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Mass-transport resistances of acid and alkaline ionomer layers: A microelectrode study part 1 - Microelectrode development
The use of microelectrodes to study localized mass-transport phenomena in fuel-cell catalyst layers is an increasingly valuable tool. However, existing microelectrode cells have been used in static, equilibrated environment modes with poorly controlled interfaces. In this work, we present a microelectrode cell design that expands the experimental space addressable by microelectrodes to include mechanical pressure, gas flow and ionomer medium, and experimental throughput. The feasibility of the design is examined for fuel-cell reactions, with oxygen reduction currents independent of mechanical pressure and gas flowrate. Finally, cell equilibration time and IR drop across the electrolyte are estimated. The new cell design is robust and provides a consistent base from which to perform more complicated studies examining mass-transport properties of ionomers and/or the electrochemical reaction kinetics of hydrogen oxidation and oxygen reduction
Enacting Productive Dialogue: Addressing the Challenge that Non-Human Cognition Poses to Collaborations Between Enactivism and Heideggerian Phenomenology
This chapter uses one particular proposal for interdisciplinary collaboration – in this case, between early Heideggerian phenomenology and enactivist cognitive science – as an example of how such partnerships may confront and negotiate tensions between the perspectives they bring together. The discussion begins by summarising some of the intersections that render Heideggerian and enactivist thought promising interlocutors for each other. It then moves on to explore how Heideggerian enactivism could respond to the challenge of reconciling the significant differences in the ways that each discourse seeks to apply the structures it claims to uncover
The ToF and Trigger electronics of the PAMELA experiment
The PAMELA satellite-borne experiment, scheduled to be launched in 2004, is designed to provide a better understanding of the antimatter component of the cosmic rays. Its ToF scintillator system will provide the primary experimental trigger and time-of-flight particle identification. The time resolution requested is σ, < 120 ps. To fulfill the detector requirements the digitization electronics should have a time resolution ≤ 50 ps and provide a wide dynamic range for charge measurements. The peculiarity of the developed electronics arises from the need to obtain such a time resolution operating in a satellite environment, which implies low-power consumption, radiation hardness, redundancy and high reliability
Order parameter for two-dimensional critical systems with boundaries
Conformal transformations can be used to obtain the order parameter for
two-dimensional systems at criticality in finite geometries with fixed boundary
conditions on a connected boundary. To the known examples of this class (such
as the disk and the infinite strip) we contribute the case of a rectangle. We
show that the order parameter profile for simply connected boundaries can be
represented as a universal function (independent of the criticality model)
raised to the power eta/2. The universal function can be determined from the
Gaussian model or equivalently a problem in two-dimensional electrostatics. We
show that fitting the order parameter profile to the theoretical form gives an
accurate route to the determination of eta. We perform numerical simulations
for the Ising model and percolation for comparison with these analytic
predictions, and apply this approach to the study of the planar rotor model.Comment: 10 pages, 14 figures. Revisions: Removed many typos, improved
presentation of most of the figure
Very High Resolution Solar X-ray Imaging Using Diffractive Optics
This paper describes the development of X-ray diffractive optics for imaging
solar flares with better than 0.1 arcsec angular resolution. X-ray images with
this resolution of the \geq10 MK plasma in solar active regions and solar
flares would allow the cross-sectional area of magnetic loops to be resolved
and the coronal flare energy release region itself to be probed. The objective
of this work is to obtain X-ray images in the iron-line complex at 6.7 keV
observed during solar flares with an angular resolution as fine as 0.1 arcsec -
over an order of magnitude finer than is now possible. This line emission is
from highly ionized iron atoms, primarily Fe xxv, in the hottest flare plasma
at temperatures in excess of \approx10 MK. It provides information on the flare
morphology, the iron abundance, and the distribution of the hot plasma.
Studying how this plasma is heated to such high temperatures in such short
times during solar flares is of critical importance in understanding these
powerful transient events, one of the major objectives of solar physics. We
describe the design, fabrication, and testing of phase zone plate X-ray lenses
with focal lengths of \approx100 m at these energies that would be capable of
achieving these objectives. We show how such lenses could be included on a
two-spacecraft formation-flying mission with the lenses on the spacecraft
closest to the Sun and an X-ray imaging array on the second spacecraft in the
focal plane \approx100 m away. High resolution X-ray images could be obtained
when the two spacecraft are aligned with the region of interest on the Sun.
Requirements and constraints for the control of the two spacecraft are
discussed together with the overall feasibility of such a formation-flying
mission
Aspects of particle production in isospin asymmetric matter
The production/absorption rate of particles in compressed and heated
asymmetric matter is studied using a Relativistic Mean Field (RMF) transport
model with an isospin dependent collision term. Just from energy conservation
in the elementary production/absorption processes we expect to see a strong
dependence of the yields on the basic Lorentz structure of the isovector
effective interaction, due to isospin effects on the scalar and vector
self-energies of the hadrons. This will be particularly evident for the ratio
of the rates of particles produced with different charges: results are shown
for \pi(+)/\pi(-), K(+)/K(0) yields. In order to simplify the analysis we
perform RMF cascade simulations in a box with periodic boundary conditions. In
this way we can better pin down all such fine relativistic effects in particle
production, that could likely show up even in realistic heavy ion collisions.
In particular, K(+,0) production is expected to be directly related to the high
density behaviour of the symmetry energy, since kaons are produced very early
during the high density stage of the collision and their mean free path is
rather large. We show that the K(+)/K(0) ratio reflects important isospin
contributions on the production rates just because of the large sensitivity
around the threshold. The results are very promising for the possibility of a
direct link between particle production data in exotic Heavy Ion Collisions and
the isospin dependent part of the Equation of State at high baryon densities.Comment: 26 pages, 8 figures; Nucl.Phys. A, accepte
An advanced seismic network in the Southern Apennines (Italy) for seismicity investigations and experimentation with earthquake early warning.
The last strong earthquake that occurred in the southern Apennines, the Irpinia earthquake on 23 November 1980 (M 6.9), was characterized by a complex rupture mechanism that ruptured three different faults (Bernard and Zollo 1989). This earthquake was well studied, and the quantity of data available has allowed a very detailed definition of the geometry and mechanisms of faults activated during this seismic event (Westaway and Jackson 1987; Pantosti and Valensise 1990).
Even more than 20 years after the main event, the seismotectonic environment that contains the fault system on which the 1980 earthquake occurred shows continued background seismic activity including moderate-sized events such as the 1996 (M 5.1), 1991 (M 5.1) and 1990 (M 5.4) events. Moreover, the locations of the microearthquakes (taken from the database of the Istituto Nazionale di Geofisica e Vulcanologia, INGV) define an epicentral area with a geometry and extent surprisingly similar to that of the 1980 earthquake and its aftershocks (figure 1A). These simple observations suggest that it may be possible to study the preparation cycles of strong earthquakes on active faults by studying the microseismicity between seismic events. With this in mind, a seismic network of large dynamic range was planned and is now in an advanced phase of completion in the southern Apennines. Called ISNet (Irpinia Seismic Network), it is equipped with sensors that can record high-quality seismic signals from both small-magnitude and strong earthquakes, from which it will be possible to retrieve information about the rupture process and try to understand the scaling relationships between small and large events.
Due to its high density, wide dynamic range, and advanced data-acquisition and data-transmission technologies, the network is being upgraded to become the core infrastructure of a prototype system for seismic early warning and rapid post-event ground-shaking evaluation in the Campania region, which has seismic hazard that ranks among the highest in Italy (Cinti et al. 2004). ISNet will be devoted to real-time estimation of earthquake location and magnitude and to measuring peak ground-motion parameters so as to provide rapid ground-shaking maps for the whole of the Campania region. The information provided by ISNet during the first seconds of a potentially damaging seismic event can be used to activate several types of security measures, such as the shutdown of critical systems and lifelines (Iervolino et al. 2006).
The implementation of a modern seismic network involves many different research and technological aspects related to the development of sophisticated data management and processing. The communication systems need to rapidly generate useful, robust, and secure alert notifications. Here we provide a general technical and seismological overview of ISNet's complex architecture and implementation.Published622-6344.1. Metodologie sismologiche per l'ingegneria sismicaJCR Journalreserve
Direct mass measurements beyond the proton drip-line
First on-line mass measurements were performed at the SHIPTRAP Penning trap
mass spectrometer. The masses of 18 neutron-deficient isotopes in the
terbium-to-thulium region produced in fusion-evaporation reactions were
determined with relative uncertainties of about , nine of them
for the first time. Four nuclides (Ho and Tm) were
found to be proton-unbound. The implication of the results on the location of
the proton drip-line is discussed by analyzing the one-proton separation
energies
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