In this paper we construct the β-fractional α-stable processes and sheets as functionals of α-stable white noises by using a transformation induced from fractional integral operators. This white noise approach is shown to be very useful in investigating their distribution and path properties (stationariness of increments, self-similarity, sample continuity, etc.). 相似文献
In this work, the tree-like carbon nanotubes (CNTs) with branches of different diameters and the wing-like CNTs with graphitic-sheets of different densities were synthesized by using plasma enhanced chemical vapor deposition. The nanostructures of the as-prepared hybrid carbon materials were characterized by scanning electron microscopy and transmission electron microscopy. The structural dependence of field electron emission (FEE) property was also investigated. It is found that both of the tree- and wing-like CNTs exhibit a lower turn-on field and higher emission current density than the pristine CNTs, which can be ascribed to the effects of branch size, crystal orientation, and graphitic-sheet density. 相似文献
An addition to the family : The introduction of β‐amino acid residues into a modified amyloid β peptide fragment resulted in well‐defined helical nanoribbons (see cryo‐TEM image) comprising β strands mainly oriented perpendicular to the ribbon axis. The nanoribbons order into a flow‐aligning nematic phase at higher concentration. The β‐strand nanoribbon structure is an addition to the known set of secondary structures adopted by β‐peptides.
The configurations, stability and electronic structures of a new class of boron sheet and related boron nanotubes are predicted within the framework of density functional theory. This boron sheet is sparser than those of recent proposals. Our theoretic results show that the stable boron sheet remains flat and is metallic. There are bands similar to the π‐bands in graphite near the Fermi level. Stable nanotubes with various diameters and chiral vectors can be rolled from the sheet. Within our study, only the thin (8, 0) nanotube with a band gap of 0.44 eV is semiconducting, while all the other thicker boron nanotubes are metallic, independent of their chirality. It indicates the possibility, in the design of nanodevices, to control the electronic transport properties of the boron nanotube through the diameter.相似文献
In this work, a sandwich-type electrochemical immunosensor for simultaneous sensitive detection of prostate specific antigen (PSA) and free prostate specific antigen (fPSA) is fabricated. Gold nanoparticles (AuNPs) modified Prussian blue and nickel hexacyanoferrates nanoparticles were firstly prepared, respectively, and then decorated onion-like mesoporous graphene sheets (denoted as Au@PBNPs/O-GS and Au@NiNPs/O-GS) as distinguishable signal tags to label different detection antibodies. Subsequently, streptavidin and biotinylated alkaline phosphatase (bio-AP) were employed to block the possible remaining active sites. With the employment of the as prepared nanohybrids, the dual catalysis amplification can be achieved by catalysis of the ascorbic acid 2-phosphate to in situ produce AA in the presence of bio-AP, and then AA was further catalyzed by Au@PBNPs/O-GS and Au@NiNPs/O-GS nanohybrids, respectively, to obtain the higher signal responses. The experiment results show that the linear range of the proposed immunosensor for simultaneous determination of fPSA is from 0.02 to 10 ng mL−1 with a detection limit of 6.7 pg mL−1 and PSA is from 0.01 to 50 ng mL−1 with a detection limit of 3.4 pg mL−1 (S/N = 3). Importantly, the proposed method offers promise for rapid, simple and cost-effective analysis of biological samples. 相似文献
Abstract Highly selective ion analysis of sub-ppm Pb(II) on a porous graphitic carbon (PGC) column, is described using ion chromatography with acidified aqueous mobile phases, post-column detection using PAR and spectrophotometric detection. Sensitivity is enhanced by on-line preconcentration of the metal prior to the chromatography using one millilitre injection volumes applied to a calix[4]arene-tetrahydroxamate based chelating precolumn. The method is applied to water samples collected from a river subjected to an industrial effluent discharge and results obtained compare favourably with those obtained using flame atomic absorption spectroscopy. 相似文献