分光光度法测定食盐中的碘

改进了有机溶剂萃取分光光度法测定食盐中碘的方法。在 H2 SO4介质中 ,用 KMn O4氧化除去食盐中 Cl-,用 HCOONa还原过剩的 KMn O4后加 KI还原食盐中 IO-3 为游离碘 ,CCl4萃取溶液中游离碘 ,于5 2 0 nm处 ,以水作参比测量吸光度。碘的浓度在 2× 10 -4— 1× 10 -3 mol· L-1范围内符合比耳定律 ,回归方程为 :C=0 .0 0 14 5 4A- 0 .0 0 0 0 112 7,相关系数 r=0 .9999。该方法简单 ,准确 ,应用于食盐中碘的测定 ,结果令人满意。     

浊点萃取-石墨炉原子吸收法测定高盐样品中的痕量铅

在pH 6～7的缓冲体系中,样品溶液中的痕量铅与加入的吡咯烷二硫代氨基甲酸铵(APDC)为络合剂形成稳定的配合物.通过70℃恒温水浴3 h,铅配合物被萃取到表面活性剂相并与水相分开.分离后的表面活性剂相室温就可配成上机待测样液.此法不但将大量基体离弃在水相,从而消除高盐带来的高背景信号干扰,并将水样或1%食盐溶液的痕量铅富集10～100倍.用氘灯校正背景石墨炉原子吸收法进行测定,方法检出限:食盐0.000 5 μg·g-1,水样0.01 μg·L-1.回收率为92.3%～104%.用于食盐、海水、井水中痕量铅的测定,结果令人满意.     

罗丹明B氧化褪色光度法测定微量碘

本文研究了在硫酸介质中 ,碘酸根在 KBr催化作用下氧化罗丹明 B使其褪色的最佳条件 ,建立了测定微量碘的新方法。通过实验 ,测得最大吸收波长为 4 90 nm ;表观摩尔吸光系数为 1 .5× 1 0 4 L· mol-1· cm-1;碘酸根测定的线性范围为 0— 3 0μg/1 0 m L;检出限为 1 .2× 1 0 -7mol/L。该方法可用于食盐中微量碘的测定     

巯基棉富集分离-火焰原子吸收光谱法测定食盐中痕量镉

通过巯基棉富集分离后 ,用火焰原子吸收光谱法测定了食盐中的痕量镉 ,研究了巯基棉富集 Cd( )的条件 ,实验回收率 92 %— 98% ,RSD<6 .0 %。本实验方法简便 ,可用于食盐中痕量镉的测定     

甲酚红氧化褪色光度法测定微量碘

本文研究了在硫酸介质中 ,碘酸根在 KBr催化作用下氧化甲酚红使其褪色的最佳条件 ,建立了测定微量碘的新方法。最大吸收波长为 5 19.5 nm,表观摩尔吸光系数为 4 .6× 10 4L· mol-1· cm-1,碘酸根测定线性范围为 10— 6 0 μg/2 5 m L。用于测定食盐和碘酸钾片剂中微量碘 ,结果令人满意     

木瓜中多糖和微量元素含量分析

苯酚 -硫酸光度法和原子吸收分光光度法分别测定了木瓜中多糖和微量元素的含量。多糖测定的相关系数为 0 .994 3,平均含糖量为 1 0 .4 9%;微量元素测定回收率为 97.1 %— 1 0 5 .9%,RSD为 2 .4 7%—7.6 0 %。本方法简单可靠 ,适用于木瓜及其制品的常规检测。     

ICP-AES测定铂金饰品抛光灰中铂、钯、金和银

提出一种 ICP- AES快速测定铂金饰品抛光灰中铂、钯、金、银的分析方法。 5 g样品经灰化处理后 ,王水提取 ,直接测定 ,该方法的检出限 Pt、Pd、Au、Ag分别为 4 6 .5、4 2 .3、10 .4和 5 .1ng·m L-1。回收率为94 .2 %— 10 3.5 %之间。相对标准偏差为 2 .8%— 4 .4 %。     

火焰原子吸收光谱法测定食盐中痕量铅

对巯基棉富集 Pb( )的条件作了研究 ,经过巯基棉分离富集后 ,用火焰原子吸收光谱法测定了食盐中的痕量铅 ,实验回收率 97.3%— 97.5 % ,RSD<5 %。方法简便 ,可用于食盐中痕量铅的测定     

火焰原子吸收光谱法测定栽培甘草中6种金属元素

浓硝酸 -高氯酸 (V∶V=4∶ 1 )常压微沸条件下消解甘草样品 ,火焰原子吸收法 (FAAS)测定甘草中的金属元素 Ca、Mg、Fe、Cu、Zn、Pb的含量 ,研究了测定不同元素的仪器最佳工作条件及溶液介质对测定结果的影响及方法的准确性和精密度研究。栽培甘草中 Ca、Mg、Fe、Cu、Zn的含量分别为 4 0 4 5 .5、71 5 .4、2 79.8、1 2 .6、1 0 .4 μg/g,Pb未检出。方法的加标回收率为 99.38%— 1 0 2 .30 %,相对标准偏差 (n=9)为0 .4 1 %— 1 .6 8%。本法简单易行 ,方便快捷 ,结果可靠。     

原子荧光光谱法测定膨润土中微量砷

建立了一种原子荧光光谱测定膨润土中微量砷的方法。研究了原子荧光光谱法测定膨润土中微量砷的前处理和干扰。样品相对标准偏差为 4 .1% ,回收率在 93.8%— 96 .5 %之间。该方法简便、快捷 ,分析结果令人满意     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.