Instanton bundles on Fano threefolds

We introduce the notion of an instanton bundle on a Fano threefold of index 2. For such bundles we give an analogue of a monadic description and discuss the curve of jumping lines. The cases of threefolds of degree 5 and 4 are considered in a greater detail.Comment: 31 page, to appear in CEJ

Electrically Driven Microcavity Exciton-Polariton Optomechanics at 20 GHz

Microcavity exciton polaritons enable the resonant coupling of excitons and photons to vibrations in the super-high-frequency (SHF, 3–30 GHz) domain. We introduce here a novel platform for coherent SHF optomechanics based on the coupling of polaritons and electrically driven SHF longitudinal acoustic phonons confined in a planar Bragg microcavity. The highly monochromatic phonons with tunable amplitudes are excited over a wide frequency range by piezoelectric transducers, which also act as efficient phonon detectors with a very large dynamical range. The microcavity platform exploits the long coherence time of polaritons as well as their efficient coupling to phonons. Furthermore, an intrinsic property of the platform is the backfeeding of phonons to the interaction region via reflections at the sample boundaries, which leads to quality factor × frequency products (Q×f) exceeding 1014  Hz as well as huge modulation amplitudes of the optical transition energies exceeding 8 meV. We show that the modulation is dominated by the phonon-induced energy shifts of the excitonic polariton component. Thus, the large modulation leads to a dynamical switching of light-matter nature of the particles from a mixed (i.e., polaritonic) one to photonlike and excitonlike states at frequencies up to 20 GHz. On the one hand, this work opens the way for electrically driven polariton optomechanics in the nonadiabatic, sideband-resolved regime of coherent control. Here, the bidirectionality of the transducers can be exploited for light-to-sound-to-rf conversion. On the other hand, the large phonon frequencies and Q×f products enable phonon control with optical readout down to the single-particle regime at relatively high temperatures (of 1 K)

Dynamically Tuned Arrays of Polariton Parametric Oscillators

Optical parametric oscillations (OPOs) - a non-linear process involving the coherent coupling of an optically excited two particle pump state to a signal and an idler states with different energies - is a relevant mechanism for optical amplification as well as for the generation of correlated photons. OPOs require states with well-defined symmetries and energies: the fine-tuning of material properties and structural dimensions to create these states remains a challenge for the realization of scalable OPO-based functionalities in semiconductor nanostructures. Here, we demonstrate a pathway towards this goal based on the control of confined microcavity exciton-polaritons modulated by the spatially and time varying dynamical potentials produced by a surface acoustic waves (SAW). The exciton-polariton are confined in um-sized intra-cavity traps fabricated by structuring a planar semiconductor microcavity during the epitaxial growth process. OPOs in these structures benefit from the enhanced non-linearities of confined systems. We show that SAW fields induce state-dependent and time-varying energy shifts, which enable the energy alignment of the confined levels with the appropriate symmetry for OPO triggering. Furthermore, the dynamic acoustic tuning, which is fully described by a theoretical model for the modulation of the confined polaritons by the acoustic field, compensates for fluctuations in symmetry and dimensions of the confinement potential thus enabling a variety of dynamic OPO regimes. The robustness of the acoustic tuning is demonstrated by the synchronous excitation of an array of confined OPOs using a single acoustic beam, thus opening the way for the realization of scalable non-linear on-chip systems.Comment: Main text: 10 pages, 7 figures Supplementary: 6 pages, 3 figure

Individual differences in growth and in accumulation of secondary metabolites in Rhodiola rosea cultivated in Western Siberia

In this study, growth parameters of underground parts and concentrations of phenylpropanoids, phenylethanoids, flavonoids, hydroxybenzoic acids, and catechins in aqueous–ethanol extracts of 6-year-old cultivated plants of Rhodiola rosea (propagated in vitro) of Altai Mountain origin were analyzed, and differences in chemical composition among plant specimens and between plant parts (rhizome and root) were evaluated. High-performance liquid chromatography detected 13 phenolic compounds. Roots contained 1.28 times higher phenylethanoids levels (1273.72 mg/100 g) than rhizomes did. Overall, the concentration of phenylethanoids in underground organs was not high and ranged from 21.36 to 103.00 mg/100 g. High variation among R. rosea individual plants was noted both in growth characteristics and in levels of secondary metabolites under our cultivation conditions. It was found that concentrations of phenylpropanoids, phenylethanoids, and catechins significantly depend on the plant part analyzed (p ≤ 0.05). Specimen No. 4 is characterized by the highest concentration of rosavins (1230.99 mg/plant) and the lowest concentration of cinnamyl alcohol (62.87 mg/plant). Despite the wide range of values, all 10 tested specimens (underground part) met the minimum requirements of the United States Pharmacopeia (2015) for rosavins (0.3%) and of the Russia State Pharmacopoeia (2015) for the average level of rosavins (roots): (1%)

Trollius austrosibiricus (Ranunculaceae), a new species from South Siberia

Trolliusaustrosibiricus Erst & Luferov, sp. nov., a new species from Russian South Siberia is described and illustrated. This new species is endemic to Western and Central Siberia. Morphologically, it is close to the East Asian species T.chinensis and T.macropetalus. However, it differs from the aforementioned species due to the morphology of the rhizomes, aerial shoots, sepals and petals. This species is also distinguished from T.asiaticus, which is widespread in Russia (Western and Eastern Siberia), Mongolia, China, north-eastern Kazakhstan and in the northeast of the European part of Russia, in having a smaller number of sepals, longer persistent styles and petals longer than sepals. In addition, an identification key for all Russian species is given and all species have been discussed

New bounds on the neutrino magnetic moment from the plasma induced neutrino chirality flip in a supernova

The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account, in a more consistent way than in earlier publications. It is shown in part that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the neutrino spin-flip. The best upper bound on the neutrino magnetic moment from SN1987A is improved by the factor of 3 to 7.Comment: 19 pages, LaTeX, 7 EPS figures, submitted to Journal of Cosmology and Astroparticle Physic

Морфология спор Parahemionitis arifolia (Cheilanthoideae, Pteridaceae)

A study of spores of the single species of the genus Parahemionitis Panigrahi was performed using the method of scanning electronic microscopy (SEM). Spores of Parahemionitis arifolia (Burm. f.) Panigrahi are tetrahedral trilete, roundish-triangular in polar position, with micro-wrinkled exospore and sculptured perispore. Sculpture of perispore is cristate-reticulate, cristae are quite regularly distributed and form reticulum with small mostly closed polygonal luminae of different shape. Laesura arms are often obscured by numerous cristae. Size of spores is 53–63 × 40–42 μm. Spores of P. arifolia are similar in perispore sculpture with those of species of some cheilanthoid ferns

Medium-Dependent Antibacterial Properties and Bacterial Filtration Ability of Reduced Graphene Oxide

Toxicity of reduced graphene oxide (rGO) has been a topic of multiple studies and was shown to depend on a variety of characteristics of rGO and biological objects of interest. In this paper, we demonstrate that when studying the same dispersions of rGO and fluorescent Escherichia coli (E. coli) bacteria, the outcome of nanotoxicity experiments also depends on the type of culture medium. We show that rGO inhibits the growth of bacteria in a nutrition medium but shows little effect on the behavior of E. coli in a physiological saline solution. The observed effects of rGO on E. coli in different media could be at least partially rationalized through the adsorption of bacteria and nutrients on the dispersed rGO sheets, which is likely mediated via hydrogen bonding. We also found that the interaction between rGO and E. coli is medium-dependent, and in physiological saline solutions they form stable flocculate structures that were not observed in nutrition media. Furthermore, the aggregation of rGO and E. coli in saline media was observed regardless of whether the bacteria were alive or dead. Filtration of the aggregate suspensions led to nearly complete removal of bacteria from filtered liquids, which highlights the potential of rGO for the filtration and separation of biological contaminants, regardless of whether they include live or dead microorganisms

Medium-Dependent Antibacterial Properties and Bacterial Filtration Ability of Reduced Graphene Oxide

Toxicity of reduced graphene oxide (rGO) has been a topic of multiple studies and was shown to depend on a variety of characteristics of rGO and biological objects of interest. In this paper, we demonstrate that when studying the same dispersions of rGO and fluorescent Escherichia coli (E. coli) bacteria, the outcome of nanotoxicity experiments also depends on the type of culture medium. We show that rGO inhibits the growth of bacteria in a nutrition medium but shows little eect on the behavior of E. coli in a physiological saline solution. The observed eects of rGO on E. coli in dierent media could be at least partially rationalized through the adsorption of bacteria and nutrients on the dispersed rGO sheets, which is likely mediated via hydrogen bonding. We also found that the interaction between rGO and E. coli is medium-dependent, and in physiological saline solutions they form stable flocculate structures that were not observed in nutrition media. Furthermore, the aggregation of rGO and E. coli in saline media was observed regardless of whether the bacteria were alive or dead. Filtration of the aggregate suspensions led to nearly complete removal of bacteria from filtered liquids, which highlights the potential of rGO for the filtration and separation of biological contaminants, regardless of whether they include live or dead microorganisms