508 research outputs found

    Fractal-like hierarchical organization of bone begins at the nanoscale

    Get PDF
    INTRODUCTION: The components of bone assemble hierarchically to provide stiffness and toughness. Deciphering the specific organization and relationship between bone’s principal components—mineral and collagen—requires answers to three main questions: whether the association of the mineral phase with collagen follows an intrafibrillar or extrafibrillar pattern, whether the morphology of the mineral building blocks is needle- or platelet-shaped, and how the mineral phase maintains continuity across an extensive network of cross-linked collagen fibrils. To address these questions, a nanoscale level of three-dimensional (3D) structural characterization is essential and has now been performed. RATIONALE: Because bone has multiple levels of 3D structural hierarchy, 2D imaging methods that do not detail the structural context of a sample are prone to interpretation bias. Site-specific focused ion beam preparation of lamellar bone with known orientation of the analyzed sample regions allowed us to obtain imaging data by 2D high-resolution transmission electron microscopy (HRTEM) and to identify individual crystal orientations. We studied higher-level bone mineral organization within the extracellular matrix by means of scanning TEM (STEM) tomography imaging and 3D reconstruction, as well as electron diffraction to determine crystal morphology and orientation patterns. Tomographic data allowed 3D visualization of the mineral phase as individual crystallites and/or aggregates that were correlated with atomic-resolution TEM images and corresponding diffraction patterns. Integration of STEM tomography with HRTEM and crystallographic data resulted in a model of 3D mineral morphology and its association with the organic matrix. RESULTS: To visualize and characterize the crystallites within the extracellular matrix, we recorded imaging data of the bone mineral in two orthogonal projections with respect to the arrays of mineralized collagen fibrils. Three motifs of mineral organization were observed: “filamentous” (longitudinal or in-plane) and “lacy” (out-of-plane) motifs, which have been reported previously, and a third “rosette” motif comprising hexagonal crystals. Tomographic reconstructions showed that these three motifs were projections of the same 3D assembly. Our data revealed that needle-shaped, curved nanocrystals merge laterally to form platelets, which further organize into stacks of roughly parallel platelets separated by gaps of approximately 2 nanometers. These stacks of platelets, single platelets, and single acicular crystals coalesce into larger polycrystalline aggregates exceeding the lateral dimensions of the collagen fibrils, and the aggregates span adjacent fibrils as continuous, cross-fibrillar mineralization. CONCLUSION: Our findings can be described by a model of mineral and collagen assembly in which the mineral organization is hierarchical at the nanoscale. First, the data reveal that mineral particles are neither exclusively needle- nor platelet-shaped, but indeed are a combination of both, because curved acicular elements merge laterally to form slightly twisted plates. This can only be detected when the organic extracellular matrix is preserved in the sample. Second, the mineral particles are neither exclusively intrafibrillar nor extrafibrillar, but rather form a continuous cross-fibrillar phase where curved and merging crystals splay beyond the typical dimensions of a single collagen fibril. Third, in the organization of the mineral phase of bone, a helical pattern can be identified. This 3D observation, integrated with previous studies of bone hierarchy and structure, illustrates that bone (as a material, as a tissue, and as an organ) follows a fractal-like organization that is self-affine. The assembly of bone components into nested, helix-like patterns helps to explain the paradoxical combination of enhanced stiffness and toughness of bone and results in an expansion of the previously known hierarchical structure of bone to at least 12 levels

    The value changes redox system the body fluid media for life processes and the action of drugs

    Get PDF
    The article presents information on the study of the possible effect of ionized liquids with different values of redox potential on the physiological processes and the action of drugs. To establish the possibility of changing the redox potential of body fluids in comparison with the arising physiological reactions and the action of drug

    Search of new pharmaceuticals on the basis of darbepoetin in the treatment of ischemic stroke: review of literature

    Get PDF
    The article contains the analysis of medical and biological publications from the global database created by the National Centre for Biology Information (NCBI), an intramural biotechnological division of the US National Library of Medicine. The authors have analyzed publications of the recent ten years. Major results of study of erythropoietins and their recombinant analogues have been generalized and systematized. There has been revealed the significant potential of the preparations of this group to be studied and used. Major advantages and drawbacks of erythropoietins and their recombinant analogues have been describe

    Multiple-quasiparticle agglomerates at \nu=2/5

    Full text link
    We investigate the dynamics of quasiparticle agglomerates in edge states of the Jain sequence for \nu=2/5. Comparison of the Fradkin-Lopez model with the Wen one is presented within a field theoretical construction, focusing on similarities and differences. We demonstrate that both models predict the same universal role for the multiple-quasiparticle agglomerates that dominate on single quasiparticles at low energy. This result is induced by the presence of neutral modes with finite velocity and is essential to explain the anomalous behavior of tunneling conductance and noise through a point contact.Comment: 6 pages, in press Physica E as proceedings of FQMT0

    Incidencia de Fusarium verticilloides y Fusarium graminearum en granos de híbridos comerciales de maíz, cosechados en la campaña 2011/2012 en seis localidades de las provincias de Tucumán y Salta

    Get PDF
    El cultivo de maíz (Zea mays L.) es afectado por patógenos fúngicos que causan podredumbres de grano y espiga. Entre los más frecuentes, se destacan por su importancia Fusarium verticillioides, F. graminearum y Aspergillus flavus ,ya que además contaminan el grano con micotoxinas. Diversas especies de Fusarium pueden dañar las mazorcas antes de la cosecha o los granos de maíz que se almacenan en condiciones inadecuadas, además de producir tizón de plántulas y pudrición de raíces y tallos. Los agentes de Fusarium asociados a la pudrición de mazorca más importantes en el mundo son Fusarium verticillioides, Fusarium graminearum, F. proliferatum y F. subglutinans. De todos ellos, F. verticillioides y F. graminearum son los más frecuentes. El objetivo del trabajo fue evaluar en laboratorio la incidencia de F. verticillioides y F. graminearum en granos de híbridos comerciales de maíz, cosechados en la campaña 2011/2012 de los ensayos de fechas de siembra y macroparcelas realizados por la Estación Experimental Agroindustrial Obispo Colombres (EEAOC) en diferentes localidades de Tucumán y Salta. La incidencia de Fusarium verticillioides, tanto para los híbridos templados como para los tropicales, osciló de 40 a 45% (valor promedio de los diferentes híbridos evaluados) en las tres fechas de siembra. En los híbridos de mezclas, la incidencia promedio para la primera y segunda fecha fue de 30% y menos del 20% para la tercera fecha. La incidencia de F. graminearum fue menor del 10% para las tres fecha de siembra y para los tres grupos de híbridos en ensayo. En los ensayos de macroparcelas, los valores promedios de incidencia de los patógenos variaron según las diferentes localidades. La incidencia de Fusarium verticillioides en la semilla fue mayor en Rosario de la Frontera (50-75%). En el Azul, Trancas y Monte Redondo se detectaron valores promedios entre 20 y 49% y los menores valores se observaron en Las Lajitas (menos de 20%). La incidencia de F. graminearum fue mayor en Las Lajitas (15-25%), mientras que en el resto de las localidades no superó el 10%.Fil: Aguaysol, N. Catalina. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; ArgentinaFil: Gonzalez, Victoria. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; ArgentinaFil: de Lisi, Vicente. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; ArgentinaFil: Reznikov, Sebastian. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; ArgentinaFil: Stegmayer, C. Adolfo. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; ArgentinaFil: Henriquez, Diego. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; ArgentinaFil: Ploper, Leonardo Daniel. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentin

    The design and in vivo testing of a locally stiffness-matched porous scaffold

    Get PDF
    An increasing volume of work supports utilising the mechanobiology of bone for bone ingrowth into a porous scaffold. However, typically during in vivo testing of implants, the mechanical properties of the bone being replaced are not quantified. Consequently there remains inconsistencies in the literature regarding ‘optimum’ pore size and porosity for bone ingrowth. It is also difficult to compare ingrowth results between studies and to translate in vivo animal testing to human subjects without understanding the mechanical environment. This study presents a clinically applicable approach to determining local bone mechanical properties and design of a scaffold with similar properties. The performance of the scaffold was investigated in vivo in an ovine model. The density, modulus and strength of trabecular bone from the medial femoral condyle from ovine bones was characterised and power-law relationships were established. A porous titanium scaffold, intended to maintain bone mechanical homeostasis, was additively manufactured and implanted into the medial femoral condyle of 6 ewes. The stiffness of the scaffold varied throughout the heterogeneous structure and matched the stiffness variation of bone at the surgical site. Bone ingrowth into the scaffold was 10.73 ± 2.97% after 6 weeks. Fine woven bone, in the interior of the scaffold, and intense formations of more developed woven bone overlaid with lamellar bone at the implant periphery were observed. The workflow presented will allow future in vivo testing to test specific bone strains on bone ingrowth in response to a scaffold and allow for better translation from in vivo testing to commercial implants

    What is novel in quantum transport for mesoscopics?

    Full text link
    The understanding of mesoscopic transport has now attained an ultimate simplicity. Indeed, orthodox quantum kinetics would seem to say little about mesoscopics that has not been revealed - nearly effortlessly - by more popular means. Such is far from the case, however. The fact that kinetic theory remains very much in charge is best appreciated through the physics of a quantum point contact. While discretization of its conductance is viewed as the exclusive result of coherent, single-electron-wave transmission, this does not begin to address the paramount feature of all metallic conduction: dissipation. A perfect quantum point contact still has finite resistance, so its ballistic carriers must dissipate the energy gained from the applied field. How do they manage that? The key is in standard many-body quantum theory, and its conservation principles.Comment: 10 pp, 3 figs. Invited talk at 50th Golden Jubilee DAE Symposium, BARC, Mumbai, 200

    Analyzing powers Ayy, Axx, Axz and Ay in the dd->3Hen reaction at 270 MeV

    Full text link
    The data on the tensor Ayy, Axx, Axz and vector Ay analyzing powers in the dd->3Hen obtained at Td= 270 MeV in the angular range 0 - 110 degrees in the c.m. are presented. The observed negative sign of the tensor analyzing powers Ayy, Axx and Axz at small angles clearly demonstrate the sensitivity to the ratio of the D and S wave component of the 3He wave function. However, the one-nucleon exchange calculations by using the standard 3He wave functions have failed to reproduce the strong variation of the tensor analyzing powers as a function of the angle in the c.m.Comment: 8 pages, 7 figures, 4 tables. Submitted to EPJ

    Panorama sanitario del cultivo de la soja en el noroeste argentino durante la campaña 2012/2013

    Get PDF
    Las enfermedades son factores que limitan la producción del de la soja (Glycine max (L.) Merrill) en el noroeste argentino (NOA). Las mismas pueden afectar raíces, tallos, hojas, vainas y/o semillas, provocando pérdidas de rendimiento. En la campaña 2012/2013 las enfermedades se presentaron en el NOA con niveles bajos de severidad en los diferentes estadios del cultivo de la soja debido principalmente a las condiciones poco predisponentes para el desarrollo de las mismas. En el presente trabajo se presentan los resultados de la prospección del estado sanitario de los cultivos de soja en la región NOA llevados a cabo por el personal de la Sección Fitopatología de la Estación Experimental Agroindustrial Obispo Colombres (EEAOC) durante la campaña 2012/2013. En los meses de febrero a marzo se observaron casos de muerte de plantas por hongos de suelo (Rhizoctonia solani, Fusarium spp), en rodales, en distintas localidades de la provincia de Tucumán, especialmente en el departamento Burruyacú, Tucumán, como así también en diferentes localidades de la provincia de Salta, principalmente en General Mosconi, departamento San Martín. A partir de mediados de marzo se registraron incrementos en la incidencia de plantas afectadas por podredumbre carbonosa (Macrophomina phaseolina). Los valores registrados fueron superiores a los observados en campañas anteriores, presentando valores que oscilaron desde 20 a 90% de incidencia en los lotes monitoreados. A lo largo de todo el ciclo, las enfermedades foliares más comunes del cultivo no resultaron gravitantes. Los niveles de mancha marrón (Septoria glycines) y de tizón de la hoja (Cercospora kikuchii), las dos enfermedades de fin de ciclo (EFC) más importantes, fueron leves, no superando el 30% de superficie foliar en el estadio R5.5 para las localidades evaluadas de la provincia de Salta y Tucumán. Pústula bacteriana (Xanhomonas axonopodis pv. glycines) y mildiú (Peronospora manshurica), se presentaron en estadios fenológicos reproductivos avanzados (R5.5) y con niveles de severidad inferior al 15% (Tablas 1). En el departamento San Martín, en el norte de Salta, se observaron niveles bajos de la mancha foliar, causada por Myrothecium roridum, también se registraron niveles bajos (15%) de mancha anillada (Corynespora cassiicola) (Tablas 1). El 21 de marzo se detectó roya asiática de la soja (Phakopsora pachyrhizi) en la localidad de Gral. Mosconi, departamento San Martín, Salta a niveles de trazas. De acuerdo a los posteriores monitoreos realizados, la enfermedad no progresó en el lote en que se hizo dicha detecciónFil: González, Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: de Lisi, Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Reznikov, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Aguaysol, N. Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Jalil, Ana C.. Universidad Nacional de Tucumán. Facultad de Agronomía y Zootecnia; ArgentinaFil: Alarcón, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Martínez, María J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Ploper, Leonardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentin
    corecore