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排序方式: 共有1059条查询结果,搜索用时 15 毫秒
91.
Brominated flame retardants in Belgian home-produced eggs: levels and contamination sources 总被引:1,自引:0,他引:1
Covaci A Roosens L Dirtu AC Waegeneers N Van Overmeire I Neels H Goeyens L 《The Science of the total environment》2009,407(15):4387-4396
The extent and the sources of contamination with brominated flame retardants (BFRs), such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD), in home-produced eggs from free-foraging chicken of Belgian private owners were investigated. Various factors, such as seasonal variability, exposure of chickens through diet (kitchen waste) and soil, and elimination of BFRs through eggs and faeces were assessed. PBDEs were more important than HBCD in terms of concentrations and detection frequency. Concentrations of PBDEs and HBCD in Belgian home-produced eggs were relatively low and comparable with reported levels from other European countries and the US. The concentrations of PBDEs (sum of 13 congeners, including BDE 209) ranged between not detected and 32 ng/g lipid weight (lw), with medians of 3.0 and < 2.0 ng/g lw for the autumn 2006 and spring 2007 campaigns, respectively. When present, BDE 209 was the major PBDE congener (45% of sum PBDEs). When BDE 209 was not detected, the PBDE profile was composed of PentaBDE (BDE 99 and BDE 47), with, in some cases, higher contribution of OctaBDE (BDE 183 and BDE 153). HBCD was also detected (< 0.4 and 2.9 ng/g lw for the autumn 2006 and spring 2007 campaigns, respectively), but at lower detection frequency. The highest HBCD value was 62 ng/g lw. The similarity between profiles and seasonal variations in the concentrations of BFRs in soil and eggs indicate that soil is an important source, but not the sole source, for eggs laid by free-foraging chicken. The contamination of eggs with PBDEs and HBCD appears to be of low concern for public health and the contribution of eggs to the total daily intake of PBDEs appears to be limited (10% for chicken owners and 5% for the average Belgian consumer). 相似文献
92.
Cutignano A d'Ippolito G Romano G Lamari N Cimino G Febbraio F Nucci R Fontana A 《Chembiochem : a European journal of chemical biology》2006,7(3):450-456
Enzymatic preparations and specialized analytical tools have shown that chloroplast-derived glycolipids are the main substrates for the biosynthetic pathway that produces antiproliferative polyunsaturated aldehydes in broken cells of the marine diatom Thalassiosira rotula. This process, which is associated with the formation of free fatty acids and lyso compounds from polar lipids but not triglycerides, is largely dependent on glycolipid hydrolytic activity, rather than phospholipase A(2) as previously suggested. Preliminary characterization of lipolytic enzymes has revealed protein bands of 40-45 kDa. Under native conditions these proteins seem to be associated with soluble aggregates that have an apparent molecular weight of approximately 200 kDa. The biochemical process, which is similar to that described in the algal-bloom forming diatom Skeletonema costatum, suggests a mechanism based on decompartmentalization and mixing of preexisting enzymes and substrates. 相似文献
93.
Footskate is a common problem encountered in interactive applications dealing with virtual character animations. It has proven difficult to fix without the use of complex numerical methods, which require expert skills for their implementations, along with a fair amount of user interaction to correct a motion. On the other hand, deformable bodies are being increasingly used in virtual reality (VR) applications, allowing users to customize their avatar as they wish. This introduces the need of adapting motions without any help from a designer, as a random user seldom has the skills required to drive the existing algorithms towards the right solution. In this paper, we present a simple method to remove footskate artifacts in VR applications. Unlike previous algorithms, our approach does not rely on the skeletal animation to perform the correction but rather on the skin. This ensures that the final foot planting really matches the virtual character’s motion. The changes are applied to the root joint of the skeleton only so that the resulting animation is as close as possible to the original one. Eventually, thanks to the simplicity of its formulation, it can be quickly and easily added to existing frameworks. 相似文献
94.
Dr. Ivan Bassanini Dr. Silvia Parapini Dr. Corinna Galli Dr. Nadia Vaiana Dr. Andrea Pancotti Prof. Nicoletta Basilico Prof. Donatella Taramelli Prof. Sergio Romeo 《ChemMedChem》2019,14(23):1982-1994
The treatment of malaria, the most common parasitic disease worldwide and the third deadliest infection after HIV and tuberculosis, is currently compromised by the dramatic increase and diffusion of drug resistance among the various species of Plasmodium, especially P. falciparum (Pf). In this view, the development of new antiplasmodial agents that are able to act via innovative mechanisms of action, is crucial to ensure efficacious antimalarial treatments. In one of our previous communications, we described a novel class of compounds endowed with high antiplasmodial activity, characterized by a pharmacophore never described before as antiplasmodial and identified by their 4,4’-oxybisbenzoyl amide cores. Here, through a detailed structure-activity relationship (SAR) study, we thoroughly investigated the chemical features of the reported scaffolds and successfully built a novel antiplasmodial agent active on both chloroquine (CQ)-sensitive and CQ-resistant Pf strains in the low nanomolar range, without displaying cross-resistance. Moreover, we conducted an in silico pharmacophore mapping. 相似文献
95.
Nawal Makhloufi Nadia Chougui Farouk Rezgui Elias Benramdane Carmen S. R. Freire Carla Vilela Armando J. D. Silvestre 《应用聚合物科学杂志》2021,138(20):50450
The present study investigated the fabrication and characterization of bio-based sustainable films composed of a terrestrial plant raw material, namely Opuntia ficus-indica (OFI) cladodes powder (CP) and a marine seaweed derivative, namely agar (A). The effect of glycerol concentration on the properties of the casted films was evaluated at four different contents, namely 30, 40, 50 and 60 wt%. The films present UV-blocking properties, as well as moderate mechanical performance, thermal stability, and water vapor transmission rate (WVTR). The results point to an increase in thickness, elongation at break, moisture content, water solubility, and WVTR with increasing glycerol content. On the contrary, Young's modulus, tensile strength, and water contact angle decreased as glycerol concentration increased. The best combination is obtained for the film with 30% glycerol, based on an intermediate compromise between physical, mechanical, thermal, and barrier properties. All these outcomes express the potentiality of the powder obtained from grinding the OFI cladodes as raw material to produce low-cost films for the development of sustainable packaging materials. 相似文献
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98.
Nadia Segura Roberta Claro da Silva Fabiana A. Schäfer de M. Soares Luiz Antonio Gioielli Iván Jachmanián 《Journal of the American Oil Chemists' Society》2011,88(12):1945-1954
Although beef tallow (BT) has been considered a hard low-trans fat convenient to be used in several bakery applications, it has some undesirable characteristics like fatty acid composition, crystallization behavior, graininess formation and poor plastic range. This work studied the modification of BT by blending at different percentages with high oleic sunflower oil (HOSFO) followed by the enzyme-catalyzed interesterification of the blends. The reduction in the solid fat content achieved by the simple blending was enhanced by the interesterification process, as a result of the increase in the concentration of the diunsaturated monosaturated type triacylglycerols. Interesterification strongly impacted too on the crystallization behavior of the blends, since products showed more homogeneous and regular crystals than the starting mixture. Results show that lipase catalyzed interesterification of BT with HOSFO offers a useful tool for the design of fats with adjustable physicochemical properties, improved with respect to that of the starting fats. 相似文献
99.
100.
This article investigates the mechanical, morphological, and thermal properties of poly(vinyl chloride) (PVC) and low‐density polyethylene (LDPE) blends, at three different concentrations: 20, 50, and 80 wt% of LDPE. Besides, composite samples that were prepared from PVC/LDPE blend reinforced with different date palm leaf fiber (DPLF) content, 10, 20, and 30 wt%, were also studied. The sample in which PVC/LDPE (20 wt%/80 wt%) had the greatest tensile strength, elongation at break, and modulus. The good thermal stability of this sample can be seen that T10% and T20% occurred at higher temperatures compared to others blends. DPLF slightly improved the tensile strength of the polymer blend matrix at 10 wt% (C10). The modulus of the composites increased significantly with increasing filler content. Ageing conditions at 80°C for 168 h slightly improved the mechanical properties of composites. Scanning electron microscopic micrographs showed that morphological properties of tensile fracture surface are in accordance with the tensile properties of these blends and composites. Thermogravimetric analysis and derivative thermogravimetry show that the thermal degradation of PVC/LDPE (20 wt%/80 wt%) blend and PVC/LDPE/DPLF (10 and 30 wt%) composites took place in two steps: in the first step, the blend was more stable than the composites. In the second step, the composites showed a slightly better stability than the PVC/LDPE (20 wt%/80 wt%) blend. Based on the above investigation, these new green composites (PVC/LDPE/DPLF) can be used in several applications. J. VINYL ADDIT. TECHNOL., 25:E88–E93, 2019. © 2018 Society of Plastics Engineers 相似文献