463 research outputs found
One-electron states and interband optical absorption in single-wall carbon nanotubes
Explicit expressions for the wave functions and dispersion equation for the
band p - electrons in single-wall carbon nanotubes are obtained within the
method of zero-range potentials. They are then used to investigate the
absorption spectrum of polarized light caused by direct interband transitions
in isolated nanotubes. It is shown that, at least, under the above
approximations, the circular dichroism is absent in chiral nanotubes for the
light wave propagating along the tube axis. The results obtained are compared
with those calculated in a similar way for a graphite plane.Comment: 16 pages, 8 figures, 1 tabl
Voluntary organizations and society–military relations in contemporary Russia
The 2014 crisis in Ukraine has refocused attention on Russia as a European security actor. Despite showing renewed military capability, compared to the post-Soviet period, Russian society–military relations have remained the same. This relationship (between society and the security organs) provides the key context for assessing security. Analysis of everyday militarization and the role of voluntary organizations (such as DOSAAF [Dobrovol'noe obshchestvo sodeistviya armii, aviatsii i flotu] and Nashi [Molodezhnoe demokraticheskoe antifashistskoe dvizheni]) in supporting the military can provide an important insight into Russian behaviour as a security actor. These organizations generate a pro-military outlook and at the same time provide training and activities, thus contributing to military effectiveness by developing the competency of young people prior to military service as well as increasing public knowledge of military affairs. However, strong support for the military, a lack of independent information, and an absence of a shared vision on how society–military relations should be developed and also represent political challenges in terms of everyday militarization. This dynamic is important for understanding both Russia's security posture and wider security implications for Europe
The Majorana Project
Building a \BBz experiment with the ability to probe neutrino mass in the
inverted hierarchy region requires the combination of a large detector mass
sensitive to \BBz, on the order of 1-tonne, and unprecedented background
levels, on the order of or less than 1 count per year in the \BBz signal
region. The MAJORANA Collaboration proposes a design based on using high-purity
enriched Ge-76 crystals deployed in ultra-low background electroformed Cu
cryostats and using modern analysis techniques that should be capable of
reaching the required sensitivity while also being scalable to a 1-tonne size.
To demonstrate feasibility, the collaboration plans to construct a prototype
system, the MAJORANA DEMONSTRATOR, consisting of 30 kg of 86% enriched \Ge-76
detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to
deploy and evaluate two different Ge detector technologies, one based on a
p-type configuration and the other on n-type.Comment: paper submitted for the 2008 Carolina International Symposium on
Neutrino Physic
How to detect fluctuating order in the high-temperature superconductors
We discuss fluctuating order in a quantum disordered phase proximate to a
quantum critical point, with particular emphasis on fluctuating stripe order.
Optimal strategies for extracting information concerning such local order from
experiments are derived with emphasis on neutron scattering and scanning
tunneling microscopy. These ideas are tested by application to two model
systems - the exactly solvable one dimensional electron gas with an impurity,
and a weakly-interacting 2D electron gas. We extensively review experiments on
the cuprate high-temperature superconductors which can be analyzed using these
strategies. We adduce evidence that stripe correlations are widespread in the
cuprates. Finally, we compare and contrast the advantages of two limiting
perspectives on the high-temperature superconductor: weak coupling, in which
correlation effects are treated as a perturbation on an underlying metallic
(although renormalized) Fermi liquid state, and strong coupling, in which the
magnetism is associated with well defined localized spins, and stripes are
viewed as a form of micro-phase separation. We present quantitative indicators
that the latter view better accounts for the observed stripe phenomena in the
cuprates.Comment: 43 pages, 11 figures, submitted to RMP; extensively revised and
greatly improved text; one new figure, one new section, two new appendices
and more reference
Mapping of HNF4α target genes in intestinal epithelial cells
© 2009 Boyd et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Optoelectronic and Excitonic Properties of Oligoacenes: Substantial Improvements from Range-Separated Time-Dependent Density Functional Theory
The optoelectronic and excitonic properties in a series of linear acenes
(naphthalene up to heptacene) are investigated using range-separated methods
within time-dependent density functional theory (TDDFT). In these rather simple
systems, it is well-known that TDDFT methods using conventional hybrid
functionals surprisingly fail in describing the low-lying La and Lb valence
states, resulting in large, growing errors for the La state and an incorrect
energetic ordering as a function of molecular size. In this work, we
demonstrate that the range-separated formalism largely eliminates both of these
errors and also provides a consistent description of excitonic properties in
these systems. We further demonstrate that re-optimizing the percentage of
Hartree-Fock exchange in conventional hybrids to match wavefunction-based
benchmark calculations still yields serious errors, and a full 100%
Hartree-Fock range separation is essential for simultaneously describing both
of the La and Lb transitions. Based on an analysis of electron-hole transition
density matrices, we finally show that conventional hybrid functionals
overdelocalize excitons and underestimate quasiparticle energy gaps in the
acene systems. The results of our present study emphasize the importance of
both a range-separated and asymptotically-correct contribution of exchange in
TDDFT for investigating optoelectronic and excitonic properties, even for these
simple valence excitations.Comment: Accepted by the Journal of Chemical Theory and Computatio
Carbon Nanotube Solar Cells
We present proof-of-concept all-carbon solar cells. They are made of a photoactive side of predominantly semiconducting nanotubes for photoconversion and a counter electrode made of a natural mixture of carbon nanotubes or graphite, connected by a liquid electrolyte through a redox reaction. The cells do not require rare source materials such as In or Pt, nor high-grade semiconductor processing equipment, do not rely on dye for photoconversion and therefore do not bleach, and are easy to fabricate using a spray-paint technique. We observe that cells with a lower concentration of carbon nanotubes on the active semiconducting electrode perform better than cells with a higher concentration of nanotubes. This effect is contrary to the expectation that a larger number of nanotubes would lead to more photoconversion and therefore more power generation. We attribute this to the presence of metallic nanotubes that provide a short for photo-excited electrons, bypassing the load. We demonstrate optimization strategies that improve cell efficiency by orders of magnitude. Once it is possible to make semiconducting-only carbon nanotube films, that may provide the greatest efficiency improvement
Designing Hybrid Gifts
Hybrid gifting combines physical artefacts and experiences with digital interactivity to generate new kinds of gifts. Our review details how gifting is a complex social phenomenon and how digital gifting is less engaging than physical gifting for both givers and receivers. Employing a Research Through Design approach, we developed a portfolio of four hybrid gifting experiences: an augmented advent calendar; edible music tracks; personalised museum tours; and a narrated city walk. Our reflection addresses three concepts: hybrid wrapping where physical gifts become wrapped in digital media and vice versa; the importance of effortful interactions that are visible and pleasurable; and the need to consider social obligation, including opportunities for acknowledgement and reciprocation, dealing with embarrassment, and recognising the distinction between giving and sharing. Our concepts provide guidance to practitioners who wish to design future gifting experiences while helping HCI researchers engage with the concept of gifting in a nuanced way
Fosmidomycin Uptake into Plasmodium and Babesia-Infected Erythrocytes Is Facilitated by Parasite-Induced New Permeability Pathways
., a mouse malaria parasite. and related parasites. Our data provide further evidence that parasite-induced new permeability pathways may be exploited as routes for drug delivery
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