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  • Articles  (1,392)
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  • 1
    Electronic Resource
    Electronic Resource
    An analysis of the characteristics of rough bed turbulent shear stresses in an open channel (1997)
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 193-210 
    Details
    ISSN: 1436-3259
    Keywords: Turbulence ; sediment ; fluvial ; river ; bursting process ; statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Entrainment of sediment particles from channel beds into the channel flow is influenced by the characteristics of the flow turbulence which produces stochastic shear stress fluctuations at the bed. Recent studies of the structure of turbulent flow has recognized the importance of bursting processes as important mechanisms for the transfer of momentum into the laminar boundary layer. Of these processes, the sweep event has been recognized as the most important bursting event for entrainment of sediment particles as it imposes forces in the direction of the flow resulting in movement of particles by rolling, sliding and occasionally saltating. Similarly, the ejection event has been recognized as important for sediment transport since these events maintain the sediment particles in suspension. In this study, the characteristics of bursting processes and, in particular, the sweep event were investigated in a flume with a rough bed. The instantaneous velocity fluctuations of the flow were measured in two-dimensions using a small electromagnetic velocity meter and the turbulent shear stresses were determined from these velocity fluctuations. It was found that the shear stress applied to the sediment particles on the bed resulting from sweep events depends on the magnitude of the turbulent shear stress and its probability distribution. A statistical analysis of the experimental data was undertaken and it was found necessary to apply a Box-Cox transformation to transform the data into a normally distributed sample. This enabled determination of the mean shear stress, angle of action and standard error of estimate for sweep and ejection events. These instantaneous shear stresses were found to be greater than the mean flow shear stress and for the sweep event to be approximately 40 percent greater near the channel bed. Results from this analysis suggest that the critical shear stress determined from Shield's diagram is not sufficient to predict the initiation of motion due to its use of the temporal mean shear stress. It is suggested that initiation of particle motion, but not continuous motion, can occur earlier than suggested by Shield's diagram due to the higher shear stresses imposed on the particles by the stochastic shear stresses resulting from turbulence within the flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02427915
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  • 2
    Electronic Resource
    Electronic Resource
    Variations of Bed Surface Sediment Size in a Channel Bend (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 81-88 
    Details
    ISSN: 1573-2932
    Keywords: channel ; bend ; sediment ; size ; gradation ; sorting ; bed ; topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Variations of sediment size and its gradation of the bed surface layer in a channel bend with nonuniform sediment are investigated experimentally. Four groups of sediment with the same initial median diameter (D0) but different initial size gradation (σ0) have been used for experiments which were run until the equilibrium bed topography was achieved. Analyses of experimental data have yielded the following results: (1) The time of equilibrium for bed evolution decreases as σ0 increases; (2) the median size of sediment (D) for a given section in the bend increases with increasing distance from the inner bank towards the outer bank, and it also increases with increasing σ0; (3) the value of D/D0 along the inner bank decreases with increasing σ0, and it also shows a gradual decrease in the upper half of the bend and a slight recovery in the lower half; and (5) the transverse variation of σ value exhibits a general trend increasing from the inner bank towards the outer bank.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018372029704
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  • 3
    Electronic Resource
    Electronic Resource
    Factors Regulating the Flux of Phosphate at the Sediment - Water Interface of a Subtropical Calcareous Lake: a Simulation Study with Intact Sediment Cores (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 401-409 
    Details
    ISSN: 1573-2932
    Keywords: phosphorus ; P flux ; microbial activity ; redox ; simulation ; Lake Kinneret ; sediment ; accumulative P release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Different factors which interactively control the flux of soluble reactive phosphorus (SRP) at the sediment-water interface (SWI) of Lake Kinneret were studied seasonally. The influence of pH, Eh and microbial activity on SRP flux at the SWI was investigated by manipulating the conditions in the overlying water of intact sediment cores. The calculated diffusive SRP flux out of the sediment was lower in cores sampled during winter and spring than during the period of amixis. Potential SRP release, as measured in the absence of microbial activity, was strongly enhanced upon the transition from oxic to anoxic conditions indicating P release from iron(III)-bound phosphorus. In spring and summer cores, an enhanced SRP flux from sediments at pH 7 in comparison to pH 8 indicated P release from carbonate-bound P which sedimented previously as result of high pH values during the algal spring bloom. Microbial uptake at the SWI was the most important sink for SRP and no net-flux occured under oxic conditions. The higher net-flux of P under anoxic conditions was linked to carbon limitation of the bacteria at the SWI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018335305539
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  • 4
    Electronic Resource
    Electronic Resource
    Bottom sediments in a humic lake with artificially increased calcium content: sink or source for phosphorus? (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 457-464 
    Details
    ISSN: 1573-2932
    Keywords: sediment ; phosphorus ; fractionation ; release ; humic lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Lake Flosek (north-eastern part of Poland) is a small shallow and without outflow lake which has been limed in 1970. The concentration of Ca was increased from 3-4 mg L-1 to 17 mg L-1 in the water and from 0.2-0.3% dry weight to 0.9-1.7% dry weight in sediments (5 cm upper layer) due to CaCO3 addition to the lake. In the spring-summer seasons of 1992 and 1993, an experimental study was conducted in Lake Flosek to assess the capacity of bottom sediments to uptake and release mineral phosphorus. The rate of phosphorus exchange between sediments and near-bottom water was experimentally measured under conditions of high (100%), and of reduced (10%) oxygen saturation in near-bottom water. To determine the component of sediments responsible for the uptake of most phosphorus, the proportions of phosphorus forms in sediments were analysed. Sediments of Lake Flosek showed a slight tendency to release phosphates. The rate of this process was similar under high (100%) and low (10%) oxygen saturations ranging from - 0.161 to + 0.200 mg P m-2 d-1. This is much lower (by 1-2 orders of magnitude) than reported from other harmonic, non-humic lakes. In the total phosphorus pool, the highest content of phosphorus was found in the organic and residual phosphorus fractions (over 70% of the total phosphorus in sediments). The largest part of the readily extractable phosphorus was found in the fraction bound to Al and humic substances (41%). Both these fractions determine a weak exchange of phosphorus between sediments and water. No difference in P-release related to P-fraction compound was found in the cores taken from three sites in the lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018395524195
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  • 5
    Electronic Resource
    Electronic Resource
    Sediment Accumulation of Nutrients (N, P) in the Eastern Gulf of Finland (Baltic Sea) (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 477-486 
    Details
    ISSN: 1573-2932
    Keywords: sediment ; nitrogen ; phosphorus ; organic matter ; cluster analysis ; Gulf of Finland ; estuaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Dry weight (DW), ignition loss (IL) and concentrations of total nitrogen (TN) and total phosphorus (TP) of the sediment surface layer (0 to 10 cm, 1 cm slices) were analyzed from 20 sites in the eastern Gulf of Finland. The distance of the sampling sites from the mouth of the River Neva explained the nutrient concentrations of the sediments well, while the effect of water depth was negligible. The increase of TN and the decrease of TP along the transect from the river mouth towards the open Gulf were caused by the diminishing share of allochthonous material supplied from the River Neva. The mean TN concentration of the different accumulation areas was about 40 % higher in the sediment surface than in the deeper layer (9 to 10 cm). The corresponding difference for TP varied from 53 to 56 %. The results suggest considerable netflux of nutrients from sediment to water. The net sediment accumulation of nutrients were estimated as 6.0 g m-2 a-1 of N and 1.7 g m-2 a-1 of P corresponding 22 000 t a-1 of N and 6 100 t a-1 of P for the whole eastern Gulf.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018399625103
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  • 6
    Electronic Resource
    Electronic Resource
    Use of enrichment, and contamination factors together with geoaccumulation indexes to evaluate the content of Cd, Cu, and Ni in the Rybnik water reservoir in Poland (1997)
    Springer
    Water, air & soil pollution 93 (1997), S. 347-365 
    Details
    ISSN: 1573-2932
    Keywords: reservoir of heated water ; contamination ; cadmium ; copper ; nickel ; sediment ; water ; enrichment factor ; geoaccumulation index ; contamination factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In this paper, the contamination degree of the Rybnik Reservoir with cadmium, copper and nickel was analyzed. Quality of the water from the reservoir was determined by drawing comparisons between the metal content in the water and both the officially permitted levels (contamination factor) and levels of metals occurring in the water of non-contaminated areas (enrichment factor). Contamination of bottom sediment with chosen metals was analyzed with reference to the metal content in mudstone (geoaccumulation index, enrichment factor, contamination factor). Trends towards changing the metal content in the bottom sediment was analyzed by determining the enrichment factor of the surface layer of the bottom sediments in relation to a deeper layer. Enrichment of the bottom sediments with metals coming from the water was also determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02404766
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of flocculation on the size distributions of bottom sediment in coastal inlets: Implications for contaminant transport (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 33-42 
    Details
    ISSN: 1573-2932
    Keywords: Aquaculture ; aggregation ; flocculation ; grain size ; sediment ; trace metal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Grain size is the most basic of classification criteria for sediments. The size distribution of a given sediment records the physical transport processes involved in its formation. By using precise grain size analysis and the model of Kranck et al. (1996a,b), it is possible to break down a sediment into the three major components from which it was formed: material deposited as flocs, material deposited as single grains from suspension, and material carried under higher energy conditions. With this method, both the amount of material deposited in a flocculated state and the maximum size, or floc limit, of the particles composing the floc can be determined. Changes in floc limit indicate changes in the aggregation dynamics of the system. As most trace metals and many other contaminants associate closely with the fine particle fraction of sediments, it is important to determine both the areal distribution and reworking history of the floc settled portion of a sediment. This paper discusses the application of the method to coastal inlets in Atlantic Canada and examines the relationship between proportion of floc-settled material and trace metal concentrations. Disaggregated inorganic grain size distributions are also used to illustrate changes in the aggregation dynamics in areas of intense aquaculture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406842
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  • 8
    Electronic Resource
    Electronic Resource
    TOTAL MERCURY AND METHYLMERCURY IN SEDIMENTS AND IN THE POLYCHAETE NEREIS DIVERSICOLOR AT GROOT BUITENSCHOOR (SCHELDT ESTUARY, BELGIUM) (1997)
    Springer
    Water, air & soil pollution 94 (1997), S. 109-123 
    Details
    ISSN: 1573-2932
    Keywords: mercury ; methylmercury ; sediment ; polychaete ; Nereis diversicolor ; methylation ; bioaccumulation ; Scheldt estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total mercury (Hg) and methylmercury (MeHg) concentrations were determined in sediments and in the polychaete worm Nereis diversicolor at 13 stations of a brackish water intertidal mudflat of the Scheldt estuary. Hg and MeHg concentrations in sediments ranged from 144 to 1192 ng g−1 dw and from 0.8 to 6 ng g−1 dw, respectively. Both Hg and MeHg concentrations increased with an increase of organic matter (OM) content and fine grain fraction. In contrast, Hg accumulation by N. diversicolor was significantly (p 〈 0.05) higher at stations with sandy sediments (mean value: 125 ng g−1 dw) than at stations with muddy sediments (mean value, 80 ng g−1), probably because Hg availability for bioaccumulation at muddy stations was reduced by high OM content of the muddy sediments. MeHg accounted for an average of 0.7% of the total Hg in sediments and 18% of the total Hg in N. diversicolor. Seasonal variations significantly affected Hg concentrations in sediments and MeHg in N. diversicolor. Total Hg concentrations in sediments were significantly (p 〈 0.05) higher in autumn and winter than in spring and summer whereas MeHg concentrations were lowest in winter compared to the other seasons. On the other hand, total Hg concentrations in the worms were lowest in spring whereas MeHg concentrations were significantly (p 〈 0.01) higher in spring and summer than in autumn and winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026434629599
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  • 9
    Electronic Resource
    Electronic Resource
    PCBs and organochlorine pesticides in lake orta (Northern Italy) sediments (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 245-254 
    Details
    ISSN: 1573-2932
    Keywords: PCB ; organochlorine pesticide ; sediment ; organic carbon content ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract PCB congeners and organochlorine pesticides (DDT, lindane and HCB) distribution were studied in Lake Orta sediments. The results indicated a contaminated area in the nor-them part of the sub-basin. The observed high levels of organochlorine compounds (OCs) may he explained by the focusing phenomenon, ie. the preferential transport of lighter and smaller particles from the emission sources to this area. The PCBs and DDT values were correlated with the organic carbon content and the heavy metal contamination. The toxicity of the sediment samples was related also to PCB content. PCBs and OCs pollution of Lake Orta was of the same order of magnitude as in Lake Como, which is the most contamined lake in Northern Italy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406864
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  • 10
    Electronic Resource
    Electronic Resource
    Assessing benthic impacts of organic enrichment from marine aquaculture (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 641-650 
    Details
    ISSN: 1573-2932
    Keywords: fish farms ; fecal waste ; sediment ; geochemistry ; metabolism ; macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Benthic observations were carried out at 22 stations in the Western Isles region of the Bay of Fundy on the east coast of Canada to evaluate impacts at salmon aquaculture sites. Eleven sites were located under salmon net-pens and 11 sites (reference or control locations) were at distances 〉 50 m from net-pens. Total S− and redox potential (Eh) in surface sediment and Benthic O2 uptake and CO2 release were sensitive indicators of benthic organic enrichment. High variability between replicate measurements of sediment gas exchange could reflect spatial patchiness in sedimentation of fecal waste and food pellets under fish pens. Biomass of deposit feeders was significantly increased at cage sites but total macrofauna biomass was similar at cage and reference locations. Surface sediment water content, modal grain size, pore water salinity and sulfate, and total biomass of macrofauna were the least sensitive indicators of enrichment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406903
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  • 11
    Electronic Resource
    Electronic Resource
    Use of Enrichment, and Contamination Factors Together with Geoaccumulation Indexes to Evaluate the Content of Cd, Cu, and Ni in the Rybnik Water Reservoir in Poland (1997)
    Springer
    Water, air & soil pollution 93 (1997), S. 347-365 
    Details
    ISSN: 1573-2932
    Keywords: reservoir of heated water ; contamination ; cadmium ; copper ; nickel ; sediment ; water ; enrichment factor ; geoaccumulation index ; contamination factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In this paper, the contamination degree of the Rybnik Reservoir with cadmium, copper andnickel was analyzed. Quality of the water from the reservoir was determined by drawingcomparisons between the metal content in the water and both the officially permitted levels(contamination factor) and levels of metals occurring in the water of non-contaminated areas(enrichment factor). Contamination of bottom sediment with chosen metals was analyzed withreference to the metal content in mudstone (geoaccumulation index, enrichment factor,contamination factor). Trends towards changing the metal content in the bottom sediment wasanalyzed by determining the enrichment factor of the surface layer of the bottom sediments inrelation to a deeper layer. Enrichment of the bottom sediments with metals coming from the waterwas also determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022121615949
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  • 12
    Electronic Resource
    Electronic Resource
    Remobilization of trace elements from polluted anoxic sediments after resuspension in oxic water (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 515-522 
    Details
    ISSN: 1573-2932
    Keywords: sediment ; dredging ; trace metal ; nutrients ; bacteria ; reoxidation ; remobilization ; microbial processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Polluted sediments are periodically subjected to resuspension processes resulting from natural events (e.g. storms, strong waves) as well as from anthropogenically induced activities (e.g. dredging). The main part of the resuspended material is initially in an anoxic state and will be reoxidized more or less quickly in the oxic water column. In laboratory experiments reflecting, as far as possible, natural conditions (e.g. constant pH) the release of Cd, Cu and Zn during this reoxidation phase was investigated. Up to 2% of the particulate bound heavy metals were remobilized from the sediments. In addition the evolution of the concentrations of the anions PO4, SO4, NO3 and NH4 were measured to examine the influence of microbial processes on the release of trace elements. Cell counts and microbial activity of certain micro-organisms during the release processes were also investigated. The investigations illustrated that biological activity has a significant effect on release. In all sediment samples the release of cadmium was delayed in comparison with the other elements even in sediments from different river systems. The influence of different microbial processes on this divergent behavior was examined. The significance of dredging activities to the remobilization processes during reoxidation of anoxic sediments in the Elbe River is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018307926920
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  • 13
    Electronic Resource
    Electronic Resource
    Water-Sediment Exchange of Nutrients During Early Diagenesis and Resuspension of Anoxic Sediments from the Northern Adriatic Sea Shelf (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 541-556 
    Details
    ISSN: 1573-2932
    Keywords: Diagenesis ; resuspension ; sediment ; pore-water ; marine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper presents the results of a study on nutrient exchange at the sediment-water interface which is caused by early diagenesis and resuspension of bottom sediments. The research was carried out on anoxic silty-clay sediment cores collected south of the Po river delta (Northern Adriatic Sea, Italy) in late summer. The early diagenetic processes were investigated by means of the integrated study of pore-water chemistry and solid phase composition. Exchange at the sediment-water interface was studied by comparing the fluxes measured in incubated cores with the fluxes calculated by modelling pore-water profiles. Nutrient exchange during resuspension was analysed by simulating a storm event in the laboratory. The high production of nutrients near the sediment-water interface is mainly caused by the anoxic degradation of organic matter and the successive reductions of Mn and Fe-oxyhydroxides and, to a lesser extent, of sulphate. The oxic degradation of organic matter occurs only at the sediment-water interface. In the incubation experiment the increases of phosphate, ammonia, nitrate, silica, and Fe in bottom waters were measured. The comparison between calculated and measured fluxes showed that: a) the fluxes are mainly controlled by molecular diffusion; b) phosphate and Fe sink because of the Fe-oxyhydroxide precipitation and c) nitrification process influences the ammonia and nitrate fluxes. Resuspension caused the release of: a) phosphate through surficial desorption and authigenic apatite dissolution; b) ammonia by means of the oxic degradation of organic matter; and c) dissolved silica generated by biogenic silica dissolution. Resuspension also caused a weak removal of Fe. The more oxic conditions following resuspension favoured the formation of a Fe-oxyhydroxide film at the sediment-water interface which inhibited the phosphate fluxes from sediments to the water column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018364111899
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  • 14
    Electronic Resource
    Electronic Resource
    The Effect of Flocculation on the Size Distributions of Bottom Sediment in Coastal Inlets: Implications for Contaminant Transport (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 33-42 
    Details
    ISSN: 1573-2932
    Keywords: Aquaculture ; aggregation ; flocculation ; grain size ; sediment ; trace metal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Grain size is the most basic of classification criteria for sediments. The size distribution of a given sediment records the physical transport processes involved in its formation. By using precise grain size analysis and the model of Kranck et al. (1996a,b), it is possible to break down a sediment into the three major components from which it was formed: material deposited as flocs, material deposited as single grains from suspension, and material carried under higher energy conditions. With this method, both the amount of material deposited in a flocculated state and the maximum size, or floc limit, of the particles composing the floc can be determined. Changes in floc limit indicate changes in the aggregation dynamics of the system. As most trace metals and many other contaminants associate closely with the fine particle fraction of sediments, it is important to determine both the areal distribution and reworking history of the floc settled portion of a sediment. This paper discusses the application of the method to coastal inlets in Atlantic Canada and examines the relationship between proportion of floc-settled material and trace metal concentrations. Disaggregated inorganic grain size distributions are also used to illustrate changes in the aggregation dynamics in areas of intense aquaculture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018307710140
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  • 15
    Electronic Resource
    Electronic Resource
    The Distribution of PCB's and Chlorinated Pesticides in Two Connected Himalayan Lakes (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 717-725 
    Details
    ISSN: 1573-2932
    Keywords: chlorinated pesticides ; PCB ; sediment ; Himalayan lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract PCBs and organochlorine pesticides were determined in water, sediment and zooplankton of two Himalayan lakes, located at different altitudes and connected to each other in such a way that Superior Lake acts as a sedimentation basin for Inferior Lake. Surficial sediments of both lakes show PCB contamination comparable to lakes of industrialised areas. Biota appear to be the main machanism responsible for micropollutant burial in the sediments of Inferior Lake, whereas inorganic particles are more relevant in Superior Lake. Physical and chemical properties of individual chemicals, particularly Henry's law constant and Kow values, seem to regulate distribution in different environmental compartments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018301220077
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  • 16
    Electronic Resource
    Electronic Resource
    Variations of bed surface sediment size in a channel bend (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 81-88 
    Details
    ISSN: 1573-2932
    Keywords: channel ; bend ; sediment ; size ; gradation ; sorting ; bed ; topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Variations of sediment size and its gradation of the bed surface laver in a channel bend with nonuniform sediment are investigated experimentally. Four groups of sediment with the same initial median diameter (D o ) but different initial size gradation (σ o ) have been used for experiments which were run until the equilibrium bed topography was achieved. Analyses of experimental data have yielded the following results: (1) The time of equilibrium for bed evolution decreases asσ o increases: (2) the median size of sediment (D) for a given section in the bend increases with increasing distance from the inner bank towards the outer bank, and it also increases with increasingσ o ; (3) the value of D/D o along the inner bank decreases with increasingσ o , and it also shows a gradual decrease in the upper half of the bend and a slight recovery in the lower half, and (5) the transverse variation ofσ value exhibits a general trend increasing from the inner bank towards the outer bank.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406847
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  • 17
    Electronic Resource
    Electronic Resource
    Factors regulating the flux of phosphate at the sediment — water interface of a subtropical calcareous lake: A simulation study with intact sediment cores (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 401-409 
    Details
    ISSN: 1573-2932
    Keywords: phosphorus ; P flux ; microbial activity ; redox ; simulation ; Lake Kinneret ; sediment ; accumulative P release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Different factors which interactively control the flux of soluble reactive phosphorus (SRP) at the sediment water irterface (SWI) of Lake Kinneret were studied seasonally. The influence of pH, Eh and microbial activity on SRP flux at the SWI was investigated by manipulating the conditions in the overlying water of intact sediment cores. The calculated diffusive SRP flux out of the sediment was lower in cores sampled during winter and spring than during the period of amixis. Potential SRP release, as measured in the absence of microbial activity, was strongly enhanced upon the transition from oxic to anoxic conditions indicating P release from iron(III)-bound phosphorus. In spring and summer cores, an enhanced SRP flux from sediments at pH 7 in comparison to pH 8 indicated P release from carbonate-bound P which sedimented previously as result of high pH values during the algal spring bloom. Microbial uptake at the SWI was the most important sink for SRP and no net-flux occured under oxic conditions. The higher net-flux of P under anoxic conditions was linked to carbon limitation ofthe bacteria at the SWI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406880
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  • 18
    Electronic Resource
    Electronic Resource
    Sediment accumulation of nutrients (N, P) in the eastern Gulf of Finland (Baltic Sea) (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 477-486 
    Details
    ISSN: 1573-2932
    Keywords: sediment ; nitrogen ; phosphorus ; organic matter ; cluster analysis ; Gulf of Finland ; estuaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Dry weight (DW), ignition loss (IL) and concentrations of total nitrogen (TN) and total phosphorus (TP) of the sediment surface layer (0 to 10 cm, 1 cm slices) were analyzed from 20 sites in the eastern Gulf of Finland. The distance of the sampling sites from the mouth of the River Neva explained the nutrient concentrations of the sediments well, while the effect of water depth was negligible. The increase of TN and the decrease of TP along the transect from the river mouth towards the open Gulf were caused by the diminishing share of allochthonous material supplied from the River Neva. The mean TN concentration of the different accumulation areas was about 40 % higher in the sediment surface than in the deeper layer (9 to 10 cm). The corresponding difference for TP varied from 53 to 56 %. The results suggest considerable netflux of nutrients from sediment to water. The net sediment accumulation of nutrients were estimated as 6.0 g m−2 a−1 of N and 1.7 g m−2 a−1 of P corresponding 22 000 t a− of N and 6 100 t a−1 of P for the whole eastern Gulf.
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    URL: http://dx.doi.org/10.1007/BF02406887
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    Remobilization of trace elements from polluted anoxic sediments after resuspension in oxic water (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 515-522 
    Details
    ISSN: 1573-2932
    Keywords: sediment ; dredging ; trace metal ; nutrients ; bacteria ; reoxidation ; remobilization ; microbial processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Polluted sediments are periodically subjected to resuspension processes resulting from natural events (e.g. storms, strong waves) as well as from anthropogenically induced activities (e.g. dredging). The main part of the resuspended material is initially in an anoxic state and will be reoxidized more or less quickly in the oxic water column. In laboratory experiments reflecting, as far as possible, natural conditions (e.g. constant pH) the release of Cd, Cu and Zn during this reoxidation phase was investigated. Up to 2% of the particulate bound heavy metals were remobilized from the sediments. In addition the evolution of the concentrations of the anions PO4, SO4, NO3 and NH4 were measured to examine the influence of microbial processes on the release of trace elements. Cell counts and microbial activity of certain micro-organisms during the release processes were also investigated. The investigations illustrated that biological activity has a significant effect on release. In all sediment samples the release of cadmium was delayed in comparison with the other elements even in sediments from different river systems. The influence of different microbial processes on this divergent behavior was examined. The significance of dredging activities to the remobilization processes during reoxidation of anoxic sediments in the Elbe River is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406891
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  • 20
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    Water-sediment exchange of nutrients during early diagenesis and resuspension of anoxic sediments from the Northern Adriatic Sea shelf (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 541-556 
    Details
    ISSN: 1573-2932
    Keywords: Diagenesis ; resuspension ; sediment ; pore-water ; marine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper presents the results of a study on nutrient exchange at the sediment-water interface which is caused by early diagenesis and resuspension of bottom sediments. The research was carried out on anoxic silty-clay sediment cores collected south of the Po river delta (Northern Adriatic Sea, Italy) in late summer. The early diagenetic processes were investigated by means of the integrated study of pore-water chemistry and solid phase composition. Exchange at the sediment-water interface was studied by comparing the fluxes measured in incubated cores with the fluxes calculated by modelling pore-water profiles. Nutrient exchange during resuspension was analysed by simulating a storm event in the laboratory. The high production of nutrients near the sediment-water interface is mainly caused by the anoxic degradation of organic matter and the successive reductions of Mn and Fe-oxyhydroxides and, to a lesser extent, of sulphate. The oxic degradation of organic matter occurs only at the sediment-water interface. In the incubation experiment the increases of phosphate, ammonia, nitrate, silica, and Fe in bottom waters were measured. The comparison between calculated and measured fluxes showed that: a) the fluxes are mainly controlled by molecular diffusion; b) phosphate and Fe sink because of the Fe-oxyhydroxide precipitation and nitrification process influences the ammonia and nitrate fluxes. Resuspension caused the release of: a) phosphate through surficial desorption and authigenic apatite dissolution; b) ammonia by means of the oxic degradation of organic matter; and c) dissolved silica generated by biogenic silica dissolution. Resuspension also caused a weak removal of Fe. The more oxic conditions following resuspension favoured the formation of a Fe-oxyhydroxide film at the sediment-water interface which inhibited the phosphate fluxes from sediments to the water column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406894
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  • 21
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    Controls on selenium distribution in wetland sediment, Benton Lake, Montana (1997)
    Springer
    Water, air & soil pollution 97 (1997), S. 323-340 
    Details
    ISSN: 1573-2932
    Keywords: carbon ; management ; sediment ; selenium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The distribution of selenium in sediment in Benton Lake is mainly controlled by the location of the dissolved selenium inputs. Selenium concentrations in sediment decrease along flow paths downgradient within the wetland system. Construction in 1961 of a pump station to increase water supply and dikes to facilitate water management, along with current water management, has increased the rate of selenium accumulation in sediments as compared to the pre-1961 natural lake. Agricultural practices (alternate crop/fallow rotation) in the non-irrigated farm land of the seleniferous Benton Lake basin also have increased selenium loading to Benton Lake. Carbon content is an important factor affecting selenium distribution in sediment but this relationship is greatly affected by dissolved selenium inputs. Amelioration of selenium contamination in Benton Lake will require a combination of land and water management modifications. Within the wetland system, minimizing the duration of inlet-perennial ponds would minimize selenium accumulation and increase the life of the refuge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407470
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  • 22
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    Selenium Associations in Estuarine Sediments: Redox Effects (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 275-282 
    Details
    ISSN: 1573-2932
    Keywords: selenium ; sediment ; estuaries ; sequential extraction ; redox potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Selenium (Se) is a contaminant of concern in environments affected by discharges from smelting and coal-burning industries. Experiments have been performed to investigate the phase associations of selenium in contaminated sediments under a range of controlled redox conditions. In this study, Se sediment associations were examined using the BCR sequential extraction technique after stabilisation at different redox states. It was shown that although most of the sediment-bound Se is associated with the operationally-defined "organic/sulfide" fraction, as the measured redox potential of the system is increased, more Se moves into the "exchangeable" and "iron/manganese oxyhydroxide" fractions. In these fractions, contaminants can be expected to be more bioavailable. As the mass of Se absorbed to sediments is typically at least an order of magnitude higher than the mass dissolved in porewaters, significant Se exposure may result from oxidative shifts in Se associations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018337928312
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  • 23
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    Carbon and Nitrogen Stable Isotope Fractionation in the Sediment of Lake Bled (Slovenia) (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 315-323 
    Details
    ISSN: 1573-2932
    Keywords: lake ; sediment ; carbon ; nitrogen ; stable isotope ; fractionation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Stable isotope composition of carbon and nitrogen in the sediment and pore water of a eutrophic freshwater lake was studied. Based on changes in the δ13C and δ15N values of dissolved components and sediment fraction, possible processes involved in the decomposition of sedimentary organic matter are outlined. The relative importance of acetate fermentation and CO2 reduction was estimated using known mathematical models, and ammonia assimilation by methanogenic bacteria is hypothesised to be the main process governing the isotope fractionation of dissolved nitrogen in pore water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018354415109
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  • 24
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    CONTROLS ON SELENIUM DISTRIBUTION IN WETLAND SEDIMENT, BENTON LAKE, MONTANA (1997)
    Springer
    Water, air & soil pollution 97 (1997), S. 323-340 
    Details
    ISSN: 1573-2932
    Keywords: carbon ; management ; sediment ; selenium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The distribution of selenium in sediment in Benton Lake is mainly controlled by the location of the dissolved selenium inputs. Selenium concentrations in sediment decrease along flow paths downgradient within the wetland system. Construction in 1961 of a pump station to increase water supply and dikes to facilitate water management, along with current water management, has increased the rate of selenium accumulation in sediments as compared to the pre–1961 natural lake. Agricultural practices (alternate crop/fallow rotation) in the non-irrigated farm land of the seleniferous Benton Lake basin also have increased selenium loading to Benton Lake. Carbon content is an important factor affecting selenium distribution in sediment but this relationship is greatly affected by dissolved selenium inputs. Amelioration of selenium contamination in Benton Lake will require a combination of land and water management modifications. Within the wetland system, minimizing the duration of inlet-perennial ponds would minimize selenium accumulation and increase the life of the refuge.
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    URL: http://dx.doi.org/10.1023/A:1026424530399
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  • 25
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    Environmental Implications of Magnetic Measurements on Recent Sediments from Lake Donghu, Wuhan (1997)
    Springer
    Water, air & soil pollution 98 (1997), S. 187-195 
    Details
    ISSN: 1573-2932
    Keywords: environment ; industrial pollution ; lake ; magnetic measurements ; metals ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mineral magnetic measurements have been made on three sediment cores from Lake Donghu, Wuhan, which reveal evidence for changes in magnetic properties of the sediments. It is suggested that the recent lake sediment profiles contain deposited magnetic minerals and atmospherically derived fly ash from industrial processes. In the cores, the record of ‘magnetite’ deposition shows that the environment of the lake has been affected by heavy industrial processes in intensity and range beginning from the 1950's onwards and remaining relatively uniform in the last decades. In Core I the record of ‘hematite’ deposition parallels that for influence of urban waste water input.
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    URL: http://dx.doi.org/10.1023/A:1026496904708
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    The distribution of PCB's and chlorinated pesticides in two connected Himalayan lakes (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 717-725 
    Details
    ISSN: 1573-2932
    Keywords: chlorinated pesticides ; PCB ; sediment ; Himalayan lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract PCBs and organochlorine pesticides were determined in water, sediment and zooplankton of two Himalayan lakes, located at different altitudes and connected to each other in such a way that Superior Lake acts as a sedimentation basin for Inferior Lake. Surficial sediments of both lakes show PCB contamination comparable to lakes of industrialised areas. Biota appear to be the main machanism responsible for micropollutant burial in the sediments of Inferior Lake, whereas inorganic particles are more relevant in Superior Lake. Physical and chemical properties of individual chemicals, particularly Henry's law constant and Kow values, seem to regulate distribution in different environmental compartments.
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    URL: http://dx.doi.org/10.1007/BF02406911
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  • 27
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    Chemical contamination and associated liver diseases in two species of fish from San Francisco Bay and Bodega Bay (1997)
    Springer
    Ecotoxicology 6 (1997), S. 35-65 
    Details
    ISSN: 1573-3017
    Keywords: chemicalpollution ; fish ; sediment ; San Francisco Bay ; liver diseases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Starry flounder (Platichthys stellatus), white croaker (Genyonemus lineatus) and sediments were collected annually from selected sites within San Francisco Bay, and a reference site in Bodega Bay between 1984--1991. Fish livers were examined for toxicopathic lesions and analysed for selected chlorinated hydrocarbons (CHs) such as PCBs, DDTs, chlordanes and dieldrin; sediment and fish stomach contents were analysed for polycyclic aromatic hydrocarbons (PAHs) and CHs; and bile was analysed for PAH metabolites. Sediment concentrations of PAHs, PCBs and DDTs; bile concentrations of PAH metabolites; and liver concentrations of PCBs, dieldrin and chlordanes were generally significantly higher at all San Francisco Bay sites compared to the Bodega Bay reference site. For both species, hydropic vacuolation of biliary epithelial cells was the most prevalent liver lesion detected and was statistically associated with sediment and tissue concentrations of PAHs or their metabolites, PCBs, DDTs, chlordanes and dieldrin. Temporal trends analyses showed that at Hunters Point, sediment PAHs and CHs increased between 1984--1991, while liver concentrations of CHs decreased. Liver concentrations of dieldrin in starry flounder decreased at all three San Francisco Bay sites
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    URL: http://dx.doi.org/10.1023/A:1018654122479
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  • 28
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    Biochemical responses to sediment-associated contaminants in brown bullhead (Ameriurus nebulosus) from the Niagara River ecosystem (1997)
    Springer
    Ecotoxicology 6 (1997), S. 13-34 
    Details
    ISSN: 1573-3017
    Keywords: Ameriurusnebulosus ; biomarkers ; sediment ; genotoxicity ; oxidativestress ; cytochrome P450
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Brown bullhead (Ameriurus nebulosus) were collected from three sites in the Niagara River ecosystem in June and September of 1991, and sediment samples from these sites were obtained in July 1991. The sites were located in the Buffalo River, the Niagara River adjacent to the Love Canal dump site, and in Black Creek, a Canadian tributary of the Niagara River which served as a reference site. Sediment samples from these sites contained measurable concentrations of various polycyclic aromatic hydrocarbons (PAHs) and chlorinated hydrocarbons (CHs). However, the Buffalo River and Love Canal samples were significantly more contaminated than those from Black Creek. Moreover, Buffalo River samples contained greater PAH concentrations than samples from the Love Canal, while the reverse was observed for CHs. Bile and liver of bullhead were used for the following analyses: fluorescent aromatic compounds in bile, a measure of exposure to PAHs, microsomal cytochrome P450 (CYP) and P450IA (CYP1A) contents and ethoxyresorufin-O-deethylase (EROD) activities, total glutathione (TH-GSH) concentrations, concentrations of 8- oxodeoxyguanosine (8-oxo-dG), and concentrations of hydrophobic DNA adducts (as measured by 32P-postlabelling). Additionally, a laboratory experiment was performed to examine CYP1A-associated responses in bullhead exposed to the model inducer, β- naphthoflavone (BNF). Results from the laboratory induction study were generally consistent with those observed in the field study, but the field study results suggested induction of CYP1A in bullhead from the reference site (Black Creek). For both field collections, fish from the Buffalo River displayed the greatest concentrations of fluorescent compounds in bile and hepatic DNA adducts, whilst fish from the Love Canal site displayed the greatest microsomal CYP1A concentrations and EROD activities. TH- GSH concentrations were significantly greater in Buffalo River fish versus Black Creek only for the June sampling. No statistically significant differences in 8-oxo-dG concentrations in bullhead hepatic DNA were observed among the sites at either sampling date. The different patterns in biochemical responses observed were consistent with sediment chemistries, and these results suggest that exposure of feral teleosts to different suites of bioavailable contaminants can be associated with expression of a characteristic array of biochemical responses
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    URL: http://dx.doi.org/10.1023/A:1018692005641
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    Equilibrium partitioning as the basis for an integrated laboratory and field assessment of the impacts of DDT, DDE and DDD in sediments (1997)
    Springer
    Ecotoxicology 6 (1997), S. 101-125 
    Details
    ISSN: 1573-3017
    Keywords: DDT ; DDE ; DDD ; equilibrium partitioning ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Many of the most biologically productive portions of streams are backwater areas which support large populations of benthic macroinvertebrates. The sediments in these locations and their associated macroinvertebrate communities are frequently subjected to chemical inputs and physical perturbations. Historically, assessment of the effects of contaminants in sediments have emphasized chemical analyses and either laboratory toxicity tests or in-stream monitoring of benthic macroinvertebrate community structure. However, combining the chemical and biological approaches provides a more powerful assessment technique. Such an integrated approach, combining laboratory water-only and sediment toxicity tests with Hyalella azteca and Chironomus tentans, field surveys of benthic macroinvertebrate community structure and evaluation of chemical data using equilibrium partitioning theory was used to assess the effects of DDT, DDE and DDD (collectively termed DDTR) in the sediments of the Huntsville Spring Branch-- Indian Creek (HSB--IC) stream system in the southeastern USA. Benthic macroinvertebrate populations in the HSB--IC system still appear to be adversely affected by DDTR residues within the sediments even though DDT discharges to the stream were stopped over 20 years ago and a major remediation project was completed in the late 1980s. This conclusion is based on a weight of evidence approach which incorporates (1) the observed sediment toxicity to C. tentans and H. azteca in laboratory tests, (2) the identification of DDTR as the likely cause of effects observed during laboratory toxicity tests, (3) the absence of appropriate sensitive species from groups such as the Ephemeroptera, Plecoptera, Trichoptera and Amphipoda, (4) the presence of reduced numbers of both total individuals and species of chironomids and oligochaetes relative to nearby streams not contaminated by DDTR and (5) the observed distribution of benthic macroinvertebrates in relation to organic carbon-normalized concentrations of DDTR and equilibrium partitioning-based predicted sediment toxic units of DDTR
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    URL: http://dx.doi.org/10.1023/A:1018610307458
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    Environmental implications of magnetic measurements on recent sediments from lake Donghu, Wuhan (1997)
    Springer
    Water, air & soil pollution 98 (1997), S. 187-195 
    Details
    ISSN: 1573-2932
    Keywords: environment ; industrial pollution ; lake ; magnetic measurements ; metals ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mineral magnetic measurements have been made on three sediment cores from Lake Donghu, Wuhan, which reveal evidence for changes in magnetic properties of the sediments. It is suggested that the recent lake sediment profiles contain deposited magnetic minerals and atmospherically derived fly ash from industrial processes. In the cores, the record of ‘magnetite’ deposition shows that the environment of the lake has been affected by heavy industrial processes in intensity and range beginning from the 1950's onwards and remaining relatively uniform in the last decades. In Core I the record of ‘hematite’ deposition parallels that for influence of urban waste water input.
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    URL: http://dx.doi.org/10.1007/BF02128657
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    PCBs and Organochlorine Pesticides in Lake Orta (Northern Italy) Sediments (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 245-254 
    Details
    ISSN: 1573-2932
    Keywords: PCB ; organochlorine pesticide ; sediment ; organic carbon content ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract PCB congeners and organochlorine pesticides (DDT, lindane and HCB) distribution were studied in Lake Orta sediments. The results indicated a contaminated area in the northern part of the sub-basin. The observed high levels of organochlorine compounds (OCs) may be explained by the focusing phenomenon, ie. the preferential transport of lighter and smaller particles from the emission sources to this area. The PCBs and DDT values were correlated with the organic carbon content and the heavy metal contamination. The toxicity of the sediment samples was related also to PCB content. PCBs and OCs pollution of Lake Orta was of the same order of magnitude as in Lake Como, which is the most contamined lake in Northern Italy.
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    URL: http://dx.doi.org/10.1023/A:1018377625587
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    Carbon and nitrogen stable isotope fractionation in the sediment of Lake Bled (Slovenia) (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 315-323 
    Details
    ISSN: 1573-2932
    Keywords: lake ; sediment ; carbon ; nitrogen ; stable isotope ; fractionation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Stable isotope composition of carbon and nitrogen in the sediment and pore water of a eutrophic freshwater lake was studied. Based on changes in the δ11C and δ15N values of dissolved components and sediment fraction. possible processes involved in the decomposition of sedimentary organic matter are outlined. The relative importance of acetate fermentation and CO2 reduction was estimated using known mathematical models, and ammonia assimilation by methanogenic bacteria is hypothesised to be the main process governing the isotope fractionation of dissolved nitrogen in pore water.
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    URL: http://dx.doi.org/10.1007/BF02406871
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    Assessing Benthic Impacts of Organic Enrichment from Marine Aquaculture (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 641-650 
    Details
    ISSN: 1573-2932
    Keywords: fish farms ; fecal waste ; sediment ; geochemistry ; metabolism ; macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Benthic observations were carried out at 22 stations in the Western Isles region of the Bay of Fundy on the east coast of Canada to evaluate impacts at salmon aquaculture sites. Eleven sites were located under salmon net-pens and 11 sites (reference or control locations) were at distances 〉 50 m from net-pens. Total S- and redox potential (Eh) in surface sediment and benthic O2 uptake and CO2 release were sensitive indicators of benthic organic enrichment. High variability between replicate measurements of sediment gas exchange could reflect spatial patchiness in sedimentation of fecal waste and food pellets under fish pens. Biomass of deposit feeders was significantly increased at cage sites but total macrofauna biomass was similar at cage and reference locations. Surface sediment water content, modal grain size, pore water salinity and sulfate, and total biomass of macrofauna were the least sensitive indicators of enrichment.
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    URL: http://dx.doi.org/10.1023/A:1018332632372
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    Total mercury and methylmercury in sediments and in the polychaeteNereis diversicolor at Groot Buitenschoor (Scheldt estuary, Belgium) (1997)
    Springer
    Water, air & soil pollution 94 (1997), S. 109-123 
    Details
    ISSN: 1573-2932
    Keywords: mercury ; methylmercury ; sediment ; polychaete ; Nereis diversicolor ; methylation ; bioaccumulation ; Scheldt estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total mercury (Hg) and methylmercury (MeHg) concentrations were determined in sediments and in the polychaete wormNereis diversicolor at 13 stations of a brackish water intertidal mudflat of the Scheldt estuary. Hg and MeHg concentrations in sediments ranged from 144 to 1192 ng g−1 dw and from 0.8 to 6 ng g−1 dw, respectively. Both Hg and MeHg concentrations increased with an increase of organic matter (OM) content and fine grain fraction. In contrast, Hg accumulation byN. diversicolor was significantly (p〈0.05) higher at stations with sandy sediments (mean value: 125 ng g−1 dw) than at stations with muddy sediments (mean value, 80 ng g−1), probably because Hg availability for bioaccumulation at muddy stations was reduced by high OM content of the muddy sediments. MeHg accounted for an average of 0.7% of the total Hg in sediments and 18% of the total Hg inN. diversicolor. Seasonal variations significantly affected Hg concentrations in sediments and MeHg inN. diversicolor. Total Hg concentrations in sediments were significantly (p〈0.05) higher in autumn and winter than in spring and summer whereas MeHg concentrations were lowest in winter compared to the other seasons. On the other hand, total Hg concentrations in the worms were lowest in spring whereas MeHg concentrations were significantly (p〈0.01) higher in spring and summer than in autumn and winter.
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    URL: http://dx.doi.org/10.1007/BF02407097
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    Selenium associations in estuarine sediments: Redox effects (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 275-282 
    Details
    ISSN: 1573-2932
    Keywords: selenium ; sediment ; estuaries ; sequential extraction ; redox potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Selenium (Se) is a contaminant of concern in environments affected by discharges from smelting and coal-burning industries. Experiments hate been performed to investigate the phase associations of selenium in contaminated sediments under a range of controlled redox conditions. In this study, Se sediment associations were examined using the BCR sequential extraction technique after stabilisation at different redox states. It was shown that although most of the sediment-bound Se is associated with the operationally-defined “organic sulfide” fraction, as the measured redox potential of the system is increased. more Se moves into the “exchangeable” and “iron manganese oxy hydroxide” fractions. In these fractions. contaminants can be expected to be more bioavailable. As the mass of Se absorbed to sediments is typically at least an order of magnitude higher than the mass dissolved in porewaters. significant Se exposure may result from oxidative shifts in Se associations.
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    URL: http://dx.doi.org/10.1007/BF02406867
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    Bottom sediments in a humic lake with artificially increased calcium content: Sink or source for phosphorus? (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 457-464 
    Details
    ISSN: 1573-2932
    Keywords: sediment ; phosphorus ; fractionation ; release ; humic lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Lake Flosek (north-eastern part of Poland) is a small shallow and without outflow lake which has been limed in 1970. The concentration of Ca was increased from 3–4 mg L−1 to 17 mg L−1 in the water and from 0.2–0.3% dry weight to 0.9–1.7% dry weight in sediments (5 cm upper layer) due to CaCO3 addition to the lake. In the spring-summer seasons of 1992 and 1993, an experimental study was conducted in Lake Flosek to assess the capacity of bottom sediments to uptake and release mineral phosphorus. The rate of phosphorus exchange between sediments and near-bottom water was experimentally measured under conditions of high (100%), and of reduced (10%) oxygen saturation in near-bottom water. To determine the component of sediments responsible for the uptake of most phosphorus, the proportions of phosphorus forms in sediments were analysed. Sediments of Lake Flosek showed a slight tendency to release phosphates. The rate of this process was similar under high (100%) and low (10%) oxygen saturations ranging from - 0.161 to + 0.200 mg P m−2 d−1. This is much lower (by 1–2 orders of magnitude) than reported from other harmonic, non-humic lakes. In the total phosphorus pool, the highest content of phosphorus was found in the organic and residual phosphorus fractions (over 70% of the total phosphorus in sediments). The largest part of the readily extractable phosphorus was found in the fraction bound to AI and humic substances (41%). Both these fractions determine a weak exchange of phosphorus between sediments and water. No difference in P-release related to P-fraction compound was found in the cores taken from three sites in the lake.
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    URL: http://dx.doi.org/10.1007/BF02406885
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    Influence of the nature of modifier in the enzymatic activity of chemical modified semipurified lipase from Candida rugosa (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 252-260 
    Details
    ISSN: 0006-3592
    Keywords: lipase ; chemical modification ; stability ; esterification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Semipurified lipase of Candida rugosa (CRSL) was subjected to chemical modification, and the activities of the modified lipase, in hydrolysis and esterification reactions, were examined. The esterification reactions were carried out in the absence and presence of isooctane. When the enzyme was modified with polyethylene glycol (PEG), two methodologies were studied. The activation of PEG with p-NO2-phenylchloroformate gives better biocatalysts than those obtained with cyanuric chloride-PEG. The chemical modification with PEG increases the stability of pure lipases in isooctane at 50°C (extreme conditions). The chemically modified enzymes are useful for biotransformations in organic solvents. In addition the nitration of tyrosines with tetranitromethane was also studied. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 252-260, 1997.
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    Effect of hypoosmotic stress on hybridoma cell growth and antibody production (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 565-570 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; hypoosmotic stress ; specific antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To investigate the response of hybridoma cells to hypoosmotic stress, S3H5/γ2bA2 and DB9G8 hybridomas were cultivated in the hypoosmolar medium [Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% serum] resulting from sodium chloride subtraction. Both hybridomas showed similar responses to hypoosmotic stress in regard to cell growth and antibody production. The cell growth and antibody production at 276 mOsm/kg were comparable to those at 329 mOsm/kg (standard DMEM). Both cells grew well at 219 mOsm/kg, though their growth and antibody production were slightly decreased. When the osmolality was further decreased to 168 mOsm/kg, the cell growth did not occur. When subjected to hyperosmotic stress, both cells displayed significantly enhanced specific antibody productivity (qAb). However, the cells subjected to hypoosmotic stress did not display enhanced qAb. Taken together, both hyperosmotic and hypoosmotic stresses depressed the growth of S3H5/γ2bA2 and DB9G8 hybridomas. However, their response to hypoosmotic stress in regard to qAb was different from that to hyperosmotic stress. © 1997 John Wiley & Sons, Inc. Biotechnol Biong 55: 565-570, 1997.
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    Production of recombinant bacterial endoglucanase as a co-product with ethanol during fermentation using derivatives of Escherichia coli KO11 (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 547-555 
    Details
    ISSN: 0006-3592
    Keywords: ethanol ; cellulose ; hemicellulose ; endoglucanase ; cellulase ; lignocellulose ; biomass ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study demonstrates a new approach to reduce the amount of fungal cellulase required for the conversion of cellulose into ethanol. Escherichia coli KO11, a biocatalyst developed for the fermentation of hemicellulose syrups, was used to produce recombinant endoglucanase as a co-product with ethanol. Seven different bacterial genes were expressed from plasmids in KO11. All produced cell-associated endoglucanase activity. KO11(pLOI1620) containing Erwinia chrysanthemi celZ (EGZ) produced the highest activity, 3,200 IU endoglucanase/L fermentation broth (assayed at pH 5.2 and 35°C). Recombinant EGZ was solubilized from harvested cells by treatment with dilute sodium dodecyl sulfate (12.5 mg/ml, 10 min, 50°C) and tested in fermentation experiments with commercial fungal cellulase (5 filter paper units/g cellulose) and purified cellulose (100 g/L). Using Klebsiella oxytoca P2 as the biocatalyst, fermentations supplemented with EGZ as a detergent-lysate of KO11(pLOI1620) produced 14%-24% more ethanol than control fermentations supplemented with a detergent-lysate of KO11(pUC18). These results demonstrate that recombinant bacterial endoglucanase can function with fungal cellulase to increase ethanol yield during the simultaneous saccharification and fermentation of cellulose. © 1997 Wiley & Sons, Inc. Biotechnol Bioeng 55: 547-555, 1997.
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    Engineering mRNA stability in E. coli by the addition of synthetic hairpins using a 5′ cassette system (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 577-580 
    Details
    ISSN: 0006-3592
    Keywords: mRNA stability ; hairpins ; gene expression control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An expression system has been developed for the introduction of DNA cassettes into the region between the transcription and translation start sites of a gene of interest. This cassette system was used to engineer mRNA stability through the introduction of hairpins at the 5′ end. A synthetic DNA cassette was designed so that the resulting mRNA hairpin would be positioned one nucleotide from the 5′ mRNA end. The hairpin-containing mRNA exhibited a half-life 3 times that of the mRNA with no hairpin, resulting in increases in both mRNA and protein levels. These results indicate that it is possible to engineer mRNA stability as an additional means of controlling gene expression. © 1997 John Wiley & Sons Inc. Biotechnol Bioeng 55: 557-580, 1997
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    Application of membrane-based preferential transport to whole broth processing (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 581-591 
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    ISSN: 0006-3592
    Keywords: adsorptive membranes ; oscillatory flow ; integrated processes ; in situ product recovery ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Preferential transport in adsorptive membranes can be used to selectively remove biochemicals directly from fermentation broths. During preferential transport, an adsorbing solute is selectively transported across the membrane while nonadsorbing solutes and cells are retained by the membrane. This technique was used to separate lysozyme directly from a feed containing lysozyme, myoglobin, and yeast cells. We found that because the oscillatory flows used in preferential transport involve strokes that are close to symmetric, they are very efficient in alleviating cake formation due to cell deposition on the membrane surface. Theoretical results suggest that, by optimizing process variables, preferential transport can lead to a continuous concentrated stream of the adsorbing protein. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 581-591, 1997.
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    In vivo analysis of metabolic dynamics in Saccharomyces cerevisiae: II. Mathematical model (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 592-608 
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    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; metabolic modeling ; sensitivity analysis ; glycolysis ; compartmentation ; transient response ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model of glycolysis in Saccharomyces cerevisiae is presented. The model is based on rate equations for the individual reactions and aims to predict changes in the levels of intra- and extracellular metabolites after a glucose pulse, as described in part I of this study. Kinetic analysis focuses on a time scale of seconds, thereby neglecting biosynthesis of new enzymes. The model structure and experimental observations are related to the aerobic growth of the yeast. The model is based on material balance equations of the key metabolites in the extracellular environment, the cytoplasm and the mitochondria, and includes mechanistically based, experimentally matched rate equations for the individual enzymes. The model includes removal of metabolites from glycolysis and TCC for biosynthesis, and also compartmentation and translocation of adenine nucleotides. The model was verified by in vivo diagnosis of intracellular enzymes, which includes the decomposition of the network of reactions to reduce the number of parameters to be estimated simultaneously. Additionally, sensitivity analysis guarantees that only those parameters are estimated that contribute to systems trajectory with reasonable sensitivity. The model predictions and experimental observations agree reasonably well for most of the metabolites, except for pyruvate and adenine nucleotides. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 592-608, 1997.
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    A novel membrane reactor design for controlled studies of interacting populations (simulation of the interaction between microorganism and plant suspension cultures) (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 609-615 
    Details
    ISSN: 0006-3592
    Keywords: interacting populations ; membrane reactor ; induced metabolic changes ; elicitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design of a reactor in which two interacting cell populations (microorganisms and plants) could grow under controlled conditions was considered. In this reactor, the cell populations are separated by a membrane which permits semi-in vivo study of induced interaction-specific changes in metabolism. In this paper, the interaction of suspension culture of Nicotiana tabacum (tobacco) and the Oomycete, Phytophthora nicotiana was simulated. The results of the computer simulation show the induced metabolic changes as a consequence of the biological interaction. The paper introduces a novel approach in the strategy for the study of interacting population in suspension cultures. This type of system has potential applications in studies of the regulation of secondary metabolism and for the production of high values pharmaceuticals. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 609-615, 1997.
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    Application of fluid mechanic and kinetic models to characterize mammalian cell detachment in a radial-flow chamber (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 616-629 
    Details
    ISSN: 0006-3592
    Keywords: cell adhesion ; radial-flow chamber ; hydrodynamic shear ; detachment kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The strength of adhesion and dynamics of detachment of murine 3T3 fibroblasts from self-assembled monolayers were measured in a radial-flow chamber (RFC) by applying models for fluid mechanics, adhesion strength probability distributions, and detachment kinetics. Four models for predicting fluid mechanics in a RFC were compared to evaluate the accuracy of each model and the significance of inlet effects. Analysis of these models indicated an outer region at large radial positions consistent with creeping flow, an intermediate region influenced by inertial dampening, and an inner region dominated by entrance effects from the axially-oriented inlet. In accompanying experiments patterns of the fraction of cells resisting detachment were constructed for individual surfaces as a function of the applied shear stress and evaluated by comparison with integrals of both a normal and a log-normal distribution function. The two functions were equally appropriate, yielding similar estimates of the mean strength of adhesion. Further, varying the Reynolds number in the inlet, Red, between 630 and 1480 (corresponding to volumetric flow rates between 0.9 and 2.1 mL/s) did not affect the mean strength of adhesion. For these same experiments, analysis of the dynamics of detachment revealed three temporal phases: 1) rapid detachment of cells at the onset of flow, consistent with a first-order homogeneous kinetic model; 2) time-dependent rate of detachment during the first 30 sec. of exposure to hydrodynamic shear, consistent with the first-order heterogeneous kinetic model proposed by Dickinson and Cooper (1995); and 3) negligible detachment, indicative of pseudo-steady state after 60 sec. of flow. Our results provide rigorous guidelines for the measurement of adhesive interactions between mammalian cells and prospective biomaterial surfaces using a RFC. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 616-629, 1997.
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    Real-time method for determining the colony-forming cell content of human hematopoietic cell cultures (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 693-700 
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    ISSN: 0006-3592
    Keywords: glucose ; lactate ; real-time determination ; hematopoietic cell culture ; colony-forming cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose and lactate metabolic rates were evaluated for cultures of cord blood (CB) mononuclear cell (MNC), peripheral blood (PB) MNC, and PB CD34+ cell cultures carried out in spinner flasks and in T-flasks in both serum-containing and serum-free media. Specific glucose uptake rates (qgluc, in micromoles per cell per hour) and lactate generation rates (qlac) correlated with the percentage of colony-forming cells (CFC) present in the culture for a broad range of culture conditions. Specifically, the time of maximum CFC percentage in each culture coincided with the time of maximum qgluc and qlac in cultures with different seeding densities and cytokine combinations. A two-population model (Qlac = α[CFC] + β([TC] - [CFC]), where [TC] is total cell concentration; Qlac is volumetric lactate production rate in micromoles per milliliter per hour; α is qlac for an average CFC; and β is qlac for an average non-CFC) was developed to describe lactate production. The model described lactate production well for cultures carried out in both T-flasks and spinner flasks and inoculated with either PB or CB MNC or PB CD34+ cells. The values for α and β that were derived from the model varied with both the inoculum density and the cytokine combination. However, preliminary results indicate that cultures carried out under the same conditions from different samples with similar initial CD34+ cell content have similar values for β and β. These findings suggest that it should be possible to use lactate production data to predict the harvest time that corresponds to the maximum number of CFC in culture. The ability to harvest ex vivo hematopoietic cultures for transplantation when CFC are at a maximum has the potential to speed the rate at which immunocompromised patients recover. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 693-700, 1997.
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    A model for light distribution and average solar irradiance inside outdoor tubular photobioreactors for the microalgal mass culture (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 701-714 
    Details
    ISSN: 0006-3592
    Keywords: tubular photobioreactors ; light distribution ; average solar irradiance ; light attenuation ; microalgae mass culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model to estimate the solar irradiance profile and average light intensity inside a tubular photobioreactor under outdoor conditions is proposed, requiring only geographic, geometric, and solar position parameters. First, the length of the path into the culture traveled by any direct or disperse ray of light was calculated as the function of three variables: day of year, solar hour, and geographic latitude. Then, the phenomenon of light attenuation by biomass was studied considering Lambert-Beer's law (only considering absorption) and the monodimensional model of Cornet et al. (1900) (considering absorption and scattering phenomena). Due to the existence of differential wavelength absorption, none of the literature models are useful for explaining light attenuation by the biomass. Therefore, an empirical hyperbolic expression is proposed. The equations to calculate light path length were substituted in the proposed hyperbolic expression, reproducing light intensity data obtained in the center of the loop tubes. The proposed model was also likely to estimate the irradiance accurately at any point inside the culture. Calculation of the local intensity was thus extended to the full culture volume in order to obtain the average irradiance, showing how the higher biomass productivities in a Phaeodactylum tricornutum UTEX 640 outdoor chemostat culture could be maintained by delaying light limitation. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 701-714, 1997.
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    Effect of agitation intensities on fungal morphology of submerged fermentation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 715-726 
    Details
    ISSN: 0006-3592
    Keywords: fungal morphology ; pellets ; hyphae ; hair of pellets ; agitation intensity ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Both parallel fermentations with Aspergillus awamori (CBS 115.52) and a literature study on several fungi have been carried out to determine a relation between fungal morphology and agitation intensity. The studied parameters include hyphal length, pellet size, surface structure or so-called hairy length of pellets, and dry mass per-wet-pellet volume at different specific energy dissipation rates. The literature data from different strains, different fermenters, and different cultivation conditions can be summarized to say that the main mean hyphal length is proportional to the specific energy dissipation rate according to a power function with an exponent of -0.25 ± 0.08. Fermentations with identical inocula showed that pellet size was also a function of the specific energy dissipation rate and proportional to the specific energy dissipation rate to an exponent of -0.16 ± 0.03. Based on the experimental observations, we propose the following mechanism of pellet damage during submerged cultivation in stirred fermenters. Interaction between mechanical forces and pellets results in the hyphal chip-off from the pellet outer zone instead of the breakup of pellets. By this mechanism, the extension of the hyphae or hair from pellets is restricted so that the size of pellets is related to the specific energy dissipation rate. Hyphae chipped off from pellets contribute free filamentous mycelia and reseed their growth. So the fraction of filamentous mycelial mass in the total biomass is related to the specific energy dissipation rate as well.To describe the surface morphology of pellets, the hyphal length in the outer zone of pellets or the so-called hairy length was measured in this study. A theoretical relation of the hairy length with the specific energy dissipation rate was derived. This relation matched the measured data well. It was found that the porosity of pellets showed an inverse relationship with the specific energy dissipation rate and that the dry biomass per-wet-pellet volume increased with the specific energy dissipation rates. This means that the tensile strength of pellets increased with the increase of specific energy dissipation rate. The assumption of a constant tensile strength, which is often used in literature, is then not valid for the derivation of the relation between pellet size and specific energy dissipation rate. The fraction of free filamentous mycelia in the total biomass appeared to be a function of the specific energy dissipation in stirred bioreactors. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 715-726, 1997.
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    On-line green fluorescent protein sensor with LED excitation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 921-926 
    Details
    ISSN: 0006-3592
    Keywords: green fluorescent protein ; sensor ; on-line monitoring ; quantitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We present an intensity based sensor designed for on-line monitoring of green fluorescent protein, a revolutionary marker of protein expression. The device consisted of a blue light emitting diode as the excitation source. A band pass excitation filter cut off light longer than 490 nm. The light was directed into a bifurcated optical fiber bundle with the common end inserted into a stainless steel housing equipped with a quartz window. The fiber bundle and stainless steel housing are steam sterilizable. The emission radiation was collected through a long wave pass filter to reject the excitation light shorter than 505 nm and was detected by a photomultiplier tube. The signal was amplified and sent to a computer for recording time course data. The sensor was tested in an Escherichia coli fermentation of JM105 transformed with pBAD-GFP. The on-line signal was compared to off-line fluorescence spectrophotometer measurements. The on-line profile closely followed the off-line. Western blot data showed that with a time shift, the sensor was able to both continuously and quantitatively monitor expression of green fluorescent protein on-line in real time. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55:921-926, 1997.
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    Comparison of Trichoplusia ni BTI-Tn-5B1-4 (high five™) and Spodoptera frugiperda Sf-9 insect cell line metabolism in suspension cultures (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 909-920 
    Details
    ISSN: 0006-3592
    Keywords: baculovirus ; insect cells ; metabolism ; Sf-9; high five™ ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nutrient utilization and byproduct accumulation were monitored in Spodoptera frugiperda Sf-9 and Trichoplusia ni BTI-Tn-5B1-4 (High Five™) cell lines during growth and following viral infection in suspension cultures in order to develop a better understanding of cell metabolism and to acquire information relevant to large scale fed-batch bioreactors. The utilization of glucose, dissolved oxygen, and amino acids were monitored in Sf-9 cell cultures grown in Sf-900 II serum-free medium (SFM) and in High Five™ cell cultures grown in both Sf-900 II and Express Five SFM. Using the optimal medium for each cell line, i.e., Sf-900 II SFM for Sf-9 cells and Express Five SFM for High Five™ cells, the cell growth rate, maximum cell density, specific glucose and glutamine utilization rates, and specific alanine production rate were comparable during cell growth. In addition, the expression level of recombinant human tissue plasminogen activator was comparable in the two cell lines on a per cell basis. It was found, however, that lactate and ammonia accumulated in High Five™ cell cultures, but not in Sf-9 cell cultures. In addition, High Five™ cells utilized asparagine more rapidly than glutamine, whereas Sf-9 cells consumed only minimal asparagine, and the oxygen utilization rate was significantly higher in High Five™ cell cultures. It was also found that the medium had a significant effect on High Five™ cell metabolism, e.g., the specific glucose utilization rate and the specific lactate and alanine production rates were significantly higher in Sf-900 II SFM than in Express Five SFM. In addition, the maximum cell density and specific asparagine utilization rate were significantly higher in Express Five SFM. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55:909-920, 1997.
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    An activity coefficient model for proteins (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 940-940 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No abstract.
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    Kinetic studies of fusarium solani pisi cutinase used in a gas/solid system: Transesterification and hydrolysis reactions (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 1-8 
    Details
    ISSN: 0006-3592
    Keywords: transesterification ; hydrolysis ; water activity ; cutinase ; gas ; bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fusarium solani cutinase supported onto Chromosorb P was used to catalyze transesterification (alcoholysis) and hydrolysis on short volatile alcohols and esters in a continuous gas/solid bioreactor. In this system, a solid phase composed of a packed enzymatic preparation was continuously percolated with carrier gas which fed substrates and removed reaction products simultaneously. A kinetic study was performed under differential operating conditions in order to get initial reaction rates. The effect of the hydration state of the biocatalyst on the kinetics was studied for 3 conditions of hydration (aw = 0.2, aw = 0.4 and aw = 0.6), the alcoholysis of propionic acid methyl ester with n-propanol, and for 5 hydration levels (from aw = 0.2 to aw = 0.6) for the hydrolysis of propionic acid methyl, ethyl or propyl esters. F. solani cutinase was found to have an unusual kinetic behavior. A sigmoid relationship between the rate of transesterification and the activity of methyl propionate was observed, suggesting some form of cooperative activation of the enzyme by one of its substrate. For the hydrolysis of short volatile propionic acid alkyl esters, threshold effects on the reaction rate, highly depending on the water activity and the substrate polarity, are reported. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 1-8, 1997.
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    Kinetics and equilibria of condensation reactions between monosaccharide pairs catalyzed by Aspergillus niger glucoamylase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 9-22 
    Details
    ISSN: 0006-3592
    Keywords: condensation reactions ; disaccharides ; equilibria ; glucoamylase ; kinetics ; monosaccharides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Arabinose, fructose, galactose, myo-inositol, lyxose, mannose, ribose, and xylose were incubated individually and with glucose in the presence of Aspergillus niger glucoamylase at pH 4.5 and 45°C. Glucoamylase condenses galactose, glucose, and mannose individually into disaccharides. It also produces mixed disaccharides when each of the eight carbohydrates is incubated with glucose. Many products were identified by gas chromatography of the derivatized reaction mixtures followed by mass spectroscopy of the individual chromatographic peaks. Galacto-, gluco-, or mannopyranosyl rings appear to be present at the nonreducing ends of all the disaccharides produced. Molecules linked through primary hydroxyl groups have the highest equilibrium constants of all products formed, since these bonds are thermodynamically favored. However, glucoamylase is capable of forming bonds with many available hydroxyl groups, as previously demonstrated when it was incubated with glucose alone. Formation rates of different bonds linking different residues vary widely. These results demonstrate that glucoamylase has a wide selectivity toward residues it will condense into disaccharides and toward bonds it will form between them. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 9-22, 1997.
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    Simulations of a LDPE reactor using computational fluid dynamics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 104-117 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computational fluid dynamics methods are used to provide three-dimensional simulations of a low-density polyethylene (LDPE) autoclave reactor under normal operating conditions. For the conditions used, the reactor is not very well mixed; thus, the common model approximation of a perfectly stirred reactor is not warranted. The simulations verify the sensitive nature of the polymerization reactors and indicate a need for optimizing operating parameters.
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    Simulation of decoking of thermal cracking coils by steam/air-mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 118-126 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rigorous approach was developed for the simulation of the decoking of an industrial cracking furnace. A one-dimensional heterogeneous reactor model, which accounts for the interfacial gradients between the process gas and the coke surface, was used to simulate reactor coils. Both the combustion and steam gasification of the coke layer were taken into account. The reactor model for the decoking was coupled with a detailed firebox simulation model. The initial profile of the coke layer thickness, required for the decoking calculations, was obtained by a run-length simulation. The evolution with time of the temperature distribution inside the cracking coil and in the furnace was generated simultaneously, which made it possible to understand the decoking operation in detail and to predict its duration accurately.
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    Dynamics of semibatch polymerization reactors: II. Pilot-plant study (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 157-165 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semibatch flow scheduling strategy proposed by Teymour and Ray (1989, 1996) is evaluated for a polymerization reaction conducted in a pilot-plant reactor. The reaction used is the free radical terpolymerization of styrene, α-methyl styrene, and acrylic acid monomers initiated by an organic peroxide initiator and carried out in the presence of a reactive glycol ether solvent. This strategy was tested in both single batch and sequential semibatch modes. The process was shown to produce polymer of constant molecular weight properties and composition as inferred from acid number and monomer conversion measurements. This process could be used for obtaining polymer products from a semibatch reactor that are of comparable quality to CSTR products. Results indicate success of this process at meeting this objective; however, practical considerations relating to agitation and temperature control need to be properly addressed to ensure this success.
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    Steady-state multiplicity in cocurrently cooled autothermal reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 127-134 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The steady-state simulation of a cocurrently cooled autothermal fixed-bed reactor was carried out using a 2-D heterogeneous mathematical model. The ammonia synthesis was chosen as a case study. Unlike the not-autothermal cocurrent reactor, which is unconditionally stable, the autothermal cocurrent reactor shows multiple steady states within a broad range of operating conditions. This finding, not reported in the literature, is explained through the mass transport from the bottom to the top of the reactor, associated with a feedback of energy. The feedback of heat, which is inherent to autothermal reactors, leads to an ignition-extinction phenomenon similar to that found in the countercurrent configuration. The influence of different parameters on the stability of the autothermal cocurrent reactor was analyzed. The regions where steady-state multiplicity occurs were compared with those presented by the autothermal countercurrent reactor. The influence of an additional heat exchanger on the reactor stability was considered.
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    Analysis of νi/κTx in solvent mixtures at the critical line (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 277-280 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    Rheological simulation of in-line bubble interactions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 265-267 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    Analysis of nucleation and crystal growth data using the interfacial supersaturation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 268-272 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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    Boiling heat transfer of Nitrogen in a thermosyphon condenser-reboiler (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 339-344 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental investigation was conducted to determine the boiling heat-transfer characteristics in a thermosyphon condenser-reboiler of air-separation plants. The test section was a plate-fin heat exchanger of practical size of 0.106 m width and 2.56 m length. The testing fluid was nitrogen. Experiments were carried out within a range of pressure from 150 to 300 kPa, submergence from 1.95 to 2.80 m, and heat flux up to 11 kW/m2 under constant wall-temperature condition. The liquid superheat at the onset of boiling was rather significant. The boiling heat-transfer coefficients obtained agreed well with Chen's correlation modified by Colburn's J factor within a mean deviation of 9.3%.
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    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430101
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    Efficient sampling technique for optimization under uncertainty (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 440-447 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The concept of robust design involves identification of design settings that make the product performance less sensitive to the effects of seasonal and environmental variations. This concept is discussed in this article in the context of batch distillation column design with feed stock variations, and internal and external uncertainties. Stochastic optimization methods provide a general approach to robust/parameter design as compared to conventional techniques. However, the computational burden of these approaches can be extreme and depends on the sample size used for characterizing the parametric variations and uncertainties. A novel sampling technique is presented that generates and inverts the Hammersley points (an optimal design for placing n points uniformly on a k-dimensional cube) to provide a representative sample for multivariate probability distributions. The example of robust batch-distillation column design illustrates that the new sampling technique offers significant computational savings and better accuracy.
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    Analysis of cake growth in cake filtration: Effect of fine particle retention (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 33-44 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equations were derived that describe the dynamics of cake growth in cake filtration, and methods for their solutions were developed. In deriving the equations, the moving boundary nature of the cake formation process and the effect of fine particle retention were considered. It was shown that fine particle retention may contribute significantly to the decrease of cake permeability and thus alters the performance of cake filtration even if the amount of fine particles involved is small. Through numerical examples, it was also demonstrated that fine particle retention in filter cakes may cause serious errors in determining the constitutive relationships from filter test data.
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    Characteristics of high-pressure liquid-solid fluidization (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 45-57 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fundamental characteristics of liquid-solid fluidization at high pressures (up to 21 MPa) and moderate temperatures (up to 89°C) are investigated. Properties under study include minimum fluidization velocity (umf), bed voidage at minimum fluidization, and bed expansion. Devices for in-situ measurements of physical properties of the liquid in the bed are developed, and measurements are carried out to quantify the pressure and temperature effects on the fluidization behavior. The results indicate that under high pressures and moderate temperatures, liquid-solid fluidization behavior is affected significantly by the variation of liquid density and viscosity with pressure. As the pressure increases, the liquid viscosity and density increase, yielding an increased drag force and buoyancy force on the particles, and hence a decreasing umf and an increasing bed expansion for a given liquid flow rate. An increase in temperature has an opposite effect on the physical properties of the liquid, increasing umf and decreasing the bed expansion for a given liquid flow rate. Various correlations proposed in the literature for umf and bed expansion, including those by Richardson and Zaki (1954) and Chitester et al. (1984), are applicable to high-pressure and high-temperature conditions when proper account is made of the liquid physical properties under bed operating conditions.
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    Asymptotic models for H2S absorption into single and blended aqueous amines (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 58-63 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Asymptotic power series solutions for the mass-transfer enhancement factor for absorption of a gas component into a liquid where it undergoes irreversible instantaneous chemical reaction(s) with one and two liquid-phase reactants are developed in this work. The Padé technique is used to extend the region of applicability (accelerate the convergence) of the four-term asymptotic power series solutions. The resulting modified asymptotic expressions for the enhancement factor show excellent accuracy over a wide range and can be used to predict enhancement factors as low as 2 with an error of about 5% compared to the exact numerical solution. Predictions of these new asymptotic solutions are compared with experimental absorption data for H2S absorption into aqueous methyldiethanolamine and H2S absorption into aqueous mixtures of methyldiethanolamine and diethanolamine obtained in a laminar-jet absorber. The absolute mean deviations of the predictions from the experimental absorption data for the single and mixed amine solutions were 4.6% and 2.4%, respectively.
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    Analysis of rate enhancement in a periodically operated trickle-bed reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 166-172 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a trickle-bed reactor (TBR) is operated periodically, the bed is fed with liquid on and off, while the gas phase passes continuously. Rates and conversions could be higher than those corresponding to the steady-state operation. In the “dry cycles” the heat generated by the reaction can drive the vaporization of the liquid phase, and a much more rapid “gas phase” reaction may occur. There is a trade-off between the potential for hot-spot formation and the fact that overall rates are higher during cycling. A qualitative understanding of the phase transition in TBRs is obtained by a simple phenomenological model that takes into account different transport and reaction mechanisms occurring in a catalytic particle under different cycling conditions. A mathematical model is used to predict results.
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    Recent advances in modeling thermodynamic properties of aqueous strong electrolyte systems (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 180-195 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Theoretical and engineering models for the thermodynamic properties of strong electrolyte solutions have advanced significantly since 1985. This progress is notable in the ability to calculate selected properties of single and mixed strong electrolyte solutions over a wide range of temperatures and compositions, including effects of various nonelectrolytes, solvents and supercritical components. Theoretical studies have begun to consider more realistic fundamental interactions between various components in these systems. There have been several successful conversions of theories based on the mean spherical approximation and perturbation methods into engineering equations, without large numbers of empirical parameters. Other theoretical models seem almost ready for application to real systems. The capability to estimate a wide variety of thermodynamic properties accurately with a consistent set of equations and a small number of adjustable parameters has been achieved by several groups over limited temperature and composition ranges. Much work remains to be done, however, to understand completely the interplay and relative importance of various contributing energy effects.
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    Vapor-liquid equilibria of the ternary mixture CH4 + C2H6 + CO2 from molecular simulation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 212-217 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The NpT + test-particle method for the calculation of vapor-liquid equilibria by molecular simulations is extended to ternary mixtures. It is applied to the system methane + ethane + carbon dioxide, for which all binary molecular interaction models are available from previous work. Methane is described as one-center Lennard-Jones fluid, ethane as two-center Lennard-Jones fluid, and carbon dioxide as two-center Lennard-Jones plus point quadrupole fluid. The unlike interactions are treated in the same way as the binary mixtures, using two parameters for each binary interaction. No ternary parameters are introduced. Vapor-liquid phase equilibria are calculated for the ternary mixture at the following temperature-pressure pairs: 233.15 K - 2 MPa; 250.5 K - 2 MPa; and 250.5 K - 3.04 MPa. Comparison of the simulation data with experimental and equation-of-state results shows excellent agreement. Bubble and dew densities are also reported.
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    Recovery and purification of paclitaxel using low-pressure liquid chromatography (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 232-242 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An efficient and economical low-pressure liquid chromatography process has been developed for paclitaxel recovery and purification directly from plant-tissue culture (PTC) broth. PTC broth is first diluted with ethanol to ensure padlitaxel dissolution and then passed through a column packed with a high-capacity polystyrene divinyl-benzene sorbent. A step increase in ethanol concentration in the mobile phase (ethanol:water) is used to concentrate and compress the taxane bands to as high as 29-fold of influent concentrations (about 1 mg/L). A recycle technique is then used to separate the concentrated paclitaxel band from other taxane bands, achieving 95% purity with more than 90% recovery and 99% purity with more than 80% recovery. In this process, the same low-pressure columns are used to capture, concentrate and purify paclitaxel. Theoretical predictions agree closely with the stepwise elution and recycle chromatography data. After validation, simulations are used to explore various design and operating alternatives. Analysis of the alternatives shows that the process cost can be further reduced by using higher feed concentration, larger loading volume, smaller particle size, and optimal gradient and recycle strategies.
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    Phase equilibria for the mean-force potential of globular protein solutions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 218-231 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When polymers are added to a solution containing proteins, the protein may deposit as an amorphous precipitate or as crystals. Experimental evidence indicates that from a thermodynamic viewpoint, an amorphous precipitate should be treated as a liquid phase dense in the protein and crystals as true solids. To understand the conditions under which protein precipitation or crystallization may occur, Gibbs-ensemble Monte Carlo simulation and Gibbs-Duhem integration techniques are used to calculate the liquid-liquid and liquid-solid phase boundaries for protein precipitation induced by polymers. In these simulations, the system is modeled using the pseudo-one-component approximation with an appropriate potential of mean force. The critical point for fluid-fluid phase equilibrium disappears as the attractive part of the mean-force potential becomes very short ranged. The accuracy of the second-order Barker and Henderson perturbation theory is examined by comparing the phase diagram predicted using this method with the simulation results. Perturbation theory is able to predict the general trends observed in the simulations but not with quantitative accuracy. Perturbation theory is then used to examine a broader range of conditions for protein deposition.
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    Influence of particle-size distribution on entrainment solid rate in fluidized bed (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 260-262 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    Simulated moving bed under linear conditions: Experimental vs. calculated results (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 935-945 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simulated moving bed (SMB) was operated for the separation of mixtures of 2-phenyl ethanol and 3-phenyl-1-propanol on columns packed with Zorbax C18 bonded silica, using a 60:40 (v/v) solution of methanol and water as the mobile phase. Series of four or eight columns were used. The experiments were carried out with low concentration mixtures, that is, under linear conditions. Band profiles of both compounds eluted from one of the columns during successive periods after steady state had been reached were recorded, as were the concentration histories at the extract and raffinate ports. These experimental results are compared to those predicted by two models: the linear ideal and the linear equilibrium-dispersive models of chromatography, applied to the SMB separator. These two models give excellent agreement between the experimental profiles and those calculated with the model. As expected, the profiles predicted by the ideal and the equilibrium-dispersive models differ only by the lack of dispersion in the profiles given by the former. The latter model is demonstrated to be a solid, reliable tool for further studies of the SMB design and optimization.
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    Gas holdup in slurry bubble columns: Effect of column diameter and slurry concentrations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 311-316 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To study the influence of particle concentration on the hydrodynamics of bubble-column slurry reactors operating in the heterogeneous flow regime, experiments were carried out in 0.10, 0.19, and 0.38-m-dia. columns using paraffinic oil as the liquid phase and slurry concentrations of up to 36 vol. %. To interpret experimental results a generalization of the “two-phase” model for gas-solid fluid beds was used to describe bubble hydrodynamics. The two phase identified are: a dilute phase consisting of fast-rising large bubbles that traverse the column virtually in plug flow and a dense phase that is identified with the liquid phase along with solid particles and entrained small bubbles. The dense phase suffers backmixing considerably. Dynamic gas disengagement was experimented in the heterogeneous flow regime to determine the gas voidage in dilute and dense phases. Experimental data show that increasing the solid concentration decreases the total gas holdup significantly, but the influence on the dilute-phase gas holdup is small. The dense-phase gas voidage significantly decreases gas holdup due to enhanced coalescene of small bubbles resulting from introduction of particles. The dense-phase gas voidage is practically independent of the column diameter. The dilute-phase gas holdup, on the other hand, decreases with increasing column diameter, and this dependence could be described adequately with a slight modification of the correlation of Krishna and Ellenberger developed for gas-liquid systems.
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    Intraparticle diffusion in hydrogenation of 3-hydroxypropanal (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 475-485 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Strong intraparticle diffusion resistance was observed and the apparent effectiveness factors were measured for the hydrogenation of 3-hydroxypropanal (HPA) to 1,3-propanediol (PD) over Ni/SiO2/Al2O3 catalyst pellets at 45 to 80°C and 2.60 to 5.15 MPa in a stirred reactor with a spinning basket. A mathematical model was proposed to describe the intraparticle diffusion and to estimate the effective diffusion coefficients of HPA, PD and hydrogen under reaction conditions by a maximum likelihood function of the apparent effectiveness factors of HPA and PD. The calculated concentration distributions of HPA, PD and hydrogen in catalyst particles reveal an excess of hydrogen at 80°C and higher temperatures, but an excess of HPA at 45°C. It results in a weak dependence of the consumption formation rate of HPA and PD on the partial pressure of hydrogen at high temperature.
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    Perturbation solution to the convection-diffusion equation with moving fronts (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 631-644 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrophoresis of a solute through a column in which its transport is governed by the convection - diffusion equation is described. Approximate solutions to the convection - diffusion equation in the limit of small diffusion are developed using perturbation methods. The diffusion coefficient and velocity are assumed to be functions of space and time such that both undergo a sudden change from one constant value to another within a thin transition zone that itself translates with a constant velocity. Two cases are considered: (1) the thickness ∊f of the transition zone is negligible compared to the diffusional length scale, so the zone may be treated as a singular boundary across which the diffusion constant and velocity suffer discontinuous changes; (2) the transition zone is considerably wider than the diffusional length scale, so the diffusion coefficient and velocity, although sharply varying, are smooth functions of position and time. A systematic perturbation expansion of the concentration distribution is presented for case 1 in terms of the small parameter ∊ = 1/Pe. A lowest order approximation is given for case 2. A suitably configured system analyzed here can lead to progressive accumulation, or focusing, of the transported solute. The degree of focusing in case 1 scales with ∊-1, whereas in case 2 it scales with (∊f∊)-1/2, and thus increases much more weakly with increasing Pe. A separation based on this concept requires development of materials and devices that allow dynamic tuning of the mass-transport properties of a medium. This would make it possible to achieve progressive focusing and separation of solutes, such as proteins and DNA fragments, in electrophoretic media with an unprecedented degree of control.
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    Continuous drying of a solid wetted with ternary mixtures (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 681-692 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence on drying selectivity of the continuous-contact mode between a solid wetted with ternary mixtures and a gas stream was theoretically studied. The liquid mixtures, ethanol-isopropanol-water and water-ethanol-acetone, were used. A mathematical model describing a gas-phase-controlled process was developed, and the influence of the process variables was studied by simulations. In addition to the inlet composition of the moisture and temperature of the solid, gas composition has the most important effect on selectivity. Small changes of gas composition, either imposed or spontaneous, may modify completely the process trajectory. The extent of these effects depends on the ratio between the flow rates of inlet gas and liquid contained in the solid. Because of their effects on the evolution of temperature and composition, the operating pressure and energy sources other than convection are also useful in controlling the selectivity. Since all these variables determine the composition of the remaining liquid and thereby product quality, their influence should be predictable. The model may be a valuable tool for exploring the process, provided that drying is gas-phase-controlled.
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    Sherwood number for a swarm of adsorbing spheroidal particles at any peclet number (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 844-846 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    Finite-element simulation of mixing: 1. Two-dimensional flow in periodic geometry (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 577-587 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Complex mixing flows and mixing parameters are calculated to evaluate mixing quality on the basis of kinematic parameters together with a statistical analysis. The results allow for a comparative evaluation in terms of geometry and flow parameters. The evaluation is limited to two-dimensional flows with moving boundaries in periodic motion such as the flow in the cross section of a twin-cam mixer. The finite-element calculation requires a remeshing procedure for every time step with special techniques to upgrade mixing variables from one time step to the next. The relative mixing quality of single cam and co: or counterrotating cam devices are compared by evaluating segregation scale, length stretch, and efficiency. The numerical results exhibit a good correspondence with their experimental counterpart.
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    Resonant microwave power absorption in slabs and cylinders (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 615-624 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Resonant power absorption is an important phenomenon during microwave heating. The resonances that occur when plane electromagnetic waves are incident on infinitely long cylinders and slabs are investigated as a function of sample dimensions. For cylinders two kinds of incident waves are studied: TMz when the electric field is oriented along the axis of the cylinder and TEz when the magnetic field is oriented along the axis. At a resonant condition the overage power absorbed by the sample is a local maximum. Due to attenuation within the sample the resonances decrease in intensity as the sample size increases. Using the dielectric properties of water, resonances are found to be a function of the ratio of the sample dimension to the wavelength of radiation, λs, in the sample. For slabs of thickness L and integer values of n, resonances occurred at L/λs = 0.5n; for cylinders of diameter D, resonances occurred at D/λs = 0.5n - 0.257. The generality of these relations to predict resonances in other food samples are shown using existing dielectric data. Resonances in cylinders for both polarizations occurred at similar radii. However, the radius at which the first resonance occurred for the TMz case was absent in the TEz case.
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    Transient behavior of pulsed particulate fluidized beds (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 625-630 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient phenomena in solid-liquid fluidized-bed systems are important in designing pulsed, countercurrent (multistage) fluidized-bed contactors of the Cloete-Streat type at high-solids flow rate. Of particular interest are the residence times or corresponding velocities of porosity gradients in the bed and the excess or overshoot height of the bed after refluidization. Theory assuming local equilibrium between holdup and velocity of the phases (local-equilibrium model) for stepwise perturbations in the liquid flow is readily available. It is investigated whether the local-equilibrium theory can be used for more complex perturbations and whether inertia effects, such as are encountered in countercurrent multistage fluidized-bed systems, can be ignored. Therefore, the detailed particle-bed model of Foscolo and Gibilaro, which incorporates inertia effects, was applied to investigate the transient behavior of fluidized-bed systems. Transient fluidization experiments were performed with a broad range of water-fluidized particles in a laboratory-scale multistage fluidized-bed contactor. The operating conditions corresponded to those for countercurrent contact.Numerical simulations with the particle-bed model predict satisfactory experimental results. The “overshoot” heights of the fluidized bed were estimated correctly by the particle-bed model, whereas the local-equilibrium model only provides a conservative estimate. However, the local-equilibrium model allows an analytical solution that is more interesting for design, as it avoids tedious calculations. The residence time of the last perturbation before the fluidized bed relaxes to steady state was estimated with similar accuracy by both models.
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    Steady spontaneous capillary flow in partially coated tubes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 645-654 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A spontaneous, steady capillary flow is produced for a liquid index in a circular tube that is partially coated with a surface modifier to create a discontinuous wetting condition between upstream and downstream portions of the tube. As a means of demonstrating that the flow configuration may prove useful as a diagnostic tool in studies concerning capillarity and the physics associated with the moving contact line, average steady velocities are predicted and compared against a large experimental data set that includes the effects of tube dimensions and fluid properties. To access a wider range of tube diameters (0.516-9.88 mm), experiments are performed employing “U-tubes” tested in the low-gravity environment of a drop tower, in addition to straight capillary tubes tested horizontally in a laboratory. The sensitivity of the steady capillary flow to surface cleanliness is dramatic.
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    Permeability of filter cakes of palm oil in relation to mechanical expression (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 673-680 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Permeability and compressibility data are required for an adequate process model for compressible-cake filtration and mechanical expression. Experimental and modeling results of the permeability of palm-oil filter cakes (a highly compressible viscoelastic material) are combined with compressibility data, leading to a model for the expression step. Permeability measurements show that permeability depends strongly on the quantity of fine particles in the cake. Removal of fine particles from the slurry before expression significantly increases the solid-phase content during expression due to higher permeability. Modeling results of the expression step show that for palm-oil filter cakes there is a pressure above which the attainable mass fraction of solids becomes independent of pressure. Decrease in specific cake resistance has two effects: a higher mass fraction of solids at the same pressure and a higher pressure at which the mass fraction of solids is not affected further.
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    Modeling and optimization of a semiregenerative catalytic naphtha reformer (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 740-753 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modeling and optimization of a semiregenerative catalytic naphtha reformer has been carried out considering most of its key constituent units. A detailed kinetic scheme involving 35 pseudocomponents connected by a network of 36 reactions in the C5-C10 range was modeled using Hougen-Watson Langmuir-Hinshelwood-type reaction-rate expressions. Deactivation of the catalyst was modeled by including the corresponding equations for coking kinetics. The overall kinetic model was parameterized by bench-marking against industrial plant data using a feed-characterization procedure developed to infer the composition of the chemical species in the feed and reformate from their measured ASTM distillation data. For the initial optimization studies, a constant reactor inlet temperature configuration that would lead to optimum operation over the entire catalyst life cycle was identified. The analysis was extended to study the time-optimal control profiles of decision variables over the run length. In addition, the constant octane case was also studied. The improvement in the objective function achieved in each case was determined. Finally, the sensitivity of the optimal results to uncertainty in reactor-model parameters was evaluated.
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    Microwave heating of the continuous flow catalytic reactor in a nonuniform electric field (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 754-760 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Temperature profiles in the continuous-flow reactor with a fixed bed placed in a nonuniform microwave field are predicted by considering specific on - off regulation of the microwave power and local distribution of the electric-field intensity. The spatial and temperature dependence of the electric-field intensity affects the heating appreciably, as shown by indirect measurements. Results of numerical calculations agree with experimental data of outlet temperature and explain temperature oscillations in the outlet flow. The model developed allows an accurate description of microwave heating in the continuous-flow reactor associated with specific regulation of microwave power. The hydrolysis of sucrose catalyzed by the strongly acidic cation-exchange resin Amberlite 200C in R-H form was chosen as the reaction system. Calculated conversions of sucrose based on predicted temperature profiles agree with experimental data.
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    Oxidative dehydrogenation of butane using membrane reactors (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 777-784 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidative dehydrogenation of butane was studied at temperatures between 450 and 550°C using a conventional fixed-bed reactor and inert membrane catalytic reactors with different feed arrangements. When inert membrane reactors were employed, a ceramic membrane was used to distribute oxygen to a fixed bed of V-Mg-O catalyst. The membrane reactor was found to be more efficient than a fixed-bed reactor under most of the conditions investigated. In addition, in the membrane reactor the formation of hot spots decreased considerably, leading to a more stable and safer operation.
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    Reaction rates in fractal vs. uniform catalysts with linear and nonlinear kinetics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1691-1699 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pore fractal objects are expected to be optimal catalysts, since material is supplied to the narrower pores, which are also shorter through the larger pores where diffusion resistance is smaller. To demonstrate this, diffusion and reaction were simulated on Sierpinski-gasket-type fractal objects and on the corresponding nonfractal uniform-pore structures of the same size, porosity and reactive area. Positive order reactions limited by Knudsen diffusion were shown to exhibit larger rates in fractal than in uniform-pore objects. Fractal catalysts also exhibited a new intermediate domain in which the rate depends only weakly on the kinetics parameters. In nonmonotomic kinetics the branching point (bifurcation point) was extremely sensitive to the pore structure.
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    Electrochemically modulated complexation process for ethylene/ethane separation (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1709-1716 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An electrochemically modulated complexation (EMC) process was designed to selectively extract and concentrate ethylene from a feed-phase mixture with ethane. Unlike previous EMC processes, where the separation was based on equilibrium solubility differences, this separation was based on differences in the rate of complexing with copper(I) solution between the two gases. The EMC process employed flowthrough electrolysis cells that electrochemically modulate aqueous-phase copper chlorides between high, copper(I), and low, copper(II), affinity states. The liquid phase in the high affinity form contracts a feed gas phase in a hollow-fiber membrane module for selective extraction and contacts the receiving gas phase in the low affinity form for concentration. Experimental results and modeling of the process are reported.
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    Synthesis of crystallization-distillation hybrid separation processes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1751-1762 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A systematic method to synthesize crystallization-distillation hybrid separation processes is presented. Two classes of hybrids are identified for binary mixtures. The first bypasses azeotropes and tangent pinches, while the second bypasses eutectics. Guidelines for flow-sheet selection are proposed based on an analysis of simple eutectic, constant relative volatility systems. In addition, the hybrids are compared to both extractive and adductive crystallization in order to determine the conditions under which solvent-based crystallization techniques outperform the proposed hybrid configurations. The method is extended to ternary mixture. The use of stream combination and complex distillation columns is also considered.
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    Dehydrogenation of propane using a packed-bed catalytic membrane reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1819-1827 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a high-temperature catalytic membrane reactor, a plug-flow reactor is combined with a gas-separative membrane. By selectively removing one of the reaction products, the reaction mixture is prevented from reaching equilibrium, and a higher conversion can be obtained. This concept is only valid for reactions that are limited by the thermodynamic equilibrium, such as the direct dehydrogenation of propane to propene. A tubular H2-selective silica membrane was characterized [αH2/C3H8 = 70-90 at 500°C] and used as the gas-separative membrane. The membrane reactor was filled with a chromia/alumina catalyst. The kinetics of the catalyst was studied. At 500°C the deactivation of the catalyst is slow, and the propene yield is almost constant for at least 10 h of operation. Under well-chosen process conditions, the propene yield is at least twice as high as the value obtained at thermodynamic equilibrium in a conventional reactor.
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    Measurement of ultrasonic forces for particle-liquid separations (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1727-1736 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The magnitude and direction of the ultrasonic radiation forces that act on individual particles in a standing-wave field were determined using a microscope-based imaging system. The forces are calculated from measured particle velocities assuming that the drag force, given by Stokes' law, is exactly counterbalanced by the imposed ultrasonic forces. The axial primary radiation force was found to vary sinusoidally with axial position and to be proportional to the local acoustic energy density, as predicted by theory. The magnitude of the transverse primary force was determined by two independent methods to be about 100-fold weaker than the axial force. Separation concepts exploiting the transverse force for cell retention have been successful despite the great disparity in magnitude between the axial and transvers-force components. This may be explained by the reduced hydrodynamic forces on aggregated particles in transverse flow due to their alignment in the sound field.
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    Surfactant effects on absorption in the presence of induced interfacial turbulence (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1909-1913 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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    Improving clay-based tailings disposal: Case study on coal tailings (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1894-1903 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The role of swelling clays in hindering the compressional dewatering characteristics of coal-mine tailings is examined. The effects of electrolyte concentration and ion exchange in improving the shear and compressional rheology are compared. Suspensions studies include actual mine tailings (thickener feed and thickener underflow) as well as synthetic clay dispersions made from clay collected from the coal seam. It was shown that the most important parameter in controlling the properties of the tailings suspension is “controlled” dispersion in the presence of a Ca2+ electrolyte concentration in excess of that required to (1) prevent initial swelling and (2) provide full cation exchange of the clay. Under these electrolyte conditions, complete delamination of the clay did not occur, and both the dewatering and handling characteristics of the resultant suspensions improved dramatically.
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    Spread and rebound of liquid droplets upon impact on flat surfaces (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2169-2179 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The spread and rebound of droplets upon impact on flat surfaces at room temperature were studied over a wide range of impact velocities (0.5-6 m/s), viscosities (1-100 mPa.s), static contact angles (30-120°), droplet sizes (1.5-3.5 mm), and surface roughnesses using a fast-shutter-speed CCD camera. The maximum spread of a droplet upon impact depended strongly on the liquid viscosity and the impact velocity. The tendency of a droplet to deposit or to rebound is determined primarily by the liquid viscosity and the liquid/substrate static contact angle. A model more broadly applicable than existing models was developed to predict maximum spread as a function of the Reynolds number, the Weber number, and the static contact angle. Based on the conservation of energy, a rebound model is proposed that predicts the tendency to rebound as a function of maximum spread and static contact angle.The maximum-spread model prediction agrees to within 10% with more than 90% of the experimental data from different sources. In the current study, the rebound model successfully predicts the tendency of a droplet to rebound.
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    Mass and thermal transport analysis of oscillating flow with absorbent polymers (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2157-2168 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new concept for removing toxic gases with respirator applications based on inhalation and exhalation through absorbent polymer-lined tubes was studied. The two-way oscillatory flow through the respirator element enables capture and expulsion of toxic vapors, which is not feasible with activated charcoal because of the adverse effect of moist breath on the charcoal efficiency. To study the influence of various material, design and operating parameters on the performance of such a respirator, a numerical model that solves the governing equations of mass and heat transport in an oscillatory flow through an absorbent polymer-lined tube was developed and utilized with experimentally measured property data. Factors investigated include respirator element geometry, polymer and toxic vapor characteristics, and flowthrough speed. Results show a large delay in toxic gas penetration over that obtained by conventional one-way flow, and define the importance of partition coefficient, flow passage size, and length and velocity. Results are compared with data from simulated breathing experiments.
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    Analytical description of the Lennard-Jones fluid and its application (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2215-2226 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simplified exponential (SEXP) approximation, combining the exponential approximation and the first-order mean spherical approximation, is proposed to improve the equation of state for the Lennard-Jones (LJ) fluid. The SEXP approximation, which can be implemented in an analytical manner, yields better radial distribution functions of the LJ fluid. Extensive comparisons with two typical perturbation theories show that the SEXP approximation is more appropriate to describe the behaviors of the LJ fluid. The latest 33-parameter modified Benedict-Webb-Rubin equation, also calculated, is inadequate in the region of phase coexistence. The SEXP approximation is applied to the calculation of methane properties with much better results than the Peng-Robinson equation of state for saturated liquid densities and second virial coefficients.
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    Temperature dependence of one-component permeation through a silicalite-1 membrane (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2203-2214 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The one-component steady-state permeation of gases through a silicalite-1 zeolite composite membrane as a function of the temperature is studied from 190 to 680 K for light hydrocarbons, noble gases, and some inorganic gases. In general, with increasing temperature the permeance shows a maximum followed by a minimum. For gases weakly adsorbed the permeance has only a minimum and for gases strongly adsorbed only a maximum is observed in the permeance. The permeance for various gases, for a feed pressure of 101 kPa, span four orders of magnitude. The lowest permeation is for i-butane at 300 K: a permeance of 0.07 × 10-8 mol. m-2.s-1.Pa-1. The highest value is observed for methane: a permeance of 70 × 10-8 mol. m-2.s-1.Pa-1 at about 240 K. A comparison between the isobars and the temperature dependence of the steady-state permeance, both at 101 kPa, shows that at the temperature where the amount adsorbed vanishes the permeance starts to increase. The temperature dependence of the steady-state fluxes through the silicalite-1 membrane can be described only if two diffusion mechanisms are taken into account. For high occupancies the mass transport can be described by equilibrium adsorption followed by surface diffusion and for low occupancies the mass transport can be described by activated gaseous diffusion. With increasing temperature the mass-transport mechanism shifts from the surface diffusion regime to the activated gaseous diffusion regime. With these two diffusivities modeling results agree well with experimental results for the one-component flux through the silicalite-1 zeolite membrane.
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    Masthead (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997) 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431101
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    Gas-filled cavity structures and local void fraction distribution in aerated stirred vessel (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2921-2931 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The local structural function obtained by a microresistivity probe at different hydrodynamic regimes is examined. The structures, such as the vortex-clinging structure, the appearance of one and two large cavities, small 3-3 structure, large 3-3 structure, and ragged cavities were recognized by frequency transformation of the time-domain structural function. An optimized phase discrimination in signal processing was used. The distribution of the local void fraction (α) in a pilot-size stirred tank was experimentally investigated, because almost no such data can be found in the literature. The two-phase mixture was composed of air and water; α was measured at 190 nodes in the vertical half-section plane of the vessel. Relative differences smaller than 9% between integrated values of α and measured gas holdups agreed reasonably well under all conditions.
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    Constrained MPCI: A weak persistent excitation approach (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2279-2288 
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    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Model-predictive control and identification (MPCI) introduced by Genceli and Nikolaou in 1996 is a novel approach to the identification of processes under constrained model-predictive control. MPCI solves an on-line optimization problem that involves (a) a standard MPC objective; (b) standard MPC constraints; and (c) persistent excitation (PE) constraints. The on-line optimization problem is computationally demanding. To alleviate that problem, we take a frequency-domain approach to formulating the PE constraints. This approach relies on the following fact: a signal is persistently exciting of order n, if its two-sided power spectrum is nonzero at no fewer than n points. Therefore, persistently exciting input signals can be parametrized over a finite horizon as a sum of sinusoid terms with nonzero coefficients. Used in the MPCI framework, the last requirement generates a set of completely decoupled reverse-convex constraints that are combinatorially tractable from a computational point of view. The effectiveness of the proposed MPCI method is demonstrated through simulations. For the SISO systems studied, computation of the global optimum could be handled combinatorially in real-time using PC hardware.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430913
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    Electronic Resource
    Design and retrofit of sensor networks in process plants (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2300-2306 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel procedure to find cost-optimal sensor networks is proposed. Cost is minimized subject to qualifying constraints that are related to certain requirements of data reconciliation. One basic qualifying constraint is a desired level of precision of reconciled values for a selected set of variables. Since precision requirements lead to multiple solutions, other qualifying constraints are proposed. These constraints are availability, resilience, and error detectability. Definitions for these terms are given and their impact on the results is presented.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430915
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