ChemInform Abstract: Symmetry of Chemical Structures: A Novel Method of Graph Automorphism Group Determination.

In order to enhance the interfacial adhesion of poly(p-phenylene terephthalamide) (PPTA) fibers to the rubber composites, a novel method to deposit multi-walled carbon nanotubes (MWCNTs) onto the surface of PPTA fibers has been proposed in this study. This chemical modification was performed through the introduction of epoxy groups by Friedel–Crafts alkylation on the PPTA fibers, the carboxylation of MWCNTs, and the ring-opening reaction between the epoxy groups and the carboxyl groups. The morphologies, chemical structures, and compositions of the surface of PPTA fibers were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results showed that MWCNTs were uniformly deposited onto the surface of PPTA fibers with the covalent bonds. The measurement of contact angles of the fibers with polar solvent and non-polar solvent indicated that the surface energy of deposited fibers significantly increased by 41.9% compared with the untreated fibers. An electronic tensile tester of single-filament and a universal testing machine were utilized to measure the strength change of the fibers after modification and the interfacial adhesion between the fibers and the rubber matrix, respectively. The results showed that the tensile strength had not been obviously reduced, and the pull-out force and peeling strength of the fibers to the rubber increased by 46.3% and 56.5%, respectively.

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Novel Techniques to Speed Up the Computation of the Automorphism Group of a Graph

Journal of Applied Mathematics ◽

10.1155/2014/934637 ◽

2014 ◽

Vol 2014 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

José Luis López-Presa ◽

Luis F. Chiroque ◽

Antonio Fernández Anta

Keyword(s):

Automorphism Group ◽

Classical Problem ◽

Search Tree ◽

Input Graph ◽

Graph Automorphism ◽

Ga Algorithm ◽

Speed Up ◽

Graph Families ◽

The Impact ◽

Asymptotic Time

Graph automorphism (GA) is a classical problem, in which the objective is to compute the automorphism group of an input graph. Most GA algorithms explore a search tree using the individualization-refinement procedure. Four novel techniques are proposed which increase the performance of any algorithm of this type by reducing the depth of the search tree and by effectively pruning it. We formally prove that a GA algorithm that uses these techniques correctly computes the automorphism group of an input graph. Then, we describe how these techniques have been incorporated into the GA algorithm conauto, asconauto-2.03, with at most an additive polynomial increase in its asymptotic time complexity. Using a benchmark of different graph families, we have evaluated the impact of these techniques on the size of the search tree, observing a significant reduction both when they are applied individually and when all of them are applied together. This is also reflected in a reduction of the running time, which is substantial for some graph families. Finally, we have compared the search tree size of conauto-2.03 against those of other popular GA algorithms, observing that, in most cases, conauto explores less nodes than these algorithms.

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Synthetic Studies Towards Spirocyclic Imine Marine Toxins Using N-Acyl Iminium Ions as Dienophiles in Diels–Alder Reactions

Synlett ◽

10.1055/s-0039-1691593 ◽

2020 ◽

Vol 31 (07) ◽

pp. 657-671

Author(s):

Jared L. Freeman ◽

Freda F. Li ◽

Daniel P. Furkert ◽

Margaret A. Brimble

Keyword(s):

Biological Activities ◽

Diels Alder ◽

Direct Access ◽

Marine Toxins ◽

Chemical Structures ◽

Marine Toxin ◽

Iminium Ions ◽

Iminium Ion ◽

Novel Method

Cyclic imine marine toxins have attracted considerable attention from the synthetic community in the past two decades due to their unique chemical structures and clinically relevant biological activities. This review presents recent efforts of our group in the development of various strategies to efficiently construct the common spirocyclic imine fragments of the cyclic imine toxins. In particular, the use of α,β-unsaturated N-acyl iminium ion dienophiles in Diels–Alder reactions are highlighted, whereby direct access to spirocyclic imine motifs was obtained and important mechanistic details were discovered. Alternative approaches to spirocyclic imine systems involving hydroamination of amino alkynes are also summarized. One such approach led to serendipitous access to N-vinyl amide products, while our most recently reported approach involving an intermolecular Diels–Alder/cross-coupling sequence using novel 2-bromo-1,3-butadienes to access 5,6-spirocyclic imines is also discussed. Additionally, the development of a novel method to construct another challenging motif present in the portimines is also introduced.1 Introduction2 Strategies towards the Spirocyclic Imine Fragment of Cyclic Imine Toxins2.1 Diels–Alder Cycloadditions of α,β-Unsaturated N-Acyl Iminium Dienophiles2.2 Early Studies Using in situ-Generated Iminium Ion Dienophiles2.3 Use of More Stable Iminium Ion Dienophiles for Diels–Alder Reactions2.4 Other Notable Strategies towards Spirocyclic Imines2.5 Recent Efforts towards the 5,6-Spirocyclic Imine Marine Toxin Portimine A2.6 Construction of Another Challenging Motif of Portimine A3 Conclusion and Future Perspectives

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Synthesis of Fullerene-Acid Conjugates

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.463-464.538 ◽

2012 ◽

Vol 463-464 ◽

pp. 538-542 ◽

Cited By ~ 1

Author(s):

Jing Zhang ◽

Li Yuan ◽

Ya Dong Zhang

Keyword(s):

Amino Acids ◽

Glutamic Acid ◽

Aspartic Acid ◽

Azomethine Ylide ◽

Hydroxyl Group ◽

Dipolar Cycloaddition ◽

Chemical Structures ◽

Ft Ir ◽

Novel Method ◽

Potential Use

N-substituted 3,4-fullero pyrrolidine was synthesized according to 1,3-Dipolar cycloaddition of the azomethine ylide. Aspartic acid and glutamic acid with protected α-amino and α-carboxyl groups were reacted with the activated hydroxyl group of N-substituted 3,4-fullero pyrrolidine, respectively. The products were deprotected, affording two novel fullerene α-amino acids, fullerene aspartic acid and fullerene glutamic acid. Their chemical structures were characterized by MALAI-TOF-MS, UV-Vis, FT-IR and 1HNMR. Both fullerene amino acids with a free amino group and a free carboxyl group would have unique property and potential use in medicine and biology. A novel method has been developed to synthesize fullerene conjugate. Their unique chemical structures make them very interesting for their potential use in medicine and biology.

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The removal and morphology of intact biofilms from implanted venous access devices

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141470 ◽

1995 ◽

Vol 53 ◽

pp. 1020-1021

Author(s):

M.A. Gregory ◽

G.P. Hadley

Keyword(s):

Patient Selection ◽

Surgical Oncology ◽

Venous Access ◽

Common Procedure ◽

Indwelling Catheters ◽

Careful Patient ◽

Novel Method ◽

The Subject ◽

Vascular Catheters ◽

Venous Access Devices

The insertion of implanted venous access systems for children undergoing prolonged courses of chemotherapy has become a common procedure in pediatric surgical oncology. While not permanently implanted, the devices are expected to remain functional until cure of the primary disease is assured. Despite careful patient selection and standardised insertion and access techniques, some devices fail. The most commonly encountered problems are colonisation of the device with bacteria and catheter occlusion. Both of these difficulties relate to the development of a biofilm within the port and catheter. The morphology and evolution of biofilms in indwelling vascular catheters is the subject of ongoing investigation. To date, however, such investigations have been confined to the examination of fragments of biofilm scraped or sonicated from sections of catheter. This report describes a novel method for the extraction of intact biofilms from indwelling catheters.15 children with Wilm’s tumour and who had received venous implants were studied. Catheters were removed because of infection (n=6) or electively at the end of chemotherapy.

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Chemical structure of diamond-like carbon thin films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010017668x ◽

1990 ◽

Vol 48 (4) ◽

pp. 710-711

Author(s):

N.-H. Cho ◽

K.M. Krishnan ◽

D.B. Bogy

Keyword(s):

Electrical Resistivity ◽

Chemical Structure ◽

Diamond Like Carbon ◽

Chemical Structures ◽

Sputtering Power ◽

Data Aquisition ◽

Equilibrium Phases ◽

Electron Energy Loss ◽

Power Densities ◽

Preparation Techniques

Diamond-like carbon (DLC) films have attracted much attention due to their useful properties and applications. These properties are quite variable depending on film preparation techniques and conditions, DLC is a metastable state formed from highly non-equilibrium phases during the condensation of ionized particles. The nature of the films is therefore strongly dependent on their particular chemical structures. In this study, electron energy loss spectroscopy (EELS) was used to investigate how the chemical bonding configurations of DLC films vary as a function of sputtering power densities. The electrical resistivity of the films was determined, and related to their chemical structure.DLC films with a thickness of about 300Å were prepared at 0.1, 1.1, 2.1, and 10.0 watts/cm2, respectively, on NaCl substrates by d.c. magnetron sputtering. EEL spectra were obtained from diamond, graphite, and the films using a JEOL 200 CX electron microscope operating at 200 kV. A Gatan parallel EEL spectrometer and a Kevex data aquisition system were used to analyze the energy distribution of transmitted electrons. The electrical resistivity of the films was measured by the four point probe method.

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