Kinetics of the hydrogen/oxygen reaction II. The explosion region in salt- and alkali-coated vessels

1952 ◽  
Vol 211 (1104) ◽  
pp. 86-95 ◽  
Keyword(s):  
Mixture Composition ◽  
Spontaneous Ignition ◽  
Vessel Size ◽  
First Order ◽  
Wide Range ◽  
Chain Theory ◽  
A Chain ◽  
The Individual ◽  
Kinetics Of ◽  
Oxygen Reaction

The first, second and third explosion limits for the hydrogen/oxygen reaction have been examined over a wide range of temperature, mixture composition, vessel size and wall coating. An expression has been derived from general chain theory which can account for the observed features of the complete explosion region. It includes and relates previously given expressions for the individual limits. The reactions found to be necessary and apparently sufficient to account for the hydrogen/oxygen spontaneous ignition peninsula are those of chain destruction in triple collisions, destruction at the wall of three different chain carriers, first-order branching, second-order branching, the regeneration of ‘dead’ chains and a chain-initiating process.

Critical examination of various approaches used for analysing helical cables

1994 ◽  
Vol 29 (1) ◽  
pp. 43-55 ◽  
Author(s):  
M Raoof ◽  
I Kraincanic
Keyword(s):  
Large Diameter ◽  
Numerical Results ◽  
Hertzian Contact ◽  
Critical Examination ◽  
First Order ◽  
Wide Range ◽  
End Conditions ◽  
Parametric Studies ◽  
The Individual ◽  
Fixed End

Using theoretical parametric studies covering a wide range of cable (and wire) diameters and lay angles, the range of validity of various approaches used for analysing helical cables are critically examined. Numerical results strongly suggest that for multi-layered steel strands with small wire/cable diameter ratios, the bending and torsional stiffnesses of the individual wires may safely be ignored when calculating the 2 × 2 matrix for strand axial/torsional stiffnesses. However, such bending and torsional wire stiffnesses are shown to be first order parameters in analysing the overall axial and torsional stiffnesses of, say, seven wire stands, especially under free-fixed end conditions with respect to torsional movements. Interwire contact deformations are shown to be of great importance in evaluating the axial and torsional stiffnesses of large diameter multi-layered steel strands. Their importance diminishes as the number of wires associated with smaller diameter cables decreases. Using a modified version of a previously reported theoretical model for analysing multilayered instrumentation cables, the importance of allowing for the influence of contact deformations in compliant layers on cable overall characteristics such as axial or torsional stiffnesses is demonstrated by theoretical numerical results. In particular, non-Hertzian contact formulations are used to obtain the interlayer compliances in instrumentation cables in preference to a previously reported model employing Hertzian theory with its associated limitations.

scholarly journals O09 Drug delivery kinetics of intravenous gentamicin in a population of neonates

2019 ◽  
Vol 104 (6) ◽  
pp. e4.2-e4
Author(s):  
G Salis ◽  
N Medlicott ◽  
D Reith
Keyword(s):  
Drug Delivery ◽  
Time Lag ◽  
Medical Science ◽  
Compartment Model ◽  
Pharmacokinetic Parameters ◽  
List Type ◽  
First Order ◽  
Model Drug ◽  
The Individual ◽  
Kinetics Of

BackgroundGentamicin is commonly used in the NICU setting and is often administered via long lines, which increases variability in the rate of administration. We aimed to model drug delivery pharmacokinetic parameters for intravenous gentamicin administered via umbilical venous catheters (UVCs).MethodsData was modelled from infusion simulations of gentamicin delivery using UVCs with a background flow rate of 0.5 ml/h.1 Different combinations of dose (2 mg, 5 mg) were given by bolus injection over 3–5 minutes, followed by a normal saline flush (1 ml, 2 ml). Gentamicin levels were measured at 5 minute intervals over an hour via high pressure liquid chromatography.Phoenix Certara (version 8.1) was used for modelling. An extravascular model with clearance removed was used to predict parameters: absorption constant (Ka), time lag (Tlag), and bioavailability (F). F was used to enable an estimate of the variability in dose administered. Different error models were tested to ascertain which best described the data.ResultsAn extravascular one compartment model with first order absorption and additive error best described the data. Estimates for the model with a 2 mg dose and 1 ml flush were Ka 0.34L/min, Tlag 1.28min, F 0.97, standard deviation (stdev) 0.14. For 2 mg, 2 ml flush, estimates were Ka 0.86L/min, Tlag 3.01min, F 0.87, stdev 0.01. For 5 mg, 1 ml flush, estimates were Ka 0.48L/min, Tlag 3.13min, F 1.03, stdev 0.12. For 5 mg, 2 ml flush, estimates were Ka 0.83L/min, Tlag 3.29min, F 1.09, stdev 0.02. For each model epsshrinkage and nshrinkage for Tlag and F were low, however nshrinkage for ka was 0.9999.ConclusionThis is the first known modelling of gentamicin delivery kinetics. The studies all had high nshrinkage for Ka, therefore the individual estimates of ka may be unreliable. Further studies with a higher number of replicates would provide more favourable data for estimating Ka.ReferenceLala AC ( 2016). Variability in neonatal gentamicin administration influencing drug delivery kinetics (Thesis, Master of Medical Science). University of Otago.Disclosure(s)No conflict of interest declared. Funding for research via the Freemasons Society of New Zealand.

scholarly journals Kinetics and Mechanism of Oxidation oft-Butylbenzylamine by Diperiodatoargentate(III) in Aqueous Alkali

2012 ◽  
Vol 9 (1) ◽  
pp. 203-210 ◽  
Author(s):  
Mahantesh A. Angadi ◽  
Suresh M. Tuwar
Keyword(s):  
Kinetic Studies ◽  
Active Species ◽  
Alkali Concentration ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Middle Range ◽  
Wide Range ◽  
Rate Of Reaction ◽  
Mechanism Of Oxidation ◽  
Kinetics Of

t-Butylbenzylamine (t-BA) is used as a free base in the synthesis of salbutamol drug. Its mechanism of oxidation was proposed from kinetic studies. The kinetics of oxidation oft-butylbenzylamine by diperiodatoargentate(III) (DPA) was studied spectrophotometrically by monitoring decrease in absorbance of DPA. The reaction was found to be first order each in [DPA] and [t-BA]. The effect of alkali concentration in a wide range on rate of reaction was studied. The rate of reaction was found to be increased with increase in [OH–] in the lower range of [OH–], decreasing effect in the middle range and at higher range again increasing effect on rate of reaction was observed. The added periodate retarded the rate of reaction. The polymerization test revealed that oxidation was occurred with the intervention free radical. A suitable mechanism was proposed for a middle range of [OH–]. The active species of silver(III) periodate for all the three different stages of [OH–] are assayed. Rate law was derived and verified. The oxidative product oft-BA was characterized by LC-ESI-MS spectra.

The Vulcanization of Elastomers. X. The Vulcanization of Natural Rubber with Thiuram Disulfides (V)

1957 ◽  
Vol 30 (3) ◽  
pp. 903-910
Author(s):  
Otto Lorenz ◽  
Walter Scheele ◽  
Wolfgang Redetzky
Keyword(s):  
Reaction Time ◽  
Natural Rubber ◽  
First Order ◽  
Wide Range ◽  
Identical Rate ◽  
Tetraethylthiuram Disulfide ◽  
Kinetics Of

Abstract The kinetics of crosslinking natural rubber during vulcanization with tetramethyl and tetraethylthiuram disulfide was investigated. The following results were derived: 1. The increase of crosslinking during vulcanization which was measured by the change of reciprocal swelling is first order over a wide range of reaction time and temperature. 2. During vulcanization, crosslinking and dithiocarbamate formation are reactions which proceed with identical rate. From this we had to conclude that the formation of dithiocarbamate is the immediate cause of the crosslink formation. 3. The concentration of the thiuram disulfide decreases much faster with respect to vulcanization time than crosslinking increases. In other words, the thiuram decrease can only be considered a reaction which precedes crosslinking.

Kinetics of the hydrogen/oxygen reaction I. The explosion region in boric acid-coated vessels

1951 ◽  
Vol 204 (1079) ◽  
pp. 465-476 ◽  
Keyword(s):  
Boric Acid ◽  
Temperature Dependence ◽  
Branching Process ◽  
Mathematical Expression ◽  
Chain Branching ◽  
Mixture Ratio ◽  
Vessel Size ◽  
Wide Range ◽  
Kinetics Of ◽  
Acid Coating

The region of low-pressure explosion for hydrogen/oxygen mixtures in boric acid-coated vessels has been observed over a wide range of temperature, vessel size and mixture ratio. The results obtained cannot be explained by any of the existing mechanisms, and appear to conflict with the present interpretation of the effects of boric-acid coating. The explosion boundary is described by a simple mathematical expression which demands the participation of a second-order chain-branching process not operative in salt-coated vessels. The previously excluded reaction H + HO 2 → OH + OH is postulated. A mechanism is outlined which successfully accounts for the shape and temperature dependence of the newly observed explosion region.

THE KINETICS OF THE THERMAL DECOMPOSITION OF DISULPHUR DECAFLUORIDE

1951 ◽  
Vol 29 (6) ◽  
pp. 508-525 ◽  
Author(s):  
W. R. Trost ◽  
R. L. McIntosh
Keyword(s):  
Nitric Oxide ◽  
Thermal Decomposition ◽  
Heterogeneous Reaction ◽  
Homogeneous Reaction ◽  
Chain Reaction ◽  
First Order ◽  
Reaction Proceeds ◽  
Total Process ◽  
A Chain ◽  
Kinetics Of

The thermal decomposition of the gas disulphur decafluoride has been studied in a metal reactor. Analytical evidence showed that the reaction proceeds according to the equation S2F10 = SF6 + SF4.The reaction was found to be largely homogeneous, as the heterogeneous reaction accounted for less than 5% of the total process. The homogeneous reaction was shown to be first order, and in the temperature range investigated the rate is given by ln k = 47.09 − 49,200/RT. A chain reaction is postulated to explain the observed rate of the reaction. The effect of nitric oxide and acetylene dichloride on the rate and products of the reaction was investigated.

Kinetics of hydrogen/oxygen reaction III. The explosion-limit equation and its applications

1952 ◽  
Vol 211 (1104) ◽  
pp. 96-109 ◽  
Keyword(s):  
Activation Energy ◽  
Size Effects ◽  
Branching Process ◽  
Inert Gases ◽  
Spontaneous Ignition ◽  
Limit Equation ◽  
Vessel Size ◽  
Chain Breaking ◽  
Explosion Limit ◽  
Kinetics Of

The explosion-limit equation is considered term by term for the evaluation of the various constants and a comparison of the experimental figures with theoretical expectations. In general, the agreement is found to be satisfactory and the equation adequate in describing the whole observed region of spontaneous ignition. Certain features of the reaction about which there still exists some uncertainty are re-examined in the light of the present work. The aspects considered are those of vessel-size effects, the overall reaction mechanism, activation energy of the branching process, surface chain-breaking efficiencies, effects of inert gases and the action of sensitizers.

The kinetics of the thermal decomposition of normal paraffin hydrocarbons III. Activation energies and possible mechanisms of molecular reactions

1950 ◽  
Vol 203 (1075) ◽  
pp. 486-501 ◽  
Keyword(s):  
Nitric Oxide ◽  
Condensation Reaction ◽  
Volume Ratio ◽  
Chain Process ◽  
Normal Reaction ◽  
First Order ◽  
Rate Of Reaction ◽  
Molecular Reaction ◽  
A Chain ◽  
Kinetics Of

In part I it was concluded that the nitric oxide-inhibited decomposition of paraffins probably represents a molecular reaction. Further experiments in which the presence of hydrogen causes a marked increase in the normal reaction but not of the inhibited reaction strengthen this conclusion, by diminishing still further the likelihood that the inhibited reaction is a chain process not suppressible by nitric oxide. Experiments on variation of the surface/volume ratio and on the coating of the vessel surface with potassium chloride have been made for the normal reaction and for the reaction inhibited by nitric oxide and by propylene respectively. The effect of the surface change is either negligible or, in certain cases, to accelerate a condensation reaction* which may vitiate the measurement of the true decomposition rate. Over limited ranges the rate of reaction, r ∞ , is connected with the pressure by the relation r ∞ = Ap 0 + Bp 2 0 , but this is probably an approximation for an expression of the form r ∞ = ap 2 0 /1 + a'p 0 + bp 2 0 /1 + b'p 0 , the reaction mechanism being composite. A reaction nearly of the first order predominates at lower pressures and one nearly of the second order at higher pressures.

scholarly journals Kinetics of the interaction of chymotrypsin with eglin c

1991 ◽  
Vol 280 (1) ◽  
pp. 27-32 ◽  
Author(s):  
B Faller ◽  
J G Bieth
Keyword(s):  
Rate Constant ◽  
Proteinase Inhibitor ◽  
Enzyme Inhibitor ◽  
Order Rate Constant ◽  
Stopped Flow ◽  
First Order ◽  
Wide Range ◽  
Eglin C ◽  
Pseudo First Order ◽  
Kinetics Of

The kinetics of binding of recombinant eglin c to bovine pancreatic chymotrypsin was studied by conventional and stopped-flow techniques. With nanomolar enzyme and inhibitor concentrations, the inhibition was fast and pseudo-irreversible (k(assoc.) = 4 x 10(6) m-1.s-1 at 7.4 and 25 degrees C). Reaction of the enzyme-inhibitor complex with alpha 1-proteinase inhibitor, an irreversible chymotrypsin ligand, resulted in a slow release of free eglin c, which was monitored by electrophoresis (k(dissoc.) approximately 1.6 x 10(-6) s-1, t1/2 approximately 5 days). The proflavin displacement method and a stopped-flow apparatus were used to monitor the association of chymotrypsin with eglin c under a wide range of inhibitor concentration and under pseudo-first-order conditions. At pH 7.4 and 25 degrees C or 5 degrees C, or at pH 5.0 and 25 degrees C, the pseudo-first-order rate constant of proflavin displacement increased linearly with eglin c up to the highest concentration tested, suggesting a one-step bimolecular association reaction: E + I in equilibrium with EI. However, kassoc. is much lower than the rate constant for a bimolecular reaction and its activation energy (66 kJ.mol-1 at pH 7.4 and 78 kJ.mol-1 at pH 5.0) is far too high for a diffusion-controlled step. The enzyme-inhibitor association may therefore occur via a loose pre-equilibrium complex EI* (Ki* much greater than 5 x 10(-4) M) that rapidly isomerizes (k2 much greater than 2 x 10(3) s-1) into an extremely stable final complex (Ki approximately 4 x 10(-13) M). Unlike other proteinase-inhibitor systems, the chymotrypsin-eglin association is virtually pH-independent.

scholarly journals The combustion of aromatic and alicyclic hydrocarbons I—The slow combustion of benzene, toluene, ethylbenzene, n -propylbenzene, n -butylbenzene, o -xylene, m -xylene, p -xylene and mesitylene

1937 ◽  
Vol 161 (904) ◽  
pp. 48-67 ◽  
Keyword(s):  
Gaseous Phase ◽  
Aromatic Compounds ◽  
Chain Mechanism ◽  
Induction Periods ◽  
Slow Combustion ◽  
Benzene Toluene ◽  
Chain Theory ◽  
Characteristic Features ◽  
A Chain ◽  
Kinetics Of

Recent work upon the kinetics of the oxidation of aliphatic hydrocarbons has led to the recognition of certain characteristic features that find a ready interpretation in terms of the chain theory of chemical reaction. Thus, for example, both paraffins and olefines exhibit well-defined induction periods, pressure limits of inflammability and a marked sensitivity to the influence of surface, that point directly to the intervention of reaction chains; and although the precise nature of the chain mechanisms is somewhat uncertain a great deal of information is available as to their length, branching characteristics, mutual interactions and stability. Corresponding data for alicyclic and aromatic compounds are, however, very scanty and only in one instance has a comprehensive systematic kinetic study been made. Fort and Hinshelwood (1930) and Amiel (1933 a, b , 1936) have investigated the slow combustion of benzene and find that whilst it shows a general resemblance to ethylene there are certain respects in which significant differences occur. Fort and Hinshelwood concluded that benzene is oxidized by a chain mechanism, the chains initiated predominantly in the gaseous phase being of short continuation.

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