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2012 Annual Conference on Experimental and Applied Mechanics

作者： Porter, Michael M. Lee, Steve Tanadchangsaeng, Nuttapol Jaremko, Matt J. Yu, Jian Meyers, Marc McKittrick, Joanna Materials Science and Engineering Program University of California San Diego 9500 Gilman Dr. San Diego CA 92093 United States Hawaii Natural Energy Institute University of Hawaii at Manoa 1680 East West Road Honolulu HI 98622 United States Department of Mechanical and Aerospace Engineering University of California San Diego 9500 Gilman Dr. San Diego CA 92093 United States

ISBN: (纸本)9781461444268

Porous hydroxyapatite-polyhydroxybutyrate (HA-PHB) composites were fabricated by infiltrating PHB micro-/nano-particles into rigid HA scaffolds via centrifugation, followed by subsequent heating at 175°C to melt the PHB into the scaffolds. HA scaffolds were obtained by heating trabecular bovine femur bone at 1,350°C to remove the organic and sinter the HA. PHB particles were recovered and purified from microbial cells by two different chemical methods, which either filled the apparent porosity of the scaffolds or coated the trabecular network of the scaffolds after heating. The mechanical properties, porosity, HA/PHB volume fractions and surface adhesion of the resulting HA-PHB composites were investigated and compared to the original HA scaffolds. The final porosities of the filled and coated composites were ∼54% and ∼67%, respectively. All of the HA-PHB composites showed a slight increase in strength with the addition of PHB. The filled composites showed no change in stiffness from the addition of PHB, while the coated composites showed an increase in stiffness over the original HA scaffolds from ∼35 to ∼105 MPa. The enhanced stiffness in the coated composites was due to strong interactions between its HA and PHB constituent phases. Very little inter-constituent adhesion was observed in the filled composites. © The Society for Experimental Mechanics, Inc. 2013.

关键词： Hydroxyapatite

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Preliminary results on biomimetic methods based on soluble ammonium phosphate precursors for the consolidation of archaeological wall paintings

Preliminary results on biomimetic methods based on soluble a...

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作者： Balonis-Sant, Magdalena Ma, Xiao Kakoulli, Ioanna Department of Materials Science and Engineering University of California Los Angeles 410 Westwood Plaza Los Angeles CA 90005-1595 United States UCLA/Getty Conservation Program Cotsen Institute of Archaeology University of California Los Angeles 308 Charles E. Young Drive North Los Angeles CA 90095-1510 United States

ISBN: (纸本)9780841229242

This research develops hydroxyapatite (HAP)-based, inorganic mineral systems for the consolidation of powdery wall paintings of archaeological significance. The scientific approach exploits biomimetic (biologically inspired design) principles to induce in situ the formation of protective HAP crystals by triggering reactions between the calcium carbonate-rich layers in wall paintings and ammonium phosphate precursors. The high solubility and absence of toxicity of ammonium phosphate precursors and the stability of the hydroxyapatite reaction product at varying pH, renders this treatment extremely promising for consolidation and protection of weathered wall paintings. Experimental trials were carried out on wall painting test blocks applying cellulose compresses of 1M and 2M solutions of diammonium hydrogen phosphate for 3 to 6 hours contact time. The consolidating effect was evaluated through microstructurally and compositionally-sensitive analytics including VPSEM-EDS, XRF, water sorption test and scotch tape test. Preliminary results indicated the formation of a porous hydroxyapatite network at the surface and subsurface of the test blocks with improved cohesion, pH-resistivity and reduced water absorption. These data show the potential of this treatment for the consolidation of powdery wall paintings and their protection from weathering and deterioration induced by natural aging and environmental action-linked effects. Copyright © 2013 American Chemical Society.

关键词： Hydroxyapatite

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An Aggregation‐Induced‐Emission Platform for Direct Visualization of Interfacial Dynamic Self‐Assembly†

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Angewandte Chemie 2014年第49期126卷

作者： Junwei Li Yuan Li Carrie Y. K. Chan Ryan T. K. Kwok Hongkun Li Pavel Zrazhevskiy Xiaohu Gao Jing Zhi Sun Anjun Qin Ben Zhong Tang MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027 (China) Department of Bioengineering University of Washington Seattle WA (USA) Physics Department Wake Forest University Winston‐Salem NC 27106 (USA) Department of Chemistry Institute for Advanced Study Institute of Molecular Functional Materials and State Key Laboratory of Molecular Neuroscience The Hong Kong University of Science & Technology Clear Water Bay Kowloon Hong Kong (China) State Key Laboratory of Luminescent Materials and Devices South China University of Technology Guangzhou 510640 (China)

An in‐depth understanding of dynamic interfacial self‐assembly processes is essential for a wide range of topics in theoretical physics, materials design, and biomedical research. However, direct monitoring of such processes is hampered by the poor imaging contrast of a thin interfacial layer. We report in situ imaging technology capable of selectively highlighting self‐assembly at the phase boundary in real time by employing the unique photophysical properties of aggregation‐induced emission. Its application to the study of breath‐figure formation, an immensely useful yet poorly understood phenomenon, provided a mechanistic model supported by direct visualization of all main steps and fully corroborated by simulation and theoretical analysis. This platform is expected to advance the understanding of the dynamic phase‐transition phenomena, offer insights into interfacial biological processes, and guide development of novel self‐assembly technologies.

关键词： Aggregationsinduzierte Emission Fluoreszenz Grenzflächen Kondensationsmuster Tetraphenylethen

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Phonons in twisted bilayer graphene

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Physical Review B 2013年第3期88卷 035428-035428页

作者： Alexandr I. Cocemasov Denis L. Nika Alexander A. Balandin E. Pokatilov Laboratory of Physics and Engineering of Nanomaterials Department of Theoretical Physics Moldova State University Chisinau MD-2009 Republic of Moldova Nano-Device Laboratory Department of Electrical Engineering Bourns College of Engineering University of California–Riverside Riverside California 92521 USA Materials Science and Engineering Program Bourns College of Engineering University of California–Riverside Riverside California 92521 USA

We theoretically investigate phonon dispersion in AA-stacked, AB-stacked, and twisted bilayer graphene with various rotation angles. The calculations are performed using the Born–von Karman model for the intralayer atomic interactions and the Lennard-Jones potential for the interlayer interactions. It is found that the stacking order affects the out-of-plane acoustic phonon modes the most. The difference in the phonon densities of states in the twisted bilayer graphene and in AA- or AB-stacked bilayer graphene appears in the phonon frequency range 90–110 cm−1. Twisting bilayer graphene leads to the emergence of different phonon branches—termed hybrid folded phonons—which originate from the mixing of phonon modes from different high-symmetry directions in the Brillouin zone. The frequencies of the hybrid folded phonons depend strongly on the rotation angle and can be used for noncontact identification of the twist angles in graphene samples. The obtained results and the tabulated frequencies of phonons in twisted bilayer graphene are important for the interpretation of experimental Raman data and in determining the thermal conductivity of these material systems.

关键词： GRAPHENE PHONON dispersion relations BILAYERS (Solid state physics) ATOMIC interactions BRILLOUIN zones THERMAL conductivity RAMAN scattering

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Polymer-nanocomposite anti-reflective coating fabricated by resonant IR matrix-assisted pulsed laser evaporation

Polymer-nanocomposite anti-reflective coating fabricated by ...

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CLEO: science and Innovations, CLEO_SI 2013

作者： Haglund, Richard F. Mayo, Daniel C. Singaravelu, Senthilraja Park, Hee-Kuwon Grigoropoulos, Costas P. Schriver, Kenneth E. Interdisciplinary Materials Science Program Vanderbilt University Nashville TN 37234-0106 United States AppliFlex LLC 110 Space Park South Nashville TN 37211 United States Department of Mechanical Engineering University of California Berkeley CA 94720-1740s United States Department of Physics and Astronomy Vanderbilt University Nashville TN 37235-1807 United States

We demonstrate a multilayer anti-reflective conformal coating for polycarbonate substrates, using a a polymer nanocomposite, fabricated by resonant infrared pulsed laser evaporation. The coating has 97% transmission, ... 详细信息

ISBN: (纸本)9781557529725

关键词： Fabrication

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Novel Hyperbranched Ferrocene-Containing Poly(boro)carbosilanes Synthesized via a Convenient "A2 + B3" Approach

Novel Hyperbranched Ferrocene-Containing Poly(boro)carbosila...

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工信部七校青年学者论坛

作者： Jie Kong Thomas Schmalz G(u)nter Motz Axel H.E.Miiller Department of Applied Chemistry School of Science Northwestern Polytechnical University Xi'an 710 Ceramic Materials Engineering University of Bayreuth D-95440 Bayreuth Germany Macromolecular Chemistry.Ⅱ University of Bayreuth D-95440 Bayreuth Germany

We report the synthesis of versatile hyperbra nched ferrocene-containing poly(boro)carbosilanes (hb PBCS) via a convenient "A2 + B3" *** types of hb-PBCS are obtained by the hydrosilylation of 1,1′-bis(dimethylsilyl)ferrocene (A2) with trivinylmethylsilane (B3)followed by modification with 9-borabicyclo[3.3.1]nonane (9-BBN) and by the hydroboration of 1,1′-bis(dimethyl vinylsilyl)ferrocene (A2) with the borane-dimethyl sulfide complex (B3), *** exclusion chromatography (SEC) results demonstrate that the well-soluble hb-PBCS possess appreciable weight-average molecular weight (Mw SEC) up to 62 300 g/mol with the polydispersity index (PDI) of 1.95-4.51.

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INFLUENCE OF ZnSt_2 ON STRUCTURE OF ACRYLATE-BASED IONOMERS WITH DIFFERENT LANTHANIDE(La(Ⅲ)) ION AND ACID CONTENTS

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Chinese Journal of Polymer science 2012年第2期30卷 316-327页

作者：宋义虎郑强 MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and EngineeringZhejiang UniversityHangzhou 310027China National Engineering Research Center for Compounding and Modification of Polymeric Materials Guiyang 550025China

A series of acrylate processing aid （ACR）-based ionomers with different lanthanide （La（III）） ion and acid contents were synthesized, and the interaction between ionomer and zinc stearate （ZnSt2） was investigated immediately after thermally annealing the ionomer/ZnSt2 （3/1 in weight） mixtures at 180℃. The results revealed that the ion groups in ionomer have a strong interaction with ZnSt2. The annealed mixtures contained hot alcohol extractable and unextractable ZnSt2. The melting of ZnSt2 and the thermal behavior of the ionomer in the annealed mixtures were seriously influenced by the contents of La（III） and acid in the ionomers. The ionomer containing 0.25 rnmol/g acid and 0.37 mmol/g La（III） has a detectable cluster phase. Annealing its ZnSt2 mixture could break down the cluster phase and lower glass transition temperature of the ionomer matrix. However, washing away the extractable ZnSt2 led to the reappearance of the cluster transition temperature and return of the glass transition temperature of matrix to the original position.

关键词： Ionomer ZnSt2 Annealing.

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Modeling and simulation of the microalgae derived hydrogen process in compact photobioreactors

Modeling and simulation of the microalgae derived hydrogen p...

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IEEE Conference on Technologies for Sustainability

作者： J. V. C. Vargas D. A. Mitchell A. B. Mariano D. O. Correa J. C. Ordonez Graduate Program in Engineering and Materials Science PIPE and Sustainable Energy Research and Development Center NPDEAS Federal University of Parana Department of Mechanical Engineering Energy and Sustainability Center and Center for Advanced Power Systems Florida State University FSU

ISBN: (纸本)9781467346290

A general transient mathematical model for managing microalgae derived hydrogen production, with temperature dependence of the cultivation medium is developed. For that, the simplified physical model combines principles of classical thermodynamics, mass, species and heat transfer, resulting in a system of differential equations which are discretized in space using a three-dimensional cell-centered finite volume scheme. A Michaelis-Menten type expression is proposed for modeling the rate of H_2 production with dependence on O_2 inhibition. Tridimensional simulations are performed in order to determine the mass fractions distributions inside a compact photobioreactor (PBR), under different operating conditions. A relatively coarse mesh was used (6048 volume elements) to obtain converged results for a large compact PBR computational domain (5m×2m×8m). The largest computational time required for obtaining results was 560 s, i.e., less than 10 min. The numerical results for microalgal growth are validated by direct comparison to experimental measurements. Hydrogen production simulations are conducted to demonstrate PBR intermittent operation (aerobic and anaerobic stages) feasibility and adequate species evolution trends in an indirect biophotolysis approach. Therefore, after experimental validation for a particular H_2 production system, it is reasonable to state that the model could be used as an efficient tool for PBR systems thermal design, control and optimization for maximum H_2 production.

关键词： Chlamydomonas reinhardtii Scenedesmus sp. Photobioreactor architecture Early stage design tool

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Chapter green nanotechnology: Development of nanomaterials for environmental and energy applications

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ACS Symposium Series 2013年 1124卷 201-229页

作者： Han, Changseok Andersen, Joel Pillai, Suresh C. Fagan, Rachel Falaras, Polycarpos Byrne, J. Anthony Dunlop, Patrick S.M. Choi, Hyeok Jiang, Wenjun O'Shea, Kevin Dionysiou, Dionysios D. Environmental Engineering and Science Program University of Cincinnati Cincinnati OH 45221-0012 United States FOCAS Institute Dublin Institute of Technology Kevin St. Dublin 8 Ireland Division of Physical Chemistry Institute of Advanced Materials Physicochemical Processes Nanotechnology and Microsystems National Center for Scientific Research Demokritos 15310 Aghia Parakevi Attikis Athens Greece Nanotechnology and Integrated BioEngineering Centre School of Engineering University of Ulster Northern-Ireland BT37 0QB United Kingdom Department of Civil Engineering University of Texas at Arlington Arlington TX 76019-0308 United States Department of Chemistry and Biochemistry Florida International University University Park Miami FL 33199 United States Nireas-International Water Research Centre University of Cyprus 20537 Nicosia Cyprus

ISBN: (纸本)9780841227842

This book chapter discusses the syntheses of various nanomaterials, for green nanotechnology applications in detail. Special attention is given to the development of emerging areas, such as environmental as well as energy materials. Various approaches for preparing nanostructured photocatalysts, such as titanium dioxide, zinc oxide, iron oxide, and metal sulfides, different conventional methods and novel methods, including sol-gel methods, hydrothermal methods, microwave-assisted methods and sonochemical methods are introduced. The use of nanomaterials as photocatalysts, supporting materials for solar cells, and disinfectants is reported for environmental remediation and energy applications. Advanced applications of nanomaterials for water detoxification, air purification, and the inactivation of pathogenic microorganisms in water as well as dye-sensitized solar cells is also discussed. The enhancement of selectivity of photocatalysis, especially TiO2 systems, for the destruction of target contaminants in water is comprehensively presented. Finally, the role of reactive oxygen species (ROS), such as hydroxyl radical (•OH), superoxide anion radical (O2•-), singlet oxygen (1O2) and hydrogen peroxide (H2O2), in semiconductor photocatalysis is introduced and various experimental techniques to detect ROS are also discussed. © 2013 American Chemical Society.

关键词： Nanostructured materials

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Origin of Overstretching Transitions in Single-Stranded Nucleic Acids

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Physical Review Letters 2013年第18期111卷 188302-188302页

作者： Zackary N. Scholl Mahir Rabbi David Lee Laura Manson Hanna S-Gracz Piotr E. Marszalek Program in Computational Biology and Bioinformatics Duke University Durham North Carolina 27708 USA Department of Mechanical Engineering and Materials Science Center for Biologically Inspired Materials and Material Systems Duke University Durham North Carolina 27708 USA Department of Molecular and Structural Biochemistry North Carolina State University Raleigh North Carolina 27708 USA

We combined single-molecule force spectroscopy with nuclear magnetic resonance measurements and molecular mechanics simulations to examine overstretching transitions in single-stranded nucleic acids. In single-stranded DNA and single-stranded RNA there is a low-force transition that involves unwinding of the helical structure, along with base unstacking. We determined that the high-force transition that occurs in polydeoxyadenylic acid single-stranded DNA is caused by the cooperative forced flipping of the dihedral angle formed between four atoms, O5’-C5’-C4’-C3’ (γ torsion), in the nucleic acid backbone within the canonical B-type helix. The γ torsion also flips under force in A-type helices, where the helix is shorter and wider as compared to the B-type helix, but this transition is less cooperative than in the B type and does not generate a high-force plateau in the force spectrums of A-type helices. We find that a similar high-force transition can be induced in polyadenylic acid single-stranded RNA by urea, presumably due to disrupting the intramolecular hydrogen bonding in the backbone. We hypothesize that a pronounced high-force transition observed for B-type helices of double stranded DNA also involves a cooperative flip of the γ torsion. These observations suggest new fundamental relationships between the canonical structures of single-and double-stranded DNA and the mechanism of their molecular elasticity.

关键词： NUCLEAR magnetic resonance spectroscopy SINGLE-stranded DNA NUCLEOTIDE sequence DEOXYRIBOSE ATOMIC force microscopy

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