36 results match your criteria: "Mechanics and Optics ITMO University[Affiliation]"

Article Synopsis
  • - Peptide dendrimers are promising for biomedical uses because they are biocompatible and have low toxicity, making them suitable for drug and gene delivery as well as nanoparticle synthesis.
  • - This study tests two theories regarding dendrimers: that NMR relaxations are unaffected by excluded volume effects and that the mobility of side and terminal segments is similar.
  • - Results show that temperature-related NMR relaxations of inner groups in two types of dendrimers are nearly the same, supporting the first theory, while terminal groups also show similar behavior, backing the second theory.
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On the Possibility of Calculating Entropy, Free Energy, and Enthalpy of Vitreous Substances.

Entropy (Basel)

March 2018

Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University), 4 Birzhevaya linia, 199034 St. Petersburg, Russia.

A critical analysis for the arguments in support of, and against, the traditional approach to thermodynamics of vitreous state is provided. In this approach one presumes that there is a continuous variation of the entropy in the glass-liquid transition temperature range, or a "" towards 0 K which produces a positive value of the entropy at → 0 K. I find that arguments given against this traditional approach use a different understanding of the thermodynamics of glass transition on cooling a liquid, because it suggests a discontinuity or "" in the variation of entropy in the glass-liquid transition range.

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Self-Assembly of Lysine-Based Dendritic Surfactants Modeled by the Self-Consistent Field Approach.

Langmuir

January 2018

St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University), Kronverkskiy pr. 49, St. Petersburg 197101, Russia.

Implementing a united atom model, we apply self-consistent field theory to study structure and thermodynamic properties of spherical micelles composed of surfactants that combine an alkyl tail with a charged lysine-based dendritic headgroup. Following experiments, the focus was on dendron surfactants with varying tail length and dendron generations G0, G1, G2. The heads are subject to acetylation modification which reduces the charge and hydrophilicity.

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We study the electro-optic properties of subwavelength-pitch deformed-helix ferroelectric liquid crystals (DHFLC) illuminated with unpolarized light. In the experimental setup based on the Mach-Zehnder interferometer, it was observed that the reference and the sample beams being both unpolarized produce the interference pattern which is insensitive to rotation of in-plane optical axes of the DHFLC cell. We find that the field-induced shift of the interference fringes can be described in terms of the electrically dependent Pancharatnam relative phase determined by the averaged phase shift, whereas the visibility of the fringes is solely dictated by the phase retardation.

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Rotating and Precessing Dissipative-Optical-Topological-3D Solitons.

Phys Rev Lett

October 2016

Vavilov State Optical Institute, 199034 Saint Petersburg, Russia and National Research University of Information Technologies, Mechanics and Optics (ITMO University), 197101 Saint Petersburg, Russia.

We predict and study a new type of three-dimensional soliton: asymmetric rotating and precessing stable topological-dissipative-optical localized structures in homogeneous media with saturable amplification and absorption. The crucial factor determining their dynamics is the ratio of the diffusion coefficients characterizing the frequency dispersion and angular selectivity (dichroism) of the scheme. These vortex solitons exist and are stable for overcritical values of the selectivity coefficients and can be realized in lasers of large sizes with saturable absorption.

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Local orientational mobility in regular hyperbranched polymers.

Phys Rev E

July 2016

Laboratoire Ondes et Matière d'Aquitaine (LOMA), CNRS UMR 5798, Talence, France.

We study the dynamics of local bond orientation in regular hyperbranched polymers modeled by Vicsek fractals. The local dynamics is investigated through the temporal autocorrelation functions of single bonds and the corresponding relaxation forms of the complex dielectric susceptibility. We show that the dynamic behavior of single segments depends on their remoteness from the periphery rather than on the size of the whole macromolecule.

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Is the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers sensitive to excluded volume interactions?

Phys Chem Chem Phys

September 2016

St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University), Kronverskiy pr. 49, St. Petersburg, 197101 Russia.

The effect of excluded volume (EV) interactions on the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers has been studied by using Brownian dynamics simulations. The study was motivated by the theory developed by Markelov et al., [J.

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Fluctuations of work in nearly adiabatically driven open quantum systems.

Phys Rev E Stat Nonlin Soft Matter Phys

February 2015

QCD Labs, COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland.

We extend the quantum jump method to nearly adiabatically driven open quantum systems in a way that allows for an accurate account of the external driving in the system-environment interaction. Using this framework, we construct the corresponding trajectory-dependent work performed on the system and derive the integral fluctuation theorem and the Jarzynski equality for nearly adiabatic driving. We show that such identities hold as long as the stochastic dynamics and work variable are consistently defined.

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Preparation of chiral quantum dots.

Nat Protoc

April 2015

1] School of Chemistry and Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) Institute, Trinity College Dublin, Dublin, Ireland. [2] Center of Information Optical Technologies, Information Technologies, Mechanics and Optics (ITMO) University, Saint Petersburg, Russia.

Chiral quantum dots (QDs) are expected to have a range of potential applications in photocatalysis, as specific antibacterial and cytotoxic drug-delivery agents, in assays, as sensors in asymmetric synthesis and enantioseparation, and as fluorescent chiral nanoprobes in biomedical and analytical technologies. In this protocol, we present procedures for the synthesis of chiral optically active QD nanostructures and their quality control using spectroscopic studies and transmission electron microscopy imaging. We closely examine various synthetic routes for the preparation of chiral CdS, CdSe, CdTe and doped ZnS QDs, as well as of chiral CdS nanotetrapods.

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By using the Scheutjens-Fleer self-consistent field approach, the structure of the fourth-generation dendrimer with attached terminal chemically different oligomeric segments is studied theoretically. It is demonstrated that an incompatibility of terminal segments with inner dendrimer units leads to formation of a "hollow" core with reduced polymer density in the dendrimer center. This effect is enhanced with a deterioration in the solvent quality for terminal segments.

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Crystal structure of 1,3-dimethyl-3-phenyl-pyrrolidine-2,5-dione: a clinically used anti-convulsant.

Acta Crystallogr Sect E Struct Rep Online

September 2014

X-Ray Structural Centre, A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilov Street, B-334, Moscow 119991, Russian Federation.

In the title compound, C12H13NO2, the five-membered ring has an envelope conformation; the disubstituted C atom lies out of the mean plane through the four other ring atoms (r.m.s.

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