Seasonal response of denitrifiers to temperature in a Quebec cropped soil

1999 ◽  
Vol 79 (4) ◽  
pp. 551-556 ◽  
Author(s):  
France Pelletier ◽  
Danielle Prévost ◽  
Gilles Laliberté ◽  
Eric van Bochove
Keyword(s):  
Arrhenius Equation ◽  
Regression Coefficient ◽  
Early Spring ◽  
Effect Of Temperature ◽  
Temperate Climate ◽  
Seasonal Effect ◽  
Root Model ◽  
Denitrification Activity ◽  
Key Words Denitrification ◽  
Incubation Temperatures

While some studies indicate no denitrification activity in early spring, others have demonstrated that denitrifiers from temperate region soils can adapt to low temperatures. The aim of the present paper was to study how seasonal changes in temperature affect denitrifying enzyme activity (DEA) in a cropped humic gleysol located in a cold temperate climate (Quebec). Soil was sampled monthly during a 16-mo period and DEA was measured at nine temperatures from 2 to 35°C. A seasonal effect of temperature on DEA was significant at all incubation temperatures and was more important in November and in May–June. The effect of temperature on DEA was better fitted with the square root model of Ratkowsky than with the Arrhenius equation. The regression coefficient b (Ratkowsky parameter) varied seasonally with a trend similar to that of DEA. These results show that the Ratkowsky model should be used instead of Arrhenius equation to describe the effect of cold temperature on denitrification. Key words: Denitrification, temperature, cold, Arrhenius equation, Ratkowsky model

A STUDY OF THE MECHANISM AND KINETICS OF THE SULPHITE PROCESS

1939 ◽  
Vol 17b (4) ◽  
pp. 121-132 ◽  
Author(s):  
J. M. Calhoun ◽  
F. H. Yorston ◽  
O. Maass
Keyword(s):  
Temperature Coefficient ◽  
Arrhenius Equation ◽  
Practical Interest ◽  
Effect Of Temperature ◽  
Wood Meal ◽  
Spruce Wood ◽  
Mechanism And Kinetics ◽  
Kinetics Of

The rate of delignification of resin extracted spruce wood-meal has been determined in calcium-base sulphite liquor at temperatures from 130 °C. down to 50 °C. No break was found in the temperature coefficient curve at the lower temperatures, the reaction following the Arrhenius equation closely. Possible mechanisms of the reaction are discussed in the light of existing theories, and the effect of temperature on the yield of pulp is pointed out for its practical interest.

Morphological and physiological dormancy in seeds of Aegopodium podagraria (Apiaceae) broken successively during cold stratification

2009 ◽  
Vol 19 (2) ◽  
pp. 115-123 ◽  
Author(s):  
Filip Vandelook ◽  
Nele Bolle ◽  
Jozef A. Van Assche
Keyword(s):  
Low Temperature ◽  
Seedling Emergence ◽  
Early Spring ◽  
Temperate Climate ◽  
Cold Stratification ◽  
Dormancy Breaking ◽  
Morphophysiological Dormancy ◽  
Temperature Requirement ◽  
Physiological Dormancy ◽  
Chilling Period

AbstractA low-temperature requirement for dormancy break has been observed frequently in temperate-climate Apiaceae species, resulting in spring emergence of seedlings. A series of experiments was performed to identify dormancy-breaking requirements of Aegopodium podagraria, a nitrophilous perennial growing mainly in mildly shaded places. In natural conditions, the embryos in seeds of A. podagraria grow in early winter. Seedlings were first observed in early spring and seedling emergence peaked in March and April. Experiments using temperature-controlled incubators revealed that embryos in seeds of A. podagraria grow only at low temperatures (5°C), irrespective of a pretreatment at higher temperatures. Seeds did not germinate immediately after embryo growth was completed, instead an additional cold stratification period was required to break dormancy completely. Once dormancy was broken, seeds germinated at a range of temperatures. Addition of gibberellic acid (GA3) had a positive effect on embryo growth in seeds incubated at 10°C and at 23°C, but it did not promote germination. Since seeds of A. podagraria have a low-temperature requirement for embryo growth and require an additional chilling period after completion of embryo growth, they exhibit characteristics of deep complex morphophysiological dormancy.

Effect of Temperature on Growth and Alpha Toxin Production by Clostridium perfringens1

1979 ◽  
Vol 42 (11) ◽  
pp. 848-851 ◽  
Author(s):  
Y. PARK ◽  
E. M. MIKOLAJCIK
Keyword(s):  
Growth Phase ◽  
Incubation Temperature ◽  
Ground Beef ◽  
Population Level ◽  
Toxin Production ◽  
Stationary Growth Phase ◽  
Effect Of Temperature ◽  
Alpha Toxin ◽  
Stationary Growth ◽  
Incubation Temperatures

Growth and alpha toxin production by a strain of Clostridium perfringens was determined in Thioglycollate medium, beef broth with ground beef, and beef broth with ground beef and soy protein. Incubation temperatures ranged from 15 to 50 C. In Thioglycollate medium, maximum alpha toxin production occurred at 35 C and was 40 times greater than that observed at 45 C. However, generation time and maximum population were approximately the same at 35 and 45 C. At 15 C, a two log cycle reduction in viable counts occurred within 6 h. Irrespective of incubation temperature, alpha toxin levels in Thioglycollate medium declined as the incubation period was extended beyond the stationary growth phase. In the beef broth with ground beef system which was studied at 35 C only, the organism grew slower and produced less toxin than in Thioglycollate medium. The amount of alpha toxin detected was influenced to a greater extent by the incubation time and temperature, the holding time beyond the stationary growth phase, and the growth medium than by the population level of C. perfringens.

Seasonal effect of humidity on human comfort in a hot summer/cold winter zone in China

2018 ◽  
Vol 28 (2) ◽  
pp. 264-277 ◽  
Author(s):  
Chao Li ◽  
Hong Liu ◽  
Baizhan Li ◽  
Aihong Sheng
Keyword(s):  
Air Quality ◽  
Relative Humidity ◽  
Effect Of Temperature ◽  
Seasonal Effect ◽  
Thermal Perception ◽  
Cold Winter ◽  
Humidity Ratio ◽  
Subjective Responses ◽  
C 23 ◽  
Different Seasons

Adaptation to different seasonal climates may affect human subjective responses to humidity. In this study, thermal comfort, humidity comfort and perceived air quality were investigated with subjects exposed in a climate chamber during spring, summer and winter. Sixty subjects were recruited in total, divided into groups of 20 subjects for each season. Temperature was set at three levels (cool, moderate and warm) during experiments in ranges of 20–28°C, 23–32°C, 16–28°C for spring, summer and winter, respectively. Likewise, relative humidity was set at three levels: 15% (low), 50% (moderate) and 85% (high). Results showed that seasonal difference had a significant effect on human subjective responses to humidity. The combined effect of temperature and relative humidity on thermal perception, humidity perception and perceived air quality was closely related to standard effective temperature (SET*), humidity ratio and air enthalpy, respectively. Comfort humidity ranges were 7.9–15.1 g/kg, 3.3–18.8 g/kg and 2.9–12.8 g/kg (humidity ratio) in spring, summer and winter, respectively. Overall, our results indicate that different comfort humidity limits should be considered for different seasons in the hot summer/cold winter zones of China.

scholarly journals THE SULFONIUM SALT OF MUSTARD GAS: BIS-ß-[BIS(ß-HYDROXYETHYL) SULFONIUM] ETHYLSULFIDE DICHLORIDE (H·2TDG)

1947 ◽  
Vol 30 (6) ◽  
pp. 457-464 ◽  
Author(s):  
Roger M. Herriott
Keyword(s):  
Activation Energy ◽  
Temperature Coefficient ◽  
Arrhenius Equation ◽  
Effect Of Temperature ◽  
Mustard Gas ◽  
Hydrolysis Constant ◽  
Dilute Solutions ◽  
Sulfonium Salt ◽  
Simple Method

1. The sulfonium salt H·2TDG is formed when H is mixed with even dilute solutions of TDG. Crystalline H·2TDG was isolated from such a reaction mixture. A simple method of preparation of this salt is outlined. 2. A material which differs from H·2TDG in that it hydrolyzes faster, is formed when H hydrolyzes in water. This material is probably H·1TDG but it was not isolated. Approximately 5 to 8 per cent of the original H is converted to this sulfonium salt. 3. The hydrolysis constant of M/100 H·2TDG has been determined at 20°, 25.5°, 37°, 75°, and 100°C., a temperature coefficient, Q10, of 3–4 was obtained. The effect of temperature is in agreement with that predicted by the Arrhenius equation. An activation energy of 26,000 calories was calculated.

scholarly journals PHOTOTROPIC CIRCUS MOVEMENTS OF LIMAX AS AFFECTED BY TEMPERATURE

1924 ◽  
Vol 7 (1) ◽  
pp. 151-169 ◽  
Author(s):  
W. J. Crozier ◽  
H. Federighi
Keyword(s):  
Animal Behavior ◽  
Body Wall ◽  
Arrhenius Equation ◽  
Dynamic Equilibrium ◽  
The Body ◽  
Effect Of Temperature ◽  
Natural Conditions ◽  
Circus Movement ◽  
Limax Maximus ◽  
Effect Of Light

1. The theory of animal phototropism requires for particular instances a knowledge of the action of light as exerted through each of two bilaterally located receptors functioning singly. The measurement of "circus movements" which this involves must be concerned with such aspects of the reaction as are demonstrably dependent upon the effect of light. 2. The negatively phototropic slug Limax maximus exhibits very definite and continuous circus movement under vertical illumination when one eye-tentacle has been removed. The amplitude of the circling movement, measured in degrees deflection per cm. of path as an index of maintained differential tonus, is intimately related to the concurrent velocity of creeping. Analysis of the orienting mechanism is facilitated by the fact that in gasteropods such as Limax the animal creeps by means of the pedal organ, but orients (turns) by a totally distinct set of muscles in the dorsal and lateral regions of the body wall. 3. The expression of the phototropic orienting tendency, with illumination constant, is greatly influenced by the temperature. Above a zone centering at 15°, the amplitude of turning (degrees per cm. of path) is determined by the temperature in accurate agreement with Arrhenius' equation for chemical reaction velocity, with the critical increment µ = 16,820; and the rate of creeping is progressively less as the temperature rises, µ for its reciprocal being 10,900. Below 15°, the velocity of creeping becomes less the the lower the temperature, µ being again 16,800; while the amplitude of orientation is limited merely by the velocity of creeping, its reciprocal being directly proportional thereto. 4. Measurements of Limax circus movements in terms of turning deflection as function of light intensity must therefore be carried out at a temperature well above 15°. 5. The analysis provides a gross physical model of how an end-result may be influenced by temperature according to the effect of temperature upon each of several interconnected processes when the "temperature vs. effect" curves for these processes dynamically intersect. 6. It is pointed out that a certain type of unpredictability (quantative variability) in animal behavior under "normal" natural conditions probably results from dynamic equilibrium there obtaining between diverse mechanisms competing for effector control (in the present case, the creeping mechanism and that for turning, in the range 14–16°C.). It follows that the unraveling of the elements of conduct necessitates experimentation under diverse abnormal conditions favoring individual mechanism of response.

The Effect of Temperature on Certain Simple Haemolytic Systems

1930 ◽  
Vol 7 (4) ◽  
pp. 390-403
Author(s):  
ERIC PONDER ◽  
J. FRANKLIN YEAGER
Keyword(s):  
Arrhenius Equation ◽  
Sodium Taurocholate ◽  
Red Cells ◽  
Effect Of Temperature ◽  
Velocity Constant ◽  
Human Red Cells

1. When saponin or sodium taurocholate are used as haemolysins for human red cells, the effect of temperature on the haemolytic process cannot be adequately described by the Arrhenius equation. 2. The failure of this equation to describe the results is due to the fact that changes of temperature affect several constants in the equation for the reaction between the lysin and the cells and not the velocity constant only. 3. It is shown that the changes of temperature produce irreversible changes both in the cells and in the lysin, which fact adds to the difficulty of analysing the results.

The Rheological Properties of Turkish Delight

2009 ◽  
Vol 6 (1) ◽  
Author(s):  
Zurriye Yilmaz ◽  
Mehmet Dogan ◽  
Mahir Alkan ◽  
Serap Dogan
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Power Law ◽  
Food Industry ◽  
Arrhenius Equation ◽  
Flow Behavior ◽  
Effect Of Temperature ◽  
Flow Properties ◽  
Different Temperatures ◽  
Dependent Flow

In the food industry, rheological properties, such as viscosity, shear rate, and shear stress, are the most important parameters required in the design of a technological process. Therefore, in this study, we determined the flow behavior and the time-dependent flow properties of Turkish Delight (TD) in the temperature range of 25-75°C using a capillar rheometer. The structure and thermal properties of TD were investigated by XRD and a simultaneous DTA/TG analysis. The shear rate values ranged from 5 to 300s-1. We found that: (i) TD behaved as non- Newtonian pseudoplastic foodstuff; (ii) while the measurement temperature increased, viscosity decreased; and (iii) TD was a rheopectic material. The effect of temperature on viscosity was described by means of the Arrhenius equation. The activation energies for the flow of pseudoplastic TD varied from 50.1-74.2 kJ/mol, depending on shear rate. Three models were used to predict the flow behavior of TD, namely, the Power law, Bingham and Casson models. The Power law model adequately described well the flow behavior of TD at different temperatures.

scholarly journals Rheological behavior of Brazilian Cherry (Eugenia uniflora L.) pulp at pasteurization temperatures

2013 ◽  
Vol 33 (1) ◽  
pp. 26-31 ◽  
Author(s):  
Alessandra Santos Lopes ◽  
Rafaella de Andrade Mattietto ◽  
Hilary Castle de Menezes ◽  
Luiza Helena Meller da Silva ◽  
Rosinelson da Silva Pena
Keyword(s):  
Rheological Behavior ◽  
Apparent Viscosity ◽  
Arrhenius Equation ◽  
Effect Of Temperature ◽  
Eugenia Uniflora ◽  
Fluid Behavior ◽  
Behavior Index

The rheological behavior of Brazilian Cherry (Eugenia uniflora L.) pulp in the range of temperatures used for pasteurization (83 to 97 °C) was studied. The results indicated that Brazilian Cherry pulp presented pseudoplastic behavior, and the Herschel-Bulkley model was considered more adequate to represent the rheological behavior of this pulp in the range of temperatures studied. The fluid behavior index (n) varied in the range from 0.448 to 0.627. The effect of temperature on the apparent viscosity was described by an equation analogous to Arrhenius equation, and a decrease in apparent viscosity with an increase in temperature was observed.

Effect of Temperature and Safeners on Glutathione Levels and Glutathione S-Transferase Activity in Maize

1991 ◽  
Vol 46 (9-10) ◽  
pp. 856-860 ◽  
Author(s):  
Daniel L. Kunkel ◽  
John C. Steffens ◽  
Robin R. Bellinder
Keyword(s):  
Low Temperatures ◽  
Herbicide Tolerance ◽  
Effect Of Temperature ◽  
Transferase Activity ◽  
Glutathione S Transferase ◽  
Different Temperatures ◽  
Maize Plants ◽  
Incubation Temperatures ◽  
Gst Activity

Abstract Studies were conducted to determine the biochemical aspects of chloroacetamide injury to maize and the mechanism by which safeners maintain herbicide tolerance, even at reduced temperatures. The objectives of these studies were threefold: one, determine whether gluta­thione (GSH) content varies in maize plants grown at three different temperatures in safener-treated and non-treated plants; two, determine whether glutathione S-transferase (GST) activ­ity varies in plants grown at different temperatures; and three, determine if GSH activity is sensitive to low temperatures in vitro. The herbicide safeners CGA -154281 [4-(dichloroacetyl)-3,4-dihydro-3-methyl-2 H-1 ,4-benzoxazine] and dichlormid [2,2-dichloro-N,N-di-2-propenylacetamide] were used with metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-n-(2-methoxy-1-methyl)acetamide] or acetochlor [2-chloro-N-(ethoxymethyl)-N-2-ethyl-6-methylphenyl)-acetamide], respectively, to determine the mechanisms of maize tolerance. CGA -154281 signifi­cantly increased GSH levels in maize seedlings grown at 27 °C compared to non-safened seed­lings, however significant differences were not seen at 17 or 37 °C. Dichlormid increased GSH levels by 1.6-fold at all growth temperatures. Both CGA -154281 and dichlormid increased GST activity significantly at all growth temperatures. The safener-induced GST activity was main­tained at in vitro incubation temperatures of 5 and 15 °C for acetochlor and metolachlor, re­spectively. In contrast, GST activity from non-safened tissue was essentially absent at these temperatures. Therefore, greater GST activity following safener treatment may result in higher levels of herbicide metabolism, even at low temperatures.

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