2,948 research outputs found
Tailoring tunnel magnetoresistance by ultrathin Cr and Co interlayers: A first-principles investigation of Fe/MgO/Fe junctions
We report on systematic ab-initio investigations of Co and Cr interlayers
embedded in Fe(001)/MgO/Fe(001) magnetic tunnel junctions, focusing on the
changes of the electronic structure and the transport properties with
interlayer thickness. The results of spin-dependent ballistic transport
calculations reveal options to specifically manipulate the tunnel
magnetoresistance ratio. The resistance area products and the tunnel
magnetoresistance ratios show a monotonous trend with distinct oscillations as
a function of the Cr thickness. These modulations are directly addressed and
interpreted by means of magnetic structures in the Cr films and by complex band
structure effects. The characteristics for embedded Co interlayers are
considerably influenced by interface resonances which are analyzed by the local
electronic structure
Gravimetry through non-linear optomechanics
We propose a new method for measurements of gravitational acceleration using
a quantum optomechanical system. As a proof-of-concept, we investigate the
fundamental sensitivity for a cavity optomechanical system for gravitational
accelerometry with a light-matter interaction of the canonical `trilinear'
radiation pressure form. The phase of the optical output of the cavity encodes
the gravitational acceleration and is the only component which needs to be
measured to perform the gravimetry. We analytically show that homodyne
detection is the optimal readout in our scheme, based on the cyclical
decoupling of light and matter, and predict a fundamental sensitivity of
ms for currently achievable optomechanical systems
which could, in principle, surpass the best atomic interferometers even for low
optical intensities. Our scheme is strikingly robust to the initial thermal
state of the mechanical oscillator as the accumulated gravitational phase only
depends on relative position separation between components of the entangled
optomechanical state arising during the evolution.Comment: 14 pages, 15 figure
A tensor network representation of path integrals: Implementation and analysis
Tensors with finite correlation afford very compact tensor network
representations. A novel tensor network-based decomposition of real-time path
integral simulations involving Feynman-Vernon influence functional is
introduced. In this tensor network path integral (TNPI) technique, the finite
temporarily non-local interactions introduced by the influence functional can
be captured very efficiently using matrix product state representation for the
path amplitude (PA) tensor. We illustrate this particular TNPI method through
various realistic examples, including a charge transfer reaction and an exciton
transfer in a dimer. We also show how it is readily applied to systems with
greater than two states by simulating a 7-site model of FMO and a molecular
wire model. The augmented propagator (AP) TNPI utilizes the symmetries of the
problem, leading to accelerated convergence and dramatic reductions of
computational effort. We also introduce an approximate method that speeds up
propagation beyond the non-local memory length. Furthermore, the structure
imposed by the tensor network representation of the PA tensor naturally
suggests other factorizations that make simulations for extended systems more
efficient. These factorizations would be the subject of future explorations.
The flexibility of the AP-TNPI framework makes it a promising new addition to
the family of path integral methods for non-equilibrium quantum dynamics.Comment: 18 pages, 15 figures. Extra example adde
Impact of solvent on state-to-state population transport in multistate systems using coherences
Understanding the pathways taken by a quantum particle during a transport
process is an enormous challenge. There are broadly two different aspects of
the problem that affect the route taken. First is obviously the couplings
between the various sites, which translates into the intrinsic "strength" of a
state-to-state channel. Apart from the inter-state couplings, the solvents
affecting the energies of the state, and their relative coupling strengths and
time-scales form the second factor. This impact of dissipative media is
significantly more difficult to analyze. Building on recently derived relations
between coherences and population derivatives, we present an analysis of the
transport that allows us to account for both the effects in a rigorous manner.
We demonstrate the richness hidden behind the transport even for a relatively
simple system, a 4-site coarse-grained model of the Fenna-Matthews-Olson
complex. The effect of the local dissipative media is highly non-trivial. We
show that while the impact on the total site population may be small, there are
dramatic changes to the pathway taken by the transport process. The ability to
untangle the dynamics at a greater granularity opens up possibilities in terms
of design of novel systems with an eye towards quantum control.Comment: 8 pages, 7 figures, supplementary information file provide
The Concilium of Information Processing Networks of Chemical Oscillators for Determining Drug Response in Patients With Multiple Myeloma
It can be expected that medical treatments in the future will be individually tailored for each patient. Here we present a step towards personally addressed drug therapy. We consider multiple myeloma treatment with drugs: bortezomib and dexamethasone. It has been observed that these drugs are effective for some patients and do not help others. We describe a network of chemical oscillators that can help to differentiate between non-responsive and responsive patients. In our numerical simulations, we consider a network of 3 interacting oscillators described with the Oregonator model. The input information is the gene expression value for one of 15 genes measured for patients with multiple myeloma. The single-gene networks optimized on a training set containing outcomes of 239 therapies, 169 using bortezomib and 70 using dexamethasone, show up to 71% accuracy in differentiating between non-responsive and responsive patients. If the results of single-gene networks are combined into the concilium with the majority voting strategy, then the accuracy of predicting the patient’s response to the therapy increases to ∼ 85%
Entanglement based tomography to probe new macroscopic forces
Quantum entanglement provides a novel way to test short distance physics in
the non-relativistic regime. We will provide a protocol to {\it potentially}
test new physics by bringing two charged massive particle interferometers
adjacent to each other. Being charged, the two superpositions will be entangled
via electromagnetic interactions mediated by the photons, including the Coulomb
and the Casimir-Polder potential. We will bring a method of {\it entanglement
based tomography} to seek time evolution of very small entanglement phases to
probe new physical effects mediated by {\it hitherto unknown macroscopic force}
which might be responsible for entangling the two charged superpositions
modelled by the Yukawa type potential. We will be able to constrain the Yukawa
couplings for m for new physics occurring
in the electromagnetic sector, and in the gravitational potential for m. Furthermore, our protocol can also
constrain the axion like particle mass and coupling, which is complimentary to
the existing experimental bounds.Comment: 7 pages, 5 fig
Studies on in vitro antiplasmodial activity of cleome rutidosperma
Malaria is a protozoal disease transmitted by the Anopheles mosquito, caused by minute parasitic protozoa of the genus Plasmodium, which infect human and insect hosts alternatively. It affects over 40% of the worldÃs population, with 120 million cases reported, and about 2 million deaths annually (1). The P. falciparum variety of the parasite accounts for 80% of cases and 90% of deaths caused by malaria. The declining efficacy of classical medication in relation to the rapid increase of parasite resistant strains, mainly of Plasmodium falciparum, as well as the greater resistance of vectors to insecticides, and the difficulty of creating efficient vaccines have led to an urgent need for new efficient antimalarial drugs (2, 3). Natural molecules may provide innovative strategies towards malarial control, hence active research groups are now working to develop new active compounds as an alternative to chloroquine, especially from artemisinin (4, 5), a plant-based antimalaria drug isolated from the Chinese plant Artemisia annua (6). Plants may well, therefore, prove to be the sources of new antimalarial in view of the success with the two important chemotherapeutic agents, quinine and artemisinin, both of which are derived from plants. Cleome rutidosperma (Capparidaceae) is a low-growing herb, up to 70 cm tall, found in waste grounds and grassy places with trifoliate leaves and small, violet-blue flowers, which turn pink as they age. The elongated capsules display the asymmetrical, dull black seeds. The plant is native to West Africa, although it has become naturalized in various parts of tropical America as well as Southeast Asia (7, 8). The diuretic, laxative, anthelmintic, antimicrobial, analgesic, anti-inflammatory, antipyretic, antioxidant and free radical scavenging activities of Cleome rutidosperma were reported earlier by the authors (9-13). The plant is used as antimalarial by the traditional healers in Cameroon and mild antiplasmodial activity of chloroform/methanol (1:1) extract of leaves of Cleome rutidosperma against chloroquine-sensitive (F32) laboratory strain of P. falciparum was reported earlier in Cameroon (14). The present study investigates the in vitro antiplasmodial activity of ethanolic extract and its fractions of aerial parts of Cleome rutidosperma against the chloroquine sensitive (CQS) D10 strain of the parasite, as well as their toxicity against a mammalian cell lines
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