An Analysis of the Temperature Dependence of Photosynthesis Considering the Kinetics of RuP2 Carboxylase and the Pool of RuP2 in Intact Leaves

1988 ◽  
Vol 15 (6) ◽  
pp. 737 ◽  
Author(s):  
VM Oja ◽  
BH Rasulov ◽  
AH Laisk
Keyword(s):  
Temperature Dependence ◽  
Short Exposure ◽  
Co2 Uptake ◽  
Mesophyll Conductance ◽  
Mesophyll Cells ◽  
Binding Reaction ◽  
Cotton Plants ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Kinetics Of

Sunflower and cotton plants were grown in growth boxes at 460 �mol m-2 s-1. The mesophyll conductance in N2, the assimilatory charge (post-illumination CO2 uptake) and the CO2 capacity (the solubility of CO2 + HCO3- + CO32-) were measured at different temperatures. The mesophyll conductance had its maximum at 29-30°C in sunflower leaves and rapidly declined at higher and lower temperatures. In cotton, the maximum occurred at a somewhat higher temperature. The assimilatory charge changed in parallel with the mesophyll conductance. When the assimilatory charge was measured after a short exposure to CO2-free N2, it remained constant at lower temperatures and declined only at superoptimal temperatures. As the assimilatory charge reflects the RuP2 pool in the leaf, the temperature dependence of the mesophyll conductance at a constant assimilatory charge reveals the actual activation energy of the CO2 binding reaction of carboxylase (together with the CO2 transport conductance in the liquid phase of mesophyll cells) which was 29 kJ mol-� for both species. At superoptimal temperatures, the primary cause for the reversible decrease of photosynthesis was a decrease in the assimilatory charge (RuP2 pool). The decrease cannot be caused by an inadequate rate of RuP2 resynthesis but is, presumably, the result of either too rapid drainage of triosephosphates to the cytosol from chloroplasts or de-energisation of thylakoids at high temperatures.

Temperature Dependence of the Kinetics of Silicon Amorphization by He Ion Implantation

1992 ◽  
Vol 279 ◽  
Author(s):  
L. Laânab ◽  
A. Roumili ◽  
M. M. Faye ◽  
N. Gessinn ◽  
A. Claverie
Keyword(s):  
Energy Density ◽  
Ion Implantation ◽  
Substrate Temperature ◽  
Temperature Dependence ◽  
Drastic Change ◽  
Density Model ◽  
Different Types ◽  
Higher Temperature ◽  
Kinetics Of ◽  
Critical Damage

ABSTRACTWe have studied by XTEM the kinetics of Si amorphization by light ion implantation (He) as a function of substrate temperature. The analysis of these kinetics has been performed within the framework of the “Critical Damage Energy Density” model which is shown to apply for temperatures up to 250 K. There is a drastic change in the efficiency of the amorphization process at about 175 K. These results are discussed and explained by considering the different types of defects (I, V, I2, V2, complexes…) that can be stabilized in c-Si depending on the temperature. Above 150 K, the amorphization proceeds through the accumulation of interstitials and vacancies while at higher temperature it proceeds through the accumulation of di-interstitials and di-vacancies left in the network after annihilation and recombination of the Frenkel pairs created by the bombardment.

scholarly journals Effects of a dicamba/MCPA/mecoprop herbicide mixture on the leaves of a barley variety

1978 ◽  
Vol 50 (3) ◽  
pp. 183-195
Author(s):  
Helena Savolainen ◽  
Kaarina Pihakaski
Keyword(s):  
Toxic Effects ◽  
Mesophyll Cells ◽  
Cell Structures ◽  
Different Temperatures ◽  
Herbicide Mixture ◽  
Higher Temperature ◽  
Electron Microscopes ◽  
Total Observation ◽  
Short Time ◽  
Observation Period

Plants of a barley cultivar Pomo were sprayed at 2-node stage with a herbicide mixture, ’Mepro Special’, containing dicamba, MCPA and mecoprop, and the plants were grown at two different temperatures. 15°C and 23° C. The effects of the herbicide on the morphology and anatomy were studied by light and electron microscopes and the effects on the chlorophyll content of leaves were studied at various intervals after the spraying. First sign of damage in the morphology of plants grown both at 23° C and 15°C were observable 10-12 days after the spraying but those in the ultrastructure as soon as 1 day after the treatment. The cells of the vascular bundle sheath were most sensitive while the mesophyll cells were unchanged during the total observation period of 12 days at 15°C. At a higher temperature injuries of various stages were observable also in the mesophyll 6 days after the treatment. The clearest alterations became visible in the chloroplasts. They swelled to spherical in shape, the intergrana and later also grana lamellae formed vesicles by dilating, later they broke down, and ultimately the plastid envelope disintegrated. The amount of starch and chlorophyll decreased, whereas the number and size of osmiophilic plastoglobuli increased significantly. The mitochondria swelled, the cristae frequently disappeared and the outer membrane of the envelope distended largely. The nucleus was best capable of resisting the toxic effects of the herbicide. The tonoplast and plasmalemma were broken down a short time before the final disintegration of the cell structures. High temperature obviously reinforced the toxic effects of the herbicide mixture.

scholarly journals Mathematical Modelling and Tray Drying Kinetics of Loquat (Eriobotrya Japonica)

2019 ◽  
Vol 9 (2) ◽  
pp. 2758-2762
Keyword(s):  
Regression Coefficient ◽  
Eriobotrya Japonica ◽  
Air Velocity ◽  
Chi Square ◽  
Drying Characteristics ◽  
Maximum Value ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Kinetics Of

The present study was aimed to investigate drying of loquat slices in tray dryer at different temperatures Drying was conducted at 45°C, 55 °C, and 65°C at constant air velocity of 0.5 m/s in tray dryer;time taken for drying of slices was 12 h, 10 h and 9h respectively. The analysed moisture data was fitted in four different drying mathematical models, i.e. Henderson and Pabis, Page, Logarithmic and Newton (Lewis).Statistical analysis predicted that Page model was best-fitted model for describing drying characteristics of loquat slices. Best-fitted model was selected by obtaining maximum value of regression coefficient (R2 ) and minimum value of chi square (χ2) and root mean square error (RSME). It was observed that shrinkage percentage was less at higher temperature as compared to the lower temperature, i.e., 45°C.

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

scholarly journals Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Khémesse Kital ◽  
Moumouny Traoré ◽  
Diégane Sarr ◽  
Moussa Mbaye ◽  
Mame Diabou Gaye Seye ◽  
...  
Keyword(s):  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Initial Rate ◽  
Reaction Medium ◽  
Standard Entropy ◽  
Step Size ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Complex Formation Process

Abstract The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

scholarly journals Torrefaction Thermogravimetric Analysis and Kinetics of Sorghum Distilled Residue for Sustainable Fuel Production

2021 ◽  
Vol 13 (8) ◽  
pp. 4246
Author(s):  
Shih-Wei Yen ◽  
Wei-Hsin Chen ◽  
Jo-Shu Chang ◽  
Chun-Fong Eng ◽  
Salman Raza Naqvi ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Pso Algorithm ◽  
Nitrogen Atmosphere ◽  
Computational Method ◽  
Weight Changes ◽  
Design And Optimization ◽  
Thermogravimetric Analyzer ◽  
Model Free ◽  
Different Temperatures ◽  
Kinetics Of

This study investigated the kinetics of isothermal torrefaction of sorghum distilled residue (SDR), the main byproduct of the sorghum liquor-making process. The samples chosen were torrefied isothermally at five different temperatures under a nitrogen atmosphere in a thermogravimetric analyzer. Afterward, two different kinetic methods, the traditional model-free approach, and a two-step parallel reaction (TPR) kinetic model, were used to obtain the torrefaction kinetics of SDR. With the acquired 92–97% fit quality, which is the degree of similarity between calculated and real torrefaction curves, the traditional method approached using the Arrhenius equation showed a poor ability on kinetics prediction, whereas the TPR kinetic model optimized by the particle swarm optimization (PSO) algorithm showed that all the fit qualities are as high as 99%. The results suggest that PSO can simulate the actual torrefaction kinetics more accurately than the traditional kinetics approach. Moreover, the PSO method can be further employed for simulating the weight changes of reaction intermediates throughout the process. This computational method could be used as a powerful tool for industrial design and optimization in the biochar manufacturing process.

scholarly journals Hydrothermal Ageing and Its Effect on Fracture Load of Zirconia Dental Implants

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3103
Author(s):  
Laurent Gremillard ◽  
Agnès Mattlet ◽  
Alexandre Mathevon ◽  
Damien Fabrègue ◽  
Bruno Zberg ◽  
...  
Keyword(s):  
Dental Implants ◽  
Fracture Load ◽  
Accelerated Ageing ◽  
Dental Ceramics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dental Restorations ◽  
Different Temperatures ◽  
Mechanical Performances ◽  
Kinetics Of

Due to growing demand for metal-free dental restorations, dental ceramics, especially dental zirconia, represent an increasing share of the dental implants market. They may offer mechanical performances of the same range as titanium ones. However, their use is still restricted by a lack of confidence in their durability and, in particular, in their ability to resist hydrothermal ageing. In the present study, the ageing kinetics of commercial zirconia dental implants are characterized by X-ray diffraction after accelerated ageing in an autoclave at different temperatures, enabling their extrapolation to body temperature. Measurements of the fracture loads show no effect of hydrothermal ageing even after ageing treatments simulated a 90-year implantation.

scholarly journals Pyrolysis and Oxidation of PAN in Dry Air. Thermoanalytical Methods

1970 ◽  
Vol 17 (1) ◽  
pp. 38-42
Author(s):  
Anna BIEDUNKIEWICZ ◽  
Pawel FIGIEL ◽  
Marta SABARA
Keyword(s):  
Temperature Increase ◽  
Heating Rates ◽  
Linear Change ◽  
Dry Air ◽  
Isothermal Conditions ◽  
Gaseous Products ◽  
Heterogeneous Processes ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
Kinetics Of

The results of investigations on pyrolysis and oxidation of pure polyacrylonitrile (PAN) and its mixture with N,N-dimethylformamide (DMF) under non-isothermal conditions at linear change of samples temperature in time are presented. In each case process proceeded in different way. During pyrolysis of pure PAN the material containing mainly the product after PAN cyclization was obtained, while pyrolysis of PAN+DMF mixture gave the product after cyclization and stabilization. Under conditions of measurements, in both temperature ranges, series of gaseous products were formed.For the PAN-DMF system measurements at different samples heating rates were performed. The obtained results were in accordance with the kinetics of heterogeneous processes theory. The process rates in stages increased along with the temperature increase, and TG, DTG and HF function curves were shifted into higher temperature range. This means that the process of pyrolysis and oxidation of PAN in dry air can be carried out in a controlled way.http://dx.doi.org/10.5755/j01.ms.17.1.246

Effects of additives on the cure kinetics of vinyl ester pultrusion resins

2021 ◽  
pp. 002199832110015
Author(s):  
Alexander Vedernikov ◽  
Yaroslav Nasonov ◽  
Roman Korotkov ◽  
Sergey Gusev ◽  
Iskander Akhatov ◽  
...  
Keyword(s):  
Vinyl Ester ◽  
Mean Squared Error ◽  
Cure Kinetics ◽  
Zinc Stearate ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Different Temperatures ◽  
Predicted Values ◽  
Kinetics Of ◽  
Final Degree

Pultrusion is a highly efficient composite manufacturing process. To accurately describe pultrusion, an appropriate model of resin cure kinetics is required. In this study, we investigated cure kinetics modeling of a vinyl ester pultrusion resin (Atlac 430) in the presence of aluminum hydroxide (Al(OH)3) and zinc stearate (Zn(C18H35O2)2) as processing additives. Herein, four different resin compositions were studied: neat resin composition, composition with Al(OH)3, composition comprising Zn(C18H35O2)2, and composition containing both Al(OH)3 and Zn(C18H35O2)2. To analyze each composition, we performed differential scanning calorimetry at the heating rates of 5, 7.5, and 10 K/min. To characterize the cure kinetics of Atlac 430, 16 kinetic models were tested, and their performances were compared. The model based on the [Formula: see text]th-order autocatalytic reaction demonstrated the best results, with a 4.5% mean squared error (MSE) between the experimental and predicted data. This study proposes a method to reduce the MSE resulting from the simultaneous melting of Zn(C18H35O2)2. We were able to reduce the MSE by approximately 34%. Numerical simulations conducted at different temperatures and pulling speeds demonstrated a significant influence of resin composition on the pultrusion of a flat laminate profile. Simulation results obtained for the 600 mm long die block at different die temperatures (115, 120, 125, and 130 °C) showed that for a resin with a final degree of cure exceeding 95% at the die exit, the maximum difference between the predicted values of pulling speed for a specified set of compositions may exceed 1.7 times.

Sign in / Sign up

Export Citation Format

Share Document