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41.
Ahmad Seif Temer S. Ahmadi Ali Bodaghi Javad Hosseini 《Journal of Molecular Structure》2009,911(1-3):19-23
The chemical shielding (CS) tensors of Gallium-71 and nitrogen-15 are computed for the first time in order to investigate the influence of Mn-doping on the electronic properties of the (5, 5) Gallium nitride nanotube (GaNNT). A GaNNT consisting of 40 Ga and 40 N atoms and having a 1.2 nm length was considered. One portal of the nanotube was capped by ten hydrogen atoms and other-end was kept open. Additionally, two other forms of this model of Mn-doped GaNNT were considered where a Mn-atom was substituted for a Ga atom either in the first or in the second layer. The calculations reveal that in both models of Mn-doped GaNNTs, the N atoms that are directly connected to the Mn atom have the smallest isotropic chemical shielding among other N atoms. These calculations were performed at the level of the density functional theory (DFT) using GAUSSIAN 03 package. The basis sets for Ga and N atoms were chosen to be 6-31G (d) and those for Mn atom were chosen to be LanL2DZ. 相似文献
42.
Andresen GB Bertsche W Bowe PD Bray CC Butler E Cesar CL Chapman S Charlton M Fajans J Fujiwara MC Funakoshi R Gill DR Hangst JS Hardy WN Hayano RS Hayden ME Hydomako R Jenkins MJ Jørgensen LV Kurchaninov L Lambo R Madsen N Nolan P Olchanski K Olin A Povilus A Pusa P Robicheaux F Sarid E El Nasr SS Silveira DM Storey JW Thompson RI van der Werf DP Wurtele JS Yamazaki Y;ALPHA Collaboration 《Physical review letters》2008,100(20):203401
Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report the first detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile and its relation to that of the electron plasma. 相似文献
43.
Algebra universalis - 相似文献
44.
Let n and r be positive integers with 1 < r < n and let K(n,r) consist of all transformations on X n = {1,...,n} having image size less than or equal to r. For 1 < r < n, there exist rank-r elements of K(n,r) which are not the product of two rank-r idempotents. With this limitation in mind, we prove that for fixed r, and for all n large enough relative to r, that there exists a minimal idempotent generating set U of K(n,r) such that all rank-r elements of K(n,r) are contained in U 3. Moreover, for all n > r > 1, there exists a minimal idempotent generating set W for K(n,r) such that not every rank-r element is contained in W 3. 相似文献
45.
SupposeG is a finite connected graph. LetC(G) denote the inclusion ordering on the connected vertex-induced subgraphs ofG. Penrice asked whetherC(G) is Sperner for general graphsG. Answering Penrice's question in the negative, we present a treeT such thatC(T) is not Sperner. We also construct a related distributive lattice that is not Sperner. 相似文献
46.
47.
Influence of halide mixing on thermal and photochemical stability of hybrid perovskites: XPS studies
Ivan S. Zhidkov Azat F. Akbulatov Andrey I. Kukharenko Seif O. Cholakh Keith J. Stevenson Pavel A. Troshinb Ernst Z. Kurmaev 《Mendeleev Communications》2018,28(4):381-383
The effect of I–/Cl–and I–/Br–mixing on the thermal and photochemical degradation of organometallic perovskite MeNH3PbI3 (MAPbI3) was studied by X-ray photoelectron spectroscopy, which revealed the opportunity to essentially increase the photo and thermal stabilities of the material depending on the level and position of halide-mixing. The largest positive effect was observed for the small concentration of chloride substituent (MAPbI2.7Cl0.3), while the full halide substitution (MAPbBr3) had a negative effect on the stability of hybrid perovskite. 相似文献
48.
Laurent Camont Yara Rhayem Raja Djelidi Jean-Louis Beaudeux Dominique Bonnefont-Rousselot 《Analytica chimica acta》2009,634(1):121-5866
The solubility and molar absorptivity of trans- and cis-resveratrol isomers in aqueous solvents are poorly described. This study aimed to develop and describe a new simple method for the determination of trans- and cis-resveratrol concentrations in aqueous solutions. Up to 300 μM trans-resveratrol was dissolved in water by sonication for 2 h. Cis-resveratrol was obtained by exposing a 100-μM trans-resveratrol aqueous solution to sunlight for 8 h, followed by HPLC separation and analysis by mass spectrometry (resveratrol oxidation products were absent). Accurate values for UV absorbance in water were ελmax=ε304 nm=30 335 M−1 cm−1, ?286 nm = 23 400 M−1 cm−1 for trans-resveratrol and ελmax=ε286 nm=14 986 M−1 cm−1, ?304 nm = 9515 M−1 cm−1 for cis-resveratrol. These values allowed us to propose formulae to assess the trans-/cis-resveratrol ratio in water, using a simple and reliable UV-vis spectrophotometric method. Statistical analysis revealed no significant difference between our UV method and the commonly used HPLC method. All these data are transferable to 150 mM NaCl and 10 mM phosphate buffer solutions, which could be particularly useful for cell culture, ex vivo and in vivo studies. 相似文献
49.
An effective combination of focused microwave-assisted extraction (FMAE) with solid-phase microextraction (SPME) prior to gas chromatography (GC) is described for the selective extraction and quantitative analysis of cocaine from coca leaves (Erythroxylum coca). This approach required switching from an organic extraction solvent to an aqueous medium more compatible with SPME liquid sampling. SPME was performed in the direct immersion mode with a universal 100 microm polydimethylsiloxane (PDMS) coated fibre. Parameters influencing this extraction step, such as solution pH, sampling time and temperature are discussed. Furthermore, the overall extraction process takes into account the stability of cocaine in alkaline aqueous solutions at different temperatures. Cocaine degradation rate was determined by capillary electrophoresis using the short end injection procedure. In the selected extraction conditions, less than 5% of cocaine was degraded after 60 min. From a qualitative point of view, a significant gain in selectivity was obtained with the incorporation of SPME in the extraction procedure. As a consequence of SPME clean-up, shorter columns could be used and analysis time was reduced to 6 min compared to 35 min with conventional GC. Quantitative results led to a cocaine content of 0.70 +/- 0.04% in dry leaves (RSD <5%) which agreed with previous investigations. 相似文献
50.
Abdolvahab Seif Sattar Ebrahimi Esmail Vessally Moein Goodarzi 《Structural chemistry》2013,24(5):1737-1745
The computational investigations are carried out on the heterodimers containing CF2Cl2 with isoelectronic and isostructure (linear triatomics) species of N2O and CO2 through MP2/aug-cc-pV(D+d)Z, MP2/aug-cc-pV(T+d)Z//MP2/aug-cc-pV(D+d)Z, and CCSD(T)/aug-cc-pV(D+d)Z//MP2/aug-cc-pV(D+d)Z levels. Five and twelve heterodimers are located on the potential energy surface of CF2Cl2–CO2 and CF2Cl2–N2O systems, respectively. Binding energies of heterodimers in the CF2Cl2–CO2 and CF2Cl2–N2O systems corrected with BSSE are in the ranges of 1.30–5.79 and 1.30–6.85 kJ/mol at the MP2/aug-cc-pV(T+d)Z//MP2/aug-cc-pV(D+d)Z level, respectively. The calculated results reveal that the five most stable heterodimers among all heterodimers obtained for the CF2Cl2–CO2 and CF2Cl2–N2O systems belong to CF2Cl2–N2O system. Therefore, CF2Cl2–N2O system has more key role than CF2Cl2–CO2 one in the atmosphere. 相似文献