scholarly journals The kinetics of the oxidation of copper. Part II. -The limiting pressure. Evidence for the lateral diffusion of adsorbed gas

1930 ◽  
Vol 128 (808) ◽  
pp. 407-417 ◽  
Keyword(s):  
Lateral Diffusion ◽  
Adsorbed Gas ◽  
A Value ◽  
Kinetics Of ◽  
Limiting Pressure

The influence of the pressure of oxygen on the rate of oxidation of copper has been studied by earlier workers. Pilling and Bedworth working at 800°C. found that the rate of oxidation continued constant as the pressure was decreased until the pressure reached 0·3 mm. Berger found a limiting pressure of 100 mm. Hinshelwood’s work makes it clear that for activated copper at 305°C. the limiting pressure is greater than 5 mm. Palmer obtained a value of about 300 mm. The object of this work was to investigate more closely the significance of the limiting pressure.

scholarly journals AKTIVITAS INULINASE OLEH Pichia manshurica DAN FUSAN F4 PADA FERMENTASI BATCH DENGAN UMBI DAHLIA (Dahlia sp) SEBAGAI SUBSTRAT

REAKTOR ◽  
2015 ◽  
Vol 14 (3) ◽  
pp. 187 ◽  
Author(s):  
Wijanarka Wijanarka ◽  
Endang Sutariningsih Soetarto ◽  
Kumala Dewi ◽  
Ari Indrianto
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Lag Phase ◽  
Growth Media ◽  
A Value ◽  
Inulinase Activity ◽  
Pichia Manshurica ◽  
Microbial Strains ◽  
Kinetics Of

ACTIVITY OF INULINASE OF Pichia Manshuria AND FUSAN F4 ON BATCH FERMENTATION UDING DAHLIA TUBER (Dahlia sp) AS A SUBSTRATE. A dahlia tuber is one of the common inulin rich crops. Inulin is formed by units of fructans, which are polymers of D-fructose. Inulinases (EC 3.2.1.7) catalyze the hydrolysis of inulin, producing fructooligosaccharides (FOS), inulooligosaccharides (IOS), pulullan, acetone, butanol and sorbitol, therefore dahlia tubers are used as growth media. The inulin hydrolyzing activity has been reported from various microbial strains Pichia manshurica and Fusan F4 which is the result of fusion protoplast. The objective of this study was to determine the activity of inulinase Pichia manshurica and Fusan F4 on the substrate dahlia tubers. Fusan F4 to increase inulinase activity compared with Pichia manshurica and to investigate the kinetics of specific growth rate (μ) and time double (g) from of Pichia manshurica and Fusan F4. The results showed that the exponential phase occurs at 0-12 hour without a lag phase. P. manshurica has a specific growth rate (μ) of 0.18/hour with time double (g) 3.90 hours and the inulinase enzyme activity of 0.56 IU, while for Fusan F4 consecutive has a value μ of 0.20/hour, g of 3.49 hours and the activity of 0.69 IU. The conclusion of this research is to improve Fusan F4 inulinase activity and the ability has to be better than the Pichia manshurica.Umbi dahlia merupakan salah satu umbi yang mengandung inulin. Inulin merupakan polimer fruktan yang dapat dipecah oleh enzim inulinase (E.C. 3.2.1.7) menjadi fruktosa. Fruktosa merupakan bahan baku dasar untuk pembuatan FOS, IOS, pulullan, aseton dan sorbitol, oleh karena itu umbi dahlia digunakan sebagai media pertumbuhan. Enzim inulinase ini secara indigenous dimiliki oleh Pichia manshurica dan Fusan F4 yang merupakan hasil fusi protoplas.Tujuan  penelitian ini adalah  untuk mengetahui aktivitas inulinase Pichia manshurica dan Fusan F4 pada substrat umbi dahlia, Fusan F4 mampu meningkatkan aktivitas inulinase dibandingkan dengan Pichia manshurica serta untuk mengetahui kinetika kecepatan pertumbuhan specifik (µ) dan waktu generasi (g) Pichia manshurica dan Fusan F4. Hasil penelitian menunjukkan bahwa fase  eksponensial terjadi pada jam ke-0 sampai jam ke-12 tanpa diikuti fase lag, Pichia manshurica mempunyai kecepatan pertumbuhan specific (µ)  sebesar 0,18/jam dengan waktu generasi (g) 3,90 jam dan aktivitas enzim inulinase yang dihasilkan sebesar 0,56 IU, sedangkan untuk fusan F4 secara berturut-turut mempunyai nilai µ sebesar 0,20/jam, g sebesar 3,49 jam dan aktivitas sebesar 0,69 IU. Kesimpulan dari penelitian ini adalah Fusan F4 mampu meningkatkan aktivitas inulinase dan mempunyai kemampuan lebih baik dibanding dengan Pichia manshurica.

Kinetics of the hydrolysis of cellobiose and p-nitrophenyl-β-D-glucoside by cellobiase of Trichoderma viride

1977 ◽  
Vol 55 (1) ◽  
pp. 19-26 ◽  
Author(s):  
R. James Maguire
Keyword(s):  
Steady State ◽  
Trichoderma Viride ◽  
Solution Temperature ◽  
Temperature Range ◽  
A Value ◽  
Steady State Kinetics ◽  
Decreasing Ph ◽  
Ph Curve ◽  
Kinetics Of ◽  
Hydrolysis Of

Cellobiase has been isolated from the crude cellulase mixture of enzymes of Trichoderma viride using column chromatographic and ion-exchange methods. The steady-state kinetics of the hydrolysis of cellobiose have been investigated as a function of cellobiose and glucose concentrations, pH of the solution, temperature, and dielectric constant, using isopropanol–buffer mixtures. The results show that (i) there is a marked activation of the reaction by initial glucose concentrations of 4 × 10−3 M to 9 × 10−2 M and strong inhibition of the reaction at higher initial concentrations, (ii) the log rate – pH curve has a maximum at pH 5.2 and enzyme pK values of 3.5 and 6.8, (iii) the energy of activation at pH 5.1 is 10.2 kcal mol−1 over the temperature range 5–56 °C, and (iv) the rate decreases from 0 to 20% (v/v) isopropanol.The hydrolysis by cellobiase (EC 3.2.1.21) of p-nitrophenyl-β-D-glucoside was examined by pre-steady-state methods in which [Formula: see text], and by steady-state methods as a function of pH and temperature. The results show (i) a value for k2 of 21 s−1 at pH 7.0 (where k2 is the rate constant for the second step in the assumed two-intermediate mechanism [Formula: see text]) (ii) a log rate–pH curve, significantly different from that for hydrolysis of cellobiose, in which the rate increases with decreasing pH below pH 4.5, is constant in the region pH 4.5–6, and decreases above pH 6 (exhibiting an enzyme pK value of 7.3), and (iii) an activation energy of 12.5 kcal mol−1 at pH 5.7 over the temperature range 10–60 °C.

scholarly journals Kinetics of ADP-induced human platelet shape change: apparent positive cooperativity

1980 ◽  
Vol 58 (1) ◽  
pp. 45-52 ◽  
Author(s):  
John G. Milton ◽  
W. Yung ◽  
C. Glushak ◽  
M. M. Frojmovic
Keyword(s):  
Light Transmission ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Hill Coefficient ◽  
A Value ◽  
The Hill ◽  
Kinetics Of ◽  
Type Response ◽  
Platelet Shape

The kinetics of ADP-induced human platelet shape change have been examined. Initial velocities of platelet shape change were estimated by two methods: (1) the slope of the initial decrease in light transmission through stirred, citrated platelet-rich plasma, and (2) direct examination of platelet morphologies by phase-contrast microscopy. In both cases, a value of the Hill coefficient, NH, significantly greater than 1 is obtained (2.0 ± 0.2 and 1.8 ± 0.2, respectively). The observed elevated value of NH is not due to a substantial fraction of the ADP being platelet bound, the presence of factors in the plasma, platelet heterogeneity, or the influence of the rate of platelet shape change reversion. Our observations suggest that ADP-induced platelet shape change may be a positively cooperative or "threshold" type response.

Substituent Effects in Electron Transfer Reactions: The Preparation and Chromium(II) Reduction of 3-Formylpentane-2,4-dionatobis(ethylenediamine)cobalt(III). Preparation of the Linkage Isomer 2-Acetylbutane-1,3-dionatobis(ethylenediamine)cobalt(III)

1975 ◽  
Vol 53 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Robert J. Balahura ◽  
N. A. Lewis
Keyword(s):  
Electron Transfer ◽  
Acidic Solution ◽  
Substituent Effects ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Linkage Isomers ◽  
A Value ◽  
Parent Complex ◽  
Kinetics Of ◽  
Sphere Mechanism

The preparation of the linkage isomers, 3-formylpentane-2,4-dionatobis(ethylenediamine)cobalt(III), (1), and 2-acetylbutane-1,3-dionatobis(ethylenediamine)cobalt(III), (2), are described. The kinetics of the reaction of Cr(OH2)62+ with 1 and the parent complex, 2,4-pentanedionatobis(ethylenediamine)cobalt(III), (3), have been studied spectrophotometrically in acidic solution. For 1, the reduction is described by the rate law −d ln [Co(III)complex]/dt = k[Cr2+], and k = 0.0863 M−1 s−1 at 25 °C, μ = 1.0 M (LiClO4). The activation parameters for this reaction were found to be ΔH≠ = 9.9 ± 0.5 kcal mol−1 and ΔS≠ = −30 ± 3 e.u. The reaction proceeded by an inner-sphere mechanism and the product of this reaction was isolated and characterized as 2-acetylbutane-1,3-dionatotetraaquochromium(III). The linkage isomer of this complex was also prepared. The parent complex (3) was not reduced by Cr(OH2)62+ at an observable rate and an upper limit for the rate constant of this reaction was assigned a value of 10−4–10−6M−1s−1 at 25 °C. The ability of the formyl group to enhance the rate of electron transfer is discussed, and the chromium(II) reduction studies of related chelated systems are compared with the results obtained in this investigation.

Mass transfer and kinetics of the chemical vapor deposition of SiC onto fibers

1998 ◽  
Vol 13 (8) ◽  
pp. 2251-2261 ◽  
Author(s):  
W. Jack Lackey ◽  
Sundar Vaidyaraman ◽  
Bruce N. Beckloff ◽  
Thomas S. Moss III ◽  
John S. Lewis
Keyword(s):  
Mass Transfer ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Atmospheric Pressure ◽  
Chemical Vapor ◽  
Total Flow ◽  
A Value ◽  
Factor Expression ◽  
Kinetics Of ◽  
Best Fit

An internally consistent set of data was generated for the chemical vapor deposition (CVD) of SiC from methyltrichlorosilane (MTS) and H2 at atmospheric pressure. A moving fiber tow was used as the substrate. Coating rates between 0.3 and 3.7 µm/min and deposition efficiencies between 24 and 48% were obtained for MTS and H2 flow rates in the range 30 to 200 cm3/min and 300 to 2000 cm3/min, respectively. The data were analyzed and found to be best fit under a mass transfer regime. Based on this fit, a value of the constant in the Chilton–Colburn j factor expression for a moving fiber tow was estimated to be 2.74 × 10−6 with a standard deviation of 3.2 × 10−7. The efficiency of the reaction was found to decrease with increases in the total flow rate, indicating that the effect of the decreased residence time of reagents in the reactor was larger than the increase in the mass transfer coefficient. Finally, a comparison between the efficiencies for a stationary and a moving tow revealed that the moving tow had a higher efficiency, possibly due to a disruption of the boundary layer by the tow motion or due to the decrease in the canning of the moving tow.

Lateral Diffusion Spreading of Two Competitive Intermetallic Phases over Free Surface

2008 ◽  
Vol 277 ◽  
pp. 9-20 ◽  
Author(s):  
Yuri S. Kaganovsky ◽  
Lyudmila N. Paritskaya ◽  
V.V. Bogdanov
Keyword(s):  
Kinetic Equations ◽  
Lateral Diffusion ◽  
Steady State Solution ◽  
Lateral Spreading ◽  
Intermetallic Phases ◽  
Dynamic Surface ◽  
Phase Layers ◽  
Intermetallic Growth Kinetics ◽  
Two Phases ◽  
Kinetics Of

The kinetics of growth and lateral spreading of intermetallic layers during surface interdiffusion in Cu – Sn system has been studied in a temperature range 160 – 200oC by the methods of optical microscopy, SEM provided with X-ray microprobe, and AFM. Lateral phase spreading over the surface is characterized by competition between two phases: Cu6Sn5 and Cu3Sn. A steady state solution for concentration distribution on the surface of growing intermetallic phases, as well as kinetic equations of lateral spreading of growing phase layers have been obtained. By comparison of experimental data on intermetallic growth kinetics with the proposed theory, the dynamic surface diffusion coefficients have been calculated.

Silicon Transport in Lateral Silicide Growth of CrSi2

1986 ◽  
Vol 71 ◽  
Author(s):  
L. R. Zheng ◽  
L. R. Doolittle ◽  
J. W. Mayer
Keyword(s):  
Growth Kinetics ◽  
Lateral Diffusion ◽  
Diffusion Couples ◽  
Si Substrates ◽  
Impurity Segregation ◽  
Silicide Growth ◽  
Device Geometry ◽  
Metal Layers ◽  
Kinetics Of ◽  
Influence Of Impurities

AbstractSilicide formation and growth are studied in three geometries: conventional planar thin films, lateral diffusion couples formed by depositing metal layers on Si islands, and device geometry couples formed by depositing metal on oxide-patterned Si substrates. The influence of impurities is studied by implanting arsenic and krypton into conventional and device geometry structures.Here we present growth kinetics of CrSi2 where the presence of impurities has a strong influence. Si transport dominates in disilicide formation and leads to erosion of contacts around the periphery of oxide windows. Implantation of arsenic suppresses CrSi 2 formation; with krypton implantation, the growth kinetics shifts from linear to square-root in character. We attribute these results to impurity segregation at interfaces or grain boundaries.

scholarly journals The kinetics of mutarotation in solution

1940 ◽  
Vol 176 (966) ◽  
pp. 352-367 ◽  
Keyword(s):  
Aqueous Solution ◽  
Room Temperature ◽  
Reducing Sugars ◽  
Arrhenius Equation ◽  
Energy Of Activation ◽  
A Value ◽  
Temperature Ranges ◽  
Velocity Coefficient ◽  
Kinetics Of ◽  
True Energy

The kinetics of the mutarotation of representative reducing sugars from the pentose, hexose and disaccharide series have been investigated polarimetrically over wide temperature ranges in aqueous solution. The dependence of the velocity coefficient, k , upon temperature is fairly well reproduced by an equation of the form ln k = C + ( J/R ) ln T - E/RT . The true energy of activation, E , is found to be some 6000 calories greater than the apparent value afforded by the Arrhenius equation at room temperature. J/R has a value of — 10, which is identified as the number of oscillators contributing to the activation. The constants C, J and E of this equation are discussed, with reference to many reactions, in terms of a theory of unimolecular reactions in solution.

A Theoretical and Experimental Investigation of the Kinetics of Ring Closure of the 3-Methyl-3-azahex-5-enyl Radical

1995 ◽  
Vol 48 (12) ◽  
pp. 2047 ◽  
Author(s):  
EW Della ◽  
AM Knill
Keyword(s):  
Activation Energy ◽  
Experimental Investigation ◽  
Force Field ◽  
Activation Barrier ◽  
Ring Closure ◽  
Force Field Calculations ◽  
Arrhenius Parameters ◽  
A Value ◽  
Kinetics Of

Evaluation of the Arrhenius parameters for ring closure of the 3-methyl-3-azahex-5-enyl radical is reported. Cyclization of the radical is found to occur with high regioselectivity giving the exo -trig product exclusively with an activation energy of 22 kJ mol-1 and log A value of 11.1. The experimental activation barrier compares favourably with that determined by force field calculations which predict a value of 21 kJ mol-1. The 3-methyl-3-azahex-5-enyl radical is therefore found to undergo ring closure some 70 times faster than the parent hex-5-enyl radical, in accord with predictions based upon geometrical considerations.

The kinetics of polysulphone formation - I. The formation of 1-butene polysulphone at 25° C

1952 ◽  
Vol 212 (1108) ◽  
pp. 96-112 ◽  
Keyword(s):  
Sulphur Dioxide ◽  
Primary Process ◽  
Propagation Process ◽  
A Value ◽  
Absorption Of Light ◽  
Rate Of Reaction ◽  
Liquid Sulphur ◽  
Rate Of Absorption ◽  
Photochemical Initiation ◽  
Kinetics Of

The formation of 1-butene polysulphone from mixtures of liquid sulphur dioxide and 1-butene has been investigated dilatometrically at 25° C. Photochemical and silver nitrate initiation have been used, most of the work being carried out in mixtures containing an excess of sulphur dioxide. There is a discrepancy, in the case of photochemical initiation, between the molecular weight as estimated from the intrinsic viscosity of the polymer, and that deter­mined from the rate of reaction and rate of absorption of light. This discrepancy is ascribed to an inefficient primary process. The variation of rate with initiator, monomer and retarder concentrations has been investigated. The initiator exponent has a value intermediate between 0.5 and 1.0, indicating the occurrence of at least two termination processes. Kinetic expressions have been deduced for various possible termination mechanisms, and. in order to obtain agreement with experiment it is necessary to assume that the propagation process involves the addition to the growing chain of a 1:1 molecular complex of 1-butene and sulphur dioxide.

Sign in / Sign up

Export Citation Format

Share Document