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101.
Summary Fibrous material is an integral part of the daily diet, and it exerts direct physiological effects throughout the gastrointestinal tract, in addition to affecting metabolic activities more indirectly. The interplay of these effects is responsible for the presumed desirable influence of fibre on weight regulation, carbohydrate and lipid metabolism, and on colon function. Numerous mechanisms of action have been identified which are related to the type and the physicochemical nature of the fibre. This review concentrates mainly on the serum cholesterol-lowering effect of dietary fibre, its colonic fermentation, and finally on some possible adverse effects that one should be aware of when consuming high amounts of dietary fibre.  相似文献   
102.
Gas hydrates are a significant energy resource and are usually detected by bottom simulating reflection and submarine geochemical anomalies. Authigenic minerals are related to gas hydrates, with carbonates, sulfates and sulfides being important tracing minerals. Authigenic tubular pyrites were collected from offshore southwest Taiwan in the South China Sea, and were investigated by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy (HRTEM). Authigenic tubular pyrite was composed of framboidal pyrite, within which nanosized graphitic carbon of low crystallinity was discovered. The graphitic carbon coexisted with pyrite and had a texture similar to carbon nanotubes and nanocones, indicating that they likely precipitated from carbon supersaturated C-H-O fluid. Pyrite may act as a catalyst for the conversion of CH 4 to C. The discovery of nanosized graphitic carbon in pyrite indicated it was deposited in sediments that were supersaturated with methane fluid. Thus, nanosized graphitic carbon may be another tracing species for submarine gas hydrates. The discovery of nanosized graphitic carbon deposited in a low temperature environment will enlighten our understanding of the laboratory synthesis and industrial production of graphitic carbon.  相似文献   
103.
本文通过考虑离子电位、环境温度以及噪声等的影响,建立了一个矿物分形生长的DLA模型.在300×300的正方格子中心处放置一个种子构成生长中心,吸引域设置为菱形,主要考虑了三个参数的影响,其中总体的表面粘附几率为Pg,范围为0~99%,用来消除噪声的影响,模拟矿物的结晶生长速度与矿物结构的关系;吸附距离d变化范围为0~9单元距离,用来模拟离子电位对矿物生长的影响;填充间隔s的变化范围为0.00~5.00单元距离,表现为环境温度对矿物生长体系的影响.进行了三组模拟,分别是固定其中2个参数,改变另一个参数.结果表明,DLA集团的分维值随模拟参数成规律性的变化,分形维数在一定的条件下随着Pg的降低、d和s的增大而增大,矿物的结构也随之从浸染状、星散状或放射状逐渐过渡到团块状.该模型只是对三维分形生长的二维平面模拟,不能完全反映整个矿物在三维受限空间中聚集生长的复杂动力学.  相似文献   
104.
介绍新型斜环永磁高梯度磁选机的基本结构,分析磁性矿粒在复合力场中的受力和捕获机理,测试该设备对某铁矿尾矿的磁选效果。该磁选机为永磁磁系,分选环为倾斜配置且分选环倾斜角度和转速可调;分选时,磁介质在底部磁场区捕收磁性矿粒,旋转到顶部非磁场区冲洗卸矿。研究结果表明:调节分选环的倾斜角度可改变磁性矿粒所受各作用力的大小,从而调节磁选粒度的下限和磁选作业的回收率;当原矿铁品位为17.81%时,经一次磁选可获得回收率为65.05%、全铁品位为29.53%的磁选精矿。该磁选机设计合理、节能,可实现连续给矿、分选和排矿。  相似文献   
105.
Liquid-solid phase change materials (PCMs) show reversible storage and release of latent heat, which has attracted extensive interests in applications for thermal energy storage. However, stubborn leakage issue may cause corrosion and extra thermal resistance. The non-wettability of melted paraffin on the oleophobic surface of diatomite has been reported by authors earlier, and the result showed that the encapsulation ratio (84.5%) of diatomite@paraffin shape-stabilized PCM greatly increased. Here, in order to prove this method equally applicable to other PCMs and porous natural clay minerals, diatomite and sepiolite were oleophobically modified to encapsulate melted stearic acid and paraffin, to form shape-stabilized PCMs. The results showed that the encapsulation ratios of 67.8% and 56.6% for diatomite@stearic acid and sepiolite@paraffin were higher than that reported in the references (28.9% and 36.8%). In addition, the encapsulation ratios of diatomite-based shape-stabilized PCMs can be also increased using different PCMs, such as n-octadecane and polyethylene glycol via the same approach. Therefore, this is a universal method for improving encapsulation ratios of shape-stabilized PCMs.  相似文献   
106.
Liu  ZhiFei  Li  XiaJing  Colin  Christophe  Ge  HuangMin 《科学通报(英文版)》2010,55(35):4058-4068
High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea (SCS) covering the period since the Last Glacial Maximum shows that illite (29%–48%), smectite (14%–45%), chlorite (17%–28%), and minor kaolinite (6%–14%) comprise the clay mineral assemblage, and that time series variation does not present glacial-interglacial cyclicity. Provenance analysis indicates three end-member sources: almost all smectite derives from Luzon, all kaolinite is sourced from the Pearl River, and illite and chlorite originate from both the Pearl River and Taiwan. By comparing clay mineral compositions in surface sediments from the three major source areas and of the SCS, we reconstructed a time series of clay mineral contribution from the major provenances to the northern slope of the SCS using the linear separation method for illite crystallinity. There were three stages of provenance change. (1) During 24.1–17.5 ka BP, contributions from Taiwan and Luzon were similar (30%–40%), while that from the Pearl River was only 25%. (2) During 17.5–14.0 ka BP, the contribution from Luzon decreased rapidly to 20%–25%, while that from Taiwan increased to 35% from an average of 25% at 18 ka BP, and that from the Pearl River increased largely to 40%. (3) During the Holocene, differences in contributions from the three major provenances increased: the contribution from Luzon increased slightly and then remained at 27%–35%, that from Taiwan increased rapidly and then remained at 55%–60%, and that from the Pearl River decreased to 15%. The change in clay mineral contributions from different provenances is influenced mainly by clay mineral production, monsoon rainfall denudation, oceanic current transport, and sea-level change.  相似文献   
107.
W油藏Z1油组为高孔低渗低阻油藏,低阻油层的地质成因复杂多样。依据Z1油组储层发育特征,研究了储层粘土矿物的类型、颗粒的分布形式和泥质含量,以及上述粘土矿物特征对Z1油组低阻的影响。研究发现,Z1油组低阻层段的粘土类型以伊蒙混层为主,其相对含量高;粘土颗粒较均匀地成薄膜状、絮状分布;平均泥质含量高。粘土矿物组构产生的附加导电性和高泥质含量是影响Z1油组低电阻率的重要因素之一。  相似文献   
108.
以4种连有不同取代基的阳离子表面活性剂为铝硅酸盐矿物捕收剂,研究各药剂对铝硅矿物的浮选能力及浮选特点。运用密度泛函理论(DFT)B3lyp/6-31G(d)方法,对4种捕收剂的阳离子结构进行优化,并计算原子电荷分布等量化参数和几何结构参数。研究结果表明:甲基的取代可增强阳离子的静电作用能力,同时,削弱它与矿物表面之间的氢键作用;苄基的取代不仅增强药剂的静电效应,而且增加氢键的结合能力;理论分析结果与浮选试验结果一致,季铵盐的浮选能力较伯胺与叔胺的强,连有苄基的季铵盐对铝硅酸盐矿物的捕收能力最强,且受pH值影响小。  相似文献   
109.
 煤炭是中国的优势能源矿产,对国民经济的发展和人民生活的改善至关重要;煤炭燃烧使用产生的污染问题已经找到科学和经济可行的清洁高效利用途径,减少CO2排放有多种选项,需要理智选择和应对;完全舍弃煤炭似为不明智的做法。提出了中国下一步发展煤炭清洁高效利用的主要开展方向。  相似文献   
110.
粘土矿物具有良好的过滤、吸附、离子交换等物理化学性能,在环境矿物学应用广泛。本文针对粘土矿物在污染治理、无机抗菌剂制备、环保建材及其他方面的应用研究进展作了综述,并分析了研究开发中的主要问题和发展趋势。  相似文献   
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