Semi-steady State Research Articles

Effects of Filter Material on the Permeability of Sapric Peat in Flexible Wall Permeability Tests

Introduction Installation of Prefabricated Vertical Drains (PVDs) is one of the alternatives for ground improvement used in peatland deposits. However, filter paper is commonly used as standard filter material to determine the permeability of peat rather than the PVD material itself. Aims This paper presents preliminary data on the effect of using two different filter materials on the permeability behavior of Sapric peat. Methods A series of flexible wall permeability tests (FWPTs) was conducted to evaluate the peat permeability behavior under compression using two filter materials. This study compared Whatman standard filter paper and Prefabricated Vertical Drain (PVD), which is a non-woven geotextile filter material. Results The results showed that both tests using filter paper and a PVD filter exhibited a high initial coefficient of permeability, which depends on the hydraulic gradient. The coefficient of permeability significantly decreased until a certain period and then diminished with time. The coefficient of permeability from PVD filter tests was found to be approximately 2.6 times higher than that of the standard filter paper under the same compression. The duration required to reach a semi-steady state flow condition from the PVD test was 0.9 times faster than the standard filter paper. The random error of the coefficient of permeability data from the tests using the PVD filter was lower than the data of the standard filter paper. Conclusion This preliminary result suggests that standard filter material might not represent the actual coefficient of permeability of Sapric peat. The coefficient of permeability value was less consistent compared to the PVD filter. The selection of filter material plays a crucial role in ensuring accurate and reliable results, especially when dealing with PVD construction in peat. Using the PVD filter in FWPT appears to be suitable for the design of PVD in peat. The findings of this study contribute to evaluating the correct parameters for engineers to design and analyze the effectiveness of the ground treatment method using PVD in peat.

Influence of climate change on the energy performance assessment of NZEB houses

The Energy Performance of Buildings (EPB) regulations aim to reduce primary energy use and carbon dioxide emissions of buildings, which are the result of creating a comfortable and healthy indoor environment. In this study, the influence of climate change on the regulatory EPB calculation results is analysed for the Flanders region in Belgium. The results of the analysis may be used by authorities to better define nearly zero energy building (NZEB) requirements today. Meteonorm has been used to simulate future climate change based on IPCC scenarios and urban heat island effect. These future climates have been implemented in a Revit-and Excel-based tool that calculates the stochastic variation of energy performance for six different dwelling typologies, based on the semi-steady state energy use calculation method applied in the regional rating method. Four different packages of measures to achieve NZEB performance (thermal insulation, energy efficient ventilation, renewable energy technologies,…) have been considered. The results for primary energy use, overheating indicator and net energy use for heating and cooling have been analysed. As may be expected, climate change is found to lead to an increase in overheating risk, an increase in cooling energy use, and a decrease in heating energy use in the analysed dwellings. Since in most cases the decrease in heating energy use outweighs the increase in cooling energy use, the total primary energy use decreases in most cases for the 2050 future climate.

Gaussian formulation based correlation for Dietz shape factor

• The correlation developed for the estimation of Dietz shape factor is based on the Gaussian formulation. • The actual Dietz shape factors are computed utilizing the method of images. • The study involves the comparison with the results of the previous simple analytical solution for the shape factor. The traditional semi-steady state inflow equation involves Dietz shape factor which depends on reservoir geometry and well location in that geometry. The actual Dietz shape factors are computed utilizing the equation based on the method of images. In this respect, the methodology for the calculation of the Dietz shape factor by means of the method of images is presented. The correlation developed for the estimation of Dietz shape factor is based on the Gaussian function. The correlation is valid for the homogeneous rectangular reservoir areas with aspect ratios in the range from 2 to 5. It is observed that the absolute difference from the actual logarithm of Dietz shape factor is less than 0.16 and 0.43 for the ratio of well coordinates to corresponding block lengths in the range from 0.2 to 0.8 and in the range from 0.15 to 0.85, respectively. The study additionally involves the comparison with the results of the previous simple analytical solution developed for prediction of the Dietz shape factor. The comparison reveals slight improvements in estimation of the Dietz shape factor by means of the developed correlation for well locations close to the borders of the reservoir area.

Bioplastic production by feeding the marine Rhodovulum sulfidophilum DSM-1374 with four different carbon sources under batch, fed-batch and semi-continuous growth regimes

In the present study, the ability of the marine bacterium Rhodovulum sulfidophilum DSM-1374 to convert, via photo-fermentative process, certain organic acids such as single carbon source (acetate, lactate, malate and succinate) into polyhydroxyalkanoate accumulations within bacterial cells is evaluated. The main goal of the investigation was poly-3-hydroxybutyrate (P3HB) synthesis by a photo-fermentative process. Of the four carbon sources, only succinate simultaneously produced P3HB and H2 (268 mg/L and 1085 mL/L respectively). Malate was the least productive source for P3HB; the other carbon sources (acetate and lactate) produced a significant amount of polymer (596 mg P3HB/L for acetate and 716 mg P3HB/L for lactate) when R. sulfidophilum was cultured in batch growth conditions. Cumulative P3HB increased significantly when the bacterium was grown under two steps: nutrient sufficient conditions (step 1) followed by macronutrient deficient conditions (step 2). The highest cumulative P3HB was observed at the end of step 2 (1000 mg/L) when R. sulfidophilum was fed with lactate under phosphorus starvation. When grown over 1200 h, under a semi-continuous regimen, the harvested dry-biomass reached a constant content of P3HB (39.1 ± 1.6 % of cell dry-weight), in the semi-steady state condition. Since lactate is an abundant byproduct of world industries, it can be used to mitigate the environmental impact in a modern circular bio-economy.

Impacts of stratigraphic heterogeneity and release pathway on the transport of bacterial cells in porous media

In order to manage and control the pathogen release from waste streams of various municipal, industrial, and agricultural pollution sources, it is crucial to investigate the impact of release pathways of such contaminants on their fate and transport in groundwater, especially in respect to natural heterogeneities encountered in aquifers. In this laboratory scale study, we investigate the impacts of different release scenarios of Escherichia coli bacteria, including spatially distributed surface recharge and single-point deep injection, as well as mono-pulse and continuous injection on the transport of Escherichia coli within both single-layered and multilayer aquifers.The results demonstrate earlier arrival of bacteria breakthrough curve (BTC) than conservative solute within a single-layer system with textural and continuum scale heterogeneities, attributed to size exclusion mechanism and preferential flow paths. Size exclusion may be responsible for multiple peaked BTCs observed in all cases of mono-pulse injection of bacteria through both single layer and multi-layer systems. The higher breakthrough of bacteria suspension introduced through a distributed source compared to the point source injection at the same flow rate (19% and 53% in middle and top layers, respectively) suggests that natural hydrologic events such as storm may be more influential in the transport of pathogens in soils than point injections of bacteria in engineering applications such as bioremediation. Moreover, our results reveal that the concentration of the semi-steady state breakthrough formed under distributed and continuous injection condition increases significantly with an increase in the recharge flow rate. This would suggest that a variation in hydrologic conditions can significantly mobilize pathogens which are already deposited in soils.

Eco-Physiological Screening of Different Tomato Genotypes in Response to High Temperatures: A Combined Field-to-Laboratory Approach.

High temperatures represent a limitation for growth and development of many crop species. Several studies have demonstrated that the yield reduction of tomato under high temperatures and drought is mainly due to a photosynthetic decline. In this paper, a set of 15 tomato genotypes were screened for tolerance to elevated temperatures by cultivating plants under plastic walk-in tunnels. To assess the potential tolerance of tomato genotypes to high temperatures, measurements of chlorophyll fluorescence, pigments content and leaf functional traits have been carried out together with the evaluation of the final yields. Based on the greenhouse trials, a group of eight putative heat-sensitive and heat-tolerant tomato genotypes was selected for laboratory experiments aimed at investigating the effects of short-term high temperatures treatments in controlled conditions. The chlorophyll fluorescence induction kinetics were recorded on detached leaves treated for 60 min at 35 °C or at 45 °C. The last treatment significantly affected the photosystem II (PSII) photochemical efficiency (namely maximum PSII quantum efficiency, Fv/Fm, and quantum yield of PSII electron transport, ΦPSII) and the non-photochemical quenching (NPQ) in the majority of genotypes. The short-term heat shock treatments also led to significant differences in the shape of the slow Kautsky kinetics and its significant time points (chlorophyll fluorescence levels minimum O, peak P, semi-steady state S, maximum M, terminal steady state T) compared to the control, demonstrating heat shock-induced changes in PSII functionality. Genotypes potentially tolerant to high temperatures have been identified. Our findings support the idea that chlorophyll fluorescence parameters (i.e., ΦPSII or NPQ) and some leaf functional traits may be used as a tool to detect high temperatures-tolerant tomato cultivars.

Determining the micro film of hexyl alcohol in laminar condition on a rotating drum

In this research, the free surface of micro film of hexyl alcohol on a partially submerged rotating drum has been predicted using CFD (computational fluid dynamics) and compared with experimental data and analytical solution. The trend of has been found very comparable with experimental and analytical solution. A Matlab code was used to model the flow and film dynamics. Computationally it was an unsteady state problem and semi-steady state was achieved. No surfactant was present on the surface. The speed of the moving rotating drum was set a ''rpm''. With the increase of rotating drum, the minimum film thickness increases with ''rpm'' (for \alpha _o = 47^{0} and for \alpha _o = 58^{0}).

Computational study of how inert additives affect the flammability of a polymer

All polymers are flammable to some degree. For safety, polymer flammability is most commonly reduced through flame retardants that are designed to primarily act chemically as opposed to physically. Here, we investigate computationally using the code Gpyro how inert additives such as hollow glass spheres (HGS) and boron nitride platelets (BNP) alter the flammability properties of glass fibre reinforced polybutylene terephthalate (PBT-GF), in a cone heater and UL94 setup. The Gpyro model is first validated against experiments and another code, both from the literature, for pure PBT-GF. According to the predictions, HGS leads to higher surface temperatures but lower temperatures in-depth, whereas adding BNP yields the opposite effect. Modelling numerically the cone heater setup shows that at 50% HGS loading, the time to ignition is reduced to a quarter while the semi-steady state mass loss rate is reduced to a third; at 50% BNP loading, the time to ignition is doubled while the peak mass loss rate is approximately doubled. In the UL94 setup, where the sample is smaller than cone heater, the effects are similar although less pronounced. A sensitivity study of the thermophysical properties shows that time to ignition is primarily controlled by emissivity, density and specific heat capacity, while peak mass loss rate is controlled by thermal conductivity and specific heat capacity. This work shows how heat transfer within a thermoplastic polymer can be utilised to improve its flammability characteristics through inert additives as well as the limitations of this retardancy approach.

Inflow performance relationship of vertical wells in fractured vuggy media during semi-steady state flow regime

The inflow performance relationship (IPR) is one of the essential key parameters that control the fluids production/injection rate from wells. The presence of the vugs in addition to fractures in carbonate reservoirs introduce many difficulties related the estimation of IPR of future wells. In this study, a novel analytical IPR of dual-permeability, triple porosity model is derived for the first time. The introduced IPR formula is derived for the standard scenario model of a vertical and fully penetrating well in a circular reservoir under single-phase flow of slightly compressible fluid. The three governing flow equations (matrix flow equation, fracture flow equation and interaction between vugs and other two continuum equation) are solved simultaneously as a system of differential equations for semi-steady state (SSS) flow regime. The generated SSS IPR is the same as Darcy's straight line IPR multiplied by an error parameter (E23) which is bounded between zero and one. A detailed investigation of the effect of the reservoir petro-physical parameters like storativities, inter-porosities and fracture to matrix permeability ratio are presented. The newly presented IPR of dual-permeability, triple porosity system can be reduced to sub-models IPRs by further modification of error parameter to fit sub-model as single permeability, triple porosity (E13) or dual permeability, dual porosity (E22). The presented IPR formula has the advantage of dividing the pressure drop of the fluid flow to two components, one for the internal resistance between different continuums (which is resented by E) and the other one is the radial flow in the same continuum toward/from well-bore. The generated IPR model is double verified using both cell pressure centred finite volume numerical simulation and conventional pressure transient analysis.

EXPERIMENTAL EVALUATION OF DLC/STEEL SLIDING CONTACTS’ OPERATIONAL ENVELOPE

In an industrial project concerning sliding bearings, a sliding pair was selected of high alloy steel vs. industrial grade DLC coated high alloy steel as a basis for an innovative design of high performance sliding bearings lubricated with a synthetic oil for use in geared transmission units. The development process required credible data on the ultimate resistance of the sliding pair to very high contact stress. An experimental evaluation was undertaken in ring-on-ring contact with an incremental semi-steady state input parameters increase. Due to restrictions in time, economy, and manufacturing, the number of specimen sets available was limited. A flexible approach to specimen use and load/velocity/time combinations was employed to deliver required test results within the available resource limitations and at constantly updated project detailed goals.

Modeling semi-steady state near-well flow performance for horizontal wells in anisotropic reservoirs

This paper presents a novel methodology to model semi-steady state horizontal well flow performance in an anisotropic reservoir taking into account flow in the near-well region for an arbitrary well trajectory. It is based on an analytical productivity model describing coupled axial reservoir flow and radial well inflow. In order to apply this model in an anisotropic reservoir, the permeability field relative to the radial direction perpendicular to the well trajectory and the axial direction along the well trajectory must first be determined. A classical space transformation is used in concert with rotational transforms to obtain a virtual isotropic model. The transformation preserves the volumes and pressures. It is not a novel concept, but different from previous approaches in the sense that it is only applied in the near-well domain to formulate an equally isotropic media. As a result, the use of this virtual isotropic model requires the Dietz shape factor for an ellipse, transformed from the original cylindrical near-well domain. The Dietz shape factors are determined numerically in this research. The semi-steady state well/near-well model is implemented in a numerical simulator incorporating formation anisotropy and wellbore hydraulics. The specific productivity index along the well trajectory is generated using the virtual configuration. Numerical results for different anisotropy ratios and also incorporating frictional losses in the well are presented. Furthermore, the well/near-well model is applied in coupling with streamline reservoir model for a water flooding case. This appears to be the first coupling of a well hydraulics model and a streamline simulator. It presents the application of the well/near-well model in integrated reservoir simulation in an efficient and accurate manner. The results demonstrate that the coupling approach with a streamline reservoir model and the well/near-well is of great potential for advanced well simulation efficiently.

Rapid mass segregation in small stellar clusters

In this paper we focus our attention on small-to-intermediate N-body systems that are, initially, distributed uniformly in space and dynamically cool (virial ratios $Q=2T/|\Omega|$ below ~0.3). In this work, we study the mass segregation that emerges after the initial violent dynamical evolution. At this scope, we ran a set of high precision N-body simulations of isolated clusters by means of HiGPUs, our direct summation N-body code. After the collapse, the system shows a clear mass segregation. This (quick) mass segregation occurs in two phases: the first shows up in clumps originated by sub-fragmentation before the deep overall collapse; this segregation is partly erased during the deep collapse to re-emerge, abruptly, during the second phase, that follows the first bounce of the system. In this second stage, the proper clock to measure the rate of segregation is the dynamical time after virialization, which (for cold and cool systems) may be significantly different from the crossing time evaluated from initial conditions. This result is obtained for isolated clusters composed of stars of two different masses (in the ratio $m_h/m_l=2$), at varying their number ratio, and is confirmed also in presence of a massive central object (simulating a black hole of stellar size). Actually, in stellar systems starting their dynamical evolution from cool conditions, the fast mass segregation adds to the following, slow, secular segregation which is collisionally induced. The violent mass segregation is an effect persistent over the whole range of N ($128 \leq N \leq 1024$) investigated, and is an interesting feature on the astronomical-observational side, too. The semi-steady state reached after virialization corresponds to a mass segregated distribution function rather than that of equipartition of kinetic energy per unit mass as it should result from violent relaxation.

Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. The neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] is used in carrying out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. Simulations with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. However, the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.

The slow phase of chlorophyll a fluorescence induction in silico: Origin of the S-M fluorescence rise.

In higher plants, algae, and cyanobacteria, chlorophyll (Chl) a fluorescence induction (ChlFI) has a fast (under a second) increasing OJIP phase and a slow (few minutes) PS(M)T phase, where O is for origin, the minimum fluorescence, J and I for intermediate levels, P for peak, S for a semi-steady state, M for a maximum (which is sometimes missing), and T for the terminal steady-state level. We have used a photosynthesis model of Ebenhöh et al. (Philos Trans R Soc B, 2014, doi: 10.1098/rstb.2013.0223 ) in an attempt to simulate the slow PS(M)T phase and to determine the origin of the S-M rise in Chlamydomonas (C.) reinhardtii cells. Our experiments in silico show that a slow fluorescence S-M rise (as that observed, e.g., by Kodru et al. (Photosynth Res 125:219-231, 2015) can be simulated only if the photosynthetic samples are initially in a so-called "state 2," when the absorption cross section (CS) of Photosystem II (PSII) is lower than that of PSI, and Chl a fluorescence is low (see, e.g., a review by Papageorgiou and Govindjee (J Photochem Photobiol B 104:258-270, 2011). In this case, simulations show that illumination induces a state 2 (s2) to state 1 (s1) transition (qT21), and a slow S-M rise in the simulated ChlFI curve, since the fluorescence yield is known to be higher in s1, when CS of PSII is larger than that of PSI. Additionally, we have analyzed how light intensity and several photosynthetic processes influence the degree of this qT21, and thus the relative amplitude of the simulated S-M phase. A refinement of the photosynthesis model is, however, necessary in order to obtain a better fit of the simulation data with the measured ChlFI curves.

Analytical coupled axial-radial semi-steady state productivity model for horizontal wells in anisotropic medium

The classical productivity models are solutions to one-dimensional radial flow equations for vertical wells at different flow conditions. A new, fully analytical model for coupled radial well inflow and axial reservoir flow has been developed under the assumption of semi-steady state flow, i.e. the axial flow and the well inflow are solved simultaneously in closed form expressions. This coupled axial-radial flow model results in a quadratic pressure profile in the axial direction and a quadratic-logarithmic pressure profile in the radial direction. The new productivity equations are formulated by using either external pressure or average reservoir pressure in addition to flowing wellbore pressure. For the special case where axial flow or radial flow is zero, it is shown that the formulas coincide with the classical formulas for radial and linear flow, respectively. The new productivity model is also developed for an anisotropic medium by implementing a space transformation in the near-well region. The anisotropic productivity model highlights the flow in the near-well region and provides flexibility in choosing configuration of near-well simulation grid blocks. An algorithm for the simulation of the near-well flow and horizontal well productivity is presented.

Analytical coupled axial-radial semi-steady state productivity model for horizontal wells in anisotropic medium

Analytical coupled axial-radial semi-steady state productivity model for horizontal wells in anisotropic medium

Research on the prediction model of annular pressure buildup in subsea wells

The temperature difference between hot flowing production (including petroleum & natural gas) and fluid in the sealed annuli leads to annular pressure buildup (APB). The pressure increase could be very high due to the low compressibility of the annulus fluid, thereby endangering the well integrity and casing safety, especially in the HPHT (high pressure high temperature) subsea wells. In this paper, a semi-steady state model is presented to predict APB; the model takes several crucial factors into account, such as the differences of annulus temperature with depths, heat transfer diverseness at various well sections, and the ratio change between isobaric thermal expansion and the isothermal compressibility. The results of the case study demonstrate that APB is directly influenced by production rate, well depth, and annular length. In these factors, APB is most sensitive to the production rate. The higher the production rate, the higher pressure increase in the annuli becomes. The model provides a practical APB prediction method that is beneficial to well integrity and casing safety during petroleum and natural gas production process.

The interpretation of secular Caspian Sea level records during the Holocene

The Caspian Sea (CS) experienced significant changes during the Holocene. The standard deviation for Caspian Sea level (CSL) variations over that interval is estimated as σ = 1.4 m. Based on well-established views, they were climate-induced variations. There are no clear links with the calendar of climatic anomalies, and climate models do not reproduce the changes. Therefore, the question about the origin of “secular” CSL fluctuations remains open. Based on general ideas about the laws of temporal dynamics relating to massive inertial objects, the observed slow changes of the CSL under the semi-steady climate state of the Holocene can be represented as resulting from the accumulation of small anomalies in the water regime, as a kind of “self-developing” system. To test this hypothesis, the model of the water balance of the CS was used. Time scale for the sea fluctuations was estimated as ∼20 years. This model is interpreted as stochastic, and from this perspective, it is a Langevin equation that incorporates the action of precipitation and evaporation as random white noise, so that the whole can be thought of as an analogue of Brownian motion. Under these conditions, the CS is represented by a system undergoing random walk. Modeling results are interpreted from the probabilistic point of view, although the model is deterministically based on the physical law of conservation of water mass. The results showed that the CSL fluctuations under steady state conditions are characterized by σ = 1.1 m, close to the empirical value. “Super-large” anomalies in CSL are not prohibited by the theory, but their development requires a correspondingly long time. However, during long periods of time, background conditions change, and uniformity of the Brownian process becomes disrupted. The origin of large transgressive/regressive stages can be different. For example, the low stand of the Enotaevkian Regression during the LGM was determined by a significant reduction in precipitation over the Volga River catchment and by a corresponding reduction in the volume of river runoff. Hence, based on modeling results, the possibility of “self-development” effects is not prohibited by the theory: there need not be any cause for specific level changes or shifts, merely the expected behavior of red noise processes.

Modeling chlorophyll a fluorescence transient: relation to photosynthesis.

To honor Academician Alexander Abramovitch Krasnovsky, we present here an educational review on the relation of chlorophyll a fluorescence transient to various processes in photosynthesis. The initial event in oxygenic photosynthesis is light absorption by chlorophylls (Chls), carotenoids, and, in some cases, phycobilins; these pigments form the antenna. Most of the energy is transferred to reaction centers where it is used for charge separation. The small part of energy that is not used in photochemistry is dissipated as heat or re-emitted as fluorescence. When a photosynthetic sample is transferred from dark to light, Chl a fluorescence (ChlF) intensity shows characteristic changes in time called fluorescence transient, the OJIPSMT transient, where O (the origin) is for the first measured minimum fluorescence level; J and I for intermediate inflections; P for peak; S for semi-steady state level; M for maximum; and T for terminal steady state level. This transient is a real signature of photosynthesis, since diverse events can be related to it, such as: changes in redox states of components of the linear electron transport flow, involvement of alternative electron routes, the build-up of a transmembrane pH gradient and membrane potential, activation of different nonphotochemical quenching processes, activation of the Calvin-Benson cycle, and other processes. In this review, we present our views on how different segments of the OJIPSMT transient are influenced by various photosynthetic processes, and discuss a number of studies involving mathematical modeling and simulation of the ChlF transient. A special emphasis is given to the slower PSMT phase, for which many studies have been recently published, but they are less known than on the faster OJIP phase.

Dimethoate-induced slow S to M chlorophyll a fluorescence transient in wheat plants

In eukaryotic oxygenic photosynthetic organisms (both plants and algae), the maximum fluorescence is at peak P, with peak M lying much lower, or being even absent. Thus, the PSMT phase, where S is semisteady state, and T is terminal state, is replaced by a monotonous P→T fluorescence decay. In the present study, we found that dimethoate-treated wheat plant leaves showed SM transient, whereas in the case of control plants monotonous P→T fluorescence decay occured. We suggest that this was partly due to quenching of fluorescence due to [H+], responsible for P to S (T) decay in control plants (Briantais et al. 1979) being replaced by state transition (state 2 to state 1) in dimethoate-treated plants (Kaňa et al. 2012).