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排序方式: 共有290条查询结果,搜索用时 15 毫秒
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研究了以甲基丙烯酸酯端基不饱和取酯树脂为主链,用甲基丙烯酸甲酯取代苯乙烯作为交联剂制成的甲基丙烯酸酯树脂(MAER)与通用型不饱和聚酯树脂(GUPR)的热裂解机理、燃烧现象。结果表明:MAER的裂角产物中苯环化合物含量(14.9%)少于GUPR(74.5%)。MAER燃烧时的发烟量和毒性也远低于GUPR。在MAER中加入三水合氧化铝(ATH)后,裂解产物中有毒物质的各类和数量更少,在燃烧时只有少量 相似文献
3.
《Inhalation toxicology》2013,25(14):952-965
Inflammation is regarded as an important mechanism behind mortality and morbidity experienced by cardiorespiratory patients exposed to urban air particulate matter (PM). Small-scale biomass combustion is an important source of particulate air pollution. In this study, we investigated association between inflammatory responses and chemical composition of PM1 emissions from seven different small-scale wood combustion appliances representing old and modern technologies. Healthy C57Bl/6J mice were exposed by intratracheal aspiration to single dose (10?mg/kg) of particulate samples. At 4 and 18?h after the exposure, bronchoalveolar lavage fluid (BALF) as well as serum was collected for subsequent analyses of inflammatory indicators (interleukin (IL)-6, IL-1β, IL-12, and IL-10; tumor necrosis factor-α (TNF-α); keratinocyte-derived chemoattractant (KC), and interferon-γ (IFN-γ)) in multiplexing assay. When the responses to the PM1 samples were compared on an equal mass basis, the PM from modern technology appliances increased IL-6, KC, and IL-1β levels significantly in BALF at 4 and 18?h after the exposure. In contrast, these responses were seen only at 4?h time point in serum. Increased cytokine concentrations correlated with metal-rich ash related compounds which were more predominant in the modern technology furnaces emissions. These particles induced both local and systemic inflammation. Instead, polycyclic hydrocarbon (PAH) rich PM1 samples from old technology (OT) evoked only minor inflammatory responses. In conclusion, the combustion technology largely affects the toxicological and chemical characteristics of the emissions. The large mass emissions of old combustion technology should be considered, when evaluating the overall harmfulness between the appliances. However, even the small emissions from modern technologies may pose significant toxic risks. 相似文献
4.
In chemical industry, usual solvents are being replaced by supercritical fluids. Last few years, extraction by these environmentally benign solvents has had much attention and now is considered as the newest separation technology. However, developing new applications and improving existing ones is based on a set of thermodynamic and physical properties of pure solutes related to phase equilibrium for which experimental values cannot be found and consequently, there is an increase need for accurate estimates of these properties. This paper is interested firstly to a thermodynamic property which is the Krichevskii parameter and secondly to a thermophysical one which is the sublimation pressure. First parameter is considered as a governor of thermodynamic properties in binary dilute mixtures near the solvent's critical point and can be calculated from some rigorous relationships and in this paper a review and a new way for its estimation are presented based on consistency of solid's solubility data in supercritical fluids and dilute solution theory. Second parameter is considered as the predominant influencer on solubility in supercritical fluids and unavailability of its experimental values presents an obstacle to thermodynamic modeling of solubility data. For this reason and as a second step, in this paper we present a new manner for its estimation. Obtained results are relevant, very promising for each considered property and the methodology can be applied for other solutes with more complex structures as Pharmaceuticals (antibiotics, drugs, anti-inflammatories …), polycyclic aromatic hydrocarbons (PAHC) and dyestuffs. 相似文献
5.
Nickel titanium (NiTi) foams were made by combustion synthesis of powders with the help of ZrH2 as foaming agent and TiB2 as endothermic agent. In this paper, we investigated the effect of elemental powder size on the foaming. The powder size of Ni and Ti affected the ignition temperature of the combustion reaction, cell morphology and microstructure of the foams. The cell morphology of the foams was also modified by the powder size of TiB2. 相似文献
6.
A combustion synthesis method has been developed for synthesis of Eu2+ doped CaAlSiN3 phosphor and its photoluminescence properties were investigated. Ca, Al, Si, and Eu2O3 powders were used as the Ca, Al, Si and Eu sources. The addition of NaN3, NH4Cl and Si3N4 powders was found to increase significantly the product yield. These powders were mixed and pressed into a compact, which was then wrapped up with an igniting agent (i.e., Mg+Fe3O4). The compact was ignited by electrical heating under a N2 pressure of ≤1.0 MPa. Effects of these experimental parameters on the product yield were investigated and a reaction mechanism was proposed. The synthesized CaAlSiN3:Eu2+ phosphor absorbs light in the region of 200–600 nm and shows a broad band emission in the region of 500–800 nm due to the 4f65d1 → 4f7 transition of Eu2+. The sample doped with Eu2+ at the optimized molar ratio of 0.04 is efficiently excited by the blue light (460 nm) and generates emission peaking at ~650 nm with peak emission intensity ~106% of a commercially available phosphor, YAG:Ce3+(P46-Y3).The internal quantum efficiency of the synthesized phosphor was measured to be 71%, compared to 69% of the YAG:Ce3+ (P46-Y3). 相似文献
7.
Zhang X Chen H Fu H Doyle PS Yan J 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(21):8103-8108
Double-stranded DNA is a dynamic molecule whose structure can change depending on conditions. While there is consensus in the literature about many structures DNA can have, the state of highly-stretched DNA is still not clear. Several groups have shown that DNA in the torsion-unconstrained B-form undergoes an “overstretching” transition at a stretching force of around 65 pN, which leads to approximately 1.7-fold elongation of the DNA contour length. Recent experiments have revealed that two distinct structural transitions are involved in the overstretching process: (i) a hysteretic “peeling” off one strand from its complementary strand, and (ii) a nonhysteretic transition that leads to an undetermined DNA structure. We report the first simultaneous determination of the entropy (ΔS) and enthalpy changes (ΔH) pertaining to these respective transitions. For the hysteretic peeling transition, we determined ΔS ∼ 20 cal/(K.mol) and ΔH ∼ 7 kcal/mol. In the case of the nonhysteretic transition, ΔS ∼ -3 cal/(K.mol) and ΔH ∼ 1 kcal/mol. Furthermore, the response of the transition force to salt concentration implies that the two DNA strands are spatially separated after the hysteretic peeling transition. In contrast, the corresponding response after the nonhysteretic transition indicated that the strands remained in close proximity. The selection between the two transitions depends on DNA base-pair stability, and it can be illustrated by a multidimensional phase diagram. Our results provide important insights into the thermodynamics of DNA overstretching and conformational structures of overstretched DNA that may play an important role in vivo. 相似文献
8.
WANGFeiFei GENGChunMei HAO WeiDong ZHAO YongDong LIQin WANG HongMei QIAN Yan 《Biomedical and environmental sciences : BES》2016,29(2):107-116
ObjectiveTo explore the relationship between different components offineparticulate matter (PM2.5) emitted from coal combustion and their cytotoxic effect in the vascular endothelial cells. MethodsCoal-fired PM2.5was sampled using a fixed-source dilution channel and flow sampler. The sample components were analyzed by ion chromatography and inductively coupled plasma atomic emission spectroscopy(ICP-AES). The PM2.5suspension was extracted using an ultrasonic water-bath method and thenhuman umbilical vein endothelial cells (EA.hy926) were treated withvarious concentrations of the PM2.5 suspension. Cell proliferation,oxidativeDNA damage, and global DNA methylation levelswere used to measurethe cellulartoxicity of PM2.5emitted fromcoalcombustion. ResultsComparedtoothertypesof coal-fired PM2.5preparations,thePM2.5 suspension from Yinchuan coal had the highest cytotoxicity.PM2.5 suspension from Datong coal hadthe highest toxic effectwhile that fromYinchuan coal had the lowest.Exposure to coal-fired PM2.5 from Jingxi coalresulted inlower 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. At the same dose, PM2.5 emitted from coal combustion could produce more severeDNAimpairmentcompared to that produced by carbon black.Cell survival rate was negatively correlated with chloride and potassiumionscontent.The5-methylcytosine(5-mC) level waspositively correlated withMnandnegatively correlated withZn levels.The 8-OHdG% level was positively correlated withboth MnandFe. ConclusionPM2.5 emitted from coal combustion can decrease cell viability, increase global DNA methylation, and causeoxidativeDNA damage inEA.hy926 cells. Metalcomponentsmay be important factors that influence cellular toxicity. 相似文献
9.
Timothy Pas Bjorn Vergauwen Guy Van den Mooter 《International journal of pharmaceutics》2018,535(1-2):47-58
Biopolymers have rarely been used so far as carriers in the formulation of amorphous solid dispersions (ASD) to overcome poor solubility of active pharmaceutical ingredients (APIs). In an attempt to enlarge our knowledge on this topic, gelatin, type 50PS was selected. A screening study was initiated in which twelve structurally different poorly soluble biopharmaceutical classification system (BCS) Class II drugs (carbamazepine, cinnarizine, diazepam, itraconazole, nifedipine, indomethacin, darunavir (ethanolate), ritonavir, fenofibrate, griseofulvin, ketoconazole and naproxen) were selected for evaluation. Solid dispersions of five different drug loadings of these twelve compounds were prepared by lyophilization and evaluated for their solid state properties by mDSC and XR(P)D, and in vitro dissolution performance. Even without any process optimization it was possible to form either fully amorphous or partially amorphous systems, depending on the API and API to carrier ratio. Hence in this respect, gelatin 50PS behaves as any other carrier. Dissolution of the API from the solid dispersions significantly exceeded that of their crystalline counterparts. This study shows the potential of gelatin as a carrier to formulate amorphous solid dispersions. 相似文献
10.
Marek Molenda Jzef Horabik Piotr Parafiniuk Anna Oniszczuk Maciej Bada Justyna Wajs Ewa Gondek Marcin Chutkowski Aleksander Lisowski Joanna Wicek Mateusz Stasiak 《Materials》2021,14(11)
The objective of the reported project was to produce wood agglomerates from popular East European species to determine their strength and combustion properties. Closed-die pellets were produced from sawdust of six types of wood common on the East European market: pine, willow, oak, poplar, birch, and beech. The properties of pellets, determined by the type of wood, were influenced by the compaction pressure and the moisture content of the sawdust. The highest average pellet density was obtained for oak sawdust, while the lowest density was obtained for poplar pellets. Expansion of pellets after removing from the die was found to be dependent on the wood species, and as expected, on compaction pressure. The pellet expansion increased after 2 h of conditioning in the laboratory and with an increase in moisture content. The highest and the smallest strength were obtained for oak pellets and for birch sawdust, respectively. The strength of the pellets increased by more than 100% with an increase in the compaction pressure from 60 MPa to 120 MPa. The average strength decreased by 65% with increasing moisture content. For all tested materials, drop resistance remained at a high level, acceptable in industrial practice. The highest calorific value of 18.97 MJ/kg was obtained for pine pellets. The highest ash value of 1.52% was obtained for willow pellets and the lowest value of 0.32% for pine pellets. 相似文献