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排序方式: 共有281条查询结果,搜索用时 343 毫秒
41.
42.
O. A. P. Tavares E. L. Medeiros 《The European Physical Journal A - Hadrons and Nuclei》2010,45(1):57-60
The partial proton emission half-life for 53mCo unstable isomer is re-examined in the framework of a semiempirical model based on tunneling through a Coulomb-plus-centrifugal-plus-overlapping
potential barrier within the spherical nucleus approximation. It is shown that the known measured half-life value of 17s is
compatible with a large prolate shape for 53mCo proton emitter and a high angular momentum ℓ = 11 assigned to the proton transition to the ground state of 52Fe . 相似文献
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44.
P. Laurêncio H. Vargues I. Fortes R. Avó M. C. R. Medeiros 《Fiber and Integrated Optics》2013,32(6):441-452
Abstract The performance degradation caused by transmission along dispersive single-mode fibers of optically generated millimeter-wave signals using up-conversion is theoretically assessed and validated by numerical simulation. Up-conversion techniques based on optical double sideband, optical single sideband, and optical carrier suppression are considered. The generation of 60 GHz by frequency tripling using the optical single sideband is shown to be particularly tolerant to the fiber dispersion. The practical imbalance of Mach-Zehnder modulators is taken into account for optical carrier suppression modulation, where the finite extinction ratio is found to increase tolerance to fiber dispersion. 相似文献
45.
Abstract This article analyzes and validates through simulation the influence of fiber nonlinearity, dispersion, and loss on the Relative Noise Intensity (RIN) spectrum at fiber output in externally modulated optical single side band (OSSB) systems. The analysis includes the RIN generated by the laser source, the effect of the OSSB modulator, and noise generated by the in-line optical amplifiers. The analysis takes into account conversion between phase noise and intensity noise introduced by fiber transmission. It is shown that, depending on the operating conditions, the system performance may be predominantly affected either by the laser RIN or by the noise generated by the in-line optical amplifiers. The impact of the OSSB modulator can be relevant when the RIN of the system is dominated by the laser noise and should therefore be considered. 相似文献
46.
The contribution of nontrivial vacuum (topological) excitations, more specifically vortex configurations of the self-dual Chern–Simons–Higgs model, to the functional partition function is considered. By using a duality transformation, we arrive at a representation of the partition function in terms of which explicit vortex degrees of freedom are coupled to a dual gauge field. By matching the obtained action to a field theory for the vortices, the physical properties of the model in the presence of vortex excitations are then studied. In terms of this field theory for vortices in the self-dual Chern–Simons–Higgs model, we determine the location of the critical value for the Chern–Simons parameter below which vortex condensation can happen in the system. The effects of self-energy quantum corrections to the vortex field are also considered. 相似文献
47.
Carbon Dots (C‐dots) from Cow Manure with Impressive Subcellular Selectivity Tuned by Simple Chemical Modification 下载免费PDF全文
Cintya D'Angelis do E. S. Barbosa Dr. José R. Corrêa Gisele A. Medeiros Gabrielle Barreto Dr. Kelly G. Magalhães Dr. Aline L. de Oliveira Prof. Dr. John Spencer Prof. Dr. Marcelo O. Rodrigues Prof. Dr. Brenno A. D. Neto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5055-5060
Improved cellular selectivity for nucleoli staining was achieved by simple chemical modification of carbon dots (C‐dots) synthesized from waste carbon sources such as cow manure (or from glucose). The C‐dots were characterized and functionalized (amine‐passivated) with ethylenediamine, affording amide bonds that resulted in bright green fluorescence. The new modified C‐dots were successfully applied as selective live‐cell fluorescence imaging probes with impressive subcellular selectivity and the ability to selectively stain nucleoli in breast cancer cell lineages (MCF‐7). The C‐dots were also tested in four other cellular models and showed the same cellular selection in live‐cell imaging experiments. 相似文献
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49.
Eliton S. Medeiros Luiz H. C. Mattoso Rubens Bernardes-Filho Delilah F. Wood William J. Orts 《Colloid and polymer science》2008,286(11):1265-1272
Nanostructured films of poly(o-ethoxyaniline) (POEA) alternated with cellulose nanofibrils (CnF) were successfully produced
by self assembly (SA) at different pH values and investigated by atomic force microscopy and ultraviolet-visible spectroscopy.
Results show that it was possible to build up films by alternating POEA and CnF layers with relatively precise architectural
control by controlling the number of layers and pH. Film thickness had a dependence on pH which is a combination of the effects
of the deposited amount for each POEA layer and the pH at which the absorption of the cellulose nanofibrils was carried out.
Comparison of alternated layers of POEA and CnF with multi-immersions of POEA at different pH values, as measured by the ratio
between slopes of the straight lines of deposited amount of polymer versus the number of self-assembled layers, shows that
alternate deposition at pH 2 has a fourfold increase in the slope. Alternatively, at pH 5, there is no significant difference
whether the deposition is alternated (POEA–CnF) or not (POEA). 相似文献
50.
The uptake of ascorbate by neuroblastoma cells using a ruthenium oxide hexacyanoferrate (RuOHCF)-modified carbon fiber disc (CFD) microelectrode (r = 14.5 microm) was investigated. By use of the proposed electrochemical sensor the amperometric determination of ascorbate was performed at 0.0 V in minimum essential medium (MEM, pH = 7.2) with a limit of detection of 25 micromol L(-1). Under the optimum experimental conditions, no interference from MEM constituents and reduced glutathione (used to prevent the oxidation of ascorbate during the experiments) was noticed. The stability of the RuOHCF-modified electrode response was studied by measuring the sensitivity over an extended period of time (120 h), a decrease of around 10% being noticed at the end of the experiment. The rate of ascorbate uptake by control human neuroblastoma SH-SY5Y cells, and cells transfected with wild-type Cu,Zn-superoxide dismutase (SOD WT) or with a mutant typical of familial amyotrophic lateral sclerosis (SOD G93A), was in agreement with the level of oxidative stress in these cells. The usefulness of the RuOHCF-modified microelectrode for in vivo monitoring of ascorbate inside neuroblastoma cells was also demonstrated. 相似文献