525 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
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
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
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
Addressing health workforce inequities in the Mindanao regions of the Philippines: tracer study of graduates from a socially-accountable, community-engaged medical school and graduates from a conventional medical school
Developing and retaining a high-quality medical workforce in low-resource countries is a worldwide challenge. The Filipino Ateneo de Zamboanga University–School of Medicine (ADZU-SOM) has adopted a strong focus on socially accountable health professional education (SAHPE) in order to address the shortage of physicians across rural and urban communities in the Western Mindanao region. A cross-sectional survey of graduates from two Philippines medical schools: ADZU-SOM in the Mindanao region and a medical school with a more conventional curriculum, found ADZU-SOM graduates were more likely to have joined the medical profession due to a desire to help others (p=0.002), came from lower socioeconomic strata (p¼0.001) and had significantly (p<0.05) more positive attitudes to community service. ADZU graduates were also more likely to currently work in Government Rural Health Units (p<0.001) or be generalist Medical Officers (p<0.001) or Rural/Municipal Health Officers (p=0.003). ADZU graduates were also less likely to work in private or specialist Government hospitals (p=0.033 and p=0.040, respectively) and be surgical or medical specialists (p=0.010 and p<0.001, respectively). The findings suggest ADZU-SOM’s SAHPE philosophy manifests in the practice choices of its graduates and that the ADZUSOM can meet the rural and urban health workforce needs of the Western Mindanao region
On the feasibility of the computational modelling of the endoluminal vacuum-assisted closure of an oesophageal anastomotic leakage
Endoluminal vacuum-assisted closure (E-VAC) is a promising therapy to treat anastomotic leakages of the oesophagus and bowel which are associated with high morbidity and mortality rates. An open-pore polyurethane foam is introduced into the leakage cavity and connected to a device that applies a suction pressure to accelerate the closure of the defect. Computational analysis of this healing process can advance our understanding of the biomechanical mechanisms at play. To this aim, we use a dual-stage finite-element analysis in which (i) the structural problem addresses the cavity reduction caused by the suction and (ii) a new constitutive formulation models tissue healing via permanent deformations coupled to a stiffness increase. The numerical implementation in an in-house code is described and a qualitative example illustrates the basic characteristics of the model. The computational model successfully reproduces the generic closure of an anastomotic leakage cavity, supporting the hypothesis that suction pressure promotes healing by means of the aforementioned mechanisms. However, the current framework needs to be enriched with empirical data to help advance device designs and treatment guidelines. Nonetheless, this conceptual study confirms that computational analysis can reproduce E-VAC of anastomotic leakages and establishes the bases for better understanding the mechanobiology of anastomotic defect healing.Fil: Comellas, Ester. Centre Internacional de Mètodes Numèrics a l'Enginyeria; EspañaFil: Bellomo, Facundo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; ArgentinaFil: Rosales, Iván. B. Braun Surgical; EspañaFil: del Castillo, Luis F.. B. Braun Surgical; EspañaFil: Sánchez, Ricardo. B. Braun Surgical; EspañaFil: Turon, Pau. B. Braun Surgical; EspañaFil: Oller, Sergio Horacio Cristobal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. Centre Internacional de Mètodes Numèrics a l'Enginyeria; España. Universidad Politécnica de Catalunya; Españ
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