5,257 research outputs found
Early Standard Model measurements with ATLAS
The measurement of Standard Model processes will be an important first step
towards exploiting the discovery potential of the Large Hadron Collider, the
highest energy accelerator ever built that will begin operation in the fall
2009. This paper presents a summary of the early physics analyses for
understanding the performance of the detector as well as the Standard Model at
the ATLAS experiment at 14 TeV centre of mass energy
FMCW Radar Performance for Atmospheric Measurements
Frequency-modulated continuous-wave radars (FMCW) have been used in the investigation of the atmosphere since the late 1960ās. FMCW radars provide tremendous sensitivity and spatial resolution compared to their pulsed counterparts and are therefore attractive for clear-air remote-sensing applications. However, these systems have some disadvantages and performance limitations that have prevented their widespread use by the atmospheric science community. In this study, system performance of atmospheric FMCW radar is analyzed and some measurement limitations for atmospheric targets are discussed. The effects of Doppler velocities and spectral widths on radar performance, radarās near-field operation, and parallax errors for two-antenna radar systems are considered. Experimental data collected by the highresolution atmospheric FMCW radar is used to illustrate typical performance qualitatively based on morphological backscattered power information. A post-processing based on single-lag covariance differences between the Bragg and Rayleigh echo is applied to estimate clear-air component from refractive index turbulence and perform quantitative analysis of FMCW radar reflectivity from atmospheric targets
Prospects for probing the structure of the proton with low-mass Drell-Yan events in ATLAS
The biggest scientific experiment in history will begin taking data in late 2009 using the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland. The LHC is designed to collide protons at an unprecedented 14 TeV centre of mass energy, enabling physicists to explore the constituents of matter at smaller scales than ever before. The Parton Distribution Functions (PDFs) are parametrizations of the proton structure and are best determined from experimental data. The PDFs are needed to calculate cross-sections or in other words the likelihood of observed physical processes, which are crucial in exploiting the discovery potential of the LHC. The prospects for measuring the Drell-Yan (DY) spectrum are assessed in the low invariant mass region below the Z boson resonance using electron-positron pairs from the initial LHC data in order to probe the proton structure and further constrain the PDFs. The analysis is based on the full simulation of the ATLAS detector response to DY electrons and background processes. Assuming 100 pb^{-1} of LHC data, the total DY cross-section in the invariant mass range from 10 GeV to 60 GeV is expected to be measured as sigma_{DY} = 5.90 pm 0.24(stat) pm 0.18(syst) nb. The result predicts an improvement over a current theoretical uncertainty of 7.6% and indicates that the PDF uncertainties can be reduced significantly with the early LHC data
Analyzing risk factors for lumpy skin disease by a geographic information system (GIS) in Turkey
ĪĪĪ ĪĪĪĪ¤ĪĪĪĪ¤ĪĪ Ī ĪĪ”ĪĪĪĪØĪLumpy skin disease (LSD) is caused by the virus of the same name and has major economic impacts on cattle breeding. In Turkey, frequent cases of cattle LSD have been reported over the last years. The present study aimed to analyze potential risk factors for LSD and provide information for controlling the spread of infectious diseases by a geographic information system (GIS). The research included cross-sectional and retrospective studies with active disease follow-up and semi-structured interviews (SSI) from August 2013 to December 2014 in Turkey. Potential risk factors for LSD were evaluated based on environmental conditions and provincial demographic and epidemiological data. Of the total of 562 observed animals, 27.22% and 2.67% of cattle were sick and died due to LSD, respectively. The morbidity rate was 26.04% in mixed and 38.18% in local breeds. The animal-level prevalence significantly differed among animals of different age, sex, and with different vaccination status (P<0.05). It was more serious in younger animals and females and during drier weather conditions. A trend of seasonality was observed in LSD occurrence. Significant risk factors affecting the prevalence of LSD were proximity to the southern border of Turkey, animal movements, and animal markets. In this process, geographical query, analysis, and thematic map production were performed by GIS
Leadership
The EYFS offers leadership challenges within ECEC which are profound and challenging, but not wholly unique to the sector. In other words, there are common features of leadership that apply to all phases of education, but it is recognised that there are specific issues relating to ECEC. This chapter explores those challenges to help identify responses which are appropriate to the sector. The chapter begins by exploring the complexity of ECEC provision in England to identify leadership and management responsibilities within the system. The key role is identified as the formal leader of settings with more than one employee. Differences between leadership and management are discussed, as is leadership as a set of social behaviours. This definition, which extends the simple measure of accountability for formal managers, allows for the exploration of shared or collective leadership approaches to creating and sustaining effective learning environments as well as ensuring the safety and welfare of young children. The discussion then moves towards identifying organisational structures and behaviours which support such ambitions. Issues specific to the sector, such as multi-agency working and a heavily gendered workforce, are explored in the context of leadership theories to guide practitioners as to their role. The chapter closes with some practical tips as to how to move beyond the notion of single accountable executive towards collective and connective leadership within each setting. This chapter aims to to: ā¢ Explore issues about leadership in relation to ECEC; ā¢ Discuss different styles of leadership and reflect on the core values that underpin ECEC; ā¢ Discuss leadership in settings in relation to contributing factors that correspond to the share value system
Root asymptotics of spectral polynomials for the Lame operator
The study of polynomial solutions to the classical Lam\'e equation in its
algebraic form, or equivalently, of double-periodic solutions of its
Weierstrass form has a long history. Such solutions appear at integer values of
the spectral parameter and their respective eigenvalues serve as the ends of
bands in the boundary value problem for the corresponding Schr\"odinger
equation with finite gap potential given by the Weierstrass -function on
the real line. In this paper we establish several natural (and equivalent)
formulas in terms of hypergeometric and elliptic type integrals for the density
of the appropriately scaled asymptotic distribution of these eigenvalues when
the integer-valued spectral parameter tends to infinity. We also show that this
density satisfies a Heun differential equation with four singularities.Comment: final version, to appear in Commun. Math. Phys.; 13 pages, 3 figures,
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Nonlocal symmetries of Riccati and Abel chains and their similarity reductions
We study nonlocal symmetries and their similarity reductions of Riccati and
Abel chains. Our results show that all the equations in Riccati chain share the
same form of nonlocal symmetry. The similarity reduced order ordinary
differential equation (ODE), , in this chain yields
order ODE in the same chain. All the equations in the Abel chain also share the
same form of nonlocal symmetry (which is different from the one that exist in
Riccati chain) but the similarity reduced order ODE, , in
the Abel chain always ends at the order ODE in the Riccati chain.
We describe the method of finding general solution of all the equations that
appear in these chains from the nonlocal symmetry.Comment: Accepted for publication in J. Math. Phy
On convergence towards a self-similar solution for a nonlinear wave equation - a case study
We consider the problem of asymptotic stability of a self-similar attractor
for a simple semilinear radial wave equation which arises in the study of the
Yang-Mills equations in 5+1 dimensions. Our analysis consists of two steps. In
the first step we determine the spectrum of linearized perturbations about the
attractor using a method of continued fractions. In the second step we
demonstrate numerically that the resulting eigensystem provides an accurate
description of the dynamics of convergence towards the attractor.Comment: 9 pages, 5 figure
Lagrangian Formalism for nonlinear second-order Riccati Systems: one-dimensional Integrability and two-dimensional Superintegrability
The existence of a Lagrangian description for the second-order Riccati
equation is analyzed and the results are applied to the study of two different
nonlinear systems both related with the generalized Riccati equation. The
Lagrangians are nonnatural and the forces are not derivable from a potential.
The constant value of a preserved energy function can be used as an
appropriate parameter for characterizing the behaviour of the solutions of
these two systems. In the second part the existence of two--dimensional
versions endowed with superintegrability is proved. The explicit expressions of
the additional integrals are obtained in both cases. Finally it is proved that
the orbits of the second system, that represents a nonlinear oscillator, can be
considered as nonlinear Lissajous figuresComment: 25 pages, 7 figure
Differentiation of dementia with Lewy bodies from Alzheimer's disease using a dopaminergic presynaptic ligand
Background: Dementia with Lewy bodies (DLB) is one of the main differential diagnoses of Alzheimer's disease (AD). Key pathological features of patients with DLB are not only the presence of cerebral cortical neuronal loss, with Lewy bodies in surviving neurones, but also loss of nigrostriatal dopaminergic neurones, similar to that of Parkinson's disease (PD). In DLB there is 40-70% loss of striatal dopamine.Objective: To determine if detection of this dopaminergic degeneration can help to distinguish DLB from AD during life.Methods: The integrity of the nigrostriatal metabolism in 27 patients with DLB, 17 with AD, 19 drug naive patients with PD, and 16 controls was assessed using a dopaminergic presynaptic ligand, I-123-labelled 2beta-carbomethoxy-3beta-(4-iodophenyl)-N-(3-fluoropropyl)nortropane (FP-CIT), and single photon emission tomography (SPET). A SPET scan was carried out with a single slice, brain dedicated tomograph (SME 810) 3.5 hours after intravenous injection of 185 MBq FP-CIT. With occipital cortex used as a radioactivity uptake reference, ratios for the caudate nucleus and the anterior and posterior putamen of both hemispheres were calculated. All scans were also rated by a simple visual method.Results: Both DLB and PD patients had significantly lower uptake of radioactivity than patients with (p<0.01) and controls (p<0.001) in the caudate nucleus and the anterior and posterior Putamen.Conclusion: FP-CIT SPET provides a means of distinguishing DLB from AD during life
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