摘要:

AbstractMetals and organic contaminants, present in the water‐column, sediment or food, are readily accumulated by aquatic organisms. Exposure to and toxic effects of contaminants can be measured in terms of the biochemical responses of the organisms—so‐called molecular biomarkers. The applications, advantages and limitations of such diagnostic and prognostic tests are discussed. The hepatic biotransformation enzyme cytochrome P4501A in fish and other vertebrates is specifically induced by organic contaminants such as aromatic hydrocarbons, PCBs and dioxins, and is used as a biomarker of exposure to organic pollution. Its induction is involved in chemical carcinogenesis via catalysis of the covalent binding of organic contaminants to DNA (DNA‐adducts). P4501A‐induction, measured as enzyme activity, enzyme amount, or mRNA, has been successively used in many field studies, involving some 27 fish species, in USA and Europe. Metallothioneins (MTs) bind and are specifically induced by metals such as Cd, Hg, Ag and Cu, and are used in both vertebrates and invertebrates as a biomarker for metal exposure. Bulky, hydrophobic DNA‐adducts are used as a biomarker for organic contaminant damage. MTs (measured at protein and mRNA levels) and DNA‐adducts (32P‐postlabelling method) have been applied less extensively in the field than P4501A, but the results are similarly encouraging. Biomarkers should be used as part of an integrated programme of pollution monitoring, involving also general measurements of biological damage and animal health, and analysis of chemical contaminants in the biota and environment. Commercial availability of antibodies and mRNA probes will accelerate the widespread application of these molec

ISSN:0268-2575    

DOI:10.1002/jctb.280570302

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe bleaching process at 90°C of an olive oil from Jaen (Spain) using natural bentonite and bentonite acid treated with H2SO4(over a concentration range between 0.50 M and 5.00 M) has been studied. The bleaching capacities of the bentonite samples were calculated by applying the Freundlich equation to the experimental data points corresponding to the bleaching process. The bleaching capacities (KFparameter) range from 2.5 × 10−7for non‐treated bentonite up to 0.85 for 2.50 M H2SO4treated bentonite. The bleaching capacity of the 5.00 M H2SO4treated bentonite (KF= 0.81) is less than that of the 2.50 M H2SO4treated bent

ISSN:0268-2575    

DOI:10.1002/jctb.280570303

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractBased on the kinetics of benzene hydrogenation, pore diffusion and catalyst deactivation, time‐dependent effectiveness behaviour of a single NiSiO2Al2O3catalyst pellet where the chemical reaction rate is determined by pore diffusion was simulated for different conditions of operation.Poisoning kinetics were measured in a series of differential reactor experiments at atmospheric total pressure at temperatures ranging from 403 to 473 K.A computed effectiveness factor has been compared with experimental values for a catalyst pellet of industrial size. A good degree of correlation between theoretical prediction and the experimental results was

ISSN:0268-2575    

DOI:10.1002/jctb.280570304

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe oxidation behavior of iron powder with oxygen was investigated in 5–25 m NaOH solutions at 5 MPa of oxygen partial pressure and 130–290°C, where m = mol(kg H2O)−1. Monodispersed micaceous iron oxide, α‐Fe2O3, was synthesized by the oxidation of iron powder with 5 MPa of oxygen in 10–16 m NaOH solutions at 250–270°C. The diameter of micaceous iron oxide greatly changed depending on the reaction conditions such as the temperature, reaction time and concentrations of NaOH and c

ISSN:0268-2575    

DOI:10.1002/jctb.280570305

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractSimultaneous biochemical reaction and separation has been successfully carried out in a continuous rotating annular chromatograph (CRAC) by saccharifying liquefied starch to maltose using the enzyme maltogenase. Maltogenase is a thermostable, exo‐acting alpha‐amylase. A simple optimisation procedure involving both volume overload and concentration overload was used. For soluble potato starch, maltose conversions of up to 79% were achieved at feed flow rates of up to 400 cm3h−1and 15–5% w/v concentrations. The resolution between maltose and dextrin w

ISSN:0268-2575    

DOI:10.1002/jctb.280570306

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe design and operation of rotating‐disk mechanical foam‐breakers (MFRDs) fitted to tower fermenters, i.e. bubble columns (BCs), treating various foaming liquids were studied. The foam‐breaking behaviour of MFRDs fitted to BCs and the foaming behaviour of BCs were investigated respectively from the changes in the required critical disk rotational speedNcand those in liquid hold‐up in the foam, øL. The effects of operating conditions onNcand øLwere evaluated quantitatively. On the basis of their results, the empirical equations for predictingNcand øLin foam‐breaking regions, useful for the design and operation of MFRDs fitted to BCs, were obtained. The level of the required foam‐breaking powerPkcof MFRDs was also clarified in relation to the level of øLwhich reflects the foaming intensity of BCs and is related to the difficulty o

ISSN:0268-2575    

DOI:10.1002/jctb.280570307

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractExtending the synthesis of furanic polyols to mixtures of sugars representative of hemicellulose hydrolyzates leads to important yields of furanic polyols of glucose and xylose together with high yields of unreacted L‐arabinos

ISSN:0268-2575    

DOI:10.1002/jctb.280570308

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractSilicone oils were microencapsulated within polyamide (nylon) membranes cross‐linked with polyethylenimine. Solubility of oxygen within the silicones, whether encapsulated or not, was approximately 6 mmol dm−3, representing solubilities approximately 20‐fold higher than that of oxygen in water. The response time of oxygen transfer from the microencapsulated oxygen carrier was less than 2.5 s; a more precise measurement was limited by the response time characteristics of the oxygen probe. Assuming that the bioreactor volume consists of 10–20% (v/v) microencapsulated silicone oil, this represents an enhancement of the oxygen reservoir by a factor ranging from 4 to 7 and improvement in oxygen transfer rates greater than 15‐fold due to the greatly increased specific surface area in comparison to conventional bubble aeration. Circulation of oxygenated silicone oils encapsulated within inert polymeric membranes may provide an efficient alternative to bioreactor oxygenation with shear sensitive cell systems, or in fermentations with high oxygen req

ISSN:0268-2575    

DOI:10.1002/jctb.280570309

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper, the effect of acetate ion (OAc−) on the extraction of cobalt(II) from sulfate media with kerosene solutions of di(2‐ethylhexyl)phosphoric acid (D2EHPA, HR) was investigated at 25°C. In the absence of acetate ions, the composition of the extracted species was graphically determined to beCoR2(HR)2at low loading of D2EHPA (α<0.06). In the presence of acetate medium, the acetate ions were co‐extracted and the mixed complexes of the typeCo2OAcqR4‐p(HR), were formed at a relatively higher loading of D2EHPA (0.10<α<0.34), whereq= 0–4 andr= 2–4 depending on the concentration o

ISSN:0268-2575    

DOI:10.1002/jctb.280570310

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe photodecomposition of 2,4‐dichlorophenoxyacetic acid (2,4‐D) in aqueous solutions has been studied by using ultraviolet radiation in an annular batch reactor. The dark reactions were negligible. For short irradiation times, a first order reaction was found with respect to the absorbed radiation and a simple mechanism of this reaction at initial times has been proposed. pH influences the reaction rate only for long times of irradiation, possibly due to the formation of humic acids in the reaction med

ISSN:0268-2575    

DOI:10.1002/jctb.280570311

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY