Search results for "ITC"
showing 10 items of 898 documents
ChemInform Abstract: Optical Switches with Biplanemers Obtained by Intramolecular Photocycloaddition Reactions of Tethered Arenes
2013
The dimerization of anthracene by a [4π + 4π] cycloaddition is one of the oldest and best known reactions in photochemistry. In the series of tethered bichromophoric arenes, this reaction type could be extended to anthracene–naphthalene, naphthalene–naphthalene and recently even to anthracene–benzene and naphthalene–benzene systems. Cyclophanes, which can be regarded as twofold or multiple tethered systems, are not discussed here. The cycloisomerizations are performed by irradiation at the long-wavelength absorption (λ > 270 nm), whereas shorter wavelengths (λ < 270 nm) lead to cycloreversions, which can be also achieved by a thermal route. The systems represent therefore a P- and T-type ph…
Trans-to-cis photoisomerization of cyclocurcumin in different environments rationalized by computational photochemistry
2020
International audience; Cyclocurcumin is a turmeric component that attracted much less attention compared to the well known curcumin. In spite of the less deep charcaterization of its properties, cyclocurcumin has shown promising anticancer effects when used in combination with curcumin. Especially, due to its peculiar molecular structure, cyclocurcumin can be regarded as an almost ideal photoswitch, whose capabilities can also be exploited for relevant biological applications. Here, by means of state-of-the-art computational methods for electronic excited-state calculations (TD-DFT, MS-CASPT2, XMS-CASPT2) we analyze in detail the absorption and photoisomerization pathways leading from the …
From Continuous to Discontinuous Transitions in Social Diffusion
2018
Models of social diffusion reflect processes of how new products, ideas or behaviors are adopted in a population. These models typically lead to a continuous or a discontinuous phase transition of the number of adopters as a function of a control parameter. We explore a simple model of social adoption where the agents can be in two states, either adopters or non-adopters, and can switch between these two states interacting with other agents through a network. The probability of an agent to switch from non-adopter to adopter depends on the number of adopters in her network neighborhood, the adoption threshold $T$ and the adoption coefficient $a$, two parameters defining a Hill function. In c…
Classification of gravitational-wave glitches via dictionary learning
2018
We present a new method for the classification of transient noise signals (or glitches) in advanced gravitational-wave interferometers. The method uses learned dictionaries (a supervised machine learning algorithm) for signal denoising, and untrained dictionaries for the final sparse reconstruction and classification. We use a data set of 3000 simulated glitches of three different waveform morphologies, comprising 1000 glitches per morphology. These data are embedded in non-white Gaussian noise to simulate the background noise of advanced LIGO in its broadband configuration. Our classification method yields a 96% accuracy for a large range of initial parameters, showing that learned diction…
Application of dictionary learning to denoise LIGO’s blip noise transients
2020
Data streams of gravitational-wave detectors are polluted by transient noise features, or ``glitches,'' of instrumental and environmental origin. In this work we investigate the use of total variation methods and learned dictionaries to mitigate the effect of those transients in the data. We focus on a specific type of transient, ``blip" glitches, as this is the most common type of glitch present in the LIGO detectors and their waveforms are easy to identify. We randomly select 100 blip glitches scattered in the data from advanced LIGO's O1 run, as provided by the citizen-science project Gravity Spy. Our results show that dictionary-learning methods are a valid approach to model and subtrac…
Stadnik and Flambaum Reply:
2016
In the comment of Avelino, Sousa and Lobo [arXiv:1506.06028], it is argued, by comparing the kinetic energy of a topological defect with the overall energy of a pulsar, that the origin of the pulsar glitch phenomenon due to the passage of networks of topological defects through pulsars is faced with serious difficulties. Here, we point out that topological defects may trigger pulsar glitches within traditional scenarios, such as vortex unpinning. If the energy transfer from a topological defect exceeds the activation energy for a single pinned vortex, this may lead to an avalanche of unpinning of vortices and consequently a pulsar glitch, and therefore the source of angular momentum and ene…
Optical Bistability and Switching in Oppositely Directed Coupler
2016
We report the optical bistability in two core oppositely directed coupler with negative index material channel. Using Langrangian variational method and Jacobi elliptic functions, we construct the solutions of the coupled nonlinear Schrodinger equations. The bistability arises due to the effective feedback mechanism as a result of opposite directionality of the phase velocity and energy flow in the negative index material channel. We report the various ways to control and manipulate the bistability threshold and hysteresis loop, which could be useful in the design and development of fast and low-threshold optical switches.
Exciton, biexciton and trion recombination dynamics in a single quantum dot under selective optical pumping
2008
Continuous wave- and time-resolved micro-photoluminescence spectroscopy has been performed on single InAs self-assembled quantum dots grown on GaAs. The presence of residual impurities (donors and acceptors) in samples with low dot density opens the possibility to switch from trion to neutral exciton states inside quantum dots by selective optical pumping. We propose a microstate model to describe the recombination dynamics of all the excitonic especies (neutral exciton, positive/negative trion and biexciton) under the considered optical pumping conditions when increasing the excitation power. © 2007 Elsevier B.V. All rights reserved.
Influence of light polarization on the dynamics of optically pumped lasers.
1990
The dynamic behavior of a coherently pumped ring laser with a homogeneously broadened four-level medium is analyzed theoretically, considering linearly polarized pump and generated laser beams. The laser is shown to be much more stable when these polarizations are parallel than when they are orthogonal. In the latter case the instability pump threshold can be as low as four times the first laser threshold, and the laser dynamics shows Lorenz-type features.
Ultracompact and Low-Power Plasmonic MZI Switch Using Cyclomer Loading
2015
We present a $2\times 2$ hybrid silicon-plasmonic thermooptic (TO) asymmetric Mach–Zehnder interferometric (MZI) switch having only 40- $\mu \text{m}$ long active cyclomer-loaded plasmonic phase arms. It requires less than 12 mW of power and has 2/5- $\mu \text{s}$ ON/OFF-times, respectively, a modulation depth higher than 90% and a 13.2-dB extinction ratio. Data traffic evaluation has been carried out using 10-Gb/s nonreturn-to-zero streams, yielding error-free operation at both switching states with power penalties ranging between 1 to 4.8 dB. The use of the cyclomer loading having a higher TO coefficient than polymethyl methacrylate has resulted to the smallest footprint among plasmonic …