111 research outputs found
Impact of soybean cropping frequency on soil carbon storage in Mollisols and Vertisols
The high cropping frequency of soybean (Glycine max [L.] Merr.), mainly as a single annual crop, in the extensive agricultural systems of South America may adversely affect the soil organic carbon (SOC) storage, which may be different between soils depending on aggregation agents. The aim of this work was to evaluate the impact of the soybean cropping frequency on the SOC storage in different soil aggregate size classes in a Mollisol and in a Vertisol in the Northeastern Pampas of Argentina under no-tillage management. In each soil, the samples were collected at 0-5, 5-15 and 15-30 cm depths in eleven cropped and one uncropped fields. The number of months occupied with soybean in relation to the total number of months occupied with crops within crop sequences, over a 6-year period, was used to calculate the soybean cropping frequency. The SOC stocks in equivalent soil mass, the SOC concentration both in the whole sample and in different aggregate size classes, and the stratification ratio of the SOC stock and of the SOC concentration were determined. The increase in soybean cropping frequency reduced the SOC stock in both soils at 0-5 cm, and in the Vertisol at 5-15 and 0-30 cm but the change was evident only between the cropped and the uncropped situation. A decrease in soybean cropping frequency resulted in a higher amount of macroaggregates (> 250 um), a higher SOC concentration and a higher stratification ratio in the Mollisol at 0-5 cm, whereas in the Vertisol the soybean cropping frequency did not affect the stratification ratio or the aggregate distribution in any size class. The increase in soybean cropping frequency reduced SOC storage only in macroaggregates (> 250 µm) in both soils at 0-5 cm, particularly in the largest macroaggregates (> 2000 µm), and more in the Mollisol than in the Vertisol. Our results show that a high soybean cropping frequency may severely affect the SOC storage in the Mollisol, and suggest that in the Vertisol this effect may lead to a reduction in the SOC storage in the long term.Fil: Novelli, Leonardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Caviglia, Octavio Pedro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos; ArgentinaFil: Melchiori, R. J. M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentin
How digital is agriculture in a subset of countries from South America? Adoption and limitations
Digital agriculture (DA) can contribute solutions to meet an increase in healthy, nutritious, and affordable food demands in an efficient and sustainable way. South America (SA) is one of the main grain and protein producers in the world but the status of DA in the region is unknown. A systematic review and case studies from Brazil, Argentina, Uruguay, and Chile were conducted to address the following objectives: (1) quantify adoption of existing DA technologies, (2) identify limitations for DA adoption; and (3) summarise existing metrics to benchmark DA benefits. Level of DA adoption was led by Brazil and Argentina followed by Uruguay and at a slower rate, Chile. GPS guidance systems, mapping tools, mobile apps and remote sensing were the most adopted DA technologies in SA. The most reported limitations to adoption were technology cost, lack of training, limited number of companies providing services, and unclear benefits from DA. Across the case studies, there was no clear definition of DA. To mitigate some of these limitations, our findings suggest the need for a DA educational curriculum that can fulfill the demand for job skills such as data processing, analysis and interpretation. Regional efforts are needed to standardise these metrics. This will allow stakeholders to design targeted initiatives to promote DA towards sustainability of food production in the region
Could Only Fermions Be Elementary?
In standard Poincare and anti de Sitter SO(2,3) invariant theories,
antiparticles are related to negative energy solutions of covariant equations
while independent positive energy unitary irreducible representations (UIRs) of
the symmetry group are used for describing both a particle and its
antiparticle. Such an approach cannot be applied in de Sitter SO(1,4) invariant
theory. We argue that it would be more natural to require that (*) one UIR
should describe a particle and its antiparticle simultaneously. This would
automatically explain the existence of antiparticles and show that a particle
and its antiparticle are different states of the same object. If (*) is adopted
then among the above groups only the SO(1,4) one can be a candidate for
constructing elementary particle theory. It is shown that UIRs of the SO(1,4)
group can be interpreted in the framework of (*) and cannot be interpreted in
the standard way. By quantizing such UIRs and requiring that the energy should
be positive in the Poincare approximation, we conclude that i) elementary
particles can be only fermions. It is also shown that ii) C invariance is not
exact even in the free massive theory and iii) elementary particles cannot be
neutral. This gives a natural explanation of the fact that all observed neutral
states are bosons.Comment: The paper is considerably revised and the following results are
added: in the SO(1,4) invariant theory i) the C invariance is not exact even
for free massive particles; ii) neutral particles cannot be elementar
Interacting entropy-corrected holographic dark energy with apparent horizon as an infrared cutoff
In this work we consider the entropy-corrected version of interacting
holographic dark energy (HDE), in the non-flat universe enclosed by apparent
horizon. Two corrections of entropy so-called logarithmic 'LEC' and power-law
'PLEC' in HDE model with apparent horizon as an IR-cutoff are studied. The
ratio of dark matter to dark energy densities , equation of state parameter
and deceleration parameter are obtained. We show that the cosmic
coincidence is satisfied for both interacting models. By studying the effect of
interaction in EoS parameter, we see that the phantom divide may be crossed and
also find that the interacting models can drive an acceleration expansion at
the present and future, while in non-interacting case, this expansion can
happen only at the early time. The graphs of deceleration parameter for
interacting models, show that the present acceleration expansion is preceded by
a sufficiently long period deceleration at past. Moreover, the thermodynamical
interpretation of interaction between LECHDE and dark matter is described. We
obtain a relation between the interaction term of dark components and thermal
fluctuation in a non-flat universe, bounded by the apparent horizon. In
limiting case, for ordinary HDE, the relation of interaction term versus
thermal fluctuation is also calculated.Comment: 20 pages, 8 figures, figures changed, some Ref. is added, changed
some sentences, accepted by General relativity and gravitation (GERG
Chemotaxis of 3T3 and SV3T3 cells to fibronectin is mediated through the cell-attachment site in fibronectin and a fibronectin cell surface receptor.
Unifying phantom inflation with late-time acceleration: scalar phantom-non-phantom transition model and generalized holographic dark energy
The unifying approach to early-time and late-time universe based on phantom
cosmology is proposed. We consider gravity-scalar system which contains usual
potential and scalar coupling function in front of kinetic term. As a result,
the possibility of phantom-non-phantom transition appears in such a way that
universe could have effectively phantom equation of state at early time as well
as at late time. In fact, the oscillating universe may have several phantom and
non-phantom phases. As a second model we suggest generalized holographic dark
energy where infrared cutoff is identified with combination of FRW parameters:
Hubble constant, particle and future horizons, cosmological constant and
universe life-time (if finite). Depending on the specific choice of the model
the number of interesting effects occur: the possibility to solve the
coincidence problem, crossing of phantom divide and unification of early-time
inflationary and late-time accelerating phantom universe. The bound for
holographic entropy which decreases in phantom era is also discussed.Comment: 13 pages, clarifications/refs added, to match with published versio
How digital is agriculture in a subset of countries from South America? Adoption and limitations.
Abstract. Digital agriculture (DA) can contribute solutions to meet an increase in healthy, nutritious, and affordable food demands in an efficient and sustainable way. South America (SA) is one of the main grain and protein producers in the world but the status of DA in the region is unknown. A systematic review and case studies from Brazil, Argentina, Uruguay, and Chile were conducted to address the following objectives: (1) quantify adoption of existing DA technologies, (2) identify limitations for DA adoption; and (3) summarise existing metrics to benchmark DA benefits. Level of DA adoption was led by Brazil and Argentina followed by Uruguay and at a slower rate, Chile. GPS guidance systems, mapping tools, mobile apps and remote sensing were the most adopted DA technologies in SA. The most reported limitations to adoption were technology cost, lack of training, limited number of companies providing services, and unclear benefits from DA. Across the case studies, there was no clear definition of DA. To mitigate some of these limitations, our findings suggest the need for a DA educational curriculum that can fulfill the demand for job skills such as data processing, analysis and interpretation. Regional efforts are needed to standardise these metrics. This will allow stakeholders to design targeted initiatives to promote DA towards sustainability of food production in the region.Special issue
A novel circular invasion assay mimics in vivo invasive behavior of cancer cell lines and distinguishes single-cell motility in vitro
Evidence-based Kernels: Fundamental Units of Behavioral Influence
This paper describes evidence-based kernels, fundamental units of behavioral influence that appear to underlie effective prevention and treatment for children, adults, and families. A kernel is a behavior–influence procedure shown through experimental analysis to affect a specific behavior and that is indivisible in the sense that removing any of its components would render it inert. Existing evidence shows that a variety of kernels can influence behavior in context, and some evidence suggests that frequent use or sufficient use of some kernels may produce longer lasting behavioral shifts. The analysis of kernels could contribute to an empirically based theory of behavioral influence, augment existing prevention or treatment efforts, facilitate the dissemination of effective prevention and treatment practices, clarify the active ingredients in existing interventions, and contribute to efficiently developing interventions that are more effective. Kernels involve one or more of the following mechanisms of behavior influence: reinforcement, altering antecedents, changing verbal relational responding, or changing physiological states directly. The paper describes 52 of these kernels, and details practical, theoretical, and research implications, including calling for a national database of kernels that influence human behavior
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