5,243 research outputs found
Adsorption of common solvent molecules on graphene and MoS from first-principles
Solvents are an essential element in the production and processing of
two-dimensional (2D) materials. For example, the liquid phase exfoliation of
layered materials requires a solvent to prevent the resulting monolayers from
re-aggregating, while solutions of functional atoms and molecules are routinely
used to modify the properties of the layers. It is generally assumed that these
solvents do not interact strongly with the layer and so their effects can be
neglected. Yet experimental evidence has suggested that explicit atomic-scale
interactions between the solvent and layered material may play a crucial role
in exfoliation and cause unintended electronic changes in the layer. Little is
known about the precise nature of the interaction between the solvent molecules
and the 2D layer. Here, we use density functional theory calculations to
determine the adsorption configuration and binding energy of a variety of
common solvent molecules, both polar and non-polar, on two of the most popular
2D materials, namely graphene and MoS. We show that these molecules are
physisorbed on the surface with negligible charge transferred between them. We
find that the adsorption strength of the different molecules is independent of
the polar nature of the solvent. However, we show the molecules induce a
significant charge rearrangement at the interface after adsorption as a result
of polar bonds in the molecule.Comment: 8 pages, 6 figure
Effect of age and nutrient restriction pre partum on beef suckler cow serum immunoglobulin concentrations, colostrum yield, composition and immunoglobulin concentration and immune status of their progeny
peer-reviewedThe effect of cow age (multiparous (MP) v. primiparous (PP)) and nutritional restriction
pre partum (grass silage ad libitum v. straw only ad libitum for the last 15 (s.d. 3.3)
days of gestation) on cow serum immunoglobulin (Ig) concentration, on colostrum yield, composition and Ig concentration and on calf serum Ig concentrations (at ~8 and 48 h post partum) using spring-calving Limousin Holstein-Friesian cows and their progeny was studied over 3 years. The method of colostrum administration (stomach tube vs. assisted suckling within 1 h post partum) on calf immune status was also investigated. When feeding colostrum the target was to give each calf 50 mL per kg birthweight via stomach tube. Colostrum yield and Ig concentration were measured
following administration of oxytocin and hand-milking of half (Experiments 1 and
2) or the complete udder (Experiment 3). Following an 8-h period after birth during
which suckling was prevented a further colostrum sample was obtained. There was no
significant difference in first milking colostrum Ig subclass concentrations between the
within-quarter fractions or between the front and rear quarters of the udder in either
MP or PP cows. Colostrum Ig subclass concentrations at second milking were 0.46 to
0.65 of that at first milking. Compared to MP cows offered silage, colostrum yield and
the mass of colostrum IgG1, IgG2, IgM, IgA and total Ig produced was lower (P < 0.001)
for PP cows and the mass of IgG1, IgM and total Ig produced was lower (P < 0.05) for MP cows offered straw. Calves from PP cows and MP cows offered straw had significantly
lower serum IgG1 and total Ig concentrations at 48 h post partum than calves
from MP cows offered silage but there was no difference (P > 0.05) between colostrum
feeding methods. In conclusion, calves from PP cows and MP cows offered straw had a
lower humoral immune status than those from MP cows offered grass silage
Effect of suckler cow genotype on cow serum immunoglobulin (Ig) levels, colostrum yield, composition and Ig concentration and subsequent immune status of their progeny
peer-reviewedSurvival of the neonatal calf is largely dependent on humoral immunity. The objective of three experiments reported here was to compare cow serum immunoglobulin (Ig) concentration, colostrum yield, composition and Ig concentration and calf serum Ig concentrations at ~8- and 48-h post partum of spring-calving Charolais (C) and Beef ×
Holstein-Friesian (BF) cows and their progeny. Cows were individually offered a restricted
allowance of grass silage pre partum in Experiments 1 and 2 and silage ad libitum in
Experiment 3. In Experiment 1 calves were assisted to suckle after parturition. In
Experiments 2 and 3, colostrum yield and Ig concentration were measured following
administration of oxytocin and hand milking of half or the complete udder, respectively. It
was intended to feed each calf 50 ml (Experiment 2) or 40 ml (Experiment 3) of colostrum
per 1 kg birth weight via stomach tube. Following an 8-h period, during which suckling
was prevented, a further colostrum sample was obtained. The decrease in cow serum IgG1
concentration pre partum was greater (P < 0.05) in BF cows than C cows. In comparison
to BF cows, C cows had a lower colostrum yield (P < 0.001) and the colostrum had lower
concentrations of dry matter (P < 0.01), crude protein (P < 0.05), fat (P < 0.05), IgG1 (P
= 0.06), IgG2 (P < 0.01), IgM (P < 0.01) and Ig total (P < 0.05). The mass of IgG1, IgG2,
IgM, IgA and Ig total in the colostrum produced was significantly lower for C cows than
BF cows. Calves from C cows had significantly lower serum Ig subclass concentration at
48-h post partum than calves from BF cows. In conclusion, due to a lower Ig mass produced
by their dams, calves from C cows had a lower humoral immune status than those
from BF cowsTeagasc Walsh Fellowship Programm
Effect of fumaric acid, calcium formate and mineral levels in diets on the intake and growth performance of newly weaned pigs
peer-reviewedThe weaned pig has limited ability to acidify its stomach contents. The objective of this study (comprising three experiments) was to examine the effect of feeding diets
containing fumaric acid (FA), calcium formate (CF) or diets of low acid binding capacity (ABC) on post-weaning pig performance. In all three experiments, pigs (10 per treatment) were weaned at 19 to 24 days, blocked on sex and weight and assigned at random to one of six treatments. In Experiment 1, treatments were: (1) control diet, (2) control 20 g/kg FA, (3) control 15 g/kg CF, (4) low Ca (2.8 g/kg) and P (5.1 g/kg) (LCaP) diet for seven days followed by the control diet, (5) LCaP diet for seven days followed by control 20 g/kg FA, and (6) LCaP diet for seven days followed by control 15 g/kg CF. In Experiment 2, treatments were: (1) control diet, (2) control 20 g/kg FA, (3) control 15 g/kg CF, (4) LCaP diet for 14 days followed by the control diet, (5) LCaP diet for 14 days followed by control 20 g/kg FA, and (6) LCaP diet for seven days followed by control diet. In Experiment 3, treatments were: (1) high Ca (HC) diet (12 g/kg), (2) medium Ca (MC) diet (9 g/kg), (3) low Ca (LC) diet (6 g/kg), (4) HC 20 g/kg FA, (5) MC 20 g/kg FA, and (6) LC 20 g/kg FA. Pigs were individually fed for 26 days. In Experiment 1, CF tended to depress daily feed intake (DFI) in the final two weeks (691 v. 759 and 749, (s.e. 19) g/day, P = 0.07) and overall average daily gain (322 v. 343 and 361 (s.e. 11) g/day, P = 0.09) compared with the control and FA supplemented diets, respectively. Feeding diets with LCaP for seven days post
weaning increased DFI (208 v. 178, (s.e. 8) g/day, P < 0.01) in week 1 and tended to
improve feed conversion rate in the first two weeks (1.65 v. 1.85, s.e. 0.10, P = 0.09). In Experiment 2, treatment had no significant effect on pig performance but feed conversion rate in weeks three and four was improved for Treatment 5 compared with
Treatment 4 (1.30 v. 1.39 (s.e. 0.06) g/g, P < 0.01). In experiment 3, FA increased (P <
0.05) pig weight at day 14 (8.4 v. 7.7 (s.e. 0.2) kg) and feed intake in weeks one and two
(223 v. 251, (s.e. 9) g/day). It is concluded that CF did not improve performance but reducing diet ABC or including FA in the diet did improve performance
Coexistance of giant tunneling electroresistance and magnetoresistance in an all-oxide magnetic tunnel junction
We demonstrate with first-principles electron transport calculations that
large tunneling magnetoresistance (TMR) and tunneling electroresistance (TER)
effects can coexist in an all-oxide device. The TMR originates from the
symmetry-driven spin filtering provided by the insulating BaTiO3 barrier to the
electrons injected from SrRuO3. In contrast the TER is possible only when a
thin SrTiO3 layer is intercalated at one of the SrRuO3/BaTiO3 interfaces. As
the complex band-structure of SrTiO3 has the same symmetry than that of BaTiO3,
the inclusion of such an intercalated layer does not negatively alter the TMR
and in fact increases it. Crucially, the magnitude of the TER also scales with
the thickness of the SrTiO3 layer. The SrTiO3 thickness becomes then a single
control parameter for both the TMR and the TER effect. This protocol offers a
practical way to the fabrication of four-state memory cells
Large bias-dependent magnetoresistance in all-oxide magnetic tunnel junctions with a ferroelectric barrier
All-oxide magnetic tunnel junctions (MTJs) incorporating functional materials
as insulating barriers have the potential of becoming the founding technology
for novel multi-functional devices. We investigate, by first-principles density
functional theory, the bias-dependent transport properties of an all-oxide
SrRuO3/BaTiO3/SrRuO3 MTJ. This incorporates a BaTiO3 barrier which can be found
either in a non-ferroic or in a ferroelectric state. In such an MTJ not only
can the tunneling magnetoresistance reach enormous values, but also, for
certain voltages, its sign can be changed by altering the barrier electric
state. These findings pave the way for a new generation of
electrically-controlled magnetic sensors.Comment: 4 pages, 5 figure
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