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Third‐Order Structure Functions of Zonal Winds in the Thermosphere Using CHAMP and GOCE Observations
2024
We use multi‐year observations of cross‐track winds (u) from the CHAllenging Minisatellite Payload (CHAMP) and the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) to calculate third‐order structure functions in the thermosphere as a function of horizontal separation (s). They are computed using the mean (〈δu3〉) and the median 〈δu3〉med$\\left({\\langle \\delta {u}^{3}\\rangle }_{\\text{med}}\\right)$and implemented over non‐polar satellite paths in both hemispheres. On height averages, 〈δu3〉 is shown to scale with s2 for s ≃ 80–1,000 km, in agreement with equivalent estimates in the lower atmosphere from aircraft observations. Conversely, 〈δu3〉med${\\langle \\delta {u}^{3}\\rangle }_{\\text{med}}$follows an s3 power law for almost the whole s range, consistent with the two‐dimensional turbulence scaling law for a direct enstrophy cascade. These scaling laws appear independent of winds in distinct atmospheric regions. Furthermore, the functions are predominantly positive, indicating a preferential cyclonic motion for the wind. Plain Language Summary The dynamics of upper atmosphere winds differ significantly from those at lower altitudes, with larger magnitudes and increased sensitivity to solar events. Satellites, especially those in polar orbits, offer an effective means of studying these winds, particularly their East‐West component. To mitigate the chaotic nature of individual measurements influenced by various physical processes, it is common to compute wind averages. A particular way of doing this is by calculating the so‐called third‐order structure functions (SFs), a statistical quantity that provides information on the underlying turbulence processes. The third‐order SFs of satellites' zonal wind observations present two main characteristics. First, they are consistently positive, predicting a preferential cyclonic rotational motion. This is, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Second, and more importantly, the functions display the same type of dependence on the horizontal distance as third‐order SFs of winds in the lower atmosphere. This suggests that similar underlying large‐scale turbulence mechanisms may be at play. Key Points Third‐order structure functions of zonal winds in the thermosphere at mid‐ and low‐ to mid‐latitudes are calculated Meso‐ and Synoptic‐scale structures share a preferential cyclonic motion in the thermosphere Measured scaling laws of third‐order structure functions seem to be independent of the atmospheric region
Journal Article
Gravity and Magnetic Exploration
by
Hinze, William J.
,
von Frese, Ralph R. B.
,
Saad, Afif H.
in
Geomagnetism
,
Gravity
,
Gravity -- Measurement
2012,2013
This combination of textbook and reference manual provides a comprehensive account of gravity and magnetic methods for exploring the subsurface using surface, marine, airborne and satellite measurements. It describes key current topics and techniques, physical properties of rocks and other earth materials, and digital data analysis methods used to process and interpret anomalies for subsurface information. Each chapter starts with an overview and concludes by listing key concepts to consolidate new learning. An accompanying website presents problem sets and interactive computer-based exercises, providing hands-on experience of processing, modeling and interpreting data. A comprehensive online suite of full-color case histories illustrates the practical utility of modern gravity and magnetic surveys. This is an ideal text for advanced undergraduate and graduate courses and reference text for research academics and professional geophysicists. It is a valuable resource for all those interested in petroleum, engineering, mineral, environmental, geological and archeological exploration of the lithosphere.
Knot invariants and higher representation theory
by
Webster, Ben
in
Knot theory
2017
We construct knot invariants categorifying the quantum knot variants for all representations of quantum groups. We show that these
invariants coincide with previous invariants defined by Khovanov for
Our technique is
to study 2-representations of 2-quantum groups (in the sense of Rouquier and Khovanov-Lauda) categorifying tensor products of
irreducible representations. These are the representation categories of certain finite dimensional algebras with an explicit
diagrammatic presentation, generalizing the cyclotomic quotient of the KLR algebra. When the Lie algebra under consideration is
We also
investigate the finer structure of these categories: they are standardly stratified and satisfy a double centralizer property with
respect to their self-dual modules. The standard modules of the stratification play an important role as test objects for functors, as
Vermas do in more classical representation theory.
The existence of these representations has consequences for the structure of
previously studied categorifications. It allows us to prove the non-degeneracy of Khovanov and Lauda’s 2-category (that its Hom spaces
have the expected dimension) in all symmetrizable types, and that the cyclotomic quiver Hecke algebras are symmetric Frobenius.
In work of Reshetikhin and Turaev, the braiding and (co)evaluation maps between representations of quantum groups are used to define
polynomial knot invariants. We show that the categorifications of tensor products are related by functors categorifying these maps,
which allow the construction of bigraded knot homologies whose graded Euler characteristics are the original polynomial knot
invariants.
Static Magnetic Fields and Their Effects
This book consists of seven chapters which that study the useful effects of static magnetic fields. The first chapter focuses on microscopic effects of uniform magnetic fields on simple organic systems like proteins, polymers, and cells where the aim of the study was to show (both experimentally and theoretically) the strength of static magnetic fields which that can overcome angular momentum from molecular thermal agitation of macromolecules, giving accurate explanation at the microscopic level of macroscopic effects of static magnetic fields. In this same direction, the second chapter deepens the discussion by explaining a very important effect of static magnetic fields on cells concerning the activation of voltage-gated calcium and sodium channels induced by static magnetic fields., explaining how also Also explained is how this effect can find its theoretical explanation and can be used for therapeutic purpose, showing possible beneficial effects from static magnetic fields. In the third chapter, effects of uniform magnetic fields on typical cells are also discussed, highlighting both harmful effects represented by alterations in ROS production and beneficial effects induced by stimulation with static magnetic fields at the cellular level. Possible beneficial effects of static magnetic fields were also highlighted in the fourth chapter in which spectroscopic observations of the response to static magnetic fields of Tau and Creb proteins in brain can be used to detect degenerative diseases and study the memory mechanism. In the fifth chapter, the response to static magnetic fields of chromosomal mechanism in the mitoses of some plant roots was shown, and an interesting hypothesis of a correlation between geological magnetic fields and evolutionary mechanisms during early phases of evolution was proposed. In the sixth chapter, a theoretical discussion on the effects of a uniform magnetic field on two-phase dielectric flows of fluids and the dynamics of bubbles under an applied uniform magnetic field was shown, that which is important in advanced applications such as the cooling system of nuclear fusion reactors. Finally, further beneficial effect of static magnetic fields was discussed in the seventh chapter, represented by using static magnetic pulses in magnetotherapy for regeneration in extreme physical activity.
Risk and Responsibility
by
Leiss, William
,
Chociolko, Christina
in
Champs électromagnétiques -- Aspect hygiénique
,
Champs électromagnétiques ELF -- Aspect hygiénique
,
Electromagnetic fields
1994
William Leiss and Christina Chociolko explain that controversies arise in part because many participants try to avoid assuming full responsibility for the consequences of the risk-taking they advocate. For example, one can indulge in the pleasure of nicotine addiction despite an awareness of the health risks and count on a publicly funded health care system to assume the responsibility for dealing with the resulting illnesses. They provide detailed case studies of the controversies over the effects of exposure to power frequency electric and magnetic fields and to the chemical pesticides alar and antisapstains. Shorter studies of exposure to tobacco, formaldehyde, and the pesticide alachlor are also presented. The authors address the difficulties of arriving at reliable scientific estimates of risk in such controversial areas, and the impact of this uncertainty on disagreements among different interest groups over how to manage those risks responsibly.
Lectures on Quantum Field Theory
2024,2025
The book covers the material of the two-semester course of quantum field theory that the author taught at Charles University and Czech Technical University in Prague for more than two decades. In the individual chapters one may find discussion of selected topics in relativistic quantum mechanics and relativistic quantum field theory; the dominant theme is quantum electrodynamics. The technique of Feynman diagrams is described in detail, as well as methods of regularization and renormalization, including some basic applications. The selection of the topics presented in the book is intended to provide the reader with the technical skills necessary for a subsequent study of theoretical particle physics. The text contains a lot of detailed explicit calculations in an extent not quite common in other available sources and this corresponds to the contents of the author’s lectures. The readership is supposed to consist primarily of university students specializing in theoretical physics or nuclear and particle physics, but the publication may also be useful to any scientifically-minded reader seriously interested in the foundations of modern physics.
Statistical Approach to Quantum Field Theory
by
Wipf, Andreas
in
Complex Systems
,
Elementary Particles, Quantum Field Theory
,
Field theory (Physics)
2013
This book opens with a self-contained introduction to path integrals in Euclidean quantum mechanics and statistical mechanics, and moves on to cover lattice field theory, spin systems, gauge theories and more. Each chapter ends with illustrative problems.
CM6: a comprehensive geomagnetic field model derived from both CHAMP and Swarm satellite observations
by
Sabaka, Terence J
,
Tøffner-Clausen Lars
,
Olsen, Nils
in
Constituents
,
Geomagnetic field
,
Geomagnetism
2020
From the launch of the Ørsted satellite in 1999, through the CHAMP mission from 2000 to 2010, and now with the Swarm constellation mission starting in 2013, satellite magnetometry has provided excellent monitoring of the near-Earth magnetic field regime. The advanced Comprehensive Inversion scheme has been applied to data before Swarm and to the Swarm data itself, but now for the first time to all the satellite data in this new era, culminating in the CM6 model. The highlights of this model include not only a continuous core magnetic field description over the entire time period 1999 to 2019.5 in good agreement with the CHAOS model series, but the addition of two new oceanic tidal magnetic sources: the larger lunar elliptic semi-diurnal constituent N2 and the lunar diurnal constituent O1. CM6 is also the parent model of the NASA/GSFC candidates for the DGRF2015 and IGRF2020 in response to the IGRF-13 call. This paper provides a full report on the development of CM6.
Journal Article
Epigenome-wide association studies: current knowledge, strategies and recommendations
by
Maltby, Vicky
,
Lechner-Scott, Jeannette
,
Scott, Rodney J.
in
Analysis
,
Biomedical and Life Sciences
,
Biomedicine
2021
The aetiology and pathophysiology of complex diseases are driven by the interaction between genetic and environmental factors. The variability in risk and outcomes in these diseases are incompletely explained by genetics or environmental risk factors individually. Therefore, researchers are now exploring the epigenome, a biological interface at which genetics and the environment can interact. There is a growing body of evidence supporting the role of epigenetic mechanisms in complex disease pathophysiology. Epigenome-wide association studies (EWASes) investigate the association between a phenotype and epigenetic variants, most commonly DNA methylation. The decreasing cost of measuring epigenome-wide methylation and the increasing accessibility of bioinformatic pipelines have contributed to the rise in EWASes published in recent years. Here, we review the current literature on these EWASes and provide further recommendations and strategies for successfully conducting them. We have constrained our review to studies using methylation data as this is the most studied epigenetic mechanism; microarray-based data as whole-genome bisulphite sequencing remains prohibitively expensive for most laboratories; and blood-based studies due to the non-invasiveness of peripheral blood collection and availability of archived DNA, as well as the accessibility of publicly available blood-cell-based methylation data. Further, we address multiple novel areas of EWAS analysis that have not been covered in previous reviews: (1) longitudinal study designs, (2) the chip analysis methylation pipeline (ChAMP), (3) differentially methylated region (DMR) identification paradigms, (4) methylation quantitative trait loci (methQTL) analysis, (5) methylation age analysis and (6) identifying cell-specific differential methylation from mixed cell data using statistical deconvolution.
Journal Article
Solar Terminator Waves Revealed as Dominant Features of Upper Thermospheric Density
2025
Observations of solar terminator waves (STWs) in thermospheric mass density (TMD) measurements above 500 km reveal STWs as dominant features of the upper thermosphere. While previous investigations have shown that STWs in the middle‐lower thermosphere have amplitudes on the order of 6%–8% of the background TMD in that region, this study shows that STWs exhibit a striking amplification with altitude, producing density perturbations of up to a factor of two near 500 km. The study analyzes STWs in TMD data across altitude, solar cycle, and both solstices, leveraging a direct comparative methodology with Challenging Minisatellite Payload, Gravity Recovery and Climate Experiment Follow‐On, and High‐Accuracy Satellite Drag Model. The first detection of a dawn STW with a magnitude comparable to dusk is made near 500 km, contrasting the asymmetry seen at lower altitudes. The newfound prominence of STWs highlights the need for further research into their generation mechanisms, role in geophysical variability, and broader implications for thermospheric modeling and spacecraft operations. Plain Language Summary The thermosphere, home to the majority of orbiting spacecraft, is a complex and dynamic region subject to disturbances from a variety of energy sources. Recent attention has been given to thermospheric perturbations known as “solar terminator waves” (STWs), which propagate westward with the solar terminator in the form of bow or wake waves. This study investigates these features by comparing observations of thermospheric mass density (TMD) from two well‐established satellite missions with the United States Space Force's operational TMD prediction model. Through a novel global comparison method, this analysis presents the first characterization of STWs in TMD observations near 500 km altitude, detailing amplitudes which reach up to a factor of two relative to the background density. The findings assert that STWs play a more substantial role in upper atmospheric dynamics than previously recognized, particularly at higher altitudes. The results indicate the need for continued research into the mechanisms driving STW generation and integrating these features into leading atmospheric models, especially those which constitute a critical component of the nation's space domain awareness infrastructure. Key Points Solar terminator waves (STWs) are observed and characterized at ≈500${\\approx} 500$ km and found to be dominant features of this region Unlike the 6%–8% amplitudes reported previously near 400 km, STWs can perturb the background density by factors of two near 500 km The first detection of a dawn STW with a magnitude comparable to its dusk counterpart is observed near 500 km
Journal Article