10,469 research outputs found
Recent Developments in Mems-Based Micro Fuel Cells
Micro fuel cells (-FC) represent promising power sources for portable
applications. Today, one of the technological ways to make -FC is to have
recourse to standard microfabrication techniques used in the fabrication of
micro electromechanical systems (MEMS). This paper shows an overview on the
applications of MEMS techniques on miniature FC by presenting several solutions
developed throughout the world. It also describes the latest developments of a
new porous silicon-based miniature fuel cell. Using a silane grafted on an
inorganic porous media as the proton-exchange membrane instead of a common
ionomer such as Nafion, the fuel cell achieved a maximum power density of 58 mW
cm-2 at room temperature with hydrogen as fuel.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Velocity fluctuations and population distribution in clusters of settling particles at low Reynolds number
A study on the spatial organization and velocity fluctuations of non Brownian
spherical particles settling at low Reynolds number in a vertical Hele-Shaw
cell is reported. The particle volume fraction ranged from 0.005 to 0.05, while
the distance between cell plates ranged from 5 to 15 times the particle radius.
Particle tracking revealed that particles were not uniformly distributed in
space but assembled in transient settling clusters. The population distribution
of these clusters followed an exponential law. The measured velocity
fluctuations are in agreement with that predicted theoretically for spherical
clusters, from the balance between the apparent weight and the drag force. This
result suggests that particle clustering, more than a spatial distribution of
particles derived from random and independent events, is at the origin of the
velocity fluctuations.Comment: 13 pages, 8 figure
Linguistic Identity and Investment in Grade 8 Core French Students
This study examines the linguistic identities and language-learning investment(s) of eight Grade 8 core French students at a Cambridge, Ontario elementary school. I address the following questions: (1) How do FSL students in a Grade 8 classroom in Ontario identify themselves linguistically? (2) Does linguistic identity play a role in studentsâ investment in French language learning? (3) Do students who perceive themselves as bilingual, multilingual, or learners of French have more success than peers who identify themselves as âEnglish onlyâ? Following Blackledge and Creese (2010), Byrd Clark (2008, 2009, 2010, 2014), Lamoureux (2012, 2014), Roy (2010), and Taylor (2009, 2014), I use ethnomethodology to understand the relationship between studentsâ multiple identities, language-learning investment, and achievement. I draw on post-structuralist theories of language learning, identity, and investment, and use discourse analysis to explore studentsâ beliefs about bi/multilingualism, languages, and the importance of learning French, to suggest improve FSL outcomes in Ontario
Wolf predation in the Burwash caribou herd, southwest Yukon
The role of wolf predation as a proximate mortality factor influencing caribou herd growth was assessed in the Burwash herd (400 animals) in the southwest Yukon between 1980 - 1982. Ten to 14 wolves in two packs preyed primarily on caribou (Rangifer tarandus caribou) and moose (Alces alces) with disproportionate consumption of caribou (relative to available biomass) in the rut and winter periods. Wolf predation was responsible for 72% of total annual mortality in 1980 - 1981 and 46% in 1981 - 1982. Losses due to human harvest varied between 7 to 13%. Additional limited data on climatic factors and winter forage indicated forage-climate were not major proximate mortality factors in 1980 - 1981, but that early-calving climate may have been a factor in increased calf mortality in 1982
Evidence for spin liquid ground state in SrDyO frustrated magnet probed by muSR
Muon spin relaxation (SR) measurements were carried out on
SrDyO, a frustrated magnet featuring short range magnetic correlations
at low temperatures. Zero-field muon spin depolarization measurements
demonstrate that fast magnetic fluctuations are present from K down to
20 mK. The coexistence of short range magnetic correlations and fluctuations at
mK indicates that SrDyO features a spin liquid ground state.
Large longitudinal fields affect weakly the muon spin depolarization, also
suggesting the presence of fast fluctuations. For a longitudinal field of
T, a non-relaxing asymmetry contribution appears below K,
indicating considerable slowing down of the magnetic fluctuations as
field-induced magnetically-ordered phases are approached.Comment: 6 pages, 4 figures, to be published as a proceeding of HFM2016 in
Journal of Physics: Conference Series (JPCS
Sound velocity and absorption measurements under high pressure using picosecond ultrasonics in diamond anvil cell. Application to the stability study of AlPdMn
We report an innovative high pressure method combining the diamond anvil cell
device with the technique of picosecond ultrasonics. Such an approach allows to
accurately measure sound velocity and attenuation of solids and liquids under
pressure of tens of GPa, overcoming all the drawbacks of traditional
techniques. The power of this new experimental technique is demonstrated in
studies of lattice dynamics, stability domain and relaxation process in a
metallic sample, a perfect single-grain AlPdMn quasicrystal, and rare gas, neon
and argon. Application to the study of defect-induced lattice stability in
AlPdMn up to 30 GPa is proposed. The present work has potential for application
in areas ranging from fundamental problems in physics of solid and liquid
state, which in turn could be beneficial for various other scientific fields as
Earth and planetary science or material research
HE II Two Phase Flow in an Inclinable 22 m Long Line
In the line of previous work done at CEA Grenoble, large size experiments were performed with the support of CERN for the validation of the LHC two phase superfluid helium cooling scheme. In order to be as close as possible to the real configuration, a straight, inclinable 22 m long line of 40 mm I.D. was built. Very accurate measurements of temperatures and pressures obtained after in situ re-calibration and verified by independent sensors allowed us to validate our two-phase flow model. Although we focus on pressure losses and heat exchange results in relation to power injected, additional measurements such as quality, void fraction, and total mass flow rate enable a complete description of the two-phase flow. Experiments were carried out to cover the whole range of the future LHC He II two-phase flow heat exchanger pipe: slope between 0 and 2.8 %, temperature between 1.8 and 2 K, total mass flow rate up to 7.5 g/s. Results confirm the validity of choice for the LHC cooling scheme
A Star in the Brainstem Reveals the First Step of Cortical Magnification
A fundamental question in the neurosciences is how central nervous system (CNS) space is allocated to different sensory inputs. Yet it is difficult to measure innervation density and corresponding representational areas in the CNS of most species. These measurements can be made in star-nosed moles (Condylura cristata) because the cortical representation of nasal rays is visible in flattened sections and afferents from each ray can be counted. Here we used electrophysiological recordings combined with sections of the brainstem to identify a large, visible star representation in the principal sensory nucleus (PrV). PrV was greatly expanded and bulged out of the brainstem rostrally to partially invade the trigeminal nerve. The star representation was a distinct PrV subnucleus containing 11 modules, each representing one of the nasal rays. The 11 PrV ray representations were reconstructed to obtain volumes and the largest module corresponded to ray 11, the mole's tactile fovea. These measures were compared to fiber counts and primary cortical areas from a previous investigation. PrV ray volumes were closely correlated with the number of afferents from each ray, but afferents from the behaviorally most important, 11th ray were preferentially over-represented. This over-representation at the brainstem level was much less than at the cortical level. Our results indicate that PrV provides the first step in magnifying CNS representations of important afferents, but additional magnification occurs at higher levels. The early development of the 11th, foveal appendage could provide a mechanism for the most important afferents to capture the most CNS space
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