Bestimmung von Phthals?ureestern in Lebensmitteln, Frauenmilch, Hausstaub und Textilien

Zusammenfassung  Es wurden 25 Lebensmittel-, 5 Frauenmilch-, 4 Staub- und 16 Textilproben auf Phthals?ureester untersucht. In allen Proben waren Phthalate nachweisbar, wobei Di(2-ethylhexyl)phthalat (DEHP) und Di-n-butylphthalat (DBP) am h?ufigsten gefunden wurden. In Rohmilchproben lagen die Gesamtphthalat-Konzentrationen im Mittel bei 0,1 mg/kg. Konsummilch wies keine h?here Belastung als Rohmilch auf, auch die Lagerung von Milchproben bis zum Ablauf des Mindesthaltbarkeitsdatums führte nicht zu h?heren Gehalten. Fettarme Milch war weniger belaster als Vollmilch. Die in Sahneproben gefundenen h?heren DEHP-sowie Gesamptphthalatgehalte lassen sich durch den h?heren Fettgehalt erkl?ren. Mit Konzentrationen von bis zu 1,54 mg/kg zeigten gemahlene Haselnüsse, Mandeln und Muskatnüsse, die in Kunststofffolie verpackt waren, eine vergleichsweise hohe Belastung. In S?uglingsnahrung waren nur Spuren von DEHP und DBP zu finden, weitete Phthals?ureester konnten nicht nachgewiesen werden. Auch die Frauenmilchproben wiesen nur geringe Gehalte von ca. 0,1 mg/kg auf, eine Akkumulation der Phthalester im menschlichen K?rper scheint also nicht stattzufinden. Au?ergew?hnlich hohe Konzentrationen wurden in Staubproben gefunden; die Werte lagen zwischen 300 und 5370 mg/kg Staub, wobei DEHP die Hauptkomponente darstellte. Die Belastung des Staubes l?sst auf eine erhebliche Bedeutung des Luftpfades beim Transfer der Phthals?ureester schlie?en. Da Staub erhebliche Anteile an Textilfasern enth?lt, wurden auch Textilien untersucht. Die Phthals?ureester-Gehalte in den Textilproben reichten von 3,42 bis 34,44 mg/kg. Die hohen Phthalester-Kontaminationen des Staubes k?nnen daher nicht durch Textilfasern erkl?rt werden. Online-Publikation: 07. Februar 2000     

微重力下燃烧温度随重力变化实验数据处理的一种方法

本文通过试验飞机抛物线飞行进行了微重力燃烧实验,采集得到数组从超重到微重段一个采样点燃烧温度随重力变化的数据,以此为基础通过应用误差理论对实验数据进行了分析处理,然后采用神经网络方法拟合出了燃烧温度随重力的变化曲线,为微重力燃烧实验数据处理提供了一种新方法.     

Disturbance cues in freshwater prey fishes: do juvenile convict cichlids and rainbow trout respond to ammonium as an ‘early warning’ signal?

Summary.  Several freshwater invertebrate and vertebrate prey species rely on chemosensory cues, including non-injury released disturbance cues, to assess and avoid local predation threats. The prevailing hypothesis is that a pulse of ammonia released by disturbed or stressed prey functions as the disturbance cue. Here, we test this hypothesis in two phylogenetically distant freshwater prey fishes, convict cichlids and rainbow trout. In our first experiment, we measured NH₄ ⁺ concentration in tanks containing shoals of cichlid or trout before and after exposure to a realistic model predator (or left undisturbed). We failed to find an increase in ambient NH₄ ⁺ concentration for either cichlids or trout. In our second experiment, we exposed cichlids or trout to NH₄ ⁺ at 0.1 or 0.5 mg L⁻¹ (or a distilled water control) and measured the change in antipredator behaviour (time moving, foraging rate and area use). We found no consistent increase in antipredator behaviour in response to NH₄ ⁺. In our third study, we exposed cichlids and trout to the disturbance cues of cichlids or trout (versus the odour of undisturbed donors). We found significant increases in antipredator behaviour, regardless of donor species, for both cichlids and trout. Thus, the results of our first two experiments do not support the hypothesis that ammonium functions as a disturbance cue in prey fishes. However, the results of our final experiment do confirm the use of disturbance cues in convict cichlids and rainbow trout and support that hypothesis that the disturbance cue is indeed some generalized metabolic byproduct.     

Biologically active secondary metabolites in white clover (Trifolium repens L.) – a review focusing on contents in the plant, plant–pest interactions and transformation

Summary.  To exploit biologically active compounds from white clover (Trifolium repens L.) for suppressing weeds and soil-borne diseases, either as isolated products (biopesticides) or through cultivars with enhanced production of these compounds, the biologically active compounds must be identified, plant content measured, and their fate in soil known. The present review summarizes the published knowledge needed for such exploitation; providing essential information on structure and concentration of flavonols, flavones, condensed tannins, isoflavones, isoflavanones, pterocarpans, coumestans, cyanogenic glucosides, and saponins in healthy and stressed white clover plants. Various stresses and particular cultivars affect the concentrations of several of the compounds. Information on biological effects and the degradation/transformation of these compounds in plants or by microorganisms is available. There is no information on the degradation pathway in soil, the mechanisms of exudation and leaching of compounds from plants, and soil sorption properties of the compounds. The clover soil fatigue problem is increasing in grasslands and causes problems especially in organic farming. Research efforts focused on biological elements of clover soil fatigue have not explained it, and the influence of secondary metabolites has not been investigated. There are few investigations into the interaction between beneficial fungi/fungal-diseases and the occurrence of biologically active secondary metabolites in white clover plants. Such studies are critical to better understand beneficial fungi and pathogens.     

天然林林龄的模拟估算及案例

林龄是森林生态系统的一个重要特征,具有生态学意义.但是目前生态学调查中对天然林林龄的估算方法有一定缺陷.在特定的环境条件下,森林有着相应的演替过程.已有林窗研究表明.长白山森林是按照一定次序演替,森林的径级结构也是有规律可循的.由于总是缺乏足够的长期系统观测数据,因此作者采用数值模拟作为替代方法.应用校正过的林窗模型模拟0～600 a的森林演替序列,比较对长白山原始天然林的采样的结果,发现目前的林龄最接近400 a.这个估测结果可以从本地区历史资料记载得到印证.     

Safe storage of selected fuels with regard to their tendency to spontaneous combustion

European standard EN 15188 is dedicated to the assessment of the tendency of solid flammable substances to spontaneous combustion. Fossil fuels and biofuels that substitute them are a frequent reason of fires caused by spontaneous combustion. Even though having different properties, both types of fuels can be assessed according to this standard by the method of the determination of the dependency of self-ignition temperature against the ratio of volume to surface area of geometrically exactly defined solid body, or based on the theory of thermal explosion according to Frank-Kamenetskii. The comparison of calculated values confirmed the agreement of both methods results, and the tendency of fuels to spontaneous combustion can be assessed by them.     

Effect of temperature on bacterial emissions in composting of swine manure

Swine manure was subjected to laboratory scale composting in order to quantify bioaerosols, i.e., airborne culturable bacteria and endotoxin, in the exhaust gas, which provided details on the effect of temperature on bacterial emissions. The concentration of airborne bacteria reached 31,250 colony-forming units (CFU)/m³ during the thermophilic stage of composting, and positively correlated with the temperature profile of the compost pile. Initially, the endotoxin concentration was 1820 endotoxin units (EU)/m³, but it decreased exponentially as the composting process proceeded. The temperature can be an excellent indicator of bacterial emissions during the composting process, indicating that the composting process requires a consistently high temperature to ensure sanitization of both compost and bacterial emissions. The cumulative emission data showed that emission factors was 11.2?13.5 CFU/g dry swine manure and that of endotoxin was 0.5?0.9 EU/g dry swine manure. The bacterial diversity in the bioaerosol was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis, revealing the presence of various gram-negative bacterial consortia.     

Numerical analysis of keyhole geometry and temperature profiles in plasma arc welding

In keyhole plasma arc welding (PAW), the formation of the keyhole involves complicated thermo-physical mechanism. The shape and dimensions of the keyhole directly determine the heat deposition along the thickness direction of the test plates, the penetration depth and the weld bead quality. Based on analysis of the forces acting on the weld pool, a keyhole model is established according to the force-balance condition on the keyhole wall. The shape and dimensions of quasi-steady state keyhole are numerically predicted. The keyhole shape and size are used to calibrate some distribution parameters of the combined volumetric heat source which takes into consideration the geometrical feature of welds with larger ratio of penetration depth to width and volumetric distribution characteristic of the plasma heat intensity along the plate thickness direction. The temperature fields on stainless steel plates are numerically simulated. The calculated fusion line at the transverse cross-section of PAW welds are compared with the experimental measurements. It is found that the predicted results are in agreement with the experimental data.     

Seasonal dependency of controlling factors on the phytoplankton production in Taihu Lake, China

In this study, 44 profiles of gross primary productivity(GPP) and sunlight, along with water temperature, Chlorophyll-a(Chla) and nutrients, were observed in Meiliang Bay of Taihu Lake, China, in the spring, summer, and fall seasons. Effects of water temperature, light,and nutrient concentration were examined in relation to the GPP-unit-Chla(GPP of algae per Chla). The results showed that the optimum temperature for the GPP of phytoplankton was 27.9°C, the optimal PNA-unit-Chla(photon number absorbed by phytoplankton per Chla) was 0.25(mol), and the HSCN-unit-Chla and HSCP-unit-Chla(half-saturation constants of nitrogen and phosphorus of algae per Chla) were 0.005(mg/L) and 0.0004(mg/L), respectively. The seasonal dependency of the effect of different factors on the GPP was analyzed. Compared with temperature and nutrients, light was found to be the most important factor affecting the GPP during the three seasons. The effect of temperature and nutrients on the GPP of phytoplankton has obvious seasonal change. In spring, temperature was the secondary factor affecting the GPP of phytoplankton, and the effect of nutrients may be negligible in the eutrophic lake on account of temperature limit, which showed that the GPP of algae was only affected by the physical process. In summer and fall, temperature didn't affect the GPP of algae, and the presence of nutrients was the secondary factor affecting the GPP of phytoplankton. From summer to fall, effect of phosphorus was weakened and effect of nitrogen was enhanced.     

Fabrication of mesoporous lignin-based biosorbent from rice straw and its application for heavy-metal-ion removal

Lignocellulosic biomass offers the most abundant renewable resource in replacing traditional fossil resources. However, it is still a major challenge to directly convert the lignin component into value-added materials. The availability of plentiful hydroxyl groups in lignin macromolecules and its unique three-dimensional structure make it an ideal precursor for mesoporous biosorbents. In this work, we reported an environmentally friendly and economically feasible method for the fabrication of mesoporous lignin-based biosorbent (MLBB) from lignocellulosic biomass through a SO₃ micro-thermal-explosion process, as a byproduct of microcrystalline cellulose. BET analysis reveal the average pore-size distribution of 5.50 nm, the average pore value of 0.35 cm³/g, and the specific surface area of 186 m²/g. The physicochemical properties of MLBB were studied by fourier transform infrared spectroscopy (FTIR), attenuated-total-reflection fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and element analysis. These results showed that there are large amounts of sulfonic functional groups existing on the surface of this biosorbent. Pb(II) was used as a model heavy-metal-ion to demonstrate the technical feasibility for heavy-metal-ion removal. Considering that lignocellulosic biomass is a naturally abundant and renewable resource and SO₃ micro-thermal-explosion is a proven technique, this biosorbent can be easily produced at large scale and become a sustainable and reliable resource for wastewater treatment.