INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2004
Jun Peng
Abstract This paper presents the computational procedures and solution strategy employed in ParCYCLIC, a parallel non-linear finite element program developed based on an existing serial code CYCLIC for the analysis of cyclic seismically-induced liquefaction problems. In ParCYCLIC, finite elements are employed within an incremental plasticity, coupled solid,fluid formulation. A constitutive model developed for simulating liquefaction-induced deformations is a main component of this analysis framework. The elements of the computational strategy, designed for distributed-memory message-passing parallel computer systems, include: (a) an automatic domain decomposer to partition the finite element mesh; (b) nodal ordering strategies to minimize storage space for the matrix coefficients; (c) an efficient scheme for the allocation of sparse matrix coefficients among the processors; and (d) a parallel sparse direct solver. Application of ParCYCLIC to simulate 3-D geotechnical experimental models is demonstrated. The computational results show excellent parallel performance and scalability of ParCYCLIC on parallel computers with a large number of processors. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Cyclic tests on steel and concrete-filled tube frames with Slit Walls

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2007
Toko Hitaka
Abstract Cyclic loading tests were performed on three one-storey steel frames and four three-storey concrete-filled tube (CFT) moment frames reinforced with a new type of earthquake-resisting element consisting of a steel plate shear wall with vertical slits. In this shear wall system, the steel plate segments between the slits behave as a series of flexural links, which provide fairly ductile response without the need for heavy stiffening of the wall. The steel shear walls and the moment frames behaved in a ductile manner up to more than 4% drift without abrupt strength degradation or loss of axial resistance. Results of these tests and complementary analysis provide a basis for an equivalent brace model to be employed in commercially available frame analysis programs. Test and analytical results suggest that the horizontal force is carried by the bolts in the middle portion of the wall,frame connection, while the vertical forces coupled with the moment in the connection are resisted by the bolts in the edge portion of the connection, for which the friction bolts in the connection should be designed. When sufficient transverse stiffening is provided, full plastic strength and non-degrading hysteretic behaviour can be achieved for this new type of shear wall. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Cyclic tests of post-tensioned precast CFT segmental bridge columns with unbonded strands

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2006
Chung-Che Chou
Abstract Two ungrouted post-tensioned, precast concrete-filled tube (CFT) segmental bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal-height circular CFT segments, and a footing. Strands were placed through the column and post-tensioned to provide a precompression of the column against the footing. One specimen also contained energy-dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum flexural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy-dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and verified a method to estimate the experimental flexural displacement using two plastic hinges in the segmental column. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Cyclic tests on large-scale models of existing bridge piers with rectangular hollow cross-section

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2003
A. V. Pinto
Abstract Cyclic tests on two large-scale models of existing bridge piers with rectangular hollow cross-section were performed in the ELSA laboratory. The prototype structure is an existing reinforced concrete highway bridge constructed in Austria in 1975. The piers presented several seismic deficiencies and consequently they showed poor hysteretic behaviour and limited deformation capacity as well as undesirable failure modes that do not comply with the requirements of modern codes for seismic-resistant structures. Experimental data are compared to numerical and empirical predictions. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Cyclic 2:1 and 1:2 Aldehyde-to-Acetone Byproduct Adducts in Aldol Reactions Promoted by Supported Proline-Incorporated Catalysts

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2009
Lital Tuchman-Shukron
Abstract Significant amounts of cyclic byproducts of aldol addition with stoichiometry deviating from a regular 1:1 addition pattern were formed when the reaction of acetone with aromatic aldehydes was promoted by polymer-supported proline-incorporated catalysts. These adducts, unprecedented in the context of the aldol reaction, are most probably formed via a multistep domino mechanism.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Enantioselective Synthesis of Functionalized 1-Benzoxepines by Phenoxide Ion Mediated 7- endo - tet Carbocyclization of Cyclic Sulfates,,

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2009
Sajal Kumar Das
Abstract A new asymmetric synthesis of 2,3-disubstituted 1-benzoxepines is described. Key steps include Sharpless asymmetricdihydroxylation of trans -,,,-unsaturated esters and phenoxide ion mediated intramolecular 7- endo - tet carbocyclization of syn -2,3-dihydroxy ester derived cyclic sulfates. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Novel Cyclic 1,2-Diacetals Derived from (2R,3R)-(+)-Tartaric Acid: Synthesis and Application as N,O Ligands for the Enantioselective Alkylation of Benzaldehyde by Diethylzinc

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2004
M. Teresa Barros
Abstract A chiral cyclic 1,2-diacetal derived from tartaric acid was used as the basic structural unit for novel ligands. Monooxazoline carbinols in which the degree of substitution of the alcohol and the nature of the stereocentre in the oxazoline ring were varied were synthesized in moderate to good yields. The influence of these structural factors on asymmetric induction was examined in the enantioselective addition of diethylzinc to benzaldehyde. Up to 60% ee was observed with a secondary or a tertiary alcohol as the metal-chelating group. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Lewis Basic Ionic Liquids-Catalyzed Conversion of Carbon Dioxide to Cyclic Carbonates

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010
Zhen-Zhen Yang
Abstract A series of easily prepared Lewis basic ionic liquids were developed for cyclic carbonate synthesis from epoxide and carbon dioxide at low pressure without utilization of any organic solvents or additives. Notably, quantitative yields together with excellent selectivity were attained when 1,8-diazabicyclo[5.4.0]undec-7-enium chloride ([HDBU]Cl) was used as a catalyst. Furthermore, the catalyst could be recycled over five times without appreciable loss of catalytic activity. The effects of the catalyst structure and various reaction parameters on the catalytic performance were investigated in detail. This protocol was found to be applicable to a variety of epoxides producing the corresponding cyclic carbonates in high yields and selectivity. Therefore, this solvent-free process thus represents an environmentally friendly example for the catalytic conversion of carbon dioxide into value-added chemicals by employing Lewis basic ionic liquids as catalyst. A possible catalytic cycle for the hydrogen bond-assisted ring-opening of epoxide and activation of carbon dioxide induced by the nucleophilic tertiary nitrogen of the ionic liquid was also proposed. [source]

Highly Enantioselective Michael Addition of Cyclic 1,3-Dicarbonyl Compounds to ,,,-Unsaturated ,-Keto Esters

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010
Xing-Kuan Chen
Abstract A highly enantioselective Michael addition of cyclic 1,3-dicarbonyl compounds to ,,,-unsaturated ,-keto esters catalyzed by amino acid-derived thiourea-tertiary-amine catalysts is presented. Using 5,mol% of a novel tyrosine-derived thiourea catalyst, a series of chiral coumarin derivatives were obtained in excellent yields (up to 99%) and with up to 96% ee under very mild conditions within a short reaction time. [source]

Ruthenium Catalyzed Selective Regio-and-Mono-Allylation of Cyclic 1,3-Diketones Using Allyl Alcohols as Substrates

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009
Stefan Gruber
Abstract The new ruthenium-sulfonate catalyst Ru(Cp*)(,3 -C3H5),(p -CH3C6H4SO3)2, (Cp*=pentamethylcyclopentadienyl), rapidly and regioselectively mono-allylates dimedone to the branched products using substituted allyl alcohols as substrates, without acid, base or other additives, under relatively mild conditions. We consider the ruthenium sulfonate to be a "green" alternative in that it uses allyl alcohols as substrate, (rather than carbonates, acetates, etc.) and therefore does not waste the leaving group. The catalyst induces rapid double allylation of various 1,3-diketones in high yield using allylic alcohol. [source]

Ligament creep recruits fibres at low stresses and can lead to modulus-reducing fibre damage at higher creep stresses: a study in rabbit medial collateral ligament model

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2002
G. M. Thornton
Ligaments are subjected to a range of loads during different activities in vivo, suggesting that they must resist creep at various stresses. Cyclic and static creep tests of rabbit medial collateral ligament were used as a model to examine creep over a range of stresses in the toe- and linear-regions of the stress,strain curve: 4.1 MPa (n =7), 7.1 MPa (n = 6), 14 MPa (n = 9) and 28 MPa (n = 6). We quantified ligament creep behaviour to determine if, at low stresses, modulus would increase in a cyclic creep test and collagen fibres would be recruited in a static creep test. At higher creep stresses, a decrease in measured modulus was expected to be a potential marker of damage. The increase in modulus during cyclic creep and the increase in strain during static creep were similar between the three toe-region stresses (4.1, 7.1, 14 MPa). However, at the linear-region stress (28 MPa), both these parameters increased significantly compared to the increases at the three toe-region stresses. A concurrent crimp analysis revealed that collagen fibres were recruited during creep, evidenced by decreased area of crimped fibres at the end of the static creep test. Interestingly, a predominance of straightened fibres was observed at the end of the 28 MPa creep test, suggesting a limited potential for fibre recruitment at higher, linear-region stresses. An additional 28 MPa (n = 6) group had mechanically detectable discontinuities in their stress,strain curves during creep that were related to reductions in modulus and suggested fibre damage. These data support the concept that collagen fibre recruitment is a mechanism by which ligaments resist creep at low stresses. At a higher creep stress, which was still only about a third of the failure capacity, damage to some ligaments occurred and was marked by a sudden reduction in modulus. In the cyclic tests, with continued cycling, the modulus increased back to original values obtained before the discontinuity suggesting that other fibres were being recruited to bear load. These results have important implications for our understanding of how fibre recruitment and stress redistribution act in normal ligament to minimize creep and restore modulus after fibre damage. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source]

Comment on "Evaluation of the Cyclic Fatigue Life of 3-mol%-Yttria-Stabilized Zirconia Bioceramic Using Biaxial Flexion"

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2002
Roy W. Rice
No abstract is available for this article. [source]

Metallocene Combinations in Ethylene Polymerization: A Cyclic and Differential Pulse Voltammetry Study

MACROMOLECULAR REACTION ENGINEERING, Issue 3 2008
Fernando Silveira
Abstract A series of metallocenes, namely [Cp2ZrCl2], [(MeCp)2ZrCl2], [(nBuCp)2ZrCl2], [(iBuCp)2ZrCl2], [(tBuCp)2ZrCl2], [Cp2TiCl2], [Et(Ind)2ZrCl2], [Et(IndH4)2ZrCl2] and [MeSi2(Ind)2ZrCl2)], were combined in a 1:1 molar ratio within a reactor for ethylene polymerization, with MAO as the cocatalyst. The catalysts were characterized by cyclic and differential pulse voltammetry. The combined systems that showed the highest and lowest activities were combined in 1:3 and 3:1 molar ratios. The catalyst activity in the ethylene polymerization reaction is discussed in terms of the estimated consumption rate, decomposition rate constant and half-life of the metallocene species formed with MAO in an ethylene atmosphere. [source]

ORIGINAL ARTICLE: Effects of Cyclic Versus Sustained Estrogen Administration on Peripheral Immune Functions in Ovariectomized Mice

AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 4 2010
Jing Li
Citation Li J, McMurray RW. Effects of cyclic versus sustained estrogen administration on peripheral immune functions in ovariectomized mice. Am J Reprod Immunol 2010; 63: 274,281 Problem, Estrogens have multiple influences on immune functions. We aimed to compare the effects of cyclic versus sustained estrogen treatments under the same accumulated dose on peripheral immune functions in ovariectomized mice. Method of study, Ovariectomized adult Balb/c mice were treated with estradiol (E2) by s.c. injection once every 4 days (total 44.8 ,g) or by pellet implantation (total 44.2 ,g). After 6 weeks of treatment, all animals were immunized with DNP-KLH. Peripheral immune functions were assessed 10 days later. Results, Both cyclic and sustained E2 treatments significantly reduced the percentage of splenic B220+sIgM+ cells, enhanced IFN-, production and suppressed IL-6 secretion from Con A-stimulated splenocytes, and increased serum anti-DNP antibody levels. No differences were found in the above responses or in uterine weight gain between the two regimens of E2 administration. Conclusion, There are no differential effects on peripheral immune functions between cyclic and sustained estrogen administration under the same total dose. [source]

Activation of olfactory-type cyclic nucleotide-gated channels is highly cooperative

THE JOURNAL OF PHYSIOLOGY, Issue 1 2005
Vasilica Nache
Cyclic nucleotide-gated (CNG) ion channels play a key role in the sensory transduction of vision and olfaction. The channels are opened by the binding of cyclic nucleotides. Native olfactory CNG channels are heterotetramers of CNGA2, CNGA4, and CNGB1b subunits. Upon heterologous expression, only CNGA2 subunits can form functional homotetrameric channels. It is presently not known how the binding of the ligands to the four subunits is translated to channel opening. We studied activation of olfactory CNG channels by photolysis-induced jumps of cGMP or cAMP, two cyclic nucleotides with markedly different apparent affinity. It is shown that at equal degree of activation, the activation time course of homotetrameric channels is similar with cGMP and cAMP and it is also similar in homo- and heterotetrameric channels with the same cyclic nucleotide. Kinetic models were globally fitted to activation time courses of homotetrameric channels. While all models containing equivalent binding sites failed, a model containing three binding sites with a ligand affinity high,low,high described the data adequately. Only the second binding step switches from a very low to a very high open probability. We propose a unique gating mechanism for homotetrameric and heterotetrameric channels that involves only three highly cooperative binding steps. [source]

Cyclic and acyclic products from the reactions between methyl 3-oxobutanoate and arylhydrazines

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2007
James L. Wardell
The molecules of methyl 3-(2-nitrophenylhydrazono)butanoate, C11H13N3O4, (I), and methyl 3-(2,4-dinitrophenylhydrazono)butanoate, C11H12N4O6, (II), both prepared from methyl 3-oxobutanoate and the corresponding nitrophenylhydrazine, exhibit polarized molecular electronic structures; in each of (I) and (II), the molecules are linked into chains by a single C,H...O hydrogen bond. The molecules of 5-hydroxy-3-methyl-1-phenyl-1H -pyrazole, C10H10N2O, (III), prepared by the reaction of methyl 3-oxobutanoate and phenylhydrazine, are linked into chains by a single O,H...N hydrogen bond. The reaction between methyl 3-oxobutanoate and 3-nitrophenylhydrazine yields 5-hydroxy-3-methyl-1-(3-nitrophenyl)-1H -pyrazole, (IV), which when crystallized from acetone yields 4-isopropylidene-3-methyl-1-(3-nitrophenyl)-1H -pyrazol-5(4H)-one, C13H13N3O3, (V). [source]

Monte Carlo study of cycloamylose: Chain conformation, radius of gyration, and diffusion coefficient

BIOPOLYMERS, Issue 2 2002
Yasushi Nakata
Abstract Cyclic (1 , 4)-,- D -glucan chains with or without excluded volume have been collected from a huge number (about 107) of linear amylosic chains generated by the Monte Carlo method with a conformational energy map for maltose, and their mean-square radii of gyration ,S2, and translational diffusion coefficients D (based on the Kirkwood formula) have been computed as functions of x (the number of glucose residues in a range from 7 to 300) and the excluded-volume strength represented by the effective hard-core radius. Both ,S2,/x and D in the unperturbed state weakly oscillate for x < 30 and the helical nature of amylose appears more pronouncedly in cyclic chains than in linear chains. As x increases, these properties approach the values expected for Gaussian rings. Though excluded-volume effects on them are always larger in cycloamylose than in the corresponding linear amylose, the ratios of ,S2, and the hydrodynamic radius of the former to the respective properties of the latter in good solvents can be slightly lower than or comparable to the (asymptotic) Gaussian-chain values when x is not sufficiently large. An interpolation expression is constructed for the relation between the gyration-radius expansion factors for linear and cyclic chains from the present Monte Carlo data and the early proposed asymptotic relation with the aid of the first-order perturbation theories. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 72,79, 2002 [source]

ChemInform Abstract: A Mild and Convenient One-Pot Two-Step Synthesis of Hydroxyiminodihydrobenzofurans Mediated by Silica Gel under Microwave Activation Conditions.

CHEMINFORM, Issue 39 2010
Deepak Kumar Barange
Abstract Cyclic 1,3-dicarbonyl compounds (I) react with various nitroolefins to furnish the title products exclusively or predominantly as (E)-isomers. [source]

ChemInform Abstract: Cobalt, Manganese, Nickel, and Vanadium Derivatives of the Cyclic 48-Tungsto-8-Phosphate [H7P8W48O184]33- .

CHEMINFORM, Issue 34 2010
Bineta Keita
Abstract The structures of the title compounds (IV) (triclinic, space group P, Z = 1), (VI) (P, Z = 1), and (VIII) (tetragonal, P4/m, Z = 2) are determined by single crystal XRD. [source]

ChemInform Abstract: ,-Arylation and Alkynylation of Cyclic ,-Iodoenones Using Palladium-Catalyzed Cross-Coupling Reactions with Trifluoroborate Salts.

CHEMINFORM, Issue 25 2010
Kemilla Gueogjian
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: InBr3 -Catalyzed Annulations of Cyclic 1,3-Diketones with Aryl Propargyl Alcohols: A Novel Synthesis of 2,4-Diaryldihydropyrans.

CHEMINFORM, Issue 42 2009
J. S. Yadav
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Stereoselective Synthesis of Hexahydroindoles and Octahydrocyclohepta[b]pyrroles via Gold(I)-Catalyzed Intramolecular 1,4-Hydroamination of Cyclic 1,3-Dienes.

CHEMINFORM, Issue 41 2009
Ming-Chang P. Yeh
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Cyclic ,-Acylvinyl Anionic Synthons: A Novel Synthesis of 2-Trimethylsilyl-3-methyl-cyclohexenone by the Wurtz,Fittig Coupling Reaction.

CHEMINFORM, Issue 33 2009
Divya Jyothi
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Nanometer-Sized Titanium Dioxide-Catalyzed Reactions of Nitric Oxide with Aliphatic Cyclic and Aromatic Amines.

CHEMINFORM, Issue 32 2009
Zhangjian Huang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Enantioselective Silicon,Boron Additions to Cyclic 1,3-Dienes Catalyzed by the Platinum Group Metal Complexes.

CHEMINFORM, Issue 16 2009
Martin Gerdin
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Sequential Coupling of the Transesterification of Cyclic Carbonates with the Selective N-Methylation of Anilines Catalyzed by Faujasites.

CHEMINFORM, Issue 7 2009
Maurizio Selva
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Ruthenium/TFA-Catalyzed Coupling of Activated Secondary Propargylic Alcohols with Cyclic 1,3-Diones: Furan versus Pyran Ring Formation.

CHEMINFORM, Issue 50 2008
Victorio Cadierno
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Tandem Conjugate Additions and 3-Aza-Cope Rearrangements of Tertiary Allyl Amines and Cyclic ,-Vinylamines with Acetylenic Sulfones.

CHEMINFORM, Issue 42 2008
Applications to Simple, Iterative Ring Expansions Leading to Medium, Large-Ring Nitrogen Heterocycles.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Highly Active and Robust Organic,Inorganic Hybrid Catalyst for the Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides.

CHEMINFORM, Issue 31 2008
Takashi Sakai
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Ir-Catalyzed Allylic Amination/Ring-Closing Metathesis: A New Route to Enantioselective Synthesis of Cyclic ,-Amino Alcohol Derivatives.

CHEMINFORM, Issue 5 2008
Jun Hee Lee
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]