350 research outputs found
Legumes for Organic Cropping Systems
A field experiment which focuses on the yield performance of both durum wheat and sunflower included in a twoyear rotation between wheat/subterranean clover and sunflower was carried out in an organic farm in Central Italy. Three factors were included in the experiment according to a factorial design: a) two different previous crop sequences (four years of alfalfa, four years of annual crops); b) three fertilization levels (without and with animal manure incorporated at 15 or 40 cm depth); c) three durum wheat genotypes (Appulo, Arcangelo and Daunia cvs). The results obtained show that a previous alfalfa meadow allows the succeeding crops (wheat and sunflower) to achieve an appropriate and stable grain yield (about 4 and 3 t ha-1, respectively) even without organic manure for two consecutive cycles. When the durum wheat follows an annual crop sequence, grain yield appears unstable and the different levels of organic fertilizer determine a negative effect in the first cycle and a positive effect in the second cycle. The reseeding capability of sunflower was reduced by animal manure treatments and, consequently, the subclover biomass and its nitrogen content were generally lower in fertilized plots. Anyway, subclover biomass, which was ploughed in after reseeding as a green manure for sunflower, proved to be effective in stabilizing sunflower grain yield, especially in plots without any organic fertilization
Alternative Cropping Systems with Self Reseeding Annual Legumes in a Mediterranean Environment
Self-reseeding winter annual legumes (subclover and snail medic) have the potential to induce a significant shift towards a less energy-intensive and more environmentally friendly management in the modern and specialized cereal cropping systems. Nevertheless their use is practically unknown in mixed stands with winter cereals, where they can contribute to supply nitrogen and to reduce herbicides input. We conceived an alternative cropping system where an annual legume performs, respectively, as living mulch in a winter cereal (winter wheat), as a cover crop after reseeding and as dry mulch for the succeeding summer cereal (corn). Trials carried out at the Tuscia University (Central Italy) in the period 1995-1997 showed that almost all the tested legumes cultivars were able both to grow sufficiently as a living mulch in the wheat and to provide a good re-establishment and an abundant mulch after the wheat harvest for the next corn. Trifolium yanninicum cv Trikkala and Trifolium subterraneum cvs Karridale and Mount Barker ranked first in reseeding capacity (up to 400 seedlings m-2) and mulch production (up to 5 t ha-1). No difference in grain yield between wheat with a living mulch and wheat in pure stand was found when legumes, such as Trifolium yanninicum cvs Trikkala and Larisa, Trifolium brachycalycinum cv Clare, Trifolium subterraneum cv Nungarin and Medicago scutellata cv Kelson, were grown in binary mixture with wheat. The aboveground biomass production of the succeeding irrigated corn crop was largely dependent on the amount of legume dry mulch left upon the ground
Color Fields on the Light-Shell
We study the classical color radiation from very high energy collisions that
produce colored particles. In the extreme high energy limit, the classical
color fields are confined to a light-shell expanding at and are associated
with a non-linear -model on the 2D light-shell with specific symmetry
breaking terms. We argue that the quantum version of this picture exhibits
asymptotic freedom and may be a useful starting point for an effective
light-shell theory of the structure between the jets at a very high energy
collider.Comment: 11 pages, no figure
Dynamical Surface Gravity in Spherically Symmetric Black Hole Formation
We study dynamical surface gravity in a general spherically symmetric setting
using Painlev\'{e}-Gullstrand (PG) coordinates. Our analysis includes several
definitions that have been proposed in the past as well as two new definitions
adapted to PG coordinates. Various properties are considered, including general
covariance, value at extremality, locality and static limit. We illustrate with
specific examples of "dirty" black holes that even for spacetimes possessing a
global timelike Killing vector, local definitions of surface gravity can differ
substantially from "non-local" ones that require an asymptotic normalization
condition. Finally, we present numerical calculations of dynamical surface
gravity for black hole formation via spherically symmetric scalar field
collapse. Our results highlight the differences between the various definitions
in a dynamical setting and provide further insight into the distinction between
local and non-local definitions of surface gravity.Comment: Final version to appear in Phys. Rev. D. Slight name change, further
improvements to numerics and presentation, 25 pages, 7 figure
Habitat Patch Diversity Evaluation for Sustainability: a Case Study of a Rural Area in Central Italy
Landscape analysis is regarded as a new tool for monitoring and judging land use patterns in terms of sustainability of human activity systems at local level. A case study of evaluation for sustainability based on habitat patch diversity in an ecoregion of Central Italy is presented. In this region, ongoing land use patterns reflect both historical adaptation to local environmental constraints and positive, social-oriented management. More protective land use patterns are mostly widespread in fragile physiographic conditions like those of the mountain areas, where woodland, shrub, and grassland patches are larger and cover more than 90% of the land. This situation is regarded as a positive outcome of the traditional public ownership regime, because public lands amount to more than 70% in the mountain areas. The hilly areas, where public property drops to 28%, presents landscape metrics showing a well balanced situation between agricultural land use and protective native woods and grasslands, which provides a fine-grained and harmonious Mediterranean landscape. In the low-land areas, with anthropic pressure and more favourable conditions for crop productivity, there is much more agricultural land, even if some mitigation in terms of biodiversity maintenance is offered by the presence of hedgerow ecotones. In these areas, landscape analysis is not able to supply meaningful information about cropping system design and practices which can maintain a sustainable level of soil fertility and quality of natural resources and processes, and further analysis at cropping system level should be carried out
Polymer quantization, singularity resolution and the 1/r^2 potential
We present a polymer quantization of the -lambda/r^2 potential on the
positive real line and compute numerically the bound state eigenenergies in
terms of the dimensionless coupling constant lambda. The singularity at the
origin is handled in two ways: first, by regularizing the potential and
adopting either symmetric or antisymmetric boundary conditions; second, by
keeping the potential unregularized but allowing the singularity to be balanced
by an antisymmetric boundary condition. The results are compared to the
semiclassical limit of the polymer theory and to the conventional Schrodinger
quantization on L_2(R_+). The various quantization schemes are in excellent
agreement for the highly excited states but differ for the low-lying states,
and the polymer spectrum is bounded below even when the Schrodinger spectrum is
not. We find as expected that for the antisymmetric boundary condition the
regularization of the potential is redundant: the polymer quantum theory is
well defined even with the unregularized potential and the regularization of
the potential does not significantly affect the spectrum.Comment: 21 pages, LaTeX including 7 figures. v2: analytic bounds improved;
references adde
Null to time-like infinity Green’s functions for asymptotic symmetries in Minkowski spacetime
Annexin A1 Released in Extracellular Vesicles by Pancreatic Cancer Cells Activates Components of the Tumor Microenvironment, through Interaction with the Formyl-Peptide Receptors
Pancreatic cancer (PC) is one of the most aggressive cancers in the world. Several extracellular
factors are involved in its development and metastasis to distant organs. In PC, the protein Annexin
A1 (ANXA1) appears to be overexpressed and may be identified as an oncogenic factor, also because it
is a component in tumor-deriving extracellular vesicles (EVs). Indeed, these microvesicles are known
to nourish the tumor microenvironment. Once we evaluated the autocrine role of ANXA1-containing
EVs on PC MIA PaCa-2 cells and their pro-angiogenic action, we investigated the ANXA1 paracrine
effect on stromal cells like fibroblasts and endothelial ones. Concerning the analysis of fibroblasts,
cell migration/invasion, cytoskeleton remodeling, and the different expression of specific protein markers,
all features of the cell switching into myofibroblasts, were assessed after administration of wild type more
than ANXA1 Knock-Out EVs. Interestingly, we demonstrated a mechanism by which the ANXA1-EVs
complex can stimulate the activation of formyl peptide receptors (FPRs), triggering mesenchymal
switches and cell motility on both fibroblasts and endothelial cells. Therefore, we highlighted the
importance of ANXA1/EVs-FPR axes in PC progression as a vehicle of intercommunication tumor
cells-stroma, suggesting a specific potential prognostic/diagnostic role of ANXA1, whether in soluble
form or even if EVs are captured in PC
Bioavailable Citrus sinensis extract: Polyphenolic composition and biological activity
Citrus plants contain large amounts of flavonoids with beneficial effects on human health. In the present study, the antioxidant and anti-inflammatory potential of bioavailable polyphenols from Citrus sinensis was evaluated in vitro and ex vivo, using the murine macrophages cell line J774A.1 and primary peritoneal macrophages. Following simulated gastro-intestinal digestion, the in vitro bioavailability of Citrus sinensis polyphenolic extract was assessed using the human cell line Caco-2 grown as monolayers on a transwell membrane. Data demonstrated a relative permeation of its compounds (8.3%). Thus, the antioxidant and anti-inflammatory effect of polyphenolic Citrus sinensis fraction (Cs) was compared to the bioavailable one (CsB). Results revealed that Citrus extract were able to reduce macrophages pro-inflammatory mediators, including nitric oxide, iNOS, COX-2 and different cytokines. Moreover, the effect of Citrus sinensis polyphenols was associated with antioxidant effects, such as a reduction of reactive oxygen species (ROS) and heme-oxygenase-1 (HO-1) increased expression. Our results provide evidence that the bioavailable polyphenolic constituents of the Citrus sinensis extract accumulate prevalently at intestinal level and could reach systemic circulation exerting their effect. The bioavailable fraction showed a higher anti-inflammatory and antioxidant potential compared to the initial extract, thus highlighting its potential nutraceutical value
Many-nodes/many-links spinfoam: the homogeneous and isotropic case
I compute the Lorentzian EPRL/FK/KKL spinfoam vertex amplitude for regular
graphs, with an arbitrary number of links and nodes, and coherent states peaked
on a homogeneous and isotropic geometry. This form of the amplitude can be
applied for example to a dipole with an arbitrary number of links or to the
4-simplex given by the compete graph on 5 nodes. All the resulting amplitudes
have the same support, independently of the graph used, in the large j (large
volume) limit. This implies that they all yield the Friedmann equation: I show
this in the presence of the cosmological constant. This result indicates that
in the semiclassical limit quantum corrections in spinfoam cosmology do not
come from just refining the graph, but rather from relaxing the large j limit.Comment: 8 pages, 4 figure
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