942 research outputs found
Optimization by response surface methodology the experimental conditions in the production of biodiesel with calcium oxide as heterogeneous catalyst
Comparison of a proprioceptive training program on stable base and unstable base
El objetivo de este estudio fue comparar dos programas de entrenamiento
propioceptivo sobre base estable (G1) y base inestable (G2). Durante 5
semanas, 18 jugadores de fútbol profesional se sometieron a un programa de
entrenamiento propioceptivo, 9 formaron el G1 y 9 G2. Se aplicó el Standard
Excursion Balance Test (Test de Estrella) antes y después de la intervención.
Los resultados intragrupo mostraron diferencias significativas en las variables
ANT.IZDO; ANTLAT.IZDO; POST.D y ANTMED.D (p<0,005) para el G1 y
ANT.D; ANT.IZDO; POSTMED.D; POSTMED.IZDO Y MED.D (p <0,005) para el
G2. No se hallaron evidencias significativas entre el entrenamiento en base
estable y base inestable para la mejora del equilibrio y la estabilidadThe aim is to compare two proprioceptive training programs on a stable (G1)
and an unstable (G2) base in terms of balance and stability. During a 5 week
period, 18 professional football players underwent a proprioceptive training
program, 9 in G1 and the other 9 in G2. The Standard Excursion Balance Test
was applied before and after the intervention program. Significant intragroup
differences were found in the variables LEFT FRONT, ANTEROLATERAL
LEFT (ANTLAT.LEFT), BACK RIGHT and ANTEROMEDIAL RIGHT
(ANTMED.RIGHT) (p<0,005) for the G1, and FRONT RIGHT, FRONT LEFT,
POSTMED.RIGHT, POSTMED.LEFT and MED.RIGHT (p <0,005) for G2. We
conclude that there are no significant differences between the unstable base
training and training stable base regarding improvement in balance and stabilit
Illusions of general relativity in Brans-Dicke gravity
Contrary to common belief, the standard tenet of Brans-Dicke theory reducing
to general relativity when omega tends to infinity is false if the trace of the
matter energy-momentum tensor vanishes. The issue is clarified in a new
approach using conformal transformations. The otherwise unaccountable limiting
behavior of Brans-Dicke gravity is easily understood in terms of the conformal
invariance of the theory when the sources of gravity have radiation-like
properties. The rigorous computation of the asymptotic behavior of the
Brans-Dicke scalar field is straightforward in this new approach.Comment: 16 pages, LaTeX, to appear in Physical Review
Production of a biodiesel-like biofuel without glycerol generation, by using Novozym 435, an immobilized Candida antarctica lipase
Background: Novozym 435, a commercial lipase from Candida antarctica, recombinant, expressed in Aspergillus niger,
immobilized on macroporous acrylic resin, has been already described in the obtention of biodiesel. It is here evaluated
in the production of a new biofuel that integrates the glycerol as monoglyceride (MG) together with two fatty acid
ethyl esters (FAEE) molecules by the application of 1,3-selective lipases in the ethanolysis reaction of sunflower oil.
Results: Response surface methodology (RSM) is employed to estimate the effects of main reaction. Optimum
conditions for the viscosity, selectivity, and conversion were determined using a multifactorial design of
experiments with three factors run by the software Stat Graphics version XV.I. The selected experimental
parameters were reaction temperature, oil/ethanol ratio and alkaline environment. On the basis of RSM analysis,
the optimum conditions for synthesis were 1/6 oil/EtOH molar ratio, 30°C, and 12.5 μl of NaOH 10 N aqueous
solutions, higher stirring than 300 rpm, for 2 h and 0.5 g of biocatalyst.
Conclusions: These obtained results have proven a very good efficiency of the biocatalyst in the studied selective
process. Furthermore, it was allowed sixteen times the successive reuse of the biocatalyst with good performanc
Obtención de un biocombustible que integra la glicerina empleando como catalizador heterogéneo KF soportado
Bounds and optimisation of orbital angular momentum bandwidths within parametric down-conversion systems
The measurement of high-dimensional entangled states of orbital angular
momentum prepared by spontaneous parametric down-conversion can be considered
in two separate stages: a generation stage and a detection stage. Given a
certain number of generated modes, the number of measured modes is determined
by the measurement apparatus. We derive a simple relationship between the
generation and detection parameters and the number of measured entangled modes.Comment: 6 pages, 4 figure
Síntesis de un nuevo biocombustible que integra la glicerina empleando óxido de calcio como catalizador heterogéneo
Biofuel that Keeps Glycerol as Monoglyceride by 1,3-Selective Ethanolysis with Pig Pancreatic Lipase Covalently Immobilized on AlPO4 Support
By using pig pancreatic lipase (EC 3.1.1.3 or PPL) as a biocatalyst, covalently
immobilized on amorphous AlPO4 support, a new second generation biodiesel was
obtained in the transesterification reaction of sunflower oil with ethanol. The resulting
biofuel is composed of fatty acid ethyl esters and monoglycerides (FAEE/MG) blended in
a 2:1 molar ratio. This novel product, which integrates glycerol as monoacylglycerols
(MG) into the biofuels composition, has similar physicochemical properties as
conventional biodiesel and also avoids the removal step of the by-product by washing of
the biodiesel with water. Immobilization of PPL was achieved by covalent attachment of
the ε-amino group of the lysine residues of PPL with the aldehyde groups of
p-hydroxybenzaldehyde linked on a hybrid organic-inorganic functionalized AlPO4
surface. With this procedure, the PPL biocatalyst was strongly fixed to the inorganic
support surface (94.3%). Nevertheless, the efficiency of the immobilized enzyme was
relatively lower compared to that of the free PPL, but it showed a remarkable stability as
well as a great capacity of reutilization (25 reuses) without a significant loss of its initial catalytic activity. Therefore, this enzymatic method allows the production of a biodiesel
which integrates the glycerol, allows a more efficient fabrication method and minimizes
the waste production as compared to the conventional alkali-catalyzed process
New Biofuel Integrating Glycerol into Its Composition Through the Use of Covalent Immobilized Pig Pancreatic Lipase
By using 1,3-specific Pig Pancreatic lipase (EC 3.1.1.3 or PPL), covalently
immobilized on AlPO4/Sepiolite support as biocatalyst, a new second-generation biodiesel
was obtained in the transesterification reaction of sunflower oil with ethanol and other
alcohols of low molecular weight. The resulting biofuel is composed of fatty acid ethyl
esters and monoglycerides (FAEE/MG) blended in a molar relation 2/1. This novel
product, which integrates glycerol as monoacylglycerols (MG) into the biofuel
composition, has similar physicochemical properties compared to those of conventional
biodiesel and also avoids the removal step of this by-product. The biocatalyst was found to
be strongly fixed to the inorganic support (75%). Nevertheless, the efficiency of the
immobilized enzyme was reduced to half (49.1%) compared to that of the free PPL. The
immobilized enzyme showed a remarkable stability as well as a great reusability (more
than 40 successive reuses) without a significant loss of its initial catalytic activity.
Immobilized and free enzymes exhibited different reaction mechanisms, according to the different results in the Arrhenius parameters (Ln A and Ea). However, the use of supported
PPL was found to be very suitable for the repetitive production of biofuel due to its facile
recyclability from the reaction mixture
- …