浅谈海外IPO定价低估与关键控制点——基于当当网的案例研究

2010年中国企业掀起了一阵赴美上市的热潮。据相关统计,2010年中国赴美上市企业数量达到42家,融资额达到38.86亿美元。当当网是全球最大的综合性中文网上购物商城,于12月8日在纽约交易所上市,以每股发行价16美元出售,首日开盘价24.48美元,涨幅53%。公司CEO不满发行价过低,掀起与“大摩女“网络

Determination of Pseudostellarin B in Pseudostellaria heterophylla by HPCE and Study on Its Fingerprints Analysis

建立了测定太子参中环肽Pseudostellarin B含量的高效毛细管电泳(HPCE)分析方法,对10种不同产地太子参中环肽Pseudostellarin B的含量进行了测定。HPCE工作条件:采用未涂层熔融石英毛细管(内径75μm,有效长度50cm),分离电压为15kV,柱温20℃,二极管阵列检测器(DAD)检测波长为203nm,缓冲液为20mmol/L硼砂(pH=9.3)溶液。在选定的工作条件下,环肽Pseudostellarin B浓度与其响应信号值之间具有较好的线性相关性(Y=0.6357X+2.546,R=0.9985),加标回收率在93.8%~105.6%之间。在此基础上进行了太子参HPCE指纹图谱研究,采用中药指纹图谱相似度计算软件对不同太子参样品的HPCE指纹图谱进行相似度计算,以系统生成的对照指纹图谱为对照模板,10份样品中有8份的相似度在0.90以上,说明该方法可用于太子参质量控制。A modern HPCE analysis method was developed for determinating cyclic peptide Pseudostellarin B in Pseudostellaria heterophylla(Miq.) Pax.Separation and determination were carried out by HPCE under the following conditions: bared fused silica capillary (50 cm×75 μm i.d.),20 mmol/L borate (pH=9.3)as buffer,the run voltage is +15 kV,detection length of UV at 203 nm,and column temperature of 20 ℃.The results indicated that the developed method was simple,accurate and reliable for the determination of Pseudostellarin B with a good linearity(Y=0.6357X+2.546,R=0.9985),and the recovery ranges of 93.8%～105.6%.Based on this method,the HPCE fingerprints of Pseudostellaria heterophylla (Miq.) Pax were established.The fingerprints were compared by the software of the similarity evaluation system for chromatographic fingerprint.The fingerprint congruence coefficients of 8 electropherograms in 10 were above 0.90.The method of HPCE fingerprint is reliable and accurate.国家自然科学基金项目(20235020);; 国家科技部攻关项目(2003BA759C

Direct Fabrication of Ultrafine Electrospinning Nanofiber

采用装配有疏水铜网的新型喷头研究了超细纳米纤维的制备.静电纺丝实现之前,首先对铜网进行了疏水处理,并将其安装于喷头前端.静电纺丝过程中,聚合物溶液由精密注射泵输送至喷头处.安装于喷头的铜网可将管道内的聚合物溶液分成多股细流从铜网网孔中流出.从铜网网孔流出的溶液细流受电场力作用被拉伸成多股独立射流,并从喷头携带走聚集的正电荷.受铜网表面疏水性和射流间电荷排斥力的影响,从铜网喷射出的多股射流都将保持其独立的轨迹而不会产生聚集.疏水铜网有利于减小纺丝射流的初始直径,并获得均匀的超细纳米纤维.利用新型的电纺丝喷头成功制备了直径20~80 nM的聚氧化乙烯(PEO)和聚乙烯醇(PVA)超细纳米纤维.实验结果表明,超细纳米纤维的直径随着电纺丝溶液浓度的增加而变大.A novel spinneret assembled with Cu grid was presented in this paper to fabricate ultrafine nanofiber directly.Before electrospinning,hydrophobic treatment was performed on the Cu grid,which was then fixed at the front end of spinneret.During electrospinning,the polymer solution was transferred to the spinneret by the precise syringe pump.Through the holes in the Cu grid,polymer solution flow was divided into several smaller ones.The fine liquid flow from each hole of Cu grid was stretched into individual jets by the electric field force,and the liquid jets carried away the positive charges accumulated on the spinneret.Due to the hydrophobic treatment and the charge repulsive force between charged jets,liquid jets emanated from Cu grid kept their own tracks without aggregation.The initial diameter of liquid jet was greatly decreased by the Cu grid after hydrophobic treatment,and the smaller jet led to finer uniform nanofiber.Polyethylene oxide(PEO) and polyvinyl alcohol(PVA) ultrafine nanofiber with the diameter of 20—80 nm were fabricated by this novel spinneret,and the diameter of ultrafine nanofiber increases with the increase of polymer solution concentration.国家自然科学基金重点资助项目(51035002);国家自然科学基金资助项目(50875222

2016年夏季南海海盆水体颗粒物粒径分布特征

颗粒物粒径分布（Particle Size Distribution,PSD）代表了颗粒物浓度与颗粒物粒径之间的关系,影响着海洋生态环境和水体光学特性等。文章基于2016年夏季航次调查的生物光学剖面数据,研究了南海海盆海域PSD的分布特征。研究发现,幂律函数可以较好地拟合南海海盆区域的PSD,对数空间中的实测的PSD与模拟的PSD平均决定系数高达0.95。PSD斜率（ξ）的分布范围为[1.27,7.65],均值为3.93±0.56。南海海盆区域表层水体的ξ均值与全球大洋表层水体的ξ均值相近,但高于海湾等表层水体的ξ均值。ξ能较好地表征颗粒物平均粒径DA的大小,两者存在明显负相关关系,即ξ值越高,DA越小;反之,DA越大。通过分析T1断面的生物光学剖面数据及总体平均的PSD剖面数据,发现PSD剖面分布特征如下:1)表层水体的ξ值相对较高,且DA值相对较低,推测可能是由于微微型藻类为主导颗粒物所致;2)ξ值极小值层出现在次表层叶绿素浓度极大值层（Subsurface Chlorophyll Maximum Layer,SCML）中,并伴随DA极大值层的出现,其原因可能是SCML中的大粒径浮游植物占比显著增加;3)弱光层中的ξ值较SCML中的高,但略低于表层的ξ值,而DA则位于表层与SCML的DA之间,这可能与浮游植物及其碎屑的絮凝、分解、沉降等过程相关。PSD特征影响着海水的固有光学特性,分析发现:由于SCML中的叶绿素浓度增加,颗粒物散射系数（bp（532））和颗粒物后向散射系数(bbp（532）)也相应呈现显著增加的趋势。弱光层中的平均bp（532）与平均bbp（532）最小。ξ与颗粒物衰减光谱斜率之间呈高分散性,Boss等（2001b）的模型适合用于粗略估算区域性的ξ分布范围及均值。国家自然科学基金(41576030,41431176,4176045,4176044,41376042);;热带海洋环境国家重点实验室自主研究项目(LTOZZ1602);;广州市科技计划重点项目(201504010034,201707020023,201607020041);;广东省科技计划重点项目(2016A020222008);;中科院A类先导专项(XDA11040302)~

塔里木沙漠公路防护林土壤微生物生物量与土壤环境因子的关系

为探讨极端干旱区风沙土土壤微生物与土壤环境因子的作用规律,采用相关分析法研究了塔里木沙漠公路防护林地土壤微生物生物量与理化因子和酶活性的关系.结果表明:土壤容重和粒径减小(R0.85)时,防护林地中土壤微生物数量和生物量有增大趋势,由容重与微生物量的相关性主导;土壤养分含量与土壤微生物数量和生物量呈正相关,主要由速效养分和放线菌、微生物生物量C、P的相关性所致;土壤酶活性与土壤微生物数量和生物量的相关性差异较大,R在0.51～0.91,主要取决于蔗糖酶、磷酸酶与放线菌、微生物量C的相关;土壤盐分增加不利于土壤微生物生物量的积累(R0.63).实践中应为干旱区林地土壤微生物营造良好的土体,促进土壤物质循环

大孔吸附树脂分离纯化龙胆药材中龙胆苦苷和马钱子苷酸的研究

目的:建立利用大孔吸附树脂对龙胆药材中龙胆苦苷和马钱子苷酸进行富集和分离纯化的方法。方法:采用加速溶剂萃取法对龙胆药材中两种有效成分进行高效提取,比较了D301,AB-8,D101,XDA-1四种大孔树脂对龙胆苦苷和马钱子苷酸的吸附性能,最终确定采用D301型大孔对脂对二者进行富集吸附,对其工艺参数进行优化,全程采用高效液相色谱进行目标化合物浓度检测。结果:化优后的工艺参数为:上样浓度:0.2 g/mL,最大上样量:0.25 g龙胆药材/g树脂,最佳静态吸附时间:8 h,采用8%和55%的乙醇溶液对龙胆苦苷和马钱子苷酸分别进行洗脱;龙胆苦苷和马钱子苷酸分别富集在8%和55%的乙醇洗脱液中,洗脱液浓缩后冷冻干燥,可得到纯度分别为74.3%和80.9%的粗产物,龙胆苦苷和马钱子苷酸的回收率分别为70.11%和67.82%。结论:此法效率较高,操作简便,即可用于实验室制备少量的难以购置的标准品,也可进行放大研究,用于工业生产。国家自然科学基金重点项目(20235020);; 青岛“2004将才计划”(04-3-JJ-11);; 共建生物医药研发测试中心(LS-05-KJZX-76)资

Application of Accelerated Solvent Extraction Technique for Analysis of Active Components in Traditional Chinese Medicinal Herbs

以两种药材为研究实例,对加速溶剂萃取法(ASE)在中药材有效成分提取研究中的应用进行了简要介绍。采用正交试验法考察了提取丹参中丹酚酸B的提取条件(萃取温度、静态萃取时间、萃取溶剂以及料液比),确定了较好的实验条件。比较了ASE、水蒸气蒸馏法、超声波提取法及索氏提取法对木香挥发油的提取效果,结果表明ASE对木香挥发油的提取效果最好。The application of accelerated solvent extraction(ASE) technique for the Analysis of active components in traditional Chinese medicinal herbs was introduced by using two kinds of herbs as examples.The conditions including extraction temperature,static extraction time,the ratio of material to solvent and solvent of ASE for extraction of salvianolic acid B in Salvia miltiorrhiza were optimized by orthogonal experiments,and the optimal conditions were obtained.Different extraction methods(ASE,steam distillation,ultrasonic wave and Soxhlet extraction) were used to extract volatile oil in Aucklandia lappa Decne.Results of the comparative experiments indicated that ASE was the most effective method in this case.All the results from these studies demonstrate that ASE is indeed a powerful tool in the preparation of herbal extracts for downstream chromatographic analysis.青岛“2004将才计划”(04-3-JJ-11);; 共建生物医药研发测试中心(LS-05-KJZX-76)资

Analysis of Alkaloids in Coptis chinensis Franch by High Performance Capillary Electrophoresis-Electrospray Ionization Time of Flight Mass Spectrometry

建立了高效毛细管电泳-电喷雾飞行时间质谱联用(HPCE-ESI-TOF/MS)快速定性分析黄连中生物碱类化合物的分析方法.使用未涂层石英毛细管,以50mmol/L乙酸铵-0.5%甲醇溶液(用氨水调至pH=7.2)作为运行缓冲液,分离电压为25kV;鞘液组成为50%甲醇-49.5%水-0.5%乙酸,鞘液流速为4μL/min;质谱选用正离子模式,碰撞电压(Fragmentor)为100V.结果表明,通过各色谱峰紫外光谱和质谱测得精确分子量结果,结合文献,对黄连中7种生物碱进行了鉴定.表明本方法简便、快速,是黄连中生物碱类化合物快速分离、鉴别的有效方法.A new method for the analysis of alkaloids in Coptis chinensis Franch was established by high performance capillary electrophoresis-electrospray ionization time of flight mass spectrometry (HPCE-ESI-TOF/MS). The real samples were separated by an uncoated capillary. 50 mmol/L ammonium acetate containing 0.5% methanol (pH=7.2) was used as the running buffer, and separation voltage was 25 kV. A coaxial sheath flow interface was used as the CE-MS interface, and a 50% methanol-49.5% water- 0.5% acetic acid mixture was used as the sheath liquid with a flow rate of 4 μL/min. The lens voltages in a positive ion mode with a collision induced dissociation (CID) voltage of 100 V were used for ESI-TOF/MS analysis. Seven alkaloids in Coptis chinensis Franch methanol extracts were separated and identified by CE-DAD and CE-ESI-TOF/MS. The coupling of HPCE separation with accurate mass measurement capability of ESI-TOF/MS provides an attractive tool for the identification of alkaloid compounds in Coptis chinensis Franch.国家自然科学基金重点项目(No.20235020);; 青岛“2004将才计划”(No.04-3-JJ-11);; 共建生物医药研发测试中心(No.LS-05-KJZX-76)资助项目

NMR Studies on Interactions between Diperoxovanadate and Imidazole-like Ligands

为探讨咪唑环上取代基团对反应平衡的影响,在模拟生理条件(0.15 mol·L~(-1)NaCl溶液)下,应用多核(~1H、~(13)C和~(51)V)、扩散排序谱(DOSY)以及变温NMR等谱学技术研究双过氧钒配合物NH_4[OV(O_2)_2{2-(2'-Pyri-dine)- [midazole}]·4H_2O(简写为bpV(Imi-Py))和咪唑类配体(咪唑、2-甲基-咪唑、4-甲基-咪唑和组氨酸)的相互作用,其从强到弱的顺序为咪唑≈4-甲基-咪唑>2-甲基-咪唑>组氨酸.研究结果表明,咪唑环上取代基团空间位阻对反应平衡产生较大影响,同时竞争配位的结果导致新的6配位过氧物种[OV(O_2)_2L]~-(L为咪唑类配体)的生成,当配体为4-甲基-咪唑和组氨酸时,生成的则是一对异构体.To understand the substituting effects of imidazole ring on the reaction equilibrium,the interactions between diperoxovanadate complex NH_4[OV(O_2)_2{2-(2'-Pyridine)-Imidazole}]·4H_2O (abbr.bpV(Imi-Py)) and a series of imidazole-like ligands (imidazole,2-methyl-imidazole,4-methyl-imidazole,and histidine) in solution were explored using multinuclear (~1H,~(13)C,and ~(51)V) magnetic resonance,diffusion ordered spectroscopy (DOSY),and variable temperature NMR in 0.15 mol·L~(-1) NaCl ionic medium for mimicking the physiological conditions.The experimental results indicated that the activities of bpV(Imi-Py) and organic ligands were as follows:imidazole≈4-methyl-imidazole>2-methyl- imidazole>histidine.The stedc effect of the organic ligands affects the reaction equilibrium.At the same time,new six- coordinated peroxovanadate species [OV(O_2)_2L]-(L=imidazole-like ligands) were formed due to the competitive coordination between 2-(2'-pyridyl)-imidazole and the imidazole-like ligands.When the ligand was 4-methyl- imidazole or histidine,a pair of isomers was formed.国家自然科学基金(20772027);; 973子课题(2003CB716005);; 湖南省自然科学基金(06JJ30004);; 中国博士后科学基金(20070410805);; 湖南省教育厅青年项目(068028);; 卫生部(福建省)卫生教育联合攻关计划(3502220051027);; 厦门市重大疾病攻关研究基金(Wkj2005-2-019);; 固体表面物理化学国家重点实验室开放基金和湖南科技大学博士基金(E55107)资