33,324 research outputs found
Comment on: "Revealing common artifacts due to ferromagnetic inclusions in highly oriented pyrolytic graphite", by M. Sepioni, R.R. Nair, I.-Ling Tsai, A.K. Geim and I.V. Grigorieva, EPL 97 (2012) 47001
This comment addresses several issues in the paper by Sepioni et al., where
it is stated that the ferromagnetism in pristine highly oriented pyrolytic
graphite (HOPG) reported by several groups in the previous years is most likely
due to impurity contamination. In this comment, clear arguments are given why
this statement is not justified. Furthermore, it is pointed out, that there are
already measurements using element-sensitive microscopic techniques, e.g. X-ray
Magnetic Circular Dichroism (XMCD) that directly proved the intrinsic origin of
the ferromagnetism in graphite, also in pristine HOPG.Comment: 1, 0 figures, 9 reference
Mesoscopic modelling of conducting and semiconducting polymers
We present generalized Monte Carlo calculations to assess the effects of texture and related key factors on the properties of polymer-based light emitting diodes. We, describe one class of mesoscopic model giving specific realizations of the polymer network. The model, with simple physically based rules, shows the effects of polymer structural order on current flow, trapping and radiative and non-radiative charge recombination within the polymer layer. Interactions between charges are included explicitly, as are image interactions with the electrodes. It is important that these Coulomb interactions are not simplified to an averaged space charge, since the local interactions can lead to effective trapping of charge, even in the absence of defective chains or impurity trapping. There proves to be an important role for trapping, in which charges are localized for times long compared with transit times. The competition between current flow, trapping and radiative and non-radiative charge recombination means that some of the trends are not intuitively obvious. For example, if radiative recombination occurs only on short polymer chains, as is the case for certain polymer systems, the internal efficiency appears to saturate for a concentration of these shorter luminescent chains of about 20-30%. As the proportion of shorter chains increases, trapping increases, whereas current efficiency decreases. Our approach provides a natural link between atomistic models of individual polymer molecules and the macroscopic descriptions of device modelling. Such mesoscopic models provide a means to design better film structures, and hence to optimize the effectiveness of new organic materials in a range of applications
Variable stars in the VVV globular clusters
Indexación: Scopus.The VVV survey observed some of the most crowded and most obscured regions in the inner Milky Way during the last years. A significant sample of the less known globular clusters in our galaxy lie there. Combining the high-resolution, wide-field, near infrared capabilities of the survey camera, the use of 5 different filters, and multi-epoch observations, we are able to overcome many of the previous challenges that prevented a proper study of these objects. Particularly, the identification of the RR Lyrae stars in these globular clusters is proving to be a fundamental tool to establish accurately their distances and reddenings, and to infer information about the Oosterhoff dichotomy that Galactic globular clusters seem to follow. © The Authors, published by EDP Sciences, 2017.https://www.epj-conferences.org/articles/epjconf/pdf/2017/21/epjconf_puls2017_01022.pd
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The Impact on Maine's Budget of Allowing Same-Sex Couples to Marry
This analysis estimates the impact of allowing same-sex couples to marry on Maine's state budget. We estimate that allowing same-sex couples to marry will result in a net gain of approximately 7.9 million
DISCOVERY OF RR LYRAE STARS IN THE NUCLEAR BULGE OF THE MILKY WAY
Indexación: Web of ScienceGalactic nuclei, such as that of the Milky Way, are extreme regions with high stellar densities, and in most cases, the hosts of a supermassive black hole. One of the scenarios proposed for the formation of the Galactic nucleus is merging of primordial globular clusters. An implication of this model is that this region should host stars that are characteristically found in old Milky Way globular clusters. RR Lyrae stars are primary distance indicators, well known representatives of old and metal-poor stellar populations, and therefore are regularly found in globular clusters. Here we report the discovery of a dozen RR Lyrae type ab stars in the vicinity of the Galactic center, i.e., in the so-called nuclear stellar bulge of the Milky Way. This discovery provides the first direct observational evidence that the Galactic nuclear stellar bulge contains ancient stars (>10 Gyr old). Based on this we conclude that merging globular clusters likely contributed to the build-up of the high stellar density in the nuclear stellar bulge of the Milky Way.http://iopscience.iop.org/article/10.3847/2041-8205/830/1/L14/meta;jsessionid=2531FBFFF06C9ECBA4852FB9D1F89851.c1.iopscience.cld.iop.or
Theoretical study of metal-polyimide interfacial properties
The aim of this work is to achieve a better understanding of metal-polyimide interfacial properties, such as bonding strength between two materials and charge transfer, and to assess the consequences for the adhesion. The effect of surface modification on adhesion is also discussed. These interfacial studies of PMDA-ODA polyimide with evaporated chromium (Cr), copper (Cu) and nickel (Ni) atoms have been performed using a self-consistent molecular dynamics method with semi-empirical quantum chemistry at the complete neglect of differential overlap level. All metals were predicted to bond strongly at six-fold rings of polyimide. Despite actual charge transfer between metal atoms and polyimide is small, the bond formation induces charge rearrangement among the polyimide atoms far from the reaction site. The adhesion of polyimide to a Ni(100) surface is predicted to be somewhat weaker than that of nickel atoms to polyimide at six-fold sites
Inverse Symmetry Breaking in Multi-Scalar Field Theories
We review how the phenomena of inverse symmetry breaking (and symmetry
nonrestoration) may arise in the context of relativistic as well as
nonrelativistic multi-scalar field theories. We discuss how the consideration
of thermal effects on the couplings produce different transition patterns for
both theories. For the relativistic case, these effects allow the appearance of
inverse symmetry breaking (and symmetry nonrestoration) at arbitrarily large
temperatures. On the other hand, the same phenomena are suppressed in the
nonrelativistic case, which is relevant for condensed matter physics. In this
case, symmetry nonrestoration does not happen while inverse symmetry is allowed
only to be followed by symmetry restoration characterizing a reentrant phase.
The aim of this paper is to give more insight concerning the, qualitatively
correct, results obtained by using one loop perturbation theory in the
evaluation of thermal masses and couplings.Comment: 7 pages, 3 figures, talk given at the workshop on Quantum Fields
Under the Influence of External Conditions, QFEXT05, Barcelona, sep-200
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