WorldWideScience

Sample records for biomineralization precursors clusters

  1. Biomineralization of a Self-assembled, Soft-Matrix Precursor: Enamel

    Science.gov (United States)

    Snead, Malcolm L.

    2015-04-01

    Enamel is the bioceramic covering of teeth, a composite tissue composed of hierarchical organized hydroxyapatite crystallites fabricated by cells under physiologic pH and temperature. Enamel material properties resist wear and fracture to serve a lifetime of chewing. Understanding the cellular and molecular mechanisms for enamel formation may allow a biology-inspired approach to material fabrication based on self-assembling proteins that control form and function. A genetic understanding of human diseases exposes insight from nature's errors by exposing critical fabrication events that can be validated experimentally and duplicated in mice using genetic engineering to phenocopy the human disease so that it can be explored in detail. This approach led to an assessment of amelogenin protein self-assembly that, when altered, disrupts fabrication of the soft enamel protein matrix. A misassembled protein matrix precursor results in loss of cell-to-matrix contacts essential to fabrication and mineralization.

  2. Clustering chlorine reactivity of haloacetic acid precursors in inland lakes.

    Science.gov (United States)

    Zeng, Teng; Arnold, William A

    2014-01-01

    Dissolved organic matter (DOM) represents the major pool of organic precursors for harmful disinfection byproducts, such as haloacetic acids (HAAs), formed during drinking water chlorination, but much of it remains molecularly uncharacterized. Knowledge of model precursors is thus a prerequisite for understanding the more complex whole water DOM. The utility of HAA formation potential data from model DOM precursors, however, is limited due to the lack of comparability to water samples. In this study, the formation kinetics of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the two predominant HAA species, were delineated upon chlorination of seventeen model DOM precursors and sixty-eight inland lake water samples collected from the Upper Midwest region of the United States. Of particular interest was the finding that the DCAA and TCAA formation rate constants could be grouped into four statistically distinct clusters reflecting the core structural features of model DOM precursors (i.e., non-β-diketone aliphatics, β-diketone aliphatics, non-β-diketone phenolics, and β-diketone phenolics). A comparative approach built upon hierarchical cluster analysis was developed to gain further insight into the chlorine reactivity patterns of HAA precursors in inland lake waters as defined by the relative proximity to four model precursor clusters. This work highlights the potential for implementing an integrated kinetic-clustering approach to constrain the chlorine reactivity of DOM in source waters.

  3. Surface reconstruction precursor to melting in Au309 clusters

    Directory of Open Access Journals (Sweden)

    Fuyi Chen

    2011-09-01

    Full Text Available The melting of gold cluster is one of essential properties of nanoparticles and revisited to clarify the role played by the surface facets in the melting transition by molecular dynamics simulations. The occurrence of elaborate surface reconstruction is observed using many-body Gupta potential as energetic model for 309-atom (2.6 nm decahedral, cuboctahedral and icosahedral gold clusters. Our results reveal for the first time a surface reconstruction as precursor to the melting transitions. The surface reconstruction lead to an enhanced melting temperature for (100 faceted decahedral and cuboctahedral cluster than (111 faceted icosahedral gold cluster, which form a liquid patch due to surface vacancy.

  4. Cluster self-organization of silicate and germanate systems: Invariant suprapolyhedral cluster precursors and self-assembly of the crystal structures of Li,TR silicates (germanates)

    International Nuclear Information System (INIS)

    The initial stages of formation of suprapolyhedral clusters (containing polyhedra of different types) in an evolving chemical system are considered. The suprapolyhedral clusters of the chain and cyclic types are used for modeling two-dimensional periodic structures. The developed model is used to search for cluster precursors in the structures of Li,TR silicates (germanates) of the known structure types. The complete threedimensional reconstruction of the self-assembly of Li,TR silicates (germanates) is performed using computer methods (with the TOPOS program package) according to the following scheme: cluster precursor → primary chain → microlayer → microframework (supraprecursor) → ... framework. Two types of invariant cyclic cluster precursors composed of the TR polyhedra linked by tetrahedra and the TR polyhedra joined by diorthotetrahedra are identified in five and two structures, respectively. It is revealed that the lithium atoms are located at the centers of all clusters. New types of two-dimensional nets with a hierarchical structure formed as a result of the packing of cyclic four-, six-, and eight-node clusters are described.

  5. Biomineralization: mineral formation by organisms

    Science.gov (United States)

    Addadi, Lia; Weiner, Steve

    2014-09-01

    Organisms form many different types of minerals, with diverse shapes and sizes. These minerals fulfill a variety of functions. Inspired by the late H A Lowenstam, Steve Weiner and Lia Addadi have addressed many questions that relate to the mechanisms by which biological organisms produce these mineral phases and how their structures relate to their functions. Addadi and Weiner have explored the manner in which macromolecules extracted from mineralized tissues can interact with some crystal planes and not others, how these macromolecules can be occluded inside the forming crystals residing preferentially on specific crystal planes, and how they can induce one polymorph of calcium carbonate and not another to nucleate. Addadi and Weiner have also identified a novel strategy used by the sea urchin to form its smooth and convoluted mineralized skeletal elements. The strategy involves the initial production by cells of a highly disordered mineral precursor phase in vesicles, and then the export of this so-called amorphous phase to the site of skeletal formation, where it crystallizes. This strategy is now known to be used by many different invertebrate phyla, as well as by vertebrates to build bones and teeth. One of the major current research aims of the Weiner--Addadi group is to understand the biomineralization pathways whereby ions are extracted from the environment, are transported and deposited inside cells within vesicles, how these disordered phases are then transferred to the site of skeletal formation, and finally how the so-called amorphous phase crystallizes. Biology has clearly evolved unique strategies for forming crystalline minerals. Despite more than 300 years of research in this field, many challenging questions still remain unanswered.

  6. Hybrid Cluster Precursors of the LaZrO Insulator for Transistors: Properties of High-Temperature-Processed Films and Structures of Solutions, Gels, and Solids.

    Science.gov (United States)

    Li, Jinwang; Zhu, Peixin; Hirose, Daisuke; Kohara, Shinji; Shimoda, Tatsuya

    2016-01-01

    In the solution processing of oxide electronics, the structure of metal-organic precursors in solution and their effect on processability and on the final structure and properties of the oxide have rarely been studied. We have observed that hybrid clusters, having inorganic cores coordinated by organic ligands, are the typical form of metal-organic precursor structures. For insulating ternary LaZrO, improved synthesis of the cluster precursor under solvothermal conditions led to low-temperature deposition of the film at 200 °C, as we will report in another paper. In the current paper, we first briefly show that solvothermal synthesis of the precursor resulted in significantly improved insulating properties (e.g., two orders lower leakage current) of high-temperature-annealed films, and then focus on the structural analysis of the cluster precursors and annealed solids and relate the results to the significant improvement of properties by solvothermal treatment of solutions. A change in the cluster core toward structural unification was brought about by solvothermal treatment, resulting in higher uniformity and higher stability of clusters. The final structure of the material maintained the features of the core structure in solution, even after annealing at high temperatures. These results demonstrate the key role played by designing cluster structure in solution. PMID:27411971

  7. Zintl Clusters as Wet-Chemical Precursors for Germanium Nanomorphologies with Tunable Composition.

    Science.gov (United States)

    Bentlohner, Manuel M; Waibel, Markus; Zeller, Patrick; Sarkar, Kuhu; Müller-Buschbaum, Peter; Fattakhova-Rohlfing, Dina; Fässler, Thomas F

    2016-02-12

    [Ge9](4-) Zintl clusters are used as soluble germanium source for a bottom-up fabrication of Ge nanomorphologies such as inverse opal structures with tunable composition. The method is based on the assembly and oxidation of [Ge9 ](4-) clusters in a template mold using SiCl4 , GeCl4 , and PCl3 leading to Si and P-containing Ge phases as shown by X-ray diffraction, Raman spectroscopy, and energy-dispersive X-ray analysis. [Ge9](4-) clusters are retained using ethylenediamine (en) as a transfer medium to a mold after removal of the solvent if water is thoroughly excluded, but are oxidized to amorphous Ge in presence of water traces. (1)H NMR spectroscopy reveals the oxidative deprotonation of en by [Ge9](4-). Subsequent annealing leads to crystalline Ge. As an example for wet-chemical synthesis of complex Ge nanomorphologies, we describe the fabrication of undoped and P-doped inverse opal-structured Ge films with a rather low oxygen contents. The morphology of the films with regular volume porosity is characterized by SEM, TEM, and grazing incidence small-angle X-ray scattering. PMID:26633085

  8. Evolutionary origins of animal skeletal biomineralization.

    Science.gov (United States)

    Murdock, Duncan J E; Donoghue, Philip C J

    2011-01-01

    The evolutionary history of biomineralization in animals is crucial to our understanding of modern mineralized tissues. Traditional methods of unravelling this history have aimed to derive a theory of the development of biomineralization through evolution by the comparison of mineralized systems in model organisms. This has led to the recognition of the 'biomineralization toolkit' and raised the question of the homology of mineralized tissues versus convergent or parallel evolution. The 'new animal phylogeny' reveals that many of the groups known to biomineralize sit among close relatives that do not, and it favours an interpretation of convergent or parallel evolution for biomineralization in animals. In addition, the fossil record of the earliest mineralized skeletons presents a rapid proliferation of biomineralization across a range of animal phyla with fossil representatives of many modern biomineralizing phyla. A synthesis of molecular, developmental, phylogenetic and fossil evidence demonstrates the convergent or parallel evolution of biomineralization in animals at the phylum level. The fossil record of the Cambrian explosion not only provides vital evidence for the evolution of animal mineralized tissues but also suggests a mechanism for its rapid and synchronous convergent origin. PMID:21625061

  9. Biomineralization

    DEFF Research Database (Denmark)

    Sand, K. K.; Pedersen, C. S.; Sjöberg, S.;

    2014-01-01

    a modern coccolithophorid, Emiliania huxleyi. We generated surface complexation constants for the branch components: malonate: 14.25 ± 0.17, succinate: 11.91 ± 0.06, tricarballylate: 14.86 ± 0.04, and citrate: 15.25 ± 0.04. The implication is that complex PS could hold promise for smart material...

  10. Genomic Insights into the Biomineralization and Environmental Function of Magnetotactic Bacteria

    Science.gov (United States)

    Lin, W.; Pan, Y.

    2015-12-01

    Microorganisms have populated the Earth for billions of years and their activities are important biologic forces shaping our planetary environments. Microbial biomineralization that selectively take up environmental elements (e.g., C, S, P, Fe) and synthesize minerals either intracellularly or extracellularly is of great interest. One of the most interesting examples of these types of organisms are magnetotactic bacteria (MTB), a polyphyletic group of prokaryotes that uptake iron from aquatic habitats and biomineralize intracellular nano-sized iron minerals of magnetite (Fe3O4) and/or greigite (Fe3S4), known as magnetosomes, and orientate and swim along the Earth's magnetic field. However, our knowledge on the biomineralization mechanisms of MTB and their environmental function remains very limited because the genomic information of most MTB is still not fully understood. By using metagenomic approaches, we have acquired genomic sequences of environmental MTB communities and discovered several conserved genomic fragments containing gene operons for magnetite or greigite biomineralization from Proteobacteria and Nitrospirae MTB. The comparison of these gene clusters has provided valuable insights into the origin and evolution of magnetosome biomineralization. We further obtained several draft genomes of uncultivated MTB belonging to the phylum Nitrospirae, which reveals a metabolic flexibility of this poorly understood magnetotactic group and indicates their considerable roles in the biogeochemical cycles of iron and sulfur.

  11. Single-step co-deposition of nanostructured tungsten oxide supported gold nanoparticles using a gold–phosphine cluster complex as the gold precursor

    International Nuclear Information System (INIS)

    The use of a molecular gold organometallic cluster in chemical vapour deposition is reported, and it is utilized, together with a tungsten oxide precursor, for the single-step co-deposition of (nanostructured) tungsten oxide supported gold nanoparticles (NPs). The deposited gold-NP and tungsten oxide supported gold-NP are highly active catalysts for benzyl alcohol oxidation; both show higher activity than SiO2 supported gold-NP synthesized via a solution-phase method, and tungsten oxide supported gold-NP show excellent selectivity for conversion to benzaldehyde. (paper)

  12. Comparison of neurosphere-like cell clusters derived from dental follicle precursor cells and retinal Müller cells

    DEFF Research Database (Denmark)

    Beck, Hans Christian; Petersen, Jørgen; Felthaus, Oliver;

    2011-01-01

    Unrelated cells such as dental follicle precursor cells (DFPCs) and retinal Müller cells (MCs) make spheres after cultivation in serum-replacement medium (SRM). Until today, the relation and molecular processes of sphere formation from different cell types remain undescribed. Thus in this study we...

  13. Uranium Biomineralization by Caulobacter crescentus

    Science.gov (United States)

    Jiao, Y.; Yung, M.; Park, D.

    2014-12-01

    It is well known that microorganisms are able to mediate removal of U(VI) from solution through reduction to insoluble U(IV) oxides under anaerobic conditions, but microbial transformation of U(VI) under aerobic conditions are less well understood. Here, we describe two processes of U(VI) transformation by the aerobic bacterium Caulobacter crescentus, known for its ubiquitous presence in aquatic systems and high U(VI) tolerance. U(VI) causes a temporary growth arrest in Caulobacter and growth recovery is not due to a decrease in U solubility, a common detoxification strategy employed by other microorganisms. Through functional reporter assays, we discovered that Caulobacter is able to reduce U(VI) bioavailability through a metabolism-dependent increase of medium pH, representing a novel U detoxification strategy. Upon recovery from growth arrest, Caulobacter proliferates with normal growth kinetics, accompanied by active U(VI) biomineralization. We found that phosphate metabolism is actively involved in the formation of U-P precipitates that are similar to autunite-group minerals. Comparisons of growth and U(VI) precipitation by wild type versus a phosphatase mutant indicates that extra-cytoplasmic phosphatase activity is not only responsible for the formation of cell-surface-bound U-P precipitates, but also plays an important role in cell survival under U stress. Our results highlight the importance of aerobic bacterial metabolism for U biogeochemistry.

  14. The magnetosome model: insights into the mechanisms of bacterial biomineralization

    OpenAIRE

    Rahn-Lee, Lilah; Komeili, Arash

    2013-01-01

    Though the most ready example of biomineralization is the calcium phosphate of vertebrate bones and teeth, many bacteria are capable of creating biominerals inside their cells. Because of the diversity of these organisms and the minerals they produce, their study may reveal aspects of the fundamental mechanisms of biomineralization in more complex organisms. The best-studied case of intracellular biomineralization in bacteria is the magnetosome, an organelle produced by a diverse group of aqu...

  15. The Magnetosome Model: Insights into the Mechanisms of Bacterial Biomineralization

    OpenAIRE

    Lilah eRahn-Lee; Arash eKomeili

    2013-01-01

    Though the most ready example of biomineralization is the calcium phosphate of vertebrate bones and teeth, many bacteria are capable of creating biominerals inside their cells. Because of the diversity of these organisms and the minerals they produce, their study may reveal aspects of the fundamental mechanisms of biomineralization in more complex organisms. The best-studied case of intracellular biomineralization in bacteria is the magnetosome, an organelle produced by a diverse group of a...

  16. Biomineral Structure and Strength of Barnacle Exoskeletons

    Science.gov (United States)

    Swift, Nathan

    2011-03-01

    Studying the construction of organic-inorganic compound structures through biomineralization is potentially very useful. During biomineral formation, organisms restructure naturally occurring minerals in conjunction with their own organically produced minerals to create new structures. While there is extensive knowledge about material properties and structure of the raw minerals themselves, insight into how specific biomineral structures and compounds contribute to an object's mechanical properties is lacking. In this study, the exoskeletons of barnacles from the genus Balanus were examined, both for their physical structure (how they're put together) and for their mechanical properties (strength, hardness, and elasticity). Scanning electron microscopy produced close-up, detailed images of the inner shell structure to determine what type of structure barnacles build during exoskeleton formation. Energy dispersive x-ray spectroscopy was used to map the elemental components of the shells. Nanoindentation tested the mechanical properties of these mapped structures to determine how certain characteristics of the exoskeleton contribute to its mechanical properties.

  17. Biominerals at the nanoscale: transmission electron microscopy methods for studying the special properties of biominerals

    DEFF Research Database (Denmark)

    Posfai, Mihaly; Kasama, Takeshi; Dunin-Borkowski, Rafal E.

    2013-01-01

    Biominerals have important functions in living organisms: apatite crystals are responsible for the strength of our bones and the hardness of our teeth, calcite and aragonite are used by many organisms for making shells, and magnetite and greigite help bacteria and birds to navigate in magnetic...... fields. In order to fulfill their roles in organisms, biominerals have strictly controlled physical and chemical properties. Transmission electron microscopy (TEM) is ideally suited for the study of the structures, arrangements, compositions, morphologies, crystallographic orientations, crystallographic...

  18. Biomineralization of uraninite and uranyl phosphate controlled by organic acids

    International Nuclear Information System (INIS)

    Biomineralization of uraninite (UO2) and uranyl phosphate minerals are both able to decrease the mobility of uranium in the environment. We examined biomineralization of UO2 and uranyl phosphate by Shewanella putrefaciens in the basic medium containing lactate as an electron donor, β- glycerolphosphate as a phosphorous source, and uranyl nitrate in the absence and presence of weak or strong complexing organic acids (WCOA or SCOA) under an anaerobic condition. In the basic medium, only biomineralization of UO2 was observed because of rapid reduction of U(VI). Biomineralization of UO2 and uranyl phosphate occurred in the media with WCOA, however the no biomineralization was occurred in the presence of SCOA. It is thought that formation of stable U(VI)-, and U(IV)- organic complexes prevents the biomineralization. These finding suggest that coexisting organic acids control the biomineralization of UO2 and uranyl phosphate minerals by microorganisms. (author)

  19. Biomineralization and magnetism of bacterial magnetosomes

    Institute of Scientific and Technical Information of China (English)

    PAN Yongxin; DENG Chenglong; LIU Qingsong; Nikolai Petersen; ZHU Rixiang

    2004-01-01

    Magnetosomes of magnetotactic bacteria are of great interest in understanding biomineralization and possible links between organisms and geomagnetic field. Fossil magnetosomes are ubiquitous in marine and lake sediments and may significantly contribute to magnetic signals. In this review, we firstly introduce some characteristics of magnetotactic bacteria, followed by considering recent progress in magnetosome formation, magnetic measurements, and identification of bacterial magnetites in bulk sediments as well as their paleoenvironmental implications. Finally, we briefly discuss potential future breakthroughs in magnetosome studies and its applications.

  20. Testing fundamentals: The chemical state of geochemical tracers in biominerals.

    Science.gov (United States)

    Branson, O.; Redfern, S. A. T.; Read, E.; Elderfield, H.

    2015-12-01

    The use of many carbonate-derived geochemical proxies is underpinned by the assumption that tracer elements are incorporated 'ideally' as impurities the mineral lattice, following relatively straightforward kinetic and thermodynamic drives. This allows comparison to inorganic precipitation experiments, and provides a systematic starting point from which to translate geochemical tracers to environmental records. Biomineral carbonates are a prominent source of geochemical proxy material, and are far from an ideal inorganic system. They are structurally and compositionally heterogeneous mineral-organic composites, produced in tightly controlled biological environments, possibly via non-classical crystal growth mechanisms. Biominerals offer numerous opportunities for tracers to be incorporated in a 'non-ideal' state. For instance, tracers could be hosted within the organic component of the structure, in interstitial micro-domains of a separate mineral phase, or in localized high-impurity clusters. If a proxy element is hosted in a non-ideal state, our understanding of its incorporation and preservation is flawed, and the theoretical basis behind the proxies derived from it must be reevaluated. Thus far, the assumption of ideal tracer incorporation has remained largely untested, owing to the spatial resolution and sensitivity limits of available techniques. Developments in high-resolution, high-sensitivity X-ray spectroscopy at Scanning Transmission X-Ray Microscopes (STXMs) have allowed us to measure trace element coordination in foraminiferal calcite, at length-scales relevant to biomineralisation processes and tracer incorporation. This instrument has allowed us to test the fundamental assumptions behind several geochemical proxy elements. We present a summary of four STXM studies, assessing the chemical state and distribution of Mg (Branson et al, 2014), B (Branson et al, 2015), S and Na (unpub.), and highlight the implications of these data for the use of these

  1. Hierarchical structure and biomineralization in cricket tooth

    CERN Document Server

    Xing, Xueqing; Cai, Quan; Mo, Guang; Du, Rong; Chen, Zhongjun; Wu, Zhonghua

    2012-01-01

    Cricket is a truculent insect with stiff and sharp teeth as a fighting weapon. The structure and possible biomineralization of the cricket teeth are always interested. Synchrotron radiation X-ray fluorescence, X-ray diffraction and small angle X-ray scattering techniques were used to probe the element distribution, possible crystalline structures and size distribution of scatterers in cricket teeth. Scanning electron microscope was used to observe the nanoscaled structure. The results demonstrate that Zn is the main heavy element in cricket teeth. The surface of the cricket teeth has a crystalline compound like ZnFe2(AsO4)2(OH)2(H2O)4. While, the interior of the teeth has a crystalline compound like ZnCl2, which is from the biomineralization. The ZnCl2-like biomineral forms nanoscaled microfibrils and their axial direction points at the top of tooth cusp. The microfibrils aggregate random into intermediate filaments, forming a hierarchical structure. A sketch map of the cricket tooth cusp was proposed and a d...

  2. Clustering

    Directory of Open Access Journals (Sweden)

    Jinfei Liu

    2013-04-01

    Full Text Available DBSCAN is a well-known density-based clustering algorithm which offers advantages for finding clusters of arbitrary shapes compared to partitioning and hierarchical clustering methods. However, there are few papers studying the DBSCAN algorithm under the privacy preserving distributed data mining model, in which the data is distributed between two or more parties, and the parties cooperate to obtain the clustering results without revealing the data at the individual parties. In this paper, we address the problem of two-party privacy preserving DBSCAN clustering. We first propose two protocols for privacy preserving DBSCAN clustering over horizontally and vertically partitioned data respectively and then extend them to arbitrarily partitioned data. We also provide performance analysis and privacy proof of our solution..

  3. Biomineralization in bryozoans: present, past and future.

    Science.gov (United States)

    Taylor, Paul D; Lombardi, Chiara; Cocito, Silvia

    2015-11-01

    Many animal phyla have the physiological ability to produce biomineralized skeletons with functional roles that have been shaped by natural selection for more than 500 million years. Among these are bryozoans, a moderately diverse phylum of aquatic invertebrates with a rich fossil record and importance today as bioconstructors in some shallow-water marine habitats. Biomineralizational patterns and, especially, processes are poorly understood in bryozoans but are conventionally believed to be similar to those of the related lophotrochozoan phyla Brachiopoda and Mollusca. However, bryozoan skeletons are more intricate than those of these two phyla. Calcareous skeletons have been acquired independently in two bryozoan clades - Stenolaemata in the Ordovician and Cheilostomata in the Jurassic - providing an evolutionary replicate. This review aims to highlight the importance of biomineralization in bryozoans and focuses on their skeletal ultrastructures, mineralogy and chemistry, the roles of organic components, the evolutionary history of bimineralization in bryozoans with respect to changes in seawater chemistry, and the impact of contemporary global changes, especially ocean acidification, on bryozoan skeletons. Bryozoan skeletons are constructed from three different wall types (exterior, interior and compound) differing in the presence/absence and location of organic cuticular layers. Skeletal ultrastructures can be classified into wall-parallel (i.e. laminated) and wall-perpendicular (i.e. prismatic) fabrics, the latter apparently found in only one of the two biomineralizing clades (Cheilostomata), which is also the only clade to biomineralize aragonite. A plethora of ultrastructural fabrics can be recognized and most occur in combination with other fabrics to constitute a fabric suite. The proportion of aragonitic and bimineralic bryozoans, as well as the Mg content of bryozoan skeletons, show a latitudinal increase into the warmer waters of the tropics. Responses

  4. Mature clustered, regularly interspaced, short palindromic repeats RNA (crRNA) length is measured by a ruler mechanism anchored at the precursor processing site.

    Science.gov (United States)

    Hatoum-Aslan, Asma; Maniv, Inbal; Marraffini, Luciano A

    2011-12-27

    Precise RNA processing is fundamental to all small RNA-mediated interference pathways. In prokaryotes, clustered, regularly interspaced, short palindromic repeats (CRISPR) loci encode small CRISPR RNAs (crRNAs) that protect against invasive genetic elements by antisense targeting. CRISPR loci are transcribed as a long precursor that is cleaved within repeat sequences by CRISPR-associated (Cas) proteins. In many organisms, this primary processing generates crRNA intermediates that are subject to additional nucleolytic trimming to render mature crRNAs of specific lengths. The molecular mechanisms underlying this maturation event remain poorly understood. Here, we defined the genetic requirements for crRNA primary processing and maturation in Staphylococcus epidermidis. We show that changes in the position of the primary processing site result in extended or diminished maturation to generate mature crRNAs of constant length. These results indicate that crRNA maturation occurs by a ruler mechanism anchored at the primary processing site. We also show that maturation is mediated by specific cas genes distinct from those genes involved in primary processing, showing that this event is directed by CRISPR/Cas loci.

  5. Physical basis for materials synthesis using biomineralization

    Energy Technology Data Exchange (ETDEWEB)

    De Yoreo, J; Orme, C; Dove, P; Teng, H

    2000-05-16

    Since the dawn of life on earth, organisms have directed the crystallization of inorganic ions from solution to form minerals that meet specific biological needs. The resulting materials often exhibit remarkable properties, making the processes involved in biomineralization of interest to a wide array of scientific disciplines. From a geochemical standpoint, perhaps the most important consequence is that CaCO{sub 3} biomineral formation occurs in the Oceans on such a large scale that it influences many aspects of seawater chemistry and results in sequestration of carbon in the form of carbonate sediments. In this manner, the products of biomineralization are preserved in the rock record and serve as an extensive chronicle of the interplay between biota and the earth system environment. From the point of view of materials synthesis, biological control over epitaxy is an elegant example of self-organization in complex molecular systems. Through selective introduction of peptides and proteins, living organisms deterministically modify nucleation, step kinetics, surface morphologies, and facet stabilities to produce nanophase materials, topologically complex single-crystals, and multi-layer composite. The resulting materials have biological functions as diverse as structural supports, porous filtration media, grinding and cutting tools, lenses, gravity sensors and magnetic guidance systems. As Table I shows, calcium carbonate minerals are ubiquitous amongst these biomineral structures. In addition , calcium carbonate is a well studied material that is easily crystallized and has known solution chemistry. Consequently, the calcium carbonate system provides an excellent model for investigating biomineralization processes. Surprisingly, in spite of the identification of carbonate biogenesis as a critical contributor to the carbon reservoir mediating climate change, and the enormous potential of biomimetic synthesis for production of tailored, crystalline nano- and micro

  6. Fungal biomineralization of montmorillonite and goethite to short-range-ordered minerals

    Science.gov (United States)

    Li, Huan; Hu, Shuijin; Polizzotto, Matthew L.; Chang, Xiaoli; Shen, Qirong; Ran, Wei; Yu, Guanghui

    2016-10-01

    Highly reactive nano-scale minerals, e.g., short-range-ordered minerals (SROs) and other nanoparticles, play an important role in soil carbon (C) retention. Yet, the mechanisms that govern biomineralization from bulk minerals to highly reactive nano-scale minerals remain largely unexplored, which critically hinders our efforts toward managing nano-scale minerals for soil C retention. Here we report the results from a study that explores structural changes during Aspergillus fumigatus Z5 transformation of montmorillonite and goethite to SROs. We examined the morphology and structure of nano-scale minerals, using high-resolution transmission electron microscopy, time-resolved solid-state 27Al and 29Si NMR, and Fe K-edge X-ray absorption fine structure spectroscopy combined with two dimensional correlation spectroscopy (2D COS) analysis. Our results showed that after a 48-h cultivation of montmorillonite and goethite with Z5, new biogenic intracellular and extracellular reactive nano-scale minerals with a size of 3-5 nm became abundant. Analysis of 2D COS further suggested that montmorillonite and goethite were the precursors of the dominant biogenic nano-scale minerals. Carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectra and their deconvolution results demonstrated that during fungus Z5 growth, carboxylic C (288.4-289.1 eV) was the dominant organic group, accounting for approximately 34% and 59% in the medium and aggregates, respectively. This result suggested that high percentage of the production of organic acids during the growth of Z5 was the driving factor for structural changes during biomineralization. This is, to the best of our knowledge, the first report of the structural characterization of nano-scale minerals by 2D COS, highlighting its potential to elucidate biomineralization pathways and thus identify the precursors of nano-scale minerals.

  7. Biomineralizations: insights and prospects from crustaceans

    Directory of Open Access Journals (Sweden)

    Gilles Luquet

    2012-03-01

    Full Text Available For growing, crustaceans have to molt cyclically because of the presence of a rigid exoskeleton. Most of the crustaceans harden their cuticle not only by sclerotization, like all the arthropods, but also by calcification. All the physiology of crustaceans, including the calcification process, is then linked to molting cycles. This means for these animals to find regularly a source of calcium ions quickly available just after ecdysis. The sources of calcium used are diverse, ranging from the environment where the animals live to endogenous calcium deposits cyclically elaborated by some of them. As a result, crustaceans are submitted to an important and energetically demanding calcium turnover throughout their life. The mineralization process occurs by precipitation of calcium carbonate within an organic matrix network of chitin-proteins fibers. Both crystalline and stabilized amorphous polymorphs of calcium carbonate are found in crustacean biominerals. Furthermore, Crustacea is the only phylum of animals able to elaborate and resorb periodically calcified structures. Notably for these two previous reasons, crustaceans are more and more extensively studied and considered as models of choice in the biomineralization research area.

  8. The magnetosome membrane protein, MmsF, is a major regulator of magnetite biomineralization in Magnetospirillum magneticum AMB-1.

    Science.gov (United States)

    Murat, Dorothée; Falahati, Veesta; Bertinetti, Luca; Csencsits, Roseann; Körnig, André; Downing, Kenneth; Faivre, Damien; Komeili, Arash

    2012-08-01

    Magnetotactic bacteria (MTB) use magnetosomes, membrane-bound crystals of magnetite or greigite, for navigation along geomagnetic fields. In Magnetospirillum magneticum sp. AMB-1, and other MTB, a magnetosome gene island (MAI) is essential for every step of magnetosome formation. An 8-gene region of the MAI encodes several factors implicated in control of crystal size and morphology in previous genetic and proteomic studies. We show that these factors play a minor role in magnetite biomineralization in vivo. In contrast, MmsF, a previously uncharacterized magnetosome membrane protein encoded within the same region plays a dominant role in defining crystal size and morphology and is sufficient for restoring magnetite synthesis in the absence of the other major biomineralization candidates. In addition, we show that the 18 genes of the mamAB gene cluster of the MAI are sufficient for the formation of an immature magnetosome organelle. Addition of MmsF to these 18 genes leads to a significant enhancement of magnetite biomineralization and an increase in the cellular magnetic response. These results define a new biomineralization protein and lay down the foundation for the design of autonomous gene cassettes for the transfer of the magnetic phenotype in other bacteria. PMID:22716969

  9. Cluster self-organization of intermetallic systems: Quasi-spherical nanocluster precursors with internal Friauf polyhedra (A-172) and icosahedra (B-137) in the Li19Na8Ba15 (hP842) crystal structure

    International Nuclear Information System (INIS)

    A combinatorial and topological analysis of Li19Na8Ba15 (hP842, a = 20 A, c = 93 A, V = 33552 A3, P3-bar) has been performed using computer methods (the TOPOS program package). Two types of crystal-forming quasi-spherical nanoclusters about 20 A in diameter with internal Friauf polyhedra (A-172) and icosahedra (B-137) have been established by the complete decomposition of the 3D factor graph of the structure into cluster substructures. Each type of nanoclusters forms close-packed 2D layers 36, which alternate along the c axis. The B-137 and A-172 nanoclusters are composed of three layers and have shell compositions (1 + 12 + 32 + 92) and (1 + 16 + 59 + 103) with local symmetries 3 and 3-bar, respectively; they were revealed for the first time in crystal structures as cluster precursors. The icosahedral B-137 nanocluster contains a 104-atom quasicrystal approximant (Samson cluster).

  10. Investigation of biomineralization by Raman spectroscopy

    Science.gov (United States)

    Fatscher, Robert William

    Biomineralization is a process in which living organism grow composite materials consisting of inorganic and organic materials. This produces a composite material consisting of both inorganic and organic components, with superior mechanical properties. In the human body bone and dentin are both examples of biominerals. In this research Raman spectroscopy was used to characterize dentin from mice and human teeth, to determine composition. In the mouse tooth samples areas of irregular dentin were found, along the inside of the tooth, to be in the process of mineralization. By analyzing the samples along these areas we were able to determine the composition of dentin and track how it changed in these area. By analysis of the mineral to matrix ratio the areas of irregular dentin were determined to have less mineral present. Observations of other organic components and collagen in increased concentrations in this area suggested these area were in the process of biomineralization. The understanding of the structure of dentin and its biomineralization process is of crucial importance when trying reproduce dentin. Scientists and engineers are able to produce dentin minerals in vitro by culturing various dental stem cells. The ability to create dentin mineral from cells could lead to methods of repairing dentin in patients, or even lead to the creation of a completely engineered tooth. While dentin-like materials can be produced in a laboratory environment, analysis and comparison of the composition of these materials must be performed to ensure the mineral produced is consistent with dentin. Mineralized nodules from six different dental stem cell lines were cultured to produce a mineralized deposit. Utilizing Raman spectroscopy, we were able to determine cell source dependent differences in a variety of dental stem cells, and compare the mineral produced to native dentin. Orthopedic implants are implants used to replace damaged bone, examples include knee, hip and dental

  11. Shedding light on fish otolith biomineralization using a bioenergetic approach.

    Science.gov (United States)

    Fablet, Ronan; Pecquerie, Laure; de Pontual, Hélène; Høie, Hans; Millner, Richard; Mosegaard, Henrik; Kooijman, Sebastiaan A L M

    2011-01-01

    Otoliths are biocalcified bodies connected to the sensory system in the inner ears of fish. Their layered, biorhythm-following formation provides individual records of the age, the individual history and the natural environment of extinct and living fish species. Such data are critical for ecosystem and fisheries monitoring. They however often lack validation and the poor understanding of biomineralization mechanisms has led to striking examples of misinterpretations and subsequent erroneous conclusions in fish ecology and fisheries management. Here we develop and validate a numerical model of otolith biomineralization. Based on a general bioenergetic theory, it disentangles the complex interplay between metabolic and temperature effects on biomineralization. This model resolves controversial issues and explains poorly understood observations of otolith formation. It represents a unique simulation tool to improve otolith interpretation and applications, and, beyond, to address the effects of both climate change and ocean acidification on other biomineralizing organisms such as corals and bivalves.

  12. Shedding Light on Fish Otolith Biomineralization Using a Bioenergetic Approach

    Science.gov (United States)

    Fablet, Ronan; Pecquerie, Laure; de Pontual, Hélène; Høie, Hans; Millner, Richard; Mosegaard, Henrik; Kooijman, Sebastiaan A. L. M.

    2011-01-01

    Otoliths are biocalcified bodies connected to the sensory system in the inner ears of fish. Their layered, biorhythm-following formation provides individual records of the age, the individual history and the natural environment of extinct and living fish species. Such data are critical for ecosystem and fisheries monitoring. They however often lack validation and the poor understanding of biomineralization mechanisms has led to striking examples of misinterpretations and subsequent erroneous conclusions in fish ecology and fisheries management. Here we develop and validate a numerical model of otolith biomineralization. Based on a general bioenergetic theory, it disentangles the complex interplay between metabolic and temperature effects on biomineralization. This model resolves controversial issues and explains poorly understood observations of otolith formation. It represents a unique simulation tool to improve otolith interpretation and applications, and, beyond, to address the effects of both climate change and ocean acidification on other biomineralizing organisms such as corals and bivalves. PMID:22110601

  13. Shedding light on fish otolith biomineralization using a bioenergetic approach.

    Directory of Open Access Journals (Sweden)

    Ronan Fablet

    Full Text Available Otoliths are biocalcified bodies connected to the sensory system in the inner ears of fish. Their layered, biorhythm-following formation provides individual records of the age, the individual history and the natural environment of extinct and living fish species. Such data are critical for ecosystem and fisheries monitoring. They however often lack validation and the poor understanding of biomineralization mechanisms has led to striking examples of misinterpretations and subsequent erroneous conclusions in fish ecology and fisheries management. Here we develop and validate a numerical model of otolith biomineralization. Based on a general bioenergetic theory, it disentangles the complex interplay between metabolic and temperature effects on biomineralization. This model resolves controversial issues and explains poorly understood observations of otolith formation. It represents a unique simulation tool to improve otolith interpretation and applications, and, beyond, to address the effects of both climate change and ocean acidification on other biomineralizing organisms such as corals and bivalves.

  14. Intracellular Ca-carbonate biomineralization is widespread in cyanobacteria.

    Science.gov (United States)

    Benzerara, Karim; Skouri-Panet, Feriel; Li, Jinhua; Férard, Céline; Gugger, Muriel; Laurent, Thierry; Couradeau, Estelle; Ragon, Marie; Cosmidis, Julie; Menguy, Nicolas; Margaret-Oliver, Isabel; Tavera, Rosaluz; López-García, Purificación; Moreira, David

    2014-07-29

    Cyanobacteria have played a significant role in the formation of past and modern carbonate deposits at the surface of the Earth using a biomineralization process that has been almost systematically considered induced and extracellular. Recently, a deep-branching cyanobacterial species, Candidatus Gloeomargarita lithophora, was reported to form intracellular amorphous Ca-rich carbonates. However, the significance and diversity of the cyanobacteria in which intracellular biomineralization occurs remain unknown. Here, we searched for intracellular Ca-carbonate inclusions in 68 cyanobacterial strains distributed throughout the phylogenetic tree of cyanobacteria. We discovered that diverse unicellular cyanobacterial taxa form intracellular amorphous Ca-carbonates with at least two different distribution patterns, suggesting the existence of at least two distinct mechanisms of biomineralization: (i) one with Ca-carbonate inclusions scattered within the cell cytoplasm such as in Ca. G. lithophora, and (ii) another one observed in strains belonging to the Thermosynechococcus elongatus BP-1 lineage, in which Ca-carbonate inclusions lie at the cell poles. This pattern seems to be linked with the nucleation of the inclusions at the septum of the cells, showing an intricate and original connection between cell division and biomineralization. These findings indicate that intracellular Ca-carbonate biomineralization by cyanobacteria has been overlooked by past studies and open new perspectives on the mechanisms and the evolutionary history of intra- and extracellular Ca-carbonate biomineralization by cyanobacteria.

  15. The Magnetosome Model: Insights into the Mechanisms of Bacterial Biomineralization

    Directory of Open Access Journals (Sweden)

    Lilah eRahn-Lee

    2013-11-01

    Full Text Available Though the most ready example of biomineralization is the calcium phosphate of vertebrate bones and teeth, many bacteria are capable of creating biominerals inside their cells. Because of the diversity of these organisms and the minerals they produce, their study may reveal aspects of the fundamental mechanisms of biomineralization in more complex organisms. The best-studied case of intracellular biomineralization in bacteria is the magnetosome, an organelle produced by a diverse group of aquatic bacteria that contains single-domain crystals of the iron oxide magnetite (Fe3O4 or the iron sulfide greigite (Fe3S4. Here, recent advances in our understanding of the mechanisms of bacterial magnetite biomineralization are discussed and used as a framework for understanding less-well studied examples, including the bacterial intracellular biomineralization of cadmium, selenium, silver, nickel, uranium, and calcium carbonate. Understanding the molecular mechanisms underlying the biological formation of these minerals will have important implications for technologies such as the fabrication of nanomaterials and the bioremediation of toxic compounds.

  16. The magnetosome model: insights into the mechanisms of bacterial biomineralization.

    Science.gov (United States)

    Rahn-Lee, Lilah; Komeili, Arash

    2013-01-01

    Though the most ready example of biomineralization is the calcium phosphate of vertebrate bones and teeth, many bacteria are capable of creating biominerals inside their cells. Because of the diversity of these organisms and the minerals they produce, their study may reveal aspects of the fundamental mechanisms of biomineralization in more complex organisms. The best-studied case of intracellular biomineralization in bacteria is the magnetosome, an organelle produced by a diverse group of aquatic bacteria that contains single-domain crystals of the iron oxide magnetite (Fe3O4) or the iron sulfide greigite (Fe3S4). Here, recent advances in our understanding of the mechanisms of bacterial magnetite biomineralization are discussed and used as a framework for understanding less-well studied examples, including the bacterial intracellular biomineralization of cadmium, selenium, silver, nickel, uranium, and calcium carbonate. Understanding the molecular mechanisms underlying the biological formation of these minerals will have important implications for technologies such as the fabrication of nanomaterials and the bioremediation of toxic compounds. PMID:24324464

  17. Temporal and spatial expression patterns of biomineralization proteins during early development in the stony coral Pocillopora damicornis.

    Science.gov (United States)

    Mass, Tali; Putnam, Hollie M; Drake, Jeana L; Zelzion, Ehud; Gates, Ruth D; Bhattacharya, Debashish; Falkowski, Paul G

    2016-04-27

    Reef-building corals begin as non-calcifying larvae that, upon settling, rapidly begin to accrete skeleton and a protein-rich skeletal organic matrix that attach them to the reef. Here, we characterized the temporal and spatial expression pattern of a suite of biomineralization genes during three stages of larval development in the reef-building coral Pocillopora damicornis: stage I, newly released; stage II, oral-aborally compressed and stage III, settled and calcifying spat. Transcriptome analysis revealed 3882 differentially expressed genes that clustered into four distinctly different patterns of expression change across the three developmental stages. Immunolocalization analysis further reveals the spatial arrangement of coral acid-rich proteins (CARPs) in the overall architecture of the emerging skeleton. These results provide the first analysis of the timing of the biomineralization 'toolkit' in the early life history of a stony coral. PMID:27122561

  18. Cluster self-organization of inorganic crystal-forming systems: Templated nanocluster precursors and self-assembly of framework MT structures of A/B,Zr silicates (A = Na, K; B = Ca, Sr)

    International Nuclear Information System (INIS)

    The basic concepts that are used to describe crystallization as a phenomenon of the hierarchical (cluster) self-organization of a chemical system are considered. The templation of theoretically possible nan-ocluster precursors composed of M octahedra and T tetrahedra by atoms of (A) alkaline and (B) alkaline earth metals is considered for the first time. A relationship between the A/B,M,T composition of templated nanocluster precursors with the composition of A/B,M silicates is established. The model that is developed is used to search for nanocluster precursors in framework MT structures of A/B,Zr silicates. Computer methods (TOPOS 4.0 program package) were used to perform complete 3D reconstruction of the self-assembly of all (four) structural types of A/B,Zr silicates (A = Na, K; B = Ca, Sr) with frameworks of the MT2O7 type: nan-ocluster precursor S30-primary chain S31-microlayer S32-microframework S33. The invariant type of mono-cyclic nanocluster precursor M2T4 (with the point symmetries 1-bar and 2), stabilized by one or two template cations (A and B), is determined. Bifurcations of the paths of evolution at the S31 level (structural branching point) are established for the self-assembly of the following frameworks: MT-1 in CaZrSi2O7 (gittinsite, C2), MT-2 in SrZrSi2O7 (P21/c); MT-3 in Na2ZrSi2O7 (parakeldyshite,), K2ZrSi2O7 (khibinskite, P21/b), and K2ZrGe2O7 (C2/c); and MT-4 in Na2ZrSi2O7 (H2O)(C2/c), Na3ScSi2O7 (Pbnm), and K3ScSi2O7 (P63/mmc).

  19. The case study of biomaterials and biominerals

    Science.gov (United States)

    Del Hoyo Martínez, Carmen

    2013-04-01

    The teaching of biomaterials as case study by on-line platform , susceptible to develop both individually and in groups, got different objectives proposed by the European Higher Education System, among which include: participate actively in the teaching-learning process by students, interpreting situations, adapt processes and solutions. It also improves oral and written communication, analytical skills and synthesis and also the ability to think critically. Biomaterials have their origin in biominerals. These are solid inorganic compounds of defined structure, consisting of molecular control mechanisms that operate in biological systems. Its main functions are: structural support, a reservoir of essential elements, sensors, mechanical protection and storage of toxic elements. Following the demand of materials compatible with certain functional systems of our body, developed biomaterials. Always meet the condition of biocompatibility. Should be tolerated by the body and do not provoke rejection. This involves a comprehensive study of physiological conditions and the anatomy of the body where a biomaterial has to be implemented. The possibility of generating new materials from biominerals has a major impact in medicine and other fields could reach as geology, construction, crystallography, etc. While the study of these issues is in its infancy today, can be viewed as an impact on the art and future technology. Planning case study that students would prepare its report for discussion in subgroups. Occurs then the pooling of individual analysis, joint case discussion and adoption by the subgroup of a consensual solution to the problem. The teacher as facilitator and coordinator of the final case analysis, sharing leads to group-wide class and said the unanimous decision reached by the students and gives his opinion on the resolution of the case. REFERENCES D.P. Ausubel. Psicología Educativa. Un punto de vista cognoscitivo. Trillas. Ed. 1983. E.W. Eisner. Procesos

  20. Data set for the proteomic inventory and quantitative analysis of chicken uterine fluid during eggshell biomineralization

    Directory of Open Access Journals (Sweden)

    Pauline Marie

    2014-12-01

    Full Text Available Chicken eggshell is the protective barrier of the egg. It is a biomineral composed of 95% calcium carbonate on calcitic form and 3.5% organic matrix proteins. Mineralization process occurs in uterus into the uterine fluid. This acellular fluid contains ions and organic matrix proteins precursors which are interacting with the mineral phase and control crystal growth, eggshell structure and mechanical properties. We performed a proteomic approach and identified 308 uterine fluid proteins. Gene Ontology terms enrichments were determined to investigate their potential functions. Mass spectrometry analyses were also combined to label free quantitative analysis to determine the relative abundance of 96 proteins at initiation, rapid growth phase and termination of shell calcification. Sixty four showed differential abundance according to the mineralization stage. Their potential functions have been annotated. The complete proteomic, bioinformatic and functional analyses are reported in Marie et al., J. Proteomics (2015 [1].

  1. Biomineralization of nanoscale single crystal hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Omokanwaye, Tiffany [Catholic University of America, BONE/CRAB Lab, Department of Biomedical Engineering, Washington, DC 20064 (United States); Wilson, Otto C., E-mail: wilsono@cua.edu [Catholic University of America, BONE/CRAB Lab, Department of Biomedical Engineering, Washington, DC 20064 (United States); Gugssa, Ayelle; Anderson, Winston [Howard University, Department of Biology, Washington, DC (United States)

    2015-11-01

    The chemical and physical characteristics of nanocrystalline hydroxyapatite particles which formed during the subcutaneous implantation of crab shell in Sprague–Dawley rats were studied using selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The initial SAED characterization evidence indicated the presence of an amorphous calcium phosphate phase. The electron dense nanophase particles which formed in the wound healing zone displayed broad diffuse rings which usually indicate a low crystalline order or amorphous phase. High resolution transmission electron microscopy (HRTEM) revealed that these mineralized regions contained discrete single crystal particles less than 5 nm in size. Micrographs taken at successively higher magnifications revealed very small nanoparticles with a hexagonal arrangement of ion channels with characteristic spacing of 0.54 nm and 0.23 nm. This study revealed that single crystal hydroxyapatite nanoparticles consisting of only a few unit cells formed via a biomineralization directed process. - Highlights: • Nanocrystalline particles were formed during in vivo implantation of crab shell using a rat model. • High resolution TEM revealed that nanoparticles were single crystals and less than 5 nm in size. • The relative distance between spots matches the expected values for hydroxyapatite.

  2. Simulation of self-organization processes in crystal-forming systems: Supramolecular cyclic R6 cluster precursors and self-assembly of TeO2- TEL ( Tellurite) and TeO2- PAR ( Paratellurite) structures

    Science.gov (United States)

    Ilyushin, G. D.

    2014-11-01

    The supramolecular chemistry of oxides of sp elements (SO2, SeO2, and TeO2) is considered. The self-assembly of TeO2- TEL ( Tellurite) and TeO2- PAR ( Paratellurite) crystal structures is simulated. Methods of combinatorial and topological analysis (TOPOS program package) are applied which are based on constructing a basis 3D network of the structure in the form of a graph, the sites of which correspond to the positions of centroids of TeO2 molecules and the edges characterize bonds between them. The topological type of the basis 2D network in the TeO2- TEL structure corresponds to graphite (C- GRA), while in the TeO2- PAR structure the basis network corresponds to the 3D diamond network (C- DIA). A nanocluster precursor of cyclic type ( R6) composed of six covalently bound TeO2 molecules (chair conformation) is established for both structures. The desymmetrization of the cyclic structure of the R6 cluster in TeO2- PAR is related to the formation of Te-Te bonds with lengths of 3.824 and 4.062 Å. The symmetry and topology code of the processes of self-assembly of 3D structures from nanocluster precursors is completely reconstructed into the form "primary chain → microlayer → microframework." In both structures R6 clusters form 2D packings with a coordination number of 6. The cluster self-assembly model explains the specific features of the morphogenesis of TeO2- TEL and TeO2- PAR (phases with low and high crystallization temperatures, respectively): platelike shape, perfect cleavage in the (110) plane, and preferred growth in the primar-chain direction [100] in the former case and growth in the direction of the primary [001] axis with the preferred formation of tetragonal prism faces (110) in the latter case.

  3. Barrierless growth of precursor-free, ultrafast laser-fragmented noble metal nanoparticles by colloidal atom clusters - A kinetic in situ study.

    Science.gov (United States)

    Jendrzej, Sandra; Gökce, Bilal; Amendola, Vincenzo; Barcikowski, Stephan

    2016-02-01

    Unintended post-synthesis growth of noble metal colloids caused by excess amounts of reactants or highly reactive atom clusters represents a fundamental problem in colloidal chemistry, affecting product stability or purity. Hence, quantified kinetics could allow defining nanoparticle size determination in dependence of the time. Here, we investigate in situ the growth kinetics of ps pulsed laser-fragmented platinum nanoparticles in presence of naked atom clusters in water without any influence of reducing agents or surfactants. The nanoparticle growth is investigated for platinum covering a time scale of minutes to 50days after nanoparticle generation, it is also supplemented by results obtained from gold and palladium. Since a minimum atom cluster concentration is exceeded, a significant growth is determined by time resolved UV/Vis spectroscopy, analytical disc centrifugation, zeta potential measurement and transmission electron microscopy. We suggest a decrease of atom cluster concentration over time, since nanoparticles grow at the expense of atom clusters. The growth mechanism during early phase (Ostwald ripening, validated experimentally by the temperature dependence of Pt nanoparticle size and growth quenching by Iodide anions. PMID:26555960

  4. Barrierless growth of precursor-free, ultrafast laser-fragmented noble metal nanoparticles by colloidal atom clusters - A kinetic in situ study.

    Science.gov (United States)

    Jendrzej, Sandra; Gökce, Bilal; Amendola, Vincenzo; Barcikowski, Stephan

    2016-02-01

    Unintended post-synthesis growth of noble metal colloids caused by excess amounts of reactants or highly reactive atom clusters represents a fundamental problem in colloidal chemistry, affecting product stability or purity. Hence, quantified kinetics could allow defining nanoparticle size determination in dependence of the time. Here, we investigate in situ the growth kinetics of ps pulsed laser-fragmented platinum nanoparticles in presence of naked atom clusters in water without any influence of reducing agents or surfactants. The nanoparticle growth is investigated for platinum covering a time scale of minutes to 50days after nanoparticle generation, it is also supplemented by results obtained from gold and palladium. Since a minimum atom cluster concentration is exceeded, a significant growth is determined by time resolved UV/Vis spectroscopy, analytical disc centrifugation, zeta potential measurement and transmission electron microscopy. We suggest a decrease of atom cluster concentration over time, since nanoparticles grow at the expense of atom clusters. The growth mechanism during early phase (<1day) of laser-synthesized colloid is kinetically modeled by rapid barrierless coalescence. The prolonged slow nanoparticle growth is kinetically modeled by a combination of coalescence and Lifshitz-Slyozov-Wagner kinetic for Ostwald ripening, validated experimentally by the temperature dependence of Pt nanoparticle size and growth quenching by Iodide anions.

  5. Pore-scale spectral induced polarization (SIP) signaturesassociated with FeS biomineral transformations

    Energy Technology Data Exchange (ETDEWEB)

    Slater, Lee; Ntarlagiannis, Dimitrios; Personna, Yves R.; Hubbard, Susan

    2007-10-01

    The authors measured Spectral Induced Polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate reducing bacteria (D. vulgaris) under anaerboci conditions, and (2) subsequent biomineral dissolution upon return to an aerobic state. The low-frequency (0.1-10 Hz peak) relaxations produced during biomineralization can be modeled with a Cole-Cole formulation, from which the evolution of the polarization magnitude and relaxation length scale can be estimated. They find that the modeled time constant is consistent with the polarizable elements being biomineral encrused pores. Evolution of the model parameters is consistent with FeS surface area increases and pore-size reduction during biomineral growth, and subsequent biomineral dissolution (FeS surface area decreases and pore expansion) upon return to the aerobic state. They conclude that SIP signatures are diagnostic of pore-scale geometrical changes associated with FeS biomineralization by sulfate reducing bacteria.

  6. Piezoelectric Templates - New Views on Biomineralization and Biomimetics.

    Science.gov (United States)

    Stitz, Nina; Eiben, Sabine; Atanasova, Petia; Domingo, Neus; Leineweber, Andreas; Burghard, Zaklina; Bill, Joachim

    2016-05-23

    Biomineralization in general is based on electrostatic interactions and molecular recognition of organic and inorganic phases. These principles of biomineralization have also been utilized and transferred to bio-inspired synthesis of functional materials during the past decades. Proteins involved in both, biomineralization and bio-inspired processes, are often piezoelectric due to their dipolar character hinting to the impact of a template's piezoelectricity on mineralization processes. However, the piezoelectric contribution on the mineralization process and especially the interaction of organic and inorganic phases is hardly considered so far. We herein report the successful use of the intrinsic piezoelectric properties of tobacco mosaic virus (TMV) to synthesize piezoelectric ZnO. Such films show a two-fold increase of the piezoelectric coefficient up to 7.2 pm V(-1) compared to films synthesized on non-piezoelectric templates. By utilizing the intrinsic piezoelectricity of a biotemplate, we thus established a novel synthesis pathway towards functional materials, which sheds light on the whole field of biomimetics. The obtained results are of even broader and general interest since they are providing a new, more comprehensive insight into the mechanisms involved into biomineralization in living nature.

  7. Uranium Biomineralization By Natural Microbial Phosphatase Activities in the Subsurface

    Energy Technology Data Exchange (ETDEWEB)

    Taillefert, Martial [Georgia Tech Research Corporation, Atlanta, GA (United States)

    2015-04-01

    This project investigated the geochemical and microbial processes associated with the biomineralization of radionuclides in subsurface soils. During this study, it was determined that microbial communities from the Oak Ridge Field Research subsurface are able to express phosphatase activities that hydrolyze exogenous organophosphate compounds and result in the non-reductive bioimmobilization of U(VI) phosphate minerals in both aerobic and anaerobic conditions. The changes of the microbial community structure associated with the biomineralization of U(VI) was determined to identify the main organisms involved in the biomineralization process, and the complete genome of two isolates was sequenced. In addition, it was determined that both phytate, the main source of natural organophosphate compounds in natural environments, and polyphosphate accumulated in cells could also be hydrolyzed by native microbial population to liberate enough orthophosphate and precipitate uranium phosphate minerals. Finally, the minerals produced during this process are stable in low pH conditions or environments where the production of dissolved inorganic carbon is moderate. These findings suggest that the biomineralization of U(VI) phosphate minerals is an attractive bioremediation strategy to uranium bioreduction in low pH uranium-contaminated environments. These efforts support the goals of the SBR long-term performance measure by providing key information on "biological processes influencing the form and mobility of DOE contaminants in the subsurface".

  8. Thermoset precursor

    International Nuclear Information System (INIS)

    This invention pertains to a distinctive thermoset precursor which is prepared by mixing a resin composition (A) which can be hardened by ionizing radiation, and a resin composition (B) which can be hardened by heat but cannot be hardened by, or is resistant to, ionizing radiation, and by coating or impregnating a molding or other substrate with a sheet or film of this mixture and irradiating this with an ionizing radiation. The principal components of composition (A) and (B) can be the following: (1) an acrylate or methacrylate and an epoxy resin and an epoxy resin hardener; (2) an unsaturated polyester resin and epoxy resin and an epoxy resin hardener; (3) a diacrylate or dimethacrylate or polyethylene glycol and an epoxy resin; (4) an epoxy acrylates or epoxy methacrylate obtained by the addition reaction of epoxy resin and acrylic or methacrylic acid

  9. Molecular approaches to understand biomineralization of shell nacreous layer.

    Science.gov (United States)

    Xie, Li-Ping; Zhu, Fang-Jie; Zhou, Yu-Juan; Yang, Chao; Zhang, Rong-Qing

    2011-01-01

    The nacreous layer of molluskan shells, which consists of highly oriented aragonitic crystals and an organic matrix (including chitin and proteins), is a product of biomineralization. This paper briefly introduces the recent research advances on nacre biomineralization of shells from bivalves and gastropods, which mainly focus on analysis of the micro- and nano-structure and components of shell nacreous layers, and investigations of the characteristics and functions of matrix proteins from nacre. Matrix proteins not only participate in construction of the organic nacre framework, but also control the nucleation and growth of aragonitic crystals, as well as determine the polymorph specificity of calcium carbonate in nacre. Moreover, the inorganic aragonite phase also plays an active role in organizing nacre microstructure. Based on these studies, several models to illustrate the formation mechanism related to lamellar nacre in bivalves, and columnar nacre in gastropods are introduced.

  10. Shedding light on fish otolith biomineralization using a bioenergetic approach

    DEFF Research Database (Denmark)

    Fablet, R.; Pecquerie, L.; de Pontual, H.;

    2011-01-01

    Otoliths are biocalcified bodies connected to the sensory system in the inner ears of fish. Their layered, biorhythm-following formation provides individual records of the age, the individual history and the natural environment of extinct and living fish species. Such data are critical for ecosys...... simulation tool to improve otolith interpretation and applications, and, beyond, to address the effects of both climate change and ocean acidification on other biomineralizing organisms such as corals and bivalves...

  11. Molecular Mechanisms of Compartmentalization and Biomineralization in Magnetotactic Bacteria

    OpenAIRE

    Komeili, Arash

    2012-01-01

    Magnetotactic bacteria are remarkable organisms with the ability to exploit the earth’s magnetic field for navigational purposes. To do this, they build specialized compartments called magnetosomes that consist of a lipid membrane and a crystalline magnetic mineral. These organisms have the potential to serve as models for the study of compartmentalization as well as biomineralization in bacteria. Additionally, they offer the opportunity to design applications that take advantage of the parti...

  12. Unexpected link between polyketide synthase and calcium carbonate biomineralization

    OpenAIRE

    Hojo, Motoki; Omi, Ai; Hamanaka, Gen; Shindo, Kazutoshi; Shimada, Atsuko; Kondo, Mariko; Narita, Takanori; Kiyomoto, Masato; Katsuyama, Yohei; Ohnishi, Yasuo; Irie, Naoki; Takeda, Hiroyuki

    2015-01-01

    Introduction Calcium carbonate biominerals participate in diverse physiological functions. Despite intensive studies, little is known about how mineralization is initiated in organisms. Results We analyzed the medaka spontaneous mutant, ha, defective in otolith (calcareous ear stone) formation. ha lacks a trigger for otolith mineralization, and the causative gene was found to encode polyketide synthase (pks), a multifunctional enzyme mainly found in bacteria, fungi, and plant. Subsequent expe...

  13. Initial formation stage and succedent biomineralization of pearls

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Fen [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Tian, Liangguang [Shandong Institute of Supervision and Inspection on Product Quality, Jinan 250100 (China); Xu, Xiangang [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Hu, Xiaobo, E-mail: xbhu@sdu.edu.cn [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)

    2014-04-01

    The initial formation stage and succedent biomineralization of pearls were studied using scanning electron microscopy, Raman spectroscopy, transmission electron microscopy and atomic force microscopy. A new initial formation phase with needle-like structure which is found to be nanocrystallites of aragonite was discovered. As a result, two possible formation modes are proposed to describe the initial formation stage of pearls. As for the succedent mineralization of “brick and mortar” structure, nanostripes were first discovered inside the “brick” (aragonite platelet), compared with the foregoing finding of nanograins. The various nanostructures of aragonite platelet allow us to reconsider the role of the inter- and intracrystalline organic material surrounding CaCO{sub 3}, and a possible biomineralization mechanism was proposed. - Highlights: • A new initial formation mineral phase was discovered in pearl. • Nanograins and nanostripes inside aragonite platelets were found in pearl. • Two possible initial formation stages were proposed for pearl. • A possible biomineralization mechanism of nacre in pearl was proposed.

  14. Synthesis, structure, and characterization of n-ligated Mo[sub 6]S[sub 8]L[sub 6] cluster complexes. Molecular precursors to Chevrel phases

    Energy Technology Data Exchange (ETDEWEB)

    Hilsenbeck, S.J.; Young, V.G. Jr.; McCarley, R.E. (Iowa State Univ., Ames, IA (United States))

    1994-04-27

    A modified method has been developed for the synthesis of the Mo[sub 6]S[sub 8] cluster unit in one step from Mo[sub 6]Cl[sub 12] via reaction with NaSH and NaOBu in refluxing n-BuOH-pyridine. The ligand-deficient Na[sub 2x]Mo[sub 6]S[sub 8+x](py)[sub y] (1) serves as a convenient starting material for the preparation of the amine complexes Mo[sub 6]S[sub 8]L[sub 6], with L = pyridine (2), pyrrolidine (4), and piperidine (5). Although propylamine readily dissolves the ligand-deficient starting material, only amorphous Mo[sub 6]S[sub 8](PrNH[sub 2])[sub 6-x] (3) could be isolated. However, the latter acts as a facile reactant for the preparation of the other complexes by ligand substitution. Crystallographic data for the complexes are as follows: Mo[sub 6]S[sub 8](py)[sub 6][center dot]2py (2), cubic, Pa[bar 3], a = 16.994(2) [angstrom], Z = 4, R = 0.0381, R[sub w] = 0.0351; Mo[sub 6]S[sub 8](pyrr)[sub 6][center dot]pyrr (4), tetragonal, I4[sub 1]/a, a = 29.933(4) [angstrom], c = 23.697(8) [angstrom], Z = 16, R = 0.0675, wR2 = 0.2036; Mo[sub 6]S[sub 8](pip)[sub 6][center dot]7pip, (5), tetragonal, in the IR at 380 [+-] 5 cm[sup [minus]1] and in the Raman at 414 [+-] 4 cm[sup [minus]1], assigned as predominantly Mo-S stretching modes. XP spectra give characteristic binding energies at 227.7 [+-] 0.1 (Mo 3d[sub 5/2]), 230.8 [+-] 0.1 (Mo 3d[sub 3/2]), 225.1 [+-] 0.3 (S 2s), 160.6 [+-] 0.1 (S 2p[sub 3/2]), and 161.8 [+-] 0.1 (S 2p[sub 1/2]) eV. Mo-Mo and Mo-S bond distances show little variation among the complexes, with average values of 2.647 and 2.454 [angstrom], respectively. The average Mo-N bond distance, 2.297 [angstrom], indicates rather weak bonding of these N-donor ligands.

  15. Role of the Template in Model Biomineralization: Synchrotron X-ray Scattering Experiments

    Science.gov (United States)

    Uysal, Ahmet

    during model hydroxyapatite biomineralization. We studied the interactions between the organic template and the pre-nucleation clusters in the calcium phosphate solution depending on the temperature and the subphase concentration. Our results show how the organic-inorganic interface becomes more suitable for oriented hydroxyapatite crystallization under physiological conditions. One of the main reasons to study biomineralization is to use the knowledge obtained to develop new methods for nano-engineering. As a demonstration of this idea, we used Langmuir monolayer of alkylthiols to grow (111)-oriented gold nanoparticles from solution in a biomimetic way. The organic molecules we used make the gold nanoparticles grow with a specific orientation. However, they also change their organization to minimize the interaction potential at the organic-inorganic interface. In fact the final structure they adapt is very similar to self-assembled monolayers of alkylthiol molecules on gold crystal surfaces, so one can say that we "reversed" the self-assembly process. It has long been assumed, although not directly observed, that the organic template controls the growth of the inorganic crystals. Our studies, taken together, show that the interaction between the organic template and the crystals is not a one way street; rather, both organic and inorganic structures may change to lower the interaction potential energy at the interface. This is usually accomplished through a structural match between the surface lattices.

  16. Special issue featuring articles from the 3rd Asian Symposium on Biomineralization

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ This issue contains a selection of nine peer-reviewed articles that were presented during the 3rd Asian Symposium on Biomineralization held in Xiamen,China on 21-23 November,2007.The symposium focused on the recent development of mechanisms of biomineralization and its applications in novel biomaterials,environmental issues,geophysics and nano-biotechnologies.

  17. Biomineralization of iron phosphate nanoparticles in yeast cells

    International Nuclear Information System (INIS)

    Amorphous iron phosphate nanoparticles mineralized in yeast cells are studied by transmission electron microscopy, Fourier transform infrared spectrograph and micro electrophoresis. Iron phosphate nanoparticles in yeast cells show uniform morphology with extensive surface roughness and disperse well. The size distribution of iron phosphate is about 50-200 nm. Fourier transform infrared spectroscopy (FT-IR) is used to analyze the chemical bond linkages between iron phosphate nanoparticles with protein macromolecules in yeast cells. The mechanism of biomineralization was simply discussed by chemical bonds and surface charges.

  18. Characterization of Uranium Tolerance and Biomineralization Potential of Caulobacter crescentus

    Science.gov (United States)

    Park, D.

    2015-12-01

    Due to its high toxicity and mobility, U(VI) poses a major environmental threat to ecosystems. The ubiquitous aerobic bacterium Caulobacter cresecentus is an attractive candidate for U(VI) bioremediation because of its ability to survive in low-nutrient environments (5, 6), tolerate high U concentrations and mineralize U(VI) aerobically through the formation of uranyl phosphate (U-Pi) precipitates. Despite these attractive environmental properties, both a systems level understanding of the adaptive response pathways involved in U tolerance and the environmental conditions affecting the biomineralization process and stability of biogenic U-Pi minerals remain limited. By measuring changes in both mRNA and protein expression during exposure to high U levels, we have identified the core stress response pathways involved in U tolerance. Pathways associated with heat shock, lipospolysaccharide biosynthesis and transport, outer membrane lipoprotein transport and outermembrane assembly were highly induced at both the RNA and protein levels. Correspondingly, removal of integral components of proteolysis pathways including clpA, clpS and degP significantly reduced U tolerance under biomineralization conditions. Surprisingly, in contrast to many other heavy metals, U did not cause oxidative stress or DNA damage. Together, these analyses indicate that U predominately targets the outermembrane and causes mis-folding of both cytoplasmic and extracytoplasmic proteins. Efforts are currently underway to characterize the morphological and structural properties of biogenic U-Pi minerals and the environmental factors that influence their production and stability. Preliminary AFM studies suggest that U-Pi minerals formed under biomineralization conditions appear morphologically distinct from those formed abiotically between U(VI) and inorganic phosphate. Additionally, we observed that biomineralization tolerates a wide pH range (pH 6-9). Our long-range goal is the development of a

  19. Biomineralization: Some complex crystallite-oriented skeletal structures

    Indian Academy of Sciences (India)

    Ashok Sahni

    2013-12-01

    The present review focuses on some specific aspects of biomineralization with regard to the evolution of the first focused visioning systems in trilobites, the formation of molluscan shell architecture, dental enamel and its biomechanical properties and the structure of the calcified amniote egg, both fossil and recent. As an interdisciplinary field, biomineralization deals with the formation, structure and mechanical strength of mineralized skeletonized tissue secreted by organisms. Mineral matter formed in this way occurs in all three domains of life and consists of several mineral varieties, of which carbonates, phosphates and opaline silica are the most common. Animals and plants need mechanical support to counteract gravitational forces on land and hydrostatic pressure in the deep ocean, which is provided by a skeletonized framework. Skeleton architecture mainly consists of basic elements represented by small usually micrometer- to nanometer-sized crystallites of calcite and aragonite for carbonate systems and apatite crystallites for phosphatic ones, and then these building blocks develop into structured more complex frameworks. As selective pressures work towards optimizing stress and response, the orientation, morphology and structural arrangement of the crystallites indicates the distribution of the stress field of the biomineralized tissue. Large animals such as the dinosaurs have to deal with large gravitational forces, but in much smaller skeletonized organism such as the coccoliths, a few micrometer in diameter made up of even smaller individual crystallites, van der Waals forces play an increasingly important role and are at present poorly understood. Skeleton formation is dependent upon many factors including ambient water chemistry, temperature and environment. Ocean chemistry has played a vital role in the origins of skeletonization, 500 to 600 million years (ma) ago with the dominance of calcium carbonate as the principal skeleton-forming tissue

  20. Pore Structures in the Biomineralized Byssus of Anomia simplex

    DEFF Research Database (Denmark)

    Frølich, Simon; Leemreize, Hanna; Thomsen, Jesper Skovhus;

    2016-01-01

    Underwater attachment is a significant challenge, for which we have no good general solutions in our technology. Yet, a number of biological organisms have evolved solutions to this problem. One intriguing approach to underwater attachment is that of the marine bivalve mussel Anomia simplex...... that uses a biomineralized byssus to permanently anchor itself to substrates. The byssus has a highly complex hierarchical structure and contains over 90 wt% CaCO3. The byssus features a complex set of porosities, presumed to be highly important for the function of the attachment system. The pore space...

  1. Natural analogue studies as supplements to biomineralization research

    Energy Technology Data Exchange (ETDEWEB)

    McNeil, M.B. [Nuclear Regulatory Commission, Washington, DC (United States)

    1995-09-01

    Chemical reactions can alter the chemistry and crystal structure of solid objects over archeological or geological times, while preserving external physical shapes. The reactions resulting in these structures offer natural analogues to laboratory experiments in biomineralization and to biologically influenced alteration of nuclear waste packages, and thus, they offer the only available way of validating models that purport waste package behavior over archaeological or geological times. Potential uses of such analogues in the construction and validation of hypothetical mechanisms of microbiological corrosion and biomineralization are reviewed. Evidence from such analogues suggests that biofilms can control materials alteration in ways usually overlooked. The newly hypothesized mechanisms involve control by biofilms of the cation flow near the solid surface and offer plausible mechanisms for the formation of mixed-cation minerals under conditions that would lead to dealloying in abiotic experiments; they also account for the formation of unusual minerals [such as posnjakite, Cu{sub 4}SO{sub 4}(OH){sub 6{center_dot}}H{sub 2}O] and mineral morphologies unusual in corrosion [malachite, Cu{sub 2}CO{sub 3}(OH){sub 2}, rarely forms botryoidally under corrosion conditions and its occasional presence on archaeological objects that appear to have undergone microbiological corrosion may be related to biofilm phenomena].

  2. Uranium Biomineralization by Natural Microbial Phosphatase Activities in the Subsurface

    Energy Technology Data Exchange (ETDEWEB)

    Sobecky, Patricia A. [Univ. of Alabama, Tuscaloosa, AL (United States)

    2015-04-06

    In this project, inter-disciplinary research activities were conducted in collaboration among investigators at The University of Alabama (UA), Georgia Institute of Technology (GT), Lawrence Berkeley National Laboratory (LBNL), Brookhaven National Laboratory (BNL), the DOE Joint Genome Institute (JGI), and the Stanford Synchrotron Radiation Light source (SSRL) to: (i) confirm that phosphatase activities of subsurface bacteria in Area 2 and 3 from the Oak Ridge Field Research Center result in solid U-phosphate precipitation in aerobic and anaerobic conditions; (ii) investigate the eventual competition between uranium biomineralization via U-phosphate precipitation and uranium bioreduction; (iii) determine subsurface microbial community structure changes of Area 2 soils following organophosphate amendments; (iv) obtain the complete genome sequences of the Rahnella sp. Y9-602 and the type-strain Rahnella aquatilis ATCC 33071 isolated from these soils; (v) determine if polyphosphate accumulation and phytate hydrolysis can be used to promote U(VI) biomineralization in subsurface sediments; (vi) characterize the effect of uranium on phytate hydrolysis by a new microorganism isolated from uranium-contaminated sediments; (vii) utilize positron-emission tomography to label and track metabolically-active bacteria in soil columns, and (viii) study the stability of the uranium phosphate mineral product. Microarray analyses and mineral precipitation characterizations were conducted in collaboration with DOE SBR-funded investigators at LBNL. Thus, microbial phosphorus metabolism has been shown to have a contributing role to uranium immobilization in the subsurface.

  3. Carbonate biomineralization in terrestrial gastropods: environmental vs. physiological constraints

    Science.gov (United States)

    Mierzwa, D.; Stolarski, J.

    2009-04-01

    Preservational potential of shells of terrestrial gastropods allows to use them as valuable (paleo)climatic proxies. Despite of the fact, that the elements incorporated in their skeleton derive almost entirely from their diet, details of the ion uptake routes have not been studied in details. This work is a first step in the investigations of element uptake and biomineralization processes in pulmonate gastropod Cepaea vindobonensis (Férussac, 1821). Although phenotypic plasticity in the shell characters of the species appears to be mainly genetic in nature, some differences seem to correlate with availability of ions used in biomineralization. For example, shells of individuals living in marginal parts of flood plains (environment extreme for the species and generally depleted in calcium) have weakened structure and faded color pattern, whereas individuals from the lime substrata form typically developed, pigmented shells with several cross-lamellar layers. Micro- and nanostructural characteristics of shells from different environments are visualized by SEM and AFM imaging techniques and some biogeochemical properties are characterized by spectroscopic and fluorescence methods. Further experiments are required to elucidate the ion/trace elements transfer between the substratum, nutrients, organism, and the shell.

  4. Structural insight into magnetochrome-mediated magnetite biomineralization

    Science.gov (United States)

    Siponen, Marina I.; Legrand, Pierre; Widdrat, Marc; Jones, Stephanie R.; Zhang, Wei-Jia; Chang, Michelle C. Y.; Faivre, Damien; Arnoux, Pascal; Pignol, David

    2013-10-01

    Magnetotactic bacteria align along the Earth's magnetic field using an organelle called the magnetosome, a biomineralized magnetite (Fe(II)Fe(III)2O4) or greigite (Fe(II)Fe(III)2S4) crystal embedded in a lipid vesicle. Although the need for both iron(II) and iron(III) is clear, little is known about the biological mechanisms controlling their ratio. Here we present the structure of the magnetosome-associated protein MamP and find that it is built on a unique arrangement of a self-plugged PDZ domain fused to two magnetochrome domains, defining a new class of c-type cytochrome exclusively found in magnetotactic bacteria. Mutational analysis, enzyme kinetics, co-crystallization with iron(II) and an in vitro MamP-assisted magnetite production assay establish MamP as an iron oxidase that contributes to the formation of iron(III) ferrihydrite eventually required for magnetite crystal growth in vivo. These results demonstrate the molecular mechanisms of iron management taking place inside the magnetosome and highlight the role of magnetochrome in iron biomineralization.

  5. Computer modeling of self-assembly of the crystal structure of zeolite Na384[Al384Si384O1536] (H2O)422 (LTN, cF4080) from suprapolyhedral cluster precursors AB2 (A-K48, B-K24)

    International Nuclear Information System (INIS)

    Combinatorial and topological analyses and a simulation of the self-assembly of zeolite crystal structure Na384Al384Si384O1536 · 422H2O (LTN, sp. gr. Fd3 bar) have been performed using computer methods (TOPOS program package). A cubic cell with the parameters a = 36.95 Å and V = 50 449 Å3 contains 768 framework-forming AlO4- and SiO4 tetrahedra (T tetrahedra). The method of complete expansion of a 3D factor graph in nonintersecting cluster substructures in the tetrahedral T framework was used to reveal nanocluster precursors: A composed of 48 T tetrahedra (A-K48) and B composed of 24 T tetrahedra (B-K24). The nanocluster precursors A and B correspond to the polyhedral T clusters (tiles) 48T-grc and 24T-toc; they are involved in the matrix self-assembly of the crystal structure within the supracluster AB2. The centers of clusters A and B occupy the positions of Mg and Cu atoms in the Laves net AB2 = MgCu2; i.e., the zeolite structure is a suprapolyhedral analog of an intermetallic compound. The self-assembly code of a 3D structure from complementary bound nanocluster precursors is completely reconstuctured in the following form: supracluster → primary chain → microlayer → microframework → ...framework. The localization of the Na+ template cations in the 6T- and 8T rings of nanocluster precursors A and B and Na+ spacer cations in the 28T-ltn tile with the formation of tetrahedral configuration and in the center of 6-ring, which arises as a result of bonding two B nanoclusters, is established.

  6. Redox control of iron biomineralization in Magnetospirillum magneticum AMB-1

    Science.gov (United States)

    Jones, Stephanie Rhianon

    Magnetotactic bacteria have evolved complex subcellular machinery to construct linear chains of magnetite nanocrystals that allow the host cell to sense direction. Each mixed-valent iron nanoparticle is mineralized from soluble iron within a membrane-encapsulated vesicle termed the magnetosome, which serves as a specialized compartment that regulates the iron, redox, and pH environment of the growing mineral. In order to dissect the biological components that control this process, we have carried out genetic and biochemical studies of proteins proposed to function in iron mineralization in Magnetospirillum magneticum AMB-1. As iron biomineralization by magnetotactic bacteria represents a particularly interesting case for understanding how the production of nanomaterials can be programmed at the genetic level, we also apply synthetic biology techniques towards the production of new cellular materials and new cellular functions. As the production of magnetite requires both the formation of Fe(II) and Fe(III), the redox components of the magnetosome play an essential role in this process. Using genetic complementation studies, we show that the redox cofactors or heme sites of the two putative redox partners, MamP and MamT, are required for magnetite biomineralization in vivo and that removal of one or both sites leads to defects in mineralization. We develop and optimize a heterologous expression method in the E. coli periplasm to cleanly isolate fully heme-loaded MamP for biochemical studies. Spectrochemical redox titrations show that the reduction potential of MamP lies in a different range than other c-type cytochrome involved in either Fe(III) reduction or Fe(II) oxidation. Nonetheless, in vitro mineralization studies with MamP and Fe(II) show that it is able to catalyze the formation of mixed-valent Fe(II)/Fe(III) oxides such as green rust. Biomineralization also requires lattice-templating proteins that guide the growth of the functional crystalline material. We

  7. In Vitro Biomineralization of Glutaraldehyde Crosslinked Chitosan Films

    Institute of Scientific and Technical Information of China (English)

    FENG Fang; LIU Yu; ZHAO Binyuan; HU Ke'ao

    2005-01-01

    The biomimetic approach was applied to study the in vitro biomineralization of series of the chitosan films crosslinked by glutaraldehyde. The deposited calcium phosphate coatings were studied using scanning electron microscopy and energy dispersive X-ray analysis. Initially, the treatment in simulated body fluid (SBF) results in the formation of single layer of calcium phosphate particles over the film surface. As immersion time in SBF increases, further nucleation and growth produce a simulated calcium phosphate coating. The Ca/P molar ratio of the calcium phosphate increases with the immersion time, showing a rapid formation of calcium-deficient phosphate material from the phase of octac1alcium phosphate. The different glutaraldehyde crosslinking degree influences the morphology and magnitude of the calcium phosphate coatings on the surface of the chitosan films.

  8. Biomineralization of magnet nanoparticles with bacterial symbionts of man

    Directory of Open Access Journals (Sweden)

    Horobets S.V.

    2014-06-01

    Full Text Available Bioinformational analysis of human’s bacterial symbionts (BS to study the process of biomineralization of biogenic magnetic nanoparticles (BMN was conducted. For this purpose in this paper a comparative analysis of amino acid sequences of proteins of magnetosome island of magnetotactic bacteria (MI MTB with human BS proteins using the program "BLAST-online" was made. A number of human BS may be potential producers of magnetic nanoparticles as evidenced by the experimental work of other authors. Considering obtained results it was shown that the interaction between tumor cells and some strains of human’s BS may occur due to the forces of magnetic dipole interaction, occuring between the endogenous magnetic nanoparticles of tumor cells and endogenous magnetosensitive particles of bacteria.

  9. Analysis by PIXE and PIGME of biomineralized tissues in the chiton Clavarizona hirtosa

    International Nuclear Information System (INIS)

    Procedures have been developed to determine, by PIXE and PIGME, the elemental composition of small samples (ca. 1 mg) of biomineralized tissue. The Fe, Ca and P contents of the radula of the chiton C. hirtosa increase considerably from the early to the late stage of mineralization. However, F is absent, indicating that at least in C. hirtosa, Ca and P biomineral deposits are most likely hydroxyapatite rather than fluoroapatite which has been reported in several other species

  10. Characterization of the pearl oyster (Pinctada martensii) mantle transcriptome unravels biomineralization genes.

    Science.gov (United States)

    Shi, Yaohua; Yu, Chengcheng; Gu, Zhifeng; Zhan, Xin; Wang, Yan; Wang, Aimin

    2013-04-01

    Pearl oyster, Pinctada martensii, is a marine bivalve species widely distributed in tropic and subtropic marine coasts. Mantle is the special tissue of P. martensii that secretes biomineralization proteins inducing shell deposition as well as iridescent nacre both in the inner shell and artificial nucleus. The pearl oyster is very efficient for artificial pearl production and is therefore an ideal organism for studies into the processes of biomineralization. However, deficiency of transcriptome information limits the insight into biomineralization mechanisms and pearl formation. In this study, we sequenced and characterized the P. martensii mantle transcriptome using 454 pyrosequencing. A total of 25,723 unique transcripts were assembled from 220,824 quality reads, followed by annotation and Gene Ontology classification analysis. A total of 146 unique transcript segments homologous to 49 reference biomineralization genes were identified, including calcineurin-binding protein, amorphous calcium carbonate binding protein 1, calmodulin, calponin-like protein, carbonic anhydrase 1, glycine-rich shell matrix protein, lysine-rich matrix protein, mantle gene or protein, nacrein, pearlin, PIF, regucalcin, and shematrin. The sequence data enabled the identification of 10,285 potential single nucleotide polymorphism loci and 7,836 putative indels, providing a resource for molecular biomarker, population genetics, and functional genomic studies. A large number of candidate genes for biomineralization were identified, considerably enriching resources for the study of shell formation. These sequence data will notably advance biomineralization and transcriptome study in pearl oyster and other Pinctada species.

  11. Deposition of calcium carbonate films by a polymer-induced liquid-precursor (PILP) process

    Science.gov (United States)

    Gower, Laurie B.; Odom, Damian J.

    2000-03-01

    A polypeptide additive has been used to transform the solution crystallization of calcium carbonate to a solidification process of a liquid-phase mineral precursor. In situ observations reveal that polyaspartate induces liquid-liquid phase separation of droplets of a mineral precursor. The droplets deposit on the substrate and coalesce to form a coating, which then solidifies into calcitic tablets and films. Transition bars form during the amorphous to crystalline transition, leading to sectorization of calcite tablets, and the defect textures and crystal morphologies are atypical of solution grown crystals. The formation of nonequilibrium crystal morphologies using an acidic polypeptide may have implications in the field of biomineralization, and the environmentally friendly aspects of this polymer-induced liquid-precursor (PILP) process may offer new techniques for aqueous-based processing of ceramic films, coatings, and particulates.

  12. 微生物成矿%Microbial Biomineralization

    Institute of Scientific and Technical Information of China (English)

    李一良; 王汝成; 周根涛; 张传伦

    2005-01-01

    微生物对生命元素如碳、氮、硫、氧和金属离子的代谢作用能显著的改变微生物周边的外部环境和其内部环境.在一系列的生物地球化学过程中,微生物参与了矿产的沉积(生物成矿)或参与了矿石和岩石的溶解(生物风化).生物成矿作用有两个途径:一个叫生物诱导成矿,通过这个过程,微生物分泌出代谢产物导致了之后的矿物颗粒的沉积;另一个叫生物控制成矿,在这个过程中,微生物在控制矿物成核和生长上起到了显著作用.微生物成因的矿物总体来说颗粒都很小和/或有着独特的同位素特征.最普遍的生物成因矿物有碳酸盐、硫化物和铁的氧化物.细胞表面和其分泌的胞外聚合物的结构可以为离子的浓缩、聚合和矿化提供模板,并起到重要作用.地球材料的仿生合成帮助我们了解了在人工条件下的生物成矿机制.此外,在地质环境中生物成因的矿物还可以作为一种生物信号,用来重建地球和其他行星的起源和演化.%Microbial metabolism of life-essential elements such as carbon, nitrogen, sulfur, oxygen and metals can significantly change the physicochemical conditions of their external or internal environments. Through a variety of biogeochemical processes, microorganisms mediate the precipitation of minerals (biomineralization) or dissolution of minerals or rocks (microbial weathering). Biomineralization can have two pathways. One is called biological induced mineralization by which organisms secrete metabolic products that result in subsequent deposition of mineral particles; another pathway is called biologically controlled mineralization by which the microbes exert a significant degree of control over the nucleation and growth of the minerals. The minerals of microbial genesis are generally characterized by small grain size and/or unique isotopic features. The most common biogenetic minerals are carbonates, sulfides and iron

  13. The Nanomechanics of Biomineralized Soft-Tissues and Organic Matrices

    Science.gov (United States)

    Bezares-Chavez, Jiddu

    The research reported on in this dissertation is concerned with the macro-molecular constitution and geometrical organization of the soft-tissue comprising the matrix of the nacreous portion of the shell of Haliotis rufescens, the Red abalone. Nacre is one of literally legions of intricate biomineralized structures that exist in nature and has long served as a paradigm for elegant and optimized structural de-sign. Biomineralization involves, inter alia, the uptake and synthesis of elements and compounds from the environment and their incorporation into highly optimized functional structures. Nacre has a structure described as a brick wall like with a matrix of biopolymer layers that are preformed and serve as a template into which nanocrystalline tiles of CaCO3 precipitate. The matrix, or what are known as inter-lamellar layers, are of particular interest as they impart both toughness and strength to the composite ceramic nacre structure. The work first involved a histochemical mapping of the macromolecular structure of the interlamellar layers; this revealed the locations of proteins and functional molecular groups that serve as nucleation sites for the ceramic tiles. Parallel studies on the nacre of Nautilus pompilius, the Chambered Nautilus, revealed the generality of the findings. Of particular interest was determining both the content and layout of chitin within these layers. In fact it was determined that chitin was organized as mostly unidirectional architecture of fibrils, with a certain fraction of fibrils laying at cross directions. Most remarkably, it was found that the fibrils possessed a very long range connectivity that spanned many tiles. This was determined by systematic atomic force (afm) and analytical optical histochemical microscopy. These findings were further verified by a unique form of mechanical testing whereby tensile testing was conducted on groups of interlamellar layers extracted from nacre. Mechanical testing led to a quantitative

  14. Biomineralization of Uranium:A Simulated Experiment and Its Significance

    Institute of Scientific and Technical Information of China (English)

    MIN Maozhong; Huifang XU; L. L. BARTON; WANG Jinping; PENG Xinjian; H. WIATROWSKI

    2005-01-01

    A simulated experimental reduction of UⅥ and the synthesis of uraninite by a sulfate-reducing bacteria,Desulfovibrio desulfuricans DSM 642, are first reported. The simulated physicochemical experimental conditions were:35℃, pH=7.0--7.4, corresponding to the environments of formation of the sandstone-hosted interlayer oxidation-zone type uranium deposits in Xinjiang, NW China. Uraninite was formed on the surface of the host bacteria after a one-week's incubation. Therefore, sulfate-reducing bacteria, which existed extensively in Jurassic sandstone-producing environments,might have participated in the biomineralization of this uranium deposit. There is an important difference in the orderdisorder of the crystalline structure between the uraninite produced by Desulfovibrio desulfuricans and naturally occurring uraninite. Long time and slow precipitation and growth of uraninite in the geological environment might have resulted in larger uraninite crystals, with uraninite nanocrystals arranged in order, whereas the experimentally produced uraninite is composed of unordered uraninite nanocrystals which, in contrast, result from the short time span of formation and rapid precipitation and growth of uraninite. The discovery has important implications for understanding genetic significance in mineralogy, and also indicates that in-situ bioremediation of U-contaminated environments and use of biotechnology in the treatment of radioactive liquid waste is being contemplated.

  15. REE compositions in fossil vertebrate dental tissues indicate biomineral preservation

    Science.gov (United States)

    Žigaite, Ž.; Kear, B.; Pérez-Huerta, A.; Jeffries, T.; Blom, H.

    2012-04-01

    Rare earth element (REE) abundances have been measured in a number of Palaeozoic and Mesozoic dental tissues using Laser Ablation Inductively Coupled Plasma Mass-spectrometry (LA-ICP-MS). Fossil vertebrates analysed comprise scales and tesserae of Silurian and Devonian acanthodians, chondrichthyans, galeaspids, mongolepids, thelodonts, as well as teeth of Cretaceous lungfish and marine reptiles. The evaluation of fossil preservation level has been made by semi-quantitative spot geochemistry analyses on fine polished teeth and scale thin sections, using Energy Dispersive X-ray Spectroscopy (EDS). Fossil teeth and scales with significant structure and colour alteration have shown elevated heavy element concentrations, and the silicification of bioapatite has been common in their tissues. Stable oxygen isotope measurements (δ18O) of bulk biomineral have been conducted in parallel, and showed comparatively lower heavy oxygen values in the same fossil tissues with stronger visible alteration. Significant difference in REE concentrations has been observed between the dentine and enamel of Cretaceous plesiosaurs, suggesting the enamel to be more geochemically resistant to diagenetic overprint.

  16. Microbial Diversity in KURT Groundwater and Biomineralization Characteristics

    International Nuclear Information System (INIS)

    The Underground Research Tunnel (URT) located in Korea Atomic Energy Research Institute (KAERI), Daejeon, South Korea was recently constructed as an experimental site to study radionuclide transport, biogeochemistry, radionuclide-mineral interactions for the geological disposal of high level nuclear waste. Groundwater sampled from URT was used to examine microbial diversity and to enrich metal reducing bacteria for studying microbe-metal interactions. Genomic analysis indicated that the groundwater contained diverse microorganisms such as metal reducers, metal oxidizers, anaerobic denitrifying bacteria, and bacteria for reductive dechlorination. Metal-reducing bacteria enriched from the groundwater was used to study metal reduction and biomineralization. The metal-reducing bacteria enriched with acetate or lactate as the electron donors showed the bacteria reduced Fe(III)-citrate, Fe(III) oxyhydroxides, Mn(IV) oxide, and Cr(VI) as the electron acceptors. Preliminary study indicated that the enriched bacteria were able to use glucose, lactate, acetate, and hydrogen as electron donors while reducing Fe(III)-citrate or Fe(III) oxyhydroxide as the electron acceptor. The bacteria exhibited diverse mineral precipitation capabilities including the formation of magnetite, siderite, and rhodochrosite. The results indicated that Fe(III)- and metal-reducing communities are present in URT at the KAERI

  17. Dynamic intratubular biomineralization following root canal obturation with pozzolan‐based mineral trioxide aggregate sealer cement

    Science.gov (United States)

    Yoo, Yeon‐Jee; Baek, Seung‐Ho; Kum, Kee‐Yeon; Shon, Won‐Jun; Woo, Kyung‐Mi

    2015-01-01

    Summary The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan‐based (Pz‐) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta‐percha (GP) and Pz‐MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz‐MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin‐material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz‐MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment. SCANNING 38:50–56, 2016. © 2015 The Authors. Scanning Published by Wiley Periodicals, Inc. PMID:26179659

  18. Dynamic intratubular biomineralization following root canal obturation with pozzolan-based mineral trioxide aggregate sealer cement.

    Science.gov (United States)

    Yoo, Yeon-Jee; Baek, Seung-Ho; Kum, Kee-Yeon; Shon, Won-Jun; Woo, Kyung-Mi; Lee, WooCheol

    2016-01-01

    The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan-based (Pz-) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta-percha (GP) and Pz-MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz-MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin-material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz-MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment.

  19. Localization of calmodulin and calmodulin-like protein and their functions in biomineralization in P. fucata

    Institute of Scientific and Technical Information of China (English)

    Zi Fang; Zhenguang Yan; Shuo Li; Qin Wang; Weizhong Cao; Guangrui Xu; Xunhao Xiong; Liping Xie; Rongqing Zhang

    2008-01-01

    Calmodulin (CaM) and calmodulin-like protein (CaLP) are two proteins involved in biomineralization. Their localizations in Pinct-ada fucata mantle epithelia were studied by Western blot (WB) analysis of the nuclear/cytosol fraction of primary cultured P. fucata mantle cells and immunogold electron microscopy. The results showed a completely different distribution of these two proteins at the subcellular level. CaM was distributed throughout both the nucleus and cytoplasm of the mantle epithelium but CaLP was distributed only in the cytoplasm. The functions of these two proteins in biomineralization were investigated by shell regeneration. During this process, the expressions of CaM and CaLP were greatly enhanced in different organelles of the mantle epithelium. Overexpression of these two proteins and a mutant of calmodulin-like protein (M-CaLP) that lacks an extra C-terminal tail in MC3T3-E1 promoted the mRNA expression of osteopontin, a biomineralization marker for osteoblasts. All of the results indicated that CaM and CaLP have completely different distributions in the mantle epithelium and affect the biomineralization process at different levels. The extra C-terminal tail of CaLP is important for its functions in biomineralization in P. fucata.

  20. Magnetite biomineralization in Magnetospirillum gryphiswaldense: time-resolved magnetic and structural studies.

    Science.gov (United States)

    Fdez-Gubieda, M Luisa; Muela, Alicia; Alonso, Javier; García-Prieto, Ana; Olivi, Luca; Fernández-Pacheco, Rodrigo; Barandiarán, José Manuel

    2013-04-23

    Magnetotactic bacteria biosynthesize magnetite nanoparticles of high structural and chemical purity that allow them to orientate in the geomagnetic field. In this work we have followed the process of biomineralization of these magnetite nanoparticles. We have performed a time-resolved study on magnetotactic bacteria Magnetospirillum gryphiswaldense strain MSR-1. From the combination of magnetic and structural studies by means of Fe K-edge X-ray absorption near edge structure (XANES) and high-resolution transmission electron microscopy we have identified and quantified two phases of Fe (ferrihydrite and magnetite) involved in the biomineralization process, confirming the role of ferrihydrite as the source of Fe ions for magnetite biomineralization in M. gryphiswaldense. We have distinguished two steps in the biomineralization process: the first, in which Fe is accumulated in the form of ferrihydrite, and the second, in which the magnetite is rapidly biomineralized from ferrihydrite. Finally, the XANES analysis suggests that the origin of the ferrihydrite could be at bacterial ferritin cores, characterized by a poorly crystalline structure and high phosphorus content.

  1. Earthquakes: hydrogeochemical precursors

    Science.gov (United States)

    Ingebritsen, Steven E.; Manga, Michael

    2014-01-01

    Earthquake prediction is a long-sought goal. Changes in groundwater chemistry before earthquakes in Iceland highlight a potential hydrogeochemical precursor, but such signals must be evaluated in the context of long-term, multiparametric data sets.

  2. Application of SEM and EDX in studying biomineralization in plant tissues.

    Science.gov (United States)

    He, Honghua; Kirilak, Yaowanuj

    2014-01-01

    This chapter describes protocols using formalin-acetic acid-alcohol (FAA) to fix plant tissues for studying biomineralization by means of scanning electron microscopy (SEM) and qualitative energy-dispersive X-ray microanalysis (EDX). Specimen preparation protocols for SEM and EDX mainly include fixation, dehydration, critical point drying (CPD), mounting, and coating. Gold-coated specimens are used for SEM imaging, while gold- and carbon-coated specimens are prepared for qualitative X-ray microanalyses separately to obtain complementary information on the elemental compositions of biominerals. During the specimen preparation procedure for SEM, some biominerals may be dislodged or scattered, making it difficult to determine their accurate locations, and light microscopy is used to complement SEM studies. Specimen preparation protocols for light microscopy generally include fixation, dehydration, infiltration and embedding with resin, microtome sectioning, and staining. In addition, microwave processing methods are adopted here to speed up the specimen preparation process for both SEM and light microscopy.

  3. Origin and Status of Homologous Proteins of Biomineralization (Biosilicification in the Taxonomy of Phylogenetic Domains

    Directory of Open Access Journals (Sweden)

    Igor E. Pamirsky

    2013-01-01

    Full Text Available The taxonomic affiliation (in the systematisation of viruses, and biological domains of known peptides and proteins of biomineralization (silicateins, silaffins, silacidins and silicase and their primary structure homologues were analyzed (methods in silico; using Uniprot database. The total number of known peptides and proteins of biosilicification was counted. The data of the quantitative distribution of the detected homologues found in nature are presented. The similarity of the primary structures of silaffins, silacidins, silicateins, silicase, and their homologues was 21–94%, 45–98%, 39–50%, and 28–40%, respectively. These homologues are found in many organisms, from the Protista to the higher plants and animals, including humans, as well as in bacteria and extracellular agents, and they perform a variety of biological functions, such as biologically controlled mineralisation. The provisional classification of these biomineralization proteins is presented. The interrelation of the origin of the first organic polymers and biomineralization is discussed.

  4. Kinetic analysis of simultaneous denitrification and biomineralization of novel Acinetobacter sp. CN86.

    Science.gov (United States)

    Su, Jun-Feng; Shi, Jing-Xin; Huang, Ting-Lin; Ma, Fang

    2016-08-15

    A novel aerobic denitrification and biomineralization strain CN86 was isolated from the Qu Jiang artificial lake. Based on phylogenetic characteristics, the isolated strain was identified as Acinetobacter species. Strain CN86 was confirmed to have the ability to perform simultaneous denitrification and biomineralization. Exponential decay equation was used for the matching of kinetic processes on denitrification and biomineralization. A highest nitrate removal rate was achieved at the pH7.0, organic concentration of 1.5g/L and temperature of 30°C. An optimal hardness removal rate was obtained at the pH9.0, organic concentration of 2.0g/L and temperature of 30°C. Strain CN86 is a suitable candidate for the simultaneous removal of nitrate and hardness in groundwater treatment. PMID:27287863

  5. Calcification in vitro of Biomineralized nanohydroxyapatite / superhydrophilic vertically aligned multiwalled carbon nanotube scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Marcele Florencio; Silva, Gislene Rodrigues; Brazil, Tayra Rodrigues; Marciano, Fernanda Roberta; Lobo, Anderson Oliveira, E-mail: loboao@yahoo.com, E-mail: aolobo@univap.br [Universidade do Vale do Paraiba (UniVap), Sao Jose dos Campos, SP (Brazil). Lab. de Nanotecnologia Biomedica; Pacheco-Soares, Cristina [Universidade do Vale do Paraiba (UniVap), Sao Jose dos Campos, SP (Brazil). Lab. de Dinamica de Compartimentos Celulares

    2013-11-01

    Nanocomposites based on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O{sub 2}) and nanohydroxyapatite (nHAp) are of great interest in bone regenerative medicine. The biomineralization using simulated body fluid (SBF) has been extensively studied to evaluate the bioactivity of biomaterials. Thus, the combination of nHAp and VAMWCNT-O{sub 2} is attractive and promising. The aim of this study was to evaluate the in vitro calcification of nHAp/VAMWCNT-O{sub 2} nanocomposites before and after the period of biomineralization in SBF. In vitro calcification of the extracellular matrix (ECM) of HOB cells in culture after 24 hours was investigated through the assay of alkaline phosphatase. These promising in vitro results validate biomineralized nHAp/VAMWCNT-O{sub 2} as possible scaffolds for bone tissue regeneration. (author)

  6. Carbonate biomineralization induced by soil bacterium Bacillus megaterium

    Science.gov (United States)

    Lian, Bin; Hu, Qiaona; Chen, Jun; Ji, Junfeng; Teng, H. Henry

    2006-11-01

    Biogenic carbonates spawned from microbial activities are common occurrences in soils. Here, we investigate the carbonate biomineralization mediated by the bacterium Bacillus megaterium, a dominant strain separated from a loess profile in China. Upon completing bacterial cultivation, the ensuring products are centrifuged, and the resultant supernatant and the concentrated bacterial sludge as well as the un-separated culture are added separately into a Ca-CO 3 containing solution for crystallization experiments. Results of XRD and SEM analysis indicate that calcite is the dominant mineral phase formed when the bacteria are present. When the supernatant alone is used, however, a significant portion of vaterite is also precipitated. Experimental results further reveal that the bacteria have a strong tendency to colonize the center area of the calcite {1 0 1¯ 4} faces. Observed crystal morphology suggests that the bacterial colony may promote the growth normal to each individual {1 0 1¯ 4} face of calcite when the cell concentration is high, but may retard it or even cause dissolution of the immediate substrate surfaces when the concentration is low. SEM images taken at earlier stages of the crystallization experiments demonstrate the nucleation of calcite on the bacterial cell walls but do not show obvious morphological changes on the nanometer- to submicron-sized nuclei. δ 13C measurements unveil that the crystals grown in the presence of bacteria are further enriched in the heavy carbon isotope, implying that the bacterial metabolism may not be the carbon sources for the mineralization. Based upon these findings, we propose a mechanism for the B. megaterium mediated calcite mineralization and conclude that the whole process involves epi- and inter-cellular growth in the local microenvironments whose conditions may be controlled by cell sequestration and proton pumping during bacterial respiration.

  7. Spatial analysis of biomineralization associated gene expression from the mantle organ of the pearl oyster Pinctada maxima

    Directory of Open Access Journals (Sweden)

    Leavesley David

    2011-09-01

    Full Text Available Abstract Background Biomineralization is a process encompassing all mineral containing tissues produced within an organism. One of the most dynamic examples of this process is the formation of the mollusk shell, comprising a variety of crystal phases and microstructures. The organic component incorporated within the shell is said to dictate this architecture. However general understanding of how this process is achieved remains ambiguous. The mantle is a conserved organ involved in shell formation throughout molluscs. Specifically the mantle is thought to be responsible for secreting the protein component of the shell. This study employs molecular approaches to determine the spatial expression of genes within the mantle tissue to further the elucidation of the shell biomineralization. Results A microarray platform was custom generated (PmaxArray 1.0 from the pearl oyster Pinctada maxima. PmaxArray 1.0 consists of 4992 expressed sequence tags (ESTs originating from mantle tissue. This microarray was used to analyze the spatial expression of ESTs throughout the mantle organ. The mantle was dissected into five discrete regions and analyzed for differential gene expression with PmaxArray 1.0. Over 2000 ESTs were determined to be differentially expressed among the tissue sections, identifying five major expression regions. In situ hybridization validated and further localized the expression for a subset of these ESTs. Comparative sequence similarity analysis of these ESTs revealed a number of the transcripts were novel while others showed significant sequence similarities to previously characterized shell related genes. Conclusions This investigation has mapped the spatial distribution for over 2000 ESTs present on PmaxArray 1.0 with reference to specific locations of the mantle. Expression profile clusters have indicated at least five unique functioning zones in the mantle. Three of these zones are likely involved in shell related activities

  8. Identification of Desirable Precursor Properties for Solution Precursor Plasma Spray

    Science.gov (United States)

    Muoto, Chigozie K.; Jordan, Eric H.; Gell, Maurice; Aindow, Mark

    2011-06-01

    In solution precursor plasma spray chemical precursor solutions are injected into a standard plasma torch and the final material is formed and deposited in a single step. This process has several attractive features, including the ability to rapidly explore new compositions and to form amorphous and metastable phases from molecularly mixed precursors. Challenges include: (a) moderate deposition rates due to the need to evaporate the precursor solvent, (b) dealing on a case by case basis with precursor characteristics that influence the spray process (viscosity, endothermic and exothermic reactions, the sequence of physical states through which the precursor passes before attaining the final state, etc.). Desirable precursor properties were identified by comparing an effective precursor for yttria-stabilized zirconia with four less effective candidate precursors for MgO:Y2O3. The critical parameters identified were a lack of major endothermic events during precursor decomposition and highly dense resultant particles.

  9. Magnetosomal matrix: ultrafine structure may template biomineralization of magnetosomes.

    Science.gov (United States)

    Taylor, A P; Barry, J C

    2004-02-01

    The organic matrix surrounding bullet-shaped, cubo-octahedral, D-shaped, irregular arrowhead-shaped, and truncated hexa-octahedral magnetosomes was analysed in a variety of uncultured magnetotactic bacteria. The matrix was examined using low- (80 kV) and intermediate- (400 kV) voltage TEM. It encapsulated magnetosomes in dehydrated cells, ultraviolet-B-irradiated dehydrated cells and stained resin-embedded fixed cells, so the apparent structure of the matrix does not appear to be an artefact of specimen preparation. High-resolution images revealed lattice fringes in the matrix surrounding magnetite and greigite magnetosomes that were aligned with lattice fringes in the encapsulated magnetosomes. In all except one case, the lattice fringes had widths equal to or twice the width of the corresponding lattice fringes in the magnetosomes. The lattice fringes in the matrix were aligned with the [311], [220], [331], [111] and [391] related lattice planes of magnetite and the [222] lattice plane of greigite. An unidentified material, possibly an iron hydroxide, was detected in two immature magnetosomes containing magnetite. The unidentified phase had a structure similar to that of the matrix as it contained [311], [220] and [111] lattice fringes, which indicates that the matrix acts as a template for the spatially controlled biomineralization of the unidentified phase, which itself transforms into magnetite. The unidentified phase was thus called pre-magnetite. The presence of the magnetosomal matrix explains all of the five properties of the biosignature of the magnetosomal chain proposed previously by Friedmann et al. and supports their claim that some of the magnetite particles in the carbonate globules in the Martian meteorite ALH84001 are biogenic. Two new morphologies of magnetite magnetosomes are also reported here (i.e. tooth-shaped and hexa-octahedral magnetosomes). Tooth-shaped magnetite magnetosomes elongated in the [110] direction are reported, and are distinct

  10. Regulating proliferation and differentiation of osteoblasts on poly(l-lactide)/gelatin composite nanofibers via timed biomineralization.

    Science.gov (United States)

    Zhang, Caijin; Cao, Man; Lan, Jinle; Wei, Pengfei; Cai, Qing; Yang, Xiaoping

    2016-08-01

    Mimicking the natural bone extracellular matrix, biomineralized nanofibers are envisioned as good choices for bone regeneration. Herein, composite nanofibers composed of poly(L-lactide) (PLLA) and gelatin (50/50, w/w) were electrospun and soaked in a modified five times simulated body fluid (SBF) for 6-24 h. Along with the soaking time, the amounts of deposited minerals increased, and the minerals transformed from dicalcium phosphate dehydrate (DCPD) to hydroxyapatite (HA). Mineral dissolution and Ca(2+) ion release of these biomineralized nanofibers were investigated by putting them in deionized water or Hank's balanced salt solution. MC3T3-E1 osteoblasts were cultured in transwell chambers without contacting the materials or on the biomineralized nanofibers directly. In the noncontact culture, the released ions were found able to enhance osteogenic differentiation more significantly in comparison with cell proliferation. In the contact culture, all biomineralized nanofibers demonstrated strong ability in promoting both cell proliferation and osteogenic differentiation. Due to the fast dissolution of DCPD, the biomineralized nanofibers obtained from short SBF soaking was found to be inferior in enhancing osteogenic differentiation. Whereas the cells displayed high levels of alkaline phosphatase activity and collagen I synthesis when the material had abundant deposition of apatite. The results revealed that cell biological behaviors were synergistically influenced by the ionic dissolution products, the composition, and the morphology of biomineralized nanofibers, which could be regulated by timed biomineralization. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1968-1980, 2016. PMID:27027483

  11. Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria.

    Science.gov (United States)

    Abreu, Fernanda; Cantão, Mauricio E; Nicolás, Marisa F; Barcellos, Fernando G; Morillo, Viviana; Almeida, Luiz Gp; do Nascimento, Fabrícia F; Lefèvre, Christopher T; Bazylinski, Dennis A; R de Vasconcelos, Ana Tereza; Lins, Ulysses

    2011-10-01

    Magnetosomes are prokaryotic organelles produced by magnetotactic bacteria that consist of nanometer-sized magnetite (Fe(3)O(4)) or/and greigite (Fe(3)S(4)) magnetic crystals enveloped by a lipid bilayer membrane. In magnetite-producing magnetotactic bacteria, proteins present in the magnetosome membrane modulate biomineralization of the magnetite crystal. In these microorganisms, genes that encode for magnetosome membrane proteins as well as genes involved in the construction of the magnetite magnetosome chain, the mam and mms genes, are organized within a genomic island. However, partially because there are presently no greigite-producing magnetotactic bacteria in pure culture, little is known regarding the greigite biomineralization process in these organisms including whether similar genes are involved in the process. Here using culture-independent techniques, we now show that mam genes involved in the production of magnetite magnetosomes are also present in greigite-producing magnetotactic bacteria. This finding suggest that the biomineralization of magnetite and greigite did not have evolve independently (that is, magnetotaxis is polyphyletic) as once suggested. Instead, results presented here are consistent with a model in which the ability to biomineralize magnetosomes and the possession of the mam genes was acquired by bacteria from a common ancestor, that is, the magnetotactic trait is monophyletic. PMID:21509043

  12. Deciphering the Physical Basis of Biomineralization through Investigations of Nanoscale Growth Processes

    Science.gov (United States)

    Dove, P. M.; Davis, K. J.; De Yoreo, J. J.; Orme, C. A.

    2001-12-01

    Microbes and higher organisms direct the formation of complex structures in controlled biomineralization. Using biologically mediated crystallization strategies that have evolved over millenia, organisms have developed the ability to produce nanophase structures as single crystals and composite materials with remarkable properties that fulfill specific functional needs. Modern organisms, as well as those found in the sediment and rock records, chronicle Nature's ability to synthesize sophisticated nanostructures. Although biomineral compositions and their morphologies are windows to interpreting environments of prosperity and decline, most current interpretations lack an understanding of fundamental processes. Hence, the physical basis of biological mineralization continues as one of Nature's best kept secrets. Recently, the biomineralization processes of marine microorganisms have emerged as particularly important owing to the use of biomineral products as paleoclimate indicators. Besides providing critical information on crystal growth history, the minor and trace elements found in these materials also behave as impurities to regulate their properties and formation rates. Using integrated approaches, we are investigating the kinetics and thermodynamics of calcite growth to decipher mechanisms of biomineral formation. Our focus is to link molecular interactions with surface processes and nanoscale controls on crystal morphology. The molecular-scale structure of the crystalline interface is a critical growth determinant, especially when considering nanocrystalline phases. By combining in situ AFM studies of growth that use carefully characterized solution chemistries with molecular modeling and surface spectroscopic investigations, we couple observations of nanoscale growth mechanisms with quantitative kinetic and thermodynamic information. This approach is showing how key inorganic growth impurities, Mg2+ and Sr2+, affect mineralization through complex ion

  13. The EM Earthquake Precursor

    Science.gov (United States)

    Jones, K. B., II; Saxton, P. T.

    2013-12-01

    Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After the 1989 Loma Prieta Earthquake, American earthquake investigators predetermined magnetometer use and a minimum earthquake magnitude necessary for EM detection. This action was set in motion, due to the extensive damage incurred and public outrage concerning earthquake forecasting; however, the magnetometers employed, grounded or buried, are completely subject to static and electric fields and have yet to correlate to an identifiable precursor. Secondly, there is neither a networked array for finding any epicentral locations, nor have there been any attempts to find even one. This methodology needs dismissal, because it is overly complicated, subject to continuous change, and provides no response time. As for the minimum magnitude threshold, which was set at M5, this is simply higher than what modern technological advances have gained. Detection can now be achieved at approximately M1, which greatly improves forecasting chances. A propagating precursor has now been detected in both the field and laboratory. Field antenna testing conducted outside the NE Texas town of Timpson in February, 2013, detected three strong EM sources along with numerous weaker signals. The antenna had mobility, and observations were noted for recurrence, duration, and frequency response. Next, two

  14. Biomineralization-inspired synthesis of functional organic/inorganic hybrid materials: organic molecular control of self-organization of hybrids.

    Science.gov (United States)

    Arakaki, Atsushi; Shimizu, Katsuhiko; Oda, Mayumi; Sakamoto, Takeshi; Nishimura, Tatsuya; Kato, Takashi

    2015-01-28

    Organisms produce various organic/inorganic hybrid materials, which are called biominerals. They form through the self-organization of organic molecules and inorganic elements under ambient conditions. Biominerals often have highly organized and hierarchical structures from nanometer to macroscopic length scales, resulting in their remarkable physical and chemical properties that cannot be obtained by simple accumulation of their organic and inorganic constituents. These observations motivate us to create novel functional materials exhibiting properties superior to conventional materials--both synthetic and natural. Herein, we introduce recent progress in understanding biomineralization processes at the molecular level and the development of organic/inorganic hybrid materials by these processes. We specifically outline fundamental molecular studies on silica, iron oxide, and calcium carbonate biomineralization and describe material synthesis based on these mechanisms. These approaches allow us to design a variety of advanced hybrid materials with desired morphologies, sizes, compositions, and structures through environmentally friendly synthetic routes using functions of organic molecules.

  15. Cuticular Biominerals of the Terrestrial Crustacean Oniscus asellus (Isopoda, Linnaeus 1758)

    Science.gov (United States)

    Mergelsberg, S. T.; Mukhopadhyay, B.; Dove, P. M.

    2013-12-01

    Biomineralization is a phenomenon observed in many eukaryotic organisms and evidence suggests this process began relatively early in the evolution of multicellular life (Marin F et al. 1996). Crustaceans form a large fraction of all eukaryotic biomineralizers by incorporating calcium carbonate (CaCO3) into their cuticle. Terrestrial species are challenged in their production of CaCO3 by the absence of calcium-rich waters. To cope with this limitation, the terrestrial crustacean Oniscus asellus recycles up to 80% (Auzou G 1953) of its total calcium during the molting process. This feat is accomplished by separate molting of the front and back cuticle, with temporary storage of the calcium carbonate as amorphous calcium carbonate (ACC) in the front half (Ziegler A 1997). These processes infer a highly efficient and regulated mechanism for biomineralization that is most likely orchestrated by a myriad of proteins (Ziegler A et al. 2012). Until recently, investigations of biomineralization were largely directed toward understanding morphology and large-scale chemistry of the minerals, ignoring the mechanistic roles of biomacromolecules in mineralization processes. More recent work suggests a high involvement of these compounds on the formation of biominerals and, in some cases, the specific polymorphs thereof (Keene EC et al. 2010). This study focuses on identifying the components of the biological mineralization matrix at each stage of the process. Using chemical demineralization of the stored ACC, all biomacromolecules can be separated and purified for subsequent analysis by MALDI-TOF mass spectrometry. To link the localized biochemistry more intimately to the polymorph of calcium carbonate that forms in the animal, the inorganic phase (';the mineral') will be monitored at each life stage using XRD and TEM. This analysis will reveal the organic components of a very precise biomineralization mechanism and may shed insight on its evolutionary origin. References: Marin

  16. Calcifying Cyanobacteria - The potential of biomineralization for Carbon Capture and Storage

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Christer G; Northen, Trent

    2010-03-26

    Employment of cyanobacteria in biomineralization of carbon dioxide by calcium carbonate precipitation offers novel and self-sustaining strategies for point-source carbon capture and sequestration. Although details of this process remain to be elucidated, a carbon-concentrating mechanism, and chemical reactions in exopolysaccharide or proteinaceous surface layers are assumed to be of crucial importance. Cyanobacteria can utilize solar energy through photosynthesis to convert carbon dioxide to recalcitrant calcium carbonate. Calcium can be derived from sources such as gypsum or industrial brine. A better understanding of the biochemical and genetic mechanisms that carry out and regulate cynaobacterial biomineralization should put us in a position where we can further optimize these steps by exploiting the powerful techniques of genetic engineering, directed evolution, and biomimetics.

  17. Proposed model for biomineralization of novel nanohydroxyapatite/vertically aligned multiwalled carbon nanotube scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Brazil, Tayra Rodrigues; Neves, Marcele Florencio das; Marciano, Fernanda Roberta; Lobo, Anderson Oliveira, E-mail: aolobo@univap.br [Universidade do Vale do Paraiba (UniVap), Sao Jose dos Campos, SP (Brazil). Lab. de Nanotecnologia Biomedica; Regiani, Inacio [Instituto Tecnologico de Aeronautica (ITA), Sao Jose dos Campos, SP (Brazil)

    2013-11-01

    For the first time, the growth mechanism of biominerals formed on plate-like nanohydroxyapatite (nHAp) electrodeposited on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O{sub 2} ) is presented and a model for the specific growth preference is discussed. VAMWCNT-O{sub 2} films were obtained by microwave-assisted chemical vapor deposition method and functionalized by oxygen plasma. nHAp/VAMWCNT-O{sub 2} nanocomposites were fabricated with a direct electrodeposition of the thin nHAp films onto the VAMWCNT-O{sub 2} films. The biomineralized 'scaffolds' were obtained by soaking nHAp/VAMWCNT-O{sub 2} in simulated body fluid for 7, 14 and 21 days. Results show that the carboxyl functional groups directly attached onto VAMWCNT tips after oxygen plasma treatment were essential for the acceleration of the OH- formation and the deposition of plate-like nHAp crystals (author)

  18. Biomineralization of unicellular organisms: an unusual membrane biochemistry for the production of inorganic nano- and microstructures.

    Science.gov (United States)

    Bäuerlein, Edmund

    2003-02-10

    With evolution, Nature has ingeniously succeeded in giving rise to an impressive variety of inorganic structures. Every organism that synthesizes biogenic minerals does so in a form that is unique to that species. This biomineralization is apparently biologically controlled. It is thus expected that both the synthesis and the form of every specific biogenic mineral is genetically determined and controlled. An investigation of the mechanism of biomineralization has only become possible with the development of modern methods in molecular biology. Unicellular organisms such as magnetic bacteria, calcareous algae, and diatoms, all of which are amongst the simplest forms of life, are particularly suited to be investigated by these methods. Crystals and composites of proteins and amorphous inorganic polymers are formed as complex structures within these organisms; these structures are not known in conventional inorganic chemistry.

  19. Calcifying cyanobacteria--the potential of biomineralization for carbon capture and storage.

    Science.gov (United States)

    Jansson, Christer; Northen, Trent

    2010-06-01

    Employment of cyanobacteria in biomineralization of carbon dioxide by calcium carbonate precipitation offers novel and self-sustaining strategies for point-source carbon capture and sequestration. Although details of this process remain to be elucidated, a carbon-concentrating mechanism, and chemical reactions in exopolysaccharide or proteinaceous surface layers are assumed to be of crucial importance. Cyanobacteria can utilize solar energy through photosynthesis to convert carbon dioxide to recalcitrant calcium carbonate. Calcium can be derived from sources such as gypsum or industrial brine. A better understanding of the biochemical and genetic mechanisms that carry out and regulate cynaobacterial biomineralization should put us in a position where we can further optimize these steps by exploiting the powerful techniques of genetic engineering, directed evolution, and biomimetics.

  20. Leading time domain seismic precursors

    Science.gov (United States)

    Boucouvalas, A. C.; Gkasios, M.; Keskebes, A.; Tselikas, N. T.

    2014-08-01

    The problem of predicting the occurrence of earthquakes is threefold. On one hand it is necessary to predict the date and magnitude of an earthquake, and on the other hand the location of the epicenter. In this work after a brief review of the state of earthquake prediction research, we report on a new leading time precursor for determining time onset of earthquake occurrence. We report the linking between earthquakes of the past with those which happen in the future via Fibonacci, Dual and Lucas numbers (FDL) numbers. We demonstrate it here with two example seed earthquakes at least 100 years old. Using this leading indicator method we can predict significant earthquake events >6.5R, with good accuracy approximately +- 1 day somewhere in the world. From a single seed we produce at least 100 trials simultaneously of which 50% are correct to +- 1day. The indicator is based on Fibonacci, Dual and Lucas numbers (FDL). This result hints that the log periodic FDL numbers are at the root of the understanding of the earthquake mechanism. The theory is based on the assumption that each occurred earthquake discontinuity can be thought of as a generating source of FDL time series. (The mechanism could well be linked to planetary orbits). When future dates are derived from clustering and convergence from previous strong earthquake dates at an FDL time distance, then we have a high probability for an earthquake to occur on that date. We set up a real time system which generates FDL time series from each previous significant earthquake (>7R) and we produce a year to year calendar of high probability earthquake dates. We have tested this over a number of years with considerable success. We have applied this technique for strong (>7R) earthquakes across the globe as well as on a restricted region such as the Greek geographic region where the magnitude is small (>4R-6.5R). In both cases the success of the method is impressive. It is our belief that supplementing this method with

  1. Cementomimetics-constructing a cementum-like biomineralized microlayer via amelogenin-derived peptides.

    Science.gov (United States)

    Gungormus, Mustafa; Oren, Ersin E; Horst, Jeremy A; Fong, Hanson; Hnilova, Marketa; Somerman, Martha J; Snead, Malcolm L; Samudrala, Ram; Tamerler, Candan; Sarikaya, Mehmet

    2012-06-01

    Cementum is the outer-, mineralized-tissue covering the tooth root and an essential part of the system of periodontal tissue that anchors the tooth to the bone. Periodontal disease results from the destructive behavior of the host elicited by an infectious biofilm adhering to the tooth root and left untreated, may lead to tooth loss. We describe a novel protocol for identifying peptide sequences from native proteins with the potential to repair damaged dental tissues by controlling hydroxyapatite biomineralization. Using amelogenin as a case study and a bioinformatics scoring matrix, we identified regions within amelogenin that are shared with a set of hydroxyapatite-binding peptides (HABPs) previously selected by phage display. One 22-amino acid long peptide regions referred to as amelogenin-derived peptide 5 (ADP5) was shown to facilitate cell-free formation of a cementum-like hydroxyapatite mineral layer on demineralized human root dentin that, in turn, supported attachment of periodontal ligament cells in vitro. Our findings have several implications in peptide-assisted mineral formation that mimic biomineralization. By further elaborating the mechanism for protein control over the biomineral formed, we afford new insights into the evolution of protein-mineral interactions. By exploiting small peptide domains of native proteins, our understanding of structure-function relationships of biomineralizing proteins can be extended and these peptides can be utilized to engineer mineral formation. Finally, the cementomimetic layer formed by ADP5 has the potential clinical application to repair diseased root surfaces so as to promote the regeneration of periodontal tissues and thereby reduce the morbidity associated with tooth loss.

  2. Sea shell diversity and rapidly evolving secretomes: insights into the evolution of biomineralization.

    Science.gov (United States)

    Kocot, Kevin M; Aguilera, Felipe; McDougall, Carmel; Jackson, Daniel J; Degnan, Bernard M

    2016-01-01

    An external skeleton is an essential part of the body plan of many animals and is thought to be one of the key factors that enabled the great expansion in animal diversity and disparity during the Cambrian explosion. Molluscs are considered ideal to study the evolution of biomineralization because of their diversity of highly complex, robust and patterned shells. The molluscan shell forms externally at the interface of animal and environment, and involves controlled deposition of calcium carbonate within a framework of macromolecules that are secreted from the dorsal mantle epithelium. Despite its deep conservation within Mollusca, the mantle is capable of producing an incredible diversity of shell patterns, and macro- and micro-architectures. Here we review recent developments within the field of molluscan biomineralization, focusing on the genes expressed in the mantle that encode secreted proteins. The so-called mantle secretome appears to regulate shell deposition and patterning and in some cases becomes part of the shell matrix. Recent transcriptomic and proteomic studies have revealed marked differences in the mantle secretomes of even closely-related molluscs; these typically exceed expected differences based on characteristics of the external shell. All mantle secretomes surveyed to date include novel genes encoding lineage-restricted proteins and unique combinations of co-opted ancient genes. A surprisingly large proportion of both ancient and novel secreted proteins containing simple repetitive motifs or domains that are often modular in construction. These repetitive low complexity domains (RLCDs) appear to further promote the evolvability of the mantle secretome, resulting in domain shuffling, expansion and loss. RLCD families further evolve via slippage and other mechanisms associated with repetitive sequences. As analogous types of secreted proteins are expressed in biomineralizing tissues in other animals, insights into the evolution of the genes

  3. Can environmental conditions trigger cyanobacterial surfaces and following carbonate formation: implication for biomineralization and biotechnology

    Science.gov (United States)

    Paulo, C.; Dittrich, M.; Zhu, T.

    2015-12-01

    In this presentation we will give an overview what kind of the factors may trigger carbonate formations at the cell surfaces under a variety of environmental conditions. As examples, we will present the results from our recent studies on formation of calcium carbonates, dolomites and bio-cements. The extracellular polymeric substances (EPS) in the Synechococcuscell envelope are recognized key players in the nucleation of carbonates in marine and freshwater environments. Yet, little is known about a nutrient contents control over the molecular composition of Synechococcus cell envelope, and consequently, biomineralization. In the first study, we investigated how a variation of the phosphorus (P) in the growth media can lead to changes in the surface reactivity of the cells and impact their ability to form carbonates. The objective of the second study is to gain insights into the spatial distribution of cyanobacterial EPS and dolomite from different sediment layers of Khor Al-Adaid sabkha (Qatar). Here, we characterized microbial mats on molecular level in respect of organic and inorganic components using in-situ 2D Raman spectroscopy and Atomic Force Microscopy (AFM) were used. Additionally, 2D chemical maps of sediment layers documented spectral characterizations of minerals and organic matter of microbial origins at high spatial resolution. Finally, we will show the results from the experiments with auto-phototrophic cyanobacteria Gloeocapsa PCC73106, which habitat on the monument surfaces, towards its application for bio-concrete, a product of microbial carbonate precipitation. We studied the biomineralization in biofilm forming Gloeocapsa PCC73106 on the concrete surface as a pre-requirement for microbial carbonate precipitation. Biomineralization on the concrete surface by live cells and killed cells were compared with that under the abiotic condition. Our experiments allow us to conclude that environmental conditions play a significant role in the control of

  4. Biomineral Processing: A Valid Eco-Friendly Alternative for Metal Extraction.

    OpenAIRE

    Sandeep Panda; Lala Behari Sukla; Jacintha Esther; Nilotpala Pradhan

    2014-01-01

    Over the past few years, the applications of certain microorganisms have gained importance in the field of applied environmental microbiology. Amongst them, biomineral processing is such field that deals with metal mining from ores, concentrates, industrial wastes, overburdens etc. under the impact of microorganisms and/or their metabolites. The most successful advancement of mineral biotechnology so far is on copper, uranium, nickel-cobalt and gold bearing ores. Treatment of mineral industry...

  5. Influence of zinc on the calcium carbonate biomineralization of Halomonas halophila

    OpenAIRE

    Rothenstein, Dirk; Baier, Johannes; Schreiber, Thomas D.; Barucha, Vera; Bill, Joachim

    2012-01-01

    Background: The salt tolerance of halophilic bacteria make them promising candidates for technical applications, like isolation of salt tolerant enzymes or remediation of contaminated saline soils and waters. Furthermore, some halophilic bacteria synthesize inorganic solids resulting in organic-inorganic hybrids. This process is known as biomineralization, which is induced and/or controlled by the organism. The adaption of the soft and eco-friendly reaction conditions of this formation proces...

  6. Probing the organic-mineral interface at the molecular level in model biominerals.

    Science.gov (United States)

    Metzler, Rebecca A; Kim, Il Won; Delak, Katya; Evans, John Spencer; Zhou, Dong; Beniash, Elia; Wilt, Fred; Abrecht, Mike; Chiou, Jau-Wern; Guo, Jinghua; Coppersmith, Susan N; Gilbert, P U P A

    2008-03-18

    It is widely known that macromolecules, such as proteins, can control the nucleation and growth of inorganic solids in biomineralizing organisms. However, what is not known are the complementary molecular interactions, organization, and rearrangements that occur when proteins interact with inorganic solids during the formation of biominerals. The organic-mineral interface (OMI) is expected to be the site for these phenomena, and is therefore extraordinarily interesting to investigate. In this report, we employ X-ray absorption near edge (XANES) spectromicroscopy to investigate the electronic structure of both calcium carbonate mineral crystals and polypeptides, and detect changing bonds at the OMI during crystal growth in the presence of polypeptides. We acquired XANES spectra from calcium carbonate crystals grown in the presence of three mollusk nacre-associated polypeptides (AP7N, AP24N, n16N) and in the presence of a sea urchin spicule matrix protein, LSM34. All these model biominerals gave similar results, including the disruption of CO bonds in calcite and enhancement of the peaks associated with C-H bonds and C-O bonds in peptides, indicating ordering of the amino acid side chains in the mineral-associated polypeptides and carboxylate binding. This is the first evidence of the mutual effect of calcite on peptide chain and peptide chain on calcite during biomineralization. We also show that these changes do not occur when Asp and Glu are replaced in the n16N sequence with Asn and Gln, respectively, demonstrating that carboxyl groups in Asp and Glu do participate in polypeptide-mineral molecular associations.

  7. Zinc isotope and transition-element dynamics accompanying hydrozincite biomineralization in the Rio Naracauli, Sardinia, Italy

    Science.gov (United States)

    Wanty, Richard B.; Podda, F.; De Giudici, Giovanni; Cidu, R.; Lattanzi, Pierfranco

    2013-01-01

    The Rio Naracauli in SW Sardinia drains part of the Ingurtosu Zn–Pb mining district, and contains extreme concentrations of dissolved Zn at near-neutral pH. In the upper reaches of the stream, pH, alkalinity and Zn concentrations are such that hydrozincite [Zn5(CO3)2(OH)6] precipitates in a biologically mediated process facilitated by a microalga (Chlorella sp.) and a cyanobacterium (Scytonema sp.). Values of δ66Zn in water and solid samples ranged from − 0.35‰ to + 0.5‰ relative to the JMC 3-0749-Lyon standard, and closely follow a mass-dependent fractionation line. Two composite samples of sphalerite, the primary ore mineral in the Ingurtosu deposits, had an average δ66Zn of + 0.15‰, similar to sphalerite measured elsewhere in hydrothermal mineral deposits. Zinc isotope measurements of the stream water and the hydrozincite forming in the stream show a consistent preference for the heavy isotope, 66Zn, in the hydrozincite relative to 64Zn. Synthetic hydrozincites produced without added bacteria have δ66Zn identical to the dissolved Zn, thus suggesting a biologically mediated mineralization process in Rio Naracauli. The average fractionation, Δhdz-water, is 0.35‰, the magnitude of which is consistent with other studies, and suggests an extracellular mechanism of the biomineralization process. Zinc concentration and dissolved δ66Zn steadily decrease in the reach of the stream where the biomineralization occurs. The biomineralization process also leads to the sequestration of Pb, Cu and Ni in the hydrozincite lattice, and the coeval precipitation of an amorphous CdCO3 solid, prompting the suggestion that if optimized, the biomineralization process might represent a feasible passive remediation strategy for streams with high Zn and other metals, and with near-neutral pH.

  8. Binding of ethanol on calcite: the role of the OH bond and its relevance to biomineralization

    DEFF Research Database (Denmark)

    Sand, K K; Yang, M; Makovicky, E;

    2010-01-01

    adsorption on calcite relative to OH from water and the consequences of the differences in interaction on crystal growth and dissolution. A combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations showed that EtOH attachment on calcite is stronger than HOH binding...... transport to and from the mineral surface, confining it to specific locations, thus providing the organism with control for biomineral morphology....

  9. Low-molecular-weight poly-carboxylate as crystal growth modifier in biomineralization

    Indian Academy of Sciences (India)

    Ballav Moni Borah; Bhaskar Jyoti Bhuyan; Gopal Das

    2006-11-01

    Construction of modified inorganic mineral with controlled mineralization analogues of those produced by nature is now of current interest for understanding the mechanism of the in vivo biomineralization processes, as well as looking for fresh industrial and technological applications. Lowmolecular-weight chiral poly-carboxylate ligands derived from naturally occurring L--amino acids have been used as model systems to study the effect of molecular properties on crystal growth modification.

  10. Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria

    OpenAIRE

    Abreu, Fernanda; Cantão, Mauricio E; Nicolás, Marisa F; Barcellos, Fernando G; Morillo, Viviana; Almeida, Luiz GP; do Nascimento, Fabrícia F; Lefèvre, Christopher T; Dennis A. Bazylinski; R de Vasconcelos, Ana Tereza; Lins, Ulysses

    2011-01-01

    Magnetosomes are prokaryotic organelles produced by magnetotactic bacteria that consist of nanometer-sized magnetite (Fe3O4) or/and greigite (Fe3S4) magnetic crystals enveloped by a lipid bilayer membrane. In magnetite-producing magnetotactic bacteria, proteins present in the magnetosome membrane modulate biomineralization of the magnetite crystal. In these microorganisms, genes that encode for magnetosome membrane proteins as well as genes involved in the construction of the magnetite magnet...

  11. Sea shell diversity and rapidly evolving secretomes: insights into the evolution of biomineralization.

    Science.gov (United States)

    Kocot, Kevin M; Aguilera, Felipe; McDougall, Carmel; Jackson, Daniel J; Degnan, Bernard M

    2016-01-01

    An external skeleton is an essential part of the body plan of many animals and is thought to be one of the key factors that enabled the great expansion in animal diversity and disparity during the Cambrian explosion. Molluscs are considered ideal to study the evolution of biomineralization because of their diversity of highly complex, robust and patterned shells. The molluscan shell forms externally at the interface of animal and environment, and involves controlled deposition of calcium carbonate within a framework of macromolecules that are secreted from the dorsal mantle epithelium. Despite its deep conservation within Mollusca, the mantle is capable of producing an incredible diversity of shell patterns, and macro- and micro-architectures. Here we review recent developments within the field of molluscan biomineralization, focusing on the genes expressed in the mantle that encode secreted proteins. The so-called mantle secretome appears to regulate shell deposition and patterning and in some cases becomes part of the shell matrix. Recent transcriptomic and proteomic studies have revealed marked differences in the mantle secretomes of even closely-related molluscs; these typically exceed expected differences based on characteristics of the external shell. All mantle secretomes surveyed to date include novel genes encoding lineage-restricted proteins and unique combinations of co-opted ancient genes. A surprisingly large proportion of both ancient and novel secreted proteins containing simple repetitive motifs or domains that are often modular in construction. These repetitive low complexity domains (RLCDs) appear to further promote the evolvability of the mantle secretome, resulting in domain shuffling, expansion and loss. RLCD families further evolve via slippage and other mechanisms associated with repetitive sequences. As analogous types of secreted proteins are expressed in biomineralizing tissues in other animals, insights into the evolution of the genes

  12. Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

    Energy Technology Data Exchange (ETDEWEB)

    Yung, M C [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jiao, Y [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-07-22

    Caulobacter crescentus is known to tolerate high levels of uranium [U(VI)], but its detoxification mechanism is poorly understood. Here we show that C. crescentus is able to facilitate U(VI) biomineralization through the formation of U-Pi precipitates via its native alkaline phosphatase activity. The U-Pi precipitates, deposited on the cell surface in the form of meta-autunite structures, have a lower U/Pi ratio than do chemically produced precipitates. The enzyme that is responsible for the phosphatase activity and thus the biomineralization process is identified as PhoY, a periplasmic alkaline phosphatase with broad substrate specificity. Furthermore, PhoY is shown to confer a survival advantage on C. crescentus toward U(VI) under both growth and nongrowth conditions. Results obtained in this study thus highlight U(VI) biomineralization as a resistance mechanism in microbes, which not only improves our understanding of bacterium-mineral interactions but also aids in defining potential ecological niches for metal-resistant bacteria.

  13. Biomineralization of uranium by PhoY phosphatase activity aids cell survival in Caulobacter crescentus.

    Science.gov (United States)

    Yung, Mimi C; Jiao, Yongqin

    2014-08-01

    Caulobacter crescentus is known to tolerate high levels of uranium [U(VI)], but its detoxification mechanism is poorly understood. Here we show that C. crescentus is able to facilitate U(VI) biomineralization through the formation of U-Pi precipitates via its native alkaline phosphatase activity. The U-Pi precipitates, deposited on the cell surface in the form of meta-autunite structures, have a lower U/Pi ratio than do chemically produced precipitates. The enzyme that is responsible for the phosphatase activity and thus the biomineralization process is identified as PhoY, a periplasmic alkaline phosphatase with broad substrate specificity. Furthermore, PhoY is shown to confer a survival advantage on C. crescentus toward U(VI) under both growth and nongrowth conditions. Results obtained in this study thus highlight U(VI) biomineralization as a resistance mechanism in microbes, which not only improves our understanding of bacterium-mineral interactions but also aids in defining potential ecological niches for metal-resistant bacteria.

  14. Amorphous calcium carbonate precipitation by cellular biomineralization in mantle cell cultures of Pinctada fucata.

    Directory of Open Access Journals (Sweden)

    Liang Xiang

    Full Text Available The growth of molluscan shell crystals is generally thought to be initiated from the extrapallial fluid by matrix proteins, however, the cellular mechanisms of shell formation pathway remain unknown. Here, we first report amorphous calcium carbonate (ACC precipitation by cellular biomineralization in primary mantle cell cultures of Pinctada fucata. Through real-time PCR and western blot analyses, we demonstrate that mantle cells retain the ability to synthesize and secrete ACCBP, Pif80 and nacrein in vitro. In addition, the cells also maintained high levels of alkaline phosphatase and carbonic anhydrase activity, enzymes responsible for shell formation. On the basis of polarized light microscopy and scanning electron microscopy, we observed intracellular crystals production by mantle cells in vitro. Fourier transform infrared spectroscopy and X-ray diffraction analyses revealed the crystals to be ACC, and de novo biomineralization was confirmed by following the incorporation of Sr into calcium carbonate. Our results demonstrate the ability of mantle cells to perform fundamental biomineralization processes via amorphous calcium carbonate, and these cells may be directly involved in pearl oyster shell formation.

  15. Biomineral Processing: A Valid Eco-Friendly Alternative for Metal Extraction.

    Directory of Open Access Journals (Sweden)

    Lala Behari Sukla

    2014-07-01

    Full Text Available Over the past few years, the applications of certain microorganisms have gained importance in the field of applied environmental microbiology. Amongst them, biomineral processing is such field that deals with metal mining from ores, concentrates, industrial wastes, overburdens etc. under the impact of microorganisms and/or their metabolites. The most successful advancement of mineral biotechnology so far is on copper, uranium, nickel-cobalt and gold bearing ores. Treatment of mineral industry effluents by microorganisms, with incidental recovery of some metal values constitutes an equally important area of biomineral processing. The most common method followed for leaching or extraction of metal values is through shake flask (a lab scale method followed by bioreactors or percolation columns (a bench scale method and finally to heap leaching (a pilot scale method. Bio-leaching of mono- and multiple-sulphides is now coming to be known as an established commercial process. The present review discusses the microorganisms involved in biomineral processing, mechanism of metal extraction, molecular methodologies adopted for microbial identification with our experience on application of microorganism.

  16. A first report of hydroxylated apatite as structural biomineral in Loasaceae - plants' teeth against herbivores.

    Science.gov (United States)

    Ensikat, Hans-Jürgen; Geisler, Thorsten; Weigend, Maximilian

    2016-01-01

    Biomineralization provides living organisms with various materials for the formation of resilient structures. Calcium phosphate is the main component of teeth and bones in vertebrates, whereas especially silica serves for the protection against herbivores on many plant surfaces. Functional calcium phosphate structures are well-known from the animal kingdom, but had not so far been reported from higher plants. Here, we document the occurrence of calcium phosphate biomineralization in the South-American plant group Loasaceae (rock nettle family), which have stinging trichomes similar to those of the well-known stinging nettles (Urtica). Stinging hairs and the smaller, glochidiate trichomes contained nanocrystalline hydroxylated apatite, especially in their distal portions, replacing the silica found in analogous structures of other flowering plants. This could be demonstrated by chemical, spectroscopic, and diffraction analyses. Some species of Loasaceae contained both calcium phosphate and silica in addition to calcium carbonate. The intriguing discovery of structural hydroxylated apatite in plants invites further studies, e.g., on its systematic distribution across the family, the genetic and cellular control of plant biomineralization, the properties and ultrastructure of calcium phosphate. It may prove the starting point for the development of biomimetic calcium phosphate composites based on a cellulose matrix. PMID:27194462

  17. A first report of hydroxylated apatite as structural biomineral in Loasaceae – plants’ teeth against herbivores

    Science.gov (United States)

    Ensikat, Hans-Jürgen; Geisler, Thorsten; Weigend, Maximilian

    2016-01-01

    Biomineralization provides living organisms with various materials for the formation of resilient structures. Calcium phosphate is the main component of teeth and bones in vertebrates, whereas especially silica serves for the protection against herbivores on many plant surfaces. Functional calcium phosphate structures are well-known from the animal kingdom, but had not so far been reported from higher plants. Here, we document the occurrence of calcium phosphate biomineralization in the South-American plant group Loasaceae (rock nettle family), which have stinging trichomes similar to those of the well-known stinging nettles (Urtica). Stinging hairs and the smaller, glochidiate trichomes contained nanocrystalline hydroxylated apatite, especially in their distal portions, replacing the silica found in analogous structures of other flowering plants. This could be demonstrated by chemical, spectroscopic, and diffraction analyses. Some species of Loasaceae contained both calcium phosphate and silica in addition to calcium carbonate. The intriguing discovery of structural hydroxylated apatite in plants invites further studies, e.g., on its systematic distribution across the family, the genetic and cellular control of plant biomineralization, the properties and ultrastructure of calcium phosphate. It may prove the starting point for the development of biomimetic calcium phosphate composites based on a cellulose matrix. PMID:27194462

  18. Modeling the environmental stability of FeS2 nanorods, using lessons from biomineralization

    International Nuclear Information System (INIS)

    Previous experimental studies have indicated that the controlled formation of anisotropic pyrite nanoparticles, such as nanorods or nanowires, is dependent on the right combination of solution chemistry and temperature. Similarly, the morphology of the individual nanocrystals during intracellular biomineralization of single nanocrystals has been attributed to the local environmental conditions, as well as the species of the micro-organism. Although there are obvious similarities, using the lessons from biomineralization to assist the laboratory synthesis of anisotropic pyrite nanostructures, and in the anticipation of environmental stability, requires a more detailed understanding of the role played by individual environmental parameters. In the present study we use a multi-scale thermodynamic model, combined with parameters obtained from first principles calculations, to investigate the formation and stability of pyrite nanorods as a function of temperature and chemical environment. The results of our systematic modeling of parameter space predict that the morphology of pyrite nanorods grown in the laboratory, or associated with biomineralization, is more likely to be a function of surface ligands and the biology of the organisms than a function of simpler environmental parameters such as temperature, pressure, concentration of sulfur and adsorption of water.

  19. Uranium biomineralization by a metal resistant Pseudomonas aeruginosa strain isolated from contaminated mine waste

    International Nuclear Information System (INIS)

    Uranium biomineralization by a metal-resistant Pseudomonas aeruginosa strain isolated from uranium mine waste was characterized for its potential in bioremediation. Uranium resistance, its cellular localization and chemical nature of uranium-bacteria interaction were elucidated. Survival and uranium biomineralization from mine water were investigated using microcosm experiments. The selected bacterium showed U resistance and accumulation (maximum of 275 mg U g-1 cell dry wt.) following incubation in 100 mg U L-1, pH 4.0, for 6 h. Transmission electron microscopy and X-ray diffraction analyses revealed that bioaccumulated uranium was deposited within the cell envelope as needle shaped U-phosphate compounds that attain crystallinity only at pH 4.0. A synergistic involvement of deprotonated phosphate and carboxyl moieties in facilitating bioprecipitation of uranium was evident from FTIR analysis. Based on these findings we attribute the localized U sequestration by this bacterium as innocuous complex to its possible mechanism of uranium resistance. Microcosm data confirmed that the strain can remove soluble uranium (99%) and sequester it as U oxide and phosphate minerals while maintaining its viability. The study showed that indigenous bacteria from contaminated site that can survive uranium and other heavy metal toxicity and sequester soluble uranium as biominerals could play important role in uranium bioremediation.

  20. Reverse tracing of precursors and earthquake precursors in Taiwan

    Institute of Scientific and Technical Information of China (English)

    WANG Li-ping; LI Yong; MA Li; ZHANG Shu-mei

    2008-01-01

    In this paper, we investigate the precursors of large earthquakes in the eastern region of Taiwan by means of the reverse tracing of precursors. We discuss the parameters which are suitable for the seismic chains and intermedi-ate-term patterns in this region and obtain the threshold of the patterns. Applying the linear discriminate method to the intermediate-term patterns of seismic chains, we present an approach for exploring the precursors of large earthquakes. The results show that this method can reduce the false alarm rate for large earthquakes in this region, and the reverse tracing of precursors can be applied to the eastern region of Taiwan.

  1. Precursor flares in OJ 287

    OpenAIRE

    Pihajoki, P.; Valtonen, M.; Zola, S.; Liakos, A.; Drozdz, M.; Winiarski, M.; Ogloza, W.; Koziel-Wierzbowska, D.; Provencal, J.; Nilsson, K.; Berdyugin, A.; Lindfors, E.; Reinthal, R.; Sillanpää, A.; Takalo, L.

    2012-01-01

    We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain the nature of these flares. Precursor flare timings from the historical light curves are compared with theoretical predictions from our model that incorporate effects of an accretion disk and post-Newtonian description for the binary black hole orbit. We find that the precursor flares coincide with the secondary black...

  2. Generation of Nonlinear Vortex Precursors

    Science.gov (United States)

    Chen, Yue-Yue; Feng, Xun-Li; Liu, Chengpu

    2016-07-01

    We numerically study the propagation of a few-cycle pulse carrying orbital angular momentum (OAM) through a dense atomic system. Nonlinear precursors consisting of high-order vortex harmonics are generated in the transmitted field due to carrier effects associated with ultrafast Bloch oscillation. The nonlinear precursors survive to propagation effects and are well separated with the main pulse, which provides a straightforward way to measure precursors. By virtue of carrying high-order OAM, the obtained vortex precursors as information carriers have potential applications in optical information and communication fields where controllable loss, large information-carrying capacity, and high speed communication are required.

  3. Generation of nonlinear vortex precursors

    CERN Document Server

    Chen, Yue-Yue; Liu, Chengpu

    2016-01-01

    We numerically study the propagation of a few-cycle pulse carrying orbital angular momentum (OAM) through a dense atomic system. Nonlinear precursors consisting of high-order vortex har- monics are generated in the transmitted field due to ultrafast Bloch oscillation. The nonlinear precursors survive to propagation effects and are well separated with the main pulse, which provide a straightforward way of measuring precursors. By the virtue of carrying high-order OAM, the obtained vortex precursors as information carriers have potential applications in optical informa- tion and communication fields where controllable loss, large information-carrying capacity and high speed communication are required.

  4. Templating Biomineralization: Surface Directed Protein Self-assembly and External Magnetic Field Stimulation of Osteoblasts

    Science.gov (United States)

    Ba, Xiaolan

    Biomineralization is a wide-spread phenomenon in the biological systems, which is the process of mineral formation by organisms through interaction between its organic contents and the inorganic minerals. The process is essential in a broad spectrum of biological phenomena ranging from bone and tooth formation to pathological mineralization under hypoxic conditions or cancerous formations. In this thesis I studied biomineralization at the earliest stages in order to obtain a better understanding of the fundamental principals involved. This knowledge is essential if we want to engineer devices which will increase bone regeneration or prevent unwanted mineral deposits. Extracellular matrix (ECM) proteins play an essential role during biomineralization in bone and engineered tissues. In this dissertation, I present an approach to mimic the ECM in vitro to probe the interactions of these proteins with calcium phosphate mineral and with each other. Early stage of mineralization is investigated by mechanical properties of the protein fibers using Scanning Probe Microscopy (SPM) and Shear Modulation Force Microscopy (SMFM). The development of mineral crystals on the protein matrices is also characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Grazing Incidence X-ray Diffraction (GIXRD). The results demonstrate complementary actions of the two ECM proteins to collect cations and template calcium phosphate mineral, respectively. Magnets have been clinically used as an "induction source" in various bone or orthodontic treatments. However, the mechanism and effects of magnetic fields remain unclear. In this dissertation, I also undertake the present investigation to study the effects of 150 mT static magnetic fields (SMF) on ECM development and cell biomineralization using MC3T3-E1 osteobalst-like cells. Early stage of biomineralization is characterized by SPM, SMFM and confocal laser scanning microscopy (CSLM). Late stage of

  5. PRECURSOR FLARES IN OJ 287

    Energy Technology Data Exchange (ETDEWEB)

    Pihajoki, P.; Berdyugin, A.; Lindfors, E.; Reinthal, R.; Sillanpaeae, A.; Takalo, L. [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, FI-21500 Piikkioe (Finland); Valtonen, M.; Nilsson, K. [Finnish Centre for Astronomy with ESO, University of Turku, FI-21500 Piikkioe (Finland); Zola, S.; Koziel-Wierzbowska, D. [Astronomical Observatory, Jagiellonian University, ul. Orla 171, PL-30-244 Krakow (Poland); Liakos, A. [Department of Astrophysics, Astronomy and Mechanics, University of Athens, GR 157 84 Zografos, Athens, Hellas (Greece); Drozdz, M.; Winiarski, M.; Ogloza, W. [Mount Suhora Observatory, Pedagogical University, ul. Podchorazych 2, PL-30-084 Krakow (Poland); Provencal, J. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Santangelo, M. M. M. [O.A.C. Osservatorio Astronomico di Capannori, Via di Valle, I-55060 Vorno, Capannori (Italy); Salo, H. [Department of Physical Sciences, University of Oulu, P.O. Box 3000, FI-90014 University of Oulu (Finland); Chandra, S.; Ganesh, S.; Baliyan, K. S., E-mail: popiha@utu.fi [Astronomy and Astrophysics Division, Physical Research Laboratory, Ahmedabad 380009 (India); and others

    2013-02-10

    We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain the nature of these flares. Precursor flare timings from the historical light curves are compared with theoretical predictions from our model that incorporate effects of an accretion disk and post-Newtonian description for the binary black hole orbit. We find that the precursor flares coincide with the secondary black hole descending toward the accretion disk of the primary black hole from the observed side, with a mean z-component of approximately z{sub c} = 4000 AU. We use this model of precursor flares to predict that precursor flare of similar nature should happen around 2020.96 before the next major outburst in 2022.

  6. Surface modification of yttria stabilized zirconia via polydopamine inspired coating for hydroxyapatite biomineralization

    Energy Technology Data Exchange (ETDEWEB)

    Zain, Norhidayu Muhamad [Medical Devices and Technology Group, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Hussain, Rafaqat [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Kadir, Mohammed Rafiq Abdul, E-mail: rafiq@biomedical.utm.my [Medical Devices and Technology Group, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia)

    2014-12-15

    Highlights: • Synthesis of functionalized yttria stabilized zirconia using polydopamine. • Improved hydrophilicity of the grafted samples with low contact angle of 44.0 ± 2.3. • Apatite layer with Ca/P ratio of 1.78 formed on the surface of the grafted samples. • Atomic percentage of Ca 2p increased by 2-fold at coating temperature of 37 °C. - Abstract: Yttria stabilized zirconia (YSZ) has been widely used as biomedical implant due to its high strength and enhanced toughening characteristics. However, YSZ is a bioinert material which constrains the formation of chemical bonds with bone tissue following implantation. Inspired by the property of mussels, the surface of YSZ ceramics was functionalized by quinone-rich polydopamine to facilitate the biomineralization of hydroxyapatite. YSZ discs were first immersed in 2 mg/mL of stirred or unstirred dopamine solution at either 25 or 37 °C. The samples were then incubated in 1.5 simulated body fluid (SBF) for 7d. The effect of coating temperature for stirred and unstirred dopamine solutions during substrate grafting was investigated on the basis of chemical compositions, wettability and biomineralization of hydroxyapatite on the YSZ functionalized surface. The results revealed that the YSZ substrate grafted at 37 °C in stirred solution of dopamine possessed significantly improved hydrophilicity (water contact angle of 44.0 ± 2.3) and apatite-mineralization ability (apatite ratio of 1.78). In summary, the coating temperature and stirring condition during grafting procedure affected the chemical compositions of the films and thus influenced the formation of apatite layer on the substrate during the biomineralization process.

  7. The role of anaerobic respiration in the immobilization of uranium through biomineralization of phosphate minerals

    Science.gov (United States)

    Salome, Kathleen R.; Green, Stefan J.; Beazley, Melanie J.; Webb, Samuel M.; Kostka, Joel E.; Taillefert, Martial

    2013-04-01

    Although bioreduction of uranyl ions (U(VI)) and biomineralization of U(VI)-phosphate minerals are both able to immobilize uranium in contaminated sediments, the competition between these processes and the role of anaerobic respiration in the biomineralization of U(VI)-phosphate minerals has yet to be investigated. In this study, contaminated sediments incubated anaerobically in static microcosms at pH 5.5 and 7.0 were amended with the organophosphate glycerol-2-phosphate (G2P) as sole phosphorus and external carbon source and iron oxides, sulfate, or nitrate as terminal electron acceptors to determine the most favorable geochemical conditions to these two processes. While sulfate reduction was not observed even in the presence of G2P at both pHs, iron reduction was more significant at circumneutral pH irrespective of the addition of G2P. In turn, nitrate reduction was stimulated by G2P at both pH 5.5 and 7.0, suggesting nitrate-reducing bacteria provided the main source of inorganic phosphate in these sediments. U(VI) was rapidly removed from solution in all treatments but was not reduced as determined by X-ray absorption near edge structure (XANES) spectroscopy. Simultaneously, wet chemical extractions and extended X-ray absorption fine structure (EXAFS) spectroscopy of these sediments indicated the presence of U-P species in reactors amended with G2P at both pHs. The rapid removal of dissolved U(VI), the simultaneous production of inorganic phosphate, and the existence of U-P species in the solid phase indicate that uranium was precipitated as U(VI)-phosphate minerals in sediments amended with G2P. Thus, under reducing conditions and in the presence of G2P, bioreduction of U(VI) was outcompeted by the biomineralization of U(VI)-phosphate minerals and U(VI) sorption at both pHs.

  8. Biomineralization changes with food supply confer juvenile scallops (Argopecten purpuratus) resistance to ocean acidification

    KAUST Repository

    Ramajo, Laura

    2015-12-08

    Future ocean acidification (OA) will affect physiological traits of marine species, with calcifying species being particularly vulnerable. As OA entails high energy demands, particularly during the rapid juvenile growth phase, food supply may play a key role in the response of marine organisms to OA. We experimentally evaluated the role of food supply in modulating physiological responses and biomineralization processes in juveniles of the Chilean scallop, Argopecten purpuratus, that were exposed to control (pH ~ 8.0) and low pH (pH ~ 7.6) conditions using three food supply treatments (high, intermediate, and low). We found that pH and food levels had additive effects on the physiological response of the juvenile scallops. Metabolic rates, shell growth, net calcification, and ingestion rates increased significantly at low pH conditions, independent of food. These physiological responses increased significantly in organisms exposed to intermediate and high levels of food supply. Hence, food supply seems to play a major role modulating organismal response by providing the energetic means to bolster the physiological response of OA stress. On the contrary, the relative expression of chitin synthase, a functional molecule for biomineralization, increased significantly in scallops exposed to low food supply and low pH, which resulted in a thicker periostracum enriched with chitin polysaccharides. Under reduced food and low pH conditions, the adaptive organismal response was to trade-off growth for the expression of biomineralization molecules and altering of the organic composition of shell periostracum, suggesting that the future performance of these calcifiers will depend on the trajectories of both OA and food supply. Thus, incorporating a suite of traits and multiple stressors in future studies of the adaptive organismal response may provide key insights on OA impacts on marine calcifiers.

  9. Biomineralization changes with food supply confer juvenile scallops (Argopecten purpuratus) resistance to ocean acidification.

    Science.gov (United States)

    Ramajo, Laura; Marbà, Núria; Prado, Luis; Peron, Sophie; Lardies, Marco A; Rodriguez-Navarro, Alejandro B; Vargas, Cristian A; Lagos, Nelson A; Duarte, Carlos M

    2016-06-01

    Future ocean acidification (OA) will affect physiological traits of marine species, with calcifying species being particularly vulnerable. As OA entails high energy demands, particularly during the rapid juvenile growth phase, food supply may play a key role in the response of marine organisms to OA. We experimentally evaluated the role of food supply in modulating physiological responses and biomineralization processes in juveniles of the Chilean scallop, Argopecten purpuratus, that were exposed to control (pH ~ 8.0) and low pH (pH ~ 7.6) conditions using three food supply treatments (high, intermediate, and low). We found that pH and food levels had additive effects on the physiological response of the juvenile scallops. Metabolic rates, shell growth, net calcification, and ingestion rates increased significantly at low pH conditions, independent of food. These physiological responses increased significantly in organisms exposed to intermediate and high levels of food supply. Hence, food supply seems to play a major role modulating organismal response by providing the energetic means to bolster the physiological response of OA stress. On the contrary, the relative expression of chitin synthase, a functional molecule for biomineralization, increased significantly in scallops exposed to low food supply and low pH, which resulted in a thicker periostracum enriched with chitin polysaccharides. Under reduced food and low pH conditions, the adaptive organismal response was to trade-off growth for the expression of biomineralization molecules and altering of the organic composition of shell periostracum, suggesting that the future performance of these calcifiers will depend on the trajectories of both OA and food supply. Thus, incorporating a suite of traits and multiple stressors in future studies of the adaptive organismal response may provide key insights on OA impacts on marine calcifiers. PMID:26644007

  10. Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering

    Directory of Open Access Journals (Sweden)

    John G. Hardy

    2016-07-01

    Full Text Available Materials based on biodegradable polyesters, such as poly(butylene terephthalate (PBT or poly(butylene terephthalate-co-poly(alkylene glycol terephthalate (PBTAT, have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16, that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering.

  11. The Impact of Small-Scale Heterogeneity on Proxies in Biomineral Archives

    Science.gov (United States)

    Gagnon, A. C.

    2015-12-01

    From the pace of the ice ages to how the carbon cycle has changed through time, much of what we know about earth history and climate dynamics is based on chemical signatures locked within minerals. Recorded as trace element anomalies or as isotopic shifts, these chemical signatures reflect how mass and energy move across the planet, as well as the response of biological systems to these changes. When viewed at the sub-micron to nano-scale however, chemical composition rarely follows a simple relationship with environmental conditions. This is especially true for the preserved CaCO3 skeletons of marine organisms, which often exhibit systematic patterns of high magnitude chemical variability at the sub-micron scale. While this biologically-driven variability can complicate the interpretation of climate records, it also represents a rich and largely untapped signal. Major advances in our understanding of both biomineralization and paleoproxies hinge on new techniques that can isolate small signals from this complexity. To probe the mechanisms controlling biomineralization and sub-micron compositional variability, we use a suite of high spatial resolution tools: NanoSIMS, ToF-SIMS, and Atom Probe Tomography (APT), together with stable isotope labels and biomineral culture. In planktonic foraminifera we conducted modified pulse chase experiments using isotope tracers to measure ion transport rates during biomineralization. By varying elemental concentrations in the surrounding seawater during these pulse chase experiments, we induced systematic shifts in the ion transport rate. The magnitude of these shifts indirectly measure the elemental composition of the calcifying microenvironment, a key and previously unmeasured parameter affecting skeletal chemistry and paleoproxy systematics. Complementary isotope tracer experiments in coral and related experiments applying APT to the organic-mineral interface in foraminifera uncovered the response of calcification to ocean

  12. Synthesis of globular precursors.

    Science.gov (United States)

    Teixidor, Francesc; Sillanpää, Reijo; Pepiol, Ariadna; Lupu, Marius; Viñas, Clara

    2015-09-01

    o-Carborane (C2 B10 H12 ) was adapted to perform as the core of globular macromolecules, dendrons or dendrimers. To meet this objective, precisely defined substitution patterns of terminal olefin groups on the carborane framework were subjected to Heck cross-coupling reactions or hydroboration leading to hydroxyl terminated arms. These led to new terminal groups (chloro, bromo, and tosyl leaving groups, organic acid, and azide) that permitted ester production, click chemistry, and oxonium ring opening to be performed as examples of reactions that demonstrate the wide possibilities of the globular icosahedral carboranes to produce new dendritic or dendrimer-like structures. Polyanionic species were obtained in high yield through the ring-opening reaction of cyclic oxonium compound [3,3'-Co(8-C4 H8 O2 -1,2-C2 B9 H10 )(1',2'-C2 B9 H11 )] by using terminal hydroxyl groups as nucleophiles. These new polyanionic compounds that contain multiple metallacarborane clusters at their periphery may prove useful as new classes of compounds for boron neutron capture therapy with enhanced water solubility and as cores to make a new class of high-boron globular macromolecules. PMID:26228947

  13. Transcriptome and biomineralization responses of the pearl oyster Pinctada fucata to elevated CO2 and temperature.

    Science.gov (United States)

    Li, Shiguo; Liu, Chuang; Huang, Jingliang; Liu, Yangjia; Zhang, Shuwen; Zheng, Guilan; Xie, Liping; Zhang, Rongqing

    2016-01-01

    Ocean acidification and global warming have been shown to significantly affect the physiological performances of marine calcifiers; however, the underlying mechanisms remain poorly understood. In this study, the transcriptome and biomineralization responses of Pinctada fucata to elevated CO2 (pH 7.8 and pH 7.5) and temperature (25 °C and 31 °C) are investigated. Increases in CO2 and temperature induced significant changes in gene expression, alkaline phosphatase activity, net calcification rates and relative calcium content, whereas no changes are observed in the shell ultrastructure. "Ion and acid-base regulation" related genes and "amino acid metabolism" pathway respond to the elevated CO2 (pH 7.8), suggesting that P. fucata implements a compensatory acid-base mechanism to mitigate the effects of low pH. Additionally, "anti-oxidation"-related genes and "Toll-like receptor signaling", "arachidonic acid metabolism", "lysosome" and "other glycan degradation" pathways exhibited responses to elevated temperature (25 °C and 31 °C), suggesting that P. fucata utilizes anti-oxidative and lysosome strategies to alleviate the effects of temperature stress. These responses are energy-consuming processes, which can lead to a decrease in biomineralization capacity. This study therefore is important for understanding the mechanisms by which pearl oysters respond to changing environments and predicting the effects of global climate change on pearl aquaculture. PMID:26732540

  14. Ubiquitylation functions in the calcium carbonate biomineralization in the extracellular matrix.

    Directory of Open Access Journals (Sweden)

    Dong Fang

    Full Text Available Mollusks shell formation is mediated by matrix proteins and many of these proteins have been identified and characterized. However, the mechanisms of protein control remain unknown. Here, we report the ubiquitylation of matrix proteins in the prismatic layer of the pearl oyster, Pinctada fucata. The presence of ubiquitylated proteins in the prismatic layer of the shell was detected with a combination of western blot and immunogold assays. The coupled ubiquitins were separated and identified by Edman degradation and liquid chromatography/mass spectrometry (LC/MS. Antibody injection in vivo resulted in large amounts of calcium carbonate randomly accumulating on the surface of the nacreous layer. These ubiquitylated proteins could bind to specific faces of calcite and aragonite, which are the two main mineral components of the shell. In the in vitro calcium carbonate crystallization assay, they could reduce the rate of calcium carbonate precipitation and induce the calcite formation. Furthermore, when the attached ubiquitins were removed, the functions of the EDTA-soluble matrix of the prismatic layer were changed. Their potency to inhibit precipitation of calcium carbonate was decreased and their influence on the morphology of calcium carbonate crystals was changed. Taken together, ubiquitylation is involved in shell formation. Although the ubiquitylation is supposed to be involved in every aspect of biophysical processes, our work connected the biomineralization-related proteins and the ubiquitylation mechanism in the extracellular matrix for the first time. This would promote our understanding of the shell biomineralization and the ubiquitylation processes.

  15. Biomineralization process occurring in iron mud of coastal seepase area of Zhoushan Island, Zhejiang Province

    Institute of Scientific and Technical Information of China (English)

    WU ZiJun; JIA Nan; YUAN LinXi; SUN LiGuang

    2008-01-01

    The biomineralization process of iron oxidizing bacteria and its influence on accumulation of metals were investigated by modern biological observation techniques (i.e., SEM and TEM) and geochemical methods, in coastal area of Zhoushan Island, Zhejiang province where a thick ancient wood layers were buried, Results show that the iron mud samples mainly contain Leptothrix-like sheaths and Gal-lionella-like stalks, which are known as neutrophilic iron-oxidizing bacteria. These two bacteria are present as obviously different abundance in two sampling sites, which may be regulated by the geo-chemistry of seepage water. The biomineralization product of iron oxidizing bacteria is ferrihydrite, a poorly ordered iron oxide, and formation of amorphous mineral is affected by the factors of bacteria, minor Si and temperature preventing any further transformation into more crystalline phases. Organic functional groups, extracellular polymers and surface charges can provide favorable nucleation sites or template for formation of iron precipitates on the bacterial surface. The mineralization process of the iron oxidizing bacteria is divided into different stages,i.e., extracellular mineralization, intracellular mineralization and the whole cell mineralization. Furthermore, due to BIOS containing the bacterial organic matter, the accumulation capacity of metals specially Fe and Co is highly increased, suggest-ing that BIOS exert a degree of controlling in the cycling of metal elements in seepage area.

  16. A Study of Chromium Adsorption on Natural Goethite Biomineralized with Iron Bacteria

    Institute of Scientific and Technical Information of China (English)

    SUN Zhenya; ZHU Chunshui; HUANG Jiangbo; GONG Wenqi; CHEN Hesheng; MU Shanbin

    2006-01-01

    Goethite, especially biogenic goethite, has high specific surface area and great capacity for the adsorption of many contaminants including metal ions and organic chelates. Chromium is a redox actively toxic metal ion that exists as either CrⅢ or CrⅥ in nature, and as such it is essential to understand its behavior of adsorption on natural goethite mineralized by iron bacteria, as Gallionella and Leptothrix in water body. The adsorption of Cr3+ and CrⅥ on naturally biomineralized goethite is studied in this paper. The results show that both Langmuir and Freundlich adsorption isothermal models are able to accurately describe the adsorption of these two ions. Investigation of SEM/EDS,TEM/EDS indicates that the two ions do not adsorb homogeneously on goethite owing to the different microstructures of goethite, and that the microspherical goethite has a greater adsorption capacity for chromium ions than the helical one. XPS data show that redox reaction of chromium on the surface of biomineralized goethite takes place in the adsorption of both Cr3+ and CrⅥ. The CrⅥ adsorbed on biogoethite is much easier to transform into CrⅢ than the oxidization of CrⅢ on the bio-goethite.

  17. Kinetics of aerobic and anaerobic biomineralization of atrazine in surface and subsurface agricultural soils in Ohio.

    Science.gov (United States)

    Tuovinen, Olli H; Deshmukh, Vaidehi; Özkaya, Bestamin; Radosevich, Mark

    2015-01-01

    The purpose of this study was to assess atrazine mineralization in surface and subsurface samples retrieved from vertical cores of agricultural soils from two farm sites in Ohio. The Defiance site (NW-Ohio) was on soybean-corn rotation and Piketon (S-Ohio) was on continuous corn cultivation. Both sites had a history of atrazine application for at least a couple of decades. The clay fraction increased at the Defiance site and the organic matter and total N content decreased with depth at both sites. Mineralization of atrazine was assessed by measurement of (14)CO2 during incubation of soil samples with [U-ring-(14)C]-atrazine. Abiotic mineralization was negligible in all soil samples. Aerobic mineralization rate constants declined and the corresponding half-lives increased with depth at the Defiance site. Anaerobic mineralization (supplemented with nitrate) was mostly below the detection at the Defiance site. In Piketon samples, the kinetic parameters of aerobic and anaerobic biomineralization of atrazine displayed considerable scatter among replicate cores and duplicate biometers. In general, this study concludes that data especially for anaerobic biomineralization of atrazine can be more variable as compared to aerobic conditions and cannot be extrapolated from one agricultural site to another. PMID:26273756

  18. Mineralogical Diversity in Lake Pavin: Connections with Water Column Chemistry and Biomineralization Processes

    Directory of Open Access Journals (Sweden)

    Jennyfer Miot

    2016-03-01

    Full Text Available As biominerals are good tracers of microbial interactions with the environment, they may provide signatures of microbial evolution and paleoenvironmental conditions. Since modern analogues of past environments help with defining proxies and biosignatures, we explored microbe mineral interactions in the water column of a maar lake, located in France: Lake Pavin. This lake is considered as a potential Precambrian ocean analogue, as it is ferruginous and meromictic, i.e., stratified with a superficial O2-rich layer (mixolimnion and a deeper permanently anoxic layer (monimolimnion. We combined bulk chemical analyses of dissolved and particulate matter in combination with electron microscopy analyses of the particulate matter at different depths along the water column. The mineralogy changed along with water chemistry, and most of the minerals were intimately associated with microorganisms. Evolution of the redox conditions with depth leads to the successive precipitation of silica and carbonates, Mn-bearing, Fe-bearing and S-containing phases, with a predominance of phosphates in the monimolimnion. This scheme parallels the currently-assessed changes of microbial diversity with depth. The present results corroborate previous studies that suggested a strong influence of microbial activity on mineralogical diversity through extracellular and intracellular biomineralization. This paper reports detailed data on mineralogical profiles of the water column and encourages extended investigation of these processes.

  19. Transcriptome and biomineralization responses of the pearl oyster Pinctada fucata to elevated CO2 and temperature

    Science.gov (United States)

    Li, Shiguo; Liu, Chuang; Huang, Jingliang; Liu, Yangjia; Zhang, Shuwen; Zheng, Guilan; Xie, Liping; Zhang, Rongqing

    2016-01-01

    Ocean acidification and global warming have been shown to significantly affect the physiological performances of marine calcifiers; however, the underlying mechanisms remain poorly understood. In this study, the transcriptome and biomineralization responses of Pinctada fucata to elevated CO2 (pH 7.8 and pH 7.5) and temperature (25 °C and 31 °C) are investigated. Increases in CO2 and temperature induced significant changes in gene expression, alkaline phosphatase activity, net calcification rates and relative calcium content, whereas no changes are observed in the shell ultrastructure. “Ion and acid-base regulation” related genes and “amino acid metabolism” pathway respond to the elevated CO2 (pH 7.8), suggesting that P. fucata implements a compensatory acid-base mechanism to mitigate the effects of low pH. Additionally, “anti-oxidation”-related genes and “Toll-like receptor signaling”, “arachidonic acid metabolism”, “lysosome” and “other glycan degradation” pathways exhibited responses to elevated temperature (25 °C and 31 °C), suggesting that P. fucata utilizes anti-oxidative and lysosome strategies to alleviate the effects of temperature stress. These responses are energy-consuming processes, which can lead to a decrease in biomineralization capacity. This study therefore is important for understanding the mechanisms by which pearl oysters respond to changing environments and predicting the effects of global climate change on pearl aquaculture.

  20. Formation of biomineral iron oxides compounds in a Fe hyperaccumulator plant: Imperata cylindrica (L.) P. Beauv.

    Science.gov (United States)

    Fuente, V; Rufo, L; Juárez, B H; Menéndez, N; García-Hernández, M; Salas-Colera, E; Espinosa, A

    2016-01-01

    We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic Belt) in an extreme acidic ecosystem (pH∼2.3) with high concentration of dissolved iron, sulphate and heavy metals. Iron biominerals were found at the cellular level in tissues of root, stem and leaf both in collected and laboratory-cultivated plants. Iron accumulated in this plant as a mix of iron compounds (mainly as jarosite, ferrihydrite, hematite and spinel phases) was characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy (MS), magnetometry (SQUID), electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX; TEM-EDX; HRSTEM). A low fraction of phosphorous was detected in this iron hyperaccumulator plant. Root and rhizomes tissues present a high proportion of ferromagnetic iron oxide compounds. Iron oxides-rich zones are localized in electron dense intra and inter-cellular aggregates that appear as dark deposits covering the inner membrane and organelles of the cell. This study aims to contribute to a better understanding of the mechanisms of accumulation, transport, distribution of iron in Imperata cylindrica. PMID:26592710

  1. Weighted Clustering

    DEFF Research Database (Denmark)

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina;

    2012-01-01

    We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both the...... partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...

  2. El Nino impact on mollusk biomineralization-implications for trace element proxy reconstructions and the paleo-archeological record.

    Directory of Open Access Journals (Sweden)

    Alberto Pérez-Huerta

    Full Text Available Marine macroinvertebrates are ideal sentinel organisms to monitor rapid environmental changes associated with climatic phenomena. These organisms build up protective exoskeletons incrementally by biologically-controlled mineralization, which is deeply rooted in long-term evolutionary processes. Recent studies relating potential rapid environmental fluctuations to climate change, such as ocean acidification, suggest modifications on carbonate biominerals of marine invertebrates. However, the influence of known, and recurrent, climatic events on these biological processes during active mineralization is still insufficiently understood. Analysis of Peruvian cockles from the 1982-83 large magnitude El Niño event shows significant alterations of the chemico-structure of carbonate biominerals. Here, we show that bivalves modify the main biomineralization mechanism during the event to continue shell secretion. As a result, magnesium content increases to stabilize amorphous calcium carbonate (ACC, inducing a rise in Mg/Ca unrelated to the associated increase in sea-surface temperature. Analysis of variations in Sr/Ca also suggests that this proxy should not be used in these bivalves to detect the temperature anomaly, while Ba/Ca peaks are recorded in shells in response to an increase in productivity, or dissolved barium in seawater, after the event. Presented data contribute to a better understanding of the effects of abrupt climate change on shell biomineralization, while also offering an alternative view of bivalve elemental proxy reconstructions. Furthermore, biomineralization changes in mollusk shells can be used as a novel potential proxy to provide a more nuanced historical record of El Niño and similar rapid environmental change events.

  3. Field Test and Evaluation of Engineered Biomineralization Technology for Sealing Existing Wells

    Energy Technology Data Exchange (ETDEWEB)

    Cunningham, Alfred [Montana State Univ., Bozeman, MT (United States)

    2015-12-21

    This research project addresses one of the goals of the U.S. Department of Energy (DOE) Carbon Storage Program (CSP) aimed at developing Advanced Wellbore Integrity Technologies to Ensure Permanent Geologic Carbon Storage. The technology field-tested in this research project is referred to as microbially induced calcite precipitation (MICP), which utilizes a biologically-based process to precipitate calcium carbonate. If properly controlled MICP can successfully seal fractures, high permeability zones, and compromised wellbore cement in the vicinity of wellbores and in nearby caprock, thereby improving the storage security of geologically-stored carbon dioxide. This report describes an MICP sealing field test performed on a 24.4 cm (9.625 inch) diameter well located on the Gorgas Steam Generation facility near Jasper, Alabama. The research was aimed at (1) developing methods for delivering MICP promoting fluids downhole using conventional oil field technologies and (2) assessing the ability of MICP to seal cement and formation fractures in the near wellbore region in a sandstone formation. Both objectives were accomplished successfully during a field test performed during the period April 1-11, 2014. The test resulted in complete biomineralization sealing of a horizontal fracture located 340.7 m (1118 feet) below ground surface. A total of 24 calcium injections and six microbial inoculation injections were required over a three day period in order to achieve complete sealing. The fractured region was considered completely sealed when it was no longer possible to inject fluids into the formation without exceeding the initial formation fracture pressure. The test was accomplished using conventional oil field technology including an 11.4 L (3.0 gallon) wireline dump bailer for injecting the biomineralization materials downhole. Metrics indicating successful MICP sealing included reduced injectivity during seal formation, reduction in pressure falloff, and

  4. Towards enamel biomimetics: Structure, mechanical properties and biomineralization of dental enamel

    Science.gov (United States)

    Fong, Hanson Kwok

    Dental enamel is the most mineralized tissue in the human body. This bioceramic, composed largely of hydroxyapatite (HAp), is also one of the most durable tissues despite a lifetime of masticatory loading and bacterial attack. The biosynthesis of enamel, which occurs in physiological conditions is a complex orchestration of protein assembly and mineral formation. The resulting product is the hardest tissue in the vertebrate body with the longest and most organized arrangement of hydroxyapatite crystals known to biomineralizing systems. Detail understanding of the structure of enamel in relationship to its mechanical function and the biomineralization process will provide a framework for enamel regeneration as well as potential lessons in the design of engineering materials. The objective of this study, therefore, is twofold: (1) establish the structure-function relationship of enamel as well as the dentine-enamel junction (DEJ) and (2) determine the effect of proteins on the enamel biomineralization process. A hierarchy in the enamel structure was established by means of various microscopy techniques (e.g. SEM, TEM, AFM). Mechanical properties (hardness and elastic modulus) associated with the microstructural features were also determined by nanoindentation. Furthermore, the DEJ was found to have a width in the range of micrometers to 10s of micrometers with continuous change in structure and mechanical properties. Indentation tests and contact fatigue tests using a spherical indenter have revealed that the structural features in the enamel and the DEJ played important roles in containing crack propagation emanating from the enamel tissue. To further understand the effect of this protein on the biominerailzation process, we have studied genetically engineered animals that express altered amelogenin which lack the known self-assembly properties. This in vivo study has revealed that, without the proper self-assembly of the amelogenin protein as demonstrated by the

  5. Isotopic clusters

    International Nuclear Information System (INIS)

    Spectra of isotopically mixed clusters (dimers of SF6) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)

  6. In Vitro Biomineralization of Glutaraldehyde Crosslinked Chitosan/Glutamic Acid Films

    Institute of Scientific and Technical Information of China (English)

    FENG Fang; LIU Yu; ZHAO Binyuan; HU Keao

    2009-01-01

    In vitrobiomineralization ofglutaraldehyde crosslinked chitosan/glutamicacid films were studied. IR and ESCA (electron spectroscopy for chemical analysis) determinations confirm that chitosan and glutamic acid are successfully crosslinked by glutaraldehyde to form chitosan-glutamic acid surfaces. Composite films were soaked in saturated Ca(OH)2 solution for 8 d and then immersed in simulated body fluid (SBF) for more than 20 d. Morphological characterizations and structure of cal-cium phosphate coatings deposited on the films were studied by SEM, XRD, and EDAX (energy dispersive X-ray analysis). Initially, the treatment in SBF results in the formation of single-layer cal-cium phosphate particles over the film surface. As immersion time increases, further nucleation and growth produce the simulated calcium-carbonate hydroxyapatite coating. ICP results show Ca/P ratio of calcium phosphate coating is a function of SBF immersion time. The inducing of glutamic acid improves the biomineralization property of chitosan films.

  7. Towards understanding biomineralization:calcium phosphate in a biomimetic minerallzation process

    Institute of Scientific and Technical Information of China (English)

    Yu-rong CAI; Rui-kang TANG

    2009-01-01

    Biomineralization processes result in organic/inorganic hybrid materials with complex shapes,hiemrchi-cal structures.and superior matefial properties. Recent developments in biominemlization and biomatarials have demonstrated that calcium phosphate particles play an important role in the formation of hard tissues in nature. In this paper,current concepts in biominemlization,such as nano assembly,biomimetic shell structure,and their applications are introduced. It is confirmed experimentally that enamel-or bone-liked apatita can be achieved by oriented aggregations using nano calcium phosphates as starting matarials. The assembly of calcium phosphate can be either promoted or inhibited by diflerent biomolecules so that the kinetics can he regulated biologically.In this paper,the role of nano calcium phosphate in tissue repair is highligllted Furthermore,a new,interesting result on biomimetie mineralization 1s Introduced,which can offer an artificial shell for living cells via a biomimatic method .

  8. Pearl formation: persistence of the graft during the entire process of biomineralization.

    Science.gov (United States)

    Arnaud-Haond, S; Goyard, E; Vonau, V; Herbaut, C; Prou, J; Saulnier, D

    2007-01-01

    Most bivalves species of the genus Pinctada are well known throughout the world for production of white or black pearls of high commercial value. For cultured pearl production, a mantle allograft from a donor is implanted into the gonad of a recipient oyster, together with a small inorganic bead. Because of the dedifferentiation of cells during the first steps of the host oyster's immunological reaction, so far the fate of the graft and its exact role in the process of pearl formation could not be determined via classical histological methods. Here we report the first molecular evidence of the resilience of the graft in the recipient organism by showing that cells containing genome from the donor are still present at the end of pearl formation. These results suggest the existence of a unique biological cooperation leading to the successful biomineralization process of nacreous secretion in pearl formation.

  9. Magneto-optical study of magnetite nanoparticles prepared by chemical and biomineralization process

    International Nuclear Information System (INIS)

    This paper deals with a magneto-optical study of suspensions of magnetosomes. These magnetosomes are synthesized by biomineralization process of magnetotactic bacteria, followed by steps of isolation and purification in order to obtain stable suspensions. The structural analysis evidences the good crystallinity of the magnetite particles with a diameter of 34 nm. Magneto-induced linear and circular anisotropy confirms the important role played by the chains in the orientation mechanism of such magnetic dipoles. Numerical adjustments of the linear anisotropy curves using a classical Langevin orientation model give the average number of magnetosomes per chain, about 12. - Highlights: → Magnetosomes chains submitted to a magnetic field produce optical anisotropy. → Anisotropy numerical adjustments give the average number of particles per chains. → This number is consistent with statistical analysis from TEM pictures.

  10. Magneto-optical study of magnetite nanoparticles prepared by chemical and biomineralization process

    Energy Technology Data Exchange (ETDEWEB)

    Dzarova, A. [Institute of Experimental Physics, SASD, Watsonova 47, 040 01 Kosice (Slovakia); Royer, F., E-mail: Francois.Royer@univ-st-etienne.f [Universite de Lyon, F-42023 Saint Etienne (France); DIOM EA 3523, Universite de Saint Etienne, Jean Monnet, F-42000 Saint Etienne (France); Timko, M. [Institute of Experimental Physics, SASD, Watsonova 47, 040 01 Kosice (Slovakia); Jamon, D. [Universite de Lyon, F-42023 Saint Etienne (France); DIOM EA 3523, Universite de Saint Etienne, Jean Monnet, F-42000 Saint Etienne (France); Kopcansky, P.; Kovac, J. [Institute of Experimental Physics, SASD, Watsonova 47, 040 01 Kosice (Slovakia); Choueikani, F. [Universite de Lyon, F-42023 Saint Etienne (France); DIOM EA 3523, Universite de Saint Etienne, Jean Monnet, F-42000 Saint Etienne (France); Gojzewski, H. [Institute of Physics, Poznan University of Technology, ul. Nieszawska 13A, 60-965 Poznan (Poland); Rousseau, J.J. [Universite de Lyon, F-42023 Saint Etienne (France); DIOM EA 3523, Universite de Saint Etienne, Jean Monnet, F-42000 Saint Etienne (France)

    2011-06-15

    This paper deals with a magneto-optical study of suspensions of magnetosomes. These magnetosomes are synthesized by biomineralization process of magnetotactic bacteria, followed by steps of isolation and purification in order to obtain stable suspensions. The structural analysis evidences the good crystallinity of the magnetite particles with a diameter of 34 nm. Magneto-induced linear and circular anisotropy confirms the important role played by the chains in the orientation mechanism of such magnetic dipoles. Numerical adjustments of the linear anisotropy curves using a classical Langevin orientation model give the average number of magnetosomes per chain, about 12. - Highlights: Magnetosomes chains submitted to a magnetic field produce optical anisotropy. Anisotropy numerical adjustments give the average number of particles per chains. This number is consistent with statistical analysis from TEM pictures.

  11. Biomineralization of a Cadmium Chloride Nanocrystal by a Designed Symmetrical Protein.

    Science.gov (United States)

    Voet, Arnout R D; Noguchi, Hiroki; Addy, Christine; Zhang, Kam Y J; Tame, Jeremy R H

    2015-08-17

    We have engineered a metal-binding site into the novel artificial β-propeller protein Pizza. This new Pizza variant carries two nearly identical domains per polypeptide chain, and forms a trimer with three-fold symmetry. The designed single metal ion binding site lies on the symmetry axis, bonding the trimer together. Two copies of the trimer associate in the presence of cadmium chloride in solution, and very high-resolution X-ray crystallographic analysis reveals a nanocrystal of cadmium chloride, sandwiched between two trimers of the protein. This nanocrystal, containing seven cadmium ions lying in a plane and twelve interspersed chloride ions, is the smallest reported to date. Our results indicate the feasibility of using rationally designed symmetrical proteins to biomineralize nanocrystals with useful properties. PMID:26136355

  12. The biomineralization and fossilization of magnetotactic bacteria: Insights from experimental and field studies

    Science.gov (United States)

    Pan, Y.; LI, J.; Menguy, N.; Deng, C.; Kissel, C.; Liu, Q.; Zhu, R.

    2015-12-01

    Magnetotactic bacteria (MTB) are widespread prokaryotes which can navigate along the Earth's magnetic field lines and produce tens to hundreds of nanocrystals of magnetite (Fe3O4) or/and greigite (Fe3S4) aligned in chain(s) within a cell. The remains of MTB (i.e. magnetofossils) within geological records have therefore been considered as potential recorders of paleomagnetic, paleoenvironmental and ancient-life signals. These intracellularly-formed nanocrystals, called magnetosomes, generally have distinctively physical, chemical and crystallographic features from those magnetic minerals produced by abiotic or extracellular mineralization processes, and therefore could be distinguished by rock magnetic and electron microscopic approaches. However, identification and quantification of magnetofossils from sediments or sedimentary rocks are nevertheless not straightforward not only due to their tiny sizes, relatively low concentration, always mixing with abiotic magnetic minerals, but also the chain collapse and crystal maghemization during post-depositional processes. Comprehensive studies on the biomineralization and fossilization of magnetosomes are therefore essential for unambiguously identifying and quantitating magnetofossils from geologic samples. In this presentation, we summarize the biomineralization processes and magnetic properties of magnetosome chains within modern cultured and uncultured MTB. Experimental studies on the effects of the chain aligning and collapsing on the magnetic properties of magnetosomes are discussed, which give useful clues to understand the possible occurrence of magnetofossils within natural materials and their corresponding magnetic changes. Recent findings in magnetofossils from marine and lake sediments, showing how to identify magnetofossils from sediments by using the comprehensive rock magnetism, ferromagnetic resonance, and transmission electron microscopy approaches, as well as their implications for sedimentary magnetism

  13. Biocompatibility and biomineralization assessment of bioceramic-, epoxy-, and calcium hydroxide-based sealers.

    Science.gov (United States)

    Bueno, Carlos Roberto Emerenciano; Valentim, Diego; Marques, Vanessa Abreu Sanches; Gomes-Filho, João Eduardo; Cintra, Luciano Tavares Angelo; Jacinto, Rogério Castilho; Dezan-Junior, Eloi

    2016-06-14

    Obturation of the root canal system aims to fill empty spaces, promoting hermetic sealing and preventing bacterial activity in periapical tissues. This should provide optimal conditions for repair, stimulating the process of biomineralization. An endodontic sealer should be biocompatible once it is in direct contact with periapical tissues. The aim of this study was to evaluate the rat subcutaneous tissue response to implanted polyethylene tubes filled with Smartpaste Bio, Acroseal, and Sealapex and investigate mineralization ability of these endodontic sealers. Forty Wistar rats were assigned to the three sealers groups and control group, (n = 10 animals/group) and received subcutaneous implants containing the test sealers, and the control group were implanted with empty tubes. After days 7, 15, 30, and 60, animals were euthanized and polyethylene tubes were removed with the surrounding tissues. Inflammatory infiltrate and thickness of the fibrous capsule were histologically evaluated. Mineralization was analyzed by Von Kossa staining and polarized light. Data were tabulated and analyzed via Kruskal-Wallis and Dunn's test. All tested materials induced a moderate inflammatory reaction in the initial periods. Smartpaste Bio induced the mildest inflammatory reactions after day 15. No difference was observed among groups after days 30 or 60. Von Kossa-positive staining and birefringent structures observed under polarized light revealed a larger mineralization area in Sealapex-treated animals followed by Smartpaste Bio-treated animals. At the end of the experiment, all tested sealers were found to be biocompatible. All sealers induced biomineralization, except Acroseal, which induced a mild tissue reaction. PMID:27305513

  14. Insights into the Role of Biomineralizing Peptide Surfactants on Making Nanoemulsion-Templated Silica Nanocapsules.

    Science.gov (United States)

    Hui, Yue; Wibowo, David; Zhao, Chun-Xia

    2016-01-26

    We recently developed a novel approach for making oil-core silica-shell nanocapsules using designed bifunctional peptides (also called biomineralizing peptide surfactants) having both surface activity and biomineralization activity. Using the bifunctional peptides, oil-in-water nanoemulsion templates can be readily prepared, followed by the silicification directed exclusively onto the oil droplet surfaces and thus the formation of the silica shell. To explore their roles in the synthesis of silica nanocapsules, two bifunctional peptides, AM1 and SurSi, were systematically studied and compared. Peptide AM1, which was designed as a stimuli-responsive surfactant, demonstrated quick adsorption kinetics with a rapid decrease in the oil-water interfacial tension, thus resulting in the formation of nanoemulsions with a droplet size as small as 38 nm. Additionally, the nanoemulsions showed good stability over 4 weeks because of the formation of a histidine-Zn(2+) interfacial network. In comparison, the SurSi peptide that was designed by modularizing an AM1-like surface-active module with a highly cationic biosilicification-active module was unable to effectively reduce the oil-water interfacial tension because of its high molecular charge at neutral pH. The slow adsorption resulted in the formation of less stable nanoemulsions with a larger size (60 nm) than that of AM1. Besides, both AM1 and SurSi were found to be able to induce biomimetic silica formation. SurSi produced well-dispersed and uniform silica nanospheres in the bulk solution, whereas AM1 generated only irregular silica aggregates. Consequently, well-defined silica nanocapsules were synthesized using SurSi nanoemulsion templates, whereas silica aggregates instead of nanocapsules predominated when templating AM1 nanoemulsions. This finding indicated that the capability of peptide surfactants to form isolated silica nanospheres might play a role in the successful fabrication of silica nanocapsules. This

  15. Meaningful Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2004-05-26

    We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.

  16. Trending analysis of precursor events

    International Nuclear Information System (INIS)

    The Accident Sequence Precursor (ASP) Program of United States Nuclear Regulatory Commission (U.S.NRC) identifies and categorizes operational events at nuclear power plants in terms of the potential for core damage. The ASP analysis has been performed on yearly basis and the results have been published in the annual reports. This paper describes the trends in initiating events and dominant sequences for 459 precursors identified in the ASP Program during the 1969-94 period and also discusses a comparison with dominant sequences predicted in the past Probabilistic Risk Assessment (PRA) studies. These trends were examined for three time periods, 1969-81, 1984-87 and 1988-94. Although the different models had been used in the ASP analyses for these three periods, the distribution of precursors by dominant sequences show similar trends to each other. For example, the sequences involving loss of both main and auxiliary feedwater were identified in many PWR events and those involving loss of both high and low coolant injection were found in many BWR events. Also, it was found that these dominant sequences were comparable to those determined to be dominant in the predictions by the past PRAs. As well, a list of the 459 precursors identified are provided in Appendix, indicating initiating event types, unavailable systems, dominant sequences, conditional core damage probabilities, and so on. (author)

  17. PAGOSA Sample Problem. Elastic Precursor

    Energy Technology Data Exchange (ETDEWEB)

    Weseloh, Wayne N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Clancy, Sean Patrick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-02-03

    A PAGOSA simulation of a flyer plate impact which produces an elastic precursor wave is examined. The simulation is compared to an analytic theory for the Mie-Grüneisen equation of state and an elastic-perfectly-plastic strength model.

  18. Structure of precursor bound NifEN: a nitrogenase FeMo cofactor maturase/insertase*

    OpenAIRE

    Kaiser, Jens T.; Hu, Yilin; Wiig, Jared A.; Rees, Douglas C.; Ribbe, Markus W.

    2011-01-01

    NifEN plays an essential role in the biosynthesis of the nitrogenase iron-molybdenum (FeMo) cofactor (M cluster). It is an α_2β_2 tetramer that is homologous to the catalytic molybdenum-iron (MoFe) protein (NifDK) component of nitrogenase. NifEN serves as a scaffold for the conversion of an iron-only precursor to a matured form of the M cluster before delivering the latter to its target location within NifDK. Here, we present the structure of the precursor-bound NifEN of Azotobacter vinelandi...

  19. Water cluster fragmentation probed by pickup experiments

    Science.gov (United States)

    Huang, Chuanfu; Kresin, Vitaly V.; Pysanenko, Andriy; Fárník, Michal

    2016-09-01

    Electron ionization is a common tool for the mass spectrometry of atomic and molecular clusters. Any cluster can be ionized efficiently by sufficiently energetic electrons, but concomitant fragmentation can seriously obstruct the goal of size-resolved detection. We present a new general method to assess the original neutral population of the cluster beam. Clusters undergo a sticking collision with a molecule from a crossed beam, and the velocities of neat and doped cluster ion peaks are measured and compared. By making use of longitudinal momentum conservation, one can reconstruct the sizes of the neutral precursors. Here this method is applied to H2O and D2O clusters in the detected ion size range of 3-10. It is found that water clusters do fragment significantly upon electron impact: the deduced neutral precursor size is ˜3-5 times larger than the observed cluster ions. This conclusion agrees with beam size characterization by another experimental technique: photoionization after Na-doping. Abundant post-ionization fragmentation of water clusters must therefore be an important factor in the interpretation of experimental data; interestingly, there is at present no detailed microscopic understanding of the underlying fragmentation dynamics.

  20. The Innate Lymphoid Cell Precursor.

    Science.gov (United States)

    Ishizuka, Isabel E; Constantinides, Michael G; Gudjonson, Herman; Bendelac, Albert

    2016-05-20

    The discovery of tissue-resident innate lymphoid cell populations effecting different forms of type 1, 2, and 3 immunity; tissue repair; and immune regulation has transformed our understanding of mucosal immunity and allergy. The emerging complexity of these populations along with compounding issues of redundancy and plasticity raise intriguing questions about their precise lineage relationship. Here we review advances in mapping the emergence of these lineages from early lymphoid precursors. We discuss the identification of a common innate lymphoid cell precursor characterized by transient expression of the transcription factor PLZF, and the lineage relationships of innate lymphoid cells with conventional natural killer cells and lymphoid tissue inducer cells. We also review the rapidly growing understanding of the network of transcription factors that direct the development of these lineages. PMID:27168240

  1. The Innate Lymphoid Cell Precursor.

    Science.gov (United States)

    Ishizuka, Isabel E; Constantinides, Michael G; Gudjonson, Herman; Bendelac, Albert

    2016-05-20

    The discovery of tissue-resident innate lymphoid cell populations effecting different forms of type 1, 2, and 3 immunity; tissue repair; and immune regulation has transformed our understanding of mucosal immunity and allergy. The emerging complexity of these populations along with compounding issues of redundancy and plasticity raise intriguing questions about their precise lineage relationship. Here we review advances in mapping the emergence of these lineages from early lymphoid precursors. We discuss the identification of a common innate lymphoid cell precursor characterized by transient expression of the transcription factor PLZF, and the lineage relationships of innate lymphoid cells with conventional natural killer cells and lymphoid tissue inducer cells. We also review the rapidly growing understanding of the network of transcription factors that direct the development of these lineages.

  2. Precursor polymer compositions comprising polybenzimidazole

    Energy Technology Data Exchange (ETDEWEB)

    Klaehn, John R.; Peterson, Eric S.; Orme, Christopher J.

    2015-07-14

    Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

  3. Data Clustering

    Science.gov (United States)

    Wagstaff, Kiri L.

    2012-03-01

    On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained

  4. Characterization of the mantle transcriptome of yesso scallop (Patinopecten yessoensis): identification of genes potentially involved in biomineralization and pigmentation.

    Science.gov (United States)

    Sun, Xiujun; Yang, Aiguo; Wu, Biao; Zhou, Liqing; Liu, Zhihong

    2015-01-01

    The Yesso scallop Patinopecten yessoensis is an economically important marine bivalve species in aquaculture and fishery in Asian countries. However, limited genomic resources are available for this scallop, which hampers investigations into molecular mechanisms underlying their unique biological characteristics, such as shell formation and pigmentation. Mantle is the special tissue of P. yessoensis that secretes biomineralization proteins inducing shell deposition as well as pigmentation on the shells. However, a current deficiency of transcriptome information limits insight into mechanisms of shell formation and pigmentation in this species. In this study, the transcriptome of the mantle of P. yessoensis was deeply sequenced and characterized using Illumina RNA-seq technology. A total of 86,521 unique transcripts are assembled from 55,884,122 reads that passed quality filters, and annotated, using Gene Ontology classification. A total of 259 pathways are identified in the mantle transcriptome, including the calcium signaling and melanogenesis pathways. A total of 237 unigenes that are homologous to 102 reported biomineralization genes are identified, and 121 unigenes that are homologous to 93 known proteins related to melanin biosynthesis are found. Twenty-three annotated unigenes, which are mainly homologous to calmodulin and related proteins, Ca2+/calmodulin-dependent protein kinase, adenylate/guanylate cyclase, and tyrosinase family are potentially involved in both biomineralization and melanin biosynthesis. It is suggested that these genes are probably not limited in function to induce shell deposition by calcium metabolism, but may also be involved in pigmentation of the shells of the scallop. This potentially supports the idea that there might be a link between calcium metabolism and melanin biosynthesis, which was previously found in vertebrates. The findings presented here will notably advance the understanding of the sophisticated processes of shell

  5. The magnetosome membrane protein, MmsF, is a major regulator of magnetite biomineralization in Magnetospirillum magneticum AMB-1

    OpenAIRE

    Murat, Dorothée; Falahati, Veesta; Bertinetti, Luca; Csencsits, Roseann; Körnig, André; Downing, Kenneth; Faivre, Damien; Komeili, Arash

    2012-01-01

    Magnetotactic bacteria (MTB) use magnetosomes, membrane bound crystals of magnetite or greigite, for navigation along geomagnetic fields. In Magnetospirillum magneticum sp. AMB-1, and other MTB, a magnetosome gene island (MAI) is essential for every step of magnetosome formation. An 8-gene region of the MAI encodes several factors implicated in control of crystal size and morphology in previous genetic and proteomic studies. We show that these factors play a minor role in magnetite biomineral...

  6. Unsupervised lineage-based characterization of primate precursors reveals high proliferative and morphological diversity in the OSVZ.

    Science.gov (United States)

    Pfeiffer, Michael; Betizeau, Marion; Waltispurger, Julie; Pfister, Sabina Sara; Douglas, Rodney J; Kennedy, Henry; Dehay, Colette

    2016-02-15

    Generation of the primate cortex is characterized by the diversity of cortical precursors and the complexity of their lineage relationships. Recent studies have reported miscellaneous precursor types based on observer classification of cell biology features including morphology, stemness, and proliferative behavior. Here we use an unsupervised machine learning method for Hidden Markov Trees (HMTs), which can be applied to large datasets to classify precursors on the basis of morphology, cell-cycle length, and behavior during mitosis. The unbiased lineage analysis automatically identifies cell types by applying a lineage-based clustering and model-learning algorithm to a macaque corticogenesis dataset. The algorithmic results validate previously reported observer classification of precursor types and show numerous advantages: It predicts a higher diversity of progenitors and numerous potential transitions between precursor types. The HMT model can be initialized to learn a user-defined number of distinct classes of precursors. This makes it possible to 1) reveal as yet undetected precursor types in view of exploring the significant features of precursors with respect to specific cellular processes; and 2) explore specific lineage features. For example, most precursors in the experimental dataset exhibit bidirectional transitions. Constraining the directionality in the HMT model leads to a reduction in precursor diversity following multiple divisions, thereby suggesting that one impact of bidirectionality in corticogenesis is to maintain precursor diversity. In this way we show that unsupervised lineage analysis provides a valuable methodology for investigating fundamental features of corticogenesis.

  7. Cluster Chemistry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  8. In vitro biomineralization of a novel hydroxyapatite/superhydrophilic multiwalled carbon nanotube nanocomposite using simulated body fluids

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Marcele Florencio; Brazil, Tayra Rodrigues; Marciano, Fernanda Roberta; Lobo, Anderson Oliveira, E-mail: aolobo@univap.br [Universidade do Vale do Paraiba(IP and D,/NANOBIO/UniVap), Sao Jose dos Campos, SP (Brazil). Inst. de Pesquisa e Desenvolvimento. Lab. de Nanotecnologia Biomedica; Soares, Luis Eduardo Silva [Universidade do Vale do Paraiba(IP and D/LEVB/UniVap), Sao Jose dos Campos, SP (Brazil). Inst. de Pesquisa e Desenvolvimento. Lab. de Espectroscopia Vibracional Biomdica; Corat, Evaldo Jose [Instituto Nacional de Pesquisa Espacial (LAS/INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Sensores e Materiais

    2013-11-01

    Nano biomaterials based on superhydrophilic vertically-aligned multi-walled carbon nanotubes (VAMWCNT-O{sub 2} ) are promising for their properties and bone tissue biocompatibility. VAMWCNT-O{sub 2} films with nanohydroxyapatite (nHAp) aim to improve mechanical properties and biocompatibility of this new nanocomposite due to its resemblance to bone matrix structure. This study aimed to produce in vitro biomineralized nHAp/VAMWCNT-O2 nanocomposites using simulated body fluid (SBF) with two different pHs (6.10 and 7.40) during 7 days to obtain a new surface design with higher crystallinity and better morphology of nHAp/VAMWCANT-O{sub 2} nanocomposites. The objective is to obtain biomineralized nano biomaterials to enable its applicability as 'scaffold' to cellular support and consequent bone tissue formation, accelerating the osseointegration. Layer densification has been achieved due to polycrystalline nano apatites deposition on surface and between the biomineralized nHAp/VAMWCNT-O{sub 2} nanocomposites, without any heat treatment. Therefore, through its characteristics and properties these nanocomposite applications can be considered extremely viable for acceleration of in vivo regenerative processes. (author)

  9. Synthesis and Characterization of Smart Block Copolymers for Biomineralization and Biomedical Applications

    Energy Technology Data Exchange (ETDEWEB)

    Mathumai Kanapathipillai

    2008-08-18

    Self-assembly is a powerful tool in forming structures with nanoscale dimensions. Self-assembly of macromolecules provides an efficient and rapid pathway for the formation of structures from the nanometer to micrometer range that are difficult, if not impossible to obtain by conventional lithographic techniques [1]. Depending on the morphologies obtained (size, shape, periodicity, etc.) these self-assembled systems have already been applied or shown to be useful for a number of applications in nanotechnology [2], biomineralization [3, 4], drug delivery [5, 6] and gene therapy [7]. In this respect, amphiphilic block copolymers that self-organize in solution have been found to be very versatile [1]. In recent years, polymer-micellar systems have been designed that are adaptable to their environment and able to respond in a controlled manner to external stimuli. In short, synthesis of 'nanoscale objects' that exhibit 'stimulus-responsive' properties is a topic gathering momentum, because their behavior is reminiscent of that exhibited by proteins [8]. By integrating environmentally sensitive homopolymers into amphiphilic block copolymers, smart block copolymers with self assembled supramolecular structures that exhibit stimuli or environmentally responsive properties can be obtained [1]. Several synthetic polymers are known to have environmentally responsive properties. Changes in the physical, chemical or biochemical environment of these polymers results in modulation of the solubility or chain conformation of the polymer [9]. There are many common schemes of engineering stimuli responsive properties into materials [8, 9]. Polymers exhibiting lower critical solution temperature (LCST) are soluble in solvent below a specific temperature and phase separate from solvent above that temperature while polymers exhibiting upper critical solution temperatures (UCST) phase separate below a certain temperature. The solubility of polymers with ionizable

  10. Synthesis and Characterization of Smart Block Copolymers for Biomineralization and Biomedical Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kanapathipillai, Mathumai [Iowa State Univ., Ames, IA (United States)

    2008-01-01

    Self-assembly is a powerful tool in forming structures with nanoscale dimensions. Self-assembly of macromolecules provides an efficient and rapid pathway for the formation of structures from the nanometer to micrometer range that are difficult, if not impossible to obtain by conventional lithographic techniques [1]. Depending on the morphologies obtained (size, shape, periodicity, etc.) these self-assembled systems have already been applied or shown to be useful for a number of applications in nanotechnology [2], biomineralization [3, 4], drug delivery [5, 6] and gene therapy [7]. In this respect, amphiphilic block copolymers that self-organize in solution have been found to be very versatile [1]. In recent years, polymer-micellar systems have been designed that are adaptable to their environment and able to respond in a controlled manner to external stimuli. In short, synthesis of 'nanoscale objects' that exhibit 'stimulus-responsive' properties is a topic gathering momentum, because their behavior is reminiscent of that exhibited by proteins [8]. By integrating environmentally sensitive homopolymers into amphiphilic block copolymers, smart block copolymers with self assembled supramolecular structures that exhibit stimuli or environmentally responsive properties can be obtained [1]. Several synthetic polymers are known to have environmentally responsive properties. Changes in the physical, chemical or biochemical environment of these polymers results in modulation of the solubility or chain conformation of the polymer [9]. There are many common schemes of engineering stimuli responsive properties into materials [8, 9]. Polymers exhibiting lower critical solution temperature (LCST) are soluble in solvent below a specific temperature and phase separate from solvent above that temperature while polymers exhibiting upper critical solution temperatures (UCST) phase separate below a certain temperature. The solubility of polymers with ionizable

  11. PKP precursors : Implications for global scatterers

    NARCIS (Netherlands)

    Waszek, Lauren; Thomas, Christine; Deuss, Arwen

    2015-01-01

    Precursors to the core phase PKP are generated by scattering of seismic energy from heterogeneities in the mantle. Here we examine a large global data set of PKP precursors in individual seismograms and array data, to better understand scattering locations. The precursor amplitudes from individual s

  12. A shell regeneration assay to identify biomineralization candidate genes in mytilid mussels.

    Science.gov (United States)

    Hüning, Anne K; Lange, Skadi M; Ramesh, Kirti; Jacob, Dorrit E; Jackson, Daniel J; Panknin, Ulrike; Gutowska, Magdalena A; Philipp, Eva E R; Rosenstiel, Philip; Lucassen, Magnus; Melzner, Frank

    2016-06-01

    Biomineralization processes in bivalve molluscs are still poorly understood. Here we provide an analysis of specifically expressed sequences from a mantle transcriptome of the blue mussel, Mytilus edulis. We then developed a novel, integrative shell injury assay to test, whether biomineralization candidate genes highly expressed in marginal and pallial mantle could be induced in central mantle tissue underlying the damaged shell areas. This experimental approach makes it possible to identify gene products that control the chemical micro-environment during calcification as well as organic matrix components. This is unlike existing methodological approaches that work retroactively to characterize calcification relevant molecules and are just able to examine organic matrix components that are present in completed shells. In our assay an orthogonal array of nine 1mm holes was drilled into the left valve, and mussels were suspended in net cages for 20, 29 and 36days to regenerate. Structural observations using stereo-microscopy, SEM and Raman spectroscopy revealed organic sheet synthesis (day 20) as the first step of shell-repair followed by the deposition of calcite crystals (days 20 and 29) and aragonite tablets (day 36). The regeneration period was characterized by time-dependent shifts in gene expression in left central mantle tissue underlying the injured shell, (i) increased expression of two tyrosinase isoforms (TYR3: 29-fold and TYR6: 5-fold) at day 20 with a decline thereafter, (ii) an increase in expression of a gene encoding a nacrein-like protein (max. 100-fold) on day 29. The expression of an acidic Asp-Ser-rich protein was enhanced during the entire regeneration process. This proof-of-principle study demonstrates that genes that are specifically expressed in pallial and marginal mantle tissue can be induced (4 out of 10 genes) in central mantle following experimental injury of the overlying shell. Our findings suggest that regeneration assays can be used

  13. Magnetite Biomineralization: Fifty years of progress, from beach-combing to the SQUID microscope

    Science.gov (United States)

    Kirschvink, J. L.; Dixson, A. D.; Raub, T.

    2012-12-01

    Magnetite biomineralization was first discovered 50 years ago as a hardening agent in the teeth of the Polyplacophoran molluscs (chitons) by the late Prof. Heinz A. Lowenstam of Caltech, when he noticed unusual erosional effects produced by their grazing in the intertidal zones of Palau (Lowenstam, 1962). Since then, biogenic magnetite has been detected in a broad range of organisms, including magnetotactic bacteria, protists, insects, fish, amphibians, reptiles, birds, and mammals including humans. In many species, the role of ferromagnetic material as a neurophysiological transducer is demonstrated clearly through the effects of pulse-remagnetization on behavior. A brief (1 uS), properly configured magnetic discharge from a rectified LC circuit, tailored to exceed the coercivity of the magnetite, will often abolish a magnetic behavioral response, or in some cases make the organism go the wrong way. This is a unique ferromagnetic effect. The genes controlling magnetite biomineralization are well characterized in several species of bacteria, and the ability of some of these bacterial genes to initiate magnetite precipitation in mammalian cell lines argues for a common descent, probably via a magnetotactic mitochondrial ancestor. Previous studies in fish reported the presence of single-domain magnetite crystals in cells near projections of the trigeminal nerve, co-located in the olfactory epithelium. Although the cells are rare, the recent development of a spinning magnetic field technique allows easy identification and isolation of these cells for individual study (Eder et al., 2012). The cells are surprisingly magnetic, with moments hundreds of times larger than typical magnetotactic bacteria. Subsequent efforts to identify the anatomical seat of magnetoreceptors have focused on the same locations in new organisms, excluding other areas. Using SQUID moment magnetometry and SQUID scanning microscopy, we report here the unexpected presence of biogenic magnetite in

  14. Molecular-Scale Structural Controls on Nanoscale Growth Processes: Step-Specific Regulation of Biomineral Morphology

    Science.gov (United States)

    Dove, P. M.; Davis, K. J.; De Yoreo, J. J.; Orme, C. A.

    2001-12-01

    Deciphering the complex strategies by which organisms produce nanocrystalline materials with exquisite morphologies is central to understanding biomineralizing systems. One control on the morphology of biogenic nanoparticles is the specific interactions of their surfaces with the organic functional groups provided by the organism and the various inorganic species present in the ambient environment. It is now possible to directly probe the microscopic structural controls on crystal morphology by making quantitative measurements of the dynamic processes occurring at the mineral-water interface. These observations can provide crucial information concerning the actual mechanisms of growth that is otherwise unobtainable through macroscopic techniques. Here we use in situ molecular-scale observations of step dynamics and growth hillock morphology to directly resolve roles of principal impurities in regulating calcite surface morphologies. We show that the interactions of certain inorganic as well as organic impurities with the calcite surface are dependent upon the molecular-scale structures of step-edges. These interactions can assume a primary role in directing crystal morphology. In calcite growth experiments containing magnesium, we show that growth hillock structures become modified owing to the preferential inhibition of step motion along directions approximately parallel to the [010]. Compositional analyses have shown that Mg incorporates at different levels into the two types of nonequivalent steps, which meet at the hillock corner parallel to [010]. A simple calculation of the strain caused by this difference indicates that we should expect a significant retardation at this corner, in agreement with the observed development of [010] steps. If the low-energy step-risers produced by these [010] steps is perpendicular to the c-axis as seems likely from crystallographic considerations, this effect provides a plausible mechanism for the elongated calcite crystal

  15. Fuzzy Clustering

    DEFF Research Database (Denmark)

    Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan;

    2000-01-01

    -mean clustering is an easy and well improved tool, which has been applied in many medical fields. We used c-mean fuzzy clustering after feature extraction from an aphasia database. Factor analysis was applied on a correlation matrix of 26 symptoms of language disorders and led to five factors. The factors...

  16. Synthesis of carbon nanotubes using natural carbon precursor: Castor oil

    Science.gov (United States)

    Raziah, A. Z.; Junizah, A. R.; Saifuddin, N.

    2012-09-01

    Castor oil has long been an article of commerce due to its versatility as it is widely used as a starting material for many industrial chemical products because of its unique structure. In this study, carbon nanotubes has been synthesized by thermal decomposition of castor oil in nitrogen atmosphere at 300-400δC using custom-made microwave processing unit. The precursor material was catalyzed by iron clusters originating from the addition of ferrocene. The morphology and characterization of the CNTs were studied and discussed by transmission electron microscopy (TEM).

  17. Precursor films in wetting phenomena

    OpenAIRE

    Popescu, M. N.; Oshanin, G.; Dietrich, S.; Cazabat, A. -M.

    2012-01-01

    The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in t...

  18. Biomineralization of a Self-Assembled Extracellular Matrix for Bone Tissue Engineering

    Energy Technology Data Exchange (ETDEWEB)

    Yizhi, M.; Yi-Xian, Q; DiMasi, E; Xiaolan, B; Rafailovich, M; Pernodet, N

    2009-01-01

    Understanding how biomineralization occurs in the extracellular matrix (ECM) of bone cells is crucial to the understanding of bone formation and the development of a successfully engineered bone tissue scaffold. It is still unclear how ECM mechanical properties affect protein-mineral interactions in early stages of bone mineralization. We investigated the longitudinal mineralization properties of MC3T3-E1 cells and the elastic modulus of their ECM using shear modulation force microscopy, synchrotron grazing incidence X-ray diffraction (GIXD), scanning electron microscopy, energy dispersive X-ray spectroscopy, and confocal laser scanning microscopy (CLSM). The elastic modulus of the ECM fibers underwent significant changes for the mineralizing cells, which were not observed in the nonmineralizing cells. On substrates conducive to ECM network production, the elastic modulus of mineralizing cells increased at time points corresponding to mineral production, whereas that of the nonmineralizing cells did not vary over time. The presence of hydroxyapatite in mineralizing cells and the absence thereof in the nonmineralizing ones were confirmed by GIXD, and CLSM showed that a restructuring of actin occurred only for mineral-producing cells. These results show that the correct and complete development of the ECM network is required for osteoblasts to mineralize. This in turn requires a suitably prepared synthetic substrate for bone development to succeed in vitro.

  19. To which extent do Scleractinian coral recruits control the early stages of their biomineralization?

    Science.gov (United States)

    Gilis, M.; Meibom, A.; Domart-Coulon, I.; Stolarski, J.; Hignette, M.; Grauby, O.; Baronnet, A.

    2013-12-01

    Scleractinian corals produce a calcium carbonate skeleton constituting the basis of coral reefs. The structure of their skeletons and their mineralizing tissue has been studied in detail in several stony corals species. It is generally accepted that the formation of specifically shaped skeletal structures by both recruits and adult scleractinian corals relies on biologically controlled mineralization processes. However, the extent to which the surrounding seawater may or may not interact with these endogenous mechanisms is still debated. In the present work, we conducted a multi-scale mineralogical study on each skeletal elements deposited by Pocillopora damicornis recruits, from 12 hours to 22 days after their settlement on a flat (artificial) substrate. High resolution scanning electron microscopy (HR-SEM) allowed characterizing these elements from their sub-micron structure to their hierarchical assembly into micro and macro-structures revealing the interplay with a highly organized nano-scale organic material. Transmission electron microscopy (TEM) and electron diffraction analysis (SAED) on ion-milled lamella extracted from two different skeletal elements produced by 2 days-old recruits brought further information on their internal organization and local crystallography. Our ultrastructural and analytical observations are discussed in light of the recently reported calcium carbonate structures obtained in in vitro and in vivo experimental crystallization studies, suggesting that both biologically-induced and controlled mechanisms might be involved in the initial stages of coral biomineralization.

  20. Biomineralization of phototrophic microbes in silica-enriched hot springs in South China

    Institute of Scientific and Technical Information of China (English)

    PENG XiaoTong; ZHOU HuaiYang; WU ZhiJun; JIANG Lei; TANG Song; YAO HuiQiang; CHEN GuangQian

    2007-01-01

    Microbial mats in two hot springs in South China were sampled for the research of mineralization of microbes and its mechanism by the methods of geology and modern biology. The results show that hot spring microbes have the key capability for enrichment of Si, Al, Fe, Ca and other elements, and the microbes are also crucial for the formation of SiO2, CaCO3, clay and so on. The extracellular polymeric substances (EPS) play important roles in the process of mineralization of hot spring microbes, which mainly takes place in the layer of EPS outside cell wall or sheath of cyanobacteria. The sheath outside cell wall, which keeps the normal metabolism of cyanobacteria during the process of mineralization on its surface, is also considerable for the biomineralization of cyanobacteria. According to structure and mineralization characteristics of two microbial mats, the process of mineralization can be divided into three stages, namely, early surface mineralization, middle degradation mineralization, and late desquamation of mineral. The above conclusions are significant for comprehension of the process of mineralization, the process of deposition and the preservation of microfossil in modern and ancient extreme environments.

  1. A model for the effects of germanium on silica biomineralization in choanoflagellates

    Science.gov (United States)

    Chappell, Helen; Ratcliffe, Sarah; Goldstein, Raymond E.

    2016-01-01

    Silica biomineralization is a widespread phenomenon of major biotechnological interest. Modifying biosilica with substances like germanium (Ge) can confer useful new properties, although exposure to high levels of Ge disrupts normal biosilicification. No clear mechanism explains why this disruption occurs. Here, we study the effect of Ge on loricate choanoflagellates, a group of protists that construct a species-specific extracellular lorica from multiple siliceous costal strips. High Ge exposures were toxic, whereas lower Ge exposures produced cells with incomplete or absent loricae. These effects can be ameliorated by restoring the germanium : silicon ratio, as observed in other biosilicifying organisms. We developed simulations of how Ge interacts with polymerizing silica. In our models, Ge is readily incorporated at the ends of silica forming from silicic acid condensation, but this prevents further silica polymerization. Our ‘Ge-capping’ model is supported by observations from loricate choanoflagellates. Ge exposure terminates costal strip synthesis and lorica formation, resulting in disruption to cytokinesis and fatal build-up of silicic acid. Applying the Ge-capping model to other siliceous organisms explains the general toxicity of Ge and identifies potential protective responses in metalloid uptake and sensing. This can improve the design of new silica biomaterials, and further our understanding of silicon metabolism. PMID:27655668

  2. Analysis of the biomineralization process on SWNT-COOH and F-SWNT films

    Energy Technology Data Exchange (ETDEWEB)

    Armentano, Ilaria [Materials Engineering Centre, UdR INSTM, NIPLAB, University of Perugia, Terni (Italy)], E-mail: Ilaria.armentano@lnl.infn.it; Alvarez-Perez, Marco Antonio; Carmona-Rodriguez, Bruno [Laboratorio de Biologia Celular y Molecular, Facultad de Odontologia, Universidad Nacional Autonoma de Mexico, Mexico D. F. (Mexico); Gutierrez-Ospina, Ivan [Universidad Autonoma Metropolitana, Xochimilco, Mexico D. F. (Mexico); Kenny, Jose Maria [Materials Engineering Centre, UdR INSTM, NIPLAB, University of Perugia, Terni (Italy); Arzate, Higinio [Laboratorio de Biologia Celular y Molecular, Facultad de Odontologia, Universidad Nacional Autonoma de Mexico, Mexico D. F. (Mexico)

    2008-12-01

    In vitro biomineralization process was investigated on functionalized single wall nanotube (SWNT) films. The films were prepared by solvent casting method by using carboxylated and fluorinated nanotubes. SWNT films were characterized by means of electron microscopy, contact angle measurements and optical absorption. The in vitro assays were performed on cultured human alveolar bone-derived cells (HABDC) to determine the capabilities of carboxylated single-walled nanotubes (SWNTs-COOH) and fluorinated single-walled nanotubes (F-SWNTs) to promote the deposit of mineral-like tissue. The results showed that the cellular response of HABDC in secreting a mineralized extracellular matrix and their consequent mineralization is dependent on the degree of functionalization of the SWNTs. Differences were found related to the kind of sidewall functionalization. Both structures promoted hydroxyapatite formation, however, calcium uptake on SWNTs-COOH increased and it was related to crystal density. From our results, it is possible to infer that CNT functionalization opens a path to future developments in new bone graft materials and techniques.

  3. Stepwise Evolution of Coral Biomineralization Revealed with Genome-Wide Proteomics and Transcriptomics.

    Directory of Open Access Journals (Sweden)

    Takeshi Takeuchi

    Full Text Available Despite the importance of stony corals in many research fields related to global issues, such as marine ecology, climate change, paleoclimatogy, and metazoan evolution, very little is known about the evolutionary origin of coral skeleton formation. In order to investigate the evolution of coral biomineralization, we have identified skeletal organic matrix proteins (SOMPs in the skeletal proteome of the scleractinian coral, Acropora digitifera, for which large genomic and transcriptomic datasets are available. Scrupulous gene annotation was conducted based on comparisons of functional domain structures among metazoans. We found that SOMPs include not only coral-specific proteins, but also protein families that are widely conserved among cnidarians and other metazoans. We also identified several conserved transmembrane proteins in the skeletal proteome. Gene expression analysis revealed that expression of these conserved genes continues throughout development. Therefore, these genes are involved not only skeleton formation, but also in basic cellular functions, such as cell-cell interaction and signaling. On the other hand, genes encoding coral-specific proteins, including extracellular matrix domain-containing proteins, galaxins, and acidic proteins, were prominently expressed in post-settlement stages, indicating their role in skeleton formation. Taken together, the process of coral skeleton formation is hypothesized as: 1 formation of initial extracellular matrix between epithelial cells and substrate, employing pre-existing transmembrane proteins; 2 additional extracellular matrix formation using novel proteins that have emerged by domain shuffling and rapid molecular evolution and; 3 calcification controlled by coral-specific SOMPs.

  4. Chemical modification of chitosan film via surface grafting of citric acid molecular to promote the biomineralization

    Science.gov (United States)

    Liu, Yang; Shen, Xin; Zhou, Huan; Wang, Yingjun; Deng, Linhong

    2016-05-01

    We develop a novel chitosan-citric acid film (abbreviated as CS-CA) suitable for biomedical applications in this study. In this CS-CA film, the citric acid, which is a harmless organic acid has been extensively investigated as a modifying agent on carbohydrate polymers, was cross-linked by 1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) onto the surface of chitosan (CS) film. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirms the graft copolymerization of the modified chitosan film (CS-CA). Surface wettability, moisturizing performance, the capacity of mineralization in vitro and biocompatibility of the films were characterized. After modification, this CS-CA film has good hydrophilicity. It is very evident that the citric acid grafting treatment significantly promotes the biomineralization of the chitosan based substrates. Cell experiments show that the MC3T3-E1 osteoblasts can adhere and proliferate well on the surface of CS-CA film. This CS-CA film, which can be prepared in large quantities and at low cost, should have potential application in bone tissue engineering.

  5. Fe2O3 magnetic nanoparticles to enhance S. lycopersicum (tomato) plant growth and their biomineralization

    Science.gov (United States)

    Shankramma, K.; Yallappa, S.; Shivanna, M. B.; Manjanna, J.

    2016-10-01

    In the present study, we demonstrate magnetic iron (III) oxide nanoparticles (Fe2O3 NPs) uptake by the Solanum lycopersicum ( S. lycopersicum) plant. The S. lycopersicum seeds were coated with Fe2O3 NPs and allowed to germinate in moistened sand bed. The seedlings are observed for 20 days, and then, it was post-treated using different amounts of Fe2O3 NPs in hydroponic solution for 10 days. The plant was allowed to grow in green house for 3 months, and uptake of NPs through roots and translocation into different parts was studied. For this, we have segmented the plants and incubated with 10 % NaOH solution. It is found that the NPs are deposited preferentially in root hairs, root tips followed by nodal and middle zone of plant. The iron present in the whole plant was quantitatively estimated by treating dry biomass of the plant in acid. The Fe2+/Fetotal increased with increasing concentration of NPs and >45 % ferrous iron suggests the biomineralization of NPs due to rich phytochemicals in plants. We believe that the present study is useful to build a base line data for novel applications in agri-nanotechnology.

  6. A unique coral biomineralization pattern has resisted 40 million years of major ocean chemistry change

    Science.gov (United States)

    Stolarski, Jarosław; Bosellini, Francesca R.; Wallace, Carden C.; Gothmann, Anne M.; Mazur, Maciej; Domart-Coulon, Isabelle; Gutner-Hoch, Eldad; Neuser, Rolf D.; Levy, Oren; Shemesh, Aldo; Meibom, Anders

    2016-01-01

    Today coral reefs are threatened by changes to seawater conditions associated with rapid anthropogenic global climate change. Yet, since the Cenozoic, these organisms have experienced major fluctuations in atmospheric CO2 levels (from greenhouse conditions of high pCO2 in the Eocene to low pCO2 ice-house conditions in the Oligocene-Miocene) and a dramatically changing ocean Mg/Ca ratio. Here we show that the most diverse, widespread, and abundant reef-building coral genus Acropora (20 morphological groups and 150 living species) has not only survived these environmental changes, but has maintained its distinct skeletal biomineralization pattern for at least 40 My: Well-preserved fossil Acropora skeletons from the Eocene, Oligocene, and Miocene show ultra-structures indistinguishable from those of extant representatives of the genus and their aragonitic skeleton Mg/Ca ratios trace the inferred ocean Mg/Ca ratio precisely since the Eocene. Therefore, among marine biogenic carbonate fossils, well-preserved acroporid skeletons represent material with very high potential for reconstruction of ancient ocean chemistry. PMID:27302371

  7. Bio-mineralization and potential biogeochemical processes in bauxite deposits: genetic and ore quality significance

    Science.gov (United States)

    Laskou, Magdalini; Economou-Eliopoulos, Maria

    2013-08-01

    The Parnassos-Ghiona bauxite deposit in Greece of karst type is the 11th largest bauxite producer in the world. The mineralogical, major and trace-element contents and δ18O, δ12C, δ34S isotopic compositions of bauxite ores from this deposit and associated limestone provide valuable evidence for their origin and biogeochemical processes resulting in the beneficiation of low grade bauxite ores. The organic matter as thin coal layers, overlying the bauxite deposits, within limestone itself (negative δ12C isotopic values) and the negative δ34S values in sulfides within bauxite ores point to the existence of the appropriate circumstances for Fe bio-leaching and bio-mineralization. Furthermore, a consortium of microorganisms of varying morphological forms (filament-like and spherical to lenticular at an average size of 2 μm), either as fossils or presently living and producing enzymes, is a powerful factor to catalyze the redox reactions, expedite the rates of metal extraction and provide alternative pathways for metal leaching processes resulting in the beneficiation of bauxite ore.

  8. Uranium Biominerals Precipitated by an Environmental Isolate of Serratia under Anaerobic Conditions.

    Directory of Open Access Journals (Sweden)

    Laura Newsome

    Full Text Available Stimulating the microbially-mediated precipitation of uranium biominerals may be used to treat groundwater contamination at nuclear sites. The majority of studies to date have focussed on the reductive precipitation of uranium as U(IV by U(VI- and Fe(III-reducing bacteria such as Geobacter and Shewanella species, although other mechanisms of uranium removal from solution can occur, including the precipitation of uranyl phosphates via bacterial phosphatase activity. Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK. When supplied with glycerol phosphate, this Serratia strain was able to precipitate 1 mM of soluble U(VI as uranyl phosphate minerals from the autunite group, under anaerobic and fermentative conditions. Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI, via reduction to nano-crystalline U(IV uraninite. Some evidence for the reduction of solid phase uranyl(VI phosphate was also observed. This study highlights the potential for Serratia and related species to play a role in the bioremediation of uranium contamination, via a range of different metabolic pathways, dependent on culturing or in situ conditions.

  9. From biominerals to biomaterials: the role of biomolecule-mineral interactions.

    Science.gov (United States)

    Perry, Carole C; Patwardhan, Siddharth V; Deschaume, Olivier

    2009-08-01

    Interactions between inorganic materials and biomolecules at the molecular level, although complex, are commonplace. Examples include biominerals, which are, in most cases, facilitated by and in contact with biomolecules; implantable biomaterials; and food and drug handling. The effectiveness of these functional materials is dependent on the interfacial properties, i.e. the extent of molecular level 'association' with biomolecules. The present article gives information on biomolecule-inorganic material interactions and illustrates our current understanding using selected examples. The examples include (i) mechanism of biointegration: the role of surface chemistry and protein adsorption, (ii) towards improved aluminium-containing materials, and (iii) understanding the bioinorganic interface: experiment and modelling. A wide range of experimental techniques (microscopic, spectroscopic, particle sizing, thermal methods and solution methods) are used by the research group to study interactions between (bio)molecules and molecular and colloidal species that are coupled with computational simulation studies to gain as much information as possible on the molecular-scale interactions. Our goal is to uncover the mechanisms underpinning any interactions and to identify 'rules' or 'guiding principles' that could be used to explain and hence predict behaviour for a wide range of (bio)molecule-mineral systems. PMID:19614576

  10. Transcription factor FoxO1 is essential for enamel biomineralization.

    Directory of Open Access Journals (Sweden)

    Ross A Poché

    Full Text Available The Transforming growth factor β (Tgf-β pathway, by signaling via the activation of Smad transcription factors, induces the expression of many diverse downstream target genes thereby regulating a vast array of cellular events essential for proper development and homeostasis. In order for a specific cell type to properly interpret the Tgf-β signal and elicit a specific cellular response, cell-specific transcriptional co-factors often cooperate with the Smads to activate a discrete set of genes in the appropriate temporal and spatial manner. Here, via a conditional knockout approach, we show that mice mutant for Forkhead Box O transcription factor FoxO1 exhibit an enamel hypomaturation defect which phenocopies that of the Smad3 mutant mice. Furthermore, we determined that both the FoxO1 and Smad3 mutant teeth exhibit changes in the expression of similar cohort of genes encoding enamel matrix proteins required for proper enamel development. These data raise the possibility that FoxO1 and Smad3 act in concert to regulate a common repertoire of genes necessary for complete enamel maturation. This study is the first to define an essential role for the FoxO family of transcription factors in tooth development and provides a new molecular entry point which will allow researchers to delineate novel genetic pathways regulating the process of biomineralization which may also have significance for studies of human tooth diseases such as amelogenesis imperfecta.

  11. A unique coral biomineralization pattern has resisted 40 million years of major ocean chemistry change.

    Science.gov (United States)

    Stolarski, Jarosław; Bosellini, Francesca R; Wallace, Carden C; Gothmann, Anne M; Mazur, Maciej; Domart-Coulon, Isabelle; Gutner-Hoch, Eldad; Neuser, Rolf D; Levy, Oren; Shemesh, Aldo; Meibom, Anders

    2016-01-01

    Today coral reefs are threatened by changes to seawater conditions associated with rapid anthropogenic global climate change. Yet, since the Cenozoic, these organisms have experienced major fluctuations in atmospheric CO2 levels (from greenhouse conditions of high pCO2 in the Eocene to low pCO2 ice-house conditions in the Oligocene-Miocene) and a dramatically changing ocean Mg/Ca ratio. Here we show that the most diverse, widespread, and abundant reef-building coral genus Acropora (20 morphological groups and 150 living species) has not only survived these environmental changes, but has maintained its distinct skeletal biomineralization pattern for at least 40 My: Well-preserved fossil Acropora skeletons from the Eocene, Oligocene, and Miocene show ultra-structures indistinguishable from those of extant representatives of the genus and their aragonitic skeleton Mg/Ca ratios trace the inferred ocean Mg/Ca ratio precisely since the Eocene. Therefore, among marine biogenic carbonate fossils, well-preserved acroporid skeletons represent material with very high potential for reconstruction of ancient ocean chemistry. PMID:27302371

  12. Fe2O3 magnetic nanoparticles to enhance S. lycopersicum (tomato) plant growth and their biomineralization

    Science.gov (United States)

    Shankramma, K.; Yallappa, S.; Shivanna, M. B.; Manjanna, J.

    2015-12-01

    In the present study, we demonstrate magnetic iron (III) oxide nanoparticles (Fe2O3 NPs) uptake by the Solanum lycopersicum (S. lycopersicum) plant. The S. lycopersicum seeds were coated with Fe2O3 NPs and allowed to germinate in moistened sand bed. The seedlings are observed for 20 days, and then, it was post-treated using different amounts of Fe2O3 NPs in hydroponic solution for 10 days. The plant was allowed to grow in green house for 3 months, and uptake of NPs through roots and translocation into different parts was studied. For this, we have segmented the plants and incubated with 10 % NaOH solution. It is found that the NPs are deposited preferentially in root hairs, root tips followed by nodal and middle zone of plant. The iron present in the whole plant was quantitatively estimated by treating dry biomass of the plant in acid. The Fe2+/Fetotal increased with increasing concentration of NPs and >45 % ferrous iron suggests the biomineralization of NPs due to rich phytochemicals in plants. We believe that the present study is useful to build a base line data for novel applications in agri-nanotechnology.

  13. Mitigation of efflorescence of wallboard by means of bio-mineralization.

    Science.gov (United States)

    Xue, Bin; Qian, Chunxiang

    2015-01-01

    Cement-based material is one of the most versatile and largest amounts of building materials which can not only be used in load-bearing structure but also be used as decoration materials, like brick, wallboard, and tile. However, white calcium carbonate always be found on the surface of wallboard. This phenomenon is generally called efflorescence, which has no damage to wallboard, but has aesthetic impact. In this research, Bacillus mucilaginosus was pre-added to the cement matrix to reduce the efflorescence of wallboard. Image processing, thermogravimetric analysis and permeability test were used to characterize the efflorescence degree of wallboard. The results showed that the bacterium captured atmospheric CO2 by carbonic anhydrase and promoted the CO2to react with Ca(OH)2. This process not only reduced the content of Ca(OH)2 but also improved the compactness of wallboard. In addition, the maximal decrease of efflorescence area of wallboard was gotten when the content of microbial was up to 4% of the mass of cementitious material and the proportion of efflorescence area reduced from 32 ± 3 to 5 ± 1% of the whole area of surface layer. At the same time, the values of compressive and flexural strength were the highest and the surface layer of wallboard was the most compact. The observed reduction of efflorescence was indeed due to the effect of bio-mineralization. This promising method was noted to be cheap, convenient, environment friendly, and which has the potential in various practical applications. PMID:26539182

  14. Analysis of an ultra hard magnetic biomineral in chiton radular teeth

    Directory of Open Access Journals (Sweden)

    James C. Weaver

    2010-01-01

    Full Text Available Recent analyses of the ultrastructural and mechanical properties of mineralized biological materials have demonstrated some common architectural features that can help explain their observed damage tolerance. Nature has accomplished this feat through the precise control of anisotropic crystal nucleation and growth processes in conjunction with nanoscale control over the self-assembly of spatially distinct organic and inorganic phases, resulting in effective inhibition of crack propagation through these materials. One such example is found in the hyper-mineralized and abrasion resistant radular teeth of the chitons, a group of herbivorous marine mollusks who have the surprising capacity to erode away the rocky substrates on which they graze1–4. Through the use of modern microscopy and nanomechanical characterization techniques, we describe the architectural and mechanical properties of the radular teeth from Cryptochiton stelleri. Chiton teeth are shown to exhibit the largest hardness and stiffness of any biominerals reported to date, being notably as much as three-fold harder than human enamel and the calcium carbonate-based shells of mollusks. We explain how the unique multi-phasic design of these materials contributes not only to their functionality, but also highlights some interesting design principles that might be applied to the fabrication of synthetic composites.

  15. Evaluating Molecular Interactions in Polycaprolactone-Biomineralized Hydroxyapatite Nanocomposites using Steered Molecular Dynamics

    Science.gov (United States)

    Sharma, Anurag; Payne, Scott; Katti, Kalpana S.; Katti, Dinesh R.

    2015-04-01

    An experimental and modeling study of a complex nanoclay-based polymeric scaffold system is presented here. A representative molecular model of polymeric nanocomposite scaffold system for bone tissue engineering applications was developed. Polymeric scaffolds were synthesized using organically modified montmorillonite clay (OMMT) with biomineralized hydroxyapatite and polycaprolactone (OMMT-HAP-PCL). The OMMT-HAP-PCL representative model was constructed and validated using transmission electron microscopy, x-ray diffraction and material density results. We observed strong molecular interactions between OMMT, hydroxyapatite (HAP) and polycaprolactone (PCL) in the OMMT-HAP-PCL system. Attractive and repulsive interactions between PCL and different constituents of OMMT and HAP indicate influence of OMMT-HAP on PCL. Polymeric scaffolds were found to have improved nanomechanical properties as compared to pristine PCL due to the introduction of OMMT-HAP. Stress-strain response for the representative OMMT-HAP-PCL model was evaluated using constant force steered molecular dynamics (SMD) simulations. Two distinct stress-strain responses observed in the system indicate a two-phase nanomechanical behavior of OMMT-HAP-PCL obtained at low and high applied stresses. The results obtained from the MD and SMD simulations provide quantitative understanding of molecular interactions between different constituents of OMMT, HAP and PCL and mechanical response in the OMMT-HAP-PCL system.

  16. Analysis of the biomineralization process on SWNT-COOH and F-SWNT films

    International Nuclear Information System (INIS)

    In vitro biomineralization process was investigated on functionalized single wall nanotube (SWNT) films. The films were prepared by solvent casting method by using carboxylated and fluorinated nanotubes. SWNT films were characterized by means of electron microscopy, contact angle measurements and optical absorption. The in vitro assays were performed on cultured human alveolar bone-derived cells (HABDC) to determine the capabilities of carboxylated single-walled nanotubes (SWNTs-COOH) and fluorinated single-walled nanotubes (F-SWNTs) to promote the deposit of mineral-like tissue. The results showed that the cellular response of HABDC in secreting a mineralized extracellular matrix and their consequent mineralization is dependent on the degree of functionalization of the SWNTs. Differences were found related to the kind of sidewall functionalization. Both structures promoted hydroxyapatite formation, however, calcium uptake on SWNTs-COOH increased and it was related to crystal density. From our results, it is possible to infer that CNT functionalization opens a path to future developments in new bone graft materials and techniques

  17. Abalone water-soluble matrix for self-healing biomineralization of tooth defects.

    Science.gov (United States)

    Wen, Zhenliang; Chen, Jingdi; Wang, Hailiang; Zhong, Shengnan; Hu, Yimin; Wang, Zhili; Zhang, Qiqing

    2016-10-01

    Enamel cannot heal by itself if damaged. Hydroxyapatite (HAP) is main component of human enamel. Formation of enamel-like materials for healing enamel defects remains a challenge. In this paper, we successfully isolated the abalone water-soluble matrix (AWSM) with 1.53wt% the abalone water-soluble protein (AWSPro) and 2.04wt% the abalone water-soluble polysaccharide (AWSPs) from abandoned abalone shell, and self-healing biomineralization of tooth defects was successfully achieved in vitro. Based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), hot field emission scanning electron microscopy (HFESEM) and energy dispersive spectrometer (EDS) analysis, the results showed that the AWSM can efficiently induce remineralization of HAP. The enamel-like HAP was successfully achieved onto etched enamel's surface due to the presence of the AWSM. Moreover, the remineralized effect of eroded enamel was growing with the increase of the AWSM. This study provides a solution to the resource waste and environmental pollution caused by abandoned abalone shell, and we provides a new method for self-healing remineralization of enamel defects by AWSM and develops a novel dental material for potential clinical dentistry application. PMID:27287112

  18. A unique coral biomineralization pattern has resisted 40 million years of major ocean chemistry change

    Science.gov (United States)

    Stolarski, Jarosław; Bosellini, Francesca R.; Wallace, Carden C.; Gothmann, Anne M.; Mazur, Maciej; Domart-Coulon, Isabelle; Gutner-Hoch, Eldad; Neuser, Rolf D.; Levy, Oren; Shemesh, Aldo; Meibom, Anders

    2016-06-01

    Today coral reefs are threatened by changes to seawater conditions associated with rapid anthropogenic global climate change. Yet, since the Cenozoic, these organisms have experienced major fluctuations in atmospheric CO2 levels (from greenhouse conditions of high pCO2 in the Eocene to low pCO2 ice-house conditions in the Oligocene-Miocene) and a dramatically changing ocean Mg/Ca ratio. Here we show that the most diverse, widespread, and abundant reef-building coral genus Acropora (20 morphological groups and 150 living species) has not only survived these environmental changes, but has maintained its distinct skeletal biomineralization pattern for at least 40 My: Well-preserved fossil Acropora skeletons from the Eocene, Oligocene, and Miocene show ultra-structures indistinguishable from those of extant representatives of the genus and their aragonitic skeleton Mg/Ca ratios trace the inferred ocean Mg/Ca ratio precisely since the Eocene. Therefore, among marine biogenic carbonate fossils, well-preserved acroporid skeletons represent material with very high potential for reconstruction of ancient ocean chemistry.

  19. Experimental comparison of micro-PIXE with other methods utilized for biomineralization studies

    Science.gov (United States)

    Cichocki, T.; Heck, D.; Jarczyk, L.; Rokita, E.; Strzalkowski, A.; Sych, M.

    1988-05-01

    The present study deals with the investigation of arterial wall mineralization i.e. of inorganic compound development within artery wall under normal or pathologic conditions. Autopsy samples of human aorta as well as fragments of aorta obtained from hypercholesterolemic rabbits were used for the experiments. The samples were investigated using micro-PIXE, PIXE and PIGE techniques, infrared and Raman spectroscopy, X-ray powder diffraction and a variety of histochemical methods in order to compare the techniques based on a proton microprobe with the other methods which aimed at the investigation of inorganic deposits. Proton microprobe measurements confirm the different composition of mineral deposits found in rabbit and human aorta samples. In the case of animal aorta the apatite crystals constitute the mineral form of deposits while for human samples we deal with a mixture of different compounds. Moreover, for rabbit aorta samples the deposits were found always in the atheromas, while in human aorta sections the mineral deposits were localized in the media of the aortic wall. The proton microprobe can be considered to be a valuable addition to the experimental methods that have been applied in the study of the biomineralization process. It permits a qualitative determination of mineral deposits in situ while infrared and Raman spectroscopy as well as X-ray powder diffraction measurements may be performed only for ashed aorta samples. The possibility of in situ measurements and high detection sensitivity seem to be the most significant advantages of a proton microprobe in the study of artery wall mineralization.

  20. Regression analysis of reported earthquake precursors. I. Presentation of data

    Science.gov (United States)

    Niazi, Mansour

    1984-11-01

    Around 700 reported precursors of about 350 earthquakes, including the negative observations, have been compiled in 11 categories with 31 subdivisions. The data base is subjected to an initial sorting and screening by imposing three restrictions on the ranges of main shock magnitude ( M≥4.0), precursory time ( t≤20 years), and the epicentral distance of observation points ( X m≤4.100.3 M ). Of the 31 subcategories of precursory phenomena, 18 with 9 data points or more are independently studied by regressing their precursory times against magnitude. The preliminary results tend to classify the precursors into three groups: 1. The precursors which show weak or no correlation between time and the magnitude of the eventual main shock. Examples of this group are foreshocks and precursory tilt. 2. The precursors which show clear scaling with magnitude. These include seismic velocity ratio ( V p/Vs), travel time delay, duration of seismic quiescence, and, to some degree, the variation of b-value, and anomalous seismicity. 3. The precursors which display clustering of precursory times around a mean value, which differs for different precursors from a few hours to a few years. Examples include the conductivity rate, geoelectric current and potential, strain, water well level, geochemical anomalies, change of focal mechanism, and the enhancement of seismicity reported only for larger earthquakes. Some of the precursors in this category, such as leveling changes and the occurrence of microseismicity, show bimodal patterns of precursory times and may partially be coseismic. In addition, each category with a sufficient number of reported estimates of distance and signal amplitude is subjected to multiple linear regression. The usefulness of these regressions at this stage appears to be limited to specifying which of the parameters shows a more significant correlation. Standard deviations of residuals of precursory time against magnitude are generally reduced when

  1. Weighted Clustering

    CERN Document Server

    Ackerman, Margareta; Branzei, Simina; Loker, David

    2011-01-01

    In this paper we investigate clustering in the weighted setting, in which every data point is assigned a real valued weight. We conduct a theoretical analysis on the influence of weighted data on standard clustering algorithms in each of the partitional and hierarchical settings, characterising the precise conditions under which such algorithms react to weights, and classifying clustering methods into three broad categories: weight-responsive, weight-considering, and weight-robust. Our analysis raises several interesting questions and can be directly mapped to the classical unweighted setting.

  2. Cluster analysis

    CERN Document Server

    Everitt, Brian S; Leese, Morven; Stahl, Daniel

    2011-01-01

    Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics.This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data.Real life examples are used throughout to demons

  3. Cluster editing

    DEFF Research Database (Denmark)

    Böcker, S.; Baumbach, Jan

    2013-01-01

    The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side. The...... algorithms for biological problems. © 2013 Springer-Verlag....... problem has been the inspiration for numerous algorithms in bioinformatics, aiming at clustering entities such as genes, proteins, phenotypes, or patients. In this paper, we review exact and heuristic methods that have been proposed for the Cluster Editing problem, and also applications of these...

  4. Sulfur-accumulating plants convert sulfate salts from soils into environmentally resilient biominerals

    Science.gov (United States)

    Robson, Thomas; Reid, Nathan; Stevens, Jason; Dixon, Kingsley

    2016-04-01

    Sulfur-accumulator plants (thiophores), which accumulate atypically high sulfur and calcium concentrations in their aerial biomass, may be suitable for revegetating and phytostabilising reactive sulfur-enriched substrates such as mine tailings, acid-sulfate soils and polluted soils. We present biogeochemical insights on thiophores from the Australian Great Sandy Desert, which accumulate up to 40 times as much sulfur (2-5 %S) versus comparator species. X-ray microanalyses revealed this accumulation relates to peculiar gypsum-like mineralisation throughout their foliage, illustrating a mechanism for sulfate removal from soils and sequestration as sparingly soluble biominerals. However, we did not know whether these species treat the excess Ca/S as a waste to be shed with senescent litter and, if so, how resilient these 'biominerals' are to photo-biodegradation once shed and so to what extent the accumulated elements are recycled back into the reactive/bioavailable sulfate reservoir. To address these questions, we sampled four foliage (phyllode) fractions from ten individuals of the thiophore, Acacia bivenosa: healthy mature phyllodes, senescent phyllodes on the branch, recently shed and older, more degraded ground litter. We selected two thiophores (A. bivenosa and A. robeorum) and a non-thiophore (A. ancistrocarpa) for detailed soil/regolith studies. Samples were collected from trenches bisected by each tree, taken from varying depth (20-500 mm) and distance from the stem (0.1-5 m). Dried foliage was cleaned, sectioned for SEM-EDXS examination and elemental compositions of foliage and soils were determined (microwave-assisted acid digestion + ICP-OES/MS). Each species generated a 'halo' of elevated S/Ca in the soil immediately beneath their crowns, although that of A. ancistrocarpa was of minor magnitude. These anomalies were confined to shallow soil (20-50 mm i.e. influenced by litter), suggesting limited S/Ca re-mobilisation from the litter. Foliar elemental

  5. Microfossils, biomolecules and biominerals in carbonaceous meteorites: implications to the origin of life

    Science.gov (United States)

    Hoover, Richard B.

    2012-11-01

    Environmental and Field Emission Scanning Electron Microscopy (ESEM and FESEM) investigations have shown that a wide variety of carbonaceous meteorites contain the remains of large filaments embedded within freshly fractured interior surfaces of the meteorite rock matrix. The filaments occur singly or in dense assemblages and mats and are often encased within carbon-rich, electron transparent sheaths. Electron Dispersive X-ray Spectroscopy (EDS) spot analysis and 2D X-Ray maps indicate the filaments rarely have detectable nitrogen levels and exhibit elemental compositions consistent with that interpretation that of the meteorite rock matrix. Many of the meteorite filaments are exceptionally well-preserved and show evidence of cells, cell-wall constrictions and specialized cells and processes for reproduction, nitrogen fixation, attachment and motility. Morphological and morphometric analyses permit many of the filaments to be associated with morphotypes of known genera and species of known filamentous trichomic prokaryotes (cyanobacteria and sulfur bacteria). The presence in carbonaceous meteorites of diagenetic breakdown products of chlorophyll (pristane and phytane) along with indigenous and extraterrestrial chiral protein amino acids, nucleobases and other life-critical biomolecules provides strong support to the hypothesis that these filaments represent the remains of cyanobacteria and other microorganisms that grew on the meteorite parent body. The absence of other life-critical biomolecules in the meteorites and the lack of detectable levels of nitrogen indicate the filaments died long ago and can not possibly represent modern microbial contaminants that entered the stones after they arrived on Earth. This paper presents new evidence for microfossils, biomolecules and biominerals in carbonaceous meteorites and considers the implications to some of the major hypotheses for the Origin of Life.

  6. Molecular interactions in biomineralized hydroxyapatite amino acid modified nanoclay: In silico design of bone biomaterials

    International Nuclear Information System (INIS)

    A simulations driven approach to design of a novel biomaterial nanocomposite system is described in this study. Nanoclays modified with amino acids (OMMT) were used to mineralize hydroxyapatite (HAP), mimicking biomineralization. Representative models of organically modified montmorillonite clay (OMMT) and OMMT-hydroxyapatite (OMMT-HAP) were constructed using molecular dynamics and validated using X-ray Diffraction (XRD), Fourier Transforms Infrared (FTIR) spectroscopy and Transmission Electron Microscopy (TEM). Attractive interactions exist between Ca atoms of HAP and C=O group of aminovaleric acid, indicating chelate formation in OMMT-HAP. Interaction energy maps describe molecular interactions among different constituents and their quantitative contributions in the OMMT and OMMT-HAP systems at both parallel and perpendicular orientations. High attractive and high repulsive interactions were found between PO43− and MMT clay as well as aminovaleric molecules in OMMT-HAP perpendicular and parallel models. Large non-bonded interactions in OMMT-HAP indicate influence of neighboring environment on PO43− in in situ HAPclay. Extensive hydrogen bonds were observed between functional hydrogen atoms of modifier and MMT clay in OMMT-HAP as compared to OMMT. Thus, HAP interacts with clay through the aminovaleric acid. This computational study provides a framework for materials design and selection for biomaterials used in tissue engineering and other areas of regenerative medicine. - Highlights: • Representative models of a hybrid nanoclay-hydroxyapatite biomaterial are built. • Interaction energy maps are constructed using a molecular dynamics. • Quantitative interactions between the three components of the biomaterial are found. • The modeling and experimental approach provides insight into the complex nanomaterial

  7. Molecular interactions in biomineralized hydroxyapatite amino acid modified nanoclay: In silico design of bone biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Katti, Dinesh R., E-mail: Dinesh.Katti@ndsu.edu; Sharma, Anurag; Ambre, Avinash H.; Katti, Kalpana S.

    2015-01-01

    A simulations driven approach to design of a novel biomaterial nanocomposite system is described in this study. Nanoclays modified with amino acids (OMMT) were used to mineralize hydroxyapatite (HAP), mimicking biomineralization. Representative models of organically modified montmorillonite clay (OMMT) and OMMT-hydroxyapatite (OMMT-HAP) were constructed using molecular dynamics and validated using X-ray Diffraction (XRD), Fourier Transforms Infrared (FTIR) spectroscopy and Transmission Electron Microscopy (TEM). Attractive interactions exist between Ca atoms of HAP and C=O group of aminovaleric acid, indicating chelate formation in OMMT-HAP. Interaction energy maps describe molecular interactions among different constituents and their quantitative contributions in the OMMT and OMMT-HAP systems at both parallel and perpendicular orientations. High attractive and high repulsive interactions were found between PO{sub 4}{sup 3−} and MMT clay as well as aminovaleric molecules in OMMT-HAP perpendicular and parallel models. Large non-bonded interactions in OMMT-HAP indicate influence of neighboring environment on PO{sub 4}{sup 3−} in in situ HAPclay. Extensive hydrogen bonds were observed between functional hydrogen atoms of modifier and MMT clay in OMMT-HAP as compared to OMMT. Thus, HAP interacts with clay through the aminovaleric acid. This computational study provides a framework for materials design and selection for biomaterials used in tissue engineering and other areas of regenerative medicine. - Highlights: • Representative models of a hybrid nanoclay-hydroxyapatite biomaterial are built. • Interaction energy maps are constructed using a molecular dynamics. • Quantitative interactions between the three components of the biomaterial are found. • The modeling and experimental approach provides insight into the complex nanomaterial.

  8. Mitigation of efflorescence of wallboard by means of bio-mineralization

    Directory of Open Access Journals (Sweden)

    Bin eXue

    2015-10-01

    Full Text Available Cement-based material is one of the most versatile and largest amount of building materials which can not only be used in load-bearing structure but also decoration materials, like brick, wallboard and tile. However, white calcium carbonate always deposit on the surface of wallboard. This phenomenon generally is called efflorescence, which is not damaging of wallboard, but has aesthetic impact. In this research, Bacillus mucilaginosus was pre-added to the cement matrix to reduce the efflorescence of wallboard. Image processing with software ImageJ, thermogravimetric analysis and permeability test were used to characterize the degree of efflorescence of wallboard. The results showed that the bacterium can capture atmospheric CO2 by carbonic anhydrase and then the CO2 react with Ca(OH2 produced by cement hydration inside the wallboard. This process can not only reduce the content of Ca(OH2 but also improve the compactness of wallboard. In addition, the efficiency of resistance to the efflorescence can be achieved when the content of microbial is 4% of cementitious material and the area proportion of surface efflorescence reduced from 32±3% to 5±1%. At the same time, compressive and flexural strength were the highest performance by means of universal testing machine test. The surface of wallboard was the most compact by SEM analysis. The observed efflorescence reduction was indeed due to the effect of bio-mineralization. This promising method is cheap, convenient and environment friendly. It can be massively applied in engineering practice and other fields.

  9. Taking nature into lab: biomineralization by heavy metal resistant streptomycetes in soil

    Directory of Open Access Journals (Sweden)

    E. Schütze

    2013-02-01

    Full Text Available Biomineralization by heavy metal resistant streptomycetes was tested to evaluate the potential influence on metal mobilities in soil. Thus, we designed an experiment adopting conditions from classical laboratory methods to natural conditions prevailing in metal-rich soils with media spiked with heavy metals, soil agar, and nutrient enriched or unamended soil incubated with the bacteria. As a result, all strains were able to form struvite minerals on tryptic soy broth (TSB media supplemented with AlCl2, MnCl2 and CuSO4, as well as on soil agar. Some strains additionally formed struvite on nutrient enriched contaminated and control soil, as well as on metal contaminated soil without addition of media components. In contrast, switzerite was exclusively formed on minimal media spiked with MnCl2 by four heavy metal resistant strains, and on nutrient enriched control soil by one strain. Hydrated nickel hydrogen phosphate was only crystallized on complex media supplemented with NiSO4 by most strains. Thus, mineralization is a~dominant property of streptomycetes, with different processes likely to occur under laboratory conditions and sub-natural to natural conditions. This new understanding may be transferred to formation of minerals in rock and sediment evolution, to ore deposit formation, and also might have implications for our understanding of biological metal resistance mechanisms. We assume that biogeochemical cycles, nutrient storage and metal resistance might be affected by formation and re-solubilization of minerals like struvite in soil at microscale.

  10. Taking nature into lab: biomineralization by heavy metal-resistant streptomycetes in soil

    Directory of Open Access Journals (Sweden)

    E. Schütze

    2013-06-01

    Full Text Available Biomineralization by heavy metal-resistant streptomycetes was tested to evaluate the potential influence on metal mobilities in soil. Thus, we designed an experiment adopting conditions from classical laboratory methods to natural conditions prevailing in metal-rich soils with media spiked with heavy metals, soil agar, and nutrient-enriched or unamended soil incubated with the bacteria. As a result, all strains were able to form struvite minerals (MgNH4PO4• 6H2O on tryptic soy broth (TSB-media supplemented with AlCl3, MnCl2 and CuSO4, as well as on soil agar. Some strains additionally formed struvite on nutrient-enriched contaminated and control soil, as well as on metal contaminated soil without addition of media components. In contrast, switzerite (Mn3(PO42• 7H2O was exclusively formed on minimal media spiked with MnCl2 by four heavy metal-resistant strains, and on nutrient-enriched control soil by one strain. Hydrated nickel hydrogen phosphate was only crystallized on complex media supplemented with NiSO4 by most strains. Thus, mineralization is a dominant property of streptomycetes, with different processes likely to occur under laboratory conditions and sub-natural to natural conditions. This new understanding might have implications for our understanding of biological metal resistance mechanisms. We assume that biogeochemical cycles, nutrient storage and metal resistance might be affected by formation and re-solubilization of minerals like struvite in soil at microscale.

  11. Evolution of Mineral-Organic Matter Associations in Sediments: From (Bio)mineralization to Burial

    Science.gov (United States)

    Estes, E.; Nordlund, D.; Wankel, S. D.; Hansel, C. M.

    2014-12-01

    Physical and chemical associations with mineral surfaces may protect organic matter (OM) from oxidative degradation and allow its preservation in soils and sediments. This study evaluates the mechanism of mineral-based preservation (MBP) and the time scale on which MBP is operative by tracking the co-evolution of oxide minerals and associated OM during mineral precipitation and ripening. Scanning transmission X-ray microscopy coupled to near edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS) as well as bulk NEXAFS demonstrate that, in laboratory systems using cell-free filtrate from pure bacterial cultures, an association between OM and biogenic manganese oxides is rapidly established. OM associated with freshly precipitated biominerals consists of proteinaceous carbon and nitrogen consistent with a microbial origin; this composition remains constant over the course of 96 hours, despite mineral aggregation and structural evolution from hexagonal to triclinic birnessite. We predict that, in natural systems, oxide minerals simultaneously drive remineralization and offer MBP. Different minerals will promote a different balance between the two, imparting a mineral-specific signature on the concentration and composition of preserved OM. We test this idea by conducting incubations of natural estuary waters spiked with compositionally and structurally diverse synthetic oxide minerals. The concentration and composition of mineral-associated OM were tracked by element analyzer-isotope ratio mass spectrometry (EA-IRMS) and STXM-NEXAFS in multiple experiments lasting between 4 weeks and 1 year. Results from incubation experiments are contrasted with natural sediment samples from a range of depositional environments in order to evaluate the potential for long-term sequestration of organic carbon in sediments facilitated by minerals.

  12. Applications of Time-Resolved Synchrotron X-ray Diffraction to Cation Exchange, Crystal Growth and Biomineralization Reactions

    International Nuclear Information System (INIS)

    Advances in the design of environmental reaction cells and in the collection of X-ray diffraction data are transforming our ability to study mineral-fluid interactions. The resulting increase in time resolution now allows for the determination of rate laws for mineral reactions that are coupled to atomic-scale changes in crystal structure. Here we address the extension of time-resolved synchrotron diffraction techniques to four areas of critical importance to the cycling of metals in soils: (1) cation exchange; (2) biomineralization; (3) stable isotope fractionation during redox reactions; and (4) nucleation and growth of nanoscale oxyhydroxides.

  13. Rheological behavior of precursor PPV monolayers

    NARCIS (Netherlands)

    Luinge, JW; Nijboer, GW; Hagting, JG; Vorenkamp, EJ; Fuller, GG; Schouten, AJ

    2004-01-01

    The rheological behavior of different precursor poly(p-phenylene vinylene) (prec-PPV) monolayers at the air-water interface was investigated using an interfacial stress rheometer (ISR). This device nicely reveals a transition of the precursor poly(2,5-dimethoxy-1,4 phenylene vinylene) (prec-DMePPV)

  14. Precursor films in wetting phenomena

    International Nuclear Information System (INIS)

    The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in the last decade similar films have been reported to occur in solid-on-solid systems. While the situations in which the thickness of such films is of mesoscopic size are fairly well understood, an intriguing and yet to be fully understood aspect is the spreading of microscopic, i.e. molecularly thin, films. Here we review the available experimental observations of such films in various liquid-on-solid and solid-on-solid systems, as well as the corresponding theoretical models and studies aimed at understanding their formation and spreading dynamics. Recent developments and perspectives for future research are discussed. (topical review)

  15. Precursor films in wetting phenomena.

    Science.gov (United States)

    Popescu, M N; Oshanin, G; Dietrich, S; Cazabat, A-M

    2012-06-20

    The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in the last decade similar films have been reported to occur in solid-on-solid systems. While the situations in which the thickness of such films is of mesoscopic size are fairly well understood, an intriguing and yet to be fully understood aspect is the spreading of microscopic, i.e. molecularly thin, films. Here we review the available experimental observations of such films in various liquid-on-solid and solid-on-solid systems, as well as the corresponding theoretical models and studies aimed at understanding their formation and spreading dynamics. Recent developments and perspectives for future research are discussed. PMID:22627067

  16. Cluster headache

    Science.gov (United States)

    Doctors do not know exactly what causes cluster headaches. They seem to be related to the body's sudden release of histamine (chemical in the body released during an allergic response) or serotonin (chemical made by nerve cells). A problem in a small area at ...

  17. Interactive Effects of Seawater Acidification and Elevated Temperature on the Transcriptome and Biomineralization in the Pearl Oyster Pinctada fucata.

    Science.gov (United States)

    Li, Shiguo; Huang, Jingliang; Liu, Chuang; Liu, Yangjia; Zheng, Guilan; Xie, Liping; Zhang, Rongqing

    2016-02-01

    Interactive effects of ocean acidification and ocean warming on marine calcifiers vary among species, but little is known about the underlying mechanisms. The present study investigated the combined effects of seawater acidification and elevated temperature (ambient condition: pH 8.1 × 23 °C, stress conditions: pH 7.8 × 23 °C, pH 8.1 × 28 °C, and pH 7.8 × 28 °C, exposure time: two months) on the transcriptome and biomineralization of the pearl oyster Pinctada fucata, which is an important marine calcifier. Transcriptome analyses indicated that P. fucata implemented a compensatory acid-base mechanism, metabolic depression and positive physiological responses to mitigate the effects of seawater acidification alone. These responses were energy-expensive processes, leading to decreases in the net calcification rate, shell surface calcium and carbon content, and changes in the shell ultrastructure. Elevated temperature (28 °C) within the thermal window of P. fucata did not induce significant enrichment of the sequenced genes and conversely facilitated calcification, which was detected to alleviate the negative effects of seawater acidification on biomineralization and the shell ultrastructure. Overall, this study will help elucidate the mechanisms by which pearl oysters respond to changing seawater conditions and predict the effects of global climate change on pearl aquaculture. PMID:26727167

  18. Organic compounds in the extrapalial fluid and haemolymph of Anodonta cygnea (L.) with emphasis on the seasonal biomineralization process.

    Science.gov (United States)

    Moura, G; Vilarinho, L; Santos, A C; Machado, J

    2000-03-01

    Bivalve mollusks, such as the freshwater mussel Anodonta cygnea, show seasonal changes in calcification. This cycle of calcification must either be a cause or a consequence for seasonal fluctuations in the organic composition of the animal's fluids, haemolymph and extrapallial fluid, the liquid media for biomineralization. We monitored the fluids of A. cygnea, throughout a 1-year cycle, for the presence of organic constituents, known to be important for biomineralization, such as proteins, glycosaminoglycans (GAGs) and hexosamines. Proteins were subjected to further study, namely through the total amino acid determination and fraction separation by agarose gel electrophoresis. GAG levels were fairly constant throughout the year, with a maximum concentration in July and a minimum in January, a feature also detected for glucosamine, although with higher fluctuations. Proteins showed highly increased concentrations during June and July, both in total amounts and individual fractions. All fractions showed similar trends throughout the year, with lowest general levels in October, the starting month of a period when some fractions were not detectable at all. All fractions ended this low period in May, when a sometimes-important increase could be detected. As to the total amino acid composition of the fluids, the general trend followed that of proteins, except for ornithine (Orn), a non-proteic amino acid. The overall fluctuations detected in the biological fluids of A. cygnea suggest that the main variation related to the calcification cycle must be quantitative, since no different compounds appear in specific periods, to achieve also specific results.

  19. Proteomic and profile analysis of the proteins laced with aragonite and vaterite in the freshwater mussel Hyriopsis cumingii shell biominerals.

    Science.gov (United States)

    Berland, Sophie; Ma, Yufei; Marie, Arul; Andrieu, Jean-Pierre; Bedouet, Laurent; Feng, Qingling

    2013-10-01

    Hyriopsis cumingii (Lea, Unionidae), a freshwater bivalve species widely distributed in China and commercially exploited for freshwater pearl production, was chosen as the reference model to investigate the protein signature in the organic scaffold matching calcium carbonate crystallization mode. This study takes advantage of different calcium carbonate habits production by the organism: aragonite in shell and pearl and vaterite in alternative pearl formation. Amino acid global composition and proteomics analysis have been undertaken to study the amino acid imbalance with respect to biominerals and microstructures. Forty peptides sequences were obtained by proteomics, of which ten are shared by all the different samples, nine are laced with aragonite; another nine with vaterite and twelve are related to pearls. Bioinformatics analysis allowed the peptides to be matched to the deduced protein sequences from EST databases and allowed functional assignment (e.g. scaffolding, strain strength, chitin binding or carbonic anhydrase function) to the proteins found in the different materials. Such panel of motifs tailored in vaterite and aragonite habits produced in a freshwater mollusk gives food for thought about organic control of the biomineralization processes.

  20. Single-cell genomics reveals potential for magnetite and greigite biomineralization in an uncultivated multicellular magnetotactic prokaryote.

    Science.gov (United States)

    Kolinko, Sebastian; Richter, Michael; Glöckner, Frank-Oliver; Brachmann, Andreas; Schüler, Dirk

    2014-10-01

    For magnetic orientation, magnetotactic bacteria biosynthesize magnetosomes, which consist of membrane-enveloped magnetic nanocrystals of either magnetite (Fe3 O4 ) or greigite (Fe3 S4 ). While magnetite formation is increasingly well understood, much less is known about the genetic control of greigite biomineralization. Recently, two related yet distinct sets of magnetosome genes were discovered in a cultivated magnetotactic deltaproteobacterium capable of synthesizing either magnetite or greigite, or both minerals. This led to the conclusion that greigite and magnetite magnetosomes are synthesized by separate biomineralization pathways. Although magnetosomes of both mineral types co-occurred in uncultured multicellular magnetotactic prokaryotes (MMPs), so far only one type of magnetosome genes could be identified in the available genome data. The MMP Candidatus Magnetomorum strain HK-1 from coastal tidal sand flats of the North Sea (Germany) was analysed by a targeted single-cell approach. The draft genome assembly resulted in a size of 14.3 Mb and an estimated completeness of 95%. In addition to genomic features consistent with a sulfate-reducing lifestyle, we identified numerous genes putatively involved in magnetosome biosynthesis. Remarkably, most mam orthologues were present in two paralogous copies with highest similarity to either magnetite or greigite type magnetosome genes, supporting the ability to synthesize magnetite and greigite magnetosomes. PMID:25079475

  1. Cluster chemistry in the Noughties: new developments and their relationship to nanoparticles.

    Science.gov (United States)

    Hogarth, Graeme; Kabir, Shariff E; Nordlander, Ebbe

    2010-07-21

    Over the past decade, the chemistry of low-valent transition metal clusters has again come to the fore, primarily as a result of the development of nanochemistry and the realization that large clusters are on the cusp of the nano-domain. This perspective focuses on these recent developments in low-valent transition metal cluster chemistry, specifically looking at cluster-nanoparticles, the use of small and medium sized clusters as nanoparticle precursors, the development of clusters as homogeneous catalysts and hydrogen uptake and storage systems, together with fundamental discoveries relating to novel transformations that can take place within the cluster framework.

  2. Effects of Reductive Biomineralization of Ferric Hydroxides on Sustained Microbial Metabolism and Contaminant Sequestration

    Science.gov (United States)

    Hansel, C. M.; Benner, S. G.; Nico, P. S.; Fendorf, S.

    2002-12-01

    , introduction of uranyl during dissimilatory iron reduction within the columns does not result in uranyl reduction, even though uranyl is the preferred (energetically) electron acceptor. Instead, the sequestration of uranyl is strongly correlated with regions of magnetite accumulation. Therefore, understanding the factors influencing Fe biomineralization pathways not only lends insight into the mechanisms of mineral formation but also provides a framework for further biogeochemical evolution and assists in predicting contaminant behavior within natural systems.

  3. Preparation of precursor for stainless steel foam

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiang-yang; LI Shan-ni; LI Jie; LIU Ye-xiang

    2008-01-01

    The effects of polyurethane sponge pretreatment and slurry compositions on the slurry loading in precursor were discussed, and the,performances of stainless steel foams prepared from precursors with different slurry loadings and different particle sizes of the stainless steel powder were also investigated. The experimental results show that the pretreatment of sponge with alkaline solution is effective to reduce the jam of cells in precursor and ensure the slurry to uniformly distribute in sponge, and it is also an effective method for increasing the slurry loading in precursor; the mass fraction of additive A and solid content in slurry greatly affect the slurry loading in precursor, when they are kept in 9%-13% and 52%-75%, respectively, the stainless steel foam may hold excellent 3D open-cell network structure and uniform muscles; the particle size of the stainless steel powder and the slurry loading in precursor have great effects on the bending strength, apparent density and open porosity of stainless steel foam; when the stainless steel powder with particle size of 44 tan and slurry loading of 0.5 g/cm3 in precursor are used, a stainless steel foam can be obtained, which has open porosity of 81.2%, bending strength of about 51.76 MPa and apparent density of about 1.0 g/cm3.

  4. Regional Innovation Clusters

    Data.gov (United States)

    Small Business Administration — The Regional Innovation Clusters serve a diverse group of sectors and geographies. Three of the initial pilot clusters, termed Advanced Defense Technology clusters,...

  5. When protein-based biomineralization meets hydrothermal synthesis: the nanostructures of the as-prepared materials are independent of the protein types.

    Science.gov (United States)

    Wang, Liqiang; Li, Xiangzhi; Jiang, Xingxing; Chen, Wansong; Hu, Lanshuang; Walle, Maru Dessie; Deng, Liu; Yang, Minghui; Liu, You-Nian; Kirin, Srećko I

    2015-12-14

    Proteins were proved to be type-independent templates for the biomineralization of iron ions into hematite mesocrystals with tunable structures and morphologies under hydrothemal conditions. Our finding could pave the way for the synthesis of mesocrystals with controlled stuctures and morphologies using templates of low-cost proteins.

  6. Synthesis and structures of metal chalcogenide precursors

    Science.gov (United States)

    Hepp, Aloysius F.; Duraj, Stan A.; Eckles, William E.; Andras, Maria T.

    1990-01-01

    The reactivity of early transition metal sandwich complexes with sulfur-rich molecules such as dithiocarboxylic acids was studied. Researchers recently initiated work on precursors to CuInSe2 and related chalcopyrite semiconductors. Th every high radiation tolerance and the high absorption coefficient of CuInSe2 makes this material extremely attractive for lightweight space solar cells. Their general approach in early transition metal chemistry, the reaction of low-valent metal complexes or metal powders with sulfur and selenium rich compounds, was extended to the synthesis of chalcopyrite precursors. Here, the researchers describe synthesis, structures, and and routes to single molecule precursors to metal chalcogenides.

  7. Atomic Layer Deposition from Dissolved Precursors.

    Science.gov (United States)

    Wu, Yanlin; Döhler, Dirk; Barr, Maïssa; Oks, Elina; Wolf, Marc; Santinacci, Lionel; Bachmann, Julien

    2015-10-14

    We establish a novel thin film deposition technique by transferring the principles of atomic layer deposition (ALD) known with gaseous precursors toward precursors dissolved in a liquid. An established ALD reaction behaves similarly when performed from solutions. "Solution ALD" (sALD) can coat deep pores in a conformal manner. sALD offers novel opportunities by overcoming the need for volatile and thermally robust precursors. We establish a MgO sALD procedure based on the hydrolysis of a Grignard reagent.

  8. Cluster forcing

    DEFF Research Database (Denmark)

    Christensen, Thomas Budde

    The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands......, Portugal and New Zealand have adopted the concept. Public sector interventions that aim to support cluster development in industries most often focus upon economic policy goals such as enhanced employment and improved productivity, but rarely emphasise broader societal policy goals relating to e...... a difference in terms of enhancing regional development but the paper also concludes that the interventions tend to follow the development path of the established industry and thus tend to neglect long term sustainable development issues while failing to escape the traditional confines of regional industrial...

  9. Clustering experiments

    CERN Document Server

    Wang, Zhengwei; Tan, Ken; Di, Zengru; Roehner, Bertrand M

    2011-01-01

    It is well known that bees cluster together in cold weather, in the process of swarming (when the ``old'' queen leaves with part of the colony) or absconding (when the queen leaves with all the colony) and in defense against intruders such as wasps or hornets. In this paper we describe a fairly different clustering process which occurs at any temperature and independently of any special stimulus or circumstance. As a matter of fact, this process is about four times faster at 28 degree Celsius than at 15 degrees. Because of its simplicity and low level of ``noise'' we think that this phenomenon can provide a means for exploring the strength of inter-individual attraction between bees or other living organisms. For instance, and at first sight fairly surprisingly, our observations showed that this attraction does also exist between bees belonging to different colonies. As this study is aimed at providing a comparative perspective, we also describe a similar clustering experiment for red fire ants.

  10. Identification and structural analysis of a novel snoRNA gene cluster from Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A Z2 snoRNA gene cluster,consisting of four antisense snoRNA genes, was identified from Arabidopsis thaliana. The sequence and structural analysis showed that the Z2 snoRNA gene cluster might be transcribed as a polycistronic precursor from an upstream promoter, and the intergenic spacers of the gene cluster encode the 'hairpin' structures similar to the processing recognition signals of yeast Saccharomyces cerevisiae polycistronic snoRNA precursor. The results also revealed that plant snoRNA gene with multiple copies is a characteristic in common, and provides a good system for further revealing the transcription and expression mechanism of plant snoRNA gene cluster.

  11. Spectromicroscopy of self-assembled protein clusters

    Energy Technology Data Exchange (ETDEWEB)

    Schonschek, O.; Hormes, J.; Herzog, V. [Univ. of Bonn (Germany)

    1997-04-01

    The aim of this project is to use synchrotron radiation as a tool to study biomedical questions concerned with the thyroid glands. The biological background is outlined in a recent paper. In short, Thyroglobulin (TG), the precursor protein of the hormone thyroxine, forms large (20 - 500 microns in diameter) clusters in the extracellular lumen of thyrocytes. The process of the cluster formation is still not well understood but is thought to be a main storage mechanism of TG and therefore thyroxine inside the thyroid glands. For human thyroids, the interconnections of the proteins inside the clusters are mainly disulfide bondings. Normally, sulfur bridges are catalyzed by an enzyme called Protein Disulfide Bridge Isomerase (PDI). While this enzyme is supposed to be not present in any extracellular space, the cluster formation of TG takes place in the lumen between the thyrocytes. A possible explanation is the autocatalysis of TG.

  12. El Niño impact on mollusk biomineralization-implications for trace element proxy reconstructions and the paleo-archeological record.

    Science.gov (United States)

    Pérez-Huerta, Alberto; Etayo-Cadavid, Miguel F; Andrus, C Fred T; Jeffries, Teresa E; Watkins, Clifton; Street, Shane C; Sandweiss, Daniel H

    2013-01-01

    Marine macroinvertebrates are ideal sentinel organisms to monitor rapid environmental changes associated with climatic phenomena. These organisms build up protective exoskeletons incrementally by biologically-controlled mineralization, which is deeply rooted in long-term evolutionary processes. Recent studies relating potential rapid environmental fluctuations to climate change, such as ocean acidification, suggest modifications on carbonate biominerals of marine invertebrates. However, the influence of known, and recurrent, climatic events on these biological processes during active mineralization is still insufficiently understood. Analysis of Peruvian cockles from the 1982-83 large magnitude El Niño event shows significant alterations of the chemico-structure of carbonate biominerals. Here, we show that bivalves modify the main biomineralization mechanism during the event to continue shell secretion. As a result, magnesium content increases to stabilize amorphous calcium carbonate (ACC), inducing a rise in Mg/Ca unrelated to the associated increase in sea-surface temperature. Analysis of variations in Sr/Ca also suggests that this proxy should not be used in these bivalves to detect the temperature anomaly, while Ba/Ca peaks are recorded in shells in response to an increase in productivity, or dissolved barium in seawater, after the event. Presented data contribute to a better understanding of the effects of abrupt climate change on shell biomineralization, while also offering an alternative view of bivalve elemental proxy reconstructions. Furthermore, biomineralization changes in mollusk shells can be used as a novel potential proxy to provide a more nuanced historical record of El Niño and similar rapid environmental change events.

  13. Precursor Parameter Identification for IGBT Prognostics

    Data.gov (United States)

    National Aeronautics and Space Administration — Precursor parameters have been identified to enable development of a prognostic approach for insulated gate bipolar transistors (IGBT). The IGBT were subjected to...

  14. Profiling Identifies Precursor Suspects: Notch Family Again!

    OpenAIRE

    Breunig, Joshua J.; Rakic, Pasko

    2010-01-01

    Newborn neurons in the adult dentate gyrus pass through several distinct precursor and progenitor classes prior to differentiation. In this issue of Cell Stem Cell, Lugert et al. (2010) characterized their strikingly different proliferative behaviors after neurogenic stimuli or aging.

  15. Progress in molecular precursors for electronic materials

    Energy Technology Data Exchange (ETDEWEB)

    Buhro, W.E. [Washington Univ., St. Louis, MO (United States)

    1996-09-01

    Molecular-precursor chemistry provides an essential underpinning to all electronic-materials technologies, including photovoltaics and related areas of direct interest to the DOE. Materials synthesis and processing is a rapidly developing field in which advances in molecular precursors are playing a major role. This article surveys selected recent research examples that define the exciting current directions in molecular-precursor science. These directions include growth of increasingly complex structures and stoichiometries, surface-selective growth, kinetic growth of metastable materials, growth of size-controlled quantum dots and quantum-dot arrays, and growth at progressively lower temperatures. Continued progress in molecular-precursor chemistry will afford precise control over the crystal structures, nanostructures, and microstructures of electronic materials.

  16. Rational design of precursors for oxide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Apblett, A.W.; Georgieva, G. [Tulane Univ., New Orleans, LA (United States)

    1993-12-31

    The use of molecular species as precursors for inorganic materials has received considerable attention in recent years. As a result, metal-organic precursors are becoming increasingly sophisticated as particular decomposition mechanisms and specific stoichiometry are integrated into their design. The authors have pursued both of these design aspects for the development of low-temperature precursors for mono- and bi-metallic oxide materials. Thus, a great variety of metal complexes with 2- and 3-oximinocarboxylic acids, acyloin oximes, 2,4-diols, and diacetone alcohol have been prepared and their thermal behavior investigated. The results of this investigation and their application to the preparation of a variety of metal, oxide ceramics, will be discussed. Particular attention will be paid to precursors for alumina, titania, zirconia, perovskite-phase ferroelectric materials, and ferrites.

  17. Strontium/Calcium and Magnesium/Calcium Ratios: Geochemical Constraints on Biomineralization in a Deep-Sea Coral

    Science.gov (United States)

    Gagnon, A. C.; Adkins, J. F.; Fernandez, D. P.; Robinson, L. F.

    2006-12-01

    Mg/Ca and Sr/Ca are both used as proxies for temperature in scleractinian coral skeletons. These tracers can also be influenced by biomineralization (vital effects) complicating proxy interpretation. We measure Sr/Ca and Mg/Ca across skeletal features in Desmophyllum dianthus, a deep-sea scleractinian coral. Since the growth environment of the deep-sea is typically invariant during the ~100 year lifetime of an individual coral, trace metal variability is attributed to biomineralization rather than environmental influences. By combining micromilling and isotope dilution- ICP-MS we determine detailed co-located Sr/Ca and Mg/Ca ratios in two individuals from the same oceanographic setting. Sr/Ca ratios vary by a relatively small amount across skeletal features, 98% loc) and has a mean value of 10.6+/-0.2. This value agrees with the inorganic aragonite temperature relationship at the temperature of coral growth for precipitation from seawater. Since Sr/Ca in the central band exhibits little variance, sampling localized to this region should yield the most precise test of a Sr/Ca paleothermometer. Unlike Sr/Ca, Mg/Ca varies dramatically across the coral skeleton. Coincident with the optically dense central band, Mg/Ca was greater than 3 mmol/mol, nearly twice that of the surrounding skeleton. The relative Mg/Ca ratios of three other D. dianthus individuals collected from separate oceanographic locations also nearly double within the central band. Outside the central band, Mg/Ca increases with decreasing Sr/Ca. Rayleigh fractionation from a closed pool may explain this behavior. Within the central band, however, Mg/Ca increases nearly twofold while Sr/Ca varies little from the surrounding skeleton. This observation suggests that a process of greater magnitude than Rayleigh fractionation influences Mg in this region. In order to take into account both metal/Ca ratios, any model explaining high Mg in the center of calcification must decouple Mg and Sr. Sr/Ca and Mg

  18. Molecular Mixed-Metal Manganese Oxido Cubanes as Precursors to Heterogeneous Oxygen Evolution Catalysts

    OpenAIRE

    Suseno, Sandy; McCrory, Charles C. L.; Tran, Rosalie; Gul, Sheraz; Yano, Junko; Agapie, Theodor

    2015-01-01

    Well-defined mixed-metal [CoMn_3O_4] and [NiMn_3O_4] cubane complexes were synthesized and used as precursors for heterogeneous oxygen evolution reaction (OER) electrocatalysts. The discrete clusters were dropcasted onto glassy carbon (GC) and indium tin oxide (ITO) electrodes, and the OER activities of the resulting films were evaluated. The catalytic surfaces were analyzed by various techniques to gain insight into the structure-function relationships of the electrocatalysts’ heterometallic...

  19. The interactions of strontium and technetium with Fe(II) bearing biominerals: Implications for bioremediation of radioactively contaminated land

    International Nuclear Information System (INIS)

    Highlights: • Bioreduction leads to Fe(II) bearing mineral phases at neutral and alkaline pH. • Tc-99 is reductively precipitated as hydrous TcO2 at neutral and alkaline pH. • Sr-90 sorbs to the biomineral phases across the pH range of study. • Stable Sr is scavenged to solids at high pH. - Abstract: At nuclear contaminated sites, microbially-mediated Fe(III) reduction under alkaline conditions opens up the potential for co-treatment of the groundwater contaminants 99Tc, though reduction to less mobile Tc(IV) phases, and 90Sr, through increased sorption and/or precipitation promoted at higher pH. In the experiments described here, microbial enrichment cultures derived from representative Sellafield sediments were used to probe the effect of microbially-mediated Fe(III) reduction on the mobility of 99Tc and Sr (as stable Sr2+ at elevated concentrations and 90Sr2+ at ultra-trace concentrations) under both neutral and alkaline conditions. The reduction of Fe(III) in enrichment culture experiments at an initial pH of 7 or 9 resulted in the precipitation of an Fe(II) bearing biomineral comprised of siderite and vivianite. Results showed that TcO4- added at 1.6 × 10−6 M was removed (>80%) from solution concurrent with Fe(III) reduction at both pH 7 and pH 9. Furthermore, X-ray absorption spectroscopy of the reduced biominerals confirmed reduction of Tc(VII) to Tc(IV). To understand Sr behaviour in these systems, Sr2+ was added to enrichment cultures at ultra-trace concentrations (2.2 × 10−10 M (as 90Sr2+)) and at higher concentrations (1.15 × 10−3 M (as stable Sr2+)). In ultra-trace experiments at pH 7, microbially active systems showed enhanced removal of 90Sr compared to the sterile control. This was likely due to sorption of 90Sr2+ to the Fe(II)-bearing biominerals that formed in situ. By contrast, at pH 9, the sterile control showed comparable removal of 90Sr to the microbially active experiment even though the Fe-minerals formed were of very

  20. Effects of collagen types II and X on the kinetics of crystallization of calcium phosphate in biomineralization

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effects of the components of cartilages matrix on the process of endochondral ossification and the kinetics of crystal growth of calcium phosphate have been studied in the presence of type II or X collagen. During the experiments, type I collagen was added as the seed material. FT-IR analysis shows that calcium phosphate crystallized on the surface of type I collagen was mainly hydroxyapatite. Both type II and X collagens could reduce the growth rate of calcium phosphate crystals, and the effect of type X collagen is more obvious. The reaction was in the fourth order in the presence of type II collagen. The results showed that type II or X collagen had the ability to make Ca2+ accumulate in the process of endochondral ossification, but has little effect on crystal growth and the product of biomineralization.

  1. Investigating the effect of electro-active ion concentration on spectral induced polarization signatures arising from biomineralization pathways

    Science.gov (United States)

    Ntarlagiannis, D.; Slater, L. D.; Williams, K. H.; Hubbard, S. S.; Wu, Y.

    2010-12-01

    Spectral induced polarization (SIP) is a proven geophysical method for detecting biomineral formation with promising applications for monitoring biogeochemical products during microbial induced sequestration of heavy metals and radionuclides in soils. SIP has been used to monitor the evolution of bioremediation-induced end-products at the uranium-contaminated U.S. Department of Energy Rifle Integrated Field Research Challenge site in Colorado. Although a significant SIP response was detected, the quantitative interpretation is non-trivial as the polarization of metallic minerals depends both on the mineral surface properties and the electrolyte chemistry. In previous experiments SIP mechanisms were studied under complex environments and individual source mechanisms could not be evaluated. Here we examine the role of electrolyte chemistry by comparing the effect of redox active / inactive ions on metallic polarization. In these abiotic experiments magnetite was used as a proxy biomineral and dispersed within columns packed with sand. Parallel columns were saturated with solutions of different concentrations of active (Fe2+) and inactive (Ca2+) ions (0.01mM-10mM) and SIP measurements made (0.1-1000 Hz). Experimental results show small, but detectable, differences in the effect of active ion and inactive ion concentration on the SIP response. To better characterize the effect of electro-active ions on metallic minerals we used a Cole - Cole type relaxation model, to describe the SIP responses. In order to better resolve the relaxation model parameters, we followed a two-step approach whereby we started with a Bayesian based inversion to resolve for the initial parameter estimates, and subsequently used these estimates as a starting model for a deterministic solution. Our results suggest that changes in the active ion concentration, in the presence of magnetite, alone are unlikely to fully explain recent SIP monitoring data from the Rifle site.

  2. Biomineralization of the Surface of PLGA-(ASP-PEG) Modified with the K_(16) and RGD-containing Peptide

    Institute of Scientific and Technical Information of China (English)

    HAO Jie; HU Zhenming; ZHENG Qixin; GUO Xiaodong; SONG Yulin

    2009-01-01

    K_(16) and RGD-containing peptide was used to modify the surface of three-dimensional PLGA-(ASP-PEG)matrix,then the modified PLGA-(ASP-PEG)was incubated in modified simulated body fluid(SBF).The biomineralization of the modified PLGA-(ASP-PEG)was explored,and the peptide was synthesized with solid phase synthesis technology and linked cova-lently to PLGA-(ASP-PEG)through cross-linker(Sulfo-LC-SPDP),which was characterized with XPS.The modified PLGA-(ASP-PEG)(Experiment group,EG)and PLGA-(ASP-PEG)(Control group,CG)were all incubated into SBF for 10 d,and the growth of hydroxyapatite(HA)nanocrys-tals was confirmed with XRD,EDS and SEM.HPLC shows that peptide purity is 94.13%,while MS analysis shows that molecular value of peptide is 2741.26.Binding energy of the sulphur in EG was 164 eV is detected by XPS,and the ratio of carbon and sulphur is 99.746:0.1014.SEM analysis demonstrates the better growth of bonelike HA nanocrystals in EG than that in CG.The component of mineral in EG consisted mainly of hydroxyapatite containing low crystalline nanocrystals,and the Ca/P ratio is about 1.60,which is similar to that of natural bone,while the Ca/P ratio in CG is 1.52. PLGA-(ASP-PEG)modified with peptide provided enough functional groups for biomineralization, and possessed the bonelike structure.

  3. Globular Cluster Formation in the Virgo Cluster

    CERN Document Server

    Moran, C Corbett; Lake, G

    2014-01-01

    Metal poor globular clusters (MPGCs) are a unique probe of the early universe, in particular the reionization era. Systems of globular clusters in galaxy clusters are particularly interesting as it is in the progenitors of galaxy clusters that the earliest reionizing sources first formed. Although the exact physical origin of globular clusters is still debated, it is generally admitted that globular clusters form in early, rare dark matter peaks (Moore et al. 2006; Boley et al. 2009). We provide a fully numerical analysis of the Virgo cluster globular cluster system by identifying the present day globular cluster system with exactly such early, rare dark matter peaks. A popular hypothesis is that that the observed truncation of blue metal poor globular cluster formation is due to reionization (Spitler et al. 2012; Boley et al. 2009; Brodie & Strader 2006); adopting this view, constraining the formation epoch of MPGCs provides a complementary constraint on the epoch of reionization. By analyzing both the l...

  4. Tufa in Northern England: depositional facies, carbonate mineral fabrics, and role of biomineralization

    Science.gov (United States)

    Manzo, E.; Mawson, M.; Perri, E.; Tucker, M. E.

    2009-04-01

    magnifications, all crystal forms seem be made of sub-spherical to rod-like nano-crystals, ranging in size from 100 to 300 nm. Other than cyanobacteria, calcified organic components like diatoms, plant tissues, and extra-cellular polymeric substances (EPS) are mineralized with the same crystal nano-elements. Conclusions Tufa formation seems strongly influenced by the inclination of the slope, water energy, the biota, including the biofilm, and the organic matter substrate (mainly EPS); super-saturation of water with respect to calcite is a pre-requisite for precipitation. The inclination of the slope determines the water energy and so the degassing of CO2 which leads to precipitation of carbonate. Photosynthesis by macrophytes, microphytes and cyanobacteria could also contribute to CO2 degassing. EPS degradation processes, particularly those involving heterotrophic micro-organisms which can induce an increase in alkalinity, could be a further mechanism of biomineralization in these tufa carbonates.

  5. Nonlinear magnetohydrodynamics of edge localized mode precursors

    International Nuclear Information System (INIS)

    A possible origin of edge-localized-mode (ELM) precursors based on nonlinear ideal peeling-ballooning mode is reported. Via nonlinear variational principle, a nonlinear evolution equation of the radial displacement is derived and solved, analytically. Besides an explosive growth in the initial nonlinear phase, it is found that the local displacement evolves into an oscillating state in the developed nonlinear phase. The nonlinear frequency of the ELM precursors scales as ωpre∼x1/3ξ^ψ,in2/3n, with x position in radial direction, ξ^ψ,in strength of initial perturbation, and n toroidal mode number

  6. Cluster Decline and Resilience

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark, 1963...... in new resources to the cluster but being quick to withdraw in times of crisis....

  7. The Skeleton Forming Proteome of an Early Branching Metazoan: A Molecular Survey of the Biomineralization Components Employed by the Coralline Sponge Vaceletia Sp.

    Directory of Open Access Journals (Sweden)

    Juliane Germer

    Full Text Available The ability to construct a mineralized skeleton was a major innovation for the Metazoa during their evolution in the late Precambrian/early Cambrian. Porifera (sponges hold an informative position for efforts aimed at unraveling the origins of this ability because they are widely regarded to be the earliest branching metazoans, and are among the first multi-cellular animals to display the ability to biomineralize in the fossil record. Very few biomineralization associated proteins have been identified in sponges so far, with no transcriptome or proteome scale surveys yet available. In order to understand what genetic repertoire may have been present in the last common ancestor of the Metazoa (LCAM, and that may have contributed to the evolution of the ability to biocalcify, we have studied the skeletal proteome of the coralline demosponge Vaceletia sp. and compare this to other metazoan biomineralizing proteomes. We bring some spatial resolution to this analysis by dividing Vaceletia's aragonitic calcium carbonate skeleton into "head" and "stalk" regions. With our approach we were able to identify 40 proteins from both the head and stalk regions, with many of these sharing some similarity to previously identified gene products from other organisms. Among these proteins are known biomineralization compounds, such as carbonic anhydrase, spherulin, extracellular matrix proteins and very acidic proteins. This report provides the first proteome scale analysis of a calcified poriferan skeletal proteome, and its composition clearly demonstrates that the LCAM contributed several key enzymes and matrix proteins to its descendants that supported the metazoan ability to biocalcify. However, lineage specific evolution is also likely to have contributed significantly to the ability of disparate metazoan lineages to biocalcify.

  8. Interactive effects of elevated temperature and CO2 levels on energy metabolism and biomineralization of marine bivalves Crassostrea virginica and Mercenaria mercenaria.

    Science.gov (United States)

    Ivanina, Anna V; Dickinson, Gary H; Matoo, Omera B; Bagwe, Rita; Dickinson, Ashley; Beniash, Elia; Sokolova, Inna M

    2013-09-01

    The continuing increase of carbon dioxide (CO2) levels in the atmosphere leads to increases in global temperatures and partial pressure of CO2 (PCO2) in surface waters, causing ocean acidification. These changes are especially pronounced in shallow coastal and estuarine waters and are expected to significantly affect marine calcifiers including bivalves that are ecosystem engineers in estuarine and coastal communities. To elucidate potential effects of higher temperatures and PCO2 on physiology and biomineralization of marine bivalves, we exposed two bivalve species, the eastern oysters Crassostrea virginica and the hard clams Mercenaria mercenaria to different combinations of PCO2 (~400 and 800μatm) and temperatures (22 and 27°C) for 15weeks. Survival, bioenergetic traits (tissue levels of lipids, glycogen, glucose and high energy phosphates) and biomineralization parameters (mechanical properties of the shells and activity of carbonic anhydrase, CA) were determined in clams and oysters under different temperature and PCO2 regimes. Our analysis showed major inter-species differences in shell mechanical traits and bioenergetics parameters. Elevated temperature led to the depletion of tissue energy reserves indicating energy deficiency in both species and resulted in higher mortality in oysters. Interestingly, while elevated PCO2 had a small effect on the physiology and metabolism of both species, it improved survival in oysters. At the same time, a combination of high temperature and elevated PCO2 lead to a significant decrease in shell hardness in both species, suggesting major changes in their biomineralization processes. Overall, these studies show that global climate change and ocean acidification might have complex interactive effects on physiology, metabolism and biomineralization in coastal and estuarine marine bivalves.

  9. Partitional clustering algorithms

    CERN Document Server

    2015-01-01

    This book summarizes the state-of-the-art in partitional clustering. Clustering, the unsupervised classification of patterns into groups, is one of the most important tasks in exploratory data analysis. Primary goals of clustering include gaining insight into, classifying, and compressing data. Clustering has a long and rich history that spans a variety of scientific disciplines including anthropology, biology, medicine, psychology, statistics, mathematics, engineering, and computer science. As a result, numerous clustering algorithms have been proposed since the early 1950s. Among these algorithms, partitional (nonhierarchical) ones have found many applications, especially in engineering and computer science. This book provides coverage of consensus clustering, constrained clustering, large scale and/or high dimensional clustering, cluster validity, cluster visualization, and applications of clustering. Examines clustering as it applies to large and/or high-dimensional data sets commonly encountered in reali...

  10. Modernization typologies industrial clusters

    Directory of Open Access Journals (Sweden)

    Karapetian, Eduard

    2011-11-01

    Full Text Available Generalized theoretical approach to the criteria of industrial clusters. On this basis, a detailed typology of industrial cluster structures, which takes into account the peculiarities of the functioning of clusters in the domestic economy.

  11. Biomineralization of Pb(II) into Pb-hydroxyapatite induced by Bacillus cereus 12-2 isolated from Lead-Zinc mine tailings.

    Science.gov (United States)

    Chen, Zhi; Pan, Xiaohong; Chen, Hui; Guan, Xiong; Lin, Zhang

    2016-01-15

    The remediation of Pb(II) through biomineralization is rergarded as a promising technique as well as an interesting phenomenon for transforming heavy metals from mobile species into very stable minerals in the environment. Studies are well needed for in-depth understanding the mechanism of Pb(II) immobilized by bacteria. In the present study, we investigated the uptake and biomineralization of Pb(II) using Bacillus cereus 12-2 isolated from lead-zinc mine tailings. The maximum Pb(II) uptake capacity of B. cereus 12-2 was 340 mg/g at pH 3.0. Zeta potential analyses and selective passivation experiments demonstrated that electrostatic attraction was the main force driving the uptake of Pb(II), while the carboxyl, amide and phosphate functional groups of the bacteria provided the binding sites for immobilizing Pb(II). XRD and TEM investigation revealed that the Pb(II) loaded on bacteria could be stepwise transformed into rod-shaped Ca2.5Pb7.5(OH)2(PO4)6 nanocrystal. Combined with protein denaturalization experiments, we proposed that the biomineralization of Pb(II) possibly consisted of two steps: (1) Rapid biosorption of Pb(II) on B. cereus 12-2 through the synergy of electrostatic attraction, ionic exchange and chelating activity of functional groups; (2) enzyme-mediated mineral transformation from amorphous precipitate to rod-shaped crystalline minerals happening gradually inside the bacteria. PMID:26468754

  12. Preliminary studies of biominerals-coated spinel LiMn2 O4 as a cathode material on electrochemical performances for Li-ion rechargeable batteries

    Science.gov (United States)

    Vediappan, Kumaran; Lee, Chang Woo

    2010-05-01

    Lithium manganese oxide (LiMn2O4) is an inexpensive and pollution-free cathode material for Li-ion rechargeable batteries. In this study, spinel LiMn2O4 cathode material was coated with biomineral powders by the mechano-chemical method. In the course of the material synthesis, citric acid and acryl amide were added to serve as a complexing agent and a gelling agent, respectively, followed by a calcination process at 700 °C for 6 h in a high-purity argon atmosphere. The spinel LiMn2O4 and biominerals-coated spinel LiMn2O4 cathode materials were, from diverse viewpoints, characterized by x-ray diffraction, field emission-scanning electron microscopy, Fourier transform infrared spectroscopy and the electrochemical cycling method to understand the mechanism of improvements in electrochemical performances. We suggest that the biominerals-coated spinel LiMn2O4 is a good candidate as a low cost and environmentally friendly cathode material showing the enlarged capacity characteristic of Li-ion rechargeable batteries.

  13. Targeting bactoprenol-coupled cell envelope precursors.

    Science.gov (United States)

    Ulm, Hannah; Schneider, Tanja

    2016-09-01

    Targeting the bactoprenol-coupled cell wall precursor lipid II is a validated antibacterial strategy. In this review, selected prototype lipid II-binding antibiotics of different chemical classes are discussed. Although these compounds attack the same molecular target, they trigger nuanced and diverse cellular effects. Consequently, the mechanisms of antibacterial resistance and the likelihood of resistance development may vary substantially. PMID:27495122

  14. PRECURSORS OF EARTHQUAKES: VLF SIGNALSIONOSPHERE IONOSPHERE RELATION

    OpenAIRE

    Mustafa ULAS; ATA, Fikret; Hasan Hüseyin BALIK

    2013-01-01

    lot of people have died because of earthquakes every year. Therefore It is crucial to predict the time of the earthquakes reasonable time before it had happed. This paper presents recent information published in the literature about precursors of earthquakes. The relationships between earthquakes and ionosphere are targeted to guide new researches in order to study further to find novel prediction methods.

  15. Fluorescent Thiol-Derivatized Gold Clusters Embedded in Polymers

    Directory of Open Access Journals (Sweden)

    G. Carotenuto

    2013-01-01

    Full Text Available Owing to aurophilic interactions, linear and/or planar Au(I-thiolate molecules spontaneously aggregate, leading to molecular gold clusters passivated by a thiolate monolayer coating. Differently from the thiolate precursors, such cluster compounds show very intensive visible fluorescence characteristics that can be tuned by alloying the gold clusters with silver atoms or by conjugating the electronic structure of the metallic core with unsaturated electronic structures in the organic ligand through the sulphur atom. Here, the photoluminescence features of some examples of these systems are shortly described.

  16. Factorial PD-Clustering

    CERN Document Server

    Tortora, Cristina; Summa, Mireille Gettler

    2011-01-01

    Factorial clustering methods have been developed in recent years thanks to the improving of computational power. These methods perform a linear transformation of data and a clustering on transformed data optimizing a common criterion. Factorial PD-clustering is based on Probabilistic Distance clustering (PD-clustering). PD-clustering is an iterative, distribution free, probabilistic, clustering method. Factorial PD-clustering make a linear transformation of original variables into a reduced number of orthogonal ones using a common criterion with PD-Clustering. It is demonstrated that Tucker 3 decomposition allows to obtain this transformation. Factorial PD-clustering makes alternatively a Tucker 3 decomposition and a PD-clustering on transformed data until convergence. This method could significantly improve the algorithm performance and allows to work with large dataset, to improve the stability and the robustness of the method.

  17. Controllable synthesis of gold nanoparticles with ultrasmall size and high monodispersity via continuous supplement of precursor.

    Science.gov (United States)

    Li, Yuanyuan; Liu, Shoujie; Yao, Tao; Sun, Zhihu; Jiang, Zheng; Huang, Yuying; Cheng, Hao; Huang, Yuanyuan; Jiang, Yong; Xie, Zhi; Pan, Guoqiang; Yan, Wensheng; Wei, Shiqiang

    2012-10-14

    Synthesis of monodisperse small Au nanoparticles in a controllable manner is of great importance for fundamental science and technical applications. Here, we report a "precursor continuous-supply" strategy for controllable synthesis of 0.9-3.3 nm Au nanoparticles with a narrow size distribution of 0.1-0.2 nm, using a weak reductant to slow-down the reducing rate of AuClPPh(3) precursor in ethanol. Time-dependent X-ray absorption and UV-Vis absorption measurements revealed that owing to the joint use of AuClPPh(3) and ethanol, the remnant AuClPPh(3) was self-supplied and the precursor concentration was maintained at a level near to its equilibrium solubility (ca. 1.65 mmol L(-1)) in ethanol. Hence the nucleation duration was extended that focused the initial size distribution of the Au clusters. With reaction going on for 58 min, most of AuClPPh(3) with a nominal Au concentration of 17.86 mmol L(-1) was converted to ethanol-soluble Au clusters with a size of about 1.0 nm, resulting in a high-yield synthesis.

  18. Possibilistic Exponential Fuzzy Clustering

    Institute of Scientific and Technical Information of China (English)

    Kiatichai Treerattanapitak; Chuleerat Jaruskulchai

    2013-01-01

    Generally,abnormal points (noise and outliers) cause cluster analysis to produce low accuracy especially in fuzzy clustering.These data not only stay in clusters but also deviate the centroids from their true positions.Traditional fuzzy clustering like Fuzzy C-Means (FCM) always assigns data to all clusters which is not reasonable in some circumstances.By reformulating objective function in exponential equation,the algorithm aggressively selects data into the clusters.However noisy data and outliers cannot be properly handled by clustering process therefore they are forced to be included in a cluster because of a general probabilistic constraint that the sum of the membership degrees across all clusters is one.In order to improve this weakness,possibilistic approach relaxes this condition to improve membership assignment.Nevertheless,possibilistic clustering algorithms generally suffer from coincident clusters because their membership equations ignore the distance to other clusters.Although there are some possibilistic clustering approaches that do not generate coincident clusters,most of them require the right combination of multiple parameters for the algorithms to work.In this paper,we theoretically study Possibilistic Exponential Fuzzy Clustering (PXFCM) that integrates possibilistic approach with exponential fuzzy clustering.PXFCM has only one parameter and not only partitions the data but also filters noisy data or detects them as outliers.The comprehensive experiments show that PXFCM produces high accuracy in both clustering results and outlier detection without generating coincident problems.

  19. Metal Reduction and Iron Biomineralization by a Psychrotolerant Fe(III)-Reducing Bacterium, Shewanella sp. Strain PV-4

    Energy Technology Data Exchange (ETDEWEB)

    Roh, Yul; Gao, Haichun; Vali, Hojatollah; Kennedy, David W.; Yang, Zamin; Gao, Weimin; Dohnalkova, Alice; Stapleton, Raymond D.; Moon, Ji-Won; Phelps, T. J.; Fredrickson, Jim K.; Zhou, Jizhong

    2006-05-01

    A marine psychrotolerant, dissimilatory Fe(III)-reducing bacterium, Shewanella sp. strain PV-4, from the microbial mat at a hydrothermal vent of Loihi Seamount in the Pacific Ocean has been further characterized, with emphases on metal reduction and iron biomineralization. The strain is able to reduce metals such as Fe(III), Co(III), Cr(VI), Mn(IV), and U(VI) as electron acceptors while using lactate, formate, pyruvate, or hydrogen as an electron donor. Growth during iron reduction occurred over the pH range of 7.0 to 8.9, a sodium chloride range of 0.05 to 5%, and a temperature range of 0 to 37°C, with an optimum growth temperature of 18°C. Unlike mesophilic dissimilatory Fe(III)-reducing bacteria, which produce mostly superparamagnetic magnetite (<35 nm), this psychrotolerant bacterium produces well-formed single-domain magnetite (>35 nm) at temperatures from 18 to 37°C. The genome size of this strain is about 4.5 Mb. Strain PV-4 is sensitive to a variety of commonly used antibiotics except ampicillin and can acquire exogenous DNA (plasmid pCM157) through conjugation.

  20. Metal Reduction and Iron Biomineralization by a Psychrotolerant Fe(III)-Reducing Bacterium, Shewanella sp. Strain PV-4

    Energy Technology Data Exchange (ETDEWEB)

    Roh, Yul; Gao, Haichun; Vali, Hojatollah; Kennedy, David W.; Yang, Zamin; Gao, Weimin; Dohnalkova, Alice; Stapleton, Raymond D.; Moon, Ji-Won; Phelps, Tommy J.; Fredrickson, Jim K.; Zhou, Jizhong

    2006-09-01

    A marine psychrotolerant, dissimilatory Fe(III)-reducing bacterium, Shewanella sp. strain PV-4, from the microbial mat at a hydrothermal vent of Loihi Seamount in the Pacific Ocean has been further characterized, with emphases on metal reduction and iron biomineralization. The strain is able to reduce metals such as Fe(III), Co(III), Cr(VI), Mn(IV), and U(VI) as electron acceptors while using lactate, formate, pyruvate, or hydrogen as an electron donor. Growth during iron reduction occurred over the pH range of 7.0 to 8.9, a sodium chloride range of 0.05 to 5%, and a temperature range of 0 to 37 C, with an optimum growth temperature of 18 C. Unlike mesophilic dissimilatory Fe(III)-reducing bacteria, which produce mostly superparamagnetic magnetite (<35 nm), this psychrotolerant bacterium produces well-formed single-domain magnetite (>35 nm) at temperatures from 18 to 37 C. The genome size of this strain is about 4.5 Mb. Strain PV-4 is sensitive to a variety of commonly used antibiotics except ampicillin and can acquire exogenous DNA (plasmid pCM157) through conjugation.

  1. Biomineralization regulation by nano-sized features in silk fibroin proteins: synthesis of water-dispersible nano-hydroxyapatite.

    Science.gov (United States)

    Huang, Xiaowei; Liu, Xi; Liu, Shanshan; Zhang, Aili; Lu, Qiang; Kaplan, David L; Zhu, Hesun

    2014-11-01

    In the present study, silk fibroin (SF) was used as a template to prepare nano-hydroxyapatite (nano-HA) via a biomineralization process. We observed that the content of SF affected both the morphology and water dispersibility of nano-HA particles. Scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), zetasizer, and Fourier transform infrared spectroscopy (FTIR) were used to examine nano-HA particle features including the surface morphology, aggregation performance, and crystallization. Rod-like nano-HA particles with desired water dispersibility were achieved when the ratio of SF/HA (calculated) was above 7:3. SEM, TEM, and zeta potential results revealed that nano-HA particles were enclosed by the SF which formed a negative charge layer preventing the aggregation of HA nanoparticles in aqueous solution. Moreover, the nano-HA particles were able to re-disperse in water without precipitation for two weeks at room temperature, 60°C, and 90°C. Our work suggested a facile and effective approach of designing water-dispersible nano-HA particles which may have wide potential application in tissue engineering especially bone regeneration.

  2. Characterization of a Monoclonal Antibody Directed against Mytilus spp Larvae Reveals an Antigen Involved in Shell Biomineralization

    Science.gov (United States)

    Calvo-Iglesias, Juan; Pérez-Estévez, Daniel; Lorenzo-Abalde, Silvia; Sánchez-Correa, Beatriz; Quiroga, María Isabel; Fuentes, José M.; González-Fernández, África

    2016-01-01

    The M22.8 monoclonal antibody (mAb) developed against an antigen expressed at the mussel larval and postlarval stages of Mytilus galloprovincialis was studied on adult samples. Antigenic characterization by Western blot showed that the antigen MSP22.8 has a restricted distribution that includes mantle edge tissue, extrapallial fluid, extrapallial fluid hemocytes, and the shell organic matrix of adult samples. Other tissues such as central mantle, gonadal tissue, digestive gland, labial palps, foot, and byssal retractor muscle did not express the antigen. Immunohistochemistry assays identified MSP22.8 in cells located in the outer fold epithelium of the mantle edge up to the pallial line. Flow cytometry analysis showed that hemocytes from the extrapallial fluid also contain the antigen intracellularly. Furthermore, hemocytes from hemolymph have the ability to internalize the antigen when exposed to a cell-free extrapallial fluid solution. Our findings indicate that hemocytes could play an important role in the biomineralization process and, as a consequence, they have been included in a model of shell formation. This is the first report concerning a protein secreted by the mantle edge into the extrapallial space and how it becomes part of the shell matrix framework in M. galloprovincialis mussels. PMID:27008638

  3. Management of cluster headache

    DEFF Research Database (Denmark)

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-01-01

    and agitation. Patients may have up to eight attacks per day. Episodic cluster headache (ECH) occurs in clusters of weeks to months duration, whereas chronic cluster headache (CCH) attacks occur for more than 1 year without remissions. Management of cluster headache is divided into acute attack treatment...

  4. Structures of Mn clusters

    Indian Academy of Sciences (India)

    Tina M Briere; Marcel H F Sluiter; Vijay Kumar; Yoshiyuki Kawazoe

    2003-01-01

    The geometries of several Mn clusters in the size range Mn13–Mn23 are studied via the generalized gradient approximation to density functional theory. For the 13- and 19-atom clusters, the icosahedral structures are found to be most stable, while for the 15-atom cluster, the bcc structure is more favoured. The clusters show ferrimagnetic spin configurations.

  5. Electromagnetic Whistler Precursors at Supercritical Interplanetary Shocks

    Science.gov (United States)

    Wilson, L. B., III

    2012-01-01

    We present observations of electromagnetic precursor waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search coil magnetometer. The precursors propagate obliquely with respect to the local magnetic field, shock normal vector, solar wind velocity, and they are not phase standing structures. All are right-hand polarized with respect to the magnetic field (spacecraft frame), and all but one are right-hand polarized with respect to the shock normal vector in the normal incidence frame. Particle distributions show signatures of specularly reflected gyrating ions, which may be a source of free energy for the observed modes. In one event, we simultaneously observe perpendicular ion heating and parallel electron acceleration, consistent with wave heating/acceleration due to these waves.

  6. [Presentation of the Lunar Precursor Robotics Program

    Science.gov (United States)

    Lavoie, Anthony R.

    2008-01-01

    The Lunar Precursor Robotics Program (LPRP) is the host program for the Exploration Systems Mission Directorate's (ESMD) lunar robotic precursor missions to the Moon. The program includes two missions, the Lunar Reconnaissance Orbiter (LRO), and the Lunar CRater Observation and Sensing Satellite (LCROSS). Both missions will provide the required lunar information to support development and operations of those systems required for Human lunar return. LPRP is developing a lunar mapping plan, Called the Lunar Mapping and Modeling Project, to create the capability to archive and present all data from LRO, LCROSS, historical lunar missions, and international lunar missions for future mission planning and operations. LPRP is also developing its educational and public outreach activities for the Vision for Space Exploration's first missions. LPRP is working closely with the Science Mission Directorate as their lunar activities come into focus.

  7. Genetic characteristics of vancomycin resistance gene cluster in Enterococcus spp.

    Science.gov (United States)

    Chunhui, Chen; Xiaogang, Xu

    2015-05-01

    Vancomycin resistant enterococci has become an important nosocomial pathogen since it is discovered in late 1980s. The products, encoded by vancomycin resistant gene cluster in enterococci, catalyze the synthesis of peptidoglycan precursors with low affinity with glycopeptide antibiotics including vancomycin and teicoplanin and lead to resistance. These vancomycin resistant gene clusters are classified into nine types according to their gene sequences and organization, or D-Ala:D-Lac (VanA, VanB, VanD and VanM) and D-Ala:D-Ser (VanC, VanE, VanG, VanL and VanN) ligase gene clusters based on the differences of their encoded ligases. Moreover, these gene clusters are characterized by their different resistance levels and infection models. In this review, we summarize the classification, gene organization and infection model of vancomycin resistant gene cluster in Enterococcus spp.

  8. Proinsulin: from hormonal precursor to neuroprotective factor

    OpenAIRE

    Flora de Pablo

    2011-01-01

    In the last decade, non-canonical functions have been described for several molecules with hormone-like activities in different stages of vertebrate development. Since its purification in the 1960s, proinsulin has been one of the best described hormonal precursors, though it has been overwhelmingly studied in the context of insulin, the mature protein secreted by the pancreas. Beginning with our discovery of the presence and precise regulation of proinsulin mRNA in early neurulation and neuro...

  9. Proinsulin: From Hormonal Precursor to Neuroprotective Factor

    OpenAIRE

    De La Rosa, Enrique J; Pablo, Flora de

    2011-01-01

    In the last decade, non-canonical functions have been described for several molecules with hormone-like activities in different stages of vertebrate development. Since its purification in the 1960s, proinsulin has been one of the best described hormonal precursors, though it has been overwhelmingly studied in the context of insulin, the mature protein secreted by the pancreas. Beginning with our discovery of the presence and precise regulation of proinsulin mRNA in early neurulation and neuro...

  10. Molecular imaging in myeloma precursor disease

    OpenAIRE

    Mena, E.; Choyke, P; Tan, E; Landgren, O; Kurdziel, K

    2011-01-01

    Multiple myeloma (MM) is consistently preceded by its pre-malignant states, monoclonal gammopathy of undetermined significance (MGUS) and/or smoldering multiple myeloma (SMM). By definition, precursor conditions do not exhibit end-organ disease (anemia, hypercalcemia, renal failure, skeletal lytic lesions, or a combination of these). However, new imaging methods are demonstrating that some patients in the MGUS or SNM category are exhibiting early signs of MM.

  11. PRECURSORS OF EARTHQUAKES: VLF SIGNALSIONOSPHERE IONOSPHERE RELATION

    Directory of Open Access Journals (Sweden)

    Mustafa ULAS

    2013-01-01

    Full Text Available lot of people have died because of earthquakes every year. Therefore It is crucial to predict the time of the earthquakes reasonable time before it had happed. This paper presents recent information published in the literature about precursors of earthquakes. The relationships between earthquakes and ionosphere are targeted to guide new researches in order to study further to find novel prediction methods.

  12. Cellular Kinetics of Perivascular MSC Precursors

    Directory of Open Access Journals (Sweden)

    William C. W. Chen

    2013-01-01

    Full Text Available Mesenchymal stem/stromal cells (MSCs and MSC-like multipotent stem/progenitor cells have been widely investigated for regenerative medicine and deemed promising in clinical applications. In order to further improve MSC-based stem cell therapeutics, it is important to understand the cellular kinetics and functional roles of MSCs in the dynamic regenerative processes. However, due to the heterogeneous nature of typical MSC cultures, their native identity and anatomical localization in the body have remained unclear, making it difficult to decipher the existence of distinct cell subsets within the MSC entity. Recent studies have shown that several blood-vessel-derived precursor cell populations, purified by flow cytometry from multiple human organs, give rise to bona fide MSCs, suggesting that the vasculature serves as a systemic reservoir of MSC-like stem/progenitor cells. Using individually purified MSC-like precursor cell subsets, we and other researchers have been able to investigate the differential phenotypes and regenerative capacities of these contributing cellular constituents in the MSC pool. In this review, we will discuss the identification and characterization of perivascular MSC precursors, including pericytes and adventitial cells, and focus on their cellular kinetics: cell adhesion, migration, engraftment, homing, and intercellular cross-talk during tissue repair and regeneration.

  13. Ionospheric precursors for crustal earthquakes in Italy

    Science.gov (United States)

    Perrone, L.; Korsunova, L. P.; Mikhailov, A. V.

    2010-04-01

    Crustal earthquakes with magnitude 6.0>M≥5.5 observed in Italy for the period 1979-2009 including the last one at L'Aquila on 6 April 2009 were considered to check if the earlier obtained relationships for ionospheric precursors for strong Japanese earthquakes are valid for the Italian moderate earthquakes. The ionospheric precursors are based on the observed variations of the sporadic E-layer parameters (h'Es, fbEs) and foF2 at the ionospheric station Rome. Empirical dependencies for the seismo-ionospheric disturbances relating the earthquake magnitude and the epicenter distance are obtained and they have been shown to be similar to those obtained earlier for Japanese earthquakes. The dependences indicate the process of spreading the disturbance from the epicenter towards periphery during the earthquake preparation process. Large lead times for the precursor occurrence (up to 34 days for M=5.8-5.9) tells about a prolong preparation period. A possibility of using the obtained relationships for the earthquakes prediction is discussed.

  14. Disinfection byproduct formation from lignin precursors.

    Science.gov (United States)

    Hua, Guanghui; Kim, Junsung; Reckhow, David A

    2014-10-15

    Lignin is the most abundant aromatic plant component in terrestrial ecosystems. This study was conducted to determine the contribution of lignin residues in natural water to the formation of disinfection byproducts (DBPs) in drinking water. We investigated the formation of different classes of DBPs from lignin model compounds, lignin polymers, and humic substances using two common disinfection techniques, chlorination and chloramination. The contributions of lignin to the overall formation of DBPs from these organic products were determined based on the observed abundances of individual lignin phenols and their DBP yields. Model lignin phenols generally produced higher trichloroacetic acid (TCAA) yields than chloroform and dichloroacetic acid (DCAA) during chlorination. Lignin phenols generally produced higher DBP yields but lower percentages of unknown total organic halogen compared to bulk humic substances and lignin polymers. The relative significance of lignin phenols as chlorination DBP precursors generally follows the order of TCAA > DCAA&chloroform. The relative significance of lignin phenols to DBP formation by chloramination follows the order: TCAA > DCAA&DCAN > chloroform. Overall, lignin phenols are more important as TCAA precursors than as chloroform and DCAA precursors.

  15. Ionospheric precursors for crustal earthquakes in Italy

    Directory of Open Access Journals (Sweden)

    L. Perrone

    2010-04-01

    Full Text Available Crustal earthquakes with magnitude 6.0>M≥5.5 observed in Italy for the period 1979–2009 including the last one at L'Aquila on 6 April 2009 were considered to check if the earlier obtained relationships for ionospheric precursors for strong Japanese earthquakes are valid for the Italian moderate earthquakes. The ionospheric precursors are based on the observed variations of the sporadic E-layer parameters (h'Es, fbEs and foF2 at the ionospheric station Rome. Empirical dependencies for the seismo-ionospheric disturbances relating the earthquake magnitude and the epicenter distance are obtained and they have been shown to be similar to those obtained earlier for Japanese earthquakes. The dependences indicate the process of spreading the disturbance from the epicenter towards periphery during the earthquake preparation process. Large lead times for the precursor occurrence (up to 34 days for M=5.8–5.9 tells about a prolong preparation period. A possibility of using the obtained relationships for the earthquakes prediction is discussed.

  16. Group IIA β-diketonate compounds as CVD-precursors for high-Tc superconductors

    International Nuclear Information System (INIS)

    The advent of the high temperature superconducting metal oxides (SMO) has prompted an increasing number of studies aimed at the development of new routes to their synthesis in particular in the form of thin films. The preferred method in this regard has been that of chemical vapor deposition (CVD); however, significant difficulties have been associated with the efficacy of commercial precursors for the Group IIA metals in particular those of the β-diketonates of barium, whose coordinative unsaturation leads to cluster formation. The development of alternative β-diketonate precursor systems has focused upon the synthesis of stable Lewis-acid base complexes by either inter- or intra- molecular stabilization. The results of these studies are described herein, along with a review of the structural studies of the parent β-diketonate complexes and their decomposition products. (orig.)

  17. Graded cluster algebras

    OpenAIRE

    Grabowski, Jan

    2015-01-01

    In the cluster algebra literature, the notion of a graded cluster algebra has been implicit since the origin of the subject. In this work, we wish to bring this aspect of cluster algebra theory to the foreground and promote its study. We transfer a definition of Gekhtman, Shapiro and Vainshtein to the algebraic setting, yielding the notion of a multi-graded cluster algebra. We then study gradings for finite type cluster algebras without coefficients, giving a full classification. Translating ...

  18. Urease-induced calcification of segmented polymer hydrogels - a step towards artificial biomineralization.

    Science.gov (United States)

    Rauner, Nicolas; Meuris, Monika; Dech, Stephan; Godde, Julia; Tiller, Joerg C

    2014-09-01

    Natural organic/inorganic composites, such as nacre, bones and teeth, are perfectly designed materials with exceptional mechanical properties. Numerous approaches have been taken to synthetically prepare such composites. The presented work describes a new way of mineralizing bulk materials on a large scale following the approach of bioinduced mineralization. To this end, a series of polymer conetworks with entrapped urease were prepared. After polymerization, the entrapped urease shows high enzymatic activity. The bioactive polymer conetworks were then treated with an aqueous mixture of urea and CaCl2. The urease-induced calcification indeed allows formation of carbonate crystals exclusively within the hydrogel even at room temperature. The influence of network composition, degree of cross-linking, immobilized urease concentration and temperature of calcification were investigated. By varying these parameters, spherical, monolithic clusters, as well as bar-like nanocrystals with different aspect ratios in spherical or dendritic arrays, are formed. The grown nanocrystals improve the stiffness of the starting material by up to 700-fold, provided that the microstructure shows a dense construction without pores and strong interaction between crystals and network. The process has the potential to generate a new class of hybrid materials that would be available on the macroscopic scale for use in lightweight design and medicine.

  19. Ediacarian sponge spicule clusters from southwestern Mongolia and the origins of the Cambrian fauna

    Science.gov (United States)

    Brasier, Martin; Green, Owen; Shields, Graham

    1997-04-01

    Carbon and strontium isotopic data are used to show that the earliest sponge spicule clusters and associated phosphatic sediments (with Anabarites) from southwestern Mongolia are of Ediacarian age. Spicule morphologies include bundles of oxeas arranged in three-dimensional quadrules, linked together at junctions by tetracts, pentacts, hexacts, or polyactines. All are referred to the Phylum Porifera, Class Hexactinellida. These sponge spicules provide the oldest remains that can be assigned without question to an extant phylum, and also the first firm evidence for filter feeding and metazoan silica biomineralization in the fossil record. It is suggested that siliceous and phosphatic members of the “Cambrian fauna” may have had their origins in eutrophic and outer shelf facies of the Late Proterozoic.

  20. Expansion of ribosomally produced natural products: a nitrile hydratase- and Nif11-related precursor family

    Directory of Open Access Journals (Sweden)

    Mitchell Douglas A

    2010-05-01

    Full Text Available Abstract Background A new family of natural products has been described in which cysteine, serine and threonine from ribosomally-produced peptides are converted to thiazoles, oxazoles and methyloxazoles, respectively. These metabolites and their biosynthetic gene clusters are now referred to as thiazole/oxazole-modified microcins (TOMM. As exemplified by microcin B17 and streptolysin S, TOMM precursors contain an N-terminal leader sequence and C-terminal core peptide. The leader sequence contains binding sites for the posttranslational modifying enzymes which subsequently act upon the core peptide. TOMM peptides are small and highly variable, frequently missed by gene-finders and occasionally situated far from the thiazole/oxazole forming genes. Thus, locating a substrate for a particular TOMM pathway can be a challenging endeavor. Results Examination of candidate TOMM precursors has revealed a subclass with an uncharacteristically long leader sequence closely related to the enzyme nitrile hydratase. Members of this nitrile hydratase leader peptide (NHLP family lack the metal-binding residues required for catalysis. Instead, NHLP sequences display the classic Gly-Gly cleavage motif and have C-terminal regions rich in heterocyclizable residues. The NHLP family exhibits a correlated species distribution and local clustering with an ABC transport system. This study also provides evidence that a separate family, annotated as Nif11 nitrogen-fixing proteins, can serve as natural product precursors (N11P, but not always of the TOMM variety. Indeed, a number of cyanobacterial genomes show extensive N11P paralogous expansion, such as Nostoc, Prochlorococcus and Cyanothece, which replace the TOMM cluster with lanthionine biosynthetic machinery. Conclusions This study has united numerous TOMM gene clusters with their cognate substrates. These results suggest that two large protein families, the nitrile hydratases and Nif11, have been retailored for

  1. Organic matter remains in the Kess Kess mounds of the Hamar Laghadad (Anti Atlas, Morocco): record of microbial biomineralization

    Science.gov (United States)

    Demasi, Fabio; Barbieri, Roberto; Guido, Adriano; Mastandrea, Adelaide; Cavalazzi, Barbara; Russo, Franco

    2010-05-01

    Carbonate Mud Mounds are well documented in the geological record, and span from Proterozoic to recent times, in shallow- and deep-water settings. They are a significant expression of the history of Earth's microbial life. The origin of carbonate mud-mounds has long been debated and the discovery of seep- and vent-related ecosystems from different geotectonic settings, associated to authigenic carbonate mounds, allowed the re-interpretation of some mounds as the product of chemosynthetic microbial mediation. We analyzed the carbonate mounds, informally called 'Kess-Kess', cropping out in the Hamar Laghdad Ridge, eastern Anti-Atlas, SE Morocco. These mounds are the most spectacularly exposed carbonate buildups of the world and, due to differential erosion, they show their original shapes and the relationships with associated strata. The origin of these buildups is still under debate and the most consistent hypotheses are related to submarine hydrothermal vents or hydrocarbon seapage in which bacteria and/or archaea plaied a prominent role in the carbonate biomineralization. To investigate the possible remains of prokaryote metabolic activity we studied the micrite precipitation processes through microfacies and biogeochemical analyses. The more indicative micrite texture is stromatolitic with very fine wrinkled lamination organized in antigravitative pattern. High resolution SEM observations suggest the presence of widespread trace of organic phantoms. The geochemical characterization of extracted organic matter was performed through the functional group analyses by FT-IR spectroscopy. The infrared spectra showed bands between 600 and 3000 cm-1. They contain stretching aliphatic bands (νCHali) at 2950, 2925 and 2850 cm-1, and deformation bands of methyl (δCH3; 1365 cm-1) and both methyl and methylene [δ(CH2 + CH3); 1458 cm-1] groups. The spectra also display the band assigned to carbonyl and/or carboxyl groups (νC=O; 1740 cm-1). The νC-O vibration appears

  2. What Makes Clusters Decline?

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    2015-01-01

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark....... The longitudinal study on the high-tech cluster reveals that technological lock-in and exit of key firms have contributed to decline. Entrepreneurship has a positive effect on the cluster’s adaptive capabilities, while multinational companies have contradicting effects by bringing in new resources to the cluster...

  3. Transcriptional properties and splicing of the flamenco piRNA cluster.

    Science.gov (United States)

    Goriaux, Coline; Desset, Sophie; Renaud, Yoan; Vaury, Chantal; Brasset, Emilie

    2014-04-01

    In Drosophila, the piRNA cluster, flamenco, produces most of the piRNAs (PIWI-interacting RNAs) that silence transposable elements in the somatic follicle cells during oogenesis. These piRNAs are thought to be processed from a long single-stranded precursor transcript. Here, we demonstrate that flamenco transcription is initiated from an RNA polymerase II promoter containing an initiator motif (Inr) and downstream promoter element (DPE) and requires the transcription factor, Cubitus interruptus. We show that the flamenco precursor transcript undergoes differential alternative splicing to generate diverse RNA precursors that are processed to piRNAs. Our data reveal dynamic processing steps giving rise to piRNA cluster precursors. PMID:24562610

  4. Room temperature strain rate sensitivity in precursor derived HfO2/Si-C-N(O ceramic nanocomposites

    Directory of Open Access Journals (Sweden)

    Ravindran Sujith

    2014-01-01

    Full Text Available Investigation on the room temperature strain rate sensitivity using depth sensing nanoindentation is carried out on precursor derived HfO2/Si-C-N(O ceramic nanocomposite sintered using pulsed electric current sintering. Using constant load method the strain rate sensitivity values are estimated. Lower strain rate sensitivity of ∼ 3.7 × 10−3 is observed and the limited strain rate sensitivity of these ceramic nanocomposites is explained in terms of cluster model. It is concluded that presence of amorphous Si-C-N(O clusters are responsible for the limited flowability in these ceramics.

  5. Do protein crystals nucleate within dense liquid clusters?

    Energy Technology Data Exchange (ETDEWEB)

    Maes, Dominique, E-mail: dommaes@vub.ac.be [Vrije Universiteit Brussel, 1050 Brussels (Belgium); Vorontsova, Maria A. [University of Houston, Houston, TX 77204 (United States); Potenza, Marco A. C.; Sanvito, Tiziano [Universita di Milano, 20133 Milano (Italy); Sleutel, Mike [Vrije Universiteit Brussel, 1050 Brussels (Belgium); Giglio, Marzio [Universita di Milano, 20133 Milano (Italy); Vekilov, Peter G. [Vrije Universiteit Brussel, 1050 Brussels (Belgium); University of Houston, Houston, TX 77204 (United States); University of Houston, Houston, TX 77204 (United States)

    2015-06-27

    The evolution of protein-rich clusters and nucleating crystals were characterized by dynamic light scattering (DLS), confocal depolarized dynamic light scattering (cDDLS) and depolarized oblique illumination dark-field microscopy. Newly nucleated crystals within protein-rich clusters were detected directly. These observations indicate that the protein-rich clusters are locations for crystal nucleation. Protein-dense liquid clusters are regions of high protein concentration that have been observed in solutions of several proteins. The typical cluster size varies from several tens to several hundreds of nanometres and their volume fraction remains below 10{sup −3} of the solution. According to the two-step mechanism of nucleation, the protein-rich clusters serve as locations for and precursors to the nucleation of protein crystals. While the two-step mechanism explained several unusual features of protein crystal nucleation kinetics, a direct observation of its validity for protein crystals has been lacking. Here, two independent observations of crystal nucleation with the proteins lysozyme and glucose isomerase are discussed. Firstly, the evolutions of the protein-rich clusters and nucleating crystals were characterized simultaneously by dynamic light scattering (DLS) and confocal depolarized dynamic light scattering (cDDLS), respectively. It is demonstrated that protein crystals appear following a significant delay after cluster formation. The cDDLS correlation functions follow a Gaussian decay, indicative of nondiffusive motion. A possible explanation is that the crystals are contained inside large clusters and are driven by the elasticity of the cluster surface. Secondly, depolarized oblique illumination dark-field microscopy reveals the evolution from liquid clusters without crystals to newly nucleated crystals contained in the clusters to grown crystals freely diffusing in the solution. Collectively, the observations indicate that the protein-rich clusters in

  6. Toward a mechanistic understanding of patterns in biomineralization and new insights for old dogmas in geological settings (Invited)

    Science.gov (United States)

    Dove, P. M.; Hamm, L.; Giuffre, A. J.; Han, N.; De Yoreo, J. J.

    2013-12-01

    The ability of organisms to mineralize tissues into skeletons and other functional structures is a remarkable achievement of biology. Yet, the physical basis for how macromolecules regulate the placement and onset of mineral formation is not well established. Efforts to understand nucleation onto organic substrates have produced two, seemingly contradictory, lines of thought: The biomineralization community widely assumes the organic matrix promotes nucleation through stereochemical matching to guide the organization of solute ions, while materials synthesis groups use simple binding assays to correlate high binding strength with good promoters of nucleation. This study reconciles the two views and provides a mechanistic explanation for template-directed nucleation by correlating heterogeneous nucleation barriers with crystal-substrate binding free energies. Using surface assembled monolayers (SAM) as simple model systems, we first measure the kinetics of calcite nucleation onto model substrates that present different functional group chemistries (carboxyl, thiol, phosphate, hydroxyl) and conformations (C11, C16 chain lengths). We find rates are substrate-specific and obey predictions of classical nucleation theory at supersaturations that extend above the solubility of amorphous calcium carbonate (ACC). Analysis of the kinetic data shows the thermodynamic barrier to nucleation is reduced by minimizing the interfacial free energy of the system, γ. We then use dynamic force spectroscopy to independently measure calcite-substrate binding free energies, ΔGb. Moreover, we show that within the classical theory of nucleation, γ and ΔGb should be linearly related. The results bear out this prediction and demonstrate that low energy barriers to nucleation correlate with strong crystal-substrate binding. This relationship is general to all functional group chemistries and conformations. These findings reconcile the long-standing concept of templated nucleation through

  7. Tissue regeneration and biomineralization in sea urchins: role of Notch signaling and presence of stem cell markers.

    Science.gov (United States)

    Reinardy, Helena C; Emerson, Chloe E; Manley, Jason M; Bodnar, Andrea G

    2015-01-01

    Echinoderms represent a phylum with exceptional regenerative capabilities that can reconstruct both external appendages and internal organs. Mechanistic understanding of the cellular pathways involved in regeneration in these animals has been hampered by the limited genomic tools and limited ability to manipulate regenerative processes. We present a functional assay to investigate mechanisms of tissue regeneration and biomineralization by measuring the regrowth of amputated tube feet (sensory and motor appendages) and spines in the sea urchin, Lytechinus variegatus. The ability to manipulate regeneration was demonstrated by concentration-dependent inhibition of regrowth of spines and tube feet by treatment with the mitotic inhibitor, vincristine. Treatment with the gamma-secretase inhibitor DAPT resulted in a concentration-dependent inhibition of regrowth, indicating that both tube feet and spine regeneration require functional Notch signaling. Stem cell markers (Piwi and Vasa) were expressed in tube feet and spine tissue, and Vasa-positive cells were localized throughout the epidermis of tube feet by immunohistochemistry, suggesting the existence of multipotent progenitor cells in these highly regenerative appendages. The presence of Vasa protein in other somatic tissues (e.g. esophagus, radial nerve, and a sub-population of coelomocytes) suggests that multipotent cells are present throughout adult sea urchins and may contribute to normal homeostasis in addition to regeneration. Mechanistic insight into the cellular pathways governing the tremendous regenerative capacity of echinoderms may reveal processes that can be modulated for regenerative therapies, shed light on the evolution of regeneration, and enable the ability to predict how these processes will respond to changing environmental conditions.

  8. Structure and Properties of Nanomaterials: From Inorganic Boron Nitride Nanotubes to the Calcareous Biomineralized Tubes of H. dianthus

    Science.gov (United States)

    Tanur, Adrienne Elizabeth

    Several nanomaterials systems, both inorganic and organic in nature, have been extensively investigated by a number of characterization techniques including atomic force microscopy (AFM), electron microscopy, Fourier transform infrared spectroscopy (FTIR), and energy dispersive x-ray spectroscopy (EDX). The first system consists of boron nitride nanotubes (BNNTs) synthesized via two different methods. The first method, silica-assisted catalytic chemical vapour deposition (SA-CVD), produced boron nitride nanotubes with different morphologies depending on the synthesis temperature. The second method, growth vapour trapping chemical vapour deposition (GVT-CVD), produced multiwall boron nitride nanotubes (MWBNNTs). The bending modulus of individual MWBNNTs was determined using an AFM three-point bending technique, and was found to be diameter-dependent due to the presence of shear effects. The second type of nanomaterial investigated is the biomineralized calcareous shell of the serpulid Hydroides dianthus. This material was found to be an inorganic-organic composite material composed of two different morphologies of CaCO3, collagen, and carboxylated and sulphated polysaccharides. The organic components were demonstrated to mediate the mineralization of CaCO3 in vitro. The final system studied is the proteinaceous cement of the barnacle Amphibalanus amphitrite. The secondary structure of the protein components was investigated via FTIR, revealing the presence of beta-sheet conformation, and nanoscale rod-shaped structures within the cement were identified as beta-sheet containing amyloid fibrils via chemical staining. These rod-shaped structures exhibited a stiffer nature compared with other structures in the adhesive, as measured by AFM nanoindentation.

  9. Tissue regeneration and biomineralization in sea urchins: role of Notch signaling and presence of stem cell markers.

    Directory of Open Access Journals (Sweden)

    Helena C Reinardy

    Full Text Available Echinoderms represent a phylum with exceptional regenerative capabilities that can reconstruct both external appendages and internal organs. Mechanistic understanding of the cellular pathways involved in regeneration in these animals has been hampered by the limited genomic tools and limited ability to manipulate regenerative processes. We present a functional assay to investigate mechanisms of tissue regeneration and biomineralization by measuring the regrowth of amputated tube feet (sensory and motor appendages and spines in the sea urchin, Lytechinus variegatus. The ability to manipulate regeneration was demonstrated by concentration-dependent inhibition of regrowth of spines and tube feet by treatment with the mitotic inhibitor, vincristine. Treatment with the gamma-secretase inhibitor DAPT resulted in a concentration-dependent inhibition of regrowth, indicating that both tube feet and spine regeneration require functional Notch signaling. Stem cell markers (Piwi and Vasa were expressed in tube feet and spine tissue, and Vasa-positive cells were localized throughout the epidermis of tube feet by immunohistochemistry, suggesting the existence of multipotent progenitor cells in these highly regenerative appendages. The presence of Vasa protein in other somatic tissues (e.g. esophagus, radial nerve, and a sub-population of coelomocytes suggests that multipotent cells are present throughout adult sea urchins and may contribute to normal homeostasis in addition to regeneration. Mechanistic insight into the cellular pathways governing the tremendous regenerative capacity of echinoderms may reveal processes that can be modulated for regenerative therapies, shed light on the evolution of regeneration, and enable the ability to predict how these processes will respond to changing environmental conditions.

  10. Accelerated transformation of brushite to octacalcium phosphate in new biomineralization media between 36.5 deg. C and 80 deg. C

    International Nuclear Information System (INIS)

    This study investigated the hydrothermal transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4.2H2O) into octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4.5H2O) in seven different newly developed biomineralization media, all inspired from the commercial DMEM solutions, over the temperature range of 36.5 deg. C to 90 deg. C with aging times varying between 1 h and 6 days. DCPD powders used in this study were synthesized in our laboratory by using a wet-chemical technique. DCPD was found to transform into OCP in the Ca2+, Mg2+, Na+, K+, HCO3-, Cl- and H2PO4- containing aqueous biomineralization media in less than 72 h at 36.5 deg. C, without stirring. The same medium was able to convert DCPD into OCP in about 2 h at 75-80 deg. C, again without a need for stirring. Samples were characterized by using powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). - Research highlights: → New biomineralization solutions developed to convert DCPD into OCP at 36.5 deg. C to 80 deg. C. → DCPD powder was the starting material. → OCP was synthesized under static conditions (no need for stirring). → OCP was synthesized in sealed glass media bottles in solutions free of Hepes or Tris. → OCP can be synthesized at 75-80 deg. C in only 2 hours in the above solutions without stirring.

  11. Crack-free polydimethylsiloxane-bioactive glass-poly(ethylene glycol) hybrid monoliths with controlled biomineralization activity and mechanical property for bone tissue regeneration.

    Science.gov (United States)

    Chen, Jing; Du, Yuzhang; Que, Wenxiu; Xing, Yonglei; Chen, Xiaofeng; Lei, Bo

    2015-12-01

    Crack-free organic-inorganic hybrid monoliths with controlled biomineralization activity and mechanical property have an important role for highly efficient bone tissue regeneration. Here, biomimetic and crack-free polydimethylsiloxane (PDMS)-modified bioactive glass (BG)-poly(ethylene glycol) (PEG) (PDMS-BG-PEG) hybrids monoliths were prepared by a facile sol-gel technique. Results indicate that under the assist of co-solvents, BG sol and PDMS and PEG could be hybridized at a molecular level, and effects of the PEG molecular weight on the structure, biomineralization activity, and mechanical property of the as-prepared hybrid monoliths were also investigated in detail. It is found that an addition of low molecular weight PEG can significantly prevent the formation of cracks and speed up the gelation of the hybrid monoliths, and the surface microstructure of the hybrid monoliths can be changed from the porous to the smooth as the PEG molecular weight increases. Additionally, the hybrid monoliths with low molecular weight PEG show the high formation of the biological apatite layer, while the hybrids with high molecular weight PEG exhibit negligible biomineralization ability in simulated body fluid (SBF). Furthermore, the PDMS-BG-PEG 600 hybrid monolith has significantly high compressive strength (32 ± 3 MPa) and modulus (153 ± 11 MPa), as well as good cell biocompatibility by supporting osteoblast (MC3T3-E1) attachment and proliferation. These results indicate that the as-prepared PDMS-BG-PEG hybrid monoliths may have promising applications for bone tissue regeneration.

  12. Development of precursors to produce metallic foams

    OpenAIRE

    Lopes, Bruno Pinto

    2011-01-01

    As espumas metálicas produzidas por metalurgia de pós têm vindo a ser cada vez mais utilizadas nas mais diversas aplicações. Actualmente estes materiais estão a ser utilizados em estruturas ultraleves, de absorção de energia e de amortecimento sonoro em veículos automóveis, comboios, eléctricos e aeronaves. O principal objectivo desta dissertação prendeu-se com o desenvolvimento de material precursor de qualidade para o fabrico de espumas de ligas de Alumínio. Para o efeito foram testados ...

  13. Biomimetic synthesis for precursor of muscone

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Muscone is a precious fragrant compound scarce in nature. Many attempts have been made to synthesize this unique natural product. In this work, the one- carbon unit transfer reaction of tetrahydrofolate coenzyme was initiated. Benzimidazolium salt was used as the tetrahydrofolate coenzyme model at formic acid oxidation level and di-Grignard reagent as the nucleophile to which one-carbon unit was transferred; the biomimetic synthesis of 2,15- hexade-canedione, a precursor of muscone, was successfully accomplished by using the addition-hydrolysis reaction of benzimidazolium salt with Grignard reagent. And an impor-tant useful method for the synthesis of muscone is provided.

  14. Triple oxygen isotopes and clumped isotopes in modern vertebrate and dinosaur biominerals: Records of paleoecology, paleoaridity, and paleo-carbon-cycling

    Science.gov (United States)

    Hu, H.; Passey, B. H.; Lehmann, S. B.; Levin, N. E.; Montanari, S.; Chin, K.; Johnson, B. J.

    2015-12-01

    The parameter Δ17O describes the departure of δ17O from an expected equilibrium relationship with δ18O, which can be caused by factors such as evaporation of parent waters, and photochemical reactions among oxygen-bearing gases in stratosphere. Hence, the Δ17O of water records information about environmental aridity, and the Δ17O of atmospheric O2 is related to atmospheric concentrations of CO2 and O2, and gross primary productivity (GPP). Vertebrates incorporate Δ17O signals of input water (e.g. drinking water and free food water) and atmospheric O2 into body water through respiration, and biominerals forming in equilibrium with body water can preserve this signal over geological timescales. The preservation of fossil biominerals can be evaluated by clumped isotopes as they record the temperature of mineralization, be it primary mineralization in the living animal (at body temperature), or secondary mineralization during diagenesis. We can distinguish the alteration of samples from the deviation between observed clumped isotope temperatures and plausible body temperatures. Meanwhile, diagenesis tends to moderate Δ17O of biominerals towards Δ17O of meteoric waters, such that measured Δ17O values reflect the minimum anomaly in fossil samples. Thus, preservation of anomalous Δ17O indicates at least partial preservation of the original signal. We present Δ17O data from both modern vertebrate and fossil dinosaur biominerals. We use a 17O-enabled body water model to explore the influence of aridity and dietary ecology on animal Δ17O, and to predict the degree of dilution of the atmospheric O2 Δ17O signal by other sources of oxygen to the animal. We observe: 1) animals consuming more leaf water than drinking water are "evaporation sensitive" (ES) animals, and have lower Δ17O relative to "evaporation insensitive" animals in the same climates; 2) ES animals from arid climates have lower Δ17O values compared to ES animals from humid climates, which forms the

  15. Star clusters and associations

    International Nuclear Information System (INIS)

    All 33 papers presented at the symposium were inputted to INIS. They dealt with open clusters, globular clusters, stellar associations and moving groups, and local kinematics and galactic structures. (E.S.)

  16. Solar-cycle precursors and predictions

    CERN Document Server

    Jiang, Jie

    2013-01-01

    The sunspot number data during the past 400 years indicates that both the profile and the amplitude of the solar cycle have large variations. Some precursors of the solar cycle were identified aiming to predict the solar cycle. The polar field and the geomagnetic index are two precursors which are received the most attention. The geomagnetic variations during the solar minima are potentially caused by the solar polar field by the connection of the solar open flux. The robust prediction skill of the polar field indicates that the memory of the dynamo process is less than 11 yrs within the framework of the Babcock-Leighton flux transport dynamo. One possible reason to get the short magnetic memory is the high magnetic diffusivity in the convective zone. Our recent studies show that the radial downward pumping is another possible reason. Based upon the mechanism, we well simulate the cycle irregularities during RGO time period. This opens the possibility to set up a standard dynamo based model to predict the sol...

  17. Precursor solitons in a flowing complex plasma

    Science.gov (United States)

    Bandyopadhyay, Pintu; Jaiswal, Surabhi; Sen, Abhijit

    2015-11-01

    We report the first experimental observation of precursor solitons in a flowing dusty plasma. The nonlinear solitary dust acoustic waves (DAWs) are excited by a supersonic mass flow of the dust particles passing over an electrostatic potential hill. In a frame where the fluid is stationary and the hill is moving the solitons propagate in the upstream direction while wake structures consisting of linear DAWs are seen to propagate in the downstream direction. The experiments have been carried out in a U-shaped Dusty Plasma Experimental (DPEx) device where kaolin particles are immersed in a DC discharge argon plasma to form the dusty plasma and a floating wire mounted on the cathode creates a potential hill. The dust flow is induced by sudden changes in the hill height and the solitary structures are seen only for supersonic flows and up to an upper limit of the flow. A theoretical model description of the phenomenon will be provided and some practical implications of such precursor excitations for a charged object moving in a plasma will be discussed.

  18. Quantum Annealing for Clustering

    OpenAIRE

    Kurihara, Kenichi; Tanaka, Shu; Miyashita, Seiji

    2014-01-01

    This paper studies quantum annealing (QA) for clustering, which can be seen as an extension of simulated annealing (SA). We derive a QA algorithm for clustering and propose an annealing schedule, which is crucial in practice. Experiments show the proposed QA algorithm finds better clustering assignments than SA. Furthermore, QA is as easy as SA to implement.

  19. Emergence of regional clusters

    DEFF Research Database (Denmark)

    Dahl, Michael S.; Østergaard, Christian Richter; Dalum, Bent

    2010-01-01

    approach to analyse how successful early firms can lead to formation of clusters. Three key determinants are identified: (1) the geographical dimension of entrepreneurial activity, (2) spinoffs from successful firms and (3) new market opportunities. The chapter studies in great detail the evolution...... of the wireless communications cluster in Northern Denmark and compare it with the evolution of other clusters....

  20. The Durban Auto Cluster

    DEFF Research Database (Denmark)

    Lorentzen, Jochen; Robbins, Glen; Barnes, Justin

    2004-01-01

    The paper describes the formation of the Durban Auto Cluster in the context of trade liberalization. It argues that the improvement of operational competitiveness of firms in the cluster is prominently due to joint action. It tests this proposition by comparing the gains from cluster activities i...

  1. Cluster Physics with Merging Galaxy Clusters

    Directory of Open Access Journals (Sweden)

    Sandor M. Molnar

    2016-02-01

    Full Text Available Collisions between galaxy clusters provide a unique opportunity to study matter in a parameter space which cannot be explored in our laboratories on Earth. In the standard LCDM model, where the total density is dominated by the cosmological constant ($Lambda$ and the matter density by cold dark matter (CDM, structure formation is hierarchical, and clusters grow mostly by merging.Mergers of two massive clusters are the most energetic events in the universe after the Big Bang,hence they provide a unique laboratory to study cluster physics.The two main mass components in clusters behave differently during collisions:the dark matter is nearly collisionless, responding only to gravity, while the gas is subject to pressure forces and dissipation, and shocks and turbulenceare developed during collisions. In the present contribution we review the different methods used to derive the physical properties of merging clusters. Different physical processes leave their signatures on different wavelengths, thusour review is based on a multifrequency analysis. In principle, the best way to analyze multifrequency observations of merging clustersis to model them using N-body/HYDRO numerical simulations. We discuss the results of such detailed analyses.New high spatial and spectral resolution ground and space based telescopeswill come online in the near future. Motivated by these new opportunities,we briefly discuss methods which will be feasible in the near future in studying merging clusters.

  2. Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

    Directory of Open Access Journals (Sweden)

    Peter Hesemann

    2014-04-01

    Full Text Available The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA, mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the “anionic templating” strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

  3. Cluster beam sources. Part 1. Methods of cluster beams generation

    Directory of Open Access Journals (Sweden)

    A.Ju. Karpenko

    2012-10-01

    Full Text Available The short review on cluster beams generation is proposed. The basic types of cluster sources are considered and the processes leading to cluster formation are analyzed. The parameters, that affects the work of cluster sources are presented.

  4. Cluster analysis for applications

    CERN Document Server

    Anderberg, Michael R

    1973-01-01

    Cluster Analysis for Applications deals with methods and various applications of cluster analysis. Topics covered range from variables and scales to measures of association among variables and among data units. Conceptual problems in cluster analysis are discussed, along with hierarchical and non-hierarchical clustering methods. The necessary elements of data analysis, statistics, cluster analysis, and computer implementation are integrated vertically to cover the complete path from raw data to a finished analysis.Comprised of 10 chapters, this book begins with an introduction to the subject o

  5. Cluster control plasma CVD for fabrication of stable a-Si:H solar cells

    Science.gov (United States)

    Shiratani, Masaharu; Hashimoto, Yuuji; Kanemitsu, Yoshinori; Seo, Hyunwoong; Kamataki, Kunihiro; Uchida, Giichiro; Itagaki, Naho; Koga, Kazunori

    2013-09-01

    Light-induced degradation of a-Si:H is the key issue for a-Si:H solar cells, because light exposure initially causes a significant reduction of the efficiency of the cells due to the degradation. In SiH4 discharges employed for a-Si:H deposition, there coexist three deposition precursors; SiH3 radicals, HOS radicals, and amorphous clusters (nanoparticles). SiH3 radicals are the main deposition precursors for ``good'' quality films, whereas clusters are the precursors to cause the light induced degradation. To suppress cluster incorporation into films, we employ, 1) magnetic field which modifies EEDF, 2) gas heating to suppress polymerization reactions in gas phase, 3) gas flow which drives clusters downstream, 4) thermophoretic force which supresses cluster deposition, and 5) a cluster eliminating filter. Our a-Si:H films deposited at 3 nm/s show a low stabilized defect density of 5 × 1015 cm-3 . To evaluate their quality as an I layer of PIN solar cells, we have measured Fill Factor (FF) of N-type c-Si/a-Si:H/Ni Schottky cells of such cluster-free a-Si:H films. Our cell shows high initial FF of 0.516, high stable FF of 0.514, and little light induced degradation ratio of 0.39%. Work supported by NEDO, PVTEC, and MEXT.

  6. A new method to extract matrix proteins directly from the secretion of the mollusk mantle and the role of these proteins in shell biomineralization.

    Science.gov (United States)

    Liu, Xiaojun; Liu, Chang; Chen, Lei; Sun, Juan; Zhou, Yujuan; Li, Qi; Zheng, Guilan; Zhang, Guiyou; Wang, Hongzhong; Xie, Liping; Zhang, Rongqing

    2011-10-01

    Considering the continuous and substantive secretory ability of the mantle in vitro, we report a new technique to produce shell-matrix proteins by inducing the mantle, after removal from the organism's body, to secrete soluble-matrix proteins into phosphate buffer. By this method, a large amount of matrix proteins could be obtained in 2 h. Experiments involving in vitro calcium carbonate crystallization and organic framework calcium carbonate crystallization indicated that these proteins retain high bioactivity and play key roles in shell biomineralization. Phosphate buffer-soluble proteins secreted by the margin of the mantles (MSPs) were used to reconstruct the stages in the growth of the prismatic layer of the decalcified organic frameworks. The MSPs were observed to aggregate calcites in vitro, and this ability enabled the mollusk to form big calcites in the prismatic layer. During shell biomineralization, an important stage after the self-assembly of the biomacromolecules and the formation of crystals is the assembly of the two parts to form a firm structure. Moreover, a new type of matrix protein, functioning as the binding factor between the crystals and the organic frameworks, was shown to exist in the phosphate buffer-soluble proteins secreted by the central part of mantles (CSPs). Nanoscale-sized bowl-like aragonites, with heights of ∼800 nm, were induced by CSPs in vitro. This method is a successful example of obtaining functional proteins through secretion by animal tissues.

  7. Clusters in nuclei

    CERN Document Server

    Beck, Christian

    Following the pioneering discovery of alpha clustering and of molecular resonances, the field of nuclear clustering is today one of those domains of heavy-ion nuclear physics that faces the greatest challenges, yet also contains the greatest opportunities. After many summer schools and workshops, in particular over the last decade, the community of nuclear molecular physicists has decided to collaborate in producing a comprehensive collection of lectures and tutorial reviews covering the field. This third volume follows the successful Lect. Notes Phys. 818 (Vol. 1) and 848 (Vol. 2), and comprises six extensive lectures covering the following topics:  - Gamma Rays and Molecular Structure - Faddeev Equation Approach for Three Cluster Nuclear Reactions - Tomography of the Cluster Structure of Light Nuclei Via Relativistic Dissociation - Clustering Effects Within the Dinuclear Model : From Light to Hyper-heavy Molecules in Dynamical Mean-field Approach - Clusterization in Ternary Fission - Clusters in Light N...

  8. Unconventional methods for clustering

    Science.gov (United States)

    Kotyrba, Martin

    2016-06-01

    Cluster analysis or clustering is a task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters). It is the main task of exploratory data mining and a common technique for statistical data analysis used in many fields, including machine learning, pattern recognition, image analysis, information retrieval, and bioinformatics. The topic of this paper is one of the modern methods of clustering namely SOM (Self Organising Map). The paper describes the theory needed to understand the principle of clustering and descriptions of algorithm used with clustering in our experiments.

  9. Spatial cluster modelling

    CERN Document Server

    Lawson, Andrew B

    2002-01-01

    Research has generated a number of advances in methods for spatial cluster modelling in recent years, particularly in the area of Bayesian cluster modelling. Along with these advances has come an explosion of interest in the potential applications of this work, especially in epidemiology and genome research. In one integrated volume, this book reviews the state-of-the-art in spatial clustering and spatial cluster modelling, bringing together research and applications previously scattered throughout the literature. It begins with an overview of the field, then presents a series of chapters that illuminate the nature and purpose of cluster modelling within different application areas, including astrophysics, epidemiology, ecology, and imaging. The focus then shifts to methods, with discussions on point and object process modelling, perfect sampling of cluster processes, partitioning in space and space-time, spatial and spatio-temporal process modelling, nonparametric methods for clustering, and spatio-temporal ...

  10. Functional Nanoporous Polymers from Block Copolymer Precursors

    DEFF Research Database (Denmark)

    Guo, Fengxiao

    Abstract Self-assembly of block copolymers provides well-defined morphologies with characteristic length scales in the nanometer range. Nanoporous polymers prepared by selective removal of one block from self-assembled block copolymers offer great technological promise due to their many potential...... applications as, e.g., membranes for separation and purification, templates for nanostructured materials, sensors, substrates for catalysis, low dielectric constant materials, photonic materials, and depots for controlled drug delivery. The development of nanoporous polymers with well controlled pore wall...... functionalities remains a great challenge due to the limitation of available polymer synthesis and the nanoscale confinement of the porous cavities. The main topic of this thesis is to develop methods for fabrication of functional nanoporous polymers from block copolymer precursors. A method has been developed...

  11. ON THE PRECURSORS OF FOSSIL GROUPS

    Directory of Open Access Journals (Sweden)

    Hrant Tovmassian

    2010-01-01

    Full Text Available Comparamos las magnitudes absolutas en la banda K de las galaxias más brillantes en cúmulos de Bautz-Morgan tipo I con las de las galaxias brillantes de grupos fósiles. Demostramos que las galaxias más brillantes en grupos fósiles son, en promedio, más débiles que sus contrapartes en los cúmulos. Además, mostramos que la luminosidad de la galaxia más brillante depende de la riqueza del cúmulo. Concluimos que los precursores de grupos fóiles fueron en promedio cúmulos po- bres.

  12. ON THE PRECURSORS OF FOSSIL GROUPS

    OpenAIRE

    Hrant Tovmassian

    2010-01-01

    Comparamos las magnitudes absolutas en la banda K de las galaxias más brillantes en cúmulos de Bautz-Morgan tipo I con las de las galaxias brillantes de grupos fósiles. Demostramos que las galaxias más brillantes en grupos fósiles son, en promedio, más débiles que sus contrapartes en los cúmulos. Además, mostramos que la luminosidad de la galaxia más brillante depende de la riqueza del cúmulo. Concluimos que los precursores de grupos fóiles fueron en promedio cúmulos po- bres.

  13. Preparation and Characterization of TaN ALD Precursors

    Institute of Scientific and Technical Information of China (English)

    Delong Zhang; Tracy Yund; Cynthia A.Hoover

    2004-01-01

    High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET > PDMAT > TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.

  14. The crustal micro-deformation anomaly and the credible precursor*

    Institute of Scientific and Technical Information of China (English)

    张雁滨; 蒋骏; 钱家栋; 陈京; 和升棋; 张燕; 和平

    2002-01-01

    @@ What is a credible seismic precursor in observation of deformation A real seismic precursor ought to be resulted from the variations in the earth strain and stress. The deformation observation can provide the information during earthquake gestation and occurrence period for us. Usually the seismic precursors can be divided into field and epicentral region precursors. The precursor information is very useful for seismic prediction from epicentral region or near epicentral region. Micro-deformation observation mainly includes tilt, strain and gravity observation. Compared with GPS, geodesy and mobile deformation observation, micro-deformation (tilt, strain) shows the change of deformation which is continual in a limited volume with dominant observed range of 10(6~10(10 m. Because the variation of the crustal nature and cracking can be directly obtained by micro-deformation observation, it is an effective way to find middle-short term and short-term precursor.

  15. Survey on Text Document Clustering

    OpenAIRE

    M.Thangamani; Dr.P.Thangaraj

    2010-01-01

    Document clustering is also referred as text clustering, and its concept is merely equal to data clustering. It is hardly difficult to find the selective information from an ‘N’number of series information, so that document clustering came into picture. Basically cluster means a group of similar data, document clustering means segregating the data into different groups of similar data. Clustering can be of mathematical, statistical or numerical domain. Clustering is a fundamental data analysi...

  16. The Impact of Seawater Saturation State on Early Skeletal Development in Larval Corals: Insights into Scleractinian Biomineralization

    Science.gov (United States)

    Cohen, A. L.; McCorkle, D. C.; de Putron, S.

    2007-12-01

    Understanding the response of coral calcification to changes in seawater saturation state (ocean acidification) could provide important insights into the fundamental processes of scleractinian biomineralization. In particular, larval calcification, which involves initiation of skeletogenesis by a previously non-calcifying planktonic planula, offers a unique opportunity to examine the role and limitations of biological control over an essentially physicochemical process. Larvae of the brooding Atlantic coral Favia fragum were settled in unmodified seawater onto clay tiles within 12h of spawning, and placed into non-through flow 30 L aquaria prior to initiation of calcification. Seawater chemistry was pre-adjusted via HCl addition and continuous bubbling with laboratory air, yielding four aragonite saturation states: Omega(aragonite) = 3.71 (unmodified), 2.4, 1.04, and 0.22. The aquaria were held at 25 °C on a 12h/12h light/dark cycle, and sets of tiles harvested at 1, 5 and 8 days post-spawning. Accretion of aragonite (confirmed by Raman spectroscopy) in all treatments indicates that the settled larvae were able to elevate the saturation state of aquarium seawater sequestered within their calcifying space. However, external aqueous carbonate chemistry had a striking effect on larval mortality, on the nature and timing of basal plate formation, on skeletal growth rates (based on the length and cross-sectional area of septa), and on the structure and organization of aragonite crystals within the septa (imaged using SEM). Larval survival rates at the two lower saturation states was only 40% of that in the control and Omega = 2.35 treatments, and skeletal growth decreased by 30 % (relative to the control) in seawater with saturation state comparable to that predicted for the mid-latitude surface ocean by 2100 AD. SEM imaging of the larval skeletons revealed significant differences in the morphology of aragonite crystals accreted under different conditions. In stark

  17. Can stable isotope fractionation in diatom and coccolith biominerals elucidate the significance of carbon concentrating mechanisms (CCMs) in the past?

    Science.gov (United States)

    Stoll, H.; Bolton, C.; Isensee, K.; Mendez-Vicente, A.; Rubio-Ramos, M.; Mejia-Ramirez, L. M.

    2012-04-01

    Carbon isotopic fractionation in fossil algal biomarkers is typically interpreted to reflect atmospheric CO2 changes assuming simple diffusive uptake of CO2 by cells, however modern algae employ a diverse array of additional strategies to concentrate DIC inside the cell (CCMs). We previously hypothesized that the size-correlated range of vital effects in carbonate liths produced by different coccolithophore species was due to variable significance of CCMs in their C acquisition, and that an absence of interspecific vital effects may reflect a reduced importance of CCMs (or more similar CCMs employed). Here, we present stable isotope data from size-separated deep-sea sediments dominated by small, intermediate and large coccoliths from time slices throughout the Cenozoic. We show that the range of coccolith vital effects is distinct during several major Cenozoic proxy-inferred climate-CO2 transitions, and where vital effects are significant their magnitude scales with cell size in the same sense as modern culture genera (increasing C and O isotope enrichment with decreasing coccolith size). Our new culture experiments with coccolithophorids reveal strong plasticity in the magnitude of stable carbon isotope vital effects in coccoliths of Calcidiscus leptoporus and Emiliania huxleyi with variable CO2. At high CO2 coccoliths of both species are more isotopically enriched, but the magnitude is greater in C. leptoporus leading to reduced interspecific offsets at high CO2. In the case of E. huxleyi, higher CO2 conditions resulted in significant reduction in the magnitude of DIC accumulation in the intracellular carbon pool, and more positive carbon isotopic values inside the particulate organic matter. A model of carbon acquisition incorporating both photosynthetic and carbonate production is used to explore mechanisms for these relationships. We also investigate fractionation in diatom organic matter and diatom biomineral-bound organic matter. While the carbon isotopic

  18. STIMULATED PLATELETS RELEASE AMYLOID β–PROTEIN PRECURSOR

    OpenAIRE

    Cole, Gregory M.; Galasko, Douglas; Shapiro, I. Paul; Saitoh, Tsunao

    1990-01-01

    Human platelets can be stimulated by thrombin or ionomycin to secrete soluble truncated amyloid β–protein precursor and particulate membrane fragments which contain C-terminal and N-terminal immunoreactive amyloid β–protein precursor. This suggests a possible circulating source of β–protein in serum which may play a role in the formation of amyloid deposits. The release of soluble amyloid β-protein precursor could be involved in normal platelet physiology.

  19. AN EVALUATION OF STRENGTHENING PRECURSORS TO INCREASE PRESCHOOLER COMPLIANCE

    OpenAIRE

    Kraus, Aaron J; Hanley, Gregory P; Cesana, Lori L; Eisenberg, Danielle; Jarvie, Adam C

    2012-01-01

    We evaluated the strategy of increasing precursors to compliance on the compliance of 2 preschool boys. Modeling and differential reinforcement were used to increase specific responses to his name being called prior to the opportunity to comply with an instruction. The precursors were stopping the ongoing activity and orienting to, making eye contact with, and saying “yes” to the instructor. High levels of precursors occurred during treatment, and increases in compliance also were observed, e...

  20. Agricultural Clusters in the Netherlands

    NARCIS (Netherlands)

    Schouten, M.A.; Heijman, W.J.M.

    2012-01-01

    Michael Porter was the first to use the term cluster in an economic context. He introduced the term in The Competitive Advantage of Nations (1990). The term cluster is also known as business cluster, industry cluster, competitive cluster or Porterian cluster. This article aims at determining and mea

  1. DSC Study on the Polyacrylonitrile Precursors for Carbon Fibers

    Institute of Scientific and Technical Information of China (English)

    Wangxi ZHANG; Musen LI

    2005-01-01

    Different polyacrylonitrile (PAN) precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry (DSC). Results showed that some commercial PAN precursor fibers displayed double separated peaks and these fibers were of high quality because of their process stability during their conversion to carbon fibers of high performance. Some fabrication processes, such as spinning, drawing, could not apparently change the DSC features of a PAN precursor fiber. It was concluded that the thermal properties of a PAN precursor fiber was mainly determined from its comonomer content type and compositions.

  2. Identification and structural analysis of a novel snoRNA gene cluster from Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    周惠; 孟清; 屈良鹄

    2000-01-01

    A 22 snoRNA gene cluster, consisting of four antisense snoRNA genes, was identified from Arabidopsis thaliana. The sequence and structural analysis showed that the 22 snoRNA gene cluster might be transcribed as a polycistronic precursor from an upstream promoter, and the in-tergenic spacers of the gene cluster encode the ’hairpin’ structures similar to the processing recognition signals of yeast Saccharomyces cerevisiae polycistronic snoRNA precursor. The results also revealed that plant snoRNA gene with multiple copies is a characteristic in common, and provides a good system for further revealing the transcription and expression mechanism of plant snoRNA gene cluster.

  3. A putative greigite-type magnetosome gene cluster from the candidate phylum Latescibacteria.

    Science.gov (United States)

    Lin, Wei; Pan, Yongxin

    2015-04-01

    The intracellular biomineralization of magnetite and/or greigite magnetosomes in magnetotactic bacteria (MTB) is strictly controlled by a group of conserved genes, termed magnetosome genes, which are organized as clusters (or islands) in MTB genomes. So far, all reported MTB are affiliated within the Proteobacteria phylum, the Nitrospirae phylum and the candidate division OP3. Here, we report the discovery of a putative magnetosome gene cluster structure from the draft genome of an uncultivated bacterium belonging to the candidate phylum Latescibacteria (formerly candidate division WS3) recently recovered by Rinke and colleagues, which contains 10 genes with homology to magnetosome mam genes of magnetotactic Proteobacteria and Nitrospirae. Moreover, these genes are phylogenetically closely related to greigite-type magnetosome genes that were only found from the Deltaproteobacteria MTB before, suggesting that the greigite genes may originate earlier than previously imagined. These findings indicate that some members of Latescibacteria may be capable of forming greigite magnetosomes, and thus may play previously unrecognized roles in environmental iron and sulfur cycles. The conserved genomic structure of magnetosome gene cluster in Latescibacteria phylum supports the hypothesis of horizontal transfer of these genes among distantly related bacterial groups in nature. PMID:25382584

  4. Clustering Categorical Data:A Cluster Ensemble Approach

    Institute of Scientific and Technical Information of China (English)

    He Zengyou(何增友); Xu Xiaofei; Deng Shengchun

    2003-01-01

    Clustering categorical data, an integral part of data mining,has attracted much attention recently. In this paper, the authors formally define the categorical data clustering problem as an optimization problem from the viewpoint of cluster ensemble, and apply cluster ensemble approach for clustering categorical data. Experimental results on real datasets show that better clustering accuracy can be obtained by comparing with existing categorical data clustering algorithms.

  5. Spatial Scan Statistic: Selecting clusters and generating elliptic clusters

    DEFF Research Database (Denmark)

    Christiansen, Lasse Engbo; Andersen, Jens Strodl

    2004-01-01

    The spatial scan statistic is widely used to search for clusters. This paper shows that the usually applied elimination of overlapping clusters to find secondary clusters is sensitive to smooth changes in the shape of the clusters. We present an algorithm for generation of set of confocal elliptic...... clusters. In addition, we propose a new way to present the information in a given set of clusters based on the significance of the clusters....

  6. Cosmology with cluster surveys

    Indian Academy of Sciences (India)

    Subhabrata Majumdar

    2004-10-01

    Surveys of clusters of galaxies provide us with a powerful probe of the density and nature of the dark energy. The red-shift distribution of detected clusters is highly sensitive to the dark energy equation of state parameter . Upcoming Sunyaev–Zel'dovich (SZ) surveys would provide us large yields of clusters to very high red-shifts. Self-calibration of cluster scaling relations, possible for such a huge sample, would be able to constrain systematic biases on mass estimators. Combining cluster red-shift abundance with limited mass follow-up and cluster mass power spectrum can then give constraints on , as well as on 8 and to a few per cents.

  7. CSR in Industrial Clusters

    DEFF Research Database (Denmark)

    Lund-Thomsen, Peter; Pillay, Renginee G.

    2012-01-01

    Purpose – The paper seeks to review the literature on CSR in industrial clusters in developing countries, identifying the main strengths, weaknesses, and gaps in this literature, pointing to future research directions and policy implications in the area of CSR and industrial cluster development...... in this field and their comments incorporated in the final version submitted to Corporate Governance. Findings – The article traces the origins of the debate on industrial clusters and CSR in developing countries back to the early 1990s when clusters began to be seen as an important vehicle for local economic...... development in the South. At the turn of the millennium the industrial cluster debate expanded as clusters were perceived as a potential source of poverty reduction, while their role in promoting CSR among small and medium-sized enterprises began to take shape from 2006 onwards. At present, there is still...

  8. Melting of sodium clusters

    CERN Document Server

    Reyes-Nava, J A; Beltran, M R; Michaelian, K

    2002-01-01

    Thermal stability properties and the melting-like transition of Na_n, n=13-147, clusters are studied through microcanonical molecular dynamics simulations. The metallic bonding in the sodium clusters is mimicked by a many-body Gupta potential based on the second moment approximation of a tight-binding Hamiltonian. The characteristics of the solid-to-liquid transition in the sodium clusters are analyzed by calculating physical quantities like caloric curves, heat capacities, and root-mean-square bond length fluctuations using simulation times of several nanoseconds. Distinct melting mechanisms are obtained for the sodium clusters in the size range investigated. The calculated melting temperatures show an irregular variation with the cluster size, in qualitative agreement with recent experimental results. However, the calculated melting point for the Na_55 cluster is about 40 % lower than the experimental value.

  9. Structures in Galaxy Clusters

    CERN Document Server

    Escalera, E; Girardi, M; Giuricin, G; Mardirossian, F; Mazure, A; Mezzetti, M

    1993-01-01

    The analysis of the presence of substructures in 16 well-sampled clusters of galaxies suggests a stimulating hypothesis: Clusters could be classified as unimodal or bimodal, on the basis of to the sub-clump distribution in the {\\em 3-D} space of positions and velocities. The dynamic study of these clusters shows that their fundamental characteristics, in particular the virial masses, are not severely biased by the presence of subclustering if the system considered is bound.

  10. Cluster Symmetries and Dynamics

    Directory of Open Access Journals (Sweden)

    Freer Martin

    2016-01-01

    Full Text Available Many light nuclei display behaviour that indicates that rather than behaving as an A-body systems, the protons and neutrons condense into clusters. The α-particle is the most obvious example of such clustering. This contribution examines the role of such α-clustering on the structure, symmetries and dynamics of the nuclei 8Be, 12C and 16O, recent experimental measurements and future perspectives.

  11. Clustering Techniques in Bioinformatics

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Masood

    2015-01-01

    Full Text Available Dealing with data means to group information into a set of categories either in order to learn new artifacts or understand new domains. For this purpose researchers have always looked for the hidden patterns in data that can be defined and compared with other known notions based on the similarity or dissimilarity of their attributes according to well-defined rules. Data mining, having the tools of data classification and data clustering, is one of the most powerful techniques to deal with data in such a manner that it can help researchers identify the required information. As a step forward to address this challenge, experts have utilized clustering techniques as a mean of exploring hidden structure and patterns in underlying data. Improved stability, robustness and accuracy of unsupervised data classification in many fields including pattern recognition, machine learning, information retrieval, image analysis and bioinformatics, clustering has proven itself as a reliable tool. To identify the clusters in datasets algorithm are utilized to partition data set into several groups based on the similarity within a group. There is no specific clustering algorithm, but various algorithms are utilized based on domain of data that constitutes a cluster and the level of efficiency required. Clustering techniques are categorized based upon different approaches. This paper is a survey of few clustering techniques out of many in data mining. For the purpose five of the most common clustering techniques out of many have been discussed. The clustering techniques which have been surveyed are: K-medoids, K-means, Fuzzy C-means, Density-Based Spatial Clustering of Applications with Noise (DBSCAN and Self-Organizing Map (SOM clustering.

  12. 15th Cluster workshop

    CERN Document Server

    Laakso, Harri; Escoubet, C. Philippe; The Cluster Active Archive : Studying the Earth’s Space Plasma Environment

    2010-01-01

    Since the year 2000 the ESA Cluster mission has been investigating the small-scale structures and processes of the Earth's plasma environment, such as those involved in the interaction between the solar wind and the magnetospheric plasma, in global magnetotail dynamics, in cross-tail currents, and in the formation and dynamics of the neutral line and of plasmoids. This book contains presentations made at the 15th Cluster workshop held in March 2008. It also presents several articles about the Cluster Active Archive and its datasets, a few overview papers on the Cluster mission, and articles reporting on scientific findings on the solar wind, the magnetosheath, the magnetopause and the magnetotail.

  13. Galaxy Clusters with Chandra

    CERN Document Server

    Forman, W; Markevitch, M L; Vikhlinin, A A; Churazov, E

    2002-01-01

    We discuss Chandra results related to 1) cluster mergers and cold fronts and 2) interactions between relativistic plasma and hot cluster atmospheres. We describe the properties of cold fronts using NGC1404 in the Fornax cluster and A3667 as examples. We discuss multiple surface brightness discontinuities in the cooling flow cluster ZW3146. We review the supersonic merger underway in CL0657. Finally, we summarize the interaction between plasma bubbles produced by AGN and hot gas using M87 and NGC507 as examples.

  14. Management of cluster headache.

    Science.gov (United States)

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-07-01

    The prevalence of cluster headache is 0.1% and cluster headache is often not diagnosed or misdiagnosed as migraine or sinusitis. In cluster headache there is often a considerable diagnostic delay - an average of 7 years in a population-based survey. Cluster headache is characterized by very severe or severe orbital or periorbital pain with a duration of 15-180 minutes. The cluster headache attacks are accompanied by characteristic associated unilateral symptoms such as tearing, nasal congestion and/or rhinorrhoea, eyelid oedema, miosis and/or ptosis. In addition, there is a sense of restlessness and agitation. Patients may have up to eight attacks per day. Episodic cluster headache (ECH) occurs in clusters of weeks to months duration, whereas chronic cluster headache (CCH) attacks occur for more than 1 year without remissions. Management of cluster headache is divided into acute attack treatment and prophylactic treatment. In ECH and CCH the attacks can be treated with oxygen (12 L/min) or subcutaneous sumatriptan 6 mg. For both oxygen and sumatriptan there are two randomized, placebo-controlled trials demonstrating efficacy. In both ECH and CCH, verapamil is the prophylactic drug of choice. Verapamil 360 mg/day was found to be superior to placebo in one clinical trial. In clinical practice, daily doses of 480-720 mg are mostly used. Thus, the dose of verapamil used in cluster headache treatment may be double the dose used in cardiology, and with the higher doses the PR interval should be checked with an ECG. At the start of a cluster, transitional preventive treatment such as corticosteroids or greater occipital nerve blockade can be given. In CCH and in long-standing clusters of ECH, lithium, methysergide, topiramate, valproic acid and ergotamine tartrate can be used as add-on prophylactic treatment. In drug-resistant CCH, neuromodulation with either occipital nerve stimulation or deep brain stimulation of the hypothalamus is an alternative treatment strategy

  15. Evolution of microstructure in mixed niobia-hybrid silica thin films from sol-gel precursors.

    Science.gov (United States)

    Besselink, Rogier; Stawski, Tomasz M; Castricum, Hessel L; ten Elshof, Johan E

    2013-08-15

    The evolution of structure in sol-gel derived mixed bridged silsesquioxane-niobium alkoxide sols and drying thin films was monitored in situ by small-angle X-ray scattering. Since sol-gel condensation of metal alkoxides proceeds much faster than that of silicon alkoxides, the incorporation of d-block metal dopants into silica typically leads to formation of densely packed nano-sized metal oxide clusters that we refer as metal oxide building blocks in a silica-based matrix. SAXS was used to study the process of niobia building block formation while drying the sol as a thin film at 40-80°C. The SAXS curves of mixed niobia-hybrid silica sols were dominated by the electron density contrast between sol particles and surrounding solvent. As the solvent evaporated and the sol particles approached each other, a correlation peak emerged. Since TEM microscopy revealed the absence of mesopores, the correlation peak was caused by a heterogeneous system of electron-rich regions and electron poor regions. The regions were assigned to small clusters that are rich in niobium and which are dispersed in a matrix that mainly consisted of hybrid silica. The correlation peak was associated with the typical distances between the electron dense clusters and corresponded with distances in real space of 1-3 nm. A relationship between the prehydrolysis time of the silica precursor and the size of the niobia building blocks was observed. When 1,2-bis(triethoxysilyl)ethane was first hydrolyzed for 30 min before adding niobium penta-ethoxide, the niobia building blocks reached a radius of 0.4 nm. Simultaneous hydrolysis of the two precursors resulted in somewhat larger average building block radii of 0.5-0.6 nm. This study shows that acid-catalyzed sol-gel polymerization of mixed hybrid silica niobium alkoxides can be rationalized and optimized by monitoring the structural evolution using time-resolved SAXS.

  16. The electromagnetic Brillouin precursor in one-dimensional photonic crystals

    NARCIS (Netherlands)

    Uitham, R.; Hoenders, B. J.

    2008-01-01

    We have calculated the electromagnetic Brillouin precursor that arises in a one-dimensional photonic crystal that consists of two homogeneous slabs which each have a single electron resonance. This forerunner is compared with the Brillouin precursor that arises in a homogeneous double-electron reson

  17. Geometrizing configurations. Heinrich Hertz and his mathematical precursors

    DEFF Research Database (Denmark)

    Lützen, Jesper

    1999-01-01

    A comparison between the methods used by Heinrich hertz and his mathematician precursors such as Liouville, Lipschitz and Darboux in order to apply differential geometry in mechanics......A comparison between the methods used by Heinrich hertz and his mathematician precursors such as Liouville, Lipschitz and Darboux in order to apply differential geometry in mechanics...

  18. Effects of rhythmic precursors on perception of stress/syllabicity

    Science.gov (United States)

    Stilp, Christian E.; Kluender, Keith R.

    2005-09-01

    Rhythmic structure is a common property of many environmental sounds including speech. Here, perceptual effects of preceding rhythmic context are assessed in experiments employing edited words for which perceived stress/syllabicity are assessed. A series of edited naturally spoken words varying perceptually from ``polite'' to ``plight,'' was created by deleting initial-vowel glottal pulses from a recording of ``polite.'' Words were identified following nonspeech precursor sequences having either trochaic (strong-weak) or iambic (weak-strong) rhythmic patterns. Precursors consisted of a harmonic spectrum (-6-dB/octave slope) filtered by four sinusoidally modulated single-pole filters. Trochaic (strong-weak) and iambic (weak-strong) rhythmic patterns were created by varying amplitude, pitch, and duration in successive segments (akin to beats) of the precursors. Precursors were comprised of two to six repetitions of these patterns. Following trochaic precursors, listeners were more likely to report hearing ``polite'' (iambic). This pattern of results indicates that perception did not assimilate to precursor pattern, consistent with rhythmic expectancy. Instead, perception shifted in a way that contrasts with precursor temporal pattern. Additional results with precursors that are more and less like speech are being conducted to further understand how auditory perception adjusts for temporal and spectral regularities. [Work supported by NIDCD.

  19. Topographical and Functional Properties of Precursors to Severe Problem Behavior

    Science.gov (United States)

    Fahmie, Tara A.; Iwata, Brian A.

    2011-01-01

    A literature search identified 17 articles reporting data on 34 subjects who engaged in precursors to severe problem behavior, which we examined to identify topographical and functional characteristics. Unintelligible vocalization was the most common precursor to aggression (27%) and property destruction (29%), whereas self- or nondirected…

  20. Precursors to Aggression Are Evident by 6 Months of Age

    Science.gov (United States)

    Hay, Dale F.; Waters, Cerith S.; Perra, Oliver; Swift, Naomi; Kairis, Victoria; Phillips, Rebecca; Jones, Roland; Goodyer, Ian; Harold, Gordon; Thapar, Anita; van Goozen, Stephanie

    2014-01-01

    We tested the hypothesis that developmental precursors to aggression are apparent in infancy. Up to three informants rated 301 firstborn infants for early signs of anger, hitting and biting; 279 (93%) were assessed again as toddlers. Informants' ratings were validated by direct observation at both ages. The precursor behaviours were…

  1. An Evaluation of Strengthening Precursors to Increase Preschooler Compliance

    Science.gov (United States)

    Kraus, Aaron J.; Hanley, Gregory P.; Cesana, Lori L.; Eisenberg, Danielle; Jarvie, Adam C.

    2012-01-01

    We evaluated the strategy of increasing precursors to compliance on the compliance of 2 preschool boys. Modeling and differential reinforcement were used to increase specific responses to his name being called prior to the opportunity to comply with an instruction. The precursors were stopping the ongoing activity and orienting to, making eye…

  2. Pair fireball precursors of neutron star mergers

    Science.gov (United States)

    Metzger, Brian D.; Zivancev, Charles

    2016-10-01

    If at least one neutron star (NS) is magnetized in a binary NS merger, then the orbital motion of the conducting companion during the final inspiral induces a strong voltage and current along the magnetic field lines connecting the NSs. If a modest fraction η of the extracted electromagnetic power extracted accelerates relativistic particles, the resulting gamma-ray emission a compact volume will result in the formation of an electron-positron pair fireball. Applying a steady-state pair wind model, we quantify the detectability of the precursor fireball with gamma-ray satellites. For η ˜ 1 the gamma-ray detection horizon of Dmax ≈ 10(Bd/1014 G)3/4 Mpc is much closer than the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo horizon of 200 Mpc, unless the NS surface magnetic field strength is very large, B_d ≲ 10^{15} G. Given the quasi-isotropic nature of the emission, mergers with weaker NS fields could contribute a nearby population of short gamma-ray bursts. Power not dissipated close to the binary is carried to infinity along the open field lines by a large-scale Poynting flux. Reconnection within this outflow, well outside of the pair photosphere, provides a potential site for non-thermal emission, such as a coherent millisecond radio burst.

  3. Identification, Selection, and Enrichment of Cardiomyocyte Precursors

    Directory of Open Access Journals (Sweden)

    Bianca Ferrarini Zanetti

    2013-01-01

    Full Text Available The large-scale production of cardiomyocytes is a key step in the development of cell therapy and tissue engineering to treat cardiovascular diseases, particularly those caused by ischemia. The main objective of this study was to establish a procedure for the efficient production of cardiomyocytes by reprogramming mesenchymal stem cells from adipose tissue. First, lentiviral vectors expressing neoR and GFP under the control of promoters expressed specifically during cardiomyogenesis were constructed to monitor cell reprogramming into precardiomyocytes and to select cells for amplification and characterization. Cellular reprogramming was performed using 5′-azacytidine followed by electroporation with plasmid pOKS2a, which expressed Oct4, Sox2, and Klf4. Under these conditions, GFP expression began only after transfection with pOKS2a, and less than 0.015% of cells were GFP+. These GFP+ cells were selected for G418 resistance to find molecular markers of cardiomyocytes by RT-PCR and immunocytochemistry. Both genetic and protein markers of cardiomyocytes were present in the selected cells, with some variations among them. Cell doubling time did not change after selection. Together, these results indicate that enrichment with vectors expressing GFP and neoR under cardiomyocyte-specific promoters can produce large numbers of cardiomyocyte precursors (CMPs, which can then be differentiated terminally for cell therapy and tissue engineering.

  4. Formation of biomolecule precursors in space

    Energy Technology Data Exchange (ETDEWEB)

    Geppert, W D [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Vigren, E [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Hamberg, M [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Zhaunerchyk, V [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Thomas, R D [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Kaminska, M [Institute of Physics, Swieetokrzyska Academy, ul. Swieokrzyska 15, PL-25406, Kielce (Poland); Millar, T J [Astrophysics Research Centre, Queen' s University Belfast, BT7 1NN, Belfast, Northern Ireland (United Kingdom); Semaniak, J [Institute of Physics, Swieetokrzyska Academy, ul. Swieokrzyska 15, PL-25406, Kielce (Poland); Roberts, H [Astrophysics Research Centre, Queen' s University Belfast, BT7 1NN, Belfast, Northern Ireland (United Kingdom); Hellberg, F [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Oesterdahl, F [Department of Physics, Royal Institute of Technology, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Ehlerding, A [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden); Larsson, M [Department of Physics, Stockholm University, Alba Nova, Roslagstullbacken 21, SE-10691, Stockholm (Sweden)

    2007-11-15

    Alcohols and nitriles not only play an important role as templates for synthesis of larger molecules in the interstellar medium and planetary atmospheres, but they can also be regarded as precursors for biomolecules. Alcohols can form carbohydrates through reaction with HCO and nitriles can be hydrolysed to amino acids in aqueous solutions, which is the final step of the well-known Strecker synthesis. Therefore the question of the pathways of formation of alcohols and nitriles and the efficiency and the product distribution of their subsequent degradation reactions in the above-mentioned astrophysical environments is of great interest. In both processes dissociative recombination reactions of protonated nitriles and alcohols may play a major role and are included in models of interstellar clouds and planetary atmospheres. However, the reaction rate coefficients and product branching ratios for the majority of these processes are so far still unknown, which adversely affects the quality of predictions of model calculations. In this Contribution, we therefore present branching ratios and rate constants of the dissociative recombination of protonated methanol (CH{sub 3}OH{sub 2}), as well as protonated acetonitrile (CH{sub 3}CNH{sup +}), acrylonitrile (C{sub 2}H{sub 3}CNH{sup +}) and cyanoacetylene (HC{sup 3}NH{sup +}). The impact of the obtained new data on model calculations of abundances of important interstellar molecules in dark clouds is discussed.

  5. Pair Fireball Precursors of Neutron Star Mergers

    CERN Document Server

    Metzger, Brian D

    2016-01-01

    If at least one neutron star (NS) is magnetized in a binary NS merger, then the orbital motion of the conducting companion through its dipole field during the final inspiral induces a strong voltage and current along the magnetic field lines connecting the two objects. If a modest fraction eta of the electromagnetic power extracted during the inspiral is used to accelerate relativistic particles, the resulting gamma-ray emission in such a compact volume will result in the formation of a thermal electron-positron pair fireball. Applying the steady-state pair wind model of Paczynski (1986), we quantify the luminosities and temperatures of the precursor fireball and its detectability with gamma-ray satellites. Under the assumption that eta ~ 1, the gamma-ray detection horizon of Dmax ~ 20(Bd/1e14 G) is much closer than the Advanced LIGO/Virgo horizon of 200 Mpc, unless the surface magnetic field of the NS is very strong, Bd > 1e15 G. Given the quasi-isotropic nature of the emission, a sub-population of mergers w...

  6. Proinsulin: from hormonal precursor to neuroprotective factor

    Directory of Open Access Journals (Sweden)

    Flora eDe Pablo

    2011-09-01

    Full Text Available In the last decade, non-canonical functions have been described for several molecules with hormone-like activities in different stages of vertebrate development. Since its purification in the 1960s, proinsulin has been one of the best described hormonal precursors, though it has been overwhelmingly studied in the context of insulin, the mature protein secreted by the pancreas. Beginning with our discovery of the presence and precise regulation of proinsulin mRNA in early neurulation and neurogenesis, we uncovered a role for proinsulin in cell survival in the developing nervous system. We subsequently demonstrated the ability of proinsulin to prevent pathological cell death and delay photoreceptor degeneration in a mouse model of retinitis pigmentosa. In this review, we focus on the evolution of proinsulin/insulin, beginning with insulin-like peptides expressed in mainly the neurosecretory cells of some invertebrates. We summarize findings related to the regulation of proinsulin expression during development and discuss the possible effects of proinsulin in neural cells or tissue, and its potential as a neuroprotective molecule.

  7. Precursors to Interstellar Shocks of Solar Origin

    Science.gov (United States)

    Gurnett, D. A.; Kurth, W. S.; Stone, E. C.; Cummings, A. C.; Krimigis, S. M.; Decker, R. B.; Ness, N. F.; Burlaga, L. F.

    2015-12-01

    On or about 2012 August 25, the Voyager 1 spacecraft crossed the heliopause into the nearby interstellar plasma. In the nearly three years that the spacecraft has been in interstellar space, three notable particle and field disturbances have been observed, each apparently associated with a shock wave propagating outward from the Sun. Here, we present a detailed analysis of the third and most impressive of these disturbances, with brief comparisons to the two previous events, both of which have been previously reported. The shock responsible for the third event was first detected on 2014 February 17 by the onset of narrowband radio emissions from the approaching shock, followed on 2014 May 13 by the abrupt appearance of intense electron plasma oscillations generated by electrons streaming outward ahead of the shock. Finally, the shock arrived on 2014 August 25, as indicated by a jump in the magnetic field strength and the plasma density. Various disturbances in the intensity and anisotropy of galactic cosmic rays were also observed ahead of the shock, some of which are believed to be caused by the reflection and acceleration of cosmic rays by the magnetic field jump at the shock, and/or by interactions with upstream plasma waves. Comparisons to the two previous weaker events show somewhat similar precursor effects, although differing in certain details. Many of these effects are very similar to those observed in the region called the "foreshock" that occurs upstream of planetary bow shocks, only on a vastly larger spatial scale.

  8. Bone formation on synthetic precursors of hydroxyapatite.

    Science.gov (United States)

    Suzuki, O; Nakamura, M; Miyasaka, Y; Kagayama, M; Sakurai, M

    1991-05-01

    The aim of this study was to investigate the reaction of skeletal tissue to various synthetic calcium phosphate (Ca-P) compounds in vivo. Five synthetic Ca-P compounds were implanted into the subperiosteal area of the calvaria of 7-week-old BALB/c mice for one to 15 weeks. Synthetic compounds were dicalcium phosphate (DCP), octacalcium phosphate (OCP), amorphous calcium phosphate (ACP), Ca-deficient hydroxyapatite and hydroxyapatile (HA). Implanted DCP, OCP and ACP were found to be converted to apatitic phase by x-ray microdiffraction analysis using undecalcified specimens. Structure of bone was found out on all of Ca-P compounds eventually at late stage under the light microscope, but the rate of bone formation calculated from a number of experiments varied on respective synthetic Ca-P compound. It was high as 80% for DCP, OCP and ACP, but was low as 5.6% for Ca-deficient HA, and no reaction was found for HA at the stage of 3 weeks. Fine filaments and granular materials in the newly formed bone matrix were detected at 7 days around the remnants of OCP particles which already converted to apatitic phase by ultrastructural study of decalcified specimens. These structures were very similar to the components of bone nodules seen in intramembranous osteogenesis. It is postulated that the precursors of HA have an important role in intramembranous osteogenesis.

  9. Enzymatic synthesis of vitamin B6 precursor

    Directory of Open Access Journals (Sweden)

    Prlainović Nevena Ž.

    2013-01-01

    Full Text Available 3-Cyano-4-ethoxymethyl-6-methyl-2-pyridone is an important precursor in the synthesis of vitamin B6, obtained in the addition reaction between 2-cyanoacetamide and 1-ethoxy-2,4-pentanedione catalyzed by lipase from Candida rugosa (triacylglycerol ester hydrolases, EC 3.1.1.3. This work shows new experimental data and mathematical modeling of lipase catalyzed synthesis of 3-cyano-4-ethoxymethyl-6-methyl-2-pyridone, starting from 1-ethoxy-2,4-pentanedione and 2-cyanoacetamide. Kinetic measurements were done at 50 oC with enzyme concentration of 1.2 % w/v. Experimental results were fitted with two kinetic models: the ordered bi-ter and ping-pong bi-ter model, and the initial rates of the reaction were found to correlate best with a ping-pong bi-ter mechanism with inhibition by 2-cyanoacetamide. Obtained specificity constants indicated that lipase from C. rugosa had higher affinity towards 1-ethoxy-2,4-pentanedione and less bulky substrates. [Projekat Ministarstva nauke Republike Srbije, br. 172013, br. III 46010 and br. 172049

  10. Bacterial Cellular Materials as Precursors of Chloroform

    Science.gov (United States)

    Wang, J.; Ng, T.; Zhang, Q.; Chow, A. T.; Wong, P.

    2011-12-01

    The environmental sources of chloroform and other halocarbons have been intensively investigated because their effects of stratospheric ozone destruction and environmental toxicity. It has been demonstrated that microorganisms could facilitate the biotic generation of chloroform from natural organic matters in soil, but whether the cellular materials itself also serves as an important precursor due to photo-disinfection is poorly known. Herein, seven common pure bacterial cultures (Acinetobacter junii, Aeromonas hydrophila, Bacillus cereus, Bacillus substilis, Escherichia coli, Shigella sonnei, Staphylococcus sciuri) were chlorinated to evaluate the yields of chloroform, dibromochloromethane, dichlorobromomethane, and bromoform. The effects of bromide on these chemical productions and speciations were also investigated. Results showed that, on average, 5.64-36.42 μg-chloroform /mg-C were generated during the bacterial chlorination, in similar order of magnitude to that generated by humic acid (previously reported as 78 μg-chloroform/mg-C). However, unlike humic acid in water chlorination, chloroform concentration did not simply increase with the total organic carbon in water mixture. In the presence of bromide, the yield of brominated species responded linearly to the bromide concentration. This study provides useful information to understand the contributions of chloroform from photodisinfection processes in coastal environments.

  11. The Amyloid Precursor Protein Controls PIKfyve Function.

    Science.gov (United States)

    Balklava, Zita; Niehage, Christian; Currinn, Heather; Mellor, Laura; Guscott, Benjamin; Poulin, Gino; Hoflack, Bernard; Wassmer, Thomas

    2015-01-01

    While the Amyloid Precursor Protein (APP) plays a central role in Alzheimer's disease, its cellular function still remains largely unclear. It was our goal to establish APP function which will provide insights into APP's implication in Alzheimer's disease. Using our recently developed proteo-liposome assay we established the interactome of APP's intracellular domain (known as AICD), thereby identifying novel APP interactors that provide mechanistic insights into APP function. By combining biochemical, cell biological and genetic approaches we validated the functional significance of one of these novel interactors. Here we show that APP binds the PIKfyve complex, an essential kinase for the synthesis of the endosomal phosphoinositide phosphatidylinositol-3,5-bisphosphate. This signalling lipid plays a crucial role in endosomal homeostasis and receptor sorting. Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals. Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo. This regulation is required for maintaining endosomal and neuronal function. Our findings establish an unexpected role for APP in the regulation of endosomal phosphoinositide metabolism with dramatic consequences for endosomal biology and important implications for our understanding of Alzheimer's disease. PMID:26125944

  12. The Amyloid Precursor Protein Controls PIKfyve Function.

    Directory of Open Access Journals (Sweden)

    Zita Balklava

    Full Text Available While the Amyloid Precursor Protein (APP plays a central role in Alzheimer's disease, its cellular function still remains largely unclear. It was our goal to establish APP function which will provide insights into APP's implication in Alzheimer's disease. Using our recently developed proteo-liposome assay we established the interactome of APP's intracellular domain (known as AICD, thereby identifying novel APP interactors that provide mechanistic insights into APP function. By combining biochemical, cell biological and genetic approaches we validated the functional significance of one of these novel interactors. Here we show that APP binds the PIKfyve complex, an essential kinase for the synthesis of the endosomal phosphoinositide phosphatidylinositol-3,5-bisphosphate. This signalling lipid plays a crucial role in endosomal homeostasis and receptor sorting. Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals. Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo. This regulation is required for maintaining endosomal and neuronal function. Our findings establish an unexpected role for APP in the regulation of endosomal phosphoinositide metabolism with dramatic consequences for endosomal biology and important implications for our understanding of Alzheimer's disease.

  13. Document Clustering Based on Semi-Supervised Term Clustering

    Directory of Open Access Journals (Sweden)

    Hamid Mahmoodi

    2012-05-01

    Full Text Available The study is conducted to propose a multi-step feature (term selection process and in semi-supervised fashion, provide initial centers for term clusters. Then utilize the fuzzy c-means (FCM clustering algorithm for clustering terms. Finally assign each of documents to closest associated term clusters. While most text clustering algorithms directly use documents for clustering, we propose to first group the terms using FCM algorithm and then cluster documents based on terms clusters. We evaluate effectiveness of our technique on several standard text collections and compare our results with the some classical text clustering algorithms.

  14. Influence of titanium precursor on photoluminescent emission of micro-cube-shaped CaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mazzo, Tatiana Martelli, E-mail: tatimazzo@gmail.com [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Avenida Almameda Saldanha da Gama, 89, Ponta da Praia, CEP 11030-400 Santos, SP (Brazil); Santilli do Nascimento Libanori, Gabriela [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Avenida Almameda Saldanha da Gama, 89, Ponta da Praia, CEP 11030-400 Santos, SP (Brazil); Moreira, Mario Lucio [Instituto de Física e Matemática, Universidade Federal de Pelotas, P.O. Box 354, Campus do Capão do Leão, 96001-970 Pelotas, RS (Brazil); Avansi Jr, Waldir [Departamento de Física, Universidade Federal de São Carlos, Jardim Guanabara, 13565-905 São Carlos, SP (Brazil); Mastelaro, Valmor Roberto [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, Arnold Schimidt, 13566-590 São Carlos, SP (Brazil); Varela, José Arana; Longo, Elson [INCTMN/LIEC, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, R. Francisco Degni, 55, Bairro Quitandinha, 14801-907 Araraquara, SP (Brazil)

    2015-09-15

    For this research, we studied the influence of titanium tetrachloride (TC) and titanium tetraisopropoxide (TTP) precursors on CaTiO{sub 3} (CTO) synthesis by employing a microwave-assisted hydrothermal (MAH) method regarding their respective short-, medium- and long-range features to determine if the use of different titanium precursors enhances the structural evolution of the material. The growth mechanism for the formation of the micro-cube-shaped CTO is proposed to obtain nanoparticle aggregation of self-assembly nanoplates. The disorder coupled to the oxygen vacancies of [TiO{sub 5}]–[TiO{sub 6}] in complex clusters in the CTO 1 powder and twists in bonding between the [TiO{sub 6}]–[TiO{sub 6}] complex clusters in the CTO 2 powder were mainly responsible for photoluminescent (PL) emission. - Highlights: • Different titanium precursors enhance the structural evolution of the material. • [TiO{sub 5}]–[TiO{sub 6}] and twists in bonding [TiO{sub 6}]–[TiO{sub 6}] were responsible for PL emission. • Micro-cube shaped was formed by nanoparticle aggregation of self-assembly nanoplates.

  15. Calcium oxalate biomineralization in plants%植物体内草酸钙的生物矿化

    Institute of Scientific and Technical Information of China (English)

    李秀丽; 张文君; 鲁剑巍; 王荔军

    2012-01-01

    草酸钙晶体在特化的植物晶异细胞内的形成是一种基本的、重要的生理代谢过程.不同植物草酸钙晶体在形态/结构上存在多样性和种间专一性,它们具有特定的尺寸和形貌,并且成核后晶体的生长和特化细胞的发育间存在显著的协同作用,这表明草酸钙的生物合成不是一种简单的化学结晶过程,而是受遗传和生物大分子的精确调控.被塑造的矿化相在特定的膜包覆空间内经历了各自不同的生物化学途径,最终形成热力学稳定相.草酸钙晶体赋予植物许多不同的功能,主要包括对高容量钙的调节和植物自我保护作用,从而间接地反映出植物在不同生境中进化的印迹.本文介绍了草酸钙晶体在植物体内合成的草酸代谢途径、钙的吸收和累积,主要讨论晶体生长过程的植物调节机制以及体外模拟生物分子对草酸钙结晶动力学过程的调控等,以期揭示植物体内草酸钙的生物矿化机制,并为仿生材料合成和人类病理结石的抑制等提供重要线索.%Calium oxalate (CaOx) biomineralization with diverse and species-specific morphologies and structures formed in specialized cells (idioblast) is a basic and important process in many plant families. During their formation there exist the synergetic interactions between cell growth/expansion and crystal nucleation/growth, indicating that the mineralization process is precisely controlled by biomacromolecules through the exquisite bio-regulation mechanisms rather than a simple chemical precipitation reaction. The mineralized phases and the final mature products formed inside cells are shaped and thermodynamically stabilized by various biomacromolecules expressed and synthesized in corresponding bio-pathways. CaOx crystals in plants fulfill a variety of crucial functions, including the high-capacity calcium regulation and self-protection of plants against herbivory by large animals as well as insects

  16. Unraveling Molecular Mechanisms for the Unusual Fossil Preservation and Biomineralization Pathways in Tlayúa, the Mexican Solenhofen

    Science.gov (United States)

    Cervini-Silva, J.; Fakra, S.; Alvarado-Ortega, J.; Cornejo-Garrido, H.; Marcus, M.; Hao, Z.; Espinosa-Arruberena, L.; Banfield, J.

    2007-12-01

    lagoon when the barrier was breached, probably during periods of heavy rains and hurricanes, or during high tides. Additionally, some fishes from Tlayua have been found to have affinities with recent families known to inhabit brackish and freshwater environments. Some of these fish preserve gut contents. Preliminary analysis of the intestinal content of these fishes has resulted in identification of freshwater insects and fern fragments. This work addresses for the first time the study of chemical and biological mechanisms contributing to fossil preservation and biomineralization pathways prevailing in Tlayúa using synchrotron techniques (XRF, - XRD, 3D--IR, XANES/EXAFS, STxM). We present chemical composition data collected from a fish egg's interior in search of fossilized structures. We also present data from well-preserved soft tissue collected from a fish soon to be named Michin scernai (newly identified specie, thus the name cannot be applied formally just yet). This fish is a Pachyrhizodontide, from the telesteos incertae sedis group already extinct. This particular sample was collected from the gastric cavity, precisely where female fish store the eggs before laying.

  17. From collisions to clusters

    DEFF Research Database (Denmark)

    Loukonen, Ville; Bork, Nicolai; Vehkamaki, Hanna

    2014-01-01

    to overcome the possible initial non-optimal collision orientations. No post-collisional cluster break up is observed. The reasons for the efficient clustering are (i) the proton transfer reaction which takes place in each of the collision simulations and (ii) the subsequent competition over the proton...

  18. Cost-Effective Clustering

    CERN Document Server

    Gottlieb, S

    2001-01-01

    Small Beowulf clusters can effectively serve as personal or group supercomputers. In such an environment, a cluster can be optimally designed for a specific problem (or a small set of codes). We discuss how theoretical analysis of the code and benchmarking on similar hardware lead to optimal systems.

  19. Coma cluster of galaxies

    Science.gov (United States)

    1999-01-01

    Atlas Image mosaic, covering 34' x 34' on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies (over 1000 members), most prominently the two giant ellipticals, NGC 4874 (right) and NGC 4889 (left). The remaining members are mostly smaller ellipticals, but spiral galaxies are also evident in the 2MASS image. The cluster is seen toward the constellation Coma Berenices, but is actually at a distance of about 100 Mpc (330 million light years, or a redshift of 0.023) from us. At this distance, the cluster is in what is known as the 'Hubble flow,' or the overall expansion of the Universe. As such, astronomers can measure the Hubble Constant, or the universal expansion rate, based on the distance to this cluster. Large, rich clusters, such as Coma, allow astronomers to measure the 'missing mass,' i.e., the matter in the cluster that we cannot see, since it gravitationally influences the motions of the member galaxies within the cluster. The near-infrared maps the overall luminous mass content of the member galaxies, since the light at these wavelengths is dominated by the more numerous older stellar populations. Galaxies, as seen by 2MASS, look fairly smooth and homogeneous, as can be seen from the Hubble 'tuning fork' diagram of near-infrared galaxy morphology. Image mosaic by S. Van Dyk (IPAC).

  20. Clustering Text Data Streams

    Institute of Scientific and Technical Information of China (English)

    Yu-Bao Liu; Jia-Rong Cai; Jian Yin; Ada Wai-Chee Fu

    2008-01-01

    Clustering text data streams is an important issue in data mining community and has a number of applications such as news group filtering, text crawling, document organization and topic detection and tracing etc. However, most methods are similarity-based approaches and only use the TF*IDF scheme to represent the semantics of text data and often lead to poor clustering quality. Recently, researchers argue that semantic smoothing model is more efficient than the existing TF.IDF scheme for improving text clustering quality. However, the existing semantic smoothing model is not suitable for dynamic text data context. In this paper, we extend the semantic smoothing model into text data streams context firstly. Based on the extended model, we then present two online clustering algorithms OCTS and OCTSM for the clustering of massive text data streams. In both algorithms, we also present a new cluster statistics structure named cluster profile which can capture the semantics of text data streams dynamically and at the same time speed up the clustering process. Some efficient implementations for our algorithms are also given. Finally, we present a series of experimental results illustrating the effectiveness of our technique.

  1. Brightest Cluster Galaxy Identification

    Science.gov (United States)

    Leisman, Luke; Haarsma, D. B.; Sebald, D. A.; ACCEPT Team

    2011-01-01

    Brightest cluster galaxies (BCGs) play an important role in several fields of astronomical research. The literature includes many different methods and criteria for identifying the BCG in the cluster, such as choosing the brightest galaxy, the galaxy nearest the X-ray peak, or the galaxy with the most extended profile. Here we examine a sample of 75 clusters from the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT) and the Sloan Digital Sky Survey (SDSS), measuring masked magnitudes and profiles for BCG candidates in each cluster. We first identified galaxies by hand; in 15% of clusters at least one team member selected a different galaxy than the others.We also applied 6 other identification methods to the ACCEPT sample; in 30% of clusters at least one of these methods selected a different galaxy than the other methods. We then developed an algorithm that weighs brightness, profile, and proximity to the X-ray peak and centroid. This algorithm incorporates the advantages of by-hand identification (weighing multiple properties) and automated selection (repeatable and consistent). The BCG population chosen by the algorithm is more uniform in its properties than populations selected by other methods, particularly in the relation between absolute magnitude (a proxy for galaxy mass) and average gas temperature (a proxy for cluster mass). This work supported by a Barry M. Goldwater Scholarship and a Sid Jansma Summer Research Fellowship.

  2. Blue emitting undecaplatinum clusters

    Science.gov (United States)

    Chakraborty, Indranath; Bhuin, Radha Gobinda; Bhat, Shridevi; Pradeep, T.

    2014-07-01

    A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents.A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents. Electronic supplementary information (ESI) available: Details of experimental procedures, instrumentation, chromatogram of the crude cluster; SEM/EDAX, DLS, PXRD, TEM, FT-IR, and XPS of the isolated Pt11 cluster; UV/Vis, MALDI MS and SEM/EDAX of isolated 2 and 3; and 195Pt NMR of the K2PtCl6 standard. See DOI: 10.1039/c4nr02778g

  3. Encapsulation of metal clusters within MFI via interzeolite transformations and direct hydrothermal syntheses and catalytic consequences of their confinement.

    Science.gov (United States)

    Goel, Sarika; Zones, Stacey I; Iglesia, Enrique

    2014-10-29

    The encapsulation of metal clusters (Pt, Ru, Rh) within MFI was achieved by exchanging cationic metal precursors into a parent zeolite (BEA, FAU), reducing them with H2 to form metal clusters, and transforming these zeolites into daughter structures of higher framework density (MFI) under hydrothermal conditions. These transformations required MFI seeds or organic templates for FAU parent zeolites, but not for BEA, and occurred with the retention of encapsulated clusters. Clusters uniform in size (1.3-1.7 nm) and exposing clean and accessible surfaces formed in BEA and FAU zeolites; their size remained essentially unchanged upon transformation into MFI. Encapsulation selectivities, determined from the relative hydrogenation rates of small (toluene) and large (alkyl arenes) molecules and defined as the ratio of the surface areas of all the clusters in the sample to that of external clusters, were very high (8.1-40.9) for both parent and daughter zeolites. Encapsulation into MFI via direct hydrothermal syntheses was unsuccessful because metal precursors precipitated prematurely at the pH and temperatures required for MFI synthesis. Delayed introduction of metal precursors and F(-) (instead of OH(-)) as the mineralizing agent in hydrothermal syntheses increased encapsulation selectivities, but they remained lower than those achieved via interzeolite transformations. These interconversions provide a general and robust strategy for encapsulation of metals when precursors can be introduced via exchange into a zeolite that can be transformed into target daughter zeolites with higher framework densities, whether spontaneously or by using seeds or structure-directing agents (SDA).

  4. Investigation of Cluster and Cluster Queuing System

    OpenAIRE

    Halifu, Saerda

    2008-01-01

    Cluster became main platform as parallel and distributed computing structure for high performance computing. Following the development of high performance computer architecture more and more different branches of natural science benefit fromhuge and efficient computational power. For instance bio-informatics, climate science, computational physics, computational chemistry, marine science, etc. Efficient and reliable computing powermay not only expending demand of existing high performance com...

  5. The Cluster Substructure - Alignment Connection

    CERN Document Server

    Plionis, M

    2002-01-01

    Using the APM cluster data we investigate whether the dynamical status of clusters is related to the large-scale structure of the Universe. We find that cluster substructure is strongly correlated with the tendency of clusters to be aligned with their nearest neighbour and in general with the nearby clusters that belong to the same supercluster. Furthermore, dynamically young clusters are more clustered than the overall cluster population. These are strong indications that cluster develop in a hierarchical fashion by anisotropy merging along the large-scale filamentary superclusters within which they are embedded.

  6. Job Oriented Monitoring Clusters

    Directory of Open Access Journals (Sweden)

    Vijayalaxmi Cigala,

    2011-03-01

    Full Text Available There has been a lot of development in the field of clusters and grids. Recently, the use of clusters has been on rise in every possible field. This paper proposes a system that monitors jobs onlarge computational clusters. Monitoring jobs is essential to understand how jobs are being executed. This helps us in understanding the complete life cycle of the jobs being executed on large clusters. Also, this paper describes how the information obtained by monitoring the jobs would help in increasing the overall throughput of clusters. Heuristics help in efficient job distribution among the computational nodes, thereby accomplishing fair job distribution policy. The proposed system would be capable of loadbalancing among the computational nodes, detecting failures, taking corrective actions after failure detection, job monitoring, system resource monitoring, etc.

  7. Pulsars in Globular Clusters

    CERN Document Server

    Camilo, F; Camilo, Fernando; Rasio, Frederic A.

    2005-01-01

    More than 100 radio pulsars have been detected in 24 globular clusters. The largest observed samples are in Terzan 5 and 47 Tucanae, which together contain 45 pulsars. Accurate timing solutions, including positions in the cluster, are known for many of these pulsars. Here we provide an observational overview of some properties of pulsars in globular clusters, as well as properties of the globular clusters with detected pulsars. The many recent detections also provide a new opportunity to re-examine theoretically the formation and evolution of recycled pulsars in globular clusters. Our brief review considers the most important dynamical interaction and binary evolution processes: collisions, exchange interactions, mass transfer, and common-envelope phases.

  8. Mathematical classification and clustering

    CERN Document Server

    Mirkin, Boris

    1996-01-01

    I am very happy to have this opportunity to present the work of Boris Mirkin, a distinguished Russian scholar in the areas of data analysis and decision making methodologies. The monograph is devoted entirely to clustering, a discipline dispersed through many theoretical and application areas, from mathematical statistics and combina­ torial optimization to biology, sociology and organizational structures. It compiles an immense amount of research done to date, including many original Russian de­ velopments never presented to the international community before (for instance, cluster-by-cluster versions of the K-Means method in Chapter 4 or uniform par­ titioning in Chapter 5). The author's approach, approximation clustering, allows him both to systematize a great part of the discipline and to develop many in­ novative methods in the framework of optimization problems. The optimization methods considered are proved to be meaningful in the contexts of data analysis and clustering. The material presented in ...

  9. On TPC cluster reconstruction

    CERN Document Server

    Dydak, F; Nefedov, Y; Wotschack, J; Zhemchugov, A

    2004-01-01

    For a bias-free momentum measurement of TPC tracks, the correct determination of cluster positions is mandatory. We argue in particular that (i) the reconstruction of the entire longitudinal signal shape in view of longitudinal diffusion, electronic pulse shaping, and track inclination is important both for the polar angle reconstruction and for optimum r phi resolution; and that (ii) self-crosstalk of pad signals calls for special measures for the reconstruction of the z coordinate. The problem of 'shadow clusters' is resolved. Algorithms are presented for accepting clusters as 'good' clusters, and for the reconstruction of the r phi and z cluster coordinates, including provisions for 'bad' pads and pads next to sector boundaries, respectively.

  10. Cool Cluster Correctly Correlated

    Energy Technology Data Exchange (ETDEWEB)

    Sergey Aleksandrovich Varganov

    2005-12-17

    Atomic clusters are unique objects, which occupy an intermediate position between atoms and condensed matter systems. For a long time it was thought that physical and chemical properties of atomic dusters monotonically change with increasing size of the cluster from a single atom to a condensed matter system. However, recently it has become clear that many properties of atomic clusters can change drastically with the size of the clusters. Because physical and chemical properties of clusters can be adjusted simply by changing the cluster's size, different applications of atomic clusters were proposed. One example is the catalytic activity of clusters of specific sizes in different chemical reactions. Another example is a potential application of atomic clusters in microelectronics, where their band gaps can be adjusted by simply changing cluster sizes. In recent years significant advances in experimental techniques allow one to synthesize and study atomic clusters of specified sizes. However, the interpretation of the results is often difficult. The theoretical methods are frequently used to help in interpretation of complex experimental data. Most of the theoretical approaches have been based on empirical or semiempirical methods. These methods allow one to study large and small dusters using the same approximations. However, since empirical and semiempirical methods rely on simple models with many parameters, it is often difficult to estimate the quantitative and even qualitative accuracy of the results. On the other hand, because of significant advances in quantum chemical methods and computer capabilities, it is now possible to do high quality ab-initio calculations not only on systems of few atoms but on clusters of practical interest as well. In addition to accurate results for specific clusters, such methods can be used for benchmarking of different empirical and semiempirical approaches. The atomic clusters studied in this work contain from a few atoms

  11. Cluster ion beam evaporation

    International Nuclear Information System (INIS)

    Cluster ions can be made by the supercooling due to adiabatic expansion of substances to be vaporized which are ejected from a nozzle. This paper is described on the recent progress of studies concerning the cluster beam. The technique of cluster ion beam has been applied for the studies of thermonuclear plasma, the fabrication of thin films, crystal growth and electronic devices. The density of cluster ion beam is larger than that of atomic ion beam, and the formation of thin films can be easily done in high vacuum. This method is also useful for epitaxial growth. Metallic vapour cluster beam was made by the help of jetting rare gas beam. Various beam sources were developed. The characteristics of these sources were measured and analyzed. (Kato, T.)

  12. Technical Note: Towards resolving in situ, centimeter-scale location and timing of biomineralization in calcareous meiobenthos - the calcein-osmotic pump method

    Science.gov (United States)

    Bernhard, J. M.; Phalen, W. G.; McIntyre-Wressnig, A.; Mezzo, F.; Wit, J. C.; Jeglinski, M.; Filipsson, H. L.

    2015-09-01

    Insights into oceanographic environmental conditions such as paleoproductivity, deep-water temperatures, salinity, ice volumes, and nutrient cycling have all been obtained from geochemical analyses of biomineralized carbonate of marine organisms. However, we cannot fully understand geochemical proxy incorporation and the fidelity of such in species until we better understand fundamental aspects of their ecology such as where and when these (micro)organisms calcify. Here, we present an innovative method using osmotic pumps and the fluorescent marker calcein to help identify where and when calcareous meiofauna calcify in situ. Method development initially involved juvenile quahogs (Mercenaria mercenaria); subsequent method refinement involved a neritic benthic foraminiferal community. Future applications of this method will allow determining the in situ growth rate in calcareous organisms and provide insights about microhabitats where paleoceanographically relevant benthic foraminifera actually calcify.

  13. A critical review of Electric Earthquake Precursors

    Directory of Open Access Journals (Sweden)

    F. Vallianatos

    2001-06-01

    Full Text Available The generation of transient electric potential prior to rupture has been demonstrated in a number of laboratory experiments involving both dry and wet rock specimens. Several different electrification effects are responsible for these observations, but how these may scale up co-operatively in large heterogeneous rock volumes, to produce observable macroscopic signals, is still incompletely understood. Accordingly, the nature and properties of possible Electric Earthquake Precursors (EEP are still inadequately understood. For a long time observations have been fragmentary, narrow band and oligo-parametric (for instance, the magnetic field was not routinely measured. In general, the discrimination of purported EEP signals relied on "experience" and ad hoc empirical rules that could be shown unable to guarantee the validity of the data. In consequence, experimental studies have produced a prolific variety of signal shape, complexity and duration but no explanation for the apparently indefinite diversity. A set of inconsistent or conflicting ideas attempted to explain such observations, including different concepts about the EEP source region (near the observer or at the earthquake focus and propagation (frequently assumed to be guided by peculiar geoelectric structure. Statistics was also applied to establish the "beyond chance" association between presumed EEP signals and earthquakes. In the absence of well constrained data, this approach ended up with intense debate and controversy but no useful results. The response of the geophysical community was scepticism and by the mid-90's, the very existence of EEP was debated. At that time, a major re-thinking of EEP research began to take place, with reformulation of its queries and objectives and refocusing on the exploration of fundamental concepts, less on field experiments. The first encouraging results began to appear in the last two years of the 20th century. Observation technologies are mature

  14. PRECOMBUSTION REMOVAL OF HAZARDOUS AIR POLLUTANT PRECURSORS

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    2000-10-09

    In response to growing environmental concerns reflected in the 1990 Clean Air Act Amendment (CAAA), the United States Department of Energy (DOE) sponsored several research and development projects in late 1995 as part of an initiative entitled Advanced Environmental Control Technologies for Coal-Based Power Systems. The program provided cost-shared support for research and development projects that could accelerate the commercialization of affordable, high-efficiency, low-emission, coal-fueled electric generating technologies. Clean coal technologies developed under this program would serve as prototypes for later generations of technologies to be implemented in the industrial sector. In order to identify technologies with the greatest potential for commercial implementation, projects funded under Phase I of this program were subject to competitive review by DOE before being considered for continuation funding under Phase II. One of the primary topical areas identified under the DOE initiative relates to the development of improved technologies for reducing the emissions of air toxics. Previous studies have suggested that many of the potentially hazardous air pollutant precursors (HAPPs) occur as trace elements in the mineral matter of run-of-mine coals. As a result, these elements have the potential to be removed prior to combustion at the mine site by physical coal cleaning processes (i.e., coal preparation). Unfortunately, existing coal preparation plants are generally limited in their ability to remove HAPPs due to incomplete liberation of the mineral matter and high organic associations of some trace elements. In addition, existing physical coal cleaning plants are not specifically designed or optimized to ensure that high trace element rejections may be achieved.

  15. The reliability of radon as seismic precursor

    Science.gov (United States)

    Emilian Toader, Victorin; Moldovan, Iren Adelina; Ionescu, Constantin; Marmureanu, Alexandru

    2016-04-01

    Our multidisciplinary network (AeroSolSys) located in Vrancea (Curvature Carpathian Mountains) includes radon concentration monitoring in five stations. We focus on lithosphere and near surface low atmosphere phenomena using real-time information about seismicity, + / - ions, clouds, solar radiation, temperature (air, ground), humidity, atmospheric pressure, wind speed and direction, telluric currents, variations of the local magnetic field, infrasound, variations of the atmospheric electrostatic field, variations in the earth crust with inclinometers, electromagnetic activity, CO2 concentration, ULF radio wave propagation, seismo-acoustic emission, animal behavior. The main purpose is to inform the authorities about risk situation and update hazard scenarios. The radon concentration monitoring is continuously with 1 hour or 3 hours sample rate in locations near to faults in an active seismic zone characterized by intermediate depth earthquakes. Trigger algorithms include standard deviation, mean and derivative methods. We correlate radon concentration measurements with humidity, temperature and atmospheric pressure from the same equipment. In few stations we have meteorological information, too. Sometime the radon concentration has very high variations (maxim 4535 Bq/m3 from 106 Bq/m3) in short time (1 - 2 days) without being accompanied by an important earthquake. Generally the cause is the high humidity that could be generated by tectonic stress. Correlation with seismicity needs information from minimum 6 month in our case. For 10605 hours, 618 earthquakes with maxim magnitude 4.9 R, we have got radon average 38 Bq/m3 and exposure 408111 Bqh/m3 in one station. In two cases we have correlation between seismicity and radon concentration. In other one we recorded high variation because the location was in an area with multiple faults and a river. Radon can be a seismic precursor but only in a multidisciplinary network. The anomalies for short or long period of

  16. Exalting in atmospheric tides as earthquake precursor

    Directory of Open Access Journals (Sweden)

    P. F. Biagi

    2003-01-01

    Full Text Available During February–March 1998, we observed a significant increase (6–8 dB in the electric field of the CZE (f = 270 kHz, Czech Republic broadcasting station at a site named AS and located in central Italy. On 13 March 1998 an earthquake (M = 5.2 occurred in Slovenia, starting a strong seismic crisis (M = 6.0 on 12 April, M = 5.1 on 6 May. The distances of the epicentres from the radio receiver were over 400 km, but the epicentres are located in a zone that is in the middle of the CZE-AS path. Previously, we advanced the hypothesis that the increase of radio-signal electric field detected could be a precursor of the Slovenia seismic crisis. At the purpose to precise the connection between this radio anomaly and the preparatory phase of the earthquakes, we analysed in detail the data collected. At first we carried out a FFT on the data and clear harmonic components with period 0.5d, 1d, 14d, 28d and 365d were revealed. These periods are characteristic of gravity tides and therefore, it seems reasonable to consider the previous harmonics in the electric field of the radio signal as components related to tides of the atmosphere, assuming as tides of the atmosphere only the linear action of gravity tides on atmosphere. Then, we carried out band pass filters on our data and we discovered that the February–March 1998 increase is mainly related to an exalting of the harmonics with period 0.5d, 1d, 14d and 28d, i.e. of the (semimonthly and (semidiurnal atmospheric tidal components in the radio signal. Supposing that this exalting is produced by a corresponding exalting of the atmospheric tides we propose a model able to explain the production of such an effect during the preparatory phase of the Slovenia earthquakes.

  17. Search for precursor eruptions among Type IIb supernovae

    CERN Document Server

    Strotjohann, Nora L; Gal-Yam, Avishay; Sullivan, Mark; Kulkarni, Shrinivas R; Shaviv, Nir J; Fremling, Christoffer; Kasliwal, Mansi M; Nugent, Peter E; Cao, Yi; Arcavi, Iair; Sollerman, Jesper; Filippenko, Alexei V; Yaron, Ofer; Laher, Russ; Surace, Jason

    2015-01-01

    The progenitor stars of several Type IIb supernovae (SNe) show indications for extended hydrogen envelopes. These envelopes might be the outcome of luminous energetic pre-explosion events, so-called precursor eruptions. We use the Palomar Transient Factory (PTF) pre-explosion observations of a sample of 27 nearby Type IIb SNe to look for such precursors during the final years prior to the SN explosion. No precursors are found when combining the observations in 15-day bins, and we calculate the absolute-magnitude-dependent upper limit on the precursor rate. At the 90% confidence level, Type IIb SNe have on average $<0.86$ precursors as bright as absolute $R$-band magnitude $-14$ in the final 3.5 years before the explosion and $<0.56$ events over the final year. In contrast, precursors among SNe IIn have a $\\gtrsim 5$ times higher rate. The kinetic energy required to unbind a low-mass stellar envelope is comparable to the radiated energy of a few-weeks-long precursor which would be detectable for the clos...

  18. Textile Industrial Clusters in China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    "National Textile Industry Cluster Development Seminar" convened, held by China National Textile and Apparel Council, 23 cities and towns were awarded as China’s Textile Industry Cluster Pilot District. By far, China’s textile industrial clusters have grown

  19. Spanning Tree Based Attribute Clustering

    DEFF Research Database (Denmark)

    Zeng, Yifeng; Jorge, Cordero Hernandez

    2009-01-01

    inconsistent edges from a maximum spanning tree by starting appropriate initial modes, therefore generating stable clusters. It discovers sound clusters through simple graph operations and achieves significant computational savings. We compare the Star Discovery algorithm against earlier attribute clustering...

  20. Cluster knockout reactions

    Indian Academy of Sciences (India)

    Arun K Jain; B N Joshi

    2014-04-01

    Cluster knockout reactions are expected to reveal the amount of clustering (such as that of , d and even of heavier clusters such as 12C, 16O etc.) in the target nucleus. In simple terms, incident medium high-energy nuclear projectile interacts strongly with the cluster (present in the target nucleus) as if it were existing as a free entity. Theoretically, the relatively softer interactions of the two outgoing particles with the residual nucleus lead to optical distortions and are treated in terms of distorted wave (DW) formalism. The long-range projectile–cluster interaction is accounted for, in terms of the finite range (FR) direct reaction formalism, as against the more commonly adopted zero-range (ZR) distorted wave impulse approximation (DWIA) formalism. Comparison of the DWIA calculations with the observed data provide information about the momentum distribution and the clustering spectroscopic factor of the target nucleus. Interesting results and some recent advancements in the area of (, 2) reactions and heavy cluster knockout reactions are discussed. Importance of the finite-range vertex and the final-state interactions are brought out.

  1. Software-Defined Cluster

    Institute of Scientific and Technical Information of China (English)

    聂华; 杨晓君; 刘淘英

    2015-01-01

    The cluster architecture has played an important role in high-end computing for the past 20 years. With the advent of Internet services, big data, and cloud computing, traditional clusters face three challenges: 1) providing flexible system balance among computing, memory, and I/O capabilities;2) reducing resource pooling overheads;and 3) addressing low performance-power efficiency. This position paper proposes a software-defined cluster (SDC) architecture to deal with these challenges. The SDC architecture inherits two features of traditional cluster: its architecture is multicomputer and it has loosely-coupled interconnect. SDC provides two new mechanisms: global I/O space (GIO) and hardware-supported native access (HNA) to remote devices. Application software can define a virtual cluster best suited to its needs from resources pools provided by a physical cluster, and traditional cluster ecosystems need no modification. We also discuss a prototype design and implementation of a 32-processor cloud server utilizing the SDC architecture.

  2. Extending Beowulf Clusters

    Science.gov (United States)

    Steinwand, Daniel R.; Maddox, Brian; Beckmann, Tim; Hamer, George

    2003-01-01

    Beowulf clusters can provide a cost-effective way to compute numerical models and process large amounts of remote sensing image data. Usually a Beowulf cluster is designed to accomplish a specific set of processing goals, and processing is very efficient when the problem remains inside the constraints of the original design. There are cases, however, when one might wish to compute a problem that is beyond the capacity of the local Beowulf system. In these cases, spreading the problem to multiple clusters or to other machines on the network may provide a cost-effective solution.

  3. Cluster Management Institutionalization

    DEFF Research Database (Denmark)

    Normann, Leo; Agger Nielsen, Jeppe

    2015-01-01

    institutionalism together with a longitudinal case-based inquiry into how cluster management has entered and penetrated the management practices of day care in Denmark. We demonstrate how cluster management became widely adopted in the day care field not only because of its intrinsic properties but also because...... legitimized at the field level, then spread, and finally translated into action in the adopting organizations. Instead, we observed entangled field and organizational-level processes. Accordingly, we argue that cluster management institutionalization is most readily understood by simultaneously investigating...

  4. Introduction to cluster dynamics

    CERN Document Server

    Reinhard, Paul-Gerhard

    2008-01-01

    Clusters as mesoscopic particles represent an intermediate state of matter between single atoms and solid material. The tendency to miniaturise technical objects requires knowledge about systems which contain a ""small"" number of atoms or molecules only. This is all the more true for dynamical aspects, particularly in relation to the qick development of laser technology and femtosecond spectroscopy. Here, for the first time is a highly qualitative introduction to cluster physics. With its emphasis on cluster dynamics, this will be vital to everyone involved in this interdisciplinary subje

  5. Dwarfs in Coma Cluster

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version This false-color mosaic of the central region of the Coma cluster combines infrared and visible-light images to reveal thousands of faint objects (green). Follow-up observations showed that many of these objects, which appear here as faint green smudges, are dwarf galaxies belonging to the cluster. Two large elliptical galaxies, NGC 4889 and NGC 4874, dominate the cluster's center. The mosaic combines visible-light data from the Sloan Digital Sky Survey (color coded blue) with long- and short-wavelength infrared views (red and green, respectively) from NASA's Spitzer Space Telescope.

  6. Raspberry Pi super cluster

    CERN Document Server

    Dennis, Andrew K

    2013-01-01

    This book follows a step-by-step, tutorial-based approach which will teach you how to develop your own super cluster using Raspberry Pi computers quickly and efficiently.Raspberry Pi Super Cluster is an introductory guide for those interested in experimenting with parallel computing at home. Aimed at Raspberry Pi enthusiasts, this book is a primer for getting your first cluster up and running.Basic knowledge of C or Java would be helpful but no prior knowledge of parallel computing is necessary.

  7. Partially supervised speaker clustering.

    Science.gov (United States)

    Tang, Hao; Chu, Stephen Mingyu; Hasegawa-Johnson, Mark; Huang, Thomas S

    2012-05-01

    Content-based multimedia indexing, retrieval, and processing as well as multimedia databases demand the structuring of the media content (image, audio, video, text, etc.), one significant goal being to associate the identity of the content to the individual segments of the signals. In this paper, we specifically address the problem of speaker clustering, the task of assigning every speech utterance in an audio stream to its speaker. We offer a complete treatment to the idea of partially supervised speaker clustering, which refers to the use of our prior knowledge of speakers in general to assist the unsupervised speaker clustering process. By means of an independent training data set, we encode the prior knowledge at the various stages of the speaker clustering pipeline via 1) learning a speaker-discriminative acoustic feature transformation, 2) learning a universal speaker prior model, and 3) learning a discriminative speaker subspace, or equivalently, a speaker-discriminative distance metric. We study the directional scattering property of the Gaussian mixture model (GMM) mean supervector representation of utterances in the high-dimensional space, and advocate exploiting this property by using the cosine distance metric instead of the euclidean distance metric for speaker clustering in the GMM mean supervector space. We propose to perform discriminant analysis based on the cosine distance metric, which leads to a novel distance metric learning algorithm—linear spherical discriminant analysis (LSDA). We show that the proposed LSDA formulation can be systematically solved within the elegant graph embedding general dimensionality reduction framework. Our speaker clustering experiments on the GALE database clearly indicate that 1) our speaker clustering methods based on the GMM mean supervector representation and vector-based distance metrics outperform traditional speaker clustering methods based on the “bag of acoustic features” representation and statistical

  8. Clustering in nuclear environment

    International Nuclear Information System (INIS)

    The properties of few-body clusters (mass number A ≤ 4) are modified if they are immersed in a nuclear medium. In particular, Pauli blocking that reflects the antisymmetrization of the many-body wave function is responsible for the medium modification of light clusters and the dissolution with increasing density. A more consistent description is given with takes also the contribution of correlations in the continuum into account. The relation between cluster formation in warm dense matter and in nuclear structure is discussed

  9. Biological Indicators in Studies of Earthquake Precursors

    Science.gov (United States)

    Sidorin, A. Ya.; Deshcherevskii, A. V.

    2012-04-01

    Time series of data on variations in the electric activity (EA) of four species of weakly electric fish Gnathonemus leopoldianus and moving activity (MA) of two cat-fishes Hoplosternum thoracatum and two groups of Columbian cockroaches Blaberus craniifer were analyzed. The observations were carried out in the Garm region of Tajikistan within the frameworks of the experiments aimed at searching for earthquake precursors. An automatic recording system continuously recorded EA and DA over a period of several years. Hourly means EA and MA values were processed. Approximately 100 different parameters were calculated on the basis of six initial EA and MA time series, which characterize different variations in the EA and DA structure: amplitude of the signal and fluctuations of activity, parameters of diurnal rhythms, correlated changes in the activity of various biological indicators, and others. A detailed analysis of the statistical structure of the total array of parametric time series obtained in the experiment showed that the behavior of all animals shows a strong temporal variability. All calculated parameters are unstable and subject to frequent changes. A comparison of the data obtained with seismicity allow us to make the following conclusions: (1) The structure of variations in the studied parameters is represented by flicker noise or even a more complex process with permanent changes in its characteristics. Significant statistics are required to prove the cause-and-effect relationship of the specific features of such time series with seismicity. (2) The calculation of the reconstruction statistics in the EA and MA series structure demonstrated an increase in their frequency in the last hours or a few days before the earthquake if the hypocenter distance is comparable to the source size. Sufficiently dramatic anomalies in the behavior of catfishes and cockroaches (changes in the amplitude of activity variation, distortions of diurnal rhythms, increase in the

  10. Islet Generation from Intra Islet Precursor Cells of Diabetic Pancreas: In Vitro Studies Depicting In Vivo Differentiation

    Directory of Open Access Journals (Sweden)

    Banerjee M

    2003-07-01

    Full Text Available CONTEXT: Beta-cells have a limited replicative capacity; hence, there is always a quest for sources of islet regeneration to compensate for the loss of functional beta-cells in diabetes. OBJECTIVE: To test the hypothesis of whether intra islet precursor cells of islets isolated from a diabetic pancreas and in vitro streptozotocin treated islets are capable of giving rise to neoislets. INTERVENTIONS: Streptozotocin treatment was given to mice and to islets isolated from normal mice. Islets were isolated from diabetic mice, cultured on matrigel coated plates with a well-defined serum free medium containing mitotic (nicotinamide and differentiating (keratinocyte growth factor agents. Initially, islets gave rise to an epithelial-like cell monolayer and, later on, differentiated into islet-like clusters. These were characterized for the ductal epithelial cell specific markers cytokeratin-19 and cytokeratin-7 and for the islet specific markers-insulin and PDX1. Insulin secretion in response to glucose and L-arginine was estimated by ELISA. RESULTS: A cytokeratin-19 and cytokeratin-7 positive precursor cell population was found scattered throughout the epithelial monolayer. Upon addition of the keratinocyte growth factor, these precursor cells gave rise to islet-like clusters which were confirmed to be islets by marker studies. Though streptozotocin treatment on islets of normal mice allowed proliferation of the epithelial monolayer, it did not give rise to neoislets under similar growth conditions. CONCLUSION: The present study reveals that streptozotocin treatment of normal islets in vitro leads to the loss of the potential of intra islet precursor cells to form neoislets; however, in streptozotocin-induced experimental diabetes, they retain their potential to generate new islets opening a novel putative way of treating diabetes.

  11. Combining cluster number counts and galaxy clustering

    Science.gov (United States)

    Lacasa, Fabien; Rosenfeld, Rogerio

    2016-08-01

    The abundance of clusters and the clustering of galaxies are two of the important cosmological probes for current and future large scale surveys of galaxies, such as the Dark Energy Survey. In order to combine them one has to account for the fact that they are not independent quantities, since they probe the same density field. It is important to develop a good understanding of their correlation in order to extract parameter constraints. We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. We employ the framework of the halo model complemented by a Halo Occupation Distribution model (HOD). We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions. Indeed, we show that the non-Gaussian covariance becomes dominant at small scales, low redshifts or high cluster masses. We discuss in particular the case of the super-sample covariance (SSC), including the effects of galaxy shot-noise, halo second order bias and non-local bias. We demonstrate that the SSC obeys mathematical inequalities and positivity. Using the joint covariance matrix and a Fisher matrix methodology, we examine the prospects of combining these two probes to constrain cosmological and HOD parameters. We find that the combination indeed results in noticeably better constraints, with improvements of order 20% on cosmological parameters compared to the best single probe, and even greater improvement on HOD parameters, with reduction of error bars by a factor 1.4-4.8. This happens in particular because the cross-covariance introduces a synergy between the probes on small scales. We conclude that accounting for non-Gaussian effects is required for the joint analysis of these observables in galaxy surveys.

  12. Evolution of clustered storage

    CERN Document Server

    CERN. Geneva; Van de Vyvre, Pierre

    2007-01-01

    The session actually featured two presentations: * Evolution of clustered storage by Lance Hukill, Quantum Corporation * ALICE DAQ - Usage of a Cluster-File System: Quantum StorNext by Pierre Vande Vyvre, CERN-PH the second one prepared at short notice by Pierre (thanks!) to present how the Quantum technologies are being used in the ALICE experiment. The abstract to Mr Hukill's follows. Clustered Storage is a technology that is driven by business and mission applications. The evolution of Clustered Storage solutions starts first at the alignment between End-users needs and Industry trends: * Push-and-Pull between managing for today versus planning for tomorrow * Breaking down the real business problems to the core applications * Commoditization of clients, servers, and target devices * Interchangeability, Interoperability, Remote Access, Centralized control * Oh, and yes, there is a budget and the "real world" to deal with This presentation will talk through these needs and trends, and then ask the question, ...

  13. Dynamic Bayesian clustering.

    Science.gov (United States)

    Fowler, Anna; Menon, Vilas; Heard, Nicholas A

    2013-10-01

    Clusters of time series data may change location and memberships over time; in gene expression data, this occurs as groups of genes or samples respond differently to stimuli or experimental conditions at different times. In order to uncover this underlying temporal structure, we consider dynamic clusters with time-dependent parameters which split and merge over time, enabling cluster memberships to change. These interesting time-dependent structures are useful in understanding the development of organisms or complex organs, and could not be identified using traditional clustering methods. In cell cycle data, these time-dependent structure may provide links between genes and stages of the cell cycle, whilst in developmental data sets they may highlight key developmental transitions. PMID:24131050

  14. Internal Cluster Structure

    CERN Document Server

    Bartelmann, Matthias; Meneghetti, Massimo; Schmidt, Robert

    2013-01-01

    The core structure of galaxy clusters is fundamentally important. Even though self-gravitating systems have no stable equilibrium state due to their negative heat capacity, numerical simulations find density profiles which are universal in the sense that they are fairly flat within a scale radius and gradually steepen farther outward, asymptotically approaching a logarithmic slope of $\\approx-3$ near the virial radius. We argue that the reason for the formation of this profile is not satisfactorily understood. The ratio between the virial radius and the scale radius, the so-called concentration, is found in simulations to be closely related to the mass and the redshift and low for cluster-sized haloes, but observed to be substantially higher at least in a subset of observed clusters. Haloes formed from cold dark matter should furthermore be richly substructured. We review theoretical and observational aspects of cluster cores here, discuss modifications by baryonic physics and observables that can provide bet...

  15. Genome mining demonstrates the widespread occurrence of gene clusters encoding bacteriocins in cyanobacteria.

    Directory of Open Access Journals (Sweden)

    Hao Wang

    Full Text Available Cyanobacteria are a rich source of natural products with interesting biological activities. Many of these are peptides and the end products of a non-ribosomal pathway. However, several cyanobacterial peptide classes were recently shown to be produced through the proteolytic cleavage and post-translational modification of short precursor peptides. A new class of bacteriocins produced through the proteolytic cleavage and heterocyclization of precursor proteins was recently identified from marine cyanobacteria. Here we show the widespread occurrence of bacteriocin gene clusters in cyanobacteria through comparative analysis of 58 cyanobacterial genomes. A total of 145 bacteriocin gene clusters were discovered through genome mining. These clusters encoded 290 putative bacteriocin precursors. They ranged in length from 28 to 164 amino acids with very little sequence conservation of the core peptide. The gene clusters could be classified into seven groups according to their gene organization and domain composition. This classification is supported by phylogenetic analysis, which further indicated independent evolutionary trajectories of gene clusters in different groups. Our data suggests that cyanobacteria are a prolific source of low-molecular weight post-translationally modified peptides.

  16. Precursor Parameter Identification for Insulated Gate Bipolar Transistor (IGBT) Prognostics

    Data.gov (United States)

    National Aeronautics and Space Administration — Precursor parameters have been identified to enable development of a prognostic approach for insulated gate bipolar transistors (IGBT). The IGBT were subjected to...

  17. Malic acid assisted precursor route to hierarchical structured nickel oxide

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haizhen [Zhejiang California International Nanosystems Institute, Zhejiang University, Hangzhou, Zhejiang (China); Qian, Yitai [Hefei National Laboratory for Physical Science at Microscale, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui (China)

    2010-05-15

    A novel malic acid assisted precursor route to prepare NiO materials with novel hierarchical structures has been investigated in this work. The Ni-based precursors can be synthesized by a malic acid-assisted hydrothermal route, which have been characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA). NiO materials can be prepared via the thermal treatment of the precursor in ambient atmosphere. The XRD, SEM, Energy dispersive X-ray spectroscopy (EDS) and UV-Vis spectroscopy of the NiO materials were also examined. The effects of the reaction conditions, such as the reaction temperature, the quantity of the raw materials on the morphologies of the precursors were discussed, which indicates that it is an effective method to synthesize NiO materials with different hierarchical structures. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Senseless acts as a binary switch during sensory organ precursor selection

    Science.gov (United States)

    Jafar-Nejad, Hamed; Acar, Melih; Nolo, Riitta; Lacin, Haluk; Pan, Hongling; Parkhurst, Susan M.; Bellen, Hugo J.

    2003-01-01

    During sensory organ precursor (SOP) specification, a single cell is selected from a proneural cluster of cells. Here, we present evidence that Senseless (Sens), a zinc-finger transcription factor, plays an important role in this process. We show that Sens is directly activated by proneural proteins in the presumptive SOPs and a few cells surrounding the SOP in most tissues. In the cells that express low levels of Sens, it acts in a DNA-binding-dependent manner to repress transcription of proneural genes. In the presumptive SOPs that express high levels of Sens, it acts as a transcriptional activator and synergizes with proneural proteins. We therefore propose that Sens acts as a binary switch that is fundamental to SOP selection.

  19. Finnish Mobile Gaming Cluster

    OpenAIRE

    Masira, Elijah; Chowdhury, Nafis Ahmed

    2014-01-01

    Abstract The Finnish mobile gaming cluster is one of the most promising industries that have been growing significantly in the past few years to become a substantial cultural export product / service of Finland. The main objective of this research was to gain a persuasive understanding about the emergence of the mobile gaming cluster in Finland and explore the factors behind its success. The literature review centers on M. E Porter’s publications on competitiveness and other publication...

  20. Clustering audiology data

    OpenAIRE

    Anwar, Naveed; Oakes, Michael; Wermter, Stefan; Heinrich, Stefan

    2010-01-01

    In this paper we describe new results of statistical and neural data mining of audiology patient records, with the ultimate aim of looking for factors influencing which patients would most benefit from being fitted with a hearing aid. We describe how a combination of neural and statistical techniques can usefully subdivide a set of patients into clusters, based on their hearing thresholds at six different frequencies, and then label the clusters with meaningful text labels. In our first exper...

  1. Industry clusters and SMEs

    OpenAIRE

    Arnoud Muizer; Gert Jan Hospers

    1999-01-01

    Studie naar de rol van clusters van bedrijven in de economie. Clusters van bedrijven krijgen een groeiende aandacht op alle bestuurlijke niveaus. De achterliggende gedachte is dat samenwerking tussen bedrijven op technologisch gebied leidt tot de creatie van extra toegevoegde waarde, niet alleen voor de samenwerkingspartners zelf, maar ook voor de lokale, regionale en nationale economie. In de studie wordt een clusterdefinitie gepresenteerd en een raamwerk dat als basis kan dienen voor nader ...

  2. Improved Single-Source Precursors for Solar-Cell Absorbers

    Science.gov (United States)

    Banger, Kulbinder K.; Harris, Jerry; Hepp, Aloysius

    2007-01-01

    Improved single-source precursor compounds have been invented for use in spray chemical vapor deposition (spray CVD) of chalcopyrite semiconductor absorber layers of thin-film cells. A "single-source precursor compound" is a single molecular compound that contains all the required elements, which when used under the spray CVD conditions, thermally decomposes to form CuIn(x)Ga(1-x)S(y)Se(2-y).

  3. Precursors of Personality Disorders in Children and Adolescents

    Directory of Open Access Journals (Sweden)

    Merve Cikili Uytun

    2015-12-01

    Full Text Available Personality disorders are common psychiatric disorders in community that cause substantial disruption of functionality. Current diagnostic systems do not include classification of personality disorders in children. However, in recent years there has been an increasing interest in investigation of personality traits and disorders at childhood and adolescence as a precursor of adult personality disorders. The aim of this article was to review the precursors of personality disorders at childhood and adolescence

  4. Intraspinal transplantation of mouse and human neural precursor cells

    OpenAIRE

    Weinger, Jason G.; Chen, Lu; Coleman, Ronald; Leang, Ronika; Plaisted, Warren C.; Loring, Jeanne F.; Lane, Thomas E

    2013-01-01

    This unit describes the preparation and transplantation of human neural precursor cells (hNPCs) and mouse neural precursor cells (mNPCs) into the thoracic region of the mouse spinal cord. The techniques in this unit also describe how to prepare the mouse for surgery by performing a laminectomy to expose the spinal cord for transplantation. Here we show NPCs genetically labeled with eGFP transplanted into the spinal cord of a mouse following viralmediated demyelination can efficiently be detec...

  5. Precursors for the polymer-assisted deposition of films

    Science.gov (United States)

    McCleskey, Thomas M.; Burrell, Anthony K.; Jia, Quanxi; Lin, Yuan

    2013-09-10

    A polymer assisted deposition process for deposition of metal oxide films is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures to yield metal oxide films. Such films can be epitaxial in structure and can be of optical quality. The process can be organic solvent-free.

  6. Secretion and processing of insulin precursors in yeast.

    OpenAIRE

    Thim, L.; Hansen, M T; Norris, K; Hoegh, I; Boel, E; Forstrom, J; Ammerer, G; Fiil, N P

    1986-01-01

    A series of dibasic insulin precursors including proinsulin was expressed and secreted from Saccharomyces cerevisiae. Recombinant plasmids were constructed to encode fusion proteins consisting of a modified mating factor alpha 1 leader sequence and an insulin precursor. The leader sequence serves to direct the fusion protein into the secretory pathway of the cell and to expose it to the Lys-Arg processing enzyme system. The secreted peptides were purified from the fermentation broth and chara...

  7. Structure and gene organization of bovine neuromedin K precursor.

    OpenAIRE

    Kotani, H.; Hoshimaru, M; Nawa, H; Nakanishi, S.

    1986-01-01

    cDNA and genomic DNA clones for the precursor of a mammalian neuropeptide tachykinin, neuromedin K, have been isolated and characterized by molecular cloning and sequence analysis. The deduced amino acid sequence indicates that the bovine neuromedin K precursor (preprotachykinin B) consists of 126 amino acid residues including a putative signal peptide. There are two preprotachykinin B mRNAs that differ only at the 5' extremity of the untranslated regions. The major mRNA species is encoded by...

  8. Centroid Based Text Clustering

    Directory of Open Access Journals (Sweden)

    Priti Maheshwari

    2010-09-01

    Full Text Available Web mining is a burgeoning new field that attempts to glean meaningful information from natural language text. Web mining refers generally to the process of extracting interesting information and knowledge from unstructured text. Text clustering is one of the important Web mining functionalities. Text clustering is the task in which texts are classified into groups of similar objects based on their contents. Current research in the area of Web mining is tacklesproblems of text data representation, classification, clustering, information extraction or the search for and modeling of hidden patterns. In this paper we propose for mining large document collections it is necessary to pre-process the web documents and store the information in a data structure, which is more appropriate for further processing than a plain web file. In this paper we developed a php-mySql based utility to convert unstructured web documents into structured tabular representation by preprocessing, indexing .We apply centroid based web clustering method on preprocessed data. We apply three methods for clustering. Finally we proposed a method that can increase accuracy based on clustering ofdocuments.

  9. Galaxy cluster's rotation

    CERN Document Server

    Manolopoulou, Maria

    2016-01-01

    We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...

  10. Cluster bomb ocular injuries

    Directory of Open Access Journals (Sweden)

    Ahmad M Mansour

    2012-01-01

    Full Text Available Purpose: To present the visual outcomes and ocular sequelae of victims of cluster bombs. Materials and Methods: This retrospective, multicenter case series of ocular injury due to cluster bombs was conducted for 3 years after the war in South Lebanon (July 2006. Data were gathered from the reports to the Information Management System for Mine Action. Results: There were 308 victims of clusters bombs; 36 individuals were killed, of which 2 received ocular lacerations and; 272 individuals were injured with 18 receiving ocular injury. These 18 surviving individuals were assessed by the authors. Ocular injury occurred in 6.5% (20/308 of cluster bomb victims. Trauma to multiple organs occurred in 12 of 18 cases (67% with ocular injury. Ocular findings included corneal or scleral lacerations (16 eyes, corneal foreign bodies (9 eyes, corneal decompensation (2 eyes, ruptured cataract (6 eyes, and intravitreal foreign bodies (10 eyes. The corneas of one patient had extreme attenuation of the endothelium. Conclusions: Ocular injury occurred in 6.5% of cluster bomb victims and 67% of the patients with ocular injury sustained trauma to multiple organs. Visual morbidity in civilians is an additional reason for a global ban on the use of cluster bombs.

  11. Detection of hydrogeochemical seismic precursors by a statistical learning model

    Directory of Open Access Journals (Sweden)

    L. Castellana

    2008-11-01

    Full Text Available The problem of detecting the occurrence of an earthquake precursor is faced in the general framework of the statistical learning theory. The aim of this work is both to build models able to detect seismic precursors from time series of different geochemical signals and to provide an estimate of number of false positives. The model we used is k-Nearest-Neighbor classifier for discriminating "no-disturbed signal", "seismic precursor" and "co-post seismic precursor" in time series relative to thirteen different hydrogeochemical parameters collected in water samples from a natural spring in Kamchachta (Russia peninsula. The measurements collected are ion content (Na, Cl, Ca, HCO3, H3BO3, parameters (pH, Q, T and gases (N2, CO2, CH4, O2, Ag. The classification error is measured by Leave-K-Out-Cross-Validation procedure. Our study shows that the most discriminative ions for detecting seismic precursors are Cl and Na having an error rates of 15%. Moreover, the most discriminative parameters and gases are Q and CH4 respectively, with error rate of 21%. The ions result the most informative hydrogeochemicals for detecting seismic precursors due to the peculiarities of the mechanisms involved in earthquake preparation. Finally we show that the information collected some month before the event under analysis are necessary to improve the classification accuracy.

  12. Risk Assessment of Infrastructure System of Systems with Precursor Analysis.

    Science.gov (United States)

    Guo, Zhenyu; Haimes, Yacov Y

    2016-08-01

    Physical infrastructure systems are commonly composed of interconnected and interdependent subsystems, which in their essence constitute system of systems (S-o-S). System owners and policy researchers need tools to foresee potential emergent forced changes and to understand their impact so that effective risk management strategies can be developed. We develop a systemic framework for precursor analysis to support the design of an effective and efficient precursor monitoring and decision support system with the ability to (i) identify and prioritize indicators of evolving risks of system failure; and (ii) evaluate uncertainties in precursor analysis to support informed and rational decision making. This integrated precursor analysis framework is comprised of three processes: precursor identification, prioritization, and evaluation. We use an example of a highway bridge S-o-S to demonstrate the theories and methodologies of the framework. Bridge maintenance processes involve many interconnected and interdependent functional subsystems and decision-making entities and bridge failure can have broad social and economic consequences. The precursor analysis framework, which constitutes an essential part of risk analysis, examines the impact of various bridge inspection and maintenance scenarios. It enables policy researchers and analysts who are seeking a risk perspective on bridge infrastructure in a policy setting to develop more risk informed policies and create guidelines to efficiently allocate limited risk management resources and mitigate severe consequences resulting from bridge failures. PMID:27575259

  13. Role of neural precursor cells in promoting repair following stroke

    Institute of Scientific and Technical Information of China (English)

    Pooya DIBAJNIA; Cindi M MORSHEAD

    2013-01-01

    Stem cell-based therapies for the treatment of stroke have received considerable attention.Two broad approaches to stem cell-based therapies have been taken:the transplantation of exogenous stem cells,and the activation of endogenous neural stem and progenitor cells (together termed neural precursors).Studies examining the transplantation of exogenous cells have demonstrated that neural stem and progenitor cells lead to the most clinically promising results.Endogenous activation of neural precursors has also been explored based on the fact that resident precursor cells have the inherent capacity to proliferate,migrate and differentiate into mature neurons in the uninjured adult brain.Studies have revealed that these neural precursor cell behaviours can be activated following stroke,whereby neural precursors will expand in number,migrate to the infarct site and differentiate into neurons.However,this innate response is insufficient to lead to functional recovery,making it necessary to enhance the activation of endogenous precursors to promote tissue repair and functional recovery.Herein we will discuss the current state of the stem cell-based approaches with a focus on endogenous repair to treat the stroke injured brain.

  14. Elements of the tsunami precursors' detection physics

    Science.gov (United States)

    Novik, Oleg; Ruzhin, Yuri; Ershov, Sergey; Volgin, Max; Smirnov, Fedor

    ionosphere from the buoy, balloon and satellite complexes. The balloon and buoy complexes will transmit data to a shore station over satellite link. The frequency ranges and sensitivity thresholds of all of the sensors of the LOAMS will be adapted to the characteristics of expected seismic signals according to the numerical research above. Computational methods and statistical analysis (e.g. seismic changes of coherence of spatially distributed sensors of different nature) of the recorded multidimensional time series will be used for prognostic interpretation. The multilevel recordings will provide a stable noise (e.g. ionosphere Pc pulsations, hard sea, industry) and seismic event detection. An intensive heat flow typical for tectonically active lithosphere zones may be considered as an energy source for advanced modifications of the LOAMS. The latter may be used as a warning system for continental and marine technologies, e.g. a sea bottom geothermal energy production. Indeed, seismic distraction of the nuclear power station Fukushima I demonstrates that similar technology hardly is able to solve the energy problems in seismically active regions. On the other hand, the LOAMS may be considered as a scientific observatory for development of the seaquake/tsunami precursor physics, i.e. seismo-hydro-electromagnetics.

  15. Cluster fusion algorithm: application to Lennard-Jones clusters

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2008-01-01

    paths up to the cluster size of 150 atoms. We demonstrate that in this way all known global minima structures of the Lennard-Jones clusters can be found. Our method provides an efficient tool for the calculation and analysis of atomic cluster structure. With its use we justify the magic number sequence......We present a new general theoretical framework for modelling the cluster structure and apply it to description of the Lennard-Jones clusters. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system and absorbing its energy at each step, we find cluster growing...... for the clusters of noble gas atoms and compare it with experimental observations. We report the striking correspondence of the peaks in the dependence of the second derivative of the binding energy per atom on cluster size calculated for the chain of the Lennard-Jones clusters based on the icosahedral symmetry...

  16. Cluster fusion algorithm: application to Lennard-Jones clusters

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2006-01-01

    paths up to the cluster size of 150 atoms. We demonstrate that in this way all known global minima structures of the Lennard-Jones clusters can be found. Our method provides an efficient tool for the calculation and analysis of atomic cluster structure. With its use we justify the magic number sequence......We present a new general theoretical framework for modelling the cluster structure and apply it to description of the Lennard-Jones clusters. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system and absorbing its energy at each step, we find cluster growing...... for the clusters of noble gas atoms and compare it with experimental observations. We report the striking correspondence of the peaks in the dependence of the second derivative of the binding energy per atom on cluster size calculated for the chain of the Lennard-Jones clusters based on the icosahedral symmetry...

  17. Predicting Solar Cycle 24 Using a Geomagnetic Precursor Pair

    Science.gov (United States)

    Pesnell, W. Dean

    2014-01-01

    We describe using Ap and F(10.7) as a geomagnetic-precursor pair to predict the amplitude of Solar Cycle 24. The precursor is created by using F(10.7) to remove the direct solar-activity component of Ap. Four peaks are seen in the precursor function during the decline of Solar Cycle 23. A recurrence index that is generated by a local correlation of Ap is then used to determine which peak is the correct precursor. The earliest peak is the most prominent but coincides with high levels of non-recurrent solar activity associated with the intense solar activity of October and November 2003. The second and third peaks coincide with some recurrent activity on the Sun and show that a weak cycle precursor closely following a period of strong solar activity may be difficult to resolve. A fourth peak, which appears in early 2008 and has recurrent activity similar to precursors of earlier solar cycles, appears to be the "true" precursor peak for Solar Cycle 24 and predicts the smallest amplitude for Solar Cycle 24. To determine the timing of peak activity it is noted that the average time between the precursor peak and the following maximum is approximately equal to 6.4 years. Hence, Solar Cycle 24 would peak during 2014. Several effects contribute to the smaller prediction when compared with other geomagnetic-precursor predictions. During Solar Cycle 23 the correlation between sunspot number and F(10.7) shows that F(10.7) is higher than the equivalent sunspot number over most of the cycle, implying that the sunspot number underestimates the solar-activity component described by F(10.7). During 2003 the correlation between aa and Ap shows that aa is 10 % higher than the value predicted from Ap, leading to an overestimate of the aa precursor for that year. However, the most important difference is the lack of recurrent activity in the first three peaks and the presence of significant recurrent activity in the fourth. While the prediction is for an amplitude of Solar Cycle 24 of

  18. The rotation of Galaxy Clusters

    OpenAIRE

    Tovmassian, Hrant M.

    2015-01-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of the cluster mean velocity over the cluster image is proposed. The search for rotation is made for flat clusters with $a/b>1.8$ and BMI type clusters which are expected to be rotating. For comparison there were studied also round clusters and clusters of NBMI type, the second by brightness galaxy in which does not differ significantly from the cluste...

  19. Stellar populations in star clusters

    CERN Document Server

    Li, Chengyuan; Deng, Licai

    2016-01-01

    Stellar populations contain the most important information about star clus- ter formation and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple stellar populations (SSPs). However, discoveries of multiple stellar populations in Galactic globular clusters have expanded our view on stellar populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple stellar populations in star clusters even more complicated. Stellar population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on stellar populations in massive clusters with different ...

  20. 洋底热液喷口系统的微生物成矿研究进展%THE RECENT PROGRESS OF SUBMARINE HYDROTHERMAL BIOMINERALIZATION

    Institute of Scientific and Technical Information of China (English)

    孙治雷; 何拥军; 李军; 齐崇阳; 李季伟; 刘维亮

    2011-01-01

    The study of biomineralization in modern hydrothermal vent system is one of the keys to the research and the exploring of the early history of the earth, the evolution of life, the subsurface biosphere and the study of terrestrial planets (such as the Mar). It has in the past decade become one of the focuses of geobiological research with the application of the microelectronic technology and molecular biology technology. Available information indicates that microorganisms play a critical role in the formation of oxy-hydroxides (for instance, Fe, Mn, S or Si oxyhydroxide) and silicates in the hydrothermal systems of the earth. Furthermore, the biomineralization of modern chemolithoautotrophic microorganisms has been iden-tified to be the nexus of the interaction between the geoshpere and the biosphere and one of the forces to push forward the in-depth study of bioscience and geosciences In this paper, we summarized the ongoing research of hydrothermal bionmieralzaiton, including the biogenic minerals, the microbial biodiversity and the interactions between the minerals and microorganisms. In the foreseeable future, the research of hydrothermal biomineralization will inspire both the development of geosciences and biosciences and deepen our understanding of the earth history, life evolution and even astrobiology.%现代洋底热液喷口系统的微生物成矿研究进展是地球自身发展、生命演化、洋底下的生物圈层以及天文微生物探索工作得以有效开展的重要保障.近10余年来,随着微电子和分子生物学技术的发展,热液系统微生物成矿研究得以拓展和深入,逐渐成为地质微生物学研究的一个热点领域.当前在全球的热液喷口系统已经发现微生物在包括Fe、Mn、S、Si的氧化物以及硅酸盐矿物的形成过程中起到了重要甚至关键性的作用,同时热液喷口系统依赖于无机化能代谢活动存在的微生物的矿化成为人们理解生命形式与无机

  1. Clustering by Pattern Similarity

    Institute of Scientific and Technical Information of China (English)

    Hai-xun Wang; Jian Pei

    2008-01-01

    The task of clustering is to identify classes of similar objects among a set of objects. The definition of similarity varies from one clustering model to another. However, in most of these models the concept of similarity is often based on such metrics as Manhattan distance, Euclidean distance or other Lp distances. In other words, similar objects must have close values in at least a set of dimensions. In this paper, we explore a more general type of similarity. Under the pCluster model we proposed, two objects are similar if they exhibit a coherent pattern on a subset of dimensions. The new similarity concept models a wide range of applications. For instance, in DNA microarray analysis, the expression levels of two genes may rise and fall synchronously in response to a set of environmental stimuli. Although the magnitude of their expression levels may not be close, the patterns they exhibit can be very much alike. Discovery of such clusters of genes is essential in revealing significant connections in gene regulatory networks. E-commerce applications, such as collaborative filtering, can also benefit from the new model, because it is able to capture not only the closeness of values of certain leading indicators but also the closeness of (purchasing, browsing, etc.) patterns exhibited by the customers. In addition to the novel similarity model, this paper also introduces an effective and efficient algorithm to detect such clusters, and we perform tests on several real and synthetic data sets to show its performance.

  2. Clustering in bubbly liquids

    Science.gov (United States)

    Figueroa, Bernardo; Zenit, Roberto

    2004-11-01

    We are conducting experiments to determine the amount of clustering that occurs when small gas bubbles ascend in clean water. In particular, we are interested in flows for which the liquid motion around the bubbles can be described, with a certain degree of accuracy, using potential flow theory. This model is applicable for the case of bubbly liquids in which the Reynolds number is large and the Weber number is small. To clearly observe the formation of bubble clusters we propose the use of a Hele-Shaw-type channel. In this thin channel the bubbles cannot overlap in the depth direction, therefore the identification of bubble clusters cannot be misinterpreted. Direct video image analysis is performed to calculate the velocity and size of the bubbles, as well as the formation of clusters. Although the walls do affect the motion of the bubbles, the clustering phenomena does occur and has the same qualitative behavior as in fully three-dimensional flows. A series of preliminary measurements are presented. A brief discussion of our plans to perform PIV measurements to obtain the liquid velocity fields is also presented.

  3. Novel LanT associated lantibiotic clusters identified by genome database mining.

    Directory of Open Access Journals (Sweden)

    Mangal Singh

    Full Text Available BACKGROUND: Frequent use of antibiotics has led to the emergence of antibiotic resistance in bacteria. Lantibiotic compounds are ribosomally synthesized antimicrobial peptides against which bacteria are not able to produce resistance, hence making them a good alternative to antibiotics. Nisin is the oldest and the most widely used lantibiotic, in food preservation, without having developed any significant resistance against it. Having their antimicrobial potential and a limited number, there is a need to identify novel lantibiotics. METHODOLOGY/FINDINGS: Identification of novel lantibiotic biosynthetic clusters from an ever increasing database of bacterial genomes, can provide a major lead in this direction. In order to achieve this, a strategy was adopted to identify novel lantibiotic biosynthetic clusters by screening the sequenced genomes for LanT homolog, which is a conserved lantibiotic transporter specific to type IB clusters. This strategy resulted in identification of 54 bacterial strains containing the LanT homologs, which are not the known lantibiotic producers. Of these, 24 strains were subjected to a detailed bioinformatic analysis to identify genes encoding for precursor peptides, modification enzyme, immunity and quorum sensing proteins. Eight clusters having two LanM determinants, similar to haloduracin and lichenicidin were identified, along with 13 clusters having a single LanM determinant as in mersacidin biosynthetic cluster. Besides these, orphan LanT homologs were also identified which might be associated with novel bacteriocins, encoded somewhere else in the genome. Three identified gene clusters had a C39 domain containing LanT transporter, associated with the LanBC proteins and double glycine type precursor peptides, the only known example of such a cluster is that of salivaricin. CONCLUSION: This study led to the identification of 8 novel putative two-component lantibiotic clusters along with 13 having a single LanM and

  4. Clusters in Light Nuclei

    CERN Document Server

    Beck, C; Zafra, A Sanchez i; Thummerer, S; Azaiez, F; Bednarczyk, P; Courtin, S; Curien, D; Dorvaux, O; Goasduff, A; ~Lebhertz, D; Nourreddine, A; ~Rousseau, M; Salsac, M -D; von Oertzen, W; Gebauer, B; Wheldon, C; Kokalova, Tz; Efimov, G; Zherebchevsky, V; Schulz, Ch; Bohlen, H G; Kamanin, D; de Angelis, G; Gadea, A; Lenzi, S; Napoli, D R; Szilner, S; Milin, M; Catford, W N; Jenkins, D G; Royer, G

    2010-01-01

    A great deal of research work has been undertaken in the alpha-clustering study since the pioneering discovery, half a century ago, of 12C+12C molecular resonances. Our knowledge of the field of the physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. In this work, the occurence of "exotic" shapes in light N=Z alpha-like nuclei is investigated. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Results on clustering aspects are also discussed for light neutron-rich Oxygen isotopes.

  5. Vanadogermanate cluster anions.

    Science.gov (United States)

    Whitfield, T; Wang, X; Jacobson, A J

    2003-06-16

    Three novel vanadogermanate cluster anions have been synthesized by hydrothermal reactions. The cluster anions are derived from the (V(18)O(42)) Keggin cluster shell by substitution of V=O(2+) "caps" by Ge(2)O(OH)(2)(4+) species. In Cs(8)[Ge(4)V(16)O(42)(OH)(4)].4.7H(2)O, 1, (monoclinic, space group C2/c (No. 15), Z = 8, a = 44.513(2) A, b = 12.7632(7) A, c = 22.923(1) A, beta = 101.376(1) degrees ) and (pipH(2))(4)(pipH)(4)[Ge(8)V(14)O(50).(H(2)O)] (pip = C(4)N(2)H(10)), 2 (tetragonal, space group P4(2)/nnm (No. 134), Z = 2, a = 14.9950(7) A, c = 18.408(1) A), two and four VO(2+) caps are replaced, respectively, and each cluster anion encapsulates a water molecule. In K(5)H(8)Ge(8)V(12)SO(52).10H(2)O, 3, (tetragonal, space group I4/m (No. 87), Z = 2, a = 15.573(1) A, c = 10.963(1) A), four VO(2+) caps are replaced by Ge(2)O(OH)(2)(4+) species, and an additional two are omitted. The cluster ion in 3 contains a sulfate anion disordered over two positions. The cluster anions are analogous to the vanadoarsenate anions [V(18)(-)(n)()As(2)(n)()O(42)(X)](m)(-) (X = SO(3), SO(4), Cl; n = 3, 4) previously reported. PMID:12793808

  6. Subcellular Distribution of Glutathione Precursors in Arabidopsis thafiana

    Institute of Scientific and Technical Information of China (English)

    Barbara Eva Koffier; Romana Maier; Bernd Zechmann

    2011-01-01

    Glutathione is an important antioxidant and has many important functions in plant development,growth and defense.Glutathione synthesis and degradation is highly compartment-specific and relies on the subcellular availability of its precursors,cysteine,glutamate,glycine and y-glutamylcysteine especially in plastids and the cytosol which are considered as the main centers for glutathione synthesis.The availability of glutathione precursors within these cell compartments is therefore of great importance for successful plant development and defense.The aim of this study was to investigate the compartmentspecific importance of glutathione precursors in Arabidopsis thaliana.The subcellular distribution was compared between wild type plants (Col-0),plants with impaired glutathione synthesis (glutathione deficient pad2-1 mutant,wild type plants treated with buthionine sulfoximine),and one complemented line (OE3) with restored glutathione synthesis.Immunocytohistochemistry revealed that the inhibition of glutathione synthesis induced the accumulation of the glutathione precursors cysteine,glutamate and glycine in most cell compartments including plastids and the cytosol.A strong decrease could be observed in γ-glutamylcysteine (γ-EC) contents in these cell compartments.These experiments demonstrated that the inhibition of y-glutamylcysteine synthetase (GSH1) - the first enzyme of glutathione synthesis - causes a reduction of γ-EC levels and an accumulation of all other glutathione precursors within the cells.

  7. Solvent effects on the photochemistry of 4-aminoimidazole-5-carbonitrile, a prebiotically plausible precursor of purines.

    Science.gov (United States)

    Szabla, Rafał; Sponer, Judit E; Sponer, Jiří; Sobolewski, Andrzej L; Góra, Robert W

    2014-09-01

    4-Aminoimidazole-5-carbonitrile (AICN) was suggested as a prebiotically plausible precursor of purine nucleobases and nucleotides. Although it can be formed in a sequence of photoreactions, AICN is immune to further irradiation with UV-light. We present state-of-the-art multi-reference quantum-chemical calculations of potential energy surface cuts and conical intersection optimizations to explain the molecular mechanisms underlying the photostability of this compound. We have identified the N-H bond stretching and ring-puckering mechanisms that should be responsible for the photochemistry of AICN in the gas phase. We have further considered the photochemistry of AICN-water clusters, while including up to six explicit water molecules. The calculations reveal charge transfer to solvent followed by formation of an H3O(+) cation, both of which occur on the (1)πσ* hypersurface. Interestingly, a second proton transfer to an adjacent water molecule leads to a (1)πσ*/S0 conical intersection. We suggest that this electron-driven proton relay might be characteristic of low-lying (1)πσ* states in chromophore-water clusters. Owing to its nature, this mechanism might also be responsible for the photostability of analogous organic molecules in bulk water.

  8. Rohlin distance and the evolution of influenza A virus: weak attractors and precursors.

    Directory of Open Access Journals (Sweden)

    Raffaella Burioni

    Full Text Available The evolution of the hemagglutinin amino acids sequences of Influenza A virus is studied by a method based on an informational metrics, originally introduced by Rohlin for partitions in abstract probability spaces. This metrics does not require any previous functional or syntactic knowledge about the sequences and it is sensitive to the correlated variations in the characters disposition. Its efficiency is improved by algorithmic tools, designed to enhance the detection of the novelty and to reduce the noise of useless mutations. We focus on the USA data from 1993/94 to 2010/2011 for A/H3N2 and on USA data from 2006/07 to 2010/2011 for A/H1N1. We show that the clusterization of the distance matrix gives strong evidence to a structure of domains in the sequence space, acting as weak attractors for the evolution, in very good agreement with the epidemiological history of the virus. The structure proves very robust with respect to the variations of the clusterization parameters, and extremely coherent when restricting the observation window. The results suggest an efficient strategy in the vaccine forecast, based on the presence of "precursors" (or "buds" populating the most recent attractor.

  9. A genome-wide analysis of nonribosomal peptide synthetase gene clusters and their peptides in a Planktothrix rubescens strain

    Directory of Open Access Journals (Sweden)

    Nederbragt Alexander J

    2009-08-01

    Full Text Available Abstract Background Cyanobacteria often produce several different oligopeptides, with unknown biological functions, by nonribosomal peptide synthetases (NRPS. Although some cyanobacterial NRPS gene cluster types are well described, the entire NRPS genomic content within a single cyanobacterial strain has never been investigated. Here we have combined a genome-wide analysis using massive parallel pyrosequencing ("454" and mass spectrometry screening of oligopeptides produced in the strain Planktothrix rubescens NIVA CYA 98 in order to identify all putative gene clusters for oligopeptides. Results Thirteen types of oligopeptides were uncovered by mass spectrometry (MS analyses. Microcystin, cyanopeptolin and aeruginosin synthetases, highly similar to already characterized NRPS, were present in the genome. Two novel NRPS gene clusters were associated with production of anabaenopeptins and microginins, respectively. Sequence-depth of the genome and real-time PCR data revealed three copies of the microginin gene cluster. Since NRPS gene cluster candidates for microviridin and oscillatorin synthesis could not be found, putative (gene encoded precursor peptide sequences to microviridin and oscillatorin were found in the genes mdnA and oscA, respectively. The genes flanking the microviridin and oscillatorin precursor genes encode putative modifying enzymes of the precursor oligopeptides. We therefore propose ribosomal pathways involving modifications and cyclisation for microviridin and oscillatorin. The microviridin, anabaenopeptin and cyanopeptolin gene clusters are situated in close proximity to each other, constituting an oligopeptide island. Conclusion Altogether seven nonribosomal peptide synthetase (NRPS gene clusters and two gene clusters putatively encoding ribosomal oligopeptide biosynthetic pathways were revealed. Our results demonstrate that whole genome shotgun sequencing combined with MS-directed determination of oligopeptides successfully

  10. Refractory chronic cluster headache

    DEFF Research Database (Denmark)

    Mitsikostas, Dimos D; Edvinsson, Lars; Jensen, Rigmor H;

    2014-01-01

    for clinical and research use. The preparation of the final consensus followed three stages. Internal between authors, a larger between all European Headache Federation members and finally an international one among all investigators that have published clinical studies on cluster headache the last five years......Chronic cluster headache (CCH) often resists to prophylactic pharmaceutical treatments resulting in patients' life damage. In this rare but pragmatic situation escalation to invasive management is needed but framing criteria are lacking. We aimed to reach a consensus for refractory CCH definition...

  11. Kinematics of Clustering

    CERN Document Server

    Wang, Steven; Metcalfe, Guy; Wu, Jie

    2014-01-01

    The dynamical system for inertial particles in fluid flow has both attracting and repelling regions, the interplay of which can localize particles. In laminar flow experiments we find that particles, initially moving throughout the fluid domain, can undergo an instability and cluster into subdomains of the fluid when the flow Reynolds number exceeds a critical value that depends on particle and fluid inertia. We derive an expression for the instability boundary and for a universal curve that describes the clustering rate for all particles.

  12. South Asian Cluster

    Directory of Open Access Journals (Sweden)

    Ionel Sergiu Pirju

    2014-12-01

    Full Text Available This article aims at presenting the South Asian cluster composed of India, Indonesia, Iran and Malaysia, the intercultural values that characterizes it, the supported leadership style and tracing the main macroeconomic considerations which characterizes them. The research is synchronic, analysing the contemporary situation of these countries without reference to their evolution in time, by using the positivist paradigm that explains the reality at one point. It will be analysed the overall cluster with the existing interactions between the countries that composes it, while the article being one of information will avoid building recommendation, or new theories.

  13. Cluster's last stand?

    OpenAIRE

    Lockwood, Mike

    1997-01-01

    On 4 June last year the first attempt to make three-dimensional measurements in space was lost when the Ariane 5 rocket veered off course and self-destructed, 39 s into its maiden flight. On board were four identical spacecraft which made up Cluster,a mission that the European Space Agency called a “cornerstone” of its Horizon 2000 scientific programme. A full description of the Cluster satellites is given in a special issue of Space Science Reviews (Escoubet et al. 1997). Their loss de...

  14. Clustering Game Behavior Data

    DEFF Research Database (Denmark)

    Bauckhage, C.; Drachen, Anders; Sifa, Rafet

    2015-01-01

    and other techniques for player profiling and play style analysis have, therefore, become popular in the nascent field of game analytics. However, the proper use of clustering techniques requires expertise and an understanding of games is essential to evaluate results. With this paper, we address game data...... scientists and present a review and tutorial focusing on the application of clustering techniques to mine behavioral game data. Several algorithms are reviewed and examples of their application shown. Key topics such as feature normalization are discussed and open problems in the context of game analytics...

  15. An Emerge Approach in Inter Cluster Similarity for Quality Clusters

    Directory of Open Access Journals (Sweden)

    H. Venkateswara Reddy

    2013-04-01

    Full Text Available Relationship between the datasets is one most important issue in recent years. The recent methods are based mostly on the numerical data, but these methods are not suitable for real time data such as web pages, business transactions etc., which are known as Categorical data. It is difficult to find relationship in categorical data. In this paper, a new approach is proposed for finding the relationshipbetween the categorical data, hence to find relationship between the clusters. The main aim is to identify the quality clusters based on the relationship between clusters. If there is no relationship between clusters then those clusters are treated as quality clusters.

  16. Partitioning tungsten between matrix precursors and chondrule precursors through relative settling

    CERN Document Server

    Hubbard, Alexander

    2016-01-01

    Recent studies of chondrites have found a tungsten isotopic anomaly between chondrules and matrix. Given the refractory nature of tungsten, this implies that W was carried into the solar nebula by at least two distinct families of pre-solar grains. The observed chondrule/matrix split requires that the distinct families were kept separate during the dust coagulation process, and that the two families of grain interacted with the chondrule formation mechanism differently. We take the co-existence of different families of solids in the same general orbital region at the chondrule-precursor size as given, and explore the requirements for them to have interacted with the chondrule formation process at significantly different rates. We show that this sorting of families of solids into chondrule and matrix destined dust had to have been at least as powerful a sorting mechanism as the relative settling of aerodynamically distinct grains at at least two scale heights above the midplane. The requirement that the chondr...

  17. Partitioning Tungsten between Matrix Precursors and Chondrule Precursors through Relative Settling

    Science.gov (United States)

    Hubbard, Alexander

    2016-08-01

    Recent studies of chondrites have found a tungsten isotopic anomaly between chondrules and matrix. Given the refractory nature of tungsten, this implies that W was carried into the solar nebula by at least two distinct families of pre-solar grains. The observed chondrule/matrix split requires that the distinct families were kept separate during the dust coagulation process, and that the two families of grain interacted with the chondrule formation mechanism differently. We take the co-existence of different families of solids in the same general orbital region at the chondrule-precursor size as given, and explore the requirements for them to have interacted with the chondrule formation process at significantly different rates. We show that this sorting of families of solids into chondrule- and matrix-destined dust had to have been at least as powerful a sorting mechanism as the relative settling of aerodynamically distinct grains at least two scale heights above the midplane. The requirement that the chondrule formation mechanism was correlated in some fashion with a dust-grain sorting mechanism argues strongly for spatially localized chondrule formation mechanisms such as turbulent dissipation in non-thermally ionized disk surface layers, and argues against volume-filling mechanisms such as planetesimal bow shocks.

  18. Combining cluster number counts and galaxy clustering

    CERN Document Server

    Lacasa, Fabien

    2016-01-01

    We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. To this end, we use a Halo Model framework complemented by a Halo Occupation Distribution model (HOD), and we work in full-sky. We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions, as the Gaussian part of the covariance can in fact become subdominant in certain configurations. We discuss in particular the case of the super-sample covariance (SSC), including the effects of galaxy shot-noise, halo second order bias and non-local bias, and demonstrating interesting mathematical properties. Using the joint covariance matrix and a Fisher matrix methodology, we examine the prospects of combining these two probes to constrain cosmological and HOD parameters. We find that the combination indeed results in noticeable better constraints, in particular because the cross-covariance introduces a synergy between the probes on small scales....

  19. Localized attack on clustering networks

    CERN Document Server

    Dong, Gaogao; Du, Ruijin; Shao, Shuai; Stanley, H Eugene; Shlomo, Havlin

    2016-01-01

    Clustering network is one of which complex network attracting plenty of scholars to discuss and study the structures and cascading process. We primarily analyzed the effect of clustering coefficient to other various of the single clustering network under localized attack. These network models including double clustering network and star-like NON with clustering and random regular (RR) NON of ER networks with clustering are made up of at least two networks among which exist interdependent relation among whose degree of dependence is measured by coupling strength. We show both analytically and numerically, how the coupling strength and clustering coefficient effect the percolation threshold, size of giant component, critical coupling point where the behavior of phase transition changes from second order to first order with the increase of coupling strength between the networks. Last, we study the two types of clustering network: one type is same with double clustering network in which each subnetwork satisfies ...

  20. Projection effects in cluster catalogues

    CERN Document Server

    Van Haarlem, M P; White, S D M

    1997-01-01

    We investigate the importance of projection effects in the identification of galaxy clusters in 2D galaxy maps and their effect on the estimation of cluster velocity dispersions. A volume limited galaxy catalogue that was derived from a Standard CDM N-body simulation was used. We select clusters using criteria that match those employed in the construction of real cluster catalogues and find that our mock Abell cluster catalogues are heavily contaminated and incomplete. Over one third (34 per cent) of clusters of richness class R>=1 are miclassifications arising from the projection of one or more clumps onto an intrinsically poor cluster. Conversely, 32 per cent of intrinsically rich clusters are missed from the R>=1 catalogues, mostly because of statistical fluctuations in the background count. Selection by X-ray luminosity rather than optical richness reduces, but does not completely eliminate, these problems. Contamination by unvirialised sub-clumps near a cluster leads to a considerable overestimation of t...

  1. Clustering of resting state networks.

    Directory of Open Access Journals (Sweden)

    Megan H Lee

    Full Text Available BACKGROUND: The goal of the study was to demonstrate a hierarchical structure of resting state activity in the healthy brain using a data-driven clustering algorithm. METHODOLOGY/PRINCIPAL FINDINGS: The fuzzy-c-means clustering algorithm was applied to resting state fMRI data in cortical and subcortical gray matter from two groups acquired separately, one of 17 healthy individuals and the second of 21 healthy individuals. Different numbers of clusters and different starting conditions were used. A cluster dispersion measure determined the optimal numbers of clusters. An inner product metric provided a measure of similarity between different clusters. The two cluster result found the task-negative and task-positive systems. The cluster dispersion measure was minimized with seven and eleven clusters. Each of the clusters in the seven and eleven cluster result was associated with either the task-negative or task-positive system. Applying the algorithm to find seven clusters recovered previously described resting state networks, including the default mode network, frontoparietal control network, ventral and dorsal attention networks, somatomotor, visual, and language networks. The language and ventral attention networks had significant subcortical involvement. This parcellation was consistently found in a large majority of algorithm runs under different conditions and was robust to different methods of initialization. CONCLUSIONS/SIGNIFICANCE: The clustering of resting state activity using different optimal numbers of clusters identified resting state networks comparable to previously obtained results. This work reinforces the observation that resting state networks are hierarchically organized.

  2. Supported heteronuclear noble metal cluster catalysts and method for preparing same

    International Nuclear Information System (INIS)

    New heteronuclear noble metal cluster complexes have been discovered and synthesized for the first time. These complexes are (pyridine)2Pt(Ir2(CO)15), (pyridine)2 Pt(Ir2(CO)7), (Pyridine)3Pt(Ru3(CO)12), ((C6H5)3P)2Pt(Ir(CO)3(P6H5)3)2, ((C6H5)3P)2Rh(CO)(IR(CO)4), and (pyridine)2Pt(Rh(CO)2(P(C6H5)3)3)2. These new heteronuclear noble metal cluster complexes are useful as supported mixed noble metal catalyst precursors. These new cluster complexes, of known stoichiometry, are deposited on anhydrous refractory inorganic oxide or carbon supports and then reduced resulting in the formation of a supported heteronuclear noble metal catalyst having the same metals stoichiometry as the starting cluster complexes. In this way, precise control can be exercised over the ratio and distribution of multiple metal components in a mixed noble metal catalyst. The usage of preformed heteronuclear noble metal cluster complexes as supported mixed metal catalyst precursors maximizes surface alloy formation and also yields unique mixed-metal cluster structures on the support surface

  3. Neurodevelopment. Parasympathetic ganglia derive from Schwann cell precursors.

    Science.gov (United States)

    Espinosa-Medina, I; Outin, E; Picard, C A; Chettouh, Z; Dymecki, S; Consalez, G G; Coppola, E; Brunet, J-F

    2014-07-01

    Neural crest cells migrate extensively and give rise to most of the peripheral nervous system, including sympathetic, parasympathetic, enteric, and dorsal root ganglia. We studied how parasympathetic ganglia form close to visceral organs and what their precursors are. We find that many cranial nerve-associated crest cells coexpress the pan-autonomic determinant Paired-like homeodomain 2b (Phox2b) together with markers of Schwann cell precursors. Some give rise to Schwann cells after down-regulation of PHOX2b. Others form parasympathetic ganglia after being guided to the site of ganglion formation by the nerves that carry preganglionic fibers, a parsimonious way of wiring the pathway. Thus, cranial Schwann cell precursors are the source of parasympathetic neurons during normal development. PMID:24925912

  4. Experimental observation of precursor solitons in a flowing complex plasma

    Science.gov (United States)

    Jaiswal, Surabhi; Bandyopadhyay, P.; Sen, A.

    2016-04-01

    The excitation of precursor solitons ahead of a rapidly moving object in a fluid, a spectacular phenomenon in hydrodynamics that has often been observed ahead of moving ships, has surprisingly not been investigated in plasmas where the fluid model holds good for low frequency excitations such as ion acoustic waves. In this Rapid Communication we report an experimental observation of precursor solitons in a flowing dusty plasma. The nonlinear solitary dust acoustic waves (DAWs) are excited by a supersonic mass flow of the dust particles over an electrostatic potential hill. In a frame where the fluid is stationary and the hill is moving the solitons propagate in the upstream direction as precursors while wake structures consisting of linear DAWs are seen to propagate in the downstream region. A theoretical explanation of these excitations based on the forced Korteweg-deVries model equation is provided and their practical implications in situations involving a charged object moving in a plasma are discussed.

  5. Experimental observation of precursor solitons in a flowing complex plasma

    CERN Document Server

    Jaiswal, Surabhi; Sen, A

    2015-01-01

    The excitation of precursor solitons ahead of a rapidly moving object in a fluid, a spectacular phenomenon in hydrodynamics that has often been observed ahead of moving ships, has surprisingly not been investigated in plasmas where the fluid model holds good for low frequency excitations such as ion acoustic waves. In this paper we report the first experimental observation of precursor solitons in a flowing dusty plasma. The nonlinear solitary dust acoustic waves (DAWs) are excited by a supersonic mass flow of the dust particles over an electrostatic potential hill. In a frame where the fluid is stationary and the hill is moving the solitons propagate in the upstream direction as precursors while wake structures consisting of linear DAWs are seen to propagate in the downstream region. A theoretical explanation of these excitations based on the forced Korteweg-deVries model equation is provided and their practical implications in situations involving a charged object moving in a plasma are discussed.

  6. Precursors and electron-positron pair loading from erupting fireballs

    CERN Document Server

    Ramirez-Ruiz, E; Lazzati, D; Ramirez-Ruiz, Enrico; Fadyen, Andrew I. Mac; Lazzati, Davide

    2002-01-01

    Recent observations suggest that long-duration gamma-ray bursts and their afterglows are produced by highly relativistic jets emitted in core-collapse explosions. As the jet makes its way out of the stellar mantle, a bow shock runs ahead and a strong thermal precursor is produced as the shock breaks out. Such erupting fireballs produce a very bright gamma-ray precursor as they interact with the thermal break-out emission. The prompt gamma-ray emission propagates ahead of the fireball before it becomes optically thin, leading to electron-positron pair loading and radiative acceleration of the external medium. The detection of such precursors would offer the possibility of diagnosing not only the radius of the stellar progenitor and the initial Lorentz factor of the collimated fireball, but also the density of the external environment.

  7. The Behaviors of Optimal Precursors during Wintertime Eurasian Blocking Onset

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhina; WANG Donghai

    2012-01-01

    In this paper the optimal precursors for wintertime Eurasian blocking onset are acquired by solving a nonlinear optimization problem whose objective function is constructed based on a blocking index with a triangular T21,three-level,quasi-geostrophic global spectral model.The winter climatological state is chosen as the reference basic state.Numerical results show that the optimal precursors are characterized by a baroclinic pattern with a westward tilt with height,which are mainly located upstream of the blocking region.For an optimization time of 5 days,these perturbations are mainly localized over the Northeast Atlantic Ocean and continental Europe. With the extension of the optimization time to 8 days,these perturbations are distributed more upstream and extensively in the zonal direction.Wave spectrum analysis reveals that the optimal precursors are composed of not only synoptic-scale (wave numbers 5 18) waves,but planetary-scale (wave numbers 0-4) waves as well.The synoptic-scale optimal precursors are mainly located in the mid-latitude area,while the planetary-scale optimal precursors focus primarily on the highlatitude region.The formation of a strong planetary-scale positive blocking anomaly is accompanied by the reinforcement of synoptic-scale perturbations and further fragmentation into two branches,in which the northern branch is generally stronger than the southern one.The eddy forcing arising from the selfinteraction of synoptic-scale disturbances is shown to be crucial in triggering the dipole blocking anomaly,and the planetary-scale optimal precursor provides the initial favorable background conditions for blocking onset.

  8. PVM Support for Clusters

    Science.gov (United States)

    Springer, P.

    2000-01-01

    The latest version of PVM (3.4.3) now contains support for a PC cluster running Linux, also known as a Beowulf system. A PVM user of a computer outside the Beowulf system can add the Beowulf as a single machine.

  9. Evolution of Galaxy Clustering

    OpenAIRE

    Bagla, J. S.

    1997-01-01

    We show that the galaxy correlation function does not evolve in proportion with the correlation function of the underlying mass distribution. Earliest galaxies cluster very strongly and the amplitude of the galaxy correlation function decreases from this large value. This continues till the average peaks have collapsed, after which, the galaxy correlation function does not evolve very strongly.

  10. Fuzzy clustering of mechanisms

    Indian Academy of Sciences (India)

    Amitabha Ghosh; Dilip Kumar Pratihar; M V V Amarnath; Guenter Dittrich; Jorg Mueller

    2012-10-01

    During the course of development of Mechanical Engineering, a large number of mechanisms (that is, linkages to perform various types of tasks) have been conceived and developed. Quite a few atlases and catalogues were prepared by the designers of machines and mechanical systems. However, often it is felt that a clustering technique for handling the list of large number of mechanisms can be very useful,if it is developed based on a scientific principle. In this paper, it has been shown that the concept of fuzzy sets can be conveniently used for this purpose, if an adequate number of properly chosen attributes (also called characteristics) are identified. Using two clustering techniques, the mechanisms have been classified in the present work and in future, it may be extended to develop an expert system, which can automate type synthesis phase of mechanical design. To the best of the authors’ knowledge, this type of clustering of mechanisms has not been attempted before. Thus, this is the first attempt to cluster the mechanisms based on some quantitative measures. It may help the engineers to carry out type synthesis of the mechanisms.

  11. Clustering under Perturbation Resilience

    CERN Document Server

    Balcan, Maria Florina

    2011-01-01

    Recently, Bilu and Linial \\cite{BL} formalized an implicit assumption often made when choosing a clustering objective: that the optimum clustering to the objective should be preserved under small multiplicative perturbations to distances between points. They showed that for max-cut clustering it is possible to circumvent NP-hardness and obtain polynomial-time algorithms for instances resilient to large (factor $O(\\sqrt{n})$) perturbations, and subsequently Awasthi et al. \\cite{ABS10} considered center-based objectives, giving algorithms for instances resilient to O(1) factor perturbations. In this paper, we greatly advance this line of work. For the $k$-median objective, we present an algorithm that can optimally cluster instances resilient to $(1 + \\sqrt{2})$-factor perturbations, solving an open problem of Awasthi et al.\\cite{ABS10}. We additionally give algorithms for a more relaxed assumption in which we allow the optimal solution to change in a small $\\epsilon$ fraction of the points after perturbation. ...

  12. Clustering high dimensional data

    DEFF Research Database (Denmark)

    Assent, Ira

    2012-01-01

    High-dimensional data, i.e., data described by a large number of attributes, pose specific challenges to clustering. The so-called ‘curse of dimensionality’, coined originally to describe the general increase in complexity of various computational problems as dimensionality increases, is known to...

  13. Detecting alternative graph clusterings.

    Science.gov (United States)

    Mandala, Supreet; Kumara, Soundar; Yao, Tao

    2012-07-01

    The problem of graph clustering or community detection has enjoyed a lot of attention in complex networks literature. A quality function, modularity, quantifies the strength of clustering and on maximization yields sensible partitions. However, in most real world networks, there are an exponentially large number of near-optimal partitions with some being very different from each other. Therefore, picking an optimal clustering among the alternatives does not provide complete information about network topology. To tackle this problem, we propose a graph perturbation scheme which can be used to identify an ensemble of near-optimal and diverse clusterings. We establish analytical properties of modularity function under the perturbation which ensures diversity. Our approach is algorithm independent and therefore can leverage any of the existing modularity maximizing algorithms. We numerically show that our methodology can systematically identify very different partitions on several existing data sets. The knowledge of diverse partitions sheds more light into the topological organization and helps gain a more complete understanding of the underlying complex network.

  14. Galactic Open Clusters

    CERN Document Server

    Von Hippel, T

    2005-01-01

    The study of open clusters has a classic feel to it since the subject predates anyone alive today. Despite the age of this topic, I show via an ADS search that its relevance and importance in astronomy has grown faster in the last few decades than astronomy in general. This is surely due to both technical reasons and the interconnection of the field of stellar evolution to many branches of astronomy. In this review, I outline what we know today about open clusters and what they have taught us about a range of topics from stellar evolution to Galactic structure to stellar disk dissipation timescales. I argue that the most important astrophysics we have learned from open clusters is stellar evolution and that its most important product has been reasonably precise stellar ages. I discuss where open cluster research is likely to go in the next few years, as well as in the era of 20m telescopes, SIM, and GAIA. Age will continue to be of wide relevance in astronomy, from cosmology to planet formation timescales, an...

  15. Disentangling Porterian Clusters

    DEFF Research Database (Denmark)

    Jagtfelt, Tue

    intertwined and that Porter’s consciously paradigmatic textbook very likely gained worldwide influence due to two interrelated factors. The first factor is the deliberately holistic gestalt figure propounded in Nations, which prompted scientific communities to pursue cluster research; the second factor...

  16. Curriculum Guide Construction Cluster.

    Science.gov (United States)

    Kline, Ken

    As part of a model construction cluster curriculum development project, this guide was developed and implemented in the Beaverton (Oregon) School District. The curriculum guide contains 16 units covering the following topics: introduction to construction jobs; safety and first aid; blueprint readings; basic mathematics; site work; framing; roofing…

  17. Isolation, cultivation and genomic analysis of magnetosome biomineralization genes of a new genus of South-seeking magnetotactic cocci within the Alphaproteobacteria

    Energy Technology Data Exchange (ETDEWEB)

    Morillo, Viviana [Universidade Federal do Rio de Janeiro; Abreu, Fernanda [Universidade Federal do Rio de Janeiro; Araujo, Ana C [Universidade Federal do Rio de Janeiro; de Almeida, Luiz G [Laboratorio Nacional de Computacao Cientifica; Enrich-Prast, Alex [Universidade Federal do Rio de Janeiro; Farina, Marcos [Universidade Federal do Rio de Janeiro; de Vasconcelos, Ana T [Laboratorio Nacional de Computacao Cientifica; Bazylinski, Dennis A [Ames Laboratory; Lins, Ulysses [Universidade Federal do Rio de Janeiro

    2014-01-01

    Although magnetotactic bacteria (MTB) are ubiquitous in aquatic habitats, they are still considered fastidious microorganisms with regard to growth and cultivation with only a relatively low number of axenic cultures available to date. Here, we report the first axenic culture of an MTB isolated in the Southern Hemisphere (Itaipu Lagoon in Rio de Janeiro, Brazil). Cells of this new isolate are coccoid to ovoid in morphology and grow microaerophilically in semi-solid medium containing an oxygen concentration ([O2]) gradient either under chemoorganoheterotrophic or chemolithoautotrophic conditions. Each cell contains a single chain of approximately 10 elongated cuboctahedral magnetite (Fe3O4) magnetosomes. Phylogenetic analysis based on the 16S rRNA gene sequence shows that the coccoid MTB isolated in this study represents a new genus in the Alphaproteobacteria; the name Magnetofaba australis strain IT-1 is proposed. Preliminary genomic data obtained by pyrosequencing shows that M. australis strain IT-1 contains a genomic region with genes involved in biomineralization similar to those found in the most closely related magnetotactic cocci Magnetococcus marinus strain MC-1. However, organization of the magnetosome genes differs from M. marinus.

  18. Structural and Optical Analysis of the Bio-mineralized Photonic Structures in the Shell of the Blue- Rayed Limpet Ansates Pellucida

    Science.gov (United States)

    Kolle, Mathias; Li, Ling; Kolle, Stefan; Weaver, James; Ortiz, Christine; Aizenberg, Joanna

    2013-03-01

    Many terrestrial biological organisms have evolved a variety of micro- and nanostructures that provide unique optical signatures including distinctive, dynamic coloration, high reflectivity or superior whiteness. Recently, photonic structures have also been found in the shells or spines of marine animals. Life under water imposes very distinct constraints on organisms relying on visual communication and on the designs and the materials involved in aquatic photonic structures. Here, we present a bio-mineralized calcium carbonate - based crystalline photonic system buried in the shell of the blue-rayed limpet Ansates pellucida. The structure consists of a layered stack of calcite lamellae with uniform thickness and inter-lamella spacing. This arrangement lies at the origin of the blue-green iridescence of the organism's characteristic stripes, which is caused by multilayer interference. The multilayer is supported by a disordered array of spherical particles with an average diameter of 300nm, likely serving to enhance the contrast of the blue stripes. We present a full structural and optical characterization of this bio-mineralised marine photonic system, supported by optical FDTD modeling. The authors gratefully acknowledge financial support by the Air Force Office of Scientific Research under Award No. FA9550-09-1-0669-DOD35CAP. M. Kolle is grateful for support from the Alexander von Humboldt - Foundation.

  19. Chitosan membranes containing micro or nano-size bioactive glass particles: evolution of biomineralization followed by in situ dynamic mechanical analysis.

    Science.gov (United States)

    Caridade, Sofia G; Merino, Esther G; Alves, Natália M; Bermudez, Verónica de Zea; Boccaccini, Aldo R; Mano, João F

    2013-04-01

    A new family of biodegradable polymer/bioactive glass (BG) composite materials has emerged based on the availability of nano-sized bioactive particles. Such novel biocomposites can have enhanced performance, in terms of mechanical properties and bioactivity, and they can be designed to be used in bone regeneration approaches. In this work, membranes of chitosan (CTS) and chitosan with bioactive glass (BG) both micron and nano sized particles (CTS/μBG, CTS/nBG, respectively) were prepared by solvent casting. Microstructural and mechanical properties were evaluated in order to compare the effects of the incorporation of micro (μBG) and nano (nBG) particles in the chitosan matrix. In vitro bioactivity tests were performed to characterize the apatite layer that is formed on the surface of the material after being immersed in simulated body fluid (SBF). The biomineralization process on the biomaterials was also followed using non-conventional dynamic mechanical analysis (DMA), both online and offline. In such DMA experiments, the change in the storage modulus, E', and the loss factor, tan δ, were measured as a function of the immersion time in SBF. The results demonstrated that CTS/nBG membranes possess enhanced mechanical properties and higher bioactivity in comparison with the CTS/μBG membranes. Such results suggest the potential of nBG for the development of bioactive composites for bone regeneration applications. PMID:23466499

  20. Not All Inner Ears are the Same: Otolith Matrix Proteins in the Inner Ear of Sub-Adult Cichlid Fish, Oreochromis Mossambicus, Reveal Insights Into the Biomineralization Process.

    Science.gov (United States)

    Weigele, Jochen; Franz-Odendaal, Tamara A; Hilbig, Reinhard

    2016-02-01

    The fish ear stones (otoliths) consist mainly of calcium carbonate and have lower amounts of a proteinous matrix. This matrix consists of macromolecules, which directly control the biomineralization process. We analyzed the composition of this proteinous matrix by mass spectrometry in a shotgun approach. For this purpose, an enhanced protein purification technique was developed that excludes any potential contamination of proteins from body fluids. Using this method we identified eight proteins in the inner ear of Oreochromis mossambicus. These include the common otolith matrix proteins (OMP-1, otolin-1, neuroserpin, SPARC and otoconin), and three proteins (alpha tectorin, otogelin and transferrin) not previously localized to the otoliths. Moreover, we were able to exclude the occurrence of two matrix proteins (starmaker and pre-cerebellin-like protein) known from other fish species. In further analyses, we show that the absence of the OMP starmaker corresponds to calcitic otoliths and that pre-cerebellin-like protein is not present at any stage during the development of the otoliths of the inner ear. This study shows O. mossambicus does not have all of the known otolith proteins indicating that the matrix proteins in the inner ear of fish are not the same across species. Further functional studies of the novel proteins we identified during otolith development are required.

  1. Data clustering algorithms and applications

    CERN Document Server

    Aggarwal, Charu C

    2013-01-01

    Research on the problem of clustering tends to be fragmented across the pattern recognition, database, data mining, and machine learning communities. Addressing this problem in a unified way, Data Clustering: Algorithms and Applications provides complete coverage of the entire area of clustering, from basic methods to more refined and complex data clustering approaches. It pays special attention to recent issues in graphs, social networks, and other domains.The book focuses on three primary aspects of data clustering: Methods, describing key techniques commonly used for clustering, such as fea

  2. Hox gene clusters in the Indonesian coelacanth, Latimeria menadoensis.

    Science.gov (United States)

    Koh, Esther G L; Lam, Kevin; Christoffels, Alan; Erdmann, Mark V; Brenner, Sydney; Venkatesh, Byrappa

    2003-02-01

    The Hox genes encode transcription factors that play a key role in specifying body plans of metazoans. They are organized into clusters that contain up to 13 paralogue group members. The complex morphology of vertebrates has been attributed to the duplication of Hox clusters during vertebrate evolution. In contrast to the single Hox cluster in the amphioxus (Branchiostoma floridae), an invertebrate-chordate, mammals have four clusters containing 39 Hox genes. Ray-finned fishes (Actinopterygii) such as zebrafish and fugu possess more than four Hox clusters. The coelacanth occupies a basal phylogenetic position among lobe-finned fishes (Sarcopterygii), which gave rise to the tetrapod lineage. The lobe fins of sarcopterygians are considered to be the evolutionary precursors of tetrapod limbs. Thus, the characterization of Hox genes in the coelacanth should provide insights into the origin of tetrapod limbs. We have cloned the complete second exon of 33 Hox genes from the Indonesian coelacanth, Latimeria menadoensis, by extensive PCR survey and genome walking. Phylogenetic analysis shows that 32 of these genes have orthologs in the four mammalian HOX clusters, including three genes (HoxA6, D1, and D8) that are absent in ray-finned fishes. The remaining coelacanth gene is an ortholog of hoxc1 found in zebrafish but absent in mammals. Our results suggest that coelacanths have four Hox clusters bearing a gene complement more similar to mammals than to ray-finned fishes, but with an additional gene, HoxC1, which has been lost during the evolution of mammals from lobe-finned fishes.

  3. Do glycine-extended hormone precursors have clinical significance?

    DEFF Research Database (Denmark)

    Rehfeld, Jens Frederik

    2014-01-01

    Half of the known peptide hormones are C-terminally amidated. Subsequent biogenesis studies have shown that the immediate precursor is a glycine-extended peptide. The clinical interest in glycine-extended hormones began in 1994, when it was suggested that glycine-extended gastrin stimulated cancer...... and clinical effects of glycine-extended precursors for most other amidated hormones than gastrin and cholecystokinin (CCK). The idea of glycine-extended peptides as independent messengers was interesting. But clinical science has to move ahead from ideas that cannot be supported at key points after decades...

  4. Differentiation of Mouse Embryonic Stem Cells into Ventral Foregut Precursors

    DEFF Research Database (Denmark)

    Rothová, Michaela; Hölzenspies, Jurriaan J; Livigni, Alessandra;

    2016-01-01

    Anterior definitive endoderm (ADE), the ventral foregut precursor, is both an important embryonic signaling center and a unique multipotent precursor of liver, pancreas, and other organs. Here, a method is described for the differentiation of mouse embryonic stem cells (mESCs) to definitive...... endoderm with pronounced anterior character. ADE-containing cultures can be produced in vitro by suspension (embryoid body) culture or in a serum-free adherent monolayer culture. ESC-derived ADE cells are committed to endodermal fates and can undergo further differentiation in vitro towards ventral foregut...

  5. Synthesis of GAP and PAMMO Homopolymers from Mesylate Polymeric Precursors

    Science.gov (United States)

    Mura, Claudio; Fruci, Stefania; Lamia, Pietro; Cappello, Miriam; Filippi, Sara; Polacco, Giovanni

    2016-04-01

    In azidic binders for solid propellants, the N3 functionality is introduced by substitution of a halogen or tosyl group, but recently the mesyl group has been suggested as an alternative. The mesylate group has two advantages, mainly related to its small dimensions and low cost. Poly(glycidyl azide) and poly 3-azidomethyl-3-methyl oxetane were prepared by using both tosylate and mesylate precursors. The azidation kinetics were studied at three different temperatures while keeping all other operating parameters the same. The results confirmed the good potential of the mesylate precursors for the production of azidic binders.

  6. 3-D rheologic model of earthquake preparation (Ⅲ): Precursor field

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    On the basis of the theory of viscoelastic displacement and strain field for the three-dimensional rheologic model of earthquake preparation, this paper mainly studies the theoretical solution of precursor field for the three-dimensional rheologic model of earthquake preparation. We derive the viscoelastic analytical expressions of the ground tilt, underground water level, earth resistivity at an arbitrary point (x, y, z) in the rheologic medium, and analyzed the earth resistivity preliminarily, providing a certain theoretical basis for the precursor analysis of seismogenic process.

  7. Quartile Clustering: A quartile based technique for Generating Meaningful Clusters

    CERN Document Server

    Goswami, Saptarsi

    2012-01-01

    Clustering is one of the main tasks in exploratory data analysis and descriptive statistics where the main objective is partitioning observations in groups. Clustering has a broad range of application in varied domains like climate, business, information retrieval, biology, psychology, to name a few. A variety of methods and algorithms have been developed for clustering tasks in the last few decades. We observe that most of these algorithms define a cluster in terms of value of the attributes, density, distance etc. However these definitions fail to attach a clear meaning/semantics to the generated clusters. We argue that clusters having understandable and distinct semantics defined in terms of quartiles/halves are more appealing to business analysts than the clusters defined by data boundaries or prototypes. On the samepremise, we propose our new algorithm named as quartile clustering technique. Through a series of experiments we establish efficacy of this algorithm. We demonstrate that the quartile clusteri...

  8. The Presence of Modifiable Residues in the Core Peptide Part of Precursor Nisin Is Not Crucial for Precursor Nisin Interactions with NisB- and NisC

    NARCIS (Netherlands)

    Khusainov, Rustem; Kuipers, Oscar P.; Hofmann, Andreas

    2013-01-01

    Precursor nisin is a model posttranslationally modified precursor lantibiotic that can be structurally divided into a leader peptide sequence and a modifiable core peptide part. The nisin core peptide clearly plays an important role in the precursor nisin - nisin modification enzymes interactions, s

  9. The Rotation of Galaxy Clusters

    Science.gov (United States)

    Tovmassian, H. M.

    2015-09-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher than the cluster mean velocity over the cluster image is proposed. The search for rotation is made for flat clusters with a/b > 1.8 and BMI type clusters which are expected to be rotating. For comparison there were studied also round clusters and clusters of NBMI type, the second by brightness galaxy, which does not differ significantly from the cluster cD galaxy. Seventeen out of studied 65 clusters are found to be rotating. It was found that the detection rate is sufficiently high for flat clusters, over 60%, and clusters of BMI type with dominant cD galaxy, ≈ 35% . The obtained results show that clusters were formed from the huge primordial gas clouds and preserved the rotation of the primordial clouds, unless they did not experience mergings with other clusters and groups of galaxies, as a result of which the rotation was prevented.

  10. The rotation of Galaxy Clusters

    CERN Document Server

    Tovmassian, Hrant M

    2015-01-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of the cluster mean velocity over the cluster image is proposed. The search for rotation is made for flat clusters with $a/b>1.8$ and BMI type clusters which are expected to be rotating. For comparison there were studied also round clusters and clusters of NBMI type, the second by brightness galaxy in which does not differ significantly from the cluster cD galaxy. Seventeen out of studied 65 clusters are found to be rotating. It was found that the detection rate is sufficiently high for flat clusters, over 60\\%, and clusters of BMI type with dominant cD galaxy, ~ 35%. The obtained results show that clusters were formed from the huge primordial gas clouds and preserved the rotation of the primordial clouds, unless they did not have merging with other clusters and groups of galaxies, in the result of which the rotation has been prevented.

  11. Single-cluster dynamics for the random-cluster model

    NARCIS (Netherlands)

    Deng, Y.; Qian, X.; Blöte, H.W.J.

    2009-01-01

    We formulate a single-cluster Monte Carlo algorithm for the simulation of the random-cluster model. This algorithm is a generalization of the Wolff single-cluster method for the q-state Potts model to noninteger values q>1. Its results for static quantities are in a satisfactory agreement with those

  12. Eclipsing binaries in open clusters

    DEFF Research Database (Denmark)

    Southworth, John; Clausen, J.V.

    2006-01-01

    Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August......Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August...

  13. Radio observations of Planck clusters

    CERN Document Server

    Kale, Ruta

    2012-01-01

    Recently, a number of new galaxy clusters have been detected by the ESA-Planck satellite, the South Pole Telescope and the Atacama Cosmology Telescope using the Sunyaev-Zeldovich effect. Several of the newly detected clusters are massive, merging systems with disturbed morphology in the X-ray surface brightness. Diffuse radio sources in clusters, called giant radio halos and relics, are direct probes of cosmic rays and magnetic fields in the intra-cluster medium. These radio sources are found to occur mainly in massive merging clusters. Thus, the new SZ-discovered clusters are good candidates to search for new radio halos and relics. We have initiated radio observations of the clusters detected by Planck with the Giant Metrewave Radio Telescope. These observations have already led to the detection of a radio halo in PLCKG171.9-40.7, the first giant halo discovered in one of the new Planck clusters.

  14. The Evolution of Cluster Substructure

    CERN Document Server

    Jeltema, T E; Bautz, M W; Buote, D A; Jeltema, Tesla E.; Canizares, Claude R.; Bautz, Mark W.; Buote, David A.

    2003-01-01

    Using Chandra archival data, we have begun a study to quantify the evolution of cluster morphology with redshift. To quantify cluster morphology, we use the power ratio method developed by Buote and Tsai (1995). Power ratios are constructed from moments of the two-dimensional gravitational potential and are, therefore, related to a cluster's dynamical state. Our sample will include around 50 clusters from the Chandra archive with redshifts between 0.11 and 1.1. These clusters were selected from two fairly complete flux-limited X-ray surveys (the ROSAT Bright Cluster Sample and the Einstein Medium Sensitivity Survey), and additional high-redshift clusters were selected from recent ROSAT flux-limited surveys. Here we present preliminary results from the first 15 clusters in this sample. Of these, eight have redshifts below 0.5, and seven have redshifts above 0.5.

  15. Textile Industrial Clusters in China

    Institute of Scientific and Technical Information of China (English)

    Nie Ting

    2010-01-01

    @@ "National Textile Industry Cluster Development Seminar" convened,held by China National Textile and Apparel Council,23 cities and towns were awarded as China's Textile Industry Cluster Pilot District.By far,China's textile industrial clusters have grown to 164,which indicate a quick and gorgeous development.These textile industrial clusters have a great impact on the local economy and even the whole national textile industry's development.

  16. [Cluster analysis in biomedical researches].

    Science.gov (United States)

    Akopov, A S; Moskovtsev, A A; Dolenko, S A; Savina, G D

    2013-01-01

    Cluster analysis is one of the most popular methods for the analysis of multi-parameter data. The cluster analysis reveals the internal structure of the data, group the separate observations on the degree of their similarity. The review provides a definition of the basic concepts of cluster analysis, and discusses the most popular clustering algorithms: k-means, hierarchical algorithms, Kohonen networks algorithms. Examples are the use of these algorithms in biomedical research. PMID:24640781

  17. Clustering analysis using Swarm Intelligence

    OpenAIRE

    Farmani, Mohammad Reza

    2016-01-01

    This thesis is concerned with the application of the swarm intelligence methods in clustering analysis of datasets. The main objectives of the thesis are ∙ Take the advantage of a novel evolutionary algorithm, called artificial bee colony, to improve the capability of K-means in finding global optimum clusters in nonlinear partitional clustering problems. ∙ Consider partitional clustering as an optimization problem and an improved antbased algorithm, named Opposition-Based A...

  18. Defining Clusters of Related Industries

    OpenAIRE

    Mercedes Delgado; Porter, Michael E.; Scott Stern

    2014-01-01

    Clusters are geographic concentrations of industries related by knowledge, skills, inputs, demand, and/or other linkages. A growing body of empirical literature has shown the positive impact of clusters on regional and industry performance, including job creation, patenting, and new business formation. There is an increasing need for cluster-based data to support research, facilitate comparisons of clusters across regions, and support policymakers and practitioners in defining regional strate...

  19. Practical Introduction to Clustering Data

    CERN Document Server

    Hartmann, Alexander K

    2016-01-01

    Data clustering is an approach to seek for structure in sets of complex data, i.e., sets of "objects". The main objective is to identify groups of objects which are similar to each other, e.g., for classification. Here, an introduction to clustering is given and three basic approaches are introduced: the k-means algorithm, neighbour-based clustering, and an agglomerative clustering method. For all cases, C source code examples are given, allowing for an easy implementation.

  20. The Assembly of Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

    2008-05-16

    We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10{sup 14.0-14.76} M{sub {circle_dot}}) formed within a pair of cosmological {Lambda}CDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host {approx} 0.1L{sub *} galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'pre-processing' in the group environment prior to their accretion into the cluster. On average, {approx} 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than {approx} 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past ({approx}< 6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with {approx} 20% incorporated into the cluster halo more than 7 Gyr ago and {approx} 20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate time-scale for late-type to early-type transformation within the cluster environment to be {approx} 6 Gyr.

  1. Massive star clusters in galaxies

    CERN Document Server

    Harris, William E

    2009-01-01

    The ensemble of all star clusters in a galaxy constitutes its star cluster system. In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCSs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GCS research, and highlight some of the outstanding questions that are emerging from recent work.

  2. Technical Note: Methionine, a precursor of methane in living plants

    Science.gov (United States)

    Lenhart, K.; Althoff, F.; Greule, M.; Keppler, F.

    2015-03-01

    When terrestrial plants were identified as producers of the greenhouse gas methane, much discussion and debate ensued not only about their contribution to the global methane budget but also with regard to the validity of the observation itself. Although the phenomenon has now become more accepted for both living and dead plants, the mechanism of methane formation in living plants remains to be elucidated and its precursor compounds to be identified. We made use of stable isotope techniques to verify the in vivo formation of methane, and, in order to identify the carbon precursor, 13C positionally labeled organic compounds were employed. Here we show that the amino acid L-methionine acts as a methane precursor in living plants. Employing 13C-labeled methionine clearly identified the sulfur-bound methyl group of methionine as a carbon precursor of methane released from lavender (Lavandula angustifolia). Furthermore, when lavender plants were stressed physically, methane release rates and the stable carbon isotope values of the emitted methane greatly increased. Our results provide additional support that plants possess a mechanism for methane production and suggest that methionine might play an important role in the formation of methane in living plants, particularly under stress conditions.

  3. Technical note: Methionine, a precursor of methane in living plants

    Directory of Open Access Journals (Sweden)

    K. Lenhart

    2014-11-01

    Full Text Available When terrestrial plants were identified as producers of the greenhouse gas methane, much discussion and debate ensued, not only about their contribution to the global methane budget, but also with regard to the validity of the observation itself. Although the phenomenon has now become more accepted for both living and dead plants, the mechanism of methane formation in living plants remains to be elucidated and its precursor compounds identified. We made use of stable isotope techniques to verify in vivo formation of methane and, in order to identify the carbon precursor, 13C-positionally labelled organic compounds were employed. Here we show that the amino acid L-methionine acts as a methane precursor in living plants. Employing 13C-labelled methionine clearly identified the sulphur-bound methyl group of methionine as a carbon precursor of methane released from lavender (Lavandula angustifolia. Furthermore, when lavender plants were stressed physically, methane release rates and the stable carbon isotope values of the emitted methane greatly increased. Our results provide additional support that plants possess a mechanism for methane production and suggest that methionine might play an important role in the formation of methane in living plants, particularly under stress conditions.

  4. Multiple Modes of Communication between Neurons and Oligodendrocyte Precursor Cells

    NARCIS (Netherlands)

    Maldonado, Paloma P; Angulo, María Cecilia

    2015-01-01

    The surprising discovery of bona fide synapses between neurons and oligodendrocytes precursor cells (OPCs) 15 years ago placed these progenitors as real partners of neurons in the CNS. The role of these synapses has not been established yet, but a main hypothesis is that neuron-OPC synaptic activity

  5. NASA's Accident Precursor Analysis Process and the International Space Station

    Science.gov (United States)

    Groen, Frank; Lutomski, Michael

    2010-01-01

    This viewgraph presentation reviews the implementation of Accident Precursor Analysis (APA), as well as the evaluation of In-Flight Investigations (IFI) and Problem Reporting and Corrective Action (PRACA) data for the identification of unrecognized accident potentials on the International Space Station.

  6. Glutamine: precursor or nitrogen donor for citrulline synthesis?

    Science.gov (United States)

    Glutamine (Gln) is considered the main precursor for citrulline (Cit) synthesis, but no attempts have been made to differentiate the contribution of Gln carbon (Gln-C) skeleton vs. the nonspecific contribution through NH3 and CO2. To study the contribution of dietary Gln-N to the synthesis of Cit, t...

  7. Reverse Detection of Short-Term Earthquake Precursors

    CERN Document Server

    Keilis-Borok, V; Gabrielov, A; Turcotte, D L

    2003-01-01

    We introduce a new approach to short-term earthquake prediction based on the concept of selforganization of seismically active fault networks. That approach is named "Reverse Detection of Precursors" (RDP), since it considers precursors in reverse order of their appearance. This makes it possible to detect precursors undetectable by direct analysis. Possible mechanisms underlying RDP are outlined. RDP is described with a concrete example: we consider as short-term precursors the newly introduced chains of earthquakes reflecting the rise of an earthquake correlation range; and detect (retrospectively) such chains a few months before two prominent Californian earthquakes - Landers, 1992, M = 7.6, and Hector Mine, 1999, M = 7.3, with one false alarm. Similar results (described elsewhere) are obtained by RDP for 21 more strong earthquakes in California (M >= 6.4), Japan (M >= 7.0) and the Eastern Mediterranean (M >= 6.5). Validation of the RDP approach requires, as always, prediction in advance for which this stu...

  8. Proteomic analysis of osteogenic differentiation of dental follicle precursor cells

    DEFF Research Database (Denmark)

    Morsczeck, Christian; Petersen, Jørgen; Völlner, Florian;

    2009-01-01

    of differentiation. In the present study we applied 2-DE combined with capillary-LC-MS/MS analysis to profile differentially regulated proteins upon differentiation of dental follicle precursor cells (DFPCs). Out of 115 differentially regulated proteins, glutamine synthetase, lysosomal proteinase cathepsin B...

  9. The miR-10 microRNA precursor family

    DEFF Research Database (Denmark)

    Tehler, Disa; Høyland-Kroghsbo, Nina Molin; Lund, Anders H

    2011-01-01

    The miR-10 microRNA precursor family encodes a group of short non-coding RNAs involved in gene regulation. The miR-10 family is highly conserved and has sparked the interest of many research groups because of the genomic localization in the vicinity of, coexpression with and regulation of the Hox...

  10. College Student Stress: A Predictor of Eating Disorder Precursor Behaviors

    Science.gov (United States)

    Shelton, Virginia L.; Valkyrie, Karena T.

    2010-01-01

    Eating disorders are compulsive behaviors that can consume a person's life to the point of becoming life threatening. Previous research found stress associated with eating disorders. College can be a stressful time. If stress predicted precursor behaviors to eating disorders, then counselors would have a better chance to help students sooner. This…

  11. Developmental Dyslexia: Early Precursors, Neurobehavioral Markers, and Biological Substrates

    Science.gov (United States)

    Benasich, April A., Ed.; Fitch, R. Holly, Ed.

    2012-01-01

    Understanding the precursors and early indicators of dyslexia is key to early identification and effective intervention. Now there's a single research volume that brings together the very latest knowledge on the earliest stages of dyslexia and the diverse genetic, neurobiological, and cognitive factors that may contribute to it. Based on findings…

  12. Transmembrane transport of peptidoglycan precursors across model and bacterial membranes

    NARCIS (Netherlands)

    van Dam, V.; Sijbrandi, R.; Kol, M.A.; Swiezewska, E.; de Kruijff, B.; Breukink, E.J.

    2007-01-01

    Translocation of the peptidoglycan precursor Lipid II across the cytoplasmic membrane is a key step in bacterial cell wall synthesis, but hardly understood. Using NBD-labelled Lipid II, we showed by fluorescence and TLC assays that Lipid II transport does not occur spontaneously and is not induced b

  13. Synthesis of new diverse macrocycles from diol precursors

    DEFF Research Database (Denmark)

    Madsen, Charlotte Marie; Hansen, Martin; Thrane, Marie V.;

    2010-01-01

    The formation of a library of diverse macrocycles with different ring sizes from two easily accessible building blocks is presented. Reacting diol precursors with electrophilic reagents lead to 17-membered sulfites and 19-membered malonates in 34–79% yield. Double-reductive amination of dialdehyd...

  14. Manganite perovskite ceramics, their precursors and methods for forming

    Energy Technology Data Exchange (ETDEWEB)

    Payne, David Alan; Clothier, Brent Allen

    2015-03-10

    Disclosed are a variety of ceramics having the formula Ln.sub.1-xM.sub.xMnO.sub.3, where 0.Itoreq.x.Itoreq.1 and where Ln is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; M is Ca, Sr, Ba, Cd, or Pb; manganite precursors for preparing the ceramics; a method for preparing the precursors; and a method for transforming the precursors into uniform, defect-free ceramics having magnetoresistance properties. The manganite precursors contain a sol and are derived from the metal alkoxides: Ln(OR).sub.3, M(OR).sub.2 and Mn(OR).sub.2, where R is C.sub.2 to C.sub.6 alkyl or C.sub.3 to C.sub.9 alkoxyalkyl, or C.sub.6 to C.sub.9 aryl. The preferred ceramics are films prepared by a spin coating method and are particularly suited for incorporation into a device such as an integrated circuit device.

  15. Observation of laser driven supercritical radiative shock precursors.

    Science.gov (United States)

    Bouquet, S; Stéhlé, C; Koenig, M; Chièze, J-P; Benuzzi-Mounaix, A; Batani, D; Leygnac, S; Fleury, X; Merdji, H; Michaut, C; Thais, F; Grandjouan, N; Hall, T; Henry, E; Malka, V; Lafon, J-P J

    2004-06-01

    We present a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using targets filled with xenon gas at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured shock quantities (electronic density and propagation velocity) are shown to be in good agreement with theory and numerical simulations. PMID:15245230

  16. The isoprenoid-precursor dependence of Plasmodium spp

    NARCIS (Netherlands)

    van der Meer, Jan-Ytzen; Hirsch, Anna K. H.

    2012-01-01

    Due to the increase in resistance of Plasmodium spp. against available antimalarials, there is a need for new, effective and innovative drugs. The non-mevalonate pathway for the biosynthesis of the universal isoprenoid precursors, which is absent in humans, is suggested as an attractive source of ta

  17. On clusters and clustering from atoms to fractals

    CERN Document Server

    Reynolds, PJ

    1993-01-01

    This book attempts to answer why there is so much interest in clusters. Clusters occur on all length scales, and as a result occur in a variety of fields. Clusters are interesting scientifically, but they also have important consequences technologically. The division of the book into three parts roughly separates the field into small, intermediate, and large-scale clusters. Small clusters are the regime of atomic and molecular physics and chemistry. The intermediate regime is the transitional regime, with its characteristics including the onset of bulk-like behavior, growth and aggregation, a

  18. Recovery Rate of Clustering Algorithms

    NARCIS (Netherlands)

    Li, Fajie; Klette, Reinhard; Wada, T; Huang, F; Lin, S

    2009-01-01

    This article provides a simple and general way for defining the recovery rate of clustering algorithms using a given family of old clusters for evaluating the performance of the algorithm when calculating a family of new clusters. Under the assumption of dealing with simulated data (i.e., known old

  19. Analytical Approximations to Galaxy Clustering

    OpenAIRE

    Mo, H. J.

    1997-01-01

    We discuss some recent progress in constructing analytic approximations to the galaxy clustering. We show that successful models can be constructed for the clustering of both dark matter and dark matter haloes. Our understanding of galaxy clustering and galaxy biasing can be greatly enhanced by these models.

  20. Geographic Projection of Cluster Composites

    NARCIS (Netherlands)

    Nerbonne, J.; Bosveld-de Smet, L.M.; Kleiweg, P.; Blackwell, A.; Marriott, K.; Shimojima, A.

    2004-01-01

    A composite cluster map displays a fuzzy categorisation of geographic areas. It combines information from several sources to provide a visualisation of the significance of cluster borders. The basic technique renders the chance that two neighbouring locations are members of different clusters as the