Miracle-dz/UniFAR-FTUs huggingface dataset:
Tip vortices--single phase and cavitating flow phenomena

Tip vortices occur wherever a lifting surface terminates in a fluid. An understanding of tip vortices is salient to the solution of many engineering problems, including lift induced drag tip inefficiency, the overturning of small planes flown into the tip wake of larger aircraft, and marine propellor tip cavitation. The tip vortex shed by several rectangular planform wings, fitted with three different tips, was studied in a water tunnel. Four techniques were employed to examine the tip vortex: (i) Surface flow visualization to reveal the early stages of vortex rollup. (ii) Double pulsed holography of buoyant, Lagrangian particle tracers for detailed tangential and axial velocity data around the vortex core. Holograms were also a source of instantaneous core structure information. (iii) Single pulse holography of air bubbles, of uniform, measured, original size. The size of the bubbles is related to the instantaneous local static pressure. The bubbles are driven by the centripetal pressure gradient forces into the vortex core, providing a means of measuring the average and transient vortex core pressure non-intrusively. (iv) Direct observation of vortex cavitation. These measurements are useful in their own right because of the considerable technological significance of tip vortex cavitation. In addition, many single phase tip flow characteristics have cavitating flow counterparts. The present study has shown that one chord downstream of the wing trailing edge virtually all the foil bound vorticity has rolled up into the trailing vortex. Armed with this knowledge one may a priori evaluate, in the near field, the tangential velocity distribution, the core axial velocity excess, and the core mean pressure. These predictions are in agreement with the experimental measurements. Three aspects of the core flow, first observed in the present study, remain analytically inexplicable: (i) The trend towards a Reynolds number dependent, axial velocity deficit with downstream distance. (ii) The unsteady core velocity, particularly immediately downstream of the foil. (iii) The vortex kinking which is coincident with highly unsteady axial core flow. As a first approximation, cavitation inception occurs when the core pressure is reduced to the vapour pressure. The large measured fluctuating core pressure explains the occurrence of inception at core pressures somewhat above p[v] and the dependence of sigma[i] on the dissolved air content. Modifying the tip geometry profoundly affects the trailing vortex. Installation of a ring wing tip can reduce the inception index relative to that of a normal rounded tip foil by a factor of three. The reduction was caused primarily by the redistribution, in the Trefftz plane, of the shed vorticity about a line and circle. Fortuitously, this redistribution caused most of the wing bound vorticity to be shed from the ring, decreasing the tip effect lift loss over the foil body.
Dark matter direct search rates in simulations of the Milky Way and Sagittarius stream

We analyze self-consistent N-body simulations of the Milky Way disk and the ongoing disruption of the Sagittarius dwarf satellite to study the effect of Sagittarius tidal debris on dark matter detection experiments. In agreement with significant previous work, we reiterate that the standard halo model is insufficient to describe the non-Maxwellian velocity distribution of the Milky Way halo in our equilibrium halo-only and halo/galaxy models, and offer suggestions for correcting for this discrepancy. More importantly, we emphasize that the dark matter component of the leading tidal arm of the Sagittarius dwarf is significantly more extended than the stellar component of the arm, and also that the dark matter and stellar streams are not necessarily coaxial and may be offset by several kpc at the point at which they impact the Galactic disk. This suggests that the dark matter component of the Sagittarius debris is likely to have a non-negligible influence on dark matter detection experiments even when the stellar debris is centered several kpc from the solar neighborhood. Relative to models without an infalling Sagittarius dwarf, the Sagittarius dark matter debris in our models induces an energy-dependent enhancement of direct search event rates of as much as ∼ 20–45%, an energy-dependent reduction in the amplitude of the annual modulation of the event rate by as much as a factor of two, a shift in the phase of the annual modulation by as much as ∼ 20 days, and a shift in the recoil energy at which the modulation reverses phase. These influences of Sagittarius are of general interest in the interpretation of dark matter searches, but may be particularly important in the case of relatively light (mχ≲20 GeV/c2) dark matter because the Sagittarius stream impacts the solar system at high speed compared to the primary halo dark matter.
Measuring the scholarly and judicial impact of accredited legal journals in South Africa

Legal scholarly journals are primarily written to influence those who read their content. Their influence is usually measured by counting the number of citations made of them in the subsequent articles and judicial publications. This study measured the impact of South African legal journals’ content, by counting the number of times these journals have been cited and mentioned in subsequent legal journal articles and judicial decisions (judgements) through the use of Google Scholar (GS) citations and Butterworth Lexis Nexis database respectively. The results of the study revealed variations in terms of the citation patterns of legal journals in legal scholarship and judicial rulings. The most heavily cited journals in South Africa are relatively new and disseminated through the open access mode, while journals which are highly cited by judges in judicial decisions or law reports appear to be those that have been in existence for a long time. Further research on the most influential legal journal articles and authors could perhaps improve the chances of South African legal journals being internationally recognised. Keywords: Scholarly impact; judicial influence; citation counting; South Africa
Semiclassical and quantum-mechanical descriptions of S2 molecular radiation

A semiclassical theory to calculate diatomic molecular radiation emission and absorption coefficients is presented in some detail. The theory is applied to the S2 {B} 3Σu-→X 3Σg- transition and the results are compared with a quantum-mechanical calculation. We show that disregarding fine structure, the semiclassical results compare very well with the average results of the quantum-mechanical theory. We conclude that the semiclassical theory is recommendable when fine structure is not important since it requires less detailed data about the molecular states and transition and its results can be computed faster.
Rotating a curvaton brane in a warped throat

In this paper we study a curvaton model obtained by considering a probe anti-D3-brane with angular motion at the bottom of a KS throat with approximate isometries. We calculate the spectrum of curvature perturbations and the non-Gaussianities of this model. Specifically, we consider the limit of relativistic rotation of the curvaton brane which leads to a small sound speed, and thus it can be viewed as an implementation of the DBI-curvaton mechanism. We find that the primordial power spectrum is nearly scale-invariant while the non-Gaussianity of local type is sizable and that of equilateral type is usually large and negative. Moreover, we study both the theoretical and observational constraints on this model, and find that there exists a sizable allowed region for the phase space of this model.
Kolmogorov complexity and derandomization

Kolmogorov complexity is a measure that describes the compressibility of a string. Strings with low complexity contain a lot of redundancy, while strings with high Kolmogorov complexity seem to lack any kind of pattern. For instance, a string such as 5555 5555 5555 5555 5555 has low complexity, while a sequence such as 1732 7356 2748 7621 6552 would have high complexity. This thesis studies different notions of resource-bounded Kolmogorov complexity. In particular it studies Levin's Kt complexity and measures Kμ that are defined in a similar manner. Levin defined his measure as Kt( x) = min{|d| + logt | U(d) = x in t steps} where U is a universal Turing machine. It is shown that, contrary to common intuition, the measures Kμ behave differently from the resource-unbounded Kolmogorov complexity, even for generous resource bounds. In particular it is argued that a property called Symmetry of Information does not hold for some of these measures Kμ. One of the main results of this thesis addresses the question of the complexity of computing the measure Kt(x) for a given string x. It can be computed in exponential time, but no meaningful lower bound is known. However, it is shown that it is complete for exponential time under efficient, non-uniform reductions (i.e., reductions computable in P/poly) as well as nondeterministic polynomial time reductions (i.e., reductions computable in NP). Further completeness results of other complexity measures for different complexity classes are obtained as well. These results are of interest as the problem of computing the Kolmogorov complexity of a string is not a typical complete problem. Most problems that are complete for a complexity classes have a clear combinatorial structure representative of the complexity class they reside in. However, the problems studied seem to lack that property. This thesis also studies the relation between (a) the ability of sets in certain complexity classes to avoid simple strings and (b) the inclusion relation between different complexity classes. For instance, it is shown that every set in P contains simple strings, if and only if NEXP ⊆ P/poly.
Diabatic effects on potential vorticity over the global tropics

Through the use of physical initialization, which relates to precipitation and precipitable water initialization we incorporate the observed rainfall and obtained a better description of the diabatic heating from a very high-resolution global model. Interpolating assimilated data sets (basic and derived) onto isentropic surfaces we carried out detailed analysis of the potential vorticity equation for the cases, 1 December 1992 and 4 October 1995. In addition to the horizontal advection of potential vorticity, the potential vorticity Ertel's equation includes contributions from both the vertical and horizontal differentials of diabatic heating and from frictional effects. Often most of these terms are of the order of 10 -12 kg -1 m 2 s -2 K. A significant contribution to the local budget of potential vorticity is provided by (1) the differentials of convective heating in rain areas and (2) the radiative heating related to shallow cloud top cooling in trade wind belts. Viewing this problem over the middle troposphere (near the 325 K isentropic surface) and lower troposphere (both slightly above (310 K) and below (305 K) the tops of undisturbed tropical stratocumulus), we find that the diabatic effects arising from differential heating contribute significantly to the generation of potential vorticity. Tropical short-range forecasts using models designed to conserve potential vorticity exhibit a very large error growth, which can be reduced significantly by including diabatic effects. Three-dimensional trajectories of air parcels in the tropical latitudes show that within 12 to 24 hours, these parcels often undergo physical processes resulting in substantial changes in potential vorticity. Non-conservation of potential vorticity appears to be important over many regions of the disturbed as well as undisturbed tropics.
Reverses Disease in Mice Encephalomyelitis: Inhibition of Engagement Experimental Autoimmune Cutting Edge: Critical Role for CD5 in

The induction phase of experimental autoimmune encephalomyelitis (EAE) in mice is T cell dependent and coreceptors that regulate T cell activation modulate disease development. We report here that mice lacking CD5, an important modulator of T cell activation, exhibit significantly delayed onset and decreased severity of EAE. The resistance to EAE in CD5 (cid:1) / (cid:1) mice was not due to the in-ability of T cells to respond efficiently to stimulation with MOG 35–55 but was associated with the presence of elevated frequency of apoptotic activated T cells in spleens and DLN. We also observed a net decrease in peripheral activated CD4 (cid:2) T cells in CD5 (cid:1) / (cid:1) spleens and DLN 10 days after immunization. We further show that in vivo blockade of CD5 engagement after induction of EAE by soluble CD5-Fc, a treatment that induces elimination of activated T cells, promoted recovery from EAE. Our studies indicate that CD5 regulates survival of activated T cells and provides a target for treatment of T cell-depen-dent autoimmune diseases such as multiple sclerosis. The Journal of Immunology, 2004, 173: 2928–2932.
Coherence resonance of a magnet-induced buckled piezoelectric energy harvester under stochastic parametric excitation

This study takes the magnet-induced buckled piezoelectric energy harvester as the object of research and employs the stochastic Melnikov method to explore the necessary conditions for occurrence of coherence resonance. The magnet-induced buckled piezoelectric energy harvester configuration is composed of a clamped–clamped beam, with one movable end subjected to an axial stochastic magnetic acting force. The model’s stochastic Melnikov function is derived and then the necessary conditions for coherence resonance are obtained. The analyses reveal that the magnet’s distance and the proof mass may influence the threshold of inter-well motion significantly. Numerical simulations are carried out, and Kramers rate is applied to prove the analytical predictions. A harvester prototype was fabricated, and the corresponding experiments were carried out for validation. The results proved the theoretical analyses and the simulation results. The influences of stochastic excitation level and magnet separation distance on the performance are thoroughly discussed. The results provide a guideline for design and optimization of the magnet-induced buckled piezoelectric energy harvester.
The impact of the phase-space density on the indirect detection of dark matter

We study the indirect detection of dark matter when the local dark matter velocity distribution depends upon position, as expected for the Milky Way and its dwarf spheroidal satellites, and the annihilation cross-section is not purely s-wave. Using a phase-space distribution consistent with the dark matter density profile, we present estimates of cosmic and gamma-ray fluxes from dark matter annihilations. The expectations for the indirect detection of dark matter can differ significantly from the usual calculation that assumes that the velocity of the dark matter particles follows a Maxwell-Boltzmann distribution.
The Unconventional Oil Supply Boom: Aggregate Price Response from Microdata

We analyze the price responsiveness of U.S. conventional and unconventional oil supply across three key stages of oil production: drilling, completion, and production. Drilling is the most important margin, with price elasticities of 1.3 and 1.6 for conventional and unconventional drilling respectively. Well productivity declines as prices rise, implying smaller net supply elasticities of about 1.1 and 1.2. Despite similar supply elasticities, the price response of unconventional supply is larger in terms of barrels because of much higher production per well (∼10x initially). Oil supply simulations show a 13-fold larger supply response due to the shale revolution. The simulations suggest that a price rise from $50 to $80 per barrel induces incremental U.S. production of 0.6MM barrels per day in 6 months, 1.4MM in 1 year, 2.4MM in 2 years, and 4.2MM in 5 years. Nonetheless, the response takes much longer than the 30 to 90 days than typically associated with the role of “swing producer. ”
Concentration and oxygen saturation of haemoglobin of 50 breast tumours determined by time-domain optical mammography

Using a dual-wavelength (670 nm, 785 nm) time-domain scanning instrument we have recorded optical mammograms of 93 patients suspected of having breast cancer which was subsequently assessed histologically. Among 65 histologically confirmed carcinomas, 54 were detectable in at least one of two optical mammograms recorded of each tumour-bearing breast in craniocaudal and mediolateral projection. Optical mammograms were based on photon counts in selected time windows of measured distributions of times of flight of photons. Optical properties of 50 carcinomas investigated at both wavelengths were derived by modelling the breast as partially homogeneous infinite slab with an embedded spherical inhomogeneity representing the tumour and by calculating the diffraction of photon density waves. In selected cases, additional information about the location of the tumour along the compression direction was used that was obtained from scans at selected offsets between source and detector optical fibres. A correlation plot of haemoglobin concentration and blood oxygen saturation of tumours and healthy tissue shows good separation between both kinds of tissue. The majority of carcinomas exhibited increased total haemoglobin concentration compared to healthy tissue.
Mechanism of laser-induced double ionization of helium

In a series of recent experiments anomalously large probabilities of laser-induced double ionization of the He atom have been observed. In this letter we analyse the clearest observation of this phenomenon, over a signal range of many orders of magnitude, by Walker et al. The analysis is carried out using a newly developed intense-field many-body S-matrix theory. For the first time good agreement between the experimental data and a theory is found. It is shown that the dominant mechanism behind the observed large probability of laser-induced double escape is a quantum mechanical process of absorption of photon energy by one of the electrons which is shared cooperatively with the other electron through the Coulomb correlation; quantitatively it turns out to be one of the largest effects of electron - electron correlation known in atomic physics.
Resolving cosmic neutrino structure: a hybrid neutrino N-body scheme

We present the first simulation capable of resolving the structure of neutrino clustering on Mpc scales. The method combines grid- and particle-based methods and achieves very good accuracy on both small and large scales, while keeping CPU consumption under control. Such simulations are not only ideal for calculating the non-linear matter power spectrum but also particularly relevant for studies of how neutrinos cluster in galaxy- or cluster-sized halos. We perform the largest neutrino N-body simulation to date, effectively containing 10 different neutrino hot dark matter components with different thermal properties.
Spitzer Mid-Infrared Spectroscopy of Infrared Luminous Galaxies at z ~ 2. I. The Spectra

We present the mid-infrared spectra obtained with the Spitzer IRS for 52 sources, selected as infrared luminous, z ≳ 1 candidates in the Extragalactic First Look Survey. The sample selection criteria are f24 μm ≳ 0.9 mJy, νfν(24 μm)/νfν(8 μm) ≳ 3.16, and νfν(24 μm)/νfν(0.7 μm) ≳ 10. Of the 52 spectra, 47 (90%) produced measurable redshifts based solely on the mid-IR spectral features, with 35/47 (74%) at 1.5 ≲ z ≲ 3.2. Keck spectroscopy of a subsample (17/47) agrees with the mid-IR redshift measurements. The observed spectra fall into three categories: (1) 33% (17/52) have strong PAH emission and are probably powered by star formation with total IR luminosity roughly a factor of 5 higher than the local starburst ULIRGs; (2) 33% (17/52) have only deep silicate absorption at 9.8 μm, indicatiing deeply embedded dusty systems—these data alone cannot determine the energetic nature of the heating sources in these systems; and (3) the remaining 34% are mid-IR continuum-dominated systems with weak PAH emission and/or silicate absorption. This subsample is probably AGNs. We derived monochromatic, rest-frame 5.8 μm, continuum luminosities (νLν), ranging from 1010.3 to 1012.6 L☉. Our spectra have mid-IR slope α5-15 μm ≳ 2.1, much redder than the median value of 1.3 for the optically selected PG quasars. From the silicate absorption feature, we estimate that roughly two-thirds of the sample have optical depth τ9.8 μm > 1. Their L1600 Å and LIR suggest that our sample is among the most luminous and most dust-enshrouded systems of its epoch. Our study has revealed a significant population of dust-enshrouded galaxies at z ~ 2, whose enormous energy output, comparable to that of quasars, is generated by AGNs, as well as starbursts. This IR-luminous population has very little overlap with submillimeter and UV-selected populations.
LOW MACH NUMBER MODELING OF TYPE IA SUPERNOVAE. IV. WHITE DWARF CONVECTION

We present the first three-dimensional, full-star simulations of convection in a white dwarf preceding a Type Ia supernova, specifically the last few hours before ignition. For these long-time calculations, we use our low Mach number hydrodynamics code, MAESTRO, which we have further developed to treat spherical stars centered in a three-dimensional Cartesian geometry. The main change required is a procedure to map the one-dimensional radial base state to and from the Cartesian grid. Our models recover the dipole structure of the flow seen in previous calculations, but our long-time integration shows that the orientation of the dipole changes with time. Furthermore, we show the development of gravity waves in the outer, stable portion of the star. Finally, we evolve several calculations to the point of ignition and discuss the range of ignition radii.
Cosmological stability bound in massive gravity and bigravity

We give a simple derivation of a cosmological bound on the graviton mass for spatially flat FRW solutions in massive gravity with an FRW reference metric and for bigravity theories. This bound comes from the requirement that the kinetic term of the helicity zero mode of the graviton is positive definite. The bound is dependent only on the parameters in the massive gravity potential and the Hubble expansion rate for the two metrics. We derive the decoupling limit of bigravity and FRW massive gravity, and use this to give an independent derivation of the cosmological bound. We recover our previous results that the tension between satisfying the Friedmann equation and the cosmological bound is sufficient to rule out all observationally relevant FRW solutions for massive gravity with an FRW reference metric. In contrast, in bigravity this tension is resolved due to different nature of the Vainshtein mechanism. We find that in bigravity theories there exists an FRW solution with late-time self-acceleration for which the kinetic terms for the helicity-2, helicity-1 and helicity-0 are generically nonzero and positive making this a compelling candidate for a model of cosmic acceleration. We confirm that the generalized bound is saturated for the candidate partially massless (bi)gravity theories but the existence of helicity-1/helicity-0 interactions implies the absence of the conjectured partially massless symmetry for both massive gravity and bigravity.