260 research outputs found
Significance Tests for Periodogram Peaks
We discuss methods currently in use for determining the significance of peaks
in the periodograms of time series. We discuss some general methods for
constructing significance tests, false alarm probability functions, and the
role played in these by independent random variables and by empirical and
theoretical cumulative distribution functions. We also discuss the concept of
"independent frequencies" in periodogram analysis. We propose a practical
method for estimating the significance of periodogram peaks, applicable to all
time series irrespective of the spacing of the data. This method, based on
Monte Carlo simulations, produces significance tests that are tailor-made for
any given astronomical time series.Comment: 22 pages, 11 Encapsulated Postscript figures, AAS LaTeX v5.2
Submitted to Ap
4pi Models of CMEs and ICMEs
Coronal mass ejections (CMEs), which dynamically connect the solar surface to
the far reaches of interplanetary space, represent a major anifestation of
solar activity. They are not only of principal interest but also play a pivotal
role in the context of space weather predictions. The steady improvement of
both numerical methods and computational resources during recent years has
allowed for the creation of increasingly realistic models of interplanetary
CMEs (ICMEs), which can now be compared to high-quality observational data from
various space-bound missions. This review discusses existing models of CMEs,
characterizing them by scientific aim and scope, CME initiation method, and
physical effects included, thereby stressing the importance of fully 3-D
('4pi') spatial coverage.Comment: 14 pages plus references. Comments welcome. Accepted for publication
in Solar Physics (SUN-360 topical issue
Sense of entitlement to support for the reconciliation of employment and family life
This article explores young European women and men’s expectations of support - from the state and employers - for reconciling paid employment and family life. It is based on a qualitative study employing focus groups with young women and men in Norway, Sweden, Portugal, Ireland and the UK. Drawing on the concept of sense of entitlement, derived from social justice theory, it was expected that the type of welfare state and ‘gender contract’ that young adults have experienced will influence their sense of entitlement to support for work and family life. Findings indicate that participants perceived their entitlement to state and employer support differently across national context. However this is moderated by gender, parental and occupational status, and particularly by awareness of provisions in other countries in the case of state support, while perceived entitlement to employer support varies according to the specific policy considered, gender and perception of benefits to employers. Some implications for public policy makers and employers are discussed
Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET
The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR
Thermomechanical erosion modelling of Baydaratskaya Bay, Russia with COSMOS
Rapid coastal erosion threatens Arctic coastal infrastructure, including communities and industrial installations. Erosion of permafrost depends on numerous processes, including thermal and mechanical behaviour of frozen and unfrozen soil, nearshore hydrodynamics, atmospheric forcing, and the presence of sea ice. The quantification and numerical modelling of these processes is essential to predicting Arctic coastal erosion. This paper presents a case study of Baydaratskaya Bay, Russia, using the COSMOS numerical model to predict thermal-mechanical erosion. In particular, this study focuses on thermoabrasional rather than thermodenudational processes. A field dataset of onshore thermal and mechanical soil characteristics was supplemented by sources from the literature to serve as input for the model. A detailed sensitivity analysis has been conducted to determine the influence of key parameters on coastal erosion rates at the study site. This case study highlights the need for expanded data collection on Arctic coastlines and provides direction for future investigations
Ammonite Faunal Dynamics Across Bio-Events During the Mid-and Late Cretaceous Along the Russian Pacific Coast
Jagt−Yazykova, E.A. 2012. Ammonite faunal dynamics across bio−events during the mid − and Late Cretaceous along th
Star clusters near and far; tracing star formation across cosmic time
© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00690-x.Star clusters are fundamental units of stellar feedback and unique tracers of their host galactic properties. In this review, we will first focus on their constituents, i.e.\ detailed insight into their stellar populations and their surrounding ionised, warm, neutral, and molecular gas. We, then, move beyond the Local Group to review star cluster populations at various evolutionary stages, and in diverse galactic environmental conditions accessible in the local Universe. At high redshift, where conditions for cluster formation and evolution are more extreme, we are only able to observe the integrated light of a handful of objects that we believe will become globular clusters. We therefore discuss how numerical and analytical methods, informed by the observed properties of cluster populations in the local Universe, are used to develop sophisticated simulations potentially capable of disentangling the genetic map of galaxy formation and assembly that is carried by globular cluster populations.Peer reviewedFinal Accepted Versio
Nocardia infection in renal transplant recipient: diagnostic and therapeutic considerations
Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents
An Observational Overview of Solar Flares
We present an overview of solar flares and associated phenomena, drawing upon
a wide range of observational data primarily from the RHESSI era. Following an
introductory discussion and overview of the status of observational
capabilities, the article is split into topical sections which deal with
different areas of flare phenomena (footpoints and ribbons, coronal sources,
relationship to coronal mass ejections) and their interconnections. We also
discuss flare soft X-ray spectroscopy and the energetics of the process. The
emphasis is to describe the observations from multiple points of view, while
bearing in mind the models that link them to each other and to theory. The
present theoretical and observational understanding of solar flares is far from
complete, so we conclude with a brief discussion of models, and a list of
missing but important observations.Comment: This is an article for a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
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