376 research outputs found
Dimer Decimation and Intricately Nested Localized-Ballistic Phases of Kicked Harper
Dimer decimation scheme is introduced in order to study the kicked quantum
systems exhibiting localization transition. The tight-binding representation of
the model is mapped to a vectorized dimer where an asymptotic dissociation of
the dimer is shown to correspond to the vanishing of the transmission
coefficient thru the system. The method unveils an intricate nesting of
extended and localized phases in two-dimensional parameter space. In addition
to computing transport characteristics with extremely high precision, the
renormalization tools also provide a new method to compute quasienergy
spectrum.Comment: There are five postscript figures. Only half of the figure (3) is
shown to reduce file size. However, missing part is the mirror image of the
part show
Quantum Dynamics of Solitons in Strongly Interacting Systems on Optical Lattices
Mean-field dynamics of strongly interacting bosons described by hard core
bosons with nearest-neighbor attraction has been shown to support two species
of solitons: one of Gross-Pitaevskii (GP-type) where the condensate fraction
remains dark and a novel non-Gross-Pitaevskii-type (non-GP-type) characterized
by brightening of the condensate fraction. Here we study the effects of quantum
fluctuations on these solitons using the adaptive time-dependent density matrix
renormalization group method, which takes into account the effect of strong
correlations. We use local observables as the density, condensate density and
correlation functions as well as the entanglement entropy to characterize the
stability of the initial states. We find both species of solitons to be stable
under quantum evolution for a finite duration, their tolerance to quantum
fluctuations being enhanced as the width of the soliton increases. We describe
possible experimental realizations in atomic Bose Einstein Condensates,
polarized degenerate Fermi gases, and in systems of polar molecules on optical
lattices
Quantized Orbits and Resonant Transport
A tight binding representation of the kicked Harper model is used to obtain
an integrable semiclassical Hamiltonian consisting of degenerate "quantized"
orbits. New orbits appear when renormalized Harper parameters cross integer
multiples of . Commensurability relations between the orbit frequencies
are shown to correlate with the emergence of accelerator modes in the classical
phase space of the original kicked problem. The signature of this resonant
transport is seen in both classical and quantum behavior. An important feature
of our analysis is the emergence of a natural scaling relating classical and
quantum couplings which is necessary for establishing correspondence.Comment: REVTEX document - 8 pages + 3 postscript figures. Submitted to
Phys.Rev.Let
Transport properties of one-dimensional interacting fermions in aperiodic potentials
Motivated by the existence of metal-insulator transition in one-dimensional
non-interacting fermions in quasiperiodic and pseudorandom potentials, we
studied interacting spinless fermion models using exact many-body Lanczos
diagonalization techniques. Our main focus was to understand the effect of the
fermion-fermion interaction on the transport properties of aperiodic systems.
We calculated the ground state energy and the Kohn charge stiffness Dc. Our
numerical results indicate that there exists a region in the interaction
strength parameter space where the system may behave differently from the
metallic and insulating phases. This intermediate phase may be characterized by
a power law scaling of the charge stiffness constant in contrast to the
localized phase where Dc scales exponentially with the size of the system.Comment: 11 pages LaTex document with 5 eps figures. Uses revtex style file
A map from 1d Quantum Field Theory to Quantum Chaos on a 2d Torus
Dynamics of a class of quantum field models on 1d lattice in Heisenberg
picture is mapped into a class of `quantum chaotic' one-body systems on
configurational 2d torus (or 2d lattice) in Schr\" odinger picture. Continuum
field limit of the former corresponds to quasi-classical limit of the latter.Comment: 4 pages in REVTeX, 1 eps-figure include
Ordering of localized moments in Kondo lattice models
We describe the transition from a ferromagnetic phase, to a disordered para-
magnetic phase, which occurs in one-dimensional Kondo lattice models with
partial conduction band filling. The transition is the quantum order-disorder
transition of the transverse-field Ising chain, and reflects double-exchange
ordered regions of localized spins being gradually destroyed as the coupling to
the conduction electrons is reduced. For incommensurate conduction band
filling, the low-energy properties of the localized spins near the transition
are dominated by anomalous ordered (disordered) regions of localized spins
which survive into the paramagnetic (ferromagnetic) phase. Many interesting
properties follow, including a diverging susceptibility for a finite range of
couplings into the paramagnetic phase. Our critical line equation, together
with numerically determined transition points, are used to determine the range
of the double-exchange interaction. Models we consider are the spin 1/2 Kondo
lattices with antiferromagnetic (Kondo) coupling, with ferromagnetic (Hund's
rule) coupling, and the Kondo lattice with repulsive interactions between the
conduction electrons.Comment: 18 pages, 6 embedded eps figures. To appear in Phys Rev
Control of Dynamical Localization
Control over the quantum dynamics of chaotic kicked rotor systems is
demonstrated. Specifically, control over a number of quantum coherent phenomena
is achieved by a simple modification of the kicking field. These include the
enhancement of the dynamical localization length, the introduction of classical
anomalous diffusion assisted control for systems far from the semiclassical
regime, and the observation of a variety of strongly nonexponential lineshapes
for dynamical localization. The results provide excellent examples of
controlled quantum dynamics in a system that is classically chaotic and offer
new opportunities to explore quantum fluctuations and correlations in quantum
chaos.Comment: 9 pages, 7 figures, to appear in Physical Review
Quasi-1D spin-1/2 Heisenberg magnets in their ordered phase: correlation functions
We study weakly coupled antiferromagnetic spin chains in their ordered phase
by combinining an exact solution of the single-chain problem with an RPA
analysis of the interchain interaction. A single chain is described by a
quantum Sine-Gordon model and dynamical staggered susceptibilities are
determined by employing the formfactor approach to quantum correlation
functions. We consider both antiferromagnetic order encountered in quasi-1D
materials like and spin-Peierls order as found in .Comment: 16 pages of revtex, 12 figure
The potential of siRNA based drug delivery in respiratory disorders: recent advances and progress
© 2019 Wiley Periodicals, Inc. Lung diseases are the leading cause of mortality worldwide. The currently available therapies are not sufficient, leading to the urgent need for new therapies with sustained anti-inflammatory effects. Small/short or silencing interfering RNA (siRNA) has potential therapeutic implications through post-transcriptional downregulation of the target gene expression. siRNA is essential in gene regulation, so is more favorable over other gene therapies due to its small size, high specificity, potency, and no or low immune response. In chronic respiratory diseases, local and targeted delivery of siRNA is achieved via inhalation. The effectual delivery can be attained by the generation of aerosols via inhalers and nebulizers, which overcomes anatomical barriers, alveolar macrophage clearance and mucociliary clearance. In this review, we discuss the different siRNA nanocarrier systems for chronic respiratory diseases, for safe and effective delivery. siRNA mediated pro-inflammatory gene or miRNA targeting approach can be a useful approach in combating chronic respiratory inflammatory conditions and thus providing sustained drug delivery, reduced therapeutic dose, and improved patient compliance. This review will be of high relevance to the formulation, biological and translational scientists working in the area of respiratory diseases
Increasing complexity and interactions of oxidative stress in chronic respiratory diseases: An emerging need for novel drug delivery systems
© 2018 Elsevier B.V. Oxidative stress is intensely involved in enhancing the severity of various chronic respiratory diseases (CRDs) including asthma, chronic obstructive pulmonary disease (COPD), infections and lung cancer. Even though there are various existing anti-inflammatory therapies, which are not enough to control the inflammation caused due to various contributing factors such as anti-inflammatory genes and antioxidant enzymes. This leads to an urgent need of novel drug delivery systems to combat the oxidative stress. This review gives a brief insight into the biological factors involved in causing oxidative stress, one of the emerging hallmark feature in CRDs and particularly, highlighting recent trends in various novel drug delivery carriers including microparticles, microemulsions, microspheres, nanoparticles, liposomes, dendrimers, solid lipid nanocarriers etc which can help in combating the oxidative stress in CRDs and ultimately reducing the disease burden and improving the quality of life with CRDs patients. These carriers improve the pharmacokinetics and bioavailability to the target site. However, there is an urgent need for translational studies to validate the drug delivery carriers for clinical administration in the pulmonary clinic
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