scholarly journals Mycorrhizal Patterns in the Roots of Dominant Festuca rubra in a High-Natural-Value Grassland

Plants ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 112
Author(s):  
Larisa Corcoz ◽  
Florin Păcurar ◽  
Victoria Pop-Moldovan ◽  
Ioana Vaida ◽  
Vlad Stoian ◽  
...  
Keyword(s):  
Festuca Rubra ◽  
Average Value ◽  
Mountain Grassland ◽  
Grassland Ecosystems ◽  
Fungal Structure ◽  
Mountain Grasslands ◽  
Colonization Frequency ◽  
Best Parameter ◽  
The Stability ◽  
General Regression

Grassland ecosystems occupy significant areas worldwide and represent a reservoir for biodiversity. These areas are characterized by oligotrophic conditions that stimulate mycorrhizal symbiotic partnerships to meet nutritional requirements. In this study, we selected Festuca rubra for its dominance in the studied mountain grassland, based on the fact that grasses more easily accept a symbiotic partner. Quantification of the entire symbiosis process, both the degree of colonization and the presence of a fungal structure, was performed using the root mycorrhizal pattern method. Analysis of data normality indicated colonization frequency as the best parameter for assessing the entire mycorrhizal mechanism, with five equal levels, each of 20%. Most of the root samples showed an intensity of colonization between 0 and 20% and a maximum of arbuscules of about 5%. The colonization degree had an average value of 35%, which indicated a medium permissiveness of roots for mycorrhizal partners. Based on frequency regression models, the intensity of colonization presented high fluctuations at 50% frequency, while the arbuscule development potential was set to a maximum of 5% in mycorrhized areas. Arbuscules were limited due to the unbalanced and unequal root development and their colonizing hyphal networks. The general regression model indicated that only 20% of intra-radicular hyphae have the potential to form arbuscules. The colonization patterns of dominant species in mountain grasslands represent a necessary step for improved understanding of the symbiont strategies that sustain the stability and persistence of these species.

scholarly journals Characteristics and Kinetics of Rosin Pentaerythritol Ester via Oxidation Process under Ultraviolet Irradiation

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2816 ◽  
Author(s):  
Yuanlin Li ◽  
Xiongmin Liu ◽  
Qiang Zhang ◽  
Bo Wang ◽  
Chang Yu ◽  
...  
Keyword(s):  
Light Intensity ◽  
Oxidation Kinetics ◽  
Pseudo First Order Reaction ◽  
Initial Oxidation ◽  
Photo Oxidation ◽  
Average Value ◽  
Pentaerythritol Ester ◽  
Fundamental Information ◽  
The Stability ◽  
Kinetics Of

A self-designed reaction device was used as a promising equipment to investigate the oxidation characteristics and kinetics of rosin pentaerythritol ester (RPE) under UV irradiation. Photo-oxidation kinetics and the initial quantum yield (Φ) of RPE were calculated. The initial oxidation product of the photo-oxidation reaction—peroxide was analyzed by iodimetry. The peroxide concentration is related to the light intensity (I) and the temperature (T), and the increasing T and I would destabilize the RPE by accelerating peroxide forming. Photo-oxidation of RPE follows the pseudo first-order reaction kinetics. The relationship between activation energy and logarithm of light intensity (ln I) is linear, and it is expressed as Ea = −4.937ln I + 45.565. Φ was calculated by the photo-oxidation kinetics, and the average value of Φ was 7.19% in the light intensity range of 200–800 μW cm−2. This research can provide fundamental information for application of RPE, and help obtain a better understanding of the stability of rosin esters.

On Canadian methodologies of probabilistic seismic risk estimation

1979 ◽  
Vol 69 (5) ◽  
pp. 1549-1566
Author(s):  
D. H. Weichert ◽  
W. G. Milne
Keyword(s):  
Ground Motion ◽  
Seismic Risk ◽  
Risk Estimation ◽  
Historical Earthquakes ◽  
Extreme Value ◽  
Probabilistic Methods ◽  
Average Value ◽  
Risk Estimates ◽  
The Stability ◽  
Comparison Of The Results

abstract Three probabilistic methods for the estimation of seismic risk have been used in Canada. A reevaluation of the extreme value method shows no advantages over the average value method of Milne and Davenport. Conceptual improvements in the underlying assumptions of the latter method are a constrained release of historical earthquakes from their presumed epicenters and the averaging of earthquake rates over variable periods. Risk estimation can then proceed as suggested by Cornell. Comparison of the results of this modification of the average number method shows similar results as the Milne and Davenport average value method. The stability of risk estimates against new earthquakes is improved, but sensitivities at typical sites toward unavoidable deterministic elements in the model are similar to the older method. For certain site-source-seismicity combinations probabilistic estimates of ground motion could become almost quasi-deterministic.

scholarly journals Land use affects the net ecosystem CO<sub>2</sub> exchange and its components in mountain grasslands

2010 ◽  
Vol 7 (8) ◽  
pp. 2297-2309 ◽  
Author(s):  
M. Schmitt ◽  
M. Bahn ◽  
G. Wohlfahrt ◽  
U. Tappeiner ◽  
A. Cernusca
Keyword(s):  
Land Use ◽  
Leaf Area ◽  
Ecosystem Respiration ◽  
Growing Season ◽  
Photon Flux ◽  
Area Index ◽  
Growing Season Length ◽  
Mountain Grassland ◽  
Mountain Grasslands ◽  
Land Use And Management

Abstract. Changes in land use and management have been strongly affecting mountain grassland, however, their effects on the net ecosystem exchange of CO2 (NEE) and its components have not yet been well documented. We analysed chamber-based estimates of NEE, gross primary productivity (GPP), ecosystem respiration (R) and light use efficiency (LUE) of six mountain grasslands differing in land use and management, and thus site fertility, for the growing seasons of 2002 to 2008. The main findings of the study are that: (1) land use and management affected seasonal NEE, GPP and R, which all decreased from managed to unmanaged grasslands; (2) these changes were explained by differences in leaf area index (LAI), biomass and leaf-area-independent changes that were likely related to photosynthetic physiology; (3) diurnal variations of NEE were primarily controlled by photosynthetically active photon flux density and soil and air temperature; seasonal variations were associated with changes in LAI; (4) parameters of light response curves were generally closely related to each other, and the ratio of R at a reference temperature/ maximum GPP was nearly constant across the sites; (5) similarly to our study, maximum GPP and R for other grasslands on the globe decreased with decreasing land use intensity, while their ratio remained remarkably constant. We conclude that decreasing intensity of management and, in particular, abandonment of mountain grassland lead to a decrease in NEE and its component processes. While GPP and R are generally closely coupled during most of the growing season, GPP is more immediately and strongly affected by land management (mowing, grazing) and season. This suggests that management and growing season length, as well as their possible future changes, may play an important role for the annual C balance of mountain grassland.

Stability of fulfilling the tasks of the municipalities of the Warmińsko-Mazurskie Province

2018 ◽  
Vol 46 (1) ◽  
pp. 69-75
Author(s):  
dr hab. Wiesława Lizińska ◽  
dr hab. Renata Marks-Bielska ◽  
dr Karolina Babuchowska ◽  
dr Magdalena Wojarska
Keyword(s):  
Stability Index ◽  
Average Level ◽  
Institutional Performance ◽  
Average Value ◽  
The Stability

The article summarises the results of the research on the stability of the municipalities of the Warmińsko-Mazurskie Province in fulfilling the tasks within the basic areas of their functioning compared with other municipalities in Poland. The research was conducted in the years 2015-2016 among 61 municipalities of the province. The results have been compared with the results of the research on 1,220 municipalities in the country. The analysis is based on the values of the stabi- lity index. The average value of the index in Poland amounted to 0.5721, and in the Warmińsko- -Mazurskie Province to 0.5890. The municipalities of the province that were characterised with the highest average value of the stability index were the urban and rural municipali-ties. The institutional performance, as well as stability at the average level was displayed by 39.34 percent of the surveyed municipalities of the Warmińsko-Mazurskie Province.

Variation of uplift pressure of debris flow on the dam bottom

2020 ◽  
Author(s):  
Xingzhang Chen ◽  
Hui Chen
Keyword(s):  
Debris Flow ◽  
Time Lag ◽  
Temporal Variations ◽  
Flow Density ◽  
Flume Experiments ◽  
Fine Content ◽  
Dam Foundation ◽  
Uplift Pressure ◽  
Average Value ◽  
The Stability

&lt;p&gt;Abstract: Uplift pressure is crucial for the stability of debris flow dam because of its reducing the effective pressure on the dam foundation and the anti-slide force of the dam. This study investigates the spatial and temporal variations of the uplift pressures during the debris flow impact processes, through a series of flume experiments. Before the debris flow impacting on the dam, the uplift pressure keeps stable due to the steady water level, and then it decreases slightly at the instant of debris flow impacting on the dam which lasts for no more than 1 s, and then increases sharply within a time lag no more than 2 s, and then decreases sharply soon afterwards. The maximal increasing ratio is 6.4 and the average value is 3, comparing with the uplift pressure before the impacting. The peak pressure occurs before the dam and decreases with the distance from the dam with a nearly linear tendency. The increment of uplift pressure also presents a similar tendency with the distance from the dam. In addition, the uplift pressure is found to be strongly influenced by the permeability of debris flow deposits, especially by the fine content of grain composition, and by the properties of the flow, such as the flow density, runoff volume and hydraulic gradient, and the pressure rises in a nearly linear form with the properties.&lt;/p&gt;&lt;p&gt;Keywords: debris flow, uplift pressure, check dam, flume experiments&lt;/p&gt;

The analysis of temperature fluctuations by pulse-counting techniques

1959 ◽  
Vol 6 (2) ◽  
pp. 261-271 ◽  
Author(s):  
A. A. Townsend
Keyword(s):  
Time Derivative ◽  
Temperature Fluctuations ◽  
Mean Value ◽  
Time Intervals ◽  
Mean Values ◽  
Average Value ◽  
Electrical Pulses ◽  
The Mean ◽  
The Stability ◽  
Better Than

To determine experimentally the mean value of a randomly fluctuating quantity, it may be necessary to measure the average value over a considerable interval of time. This problem arose in a recent study of the temperature fluctuations over a heated horizontal plate, and a system was used that depended on the counting of electrical pulses generated at a rate proportional to the quantity being measured. The advantage of this technique is that mean values may be measured over time intervals of almost unlimited length with little added difficulty for the experimenter. Circuits are described which measure: (a) the mean square of a fluctuating quantity and of its time-derivative, (b) the statistical distribution of the fluctuations, (c) the mean frequency of the fluctuation assuming a particular value, and (d) the mean product of two fluctuating quantities. Over the range of use, the stability and linearity of the calibrations is better than 1%, more than sufficient for work on natural convection. In its present form, the equipment responds uniformly to all frequencies below 100 c/s, but it would not be difficult to extend this range of response to higher frequencies.

scholarly journals The practical use of variation principles in non-linear mechanics

1962 ◽  
Vol 2 (3) ◽  
pp. 357-368 ◽  
Author(s):  
J. M. Blatt ◽  
J. N. Lyness
Keyword(s):  
Initial Conditions ◽  
Variation Principle ◽  
Linear Vibration ◽  
Average Value ◽  
True Motion ◽  
Non Linear ◽  
Vibration Problems ◽  
The Stability ◽  
Non Linear Mechanics ◽  
Small Disturbances

AbstractContrary to the general impression that variation principles are of purely theoretical interest, we show by means of examples that they can lead to considerable practical advantages in the solution of non-linear vibration problems. In this paper, we develop a variation principle for the period of a free oscillation, as a function of the average value of the Lagrangian over one period. Even extremely simple-minded approximations to the true motion lead to excellent values for the period. The stability of such free oscillations against small disturbances of the initial conditions is treated in a previous paper.

The stability of viscous fluid flow between rotating cylinders

1937 ◽  
Vol 33 (1) ◽  
pp. 41-61 ◽  
Author(s):  
S. Goldstein
Keyword(s):  
Angular Velocity ◽  
Wave Length ◽  
Steady Motion ◽  
Circular Cylinders ◽  
Critical Flow ◽  
Average Value ◽  
Time Period ◽  
Component Velocity ◽  
The Stability ◽  
Image Position

The stability of the motion of viscous incompressible fluid, of density ρ and kinematic viscosity ν, between two infinitely long coaxial circular cylinders, of radiiaanda+d, whered/ais small, is investigated mathematically by the method of small oscillations. The inner cylinder is rotating with angular velocity ω and the outer one with angular velocity αω, and there is a constant pressure gradient parallel to the axis. The fluid therefore has a component velocityWparallel to the axis, in addition to the velocity round the axis. A disturbance is assumed which is symmetrical about the axis and periodic along it. The critical disturbance, which neither increases nor decreases with the time, is periodic with respect to the time (except whenW= 0, when the critical disturbance is a steady motion). As Reynolds number of the flow we take ||d/ν, whereis the average value ofWacross the annulus, and we denote bylthe wave-length of the disturbance along the axis, by σ/2π the time period of the critical flow, bycthe wavelength of the critical flow, byωcthe critical value of ω, and we putapproximately, if α is not nearly equal to 1.

scholarly journals Influence of perylenediimide–pyrene supramolecular interactions on the stability of DNA-based hybrids: Importance of electrostatic complementarity

2014 ◽  
Vol 10 ◽  
pp. 1589-1595 ◽  
Author(s):  
Christian B Winiger ◽  
Simon M Langenegger ◽  
Oleg Khorev ◽  
Robert Häner
Keyword(s):  
Double Helix ◽  
Building Blocks ◽  
Supramolecular Interactions ◽  
Stacking Interactions ◽  
Average Value ◽  
Π Stacking ◽  
Dna Strands ◽  
Polycyclic Aromatic ◽  
The Stability ◽  
Dna Double Helix

Aromatic π–π stacking interactions are ubiquitous in nature, medicinal chemistry and materials sciences. They play a crucial role in the stacking of nucleobases, thus stabilising the DNA double helix. The following paper describes a series of chimeric DNA–polycyclic aromatic hydrocarbon (PAH) hybrids. The PAH building blocks are electron-rich pyrene and electron-poor perylenediimide (PDI), and were incorporated into complementary DNA strands. The hybrids contain different numbers of pyrene–PDI interactions that were found to directly influence duplex stability. As the pyrene–PDI ratio approaches 1:1, the stability of the duplexes increases with an average value of 7.5 °C per pyrene–PDI supramolecular interaction indicating the importance of electrostatic complementarity for aromatic π–π stacking interactions.

scholarly journals Impact of regional weather anomalies on the agroecosystems of the Left Bank Forest Steppe

2016 ◽  
pp. 32-38
Author(s):  
H. Dovhal ◽  
N. Voloshyna
Keyword(s):  
Agricultural Sector ◽  
Climatic Conditions ◽  
Forest Steppe ◽  
Moisture Regime ◽  
Left Bank ◽  
Agricultural Ecosystem ◽  
Average Value ◽  
The Stability ◽  
Ecosystem Complex

Importance of the territory climatic conditions as unpredictable dynamic changes problem that forms a threat to the development of the agricultural sector of the country was investigated. The problem comes from the fact that for food security of agricultural ecosystem it is rather vulnerable to change of climatic parameters, and agriculture belongs to branches which are especially sensitive to climatic changes impact. We analyzed long-term data figures for the period 1995 to 2014, which describe the temperature and moisture regime of Lubny (Poltava region). The main trends and patterns of their dynamics were established, the degree of deviation from the long-term norm was given. The author determined the relationship of the territorial climatic conditions changes and agricultural ecosystem performance and stability and also the potential consequences of the adverse effects. As a result, it was found that the expansion of the growing season crops, due to the increase in temperature and the average value of the classical heat supply plant index, may impair the stability of the agricultural ecosystem complex and reduce its performance. At the same time, one of the adapting agricultural production ways to climate change, which does not require any additional costs, is to optimize the placement of crops due to the harmonization of the production specialization ratio in accordance with the area conditions.

Sign in / Sign up

Export Citation Format

Share Document