scholarly journals THE EFFECT OF EXPOSURE PERIOD AND TEMPERATURE ON THE PHOTOSENSORY PROCESS IN CIONA

1926 ◽  
Vol 8 (3) ◽  
pp. 291-301 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Latent Period ◽  
Chemical Reaction ◽  
Photochemical Reaction ◽  
Oxidation Reaction ◽  
Arrhenius Equation ◽  
Exposure Period ◽  
Secondary Reaction ◽  
Primary Reaction ◽  
Iron Compounds ◽  
Reaction Proceeds

1. Experiments are presented which show that the latent period in the photosensory response of Ciona is inversely proportional to the duration of the exposure period to light. From this it is found that the velocity of the chemical reaction which determines the latent period is directly proportional to the concentration of photochemical products formed during the exposure period. This is interpreted as showing that the two processes form a coupled photochemical reaction, of which the secondary reaction proceeds only in the presence of products from the primary reaction. This coupling may be a catalysis or a direct chemical relation. 2. Further experiments show that the relation between temperature and the latent period is accurately described by the Arrhenius equation in which µ = 16,200. The precise numerical value of µ tentatively identifies the latent period process as an oxidation reaction which is catalyzed by iron. 3. The photocatalytic properties of certain iron compounds are used as a model for the coupled photochemical reaction suggested for the photosensory mechanism of Ciona and Mya.

scholarly journals THE NATURE OF THE LATENT PERIOD IN THE PHOTIC RESPONSE OF MYA ARENARIA

1919 ◽  
Vol 1 (6) ◽  
pp. 657-666 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Latent Period ◽  
Linear Function ◽  
Chemical Reaction ◽  
Photochemical Reaction ◽  
Exposure Period ◽  
Photochemical Activity ◽  
Mya Arenaria ◽  
Effect Of Temperature ◽  
Photic Response

The latent period in the response of Mya to illumination varies inversely as the duration of the exposure to which it is subjected. The reciprocal of the latent period, measuring the velocity of the process which underlies it, is a linear function of the exposure period. Since the duration of the exposure represents the amount of photochemical activity, it is concluded that the substances formed at that time act to catalyze a chemical reaction which determines the duration of the latent period. This explanation is in accord with the previous work on the photochemical reaction and with the effect of temperature on the latent period. As a result of the combined investigations there is presented a concrete hypothesis for the mechanism of photic reception in Mya.

scholarly journals SENSORY EQUILIBRIUM AND DARK ADAPTATION IN MYA ARENARIA

1919 ◽  
Vol 1 (5) ◽  
pp. 545-558 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Short Interval ◽  
Bimolecular Reaction ◽  
Mya Arenaria ◽  
Rational Explanation ◽  
Order Of Magnitude ◽  
Photosensitive Substance

1. The reaction time of Mya to light is composed of two parts. The first, a sensitization period, is an exceedingly short interval of the order of magnitude associated with photographic processes. The second is a latent period of about 1.3 seconds, during which Mya need not remain exposed to the stimulating light. 2. The process of dark adaptation in Mya is orderly. Its progress may be represented by the formation of a photosensitive substance according to the dynamics of a bimolecular reaction. See PDF for Structure 3. Photosensory equilibrium as represented by the light- and dark-adapted conditions finds a rational explanation in terms of the "stationary state" of a reversible photochemical reaction involving a photosensitive substance and its two precursors. 4. There are two corollaries to this hypothesis. The first requires that the reaction time at sensory equilibrium for a given intensity should vary inversely with the temperature; the second, that the rate of dark adaptation should vary directly with the temperature. Experiments verified both of these requirements.

scholarly journals DARK ADAPTATION AND THE LIGHT-GROWTH RESPONSE OF PHYCOMYCES

1929 ◽  
Vol 12 (3) ◽  
pp. 391-400 ◽  
Author(s):  
E. S. Castle
Keyword(s):  
Latent Period ◽  
Dark Adaptation ◽  
Growth Response ◽  
Light Adaptation ◽  
Exposure Period ◽  
Bimolecular Reaction ◽  
Dark Reaction ◽  
Action Time ◽  
Kinetics Of ◽  
Photochemical Action

1. A single-celled, elongating sporangiophore of Phycomyces responds to a sufficient increase in intensity of illumination by a brief increase in growth rate. This is the "light-growth response" of Blaauw. 2. The reaction time is compound, consisting of an exposure period and a latent period (this comprising both the true latent period resulting from photochemical action and any "action time" necessary for the response). During the latter period the plant may be in darkness, responding nevertheless at the end of the latent period. 3. Both light adaptation and dark adaptation occur in the sporangiophore. The kinetics of dark adaptation can be accounted for on the basis of a bimolecular reaction, perhaps modified by autocatalysis. Attention is called to the bimolecular nature of the "dark" reaction in all other photosensory systems that have been studied, in spite of the diversity of the photosensitive substances themselves and of the different forms of the responses to light.

RADIATION CHEMISTRY OF CYCLOHEXANE: IV. PRIMARY PRODUCT YIELDS IN THE IRRADIATION OF CYCLOHEXANE

1961 ◽  
Vol 39 (12) ◽  
pp. 2381-2388 ◽  
Author(s):  
P. J. Dyne ◽  
J. A. Stone
Keyword(s):  
Radiation Chemistry ◽  
Secondary Reaction ◽  
Reaction Products ◽  
Primary Reaction ◽  
Product Yields ◽  
Primary Products ◽  
High Irradiation

The radiolysis of cyclohexane has been studied at low total doses and initial G values have been determined. Ninety-nine per cent of the evolved hydrogen has been accounted for in hydrogen-deficient products. Cyclohexene, bicyclohexyl, and cyclohexyl-hexene-1 have been identified as primary reaction products. Cyclohexyl-cyclohexene has been identified as a secondary reaction product. The use of high irradiation doses has been shown to lead to decreases in the initial G values of all primary products.

Highly efficient luminescent benzoylimino derivative and fluorescent probe from a photochemical reaction of imidazole as an oxygen sensor

2019 ◽  
Vol 55 (7) ◽  
pp. 977-980 ◽  
Author(s):  
Yue Yu ◽  
Ruiyang Zhao ◽  
Changjiang Zhou ◽  
Xiaoyi Sun ◽  
Shizhao Wang ◽  
...  
Keyword(s):  
Fluorescent Probe ◽  
Chemical Reaction ◽  
Photochemical Reaction ◽  
Oxygen Sensor ◽  
Highly Efficient

The newly-discovered photo-chemical reaction of imidazole, producing highly luminescent benzoylimino product, showed great potentials in fluorescent probe as an oxygen sensor.

Structural reasons for the formation of multicomponent products and the influence of high pressure

2021 ◽  
Vol 77 (3) ◽  
Author(s):  
Krzysztof A. Konieczny ◽  
Julia Bąkowicz ◽  
Damian Paliwoda ◽  
Mark R. Warren ◽  
Arkadiusz Ciesielski ◽  
...  
Keyword(s):  
High Pressure ◽  
Photochemical Reaction ◽  
Unit Cell Volume ◽  
Reaction Rate ◽  
Crystalline Form ◽  
Reaction Centre ◽  
High Elasticity ◽  
Reaction Proceeds ◽  
Kinetics Of

(S)-(−)-1-Phenylethanaminium 4-(2,4,6-triisopropylbenzoyl)benzoate (S-PEATPBB) undergoes a photochemical reaction in its crystalline form upon UV irradiation and forms three different products: the first product is the result of a Yang cyclization with the participation of the δ-H atom of o-isopropyl (product D) and the second and third products are obtained via a Norrish–Yang reaction with the involvement of the γ-H atom of 2-isopropyl (product P) and 6-isopropyl (product Z). These products are formed in different proportions (D > P >> Z). The path and kinetics of the reaction were monitored step-by-step using crystallographic methods, both under ambient and high-pressure conditions. The reactivity of S-PEATPBB depends strongly on the geometry of the reaction centre and the volume of the reaction cavity. Due to the geometrical preferences making the cyclization reaction easier to proceed, product D dominates over the other products, while the formation of product Z becomes difficult or almost impossible at high pressure. The reaction proceeds with an increase of the unit-cell volume, which, suppressed by high pressure, results in a significant decrease of the reaction rate. The crystal lattice of S-PEATPBB shows high elasticity. The quality of the partially reacted crystal remains the same after decompression from 0.75 GPa to 0.1 MPa.

scholarly journals Seasonal Infection of the Weed Dyer's Woad by a Puccinia sp. Rust Used for Biocontrol, and Effects of Temperature on Basidiospore Production

Plant Disease ◽  
2000 ◽  
Vol 84 (7) ◽  
pp. 753-759 ◽  
Author(s):  
Karen M. Flint ◽  
Sherman V. Thomson
Keyword(s):  
Latent Period ◽  
Exposure Period ◽  
Spore Production ◽  
Symptom Expression ◽  
Optimum Temperature ◽  
Field Evidence ◽  
Effects Of Temperature ◽  
Seasonal Infection

Potted dyer's woad rosettes exposed to natural rust inoculum at field sites became infected when exposed from late April through early July, depending upon the location. The latent period between exposure and symptom expression varied from 9 to 54 weeks. The length of this latent period was unrelated to either the age of plants at exposure or the exposure period itself. The age of rosettes at the time of exposure did not affect the incidence of infection. Fall infection of potted rosettes occurred, but the incidence was low. When naturalized stands of woad were inoculated with teliosori, either fresh or dried, the incidence of infection was 58 to 76%, compared with 2 to 7% incidence in noninoculated plants. Basidiospores were readily produced from intact teliosori when suspended over water agar, with the highest rate of production between 3 and 6 h of incubation, at 10 to 20°C. The optimum temperature for basidiospore production over a 24-h period was 15°C, but they were produced at temperatures as low as 5°C, although not at 25°C. These lower-than-expected temperatures for spore production corroborate the field evidence that dyer's woad rust most actively infects in springtime, when temperatures are comparatively low and rainfall is more frequent.

scholarly journals PHYSIOLOGICAL ONTOGENY

1926 ◽  
Vol 9 (6) ◽  
pp. 781-788 ◽  
Author(s):  
Henry A. Murray ◽  
Keyword(s):  
Chemical Reaction ◽  
Heart Muscle ◽  
Arrhenius Equation ◽  
Embryonic Heart ◽  
Contraction Rate ◽  
The Relationship ◽  
Special Case

1. The Arrhenius equation giving the relationship between the velocity of chemical reaction and temperature, was found suitable for the special case of the contraction rate of embryonic heart muscle fragments. 2. There was no constancy in the values of µ for the rate of contraction in culture, nor was the scattering evenly distributed around certain (more than one) points. 3. There seemed to be no correlation between µ and other functions such as the contraction rate, the site from which the piece was removed, the age of the embryo, etc.

scholarly journals Intermediate reactions in the binding of aminoacyl-transfer ribonucleic acid to rat liver ribosomes. Formation and properties of an aminoacyl-transfer ribonucleic acid–transferase I complex

1972 ◽  
Vol 126 (4) ◽  
pp. 923-931 ◽  
Author(s):  
J. Hradec
Keyword(s):  
Ion Exchange ◽  
Rat Liver ◽  
Ribonucleic Acid ◽  
Cellulose Nitrate ◽  
Stable Complex ◽  
Primary Reaction ◽  
Preparative Isolation ◽  
Reaction Proceeds ◽  
Aminoacyl Transfer ◽  
Liver Ribosomes

1. Transferase I of rat liver binds aminoacyl-tRNA to form a relatively stable complex, which is retained on cellulose nitrate filters. This reaction proceeds at both 0°C and 37°C and is inhibited by GTP. The resulting product is stabilized by GTP and Mg2+. 2. Only very low quantities of deacylated tRNA are bound by transferase I. 3. Methods are described for the preparative isolation of the transferase I–aminoacyl-tRNA complex from incubation mixtures by using ion-exchange procedures. 4. The transferase I–aminoacyl-tRNA complex becomes readily bound to ribosomes. The presence of Mg2+ is essential for the binding. GTP stimulates this reaction but is not absolutely required. 5. It is concluded that the formation of the transferase I–aminoacyl-tRNA complex may be the primary reaction in the binding of aminoacyl-tRNA to mammalian ribosomes and that, unlike in bacterial systems, GTP is not absolutely required for this step.

Investigations into the Silica/Silane Reaction System

1997 ◽  
Vol 70 (4) ◽  
pp. 608-623 ◽  
Author(s):  
Udo Goerl ◽  
Andrea Hunsche ◽  
Arndt Mueller ◽  
H. G. Koban
Keyword(s):  
Silica Surface ◽  
Reaction System ◽  
Rolling Resistance ◽  
Kinetic Studies ◽  
Reaction Model ◽  
Secondary Reaction ◽  
Primary Reaction ◽  
Silanol Groups ◽  
Precipitated Silica ◽  
Low Concentrations

Abstract Silica in combination with organosilanes (e.g. [bis(3-triethoxysilylpropyl)tetrasulfane] = TESPT) has recently become more important in tire applications. Their use in tire treads leads to an improvement in rolling resistance and wet traction. The requirements for the attainment of these properties are, that the triethoxysilyl groups of TESPT react with the silanol groups on the silica surface during compounding, and the polymer active groups react with the polymer during cure. The reaction of precipitated silica with this silane was investigated. The influence of various parameters on the reaction type and the reaction kinetics was considered. The results of the investigation obtained using 29Si-CP/MAS solid state NMR spectroscopy agree well with a horizontal reaction model in which a single siloxane bond is first formed with the silica surface (primary reaction). It is followed by condensation reactions between silanol groups of silane molecules which are already bound to the silica surface (secondary reaction). The kinetic studies data show a clear difference between the fast primary reaction and the slow secondary reaction. Both reactions become more rapid in acidic and alkaline pH ranges. The primary reaction accelerates up to a particular H2O content after which the rate remains constant. The secondary reaction keeps on accelerating with rising H2O content. Modification with different silane concentrations showed a higher rate constant at low concentrations.

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