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Experimental Characterization of Fabricated (310) and (210) Symmetrical Tilt High-Angle Grain Boundaries in Bicrystalline Copper Thin Films Using NaCl Substrates
No full textA novel sintering method of bridging the two mechanically polished and oriented single-crystals together face-to-face in a non- environmental controlled atmosphere to fabricate the bicrystal substrate of NaCl of macroscopic thickness, with a common zone axis and having planarity over large areas, has been developed. Epitaxial [001] bicrystalline thin face-centered cubic (fcc) metal film of surface-reactive metal-containing tilt grain boundary across the interface is first grown in high vacuum directly by flash deposition on initially fabricated [001] oriented bicrystalline substrate of NaCl. The [001] tilt boundary, thus produced, and is examined by electron microscopy to characterize grain boundary morphology and structure. The findings of some preliminary investigations are then presented. A distinct atomic structure is observed for 310 and 210 inclination. Both HAADF-STEM and Diffraction images reveal that such fabricated high-angle grain boundary accommodates minor deviations from the exact high coincidence density σ=5 misorientation. The potential use of the present technique is extended to produce a wide variety of homophase bicrystals, containing grain boundaries at the midplane, normal to any crystallographic surface without the necessity of a separate bonding operation
Exploring the impact of sheet thickness scaling on Nanosheet FET gate electrostatics using k.p based simulations
No full textThis work explores the impact of sheet thickness scaling on gate electrostatics of NsFETs using k.p simulation. It is shown that thin channel NsFETs exhibit higher threshold voltage irrespective of the substrate orientation and channel material. However, the influence of geometrical confinement varies among different substrate orientations and channel materials due to variations in carrier quantization mass. It is also shown that thin channel NsFETs deliver higher inversion charges at equivalent gate over-drive voltages, thereby offering enhanced gate electrostatics. However, the advantage of gate electrostatics in thin channel NsFETs is limited by quantum capacitance. Optimizing the sub-band structure through strategic selection of substrate orientations and channel materials is essential to regulate quantum capacitance and to fully exploit the benefits of sheet thickness scaling in NsFETs
Structural insights into the recognition of RALF peptides by FERONIA receptor kinase during Brassicaceae pollination
No full textEnsuring species integrity and successful reproduction is pivotal for the survival of angiosperms. Members of Brassicaceae family employ a “lock and key” mechanism involving stigmatic (sRALFs) and pollen RALFs (pRALFs) binding to FERONIA, a Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) receptor, to establish a prezygotic hybridization barrier. In the absence of compatible pRALFs, sRALFs bind to FERONIA, inducing a lock state for pollen tube penetration. Conversely, compatible pRALFs act as a key, facilitating successful fertilization. Competing pRALFs reduce the sRALFs binding to FERONIA in a dose-dependent manner, enabling pollen tube penetration. Despite its crucial role in Brassicaceae hybridization, the structural basis of this binding remains elusive owing to the highly flexible nature of RALF peptides. Using advanced structural modeling techniques and flexible peptide molecular docking, this study reveals that pRALFs and sRALFs bind to negatively charged pockets in FERONIA with varying binding affinities. Our study unveils the structural basis of this binding, shedding light on the molecular mechanism underlying hybridization barriers in Brassicaceae
Dynamic mass generation on two-dimensional electronic hyperbolic lattices
No full textFree electrons hopping on hyperbolic lattices embedded on a negatively curved space can foster (a) Dirac liquids, (b) Fermi liquids, and (c) flat bands, respectively characterized by a vanishing, constant, and divergent density of states near the half filling. From numerical self-consistent mean-field Hartree analyses, we show that nearest-neighbor Coulomb and on-site Hubbard repulsions respectively give rise to charge-density-wave and antiferromagnetic orders featuring staggered patterns of average electronic density and magnetization in all these systems, when the hyperbolic tessellation is accomplished by periodic arrangements of even p-gons. Both quantum orders dynamically open mass gaps near the charge neutrality point via spontaneous symmetry breaking. Only on hyperbolic Dirac materials these orderings take place via quantum phase transitions (QPTs) beyond critical interactions, which however decrease with increasing curvature, showcasing curvature-induced weak-coupling QPTs. We present scaling of these masses with the corresponding interaction strengths
Propagation and energy dissipation of shock waves in the solar chromosphere
No full textThe solar atmosphere is permeated by various types of waves that originate from subsurface convection. As these waves propagate upward, they encounter they encounter a steep decrease in the density of the medium, leading to their steepening into shock waves. These shock waves typically exhibit a characteristic sawtooth pattern in wavelength–time (–t) plots of various chromospheric spectral lines, viz., Hα, Caii 8542 Åto name a few. In this study, we investigate the propagation of shock waves in the lower solar atmosphere using coordinated observations from the Swedish 1-meter Solar Telescope (SST), the Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory (SDO). Our analysis reveals that after forming in the chromosphere, these shock waves travel upward through the solar atmosphere, with their signatures detectable not only in the transition region but also in low coronal passbands. These shock waves dissipate their energy into the chromosphere as they propagate. In certain cases, the energy deposited by these waves is comparable to the radiative losses of the chromosphere, highlighting their potential role in chromospheric heating. Our findings reported here provide crucial insights into wave dynamics in the lower solar atmosphere and their contribution to the energy transport process in the chromosphere
Enhancing Key Rates of QKD Protocol by Coincidence Detection
No full textIn theory, quantum key distribution (QKD) provides unconditional security; however, its practical implementations are susceptible to exploitable vulnerabilities. This investigation tackles the constraints in practical QKD implementations using weak coherent pulses. The conventional approach of using decoy pulses is improved by integrating it with the coincidence detection (CD) protocol. Additionally, an easy-to-implement technique is employed to compute asymptotic key rates for the protocol secure under specific photon number splitting (PNS) attacks. Furthermore, an experimental implementation of the protocol, where it is demonstrated that monitoring coincidences in the decoy state protocol leads to enhanced key rates under realistic experimental conditions, is carried out
Decorated Graphene Quantum Dots on “Puckered” Graphene Quantum Sheets for Photosensing Applications
No full textThis report shows the cost-effective synthesis of “puckered” graphene quantum sheets (GQSs) decorated by graphene quantum dots (GQDs) utilizing the hydrothermal method. The unique puckered architecture helps the entrapment of incident photons and enhances optoelectronic sensitivity. The decorated GQDs are typically ∼3.9 nm in size, while the GQSs are ∼19 nm thick. The GQDs on the sheets form a connected and uniform layer, enabling improved electron transport across the interface of the light-dependent resistors (LDRs). The enhancement ratio (ROFF/RON) of the devices postcoating of puckered GQSs decorated by GQDs is improved by 34% compared to commercial LDRs. The response time is comparable to that of the commercially available LDRs, but the decay time is increased by 61% due to the efficient photon trapping within the puckered layer of GQSs. Experimentally, it has been found that the overall contribution of increased sp2 % (83%), reduced ratio of intensity Raman “D” peak/intensity Raman “G” peak (0.04), increased ratio of intensity Raman “2D” peak/intensity Raman “G” peak (0.60), and low work function (4.33 eV) in the puckered GQS decorated by GQDs help to increase photosensitivity. This technique and the unique architecture of two-dimensional sheets are cost-effective for the mass production of photodetectors and coating materials for enhanced light trapping and conversion to electric current. The present work will open avenues for the development of photon detectors used in quantum and semiconducting technologies
Atmospheric drivers of extreme precipitation events in the Indian sub-continent
No full textExtreme precipitation events in the Indian sub-continent have profound socio-economic and environmental impacts, particularly due to their role in triggering flash floods. These events are driven by a combination of atmospheric conditions, moisture sources and pathways, geomorphology, and hydrometeorology. However, while the hydrometeorological and geomorphological factors have been extensively studied, the role of atmospheric drivers and moisture pathways remains underexplored, creating a significant research gap. To address this gap, we analyzed the atmospheric processes and moisture sources contributing to widespread extreme hourly precipitation events across the Indian subcontinent during the period 1981–2020. Using a combination of reanalysis datasets, event detection algorithms, and moisture tracking methods, we identified the spatial and temporal distribution of these events. We find the Himalayas as a major hotspot, with most extreme events occurring during the Indian summer monsoon season. We find recycled moisture from land surfaces is the dominant source of moisture in the Himalayas, whereas moisture from the Arabian Sea and the Bay of Bengal primarily drives precipitation extremes in peninsular India. Our findings highlight the interconnected dynamics between the atmosphere, land, and ocean in driving extreme precipitation. The study underscores the importance of incorporating atmospheric drivers into disaster management frameworks and early warning systems to enhance preparedness and mitigate impacts effectively
Evaluating pre-trained Large Language Models on zero shot prompts for parallelization of source code
No full textLarge Language Models (LLMs) have become prominent in the software development life cycle, yet the generation of performant source code, particularly through automatic parallelization, remains underexplored. This study compares 23 pre-trained LLMs against the Intel C Compiler (icc), a state-of-the-art auto-parallelization tool, to evaluate their effectiveness in transforming sequential C source code into parallelized versions. Using 30 kernels from the PolyBench C benchmarks, we generated 667 parallelized code versions to assess LLMs’ zero-shot parallelization capabilities. Our experiments reveal that LLMs can outperform icc in non-functional aspects like speedup, with 26.66% of cases surpassing icc's performance. The best LLM-generated code achieved a 7.5× speedup compared to icc's 1.08×. However, only 90 of the 667 generated versions (13.5%) were error-free and functionally correct, underscoring significant reliability challenges. After filtering out versions with compilation errors or data race issues through detailed memory and threading analysis, notable performance gains were observed. Challenges include increased cache miss rates and branch misses with higher thread counts, indicating that simply adding threads does not ensure better performance. Optimizing memory access, managing thread interactions, and validating code correctness are critical for LLM-generated parallel code. Our findings demonstrate that, even without fine-tuning or advanced prompting techniques, pre-trained LLMs can compete with decades-old non-LLM compiler technology in zero-shot sequential-to-parallel code translation. This highlights their potential in automating code parallelization while emphasizing the need to address reliability and performance optimization challenges