On the inner Double-Resonance Raman scattering process in bilayer graphene

The dispersion of phonons and the electronic structure of graphene systems can be obtained experimentally from the double-resonance (DR) Raman features by varying the excitation laser energy. In a previous resonance Raman investigation of graphene, the electronic structure was analyzed in the framework of the Slonczewski-Weiss-McClure (SWM) model, considering the outer DR process. In this work we analyze the data considering the inner DR process, and obtain SWM parameters that are in better agreement with those obtained from other experimental techniques. This result possibly shows that there is still a fundamental open question concerning the double resonance process in graphene systems.Comment: 5 pages, 3 figure

Percolation model for structural phase transitions in Li1−x_{1-x}Hx_xIO3_3 mixed crystals

A percolation model is proposed to explain the structural phase transitions found in Li$_{1-x}$H$_x$IO$_3$ mixed crystals as a function of the concentration parameter $x$. The percolation thresholds are obtained from Monte Carlo simulations on the specific lattices occupied by lithium atoms and hydrogen bonds. The theoretical results strongly suggest that percolating lithium vacancies and hydrogen bonds are indeed responsible for the solid solution observed in the experimental range $0.22 < x < 0.36$.Comment: 4 pages, 2 figure

Low frequency Raman studies of multi-wall carbon nanotubes: experiments and theory

In this paper, we investigate the low frequency Raman spectra of multi-wall carbon nanotubes (MWNT) prepared by the electric arc method. Low frequency Raman modes are unambiguously identified on purified samples thanks to the small internal diameter of the MWNT. We propose a model to describe these modes. They originate from the radial breathing vibrations of the individual walls coupled through the Van der Waals interaction between adjacent concentric walls. The intensity of the modes is described in the framework of bond polarization theory. Using this model and the structural characteristics of the nanotubes obtained from transmission electron microscopy allows to simulate the experimental low frequency Raman spectra with an excellent agreement. It suggests that Raman spectroscopy can be as useful regarding the characterization of MWNT as it is in the case of single-wall nanotubes.Comment: 4 pages, 2 eps fig., 2 jpeg fig., RevTex, submitted to Phys. Rev.

Characterizing top gated bilayer graphene interaction with its environment by Raman spectroscopy

In this work we study the behavior of the optical phonon modes in bilayer graphene devices by applying top gate voltage, using Raman scattering. We observe the splitting of the Raman G band as we tune the Fermi level of the sample, which is explained in terms of mixing of the Raman (Eg) and infrared (Eu) phonon modes, due to different doping in the two layers. We theoretically analyze our data in terms of the bilayer graphene phonon self-energy which includes non-homogeneous charge carrier doping between the graphene layers. We show that the comparison between the experiment and theoretical model not only gives information about the total charge concentration in the bilayer graphene device, but also allows to separately quantify the amount of unintentional charge coming from the top and the bottom of the system, and therefore to characterize the interaction of bilayer graphene with its surrounding environment

Dietary inflammatory index and prevalence of overweight and obesity in Brazilian graduates from the Cohort of Universities of Minas Gerais (CUME project)

Objectives: The aim of this study was to evaluate the independent association of the dietary inflammatory index (DII ) score with overweight and obesity in Brazilian participants of the Cohort of Universities of Minas Gerais (CUME project). Methods: This was a cross-sectional study consisting of 3,151 graduates and postgraduates (2197 women) with a mean (SD) age of 36.3 y (§9.4 y). Sociodemographic characteristics, lifestyle, and anthropometric data were assessed via online self-reported questionnaire. Additionally, a validated food frequency questionnaire with 144 food items was used to generate energy-adjusted DII (E-DIITM) scores, which evaluated the inflammatory potential of the diet. Results: The prevalence of overweight and obesity were 28.2% and 11%, respectively. Participants in the highest E-DII quartile (most proinflammatory diet) were more likely to be smokers/former smokers; sedentary; and consumers of red and ultra-processed meats, fats and oils (excluding olive oil), bottled fruit juices and soft drinks, sugars, sweets, and higher overall caloric intake, compared with the first quartile of E-DII. Both men and women in the fourth E-DII quartile had the highest prevalence of overweight and obesity (prevalence ratio [PR], 1.35; 95% confidence interval [CI], 1.14 1.59 and PR, 1.97; 95% CI, 1.20 3.22, respectively, in men; PR, 1.38; 95% CI, 1.17 to 1.65 and PR, 1.95; 95% CI, 1.31 2.90, respectively, in women). Conclusion: The most proinflammatory dietary pattern was associated with a higher prevalence of overweight and obesity and other unhealthy lifestyles including being sedentary, smoking, and consuming a obesogenic diet

Outdoor Field Experience with Autonomous RPC Based Stations

In the last two decades Resistive Plate Chambers were employed in the Cosmic Ray Experiments COVER-PLASTEX and ARGO/YBJ. In both experiments the detectors were housed indoors, likely owing to gas distribution requirements and the need to control environment variables that directly affect RPCs operational stability. But in experiments where Extended Air Shower (EAS) sampling is necessary, large area arrays composed by dispersed stations are deployed, rendering this kind of approach impossible. In this situation, it would be mandatory to have detectors that could be deployed in small standalone stations, with very rare opportunities for maintenance, and with good resilience to environmental conditions. Aiming to meet these requirements, we started some years ago the development of RPCs for Autonomous Stations. The results from indoor tests and measurements were very promising, both concerning performance and stability under very low gas flow rate, which is the main requirement for Autonomous Stations. In this work we update the indoor results and show the first ones concerning outdoor stable operation. In particular, a dynamic adjustment of the high voltage is applied to keep gas gain constant.Peer Reviewe

Relationship between body image disturbance and incidence of depression: the SUN prospective cohort.

Background: Body image disturbance is an increasing probleminWestern societies and is associated with a number of mental health outcomes including anorexia, bulimia, bodydysmorphia, and depression. The aim of this study was to assess the association between body image disturbance and the incidence of depression. Methods: This study included 10,286 participants from a dynamic prospective cohort of Spanish university graduates,whowere followed-up for a median period of 4.2 years (Seguimiento Universidad de Navarra – the SUN study). The key characteristic of the study is the permanently open recruitment that started in 1999. The baseline questionnaire included information about body mass index (BMI) and the nine figure schemes that were used to assess body size perception. These variables were grouped according to recommended classifications and the difference between BMI and body size perception was considered as a proxy of body image disturbance. A subject was classified as an incident case of depression if he/she was initially free of depression and reported a physician-made diagnosis of depression and/or the use of antidepressant medication in at least one of the follow-up questionnaires. The association between body image disturbance and the incidence of depression was estimated by calculating the multivariable adjusted Odds Ratio (OR) and its 95% Confidence Interval (95% CI), using logistic regression models. Results: The cumulative incidence of depression during follow-up in the cohort was 4.8%. Men who underestimated their body size had a high percentage of overweight and obesity (50.1% and 12.6%, respectively), whereas women who overestimated their body size had a high percentage of underweight (87.6%). The underestimation exhibited a negative association with the incidence of depression among women (OR: 0.72, 95% CI: 0.54 – 0.95), but this effect disappeared after adjusting for possible confounding variables. The proportion of participants who correctly perceived their body size was high (53.3%) and gross misperception was seldom found, with most cases selecting only one silhouette below (42.7%) or above (2.6%) their actual BMI. Conclusion: We found no association between body image disturbance and subsequent depression in a cohort of university graduates in Spain

Density functional theory calculations of the carbon ELNES of small diameter armchair and zigzag nanotubes: core-hole, curvature and momentum transfer orientation effects

We perform density functional theory calculations on a series of armchair and zigzag nanotubes of diameters less than 1nm using the all-electron Full-Potential(-Linearised)-Augmented-Plane-Wave (FPLAPW) method. Emphasis is laid on the effects of curvature, the electron beam orientation and the inclusion of the core-hole on the carbon electron energy loss K-edge. The electron energy loss near-edge spectra of all the studied tubes show strong curvature effects compared to that of flat graphene. The curvature induced $\pi-\sigma$ hybridisation is shown to have a more drastic effect on the electronic properties of zigzag tubes than on those of armchair tubes. We show that the core-hole effect must be accounted for in order to correctly reproduce electron energy loss measurements. We also find that, the energy loss near edge spectra of these carbon systems are dominantly dipole selected and that they can be expressed simply as a proportionality with the local momentum projected density of states, thus portraying the weak energy dependence of the transition matrix elements. Compared to graphite, the ELNES of carbon nanotubes show a reduced anisotropy.Comment: 25 pages, 15 figures, revtex4 submitted for publication to Phys. Rev.

Association between yogurt consumption and the risk of metabolic syndrome over 6 years in the SUN study

Background: The role of yogurt consumption in the development of metabolic syndrome (MetS) is not fully understood and the available epidemiologic evidence is scarce. The aim of our study was to assess the association between total, whole-fat, or low-fat yogurt consumption and the risk of developing MetS. Methods: Yogurt consumption was assessed at baseline through a 136-item validated FFQ. MetS was defined following the harmonized definition for MetS according to the AHA and the IDF criteria. Logistic regression models were used. Results: During the first 6-y of follow-up of the SUN cohort, 306 incident cases of MetS were identified. Frequent consumption [≥875 g/week (≥7 servings/week) versus ≤ 250 g/week (2 servings/week)] of total, whole-fat and low-fat yogurt consumption showed non-significant inverse associations with MetS [OR = 0.84 (95% CI: 0.60-1.18); 0.98 (95% CI: 0.68-1.41); and 0.63 (95% CI: 0.39-1.02) respectively]. Only one component of the MetS, central adiposity, was inversely associated with total and whole-fat yogurt consumption [OR = 0.85 (95% CI: 0.74-0.98) and 0.85 (95% CI: 0.73-0.99) respectively]. In the joint assessment of exposure to total yogurt consumption and fruit consumption, those in the highest category of total yogurt consumption, and having a high fruit consumption (above the median ≥264.5 g/day) exhibited a significantly lower risk of developing MetS [OR = 0.61 (95% CI: 0.38-0.99)] compared with those in the lowest category of total yogurt consumption and had fruit consumption below the study median. Conclusion: No significant association between yogurt consumption and MetS was apparent. Only one component out of the 5 MetS criteria, central adiposity, was inversely associated with high yogurt consumption. The combination of high consumption of both yogurt and fruit was inversely associated with the development of MetS

Snacking between main meals is associated with a higher risk of metabolic syndrome in a Mediterranean cohort: the SUN Project (Seguimiento Universidad de Navarra)

OBJECTIVE: To evaluate the association of snacking between main meals with the risk of developing metabolic syndrome. DESIGN: A dynamic prospective cohort study (the SUN Project; Seguimiento Universidad de Navarra). Snack consumption was evaluated using the question: 'Do you have the habit of snacking between main meals?' Metabolic syndrome was defined according to the updated harmonizing criteria. We estimated multivariable-adjusted relative risks (RR) of metabolic syndrome and their 95 % confidence intervals using Poisson regression models. An exploratory factor analysis was also used to identify patterns of snacking. SETTING: University of Navarra, Spain. SUBJECTS: The study included 6851 university graduates, initially free of metabolic syndrome, and followed-up them for a median of 8·3 years. RESULTS: Among our participants, 34·6% reported usual snacking between main meals. The cumulative incidence of metabolic syndrome was 5·1 % (9·5% among men and 2·8% among women). Snacking between main meals was significantly associated with higher risk for developing metabolic syndrome after multivariable adjustment (RR=1·44; 95%CI 1·18, 1·77). Higher adherence to an 'unhealthy snacking pattern' was also independently associated with increased incidence of metabolic syndrome (fourth quartile of adherence compared with non-snacking: RR=1·68; 95% CI 1·23, 2·29; P for trend <0·001). CONCLUSIONS: Our findings suggest that avoidance of snacking between main meals can be included among the preventive approaches to reduce the risk of metabolic syndrome development, especially when snacks contain foods of poor nutritional quality