6,298 research outputs found
On Higher Derivatives as Constraints in Field Theory: a Geometric Perspective
We formalize geometrically the idea that the (de Donder) Hamiltonian
formulation of a higher derivative Lagrangian field theory can be constructed
understanding the latter as a first derivative theory subjected to constraints.Comment: 7 page
Exact infinite-time statistics of the Loschmidt echo for a quantum quench
The equilibration dynamics of a closed quantum system is encoded in the
long-time distribution function of generic observables. In this paper we
consider the Loschmidt echo generalized to finite temperature, and show that we
can obtain an exact expression for its long-time distribution for a closed
system described by a quantum XY chain following a sudden quench. In the
thermodynamic limit the logarithm of the Loschmidt echo becomes normally
distributed, whereas for small quenches in the opposite, quasi-critical regime,
the distribution function acquires a universal double-peaked form indicating
poor equilibration. These findings, obtained by a central limit theorem-type
result, extend to completely general models in the small-quench regime.Comment: 4 pages, 2 figure
The Assembly of the LHC Short Straight Sections at CERN: Work Organization, Quality Assurance and Lessons Learned
After 4 years of activity, the assembly of approximately 500 Short Straight Sections (SSS) for the LHC has come to an end at the beginning of 2007. This activity, which was initially foreseen in European industry, was in-sourced at CERN because of the insolvency of the prime contractor. While the quadrupole cold masses were produced in industry, the assembly within their cryostats was transferred to CERN and executed by an external company under a result-oriented contract. CERN procured cryostat components, set up a dedicated 2000 m2 assembly hall with all the specific assembly equipment and tooling and defined the assembly and testing procedures. The contractor took up responsibility for the delivery, on time, of assemblies according to the required quality. A dedicated CERN production and quality assurance team was constituted. A specific quality assurance plan was set up involving 2 additional contractors responsible for weld inspections on a total of about 20'000 assembly welds and the execution of about 3300 leak detection tests. This paper presents the organizational aspects of the activity and the experience gained throughout the production. The learning curves and statistics by type of non-conformities detected and general quality assurance aspects are presented and discussed. The main lessons learnt are summarized, in an attempt to draw some conclusions which could be useful in making strategic choices for the cryostat assembly in future large-scale accelerators
BR-5133 (MILHACRE): milho precoce para cultivo no Estado do Acre.
A época de plantio de milho no Estado do Acre concentra-se da segunda quinzena de setembro ao final de outubro, período de início das chuvas. A precipitação pluviométrica anual situa-se e, torno de 2000mm, distribuída de outubro a maio. No Acre, embora em pequena escala, os produtores praticam um segundo cultivo de março a julho, sem necessidade de irrigação suplementar. Este plantio, se efetuado com base técnica e material genético melhorado, adaptado às condições edafoclimáticas locais, propiciará vantagens tão consideráveis para os agricultores, que resultará na intensificação do cultivo do milho nessa época e, consequentemente, aumento da produção do Estado.bitstream/item/81150/1/CPAF-AC-COM.-TEC.-61-95.pd
New properties of scalar field dynamics in brane isotropic cosmological models
Several aspects of scalar field dynamics on a brane which differs from
corresponding regimes in the standard cosmology are investigated. We consider
asymptotic solution near a singularity, condition for inflation and bounces and
some detail of chaotic behavior in the brane model. Each results are compared
with those known in the standard cosmology.Comment: 13 pages with 2 eps figures, submitted to Astronomy Letter
Behavioral types in programming languages
A recent trend in programming language research is to use behav- ioral type theory to ensure various correctness properties of large- scale, communication-intensive systems. Behavioral types encompass concepts such as interfaces, communication protocols, contracts, and choreography. The successful application of behavioral types requires a solid understanding of several practical aspects, from their represen- tation in a concrete programming language, to their integration with other programming constructs such as methods and functions, to de- sign and monitoring methodologies that take behaviors into account. This survey provides an overview of the state of the art of these aspects, which we summarize as the pragmatics of behavioral types
A Giant Hand Lipoma As a Rare Cause of Secondary Carpal Tunnel Syndrome - a Case Report
Introduction: Lipomas are a rare cause of compressive neuropathy and they lead to atypical clinical presentation that can mimic carpal tunnel syndrome.
Case presentation: The authors describe a rare presentation of a carpal tunnel syndrome recurrence after a hand giant lipoma, presenting with rapidly compression neuropathy of the median nerve, 6 months after de primary surgery.
Discussion: Lipomas are common benign soft tumours. Their occurrence in the hand remains rare and they rarely cause secondary entrapment neuropathies. Carpal tunnel syndrome is mostly idiopathic and bilateral. Local factors should be suspected when these neuropathies present with atypical symptomatology or even when they recur after primary conventional surgical release. Investigation should consider images studies as this correct preoperative assessment leads to successful diagnosis and treatment.info:eu-repo/semantics/publishedVersio
Combining airborne gas and aerosol measurements with HYSPLIT: a visualization tool for simultaneous evaluation of air mass history and back trajectory consistency
The history of air masses is often investigated using backward trajectories
to gain knowledge about processes along the air parcel path as well as
possible source regions. Here, we describe a refined approach that
incorporates airborne gas, aerosol, and environmental data into back
trajectories and show how this technique allows for simultaneous evaluation
of air mass history and back trajectory reliability without the need to
calculate trajectory errors.
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We use the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT)
model and add a simple semi-automated computing routine to facilitate
high-frequency coverage of back trajectories initiated along free
tropospheric (FT) flight tracks and profiles every 10 s. We integrate our in
situ physiochemical data by color-coding each of these trajectories with its
corresponding in situ tracer values measured at the back trajectory start
points along the flight path. The unique color for each trajectory aids
assessment of trajectory reliability through the visual clustering of air
mass pathways of similar coloration.
Moreover, marked changes in trajectories associated with marked changes evident
in measured physiochemical or thermodynamic properties of an air mass add credence
to trajectories. This is particularly true when these air mass properties are
linked to trajectory features characteristic of recognized sources or processes.
This visual clustering of air mass pathways is of particular value for large-scale 3-D flight tracks
common to aircraft experiments where air mass features of interest are often
spatially distributed and temporally separated.
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The cluster-visualization tool used here reveals that most FT back
trajectories with pollution signatures measured in the central equatorial
Pacific reach back to sources on the South American continent over
10 000 km away and 12 days back in time, e.g., the Amazonian basin. We also
demonstrate the distinctions in air mass properties between these and
trajectories that penetrate deep convection in the Inter-Tropical Convergence
Zone. Additionally, for the first time we show consistency of modeled
precipitation along back trajectories with scavenging signatures in the
aerosol measured for these trajectories
Estudo comparativo da distribuição espacial de duas espécies arbóreas: maçaranduba (Manilkar huberi (Ducke) Cheval) e Tauari (Couratari guianensis) existentes no Jardim Botânico Bosque Rodrigues Alves.
Distribuição espacial de Vouacapoua americana Aubl. (acapú), em um fragmento de floresta urbana, Jardim Botânico Bosque Rodrigues Alves.
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