共查询到20条相似文献,搜索用时 0 毫秒
1.
Abstract The T value represents the HOMO-LUMO energy separation of a ?-electronic system weighted with the number of conjugated atoms. We found that this value is kept almost constant for the polyene references defined graph-theoretically for isolated-pentagon isomers of fullerenes with up to 100 carbon atoms. on this numerical basis, the T value can safely be considered as a realistic index of kinetic stability or chemical inertness for all fullerenes without abutting pentagons. 相似文献
2.
Kazuyuki Tohji Kan Saito Balachandran Jeyadevan Isao Matsuoka Toshiaki Sogabe Ken Nagasawa 《Fullerenes, Nanotubes and Carbon Nanostructures》1997,5(1):33-47
Production of fullereries using electrodes made of four kinds of pure carbon bearing materials and artificial graphite doped with seven kinds of elements such as B, Y, La, Gd, Ce, Pr and Nd have been examined. The yields of fullerenes were in a range between 12-20% of the soot produced for all pure carbon electrodes, even though the vaporization rate of amorphous carbon electrodes was about ten times higher than that of the natural graphite electrodes. However, for the doped graphite electrodes, the yield of fullerenes was less than 5%. From the above results it is concluded that fullerenes can be effectively produced with the pure carbon electrodes made of any form of carbon bearing materials used in this study and there is little material dependence on the yield of fullerences. Furthermore, the experiments using the artificaial graphite electrodes doped with metal elements suggests that the purity of the carbon electrodes affects the yeld of fullerenes greatly. 相似文献
3.
A Fourier component of the potential energy of interaction between two atoms has been presented as a polynomial of the biquadratic atomic form factor. A numerical calculation has been performed in the screened Coulomb potential approximation. It is demonstrated that the account for the Pauli principle leads to the occurrence of a potential barrier and an additional region of attraction of two atoms. This model is shown to agree qualitatively with the results of the density-functional-theory calculation. 相似文献
4.
Abstract In view of recent experiments we extend our previous growth model for fullerene formation. It becomes clear how a high efficiency of C60 formation is achieved. We estimate the size dependence of intermediate structures along the most efficient growth route and furthermore the stability of Si2o, Ge2o vs. the unstable C20- 相似文献
5.
In view of recent experiments we extend our previous growth model for fullerene formation. It becomes clear how a high efficiency of C60 formation is achieved. We estimate the size dependence of intermediate structures along the most efficient growth route and furthermore the stability of Si2o, Ge2o vs. the unstable C20- 相似文献
6.
Radiochemistry - Effect of carbon substrates materials (graphene oxide, reduced graphene oxide, single-walled carbon nanotubes) on the result of tritium introduction into dalargin peptide was... 相似文献
7.
J. L. Ricardo-Ch vez J. Dorantes-D vila H. Terrones 《Fullerenes, Nanotubes and Carbon Nanostructures》1998,6(5):769-786
The electronic structure of some relevant carbon fullerenes are determined by using a sp-electron tight-binding Hamiltonian including Coulomb interactions in the Hartree-Fock approximation. Surfaces with positive, non-positive and mixed curvatures are considered in order to study the effect of the local environment on the relevant electronic properties. Nanotubes having different diameters and helicities are analyzed and the results are compared with previous calculations. In each case, the equilibrium bond-length R is optimized by maximizing the cohesive energy Ecoh(N). The perspectives and extensions of this study are also discussed. 相似文献
8.
S. M. Umaev A. A. Levchenko N. N. Kolesnikov S. V. Filatov 《Journal of Low Temperature Physics》2017,187(1-2):166-171
We investigated the emission properties of charge sources based on carbon nanotubes prepared by arc discharge deposition of nanotubes onto a flat copper substrate (Borisenko et al. in Instrum Exp Tech 57(6):755, 2014; Low Temp Phys 41(7):567, 2015). The charge sources were submerged into superfluid helium at temperature \(T=1.3\) K. The collector fixed above the charge source at a distance of 0.3 mm was connected to an electrometer. The current of charges was measured by the electrometer when a high voltage was applied to the charge source. In the originally prepared source, the emission of charges (electrons) on the level of \(10^{-10}\hbox {A}\) is observed at a negative voltage above \(U=80\) V and increases with increasing voltage. If the source of charge was kept in liquid helium for 15 h, the current–voltage characteristic changed significantly. The current of charges on the same level of \(10^{-10}\) A was registered at a voltage of \(U=150\) V. Extraction of gases from the source placed in a vacuum chamber at room temperature for 48 h leads to the complete recovery of the emission properties. One can assume that the degradation of the emission properties of the sources is associated with the adsorption of helium atoms by carbon nanotubes at low temperatures. We did not observe any degradation of the emission properties of the charge sources in the case of positive charges injection into superfluid helium. 相似文献
9.
Chiampi M. Crotti G. Giordano D. 《IEEE transactions on instrumentation and measurement》2007,56(2):300-304
This paper describes the design process, the specific features, and the characterization procedures of the Istituto Nazionale di Ricerca Metrologica (I.N.RI.M.) set up for the generation of reference magnetic fields in the frequency range from 1 to 100 kHz. Numerical techniques, validated by comparison with experimental data, make it possible to choose the best solutions for obtaining magnetic flux densities up to 100 muT at 1 kHz and 25 muT at 100 kHz with relative uncertainty from a few parts in 103 up to the percent 相似文献
10.
David R. Worthen Michael Jay Paul M. Bummer 《Drug development and industrial pharmacy》2001,27(4):277-286
Despite the development of newer antifungal drugs, the polyene antifungals continue to be the most potent broad-spectrum fungicides available for clinical use. The incidence and severity of fungal infections are on the rise, underscoring the need for new and more effective antifungal drugs. Thus, the search for new polyene antifungals is ongoing. The limited solubility, polymorphic character, and inherent chemical instability of these compounds make their economical recovery and purification from mass culture challenging problems in biotechnology. This article provides a comprehensive review of the methods that have been developed for the recovery and purification of amphotericin B and nystatin, the two most important polyenes currently in clinical use. 相似文献
11.
《Drug development and industrial pharmacy》2013,39(4):277-286
Despite the development of newer antifungal drugs, the polyene antifungals continue to be the most potent broad-spectrum fungicides available for clinical use. The incidence and severity of fungal infections are on the rise, underscoring the need for new and more effective antifungal drugs. Thus, the search for new polyene antifungals is ongoing. The limited solubility, polymorphic character, and inherent chemical instability of these compounds make their economical recovery and purification from mass culture challenging problems in biotechnology. This article provides a comprehensive review of the methods that have been developed for the recovery and purification of amphotericin B and nystatin, the two most important polyenes currently in clinical use. 相似文献
12.
M. Shibata T. Arai A. Fukuda H. Funahashi T. Haseyama S. Ikeda K. Imai Y. Isozumi T. Kato Y. Kido A. Matsubara S. Matsuki T. Mizusaki R. Nakanishi T. Nishimura D. Ohsawa A. Sawada Y. Takahashi M. Tosaki S. Yamada K. Yamamoto 《Journal of Low Temperature Physics》2008,151(3-4):1043-1048
A microwave single-photon detector was developed with highly-excited alkaline Rydberg-atoms in a cooled resonant cavity to
search for dark matter axions. This detector belongs to a microwave single-photon counter, thus being free from the standard
quantum limit (SQL). High sensitivity of the present detector system was demonstrated by measuring the thermal blackbody radiations
in the cavity at temperatures as low as 70 mK where the sensitivity is below the SQL.
The detection sensitivity of the present system is mainly limited by stray electric fields present in the detection region.
Practical design of a new experimental scheme with a guiding electric field through the atomic-beam trajectory is here presented
and discussed to avoid the effect of stray electric field and thus to improve the detection sensitivity.
相似文献
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14.
采用有限元法,模拟了用渗碳-脱碳化学热处理和外加涂层制备的新型金属结构材料中碳原子的扩散情况以及最终的碳浓度分布,分析了涂层尺寸对碳浓度分布的影响.结果表明,在涂层尺寸为0.4~0.5mm的条件下,渗碳过程中当外界碳势为1.48%(质量分数)、传质系数为1.34×10-7m/s时或脱碳过程中当外界碳势为0%(质量分数)、传质系数为1×10-7m/s时,材料比较容易获得外软内硬的力学性能.薄膜尺寸分别为0.4mm和0.5mm时,渗碳时间为900~1000s和1300~1400s,相应的脱碳时间为1800~1900s和2200~2300s时可获得最佳的扩散效果. 相似文献
15.
Technical Physics Letters - A method of graphene synthesis on the surface of copper foil by cold implantation of carbon recoil atoms is considered. It is established that monolayer graphene films... 相似文献
16.
Tetsu Mieno 《Fullerenes, Nanotubes and Carbon Nanostructures》1995,3(4):429-435
Deposition of carbon atoms on a cathode in a DC arc discharge to produce fullerenes is reduced by JxB force of a magnetic field in an arc flame. By this modification, more effective synthesis of fullerenes and easier control of discharge conditions are achieved. 相似文献
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18.
Ram Seshadri A. Govindraj C. N. R. Rao 《Fullerenes, Nanotubes and Carbon Nanostructures》1993,1(4):547-556
A 1:1 monoadduct of 1-aminobutane with C60, C60(H)(n-C4H9NH), has been characterized by mass spectrometry, infrared spectroscopy and other techniques. Addition of 1,4-diaminobutane to C60 gives rise to a 1:2 adduct of the diamine with C60, while hydrazine hydrate gives multiple addition products. Under conditions of diimide reduction, C60 gives products resulting from the addition of hydrazine units as well as reduction. 相似文献
19.
Ash Mohammad Abbas 《Scientometrics》2011,88(1):107-131
Devising an index to measure the quality of research is a challenging task. In this paper, we propose a set of indices to
evaluate the quality of research produced by an author. Our indices utilize a policy that assigns the weights to multiple
authors of a paper. We have considered two weight assignment policies: positionally weighted and equally weighted. We propose two classes of weighted indices: weighted h-indices and weighted citation h-cuts. Further, we compare our weighted h-indices with the original h-index for a selected set of authors. As opposed to h-index, our weighted h-indices take into account the weighted contributions of individual authors in multi-authored papers, and may serve as an
improvement over h-index. The other class of weighted indices that we call weighted citation h-cuts take into account the number of citations that are in excess of those required to compute the index, and may serve as a supplement
to h-index or its variants. 相似文献
20.
Nam J Rubinstein J 《Journal of the Optical Society of America. A, Optics, image science, and vision》2005,22(9):1709-1716
We propose to use weighted Zernike functions to represent the aberrations of an eye. Methods for computing the phase of an aberrated ophthalmic wavefront in terms of weighted Zernike functions are discussed. In particular, we consider several options for integrating the phase out of its measured slopes. The weighted functions involve a free parameter. Clinical data on subjective refraction and aberration maps of individual subjects are used to determine an estimate for this parameter. 相似文献