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Debugging software, i.e., the localization of faults and their repair, is a main activity in software engineering. Therefore, effective and efficient debugging is one of the core skills a software engineer must develop. However, the teaching of debugging techniques is usually very limited or only taught in indirect ways, e.g., during software projects. As a result, most Computer Science (CS) students learn debugging only in an ad-hoc and unstructured way. In this work, we present our approach called Simulated Interactive Debugging that interactively guides students along the debugging process. The guidance aims to empower the students to repair their solutions and have a proper "learning" experience. We envision that such guided debugging techniques can be integrated into programming courses early in the CS education curriculum. To perform an initial evaluation, we developed a prototypical implementation using traditional fault localization techniques and large language models. Students can use features like the automated setting of breakpoints or an interactive chatbot. We designed and executed a controlled experiment that included this IDE-integrated tooling with eight undergraduate CS students. Based on the responses, we conclude that the participants liked the systematic guidance by the assisted debugger. In particular, they rated the automated setting of breakpoints as the most effective, followed by the interactive debugging and chatting, and the explanations for how breakpoints were set. In our future work, we will improve our concept and implementation, add new features, and perform more intensive user studies.

The Bayesian elastic net regression model is characterized by the regression coefficient prior distribution, the negative log density of which corresponds to the elastic net penalty function. While Markov chain Monte Carlo (MCMC) methods exist for sampling from the posterior of the regression coefficients given the penalty parameters, full Bayesian inference that incorporates uncertainty about the penalty parameters remains a challenge due to an intractable integrable in the posterior density function. Though sampling methods have been proposed that avoid computing this integral, all correctly-specified methods for full Bayesian inference that have appeared in the literature involve at least one "Metropolis-within-Gibbs" update, requiring tuning of proposal distributions. The computational landscape is complicated by the fact that two forms of the Bayesian elastic net prior have been introduced, and two representations (with and without data augmentation) of the prior suggest different MCMC algorithms. We review the forms and representations of the prior, discuss all combinations of these different treatments for the first time, and introduce one combination of form and representation that has yet to appear in the literature. We introduce MCMC algorithms for full Bayesian inference for all treatments of the prior. The algorithms allow for direct sampling of all parameters without any "Metropolis-within-Gibbs" steps. The key to the new approach is a careful transformation of the parameter space and an analysis of the resulting full conditional density functions that allows for efficient rejection sampling. We make empirical comparisons between our approaches and existing MCMC samplers for different data structures.

To optimize interventions for improving wellness, it is essential to understand habits, which wearable devices can measure with greater precision. Using high temporal resolution biometric data taken from the Oura Gen3 ring, we examine daily and weekly sleep and activity patterns of a cohort of young adults (N=582) in their first semester of college. A high compliance rate is observed for both daily and nightly wear, with slight dips in wear compliance observed shortly after waking up and also in the evening. Most students have a late-night chronotype with a median midpoint of sleep at 5AM, with males and those with mental health impairment having more delayed sleep periods. Social jetlag, or the difference in sleep times between free days and school days, is prevalent in our sample. While sleep periods generally shift earlier on weekdays and later on weekends, sleep duration on both weekdays and weekends is shorter than during prolonged school breaks, suggesting chronic sleep debt when school is in session. Synchronized spikes in activity consistent with class schedules are also observed, suggesting that walking in between classes is a widespread behavior in our sample that substantially contributes to physical activity. Lower active calorie expenditure is associated with weekends and a delayed but longer sleep period the night before, suggesting that for our cohort, active calorie expenditure is affected less by deviations from natural circadian rhythms and more by the timing associated with activities. Our study shows that regular sleep and activity routines may be inferred from consumer wearable devices if high temporal resolution and long data collection periods are available.

Tokenization is a necessary component within the current architecture of many language models, including the transformer-based large language models (LLMs) of Generative AI, yet its impact on the model's cognition is often overlooked. We argue that LLMs demonstrate that the Distributional Hypothesis (DH) is sufficient for reasonably human-like language performance, and that the emergence of human-meaningful linguistic units among tokens motivates linguistically-informed interventions in existing, linguistically-agnostic tokenization techniques, particularly with respect to their roles as (1) semantic primitives and as (2) vehicles for conveying salient distributional patterns from human language to the model. We explore tokenizations from a BPE tokenizer; extant model vocabularies obtained from Hugging Face and tiktoken; and the information in exemplar token vectors as they move through the layers of a RoBERTa (large) model. Besides creating sub-optimal semantic building blocks and obscuring the model's access to the necessary distributional patterns, we describe how tokenization pretraining can be a backdoor for bias and other unwanted content, which current alignment practices may not remediate. Additionally, we relay evidence that the tokenization algorithm's objective function impacts the LLM's cognition, despite being meaningfully insulated from the main system intelligence.

The spectrum of the first supernova light (i.e., the shock breakout and early cooling emission) is an important diagnostic for the state of the progenitor star just before explosion. We consider a streamlined model describing the emergent shock breakout spectrum, which enables a straightforward classification of the possible observed spectra during the early planar phase. The overall spectral evolution is determined by a competition between three important time-scales: the diffusion time $t_{\rm{bo}}$ of the shell producing the breakout emission, the light-crossing time of this shell $t_{\rm{lc}}$, and the time $t_{\rm{eq}}$ at which the observer starts to see layers of the ejecta where the gas and radiation are in thermal equilibrium. There are five allowed orderings of these time-scales, resulting in five possible scenarios with distinct spectral behaviours. Within each scenario, the spectrum at a given time is one of five possible types, which are approximately described by broken power-laws; we provide the spectral and temporal indices of each power-law segment, and the time evolution of the break frequencies. If high-cadence multi-wavelength observations can determine the relevant breakout scenario in future events, strong constraints can be placed on the physical conditions at the site of shock breakout., Comment: 6 pages, 3 figures, submitted to MNRAS Letters

Despite two decades since the discovery of low-luminosity gamma-ray bursts, their origin remains poorly understood. In events such as GRB 060218, shock breakout from a progenitor with an extended ($10^{13}$ - $10^{14}$ cm), low-mass (0.01 - 0.1 M$_\odot$) envelope provides one possible interpretation for the smooth prompt X-ray emission lasting $\sim 1000$ s and the early optical peak at $\sim 0.5$ d. However, current shock breakout models have difficulties explaining the unexpectedly strong optical emission at $\sim 100$ s, the simultaneous presence of blackbody and power-law components in the X-ray spectrum, and the rapid evolution of the peak energy. We suggest that these peculiar features can be explained by a recently realized shock breakout scenario, in which the gas and the radiation are initially out of thermal equilibrium, but they achieve equilibrium on a time-scale faster than the light-crossing time of the envelope. In this non-standard case, due to the effects of light travel time, the observed X-ray spectrum is a multi-temperature blend of blackbody and free-free components. The free-free emission is spectrally broad, peaking in hard X-rays while also enhancing the early optical signal. As the system thermalizes, the free-free component quickly evolves toward lower energies, reproducing the observed rapid peak energy decay. To match observations, we find that more than $10^{50}$ erg must be deposited in the envelope, which may be accomplished by a choked jet. These results strengthen the case for a shock breakout origin of $ll$GRBs, and provide further evidence connecting $ll$GRBs to peculiar progenitors with extended low-mass envelopes., Comment: 17 pages, 6 figures, submitted to MNRAS

The first light that escapes from a supernova explosion is the shock breakout emission, which produces a bright flash of UV or X-ray radiation. Standard theory predicts that the shock breakout spectrum will be a blackbody if the gas and radiation are in thermal equilibrium, or a Comptonized free-free spectrum if not. Using recent results for the post-breakout evolution which suggest that lower-temperature ejecta are probed earlier than previously thought, we show that another scenario is possible in which the gas and radiation are initially out of equilibrium, but the time when thermalized ejecta are revealed is short compared to the light-crossing time of the system. In this case, the observed spectrum differs significantly from the standard expectation, as the non-negligible light travel time acts to smear the spectrum into a complex multi-temperature blend of blackbody and free-free components. For typical parameters, a bright multi-wavelength transient is produced, with the free-free emission being spread over a wide frequency range from optical to hard X-rays, and the blackbody component peaking in soft X-rays. We explore the necessary conditions to obtain this type of unusual spectrum, finding that it may be relevant for bare blue supergiant progenitors, or for shocks with a velocity of $v_{\rm bo} \sim 0.1c$ breaking out from an extended medium of radius $R_{\rm env}$ with a sufficiently high density $\rho_{\rm bo} \gtrsim 4\times 10^{-12}\text{ g cm}^{-3} (R_{\rm env}/10^{14} \text{cm})^{-15/16}$. An application to low-luminosity gamma-ray bursts is considered in a companion paper., Comment: 26 pages, 9 figures, submitted to MNRAS

Cybersecurity threats in automotive systems pose significant risks to safety and reliability. This article introduces a methodology integrating threat-informed dynamic security modelling with a Threat Analysis and Risk Assessment workflow. Using the example of an In-Vehicle Infotainment system, we demonstrate the methodology's application in risk management to strengthen automotive resiliency., Comment: Preprint under submission

As software development increasingly adopts automation, bot-driven development (BotDD) represents a transformative shift where bots assume proactive roles in coding, testing, and project management. In bot-driven development, bots go beyond support tasks, actively driving development workflows by making autonomous decisions, performing independent assessments, and managing code quality and dependencies. This paper explores how bot-driven development impacts traditional development roles, particularly in redefining driver-navigator dynamics, and aligns with DevOps goals for faster feedback, continuous learning, and efficiency. We propose a research agenda addressing challenges in bot-driven development, including skill development for developers, human-bot trust dynamics, optimal interruption frequency, and ethical considerations. Through empirical studies and prototype systems, our aim is to define best practices and governance structures for integrating bot-driven development into modern software engineering., Comment: BotSE 2025: International Workshop on Bots in Software Engineering

The common phrase 'representation matters' asserts that media has a measurable and important impact on civic society's perception of self and others. The representation of health in media, in particular, may reflect and perpetuate a society's disease burden. Here, for the top 10 major causes of death in the United States, we examine how cinematic representation of overall and by-gender mortality diverges from reality. Using crowd-sourced data on film deaths from Cinemorgue Wiki, we employ natural language processing (NLP) techniques to analyze shifts in representation of deaths in movies versus the 2021 National Vital Statistic Survey (NVSS) top ten mortality causes. Overall, movies strongly overrepresent suicide and, to a lesser degree, accidents. In terms of gender, movies overrepresent men and underrepresent women for nearly every major mortality cause, including heart disease and cerebrovascular disease. The two exceptions for which women are overrepresented are suicide and accidents. We discuss the implications of under- and over-representing causes of death overall and by gender, as well as areas of future research., Comment: 10 pages, 2 figures, 1 appendix page

This article presents the latest results of our ALMA program to study circumstellar disk characteristics as a function of orbital and stellar properties in a sample of young binary star systems known to host at least one disk. Optical and infrared observations of the eccentric, ~48-year period binary DF Tau indicated the presence of only one disk around the brighter component. However, our 1.3 mm ALMA thermal continuum maps show two nearly-equal brightness components in this system. We present these observations within the context of updated stellar and orbital properties which indicate that the inner disk of the secondary is absent. Because the two stars likely formed together, with the same composition, in the same environment, and at the same time, we expect their disks to be co-eval. However the absence of an inner disk around the secondary suggests uneven dissipation. We consider several processes which have the potential to accelerate inner disk evolution. Rapid inner disk dissipation has important implications for planet formation, particularly in the terrestrial-planet-forming region., Comment: 18 pages, 8 figures, accepted to AJ

We explore synergies between the Nancy Grace Roman Space Telescope High Latitude Wide Area Survey (HLWAS) and CMB experiments, specifically Simons Observatory (SO) and CMB-Stage4 (S4). Our simulated analyses include weak lensing, photometric galaxy clustering, CMB lensing, thermal SZ, and cross-correlations between these probes. While we assume the nominal 16,500 square degree area for SO and S4, we consider multiple survey designs for Roman that overlap with Rubin Observatory's Legacy Survey of Space and Time (LSST): the 2000 square degree reference survey using four photometric bands, and two shallower single-band surveys that cover 10,000 and 18,000 square degree, respectively. We find a ~2x increase in the dark energy figure of merit when including CMB-S4 data for all Roman survey designs. We further find a strong increase in constraining power for the Roman wide survey scenario cases, despite the reduction in galaxy number density, and the increased systematic uncertainties assumed due to the single band coverage. Even when tripling the already worse systematic uncertainties in the Roman wide scenarios, which reduces the 10,000 square degree FoM from 269 to 178, we find that the larger survey area is still significantly preferred over the reference survey (FoM 64). We conclude that for the specific analysis choices and metrics of this paper, a Roman wide survey is unlikely to be systematics-limited (in the sense that one saturates the improvement that can be obtained by increasing survey area). We outline several specific implementations of a two-tier Roman survey (1000 square degree with 4 bands, and a second wide tier in one band) that can further mitigate the risk of systematics for Roman wide concepts., Comment: Comments welcome!

In the months leading up to political elections in the United States, forecasts are widespread and take on multiple forms, including projections of what party will win the popular vote, state ratings, and predictions of vote margins at the state level. It can be challenging to evaluate how accuracy changes in the lead up to Election Day or to put probabilistic forecasts into historical context. Moreover, forecasts differ between analysts, highlighting the many choices in the forecasting process. With this as motivation, here we take a more comprehensive view and begin to unpack some of the choices involved in election forecasting. Building on a prior compartmental model of election dynamics, we present the forecasts of this model across months, years, and types of race. By gathering together monthly forecasts of presidential, senatorial, and gubernatorial races from 2004--2022, we provide a larger-scale perspective and discuss how treating polling data in different ways affects forecast accuracy. We conclude with our 2024 election forecasts (upcoming at the time of writing)., Comment: For our 2024 forecasts, see: https://c-r-u-d.gitlab.io/2024/. Our code is available at: https://gitlab.com/alexandriavolkening/forecasting-elections-using-compartmental-models-2

The reported discovery of a cold ($\sim$10$^4~\text{K}$) disc-like structure around the super-massive black hole at the centre of the Milk Way, Sagittarius A* (Sgr A*), has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its immediate vicinity. State-of-the-art simulations do not agree on whether or not such a disc can indeed be a product of the multiple stellar wind interactions of the mass-losing stars in the region. This study aims to constrain the conditions for the formation of a cold disc as a natural outcome of the system of the mass-losing stars orbiting around Sgr A*, to investigate if the disc is a transient or long-lasting structure, and to assess the validity of the model through direct comparisons with observations. We conduct a set of hydrodynamic simulations of the observed Wolf-Rayet (WR) stars feeding Sgr A* using the finite-volume adaptive mesh-refinement code Ramses. We focus, for the first time, on the impact of the chemical composition of the plasma emanating from the WR stars. The simulations show that the chemical composition of the plasma affects the radiative cooling enough to impact the properties of the medium such as density and temperature and, as a consequence, the rate at which the material inflows onto Sgr A*. We demonstrated that the formation of a cold disc from the stellar winds is possible for certain chemical compositions that are consistent with the current observational constraints. However, even in such a case, it is not possible to reproduce the reported properties of the observed disc-like structure, namely its inclination and hydrogen recombination line fluxes. We conclude that the stellar winds on their own cannot form the cold disc around Sgr A* inferred from the observations. Either relevant ingredients are still missing in the model, or the interpretation of the observed data needs to be revised., Comment: Submitted to A&A, 17 pages, 11 figures (+2 pages, +2 figures in Appendix)

Harmful cyanobacterial blooms (CBs) have a growing global prevalence, emerging as a significant environmental concern due to their potential toxicity. Understanding how the different mechanisms affect CBs is crucial to develop actionable management strategies. For this, we derive a stoichiometric dynamical system that describes the qualitative population dynamics of cyanobacteria and their toxicity in north-temperate freshwater ecosystems. Our model quantifies the hypoxic effects of CBs on fish mortality and the effect of microcystin-LR (MC-LR), a potent toxin produced by cyanobacteria, on aquatic macro-invertebrates, phytoplankton, and fish species. By fitting the model to lakes with varying physical characteristics, eutrophic conditions, and water temperature, we can delineate and understand the driving components of CBs. We show that decreases in water exchange rate, depth of epilimnion, or light attenuation increases bloom intensity and duration. Furthermore, our models concur that eutrophication and increasing water temperatures exacerbate the intensity of CBs. We observe a severe bioaccumulative effect of MC-LR in aquatic species, stressing the potential impact on humans and other terrestrial animals. We validate our model with field measurements demonstrating its applicability to several realistic lake conditions. These insights are essential for informing targeted interventions to reduce CBs and their ecological impacts., Comment: Main Document: 11 pages

The Nancy Grace Roman Space Telescope, set to launch in 2026, will bring unprecedented precision to measurements of weak gravitational lensing. Because weak lensing is an inherently small signal, it is imperative to minimize systematic errors in measurements as completely as possible; this will ensure that the lensing measurements can be used to their full potential when extracting cosmological information. In this paper, we use laboratory tests of the Roman detectors, simulations of the Roman High Latitude Survey observations, and the proposed Roman image combination pipeline to investigate the magnitude of detector read noise biasing on weak lensing measurements from Roman. First, we combine lab-measured detector noise fields with simulated observations and propagate these images through the Roman image combination pipeline, IMCOM. We characterize the specific signatures of the noise fields in the resultant images and find that noise contributes to the combined images most strongly at scales relevant to physical characteristics of the detector including PSF shape, chip boundaries, and roll angles. We then measure shapes of simulated stars and galaxies and determine the magnitude of noise-induced shear bias on these measurements. We find that star shape correlations satisfy the system noise requirements as defined by the Roman Science Requirements Document. However, for galaxies fainter than $m_{\rm AB}\simeq24$, correction for noise correlations will be needed in order to ensure confidence in shape measurements in any observation band., Comment: 22 pages, 15 figures. Updated to version accepted to PASP

The Nancy Grace Roman Space Telescope will implement a devoted weak gravitational lensing program with its High Latitude Wide Area Survey. For cosmological purposes, a critical step in Roman image processing is to combine dithered undersampled images into unified oversampled images and thus enable high-precision shape measurements. IMCOM is an image coaddition algorithm which offers control over point spread functions in output images. This paper presents the refactored IMCOM software, featuring full object-oriented programming, improved data structures, and alternative linear algebra strategies for determining coaddition weights. Combining these improvements and other acceleration measures, to produce almost equivalent coadded images, the consumption of core-hours has been reduced by about an order of magnitude. We then re-coadd a $16 \times 16 \,{\rm arcmin}^2$ region of our previous image simulations with three linear algebra kernels in four bands, and compare the results in terms of IMCOM optimization goals, properties of coadded noise frames, and measurements of simulated stars. The Cholesky kernel is efficient and relatively accurate, yet its irregular windows for input pixels slightly bias coaddition results. The iterative kernel avoids this issue by tailoring input pixel selection for each output pixel; it yields better noise control, but can be limited by random errors due to finite tolerance. The empirical kernel coadds images using an empirical relation based on geometry; it is inaccurate, but being much faster, it provides a valid option for "quick look" purposes. We fine-tune IMCOM hyperparameters in a companion paper., Comment: 38 pages, 22 figures, submitted to ApJSupp

We investigate the Lyman-$\alpha$ (Ly$\alpha$) and Lyman continuum (LyC) properties of the Sunburst Arc, a $z=2.37$ gravitationally lensed galaxy with a multiply-imaged, compact region leaking LyC and a triple-peaked Ly$\alpha$ profile indicating direct Ly$\alpha$ escape. Non-LyC-leaking regions show a redshifted Ly$\alpha$ peak, a redshifted and central Ly$\alpha$ peak, or a triple-peaked Ly$\alpha$ profile. We measure the properties of the Ly$\alpha$ profile from different regions of the galaxy using $R\sim5000$ Magellan/MagE spectra. We compare the Ly$\alpha$ spectral properties to LyC and narrowband Ly$\alpha$ maps from Hubble Space Telescope (HST) imaging to explore the subgalactic Ly$\alpha-$LyC connection. We find strong correlations (Pearson correlation coefficient $r>0.6$) between the LyC escape fraction ($f_{\rm esc}^{\rm LyC}$) and Ly$\alpha$ (1) peak separation $v_{\rm{sep}}$, (2) ratio of the minimum flux density between the redshifted and blueshifted Ly$\alpha$ peaks to continuum flux density $f_{\rm{min}}/f_{\rm{cont}}$, and (3) equivalent width. We favor a complex \ion{H}{1} geometry to explain the Ly$\alpha$ profiles from non-LyC-leaking regions and suggest two \ion{H}{1} geometries that could diffuse and/or rescatter the central Ly$\alpha$ peak from the LyC-leaking region into our sightline across transverse distances of several hundred parsecs. Our results emphasize the complexity of Ly$\alpha$ radiative transfer and its sensitivity to the anisotropies of \ion{H}{1} gas on subgalactic scales. Large differences in the physical scales on which we observe spatially variable direct escape Ly$\alpha$, blueshifted Ly$\alpha$, and escaping LyC photons in the Sunburst Arc underscore the importance of resolving the physical scales that govern Ly$\alpha$ and LyC escape., Comment: Submitted to The Astrophysical Journal with revisions from the first referee report. Comments welcome

The Aitken method is a useful approach for decomposing mid-IR polarimetry of silicates into emissive and absorptive components along the line-of-sight in astronomical sources. Here we extend this method to include the effects of polarization caused by scattering from graphite or similar particles located along the same sightlines. To illustrate the application of the extended method, we apply it in the reduction and analysis of CanariCam multi-wavelength imaging polarimetry observations of the Egg Nebula, W3 IRS5, and W51 IRS2, and also spectropolarimetry of W3 IRS5. We compare these results to those obtained with the original Aitken method and show that the data are generally fit much better when this third component, i.e., scattering, is incorporated into the analysis. Including scattering in the decomposition of polarimetry produces better results for the emissive and absorptive components, and in particular for the position angle (PA) of those polarization components. The distribution of the difference between absorptive PA and emissive PA is then found to be more peaked at a fixed angle, nearly perpendicular. This supports the theory that mid-IR polarization arises from elongated dust grains aligned along magnetic field lines, since then the PA of emissive and absorptive polarization would be approximately perpendicular. When significant scattering is not present the extended Aitken method produces the same results as the original method., Comment: 27 pages, 24 figures, 1 table

We explore the dynamics of qubit-state purity in the presence of transverse noise that is anisotropically distributed in the Bloch-sphere XY plane. We perform Ramsey experiments with noise injected along a fixed laboratory-frame axis and observe oscillations in the purity at twice the qubit frequency arising from the intrinsic qubit Larmor precession. We probe the oscillation dependence on the noise anisotropy, orientation, and power spectral density, using a low-frequency fluxonium qubit. Our results elucidate the impact of transverse noise anisotropy on qubit decoherence and may be useful to disentangle charge and flux noise in superconducting quantum circuits.

Ensuring annotator quality in training and evaluation data is a key piece of machine learning in NLP. Tasks such as sentiment analysis and offensive speech detection are intrinsically subjective, creating a challenging scenario for traditional quality assessment approaches because it is hard to distinguish disagreement due to poor work from that due to differences of opinions between sincere annotators. With the goal of increasing diverse perspectives in annotation while ensuring consistency, we propose \texttt{ARTICLE}, an in-context learning (ICL) framework to estimate annotation quality through self-consistency. We evaluate this framework on two offensive speech datasets using multiple LLMs and compare its performance with traditional methods. Our findings indicate that \texttt{ARTICLE} can be used as a robust method for identifying reliable annotators, hence improving data quality.

This paper provides an overview of recent historical research regarding scientifically-informed challenges to the idea that the stars are other suns orbited by other inhabited earths -- an idea that came to be known as "the Plurality of Worlds". Johannes Kepler in the seventeenth century, Jacques Cassini in the eighteenth, and William Whewell in the nineteenth each argued against "pluralism" based on what in their respective times was solid science. Nevertheless, pluralism remained popular despite these and other scientific challenges. This history will be of interest to the astronomical community so that it is better positioned to avoid difficulties should the historical trajectory of pluralism continue, especially as it persists in the popular imagination., Comment: 17 pages, 6 figures. Posted to arXiv 6+ months after publication, in accordance with Cambridge University Press & Assessment "Licence to Publish" regarding "accepted manuscript"

In his 1616 discourse on the tides, Galileo claimed that diurnal tides occurred in Lisbon, Portugal, bolstering his theory of the tides. Lisbon does not feature such tides, but in an exchange of letters in 1629-1630, Giovanfrancesco Buonamici provided Galileo with information on where such tides could be found. Buonamici referred Galileo to the Regimiento de Navegaci\'on of Andr\'es Garc\'ia de C\'espedes, and to the Descrittione di Tutti i Paesi Bassi of Lodovico Guicciardini. Galileo omitted any information on where diurnal tides occurred from his 1632 Dialogue, perhaps unintentionally, leaving him open to criticism. Buonamici's material militates against that criticism., Comment: 13 pages, 3 figures

The emergence of Autonomous Vehicles (AVs) has spurred research into testing the resilience of their perception systems, i.e. to ensure they are not susceptible to making critical misjudgements. It is important that they are tested not only with respect to other vehicles on the road, but also those objects placed on the roadside. Trash bins, billboards, and greenery are all examples of such objects, typically placed according to guidelines that were developed for the human visual system, and which may not align perfectly with the needs of AVs. Existing tests, however, usually focus on adversarial objects with conspicuous shapes/patches, that are ultimately unrealistic given their unnatural appearances and the need for white box knowledge. In this work, we introduce a black box attack on the perception systems of AVs, in which the objective is to create realistic adversarial scenarios (i.e. satisfying road design guidelines) by manipulating the positions of common roadside objects, and without resorting to `unnatural' adversarial patches. In particular, we propose TrashFuzz , a fuzzing algorithm to find scenarios in which the placement of these objects leads to substantial misperceptions by the AV -- such as mistaking a traffic light's colour -- with overall the goal of causing it to violate traffic laws. To ensure the realism of these scenarios, they must satisfy several rules encoding regulatory guidelines about the placement of objects on public streets. We implemented and evaluated these attacks for the Apollo, finding that TrashFuzz induced it into violating 15 out of 24 different traffic laws., Comment: Currently under review by IEEE Transactions on Software Engineering (TSE)

Activation engineering is becoming increasingly popular as a means of online control of large language models (LLMs). In this work, we extend the idea of inference-time steering with vectors that represent a behavioral direction of interest to tuning those vectors directly into the model, obviating the need for online control. First, we identify activation vectors related to honesty in an open-source LLM (Llama-2-13b-chat). Next, we demonstrate that model output can be made more or less honest by adding positive or negative multiples of these vectors to residual stream activations during generation. Then, we show that a similar effect can be achieved by fine-tuning the vectors directly into the model, by use of a dual loss function based on the cosine similarity of residual stream activations to the vectors combined with a standard token-based loss ("representation tuning"). Finally, we compare the generations in response to honesty-probing prompts from the resulting models to those from models fine-tuned with a token-based loss alone, and to those from the untuned model subjected to online steering. Overall, fine-tuning the vectors into the models using the cosine similarity plus token loss showed a stronger effect than online steering, and generalized better than using the standard loss, suggesting the potential utility of this approach as a safety measure. Code and data are available at https://github.com/cma1114/representation_tuning. Tuned models are available at https://huggingface.co/collections/cackerman/representation-tuning-66da1e5ab41cd1b824687d9f., Comment: 10 pages, 7 figures, 6 tables

Interest in the study and analysis of dynamic processes in the social, behavioral, and health sciences has burgeoned in recent years due to the increased availability of intensive longitudinal data. However, how best to model and account for the persistent heterogeneity characterizing such processes remains an open question. The multi-VAR framework, a recent methodological development built on the vector autoregressive model, accommodates heterogeneous dynamics in multiple-subject time series through structured penalization. In the original multi-VAR proposal, individual-level transition matrices are decomposed into common and unique dynamics, allowing for generalizable and person-specific features. The current project extends this framework to allow additionally for the identification and penalized estimation of subgroup-specific dynamics; that is, patterns of dynamics that are shared across subsets of individuals. The performance of the proposed subgrouping extension is evaluated in the context of both a simulation study and empirical application, and results are compared to alternative methods for subgrouping multiple-subject, multivariate time series.

Quantum states undergoing quantum chaotic dynamics are expected to evolve into featureless states at late times. While this expectation holds true on an average, coarse-grained level, it is unclear if this expectation applies to higher statistical moments, as symmetries typically present in physical systems constrain the exploration of phase space. Here we study the universal structure of late-time ensembles obtained from unitary dynamics in quantum chaotic systems with symmetries, such as charge or energy conservation. We identify two limiting universal regimes depending on the initial condition. When the initial state is typical -- all the moments of the symmetry operators are equal to those of pure random states -- then the late-time ensemble is indistinguishable from the Haar ensemble in the thermodynamic limit and at the level of higher statistical moments. Otherwise, atypical initial states evolve into non-universal ensembles which can be distinguished from the Haar ensemble from simple measurements or subsystem properties. Interestingly, such atypical initial conditions are not rare, even when considering product state initial conditions, and can be found in the middle of the spectrum of Hamiltonians known to be `maximally' chaotic. In the limiting case of initial states with negligible variance of the symmetry operator (e.g., states with fixed particle number or states with negligible energy variance), the late-time ensemble has universal behavior captured by constrained RMT ensembles. Our work shows that even though midspectrum states do not explore ergodically all of phase space at late times, the late-time ensemble typically -- but not always -- exhibits the same average and sample-to-sample fluctuations as the Haar ensemble., Comment: 14 pages, 5 figures

Primordial black holes (PBHs) are theorized objects that may make up some - or all - of the dark matter in the universe. At the lowest allowed masses, Hawking radiation (in the form of photons or electrons and positrons) is the primary tool to search for PBHs. This paper is part of an ongoing series in which we aim to calculate the $O(\alpha)$ corrections to Hawking radiation from asteroid-mass primordial black holes, based on a perturbative quantum electrodymanics (QED) calculation on Schwarzschild background. Silva et. al. (2023) divided the corrections into dissipative and conservative parts; this work focuses on the numerical computation of the dissipative $O(\alpha)$ corrections to the photon spectrum. We generate spectra for primordial black holes of mass $M=1$-$8 \times 10^{21} m_{\rm planck}$. This calculation confirms the expectation that at low energies, the inner bremsstrahlung radiation is the dominant contribution to the Hawking radiation spectrum. At high energies, the main $O(\alpha)$ effect is a suppression of the photon spectrum due to pair production (emitted $\gamma\rightarrow e^+e^-$), but this is small compared to the overall spectrum. We compare the low-energy tail in our curved spacetime QED calculation to several approximation schemes in the literature, and find deviations that could have important implications for constraints from Hawking radiation on primordial black holes as dark matter., Comment: 28 pages, 15 figures, to be submitted to Physical Review D, spectra to be released upon acceptance

Non-LTE radiative transfer is a key tool for modern astrophysics: it is the means by which many key synthetic observables are produced, thus connecting simulations and observations. Radiative transfer models also inform our understanding of the primary formation layers and parameters of different spectral lines, and serve as the basis of inversion tools used to infer the structure of the solar atmosphere from observations. The default approach for computing the radiation field in multidimensional solar radiative transfer models has long remained the same: a short characteristics, discrete ordinates method, formal solver. In situations with complex atmospheric structure and multiple transitions between optically-thick and -thin regimes these solvers require prohibitively high angular resolution to correctly resolve the radiation field. Here, we present the theory of radiance cascades, a technique designed to exploit structure inherent to the radiation field, allowing for efficient reuse of calculated samples, thus providing a very high-resolution result at a fraction of the computational cost of existing methods. We additionally describe our implementation of this method in the DexRT code, and present initial results of the synthesis of a snapshot of a magnetohydrodynamic model of a solar prominence formed via levitation-condensation. The approach presented here provides a credible route for routinely performing multidimensional radiative transfer calculations free from so-called ray effects, and scaling high-quality non-LTE models to next-generation high-performance computing systems with GPU accelerators., Comment: 21 pages, 14 figures, ancillary videos. To be submitted to RASTI

Directional wave speeds variations in anisotropic elastic solids enables material characterisation capabilities, such as determination of elastic constants and volumetric measurement of crystallographic texture. However, achieving such measurements is challenging especially on samples with complex geometries. Here we propose the use of Green's Function reconstruction from diffuse ultrasonic wave fields for accurate velocity measurements on components with arbitrary geometries. Strategies for accurate reconstruction, including averaging over an increased number of different source locations, using longer window lengths of diffuse fields, and accurately deconvolving a source-dependent factor, were implemented to achieve satisfactory convergence towards Green's Function. Additionally, low signal intensity challenges from laser interferometers were overcome to enable non-contact measurement of the wave speeds, by making use of simultaneous excitation of sources to increase signal-to-noise ratio and signal normalisation to account for energy dissipation of diffuse fields. With successful demonstration using both phased array and laser receivers, this advancement fundamentally broadens acoustic wave velocity measurement capabilities to a wider range of environments and holds promise for future material characterisation of complex-shaped components.

Human feedback is essential for building human-centered AI systems across domains where disagreement is prevalent, such as AI safety, content moderation, or sentiment analysis. Many disagreements, particularly in politically charged settings, arise because raters have opposing values or beliefs. Vicarious annotation is a method for breaking down disagreement by asking raters how they think others would annotate the data. In this paper, we explore the use of vicarious annotation with analytical methods for moderating rater disagreement. We employ rater cohesion metrics to study the potential influence of political affiliations and demographic backgrounds on raters' perceptions of offense. Additionally, we utilize CrowdTruth's rater quality metrics, which consider the demographics of the raters, to score the raters and their annotations. We study how the rater quality metrics influence the in-group and cross-group rater cohesion across the personal and vicarious levels., Comment: Accepted at EMNLP 2024 Findings

An intrinsically causal approach to lifting factorization, called the Causal Complementation Algorithm, is developed for arbitrary two-channel perfect reconstruction FIR filter banks. This addresses an engineering shortcoming of the inherently noncausal strategy of Daubechies and Sweldens for factoring discrete wavelet transforms, which was based on the Extended Euclidean Algorithm for Laurent polynomials. The Causal Complementation Algorithm reproduces all lifting factorizations created by the causal version of the Euclidean Algorithm approach and generates additional causal factorizations, which are not obtainable via the causal Euclidean Algorithm, possessing degree-reducing properties that generalize those furnished by the Euclidean Algorithm. In lieu of the Euclidean Algorithm, the new approach employs Gaussian elimination in matrix polynomials using a slight generalization of polynomial long division. It is shown that certain polynomial degree-reducing conditions are both necessary and sufficient for a causal elementary matrix decomposition to be obtainable using the Causal Complementation Algorithm, yielding a formal definition of ``lifting factorization'' that was missing from the work of Daubechies and Sweldens., Comment: 28 pages, 2 figures. Submitted for publication

Autonomous Vehicles (AVs) rely on sophisticated Autonomous Driving Systems (ADSs) to provide passengers a satisfying and safe journey. The individual preferences of riders plays a crucial role in shaping the perception of safety and comfort while they are in the car. Existing ADSs, however, lack mechanisms to systematically capture and integrate rider preferences into their planning modules. To bridge this gap, we propose $\mu$Drive, an event-based Domain-Specific Language (DSL) designed for specifying autonomous vehicle behaviour. $\mu$Drive enables users to express their preferences through rules triggered by contextual events, such as encountering obstacles or navigating complex traffic situations. These rules dynamically adjust the parameter settings of the ADS planning module, facilitating seamless integration of rider preferences into the driving plan. In our evaluation, we demonstrate the feasibility and efficacy of $\mu$Drive by integrating it with the Apollo ADS framework. Our findings show that users can effectively influence Apollo's planning through $\mu$Drive, assisting ADS in achieving improved compliance with traffic regulations. The response time for $\mu$Drive commands remains consistently at the second or millisecond level. This suggests that $\mu$Drive may help pave the way to more personalizsed and user-centric AV experiences.

We examine the holonomy-perturbed traceless SU(2) character variety of the trivial four-stranded tangle {p_1,p_2,p_3,p_4} X [0,1] in S^2 X [0,1] equipped with a strong marking, either an earring or a bypass. Viewing these marked tangles as endomorphisms in the cobordism category from the four-punctured sphere to itself, we identify the images of these endomorphisms in the Weinstein symplectic partial category under the partially defined holonomy-perturbed traceless character variety functor. We express these endomorphisms on immersed curves in the pillowcase in terms of doubling and figure eight operations and prove they have the same image., Comment: 42 pages, 10 figures

Ultrasonic processing of solidifying metals in additive manufacturing can provide grain refinement and advantageous mechanical properties. However, the specific physical mechanisms of microstructural refinement relevant to laser-based additive manufacturing have not been directly observed because of sub-millimeter length scales and rapid solidification rates associated with melt pools. Here, high-speed synchrotron X-ray imaging is used to observe the effect of ultrasonic vibration directly on melt pool dynamics and solidification of Al6061 alloy. The high temporal and spatial resolution enabled direct observation of cavitation effects driven by a 20.2 kHz ultrasonic source. We utilized multiphysics simulations to validate the postulated connection between ultrasonic treatment and solidification. The X-ray results show a decrease in melt pool and keyhole depth fluctuations during melting and promotion of pore migration toward the melt pool surface with applied sonication. Additionally, the simulation results reveal increased localized melt pool flow velocity, cooling rates, and thermal gradients with applied sonication. This work shows how ultrasonic treatment can impact melt pools and its potential for improving part quality.

Hawking radiation sets stringent constraints on Primordial Black Holes (PBHs) as a dark matter candidate in the $M \sim 10^{16} \ \mathrm{g}$ regime based on the evaporation products such as photons, electrons, and positrons. This motivates the need for rigorous modeling of the Hawking emission spectrum. Using semi-classical arguments, Page [Phys. Rev. D 16, 2402 (1977)] showed that the emission of electrons and positrons is altered due to the black hole acquiring an equal and opposite charge to the emitted particle. The Poisson fluctuations of emitted particles cause the charge $Z|e|$ to random walk, but since acquisition of charge increases the probability of the black hole emitting another charged particle of the same sign, the walk is biased toward $Z=0$, and $P(Z)$ approaches an equilibrium probability distribution with finite variance $\langle Z^2\rangle$. This paper explores how this ``stochastic charge'' phenomenon arises from quantum electrodynamics (QED) on a Schwarzschild spacetime. We prove that (except for a small Fermi blocking term) the semi-classical variance $\langle Z^2 \rangle$ agrees with the variance of a quantum operator $\langle \hat{\cal Z}^2 \rangle$, where $\hat{\cal Z}$ may be thought of as an ``atomic number'' that includes the black hole as well as charge near it (weighted by a factor of $2M/r$). In QED, the fluctuations in $\hat{\cal Z}$ do not arise from the black hole itself (whose charge remains fixed), but rather as a collective effect in the Hawking-emitted particles mediated by the long-range electromagnetic interaction. We find the rms charge $\langle Z^2\rangle^{1/2}$ asymptotes to 3.44 at small PBH masses $M \lesssim 2\times 10^{16}\,$g, declining to 2.42 at $M=5.2\times 10^{17}\,$g., Comment: 36 pages, 3 figures

The geomagnetic "solar flare effect" (SFE) results from excess ionization in the Earth's ionosphere, famously first detected at the time of the Carrington flare in 1859. This indirect detection of a flare constituted one of the first cases of "multimessenger astronomy," whereby solar ionizing radiation stimulates ionospheric currents. Well-observed SFEs have few-minute time scales and perturbations of >10 nT, with the greatest events reaching above 100 nT. In previously reported cases the SFE time profiles tend to resemble those of solar soft X-ray emission, which ionizes the D-region; there is also a less-well-studied contribution from Lyman-alpha. We report here a specific case, from flare SOL2024-03-10 (M7.4), in which an impulsive SFE deviated from this pattern. This flare contained an "early impulsive" component of exceptionally hard radiation, extending up to gamma-ray energies above 1 MeV, distinctly before the bulk of the flare soft X-ray emission. We can characterize the spectral distribution of this early-impulsive component in detail, thanks to the modern extensive wavelength coverage. A more typical gradual SFE occurred during the flare's main phase. We suggest that events of this type warrant exploration of the solar physics in the "impulse response" limit of very short time scales., Comment: MNRAS to be published

The molecular-to-atomic gas ratio is crucial to the evolution of the interstellar medium in galaxies. We investigate the balance between the atomic ($\Sigma_{\rm HI}$) and molecular gas ($\Sigma_{\rm H2}$) surface densities in eight nearby star-forming galaxies using new high-quality observations from MeerKAT and ALMA (for HI and CO, respectively). We define the molecular gas ratio as $R_{\rm mol} = \Sigma_{\rm H2} / \Sigma_{\rm HI}$ and measure how it depends on local conditions in the galaxy disks using multi-wavelength observations. We find that, depending on the galaxy, HI is detected at $>3\sigma$ out to 20-120 kpc in galactocentric radius ($r_{\rm gal}$). The typical radius at which $\Sigma_{\rm HI}$ reaches 1~$\rm M_\odot~pc^{-2}$ is $r_{\rm HI}\approx22$~kpc, which corresponds to 1-3 times the optical radius ($r_{25}$). $R_{\rm mol}$ correlates best with the dynamical equilibrium pressure, P$_{\rm DE}$, among potential drivers studied, with a median correlation coefficient of $<\rho>=0.89$. Correlations between $R_{\rm mol}$ and star formation rate, total gas and stellar surface density, metallicity, and $\Sigma_{\rm SFR}$/P$_{\rm DE}$ are present but somewhat weaker. Our results also show a direct correlation between P$_{\rm DE}$ and $\Sigma_{\rm SFR}$, supporting self-regulation models. Quantitatively, we measure similar scalings as previous works and attribute the modest differences that we find to the effect of varying resolution and sensitivity. At $r_{\rm gal} {\gtrsim}0.4~r_{25}$, atomic gas dominates over molecular gas, and at the balance of these two gas phases, we find that the baryon mass is dominated by stars, with $\Sigma_{*} > 5~\Sigma_{\rm gas}$. Our study constitutes an important step in the statistical investigation of how local galaxy properties impact the conversion from atomic to molecular gas in nearby galaxies., Comment: accepted for publication in A&A; 20 pages, 12 Figures (+4 appendix pages)

The integration of artificial intelligence (AI) in educational measurement has revolutionized assessment methods, enabling automated scoring, rapid content analysis, and personalized feedback through machine learning and natural language processing. These advancements provide timely, consistent feedback and valuable insights into student performance, thereby enhancing the assessment experience. However, the deployment of AI in education also raises significant ethical concerns regarding validity, reliability, transparency, fairness, and equity. Issues such as algorithmic bias and the opacity of AI decision-making processes pose risks of perpetuating inequalities and affecting assessment outcomes. Responding to these concerns, various stakeholders, including educators, policymakers, and organizations, have developed guidelines to ensure ethical AI use in education. The National Council of Measurement in Education's Special Interest Group on AI in Measurement and Education (AIME) also focuses on establishing ethical standards and advancing research in this area. In this paper, a diverse group of AIME members examines the ethical implications of AI-powered tools in educational measurement, explores significant challenges such as automation bias and environmental impact, and proposes solutions to ensure AI's responsible and effective use in education., Comment: 59 pages, 3 figures, a joint work of the Special Interest Group on Artificial Intelligence in Measurement and Education (AIME) from the National Council of Measurement in Education (NCME)

We consider the state transfer properties of continuous time quantum walks on trees of diameter 4. We characterize all pairs of strongly cospectral vertices in trees of diameter 4, finding that they fall into pairs of three different types. For each type, we construct an infinite family of diameter 4 trees for which there is pretty good state transfer between the pair of strongly cospectral vertices. Moreover, for two of those types, for each tree in the infinite family, we give an explicit sequence of readout times at which the fidelity of state transfer converges to $1$. For strongly cospectral vertices of the remaining type, we identify a sequence of trees and explicit readout times so that the fidelity of state transfer between the strongly cospectral vertices approaches $1.$ We also prove a result of independent interest: for a graph with the property that the fidelity of state transfer between a pair of vertices at time $t_k$ converges to $1$ as $k \rightarrow \infty,$ then the derivative of the fidelity at $t_k$ converges to $0$ as $k \rightarrow \infty. $

Hydrodynamic simulations of the stellar winds from Wolf-Rayet stars within the Galactic Center can provide predictions for the X-ray spectrum of supermassive black hole Sgr A*. Herein, we present results from updated smooth particle hydrodynamics simulations, building on the architecture of Cuadra et al. (2015); Russell et al. (2017), finding that a cold gas disk forms around Sgr A* with a simulation runtime of 3500 years. This result is consistent with previous grid-based simulations, demonstrating that a cold disk can form regardless of numerical method. We examine the plasma scenarios arising from an environment with and without this cold disk, by generating synthetic spectra for comparison to the quiescent Fe K alpha Sgr A* spectrum from Chandra HETG-S, taken through the Chandra X-ray Visionary Program. We find that current and future X-ray missions are unlikely to distinguish between the kinematic signatures in the plasma in these two scenarios. Nonetheless, the stellar wind plasma model presents a good fit to the dispersed Chandra spectra within 1.5" of Sgr A*. We compare our results to the Radiatively Inefficient Accretion Flow (RIAF) model fit to the HETG-S spectrum presented in Paper I and find that the Bayesian model evidence does not strongly favor either model. With 9" angular resolution and high spectral resolution of the X-IFU, NewAthena will offer a clearer differentiation between the RIAF plasma model and hydrodynamic simulations, but only a future X-ray mission with arcsecond resolution will significantly advance our understanding of Sgr A*'s accretion flow in X-rays., Comment: 14 pages, 6 figures. Accepted for publication in ApJ

The extreme low-luminosity supermassive black hole Sgr A* provides a unique laboratory in which to test radiatively inefficient accretion flow (RIAF) models. Previous fits to the quiescent Chandra ACIS-S spectrum found a RIAF model with an equal inflow-outflow balance works well. In this work, we apply the RIAF model to the Chandra HETG-S spectrum obtained through the Chandra X-ray Visionary Program, which displays features suggestive of temperature and velocity structures within the plasma. A comprehensive forward model analysis accounting for the accretion flow geometry and HETG-S instrumental effects is required for a full interpretation of the quiescent Chandra HETG-S spectrum. We present a RIAF model that takes these effects into account. Our fits to the high-resolution gratings spectrum indicate an inflow balanced by an outflow ($s \sim 1$) alongside a temperature profile that appears shallower than what would be expected from a gravitational potential following $1/r$. The data require that the abundance of Iron relative to solar is $Z_{Fe} < 0.32 Z_\odot$ (90\% credible interval), much lower than the $2~Z_\odot$ metallicity measured in nearby late-type giants. While future missions like NewAthena will provide higher spectral resolution, source separation will continue to be a problem. Leveraging Chandra's unparalleled spatial resolution, which is not expected to be surpassed for decades, remains essential for detailed investigations of the densely populated Galactic Center in X-rays., Comment: 11 pages, 5 figures, 1 table. Accepted for publication in ApJ

As part of the Young Exoplanets Spectroscopic Survey (YESS), this study explores the spot variability of 13 T Tauri Stars (TTSs) in the near-infrared $H$ band, using spectra from the Immersion GRating INfrared Spectrometer (IGRINS). By analyzing effective temperature ($T_{\rm eff}$) sensitive lines of atomic FeI at ~1.56259 um and ~1.56362 um, and molecular OH at ~1.56310 um and ~1.56317 um, we develop an empirical equivalent width ratio (EWR) relationship for $T_{\rm eff}$ in the range of 3400-5000 K. This relationship allows for precise relative $T_{\rm eff}$ estimates to within tens of Kelvin and demonstrates compatibility with solar metallicity target models. However, discrepancies between observational data and model predictions limit the extension of the $T_{\rm eff}$-EWR relationship to a broader parameter space. Our study reveals that both classical and weak-line TTSs can exhibit $T_{\rm eff}$ variations exceeding 150 K over a span of two years. The detection of a quarter-phase delay between the EWR and radial velocity phase curves in TTSs indicates spot-driven signals. A phase delay of 0.06 $\pm$ 0.13 for CI Tau, however, suggests additional dynamics, potentially caused by planetary interaction, inferred from a posited 1:1 commensurability between the rotation period and orbital period. Moreover, a positive correlation between $T_{\rm eff}$ variation amplitude and stellar inclination angle support the existence of high-latitude spots on TTSs, further enriching our understanding of stellar surface activity in young stars., Comment: 31 pages, 19 figures, and 5 tables. Accepted to ApJ

We explored the impact that Doppler dimming and brightening effects from bulk motions of solar prominences have on the formation of Lya, Ha, and MgII h line profiles. We compared two schemes in which these effects manifest; when the prominence is moving radially away from the solar surface (radial case), and when the prominence is moving parallel to the solar surface (horizontal case). To do this, we analysed 13,332 model profiles generated through the use of the 1D NLTE (i.e. departures from Local Thermodynamic equilibrium) radiative transfer (RT) code Promweaver, built on the Lightweaver NLTE RT framework to mimic the behaviour and output of the 1D NLTE RT code PROM. We found that horizontal velocities are just as, or more important than radial velocities. This demonstrates that horizontal velocities need to be accounted for when attempting to do any sort of forward modelling., Comment: 6 pages, 4 figures, 1 table

In this paper we demonstrate the use of plasmonic focusing in conjunction with non-linear photoemisison to develop geometrically flat nanoscale electron sources with less than 40 pm-rad root mean squared (rms) normalized transverse emittance. Circularly polarized light is incident on a gold Archimedean spiral structure to generate surface-plasmon-polaritons which interfere coherently at the center resulting in a 50 nm rms emisison area. Such a nanostructured flat surface enables simultaneous spatio-temporal confinement of emitted electrons at the nanometer and femtosecond level and can be used as an advanced electron source for high-repetition-rate ultrafast electron diffraction and microscopy experiments as well as next-generation of miniaturized particle accelerators.

We present the results of a series of 3D special relativistic hydrodynamic simulations of a gamma-ray burst (GRB) jet in a massive circumstellar medium (CSM) surrounding the progenitor star. Our simulations reproduce the jet morphology transitioning from a well-collimated state to a thermal pressure-driven state for a range of CSM masses and outer radii. The jet-CSM interaction redistributes the jet energy to materials expanding into a wide solid angle and results in a quasi-spherical ejecta with 4-velocities from $\Gamma\beta\simeq 0.1$ to $\simeq 10$. The mass and kinetic energy of the ejecta with velocities faster than $0.1c$ are typically of the order of $0.1\,M_\odot$ and $10^{51}\,\mathrm{erg}$ with only a weak dependence on the CSM mass and radius for the explored CSM parameter ranges. We find that the numerically obtained density structure of the mildly relativistic ejecta is remarkably universal. The radial density profile is well approximated as a power-law function of the radial velocity with an index of $-5$, $\rho\propto v^{-5}$, in agreement with our previous simulations and other studies, as well as those suggested from recent studies on early-phase spectra of supernovae associated with GRBs. Such fast ejecta rapidly becomes transparent following its expansion. Gradually releasing the trapped thermal photons, the ejecta gives rise to bright UV--optical emission within $\sim 1$ day. We discuss the potential link of the relativistic ejecta resulting from jet-CSM interaction to GRB-associated supernovae as well as fast and blue optical transients., Comment: 22 pages, 11 figures, accepted for publication in PASJ

The recent advancements in electronics manufacturing has necessitated the demand for miniaturization of electronic components. In particular, the product sizes for passive components have evolved from 1005 (1.0x0.5mm) which is roughly the size of a grain of sand to 0201 (0.25x0.125mm) which is 1/16th the size of a grain of sand. Grain size distribution and composition play a vital role in tailoring the demands for reliably shrinking dimension of passives. The study focuses on analyzing the effect of grain size and composition, which plays a significant role in maintaining high yield output during the manufacturing processes. The objective of this study is to compare the grain morphology and its effect on defect generation mechanism for 0201 resistors. The experimental setup was prepared to evaluate the grain structure as per ASTM E112-3 test standards. The 0201 resistor samples from three different vendors were assembled on test vehicle PCB (Printed Circuit Board). The resulting observations of the study showed that tombstoning defect was observed during the reflow process for Vendor A. Scanning Electron Microscope (SEM) results showed the presence of microstructural difference in the tin grain size of resistors. The tin grain size for Vendor A was observed to be 2 microns, whereas the grain size for Vendors B and C were 4 and 5 microns, respectively. Furthermore, the results of grain size measurements performed using the intercept method showed that a grain size number of 13 and 13.6 was observed for Vendors B and C, whereas a grain size number of 15 was observed for Vendor A. The second phase of the study focuses on techniques for improving the grain size number to mitigate the tombstoning defect. It was observed that using an alternate plating solution during the manufacturing of passives resulted in decreased grain size number while containing the tombstoning issue.