Distribution by Scientific Domains

Kinds of Embedding

  • paraffin embedding

  • Selected Abstracts

    Embedding of analytic function spaces with given mean growth of the derivative

    Óscar Blasco
    Abstract If , is a positive function defined in [0, 1) and 0 < p < ,, we consider the space ,(p, ,) which consists of all functions f analytic in the unit disc ,, for which the integral means of the derivative Mp(r, f ,) = 0 < r < 1, satisfy Mp(r, f ,) = O(, (r)), as r , 1. In this paper, for any given p , (0, 1), we characterize the functions ,, among a certain class of weight functions, to be able to embedd ,(p, ,) into classical function spaces. These results complement other previously obtained by the authors for p , 1. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Reduction of CuO and Cu2O with H2: H Embedding and Kinetic Effects in the Formation of Suboxides.

    CHEMINFORM, Issue 50 2003
    Jae Y. Kim
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    Centrality Based Visualization of Small World Graphs

    F. Van Ham
    Abstract Current graph drawing algorithms enable the creation of two dimensional node-link diagrams of huge graphs. However, for graphs with low diameter (of which "small world" graphs are a subset) these techniques begin to break down visually even when the graph has only a few hundred nodes. Typical algorithms produce images where nodes clump together in the center of the screen, making it hard to discern structure and follow paths. This paper describes a solution to this problem, which uses a global edge metric to determine a subset of edges that capture the graph's intrinsic clustering structure. This structure is then used to create an embedding of the graph, after which the remaining edges are added back in. We demonstrate applications of this technique to a number of real world examples. [source]

    Sortal Structures: Supporting Representational Flexibility for Building Domain Processes

    Rudi Stouffs
    The approach is constructive, based on a part relation on elements within a sort, which enables the recognition of emergent information. The use of data functions as a sort provides for the embedding of data queries within a representational structure. We discuss the application of sorts to supporting alternative data views, illustrating this through a case study in building construction. [source]

    Augmenting LZ-77 with authentication and integrity assurance capabilities

    Mikhail J. Atallah
    Abstract The formidable dissemination capability allowed by the current network technology makes it increasingly important to devise new methods to ensure authenticity and integrity. Nowadays it is common practice to distribute documents in compressed form. In this paper, we propose a simple variation on the classic LZ-77 algorithm that allows one to hide, within the compressed document, enough information to warrant its authenticity and integrity. The design is based on the unpredictability of a certain class of pseudo-random number generators, in such a way that the hidden data cannot be retrieved in a reasonable amount of time by an attacker (unless the secret bit-string key is known). Since it can still be decompressed by the original LZ-77 algorithm, the embedding is completely ,transparent' and backward-compatible, making it possible to deploy it without disrupting service. Experiments show that the degradation in compression due to the embedding is almost negligible. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    REMEDIATION AND LOCAL GLOBALIZATIONS: How Taiwan's "Digital Video Knights-Errant Puppetry" Writes the History of the New Media in Chinese

    This article analyzes the Pili International Multimedia Company's "digital video knights-errant puppetry" serials, a popular culture genre unique to Taiwan, to answer two questions. First, how do digital technologies, originally developed to meet the needs of the American military and entertainment industries, become embedded in a different cultural context? Second, how does this embedding allow media technologies to become something through which distinctly local models of globalization itself may be imagined? Analyzing both the style of the serials and the discourse of producers and fans, I argue that new media technologies, despite their foreign origins, may not only be adapted or resisted, but may also come to be imagined as emerging from local aesthetics and local needs. Through the specific ways they utilize both digital and traditional technologies, the Pili producers and fans construct a utopian vision of what globalization might look like if Taiwan were at the center. [source]

    Biofilm formation by algae as a mechanism for surviving on mine tailings

    J. Viridiana García-Meza
    Abstract Photosynthetic biofilms successfully colonize the sediments of a mine tailings reservoir (Guanajuato, Mexico) despite the high metal concentrations that are present. To elucidate the mechanisms of biofilm survival despite metal ores, experiments were performed to evaluate the response of seminatural biofilms to Cu, Zn, and a combination of both metals at concentrations observed in the field. The biofilms were composed mostly of the chlorophyte Chlorococcum sp. and the cyanobacterium Phormidium sp., and their response to the two added metals was described by measurements of extracellular polymeric substances (EPS) and in vivo fluorescence. The photosynthetic efficiency and the minimal chlorophyll fluorescence of dark-adapted cells were measured by multiwavelength pulse amplitude,modulated fluorometry. The photosynthetic efficiency of light-adapted cells (,PSII) also was measured. Metal exposure increased the EPS production of biofilms, as visualized with confocal laser-scanning microscopy. Extracellular polymeric substances enhanced the extracellular metal accumulation from the first day of metal exposure. Metals provoked changes in the relative abundance of the dominant taxa because of a species-specific response to the metals when added individually. Metals affected the ,psii less than the total biomass, suggesting ongoing activity of the surviving biofilms. Survival of individual biofilm photosynthetic cells was found to resume from the embedding in the mucilaginous structure, which immobilizes the metals extracellularly. The survival of biofilms under mixed-metal exposure has practical applications in the remediation of mine tailings. [source]

    Localisation and distribution of hyaluronan in normal bone marrow matrix: a novel method to evaluate impending fibrosis?

    Gunnel Sundström
    Abstract: Bone marrow trephine biopsies from 30 healthy volunteers, 10 men and 20 women aged 18,60 yr were obtained for identification and localisation of hyaluronan (HYA). Fixation, decalcification and embedding were performed by two different methods, with identical results in both. For comparison bone marrow trephine biopsies from three patients with different haematological diseases and known fibrosis were studied. All bone marrow specimens were also stained for reticulin grading. HYA was found in the bone marrow specimens from healthy individuals in a pattern that was concordant with the reticulin staining, the common way of visualising bone marrow fibrosis. In bone marrow from the patients with known fibrosis the HYA and reticulin staining were both more intense and abundant. Interestingly, HYA was also found intracellularly in eosinophilic cells in normal bone marrow. HYA is a polysaccharide unique both in structural and biological properties, and in excess it may predict bone marrow fibrosis. [source]

    Mechanical Properties of Compound Extruded Aircraft Stringer Profiles Under Cyclic Loading,

    Kay A. Weidenmann
    The worldwide competition in the field of aircraft structures leads to an increasing need for functionality and safety as well as for cost and weight reduction. For instance stringers could be directly welded on the aircraft's skin sheet. The requirements to be met are increased safety against crack initiation and crack growth as well as improved residual strength against failure after harmful impact of foreign objects. The application of continuously reinforced aluminium profiles which are manufactured by compound extrusion leads to increased strength and stiffness of the profiles by combining the aluminium matrix with high strength wires. Thus aircraft stringers of such profiles represent an innovative concept with improved properties. The characterisation of compound extrusions based on medium and high strength aircraft aluminium alloys EN AW-6056 and EN AW-2099 shows that a good embedding of the reinforcing high strength wires (Co-based and Fe-based) can be achieved. Furthermore the mechanical properties under cyclic loading of the profiles were measured and the S/N-curves for the different compound combinations were determined. Subsequently the crack initiation and propagation was analysed by using metallographic and SEM investigations. The fatigue resistance of reinforced specimens is increased compared to unreinforced ones. The fatigue cracks originate at the surface of unreinforced specimen while the cracks in reinforced specimens are initiated at the wire,matrix interface. [source]

    Proton hexality in GUTs and strings

    S. Förste
    Abstract Proton hexality is a discrete symmetry ensuring the stability of the proton under dimension four and five interactions. We discuss the embedding of proton hexality into Grand Unified Theories. This leads naturally to the concept of extra dimensions and string theory. This talk is based on a collaboration with results to be published shortly [1]. [source]

    Compactifications of the heterotic string with unitary bundles

    T. Weigand
    Abstract We describe a large new class of four-dimensional supersymmetric string vacua defined as compactifications of the E8 × E8 and the SO(32) heterotic string on smooth Calabi-Yau threefolds with unitary gauge bundles and heterotic five-branes. The conventional gauge symmetry breaking via Wilson lines is replaced by the embedding of non-flat line bundles into the ten-dimensional gauge group, thus opening up the way for phenomenologically interesting string compactifications on simply connected manifolds. After a detailed analysis of the four-dimensional effective theory we exemplify the general framework by means of a couple of explicit examples involving the spectral cover construction of stable holomorphic bundles. As for the SO(32) heterotic string, the resulting vacua can be viewed, in the S-dual Type I picture, as a generalisation of magnetized D9/D5-brane models. In the case of the E8 × E8 string, we find a natural way to construct realistic MSSM-like models, either directly or via a flipped SU(5) GUT scenario. [source]

    Generalizations of the AdS/CFT correspondence,

    I. Kirsch
    Abstract We consider generalizations of the AdS/CFT correspondence in which probe branes are embedded in gravity backgrounds dual to either conformal or confining gauge theories. These correspond to defect conformal field theories (dCFT) or QCD-like theories with fundamental matter, respectively. Moreover, starting from the dCFT we discuss the deconstruction of intersecting M5-branes and M-theory. We obtain the following results: i) Holography of defect conformal field theories. We consider holography for a general D3-Dp brane intersection in type IIB string theory (p , {3,5,7}). The corresponding near-horizon geometry is given by a probe AdS-brane in AdS5 × S5. The dual defect conformal field theory describes ,, = 4 super Yang-Mills degrees of freedom coupled to fundamental matter on a lower-dimensional space-time defect. We derive the spectrum of fluctuations about the brane embedding and determine the behaviour of correlation functions involving defect operators. We also study the dual conformal field theory in the case of intersecting D3-branes. To this end, we develop a convenient superspace approach in which both two- and four-dimensional fields are described in a two-dimensional (2,2) superspace. We show that quantum corrections vanish to all orders in perturbation theory, such that the theory remains a (defect) conformal field theory when quantized. ii) Flavour in generalized AdS/CFT dualities. We present a holographic non-perturbative description of QCD-like theories with a large number of colours by embedding D7-brane probes into two non-supersymmetric gravity backgrounds. Both backgrounds exhibit confinement of fundamental matter and a discrete glueball and meson spectrum. We numerically compute the quark condensate and meson spectrum associated with these backgrounds. In the first background, we find some numerical evidence for a first order phase transition at a critical quark mass where the D7 embedding undergoes a geometric transition. In the second, we find a chiral symmetry breaking condensate as well as the associated Goldstone boson. iii) Deconstruction of extra dimensions. We apply the deconstruction method to the dCFT of intersecting D3-branes to obtain a field theory description for intersecting M5-branes. The resulting theory corresponds to two six-dimensional (2,0) superconformal field theories which we show to have tensionless strings on their four-dimensional intersection. Moreover, we argue that the SU(2)L R-symmetry of the dCFT matches the manifest SU(2) R-symmetry of the M5-M5 intersection. We finally explore the fascinating idea of deconstructing M-theory itself. We give arguments for an equivalence of M-theory on a certain background with the Higgs branch of a four-dimensional non-supersymmetric (quiver) gauge theory: in addition to a string theoretical motivation, we find wrapped M2-branes in the mass spectrum of the quiver theory at low energies. [source]

    Functional Chromium Wheel-Based Hybrid Organic,Inorganic Materials for Dielectric Applications

    Vito Di Noto
    Abstract The first example of organic,inorganic hybrid materials based on the embedding of a chromium,nickel wheel cluster {[(n-C3H7)2NH2]- [Cr7NiF8(O2C4H5)16]} (Cr7Ni) into poly(methyl methacrylate) (PMMA) and the characterization of the dielectric properties of the obtained material is described. By an optimized copolymerization of the methacrylate-functionalized chromium,nickel wheel with methyl methacrylate in a cluster/monomer 1:200 molar mixture, a homogeneous hybrid material CrNi_MMA200 is obtained. The electrical responses of the non-doped PMMA and of the hybrid material were studied by broadband dielectric spectroscopy (BDS) from 0.01,Hz to 10,MHz and over the temperature range of 5,115,°C. The permittivity profiles reveal two relaxation peaks in the materials, which correspond to the , and , relaxation modes of the PMMA matrix. The position of these modes shifts toward higher frequencies as temperature increases. BDS is a powerful tool revealing the intimate miscibility of the various components of the hybrid material, thus indicating that, on a molecular scale, the material proposed is a homogeneous system. Finally, a value of the dielectric constant of 2.9 at 25,°C and 1,kHz is determined. This value is noticeably lower than the value of 3.2 obtained for pristine PMMA prepared following the same synthesis protocol. Thus, these results classify the hybrid CrNi_MMA200 as an appealing starting material for the development of dielectric polymeric layers for the development of innovative capacitors, transistors, and other microelectronic devices. The vibrational properties of the hybrid materials are investigated by Fourier-transform infrared (FT-IR) and Raman spectroscopy, whereas the thermal behavior is analyzed by thermogravimetric analysis (TGA). Swelling experiments are used to qualitatively evaluate the crosslinking density of the hybrid materials. The integrity of the wheels once embedded in the macromolecular backbone is confirmed by extended X-ray absorption fine structure (EXAFS) and electron spin resonance (EPR) spectroscopic measurements. [source]

    Determination of Size, Morphology, and Nitrogen Impurity Location in Treated Detonation Nanodiamond by Transmission Electron Microscopy

    Stuart Turner
    Abstract Size, morphology, and nitrogen impurity location, all of which are all thought to be related to the luminescent properties of detonation nanodiamonds, are determined in several detonation nanodiamond samples using a combination of transmission electron microscopy techniques. Results obtained from annealed and cleaned detonation nanodiamond samples are compared to results from conventionally purified detonation nanodiamond. Detailed electron energy loss spectroscopy combined with model-based quantification provides direct evidence for the sp3 like embedding of nitrogen impurities into the diamond cores of all the studied nanodiamond samples. Simultaneously, the structure and morphology of the cleaned detonation nanodiamond particles are studied using high resolution transmission electron microscopy. The results show that the size and morphology of detonation nanodiamonds can be modified by temperature treatment and that by applying a special cleaning procedure after temperature treatment, nanodiamond particles with clean facets almost free from sp2 carbon can be prepared. These clean facets are clear evidence that nanodiamond cores are not necessarily in coexistence with a graphitic shell of non-diamond carbon. [source]

    Boron Nanotube,Polymer Composites: Towards Thermoconductive, Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as Fillers (Adv. Funct.

    Composites formed through embedding of high-concentration boron nitride nanotubes in polymers are reported by C. Y. Zhi et al. on page 1857. The composites possess high thermal conductivity, high break-over voltage, low coefficient of thermal expansion, and other favorable properties. These polymeric composites are promising highly thermoconductive electrically insulating materials for a range of applications. [source]

    Geophysical exploration for interlayer slip breccia gold deposits: example from Pengjiakuang gold deposit, Shandong Province, China

    Z. Qingdong
    ABSTRACT Interlayer slipping breccia-type gold deposit , a new type of gold deposit, defined recently in the northern margin of the Jiaolai Basin, Shandong Province, China , occurs in interlayer slip faults distributed along the basin margin. It has the features of large orebody thickness (ranging from 14 m to 46 m, with an average thickness of 30 m), shallow embedding (0,50 m thickness of cover), low tenor of gold ore (ranging from 3 g/t to 5 g/t), easy mining and ore dressing. This type of gold deposit has promising metallogenic forecasting and potential for economic exploitation. A ground gamma-ray survey in the Pengjiakuang gold-ore district indicates that the potassium/thorium ratio is closely related to the mineralization intensity, i.e. the larger the potassium/thorium ratio, the higher the mineralization. The gold mineralized alteration zone was defined by a potassium/thorium ratio of 0.35. A seismic survey confirms the location of the top and bottom boundaries and images various features within the Pengjiakuang gold mineralization belt. The gold-bearing shovel slipped belt dips to the south at an angle of 50,55° at the surface and 15,20° at depth. The seismic profile is interpreted in terms of a structural band on the seismic section characterized by a three-layered model. The upper layer is represented by weakly discontinuous reflections that represent the overlying conglomerates. A zone of stronger reflections representing the interlayer slip fault (gold-bearing mineralized zone) is imaged within the middle of the section, while the strongest reflections are in the lower part of the section and represent metamorphic rocks at depth. At the same time, the seismic reflection survey confirms the existence of a granite body at depth, indicating that ore-forming fluids may be related to the granite. A CSAMT survey showed that the gold-bearing mineralized zone is a conductive layer and contains a low-resistivity anomaly ranging from 2 ,m to 200 ,m. [source]

    Cover Picture: Fabrication of Stable Metallic Patterns Embedded in Poly(dimethylsiloxane) and Model Applications in Non-Planar Electronic and Lab-on-a-Chip Device Patterning (Adv. Funct.

    Abstract A composite image is shown that highlights examples of device architectures that either incorporate or exploit polymer-embedded metallic microstructures. In work reported by Nuzzo and co-workers on p.,557, new applications of soft lithography, in conjunction with advanced forms of multilayer metallization, are used to construct these exceptionally durable structures. They are suitable for use in non-planar lithographic patterning, and as device components finding applications ranging from microelectronics to Lab-on-a-Chip analytical systems. This article describes the fabrication of durable metallic patterns that are embedded in poly(dimethylsiloxane) (PDMS) and demonstrates their use in several representative applications. The method involves the transfer and subsequent embedding of micrometer-scale gold (and other thin-film material) patterns into PDMS via adhesion chemistries mediated by silane coupling agents. We demonstrate the process as a suitable method for patterning stable functional metallization structures on PDMS, ones with limiting feature sizes less than 5,,m, and their subsequent utilization as structures suitable for use in applications ranging from soft-lithographic patterning, non-planar electronics, and microfluidic (lab-on-a-chip, LOC) analytical systems. We demonstrate specifically that metal patterns embedded in both planar and spherically curved PDMS substrates can be used as compliant contact photomasks for conventional photolithographic processes. The non-planar photomask fabricated with this technique has the same surface shape as the substrate, and thus facilitates the registration of structures in multilevel devices. This quality was specifically tested in a model demonstration in which an array of one hundred metal oxide semiconductor field-effect transistor (MOSFET) devices was fabricated on a spherically curved Si single-crystalline lens. The most significant opportunities for the processes reported here, however, appear to reside in applications in analytical chemistry that exploit devices fabricated using the methods of soft lithography. Toward this end, we demonstrate durably bonded metal patterns on PDMS that are appropriate for use in microfluidic, microanalytical, and microelectromechanical systems. We describe a multilayer metal-electrode fabrication scheme (multilaminate metal,insulator,metal (MIM) structures that substantially enhance performance and stability) and use it to enable the construction of PDMS LOC devices using electrochemical detection. A polymer-based microelectrochemical analytical system, one incorporating an electrode array for cyclic voltammetry and a microfluidic system for the electrophoretic separation of dopamine and catechol with amperometric detection, is demonstrated. [source]

    A robust algorithm for configurational-force-driven brittle crack propagation with R-adaptive mesh alignment

    C. Miehe
    Abstract The paper considers a variational formulation of brittle fracture in elastic solids and proposes a numerical implementation by a finite element method. On the theoretical side, we outline a consistent thermodynamic framework for crack propagation in an elastic solid. It is shown that both the elastic equilibrium response as well as the local crack evolution follow in a natural format by exploitation of a global Clausius,Planck inequality in the sense of Coleman's method. Here, the canonical direction of the crack propagation associated with the classical Griffith criterion is the direction of the material configurational force which maximizes the local dissipation at the crack tip and minimizes the incremental energy release. On the numerical side, we exploit this variational structure in terms of crack-driving configurational forces. First, a standard finite element discretization in space yields a discrete formulation of the global dissipation in terms configurational nodal forces. As a consequence, the constitutive setting of crack propagation in the space-discretized finite element context is naturally related to discrete nodes of a typical finite element mesh. Next, consistent with the node-based setting, the discretization of the evolving crack discontinuity is performed by the doubling of critical nodes and interface segments of the mesh. Critical for the success of this procedure is its embedding into an r-adaptive crack-segment reorientation procedure with configurational-force-based directional indicator. Here, successive crack releases appear in discrete steps associated with the given space discretization. These are performed by a staggered loading,release algorithm of energy minimization at frozen crack state followed by the successive crack releases at frozen deformation. This constitutes a sequence of positive-definite discrete subproblems with successively decreasing overall stiffness, providing an extremely robust algorithmic setting in the postcritical range. We demonstrate the performance of the formulation by means of representative numerical simulations. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Are we aware of all complications following body piercing procedures?

    Bogus, aw Antoszewski MD
    Background, The popularity of body piercing procedures is increasing around the world. Body piercing, depending on the age and social group, is believed to involve up to 51% of the general population. Complications following piercing procedures are variable. Objective, To present an unusual complication after lower lip piercing , embedding of a stud into the lip , and to determine why it occurred from the side of the mucous membrane and not from the side of the skin. Methods, A 21-year-old man presented to the plastic surgery outpatient clinic with embedding of piercing into the lower lip. Results, In lateral X-ray film, a metallic shadow was observed in the area of the oral soft tissues. The length of the stick was only 8 mm. In this patient, a stick that was too short in relation to the thickness of the lip was used. In this situation, the ends of the stud pressed too strongly on the surrounding tissues. Consequently, this may have caused necrosis of the mucous membrane and embedding of the stud into the lip. Conclusion, The observations described confirm a higher susceptibility to mechanical pressure of the mucous membrane than of the skin. An increasing rate of complications after body piercing reflects a lack of medical knowledge in individuals performing such procedures. [source]

    Preparation and properties of dynamically cured PP/MAH- g -EVA/epoxy blends

    Xueliang Jiang
    Abstract A method concerning with the simultaneous reinforcing and toughening of polypropylene (PP) was reported. Dynamical cure of the epoxy resin with 2-ethylene-4-methane-imidazole (EMI-2,4) was successfully applied in the PP/maleic anhydride-grafted ethylene-vinyl acetate copolymer (MAH- g -EVA), and the obtained blends named as dynamically cured PP/MAH- g -EVA/epoxy blends. The stiffness and toughness of the blends are in a good balance, and the smaller size of epoxy particle in the PP/MAH- g -EVA/epoxy blends shows that MAH- g -EVA was also used as a compatibilizer. The structure of the dynamically cured PP/MAH- g -EVA/epoxy blends is the embedding of the epoxy particles by the MAH- g -EVA. The cured epoxy particles as organic filler increases the stiffness of the PP/MAH- g -EVA blends, and the improvement in the toughness is attributed to the embedded structure. The tensile strength and flexural modulus of the blends increase with increasing the epoxy resin content, and the impact strength reaches a maximum of 258 J/m at the epoxy resin content of 10 wt %. DSC analysis shows that the epoxy particles in the dynamically cured PP/MAH- g -EVA/epoxy blends could have contained embedded MAH- g -EVA, decreasing the nucleating effect of the epoxy resin. Thermogravimetric results show the addition of epoxy resin could improve the thermal stability of PP, the dynamically cured PP/MAH- g -EVA/epoxy stability compared with the pure PP. Wide-angle x-ray diffraction analysis shows that the dynamical cure and compatibilization do not disturb the crystalline structure of PP in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Proteomic analysis of RCL2 paraffin-embedded tissues

    V. Belief
    Abstract Histopathological diagnosis in most of the world's hospitals is based upon formalin-fixed and paraffin-embedded (FFPE) tissues. Although this standard fixation and embedding procedure keeps the tissue in excellent form for morphological and immunohistological analysis, FFPE is inappropriate for nucleic acids and protein studies. We investigated the potential value of RCL2, a new non-toxic fixative, for sparing proteins preserved in paraffin-embedded tissues. Normal colonic mucosa tissue was fixed in RCL2 prior to paraffin embedding (RCL2P), and then processed for quality and quantity of protein conservation, as compared to frozen and FFPE tissues using complementary proteomic analysis approaches. Using 4 different protein extraction protocols, RCL2P tissue consistently showed the highest protein yield. Similar protein patterns were observed with RCL2P and frozen tissues using mono and bi-dimensional electrophoresis. Moreover, membrane, cytoplasmic and nuclear proteins, as well as phosphorylated proteins, were successfully detected using western-blot. Furthermore, protein patterns observed by mass spectrometry analysis after laser-captured microdissection were found to be identical for frozen and RCL2-fixed tissues. At last, immunohistochemistry using various antibodies showed comparable results between both tissue storage methods. We concluded that RCL2 has great potential for performing both morphological and molecular analyses on the same archival paraffin-embedded tissue sample, and can be a new method for investigating protein biomarkers. [source]

    A subpopulation of peritoneal macrophages form capillary-like lumens and branching patterns in vitro

    Mirela Anghelina
    Abstract Objective: We have previously shown that monocytes/macrophages (MC/Mph) influence neovascularization by extracellular matrix degradation, and by direct incorporation into growing microvessels. To date, neither the phenotype of these cells, nor the stages of their capillary-like conversion were sufficiently characterized. Methods: We isolated mouse peritoneal Mph from transgenic mice expressing fluorescent proteins either ubiquitously, or specifically in the myelocytic lineage. These Mph were embedded in Matrigel which contained fluorescent protease substrates, exposed to an MCP-1 chemotactic gradient, and then examined by confocal microscopy after various intervals. Results: Within 3 hrs after gel embedding, we detected TIMP-1 and MMP-12 dependent proteolysis of the matrix surrounding Mph, mostly in the direction of high concentrations of MCP-1. After 2 days, Mph developed intracellular vacuoles containing degradation product. At 5 days these vacuoles were enlarged and/or fused to generate trans-cellular lumens in approximately 10% of cells or more (depending on animal's genetic background). At this stage, Mph became tubular, and occasionally organized in three-dimensional structures resembling branched microvessels. Conclusion: Isolated mouse peritoneal Mph penetrate Matrigel and form tunnels via a metalloprotease-driven proteolysis and phagocytosis. Following a morphological adjustment driven by occurrence, enlargement and/or fusion process of intracellular vacuoles, similar to that described in bona fide endothelium, a subpopulation of these cells end up by lining a capillary-like lumen in vitro. Thus we show that adult Mph, not only the more primitive ,endothelial progenitors', have functional properties until now considered defining of the endothelial phenotype. [source]

    Models for the treatment of crystalline solids and surfaces

    Karl Jug
    Abstract Crystalline solids and surfaces have become a subject of growing interest. The difficulty of a comprehensive description of a variety of phenomena by a single method has led to the development of many models. These models can be classified as nonperiodic and periodic models. The former include free clusters, saturated clusters, and embedded clusters. The latter two models serve to remove the boundary effects of the free clusters. No perfect avoidance of such effects can be achieved in this way. The cyclic cluster model overcomes this difficulty in a natural way. It is periodic with a finite periodicity. An embedding can take into account a long-range effect in ionic crystals. Previous periodic approaches relied on the large unit cell model, which is related to the supercell approach. For perfect crystals the conventional unit cell approach is a well-known standard. However, its disadvantage is the unphysical periodicity of defects, which is avoided in the cyclic cluster model. The present article presents a description of these models together with selective applications to solid-state systems and surfaces. © 2004 Wiley Periodicals, Inc. J Comput Chem 13: 1551,1567, 2004 [source]

    Cryoimmobilization and three-dimensional visualization of C. elegans ultrastructure

    T. Müller-Reichert
    Summary Caenorhabditis elegans is one of the most important genetic systems used in current biological research. Increasingly, these genetics-based research projects are including ultrastructural analyses in their attempts to understand the molecular basis for cell function. Here, we present and review state-of-the-art methods for both ultrastructural analysis and immunogold localization in C. elegans. For the initial cryofixation, high-pressure freezing is the method of choice, and in this article we describe two different strategies to prepare these nematode worms for rapid freezing. The first method takes advantage of transparent, porous cellulose capillary tubes to contain the worms, and the second packs the worms in E. coli and/or yeast paste prior to freezing. The latter method facilitates embedding of C. elegans in a thin layer of resin so individual worms can be staged, selected and precisely orientated for serial sectioning followed by immunolabelling or electron tomography. [source]

    Attachment, decay, and social network

    Ronald S. Burt
    To study decay in attachment to an organization, I analyse data on women who obtained an MBA from the University of Chicago's Graduate School of Business (GSB). I measure attachment in terms of network embedding: an alumna is attached to the GSB to the extent that people close to her graduated from the GSB. Behavioral data corroborate the network data in that alumnae measured to be more attached are more likely to have joined an alumni club and made a financial contribution to the school. The hypothesis is that alumnae attachment will decay over time, more slowly when the school is deeply embedded in an alumna's network, more quickly when disruptive events compete for the alumna's time and energy. As expected, attachment declines across the years after graduation (linearly for the first 20 years to about half its initial level), and decay is inhibited when connections with GSB graduates are embedded in stable relations of family, work, or long-term friendship. Decay is remarkably robust to events after graduation (which account for only 2 per cent of explained variance in attachment). In other words, an alumna's attachment today was largely determined while she was in school. The results should be of practical value to people who design programmes to build personal attachment to organizations, and of theoretical interest to scholars who study such connections. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    The social dimension of the Southern Vowel Shift: Gender, age and class

    Valerie Fridland
    The three most broadly recognized dialect areas of American Regional English are currently being re-defined by, in some cases, sweeping changes that alter the way vowels are being pronounced in the South, North and West. While research into the changes in urban Northern dialects has contributed a fairly broad picture of both the phonetic and social character of the Northern Cities Shift (NCS), the changes affecting the Southern region of the U.S. have received less attention, particularly in terms of social distribution and dissemination. This paper seeks to address the question of how successfully changes in the high and mid front and back vowels in the South are being disseminated throughout a local urban community and how these changes fit in with changes occurring in other American dialects. In addition, the paper weighs the attraction to local or national norms in determining the success and diffusion of each of the shifts relative to the social environment in which they are developing and attempts to relate the local social embedding of the shifts to their meaning in the larger national context. [source]

    Architectural support in industry: a reflection using C-POSH

    R. J. Bril
    Abstract Software architecture plays a vital role in the development (and hence maintenance) of large complex systems (containing millions of lines of code) with a long lifetime. It is therefore required that the software architecture is also maintained, i.e., sufficiently documented, clearly communicated, and explicitly controlled during its life-cycle. In our experience, these requirements cannot be met without appropriate support. Commercial-off-the-shelf support for architectural maintenance is still scarcely available, if at all, implying the need to develop appropriate proprietary means. In this paper, we reflect upon software architecture maintenance taken within three organizations within Philips that develop professional systems. We extensively describe the experience gained with introducing and embedding of architectural support in these three organizations. We focus on architectural support in the area of software architecture recovery, visualization, analysis, and verification. In our experience, the support must be carried by a number of pillars of software development, and all of these pillars have to go through a change process to ensure sustainable embedding. Managing these changes requires several key roles to be fulfilled in the organization: a champion, a company angel, a change agent, and a target. We call our reflection model C-POSH, which is an acronym for Change management of the four identified pillars of software development: Process, Organization, Software development environment, and Humans. Our experiences will be presented in terms of the C-POSH model. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Sintering of AlN Using CaO-Al2O3 as a Sintering Additive: Chemistry and Microstructural Development

    Eirik Hagen
    The densification of aluminum nitride using Ca12Al14O33 as a sintering aid has been studied with emphasis on the effect of using coarse or fine powder, the amount of sintering aid, the sintering temperature, and embedding. Both crystalline and amorphous grain boundary phases were observed. Significant weight losses were observed for coarse-grained samples, and if suitable embedding was not used. Porous and coarse-grained ceramics with high contiguity and minor amounts of secondary phases were obtained by enhanced evaporation while dense ceramics were obtained limiting the evaporation. High weight losses in the graphite environment resulted in formation of a dense AlN surface layer. [source]

    A composite material model for improved bone formation

    Silvia Scaglione
    Abstract The combination of synthetic polymers and calcium phosphates represent an improvement in the development of scaffolds for bone-tissue regeneration. Ideally, these composites provide both mechanically and architecturally enhanced performances; however, they often lack properties such as osteoconductivity and cell bioactivation. In this study we attempted to generate a composite bone substitute maximizing the available osteoconductive surface for cell adhesion and activity. Highly porous scaffolds were prepared through a particulate leaching method, combining poly-,-caprolactone (PCL) and hydroxyapatite (HA) particles, previously coated with a sucrose layer, to minimize their embedding by the polymer solution. Composite performances were evaluated both in vitro and in vivo. In PCL,sucrose-coated HA samples, the HA particles were almost completely exposed and physically distinct from the polymer mesh, while uncoated control samples showed ceramic granules massively covered by the polymer. In vivo results revealed a significant extent of bone deposition around all sucrose-coated HA granules, while only parts of the control uncoated HA granules were surrounded by bone matrix. These findings highlight the possibility of generating enhanced osteoconductive materials, basing the scaffold design on physiological and cellular concepts. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Surface Grafting of PEO-Based Star-Shaped Molecules for Bioanalytical and Biomedical Applications

    Peter Gasteier
    Abstract This article reviews surface grafting of star-shaped PEO. The use of star-shaped polymers is compared to linear PEO chains regarding the layer preparation and the ability of the resulting surfaces to resist protein adsorption. We then focus on the use of end-functionalized, star-shaped, PEO-based prepolymers that are able to form covalent crosslinks and functional polymer networks on the substrate. Examples are given for specific protein adsorption as well as for cell adhesion on such layers by covalent embedding of biofunctional molecules. The possibility of coating biomedically relevant polymer substrates in three-dimensional geometries is discussed and examples are shown for poly(ethylene terephthalate) monofilament constructs. [source]