Active Sites and Carbon Gasification Kinetics: Theoretical Treatment and Experimental Results

Extracts from plant materials have great potential as alternatives to inorganic corrosion inhibitors, which typically have harmful consequences. Experimental and theoretical methodologies studied the effectiveness of agricultural waste, namely, date palm seed extract as a green anti-corrosive agent in 0.5 M hydrochloric acid. Experimental results showed that immersion time and temperature are closely related to the effectivity of date palm seed as a corrosion inhibitor. The inhibition efficiency reduced from 95% to 91% at 1400 ppm when the immersion time was increased from 72 h to 168 h. The experimental results also indicated that the inhibition efficiency decreased as the temperature increased. The presence of a protective layer of organic matter was corroborated by scanning electron microscopy. The adsorption studies indicated that date palm seed obeyed Langmuir adsorption isotherm on the carbon steel surface, and Gibbs free energy values were in the range of −33.45 to −38.41 kJ·mol−1. These results suggested that the date palm seed molecules interacted with the carbon steel surface through mixture adsorption. Theoretical calculations using density functional theory showed that the capability to donate and accept electrons between the alloy surface and the date palm seed inhibitor molecules is critical for adsorption effectiveness. The HOMO and LUMO result indicated that the carboxyl (COOH) group and C=C bond were the most active sites for the electron donation-acceptance type of interaction and most auxiliary to the adsorption process over the Fe surface.

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On the catalytic dehydrogenation of naphthenes II. Competition experiments and energies of C-H bonds

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1947.0078 ◽

1947 ◽

Vol 190 (1022) ◽

pp. 309-328 ◽

Cited By ~ 2

Keyword(s):

Activation Energy ◽

Active Sites ◽

Catalyst Surface ◽

Resonance Energy ◽

Activation Energies ◽

Theoretical Treatment ◽

Catalytic Dehydrogenation ◽

Simple Relationship ◽

Hydrogen Atoms ◽

Methyl Cyclohexane

The rates of dehydrogenation in competition experiments using mixtures of two naphthenes, or a naphthene and a cyclic mono-olefine or two cyclic mono-olefines, have been examined theoretically and experimentally for the stationary state conditions. Provided the two reactants can occupy the same sites on the catalyst surface, then the ratio of the rates should be directly proportional to the ratio of the partial pressures at any instant. Theory suggests that a constant which can be derived from these competition experiments should be independent of the overall pressures, or of the initial ratio of concentrations or of the overall extent of dehydrogenation. Further, the ratio of the rates in competition should bear no simple relationship to the ratio of the individual rates alone, but should be related to the slopes of the 1/rate against 1/pressure plot for the two components considered separately. Moreover, the constant should be a ratio of two functions each of which is characteristic of one of the naphthenes. The theoretical conclusions have been confirmed experimentally which proves either that the groups of active sites on the catalyst surface are widely separated or that any set of sites is available for the reaction of any molecular species, and no interference takes place between naphthene molecules adsorbed on adjacent sites. Proof that a naphthene and cyclohexene are dehydrogenated on the same sites is supplied by the observation that a constant is obtained when different mixtures of cyclohexene and trans -1:4-dimethyl cyclohexane are allowed to compete for the surface. The ratios for methyl, ethyl, the three dimethyl and the three trimethyl cyclohexanes in competition with cyclohexane have been accurately determined at temperatures of 400 and 450° C. From the constants so derived the activation energy differences for the removal of the first pair of hydrogen atoms has been obtained. These values are discussed in terms of the possible transition complexes, and it is shown that the reaction proceeds by the loss of a pair of hydrogen atoms simultaneously and not by a half-hydrogenated state mechanism. Using these activation energies and the experimentally found overall activation energy of 36 kcal./g. mol., the resonance energy per resonating structure was determined as 1-73 kcal. This is in good agreement with the energies of C-H bonds in alkyl radicals (2-2 kcal./g.mol./ resonating structure). The theoretical treatment suggests that the weakest C-H link in methyl cyclohexane should be in the three position to the methyl group. A study of the activation energies involved shows that the methyl cyclohexene produced from methyl cyclohexane is not 1-methyl-1-cyclohexene, thus confirming the theoretical deduction.

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The Mechanics of Flash in Drop Forging-Temperature and Speed Effects

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1976_190_048_02 ◽

1976 ◽

Vol 190 (1) ◽

pp. 457-466 ◽

Cited By ~ 1

Author(s):

T. A. Dean

Keyword(s):

Metal Flow ◽

Experimental Results ◽

Theoretical Treatment ◽

Axisymmetric Cavity ◽

Die Filling ◽

Drop Forging

SYNOPSIS Forging tests have been made using axisymmetric cavity dies with various flash geometries. For a particular flash geometry greater ‘rise’ was obtained with thinner flash. Also greater rise was obtained on a hammer than on a press, the load requirements being greater on the higher speed machine. Modes of metal flow were similar at all preheat temperatures. Theoretical treatment of the later stages of die filling, considering metal flow to be significant only in the region of the flash land, is able to describe the main features of the experimental results.

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SEQUENCE-BASED PREDICTION OF PROTEIN B-FACTORS WITH DUAL SUPERVIZED LEARNING MODELS

Biomedical Engineering Applications Basis and Communications ◽

10.4015/s1016237210002146 ◽

2010 ◽

Vol 22 (05) ◽

pp. 385-391

Author(s):

Yu-Cheng Liu ◽

Shien-Ching Hwang ◽

Yu-Feng Huang ◽

Win-Li Lin ◽

Yen-Jen Oyang ◽

...

Keyword(s):

Correlation Coefficient ◽

Prediction Accuracy ◽

Active Sites ◽

Pearson Correlation ◽

Experimental Results ◽

Structural Flexibility ◽

Dual Model ◽

Functional Sites ◽

High Degree ◽

Model Approach

The B-factor, which is also known as temperature factor or Debby–Waller factor, is an important structural flexibility index of the ground-state protein conformation. In particular, the B-factors associated with a segment of residues, reflect the local flexibility of the corresponding protein tertiary substructure. Recent studies have shown that, for certain families of proteins, there exists a high-degree of correlation between the B-factors and the protein functional sites, including antigenic regions, enzyme active sites, and nucleotide binding sites. This paper presents a sequence–based predictor of B-factors with a dual-model approach. The design of the dual-model approach has been aimed at exploiting the bi-modal distribution of B-factors in order to achieve higher prediction accuracy. In this paper, the prediction accuracy is measured by Pearson correlation coefficient. Experimental results show that the dual-model predictor proposed in this article is capable of delivering superior correlation coefficient in comparison with two predictors reported in two latest papers. Though experimental results show that the dual-model proposed in this paper really works more effectively than the conventional approach, it is of interest to continue investigating more advanced designs since there exists a strong correlation between B-factors and protein functional sites. In this respect, identifying additional physiochemical properties that are related to structural flexibility deserves a high-degree of attention.

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Re-evaluation of the glycerol-3-phosphate dehydrogenase/l-lactate dehydrogenase enzyme system. Evidence against the direct transfer of NADH between active sites

Biochemical Journal ◽

10.1042/bj2780875 ◽

1991 ◽

Vol 278 (3) ◽

pp. 875-881 ◽

Cited By ~ 6

Author(s):

S P J Brooks ◽

K B Storey

Keyword(s):

Lactate Dehydrogenase ◽

Active Sites ◽

Reaction Rate ◽

Experimental Results ◽

Transfer Model ◽

Rabbit Muscle ◽

Direct Transfer ◽

Theoretical Predictions ◽

Glycerol 3 Phosphate Dehydrogenase

An investigation of the direct transfer of metabolites from rabbit muscle L-lactate dehydrogenase (LDH, EC 1.1.1.27) to glycerol-3-phosphate dehydrogenase (GPDH, EC 1.1.1.8) revealed discrepancies between theoretical predictions and experimental results. Measurements of the GPDH reaction rate at a fixed NADH concentration and in the presence of increasing LDH concentrations gave experimental results similar to those previously obtained by Srivastava, Smolen, Betts, Fukushima, Spivey & Bernhard [(1989) Proc. Natl. Acad. Sci. U.S.A. 86, 6464-6468]. However, a mathematical solution of the direct-transfer-mechanism equations as described by Srivastava et al. (1989) showed that the direct-transfer model did not adequately describe the experimental behaviour of the reaction rate at increasing LDH concentrations. In addition, experiments designed to measure the formation of an LDH4.NADH.GPDH2 complex, predicted by the direct-transfer model, indicated that no significant formation of tertiary complex occurred. An examination of other kinetic models, developed to describe the LDH/GPDH/NADH system better, revealed that the experimental results may be best explained by assuming that free NADH, and not E1.NADH, is the sole substrate for GPDH. These results suggest that direct transfer of NADH between rabbit muscle LDH and GPDH does not occur in vitro.

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Condensation Phenomena in High Speed Flow of Steam—Experimental Apparatus

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1973_187_013_02 ◽

1973 ◽

Vol 187 (1) ◽

pp. 199-205 ◽

Cited By ~ 1

Author(s):

B. A. Campbell ◽

F. Bakhtar

Keyword(s):

Cross Section ◽

Test Section ◽

High Speed ◽

Rectangular Cross Section ◽

Experimental Results ◽

Theoretical Treatment ◽

Wet Steam ◽

High Speed Flow ◽

Speed Flow ◽

Experimental Apparatus

The paper describes a steam circuit for studies of nucleation and behaviour of wet steam. The test section is a duct of rectangular cross-section in which particular geometries are produced by fitting shaped profiles to its sides. To deliver steam to the test section, at required conditions, a turbine, cooler and superheater are included in the circuit. The experimental results presented are concerned with the variations of Wilson point as a function of pressure. Comparisons are made with the results of a theoretical treatment already published (1)‡ and agreement is shown to be good.

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The flow of thin liquid films between rollers

Journal of Fluid Mechanics ◽

10.1017/s0022112061000846 ◽

1961 ◽

Vol 11 (1) ◽

pp. 33-50 ◽

Cited By ~ 109

Author(s):

E. Pitts ◽

J. Greiller

Keyword(s):

Flow Regime ◽

Liquid Films ◽

Thin Liquid Films ◽

Experimental Results ◽

Critical Conditions ◽

Theoretical Treatment ◽

Uniform Thickness ◽

Full Agreement ◽

Low Speeds

When rollers, placed horizontally and side by side so that each is half immersed in a tank of liquid, rotate in opposite directions, liquid is carried through the gap between them and divides to form a sheet over each roller. At low speeds the sheets are of uniform thickness across the width of the rollers, but at higher speeds they are regularly ridged owing to alternate increase and decrease in thickness. Preliminary observations led to the development of an approximate theoretical treatment of the even-flow régime and the critical conditions when the ribbed flow is about to begin. Results of this work are in full agreement with detailed experimental results.

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Saccharification Kinetics at Optimised Conditions of Tapioca by Glucoamylase Immobilised on Mesostructured Cellular Foam Silica

Eurasian Chemico-Technological Journal ◽

10.18321/ectj764 ◽

2018 ◽

pp. 311

Author(s):

J. Agustian ◽

L. Hermida

Keyword(s):

Design Of Experiment ◽

Active Sites ◽

Large Scale ◽

Chemical Compounds ◽

Quadratic Polynomial ◽

Experimental Results ◽

Kinetic Constants ◽

Box Behnken Design ◽

Dextrose Equivalent ◽

Good Agreement

As insoluble substrates such as tapioca can be used to make chemical compounds, saccharification of tapioca by glucoamylase immobilised on mesostructured cellular foam (MCF) silica using Box-Behnken Design of experiment was conducted to optimize this process so that the experimental results can be used to develop large-scale operations. The experiments gave dextrose equivalent (DE) values of 6.15–69.50% (w/w). Factors of pH and temperature affected the process highly. The suggested quadratic polynomial model is significant and considered acceptable (R2 = 99.78%). Justification of the model confirms its validity and adequacy where the predicted DE shows a good agreement with the experimental results. The kinetic constants (Vmax, KM) produced by the immobilised enzyme differed highly from the values yielded by free glucoamylase indicating reduction of substrate access to enzyme active sites had occurred.

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