraction analysis of the breakage-reunion domain of DNA gyrase from a species containing one unique type II topoisomerase

Comparison of the bond strength of ceramics to Co-Cr alloys made by casting and selective laser melting.

Science.gov (United States)

Lawaf, Shirin; Nasermostofi, Shahbaz; Afradeh, Mahtasadat; Azizi, Arash

2017-02-01

Considering the importance of metal-ceramic bond, the present study aimed to compare the bond strength of ceramics to cobalt-chrome (Co-Cr) alloys made by casting and selective laser melting (SLM). In this in-vitro experimental study, two sample groups were prepared, with one group comprising of 10 Co-Cr metal frameworks fabricated by SLM method and the other of 10 Co-Cr metal frameworks fabricated by lost wax cast method with the dimensions of 0.5 × 3 × 25 mm (following ISO standard 9693). Porcelain with the thickness of 1.1 mm was applied on a 3 × 8-mm central rectangular area of each sample. Afterwards, bond strengths of the samples were assessed with a Universal Testing Machine. Statistical analysis was performed with Kolmogorov-Smirnov test and T-test. Bond strength in the conventionally cast group equaled 74.94 ± 16.06 MPa, while in SLM group, it equaled 69.02 ± 5.77 MPa. The difference was not statistically significant ( P ≤ .05). The results indicated that the bond strengths between ceramic and Co-Cr alloys made by casting and SLM methods were not statistically different.

Tooth breakage in patients injected with 224Ra

International Nuclear Information System (INIS)

Sonnabend, E.; Spiess, H.; Mays, C.W.

1986-01-01

Tooth breakage has been common among the 224 Ra patients, especially those injected as teenagers. The fracture of 1 or more teeth was reported by 26% (8/31) of boys and 23% (7/30) of girls injected with 224 Ra at 16-20 years of age. Combining results from all age groups, the incidence of tooth fractures increased significantly with dose (P=0.01). Unlike the normal loss of permanent teeth by periodontal disease, in which the entire tooth is lost, the tooth loss following 224 Ra injection was primarily from tooth resorption near the gum line causing the tooth crowns to break off easily. Eventually the tooth roots may either become incorporated into the jawbone or are resorbed and replaced with bone. These tooth fractures resembled those observed in the U.S. radium dial painters and in dogs injected with bone-seeking α-emitters. (orig.)

Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

Energy Technology Data Exchange (ETDEWEB)

Colby, Denise; Bergman, Robert; Ellman, Jonathan

2010-05-13

Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

Comparison of Selected Parameters of Redox Homeostasis in Patients with Ataxia-Telangiectasia and Nijmegen Breakage Syndrome

Directory of Open Access Journals (Sweden)

Barbara Pietrucha

2017-01-01

Full Text Available This study compared the antioxidant status and major lipophilic antioxidants in patients with ataxia-telangiectasia (AT and Nijmegen breakage syndrome (NBS. Total antioxidant status (TAS, total oxidant status (TOS, oxidative stress index (OSI, and concentrations of coenzyme Q10 (CoQ10 and vitamins A and E were estimated in the plasma of 22 patients with AT, 12 children with NBS, and the healthy controls. In AT patients, TAS (median 261.7 μmol/L was statistically lower but TOS (496.8 μmol/L was significantly elevated in comparison with the healthy group (312.7 μmol/L and 311.2 μmol/L, resp.. Tocopherol (0.8 μg/mL and CoQ10 (0.1 μg/mL were reduced in AT patients versus control (1.4 μg/mL and 0.3 μg/mL, resp.. NBS patients also displayed statistically lower TAS levels (290.3 μmol/L, while TOS (404.8 μmol/L was comparable to the controls. We found that in NBS patients retinol concentration (0.1 μg/mL was highly elevated and CoQ10 (0.1 μg/mL was significantly lower in comparison with those in the healthy group. Our study confirms disturbances in redox homeostasis in AT and NBS patients and indicates a need for diagnosing oxidative stress in those cases as a potential disease biomarker. Decreased CoQ10 concentration found in NBS and AT indicates a need for possible supplementation.

Breakage and drying behaviour of granules in a continuous fluid bed dryer: Influence of process parameters and wet granule transfer.

Science.gov (United States)

De Leersnyder, F; Vanhoorne, V; Bekaert, H; Vercruysse, J; Ghijs, M; Bostijn, N; Verstraeten, M; Cappuyns, P; Van Assche, I; Vander Heyden, Y; Ziemons, E; Remon, J P; Nopens, I; Vervaet, C; De Beer, T

2018-03-30

Although twin screw granulation has already been widely studied in recent years, only few studies addressed the subsequent continuous drying which is required after wet granulation and still suffers from a lack of detailed understanding. The latter is important for optimisation and control and, hence, a cost-effective practical implementation. Therefore, the aim of the current study is to increase understanding of the drying kinetics and the breakage and attrition phenomena during fluid bed drying after continuous twin screw granulation. Experiments were performed on a continuous manufacturing line consisting of a twin-screw granulator, a six-segmented fluid bed dryer, a mill, a lubricant blender and a tablet press. Granulation parameters were fixed in order to only examine the effect of drying parameters (filling time, drying time, air flow, drying air temperature) on the size distribution and moisture content of granules (both of the entire granulate and of size fractions). The wet granules were transferred either gravimetrically or pneumatically from the granulator exit to the fluid bed dryer. After a certain drying time, the moisture content reached an equilibrium. This drying time was found to depend on the applied airflow, drying air temperature and filling time. The moisture content of the granules decreased with an increasing drying time, airflow and drying temperature. Although smaller granules dried faster, the multimodal particle size distribution of the granules did not compromise uniform drying of the granules when the target moisture content was achieved. Extensive breakage of granules was observed during drying. Especially wet granules were prone to breakage and attrition during pneumatic transport, either in the wet transfer line or in the dry transfer line. Breakage and attrition of granules during transport and drying should be anticipated early on during process and formulation development by performing integrated experiments on the granulator

Chromosomal Instability and Molecular Defects in Induced Pluripotent Stem Cells from Nijmegen Breakage Syndrome Patients

Directory of Open Access Journals (Sweden)

Tomer Halevy

2016-08-01

Full Text Available Nijmegen breakage syndrome (NBS results from the absence of the NBS1 protein, responsible for detection of DNA double-strand breaks (DSBs. NBS is characterized by microcephaly, growth retardation, immunodeficiency, and cancer predisposition. Here, we show successful reprogramming of NBS fibroblasts into induced pluripotent stem cells (NBS-iPSCs. Our data suggest a strong selection for karyotypically normal fibroblasts to go through the reprogramming process. NBS-iPSCs then acquire numerous chromosomal aberrations and show a delayed response to DSB induction. Furthermore, NBS-iPSCs display slower growth, mitotic inhibition, a reduced apoptotic response to stress, and abnormal cell-cycle-related gene expression. Importantly, NBS neural progenitor cells (NBS-NPCs show downregulation of neural developmental genes, which seems to be mediated by P53. Our results demonstrate the importance of NBS1 in early human development, shed light on the molecular mechanisms underlying this severe syndrome, and further expand our knowledge of the genomic stress cells experience during the reprogramming process.

Comparative evaluation of shear bond strength of metallic brackets bonded with two different bonding agents under dry conditions and with saliva contamination.

Science.gov (United States)

Khanehmasjedi, Mashallah; Naseri, Mohammad Ali; Khanehmasjedi, Samaneh; Basir, Leila

2017-02-01

This study compared the shear bond strength of metallic brackets bonded with Single Bond and Assure bonding agents under dry and saliva-contamination conditions. Sixty sound premolar teeth were selected, and stainless-steel brackets were bonded on enamel surfaces with Single Bond and Assure bonding agents under dry condition or with saliva contamination. Shear bond strength values of brackets were measured in a universal testing machine. The adhesive remnant index scores were determined after debonding of the brackets under a stereomicroscope. One-way analysis of variance (ANOVA) was used to analyze bond strength. Two-by-two comparisons were made with post hoc Tukey tests (pbrackets to tooth structure were 9.29±8.56 MPa and 21.25±8.93 MPa with the use of Assure resin bonding agent under saliva-contamination and dry conditions, respectively. These values were 10.13±6.69 MPa and 14.09±6.6 MPa, respectively, under the same conditions with the use of Single Bond adhesive. Contamination with saliva resulted in a significant decrease in the bond strength of brackets to tooth structure with the application of Assure adhesive resin (pbrackets to tooth structures. Contamination with saliva significantly decreased the bond strength of Assure bonding agent compared with dry conditions. Copyright © 2016. Published by Elsevier Taiwan LLC.

In vitro Comparative Evaluation of Tensile Bond Strength of 6(th), 7(th) and 8(th) Generation Dentin Bonding Agents.

Science.gov (United States)

Kamble, Suresh S; Kandasamy, Baburajan; Thillaigovindan, Ranjani; Goyal, Nitin Kumar; Talukdar, Pratim; Seal, Mukut

2015-05-01

Newer dentin bonding agents were developed to improve the quality of composite restoration and to reduce time consumption in its application. The aim of the present study was to evaluate tensile bond strength of 6(th), 7(th) and 8(th) generation bonding agents by in vitro method. Selected 60 permanent teeth were assigned into 20 in each group (Group I: 6(th) generation bonding agent-Adper SE plus 3M ESPE, Group II: 7(th) generation bonding agent-G-Bond GC Corp Japan and Group III: 8(th) generation dentin adhesives-FuturaBond, DC, Voco, Germany). With high-speed diamond disc, coronal dentin was exposed, and selected dentin bonding agents were applied, followed by composite restoration. All samples were saved in saline for 24 h and tensile bond strength testing was done using a universal testing machine. The obtained data were tabulated and statistically analyzed using ANOVA test. The tensile bond strength readings for 6(th) generation bonding agent was 32.2465, for 7(th) generation was 31.6734, and for 8(th)-generation dentine bonding agent was 34.74431. The highest tensile bond strength was seen in 8(th) generation bonding agent compared to 6(th) and 7(th) generation bonding agents. From the present study it can be conclude that 8(th) generation dentine adhesive (Futura DC, Voco, Germany) resulted in highest tensile bond strength compared to 6(th) (Adper SE plus, 3M ESPE) and 7(th) generation (G-Bond) dentin bonding agents.

Toughening elastomers with sacrificial bonds and watching them break

Science.gov (United States)

Creton, Costantino

2014-03-01

Most unfilled elastomers are relatively brittle, in particular when the average molecular weight between crosslinks is lower than the average molecular weight between entanglements. We created a new class of tough elastomers by introducing isotropically prestretched chains inside ordinary acrylic elastomers by successive swelling and polymerization steps. These new materials combine a high entanglement density with a densely crosslinked structure reaching elastic moduli of 4 MPa and fracture strength of 25 MPa. The highly prestretched chains are the minority in the material and can break in the bulk of the material before catastrophic failure occurs, increasing the toughness of the material by two orders of magnitude up to 5 kJ/m2. To investigate the details of the toughening mechanism we introduced specific sacrificial dioxetane bonds in the prestretched chains that emit light when they break. In uniaxial extension cyclic experiments, we checked that the light emission corresponded exactly and quantitatively to the energy dissipation in each cycle demonstrating that short chains break first and long chains later. We then watched crack propagation in notched samples and mapped spatially the location of bond breakage ahead of the crack tip before and during propagation. This new toughening mechanism for elastomers creates superentangled rubbers and is ideally suited to overcome the trade-off between toughness and stiffness of ordinary elastomers. We gratefully acknowledge funding from DSM Ahead

Cellular DNA breakage by soy isoflavone genistein and its methylated structural analogue biochanin A.

Science.gov (United States)

Ullah, Mohd Fahad; Shamim, Uzma; Hanif, Sarmad; Azmi, Asfar S; Hadi, Sheikh M

2009-11-01

Epidemiological studies have indicated that populations with high isoflavone intake through soy consumption have lower rates of breast, prostate, and colon cancer. The isoflavone polyphenol genistein in soybean is considered to be a potent chemopreventive agent against cancer. In order to explore the chemical basis of chemopreventive activity of genistein, in this paper we have examined the structure-activity relationship between genistein and its structural analogue biochanin A. We show that both genistein and its methylated derivative biochanin A are able to mobilize nuclear copper in human lymphocyte, leading to degradation of cellular DNA. However, the relative rate of DNA breakage was greater in the case of genistein. Further, the cellular DNA degradation was inhibited by copper chelator (neocuproine/bathocuproine) but not by compounds that specifically bind iron and zinc (desferrioxamine mesylate and histidine, respectively). We also compared the antioxidant activity of the two isoflavones against tert-butylhydroperoxide-induced oxidative breakage in lymphocytes. Again genistein was found to be more effective than biochanin A in providing protection against oxidative stress induced by tert-butylhydroperoxide. It would therefore appear that the structural features of isoflavones that are important for antioxidant properties are also the ones that contribute to their pro-oxidant action through a mechanism that involves redox cycling of chromatin-bound nuclear copper.

Control of HOD photodissociation dynamics via bond-selective infrared multiphoton excitation and a femtosecond ultraviolet laser pulse

DEFF Research Database (Denmark)

Amstrup, Bjarne; Henriksen, Niels Engholm

1992-01-01

moment, excites the molecule to a dissociative electronic state. We consider the HOD molecule which is ideal due to the local mode structure of the vibrational states. It is shown that selective and localized bond stretching can be created in simple laser fields. When such a nonstationary vibrating HOD...... molecule is photodissociated with a short laser pulse (~5 fs) complete selectivity between the channels H+OD and D+OH is observed over the entire absorption band covering these channels. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

A Global Stock and Bond Model

OpenAIRE

Connor, Gregory

1996-01-01

Factor models are now widely used to support asset selection decisions. Global asset allocation, the allocation between stocks versus bonds and among nations, usually relies instead on correlation analysis of international equity and bond indexes. It would be preferable to have a single integrated framework for both asset selection and asset allocation. This framework would require a factor model applicable at an asset or country level, as well as at a global level,...

Relation between plasmons and the valence-band density-of-states in polymethylmethacrylate - influence of ion irradiation on damage selectivity

International Nuclear Information System (INIS)

Moliton, J.P.; Jussiaux, C.; Trigaud, T.; Lazzaroni, R.; Lhost, O.; Bredas, J.L.; Kihn, Y.; Sevely, J.

1996-01-01

A physical model is presented that aims at rationalizing the selectivity of bond breakage observed when polymethylmethacrylate is irradiated by ions in the 10-500 keV energy range. This model, previously proposed by Brandt and Ritchie, is based on electronic collective effects. The coupling between the pure plasma oscillation at omega(p) and the oscillation of free electrons at [omega(k0)(2)](1/2) makes the whole electronic population resonant at the frequency omega(rp) = (omega(p)(2) + [omega(k0)(2)])(1/2). By computing the valence-band density of states, we calculate [omega(k0)(2)] and then deduce the theoretical value of omega(rp). On the other hand, we provide an experimental measurement of omega(rp) and study its dependence on ion fluence by electron-energy-loss spectroscopy. The validity of the model of Brandt and Ritchie is then discussed in the light of both theoretical and experimental data. (author)

Two-dimensional gold nanostructures with high activity for selective oxidation of carbon–hydrogen bonds

KAUST Repository

Wang, Liang

2015-04-22

Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic. Here we report the facile synthesis of 2D gold nanosheets via a wet chemistry method, by using layered double hydroxide as the template. Detailed characterization with electron microscopy and X-ray photoelectron spectroscopy demonstrates that the nanosheets are negatively charged and [001] oriented with thicknesses varying from single to a few atomic layers. X-ray absorption spectroscopy reveals unusually low gold–gold coordination numbers. These gold nanosheets exhibit high catalytic activity and stability in the solvent-free selective oxidation of carbon–hydrogen bonds with molecular oxygen.

Two-dimensional gold nanostructures with high activity for selective oxidation of carbon-hydrogen bonds

Science.gov (United States)

Wang, Liang; Zhu, Yihan; Wang, Jian-Qiang; Liu, Fudong; Huang, Jianfeng; Meng, Xiangju; Basset, Jean-Marie; Han, Yu; Xiao, Feng-Shou

2015-04-01

Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic. Here we report the facile synthesis of 2D gold nanosheets via a wet chemistry method, by using layered double hydroxide as the template. Detailed characterization with electron microscopy and X-ray photoelectron spectroscopy demonstrates that the nanosheets are negatively charged and [001] oriented with thicknesses varying from single to a few atomic layers. X-ray absorption spectroscopy reveals unusually low gold-gold coordination numbers. These gold nanosheets exhibit high catalytic activity and stability in the solvent-free selective oxidation of carbon-hydrogen bonds with molecular oxygen.

When, where and how the bridge breaks: anaphase bridge breakage plays a crucial role in gene amplification and HSR generation

International Nuclear Information System (INIS)

Shimizu, Noriaki; Shingaki, Kenta; Kaneko-Sasaguri, Yukiko; Hashizume, Toshihiko; Kanda, Teru

2005-01-01

Amplified genes are frequently localized on extrachromosomal double minutes (DMs) or in chromosomal homogenously staining regions (HSRs). We previously showed that a plasmid bearing a mammalian replication initiation region could efficiently generate DMs and HSRs after transfection into human tumor cell lines. The Breakage-Fusion-Bridge (BFB) cycle model, a classical model that explains how HSRs form, could also be used to explain how the transfected plasmids generate HSRs. The BFB cycle model involves anaphase bridge formation due to the presence of dicentric chromosomes, followed by the breakage of the bridge. In this study, we used our plasmid-based model system to analyze how anaphase bridges break during mitosis. Dual-color fluorescence in situ hybridization analyses revealed that anaphase bridges were most frequently severed in their middle irrespective of their lengths, which suggests that a structurally fragile site exists in the middle of the anaphase bridge. Breakage of the chromosomal bridges occurred prior to nuclear membrane reformation and the completion of cytokinesis, which indicates that mechanical tension rather than cytokinesis is primarily responsible for severing anaphase bridges. Time-lapse observation of living cells revealed that the bridges rapidly shrink after being severed. If HSR length was extended too far, the bridge could no longer be resolved and became tangled depending on the tension. The unbroken bridge appeared to inhibit the completion of cytokinesis. These observations strongly suggest that anaphase bridges are highly elastic and that the length of the spindle axis determines the maximal HSR length

[Correlation of single-cell gel electrophoresis and mitomycin C-induced chromosomal breakage for chromosomal instabiligy in children with Fanconi anemia].

Science.gov (United States)

Zhang, Li; Liu, Qiang; Zou, Yao; Liu, Xiao-ming; Zhang, Jia-yuan; Wang, Shu-chun; Chen, Xiao-juan; Guo, Ye; Yang, Wen-yu; Ruan, Min; Liu, Tian-feng; Liu, Fang; Cai, Xiao-jin; Chen, Yu-mei; Zhu, Xiao-fan

2013-02-01

Fanconi anemia (FA) is characterized by bone marrow failure, congenital abnormalities and predisposition to neoplasia. Hypersensitivity of FA cells to the clastogenic effect of mitomycin C (MMC) provides a unique marker for the diagnosis before the beginning of hematological manifestations. The aim of this study was to evaluate the relationship between Single-Cell Gel Electrophoresis (SCGE) and mitomycin C-induced chromosomal breakage in children with FA. Between January 2007 and June 2011, 248 children (results of the two methods and compared with each other. The receiver operating characteristic (ROC) curve was used to evaluate the parameters in SCGE. Seventeen patients were diagnosed as FA and 231 as non-FA. Chromosomal breakage was found to be significantly higher in FA patients [(32.2 ± 4.8)%] than non-FA [(19.9 ± 3.0)%] and controls[(21.6 ± 4.8)%] when induced by MMC 80 ng/ml. The parameters of SCGE were significantly different between FA patients and non-FA or controls. All the parameters were rectilinearly correlated with MMC (P = 0.000). The most closely correlated parameter was the rate of comet cell (r = 0.848, P = 0.000). The results of ROC curves suggested the comet cell rate (0.999) was more important. SCGE might be used to discriminate between FA and non-FA individuals. The relationship between SCGE and MMC-induced chromosomal breakage was significant. The rate of comet cell was the important parameter.

Quantification of the selective activation of C--H bonds in short chain alkanes: The reactivity of ethane, propane, isobutane, n-butane, and neopentane on Ir(111)

International Nuclear Information System (INIS)

Johnson, D.F.; Weinberg, W.H.

1995-01-01

The initial probabilities of precursor-mediated, dissociative chemisorption of the saturated hydrocarbons 13 C-labeled ethane, propane, isobutane, n-butane, and neopentane on the close-packed Ir(111) surface have been measured. The selective activation of primary (1 degree), secondary (2 degree), and tertiary (3 degree) C--H bonds has been quantified by examining the reactivities of the selectively deuterated isotopomers of propane, C 3 H 8 , CH 3 CD 2 CH 3 , and C 3 D 8 , and of isobutane, (CH 3 ) 3 CH, (CH 3 ) 3 CD, and (CD 3 ) 3 CH. With respect to the bottom of the physically adsorbed well for each hydrocarbon, the apparent C--H bond activation energies have been found to be 10.4±0.3 kcal/mol (ethane), 11.4±0.3 kcal/mol (propane), 11.5±0.3 kcal/mol (n-butane), 11.3±0.3 kcal/mol (i-butane), and 11.3±0.3 kcal/mol (neopentane). For all the alkanes examined, the ratios of the preexponential factors of the rate coefficients of reaction and desorption are 1x10 -2 . The C--D bond activation energies are higher than the corresponding C--H bond activation energies by 480 cal/mol (ethane), 630 cal/mol (propane), and 660 cal/mol (i-butane). By analyzing the primary kinetic isotope effects for the selectively deuterated isotopomers of propane and isobutane, the 2 degree C--H bond activation energy is found to be 310±160 cal/mol less than the 1 degree C--H bond activation energy on this surface, and similarly, 3 degree C--H bond cleavage is less by 80±70 cal/mol. The quantification of the branching ratios within the C--H bond activation channel for propane and isobutane on this surface shows that the formation of 1 degree-alkyl intermediates is, in general, favored over the formation of either 2 degree- or 3 degree-alkyl intermediates. (Abstract Truncated)

Understanding Boron through Size-Selected Clusters: Structure, Chemical Bonding, and Fluxionality

Energy Technology Data Exchange (ETDEWEB)

Sergeeva, Alina P.; Popov, Ivan A.; Piazza, Zachary A.; Li, Wei-Li; Romanescu, Constantin; Wang, Lai S.; Boldyrev, Alexander I.

2014-04-15

��/C analogy. It is believed that the electronic transmutation concept will be effective and valuable in aiding the design of new boride materials with predictable properties. The study of boron clusters with intermediate properties between those of individual atoms and bulk solids has given rise to a unique opportunity to broaden the frontier of boron chemistry. Understanding boron clusters has spurred experimentalists and theoreticians to find new boron-based nanomaterials, such as boron fullerenes, nanotubes, two-dimensional boron, and new compounds containing boron clusters as building blocks. Here, a brief and timely overview is presented addressing the recent progress made on boron clusters and the approaches used in the authors’ laboratories to determine the structure, stability, and chemical bonding of size-selected boron clusters by joint photoelectron spectroscopy and theoretical studies. Specifically, key findings on all-boron hydrocarbon analogues, metal-centered boron wheels, and electronic transmutation in boron clusters are summarized.

Mechanical Properties of Photovoltaic Silicon in Relation to Wafer Breakage

Science.gov (United States)

Kulshreshtha, Prashant Kumar

This thesis focuses on the fundamental understanding of stress-modified crack-propagation in photovoltaic (PV) silicon in relation to the critical issue of PV silicon "wafer breakage". The interactions between a propagating crack and impurities/defects/residual stresses have been evaluated for consequential fracture path in a thin PV Si wafer. To investigate the mechanism of brittle fracture in silicon, the phase transformations induced by elastic energy released at a propagating crack-tip have been evaluated by locally stressing the diamond cubic Si lattice using a rigid Berkovich nanoindenter tip (radius ≈50 nm). Unique pressure induced phase transformations and hardness variations have been then related to the distribution of precipitates (O, Cu, Fe etc.), and the local stresses in the wafer. This research demonstrates for the first time the "ductile-like fracture" in almost circular crack path that significantly deviates from its energetically favorable crystallographic [110](111) system. These large diameter (≈ 200 mm) Si wafers were sliced to less than 180 microm thickness from a Czochralski (CZ) ingot that was grown at faster than normal growth rates. The vacancy (vSi) driven precipitation of oxygen at enhanced thermal gradients in the wafer core develops large localized stresses (upto 100 MPa) which we evaluated using Raman spectral analysis. Additional micro-FTIR mapping and microscopic etch pit measurements in the wafer core have related the observed crack path deviations to the presence of concentric ring-like distributions of oxygen precipitates (OPs). To replicate these "real-world" breakage scenarios and provide better insight on crack-propagation, several new and innovative tools/devices/methods have been developed in this study. An accurate quantitative profiling of local stress, phase changes and load-carrying ability of Si lattice has been performed in the vicinity of the controlled micro-cracks created using micro-indentations to represent

Coke properties in relation to charge preparation techniques. [Selective crushing

Energy Technology Data Exchange (ETDEWEB)

Morozov, O S

1979-01-01

Selective crushing is essential to obtain the required coke properties, so that in the coarse fractions there is a considerable reduction in the middlings and dirt normally difficult to crush. These are at the same time enriched with vitrinite so that there is an increase in the coal substance as such, reflected in improved caking capacity in the coarse size range. Various methods of selective crushing are employed, including air entrainment mills, fluidised bed systems. Other advantages claimed for selective crushing are the uniform pore distribution and air permeability and also the diminished breakage stress.

Wnt11b is involved in cilia-mediated symmetry breakage during Xenopus left-right development.

Directory of Open Access Journals (Sweden)

Peter Walentek

Full Text Available Breakage of bilateral symmetry in amphibian embryos depends on the development of a ciliated epithelium at the gastrocoel roof during early neurulation. Motile cilia at the gastrocoel roof plate (GRP give rise to leftward flow of extracellular fluids. Flow is required for asymmetric gene expression and organ morphogenesis. Wnt signaling has previously been involved in two steps, Wnt/ß-catenin mediated induction of Foxj1, a regulator of motile cilia, and Wnt/planar cell polarity (PCP dependent cilia polarization to the posterior pole of cells. We have studied Wnt11b in the context of laterality determination, as this ligand was reported to activate canonical and non-canonical Wnt signaling. Wnt11b was found to be expressed in the so-called superficial mesoderm (SM, from which the GRP derives. Surprisingly, Foxj1 was only marginally affected in loss-of-function experiments, indicating that another ligand acts in this early step of laterality specification. Wnt11b was required, however, for polarization of GRP cilia and GRP morphogenesis, in line with the known function of Wnt/PCP in cilia-driven leftward flow. In addition Xnr1 and Coco expression in the lateral-most GRP cells, which sense flow and generate the first asymmetric signal, was attenuated in morphants, involving Wnt signaling in yet another process related to symmetry breakage in Xenopus.

Further delineation of the Nijmegen breakage syndrome

International Nuclear Information System (INIS)

Taalman, R.D.; Hustinx, T.W.; Weemaes, C.M.; Seemanova, E.; Schmidt, A.; Passarge, E.; Scheres, J.M.

1989-01-01

We report on five independent families with a chromosome instability disorder that earlier had been called the Nijmegen breakage syndrome (NBS). These families, two from the Netherlands and three from Czechoslovakia, had a total of eight patients, five of whom are still alive. The main clinical manifestations were microcephaly, short stature, a ''bird-like'' face, immunological defects involving both the humoral and cellular system. In four of the five living patients it has been possible to study the chromosomes of cultured lymphocytes. The basic karyotype in these patients were normal, but in 17% to 35% of the metaphases rearrangements were found, preferentially involving chromosomes 7 and/or 14 at the sites 7p13, 7q34, and 14q11. The chromosomes of all five living patients were very sensitive to ionizing radiation. In addition, the DNA synthesis in their cultured lymphocytes and fibroblasts was more resistant to X-rays than in cells from controls. The NBS shares a number of important features with ataxia telangiectasia (AT). Both syndromes are characterized by the occurrence of typical rearrangements of chromosomes 7 and/or 14, cellular and chromosomal hypersensitivity to X-irradiation, radioresistance of DNA replication and immunodeficiency. However, there are also obvious differences: NBS patients have microcephaly but neither ataxia nor telangiectasia, and in contrast to the situation in AT the alpha-fetoprotein level in their serum is normal

Metallurgical investigation of wire breakage of tyre bead grade

Directory of Open Access Journals (Sweden)

Piyas Palit

2015-10-01

Full Text Available Tyre bead grade wire is used for tyre making application. The wire is used as reinforcement inside the polymer of tyre. The wire is available in different size/section such as 1.6–0.80 mm thin Cu coated wire. During tyre making operation at tyre manufacturer company, wire failed frequently. In this present study, different broken/defective wire samples were collected from wire mill for detailed investigation of the defect. The natures of the defects were localized and similar in nature. The fracture surface was of finger nail type. Crow feet like defects including button like surface abnormalities were also observed on the broken wire samples. The defect was studied at different directions under microscope. Different advanced metallographic techniques have been used for detail investigation. The analysis revealed that, white layer of surface martensite was formed and it caused the final breakage of wire. In this present study we have also discussed about the possible reason for the formation of such kind of surface martensite (hard-phase.

Bonded stacked-ring insulator for the Antares electron gun

International Nuclear Information System (INIS)

Stine, R.D.; Allen, G.R.; Eaton, E.; Weinstein, B.

1982-01-01

A large diameter insulator utilizing epoxy bonding which has sufficient mechanical strength to support the 3000 kg cathode/grid assembly was developed. Bonding the insulator simplifies the handling and reduces the number of 0-ring seals to a minimum. We have described the material selection, bonding techniques and electrical design approach

The verification of the Taylor-expansion moment method in solving aerosol breakage

Directory of Open Access Journals (Sweden)

Yu Ming-Zhou

2012-01-01

Full Text Available The combination of the method of moment, characterizing the particle population balance, and the computational fluid dynamics has been an emerging research issue in the studies on the aerosol science and on the multiphase flow science. The difficulty of solving the moment equation arises mainly from the closure of some fractal moment variables which appears in the transform from the non-linear integral-differential population balance equation to the moment equations. Within the Taylor-expansion moment method, the breakage-dominated Taylor-expansion moment equation is first derived here when the symmetric fragmentation mechanism is involved. Due to the high efficiency and the high precision, this proposed moment model is expected to become an important tool for solving population balance equations.

Hydrogen bond based smart polymer for highly selective and tunable capture of multiply phosphorylated peptides.

Science.gov (United States)

Qing, Guangyan; Lu, Qi; Li, Xiuling; Liu, Jing; Ye, Mingliang; Liang, Xinmiao; Sun, Taolei

2017-09-06

Multisite phosphorylation is an important and common mechanism for finely regulating protein functions and subsequent cellular responses. However, this study is largely restricted by the difficulty to capture low-abundance multiply phosphorylated peptides (MPPs) from complex biosamples owing to the limitation of enrichment materials and their interactions with phosphates. Here we show that smart polymer can serve as an ideal platform to resolve this challenge. Driven by specific but tunable hydrogen bonding interactions, the smart polymer displays differential complexation with MPPs, singly phosphorylated and non-modified peptides. Importantly, MPP binding can be modulated conveniently and precisely by solution conditions, resulting in highly controllable MPP adsorption on material surface. This facilitates excellent performance in MPP enrichment and separation from model proteins and real biosamples. High enrichment selectivity and coverage, extraordinary adsorption capacities and recovery towards MPPs, as well as high discovery rates of unique phosphorylation sites, suggest its great potential in phosphoproteomics studies.Capture of low-abundance multiply phosphorylated peptides (MPPs) is difficult due to limitation of enrichment materials and their interactions with phosphates. Here the authors show, a smart polymer driven by specific but tunable hydrogen bonding interactions can differentially complex with MPPs, singly phosphorylated and non-modified peptides.

Dilemmas in zirconia bonding: A review

Directory of Open Access Journals (Sweden)

Obradović-Đuričić Kosovka

2013-01-01

Full Text Available This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability. The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

Effect of Miracle Fruit (Synsepalum dulcificum) Seed Oil (MFSO®) on the Measurable Improvement of Hair Breakage in Women with Damaged Hair: A Randomized, Double-blind, Placebo-controlled, Eight-month Trial.

Science.gov (United States)

Del Campo, Roberta; Zhang, Yu; Wakeford, Charles

2017-11-01

Background: Hair breakage is a common unrecognized form of hair loss in women most often the result of hair weathering and traumatic grooming practices. Lipids are major determinants of the physical properties of the hair. Synsepalum dulcificum seed oil (MFSO ® ; Miracle Fruit Oil Co., Miami Beach, Florida), is an exotic fruit oil with physicochemical properties suited to providing a superior ability to reduce hair breakage. Objective: To assess the safety and efficacy of a hair oil containing MFSO and its effects on hair breakage rates. Methods: Healthy, long-haired women (age range: 19-63 years, mean age: 36.7 years, standard deviation: 10.77 years) with excessive hair breakage were randomized in this double-blind, placebo-controlled study to receive MFSO (n=24), vehicle (n=17), or argan oil (n=16). Measurements of hair length, hair diameter, and Hair Mass Index were performed at baseline, Month 4, and Month 8. Hair Breakage Index and the Healthy Hair Index values were calculated from the trichometer measurements, and subject self-assessment questionnaires were conducted. The primary efficacy endpoints were the percent change in Healthy Hair Index 75 and Healthy Hair Index 50 measurements from baseline to the eighth month. Results: The Healthy Hair Index calculations, expressed as percent change from baseline to Month 4 and from baseline to Month 8, revealed that the MFSO ® treatment group improved by 103.6 percent and 215.7 percent for the Healthy Hair Index 75 and 133.7 and 188.3 percent for the Healthy Hair Index 50 values, respectively. When compared with the vehicle and the argan oil brand groups, the Healthy Hair Index levels were significantly higher (p oil treatment group was better than each of the other two treatment groups by at least 117.6 percent and 234.9 percent for the Healthy Hair Index 75 and 316.5 percent and 312 percent for the Healthy Hair Index 50 values, respectively, thereby achieving the primary efficacy objective. Subjects favored the

Manufacturing and sustainability of bonding systems for grinding tools

OpenAIRE

Linke, B

2016-01-01

© 2016, German Academic Society for Production Engineering (WGP). Grinding and honing processes are quality-defining operations in the production of many modern products. Process performance and product quality are contingent on selecting the correct abrasive tool for a specific application. Thus, tools with different bonding systems are used, namely resin bonded tools, vitrified bonded tools, and metallic bonded tools. Tool manufacturers have great knowledge in the choice and intricate prod...

Clinical heterogeneity and chromosome breakage in Iranian patients suspicious of Fanconi anemia

Directory of Open Access Journals (Sweden)

Ghasemi Firoozabadi S

2007-10-01

Full Text Available Background: Fanconi anemia (FA is a rare autosomal recessive disorder characterized by short stature, skeletal anomalies, increased incidence of solid tumors and leukemia, and bone marrow failure (aplastic anemia. FA has been reported in all races and ethnic groups and affects men and women in an equal proportion. The frequency of FA has been estimated at approximately 1 per 360,000 live births. In some populations, including Ashkenazi Jews, Turks, Saudi Arabians and Iranians, this frequency appears to be higher, probably as a result of the founder effect and consanguineous marriage. Because of extensive genetic and clinical heterogeneity (the age of onset, clinical manifestations and survival, diagnosis of FA on the basis of clinical data alone is unreliable and its molecular diagnosis is difficult. The diagnosis of FA exploits the hypersensitivity of FA lymphocytes and fibroblasts to bifunctional alkylating agents such as mitomycin C (MMC, diepoxybutane (DEB and nitrogen mustard and differentiates it from idiopathic aplastic anemia. In this study, in addition to the patients' clinical profiles, a cytogenetic test using MMC was implemented for an accurate diagnosis of Fanconi anemia.Methods: In this study, the lymphocytes of 20 patients referred for FA, and those of their normal sex-matched controls, were treated with three different concentrations of mitomycin C (20, 30, 40 ng/ml. Slides were prepared and solid stained. In order to determine the number and kind of chromosome abnormalities, 50 metaphase spreads from each culture were analyzed. Clinical information was obtained from patient files.Results: Five patients manifested increased chromosome breakage with MMC, confirming the FA diagnosis. Two different concentrations of MMC (30, 40 ng/ml were most effective.Conclusion: The chromosomal breakage test is important for the accurate diagnosis of Fanconi anemia. DNA crosslinking agents used to treat idiopathic aplastic anemia may be

Welding, Bonding and Fastening, 1984

Science.gov (United States)

Buckley, J. D. (Editor); Stein, B. A. (Editor)

1985-01-01

A compilation of papers presented in a joint NASA, American Society for Metals, The George Washington University, American Welding Soceity, and Society of Manufacturing Engineers conference on Welding, Bonding, and Fastening at Langley Research Center, Hampton, VA, on October 23 to 25, 1984 is given. Papers were presented on technology developed in current research programs relevant to welding, bonding, and fastening of structural materials required in fabricating structures and mechanical systems used in the aerospace, hydrospace, and automotive industries. Topics covered in the conference included equipment, hardware and materials used when welding, brazing, and soldering, mechanical fastening, explosive welding, use of unique selected joining techniques, adhesives bonding, and nondestructive evaluation. A concept of the factory of the future was presented, followed by advanced welding techniques, automated equipment for welding, welding in a cryogenic atmosphere, blind fastening, stress corrosion resistant fasteners, fastening equipment, explosive welding of different configurations and materials, solid-state bonding, electron beam welding, new adhesives, effects of cryogenics on adhesives, and new techniques and equipment for adhesive bonding.

The coevolution of long-term pair bonds and cooperation.

Science.gov (United States)

Song, Z; Feldman, M W

2013-05-01

The evolution of social traits may not only depend on but also change the social structure of the population. In particular, the evolution of pairwise cooperation, such as biparental care, depends on the pair-matching distribution of the population, and the latter often emerges as a collective outcome of individual pair-bonding traits, which are also under selection. Here, we develop an analytical model and individual-based simulations to study the coevolution of long-term pair bonds and cooperation in parental care, where partners play a Snowdrift game in each breeding season. We illustrate that long-term pair bonds may coevolve with cooperation when bonding cost is below a threshold. As long-term pair bonds lead to assortative interactions through pair-matching dynamics, they may promote the prevalence of cooperation. In addition to the pay-off matrix of a single game, the evolutionarily stable equilibrium also depends on bonding cost and accidental divorce rate, and it is determined by a form of balancing selection because the benefit from pair-bond maintenance diminishes as the frequency of cooperators increases. Our findings highlight the importance of ecological factors affecting social bonding cost and stability in understanding the coevolution of social behaviour and social structures, which may lead to the diversity of biological social systems. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

Adhesive bonding using variable frequency microwave energy

Science.gov (United States)

Lauf, Robert J.; McMillan, April D.; Paulauskas, Felix L.; Fathi, Zakaryae; Wei, Jianghua

1998-01-01

Methods of facilitating the adhesive bonding of various components with variable frequency microwave energy are disclosed. The time required to cure a polymeric adhesive is decreased by placing components to be bonded via the adhesive in a microwave heating apparatus having a multimode cavity and irradiated with microwaves of varying frequencies. Methods of uniformly heating various articles having conductive fibers disposed therein are provided. Microwave energy may be selectively oriented to enter an edge portion of an article having conductive fibers therein. An edge portion of an article having conductive fibers therein may be selectively shielded from microwave energy.

Shear bond strength of self-etch and total-etch bonding systems at different dentin depths

Directory of Open Access Journals (Sweden)

Ana Carolina Maito Villela-Rosa

2011-04-01

Full Text Available The purpose of this study was to evaluate the dentin shear bond strength of four adhesive systems (Adper Single Bond 2, Adper Prompt L-Pop, Magic Bond DE and Self Etch Bond in regards to buccal and lingual surfaces and dentin depth. Forty extracted third molars had roots removed and crowns bisected in the mesiodistal direction. The buccal and lingual surfaces were fixed in a PVC/acrylic resin ring and were divided into buccal and lingual groups assigned to each selected adhesive. The same specimens prepared for the evaluation of superficial dentin shear resistance were used to evaluate the different depths of dentin. The specimens were identified and abraded at depths of 0.5, 1.0, 1.5 and 2.0 mm. Each depth was evaluated by ISO TR 11405 using an EMIC-2000 machine regulated at 0.5 mm/min with a 200 Kgf load cell. We performed statistical analyses on the results (ANOVA, Tukey and Scheffé tests. Data revealed statistical differences (p < 0.01 in the adhesive and depth variation as well as adhesive/depth interactions. The Adper Single Bond 2 demonstrated the highest mean values of shear bond strength. The Prompt L-Pop product, a self-etching adhesive, revealed higher mean values compared with Magic Bond DE and Self Etch Bond adhesives, a total and self-etching adhesive respectively. It may be concluded that the shear bond strength of dentin is dependent on material (adhesive system, substrate depth and adhesive/depth interaction.

Suppress orthotopic colon cancer and its metastasis through exact targeting and highly selective drug release by a smart nanomicelle.

Science.gov (United States)

Zhu, Chunqi; Zhang, Hanbo; Li, Wei; Luo, Lihua; Guo, Xiaomeng; Wang, Zuhua; Kong, Fenfen; Li, Qingpo; Yang, Jie; Du, Yongzhong; You, Jian

2018-04-01

The treatment of metastatic cancer is a huge challenge at the moment. Highly precise targeting delivery and drug release in tumor have always been our pursuit in cancer therapy, especially to advance cancer with metastasis, for increasing the efficacy and biosafety. We established a smart nanosized micelle, formed by tocopherol succinate (TOS) conjugated hyaluronic acid (HA) using a disulfide bond linker. The micelle (HA-SS-TOS, HSST) can highly specifically bind with CD44 receptor over-expressed tumor, and response selectively to high GSH level in the cells, inducing disulfide bond breakage and the release of the payload (paclitaxel, PTX). To predict the antitumor efficacy of the micelles more clinically, we established an orthotopic colon cancer model with high metastasis rate, which could be visualized by the luciferase bioluminescence. Our data confirmed CD44 high expression in the colon cancer cells. Highly matching between the micellar fluorescence and bioluminescence of cancer cells in intestines demonstrated an exact recognition of our micelles to orthotopic colon tumor and its metastatic cells, attributing to the mediation of CD44 receptors. Furthermore, the fluorescence of the released Nile Red from the micelles was found only in the tumor and its metastatic cells, and almost completely overlapped with the bioluminescence of the cancer cells, indicating a highly selective drug release. Our micelles presented an excellent therapeutic effect against metastatic colon cancer, and induced significantly prolonged survival time for the mice, which might become a promising nanomedicine platform for the future clinical application against advanced cancers with high CD44 receptor expression. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mobilization of Copper ions by Flavonoids in Human Peripheral Lymphocytes Leads to Oxidative DNA Breakage: A Structure Activity Study

Science.gov (United States)

Arif, Hussain; Rehmani, Nida; Farhan, Mohd; Ahmad, Aamir; Hadi, Sheikh Mumtaz

2015-01-01

Epidemiological studies have linked dietary consumption of plant polyphenols with lower incidence of various cancers. In particular, flavonoids (present in onion, tomato and other plant sources) induce apoptosis and cytotoxicity in cancer cells. These can therefore be used as lead compounds for the synthesis of novel anticancer drugs with greater bioavailability. In the present study, we examined the chemical basis of cytotoxicity of flavonoids by studying the structure–activity relationship of myricetin (MN), fisetin (FN), quercetin (QN), kaempferol (KL) and galangin (GN). Using single cell alkaline gel electrophoresis (comet assay), we established the relative efficiency of cellular DNA breakage as MN > FN > QN > KL > GN. Also, we determined that the cellular DNA breakage was the result of mobilization of chromatin-bound copper ions and the generation of reactive oxygen species. The relative DNA binding affinity order was further confirmed using molecular docking and thermodynamic studies through the interaction of flavonoids with calf thymus DNA. Our results suggest that novel anti-cancer molecules should have ortho-dihydroxy groups in B-ring and hydroxyl groups at positions 3 and 5 in the A-ring system. Additional hydroxyl groups at other positions further enhance the cellular cytotoxicity of the flavonoids. PMID:26569217

A rod-packing microporous hydrogen-bonded organic framework for highly selective separation of C2H2/CO2at room temperature

KAUST Repository

Li, Peng

2014-11-13

Self-assembly of a trigonal building subunit with diaminotriazines (DAT) functional groups leads to a unique rod-packing 3D microporous hydrogen-bonded organic framework (HOF-3). This material shows permanent porosity and demonstrates highly selective separation of C2H2/CO2 at ambient temperature and pressure.

A rod-packing microporous hydrogen-bonded organic framework for highly selective separation of C2H2/CO2at room temperature

KAUST Repository

Li, Peng; He, Yabing; Zhao, Yunfeng; Weng, Linhong; Wang, Hailong; Krishna, Rajamani A A; Wu, Hui; Zhou, Wei; O'Keeffe, Michael A.; Han, Yu; Chen, Banglin

2014-01-01

Self-assembly of a trigonal building subunit with diaminotriazines (DAT) functional groups leads to a unique rod-packing 3D microporous hydrogen-bonded organic framework (HOF-3). This material shows permanent porosity and demonstrates highly selective separation of C2H2/CO2 at ambient temperature and pressure.

X-ray-induced breakage and rejoining of human interphase chromosomes

International Nuclear Information System (INIS)

Cornforth, M.N.; Bedford, J.S.

1983-01-01

A method was developed for the high-resolution measurement of breaks in prematurely condensed chromosomes at the G 1 phase of the cell cycle. The dose response for fragments (breaks) produced immediately after x-irradiation of confluent cultures of normal human cells was linear down to 10.9 rad (0.109 Gy) and extrapolated to zero effect at zero dose. The curve had a slope of 0.063 breaks per cell per rad, which is at least an order of magnitude greater than that for breaks scored in the same cells after they have progressed to mitosis following subculture. When incubated at 37 0 C half of the breaks disappeared in 2 hours. A slower, perhaps nonrejoining component was apparent at later incubation times. The initial rate of break rejoining was similar to the rate of increase in survival after incubation because of the repair of potentially lethal damage and is also in close agreement with recently reported values for the rejoining of double-strand breakage in DNA

Protection of halogenated DNA from strand breakage and sister-chromatid exchange induced by the topoisomerase I inhibitor camptothecin

International Nuclear Information System (INIS)

Orta, Manuel Luis; Mateos, Santiago; Cantero, Gloria; Wolff, Lisa J.; Cortes, Felipe

2008-01-01

The fundamental nuclear enzyme DNA topoisomerase I (topo I), cleaves the double-stranded DNA molecule at preferred sequences within its recognition/binding sites. We have recently reported that when cells incorporate halogenated nucleosides analogues of thymidine into DNA, it interferes with normal chromosome segregation, as shown by an extraordinarily high yield of endoreduplication, and results in a protection against DNA breakage induced by the topo II poison m-AMSA [F. Cortes, N. Pastor, S. Mateos, I. Dominguez, The nature of DNA plays a role in chromosome segregation: endoreduplication in halogen-substituted chromosomes, DNA Repair 2 (2003) 719-726; G. Cantero, S. Mateos, N. Pastor; F. Cortes, Halogen substitution of DNA protects from poisoning of topoisomerase II that results in DNA double-strand breaks (DSBs), DNA Repair 5 (2006) 667-674]. In the present investigation, we have assessed whether the presence of halogenated nucleosides in DNA diminishes the frequency of interaction of topo I with DNA and thus the frequency with which the stabilisation of cleavage complexes by the topo I poison camptothecin (CPT) takes place, in such a way that it protects from chromosome breakage and sister-chromatid exchange. This protective effect is shown to parallel a loss in halogen-substituted cells of the otherwise CPT-increased catalytic activity bound to DNA

Selectivity of calixarene-bonded silica-phases in HPLC: description of special characteristics with a multiple term linear equation at two different pH-values.

Science.gov (United States)

Schneider, Christian; Meyer, Rüdiger; Jira, Thomas

2008-09-01

Six different calixarene-bonded phases were characterized by analyzing 36 and 26 solutes at pH 3 and 7, respectively. Dolan and Snyder's multiple term linear equation was used to correlate retention factors k' to parameters of the solutes and columns. The column parameters have been related to molecular properties of the stationary phases and new suggestions were made for the interpretation of steric selectivity. Ionic and polar interactions have been found dependent on pH value, while steric interactions are less dependent and hydrophobic interactions remain unchanged. Distinct differences of the supported interactions were confirmed between the calixarene-bonded and the common alkyl-bonded silicas. By use of the parameters, values of k' can be estimated with an average deviation of 2.50 and 7.92% at low and neutral pH-value, respectively.

Deflection estimation of a wind turbine blade using FBG sensors embedded in the blade bonding line

International Nuclear Information System (INIS)

Kim, Sang-Woo; Kang, Woo-Ram; Jeong, Min-Soo; Lee, In; Kwon, Il-Bum

2013-01-01

Estimating the deflection of flexible composite wind turbine blades is very important to prevent the blades from hitting the tower. Several researchers have used fiber Bragg grating (FBG) sensors—a type of optical fiber sensor (OFS)—to monitor the structural behavior of the blades. They can be installed on the surface and/or embedded in the interior of composites. However, the typical installation positions of OFSs present several problems, including delamination of sensing probes and a higher risk of fiber breakage during installation. In this study, we proposed using the bonding line between the shear web and spar cap as a new installation position of embedded OFSs for estimating the deflection of the blades. Laboratory coupon tests were undertaken preliminarily to confirm the strain measuring capability of embedded FBG sensors in adhesive layers, and the obtained values were verified by comparison with results obtained by electrical strain gauges and finite element analysis. We performed static loading tests on a 100 kW composite wind turbine blade to evaluate its deflections using embedded FBG sensors positioned in the bonding line. The deflections were estimated by classical beam theory considering a rigid body rotation near the tip of the blade. The evaluated tip deflections closely matched those measured by a linear variable differential transformer. Therefore, we verified the capability of embedded FBG sensors for evaluating the deflections of wind turbine blades. In addition, we confirmed that the bonding line between the shear web and spar cap is a practical location to embed the FBG sensors. (paper)

Effects of recycling and bonding agent application on bond strength of stainless steel orthodontic brackets.

Science.gov (United States)

Bahnasi, Faisal I; Abd-Rahman, Aida Na; Abu-Hassan, Mohame I

2013-10-01

1) to assess different methods of recycling orthodontic brackets, 2) to evaluate Shear Bond Strength (SBS) of (a) new, (b) recycled and (c) repeated recycled stainless steel brackets (i) with and (ii) without bracket base primer. A total of 180 extracted human premolar teeth and 180 premolar stainless steel brackets were used. One hundred teeth and 100 brackets were divided into five groups of 20-teeth each. Four methods of recycling orthodontic brackets were used in each of the first four groups while the last one (group V) was used as the control. Groups (I-V) were subjected to shear force within half an hour until the brackets debond. SBS was measured and the method showing the highest SBS was selected. A New group (VI) was recycled twice with the selected method. Six subgroups (1-6) were established; the primer was applied for three sub-groups, and the composite was applied for all brackets. Brackets were subjected to the same shear force, and SBS was measured for all sub-groups. There was a significant difference between the mean SBS of the sandblasting method and the means of SBS of each of the other three methods. There was however, no significant difference between the mean SBS of the new bracket and the mean SBS of recycled bracket using sandblasting. The mean SBS of all sub-groups were more than that recommended by Reynolds (17) in 1975. Brackets with primer showed slightly higher SBS compared to those of brackets without bonding agent. To decrease cost, sandblasted recycled orthodontic brackets can be used as an alternative to new brackets. It is recommended to apply a bonding agent on the bracket base to provide greater bond strength. Key words:Recycled bracket, shear bond strength, sandblasting, stainless steel orthodontic bracket.

Effects of recycling and bonding agent application on bond strength of stainless steel orthodontic brackets

Science.gov (United States)

Bahnasi, Faisal I.; Abu-Hassan, Mohame I.

2013-01-01

Objectives: 1) to assess different methods of recycling orthodontic brackets, 2) to evaluate Shear Bond Strength (SBS) of (a) new, (b) recycled and (c) repeated recycled stainless steel brackets (i) with and (ii) without bracket base primer. Study Design: A total of 180 extracted human premolar teeth and 180 premolar stainless steel brackets were used. One hundred teeth and 100 brackets were divided into five groups of 20-teeth each. Four methods of recycling orthodontic brackets were used in each of the first four groups while the last one (group V) was used as the control. Groups (I-V) were subjected to shear force within half an hour until the brackets debond. SBS was measured and the method showing the highest SBS was selected. A New group (VI) was recycled twice with the selected method. Six subgroups (1-6) were established; the primer was applied for three sub-groups, and the composite was applied for all brackets. Brackets were subjected to the same shear force, and SBS was measured for all sub-groups. Results: There was a significant difference between the mean SBS of the sandblasting method and the means of SBS of each of the other three methods. There was however, no significant difference between the mean SBS of the new bracket and the mean SBS of recycled bracket using sandblasting. The mean SBS of all sub-groups were more than that recommended by Reynolds (17) in 1975. Brackets with primer showed slightly higher SBS compared to those of brackets without bonding agent. Conclusion: To decrease cost, sandblasted recycled orthodontic brackets can be used as an alternative to new brackets. It is recommended to apply a bonding agent on the bracket base to provide greater bond strength. Key words:Recycled bracket, shear bond strength, sandblasting, stainless steel orthodontic bracket. PMID:24455081

T. thermophila group I introns that cleave amide bonds

Science.gov (United States)

Joyce, Gerald F. (Inventor)

1997-01-01

The present invention relates to nucleic acid enzymes or enzymatic RNA molecules that are capable of cleaving a variety of bonds, including phosphodiester bonds and amide bonds, in a variety of substrates. Thus, the disclosed enzymatic RNA molecules are capable of functioning as nucleases and/or peptidases. The present invention also relates to compositions containing the disclosed enzymatic RNA molecule and to methods of making, selecting, and using such enzymes and compositions.

Self-assembly of a [2 x 2] hydrogen bonded grid

NARCIS (Netherlands)

Lipkowski, P.R.; Bielejewska, A.G.; Kooijman, Huub; Spek, Anthony L.; Timmerman, P.; Reinhoudt, David

1999-01-01

Formation of 24 cooperative hydrogen bonds drives the spontaneous assembly of a rigid bifunctional trimelamine and bis(barbituric acid) to give selectively the [2 × 2] hydrogen-bonded grid, in preference to the corresponding [1 × 1] or polymeric assemblies.

Mobilization of Copper ions by Flavonoids in Human Peripheral Lymphocytes Leads to Oxidative DNA Breakage: A Structure Activity Study

Directory of Open Access Journals (Sweden)

Hussain Arif

2015-11-01

Full Text Available Epidemiological studies have linked dietary consumption of plant polyphenols with lower incidence of various cancers. In particular, flavonoids (present in onion, tomato and other plant sources induce apoptosis and cytotoxicity in cancer cells. These can therefore be used as lead compounds for the synthesis of novel anticancer drugs with greater bioavailability. In the present study, we examined the chemical basis of cytotoxicity of flavonoids by studying the structure–activity relationship of myricetin (MN, fisetin (FN, quercetin (QN, kaempferol (KL and galangin (GN. Using single cell alkaline gel electrophoresis (comet assay, we established the relative efficiency of cellular DNA breakage as MN > FN > QN > KL > GN. Also, we determined that the cellular DNA breakage was the result of mobilization of chromatin-bound copper ions and the generation of reactive oxygen species. The relative DNA binding affinity order was further confirmed using molecular docking and thermodynamic studies through the interaction of flavonoids with calf thymus DNA. Our results suggest that novel anti-cancer molecules should have ortho-dihydroxy groups in B-ring and hydroxyl groups at positions 3 and 5 in the A-ring system. Additional hydroxyl groups at other positions further enhance the cellular cytotoxicity of the flavonoids.

Shear bond strength of precoated orthodontic brackets: an in vivo study

OpenAIRE

Hassan, Ali H

2010-01-01

Ali H HassanDepartment of Preventive Dental Sciences, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi ArabiaObjective: To evaluate the shear bond strength of precoated orthodontic brackets bonded with self-etching primer relative to that of noncoated conventionally-bonded brackets at two different time intervals.Methods: Twenty-one subjects were selected for randomized split-mouth bonding of two types of brackets to the maxillary arch. Half of the teeth had precoated brackets b...

Longevity of Self-etch Dentin Bonding Adhesives Compared to Etch-and-rinse Dentin Bonding Adhesives: A Systematic Review.

Science.gov (United States)

Masarwa, Nader; Mohamed, Ahmed; Abou-Rabii, Iyad; Abu Zaghlan, Rawan; Steier, Liviu

2016-06-01

A systematic review and meta-analysis were performed to compare longevity of Self-Etch Dentin Bonding Adhesives to Etch-and-Rinse Dentin Bonding Adhesives. The following databases were searched for PubMed, MEDLINE, Web of Science, CINAHL, the Cochrane Library complemented by a manual search of the Journal of Adhesive Dentistry. The MESH keywords used were: "etch and rinse," "total etch," "self-etch," "dentin bonding agent," "bond durability," and "bond degradation." Included were in-vitro experimental studies performed on human dental tissues of sound tooth structure origin. The examined Self-Etch Bonds were of two subtypes; Two Steps and One Step Self-Etch Bonds, while Etch-and-Rinse Bonds were of two subtypes; Two Steps and Three Steps. The included studies measured micro tensile bond strength (μTBs) to evaluate bond strength and possible longevity of both types of dental adhesives at different times. The selected studies depended on water storage as the aging technique. Statistical analysis was performed for outcome measurements compared at 24 h, 3 months, 6 months and 12 months of water storage. After 24 hours (p-value = 0.051), 3 months (p-value = 0.756), 6 months (p-value=0.267), 12 months (p-value=0.785) of water storage self-etch adhesives showed lower μTBs when compared to the etch-and-rinse adhesives, but the comparisons were statistically insignificant. In this study, longevity of Dentin Bonds was related to the measured μTBs. Although Etch-and-Rinse bonds showed higher values at all times, the meta-analysis found no difference in longevity of the two types of bonds at the examined aging times. Copyright © 2016 Elsevier Inc. All rights reserved.

Evaluation of the mechanical properties and porcelain bond strength of cobalt-chromium dental alloy fabricated by selective laser melting.

Science.gov (United States)

Wu, Lin; Zhu, Haiting; Gai, Xiuying; Wang, Yanyan

2014-01-01

Limited information is available regarding the microstructure and mechanical properties of dental alloy fabricated by selective laser melting (SLM). The purpose of this study was to evaluate the mechanical properties of a cobalt-chromium (Co-Cr) dental alloy fabricated by SLM and to determine the correlation between its microstructure and mechanical properties and its porcelain bond strength. Five metal specimens and 10 metal ceramic specimens were fabricated to evaluate the mechanical properties of SLM Co-Cr dental alloy (SLM alloy) with a tensile test and its porcelain bond strength with a 3-point bending test. The relevant properties of the SLM alloy were compared with those of the currently used Co-Cr dental alloy fabricated with conventional cast technology (cast alloy). The Student t test was used to compare the results of the SLM alloy and the cast alloy (α=.05). The microstructure of the SLM alloy was analyzed with a metallographic microscope; the metal ceramic interface of the SLM porcelain bonded alloy was studied with scanning electron microscopy, energy dispersive x-ray spectroscopy, and an electron probe microanalyzer. Both the mean (standard deviation) yield strength (884.37 ± 8.96 MPa) and tensile strength (1307.50 ±10.65 MPa) of the SLM alloy were notably higher than yield strength (568.10 ± 30.94 MPa) and tensile strength (758.73 ± 25.85 MPa) of the currently used cast alloy, and the differences were significant (P.05). Microstructure analysis suggested that the SLM alloy had a dense and obviously orientated microstructure, which led to excellent mechanical properties. Analysis from scanning electron microscopy, energy dispersive x-ray spectroscopy, and the electron probe microanalyzer indicated that the SLM alloy had an intermediate layer with elemental interpenetration between the alloy and the porcelain, which resulted in an improved bonding interface. Compared with the currently used cast alloy, SLM alloy possessed improved mechanical

Tool breakage detection from 2D workpiece profile using vision method

International Nuclear Information System (INIS)

Lee, W K; Ratnam, M M; Ahmad, Z A

2016-01-01

In-process tool breakage monitoring can significantly save cost and prevent damages to machine tool. In this paper, a machine vision approach was employed to detect the tool fracture in commercial aluminium oxide ceramic cutting tool during turning of AISI 52100 hardened steel. The contour of the workpiece profile was captured with the aid of backlighting during turning using a high-resolution DSLR camera with a shutter speed of 1/4000 s. The surface profile of the workpiece was extracted to sub-pixel accuracy using the invariant moment method. The effect of fracture in ceramic cutting tools on the surface profile signature of the machined workpiece using autocorrelation was studied. Fracture in the aluminum oxide ceramic tool was found to cause the peaks of autocorrelation function of the workpiece profile to decrease rapidly as the lag distance increased. The envelope of the peaks of the autocorrelation function was observed to deviate significantly from one another at different workpiece angles when the tool has fractured due to the continuous fracture of ceramic cutting insert during machining. (paper)

Evidence for porphyrins bound, via ester bonds, to the Messel oil shale kerogen by selective chemical degradation experiments

Science.gov (United States)

Huseby, B.; Ocampo, R.

1997-09-01

High amounts of nickel mono- and di-acid porphyrins were released from Messel oil shale kerogen (Eocene, Germany) by selective chemical degradation (acid and base hydrolysis). The released porphyrin fractions were quantified (UV-vis) and their constituents isolated and characterized at the molecular level (UV-vis, MS, NMR). The mono-acid porphyrin fraction released contained four compounds of similar abundance which arise from an obvious chlorophyll or bacteriochlorophyll precursor. The di-acid porphyrin fraction was, however, dominated by far by one compound, mesoporphyrin IX, which must have originated from heme-like precursors (heme, cytochromes, etc.). These results show unambigously that the released mono- and di-acid porphyrins were linked to the macromolecular kerogen network via ester bonds and suggest that precursor heme-like pigments could be selectively and/or more readily incorporated into the macromolecular kerogen network than precursor chlorophylls and bacteriochlorophylls.

Hallermann-Streiff syndrome associated with small cerebellum, endocrinopathy and increased chromosomal breakage.

Science.gov (United States)

Hou, J W

2003-07-01

Hallermann-Streiff syndrome (HSS) is a rare clinic entity of unknown aetiology. Further clinical and metabolic-genetic evaluations are indicated. A 2-mo-old female baby presented with ocular abnormalities and severe failure to thrive since birth. The clinical features were compatible with the diagnosis of HSS. Further imaging, metabolic and cytogenetic examinations were performed. Features characteristic of HSS were dyscephaly with mandibular and nasal cartilage hypoplasia, microphthalmia, bilateral cataracts with congenital glaucoma, natal teeth and proportionate dwarfism. Rare anomalies such as choanal atresia and small cerebellum, very low insulin-like growth factor I level, hypothyroidism, generalized organic aciduria were also noticed. An increased chromosomal breakage rate is suggestive of the existence of some DNA repair defects in HSS patients. The associated anomalies in this patient may broaden the clinical spectrum of HSS. Underlying conditions of organic aciduria, growth factor deficiency and impaired DNA repair are likely to contribute to the progeria-like facies, congenital cataracts and growth failure.

Enamel and dentin bond strength following gaseous ozone application.

Science.gov (United States)

Cadenaro, Milena; Delise, Chiara; Antoniollo, Francesca; Navarra, Ottavia Chiara; Di Lenarda, Roberto; Breschi, Lorenzo

2009-08-01

To evaluate the effects of gaseous ozone application on enamel and dentin bond strength produced by two self-etching adhesive systems. The shear bond strength test was conducted to assess adhesion on enamel (protocol 1), while the microtensile bond strength test was performed on dentin (protocol 2). Protocol 1: 96 bovine incisors were randomly divided into 4 groups, and enamel surfaces were bonded in accordance with the following treatments: (1E) ozone + Clearfil Protect Bond; (2E) Clearfil Protect Bond (control); (3E) ozone + Xeno III; (4E) Xeno III (control). Ozone gas was applied for 80 s. Shear bond strength was measured with a universal testing machine. Protocol 2: 40 noncarious human molars were selected. Middle/deep dentin was exposed and bonded in accordance with the following treatments: (1D) ozone+Clearfil Protect Bond; (2D) Clearfil Protect Bond (control); (3D) ozone+Xeno III (4D) Xeno III (control). Four-mm-thick buildups were built on the adhesives, then specimens were sectioned in accordance with the nontrimming technique. Specimens were stressed until failure occurred, and failure modes were analyzed. Shear bond and microtensile bond strength data were analyzed using two-way ANOVA and Tukey's post-hoc test. No statistical differences were found between ozone treated specimens and controls, neither on enamel nor on dentin irrespective of the tested adhesive. Clearfil Protect Bond showed higher bond strength to enamel than Xeno III, irrespective of the ozone treatment (p enamel and dentin bond strength.

Biomonitoring of genotoxic risk in radar facility workers: comparison of the comet assay with micronucleus assay and chromatid breakage assay

International Nuclear Information System (INIS)

Garaj-Vrhovac, V.; Kopjar, N.

2003-01-01

Genotoxic risks of occupational exposure in a radar facility were evaluated by using alkaline comet assay, micronucleus assay and chromatid breakage assay on peripheral blood leukocytes in exposed subjects and corresponding controls. Results show that occupational exposure to microwave radiation correlates with an increase of genome damage in somatic cells. The levels of DNA damage in exposed subjects determined by using alkaline comet assay were increased compared to control and showed interindividual variations. Incidence of micronuclei was also significantly increased compared to baseline control values. After short exposure of cultured lymphocytes to bleomycin, cells of occupationally exposed subjects responded with high numbers of chromatid breaks. Although the level of chromosome damage generated by bleomycin varied greatly between individuals, in exposed subjects a significantly elevated number of chromatid breaks was observed. Our results support data reported in literature indicating that microwave radiation represents a potential DNA-damaging hazard. Alkaline comet assay is confirmed as a sensitive and highly reproducible technique for detection of primary DNA damage inflicted in somatic cells. Micronucleus assay was confirmed as reliable bio-markers of effect and chromatid breakage assay as sensitive bio-marker of individual cancer susceptibility. The results obtained also confirm the necessity to improve measures and to perform accurate health surveillance of individuals occupationally exposed to microwave radiation

Adhesive Bonding to Computer-aided Design/ Computer-aided Manufacturing Esthetic Dental Materials: An Overview.

Science.gov (United States)

Awad, Mohamed Moustafa; Alqahtani, H; Al-Mudahi, A; Murayshed, M S; Alrahlah, A; Bhandi, Shilpa H

2017-07-01

To review the adhesive bonding to different computer-aided design/computer-aided manufacturing (CAD/CAM) esthetic restorative materials. The use of CAD/CAM esthetic restorative materials has gained popularity in recent years. Several CAD/ CAM esthetic restorative materials are commercially available. Adhesive bonding is a major determinant of success of CAD/ CAM restorations. Review result: An account of the currently available bonding strategies are discussed with their rationale in various CAD/ CAM materials. Different surface treatment methods as well as adhesion promoters can be used to achieve reliable bonding of CAD/CAM restorative materials. Selection of bonding strategy to such material is determined based on its composition. Further evidence is required to evaluate the effect of new surface treatment methods, such as nonthermal atmospheric plasma and self-etching ceramic primer on bonding to different dental ceramics. An understanding of the currently available bonding strategies to CA/CAM materials can help the clinician to select the most indicated system for each category of materials.

Evidence for high-pressure-induced rupture of hydrogen bonds in LH2 photosynthetic antenna pigment-protein complexes

International Nuclear Information System (INIS)

Kangur, L; Leiger, K; Freiberg, A

2008-01-01

The bacteriochlorophyll a-containing LH2 light harvesting complex is an integral membrane protein that catalyzes the photosynthetic process in purple photosynthetic bacteria. The LH2 complexes from Rhodobacter sphaeroides show characteristic strong absorbance at 800 and 850 nm due to the bacteriochlorophyll a molecules confined in two separate areas of the protein. Using these cofactors as intrinsic probes to monitor changes in membrane protein structure, we investigate the response to high hydrostatic pressure up to 2.1 GPa of LH2 complexes embedded into natural membrane environment or extracted with detergent. We demonstrate that high pressure does induce significant alterations to the tertiary structure of the protein in proximity of the protein-bound bacteriochlorophyll a molecules, including breakage of the hydrogen bond they are involved in. The membrane-embedded complexes appear more resilient to damaging effects of the compression than the complexes extracted into detergent environment. This difference has tentatively been explained by more compact structure of the membrane-embedded complexes

Evidence for high-pressure-induced rupture of hydrogen bonds in LH2 photosynthetic antenna pigment-protein complexes

Energy Technology Data Exchange (ETDEWEB)

Kangur, L; Leiger, K; Freiberg, A [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia)

2008-07-15

The bacteriochlorophyll a-containing LH2 light harvesting complex is an integral membrane protein that catalyzes the photosynthetic process in purple photosynthetic bacteria. The LH2 complexes from Rhodobacter sphaeroides show characteristic strong absorbance at 800 and 850 nm due to the bacteriochlorophyll a molecules confined in two separate areas of the protein. Using these cofactors as intrinsic probes to monitor changes in membrane protein structure, we investigate the response to high hydrostatic pressure up to 2.1 GPa of LH2 complexes embedded into natural membrane environment or extracted with detergent. We demonstrate that high pressure does induce significant alterations to the tertiary structure of the protein in proximity of the protein-bound bacteriochlorophyll a molecules, including breakage of the hydrogen bond they are involved in. The membrane-embedded complexes appear more resilient to damaging effects of the compression than the complexes extracted into detergent environment. This difference has tentatively been explained by more compact structure of the membrane-embedded complexes.

Functionalized Cobalt Triarylcorrole Covalently Bonded with Graphene Oxide: A Selective Catalyst for the Two- or Four-Electron Reduction of Oxygen.

Science.gov (United States)

Tang, Jijun; Ou, Zhongping; Guo, Rui; Fang, Yuanyuan; Huang, Dong; Zhang, Jing; Zhang, Jiaoxia; Guo, Song; McFarland, Frederick M; Kadish, Karl M

2017-08-07

A cobalt triphenylcorrole (CorCo) was covalently bonded to graphene oxide (GO), and the resulting product, represented as GO-CorCo, was characterized by UV-vis, FT-IR, and micro-Raman spectroscopy as well as by HRTEM, TGA, XRD, XPS, and AFM. The electrocatalytic activity of GO-CorCo toward the oxygen reduction reaction (ORR) was then examined in air-saturated 0.1 M KOH and 0.5 M H 2 SO 4 solutions by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode and/or a rotating ring-disk electrode. An overall 4-electron reduction of O 2 is obtained in alkaline media while under acidic conditions a 2-electron process is seen. The ORR results thus indicate that covalently bonded GO-CoCor can be used as a selective catalyst for either the 2- or 4-electron reduction of oxygen, the prevailing reaction depending upon the acidity of the solution.

Monitoring of DNA breakage in embryonic stages of the African catfish Clarias gariepinus (Burchell, 1822) after exposure to lead nitrate using alkaline comet assay.

Science.gov (United States)

Osman, Alaa G M; Mekkawy, Imam A; Verreth, Johan; Wuertz, Sven; Kloas, Werner; Kirschbaum, Frank

2008-12-01

Increasing lead contamination in Egyptian ecosystems and high lead concentrations in food items have raised concern for human health and stimulated studies on monitoring ecotoxicological impact of lead-caused genotoxicity. In this work, the alkaline comet assay was modified for monitoring DNA strand breakage in sensitive early life stages of the African catfish Clarias gariepinus. Following exposure to 100, 300, and 500 microg/L lead nitrate, DNA strand breakage was quantified in embryos at 30, 48, 96, 144, and 168 h post-fertilization (PFS). For quantitative analysis, four commonly used parameters (tail % DNA, %TDNA; head % DNA, %HDNA; tail length, TL; tail moment, TM) were analyzed in 96 nuclei (in triplicates) at each sampling point. The parameter %TDNA revealed highest resolution and lowest variation. A strong correlation between lead concentration, time of exposure, and DNA strand breakage was observed. Here, genotoxicity detected by comet assay preceded the manifested malformations assessed with conventional histology. Qualitative evaluation was carried out using five categories are as follows: undamaged (%TDNA 75%) nuclei confirming a dose and time-dependent shift towards increased frequencies of highly and extremely damaged nuclei. A protective capacity provided by a hardened chorion is a an interesting finding in this study as DNA damage in the prehatching stages 30 h-PFS and 48 h-PFS was low in all treatments (qualitative and quantitative analyses). These results clearly show that the comet assay is a sensitive tool for the detection of genotoxicity in vulnerable early life stages of the African catfish and is a method more sensitive than histological parameters for monitoring genotoxic effects. 2008 Wiley Periodicals, Inc.

Bonding brackets to porcelain: in vitro study

Directory of Open Access Journals (Sweden)

Sant'Anna Eduardo Franzotti

2002-01-01

Full Text Available The aim of this research was to verify, in vitro, the effect of various porcelain surface treatments on the shear strength of orthodontic brackets bonded to porcelain and the mode of fracture after debonding. Eighty-eight samples of metallic supported feldspathic porcelain were randomly divided into four groups according to their surface preparation as follows: the porcelain was maintained intact (GI, roughened with a diamond bur (GII, etched with 10% hydrofluoric acid (GIII, or sandblasted with aluminum oxide (GIV. The specimens were treated with silane (Scothprime and brackets were bonded with Concise. Each sample was subjected to a shear load at a crosshead speed of 1 mm/min and a recording was made at the point of failure. Bond strengths, adequate to withstand the application of orthodontic forces, were achieved in all groups. The Kruskal-Wallis statistical test showed no significant differences in bond strength between the groups (p>0.05. However, many more porcelain fractures occurred on deglazed porcelain. This study indicates that with the appropriate material selection, the silane/composite procedure alone may be adequate for bonding.

Valence bond model potential energy surface for H4

International Nuclear Information System (INIS)

Silver, D.M.; Brown, N.J.

1980-01-01

Potential energy surfaces for the H 4 system are derived using the valence bond procedure. An ab initio evaluation of the valence bond energy expression is described and some of its numerical properties are given. Next, four semiempirical evaluations of the valence bond energy are defined and parametrized to yield reasonable agreement with various ab initio calculations of H 4 energies. Characteristics of these four H 4 surfaces are described by means of tabulated energy minima and equipotential contour maps for selected geometrical arrangements of the four nuclei

Alkane Activation at Ambient Temperatures: Unusual Selectivities, C-C, C-H Bond Scission versus C-C Bond Coupling

NARCIS (Netherlands)

Trionfetti, C.; Agiral, A.; Gardeniers, Johannes G.E.; Lefferts, Leonardus; Seshan, Kulathuiyer

2008-01-01

Activating bonds: A cold plasma generated by dielectric barrier discharge in a microreactor converts alkanes (C1–C3) at atmospheric pressure. Large amounts of products with higher molecular weight than the starting hydrocarbons are observed showing that C-H activation at lower T favourably leads to

Responding to chromosomal breakage during M-phase: insights from a cell-free system

Directory of Open Access Journals (Sweden)

Costanzo Vincenzo

2009-07-01

Full Text Available Abstract DNA double strand breaks (DSBs activate ATM and ATR dependent checkpoints that prevent the onset of mitosis. However, how cells react to DSBs occurring when they are already in mitosis is poorly understood. The Xenopus egg extract has been utilized to study cell cycle progression and DNA damage checkpoints. Recently this system has been successfully used to uncover an ATM and ATR dependent checkpoint affecting centrosome driven spindle assembly. These studies have led to the identification of XCEP63 as major target of this pathway. XCEP63 is a coiled-coil rich protein localized at centrosome essential for proper spindle assembly. ATM and ATR directly phosphorylate XCEP63 on serine 560 inducing its delocalization from centrosome, which in turn delays spindle assembly. This pathway might contribute to regulate DNA repair or mitotic cell survival in the presence of chromosome breakage.

Shear bond strength of two bonding systems on dentin surfaces prepared with Er:YAG laser

International Nuclear Information System (INIS)

Dall'Magro, Eduardo

2001-01-01

The purpose of this study was to examine the shear bond strength of two bonding dentin systems, one 'one step' (Single Bond - 3M) and one 'self-etching' (Prompt-L-ESPE), when applied on dentin surfaces prepared with Er:YAG laser (2,94μm) that underwent ar not, acid etched. Forty one human molars just extracted were selected and after the cut with diamond disc and included in acrylic resin, resulting in 81 specimens (hemi crowns). After, the specimens were divided in one group treated with sand paper and another two groups treated with Er:YAG laser with 200 mJ and 250 mJ of energy and 2 Hz of frequency. Next, the prepared surfaces received three treatments with following application: 1) acid + Single Bond + Z 250 resin, 2) prompt-L-Pop + Z 250 resin, and 3) acid without, Single Bond + Z 250 resin. The Z 250 resin was applied and photopolymerized in increments on a Teflon matrix that belonged to an apparatus called 'Assembly Apparatus' machine producing cylinders of 3,5 mm of diameter and 5 mm of height. After these specimens were submitted to thermo cycling during 1 minute the 55 deg C and during 1 minute with 5 deg C with a total of 500 cycles for specimen, and the measures of shear bond strength were abstained using EMIC model DL 2000 rehearsed machine, with speed of 0,5 mm/min, measuring the final rupture tension (Mpa). The results showed an statistic superiority of 5% of probability level in dentin flattened with sandpaper and with laser using 200 mJ of energy with aspect to the ones flattened with laser using 250 mJ of energy. It was observed that using 'Single Bond' bonding dentin system the marks were statistically superior at 5% of probability with reference to the use of the Prompt-L-Pop adhesive system. So, it was concluded that Er:YAG Laser with 200 mJ of energy produced similar dentin cavity prepare than sandpaper and Single Bond seemed the best bonding agent system between restorative material and dentin. (author)

Examining student heuristic usage in a hydrogen bonding assessment.

Science.gov (United States)

Miller, Kathryn; Kim, Thomas

2017-09-01

This study investigates the role of representational competence in student responses to an assessment of hydrogen bonding. The assessment couples the use of a multiple-select item ("Choose all that apply") with an open-ended item to allow for an examination of students' cognitive processes as they relate to the assignment of hydrogen bonding within a structural representation. Response patterns from the multiple-select item implicate heuristic usage as a contributing factor to students' incorrect responses. The use of heuristics is further supported by the students' corresponding responses to the open-ended assessment item. Taken together, these data suggest that poor representational competence may contribute to students' previously observed inability to correctly navigate the concept of hydrogen bonding. © 2017 by The International Union of Biochemistry and Molecular Biology, 45(5):411-416, 2017. © 2017 The International Union of Biochemistry and Molecular Biology.

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.

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.

Modifications of the alpha,beta-double bond in chalcones only marginally affect the antiprotozoal activities

DEFF Research Database (Denmark)

Nielsen, S F; Kharazmi, A; Christensen, S B

1998-01-01

Methods for selective alkylation of chalcones in the alpha- or beta-position and for selective reduction of the alpha,beta-double bond have been developed. The antiparasitic potencies of the alpha,beta-double bond modified chalcones only differ marginally from the potencies of the parent chalcones...

Body of Knowledge (BOK) for Copper Wire Bonds

Science.gov (United States)

Rutkowski, E.; Sampson, M. J.

2015-01-01

Copper wire bonds have replaced gold wire bonds in the majority of commercial semiconductor devices for the latest technology nodes. Although economics has been the driving mechanism to lower semiconductor packaging costs for a savings of about 20% by replacing gold wire bonds with copper, copper also has materials property advantages over gold. When compared to gold, copper has approximately: 25% lower electrical resistivity, 30% higher thermal conductivity, 75% higher tensile strength and 45% higher modulus of elasticity. Copper wire bonds on aluminum bond pads are also more mechanically robust over time and elevated temperature due to the slower intermetallic formation rate - approximately 1/100th that of the gold to aluminum intermetallic formation rate. However, there are significant tradeoffs with copper wire bonding - copper has twice the hardness of gold which results in a narrower bonding manufacturing process window and requires that the semiconductor companies design more mechanically rigid bonding pads to prevent cratering to both the bond pad and underlying chip structure. Furthermore, copper is significantly more prone to corrosion issues. The semiconductor packaging industry has responded to this corrosion concern by creating a palladium coated copper bonding wire, which is more corrosion resistant than pure copper bonding wire. Also, the selection of the device molding compound is critical because use of environmentally friendly green compounds can result in internal CTE (Coefficient of Thermal Expansion) mismatches with the copper wire bonds that can eventually lead to device failures during thermal cycling. Despite the difficult problems associated with the changeover to copper bonding wire, there are billions of copper wire bonded devices delivered annually to customers. It is noteworthy that Texas Instruments announced in October of 2014 that they are shipping microcircuits containing copper wire bonds for safety critical automotive applications

Physical mechanisms of Cu-Cu wafer bonding

International Nuclear Information System (INIS)

Rebhan, B.

2014-01-01

Modern manufacturing processes of complex integrated semiconductor devices are based on wafer-level manufacturing of components which are subsequently interconnected. When compared with classical monolithic bi-dimensional integrated circuits (2D ICs), the new approach of three-dimensional integrated circuits (3D ICs) exhibits significant benefits in terms of signal propagation delay and power consumption due to the reduced metal interconnection length and allows high integration levels with reduced form factor. Metal thermo-compression bonding is a process suitable for 3D interconnects applications at wafer level, which facilitates the electrical and mechanical connection of two wafers even processed in different technologies, such as complementary metal oxide semiconductor (CMOS) and microelectromechanical systems (MEMS). Due to its high electrical conductivity, copper is a very attractive material for electrical interconnects. For Cu-Cu wafer bonding the process requires typically bonding for around 1 h at 400°C and high contact pressure applied during bonding. Temperature reduction below such values is required in order to solve issues regarding (i) throughput in the wafer bonder, (ii) wafer-to-wafer misalignment after bonding and (iii) to minimise thermo-mechanical stresses or device degradation. The aim of this work was to study the physical mechanisms of Cu-Cu bonding and based on this study to further optimise the bonding process for low temperatures. The critical sample parameters (roughness, oxide, crystallinity) were identified using selected analytical techniques and correlated with the characteristics of the bonded Cu-Cu interfaces. Based on the results of this study the impact of several materials and process specifications on the bonding result were theoretically defined and experimentally proven. These fundamental findings subsequently facilitated low temperature (LT) metal thermo-compression Cu-Cu wafer bonding and even room temperature direct

Promotion Effect of Alkali Metal Hydroxides on Polymer-Stabilized Pd Nanoparticles for Selective Hydrogenation of C–C Triple Bonds in Alkynols

OpenAIRE

Nikoshvili, Linda Zh.; Bykov, Alexey V.; Khudyakova, Tatiana E.; Lagrange, Thomas; Héroguel, Florent; Luterbacher, Jeremy S.; Matveeva, Valentina G.; Sulman, Esther M.; Dyson, Paul J.; Kiwi-Minsker, Lioubov

2017-01-01

Postimpregnation of Pd nanoparticles (NPs) stabilized within hyper-cross-linked polystyrene with sodium or potassium hydroxides of optimal concentration was found to significantly increase the catalytic activity for the partial hydrogenation of the C–C triple bond in 2-methyl-3-butyn-2-ol at ambient hydrogen pressure. The alkali metal hydroxide accelerates the transformation of the residual Pd(II) salt into Pd(0) NPs and diminishes the reaction induction period. In addition, the selectivity t...

Cypripedium calceolus germination in situ: seed longevity, and dormancy breakage by long incubation and cold winters

Directory of Open Access Journals (Sweden)

Hanne N. Rasmussen

2012-02-01

Full Text Available A successful in situ germination experiment with Cypripedium calceolus, the European Lady’s slipper, is reported here for the first time. The seeds originated from controlled pollinations within and between two closely related Danish populations. The seeds were sown ripe in seed packets in proximity of mother plants. Germination was first observed after 4.5 y in the ground, following two successive cold and snowy winters, and only in one population. Seedlings expanded through the sides of the broken testa and were hair-less. A corresponding set of seeds, germinated in vitro as asymbiotic controls, responded positively to repeated cold stratifications after long incubation, suggesting that time (leaching? and chilling are dormancy breakage factors.

Effects of hyperthermia on radiation-induced chromosome breakage and loss in excision repair deficient Drosophila melanogaster

International Nuclear Information System (INIS)

Mittler, S.

1986-01-01

Hyperthermia increased radiosensitivity with respect to γ-ray induced chromosome loss and breakage in all stages of spermatogenesis in the wild type Oregon R strain of Drosophila melanogaster, whereas hyperthermia increased radiosensitivity to a lesser extent in cn mus(2) 201sup(D1), an excision repair mutant with 0 per cent excision capacity and in mus(3) 308sup(D1), a strain with 24 per cent excision capacity. The differences in hyperthermia-induced radiation sensitivity between the excision repair mutants and the wild strain may be due to the hyperthermia affecting the excision repair mechanism, suggesting that one of the possible mechanisms involved in hyperthermia-increased radiosensitivity is an effect on excision repair. (author)

Shear bond strength of two 2-step etch-and-rinse adhesives when bonding ceramic brackets to bovine enamel.

Science.gov (United States)

Godard, Marion; Deuve, Benjamin; Lopez, Isabelle; Hippolyte, Marie-Pascale; Barthélemi, Stéphane

2017-09-01

The present study assessed a fracture analysis and compared the shear bond strength (SBS) of two 2-step etch-and-rinse (E&R) adhesives when bonding ceramic orthodontic brackets to bovine enamel. Thirty healthy bovine mandibular incisors were selected and were equally and randomly assigned to 2 experimental groups. Ceramic brackets (FLI Signature Clear ® , RMO) were bonded onto bovine enamel using an adhesive system. In group 1 (n=15), the conventional E&R adhesive (OrthoSolo ® +Enlight ® , Ormco) was used, and in group 2 (n=15), the new E&R adhesive limited to ceramic bracket bonding (FLI ceramic adhesive ® : FLI sealant resin ® +FLI adhesive paste ® , RMO) was used. In order to obtain appropriate enamel surfaces, the vestibular surfaces of mandibular bovine incisors were flat ground. After bonding, all the samples were stored in distilled water at room temperature for 21 days and subsequently tested for SBS, using the Instron ® universal testing machine. The Adhesive Remnant Index (ARI) scores were evaluated. Failure modes were assessed using optical microscopy at magnification ×40. A statistic data analysis was performed using the Mann-Whitney U-test (Penamel/adhesive interface. A statistically significant difference was found for the ARI scores between the two groups (P=0.00996). Only two fractured brackets, which remained bonded onto the bovine enamel, were reported. Both occurred in group 1. When bonded to ceramic brackets, FLI ceramic adhesive ® (RMO) was demonstrated to be very predictable and safe for clinical application in enamel bonding, whereas the results obtained with the conventional adhesive system (OrthoSolo ® +Enlight ® , Ormco) were less reproducible and revealed slightly excessive shear bond strength values. Copyright © 2017 CEO. Published by Elsevier Masson SAS. All rights reserved.

Microshear bonding effectiveness of different dentin regions

Directory of Open Access Journals (Sweden)

Anelise F Montagner

2015-01-01

Full Text Available Aim: The aim of this in vitro study was to evaluate the influence of dentin surfaces with different tubule orientation on bond strength of a multimode adhesive system. Materials and Methods: Twenty human molars were selected and prepared in different ways in order to produce different dentin regions. The teeth were randomized (n = 5 according to the application modes of a multimode adhesive system (etch-and-rinse and self-etching and to the dentin region (occlusal and proximal - 1.5 mm depth from dentinoenamel junction. Cylindrical restorations were performed on dentin with a starch tube. The samples remained immersed in distilled water for 24 h and the microshear bond strength (μSBS test was performed. The μSBS values were expressed in MPa and analyzed with ANOVA and Tukey′s test (P < 0.05. Results: There was no significant difference in the bond strength values between the application modes of the adhesive system (P = 0.19; however, the dentin regions (P < 0.05 significantly affected the μSBS. The proximal dentin presented higher bond strength values than occlusal dentin. Conclusion: The dentin surfaces with different tubule orientation influenced the bonding effectiveness of the adhesive system tested.

Imaging study of lymphoreticular tumor development in ataxia-telangiectasia and Nijmegen breakage syndrome

International Nuclear Information System (INIS)

Martinez-Leon, M. I.; Ceres-Ruiz, L.; Cuesta, M. A.; Garcia-Martin, F. J.

2003-01-01

Ataxia-telangiectasia (AT), or Louis-Bar syndrome, is an autosomal recessive illness characterized by progressive cerebellar ataxia, oculo-cutaneous telangiectasia, immunodeficiency combined with susceptibility to sinopulmonary infections and high incidence of neoplastic development. Nijmegen breakage syndrome (NBS) is a variant of AT, is also an autosomal recessive illness that presents cerebellar ataxia, as well as combined immunodeficiency and a tendency toward tumor development. Contrary to Louis-Bar syndrome, it doesn't present telangiectasia and exhibits a characteristics phenotype (short stature, bird-like face and microcephaly). Both entities are classified as syndrome of chromosomal instability or chromosomal fragility, a group which also includes Bloom syndrome and Fanconi anemia. All of these show an increase in the frequency of neoplastic pathologies, mainly lymphoid tumors. We present three patients,two with AT and one with NBS, who developed different lymphoma types in the course of the illness. We highlight the most outstanding aspects from a clinical-radiological point of view. (Author) 17 refs

Binding of Multiple Rap1 Proteins Stimulates Chromosome Breakage Induction during DNA Replication.

Directory of Open Access Journals (Sweden)

Greicy H Goto

2015-08-01

Full Text Available Telomeres, the ends of linear eukaryotic chromosomes, have a specialized chromatin structure that provides a stable chromosomal terminus. In budding yeast Rap1 protein binds to telomeric TG repeat and negatively regulates telomere length. Here we show that binding of multiple Rap1 proteins stimulates DNA double-stranded break (DSB induction at both telomeric and non-telomeric regions. Consistent with the role of DSB induction, Rap1 stimulates nearby recombination events in a dosage-dependent manner. Rap1 recruits Rif1 and Rif2 to telomeres, but neither Rif1 nor Rif2 is required for DSB induction. Rap1-mediated DSB induction involves replication fork progression but inactivation of checkpoint kinase Mec1 does not affect DSB induction. Rap1 tethering shortens artificially elongated telomeres in parallel with telomerase inhibition, and this telomere shortening does not require homologous recombination. These results suggest that Rap1 contributes to telomere homeostasis by promoting chromosome breakage.

Titanium dioxide nanoparticles induce oxidative stress and DNA-adduct formation but not DNA-breakage in human lung cells

Directory of Open Access Journals (Sweden)

Schins Roel PF

2009-06-01

Full Text Available Abstract Titanium dioxide (TiO2, also known as titanium (IV oxide or anatase, is the naturally occurring oxide of titanium. It is also one of the most commercially used form. To date, no parameter has been set for the average ambient air concentration of TiO2 nanoparticles (NP by any regulatory agency. Previously conducted studies had established these nanoparticles to be mainly non-cyto- and -genotoxic, although they had been found to generate free radicals both acellularly (specially through photocatalytic activity and intracellularly. The present study determines the role of TiO2-NP (anatase, ∅ in vitro. For comparison, iron containing nanoparticles (hematite, Fe2O3, ∅ 2-NP did not induce DNA-breakage measured by the Comet-assay in both cell types. Generation of reactive oxygen species (ROS was measured acellularly (without any photocatalytic activity as well as intracellularly for both types of particles, however, the iron-containing NP needed special reducing conditions before pronounced radical generation. A high level of DNA adduct formation (8-OHdG was observed in IMR-90 cells exposed to TiO2-NP, but not in cells exposed to hematite NP. Our study demonstrates different modes of action for TiO2- and Fe2O3-NP. Whereas TiO2-NP were able to generate elevated amounts of free radicals, which induced indirect genotoxicity mainly by DNA-adduct formation, Fe2O3-NP were clastogenic (induction of DNA-breakage and required reducing conditions for radical formation.

Adhesive bonds for optics: analysis and trade-offs

Science.gov (United States)

Daly, John G.; Hawk, Matthew D.

2017-08-01

Fastening optical elements with adhesives presents challenges when dissimilar materials (almost always the case) are encountered and environmental exposures from temperature changes, shock and vibration must be met. A brief review of standard processes will be followed by a selection criteria for the optic, its substrate, the bond geometry, surface preparation, application and cure. Common analysis practices will be compared to Finite Element models. The impact of stress in terms of distortion and level of risk of bond failure is highlighted. Trade-offs will be presented as aids in determination of the best approach. Some areas addressed will be different adhesive types, matching CTE's, stress effects, athermal bonds, monolithic designs, and the use of flexures.

Bond efficacy and interface morphology of self-etching adhesives to ground enamel.

Science.gov (United States)

Abdalla, Ali I; El Zohairy, Ahmed A; Abdel Mohsen, Mohamed M; Feilzer, Albert J

2010-02-01

This study compared the microshear bond strengths to ground enamel of three one-step self-etching adhesive systems, a self-etching primer system and an etch-and-rinse adhesive system. Three self-etching adhesives, Futurabond DC (Voco), Clearfil S Tri Bond (Kuraray) and Hybrid bond (Sun-Medical), a self-etching primer, Clearfil SE Bond (Kuraray), and an etch-and-rinse system, Admira Bond (Voco), were selected. Thirty human molars were used. The root of each tooth was removed and the crown was sectioned into halves. The convex enamel surfaces were reduced by polishing on silicone paper to prepare a flat surface. The bonding systems were applied on this surface. Prior to adhesive curing, a hollow cylinder (2.0 mm height/0.75 mm internal diameter) was placed on the treated surfaces. A resin composite was then inserted into the tube and cured. After water storage for 24 h, the tube was removed and shear bond strength was determined in a universal testing machine at a crosshead speed of 0.5 mm/min. The results were analyzed with ANOVA and the Tukey.-Kramer test at a 59 degrees confidence level. The enamel of five additional teeth was ground, and the etching component of each adhesive was applied and removed with absolute ethanol instead of being light cured. These teeth and selected fractured surfaces were examined by SEM. Adhesion to ground enamel of the Futurabond DC (25 +/- 3.5 MPa) and Clearfil SE Bond (23 +/- 2.9 MPa) self-etching systems was not significantly different from the etch-and-rinse system Admira Bond (27 +/- 2.3 MPa). The two self-etching adhesives Clearfil S Tri bond and Hybrid Bond demonstrated significantly lower bond strengths (14 +/- 1.4 MPa; 11 +/- 1.9 MPa) with no significant differences between them (p adhesive systems are dependent on the type of adhesive system. Some of the new adhesive systems showed bond strength values comparable to that of etch-and-rinse systems. There was no correlation between bond strength and morphological changes in

Development of HIP bonding procedure and mechanical properties of HIP bonded joints for reduced activation ferritic steel F-82H

International Nuclear Information System (INIS)

Oda, Masahiro; Kurasawa, Toshimasa; Kuroda, Toshimasa; Hatano, Toshihisa; Takatsu, Hideyuki

1997-03-01

Structural materials of blanket components in fusion DEMO reactors will receive a neutron wall load more than 3-5MW/m 2 as well as exposed by surface heat flux more than 0.5MW/m 2 . A reduced activation ferritic steel F-82H has been developed by JAERI in collaboration with NKK from viewpoints of resistance for high temperature and neutron loads and lower radioactivity. This study intends to obtain basic performance of F-82H to establish the fabrication procedure of the first wall and blanket box by using Hot Isostatic Pressing (HIP) bonding. Before HIP bonding tests, effects of heat treatment temperature and surface roughness on mechanical properties of joints were investigated in the heat treatment tests and diffusion bonding tests, respectively. From these results, the optimum HIP bonding conditions and the post heat treatment were selected. Using these conditions, the HIP bonding tests were carried out to evaluate HIP bondability and to obtain mechanical properties of the joints. Sufficient HIP bonding performance was obtained under the temperature of 1040degC, the compressive stress of 150MPa, the holding time of 2h, and the surface roughness ∼μ m. Mechanical properties of HIP bonded joints with these conditions were similar to those of as-received base metal. An oxide formation on the surface to be bonded would need to be avoided for sufficient bonding. The bonding ratio, Charpy impact value and fatigue performance of the joints strongly depended on the HIP conditions, especially temperature, while micro-structure, Vickers hardness and tensile properties had little dependence on the HIP temperature. The surface roughness strongly affected the bonding ratio and would be required to be in the level of a few μ m. In the HIP bonding test of the welded material, the once-melted surface could be jointed by the HIP bonding under the above-mentioned procedure. (J.P.N.)

Enamel Wetness Effects on Microshear Bond Strength of Different Bonding Agents (Adhesive Systems): An in vitro Comparative Evaluation Study.

Science.gov (United States)

Kulkarni, Girish; Mishra, Vinay K

2016-05-01

The purpose of this study was to compare the effect of enamel wetness on microshear bond strength using different adhesive systems. To evaluate microshear bond strength of three bonding agents on dry enamel; to evaluate microshear bond strength of three bonding agents on wet enamel; and to compare microshear bond strength of three different bonding agents on dry and wet enamel. Sixty extracted noncarious human premolars were selected for this study. Flat enamel surfaces of approximately 3 mm were obtained by grinding the buccal surfaces of premolars with water-cooled diamond disks. This study evaluated one etch-and-rinse adhesive system (Single Bond 2) and two self-etching adhesive systems (Clearfil SE Bond and Xeno-V). The specimens were divided into two groups (n = 30). Group I (dry) was air-dried for 30 seconds and in group II (wet) surfaces were blotted with absorbent paper to remove excess water. These groups were further divided into six subgroups (n = 10) according to the adhesives used. The resin composite, Filtek Z 250, was bonded to flat enamel surfaces that had been treated with one of the adhesives, following the manufacturer's instructions. After being stored in water at 37°C for 24 hours, bonded specimens were stressed in universal testing machine (Fig. 3) at a crosshead speed of 1 mm/min. The data were evaluated with one-way and two-way analysis of variance (ANOVA), t-test, and Tukey's Multiple Post hoc tests (a = 0.05). The two-way ANOVA and Tukey's Multiple Post hoc tests showed significant differences among adhesive systems, but wetness did not influence microshear bond strength (p = 0.1762). The one-way ANOVA and t-test showed that the all-in-one adhesive (Xeno-V) was the only material influenced by the presence of water on the enamel surface. Xeno-V showed significantly higher microshear bond strength when the enamel was kept wet. Single Bond 2 adhesive showed significantly higher microshear bond strength as compared with Xeno-V adhesive but no

In-vitro orthodontic bond strength testing : A systematic review and meta-analysis

NARCIS (Netherlands)

Finnema, K.J.; Ozcan, M.; Post, W.J.; Ren, Y.J.; Dijkstra, P.U.

INTRODUCTION: The aims of this study were to systematically review the available literature regarding in-vitro orthodontic shear bond strength testing and to analyze the influence of test conditions on bond strength. METHODS: Our data sources were Embase and Medline. Relevant studies were selected

Tunable differentiation of tertiary C-H bonds in intramolecular transition metal-catalyzed nitrene transfer reactions.

Science.gov (United States)

Corbin, Joshua R; Schomaker, Jennifer M

2017-04-13

Metal-catalyzed nitrene transfer reactions are an appealing and efficient strategy for accessing tetrasubstituted amines through the direct amination of tertiary C-H bonds. Traditional catalysts for these reactions rely on substrate control to achieve site-selectivity in the C-H amination event; thus, tunability is challenging when competing C-H bonds have similar steric or electronic features. One consequence of this fact is that the impact of catalyst identity on the selectivity in the competitive amination of tertiary C-H bonds has not been well-explored, despite the potential for progress towards predictable and catalyst-controlled C-N bond formation. In this communication, we report investigations into tunable and site-selective nitrene transfers between tertiary C(sp 3 )-H bonds using a combination of transition metal catalysts, including complexes based on Ag, Mn, Rh and Ru. Particularly striking was the ability to reverse the selectivity of nitrene transfer by a simple change in the identity of the N-donor ligand supporting the Ag(i) complex. The combination of our Ag(i) catalysts with known Rh 2 (ii) complexes expands the scope of successful catalyst-controlled intramolecular nitrene transfer and represents a promising springboard for the future development of intermolecular C-H N-group transfer methods.

Retainer Positioner

Directory of Open Access Journals (Sweden)

Sanjeeb Kumar Sahu

2012-01-01

Full Text Available Several techniques are used to keep the retainer wire in the proper position during direct bonding, of lingual bonded retainers. Proper placement helps prevent occlusal wear of the composite over the retainer wire, thus reducing the risk of breakage. This article describes a new chairside time saving retainer positioner which allows accurate placement and direct bonding of all types of fixed lingual retainers, with solid or multistranded wires.

Effect of ethanol-wet-bonding technique on resin–enamel bonds

Directory of Open Access Journals (Sweden)

Muhammet Kerim Ayar

2014-03-01

Conclusion: The ethanol-wet-bonding technique may increase the bond strength of commercial adhesives to enamel. The chemical composition of the adhesives can affect the bond strength of adhesives when bonding to acid-etched enamel, using the ethanol-wet-bonding technique. Some adhesive systems used in the present study may simultaneously be applied to enamel and dentin using ethanol-wet-bonding. Furthermore, deploying ethanol-wet-bonding for the tested commercial adhesives to enamel can increase the adhesion abilities of these adhesives to enamel.

Thermal stability and chemical bonding states of AlOxNy/Si gate stacks revealed by synchrotron radiation photoemission spectroscopy

International Nuclear Information System (INIS)

He, G.; Toyoda, S.; Shimogaki, Y.; Oshima, M.

2010-01-01

Annealing-temperature dependence of the thermal stability and chemical bonding states of AlO x N y /SiO 2 /Si gate stacks grown by metalorganic chemical vapor deposition (MOCVD) using new chemistry was investigated by synchrotron radiation photoemission spectroscopy (SRPES). Results have confirmed the formation of the AlN and AlNO compounds in the as-deposited samples. Annealing the AlO x N y samples in N 2 ambient in 600-800 deg. C promotes the formation of SiO 2 component. Meanwhile, there is no formation of Al-O-Si and Al-Si binding states, suggesting no interdiffusion of Al with the Si substrate. A thermally induced reaction between Si and AlO x N y to form volatile SiO and Al 2 O is suggested to be responsible for the full disappearance of the Al component that accompanies annealing at annealing temperature of 1000 deg. C. The released N due to the breakage of the Al-N bonding will react with the SiO 2 interfacial layer and lead to the formation of the Si 3 -N-O/Si 2 -N-O components at the top of Si substrate. These results indicate high temperature processing induced evolution of the interfacial chemistry and application range of AlO x N y /Si gate stacks in future CMOS devices.

Isolation and characterization of a uranium(VI)-nitride triple bond

Science.gov (United States)

King, David M.; Tuna, Floriana; McInnes, Eric J. L.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.

2013-06-01

The nature and extent of covalency in uranium bonding is still unclear compared with that of transition metals, and there is great interest in studying uranium-ligand multiple bonds. Although U=O and U=NR double bonds (where R is an alkyl group) are well-known analogues to transition-metal oxo and imido complexes, the uranium(VI)-nitride triple bond has long remained a synthetic target in actinide chemistry. Here, we report the preparation of a uranium(VI)-nitride triple bond. We highlight the importance of (1) ancillary ligand design, (2) employing mild redox reactions instead of harsh photochemical methods that decompose transiently formed uranium(VI) nitrides, (3) an electrostatically stabilizing sodium ion during nitride installation, (4) selecting the right sodium sequestering reagent, (5) inner versus outer sphere oxidation and (6) stability with respect to the uranium oxidation state. Computational analyses suggest covalent contributions to U≡N triple bonds that are surprisingly comparable to those of their group 6 transition-metal nitride counterparts.

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.

Application of correspondence analysis in the assessment of mine tailings dam breakage risk in the Mediterranean region.

Science.gov (United States)

Salgueiro, Ana Rita; Pereira, Henrique Garcia; Rico, Maria-Teresa; Benito, Gerado; Díez-Herreo, Andrés

2008-02-01

A new statistical approach for preliminary risk evaluation of breakage in tailings dam is presented and illustrated by a case study regarding the Mediterranean region. The objective of the proposed method is to establish an empirical scale of risk, from which guidelines for prioritizing the collection of further specific information can be derived. The method relies on a historical database containing, in essence, two sets of qualitative data: the first set concerns the variables that are observable before the disaster (e.g., type and size of the dam, its location, and state of activity), and the second refers to the consequences of the disaster (e.g., failure type, sludge characteristics, fatalities categorization, and downstream range of damage). Based on a modified form of correspondence analysis, where the second set of attributes are projected as "supplementary variables" onto the axes provided by the eigenvalue decomposition of the matrix referring to the first set, a "qualitative regression" is performed, relating the variables to be predicted (contained in the second set) with the "predictors" (the observable variables). On the grounds of the previously derived relationship, the risk of breakage in a new case can be evaluated, given observable variables. The method was applied in a case study regarding a set of 13 test sites where the ranking of risk obtained was validated by expert knowledge. Once validated, the procedure was included in the final output of the e-EcoRisk UE project (A Regional Enterprise Network Decision-Support System for Environmental Risk and Disaster Management of Large-Scale Industrial Spills), allowing for a dynamic historical database updating and providing a prompt rough risk evaluation for a new case. The aim of this section of the global project is to provide a quantified context where failure cases occurred in the past for supporting analogue reasoning in preventing similar situations.

Observed mechanism for the breakup of small bundles of cellulose Iα and Iβ in ionic liquids from molecular dynamics simulations.

Science.gov (United States)

Rabideau, Brooks D; Agarwal, Animesh; Ismail, Ahmed E

2013-04-04

Explicit, all-atom molecular dynamics simulations are used to study the breakup of small bundles of cellulose Iα and Iβ in the ionic liquids [BMIM]Cl, [EMIM]Ac, and [DMIM]DMP. In all cases, significant breakup of the bundles is observed with the initial breakup following a common underlying mechanism. Anions bind strongly to the hydroxyl groups of the exterior strands of the bundle, forming negatively charged complexes. Binding also weakens the intrastrand hydrogen bonds present in the cellulose strands, providing greater strand flexibility. Cations then intercalate between the individual strands, likely due to charge imbalances, providing the bulk to push the individual moieties apart and initiating the separation. The peeling of an individual strand from the main bundle is observed in [EMIM]Ac with an analysis of its hydrogen bonds with other strands showing that the chain detaches glucan by glucan from the main bundle in discrete, rapid events. Further analysis shows that the intrastrand hydrogen bonds of each glucan tend to break for a sustained period of time before the interstrand hydrogen bonds break and strand detachment occurs. Examination of similar nonpeeling strands shows that, without this intrastrand hydrogen bond breakage, the structural rigidity of the individual unit can hinder its peeling despite interstrand hydrogen bond breakage.

Plasmid marker rescue transformation proceeds by breakage-reunion in Bacillus subtilis

International Nuclear Information System (INIS)

Weinrauch, Y.; Dubnau, D.

1987-01-01

Bacillus subtilis carrying a plasmid which replicates with a copy number of about 1 was transformed with linearized homologous plasmid DNA labeled with the heavy isotopes 2 H and 15 N, in the presence of 32 Pi and 6-(p-hydroxyphenylazo)-uracil to inhibit DNA replication. Plasmid DNA was isolated from the transformed culture and fractionated in cesium chloride density gradients. The distribution of total and donor plasmid DNA was examined, using specific hybridization probes. The synthesis of new DNA, associated with the integration of donor moiety, was also monitored. Donor-specific sequences were present at a density intermediate between that of light and hybrid DNA. This recombinant DNA represented 1.4% of total plasmid DNA. The latter value corresponded well with the transforming activity (1.7%) obtained for the donor marker. Newly synthesized material associated with plasmid DNA at the recombinant density amounted to a minor portion of the recombinant plasmid DNA. These data suggest that, like chromosomal transformation, plasmid marker rescue transformation does not require replication for the integration of donor markers and, also like chromosomal transformation, proceeds by a breakage-reunion mechanism. The extent of donor DNA replacement of recipient DNA per plasmid molecule of 54 kilobases (27 kilobase pairs) was estimated as 16 kilobases

The UV-light and X-irradiation induced conversion of p-phenoxyphenol in aqueous solution at 250C

International Nuclear Information System (INIS)

Ehrl, A.

1975-01-01

UV-photolysis and X-radiolysis of p-phenoxyphenol was expected to yield products analogous to those of thyronine, after aromatic structures being equivalent. When exposed to UV-light, p-phenoxyphenol was found being selectively converted into phenylhydroquinone in consequence of intramolecular rearrangement. The reaction heat was estimated applying bond energies to the conversion and comparing the result with differences in the combustion heat of homologous compounds. After X-irradiation, phenylhydroquinone however was not present. Formation of the irradiation products phenol, hydroquinone, p-benzoquinone and pyrocatechol presumed breakage of substrate molecules in consequence of intermolecular interaction with transient water radiolysis species. (orig.) [de

Halogen bonding: A new retention mechanism for the solid phase extraction of perfluorinated iodoalkanes

International Nuclear Information System (INIS)

Yan Xiaoqing; Shen Qianjin; Zhao Xiaoran; Gao Haiyue; Pang Xue; Jin Weijun

2012-01-01

Highlights: ► Halogen bonding (XB) is firstly utilised in solid phase extraction. ► The perfluorinated iodine alkanes can be extracted by C-I⋯Cl − halogen bonding. ► The C-I⋯Cl − halogen bond is well characterised by spectroscopy methods. ► The analytes with strong halogen-bonding abilities can be selectively extracted. - Abstract: For the first time, halogen-bonding interaction is utilised in the solid phase extraction of perfluorinated iodoalkane (PFI). Nine PFIs, as model analytes, were tested, and analyses by UV, 19 F NMR and Raman spectroscopies demonstrate that the PFIs are extracted by a strong anion exchange (SAX) sorbent from n-hexane due to the C-I⋯Cl − halogen-bonding interactions. The results also show that the adsorptivities of SAX for the diiodoperfluoro-alkanes (diiodo-PFIs) were much stronger than those for the perfluoroalkyl iodides (monoiodo-PFIs). Specifically, the recoveries for 1,6-diiodoperfluorohexane and 1,8-diiodoperfluorooctane were higher than 80% when 100 mL of sample spiked with a 5 ng mL −1 analyte mixture was extracted. Interestingly, SAX had no adsorption for hexafluorobenzene at all, which is known to be unable to form a halogen bond with Cl − . The analytical performance of the halogen bond-based SPE-GC–MS method for the diiodo-PFIs was also examined in soil samples. The sorbent SAX enabled the selective extraction of four diiodo-PFIs successfully from soil samples. The recoveries of the diiodo-PFIs extracted from 5 g soil sample at the 100 ng g −1 spike level were in the range of 73.2–93.8% except 26.8% for 1,2-diiodoperfluoroethane. The limit of detection varied from 0.02 to 0.04 ng g −1 in soil samples. Overall, this work reveals the great application potential of halogen bonding in the field of solid phase extraction to selectively extract compounds with strong halogen-bonding abilities.

Orthodontic bracket bonding without previous adhesive priming: A meta-regression analysis.

Science.gov (United States)

Altmann, Aline Segatto Pires; Degrazia, Felipe Weidenbach; Celeste, Roger Keller; Leitune, Vicente Castelo Branco; Samuel, Susana Maria Werner; Collares, Fabrício Mezzomo

2016-05-01

To determine the consensus among studies that adhesive resin application improves the bond strength of orthodontic brackets and the association of methodological variables on the influence of bond strength outcome. In vitro studies were selected to answer whether adhesive resin application increases the immediate shear bond strength of metal orthodontic brackets bonded with a photo-cured orthodontic adhesive. Studies included were those comparing a group having adhesive resin to a group without adhesive resin with the primary outcome measurement shear bond strength in MPa. A systematic electronic search was performed in PubMed and Scopus databases. Nine studies were included in the analysis. Based on the pooled data and due to a high heterogeneity among studies (I(2)  =  93.3), a meta-regression analysis was conducted. The analysis demonstrated that five experimental conditions explained 86.1% of heterogeneity and four of them had significantly affected in vitro shear bond testing. The shear bond strength of metal brackets was not significantly affected when bonded with adhesive resin, when compared to those without adhesive resin. The adhesive resin application can be set aside during metal bracket bonding to enamel regardless of the type of orthodontic adhesive used.

Simulating progressive social transfers. Gas subsidies and solidarity bonds in Ecuador

International Nuclear Information System (INIS)

Cuesta, J.; Ponce, J.; Leon, M.

2004-02-01

After two decades of neglect, social expending has become a cornerstone in the current fight against poverty in Ecuador. Ecuador is presently considering the elimination of regressive gas subsidies and the shift of these resources into pro-poor targeted Solidarity Bonds. Great distributive gains are expected from this reform. There are, however, a number of considerations that may prevent this policy shift from obtaining substantial poverty and equality gains. Despite their regressivity, implicit gas subsidies still represent a considerable proportion of total household consumption among poor households. Also, solidarity bonds siphon off a substantial share of their total benefits to middle income groups. This paper estimates the redistributive consequences of policy reforms on gas subsidies and solidarity bonds in Ecuador. A simulation methodology estimates both direct and indirect (labour-driven) distributive effects of four alternative scenarios: (1) total elimination of gas subsidies; (2) selective elimination of gas subsidies among non-poor households; (3) total elimination of gas subsidies and shift of resources to solidarity bonds targeted to the poor; (4) selective elimination of gas subsidies and shift of resources to solidarity bonds targeted to the poor. Estimates confirm that the redistributive gains from these reforms are rather small both for poverty and inequality. Incentives to work following the elimination of subsidies compensate, or even outdo, immediate poverty rises. Also, the elimination of gas subsidies without further expansion of subsidy bonds will unambiguously increase poverty in Ecuador between one and one and a half percent points

Bond strength of universal adhesives: A systematic review and meta-analysis.

Science.gov (United States)

Rosa, Wellington Luiz de Oliveira da; Piva, Evandro; Silva, Adriana Fernandes da

2015-07-01

A systematic review was conducted to determine whether the etch-and-rinse or self-etching mode is the best protocol for dentin and enamel adhesion by universal adhesives. This report followed the PRISMA Statement. A total of 10 articles were included in the meta-analysis. Two reviewers performed a literature search up to October 2014 in eight databases: PubMed, Web of Science, Scopus, BBO, SciELO, LILACS, IBECS and The Cochrane Library. In vitro studies evaluating the bond strength of universal adhesives to dentin and/or enamel by the etch-and-rinse and self-etch strategies were eligible to be selected. Statistical analyses were conducted using RevMan 5.1 (The Cochrane Collaboration, Copenhagen, Denmark). A global comparison was performed with random-effects models at a significance level of puniversal adhesives (p≥0.05). However, for the ultra-mild All-Bond Universal adhesive, the etch-and-rinse strategy was significantly different than the self-etch mode in terms of dentin micro-tensile bond strength, as well as in the global analysis of enamel micro-tensile and micro-shear bond strength (p≤0.05). The enamel bond strength of universal adhesives is improved with prior phosphoric acid etching. However, this effect was not evident for dentin with the use of mild universal adhesives with the etch-and-rinse strategy. Selective enamel etching prior to the application of a mild universal adhesive is an advisable strategy for optimizing bonding. Copyright © 2015 Elsevier Ltd. All rights reserved.

The extended variant of the bond valence-bond length correlation curve for boron(III)-oxygen bonds

International Nuclear Information System (INIS)

Sidey, Vasyl

2015-01-01

The extended variant of the bond valence (s)-bond length (r) correlation curve for boron(III)-oxygen bonds has been closely approximated using the three-parameter function s = [k/(r - l)] - m, where s is measured in valence units (vu), r is measured in Aa, k = 0.53 Aa.vu, l = 0.975(1) Aa and m = 0.32 vu. The function s = exp[(r 0 - r)/b] traditionally used in the modern bond valence model requires the separate set of the bond valence parameters (r 0 = 1.362 Aa; b = 0.23 Aa) in order to approximate the above s-r curve for the bonds shorter than ∝1.3 Aa.

Understanding Bonds - Denmark

DEFF Research Database (Denmark)

Rimmer, Nina Røhr

2016-01-01

Undervisningsmateriale. A bond is a debt security, similar to an ”I Owe You document” (IOU). When you purchase a bond, you are lending money to a government, municipality, corporation, federal agency or other entity known as the issuer. In return for the loan, the issuer promises to pay you...... a specified rate of interest during the life of the bond and to repay the face value of the bond (the principal) when it “matures,” or comes due. Among the types of bonds you can choose from are: Government securities, municipal bonds, corporate bonds, mortgage and asset-backed securities, federal agency...... securities and foreign government bonds....

Percutaneous self-injury to the femoral region caused by bur breakage during surgical extraction of a patient's impacted third molar.

Science.gov (United States)

Yu, Tae Hoon; Lee, Jun; Kim, Bong Chul

2015-10-01

Extraction of an impacted third molar is one of the most frequently performed techniques in oral and maxillofacial surgery. Surgeons can suffer numerous external injuries while extracting a tooth, with percutaneous injuries to the hand being the most commonly reported. In this article, we present a case involving a percutaneous injury of the surgeon's femoral region caused by breakage of the fissure bur connected to the handpiece during extraction of the third molar. We also propose precautions to prevent such injuries and steps to be undertaken when they occur.

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.

Selective control of photodissociation in deutereted water molecule HOD

International Nuclear Information System (INIS)

Adhikari, S.; Deshpande, Sarin; Sarma, Manabendra; Kurkal, Vandana; Mishra, M.K.

2006-01-01

Bond dissociation in the deutereted water molecule HOD has been investigated to explore the possibility of selective control of dissociation of O-H and O-D bonds using simple field profiles and initial states that do not require high overtone excitations. Preliminary results indicate that considerable selectivity in dissociation of O-H and O-D bonds can be achieved using fundamental and first overtone excitations only and use of field optimized initial state (FOIST) based scheme with appropriate choice of field parameters and initial states may enhance both selectivity and yield

Portfolio selection with heavy tails

NARCIS (Netherlands)

Hyung, N.; Vries, de C.G.

2007-01-01

Consider the portfolio problem of choosing the mix between stocks and bonds under a downside risk constraint. Typically stock returns exhibit fatter tails than bonds corresponding to their greater downside risk. Downside risk criteria like the safety first criterion therefore often select corner

Amalgam shear bond strength to dentin using different bonding agents.

Science.gov (United States)

Vargas, M A; Denehy, G E; Ratananakin, T

1994-01-01

This study evaluated the shear bond strength of amalgam to dentin using five different bonding agents: Amalgambond Plus, Optibond, Imperva Dual, All-Bond 2, and Clearfil Liner Bond. Flat dentin surfaces obtained by grinding the occlusal portion of 50 human third molars were used for this study. To contain the amalgam on the tooth surface, cylindrical plastic molds were placed on the dentin and secured with sticky wax. The bonding agents were then applied according to the manufacturers' instructions or light activated and Tytin amalgam was condensed into the plastic molds. The samples were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. Analysis by one-way ANOVA indicated significant difference between the five groups (P < 0.05). The bond strength of amalgam to dentin was significantly higher with Amalgambond Plus using the High-Performance Additive than with the other four bonding agents.

In vitro Evaluation of Effect of Dental Bleaching on the Shear Bond Strength of Sapphire Orthodontics Brackets Bonded with Resin Modified Glass Ionomer Cement

Directory of Open Access Journals (Sweden)

Zainab M Kadhom

2017-11-01

Full Text Available Aim: This study aimed to assess the effect of various types of bleaching agents on the shear bond strength of sapphire brackets bonded to human maxillary premolar teeth using resin modified glass ionomer cement (RMGIC and to determine the site of bond failure. Materials and Methods: Thirty freshly extracted maxillary human premolars were selected and assigned into three equal groups, ten teeth in each. The first group was the control (unbleached group; the second group comprised teeth bleached with hydrogen peroxide group (HP 37.5% (in-office bleaching while the third group included teeth bleached with carbamide peroxide group (CP 16% (at-home bleaching. The teeth in the experimental groups were bleached and stored in water one day then bonded with sapphire brackets using RMGIC with the control group and left another day. De-bonding was performed using Instron universal testing machine. To determine the site of bond failure, both the enamel surface and bracket base of each tooth were examined under magnifying lens (20X of a stereomicroscope. Results: Results showed statistically highly significant difference in the shear bond strengths between control group and both of bleaching groups being low in the control group. Score III was the predominant site of bond failure in all groups. Conclusions: RMGIC provides adequate bond strength when bonding the sapphire brackets to bleached enamel; this bonding was strong enough to resist both the mechanical and masticatory forces. Most of the adhesive remained on the brackets, so it reduced the time required for removal of the bonding material’s remnants during enamel finishing and polishing.

13 CFR 115.60 - Selection and admission of PSB Sureties.

Science.gov (United States)

2010-01-01

... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Selection and admission of PSB Sureties. 115.60 Section 115.60 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION SURETY BOND GUARANTEE Preferred Surety Bond (PSB) Guarantees § 115.60 Selection and admission of PSB Sureties. (a) Selection of PSB Sureties. SBA's selection o...

Selective Acid Etching Improves the Bond Strength of Universal Adhesive to Sound and Demineralized Enamel of Primary Teeth.

Science.gov (United States)

Antoniazzi, Bruna Feltrin; Nicoloso, Gabriel Ferreira; Lenzi, Tathiane Larissa; Soares, Fabio Zovico Maxnuck; Rocha, Rachel de Oliveira

To evaluate the influence of enamel condition and etching strategy on bond strength of a universal adhesive in primary teeth. Thirty-six primary molars were randomly assigned to six groups (n = 6) according to the enamel condition (sound [S] and demineralized [DEM]/cariogenic challenge by pH cycling prior to restorative procedures) and adhesive system (Scotchbond Universal Adhesive [SBU]) used in either etch-and-rinse (ER) or selfetching (SE) mode, with Clearfil SE Bond as the self-etching control. The adhesives were applied to flat enamel surfaces and composite cylinders (0.72 mm2) were built up. After 24-h storage in water, specimens were subjected to the microshear test. Bond strength (MPa) data were analyzed using two-way ANOVA and Tukey's post-hoc tests (α = 0.05). Significant differences were found considering the factors adhesive system (p = 0.003) and enamel condition (p = 0.001). Demineralized enamel negatively affected the bond strength, with μSBS values approximately 50% lower than those obtained for sound enamel. SBU performed better in etch-and-rinse mode, and the bond strength found for SBU applied in self-etching mode was similar to that of CSE. Enamel etching with phosphoric acid improves the bond strength of a universal adhesive system to primary enamel. Demineralized primary enamel results in lower bond strength.

Convertible bond valuation focusing on Chinese convertible bond market

OpenAIRE

Yang, Ke

2010-01-01

This paper mainly discusses the methods of valuation of convertible bonds in Chinese market. Different from common convertible bonds in European market, considering the complicate features of Chinese convertible bond, this paper represents specific pricing approaches for pricing convertible bonds with different provisions along with the increment of complexity of these provisions. More specifically, this paper represents the decomposing method and binomial tree method for pricing both of Non-...

In vitro evaluation of an alternative method to bond molar tubes

Directory of Open Access Journals (Sweden)

Célia Regina Maio Pinzan-Vercelino

2011-02-01

Full Text Available Despite the advances in bonding materials, many clinicians today still prefer to place bands on molar teeth. Molar bonding procedures need improvement to be widely accepted clinically. OBJECTIVE: The purpose of this study was to evaluate the shear bond strength when an additional adhesive layer was applied on the occlusal tooth/tube interface to provide reinforcement to molar tubes. MATERIAL AND METHODS: Sixty third molars were selected and allocated to the 3 groups: group 1 received a conventional direct bond followed by the application of an additional layer of adhesive on the occlusal tooth/tube interface, group 2 received a conventional direct bond, and group 3 received a conventional direct bond and an additional cure time of 10 s. The specimens were debonded in a universal testing machine. The results were analyzed statistically by ANOVA and Tukey's test (α=0.05. RESULTS: Group 1 had a significantly higher (p0.05. CONCLUSIONS: The present in vitro findings indicate that the application of an additional layer of adhesive on the tooth/tube interface increased the shear bond strength of the bonded molar tubes.

Advanced Nano fibrous textile based dressing material for treating ...

Indian Academy of Sciences (India)

57

3 Department for Management of Science and Technology Development, Ton Duc .... only amplify the duration of inflammation phase but also cause persistent ... loss of mechanical function due to sudden breakage of chemical bonds limit its.

Copper wire bonding

CERN Document Server

Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

2014-01-01

This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

Development of bonding techniques between tungsten and copper alloy for plasma facing components by HIP method (2). Bonding between tungsten and DS-copper

International Nuclear Information System (INIS)

Saito, Shigeru; Fukaya, Kiyoshi; Eto, Motokuni; Ishiyama, Shintaro; Akiba, Masato

2000-02-01

Recently, W (tungsten)-alloys are considered as plasma facing material (PFM) for ITER because of these many favorable properties such as high melting point (3655 K), relatively high thermal conductivity and higher resistivity for plasma sputtering. On the other hand, Cu-alloys, especially DS (dispersion strengthened)-Cu, are proposed as heat sink materials because of its high thermal conductivity and good mechanical properties at high temperature. Plasma facing components (PFC) are designed as the duplex structure where W armor tiles are bonded with Cu-alloy heat sink. Then, we started the bonding technology development by hot isostatic press (HIP) method to bond W with Cu-alloys because of its many advantages. Until now, it was reported that we could get the best HIP bonding conditions for W and OFHC-Cu and the tensile strength was similar with HIP treated OFHC-Cu. In this experiments, bonding tests of W and DS-Cu with insert material were performed. As insert material, OFHC-Cu was used with different thickness. Bonding conditions were selected as 1273 K x 2 hours x 147 MPa. Bonding tests with 0.3 to 1.8 mm thickness OFHC-Cu were successfully bonded but with 0.1 mm thickness was not bonded. From the results of tensile tests, the tensile strength of the specimens with 0.3 and 0.5 mm thickness were decreased at elevated temperature. It was shown that over 1.0 mm thickness OFHC-Cu insert may be needed and the tensile strength were a little higher than that of HIP treated OFHC-Cu. (author)

Effect of Bonding Pressure and Bonding Time on the Tensile Properties of Cu-Foam / Cu-Plate Diffusion Bonded Joint

International Nuclear Information System (INIS)

Kim, Sang-Ho; Heo, Hoe-Jun; Kang, Chung-Yun; Yoon, Tae-Jin

2016-01-01

Open cell Cu foam, which has been widely utilized in various industries because of its high thermal conductivity, lightweight and large surface area, was successfully joined with Cu plate by diffusion bonding. To prevent excessive deformation of the Cu foam during bonding process, the bonding pressure should be lower than 500 kPa at 800 ℃ for 60 min and bonding pressure should be lowered with increasing holding time. The bonding strength was evaluated by tensile tests. The tensile load of joints increased with the bonding pressure and holding time. In the case of higher bonding pressure or time, the bonded length at the interface was usually longer than the cross-sectional length of the foam, so fracture occurred at the foam. For the same reason, base metal (foam) fracture mainly occurred at the node-plate junction rather than in the strut-plate junction because the bonded surface area of the node was relatively larger than that of the strut.

SHORT- AND LONG-TERM BOND STRENGTHS OF A GOLD STANDARD

Directory of Open Access Journals (Sweden)

Safa TUNCER

2015-04-01

Full Text Available Purpose: The aim of this study was to investigate the micro tensile bond strength of a self-etch adhesive system following 1 year storage in water. Materials and Methods: 10 sound human molar teeth were used for micro tensile bond strength test. Twostep self-etch dentin adhesive (Clearfil SE Bond® was applied to the flat dentin surfaces according to the manufacturer’s instructions. Composite blocks (Z- 250; 3M ESPE of 5 mm in height have been prepared by using layering technique. Teeth were stored in water for 24 hours at 37°C and longitudinally sectioned to obtain dentin sticks of 1 mm2.Randomly selected samples from half of the teeth were immediately subjected to micro tensile test and. Remaining specimens were tested after 1 year storage in water. Bond strengths were calculated in megapascal (MPa. Results: Means and standard deviations of the Clearfil SE Bond® micro tensile bond strength values were, respectively, 37.31 ± 13.77 MPa and 24.78 ± 2.99 MPa after 24 h and 1 year of storage in water. The difference was statistically significant (p=0.031. Conclusion: Long-term storage in water decreased the micro tensile bond strength values of the twostep self-etch adhesive which has been accepted as the gold standard in bond strength tests.

Bond Issues.

Science.gov (United States)

Pollack, Rachel H.

2000-01-01

Notes trends toward increased borrowing by colleges and universities and offers guidelines for institutions that are considering issuing bonds to raise money for capital projects. Discussion covers advantages of using bond financing, how use of bonds impacts on traditional fund raising, other cautions and concerns, and some troubling aspects of…

Room temperature Cu-Cu direct bonding using surface activated bonding method

International Nuclear Information System (INIS)

Kim, T.H.; Howlader, M.M.R.; Itoh, T.; Suga, T.

2003-01-01

Thin copper (Cu) films of 80 nm thickness deposited on a diffusion barrier layered 8 in. silicon wafers were directly bonded at room temperature using the surface activated bonding method. A low energy Ar ion beam of 40-100 eV was used to activate the Cu surface prior to bonding. Contacting two surface-activated wafers enables successful Cu-Cu direct bonding. The bonding process was carried out under an ultrahigh vacuum condition. No thermal annealing was required to increase the bonding strength since the bonded interface was strong enough at room temperature. The chemical constitution of the Cu surface was examined by Auger electron spectroscope. It was observed that carbon-based contaminations and native oxides on copper surface were effectively removed by Ar ion beam irradiation for 60 s without any wet cleaning processes. An atomic force microscope study shows that the Ar ion beam process causes no surface roughness degradation. Tensile test results show that high bonding strength equivalent to bulk material is achieved at room temperature. The cross-sectional transmission electron microscope observations reveal the presence of void-free bonding interface without intermediate layer at the bonded Cu surfaces

The selective addition of water

NARCIS (Netherlands)

Resch, V.; Hanefeld, U.

2014-01-01

Water is omnipresent and essential. Yet at the same time it is a rather unreactive molecule. The direct addition of water to C[double bond, length as m-dash]C double bonds is therefore a challenge not answered convincingly. In this perspective we critically evaluate the selectivity and the

Pressure bonding molybdenum alloy (TZM) to reaction-bonded silicon nitride

International Nuclear Information System (INIS)

Huffsmith, S.A.; Landingham, R.L.

1978-01-01

Topping cycles could boost the energy efficiencies of a variety of systems by using what is now waste heat. One such topping cycle uses a ceramic helical expander and would require that a reaction-bonded silicon nitride (RBSN) rotor be bonded to a shaft of TZM (Mo-0.5 wt % Ti-0.08 wt % Zr). Coupon studies show that TZM can be bonded to RBSN at 1300 0 C and 69 MPa if there is an interlayer of MoSi 2 . A layer of finely ground (10 μm) MoSi 2 facilitates bond formation and provides a thicker bond interface. The hardness and grain structure of the TZM and RBSN were not affected by the temperature and pressure required to bond the coupons

A Rare Incidence of Breakage of tip of Micropituitary Forceps during Percutaneous Discectomy - How to Remove it: A Case Report

Directory of Open Access Journals (Sweden)

Sureisen M

2015-11-01

Full Text Available Breakage of the tip of the micropituitary forceps during spine surgery is a rare occurrence. Retrieval of the broken tip could be a challenge in minimally invasive surgeries due to limitation of access and retrieval instruments. We describe our experience in handling such a situation during percutaneous radiofrequency discectomy. The removal was attempted, without converting into open surgery, by utilising percutaneous endoscopic lumbar discectomy working cannula and guided by image intensifier. We were able to remove the fragment without any significant morbidity to the patient. This technique for removal has not been reported previously in the literature.

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

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...

Microtensile bond strength of contemporary adhesives to primary enamel and dentin.

Science.gov (United States)

Marquezan, Marcela; da Silveira, Bruno Lopes; Burnett, Luiz Henrique; Rodrigues, Célia Regina Martins Delgado; Kramer, Paulo Floriani

2008-01-01

The purpose of this study was to assess bond strength of three self-etching and two total-etch adhesive systems bonded to primary tooth enamel and dentin. Forty extracted primary human molars were selected and abraded in order to create flat buccal enamel and occlusal dentin surfaces. Teeth were assigned to one of the adhesive systems: Adper Scotch Bond Multi Purpose, Adper Single Bond 2, Adper Prompt L-Pop, Clearfil SE Bond and AdheSE. Immediately to adhesive application, a composite resin (Filtek Z250) block was built up. After 3 months of water storage, each sample was sequentially sectioned in order to obtain sticks with a square cross-sectional area of about 0.72 mm2. The specimens were fixed lengthways to a microtensile device and tested using a universal testing machine with a 50-N load cell at a crosshead speed of 0.5 mm/min. Microtensile bond strength values were recorded in MPa and compared by Analysis of Variance and the post hoc Tukey test (a = 0.05). In enamel, Clearfil SE Bond presented the highest values, followed by Adper Single Bond 2, AdheSE and Adper Scotch Bond Multi Purpose, without significant difference. The highest values in dentin were obtained with Adper Scotch Bond Multi Purpose and all other adhesives did not present significant different values from that, except Adper Prompt L-Pop that achieved the lowest bond strength in both substrates. Adper Scotch Bond Multi Purpose and Adper Single Bond 2 presented significantly lower values in enamel than in dentin although all other adhesives presented similar results in both substrates. contemporary adhesive systems present similar behaviors when bonded to primary teeth, with the exception of the one-step self-etching system; and self-etching systems can achieve bond strength values as good in enamel as in dentin of primary teeth.

Breakage mechanics for granular materials in surface-reactive environments

Science.gov (United States)

Zhang, Yida; Buscarnera, Giuseppe

2018-03-01

It is known that the crushing behaviour of granular materials is sensitive to the state of the fluids occupying the pore space. Here, a thermomechanical theory is developed to link such macroscopic observations with the physico-chemical processes operating at the microcracks of individual grains. The theory relies on the hypothesis that subcritical fracture propagation at intra-particle scale is the controlling mechanism for the rate-dependent, water-sensitive compression of granular specimens. First, the fracture of uniaxially compressed particles in surface-reactive environments is studied in light of irreversible thermodynamics. Such analysis recovers the Gibbs adsorption isotherm as a central component linking the reduction of the fracture toughness of a solid to the increase of vapour concentration. The same methodology is then extended to assemblies immersed in wet air, for which solid-fluid interfaces have been treated as a separate phase. It is shown that this choice brings the solid surface energy into the dissipation equations of the granular matrix, thus providing a pathway to (i) integrate the Gibbs isotherm with the continuum description of particle assemblies and (ii) reproduce the reduction of their yield strength in presence of high relative humidity. The rate-effects involved in the propagation of cracks and the evolution of breakage have been recovered by considering non-homogenous dissipation potentials associated with the creation of surface area at both scales. It is shown that the proposed model captures satisfactorily the compression response of different types of granular materials subjected to varying relative humidity. This result was achieved simply by using parameters based on the actual adsorption characteristics of the constituting minerals. The theory therefore provides a physically sound and thermodynamically consistent framework to study the behaviour of granular solids in surface-reactive environments.

Analysis of factors influencing the bond strength in roll bonding processes

Science.gov (United States)

Khaledi, Kavan; Wulfinghoff, Stephan; Reese, Stefanie

2018-05-01

Cold Roll Bonding (CRB) is recognized as an industrial technique in which the metal sheets are joined together in order to produce laminate metal composites. In this technique, a metallurgical bond resulting from severe plastic deformation is formed between the rolled metallic layers. The main objective of this paper is to analyse different factors which may affect the bond formation in rolling processes. To achieve this goal, first, an interface model is employed which describes both the bonding and debonding. In this model, the bond strength evolution between the metallic layers is calculated based on the film theory of bonding. On the other hand, the debonding process is modelled by means of a bilinear cohesive zone model. In the numerical section, different scenarios are taken into account to model the roll bonding process of metal sheets. The numerical simulation includes the modelling of joining during the roll bonding process followed by debonding in a Double Cantilever Beam (DCB) peeling test. In all simulations, the metallic layers are regarded as elastoplastic materials subjected to large plastic deformations. Finally, the effects of some important factors on the bond formation are numerically investigated.

Microtensile dentin bond strength of fifth with five seventh-generation dentin bonding agents after thermocycling: An in vitro study

Directory of Open Access Journals (Sweden)

Bruhvi Poptani

2012-01-01

Full Text Available Objectives: The objective of this in vitro study was to compare the microtensile dentin bond strength (μTBS of five seventh-generation dentin bonding agents (DBA with fifth-generation DBA before and after thermocycling. Materials and Methods: Ten extracted teeth were assigned to fifth generation control group (optibond solo and each of the five experimental groups namely, Group I (G-Bond ,Group II (S 3 Clearfil, Group III (One Coat 7.0, Group IV (Xeno V, and Group V (Optibond all in one. The crown portions of the teeth were horizontally sectioned below the central groove to expose the dentin. The adhesive resins from all groups were bonded to the teeth with their respective composites. Specimens of sizes 1 × 1 × 6 mm 3 were obtained. Fifty specimens that bonded to dentin from each group were selected. Twenty-five of the specimens were tested for debonding without thermocycling and the remaining were subjected to thermocycling followed by μTBS testing. The data were analyzed with one-way ANOVA and Dunnett′s-test for comparison with the reference group(Vth Generation. Results: There was no significant difference (P > 0.05 between the fifth- and seventh-generation adhesives before and after thermocycling. The results of our study showed significantly higher value (P < 0.05 of μTBS of seventh-generation Group II (Clearfil S 3 compared to the fifth-generation before and after thermocycling. Conclusion: The study demonstrated that the Clearfil S 3 bond had the highest μTBS values. In addition, of the five tested seventh-generation adhesive resins were comparable to the fifth-generation DBA.

Simultaneous bond degradation and bond formation during phenol-formaldehyde curing with wood

Science.gov (United States)

Daniel J. Yelle; John Ralph

2016-01-01

Bonding of wood using phenol–formaldehyde adhesive develops highly durable bonds. Phenol– formaldehyde is believed to form primary bonds with wood cell wall polymers (e.g., lignin). However, it is unclear how this adhesive interacts and bonds to lignin. Through wood solubilisation methodologies, earlywood and latewood bonded assemblies were characterized using two-...

Shear Bond Strengths of Different Adhesive Systems to Biodentine

Science.gov (United States)

Odabaş, Mesut Enes; Bani, Mehmet; Tirali, Resmiye Ebru

2013-01-01

The aim of this study was to measure the shear bond strength of different adhesive systems to Biodentine with different time intervals. Eighty specimens of Biodentine were prepared and divided into 8 groups. After 12 minutes, 40 samples were randomly selected and divided into 4 groups of 10 each: group 1: (etch-and-rinse adhesive system) Prime & Bond NT; group 2: (2-step self-etch adhesive system) Clearfil SE Bond; group 3: (1-step self-etch adhesive systems) Clearfil S3 Bond; group 4: control (no adhesive). After the application of adhesive systems, composite resin was applied over Biodentine. This procedure was repeated 24 hours after mixing additional 40 samples, respectively. Shear bond strengths were measured using a universal testing machine, and the data were subjected to 1-way analysis of variance and Scheffé post hoc test. No significant differences were found between all of the adhesive groups at the same time intervals (12 minutes and 24 hours) (P > .05). Among the two time intervals, the lowest value was obtained for group 1 (etch-and-rinse adhesive) at a 12-minute period, and the highest was obtained for group 2 (two-step self-etch adhesive) at a 24-hour period. The placement of composite resin used with self-etch adhesive systems over Biodentine showed better shear bond strength. PMID:24222742

Non-Classical C–H···X Hydrogen Bonding and Its Role in Asymmetric Organocatalysis

KAUST Repository

Ajitha, Manjaly John; Huang, Kuo-Wei

2016-01-01

Non-classical hydrogen bonds (NCHBs) have attracted significant interest in the past decade particularly because of their important role in asymmetric catalytic systems. These weak interactions (< 4 kcal/mol) offer much flexibility1 Introduction2 Hydrogen Bonds (HBs) and Non-Classical Hydrogen Bonds (NCHBs)3 Early Developments in NCHBs4 Selected Examples of NCHBs in Organic Transformations5 Recent Examples of NCHBs in Enantioselective Reactions6 Conclusions and Outlook

Bond strength of masonry

NARCIS (Netherlands)

Pluijm, van der R.; Vermeltfoort, A.Th.

1992-01-01

Bond strength is not a well defined property of masonry. Normally three types of bond strength can be distinguished: - tensile bond strength, - shear (and torsional) bond strength, - flexural bond strength. In this contribution the behaviour and strength of masonry in deformation controlled uniaxial

Comparative evaluation of shear bond strength of metallic brackets bonded with two different bonding agents under dry conditions and with saliva contamination

Directory of Open Access Journals (Sweden)

Mashallah Khanehmasjedi

2017-02-01

Conclusion: Application of Single Bond and Assure bonding agents resulted in adequate bond strength of brackets to tooth structures. Contamination with saliva significantly decreased the bond strength of Assure bonding agent compared with dry conditions.

[Influence of thermalcycling on bonding durability of self-etch adhesives with dentin].

Science.gov (United States)

Tian, Fu-cong; Wang, Xiao-yan; Gao, Xue-jun

2014-04-18

To investigate influence of thermalcycling on the bonding durability of two one-step products [Adper Prompt (AP) and G-bond (GB)] and one two-step self-etching adhesive [Clearfil SE bond (SE)] with dentin in vitro. Forty-two extracted human molars were selected. The superficial dentin was exposed by grinding off the enamel. The teeth were randomly distributed into six groups with varied bonding protocols. The adhesives were applied to the dentin surface. Composite crowns were built up, then the samples were cut longitudinally into sticks with 1.0 mm×1.0 mm bonding area [for microtensile bond strength (MTBS) testing] or 1.0 mm thick slabs (for nanoleakage observation). Bonding performance was evaluated with or without thermalcyling. For the MTBS testing, the strength values were statistically analysed using One-Way ANOVA. Four slabs in each group were observed for nanoleakage by SEM with a backscattered electron detector. Thermalcycling procedures affected MTBS. In the two one-step groups, the MTBS decreased significantly (Padhesives showed lower MTBS than two-step bonding system after aging.For AP and GB, continuous nanoleakage appearance was notable and more obvious than for SE. Thermalcycling can affect the bonding performance of self-etch adhesives including decrease of bond strength and nanoleakage pattern. one-step self-etch adhesives showed more obvious change compared with their two-step counterparts.

Recent Advances in Adhesive Bonding - The Role of Biomolecules, Nanocompounds, and Bonding Strategies in Enhancing Resin Bonding to Dental Substrates.

Science.gov (United States)

Münchow, Eliseu A; Bottino, Marco C

2017-09-01

To present an overview on the main agents (i.e., biomolecules and nanocompounds) and/or strategies currently available to amplify or stabilize resin-dentin bonding. According to studies retrieved for full text reading (2014-2017), there are currently six major strategies available to overcome resin-dentin bond degradation: (i) use of collagen crosslinking agents, which may form stable covalent bonds with collagen fibrils, thus strengthening the hybrid layer; (ii) use of antioxidants, which may allow further polymerization reactions over time; (iii) use of protease inhibitors, which may inhibit or inactivate metalloproteinases; (iv) modification of the bonding procedure, which may be performed by using the ethanol wet-bonding technique or by applying an additional adhesive (hydrophobic) coating, thereby strengthening the hybrid layer; (v) laser treatment of the substrate prior to bonding, which may cause specific topographic changes in the surface of dental substrates, increasing bonding efficacy; and (vi) reinforcement of the resin matrix with inorganic fillers and/or remineralizing agents, which may positively enhance physico-mechanical properties of the hybrid layer. With the present review, we contributed to the better understanding of adhesion concepts and mechanisms of resin-dentin bond degradation, showing the current prospects available to solve that problematic. Also, adhesively-bonded restorations may be benefited by the use of some biomolecules, nanocompounds or alternative bonding strategies in order to minimize bond strength degradation.

Two component injection moulding: an interface quality and bond strength dilemma

DEFF Research Database (Denmark)

Islam, Mohammad Aminul; Hansen, Hans Nørgaard; Tang, Peter Torben

2008-01-01

on quality parameters of the two component parts. Most engineering applications of two component injection moulding calls for high bond strength between the two polymers, on the other hand a sharp and well-defined interface between the two polymers are required for applications like selective metallization...... of polymers, parts for micro applications and also for the aesthetic purpose of the final product. The investigation presented in this paper indicates a dilemma between obtaining reasonably good bond strength and at the same time keeping the interface quality suitable for applications. The required process...... conditions for a sharp and well-defined interface are exactly the opposite of what is congenial for higher bond strength. So in the production of two component injection moulded parts, there is a compromise to make between the interface quality and the bond strength of the two polymers. Also the injection...

A moving boundary problem and orthogonal collocation in solving a dynamic liquid surfactant membrane model including osmosis and breakage

Directory of Open Access Journals (Sweden)

E.C. Biscaia Junior

2001-06-01

Full Text Available A dynamic kinetic-diffusive model for the extraction of metallic ions from aqueous liquors using liquid surfactant membranes is proposed. The model incorporates undesirable intrinsic phenomena such as swelling and breakage of the emulsion globules that have to be controlled during process operation. These phenomena change the spatial location of the chemical reaction during the course of extraction, resulting in a transient moving boundary problem. The orthogonal collocation method was used to transform the partial differential equations into an ordinary differential equation set that was solved by an implicit numerical routine. The model was found to be numerically stable and reliable in predicting the behaviour of zinc extraction with acidic extractant for long residence times.

29 CFR 2580.412-19 - Term of the bond, discovery period, other bond clauses.

Science.gov (United States)

2010-07-01

... SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580.412-19 Term of the bond, discovery... 29 Labor 9 2010-07-01 2010-07-01 false Term of the bond, discovery period, other bond clauses... new bond must be obtained each year. There is nothing in the Act that prohibits a bond for a term...

Investigation of ball bond integrity for 0.8 mil (20 microns) diameter gold bonding wire on low k die in wire bonding technology

Science.gov (United States)

Kudtarkar, Santosh Anil

Microelectronics technology has been undergoing continuous scaling to accommodate customer driven demand for smaller, faster and cheaper products. This demand has been satisfied by using novel materials, design techniques and processes. This results in challenges for the chip connection technology and also the package technology. The focus of this research endeavor was restricted to wire bond interconnect technology using gold bonding wires. Wire bond technology is often regarded as a simple first level interconnection technique. In reality, however, this is a complex process that requires a thorough understanding of the interactions between the design, material and process variables, and their impact on the reliability of the bond formed during this process. This research endeavor primarily focused on low diameter, 0.8 mil thick (20 mum) diameter gold bonding wire. Within the scope of this research, the integrity of the ball bond formed by 1.0 mil (25 mum) and 0.8 mil (20 mum) diameter wires was compared. This was followed by the evaluation of bonds formed on bond pads having doped SiO2 (low k) as underlying structures. In addition, the effect of varying the percentage of the wire dopant, palladium and bonding process parameters (bonding force, bond time, ultrasonic energy) for 0.8 mil (20 mum) bonding wire was also evaluated. Finally, a degradation empirical model was developed to understand the decrease in the wire strength. This research effort helped to develop a fundamental understanding of the various factors affecting the reliability of a ball bond from a design (low diameter bonding wire), material (low k and bonding wire dopants), and process (wire bonding process parameters) perspective for a first level interconnection technique, namely wire bonding. The significance of this research endeavor was the systematic investigation of the ball bonds formed using 0.8 mil (20 microm) gold bonding wire within the wire bonding arena. This research addressed low k

Cryosolution infrared study of hydrogen bonded halothane acetylene complex

Science.gov (United States)

Melikova, S. M.; Rutkowski, K. S.; Rospenk, M.

2018-05-01

The interactions between halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) and acetylene (C2H2) are studied by FTIR spectroscopy. Results obtained in liquid cryosolutions in Kr suggest weak complex formation stabilized by H - bond. The complexation enthalpy (∼11 kJ/mol) is evaluated in a series of temperature measurements (T ∼ 120-160 K) of integrated intensity of selected bands performed in liquefied Kr. The quantum chemical MP2/6-311++G(2d,2p) calculations predict four different structures of the complex. The most stable and populated (94% at T∼120 K) structure corresponds to the H - bond between H atom of halothane and pi-electron of triple bond between C atoms of acetylene. Wave numbers of vibrational bands of the most stable structure are calculated in anharmonic approximation implemented in Gaussian program.

Structure phenomena in the bond zone of explosively bonded plates

International Nuclear Information System (INIS)

Livne, Z.

1979-12-01

In the bond areas of couples of explosively bonded plates, there are often zones, generally designated as ''molten pockets'', which have undergone melting and solidification. The object of the present study was to investigate molten pockets, which have a decisive effect on bond quality. The experimental samples for the study were chosen in consideration of the mutual behaviour of the plates constituting the couples, according to their equilibrium phase diagrams. To facilitate the investigation, large plates were bonded under conditions that enabled to to obtain wavy bond zones that included relatively large molten pockets. To clarify the complex nature of molten pockets and their surroundings, a wide variety of methods were employed. It was found that the shape and composition of molten pockets largely depend upon the mechanism of formation of both the bond wave and the molten pockets. It was also found that the composition of molten pockets is not homogeneous, which is manifest in the modification of the composition of the pockets, the solidification morphology, the phases, which have been identified by X-ray diffraction, and the bond strenght and hardness. Moreover, the different solidification morphologies revealed by metallography were found to depend upon the types of plates bonded, the bonding conditions and the location of pockets in the wavy interface. For molten pockets, cooling rates of 10 4 to 10 5 (degC/sec) have been deduced from interdendritic spacing, and found to be in good agreement with calculations after a mathematical model. It seems that the fast cooling rates and the steep temperature gradients are at the origin of the particular solidification phenomena observed in molten pockets

High-temperature, high-pressure bonding of nested tubular metallic components

International Nuclear Information System (INIS)

Quinby, T.C.

1980-01-01

This invention is a tool for effecting high-temperature, high compression bonding between the confronting faces of nested, tubular, metallic components. In a typical application, the tool is used to produce tubular target assemblies for irradiation in nuclear reactors or particle accelerators, the target assembly comprising a uranium foil and an aluminum-alloy substrate. The tool preferably is composed throughout of graphite. It comprises a tubular restraining member in which a mechanically expandable tubular core is mounted to form an annulus with the member. The components to be bonded are mounted in nested relation in the annulus. The expandable core is formed of individually movable, axially elongated segments whose outer faces cooperatively define a cylindrical pressing surface and whose inner faces cooperatively define two opposed, inwardly tapered, axial bores. Tapered rams extend respectively into the bores. The loaded tool is mounted in a conventional hot-press provided with evacuation means, heaters for maintaining its interior at bonding temperature, and hydraulic cylinders for maintaining a selected inwardly directed pressure on the tapered rams. With the hotpress evacuated and the loaded tool at the desired temperature, the cylinders are actuated to apply the selected pressure to the rams. The rams in turn expand the segmented core to maintain the nested components in compression against the restraining member. These conditions are maintained until the confronting faces of the nested components are joined in a continuous, uniform bond characterized by high thermal conductivity

High-temperature, high-pressure bonding of nested tubular metallic components

Science.gov (United States)

Quinby, T.C.

A tool is described for effecting high-temperature, high-compression bonding between the confronting faces of nested, tubular, metallic components. In a typical application, the tool is used to produce tubular target assemblies for irradiation in nuclear reactors or particle accelerators. The target assembly comprising a uranum foil and an aluninum-alloy substrate. The tool is composed of graphite. It comprises a tubular restraining member in which a mechanically expandable tubular core is mounted to form an annulus. The components to be bonded are mounted in nested relation in the annulus. The expandable core is formed of individually movable, axially elongated segments whose outer faces cooperatively define a cylindrical pressing surface and whose inner faces cooperatively define two opposed, inwardly tapered, axial bores. Tapered rams extend into the bores. The loaded tool is mounted in a conventional hot-press provided with evacuation means, heaters for maintaining its interior at bonding temperature, and hydraulic cylinders for maintaining a selected inwardly directed pressure on the tapered rams. With the hot-press evacuated and the loaded tool at the desired temperature, the cylinders are actuated to apply the selected pressure to the rams. The rams in turn expand the segmented core to maintain the nested components in compression against the restraining member. These conditions are maintained until the confronting faces of the nested components are joined in a continuous, uniform bond characterized by high thermal conductivity.

Cooperativity in Surface Bonding and Hydrogen Bonding of Water and Hydroxyl at Metal Surfaces

DEFF Research Database (Denmark)

Schiros, T.; Ogasawara, H.; Naslund, L. A.

2010-01-01

of the mixed phase at metal surfaces. The surface bonding can be considered to be similar to accepting a hydrogen bond, and we can thereby apply general cooperativity rules developed for hydrogen-bonded systems. This provides a simple understanding of why water molecules become more strongly bonded...... to the surface upon hydrogen bonding to OH and why the OH surface bonding is instead weakened through hydrogen bonding to water. We extend the application of this simple model to other observed cooperativity effects for pure water adsorption systems and H3O+ on metal surfaces.......We examine the balance of surface bonding and hydrogen bonding in the mixed OH + H2O overlayer on Pt(111), Cu(111), and Cu(110) via density functional theory calculations. We find that there is a cooperativity effect between surface bonding and hydrogen bonding that underlies the stability...

Influence of dentinal regions on bond strengths of different adhesive systems.

Science.gov (United States)

Ozer, F; Unlü, N; Sengun, A

2003-06-01

This in vitro study assessed comparatively the shear bond strengths of three composite resins, 3M Valux Plus (3MVP), Herculite (H), Clearfil AP-X (CAP-X), a polyacid modified composite resin Dyract (D), and a resin modified glass-ionomer materials Vitremer (V), to cervical and buccal dentine regions of extracted human molar teeth. Four different bonding systems, 3M ScotchBond Multipurpose (SB), Clearfil Liner Bond 2 (LB2), Opti Bond (OB), and Prime & Bond 2.1 (PB 2.1) were used with the manufacturer's respective composite and compomer materials. One hundred freshly extracted mandibular molar teeth were selected for this study. Flat buccal dentine surfaces were created on 50 teeth and cylindrical rods of the five materials were bonded to the dentine surfaces. For assessment of cervical bond strengths, the materials were bonded to mesial and distal enamel bordered occlusal dentinal surfaces of the remaining 50 teeth. The five groups of restorative procedures were applied as follows; Group 1: SB + 3MVP, Group 2: LB2 + CAP-X, Group 3: OB + H, Group 4: PB2.1 + D, Group 5: Vitremer primer (VP) VP + V. Each restorative procedure thus had 20 specimens (10 buccal + 10 cervical). After 24 h of water storage (37 degrees C), the specimens were tested on a Universal Testing machine in shear with a cross head speed of 0.5 mm min-1. The bond strength values were calculated in MPa and the results were evaluated statistically using Kruskal-Wallis one-way/anova and Mann-Whitney U-tests. It was found that the bond strengths of SB + 3MVP, LB2 + CAP-X and VP + V to buccal dentine surfaces were significantly stronger (P 0.05). Vitremer was found the least successful adhesive material in terms of shear bond strength on both buccal and occluso-cervical dentine surfaces.

Numerical study of agglomerate abrasion in a tumbling mixer

NARCIS (Netherlands)

Thanh Nguyen, [No Value; Willemsz, Tofan; Frijlink, Henderik; Maarschalk, Kees van der Voort

2014-01-01

A numerical simulation using the Discrete Element Method (DEM) was performed to investigate the phenomena concerning the abrasion and breakage of agglomerates in a diffusion powder mixer. Agglomerates were created by defining a single structure of particles with bonds of different strengths using

Manufacture of Strand Board Bonded with Disposal Expanded Polystyrene as Binder

OpenAIRE

Hermawan, Andi; Ohuchi, Takeshi; Fujimoto, Noboru; 大内, 毅; 藤本, 登留

2010-01-01

The objective of this study was to evaluate the physical and mechanical properties of strand board bonded with disposal expanded polystyrene (EPS) as binder. The strand board was manufactured using strand made from Douglas-fir beams selected from construction scrap wood. The strands were oriented, and two types of three-layer (face-core-face) strand board were manufactured: one in which the board bounded with only disposal EPS (P board), and the other in which the board bonded with disposal...

Bond lengths and bond strengths in compounds of the 5f elements

International Nuclear Information System (INIS)

Zachariasen, W.H.

1975-01-01

The variation of bond length (D) with bond strength (S) in normal valence compounds of 3d, 4d, 5d-4f, and 6d-5f elements can be represented approximately as D(S)=D(0.5) F(S), where D(0.5) is a characteristic constant for a given bond and F(S) an empirical function which is the same for all bonds. A bond strength Ssub(ij)=ssub(ji) is assigned to the bond between atoms i and j such that Σsub(j) Ssub(ij)=vsub(i) and Σsub(i) Ssub(ij)=vsub(j), where vsub(i) and vsub(j) are the normal valences of the two atoms. The function F(S) decreases monotonically with increasing S, and is normalized to unity at S=0.5, so that the constant D(0.5) has the physical meaning of being the bond length adjusted to S=0.5. The method described above was used to interpret and systematize the experimental results on bond lengths in oxides, halides, and oxyhalides of the 5f elements. (U.S.)

The effect of different surface treatments of stainless steel crown and different bonding agents on shear bond strength of direct composite resin veneer

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Ajami B

2007-01-01

Full Text Available Background and Aim: Stainless steel crown (SSC is the most durable and reliable restoration for primary teeth with extensive caries but its metalic appearance has always been a matter of concern. With advances in restorative materials and metal bonding processes, composite veneer has enhanced esthetics of these crowns in clinic. The aim of this study was to evaluate the shear bond strength of SSC to composite resin using different surface treatments and adhesives. Materials and Methods: In this experimental study, 90 stainless steel crowns were selected. They were mounted in molds and divided into 3 groups of 30 each (S, E and F. In group S (sandblast, buccal surfaces were sandblasted for 5 seconds. In group E (etch acidic gel was applied for 5 minutes and in group F (fissure bur surface roughness was created by fissure diamond bur. Each group was divided into 3 subgroups (SB, AB, P based on different adhesives: Single Bond, All Bond2 and Panavia F. Composite was then bonded to specimens. Cases were incubated in 100% humidity at 37°C for 24 hours. Shear bond strength was measured by Zwick machine with crosshead speed of 0.5 mm/min. Data were analyzed by ANOVA test with p0.05 so the two variables were studied separately. No significant difference was observed in mean shear bond strength of composite among the three kinds of adhesives (P>0.05. Similar results were obtained regarding surface treatments (P>0.05. Conclusion: Based on the results of this study, treating the SSC surface with bur and using single bond adhesive and composite can be used successfully to obtain esthetic results in pediatric restorative treatments.

Interaction between benzenedithiolate and gold: Classical force field for chemical bonding

Science.gov (United States)

Leng, Yongsheng; Krstić, Predrag S.; Wells, Jack C.; Cummings, Peter T.; Dean, David J.

2005-06-01

We have constructed a group of classical potentials based on ab initio density-functional theory (DFT) calculations to describe the chemical bonding between benzenedithiolate (BDT) molecule and gold atoms, including bond stretching, bond angle bending, and dihedral angle torsion involved at the interface between the molecule and gold clusters. Three DFT functionals, local-density approximation (LDA), PBE0, and X3LYP, have been implemented to calculate single point energies (SPE) for a large number of molecular configurations of BDT-1, 2 Au complexes. The three DFT methods yield similar bonding curves. The variations of atomic charges from Mulliken population analysis within the molecule/metal complex versus different molecular configurations have been investigated in detail. We found that, except for bonded atoms in BDT-1, 2 Au complexes, the Mulliken partial charges of other atoms in BDT are quite stable, which significantly reduces the uncertainty in partial charge selections in classical molecular simulations. Molecular-dynamics (MD) simulations are performed to investigate the structure of BDT self-assembled monolayer (SAM) and the adsorption geometry of S adatoms on Au (111) surface. We found that the bond-stretching potential is the most dominant part in chemical bonding. Whereas the local bonding geometry of BDT molecular configuration may depend on the DFT functional used, the global packing structure of BDT SAM is quite independent of DFT functional, even though the uncertainty of some force-field parameters for chemical bonding can be as large as ˜100%. This indicates that the intermolecular interactions play a dominant role in determining the BDT SAMs global packing structure.

A remarkable enhancement of selectivity towards versatile analytes by a strategically integrated H-bonding site containing phase.

Science.gov (United States)

Mallik, Abul K; Qiu, Hongdeng; Kuwahara, Yutaka; Takafuji, Makoto; Ihara, Hirotaka

2015-09-28

A double β-alanylated L-glutamide-derived organic phase has been newly designed and synthesized in such a way that integrated H-bonding (interaction) sites make it very suitable for the separation of versatile analytes, including shape-constrained isomers, and nonpolar, polar and basic compounds. The β-alanine residues introduced into two long-chain alkyl group moieties provide ordered polar groups through H-bonding among the amide groups.

Voltage-assisted polymer wafer bonding

International Nuclear Information System (INIS)

Varsanik, J S; Bernstein, J J

2012-01-01

Polymer wafer bonding is a widely used process for fabrication of microfluidic devices. However, best practices for polymer bonds do not achieve sufficient bond strength for many applications. By applying a voltage to a polymer bond in a process called voltage-assisted bonding, bond strength is shown to improve dramatically for two polymers (Cytop™ and poly(methyl methacrylate)). Several experiments were performed to provide a starting point for further exploration of this technique. An optimal voltage range is experimentally observed with a reduction in bonding strength at higher voltages. Additionally, voltage-assisted bonding is shown to reduce void diameter due to bond defects. An electrostatic force model is proposed to explain the improved bond characteristics. This process can be used to improve bond strength for most polymers. (paper)

Bond Strength of Resin Composite to Dentin with Different Adhesive Systems: Influence of Relative Humidity and Application Time.

Science.gov (United States)

Amsler, Fabienne; Peutzfeldt, Anne; Lussi, Adrian; Flury, Simon

2015-06-01

To investigate the influence of relative humidity and application time on bond strength to dentin of different classes of adhesive systems. A total of 360 extracted human molars were ground to mid-coronal dentin. The dentin specimens were treated with one of six adhesive systems (Syntac Classic, OptiBond FL, Clearfil SE Bond, AdheSE, Xeno Select, or Scotchbond Universal), and resin composite (Filtek Z250) was applied to the treated dentin surface under four experimental conditions (45% relative humidity/application time according to manufacturers' instructions; 45% relative humidity/reduced application time; 85% relative humidity/application time according to manufacturers' instructions; 85% relative humidity/reduced application time). After storage (37°C, 100% humidity, 24 h), shear bond strength (SBS) was measured and data analyzed with nonparametric ANOVA followed by Kruskal-Wallis tests and Mann-Whitney U-tests with Bonferroni-Holm correction for multiple testing (level of significance: α = 0.05). Increased relative humidity and reduced application time had no effect on SBS for Clearfil SE Bond and Scotchbond Universal (p = 1.00). For Syntac Classic, OptiBond FL, AdheSE, and Xeno Select there was no effect on SBS of reduced application time of the adhesive system (p ≥ 0.403). However, increased relative humidity significantly reduced SBS for Syntac Classic, OptiBond FL, and Xeno Select irrespective of application time (p ≤ 0.003), whereas for AdheSE, increased relative humidity significantly reduced SBS at recommended application time only (p = 0.002). Generally, increased relative humidity had a detrimental effect on SBS to dentin, but reduced application time had no effect.

Effect of composite warming on shear bond strength.

Science.gov (United States)

McDaniel, Thomas F; Sigrist, Thomas W; Johnson, Gary M

2018-01-01

Several manufacturers produce devices designed to warm composite resins used in restorative dentistry. Previous investigators have examined the effects of heating composite restorative resins prior to placement and polymerization. Heating has been reported to reduce viscosity, improve ease of placement, enhance monomer conversion, and reduce microleakage. The aim of the present study was to compare shear bond strengths of room temperature (22°C) and prewarmed (54°C) restorative composite resin. Extracted bovine mandibular incisors were sectioned sagittally and embedded in acrylic cylinders. Enamel was selectively etched with 37% phosphoric acid, rinsed, and dried. Self-etching primer was applied to both enamel and dentin. Self-etching adhesive was then applied and photopolymerized. Composite resin capsules were then divided into prewarmed and room temperature groups. Fourteen composite specimens prewarmed in an incubator were applied to the prepared enamel and dentin and photopolymerized. Fourteen room temperature composite specimens were likewise placed. After storage in water for 24 hours, all composite specimens were subjected to shear stress testing. The resulting data were analyzed with a t test (P = 0.05). There was no statistically significant difference between the shear bond strengths of the prewarmed and room temperature composite resin specimens. Warming does not appear to affect bond strength of composite resin bonded to both dentin and enamel.

5-bp Classical Satellite DNA Loci from Chromosome-1 Instability in Cervical Neoplasia Detected by DNA Breakage Detection/Fluorescence in Situ Hybridization (DBD-FISH

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Jaime Gosálvez

2013-02-01

Full Text Available We aimed to evaluate the association between the progressive stages of cervical neoplasia and DNA damage in 5-bp classical satellite DNA sequences from chromosome-1 in cervical epithelium and in peripheral blood lymphocytes using DNA breakage detection/fluorescence in situ hybridization (DBD-FISH. A hospital-based unmatched case-control study was conducted in 2011 with a sample of 30 women grouped according to disease stage and selected according to histological diagnosis; 10 with low-grade squamous intraepithelial lesions (LG-SIL, 10 with high-grade SIL (HG-SIL, and 10 with no cervical lesions, from the Unidad Medica de Alta Especialidad of The Mexican Social Security Institute, IMSS, Mexico. Specific chromosome damage levels in 5-bp classical satellite DNA sequences from chromosome-1 were evaluated in cervical epithelium and peripheral blood lymphocytes using the DBD-FISH technique. Whole-genome DNA hybridization was used as a reference for the level of damage. Results of Kruskal-Wallis test showed a significant increase according to neoplastic development in both tissues. The instability of 5-bp classical satellite DNA sequences from chromosome-1 was evidenced using chromosome-orientation FISH. In conclusion, we suggest that the progression to malignant transformation involves an increase in the instability of 5-bp classical satellite DNA sequences from chromosome-1.

5-bp Classical Satellite DNA Loci from Chromosome-1 Instability in Cervical Neoplasia Detected by DNA Breakage Detection/Fluorescence in Situ Hybridization (DBD-FISH).

Science.gov (United States)

Cortés-Gutiérrez, Elva I; Ortíz-Hernández, Brenda L; Dávila-Rodríguez, Martha I; Cerda-Flores, Ricardo M; Fernández, José Luis; López-Fernández, Carmen; Gosálvez, Jaime

2013-02-19

We aimed to evaluate the association between the progressive stages of cervical neoplasia and DNA damage in 5-bp classical satellite DNA sequences from chromosome-1 in cervical epithelium and in peripheral blood lymphocytes using DNA breakage detection/fluorescence in situ hybridization (DBD-FISH). A hospital-based unmatched case-control study was conducted in 2011 with a sample of 30 women grouped according to disease stage and selected according to histological diagnosis; 10 with low-grade squamous intraepithelial lesions (LG-SIL), 10 with high-grade SIL (HG-SIL), and 10 with no cervical lesions, from the Unidad Medica de Alta Especialidad of The Mexican Social Security Institute, IMSS, Mexico. Specific chromosome damage levels in 5-bp classical satellite DNA sequences from chromosome-1 were evaluated in cervical epithelium and peripheral blood lymphocytes using the DBD-FISH technique. Whole-genome DNA hybridization was used as a reference for the level of damage. Results of Kruskal-Wallis test showed a significant increase according to neoplastic development in both tissues. The instability of 5-bp classical satellite DNA sequences from chromosome-1 was evidenced using chromosome-orientation FISH. In conclusion, we suggest that the progression to malignant transformation involves an increase in the instability of 5-bp classical satellite DNA sequences from chromosome-1.

From ketones to esters by a Cu-catalyzed highly selective C(CO)-C(alkyl) bond cleavage: aerobic oxidation and oxygenation with air.

Science.gov (United States)

Huang, Xiaoqiang; Li, Xinyao; Zou, Miancheng; Song, Song; Tang, Conghui; Yuan, Yizhi; Jiao, Ning

2014-10-22

The Cu-catalyzed aerobic oxidative esterification of simple ketones via C-C bond cleavage has been developed. Varieties of common ketones, even inactive aryl long-chain alkyl ketones, are selectively converted into esters. The reaction tolerates a wide range of alcohols, including primary and secondary alcohols, chiral alcohols with retention of the configuration, electron-deficient phenols, as well as various natural alcohols. The usage of inexpensive copper catalyst, broad substrate scope, and neutral and open air conditions make this protocol very practical. (18)O labeling experiments reveal that oxygenation occurs during this transformation. Preliminary mechanism studies indicate that two novel pathways are mainly involved in this process.

30 CFR 281.33 - Bonds and bonding requirements.

Science.gov (United States)

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF MINERALS OTHER THAN OIL, GAS, AND SULPHUR IN THE OUTER CONTINENTAL SHELF Financial Considerations § 281.33...

Are Bonding Agents being Effective on the Shear Bond Strength of Orthodontic Brackets Bonded to the Composite?

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Fahimeh Farzanegan

2014-06-01

Full Text Available Introduction: One of the clinical problems in orthodontics is the bonding of brackets tocomposite restorations. The aim of this study was to evaluate the shear bondstrength of brackets bonded to composite restorations using Excite. Methods:Forty brackets were bonded to composite surfaces, which were embedded inacrylic resin. One of the following four protocols was employed for surfacepreparation of the composite: group 1 37% phosphoric acid for 60 seconds, group2 roughening with a diamond bur plus 37% phosphoric acid for 60 seconds, group3 37% phosphoric acid for 60 seconds and the applying Excite®, group4 roughening with diamond bur plus 37% phosphoric acid for 60 seconds andapplying Excite®. Maxillary central brackets were bonded onto thecomposite prepared samples with Transbond XT. Shear Bond Strength (SBS wasmeasured by a universal testing machine. The ANOVA and Tukey test was utilizedfor data analysis. Results: There was a significant difference betweenthe four groups (P

A novel shredder for municipal solid waste (MSW): influence of feed moisture on breakage performance.

Science.gov (United States)

Luo, Siyi; Xiao, Bo; Xiao, Lei

2010-08-01

A novel MSW shredder was presented but many aspects of the shredder have not been fully characterized. The feed moisture is an important factor that influences crushing performance. This paper focuses on the effect of feed moisture. The breakage of municipal solid waste (MSW) at several moisture levels (0%, 10%, 20%, 40% and 60%) was conducted with a laboratory shredder to investigate the effect of feed moisture on product size distribution and specific energy consumption under two different hydraulic pressures (40 and 60 kg/cm(2)). The results showed definite effects of feed moisture on the product size distribution and specific energy consumption: there is a tendency for the fine production in products to decrease with increasing amounts of water content in the feed; with the increasing feed moisture, specific energy shows an increasing trend; the specific energy and product size distribution under lower hydraulic pressure is more sensitive to the feed moisture than it is under higher hydraulic pressure. (c) 2010. Published by Elsevier Ltd. All rights reserved.

Chromosomes of older humans are more prone to aminopterine-induced breakage

International Nuclear Information System (INIS)

Esposito, D.; Fassina, G.; Szabo, P.; Weksler, M.; De Angelis, P.; Siniscalco, M.; Rodgers, L.

1989-01-01

The authors have adopted a simplified version of the cell hybrid cotransfer method to test the hypothesis that human lymphocytes derived from elderly individuals have a higher chromosome instability. Peripheral blood lymphocytes from old male individuals and young controls were fused with a Chinese hamster cell line (CHO-YH21), yielding 10 HAT-resistant rodent-human clones from the old propositi and 22 from the young controls. Both series of hybrid clones were analyzed with respect to the retention of the enzyme glucose-6-phosphate dehydrogenase and the surface antigen MIC2 identified by monoclonal antibody 12E7, two human X chromosome-linked markers located at opposite ends of the X chromosome. Cell hybrid clones with an X chromosome from a young control retained both markers in about 70% of the cells. In contrast, cell hybrid clones with an X chromosome from an old donor retained the MIC2 marker in only 30% of their cells. Slot-blot hybridization studies have established that the observed loss of the MIC2 marker is due to loss of the coding gene, not to suppression of its expression. T lymphocytes from old donors were also found to have an LD 50 for aminopterine significantly lower than the concentration of this drug in the HAT medium used to grow the hybrids. They speculate that the higher rate of chromosomal breakage and of marker loss observed along the old-age X chromosomes could be the result of molecular scars accumulated with aging at sites of constitutive chromosomal fragility

T-lymphoblastic leukemia/lymphoma in macedonian patients with Nijmegen breakage syndrome

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Kocheva SA

2016-06-01

Full Text Available Nijmegen breakage syndrome (NBS is a rare autosomal recessive chromosomal instability disorder characterized by microcephaly, immunodeficiency, radiosensitivity and a very high predisposition to malignancy. The gene responsible for the disease, NBS1, is located on chromosome 8q21 and encodes a protein called nibrin. After identification of the gene, a truncating 5 bp deletion, 657-661delACAAA, was identified as the disease-causing mutation in patients with the NBS. In this report, we describe two patients with NBS and T-lymphoblastic leukemia/lymphoma in a Macedonian family. To the best of our knowledge, this is the first family with NBS reported from Macedonia. Both children presented with microcephaly, syndactyly and the development of T cell lymphoblastic lekemia/lymphoma at the age of 7 and 10 years, respectively. The molecular analysis of NBS1 genes in our patients showed homozygosity for the 657del5 mutation in the NBS1 gene. The parents were heterozygotes for the 657del5 mutation and they had no knowledge of a consanguineous relationship. The first child was treated with the International Berlin-Frankfurt-Münster (BFM-Non Hodgkin lymphoma (NHL protocol and achieved a complete remission that lasted for 21 months. Subsequently, he developed a medullar relapse with hyperleukocytosis and died due to lethal central nervous system (CNS complications. The second child was treated according to the International Collaborative Treatment Protocol for Children and Adolescents with Acute Lymphoblastic Leukemia 2009 (AIOP-BFM ALL 2009 protocol. Unfortunately, remission was not achieved.

T-lymphoblastic leukemia/lymphoma in macedonian patients with Nijmegen breakage syndrome.

Science.gov (United States)

Kocheva, S A; Martinova, K; Antevska-Trajkova, Z; Coneska-Jovanova, B; Eftimov, A; Dimovski, A J

2016-07-01

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive chromosomal instability disorder characterized by microcephaly, immunodeficiency, radiosensitivity and a very high predisposition to malignancy. The gene responsible for the disease, NBS1 , is located on chromosome 8q21 and encodes a protein called nibrin. After identification of the gene, a truncating 5 bp deletion, 657-661delACAAA, was identified as the disease-causing mutation in patients with the NBS. In this report, we describe two patients with NBS and T-lymphoblastic leukemia/lymphoma in a Macedonian family. To the best of our knowledge, this is the first family with NBS reported from Macedonia. Both children presented with microcephaly, syndactyly and the development of T cell lymphoblastic lekemia/lymphoma at the age of 7 and 10 years, respectively. The molecular analysis of NBS1 genes in our patients showed homozygosity for the 657del5 mutation in the NBS1 gene. The parents were heterozygotes for the 657del5 mutation and they had no knowledge of a consanguineous relationship. The first child was treated with the International Berlin-Frankfurt-Münster (BFM)-Non Hodgkin lymphoma (NHL) protocol and achieved a complete remission that lasted for 21 months. Subsequently, he developed a medullar relapse with hyperleukocytosis and died due to lethal central nervous system (CNS) complications. The second child was treated according to the International Collaborative Treatment Protocol for Children and Adolescents with Acute Lymphoblastic Leukemia 2009 (AIOP-BFM ALL 2009) protocol. Unfortunately, remission was not achieved.

Insertion reactions into Pd[bond]O and Pd[bond]N bonds: preparation of alkoxycarbonyl, carbonato, carbamato, thiocarbamate, and thioureide complexes of palladium(II).

Science.gov (United States)

Ruiz, José; Martínez, M Teresa; Florenciano, Félix; Rodríguez, Venancio; López, Gregorio; Pérez, José; Chaloner, Penny A; Hitchcock, Peter B

2003-06-02

Mononuclear palladium hydroxo complexes of the type [Pd(N[bond]N)(C(6)F(5))(OH)] [(N[bond]N = 2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'-bipyridine (Me(2)bipy), 1,10-phenanthroline (phen), or N,N,N',N'-tetramethylethylenediamine (tmeda)] have been prepared by reaction of [Pd(N[bond]N)(C(6)F(5))(acetone)]ClO(4) with KOH in methanol. These hydroxo complexes react, in methanol, with CO (1 atm, room temperature) to yield the corresponding methoxycarbonyl complexes [Pd(N[bond]N)(C(6)F(5))(CO(2)Me)]. Similar alkoxycarbonyl complexes [Pd(N[bond]N)(C(6)F(5))(CO(2)R)] (N[bond]N = bis(3,5-dimethylpyrazol-1-yl)methane); R = Me, Et, or (i)Pr) are obtained when [Pd(N[bond]N)(C(6)F(5))Cl] is treated with KOH in the corresponding alcohol ROH and CO is bubbled through the solution. The reactions of [Pd(N[bond]N)(C(6)F(5))(OH)] (N[bond]N = bipy or Me(2)bipy) with CO(2), in tetrahydrofuran, lead to the formation of the binuclear carbonate complexes [(N[bond]N)(C(6)F(5))Pd(mu-eta(2)-CO(3))Pd(C(6)F(5))(N[bond]N)]. Complexes [Pd(N[bond]N)(C(6)F(5))(OH)] react in alcohol with PhNCS to yield the corresponding N-phenyl-O-alkylthiocarbamate complexes [Pd(N[bond]N)(C(6)F(5))[SC(OR)NPh

The Nature of the Hydrogen Bond Outline of a Comprehensive Hydrogen Bond Theory

CERN Document Server

Gilli, Gastone

2009-01-01

Hydrogen bond (H-bond) effects are known: it makes sea water liquid, joins cellulose microfibrils in trees, shapes DNA into genes and polypeptide chains into wool, hair, muscles or enzymes. Its true nature is less known and we may still wonder why O-H...O bond energies range from less than 1 to more than 30 kcal/mol without apparent reason. This H-bond puzzle is re-examined here from its very beginning and presented as an inclusive compilation of experimental H-bond energies andgeometries.New concepts emerge from this analysis: new classes of systematically strong H-bonds (CAHBs and RAHBs: cha

Hydrogen bonding in ionic liquids.

Science.gov (United States)

Hunt, Patricia A; Ashworth, Claire R; Matthews, Richard P

2015-03-07

Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (ρBCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H σ* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak

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.

Bonding effectiveness of self-etch adhesives to dentin after 24 h water storage.

Science.gov (United States)

Sarr, Mouhamed; Benoist, Fatou Leye; Bane, Khaly; Aidara, Adjaratou Wakha; Seck, Anta; Toure, Babacar

2018-01-01

This study evaluated the immediate bonding effectiveness of five self-etch adhesive systems bonded to dentin. The microtensile bond strength of five self-etch adhesives systems, including one two-step and four one-step self-etch adhesives to dentin, was measured. Human third molars had their superficial dentin surface exposed, after which a standardized smear layer was produced using a medium-grit diamond bur. The selected adhesives were applied according to their respective manufacturer's instructions for μTBS measurement after storage in water at 37°C for 24 h. The μTBS varied from 11.1 to 44.3 MPa; the highest bond strength was obtained with the two-step self-etch adhesive Clearfil SE Bond and the lowest with the one-step self-etch adhesive Adper Prompt L-Pop. Pretesting failures mainly occurring during sectioning with the slow-speed diamond saw were observed only with the one-step self-etch adhesive Adper Prompt L-Pop (4 out of 18). When bonded to dentin, the self-etch adhesives with simplified application procedures (one-step self-etch adhesives) still underperform as compared to the two-step self-etch adhesive Clearfil SE Bond.

Enamel Bond Strength of New Universal Adhesive Bonding Agents.

Science.gov (United States)

McLean, D E; Meyers, E J; Guillory, V L; Vandewalle, K S

2015-01-01

Universal bonding agents have been introduced for use as self-etch or etch-and-rinse adhesives depending on the dental substrate and clinician's preference. The purpose of this study was to evaluate the shear bond strength (SBS) of composite to enamel using universal adhesives compared to a self-etch adhesive when applied in self-etch and etch-and-rinse modes over time. Extracted human third molars were used to create 120 enamel specimens. The specimens were ground flat and randomly divided into three groups: two universal adhesives and one self-etch adhesive. Each group was then subdivided, with half the specimens bonded in self-etch mode and half in etch-and-rinse mode. The adhesives were applied as per manufacturers' instructions, and composite was bonded using a standardized mold and cured incrementally. The groups were further divided into two subgroups with 10 specimens each. One subgroup was stored for 24 hours and the second for six months in 37°C distilled water and tested in shear. Failure mode was also determined for each specimen. A three-way analysis of variance (ANOVA) found a significant difference between groups based on bonding agent (p0.05). Clearfil SE in etch-and-rinse and self-etch modes had more mixed fractures than either universal adhesive in either mode. Etching enamel significantly increased the SBS of composite to enamel. Clearfil SE had significantly greater bond strength to enamel than either universal adhesive, which were not significantly different from each other.

Effect of intracanal medicament on bond strength of fibre posts

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Huda Melike Bayram

2016-07-01

Full Text Available The aim of this study was to evaluate the effect of calcium hydroxide (CH, triple antibiotic paste (TAP and double antibiotic paste (DAP on the push-out bond strengths of three different self-adhesive resin cements. Forty-eight single-rooted human maxillary central incisors were selected. The crowns were removed and the root canals were performed. After the irrigation protocols, the post space was prepared. The teeth were then randomly divided into a control group (no intracanal medicament and three medicament groups (n = 12 for each group. After three weeks, the medicaments were removed using 17% ethylenediaminetetraacetic acid, 2.5% sodium hypochlorite and EndoActivator agitation. The teeth were divided into three subgroups according to the fibre-post luting cement: Maxcem Elite, RelyX Unicem and BisCem. The specimens were sectioned and the push-out test was performed. One-way analysis of variance and Tukey's post hoc tests were used for statistical analyses. Regarding the type of cement, BisCem had significantly lower bond strength values than Maxcem and RelyX. There was no significant difference between the bond strength values of Maxcem and RelyX (p > 0.05. The TAP-RelyX group had the highest bond strength value and the DAP-BisCem group had the lowest bond strength value. RelyX and Maxcem had higher bond strength to root canal dentin than BisCem. The bond strength of BisCem, RelyX and Maxcem was not negatively affected by the use of DAP, CH and TAP as intracanal medicaments.

Ultrastructural Analysis and Long-term Evaluation of Composite-Zirconia Bond Strength.

Science.gov (United States)

Aboushelib, Moustafa N; Ragab, Hala; Arnaot, Mohamed

2018-01-01

To evaluate the influence of different aging techniques on zirconia-composite microtensile bond strength using different surface treatments over a 5-year follow-up period. Zirconia disks received three surface treatments: airborne-particle abrasion with 50-μm aluminum oxide particles, selective infiltration etching (SIE), or fusion sputtering (FS). The specimens were bonded to pre-aged composite disks using a composite cement containing phosphate monomers (Panavia F2.0). Bonded specimens were sectioned into microbars (1 x 1 x 6 mm) using a precision cutting machine, and all microbars received thermocycling (15,000 cycles between 5°C and 55°C). Initial microtensile bond strength was evaluated, and the test was repeated after storage in the following media for five years (artificial saliva, 20% ethanol, 5% NaOH, 4% acetic acid, and 5% phosphoric acid). The test was repeated every 12 months for 5 years. Scanning electron microscopic images were used to analyze the zirconia-composite interface. A repeated measures ANOVA and Bonferroni post-hoc tests were used to analyze the data (n = 20, α = 0.05). Significantly higher microtensile bond strength was observed for SIE compared to fusion sputtering and airborne particle abrasion. Five years of artificial aging resulted in significant reduction of zirconia-composite bond strength for all tested specimens. Zirconia-composite bond strength was more sensitive to storage in sodium hydroxide and phosphoric acid, while it was least affected when stored under saliva. These changes were related to the mechanism of ultra-structural interaction between surface treatment and adhesive, as deterioration of the hybrid layer (composite-infiltrated ceramic) was responsible for bond degeneration. Zirconia-composite bond strength was influenced by 5 years of artificial aging.

Using Diffusion Bonding in Making Piezoelectric Actuators

Science.gov (United States)

Sager, Frank E.

2003-01-01

and pressure for a specified curing time. The pressure, temperature, and time depend on the piezoelectric material selected. At the end of the diffusion-bonding process, the resulting laminated piezoelectric actuator is tested to verify the adequacy of the mechanical output as a function of an applied DC voltage.

Strength of Al and Al-Mg/alumina bonds prepared using ultrahigh vacuum diffusion bonding

International Nuclear Information System (INIS)

King, W.E.; Campbell, G.H.; Wien, W.L.; Stoner, S.L.

1994-01-01

The authors have measured the cross-breaking strength of Al and Al-Mg alloys bonded with alumina. Diffusion bonding of Al and Al-Mg alloys requires significantly more bonding time than previously thought to obtain complete bonding. In contrast to previous diffusion bonding studies, fracture morphologies are similar to those obtained in bonds formed by liquid phase reaction; i.e., bonds are as strong or stronger than the ceramic; and fracture tends to propagate in the metal for pure Al and near the interface in the ceramic for the alloys. There are indications that the fracture morphology depends on Mg content and therefore on plasticity in the metal

Hydrogen bonding of formamide, urea, urea monoxide and their thio

Indian Academy of Sciences (India)

Ab initio and DFT methods have been employed to study the hydrogen bonding ability of formamide, urea, urea monoxide, thioformamide, thiourea and thiourea monoxide with one water molecule and the homodimers of the selected molecules. The stabilization energies associated with themonohydrated adducts and ...

Manufacturing study of Be, W and CFC bonded structures for plasma-facing components

Science.gov (United States)

Onozuka, M.; Hirai, S.; Kikuchi, K.; Oda, Y.; Shimizu, K.

2004-08-01

A manufacturing study has been conducted for Be, W, and CFC bonded structures employed in plasma-facing components for the ITER. For Be tiles bonded to the Cu-Cr-Zr alloy heat sink with stainless-steel cooling pipes, a one-axis hot press with two heating processes has been used to bond the three materials. An Al-Si base interlayer has been used to bond Be to the Cu-alloy. The heating processes have been selected to match the required heat treatment conditions for the Cu-alloy. Because of the limited heat processes using a conventional hot press, the manufacturing cost can be minimized. For both the W and CFC tiles, the materials have been brazed at the same time to the Cu-alloy. Ni-Cu-Mn and Cu-Ti brazing materials have been used for the W and CFC tiles, respectively. Using the above bonding techniques, partial mockups of a blanket first-wall panel and divertor target have been successfully manufactured.

Manufacturing study of Be, W and CFC bonded structures for plasma-facing components

International Nuclear Information System (INIS)

Onozuka, M.; Hirai, S.; Kikuchi, K.; Oda, Y.; Shimizu, K.

2004-01-01

A manufacturing study has been conducted for Be, W, and CFC bonded structures employed in plasma-facing components for the ITER. For Be tiles bonded to the Cu-Cr-Zr alloy heat sink with stainless-steel cooling pipes, a one-axis hot press with two heating processes has been used to bond the three materials. An Al-Si base interlayer has been used to bond Be to the Cu-alloy. The heating processes have been selected to match the required heat treatment conditions for the Cu-alloy. Because of the limited heat processes using a conventional hot press, the manufacturing cost can be minimized. For both the W and CFC tiles, the materials have been brazed at the same time to the Cu-alloy. Ni-Cu-Mn and Cu-Ti brazing materials have been used for the W and CFC tiles, respectively. Using the above bonding techniques, partial mockups of a blanket first-wall panel and divertor target have been successfully manufactured

Resistance of Bonded Composite Restorations on Fractures of Endodontically Treated Teeth

Directory of Open Access Journals (Sweden)

AR Daneshkazemi

2005-01-01

Full Text Available Introduction: This study was performed to evaluate the effect of dentine bonding agents and Glass Ionomer cement beneath composite restorations and its resistance on fractures of endodontically treated teeth. Material and Methods: Forty sound maxillary teeth were selected; ten of them for positive control, and on the rest, RCT and MOD cavity preparations were done with standard methods. Then, the teeth were divided to four groups: 1-Sound teeth for positive control. 2-Prepared without any restoration for negative control. 3-Prepared and restored with Vitrabond(3M, USA, Single bond(3M, USA and Z100(3M, USA resin composite. 4-Prepared and restored by Single bond and Z100 resin composite. Specimens were subjected to compressive load by Instron 8502 until fracture occurred. Results: Group 1 showed the highest resistance to compressive forces followed by group 4,3&2 respectively. ANOVA, t test and Chi-square tests indicated significant difference between all the groups. Conclusion: Use of dentine bonding agents and resin composite increases resistance of endodontically treated teeth to fractures more than teeth restored with sandwich of glass ionomer cements, dentine bonding agents and resin composite.

Safe and Liquid Mortgage Bonds

DEFF Research Database (Denmark)

Dick-Nielsen, Jens; Gyntelberg, Jacob; Lund, Jesper

This paper shows that strict match pass-through funding of covered bonds provides safe and liquid mortgage bonds. Despite a 30% drop in house prices during the 2008 global crisis Danish mortgage bonds remained as liquid as most European government bonds. The Danish pass-through system effectively...... eliminates credit risk from the investor's perspective. Similar to other safe bonds, funding liquidity becomes the main driver of mortgage bond liquidity and this creates commonality in liquidity across markets and countries. These findings have implications for how to design a robust mortgage bond system...

Comparative TEM study of bonded silicon/silicon interfaces fabricated by hydrophilic, hydrophobic and UHV wafer bonding

International Nuclear Information System (INIS)

Reznicek, A.; Scholz, R.; Senz, S.; Goesele, U.

2003-01-01

Wafers of Czochralski-grown silicon were bonded hydrophilically, hydrophobically and in ultrahigh vacuum (UHV) at room temperature. Wafers bonded hydrophilically adhere together by hydrogen bonds, those bonded hydrophobically by van der Waals forces and UHV-bonded ones by covalent bonds. Annealing the pre-bonded hydrophilic and hydrophobic wafer pairs in argon for 2 h at different temperatures increases the initially low bonding energy. UHV-bonded wafer pairs were also annealed to compare the results. Transmission electron microscopy (TEM) investigations show nano-voids at the interface. The void density depends on the initial bonding strength. During annealing the shape, coverage and density of the voids change significantly

Evaluation of a New Nano-filled Bonding Agent for Bonding Orthodontic Brackets as Compared to a Conventional Bonding Agent: An in vitro Study

Directory of Open Access Journals (Sweden)

Sandesh S Pai

2012-01-01

Conclusion: Although both bonding agents provide clinically acceptable levels of bond strength, the technique to bond the nano-filled Prime and Bond NT is more cumbersome as compared to the Transbond XT material, which makes the latter a more popular choice in the clinical set up. If the application procedures for the Prime and Bond NT can be simplified then it could be a convenient option in the orthodontic practice.

[The durability of three self-etch adhesives bonded to dentin].

Science.gov (United States)

Tian, Fu-Cong; Wang, Xiao-Yan; Gao, Xue-Jun

2013-04-01

To investigate the durability of self-etch adhesives bonded to dentin in vitro. Forty-two extracted human molars were selected and occlusal dentin surfaces were exposed. The teeth were randomly distributed into three groups based on adhesives applied. The one-step self-etch adhesive B(Adper Prompt) and C(G-Bond) and two-step self-etch adhesive A (Clearfil SE bond) were used. After application of the adhesives to the dentin surfaces, composite crowns were built up, after 24 h water storage, the teeth were sectioned longitudinally into sticks (1.0 mm×1.0 mm bonding area) for microtensile testing or slabs (1 mm thick) for scanning electron microscopec (SEM) observation. Bonding strength (mTBS) and nano-leakage were evaluated immediately after cutting or after 6 months in water. The mTBS was analyzed using one-way ANOVA (SPSS 13.0). The nanoleakage was observed by SEM with a backscattered electron detector. Both adhesives and water storage time affected the mTBS. All adhesives showed decreased bond strength after six-month water aging [A dropped from (40.60 ± 5.76) MPa to (36.04 ± 3.15) MPa; B dropped from (19.06 ± 1.50) MPa to (11.19 ± 1.97) MPa; C dropped from (17.75 ± 1.10) MPa to (9.14 ± 1.15) MPa] (P adhesives tested were probably influenced by water aging, however, the two-step adhesive showed better durability than the one-step adhesives.

CMPO-calix[4]arenes with spacer containing intramolecular hydrogen bonding: Effect of local rigidification on solvent extraction toward f-block elements

International Nuclear Information System (INIS)

Chu, Hongzhu; He, Lutao; Jiang, Qian; Fang, Yuyu; Jia, Yiming; Yuan, Xiangyang; Zou, Shuliang; Li, Xianghui; Feng, Wen; Yang, Yuanyou; Liu, Ning; Luo, Shunzhong; Yang, Yanqiu; Yang, Liang; Yuan, Lihua

2014-01-01

Highlights: • Three CMPO-calix[4]arenes with spacer containing intramolecular hydrogen bonds were designed and synthesized. • The influence of local rigidification caused by intramolecular hydrogen bonds upon extraction of f-elements was investigated. • Selective extraction is realized via tuning local chelating surroundings by aid of intramolecular hydrogen bonds. -- Abstract: To understand intramolecular hydrogen bonding in effecting liquid–liquid extraction behavior of CMPO-calixarenes, three CMPO-modified calix[4]arenes (CMPO-CA) 5a–5c with hydrogen-bonded spacer were designed and synthesized. The impact of spacer rotation that is hindered by introduction of intramolecular hydrogen bonding upon extraction of La 3+ , Eu 3+ , Yb 3+ , Th 4+ , and UO 2 2+ has been examined. The results show that 5b and 5c containing only one hydrogen bond with a less hindered rotation spacer extract La 3+ more efficiently than 5a containing two hydrogen bonds with a more hindered rotation spacer, demonstrating the importance of local rigidification of spacer in the design of extractants in influencing the coordination environment. The large difference in extractability between La 3+ and Yb 3+ (or Eu 3+ ) by 5b (or 5c), and the small difference by 5a, suggests intramolecular hydrogen bonding do exert pronounced influence upon selective extraction of light and heavy lanthanides. Log–log plot analysis indicates a 1:1, 2:1 and 1:1 stoichiometry (ligand/metal) for the extracted complex formed between 5b and La 3+ , Th 4+ , UO 2 2+ , respectively. Additionally, their corresponding acyclic analogs 7a–7c exhibit negligible extraction toward these metal ions. These results reveal the possibility of selective extraction via tuning local chelating surroundings of CMPO-CA by aid of intramolecular hydrogen bonding

Ultrafast dynamics of hydrogen bond exchange in aqueous ionic solutions.

Science.gov (United States)

Park, Sungnam; Odelius, Michael; Gaffney, Kelly J

2009-06-04

The structural and dynamical properties of aqueous ionic solutions influence a wide range of natural and biological processes. In these solutions, water has the opportunity to form hydrogen bonds with other water molecules and anions. Knowing the time scale with which these configurations interconvert represents a key factor to understanding the influence of molecular scale heterogeneity on chemical events in aqueous ionic solutions. We have used ultrafast IR spectroscopy and Car-Parrinello molecular dynamics (CPMD) simulations to investigate the hydrogen bond (H-bond) structural dynamics in aqueous 6 M sodium perchlorate (NaClO4) solution. We have measured the H-bond exchange dynamics between spectrally distinct water-water and water-anion H-bond configurations with 2DIR spectroscopy and the orientational relaxation dynamics of water molecules in different H-bond configurations with polarization-selective IR pump-probe experiments. The experimental H-bond exchange time correlates strongly with the experimental orientational relaxation time of water molecules. This agrees with prior observations in water and aqueous halide solutions, and has been interpreted within the context of an orientational jump model for the H-bond exchange. The CPMD simulations performed on aqueous 6 M NaClO4 solution clearly demonstrate that water molecules organize into two radially and angularly distinct structural subshells within the first solvation shell of the perchlorate anion, with one subshell possessing the majority of the water molecules that donate H-bonds to perchlorate anions and the other subshell possessing predominantly water molecules that donate two H-bonds to other water molecules. Due to the high ionic concentration used in the simulations, essentially all water molecules reside in the first ionic solvation shells. The CPMD simulations also demonstrate that the molecular exchange between these two structurally distinct subshells proceeds more slowly than the H-bond

Bonding of universal adhesives to dentine--Old wine in new bottles?

Science.gov (United States)

Chen, C; Niu, L-N; Xie, H; Zhang, Z-Y; Zhou, L-Q; Jiao, K; Chen, J-H; Pashley, D H; Tay, F R

2015-05-01

Multi-mode universal adhesives offer clinicians the choice of using the etch-and-rinse technique, selective enamel etch technique or self-etch technique to bond to tooth substrates. The present study examined the short-term in vitro performance of five universal adhesives bonded to human coronal dentine. Two hundred non-carious human third molars were assigned to five groups based on the type of the universal adhesives (Prime&Bond Elect, Scotchbond Universal, All-Bond Universal, Clearfil Universal Bond and Futurabond U). Two bonding modes (etch-and-rinse and self-etch) were employed for each adhesive group. Bonded specimens were stored in deionized water for 24h or underwent a 10,000-cycle thermocycling ageing process prior to testing (N=10). Microtensile bond testing (μTBS), transmission electron microscopy (TEM) of resin-dentine interfaces in non-thermocycled specimens and scanning electron microscopy (SEM) of tracer-infused water-rich zones within hybrid layers of thermocycled specimens were performed. Both adhesive type and testing condition (with/without thermocycling) have significant influences on μTBS. The use of each adhesive in either the etch-and-rinse or self-etch application mode did not result in significantly different μTBS to dentine. Hybrid layers created by these adhesives in the etch-and-rinse bonding mode and self-etch bonding mode were ∼5μm and ≤0.5μm thick respectively. Tracer-infused regions could be identified within the resin-dentine interface from all the specimens prepared. The increase in versatility of universal adhesives is not accompanied by technological advances for overcoming the challenges associated with previous generations of adhesives. Therapeutic adhesives with bio-protective and bio-promoting effects are still lacking in commercialized adhesives. Universal adhesives represent manufacturers' attempt to introduce versatility in product design via adaptation of a single-bottle self-etch adhesive for other application

Formaldehyde formation in coupled oxidation of methane and methanol over V2O5 and MoO3 silica supported catalysts

International Nuclear Information System (INIS)

Lojewska, J.; Makowski, W.; Fajardo Farre, A.; Dziembaj, R.

2003-01-01

The effect of methanol on partial oxidation of methane has been studied on standard molybdena and vanadia catalysts supported on silica. Prior to catalytic tests the catalysts were characterized by BET, SEM/EDAX and TPR/O methods. Three types of catalytic tests were performed giving temperature and contact time dependence on the catalyst activity and selectivity: partial oxidations of methane, methanol and methane/methanol mixtures. The methanol showed an activating impact on the partial oxidation of methane over all used catalysts samples, but the strongest one over Mo 3 /SiO 2 . In the absence of CH 3 OH the only catalyst, which exhibited HCHO selectivity, was low loaded vanadia catalyst. It has been put forward that methanol may enhance formation of oxygen active species, prerequisites for activating methane molecules, through reducing vanadia cations and causing breakage of vanadium oxygen bonds. (author)

Deproteinization of fluorosed enamel with sodium hypochlorite enhances the shear bond strength of orthodontic brackets: An In vitro study

Directory of Open Access Journals (Sweden)

Rekha Sharma

2017-01-01

Full Text Available Context: Improving bonding strength to fluorosed teeh. Aims: To determine the effect of deproteinization using 5.25% sodium hypochlorite (NaOCl prior to acid etching on shear bond strength of orthodontic brackets bonded to fluorosed teeth. Settings and Design: In vitro experimental study. Methods and Material: Forty freshly extracted human mandibular first premolars with TFI 4 were selected and divided into two groups of 20 each. In Group I the teeth were acid etched with 37% phosphoric acid and bonded with composite. In Group II the teeth were deproteinized with 5.25% NaOCl prior to acid etching with 37% phosphoric acid and were bonded with composite. Samples were then subjected to shear bond test by Instron Universal Testing machine. The sample from each group were selected for the SEM study (prior to bonding to analyze the etching patterns achieved. Statistical Analysis Used: Data was checked for normality by Shapiro Wilk Test, to compare the two groups unpaired t test was used. P value was predetermined at ≤ 0.05. Results: The S BS of Group II (11.75 ± 2.83 MPa was higher than Group I (7.44 ± 2.43 MPa and the difference was statistically significant (P = 0.000. On SEM the etching pattern was more of type 1 and 2 in Group II. Conclusions: Deproteinization using 5.25% NaOCl prior to acid etching significantly increases the shear bond strength of brackets bonded to fluorosed teeth and can be used as a convenient and effective option in orthodontic bonding to fluorosed teeth.

Mechanism of bonding and debonding using surface activated bonding method with Si intermediate layer

Science.gov (United States)

Takeuchi, Kai; Fujino, Masahisa; Matsumoto, Yoshiie; Suga, Tadatomo

2018-04-01

Techniques of handling thin and fragile substrates in a high-temperature process are highly required for the fabrication of semiconductor devices including thin film transistors (TFTs). In our previous study, we proposed applying the surface activated bonding (SAB) method using Si intermediate layers to the bonding and debonding of glass substrates. The SAB method has successfully bonded glass substrates at room temperature, and the substrates have been debonded after heating at 450 °C, in which TFTs are fabricated on thin glass substrates for LC display devices. In this study, we conducted the bonding and debonding of Si and glass in order to understand the mechanism in the proposed process. Si substrates are also successfully bonded to glass substrates at room temperature and debonded after heating at 450 °C using the proposed bonding process. By the composition analysis of bonding interfaces, it is clarified that the absorbed water on the glass forms interfacial voids and cause the decrease in bond strength.

Effect of nanoscale surface roughness on the bonding energy of direct-bonded silicon wafers

Science.gov (United States)

Miki, N.; Spearing, S. M.

2003-11-01

Direct wafer bonding of silicon wafers is a promising technology for manufacturing three-dimensional complex microelectromechanical systems as well as silicon-on-insulator substrates. Previous work has reported that the bond quality declines with increasing surface roughness, however, this relationship has not been quantified. This article explicitly correlates the bond quality, which is quantified by the apparent bonding energy, and the surface morphology via the bearing ratio, which describes the area of surface lying above a given depth. The apparent bonding energy is considered to be proportional to the real area of contact. The effective area of contact is defined as the area sufficiently close to contribute to the attractive force between the two bonding wafers. Experiments were conducted with silicon wafers whose surfaces were roughened by a buffered oxide etch solution (BOE, HF:NH4F=1:7) and/or a potassium hydroxide solution. The surface roughness was measured by atomic force microscopy. The wafers were direct bonded to polished "monitor" wafers following a standard RCA cleaning and the resulting bonding energy was measured by the crack-opening method. The experimental results revealed a clear correlation between the bonding energy and the bearing ratio. A bearing depth of ˜1.4 nm was found to be appropriate for the characterization of direct-bonded silicon at room temperature, which is consistent with the thickness of the water layer at the interface responsible for the hydrogen bonds that link the mating wafers.

The Bond Fluctuation Model and Other Lattice Models

Science.gov (United States)

Müller, Marcus

Lattice models constitute a class of coarse-grained representations of polymeric materials. They have enjoyed a longstanding tradition for investigating the universal behavior of long chain molecules by computer simulations and enumeration techniques. A coarse-grained representation is often necessary to investigate properties on large time- and length scales. First, some justification for using lattice models will be given and the benefits and limitations will be discussed. Then, the bond fluctuation model by Carmesin and Kremer [1] is placed into the context of other lattice models and compared to continuum models. Some specific techniques for measuring the pressure in lattice models will be described. The bond fluctuation model has been employed in more than 100 simulation studies in the last decade and only few selected applications can be mentioned.

Effect of Adhesive Type on the Shear Bond Strength of Metal Brackets to Two Ceramic Substrates

Directory of Open Access Journals (Sweden)

Mohammad Sadegh Ahmad Akhoundi

2014-04-01

Full Text Available Increased number of adult patients requesting orthodontic treatment result in bonding bracket to ceramic restorations more than before. The aim of this study was to evaluate and compare the shear bond strength of orthodontic brackets bonded to two types of ceramic bases with conventional orthodontic bonding resin and a new nano-filled composite resin.Twenty four feldespathic porcelain and 24 lithium disilicate ceramic disks were fabricated. All of the samples were conditioned by sandblasting, hydrofluoric acid and silane. Maxillary incisor metal brackets were bonded to half of the disks in each group by conventional orthodontic bonding resin and the other half bonded with a nano-filled composite. The samples then were thermocycled for 2000 cycle between 5-55° C. Shear bond strength was measured and the mode of failure was examined. Randomly selected samples were also evaluated by SEM.The lowest bond strength value was found infeldespathic ceramic bonded by nano-filled composite (p<0.05. There was not any statistically significant difference between other groups regarding bond strength. The mode of failure in the all groups except group 1 was cohesive and porcelain damages were detected.Since less damages to feldspathic porcelain was observed when the nano-filled composite was used to bond brackets, the use of nano-filled composite resins can be suggested for bonding brackets to feldspathic porcelain restorations.

C-H Bond Functionalization via Hydride Transfer: Direct Coupling of Unactivated Alkynes and sp3 C-H Bonds Catalyzed by Platinum Tetraiodide

Science.gov (United States)

Vadola, Paul A.; Sames, Dalibor

2010-01-01

We report a catalytic intramolecular coupling between terminal unactivated alkynes and sp3 C-H bonds via the through-space hydride transfer (HT-cyclization of alkynes). This method enables one-step preparation of complex heterocyclic compounds by α-alkenylation of readily available cyclic ethers and amines. We show that PtI4 is an effective Lewis acid catalyst for the activation of terminal alkynes for the hydride attack and subsequent C-C bond formation. In addition, we have shown that the activity of neutral platinum salts (PtXn) can be modulated by the halide ligands. This modulation in turn allows for fine-tuning of the platinum center reactivity to match the reactivity and stability of selected substrates and products. PMID:19852462

Australia's Bond Home Bias

OpenAIRE

Anil V. Mishra; Umaru B. Conteh

2014-01-01

This paper constructs the float adjusted measure of home bias and explores the determinants of bond home bias by employing the International Monetary Fund's high quality dataset (2001 to 2009) on cross-border bond investment. The paper finds that Australian investors' prefer investing in countries with higher economic development and more developed bond markets. Exchange rate volatility appears to be an impediment for cross-border bond investment. Investors prefer investing in countries with ...

The CDS and the Government Bonds Markets During the Last Financial Crisis

Directory of Open Access Journals (Sweden)

Križanič France

2015-11-01

Full Text Available Financial market had developed a special instrument to insure the buyers of bonds. This instrument is so called Credit Default Swap (CDS. The CDS price is a kind of insurance premium that the buyer of CDS pays to the seller of CDS in exchange for compensation of possible loss in operation. Paper analyses causality between CDS price and dynamics of bond yields and influence of macroeconomic factors on it in four selected countries during the last financial crisis. Analysis results show that there is no important macroeconomic variable included in the analysis that preceded the CDS prices connected with German government bonds. Sellers of CDS were apparently aware of the systemic nature of the financial crisis in the euro area. In the case of the United Kingdom, Russia and Slovenia we can observe the unemployment rate as the most important macroeconomic variable that preceded the CDS prices for government bonds.

Proposal of new bonding technique 'Instantaneous Liquid Phase (ILP) Bonding'

International Nuclear Information System (INIS)

Zhang, Yue-Chang; Nakagawa, Hiroji; Matsuda, Fukuhisa.

1987-01-01

A new bonding technique named ''Instantaneous Liquid Phase (ILP) bonding'' suitable mainly for welding dissimilar materials was proposed by which instantaneous melting of one or two of the faying surfaces is utilized. The processes of ILP bonding are mainly consisted of three stages, namely the first stage forming thin liquid layer by rapid heating, the second stage joining both specimens by thin liquid layer, and the third stage cooling the specimens rapidly to avoid the formation of brittle layer. The welding temperatures of the specimens to be welded in ILP bonding are generally differentiated from each other. ILP bonding was applied for a variety of combinations of dissimilar materials of aluminum, aluminum alloys, titanium, titanium alloy, carbon steel, austenitic stainless steel, copper and tungsten, and for similar materials of stainless steel and nickel-base alloy. There were no microvoids in these welding joints, and the formation of brittle layer at the bonding interface was suppressed. The welded joints of Al + Ti, Cu + carbon steel and Cu + austenitic stainless steel showed the fracture in base metal having lower tensile strength. Further, the welded joints of Al + carbon steel, Al alloy + Ti, Al alloy + carbon steel or + austenitic stainless steel, Ti + carbon steel or + austenitic stainless steel showed better tensile properties in the comparison with diffusion welding. Furthermore, ILP bonding was available for welding same materials susceptible to hot cracking. Because of the existence of liquid layer, the welding pressure required was extremely low, and preparation of faying surface by simple tooling or polishing by no.80 emery paper was enough. The change in specimen length before and after welding was relatively little, only depending on the thickness of liquid layer. The welding time was very short, and thus high welding efficiency was obtained. (author)

Shear Bond Strength of Orthodontic Brackets Bonded to Zirconium Crowns.

Science.gov (United States)

Mehmeti, Blerim; Azizi, Bleron; Kelmendi, Jeta; Iljazi-Shahiqi, Donika; Alar, Željko; Anić-Milošević, Sandra

2017-06-01

An increasing demand for esthetic restorations has resulted in an increased use of all-ceramic restorations, such as zirconium. However, one of the challenges the orthodontist must be willing to face is how to increase bond strength between the brackets and various ceramic restorations.Bond strength can beaffected bybracket type, by the material that bracketsaremade of, and their base surface design or retention mode. ​: A im: of this study was to perform a comparative analysis of the shear bond strength (SBS) of metallic and ceramic orthodontic brackets bonded to all-zirconium ceramic surfaces used for prosthetic restorations, and also to evaluate the fracture mode of these two types of orthodontic brackets. Twenty samples/semi-crowns of all-zirconium ceramic, on which orthodontic brackets were bonded, 10 metallic and 10 ceramic polycrystalline brackets, were prepared for this research. SBS has been testedby Universal Testing Machine, with a load applied using a knife edged rod moving at a fixed rate of 1 mm/min, until failure occurred. The force required to debond the brackets was recorded in Newton, then SBS was calculated to MPa. In addition, the samples were analyzed using a digital camera magnifier to determine Adhesive Remnant Index (ARI). Statistical data were processed using t-test, and the level of significance was set at α = 0.05. Higher shear bond strength values were observed in metallic brackets bonded to zirconium crowns compared tothoseof ceramic brackets, with a significant difference. During the test, two of the ceramic brackets were partially or totally damaged. Metallic brackets, compared to ceramic polycrystalline brackets, seemed tocreate stronger adhesion with all-zirconium surfaces due to their better retention mode. Also, ceramic brackets showed higher fragility during debonding.

Deciphering effects of functional groups and electron density on azo dyes degradation by graphene loaded TiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zhang, Qian [College of Chemical Engineering, HuaQiao University, Xiamen 361021 (China); Liang, Xiao [School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Chen, Bor-Yann [Department of Chemical and Materials Engineering, National I-Lan University, 26047, Taiwan (China); Chang, Chang-Tang, E-mail: ctchang@niu.edu.tw [Department of Environmental Engineering, National I-Lan University, 26047, Taiwan (China)

2015-12-01

Highlights: • The degradation pathways of RB5, RB171 and RR198 have been identified. • The favorable bond to be broken under photo degradation was deciphered in this research. • The breakages of the bonds were due to the electron density changes around the bonds. • The hydroxyl radicals as the main oxidized species were confirmed by positive hole trapper and ESR. - Abstract: This study tended to decipher the mechanism of photo degradation of azo dyes, which bond was favorable to be broken for application of wastewater decolorization. That is, from chemical structure perspective, the critical substituents to affect electron donor/acceptor for dye degradation would be identified in this research. The model reactive blacks (RB5), reactive blue 171 (RB171) and reactive red 198 (RR198) were degraded by graphene loaded TiO{sub 2}, indicating how the electron withdrawing and releasing groups affect azo dye degradability. The byproducts and intermediate products were analyzed by ultraviolet–visible spectroscopy (UV–vis), gas chromatography–mass spectrometry (GC–MS) and ion chromatography (IC). Furthermore, the radicals involved in the reaction were found by electron paramagnetic resonance (ESR) to confirm the main oxidized species of hydroxyl radicals rather than the light generated positive holes. The finding revealed that the breakages of the bonds were due to the electron density changes around the bonds. This principle can be applicable not only for RB5 degradation, but also for reactive blue 171 (RB171), reactive red 198 (RR198) and some other textile dyes.

Single-Molecule Rotational Switch on a Dangling Bond Dimer Bearing.

Science.gov (United States)

Godlewski, Szymon; Kawai, Hiroyo; Kolmer, Marek; Zuzak, Rafał; Echavarren, Antonio M; Joachim, Christian; Szymonski, Marek; Saeys, Mark

2016-09-27

One of the key challenges in the construction of atomic-scale circuits and molecular machines is to design molecular rotors and switches by controlling the linear or rotational movement of a molecule while preserving its intrinsic electronic properties. Here, we demonstrate both the continuous rotational switching and the controlled step-by-step single switching of a trinaphthylene molecule adsorbed on a dangling bond dimer created on a hydrogen-passivated Ge(001):H surface. The molecular switch is on-surface assembled when the covalent bonds between the molecule and the dangling bond dimer are controllably broken, and the molecule is attached to the dimer by long-range van der Waals interactions. In this configuration, the molecule retains its intrinsic electronic properties, as confirmed by combined scanning tunneling microscopy/spectroscopy (STM/STS) measurements, density functional theory calculations, and advanced STM image calculations. Continuous switching of the molecule is initiated by vibronic excitations when the electrons are tunneling through the lowest unoccupied molecular orbital state of the molecule. The switching path is a combination of a sliding and rotation motion over the dangling bond dimer pivot. By carefully selecting the STM conditions, control over discrete single switching events is also achieved. Combined with the ability to create dangling bond dimers with atomic precision, the controlled rotational molecular switch is expected to be a crucial building block for more complex surface atomic-scale devices.

Novel electrochemical approach to study corrosion mechanism of Al-Au wire-bond pad interconnections

DEFF Research Database (Denmark)

Elisseeva, O. V.; Bruhn, A.; Cerezo, J.

2013-01-01

A gold-aluminium material combination is typically employed as an interconnection for microelectronic devices. One of the reliability risks of such devices is that of corrosion of aluminium bond pads resulting from the galvanic coupling between an aluminium bond pad and a gold wire. The research...... presented in this manuscript focuses on studying bond pad corrosion by selecting an appropriate model system and a dedicated set of electrochemical and analytical experimental tools. Taking into account the complex three-dimensional structure and the small dimensions of Au-Al interconnections (around 50......-100 μm), a dedicated and novel experimental approach was developed. Au-Al covered silicon chips were developed under clean room conditions. Three-dimensional electrodes were mimicked as flat, two-dimensional bond pad model systems, allowing the use of microelectrochemical local probe techniques. Thin...

Integration of European Bond Markets

DEFF Research Database (Denmark)

Christiansen, Charlotte

2014-01-01

I investigate the time variation in the integration of EU government bond markets. The integration is measured by the explanatory power of European factor portfolios for the individual bond markets for each year. The integration of the government bond markets is stronger for EMU than non-EMU memb......I investigate the time variation in the integration of EU government bond markets. The integration is measured by the explanatory power of European factor portfolios for the individual bond markets for each year. The integration of the government bond markets is stronger for EMU than non...

Palladium-catalyzed meta-selective C-H bond activation with a nitrile-containing template: computational study on mechanism and origins of selectivity.

Science.gov (United States)

Yang, Yun-Fang; Cheng, Gui-Juan; Liu, Peng; Leow, Dasheng; Sun, Tian-Yu; Chen, Ping; Zhang, Xinhao; Yu, Jin-Quan; Wu, Yun-Dong; Houk, K N

2014-01-08

Density functional theory investigations have elucidated the mechanism and origins of meta-regioselectivity of Pd(II)-catalyzed C-H olefinations of toluene derivatives that employ a nitrile-containing template. The reaction proceeds through four major steps: C-H activation, alkene insertion, β-hydride elimination, and reductive elimination. The C-H activation step, which proceeds via a concerted metalation-deprotonation (CMD) pathway, is found to be the rate- and regioselectivity-determining step. For the crucial C-H activation, four possible active catalytic species-monomeric Pd(OAc)2, dimeric Pd2(OAc)4, heterodimeric PdAg(OAc)3, and trimeric Pd3(OAc)6-have been investigated. The computations indicated that the C-H activation with the nitrile-containing template occurs via a Pd-Ag heterodimeric transition state. The nitrile directing group coordinates with Ag while the Pd is placed adjacent to the meta-C-H bond in the transition state, leading to the observed high meta-selectivity. The Pd2(OAc)4 dimeric mechanism also leads to the meta-C-H activation product but with higher activation energies than the Pd-Ag heterodimeric mechanism. The Pd monomeric and trimeric mechanisms require much higher activation free energies and are predicted to give ortho products. Structural and distortion energy analysis of the transition states revealed significant effects of distortions of the template on mechanism and regioselectivity, which provided hints for further developments of new templates.

Enantioselective functionalization of allylic C-H bonds following a strategy of functionalization and diversification.

Science.gov (United States)

Sharma, Ankit; Hartwig, John F

2013-11-27

We report the enantioselective functionalization of allylic C-H bonds in terminal alkenes by a strategy involving the installation of a temporary functional group at the terminal carbon atom by C-H bond functionalization, followed by the catalytic diversification of this intermediate with a broad scope of reagents. The method consists of a one-pot sequence of palladium-catalyzed allylic C-H bond oxidation under neutral conditions to form linear allyl benzoates, followed by iridium-catalyzed allylic substitution. This overall transformation forms a variety of chiral products containing a new C-N, C-O, C-S, or C-C bond at the allylic position in good yield with a high branched-to-linear selectivity and excellent enantioselectivity (ee ≤97%). The broad scope of the overall process results from separating the oxidation and functionalization steps; by doing so, the scope of nucleophile encompasses those sensitive to direct oxidative functionalization. The high enantioselectivity of the overall process is achieved by developing an allylic oxidation that occurs without acid to form the linear isomer with high selectivity. These allylic functionalization processes are amenable to an iterative sequence leading to (1,n)-functionalized products with catalyst-controlled diastereo- and enantioselectivity. The utility of the method in the synthesis of biologically active molecules has been demonstrated.

Fusion-bonded fluidic interconnects

International Nuclear Information System (INIS)

Fazal, I; Elwenspoek, M C

2008-01-01

A new approach to realize fluidic interconnects based on the fusion bonding of glass tubes with silicon is presented. Fusion bond strength analyses have been carried out. Experiments with plain silicon wafers and coated with silicon oxide and silicon nitride are performed. The obtained results are discussed in terms of the homogeneity and strength of fusion bond. High pressure testing shows that the bond strength is large enough for most applications of fluidic interconnects. The bond strength for 525 µm thick silicon, with glass tubes having an outer diameter of 6 mm and with a wall thickness of 2 mm, is more than 60 bars after annealing at a temperature of 800 °C

Cement bond evaluation method in horizontal wells using segmented bond tool

Science.gov (United States)

Song, Ruolong; He, Li

2018-06-01

Most of the existing cement evaluation technologies suffer from tool eccentralization due to gravity in highly deviated wells and horizontal wells. This paper proposes a correction method to lessen the effects of tool eccentralization on evaluation results of cement bond using segmented bond tool, which has an omnidirectional sonic transmitter and eight segmented receivers evenly arranged around the tool 2 ft from the transmitter. Using 3-D finite difference parallel numerical simulation method, we investigate the logging responses of centred and eccentred segmented bond tool in a variety of bond conditions. From the numerical results, we find that the tool eccentricity and channel azimuth can be estimated from measured sector amplitude. The average of the sector amplitude when the tool is eccentred can be corrected to the one when the tool is centred. Then the corrected amplitude will be used to calculate the channel size. The proposed method is applied to both synthetic and field data. For synthetic data, it turns out that this method can estimate the tool eccentricity with small error and the bond map is improved after correction. For field data, the tool eccentricity has a good agreement with the measured well deviation angle. Though this method still suffers from the low accuracy of calculating channel azimuth, the credibility of corrected bond map is improved especially in horizontal wells. It gives us a choice to evaluate the bond condition for horizontal wells using existing logging tool. The numerical results in this paper can provide aids for understanding measurements of segmented tool in both vertical and horizontal wells.

Composite Bonding to Stainless Steel Crowns Using a New Universal Bonding and Single-Bottle Systems

Directory of Open Access Journals (Sweden)

Mohammad Ali Hattan

2013-01-01

Full Text Available Aim. The aim of this study is to evaluate the shear bond strength of nanocomposite to stainless steel crowns using a new universal bonding system. Material and Methods. Eighty (80 stainless steel crowns (SSCs were divided into four groups (20 each. Packable nanocomposite was bonded to the lingual surface of the crowns in the following methods: Group A without adhesive (control group, Group B using a new universal adhesive system (Scotchbond Universal Adhesive, 3M ESPE, Seefeld, Germany, and Group C and Group D using two different brands of single-bottle adhesive systems. Shear bond strengths were calculated and the types of failure also were recorded. Results. The shear strength of Group B was significantly greater than that of other groups. No significant differences were found between the shear bond strengths of Groups C and D. The control group had significantly lower shear bond strength ( to composite than the groups that utilized bonding agents. Conclusion. Composites bonding to stainless steel crowns using the new universal bonding agent (Scotchbond Universal Adhesive, 3M ESPE, Seefeld, Germany show significantly greater shear bond strengths and fewer adhesive failures when compared to traditional single-bottle systems.

Interstellar hydrogen bonding

Science.gov (United States)

Etim, Emmanuel E.; Gorai, Prasanta; Das, Ankan; Chakrabarti, Sandip K.; Arunan, Elangannan

2018-06-01

This paper reports the first extensive study of the existence and effects of interstellar hydrogen bonding. The reactions that occur on the surface of the interstellar dust grains are the dominant processes by which interstellar molecules are formed. Water molecules constitute about 70% of the interstellar ice. These water molecules serve as the platform for hydrogen bonding. High level quantum chemical simulations for the hydrogen bond interaction between 20 interstellar molecules (known and possible) and water are carried out using different ab-intio methods. It is evident that if the formation of these species is mainly governed by the ice phase reactions, there is a direct correlation between the binding energies of these complexes and the gas phase abundances of these interstellar molecules. Interstellar hydrogen bonding may cause lower gas abundance of the complex organic molecules (COMs) at the low temperature. From these results, ketenes whose less stable isomers that are more strongly bonded to the surface of the interstellar dust grains have been observed are proposed as suitable candidates for astronomical observations.

Optimising hydrogen bonding in solid wood

DEFF Research Database (Denmark)

Engelund, Emil Tang

2009-01-01

The chemical bonds of wood are both covalent bonds within the wood polymers and hydrogen bonds within and between the polymers. Both types of bonds are responsible for the coherence, strength and stiffness of the material. The hydrogen bonds are more easily modified by changes in load, moisture...... and temperature distorting the internal bonding state. A problem arises when studying hydrogen bonding in wood since matched wood specimens of the same species will have very different internal bonding states. Thus, possible changes in the bonding state due to some applied treatment such as conditioning...... maintaining 100 % moisture content of the wood. The hypothesis was that this would enable a fast stress relaxation as a result of reorganization of bonds, since moisture plasticizes the material and temperature promotes faster kinetics. Hereby, all past bond distortions caused by various moisture, temperature...

Microstructure and properties of hot roll bonding layer of dissimilar metals. 2. Bonding interface microstructure of Zr/stainless steel by hot roll bonding and its controlling

International Nuclear Information System (INIS)

Yasuyama, Masanori; Ogawa, Kazuhiro; Taka, Takao; Nakasuji, Kazuyuki; Nakao, Yoshikuni; Nishimoto, Kazutoshi.

1996-01-01

The hot roll bonding of zirconium and stainless steel inserted with tantalium was investigated using the newly developed rolling mill. The effect of hot rolling temperatures of zirconium/stainless steel joints on bonding interface structure was evaluated. Intermetallic compound layer containing cracks was observed at the bonding interface between stainless steel and tantalium when the rolling temperature was above 1373K. The hardness of the bonding layer of zirconium and tantalium bonded above 1273K was higher than tantalium or zirconium base metal in spite of absence of intermetallic compound. The growth of reaction layer at the stainless steel and tantalium interface and at the tantalium and zirconium interface was conforming a parabolic low when that was isothermally heated after hot roll bonding, and the growth rate was almost same as that of static diffusion bonding without using hot roll bonding process. It is estimated that the strain caused by hot roll bonding gives no effect on the growth of reaction layer. It was confirmed that the dissimilar joint of zirconium and stainless steel with insert of tantalium having the sound bonding interface were obtained at the suitable bonding temperature of 1173K by the usage of the newly developed hot roll bonding process. (author)

Investigations on organolead compounds V. Lead---lead bond cleavage reactions of hexaphenyldilead

NARCIS (Netherlands)

Willemsens, L.C.; Kerk, G.J.M. van der

1968-01-01

It has been shown that a number of nucleophilic and weakly electrophilic reagents (organolithium and organomagnesium compounds, metallic lithium, potassium permanganate, sodium ethoxide, diaryl disulphides, sulphur, ozone, hypochlorous acid and iodine/iodide) selectively cleave the lead---lead bond

Minimization of Basis Risk in Parametric Earthquake Cat Bonds

Science.gov (United States)

Franco, G.

2009-12-01

second disfavors the investor who loses part of the investment without a reasonable cause. A streamlined and fairly automated methodology has been developed to design parametric triggers that minimize the basis risk while still maintaining their level of relative simplicity. Basis risk is minimized in both, first and second generation, parametric cat bonds through an optimization procedure that aims to find the most appropriate magnitude thresholds, geographic zones, and weight index values. Sensitivity analyses to different design assumptions show that first generation cat bonds are typically affected by a large negative basis risk, namely the risk that the bond will not trigger for events within the risk level transferred, unless a sufficiently small geographic resolution is selected to define the trigger zones. Second generation cat bonds in contrast display a bias towards negative or positive basis risk depending on the degree of the polynomial used as well as on other design parameters. Two examples are presented, the construction of a first generation parametric trigger mechanism for Costa Rica and the design of a second generation parametric index for Japan.

BONDING ALUMINUM METALS

Science.gov (United States)

Noland, R.A.; Walker, D.E.

1961-06-13

A process is given for bonding aluminum to aluminum. Silicon powder is applied to at least one of the two surfaces of the two elements to be bonded, the two elements are assembled and rubbed against each other at room temperature whereby any oxide film is ruptured by the silicon crystals in the interface; thereafter heat and pressure are applied whereby an aluminum-silicon alloy is formed, squeezed out from the interface together with any oxide film, and the elements are bonded.

Relationship between thin-film bond strength as measured by a scratch test, and indentation hardness for bonding agents.

Science.gov (United States)

Kusakabe, Shusuke; Rawls, H Ralph; Hotta, Masato

2016-03-01

To evaluate thin-film bond strength between a bonding agent and human dentin, using a scratch test, and the characteristics and accuracy of measurement. One-step bonding agents (BeautiBond; Bond Force; Adper Easy Bond; Clearfil tri-S Bond) and two-step bonding agents (Cleafil SE Bond; FL-Bond II) were investigated in this study. Flat dentin surfaces were prepared for extracted human molars. The dentin surfaces were ground and bonding agents were applied and light cured. The thin-film bond strength test of the specimens was evaluated by the critical load at which the coated bonding agent failed and dentin appeared. The scratch mark sections were then observed under a scanning electron microscope. Indentation hardness was evaluated by the variation in depth under an applied load of 10gf. Data were compared by one-way ANOVA with the Scheffé's post hoc multiple comparison test (pstrength and indentation hardness were analyzed using analysis of correlation and covariance. The thin-film bond strength of two-step bonding agents were found to be significantly higher than that of one-step bonding agents with small standard deviations. Scratch marks consistently showed adhesive failure in the vicinity of the bonding agent/dentin interface. The indentation hardness showed a trend that two-step bonding agents have greater hardness than one-step bonding agents. A moderately significant correlation (r(2)=0.31) was found between thin-film bond strength and indentation hardness. Thin-film bond strength test is a valid and reliable means of evaluating bond strength in the vicinity of the adhesive interface and is more accurate than other methods currently in use. Further, the thin-film bond strength is influenced by the hardness of the cued bonding agent. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Comparison of shear bond strength of stainless steel brackets bonded with three light- cured adhesives

Directory of Open Access Journals (Sweden)

Zahra Minaei Basharik

2015-09-01

Full Text Available Introduction: The bonding process of the brackets to enamel has been a critical issue in orthodontic research. The purpose of this study was to evaluate the shear bond strength of 3 light-cured adhesives (transbond XT, Z250, light bond. Materials &Methods: In this study sixty extracted human premolars were collected and randomly divided into 3 test groups. All teeth were etched by 37% phosphoric acid. In first group brackets were bonded by Transbond XT adhesive, in group two brackets were bonded by Light bond adhesive and in third group were bonded by filtek Z250 composite. All of them were cured with Ortholux xt for 40 seconds.24 hours after thermocycling, Shear Bond Strength (SBS values of these brackets were recorded using a Universal Testing Machine. Adhesive Remnant Index (ARI scores were determined after the failure of the brackets, using Stereo Microscope the data were analyzed using ANOVA and Chi-square tests. Results: Mean shear bond strength of Transbond XT, light bond and Z250 were 28.9±2.25 MPa, 25.06±1.98 MPa and 26.8±2.57 MPa, respectively. No significant difference was observed in the SBS among the groups and a clinically acceptable SBS was found for the three adhesives. ARI scores were not significantly different between the various groups (P>0.05. Conclusion: This study showed that the Z250 can be used as light bond and transbond xt to bond orthodontic brackets and ARI and SBS scores were not significantly different.

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.

In Vitro Evaluation of Shear Bond Strength of Self Etching Primers to Dentin

Directory of Open Access Journals (Sweden)

Reena Vora

2012-01-01

Full Text Available Objectives: To evaluate and compare the shear bond strength of four self etching primer adhesives to dentin. Materials & Methods: A total of 75 extracted human maxillary and mandibular molars were selected for the study. The teeth were divided into 5 groups of 15 teeth each, Group A- AdheSE (Ivoclar Vivadent, Group B-Adper prompt (3M ESPE, Group C- i bond (Heraeus-Kulzer, Group D-XenoIII (Dentsply, De Trey Group E-Single bond (3M ESPE was used and served as control. All the adhesives were applied according to the manufacturer′s instructions. Composite post was built on these bonded surfaces using Z-100 hybrid composite. The teeth were subjected to thermocycling for 500 cycles between 5°C to 55°C. The teeth were then mounted on universal testing machine and fractured under a shearing load, applied at a speed of 0.2mm/min. The readings were noted, tabulated and shear bond strength calculated in Mega Pascal (Mpa units. Results: There was significant difference in the mean shear bond strength of the four self etching primers, adhesives tested. Shear strength values were in the range of 16.57 to 21.73 Mpa. Xeno III gave the highest mean of shear bond strength whereas Adhe SE showed the lowest value of shear strength. Conclusion: Based on the results of the study, it can be concluded that contemporary self etching primer adhesives bond successfully to dentin. Moreover the bonding ability of Self Etching Systems seems to be comparable to the conventional Total Etch Systems.

Spectrally- and Time-Resolved Sum Frequency Generation (STiR-SFG): a new tool for ultrafast hydrogen bond dynamics at interfaces.

Science.gov (United States)

Benderskii, Alexander; Bordenyuk, Andrey; Weeraman, Champika

2006-03-01

The recently developed spectrally- and time-resolved Sum Frequency Generation (STiR-SFG) is a surface-selective 3-wave mixing (IR+visible) spectroscopic technique capable of measuring ultrafast spectral evolution of vibrational coherences. A detailed description of this measurement will be presented, and a noniterative method or deconvolving the laser pulses will be introduced to obtain the molecular response function. STiR-SFG, combined with the frequency-domain SFG spectroscopy, was applied to study hydrogen bonding dynamics at aqueous interfaces (D2O/CaF2). Spectral dynamics of the OD-stretch on the 50-150 fs time scale provides real-time observation of ultrafast H-bond rearrangement. Tuning the IR wavelength to the blue or red side of the OD-stretch transition, we selectively monitor the dynamics of different sub-ensembles in the distribution of the H-bond structures. The blue-side excitation (weaker H-bonding) shows monotonic red-shift of the OD-frequency. In contrast, the red-side excitation (stronger H-bonding structures) produces a blue-shift and a recursion, which may indicate the presence of an underdamped intermolecular mode of interfacial water. Effect of electrolyte concentration on the H-bond dynamics will be discussed.

Experimental Investigations on the Influence of Adhesive Oxides on the Metal-Ceramic Bond

Directory of Open Access Journals (Sweden)

Susanne Enghardt

2015-01-01

Full Text Available The objective of this study was to test the influence of selected base metals, which act as oxide formers, on the metal-ceramic bond of dental veneer systems. Using ion implantation techniques, ions of Al, In and Cu were introduced into near-surface layers of a noble metal alloy containing no base metals. A noble metal alloy with base metals added for oxide formation was used as a reference. Both alloys were coated with a low-temperature fusing dental ceramic. Specimens without ion implantation or with Al2O3 air abrasion were used as controls. The test procedures comprised the Schwickerath shear bond strength test (ISO 9693-1, profile height (surface roughness measurements (ISO 4287; ISO 4288; ISO 25178, scanning electron microscopy (SEM imaging, auger electron spectroscopy (AES and energy dispersive X-ray analysis (EDX. Ion implantation resulted in no increase in bond strength. The highest shear bond strengths were achieved after oxidation in air and air abrasion with Al2O3 (41.5 MPa and 47.8 MPa respectively. There was a positive correlation between shear bond strength and profile height. After air abrasion, a pronounced structuring of the surface occurred compared to ion implantation. The established concentration shifts in alloy and ceramic could be reproduced. However, their positive effects on shear bond strength were not confirmed. The mechanical bond appears to be of greater importance for metal-ceramic bonding.

Structural Glass Beams with Embedded Glass Fibre Reinforcement

NARCIS (Netherlands)

Louter, P.C.; Leung, Calvin; Kolstein, M.H.; Vambersky, J.N.J.A.; Bos, Freek; Louter, Pieter Christiaan; Veer, Fred

2010-01-01

This paper investigates the possibilities of pultruded glass fibre rods as embedded reinforcement in SentryGlas (SG) laminated glass beams. To do so, a series of pullout tests, to investigate the bond strength of the rods to the laminate, and a series of beam tests, to investigate the post-breakage

Unique Bond Breaking in Crystalline Phase Change Materials and the Quest for Metavalent Bonding.

Science.gov (United States)

Zhu, Min; Cojocaru-Mirédin, Oana; Mio, Antonio M; Keutgen, Jens; Küpers, Michael; Yu, Yuan; Cho, Ju-Young; Dronskowski, Richard; Wuttig, Matthias

2018-05-01

Laser-assisted field evaporation is studied in a large number of compounds, including amorphous and crystalline phase change materials employing atom probe tomography. This study reveals significant differences in field evaporation between amorphous and crystalline phase change materials. High probabilities for multiple events with more than a single ion detected per laser pulse are only found for crystalline phase change materials. The specifics of this unusual field evaporation are unlike any other mechanism shown previously to lead to high probabilities of multiple events. On the contrary, amorphous phase change materials as well as other covalently bonded compounds and metals possess much lower probabilities for multiple events. Hence, laser-assisted field evaporation in amorphous and crystalline phase change materials reveals striking differences in bond rupture. This is indicative for pronounced differences in bonding. These findings imply that the bonding mechanism in crystalline phase change materials differs substantially from conventional bonding mechanisms such as metallic, ionic, and covalent bonding. Instead, the data reported here confirm a recently developed conjecture, namely that metavalent bonding is a novel bonding mechanism besides those mentioned previously. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shear bond strength and debonding characteristics of metal and ceramic brackets bonded with conventional acid-etch and self-etch primer systems: An in-vivo study.

Science.gov (United States)

Mirzakouchaki, Behnam; Shirazi, Sajjad; Sharghi, Reza; Shirazi, Samaneh; Moghimi, Mahsan; Shahrbaf, Shirin

2016-02-01

Different in-vitro studies have reported various results regarding shear bond strength (SBS) of orthodontic brackets when SEP technique is compared to conventional system. This in-vivo study was designed to compare the effect of conventional acid-etching and self-etching primer adhesive (SEP) systems on SBS and debonding characteristics of metal and ceramic orthodontic brackets. 120 intact first maxillary and mandibular premolars of 30 orthodontic patients were selected and bonded with metal and ceramic brackets using conventional acid-etch or self-etch primer system. The bonded brackets were incorporated into the wire during the study period to simulate the real orthodontic treatment condition. The teeth were extracted and debonded after 30 days. The SBS, debonding characteristics and adhesive remnant indices (ARI) were determined in all groups. The mean SBS of metal brackets was 10.63±1.42 MPa in conventional and 9.38±1.53 MPa in SEP system, (P=0.004). No statistically significant difference was noted between conventional and SEP systems in ceramic brackets. The frequency of 1, 2 and 3 ARI scores and debonding within the adhesive were the most common among all groups. No statistically significant difference was observed regarding ARI or failure mode of debonded specimens in different brackets or bonding systems. The SBS of metal brackets bonded using conventional system was significantly higher than SEP system, although the SBS of SEP system was clinically acceptable. No significant difference was found between conventional and SEP systems used with ceramic brackets. Total SBS of metal brackets was significantly higher than ceramic brackets. Due to adequate SBS of SEP system in bonding the metal brackets, it can be used as an alternative for conventional system. Shear bond strength, Orthodontic brackets, Adhesive remnant index, self-etch.

Phenylacetylene and H bond

Indian Academy of Sciences (India)

... all resembling H bonds. Non-linear H bonds due to secondary interactions. C-H stretching frequency shows blue shift. Heavy atom distances are longer than the sum of van der Waals radii. Formed a task group through IUPAC to come up with a modern definition of H bond. 15 international experts including Desiraju.

Origin of the X-Hal (Hal = Cl, Br) bond-length change in the halogen-bonded complexes.

Science.gov (United States)

Wang, Weizhou; Hobza, Pavel

2008-05-01

The origin of the X-Hal bond-length change in the halogen bond of the X-Hal...Y type has been investigated at the MP2(full)/6-311++G(d,p) level of theory using a natural bond orbital analysis, atoms in molecules procedure, and electrostatic potential fitting methods. Our results have clearly shown that various theories explaining the nature of the hydrogen bond cannot be applied to explain the origin of the X-Hal bond-length change in the halogen bond. We provide a new explanation for this change. The elongation of the X-Hal bond length is caused by the electron-density transfer to the X-Hal sigma* antibonding orbital. For the blue-shifting halogen bond, the electron-density transfer to the X-Hal sigma* antibonding orbital is only of minor importance; it is the electrostatic attractive interaction that causes the X-Hal bond contraction.

Additional disulfide bonds in insulin

DEFF Research Database (Denmark)

Vinther, Tine N; Pettersson, Ingrid; Huus, Kasper

2015-01-01

The structure of insulin, a glucose homeostasis-controlling hormone, is highly conserved in all vertebrates and stabilized by three disulfide bonds. Recently, we designed a novel insulin analogue containing a fourth disulfide bond located between positions A10-B4. The N-terminus of insulin's B......-chain is flexible and can adapt multiple conformations. We examined how well disulfide bond predictions algorithms could identify disulfide bonds in this region of insulin. In order to identify stable insulin analogues with additional disulfide bonds, which could be expressed, the Cβ cut-off distance had...... in comparison to analogues with additional disulfide bonds that were more difficult to predict. In contrast, addition of the fourth disulfide bond rendered all analogues resistant to fibrillation under stress conditions and all stable analogues bound to the insulin receptor with picomolar affinities. Thus...

Orthodontic brackets removal under shear and tensile bond strength resistance tests - a comparative test between light sources

Science.gov (United States)

Silva, P. C. G.; Porto-Neto, S. T.; Lizarelli, R. F. Z.; Bagnato, V. S.

2008-03-01

We have investigated if a new LEDs system has enough efficient energy to promote efficient shear and tensile bonding strength resistance under standardized tests. LEDs 470 ± 10 nm can be used to photocure composite during bracket fixation. Advantages considering resistance to tensile and shear bonding strength when these systems were used are necessary to justify their clinical use. Forty eight human extracted premolars teeth and two light sources were selected, one halogen lamp and a LEDs system. Brackets for premolar were bonded through composite resin. Samples were submitted to standardized tests. A comparison between used sources under shear bonding strength test, obtained similar results; however, tensile bonding test showed distinct results: a statistical difference at a level of 1% between exposure times (40 and 60 seconds) and even to an interaction between light source and exposure time. The best result was obtained with halogen lamp use by 60 seconds, even during re-bonding; however LEDs system can be used for bonding and re-bonding brackets if power density could be increased.

Water Revisited

Science.gov (United States)

Stillinger, Frank H.

1980-07-01

Liquid water consists of a macroscopically connected, random network of hydrogen bonds, with frequent strained and broken bonds, that is continually undergoing topological reformation. Anomalous properties of water arise from the competition between relatively bulky ways of connecting molecules into local patterns characterized by strong bonds and nearly tetrahedral angles and more compact arrangements characterized by more strain and bond breakage. However, these alternatives constitute virtually a continuum of architectural possibilities rather than a discrete pair of options. The singular behavior of supercooled water near -45 degrees C and the ``hydrophobic'' attraction between nonpolar entities are due to the same underlying phenomenon, namely, the clumping tendency of relatively strain-free convex cages or polyhedra.

Effect of mode of polymerization of bonding agent on shear bond strength of autocured resin composite luting cements.

Science.gov (United States)

Dong, Cecilia C S; McComb, Dorothy; Anderson, James D; Tam, Laura E

2003-04-01

There have been anecdotal reports of low bond strength with autocured resin composite materials, particularly when light-cured bonding agents that combine primer and adhesive in a 1-bottle preparation are used. The objective of this study was to determine if the mode of polymerization of the bonding agent influences the strength of the attachment of autocured resin composite luting cements to dentin. The shear bond strength of 2 resin luting cements, Calibra and RelyX ARC, polymerized by autocuring, in combination with 4 different bonding agents, Scotchbond Multipurpose Plus, Prime & Bond NT, IntegraBond and Single Bond, polymerized to bovine dentin by light-curing, autocuring or dual-curing, was determined. The pH of each bonding agent and its components was measured. Two-way analysis of variance was used to test the effect of cement and adhesive on shear bond strength. For each bonding agent, the adhesive variable combined the factors product brand and mode of polymerization. With significant interaction among the above variables, the least square means of the 16 combinations of resin cement and adhesive were compared. There was no consistent relationship between shear bond strength and mode of polymerization of the bonding agent. Significant differences in bond strength were specific to the proprietary brand of bonding agent. The pH of the bonding agent depends on the manufacturer's formulation, and low pH may contribute to low bond strength. The low in vitro bond strength occurring with some combinations of bonding agent and resin cement could be clinically significant.

Bond strength of orthodontic light-cured resin-modified glass ionomer cement.

Science.gov (United States)

Cheng, Hsiang Yu; Chen, Chien Hsiu; Li, Chuan Li; Tsai, Hung Huey; Chou, Ta Hsiung; Wang, Wei Nan

2011-04-01

The purpose of this study was to compare the bond strengths and debonded interfaces achieved with light-cured resin-modified glass ionomer cement (RMGIC) and conventional light-cured composite resin. In addition, the effects of acid etching and water contamination were examined. One hundred human premolars were randomly divided into five equal groups. The mini Dyna-lock upper premolar bracket was selected for testing. The first four groups were treated with light-cured RMGIC with or without 15 per cent phosphoric acid-etching treatment and with or without water contamination preceding bracket bonding. The control samples were treated with the conventional light-cured Transbond composite resin under acid etching and without water contamination. Subsequently, the brackets were debonded by tensile force using an Instron machine. The modified adhesive remnant index (ARI) scores were assigned to the bracket base of the debonded interfaces using a scanning electron microscope. The bond strength and modified ARI scores were determined and analysed statistically by one-way analysis of variance and chi-square test. Under all four conditions, the bond strength of the light-cure RMGIC was equal to or higher than that of the conventional composite resin. The highest bond strength was achieved when using RMGIC with acid etching but without water contamination. The modified ARI scores were 2 for Fuji Ortho LC and 3 for Transbond. No enamel detachment was found in any group. Fifteen per cent phosphoric acid etching without moistening the enamel of Fuji Ortho LC provided the more favourable bond strength. Enamel surfaces, with or without water contamination and with or without acid etching, had the same or a greater bond strength than Transbond.

Effect of adhesive resin cements on bond strength of ceramic core materials to dentin.

Science.gov (United States)

Gundogdu, M; Aladag, L I

2018-03-01

The aim of the present study was to evaluate the effects of self-etch and self-adhesive resin cements on the shear bond strength of ceramic core materials bonded to dentin. Extracted, caries-free, human central maxillary incisor teeth were selected, and the vestibule surfaces were cut flat to obtain dentin surfaces. Ceramic core materials (IPS e.max Press and Prettau Zirconia) were luted to the dentin surfaces using three self-etch adhesive systems (Duo-Link, Panavia F 2.0, and RelyX Ultimate Clicker) and two self-adhesive resin systems (RelyX U200 Automix and Maxcem Elite). A shear bond strength test was performed using a universal testing machine. Failure modes were observed under a stereomicroscope, and bonding interfaces between the adhesive resin cements and the teeth were evaluated with a scanning electron microscope. Data were analyzed with Student's t-test and one-way analysis of variance followed by Tukey's test (α = 0.05). The type of adhesive resin cement significantly affected the shear bond strengths of ceramic core materials bonded to dentin (P materials when the specimens were luted with self-adhesive resin cements (P materials.

Shear bond strength of orthodontic brackets bonded with different self-etching adhesives.

Science.gov (United States)

Scougall Vilchis, Rogelio José; Yamamoto, Seigo; Kitai, Noriyuki; Yamamoto, Kohji

2009-09-01

The purpose of this study was to compare the shear bond strength (SBS) of orthodontic brackets bonded with 4 self-etching adhesives. A total of 175 extracted premolars were randomly divided into 5 groups (n = 35). Group I was the control, in which the enamel was etched with 37% phosphoric acid, and stainless steel brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif). In the remaining 4 groups, the enamel was conditioned with the following self-etching primers and adhesives: group II, Transbond Plus and Transbond XT (3M Unitek); group III, Clearfil Mega Bond FA and Kurasper F (Kuraray Medical, Tokyo, Japan); group IV, Primers A and B, and BeautyOrtho Bond (Shofu, Kyoto, Japan); and group V, AdheSE and Heliosit Orthodontic (Ivoclar Vivadent AG, Liechtenstein). The teeth were stored in distilled water at 37 degrees C for 24 hours and debonded with a universal testing machine. The adhesive remnant index (ARI) including enamel fracture score was also evaluated. Additionally, the conditioned enamel surfaces were observed under a scanning electron microscope. The SBS values of groups I (19.0 +/- 6.7 MPa) and II (16.6 +/- 7.3 MPa) were significantly higher than those of groups III (11.0 +/- 3.9 MPa), IV (10.1 +/- 3.7 MPa), and V (11.8 +/- 3.5 MPa). Fluoride-releasing adhesives (Kurasper F and BeautyOrtho Bond) showed clinically acceptable SBS values. Significant differences were found in the ARI and enamel fracture scores between groups I and II. The 4 self-etching adhesives yielded SBS values higher than the bond strength (5.9 to 7.8 MPa) suggested for routine clinical treatment, indicating that orthodontic brackets can be successfully bonded with any of these self-etching adhesives.

Comparison of Shear Bond Strength of RMGI and Composite Resin for Orthodontic Bracket Bonding

Science.gov (United States)

Yassaei, Soghra; Davari, Abdolrahim; Goldani Moghadam, Mahjobeh; Kamaei, Ahmad

2014-01-01

Objective: The aim of this study was to compare the shear bond strength (SBS) of resin modified glass ionomer (RMGI) and composite resin for bonding metal and ceramic brackets. Materials and Methods: Eighty-eight human premolars extracted for orthodontic purposes were divided into 4 groups (n=22). In groups 1 and 2, 22 metal and ceramic brackets were bonded using composite resin (Transbond XT), respectively. Twenty-two metal and ceramic brackets in groups 3 and 4, respectively were bonded using RMGI (Fuji Ortho LC, Japan). After photo polymerization, the teeth were stored in water and thermocycled (500 cycles between 5° and 55°). The SBS value of each sample was determined using a Universal Testing Machine. The amount of residual adhesive remaining on each tooth was evaluated under a stereomicroscope. Statistical analyses were done using two-way ANOVA. Results: RMGI bonded brackets had significantly lower SBS value compared to composite resin bonded groups. No statistically significant difference was observed between metal and ceramic brackets bonded with either the RMGI or composite resin. The comparison of the adhesive remnant index (ARI) scores between the groups indicated that the bracket failure mode was significantly different among groups (Porthodontic bonding purposes; however the provided SBS is still within the clinically acceptable range. PMID:25628663

DNA Amplification by Breakage/Fusion/Bridge Cycles Initiated by Spontaneous Telomere Loss in a Human Cancer Cell Line

Directory of Open Access Journals (Sweden)

Anthony W.l. Lo

2002-01-01

Full Text Available The development of genomic instability is an important step in generatingthe multiple genetic changes required for cancer. One consequence of genomic instability is the overexpression of oncogenes due to gene amplification. One mechanism for gene amplification is the breakagelfusionlbridge (B/F/Bcyclethatinvolvesthe repeated fusion and breakage of chromosomes following the loss of a telomere. B/F/B cycles have been associated with low-copy gene amplification in human cancer cells, and have been proposed to be an initiating event in high-copy gene amplification. We have found that spontaneous telomere loss on a marker chromosome 16 in a human tumor cell line results in sister chromatid fusion and prolonged periods of chromosome instability. The high rate of anaphase bridges involving chromosome 16 demonstrates that this instability results from B/F/B cycles. The amplification of subtelomeric DNA on the marker chromosome provides conclusive evidence that B/F/B cycles initiated by spontaneous telomere loss are a mechanism for gene amplification in human cancer cells.

Shear bond strength of amalgam to dentin using different dentin adhesive systems

Directory of Open Access Journals (Sweden)

Farimah Sardari

2012-01-01

Full Text Available Background and Aims: The aim of this in vitro study was to assess the shear bond strength of amalgam to dentin using four dentin adhesive systems.Materials and Methods: One hundred human molars were selected. After enamel removal, a dentin cylinder with 3 mm thickness was prepared. Eighty specimens were resorted with amalgam and four dentin adhesive systems as follows (n=20: group 1, Scotch Bond Multi-Purpose; group 2, One Coat Bond; group 3, PQ1; and group 4, Panavia-F. In group 5, 20 specimens were resorted with amalgam and varnish as control group. The specimens were incubated at 37°C for 24 h. The shear bond strengths were then measured by using push out method. The data were analyzed by one-way ANOVA and post hoc Duncan's tests.Results: Mean values for bond strengths of test groups were as follows: group 1=21.03±8.9, group 2=23.47±9, group 3=13.16±8.8, group 4=20.07±8.9 and group 5=14.15±8.7 MPa±SD. One-way ANOVA showed the statistically significant difference between the bond strengths of five groups (P=0.001. Post hoc Duncan's test showed significant difference between groups 1and 3 (P=0.008, groups 1 and 5 (P=0.019, groups 2 and 5 (P=0.0008, groups 4 and 5 (P=0.042, and groups 3 and 4 (P=0.018.Conclusion: Results of this study showed that the bond strength of amalgam to dentin using One Coat Bond as dentin adhesive system was higher than that observed in other dentin adhesive systems.

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...

Composite bonding to stainless steel crowns using a new universal bonding and single-bottle systems.

Science.gov (United States)

Hattan, Mohammad Ali; Pani, Sharat Chandra; Alomari, Mohammad

2013-01-01

Aim. The aim of this study is to evaluate the shear bond strength of nanocomposite to stainless steel crowns using a new universal bonding system. Material and Methods. Eighty (80) stainless steel crowns (SSCs) were divided into four groups (20 each). Packable nanocomposite was bonded to the lingual surface of the crowns in the following methods: Group A without adhesive (control group), Group B using a new universal adhesive system (Scotchbond Universal Adhesive, 3M ESPE, Seefeld, Germany), and Group C and Group D using two different brands of single-bottle adhesive systems. Shear bond strengths were calculated and the types of failure also were recorded. Results. The shear strength of Group B was significantly greater than that of other groups. No significant differences were found between the shear bond strengths of Groups C and D. The control group had significantly lower shear bond strength (P universal bonding agent (Scotchbond Universal Adhesive, 3M ESPE, Seefeld, Germany) show significantly greater shear bond strengths and fewer adhesive failures when compared to traditional single-bottle systems.

77 FR 29472 - Surety Companies Acceptable on Federal Bonds-Termination: Atlantic Bonding Company, Inc.

Science.gov (United States)

2012-05-17

... be accepted from this company, and bonds that are continuous in nature should not be renewed. The... DEPARTMENT OF THE TREASURY Fiscal Service Surety Companies Acceptable on Federal Bonds--Termination: Atlantic Bonding Company, Inc. AGENCY: Financial Management Service, Fiscal Service, Department...

The reaction of astatine with aromatic diazonium compounds

International Nuclear Information System (INIS)

Visser, G.W.M.; Diemer, E.L.

1982-01-01

Astatine reacts prefrentially with that type of aromatic diazonium salt that decomposes via a radical reaction channel (homolytic breakage of the C-N bond). The dediazonation with p-aminobenzoic acid and p-toluidine as model compounds was investigated through estatin produced in the 209 Bi(α,2n) 211 At reaction. (author)

Radiation effects on components of orally administrated medicines

International Nuclear Information System (INIS)

Akhmatovich-Shmajke, T.; Yuz'byak, Kh.; Ovcharchik, A.

1976-01-01

Physicochemical changes occuring in starch, lactose, sucrose, gum arabic, talc, polyvinylpyrrolidone (PVP), and magnesium stearate irradiated on an electronic linear accelerator type LUE-13/9 were studied. Bond breakage in sugars and molecular degradation in starch and PVP were noted. Paramagnetic centers were found to form in most of the test substances. (author)

The Load-Bearing Capacity of Timber-Glass Composite I-Beams Made with Polyurethane Adhesives

Science.gov (United States)

Rodacki, Konrad

2017-12-01

This article discusses the issue of composite timber-glass I-beams, which are an interesting alternative for load-bearing beams of ceilings and roofs. The reasoning behind the use of timber-glass I-beams is the combination of the best features of both materials - this enables the creation of particularly safe beams with regard to structural stability and post-breakage load capacity. Due to the significant differences between the bonding surfaces of timber and glass, a study on the adhesion of various adhesives to both surfaces is presented at the beginning of the paper. After examination, two adhesives were selected for offering the best performance when used with composite beams. The beams were investigated using a four-point bending test under quasi-static loading.

Influence of bleaching and desensitizing gel on bond strength of orthodontic brackets

Directory of Open Access Journals (Sweden)

Fernanda Alves Rodrigues Britto

2015-04-01

Full Text Available OBJECTIVE: The objective of this study was to assess, in vitro, the influence of bleaching gel and the use of desensitizing agent over bond strength of ceramic brackets bonded to bovine enamel. METHODS: One hundred bovine incisors were selected and randomly divided into five groups (n = 20: Group 1, control group (without bleaching; Group 2, bleached with 35% hydrogen peroxide; Group 3, bleached with 35% hydrogen peroxide (three applications, 15 minutes each and desensitizing agent applied for 10 minutes; Group 4, bleached with 35% hydrogen peroxide for 40 minutes; Group 5, bleached with 35% hydrogen peroxide for 40 minutes with desensitizing agent applied for 10 minutes. Brackets were bonded 7 days after bleaching and submitted to shear bond strength test after 24 hours at a compression rate of 1 mm/minute. After fracture, the adhesive remnant index (ARI was assessed under stereoscopic at 40 x magnification. Shear strength data (MPa were submitted to one-way ANOVA and Tukey's test with significance level set at 5%. RESULTS: Group 5 (29.33 MPa showed significantly higher bond strength than Group 1 (19.19 MPa, Group 2 (20.59 MPa and Group 4 (23.25 MPa, but with no difference in comparison to Group 3. There was no significant difference among the other groups. The adhesive remnant index showed predominance of score 3, that is, all resin remained adhered to enamel for all groups. CONCLUSION: Bleaching with 35% hydrogen peroxide with calcium associated with desensitizing agent application produced higher bond strength values of brackets bonded to bovine enamel.

Repair Bond Strength of Aged Resin Composite after Different Surface and Bonding Treatments

Directory of Open Access Journals (Sweden)

Michael Wendler

2016-07-01

Full Text Available The aim of this study was to compare the effect of different mechanical surface treatments and chemical bonding protocols on the tensile bond strength (TBS of aged composite. Bar specimens were produced using a nanohybrid resin composite and aged in distilled water for 30 days. Different surface treatments (diamond bur, phosphoric acid, silane, and sandblasting with Al2O3 or CoJet Sand, as well as bonding protocols (Primer/Adhesive were used prior to application of the repair composite. TBS of the specimens was measured and the results were analyzed using analysis of variance (ANOVA and the Student–Newman–Keuls test (α = 0.05. Mechanically treated surfaces were characterized under SEM and by profilometry. The effect of water aging on the degree of conversion was measured by means of FTIR-ATR spectroscopy. An important increase in the degree of conversion was observed after aging. No significant differences in TBS were observed among the mechanical surface treatments, despite variations in surface roughness profiles. Phosphoric acid etching significantly improved repair bond strength values. The cohesive TBS of the material was only reached using resin bonding agents. Application of an intermediate bonding system plays a key role in achieving reliable repair bond strengths, whereas the kind of mechanical surface treatment appears to play a secondary role.

Shear Bond Strength of Three Orthodontic Bonding Systems on Enamel and Restorative Materials.

Science.gov (United States)

Hellak, Andreas; Ebeling, Jennifer; Schauseil, Michael; Stein, Steffen; Roggendorf, Matthias; Korbmacher-Steiner, Heike

2016-01-01

Objective. The aim of this in vitro study was to determine the shear bond strength (SBS) and adhesive remnant index (ARI) score of two self-etching no-mix adhesives (iBond ™ and Scotchbond ™ ) on different prosthetic surfaces and enamel, in comparison with the commonly used total etch system Transbond XT ™ . Materials and Methods . A total of 270 surfaces (1 enamel and 8 restorative surfaces, n = 30) were randomly divided into three adhesive groups. In group 1 (control) brackets were bonded with Transbond XT primer. In the experimental groups iBond adhesive (group 2) and Scotchbond Universal adhesive (group 3) were used. The SBS was measured using a Zwicki 1120 ™ testing machine. The ARI and SBS were compared statistically using the Kruskal-Wallis test ( P ≤ 0.05). Results . Significant differences in SBS and ARI were found between the control group and experimental groups. Conclusions . Transbond XT showed the highest SBS on human enamel. Scotchbond Universal on average provides the best bonding on all other types of surface (metal, composite, and porcelain), with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures on restorative materials in patients. If metal brackets have to be bonded to a metal surface, the use of a dual-curing resin is recommended.

Antibacterial Activity of Commercial Dentine Bonding Systems against E. faecalis–Flow Cytometry Study

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Monika Lukomska-Szymanska

2017-04-01

Full Text Available Literature presents inconsistent results on the antibacterial activity of dentine bonding systems (DBS. Antibacterial activity of adhesive systems depends on several factors, including composition and acidity. Flow cytometry is a novel detection method to measure multiple characteristics of a single cell: total cell number, structural (size, shape, and functional parameters (viability, cell cycle. The LIVE/DEAD® BacLightTM bacterial viability assay was used to evaluate an antibacterial activity of DBS by assessing physical membrane disruption of bacteria mediated by DBS. Ten commercial DBSs: four total-etching (TE, four self-etching (SE and two selective enamel etching (SEE were tested. Both total-etching DBS ExciTE F and OptiBond Solo Plus showed comparatively low antibacterial activity against E. faecalis. The lowest activity of all tested TE systems showed Te-Econom Bond. Among SE DBS, G-ænial Bond (92.24% dead cells followed by Clearfil S3 Bond Plus (88.02% and Panavia F 2.0 ED Primer II (86.67% showed the highest antibacterial activity against E. faecalis, which was comparable to isopropranol (positive control. In the present study, self-etching DBS exhibited higher antimicrobial activity than tested total-etching adhesives against E. faecalis.

Bond strength of two component injection moulded MID

DEFF Research Database (Denmark)

Islam, Mohammad Aminul; Hansen, Hans Nørgaard; Tang, Peter Torben

2006-01-01

Most products of the future will require industrially adapted, cost effective production processes and on this issue two-component (2K) injection moulding is a potential candidate for MID manufacturing. MID based on 2k injection moulded plastic part with selectively metallised circuit tracks allows...... the two different plastic materials in the MID structure require good bonding between them. This paper finds suitable combinations of materials for MIDs from both bond strength and metallisation view-point. Plastic parts were made by two-shot injection moulding and the effects of some important process...... the integration of electrical and mechanical functionalities in a real 3D structure. If 2k injection moulding is applied with two polymers, of which one is plateable and the other is not, it will be possible to make 3D electrical structures directly on the component. To be applicable in the real engineering field...

Predicting Bond Betas using Macro-Finance Variables

DEFF Research Database (Denmark)

Aslanidis, Nektarios; Christiansen, Charlotte; Cipollini, Andrea

We conduct in-sample and out-of-sample forecasting using the new approach of combining explanatory variables through complete subset regressions (CSR). We predict bond CAPM betas and bond returns conditioning on various macro-fi…nance variables. We explore differences across long-term government ...... bonds, investment grade corporate bonds, and high-yield corporate bonds. The CSR method performs well in predicting bond betas, especially in-sample, and, mainly high-yield bond betas when the focus is out-of-sample. Bond returns are less predictable than bond betas....

LED Die-Bonded on the Ag/Cu Substrate by a Sn-BiZn-Sn Bonding System

Science.gov (United States)

Tang, Y. K.; Hsu, Y. C.; Lin, E. J.; Hu, Y. J.; Liu, C. Y.

2016-12-01

In this study, light emitting diode (LED) chips were die-bonded on a Ag/Cu substrate by a Sn-BixZn-Sn bonding system. A high die-bonding strength is successfully achieved by using a Sn-BixZn-Sn ternary system. At the bonding interface, there is observed a Bi-segregation phenomenon. This Bi-segregation phenomenon solves the problems of the brittle layer-type Bi at the joint interface. Our shear test results show that the bonding interface with Bi-segregation enhances the shear strength of the LED die-bonding joints. The Bi-0.3Zn and Bi-0.5Zn die-bonding cases have the best shear strength among all die-bonding systems. In addition, we investigate the atomic depth profile of the deposited Bi-xZn layer by evaporating Bi-xZn E-gun alloy sources. The initial Zn content of the deposited Bi-Zn alloy layers are much higher than the average Zn content in the deposited Bi-Zn layers.

Periodic density functional theory study of ethylene hydrogenation over Co3O4 (1 1 1) surface: The critical role of oxygen vacancies

International Nuclear Information System (INIS)

Lu, Jinhui; Song, JiaJia; Niu, Hongling; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

2016-01-01

Highlights: • H 2 dissociates in heterolytic way following H atoms migration to form O−H bond. • H 2 dissociation occurs at low temperature on perfect and oxygen defective Co 3 O 4 . • Oxygen vacancy promotes hydrogenation thermodynamically and kinetically. • O−H bond is weakened on oxygen defective surface. • Hydrogenation requires compromise between H−H activation and O−H breakage. - Abstract: Recently, metal oxides are attracting increasing interests as hydrogenation catalyst. Herein we studied the hydrogenation of ethylene on perfect and oxygen defective Co 3 O 4 (1 1 1) using periodic density functional theory. The energetics and pathways of ethylene hydrogenation to ethane were determined. We have demonstrated that (i) H 2 dissociation on Co 3 O 4 is a complicated two-step process through a heterolytic cleavage, followed by the migration of H atom and finally yields the homolytic product on both perfect and oxygen defective Co 3 O 4 (1 1 1) surfaces easily. (ii) After introducing the surface oxygen vacancy, the stepwise hydrogenation of ethylene by atomic hydrogen is much easier than that on perfect surface due to the weaker bond strength of OH group. The strength of O−H bond is a crucial factor for the hydrogenation reaction which involves the breakage of O−H bond. The formation of oxygen vacancy increases the electronic charges at the adjacent surface O, which reduces its capability of further gaining electrons from adsorbed atomic hydrogen and then weakens the strength of O−H bond. These results emphasize the importance of the oxygen vacancies for hydrogenation on metal oxides.

Orthodontic brackets removal under shear and tensile bond strength resistance tests – a comparative test between light sources

International Nuclear Information System (INIS)

Silva, P C G; Porto-Neto, S T; Lizarelli, R F Z; Bagnato, V S

2008-01-01

We have investigated if a new LEDs system has enough efficient energy to promote efficient shear and tensile bonding strength resistance under standardized tests. LEDs 470 ± 10 nm can be used to photocure composite during bracket fixation. Advantages considering resistance to tensile and shear bonding strength when these systems were used are necessary to justify their clinical use. Forty eight human extracted premolars teeth and two light sources were selected, one halogen lamp and a LEDs system. Brackets for premolar were bonded through composite resin. Samples were submitted to standardized tests. A comparison between used sources under shear bonding strength test, obtained similar results; however, tensile bonding test showed distinct results: a statistical difference at a level of 1% between exposure times (40 and 60 seconds) and even to an interaction between light source and exposure time. The best result was obtained with halogen lamp use by 60 seconds, even during re-bonding; however LEDs system can be used for bonding and re-bonding brackets if power density could be increased

Oxidative addition of C--H bonds in organic molecules to transition metal centers

International Nuclear Information System (INIS)

Bergman, R.G.

1989-04-01

Alkanes are among the most chemically inert organic molecules. They are reactive toward a limited range of reagents, such as highly energetic free radicals and strongly electrophilic and oxidizing species. This low reactivity is a consequence of the C--H bond energies in most saturated hydrocarbons. These values range from 90 to 98 kcal/mole for primary and secondary C--H bonds; in methane, the main constituent of natural gas, the C--H bond energy is 104 kcal/mole. This makes methane one of the most common but least reactive organic molecules in nature. This report briefly discusses the search for metal complexes capable of undergoing the C--H oxidative addition process allowing alkane chemistry to be more selective than that available using free radical reagents. 14 refs

Comparison of shear bond strength of amalgam bonded to primary and permanent dentin

Directory of Open Access Journals (Sweden)

Mahdi S

2008-06-01

Full Text Available Amalgam′s non-adhesive characteristics necessitate cavity preparations incorporating retentive features, which often require the removal of non-carious tooth structure. Use of adhesives beneath amalgam restorations, would be helpful to overcome this disadvantage. This study was undertaken to compare the mean shear bond strength of amalgam bonded to primary and permanent dentin, to evaluate the efficacy of amalgam adhesives in pediatric dentistry.27 primary and 28 permanent posterior teeth with intact buccal or lingual surfaces were grounded to expose dentin and wet-polished with 400-grit silicone carbide paper. Scotchbond Multi Purpose Plus adhesive system was applied to the dentin surfaces and light cured. Amalgam was condensed onto the treated dentin through a plastic mold.shear bond strength testing was done using an Instron Universal testing machine, at a crosshead speed of 0.5 mm/min.The data were analyzed by independent samples t-test The difference among the two groups was not statistically significant (p>0.05 Bonded amalgam showed the same level of bond strength to primary and permanent dentin; so, application of amalgam bonding agents in pediatric dentistry can be recommended.

Comparison of the tensile bond strength of high-noble, noble, and base metal alloys bonded to enamel.

Science.gov (United States)

Sen, D; Nayir, E; Pamuk, S

2000-11-01

Although the bond strengths of various resin composite luting materials have been reported in the literature, the evaluation of these systems with various cast alloys of different compositions has not been completely clarified. To evaluate the tensile bond strength of sandblasted high-noble, noble, and base metal alloys bonded to etched enamel by 2 different bonding agents of different chemical composition: Panavia-Ex (BIS-GMA) and Super-Bond (4-META acrylic). Flat enamel surfaces were prepared on buccal surfaces of 60 extracted noncarious human incisors. Teeth were divided into 3 groups of 20 each. Twenty circular disks of 5 mm diameter were prepared for casting for each group. Group I was cast with a high-noble, group II with a noble, and group III with a base metal alloy. The surfaces of the disks were sandblasted with 250 microm Al(2)O(3). Ten disks of each group were bonded to exposed enamel surfaces with Super-Bond and 10 disks with Panavia-Ex as recommended by the manufacturer. The tensile bond strength was measured with an Instron universal testing machine with a crosshead speed of 0.5 mm/min until failure occurred. Two-way ANOVA was used to evaluate the results. The differences in bond strengths of Super-Bond and Panavia-Ex with different alloys were not significant. The highest bond strengths were obtained in base metal alloys, followed by noble and high-noble alloys. These results were significant. Panavia-Ex and Super-Bond exhibited comparable tensile bond strengths. For both luting agents, the highest bond strengths were achieved with base metal alloys and the lowest with high-noble alloys.

Selective disulfide reduction for labeling and enhancement of Fab antibody fragments

International Nuclear Information System (INIS)

Kirley, Terence L.; Greis, Kenneth D.; Norman, Andrew B.

2016-01-01

Many methods have been developed for chemical labeling and enhancement of the properties of antibodies and their common fragments, including the Fab and F(ab’) 2 fragments. Somewhat selective reduction of some antibody disulfide bonds has been previously achieved, yielding antibodies and antibody fragments that can be labeled at defined sites, enhancing their utility and properties. Selective reduction of the two hinge disulfide bonds present in F(ab’) 2 fragments using mild reduction has been useful. However, such reduction is often not quantitative and results in the reduction of multiple disulfide bonds, and therefore subsequent multiple labeling or conjugation sites are neither homogenous nor stoichiometric. Here, a simple and efficient selective reduction of the single disulfide bond linking the partial heavy chain and the intact light chain which compose the Fab fragment is accomplished utilizing tris(2-carboxyethyl)phosphine (TCEP) immobilized on agarose beads. The resultant reduced cysteine residues were labeled with several cysteine-selective fluorescent reagents, as well as by cysteine-directed PEGylation. These two cysteine residues can also be re-ligated by means of a bifunctional cysteine cross-linking agent, dibromobimane, thereby both restoring a covalent linkage between the heavy and light chains at this site, far removed from the antigen binding site, and also introducing a fluorescent probe. There are many other research and clinical uses for these selectively partially reduced Fab fragments, including biotinylation, toxin and drug conjugation, and incorporation of radioisotopes, and this technique enables simple generation of very useful Fab fragment derivatives with many potential applications. - Highlights: • TCEP agarose is effective for selective reduction of a single Fab disulfide bond. • This disulfide is solvent accessible and distant from the antigen binding site. • A variety of buffers of varying pHs can be used, simplifying

Irradiation performance of helium-bonded uranium--plutonium carbide fuel elements

International Nuclear Information System (INIS)

Latimer, T.W.; Petty, R.L.; Kerrisk, J.F.; DeMuth, N.S.; Levine, P.J.; Boltax, A.

1979-01-01

The current irradiation program of helium-bonded uranium--plutonium carbide elements is achieving its original goals. By August 1978, 15 of the original 171 helium-bonded elements had reached their goal burnups including one that had reached the highest burnup of any uranium--plutonium carbide element in the U.S.--12.4 at.%. A total of 66 elements had attained burnups over 8 at.%. Only one cladding breach had been identified at that time. In addition, the systematic and coordinated approach to the current steady-state irradiation tests is yielding much needed information on the behavior of helium-bonded carbide fuel elements that was not available from the screening tests (1965 to 1974). The use of hyperstoichiometric (U,Pu)C containing approx. 10 vol% (U,Pu) 2 C 3 appears to combine lower swelling with only a slightly greater tendency to carburize the cladding than single-phase (U,Pu)C. The selected designs are providing data on the relationship between the experimental parameters of fuel density, fuel-cladding gap size, and cladding type and various fuel-cladding mechanical interaction mechanisms

Tunable GLUT-Hexose Binding and Transport via Modulation of Hexose C-3 Hydrogen-Bonding Capabilities.

Science.gov (United States)

Kumar Kondapi, Venkata Pavan; Soueidan, Olivier-Mohamad; Cheeseman, Christopher I; West, Frederick G

2017-06-12

The importance of the hydrogen bonding interactions in the GLUT-hexose binding process (GLUT=hexose transporter) has been demonstrated by studying the binding of structurally modified d-fructose analogues to GLUTs, and in one case its transport into cells. The presence of a hydrogen bond donor at the C-3 position of 2,5-anhydro-d-mannitol derivatives is essential for effective binding to GLUT5 and transport into tumor cells. Surprisingly, installation of a group that can function only as a hydrogen bond acceptor at C-3 resulted in selective recognition by GLUT1 rather than GLUT5. A fluorescently labelled analogue clearly showed GLUT-mediated transport and low efflux properties of the probe. This study reveals that a single positional modification of a 2,5-anhydro-d-mannitol derivative is sufficient to switch its binding preference from GLUT5 to GLUT1, and uncovers general scaffolds that are suitable for the potential selective delivery of molecular payloads into tumor cells via GLUT transport machinery. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Biological and neural bases of partner preferences in rodents: models to understand human pair bonds].

Science.gov (United States)

Coria-Avila, G A; Hernández-Aguilar, M E; Toledo-Cárdenas, R; García-Hernández, L I; Manzo, J; Pacheco, P; Miquel, M; Pfaus, J G

To analyse the biological and neural bases of partner preference formation in rodents as models to understand human pair bonding. Rodents are social individuals, capable of forming short- or long-lasting partner preferences that develop slowly by stimuli like cohabitation, or rapidly by stimuli like sex and stress. Dopamine, corticosteroids, oxytocin, vasopressin, and opioids form the neurochemical substrate for pair bonding in areas like the nucleus accumbens, the prefrontal cortex, the piriform cortex, the medial preoptic area, the ventral tegmental area and the medial amygdala, among others. Additional areas may participate depending on the nature of the conditioned stimuli by which and individual recognizes a preferred partner. Animal models help us understand that the capacity of an individual to display long-lasting and selective preferences depends on neural bases, selected throughout evolution. The challenge in neuroscience is to use this knowledge to create new solutions for mental problems associated with the incapacity of an individual to display a social bond, keep one, or cope with the disruption of a consolidated one.

Usulan Pengembangan Komunikasi Pemasaran Melalui Strategi Customer Bonding (Studi Kasus : Supermarket Hero di Jakarta

Directory of Open Access Journals (Sweden)

Ronald Sukwadi

2012-03-01

Full Text Available The consequence of competition is the decrease of the number of customers which causes Hero Supermarket closed down several of its outlets. This decrease is also caused by the existence of internal issue of marketing communication (promotion which lacked a strong concept. The ineffective selection of communication channel which in turn fails to conform the activity to the public. For that, the identification in marketing communication activity through Customer Bonding strategy is needed. Through marketing communication program assessment with Customer Bonding (Awareness Bonding, Relationship Bonding, and Advocacy Bonding, intensity of marketing communication problem can be identified, through survey assessment (management and costumer, analyzed with statistical testing like validity and reliability test, Spearman Correlation test and Cross tab test. The questionnaires will be given to 13 respondents from Hero Management by using quota sampling and 100 customers using stratified sampling.               Through marketing communication program assessment using Customer Bonding, marketing communication intensity and correlation analysis between marketing communication program and consumer loyalty are obtained. From this analysis, it is shown that there is noise in marketing communication that influences information sending to customer. Hero must maintain marketing communication program which focuses in marketing program that have competitive advantages. Beside that, evaluation has always to be done in order to improve customer loyalty. Keywords: communication, customer bonding, loyalty

Low-temperature Au/a-Si wafer bonding

International Nuclear Information System (INIS)

Jing, Errong; Xiong, Bin; Wang, Yuelin

2011-01-01

The Si/SiO 2 /Ti/Au–Au/Ti/a-Si/SiO 2 /Si bonding structure, which can also be used for the bonding of non-silicon material, was investigated for the first time in this paper. The bond quality test showed that the bond yield, bond repeatability and average shear strength are higher for this bonding structure. The interfacial microstructure analysis indicated that the Au-induced crystallization of the amorphous silicon process leads to big Si grains extending across the bond interface and Au filling the other regions of the bond interface, which result into a strong and void-free bond interface. In addition, the Au-induced crystallization reaction leads to a change in the IR images of the bond interface. Therefore, the IR microscope can be used to evaluate and compare the different bond strengths qualitatively. Furthermore, in order to verify the superiority of the bonding structure, the Si/SiO 2 /Ti/Au–a-Si/SiO 2 /Si (i.e. no Ti/Au layer on the a-Si surface) and Si/SiO 2 /Ti/Au–Au/Ti/SiO 2 /Si bonding structures (i.e. Au thermocompression bonding) were also investigated. For the Si/SiO 2 /Ti/Au–a-Si/SiO 2 /Si bonding structure, the poor bond quality is due to the native oxide layer on the a-Si surface, and for the Si/SiO 2 /Ti/Au–Au/Ti/SiO 2 /Si bonding structure, the poor bond quality is caused by the wafer surface roughness which prevents intimate contact and limits the interdiffusion at the bond interface.

Manufacturing study of beryllium bonded structures

International Nuclear Information System (INIS)

Onozuka, M.; Hirai, S.; Kikuchi, K.; Oda, Y.; Shimizu, K.

2004-01-01

Manufacturing study has been conducted on Be-bonded structures employed in the first-wall panel of the blanket system for the ITER. For Be tiles bonded to the Cu-Cr-Zr alloy heat sink with stainless-steel cooling pipes, a one-axis hot press with two heating process has been used to bond the three materials. First, Cu-alloy and SS materials are bonded diffusively. Then, Be tiles are bonded to the pre-bonded structure under 20 MPa and at 560 degree C. An Al-Si base interlayer has been used to bond Be to the Cu-Alloy. Because of the limited heat processes using a conventional hot press, the manufacturing cost can be minimized. Using the above bonding techniques, a partial mockup of a blanket first-wall panel with 16 Be tiles (with 50 mm in size) has been successfully manufactured. (author)

Iminobisphosphines to (non-)symmetrical diphosphinoamine ligands : Metal-induced synthesis of diphosphorus nickel complexes and application in ethylene oligomerisation reactions

NARCIS (Netherlands)

Boulens, Pierre; Lutz, Martin|info:eu-repo/dai/nl/304828971; Jeanneau, Erwann; Olivier-Bourbigou, Hélène; Reek, Joost N H; Breuil, Pierre Alain R

2014-01-01

We describe the synthesis of a range of novel iminobisphosphine ligands based on a sulfonamido moiety [R1SO2N=P(R 2)2-P(R3)2]. These molecules rearrange in the presence of nickel by metal-induced breakage of the P-P bond to yield symmetrical and nonsymmetrical diphosphinoamine nickel complexes of

REUSABILITY OF BOND ELUT CERTIFY COLUMNS FOR THE EXTRACTION OF DRUGS FROM PLASMA

NARCIS (Netherlands)

CHEN, XH; FRANKE, JP; WIJSBEEK, J; DEZEEUW, RA

1993-01-01

The reusability of Bond Elut Certify columns for the extraction of toxicologically relevant drugs from plasma has been evaluated. Pentobarbital, hexobarbital, mepivacaine, trimipramine and clonazepam were selected as test drugs to represent various classes of drugs. The columns were regenerated

Effect of sodium benzoate on DNA breakage, micronucleus formation and mitotic index in peripheral blood of pregnant rats and their newborns

Directory of Open Access Journals (Sweden)

Cetin Saatci

2016-11-01

Full Text Available Sodium benzoate (SB is one of the most widely used additives in food products in the world. The aim of this study was to assess the effect of three different concentrations of SB on the DNA breakage in liver cells and on the micronuclei formation and the mitotic index in lymphocytes of pregnant rats and their fetuses, as well as to evaluate the effects of SB on the fetus development. The results showed that general genomic injuries were present in almost all the liver cell samples obtained from the SB group compared with the control (non-treated group. This indicates that SB usage may cause DNA damage and increase micronuclei formation. We recommend that pregnant women should avoid consuming foodstuffs containing SB as an additive.

The choice among non-callable bonds and make whole, claw back and otherwise ordinary callable bonds

OpenAIRE

Booth, LD; Gounopoulos, D; Skinner, F

2012-01-01

This paper seeks to explain determinates of the choice and the pricing of various types of callable and non-callable bonds. We find that the popularity of different types of callable and non-callable bonds is significantly related to the economic environment. In addition, the popularity of claw back bonds appear to be driven by agency considerations, make whole bonds by the debt overhang problem, ordinary callable bonds by the need by banks to deal with interest rate changes and non-callable ...

Proposal of guideline for bonding to prevention of hydrogen embrittlement at Ta/Zr bond interface. Hydrogen embrittlement in SUS304ULC/Ta/Zr explosive bonded joint

International Nuclear Information System (INIS)

Saida, Kazuyoshi; Fujimoto, Tetsuya; Nishimoto, Kazutoshi

2010-01-01

The occurrence condition of hydrogen embrittlement cracking at Ta/Zr bond interface was investigated with respect to the hydrogen content and applied stress in order to propose a guideline for the explosive bonding procedure to prevention of hydrogen embrittlement. Hydrogen charging test was conducted for SUS304ULC/Ta/Zr explosive bonded joints applied the different flexural strains. A hydrogen embrittlement crack occurred in the Zr substrate at Ta/Zr bond interface after hydrogen charging, and it was initiated at shorter charging times when the augmented strain was increased. The occurrence condition of hydrogen embrittlement cracking at Ta/Zr bond interface was shifted to lower stress and hydrogen content with an increase in the amount of explosive during bonding. It was suggested that hydrogen embrittlement in Ta/Zr explosive bonded joint could be inhibited by reducing the initial hydrogen content in Ta substrate less than approx. 5 ppm. (author)

Rydberb bonding in (NH4)2

International Nuclear Information System (INIS)

Boldyrev, A.I.; Simons, J.

1992-01-01

Chemical binding of two monovalent Rydberg species to form a singlet-state Rydberg dimer molecule is predicted to be possible Ab initio electronic structure methods that include electron correlation (at levels up through QCISD(T)/6-31++G** MP2(full)/6-31++G** + ZPE) are shown to be essential to achieving a proper description of such bonding. The (NH 4 ) molecule, selected as the prototype for this study, is shown to be bound with respect to its Rydberg-species fragments, 2NH 4 by 7.5-9.7 kcal/mol, depending on the level of treatment of electron correlation, and to be electronically stable (by ca.4 eV) with respect to (NH 4 ) 2 + at the neutral's equilibrium geometry. The (NH 4 ) 2 Rydberg dimer is thermodynamically unstable with respect to 2NH 3 + H 2 by 86-89 kcal/mol mol yet possesses all real vibrational frequencies; it is thus a metastable molecular held together by a weak Rydberg bond. The dissociation energy of the (NH 4 ) 2 + cation to form NH 4 + + NH 4 is found to be larger than that of the neutral (NH 4 ) 2 . 12 refs., 4 figs., 9 tabs

Formation of the market of high-bond (junk bonds in the United States in 1970–1980 years

Directory of Open Access Journals (Sweden)

Moshenskyi S.Z.

2017-03-01

Full Text Available Market of high-yield bonds (also known as «junk bonds» began to emerge in the US in the mid-1970s and was associated with the activities of «junk bond king» Michael Milken from Drexel investment company. Junk bonds emitents are small and newly established companies which cannot get a high credit rating. Emission of high-yield (8–10 % bond was their only chance to find its place in the financial market. Michael Milken realized the potential of these bonds, which, in fact, were often quite reliable securities, and started organizing their emissions by selling junk bonds to Savings and Loan Associations and other investors. In the 1980 issue of such bonds used for aggressive corporate takeovers, which supplied the capital from junk bonds market. Some of takeovers carried out in violation of laws that led to the arrest of Michael Milken, Drexel bankruptcy and the collapse of the entire junk bonds market.

Effect of double-layer application on dentin bond durability of one-step self-etch adhesives.

Science.gov (United States)

Taschner, M; Kümmerling, M; Lohbauer, U; Breschi, L; Petschelt, A; Frankenberger, R

2014-01-01

The aim of this in vitro study was 1) to analyze the influence of a double-layer application technique of four one-step self-etch adhesive systems on dentin and 2) to determine its effect on the stability of the adhesive interfaces stored under different conditions. Four different one-step self-etch adhesives were selected for the study (iBondSE, Clearfil S(3) Bond, XenoV(+), and Scotchbond Universal). Adhesives were applied according to manufacturers' instructions or with a double-layer application technique (without light curing of the first layer). After bonding, resin-dentin specimens were sectioned for microtensile bond strength testing in accordance with the nontrimming technique and divided into 3 subgroups of storage: a) 24 hours (immediate bond strength, T0), b) six months (T6) in artificial saliva at 37°C, or c) five hours in 10 % NaOCl at room temperature. After storage, specimens were stressed to failure. Fracture mode was assessed under a light microscope. At T0, iBond SE showed a significant increase in microtensile bond strength when the double-application technique was applied. All adhesive systems showed reduced bond strengths after six months of storage in artificial saliva and after storage in 10% NaOCl for five hours; however at T6, iBond SE, Clearfil S(3) Bond, and XenoV(+) showed significantly higher microtensile bond strength results for the double-application technique compared with the single-application technique. Scotchbond Universal showed no difference between single- or double-application, irrespective of the storage conditions. The results of this study show that improvements in bond strength of one-step self-etch adhesives by using the double-application technique are adhesive dependent.

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.

Shear bond strength of composite bonded with three adhesives to Er,Cr:YSGG laser-prepared enamel.

Science.gov (United States)

Türkmen, Cafer; Sazak-Oveçoğlu, Hesna; Günday, Mahir; Güngör, Gülşad; Durkan, Meral; Oksüz, Mustafa

2010-06-01

To assess in vitro the shear bond strength of a nanohybrid composite resin bonded with three adhesive systems to enamel surfaces prepared with acid and Er,Cr:YSGG laser etching. Sixty extracted caries- and restoration-free human maxillary central incisors were used. The teeth were sectioned 2 mm below the cementoenamel junction. The crowns were embedded in autopolymerizing acrylic resin with the labial surfaces facing up. The labial surfaces were prepared with 0.5-mm reduction to receive composite veneers. Thirty specimens were etched with Er,Cr:YSGG laser. This group was also divided into three subgroups, and the following three bonding systems were then applied on the laser groups and the other three unlased groups: (1) 37% phosphoric acid etch + Bond 1 primer/adhesive (Pentron); (2) Nano-bond self-etch primer (Pentron) + Nano-bond adhesive (Pentron); and (3) all-in-one adhesive-single dose (Futurabond NR, Voco). All of the groups were restored with a nanohybrid composite resin (Smile, Pentron). Shear bond strength was measured with a Zwick universal test device with a knife-edge loading head. The data were analyzed with two-factor ANOVA. There were no significant differences in shear bond strength between self-etch primer + adhesive and all-in-one adhesive systems for nonetched and laser-etched enamel groups (P > .05). However, bond strength values for the laser-etched + Bond 1 primer/adhesive group (48.00 +/- 13.86 MPa) were significantly higher than the 37% phosphoric acid + Bond 1 primer/adhesive group (38.95 +/- 20.07 MPa) (P enamel surface more effectively than 37% phosphoric acid for subsequent attachment of composite material.

Fatigue aging of adhesive bonds

International Nuclear Information System (INIS)

DeLollis, N.J.

1979-01-01

A year long study has been made of the effect of fatigue on the bond between two epoxy encapsulant formulations and a fused alumina disc. The variables studied included isothermal aging at temperatures up to and including the cure temperature and cyclic thermal aging from +74 to -54 0 C. The encapsulants were glass microballoon filled epoxies differing only in curing agents. One was cured with an aromatic amine eutectic (Shell Curing Agent Z). The other was cured with diethanolamine. The Z cured encapsulant bond failed completely at the bond interface with little or no aging; infrared evidence indicated a soluble interlayer as a possible cause of failure. The diethanolamine cured encapsulant survived a year of isothermal aging with little or no evidence of bond degradation. Cyclic thermal aging resulted in gradual bond failure with time. An extrapolation of the cyclic aging data indicates that the stresses induced by thermal cycling would result in complete bond failure in about 1200 days

Association of bond, market, operational, and financial factors with multi-hospital system bond issues.

Science.gov (United States)

Carpenter, C E; McCue, M J; Hossack, J B

2001-01-01

Despite the growth of multi-hospital systems in the 1990s, their performance in the tax-exempt bond market has not been adequately evaluated. The purpose of this study is to compare bonds issued by multi-hospital systems to those issued by individual hospitals in terms of bond, market, operational, and financial characteristics. The study sample includes 2,078 newly issued, tax-exempt, revenue bonds between 1991 and 1997. The findings indicate that multi-hospital systems issued larger amounts of debt at a lower cost, were more likely to be insured, had higher debt service coverage and higher operating margins.

Tensile Bond Strength of Metal Bracket Bonding to Glazed Ceramic Surfaces With Different Surface Conditionings

Directory of Open Access Journals (Sweden)

M. Imani

2011-12-01

Full Text Available Objective: The objective of this study was to compare the tensile bond strength of metal brackets bonding to glazed ceramic surfaces using three various surface treatments.Materials and Methods: Forty two glazed ceramic disks were assigned to three groups. In the first and second groups the specimens were etched with 9.5% hydrofluoric acid (HFA. Subsequently in first group, ceramic primer and adhesive were applied, but in second group a bonding agent alone was used. In third group, specimens were treated with 35% phosphoric acid followed by ceramic primerand adhesive application. Brackets were bonded with light cure composites. The specimens were stored in distilled water in the room temperature for 24 hours and thermocycled 500 times between 5°C and 55°C. The universal testing machine was used to test the tensile bond strength and the adhesive remenant index scores between three groups was evaluated. The data were subjected to one-way ANOVA, Tukey and Kruskal-Wallis tests respectively.Results: The tensile bond strength was 3.69±0.52 MPa forfirst group, 2.69±0.91 MPa for second group and 3.60±0.41 MPa for third group. Group II specimens showed tensile strength values significantly different from other groups (P<0.01.Conclusion: In spite of limitations in laboratory studies it may be concluded that in application of Scotch bond multipurpose plus adhesive, phosphoric acid can be used instead of HFA for bonding brackets to the glazed ceramic restorations with enough tensile bond strength.

A novel bonding method for fabrication of PET planar nanofluidic chip with low dimension loss and high bonding strength

International Nuclear Information System (INIS)

Yin, Zhifu; Zou, Helin; Sun, Lei; Xu, Shenbo; Qi, Liping

2015-01-01

Plastic planar nanofluidic chips are becoming increasingly important for biological and chemical applications. However, the majority of the present bonding methods for planar nanofluidic chips suffer from high dimension loss and low bonding strength. In this work, a novel thermal bonding technique based on O 2 plasma and ethanol treatment was proposed. With the assistance of O 2 plasma and ethanol, the PET (polyethylene terephthalate) planar nanofluidic chip can be bonded at a low bonding temperature of 50 °C. To increase the bonding rate and bonding strength, the O 2 plasma parameters and thermal bonding parameters were optimized during the bonding process. The tensile test indicates that the bonding strength of the PET planar nanofluidic chip can reach 0.954 MPa, while the auto-fluorescence test demonstrates that there is no leakage or blockage in any of the bonded micro- or nanochannels. (paper)

Oregon School Bond Manual. Fifth Edition.

Science.gov (United States)

Oregon State Dept. of Education, Salem.

To help school districts comply with Oregon's school bond laws, this manual provides guidelines for school district attorneys and personnel in the issuance and sale of school bonds. The document describes the proper time sequence of the bonding procedure, including elections, school board authorizations, necessary certificates, bond registration…

Comparison of shear bond strength between unfilled resin to dry enamel and dentin bonding to moist and dry enamel

Directory of Open Access Journals (Sweden)

Yasini E.

2005-05-01

Full Text Available Statement of Problem: The use of dentine bondings on enamel and dentin in total etch protocols has recently become popular. Unfilled resin is hydrophobic and dentin bonding is hydrophilic in nature. This chemical difference could be effective in enamel bonding process. Purpose: The aim of this study was to compare the shear bond strength of unfilled resin to dry enamel and dentin bonding to dry and moist enamel. Materials and Methods: In this experimental study, a total of 30 incisor teeth were used. The specimens were randomly assigned to three groups of 10. 37% phosphoric acid etchant was applied to the enamel surfaces in each group for 15 seconds, rinsed with water for 20 seconds and dried for 20 seconds with compressed air in groups one and two. After conditioning, group 1 received unfilled resin (Margin Bond, Colten and group 2 received dentin bonding (Single Bond, 3M and in group 3 after conditioning and rinsing with water, a layer of dentin bonding (Single Bond was applied on wet enamel. The enamel and dentin bonding were light cured for 20 seconds. A ring mold 3.5 mm in diameter and 2 mm height was placed over the specimens to receive the composite filling material (Z100, 3M. The composite was cured for 40 seconds. The specimens were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. The findings were analyzed by ANOVA One-Way and Tukey HSD tests. Results: Shear bond strength of dentin bonding to dry enamel was significantly less than unfilled resin to dry enamel (P<0.05. There was no significant difference between the bond strength of dentin bonding to moist and dry enamel. In addition bond strength of dentin bonding to wet enamel was not significantly different from unfilled resin to dry enamel. Conclusion: Based on the findings of this study, it is suggested that enamel surface should remain slightly moist after etching before bonding with single bond but when using unfilled resin, the

UV-light exposure of insulin: pharmaceutical implications upon covalent insulin dityrosine dimerization and disulphide bond photolysis.

Science.gov (United States)

Correia, Manuel; Neves-Petersen, Maria Teresa; Jeppesen, Per Bendix; Gregersen, Søren; Petersen, Steffen B

2012-01-01

In this work we report the effects of continuous UV-light (276 nm, ~2.20 W.m(-2)) excitation of human insulin on its absorption and fluorescence properties, structure and functionality. Continuous UV-excitation of the peptide hormone in solution leads to the progressive formation of tyrosine photo-product dityrosine, formed upon tyrosine radical cross-linkage. Absorbance, fluorescence emission and excitation data confirm dityrosine formation, leading to covalent insulin dimerization. Furthermore, UV-excitation of insulin induces disulphide bridge breakage. Near- and far-UV-CD spectroscopy shows that UV-excitation of insulin induces secondary and tertiary structure losses. In native insulin, the A and B chains are held together by two disulphide bridges. Disruption of either of these bonds is likely to affect insulin's structure. The UV-light induced structural changes impair its antibody binding capability and in vitro hormonal function. After 1.5 and 3.5 h of 276 nm excitation there is a 33.7% and 62.1% decrease in concentration of insulin recognized by guinea pig anti-insulin antibodies, respectively. Glucose uptake by human skeletal muscle cells decreases 61.7% when the cells are incubated with pre UV-illuminated insulin during 1.5 h. The observations presented in this work highlight the importance of protecting insulin and other drugs from UV-light exposure, which is of outmost relevance to the pharmaceutical industry. Several drug formulations containing insulin in hexameric, dimeric and monomeric forms can be exposed to natural and artificial UV-light during their production, packaging, storage or administration phases. We can estimate that direct long-term exposure of insulin to sunlight and common light sources for indoors lighting and UV-sterilization in industries can be sufficient to induce irreversible changes to human insulin structure. Routine fluorescence and absorption measurements in laboratory experiments may also induce changes in protein

UV-light exposure of insulin: pharmaceutical implications upon covalent insulin dityrosine dimerization and disulphide bond photolysis.

Directory of Open Access Journals (Sweden)

Manuel Correia

Full Text Available In this work we report the effects of continuous UV-light (276 nm, ~2.20 W.m(-2 excitation of human insulin on its absorption and fluorescence properties, structure and functionality. Continuous UV-excitation of the peptide hormone in solution leads to the progressive formation of tyrosine photo-product dityrosine, formed upon tyrosine radical cross-linkage. Absorbance, fluorescence emission and excitation data confirm dityrosine formation, leading to covalent insulin dimerization. Furthermore, UV-excitation of insulin induces disulphide bridge breakage. Near- and far-UV-CD spectroscopy shows that UV-excitation of insulin induces secondary and tertiary structure losses. In native insulin, the A and B chains are held together by two disulphide bridges. Disruption of either of these bonds is likely to affect insulin's structure. The UV-light induced structural changes impair its antibody binding capability and in vitro hormonal function. After 1.5 and 3.5 h of 276 nm excitation there is a 33.7% and 62.1% decrease in concentration of insulin recognized by guinea pig anti-insulin antibodies, respectively. Glucose uptake by human skeletal muscle cells decreases 61.7% when the cells are incubated with pre UV-illuminated insulin during 1.5 h. The observations presented in this work highlight the importance of protecting insulin and other drugs from UV-light exposure, which is of outmost relevance to the pharmaceutical industry. Several drug formulations containing insulin in hexameric, dimeric and monomeric forms can be exposed to natural and artificial UV-light during their production, packaging, storage or administration phases. We can estimate that direct long-term exposure of insulin to sunlight and common light sources for indoors lighting and UV-sterilization in industries can be sufficient to induce irreversible changes to human insulin structure. Routine fluorescence and absorption measurements in laboratory experiments may also induce changes

Optimal Investment in Structured Bonds

DEFF Research Database (Denmark)

Jessen, Pernille; Jørgensen, Peter Løchte

The paper examines the role of structured bonds in the optimal portfolio of a small retail investor. We consider the typical structured bond essentially repacking an exotic option and a zero coupon bond, i.e. an investment with portfolio insurance. The optimal portfolio is found when the investment...

46 CFR Sec. 10 - Bonds.

Science.gov (United States)

2010-10-01

... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form 25...

Common Factors in International Bond Returns

NARCIS (Netherlands)

Driessen, J.J.A.G.; Melenberg, B.; Nijman, T.E.

2000-01-01

In this paper we estimate and interpret the factors that jointly determine bond returns of different maturities in the US, Germany and Japan.We analyze both currency-hedged and unhedged bond returns.For currency-hedged bond returns, we find that five factors explain 96.5% of the variation of bond

7 CFR 1726.27 - Contractor's bonds.

Science.gov (United States)

2010-01-01

... 7 Agriculture 11 2010-01-01 2010-01-01 false Contractor's bonds. 1726.27 Section 1726.27... AGRICULTURE ELECTRIC SYSTEM CONSTRUCTION POLICIES AND PROCEDURES General § 1726.27 Contractor's bonds. (a) RUS Form 168b, Contractor's Bond, shall be used when a contractor's bond is required by RUS Forms 200, 257...

Cis–Trans Amide Bond Rotamers in β-Peptoids and Peptoids: Evaluation of Stereoelectronic

DEFF Research Database (Denmark)

Laursen, Jonas Striegler; Engel-Andreasen, Jens; Fristrup, Peter

2013-01-01

to folding propensity. Thus, we here report an investigation of the effect of structural variations on the cis–trans amide bond rotamer equilibria in a selection of monomer model systems. In addition to various side chain effects, which correlated well with previous studies of α-peptoids, we present...... the synthesis and investigation of cis–trans isomerism in the first examples of peptoids and β-peptoids containing thioamide bonds as well as trifluoroacetylated peptoids and β-peptoids. These systems revealed an increase in the preference for cis-amides as compared to their parent compounds, and thus provide...

Shear bond strength of different adhesive systems to normal and caries-affected dentin

Directory of Open Access Journals (Sweden)

Niloofar Shadman

2015-10-01

Full Text Available BACKGROUND AND AIM: According to the effect of the adhesive and substrate type on the bond strength, examination of the adhesive is required in all aspects. The aim of this study was to evaluate the shear bond strength of different adhesive systems to normal dentin (ND and caries affected dentin (CAD in permanent teeth. METHODS: Thirty extracted molars with small occlusal caries were selected. After preparation and determination of ND and CAD by caries detector, teeth were divided into three groups and treated with one of the two tested adhesives: Single Bond 2 (SB2, Scotchbond Universal with etch (SBU-ER, and Scotchbond Universal without etch (SBU-SE. Then composite (Filtek Z-250 XT were attached to the surfaces and cured. After water storage (24 hours and thermocycling (500 cycles 5-55 °C, bond strength was calculated and failure modes were determined by stereomicroscope. The data were analyzed by one-way ANOVA and post-hoc test [Tukey HSD (honest significant difference] and with P ˂ 0.050 as the level of significance. RESULTS: Only SBU-ER had significantly higher shear bond strength than SBU-SE in ND (P = 0.027 and CAD (P = 0.046. Bond strength in SBU-ER the highest and in SBU-SE had the lowest amounts in CAD and ND. There was no significant difference in each group between ND and CAD. CONCLUSION: The 2-step etch-and-rinse adhesive (SBU-ER had higher bond strength to ND and CAD than the selfetch adhesive (SBU-SE.

Variation in social systems within Chaetodon butterflyfishes, with special reference to pair bonding

KAUST Repository

Nowicki, Jessica P.

2018-04-11

For many animals, affiliative relationships such as pair bonds form the foundation of society and are highly adaptive. Animal systems amenable for comparatively studying pair bonding are important for identifying underlying biological mechanisms, but mostly exist in mammals. Better establishing fish systems will enable comparison of pair bonding mechanisms across taxonomically distant lineages that may reveal general underlying mechanistic principles. We examined the utility of wild butterflyfishes (f: Chaetodontidae; g: Chaetodon) for comparatively studying pair bonding. Using stochastic character mapping, we provide the first analysis of the evolutionary history of butterflyfish sociality, revealing that pairing is ancestral, with at least seven independent transitions to gregarious grouping and solitary behavior since the late Miocene. We then formally verified social systems in six sympatric and widespread species representing a clade with one ancestrally reconstructed transition from paired to solitary grouping at Lizard Island, Australia. In situ observations of the size, selective affiliation and aggression, fidelity, and sex composition of social groups confirmed that Chaetodon baronessa, C. lunulatus, and C. vagabundus are predominantly pair bonding, whereas C. rainfordi, C. plebeius, and C. trifascialis are predominantly solitary. Even in the predominantly pair bonding species, C. lunulatus, a proportion of adults (15%) are solitary. Importantly, inter- and intra-specific differences in social systems do not co-vary with other previously established attributes, including parental care. Hence, the proposed butterflyfish populations are promising for inter- and intra-species comparative analyses of pair bonding and its mechanistic underpinnings. Avenues for further developing the system are proposed, including determining whether the aforementioned utility of these species applies across their geographic disruptions.

Nickel-Catalyzed C–O Bond-Cleaving Alkylation of Esters: Direct Replacement of the Ester Moiety by Functionalized Alkyl Chains

KAUST Repository

Liu, Xiangqian; Jia, Jiaqi; Rueping, Magnus

2017-01-01

Two efficient protocols for the nickel-catalyzed aryl–alkyl cross-coupling reactions using esters as coupling components have been established. The methods enable the selective oxidative addition of nickel to acyl C–O and aryl C–O bonds and allow the aryl–alkyl cross-coupling via decarbonylative bond cleavage or through cleavage of a C–O bond with high efficiency and good functional group compatibility. The protocols allow the streamlined, unconventional utilization of widespread ester groups and their precursors, carboxylic acids and phenols, in synthetic organic chemistry.

Nickel-Catalyzed C–O Bond-Cleaving Alkylation of Esters: Direct Replacement of the Ester Moiety by Functionalized Alkyl Chains

KAUST Repository

Liu, Xiangqian

2017-06-07

Two efficient protocols for the nickel-catalyzed aryl–alkyl cross-coupling reactions using esters as coupling components have been established. The methods enable the selective oxidative addition of nickel to acyl C–O and aryl C–O bonds and allow the aryl–alkyl cross-coupling via decarbonylative bond cleavage or through cleavage of a C–O bond with high efficiency and good functional group compatibility. The protocols allow the streamlined, unconventional utilization of widespread ester groups and their precursors, carboxylic acids and phenols, in synthetic organic chemistry.

Evaluation of microtensile bond strength of total-etch, self-etch, and glass ionomer adhesive to human dentin: An in vitro study

Directory of Open Access Journals (Sweden)

Neelima Lakshmi

2008-01-01

Full Text Available Aim: To evaluate the microtensile bond strength of Single Bond, AdheSE, and Fuji Bond LC to human dentin. Fifteen non-carious third molars were selected for the study. The teeth were randomly divided into three groups of five teeth each. Each group was given a different bonding treatment. Group I was treated with Single Bond (3M, ESPE, group II with AdheSE (Ivoclar, Vivadent, and group III was treated with Fuji Bond LC (GC America. A T-band metal matrix was placed and composite resin bonded on to the tooth surface using appropriate bonding agents. The composite resin was packed in increments and light cured. Each tooth was sectioned to obtain 1 mm x 1 mm beams of dentin-resin samples. Tensile bond testing was done using a universal testing machine (Instron at a cross-head speed of 0.5 mm/min. Results: The mean bond strength of Single Bond (35.5 MPa was significantly higher than that of AdheSE (32.8 MPa and Fuji Bond LC (32.6 MPa. The difference between the microtensile bond strength values of AdheSE and Fuji Bond LC was statistically insignificant. Inference: Though the bond strength of AdheSE and Fuji Bond LC was above 30 MPa, it was less than that of Single Bond as evaluated by testing of microtensile bond strength.

Relationship between surface area for adhesion and tensile bond strength--evaluation of a micro-tensile bond test.

Science.gov (United States)

Sano, H; Shono, T; Sonoda, H; Takatsu, T; Ciucchi, B; Carvalho, R; Pashley, D H

1994-07-01

The purpose of this study was to test the null hypothesis that there is no relationship between the bonded surface area of dentin and the tensile strength of adhesive materials. The enamel was removed from the occlusal surface of extracted human third molars, and the entire flat surface was covered with resin composite bonded to the dentin to form a flat resin composite crown. Twenty-four hours later, the bonded specimens were sectioned parallel to the long axis of the tooth into 10-20 thin sections whose upper part was composed of resin composite with the lower half being dentin. These small sections were trimmed using a high speed diamond bur into an hourglass shape with the narrowest portion at the bonded interface. Surface area was varied by altering the specimen thickness and width. Tensile bond strength was measured using custom-made grips in a universal testing machine. Tensile bond strength was inversely related to bonded surface area. At surface areas below 0.4 mm2, the tensile bond strengths were about 55 MPa for Clearfil Liner Bond 2 (Kuraray Co., Ltd.), 38 MPa for Scotchbond MP (3M Dental Products), and 20 MPa for Vitremer (3M Dental Products). At these small surface areas all of the bond failures were adhesive in nature. This new method permits measurement of high bond strengths without cohesive failure of dentin. It also permits multiple measurements to be made within a single tooth.

Selective hydrodeoxygenation of biomass-derived oxygenates to unsaturated hydrocarbons using molybdenum carbide catalysts.

Science.gov (United States)

Ren, Hui; Yu, Weiting; Salciccioli, Michael; Chen, Ying; Huang, Yulin; Xiong, Ke; Vlachos, Dionisios G; Chen, Jingguang G

2013-05-01

Which cleavage do you prefer? With a combination of density functional theory (DFT) calculations, surface science studies, and reactor evaluations, Mo(2)C is identified as a highly selective HDO catalyst to selectively convert biomass-derived oxygenates to unsaturated hydrocarbons through selective C-O bond scissions without C-C bond cleavage. This provides high-value HDO products for utilization as feedstocks for chemicals and fuels; this also reduces the overall consumption of H2 . Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of thermo-mechanical cycling on porcelain bonding to cobalt-chromium and titanium dental alloys fabricated by casting, milling, and selective laser melting.

Science.gov (United States)

Antanasova, Maja; Kocjan, Andraž; Kovač, Janez; Žužek, Borut; Jevnikar, Peter

2018-04-01

The aim has been to determine the effect of thermo-mechanical cycling on shear-bond-strength (SBS) of dental porcelain to Co-Cr and Ti-based alloys fabricated by casting, computer-numerical-controlled milling, and selective-laser-melting (SLM). Seven groups (n=22/group) of metal cylinders were fabricated by casting (Co-Cr and commercially pure-cpTi), milling (Co-Cr, cpTi, Ti-6Al-4V) or by SLM (Co-Cr and Ti-6Al-4V) and abraded with airborne-particles. The average surface roughness (R a ) was determined for each group. Dental porcelain was applied and each metal-ceramic combination was divided into two subgroups - stored in deionized water (24-h, 37°C), or subjected to both thermal (6000-cycles, between 5 and 60°C) and mechanical cycling (10 5 -cycles, 60N-load). SBS test-values and failure modes were recorded. Metal-ceramic interfaces were analyzed with a focused-ion-beam/scanning-electron-microscope (FIB/SEM) and energy-dispersive-spectroscopy (EDS). The elastic properties of the respective metal and ceramic materials were evaluated by instrumented-indentation-testing. The oxide thickness on intact Ti-based substrates was measured with Auger-electron-spectroscopy (AES). Data were analyzed using ANOVA, Tukey's HSD and t-tests (α=0.05). The SBS-means differed according to the metal-ceramic combination (p<0.0005) and to the fatigue conditions (p<0.0005). The failure modes and interface analyses suggest better porcelain adherence to Co-Cr than to Ti-based alloys. Values of R a were dependent on the metal substrate (p<0.0005). Ti-based substrates were not covered with thick oxide layers following digital fabrication. Ti-based alloys are more susceptible than Co-Cr to reduction of porcelain bond strength following thermo-mechanical cycling. The porcelain bond strength to Ti-based alloys is affected by the applied metal processing technology. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Evaluation of Shear Bond Strength of Orthodontic Brackets Bonded with Nano-Filled Composites

OpenAIRE

Chalipa, Javad; Akhondi, Mohammad Sadegh Ahmad; Arab, Sepideh; Kharrazifard, Mohammad Javad; Ahmadyar, Maryam

2013-01-01

Objectives: The purpose of this study was to evaluate the shear bond strength (SBS) of orthodontic brackets bonded with two types of nano-composites in comparison to a conventional orthodontic composite. Materials and Methods: Sixty extracted human first premolars were randomly divided into 3 groups each containing 20 teeth. In group I, a conventional orthodontic composite (Transbond XT) was used to bond the brackets, while two nano-composites (Filtek TM Supreme XT and AELITE Aesthetic Enamel...

Diffusionless bonding of aluminum to Zircaloy-2

International Nuclear Information System (INIS)

Watson, R.D.

1965-04-01

Aluminum can be bonded to zirconium without difficulty even when a thin layer of oxide is present on the surface of the zirconium . No detectable diffusion takes place during the bonding process. The bond layer can be stretched as much. as 8% without affecting the bond. The bond can be heated for 1000 hours at 260 o C (500 o F), and can be water quenched from 260 o C (500 o F) without any noticeable change in the bond strength. An extrusion technique has been devised for making transition sections of aluminum bonded to zirconium which can then be used to join these metals by conventional welding. Welding can be done close to the bond zone without seriously affecting the integrity of the bond. This method of bonding aluminum to Zircaloy-2 is covered by Canadian patent 702,438 January 26, 1965. (author)

Mechatronic modeling and simulation using bond graphs

CERN Document Server

Das, Shuvra

2009-01-01

Introduction to Mechatronics and System ModelingWhat Is Mechatronics?What Is a System and Why Model Systems?Mathematical Modeling Techniques Used in PracticeSoftwareBond Graphs: What Are They?Engineering SystemsPortsGeneralized VariablesBond GraphsBasic Components in SystemsA Brief Note about Bond Graph Power DirectionsSummary of Bond Direction RulesDrawing Bond Graphs for Simple Systems: Electrical and MechanicalSimplification Rules for Junction StructureDrawing Bond Graphs for Electrical SystemsDrawing Bond Graphs for Mechanical SystemsCausalityDrawing Bond Graphs for Hydraulic and Electronic Components and SystemsSome Basic Properties and Concepts for FluidsBond Graph Model of Hydraulic SystemsElectronic SystemsDeriving System Equations from Bond GraphsSystem VariablesDeriving System EquationsTackling Differential CausalityAlgebraic LoopsSolution of Model Equations and Their InterpretationZeroth Order SystemsFirst Order SystemsSecond Order SystemTransfer Functions and Frequency ResponsesNumerical Solution ...

Factors affecting the shear bond strength of metal and ceramic brackets bonded to different ceramic surfaces.

Science.gov (United States)

Abu Alhaija, Elham S J; Abu AlReesh, Issam A; AlWahadni, Ahed M S

2010-06-01

The aims of this study were to evaluate the shear bond strength (SBS) of metal and ceramic brackets bonded to two different all-ceramic crowns, IPS Empress 2 and In-Ceram Alumina, to compare the SBS between hydrofluoric acid (HFA), phosphoric acid etched, and sandblasted, non-etched all-ceramic surfaces. Ninety-six all-ceramic crowns were fabricated resembling a maxillary left first premolar. The crowns were divided into eight groups: (1) metal brackets bonded to sandblasted 9.6 per cent HFA-etched IPS Empress 2 crowns; (2) metal brackets bonded to sandblasted 9.6 per cent HFA-etched In-Ceram crowns; (3) ceramic brackets bonded to sandblasted 9.6 per cent HFA-etched IPS Empress 2 crowns; (4) ceramic brackets bonded to sandblasted 9.6 per cent HFA-etched In-Ceram crowns; (5) metal brackets bonded to sandblasted 37 per cent phosphoric acid-etched IPS Empress 2 crowns; (6) metal brackets bonded to sandblasted 37 per cent phosphoric acid-etched In-Ceram crowns; (7) metal brackets bonded to sandblasted, non-etched IPS Empress 2 crowns; and (8) metal brackets bonded to sandblasted, non-etched In-Ceram crowns. Metal and ceramic orthodontic brackets were bonded using a conventional light polymerizing adhesive resin. An Instron universal testing machine was used to determine the SBS at a crosshead speed of 0.1 mm/minute. Comparison between groups was performed using a univariate general linear model and chi-squared tests. The highest mean SBS was found in group 3 (120.15 +/- 45.05 N) and the lowest in group 8 (57.86 +/- 26.20 N). Of all the variables studied, surface treatment was the only factor that significantly affected SBS (P Empress 2 and In-Ceram groups.

Method to improve commercial bonded SOI material

Science.gov (United States)

Maris, Humphrey John; Sadana, Devendra Kumar

2000-07-11

A method of improving the bonding characteristics of a previously bonded silicon on insulator (SOI) structure is provided. The improvement in the bonding characteristics is achieved in the present invention by, optionally, forming an oxide cap layer on the silicon surface of the bonded SOI structure and then annealing either the uncapped or oxide capped structure in a slightly oxidizing ambient at temperatures greater than 1200.degree. C. Also provided herein is a method for detecting the bonding characteristics of previously bonded SOI structures. According to this aspect of the present invention, a pico-second laser pulse technique is employed to determine the bonding imperfections of previously bonded SOI structures.

Bonding Durability of Four Adhesive Systems

Directory of Open Access Journals (Sweden)

Leila Atash Biz Yeganeh

2016-04-01

Full Text Available Objectives: This study aimed to compare the durability of four adhesive systems by assessing their microtensile bond strength (MTBS and microleakage during six months of water storage.Materials and Methods: A total of 128 human third molars were used. The adhesives tested were Scotch Bond Multipurpose (SBMP, Single Bond (SB, Clearfil-SE bond (CSEB, and All-Bond SE (ABSE. After sample preparation for MTBS testing, the microspecimens were subjected to microtensile tester after one day and six months of water storage. For microleakage evaluation, facial and lingual class V cavities were prepared and restored with composite. After thermocycling, microleakage was evaluated. Bond strength values were subjected to one-way ANOVA and Tamhane’s test, and the microleakage data were analyzed by the Kruskal-Wallis, Dunn, Mann Whitney and Wilcoxon tests (P<0.05.Results: Single Bond yielded the highest and ABSE yielded the lowest bond strength at one day and six months. Short-term bond strength of SBMP and CSEB was similar. After six months, a significant decrease in bond strength was observed in ABSE and SBMP groups. At one day, ABSE showed the highest microleakage at the occlusal margin; however, at the gingival margin, there was no significant difference among groups. Long-term microleakage of all groups at the occlusal margins was similar, whilst gingival margins of SBMP and SB showed significantly higher microleakage.Conclusion: The highest MTBS and favorable sealability were obtained by Clearfil SE bond. Water storage had no effect on microleakage of self-etch adhesives at the gingival margin or MTBS of CSEB and SB. 

Microstructure and bonding mechanism of Al/Ti bonded joint using Al-10Si-1Mg filler metal

International Nuclear Information System (INIS)

Sohn, Woong H.; Bong, Ha H.; Hong, Soon H.

2003-01-01

The microstructures and liquid state diffusion bonding mechanism of cp-Ti to 1050 Al using an Al-10.0wt.%Si-1.0wt.%Mg filler metal with 100 μm in thickness have been investigated at 620 deg. C under 1x10 -4 Torr. The effects of bonding process parameters on microstructure of bonded joint have been analyzed by using an optical microscope, AES, scanning electron microscopy and EDS. The interfacial bond strength of Al/Ti bonded joints was measured by the single lap shear test. The results show that the bonding at the interface between Al and filler metal proceeds by wetting the Al with molten filler metal, and followed by removal of oxide layer on surface of Al. The interface between Al and filler metal moved during the isothermal solidification of filler metal by the diffusion of Si from filler metal into Al layer. The interface between Al and filler metal became curved in shape with increasing bonding time due to capillary force at grain boundaries. The bonding at the interface between Ti and filler metal proceeds by the formation of two different intermetallic compound layers, identified as Al 5 Si 12 Ti 7 and Al 12 Si 3 Ti 5 , followed by the growth of the intermetallic compound layers. The interfacial bond strength at Al/Ti joint increased with increasing bonding time up to 25 min at 620 deg. C. However, the interfacial bond strength of Al/Ti joint decreased after bonding time of 25 min at 620 deg. C due to formation of cavities in Al near Al/intermetallic interfaces

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.

Bonding with Your Baby

Science.gov (United States)

... the future bonding of the child and parent. Adoptive parents may be concerned about bonding with their ... general emotional support. And it's OK to ask family members and friends for help in the days — ...

Oregon School Bond Manual. Fourth Edition.

Science.gov (United States)

Oregon State Dept. of Education, Salem.

The manual is intended to guide attorneys and officials of school districts in the issuance and sale of school district bonds. Purchasers of school district bonds rely on the recommendations of accredited bond attorneys who render opinions concerning the validity and legality of bond issues offered for sale. This manual is designed to assist in…

27 CFR 24.146 - Bonds.

Science.gov (United States)

2010-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bonds. 24.146 Section 24.146 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE.... (c) Wine vinegar plant bond. The proprietor of a wine vinegar plant who withdraws wine from a bonded...

Shear Bond Strength of Three Orthodontic Bonding Systems on Enamel and Restorative Materials

Directory of Open Access Journals (Sweden)

Andreas Hellak

2016-01-01

Full Text Available Objective. The aim of this in vitro study was to determine the shear bond strength (SBS and adhesive remnant index (ARI score of two self-etching no-mix adhesives (iBond™ and Scotchbond™ on different prosthetic surfaces and enamel, in comparison with the commonly used total etch system Transbond XT™. Materials and Methods. A total of 270 surfaces (1 enamel and 8 restorative surfaces, n=30 were randomly divided into three adhesive groups. In group 1 (control brackets were bonded with Transbond XT primer. In the experimental groups iBond adhesive (group 2 and Scotchbond Universal adhesive (group 3 were used. The SBS was measured using a Zwicki 1120™ testing machine. The ARI and SBS were compared statistically using the Kruskal–Wallis test (P≤0.05. Results. Significant differences in SBS and ARI were found between the control group and experimental groups. Conclusions. Transbond XT showed the highest SBS on human enamel. Scotchbond Universal on average provides the best bonding on all other types of surface (metal, composite, and porcelain, with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures on restorative materials in patients. If metal brackets have to be bonded to a metal surface, the use of a dual-curing resin is recommended.

Bonding polycarbonate brackets to ceramic: : Effects of substrate treatment on bond strength

NARCIS (Netherlands)

Özcan, Mutlu; Vallittu, Pekka K.; Peltomäki, Timo; Huysmans, Marie-Charlotte; Kalk, Warner

2004-01-01

This study evaluated the effects of 5 different surface conditioning methods on the bond strength of polycarbonate brackets bonded to ceramic surfaces with resin based cement. Six disc-shaped ceramic specimens (feldspathic porcelain) with glazed surfaces were used for each group. The specimens were

Synthesis of 1,2,4-Triazoles via Oxidative Heterocyclization: Selective C-N Bond Over C-S Bond Formation.

Science.gov (United States)

Gogoi, Anupal; Guin, Srimanta; Rajamanickam, Suresh; Rout, Saroj Kumar; Patel, Bhisma K

2015-09-18

The higher propensity of C-N over C-S bond forming ability was demonstrated, through formal C-H functionalization during the construction of 4,5-disubstituted 1,2,4-triazole-3-thiones from arylidenearylthiosemicarbazides catalyzed by Cu(II). However, steric factors imparted by the o-disubstituted substrates tend to change the reaction path giving thiodiazole as the major or an exclusive product. Upon prolonging the reaction time, the in situ generated thiones are transformed to 4,5-disubstituted 1,2,4-triazoles via a desulfurization process. Two classes of heterocycles viz. 4,5-disubstituted 1,2,4-triazole-3-thiones and 4,5-disubstituted 1,2,4-triazoles can be synthesized from arylidenearylthiosemicarbazides by simply adjusting the reaction time. Desulfurization of 1,2,4-triazole-3-thiones is assisted by thiophilic Cu to provide 1,2,4-triazoles with concomitant formation of CuS and polynuclear sulfur anions as confirmed from scanning electron microscope and energy dispersive X-ray spectroscopy measurements. A one-pot synthesis of an antimicrobial compound has been successfully achieved following this strategy.

Three methods to measure RH bond energies

International Nuclear Information System (INIS)

Berkowitz, J.; Ellison, G.B.; Gutman, D.

1993-01-01

In this paper the authors compare and contrast three powerful methods for experimentally measuring bond energies in polyatomic molecules. The methods are: radical kinetics; gas phase acidity cycles; and photoionization mass spectroscopy. The knowledge of the values of bond energies are a basic piece of information to a chemist. Chemical reactions involve the making and breaking of chemical bonds. It has been shown that comparable bonds in polyatomic molecules, compared to the same bonds in radicals, can be significantly different. These bond energies can be measured in terms of bond dissociation energies

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

The nature of hydrogen-bonding interactions in nonsteroidal anti-inflammatory drugs revealed by polarized IR spectroscopy

Science.gov (United States)

Hachuła, Barbara

2018-01-01

The influence of hydrogen-bonding interactions in the solid phase on the IR spectroscopic pattern of the νOsbnd H band of nonsteroidal anti-inflammatory drugs (NSAIDs) was studied experimentally by IR spectroscopy with the use of polarized light at two temperatures (293 K and 77 K) and in isotopic dilution. The neat and deuterated crystals of (S)-naproxen ((S)-NPX), (R)-flurbiprofen ((R)-FBP), (RS)-flurbiprofen ((RS)-FBP) and (RS)-ketoprofen ((RS)-KTP) were obtained by melt crystallization between the two squeezed CaF2 plates. The vibrational spectra of selected α-aryl propionic acid derivatives (2APAs) reflected the characteristics of their hydrogen-bond networks, i.e., 2APAs were characterized by the chain ((S)-NPX, (R)-FBP) and by dimeric ((RS)-FBP, (RS)-KTP) arrangement of hydrogen bonds in the crystal lattice. Spectroscopic results showed that the interchain (through-space) exciton coupling, between two laterally-spaced hydrogen bonds, dominates in the crystals of four NSAIDs. The same exciton coupled hydrogen bonds were also responsible for the H/D isotopic recognition mechanism in the crystalline spectra of deuterated 2APAs. The presented spectral results may help to predict the hydrogen bond motifs in the crystalline NSAIDs, which structures are not yet known, based on their IR spectra of hydrogen bond in the crystals.

A meta-selective C-H borylation directed by a secondary interaction between ligand and substrate

Science.gov (United States)

Kuninobu, Yoichiro; Ida, Haruka; Nishi, Mitsumi; Kanai, Motomu

2015-09-01

Regioselective C-H bond transformations are potentially the most efficient method for the synthesis of organic molecules. However, the presence of many C-H bonds in organic molecules and the high activation barrier for these reactions make these transformations difficult. Directing groups in the reaction substrate are often used to control regioselectivity, which has been especially successful for the ortho-selective functionalization of aromatic substrates. Here, we describe an iridium-catalysed meta-selective C-H borylation of aromatic compounds using a newly designed catalytic system. The bipyridine-derived ligand that binds iridium contains a pendant urea moiety. A secondary interaction between this urea and a hydrogen-bond acceptor in the substrate places the iridium in close proximity to the meta-C-H bond and thus controls the regioselectivity. 1H NMR studies and control experiments support the participation of hydrogen bonds in inducing regioselectivity. Reversible direction of the catalyst through hydrogen bonds is a versatile concept for regioselective C-H transformations.

Localisation and quantification of alkali-labile sites in human spermatozoa by DNA breakage detection-fluorescence in situ hybridisation.

Science.gov (United States)

Cortés-Gutiérrez, E I; Dávila-Rodríguez, M I; Cerda-Flores, R M; Fernández, J L; López-Fernández, C; Aragón Tovar, A R; Gosálvez, J

2015-03-01

The localisation and quantification of constitutive alkali-labile sites (ALSs) were investigated using a protocol of DNA breakage detection plus fluorescence in situ hybridisation (DBD-FISH) and alkaline single-cell gel electrophoresis (SCGE or comet assay), in spermatozoa of infertile and fertile men. Semen samples from 10 normozoospermic patients undergoing infertility treatment and 10 fertile men were included in this study. ALSs were localised and quantified by DBD-FISH. The region most sensitive to alkali treatment in human spermatozoa was located in the basal region of the head. ALSs were more frequent in spermatozoa of infertile men than in those of fertile men. These results were confirmed by SCGE comet assays. In conclusion, the most intense localisation of hybridisation signals in human spermatozoa, representing the highest density of constitutive ALSs, was not randomly distributed and was predominantly located in the base of the head. Moreover, infertile men presented with an increase in ALS frequency. Further studies are necessary to determine the association between ALS, sperm chromatin organisation and infertility. © 2014 Blackwell Verlag GmbH.