1,051 research outputs found

    Qualitative features of periodic solutions of KdV

    Full text link
    In this paper we prove new qualitative features of solutions of KdV on the circle. The first result says that the Fourier coefficients of a solution of KdV in Sobolev space HN,N0H^N,\, N\geq 0, admit a WKB type expansion up to first order with strongly oscillating phase factors defined in terms of the KdV frequencies. The second result provides estimates for the approximation of such a solution by trigonometric polynomials of sufficiently large degree

    Atomic Force Microscopy Study of Human Tooth Enamel Surfaces

    Get PDF
    Human enamel features from individual crystals up to prisms were observed by atomic force microscopy (AFM). Low magnification images of vestibular tooth surfaces show the existence of enamel prisms appearing as deep holes. Individual, parallel enamel crystals show lateral faces elongated and formed by the (100) planes of hydroxyapatite (HA). Height differences between (001) faces create the roughness of enamel surface. Individual (001) crystal faces can be observed clearly at higher magnification and show the characteristic hexagonal shape with 60° angles between (100) faces. This study confirms the applicability of AFM for studying biological hydroxyapatite crystals

    Heathlands, fire and grazing. A paleoenvironmental view of las Hurdes (Caceres, Spain) history during the last 1200 years

    Get PDF
    Objetivo del estudio: Se hace un estudio diacrónico del cambio de vegetación a través del análisis palinológico de depósitos sedimentarios. Ésta es una herramienta esencial tanto para diseñar estrategias de sonido en la gestión del paisaje como para comprender su carácter dinámico y antropogénico. Área de estudio: La Meseguera (Ladrillar, Cáceres, España) está situada en la región de Hurdes, en la parte occidental de Sistema Ibérico y comenzó a desarrollarse a principios del período islámico (aproximadamente 770 d C), en una zona ampliamente dominado por el breza. Material y métodos: Polen, palinomorfos no polínicos y la tasa de acumulación de carbón (CHAR) combinada con los datos históricos son indicadores útiles para evaluar el papel creciente de la influencia humana sobre la vegetación. Principales resultados: El uso del fuego y la ganadería representa los principales impulsores del cambio del paisaje en el curso de la historia. El establecimiento de planes de reforestación en bosques, a partir de mediados del siglo XX, cambió sustancialmente en las características regionales. La presencia esporádica de pólenes de haya es detectada hasta el siglo XVI, lo que implica su presencia más occidental en el Sistema Ibérico Central. Aspectos destacados de la investigación: La integración del análisis del polen y los datos históricos es una herramienta esencial a los cambios en la vegetación del Holoceno. Estos cambios se han debido principalmente a perturbaciones antropogénicas, específicamente al fuego y a la ganadería.Aim of study: The diachronic study of vegetation change through palynological analysis of sedimentary deposits is an essential tool both to design sound strategies on landscape management and to understand its anthropogenic dynamics. Area of study: La Meseguera mire (Ladrillar, Cáceres, Spain) is located in the Hurdes region in the western part of Iberian Central System and started to develop at the beginning of the Islamic period (ca. 770 cal AD), in an area widely dominated by heathland. Material and methods: Pollen, non-pollen palynomorphs and charcoal accumulation rate (CHAR) combined with historical data are useful indicators to assess the increasing role of human influence on vegetation. Main results: The use of fire and livestock husbandry represents the main drivers of landscape change in the course of the history. The establishment of forest afforestation plans, from the middle of 20th century, changed substantially the regional features. The sporadic presence of beech pollen is detected until 16th century, which implies the most western location in the Iberian Central Mountain System. Research highlights: The integration of pollen analysis and historical data is an essential tool when studying the changes in Holocene vegetation. These changes have been mainly driven by anthropogenic disturbances, more specifically by fire and livestock husbandry.peerReviewe

    Fibronectin-Cleaving Activity in Bronchial Secretions of Patients with Cystic Fibrosis

    Get PDF
    In cystic fibrosis, colonization of the airways with Pseudomonas aeruginosa follows colonization with Staphylococcus aureus and is related to accelerated deterioration of pulmonary function. Because P. aeruginosa adheres better to cell surfaces devoid of fibronectin, we searched for fibronectin-cleaving activity in bronchial secretions and saliva from 24 patients with cystic fibrosis who were followed up for 4.5 y and from two control groups. Proteolytic activity against 125I-labeled fibronectin wascontinuously present in cystic fibrosis bronchial secretions; significantly higher fibronectin-cleaving activity was found in older vs. younger patients, in patients with advanced disease stages determined by a five-stage scoring system, and in those colonized with P. aeruginosa. The fibronectin-cleaving activity was due to neutrophil elastase and cathepsin G. Cystic fibrosis bronchial secretions had proteolytic activity against surface fibronectin of airway mucosal cells. Thus fibronectin-cleaving activity of bronchial secretions rather than of saliva may favor P. aeruginosa colonization of the upper respiratory tract in individuals with cystic fibrosi

    Long-term outcome of surgery for perianal Crohn's fistula

    Get PDF

    Comparative efficacies of imipenem, oxacillin and vancomycin for therapy of chronic foreign body infection due to methicillin-susceptible and -resistant Staphylococcus aureus

    Get PDF
    The efficacies of imipenem when directed against methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) strains of Staphylococcus aureus were compared with those of oxacillin and vancomycin in a subcutaneous rat model, using chronically infected tissue cages. At three weeks after inoculation, stable chronic infections were established with average bacterial counts exceeding 106cfu/mL tissue cage fluid for both strains. Intraperitoneal administration (twice a day for 7 days) of imipenem (80 mg/kg) or oxacillin (200 mg/kg) produced peak levels of 23 or 45 mg/L and trough levels of < 0⋅1 and 5⋅7 mg/L, respectively. The therapeutic regimens of either imipenem (P < 0⋅001) or oxacillin (P < 0⋅02) administered for 7 days led to significant reductions in bacterial counts in the tissue cage fluids of animals chronically infected with MSSA. In contrast, imipenem was not effective against chronic MRSA tissue cage infections, despite the relatively low MIC of the infecting strain and the use of high dose (120 mg/kg) therapy. In-vitro susceptibility testings of MRSA performed before and after imipenem therapy demonstrated the emergence of a highly resistant subpopulatio

    Immunization of Noncolonized Cystic Fibrosis Patients against Pseudomonas aeruginosa

    Get PDF
    The long-term safety and immunogenicity of a polyvalent Pseudomonas aeruginosa conjugate vaccine was evaluated in 30 noncolonized cystic fibrosis patients. Four doses were administered over 3 years, and patients were followed for a mean of 38 months. No acute or long-term adverse effects were noted. Immunization engendered a significant antibody response to all vaccine components. A decline in titers during year 3 of observation was associated with a marked rise in the isolation of P. aeruginosa. This organism was isolated repeatedly from the respiratory tract of 4 patients and only once from 7 patients. The remaining patients were repeatedly culture-negative. Only 1 patient showed clinical deterioration associated with multiple isolations of P. aeruginos

    Affinity Constants of Naturally Acquired and Vaccine-Induced Anti-Pseudomonas aeruginosa Antibodies in Healthy Adults and Cystic Fibrosis Patients

    Get PDF
    Naturally acquired anti-Pseudomonas aeruginosa antibody fails to afford protection against repeated P. aeruginosa bronchopulmonary exacerbations in cystic fibrosis (CF) patients. In an effort to explain this phenomenon, the titer and affinity constants of serum anti-lipopolysaccharide (LPS) IgG were determined in five study groups: healthy adults before and after immunization with a polyvalent LPS-based vaccine, healthy noncolonized CF patients before and after immunization, nonimmunized CF patients with significantly elevated anti-LPS antibody titers without documented colonization, recently colonized CF patients before and after immunization, and nonimmunized CF patients chronically colonized with P. aeruginosa. Immunization elicited a significant rise in total anti-LPS immunoglobulin levels and affinity constants in both healthy adults and CF patients. Although chronically colonized patients had elevated levels of total anti-LPS antibody, these antibodies possessed affinities at least tOO-fold less than those of vaccine-induced antibodie
    corecore