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排序方式: 共有2071条查询结果,搜索用时 15 毫秒
981.
Dr. Md Mokhlesur Rahman Irin Sultana Dr. Tianyu Yang Dr. Zhiqiang Chen Dr. Neeraj Sharma Dr. Alexey M. Glushenkov Prof. Ying Chen 《Angewandte Chemie (International ed. in English)》2016,55(52):16059-16063
A simple, cost‐effective, and easily scalable molten salt method for the preparation of Li2GeO3 as a new type of high‐performance anode for lithium‐ion batteries is reported. The Li2GeO3 exhibits a unique porous architecture consisting of micrometer‐sized clusters (secondary particles) composed of numerous nanoparticles (primary particles) and can be used directly without further carbon coating which is a common exercise for most electrode materials. The new anode displays superior cycling stability with a retained charge capacity of 725 mAh g?1 after 300 cycles at 50 mA g?1. The electrode also offers excellent rate capability with a capacity recovery of 810 mAh g?1 (94 % retention) after 35 cycles of ascending steps of current in the range of 25–800 mA g?1 and finally back to 25 mA g?1. This work emphasizes the importance of exploring new electrode materials without carbon coating as carbon‐coated materials demonstrate several drawbacks in full devices. Therefore, this study provides a method and a new type of anode with high reversibility and long cycle stability. 相似文献
982.
Eric P. Kelson Proma P. Phengsy Atta M. Arif 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(5):517-519
The aldehyde moiety in the title complex, chloro(2‐pyridinecarboxaldehyde‐N,O)(2,2′:6′,2′′‐terpyridine‐κ3N)ruthenium(II)–chloro(2‐pyridinecarboxylic acid‐N,O)(2,2′:6′,2′′‐terpyridine‐κ3N)ruthenium(II)–perchlorate–chloroform–water (1.8/0.2/2/1/1), [RuCl(C6H5NO)(C15H11N3)]1.8[RuCl(C6H5NO2)(C15H11N3)]0.2(ClO4)2·CHCl3·H2O, is a structural model of substrate coordination to a transfer hydrogenation catalyst. The title complex features two independent RuII complex cations that display very similar distorted octahedral coordination provided by the three N atoms of the 2,2′:6′,2′′‐terpyridine ligand, the N and O atoms of the 2‐pyridinecarboxaldehyde (pyCHO) ligand and a chloride ligand. One of the cation sites is disordered such that the aldehyde group is replaced by a 20 (1)% contribution from a carboxylic acid group (aldehyde H replaced by carboxyl O—H). Notable dimensions in the non‐disordered complex cation are Ru—N 2.034 (2) Å and Ru—O 2.079 (2) Å to the pyCHO ligand and O—C 1.239 (4) Å for the pyCHO carbonyl group. 相似文献
983.
Production of High Purity Multi-Walled Carbon Nanotubes from Catalytic Decomposition of Methane 总被引:1,自引:0,他引:1 下载免费PDF全文
Kong Bee Hong Aidawati Azlin Binti Ismail Mohamed Ezzaham Bin Mohd Mahayuddin Abdul Rahman Mohamed Sharif Hussein Sharif Zein 《天然气化学杂志》2006,15(4):266-270
Acid-based purification process of multi-walled carbon nanotubes (MWNTs) produced via catalytic decomposition of methane with NiO/TiO2 as a catalyst is described. By combining the oxidation in air and the acid refluxes, the impurities, such as amorphous carbon, carbon nanoparticles, and the NiO/TiO2 catalyst, are eliminated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirm the removal of the impurities. The percentage of the carbon nanotubes purity was analyzed using thermal gravimetric analysis (TGA). Using this process, 99.9 wt% purity of MWNTs was obtained. 相似文献
984.
Rakesh K. Sindhu Rishu Verma Twinkle Salgotra Md. Habibur Rahman Muddaser Shah Rokeya Akter Waheed Murad Sidra Mubin Parveen Bibi Safaa Qusti Eida M. Alshammari Gaber El-Saber Batiha Micha Tomczyk Hayder M. Al-kuraishy 《Molecules (Basel, Switzerland)》2021,26(17)
Breast cancer persists as a diffuse source of cancer despite persistent detection and treatment. Flavonoids, a type of polyphenol, appear to be a productive option in the treatment of breast cancer, because of their capacity to regulate the tumor related functions of class of compounds. Plant polyphenols are flavonoids that appear to exhibit properties which are beneficial for breast cancer therapy. Numerous epidemiologic studies have been performed on the dynamic effect of plant polyphenols in the prevention of breast cancer. There are also subclasses of flavonoids that have antioxidant and anticarcinogenic activity. These can regulate the scavenging activity of reactive oxygen species (ROS) which help in cell cycle arrest and suppress the uncontrolled division of cancer cells. Numerous studies have also been performed at the population level, one of which reported a connection between cancer risk and intake of dietary flavonoids. Breast cancer appears to show intertumoral heterogeneity with estrogen receptor positive and negative cells. This review describes breast cancer, its various factors, and the function of flavonoids in the prevention and treatment of breast cancer, namely, how flavonoids and their subtypes are used in treatment. This review proposes that cancer risk can be reduced, and that cancer can be even cured by improving dietary intake. A large number of studies also suggested that the intake of fruit and vegetables is associated with reduced breast cancer and paper also includes the role and the use of nanodelivery of flavonoids in the healing of breast cancer. In addition, the therapeutic potential of orally administered phyto-bioactive compounds (PBCs) is narrowed because of poor stability and oral bioavailability of compounds in the gastrointestinal tract (GIT), and solubility also affects bioavailability. In recent years, creative nanotechnology-based approaches have been advised to enhance the activity of PBCs. Nanotechnology also offers the potential to become aware of disease at earlier stages, such as the detection of hidden or unconcealed metastasis colonies in patients diagnosed with lung, colon, prostate, ovarian, and breast cancer. However, nanoformulation-related effects and safety must not be overlooked. This review gives a brief discussion of nanoformulations and the effect of nanotechnology on herbal drugs. 相似文献
985.
Reported are the syntheses, crystal structure determinations from single-crystal X-ray diffraction, and magnetic properties of two new ternary compounds, Eu11Cd6Sb12 and Eu11Zn6Sb12. Both crystallize with the complex Sr11Cd6Sb12 structure type—monoclinic, space group C2/m (no. 12), Z=2, with unit cell parameters a=31.979(4) Å, b=4.5981(5) Å, c=12.3499(14) Å, β=109.675(1)° for Eu11Zn6Sb12, and a=32.507(2) Å, b=4.7294(3) Å, c=12.4158(8) Å, β=109.972(1)° for Eu11Cd6Sb12. Their crystal structures are best described as made up of polyanionic and ribbons of corner-shared ZnSb4 and CdSb4 tetrahedra and Eu2+ cations. A notable characteristic of these structures is the presence of Sb-Sb interactions, which exist between two tetrahedra from adjacent layers, giving rise to unique channels. Detailed structure analyses shows that similar bonding arrangements are seen in much simpler structure types, such as Ca3AlAs3 and Ca5Ga2As6 and the structure can be rationalized as their intergrowth. Temperature-dependent magnetization measurements indicate that Eu11Cd6Sb12 orders anti-ferromagnetically below 7.5 K, while Eu11Zn6Sb12 does not order down to 5 K. Resistivity measurements confirm that Eu11Cd6Sb12 is poorly metallic, as expected for a Zintl phase. 相似文献
986.
Talal Rahman 《Numerical Algorithms》2011,58(2):235-260
We propose a simple and effective hybrid (multiplicative) Schwarz precondtioner for solving systems of algebraic equations
resulting from the mortar finite element discretization of second order elliptic problems on nonmatching meshes. The preconditioner
is embedded in a variant of the classical preconditioned conjugate gradient (PCG) for an effective implementation reducing
the cost of computing the matrix-vector multiplication in each iteration of the PCG. In fact, it serves as a framework for
effective implementation of a class of hybrid Schwarz preconditioners. The preconditioners of this class are based on solving
a sequence of non-overlapping local subproblems exactly, and the coarse problems either exactly or inexactly (approximately).
The classical PCG algorithm is reformulated in order to make reuse of the results of matrix-vector multiplications that are
already available from the preconditioning step resulting in an algorithm which is cost effective. An analysis of the proposed
preconditioner, with numerical results, showing scalability with respect to the number of subdomains, and a convergence which
is independent of the jumps of the coefficients are given. 相似文献
987.
On the basis of electronic structure calculations, we show that the long range Coulomb interaction provides the driving mechanism for oxygen overlayer formation on Cu(001). We illustrate that this interaction in the precursor c(2 x 2) phase induces a missing row reconstruction of Cu(001), and leads to the (2sqrt[2] x sqrt[2])R45 degrees O structure, which has strong covalent pO-dCu coupling. For the c(2 x 2)O overlayer on Ni(001) and Cu(001), we show that pO-dNi bonding is larger than pO-dCu and serves to neutralize the perturbation of the Coulomb interaction induced by the O overlayer. Consequently, c(2 x 2)O/Ni(001)) is stable while c(2 x 2)O/Cu(001) exists only in limited environments. 相似文献
988.
Cobalt doped zinc oxide (ZnO:Co) thin films were deposited on glass substrates by ultrasonic spray technique decomposition of Zinc acetate dihydrate and cobalt acetate tetrahydrate in an ethanol solution with film thickness. All films are polycrystalline with a hexagonal wurtzite-type structure with a preferential orientation according to the direction (0 0 2), with the maximum crystallite size was found of 59.42 nm at 569 nm. The average transmittance of all films is about 65–95% measured by UV–vis analyzer. The band gap energy increased from 3.08 to 3.32 eV with increasing the film thickness from 192 to 569 nm. The increase of the electrical conductivity with increases in the film thickness to maximum value of 9.27 (Ω cm)−1 can be explained by the increase in carrier concentration and displacement of the electrons of the films. The correlation between the band gap and crystal structure suggests that the band gap energy of Co doped ZnO is influenced by the crystallite size and the mean strain. 相似文献
989.
I. Kashif Samy A. Rahman A.A. Soliman E.M. Ibrahim E.K. Abdel-Khalek A.G. Mostafa A.M. Sanad 《Physica B: Condensed Matter》2009,404(21):3842-3849
Sodium borate glasses containing iron and molybdenum ions with the total concentration of transition ions constant and gradual substitution of sodium oxide (network modifier) by borate oxide (network former) was prepared. Densities, molar volume, DC and AC conductivities are measured. The trends of these properties are attributed to changes in the glass network structure. Their DC and AC conductivity increased with increasing NaO concentration. The increase of AC conductivity of sodium borate glasses is attributed to the chemical composition and the hopping mechanism of conduction. Measurements of the dielectric constant (ε) and dielectric loss (tan δ) as a function of frequency (50 Hz–100 kHz) and temperature (RT—600 K) indicate that the increase in dielectric constant and loss (ε and tan δ) values with increasing sodium ion content could be attributed to the assumption that Fe and Mo ions tend to assume network-forming position in the glass compositions studied.The variation of the value of frequency exponent s for all glass samples as the function of temperature at a definite frequency indicates that the value of s decreases with increasing the temperature which agrees with the correlated barrier-hopping (CBH) model. 相似文献
990.
Sad?k?Kaka?Email author Alm?la?G.?Yaz?c?o?lu Arif?Cem?G?zükara 《Heat and Mass Transfer》2011,47(8):879-891
For a variety of fields in which micro-mechanical systems and electronic components are used, fluid flow and heat transfer
at the microscale needs to be understood and modeled with an acceptable reliability. In general, models are prepared by making
some extensions to the conventional theories by including the scaling effects that become important for microscale. Some of
these effects are; axial conduction, viscous dissipation, and rarefaction. In addition to these effects, temperature variable
thermal conductivity and viscosity may become important in microscale gas flows due to the high temperature gradients that
may exist in the fluid. For this purpose, simultaneously developing, single phase, laminar and incompressible air flow in
a microtube and in the micro gap between parallel plates is numerically analyzed. Navier–Stokes and energy equations are solved
and the variation of Nusselt number along the channel is presented in tabular and graphical forms as a function of Knudsen,
Peclet, and Brinkman numbers, including temperature variable thermal conductivity and viscosity. 相似文献