1,272 research outputs found
Graphene coatings: An efficient protection from oxidation
We demonstrate that graphene coating can provide an efficient protection from
oxidation by posing a high energy barrier to the path of oxygen atom, which
could have penetrated from the top of graphene to the reactive surface
underneath. Graphene bilayer, which blocks the diffusion of oxygen with a
relatively higher energy barrier provides even better protection from
oxidation. While an oxygen molecule is weakly bound to bare graphene surface
and hence becomes rather inactive, it can easily dissociates into two oxygen
atoms adsorbed to low coordinated carbon atoms at the edges of a vacancy. For
these oxygen atoms the oxidation barrier is reduced and hence the protection
from oxidation provided by graphene coatings is weakened. Our predictions
obtained from the state of the art first-principles calculations of electronic
structure, phonon density of states and reaction path will unravel how a
graphene can be used as a corrosion resistant coating and guide further studies
aiming at developing more efficient nanocoatings.Comment: under review in PRB;
http://link.aps.org/doi/10.1103/PhysRevB.85.15544
Laying hens behave as omnivores with poultry meal included in their diet
This study was conducted to determine egg yield performance and quality, animal partiality to poultry meal, and consumer preferences for eggs produced by various feeding methods. A total of 72 Nick Brown laying hens, aged 22 weeks, were offered three feeding methods with 24 replicates per treatment and one hen per experimental unit. These methods consisted of i) vegetarian (no poultry meal), ii) omnivorous (5% poultry meal), and iii) a choice between vegetarian and omnivorous. Feed and water were provided ad libitum. The study lasted for 10 weeks. Feeding methods did not affect feed intake, feed conversion ratio, egg yield, and egg quality. However, they affected the malondialdehyde (MDA) value of eggs on the 42nd day of storage significantly (P <0.05). The highest MDA value was obtained from the eggs of ‘omnivorous’ hens. More hens (51.4%) in the choice group preferred omnivorous feed to ‘vegetarian’. Panellists found organoleptic differences among sample eggs from hens subjected to various feeding methods. They reported that the eggs obtained from vegetarian hens were preferable. The conclusions were that i) no feeding method changed egg yield performance and quality, ii) omnivorous feeding shortened the shelf-life of eggs, iii) hens with a choice of feed did not reject the omnivorous diet, but increased their intake, and iv) the panellists disliked eggs from the omnivorous hens. Finally, these preferences should be considered in legislation for poultry feeding and animal husbandry
Unparticle Physics in the Moller Scattering
We investigate the virtual effects of vector unparticles in the Moller
scattering. We derive the analytic expression for scattering amplitudes with
unpolarized beams. We obtain 95% confidence level limits on the unparticle
couplings and with integrated luminosity of
and and 500 GeV energies. We show
that limits on are more sensitive than .Comment: 10 pages, 5 figures, 4 table
Strong coupling constants of bottom and charmed mesons with scalar, pseudoscalar and axial vector kaons
The strong coupling constants, , ,
, , and
, where , and are scalar, pseudoscalar
and axial vector kaon mesons, respectively are calculated in the framework of
three-point QCD sum rules. In particular, the correlation functions of the
considered vertices when both and mesons are off-shell
are evaluated. In the case of , which is either or
, the mixing between these two states are also taken into account. A
comparison of the obtained result with the existing prediction on
as the only coupling constant among the considered
vertices, previously calculated in the literature, is also made.Comment: 20 Pages, 3 Figures and 8 Table
Efecto de diferentes métodos de extracción sobre la actividad antioxidante del azafrán, contenido total de fenoles y crocina y efecto protector del extracto de azafrán sobre la estabilidad oxidativa de los aceites vegetales comunes
Saffron consists of bioactive compounds with health-promoting properties and is mainly used in medicine, flavoring and coloring. In this study, we aimed to investigate the effect of extraction methods on the antioxidant activity of saffron (Crocus sativus L.) extracts (SE) and to evaluate the antioxidant performance of SE in vegetable oils. Saffron stigmas were extracted in water, ethanol, methanol, and their combinations using maceration extraction (ME), ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), and the combination of UAE with MAE. The results showed that the sample extracted by methanol/water (50:50) using the combination of UAE with MAE methods had the highest amount of total phenolic content (31.56 mg/g GAE) and antioxidant activity (83.24% inhibition). The extract with the highest antioxidant activity was freeze-dried before incorporation into oil samples. Freeze-dried SE contained trans-crocin-4 and trans-crocin-3 (most abundant constituents), kaempferol, and picrocrocin. Moreover, the addition of SE at 1000 ppm resulted in a significant increase in the oxidative stability of canola (CAO), sunflower (SO), and corn oil (COO).El azafrán contiene compuestos bioactivos con propiedades promotoras de la salud de uso destacado en medicina, saborizante y colorante. En este estudio, nuestro objetivo fue investigar el efecto de los métodos de extracción sobre la actividad antioxidante de los extractos (EA) de azafrán (Crocus sativus L.) y evaluar el rendimiento antioxidante de EA en aceites vegetales. Los estigmas de azafrán se extrajeron en agua, etanol, metanol y sus combinaciones, mediante extracción por maceración (EM), extracción asistida por ultrasonidos (EAU), extracción asistida por microondas (EAM) y la combinación de EAU con EAM. Los resultados mostraron que la muestra extraída con metanol/agua (50:50) usando la combinación de métodos EAU con EAM tuvo la mayor cantidad de fenoles totales (31.56 mg/g GAE) y actividad antioxidante (83.24 % de inhibición). El extracto que incluía la mayor actividad antioxidante se liofilizó antes de incorporarlo a las muestras de aceite. El SE liofilizado contenía trans-crocina-4 y trans-crocina-3 (los constituyentes más abundantes), kaempferol y picrocrocina. Además, la adición de 1000 ppm de EA dio como resultado un aumento significativo en la estabilidad oxidativa del aceite de canola (C), girasol (G) y maíz (M)
Early phases of different types of isolated neutron star
Two Galactic isolated strong X-ray pulsars seem to be in the densest
environments compared to other types of Galactic pulsar. X-ray pulsar
J1846-0258 can be in an early phase of anomalous X-ray pulsars and soft gamma
repeaters if its average braking index is ~1.8-2.0. X-ray pulsar J1811-1925
must have a very large average braking index (n~11) if this pulsar was formed
by SN 386AD. This X-ray pulsar can be in an early phase of evolution of the
radio pulsars located in the region P~50-150 ms and \.{P}~10
s/s of the P-\.{P} diagram. X-ray/radio pulsar J0540-69 seems to be evolving in
the direction to the dim isolated thermal neutron star region on the P-\.{P}
diagram. Possible progenitors of different types of neutron star are also
discussed.Comment: to appear in the International Journal of Modern Physics
Kraus representation of damped harmonic oscillator and its application
By definition, the Kraus representation of a harmonic oscillator suffering
from the environment effect, modeled as the amplitude damping or the phase
damping, is directly given by a simple operator algebra solution. As examples
and applications, we first give a Kraus representation of a single qubit whose
computational basis states are defined as bosonic vacuum and single particle
number states. We further discuss the environment effect on qubits whose
computational basis states are defined as the bosonic odd and even coherent
states. The environment effects on entangled qubits defined by two different
kinds of computational basis are compared with the use of fidelity.Comment: 9 pages, 3 figure
Spraying opened sugar beet pulp silage with oregano essential oil helps to sustain quality and stability
This study was conducted to determine the effects of spraying oregano essential oil (OEO) onto sugar beet pulp silage (SBPS) on silage quality and aerobic stability after opening. A factorial experiment with three replicates of three treatments and four time periods was conducted using laboratory-type plastic silos. The treatments were an untreated control, silage sprayed with 10 ml/75 cm2 OEO, and silage sprayed with 20 ml/75 cm2 OEO. The silages were sampled at 0, 72, 120, and 168 hours after spraying. Temperature, L*, a*, and b* colour values, pH, water-soluble carbohydrates, crude nutrient contents, Fleig score, metabolizable energy (ME) value, lactic acid bacteria (LAB), total live bacteria (TLB), yeast, and mould formation were assessed. Spraying OEO onto SBPS did not affect L*, a*, and b* values, pH, water-soluble carbohydrates, and Fleig score values, but decreased temperature. Spraying OEO onto the silage increased organic matter, ether extract, acid detergent fibre, neutral detergent fibre and acid detergent lignin contents without affecting crude protein, crude fibre, nitrogen free extract, and ME contents. Irrespective of treatment, crude protein, ether extract, acid detergent fibre, acid detergent lignin, nitrogen free extract, Fleig score, and ME contents of silages increased with time after spraying. The OEO spraying reduced LAB, TLB, and yeast contents in silages. In conclusion, OEO spraying onto opened SBPS reduced LAB, TLB, and yeast formation and stopped mould growth up to 72 hours without affecting their nutritional properties, suggesting that OEO could be used to ensure the stability of SBPS.
Keywords: aerobic stability, mould growth, silage microbiology, nutrients, feeding managemen
Formation and diffusion characteristics of Pt clusters on graphene, 1H-MoS2 and 1T-TaS2
Many experiments have revealed that the surfaces of graphene and graphene-like structures can play an active role as a host surface for clusterization of transition metal atoms. Motivated by these observations, we investigate theoretically the adsorption, diffusion and magnetic properties of Pt clusters on three different two-dimensional atomic crystals using first principles density functional theory. We found that monolayers of graphene, molybdenum disulfide (1H-MoS2) and tantalum disulfide (1T-TaS2) provide different nucleation characteristics for Pt cluster formation. At low temperatures, while the bridge site is the most favorable site where the growth of a Pt cluster starts on graphene, top-Mo and top-Ta sites are preferred on 1H-MoS2 and 1T-TaS2, respectively. Ground state structures and magnetic properties of Ptn clusters (n = 2,3,4) on three different monolayer crystal structures are obtained. We found that the formation of Pt2 dimer and a triangle-shaped Pt3 cluster perpendicular to the surface are favored over the three different surfaces. While bent rhombus shaped Pt4 is formed on graphene, the formation of tetrahedral shaped clusters are more favorable on 1H-MoS2 and 1T-TaS2. Our study of the formation of Ptn clusters on three different monolayers provides a gateway for further exploration of nanocluster formations on various surfaces.Flemish Science Foundation (FWO-Vl); Methusalem foundation of the Flemish government; FWO Pegasus Long Marie Curie Fellowshi
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