Thermoelectric performance of weakly coupled granular materials

We study thermoelectric properties of inhomogeneous nanogranular materials for weak tunneling conductance between the grains, g_t < 1. We calculate the thermopower and figure of merit taking into account the shift of the chemical potential and the asymmetry of the density of states in the vicinity of the Fermi surface. We show that the weak coupling between the grains leads to a high thermopower and low thermal conductivity resulting in relatively high values of the figure of merit on the order of one. We estimate the temperature at which the figure of merit has its maximum value for two- and three-dimensional samples. Our results are applicable for many emerging materials, including artificially self-assembled nanoparticle arrays.Comment: 4 pages, 3 figure

The Effect of High Background and Dead Time of an InGaAs/InP Single-Photon Avalanche Photodiode on the Registration of Microsecond Range Near-Infrared Luminescence

The effects of a high background count and a microsecond dead time interval on a gated InGaAs/InP single-photon avalanche photodiode (SPAD) during microsecond luminescence decay registration are discussed. It is shown that the background count rate of the SPAD limits its use for time-resolved and steady-spectral measurements, and that a “pile-up” effect appears in the microsecond range

Thermoelectric performance of granular semiconductors

We study thermoelectric properties of granular semiconductors with weak tunneling conductance between the grains, g_t < 1. We calculate the thermopower and figure of merit taking into account the shift of the chemical potential and the asymmetry of the density of states in the vicinity of the Fermi surface due to n- or p-type doping in the Efros-Shklovskii regime for temperatures less than the charging energy. We show that for weakly coupled semiconducting grains the figure of merit is optimized for grain sizes of order 5nm for typical materials and its values can be larger than one. We also study the case of compensated granular semiconductors and show that in this case the thermopower can be still finite, although two to three orders of magnitude smaller than in the uncompensated regime.Comment: 4 pages, 4 figure

Ammonia masers toward G358.931-0.030

We report the detection of ammonia masers in the non-metastable (6, 3), (7, 5) and (6, 5) transitions, the latter is the first unambiguous maser detection of that transition ever made. Our observations include the first VLBI detection of ammonia maser emission, which allowed effective constrain of the (6, 5) maser brightness temperature. The masers were detected towards G358.931-0.030, a site of 6.7-GHz class~II methanol maser emission that was recently reported to be undergoing a period of flaring activity. These ammonia masers appear to be flaring contemporaneously with the class~II methanol masers during the accretion burst event of G358.931-0.030. This newly detected site of ammonia maser emission is only the twelfth such site discovered in the Milky Way. We also report the results of an investigation into the maser pumping conditions, for all three detected masing transitions, through radiative transfer calculations constrained by our observational data. These calculations support the hypothesis that the ammonia (6, 5) maser transition is excited through high colour temperature infrared emission, with the (6, 5) and (7, 5) transition line-ratio implying dust temperatures >400K. Additionally, we detect significant linearly polarised emission from the ammonia (6, 3) maser line. Alongside our observational and radiative transfer calculation results, we also report newly derived rest frequencies for the ammonia (6, 3) and (6, 5) transitions.Comment: Accepted into MNRAS 2023 April 24. 13 pages, 5 figures, 3 table

Discovery of a New Class i Methanol Maser Transition at 266.8 GHz

We report the detection of a new class I methanol maser candidate from the 52-41 E transition (266.8 GHz). This methanol transition has been detected toward a nearby high-mass star-forming region G352.630-1.067 (distance ∼0.7 kpc), in Submillimeter Array (SMA) observations. The new candidate transition has a similar spatial distribution as the 42-31 E (218.4 GHz) and 8-1-70 E (229.7 GHz) transitions, which are known class I maser transitions. Thermal methanol emission in this source is confined to a central hot core, while the three class I maser transitions are detected in two additional regions. These two maser-only emission regions are clearly associated with shocked gas traced by 2 μm Ks-band and thermal v = 0, J = 5-4 SiO molecular emission. In contrast to the thermal methanol emission from the hot core, the three class I maser transitions show an positive trend in the rotation diagram for the two maser regions. Large velocity gradient modeling of the 266.8, 218.4, and 229.7 GHz transitions shows that the 266.8 GHz transition can be a maser for a wide range of conditions. The intensity ratios for the three methanol transitions detected in maser regions can be reproduced under conditions that are typical for class I methanol maser sites. These facts all support the hypothesis that the detected emission from the 266.8 GHz methanol (52-41 E) transition is masing. © 2019. The American Astronomical Society

ALMA sub-mm maser and dust distribution of VY Canis Majoris

Cool, evolved stars have copious, enriched winds. The structure of these winds and the way they are accelerated is not well known. We need to improve our understanding by studying the dynamics from the pulsating stellar surface to about 10 stellar radii, where radiation pressure on dust is fully effective. Some red supergiants have highly asymmetric nebulae, implicating additional forces. We retrieved ALMA Science Verification data providing images of sub-mm line and continuum emission from VY CMa. This enables us to locate water masers with milli-arcsec precision and resolve the dusty continuum. The 658-, 321- and 325-GHz masers lie in irregular, thick shells at increasing distances from the centre of expansion. For the first time this is confirmed as the stellar position, coinciding with a compact peak offset to the NW of the brightest continuum emission. The maser shells (and dust formation zone) overlap but avoid each other on tens-au scales. Their distribution is broadly consistent with excitation models but the conditions and kinematics appear to be complicated by wind collisions, clumping and asymmetries.Comment: Letter 4 pages, 5 figures plus appendix with 3 figures. Accepted by Astronomy and Astrophysics Letter

Targeted therapy for high-grade glioma with the TGF-β2 inhibitor trabedersen: results of a randomized and controlled phase IIb study

This randomized, open-label, active-controlled, dose-finding phase IIb study evaluated the efficacy and safety of trabedersen (AP 12009) administered intratumorally by convection-enhanced delivery compared with standard chemotherapy in patients with recurrent/refractory high-grade glioma. One hundred and forty-five patients with central reference histopathology of recurrent/refractory glioblastoma multiforme (GBM) or anaplastic astrocytoma (AA) were randomly assigned to receive trabedersen at doses of 10 or 80 µM or standard chemotherapy (temozolomide or procarbazine/lomustine/vincristine). Primary endpoint was 6-month tumor control rate, and secondary endpoints included response at further timepoints, survival, and safety. Six-month tumor control rates were not significantly different in the entire study population (AA and GBM). Prespecified AA subgroup analysis showed a significant benefit regarding the 14-month tumor control rate for 10 µM trabedersen vs chemotherapy (p= .0032). The 2-year survival rate had a trend for superiority for 10 µM trabedersen vs chemotherapy (p = .10). Median survival for 10 µM trabedersen was 39.1 months compared with 35.2 months for 80 µM trabedersen and 21.7 months for chemotherapy (not significant). In GBM patients, response and survival results were comparable among the 3 arms. Exploratory analysis on GBM patients aged ≤55 years with Karnofsky performance status >80% at baseline indicated a 3-fold survival at 2 and 3 years for 10 µM trabedersen vs chemotherapy. The frequency of patients with related or possibly drug-related adverse events was higher with standard chemotherapy (64%) than with 80 µM trabedersen (43%) and 10 µM trabedersen (27%). Superior efficacy and safety for 10 µM trabedersen over 80 µM trabedersen and chemotherapy and positive risk–benefit assessment suggest it as the optimal dose for further clinical development in high-grade glioma

Development of High Granular Neutron Time-of-Flight Detector for the BM@N experiment

The HGND (High Granular Neutron Detector) is developed for the BM@N (Baryonic Matter at Nuclotron) experiment on the extracted beam of the Nuclotron at JINR, Dubna. The HGND will be used to measure the azimuthal flow of neutrons produced with energies ranging from 300 to 4000 MeV in heavy-ion collisions at beam energies of 2--4 AGeV. The azimuthal flow of charged particles will be measured using the BM@N magnet spectrometer. The data on the azimuthal flow of neutrons will shed light on the study of the high-density Equation of State (EoS) of isospin-symmetric nuclear matter, which is crucial for studying astrophysical phenomena such as neutron stars and their mergers. The HGND has a highly granular structure with approximately 2000 plastic scintillation detectors (cells), each measuring 4$\times$4$\times$2.5 cm$^3$. These detectors are arranged in 16 layers, with 121 detectors in each layer, and are subdivided by copper absorber plates with a thickness of 3 cm. The light from each cell is detected with SiPM (Silicon Photomultiplier) with an active area of 6$\times$6 mm$^2$. Developed multi-channel TDC board based on the Kintex FPGA chip with a bin width of 100 ps will be used to perform precise timestamp and amplitude measurement using Time-over-Threshold (ToT) method. Good spatial resolution due to the high granularity together with a cell's time resolution of 100-150 ps ensures neutron reconstruction with good energy resolution. The design of the detector as well as the results from test measurements and simulations have been presented

The Tunka Experiment: Towards a 1-km^2 Cherenkov EAS Array in the Tunka Valley

The project of an EAS Cherenkov array in the Tunka valley/Siberia with an area of about 1 km^2 is presented. The new array will have a ten times bigger area than the existing Tunka-25 array and will permit a detailed study of the cosmic ray energy spectrum and the mass composition in the energy range from 10^15 to 10^18 eV.Comment: 3 pages, 2 figures, to be published in IJMP

Расстояния и другие меры близости на множестве черно-белых цифровых изображений

In the paper is formulated series of functions in a set of pairs of black-and-white digital images. Series of functions are either distance or distance analogue. This functions allows, on the one hand, to solve a problem of discerning images, and on the other hand, to measure similarity. Applications of this approach to textures are examined.Строится серия функций на множестве пар черно-белых цифровых изображений, являющихся либо расстоянием, либо аналогом расстояния. Предложенные функции позволяют, с одной стороны, решать задачи различения изображений, а с другой стороны, дают некую меру сходства. Рассмотрены прило¬жения такого подхода к текстурам