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991.
Malek Taher Maghsoodlou Ghasem Marandi Nourallah Hazeri Sayyed Mostafa Habibi-Khorassani Ali Akbar Mirzaei 《Molecular diversity》2011,15(1):227-231
5-Aryl-6-(alkyl- or aryl-amino)-1,3-dimethylfuro [2,3-d]pyrimidine derivatives were obtained by in situ reaction alkyl or aryl isocyanides and pyridinecarbaldehyde derivatives in
the presence of 1,3-dimethylbarbituric acid in dichloromethane without any prior activation or modifications. 相似文献
992.
The aim of this review is to provide an overview of the contributions and recent advances made by Iranian scientists in the
field of isocyanide-based reactions between 1999 and 2009. With over 100 publications during this period, Iranians are responsible
for approximately 10% of all publications in the world involving isocyanide-based multicomponent reactions (IMCRs). Some important
aspects of these IMCRs include the execution of reactions in green reaction mediums like water or ethanol, high atom economies,
mild reaction conditions, high yields, and catalyst-free processes. On the other hand, in most of these reactions, new classes
of heterocyclic compounds with potential biological and medicinal activities have been reported. 相似文献
993.
Ali M. Soltani Seyed H. Tabatabaeian Payam Hanafizadeh Jahanyar Bamdad Soofi 《Journal of nanoparticle research》2011,13(12):7303-7312
Dozens of countries are executing national nanotechnology plans. No rigorous evaluation scheme for these plans exists, although
stakeholders—especially policy makers, top-level agencies and councils, as well as the society at large—are eager to learn
the outcome of these policies. In this article, we recommend an evaluation scheme for national nanotechnology policies that
would be used to review the whole or any component part of a national nanotechnology plan. In this scheme, a component at
any level of aggregation is evaluated. The component may be part of the plan’s overarching policy goal, which for most countries
is to create wealth and improve the quality of life of their nation with nanotechnology. Alternatively, the component may
be a programme or an activity related to a programme. The evaluation could be executed at different times in the policy’s
life cycle, i.e., before the policy is formulated, during its execution or after its completion. The three criteria for policy
evaluation are appropriateness, efficiency and effectiveness. The evaluator should select the appropriate qualitative or quantitative
methods to evaluate the various components of national nanotechnology plans. 相似文献
994.
Numerical investigation of laminar free convection heat transfer in the vertical parallel plate channel with asymmetric heating
is presented. Both inlet and exit effects are included into the analysis. A numerical solution is obtained for a Prandtl number
of 0.71 and for modified Rayleigh number [`(Ra)]\overline {Ra} = 10−1 ÷ 105, and varying heating ratio TR = 0 ÷ 1 and aspect ratio A = 10. Fully elliptic Navier-Stokes and energy equations are solved using the finite volume techniques with staggered grid
arrangements. The obtained results show a strong influence of the temperature ratio on local and average heat transfer coefficient
on the hot and cold plates. With reduction of TR the heat transfer parameter on the hot wall grows, and on the cold one, on the contrary, it decreases. As a result, the total
heat exchange from two plates depends poorly on the parameter TR. 相似文献
995.
Nosheen Akbar Bilal Masud Saba Noor 《The European Physical Journal A - Hadrons and Nuclei》2011,47(10):124
We propose some extensions of the quark potential model to hybrids, fit them to the lattice data and use them for the purpose of calculating the masses, root mean square radii and wave functions at the origin of the conventional and hybrid charmonium mesons. We treat the ground and excited gluonic field between a quark and an antiquark as in the Born-Oppenheimer expansion, and use the shooting method to numerically solve the required Schrödinger equation for the radial wave functions; from these wave functions we calculate the mesonic properties. For masses we also check through a Crank Nichelson discretization. For hybrid charmonium mesons, we consider the exotic quantum number states with J PC = 0+?, 1?+ and 2+?. We also compare our results with the experimentally observed masses and theoretically predicted results of the other models. Our results have implications for scalar form factors, energy shifts, magnetic polarizabilities, decay constants, decay widths and differential cross-sections of conventional and hybrid mesons. 相似文献
996.
A. Ali Yusuf A.K. Yahya Nawazish A. Khan F. Md. Salleh E. Marsom N. Huda 《Physica C: Superconductivity and its Applications》2011,471(11-12):363-372
Substitution of Ge4+ in place of Cu in Tl0.85Cr0.15Sr2CaCu2?xGexO7?δ (x = 0–0.6) showed initial increase in zero critical temperature value, Tc zero from 98 K (x = 0) to 100 K (x = 0.1) and in the range of 85–86 K for x = 0.2–0.3. The slow decrease in Tc zero is unexpected as tetravalent Ge4+ substitution is expected to strongly reduce hole concentration in the samples and suppress Tc zero. Excess conductivity analyses of resistance versus temperature data based on Asmalazov–Larkin (AL) theory revealed that the substitution induced 2D-to-3D transition of fluctuation induced conductivity with the highest transition temperature, T2D–3D observed at x = 0.1. FTIR spectroscopy analysis indicates Ge4+ substitution cause reduction in CuO2/GeO2 interplanar distance while our calculation based on Lawrence–Doniach model revealed highest superconducting coherence length, ξc(0) and interplanar coupling, J at x = 0.3. On the other hand, substitution of divalent Mg2+ for Ca2+ in (Tl0.5Pb0.5)(Sr1.8Yb0.2)(Ca1?yMgy)Cu2O7 (y = 0–1.0), which is not expected to directly vary hole concentration, surprisingly caused Tc zero to increase from 89.6 K (y = 0) to an optimum value of 95.9 K (y = 0.6) before decreasing with further increase in y. Excess conductivity analyses showed 2D-to-3D transition of fluctuation induced conductivity for all samples where the highest T2D–3D was at y = 0.4. Similar calculation revealed highest values of ξc(0) and J also at y = 0.4. FTIR analysis of the samples indicates inequivalent Cu(1)O(2)Pb/Tl lengths and possible tilting of CuO2 plane as a result of Mg2+ substitution. The increased ξc(0) and J as a result of the Ge4+ and Mg2+ substitutions are suggested to contributed to sustenance of superconductivity above 80 K in the samples. 相似文献
997.
A.A. Khurram Nawazish A. Khan Shakeel Ahmad Ali Awais 《Physica C: Superconductivity and its Applications》2011,471(1-2):35-41
The Cu1?xTlxBa2Ca1Cu2O8?δ superconductor thin film samples were bombarded with protons, Si and Au ions of energies 6, 20 and 20 MeV respectively using 5MV tandem pelletron accelerator at Experimental Physics Labs. Each un-irradiated sample had different values of normal state resistivity and the zero resistance critical temperature. The zero resistivity critical temperature has been increased after the irradiation by Si and Au ions. The fluctuation induced conductivity (FIC) analysis of the as-prepared and the ion irradiated samples were performed in the light of Aslamasov–Larkin (AL) theory. The FIC analysis has shown three dimensional (3D) fluctuations in the order parameter in all the samples along with a cross-over to two dimensional (2D) fluctuations at higher temperature. The 3D–2D cross-over temperature has been shifted to higher values after the ion irradiation. Moreover, a direct correlation between the zero resistivity critical temperature, 2D–3D cross-over temperature (TLD) and superconductivity fluctuation temperature (Tscf) was observed. These studies have shown that the fluctuation induced conductivity (excess conductivity) depends on the density of defects and is independent of their nature. 相似文献
998.
Abbas Afkhami Tayyebeh Madrakian Ali Shirzadmehr Hasan Bagheri Masoumeh Tabatabaee 《Ionics》2011,18(9):881-889
An effective potentiometric sensor had been fabricated for the rapid determination of Pb2+ based on carbon paste electrode consisting of room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), multiwalled carbon nanotubes (MWCNTs), nanosilica, synthesized Schiff base, as an ionophore, and graphite powder. The constructed nanocomposite electrode showed better sensitivity, selectivity, response time, response stability, and lifetime in comparison with typical Pb2+ carbon paste electrode for the successfully determination of Pb2+ ions in water and in waste water samples. The best response for nanocomposite electrode was obtained with electrode composition of 18% ionophore, 20% BMIM-PF6, 49% graphite powder, 10% MWCNT, and 3% nanosilica. The new electrode exhibited a Nernstian response (29.76?±?0.10 mV decade?1) toward Pb2+ ions in the range of 5?×?10?9?C1.0?×?10?1 mol L?1 with a detection limit of 2.51?×?10?9 mol L?1. The potentiometric response of prepared sensor is independent of the pH of test solution in the pH range of 4.5?C8.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition, and heavy metal ions. 相似文献
999.
A. A. Karimi Zarchi N. Mokhtari M. Arfan T. Rehman M. Ali M. Amini R. Faridi Majidi A. R. Shahverdi 《Applied Physics A: Materials Science & Processing》2011,103(2):349-353
In this study a sunlight-induced method for rapid synthesis of silver nanoparticles using an ethanol extract of Andrachnea chordifolia is described. The silver nitrate solutions (1 mM) containing the ethanol extract of Andrachnea chordifolia were irradiated by both sunlight radiation and by sunlight radiation passed through different colored filters (red, yellow
or green). The smallest size of silver nanoparticles was obtained when a silver ion solution was irradiated for 5 minutes
by direct sunlight radiation. Further examination of the shape and size and of the surface chemistry of these biogenic silver
nanoparticles, which were prepared under sunlight radiation, was carried out using transmission electron microscopy and infrared
spectroscopy, respectively. Transmission electron microscopy images show spherical particles with an average size of 3.4 nm.
Hydroxyl residues were also detected on the surface of these biogenic silver nanoparticles fabricated using plant extract
of Andrachnea chordifolia under sunlight radiation. Our study on the reduction of silver ions by this plant extract in darkness shows that the synthesis
process can take place under dark conditions at much longer incubations (48 hours). Larger silver polydispersed nanoparticles
ranging in size from 3 to 30 nm were obtained when the silver ions were treated with the ethanol extract of Andrachnea chordifolia under dark conditions for 48 hours. 相似文献
1000.