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Cold War Feminism as a Postcolonial Methodology: Middlebrow Literature in (South) Korea
No full textThis presentation explores narratives of Cold War Feminism as a methodology – a strategic practice of several women writers in the postcolonial era – by focusing on two leading female writers at the time as case studies. The presentation will start with a short introduction on middlebrow literature and Cold War Feminism, and discuss how women’s travel narratives fit in these categories. In this period, the genre of travel abroad narratives was highly reliant on state support, both from inside and outside the Korean peninsula. A limited number of elite women writers, including Mo Youn Sook and Kim Marl-bong, could visit Europe to participate in international meetings organized by the United Nations. Other government initiatives included the United Kingdom’s “goodwill tours.” Such events were connected to the Cultural Cold War, the extension of Cold War politics in the cultural domain. After such visits, these women actively published their travelogues, conveying their impressions of Europe and European women to Korean readers. Postcolonial Korean women’s travel narratives markedly differ from earlier European travelogues published by so-called New Women based on their travels in the 1920s –30s. This has to do with the fact that, after 1945, foreign travel of South Koreans was monitored by the South Korean state, and in many cases, had to be supported by the United States and their allies. </p
Nanodiamond-Based Sensing: A revolution for biosensors in capturing elusive bio-signals in living cells
Get PDFCells constantly produce elusive bio-signals, such as cellular forces, free radicals, and molecular interactions, that are important for understanding diseases and treatment effects. However, detecting these signals is challenging because of issues with sensitivity, specificity, and the complexity of biological systems. Owing to their unique properties, nanodiamonds have emerged as a promising platform for detecting such elusive bio-signals, providing enhanced precision and effectiveness in diagnostics and therapies. In this review, we explore the detection of intracellular elusive bio-signals using nitrogen-vacancy (NV) centers in nanodiamonds, presenting case studies on their applications in cell force, free radicals, molecular interactions, and nanoscale thermometry. Moreover, we explore the design and applications of nanodiamonds as nanocarriers in quantum sensors and drug delivery systems.published_or_final_versio
Three-dimensional auxetic metamaterials with extremely tunable flexible behavior
Get PDFFlexible auxetic metamaterials has demonstrated significant potential in engineering applications. However, most existing flexible auxetic metamaterials are limited to two-dimensional (2D) designs, restricting their utility in real 3D engineering scenarios. Here we represent a versatile strategy for designing 3D auxetic metamaterials that showcase extraordinary flexibility, recoverability, and programmability which is accomplished by embedding truss lattice with elastic spring into rotating rigid frameworks. We exemplify this approach with the eccentric spring connected rotating octet truss structures (ROCT-S) through experimental, numerical, and theoretical analysis. Under in-plane tension, engineering stress of the proposed eccentric spring connected rotating octet truss structures in two directions (ROCT-S-2D) is approximately 9.4 × 10−6 of the base material's modulus at an average strain of 161 %. Simultaneously, the programmable mechanical performance of the ROCT-S-2D under out-plane compression is decoupling with their in-plane performance and can be designed to support a load exceeding 12,800 times its own weight. The robust and adaptable mechanical performance of ROCT-S highlight its broad applicability, spanning electronics and biomedical devices to wearable flexible protective gear, paving the way for advanced 3D auxetic metamaterials in practical engineering solutions.published_or_final_versio
Thermal protection mechanism of UHTCs-modified C/C composites in high temperature gas scouring coupling environments
No full textExamining the coupling analysis between environment and material system is prerequisite for advancing the reliability design of thermal protection system components in aerospace applications. To elucidate the resistance of C/C composites to high-temperature gas-flow erosion, C/C–MeC–SiC composites (Me: Hf, Zr, Ti, Ta, Nb, W) were prepared by reactive melt infiltration. The thermal loading characteristics of DC plasma torch (Ar–O2 atmosphere, 2500 °C) were simulated by finite element analysis, as well as the ablation resistance was analyzed theoretically and experimentally. The ablation-resistant behaviors of carbon-based composites were investigated by theoretical calculations and experimental verification. The results show that the higher temperature resistance of HfC (0.69 μm/s), ZrC (−1.58 μm/s) and their oxidation products become the primary mechanism for the skeletal support of the oxide layer. The high fluidity of TiO2 rapidly forms an oxide layer but also exacerbates the volatilization of gaseous by-products (TiC, 3.02 μm/s). Due to the volatility of WO3, WC is limited to short-term ablation resistance (−2.11 μm/s). The oxidation products of NbC and TaC are directional and are expected to rapidly fill the porous structure under thermal shock. Coupled fluid-thermal-structural simulations elucidate the heat flux density, temperature, and stress distributions of different systems of composites under heterogeneous ablation, consistent with the post-ablation morphological trends. </p
Low-temperature preparation of C/C-W-Cu composites with enhanced particle impact and ablation resistance
No full textHerein, C/C-W-Cu composites were innovatively developed by a molten salt assisted reactive infiltration method, with the preparation temperature of only 1300 ℃, far lower than the traditional infiltration temperatures. The as-prepared C/C-W-Cu composites exhibited better particle erosion and high-temperature ablation resistance than C/C composites, with a linear variation rate decrease of 99.5 % and 80.3 % under particle impact (70 m/s, 10 s) and oxyacetylene ablation (2.4 MW/m2, 120 s) conditions, respectively. The improved protection performance can be attributed to the synergistic effects of ductile deformation of the surface W-Cu metal layer and transpiration cooling of the filled Cu phase, which prevents serious carbon fiber damage and ensures a low response of surface ablation temperature (∼1400 ℃). </p
The multiwavelength correlations quest for central engines of GRB plateaus: Magnetar vs black hole spin-down
No full textThis manuscript presents a multilevel analysis of gamma-ray bursts (GRBs). We focus on the plateau phase, which is often observed in the light curves (LCs) of GRBs. We discuss its observational properties and then thoroughly examine possible theoretical models to explain them. Inspired by the limitations of many currently known models, we introduce a novel scenario of an LC powered by the kinetic energy of a rotating black hole (BH). We investigate observational correlations between the properties of GRBs across the gamma, X-ray, and optical bands during the prompt and plateau phases of their LCs. Our analysis includes all GRBs with known redshifts detected by the Neil Gehrels Swift Observatory (Swift) and the Fermi Gamma-ray Space Telescope (Fermi), as well as ground-based optical telescopes. We identify a tight correlation with the R2 coefficient of ∼0.89 for the three-dimensional Dainotti relation between the luminosity at the end of the plateau, its duration measured by Swift, and the peak luminosity measured by Fermi in the 10-1000 keV band. When accounting for redshift evolution, we achieve very small intrinsic scatter σint=0.25±0.04 (∼43% reduction compared to the previous results). Additionally, we explore correlations involving the optical luminosity at the end of the plateau, yielding promising results. We investigate the clustering of different classes of GRBs in the investigated parameter space and discuss its impact on the aforementioned correlations as well as Eiso-Epeak⁎ correlation. Notably, we demonstrate how to use the correlations as a powerful class discriminator. Finally, we discuss the theory supporting the evidence of the plateau emission. We present a new paradigm for the GRB plateau: energy extraction from a quickly rotating black hole (BH) via spin-down by a magnetically arrested disk (MAD). We compare this model with observations and explain multiple observed features. We predict the plateau luminosity - time anti-correlation and discuss the cosmological evolution within this proposed model. Furthermore, within this new model, we discuss the possible physical origin of the clustering of long and short GRBs in the parameter space of plateau luminosity - time - prompt luminosity.link_to_subscribed_fulltex
Einstein Probe Discovery of EPJ005245.1−722843: A Rare Be–White Dwarf Binary in the Small Magellanic Cloud?
No full textOn 2024 May 27, the Wide-field X-ray Telescope on board the Space Sciences, University of Chinese Academy of Einstein Probe (EP) mission detected enhanced X-ray emission from a new transient source in the Small Magellanic Cloud during its commissioning phase. Prompt follow-up with the EP Follow-up X-ray Telescope, the Swift X-ray Telescope. and NICER have revealed a very soft, thermally emitting source (kT ~ 0.1 keV at the outburst peak) with an X-ray luminosity of L ~ 4 × 1038 erg s−1, labeled EP J005245.1−722843. This supersoft outburst faded very quickly in a week's time. Several emission lines and absorption edges were present in the X-ray spectrum, including deep nitrogen (0.67 keV) and oxygen (0.87 keV) absorption edges. The X-ray emission resembles the supersoft source phase of typical nova outbursts from an accreting white dwarf (WD) in a binary system, despite the X-ray source being historically associated with an O9-B0e massive star exhibiting a 17.55 day periodicity in the optical band. The discovery of this supersoft outburst suggests that EP J005245.1−722843 is a BeWD X-ray binary: an elusive evolutionary stage where two main-sequence massive stars have undergone a common envelope phase and experienced at least two episodes of mass transfer. In addition, the very short duration of the outburst and the presence of Ne features hint at a rather massive, i.e., close to the Chandrasekhar limit, Ne–O WD in the system.link_to_subscribed_fulltex
A fast X-ray transient from a weak relativistic jet associated with a type Ic-BL supernova
No full textMassive stars end their lives as core-collapse supernovae, among which some extremes are broad-lined type Ic supernovae from Wolf–Rayet stars associated with long-duration gamma-ray bursts (LGRBs) with powerful relativistic jets. Their less-extreme brethren make unsuccessful jets that are choked inside the stars, appearing as X-ray flashes or low-luminosity GRBs. However, there exists a population of extragalactic fast X-ray transients with timescales ranging from seconds to thousands of seconds, whose origins remain obscure. Here we report the discovery of the bright X-ray transient EP240414a detected by the Einstein Probe, which is associated with the type Ic supernova SN 2024gsa at a redshift of 0.401. The X-ray emission evolution is characterized by a very soft energy spectrum peaking at <1.3 keV, which makes it different from known LGRBs, X-ray flashes or low-luminosity GRBs. Follow-up observations at optical and radio bands revealed the existence of a weak relativistic jet that interacts with an extended shell surrounding the progenitor star. Located on the outskirts of a massive galaxy, this event reveals a population of explosions of Wolf–Rayet stars characterized by a less powerful engine that drives a successful but weak jet, possibly owing to a progenitor star with a smaller core angular momentum than in traditional LGRB progenitors.link_to_subscribed_fulltex
Designing Mathematics Hybrid Classrooms in High School: The Case of Valeria
No full textOnline mathematics learning is spreading among tertiary education. One of the challenges for secondary mathematics teachers is to prepare their students to learn in this new format. MOOC videos delivered online for free are one of these formats, and it is necessary to investigate how teachers’ beliefs and goals influence their choices about planning and delivering mathematics lessons that resort to this kind of resource. In this chapter, the case of Valeria illuminates important relations between a teacher's beliefs about her students, and her attitudes towards technology.link_to_subscribed_fulltex
Hierarchical Yolk-Shell Silicon/Carbon Anode Materials Enhanced by Vertical Graphene Sheets for Commercial Lithium-Ion Battery Applications
No full textYolk-shell structured silicon/carbon (YS-Si/C) anode materials show promise for commercial lithium-ion batteries (LIBs) because of their high specific capacity and excellent cycling life. However, their commercialization has not been realized despite nearly a decade of research, primarily due to poor mechanical strength, limited rate capability, and low energy density. This study reports a hierarchical YS-Si/C anode material synthesized via thermal chemical vapor deposition for the growth of vertical graphene sheets (VGSs), polymer self-assembly, and one-step carbonization, which establishes connections between the Si core and carbon shell through VGSs, enhancing the electrochemical and mechanical characteristics of the YS-Si/C material. The unique material outperforms VGSs-free composites, which presents a high specific capacity of 1683.2 mAh g−1 at 0.1 C, excellent rate performance of 552.2 mAh g−1 at 10 C, and superior capacity retention of 80.1% after 1000 cycles. When matched with LiNi0.8Co0.1Mn0.1O2 cathodes, the ampere-hour-level pouch cell delivers high gravimetric and volumetric energy densities of 429.2 Wh kg−1 and 1083 Wh L−1, respectively. Finite element analysis shows that VGSs reduce stress concentration on the carbon shell, helping hollow materials withstand industrial electrode calendaring. This work demonstrates potential for the commercial application of YS-Si/C anode materials in practical LIBs.link_to_subscribed_fulltex