10,637 research outputs found
On the equivalence of Lambda(t) and gravitationally induced particle production cosmologies
The correspondence between cosmological models powered by a decaying vacuum
energy density and gravitationally induced particle production is investigated.
Although being physically different in the physics behind them we show that
both classes of cosmologies under certain conditions can exhibit the same
dynamic and thermodynamic behavior. Our method is applied to obtain three
specific models that may be described either as Lambda(t)CDM or gravitationally
induced particle creation cosmologies. In the point of view of particle
production models, the later class of cosmologies can be interpreted as a kind
of one-component unification of the dark sector. By using current type Ia
supernovae data, recent estimates of the cosmic microwave background shift
parameter and baryon acoustic oscillations measurements we also perform a
statistical analysis to test the observational viability within the two
equivalent classes of models and we obtain the best-fit of the free parameters.
By adopting the Akaike information criterion we also determine the rank of the
models considered here. Finally, the particle production cosmologies (and the
associated decaying Lambda(t)-models) are modeled in the framework of field
theory by a phenomenological scalar field model.Comment: 9 pages, 3 figures, new comments and 8 references added. Accepted for
publication in Physics Letters
Statistical Mechanics Characterization of Neuronal Mosaics
The spatial distribution of neuronal cells is an important requirement for
achieving proper neuronal function in several parts of the nervous system of
most animals. For instance, specific distribution of photoreceptors and related
neuronal cells, particularly the ganglion cells, in mammal's retina is required
in order to properly sample the projected scene. This work presents how two
concepts from the areas of statistical mechanics and complex systems, namely
the \emph{lacunarity} and the \emph{multiscale entropy} (i.e. the entropy
calculated over progressively diffused representations of the cell mosaic),
have allowed effective characterization of the spatial distribution of retinal
cells.Comment: 3 pages, 1 figure, The following article has been submitted to
Applied Physics Letters. If it is published, it will be found online at
http://apl.aip.org
Majority-Vote Model on a Random Lattice
The stationary critical properties of the isotropic majority vote model on
random lattices with quenched connectivity disorder are calculated by using
Monte Carlo simulations and finite size analysis. The critical exponents
and are found to be different from those of the Ising and
majority vote on the square lattice model and the critical noise parameter is
found to be .Comment: 4 pages, 6 figure
An anthropologic study on strategies for addressing health problems among the elderly in BambuÃ, Minas Gerais State, Brazil
Saline stress and cell toxicity evaluation using suspended plant cell cultures of horticultural crops grown in a bioreactor
Crop salt damage consists, usually, of leaf burn and defoliation, and it is associated with accumulation of toxic levels of sodium and/or chloride in leaf cells (Storey and Walker, 1999). The cell and tissue culture are simple biological systems that offer a direct approach to the metabolic changes. The plant cell growth in a controlled environment, as a bioreactor, is a unique tool for cell ion transport studies.
Cell suspension culture of citrus cell line was exposed to a medium containing
different sodium chloride concentrations (0mM, 42.7mM and 85.5mM). The growth
profile of control cells (absence of NaCl) and 85.5mM cells were similar. The lack of
inhibition of biomass accumulation, of all tested saline conditions clearly showed
that the level of NaCl concentration used was not toxic for the cell metabolism. Also
its ability to resist to 85.5mM NaCl can be on evidence that this suspension cel culture might have salt tolerance characteristics
Alleviation of salt stress using exogenous proline on a citrus cell line
Salinity constitutes an important abiotic problem since ancient times, world-wide, for it leads to a decrease in productivity of crops with agronomic value. Under salt stress conditions, plant cells develop strategies to cope with Na+ and Cl-, including exclusion and compartmentalisation, induction of antioxidant enzymatic systems and compatible solutes accumulation, such as proline. The precise function of this osmolyte still remains unclear. Proline may act on osmotic adjustment, as a free radical scavenger, protecting enzymes and avoiding DNA damages. It has been also suggested the role of proline in prevention of lipid peroxidation and as a signalling/regulatory molecule. A salt-sensitive Citrus sinensis ‘Valencia late’ cell line has a smaller growth rate and accumulates proline in the presence of NaCl (>200 mM). The addition of external proline to this cell line was evaluated in terms of cell metabolism. A positive influence on the relieve of salt stress symptoms due to the presence of exogenous proline 5 mM and 100 mM NaCl was obtained, with increased growth of this salt sensitive citrus cell line.info:eu-repo/semantics/publishedVersio
Production of bioethanol from sweet potato, agro industrial wastes
One fraction of the existent petroleum is not extractable or the difficulties associated to extraction are
very expensive making them unviable. This situation leads to a decrease in petroleum stocks all over
the world and a resulting increment on its price, affecting in particular the transportation sector, since
there is no relevant alternative to fossil petroleum
Microbial production of curcumin
First Online: 01 October 2022Curcumin, a polyphenol produced by turmeric (Curcuma longa), has attracted increased attention due to its potential as a novel cancer-fighting drug. However, to satisfy the required curcumin demand for health-related studies, high purity curcumin preparations are required, which are difficult to obtain and are very expensive. Curcumin and other curcuminoids are usually obtained through plant extraction. However, these polyphenols accumulate in low amounts over long periods in the plant and their extraction process is costly and not environmentally friendly. In addition, curcumin chemical synthesis is complex. All these reasons limit the advances in studies related to the in vitro and in vivo curcumin biological activities. The microbial production of curcumin appears as a solution to overcome the limitations associated with the currently used methods. Curcumin biosynthesis begins with the conversion of the aromatic amino acids, phenylalanine and tyrosine, into phenylpropanoids, the curcuminoid precursors. The phenylpropanoids are then activated through condensation with a CoA molecule. Afterwards, curcuminoids are synthesized by the action of type III polyketide synthases (PKS) that combine two activated phenylpropanoids and a malonyl-CoA molecule. To engineer microbes to produce curcumin, the curcuminoid biosynthetic genes must be introduced as microorganisms lack the enzymatic reactions responsible to synthesize curcuminoids. In this chapter, the advances regarding the microbial production of curcumin are exposed. The heterologous production of curcumin has been mainly achieved in the bacteria Escherichia coli. However, other microorganisms have already been explored. Besides the introduction of curcumin biosynthetic genes, the optimization of the microbial chassis must also be considered to maximize the production yields. The strategies employed for this purpose are also herein presented. The maximum titer of curcumin produced by a genetically engineered E. coli was 563.4 mg/L with a substrate conversion yield of 100% from supplemented ferulic acid. Moreover, the de novo production of curcumin was accomplished in E. coli reaching 3.8 mg/L of curcumin. Overall, the recent developments on curcumin heterologous production are very encouraging.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/BIO/04469/2020 unit, and by LABBELS – Associate Laboratory in Biotechnology, Bioengineering and Microelectromechnaical Systems, LA/P/0029/2020. J.R. is recipient of a doctoral fellowship (SFRH/BD/138325/2018) supported by a doctoral advanced training funded by FCT.info:eu-repo/semantics/publishedVersio
Inhibition of human neutrophil oxidative burst by pyrazolone derivatives
The risk of agranulocytosis associated with the use of pyrazolone drugs at therapeutical doses and for short periods of time has been considered
to be very low. However, little or no attention at all has been devoted to the possible hindrance of neutrophil burst and scavenging of neutrophilgenerated
reactive oxygen species (ROS) by these compounds. Such an effect could be beneficial in the case of overactivation of neutrophils but
could also be highly detrimental if the number of circulating neutrophils is already decreased. Thus, the aim of the present study was to evaluate
the putative inhibitory effect of the pyrazolones dipyrone, aminopyrine, isopropylantipyrine, and antipyrine against human neutrophil burst and
their scavenging activity against O2
S!, H2O2, HOS, ROOS, and HOCl. The obtained results showed that dipyrone and aminopyrine prevent
phorbol-12-myristate-13-acetate-induced neutrophil burst with high efficiency, while isopropylantipyrine had little effect and antipyrine had no
effect at all. Dipyrone and aminopyrine were highly potent scavengers of HOS and HOCl, while, in accordance with the neutrophil burst results,
isopropylantipyrine had little effect and antipyrine had no effect at all against these two ROS. None of the studied pyrazolones was capable of
scavenging O2
S! or H2O2, while dipyrone was shown to be the most reactive against ROOS
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