Integral Flux Research Articles

Prospects for a survey of the galactic plane with the Cherenkov Telescope Array

Approximately one hundred sources of very-high-energy (VHE) gamma rays are known in the Milky Way, detected with a combination of targeted observations and surveys. A survey of the entire Galactic Plane in the energy range from a few tens of GeV to a few hundred TeV has been proposed as a Key Science Project for the upcoming Cherenkov Telescope Array Observatory (CTAO). This article presents the status of the studies towards the Galactic Plane Survey (GPS). We build and make publicly available a sky model that combines data from recent observations of known gamma-ray emitters with state-of-the-art physically-driven models of synthetic populations of the three main classes of established Galactic VHE sources (pulsar wind nebulae, young and interacting supernova remnants, and compact binary systems), as well as of interstellar emission from cosmic-ray interactions in the Milky Way. We also perform an optimisation of the observation strategy (pointing pattern and scheduling) based on recent estimations of the instrument performance. We use the improved sky model and observation strategy to simulate GPS data corresponding to a total observation time of 1620 hours spread over ten years. Data are then analysed using the methods and software tools under development for real data. Under our model assumptions and for the realisation considered, we show that the GPS has the potential to increase the number of known Galactic VHE emitters by almost a factor of five. This corresponds to the detection of more than two hundred pulsar wind nebulae and a few tens of supernova remnants at average integral fluxes one order of magnitude lower than in the existing sample above 1 TeV, therefore opening the possibility to perform unprecedented population studies. The GPS also has the potential to provide new VHE detections of binary systems and pulsars, to confirm the existence of a hypothetical population of gamma-ray pulsars with an additional TeV emission component, and to detect bright sources capable of accelerating particles to PeV energies (PeVatrons). Furthermore, the GPS will constitute a pathfinder for deeper follow-up observations of these source classes. Finally, we show that we can extract from GPS data an estimate of the contribution to diffuse emission from unresolved sources, and that there are good prospects of detecting interstellar emission and statistically distinguishing different scenarios.Thus, a survey of the entire Galactic plane carried out from both hemispheres with CTAO will ensure a transformational advance in our knowledge of Galactic VHE source populations and interstellar emission.

Beams of electrons, gammas and fast neutrons at BINP

An overview of test beam facilities at Budker Institute of Nuclear Physics (BINP) is presented. Facility for generation of extracted beams of electrons was designed at BINP for testing of detector prototypes in HEP field. The electron beam energy is from 100[Formula: see text]MeV to 3.5[Formula: see text]GeV. Since 2011, the facility has been used successfully for testing various detector prototypes. On the base of VEPP–4M collider, it is possible to obtain gamma beams too. The energy scale and resolution of calorimeters can be calibrated using edges of Compton and bremsstrahlung spectra. A facility for boron–neutron capture therapy (BNCT) was upgraded to perform radiation tests with fast neutrons with the integral flux up to [Formula: see text][Formula: see text]n/cm2. In 2022, the experiment on the study of the radiation hardness of optical fibers for the laser calibration system of electromagnetic calorimeter and the CMS detector was carried out. It has been demonstrated for the first time that at the BINP it is possible to operate with such doses. It could be further used for the wide range of radiation test tasks related with the development of facilities for HEP.

A Multiwavelength Study to Decipher the 2017 Flare of the Blazar OJ 287

In 2017 February, the blazar OJ 287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3–10 keV) band, as measured by the Swift X-ray Telescope. This event coincides with a very-high-energy (VHE) γ-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of 10σ (from 2016 December 9 to 2017 March 31). The time-averaged VHE γ-ray spectrum was consistent with a soft power law (Γ = −3.81 ± 0.26) and an integral flux corresponding to ∼2.4% that of the Crab Nebula above the same energy. Contemporaneous data from multiple instruments across the electromagnetic spectrum reveal a complex flaring behavior, primarily in the soft X-ray and VHE bands. To investigate the possible origin of such an event, our study focuses on three distinct activity states: before, during, and after the 2017 February peak. The spectral energy distributions during these periods suggest the presence of at least two nonthermal emission zones, with the more compact one responsible for the observed flare. Broadband modeling results and observations of a new radio knot in the jet of OJ 287 in 2017 are consistent with a flare originating from a strong recollimation shock outside the radio core.

Search for photons above 1018 eV by simultaneously measuring the atmospheric depth and the muon content of air showers at the Pierre Auger Observatory

The Pierre Auger Observatory is the most sensitive instrument to detect photons with energies above 1017 eV. It measures extensive air showers generated by ultrahigh energy cosmic rays using a hybrid technique that exploits the combination of a fluorescence detector with a ground array of particle detectors. The signatures of a photon-induced air shower are a larger atmospheric depth of the shower maximum (Xmax) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced cascades. In this work, a new analysis technique in the energy interval between 1 and 30 EeV (1 EeV=1018 eV) has been developed by combining the fluorescence detector-based measurement of Xmax with the specific features of the surface detector signal through a parameter related to the air shower muon content, derived from the universality of the air shower development. No evidence of a statistically significant signal due to photon primaries was found using data collected in about 12 years of operation. Thus, upper bounds to the integral photon flux have been set using a detailed calculation of the detector exposure, in combination with a data-driven background estimation. The derived 95% confidence level upper limits are 0.0403, 0.01113, 0.0035, 0.0023, and 0.0021 km−2 sr−1 yr−1 above 1, 2, 3, 5, and 10 EeV, respectively, leading to the most stringent upper limits on the photon flux in the EeV range. Compared with past results, the upper limits were improved by about 40% for the lowest energy threshold and by a factor 3 above 3 EeV, where no candidates were found and the expected background is negligible. The presented limits can be used to probe the assumptions on chemical composition of ultrahigh energy cosmic rays and allow for the constraint of the mass and lifetime phase space of super-heavy dark matter particles. Published by the American Physical Society 2024

Prediction of geomagnetic storms associated with interplanetary coronal mass ejections

Geomagnetic storms have a significant impact on the performance of technical systems both in space and on Earth. The sources of strong geomagnetic storms are most often interplanetary coronal mass ejections (ICMEs), generated by coronal mass ejections (CMEs) in the solar corona. The ICME forecast is based on regular optical observations of the Sun, which make it possible to detect CMEs at the formation stage. It is known that the intensity of geomagnetic storms correlates with the magnitude of the southern component of the magnetic field (Bz) of the ICME. However, it is not possible yet to predict the sign and magnitude ofBzfrom solar observations for the operational forecast of an arbitrary CME. Under these conditions, a preliminary forecast of the magnetic storm probability can be obtained under the assumption that the strength of the storm is related to the magnitude of the magnetic flux from the eruption region, observed as dimming. In this paper we examine the relationship between the integral magnetic flux from the dimming region and the probability that CMEs associated with them will cause geomagnetic storms, using a series of 37 eruptive events in 2010–2012. It is shown that there is a general trend toward an increase in the ICMEs geoefficiency with an increase in the magnitude of the magnetic flux from the dimming region. It has been demonstrated that the frequency of moderate and severe storms observation increases in cases of complex events associated with the interaction of CMEs with other solar wind streams in the heliosphere.

Search for MeV gamma-ray emission from TeV bright red dwarfs with COMPTEL

The SHALON atmospheric Cherenkov telescope has detected very high energy gamma-ray emission at TeV energies from eight red dwarfs, namely, V388 Cas, V547 Cas, V780 Tau, V962 Tau, V1589 Cyg, GJ 1078, GJ 3684 and GL 851.1. Consequently, these red dwarfs have been suggested as sources of ultra-high energy cosmic rays. In this work, we search for soft gamma-ray emission from these TeV bright red dwarfs between 0.75–30 MeV using archival data from the COMPTEL gamma-ray imaging telescope, as a follow-up to a similar search for GeV gamma-ray emission using the Fermi-LAT telescope. Although, prima-facie, we detect non-zero photon flux from three red dwarfs with high significance, these signals can attributed to contamination from nearby sources such as Crab and Cygnus, which are within the angular resolution of COMPTEL, and have been previously detected as very bright point sources at MeV energies. Therefore, we could not detect any statistically significant signal (> 3σ) from any of these eight red dwarfs from 0.75–30 MeV. We then report the 95% confidence level upper limits on the differential photon flux (at 30 MeV), integral photon flux and integral energy flux for all of the eight red dwarfs. The integral energy flux limits range between 10-11 - 10-10-ergs/cm2/s.

Comparisons between Resolved Star Formation Rate and Gas Tracers in the Strongly Lensed Galaxy SDSS J0901+1814 at Cosmic Noon

We report new radio observations of SDSS J090122.37+181432.3, a strongly lensed star-forming galaxy at z = 2.26. We image 1.4 GHz (L-band) and 3 GHz (S-band) continuum using the Very Large Array (VLA) and 1.2 mm (band 6) continuum with Atacama Large Millimeter/submillimeter Array, in addition to the CO(7–6) and C i(3 P 2→3 P 1) lines, all at ≲1.″7 resolution. Based on the VLA integrated flux densities, we decompose the radio spectrum into its free–free (FF) and nonthermal components. The infrared–radio correlation parameter qTIR=2.65−0.31+0.24 is consistent with expectations for star-forming galaxies. We obtain radio continuum-derived star formation rates (SFRs) that are free of dust extinction, finding 620−220+280M⊙yr−1 , 230−160+570M⊙yr−1 , and 280−120+460M⊙yr−1 from the FF emission, nonthermal emission, and when accounting for both emission processes, respectively, in agreement with previous results. We estimate the gas mass from the C i(3 P 2→3 P 1) line as M gas = (1.2 ± 0.2) × 1011 M ☉, which is consistent with prior CO(1–0)-derived gas masses. Using our new IR and radio continuum data to map the SFR, we assess the dependence of the Schmidt–Kennicutt relation on choices of SFR and gas tracer for ∼kpc scales. The different SFR tracers yield different slopes, with the IR being the steepest, potentially due to highly obscured star formation in J0901. The radio continuum maps have the lowest slopes and overall fidelity for mapping the SFR, despite producing consistent total SFRs. We also find that the Schmidt–Kennicutt relation slope is flattest when using CO(7–6) or C i(3 P 2→3 P 1) to trace gas mass, suggesting that those transitions are not suitable for tracing the bulk molecular gas in galaxies like J0901.

Distribution of methane in the upper water layer of the northern Black Sea: Seasonal and daily trends and seawater-air emissions

We report on methane (CH4) concentration measurements in the northern Black Sea area conducted during 6 cruises with R/V Professor Vodyanitsky from 2017 to 2019. Our work is a multi-season study at a uniform station grid covering an area of 88 × 103 km2 and including three latitudinal transects that comprises both surface and vertical profile water-column measurements. The main goal of the work was to assess the seasonal patterns of vertical CH4 structure in the aerobic water column (upper 100 m) and its emission to the atmosphere.In surface waters, the mean dissolved CH4 concentration ranged from 2.6 nmol L−1 detected in November 2018 to 11.5 nmol L−1 measured in June–July 2018, respectively. Calculated CH4 seawater-air fluxes and saturations were mostly positive (i.e. net flux to atmosphere), and winter fluxes (2.6 μmol m−2 d−1) were higher than summer fluxes (1.6 μmol m−2 d−1) due to the higher wind speed. The integral CH4 flux from the whole study area (88 × 103 km2) ranged from 84 to 235 kM day−1.It was shown that, on average, the methane concentration in the upper layer for deep-water stations where the seabed is located at depths >160 m (σt >16.2) was lower compared to stations at shallow water depths (28–140 m, σt <16.2). The most distinct difference was obtained for the summer season (June–July 2018) and a less significant difference – for spring (April–May 2019) and winter season (November–December 2018). During these seasons the water column was also considerably less saturated in CH4 compared to the entire monitoring period. We observed subsurface maxima, which were generally located at the base of the thermocline and exceeded 100 nmol L−1 at some stations. Exceptions were observed in October 2019 (cruise 110), when vertical CH4 distributions were characterized by two-peaks at ∼20 and ∼50 m depth. The strong influence of the thermohaline structure on the water column CH4 distribution has also been shown in studies of daily dynamics of CH4 vertical profiles in the shallow water region. Despite the high variability of CH4 concentrations, significant similarities in vertical distributions of CH4 and chlorophyll-a for which sub-surface maxima coincided at some stations, are shown. Extremely high concentrations of CH4 (up to 351 nmol L−1) in the near-bottom water layer were revealed during all seasons at the station near the Dnieper paleo-channel at the northwestern edge of the study area. This enrichment is assumed to be caused by methane emissions from gas seeps densely located in this region.

Stabilizing massless fields with fluxes in Landau-Ginzburg models

Recent work on flux compactifications suggests that the tadpole constraint generically allows only a limited number of complex structure moduli to become massive, i.e., be stabilized at quadratic order in the spacetime superpotential. We study the effects of higher-order terms systematically around the Fermat point in the 19 Landau-Ginzburg model. This model lives at strong coupling and features no Kähler moduli. We show that indeed massless fields can be stabilized in this fashion. We observe that, depending on the flux, this mechanism is more effective when the number of initially massless fields is large. These findings are compatible with both the tadpole conjecture and the massless Minkowski conjecture. Along the way, we complete the classification of integral flux vectors with small tadpole contribution. Thereby we are closing in on a future complete understanding of all possible flux configurations in the 19 Landau-Ginzburg model.

ASKAP-EMU Discovery of New Galactic SNR Candidate: Unicycle (G312.65+2.87)

We present the serendipitous discovery of a low surface brightness Galactic supernova remnant candidate, Unicycle (G312.65+2.87). Unicycle was initially discovered in the Evolutionary Map of the Universe large-scale radio survey at 943.5 MHz. We measure a diffuse shell (D = 288″ × 300″) and an integrated flux density of S I 944 MHz = 150 ± 20 mJy. We estimate the most likely intrinsic diameters of 30 < D < 36 pc or 42 < D < 47 pc, corresponding to distances of 10 < d < 12 kpc or 14 < d < 16 kpc, placing it within either the Scutum–Centaurus or outer Sagittarius spiral arms.

Subgrid moving contact line model for direct numerical simulations of bubble dynamics in pool boiling of pure fluids

This contact line vicinity model is conceived as a subgrid model for the DNS of bubble growth in boiling. The model is based on the hydrodynamic multiscale theory and is suitable for the partial wetting case. On the smallest length scale (distance from the contact line) ∼ 100 nm, the interface slope is controlled by the Voinov angle. It is the static apparent contact angle (ACA) that forms due to evaporation, similarly to previous models neglecting the contact line motion. The calculation of the Voinov angle is performed with the generalized lubrication approximation and includes several nanoscale effects like those of Kelvin and Marangoni, vapor recoil, hydrodynamic slip length and interfacial kinetic resistance. It provides the finite values of the heat flux, pressure and temperature at the contact line. The dynamic ACA is obtained with the Cox-Voinov formula. The microscopic length of the Cox-Voinov formula (Voinov length) is controlled mainly by the hydrodynamic slip. The integral heat flux passing through the contact line vicinity is almost independent of the nanoscale phenomena, with the exception of the interfacial kinetic resistance and is mostly defined by the dynamic ACA. Both the dynamic ACA and the integral heat flux are the main output parameters of the subgrid model, while the local superheating and the microscopic contact angle are the main input parameters. The model is suitable for the grid sizes > 1 µm.

Applying machine learning in the investigation of the link between the high-velocity streams of charged solar particles and precipitation-induced floods.

This study explores a possible link between solar activity and floods caused by precipitation. For this purpose, discrete blocks of data for 89 separate flood events in Europe in the period 2009-2018 were used. Solar activity parameters with a time lag of 0-11days were used as input data of the model, while precipitation data in the 12days preceding the flood were used as output data. The level of randomness of the input and output time series was determined by correlation analysis, while the potential causal relationship was established by applying machine learning classification predictive modeling. A total of 25 distinct machine-learning algorithms and four model ensembles were applied. It was shown that in 81% of cases, the designed model could explain the occurrence or absence of precipitation-induced floods 9days in advance. Differential proton flux in the 0.068-0.115MeV and integral proton flux > 2.5MeV were found to be the most important factors for forecasting precipitation-induced floods. The study confirmed that machine learning is a valuable technique for establishing nonlinear relationships between solar activity parameters and the onset of floods induced by precipitation.

Giant radio galaxies in the LOFAR deep fields

The reason why some radio galaxies (RGs) grow to form so-called giant radio galaxies (GRGs) with sizes $&gt;$ 700 kpc, is still unknown. In this study, we compare the radio, optical and environmental properties of GRGs with those of a control sample of smaller RGs we found in the three LOw-Frequency ARray (LOFAR) deep fields, namely the Bo\"otes, ELAIS-N1, Lockman Hole, for a total area of approx 95 deg$^2$. We inspected the LOFAR deep fields and created a catalogue of 1609 extended radio galaxies (ERGs). By visual inspection, we identified their host galaxies and spectroscopically or photometrically classified 280 of these as GRGs. We studied their properties, such as their accretion state, stellar mass and star formation rate (SFR) using deep optical and infrared survey data. Moreover, we explored the environment in terms of the surface number density of neighbouring galaxies within these surveys. Integrated flux densities and radio luminosities were also determined for a subset of ERGs through available survey images at 50, 150, 610, and 1400 MHz to compute integrated spectral indices. Considering the fraction of GRGs displaying an FRII morphology alongside the host galaxy properties, we suggest that GRGs consistently possess sufficient power to overcome jet frustration caused by the interstellar medium. Moreover, clear differences emerge in the environmental densities between GRGs and smaller RGs, using the number of neighbouring galaxies within 10 Mpc from the host galaxy as a proxy. GRGs preferentially reside in sparser environments compared to their smaller counterparts. In particular, only 3.6&lt;!PCT!&gt; of the GRGs reside within a 3D comoving distance of 5 Mpc from a previously reported galaxy cluster. We found that larger sources exhibit steeper integrated spectral indices, suggesting that GRGs are late-stage versions of RGs. These results suggest that GRGs are amongst the oldest radio sources with the most stable nuclear activity that reside in sparse environments.

Numerical analysis of flow and heat transfer characteristics of double-layer heterogeneous single crystal diamond microchannel heat sinks

In order to solve the heat dissipation problems associated with highly integrated and high heat flux microelectronic devices, in this work, a novel type double-layer heterogeneous single crystal diamond microchannel heat sink (DLH-SCD-MCHS) is designed and numerically analyzed, in which the upper channel is rectangular and the lower channel consists of various cavities and rib combinations. The comprehensive performance of the DLH-SCD-MCHS was analyzed by the correlation with pumping power and thermal resistance, and the enhanced heat transfer factor (η). The outcome shows that the DLH-SCD-MCHS significantly enhances the heat transfer while appropriately sacrificing part of the pressure drop. Compared with the traditional double-layer microchannel heat sink (DL-MCHS), the pressure drop of DLH-SCD-MCHS is increased by 23.8–43.5 %, the heat transfer coefficient is enhanced by 74.5–117.1 %, and the η is improved by 62.5–87.4 %. The DLH-SCD-MCHS can reduce the irreversible loss, and the minimum augmentation entropy generation number is 0.64 for the DLH-SCD-MCHS with rectangular cavity and rectangular rib (Model V). As Re = 874, the relative rib width, the relative rib length and the relative position of the ribs of the Model V are 0.5, 0.571 and 0.5, respectively, the maximum η is 1.97. The DLH-SCD-MCHS provides new insights for the management of the heat transfer system of microelectronic devices.

Multi-antenna probing of absorbing regions inside and outside Cassiopeia A

Context. Cassiopeia A occupies an important place among supernova remnants (SNRs) in low-frequency radio astronomy. Located in our Galaxy, this powerful radio source emits synchrotron radiation that propagates through the SNR environment and the ionized interstellar medium. The analysis of its continuum spectrum from low frequency observations reveals the evolution of the SNR absorption properties over time and suggests a method for probing unshocked ejecta and the SNR interaction with the circumstellar medium (CSM). Aims. In this paper, we present low-frequency measurements of the integrated spectrum of Cassiopeia A to find the typical values of free-free absorption parameters towards this SNR in the middle of 2023. We also add new results to track its slowly evolving and decreasing integrated flux density. Methods. We used the New Extension in Nançay Upgrading LOFAR (NenuFAR) and the Ukrainian Radio Interferometer of NASU (URAN–2, Poltava) for measuring the continuum spectrum of Cassiopeia A within the frequency range of 8–66 MHz. The radio flux density of Cassiopeia A relative to the calibration source, the radio galaxy Cygnus A, has been obtained on June–July, 2023 with two sub-arrays for each radio telescope, used as a two-element correlation interferometer. Results. We measured the values of parameters such as the emission measure, electron temperature and average number of ion charges, for both the internal and external absorbing ionized gas towards Cassiopeia A from its integrated spectrum. Generally, their values are comparable to those presented in the literature, but their slight differences demonstrate the evolution of free-free absorption parameters in this SNR. Based on high accuracy of the measurements, we have detected the SNR–CSM interaction. This led to the fact that the maximum of this continuous spectrum, decreasing in intensity, changed in frequency from past higher values to lower ones over time. Probably, such changes occur periodically in which the spectral peak can move in the direction of both higher frequencies and lower ones. This effect is mainly caused by the evolution of emission measure outside Cassiopeia A. Conclusions. The integrated flux-density spectrum of Cassiopeia A obtained with the NenuFAR and URAN–2 interferometric observations opens up new possibilities for continuous monitoring the ionized gas properties in and around Cassiopeia A to observe the evolution of unshocked ejecta and the SNR-CSM interaction in future studies.

Alternating Conditional Expectations: Introducing a Non‐Parametric Statistical Method to Interpret Long‐Term Greenhouse Gas Flux Measurements Over Semi‐Arid and Wetland Ecosystems

AbstractWe explore the potential of using a non‐parametric statistical method called Alternating Conditional Expectations, ACE, to quantify functional relationships in biogeosciences. Here, ACE is used to quantify the non‐linear and multi‐faceted responses of greenhouse gas fluxes to a set of biophysical forcings, when the shapes of those response surfaces are unknown. We evaluated the statistical method over two contrasting ecosystems and two contrasting time steps. One case involved quantifying the biophysical controls of water vapor and carbon dioxide (CO2) fluxes over a semi‐arid oak savanna using daily integrated fluxes. The other case evaluated the responses of CO2 and methane (CH4) flux measurements to a set of biophysical forcings at a restored tidal wetland using thirty‐minute averages. The statistical model, based on 4 independent variables, explained up over 90% of the variation in daily integrated flux densities of water vapor and net carbon dioxide exchange at the savanna site. This fit was defined by distinct non‐linear responses to such drivers as gross primary production, photosynthetically active radiation, air temperature, vapor pressure deficit and soil moisture. At the tidal wetland site, we evaluated net carbon dioxide and methane fluxes with short‐term measurements to capture the influence of rising and falling tides and seasonality in biological activity. The statistical model defined the shape of the forcing of fluxes due to the roles of carbon exudates, water table depth, oxygen level in the water column, temperature and vegetation status. The statistical fits of the greenhouse gas fluxes were less precise than the savanna case. The fetch varies on a run‐to‐run basis as it is comprised of a heterogeneous mosaic of open water and vegetation. Furthermore, it is difficult to monitor the environmental conditions of the archaea and bacteria in the sediments that produce methane and carbon dioxide.

Simulation of spectral observations of an eruptive prominence

The paper presents the results of an analysis of observations of an eruptive prominence on the MFS and HSFA2 spectrographs of the Ondřejov Observatory (Astronomical Institute, Czech Republic) in the lines of hydrogen, helium and calcium. After processing the spectra, the integral radiation fluxes in the lines were determined and a theoretical calculation of the physical parameters of the plasma was carried out using a model in the absence of local thermodynamic equilibrium. A comparison of the observed and calculated values showed that the observed radiation fluxes in the lines can be explained in a model of stationary gas radiation taking into account the opacity in the spectral lines. To calculate theoretical fluxes, in some cases it was necessary to introduce radiation from several layers with different temperatures and heights. The calculated radiation fluxes agree with the observed ones with an accuracy of 10%. As a result of the simulation, the main parameters of the prominence plasma were obtained: temperature, concentration, etc. The values of radiation fluxes in the spectral lines indicate the inhomogeneity of the emitting gas, and there may be regions next to each other whose temperatures differ by an order of magnitude.

Optical luminescent properties of eggs

Relevance. Optical photoluminescent properties of poultry eggs can serve as indicators of their quality both for incubation processes and for food technology processes. At the initial stage, it is important to evaluate the spectral characteristics of excitation and luminescence, as well as the parameters of table and incubation eggs of different quality and with different shell color.Methods. Chicken eggs of Chinese silk and Hysex brown crosses, as well as samples of duck, goose and quail eggs were used for research. The measurements were carried out on a diffraction spectrofluorimeter “Fluorat02-Panorama” with built-in software “Panorama Pro”. The obtained spectral characteristics were used to calculate the energy (integral absorption capacity and luminescence flux, spectrum energy) and statistical parameters (expectation, variance, asymmetry, kurtosis), as well as the Stokes shift.Results. Photoluminescent properties of poultry eggs are manifested in the ultraviolet region of the spectrum. Qualitatively, the spectra of different species of domestic birds are similar with a slight difference in the Stokes shift. For fertilized chicken eggs, the photoluminescence flux is 2.7 times greater than that of unfertilized eggs, while the spread of values for unfertilized eggs is 5.6 times less. Spectrum parameters such as asymmetry and kurtosis differ significantly for the luminescence of dark and light-shell chicken eggs. For table eggs, the integral energy parameters are 2.8–3.1 times greater than those of incubation eggs.

Rayleigh–Bénard convection with an immersed floating body

The paper presents the results of an experimental and numerical study of turbulent thermal convection in a rectangular box containing an extended immersed free-floating plate. Varying the values of control parameters, such as Rayleigh number, aspect ratio and vertical position of the plate, provides a wide range of possible modes, from immobile and purely periodic to stochastic. We have shown that stable periodic motions occur when the plate floats close to one of the heat exchangers. An increase in the distance between the plate and the heat exchanger breaks the periodic motion and (at moderate Rayleigh numbers) leads to a pronounced asymmetry, when the plate stays close to one of the walls most of the time, makes rare excursions to the opposite wall and immediately returns. As the Rayleigh number increases, the plate motions from one edge of the box to the other reappear, but always have an irregular character. Regarding the dependence of the system behaviour on the geometry of the box, both lower and upper limits of periodic plate motions were found in the experiments. In the numerical simulations, the upper limit was not achieved – the plate moves quasi-periodically through the chain of vortices of different signs even at the largest aspect ratio being considered. The heat-insulating floating plate provides the spatial and temporal variation of the heat flux and reduces the integral heat flux, but the reduction in heat flux depends significantly on the vertical position of the plate.

Off-nuclear H2O maser and dense molecular gas in NGC 1068

ABSTRACT The results of high-resolution spectral-line observations of dense molecular gas are presented towards the nuclear region of the type 2 Seyfert galaxy NGC 1068. MERLIN observations of the 22 GHz H2O maser were made for imaging the known off-nuclear maser emission at radio jet component located about 0.3 arcsec north-east of the radio nucleus in the galaxy. High angular resolution ALMA observations have spatially resolved the molecular gas emissions of HCN and HCO+ in this region. The off-nuclear maser spots are found to nearly overlap with a ring-like molecular gas structure and are tracing an evolving shock-like structure, which appears to be energized by interaction between the radio jet and circumnuclear medium. The scenario of the dynamic jet–ISM interaction is further supported by a systematic shift of the centroid velocities of the off-nuclear maser features over a period of 35 yr. The enhanced integrated flux ratios of the HCN to HCO+ line emission features at component C suggest a kinetic temperature Tk ≳ 300 K and an H2 density of ≳ 106 cm−3, which are conditions where water masers may be formed. The diagnostics of the masering action in this jet–ISM interaction region is exemplary for galaxies hosting off-nuclear H2O maser emission.