960 resultados para 21-MUC 8


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The reaction of anhydrous PrCl3 with Na(C9H7) in 1.2 mole ratio in THF gives [(C9H7)(2)PrCl(THF)](2)1. 1 crystallized in monoclinic system, space group P2(1)/c with a = 7.808(2), b = 17.796(6), c = 14.070(4) Angstrom, beta = 93.97(2)degrees, V= 1950.3(9) Angstrom(3), Dcalcd = 1.63 g/cm(3) and Z = 2. Each Pr ion is surrounded by two indenyl, two Cl and one THF in a roughly trigonal bipyramid arrangement with average Pr-C(ring) and Pr-Cl distances of 2.81 and 2.84 Angstrom. The reaction of LaCl3 with Na(C9H7) in 1:3 mole ratio gives (C9H7)(3)LaTHF 2, which crystallizes in the monoclinic space group P2(1)/a with unit cell constants a = 21.871(8), b = 10.585(3), c = 23.652(7) Angstrom,beta = 114.62(2)degrees, V = 4977.9 Angstrom(3) and Z = 8. (C) 1997 Elsevier Science S.A.

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本文从赤潮发生前的现场模拟实验、赤潮发生时的现场培养实验和赤潮发生过程中的现场调查等方面,较为系统地研究了东海大规模赤潮对微型浮游动物群落结构的影响。 2005年长江口及邻近海区赤潮发生前,赤潮973MC2005-03航次在本海区进行了综合调查,期间分别于4月27日、5月4日和5月8日,在zzf1、zc18a和ra5三个站位利用现场船基培养的方法,研究了添加到赤潮密度106 cells L-1的东海原甲藻(Prorocentrum donghaiense)对微型浮游动物群落结构的影响。结果发现,赤潮密度的东海原甲藻对小型无壳纤毛虫的种群数量影响较大,而对中大型砂壳纤毛虫的影响较小,从而使得微型浮游动物群落有向中大型砂壳纤毛虫演替的趋势。在zzf1站位,小型无壳纤毛虫占绝对优势,添加东海原甲藻72 h后,优势种由管游虫(Cyrtostrombidium sp.)演替为另一种小型无壳纤毛虫急游虫4(Strombidium sp.4);在以中型砂壳纤毛虫百乐拟铃虫(Tintinnospsis beroidea)为优势种的zc18a站位,仍然是以此为优势种,但其在群落中的优势度更加明显;ra5站位也是以小型无壳纤毛虫为主,添加东海原甲藻72 h后,其群落结构由急游虫2(Strombidium sp.2)向中大型砂壳纤毛虫纤毛虫百乐拟铃虫和亚速岛网纹虫(Favella azorica)演替。不同站位微型浮游动物群落结构变化的差异与其本身的群落结构组成有一定关系,也与浮游植物的群落组成有关。zzf1和ra5站位实验组中微型浮游动物的总丰度和总生物量都低于对照组,而zc18a站位变化不明显,这是由于前两个站位实验组中的优势种管游虫(zzf1站位)和急游虫2(ra5站位)的丰度和生物量迅速下降,而zc18a站位实验组的优势种百乐拟铃虫的丰度和生物量比较稳定造成的。 2005年长江口及邻近海区赤潮发生时,赤潮973 MC2005-04航次在本海区进行了综合调查,期间分别于5月26日、5月28日、5月28日和5月29日,在xzm1、srb、sra1和hb8a四个站位利用现场培养的方法,研究了东海大规模赤潮对微型浮游动物群落结构的影响。结果发现,东海大规模赤潮对微型浮游动物群落结构的影响与赤潮藻的密度密切相关:xzm1、srb和sra1站位是赤潮区,两种赤潮藻的总密度分别为,1.3×106 cells L-1、1.8×106 cells L-1和5.6×106 cells L-1,而hb8a站位位于非赤潮区,两种赤潮藻的总密度仅为5×105 cells L-1;实验进行72 h后,在以大型砂壳纤毛虫网纹虫和筒壳虫(Tintinnidium sp.)为主的xzm1、srb和sra1站位,仍然是以这些大型砂壳纤毛虫为主,且其在群落中的百分比显著增大,尤其在赤潮藻密度最高的的sra1站位,这种演替趋势表现的最明显;而在以小型无壳纤毛虫急游虫2为主的hb8a站位,微型浮游动物群落向中型砂壳纤毛虫真丁丁虫(Eutintinnus sp.)演替。培养过程中微型浮游动物总丰度的变化以及总生物量的变化都与赤潮藻的密度密切相关:赤潮藻密度较低的xzm1站位和srb站位变化不大;赤潮藻密度较高的sra1站位则快速下降;而非赤潮区的hb8a站位呈快速上升的趋势。以上结果进一步表明东海大规模赤潮能使微型浮游动物群落向中大型砂壳纤毛虫演替。 在2006年4月18日-5月30日,赤潮973项目MC2006航次在长江口及其邻近海区围绕东海原甲藻和米氏凯伦藻赤潮进行了综合调查。为了研究该过程中微型浮游动物群落结构的变化,我们在南北5个断面共计21个站位进行了取样,样品涉及赤潮发生前期、发生期和消退期。本次调查共发现纤毛虫66种,其中砂壳纤毛虫有8属37种,寡毛类无壳纤毛虫25种,另外还有前口类3属4种。在赤潮发生前之前,小型无壳纤毛虫的丰度普遍较高,平均值为1574 ind L-1,而中大型砂壳纤毛虫的丰度普遍偏低,平均值仅为14 ind L-1;赤潮发生以后,在大多数站位小型无壳纤毛虫的丰度出现不同程度的下降,平均值降为171 ind L-1,而中大型砂壳纤毛虫的丰度出现一定程度的上升,平均值增至216 ind L-1。赤潮消退时,小型无壳纤毛虫丰度的平均值降为109 ind L-1,而中大型砂壳纤毛虫的丰度继续增长,变为401 ind L-1。不同微型浮游动物百分比的统计结果也表明:微型浮游动物群落由小型无壳纤毛虫向中大型砂壳纤毛虫演替的趋势:小型无壳纤毛虫在群落中百分比的平均值由赤潮发生前的62 %变为赤潮发生时的32 %,至赤潮消退时又降为15 %;而中大型砂壳纤毛虫百分比的平均值从赤潮发生前的10 %变为赤潮发生时的24 %,至赤潮消退时增至50 %。典型站位za3、za5、zb7和zb9的结果再次表明了赤潮发生过程中微型浮游动物群落由小型无壳纤毛虫向中大型砂壳纤毛虫演替的趋势。 由以上赤潮发生前的现场模拟实验、赤潮发生时的现场培养实验和赤潮发生过程中的现场调查的结果均可见,东海大规模赤潮可以改变微型浮游动物的群落结构,呈现由小型无壳纤毛虫向中大型砂壳纤毛虫演替的趋势,进而有可能影响中大型浮游动物等摄食者的种群数量和群落结构,最终可能会影响整个海洋生态系统的结构和功能。

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本文研究了16口虾塘的饲料投喂量、水位、盐度、透明度、水温、pH、溶解氧浓度、NH3-N浓度、水色、对虾体长及浮游植物的种类和数量等水体理化因子和生物因子的变化。经过统计分析结果如下: 在养殖前4个月饲料的日平均投喂量基本上呈一个倒“U”型。即随着养殖时间的推移,饲料日平均投喂量逐渐增大,到养殖60 d左右,饲料日平均投喂量达到了最大值,然后进入一个平台期,平台期大约维持30 d左右,随后饲料日平均投喂量逐渐减少。在120 d~130 d饲料日平均投喂量降到最低点后又逐渐回升。 水位平均值变化趋势基本相同,均为前浅后深,即随着养殖时间的推移养殖水位平均值逐渐加深 。 盐度变化趋势基本相同,均为前低后高,即随着养殖时间的推移养殖水体盐度逐渐升高。 透明度的总体变化趋势为:早上透明度比下午大,前期透明度比后期大。 水温基本上是随着养殖时间的推移而逐渐下降。6:30的水温比17:30的水温低。且6:30水温与17:30水温基本上呈平行趋势。 pH变化的总体趋势为:前期较高,随着养殖时间的推移pH逐渐下降,到中期(90d左右)pH降到最低点,尔后又逐渐上升,略呈“V”字形。早上的pH比下午的低。且早上的pH与下午的pH基本上呈平行趋势,间或有较大波动。 6:30时溶解氧浓度的平均值随着养殖时间的推移而逐渐增高。17:30时溶解氧浓度的平均值在整个养殖过程中比较平稳。同时,17:30时溶解氧浓度的平均值高于6:30,养殖前期(前90d)这种趋势更明显。 NH3-N浓度的平均值随着养殖时间的推移而逐渐增高。在养殖后期NH3-N浓度的波动较大。同时,养殖过程中17:30时NH3-N浓度的平均值高于6:30。 6:30时出现9~21号水色,它们出现的比例分别为:9号占0.1%,10号占0.3%,11号占1.1%, 12号0.6%,13号1.5%,14号占3.7%,15号占7.1%,16号占17.5%,17号占22.0%,18号占15.9%,19号占13.7%,20号10.9%,21号占5.8%;17:30时出现11~21号水色,它们出现的比例分别为11号占0.1%, 12号占0.3%,13号占1.2%,14号占4.0%,15号占6.0%,16号占17.8%,17号占24.7%,18号占18.1%,19号占11.8%,20号占9.7%,21号5.7%。 在11种典型水色中共检出浮游植物67种。其中11号水色检出16种,优势种为诺马斜纹藻(占总数47.1%)和菱形海线藻(占总数29.8%)。12号水色共检出16种,优势种为原甲藻(占总数40.85%)和圆筛藻(占总数20.73%)。13号水色共检出16种,优势种为颤藻(占总数45.58%)。14号水色共检出18种,优势种为拟货币直链藻(占总数56.73%)和膝沟藻(占总数12.87%)。15号水色共检出18种,优势种为诺马斜纹藻(占总数64.76%)。16号水色共检出16种,优势种为拟货币直链藻(占总数69.93%)。17号水色共检出14种,优势种为诺马斜纹藻(占总数62.56%)和膝沟藻(占总数15.76%)。18号水色共检出21种,优势种为拟货币直链藻(占总数71.19%)。19号水色共检出18种,优势种为圆筛藻(占总数94.99%)。20号水色共检出18种,优势种为圆筛藻(占总数87.14%)。21号水色共检出15种,优势种为拟货币直链藻(占总数59.80%)和萎软几内亚藻(占总数17.57%)。 相关分析结果表明高位池理化因子中对水色的主要影响因素:17:30PH值、养殖生物量、17:30NH3-N、17:30 透明度、水交换量。 对体长的主要影响因素为 6:30溶解氧、水交换量、17:30水色、饲料投喂量、盐度、17:30透明度、17:30水温、6:30NH3-N。 对对虾本身生物学形状对体重的影响研究表明体长、头胸甲长、胸宽、额剑下缘刺数目对体重的通径系数达到显著水平,它们是直接影响体重的重要指标,其中体长对体重的直接影响(0.428**)最大,是影响体重的最主要因素,其次为头胸甲长(0.290**)和胸宽(0.245**),额剑下缘刺数对体重的直接影响(0.070*)较小;胸高与体重的相关程度很大(0.7923),但它与额剑上缘刺数对体重的直接影响都非常小,主要通过其他性状间接影响活体重,是影响体重的次要因素。

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2009

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Several studies have suggested that men with raised plasma triglycerides (TGs) in combination with adverse levels of other lipids may be at special risk of subsequent ischemic heart disease (IHD). We examined the independent and combined effects of plasma lipids at 10 years of follow-up. We measured fasting TGs, total cholesterol (TC), and high density lipoprotein cholesterol (HDLC) in 4362 men (aged 45 to 63 years) from 2 study populations and reexamined them at intervals during a 10-year follow-up. Major IHD events (death from IHD, clinical myocardial infarction, or ECG-defined myocardial infarction) were recorded. Five hundred thirty-three major IHD events occurred. All 3 lipids were strongly and independently predictive of IHD after 10 years of follow-up. Subjects were then divided into 27 groups (ie, 33) by the tertiles of TGs, TC, and HDLC. The number of events observed in each group was compared with that predicted by a logistic regression model, which included terms for the 3 lipids (without interactions) and potential confounding variables. The incidence of IHD was 22.6% in the group with the lipid risk factor combination with the highest expected risk (high TGs, high TC, and low HDLC) and 4.7% in the group with the lowest expected risk (P

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In this paper, the leaky-mode theory is applied to take into account for the dielectric losses in millimetre waveband inhomogeneous leaky-wave antennas. A practical dielectric-filled cosine-tapered periodic leaky-wave antenna working in the 45GHz band is studied, showing how the desired sidelobes level and directivity are spoilt due to the effect of the losses. An iterative procedure is used to correct the negative effects of the losses in the radiation patterns of the leaky-wave structure. It is also shown the practical limits of the proposed correction approach. The leaky-mode theory is applied for the first time to compensate the losses in a practical leaky-wave antenna in hybrid waveguide printed circuit technology. This leaky-mode theory is validated with full-wave three-dimensional finite element method simulations of the designed antenna.

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Poly (methyl methacrylate) (PMMA) bone cement—multi walled carbon nanotube (MWCNT) nanocomposites with weight loadings ranging from 0.1 to 1.0 wt% were prepared. The MWCNTs investigated were unfunctionalised, carboxyl and amine functionalised MWCNTs. Mechanical properties of the resultant nanocomposite cements were characterised as per international standards for acrylic resin cements. These mechanical properties were influenced by the type and wt% loading of MWCNT used. The morphology and degree of dispersion of the MWCNTs in the PMMA matrix at different length scales were examined using field emission scanning electron microscopy. Improvements in mechanical properties were attributed to the MWCNTs arresting/retarding crack propagation through the cement by providing a bridging effect and hindering crack propagation. MWCNTs agglomerations were evident within the cement microstructure, the degree of these agglomerations was dependent on the weight fraction and functionality of MWCNTs incorporated into the cement.

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The strategic incorporation of bioresorbable polymeric additives to calcium-deficient hydroxyapatite cement may provide short-term structural reinforcement and modify the modulus to closer match bone. The longer-term resorption properties may also be improved, creating pathways for bone in-growth. The aim of this study was to investigate the resorption process of a calcium phosphate cement system containing either in polyglycolic acid tri-methylene carbonate particles or polyglycolic acid fibres. This was achieved by in vitro aging in physiological conditions (phosphate buffered solution at 37°C) over 12 weeks. The unreinforced CPC exhibited an increase in compressive strength at 12 weeks, however catastrophic failure was observed above a critical loading. The fracture behaviour of cement was improved by the incorporation of PGA fibres; the cement retained its cohesive structure after critical loading. Gravimetric analysis and scanning electron microscopy showed a large proportion of the fibres had resorbed after 12 weeks allowing for the increased cement porosity, which could facilitate cell infiltration and faster integration of natural bone. Incorporating the particulate additives in the cement did not provide any mechanism for mechanical property augmentation or did not demonstrate any appreciable level of resorption after 12 weeks.

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Aims To investigate mortality in South Asian patients with insulin-treated diabetes and compare it with mortality in non South Asian patients and in the general population.

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Asthma is a major risk cofactor for anaphylactic deaths in children with peanut allergy. Peanut allergy is generally thought to be a lifelong condition, but some children outgrow their coexistent asthma. It has recently been shown that children who have ‘outgrown’ their asthma symptoms may have ongoing eosinophilic airways inflammation. The need for regular inhaled corticosteroid treatment in peanut allergic children and adolescents who have outgrown their asthma is however unclear. The aims of our study were to look at fractional exhaled nitric oxide levels (FeNO), as a non-invasive marker of eosinophilic airways inflammation, in peanut allergic children and assess whether children with outgrown asthma had elevated levels. Children with peanut allergy were recruited at two pediatric allergy clinics in Belfast, UK. Exhaled nitric oxide levels (FeNO) were measured using the Niox Mino in all children. Of the 101 peanut allergic children who consented for enrolment in the study, 94 were successfully able to use the NIOX Mino. Age range was 4–15 yr (median 10 yr); 61% were boys. Thirty (32%) had never wheezed, 37 (39%) had current treated asthma, 20 (21%) had at least 1 wheezing episode within the last year but were not taking any regular asthma medication (wheeze no treatment), and 7 (7%) had outgrown asthma. All children with outgrown asthma had elevated levels of FeNO (>35 ppb), and 75% of children defined as ‘wheeze no treatment’ had elevated FeNO levels (>35 ppb). Outgrown asthma and children defined as ‘wheeze no treatment’ had higher levels of FeNO than those with no history of wheeze or current treated asthma (p = 0.003). In children with peanut allergy, we found that those who had outgrown asthma had elevated FeNO levels in keeping with ongoing eosinophilic airways inflammation.

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A new inline coupling topology for narrowband helical resonator filters is proposed that allows to introduce selectively located transmission zeros (TZs) in the stopband. We show that a pair of helical resonators arranged in an interdigital configuration can realize a large range of in-band coupling coefficient values and also selectively position a TZ in the stopband. The proposed technique dispenses the need for auxiliary elements, so that the size, complexity, power handling and insertion loss of the filter are not compromised. A second order prototype filter with dimensions of the order of 0.05 lambda, power handling capability up to 90 W, measured insertion loss of 0.18 dB and improved selectivity is presented.

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The reactions of surface functional groups have an important role in controlling conversion of char nitrogen to NOx during coal combustion. This study involved an investigation of the thermal stability and reactions of nitrogen surface functional groups in nanoporous carbons. Four suites of carbons, which were used as models for coal chars, were prepared with a wide range of nitrogen and oxygen contents and types of functional groups. The porous structures of the carbons were characterized by gas adsorption methods while chemical analysis, X-ray photoelectron spectroscopy, and X-ray near edge structure spectroscopy were used to characterize the surface functional groups. Temperature programmed desorption and temperature programmed reduction methods were used to study the reactivity of the surface functional groups during heat treatment under inert and reducing conditions. Heat treatment studies show that the order of stability of the functional groups is quaternary nitrogen > pyridinic > pyrrolic > pyridine N-oxide. Pyridine N-oxide surface groups desorb NO and form N-2 via surface reactions at low temperature. Pyrrolic and pyridinic functional groups decompose and react with surface species to give NH3, HCN, and N-2 as desorption products, but most pyrrolic groups are preferentially converted to pyridinic and quaternary nitrogen. The main desorption product is N-2. Approximately 15-40 wt % of the original nitrogen was retained in the carbons mainly as quaternary nitrogen after heat treatment to 1673 K. The results are discussed in terms of decomposition ranges for surface functional groups and reaction mechanisms of surface species.