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1.
The complex species of UO2(HA)(H2A)+ and UO2(HA)2 were identified in the ascorbic acid solution of uranyl ion at pH<2.1 and pH>2.1, respectively. Polarographic wave was proved to be the simultaneous reduction of UO2+2 and UO2(HA)(H2A)+ at pH <2.1. However, at pH>2.1, the wave is due to the reduction of U02(HA)2 The stability constants of the two complex species were found to be 5.1×10+ and 1.0×105, respectively. The hydrolysis constant of uranyl ion in the solution of ascorbic acid was determined. 相似文献
2.
Fu A Huang X Li J Yuen T Lin CL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(10):2239-2247
Controlled synthesis of transition metal complexes with mixed ligands has led to two new compounds with the same empirical formula [Fe(N3)2(4,4'-bpy)] (4,4'-bpy=4,4'- bipyridine). The compound 2D-[Fe(N3)2(4,4'-bpy)] (I) contains end-on (EO) bridging azido ligands. It crystallizes in the orthorhombic crystal system, space group Cmmm (No. 65): a=11.444(2) A, b=15.181(3) A, c=3.458(1) A, V=600.8(2) A(3), and Z=2. The compound 3D-[Fe(N3)2(4,4'-bpy)] (II) contains end-to-end (EE) azido bridges. It belongs to the tetragonal crystal system, space group P4(1)2(1)2 (No. 92): a=8.132(1) A, b=8.132(1) A, c=16.708(3) A, V=1104.9(5) A(3), and Z=4. Crystals of I and II have been grown by the diffusion method. Phase-pure samples of both compounds have been obtained by means of an optimal solution synthesis. Spontaneous long-range magnetic ordering was found in both I and II, with I being a metamagnet, and II being a ferromagnet. For I, in the low-field region, multiple transitions at TN1=20 K and TN2=5 K were observed, and these indicated the existence of Fe moment reorientation. Heat capacity measurements on II confirmed ferromagnetic transition at TC=20 K. 相似文献
3.
A new analytical approach for the detection of Ni2+ utilizing an attenuated total reflection (ATR) technique is discussed in this paper. Nickel detection was accomplished on a silicon ATR parallelogram crystal uniformly coated by a ca. 1.5-microm Nafion film embedded with dimethylglyoxime (DMG) probe molecules. The detection of Ni2+ is based on the appearance of a unique infrared absorption peak at 1572 cm(-1) that corresponds to the C=N stretching mode in the nickel dimethylglyoximate, Ni(DMG)2, complex. The suitable operational pH range for the nickel infrared sensor is between 6 - 8. High alkalinity in the sample solution causes a leaching of Ni(DMG)2. The detection limit of the nickel infrared sensor is 1 ppm in a sample solution of pH = 8. Interference studies revealed that Cu2+ could compete with Ni2+ for the DMG sites in the Nafion matrix. The new nickel detection methodology can be potentially utilized, after further improvement, in field analysis to locate hot spots contaminated with a high ppm of Ni2+. 相似文献
4.
Sheng-Ping Wang Shang-Wen Lin Chuan-Jen Chyan 《Mathematical and Computer Modelling》2011,53(5-6):985-990
This work gives a criterion for the existence of positive solutions for nonlinear second order ordinary differential equations with two-point boundary conditions on time scales. Moreover, for some source terms which are in the sense of sublinear or superlinear, we also formulate corollaries and examples for applications and we improve previous results related with the first eigenvalue discussed by Professor Li. 相似文献
5.
Cumulant functions are introduced to describe the statistical state of a radiation field. These functions are simply related
to the optical coherence functions but have some interesting features. It is shown that if the cumulant functions of all orders
greater than some numberN
0 vanish then they also vanish for all orders greater than 2. Thermal field is the only field having this property. This property
holds whether the field is described by a classical stochastic process or by a quantum density operator. Further the particular
operator ordering used in defining these cumulant functions for the quantized field affects only the second order cumulant
function. To describe the statistical state of a vector field such as partially polarized or unpolarized radiation, one would
need to introduce cumulant tensors. 相似文献
6.
MA Freitas CL Hendrickson AG Marshall 《Rapid communications in mass spectrometry : RCM》1999,13(15):1639-1642
We present a novel approach for the determination of activation energy for the unimolecular dissociation of a large (>50 atoms) ion, based on measurement of the unimolecular dissociation rate constant as a function of continuous-wave CO(2) laser intensity. Following a short ( approximately 1 s) induction period, CO(2) laser irradiation produces an essentially blackbody internal energy distribution, whose 'temperature' varies inversely with laser intensity. The only currently available method for measuring such activation energies is blackbody infrared radiative dissociation (BIRD). Compared with BIRD, FRAGMENT: (a) eliminates the need to heat the surrounding ion trap and vacuum chamber to each of several temperatures (each requiring hours for temperature equilibration); (b) offers a three-fold wider range of effective blackbody temperature; and (c) extends the range of applications to include initially cold ions (e.g., gas-phase H/D exchange). Our FRAGMENT-determined activation energy for dissociation of protonated bradykinin, 1.2 +/- 0.1 eV, agrees within experimental error to the value, 1.3 +/- 0.1 eV, previously reported by Williams et al. from BIRD experiments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
7.
Potentiometric detection of trace levels of metallic contamination onset in hydrofluoric acid using a silicon-based sensor in conjunction with two non-contaminating reference electrode systems is presented in this paper. In the first case, conductive diamond was used as a non-contaminating reference electrode. Cyclic voltammetry and open-circuit potential experiments demonstrated the feasibility of using a conductive diamond film electrode as a quasi-reference electrode in the HF solution. In the second case, a dual silicon electrode system was used with one of the silicon-based electrodes protected with an anion permeable membrane behaving as the quasi-reference electrode. The dual silicon sensing electrode system possessed an additional operational advantage of being unaffected by the solution acidity. Though both sensing configurations were able to detect the metal ion contamination onsets at the parts-per-trillion to parts-per-billion levels, the dual silicon electrode design showed a greater compatibility for the on-line detection of metallic impurities in HF etching baths commonly used in semiconductor processing. 相似文献
8.
9.
Chuan Jen Chyan 《Journal of Difference Equations and Applications》2013,19(5):403-413
Values of λ are determined for which there exist positive solutions of the 2mth order differential equation on a measure chain, (-1)m x ?2m (t)=λa(t)f(u(σ(t))), y? [0,1], satisfying α i+1 u ?21(0)+0, γ i+1 u ?21(σ(1))=0, 0≤i≤m?1 with αi,βi,γi,δi≥0, where a and f are positive valued, and both lim x-0+ (f(x)/x) and lim x-0+ (f(x)/x) exist. 相似文献
10.
Supply chain design is becoming a core competency, and the enterprise resource planning (ERP) system is expected to be an integral component of supply chain management (SCM). Installing an ERP system is, however, expensive and risky. IT managers must decide how to use their limited resources and invest in the right product. Can an ERP system directly improve SCM competency? This study proposes a conceptual framework featuring the ERP benefits and SCM competencies, and examines the impacts of the former on the latter. The results confirm the operational, managerial, and strategic benefits of ERP for the SCM competencies, but not the IT infrastructure and organizational benefits as significant predictors of them. Moreover, more than 80% of respondents think it necessary to first adopt an ERP system as the backbone of company operations before deploying other enterprise systems (ES), such as the SCM system. 相似文献