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101.
Tatjana Topalovic Vincent A. Nierstrasz Lorenzo Bautista Dragan Jocic Antonio Navarro Marijn M. C. G. Warmoeskerken 《Cellulose (London, England)》2007,14(4):385-400
Hydrogen peroxide can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating dinuclear tri-μ-oxo
bridged manganese(IV) complex of the ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (MnTACN) as the catalyst in the bleaching
solution. The catalytic system was found to be more selective under the conditions applied than the non-catalytic H2O2 system, showing better bleaching performance while causing slightly lower decrease in degree of polymerization (DP) of cellulose.
In order to gain fundamental knowledge of the bleach effect on cotton fibers and cellulose as its main component, especially
after catalytic bleaching, X-ray Photoelectron Spectroscopy (XPS) was used to study surface chemical effects. The Washburn
method was applied to investigate wetting properties, and liquid porosity was used to obtain pore volume distribution (PVD)
plots. Parallel analyzes performed on model cotton fabric, i.e. “clean” cotton fabric stained with morin - a pigment regularly
found in native cotton fiber, helped to differentiate between pigment oxidation and other bleaching effects produced on the
(regular) industrially scoured cotton fabric. Bleaching was not limited to the chemical action but also affected cotton fiber
capillary parameters most likely due to the removal of non-cellulosic materials as well as chain-shortened cellulose. 相似文献
102.
《Electroanalysis》2003,15(4):254-262
The new electrochemical double pulse technique, known as additive differential normal pulse voltammetry (ADNPV) when there is no restriction on the duration of both pulses, and additive differential pulse voltammetry (ADPV) when t2?t1, has been applied to a pseudo‐first‐order catalytic mechanism. The expressions obtained here are applicable to planar and spherical electrodes, of any radius. This is of great interest since the size of the electrode plays an important role in the preponderating of diffusive and kinetics processes. The signal obtained with this technique presents the same morphological characteristics as the triple pulse technique, double differential pulse voltammetry (DDPV) and is more advantageous than DDPV and than the double pulse one, differential pulse voltammetry (DPV). 相似文献
103.
Groshev gave a characterization of the union of domains of partial attraction of all Poisson laws in 1941. His classical condition is expressed by the underlying distribution function and disguises the role of the mean of the attracting distribution. In the present paper we start out from results of the recent probabilistic approach and derive characterizations for any fixed >0 in terms of the underlying quantile function. The approach identifies the portion of the sample that contributes the limiting Poisson behavior of the sum, delineates the effect of extreme values, and leads to necessary and sufficient conditions all involving . It turns out that the limiting Poisson distributions arise in two qualitatively different ways depending upon whether >1 or <1. A concrete construction, illustrating all the results, also shows that in the boundary case when =1 both possibilities may occur. 相似文献
104.
Pierre Braunstein 《Journal of organometallic chemistry》2004,689(24):3953-3967
In this account, we focus on results from our laboratory to illustrate recent developments in various fields of organometallic chemistry. Studies on hemilabile P,N donor ligands and on the ion-pair behaviour of cationic Pd(II) complexes have led to the full characterization of complexes with η1-allyl ligands. This still rare bonding mode for the allyl ligand in palladium chemistry allows facile insertion of CO into the Pd-C σ-bond, in contrast to the situation in related η3-allyl Pd(II) complexes. In order to develop new homogeneous catalysts for the selective dimerization and oligomerization of ethylene, a range of Ni(II) complexes have been prepared with new chelating P,N ligands where P represents a phosphine, phosphinite or phosphonite donor group and N a pyridine or oxazoline moiety. Finally, we shall examine bottom-up approaches to the formation of new nanomaterials of magnetic or catalytic interest by covalent anchoring of metal complexes and clusters into mesoporous materials using functional phosphine or alkyne ligands containing an alkoxysilyl group. 相似文献
105.
Narcís Homs Jordi Llorca Montserrat Riera Jordi Jolis Jos-Luis G. Fierro Joaquim Sales Pilar Ramírez de la Piscina 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):251-259
Silica-supported trimetallic catalysts containing Pt, Sn and a group 13 metal (PtSnM, M=Ga, In, Tl) were prepared by consecutive impregnation steps from cis-[PtCl2(PPh3)2] and chloride precursors. X-ray diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (ED) and energy dispersive X-ray analysis (EDX) showed large platelet-like particles of PtSn1−xMx phases. PtSnGa catalyst with a Pt/(Sn+Ga) molar ratio of 1.72 showed a bimodal particle distribution and a Pt phase was identified. Differences in surface structures were also revealed by the performance of catalysts in the dehydrogenation of n-hexane. For PtSnIn and PtSnTl (Pt/(Sn+M) molar ratio of about 1) the dehydrogenation was favoured. In contrast, PtSnGa catalyst yielded hydrogenolysis products. Photoelectron spectra showed the Pt 4f7/2 level at a binding energy of 70.0–71.8 eV in all cases. Moreover, the FT-IR spectra of chemisorbed CO on the PtSnGa showed a slight shift in the ν(CO) toward higher values with respect to the monometallic catalyst, pointing to an electronic effect in accordance with photoelectron spectroscopy. 相似文献
106.
为了探寻电流脉冲泄流时,设备的接地是否有效可靠,用FDTD法分析了脉冲泄流时均一土壤、分层土壤及局部改善土壤的电导率对冲击接地阻抗(TGR)的影响。结果表明:大地电导率对冲击接地阻抗的影响很大;对均一土壤,TGR随大地电导率的增大而减小,大地电导率越大,TGR对接地体的埋深越不敏感。对分层土壤,接地体要埋在大地电导率大的土壤层中,且不要靠近交界面;局部改善大地导电性能对降低TGR效果明显,TGR对改善区域的体积非常敏感,而当电导率大于一定值时,大地电导率的再增加,对TGR的影响不明显。 相似文献
107.
108.
在中性pH值的缓冲溶液中,血红蛋白作催化剂,维生素B6与过氧亚硝酸活性氧(ONOO-)发生反应,维生素B6原来位于391 nm处的强烈的荧光发射峰消失,而在384 nm和424 nm处出现了两个新的荧光峰.据此建立了血红蛋白一维生素B6体系高灵敏检测ONOO-活性氧的新方法.方法的线性范围为5.24×10-8~2.62×10-6mol/L,检出限为2.62×10-9mol/L,对1.31×10-7mol/L的ONOO-溶液测定的相对标准偏差为3.75%(n=7). 相似文献
109.
Ying Lv Bofeng Zhang Guobing Zou Xiaodong Yue Zhikang Xu Haiyan Li 《Entropy (Basel, Switzerland)》2022,24(7)
Domain adaptation aims to learn a classifier for a target domain task by using related labeled data from the source domain. Because source domain data and target domain task may be mismatched, there is an uncertainty of source domain data with respect to the target domain task. Ignoring the uncertainty may lead to models with unreliable and suboptimal classification results for the target domain task. However, most previous works focus on reducing the gap in data distribution between the source and target domains. They do not consider the uncertainty of source domain data about the target domain task and cannot apply the uncertainty to learn an adaptive classifier. Aimed at this problem, we revisit the domain adaptation from source domain data uncertainty based on evidence theory and thereby devise an adaptive classifier with the uncertainty measure. Based on evidence theory, we first design an evidence net to estimate the uncertainty of source domain data about the target domain task. Second, we design a general loss function with the uncertainty measure for the adaptive classifier and extend the loss function to support vector machine. Finally, numerical experiments on simulation datasets and real-world applications are given to comprehensively demonstrate the effectiveness of the adaptive classifier with the uncertainty measure. 相似文献
110.
研究了醇氧化酶-过氧化氢酶联合的酶促反应的最佳条件,建立了简便测定乙醇的吸光光度法,乙醇浓度在0.0686~5.115 mmol/L范围内符合比尔定律,回归方程为:A=0.00403 0.08585c(mmol/L),相关系数为0.9986,检出限为0.0172 mmol/L(S/N=3),本法所用仪器简单,已用于酒后唾液中乙醇的测定。 相似文献