1,438 research outputs found
Test in a beam of large-area Micromegas chambers for sampling calorimetry
Application of Micromegas for sampling calorimetry puts specific constraints
on the design and performance of this gaseous detector. In particular, uniform
and linear response, low noise and stability against high ionisation density
deposits are prerequisites to achieving good energy resolution. A
Micromegas-based hadronic calorimeter was proposed for an application at a
future linear collider experiment and three technologically advanced prototypes
of 11 m were constructed. Their merits relative to the
above-mentioned criteria are discussed on the basis of measurements performed
at the CERN SPS test-beam facility
Internal convection in thermoelectric generator models
Coupling between heat and electrical currents is at the heart of
thermoelectric processes. From a thermal viewpoint this may be seen as an
additional thermal flux linked to the appearance of electrical current in a
given thermoelectric system. Since this additional flux is associated to the
global displacement of charge carriers in the system, it can be qualified as
convective in opposition to the conductive part associated with both phonons
transport and heat transport by electrons under open circuit condition, as,
e.g., in the Wiedemann-Franz relation. In this article we demonstrate that
considering the convective part of the thermal flux allows both new insight
into the thermoelectric energy conversion and the derivation of the maximum
power condition for generators with realistic thermal coupling.Comment: 8 pages, 3 figure
Poster 261: Increased Functional Connectivity between Pain‐Affect and Body‐Perception Brain Regions in Fibromyalgia
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146909/1/pmr2s217.pd
Electronic thermal transport in strongly correlated multilayered nanostructures
The formalism for a linear-response many-body treatment of the electronic
contributions to thermal transport is developed for multilayered
nanostructures. By properly determining the local heat-current operator, it is
possible to show that the Jonson-Mahan theorem for the bulk can be extended to
inhomogeneous problems, so the various thermal-transport coefficient integrands
are related by powers of frequency (including all effects of vertex corrections
when appropriate). We illustrate how to use this formalism by showing how it
applies to measurements of the Peltier effect, the Seebeck effect, and the
thermal conductance.Comment: 17 pages, 4 figures, submitted to Phys. Rev.
MICROMEGAS chambers for hadronic calorimetry at a future linear collider
Prototypes of MICROMEGAS chambers, using bulk technology and analog readout,
with 1x1cm2 readout segmentation have been built and tested. Measurements in
Ar/iC4H10 (95/5) and Ar/CO2 (80/20) are reported. The dependency of the
prototypes gas gain versus pressure, gas temperature and amplification gap
thickness variations has been measured with an 55Fe source and a method for
temperature and pressure correction of data is presented. A stack of four
chambers has been tested in 200GeV/c and 7GeV/c muon and pion beams
respectively. Measurements of response uniformity, detection efficiency and hit
multiplicity are reported. A bulk MICROMEGAS prototype with embedded digital
readout electronics has been assembled and tested. The chamber layout and first
results are presented
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Apportionment of primary and secondary organic aerosols in Southern California during the 2005 Study of Organic Aerosols in Riverside (SOAR-1)
Ambient sampling was conducted in Riverside, California during the 2005 Study of Organic Aerosols in Riverside to characterize the composition and sources of organic aerosol using a variety of state-of-the-art instrumentation and source apportionment techniques. The secondary organic aerosol (SOA) mass is estimated by elemental carbon and carbon monoxide tracer methods, water soluble organic carbon content, chemical mass balance of organic molecular markers, and positive matrix factorization of high-resolution aerosol mass spectrometer data. Estimates obtained from each of these methods indicate that the organic fraction in ambient aerosol is overwhelmingly secondary in nature during a period of several weeks with moderate ozone concentrations and that SOA is the single largest component of PM1 aerosol in Riverside. Average SOA/OA contributions of 70−90% were observed during midday periods, whereas minimum SOA contributions of ~45% were observed during peak morning traffic periods. These results are contrary to previous estimates of SOA throughout the Los Angeles Basin which reported that, other than during severe photochemical smog episodes, SOA was lower than primary OA. Possible reasons for these differences are discussed
On the Expressivity and Applicability of Model Representation Formalisms
A number of first-order calculi employ an explicit model representation
formalism for automated reasoning and for detecting satisfiability. Many of
these formalisms can represent infinite Herbrand models. The first-order
fragment of monadic, shallow, linear, Horn (MSLH) clauses, is such a formalism
used in the approximation refinement calculus. Our first result is a finite
model property for MSLH clause sets. Therefore, MSLH clause sets cannot
represent models of clause sets with inherently infinite models. Through a
translation to tree automata, we further show that this limitation also applies
to the linear fragments of implicit generalizations, which is the formalism
used in the model-evolution calculus, to atoms with disequality constraints,
the formalisms used in the non-redundant clause learning calculus (NRCL), and
to atoms with membership constraints, a formalism used for example in decision
procedures for algebraic data types. Although these formalisms cannot represent
models of clause sets with inherently infinite models, through an additional
approximation step they can. This is our second main result. For clause sets
including the definition of an equivalence relation with the help of an
additional, novel approximation, called reflexive relation splitting, the
approximation refinement calculus can automatically show satisfiability through
the MSLH clause set formalism.Comment: 15 page
Large Area Micromegas Chambers with Embedded Front-end Electronics for Hadron Calorimetry
AbstractMicromegas (Micro-mesh gaseous structure) is an attractive technology for applications in particle physics experiments (TPC, calorimeters, muon systems, etc.). The most important results of an extensive R&D program aiming to develop a new generation of a fine-grained hadron calorimeter with low power consumption digital readout using Micromegas chambers as an active element are presented. In 2010, the first large scale prototype of Micromegas chamber with almost 8000 readout channels has been built and tested with high energy particle beams at CERN. The fundamental results, such as detection effciency, hit multiplicity, gain stability, response uniformity and effect of power pulsing of the detector front-end electronics are reported. Eventually, the development and test of the second generation of the large scale prototype with new readout electronics and some important improvements of its mechanical design is described and the prospective towards the construction of a technological prototype of a 4.5 λ deep digital calorimeter for a future linear collider is also given
Resistive micromegas for sampling calorimetry
MicromegasInternational audienceMicromegas is an attractive option for a gaseous sampling calorimeter. It delivers proportional and fast signals, achieves high efficiency to minimum ionising particles with a compact design and shows well-uniform performance over meter-square areas. The current R&D focuses on large- size spark-protected Micromegas with integrated front-end electronics. It targets an application at future linear colliders (LC) and possible upgrades of LHC experiments for the running at high luminosity. In the later case, occasional sparking should be suppressed to avoid dead-time and technical solutions using resistive coatings are investigated. Small prototypes of resistive and non-resistive Micromegas were constructed and tested in a beam at DESY. Results are reported with emphasis on the impact of the resistive layer on the detector performance
Resting state cortico-cerebellar functional connectivity networks: a comparison of anatomical and self-organizing map approaches.
The cerebellum plays a role in a wide variety of complex behaviors. In order to better understand the role of the cerebellum in human behavior, it is important to know how this structure interacts with cortical and other subcortical regions of the brain. To date, several studies have investigated the cerebellum using resting-state functional connectivity magnetic resonance imaging (fcMRI; Krienen and Buckner, 2009; O'Reilly et al., 2010; Buckner et al., 2011). However, none of this work has taken an anatomically-driven lobular approach. Furthermore, though detailed maps of cerebral cortex and cerebellum networks have been proposed using different network solutions based on the cerebral cortex (Buckner et al., 2011), it remains unknown whether or not an anatomical lobular breakdown best encompasses the networks of the cerebellum. Here, we used fcMRI to create an anatomically-driven connectivity atlas of the cerebellar lobules. Timecourses were extracted from the lobules of the right hemisphere and vermis. We found distinct networks for the individual lobules with a clear division into "motor" and "non-motor" regions. We also used a self-organizing map (SOM) algorithm to parcellate the cerebellum. This allowed us to investigate redundancy and independence of the anatomically identified cerebellar networks. We found that while anatomical boundaries in the anterior cerebellum provide functional subdivisions of a larger motor grouping defined using our SOM algorithm, in the posterior cerebellum, the lobules were made up of sub-regions associated with distinct functional networks. Together, our results indicate that the lobular boundaries of the human cerebellum are not necessarily indicative of functional boundaries, though anatomical divisions can be useful. Additionally, driving the analyses from the cerebellum is key to determining the complete picture of functional connectivity within the structure
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