11 results
Contributors
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- By Mitchell Aboulafia, Frederick Adams, Marilyn McCord Adams, Robert M. Adams, Laird Addis, James W. Allard, David Allison, William P. Alston, Karl Ameriks, C. Anthony Anderson, David Leech Anderson, Lanier Anderson, Roger Ariew, David Armstrong, Denis G. Arnold, E. J. Ashworth, Margaret Atherton, Robin Attfield, Bruce Aune, Edward Wilson Averill, Jody Azzouni, Kent Bach, Andrew Bailey, Lynne Rudder Baker, Thomas R. Baldwin, Jon Barwise, George Bealer, William Bechtel, Lawrence C. Becker, Mark A. Bedau, Ernst Behler, José A. Benardete, Ermanno Bencivenga, Jan Berg, Michael Bergmann, Robert L. Bernasconi, Sven Bernecker, Bernard Berofsky, Rod Bertolet, Charles J. Beyer, Christian Beyer, Joseph Bien, Joseph Bien, Peg Birmingham, Ivan Boh, James Bohman, Daniel Bonevac, Laurence BonJour, William J. Bouwsma, Raymond D. Bradley, Myles Brand, Richard B. Brandt, Michael E. Bratman, Stephen E. Braude, Daniel Breazeale, Angela Breitenbach, Jason Bridges, David O. Brink, Gordon G. Brittan, Justin Broackes, Dan W. Brock, Aaron Bronfman, Jeffrey E. Brower, Bartosz Brozek, Anthony Brueckner, Jeffrey Bub, Lara Buchak, Otavio Bueno, Ann E. Bumpus, Robert W. Burch, John Burgess, Arthur W. Burks, Panayot Butchvarov, Robert E. Butts, Marina Bykova, Patrick Byrne, David Carr, Noël Carroll, Edward S. Casey, Victor Caston, Victor Caston, Albert Casullo, Robert L. Causey, Alan K. L. Chan, Ruth Chang, Deen K. Chatterjee, Andrew Chignell, Roderick M. Chisholm, Kelly J. Clark, E. J. Coffman, Robin Collins, Brian P. Copenhaver, John Corcoran, John Cottingham, Roger Crisp, Frederick J. Crosson, Antonio S. Cua, Phillip D. Cummins, Martin Curd, Adam Cureton, Andrew Cutrofello, Stephen Darwall, Paul Sheldon Davies, Wayne A. Davis, Timothy Joseph Day, Claudio de Almeida, Mario De Caro, Mario De Caro, John Deigh, C. F. Delaney, Daniel C. Dennett, Michael R. DePaul, Michael Detlefsen, Daniel Trent Devereux, Philip E. Devine, John M. Dillon, Martin C. Dillon, Robert DiSalle, Mary Domski, Alan Donagan, Paul Draper, Fred Dretske, Mircea Dumitru, Wilhelm Dupré, Gerald Dworkin, John Earman, Ellery Eells, Catherine Z. Elgin, Berent Enç, Ronald P. Endicott, Edward Erwin, John Etchemendy, C. Stephen Evans, Susan L. Feagin, Solomon Feferman, Richard Feldman, Arthur Fine, Maurice A. Finocchiaro, William FitzPatrick, Richard E. Flathman, Gvozden Flego, Richard Foley, Graeme Forbes, Rainer Forst, Malcolm R. Forster, Daniel Fouke, Patrick Francken, Samuel Freeman, Elizabeth Fricker, Miranda Fricker, Michael Friedman, Michael Fuerstein, Richard A. Fumerton, Alan Gabbey, Pieranna Garavaso, Daniel Garber, Jorge L. A. Garcia, Robert K. Garcia, Don Garrett, Philip Gasper, Gerald Gaus, Berys Gaut, Bernard Gert, Roger F. Gibson, Cody Gilmore, Carl Ginet, Alan H. Goldman, Alvin I. Goldman, Alfonso Gömez-Lobo, Lenn E. Goodman, Robert M. Gordon, Stefan Gosepath, Jorge J. E. Gracia, Daniel W. Graham, George A. Graham, Peter J. Graham, Richard E. Grandy, I. Grattan-Guinness, John Greco, Philip T. Grier, Nicholas Griffin, Nicholas Griffin, David A. Griffiths, Paul J. Griffiths, Stephen R. Grimm, Charles L. Griswold, Charles B. Guignon, Pete A. Y. Gunter, Dimitri Gutas, Gary Gutting, Paul Guyer, Kwame Gyekye, Oscar A. Haac, Raul Hakli, Raul Hakli, Michael Hallett, Edward C. Halper, Jean Hampton, R. James Hankinson, K. R. Hanley, Russell Hardin, Robert M. Harnish, William Harper, David Harrah, Kevin Hart, Ali Hasan, William Hasker, John Haugeland, Roger Hausheer, William Heald, Peter Heath, Richard Heck, John F. Heil, Vincent F. Hendricks, Stephen Hetherington, Francis Heylighen, Kathleen Marie Higgins, Risto Hilpinen, Harold T. Hodes, Joshua Hoffman, Alan Holland, Robert L. Holmes, Richard Holton, Brad W. Hooker, Terence E. Horgan, Tamara Horowitz, Paul Horwich, Vittorio Hösle, Paul Hoβfeld, Daniel Howard-Snyder, Frances Howard-Snyder, Anne Hudson, Deal W. Hudson, Carl A. Huffman, David L. Hull, Patricia Huntington, Thomas Hurka, Paul Hurley, Rosalind Hursthouse, Guillermo Hurtado, Ronald E. Hustwit, Sarah Hutton, Jonathan Jenkins Ichikawa, Harry A. Ide, David Ingram, Philip J. Ivanhoe, Alfred L. Ivry, Frank Jackson, Dale Jacquette, Joseph Jedwab, Richard Jeffrey, David Alan Johnson, Edward Johnson, Mark D. Jordan, Richard Joyce, Hwa Yol Jung, Robert Hillary Kane, Tomis Kapitan, Jacquelyn Ann K. Kegley, James A. Keller, Ralph Kennedy, Sergei Khoruzhii, Jaegwon Kim, Yersu Kim, Nathan L. King, Patricia Kitcher, Peter D. Klein, E. D. Klemke, Virginia Klenk, George L. Kline, Christian Klotz, Simo Knuuttila, Joseph J. Kockelmans, Konstantin Kolenda, Sebastian Tomasz Kołodziejczyk, Isaac Kramnick, Richard Kraut, Fred Kroon, Manfred Kuehn, Steven T. Kuhn, Henry E. Kyburg, John Lachs, Jennifer Lackey, Stephen E. Lahey, Andrea Lavazza, Thomas H. Leahey, Joo Heung Lee, Keith Lehrer, Dorothy Leland, Noah M. Lemos, Ernest LePore, Sarah-Jane Leslie, Isaac Levi, Andrew Levine, Alan E. Lewis, Daniel E. Little, Shu-hsien Liu, Shu-hsien Liu, Alan K. L. Chan, Brian Loar, Lawrence B. Lombard, John Longeway, Dominic McIver Lopes, Michael J. Loux, E. J. Lowe, Steven Luper, Eugene C. Luschei, William G. Lycan, David Lyons, David Macarthur, Danielle Macbeth, Scott MacDonald, Jacob L. Mackey, Louis H. Mackey, Penelope Mackie, Edward H. Madden, Penelope Maddy, G. B. Madison, Bernd Magnus, Pekka Mäkelä, Rudolf A. Makkreel, David Manley, William E. Mann (W.E.M.), Vladimir Marchenkov, Peter Markie, Jean-Pierre Marquis, Ausonio Marras, Mike W. Martin, A. P. Martinich, William L. McBride, David McCabe, Storrs McCall, Hugh J. McCann, Robert N. McCauley, John J. McDermott, Sarah McGrath, Ralph McInerny, Daniel J. McKaughan, Thomas McKay, Michael McKinsey, Brian P. McLaughlin, Ernan McMullin, Anthonie Meijers, Jack W. Meiland, William Jason Melanson, Alfred R. Mele, Joseph R. Mendola, Christopher Menzel, Michael J. Meyer, Christian B. Miller, David W. Miller, Peter Millican, Robert N. Minor, Phillip Mitsis, James A. Montmarquet, Michael S. Moore, Tim Moore, Benjamin Morison, Donald R. Morrison, Stephen J. Morse, Paul K. Moser, Alexander P. D. Mourelatos, Ian Mueller, James Bernard Murphy, Mark C. Murphy, Steven Nadler, Jan Narveson, Alan Nelson, Jerome Neu, Samuel Newlands, Kai Nielsen, Ilkka Niiniluoto, Carlos G. Noreña, Calvin G. Normore, David Fate Norton, Nikolaj Nottelmann, Donald Nute, David S. Oderberg, Steve Odin, Michael O’Rourke, Willard G. Oxtoby, Heinz Paetzold, George S. Pappas, Anthony J. Parel, Lydia Patton, R. P. Peerenboom, Francis Jeffry Pelletier, Adriaan T. Peperzak, Derk Pereboom, Jaroslav Peregrin, Glen Pettigrove, Philip Pettit, Edmund L. Pincoffs, Andrew Pinsent, Robert B. Pippin, Alvin Plantinga, Louis P. Pojman, Richard H. Popkin, John F. Post, Carl J. Posy, William J. Prior, Richard Purtill, Michael Quante, Philip L. Quinn, Philip L. Quinn, Elizabeth S. Radcliffe, Diana Raffman, Gerard Raulet, Stephen L. Read, Andrews Reath, Andrew Reisner, Nicholas Rescher, Henry S. Richardson, Robert C. Richardson, Thomas Ricketts, Wayne D. Riggs, Mark Roberts, Robert C. Roberts, Luke Robinson, Alexander Rosenberg, Gary Rosenkranz, Bernice Glatzer Rosenthal, Adina L. Roskies, William L. Rowe, T. M. Rudavsky, Michael Ruse, Bruce Russell, Lilly-Marlene Russow, Dan Ryder, R. M. Sainsbury, Joseph Salerno, Nathan Salmon, Wesley C. Salmon, Constantine Sandis, David H. Sanford, Marco Santambrogio, David Sapire, Ruth A. Saunders, Geoffrey Sayre-McCord, Charles Sayward, James P. Scanlan, Richard Schacht, Tamar Schapiro, Frederick F. Schmitt, Jerome B. Schneewind, Calvin O. Schrag, Alan D. Schrift, George F. Schumm, Jean-Loup Seban, David N. Sedley, Kenneth Seeskin, Krister Segerberg, Charlene Haddock Seigfried, Dennis M. Senchuk, James F. Sennett, William Lad Sessions, Stewart Shapiro, Tommie Shelby, Donald W. Sherburne, Christopher Shields, Roger A. Shiner, Sydney Shoemaker, Robert K. Shope, Kwong-loi Shun, Wilfried Sieg, A. John Simmons, Robert L. Simon, Marcus G. Singer, Georgette Sinkler, Walter Sinnott-Armstrong, Matti T. Sintonen, Lawrence Sklar, Brian Skyrms, Robert C. Sleigh, Michael Anthony Slote, Hans Sluga, Barry Smith, Michael Smith, Robin Smith, Robert Sokolowski, Robert C. Solomon, Marta Soniewicka, Philip Soper, Ernest Sosa, Nicholas Southwood, Paul Vincent Spade, T. L. S. Sprigge, Eric O. Springsted, George J. Stack, Rebecca Stangl, Jason Stanley, Florian Steinberger, Sören Stenlund, Christopher Stephens, James P. Sterba, Josef Stern, Matthias Steup, M. A. Stewart, Leopold Stubenberg, Edith Dudley Sulla, Frederick Suppe, Jere Paul Surber, David George Sussman, Sigrún Svavarsdóttir, Zeno G. Swijtink, Richard Swinburne, Charles C. Taliaferro, Robert B. Talisse, John Tasioulas, Paul Teller, Larry S. Temkin, Mark Textor, H. S. Thayer, Peter Thielke, Alan Thomas, Amie L. Thomasson, Katherine Thomson-Jones, Joshua C. Thurow, Vzalerie Tiberius, Terrence N. Tice, Paul Tidman, Mark C. Timmons, William Tolhurst, James E. Tomberlin, Rosemarie Tong, Lawrence Torcello, Kelly Trogdon, J. D. Trout, Robert E. Tully, Raimo Tuomela, John Turri, Martin M. Tweedale, Thomas Uebel, Jennifer Uleman, James Van Cleve, Harry van der Linden, Peter van Inwagen, Bryan W. Van Norden, René van Woudenberg, Donald Phillip Verene, Samantha Vice, Thomas Vinci, Donald Wayne Viney, Barbara Von Eckardt, Peter B. M. Vranas, Steven J. Wagner, William J. Wainwright, Paul E. Walker, Robert E. Wall, Craig Walton, Douglas Walton, Eric Watkins, Richard A. Watson, Michael V. Wedin, Rudolph H. Weingartner, Paul Weirich, Paul J. Weithman, Carl Wellman, Howard Wettstein, Samuel C. Wheeler, Stephen A. White, Jennifer Whiting, Edward R. Wierenga, Michael Williams, Fred Wilson, W. Kent Wilson, Kenneth P. Winkler, John F. Wippel, Jan Woleński, Allan B. Wolter, Nicholas P. Wolterstorff, Rega Wood, W. Jay Wood, Paul Woodruff, Alison Wylie, Gideon Yaffe, Takashi Yagisawa, Yutaka Yamamoto, Keith E. Yandell, Xiaomei Yang, Dean Zimmerman, Günter Zoller, Catherine Zuckert, Michael Zuckert, Jack A. Zupko (J.A.Z.)
- Edited by Robert Audi, University of Notre Dame, Indiana
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- Book:
- The Cambridge Dictionary of Philosophy
- Published online:
- 05 August 2015
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- 27 April 2015, pp ix-xxx
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M13 Bacteriophage Biolaminates for Nanomaterials with Improved Stiffness
- Christopher M. Warner, Amitabh Ghoshal, Michael F. Cuddy, Aimee R. Poda, Natalie D. Barker, Daniel E. Morse, Seung-Wuk Lee, Edward J. Perkins
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1722 / 2015
- Published online by Cambridge University Press:
- 16 June 2015, mrsf14-1722-f11-03
- Print publication:
- 2015
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In nature, biomolecules guide the formation of hierarchically-ordered, lightweight, inorganic-organic composites such as corals, shells, teeth and bones. M13 bacteriophage has been used to mimic bio-inspired material development due to its rigid, nanoscale rod-like morphology. Liquid-crystalline monolayers of genetically engineered phage have been used to template crystallization of thin layers of inorganic and metallic materials. We have created thin films composed of engineered M13 phage capable of binding inorganic components. We employed both a dip-cast and a drop-cast film fabrication method on both smooth and rough gold, silica and glass casting surfaces to create thin films and 3D structures of various degrees of hierarchical order. We have found the engineered M13 phage and the inorganic mineral significantly affected both film morphology and the mechanical properties of the film. Similarly, film fabrication parameters such as solution chemistry, temperature, and pulling speed affected film properties. Using a calcium phosphate biomineralized 4E phage, film thickness increased linearly with the number of layers/dips in the phage solution. The stiffness of these composites (Young's modulus) were >80 GPa for mineralized, multilayer films. These materials are an order of magnitude stiffer than the biological equivalent collagen. Stiffness, however, does not appear to increase in a multilayer film beyond a saturation point. Ultimately, we have developed a platform for phage-based bio-composites for developing high performance materials.
Transforming large-scale industrially produced carbon nanotubes to high-performance electrode materials for lithium-ion batteries
- Hong-Li Zhang, Daniel E. Morse
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- Journal:
- Journal of Materials Research / Volume 27 / Issue 2 / 28 January 2012
- Published online by Cambridge University Press:
- 13 December 2011, pp. 410-416
- Print publication:
- 28 January 2012
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Large-scale industrial production of carbon nanotubes (CNTs) has recently become available, but there are relatively few reports of the investigation of these industrially produced bulk CNTs as potential electrode materials for electrochemical energy storage such as lithium-ion batteries (LIBs). Here, we report our evaluation of the electrochemical performance of the industrially produced CNTs from one manufacturer and our utilization of a kinetically controlled, vapor diffusion synthesis method combined with in-situ carbothermal reduction to homogeneously grow nanocrystalline tin (Sn) particles (∼200 nm) in the matrix of the CNTs, yielding a Sn@CNTs composite. After surface coating with a layer of carbon coating (3–4 nm), this composite was transformed to a surface-modified Sn@CNTs composite that exhibited much higher reversible capacity, initial Coulombic efficiency, and rate capacity than the pristine CNTs as anode materials for LIB.
Organic broccoli production on transition soils: Comparing cover crops, tillage and sidedress N
- Daniel L. Schellenberg, Ronald D. Morse, Gregory E. Welbaum
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- Journal:
- Renewable Agriculture and Food Systems / Volume 24 / Issue 2 / June 2009
- Published online by Cambridge University Press:
- 26 February 2009, pp. 85-91
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Little information is available about how farmers in transition to organic practices should manage short- and long-term N fertility. The objectives of this research were (1) to evaluate the leguminous cover crops lablab (Dolichos lablab L.), soybean (Glycine max L.), sunn hemp (Crotalaria juncea L.) and a mixture of sunn hemp and cowpea (Vigna sinensis Endl.) as N sources; (2) to compare N availability and broccoli yield when cover crops were incorporated with conventional tillage (CT) or retained as a surface mulch using no-tillage (NT) practices; and (3) to quantify the amount of supplemental sidedress nitrogen required to maximize the yield of organic broccoli (Brassica oleracea Group Italica) on transition soils. Broccoli was grown during the first year after organic transition in the spring and fall of 2006 at the Kentland Agricultural Research Farm near Blacksburg, VA. Spring (P<0.001) and fall (P<0.001) broccoli yield increased as the rate of sidedress N was increased up to 112 kg N ha−1, and showed a quadratic correlation with leaf N (P=<0.001, R2=0.80 and P=<0.001, R2=0.38, respectively). There was no difference in spring broccoli yield between CT and NT; however, CT produced the highest yield in the fall crop. At low sidedress N rates, leaf N was highest in CT plots, but tillage had no effect on N uptake at high N rates. This indicates that early season and perhaps total plant-available mineralized N was greater in CT than NT; however, potential N deficiency in NT soil may be compensated by sidedress N. Broccoli yield was not affected by leguminous cover crop, even though the quantity of cover crop biomass and N contribution was different among species. This suggests that N availability from leguminous cover crops may be impacted by other ecological processes such as soil microbial activity. This study shows that organic CT and NT growers can maximize broccoli yield in transition soils low in N availability, by using leguminous cover crops in combination with moderate amounts of sidedress N.
Low temperature growth and laser-induced phase transformation of perovskite oxide films for uncooled IR detector applications
- Wendy Sarney, John W Little, Frank E Livingston, Krisztian Niesz, Melanie W Cole, Daniel E Morse
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1199 / 2009
- Published online by Cambridge University Press:
- 31 January 2011, 1199-F03-56
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- 2009
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Pyroelectric infrared (IR) detectors based on perovskite oxides are of interest in part because of their lack of need for cooling, which makes them relatively more affordable and operationally simpler than cooled photon detector systems. We are investigating two methods for low-cost growth of perovskite oxide thin films, namely, a bio-inspired, low-temperature synthesis method and a modified industry-standard metalorganic solution deposition (MOSD) method. Subsequent to film synthesis, we utilize direct-write laser phase conversion and micro-electro-mechanical systems (MEMS) fabrication for development of an uncooled IR focal plane array (FPA). Film growth, crystallization and MEMS processes are compatible with monolithic integration of the detector pixels directly onto Si readout integrated circuits (ROICs).
Very Low-Temperature, Gram-Scale Synthesis of Monodisperse BaTiO3 Nanocrystals via an Interfacial Hydrolysis Reaction
- Daniel E. Morse, Richard L. Brutchey
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1094 / 2008
- Published online by Cambridge University Press:
- 01 February 2011, 1094-DD05-01
- Print publication:
- 2008
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A vapor diffusion sol-gel method is reviewed for the preparation of high-quality BaTiO3 nanocrystals on the gram scale at very low temperatures. The synthesis is based on the kinetically controlled introduction of water into a solution of the bimetallic alkoxide, BaTi(O2C4H9)6, where slow hydrolysis then occurs at the vapor-solution interface followed by nucleation and nanocrystal growth at 16 °C. The resulting 6-nm, quasi-spherical nanocrystals are both monodisperse (without stabilizing agents or size selecting purification) and highly crystalline (without any post-synthesis heat treatment), and are isolated in yields near 100%. Based on new permittivity and calorimetry data, the crystal structure of the nanocrystals is most likely in the paraelectric cubic phase (space group Pm3m) at room temperature, which corroborates previous diffraction data. It was also demonstrated that the BaTiO3 nanocrystals can be doped with trivalent lanthanum cations using the same low-temperature vapor diffusion sol-gel method to yield donor-doped Ba1−xLaxTiO3, which exhibits a considerable PTCR effect.
Micromechanical properties of biological silica in skeletons of deep-sea sponges
- Alexander Woesz, James C. Weaver, Murat Kazanci, Yannicke Dauphin, Joanna Aizenberg, Daniel E. Morse, Peter Fratzl
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- Journal:
- Journal of Materials Research / Volume 21 / Issue 8 / August 2006
- Published online by Cambridge University Press:
- 01 August 2006, pp. 2068-2078
- Print publication:
- August 2006
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The silica skeleton of the deep-sea sponge Euplectella aspergillum was recently shown to be structured over at least six levels of hierarchy with a clear mechanical functionality. In particular, the skeleton is built of laminated spicules that consist of alternating layers of silica and organic material. In the present work, we investigated the micromechanical properties of the composite material in spicules of Euplectella aspergillum and the giant anchor spicule of Monorhaphis chuni. Organic layers were visualized by backscattered electron imaging in the environmental scanning electron microscope. Raman spectroscopic imaging showed that the organic layers are protein-rich and that there is an OH-enrichment in silica near the central organic filament of the spicule. Small-angle x-ray scattering revealed the presence of nanospheres with a diameter of only 2.8 nm as the basic units of silica. Nanoindentation showed a considerably reduced stiffness of the spicule silica compared to technical quartz glass with different degrees of hydration. Moreover, stiffness and hardness were shown to oscillate as a result of the laminate structure of the spicules. In summary, biogenic silica from deep-sea sponges has reduced stiffness but an architecture providing substantial toughening over that of technical glass, both by structuring at the nanometer and at the micrometer level.
High-speed photography of the development of microdamage in trabecular bone during compression
- Philipp J. Thurner, Blake Erickson, Zachary Schriock, John Langan, Jeff Scott, Maria Zhao, James C. Weaver, Georg E. Fantner, Patricia Turner, Johannes H. Kindt, Georg Schitter, Daniel E. Morse, Paul K. Hansma
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- Journal:
- Journal of Materials Research / Volume 21 / Issue 5 / May 2006
- Published online by Cambridge University Press:
- 01 May 2006, pp. 1093-1100
- Print publication:
- May 2006
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The mechanical properties of healthy and diseased bone tissue were extensively studied in mechanical tests. Most of this research was motivated by the immense costs of health care and social impacts due to osteoporosis in post-menopausal women and the aged. Osteoporosis results in bone loss and change of trabecular architecture, causing a decrease in bone strength. To address the problem of assessing local failure behavior of bone, we combined mechanical compression testing of trabecular bone samples with high-speed photography. In this exploratory study, we investigated healthy, osteoarthritic, and osteoporotic human vertebral trabecular bone compressed at high strain rates. Apparent strains were found to transfer into to a broad range of local strains. Strained trabeculae were seen to whiten with increasing strain. Comparison of whitened regions seen in high-speed photography sequences with scanning electron micrographs showed that the observed whitening was due to the formation of microcracks. From the results of a motion energy filter applied to the recorded movies, we saw that the whitened areas are, presumably, also areas of high deformation. In summary, high-speed photography allows the detection of microdamage in real time, leading toward a better understanding of the local processes involved in bone failure.
Angular Fourier Mapping; Highlighting lattice structures without destroying original data
- Johannes H. Kindt, James B. Thompson, George T. Paloczi, Martina Michenfelder, Bettye L. Smith, Galen Stucky, Daniel E. Morse, Paul K. Hansma
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- Journal:
- MRS Online Proceedings Library Archive / Volume 620 / 2000
- Published online by Cambridge University Press:
- 14 March 2011, M4.2.1
- Print publication:
- 2000
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A two-dimensional Fourier transformation, FT, is used to isolate two different lattice structures within one scanning probe microscope, SPM, image. The isolated structures are then used to create a two-color map that encodes the presence of these structures within the image. The color map is normalized in brightness and then used to color-code the original black and white SPM data. The distribution of different structures becomes obvious, while all original brightness information is preserved in this combined image.
Learning From Biological Systems: Novel Routes to Biomimetic Synthesis of Ordered Silica Structures
- Jennifer N. Chal, Katsuhiko Shimizu, Yan Zhou, Sean C. Christiansen, Bradley F. Chmelka, Timothy J. Deming, Galen D. Stucky, Daniel E. Morse
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- Journal:
- MRS Online Proceedings Library Archive / Volume 599 / 1999
- Published online by Cambridge University Press:
- 10 February 2011, 239
- Print publication:
- 1999
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Biological systems have evolved mechanisms that precisely control inorganic structures on both the micro- and nanoscale, operating at ambient pressures and temperatures. In both the calcium carbonate, calcium phosphate and silicon dioxide utilizing organisms, proteins and polysaccharides have been found to play integral roles in the organization of these biominerals[1–3]. The organic constituents generally have been thought to act as direct templates or modulators for the deposition of the particular mineral. We have explored the synthesis and structural control of silica by the marine sponge, Tethya aurantia. Needles of amorphous silica comprise the skeletal system of this organism, representing 75% of the dry weight of the organism. These glassy needles, called spicules, are 2 mm in length and 30 μn in width[4,5]. We have characterized the structure, genetics and functions of the proteins that form an occluded axial filament within each silica spicule. Based on our discovery, a unique structure-directing catalytic mechanism exhibited by these protein filaments, and the structural determinants responsible for the catalytic activity, we have designed novel block copolypeptides that catalyze and spatially direct he condensation of silicon alkoxides to form organized silica structures ranging from transparent spheres to lath-like structures at ambient pressure, low temperature and neutral pH.
Genetic Coding in Biomineralization of Microlaminate Composites
- Daniel E. Morse, Marios A. Cariolou, Galen D. Stucky, Charlotite M. Zaremba, Paul K. Hansma
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- Journal:
- MRS Online Proceedings Library Archive / Volume 292 / 1992
- Published online by Cambridge University Press:
- 15 February 2011, 59
- Print publication:
- 1992
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Biomineralization is precisely controlled by complex templating relationships ultimately encoded in the genes. In the formation of the molluscan shell, polyanionic pleated sheet proteins serve as templates for the nucleation and epitaxial growth of calcium carbonate crystalline domains to yield microlaminate composites of exceptional strength and crystal ordering. The strength and fracture-resistance of these composites far exceed those of the minerals themselves, as a result of both the capacity for flexible deformation of the organic matrix layers and the retardation of crack propagation at each mineral-organic interface. The basic principles controlling low temperature biosynthesis of these materials thus are of both fundamental and applied importance. The abalone shell consists of microlaminates with a remarkable regularity of lamina thickness (ca. 0.5 micron), the formation of which defies present understanding. We have found that shells of abalone larvae formed prior to metamorphosis contain only aragonite, whereas the adult shell made after metamorphosis contains both aragonite and calcite. This transition is accompanied by a switch in genetic expression of the template proteins, suggesting that the premetamorphic protein may serve as a template for aragonite nucleation and growth, while template proteins synthesized after metamorphosis may direct crystallization of calcite. These analyses are based on improvements we recently reported for the detection and purification of proteins from the demineralized shell matrix. Genetic cloning experiments now in progress are aimed at discovering additional protein sequences responsible for the programmed control of crystal phase termination, since it is the termination and reinitiation of mineralization that is responsible for the regularity of highly ordered microlaminates produced in nature.