数学校正消除光度法中色泽干扰的研究Ⅱ：磷铋钼蓝光度法直接测定钒铁中磷

本文详细叙述了用数学校正消除基体钒对磷铋钼蓝光度法测定磷的干扰方法。建立了在７１０ｎｍ滤长处测定四价钒和磷铋钼蓝的混合吸光度值，以数学校正解析钒铁中磷含量的分析方法。实验表明：该法测定结果可靠，且显著地降低了分析成本。     

钼蓝分光光度法联合测定钢铁中磷砷

基于磷、砷具有相似的化学性质,在一定的酸度条件下,磷、砷都与钼酸铵和铋盐形成磷铋钼杂多酸、砷铋钼杂多酸,在抗坏血酸的作用下还原成磷铋钼蓝和砷铋钼蓝,且其吸光度值具有加合性,测定磷、砷合量的吸光度值后,用亚硫酸钠-硫代硫酸钠-溴化钾复合还原剂还原掩蔽砷,测定磷的吸光度值,从而可以分别测定磷、砷的含量。大多数的金属离子不干扰磷、砷的测定,只有硅在一定的酸度下产生干扰,可以用提高显色酸度的方法来消除,对于高含量硅可以通过分离除去。方法的线性范围为磷:0~0.75μg/mL;砷:0~1.25μg/mL。掩蔽还原砷后磷的显色稳定性较差,加入乳酸得到了改善。本方法用于实验室快速测定钢铁中的磷和砷。     

数学校正消除光度法中色泽干扰的研究Ⅱ——磷铋钼蓝光度法直接测定钒铁中磷量

本文详细叙述了用数学校正消除基体钒对磷铋钼蓝光度法测定磷的干扰的方法.建立了在710nm波长处测定四价钒和磷铋钼蓝的混合吸光度值,以数学校正解析钒铁中磷含量的分析方法.实验表明;该法测定结果准确可靠,且显著地降低了分析成本.     

钛磷钼络合物光度法测定合金钢中高钼

本文介绍了钛磷钼三元络合物光度法测定合金钢中高钼,进行了一些条件试验,结果表明:在硫酸、盐酸介质中均可显色,但在盐酸介质中稳定性差,硫酸酸度3～6N吸光度一致,选用盐酸酸度1N,硫酸酸度4N,即50毫升显色液中含50毫升5N硫酸,10毫升5N盐酸;其中含0.1～0.8毫升磷酸吸光度基本一致,随着磷酸量增加,显色液稳定性变差,选用0.3毫升为宜;3～10毫升二氯化锡吸光度一致,选用5毫升;3～10毫升四氯化钛吸光度变化不大,选用5毫升为宜;钢中常见元素允许量(毫克):W(2),Cr、V(1),Mn、Ni、A     

钨制品中磷的测定

在H2SO4酸性介质中，样品中的磷酸盐与酸性钼酸铵、氯化亚锡反应形成磷钼蓝配合物。利用甘油作为增溶剂，可以在水相直接测定微量磷。配合物的最大吸收位于690nm波长处。P的质量浓度在0～2．5μg／50mL与吸光度成正比。研究了显色反应的适宜条件、共存离子的影响。     

数学校正镍干扰分光光度法测定镍铁中磷

探讨了用数学校正消除基体镍对磷铋钼蓝光度法测定磷干扰的方法。试验结果表明,在磷铋钼蓝光度法测定磷的条件下,镍(Ⅱ)不与显色剂发生显色反应,但其色泽干扰磷的测定;镍(Ⅱ)的吸光度与其浓度成正比,镍(Ⅱ)的色泽与磷铋钼蓝的色泽具有良好的加和性。据此建立了消除镍干扰的数学校正法。方法用于镍铁样品中磷的测定,测定结果与参比溶液消除法一致。     

有机液体吸光度检测仪的开发应用

湿法冶金生产工艺中,有机萃取是常见的工艺,生产过程中有机液体的颜色及色深(吸光度),是工艺指标性参数,但是对于有机液体的在线测量,因缺乏成熟的仪器,目前大多靠人眼目测和实验室比对的方式。我们以比尔-朗伯定律为理论依据,通过对有机液体吸光度变化与光电吸收关系的研究,开发了有机液体吸光度检测仪,并投入了现场应用,取得了良好的效果。     

赤泥盐酸浸出液中钪的分光光度测定

考察了温度、时间、显色剂用量、酸度对待测溶液吸光度的影响,结果表明:温度对吸光度值不产生大的影响,在室温下测试即可;溶液显色在前8min内不稳定,其显色时间一定要达到10 min,溶液颜色保持16h不发生太大的变化;显色剂氯代磺酚C和Sc(Ⅲ)1∶1络合稳定,其溶液加入量确定为3ml;酸度对吸光度有较大的影响,待测溶液...     

滴定法和光度法在铌铁合金测定中的应用

试样以过氧化钠熔融后,用热水浸取、定容,过滤使铝、磷与铌、钽、铁、钛等元素沉淀分离。经分离后的铝,在p H4.5酸性介质中加入过量的EDTA标准溶液,以PAN为指示剂,用硫酸铜标准溶液滴定过剩的EDTA,与铝配位络合的EDTA用氟化铵取代释放后,再用硫酸铜标准溶液滴定求得铝量。滤液中磷在过氧化钠熔融时已被氧化,在有铁离子存在的情况下,于硝酸介质中,用钼酸铵-酒石酸钾钠混合溶液掩蔽硅并使磷生成磷钼黄,以氟化钠-氯化亚锡掩蔽铁,并将磷钼黄还原为磷钼蓝,测定吸光度求得磷量。在草酸介质中,变色酸与钛生成红色络合物,用光度法测定吸光度值求得含钛量。实验证明,该方法有较好的精密度和准确度,能满足冶金生产的需求。     

催化比色法测定地质试样中痕量金

利用金(Ⅲ)在甲酸还原磷钼酸的反应中有良好的催化作用,加入Hg(Ⅱ)可以增强金的催化活性。该体系溶液至少可稳定24小时。本文在文献基础上增加显色反应煮沸时间,提高了吸光度,可测定0.0001     

Formation of electrical field accompanying temperature jump in isolated spinach chloroplasts

Temperature-jump-induced absorbance changes of spinach chloroplasts in the dark were studied. After the temperature rise, a fast absorbance decrease and a succeeding slow absorbance increase were observed at the wavelength of 515 nm. The spectrum of the fast phase had positive maxima (increase in absorbance) at 430, 470 and 673 nm and a negative maxima (decrease in absorbance) at 525 nm. Permeant ions, tetraphenylboron-, tetraphenylarsonium+, and tetraphenylphosphonium+, decreased the extent of the fast absorbance change and increased the rate of slow recovery. Additions of inorganic potassium salts had a similar effect. Valinomycin, added in the presence of potassium ion, also increased the rate of slow recovery. These ions and ionophore had a parallel effect also on the recovery of flash-induced 515-nm absorbance change in chloroplasts. Electroneutral nigerericin did not affect the temperature-jump-induced absorbanc change. These results suggest the formation of electrical field across the thylakoid membrane in the dark accompanying the temperature rise. A possible involvement of the movement of water molecules (thermo-osmosis) in the observed absorbance changes is also discussed.     

冷轧薄钢板退火再结晶的计算机模拟

采用Monte Carlo方法和简化的物理模型所编制的程序较好地模拟了冷轧钢板退火组织的演变过程及变化规律，模拟程序所演示的退火过程晶粒尺寸和再结晶百分比变化与实验所得到的结果一致。     

Head and neck manifestations of plasma cell neoplasms

Absorbance changes were monitored from 250 to 650 nm during the first microsecond after photolysis of detergent suspensions of bovine rhodopsin at 20 degrees C. Global analysis of the resulting data produced difference spectra for bathorhodopsin, BSI and lumirhodopsin which give the change in absorbance of the aromatic amino acid side chains in these photointermediates relative to rhodopsin. These spectra show that the significant bleaching of absorbance near 280 nm, which has been seen previously for the lumirhodopsin, metarhodopsin I and metarhodopsin II intermediates, extends to times as early as bathorhodopsin. Because no corresponding absorbance increase is observed in the 250-275 nm region, the earliest bleaching of the 280 nm absorbance in rhodopsin is attributed to disruption of a hyperchromic interaction affecting Trp265. Partial decay of this 280 nm bleaching as bathorhodopsin converts to BSI takes place maximally near 290 nm, where Trp265 has been shown to absorb, and could be due to the ring of the retinylidene chromophore resuming a position at the BSI stage that reestablishes the hyperchromic interaction with Trp265. A subsequent change in the 250-300 nm region, which has no counterpart in the visible chromophore bands, indicates the possible presence of a protein-localized process as lumirhodopsin is formed.     

Melting of a DNA hairpin without hyperchromism

UV absorbance spectroscopy is the most common method for detecting nucleic acid structural transitions and obtaining thermodynamic parameters. UV-detected melting has been used to determine stabilities of nucleic acid hairpins, duplexes, triplexes, and higher order structures and to determine thermodynamic effects of unusual or modified bases and mismatched base-pairs. We report that in some cases UV absorbance spectroscopy is an inadequate analytical technique for these purposes. Some critical transitions are invisible to UV absorbance spectroscopy. For example, the conversion of dodecamer d(CGCAAATTCGCG) from hairpin to random coil is not accompanied by hyperchromism. Circular dichroism (CD) spectroscopy (263 nm) clearly detects two transitions for this dodecamer, each giving a pronounced change in ellipiticity. The concentration dependence of the low-temperature transition and the concentration independence of the high-temperature transition indicate that the predominant state converts from duplex to hairpin to random coil as the temperature increases. These assignments are confirmed by comparison to oligonucleotides of similar sequence that undergo a hairpin to coil transition only. In contrast to CD spectroscopy, UV absorbance spectroscopy shows only a single transition. The transition detected by UV absorbance spectroscopy corresponds to the low-temperature transition detected by CD. UV absorbance spectroscopy does not detect the second transition at any wavelength (from 218 to 310 nm) (by changes) in either absorbance or its derivative with temperature.     

Ligand binding and conformation change in the dimeric hemoglobin of the clam Scapharca inaequivalvis

The reaction with carbon monoxide of the cooperative dimeric hemoglobin from Scapharca inaequivalvis has been examined by flash photolysis. In the nanosecond time range, geminate rebinding of 5% of dissociated CO occurs with a rate constant of 1.4 x 10(7) s-1. There is a change in absorbance of deoxyhemoglobin following photolysis at a rate of 1.2 x 10(6) s-1, consistent with a shift in the position of the Soret band to longer wavelengths. The amplitude of the change is proportional to the population of deoxydimer. In much of the Soret region this change is greater than the absorbance excursion associated with geminate recombination. There is at least one other slower change associated with the singly liganded species. Geminate rebinding of NO has components of 50, 8, and 0.035 ns-1, accounting for 75%, 25%, and less than 1% of the total reaction observed after a 35-ps photolysis flash. Simulation of diffusion of NO by molecular dynamics shows the ligands moving from the heme pocket to a subsidiary space between the edge of the heme and the surface of the protein.     

The equilibrium constant of beta-cyclodextrin-phenolphtalein complex; influence of temperature and tetrahydrofuran addition

The temperature influence on creation of a supramolecular complex in which beta-cyclodextrin (beta-CD) is the host molecule and phenolphtalein (PP) is the guest has been studied in aqueous solution by UV-visible absorption spectroscopy. The decrease of temperature of beta-cyclodextrin-phenolphtalein system resulted in a decrease in absorbance of the UV-vis spectrum. Under favourable conditions (0.1 mM beta-CD, 30 microM PP) the termochromic effect is very significant (approximately =0.1 U of absorbance/10 degrees C). The formation constant of inclusion complex was determined at various temperatures (from 10 to 70 degrees C) using Scott's equation. The association constants (K11) for the binding in 0.02 M sodium carbonate (pH 10.5) at 10 and 70 degrees C are 7.44 and 0.26 x 10(4) M(-1) respectively. The stoichiometric ratio of investigated complex was found to be 1:1 on wide range of beta-cyclodextrin:phenolphtalein concentration ratio (from 0.8:1 to 427:1). Additionally, strong interaction between cyclodextrin and tetrahydrofuran (THF) was observed and the inhibitory effect of tetrahydrofurane on the association of beta-CD PP complex was studied. From linear Van't Hoff plots thermodynamic parameters such as: the change of enthalpy (deltaH(o)) and change of entropy (deltaS(o)) were estimated and interpreted.     

炼钢工艺流程氧氮含量变化分析

氧、氮存在于钢中对钢材质量有着重要影响,本文结合炼钢各工艺点的实际控制,对两炉45#钢转炉、精炼、连铸工艺流程取样分析钢中氧、氮含量,找出炼钢各工艺环节氧、氮含量变化规律,明确炼钢生产各工艺环节降低氧、氮含量应该承担的任务,提出降低氧,氮含量的措施,有利于炼钢改进工艺,从而达到提高质量的目的。     

Short-term treatment with prostaglandin E1 analogue has long-term preventive effects on intimal thickening in balloon-injured rat carotid arteries

Based on the absorbance change of indicators with the concentration of hydrogen ion released from an enzyme-catalyzed reaction, a convenient colorimetric method was established for the assay of acidic phospholipase A2 and glycogen phosphorylase b. Brilliant yellow and bromothymol blue were chosen as indicators for assays of acidic phospholipase A2 and glycogen phosphorylase b by following the absorbance changes at 495 and 615 nm, respectively. The method is simple, sample-saving, sensitive and valid for a wide range of enzyme concentrations. It can be extended for assaying other enzymes catalyzing reactions with hydrogen ion concentration changes.     

Oxidative titrations of reduced cytochrome aa3: correlation of midpoint potentials and extinction coefficients observed at three major absorption bands

Anaerobic oxidative titrations of purified cytochrome aa3 were monitored at three wavelengths (444, 604, and 820 nm), in both the absence and the presence of carbon monoxide. Computer simulation of each titration curve was utilized to ascertain the midpoint potentials of the four oxidation-reduction centers of the enzyme. For experiments performed under nitrogen, two components were found to titrate with low potential (heme aL = 220 mV, CuL = 240 mV) and two with high potential (heme ath, cuH = 340 mV), consistent with results obtained previously in reductive titrations. Unequal heme extinction coefficients were observed at 444 nm. Oxidation by either potassium ferricyanide or 1,1'-bis(hydroxymethyl)ferricinium ion showed that the low potential heme component contributed 75% of the absorbance change at 444 nm. At 820 nm, the entire absorbance change could be attributed to a single, low potential copper component. Midpoint potentials calculated for the carbon monoxide complexed enzyme agreed with previously reported values. The copper components retained the values observed under nitrogen, while the titratable heme group gave an apparent midpoint potential of 260 mV. These results enable us to assign absorbance changes at various wavelengths to specific redox components of cytochrome aa3.     

Affective tone during environmental regularity and change.

"Two groups experienced environmental regularity, which consisted of eight presentations of an initially novel series of events." Subgroups then experienced different degrees of change in the order of a final event series. "The results indicated that as the series was repeated (environmental regularity), affective tone [as measured by sentence completion] was initially negative, became positive, and then became negative again. [A]… relatively moderate degree of [event order] change was associated with affective change in the positive direction. The results are somewhat consistent with the proposition that greatly unexpected and completely expected situations arouse negative affect, while moderately unexpected situations arouse positive affect." From Psyc Abstracts 36:04:4CC38M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)