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排序方式: 共有604条查询结果,搜索用时 31 毫秒
1.
Bakhtar Ullah Yuli Zhou Jingwen Chen Zongbi Bao Yiwen Yang Qiwei Yang Qilong Ren Zhiguo Zhang 《Tetrahedron letters》2019,60(4):348-351
Thiourea itself has been introduced as a mild and efficient organocatalyst for the oxidative α -cyanation of N-aryltetrahydroisoquinolines (THIQs) with trimethylsilyl cyanide (TMSCN), giving the corresponding products in good to excellent yields. Experimental investigations demonstrated that thiourea acts as a radical initiator by abstracting hydroxyl radical (OH) from tert-butyl hydroperoxide (TBHP) directly instead of non-covalent hydrogen bondings (H-bondings) activation. The use of thiourea as a radical initiator offers a new avenue for innovative chemical transformations in organocatalyzed radical chemistry. 相似文献
2.
The liquid-liquid extraction, ion and precipitate flotation of Co(II) from chloride media of 1·10–4M initial Co(II) concentration and =0.1 have been investigated using decanoic acid and the results are compared. Organic solvents used were chloroform in the case of liquid-liquid extraction and ethanol (used as a solvent for the collector and a frother) in the case of flotation. From the results it appears that liquid-liquid extraction takes place through the formation of the complex: (CoR2)2(HR)2 but flotation occurs through the formation of a surface active product which has the empirical formula CoR2. The effects of pH and of decanoic acid concentration on the three separation processes were also investigated and the results discussed. Good agreement was observed between the experimental precipitate flotation curves and the theoretical curve calculated from the data published for Co(II) hydrolysis. 相似文献
3.
Md Sharif Ullah Vladimir V. Zhivonitko Anatoliy Samoylenko Artem Zhyvolozhnyi Sirja Viitala Santeri Kankaanp Sanna Komulainen Leif Schrder Seppo J. Vainio Ville-Veikko Telkki 《Chemical science》2021,12(24):8311
Exosomes are a subset of secreted lipid envelope-encapsulated extracellular vesicles (EVs) of 50–150 nm diameter that can transfer cargo from donor to acceptor cells. In the current purification protocols of exosomes, many smaller and larger nanoparticles such as lipoproteins, exomers and microvesicles are typically co-isolated as well. Particle size distribution is one important characteristics of EV samples, as it reflects the cellular origin of EVs and the purity of the isolation. However, most of the physicochemical analytical methods today cannot illustrate the smallest exosomes and other small particles like the exomers. Here, we demonstrate that diffusion ordered spectroscopy (DOSY) nuclear magnetic resonance (NMR) method enables the determination of a very broad distribution of extracellular nanoparticles, ranging from 1 to 500 nm. The range covers sizes of all particles included in EV samples after isolation. The method is non-invasive, as it does not require any labelling or other chemical modification. We investigated EVs secreted from milk as well as embryonic kidney and renal carcinoma cells. Western blot analysis and immuno-electron microscopy confirmed expression of exosomal markers such as ALIX, TSG101, CD81, CD9, and CD63 in the EV samples. In addition to the larger particles observed by nanoparticle tracking analysis (NTA) in the range of 70–500 nm, the DOSY distributions include a significant number of smaller particles in the range of 10–70 nm, which are visible also in transmission electron microscopy images but invisible in NTA. Furthermore, we demonstrate that hyperpolarized chemical exchange saturation transfer (Hyper-CEST) with 129Xe NMR indicates also the existence of smaller and larger nanoparticles in the EV samples, providing also additional support for DOSY results. The method implies also that the Xe exchange is significantly faster in the EV pool than in the lipoprotein/exomer pool.Diffusion and xenon NMR based methods to determine a very broad range of sizes and sub-sets of extracellular vesicles. 相似文献
4.
Ion, precipitate and adsorbing colloid flotation of cobalt(II) have been investigated at different pH values, using N-dodecylpyridinium chloride (DPCl), A strong cationic surfactant, and sodium lauryl sulfate (NaLS), a strong anionic surfactant, as collectors. In case of adsorbing colloid flotation, hydrous manganese dioxide was used as an adsorbent. The precipitate flotation curves experimentally obtained with the two tested collectors were compared with the corresponding theoretical one calculated from the data published for Co(II) hydrolysis. The effects of the collector concentration, ageing of the water-MnO2–Co(II) system, bubbling time period, cobalt(II) concentration and foreign salts on the percent removal of Co(II) by adsorbing colloid flotation using DPCl as collector were determined. Removals approaching 100% could be achieved under the optimum conditions. 相似文献
5.
Summary The effects of pH, gas flow rate and collector concentration on the rate of thorium removal by foaming with sodium lauryl sulphate have been investigated. The obtained data indicate that only aged hydrated thorium oxide is removed by a flotation mechanism. All the other colloidal and condensed thorium species as well as the colloidal sublates which are formed between the dissolved thorium species and the collector anions appear to be removed by partition and their removal rates could be described by a reversible first-order rate equation. The obtained results are discussed in terms of thorium hydrolysis.
With 7 figures 相似文献
Zusammenfassung Der Einfluß der pH-Werte, Gasdurchflußmengen und Kollektor-Konzentration auf die Geschwindigkeit der Entfernung des Thoriums durch Schaumbildung mit Natrium-Lauryl-Sulfat wurde untersucht. Die Ergebnisse zeigen, daß das gealterte, wässerige Thoriumoxid durch Flotations-Mechanismen entfernt wird. Die anderen kolloidalen und kondensierten Thorium-Spezien und auch die Kolloidalprodukte, die durch Reaktionen zwischen den gelösten Thoriumspezien und den Kollektor-Anionen formiert sind, sind durch die Verteilung entfernt worden. Die Entfernungsgeschwindigkeit kann beschrieben werden durch eine reversible 1. Ordnungs-Gleichung. Die Ergebnisse werden in Abhängigkeit einer ThoriumHydrolyse diskutiert.
With 7 figures 相似文献
6.
Bose G Nguyen VT Ullah E Lahiri S Görls H Langer P 《The Journal of organic chemistry》2004,69(26):9128-9134
The Lewis acid mediated domino "[3+3]-cyclization-homo-Michael" reaction of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes allows an efficient one-pot synthesis of functionalized salicylates containing a halogenated side chain. A great variety of substitution patterns could be realized by variation of the starting materials and of the Lewis acid. The mechanism of the domino process was studied. 相似文献
7.
A variational analysis of the spiked harmonic oscillator Hamiltonian –d
2/dr2 +r
2 +/r
5/2,>0, is reported. A trial function automatically satisfying both the Dirichlet boundary condition at the origin and the boundary condition at infinity is introduced. The results are excellent for a very large range of values of the coupling parameter, suggesting that the present variational function is appropriate for the treatment of the spiked oscillator in all its regimes (strong, moderate, and weak interactions). 相似文献
8.
Summary 3,4-Dicyano-5-aminopyrazole, H3,4(CN)25NH2pz (L) reacts either with anhydrous MCl2 or with [M(PPh3)2Cl2] to yield ML4Cl2 complexes (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd or Hg), whose monomeric and covalent natures have been confirmed by their solubility in most non-polar solvents and their low electrical conductivities. The bonding mode of substituted pyrazole is inferred from the position of the (C-N) band in the i.r. spectra. The electronic spectra and the magnetic moments of these compounds were recorded. 相似文献
9.
Mohammad Shakir Shahul Hameed Farha Firdaus Saji P. Varkey 《Transition Metal Chemistry》1995,20(2):142-143
Summary Adducts of dichlorosulphato bis(1,3-propylenediamine)-metal(II) complexes with dialkyltin dichlorides, [R2Sn(MeCN) 2]2[M(NH(CH2)3NH)2(SO3Cl)2] (M = Cr, Fe, Co, Ni or Cu; R = Me or n-Bu) have been prepared. The positive shift in the symmetric SO3 stretch and splitting of the doubly degenerate (E) modes in their i.r. spectra suggest a covalent linkage for the SO3Cl– group. The adducts are non-electrolytes; magnetic moments and ligand field data suggest that each SO3Cl– group is monodentate, generating an octahedral geometry around the metal ions, except for NiII where tetragonal distortion is observed.Author to whom all correspondence should be directed. 相似文献
10.
Summary The number and positions of the i.r. active modes in ethylenediamine complexes of M(SO3Cl)2 (M = Mn, Fe, Co, Ni or Cu) suggest that the SO3Cl– anion is covalently bound in these non-electrolytic complexes. Magnetic moments and ligand field data suggest that each SO3Cl– group is monodentate, giving an octahedral geometry around the metal ions. 相似文献