Electron spin resonance study of puff-resolved free radical formation in mainstream cigarette smoke

Puff-by-puff resolved gas phase free radicals were measured in mainstream smoke from Kentucky 2R4F reference cigarettes using ESR spectroscopy. Three spin-trapping reagents were evaluated: PBN, DMPO and DEPMPO. Two procedures were used to collect gas phase smoke on a puff-resolved basis: i) the accumulative mode, in which all the gas phase smoke up to a particular puff was bubbled into the trap (i.e., the 5th puff corresponded to the total smoke from the 1st to 5th puffs). In this case, after a specified puff, an aliquot of the spin trap was taken and analysed; or, ii) the individual mode, in which the spin trap was analysed and then replaced after each puff. Spin concentrations were determined by double-integration of the first derivative of the ESR signal. This was compared with the integrals of known standards using the TEMPO free radical. The radicals trapped with PBN were mainly carbon-centred, whilst the oxygen-centred radicals were identified with DMPO and DEPMPO. With each spin trap, the puff-resolved radical concentrations showed a characteristic pattern as a function of the puff number. Based on the spin concentrations, the DMPO and DEPMPO spin traps showed better trapping efficiencies than PBN. The implication for gas phase free radical analysis is that a range of different spin traps should be used to probe complex free radical reactions in cigarette smoke

Scaling in long term data sets of geomagnetic indices and solar wind ϵ as seen by WIND spacecraft

We study scaling in fluctuations of the geomagnetic indices (AE, AU, and AL) that provide a measure of magnetospheric activity and of the ε parameter which is a measure of the solar wind driver. Generalized structure function (GSF) analysis shows that fluctuations exhibit self-similar scaling up to about 1 hour for the AU index and about 2 hours for AL, AE and ε when the most extreme fluctuations over 10 standard deviations are excluded. The scaling exponents of the GSF are found to be similar for the three AE indices, and to differ significantly from that of ε. This is corroborated by direct comparison of their rescaled probability density functions

A sandpile model with tokamak-like enhanced confinement phenomenology

Confinement phenomenology characteristic of magnetically confined plasmas emerges naturally from a simple sandpile algorithm when the parameter controlling redistribution scalelength is varied. Close analogues are found for enhanced confinement, edge pedestals, and edge localised modes (ELMs), and for the qualitative correlations between them. These results suggest that tokamak observations of avalanching transport are deeply linked to the existence of enhanced confinement and ELMs.Comment: Manuscript is revtex (latex) 1 file, 7 postscript figures Revised version is final version accepted for publication in PRL Revisions are mino

A sampling method for quantifying the information content of IASI channels

There is a vast amount of information about the atmosphere available from instruments on board satellites. One example is the Infrared Atmospheric Sounding Interferometer (IASI) instrument, which measures radiances emitted from Earth’s atmosphere and surface in 8461 channels. It is difficult to transmit, store, and assimilate such a large amount of data. A practical solution to this has been to select a subset of a few hundred channels based on those that contain the most useful information. Different measures of information content for objective channel selection have been suggested for application to variational data assimilation. These include mutual information and the degrees of freedom for signal. To date, the calculation of these measures of information content has been based on the linear theory that is at the heart of operational variational data assimilation. However, the retrieval of information about the atmosphere from the satellite radiances can be highly nonlinear. Here, a sampling method for calculating the mutual information that is free from assumptions about the linearity of the relationship between the observed radiances and the state variables is examined. It is found that large linearization errors can indeed lead to large discrepancies in the value of mutual information. How this new estimate of information content can be used in channel selection is addressed, with particular attention given to the efficiency of the new method. It is anticipated that accounting for the nonlinearity in the channel selection will be beneficial when using nonlinear data assimilation methods currently in development

#Bieber + #Blast = #BieberBlast: Early Prediction of Popular Hashtag Compounds

Compounding of natural language units is a very common phenomena. In this paper, we show, for the first time, that Twitter hashtags which, could be considered as correlates of such linguistic units, undergo compounding. We identify reasons for this compounding and propose a prediction model that can identify with 77.07% accuracy if a pair of hashtags compounding in the near future (i.e., 2 months after compounding) shall become popular. At longer times T = 6, 10 months the accuracies are 77.52% and 79.13% respectively. This technique has strong implications to trending hashtag recommendation since newly formed hashtag compounds can be recommended early, even before the compounding has taken place. Further, humans can predict compounds with an overall accuracy of only 48.7% (treated as baseline). Notably, while humans can discriminate the relatively easier cases, the automatic framework is successful in classifying the relatively harder cases.Comment: 14 pages, 4 figures, 9 tables, published in CSCW (Computer-Supported Cooperative Work and Social Computing) 2016. in Proceedings of 19th ACM conference on Computer-Supported Cooperative Work and Social Computing (CSCW 2016

South-north asymmetry of field-aligned currents in the magnetotail observed by Cluster

We statistically investigated features of the field-aligned current (FAC) distribution in plasma sheet boundary layers between 17 and 19 RE in the magnetotail using the curlometer technique to calculate the current from four-point magnetic field measurements taken in 2001. The results show that the FAC distribution in the plasma sheet boundary layers in the magnetotail has dusk-dawn asymmetry, earthward-tailward (polarity) asymmetry, and north-south asymmetry. The occurrence and polarities of FACs in the Northern Hemisphere are different from those in the Southern Hemisphere. The average density and the standard deviation of the FACs that are most likely to be connected to the Earth are 4.90 nA m−2 and 2.55 nA m−2 in the Northern Hemisphere and 4.21 nA m−2 and 1.80 nA m−2 in the Southern Hemisphere, respectively. For investigating the mechanism of the north-south asymmetry, we mapped the FACs along the field line into the polar region. The footprints of the FACs also show a difference between the Southern and Northern hemispheres (as a function of mapped latitude). These characteristics suggest a north-south asymmetry of the FACs in the magnetosphere. Further investigation is needed to identify the causes of this asymmetry, although the configuration of the magnetosphere, the polar cap boundary, the conductivity in the ionosphere, or the various solar wind-magnetosphere interaction processes all may be contributors. That the FAC densities are different between the hemispheres suggests that an important source of these currents must be a voltage generator

Variabilidade genética entre javalis (sus scrofa scrofa), híbridos e suínos por meio de marcadores microssatélites.

Os híbridos entre javalis e suínos é bastante comum. Assim, tem-se detectado polimorfismo em javalis, variando o número de cromossomos de 36 a 38. No experimento foram utilizados os animais agrupados em 5 grupos genéticos: grupo I - 59 suínos domésticos com 2n = 38; grupo II - 46 javalis puros de origem (PO) com 2n = 36; grupo III - 6 híbridos, com 2n=36; grupo IV - 30 híbridos com 2n=37 e grupo V - 10 híbridos com 2n=38. O DNA genômico foi extraído e, posteriormente, amplificou-se, pela técnica de PCR, os fragmentos desses microssatélites - IGF1, ACTG2, TNFB -, os quais foram desenvolvidos para a subespécie Sus scrofa domestica. O objetivo do presente trabalho foi avaliar a heterozigosidade esperada (He) e observada (Ho) e o coeficiente de endogamia (FIS) dentro de cada população e testar as relações existentes entre os cinco grupos genéticos para estabelecer a distância genética entre eles. Os valores médios de heterozigosidades variaram 0,537-0,7871 e apresentam-se inferiores aos valores médios de heterozigosidades esperadas (0,6749-0,8279).Os valores de FIS para os Grupos II e III foram negativos, -0,005 e -0,037 respectivamente nestas populações. Nos demais grupos os valores de FIS foram positivos

Semiconducting Monolayer Materials as a Tunable Platform for Excitonic Solar Cells

The recent advent of two-dimensional monolayer materials with tunable optoelectronic properties and high carrier mobility offers renewed opportunities for efficient, ultra-thin excitonic solar cells alternative to those based on conjugated polymer and small molecule donors. Using first-principles density functional theory and many-body calculations, we demonstrate that monolayers of hexagonal BN and graphene (CBN) combined with commonly used acceptors such as PCBM fullerene or semiconducting carbon nanotubes can provide excitonic solar cells with tunable absorber gap, donor-acceptor interface band alignment, and power conversion efficiency, as well as novel device architectures. For the case of CBN-PCBM devices, we predict the limit of power conversion efficiencies to be in the 10 - 20% range depending on the CBN monolayer structure. Our results demonstrate the possibility of using monolayer materials in tunable, efficient, polymer-free thin-film solar cells in which unexplored exciton and carrier transport regimes are at play.Comment: 7 pages, 5 figure