Effect of wheel track on the density and composition of weeds in a maize crop

El objetivo de este estudio fue analizar si la compactación producida por la rodada del tractor durante las operaciones de siembra influye en la composición y densidad de malas hierbas en cultivo de maíz. Para ello se llevó a cabo el conteo e identificación de las especies presentes en 160 unidades muestrales localizadas en la interlínea de cultivo, de las cuales la mitad estaba afectada por la rodada del tractor y la otra mitad no. El contraste de medias entre los datos con rodada y sin rodada para la riqueza de especies, densidad total y densidad por especies se realizó mediante el test de Mann-Whitney. Los resultados han puesto de manifiesto que las especies principales, a excepción de “Cyperus rotundus”, fueron significativamente más abundantes en las interlíneas con rodada. En relación a la comunidad arvense, ésta fue igualmente más diversa y abundante en las interlíneas con rodada.The aim of this study was to analyze whether the compaction caused by the tractor during sowing operations affects the composition and density of the weed flora in maize crops. For that, 160 sample units were taken in the crop interline, where half of them were affected by the tractor tread and the other half not. In each sampling unit we carried out the count and identification of weed species. The Mann-Whitney test was performed to contrast differences in species richness, total and individual species densities between tractor-tread and not tractor-tread data. The results revealed that the main species, except for “Cyperus rotundus” were significantly more abundant in the interline with tractor tread. In relation to the weed community, it was also more diverse and abundant in the interline with tractor tread

Compaction caused by soil tillage and seedbed preparation: effects on weed emergence in a barley crop

El objetivo principal de este trabajo fue evaluar los efectos de la compactación producida por la frecuencia de pases y el tipo de apero utilizado en la siembra del cereal, sobre la emergencia de las malas hierbas. Se utilizó un diseño en parcelas subdivididas con 4 repeticiones, con la labor primaria (fresa vs. cultivador) en parcelas principales y el pase de rulo (liso vs. pratenses) en subparcelas. Se tomaron datos de malas hierbas (densidad, biomasa) y de propiedades físicas del suelo (compactación, densidad aparente). Los resultados no han mostrado diferencias debidas a la labor primaria en ninguna de las variables analizadas, pero sí en función del tipo y frecuencia de pases de rulo, observándose menor densidad y biomasa de malas hierbas cuanto mayor era el número de pases de rulo, especialmente el liso, coincidiendo con los suelos más compactados. Sin embargo, parece existir un límite en el cual dejan de producirse efectos significativos debido a una sobrecompactación (e.g. doble pase de rulo y zona de rodada).The main objective of this work was to evaluate the effects of the compaction produced by the frequency of passes and the type of implement used in seedbed preparation, on weed emergence. A split-plot design with 4 replications was used, with the primary tillage (cultivator vs. rotary tiller) in main plots and rolling (flat roller vs. Cambridge roller) in subplots. Weeds data (density, biomass) and soil physical properties (compaction, bulk density) were assessed. The results showed no differences due to the primary tillage in any of the analyzed variables. However, the type and frequency of roller passes resulted in significant differences in weed abundance, with lower weed density and biomass when the number of roller passes was greater (especially flat roller), which coincided with the higher compaction. However, it seems to be a limit at which significant effects no longer occur due to an overcompaction (e.g. double roller pass and tractor wheel traffic)

Accompanying weeds of a poplar energy crop under different management strategies

Se han evaluado los efectos de distintas estrategias de manejo sobre las poblaciones de malas hierbas y la productividad (i.e. biomasa) de un cultivo energético de chopo en la zona centro de España. Para ello, se han realizado dos estudios: 1) análisis durante el primer año de cultivo, el más sensible a la competencia con arvenses, repetido tres veces; y 2) valoración al cabo de los tres años de duración del turno de corte. Los resultados han puesto de manifiesto una evolución de la flora arvense con el tiempo, encontrando cambios significativos según la estrategia de manejo. Al finalizar el turno de tres años, las estrategias más productivas fueron la cubierta vegetal sembrada con “Lolium multiflorum” y la basada en herbicidas, coincidiendo con una menor competencia de malas hierbas respecto a la estrategia estándar basada en labores.We have evaluated the effects of different management strategies on weed populations and productivity (i.e. biomass) of a poplar energy crop in central Spain. To do this, two studies have been performed: 1) analysis performed during the first year of production, the most sensitive to competition with weeds, repeated three times; and 2) an assessment after the three-year harvest cycle. The results have revealed a weed flora evolution over time, finding significant changes as a function of management strategies. At the end of the three-year harvest cycle, the most productive strategies were cover crop sown with “Lolium multiflorum” and that based on herbicides, coinciding with less competition with weeds compared to the standard strategy based on tillage

Stochastic semiclassical fluctuations in Minkowski spacetime

The semiclassical Einstein-Langevin equations which describe the dynamics of stochastic perturbations of the metric induced by quantum stress-energy fluctuations of matter fields in a given state are considered on the background of the ground state of semiclassical gravity, namely, Minkowski spacetime and a scalar field in its vacuum state. The relevant equations are explicitly derived for massless and massive fields arbitrarily coupled to the curvature. In doing so, some semiclassical results, such as the expectation value of the stress-energy tensor to linear order in the metric perturbations and particle creation effects, are obtained. We then solve the equations and compute the two-point correlation functions for the linearized Einstein tensor and for the metric perturbations. In the conformal field case, explicit results are obtained. These results hint that gravitational fluctuations in stochastic semiclassical gravity have a ``non-perturbative'' behavior in some characteristic correlation lengths.Comment: 28 pages, RevTeX, no figure

Analysis of the physiological parameters of young spanish badminton players.

El objetivo de nuestro estudio es conocer las características fisiológicas de los jugadores juveniles de bádminton de alto nivel y comparar los parámetros fisiológicos obtenidos en el laboratorio y durante un partido. Se estudiaron 19 jugadores en edad juvenil, 12 varones y 7 mujeres. A todos se les realizó una prueba de esfuerzo máxima en el laboratorio y mediciones antropométricas. Durante la competición se les monitorizó la frecuencia cardiaca, se analizó la concentración de lactato y se valoró su percepción subjetiva al esfuerzo (RPE). El consumo máximo de oxigeno (VO2 máx.) medio se situaba en 56,07 +/- 6,5 ml/Kg/min. El pico de lactato en 3,18 +/- 1,78 mML-1 y la frecuencia cardiaca máxima media (FC máx.) era de 196,75 +/- 5,29 p. p. m., sin diferencias significativas en ninguno de los parámetros estudiados entre varones y hembras en el laboratorio y la competiciónThe aim of our study was to determine the physiological characteristics of young badminton high level players and to compare the physiological parameters obtained in the laboratory and during a match. Nineteen youth players were studied, 12 men and 7 women. A maximal exercise test in the laboratory was performed to the patients and anthropometrics parameters were taken. Their heart rate, lactate concentration and subjective ratings of perceived exertion were tested during competition. The maximum oxygen consumption (VO2 max) has averaged 56.07 + / - 6.5 ml/Kg/min. The peak lactate 3.18 + / - 1.78 MML-1 and the average maximum heart rate (HR max) was 196.75 + / - 5.29 ppm, no significant differences in any of the parameters studied between males and females or between the laboratory and the competitionEl presente trabajo ha sido realizado gracias a una beca de investigación del Centro de Medicina Deportiva de la Comunidad de Madrid (Orden 3025/2010

Linear Response, Validity of Semi-Classical Gravity, and the Stability of Flat Space

A quantitative test for the validity of the semi-classical approximation in gravity is given. The criterion proposed is that solutions to the semi-classical Einstein equations should be stable to linearized perturbations, in the sense that no gauge invariant perturbation should become unbounded in time. A self-consistent linear response analysis of these perturbations, based upon an invariant effective action principle, necessarily involves metric fluctuations about the mean semi-classical geometry, and brings in the two-point correlation function of the quantum energy-momentum tensor in a natural way. This linear response equation contains no state dependent divergences and requires no new renormalization counterterms beyond those required in the leading order semi-classical approximation. The general linear response criterion is applied to the specific example of a scalar field with arbitrary mass and curvature coupling in the vacuum state of Minkowski spacetime. The spectral representation of the vacuum polarization function is computed in n dimensional Minkowski spacetime, and used to show that the flat space solution to the semi-classical Einstein equations for n=4 is stable to all perturbations on distance scales much larger than the Planck length.Comment: 22 pages: This is a significantly expanded version of gr-qc/0204083, with two additional sections and two new appendices giving a complete, explicit example of the semi-classical stability criterion proposed in the previous pape

Reverse Trojan-horse effect decreased wastewater toxicity in the presence of inorganic nanoparticles

We studied the toxicological interaction of 46 micropollutants from a biologically treated wastewater effluent in mixtures with silica, amine-modified silica, titanium dioxide and magnetite nanoparticles. The pollutants tracked in this work were polar pharmaceuticals belonging to different therapeutic groups, some of their metabolites and artificial sweeteners, the concentrations of which were mostly in the tens to hundreds of ng L-1 range. The results showed particularly high adsorption for furosemide, gemfibrozil and the aminopyrine metabolite 4FAA. There was preferential adsorption of the less polar compounds on the less polar nanoparticles. The total amounts of compounds adsorbed and quantified were 13.4, 4.8, 10.8 and 7.1 μg g-1 for SiO2, SiO2-NH2, TiO2 and Fe3O4, respectively. The toxicity of wastewater-nanoparticle mixtures was assessed using the bioluminescent cyanobacterium Anabaena sp. PCC 7120 CPB4337. The interactions were quantified by means of the combination index (CI)-isobologram method. The binary mixtures of wastewater with SiO2, SiO2-NH2 and TiO2 displayed antagonism for the lower affected fractions, which corresponded to the lower concentrations. For higher effects and for the Fe3O4 nanoparticles over the whole tested range, the mixtures were additive leading to synergism for the higher affected fractions. No internalization was observed. The results showed that the reduced toxicant bioavailability due to the interaction with nanoparticles is relevant for micropollutants at environmental concentrations. The amount of anthropogenic pollutants retained by metal oxide nanoparticles has significant toxicological effectsFinancial support was provided by FP7-ERA-Net Susfood, 2014/00153/001, the Spanish Ministry of Economy, CTM2013-45775-C2-1-R and CTM2013-45775-C2-2-R and the Dirección General de Universidades e Investigación de la Comunidad de Madrid, Network S2013/MAE-271

Stochastically Fluctuating Black-Hole Geometry, Hawking Radiation and the Trans-Planckian Problem

We study the propagation of null rays and massless fields in a black hole fluctuating geometry. The metric fluctuations are induced by a small oscillating incoming flux of energy. The flux also induces black hole mass oscillations around its average value. We assume that the metric fluctuations are described by a statistical ensemble. The stochastic variables are the phases and the amplitudes of Fourier modes of the fluctuations. By averaging over these variables, we obtain an effective propagation for massless fields which is characterized by a critical length defined by the amplitude of the metric fluctuations: Smooth wave packets with respect to this length are not significantly affected when they are propagated forward in time. Concomitantly, we find that the asymptotic properties of Hawking radiation are not severely modified. However, backward propagated wave packets are dissipated by the metric fluctuations once their blue shifted frequency reaches the inverse critical length. All these properties bear many resemblences with those obtained in models for black hole radiation based on a modified dispersion relation. This strongly suggests that the physical origin of these models, which were introduced to confront the trans-Planckian problem, comes from the fluctuations of the black hole geometry.Comment: 32 page

Rapid test for identification of a highly transmissible Mycobacterium tuberculosis beijing strain of sub-Saharan origin

The development of a rapid test to identify Mycobacterium tuberculosis Beijing isolates and specifically strain GC1237, coming from a sub-Saharan country, is needed due to its alarming wide spread on Gran Canaria Island (Spain). A rapid test that detects IS6110 present between dnaA and dnaN in the Beijing strains and in a specific site for GC1237 (Rv2180c) has been developed. This test would be a useful tool in the surveillance of subsequent cases

Geochemical influence of soil on leaf and grape (Vitis vinifera L. 'Cencibel') composition in La Mancha region (Spain)

The main purpose of the study was to evaluate major and trace elements contained in topsoil from representative plots of vineyards located in La Mancha, Spain, to obtain an elemental fingerprint of vines. The samples evaluated were obtained from topsoil in six different plots, belonging to the region of La Mancha, characterized by the cultivation of vineyards (near 189.127 ha). Twenty different vines from each plot were chosen to take samples from grapes, petioles and leaves. Analyses were carried out by X-ray Fluorescence applied on soils and dried vegetal matter. Biological Absorption Coefficient (BAC) was calculated to assess the uptake of minerals by vines as a function of their specific content in soil. The BAC in leaves and grapes was very similar for all studied elements. High contents of Ca, Sr, Ni and rare earth elements (La, Ce and Nd) were found along with low contents in Al, Zr, Ba, Cu, Zn and Pb, and normal contents in the rest of the elements. BAC in grapes was lower for the majority of the studied elements but it is interesting to underline the contents of Cs, K, Nb, Ce, Zn and Sr as possible markers of soil fingerprinting in the resulting wines.