170,684 research outputs found
Input of atmospheric particles into forest stands by dry deposition
No full textIn this study the dry input of atmospheric particles into a forest stand is quantified. A wash-off-method using the natural leaf surfaces as collectors of the dry deposition was chosen. The direct on-site-measurement on living branches were achieved in a spruce stand (Picea abies (L.) Karst) at Solling, Germany. The ion exchange processes occurring on natural branches can reliably be quantified through immediate sequential washings. In order to calculate also the gas dry deposition of those trace elements which occur in both particle and gas phases, a resistance model was used. From these results the deposition velocity of particulate aerosol components into the forest stand was calculated. Dry particle deposition constitutes an important part of the total matter input into the forest ecosystem. Just the nitrogen input into Solling only by dry deposition (from particle-, mist-, and gas-deposition) with about 30 kg N ha(-1) a(-1) already exceeds the critical load of 20 kg N ha(-1) a(-1) by far, and this is without even considering the additional load by wet deposition which amounts to 15 kg ha(-1) a(-1). These findings are of greatest ecological importance, as the damage to the stability of the forest ecosystem caused by increased nitrogen input is considerable. Only a quick and drastic reduction of sulphur and nitrogen emissions could stop the further increase of the nutritient imbalance and the progressing acidification of this ecosystem
The chemical composition and sources of the bulk deposition on Lake Kinneret (The Sea of Galilee), Israel
No full textThe chemical composition of the bulk deposition into Lake Kinneret, Israel was determined for the three hydrological years from 1992 to 1995. The fluxes of the elements and ions in the bulk deposition around the lake are fairly uniform although some local effects due to anthropogenic activity are observed; temporal effects are more pronounced. Na and Cl fluxes are greatly affected by rainfall that has passed over the Mediterranean Sea whilst Ca fluxes increase during dust storm episodes. The amount of each of the determined constituents entering the lake was calculated. The major chemical constituent entering the lake (except Ca) is SO(4) whose main source is long-range transport from Europe. Enrichment factor analysis shows that the insoluble portion of the bulk deposition has the same characteristics as regional (and Saharan) dust storms, whilst the soluble portion is strongly affected by the marine environment. Significant additions to the previously known input of nitrogen and phosphorous enter the lake due to bulk deposition: 10% for nitrogen and 40% for phosphorous. The Pb content of the lake sediments correlates with Pb usage in petrol. Full experimental results are given in the electronic appendices. (C) 2008 Elsevier Ltd. All rights reserved
"Den gode lärarens" förutsättningar och ansvar : En studie om de lärarfackliga medlemstidningarnas bild av lärares förutsättningar, villkor och ansvar
No full textSyftet med föreliggande uppsats är att diskutera föreställningar om "den gode läraren" och
vilka förutsättningar som krävs för att dessa visioner ska kunna realiseras. Hur har
föreställningar om "den gode läraren" samt förutsättningar för läraryrket diskuterats i tidigare
forskning och hur skrivs förutsättningarna för att "ett gott lärarskap" fram i lärarfackens
medlemstidningar, och då särskilt avseende arbetstidens användning och lärares ansvar? Vi
har valt att analysera ”den gode lärarens” ansvar och förutsättningar utifrån tidigare forskning
samt genom en kvalitativ analys av artiklar i Lärarförbundets och Lärarnas Riksförbunds
medlemstidningar, Lärarnas Tidning och Skolvärlden. Vi har kommit till den slutsatsen att vi
lyckats besvara hur lärare framställs i medlemstidningarna, men i uppsatsen ges även
ytterligare dimensioner av problematiken genom att lyfta fram aspekter och ståndpunkter
yttrade på den allmänna publika mediearenan som debattprogram på tv och debattinlägg i
Göteborgs Posten. Resultat visar att ”den gode läraren” förefaller ha fått en utökad
arbetsbörda bland annat på grund av ökade krav på dokumentation. Elevernas och
föräldrarnas inflytande på lärarens arbetssätt har påverkat lärarens förutsättningar i sin
yrkesroll. Elever arbetar i idag i större utsträckning med individuella projekt och eget arbete,
vilket har fått följder för både läraren som har färre lärarledda lektioner och för de svagare
eleverna, som har svårare att arbeta individuellt. Läraryrket har blivit allt mer komplext och
svårdefinierbart. Lärares ansvar är större än det finns förutsättningar att klara, vilket fått stor
betydelse för läraryrket.
The amount and nature of the dustfall on Lake Kinneret (the Sea of Galilee), Israel: flux and fractionation
No full textThe dustfall flux on Lake Kinneret, Israel was measured by a network of 15 sampling stations around the lake over a 3 year period, with partial measurements over a further 2 years. The dustfall was characterized by dividing it into fractions including inorganic water insoluble matter (IWI), i.e. insoluble minerals; inorganic water soluble matter (IWS); and total organic matter (TORG). The total dustfall was fairly constant over the years with a mean input of 12,000 t on the 170 km(2) lake surface. The proportion of atmospheric input to total solids entering the lake is inversely dependent on the amount of rain in a particular year and varied between 17% and 46% (mean = 34%). The dustfall is composed of roughly equal proportions of TORG, IWI and IWS. The organic matter itself is about 50% water soluble. The most variable fraction of the dustfall is the insoluble mineral content (IWI) which is dependent on violent dust storms usually occurring in spring and autumn. The amount of aeolian matter entering the lake is sufficiently large, compared to the fluvial input, to have a significant effect on the water quality. Much of the dustfall entering the lake is more finely divided than the fluvial suspended matter and this will presumably increase its relative effect. (C) 2003 Elsevier Ltd. All rights reserved
Fløyelskinn og gode knær : bokomtale
No full textBokanmeldelse av L. C. Olafsen: Fløyelskinn og gode knær. Snøfugl forlag. 201
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
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
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
Allometric equations for biomass estimations in Cameroon and pan moist tropical equations including biomass data from Africa
No full textMoist tropical forests in Africa and elsewhere store large amounts of carbon and need accurate allometric regressions for their estimation. In Africa the absence of species-specific or mixed-species allometric equations has lead to broad use of pan moist tropical equations to estimate tree biomass. This lack of information has raised many discussions on the accuracy of these data, since equations were derived from biomass collected outside Africa. Mixed-species regression equations with 71 sample trees using different input variables such as diameter, diameter and height, product of diameter and height, and wood density were developed to estimate total aboveground biomass and biomass of leaves and branches for a Cameroon forest. Our biomass data was added to 372 biomass data collected across different moist tropical forests in Asia and South America to develop new pan moist tropical allometric regressions. Species-specific and mixed-species height diameter regression models were also developed to estimate heights using 3833 trees. Using only diameter as input variable, the mixed-species regression model estimates the aboveground biomass of the study site with an average error of 7.4%. Adding height or wood density did not improve significantly the estimations. Using the three variables together improved the precision with an average error of 3.4%. For general allometric equations tree height was a good predictor variable. The best pan moist tropical equation was obtained when the three variables were added together followed by the one which includes diameter and height. This study provides height diameter relationships and wood density of 31 species. The pan moist tropical equation developed by Chave et al. (2005), estimates total aboveground biomass across different sites with an average error of 20.3% followed by equations developed in the present study with an average error of 29.5%. (C) 2010 Published by Elsevier B.V
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
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