The dynamic instability of the parabolic shells in a supersonic gas flow is analyzed numerically. Such structures describe a rocket fairing. Finite degrees of freedom dynamical system is obtained by ...the assumed-modes method to describe the shell motions. The numerical approach for calculations the modes of the shell self-sustained vibrations is suggested. The Mach numbers range of the shell dynamic instability is analyzed numerically. The influence of the paraboloid height on the regions of the dynamic instability is analyzed. The frequencies of the self-sustained vibrations are investigated. The effect of the shell boundary conditions on the regions of the dynamic instability is analyzed.
The Mainz neutrino mass experiment investigates the endpoint region of the tritium
β decay spectrum to determine the mass of the electron antineutrino. By the recent upgrade the former problem of ...dewetting T
2 films has been solved and the signal-to-background-ratio was improved by a factor of 10. The latest measurement leads to
m
ν
2=−3.7±5.3
stat
±2.1
sys
eV
2/c
4
, from which an upper limit of
m
ν<2.8
eV/c
2
(95% C.L.) is derived. Some indication for the anomaly, reported by the Troitsk group, was found, but its postulated half year period is contradicted by our data.
Results of the “Troitsk
ν-mass” experiment on the search for the neutrino rest mass in the tritium beta-decay are presented. Study of time dependence of anomalous, bump-like structure at the end of ...beta spectrum reported earlier gives indication of periodic shift of the position of the bump with respect to the end-point energy with a period of 0.5 year. A new upper limit for electron antineutrino rest mass
m
ν
<2.5 eV/c
2 95% C.L. is derived after accounting for the bump.
The objective of the KArlsruhe TRItium Neutrino experiment (KATRIN) is a direct measurement of the absolute mass of the electron (anti)neutrino by means of a precise study of the endpoint region of ...the tritium beta spectrum. The expected sensitivity of KATRIN to the neutrino mass is 0.2 eV (90% CL). The experimental set-up consists of four main parts: a source of electrons from tritium beta decay, a pre-spectrometer, a unique electron spectrometer with very high energy resolution and a multi pixel detector for low energy beta particles. A "Windowless Gaseous Tritium Source" (WGTS) with differential pumping of tritium is foreseen as the main source in KATRIN. This kind of source represents a gas dynamic system with the source tube 90 mm in diameter and 10 m in length placed in a strong magnetic field and differential pumping stages at both ends of this tube. Tritium gas will be injected in the centre of the source tube producing a gas flow directed to the ends. After pumping down by the differential pumps, compressing up to several hundreds millibars by the transfer pump and purification on the palladium membrane filter, tritium will be injected back to the source tube. The estimated flow rate of the circulated tritium is 1.8 standard cubic centimeters per second (sccs), which corresponds to 2.4×10
-4
g/s (40 g/day). The stability of gas density and isotope composition in the source tube should be provided on the level of 0.1%. This paper will describe the design concept of the WGTS and will discuss the tritium processing techniques associated with the KATRIN experiment.
It is well-known that soil allelotoxicity and the water stability of soil structure are determined by the entry of plant residues into the soil, but the relationship of these soil properties has not ...been investigated. Soil samples from the fields of the Federal Research Center “Nemchinovka” after growing 25 cultivars of spring and winter wheat on plots with sod-podzolic soil are selected in this study. The effect of the soil’s allelotoxicity of plot samples on the germination of spring wheat seed of the Liza cultivar is studied by the biotesting method. The water stability of the soil structure is determined for the same samples. The existence of a sigmoid dependence between the allelotoxicity of soil samples and their water stability with a correlation greater than 95% is established. The presence of this dependence is apparently related to the increase in the soil’s water stability with an increase in the amount of fresh plant residues entering them, which is known from the literature, and the transition of the allelotoxins’ effects from stimulation to suppression with a growth in their concentration in soils.
Plant Stress and Allelotoxicity of Soils Sandukhadze, B. I.; Fedotov, G. N.; Davydova, N. V. ...
Doklady. Biological sciences,
08/2022, Letnik:
505, Številka:
1
Journal Article
Recenzirano
Stress exposures during vegetation are known to reduce the yield in crops, but the intensity and duration of stress is rather difficult to determine from the crop loss. Allelotoxins are released from ...plants into soil on exposure to stress factors. Soil allelotoxicity after vegetation was assumed to provide a diagnostic parameter that characterizes the total stress effect on crops. To verify the assumption, changes in soil allelotoxicity were studied after vegetation of three winter wheat cultivars fed with different amounts of nitrogen fertilizers. The cultivars Nemchinovskaya 85, Moskovskaya 39, and Lutescens 982/08 were found to differently respond to fertilizing. Nemchinovskaya 85 and Lutescens 982/08 showed lower stress responses at higher doses of nitrogen fertilizers, while their responses were appreciable when soil nitrogen was lacking. In the case of Moskovskaya 39, higher doses of nitrogen fertilizers caused an adverse reaction of increased allelotoxin release. Stepwise nitrogen fertilization was concluded to be necessary for preventing delayed plant development in the case of this cultivar. The results confirmed that soil allelotoxicity measured growing plants can serve as an indicator of stress caused by the growth conditions and use of various agricultural techniques.
Abstract
There are three major negative factors, which constrain the potential productivity of spring wheat in the Central Region. The first is the damage of the plants inflicted by Oscinella frit. ...The crops being heavily pitted and their slow growth due to internal and external infection caused the second biological minimum. The third limiting factor were the spring droughts, commonplace for the Central Region. All those three factors proportionally influence the spring wheat productive stalk density. In agricultural conditions of the Central Region, the high positive correlation between spring wheat yield and number of productive stems per 1 m
2
was observed. This correlation proven to be stable by years. By concentrating selection-breeding efforts on such parameter improvement, several new, highly productive varieties, which demonstrated their superiority over the standard one, were created. Thus, one of the most important principles in new Central Region spring wheat varieties development is the creation of varieties with high potential productivity, provided by higher productive stalk density (no less than 450-500 plant per 1 m
2
) even in different humidity conditions – in combination with other main yield structural elements.
Abstract
This work is devoted to the study of spring soft wheat samples collection material. Eighty collection specimens were evaluated, divided by their origin into four groups. The assessment was ...carried out according to the limiting characteristics for spring wheat: high productivity, stable over the years, resistance to biotic and abiotic environmental factors. A two-year field test made it possible to compare different groups in terms of yield, and to identify the most promising varieties and lines for the conditions of the Central Non-Black Earth Region. The evaluation of the collection samples of origin various groups showed that the varieties and lines of their own selection were the most adapted to the soil and climatic conditions of the Central Non-Chernozem region. The new lines of spring wheat, along with a high level of yield, showed resistance to biotic and abiotic stressors. Varieties of foreign selection are distinguished by a strong non-spreading stem, high density of the stem, as well as high resistance to the most harmful leaf diseases. Of particular interest are the varieties of the Belarusian selection Darya, Dalech, Viza, Rostan with a high yield potential at the level of 5.0-6.0 t/ha.
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