摘要:

AbstractTechnetium‐aspirin and technetium‐aspirin‐like molecule complexes were prepared. The structure ofN‐acetylanthranilic acid (NAA) has been decided through CNDO calculations. The ionization potential and electron affinity of the NAA molecule as well as the charge densities were calculated. Comparative studies of the electronic absorption spectra of acetylthiosalicylic acid (ATS) and aspirin (Asp) reveal the structure resemblance in which the acetyl carbonyl group is perpendicular to the plane of the corresponding organic acid. The studies of the electronic absorption spectra of NAA and anthranilic acid reveal the planarity of the NAA molecule. The electronic absorption spectra of Tc(V)‐Asp and Tc(V)‐ATS complexes have two characteristic absorption bands at 450 and 600 nm, but the Tc(V)‐NAA spectrum has one characteristic band at 450 nm. As a comparative study, Mo‐ATS complex was prepared and its electronic absorption spectrum is comparable with the Tc‐ATS

ISSN:0268-2575    

DOI:10.1002/jctb.280560302

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractMass transfer plays an important role in solid state fermentation (SSF) systems. Earlier work on SSF in tray bioreactors7indicated that steep gaseous concentration gradients developed within the substrate bed, owing to mass transfer resistances, which may adversely affect the bioreactor performance. For all practical purposes these gradients have been eliminated using a packed bed column bioreactor with forced aeration. Gaseous concentrations (oxygen and carbon dioxide) and enzyme activities were measured at various bed heights for various air flow rates during the course of fermentation. The results indicated that concentration gradients were decreased effectively by increasing air flow rate. For example, the actual oxygen and carbon dioxide concentration gradients reduced from 0.07% (v/v) cm−1and 0.023% (v/v) cm−1to 0.007% (v/v) cm−1and 0.0032% (v/v) cm−1respectively when the air flow rate was increased from 5 dm3min−1to 25 dm3min−1. This resulted in an overall improvement in the performance of the bioreactor in terms of enzyme

ISSN:0268-2575    

DOI:10.1002/jctb.280560303

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe preparation of magnesia has been investigated with the object of preparing a catalyst support material that maintained high surface area after heating to high temperatures. The effect of precipitation, ageing, washing, drying and calcining on the surface area and porosity of magnesia has been studied. It was found possible to produce stable magnesia by washing with methanol or acetone, but the surface area was low for most catalytic applications.

ISSN:0268-2575    

DOI:10.1002/jctb.280560304

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractEthanol—oleic acid esterification by a free and microencapsulated lipase fromMucor miehei, using dodecane as solvent and phosphatidylcholine as surfactant, was studied.The initial esterification rate was influenced by the water content in the biphasic system. Kinetic studies with free and microencapsulated enzyme showed that the microencapsulation led to an increase of the kinetic parameters (VmaxandKm), probably due to an increase of the interfacial area. The reaction rate was also affected by the shaking rate, the temperature and the pH. The optimal temperature and pH achieved were, respectively, 40°C and 4.5 using free enzyme, and 50°C and 6 using microencapsulated enz

ISSN:0268-2575    

DOI:10.1002/jctb.280560305

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the case of submerged multijets impinging on to a flat surface, the limiting current densities were measured at microelectrodes, fixed flush with the target surface using diffusion controlled electrode reactions (i.e. reduction of ferricyanide ion). The height of the multijet distributor from the target surface (Y) was varied from 5 to 9 cm. The numbers of holes of the distributor (N) studied were 76 and 141. The variation of mass transfer data with radial distance reveals the existence of two different regions, i.e. the impingement region and the wall jet region. The mass transfer rate increased with increase inYin the impingement region. The effect ofYis negligible in the wall jet region. Decrease inNdecreases the mass transfer rate in both the regions. The data are correlated separately for the two regions.

ISSN:0268-2575    

DOI:10.1002/jctb.280560306

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractLactococci were encapsulated within gelatin membranes cross‐linked with toluene‐2,4‐diisocyanate at an oil/water interface. Reagent toxicity was avoided by use of vegetable or silicone oil as a dispersant, and by minimizing cell exposure to the water insoluble cross‐linking agent during membrane formulation. Growth of cells within the gelatin microcapsules was observed during fermentation and acidification activity of the encapsulated cells increased with subsequent reuse. A microencapsulated cell density of 109cfu cm−3resulted in acidification of milk to pH 5.5 within 2.8 h, similar to that achieved in free cell ferm

ISSN:0268-2575    

DOI:10.1002/jctb.280560307

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractButyraldehyde is an important chemical for many industrial applications, especially in the production of polyvinylbutyral. A systematic study of its synthesis by catalytic dehydrogenation of butanol, using zinc oxide as catalyst has been carried out. The effect of the method of preparation of zinc oxide on its catalytic activity for the title reaction has also been studied. The optimum conditions for maximum yield have been worked out and on the basis of secondary electron micrograms the reasons for higher activity/selectivity in the case of zinc oxide calcined from zinc hydroxide is attributed to the presence of hexagonal morphology. A kinetic study for the best zinc oxide catalyst has been carried out and the rate equation has been determined.

ISSN:0268-2575    

DOI:10.1002/jctb.280560308

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe carbonization of CaS in water suspension was studied. The process takes place under diffusion control. The complicated process mechanism causes the appearance of a compensation effect. By increasing the carbon dioxide partial pressure, the probability of interaction is raised, which leads to the increase of the pre‐exponential factor. When the chemical reaction is faster then less porous CaCO3is deposited and as a result the apparent activation energy is increase

ISSN:0268-2575    

DOI:10.1002/jctb.280560309

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractA mathematical model was developed for affinity biosensors where the detection principle is based on competitive displacement of a protein from an immobilized ligand. Two competing binding reactions between analyte and protein molecules in the bulk liquid phase, and immobilized ligand and protein molecules in the solid phase, were assumed to be in equilibrium. Theoretical calibration curves relating the signal generated, which is the total protein concentration detected in the bulk liquid phase, to the analyte concentration were calculated from this model. The simulated results indicated several important variables to consider when constructing the biosensor. The amount of responsive protein and immobilized ligand initially loaded and the relative binding strength of both the analyte and the ligand toward the protein will influence the biosensor's performance. Experiments have been carried out to verify this model, using bovine rennin as the protein, pepstatin‐agarose as the immobilized ligand, and pepstatin as the analyte. The experimental data agreed reasonably well with the simulated results from the model. This mathematical model seemed to be sufficient for describing the behavior of affinity biosensors based on competitive displacement and suitable for design purpose

ISSN:0268-2575    

DOI:10.1002/jctb.280560310

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe distance‐based topological indices and connectivity indices were computed for various homologues of hydroxyoximes and correlated with the partition data and the rate of copper extraction from acidic sulphate solutions. The distance‐based topological indices are more sensitive to the structural changes in extractant molecule than the connectivity indi

ISSN:0268-2575    

DOI:10.1002/jctb.280560311

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY