32,770 research outputs found
Triphilic ionic-liquid mixtures: fluorinated and non-fluorinated aprotic ionic-liquid mixtures
We present here the possibility of forming triphilic mixtures from alkyl- and fluoroalkylimidazolium ionic liquids, thus, macroscopically homogeneous mixtures for which instead of the often observed two domainspolar and nonpolarthree stable microphases are present: polar, lipophilic, and fluorous ones. The fluorinated side chains of the cations indeed self-associate and form domains that are segregated from those of the polar and alkyl domains. To enable miscibility, despite the generally preferred macroscopic separation between fluorous and alkyl moieties, the importance of strong hydrogen bonding is shown. As the long-range structure in the alkyl and fluoroalkyl domains is dependent on the composition of the liquid, we propose that the heterogeneous, triphilic structure can be easily tuned by the molar ratio of the components. We believe that further development may allow the design of switchable, smart liquids that change their properties in a predictable way according to their composition or even their environment
Contacting single bundles of carbon nanotubes with alternating electric fields
Single bundles of carbon nanotubes have been selectively deposited from
suspensions onto sub-micron electrodes with alternating electric fields. We
explore the resulting contacts using several solvents and delineate the
differences between Au and Ag as electrode materials. Alignment of the bundles
between electrodes occurs at frequencies above 1 kHz. Control over the number
of trapped bundles is achieved by choosing an electrode material which
interacts strongly with the chemical functional groups of the carbon nanotubes,
with superior contacts being formed with Ag electrodes.Comment: 4 pages, RevTe
Implicit integration scheme for porous viscoplastic potential-based constitutive equations
This paper deals with a viscoplastic potential-based model allowing thermomechanical damage behavior modeling of porous materials. The model describes rate dependent effects, hardening, creep as well as defects coalescence and propagation. Kinematic and isotropic hardening effects are taken into account by a set of internal state variables. The integration and implementation of the model into the FE code using a fully implicit integration scheme is exposed. Finally, it 19s used to predict mechanical behaviour degradation of solder layers used in power electronic packaging. Stress-strain behaviour and the evolution of volumic fraction of voids for the material under cyclic loading are presented
Backbone of complex networks of corporations: The flow of control
We present a methodology to extract the backbone of complex networks based on
the weight and direction of links, as well as on nontopological properties of
nodes. We show how the methodology can be applied in general to networks in
which mass or energy is flowing along the links. In particular, the procedure
enables us to address important questions in economics, namely, how control and
wealth are structured and concentrated across national markets. We report on
the first cross-country investigation of ownership networks, focusing on the
stock markets of 48 countries around the world. On the one hand, our analysis
confirms results expected on the basis of the literature on corporate control,
namely, that in Anglo-Saxon countries control tends to be dispersed among
numerous shareholders. On the other hand, it also reveals that in the same
countries, control is found to be highly concentrated at the global level,
namely, lying in the hands of very few important shareholders. Interestingly,
the exact opposite is observed for European countries. These results have
previously not been reported as they are not observable without the kind of
network analysis developed here.Comment: 24 pages, 12 figures, 2nd version (text made more concise and
readable, results unchanged
The VLQ Calorimeter of H1 at HERA: A Highly Compact Device for Measurements of Electrons and Photons under Very Small Scattering Angles
In 1998, the detector H1 at HERA has been equipped with a small backward
spectrometer, the Very Low Q^2 (VLQ) spectrometer comprising a silicon tracker,
a tungsten - scintillator sandwich calorimeter, and a Time-of-Flight system.
The spectrometer was designed to measure electrons scattered under very low
angles, equivalent to very low squared four - momentum transfers Q^2, and high
energy photons with good energy and spatial resolution. The VLQ was in
operation during the 1999 and 2000 run periods. This paper describes the design
and construction of the VLQ calorimeter, a compact device with a fourfold
projective energy read-out, and its performance during test runs and in the
experiment.Comment: 32 pages, 25 figures, 2 tables (To be submitted to Nucl. Instrum.
Meth. A
Electrical and galvanomagnetic properties of AuAl2+6%Cu intermetallic compounds at low temperatures
The AuAl2 intermetallic compounds are of substantial interest in view of their application potential. The investigated intermetallics AuAl 2+6%Cu were prepared from fine powders of AuAl2 and Cu by vacuum sputtering on a glass substrate and consisted of films with a thickness of about one micrometer. The films were annealed. The temperature and field dependence of the electroresistivity, the magnetoresistivity and the Hall effect of AuAl2+6%Cu films were measured in the temperature interval from 4.2 to 100 K and at magnetic fields of up to 15 T. We demonstrate that the temperature dependence of the electroresistivity has a minimum at T = 20 K and a metallic behavior above this temperature. The magnetoresistivity is very small (less then 1%), positive at low temperatures and negative above 12 K. The Hall coefficient is positive, which corresponds to the holes in a one zone model with a charge carrier concentration of about 1.6 1020 cm-3. © Published under licence by IOP Publishing Ltd
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