1,423 research outputs found
The effective Lagrangian of dark energy from observations
Using observational data on the expansion rate of the universe (H(z)) we
constrain the effective Lagrangian of the current accelerated expansion. Our
results show that the effective potential is consistent with being flat i.e., a
cosmological constant; it is also consistent with the field moving along an
almost flat potential like a pseudo-Goldstone boson. We show that the potential
of dark energy does not deviate from a constant at more than 6% over the
redshift range 0 < z < 1. The data can be described by just a constant term in
the Lagrangian and do not require any extra parameters; therefore there is no
evidence for augmenting the number of parameters of the LCDM paradigm. We also
find that the data justify the effective theory approach to describe
accelerated expansion and that the allowed parameters range satisfy the
expected hierarchy. Future data, both from cosmic chronometers and baryonic
acoustic oscillations, that can measure H(z) at the % level, could greatly
improve constraints on the flatness of the potential or shed some light on
possible mechanisms driving the accelerated expansion. Besides the above
result, it is shown that the effective Lagrangian of accelerated expansion can
be constrained from cosmological observations in a model-independent way and
that direct measurements of the expansion rate H(z) are most useful to do so.Comment: 9 pages, 3 figures, JCAP submitted. This paper presents a
reconstruction of the dark energy potential. It is a companion to Moresco et
al. 2012a, which presents new H(z) results and Moresco et al. 2012b, which
provides cosmological parameter constraint
Improved drought tolerance in wheat is required to unlock the production potential of the Brazilian Cerrado.
ABSTRACT Improving rainfed wheat cultivation in central Brazil, where the Cerrado biome (Brazilian savanna) is predominant, remains a bottleneck for future increases in domestic wheat production. In the Cerrado, the limited water availability during the wheat-growing season is an obstacle to increase wheat yield. To address this issue, the physiological and molecular drought response of wheat and the environmental conditions of this region must be better understood. In this review, we characterized the impact of drought on rainfed wheat production in the Cerrado. Based on the peculiarities of this environment, we suggest that certain traits should be prioritized in selection. These traits and their molecular basis are important to raise wheat yields in the Cerrado and also to improve food security in Brazil, one of the top wheat-importing countries in the world
Ccdc11 is a novel centriolar satellite protein essential for ciliogenesis and establishment of left-right asymmetry
The establishment of left–right (L-R) asymmetry in vertebrates is dependent on the sensory and motile functions of cilia during embryogenesis. Mutations in CCDC11 disrupt L-R asymmetry and cause congenital heart disease in humans, yet the molecular and cellular functions of the protein remain unknown. Here we demonstrate that Ccdc11 is a novel component of centriolar satellites—cytoplasmic granules that serve as recruitment sites for proteins destined for the centrosome and cilium. Ccdc11 interacts with core components of satellites, and its loss disrupts the subcellular organization of satellite proteins and perturbs primary cilium assembly. Ccdc11 colocalizes with satellite proteins in human multiciliated tracheal epithelia, and its loss inhibits motile ciliogenesis. Similarly, depletion of CCDC11 in Xenopus embryos causes defective assembly and motility of cilia in multiciliated epidermal cells. To determine the role of CCDC11 during vertebrate development, we generated mutant alleles in zebrafish. Loss of CCDC11 leads to defective ciliogenesis in the pronephros and within the Kupffer’s vesicle and results in aberrant L-R axis determination. Our results highlight a critical role for Ccdc11 in the assembly and function of motile cilia and implicate centriolar satellite–associated proteins as a new class of proteins in the pathology of L-R patterning and congenital heart disease
An effective theory of accelerated expansion
We work out an effective theory of accelerated expansion to describe general
phenomena of inflation and acceleration (dark energy) in the Universe. Our aim
is to determine from theoretical grounds, in a physically-motivated and model
independent way, which and how many (free) parameters are needed to broadly
capture the physics of a theory describing cosmic acceleration. Our goal is to
make as much as possible transparent the physical interpretation of the
parameters describing the expansion. We show that, at leading order, there are
five independent parameters, of which one can be constrained via general
relativity tests. The other four parameters need to be determined by observing
and measuring the cosmic expansion rate only, H(z). Therefore we suggest that
future cosmology surveys focus on obtaining an accurate as possible measurement
of to constrain the nature of accelerated expansion (dark energy and/or
inflation).Comment: In press; minor changes, results unchange
Phenotypical Characters Associated with the Loss of the Seed and the Production of Biomass in \u3ci\u3ePanicum coloratum\u3c/i\u3e var. \u3ci\u3emakarikariense\u3c/i\u3e
Since the beginning of humanity, plants have been manipulated by humans by artificial selection to obtain changes in their characteristics. This progress has been achieved through the domestication of the species. Panicum coloratum is a species of summer perennial grass, megathermic, tolerates waterlogging, cold and slightly saline soils. It is of African origin and used as fodder in various parts of the world. In Argentina around 130.500 hectares are sown, the most widespread varieties are: var. coloratum, and var. makarikariense Goossens. Its characteristics of determined flowering and ununiform ripening within the panicle, added to a very low retention of the seeds after maturation, establish serious difficulties in harvesting quality seeds. Megathermic forage species are good producers in forage quantity and, in turn, possess good quality. The objective of the work was to study the dynamics of seed dehiscence and the forage production of two cultivars of Panicum coloratum var. makarikariense (cv. Kapivera and cv. Bambatsi). The seed fall was evaluated weekly for 70 days between March-May 2017 and 2019 on 15 random inflorescences of each cultivar. Once the seed harvest was completed in May 2017 and 2019, the panicles were cut and the panicle height, panicle length, rachis length, wet weight, dry weight and percentage of dry matter were analyzed. Through a χ² distribution, it was found that there is experimental evidence that indicates that the dynamics of seed fall are different among cultivars. An analysis of main components was carried out in each year under study to simultaneously evaluate all the variables related to biomass, in the two ACPs mentioned there was not a defined grouping of the plants according to the cultivation to which they correspond
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