484 research outputs found
Zero Energy of Plane-Waves for ELKOs
We consider the ELKO field in interaction through contorsion with its own
spin density, and we investigate the form of the consequent autointeractions;
to do so we take into account the high-density limit and find plane wave
solutions: such plane waves give rise to contorsional autointeractions for
which the Ricci metric curvature vanishes and therefore the energy density is
equal to zero identically. Consequences are discussed.Comment: 7 page
Interferência Do Volume De Calda, Crescimento Dos Frutos E Precipitação Pluviométrica Sobre Os Depósitos Da Pulverização No Período De Controle Da Mancha Preta Dos Citros
Citrus black spot (CBS) caused by Guignardia citricarpa is one of the most serious Brazilian citrus diseases. This study aims to assess the interference of three application volumes in spray deposition citrus fruit, as well as fruit growth and rainfall effects on spray deposit reduction during the CBS control period. The experiment was carried out in a commercial citrus orchard, with sixteen-year-old trees of the Valencia variety, in Mogi Guaçu, São Paulo State, Brazil. The spray volumes were: 3.5 (1333L ha-1), 4.5 (1714L ha-1) and 8.5 (3238L ha-1) litres per tree, sprayed by an airblast sprayer using fungicides at recommended periods for disease control. The spray deposition quantification and residue was done by spectrophotometry using a copper oxychloride tracer. Samples were collected in three height zones of the tree (top, middle and bottom) and placed between trees on line plantation. Spray depositions were significantly smaller in the first application as a consequence of reduced fruit size. The spray losses on average for each day of rainfall ranged from 4.0 to 5.7%. There was no significant difference between application volumes regarding spray deposition on citrus fruit,which makes possible the reduction of application volumes, however, it is necessary to improve spraying techniques for the top zone of the citrus tree. © 2016, Universidade Federal de Santa Maria. All rights reserved.46582583
A modified theory of gravity with torsion and its applications to cosmology and particle physics
In this paper we consider the most general least-order derivative theory of
gravity in which not only curvature but also torsion is explicitly present in
the Lagrangian, and where all independent fields have their own coupling
constant: we will apply this theory to the case of ELKO fields, which is the
acronym of the German \textit{Eigenspinoren des LadungsKonjugationsOperators}
designating eigenspinors of the charge conjugation operator, and thus they are
a Majorana-like special type of spinors; and to the Dirac fields, the most
general type of spinors. We shall see that because torsion has a coupling
constant that is still undetermined, the ELKO and Dirac field equations are
endowed with self-interactions whose coupling constant is undetermined: we
discuss different applications according to the value of the coupling constants
and the different properties that consequently follow. We highlight that in
this approach, the ELKO and Dirac field's self-interactions depend on the
coupling constant as a parameter that may even make these non-linearities
manifest at subatomic scales.Comment: 21 page
Superinflation, quintessence, and nonsingular cosmologies
The dynamics of a universe dominated by a self-interacting nonminimally
coupled scalar field are considered. The structure of the phase space and
complete phase portraits are given. New dynamical behaviors include
superinflation (), avoidance of big bang singularities through
classical birth of the universe, and spontaneous entry into and exit from
inflation. This model is promising for describing quintessence as a
nonminimally coupled scalar field.Comment: 4 pages, 2 figure
Neoctangium travassosi (Digenea: Microscaphidiidae) in sea turtles from South America
ABSTRACT Sea turtles are endangered animals that present cosmopolitan distribution. Anthropic actions have been considered important causes for the reduction of sea turtle population, but natural aspects such as parasitism may also contribute to their decline. This study aimed to report the occurrence of parasites in stranded dead sea turtles found in an area known as Potiguar Basin, northeastern Brazil, from 2010 to 2019. They were identified and classified according to the carapace length. At post-mortem analyses all organs were examined, parasites collected and morphologically identified. Ecological parasitic indexes as prevalence (P), mean intensity (MI) and mean abundance (MA) were calculated. A total of 80 Chelonia mydas and 5 Eretmochelys imbricata were assessed. Neoctangium travassosi was detected in both species presenting P = 20%, MI = 4.19 and MA = 0.84 for C. mydas and P = 60%, MI = 1.67 and MA = 1.0 for E. imbricata. This is the first report of N. travassosi parasitizing E. imbricata in South America. Finally, the retrieval of these parasites is a warning regarding the need for further studies to assess the impact of this parasitism on the health and conservation of sea turtles
Coupled oscillators as models of phantom and scalar field cosmologies
We study a toy model for phantom cosmology recently introduced in the
literature and consisting of two oscillators, one of which carries negative
kinetic energy. The results are compared with the exact phase space picture
obtained for similar dynamical systems describing, respectively, a massive
canonical scalar field conformally coupled to the spacetime curvature, and a
conformally coupled massive phantom. Finally, the dynamical system describing
exactly a minimally coupled phantom is studied and compared with the toy model.Comment: 18 pages, LaTeX, to appear in Physical Review
Structural assessment, toxicity, and increased antimicrobial activity
Scorpion venom is a rich source of biologically active components and various peptides with high-potential therapeutic use that have been characterized for their antimicrobial and antiproliferative activities. Stigmurin is a peptide identified from the Tityus stigmurus venom gland with high antibacterial and antiproliferative activities and low toxicity. Amino acid substitutions in peptides without a disulfide bridge sequence have been made with the aim of reducing their toxicity and increasing their biological activities. The purpose of this study was to evaluate the structural conformation and structural stability, as well as antimicrobial, antiproliferative, and hemolytic activities of two peptide analogs to Stigmurin, denominated StigA6 and StigA16. In silico analysis revealed the α-helix structure for both analog peptides, which was confirmed by circular dichroism. Data showed that the net charge and hydrophobic moment of the analog peptides were higher than those for Stigmurin, which can explain the increase in antimicrobial activity presented by them. Both analog peptides exhibited activity on cancerous cells similar to the native peptide; however, they were less toxic when tested on the normal cell line. These results reveal a potential biotechnological application of the analog peptides StigA6 and StigA16 as prototypes to new therapeutic agents.publishersversionpublishe
Evaluation of resistance to Tomato severe rugose virus (ToSRV) in Capsicum spp. genotypes
CHIRAL BACKGROUND FOR THE TWO PION EXCHANGE NUCLEAR POTENTIAL: A PARAMETRIZED VERSION
We argue that the minimal chiral background for the two-pion exchange
nucleon-nucleon interaction has nowadays a rather firm conceptual basis, which
entitles it to become a standard ingredient of any modern potential. In order
to facilitate applications, we present a parametrized version of a
configuration space potential derived previously. We then use it to assess the
phenomenological contents of some existing NN potentials.Comment: REVTEX style, 16 pages, 5 PostScript figures compressed, tarred and
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Dimensionless cosmology
Although it is well known that any consideration of the variations of
fundamental constants should be restricted to their dimensionless combinations,
the literature on variations of the gravitational constant is entirely
dimensionful. To illustrate applications of this to cosmology, we explicitly
give a dimensionless version of the parameters of the standard cosmological
model, and describe the physics of Big Bang Neucleosynthesis and recombination
in a dimensionless manner. The issue that appears to have been missed in many
studies is that in cosmology the strength of gravity is bound up in the
cosmological equations, and the epoch at which we live is a crucial part of the
model. We argue that it is useful to consider the hypothetical situation of
communicating with another civilization (with entirely different units),
comparing only dimensionless constants, in order to decide if we live in a
Universe governed by precisely the same physical laws. In this thought
experiment, we would also have to compare epochs, which can be defined by
giving the value of any {\it one} of the evolving cosmological parameters. By
setting things up carefully in this way one can avoid inconsistent results when
considering variable constants, caused by effectively fixing more than one
parameter today. We show examples of this effect by considering microwave
background anisotropies, being careful to maintain dimensionlessness
throughout. We present Fisher matrix calculations to estimate how well the fine
structure constants for electromagnetism and gravity can be determined with
future microwave background experiments. We highlight how one can be misled by
simply adding to the usual cosmological parameter set
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