Elementary Energy Release Events in Solar Flares

Most theoretical investigations of particle acceleration during solar flares cannot be applied to observations for detailed study of the time evolution. We propose a phenomenological model for turbulence evolution and stochastic particle acceleration that links observations to the energy release and particle acceleration through two coefficients characterizing particle interactions with turbulent electromagnetic fields. In the linear regime the particle distribution does not affect the turbulence energy cascade. It is shown that electron acceleration critically depends on the intensity of small-scale turbulence and an impulsive non-thermal component only appears near the peak of the gradually evolving turbulence intensity. The model naturally reproduces the soft-hard-soft pattern of hard X-ray pulses, and we attribute the observed change in flux and spectral index correlation from the rise to decay phase of some pulses to changes in the background plasma. Detailed modeling of well-observed individual events will probe the energy release processes.Comment: 12 pages, 2 figures, Accepted by ApJ

RHESSI Observations of a Simple Large X-ray Flare on 11-03-2003

We present data analysis and interpretation of a simple X-class flare observed with RHESSI on November 3, 2003. In contrast to other X-class flares observed previously, this flare shows a very simple morphology with well defined looptop (LT) and footpoint (FP) sources. The almost monotonic upward motion of the LT source and increase in separation of the two FP sources are consistent with magnetic reconnection models proposed for solar flares. In addition, we find that the source motions are relatively slower during the more active phases of hard X-ray emission; the emission centroid of the LT source shifts toward higher altitudes with the increase of energy; the separation between the LT emission centroids at two different photon energies is anti-correlated with the FP flux. Non-uniformity of the reconnecting magnetic fields could be a possible explanation of these features.Comment: To appear in the Astrophysical Journal Letters (12 pages, 4 figures

Stochastic Acceleration of Electrons and Protons. I. Acceleration by Parallel Propagating Waves

Stochastic acceleration of electrons and protons by waves propagating parallel to the large scale magnetic fields of magnetized plasmas is studied with emphasis on the feasibility of accelerating particles from a thermal background to relativistic energies and with the aim of determining the relative acceleration of the two species in one source. In general, the stochastic acceleration by these waves results in two distinct components in the particle distributions, a quasi-thermal and a hard nonthermal, with the nonthermal one being more prominent in hotter plasmas and/or with higher level turbulence. This can explain many of the observed features of solar flares. Regarding the proton to electron ratio, we include the effects of $^4$He in the dispersion relation and the damping of the turbulent waves by the thermal background plasma. The relative acceleration of protons and electrons is very sensitive to the ratio of the electron plasma frequency to its gyro-frequency. Protons are preferentially accelerated in weakly magnetized plasmas. The formalism developed here is applicable to the acceleration of other ion species and to other astrophysical systems.Comment: 53 pages and 15 figures, To be published in Ap

Effects of dietary oxidized fish oil on the growth performance, intestinal health, and antioxidant capacity of zebrafish

This study aimed to investigate the effects of oxidized fish oil (OFO) on growth performance, intestinal health, and antioxidant function and to determine the minimum concentration of oxidized fish oil to cause irreversible damage to the intestinal tissue structure of zebrafish. A 30-day feeding trial on zebrafish (average weight 0.054 g) was conducted in triplicate groups of fish fed four test diets containing different concentrations of OFO: 0% OFO (OFF, blank control), 2% OFO (OF1), 4% OFO (OF2), and 6% OFO (OF3). The body weight gain (WG), specific growth rates (SGR), feed conversion ratio (FCR), survival rate (SR), and antioxidant function {glutathione peroxidase (GSH-PX), total superoxide dismutase (T-SOD), catalase (CAT), and malondialdehyde (MDA)} were recorded. The intestinal structure was observed at the end of the trial. After the 14-day experimental period, Final body weight (FBW), WG, and SGR decreased significantly with the increase in the concentration of feed OFO (P < 0.05), while FCR showed a downward trend. The activity of T-SOD decreased significantly, the activities of GSH-PX and CAT, and the MDA content increased significantly with the increase in the concentration of feed OFO (P < 0.05). The intestinal morphological damage score showed an upward trend with the increase in the concentration of OFO, and it was significantly higher in group OF2 and OF3 than in group OF1 (P < 0.05). After the 28-day test period, the experimental indexes and intestinal antioxidant function trends were the same as those on 14 days. The increased OFO concentration significantly increased the intestinal morphological injury score (P < 0.05). These results demonstrated that adding 4% OFO to the feed for 14 days could induce irreversible damage to the intestinal tissue structure, weaken the antioxidant function, and decrease the growth performance of zebrafish

Stochastic Electron Acceleration in Shell-Type Supernova Remnants II

We discuss the generic characteristics of stochastic particle acceleration by a fully developed turbulence spectrum and show that resonant interactions of particles with high speed waves dominate the acceleration process. To produce the relativistic electrons inferred from the broadband spectrum of a few well-observed shell-type supernova remnants in the leptonic scenario for the TeV emission, fast mode waves must be excited effectively in the downstream and dominate the turbulence in the subsonic phase. Strong collisionless non-relativistic astrophysical shocks are studied with the assumption of a constant Aflven speed. The energy density of non-thermal electrons is found to be comparable to that of the magnetic field. With reasonable parameters, the model explains observations of shell-type supernova remnants. More detailed studies are warranted to better understand the nature of supernova shocks.Comment: 5 pages, 7 figures, submitted to Proceedings of the Conference on "2008 Heidelberg International Symposium on High Energy Gamma-Ray Astronomy

Monolithic quantum-dot distributed feedback laser array on silicon

Electrically-pumped lasers directly grown on silicon are key devices interfacing silicon microelectronics and photonics. We report here, for the first time, an electrically-pumped, room-temperature, continuous-wave (CW) and single-mode distributed feedback (DFB) laser array fabricated in InAs/GaAs quantum-dot (QD) gain material epitaxially grown on silicon. CW threshold currents as low as 12 mA and single-mode side mode suppression ratios (SMSRs) as high as 50 dB have been achieved from individual devices in the array. The laser array, compatible with state-of-the-art coarse wavelength division multiplexing (CWDM) systems, has a well-aligned channel spacing of 20 0.2 nm and exhibits a record wavelength coverage range of 100 nm, the full span of the O-band. These results indicate that, for the first time, the performance of lasers epitaxially grown on silicon is elevated to a point approaching real-world CWDM applications, demonstrating the great potential of this technology

Preventing the immense increase in the life-cycle energy and carbon footprints of LLM-powered intelligent chatbots

Intelligent chatbots powered by large language models (LLMs) have recently been sweeping the world, with potential for a wide variety of industrial applications. Global frontier technology companies are feverishly participating in LLM-powered chatbot design and development, providing several alternatives beyond the famous ChatGPT. However, training, fine-tuning, and updating such intelligent chatbots consume substantial amounts of electricity, resulting in significant carbon emissions. The research and development of all intelligent LLMs and software, hardware manufacturing (e.g., graphics processing units and supercomputers), related data/operations management, and material recycling supporting chatbot services are associated with carbon emissions to varying extents. Attention should therefore be paid to the entire life-cycle energy and carbon footprints of LLM-powered intelligent chatbots in both the present and future in order to mitigate their climate change impact. In this work, we clarify and highlight the energy consumption and carbon emission implications of eight main phases throughout the life cycle of the development of such intelligent chatbots. Based on a life-cycle and interaction analysis of these phases, we propose a system-level solution with three strategic pathways to optimize the management of this industry and mitigate the related footprints. While anticipating the enormous potential of this advanced technology and its products, we make an appeal for a rethinking of the mitigation pathways and strategies of the life-cycle energy usage and carbon emissions of the LLM-powered intelligent chatbot industry and a reshaping of their energy and environmental implications at this early stage of development