Effect of hydrogen adsorption on the quasiparticle spectra of graphene

We use the non-interacting tight-binding model to study the effect of isolated hydrogen adsorbates on the quasiparticle spectra of single-layer graphene. Using the Green's function approach, we obtain analytic expressions for the local density of states and the spectral function of hydrogen-doped graphene, which are also numerically evaluated and plotted. Our results are relevant for the interpretation of scanning tunneling microscopy and angle-resolved photoemission spectroscopy data of functionalized graphene.Comment: 4 pages, 3 figures, minor corrections to tex

Inhibition of adrenal steroidogenesis and heat shock protein 70 induction in neonatally feed restricted broiler chickens under heat stress condition.

This study was conducted to determine the roles of plasma corticosterone concentration (CORT) and heat shock protein 70 (Hsp70) expression in the acquisition of thermotolerance in broiler chickens subjected to neonatal feed restriction.Equal numbers of chicks were divided into one of the four feeding regimens: ad libitum (control), 60% feed restriction on days 4, 5 and 6 (FR60), 60% feed restriction on days 4, 5 and 6 + 1500 mg/kg metyrapone (FR60M) and 60% feed restriction on days 4, 5 and 6 + 1500 mg/kg quercetin (FR60Q). From 35 to 42 days of age, all birds were exposed to 37 ± 1°C and 70-80% relative humidity for 3 h/day. The neonatal feed restriction elevated heterophil to lymphocyte ratios (HLR), CORT and Hsp70 expression in FR60 chicks. The FR60M and FR60Q treatments suppressed CORT and Hsp70 expression, respectively. Subjecting birds to FR60 improved feed conversion ratio (FCR) and body weight gain, and reduced HLR when compared to controls in response to heat exposure. Following heat exposure, the HLR and weight gain of FR60M and control birds were not significantly different. Although FR60Q chickens had improved FCR and weight gain, their HLR were similar to controls following heat exposure. The control birds had significantly lower CORT than other groups in response to heat exposure. The Hsp70 expression of FR60 and FR60Q birds was lower than those of control and FR60M groups. It is concluded that Hsp70 expression didnot appear to be a major indicator of thermotolerance acquisitionin neonataly manipulated broiler chickens

High-fat diets rich in n-3 polyunsaturated fatty acids delay onset of insulin resistance in rats

Insulin resistance is a growing worldwide syndrome that predispose human to a number of chronic diseases such as diabetes and cardiovascular diseases. Various studies have indicated that insulin action is highly influenced by diet compositions particularly dietary fat intake and proportion of n-3 and n-6 Polyunsaturated Fatty Acids (PUFA). The current study was designed to assess the influence of High Fat Diet (HFD) with different n-6: n-3 Fatty Acid Ratios (FAR) on insulin sensitivity, plasma triacylglycerol (TAG) and lipoprotein profile. Forty male Sprague-Dawley rats were randomly allocated into four groups and received the isocaloric high fat diets enriched with either high n-6: n-3 fatty acid ratio (HFAR), medium n-6: n-3 fatty acid ratio (MFAR), low n-6: n-3 fatty acid ratio (LFAR) and compared with control rats fed standard chow (CTRL). The plasma insulin level of HFAR fed rats manifested significantly (P<0.05) higher concentration in most of the time points compared to the other groups. The corresponding insulin AUC (ng/L/120min) and insulin sensitivity index of HFAR fed rats appeared to be significantly higher (P<0.05) than CTRL (335.5±38.5), LFAR (273.7±37.6) and MFAR (265.9±21.7) groups. Blood lipid profile were found to be healthier in the LFAR and MFAR supplemented groups with significantly (P<0.05) lower total cholesterol and TAG levels. This study showed the possible protective effect against insulin resistance when low n-6: n-3 fatty acid ratio in high fat diets are applied in a rat model

Strained graphene: tight-binding and density functional calculations

We determine the band structure of graphene under strain using density functional calculations. The ab-initio band strucure is then used to extract the best fit to the tight-binding hopping parameters used in a recent microscopic model of strained graphene. It is found that the hopping parameters may increase or decrease upon increasing strain, depending on the orientation of the applied stress. The fitted values are compared with an available parametrization for the dependence of the orbital overlap on the distance separating the two carbon atoms. It is also found that strain does not induce a gap in graphene, at least for deformations up to 10%

Changes in blood parameters and electroencephalogram of cattle as affected by different stunning and slaughter methods in cattle

The present study aimed to provide a comparative analysis of the effects of penetrative stunning, non-penetrative stunning and post-slaughter stunning on biochemical parameters and electroencephalogram (EEG) associated with stress in heifers and steers. Ten animals were assigned to each of the following four treatment groups: (1) animals were subjected to conventional halal slaughter (a clean incision through the structures on the ventral neck at the approximate level of vertebrae C2–C3 – the trachea, oesophagus, carotid arteries and jugular veins) and post-cut penetrating mechanical stun within 10–20 s of the halal cut (U); (2) high-power non-penetrating mechanical stunning using a mushroom-headed humane killer, followed by conventional halal slaughter (HPNP); (3) low-power non-penetrating mechanical percussive stunning using a mushroom-headed humane killer, followed by conventional halal slaughter (LPNP); and (4) penetrative stunning using a captive-bolt pistol humane killer, followed by conventional halal slaughter (P). For each animal, blood samples and electroencephalogram recordings were taken before stunning, post-stunning (if applicable) and post-slaughter, and plasma concentrations of cortisol, adrenocorticotrophic hormone (ACTH), adrenaline, noradrenaline and β-endorphin were determined. Irrespective of the stunning method, except for percentage change in plasma concentrations of noradrenaline, the values of blood parameters attained before and after stunning were not significantly different. The plasma noradrenaline concentration of the HPNP animals was significantly elevated following stunning. Following slaughter, the percentage change of plasma ACTH concentration in the P animals was significantly elevated. Neither stunning method nor sampling time had a significant effect on plasma β-endorphin concentration. On the basis of the EEG results, penetrative stunning seemed to be better in maximising the possibility of post-stunning insensibility, whereas U animals appeared to demonstrate an evident increase in EEG activity which is consistent with the presence of post-slaughter noxious stimuli associated with tissue cut and injury. The U animals had consistently higher, if not the highest, RMS values than did other stunned animals. This indicates a degree of EEG changes associated with stress and pain. On the basis of EEG data, our results suggested that penetrative stunning would be the most reliable method of ensuring insensibility and minimising pain. However, at slaughter, the P animals showed a dramatic elevation in the percentage change of circulating ACTH, suggesting physiological stress response. On a cautionary note, the results are not unequivocal, and it may be that the range of analyses available to researchers at this point of time are not sufficiently specific to allow definitive conclusions to be drawn

Energy gap opening in submonolayer lithium on graphene: Local density functional and tight-binding calculations

The adsorption of an alkali-metal submonolayer on graphene occupying every third hexagon of the honeycomb lattice in a commensurate $(\sqrt{3}\times\sqrt{3})R30^\circ$ arrangement induces an energy gap in the spectrum of graphene. To exemplify this type of band gap, we present \textit{ab initio} density functional theory calculations of the electronic band structure of C$_6$Li. An examination of the lattice geometry of the compound system shows the possibility that the nearest-neighbor hopping amplitudes have alternating values constructed in a Kekul\'e-type structure. The band structure of the textured tight-binding model is calculated and shown to reproduce the expected band gap as well as other characteristic degeneracy removals in the spectrum of graphene induced by lithium adsorption. More generally we also deduce the possibility of energy gap opening in periodic metal on graphene compounds C$_x$M if $x$ is a multiple of 3.Comment: 7 pages, 5 figures, published versio

Comment on "Band structure engineering of graphene by strain: First-principles calculations"

In their first-principles calculations of the electronic band structure of graphene under uniaxial strain, Gui, Li, and Zhong [Phys. Rev. B \textbf{78}, 075435 (2008)] have found opening of band gaps at the Fermi level. This finding is in conflict with the tight-binding description of graphene which is closed gap for small strains. In this Comment, we present first-principles calculations which refute the claim that strain opens band gaps in graphene.Comment: published versio

Strain- and Adsorption-Dependent Electronic States and Transport or Localization in Graphene

The chapter generalizes results on influence of uniaxial strain and adsorption on the electron states and charge transport or localization in graphene with different configurations of imperfections (point defects): resonant (neutral) adsorbed atoms either oxygen- or hydrogen-containing molecules or functional groups, vacancies or substitutional atoms, charged impurity atoms or molecules, and distortions. To observe electronic properties of graphene-admolecules system, we applied electron paramagnetic resonance technique in a broad temperature range for graphene oxides as a good basis for understanding the electrotransport properties of other active carbons. Applied technique allowed observation of possible metal-insulator transition and sorption pumping effect as well as discussion of results in relation to the granular metal model. The electronic and transport properties are calculated within the framework of the tight-binding model along with the Kubo-Greenwood quantum-mechanical formalism. Depending on electron density and type of the sites, the conductivity for correlated and ordered adsorbates is found to be enhanced in dozens of times as compared to the cases of their random distribution. In case of the uniaxially strained graphene, the presence of point defects counteracts against or contributes to the band-gap opening according to their configurations. The band-gap behaviour is found to be nonmonotonic with strain in case of a simultaneous action of defect ordering and zigzag deformation. The amount of localized charge carriers (spins) is found to be correlated with the content of adsorbed centres responsible for the formation of potential barriers and, in turn, for the localization effects. Physical and chemical states of graphene edges, especially at a uniaxial strain along one of them, play a crucial role in electrical transport phenomena in graphene-based materials.Comment: 16 pages, 10 figure