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181.
The preliminary validation of a high-performance liquid chromatography particle beam mass spectrometry method (HPLC-PB/MS) with electron impact ionization source for analysis of botanical extracts is presented. The LC-PB/MS system was evaluated for the analysis of ephedrine alkaloids using ephedra-containing National Institute of Standards and Technology dietary supplement standard reference materials (SRMs) 3241 Ephedra Sinica Stapf Native Extract and 3242 Ephedra Sinica Stapf Commercial Extract. The ephedrine alkaloids were separated by reversed-phase chromatography using a phenyl column at room temperature. A linear gradient method with a mobile phase composition varying from 5:95 [MeOH:0.1% trifluoroacetic acid (TFA) in water] to 20:80 (MeOH:0.1% TFA in water) at a flow rate of 1.0 ml/min, with an analysis time of less than 20 min, was used. The source block temperature was evaluated to determine the optimal operating conditions by monitoring the intensities and fragmentation patterns of the ephedrine alkaloids. Ephedrine and N-methylephedrine were taken as a representative of the test alkaloids. The LODs on the sub-nanogram level were achieved, with ephedrine, pseudoephedrine, and methylephedrine in the SRMs quantified by a standard addition method with recoveries of > or = 86% and RSDs of < or = 14% (n = 3). 相似文献
182.
Krylov V. B. Ushakova N. A. Ustyuzhanina N. E. Preobrazhenskaya M. E. Yashunsky D. V. Menshov V. M. Tsvetkov D. E. Sharma G. V. M. Radha Krishna P. Nifantiev N. E. 《Russian Chemical Bulletin》2010,59(1):232-235
Persulfated derivatives of natural polyhydroxy compounds, such as lignans secoisolariciresinol, and isolariciresinol, flavonoid
dihydroquercetin, and myo-inositol, have been synthesized. The ability of these compounds to inhibit the intrinsic pathway of blood coagulation (APTT-test)
and to reduce the activity of coagulation factor Xa in the presence of antithrombin(III) has been studied. 相似文献
183.
Patwa AN Gonnade RG Kumar VA Bhadbhade MM Ganesh KN 《The Journal of organic chemistry》2010,75(24):8705-8708
X-ray crystallographic studies of methylene linked Ferrocene-bis(thymine/uracil) conjugates Fc(T:T)(M) and Fc(U:U)(M) reveal base dependent 2-D supramolecular assemblies generated via wobble self-pairing for bis-thymine and reverse wobble self-pairing for bis-uracil conjugates, differing in architecture from the corresponding butylene spacer linked conjugates. 相似文献
184.
Kulkarni NV Budagumpi S Kurdekar GS Revankar VK Didagi S 《Chemical & pharmaceutical bulletin》2010,58(12):1569-1575
A novel Cu(II) and Zn(II) complexes of triazolo-quinoline derivatives were synthesized by in situ method and were characterized by the spectro-analytical methods and their pharmacological properties were evaluated. The compound C3 has exhibited promising anticonvulsant activity towards the electroshock induced seizures in Wistar rats and possesses low toxicity, providing a high safety profile. 相似文献
185.
186.
T. Raghavendra RaoCh. Rama Krishna U.S. Udayachandran ThampyCh. Venkata Reddy Y.P. ReddyP. Sambasiva Rao R.V.S.S.N. Ravikumar 《Physica B: Condensed Matter》2011,406(11):2132-2137
The effect of Li2O content in vanadyl doped 20ZnO+xLi2O+(30−x)Na2O+50B2O3 (5≤x≥25) glasses has been studied with respect to their physical and structural properties. The absence of sharp peaks in XRD spectra of these glass samples confirms the amorphous nature. The physical parameters like density, refractive index, ionic concentration and electronic polarizability vary non-linearly with x mol% depending on the diffusivities of alkali ions. EPR and optical absorption spectra reveal that the resonance signals are characteristics of VO2+ ions in tetragonally compressed octahedral site. Spin-Hamiltonian, crystal field, tetragonal field and bonding parameters are found to be in good agreement with the other reported glass systems. The tetragonal distortion (g⊥-g∥) and Dt reveals that their values vary non-linearly with Li2O content and reaches a minimum at x=10 mol%. An anomaly of character has been observed in all the properties of vanadyl doped glass systems, which gives a clear indication of mixed alkali effect. 相似文献
187.
M.S.R.N. Kiran M. Ghanashyam Krishna K.A. Padmanabhan 《Solid State Communications》2011,151(7):561-563
Titanium nitride films of a thickness of ∼1.5 μm were deposited on amorphous and crystalline substrates by DC reactive magnetron sputtering at ambient temperature with 100% nitrogen in the sputter gas. The growth of nanostructured, i.e. crystalline nano-grain sized, films at ambient temperature is demonstrated. The microstructure of the films grown on crystalline substrates reveals a larger grain size/crystallite size than that of the films deposited on amorphous substrates. Specular reflectance measurements on films deposited on different substrates indicate that the position of the Ti-N 2s band at 2.33 eV is substrate-dependent, indicating substrate-mediated stoichiometry. This clearly demonstrates that not only structure and microstructure, but also chemical composition of the films is substrate-influenced. The films deposited on amorphous substrates display lower hardness and modulus values than the films deposited on crystalline substrates, with the highest value of hardness being 19 GPa on a lanthanum aluminate substrate. 相似文献
188.
Miniaturized and tunable optical components, such as the waveguide, lens, and prism, have been of great interest for lab-on-chip systems. This Letter reports an optofluidic aperture stop formed by the liquid-core/liquid-cladding flow. The aperture size can be tuned accordingly by adjusting the flow rates. Manipulation of the aperture size allows control of the amount of light passing through the corresponding optical system as well as the angular aperture on the image side. This optofluidic aperture enables lab-on-chip optical systems to have a greater flexibility and more functionalities. 相似文献
189.
The large rank of a finite semigroup \(\Gamma \) , denoted by \(r_5(\Gamma )\) , is the least number \(n\) such that every subset of \(\Gamma \) with \(n\) elements generates \(\Gamma \) . Howie and Ribeiro showed that \(r_5(\Gamma ) = |V| + 1\) , where \(V\) is a largest proper subsemigroup of \(\Gamma \) . This work considers the complementary concept of subsemigroups, called prime subsets, and gives an alternative approach to find the large rank of a finite semigroup. In this connection, the paper provides a shorter proof of Howie and Ribeiro’s result about the large rank of Brandt semigroups. Further, this work obtains the large rank of the semigroup of order-preserving singular selfmaps. 相似文献
190.
Arup Chattopadhyay B. Krishna Das Jaydeb Sarkar S. Sarkar 《Integral Equations and Operator Theory》2014,79(4):567-577
Doubly commuting invariant subspaces of the Bergman space and the Dirichlet space over the unit polydisc \({\mathbb{D}^n}\) (with \({n \geq 2}\) ) are investigated. We show that for any non-empty subset \({\alpha=\{\alpha_1,\ldots,\alpha_k\}}\) of \({\{1,\ldots,n\}}\) and doubly commuting invariant subspace \({\mathcal{S}}\) of the Bergman space or the Dirichlet space over \({\mathbb{D}^n}\) , restriction of the multiplication operator tuple on \({\mathcal{S}, M_{\alpha}|_\mathcal{S}:=(M_{z_{\alpha_1}}|_\mathcal{S},\ldots, M_{z_{\alpha_k}}|_\mathcal{S})}\) , always possesses generating wandering subspace of the form $$\bigcap_{i=1}^k(\mathcal{S}\ominus z_{\alpha_i}\mathcal{S})$$ . 相似文献