The resonant excitation of the
83
Kr first excited nuclear level (
E
= 9.4 keV) by solar axions whose fluxes depend on the axion–electron coupling constant
g
Ae
is sought. The γ- and X-ray photons ...and the conversion and Auger electrons from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences). As a result, a new constraint
≤ 1.50 × 10
–17
(90% C.L.) has been obtained for the axion–electron and axion–nucleon coupling constants, which corresponds to new constraints on the axion mass
m
A
≤ 320 eV and
m
A
≤ 4.6 eV in the KSVZ and DFSZ axion models, respectively.
Working characteristics of the New Low-Background Laboratory (DULB-4900) Gavriljuk, Ju.M.; Gangapshev, A.M.; Gezhaev, A.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2013, Letnik:
729
Journal Article
Recenzirano
Odprti dostop
The Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Science is one of the first and biggest underground laboratories in the world specially constructed to ...carry out different types of experiments in the field of nuclear physics, particle and astroparticle physics. Main technical characteristics of the new low-background laboratory DULB-4900 of the BNO are presented. The laboratory is located at a distance of 3700m from the main entrance of the observatory tunnel in the hall with dimensions ~6×6×40m3. Thickness of the mountain rock over DULB corresponds to 4900m w.e. and this deep location provides the cosmic ray flux reduction with the factor of about 107. The methods and results of the background level measurements both in the hall and operating facilities are given. Contamination of the radioactive 222Rn gas has been also measured in the air by using direct detection of γ-radiation of its daughter 214Bi distributed inside the volume of the low-background chamber. The results of the data analysis are presented and discussed.
•Main technical characteristics of the new unique Deep Underground Low Background laboratory of the Baksan Neutrino Observatory are presented.•The rock overburden of 4900m w.e. reduces the cosmic muon flux down to about (3.0±0.15)×109muonscm−2s−1.•The methods and results of the background level measurements both in the hall and operating facilities are given.
Resonance excitation of the
83
Kr first nuclear level (
E
= 9.4 keV) by solar axions formed via the Primakoff mechanism is sought. The γ- and X-ray photons and the conversion and Auger electrons ...arising from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion–photon coupling constant and the axion mass:|
g
A
γ
×
m
A
| ≤ 6.3 × 10
-17
In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of
m
A
≤ 12.7 eV at 95% C.L.
We have compared the impact of heavy metals (HMs: Cu 660 + Zn 1100 + Pb 650 mg/kg) on agrosoddy-podzolic soils (Albic Retisols (Loamic, Aric, Cutanic, Ochric)) of two arable fields (Chashnikovo, ...Moscow oblast) with different contents of organic carbon (C
org
3.86 and 1.30%) and different fertility levels using indicators of acute and chronic phytotoxicity. At the same level of polymetallic contamination, the responses of test plants to the presence of high concentrations of HMs and potential remediants (lignohumate and biochar) in soils of the same type with different C
org
contents noticeably differ with respect to plant growth parameters and metal accumulation in the phytomass. The HMs contamination of low-fertile soil leads to the complete death of plants in the pot experiment, while plants on highly fertile soil continued to develop until flowering with only slight deviations from the control. Experimental data on the contents of total and water-soluble forms of HMs and nutrients in the studied soils are presented. The relationships between the chemical composition of soils and the results of phytotests have been found using the principal component analysis. It is shown that the threefold difference in the content of C
org
between the soils of the same texture and acidity (pH) result in significantly different response of test plants to the same concentration of HMs. The necessity of correcting the standards for the permissible concentration of HMs in soils with due account for the C
org
content in addition to pH and texture is discussed.
The influence of polyelectrolyte-based soil conditioners on the qualitative and quantitative composition of soil organic matter (SOM) was studied for two soils: sandy Dystric Arenosol (Aric) with 1% ...of C and silt loamy Abruptic Luvisol (Siltic, Cutanic) with 2% of C. The investigated polymer formulations included a synthetic polycation poly(diallyldimethylammonium chloride) (PDADMAC), a humic-based polyanion (commercial humic product Lignohumate, LH), and an interpolyelectrolyte complex (IPEC) prepared from PDADMAC and LH. In laboratory experiments, soils were treated with polymers and the composition of SOM was analyzed and compared with the control. The effect of polyelectrolytes on the molecular weight distribution and amphiphilic properties of SOM was evaluated using low-pressure size-exclusion chromatography and reversed-phase hydrophobic interaction chromatography. It was shown that the effect of polyelectrolytes differs depending both on the chemical nature and composition of polymers’ functional groups and on the soil properties. Polyanionic LH promoted mobilization of labile humic fractions, whereas polycationic PDADMAC was adsorbed in non-labile fractions. Positively charged IPEC occupied an intermediate position increasing the yield of mobile fractions only in sandy soil. The weighted average molecular weight of SOM slightly decreased with the application of all the polymers. The impact of IPEC on the distribution of hydrophobic and hydrophilic fractions depended on the native humus properties. In clay loam, it increased the proportion of the hydrophilic fraction, whereas in sandy soil the proportion of hydrophobic fractions was higher. Soil organic matter in the sandy low-humus soil provided more distinct effects of polymer application. In contrast, in a more humified loamy soil, polymers were immobilized by binding with the soil organomineral matrix and their effect on the SOM was weak.
It is necessary to take into account the neutron background in almost all low-background research. In this paper an estimated neutron flux in the underground laboratory DULB-4900 of BNO INR RAS is ...presented. The estimation is based on results of measurements of radionuclide content in surrounding rock (granite).
The effect of commercial humic product Lignohumate
®
on the biological activity of Latosol under long-term agricultural use with application of pesticides at the Bali Island (Indonesia) was evaluated ...in model experiments. It was shown that the application of lignohumate in a concentration gradient 0.025–2.5 mg/g resulted in increase in soil microbial community respiration rate by 10–30%, proportionally to the rate applied. As the application rate of Lignohumate increased, a significant threefold increase of nitrogen fixation intensity caused by the activation of bacteria of the Oxalobacteriaceae family was observed. In general, the bacterial community of Latosol consisted of more than 85% of the representatives of four phyla: Proteobacteria, Firmicutes, Chloroflexi, and Acidobacteria. Lignohumate at application rates higher than 0.025 mg/g promoted an increase of methane formation, whereas gaseous nitrogen losses due to denitrification reduced. An important practical conclusion on the reduction of a toxic effect of pesticides in the presence of lignohumate and its positive effect on soil biological activity and nitrogen balance in the Latosol under intensive agricultural use was made.
The descriptive ability of two integral biotic indices obtained from laboratory experimental data focused on estimating the effects of humic products (HPs) on the microbiota under conditions of ...copper contamination in a model soil substrate is evaluated. The “Standard Soil” prepared from sand, kaolin, and peat (ISO 11268-1) as recommended for the assessment of biological effects was used. To summarize the results of ecotoxicological studies of Cu-polluted samples (660 mg Cu/kg) and to provide the integral estimation of HPs impact on the microbiota, two statistical models were used: the Harrington’s desirability function
D
and the integrated parameter of the soil microbial system sustainability
G
(ratio of biodiversity to instability) using multisubstrate testing. The indices obtained based on two sets of multidimensional data were compared in their descriptive ability when estimating the detoxifying efficiency of HPs. It was found that HPs mainly stimulate multispecies bacterial complexes, while the test cultures representing higher plants and algae are less sensitive to their impact. Three of the five studied HPs showed a pronounced detoxifying effect and improved the state of the studied system. Both integral biotic indices—the generalized Harrington desirability function
D
and the General sustainability parameter of the system
G
—demonstrated a similar effect vector. For the purpose of environmental regulation, the use of the integrated approach based on a generalized desirability function could be recommended due to its higher completeness and reliability of the system of biotic indicators.
Humic substances (HS) have a direct impact on living cells, causing a wide range of various biological effects, and stimulating or inhibiting fungal growth. Therefore, it is important to reveal ...cellular indicators that could indicate the nature and level of HS’ effects on living organisms. Paying attention to the important role of lipid and osmolytes in adaptation to stress, the aim of this work was to study the composition of osmolytes and lipids in the growth dynamics of the phytopathogenic melanin-containing fungus Alternaria alternata under the influence of humic acid (HA). HA was isolated from a commercial peat humic product. For cultivation, liquid Czapek medium with the addition of 200 mg/l HA (HA variant) was used, and with no HA for the control variant. The main osmolytes of the fungal mycelium were glucose, mannitol, and trehalose. Both in the control and in HA variants, a general pattern was observed during the growth process; the amount of glucose increased against the background of a decrease of mannitol. In the control, the amount of trehalose increased significantly by the stage of active melanin formation (day 4), while under the influence of HA, such an increase was not observed. Membrane lipids were represented by phospholipids, sphingolipids, and sterols. A characteristic feature of A. alternata was a high proportion of phosphatidic acids (PA) in the composition of membrane lipids. The amount and proportion of PA decreased during growth in the control, while under the influence of HA such decline was not observed. The influence of HA induced the increase in the amount of sterols (St) and phosphatidylcholines (PC) that were able to stabilise the membrane lipid bilayer. We can assume that general cellular response of A. alternata to HA influence, being expressed as a higher amount of PA, PC, St and a lower level of trehalose in comparison with the control, indicates the an absence of inhibition of growth processes of this phytopathogenic melanin-producing fungus. The effect of HA on the qualitative and quantitative composition of the osmolytes and membrane lipids of A. alternata may cause changes of virulence and stress resistance of this phytopathogen.
•Humic acid (HA) has a non-stressful effect on growth of the fungus Alternaria alternata.•A feature of fungal membrane lipids is a high proportion of phosphatidic acids (PA).•The amount of PA decreases in the control variant but not under HA influence.•HA leads to an increase in phosphatidylcholines and sterols levels.•HA inhibits trehalose accumulation in comparison with control.
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