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排序方式: 共有192条查询结果,搜索用时 15 毫秒
71.
Fernandez-Lima FA Post J DeBord JD Eller MJ Verkhoturov SV Della-Negra S Woods AS Schweikert EA 《Analytical chemistry》2011,83(22):8448-8453
In the present work, the advantages of a new, 100 kV platform equipped with a massive gold cluster source for the analysis of native biological surfaces are shown. Inspection of the molecular ion emission as a function of projectile size demonstrates a secondary ion yield increase of ~100× for 520 keV Au(400)(4+) as compared to 130 keV Au(3)(1+) and 43 keV C(60). In particular, yields of tens of percent of molecular ions per projectile impact for the most abundant components can be observed with the 520 keV Au(400)(4+) probe. A comparison between 520 keV Au(400)(4+) time-of-flight-secondary ion mass spectrometry (TOF-SIMS) and matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) data showed a similar pattern and similar relative intensities of lipid components across a rat brain sagittal section. The abundant secondary ion yield of analyte-specific ions makes 520 keV Au(400)(4+) projectiles an attractive probe for submicrometer molecular mapping of native surfaces. 相似文献
72.
Faiza Zidouni Kendil Eckhard Krepper Anis Bousbia Salah Dirk Lucas Amina Mataoui 《Nuclear Engineering and Design》2011,241(10):4111-4121
The current paper presents the prediction results of a bubbly flow under plunging jet conditions using multiphase mono- and poly-dispersed approaches. The models consider interfacial momentum transfer terms arising from drag, lift, and turbulent dispersion force for the different bubble sizes. The turbulence is modeled by an extended k–? model which accounts for bubble induced turbulence. Furthermore in case of a poly-dispersed air–water flow the bubble size distribution, bubble break-up and coalescence processes as well as different gas velocities in dependency on the bubble diameter are taken into account using the Inhomogeneous MUSIG model. This model is a generalized inhomogeneous multiple size group model based on the Eulerian modeling framework which was developed in the framework of a cooperative work between ANSYS-CFX and Forschungszentrum Dresden-Rossendorf (FZD). The latter is now implemented into the CFD code CFX.According to the correlation on the lateral lift force obtained by Tomiyama (1998); this force changes its sign in dependence on the bubble size. Consequently the entrained small bubbles are trapped below the jet. They can escape from the bubble plume only by turbulent fluctuations or by coalescence. If the size of the bubbles generated by coalescence exceeds the size at which the lift force changes its sign these large bubbles go out from the plume and rise to the surface.A turbulent model based on an additional source term for turbulence kinetic energy and turbulence eddy dissipation equation is compared to the common concept for modeling the turbulence quantities proposed by Sato et al. (1981). It has been found that the large bubble distribution is slightly affected by the turbulence modeling which affects particularly the bubble coalescence and break-up process. 相似文献
73.
Moulay Hadj Ahmed Mazouz Amina Aiche Doumi Bendouma Abdelkader Tadjer 《Journal of Superconductivity and Novel Magnetism》2017,30(8):2091-2097
We have performed first-principles calculations to investigate the structural, electronic, magnetic, lattice dynamics, and thermodynamic properties of ferromagnetic alkaline earth metal nitrides CaN, SrN, and BaN in the rocksalt structure using the plane-wave pseudopotential approach to the density functional theory within local density and generalized gradient approximations for the exchange and correlation potential. The linear response to the density functional theory allowed us to calculate the phonon dispersion spectra for these compounds. We reported also the results on thermodynamic properties as a function of temperature calculated by using the quasiharmonic approximation. 相似文献
74.
Amina Ouadah Tianwei Luo Shuitao Gao Changjin Zhu 《International Journal of Hydrogen Energy》2018,43(32):15466-15480
A new hybrid based polyphosphazene backbone is synthesized via a series of reactions (ring opening of polyphosphazene, bromination, grafting groups, Atom transfer radical polymerization (ATRP) and sulfonation) with a controlled degree of sulfonation. The synthesis is proved via the 1H NMR analysis at different steps. The corresponding membranes were elaborated via a casting method and characterized by 1H NMR, FTIR, and XPS. Conductivity of the synthesized proton exchange membranes is as good as that of the commercial Nafion and displays at the same time a low swelling ratio and water uptake due to the cross-linking process. The membrane's activation energies are very low confirming the easy transport through the channels. As matter of fact, the morphology study reveals a well hydrophilic/hydrophobic nanophase separation. The present membranes are chemically and thermally very stable, no significant weight loss was observed after the Fenton's reagent test and no thermal degradation occurs at temperatures lower than 250 °C (considered high temperature for nowadays proton exchange membranes). 相似文献
75.
Abd El-atty Saied M. El-taweel Amina El-Rabaie S. 《Neural computing & applications》2018,30(11):3509-3522
Neural Computing and Applications - In this paper, we develop an analytical framework for modeling the transmission of nanoscale information in nanonetwork-based molecular communication and aware... 相似文献
76.
Amina Zelmat Hocine Hadi Malek Amiali Tanya Gashovska 《The International journal of environmental studies》2017,74(2):262-274
The permeabilized membrane state of a pulsed electric field (PEF) treated biological sample is invisible to the naked eye, but can be deduced as the permeabilization causes loss of the insulating properties of the membrane, which can be determined by measuring the electrical impedance. This paper reports a spectroscopic analysis of a PEF treated and untreated potato sample to determine the electrical components of the biological tissue equivalent circuit model. The measurements concern flat potato samples which were subjected to different values of factors such as electric field, pulse number, pulse width and frequency. Cole–Cole plots are used to calculate the pore resistance and capacitance. This method of impedance measurement is used to establish the appropriate equivalent circuit model of the potato tissue according to the measured data, and thus explanations about the cell model from the impedance spectra are deduced. The PEF parameters had significant effect on the impedance and structural changes of the biological tissue. The treatment frequency does not have significant effect on the impedance when the electrical field, pulse number and width are kept constant. 相似文献
77.
Barbieri Alan Piemontese Amina Colavolpe Giulio 《Wireless Communications, IEEE Transactions on》2009,8(2):535-540
We consider a terrestrial wireless channel, whose statistical model under flat-fading conditions is due to Clarke. A lot of papers in the literature deal with receivers for this scenario, aiming at estimating and tracking the time-varying channel, possibly with the aid of known (pilot) symbols. A common approach to derive receivers of reasonable complexity is to resort to a Kalman filter which is based on an approximation of the actual fading process as autoregressive moving-average (ARMA) of a given order. The aim of this paper is to show that the approximation of the actual fading process, usually exploited in the literature, is far from effective. Thus, we present a novel technique, based on an off-line minimization of the mean square error of the channel estimate, which ensures a considerable gain in terms of bit-error rate for Kalman-based receivers without increasing the receiver complexity. Moreover, we also propose a novel approximation, to be employed in Kalman smoothers proposed for iterative detection schemes, which allows further performance improvements without a significant increase of the computational complexity. 相似文献
78.
Kassin Saul M.; Tubb V. Anne; Hosch Harmon M.; Memon Amina 《Canadian Metallurgical Quarterly》2002,57(5):378
Responds to the comments by M. L. McCullough (see record 2002-12932-018) on the original article (see record 2001-17140-001) which discussed eyewitness testimony. The current author states that McCullough's commentary rests on a foundation of assumptions that were both na?ve and erroneous. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
79.
Amina Nemchi Ahmed Bouzidane Marc Thomas Asma Abed 《Tribology - Materials, Surfaces & Interfaces》2018,12(2):59-70
This paper presents a theoretical study of the effects of Poiseuille Reynolds number and eccentricity ratio on the performance of four-pad hydrostatic squeeze film dampers. The finite difference method has been used to solve Reynolds equation based on Constantinescu’s turbulent lubrication theory. The numerical results obtained are analysed and compared between three and four-lobe hybrid journal bearings. The computed results indicate that the performance of a hydrostatic squeeze film damper loaded between pads is significantly influenced by the flow regimes. The results presented in this work can be useful to the bearing designers. 相似文献
80.
Mahmoud Balbaa Sahar Abbas Seham El-Deen Amina Hassab Olfat Awad 《The International journal of environmental studies》2013,70(6):563-573
Among many tested enzymes, lipase was found to be the one most affected by schistosomiasis in human serum, where it is increased eightfold. Arylsulfatases A and B and aspartyl protease displayed a significant decrease in the serum, while other enzymes showed a significant increase. α‐Amylase and Leucine aminopeptidase were significantly increased and arylsulfatase B showed a significant decrease. Arylsulfatase B from a patient's leucocytes did not show either changed kinetic behaviour or temperature‐dependent conformational changes. These results indicate that the diminished activity of this enzyme may be attributed to an opposing mechanism of regulation. 相似文献