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41.
A new, convenient method for the syntheses of 2-substituted benzimidazole and benzothizole is described. Short reaction times, large-scale synthesis, easy and quick isolation of the products, excellent chemoselectivity, and excellent yields are the main advantages of this procedure. 相似文献
42.
Highly hydrolytic and thermally stable sandwich-type polyoxometallates of [(A-β-SiW9O34)2(MOH2)3CO3]13− (M = Y3+ and Yb3+) have been synthesized at room temperature by stoichiometric reactions of the trilacunary ligand with M3+ in 0.1 M carbonate solution. The new complexes were isolated as sodium and mixed sodium/potassium salts and were characterized by elemental analysis, IR, 13C and 29Si NMR, UV–Vis spectroscopy, TGA, DSC and single crystal structure analysis. The crystal structure of the complexes consist of two lacunary Keggin moieties which are linked by a (H2OMO)3C belt into an assembly of virtual C2 symmetry. Each M3+ ion adopts a mono-capped trigonal-prismatic coordination. The C2 axis of the complexes and the local 3-fold axis of the MO6 group lies in the (H2OMO)3C belt plane. The trigonal prismatic geometry is achieved by the two terminal oxygen atoms of an edge shared pair of WO6 octahedra from each moiety and two oxygen from the belt, and the cap by one external water ligand. The hydrolytic and thermal stabilities of the complexes and the reasons that prove the retention of the isomeric form of the trilacunary ligand upon complexation are discussed. 相似文献
43.
Zhili Peng Shanghao Li Xu Han Abdulrahman O. Al-Youbi Abdulaziz S. Bashammakh Mohammad S. El-Shahawi Roger M. Leblanc 《Analytica chimica acta》2016
Peptides and proteins have become very promising drug candidates in recent decades due to their unique properties. However, the application of these drugs has been limited by their high enzymatic susceptibility, low membrane permeability and poor bioavailability when administered orally. Considerable efforts have been made to design and develop drug delivery systems that could transport peptides and proteins to targeted area. Although it is of great importance to determine the composition after loading a drug to the carrier, the ability to do so is significantly limited by current analytical methods. In this letter, five important proteins, α1-antitrypsin, hemoglobin human, human serum albumin, human transferrin and r-globulin were chemically conjugated to two model drug carriers, namely carbon dots and polymer O-(2-carboxyethyl) polyethylene glycol. A simple yet convenient method based on circular dichroism spectroscopy was developed to determine the compositions of the various protein-carrier conjugates. 相似文献
44.
Rhodium‐Catalyzed Oxidative Benzannulation of N‐Pivaloylanilines with Internal Alkynes through Dual C−H Bond Activation: Synthesis of Highly Substituted Naphthalenes
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Dr. Xuan Zhang Dr. Xiaoqiang Yu Dr. Xiujuan Feng Prof. Dr. Yoshinori Yamamoto Dr. Abdulrahman I. Almansour Dr. Natarajan Arumugam Dr. Raju Suresh Kumar Prof. Dr. Ming Bao 《化学:亚洲杂志》2016,11(22):3241-3250
An efficient method was developed for the synthesis of highly substituted naphthalenes through rhodium‐catalyzed oxidative benzannulation of N‐pivaloylanilines with internal alkynes. The benzannulation reaction proceeded smoothly through dual C?H bond activation to produce the corresponding highly substituted naphthalene products in satisfactory to good yields. 相似文献
45.
46.
Safaa El-Nahas Abdulrahem S. Arafat Hanan Salah El Din Abdulrahman G. Alhamzani Mortaga M. Abou-Krisha Hesham M. Alsoghier 《Molecules (Basel, Switzerland)》2021,26(22)
The strategic idea in this work was to increase pH values by employing natural alkali sources (i.e., HCO3− and CO32−) from four tested agro-ashes as an alternative to chemicals (i.e., lime or soda ash). The considerable proportion of carbonates and bicarbonates in the investigated ash products had remarkable features, making them viable resources. All ash materials showed a significant ability for Ca ion elimination at high initial Ca ion concentrations. A slight quantity of ash (10 g/L) was sufficient for usage on very hard water contents up to 3000 ppm. Finally, the tested agro-ash was free of cost. Furthermore, unlike other conventional precipitants, such as NaOH, Ca(OH)2, NaHCO3, Na2CO3, and CaO, they are cost effective and ecologically sustainable. There is no need to employ any additional chemicals or modify the agro-ash materials throughout the treatment process. The benefits of the manufactured ash were assessed using a SWOT analysis. 相似文献
47.
High sensitive determination of trace amount of cobalt by catalytic adsorptive stripping voltammetry
S. Bahrami S. Abbasi Y. A. Ghorbani A. A. Miran-Beigi 《Russian Journal of Electrochemistry》2009,45(2):208-214
A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented.
The method is based on adsorptive accumulation of cobalt-CCA (calcon carboxylic acid) complex onto a hanging mercury drop
electrode followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction
current is enhanced catalytically by nitrite. The effect of various parameters such as pH, concentration of CCA, concentration
of nitrite, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum condition
for the analysis of cobalt, include pH 5.2 (Acetate buffer), 2.1 μM clacon carboxylic acid, 0.032 M sodium nitrite and an
accumulation potential of 0.05 V (versus Ag/AgCl). Under these optimum conditions and for an accumulation time of 60 s, the
measured peak current at −0.480 V is proportional to the concentration of cobalt over the entire concentration range tested
0.003–2.0 ng ml−1 with a detection limit of 1 pg ml−1 for an accumulation time of 60 s and 2.0–10.0 ng ml−1 for an accumulation time of 40 s. The relative standard deviations for ten replicate measurement of 0.5 ng ml−1 of cobalt were 3.1%. The main advantage of this new system is the microtrace Co(II) determination by ASV. The method was
applied to determination of cobalt in a water sample and some analytical grade salts with satisfactory results.
Published in Elektrokhimiya in Russian, 2009, Vol. 45, No. 2, pp. 221–228.
The article is published in the original. 相似文献
48.
Abdulrahman Seleim Shahrzad Towfighian Emmanuel Delande Eihab Abdel-Rahman Glenn Heppler 《Nonlinear dynamics》2012,69(1-2):615-633
The dynamics of a close-loop electrostatic MEMS resonator, proposed as a platform for ultra sensitive mass sensors, is investigated. The parameter space of the resonator actuation voltage is investigated to determine the optimal operating regions. Bifurcation diagrams of the resonator response are obtained at five different actuation voltage levels. The resonator exhibits bi-stability with two coexisting stable equilibrium points located inside a lower and an upper potential wells. Steady-state chaotic attractors develop inside each of the potential wells and around both wells. The optimal region in the parameter space for mass sensing purposes is determined. In that region, steady-state chaotic attractors develop and spend most of the time in the safe lower well while occasionally visiting the upper well. The robustness of the chaotic attractors in that region is demonstrated by studying their basins of attraction. Further, regions of large dynamic amplification are also identified in the parameter space. In these regions, the resonator can be used as an efficient long-stroke actuator. 相似文献
49.
Farrokhi Chaykandi Zahra Bahrami Ali Mohammadnejad Shahram 《Optical and Quantum Electronics》2018,50(7):1-20
Optical and Quantum Electronics - A theoretical analysis of the modulational instability (MI) in a nonlinear oppositely directional coupler with one channel fabricated from nonlinear medium having... 相似文献
50.
In this study, the effect of Mg substitution on structural, magnetic and electrical properties of La0.75Sr0.25Mn1?xMgxO3 and La0.75Sr0.25?xMgxMnO3 (nominal compositions) samples are investigated by XRD, Ac susceptibility and electrical resistivity measurements. It is found that Mg does not replace La in the perovskite lattice. Also the results show that by increasing Mg doping levels, the paramagnetic–ferromagnetic and metal–insulator transition temperatures decrease. The reason for decreasing transition temperatures with increasing Mg concentration is, that the long-range FM order has been destroyed by the Mg, which is randomly occupying Mn site. This leads to the suppression of double-exchange interaction in the Mn3+–O–Mn4+ networks. Also the reentrant spin glass (RSG) state accompanied by FM transition, exists in high doped samples. The RSG state could be understood on the basis of double exchange ferromagnetic interaction in Mn3+–O–Mn4+ and super-exchange antiferromagnetic interaction in the Mn4+–O–Mn4+ networks. 相似文献