1,686 research outputs found
Mineral content in semiarid grassland systems affected by community structure and soil characteristics
This work was supported by the European Union project nÂș 8001-CT90-0021.Mineral element concentrations in plants and their relationships with botanical composition and soil characteristics were analyzed over two consecutive years in herbage samples from semiarid grassland systems (central-western Spain) affected by a topographic gradient. There were not significant differences in the mineral concentration of the plant community between sampling years suggesting that factors other than those related to interannual climatic variation are more important in determining the mineral concentration of plant community in semiarid grasslands.
A significant effect of slope position on aboveground biomass production, soil characteristics and plant tissue nutrient contents was found. As compared to the upper and middle zones, the lower zones of slope showed greater aboveground biomass production, a lower proportion of forbs, a higher proportion of grasses, higher concentrations of N, Ca, Mg and Na in botanical groups, and lower concentrations of P and K in botanical components. Stepwise multiple regression analysis showed that most of the variation in N, P, K, Ca, and Mg concentrations in the plant community along the slope can be explained by botanical composition and its specific mineral content. Several soil properties (organic matter, total N, total C, coarse sand) proved to be significantly correlated with the N, Ca, Mg, and Na concentrations of grasses, legumes and forbs, indicating an increase in plant tissue concentrations with increasing eutrophic status in soil from the upper to the lower zones of the slope. The P and K concentrations of legumes and forbs varied according to the phosphorus or potassium contents in soil, which decreased from the upper and middle to the lower zones. The results showed that the mineral concentrations of botanical components were dependent on soil characteristics in different ways.Peer reviewe
Chemistry of a Nitrosyl Ligand Âż:Âż-Bridging a Ditungsten Center: rearrangement and NâO Bond cleavage reactions
The novel nitrosyl-bridged complex [W2Cp2(ÎŒ-PtBu2)(ÎŒ-Îș:η-NO)(CO)(NO)](BAr4) [Ar = 3,5-C6H3(CF3)2] was prepared in a multistep procedure starting from the hydride [W2Cp2(ÎŒ-H)(ÎŒ-PtBu2)(CO)4] and involving the new complexes [W2Cp2(ÎŒ-PtBu2)(CO)4](BF4), [W2Cp2(ÎŒ-PtBu2)(CO)2(NO)2](BAr4), and [W2(ÎŒ-Îș:η5-C5H4)Cp(ÎŒ-PtBu2)(CO)(NO)2] as intermediates, which follow from reactions with HBF4·OEt2, NO, and Me3NO·2H2O, respectively. The nitrosyl-bridged cation easily added chloride upon reaction with [N(PPh3)2]Cl, with concomitant NO rearrangement into the terminal coordination mode, to give [W2ClCp2(ÎŒ-PtBu2)(CO)(NO)2], and underwent NâO and WâW bond cleavages upon the addition of CNtBu to give the mononuclear phosphinoimido complex [WCp(NPtBu2)(CNtBu)2](BAr4). Another NâO bond cleavage was induced upon photochemical decarbonylation at 243 K, which gave the oxo- and phosphinito-bridged nitrido complex [W2Cp2(N)(ÎŒ-O)(ÎŒ-OPtBu2)(NO)](BAr4), likely resulting from a NâO bond cleavage step following decarbonylation
Generating functions and companion symmetric linear functionals
14 pages, no figures.-- MSC2000 codes: 33C45, 42C05.MR#: MR2004670 (2004i:33016)Zbl#: Zbl 1047.33004In this contribution we analyze the generating functions for polynomials orthogonal with respect to a symmetric linear functional u, i.e., a linear application in the linear space of polynomials with complex coefficients such that . In some cases we can deduce explicitly the expression for the generating function where {Pn}n is the sequence of orthogonal polynomials with respect to u.Second author (S.G.M.)'s research supported by Junta de AndalucĂa, Grupo de InvestigaciĂłn FQM 0178. Third author (F.M.)'s research supported by DirecciĂłn General de InvestigaciĂłn (Ministerio de Ciencia y TecnologĂa) of Spain, Grant BFM 2000-0206-C04-01 and INTAS Project 2000-272.Publicad
Estimation of mineral content in natural grasslands by near infrared reflectance spectroscopy
Near infrared reflectance spectroscopy (NIRS) was tested to predict nitrogen and mineral concentration (N, P, K, Ca, Mg, Na, Mn, Fe, Cu and Zn) in natural grassland samples. The samples were taken from different community types according to the topographic gradient, at different maturation stages and during a period of four consecutive years. A subset of 95 samples was selected on the basis of the spectral variation. Chemical values from the calibratĂon sample set were regressed on the corresponding spectral data using a stepwise multiple regression analysĂs. Another subset of 75 samples was used as the validation set. Standard errors of prediction and correlation coefficients, respectively, were: 0.71 and 0.97 (N), 0.22 and 0.73 (P), 1.83 and 0.84 (K), 0.83 and 0.92 (Ca), 0.15 and 0.92 (Mg),
3.94 and 0.66 (Na), 44 and 0.84 (Mn), 19 and 0.75 (Fe), 1.01 and 0.77 (Cu), 3.9 and 0.79 (Zn).This work was supported by the European UnĂon (Contract N 8001-CT90-0021). Thanks are due to L.G. Criado, C. EstĂ©vez and M. HernĂĄndez for their assistance in the field work.Peer reviewe
Cytokine-like activity of European sea bass ISG15 protein on RGNNV-infected Eâ11 cells
IFN-I generates an antiviral state by inducing the expression of numerous genes, called IFN-stimulated genes,
ISGs, including ISG15, which is the only ISG with cytokine-like activity. In a previous study, we developed the
Dl_ISG15_E11 cell line, which consisted of E11 cells able to express and secrete sea bass ISG15. The current study
is a step forward, analysing the effect of secreted sea bass ISG15 on RGNNV replication in E11 cells, and looking
into its immunomodulatory activity in order to corroborate its cytokine-like activity. The medium from ISG15-
produccing cells compromised RGNNV replication, as it has been demonstrated both, by reduction in the viral
genome synthesis and, specially, in the yield of infective viral particles. The implication of sea bass ISG15 in this
protection has been demonstrated by ISG15 removal, which decreased the percentage of surviving cells upon
viral infection, and by incubation of RGNNV-infected cells with a recombinant sea bass ISG15 protein, which
resulted in almost full protection. Furthermore, the immunomodulatory activity of extracellular sea bass ISG15
has been demonstrated, which reaffirms a cytokine-like role for this proteinThis study has been supported by projects AGL2017-84644-R (MINECO/AEI/FEDER, UE) (Spanish Government) and UMA20-
FEDERJA-103 (ConsejerĂa de EconomĂa y Conocimiento/Programa Operativo FEDER 2014â20, UE) (Junta de AndalucĂa). Funding for open access charge: Universidad de M Ìalaga/CBUA. Authors thank I. Bandin for the viral isolate
Experience with the use of Rituximab for the treatment of rheumatoid arthritis in a tertiary Hospital in Spain: RITAR study
There is evidence supporting that there are no
relevant clinical differences between dosing rituximab 1000 mg or 2000 mg
per cycle in rheumatoid arthritis (RA) patients in clinical trials, and low-dose
cycles seem to have a better safety profile. Our objective was to describe the
pattern of use of rituximab in real-life practice conditions.
Methods: Rituximab for RA in clinical practice (RITAR) study is a retrospective cohort study from 2005 to 2015. Eligibility criteria were RA adults
treated with rituximab for active articular disease. Response duration was
the main outcome defined as months elapsed from the date of rituximab
first infusion to the date of flare. A multivariable analysis was performed
to determine the variables associated with response duration.
Results: A total of 114 patients and 409 cycles were described, 93.0%
seropositive and 80.7% women. Rituximab was mainly used as second-line
biological therapy. On demand retreatment was used in 94.6% of cases
versus fixed 6 months retreatment in 5.4%. Median response duration
to on demand rituximab cycles was 10 months (interquartile range,
7â13). Multivariable analysis showed that age older than 65 years, number
of rituximab cycles, seropositivity, and first- or second-line therapy were
associated with longer response duration. The dose administered at each
cycle was not significantly associated with response duration.
Conclusions: Our experience suggests that 1000 mg rituximab single infusion on demand is a reasonable schedule for long-term treatment of those
patients with good response after the first cycles, especially in seropositive
patients and when it is applied as a first- or second-line biological therap
Bioinduced precipitation of barite and celestite in dolomite microbialites Examples from Miocene lacustrine sequences in the Madrid and Duero Basins, Spain
This paper provides an ancient analogue for biologically mediated celestite and barite formation in dolomite precipitating microbial mats developed in lacustrine environments during the Miocene. Barite and celestite occurrences were studied in three temporally and spatially separated sedimentary successions: S1 and S2 in the Madrid Basin and S3 in the Duero Basin. In S1, macrocrystalline selenite gypsum occurs as laterally continuous beds; in the two other successions (S2 and S3), calcite pseudomorphs of lenticular gypsum aggregates are hosted in dolomite beds as evidence for the former presence of this evaporite. In S1, only celestite is associated with dolomite. Celestite crystals occur as both intergrown clusters, concentrated in pockets likely created by the dissolution of intrasedimentary anhydrite precursors, and as single precipitates associated with dolomite masses that replace selenite gypsum. Celestite crystals are nucleated commonly on organic substances that are pervasively associated with them. In S2 and S3, scarce single celestite crystals are restricted to calcite pseudomorphs after gypsum, whereas barite is the sulphate precipitated in the pseudomorphs' surroundings. Barite is commonly present as patchy poikilotopic crystals which include microbial structures and is embedded in organic matter. Additionally, barite is found as a secondary precipitate within Ba-bearing feldspars. Feldspar weathering is, thus, envisaged as amajor source of barium at these sites. Petrographical, isotopic and compositional observations point out that the barite and celestite formation was not caused by abiological processes only. Rather, the patchy distribution of the sulphates, close links to organic matter with biogenic isotope signatures, and inclusion of microbial structures, such as biologically mediated dolomite, provides evidence for the involvement of microbes in the formation of the sulphates. The coprecipitation of barite and celestite with dolomite entails complex interactions between different microorganisms and reinforces the biological formation of dolomite in saline lakes
Effect of corrosion degree on different steel ductility parameters, based on 'Equivalent Steel' criterion
One of the meaningful effects of concrete reinforcement steel corrosion on concrete structures is the decrease of mechanical properties, specifically the ductility of steel. The term ductility of steel refers to a group of properties which determine the reinforced concrete structures (RCS) and it is necessary to take this property into account for the recalculation of structures that have been already corroded until the point to condition in many occasions the analysis methodology. The paper aims to discuss these issues
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