Predicting degradability parameters of diets for ruminants using regressions on chemical components

BACKGROUND: Dry matter degradability (DMD) parameters (a, b and c in the Ørskov and McDonald model) are usually determined by the nylon bag technique. The aim of this study was to estimate DMD parameters of ruminant mixed diets, which are in general unavailable, through multiple linear regressions on their chemical composition (ash, crude protein, neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL)). The regressions were based on data from 77 feeds. RESULTS: The prediction model for a was reduced to a simple linear regression on NDF (adjusted R² = 0.727, F test P < 0.001). A regression model for b was obtained with ADL as the sole predictor (adjusted R² = 0.691, P < 0.001). The model's upper asymptote (a + b) was predicted from ADL, NDF and ash (adjusted R² = 0.908, P < 0.001). Modelling c proved more difficult (adjusted R² with all five predictors = 0.481, P < 0.001). CONCLUSION: Regressing model parameters on feed chemical composition is a promising method for estimating the degradability of mixed diets, providing an alternative to invasive and expensive laboratory techniques. Copyright © 2010 Society of Chemical Industry     

Effect-directed analysis of Ah receptor-mediated activities caused by PAHs in suspended particulate matter sampled in flood events

Suspended particulate matter (SPM) sampled during a flood event in the year 2004 at the rivers Neckar and Rhine (Southwest Germany) was assessed for aryl hydrocarbon receptor (AhR)-mediated activities using EROD induction in the rainbow trout liver cell line RTL-W1. All EROD inductions were normalized to the positive control TCDD and given as bio-TEQ values. Since all samples indicated elevated AhR-mediated toxicities, an effect-directed analysis (EDA) was applied to identify substances causing the effects. In three primary fractions (F1 to F3) non-polar aliphatics, non-polar aromatic substances and more polar substances were separated. Fraction F2, co-eluting with non-polar polyaromatic substances (PACs) including polycyclic aromatic hydrocarbons (PAHs) gave highest AhR-agonistic effects and, thus, were sub-fractionated into seven secondary fractions (F2-1 to F2-7). Fraction F2-1, co-eluting with PCBs and PCDD/Fs, did not cause AhR-agonist activities. F2-2 to F2-4 containing PACs of less than 16 aromatic C-atoms produced minor activities. Highest inductions were detected with fraction F2-5 to F2-7, containing substances of more than 16 aromatic C-atoms (bio-TEQs up to approximately 4500 pg/g).Concentrations and relative potencies (REPs) of priority EPA-PAHs allowed the calculation of chemical toxicity equivalent concentrations (chem-TEQ values). Based on the chem-TEQs, EPA-PAHs explained between 5 and 58% of crude extract bio-TEQs from both rivers. Whereas fractions F2-1 to F2-4 indicated no biological activities, EPA-PAHs in fraction F2-5 to F2-7 accounted for 2 to 137% of AhR-related activities.     

1227两种测定方法的对比和分析

通过实验对测定十二烷基二甲基苄基氯化铵活性物含量的两种方法进行了比较和分析。结果表明,两种测定方法无显著性差异,都适用于检测常规产品。其中四苯硼钠滴定法(HG/T 2230—2006))由于液相容易有结块挂壁现象,使测定值偏低,受温度影响变化大,不适于检测高含量加防冻剂的产品,但其精密度较好。四苯硼钠两相滴定法(QB 1915—1913)抗干扰能力强,适用范围广,但要注意观察终点的判断。     

LotusNotes邮件群件系统规划初探

列举了 Ｌｏｔｕｓ Ｎｏｔｅｓ邮件群件系统规划过程中需要注意的若干重要环节，并对该系统的网络拓扑结构以及命名网络规划的原则做了进一步的分析和探讨。     

Historic brownfields and industrial activity in Kingston, Ontario: Assessing potential contributions to mercury contamination in sediment of the Cataraqui River

The waterfront of historic Kingston, Ontario (pop: 113,000) has been used for industrial activities for over a century. More than 40 industries have existed within the inner harbour, and while many of these industries are no longer present, the properties that they operated on remain as potential sources of persistent contamination to the present day, including mercury. To assess the extent and distribution of total mercury (THg) contamination, 21 sediment cores as well as pore water samples were collected within the inner harbour of Kingston. The spatial distribution of THg in the surface sediment is not homogenous; with concentrations in the surface sediment along the southwestern shoreline, adjacent to the former industrial properties, are significantly greater (p < 0.01) than the rest of the inner harbour, and were above the Federal severe effect limit (> 2000 ug/kg;) guideline for sediment. MeHg was detected in some sediment cores, and was found to have a significant, positive correlation with [THg] in the surface sediment (0-5 cm). THg was not found in storm sewer discharges, but was detected in terrestrial soil near the Kingston Rowing Club at a concentration of more than 4000 ug/kg. Significant [THg] was detected in runoff draining from contaminated shoreline soils, indicating that erosion from terrestrial sources may be an ongoing source of Hg to the sediment. It can be concluded that there is an increased risk over time to surrounding ecosystems where properties with historical contamination are not remediated until they are developed.     

Oxygenated blend design and its effects on reducing diesel particulate emissions

In order to meet Euro IV emission standards, diesel vehicles are compelled to install exhaust aftertreatment devices, which largely increases the overall cost. This paper explores the possibility to significantly reduce the particulate matter (PM) emissions by new fuel design. Several oxygenated blends were obtained by mixing the biodiesel, ethanol, dimethyl carbonate (DMC), and diesel fuels. The tests were conducted on two heavy-duty diesel engines, both with a high-pressure injection system and a turbocharger. The total PM and its dry soot (DS) and soluble organic fraction (SOF) constituents were analyzed corresponding to their specific fuel physiochemical properties. A blended fuel that contains biodiesel, DMC, and high cetane number diesel fuels was chosen eventually to enable the diesel engines to meet the Euro IV emission regulation. Based on the test results, the basic design principles were derived for the oxygenated blends that not only need the high oxygen content, but also the high cetane number and the low sulfur and low aromatic contents.     

Indoor aerosols: from personal exposure to risk assessment

Motivated by growing considerations of the scale, severity, and risks associated with human exposure to indoor particulate matter, this work reviewed existing literature to: (i) identify state‐of‐the‐art experimental techniques used for personal exposure assessment; (ii) compare exposure levels reported for domestic/school settings in different countries (excluding exposure to environmental tobacco smoke and particulate matter from biomass cooking in developing countries); (iii) assess the contribution of outdoor background vs indoor sources to personal exposure; and (iv) examine scientific understanding of the risks posed by personal exposure to indoor aerosols. Limited studies assessing integrated daily residential exposure to just one particle size fraction, ultrafine particles, show that the contribution of indoor sources ranged from 19% to 76%. This indicates a strong dependence on resident activities, source events and site specificity, and highlights the importance of indoor sources for total personal exposure. Further, it was assessed that 10–30% of the total burden of disease from particulate matter exposure was due to indoor‐generated particles, signifying that indoor environments are likely to be a dominant environmental factor affecting human health. However, due to challenges associated with conducting epidemiological assessments, the role of indoor‐generated particles has not been fully acknowledged, and improved exposure/risk assessment methods are still needed, together with a serious focus on exposure control.     

Comparison of short-term exposure to particle number, PM10 and soot concentrations on three (sub) urban locations

Recent interest has focused on the health effects of ultrafine particles because of the documented toxicity and the larger concentration contrast near motorways of UFP than for PM10 or PM2.5. There are only few studies that have measured UFP at inner-city streets simultaneously with other PM components.The aim of this study was to compare the contrast of UFP, PM₁₀ and soot measured simultaneously at 3 inner-city locations, namely a moderately busy street (15,000 vehicles/day), a city and a suburban background location.Simultaneously, measurements of particle number concentrations (PNC), PM₁₀ and soot have been conducted on three locations in and around Utrecht, a medium-sized city in the Netherlands for 20 weekdays in autumn 2008. Measurements were done for 6-h during afternoon and early evening.The mean PNC at the street location was more than 3 times higher than at the two background locations. The contrast was similar for soot concentrations. In PM₁₀ concentrations less contrast was found, namely 1.8 times. Mean PNC concentrations were poorly correlated with PM₁₀ and soot. At the street location, high temporal variation of PNC concentrations occurred within each sampling day, probably related to variations in traffic volumes, high-emission individual vehicles and wind direction. Temporal variation was smaller at the two background locations. Occasional unexplained short-term peaks occurred at the suburban background location. A relatively high correlation between PNC minute values at the two background locations was found, pointing to similar area-wide sources. Typically low correlations were found with the street locations, consistent with the dominant impact of local traffic.A large contrast between two background locations and a moderately busy urban street location was found for PNC and soot, comparable to previous studies of much busier motorways. Temporal variation of PNC was higher at the street location and uncorrelated with background variations.     

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 深入分析了有机物切割刀具用钢的使用性能要求及相应的力学性能要求，为获得优异的切割性能，有机物切割刀具用钢必须具备超高的刀口硬度及刃口锋利性，并具有适当的韧性。由此分析了有机物切割刀具用钢的合金化原理与强韧化原理。为获得良好的刃口锋利性，必须采用高碳低合金或非合金钢。设计了一种有机物切割刀具用钢，采用特殊热处理工艺，通过高碳马氏体强化以及微细弥散的合金渗碳体沉淀强化可显著提高钢的硬度实现超硬化，而通过合金渗碳体及VC联合阻止晶粒长大产生明显的晶粒细化效果可提高钢的韧性。