To test how environmental conditions in the Arctic and the resulting ecological adaptations affect accumulation of persistent organic pollutants (POPs) in the marine food web, bioaccumulation of four polychlorinated biphenyls (PCBs) in an arctic (Barents Sea 77 °N-82 °N) and a temperate marine (Baltic Sea 54 °N-62 °N) food web were compared. Three different trophic levels were studied (zooplankton, fish, and seal), representing the span from first-level consumer to top predator. Previously published high-quality data on PCB water concentrations in the two areas were used for calculation of bioaccumulation factors (BAF). BAF was calculated as the ratio of the PCB concentration in the organism ([PCB]org; pg/kg lipid) to the dissolved water concentration (Cw; pg/L). The BAFArctic:BAFTemperate ratios were above 1 for all four PCB congeners in zooplankton (6.4-13.8) and planktivorous fish (2.9-5.0)), whereas the ratios were below 1 in seal. The mean ratio between arctic and temperate BAFs for all trophic levels and congeners (BAFArcti:BAFTemperate) was 4.8. When the data were corrected for the seawater temperature difference between the two ecosystems, the ratio was 2.0. We conclude that bioaccumulation differences caused by ecological or physiological adaptations of organisms between the two ecosystems were well within a water concentration variability of 50%. Further, our data support the hypothesis that lower seawater temperature lead to a thermodynamically favoured passive partitioning to organic matrices and thus elevated ambient BAFs in the Arctic compared to the Baltic Sea. This would imply that bioaccumulation in the Arctic may be described in the same way as bioaccumulation in temperate regions, e.g. by the use of mechanistic models parameterised for the Arctic. 相似文献
Porous crystalline TiO2 films can be prepared at low temperatures (80 °C) by surfactant-assisted electrodeposition from TiCl3 solution. Nevertheless, up to now calcination at high temperatures (typically 450 °C) was still necessary to establish a good performance of these films in dye-sensitized solar cells (DSSC). With this study we report that water vapour treatment at much lower temperatures (150 °C) for 1 week improves the performance of the films in DSSC to the same degree as calcination although the overall crystallinity remains lower. Reason for the good efficiency is that the porous structure stays intact and thus the dye molecules can be better adsorbed. Avoiding high temperatures during the preparation process of TiO2 films for the application in DSSC enables the use of polymer substrates for the fabrication of flexible solar cells. 相似文献
The miniaturization of chemical or biochemical analysis systems to micro- or nanoscale dimension allows dramatic acceleration of chemical processes and a high degree of parallelism. In this paper, we present a monolithically integrated application specific lab-on-microchip device (ALM) [1], [2] for on-chip capillary electrophoresis (μ-CE) with an organic light-emitting diode (OLED) as excitation light source and a tunable a-Si:H multispectral photodiode for colorimetric analysis. The purpose of this work is to adapt the spectral response of a tunable multispectral photodiode to individual fluorescence spectra of different dyes. 相似文献
Twenty flours from 16 different barley varieties cultivated in 1990 and 1992, and a Swedish reference flour, were fermented by Lactobacillus plantarum A1 to sour doughs. Barley breads (40% barley/60% wheatflour) from each flour type were baked with and without an admixture of barley sour dough in order to investigate how the sour dough admixture would affect the baking properties. A trained panel carried out sensory evaluation by conventional profiling on breads made from three of the barley varieties and the Swedish reference flour, made with and without sour dough admixture.
The barley varieties influenced both the sour dough properties and the properties of the barley bread. The pH of bread with sour dough ranged from 4.6 to 4.8 as compared to 5.4 to 5.6 in bread without sour dough. The acidity of the breads with sour dough ranged from 4.1 to 5.0 ml NaOH/ 10 g bread crumb as compared to 2.4 to 3.6 in breads without sour dough. In 14 of the twenty bread types an addition of sour dough lowered the bread volume. Breads with a sour dough admixture scored higher for total taste and acidulous taste than breads without sour dough. The β-glucan content of the flours had no significant influence on the sour dough or the sensory characteristics of the bread, except for the breadcrumb colour. 相似文献
Neutron radiography (NR) is compared with the commonly used carrier gas hot extraction (CGHE) technique. We performed isothermal hydrogen effusion experiments at 623 K to study the mass transport kinetics. The investigated material was technical iron. The quantification of the hydrogen mass flow is done for NR by using concentration standards. The temporal hydrogen concentration evolution in the sample coincides well for both methods, i.e. NR and CGHE, and is in good agreement with literature. The advantages of the NR method are the non-destructive nature of measuring and the in-situ determination of hydrogen concentrations with high spatial and temporal resolution. Remaining hydrogen inside the sample can be identified directly by the NR method. 相似文献
Computer-based forensic handwriting analysis requires sophisticated methods for the pre-processing of digitized paper documents,
in order to provide high-quality digitized handwriting, which represents the original handwritten product as accurately as
possible. Due to the requirement of processing a huge amount of different document types, neither a standardized queue of
processing stages, fixed parameter sets nor fixed image operations are qualified for such pre-processing methods. Thus, we
present an open layered framework that covers adaptation abilities at the parameter, operator, and algorithm levels. Moreover,
an embedded module, which uses genetic programming, might generate specific filters for background removal on-the-fly. The
framework is understood as an assistance system for forensic handwriting experts and has been in use by the Bundeskriminalamt,
the federal police bureau in Germany, for two years. In the following, the layered framework will be presented, fundamental
document-independent filters for textured, homogeneous background removal and for foreground removal will be described, as
well as aspects of the implementation. Results of the framework-application will also be given.
Received July 12, 2000 / Revised October 13, 2000 相似文献
Type II diabetes mellitus (T2DM) is associated with β‐cell failure, which correlates with the formation of pancreatic islet amyloid deposits. The human islet amyloid polypeptide (hIAPP) is the major component of islet amyloid and undergoes structural changes followed by self‐association and pathological tissue deposition during aggregation in T2DM. There is clear evidence that the aggregation process is accelerated in the presence of particular lipid membranes. Whereas hIAPP aggregation has been extensively studied in homogeneous model membrane systems, especially negatively charged lipid bilayers, information on the interaction of hIAPP with heterogeneous model raft membranes has been missing until now. In the present study, we focus on the principles of aggregation and amyloid formation of hIAPP in the presence of model raft membranes. Time‐lapse tapping mode AFM and confocal fluorescence microscopy experiments followed membrane permeabilization and localization of hIAPP in the raft membrane. Together with the ThT and WST‐1 assay, the data revealed elevated cytotoxicity of hIAPP oligomers on INS‐1E cells.相似文献
In the cheese industry, the concentration of milk using ultrafiltration for continuous soft and fresh cheese production is standard technology. The object of the work presented here was to produce a semi-hard cheese of quality and composition comparable to that of traditionally made cheese from highly concentrated microfiltered milk retentate. Two different membrane systems were tested for the production of high viscous milk retentate with high dry matter content. For milk containing 3.2% fat and skim milk, a concentration factor of 6.6 and 9.1 respectively was obtained using the MF/UF/UF pilot plant fitted with cassette modules. Milk containing 3.2% fat was concentrated in batches by a factor of 5.7 in the pilot plant using a ceramic membrane. Using minimal curd separation, a semi-hard one day old cheese with a dry matter of 533 g/kg, moisture on a fat-free basis (MFFB) of 626 g/kg and fat on a dry basis (FDB) value of 478 g/kg was made from the milk retentate produced with the ceramic module. The ripened cheese fulfilled the legal requirements of a traditionally produced semi-hard cheese with superb sensory qualities. Using the MF/UF/UF plant, a dry matter of 495 g/kg (MFFB 669 g/kg, FDB 493 g/kg) was achieved in a semi-hard cheese made from skim milk retentate. Our results suggest that by using a larger spacer distance in the last loop of the MF/UF/UF plant, combined with new hybrid technologies, semi-hard cheese production from full concentrate milk will soon become possible. 相似文献