Comparison between the 127I2 Stabilized He-Ne Lasers at 633 nm and 612 nm of the BIPM and the IMGC

In November 1981, a comparison between BIPM and IMGC He-Ne lasers stabilized to saturated absorption lines of 127I2, at the wavelengths ? = 633 nm and ? = 612 nm has been made at the BIPM. At 633 nm, a repeatability and a reproducibility within +1 × 10-11 · ? have been obtained. At 612 nm, a repeatability within a few 10-11 · ? only for one laser and a reproducibility of ± 2 × 10-10 · ? have been obtained.     

正压漏孔校准装置优化设计

针对目前正压漏孔校准工作中存在的测量下限指标低、测量不确定度大等问题,提出了正压漏孔校准装置的优化设计方法.采用特殊设计,将定容室的容积减小到10 mL以下,降低了气体累计时间,延伸了测量下限.采用主、被动相结合的恒温方法提高恒温精度,使得测量系统温度变化在校准时间内小于0.02 K,减小了温度漂移引入的虚流量及测量不确定度.在恒压法正压漏孔校准方法中,提出采用直径小于1 mm的精密细活塞及适用的动密封结构.可以将测量下限延伸到10-7Pa·m3/s 量级.通过以上方法,可使正压漏孔校准装置的测量下限优于5×10-7 Pa·m3/s,不确定度小于5%,同时具有较高的工作效率.     

Two-layered dissolving microneedles for percutaneous delivery of sumatriptan in rats

A novel transdermal delivery of sumatriptan (ST) was attempted by application of dissolving microneedle (DM) technology. Dextran DM (d-DM) and hyaluronate DM (h-DM) were prepared by adding ST solution to dextran solution or hyaluronic acid solution. One DM chip, 1.0?×?1.0?cm, contains 100 microneedle arrays in a 10?×?10 matrix. The mean lengths of DMs were 496.6?±?2.9 μm for h-DM and 494.5?±?1.3 μm for d-DM. The diameters of the array basement were 295.9?±?3.9 μm (d-DM) and 291.7?±?3.0 μm (h-DM), where ST contents were 31.6?±?4.5?μg and 24.1?±?0.9?μg. These results suggest that ST was stable in h-DM. Each DM was administered to rat abdominal skin. The maximum plasma ST concentrations, Cmax, and the areas under the plasma ST concentration versus time curves (AUC) were 44.6?±?4.9?ng/ml and 24.6?±?3.9?ng · h/ml for h-DM and 38.4?±?2.7?ng/ml and 14.1?±?1.5?ng · h/ml for d-DM. The bioavailabilities of ST from DMs were calculated as 100.7?±?18.8% for h-DM and 93.6?±?10.2% for d-DM. Good dose dependency was observed on Cmax and AUC. The stability study of ST in DM was performed for 3 months under four different conditions, ?80, 4, 23, and 50°C. At the end of incubation period, they were, respectively, 100.0?±?0.3%, 97.8?±?0.2%, 98.8?±?0.2%, and 100.7?±?0.1%. These suggest the usefulness of DM as a noninvaisive transdermal delivery system of ST to migraine therapy.     

Extracting transport parameters in GaAs nanopillars grown by selective-area epitaxy

We investigate the transport properties in p-type GaAs nanopillars (NPs) grown on GaAs(111) B substrates using selective-area epitaxy by studying single-NP field-effect transistors. Experimental results indicate that normalized resistance and field-effect mobility are highly sensitive to NP dimensions. Both in situ and ex?situ chemical surface passivation techniques are found to significantly improve conductivity and mobility, especially for the smaller diameter NPs. A semi-empirical model based on diameter dependent mobility is used to extract actual doping levels and surface state density by fitting normalized resistance as a function of NP diameter. Surface state densities before and after passivation are found to be 5?×?10(12)?cm(-2)?eV(-1) and 7?×?10(10)?cm(-2)?eV(-1), respectively.     

TiZrV吸气剂薄膜吸气性能的研究

TiZrV合金在180℃下加热24 h即可激活,是迄今发现的激活温度最低的非蒸散型吸气剂,已在粒子加速器领域得到应用。采用直流磁控溅射法在不锈钢管道内壁获得了TiZrV薄膜,并研究了薄膜对CO和H2的吸气性能。在200℃下加热24 h后TiZrV对CO和H2的抽速分别为0.23和0.02 L.s-1.cm-2,吸气容量分别为6.8×10-5和6.6×10-2Pa.L.cm-2,且随着激活温度和时间的增加,吸气性能会有所提高。     

Carbon nanotube composite coated platinum electrode for detection of Ga(III)

This study demonstrates the application of composite multi-walled carbon nanotube (MWCNT) polyvinylchloride (MWNT-PVC) based on 7-(2-hydroxy-5-methoxybenzyl)-5,6,7,8,9,10-hexahydro-2H benzo [b][1,4,7,10,13] dioxa triaza cyclopentadecine-3,11(4H,12H)-dione ionophore for gallium sensor. The sensor shows a good Nernstian slope of 19.68 ± 0.40 mV/decade in a wide linear range concentration of 7.9 × 10(-7) to 3.2 × 10(-2)M of Ga(NO(3))(3). The detection limit of this electrode is 5.2 × 10(-7)M of Ga(NO(3))(3). This proposed sensor is applicable in a pH range of 2.7-5.0. It has a short response time of about 10s and has a good selectivity over nineteen various metal ions. The practical analytical utility of this electrode is demonstrated by measurement of Ga(III) in river water.     

比较法校准氦真空参考漏孔漏率及合成不确定度评定

直接比对法是氦质谱检漏仪在稳定工作和引入气体相同条件下,将参考漏孔流出的氦气和标准漏孔提供的已知流量的氦气分别引入校准室中,用氦质谱检漏仪分别测量氦气产生的离子流,通过比较两次离子流的测量值计算出参考漏孔漏率的一种校准方法。这种校准范围为1×10-7Pa.m3/s~1×10-10Pa.m3/s。对同一参考漏孔,采用同样的校准测量,可以采用高斯分布统计的方法获得校准不确定度,其他不确定度分量由氦质谱检漏仪组成的校准装置决定,其合成相对不确定度可达到10%。     

Interactions of vitamin K3 with herring-sperm DNA using spectroscopy and electrochemistry

By means of ultraviolet-visible (UV-Vis) and fluorescence spectra, the binding ratio between vitamin K(3) and herring-sperm DNA in a physiological pH environment (pH = 7.40) was determined as n(K3):n(DNA) = 2:1, and the binding constants of vitamin K(3) binding to DNA at different temperatures were determined as K(θ)(298K) = 1.28 × 10(5) L·mol(-1) and K(θ)(310K) = 7.19 × 10(4) L·mol(-1), which were confirmed using the double reciprocal method are Δ(r)H(m)(θ) = -3.57 × 10(4) J·mol(-1), Δ(r)G(m)(θ) = -2.92 × 10(4) J·mol(-1), and Δ(r)S(m)(θ) = 217.67 J·mol(-1)K(-1). The driving power of this process was enthalpy. An intercalation binding of the vitamin K(3) with DNA was supported by a competitive experiment using acridine orange (AO) as a spectral probe. By combination analysis of the Scatchard method and cyclic voltammetry, we suggested that the interaction mode between vitamin K(3) and herring-sperm DNA would be a mixed mode. The quinonoid, duality fused-ring of vitamin K(3) can intercalate into the base pairs of DNA, and there is an electrostatic binding along with intercalation binding.     

National Ignition Facility system alignment

The National Ignition Facility (NIF) is the world's largest optical instrument, comprising 192 37?cm square beams, each generating up to 9.6?kJ of 351?nm laser light in a 20?ns beam precisely tailored in time and spectrum. The Facility houses a massive (10?m diameter) target chamber within which the beams converge onto an ～1?cm size target for the purpose of creating the conditions needed for deuterium/tritium nuclear fusion in a laboratory setting. A formidable challenge was building NIF to the precise requirements for beam propagation, commissioning the beam lines, and engineering systems to reliably and safely align 192 beams within the confines of a multihour shot cycle. Designing the facility to minimize drift and vibration, placing the optical components in their design locations, commissioning beam alignment, and performing precise system alignment are the key alignment accomplishments over the decade of work described herein. The design and positioning phases placed more than 3000 large (2.5?m×2?m×1?m) line-replaceable optics assemblies to within ±1?mm of design requirement. The commissioning and alignment phases validated clear apertures (no clipping) for all beam lines, and demonstrated automated laser alignment within 10?min and alignment to target chamber center within 44?min. Pointing validation system shots to flat gold-plated x-ray emitting targets showed NIF met its design requirement of ±50?μm rms beam pointing to target chamber. Finally, this paper describes the major alignment challenges faced by the NIF Project from inception to present, and how these challenges were met and solved by the NIF design and commissioning teams.     

Impedimetric and potentiometric investigation of a sulfate anion-selective electrode: experiment and simulation

A new anion-selective polyvinyl chloride (PVC) membrane electrode based on {6,6'-diethoxy-2,2'-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]diphenolato}nickel(II)monohydrate as a carrier for the sulfate anion is reported. In this work, a new strategy for optimizing membrane components by electrochemical impedance spectroscopy (EIS) is presented. The performance of this electrode was investigated using potentiometric and EIS techniques. The potentiometric results indicated that the prepared electrode had a Nernstian slope of -28.9 ± 0.1 mV in a linear concentrations range of 1.0 × 10(-6) to 3.0 × 10(-1) M, a detection limit of 6.3 × 10(-7) M, an applied pH range of 4.0-9.0, and a response time of less than 15 s; while using the EIS technique, the linear concentrations range was 1.0 × 10(-9) to 1.0 × 10(-1) M and the pH range increased to 4.0-10.0. Finally, the impedance spectra were simulated using the Maple 13 software. A comparison of the experimental data and information obtained from the simulation confirmed the accuracy of the impedance measurement of this electrode.     

Sensitized enantioselective laser-induced phosphorescence detection in chiral capillary electrophoresis

The sensitivity of enantioselective cyclodextrin-induced room-temperature phosphorescence detection of camphorquinone (CQ) is enhanced using sensitization via a donor with a high extinction coefficient. The enantiomeric distinction is based on the different phosphorescence lifetimes of (+)-CQ and (-)-CQ after their complexation with α-cyclodextrin (α-CD). The collisional Dexter energy transfer from the selected donor 2,6-naphthalenedisulfonic acid (2,6-NS) to the acceptor CQ is still very efficient despite the inclusion of the acceptor into CD. For coupling to the chiral separation of (±)-CQ in cyclodextrin-based electrokinetic chromatography, the donor was added to the deoxygenated background electrolyte that consisted of 20 mM α-CD, 10 mM carboxymethyl-β-CD, and 25 mM borate buffer at pH 9.0. Time-resolved batch studies on sensitized phosphorescence show a significant enantioselectivity for (+)- and (-)-CQ in the presence of both α-CD and CM-β-CD although the lifetime difference is somewhat reduced with respect to direct excitation. The enantiomers were distinguished after their separation using an online time-resolved detection system. Excitation was performed at 266 nm with a pulsed, small-sized, quadrupled Nd:YAG laser. With 1 × 10(-5) M 2,6-NS, limits of detection of 4.1 × 10(-8) M and 5.2 × 10(-8) M were found for (+)-CQ and (-)-CQ, respectively. The online measured lifetimes were 238 ± 8 μs for (+)-CQ and 126 ± 10 μs for (-)-CQ. The method was used to determine the concentration of (±)-CQ leaching from a cured dental resin into water. The extracts contained 4.7 ± 0.1 × 10(-7) M of both (+)-CQ and (-)-CQ.     

聚吡咯包覆FeCl3-石墨层间化合物的制备与电化学储钠性能

以FeCl₃和天然鳞片石墨为原料,通过融盐法制得1阶FeCl₃插层的石墨层间化合物(FeCl₃-GIC)。用原位聚合法对FeCl₃-GIC进行聚吡咯(PPy)包覆改性,形成具有核壳结构的(FeCl₃-GIC)@PPy复合材料。通过多种表征方法研究聚吡咯包覆前后FeCl₃-GIC的表面形貌和微观结构变化。结果表明:聚吡咯均匀致密地包覆在十微米级的FeCl₃-GIC颗粒外部,包覆层厚度为35 nm,经过聚吡咯包覆后(FeCl₃-GIC)@PPy的导电性能显著提高((FeCl₃-GIC)@PPy粉末电阻率2.3×10?3 Ω·cm,FeCl₃-GIC粉末电阻率3.1×10?3 Ω·cm)。采用多种电化学测试探究产物的钠离子存储特性,聚吡咯外壳能够显著提高FeCl₃-GIC作为钠离子电池负极材料的充放电容量、倍率性能和循环性能。在0.1 A·g?1电流密度下循环100次后,FeCl₃-GIC的比容量逐渐衰减到157 mA·h·g?1,而(FeCl₃-GIC)@PPy材料的比容量达到281 mA·h·g?1左右且容量基本保持不变;在电流密度1 A·g?1的条件下循环500次后,(FeCl₃-GIC)@PPy的比容量仍有181 mA·h·g?1,容量保持率约为89%。      

KOH活化法制备气体分离用炭分子筛膜

选用KOH为活化剂,利用化学活化法制备炭分子筛膜,考察在热塑性酚醛树脂(PFNR)涂膜液中添加不同质量分数的KOH对炭分子筛膜的影响.结果表明,在炭化过程中,KOH的加入可促进炭分子筛膜孔径的均匀分布,使炭分子筛膜具有发达的孔隙结构.当KOH在PFNR中的添加量从0％增加到4％时,H2的渗透速率由23.68×10-10 mol·m-2·s-1·pa-1提高到28.6×10-10 mol·m-2·s-1·Pa-1;但H2/N2和H2/CH4的分离系数明显下降,分别从471.3下降到147.5、540下降到270.CO2/CH4和O2/N2的分离系数只有轻微下降.     

共沉淀法制备Cu掺杂的钙钛矿型混合导体透氧材料

采用并流共沉淀法合成了掺杂Cu的钙钛矿型混合导体透氧膜材料.考察了pH值、陈化时间等制备条件对前驱体性质和膜片透氧性能的影响,采用TG-DSC考察了复合氧化物粉体的生成过程,采用XRD、TEM对粉体的结构和形态进行了表征,对材料进行了透氧性能测试并与固相反应法作了比较.结果表明,pH=10～11,陈化时间为10小时是最佳的前驱体制备条件,合成温度为800℃即可得到纯相钙钛矿结构的粉体,其平均颗粒直径为90nm,透氧测试结果显示,制备方法和Cu掺杂量对膜片的透氧性能有显著影响,900℃时共沉淀法制备的SrFe0.6Ti0.1Cu0.3O3-δ的透氧量达到O.64ml·min～·cm-2(STP).     

Transdermal delivery of alprazolam from a monolithic patch: formulation based on in vitro characterization

Alprazolam, a benzodiazepine widely used for the treatment of psychiatric disorders, has been aimed to be formulated in a transdermal delivery system (TDS) prototype. A series of TDS prototypes dosed in all cases at 0.35 mg·cm(-2) of alprazolam were prepared as a monolithic drug in adhesive matrix using acrylic pressure-sensitive adhesives (PSA) of acrylate vinyl acetate (Duro-tack(?)). The effects of several permeation enhancers as azone, transcutol, propylene glycol, dodecyl alcohol, decyl alcohol, diethanolamine, N-methyl pyrrolidone and lauric acid were studied. Prototypes have been characterized based on adhesion parameters (peel adhesion and shear adhesion), in vitro human skin permeation and in vitro drug release according to European Pharmacopoeia for the selected prototype. Best results show that a combination of permeation enhancers from different chemical groups is able to provide almost a 33 fold increase in the transdermal alprazolam flux of an aqueous saturated dispersion (from 0.054?±?0.019 to 1.76?±?0.21 μg h.cm(-2)). Based on these in vitro flux data, a predictive simulation of the achievable plasmatic levels was performed assuming a constant systemic infusion of drug. In summary, it is possible to obtain a prototype of a TDS of alprazolam with adequate adhesive properties (peel adhesion and shear adhesion) and able to predict sustained therapeutic plasmatic levels.     

Low-resistance ohmic contacts to SiC nanowires and their applications to field-effect transistors

We report on the electrical characterization of two ohmic contacts (Ti/Au and Ni/Au) to unintentionally doped silicon carbide nanowires (SiCNWs) using the modified transmission line model (TLM) method. Our results indicate that subsequently deposited Ni/Au ohmic contacts on SiCNWs had ～40 times lower specific contact resistances (SCRs) of 5.9 × 10(-6) ± 8.8 × 10(-6)?Ω?cm(2) compared to the values of Ti/Au ohmic contacts (2.6 × 10(-4) ± 3.4 × 10(-4)?Ω?cm(2)). We also conducted a comparison study of the electrical characteristics of top-gated SiCNW field-effect transistors (FETs) with two different ohmic contacts as used for ohmic contact studies. The electrical transport measurements on the SiCNW FET with Ni/Au ohmic contacts show much lower resistance contacts to SiC NWs and better FET performances than those for Ti/Au ohmic contact-based FETs.     

Biopharmaceutics classification by high throughput solubility assay and PAMPA

The purpose of the present study was to examine the relevancy of the high throughput solubility assay and permeability assay to the biopharmaceutics classification system (BCS). Solubility and permeability were measured by high throughput solubility assay (HTSA) and parallel artificial membrane permeation assay (PAMPA), respectively. High throughput solubility assay was performed using simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid without bile acid (SIF, pH 6.8). We categorize 18 drugs based on the BCS using HTSA and PAMPA. Fourteen out of 18 drugs were correctly classified (78% success rate). The result of the present study showed that HTSA could predict BCS class with a high success rate, and PAMPA could also be useful to predict the permeation of drugs.     

An Intercomparison of Hydrogen and Cesium Frequency Standards

Intercomparisons of average frequency and of frequency stability were made among one Hewlett-Packard 5060A cesium beam, two Varian Associates H-10 atomic hydrogen masers, and the National Bureau of Standards NBS III cesium beam designated as the United States Frequency Standard. Each of the standards displayed a white noise frequency fluctuation behavior with a transition into an approximate flicker of frequency fluctuation behavior for longer time intervals. The rms fractional frequency fluctuation between adjacent samples, ?(?, N = 2), was 6 × 10-11?-1/2 down to a flicker level of about 3×10-13 for the hp 5060A cesium beam (102 ? ? ? 104s), 1 × 10-11?-1/2 down to a flicker level of less than 1×10-13 for NBS III cesium beam (102 ? ? ? 104s), and 5×10-13?-1/2 down to a flicker level of about 1×10-14 for the H-10 hydrogen masers (1 ? ? ? 104s). The accuracy capabilities of NBS III and H-10 #4 are now 1.1×10-12 and 0.47×10-12, respectively (1? estimate). A discrepancy of only 1.1 parts in 1012 was observed between the average frequencies of the hp 5060A cesium beam and the NBS III cesium beam, with the former being higher in frequency. In terms of the frequency of the Cs133 hyperfine transition (F=4, mF = 0)?(F=3, mF = 0), defined as 9 192 631 770.0000 Hertz, the measured frequency of the H1 hyperfine transition (F=1, mF = 0) ?-F = 0, mF = 0) was vH=1 420 405 751.7864±0.0017 Hertz.     

Poly(vinyl) chloride membrane copper-selective electrode based on 1-phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione

1-Phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H(2)L) was used as an effective ionophore for copper-selective poly(vinyl) chloride (PVC) membrane electrodes. Optimization of the composition of the membrane and of the conditions of the analysis was performed, and under the optimized conditions the electrode has a detection limit of 6.30×10(-7) M Cu(II) at pH 4.0 with response time 10s and displays a linear EMF versus log[Cu(2+)] response over the concentration range 2.0×10(-6) to 5.0×10(-3) M Cu(II) with a Nernstian slope of 28.80±0.11 mV/decade over the pH range of 3.0-8.0. The sensor is stable for 9 weeks and exhibits good selectivity with respect to alkali, alkali earth and transition metal ions (e.g. Na(+), K(+), Ba(2+), Ca(2+), Zn(2+), Cd(2+), Co(2+), Mn(2+), Ni(2+), Fe(2+), Al(3+)) in the 3.0-8.0 pH range. It was successfully applied for the direct determination of copper(II) in zinc, aluminum and nickel based alloys, in soils polluted by oil, and as an indicator electrode for potentiometric titration of copper ions with EDTA.     

Infinite-dilution diffusion coefficients of complex ions from solution conductivity data

A technique is presented for determining infinite-dilution diffusion coefficients of complex ions from solution conductivity data. The method involves measuring the conductivities of dilute solutions in which the distribution of complex ions is systematically varied and statistically regressing the data to an equation that effectively relates individual ion diffusion coefficients to solution conductivity. The procedure is simple and requires no specialized equipment to perform. Unlike methods that require a concentration gradient, the solution composition is homogeneous and at equilibrium during measurements, which is a significant advantage when labile complexes are being studied. In this paper, diffusion coefficients of cuprous cyanide complexes are determined. Statistical analysis yields the infinite-dilution diffusion coefficients of Cu(CN)(2)(-), Cu(CN)(3)(2-), and Cu(CN)(4)(3-) at 25 °C as 1.43 × 10(-5) ± 9%, 1.08 × 10(-5) ± 9%, and 6.21 × 10(-6) ± 22% cm(2)/s, respectively.