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81.
Addition of Isocyanides to Tetramesityldigermene: A Comparison of the Reactivity between Surface and Molecular Digermenes
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Nada Y. Tashkandi Emily E. Cook Jeremy L. Bourque Prof. Kim M. Baines 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):14006-14012
The reaction of benzyl isocyanide, tert‐butyl isocyanide, and 2,6‐dimethylphenyl isocyanide with tetramesityldigermene (Mes2Ge=GeMes2) was examined. Whereas the addition of benzyl isocyanide gave the C?NC activation product, Mes2Ge(CH2Ph)Ge(CN)Mes2, tert‐butyl isocyanide, and 2,6‐dimethylphenyl isocyanide did not give stable adducts, rather the rate of conversion of the digermene to the corresponding cyclotrigermane was accelerated. A comparison between the reactivity of the isocyanides with Mes2Ge=GeMes2 and the Ge(100)‐2×1 surface was made and some insights into the surface chemistry are offered. 相似文献
82.
Fluid flow and heat transfer characteristics around a semi-circular tube in cross flow were experimentally and numerically
investigated. Three different tube-flow arrangements were considered. Firstly, the flat surface of the tube was placed parallel
to the freestream flow; secondly, the flat surface of the tube was facing the upstream flow and thirdly, the curved surface
of the tube was facing the upstream flow. For the second and the third arrangements, different angles of attack were studied.
Flow visualization was carried out to illustrate streamlines around the tube and to verify flow patterns obtained from the
numerical calculations. It was found that: (1) for any angle of attack, the arrangement of the curved surface facing the flow
gave higher average Nusselt number than the arrangement of the flat surface facing the flow and (2) for all tube-flow arrangements,
increasing the angle of attack slightly increases the average Nusselt number. Correlations of Nusselt numbers in terms of
Reynolds number and angle of attack were deduced from the experimental results for the three arrangements. The comparisons
between the experimental data, correlations’ predictions and numerical results showed reasonable agreements. 相似文献
83.
S. A. Nada 《Heat and Mass Transfer》2006,43(2):135-148
Heat transfer characteristics of a slot/slots jet air impinging on a cylinder have been experimentally investigated for two different orientations of slot/slots jet plan with respect to cylinder axis. The experiments were carried out to study the effects of orientation of slot/slots jet plan with respect to cylinder axis on the rate of heat transfer from the cylinder. Two different jet–cylinder configurations were studied: (1) single slot jet aligned with cylinder axis (slot length = cylinder length), and (2) multiple slot jets equally spaces distributed orthogonal to cylinder axis (each slot length = cylinder diameter and sum of slots lengths = cylinder length). For each configuration, parametric effects of Reynolds numbers (Re) ranging from 1,000 to 10,000, dimensionless slot widths (W/d) ranging from 0.125 to 0.5, and dimensionless slot orifice-to-cylinder spacing (Z/W) ranging from 1 to 12 on local and average Nusselt numbers around cylinder surface have been investigated. The results showed that: (1) cooling the cylinder by multiple slots jets situated orthogonal to cylinder axis gave more uniform surface temperature distributions and higher heat transfer rate than the case of cooling the cylinder by single slot jet aligned with cylinder axis, (2) for both configurations the Nusselt number around the cylinder increased with increasing Re and W/d, and (3) for both configurations there was a certain Z/W in the range 4<Z/W<6 at which the stagnation and mean Nusselt number were maximum. Correlations for the mean Nusselt numbers around cylinder surface have been presented for both configurations. Comparisons between the correlations predictions and the present and other previous experimental data have been conducted. 相似文献
84.
A novel and effective electrochemical sensor for the determination of morphine (MO) in 0.04 mol L(-1) universal buffer solution (pH 7.4) is introduced using gold nanoparticles electrodeposited on a Nafion modified carbon paste electrode. The effect of various experimental parameters including pH, scan rate and accumulation time on the voltammetric response of MO was investigated. At the optimum conditions, the concentration of MO was determined using differential pulse voltammetry (DPV) in a linear range of 2.0 × 10(-7) to 2.6 × 10(-4) mol L(-1) with a correlation coefficient of 0.999, and a detection limit of 13.3 × 10(-10) mol L(-1), respectively. The effect of common interferences on the current response of morphine namely ascorbic acid (AA) and uric acid (UA) is studied. The modified electrode can be used for the determination of MO spiked into urine samples, and excellent recovery results were obtained. 相似文献
85.
JPC – Journal of Planar Chromatography – Modern TLC - This research article describes a simple and sensitive thin-layer chromatographic (TLC)-densitometric method for simultaneous... 相似文献
86.
87.
Utility of 6‐Amino‐2‐thiouracils as a Core of Biologically Potent Polynitrogen–Sulfur Fused Heterocycles
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Samira T. Rabie Reham A. Abdel‐Monem Nadia R. Mohamed Ahmed I. Hashem Afaf A. Nada 《Journal of heterocyclic chemistry》2014,51(Z1):E189-E196
One pot three‐component reaction was assisted to form some new pyridopyrimidine derivatives to be investigated as antimicrobial and antitumor agents. The newly synthesized compounds showed high significant antimicrobial activity against the applied strains of both Gram‐positive and Gram‐negative bacteria and fungi. The cytotoxic activity of some compounds was evaluated as inhibitor of growth in both human liver carcinoma and breast cell lines. The results showed that some compounds exhibited very high cytotoxicity against human liver cell line and breast cancer cells. 相似文献
88.
Maha M. Abdelrahman Amal B. Ahmed Mahmoud A. Omar Sayed M. Derayea Nada S. Abdelwahab 《Journal of separation science》2020,43(15):2981-2988
Citicoline and piracetam were subjected separately to different stress conditions as recommended by the international conference on harmonization. In addition, new stability indicating thin layer chromatographic and ultra high performance liquid chromatographic methods have been developed and validated for simultaneous determination of citicoline and piracetam in presence of their degradation products. Separation on the proposed thin layer chromatographic method was carried out using a developing system containing methanol:chloroform:ammonium chloride buffer (9:1:2, v/v/v) on silica gel plates at 230 nm. On the other hand, the mobile phase in the ultra high performance liquid chromatographic method was composed of water (containing 0.1% triethylamine):ethanol (92:8, v/v). The flow rate was 1 mL/min and ultraviolet detection was at 230 nm. Moreover, results of the developed methods were statistically compared to those obtained by the reported high‐performance liquid chromatography method and no significant difference between them was found. The greenness profile of ultra high performance liquid chromatographic method was assessed and compared with those of the previously published high‐performance liquid chromatography methods, it was noticed that the proposed ultra high performance liquid chromatographic method more environmentally friendly and greener than other methods. 相似文献
89.
Umakanta Sarker Md. Golam Rabbani Shinya Oba Wagdy M. Eldehna Sara T. Al-Rashood Nada M. Mostafa Omayma A. Eldahshan 《Molecules (Basel, Switzerland)》2022,27(9)
The underutilized Amaranthus leafy vegetables are a unique basis of pigments such as β-cyanins, β-xanthins, and betalains with radical scavenging capacity (RSC). They have abundant phytonutrients and antioxidant components, such as pigments, vitamins, phenolics, and flavonoids. Eight selected genotypes (four genotypes from each species) of underutilized Amaranthus leafy vegetables were evaluated for phytonutrients, pigments, vitamins, phenolics, flavonoids, and antioxidants in a randomized complete block design under ambient field conditions with three replicates. The studied traits showed a wide range of variations across eight genotypes of two species of Amaranthus leafy vegetables. The highest fat, β-xanthins, K, dietary fiber, Mg, β-cyanins, Mn, chlorophyll ab, Zn, TP, TF, betalains, chlorophyll a content, and (RSC) (DPPH) and RSC (ABTS+) were obtained from A. tricolor accessions. Conversely, the highest protein, Cu, carbohydrates, Ca, and chlorophyll b content were obtained from A. lividus accessions. The highest dry matter, carotenoids, Fe, energy, and ash were obtained from A. tricolor and A. lividus. The accession AT2 confirmed the highest vit. C and RSC (DPPH) and RSC (ABTS+); AT5 had the highest TP content; and AT12 had the highest TF content. A. tricolor accessions had high phytochemicals across the two species, such as phytopigments, vitamins, phenolics, antioxidants, and flavonoids, with considerable nutrients and protein. Hence, A. tricolor accessions can be used as high-yielding cultivars comprising ample antioxidants. The correlation study revealed that vitamin C, pigments, flavonoids, β-carotene, and phenolics demonstrated a strong RSC, and showed a substantial contribution to the antioxidant potential (AP) of A. tricolor. The investigation exposed that the accessions displayed a plentiful origin of nutritional values, phytochemicals, and AP with good quenching ability of reactive oxygen species (ROS) that provide enormous prospects for nourishing the mineral-, antioxidant-, and vitamin-threatened community. 相似文献
90.
The X-ray structure of (Ph3P)2Ag(SOC2SO)Ag(PPh3)2 shows this complex as the second authentic example containing a bridging trans-1,2-dithiooxalate ligand. The compound crystallizes in the monoclinic space group P21/c with a=13.159(2), b=11.895(2), c=20.939(5)Å, β= 101.35(2)° and Z = 2. The structure was solved by Patterson and Fourier methods for 5649 diffractometer data and refined to a final R value of 0.066 for 03545 observed reflections. The dimensions of the dithiooxalate bridge are compared with those of the corresponding trans-dithiooxalate in (Ph4As)4 (O2C2S2)2In(SOC2SO)In(S2C2O2)2]. Differences between structures containing bridging trans-dithiooxalate or bridging cis-dithiooxalate, respectively, are discussed. 相似文献