629 research outputs found
Wheat straw and lipids: UV-mutagenized Yarrowia lipolytica for the conversion of wheat straw hydrolysate into lipids
ArticleDue to the rising energy demand of our modern society and the finite amounts of
petroleum-based fuels, renewable forms of energy have become extremely important. Bio-based
fuels like bioethanol and biodiesel represent an already applied and accepted alternative.
Biodiesel is currently mainly produced from plant oils. A new and promising alternative, which
avoids the use of food crops, is the cultivation of the oleaginous yeast Yarrowia lipolytica, which
possesses the capacity to accumulate up to 40% of its biomass in form of lipids. Moreover, this
non-conventional yeast is able to metabolize a broad range of carbon-sources, presenting a
sustainable alternative to reutilize a wide spectrum of waste substrates. This makes it an
auspicious candidate for the generation of non-edible oils for biodiesel production. In this work,
we aimed to generate a Y. lipolytica mutant strain with enhanced lipid production when grown on
wheat straw hydrolysate as sole carbon source. Therefore, UV mutagenesis was applied and
mutants with a high-lipid content were selected by their ability to grow in the presence of the
fatty acid inhibitor cerulenin. Further, growth of the mutants on wheat straw hydrolysate was
evaluated. The fatty acid composition was analysed by GC-FID and the calculated total lipid
content revealed an up to 33% increase compared to the wild type strain. Fermentation
optimisation and the combination of various waste substrates as carbon sources are expected to
further increase the total lipid yield by the Y. lipolytica mutant strain and serve as initial point for
its industrial scale evaluation
Multi-objective optimal longitudinal flight control system design for large flexible transport aircraft
This paper presents a multi-objective evolutionary algorithm design of a longitudinal optimal controller for a large flexible transport aircraft. The algorithm uses a mixed optimization approach based on a combination of Linear Quadratic Regulator (LQR) control and a Multi-Objective Genetic Algorithm (MOGA) to search over a set of possible weighting function structures and parameter values in order to satisfy a number of conflicting design criteria. The proposed approach offers a number of potential optimal solutions lying on or near the Pareto optimal front of competing objectives. The approach is explained in this paper and some results are presented
Total Chiral Symmetry Breaking during Crystallization: Who needs a "Mother Crystal"?
Processes that can produce states of broken chiral symmetry are of particular
interest to physics, chemistry and biology. Chiral symmetry breaking during
crystallization of sodium chlorate occurs via the production of secondary
crystals of the same handedness from a single "mother crystal" that seeds the
solution. Here we report that a large and "symmetric" population of D- and
L-crystals moves into complete chiral purity disappearing one of the
enantiomers. This result shows: (i) a new symmetry breaking process
incompatible with the hypothesis of a single "mother crystal"; (ii) that
complete symmetry breaking and chiral purity can be achieved from an initial
system with both enantiomers. These findings demand a new explanation to the
process of total symmetry breaking in crystallization without the intervention
of a "mother crystal" and open the debate on this fascinating phenomenon. We
present arguments to show that our experimental data can been explained with a
new model of "complete chiral purity induced by nonlinear autocatalysis and
recycling".Comment: 5 pages, 4 figures, Added reference
A Fine Grain Sentiment Analysis with Semantics in Tweets
Social networking is nowadays a major source of new information in the world. Microblogging sites like Twitter have millions of active users (320 million active users on Twitter on the 30th September 2015) who share their opinions in real time, generating huge amounts of data. These data are, in most cases, available to any network user. The opinions of Twitter users have become something that companies and other organisations study to see whether or not their users like the products or services they offer. One way to assess opinions on Twitter is classifying the sentiment of the tweets as positive or negative. However, this process is usually done at a coarse grain level and the tweets are classified as positive or negative. However, tweets can be partially positive and negative at the same time, referring to different entities. As a result, general approaches usually classify these tweets as “neutral”. In this paper, we propose a semantic analysis of tweets, using Natural Language Processing to classify the sentiment with regards to the entities mentioned in each tweet. We offer a combination of Big Data tools (under the Apache Hadoop framework) and sentiment analysis using RDF graphs supporting the study of the tweet’s lexicon. This work has been empirically validated using a sporting event, the 2014 Phillips 66 Big 12 Men’s Basketball Championship. The experimental results show a clear correlation between the predicted sentiments with specific events during the championship
Heavy-light quark pseudoscalar and vector mesons at finite temperature
The temperature dependence of the mass, leptonic decay constant, and width of
heavy-light quark peseudoscalar and vector mesons is obtained in the framework
of thermal Hilbert moment QCD sum rules. The leptonic decay constants of both
pseudoscalar and vector mesons decrease with increasing , and vanish at a
critical temperature , while the mesons develop a width which increases
dramatically and diverges at , where is the temperature for
chiral-symmetry restoration. These results indicate the disappearance of
hadrons from the spectral function, which then becomes a smooth function of the
energy. This is interpreted as a signal for deconfinement at . In
contrast, the masses show little dependence on the temperature, except very
close to , where the pseudoscalar meson mass increases slightly by 10-20
%, and the vector meson mass decreases by some 20-30
Phytochemical characterization of Tabernanthe iboga root bark and its effects on dysfunctional metabolism and cognitive performance in high-fat-fed C57BL/6J mice
Preparations of the root bark of Tabernanthe iboga have long been used in Central and West African traditional medicine to combat fatigue, as a neuro-stimulant in rituals, and for treatment of diabetes. The principal alkaloid of T. iboga, ibogaine, has attracted attention in many countries around the world for providing relief for opioid craving in drug addicts. Using a plant metabolomics approach, we detected five phenolic compounds, including 3- O-caffeoylquinic acid, and 30 alkaloids, seven of which were previously reported from T. iboga root bark. Following a report that iboga extracts contain insulinotropic agents, we aimed to determine the potential alleviating effects of the water extract of iboga root bark on high-fat diet (HFD)-induced hyperglycemia as well as its effects on cognitive function in male C57BL/6J mice. Feeding a HFD to mice for 10 weeks produced manifestations of metabolic syndrome such as increased body weight and increased plasma levels of glucose, triacylglycerols, total cholesterol, LDL-cholesterol, insulin, leptin, and pro-inflammatory mediators (IL-6, MCP-1, ICAM-1), as compared to mice fed a low-fat diet (LFD). Supplementation of HFD with iboga extract at ibogaine doses of 0.83 (low) and 2.07 (high) mg/kg/day did not improve these HFD-induced metabolic effects except for a reduction of plasma MCP-1 in the low dose group, indicative of an anti-inflammatory effect. When the HFD mice were tested in the water maze, the high-dose iboga extract caused hippocampus-dependent impairments in spatial learning and memory, as compared to mice receiving only a HFD.Peer reviewedFinal Published versio
Design of eco-friendly fabric softeners: structure, rheology and interaction with cellulose nanocrystals
Concentrated fabric softeners are water-based formulations containing around
10 - 15 wt. % of double tailed esterquat surfactants primarily synthesized from
palm oil. In recent patents, it was shown that a significant part of the
surfactant contained in today formulations can be reduced by circa 50 % and
replaced by natural guar polymers without detrimental effects on the deposition
and softening performances. We presently study the structure and rheology of
these softener formulations and identify the mechanisms at the origin of these
effects.
The polymer additives used are guar gum polysaccharides, one cationic and one
modified through addition of hydroxypropyl groups. Formulations with and
without guar polymers are investigated using optical and cryo-transmission
electron microscopy, small-angle light and Xray scattering and finally
rheology. Similar techniques are applied to study the phase behavior of
softener and cellulose nanocrystals considered here as a model for cotton.
The esterquat surfactants are shown to assemble into micron-sized vesicles in
the dilute and concentrated regimes. In the former, guar addition in small
amounts does not impair the vesicular structure and stability. In the
concentrated regime, cationic guars induce a local crowding associated to
depletion interactions and leads to the formation of a local lamellar order. In
rheology, adjusting the polymer concentration at one tenth that of the
surfactant is sufficient to offset the decrease of the elastic property
associated with the surfactant reduction. In conclusion, we have shown that
through an appropriate choice of natural additives it is possible to lower the
concentration of surfactants in fabric conditioners by about half, a result
that could represent a significant breakthrough in current home care
formulations.Comment: 10 pages 8 figure
New upper bounds for the density of translative packings of three-dimensional convex bodies with tetrahedral symmetry
In this paper we determine new upper bounds for the maximal density of translative packings of superballs in three dimensions (unit balls for the -norm) and of Platonic and Archimedean solids having tetrahedral symmetry.
These bounds give strong indications that some of the lattice packings of superballs found in 2009 by Jiao, Stillinger, and Torquato are indeed optimal among all translative packings. We improve Zong's recent upper bound for the maximal density of translative packings of regular tetrahedra from to , getting closer to the best known lower bound of .
We apply the linear programming bound of Cohn and Elkies which originally was designed for the classical problem of packings of round spheres. The proofs of our new upper bounds are computational and rigorous. Our main technical contribution is the use of invariant theory of pseudo-reflection groups in polynomial optimization
The night-sky at the Calar Alto Observatory II: The sky at the near infrared
We present here the characterization of the night sky-brightness at the
near-infrared, the telescope seeing, and the fraction of useful time at the
Calar Alto observatory. For this study we have collected a large dataset
comprising 7311 near-infrared images taken regularly along the last four years
for the ALHAMBRA survey (J, H and Ks-bands), together with a more reduced
dataset of additional near-infrared images taken for the current study. In
addition we collected the information derived by the meteorological station at
the observatory during the last 10 years, together with the results from the
cloud sensor for the last ~2 years. We analyze the dependency of the
near-infrared night sky-brightness with the airmass and the seasons, studying
its origins and proposing a zenithal correction. A strong correlation is found
between the night sky-brightness in the Ks-band and the air temperature, with a
gradient of ~ -0.08 mag per 1 C degree. The typical (darkest) night
sky-brightness in the J, H and Ks-band are 15.95 mag (16.95 mag), 13.99 mag
(14.98 mag) and 12.39 mag (13.55 mag), respectively. These values show that
Calar Alto is as dark in the near-infrared as most of the other astronomical
astronomical sites in the world that we could compare with. Only Mauna Kea is
clearly darker in the Ks-band. The typical telescope seeing at the 3.5m is
~1.0" when converted to the V-band, being only slightly larger than the
atmospheric seeing measured at the same time by the seeing monitor, ~0.9".
Finally we estimate the fraction of useful time based on the relative humidity,
gust wind speed and presence of clouds. This fraction, ~72%, is very similar to
the one derived in Paper I, based on the fraction of time when the extinction
monitor is working.Comment: 15 pages, 6 figures, accepted to be published in PAS
- …