169,850 research outputs found
Effect of clay silylation on curing and mechanical and thermal properties of unsaturated polyester/montmorillonite nanocomposites
No full textThis workfocusesonthechemicalmodification ofmontmorillonite(MMT)(Cloisites Na) withcompa- tible silanes,vinyltriethoxysilane(CVTES)and γ-methacryloxypropyltrimethoxysilane(CMPS)inorderto preventagglomerationandtoimprovemontmorilloniteinteractionwithanunsaturatedpolyesterresin matrix seekingtoachieveamultifunctionalcomposite.Claysweredispersedintheresinbymechanical stirring andsonicationandthenanocompositeswerepreparedbyresintransferintoamold.Theme- chanical, morphological,thermaland flammability propertiesoftheobtainedcompositeswerecom- pared withthosepreparedusingcommercialCloisites 30B (C30B)andCloisites 15A(C15A)clays.Ad- vantagesofusingsilane-modified clays(CVTESandCMPS)ascomparedwithorganic-modified clays (C30B andC15A)canbesummarizedassimilar flexuralstrengthandlinearburningratebuthigher storagemodulusandimprovedadhesiontothepolyesterresinwithconsequenthigherthermalde- flection temperatureandreinforcementeffectivenessathighertemperatures.However,organicmodified claysshowedbetterdispersion(tendencytoexfoliate)andconsequentlydelayedthermalvolatilization due totheclaybarriereffec
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Giant “Twin” Aneurysm of the Thoracic Aorta
No full textAn 86-year-old female patient was referred to our division with sudden chest pain. On
chest x-ray, a huge dilation of the mediastinum was observed (A). The patient underwent
emergent computed tomography of the chest (B), which revealed a giant aneurysm
involving both the ascending and descending portions of the thoracic aorta, with a peculiar
aspect similar to a “twin aorta” (C). The left chest cavity was almost entirely occupied by
the 2 aneurysms. Because of the presence of left pleural fluid, an emergent procedure was proposed
but was refused by the patient. Despite accurate pressure control and intensive care unit
monitoring, the patient experienced irreversible sudden cardiac arrest the following night
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Deltoido pectoralis approach to axillary vessels for full flow cardiopulmonary bypass.
No full textAbstract: Axillary artery has been proposed as a safe and effective alternative for arterial cannulation in surgical procedures involving ascending aorta and/or aortic arch, and is nowadays the site of choice in many centres. Advantages of axillary artery cannulation include antegrade flow and the possibility of selective mono-hemispherical brain perfusion during circulatory arrest. Experiences with the axillary vein cannulation, however, are scarce. Here we report our preliminary experience with axillo-axillary cardiopulmonary bypass, through both axillary artery and vein cannulation (using echo-guided Seldinger technique) at deltoido-pectoralis groove. We have used such an approach in 5 cases of redo surgery on ascending aorta and we have not had any inconvenience during cardiopulmonary bypass. Full flow was maintained in all patients (in 2 with vacuum assisted drainage) including 2 cases with deep hypothermic circulatory arrest. In conclusion such an approach seems to be feasible and effective and can be safety performed providing that accurate TE echo monitoring is provided. (C) 2009 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Thermal and fire retardancy studies of clay-modified unsaturated polyester/glass fiber composites
No full textThe aim of this study was to investigate the effect of
new, cation-exchanged, and silane modified montmo-
rillonite nanoclays fillers on thermal, mechanical and
flammability characteristics of polyester/glass fiber
composites in comparison with composites prepared
with calcium carbonate filler. The coefficient of thermal
expansion showed reduced values for silane-modified
samples. All the composites decomposed at lower
temperatures in air and their degradation behavior dif-
fered from those exposed to nitrogen. The glass fibers
acted as a physical barrier before combustion and the
catalytic effect of the clay was less pronounced for
silane-modified samples. The peak of heat release and
linear burning rate for the silane-modified Cloisite 30B
sample was reduced. However, the limiting oxygen
index did not show significant changes. In general,
consequent to clay addition, these composites showed
improved fire performance, shorter fire duration and
slower fire growth and maintained better mechanical
properties than those with calcium carbonate filler
Sodium montmorillonite modified with methacryloxy and vinylsilanes: Influence of silylation on the morphology of clay/unsaturated polyester nanocomposites
No full textUnsaturated polyester resins are widely used in the automotive, construction and naval industries. To further widen their application, they may be combinedwith clay minerals, which are advantageous due to their thermal, barrier, inflammability and stiffness characteristics. In order to avoid agglomeration and improve the interaction of Cloisite® Na+ montmorillonite (Mt)with an unsaturated polyester matrix, this study focused on clay minerals modified with compatible silanes, vinyltriethoxysilane (VTES) and γ-methacryloxypropyltrimethoxysilane (MPS), and their use in composites in comparison with nanocomposites prepared using commercial clays (Cloisite® 30B and Cloisite® 15A). Functionalization of Cloisite®NawithMPS and VTESwas confirmed by the appearance of characteristic infrared bands and the increase in the basal spacing. The nanocomposites containing silane-modified clays prepared in hydro-alcoholic solution showed the best result compared with ethanol solution. The presence of iron changed the color of the CNa and C30B samples and all of those prepared with silane modified Na-Mt-clays
Description and Classification of Typical Coastal Marine Ecosystems
No full textPROGRESS REPT. PROGRAM - RADIATION PROTECT. 1981, OFFICE OFFICIAL PUBLIC. EUROP. COMMUN., 5 RUE DU COMMERCE, L-2985 LUXEMBOURG
- …
