25,430 research outputs found
Single fermion manipulation via superconducting phase differences in multiterminal Josephson junctions
We show how the superconducting phase difference in a Josephson junction may
be used to split the Kramers degeneracy of its energy levels and to remove all
the properties associated with time reversal symmetry. The superconducting
phase difference is known to be ineffective in two-terminal short Josephson
junctions, where irrespective of the junction structure the induced Kramers
degeneracy splitting is suppressed and the ground state fermion parity must
stay even, so that a protected zero-energy Andreev level crossing may never
appear. Our main result is that these limitations can be completely avoided by
using multi-terminal Josephson junctions. There the Kramers degeneracy breaking
becomes comparable to the superconducting gap, and applying phase differences
may cause the change of the ground state fermion parity from even to odd. We
prove that the necessary condition for the appearance of a fermion parity
switch is the presence of a "discrete vortex" in the junction: the situation
when the phases of the superconducting leads wind by . Our approach
offers new strategies for creation of Majorana bound states as well as spin
manipulation. Our proposal can be implemented using any low density, high
spin-orbit material such as InAs quantum wells, and can be detected using
standard tools.Comment: Source code available as ancillary files. 10 pages, 7 figures. v2:
minor changes, published versio
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Graphene-polyelectrolyte multilayer membranes with tunable structure and internal charge
One great advantage of graphene-polyelectrolyte multilayer (GPM) membranes is their tunable structure and internal charge for improved separation performance. In this study, we synthesized GO-dominant GPM membrane with internal negatively-charged domains, polyethyleneimine (PEI)-dominant GPM membrane with internal positively-charged domains and charge-balanced dense/loose GPM membranes by simply adjusting the ionic strength and pH of the GO and PEI solutions used in layer-by-layer membrane synthesis. A combined system of quartz crystal microbalance with dissipation (QCM-D) and ellipsometry was used to analyze the mass deposition, film thickness, and layer density of the GPM membranes. The performance of the GPM membranes were compared in terms of both permeability and selectivity to determine the optimal membrane structure and synthesis strategy. One effective strategy to improve the GPM membrane permeability-selectivity tradeoff is to assemble charge-balanced dense membranes under weak electrostatic interactions. This balanced membrane exhibits the highest MgCl2 selectivity (∼86%). Another effective strategy for improved cation removal is to create PEI-dominant membranes that provide internal positively-charged barrier to enhance cation selectivity without sacrificing water permeability. These findings shine lights on the development of a systematic approach to push the boundary of permeability-selectivity tradeoff for GPM membranes
The difference of boundary effects between Bose and Fermi systems
In this paper, we show that there exists an essential difference of boundary
effects between Bose and Fermi systems both for Dirichlet and Neumann boundary
conditions: at low temperatures and high densities the influence of the
boundary on the Bose system depends on the temperature but is independent of
the density, but for the Fermi case the influence of the boundary is
independent of the temperature but depends on the density, after omitting the
negligible high-order corrections. We also show that at high temperatures and
low densities the difference of the influence of the boundary between Bose and
Fermi systems appears in the next-to-leading order boundary contribution, and
the leading boundary contribution is independent of the density. Moreover, for
calculating the boundary effects at high temperatures and low densities, since
the existence of the boundary modification causes the standard virial expansion
to be invalid, we introduce a modified virial expansion.Comment: 8 page
Insecticidal, brine shrimp cytotoxicity, antifungal and nitric oxide free radical scavenging activities of the aerial parts of Myrsine africana L.
The crude methanolic extract and various fractions derived from the aerial parts of Myrsine africana were screened in vitro for possible insecticidal, antifungal, brine shrimp lethality and nitric oxide free radical scavenging activities. Low insecticidal activity (20 %) was shown by chloroform (CHCl3) and aqueous fractions against Tribolium castaneum and Rhizopertha dominica, respectively. Good cytotoxic activity (66.66 %) was shown by the n-hexane fraction of the plant at 1000 μg/ml. The rest of the fractions showed low lethality at higher doses. No antifungal activity was observed for the crude extract and fractions screened against various fungal strains. The plant crude extract and fractions showed a concentration dependent nitric oxide free radical scavenging activity.Key words: Myrsine africana, insecticidal, brine shrimp lethality, antifungal and nitric oxide free radical scavenging assay
Diffeomorphic random sampling using optimal information transport
In this article we explore an algorithm for diffeomorphic random sampling of
nonuniform probability distributions on Riemannian manifolds. The algorithm is
based on optimal information transport (OIT)---an analogue of optimal mass
transport (OMT). Our framework uses the deep geometric connections between the
Fisher-Rao metric on the space of probability densities and the right-invariant
information metric on the group of diffeomorphisms. The resulting sampling
algorithm is a promising alternative to OMT, in particular as our formulation
is semi-explicit, free of the nonlinear Monge--Ampere equation. Compared to
Markov Chain Monte Carlo methods, we expect our algorithm to stand up well when
a large number of samples from a low dimensional nonuniform distribution is
needed.Comment: 8 pages, 3 figure
Identifying professionals' needs in integrating electronic pain monitoring in community palliative care services: an interview study
Background: Poor pain assessment is a barrier to effective pain control. There is growing interest internationally in the development and implementation of remote monitoring technologies to enhance assessment in cancer and chronic disease contexts. Findings describe the development and testing of pain monitoring systems but research identifying the needs of health professionals to implement routine monitoring systems within clinical practice is limited. Aim: To inform the development and implementation strategy of an electronic pain monitoring system, PainCheck, by understanding palliative care professionals’ needs when integrating PainCheck into routine clinical practice. Design: Qualitative study using face-to-face interviews. Data were analysed using framework analysis Setting/participants: Purposive sample of health professionals managing the palliative care of patients living in the community Results: Fifteen interviews with health professionals took place. Three meta-themes emerged from the data: 1) Uncertainties about integration of PainCheck and changes to current practice; 2) Appraisal of current practice; 3) Pain management is everybody’s responsibility Conclusions: Even the most sceptical of health professionals could see the potential benefits of implementing an electronic patient-reported pain monitoring system. Health professionals have reservations about how PainCheck would work in practice. For optimal use PainCheck needs embedding within existing electronic health records. Electronic pain monitoring systems have the potential to enable professionals to support patients’ pain management more effectively but only when barriers to implementation are appropriately identified and addressed
Evidence for a direct band gap in the topological insulator Bi2Se3 from theory and experiment
Using angle-resolved photoelectron spectroscopy and ab-initio GW
calculations, we unambiguously show that the widely investigated
three-dimensional topological insulator Bi2Se3 has a direct band gap at the
Gamma point. Experimentally, this is shown by a three-dimensional band mapping
in large fractions of the Brillouin zone. Theoretically, we demonstrate that
the valence band maximum is located at the Brillouin center only if many-body
effects are included in the calculation. Otherwise, it is found in a
high-symmetry mirror plane away from the zone center.Comment: 8 pages, 4 figure
Parasiticidal, antifungal and antibacterial activities of Onosma griffithii Vatke
Onosma griffithii was screened for possible pharmacological activities. The crude methanolic extract (MeOH) and its fractions demonstrated parasiticidal activity (IC 50 (ìg/ml ± S.D) = 31.03 ± 0.23) against Leishmania major. Based on the IC 50 values, the potency of the standard drug (Pentamidine) and test fractions were of the order as: Pentamidine > crude extract > n-hexane fraction > ethyl acetate (ETOAc) fraction > chloroform fraction (CHCl3) fraction > n-butanol (BUOH) fraction > aqueous fraction. Similarlymoderate antifungal activity was displayed by the crude methanolic extract against Aspergillus flavus and Fusarium solani. Against the Staphylococcus aureus, the aqueous fraction demonstrated moderate antibacterial activity
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