Miracle-dz/UniFAR-FTUs huggingface dataset:
Cooperative elliptic instability of a vortex pair

In this paper, we investigate the three-dimensional instability of a counter-rotating vortex pair to short waves, which are of the order of the vortex core size, and less than the inter-vortex spacing. Our experiments involve detailed visualizations and velocimetry to reveal the spatial structure of the instability for a vortex pair, which is generated underwater by two rotating plates. We discover, in this work, a symmetry-breaking phase relationship between the two vortices, which we show to be consistent with a kinematic matching condition for the disturbances evolving on each vortex. In this sense, the instabilities in each vortex evolve in a coupled, or ‘cooperative’, manner. Further results demonstrate that this instability is a manifestation of an elliptic instability of the vortex cores, which is here identified clearly for the first time in a real open flow. We establish a relationship between elliptic instability and other theoretical instability studies involving Kelvin modes. In particular, we note that the perturbation shape near the vortex centres is unaffected by the finite size of the cores. We find that the long-term evolution of the flow involves the inception of secondary transverse vortex pairs, which develop near the leading stagnation point of the pair. The interaction of these short-wavelength structures with the long-wavelength Crow instability is studied, and we observe significant modifications in the longevity of large vortical structures.
Energy Transfer during Silicon Irradiation by Femtosecond Laser Pulse

Measurements of the total energy reflected from crystalline and amorphous silicon illuminated by a femtosecond laser pulse are reported, for wavelengths of 0.62 and 0.31 \ensuremath{\mu}m. The results are interpreted by use of a highly nonlinear regime of light propagation in the dense plasma of electrons and holes ($e\ensuremath{-}h$). Densities higher than ${10}^{22}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ are reached. We demonstrate that free-carrier absorption is dominated by $e\ensuremath{-}h$ collisions.
A simplified vortex model of propeller and wind-turbine wakes

Abstract A new vortex model of inviscid propeller and wind-turbine wakes is proposed based on an asymptotic expansion of the Biot–Savart induction law to account for the finite vortex core size. The circulation along the blade is assumed to be constant from the blade root to the tip approximating a turbine with maximum power production for given operating conditions. The model iteratively calculates the tip-vortex path, allowing the wake to expand/contract freely, and is afterward able to evaluate the velocity field in the whole domain. The ‘roller-bearing analogy’, proposed by Okulov and Sørensen (J. Fluid Mech., vol. 649, 2010, pp. 497–508), is used to determine the vortex core size. A comparison of the main outcomes of the present model with the general momentum theory is performed in terms of the operating parameters (namely the number of blades, the tip-speed ratio, the blade circulation and the vortex core size), demonstrating good agreement between the two. Furthermore, experimental data have been compared with the model outputs to validate the model under real operating conditions.
Photometric membership and metallicities of red giant candidates in selected open clusters

As part of a long-term project to determine abundances and astrophysical properties of evolved red stars in open clusters, we present high-precision DDO photoelectric observations for a sample of 33 red giant candidates projected in the fields of nine Galactic open clusters. These data are supplemented with UBV photoelectric photometry of 24 of these stars as well as with CORAVEL radial-velocity observations for 13 red giant candidates in four of the clusters. We also present Washington photoelectric photometry of a small sample of red giant candidates of the open cluster Ruprecht 97. The likelihood of cluster membership for each star photometrically observed and for 23 additional red giant candidates with UBV and DDO data available in the literature, is evaluated by using two independent photometric criteria. Nearly 82% of the analysed stars are found to have a high probability of being cluster giants. Photometric membership probabilities show very good agreement with those obtained from CORAVEL radial velocities. While E(B - V) colour excesses were determined from combined B - V and DDO colours, calibrations of the DDO system were used to derive MK spectral types, effective temperatures and metallicities.The derived DDO metallicities range between values typical of moderately metal-poor clusters ([Fe/H] = -0.19) to moderately metal-rich ([Fe/H] = 0.25) ones. (c) 2009 WILEY-VCH Verla, GmbHC KGaA, Weinheim.
Comparison of hybrid and baseline ELMy H-mode confinement in JET with the carbon wall

The confinement in JET baseline type I ELMy H-mode plasmas is compared to that in so-called hybrid H-modes in a database study of 112 plasmas in JET with the carbon fibre composite (CFC) wall. The baseline plasmas typically have βN ∼ 1.5–2, H98 ∼ 1, whereas the hybrid plasmas have βN ∼ 2.5–3, H98 < 1.5. The database study contains both low- (δ ∼ 0.2–0.25) and high-triangularity (δ ∼ 0.4) hybrid and baseline H-mode plasmas from the last JET operational campaigns in the CFC wall from the period 2008–2009. Based on a detailed confinement study of the global as well as the pedestal and core confinement, there is no evidence that the hybrid and baseline plasmas form separate confinement groups; it emerges that the transition between the two scenarios is of a gradual kind rather than demonstrating a bifurcation in the confinement. The elevated confinement enhancement factor H98 in the hybrid plasmas may possibly be explained by the density dependence in the τ98 scaling as n0.41 and the fact that the hybrid plasmas operate at low plasma density compared to the baseline ELMy H-mode plasmas. A separate regression on the confinement data in this study shows a reduction in the density dependence as n0.09±0.08. Furthermore, inclusion of the plasma toroidal rotation in the confinement regression provides a scaling with the toroidal Alfvén Mach number as and again a reduced density dependence as n0.15±0.08. The differences in pedestal confinement can be explained on the basis of linear MHD stability through a coupling of the total and pedestal poloidal pressure and the pedestal performance can be improved through plasma shaping as well as high β operation. This has been confirmed in a comparison with the EPED1 predictive pedestal code which shows a good agreement between the predicted and measured pedestal pressure within 20–30% for a wide range of βN ∼ 1.5–3.5. The core profiles show a strong degree of pressure profile consistency. No beneficial effect of core density peaking on confinement could be identified for the majority of the plasmas presented here as the density peaking is compensated by a temperature de-peaking resulting in no or only a weak variation in the pressure peaking. The core confinement could only be optimized in case the ions and electrons are decoupled, in which case the ion temperature profile peaking can be enhanced, which benefits confinement. In this study, the latter has only been achieved in the low-triangularity hybrid plasmas, and can be attributed to low-density operation. Plasma rotation has been found to reduce core profile stiffness, and can explain an increase in profile peaking at small radius ρtor = 0.3.
Temporal Position of Discharges in Single Auditory Nerve Fibers within the Cycle of a Sine‐Wave Stimulus: Frequency and Intensity Effects

Period histograms, which display the distribution of spikes throughout the period of a periodic stimulus, were computed for discharges recorded from single auditory nerve fibers of the squirrel monkey when low‐frequency tones were employed. For frequencies up to about 4 kHz, where phase locking is observed, the average phase angle of the discharges was tracked as frequency was varied in small steps from low to high. To a first approximation, the cumulative shift in average phase angle is a linear function of frequency as would be observed for an ideal delay line. The slopes of these phase‐versus‐frequency lines were found to be related through a power law to the best frequencies of the fibers. Thus, it seems possible to estimate the travel time of a mechanical disturbance between the oval window and any point on the cochlear partition. A more detailed examination revealed that average phase angle is also sensitive to intensity, depending upon the relation of the stimulating frequency to the best frequency. For stimulating frequencies below best frequency, discharges tend to occur progressively later in the cycle as intensity increases. Above best frequency, an opposite tendency often prevails if a change in phase angle occurs. At or near best frequency, little change in average phase angle is noted as intensity varies.
Arbeitsbelastungen und Rehabilitationsbedarf bei älteren Erwerbstätigen mit und ohne Migrationshintergrund – Ergebnisse der lidA Kohortenstudie

Zusammenfassung Ziel der Studie Der Bedarf an medizinischen Rehabilitationsmaßnahmen wird zukünftig durch die Erhöhung des Rentenalters und den demographischen Wandel steigen. Der Bedarf wird u. A. durch das Maß an Arbeitsbelastungen bestimmt. Ziel ist es zu untersuchen, ob Erwerbstätige mit Migrationshintergrund (EmM) häufiger hohen Arbeitsbelastungen ausgesetzt sind und häufiger einen hohen Bedarf als Erwerbstätige ohne Migrationshintergrund (EoM) haben. Ebenso wird geprüft, ob sich ein möglicherweise höherer Bedarf bei EmM durch höhere Arbeitsbelastungen erklären lässt. Methodik Die lidA-Studie ist eine deutschlandweite, prospektive Kohortenstudie zu Arbeit, Alter, Gesundheit und Erwerbsteilhabe. 4724 sozialversicherungspflichtig Beschäftigte (2443 weiblich, 2281 männlich) der Geburtsjahrgänge 1959 und 1965 wurden computergestützt persönlich befragt. Daten der ersten Studienwelle (2011) wurden mittels multipler logistischer Regressionsanalysen, adjustiert für soziodemographische Faktoren (Alter, Geschlecht, Bildung und Haushaltsäquivalenzeinkommen), analysiert. Der Einfluss des Migrationshintergrundes, der Staatsangehörigkeit und hoher Arbeitsbelastungen auf den medizinischen Rehabilitationsbedarf wurde geschätzt. Ergebnisse Besonders betroffen von hohen Arbeitsbelastungen sind in dieser Stichprobe EmM der 1. Generation in Vergleich zu EoM. Die subjektiv erlebten Arbeitsbelastungen bei EoM und EmM der 2. Generation liegen auf einem vergleichbaren Niveau. Zwischen den EmM mit deutscher und ausländischer Staatsangehörigkeit finden sich dagegen keine Unterschiede. Ein höherer Rehabilitationsbedarf zeigt sich nach Adjustierung für soziodemographische und arbeitsbelastungsbezogene Faktoren für die EmM der 1. Generation (nicht signifikant) im Vergleich zu EoM und EmM der 2. Generation, nicht aber für EmM mit ausländischer im Vergleich zu EmM mit deutscher Staatsangehörigkeit. Schlussfolgerungen EmM der 1. Generation sind häufiger hohen Arbeitsbelastungen ausgesetzt und weisen häufiger einen hohen Rehabilitationsbedarf auf als EoM und EmM der 2. Generation. Der Migrationshintergrund selbst ist keine Determinante für einen erhöhten Rehabilitationsbedarf. Der höhere Rehabilitationsbedarf lässt sich vielmehr durch die bei EmM der 1. Generation häufiger anzutreffenden arbeitsbedingten Belastungen sowie soziodemografische Merkmale erklären. Differenzierte Betrachtungen der Untergruppen von EmM sind wichtig, um besondere Bedarfe zu erkennen und eine Unterversorgung (z. B. bedingt durch Zugangsbarrieren) zu vermeiden.
Two-dimensional birefringence measurement using the phase shifting technique

The phase shifting technique for the measurement of a twodimensional birefringence distribution is described and discussed. The birefringent phase difference and azimuthal angle of a transparent material can be determined in the dependence of both measurements on the amplitude and phase of the polarization interferometry. A half-wave plate and a Babinet-Soleil compensator are used as phase shifters for the phase shifting technique. It can measure 256 x 256 values of the birefringent phase difference and azimuthal angle in a short time with sufficient accuracy. This method does not require moving the sample mechanically. The results and procedures for measuring such a birefringence distribution of optical components such as a calibrated Babinet-Soleil compensator, a lens, and a roof prism are discussed.
On the generalized pantograph functional-differential equation

The generalized pantograph equation y′(t) = Ay(t) + By(qt) + Cy′(qt), y(0) = y0, where q ∈ (0, 1), has numerous applications, as well as being a useful paradigm for more general functional-differential equations with monotone delay. Although many special cases have been already investigated extensively, a general theory for this equation is lacking–its development and exposition is the purpose of the present paper. After deducing conditions on A, B, C ∈ ℂd×d that are equivalent to well-posedness, we investigate the expansion of y in Dirichlet series. This provides a very fruitful form for the investigation of asymptotic behaviour, and we duly derive conditions for limt⋅→∞y(t) = 0. The behaviour on the stability boundary possesses no comprehensive explanation, but we are able to prove that, along an important portion of that boundary, y is almost periodic and, provided that q is rational, it is almost rotationally symmetric. The paper also addresses itself to a detailed analysis of the scalar equation y′(t) = by(qt), y(0) = 1, to high-order pantograph equations, to a phenomenon, similar to resonance, that occurs for specific configurations of eigenvalues of A, and to the equation Y′(t) = AY(t) + Y(qt) B, Y(0) = Y0.
LEAST-SQUARES MODIFICATION OF STOKES' FORMULA WITH EGM08

Abstract Least‐squares modifcation is an optimal method of modifying Stokes’ formula. Tis method can be categorized as a generalization of the spectral combination methods as it considers the truncation error of the integral formulas in its combination process. In short, this method involves the modifcation parameters based on minimizing the error of terrestrial gravimetric data, satellite data and the truncation error of the integral. In this respect, the choice of the geopotential model defnitely plays an important role. Tis paper uses the recent combined geopotential model EGM08 for generating the spectra of gravity anomaly and its error. Numerical results show that EGM08 improves least‐squares modifcation by about 10 cm comparing to the traditional way.
An Experimental Study of 3s23pk and 3s3pk+1 in the CI I, S I, P I, Si I, and AI I Isoelectronic Sequences

New measurements and identifications of the transitions 3s23pk-3s3pk+1 have been made in the spectra of S IV, K IV-VII, Ca V-VIII, Sc VI-IX, Ti VII-X, V VII-XI, Cr VIII-XI, Mn IX-XI, and Fe X, XI. The energy parameters of the ground configurations have been determined and expressed as functions of Z by semi-empirical formulae in the S I, P I, Si I, and Al I isoelectronic sequences. Predicted wavelengths for some 150 forbidden lines of astrophysical interest are tabulated.
X-ray spectra of cataclysmic variables from the Einstein Observatory

We determine X-ray spectral parameters of 32 cataclysmic variables observed with the Einstein imaging proportional counter, by fitting an optically thin, thermal bremsstrahlung spectrum to the final, reprocessed version of the raw data. The conclusions of earlier studies, based on the first processing of the data, are not substantially changed.
Dense Molecular Clumps Associated with Young Clusters in Massive Star-forming Regions

We present the results of C18O observations by the 45 m Nobeyama radio telescope toward dense clumps with young clusters in nine massive star-forming regions. We identified 39 clumps whose mass, radius, and line width range from 15 to 1500 M☉, from 0.14 to 0.76 pc, and from 0.6 to 3.2 km s-1, respectively. The clumps associated with massive (proto)stars have a large line width (~2.5 km s-1) and a large mass (~500 M☉). Most of the clumps are sufficiently gravitationally bound because they have a virial mass similar to the gas mass, and the average H2 density of the clumps increases with increasing internal kinetic motion. Next, we found two relations, one between the number density of associated 2MASS sources and the average H2 density of the clump and the other between the number density of sources and the star formation efficiency of the clump. From these results, we suggest that a structure, whose size scale is ~0.3 pc, with a high average H2 density is required in order for cluster formation to occur. In addition, we found that the internal kinetic motion of a clump has to be large in order to form massive stars, because there is a good correlation between the maximum mass of associated stars and the line width of the clump. Such clumps with large internal motion must generally have a high average H2 density in order to be gravitationally bound. Thus, massive stars are formed in a dense cluster.
Terahertz pulsed imaging in vivo

Terahertz (1012 Hz) pulsed imaging is a totally non-destructive and non-ionising imaging modality and thus potential applications in medicine are being investigated. In this paper we present results using our hand-held terahertz probe that has been designed for in vivo use. In particular, we use the terahertz probe to perform reflection geometry in vivo measurements of human skin. The hand-held terahertz probe gives more flexibility than a typical flat-bed imaging system, but it also results in noisier data and requires existing processing methods to be improved. We describe the requirements and limitations of system geometry, data acquisition rate, image resolution and penetration depth and explain how various factors are dependent on each other. We show how some of the physical limitations can be overcome using novel data processing methods.
Field‐aligned electrons at the lobe/plasma sheet boundary in the mid‐to‐distant magnetotail and their association with reconnection

We have surveyed field‐aligned electrons at the lobe/plasma sheet boundary and their association with reconnection in the distant magnetotail where reconnection is quasi‐steady and large scale. Asymmetric (in energy) counterstreaming electrons are detected in ∼30% of the boundary crossings when high‐speed flows are present in the plasma sheet. In 98% of the electron beam cases the low‐energy electrons are directed toward and the higher‐energy electrons directed away from the X‐line. The well‐organized (by the signs of Bx and Vx) quadrupolar pattern of the electrons indicates that these electrons are associated with reconnection. The low‐energy electrons could be the outer part of the Hall current loop, similar to previous reports in the near‐Earth region. The mean electron energy in the distant tail is a factor of ten lower than in the near‐Earth tail. Our observations suggest that the Hall effect can be detected even at large distances from the diffusion region.
The dynamics of a deformable drop suspended in an unbounded Stokes flow

The velocity fields in and around a deformed drop suspended in an arbitrary (albeit Stokesian) unbounded flow field are solved. The usefulness of the solution is demonstrated by solving the drag force and lateral migration of a drop suspended in an unbounded Poiseuillian field. It is demonstrated that, due to the deformation of the drop, there exists a radial component of the settling velocity. The direction of the radial migration depends primarily on the product UHR (the Hadamard-Rybczynski terminal settling velocity) by U0 (the maximum Poiseuillian velocity). A positive product results in a lateral migration away from the location of maximum velocity; the converse also holds.
Application of the beta‐binomial model for the detection of rare marine benthos using point intercept techniques

The beta‐binomial distribution is used to provide estimates of the probability of detecting a rare species, the smallest proportion cover detectable with a stated confidence for a survey, and is a method for estimating the sample size required to detect a species with a stated presence at a stated level of confidence for independent clusters of binary data. The equations, while general, were derived in the context of marine benthic video transects and are useful for evaluating a wide range of existing surveys or designing new surveys. Application of the equations is demonstrated for a data set collected from three marine surveys on the Great Barrier Reef in Australia. Copyright © 2006 John Wiley & Sons, Ltd.
EXCITATION OF DRIFT INSTABILITIES IN THERMIONIC PLASMAS

Low-frequency oscillations travelling near the electron pressure gradient drift velocity in Cs or K plasmas have been observed to exist only in the presence of an ion sheath at the cathodes. It is suggested that these waves are self-exciting `universal' instabilities in the presence of finite resistivity and that their excitation is connected with the insulating properties of an ion sheath, which allow the perturbation amplitude to be finite at the sheath edge. This leads to overstable oscillations with λ|| longer than the length of the machine, a strange concept which is explained physically. Although the solution of the problem involves sheath-type boundary conditions, for an isothermal plasma the criterion for onset of instability can be stated rather simply. The predicted critical sheath voltage agrees well with observations. It appears that alkali-metal plasmas with electron sheaths are quiescent only by virtue of stabilization by conducting end-plates; however, this feature makes such plasmas particularly valuable for the study of the onset of long-wavelength drift instabilities.
Broken symmetries in field theory

The thesis discusses the role of symmetries in Quantum Field Theory. Quantum Field Theory is the mathematical framework to describe the physics of elementary particles. A symmetry here means a transformation under which the model at hand is invariant. Three types of symmetry are distinguished: 1. Internal symmetries, 2. Space-time symmetries and 3. Supersymmetries. Supersymmetry is discussed in detail in the first chapter, where emphasis is put on attempts to formulate this symmetrie on a space-time lattice, with the ultimate goal to contribute to the study of computer simulations of this symmetry. Main conclusion here is that two types of mathematical framework to approach this issue are shown to be mathematically inconsistent. The quantum mechanical breaking due regularization and renormalization effects of conformal symmetries (which are a type of space-time symmetries) is discussed in chapters 2 and 3. In chapter 2 in the context of the Non-Linear Schroedinger model, in chapter 3 in the context of the Jackiw-Pi model. Main conclusion here is that the conformal symmetries of both models break quantum mechanically. However, in case of the Jackiw-Pi model these symmetries survive under a special condition which also allows vortex solutions.
DECAY OF AN ATOM COUPLED STRONGLY TO A RESERVOIR

An approach to the decay of a two-state quantum system coupled to a resonant environment is developed in terms of exact (nonperturbative) master equations. Starting from a quantum optical model of a two-level system coupled to a heatbath, it is shown that the effect of the bath can be replaced by one or more pseudomodes. This description is valid for a wide class of analytic density-of-state functions and it leads to exact master equations which fully describe the non-Markovian decay of the quantum system without the use of perturbation theory, the Born approximation, or the Markov approximation. Two examples are given: a simple model of a density-of-states gap which has two poles, and a non-Lorentzian resonance.