Miracle-dz/UniFAR-FTUs huggingface dataset:
Impact of MBE deposition conditions on InAs/GaInSb superlattices for very long wavelength infrared detection

The objective of this work is to establish molecular beam epitaxy (MBE) growth processes that can produce high quality InAs/GaInSb superlattice (SL) materials specifically tailored for very long wavelength infrared (VLWIR) detection. To accomplish this goal, several series of MBE growth optimization studies, using a SL structure of 47.0 Å InAs/21.5 Å Ga0.75In0. 25Sb, were performed to refine the MBE growth process and optimize growth parameters. Experimental results demonstrated that our “slow” MBE growth process can consistently produce an energy gap near 50 meV. This is an important factor in narrow band gap SLs. However, there are other growth factors that also impact the electrical and optical properties of the SL materials. The SL layers are particularly sensitive to the anion incorporation condition formed during the surface reconstruction process. Since antisite defects are potentially responsible for the inherent residual carrier concentrations and short carrier lifetimes, the optimization of anion incorporation conditions, by manipulating anion fluxes, anion species, and deposition temperature, was systematically studied. Optimization results are reported in the context of comparative studies on the influence of the growth temperature on the crystal structural quality and surface roughness performed under a designed set of deposition conditions. The optimized SL samples produced an overall strong photoresponse signal with a relatively sharp band edge that is essential for developing VLWIR detectors. A quantitative analysis of the lattice strain, performed at the atomic scale by aberration corrected transmission electron microscopy, provided valuable information about the strain distribution at the GaInSb-on-InAs interface and in the InAs layers, which was important for optimizing the anion conditions.
Observer with a constant proper acceleration

Relying on the equivalence principle, a first approach of the general theory of relativity is presented using the spacetime metric of an observer with a constant proper acceleration. Within this non-inertial frame, the equation of motion of a freely moving object is studied and the equation of motion of a second accelerated observer with the same proper acceleration is examined. A comparison of the metric of the accelerated observer with the metric due to a gravitational field is also performed.
Comparison of homogeneous and heterogeneous tissue models for coil optimization in neural stimulation

In stimulation of peripheral nerves by strong pulsed magnetic fields, it is desirable to produce a well-focused activating function. Previous analyses and an experiment have indicated that quadruple coils provide many advantages. An analytical solution has been obtained for a homogeneous cylindrical volume conductor, and a finite difference numerical solution for a realistic heterogeneous model of a human forearm. In both models it has been assumed that nerves are straight and long, and therefore the activating function is an induced field derivative in the neuron direction. The magnitudes of the activating function for various coil geometries are compared for the two models.
Holographic quantum information and (de)confinement

Analysing the phenomenon of deconfinement from a holographic point of view, it appears that the brane configuration in the bulk, corresponding to the confinement phase imposes a restriction on the strength of the holographic quantum error correction procedure. This restriction is partially removed when the transition to a deconfined phase occurs. The brane configurations corresponding to the bulk instantons are analysed and it is shown that they cannot reach the region of the bulk that would ensure maximal error protection in the confinement phase, while keeping non-zero instanton size. In the deconfinement phase on the other side, we have a configuration that allows a higher degree of quantum error protection, still preventing the maximal protection allowed by the holographic principle. This suggests that the strength of quantum error correction codes in QCD systems is fundamentally limited both in confinement and deconfinement phases.
Acoustic cues for vowel nasalization: A simulation study

The manner in which vowel spectra are modified as the degree of the nasal coupling is varied was investigated by means of a simulation of the vocal‐tract system. Connecting a side cavity, which represents the nasal sinuses, to the main nasal tract, speech synthesis by simulation could produce naturally sounding nasalized vowels [S. Maeda, “The role of the sinus cavities in the production of nasal vowels,” Proc. IEEE ICASSP82, Paris, 911–914 (1982)]. Such spectral variations were studied in detail to shed some light on acoustic cues for vowel nasalization. The advantage of the simulation approach is that the acoustic characteristics of the nasalized vowels can be calculated for arbitrary coupling magnitude, with a realistic vocal‐tract model. The computed vocal‐tract transfer functions were then converted to pseudo‐auditory excitation patterns. A consistent effect of the coupling, for the 11 French vowels that were investigated, was a flattening of the excitation patterns, extending in the frequency range .
Geometrodynamics of variable-speed-of-light cosmologies

Variable-speed-of-light (VSL) cosmologies are currently attracting interest as an alternative to inflation. We investigate the fundamental geometrodynamic aspects of VSL cosmologies and provide several implementations which do not explicitly break Lorentz invariance (no ``hard'' breaking). These ``soft'' implementations of Lorentz symmetry breaking provide particularly clean answers to the question ``VSL with respect to what? '' The class of VSL cosmologies we consider are compatible with both classical Einstein gravity and low-energy particle physics. These models solve the ``kinematic'' puzzles of cosmology as well as inflation does, but cannot by themselves solve the flatness problem, since in their purest form no violation of the strong energy condition occurs. We also consider a heterotic model (VSL plus inflation) which provides a number of observational implications for the low-redshift universe if \ensuremath{\chi} contributes to the ``dark energy'' either as CDM or quintessence. These implications include modified gravitational lensing, birefringence, variation of fundamental constants and rotation of the plane of polarization of light from distant sources.
Observations of solitary wave dynamics of film flows

Experimental results are reported on non-stationary evolution and interactions of waves forming on water and water–glycerol solution flowing along an inclined plane. A nonlinear wave generation process leads to a large number of solitary humps with a wide variety of sizes. A uorescence imaging method is applied to capture the evolution of film height in space and time with accuracy of a few microns. Coalescence – the inelastic interaction of solitary waves resulting in a single hump – is found to proceed at a timescale correlated to the difference in height between the interacting waves. The correlation indicates that waves of similar height do not merge. Transient phenomena accompanying coalescence are reported. The front-running ripples recede during coalescence, only to reappear when the new hump recovers its teardrop shape. The tail of the resulting solitary wave develops an elevated substrate relative to the front, which decays exponentially in time; both observations about the tail confirm theoretical predictions. In experiments with water, the elevated back substrate is unstable, yielding to a tail oscillation with wavelength similar to that of the front-running ripples. This instability plays a key role in two complex interaction phenomena observed: the nucleation of a new crest between two interacting solitary humps and the splitting of a large hump (that has grown through multiple coalescence events) into solitary waves of similar size.
Results from an extensive Einstein stellar survey.

We report the preliminary results of the Einstein Observatory stellar X-ray survey. To date, 143 soft X-ray sources have been identified with stellar counterparts, leaving no doubt that stars in general constitute a pervasive class of low-luminosity galactic X-ray sources. We have detected stars along the entire main sequence, of all luminosity classes, pre-main sequence stars as well as very evolved stars. Early type OB stars have X-ray luminosities in the range approx.10/sup 31/ to approx.10/sup 34/ ergs s/sup -1/; late type stars show a somewhat lower range of X-ray emission levels, from approx.10/sup 26/ to approx.10/sup 31/ ergs s/sup -1/. Late type main-sequence stars show little dependence of X-ray emission levels upon stellar effective temperature; similarly, the observations suggest weak, if any, dependence of X-ray luminosity upon effective gravity. Instead, the data show a broad range of emission levels (approx.three orders of magnitude) throughout the main sequence later than F0. Comparison of the data with published theories of acoustically heated coronae shows that these models are inadequate to explain our results. The data are consistent with magnetically dominated coronae, as in the solar case.
Model Based Design of a Novel Process for Nitrogen Removal from Concentrated Flows

A new process for biological nitrification was developed that is operated in a single aerated reactor at relatively high temperature and pH. This process, termed SHARON, was designed to achieve substantial ammonia conversion at high reaction rates for relatively concentrated flows, rather than to meet strict effluent standards. First large scale applications that are under construction now, aim at treating reject water from a sludge digestion unit. The SHARON process operates without sludge retention, and ammonium oxidation is stopped at nitrite, which saves on aeration costs. Denitrification is used as a cheap means to control the pH. Under typical conditions, no heating is necessary due to the heat production by the reactions. Overall processing costs are less than 50% of other techniques. This contribution focuses on model development for process design calculations at full scale. Underlying kinetic principles, and especially their pH dependency, are highlighted as well.
OH in Saturn's magnetosphere: Observations and implications

The discovery of OH in Saturn's inner magnetosphere changed our view of this region from one where plasma dominated the physics to one where neutrals are dominant. We revisit Hubble Space Telescope observations of OH and derive revised OH brightnesses for observations in 1992, 1994, and 1995. These OH observations as well as Voyager observations are used as constraints on a model of neutral and plasma interactions. We find that the neutral source required to produce the observed OH brightnesses is 1.4×10 27 H 2 O s -1 , with a sharp peak in the neutral source rate near 4.5 R S . A good fit to the data requires OH densities of over 700 cm -3 at 4.5 R S . Rapid diffusion times, about 5 days at 6 R S , are required to match the observed ion densities. We find that the plasma and neutral composition vary with distance from Saturn, and make predictions for the ion and neutral densities as a function of radius.
The Fossil Starburst in M82

We present high-resolution HST imaging in the optical (WFPC2) and near-infrared (NICMOS) of a disk region 1 kpc northeast of the starburst core in the nearby galaxy M82. This region, M82 "B," has been suspected to be a fossil starburst site in which an intense episode of star formation occurred over 100 Myr ago, and our new observations confirm this interpretation. M82 thus presents us with the opportunity to observe both active and evolved starburst environments at close range. The surface brightness of M82 B is well above normal for galactic disks and comparable to the core surface brightnesses in spiral galaxies. Its intrinsic surface brightness at an age of 10 Myr was comparable to that found in the present-day nuclear starburst, indicating an event of comparable amplitude. We find a large, evolved system of super star clusters in M82 B. Using size as a criterion to distinguish cluster candidates from point sources, we identify a total of 113 super star cluster candidates. We use a two-color BVI diagram and evolutionary spectral synthesis models to separately estimate the extinction and age of each cluster. The clusters range in absolute magnitude from M = -6 to -10, with a peak at -7.5. The derived age distribution suggests steady, continuing cluster formation at a modest rate at early times (>2 Gyr ago), followed by a concentrated formation episode ∼600 Myr ago and more recent suppression of cluster formation. The peak episode coincides with independent dynamical estimates for the last tidal encounter with M81, which presumably induced the starburst. Our J- and H-band observations resolve the bright giant population in M82's disk for the first time. Star formation evidently continued in M82 B until about 20–30 Myr ago, but none is found associated with the youngest generations in the nuclear starburst (age ≲ 15 Myr). After correcting the cluster luminosity function to a fiducial age of 50 Myr, we find that the bright end is characterized by a power-law slope with α = -1.2 ± 0.3, similar to that of other young cluster systems in interacting galaxies. There is tentative evidence for broadening of the luminosity function due to dynamical destruction of lower mass clusters. Cluster sizes (2.34 ≤ Reff ≲ 10 pc, or 2.4 ≲ Rcore ≲ 7.9 pc) and estimated masses (a median of 105 M⊙) are consistent with values found for young super star cluster populations in M82's core and other galaxies and with the progenitors of globular clusters.
Hydra: Serialization-Free Network Ordering for Strongly Consistent Distributed Applications

Many distributed systems, e.g., state machine replication and distributed databases, rely on establishing a consistent order of operations on groups of nodes in the system. Tradition-ally, this ordering has been established by application-level protocols like Paxos or two-phase locking. Recent work has shown significant performance improvements are attainable by making ordering a network service, but current network sequencing implementations require routing all requests through a single sequencer – leading to scalability, fault tolerance, and load balancing limitations. Our work, Hydra, overcomes these limitations by using a distributed set of network sequencers to provide network ordering. Hydra leverages loosely synchronized clocks on network sequencers to establish message ordering across them, per-sequencer sequence numbers to detect message drops, and periodic timestamp messages to enforce progress when some sequencers are idle. To demonstrate the benefit of Hydra, we co-designed a state machine replication protocol and a distributed transactional system using the Hydra network primitive. Compared to serialization-based network ordering systems, Hydra shows equivalent performance improvement over traditional approaches in both applications, but with significantly higher scalability, shorter sequencer failover time, and better network-level load balancing.
Self-dilating viscous fingers in wedge-shaped Hele-Shaw cells

Viscous fingering in a wedge-shaped Hele-Shaw cell is analyzed. The shape of a self-dilating viscous finger is shown to obey a time-independent nonlinear integrodifferential equation that is solved numerically. The results show that there is a continuum of zero-surface-tension solutions for any wedge angle between 0 and π/2. When surface tension is taken into account only a discrete set of solutions exist. In contrast to the classical case, different branches merge for finite values of the surface tension parameters.
Ab Initio Mismatched Interface Theory of Graphene on α-RuCl_{3}: Doping and Magnetism.

Recent developments in twisted and lattice-mismatched bilayers have revealed a rich phase space of van der Waals systems and generated excitement. Among these systems are heterobilayers, which can offer new opportunities to control van der Waals systems with strong in plane correlations such as spin-orbit-assisted Mott insulator α-RuCl_{3}. Nevertheless, a theoretical ab initio framework for mismatched heterobilayers without even approximate periodicity is sorely lacking. We propose a general strategy for calculating electronic properties of such systems, mismatched interface theory (MINT), and apply it to the graphene/α-RuCl_{3} (GR/α-RuCl_{3}) heterostructure. Using MINT, we predict uniform doping of 4.77% from graphene to α-RuCl_{3} and magnetic interactions in α-RuCl_{3} to shift the system toward the Kitaev point. Hence, we demonstrate that MINT can guide targeted materialization of desired model systems and discuss recent experiments on GR/α-RuCl_{3} heterostructures.
Angular Momentum Extraction by Gravity Waves in the Sun

We review the behavior of the oscillating shear layer produced by gravity waves below the surface convection zone of the Sun. We show that, under asymmetric filtering produced by this layer, gravity waves of low spherical order that are stochastically excited at the base of the convection zone of late-type stars can extract angular momentum from their radiative interior. The timescale for this momentum extraction in a Sun-like star is on the order of 107 yr. The process is particularly efficient in the central region, and it could produce there a slowly rotating core.
ALMA Observations of Supernova Remnant N49 in the LMC. I. Discovery of CO Clumps Associated with X-Ray and Radio Continuum Shells

N49 (LHA 120-N49) is a bright X-ray supernova remnant (SNR) in the Large Magellanic Cloud. We present new 12CO (J = 1–0, 3–2), H i, and 1.4 GHz radio continuum observations of the SNR N49 using Mopra, ASTE, ALMA, and ATCA. We have newly identified three H i clouds using ATCA with an angular resolution of ∼20″: one associated with the SNR and the others located in front of the SNR. Both the CO and H i clouds in the velocity range from 281 to 291 km s−1 are spatially correlated with both the soft X-rays (0.2–1.2 keV) and the hard X-rays (2.0–7.0 keV) of N49 on a ∼10 pc scale. CO 3–2/1–0 intensity ratios indicate higher values of the CO cloud toward the SNR shell with an angular resolution of ∼45″, and thus a strong interaction was suggested. Using the ALMA, we have spatially resolved CO clumps embedded within or along the southeastern rim of N49 with an angular resolution of ∼3″. Three of the CO clumps are rim brightened on a 0.7–2 pc scale in both hard X-rays and the radio continuum: this provides further evidence for dynamical interactions between the CO clumps and the SNR shock wave. The enhancement of the radio synchrotron radiation can be understood in terms of magnetic field amplification around the CO clumps via a shock–cloud interaction. We also present a possible scenario in which the recombining plasma that dominates the hard X-rays from N49 was formed via thermal conduction between the SNR shock waves and the cold/dense molecular clumps.
Is conformal symmetry really anomalous

The conformal anomaly (also known as the stress-energy trace anomaly) of an interacting quantum theory, associated with violation of Weyl (conformal) symmetry by quantum effects, can be amended if one endows the theory with a dilatation current coupled to a vector field that is the gauge connection of local Weyl symmetry transformations. The natural candidate for this Weyl connection is the trace of the geometric torsion tensor, especially if one recalls that pure (Cartan-Einstein) gravity with torsion is conformal. We first point out that both canonical and path integral quantisation respect Weyl symmetry. The only way quantum effects can violate conformal symmetry is by the process of regularization. However, if one calculates an effective action from a conformally invariant classical theory by using a regularisation procedure that is conform with Weyl symmetry, then the conformal Ward identities will be satisfied. In this sense Weyl symmetry is not broken by quantum effects. This work suggests that Weyl symmetry can be treated on equal footing with gauge symmetries and gravity, for which an infinite set of Ward identities guarantees that they remain unbroken by quantum effects.
Theory of quantized Hall effect at low temperatures

At millikelvin temperatures the quantized Hall effect (QHE) is characterized by sharp steps connecting the quantized Hall resistance plateaus. We explain this behavior on the basis of the single-electron approximation and continuum percolation theory. It is shown that even when the magnetic field corresponds to partially filled Landau level on average, locally the sample breaks into patches having the occupation numbers 0 or 1. This represents a peculiar type of the metal-insulator transition, driven by disorder. Extended (global) electron states may not exist at equilibrium or arbitrarily small applied voltage $V$. Global states begin to appear at a certain critical voltage ${V}_{\mathrm{cr}}$, which is of the order of characteristic magnitude of potential fluctuations on the scale of the sample size. For small $Vg{V}_{\mathrm{cr}}$ the fraction of global states is still small owing to the smallness of the average electric field compared with the fluctuating field in the inversion layer. Because of this, transitions between the QHE plateaus require only a minor change in the density of states and at $T=0$ they occur in small intervals of the magnetic field. Owing to the tail of the Fermi-Dirac distribution at nonzero $T$ the deviation of the Hall conductivity from its nearest quantized value, $(\frac{{e}^{2}}{h})\ifmmode\times\else\texttimes\fi{}\mathrm{integer}$, is activated. This explains the plateau flatness and the high precision of the QHE measurements of the fine-structure constant.
A surface brightness-metallicity relation for dwarf galaxies : the effect of density thresholds for star formation ?

It is well known that dwarf galaxies exhibit a luminosity (or mass)-metallicity relation. However, since dwarfs also display a surface brightness-luminosity relation (whether real or due to selection effects), the relationship can be alternatively considered to be between metallicity and surface brightness. Such a relationship is shown to be easily produced if there is a gas density threshold below which massive star formation is cut off. The stellar metallicity distributions for two simple models incorporating such a cut-off are calculated.
Freezing in the hierarchy problem

Models with a tiny coupling $\lambda$ between the dark matter and the Standard Model, $\lambda \sim v/M_\text{Pl}\sim 10^{-16}$, can yield the measured relic abundance through the thermal process known as freeze-in. We propose to interpret this small number in the context of perturbative large $N$ theories, where couplings are suppressed by inverse powers of $N$. Then $N \sim M_{\rm Pl}^2/v^2$ gives the observed relic density. Additionally, the ultimate cutoff of the Standard Model is reduced to $\sim 4\,\pi\, M_\text{Pl}/\sqrt{N} \sim 4\, \pi\, v$, thereby solving the electroweak hierarchy problem. These theories predict a direct relation between the Standard Model cutoff and the dark matter mass, linking the spectacular collider phenomenology associated with the low gravitational scale to the cosmological signatures of the dark sector. The dark matter mass can lie in the range from hundreds of keV to hundreds of GeV. Possible cosmological signals include washing out power for small scale structure, indirect detection signals from dark matter decays, and a continuous injection of electromagnetic and hadronic energy throughout the history of the Universe.