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Abstract Wave reflection and refraction at a time interface follow different conservation laws compared to conventional scattering at a spatial interface. This study presents the experimental demonstration of refraction and reflection of flexural waves across a temporal boundary in a continuum-based mechanical metabeam, and unveils opportunities that emerge by tailoring temporal scattering phenomena for phononic applications. We observe these phenomena in an elastic beam attached to an array of piezoelectric patches that can vary in time the effective elastic properties of the beam. Frequency conversion and phase conjugation are observed upon a single temporal interface. These results are consistent with the temporal Snell’s law and Fresnel equations for temporal interfaces. Further, we illustrate the manipulation of amplitude and frequency spectra of flexural wave temporal refraction and reflection through multi-stepped temporal interfaces. Finally, by implementing a smooth time variation of wave impedance, we numerically and experimentally demonstrate the capabilities of the temporal metabeam to realize waveform morphing and information coding. Our findings enable precise control over wave amplitude and frequency through temporally modulated mechanical systems, providing a concrete framework for designing time-mechanical metamaterials and time-phononic crystals. 

This research-to-practice WIP paper describes the development and evaluation of a generative Large Language Model (gLLM)-based autograder for computer programming assignments. Manual grading is becoming increasingly unsustainable due to growing student enrollment and the demand for timely, high-quality feedback. To address these challenges, this study explores the use of automated grading tools to reduce instructors' workload and improve scalability. The proposed autograder takes a “reverse-engineering” approach, i.e., it converts student code into structured natural language summaries, which are then compared against predefined grading rubrics. An evaluation is performed using an external dataset (the Menagerie dataset), which contains real student submissions graded by four human graders. The objective is to assess the alignment between grades assigned by the autograder and those assigned by human graders. Findings indicate that the autograder closely matches human grading when letter grades are considered, though it performs less accurately with fine-grained numerical scores. While not yet a complete substitute for human assessment, the autograder shows strong potential as a scalable, efficient tool for supporting grading in programming education. 

Many extended reality (XR) devices present different views to the left and right eyes. Unwanted colorimetric differences between these views can cause perceptual artifacts that degrade binocular image quality. We present an image‐computable model designed to predict the appearance of binocular views with colorimetric differences in XR displays. The model is fitted to data from a recent perceptual study in which people provided multidimensional responses about the appearance of stimuli simulating an optical see‐through augmented reality device with interocular intensity differences. This work can be used to create preliminary assessments of binocular artifact appearance and inform XR display design. 

Diluted magnetic semiconductor (DMS) systems have been extensively studied in recent decades. DMSs provides a platform where charge transport and magnetic ordering phenomena exhibit unique interplays, together with possible applications to spin-dependent electronics (spintronics) devices. Initial development of ferromagnetic (FM) DMS systems centered around III-V semiconductors doped with dilute transition metals, such as (Ga,Mn)As, obtained by co-doping of spin and charge. More recently, independent spin and charge doping was first achieved in Li(Zn,Mn)As, a DMS system based on I-II-V semiconductor, with charge doping via variable Li concentrations and spin doping via iso-valent (Zn,Mn) substitutions. Although more than 30 new DMS systems with independent spin and charge doping have been synthesized since then, the main research emphasis has been put on development and characterization of systems with higher FM Curie temperature (TC) and different crystal structures suitable for possible formation of heterostructure devices. This article focuses on a new DMS material Na(Zn,Mn)Sb, which exhibits a spin glass (SG) ordering, together with metal-insulator transition (MIT) and colossal negative magnetoresistance (CMR) as a function of independent spin and charge doping and application of external magnetic fields. MIT and CMR phenomena are elucidated by magneto transport, magnetization, angle resolved photoemission spectroscopy (ARPES), and scanning tunneling microscopy (STM) measurements, and by band calculations which demonstrate development and disappearance of energy gap. Magnetic order and dynamic spin fluctuations are probed with muon spin relaxation (μSR) and magnetization, and the results for Na(Zn,Mn)Sb are compared to those from FM DMS systems Li(Zn,Mn)As, Li(Zn,Mn)P, and Li(Zn,Mn,Cu)As. First-principles calculations are performed for Na(Zn,Mn)Sb, (Ga,Mn)As and Li(Zn,Mn)P to highlight the roles of charge and spin doping on exchange interactions mediated by nearest neighbor super-exchange coupling and oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling via conduction electrons. These studies reveal (1) MIT and CMR of Na(Zn,Mn)Sb manifest as a response to spin configurations as spin-driven transport phenomena; (2) a dynamic critical behavior is observed in SG transition of Na(Zn,Mn)Sb, in contrast to more first-order-like magnetic evolutions in other FM DMS systems; (3) charge doping supports FM coupling additive to direct AFM exchange interaction between nearest-neighbor Mn pairs; and (4) a widely different coercive fields seen in different families of FM and SG DMS systems can be explained by geometrical frustration of AFM interaction in underlying lattice for Mn spin network 

Meiotic recombination between homologous chromosomes is vital for maximizing genetic variation among offspring. However, sex-determining regions are often rearranged and blocked from recombination. It remains unclear whether rearrangements or other mechanisms might be responsible for recombination suppression. Here, we uncover that the deficiency of the DNA cytosine methyltransferase DNMT1 in the green algaChlamydomonas reinhardtiicauses anomalous meiotic recombination at the mating-type locus (MT), generating haploid progeny containing bothplusandminusmating-type markers due to crossovers withinMT. The deficiency of a histone methyltransferase for H3K9 methylation does not lead to anomalous recombination. These findings suggest that DNA methylation, rather than rearrangements or histone methylation, suppresses meiotic recombination, revealing an unappreciated biological function for DNA methylation in eukaryotes. 

This research paper describes a study of using real-world vulnerabilities to motivate computer science students to-wards learning secure programming. Given the rise in cybersecurity incidents due to programming errors, there is a pressing need to improve programmers' secure programming skills. Despite educators' numerous efforts towards this goal, communicating the importance of this training to students remains a challenge. Grounding on the theory of intrinsic motivation, we propose that exposing students to authentic, relatable vulnerabilities can significantly enhance their learning orientation towards secure programming. Our approach involves selecting vulnerabilities from the National Vulnerability Database that are both relatable to students and understandable without extensive external context. These vulnerabilities are transformed into comprehensive course modules, each featuring a demonstrative video, source code snippets of the vulnerability and its patch, and associated developer communications about the vulnerability. We assess the impact of one of our course modules on students' learning disposition through a study conducted in two universities in an identical setting. The study results indicate that students appreciate seeing real-world vulnerabilities in detail, especially the video we recorded reproducing the vulnerability, and that they gain in self-efficacy after completing the module. 

Elastic surface waves pumping is realized by a smart pillar-type metasurface.