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41.
The structure of biological molecules plays an important role in many biological processes. The variation of ambient parameters
such as pH, temperature or pressure can influence important properties of protein molecules like conformation or stability.
By means of the perturbed angular correlation (PAC) technique and atomic force microscopy (AFM) a conformation change of bovine
serum albumin (BSA) molecules has been studied as a function of the pH value of the BSA solution. The observed decrease of
the rotational correlation time and the increase of molecule diameter as a function of pH were attributed to conformational
changes of bovine serum albumin induced by different pH values of the BSA solution. 相似文献
42.
W.-D. Zeitz S. Unterricker F. Schneider V. Samokhvalov K. Potzger A. Weber M. Dietrich 《Hyperfine Interactions》2004,158(1-4):437-441
The magnetic response of europium in γ-cerium and in platinum was studied by applying the perturbed angular correlation spectroscopy.
The probe nuclei were 147Eu(11/2−) and 149Eu(11/2−). The response in γ-Ce was determined by the electronic S = J = 7/2 ground state of divalent Eu. In Pt, on the other hand, Eu is trivalent (J = 0 ground state). Here the magnetic contributions originate from Van Vleck terms of the whole multiplet system. 相似文献
43.
A. F. Pasquevich A. M. RodrÍguez H. Saitovitch P. R. J. Silva 《Hyperfine Interactions》2004,158(1-4):383-387
The perturbed angular correlation (PAC) technique was applied to study the electric field gradients at 111In sites in CdIn2O4. The measurements were carried out at temperatures in the range 150–1073 K. The aims of the study were both to characterize
the quadrupole interactions of the tracers and to determine the distribution of indium ions among the available sites in the
spinel structure. Room temperature measurements corresponding to samples cooled at different rates are also reported.
aAlso at Comisión de Investigasiones Científicas de la Provincia de Buenos Aires, Argentina. 相似文献
44.
45.
Jean-Claude Douai 《代数通讯》2013,41(9):3963-3968
Using the Tate–Poitou duality, Sansuc proved that the group III1(K, G) is stably K-birational invariant of G for a connected linear algebraic group defined over a number field K. In this paper, we consider the case where K is a function field, in one variable over a PAC field (K is a “good” field in sense Colliot–Thélène and Kunyavskii). We show that the group III1(K, G) is stably K-birational invariant when G is a connected reductive K-group. Since we no longer have the Tate–Poitou duality at our disposition, we use the flasque resolutions of Colliot–Thélène and Sansuc. En utilisant la dualité de Tate–Poitou, Sansuc a établi le caractère d'invariant stablement K-birationnel du groupe III1(K, G) pour un groupe algébrique linéaire connexe G défini sur un corps de nombres K. Dans cet article, nous considérons le cas où K est un corps de fonctions en une variable sur un corps PAC (K est un “bon” corps au sens de Colliot–Thélène et Kunyavskii). Nous montrons le caractère d'invariant stablement K-birationnel du groupe III1(K, G) pour un K-groupe réductif connexe G. Comme nous n'avons plus à notre disposition la dualité de Tate–Poitou, nous devons utiliser les résolutions flasques de Colliot–Thélène et Sansuc. 相似文献
46.
苯乙烯对人体健康和自然环境具有极大的危害,是国际卫生组织确认的致癌物。历年来,苯乙烯泄漏事故频繁发生,对饮用水安全造成了极大的隐患。对水中苯乙烯污染进行快速监测并采取切实有效的应急处理措施有助于保障饮用水的卫生安全。利用三维荧光光谱技术对苯乙烯的水溶液进行分析,发现在Ex255/Em305处有一个明显的荧光峰,荧光峰值与苯乙烯溶液浓度呈现良好的线性相关,相关系数r达到了0.995 7,其颜色随浓度增加而变深。苯乙烯中共有4个共轭π键,其中苯环具有大的共轭π键结构,乙烯基上同样具有一个共轭π键。同时,苯乙烯的分子结构中,碳原子处于同一个平面上,属于平面构型且具有一定的刚性,符合强荧光物质所具有的特征。因此通过三维荧光扫描结合苯乙烯的荧光特性,能快速测定水体中苯乙烯浓度及判断水体的污染程度。粉末活性炭可以有效地吸附去除水中的苯乙烯。当苯乙烯在源水中的浓度达到《生活饮用水卫生标准》规定的限值0.02 mg·L-1时,采用180目的粉末活性炭,投加量为15 mg·L-1时,苯乙烯浓度可降至0.001 mg·L-1,去除率达95.5%。 相似文献
47.
增效反应中聚合氯化铝红外结构特征的变化 总被引:9,自引:0,他引:9
对聚合氯化铝 (PAC)进行增效改性是制备高性能无机高分子絮凝剂的重要手段之一。用多核络合剂络合、聚合硅酸交联和聚丙烯酰胺复合三种增效方法改性PAC ,分别获得了结构有别于PAC的新型絮凝剂CO PAC ,CR PAC和PAM PAC。其傅里叶红外光谱 (FTIR)表明 ,在三种无机高分子结构中均存在Al—OH以外的新化学键 ,且原有基团的特征吸收峰位置因受结构畸变而发生一定的低频红移 ,证实了PAC增效反应并不是单纯的物理混合加成作用 ,而是形成了具有特殊结构的无机高分子的化学反应。这类无机高分子絮凝剂所具有的优良絮凝特性是由增效剂和PAC间以化学作用为主的物理化学因素共同作用的结果。 相似文献
48.
G.N. Darriba L.A. Errico E.L Muoz D. Richard P.D. Eversheim M. Rentería 《Physica B: Condensed Matter》2009,404(18):2739-2741
We report perturbed-angular-correlation (PAC) experiments on 181Hf(→181Ta)-implanted corundum Cr2O3 powder samples in order to determine the magnitude and symmetry of the electric-field gradient (EFG) tensor at Ta donor impurity sites of this semiconductor. These results are analyzed in the framework of ab initio full-potential augmented-plane wave plus local orbitals (FP−APW+lo) calculations. The results are also compared with EFG results coming from PAC experiments in isomorphous α-Al2O3 and α-Fe2O3 doped with 111In→111Cd and 181Hf→181Ta tracers. This combined analysis enables us to quantify the magnitude of the lattice relaxations induced by the presence of the impurity and to determine the charge state of the impurity donor level introduced by Ta in the band gap of the semiconductor. 相似文献
49.
V. Samokhvalov F. Schneider S. Unterricker M. Dietrich 《Hyperfine Interactions》2004,158(1-4):217-221
The amorphous ferromagnetic alloy Fe79/B16/Si5 was investigated by PAC. For that the probe atoms 111In(111Cd) and 111mCd were implanted at the ISOLDE on-line separator. The distributions of magnetic hyperfine fields were determined. Below the crystallization temperature α-Fe clusters could be observed. For comparison Mössbauer transmission experiments were performed. 相似文献
50.
Rais A. Yousif A. A. Gismelseed A. Elzain M. E. Al Rawas A. Al-Omari I. A. 《Hyperfine Interactions》2004,158(1-4):229-233
PAC measurements on 111In(111Cd) implanted and thermally treated α-Fe have shown an indication for a cubic defect with the 111Cd probe in the centre of it. The measured room temperature (R. T.) magnetic hyperfine fields are B
hf1 = −38.4(8) T for substitution and B
hf2 = +11.5(3) T for the cubic defect. Additionally, probes with pure quadrupole frequency distributions were observed, which
are incorporated in surface contaminations. 相似文献