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关键词： Nutrition   Photoblastic   Rhizoid   Seed physiology   Seedling development   HABENARIA-MACROCERATITIS ORCHIDACEAE   DACTYLORHIZA-MAJALIS ORCHIDACEAE   IN-VITRO GERMINATION   ASYMBIOTIC GERMINATION   SYMBIOTIC GERMINATION   ALPHA-AMYLASE   TERRESTRIAL   CULTURE   GROWTH   PROPAGATION  

摘要： The effects of carbohydrate availability, carbohydrate source, nutrient availability and illumination on germination and early development of Bletia purpurea (Orchidaceae) seeds were investigated using asymbiotic seed germination. Of special interest was determining the minimum nutritional and light requirements for the completion of germination. Germination and development was limited when seeds were cultured in darkness without sucrose. Seeds were able to germinate under illuminated conditions even in the absence of sucrose and this effect was enhanced when mineral nutrients were incorporated into media. Sucrose, fructose, glucose and trehalose enhanced germination and seedling development while mannitol and sorbitol did not. These data suggest that carbohydrates, either as products of photosynthesis, from symbiotic fungi in situ or as exogenously supplied sugars in vitro, play an important role in regulating seed germination by fulfilling an energy requirement. This hypothesis has been often expressed but rarely satisfactorily tested. Mineral nutrients appear to be less important for germination than carbohydrates. The differential effect of sucrose, fructose, glucose and trehalose at two different concentrations on rhizoid production indicates carbohydrates may play a role in regulating rhizoid production.

关键词： Nearest neighbor   Sample weighting   Loss function   Large margin   ALGORITHMS  

摘要： The nearest neighbor classification is a simple and yet effective technique for pattern recognition. Performance of this technique depends significantly on the distance function used to compute similarity between examples. Some techniques were developed to learn weights of features for changing the distance structure of samples in nearest neighbor classification. In this paper, we propose an approach to learning sample weights for enlarging margin by using a gradient descent algorithm to minimize margin based classification loss. Experimental analysis shows that the distances trained in this way reduce the loss of the margin and enlarge the hypothesis margin on several datasets. Moreover, the proposed approach consistently outperforms nearest neighbor classification and some other state-of-the-art methods. (c) 2010 Elsevier B.V. All rights reserved.

关键词： Polymerized triacylglycerides (PTG)   Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR)   Partial least squares-discriminant analysis (PLS-DA)   Partial least squares (PLS) regression   TRANSFORM-INFRARED-SPECTROSCOPY   ILLICIT STREET DRUGS   EDIBLE OILS   MULTIVARIATE CALIBRATION   RAMAN SPECTROSCOPY   OLIVE OILS   FATS   SPECTRA   PARAMETERS   SPECTROMETRY  

摘要： The selection of an appropriate calibration set is a critical step in multivariate method development. In this work, the effect of using different calibration sets, based on a previous classification of unknown samples, on the partial least squares (PLS) regression model performance has been discussed. As an example, attenuated total reflection (ATR) mid-infrared spectra of deep-fried vegetable oil samples from three botanical origins (olive, sunflower, and corn oil), with increasing polymerized triacylglyceride (PTG) content induced by a deep-frying process were employed. The use of a one-class-classifier partial least squares-discriminant analysis (PLS-DA) and a rooted binary directed acyclic graph tree provided accurate oil classification. Oil samples fried without foodstuff could be classified correctly, independent of their PTG content. However, class separation of oil samples fried with foodstuff, was less evident. The combined use of double-cross model validation with permutation testing was used to validate the obtained PLS-DA classification models, confirming the results. To discuss the usefulness of the selection of an appropriate PLS calibration set, the PTG content was determined by calculating a PLS model based on the previously selected classes. In comparison to a PLS model calculated using a pooled calibration set containing samples from all classes, the root mean square error of prediction could be improved significantly using PLS models based on the selected calibration sets using PLS-DA, ranging between 1.06 and 2.91% (w/w).

关键词： Photosynthesis   Evolution   Reaction center   Tyrosine oxidation   Manganese   Oxygen-evolving complex   Rhodobacter sphaeroides   Purple bacteria   RHODOBACTER-SPHAEROIDES R-26   PRIMARY CHARGE-SEPARATION   INITIAL ELECTRON-TRANSFER   BACTERIOCHLOROPHYLL DIMER   CRYSTAL-STRUCTURE   PROTON RELEASE   PRIMARY DONOR   OXIDATION   WATER   DEPENDENCE  

摘要： In photosynthetic organisms, such as purple bacteria, cyanobacteria, and plants, light is captured and converted into energy to create energy-rich compounds. The primary process of energy conversion involves the transfer of electrons from an excited donor molecule to a series of electron acceptors in pigment-protein complexes. Two of these complexes, the bacterial reaction center and photosystem II, are evolutionarily related and structurally similar. However, only photosystem II is capable of performing the unique reaction of water oxidation. An understanding of the evolutionary process that lead to the development of oxygenic photosynthesis can be found by comparison of these two complexes. In this review, we summarize how insight is being gained by examination of the differences in critical functional properties of these complexes and by experimental efforts to alter pigment-protein interactions of the bacterial reaction center in order to enable it to perform reactions, such as amino acid and metal oxidation, observable in photosystem II.

关键词： 木材检验   企业经营   管理   作用  

摘要： 提高经济效益的主要环节之一包括木材检验工作,因为检验工作是术材生产、销售的质量保证,是减少木材浪费、提高木材售价的源泉.这就要求各级部门对木材检验予高度重视,实行倾斜政策,突出木材检验在森工企业中的地位,只有这样才能充分发挥木材检验在治危兴林中的作用.

关键词： 旅游合同   责任形式  

摘要： 在旅游合同违约中,采取补救措施往往与旅游营业人违反瑕疵担保义务联系在一起.当旅游给付存在瑕疵时,旅游者在一定条件下可以提出改善、减少价金等请求.

关键词： 检地合作   检验检疫   普法  

摘要： 在我国对外开放口岸和大中城外以外的绝大部分地区,由于没有设置检验检疫机构,检验检疫社会认知度较低,普法宣传难度较大.笔者认为应借助地方政府和相关职能部门,在建立普法合作机制、建立普法协调机制和创新普法学法载体等三个方面,积极构建'检地合作',提高检验检疫普法的有效性,为我国经济建设服务.

关键词： 股指期货   价格发现   协整检验   脉冲响应   方差分解  

摘要： 每一个发展良好的资本市场都离不开健全丰富的金融产品体系、健康并富有活力的融资主体、广大理性的投资群体以及完善的市场交易制度。股票指数期货作为金融产品体系中一个不可缺少的组成部分,在全球金融市场上发挥着举足轻重的作用。股指期货由于具备交易标的操作性强、多空操作不受限制的优势以及低交易成本、高交易效率等优点,在各国金融市场上成为最快速反映宏观经济变动趋势,反映市场信息和投资者交易情绪的晴雨表,并且具备价格发现、套期保值和套利等功能。 中国金融交易所成立已经有近5年的时间,交易所成立以来,一直在积极筹备股指期货的上市工作。2006年10月推出了沪深300股指期货仿真交易,在其健康运行了3年多后,2010年4月,中金所又推出了沪深300股指期货的实盘交易,股指期货的推出,是我国资本市场迈向成熟的里程碑事件。股指期货价格发现、套期保值、套利等作用的发挥能够满足交易者规避系统性风险的需要,提高资金的使用效率,极大地提高我国资本市场的活力。 股指期货的价格发现作用则是其发挥其他功能的基础,正是由于股指期货是未来大盘指数现货的无偏估计,投资者利用股指期货进行套期保值和套利才成为可能。本文就选取了上市1年左右的沪深300股指期货交易数据,利用理论分析和实证分析的方法,从股指期货与指数现货之间的领先滞后关系以及股指期货在价格发现过程中的主导作用两个方面对我国股指期货市场的价格发现作用进行了研究。本文首先简单介绍了我国股指期货的发展状况,其次注重分析了其价格发现作用的理论基础,然后利用实证模型对其价格发现作用作了深入的研究。具体而言,利用E-G两步法和Johansen协整关系检验发现,期货市场和现货市场之间具有长期稳定的关系,利用Granger因果关系检验发现,现货市场的价格变化是引起期货市场价格变化的原因,利用ECM模型发现两市场相互影响,现货价格对期货价格具有正向引导作用,从而证明了现货市场领先期货市场变动。而后利用脉冲响应函数发现,指数现货对股指期货的短期影响较小,但有较为稳定的长期影响,而股指期货对指数现货的短期影响较大,但长期来看,并没有显著的影响。利用方差分解模型发现,现货市场在价格发现过程中起主导作用,沪深300股指期货的价格发现作用并没有显著地体现出来。最后,本文结合实证结果对股指期货价格发现作用较现货市场弱的原因进行了分析,主要由期货市场流动性不足,交易者结构单一,股票市场交易制度不完善和市场信息并未完全体现等原因所致。可以预见的是,伴随着我国资本市场直接融资比例的逐步提高,股指期货市场的交易制度将会逐步完善,资本市场产品也会日益丰富,我国股指期货市场的优势会日益显现,价格发现作用也将体现出来。

关键词： 电子天平   检定   质量控制  

摘要： 本文从电子天平原理出发,对检验过程中电子天平的检定对质量控制的作用进行论述.

关键词： 临床微生物学检验   医院感染检测  

摘要： 随着医疗技术的发展,各种侵入性操作治疗手段的使用,肿瘤化疗,激素和免疫抑制剂的广泛应用,医院感染问题日益突出。抗生素的广泛应用,在有效治疗感染的同时,也诱发或导致治疗更加