反应酸度对银盐法测定水源水中砷的稳定性影响

目的:探讨反应酸度对银盐法测定水源水中砷的稳定性影响,分析可能存在的影响因素。方法:平行取50m L砷含量为0.025 mg/L的河水试样5份,分别加入3.0、3.5、4.0、5.0、6.0 ml的硫酸(1+1),反应温度在20℃条件下,观察上述不同酸度对水中砷测定结果的影响;对浓度为0.025 mg/L和0.05 mg/L的含砷试样10d内10批平行样测定,采用t检验法衡量测定的稳定性,水砷测定按照水和废水监测分析方法(GB7485-87)中银盐法进行。结果:硫酸加入量3.0~6.0 ml时,样品回收率范围为80.1%~92.6%(F=4.38,P0.05),在硫酸(1+1)加入量5m L条件下,对试样的稳定性影响不显著(t值分别为2.04、1.76t0.05(9)=2.26)。结论:在银盐法测定水砷中,必须控制反应体系酸度才能确保测定结果有一定的精密度和准确度。     

反相高效液相色谱法测定可乐中咖啡因的含量

建立用反相高效液相色谱法(RPLC)测定可乐中咖啡因的方法。可乐试样先用超声清洗器在40℃下超声5min,然后经前处理柱过滤,除去绝大部分有机物,最后经过0.45μm水系滤膜过滤后方可进样,通过Diomonsil C18(2)5 u色谱柱分离,以甲醇+水混合溶液为流动相进行洗脱,于286 nm波长下紫外检测。咖啡因在10～150μg/mL范围内的线性关系良好,在加标水平为60,80,100μg/mL时,被测物的回收率为96.8%～101.8%。     

毛细管电泳测定大黄素主成分的含量

以熔融石英毛细管柱(60.2 cm×50μm,有效长度50 cm)为分离柱,70 mmol/L Na2B4O7、70 mmol/LNa2CO3和80 mmol/L羟丙基-β-环糊精(pH 9.7)为分离缓冲溶液,测定了纯化后的大黄素的主成分含量为98.50%,方法精密度为0.1%(n=9),并与高效液相色谱法的测定结果进行了比较,二者无显著性差异.     

LC-MS同时测定大鼠脑脊液中谷氨酸和γ-氨基丁酸的方法研究

建立LC-MS同时检测大鼠脑脊液中谷氨酸和γ-氨基丁酸的方法。采用安捷伦ZORBAX SIL(4.6 mm×250 mm×5μm)硅胶正相色谱柱,流动相为甲醇-水(0.1%甲酸)=50∶50(v/v),梯度洗脱,流速为1 m L/min。电喷雾离子源(eletrospray ionization,ESI)采用正离子化方式,以多重反应检测(multiple reaction monitoring,MRM)方式进行检测,用于定量分析的离子反应分别为m/z 148.1→m/z 84.1(谷氨酸,[M+H]+),m/z 104.1→m/z 87.1(γ-氨基丁酸,[M+H]+)。测定大鼠脑脊液中谷氨酸在500~2 500μg/L和γ-氨基丁酸在50~250μg/L质量浓度范围内,浓度与峰面积呈良好的线性关系。该方法简便、准确、灵敏度高,专属性强,重复性好,适用于脑脊液中谷氨酸和γ-氨基丁酸的同时测定,可为氨基酸类神经递质提供有效的检测手段。     

硅基电泳芯片非接触电导检测器

研制了一种集成于硅基电泳芯片分离沟道末端侧壁的新型二电极非接触电导检测器.讨论了影响电导检测响应灵敏度的相关因素;采用MEMS分析软件及等效电路模拟仿真,确定了检测器的相关参数,电极长度为550μm,宽度为15μm,间距为80μm,绝缘层厚度为1μm,电导检测工作频率为300 kHz.在加工技术中,选用SOI(sili-con on insulator)基片制作十字形微沟道及集成电导检测电极,采用深刻蚀和隔离技术使检测电极被完全隔离成孤岛,利用硼掺杂技术在分离沟道末端侧壁形成立体电极,获得了集成非接触电导检测电极的硅基电泳芯片.在外加Vpp为10 V、工作频率为300 kHz的正弦波激励下,进行了Na+无机阳离子浓度梯度实验以及Na+和Li+混合无机阳离子的电泳分离检测.结果表明,Na+浓度在1×10-9～1×10-4 mol/L范围内,电导响应信号随着离子浓度的增加而增大,检出限达到1×10-9 mol/L;Na+和Li+混合无机阳离子的分离度达到2.0,实现基线分离.     

葡萄糖酰胺非离子双子表面活性剂的制备与表征

以烷基胺、1,3-二溴丙烷为主要原料,采用两步法合成了不同碳链长度(n=8、12、16)的N,N′-二烷基(8/12/16)-N,N′-二葡萄糖丙二酰胺非离子双子表面活性剂。通过FTIR与1 HNMR对产物的结构进行了表征,用悬滴法对其表面张力进行了测定,用动态光散射对其粒度分布进行了测定,用改进Ross-Miles法对样品的泡沫性能进行了测定。结果表明:合成的葡萄糖酰胺非离子双子表面活性剂(8/12/16)的临界胶束浓度(cmc)及γcmc分别为5.627×10-3 mol/L、4.42×10-4 mol/L、2.96×10-3 mol/L和36.20mN/m、30.22mN/m、46.35mN/m;双子表面活性剂溶液粒径分布在130～1050nm;双子表面活性剂泡沫性能良好。     

人血浆中盐酸沙格雷酯的UPLC-MS/MS测定及药代动力学研究

建立一种快速、准确测定人血浆中盐酸沙格雷酯的UPLC-MS/MS分析方法。以阿立哌唑为内标,0.2 m L含药血浆经乙腈沉淀蛋白后进样分析;流动相组成为乙腈:0.01 mol/L甲酸铵水溶液=30∶70,梯度洗脱方式,乙腈比例在2 min内从30%变为65%,流量0.3 m L/min,柱温为35℃,进样量3μL。质谱条件:气动辅助电喷雾离子化(ESI)源;正离子检测(MRM)模式,盐酸沙格雷酯质荷比为(m/z 430.1→m/z 135.1)和内标阿立哌唑质荷比为(m/z 448.1→m/z285.1)。结果表明:盐酸沙格雷酯在10.0~1 280.0 ng/m L范围内呈线性,定量限为10.0 ng/m L,基质效应影响小,日内、日间变异系数均小于13.3%,相对回收率在92.0%~118.2%之间。该方法准确、快速、灵敏,可用于微量血浆的盐酸沙格雷酯血药浓度测定、人体内药代动力学及生物等效性研究。     

戊二醛-硫酸混合交联壳聚糖/聚砜复合纳滤膜的结构与性能

以聚砜超滤膜(截留分子量10 000)为基膜,壳聚糖乙酸溶液为铸膜液,使用相转化法制备了戊二醛-硫酸混合交联壳聚糖/聚砜复合纳滤膜,并研究了壳聚糖浓度、戊二醛-硫酸混合交联剂等因素对该膜分离效果的影响.在操作压力1.6 MPa、流量30 L/h、20℃条件下,测得纯水通量为12.84 L/(m2.h),对2 000 mg/L的NaCl、MgCl2、Na2SO4和MgSO4的截留率分别为6.6%,94.5%,34%和80.4%,水通量依次为6.93,11.92,6.95和6.73 L/(m2.h);对分子量不低于280的有机物截留率高于90%;对0.01～0.1 mol/L KCl溶液在0.1～0.7 MPa下测定膜的流动电位为60～6 mV/MPa.电解质离子分离机理取决于膜与电解质离子之间的电荷作用.     

HPLC法同时测定冬虫夏草中5种核苷类成分

用高效液相色谱法同时测定冬虫夏草中鸟嘌呤、胸腺嘧啶、腺嘌呤、腺苷、虫草素5种核苷类成分的含量。采用色谱柱为Aichrom Bond-AQ C18柱(250 mm×4.6 mm×5μm),以乙腈-水(7∶93)为流动相,流量为0.8 m L/min,检测波长254 nm,柱温30℃。鸟嘌呤、胸腺嘧啶、腺嘌呤、腺苷、虫草素的质量浓度分别在1.01~5.50μg/m L(r=0.9995)、0.05~1.01μg/m L(r=0.999 8)、0.20~1.98μg/m L(r=0.999 5)、1.01~5.07μg/m L(r=0.999 5)、0.10~1.03μg/m L(r=0.999 6)的范围内与峰面积线性关系良好,平均加样回收率分别为99.1%,97.8%,98.6%,100.4%,99.2%,RSD(n=5)分别为1.15%,2.34%,2.01%,1.75%,1.50%。该方法简便快速、准确度高、重现性好,可用于同时测定冬虫夏草中鸟嘌呤、胸腺嘧啶、腺嘌呤、腺苷、虫草素5种核苷类成分。     

槲皮素在分子印迹聚合物修饰碳糊电极上的电化学行为及测定

建立分子印迹聚合物修饰碳糊电极测定药物中槲皮素含量的新方法。以槲皮素为模板分子,甲基丙烯酸为功能单体,偶氮二异丁腈为引发剂,乙二醇二甲基丙烯酸酯为交联剂,通过沉淀聚合法制得槲皮素分子印迹聚合物,以m(石墨+聚合物):m(石蜡)=4∶1比例混合制成的印迹聚合物修饰碳糊电极作为工作电极。在0 V富集150 s,然后从0~0.6 V以100 m V/s扫速线性扫描,记录其在0.338 V的峰电流。槲皮素物质量浓度在1.25×10-6~4.0×10-5 mol/L与峰电流呈良好的线性关系(r=0.995 0),检出限为4.72×10-8mol/L,应用该方法测定胶囊中槲皮素的含量,测得回收率为96.7%~105.6%。该修饰电极具有较高的选择性和灵敏度,可用于槲皮素的测定。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.