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901.
The roots and rhizomes of various valeriana species are currently used as a sleeping aid or mild sedative. A liquid chromatography method has been developed that permits the analysis of chlorogenic acid, lignans, flavonoids, valerenic acids, and valpotrates in various valerian samples. The best results were obtained with a Phenomenex Luna C18(2) column using gradient elution with a mobile phase consisting of water and 0.05% phosphoric acid and 2-100% acetonitrile-methanol (1 + 1) with 0.05% phosphoric acid. The flow rate was 0.8 mL/min and ultraviolet detection was at 207, 225, 254, 280, and 325 nm. Different valerian species and commercial products showed remarkable quantitative variations. Chlorogenic acid (0.2-1.2%), 3 lignans, linarin (0.002-0.24%), and valepotriates were detected in all the valeriana species analyzed. Highest amounts of valerenic acids were detected in V. officinalis L., trace amounts in V. sitchensis, and none in the other species analyzed. 相似文献
902.
Hasan M. Khan Muhammad Ismail Muhammad Abid Zia Khalid Khan 《Isotopes in environmental and health studies》2013,49(2):295-301
The analysis of gamma-emitting radionuclides in nature, i.e. 226Ra, 232Th, 40K and 137Cs, has been carried out in soil samples collected from Peshawar University Campus and surrounding areas using a high purity germanium detector coupled with a computer-based high-resolution multichannel analyser. The activity concentrations in soil ranged from 30.20±0.65 to 61.90±0.95, 50.10±0.54 to 102.80±1.04, 373.60±4.56 to 1082±11.38 and 9.50±0.11 to 46.60±0.42 Bq kg?1 for 226Ra, 232Th, 40K and 137Cs, with a mean value of 45±7.70, 67±12.50, 878±180 and 19±9.20 Bq kg?1, respectively. The radium equivalent activity, internal and external hazard indices have mean values of 203.40±29.40 Bq kg?1, 0.56 and 0.68, respectively. The mean values of outdoor and indoor absorbed dose rates in air and the annual effective dose equivalents were found to be 106.50 and 128 nGy h?1 and 0.19 and 0.54 mSv y?1, respectively. In the present study, 40K was the major radionuclide present in soil samples. The presence of 137Cs indicates that this area also received some fallout from the nuclear accident of the Chernobyl power plant in 1986. The activity concentrations of radionuclides found in soil samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the public. 相似文献
903.
Single phase polycrystalline BaZr0.3Ce0.5Y0.1Yb0.1O3 - δ electrolyte material was prepared by solid state reaction route. Rietveld analysis of the XRD data confirms the tetragonal symmetry in the I4/mcm space group with unit cell parameters of a = b = 6.0567(3) Å and c = 8.5831(5) Å. The addition of ZnO as a sintering additive was found to reduce the sintering temperature and enhance both overall sinterability and grain growth. Sintering temperature was reduced by 200–300 °C, and a very high relative density of about 98% was achieved at 1400 °C. Impedance spectroscopy in humidified 5% H2/Ar atmosphere shows that the protonic conductivity at 600 °C was 8.60 × 10?3 S cm?1. Thermal analysis performed in pure CO2 atmosphere shows very good chemical stability up to 1200 °C. Good biaxial flexure strength of 100–200 MPa was reported which makes this material a promising electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs). 相似文献
904.
M. Y. Naz S. Shukrullah A. Ghaffar N. U. Rehman Y. Khan 《Journal of Applied Mechanics and Technical Physics》2016,57(2):211-218
The objective of the work is to test a nickel–chrome alloy as a probe tip material for characterization of discharge plasmas. In order to meet the objective, a symmetric triple Langmuir probe diagnostic system and an associated driving circuit are designed and tested in an inductively coupled plasma generated by a 13.56-MHz radio frequency source coupled with an automated impedance match network. This probe is used to measure the electron temperature, electron number density, and ion saturation current as functions of the input power of the radio frequency source and the filling gas pressure. An increasing trend is noticed in the electron temperature and electron number density with an increase in the input power, whilst a decreasing trend is evident in these parameters with an increase in the nitrogen gas pressure. The overall inaccuracies in electron temperature and electron number density measurements are 5–12% and 3–13%, respectively. 相似文献
905.
Uzma Habib Amin Badshah Ulrich Flörke Rizwana Aleem Qureshi Bushra Mirza Nazar-ul-Islam Azeem Khan 《Journal of chemical crystallography》2009,39(10):730-734
Abstract The reaction of Cu(OOCCH3)2·H2O with (2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl) pyrimidine (trimethoprim) in ethanolic solution at 80 °C affords the title
complex which has been characterized by elemental, IR, and NMR (1H and 13C).The crystal structure has been determined by single crystal X-ray diffraction. Compound 1 (C36H48Cu2N8O14) is triclinic, space group P-1 with a = 7.2676(4) ?, b = 11.6721(7) ?, c = 12.8279(8) ?, α = 95.839(1)°, β = 93.456(1)°, γ = 105.541(1)°, Z = 1. Two copper atoms are coordinated directly to each other as well as are held together by four bridging aceto groups.
Each copper atom is also bonded opposite the Cu–Cu vector to a trimethoprim molecule through the N(1) atom of the pyrimidine
ring. Trimethoprim acts as a monodentate ligand through the pyrimidine nitrogen N(1) atom. The complex was screened for the
activity against several bacteria, showing more activity against bacteria as compared to trimethoprim.
Graphical Abstract To enhance the activity of trimethoprim, its derivative was prepared and there bacterial activity against several bacteria
was analyzed.
相似文献
906.
Uzma Habib Amin Badshah Ulrich Flörke Rizwana Aleem Qureshi Bushra Mirza Nazar-ul-Islam Azeem Khan 《Journal of chemical crystallography》2009,39(8):607-611
Abstract The title copper (II) complex with Trimethoprim was prepared at 20–25 °C and its crystal structure was determined by single
crystal X-ray diffraction. Compound (C36H50Cu3N8O16) is triclinic, space group P-1 with a = 6.4642(5) ?, b = 12.5495(9) ?, c = 13.4911(10) ?, α = 77.518(1)°, β = 85.326(1)°, γ = 84.413(2)°, Z = 1. In this compound, three copper atoms are bonded to each other, two terminal coppers are bonded to three oxygen atoms
and N1 of pyrimidine ring of Trimethoprim and central copper is bonded to four oxygen atoms. The amino nitrogen atoms are not involved
in the coordination to the metal.
Graphical Abstract To enhance the activity of trimethoprim, its derivative was prepared and there bacterial activity against several bacteria
was analyzed.
相似文献
907.
Salman Nisar Sohaib Z. Khan Muhammad Ali Lin Li Mohammed A. Sheikh 《Journal of Russian Laser Research》2014,35(2):182-192
Laser cutting of glass using the controlled fracture technique leads to cut path deviation at the leading and trailing edges of the float glass sheet. In this technique, thermal stresses are used to induce the crack, and the material is separated along the cutting path by extending the crack. We show that the cut path deviation is partly due to high magnitudes of thermal stresses generated near the sheet edges. The absorption of intense radiation from the CO2 and diode laser beams in the glass causes local temperature increases and consequently generates different thermal fields and stress distributions due to surface and volumetric heat absorption. In this paper, we report the effect of the CO2 and diode laser wavelength interaction with the float glass and its effect on the magnitudes of thermal stresses generated near the edges of the glass sheet. We simulate the distribution of the thermal stress and temperature using finite-element analysis software Abaqus and validate it against the experimental data. We show that the CO2 laser produces a lower surface quality and a larger cut path deviation at the leading and trailing edges of the glass sheet as compared to the diode laser. 相似文献
908.
Fingerprint image enhancement using multi-scale DDFB based diffusion filters and modified Hong filters 总被引:1,自引:0,他引:1
The main task of a fingerprint image enhancement is to enhance the image in such a way that it not only remove the noise but also enhance the reliable minutiae points. For this purpose, in this paper we propose a multi-scale decimation-free directional filter bank method for reliable orientation estimation. This reliable orientation is used in coherence enhancement diffusion and in Gabor filter based enhancement, which overcomes the drawbacks of these two methods. Experimental results show that the proposed method not only enhances the images but also facilitates the minutiae algorithm, by enhancing the true minutiae points. 相似文献
909.
Balandin S. F. Donchenko V. A. Myshkin V. F. Potekaev A. I. Khan V. A. Orazymbetova A. K. Ospanova N. A. 《Russian Physics Journal》2022,65(2):355-364
Russian Physics Journal - The interaction mechanisms of low-energy long-duration (~1 ms) laser pulses with dispersed particles in air are considered. The basic equations describing the mechanisms... 相似文献
910.
Lv C Hu J Zhou H Li Z Khan RN Wei Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8681-8691
The functionalization of polyoxometalates (POMs), especially with an amino group to yield organonitrogenous derivatives of POMs, is an efficient approach to the enrichment of their structures and the diversification of their properties for various applications. The mechanism for the formation of organonitrogenous-derivatized hexamolybdates was explored by investigating the monofunctionalization of the [Mo(6)O(19)](2-) ion with methylamine using the density functional theory (DFT) method. The calculations show that the direct imidoylization of hexamolybdate with methylamine is both kinetically and thermodynamically unfavorable. However, this imidoylization was found to take place readily in the presence of dimethylcarbodiimide (DMC), for which the free-energy barrier was calculated to be +32.5 kcal mol(-1) in acetonitrile. Moreover, various factors controlling the efficiency of the imidoylization were examined. The calculations show that [W(5)MoO(19)](2-) has a relatively lower reactivity than [Mo(6)O(19)](2-), and that the imidoylization of [W(6)O(19)](2-) is an unfavorable process. With respect to the effect of carbodiimides, it is found that the catalytic activity is directly proportional to the electron-withdrawing effects of the substituents. As to the reactivity of R-NH(2) , the computation results indicate that the free-energy barriers of the substitution reactions are linearly correlated with the basicity constants (pK(b)) of the amino groups. It is noteworthy that the introduction of the proton dramatically decreases the free-energy barrier of the imidoylization of [Mo(6)O(19)](2-) catalyzed by DMC to 24.3 kcal mol(-1) in acetonitrile. 相似文献