8,024 research outputs found
Dipole–dipole interaction in superparamagnetic nanocrystalline Fe63.5Cr10Si13.5B9Cu1Nb3
Cr-substituted Finemet-type nanocrystalline alloy (Fe63.5Cr10Si13.5B9Cu1Nb3) has been studied by
differential scanning calorimetry, x-ray diffraction, Mo¨ssbauer spectroscopy, and magnetic
measurements. The Curie temperature of the remaining amorphous phase decreases as the
crystalline volume fraction increases, reaching values below room temperature. This feature makes
the alloy adequate for studying the magnetic decoupling of the ~Fe,Si! nanocrystals at moderated
temperatures and, in particular, the superparamagnetic relaxation in broad temperature and
crystalline fraction ranges. It was shown that the anomalous dependence of the coercive field on the
annealing temperature can be satisfactorily explained assuming a dipolar-type interaction between
the crystallites.DGES del Gobierno español-PB97-1119-CO2-01Fondo de investigación del gobierno húngaro-OTKA T-030753Academia de Ciencias de HungrÃa-AKP 98-25 2,
Isolation of polyphenols from spent coffee grounds and silverskin by mild hydrothermal pretreatment
In the present study, a new method for isolation of polyphenols (PP) from spent coffee grounds (SCG) and coffee silverskin (CS) is described. The method consisted in a mild hydrothermal pretreatment at 120 °C, during 20 min, using a liquid to solid ratio of 20 ml/g. PP (determined as gallic acid equivalents, GAE) were the most abundant components in the extracts produced by this method, corresponding to 32.92 mgGAE/gSCG and 19.17 mgGAE/gCS, among of which, flavonoids corresponded to 8.29 and 2.73 mg quercetin equivalents/g of SCG and CS, respectively. Both extracts presented antioxidant activity but the results were higher for SCG extract, probably due to the highest content of PP present. Negligible effects (less than 1% solubilisation) were caused by the hydrothermal pretreatment on cellulose, hemicellulose and protein fractions of these materials. Some minerals elements were present in the extracts, potassium being the most abundant. Hydrothermal pretreatment under mild conditions was demonstrated to be an efficient method to recover antioxidant PP from coffee residues
Noves dades sobre la presència de cerà mica ibèrica al mediterrani occidental: Materials republicans i imperials de les comarques gironines
Improving the accuracy of wood moisture content estimation in four European softwoods from Spain
Aim of study: To obtain improved models to predict, with an error of less than ± 2.0%, the gravimetric moisture content in four different softwoods commonly present in the Spanish and European markets, based on electrical resistance measurements. This improved moisture content estimation is useful not only for assessing the quality of wood products, especially in the case of laminated products, during the transformation and delivery process, but also for accurately monitoring the evolution of moisture in wood present in bridges and buildings, which is of great importance for its maintenance and service life improvement.Area of study: The study was carried out on samples of Scots, laricio, radiata and  maritime pines of Spanish provenances.Material and methods: On 50x50x20 mm3 solid wood samples (36 per species, 9 per condition), conditioned at 20ºC (±05ºC) and 40±5%, 65±5%, 80±5% or 90±5% Relative Humidity (RH), electrical resistance and oven-dry moisture content was measured. The Samuelsson's model was fitted to data to explain the relationship between the two variables. The accuracy of the model was evaluated by the use of an external sample.Main results: With the proposed mathematical functions the wood moisture content can be estimated with an error of ±0.9% in the four species, confirming the effectiveness of this nondestructive methodology for accurate estimation and monitoring of moisture content.Research highlights: our results allow the improvement of the moisture content estimation technique by resistance-type methodologies.Keywords: Resistance-type moisture meter; species correction.Abbreviations used: MC: Moisture content; RH: relative Humidity; R: electrical resistance; RP: wood electrical resistance measured parallel to the grain; RT: electrical resistance measured perpendicular (transversally) to the grain; GM-MC: gravimetrically measured moisture content
Hydrothermal pretreatment of spent coffee and silverskin for polyphenols recovery
Coffee is one of the most consumed beverages around the world. As a
consequence of this big market, huge amounts of residues are also
generated every year as a result of the coffee beans processing. Spent
coffee grounds (SCG, Figure 1a), for example, are obtained in significant
amounts during the process for instant coffee elaboration, and is also
obtained in large amounts in restaurants, bars and cafeterias; while coffee
silverskin (CS, Figure 1b) is the main residue obtained during the beans
roasting step [1].
Interest in reusing these residues has increased in the last years for economic and environmental concerns.
Additionally, such coffee wastes contain in their composition several compounds of interest for application in food,
cosmetic and pharmaceutical areas [1]. The presence of polyphenols (PP) in SCG and CS has been reported in
several studies, and some technologies have also been proposed for the recovery of these compounds from such
coffee residues, among of which the use of organic solvents is usually proposed due to their efficient extraction
capacity. However, the use of organic solvents generates a toxic effluent that needs to be treated before discharging
to the environment. As an alternative to avoid this problem, the present study evaluated the possibility of recovering
PP by hydrothermal pretreatment of SCG and CS. By using this strategy, the residues are submitted to a reaction
using only water as extraction solvent under higher temperature conditions than those usually employed for
extraction with organic solvents, and the use of these toxic chemicals is avoided.
The hydrothermal pretreatment of SCG and CS consisted in using 20 mL of distilled water to each gram of residue,
and the reactions were maintained at 120 ºC during 20 min. The total amount of PP in the extracts was quantified as
gallic acid equivalents (GAE). The extracts produced under these conditions contained 32.9 mg GAE/g SCG and
19.2 mg GAE/g CS, among of which, flavonoids corresponded to 25% and 14% of the total PP in SCG and CS,
respectively. These results were higher than the amounts recovered in previous studies using organic solvents
(methanol and ethanol) as extraction agent [2, 3]. It was then concluded that is possible to use a hydrothermal
pretreatment to efficiently recover PP from coffee wastes. Further studies will be focused on the selection of the
extraction conditions that maximize the recovery results
Argon assisted chemical vapor deposition of CrO: an efficient process leading to high quality epitaxial films
A comparative study of the structural, microstructural and magnetic
properties of CrO thin films grown onto (110) and (100) TiO rutile
single crystal substrates by chemical vapor deposition (CVD), using CrO as
chromium precursor and either oxygen or argon as carrier gas is presented. Our
results show that growth under argon carrier gas leads to high quality CrO
epilayers with structural and magnetic properties similar to those obtained
using the more standard oxygen carrier gas. Furthermore, we interpret the
larger magnetic coercivity observed for the (110) oriented films in terms of
their microstructure, in particular of the highest strain and edge roughness of
the building structures of the CrO epilayers, which are settled by the
substrate crystallographic orientation.Comment: 27 pages, 2 tables, 8 figure
The thickness of a liquid layer on the free surface of ice as obtained from computer simulation
Molecular dynamic simulations were performed for ice Ih with a free surface
by using four water models, SPC/E, TIP4P, TIP4P/Ice and TIP4P/2005. The
behavior of the basal plane, the primary prismatic plane and of the secondary
prismatic plane when exposed to vacuum was analyzed. We observe the formation
of a thin liquid layer at the ice surface at temperatures below the melting
point for all models and the three planes considered. For a given plane it was
found that the thickness of a liquid layer was similar for different water
models, when the comparison is made at the same undercooling with respect to
the melting point of the model. The liquid layer thickness is found to increase
with temperature. For a fixed temperature it was found that the thickness of
the liquid layer decreases in the following order: the basal plane, the primary
prismatic plane, and the secondary prismatic plane. For the TIP4P/Ice model, a
model reproducing the experimental value of the melting temperature of ice, the
first clear indication of the formation of a liquid layer appears at about -100
Celsius for the basal plane, at about -80 Celsius for the primary prismatic
plane and at about -70 Celsius for the secondary prismatic plane.Comment: 41 pages and 13 figure
Eclipsing Binaries Showing Light Time Effect
Four eclipsing binaries, which show apparent changes of period, have been
studied with respect to a possible presence of the light time effect. With a
least squares method we calculated new light elements of these systems, the
mass function of the predicted third body, and its minimum mass. We discuss the
probability of the presence of such bodies in terms of mass function, changes
in radial velocity and third light in solution of light curves.Comment: 4 pages, 4 figures, 1 table, conference proceeding
Spain 2011 pension reform
The aim of this paper is to evaluate the impact of the Spanish pension reform enacted in 2011.
We use an accounting model with heterogeneous agents and overlapping generations in order to
project revenues and expenditures of the pension system for the next four decades. Specifically,
we analyze the impact of changes in the replacement rate, in the period of calculation and
the delay of the retirement age. We obtain results under two alternative migration scenarios:
(i) a combination of the latest figures released by the INE, which forecast a reduced annual
immigration net flow of some 70,000 persons; and (ii) a revised scenario featuring a more
generous hypothesis concerning this net flow. We demonstrate that the results show that these
three changes instigated by the reform could imply a savings of about 3 percentage points of
GDP in 2051. However, we couldn’t include in the evaluation the sustainability factor (that
transform the Spanish system in a defined contribution scheme) that will start in 2027 due to
the lack of details in the text of the Reform. Finally, we analyze the changes in average pensions
by gender, skill, and nationalit
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