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Despite the recent advances in quantum technology, the problem of controlling the light emission properties of quantum emitters used in numerous applications remains: a large spectral width, low intensity, blinking, photodegradation, biocompatibility, etc . In this work, we present the theoretical and experimental investigation of quantum light sources - mesoscopic systems consisting of fluorescent molecules in a thin polydopamine layer coupled with metallic or dielectric nanoparticles. Polydopamines possess many attractive adhesive and optical properties that promise their use as host media for dye molecules. However, numerous attempts to incorporate fluorescent molecules into polydopamines have failed, as polydopamine has been shown to be a very efficient fluorescence quencher through Förster resonance energy transfer and/or photoinduced electron transfer. Using the system as an example, we demonstrate new insights into the interactions between molecules and electromagnetic fields by carefully shaping its energy levels through strong matter-wave coupling of molecules to metallic nanoparticles. We show that the strong coupling effectively suppresses the quenching of fluorescent molecules in polydopamine, opening new possibilities for imaging.

The tick-borne encephalitis (TBE) virus has been confirmed by molecular analysis in the Caucasus region for the first time. The virus obtained from a tick Ixodes ricinus ex Caspian green lizard belongs to the Zausaev strain of the Siberian subtype (not to a strain of the European subtype highly distributed in the territories adjacent to the Caucasus). This unusual record indicates the need to study the role of lizards in the circulation of natural focal infections.

Existing methods for the creation of subwavelength resonators use either structures with negative permittivity, by exploiting subwavelength plasmonic resonances, or dielectric structures with a high refractive index, which reduce the wavelength. Here, we provide an alternative to these two methods based on a modification of the modes of dielectric resonators by means of an active medium. On the example of the dielectric active layer of size substantially smaller than a half-wavelength of light, we demonstrate that there is a gain at exceeding of which the change in phase due to the reflection at the layer boundaries compensates the change in phase due to propagation over the layer. Above this value of the gain, an unconventional mode forms, in which the phase shift after a round-trip of the light is zero. We show that this mode can be exploited to create a laser, the size of which is much smaller than the wavelength of the generated light and scales inversely with the square of absolute value of the refractive index in the active medium. Our results pave the way to creation of dielectric lasers of subwavelength size.

Rock lizards of the genus Darevskia are interesting research models due to their asexual reproduction. Ectoparasitic mites and ticks of these lizards are poorly known, despite some of these chelicerates being vector pathogens of humans and wildlife. Here we document and curate previously known data on ectoparasitic Acari of rock lizards and, based on our extensive survey, provide an annotated list of these ectoparasitic arthropods (six tick species, one macronyssid species, and seven chigger species). We also provide new host records ( Ixodes ricinus on Darevskia caucasica , D. dryada , D. mixta , and D. szczerbaki ; Haemaphysalis sulcata on D. rudis ; Odontacarus saxicolis on D. brauneri ); and new geographical records ( O. saxicolis in Russia and Georgia).

Photobleaching is one of the basic chemical processes that occur naturally in organic molecules. In this work, we investigate the quantum dynamics of Cy 7.5 dye molecules optically coupled to Au nanorod particles and experimentally demonstrate the decrease of the photobleaching rate in this hybrid system. We discover the effect of a resonance-like behavior not observed before for any type of emitter─the photobleaching rate of the dye molecules reaches a minimum for a suitable number of molecules coupled to the nanoparticle. The manifestation of the effect is the consequence of shifts in the energy levels in the hybrid system caused by the change in the number of molecules coupled to a nanoparticle. The energy shifts are the prerequisite for the effective depopulation of the triplet level, which is responsible for the photodegradation mechanism. The discovered effect paves the way for increasing the efficiency of optoelectronic and photovoltaic devices.

In this Letter, we give a new, to the best of our knowledge, perspective on the origin of light coherence in lasers. We demonstrate that a coherence appears below the lasing threshold and manifests itself as long-range correlations between polarizations of active medium atoms. These correlations contribute to the formation of a collective state of atomic polarizations and electromagnetic field modes, which interacts more effectively with the active medium and lases when pumping exceeds the lasing threshold. We demonstrate that inhibiting these atomic correlations leads to the destruction of the collective state and suppression of lasing. The obtained results open up new ways to control coherence.

Usually, the cavity is considered an intrinsic part of laser design to enable coherent emission. For different types of cavities, it is assumed that the light coherence is achieved by different ways. We show that regardless of the type of cavity, the lasing condition is universal and is determined by the ratio of the width of the atomic spectrum to the product of the number of atoms and the spontaneous radiation rate in the laser structure. We demonstrate that cavity does not play a crucial role in lasing since it merely decreases the threshold by increasing the photon emission rate thanks to the Purcell effect. A threshold reduction can be achieved in a cavity-free structure by tuning the local density of states of the electromagnetic field. This paves the way for the design of laser devices based on cavity-free systems.

The creation of nanoscale lasers that operate above a coherent threshold is a challenging problem. We propose a way to circumvent this issue using systems in which a strong coupling regime is achieved between the light and the active medium. In the strong coupling regime, energy oscillations take place between the EM field in the cavity and the atoms. We show that by applying appropriate time modulation to the pumping, it is possible to control these energy oscillations in such a way that coherence in the laser system appears below the lasing threshold. In this approach, the radiation linewidth is two orders of magnitude smaller than the linewidth of a conventional laser for the same photon number. In addition, the second order coherence function of the output radiation is reduced from two to one before the system reaches a positive population inversion. Our results pave the way for the creation of nanoscale sources of coherent radiation that can operate below the lasing threshold.

We suggest a quantum description of Rayleigh light scattering on atoms. We show that an entangled state of the excited atom and the incident photon is formed during the scattering. Due to entanglement, a photon is never completely absorbed by the atom. The formation of the scattering spectrum is considered as a relaxation of incident photons to the reservoir of free space modes that are in thermal equilibrium. Additional excitations of the reservoir modes occurring during scattering are treated as scattered light. We show that even if the frequency of incident photons is incommensurate with an atomic transition frequency, the scattered light spectrum has a maximum at the frequency of incident photons. In addition, the linewidth of the scattered light is much smaller than that of the spontaneous emission of a single atom. Therefore, the process can be considered as elastic.

Ilya S. Darevsky co-described 70 taxa (three genera, 46 species, 21 subspecies) in 44 publications belonging to five orders, eight families of amphibians and reptiles during his career in herpetology. Of this number, three taxa are fossil and 57 taxa are currently considered as valid. By the regions where new taxa were discovered Southeast Asia and Western Asia (includes Caucasus and Asia Minor) dominates. The largest number of descriptions was published in the Russian Journal of Herpetology.

We develop a theory of lasing of a collection of pumped active atoms without a resonator (either regular or random). Due to spontaneous emission into free space, phases of free space electromagnetic modes fluctuate. These phase fluctuations can be reduced to frequency fluctuations. The closer the frequency of fluctuation to the transition frequency of the active atoms, the higher lifetime of the fluctuation. We show that because of this, the average frequency of modes pulls toward the transition frequency. This leads to a maximum in the density of states of the electromagnetic field and a decrease of the mode group velocity. Consequently, the coupling of modes with atoms as well as the lifetime of fluctuations increase. Thus, mode pulling provides positive feedback. When the pump rate exceeds a certain threshold, the lifetime of one of the realized fluctuations diverges, and radiation becomes coherent.

We present information on primary type specimens for 13,282 species and subspecies of reptiles compiled in the Reptile Database, that is, holotypes, neotypes, lectotypes, and syntypes. These represent 99.4% of all 13,361 currently recognized taxa (11,050 species and 2311 subspecies). Type specimens of 653 taxa (4.9%) are either lost or not located, were never designated, or we did not find any information about them. 51 species are based on iconotypes. To map all types to physical collections we have consolidated all synonymous and ambiguous collection acronyms into an unambiguous list of 364 collections holding these primary types. The 10 largest collections possess more than 50% of all (primary) reptile types, the 36 largest collections possess more than 10,000 types and the largest 73 collections possess over 90% of all types. Of the 364 collections, 107 hold type specimens of only 1 species or subspecies. Dozens of types are still in private collections. In order to increase their utility, we recommend that the description of type specimens be supplemented with data from high-resolution images and CT-scans, and clear links to tissue samples and DNA sequence data (when available). We request members of the herpetological community provide us with any missing type information to complete the list.

Several recent papers have reviewed the life and work of French herpetologist Louis Amédée Lantz. They have detailed the composition of his collections deposited in several museums. However, since then, several other important specimens from his collections deposited at the Natural History Museum (NHM, UK) have come to light and we here present all of them in detail. We discovered paralectotypes of Lacerta saxicola obscura Lantz Cyrén (BMNH 1918.11.21.5-7), syntypes of Lacerta boemica Sukhov (BMNH 1960.1.4.26-30, BMNH 1965.337-342) and Lacerta viridis media Lantz Cyrén (BMNH 1960.1.4.25, 1966.512). We also identified numerous specimens from the French Mediterranean islands in Lantz's collection deposited at the NHM, some of which represent the first reported specimens of their species from certain islands. We here provide data on all these specimens. We also place the Mediterranean island specimens from the Lantz collection in their historical context and emphasize the historical and taxonomic value of these collections.

Properties of light sources based on amplified spontaneous emission (ASE) are similar to the properties of lasers in many regards. However, even though ASE has been widely studied, its photon statistics have not been settled. There are no reliable theoretical estimates or unambiguous experimental data for the second-order coherence function of photons that characterizes the coherence properties of a light source. Our computer simulation clearly establishes that, independently of pump power, the light produced by ASE is similar to that of a thermal source. This result lays bare the fundamental difference between ASE radiation and laser radiation.

We show that a two-level atom with a high transition frequency ω SO can be inverted via non-radiative interaction with a cluster of excited low-frequency two-level atoms or quantum oscillators whose transition frequencies are smaller than ω SO . This phenomenon occurs due to the Förster resonant energy transfer arising during a train of quantum superoscillation of low-frequency two-level atoms. The suggested model could explain the mechanism of biophoton emission.