780 research outputs found
Sunflower under conventional and organic farming systems: results from a long term experiment in Central Italy
Sunflower productivity under organic and conventional agricultural systems was studied between 2002 and 2004 in the frame of the MASCOT experiment (Mediterranean Arable Systems COmparison Trial), established in 2001. The aim was to compare organic and conventional management systems for a typical arable crop rotation of Central Italy in the long-term. Sunflower was cultivated as a part of a five-year stockless arable crop rotation (sugar beet-common wheatsunflower-pigeon bean-durum wheat). In the organic system, red clover (Trifolium pratense) is interseeded in common and durum wheat and used as a green manure for sunflower or sugar beet. Grain yield of organically-grown sunflower was lower by 41%, 17% and 44% in 2002, 2003 and 2004 respectively, but no significant differences in percent seed oil content were found between the conventional and organic sunflower in two years out of three
Localizzazione probabilistica 3D (NonLinLoc) applicata all’area calabro-peloritana
Sono presentati e discussi i risultati
preliminari relativi ad una ri-localizzazione
probabilistica non-lineare 3D dei terremoti
dell’area compresa tra il Tirreno meridionale
e l’Arco Calabro-Peloritano (Italia
meridionale).
Scopo del lavoro è dimostrare che
l’applicazione di un’approccio probabilistico
non-lineare nella localizzazione dei terremoti
può fornire dei risultati più accurati ai fini
della sorveglianza, ovviando al problema
degli outlier, rispetto alle tecniche di
localizzazione lineari (e.g. Hypoellipse), che
minimizzano simultaneamente tutti i residui
tra fasi osservate e calcolate.
Il programma utilizzato è NonLinLoc
[Lomax, et al., 2000; Lomax, et al., 2001;
Lomax, 2005; http://www.alomax.net/nlloc;
NonLinLoc di seguito] il quale permette di
effettuare un’efficiente ricerca globale dello
spazio dei parametri ipocentrali (coordinate
spaziali e tempo origine) ottenendo una
stima della funzione densitĂ di probabilitĂ
(pdf, probability density function) a
posteriori. La pdf fornisce una descrizione
completa della localizzazione e delle sue
incertezze; il campionamento dello spazio
dei parametri ipocentrali è stato fatto
mediante la tecnica Oct-tree nella regione
compresa tra 37.75 e 39.40 N in latitudine e
tra 14.80 e 16.80 E in longitudine, e
utilizzando tutti gli eventi con profonditĂ H
≤30 km.
La struttura dell’Oct-tree è stata imposta in
100,000 celle ed un insieme di queste celle
viene poi salvata in modo da poter
rappresentare graficamente la pdf mediante
nubi di punti a diversa densitĂ .
Il dataset utilizzato per le nostre analisi è
composto da 1,304 terremoti, di 1.0<M<4.3,
registrati nel periodo compreso tra il 1994 e
il 2006; il modello di velocità 3D adottato è
stato ottenuto da Barberi et al., 2008 [poster
presentato a questo convegno] invertendo lo stesso dataset, mediante l’utilizzo del
software TomoDD.
I risultati ottenuti sono stati confrontati sia
con le localizzazioni 1D (Hypoellipse) che
con quelle 3D. Si evidenzia una maggiore
clusterizzazione degli eventi e, soprattutto,
un evidente miglioramento della qualitĂ delle
localizzazioni utilizzando il modello di
velocitĂ crostale 3D. Per cui riteniamo che,
l’applicazione del metodo probabilistico
associato ad un buon modello di velocitĂ 3D,
può essere utilizzato ai fini di sorveglianza
Localizzazione probabilistica 3D (NonLinLoc) applicata all’area calabro-peloritana
Sono presentati e discussi i risultati
preliminari relativi ad una ri-localizzazione
probabilistica non-lineare 3D dei terremoti
dell’area compresa tra il Tirreno meridionale
e l’Arco Calabro-Peloritano (Italia
meridionale).
Scopo del lavoro è dimostrare che
l’applicazione di un’approccio probabilistico
non-lineare nella localizzazione dei terremoti
può fornire dei risultati più accurati ai fini
della sorveglianza, ovviando al problema
degli outlier, rispetto alle tecniche di
localizzazione lineari (e.g. Hypoellipse), che
minimizzano simultaneamente tutti i residui
tra fasi osservate e calcolate.
Il programma utilizzato è NonLinLoc
[Lomax, et al., 2000; Lomax, et al., 2001;
Lomax, 2005; http://www.alomax.net/nlloc;
NonLinLoc di seguito] il quale permette di
effettuare un’efficiente ricerca globale dello
spazio dei parametri ipocentrali (coordinate
spaziali e tempo origine) ottenendo una
stima della funzione densitĂ di probabilitĂ
(pdf, probability density function) a
posteriori. La pdf fornisce una descrizione
completa della localizzazione e delle sue
incertezze; il campionamento dello spazio
dei parametri ipocentrali è stato fatto
mediante la tecnica Oct-tree nella regione
compresa tra 37.75 e 39.40 N in latitudine e
tra 14.80 e 16.80 E in longitudine, e
utilizzando tutti gli eventi con profonditĂ H
≤30 km.
La struttura dell’Oct-tree è stata imposta in
100,000 celle ed un insieme di queste celle
viene poi salvata in modo da poter
rappresentare graficamente la pdf mediante
nubi di punti a diversa densitĂ .
Il dataset utilizzato per le nostre analisi è
composto da 1,304 terremoti, di 1.0<M<4.3,
registrati nel periodo compreso tra il 1994 e
il 2006; il modello di velocità 3D adottato è
stato ottenuto da Barberi et al., 2008 [poster
presentato a questo convegno] invertendo lo stesso dataset, mediante l’utilizzo del
software TomoDD.
I risultati ottenuti sono stati confrontati sia
con le localizzazioni 1D (Hypoellipse) che
con quelle 3D. Si evidenzia una maggiore
clusterizzazione degli eventi e, soprattutto,
un evidente miglioramento della qualitĂ delle
localizzazioni utilizzando il modello di
velocitĂ crostale 3D. Per cui riteniamo che,
l’applicazione del metodo probabilistico
associato ad un buon modello di velocitĂ 3D,
può essere utilizzato ai fini di sorveglianza
Double-difference tomography at Mt. Etna volcano
Double-difference tomography at Mt Etna volcano was realized by using the tomographic
algorithm developped by Monteiller et al. (2005), in which the travel-time computation was performed using a finite-difference solution of the Eikonal equation
(Podvin and Lecomte, 1991) and a posteriori ray-tracing. The inverse problem was
solved using a probabilistic approach (Tarantola and Valette, 1982). The optimal a
priori information (correlation length and a priori model variance) was found experimentally
by performing tomographies for correlation lengths and variances varying in
large intervals. This probabilistic approach allowed us to use a sech pdf for representing
errors in differential times. Data were travel-times and time delays provided by a
set of 329 earthquakes, well-recorded by the INGV-CT seismic network (50 stations)
on the Mt Etna volcano during the seismo-volcanic crisis occurring between October
2002 and January 2003. Checkerboard tests realized with this geometry and earthquake
pairs showed that the model can be correctly reconstructed in a significant area
around Mt Etna volcano. Results of the P and S-wave double-difference tomography
clearly evidenced two concentric features: a fast central cylindrical core, probably of
intrusive origin, surrounded by a slow annealed body, which could be related to partial melting
Double-difference tomography at Mt Etna volcano: Preliminary results
We performed a preliminary double-difference tomographic study using
earthquake data recorded by the INGV-Catania seismic network during the
large seismic and eruptive crisis of 2002-2003 at Mt Etna volcano. Compared
to previous models, first results presented from the inversion of travel-time
differences, tend to show an increase in the velocity contrast between the fast
core and the slow periphery of the volcano
Receiver Function Analysis at Stromboli Volcano (Italy)
This study focuses on constraining the crust and upper mantle discontinuities at Stromboli
volcano by applying the receiver function (RF) analysis. This technique utilizes
the waveforms of P-SV conversions generated by discontinuities to infer the structure
beneath the seismic stations. RFs have been obtained by deconvolving the vertical
component of teleseismic P-wave records from the corresponding rotate horizontal
components applying the Multi-Taper Spectral Correlation technique. For this study
the seismograms of about 125 teleseismic earthquakes (M greater than 6.0), recorded
between 2004 and 2006 at 13 broad-band seismic stations deployed by the INGV, have
been considered. A preliminar characterization of the structure beneath the stations has
been inferred from the stacking of teleseismic Ps converted waves and multiply converted
waves at the seismic interface. The analysis, at frequency of 1 and 2 Hz, show
a horizontal seismic discontinuity at an average depth of about 17 km and a Vp/Vs
ratio lower than 1.73. This discontinuity explains the positive pulses about 1.9 s and
7.5 s after the direct P arrival. These pulses can be interpreted as Ps and PpPs converted
phases, respectively. The depth of this discontinuity is in agreement with the
Moho-depth obtained in independent studies
Ordered interfaces for dual easy axes in liquid crystals
International audienceUsing nCB films adsorbed on MoS 2 substrates studied by x-ray diffraction, optical microscopy and Scanning Tunneling Microscopy, we demonstrate that ordered interfaces with well-defined orientations of adsorbed dipoles induce planar anchoring locked along the adsorbed dipoles or the alkyl chains, which play the role of easy axes. For two alternating orientations of the adsorbed dipoles or dipoles and alkyl chains, bi-stability of anchoring can be obtained. The results are explained using the introduction of fourth order terms in the phenomenological anchoring potential, leading to the demonstration of first order anchoring transition in these systems. Using this phenomenological anchoring potential, we finally show how the nature of anchoring in presence of dual easy axes (inducing bi-stability or average orientation between the two easy axes) can be related to the microscopical nature of the interface. Introduction Understanding the interactions between liquid crystal (LC) and a solid substrate is of clear applied interest, the vast majority of LC displays relying on control of interfaces. However this concerns also fundamental problems like wetting phenomena and all phenomena of orientation of soft matter bulk induced by the presence of an interface. In LCs at interfaces, the so-called easy axes correspond to the favoured orientations of the LC director close to the interface. If one easy axis only is defined for one given interface, the bulk director orients along or close to this axis [1]. It is well known that, in anchoring phenomena, two major effects compete to impose the anchoring directions of a liquid crystal, first, the interactions between molecules and the interface, second, the substrate roughness whose role has been analyzed by Berreman [2]. The influence of adsorbed molecular functional groups at the interface is most often dominant with, for example in carbon substrates, a main influence of unsaturated carbon bonds orientation at the interface [3]. In common LC displays, there is one unique easy axis, but modifications of surfaces have allowed for the discovery of promising new anchoring-related properties. For instance, the first anchoring bi-stability has been established on rough surfaces, associated with electric ordo-polarization [4] and the competition between a stabilizing short-range term and a destabilizing long-range term induced by an external field, can induce a continuous variation of anchoring orientation [5]. More recently, surfaces with several easy axes have been studied extensively. It has been shown that control of a continuous variation of director pretilt, obtained in several systems [6, 7], is associated with the presence of two different easy axes, one perpendicular to the substrate (homeotropic) and one planar [7, 8]. Similar models can explain the continuous evolution of anchoring between two planar orientations observed on some crystalline substrates [9]. However, in the same time, two easy axes can also lead to anchoring bi-stability [10, 11] or discontinuous transitions of anchoring [9], which is not compatible with the model established to interpret observed control of pretilt. In order to be able to predict if bi-stability or continuous combination of the two easy axes occurs for one given system, it becomes necessary to understand the microscopic origin of the easy axes
Organic farming systems for adaptation to and mitigation of climate change: Effects on soil fertility and resource use efficiency
Organic farming is pointed as one of the most sustainable farming practices in terms of environmental sustainability and climate change mitigation potential. At the core of organic farming practices there are practices aimed at improving soil fertility, increasing soil C content and enhancing system biodiversity. A long-term field experiment (LTE) (MASCOT) was started on 2001 in San Piero a Grado, Pisa (Italy) with the aim to compare two different cropping systems, one managed organically and one conventionally, in terms of agronomical, economic and environmental sustainability. In 2016, the MASCOT was redesigned as a full system trial and the organic system was reshaped according to up to date agroecological standards. Climate change adaptation capacity of the two systems is being assessed through agronomic and economic parameters, whilst greenhouse gas emission mitigation potential is mainly expressed in terms of soil C sequestration
- …