550 research outputs found
Nonlinear metal-dielectric nanoantennas for light switching and routing
We introduce a novel hybrid metal-dielectric nanoantenna composed of
dielectric (crystalline silicon) and metal (silver) nanoparticles. A
high-permittivity dielectric nanoparticle allows to achieve effective light
harvesting, and nonlinearity of a metal nanoparticle controls the radiation
direction. We show that the radiation pattern of such a nanoantenna can be
switched between the forward and backward directions by varying only the light
intensity around the level of 11 MW/cm, with the characteristic switching
time of 260 fs.Comment: 9 pages, 5 figures, submitted to New J. Phy
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Digging into Lipid Membrane Permeation for Cardiac Ion Channel Blocker d-Sotalol with All-Atom Simulations.
Interactions of drug molecules with lipid membranes play crucial role in their accessibility of cellular targets and can be an important predictor of their therapeutic and safety profiles. Very little is known about spatial localization of various drugs in the lipid bilayers, their active form (ionization state) or translocation rates and therefore potency to bind to different sites in membrane proteins. All-atom molecular simulations may help to map drug partitioning kinetics and thermodynamics, thus providing in-depth assessment of drug lipophilicity. As a proof of principle, we evaluated extensively lipid membrane partitioning of d-sotalol, well-known blocker of a cardiac potassium channel Kv11.1 encoded by the hERG gene, with reported substantial proclivity for arrhythmogenesis. We developed the positively charged (cationic) and neutral d-sotalol models, compatible with the biomolecular CHARMM force field, and subjected them to all-atom molecular dynamics (MD) simulations of drug partitioning through hydrated lipid membranes, aiming to elucidate thermodynamics and kinetics of their translocation and thus putative propensities for hydrophobic and aqueous hERG access. We found that only a neutral form of d-sotalol accumulates in the membrane interior and can move across the bilayer within millisecond time scale, and can be relevant to a lipophilic channel access. The computed water-membrane partitioning coefficient for this form is in good agreement with experiment. There is a large energetic barrier for a cationic form of the drug, dominant in water, to cross the membrane, resulting in slow membrane translocation kinetics. However, this form of the drug can be important for an aqueous access pathway through the intracellular gate of hERG. This route will likely occur after a neutral form of a drug crosses the membrane and subsequently re-protonates. Our study serves to demonstrate a first step toward a framework for multi-scale in silico safety pharmacology, and identifies some of the challenges that lie therein
Coherent X-ray radiation of a relativistic electron in a bilayer amorphous layer β single crystal target
A theory of coherent X-ray radiation is proposed, which is generated when a relativistic electron is transversing a hybrid target consisting of two parallel plates: amorphous and crystalline. Within a two-wave approximation of the dynamic diffraction theory, expressions describing the spectral-angular density of coherent radiation from this target are obtaine
Diffracted transition radiation of a relativistic electron in a three-layer structure
We develop a theory of coherent X-ray radiation of a relativistic electron crossing a three-layer structure consisting of two amorphous layers and a crystal layer. The particular case when the second amor- phous layer is a vacuum is considered. Expressions describing the spectral and angular distributions of coher-ent radiation in such a structure are derived and analyze
ΠΡΠ΅Π΄Π²Π°ΡΠΈΡΠ΅Π»ΡΠ½Π°Ρ ΠΎΡΠ΅Π½ΠΊΠ° ΡΠ½Π΅ΡΠ³ΠΎΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ Π·Π΄Π°Π½ΠΈΠΉ Π²Β ΡΡΠ»ΠΎΠ²ΠΈΡΡ ΡΠ΅Π·ΠΊΠΎ ΠΊΠΎΠ½ΡΠΈΠ½Π΅Π½ΡΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΊΠ»ΠΈΠΌΠ°ΡΠ°
Construction of energy-efficient buildings becomes a top priority for many countries. Yet certain obstacles in achieving internal environment comfort standards remain in regions with extreme continental climate. In addition to engineering and economic challenges, there exist design process issues since design data should closely correspond with resulting performance of the building. This paper focuses on accurate energy demand estimation during design stage. Two types of buildings designed for Ural-Siberian region of Russia and for Kazakhstan are examined: detached and medium-rise apartment buildings. Most influential factors are taken into consideration and general recommendations on improving energy efficiency using effective combination of structural and engineering solutions are given. Adaptation of design procedure in terms of extreme continental climate made by means of simplified but precise Passive House planning tool is demonstrated.Π‘ΡΡΠΎΠΈΡΠ΅Π»ΡΡΡΠ²ΠΎ ΡΠ½Π΅ΡΠ³ΠΎΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΡΡ
Π·Π΄Π°Π½ΠΈΠΉ ΡΠ²Π»ΡΠ΅ΡΡΡ ΠΏΡΠΈΠΎΡΠΈΡΠ΅ΡΠ½ΡΠΌ Π½Π°ΠΏΡΠ°Π²Π»Π΅Π½ΠΈΠ΅ΠΌ Π΄Π»Ρ ΠΌΠ½ΠΎΠ³ΠΈΡ
ΡΡΡΠ°Π½. ΠΠ΄Π½Π°ΠΊΠΎ Π² ΡΠ΅Π³ΠΈΠΎΠ½Π°Ρ
Ρ ΡΡΡΠΎΠ²ΡΠΌ ΠΊΠ»ΠΈΠΌΠ°ΡΠΎΠΌ ΡΠ°ΡΡΠΎ Π²ΠΎΠ·Π½ΠΈΠΊΠ°ΡΡ ΠΏΡΠΎΠ±Π»Π΅ΠΌΡ Π΄ΠΎΡΡΠΈΠΆΠ΅Π½ΠΈΡ Π½ΠΎΡΠΌΠ°ΡΠΈΠ²Π½ΡΡ
ΠΏΠΎΠΊΠ°Π·Π°ΡΠ΅Π»Π΅ΠΉ ΠΊΠΎΠΌΡΠΎΡΡΠ° Π²Π½ΡΡΡΠ΅Π½Π½Π΅ΠΉ ΡΡΠ΅Π΄Ρ. Π ΠΈΠ΄Π΅Π°Π»Π΅ ΠΏΡΠΎΠ΅ΠΊΡΠ½ΡΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΡ ΠΏΠΎΡΡΠ΅Π±Π½ΠΎΡΡΠ΅ΠΉ Π² ΡΠ»Π΅ΠΊΡΡΠΎΡΠ½Π΅ΡΠ³ΠΈΠΈ Π½Π° ΠΎΡΠΎΠΏΠ»Π΅Π½ΠΈΠ΅ ΠΈ ΠΊΠΎΠ½Π΄ΠΈΡΠΈΠΎΠ½ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ Π·Π΄Π°Π½ΠΈΡ Π΄ΠΎΠ»ΠΆΠ½Ρ ΡΠΎΡΠ½ΠΎ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΎΠ²Π°ΡΡ ΠΈΡΠΎΠ³ΠΎΠ²ΡΠΌ ΠΏΠΎΠΊΠ°Π·Π°ΡΠ΅Π»ΡΠΌ. Π ΡΡΠΎΠΉ ΡΡΠ°ΡΡΠ΅ ΡΠ°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°ΡΡΡΡ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠΈ ΡΠΎΡΠ½ΠΎΠ³ΠΎ ΠΏΡΠΎΠ³Π½ΠΎΠ·ΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΡΠ½Π΅ΡΠ³ΠΎΠΏΠΎΡΡΠ΅Π±Π»Π΅Π½ΠΈΡ Π½Π° ΡΡΠ°Π΄ΠΈΠΈ ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ. ΠΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΎ Π΄Π²Π° ΡΠΈΠΏΠ° Π·Π΄Π°Π½ΠΈΠΉ, ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΡΠ΅ΠΌΡΡ
Π΄Π»Ρ Π£ΡΠ°Π»ΠΎ-Π‘ΠΈΠ±ΠΈΡΡΠΊΠΎΠ³ΠΎ ΡΠ΅Π³ΠΈΠΎΠ½Π° Π ΠΎΡΡΠΈΠΈ ΠΈ ΠΠ°Π·Π°Ρ
ΡΡΠ°Π½Π°: ΠΈΠ½Π΄ΠΈΠ²ΠΈΠ΄ΡΠ°Π»ΡΠ½ΡΠΉ Π΄ΠΎΠΌ ΠΈ ΠΌΠ½ΠΎΠ³ΠΎΠΊΠ²Π°ΡΡΠΈΡΠ½ΡΠΉ Π΄ΠΎΠΌ ΡΡΠ΅Π΄Π½Π΅ΠΉ ΡΡΠ°ΠΆΠ½ΠΎΡΡΠΈ. ΠΠ°Π½Ρ ΡΠ΅ΠΊΠΎΠΌΠ΅Π½Π΄Π°ΡΠΈΠΈ ΠΏΠΎ ΡΠ½ΠΈΠΆΠ΅Π½ΠΈΡ ΡΠ½Π΅ΡΠ³ΠΎΠΏΠΎΡΡΠ΅Π±Π»Π΅Π½ΠΈΡ Π·Π΄Π°Π½ΠΈΠΉ ΠΏΡΡΠ΅ΠΌ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΠ³ΠΎ ΡΠΎΡΠ΅ΡΠ°Π½ΠΈΡ ΠΊΠΎΠ½ΡΡΡΡΠΊΡΠΈΠ²Π½ΡΡ
ΠΈ ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΡΡ
ΡΠ΅ΡΠ΅Π½ΠΈΠΉ. ΠΠΎΠΊΠ°Π·Π°Π½ ΡΡΠ΅Ρ ΠΎΡΠ½ΠΎΠ²Π½ΡΡ
ΡΠ°ΠΊΡΠΎΡΠΎΠ², Π²Π»ΠΈΡΡΡΠΈΡ
Π½Π° ΡΠ½Π΅ΡΠ³Π΅ΡΠΈΡΠ΅ΡΠΊΠΈΠΉ Π±Π°Π»Π°Π½Ρ Π·Π΄Π°Π½ΠΈΠΉ. ΠΠ° ΠΏΡΠΈΠΌΠ΅ΡΠ΅ ΠΠ°ΠΊΠ΅ΡΠ° ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΠ°ΡΡΠΈΠ²Π½ΠΎΠ³ΠΎ Π΄ΠΎΠΌΠ° 2007 ΠΏΡΠΈΠ²Π΅Π΄Π΅Π½ ΠΏΡΠΈΠΌΠ΅Ρ Π°Π΄Π°ΠΏΡΠ°ΡΠΈΠΈ ΡΠΏΡΠΎΡΠ΅Π½Π½ΠΎΠΉ, Π½ΠΎ Π΄ΠΎΡΡΠ°ΡΠΎΡΠ½ΠΎ ΡΠΎΡΠ½ΠΎΠΉ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠΈ ΡΠ°ΡΡΠ΅ΡΠ° ΠΊ ΡΠ΅Π·ΠΊΠΎ ΠΊΠΎΠ½ΡΠΈΠ½Π΅Π½ΡΠ°Π»ΡΠ½ΡΠΌ ΠΊΠ»ΠΈΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΡΠ»ΠΎΠ²ΠΈΡΠΌ
Resolving the mystery of milliwatt-threshold opto-mechanical self-oscillation in dual-nanoweb fiber
It is interesting to pose the question: How best to design an optomechanical device, with no electronics, optical cavity, or laser gain, that will self-oscillate when pumped in a single pass with only a few mW of single-frequency laser power? One might begin with a mechanically resonant and highly compliant system offering very high optomechanical gain. Such a system, when pumped by single-frequency light, might self-oscillate at its resonant frequency. It is well-known, however, that this will occur only if the group velocity dispersion of the light is high enough so that phonons causing pump-to-Stokes conversion are sufficiently dissimilar to those causing pump-to-anti-Stokes conversion. Recently it was reported that two light-guiding membranes 20 ΞΌm wide, βΌ500 nm thick and spaced by βΌ500 nm, suspended inside a glass fiber capillary, oscillated spontaneously at its mechanical resonant frequency (βΌ6 MHz) when pumped with only a few mW of single-frequency light. This was surprising, since perfect Raman gain suppression would be expected. In detailed measurements, using an interferometric side-probing technique capable of resolving nanoweb movements as small as 10 pm, we map out the vibrations along the fiber and show that stimulated intermodal scattering to a higher-order optical mode frustrates gain suppression, permitting the structure to self-oscillate. A detailed theoretical analysis confirms this picture. This novel mechanism makes possible the design of single-pass optomechanical oscillators that require only a few mW of optical power, no electronics nor any optical resonator. The design could also be implemented in silicon or any other suitable material
Coherent control of flexural vibrations in dual-nanoweb fibers using phase-modulated two-frequency light
Coherent control of the resonant response in spatially extended
optomechanical structures is complicated by the fact that the optical drive is
affected by the back-action from the generated phonons. Here we report a new
approach to coherent control based on stimulated Raman-like scattering, in
which the optical pressure can remain unaffected by the induced vibrations even
in the regime of strong optomechanical interactions. We demonstrate
experimentally coherent control of flexural vibrations simultaneously along the
whole length of a dual-nanoweb fiber, by imprinting steps in the relative phase
between the components of a two-frequency pump signal,the beat frequency being
chosen to match a flexural resonance. Furthermore, sequential switching of the
relative phase at time intervals shorter than the lifetime of the vibrations
reduces their amplitude to a constant value that is fully adjustable by tuning
the phase-modulation depth and switching rate. The results may trigger new
developments in silicon photonics, since such coherent control uniquely
decouples the amplitude of optomechanical oscillations from power-dependent
thermal effects and nonlinear optical loss.Comment: This 11 pages-long document includes the main text with 8 figures and
an appendix with one figur
Hydrobionts of a freshwater oil-polluted northern lake: bioaccumulation of heavy metals in fish and the rate of ecosystem recovery
The response of phytoplankton, zooplankton, benthic and fish community structure to one of the biggest oil spill in history of Komi Republic (north-west part of Russia) was investigated using data from a long-term survey off the polluted lake. The characteristics of aquatic freshwater communities observed in the study area 10, 11 and 22 years after the spill (1994) were compared to find out the rate of natural recovery of the ecosystem after oil decontamination of bottom sediments. The concentrations of fifteen trace metals (Al, Cr, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Pb, U, Bi, Th) were analyzed in the tissues (muscle) of three fish species. The concentrations of Al (3-309 mg/kg), Cr (0,1-3,71 mg/kg), Fe (8,6-317 mg/kg), and Cu (0,09-99 mg/kg) in fishes from polluted lake resulted in most cases higher than reference thresholds. Quantitative and qualitative indicators of aquatic invertebrates from polluted lake reach those one of unpolluted lake but do not fully recover 22 years after the spill, despite that oil concentration in water column and in bottom sediments was lower than reference tresholds. We conclude that natural recovery rate of aquatic freshwater ecosystems in northern regions after oil pollution is extremely low. The purification of water and bottom sediments of oil-polluted northern water bodies is necessary for stimulation of ecosystem restoration
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