The title compound (C5Me5)2U(OtBu)(SePh) (1) was synthesized and characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. This system represents
a unique example of an actinide complex with two different group 16 elements coordinated to the metal center and the first
mixed-ligand actinide alkoxide-selenide complex. The complex crystallizes in the orthorhombic space group Pbca with unit cell parameters a = 17.830(7) ?, b = 14.973(6) ?, c = 21.254(8) ?, V = 5674(4) ?3, Z = 8, Dcalc = 1.727 Mg/m3. The uranium(IV) mixed-ligand alkoxide-selenide complex adopts a pseudo-tetrahedral geometry, with the tert-butoxide and phenylselenide ligands occupying the plane bisecting the metallocene unit. Structural comparisons of the complex
(C5Me5)2U(OtBu)(SePh) (1) are made with related selenide and alkoxide uranium(IV) complexes. 相似文献
Previous studies reporting relaxation times within atherosclerotic plaque have typically used dedicated small-bore high-field systems and small sample sizes. This study reports quantitative T1, T2 and T2? relaxation times within plaque tissue at 1.5 T using spatially co-matched histology to determine tissue constituents.
Methods
Ten carotid endarterectomy specimens were removed from patients with advanced atherosclerosis. Imaging was performed on a 1.5-T whole-body scanner using a custom built 10-mm diameter receive-only solenoid coil. A protocol was defined to allow subsequent computation of T1, T2 and T2? relaxation times using multi-flip angle spoiled gradient echo, multi-echo fast spin echo and multi-echo gradient echo sequences, respectively. The specimens were subsequently processed for histology and individually sectioned into 2-mm blocks to allow subsequent co-registration. Each imaging sequence was imported into in-house software and displayed alongside the digitized histology sections. Regions of interest were defined to demarcate fibrous cap, connective tissue and lipid/necrotic core at matched slice-locations. Relaxation times were calculated using Levenberg-Marquardt's least squares curve fitting algorithm. A linear-mixed effect model was applied to account for multiple measurements from the same patient and establish if there was a statistically significant difference between the plaque tissue constituents.
Results
T2 and T2? relaxation times were statistically different between all plaque tissues (P=.026 and P=.002 respectively) [T2: lipid/necrotic core was lower 47±13.7 ms than connective tissue (67±22.5 ms) and fibrous cap (60±13.2 ms); T2?: fibrous cap was higher (48±15.5ms) than connective tissue (19±10.6 ms) and lipid/necrotic core (24±8.2 ms)]. T1 relaxation times were not significantly different (P=.287) [T1: Fibrous cap: 933±271.9 ms; connective tissue (1002±272.9 ms) and lipid/necrotic core (1044±304.0 ms)]. We were unable to demarcate hemorrhage and calcium following histology processing.
Conclusions
This study demonstrates that there is a significant difference between qT2 and qT2? in plaque tissues types. Derivation of quantitative relaxation times shows promise for determining plaque tissue constituents. 相似文献
The development of new electrocatalysts with the aim of enhancing the rate of electrochemical reactions has been a long-term
goal of electrochemists. In part, this is due to the great importance of electrocatalysts in energy generation and environmental
concerns. In this review, various methods of the preparation of nanostructured electrocatalysts and their applications after
attachment to the electrode surface are described. Diazonium chemistry has been extensively used for the preparation and attachment
of nanostructured electrocatalysts and this review thus describes the recent developments and applications of this chemistry
in electrocatalysis. The preparation of nanostructured electrocatalysts including grafted molecular films and metal nanoparticles
physically adsorbed on electrode surfaces and those attached to the surface by molecular links using diazonium chemistry is
reviewed. Two methods for the attachment of nanoparticles by simple physical adsorption and by electrochemical deposition
on molecular films are described and the electrochemical response of nanostructured electrocatalysts for some of the most
common electrochemical reactions is discussed. 相似文献
The cathodic reduction of oxygen in 1 mol dm−3 sodium hydroxide solutions has been investigated at several types of titanium oxide cathodes. Layers of TiO2 were prepared on titanium by spraying and thermal decomposition of solutions of titanium n-butoxide in 2-propanol and titanium tetrachloride in methanol+water and also by anodization; the reduction was also studied at Ebonex®, a conducting ceramic consisting mainly of Ti5O9. In all cases, the reduction of oxygen occurs largely by a 4e− reaction to water and the reaction occurs at potentials close to −1.0 V vs. SCE. Cyclic voltammetry in the absence of oxygen shows that, at these potentials, the surfaces undergo reduction and the electrochemistry of the Fe(CN)64− /Fe(CN)63− couple has been used to probe further the properties of the TiO2 surfaces. 相似文献
For various levels of confidence (i.e., 80 and 90%) and ratios (K = sigmap2/sigmaN2, where sigmap2 and sigmaN2 are the analyte variances for the positive and negative distributions, respectively), sample sizes sufficient to test the requirements that a given method detects > or = 90% of the positives (> or = 5 ppm of a given analyte) while misclassifying < or = 10% of the negatives (implying a specificity rate, true negatives that will be correctly classified, of 90%) were estimated by using a rationale that minimizes the cost of sampling. 相似文献
Plasma Chemistry and Plasma Processing - Improved utilization of organic waste for fertilizer has significant worldwide economic and ecological potential and the use of plasma can help unlock this... 相似文献
A standing iceberg illustrates how the soft PNP pincer ligand challenges the metallocene dominance (ship) in actinide chemistry, as described by J. L. Kiplinger and co‐workers in their Communication on page 3681 ff. Replacement of C5Me5 by the PNP ligand is a successful strategy for the promotion of new reactivities and to support new actinide structures. The specific electronic and steric properties of the PNP ligand enable access to structures not available for the C5Me5 ligand set and as yet unreported for uranium. (We thank Mr. Anthony Mancinco for the design of the graphic.)