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Stellar-driven galactic winds are multiphase outflows of energy and matter connecting the interstellar and circumgalactic media (CGM) with the intergalactic medium. Galactic winds contain a hot and diffuse phase detected in X-rays, and a cold and dense phase detected via emission and absorption lines from the ions populating the outflow. The ion production within galactic winds largely depends on the background UV radiation field produced by star formation, and this in turn depends on the age of the starburst, the gas metallicity, the proximity of the outflowing gas to the central star-forming regions. Our study probes the influence of the proximity of wind-cloud systems to the UV background source, and the effects of magnetic fields on the N V ion production through the analysis of synthetic column densities and spectral lines. We utilise magnetohydrodynamical simulations to study weakly-magnetised wind-cloud systems, and extract synthetic spectral lines with Trident and yt. Our simulations indicate that magnetic fields transverse to the wind have a shielding effect on dense gas, producing broader N V absorption lines. Also, a weak (distant) UV background produces N V only in the outer cloud layers with no spectral signature, while a strong (nearby) UV background produces it in the cloud core with a narrow spectral line. Overall, transverse magnetic fields and a UV radiation at 50 kpc produce the stronger N V spectral lines., Comment: 5 pages, 1 figure, accepted for publication in the International Astronomical Union Proceedings Series (IAU General Assembly 2024)

We report the fabrication and characteristics of GaAs/Si p+/n+ heterojunction tunnel diodes. These diodes were fabricated via grafting the freestanding single-crystalline p-type degenerately doped GaAs (4E19 cm-3) nanomembrane (NM) onto single-crystalline n-type Si (5E19 cm-3) substrate. At the heterointerface, an amorphous ultrathin oxygen-enriched layer (UOL) was intentionally engineered through chemical oxidation and atomic layer deposition (ALD). Scanning transmission electron microscopy (STEM) confirmed the formation of the UOL and the single crystallinity of the grafted junction. The resulting tunnel diodes consistently exhibited negative differential resistance (NDR) behavior at room temperature, with a high maximum peak-to-valley current ratio (PVCR) of 36.38, valley voltages ranging from 1.3 to 1.8 V, and a peak tunneling current density of 0.95 kA/cm2. This study not only highlights the critical roles of the UOL as both an interface improvement layer and a quantum tunneling medium, but also establishes "semiconductor grafting" as an effective and versatile method for high-performance, lattice-mismatched heterojunction devices., Comment: 4 pages, 5 figures

Unconventional superconductivity in heavy-fermion systems appears often near magnetic quantum critical points (QCPs). This seems to be the case also for CeRh2As2 (Tc $\approx$ 0.31 K). CeRh2As2 shows two superconducting (SC) phases, SC1 and SC2, for a magnetic field along the c axis of the tetragonal unit cell, but only the SC1 phase is observed for a field along the basal plane. Furthermore, another ordered state (phase-I) is observed below T0 $\approx$ 0.48 K whose nature is still unclear: Thermodynamic and magnetic measurements pointed to a non magnetic multipolar state, but recent $\mu$SR and NQR/NMR experiments have clearly detected antiferromagnetic (AFM) order below T0 . Also, quasi-two-dimensional AFM fluctuations were observed in NMR and neutron-scattering experiments above T0. The proximity of a QCP is indicated by non-Fermi-liquid (NFL) behavior observed above the ordered states in both specific heat $C(T)/T \propto T^{-0.6}$ and resistivity $\rho(T) \propto T^{0.5}$. These T-dependencies are not compatible with any generic AFM QCP. Because of the strong magnetic-field anisotropy of both the SC phase and phase I, it is possible to study a field-induced SC QCP as well a phase-I QCP by varying the angle $\alpha$ between the field and the c axis. Thus, by examining the behavior of the electronic specific-heat coefficient C(T)/T across these QCPs, we can determine which phase is associated with the NFL behavior. Here, we present low-temperature specific-heat measurements taken in a magnetic field as high as 21 T applied at several angles $\alpha$. We observe that the NFL behavior does very weakly depend on the field and on the angle $\alpha$, a result that is at odd with that observations in standard magnetic QCPs. This suggests a nonmagnetic origin of the quantum critical fluctuations., Comment: 10 pages, 7 figures

This paper addresses the problem of autonomous UAV search missions, where a UAV must locate specific Entities of Interest (EOIs) within a time limit, based on brief descriptions in large, hazard-prone environments with keep-out zones. The UAV must perceive, reason, and make decisions with limited and uncertain information. We propose NEUSIS, a compositional neuro-symbolic system designed for interpretable UAV search and navigation in realistic scenarios. NEUSIS integrates neuro-symbolic visual perception, reasoning, and grounding (GRiD) to process raw sensory inputs, maintains a probabilistic world model for environment representation, and uses a hierarchical planning component (SNaC) for efficient path planning. Experimental results from simulated urban search missions using AirSim and Unreal Engine show that NEUSIS outperforms a state-of-the-art (SOTA) vision-language model and a SOTA search planning model in success rate, search efficiency, and 3D localization. These results demonstrate the effectiveness of our compositional neuro-symbolic approach in handling complex, real-world scenarios, making it a promising solution for autonomous UAV systems in search missions.

We report on single crystal growth and physical properties of the quantum critical Kondo-lattice system YbNi$_4$(P$_{1-x}$As$_{x}$)$_2$ with $0\leq x\leq 1$ which hosts a ferromagnetic quantum critical point at $x \approx 0.1$. We performed measurements of the magnetization, electrical resistivity, thermopower, heat capacity, and resonant X-ray emission spectroscopy. Arsenic substitution leads to a homogeneous increase of the unit-cell volume, with well-defined As-concentrations in large parts of the single crystals. All data consistently show that with increasing $x$ the Kondo temperature increases, while the magnetic anisotropy observed at low $x$ fully vanishes towards $x=1$. Consequently, at low temperatures, the system shows a crossover from pronounced non-Fermi liquid behaviour for $x \leq 0.2$ to a Fermi liquid behavior for $x > 0.2$ with weak correlations. There is a continuous change in Yb valence from nearly trivalent at low $x$ to a slightly lower value for $x = 0.6$, which correlates with the Kondo temperature. Interestingly, specific heat measurements at very low temperatures show that $C/T$ strongly increases towards lower $T$ for $x = 0.13$ and $x = 0.2$ with a very similar power law. This suggests that in YbNi$_4$(P$_{1-x}$As$_{x}$)$_2$ a quantum critical region rather than a quantum critical point might exist.

The expanding molecular ring (EMR) manifests itself as a parallelogram in the position-velocity diagram of spectral line emission from the Central Molecular Zone (CMZ) surrounding the Galacic centre (GC). Using multiwavelength data, we investigate the gas kinematics, star formation activity, and the presence of shocked gas in a 200 pc long high velocity gas stream (V~ +150 km/s) with a double helix morphology named the helix stream, that is located 15-55 pc above the CMZ and is kinematically associated with the EMR/parallelogram. We carried out molecular line observations using the IRAM 30m, Yebes 40m, and APEX 12m telescopes. The detection of four rotational transitions of the SiO molecule indicate the presence of shocks. We derived the SiO column densities and abundances in different regions of the helix stream. The presence of protostellar clumps and a candidate HII region signify the ongoing star formation activity within the helix stream. The cloud is massive (2.5x10^6 M_sun) and highly turbulent. We find evidence of cloud-cloud collisions towards the eastern edge (l~1.3{\deg}), suggesting a dynamic interaction with the CMZ. An expanding shell is detected within the cloud with radius of 6.7 pc and an expansion velocity of 35 km/s. The shell might be powered by several supernovae or a single hypernova. The SiO abundance within the helix stream implies extensive shock processes occurring on large scales. The helical or cork-screw velocity structure of the helix stream indicates twisting and turning motions within the cloud. We propose that the helix stream is the continuation of the near side bar lane, that is overshooting after brushing the CMZ. Our findings carry profound implications for understanding star formation in extreme conditions and elucidate the intricate properties of gas and dust associated with nuclear inflows in barred spiral galaxies., Comment: 20 pages, 20 figures, 4 tables, accepted for publication in A&A

It has been known for many years that methods inspired by string theory, such as the worldline formalism, allow one to write down integral representations that combine large numbers of Feynman diagrams of different topologies. However, to make this fact useful for state-of-the-art calculations one has to confront non-standard integration problems where neither the known integration techniques for Feynman diagrams nor algebraic manipulation programs are of much help. Here I will give a progress report on this long-term project focussing on photon amplitudes at one and two loops, in vacuum and in external fields., Comment: 13 pages, 3 figures, talk given by Christian Schubert at Loops and Legs in Quantum Field Theory (LL2024), 14-19 April 2024, Wittenberg, Germany

Pareto optimal solutions are conceived for radar beamforming error (RBE) and sum rate maximization in short-packet (SP) millimeter-wave (mmWave) integrated sensing and communication (ISAC). Our ultimate goal is to realize ultra-reliable low-latency communication (uRLLC) and real-time sensing capabilities for 6G applications. The ISAC base station (BS) transmits short packets in the downlink (DL) to serve multiple communication users (CUs) and detect multiple radar targets (RTs). We investigate the performance trade-off between the sensing and communication capabilities by optimizing both the radio frequency (RF) and the baseband (BB) transmit precoder (TPC), together with the block lengths. The optimization problem considers the minimum rate requirements of the CUs, the maximum tolerable radar beamforming error (RBE) for the RTs, the unit modulus (UM) elements of the RF TPC, and the finite transmit power as the constraints for SP transmission. The resultant problem is highly non-convex due to the intractable rate expression of the SP regime coupled with the non-convex rate and UM constraints. To solve this problem, we propose an innovative two-layer bisection search (TLBS) algorithm, wherein the RF and BB TPCs are optimized in the inner layer, followed by the block length in the outer layer. Furthermore, a pair of novel methods, namely a bisection search-based majorizer and minimizer (BMM) as well as exact penalty-based manifold optimization (EPMO) are harnessed for optimizing the RF TPC in the inner layer. Subsequently, the BB TPC and the block length are derived via second-order cone programming (SOCP) and mixed integer programming methods, respectively. Finally, our exhaustive simulation results reveal the effect of system parameters for various settings on the RBE-rate region of the SP mmWave ISAC system and demonstrate a significantly enhanced performance compared to the benchmarks., Comment: 15 pages, 13 figures

Commercial adiabatic demagnetisation refrigerators still employ the same hydrated salts that were first introduced over 85 years ago. The inherent limitations of these insulating magnetocalorics - poor thermal conductivity at sub-Kelvin temperatures, low entropy density, corrosiveness - can be overcome by a new generation of rare-earth based metallic magnetocalorics. Here, we present the metallic magnetocaloric YbNi1.6 Sn as an attractive alternative to conventional refrigerants. YbNi1.6Sn retains high entropy into the 100 mK regime and avoids the noble metal constituents of alternative refrigerants. Demagnetisation tests demonstrate that YbNi1.6Sn enables economical and durable alternatives to traditional cooling devices for temperatures reaching below 120 mK. We find that the magnetocaloric properties of this material are facilitated by unusually small Kondo and RKKY interactions, which position YbNi1.6Sn in the extreme local moment limit on the generalised Kondo lattice phase diagram., Comment: 9 pages, 4 figures

Galactic superbubbles are triggered by stellar feedback in the discs of star-forming galaxies. They are important in launching galactic winds, which play a key role in regulating the mass and energy exchange in galaxies. Observations can only reveal projected information and the 3D structure of such winds is quite complex. Therefore, numerical simulations are required to further our understanding of such structures. Here, we describe hydrodynamical simulations targeting two spatial scales. Large-scale superbubble models reveal supernova-driven outflows, and their subsequent merging, which leads to galactic wind formation. Additionally, the turbulence parameter $\sigma_t$ not only affects disc formation, but also influences mass and energy characteristics, controlling gas distribution and the injection rate in the simulated star formation zone. Small-scale wind-multicloud models indicate that isolated clouds are susceptible to instabilities, leading to fragmentation and dense gas destruction. In contrast, in closer cloud configurations, the condensation mechanism becomes important owing to hydrodynamic shielding, which helps to maintain the cold material throughout the evolution of the system. These simulations provide a comprehensive picture of galactic winds, showing how large-scale superbubble dynamics create the environment where small-scale wind-multicloud interactions shape the interstellar and circumgalactic media, ultimately regulating galaxy evolution., Comment: Published in Journal of Physics: Conference Series - XVIII: Encuentro de F\'isica (Physics EPN 2023), available online at: https://doi.org/10.1088/1742-6596/2796/1/012004

The interstellar medium (ISM) is a key ingredient of galaxies and their evolution, consisting of multiphase, turbulent dust and gas. Some of the star-forming regions in our Galaxy originate from cloud-cloud and wind-cloud collisions, which generate shock waves that change the physical and chemical properties of the gas. We utilise our own python-based shock-finding algorithm to study the properties and distribution of shocks in interstellar collisions. Such interactions are studied via 3D numerical simulations with different initial conditions: Cloud-cloud collisions (CCc): We identify four stages of evolution: pre-collision, compression, pass-through, and dissipation. We also vary the size of one of the colliding clouds. Larger clouds facilitate cloud erosion and the formation of more and stronger shocks at early stages. Shock distributions are also time-dependent, as strong shocks are only produced during the early stages. As the collisions evolve, turbulent kinetic energy is rapidly dissipated, so most perturbations become subsonic waves at late times. Wind-cloud collisions (WCc): we identify four stages: compression, stripping, expansion, and break-up. We study the evolution of several diagnostics in these clouds: energies (thermal and kinetic), temperature, displacement of the centre of mass, and mass-weighted averages of the cloud density and acceleration. We show, that the geometry of the cloud impact the diagnostic parameters, for example, smoothing the edges of the cloud leads to enhanced mass losses and dispersion, but has little impact on the shock distribution., Comment: In press, Journal of Physics: Conference Series XVIII: Encuentro de Fisica (Physics EPN 2023)

The impact of using artificial intelligence (AI) to guide patient care or operational processes is an interplay of the AI model's output, the decision-making protocol based on that output, and the capacity of the stakeholders involved to take the necessary subsequent action. Estimating the effects of this interplay before deployment, and studying it in real time afterwards, are essential to bridge the chasm between AI model development and achievable benefit. To accomplish this, the Data Science team at Stanford Health Care has developed a Testing and Evaluation (T&E) mechanism to identify fair, useful and reliable AI models (FURM) by conducting an ethical review to identify potential value mismatches, simulations to estimate usefulness, financial projections to assess sustainability, as well as analyses to determine IT feasibility, design a deployment strategy, and recommend a prospective monitoring and evaluation plan. We report on FURM assessments done to evaluate six AI guided solutions for potential adoption, spanning clinical and operational settings, each with the potential to impact from several dozen to tens of thousands of patients each year. We describe the assessment process, summarize the six assessments, and share our framework to enable others to conduct similar assessments. Of the six solutions we assessed, two have moved into a planning and implementation phase. Our novel contributions - usefulness estimates by simulation, financial projections to quantify sustainability, and a process to do ethical assessments - as well as their underlying methods and open source tools, are available for other healthcare systems to conduct actionable evaluations of candidate AI solutions.

Stellar-driven galactic winds regulate the mass and energy content of star-forming galaxies. Emission- and absorption-line spectroscopy shows that these outflows are multiphase and comprised of dense gas clouds embedded in much hotter winds. Explaining the presence of cold gas in such environments is a challenging endeavour that requires numerical modelling. In this paper we report a set of 3D hydrodynamical simulations of supersonic winds interacting with radiative and adiabatic multicloud systems, in which clouds are placed along a stream and separated by different distances. As a complement to previous adiabatic, subsonic studies, we demonstrate that hydrodynamic shielding is also triggered in supersonic winds and operates differently in adiabatic and radiative regimes. We find that the condensation of warm, mixed gas in between clouds facilitates hydrodynamic shielding by replenishing dense gas along the stream, provided that its cooling length is shorter than the cloud radius. Small separation distances between clouds also favour hydrodynamic shielding by reducing drag forces and the extent of the mixing region around the clouds. In contrast, large separation distances promote mixing and dense gas destruction via dynamical instabilities. The transition between shielding and no-shielding scenarios across different cloud separation distances is smooth in radiative supersonic models, as opposed to their adiabatic counterparts for which clouds need to be in close proximity. Overall, hydrodynamic shielding and re-condensation are effective mechanisms for preserving cold gas in multiphase flows for several cloud-crushing times, and thus can help understand cold gas survival in galactic winds., Comment: 16 pages, 11 figures. Submitted to MNRAS. Comments are welcome

Galactic winds probe how stellar feedback regulates the mass and metallicity of galaxies. Observations show that galactic winds are multiphase and magnetised. In the local Universe, the dense phase is traced by emission and absorption lines, which reveal the presence of fast-moving clouds embedded in hot streams. Simulations tell us that magnetic fields can shield such clouds and delay their disruption, but there is little discussed on their observational effects. Using 3D MHD simulations, we study the influence of two orientations of the magnetic field (aligned and transverse) on the cloud morphology, temperature and density structure, mixing fraction, ion kinematics, column densities, and absorption spectra. We study supersonic wind-cloud systems with radiative processes, and develop a framework to extract ion column density maps and synthetic absorption spectra. The framework relies on studying ion populations and creating down-the-barrel spectra via an interface that links our PLUTO simulations to TRIDENT using YT, CLOUDY, and STARBURST99. We find that the transverse magnetic field makes the cloud asymmetric, shields and protects dense cold gas, and reduces mixing fractions compared to the aligned case. Ions can reach higher velocities in the transverse field case. The imprints of the initial orientation of the field on the synthetic spectra are: in the cold phase we find no signature of C ii and Si ii when the field is aligned, in the intermediate phase traced by C iv and Si iv we find broader lines in the transverse case, and in the warm phase we find deeper lines for O vi and N v in the aligned case, but they are less sensitive to the field orientation. Magnetic fields significantly affect the absorption spectra of cold clouds. Intermediate ions are the most sensitive to the magnetic field orientation and can potentially yield information about magnetic field topology., Comment: 18 pages, 13 figures

We carry out a detailed study of the three-point fermion-photon interaction vertex at one loop order for massive fermions in reduced quantum electrodynamics. This calculation is carried out in arbitrary covariant gauges and space-time dimensions within a recently proposed innovative approach based upon an efficient combination of the first and second order formalisms of quantum electrodynamics. This procedure provides a natural decomposition of the vertex into its components which are longitudinal and transverse to the photon momentum. It also separates the spin and scalar degrees of freedom of a fermion interacting electromagnetically, allowing us to readily establish the gauge-independence of the Pauli form factor and compute it in an expeditious manner. All incoming and outgoing momenta are taken off-shell at the outset. However, we present results for cases of particular kinematic interest whenever required. For the sake of completeness, we also provide expressions for the massive fermion self energy and photon vacuum polarization, verifying known expressions for massless reduced quantum electrodynamics and computing the renormalization constants ${\cal Z}_1$, ${\cal Z}_2$ and ${\cal Z}_3$. As we provide general expressions for the computed Green functions, we readily reproduce and confirm the results for standard quantum electrodynamics. Comparing the two cases, we infer that the Pauli form factor for reduced quantum electrodynamics is $8/3$ times that for the standard QED in four dimensions, implying a higher Land\'e $g$-factor. We expect our perturbative calculation of the fermion-photon vertex to serve as a guide for any non-perturbative construction of this Green function, invariably required in the Schwinger-Dyson equation studies of the subject., Comment: 14 pages, 5 figures

The COVID-19 pandemic has presented significant challenges to the healthcare industry and society as a whole. With the rapid development of COVID-19 vaccines, social media platforms have become a popular medium for discussions on vaccine-related topics. Identifying vaccine-related tweets and analyzing them can provide valuable insights for public health research-ers and policymakers. However, manual annotation of a large number of tweets is time-consuming and expensive. In this study, we evaluate the usage of Large Language Models, in this case GPT-4 (March 23 version), and weak supervision, to identify COVID-19 vaccine-related tweets, with the purpose of comparing performance against human annotators. We leveraged a manu-ally curated gold-standard dataset and used GPT-4 to provide labels without any additional fine-tuning or instructing, in a single-shot mode (no additional prompting).