4,271 research outputs found
Off Resonant Pumping for Transition from Continuous to Discrete Spectrum and Quantum Revivals in Systems in Coherent States
We show that in parametrically driven systems and, more generally, in systems
in coherent states, off-resonant pumping can cause a transition from a
continuum energy spectrum of the system to a discrete one, and result in
quantum revivals of the initial state. The mechanism responsible for quantum
revivals in the present case is different from that in the non-linear
wavepacket dynamics of systems such as Rydberg atoms. We interpret the reported
phenomena as an optical analog of Bloch oscillations realized in Fock space and
propose a feasible scheme for inducing Bloch oscillations in trapped ions.Comment: 5 pages, 4 figures, submitted to Jnl. of Optics
Quantum phase space distributions in thermofield dynamics
It is shown that the the quantum phase space distributions corresponding to a
density operator can be expressed, in thermofield dynamics, as overlaps
between the state and "thermal" coherent states. The usefulness
of this approach is brought out in the context of a master equation describing
a nonlinear oscillator for which exact expressions for the quantum phase
distributions for an arbitrary initial condition are derived.Comment: 17 pages, revtex, no figures. number of pages were incorrectly stated
as 3 instead of 17. No other correction
Securing IoT with Trusted Authority Validation in Homomorphic Encryption Technique with ABE
Existing security system includes levels of encryption. IoT access is very important aspect. Failure of IoT security can cause more risks of physical and logical damage. IoT contain both functionalities including physical or computational process. In proposed approach, levels of encryption are enhanced by increasing levels of security. User can access IoT through central trusted authority only. Instead of actual data like user credentials or I/O functionality of Internet of things, encrypted data is delivered. Trusted authorities are been involved in secured IoT access structure by considering their credentials. Trusted authority is selected randomly, based on randomized selection algorithm. Based on secured logic, decryption key will be delivered to the IoT through separate channel by trusted authority. Session management has been added by considering initial and waiting time after which all encryption or decryption data will be expired. Homomorphism is applied in encryption process where proposed logic is applied on considered data after which again RSA algorithm is applied. Overall, proposed logical approach, homomorphism, session management, secured access structure and trusted authority involvement improves the security level in IoT access process
Suppression of auxin stimulated growth of barley coleoptile sections by endosulfan
Endosulfan, a cyclic sulphurous acid ester commonly used as a broad spectrum insecticide, suppressed the elongation of barley coleoptiles. Indoleacetic acid at optimum concentration overcame the inhibition of growth of coleoptiles treated with 10 ppm endosulfan. However, perfusion of the coleoptile sections with endosulfan and subsequent treatment with indoleacetic acid could not stimulate cell elongation to the extent observed in the control
Entanglement by linear SU(2) transformations: generation and evolution of quantum vortex states
We consider the evolution of a two-mode system of bosons under the action of
a Hamiltonian that generates linear SU(2) transformations. The Hamiltonian is
generic in that it represents a host of entanglement mechanisms, which can thus
be treated in a unified way. We start by solving the quantum dynamics
analytically when the system is initially in a Fock state. We show how the two
modes get entangled by evolution to produce a coherent superposition of vortex
states in general, and a single vortex state under certain conditions. The
degree of entanglement between the modes is measured by finding the explicit
analytical dependence of the Von Neumann entropy on the system parameters. The
reduced state of each mode is analyzed by means of its correlation function and
spatial coherence function. Remarkably, our analysis is shown to be equally as
valid for a variety of initial states that can be prepared from a two-mode Fock
state via a unitary transformation and for which the results can be obtained by
mere inspection of the corresponding results for an initial Fock state. As an
example, we consider a quantum vortex as the initial state and also find
conditions for its revival and charge conjugation. While studying the evolution
of the initial vortex state, we have encountered and explained an interesting
situation in which the entropy of the system does not evolve whereas its wave
function does. Although the modal concept has been used throughout the paper,
it is important to note that the theory is equally applicable for a
two-particle system in which each particle is represented by its bosonic
creation and annihilation operators.Comment: 6 figure
Preparation of Silica Nanoparticles and Its Beneficial Role in Cementitious Materials
Spherical silica nanoparticles (nâSiO2) with
controllable size have been synthesized using
tetraethoxysilane as starting material and ethanol as
solvent by solâgel method. Morphology and size of the
particles was controlled through surfactants. Sorbitan
monolaurate, sorbitain monopalmitate and sorbitain
monostearate produced silica nanoparticles of varying
sizes (80â150 nm), indicating the effect of chain length of
the surfactant. Increase in chain length of nonâionic
surfactant resulted in decreasing particle size of silica
nanoparticles. Further, the size of silica particles was also
controlled using NH3 as base catalyst. These silica
nanoparticles were incorporated into cement paste and
their role in accelerating the cementitious reactions was
investigated. Addition of silica nanoparticles into cement
paste improved the microstructure of the paste and
calcium leaching is significantly reduced as nâSiO2 reacts
with calcium hydroxide and form additional calciumâ
silicateâhydrate (CâSâH) gel. It was found that calcium
hydroxide content in silica nanoparticles incorporated
cement paste reduced ~89% at 1 day and up to ~60% at 28
days of hydration process. Synthesized silica particles
and cement paste samples were characterized using
scanning electron microscopy (SEM), powder Xâray
diffraction (XRD), infrared spectroscopy (IR) and
thermogravimetric analysis (TGA)
Multi-band optical-NIR variability of blazars on diverse timescales
To search for optical variability on a wide range of timescales, we have
carried out photometric monitoring of two flat spectrum radio quasars, 3C 454.3
and 3C 279, plus one BL Lac, S5 0716+714, all of which have been exhibiting
remarkably high activity and pronounced variability at all wavelengths. CCD
magnitudes in B, V, R and I pass-bands were determined for 7000 new
optical observations from 114 nights made during 2011 - 2014, with an average
length of 4 h each, at seven optical telescopes: four in Bulgaria, one
in Greece, and two in India. We measured multiband optical flux and colour
variations on diverse timescales. Discrete correlation functions were computed
among B, V, R, and I observations, to search for any time delays. We found weak
correlations in some cases with no significant time lags. The structure
function method was used to estimate any characteristic time-scales of
variability. We also investigated the spectral energy distribution of the three
blazars using B, V, R, I, J and K pass-band data. We found that the sources
almost always follows a bluer-when-brighter trend. We discuss possible physical
causes of the observed spectral variability.Comment: Accepted for publication in MNRAS, 16 pages, 11 figures, 5 tables,
plus supplementary material containing additional figures and tables (please
contact authors for it
Cytokine cascade in dengue hemorrhagic fever: implications for pathogenesis
Dengue virus produces a mild acute febrile illness, dengue fever (DF) and a severe illness, dengue hemorrhagic fever (DHF). The characteristic feature of DHF is increased capillary permeability leading to extensive plasma leakage in serous cavities resulting in shock. The pathogenesis of DHF is not fully understood. This paper presents a cascade of cytokines, that in our view, may lead to DHF. The main feature is the early generation of a unique cytokine, human cytotoxic factor (hCF) that initiates a series of events leading to a shift from Th1-type response in mild illness to a Th2-type response resulting in severe DHF. The shift from Th1 to Th2 is regulated by the relative levels of interferon-gamma and interleukin (IL)-10 and between IL-12 and transforming growth factor-ÎČ , which showed an inverse relationship in patients with DF
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