Abstract
Objectives of the TAIGA Astrophysical complex include the study of the flux of charged cosmic rays and diffuse gamma rays with energies above 100 TeV. This complex is located in the Tunka ...Valley about 50 km from Lake Baikal at the site of the Tunka-133 Cherenkov facility. TAIGA includes the TAIGA-HiSCORE wide-angle Cherenkov array, the network of Imaging Atmospheric Cherenkov Telescopes (TAIGA-IACT), the Tunka-Grande and TAIGA-Muon scintillation arrays. In this work, we present the results of an analysis of the joint events of the Tunka-Grande scintillation array and TAIGA-HiSCORE and Tunka-133 Cherenkov facilities. The results verify sufficient accuracy of the scintillation experiment for the hybrid study of mass composition of cosmic rays and gamma-hadron separation.
•Growing the Ag NPs in the PVA matrix during the drying of the composition.•The ability of achievement of high concentrations of Ag NPs.•The time interval during which drying PVA composition can be ...modified is 2.5h.•SEM micrographs confirm the conclusions relative to the sizes of Ag NPs drawn on the basis of absorption spectra.
Unlike traditional methods of introduction of prepared metal nanoparticles into polymer composition, in our method Ag nanoparticles (NPs) are formed in the course of drying of molding composition on the basis of polyvinyl alcohol (PVA) due to slow reduction of ions Ag by “soft” organic reducing agents – quaternary ammonium compounds. The sizes of Ag NPs are determined and character of their distribution on the surface of PVA film is established by means of spectrophotometry, atomic force microscopy (AFM), transmission (TEM) and scanning (SEM) electron microscopy. Correlation is found between the data on absorption spectra and micrographs done by means of optical microscopy, AFM, TEM and SEM. Variations of the sizes and features of Ag NPs distribution in the polymeric film are examined.
Pollen grains emitted from vegetation can release subpollen particles (SPPs)
that contribute to the fine fraction of atmospheric aerosols and may act as
cloud condensation nuclei (CCN), ice nuclei ...(IN), or aeroallergens. Here, we
investigate and characterize the hygroscopic growth and CCN activation of
birch, pine, and rapeseed SPPs. A high-humidity tandem differential mobility
analyzer (HHTDMA) was used to measure particle restructuring and water
uptake over a wide range of relative humidity (RH) from 2 % to 99.5 %,
and a continuous flow CCN counter was used for size-resolved measurements of
CCN activation at supersaturations (S) in the range of 0.2 % to 1.2 %.
For both subsaturated and supersaturated conditions, effective
hygroscopicity parameters, κ, were obtained by Köhler model
calculations. Gravimetric and chemical analyses, electron microscopy, and
dynamic light scattering measurements were performed to characterize further
properties of SPPs from aqueous pollen extracts such as chemical composition
(starch, proteins, DNA, and inorganic ions) and the hydrodynamic size
distribution of water-insoluble material. All investigated SPP samples
exhibited a sharp increase of water uptake and κ above
∼95 % RH, suggesting a liquid–liquid phase separation
(LLPS). The HHTDMA measurements at RH >95 % enable closure
between the CCN activation at water vapor supersaturation and hygroscopic
growth at subsaturated conditions, which is often not achieved when hygroscopicity tandem differential mobility analyzer (HTDMA) measurements are performed at lower RH where the water uptake and effective
hygroscopicity may be limited by the effects of LLPS. Such effects may be
important not only for closure between hygroscopic growth and CCN activation
but also for the chemical reactivity, allergenic potential, and related
health effects of SPPs.
Leaf traits, the rate of gas exchange, and biomass were examined in five plurizonal species (
Alisma plantago-aquatica
L.,
Carex acuta
L.,
Eleocharis palustris
(L.) Roem. et Schult.,
Phalaris ...arundinacea
L., and
Typha angustifolia
L.) of emergent plants growing in wetlands of forest (Middle Urals) and steppe (South Urals) zones. It was found that changes in the leaf thickness, leaf mass per area (LMA), the transpiration rate, and characteristics of the pigment complex associated with a rise in aridity were species-specific. Structural reorganization of the leaves of wetland plants growing in conditions of steppe wetland showed a general pattern of an increase in leaf density (1.2–2 times) and a reduction in leaf area (by 42–54%). This trend was accompanied by a reduction in the photosynthesis rate per 1 m
2
(1.2–3.4 times) or per 1 mg of chlorophyll (by 29–63%). In two species,
P. arundinacea
and
T. angustifolia
, we detected a decrease in stomatal conductance by 2 and 4.8 times, respectively, in more arid conditions. Analysis of interspecific relations between plant productivity and leaf parameters has shown that plant biomass positively correlated with leaf area (
r
= 0.84,
P
< 0.01) and with the photosynthesis rate per leaf area unit (
r
= 0.97,
P
< 0.001) both in the regions of the Middle and South Urals. On the whole, structural changes in the leaves associated with adaptation of plant water relations to semiarid climate lead to a decrease in photosynthetic activity of leaves and, therefore, a decline of plant height and productivity of emergent plants growing in steppe wetland.
The content of chlorophylls (Сhl)
a
and
b
and carotenoids (Сar) during the growing season was studied in the leaves of 31 species of steppe and forest plants. In contrast to forest plants, steppe ...plants possessed less chlorophylls and carotenoids per leaf mass (2 and 1.5 times, respectively), a low Сhl/Сar ratio, a greater (1.5 times) content of carotenoids per leaf area, and a high Сhl
a
/
b
ratio. In spite of the low chlorophyll content per leaf mass in steppe plants, their content per leaf area was similar to forest species (3–4 mg/dm
2
) owing to their thicker and denser leaves. This suggests that the plants of steppe and forest communities have the same potential ability to intercept solar energy in this locality. In the period of active vegetation (mid-June -early August), parameters of the pigment complex were stable both in steppe and forest communities. However, steppe plants demonstrated the modified in content of Car and Сhl
b
, as well as Сhl/Сar and Chl
a
/
b
ratios, in the beginning and at the end of the season that indicated a reorganization of the light-harvesting complex. Intraspecific variation of parameters during the season was two or three times lower than interspecific. High interspecific variation in forest plants were achieved due to the presence of species with thick long-lived leaves. It was concluded that the chlorophyll content per leaf area reflects the adaptation of plants to climatic conditions of the geographic region, whereas pigment contents per leaf mass shows adaptation to local irradiation in plant community (forest or steppe).
An analysis is performed of the spectrum of gamma rays from the Crab Nebula in the 4–100 TeV range of energies, obtained using data from two Atmospheric Cherenkov Telescopes that are part of the ...TAIGA complex. A way of selecting and restoring the energy of gamma rays is described that includes a procedure for restoring the energy spectrum.
New coordination compounds of cobalt(II), nickel(II), and copper(II) halides with 2-(3,5-dimethylpyrazol-1-yl)benzimidazole (L) of the composition CoLCl
2
(
1
), CoL
2
Cl
2
· 2H
2
O · EtOH (
2
), ...NiL(H
2
O)
4
Cl
2
· H
2
O · EtOH (
3
), NiL
2
Cl
2
· 2H
2
O · EtOH (
4
), and CuL
2
BrBr · H
2
O (
5
) were synthesized. The compounds were characterized by electronic (diffuse reflectance) spectroscopy, IR spectroscopy, and powder X-ray diffraction. The crystal structures of compounds
1, 3
, and
5
were determined by single-crystal X-ray diffraction. The cytotoxic properties of the ligand and compound
5
were evaluated in the
Hep
-2 cell line.
Mixed oxides 1%Cs/Mg
x
Co
3–
x
O
4
(
х
= 0–0.9) with a spinel structure are synthesized by precipitation from nitrate solutions using (NH
4
)
2
CO
3
as the precipitating agent and the subsequent ...modification of the dry precipitate with cesium by the Pechini method and calcining. The synthesized samples are studied by XRD, BET, SEM, TPR, and TPD methods. It is shown that an increase in the magnesium content leads to a significant decrease in the degree of crystallization of the oxides, an increase in the specific surface area, and the formation of loosely bound oxygen species, which contributes to an increase in the catalytic activity of the samples in nitrous oxide decomposition at temperatures of 150–400°С. The highest activity is exhibited by the 1%Cs/Mg
0.1
Co
2.9
O
4
catalyst characterized by the presence of the maximum amount of loosely bound oxygen species. It is shown that the presence of oxygen or water in the reaction mixture leads to a decrease in the catalyst activity at 250°C by 10 or 80%, respectively; after that, the catalyst exhibits a stable on-stream behavior for at least 25 h. The catalyst activity is restored after a heat treatment.
Nanoparticles of Co
1 –
x
Mg
x
Fe
2
O
4
with
x
equal to 0, 0.2, 0.4, 0.6, 0.8, and 1.0 have been synthesized. For all values of
x
, they are nanocrystals with a cobalt ferrite structure and an ...average linear size (
nm. Based on the analysis of the Mössbauer effect spectra, the Co
2+
ions were shown to occupy only octahedral positions at all values of
x
. The experimentally obtained dependence of the nanoparticles magnetization on
x
corresponds to the dependence calculated using the Mössbauer effect data, except for the sample with
. The effective magnetic anisotropy constant estimated for 0 K from the analysis of the coercive force temperature dependences decreases from
at
to
erg/cm
3
at
and drops sharply to
erg/cm
3
at
.
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