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Observation Shows (observation + shows)
Selected AbstractsChlamydiae and polymorphonuclear leukocytes: unlikely allies in the spread of chlamydial infectionFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2008Roger G. Rank Abstract While much is known about the attachment of the chlamydiae to the host cell and intracellular events during the developmental cycle, little is known about the mechanism(s) by which elementary bodies exit the cell. In this report, we use the guinea-pig conjunctival model of Chlamydia caviae infection to present in vivo ultrastructural evidence supporting two mechanisms for release of chlamydiae from the mucosal epithelia. Four days after infection, histopathologic observation shows an intense infiltration of polymorphonuclear leukocytes (PMN) in the conjunctival epithelium. Using transmission electron microscopy, a gradient-directed PMN response to chlamydiae-infected epithelial cells was observed. As PMN infiltration intensifies, epithelial hemidesmosome/integrin/focal adhesion adherence with the basal lamina is disconnected and PMNs literally lift off and release infected superficial epithelia from the mucosa. Many of these infected cells appear to be healthy with intact microvilli, nuclei, and mitochondria. While lysis of some infected cells occurs with release of chlamydiae into the extracellular surface milieu, the majority of infected cells are pushed off the epithelium. We propose that PMNs play an active role in detaching infected cells from the epithelium and that these infected cells eventually die releasing organisms but, in the process, move to new tissue sites via fluid dynamics. [source] Tectonic environments of ancient civilizations in the eastern hemisphereGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 5 2008Eric R. Force The map distribution of ancient civilizations shows a remarkable correspondence with tectonic boundaries related to the southern margin of the Eurasian plate. Quantification of this observation shows that the association is indeed significant, and both historical records and archaeoseismological work show that these civilizations commonly suffered earthquake damage. Close association of ancient civilizations with tectonic activity seems to be a pattern of some kind. In the hope that dividing the civilizations into subsets might clarify the meaning of this relation, primary and derivative civilizations were compared. Derivative civilizations prove to be far more closely related to the tectonic boundaries. Similarly, the civilizations that endured the longest (and that have been described as most static) are systematically the farthest from plate boundaries. It is still unclear how the relation actually worked in ancient cultures, i.e., what aspects of tectonism promoted complexity. Linkages to water and other resources, trade (broadly construed), and societal response seem likely. Volcanism appears not to be involved. © 2008 Wiley Periodicals, Inc. [source] A reactive polymer for toughening epoxy resinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Hsu-Chiang Kuan Abstract Epoxy resins are hardly toughened by low weight content of tougheners. In this study, 5 wt % polyurea was adopted to significantly toughen piperidine-cured epoxy, as fracture toughness improved from 0.78 to 1.98 MPa m1/2. We focused on the reactions and morphology evolution of epoxy/polyurea mixture. The polyurea molecular weight was reduced by the exchange reactions of polyurea with epoxy during mixing, as evidenced by gel permeation chromatograph and Fourier transform infrared spectroscopy. As a result, epoxy molecules were chemically bonded with polyurea, improving particle content and interface thickness. Transmission electron microscope observation shows that (a) polyurea in situ formed nanoparticles in matrix which subsequently aggregate into micron-sized particles of thick interface with matrix; and (b) the particles became less stainable with increasing the mixing time, because the reactions promoted high levels of crosslink density of the particles which were thus more resistant to the diffusion of staining chemicals. Longer mixing time improved, obviously, the fracture toughness of epoxy/polyurea composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Synthesis of hafnium tungstate by a CO2 laser and its microstructure and Raman spectroscopic studyJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2008E. J. Liang Abstract Densely packed hafnium tungstate blocks were synthesized by rapid solidification with a CO2 laser. It is shown that the optimum synthesis conditions for HfW2O8 are around 700 W laser power and 1 mm/s scan speed. Scanning electron microscopy (SEM) observation shows that the blocks consist of oriented nano-threads/rods that grew horizontally on the surface region and vertically in the interior. The orientations of the nanostructures are governed by the heat transfer directions on the surface and in the interior. Raman spectroscopic and X-ray diffraction studies show that the samples solidified in the cubic structure with minor contents of the orthorhombic phase. This is explained by a compressive stress induced during the rapid solidification process due to a sudden drop of temperature of the molten pool to the ambient. The stress is estimated to be about 0.6 GPa by comparison with high-pressure Raman study. Some specific Raman bands appear in the samples synthesized with the laser synthetic route but not in the sample by solid-state reaction. Copyright © 2008 John Wiley & Sons, Ltd. [source] Variation in oxygen isotope fractionation during cellulose synthesis: intramolecular and biosynthetic effectsPLANT CELL & ENVIRONMENT, Issue 10 2006LEONEL STERNBERG ABSTRACT The oxygen isotopic composition of plant cellulose is commonly used for the interpretations of climate, ecophysiology and dendrochronology in both modern and palaeoenvironments. Further applications of this analytical tool depends on our in-depth knowledge of the isotopic fractionations associated with the biochemical pathways leading to cellulose. Here, we test two important assumptions regarding isotopic effects resulting from the location of oxygen in the carbohydrate moiety and the biosynthetic pathway towards cellulose synthesis. We show that the oxygen isotopic fractionation of the oxygen attached to carbon 2 of the glucose moieties differs from the average fractionation of the oxygens attached to carbons 3,6 from cellulose by at least 9%, for cellulose synthesized within seedlings of two different species (Triticum aestivum L. and Ricinus communis L.). The fractionation for a given oxygen in cellulose synthesized by the Triticum seedlings, which have starch as their primary carbon source, is different than the corresponding fractionation in Ricinus seedlings, within which lipids are the primary carbon source. This observation shows that the biosynthetic pathway towards cellulose affects oxygen isotope partitioning, a fact heretofore undemonstrated. Our findings may explain the species-dependent variability in the overall oxygen isotope fractionation during cellulose synthesis, and may provide much-needed insight for palaeoclimate reconstruction using fossil cellulose. [source] Triamcinolone-impregnated nasal dressing following endoscopic sinus surgery: A randomized, double-blind, placebo-controlled study,,THE LARYNGOSCOPE, Issue 6 2010David W. J. Côté MD Abstract Objectives/Hypothesis: To evaluate the impact of steroid-impregnated absorbable nasal dressing on wound healing and surgical outcomes after endoscopic sinus surgery (ESS). Study Design: A prospective, randomized, double-blinded, placebo-controlled trial. Methods: Chronic rhinosinusitis patients with polyposis who were to undergo bilateral endoscopic sinus surgery were recruited and randomized to receive triamcinolone-impregnated bioresorbable dressing (Nasopore; Stryker Canada, Hamilton, Ontario, Canada) in one nasal cavity and saline-impregnated dressing contralaterally. Postoperative healing assessments of edema, crusting, secretions, and scarring were done at postoperative days 7, 14, 28 and at 3 and 6 months using validated Lund-Kennedy and Perioperative Sinus Endoscopy (POSE) scores. Results: Analysis of 19 enrolled patients having completed observation shows no significant difference between the cavity scores preoperatively using both the POSE and Lund-Kennedy scores. There was, however, a statistically significant difference at day 7 and 14 in both the Lund-Kennedy (P = .04 and P = .03, respectively) and POSE scores (P = .03 and P = .001, respectively) for the treatment and control groups, and a significant difference was also detected between the groups at 3- and 6-month observations (Lund-Kennedy, P = .007 and P = .02, respectively; POSE, P = .049 and P = .01, respectively). Conclusions: Data analysis suggests a significant improvement in early postoperative healing in nasal cavities receiving triamcinolone-impregnated absorbable nasal packing following ESS and is also associated with improved healing up to 6 months postoperatively. [source] Radiolysis of Confined Water: Hydrogen Production at a High Dose RateCHEMPHYSCHEM, Issue 12 2005Sophie Le Caër Dr. Abstract The production of molecular hydrogen in the radiolysis of dried or hydrated nanoporous controlled-pore glasses (CPG) has been carefully studied using 10 MeV electron irraditation at high dose rate. In all cases, the H2 yield increases when the pore size decreases. Moreover, the yields measured in dried materials are two orders of magnitude smaller than those obtained in hydrated glasses. This proves that the part of the H2 coming from the surface of the material is negligible in the hydrated case. Thus, the measured yields correspond to those of nanoconfined water. Moreover, these yields are not modified by the presence of potassium bromide, which is a hydroxyl radical scavenger. This experimental observation shows that the back reaction between H2 and HO. does not take place in such confined environments. These porous materials have been characterized before and after irradiation by means of Fourier-transform infrared (FT-IR) spectroscopy, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) techniques, which helps to understand the elementary processes taking place in this type of environment, especially the protective effect of water on the surface in the case of hydrated glasses. [source] Toward a consistent reanalysis of the upper stratosphere based on radiance measurements from SSU and AMSU-ATHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 645 2009Shinya Kobayashi Abstract Radiance measurements from the Stratospheric Sounding Unit (SSU) and the Advanced Microwave Sounding Unit (AMSU-A) are the primary source of information for stratospheric temperature in reanalyses of the satellite era. To improve the time consistency of the reanalyses, radiance biases need to be properly understood and accounted for in the assimilation system. The investigation of intersatellite differences between SSU and AMSU-A radiance observations shows that these differences are not accurately reproduced by the operational version of the radiative transfer model for the TIROS Operational Vertical Sounder (RTTOV-8). We found that this deficiency in RTTOV was mainly due to the treatment of the Zeeman effect (splitting of the oxygen absorption lines at 60 GHz) and to changes in the spectral response function of the SSU instrument that are not represented in RTTOV. On this basis we present a revised version of RTTOV that can reproduce SSU and AMSU-A intersatellite radiance differences more accurately. Assimilation experiments performed with the revised version of RTTOV in a four-dimensional variational analysis system (4D-Var) show some improvements in the stratospheric temperature analysis. However, significant jumps in the stratospheric temperature analysis still occur when switching satellites, which is due to the fact that systematic errors in the forecast model are only partially constrained by observations. Using a one-dimensional retrieval equation, we show that both the extent and vertical structure of the partial bias corrections must inevitably change when the nature of the radiance measurement changes with the transition from SSU to AMSU-A. Copyright © 2009 Royal Meteorological Society [source] Data assimilation of high-density observations.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 605 2005I: Impact on initial conditions for the MAP/SOP IOP2b Abstract An attempt is made to evaluate the impact of the data assimilation of high-frequency data on the initial conditions. The data assimilation of all the data available on the Mesoscale Alpine Program archive for a test case is performed using the objective analysis and the Variational Data Assimilation (Var) techniques. The objective analysis is performed using two different schemes: Cressman and multiquadric; 3D-Var is used for the variational analysis. The European Centre for Medium-Range Weather Forecasts analyses are used as first guess, and they are blended together with the observations to generate an improved set of mesoscale initial and boundary conditions for the Intensive Observing Period 2b (17,21 September 1999). A few experiments are performed using the initialization procedure of MM5, the mesoscale model from Penn State University/National Center for Atmospheric Research. The comparison between improved initial conditions and observations shows: (i) the assimilation of the surface and upper-air data has a large positive impact on the initial conditions depending on the technique used for the objective analysis; (ii) a large decrease of the error for the meridional component of the wind V at the initial time is found, if assimilation of three-hourly data is performed by objective analysis; (iii) a comparable improvement of the initial conditions with respect to the objective analysis is found if 3D-Var is used, but a large error is obtained for the V component of the wind. Copyright © 2005 Royal Meteorological Society [source] Data assimilation of high-density observations.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 605 2005II: Impact on the forecast of the precipitation for the MAP/SOP IOP2b Abstract The impact of the data assimilation of high-density (space and time) data on the precipitation forecast is evaluated by improving the initial conditions of a mesoscale model. The high-frequency data allow for improving the three-hourly initial and boundary conditions as well. The data assimilation is performed using initial objective analysis (Cressman and multiquadric schemes) and 3D-Var. The MM5 (version 3) mesoscale model from Penn State University/National Center for Atmospheric Research is used to evaluate the impact of the improved initial and boundary conditions on the model simulations. The comparison of model results with observations shows: (i) the forecast of the precipitation at high resolution produces better results than those without data assimilation only if three-hourly data are assimilated by multiquadric; (ii) the mean error of the model rainfall largely decreases only if 3D-Var is used, but no comparable improvement in the spatial distribution of the precipitation is found; (iii) the improvement for the rainfall is not as good as it is for the initial conditions for all experiments. Moreover, the observations ingested by objective analysis modify both the amount and the timing of the precipitation on the Po valley. On the other hand, 3D-Var modifies only the amount of the precipitation, but both techniques barely recover large-model failure. Copyright © 2005 Royal Meteorological Society [source] | ||||||||||||||||