二（2-乙基己基）磷酸络合萃取邻氨基苯酚的机理

在二（2-乙基己基）磷酸（D2EHPA）络合萃取邻氨基苯酚（OAP）实验中,研究了稀释剂种类、溶液的初始pH值等因素对OAP稀溶液分配比（D）的影响。溶液的初始pH值对萃取结果影响较大,当初始pH值在pKa1和pKa2之间时,分配比出现峰值;二（2-乙基己基）磷酸主要是通过离子缔合和质子交换来实现萃取的,而稀释剂则主要是物理萃取,在同一浓度下,二（2-乙基己基）磷酸的萃取能力随稀释剂的极性增大而提高,极性环境优于惰性稀释剂环境。红外光谱分析证明萃取过程存在离子交换和离子缔合反应。     

关于过硫酸钾氧化-紫外分光光度法测定水中总氮方法改进探讨

针对海水中总氮的测定较繁琐,中间过程长,干扰物质多,分析时间长,重现性差,提出了采用硼酸-氢氧化钠缓冲体系,通过控制溶液酸碱度,消除海水中钙、镁离子对测定的干扰,实现用碱性过硫酸钾氧化-紫外分光光度法直接测定海水中总氮含量.对于成分复杂,色度较高且铵氮含量较高的地表水,采取延长消解时间,降低溶液酸碱性来抑制氨氮挥发所造...     

EDTA滴定法测定草酸中硫酸根

在马弗炉(200℃)灼烧至草酸全部挥发,滴加(1 1)盐酸,使刚果红试纸由红变蓝色(或调节pH到4左右),除去二氧化碳。加入钡镁混合液,沉淀6h(或放置过夜)。加入(1 1)氨水调节pH值约为8—9,加入10mL氨-氯化铵缓冲溶液,2滴铬黑T指示剂,用EDTA标准溶液滴定SO2-4含量。     

柠檬酸与钛络合过程的拉曼光谱分析

采用向柠檬酸溶液中直接滴入四氯化钛的方法,实现了钛与柠檬酸的络合反应。向络合溶液中滴入氨水调节pH值,对特定的pH值溶液进行了拉曼光谱的测量,详细分析了(TiO)、(CO)等振动峰的归属。对络合离子基团的结构进行了模拟和光谱计算,所得到的结果和实验值符合得较好。     

颗粒状纳米碳酸钡锶钙的研制

介绍一种气-液相合成技术合成氧化物阴极用三元碳酸盐,研究沉淀温度、浓度及搅拌速率对合成碳酸钡锶钙结晶形貌的影响,分析其结晶过程.通过优化合成溶液温度及合成浓度,控制碳酸盐的成核和生长速率,合成了一种颗粒状纳米三元碳酸盐,并进行直流发射测试.实验表明,这种纳米碳酸盐能明显提高氧化物阴极的发射性能.     

磷酸酯化改性梨渣吸附污染水体中锌离子的研究

以砀山梨渣为原料,经磷酸酯化改性,制备一种酯化梨渣阳离子吸附剂,用批次实验法研究了其在不同实验条件下（pH值、吸附剂量、吸附质浓度和吸附时间）对金属锌离子的吸附性能。结果表明,溶液pH=3.5时,锌离子吸附达到最大值;酯化梨渣≥5g.L-1能除去锌离子为100mg.L-1溶液中的96%锌离子。改性梨渣对锌离子的吸附符合Langmuir吸附等温线模型,最大吸附能力为28.986mg.g-1。锌离子达到吸附平衡的时间为30min;准一级反应动力学方程y=-0.0615x＋2.4437（r2=0.9921）描述锌离子在改性梨渣上的吸附过程。     

2-对二甲氨基苯基-5-氟-6-吗啉苯并咪唑的合成及其光谱学性质研究

合成了一种新的取代苯并咪唑化合物 ,2 对二甲氨基苯基 5 氟 6 吗啉苯并咪唑 ,采用紫外 可见光谱、荧光光谱及荧光寿命等方法探讨了溶液pH值对该化合物吸收光谱的影响及其与 β 环糊精的作用。结果表明 ,pH >7 0时 ,该化合物在溶液中主要以中性分子状态存在 ,当 3 8相似文献   

PZ等添加剂对氨法脱碳影响的实验研究

本文在湿壁塔实验台上,针对2.67 mol/L氨水溶液分别混入0.1 mol/L的PZ(哌嗪)、AMP(2-氨基-2-甲基-1-丙醇)、AMPD(2-氨基-2-甲基-1,3-丙二醇)和THAM(2-氨基-2-羟甲基-1,3-丙二醇)等有机胺添加剂吸收CO_2的过程,进行了20℃下的气液传质和反应动力学实验研究。实验结果表明,混入PZ可以最有效地提高氨水的吸收速率。本文还在20℃下分别进行了2.67 mol/L氨水和0.1 mol/L PZ单独吸收CO_2的吸收速率实验,研究发现,氨水和PZ的混合溶液吸收CO_2的速率强于两者单独吸收的简单加合,二者在吸收过程中相互促进。研究还发现,氨水和PZ混合溶液吸收CO_2的相互促进率最大可达近50%。     

磁化水防垢机理的探索

磁化水防垢效果与磁场处理条件有一定的关系,但井不是唯一决定的因素,水质也起了重要作用. 一、水质分析 各种天然水内都溶解有一定数量的杂质,其主要成份是钙、镁等盐类.所谓硬度就是指这两种盐类的含量.它们在水中常以两种形式存在: (1)钙、镁的碳酸盐:有碳酸钙(CaCO3)、碳酸镁(MgCO3)、重碳酸钙[Ca(HCO3)2]和重碳酸镁[Mg(HCO3)2]等.这些盐形成的硬度叫做碳酸盐硬度. (2)钙、镁的非碳酸盐:有硫酸钙(CaSO4)、硫酸镁(MgSO4)、氯化钙(CaCl2)、氯化镁(MgCl2)和硅酸钙CaSiO3等.这些盐形成的硬度叫做非碳酸盐硬度. 有的天然水中还含…     

不同pH调节剂对燃烧法制备纳米LaMnO3的影响

采用TG/DSC、XRD和SEM系统考察了K2CO3、NaOH、KOH和氨水等不同pH调节剂调节前驱物溶液pH值,对燃烧法制备的纳米LaMnO3粉体的晶相组成和微观形貌的影响.结果表明:不同的pH调节剂和前驱物溶液pH值对燃烧产物的晶相组成、晶粒大小和微观形貌都有显著的影响.其中以KOH作pH调节剂,pH=13的碱性环...     

Magnetism in nanometer-thick TiOx/Co/TiOx/TiN/Si multilayered structures

Most studies on Co-doped TiO₂ system were focused on thin films grown by MBE-based methods. In this work we report the ferromagnetism of nanometer-thick-layered TiO₂/Co/TiO₂/TiN film grown on Si substrate by conventional magnetron sputtering. For the growth of TiO₂ on silicon, a non-oxide thermally stable material, TiN, was introduced to prevent Ti penetration into the Si substrate. Structural, magnetic, and transport measurements respectively by Raman, SQUID and Hall effect show that our samples are n-type semiconductors and exchange bias effect due to exchange coupling between Co and interfacial CoO. For the rapid vacuum annealed specimen, we found an enhanced loss and a Perminvar-type constricted hysteresis loop, which attributed to pinning of domain walls due to an induced anisotropy by the pair ordering in the metallic alloy of Co-Ti-Si.     

Spin-glass-like behavior in ZnxCryAlzSe4

The magnetic and electrical properties of the Al-doped polycrystalline spinels Zn_xCr_yAl_zSe₄ (0.13≤z≤0.55) with the antiferromagnetic (AFM) order and semiconducting behavior were investigated. A complex antiferromagnetic structure below a Néel temperature T_N≈23 K for the samples with z up to 0.4 contrasting with the strong ferromagnetic (FM) interactions evidenced by a large positive Curie-Weiss temperature θ_CW decreasing from 62.2 K for z=0.13 to 37.5 K for z=0.55 was observed. Detailed investigations revealed a divergence between the zero-field-cooling (ZFC) and field-cooling (FC) susceptibilities at temperature less than T_N suggesting bond frustration due to competing ferromagnetic and antiferromagnetic exchange interactions in the compositional range 0.13≤z≤0.4. Meanwhile, for z=0.55 a spin-glass-like behavior of cluster type with randomly oriented magnetic moments is observed as the ZFC-FC splitting goes up to the freezing temperature T_f=11.5 K and the critical fields connected both with a transformation of the antiferromagnetic spin spiral via conical magnetic structure into ferromagnetic phase disappear.     

Context effects in recognizing syllable-final /z/ and /s/ in different phrasal positions

An examination of the effect of phrase-final lengthening on the temporal correlates of voicing in syllable-final /s/ and /z/ was conducted. Discriminant analyses revealed that a combination of vowel duration, frication duration, and the duration of simultaneous voicing and frication was quite successful in determining voicing independently of phrase-final lengthening. Two perceptual experiments revealed that human listeners' recognition of the segments does benefit from hearing the syllables in sentential context as opposed to when they are excised from context and presented in isolation. The benefit was greatest for /s/ in phrase-final position and /z/ in phrase-internal position. This suggests that the presence of sentential context allows listeners to factor out the influence of phrase-final lengthening on vowel duration and to more accurately interpret this cue to voicing of the final fricative. These findings extend previous results on rate-dependent processing of overall speaking rate to the processing of local speaking rate. By doing so, they provide further evidence of the importance of extended phonetic context in speech recognition.     

Velopharyngeal aerodynamics of /m/ and /p/ in tracheoesophageal speech

The purpose of this study was to compare oral pressure (P_o), nasal airflow (V_n), and velopharyngeal (VP) orifice area estimates from 12 tracheoesophageal (TE) and 12 laryngeal speakers as they produced /p/ and /m/ in syllable series. The findings were as follows: (1) TE speakers produced greater P_o than the laryngeal speakers; (2) for /p/, TE speakers generated V_n, and VP orifice area estimates comparable with, or less than, the laryngeal speakers; and (3) for /m/, TE speakers had V_n and VP orifice area estimates greater than the laryngeal speakers. The elevated P_o could be the result of several factors such as high source driving pressures and vocal tract volume changes postlaryngectomy. Attempts at more precise articulation, and subsequently less coarticulation, by the TE speakers may explain the V_n and VP orifice area estimates for /p/ and /m/. TE speakers may be limiting the oral-nasal cavity coupling for /p/ (smaller VP gap, less V_n) in an attempt to produce a very precise oral /p/. For /m/, TE speakers may be attempting to overtly mark the consonant as a nasal (greater V_n, larger VP gap). Further studies are needed to confirm/refute the explanations postulated here regarding the VP aerodynamic differences that were identified.     

Variability in production of the vowels /i/ and /a/

A hypothesis on the nature of articulatory targets for the vowels /i/ and /a/ is proposed, based on acoustic considerations and vowel articulations. The conjecture is that positioning of points on the tongue surface in a repetition experiment should be most accurate in the direction perpendicular to the vocal-tract midline, at the acoustically critical point of maximal constriction for each vowel. The hypothesis was tested by: examining x-ray microbeam data for three speakers, conducting a partial acoustical analysis, and performing a modeling study. Distributions were plotted of the midsagittal locations of three tongue points at the time of maximal excursion toward the vowel target for numbers of examples of the vowels, embedded in a variety of phonetic contexts. More variation was found along a direction parallel to the vocal tract midline than perpendicular to the midline, supporting the hypothesis. Statistics on formant values for one subject have been calculated, and pairwise regressions of displacement and formant data have been run. An articulatory synthesizer [Rubin et al., J. Acoust. Soc. Am. 70, 321-328 (1981)] has been manipulated through displacements similar to the subject's articulatory variation. Although articulatory synthesis showed systematic relationships between articulatory relationships and formant frequencies, there were no significant correlations between the subject's measured articulatory displacements and his formant data. These additional results raise questions about the methodology and point to the need for additional work for an adequate test of the hypothesis.     

Tunneling magnetoresistance in exchange-biased CoFeB/AlOx/Co/IrMn junctions

A series of exchange-biased magnetic tunneling junctions (MTJs) were made in an in-plane deposition field (h) = 500 Oe. The deposition sequence was Si(1 0 0)/Ta(30 Å)/CoFeB(75 Å)/AlO_x(d Å)/Co(75 Å)/IrMn(90 Å)/Ta(100 Å), where d was varied from 12 Å to 30 Å. The MTJ was formed by the cross-strip method with a junction area of 0.0225 mm². The tunneling magnetoresistance (ΔR/R) of each MTJ was measured. The high-resolution cross-sectional transmission electron microscopic (HR X-TEM) image shows the very smooth interface and clear microstructure. X-ray diffraction (XRD) demonstrates that the IrMn layer of the MTJ exhibits a (1 1 1) texture. From the results (ΔR/R) increases from 17% to 50%, as d increases from 12 Å to 30 Å. The tunneling resistance (R_o) of these junctions ranges from 150 Ω to 250 Ω. The exchange-biasing field (H_ex) of the MTJ is 50-95 Oe. Finally, the saturation resistance (R_s) was measured as a function of the angle (α) of rotation, where α is the angle between h and the in-plane saturation field (H_s) = 1.1 kOe. The following figure presents the dependence of R_s on α, instead of originally expected independence, the curve actually varies with a period of π.     

Optical measurement of KB/KS divergence in nematics

A direct optical analysis of the divergence of the elastic constant ratio K_B/K_S in a nematic material near the T_AN transition temperature is presented. The results are in excellent agreement with what obtained from more complicated techniques. The method used exhibits a large number of advantage with respect to the conventional ones.     

Fine-grained variation in caregivers' /s/ predicts their infants' /s/ category

Within the debate on the mechanisms underlying infants' perceptual acquisition, one hypothesis proposes that infants' perception is directly affected by the acoustic implementation of sound categories in the speech they hear. In consonance with this view, the present study shows that individual variation in fine-grained, subphonemic aspects of the acoustic realization of /s/ in caregivers' speech predicts infants' discrimination of this sound from the highly similar /∫/, suggesting that learning based on acoustic cue distributions may indeed drive natural phonological acquisition.     

Electrical peculiarities in Al/Si/Ge/…/Ge/Si and Al/SiGe/Si structures

The current–voltage (I–V) and capacitance–voltage (C–V) behaviour of different Si/Ge multilayers and SiGe single layers prepared on p-type Si substrates by magnetron sputtering and annealing, has been studied in the temperature range of 80–320 K by using Al Schottky contacts as test structures. Although a significant influence of the microstructure of the Si/Ge multilayers and SiGe layers was obtained on the electrical behaviour of the structures, the structures exhibited similar specific features.     

Electronegativity and tetragonal distortions in AIIBIVCV2 semiconductors

Empirical correlations are established between the tetragonal distortions 2-c/a and dielectrically defined electronegativities based on polarizabilities of AⁿB^8-n compounds. Optical data, including the birefringence parameter δn = n_e - n_o, are summarized. No simple relation is found to exist between δn and the principal optical gaps and tetragonal distortions of seven chalcopyrite compounds.