Showing papers by "Wageningen University and Research Centre published in 1995"

Flavonoid intake and long-term risk of coronary heart disease and cancer in the seven countries study.

Abstract: Objective: To determine whether flavonoid intake explains differences in mortality rates from chronic diseases between populations. Design: Cross-cultural correlation study. Setting/Participants: Sixteen cohorts of the Seven Countries Study in whom flavonoid intake at baseline around 1960 was estimated by flavonoid analysis of equivalent food composites that represented the average diet in the cohorts. Main Outcome Measures: Mortality from coronary heart disease, cancer (various sites), and all causes in the 16 cohorts after 25 years of follow-up. Results: Average intake of antioxidant flavonoids was inversely associated with mortality from coronary heart disease and explained about 25% of the variance in coronary heart disease rates in the 16 cohorts. In multivariate analysis, intake of saturated fat (73%;P=.0001), flavonoid intake (8%;P=.01), and percentage of smokers per cohort (9%;P=.03) explained together, independent of intake of alcohol and antioxidant vitamins, 90% of the variance in coronary heart disease rates. Flavonoid intake was not independently associated with mortality from other causes. Conclusions: Average flavonoid intake may partly contribute to differences in coronary heart disease mortality across populations, but it does not seem to be an important determinant of cancer mortality. (Arch Intern Med. 1995;155:381-386)

Anaerobic digestion and wastewater treatment systems

Abstract: Upflow Anaerobic Sludge Bed (UASB) wastewater (pre-)treatment systems represent a proven sustainable technology for a wide range of very different industrial effluents, including those containing toxic/inhibitory compounds. The process is also feasible for treatment of domestic wastewater with temperatures as low as 14-16 degrees C and likely even lower. Compared to conventional aerobic treatment systems the anaerobic treatment process merely offers advantages. This especially is true for the rate of start-up. The available insight in anaerobic sludge immobilization (i.e. granulation) and growth of granular anaerobic sludge in many respects suffices for practice. In anaerobic treatment the immobilization of balanced microbial communities is essential, because the concentration of intermediates then can be kept sufficiently low. So far ignored factors like the death and decay rate of organisms are of eminent importance for the quality of immobilized anaerobic sludge. Taking these factors into account, it can be shown that there does not exist any need for 'phase separation' when treating non- or slightly acidified wastewaters. Phase separation even is detrimental in case the acidogenic organisms are not removed from the effluent of the acidogenic reactor, because they deteriorate the settleability of granular sludge and also negatively affect the formation and growth of granular sludge. The growing insight in the role of factors like nutrients and trace elements, the effect of metabolic intermediates and end products opens excellent prospects for process control, e.g. for the anaerobic treatment of wastewaters containing mainly methanol. Anaerobic wastewater treatment can also profitably be applied in the thermophilic and psychrophilic temperature range. Moreover, thermophilic anaerobic sludge can be used under mesophilic conditions. The Expanded Granular Sludge Bed (EGSB) system particularly offers big practical potentials, e.g. for very low strength wastewaters (COD << 1 g/l) and at temperatures as low as 10 degrees C. In EGSB-systems virtually all the retained sludge is employed, while compared to UASB-systems also a substantially bigger fraction of the immobilized organisms (inside the granules) participates in the process, because an extraordinary high substrate affinity prevails in these systems. It looks necessary to reconsider theories for mass transfer in immobilized anaerobic biomass. Instead of phasing the digestion process, staging of the anaerobic reactors should be applied. In this way mixing up of the sludge can be significantly reduced and a plug flow is promoted. A staged process will provide a higher treatment efficiency and a higher process stability. This especially applies for thermophilic systems.

Enhanced biodegradation of aromatic pollutants in cocultures of anaerobic and aerobic bacterial consortia

Abstract: Toxic aromatic pollutants, concentrated in industrial wastes and contaminated sites, can potentially be eliminated by low cost bioremediation systems. Most commonly, the goal of these treatment systems is directed at providing optimum environmental conditions for the mineralization of the pollutants by naturally occurring microflora. Electrophilic aromatic pollutants with multiple chloro, nitro and azo groups have proven to be persistent to biodegradation by aerobic bacteria. These compounds are readily reduced by anaerobic consortia to lower chlorinated aromatics or aromatic amines but are not mineralized further. The reduction increases the susceptibility of the aromatic molecule for oxygenolytic attack. Sequencing anaerobic and aerobic biotreatment steps provide enhanced mineralization of many electrophilic aromatic pollutants. The combined activity of anaerobic and aerobic bacteria can also be obtained in a single treatment step if the bacteria are immobilized in particulate matrices (e.g. biofilm, soil aggregate, etc.). Due to the rapid uptake of oxygen by aerobes and facultative bacteria compared to the slow diffusion of oxygen, oxygen penetration into active biofilms seldom exceeds several hundred micrometers. The anaerobic microniches established inside the biofilms can be applied to the reduction of electron withdrawing functional groups in order to prepare recalcitrant aromatic compounds for further mineralization in the aerobic outer layer of the biofilm. Aside from mineralization, polyhydroxylated and chlorinated phenols as well as nitroaromatics and aromatic amines are susceptible to polymerization in aerobic environments. Consequently, an alternative approach for bioremediation systems can be directed towards incorporating these aromatic pollutants into detoxified humic-like substances. The activation of aromatic pollutants for polymerization can potentially be encouraged by an anaerobic pretreatment step prior to oxidation. Anaerobic bacteria can modify aromatic pollutants by demethylating methoxy groups and reducing nitro groups. The resulting phenols and aromatic amines are readily polymerized in a subsequent aerobic step.

Biological sulphide oxidation in a fed‐batch reactor

Abstract: This study shows that, in a sulphide-oxidizing bioreactor with a mixed culture of Thiobacilli, the formation of sulphur and sulphate as end-products from the oxidation of sulphide can be controiledinstantaneously and reversibiy by the amount of oxygen supplied. It was found that at sulphide loading rates of up to 2.33 mmol7/L . h, both products can be formed already at oxygen concentrations below 0.1 mg/L. Because the microorganisms tend to form sulphate rather than forming sulphur, the oxygen concentration is not appropriate to optimize the sulphur production. Within less than 2 h, the system can be switched reversibly from sulphur to sulphate formation by adjusting the oxygen flow. This is below the minimum doubling time (2.85 h) of, e.g., Thiobacillus neapolitanus and Thiobacillus 0,(18) which indicates that one metabolic type of organism can probably perform both reactions. Under highly oxygen-limited circumstances, that is, at an oxygen/sulphide consumption ratio below 0.7 mol . h(-1) mol . h(-1) thiosulphate is abundantly formed. Because the chemical sulphide oxidation results mainly in the formation of thiosulphate, it is concluded that, under these circumstances, the biological oxidation capacity of the system is lower than the chemical oxidation capacity. The oxidation rate of the chemical sulphide oxidation can be described by a first-order process (k =-0.87 h(-1)).(c) 1995 John Wiley & Sons, Inc.

Spirometric reference values for white European children and adolescents: Polgar revisited.

Abstract: We analyzed six spirometric data sets collected in the Netherlands, Austria, the United Kingdom, Spain, and Italy. The objectives were to establish whether (1) it was possible to describe spirometric indices from childhood to adulthood, taking into account the adolescent growth spurt, and (2) there are systematic differences in ventilatory function between children and adolescents in different parts of Western Europe. The study comprised 2,269 girls and 3,592 boys, aged 6–21 years. The range in standing height was 110–185 in girls, 110–205 in boys. The model applicable to all data sets was In FVC or In FEV1 = a + (b + c · A)· H, where H = standing height and A = age; this model prevents the phase shift between the adolescent growth spurt in length and lung volume from leading to an age-dependent bias in predicted values. There was surprising agreement between most of the data sets; systematic differences are probably due to technical factors arising from ATPS-BTPS corrections and from defining the end of breath with pneumotachometer systems. Taking those into account, prediction equations for FVC, FEV1, and FEV1%FVC were developed with “lower limits of normal” which should be applicable to children and adolescents of European descent. It is proposed that the approach of analyzing available data sets should also be applied to other ventilatory indices, data collected in adults and elderly subjects, or in other ethnic groups, and that an international data base be set up to that end. © 1995 Wiley-Liss, Inc.

Toxicity of N-substituted aromatics to acetoclastic methanogenic activity in granular sludge.

Abstract: N-substituted aromatics are important priority pollutants entering the environment primarily through anthropogenic activities associated with the industrial production of dyes, explosives, pesticides, and pharmaceuticals. Anaerobic treatment of wastewaters discharged by these industries could potentially be problematical as a result of the high toxicity of N-substituted aromatics. The objective of this study was to examine the structure-toxicity relationships of N-substituted aromatic compounds to acetoclastic methanogenic bacteria. The toxicity was assayed in serum flasks by measuring methane production in granular sludge. Unacclimated cultures were used to minimize the biotransformation of the toxic organic chemicals during the test. The nature and the degree of the aromatic substitution were observed to have a profound effect on the toxicity of the test compound. Nitroaromatic compounds were, on the average, over 500-fold more toxic than their corresponding aromatic amines. Considering the facile reduction of nitro groups by anaerobic microorganisms, a dramatic detoxification of nitroaromatics towards methanogens can be expected to occur during anaerobic wastewater treatment. While the toxicity exerted by the N-substituted aromatic compounds was closely correlated with compound apolarity (log P), it was observed that at any given log P, N-substituted phenols had a toxicity that was 2 orders of magnitude higher than that of chlorophenols and alkylphenols. This indicates that toxicity due to the chemical reactivity of nitroaromatics is much more important than partitioning effects in bacterial membranes.

Self-Organization of Amphiphilic Porphyrins at the Air-Water-Interface

Abstract: The Langmuir-Blodgett film forming properties of a series of pyridyl((hexadecyloxy)phenyl)porphyrins have been examined. Good monolayers of these compounds have been prepared in most cases without the use of matrix molecules and the monolayers are readily transferable to glassy slides. The small mean molecular areas, as obtained from the surface-pressure-area isotherms, indicate a tilted orientation of the porphyrin rings with respect to the water surface. It was found by means of UV-vis absorption spectroscopy at the air-water interface and by Brewster angle microscopy that intermolecular interaction between porphyrin rings mutually directs the organization at submonolayer coverage. Upon compression, the self-assembled domains come into close contact without reorganization of the layer structure. It was also demonstrated that porphyrins with three and four aliphatic side chains self-assembled into a highly-ordered arrangement in contrast to the porphyrins with one and two alkyl chains. 28 refs., 5 figs., 2 tabs.

Steroid Hormones Stimulate Germination and Tube Growth of in Vitro Matured Tobacco Pollen.

Abstract: A study of the effects of different steroids on germination and tube growth of tobacco pollen (Nicotiana tabacum L. cv Petit Havana SR1) matured in vitro is presented. Application of the mammalian steroid sex hormones (testosterone, progesterone, and estradiol) resulted in a stimulation of pollen germination and tube elongation. The presence of both steroids and flavonols in the germination medium strongly enhanced the growth of tobacco male gametophytes.

Ozone chemistry changes in the troposphere and consequent radiative forcing of climate.

Abstract: A global three-dimensional transport/chemistry model of the troposphere has been applied to simulate changes in the chemical composition of the troposphere since pre-industrial times. Calculated increases of tropospheric O3 have been evaluated with a radiative transfer model. Our calculations confirm earlier studies that the combined effects of anthropogenic NOx, CO and CH4 emissions cause a strong enhancement of O3 levels throughout the global troposphere, while this blend of emissions does not seem to have affected global average OH concentrations significantly. In fact, anthropogenic NOx induced photochemistry may have compensated for the strong OH reduction which would have resulted from anthropogenic CO and CH4 emissions alone. Our model simulations suggest that during the past 1.5 Century net photochemical 03 formation in the global troposphere has changed sign, from -87 Tg/yr to 427 Tg/yr, caused mostly by anthropogenic emissions in the mid- latitude northern hemisphere and to a lesser extent by biomass burning emissions in the tropics. We calculate that the global O3 burden in the troposphere has increased by a factor of 1.7, the CO burden by a factor of 2.5 and that of H2O2 by a factor of 2. Preliminary calculations suggest that the global mean radiative forcing of climate by increasing tropospheric O3 is 0.55 W/m2 for the month July, maximizing in the mid-latitude northern hemisphere, and 0.44 W/m2 for January; the annual average, about 0.5 W/m2, is approximately one third of the radiative forcing by increasing CO2.

Quantifying Economic Benefits of Sow-Herd Management Information Systems Using Panel Data

Abstract: Economic benefits of management information systems (MIS) in sow farming were quantified by combining data from two survey studies. Panel analysis was conducted through estimation of a mixed-effects model by ordinary least-squares. Effects were analyzed both within farms and over farms at the same time, controlling for self-selection bias and changes over time. Adjusted for other effects in the model, production on farms adopting MIS increased by 0.56 piglets per sow per year, indicating a return on investment of between 220% and 348%. Additional tests and checks indicate that this outcome is robust.

Oxidation of anthracene in water-solvent mixtures by the white rot fungus, Bjerkandera sp. strain BOS55.

Abstract: Polycyclic aromatic hydrocarbons (PAH) are persistent priority pollutants of soil and sediments. The use of white-rot fungi has been proposed as a means of bioremediating PAH-polluted sites. However, higher PAH compounds of low bioavailability in polluted soil are biodegraded slowly. In order to enhance their bioavailability, PAH solubilization, can be increased in water/solvent mixtures. The oxidation of a model PAH compound, anthracene, in the presence of cosolvents by the white-rot fungus, Bjerkandera sp. strain BOS55 was investigated. Acetone and ethanol at 5% were toxic to this fungus when added at the time of inoculation. However, when solvents up to 20% (v/v) were added to 9-day-old cultures, ligninolytic activity as indicated by Poly R-478 dye decolorization and anthracene oxidation was evident for several days. Since 20% solvent was toxic to cells, the oxidation of anthracene can be attributed to extracellular peroxidases, which were shown to tolerate the solvent. Solvent additions of 11%–21% (v/v) acetone or ethanol increased the rate of anthracene bioconversion to anthraquinone in liquid medium by a factor of 2–3 compared to fungal cultures receiving 1%–3% solvent.

The effects of local stiffness disparity on the surface segregation from binary polymer blends

Abstract: The surface segregation from free space polymer blends based on purely entropic effects is investigated using computer simulation and integral equation theory. Computer simulations are performed for tangent‐hard‐sphere chains of length ranging from short 10 bead chains to experimentally realistic 500 bead chains. The chain segments of one species experience a bending potential which is introduced between any two consecutive bonds and this serves to make this component stiffer than the other blend component. Computer simulations and numerical wall polymer reference interaction site model (wall‐PRISM) integral equation calculations for finite hard core athermal chains demonstrate that at liquidlike densities the segments of the stiffer polymer always partition to a neutral surface, apparently independent of the length of the polymer chains in question. Although the primary factor affecting this segregation is the better local packing of the stiff chains at the surface, lattice mean‐field calculations sugges...

Information Technology, Competition and Market Transformations: Re-engineering the Dutch Flower Auctions

Abstract: The Dutch flower auctions have played a critical role in the world cut-flower industry by providing efficient centers for price determination and transactions of flowers between buyers and sellers. These auctions owned by Dutch cut-flower grower cooperatives have traditionally used the A¢Â€ÂœDutch auctionA¢Â€Â as the mechanism for price determination. This paper considers how changing patters of international competition, buyer preferences and information technology are likely to effect the organization of the Dutch flower auction. We provide a framework for analyzing the merits of different transaction models and use this framework to evaluate the strengths and weaknesses of existing and proposed electronic auction models for trading flowers. We propose information technology will enable new forms of trading that will partly replace and supplement the traditional Dutch auction as a method of organizing price determination and transactions. We identify how electronic trading will differ from prior mechanisms, and consider key challenges to the implementation of new auction models. Specifically we illustrate how the current auctions have been structured to serve the interests of growers, while electronic markets will primarily benefit buyers. Thus we highlight the importance of altering incentive and ownership structures in the Dutch flower industry to effectively transition to new electronic markets. This case illustrates the various complex issues that arise in the design and implementation of electronic markets, in settings characterized by changing technologies, pre-existing organizational processes and power structures.