The emergence of quantum capacitance in epitaxial graphene

We found an intrinsic redistribution of charge arises between epitaxial graphene, which has intrinsically n-type doping, and an undoped substrate. In particular, we studied in detail epitaxial graphene layers thermally elaborated on C-terminated $4H$-$SiC$ ($4H$-$SiC$ ($000{\bar{1}}$)). We have investigated the charge distribution in graphene-substrate systems using Raman spectroscopy. The influence of the substrate plasmons on the longitudinal optical phonons of the $SiC$ substrates has been detected. The associated charge redistribution reveals the formation of a capacitance between the graphene and the substrate. Thus, we give for the first time direct evidence that the excess negative charge in epitaxial monolayer graphene could be self-compensated by the $SiC$ substrate without initial doping. This induced a previously unseen redistribution of the charge-carrier density at the substrate-graphene interface. There a quantum capacitor appears, without resorting to any intentional external doping, as is fundamentally required for epitaxial graphene. Although we have determined the electric field existing inside the capacitor and revealed the presence of a minigap ($\approx 4.3meV$) for epitaxial graphene on $4H$-$SiC$ face terminated carbon, it remains small in comparison to that obtained for graphene on face terminated $Si$. The fundamental electronic properties found here in graphene on $SiC$ substrates may be important for developing the next generation of quantum technologies and electronic/plasmonic devices.Comment: 26 pages, 8 figures, available online as uncorrected proof, Journal of Materials Chemistry C (2016

Predictors of oral hygiene practices among primary school children of Alzintan City, Libya

Background: Good oral health is essential for the well-being and development of young children. Preservation of good oral hygiene in children is important for the development of strong, healthy teeth and to decrease the possibility of dental caries. Oral health is maintained by regular eating and drinking, as well as daily mechanical and pharmacological cleaning of the mouth, for example, brushing teeth with fluoride toothpaste and flossing. The aim of the study is to determine oral hygiene practices among public primary school children in Al Zintan City, Libya. Methodology: A cross sectional study was conducted in three public primary schools in Al Zintan City, Libya. A total of 100 school children aged 9-12 years old participated in the study. Random sampling method was used. Result: Response rate was 92%. There was 53.3% of respondents who had correct practices on oral hygiene, and 46.7% of respondents had incorrect practices on oral hygiene. It was observed that statistically significant association was found between oral hygiene practices and different age groups of respondents (P = 0.04). There was no significant association between oral hygiene practices and other socio demographic characteristics (P > 0.05). No statistically significant association regarding oral hygiene practices between children with high and low knowledge, good and bad dietary habits, positive and negative dental history (P > 0.05). Oral hygiene practices are significantly associated with attitude toward oral hygiene among primary school children of Al Zintan City, Libya (P < 0.01). Conclusion: Correct oral hygiene practices is better among school children of older age. In addition, school children whose father had higher education level have correct oral hygiene practices. Attitude towards oral hygiene is one of the important predictors of oral hygiene practices

Predictions of selected flavour observables within the Standard Model

This letter gathers a selection of Standard Model predictions issued from the metrology of the CKM parameters performed by the CKMfitter group. The selection includes purely leptonic decays of neutral and charged B, D and K mesons. In the light of the expected measurements from the LHCb experiment, a special attention is given to the radiative decay modes of B mesons as well as to the B-meson mixing observables, in particular the semileptonic charge asymmetries a^d,s_SL which have been recently investigated by the D0 experiment at Tevatron. Constraints arising from rare kaon decays are addressed, in light of both current results and expected performances of future rare kaon experiments. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.Comment: 8 pages, 1 figure, 2 tables. Typos corrected and discussion of agreement between SM and data update

Lung function profiles and aerobic capacity of adult cigarette and hookah smokers after 12 weeks intermittent training

Introduction: Pulmonary function is compromised in most smokers. Yet it is unknown whether exercise training improves pulmonary function and aerobic capacity in cigarette and hookah smokers and whether these smokers respond in a similar way as do non-smokers.Aim: To evaluate the effects of an interval exercise training program on pulmonary function and aerobic capacity in cigarette and hookah smokers.Methods: Twelve cigarette smokers, 10 hookah smokers, and 11 non-smokers participated in our exercise program. All subjects performed 30 min of interval exercise (2 min of work followed by 1 min of rest) three times a week for 12 weeks at an intensity estimated at 70% of the subject’s maximum aerobic capacity (VO2max). Pulmonary function was measured using spirometry, and maximum aerobic capacity was assessed by maximal exercise testing on a treadmill before the beginning and at the end of the exercise training program.Results: As expected, prior to the exercise intervention, the cigarette and hookah smokers had significantly lower pulmonary function than the non-smokers. The 12-week exercise training program did not significantly affect lung function as assessed by spirometry in the non-smoker group. However, it significantly increased both forced expiratory volume in 1 second and peak expiratory flow (PEF) in the cigarette smoker group, and PEF in the hookah smoker group. Our training program had its most notable impact on the cardiopulmonary system of smokers. In the non-smoker and cigarette smoker groups, the training program significantly improved VO2max (4.4 and 4.7%, respectively), v VO2max (6.7 and 5.6%, respectively), and the recovery index (7.9 and 10.5%, respectively).Conclusions: After 12 weeks of interval training program, the increase of VO2max and the decrease of recovery index and resting heart rate in the smoking subjects indicated better exercise tolerance. Although the intermittent training program altered pulmonary function only partially, both aerobic capacity and life quality were improved. Intermittent training should be advised in the clinical setting for subjects with adverse health behaviors.Keywords: cigarette smokers; hookah smokers; pulmonary function; aerobic capacity; interval trainin

La baisse de la densité osseuse au cours des maladies inflammatoires chroniques de l’intestin : prévalence et facteurs de risqué

Introduction: La baisse de la densité minérale osseuse représente la principale manifestation osseuse décrite au cours des maladies inflammatoires chroniques de l'intestin. En Tunisie, très peu d'études ont rapportés sa prévalence et ses facteurs de risque. Le but de ce travail était de déterminer la prévalence de la perte osseuse au cours des maladies inflammatoires chroniques de l'intestin, et rechercher ses facteurs de risque. Méthodes: Patients et méthodes: étude ouverte transversale, réalisée de 2007 jusqu'à 2012. Résultats: 146 cas étaient colligés, dont 105 avaient une maladie de Crohn (71,9%) et 41 avaient une rectocolite hémorragique (28,1%). Il s'agissait de 62 hommes et 84 femmes. L'âge moyen était de 33,18 ans. La perte osseuse était trouvée chez 85 patients (58,2%). Il s'agissait d'une ostéopénie dans 57 cas et d'ostéoporose dans 28 cas. Les facteurs de risque de perte osseuse étaient une activité physique limitée  (p=0,013), un indice de masse corporel '20 kg/m2 (p=0,015), une maladie active (p=0,035), l'étendue de l'atteinte intestinale (p=0,006) et une dose cumulée de corticothérapie dépassant 4,5g de Prednisone (p=0,003). Conclusion: La déminéralisation osseuse est une complication fréquente mais non constante. Ceci justifie un dépistage précoce chez les patients à risque, qui pourront ainsi bénéficier d'un traitement substitutif.Key words: Maladie de Crohn, recto-colite hémorragique, densité minérale osseuse, ostéopénie, ostéoporos

Molecular oxygen generation from the reaction of water cations with oxygen atoms

© 2019 Author(s). The oxywater cation (H2OO+), previously shown to form barrierlessly in the gas phase from water cations and atomic oxygen, is proposed here potentially to possess a 2A″ ← 4A″ excitation leading to the H2⋯O2+ complex. This complex could then easily decompose into molecular hydrogen and the molecular oxygen cation. The present quantum chemical study shows that the necessary electronic transition takes place in the range of 1.92 eV (645 nm), in the orange-red range of the visible and solar spectrum, and dissociation of the complex only requires 5.8 kcal/mol (0.25 eV). Such a process for the abiotic, gas phase formation of O2 would only need to be photocatalyzed by visible wavelength photons. Hence, such a process could produce O2 at the mesosphere/stratosphere boundary as climate change is driving more water into the upper atmosphere, in the comet 67P/Churyumov-Gerasimenko where surprisingly high levels of O2 have been observed, or at gas-surface (ice) interfaces