169,935 research outputs found
Forage quality improves but ecosystem multifunctionality declines under drought and frequent cutting in dry grassland mesocosms
No full textDry grasslands are vast, socioeconomically and ecologically important environments, which are increasingly threatened by multiple stressors. We tested whether plant cover composition could mitigate ecosystem services loss under multiple stressors in dry grassland mesocosms by growing the grass sorghum (Sorghum bicolor) alone (Grass cover) or together with the legume serradella (Ornithopus sativus) (Mixed cover) under frequent cutting and/or increasing water stress. We assessed erosion control, carbon sequestration, forage quantity and quality, and soil fertility, individually and simultaneously (i.e., multifunctionality). Contrary to our hypothesis, the Mixed cover did not improve ecosystem services compared to the Grass cover, except for forage quality, which improved by 30%. In general, the stressors had negative effects: cutting reduced erosion control by 20%, forage quantity by 50%, soil fertility by 40% and multifunctionality by 20%, and severe water stress decreased carbon sequestration by 40%, forage quantity by 30%, soil fertility by 10%, and multifunctionality by 10%. Water stress caused 100% serradella mortality, underscoring this legume’s vulnerability to increasing aridity. Combined stressors yielded the lowest service provision. Forage quality was the only service that improved under stress: cutting improved it by 40% and severe water stress by 60%. Our results suggest that while systems combining grasses and legumes may enhance forage quality, grass-dominated systems appear more resilient to multiple stressors in drylands, largely due to their superior efficiency in accessing and conserving limited water and nutrient resources. Given the ongoing trends of aridification and land-use intensification, future research should explore adaptive management strategies that prioritize resource-efficient plant species, foster belowground resource retention, and optimize grazing regimes to sustain resilience and multifunctionality in dry grasslands
Preface Topical Issue "Energy storage and release: Models meet radio observations"
No full textFil: Marqué, C.. Royal Observatory of Belgium; BélgicaFil: Nindos, A.. University of Ioannina; GreciaFil: van Driel Gesztelyi, Lidia. Centre National de la Recherche Scientifique. Observatoire de Paris; FranciaFil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
On the relationship between magnetic field strength and loop lengths in solar coronal active regions
No full textBy assuming that coronal active regions are made up of many loops, we investigate the relationship between the average magnetic field strength and loop length for a sample of active regions observed by the Soft X-ray Telescope aboard Yohkoh. We use photospheric magnetic data from the Michelson Doppler Imager and compute extrapolated field lines that match the observed soft X-ray emission. We compare our results with a previous study and find them to be consistent and a logical extension of such work. Such studies have important implications for solar coronal heating models.
Fil: Jain, R.. University of Sheffield. Department of applied mathematics; Reino UnidoFil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
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
Common mycorrhizal network may not facilitate plant species coexistence under very low fertility conditions
No full textHere, we assessed if the establishment of a common mycorrhizal network (CMN) could facilitate plant species coexistence and improve plant productivity. For that we conducted a mesocosms experiment to grow serradella (Ornithopus sativus Brot., a nitrogen fixing legume) and maize (Zea mays L., a C4 grass). Besides the native arbuscular mycorrhizal inoculum, we further inoculated the mesocosms with a commercial mixture of arbuscular mycorrhizal fungal spores. The establishment of a CMN (and of plant roots) was prevented by physically disrupting a potential connection between the two plant species every week. After 12 weeks of growth in a greenhouse, we measured foliar SPAD values, harvested the plants and analyzed plant biomass and mycorrhizal traits, soil organic matter and water content. Although not always significant, disturbance increased plant biomass and density, and leaf SPAD values. Also, disturbance increased the percentage of hyphae in serradella roots and tended to increase all mycorrhizal components for both species. While there were no differences in soil organic matter concentration between treatments, there was an
increase in relation to the original soil mixture. Contrary to our hypothesis, our results suggest that frequently disturbing the CMN (and plant roots) had a positive effect on plant productivity possibly by preventing plant species competition. Moreover, the increase in soil organic matter observed in all treatments highlights the crucial role that vegetation cover plays in controlling soil degradation and desertification in drylands, and in stimulating soil function and resilience
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
Early rehabilitative treatment for pediatric acute disseminated encephalomyelitis: case report.
No full textAlthough the diagnosis of and therapy for Acute Disseminated Encephalomyelitis (ADEM) have been extensively investigated, the role of rehabilitation in modifying its functional outcome has received little attention in the literature so far. We report a case of pediatric ADEM who showed complete functional recovery following early rehabilitative treatment, started in the Intensive Care Unit
Zones with quasi-discontinuous magnetic connections in the photosphere and solar flares
No full textThe topological structure of active regions is related with flare brightening. (Mandrini et a!, 1991, 1993; Démoulin et ai, 1992, 1993, 1994). In these works, we modeled the observed longitudinal magnetic field by means of a discrete number of sub-photospheric magnetic poles, and derived the magnetic topology taking into account the connections between these poles (source method, MF). We present here a new method (quasi-discontinuity method, MQD). It finds the regions above the photosphere where the connectivity of field lines changes drastically.Asociación Argentina de Astronomí
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
Interplanetary flux rope ejected from an X-ray bright point
No full textUsing multi-instrument and multi-wavelength observations (SOHO/MDI and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal magnetic field of a tiny bipole combined with modelling of Wind in situ data, we provide evidences for the smallest event ever observed which links a sigmoid eruption to an interplanetary magnetic cloud (MC). The tiny bipole, which was observed very close to the solar disc centre, had a factor one hundred less flux than a classical active region (AR). In the corona it had a sigmoidal structure, observed mainly in EUV, and we found a very high level of non-potentiality in the modelled magnetic field, 10 times higher than we have ever found in any AR. From May 11, 1998, and until its disappearance, the sigmoid underwent three intense impulsive events. The largest of these events had extended EUV dimmings and a cusp. The Wind spacecraft detected 4.5 days later one of the smallest MC ever identified (about a factor one hundred times less magnetic flux in the axial component than that of an average MC). The link between this last eruption and the interplanetary magnetic cloud is supported by several pieces of evidence: good timing, same coronal loop and MC orientation, same magnetic field direction and magnetic helicity sign in the coronal loops and in the MC. We further quantify this link by estimating the magnetic flux (measured in the dimming regions and in the MC) and the magnetic helicity (pre- to post-event change in the solar corona and helicity content of the MC). Within the uncertainties, both magnetic fluxes and helicities are in reasonable agreement, which brings further evidences of their link. These observations show that the ejections of tiny magnetic flux ropes are indeed possible and put new constraints on CME models
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