147 research outputs found
The Emergence of Superconducting Systems in Anti-de Sitter Space
In this article, we investigate the mathematical relationship between a (3+1)
dimensional gravity model inside Anti-de Sitter space , and a (2+1)
dimensional superconducting system on the asymptotically flat boundary of (in the absence of gravity). We consider a simple case of the Type II
superconducting model (in terms of Ginzburg-Landau theory) with an external
perpendicular magnetic field . An interaction potential is introduced
within the Lagrangian system. This provides more flexibility within the model,
when the superconducting system is close to the transition temperature .
Overall, our result demonstrates that the two Ginzburg-Landau differential
equations can be directly deduced from Einstein's theory of general relativity.Comment: 10 pages, 2 figure
Introduction to Graphene Electronics -- A New Era of Digital Transistors and Devices
The speed of silicon-based transistors has reached an impasse in the recent
decade, primarily due to scaling techniques and the short-channel effect.
Conversely, graphene (a revolutionary new material possessing an atomic
thickness) has been shown to exhibit a promising value for electrical
conductivity. Graphene would thus appear to alleviate some of the drawbacks
associated with silicon-based transistors. It is for this reason why such a
material is considered one of the most prominent candidates to replace silicon
within nano-scale transistors. The major crux here, is that graphene is
intrinsically gapless, and yet, transistors require a band-gap pertaining to a
well-defined ON/OFF logical state. Therefore, exactly as to how one would
create this band-gap in graphene allotropes is an intensive area of growing
research. Existing methods include nano-ribbons, bilayer and multi-layer
structures, carbon nanotubes, as well as the usage of the graphene substrates.
Graphene transistors can generally be classified according to two working
principles. The first is that a single graphene layer, nanoribbon or carbon
nanotube can act as a transistor channel, with current being transported along
the horizontal axis. The second mechanism is regarded as tunneling, whether
this be band-to-band on a single graphene layer, or vertically between adjacent
graphene layers. The high-frequency graphene amplifier is another talking point
in recent research, since it does not require a clear ON/OFF state, as with
logical electronics. This paper reviews both the physical properties and
manufacturing methodologies of graphene, as well as graphene-based electronic
devices, transistors, and high-frequency amplifiers from past to present
studies. Finally, we provide possible perspectives with regards to future
developments.Comment: This is an updated version of our review article, due to be published
in Contemporary Physics (Sept 2013). Included are updated references, along
with a few minor corrections. (45 pages, 19 figures
From graphene and topological insulators to Weyl semimetals
Here we present a short introduction into physics of Dirac materials. In particular we
review main physical properties of various two-dimensional crystals such as graphene, sil-
icene, germanene and others.We comment on the origin of their buckled two-dimensional
shape, and address the issues created by Mermin-Wagner theorem prohibiting the exis-
tence of strictly two-dimensional,
at crystals. Then we describe main ideas which were
leading to the discovery of two and three-dimensional topological insulators and Weyl
fermions. We describe some of their outstanding electronic properties which have been
originating due to the existence of the Dirac gapless spectrum. We also compare simplest
devices made of Dirac materials. Analogies and di erences between Dirac materials and
optics are also discussed
First data from DM-Ice17
We report the first analysis of background data from DM-Ice17, a direct-detection dark matter experiment
consisting of 17 kg of NaI(Tl) target material. It was codeployed with IceCube 2457 m deep in the South Pole
glacial ice in December 2010 and is the first such detector operating in the Southern Hemisphere. The
background rate in the 6.5β8.0 keVee region is measured to be 7.9 οΏ½ 0.4 counts=day=keV=kg. This is
consistent with the expected background from the detector assemblies with negligible contributions from
the surrounding ice. The successful deployment and operation of DM-Ice17 establishes the South Pole ice
as a viable location for future underground, low-background experiments in the Southern Hemisphere. The
detector assembly and deployment are described here, as well as the analysis of the DM-Ice17 backgrounds
based on data from the first two years of operation after commissioning, July 2011βJune 2013
Measurement of muon annual modulation and muon-induced phosphorescence in NaI(TI) crystals with DM-Ice17
We report the measurement of muons and muon-induced phosphorescence in DM-Ice17, a NaI(Tl) direct detection dark matter experiment at the South Pole. Muon interactions in the crystal are identified by their observed pulse shape and large energy depositions. The measured muon rate in DM-Ice17 is 2.93Β±0.04ββΞΌ/crystal/day with a modulation amplitude of 12.3Β±1.7%, consistent with expectation. Following muon interactions, we observe long-lived phosphorescence in the NaI(Tl) crystals with a decay time of 5.5Β±0.5ββs. The prompt energy deposited by a muon is correlated to the amount of delayed phosphorescence, the brightest of which consist of tens of millions of photons. These photons are distributed over tens of seconds with a rate and arrival timing that do not mimic a scintillation signal above 2ββkeVee. While the properties of phosphorescence vary among individual crystals, the annually modulating signal observed by DAMA cannot be accounted for by phosphorescence with the characteristics observed in DM-Ice17
RSPCA and the criminology of social control
This paper contributes to a rethinking of animal abuse control and animal welfare protection in criminology, specifically, and in the social sciences more broadly. We do this, first, through a broad mapping of the institutional control complex around animal abuse in contemporary Britain. Second, we focus on the institutional strategies and practices, past and present, of the main agency of animal protection, and the policing thereof, in this society, namely the Royal Society for the Prevention of Cruelty to Animals (RSPCA). In looking back to this charityβs growth since the first decades of the nineteenth century at the time of the birth of modern industrial capitalism and also to its current rationale and practices as a late-modern, corporate organisation, we explore the seeming paradox of a private body taking a lead on the regulation and prosecution of illegalities associated with animal-human relationships. Finally, the ideology and strategy of the RSPCA are explored in the context of the often visceral and culturally influential βmorality warβ associated with proponents, respectively, of animal rights (βabolitionβ) and βanthropicβ welfare proponents (βregulationβ and βprotectionβ)
First search for a dark matter annual modulation signal with NaI(Tl) in the Southern Hemisphere by DM-Ice17
We present the first search for a dark matter annual modulation signal in the Southern Hemisphere conducted with NaI(Tl) detectors, performed by the DM-Ice17 experiment. Nuclear recoils from dark matter interactions are expected to yield an annually modulated signal independent of location within the Earthβs hemispheres. DM-Ice17, the first step in the DM-Ice experimental program, consists of 17 kg of NaI(Tl) located at the South Pole under 2200 m.w.e. overburden of Antarctic glacial ice. Taken over 3.6 years for a total exposure of 60.8 kg yr, DM-Ice17 data are consistent with no modulation in the energy range of 4β20 keV, providing the strongest limits on weakly interacting massive particle dark matter from a direct detection experiment located in the Southern Hemisphere. The successful deployment and stable long-term operation of DM-Ice17 establishes the South Pole ice as a viable location for future dark matter searches and in particular for a high-sensitivity NaI(Tl) dark matter experiment to directly test the DAMA/LIBRA claim of the observation of dark matter
Targets for introduction of pests and disease resistance into crops by genetic engineering: report of a review funded by MAFF
Presynaptic External Calcium Signaling Involves the Calcium-Sensing Receptor in Neocortical Nerve Terminals
Nerve terminal invasion by an axonal spike activates voltage-gated channels, triggering calcium entry, vesicle fusion, and release of neurotransmitter. Ion channels activated at the terminal shape the presynaptic spike and so regulate the magnitude and duration of calcium entry. Consequently characterization of the functional properties of ion channels at nerve terminals is crucial to understand the regulation of transmitter release. Direct recordings from small neocortical nerve terminals have revealed that external [Ca(2+)] ([Ca(2+)](o)) indirectly regulates a non-selective cation channel (NSCC) in neocortical nerve terminals via an unknown [Ca(2+)](o) sensor. Here, we identify the first component in a presynaptic calcium signaling pathway.By combining genetic and pharmacological approaches with direct patch-clamp recordings from small acutely isolated neocortical nerve terminals we identify the extracellular calcium sensor. Our results show that the calcium-sensing receptor (CaSR), a previously identified G-protein coupled receptor that is the mainstay in serum calcium homeostasis, is the extracellular calcium sensor in these acutely dissociated nerve terminals. The NSCC currents from reduced function mutant CaSR mice were less sensitive to changes in [Ca(2+)](o) than wild-type. Calindol, an allosteric CaSR agonist, reduced NSCC currents in direct terminal recordings in a dose-dependent and reversible manner. In contrast, glutamate and GABA did not affect the NSCC currents.Our experiments identify CaSR as the first component in the [Ca(2+)](o) sensor-NSCC signaling pathway in neocortical terminals. Decreases in [Ca(2+)](o) will depress synaptic transmission because of the exquisite sensitivity of transmitter release to [Ca(2+)](o) following its entry via voltage-activated Ca(2+) channels. CaSR may detects such falls in [Ca(2+)](o) and increase action potential duration by increasing NSCC activity, thereby attenuating the impact of decreases in [Ca(2+)](o) on release probability. CaSR is positioned to detect the dynamic changes of [Ca(2+)](o) and provide presynaptic feedback that will alter brain excitability
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