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691.
The reaction mechanism of sulfur vapor (S) with nitrite ion (NO2
−) has been investigated theoretically on the triplet and singlet potential energy surfaces (PESs). All stationary points for
the title reaction have been optimized at the B3LYP/6-311+G(3df) level. The energetic data have been obtained at the CCSD(T)//B3LYP
level employing the 6-311+G(3df) basis set. Five stable collision complexes, 3IN1 (S–ONO−), 3IN2 (cyclic SONO−), 1IN1 (cis S–ONO−), 1IN2 (S–NO2
−), and 1IN3 (trans S–ONO−), have been considered on the triplet and singlet PESs through barrier-less and exothermic processes. By starting from these
complexes, a simple mechanism has been obtained on the triplet PES while a complex mechanism has been considered on the singlet
PES. The calculated results show that there are no favorable paths for the reaction of S with NO2
− on the singlet PES. Therefore, the S + NO2
− reaction proceeds only on the triplet PES to produce 3SO + 3NO− as main products. The results from the comparative study of S + NO2
− reaction mechanism with S + O3 (as isoelectronic and isostructure reactions) on the singlet PES show similarities in the overall trend of reaction mechanism
and atom connectivity and differences in the stability of intermediates and the energy barriers of transition states. 相似文献
692.
693.
Morteza Seddighin 《Linear algebra and its applications》2009,430(10):2566-1408
In a number of his recent papers Karl Gustafson has outlined the similarities between the Antieigenvalue Theory he founded and several finite dimensional matrix optimization theorems for positive matrices arising in statistics. In this paper, we will show how the techniques that the author and Karl Gustafson have used for computation of Antieigenvalues can also be applied to prove and generalize these matrix optimization theorems in statistics. We will primarily focus on two techniques which we have used in Antieigenvalue computations in recent years. These two techniques are a two nonzero component property for certain class of functionals, and converting the matrix optimization problems in statistics to a convex programing problem. Indeed, these two techniques allow us to generalize some of the matrix optimization problems arising in statistics to strongly accretive operators on finite or infinite dimensional Hilbert spaces. 相似文献
694.
The Sunn pest, Eurygaster integriceps Put. (Hemiptera: Scutelleridae), is a key pest of wheat in the Middle East and some other areas which causes severe qualitative and quantitative damage. The objective of the current work is to describe the morphology of the midgut of E. integriceps adult. Microscopic studies revealed that foregut consists of oral cavity, pharynx and oesophagus likely other phytophagous Hemiptera. In the Midgut, four anatomical regions could be identified: the first ventriculus (V1), the second ventriculus (V2), the third ventriculs (V3), and the fourth ventriculus (V4). The microvilli and perimicrovillar membrane (PMM) were found in V1-V3 regions with columnar cells characterized by presence of mitochondria, rough endoplasmic reticulum and basal infoldings in the basal portion. However, V2 and V3 showed less developed basal plasma membrane infoldings. Three cell types: columnar, endocrine and regenerative cells were found in V1-V3. The V4 region showed different histological features from the other three midgut regions by showing a vacuolated epithelium with crypts storing symbiotic bacteria. The hindgut had a short ileum followed by a well-developed rectum with an epithelial cell layer and a thin cuticular intima. The current results suggest V1-V3 midgut regions play a role in enzyme and absorption, whereas V4 seems to have no function in digestion. 相似文献
695.
This article presents a connection between fuzzy preordered structures and hyperstructures. Firstly, we introduce the notion of fuzzy preordered semigroup and then, we construct a semihypergroup associated with it, giving some properties of the associated hyperstructure. Secondly, we define the notion of fuzzy preordered ring in order to construct a fuzzy hyperring. 相似文献
696.
Behshid Behdadfar Ahmad Kermanpur Hojjat Sadeghi-Aliabadi Maria del Puerto Morales Morteza Mozaffari 《Journal of magnetism and magnetic materials》2012
Superparamagnetic and monodispersed aqueous ferrofluids of Zn substituted magnetite nanoparticles (ZnxFe3−xO4, x=0, 0.25, 0.3, 0.37 and 0.4) were synthesized via hydrothermal-reduction route in the presence of citric acid, which is a facile, low energy and environmental friendly method. The synthesized nanoparticles were characterized by X ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, scanning and transmission electron microscopy (SEM and TEM) and the dynamic light scattering (DLS) method. The results showed that a certain amount of citric acid was required to obtain single phase Zn substituted magnetite nanoparticles. Citric acid acted as a modulator and reducing agent in the formation of spinel structure and controlled nanoparticle size and crystallinity. Mean particle sizes of the prepared nanoparticles were around 10 nm. The results that are obtained from XRD, magnetic and power loss measurements showed that the crystallinity, saturation magnetization (MS) and loss power of the synthesized ferrofluids were all influenced by the substitution of Zn in the structure of magnetite. The Zn substituted magnetite nanoparticles obtained by this route showed a good stability in aqueous medium (pH 7) and hydrodynamic sizes below 100 nm and polydispersity indexes below 0.2. The calculated intrinsic loss power (ILP) for the sample x=0.3 (e.g. 2.36 nH m2/kg) was comparable to ILP of commercial ferrofluids with similar hydrodynamic sizes. 相似文献
697.