Impurity assisted nanoscale localization of plasmonic excitations in graphene

The plasmon modes of pristine and impurity doped graphene are calculated, using a real-space theory which determines the non-local dielectric response within the random phase approximation. A full diagonalization of the polarization operator is performed, allowing the extraction of all its poles. It is demonstrated how impurities induce the formation of localized modes which are absent in pristine graphene. The dependence of the spatial modulations over few lattice sites and frequencies of the localized plasmons on the electronic filling and impurity strength is discussed. Furthermore, it is shown that the chemical potential and impurity strength can be tuned to control target features of the localized modes. These predictions can be tested by scanning tunneling microscopy experiments.Comment: 5 pages, 4 figure

Minimal physical requirements for crystal growth self-poisoning

Citation: Whitelam, S., Dahal, Y. R., & Schmit, J. D. (2016). Minimal physical requirements for crystal growth self-poisoning. Journal of Chemical Physics, 144(6), 7. doi:10.1063/1.4941457Self-poisoning is a kinetic trap that can impair or prevent crystal growth in a wide variety of physical settings. Here we use dynamic mean-field theory and computer simulation to argue that poisoning is ubiquitous because its emergence requires only the notion that a molecule can bind in two (or more) ways to a crystal; that those ways are not energetically equivalent; and that the associated binding events occur with sufficiently unequal probability. If these conditions are met then the steady-state growth rate is in general a non-monotonic function of the thermodynamic driving force for crystal growth, which is the characteristic of poisoning. Our results also indicate that relatively small changes of system parameters could be used to induce recovery from poisoning. (C) 2016 AIP Publishing LLC

The association of sleep problem, dietary habits and physical activity with weight status of adolescents in Nepal.

Overweight/obesity among adolescents is an emerging public health issue worldwide. However, the evidence on the determinants of body weight status and lifestyle behaviors among Nepalese adolescents is limited. This study aims to explore the sleep characteristics, dietary habits, and physical activity and its association with body mass index (BMI) among Nepalese adolescents. A cross-sectional study was conducted between July and November 2019 among 627 randomly selected adolescents from eight schools located in Kathmandu Metropolitan City, Nepal. A self-administrated structure questionnaire was used to collect the data. Anthropometric measurements (adolescent's BMI), sleep characteristics, dietary habits, and physical activity were assessed using validated tools. Multinomial logistic regression analyses assessed the association between covariates and BMI categories. The statistical significance was considered at p-value < 0.05 and 95% confidence intervals (CIs). The overall prevalence of underweight and overweight/obesity among adolescents was 9.1% (95% CI: 7.1-11.6) and 23.7% (95% CI: 20.6-27.7) respectively. In multinomial logistic regression, adolescents who reported sleep problem compared to those with no such problem (Relative risk ratio (RRR) = 13.37, 95% CI: 7.14-25.05), adolescents who had obstructive sleep apnea (OSA) symptoms (RRR = 3.21, 95% CI:1.31-7.86), who consumed soft drink ≥1 time/day in past 1 months (RRR = 5.44, 95% CI: 2.93-10.10), consumed high-fat dietary ≥2 times/day (RRR = 2.17, 95% CI: 1.18-3.99), and had a habit of junk food consumptions (RRR = 5.71, 95% CI:2.55-12.82), adolescents who had 5-6 h/day sedentary behavior (RRR = 3.21, 95% CI: 1.14-9.09), adolescents from Terai/Madhesi castes (RRR = 2.81, 95% CI: 1.19-6.64) and adolescents whose father was employed (RRR = 2.04, 95% CI: 1.04-3.98) were at increased risk of being overweight/obesity. In contrast, adolescents aged 14-16 years had 71% lower (RRR = 0.29, 95% CI: 0.16-0.52), and adolescents who consumed less than five food groups had 45% lower (RRR = 0.55, 95% CI: 0.31-0.97) risk of being overweight/obesity compared to 12-14 years age groups and consumed more than five food groups respectively. The findings of this study warrant immediate interventions to improve the lifestyle to reduce overweight/obesity among Nepalese adolescents. Creating a conducive environment, both at school and home is essential to encourage adolescents for the adoption of healthy lifestyle behaviors

Quantum Magnetic Properties in Perovskite with Anderson Localized Artificial Spin-1/2

Quantum magnetic properties in a geometrically frustrated lattice of spin-1/2 magnet, such as quantum spin liquid or solid and the associated spin fractionalization, are considered key in developing a new phase of matter. The feasibility of observing the quantum magnetic properties, usually found in geometrically frustrated lattice of spin-1/2 magnet, in a perovskite material with controlled disorder is demonstrated. It is found that the controlled chemical disorder, due to the chemical substitution of Ru ions by Co-ions, in a simple perovskite CaRuO3 creates a random prototype configuration of artificial spin-1/2 that forms dimer pairs between the nearest and further away ions. The localization of the Co impurity in the Ru matrix is analyzed using the Anderson localization formulation. The dimers of artificial spin-1/2, due to the localization of Co impurities, exhibit singlet-to-triplet excitation at low temperature without any ordered spin correlation. The localized gapped excitation evolves into a gapless quasi-continuum as dimer pairs break and create freely fluctuating fractionalized spins at high temperature. Together, these properties hint at a new quantum magnetic state with strong resemblance to the resonance valence bond system.Comment: 8 pages, 6 figure

INDOOR RADON SURVEY IN NEPAL USING PASSIVE TECHNIQUE SOLID STATE NUCLEAR TRACK DETECTOR

Context: It has been proved from many epidemiological studies that the inhalation of the radioactive, inert gas radon (222Rn) is the main cause of lungs cancer after smoking.&nbsp;Objective: The survey was conducted to estimate the indoor radon concentration, the annual effective dose rate and the annual dose equivalent rate to the lung.&nbsp;Material and Methods: Altogether 50 dwellings were chosen randomly at 5 different districts of Nepal. The dosimetric measurements were carried out over a period of 3 months using time-integrated passive radon detectors, CR-39 based on type II Solid State Nuclear Track Detector (SSNTD) technique. The type of houses was concrete with plastered walls and mud house.&nbsp;Results: The minimum concentration of radon in the study areas was found to be &lt;20Bq.m-3&nbsp;and the maximum concentration was 110±20Bq.m-3. Also the corresponding values of annual effective dose and annual equivalent dose to the lung respectively varied from &lt;0.60 to 3.30mSv.y-1&nbsp;and 0.16—10-7&nbsp;to 0.88×10-7&nbsp;Sv.y-1. The uncertainty was measured at 95% confidence level.&nbsp;Conclusion: The indoor radon concentration varies considerably with the ventilation condition, lifestyle of the people, construction of the dwellings and climate of the areas. The measurements show that the radon concentrations were found to be well below the reference levels of ICRP. KEYWORDS:&nbsp;Indoor Radon; Annual Effective Dose; CR-39; Ventilation Condition; Dwelling