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991.
meso—四—(3,5—二溴—4—羟基苯—卟啉分光光度法测定铅 总被引:1,自引:0,他引:1
meso-四(3,5-二溴-4-羟基苯)卟啉[T(DBHP)P],一种新的溴代卟啉可用作测定铅的试剂.当8-羟基喹啉存在时,铅可在碱性介质中迅速与T(DBHP)P反应生成配合物.该配合物的Soret带位于479nm,摩尔吸光率为2.4×10~5 L/(mol·cm).在25ml溶液中0~11μg铅符合比耳定律.本法的选择性显著高于未溴代的meso-四(4-羟基苯)卟啉[T(4-HP)P]法.用本法通过碘化物-MIBK萃取后测定了铁矿和金属锌中的铅,结果良好. 相似文献
992.
本文报告治疗随访颈椎病患者383例:男205,女178;40岁以上319,39岁以下74;神经根型278,脊髓型29,椎动脉型8,交感型8。混合型15及颈型34例。肩胛区压痛:单侧111例,双侧31例(压痛区173处)占38.4%。合并冻结肩2例,网球肘2例,神经系疾病5例,前纵韧带骨化(OALL)9例,后纵韧带骨化(OPLL)1例,项韧带骨化(ONL)5例。在调查中同时发现年青人亦易患颈椎病(颈椎间盘早期退行性变)占0.8%。本文颈椎病发病率较高占4.8%,并有6例做了手术治疗。提出各种X线客观检查应与临床症状体征相符,才能诊断颈椎病。为了更符合颈椎病复杂的病理改变及临床表现,提出“颈椎间盘综合征”(Intercerical disc Syndrome)一词。颈椎病的治疗,非手术综合治疗包括以按摩为主,服药、神经阻滞疗法、离子导入及穿戴CVPC—1型塑料围领或颈牵引为铺的治疗方法。结果:治愈与好转者占81.4%。手术治疗有前路手术:椎间盘切除,后骨刺刮除及椎间植骨术(合并OALL及吞咽困难者亦可能行前路手术);后路手术:椎板广泛减压,后纵韧带骨化及项韧带骨化的切除手术,本组15例手术患者,治愈及好转者占93.3%。 相似文献
993.
As a significant measure of software security evaluation, software reliability evaluation is also the basis of software safe operation. Traditional software system security evaluation methods are qualitative evaluation based on the functional and structural measurements, and it often ignores quantitative research based on invalidity and fault. This paper propose a stochastic transition function as a measure parameters of the reliability of stochastic Petri nets (SPN) theory. By calculating the probability of stability of the system, failure and mean time to first failure, it establishes an evaluation and measurement method for software reliability. With example analysis, the method can conduct effective evaluation on the software reliability index quickly and accurately, and meanwhile provides a new method for the software security evaluation. 相似文献
994.
为探索湿热预处理对餐厨垃圾高温干式厌氧消化的影响,在含固率为20%、发酵温度55℃的条件下进行厌氧发酵试验。采用L9(33)正交试验设计,研究湿热预处理的加水率、温度、时间对餐厨垃圾干式厌氧消化产沼气的影响。结果表明:湿热处理后餐厨垃圾的理化性质有明显变化,日产气量、累积产气量以及TS和VS的去除率明显升高。当湿热预处理条件为加水率50%、温度120℃、时间80 min时,SCOD值最高,为101050 mg/L,比未处理时提高了5.6倍。同样,该条件下日产气量出现的两个产气峰值最高,累积产气量也最高,为269.10 ml/gVS,与未处理相比累积产气量提高49.4%。各因素对餐厨垃圾厌氧发酵产气量影响的主次关系为:温度>时间>加水率,处理温度和处理时间对产气量有显著性影响,加水率对产气量影响较弱。 相似文献
995.
为了有效判断网络数据包是否存在被攻击的可能性,在以往的研究基础上提出了一种新的检测算法DMPS(Detec-tion method based of particle susarm)。首先该算法根据数据包属性的离散度定义了状态检测指标,并利用粒子群优化方法给出了标准差分布的计算流程,以此判断数据包的异常状况。最后,通过OPNET和Matlab进行仿真实验,深入研究了影响该算法的关键因素,同时对比了与其他算法之间的性能状况,结果表明DMPS具有较好的适应性。
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996.
Li-Chun Wang Kuan-Yu Chen Huichin Pan Chia-Chieh Wu Po-Hsuan Chen Yuan-Ting Liao Chin Li Min-Lang Huang Kuang-Ming Hsiao 《Cellular and molecular life sciences : CMLS》2011,68(7):1255-1267
We have utilized Caenorhabditis elegans as a model to investigate the toxicity and underlying mechanism of untranslated CAG repeats in comparison to CUG repeats.
Our results indicate that CAG repeats can be toxic at the RNA level in a length-dependent manner, similar to that of CUG repeats.
Both CAG and CUG repeats of toxic length form nuclear foci and co-localize with C. elegans muscleblind (CeMBL), implying that CeMBL may play a role in repeat RNA toxicity. Consistently, the phenotypes of worms expressing
toxic CAG and CUG repeats, including shortened life span and reduced motility rate, were partially reversed by CeMbl over-expression. These results provide the first experimental evidence to show that the RNA toxicity induced by expanded
CAG and CUG repeats can be mediated, at least in part, through the functional alteration of muscleblind in worms. 相似文献
998.
999.
Perfluorooctane sulfonate (PFOS) and other fluorochemicals in viscera and muscle of farmed pigs and chickens in Beijing,China 总被引:2,自引:0,他引:2
Eleven perfluorinated compounds (PFCs) were determined in tissue samples from farmed pigs and chickens (n=143) that were purchased in Beijing in March 2009. The total PFCs mean concentration was the highest in pig liver (3.438 ng g–1 wet weight (ww)), followed by pig kidney (0.508 ng g–1 (ww)), pig heart (0.167 ng g–1 (ww)), chicken liver (0.098 ng g–1 (ww)), chicken heart (0.050 ng g–1 (ww)), pork loin (0.018 ng g–1 (ww)), and chicken breast (0.012 ng g–1 (ww)). Among the PFCs analyzed, perfluorooctane sulfonate (PFOS) was the predominant compound in viscera and muscle of farmed pigs and chickens. In addition, a strong linear correlation (r = 0.932) was observed between the concentrations of PFOS and perfluoroundecanoic acid (PFUnDA) in pig liver. Our preliminary conclusion is that there is little potential risk of exposure to PFCs via the consumption of these products in Beijing. 相似文献
1000.
Using the generalized dynamic factor model, this study constructs three predictors of crude oil price volatility: a fundamental (physical) predictor, a financial predictor, and a macroeconomic uncertainty predictor. Moreover, an event‐triggered predictor is constructed using data extracted from Google Trends. We construct GARCH‐MIDAS (generalized autoregressive conditional heteroskedasticity–mixed‐data sampling) models combining realized volatility with the predictors to predict oil price volatility at different forecasting horizons. We then identify the predictive power of the realized volatility and the predictors by the model confidence set (MCS) test. The findings show that, among the four indexes, the financial predictor has the most predictive power for crude oil volatility, which provides strong evidence that financialization has been the key determinant of crude oil price behavior since the 2008 global financial crisis. In addition, the fundamental predictor, followed by the financial predictor, effectively forecasts crude oil price volatility in the long‐run forecasting horizons. Our findings indicate that the different predictors can provide distinct predictive information at the different horizons given the specific market situation. These findings have useful implications for market traders in terms of managing crude oil price risk. 相似文献