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排序方式: 共有171条查询结果,搜索用时 15 毫秒
21.
Mujeebur Rahman Khan Vojtech Adam Tanveer Fatima Rizvi Baohong Zhang Faheem Ahamad Izabela Joko Ye Zhu Mingying Yang Chuanbin Mao 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(37)
In this Review, an effort is made to discuss the most recent progress and future trend in the two‐way traffic of the interactions between plants and nanoparticles (NPs). One way is the use of plants to synthesize NPs in an environmentally benign manner with a focus on the mechanism and optimization of the synthesis. Another way is the effects of synthetic NPs on plant fate with a focus on the transport mechanisms of NPs within plants as well as NP‐mediated seed germination and plant development. When NPs are in soil, they can be adsorbed at the root surface, followed by their uptake and inter/intracellular movement in the plant tissues. NPs may also be taken up by foliage under aerial deposition, largely through stomata, trichomes, and cuticles, but the exact mode of NP entry into plants is not well documented. The NP–plant interactions may lead to inhibitory or stimulatory effects on seed germination and plant development, depending on NP compositions, concentrations, and plant species. In numerous cases, radiation‐absorbing efficiency, CO2 assimilation capacity, and delay of chloroplast aging have been reported in the plant response to NP treatments, although the mechanisms involved in these processes remain to be studied. 相似文献
22.
Shenghua Wu Haifang Wen Weiguang Zhang Shihui Shen Louay N. Mohammad Ahmed Faheem 《International Journal of Pavement Engineering》2019,20(1):33-43
As a result of repeated rehabilitation efforts over the past few decades, often asphalt pavements have become deep-strength pavements. Consequently, top-down cracking has become a primary distress type. In particular, the top-down cracking performance of warm mix asphalt (WMA) pavements, i.e. how does it compare with similar hot mix asphalt (HMA) pavements is largely unclear mainly due to the lack of field performance data. This paper presents an effort of monitoring the top-down cracking performance of 28 pavement projects including WMA pavements and their corresponding HMA control pavements with service lives ranging between 4 and 10 years. These pavements cover different climate zones, WMA technologies, service years, pavement structures and traffic volume levels. Two rounds of distress surveys were conducted at a two-year interval, and the material (asphalt binder and mixture) properties of the pavements were determined using field cores. The top-down cracking performance of the HMA and WMA pavements was compared based on the first and second round distress surveys. It was found that the HMA and WMA pavement in general exhibited comparable performance. The significant determinants (material properties) for top-down cracking were determined, which were vertical failure deformation of mixes measured at 20 °C from indirect tension test. 相似文献
23.
Nasser A.M. Barakat K.A. Khalil Faheem A. Sheikh A.M. Omran Babita Gaihre Soeb M. Khil Hak Yong Kim 《Materials science & engineering. C, Materials for biological applications》2008,28(8):1381-1387
In the present study, subcritical water and alkaline hydrolysis methods are proposed methodologies for extraction of natural hydroxyapatite bioceramic from bovine bone. In these processes, the bovine bones powder were treated by high pressure water at 250 °C for 1 h and 25% (wt) sodium hydroxide at 250 °C for 5 h, respectively. Also the conventional calcination methodology has been utilized as well (T = 850 °C for 1 h). The obtained apatites from the three treatment processes have been characterized by powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT IR), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), electron scanning microscopy (SEM), energy dispersive X-ray analysis (EDX) and field emission scanning electron microscopy (FE SEM). FT IR and XRD results affirmed that both the proposed methods and the traditional one can eliminate the collagen and other organic materials present in the bovine bones. The physiochemical characterizations for the obtained apatites have proved that the subcritical water and the alkaline hydrolysis relatively preserve the carbonate content present in the biological apatite, so they yield carbonated hydroxyapatite which is medically preferable. While, the thermal process produces almost hydroxyapatite carbonate-free. 相似文献
24.
Nawazish A. Khan Faheem Ashraf M. Mumtaz Naghma Haider 《Journal of Superconductivity and Novel Magnetism》2008,21(5):279-287
The effect of self-doping and substitution of elements of higher and lower electronegativity, such as Bi, Hg, Nb, Pd, Li,
Na, K, on the superconducting properties of Cu0.5Tl0.5−x
M
x
Ba2Ca2Cu3O10−δ
with x=0.25 is investigated. These experiments demonstrated that the elements of lower electronegativity such as Li, Na, and K can
easily liberate their outer most s-electron that could be supplied to the conducting CuO2 planes of Cu0.5Tl0.5−x
M
x
Ba2Ca2Cu3O10−δ
superconductor, and as a result, we get enhanced superconducting properties. However, highly electro-negative elements hinder
the transfer of carriers from charge reservoir layer to the conducting CuO2 planes and promote inferior superconducting properties. In the present studies, we have investigated the effect of post-annealing
in nitrogen and oxygen atmospheres for optimizing the carriers in conducting CuO2 planes of Cu0.5Tl0.5−x
M
x
Ba2Ca2Cu3O10−δ
(M=Bi,Hg,Nb,Pd,Li,Na,K) superconductor. These studies are important since the density of carriers in the conducting CuO2 planes determines the Fermi-vector k
F and Fermi velocity v
F of the carriers, which ultimately brings about the final superconducting state of the system.
相似文献
25.
Structural and magnetic properties of Zn1-xcoxO nanorods prepared by microwave irradiation technique
Ahmed F Kumar S Arshi N Anwar MS Koo BH Lee CG 《Journal of nanoscience and nanotechnology》2012,12(2):1386-1389
We have successfully synthesized large-scale aggregative flowerlike Zn1-xCo(x)O (0.0 < or = x < or = 0.07) nanostructures, consisting of many branches of nanorods at different orientations with diameter within 100-150 nm (tip diameter approximately 50 nm) and length of approximately 1 microm. The rods were prepared using Zinc nitrate, cobalt nitrate and KOH in 180 Watt microwave radiation for short time interval. The synthesized nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and DC magnetization measurements. XRD and TEM results indicate that the novel flowerlike nanostructures are hexagonal with wurtzite structure and Co ions were successfully incorporated into the lattice position of Zn ions in ZnO matrix. The selected area electron diffraction (SAED) pattern reveals that the nanorods are single crystal in nature and preferentially grow along [0 0 1] direction. Magnetic studies show that Zn1-xCo(x)O nanorods exhibit room temperature ferromagnetism. This novel nanostructure could be a promising candidate for a variety of future spintronic applications. 相似文献
26.
27.
Muzafar A. Kanjwal Nasser A. M. Barakat Faheem A. Sheikh Myung Seob Khil Hak Yong Kim 《Journal of Materials Science》2008,43(16):5489-5494
In this work, nanobelt mats consisting of three potential metal oxides have been produced using the electrospinning technique.
An aqueous solution of cobalt acetate tetra-hydrate, copper acetate mono-hydrate, and manganese acetate tetra-hydrate was
mixed with poly(vinyl alcohol) solution to prepare a sol–gel which was electrospun at 20 kV. The obtained nanofiber mats have
been vacuously dried at 80 °C for 24 h and then calcined in air atmosphere at different temperatures and soaking times. The
utilized physiochemical characterizations have affirmed that nanobelts composed of three oxides (Co3O4, CuO, and MnO2) can be prepared by calcination at a temperature of 600 °C for 1 h. High-resolution transmission electron microscope and
selected area electron pattern images revealed good crystallinity for the synthesized nanobelts. 相似文献
28.
M. Mumtaz Nawazish A. Khan Faheem Ashraf 《Journal of Superconductivity and Novel Magnetism》2011,24(6):1985-1989
The relatively higher electronegative elements (M = Pd, Nb, Bi, Hg) have been partially doped at Tl sites in Cu0.5Tl0.5−x
M
x
Ba2O4−δ
(x=0,0.25) charge reservoir layer of Cu0.5Tl0.5−x
M
x
Ba2Ca2Cu3O10−δ
superconductor. These elements may retain more oxygen in the charge reservoir layer due to their higher electronegativity
as compared to Tl, and the higher population of oxygen in the charge reservoir layer can optimize the charge carriers’ density
in the conducting CuO2 planes. The optimum density of mobile charge carriers in the conducting CuO2 increases Fermi wave-vector K
F and Fermi velocity v
F of the carriers, which results in the improvement of superconducting properties of the material. 相似文献
29.
Zhang F Lees E Amin F Rivera Gil P Yang F Mulvaney P Parak WJ 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(22):3113-3127
Water solubilization of nanoparticles is a fundamental prerequisite for many biological applications. To date, no single method has emerged as ideal, and several different approaches have been successfully utilized. These 'phase-transfer' strategies are reviewed, indicating key advantages and disadvantages, and a discussion of conjugation strategies is presented. Coating of hydrophobic nanoparticles with amphiphilic polymers provides a generic pathway for the phase transfer of semiconductor, magnetic, metallic, and upconverting nanoparticles from nonpolar to polar environments. Amphiphilic polymers that include maleimide groups can be readily functionalized with chemical groups for specific applications. In the second, experimental part, some of the new chemical features of such polymer-capped nanoparticles are demonstrated. In particular, nanoparticles to which a pH sensitive fluorophore has been attached are described, and their use for intracellular pH-sensing demonstrated. It is shown that the properties of analyte-sensitive fluorophores can be tuned by using interactions with the underlying nanoparticles. 相似文献
30.
The aim of this study was to investigate the effect of elastane linear density and draft ratio on the physical and mechanical properties of core-spun yarns. Twenty yarn samples were prepared on industrial scale in a spinning mill with two different yarn linear densities, each with different two elastane deniers and five draft ratios. It was found that core-spun yarn’s tenacity, elongation and hairiness are affected not only by the overall yarn linear density but also by the elastane linear density and the draft ratio. However, the effect of elastane linear density and draft ratio was not found to be statistically significant on the yarn mass variations and total imperfections, which are only affected by the overall yarn liner density. A statistically significant interaction for yarn elongation at break was found between the yarn liner density and the elastane linear density concluding that elastane linear density used in the core must be compatible with the overall yarn liner density for attaining the best yarn elongation. 相似文献