Supernova Neutrino in a Strangeon Star Model

The neutrino burst detected during supernova SN1987A is explained in a strangeon star model, in which it is proposed that a pulsar-like compact object is composed of strangeons (strangeon: an abbreviation of "strange nucleon"). A nascent strangeon star's initial internal energy is calculated, with the inclusion of pion excitation (energy around 10^53 erg, comparable to the gravitational binding energy of a collapsed core). A liquid-solid phase transition at temperature ~ 1-2 MeV may occur only a few ten-seconds after core-collapse, and the thermal evolution of strangeon star is then modeled. It is found that the neutrino burst observed from SN 1987A could be re-produced in such a cooling model.Comment: 15 pages, 7 figures, 1 tabe

Spatial-temporal Evolution and Its Influencing Factors of Tourism Eco-efficiency in China

Eco-efficiency is an invaluable indicator for the measurement of the relationship between production activities and environmental depletion. This study measures the tourism eco-efficiency of 30 provinces in China from 2005 to 2020 based on the super-efficiency SBM model, and explores its spatial-temporal evolution characteristics using the kernel density function, standard deviation ellipse, and center of gravity model. Then, the influencing factors of the tourism eco-efficiency in China are analyzed by Tobit regression model. The results show that the tourism eco-efficiency of China is generally fluctuating upwards, but has not yet reached the maximum production possibility frontier. The kernel density curve shows a unimodal-bimodal-unimodal pattern, while the inter-provincial differences have been decreasing and becoming more balanced. The center of gravity of tourism eco-efficiency is located at the junction of Henan and Hubei province and generally moves to the south (slightly to the southwest). Meanwhile, it is revealed that the level of economic development and the tourism eco-efficiency has a significant inverted U-shaped relationship. The level of economic openness, traffic conditions, and tourism eco-efficiency is positively correlated. The environmental regulations and industrial structure have a negative but limited impact on tourism eco-efficiency. Finally, recommendations and suggestions for policy formulation to promote quality and sustainable development of the tourism industry are put forward, such as increasing investment in ecological protection and governance in tourism development, improving capacity-building in allocating green and low-carbon technologies and resources, strengthening tourism infrastructure construction, and enhancing environmental governance systems and mechanisms

A Guideline for Silicon Carbide MOSFET Thermal Characterization based on Source-Drain Voltage

Thermal transient measurement based on source-drain voltage is a standard method to characterize thermal properties of silicon semiconductors but is doubtful to be directly applied to silicon carbide (SiC) devices. To evaluate its feasibility and limitations, this paper conducts a comprehensive investigation into its accuracy, resolution, and stability towards yielding the structure information of SiC MOSFET using the source-drain voltage as the temperature sensitive electrical parameter. The whole characterization process involves two main procedures and associated key testing parameters, such as gate voltages, sensing and heating currents, etc. Their impacts on both the static and dynamic performances are also investigated with the aim of providing a guideline for conducting a reproducible thermal transient measurement for SiC MOSFETs

Toward accurate cerebral blood flow estimation in mice after accounting for anesthesia

Purpose: To improve the accuracy of cerebral blood flow (CBF) measurement in mice by accounting for the anesthesia effects.Methods: The dependence of CBF on anesthesia dose and time was investigated by simultaneously measuring respiration rate (RR) and heart rate (HR) under four different anesthetic regimens. Quantitative CBF was measured by a phase-contrast (PC) MRI technique. RR was evaluated with a mouse monitoring system (MouseOX) while HR was determined using an ultrashort-TE MRI sequence. CBF, RR, and HR were recorded dynamically with a temporal resolution of 1 min in a total of 19 mice. Linear regression models were used to investigate the relationships among CBF, anesthesia dose, RR, and HR.Results: CBF, RR, and HR all showed a significant dependence on anesthesia dose (p < 0.0001). However, the dose in itself was insufficient to account for the variations in physiological parameters, in that they showed a time-dependent change even for a constant dose. RR and HR together can explain 52.6% of the variations in CBF measurements, which is greater than the amount of variance explained by anesthesia dose (32.4%). Based on the multi-parametric regression results, a model was proposed to correct the anesthesia effects in mouse CBF measurements, specifically CBFcorrected=CBF+0.58RR−0.41HR−32.66Dose. We also reported awake-state CBF in mice to be 142.0 ± 8.8 mL/100 g/min, which is consistent with the model-predicted value.Conclusion: The accuracy of CBF measurement in mice can be improved by using a correction model that accounts for respiration rate, heart rate, and anesthesia dose

Experimental Quantum Communication Overcomes the Rate-loss Limit without Global Phase Tracking

Secure key rate (SKR) of point-point quantum key distribution (QKD) is fundamentally bounded by the rate-loss limit. Recent breakthrough of twin-field (TF) QKD can overcome this limit and enables long distance quantum communication, but its implementation necessitates complex global phase tracking and requires strong phase references which not only add to noise but also reduce the duty cycle for quantum transmission. Here, we resolve these shortcomings, and importantly achieve even higher SKRs than TF-QKD, via implementing an innovative but simpler measurement-device-independent QKD which realizes repeater-like communication through asynchronous coincidence pairing. Over 413 and 508 km optical fibers, we achieve finite-size SKRs of 590.61 and 42.64 bit/s, which are respectively 1.80 and 4.08 times of their corresponding absolute rate limits. Significantly, the SKR at 306 km exceeds 5 kbit/s and meets the bitrate requirement for live one-time-pad encryption of voice communication. Our work will bring forward economical and efficient intercity quantum-secure networks.Comment: 29 pages, 10 figures, 3 table

Effect of heat input on nanomechanical properties of wire-arc additive manufactured Al 4047 alloys

Heat input is one of the most important process parameters during additive manufacturing (AM). It is of great significance to understand the effect of heat input on the microstructure and nanomechanical properties, as well as the underlying mechanisms. Wire-arc additive manufactured (WAAM-ed) Al 4047 alloys under different heat inputs were produced and studied in this work. The as-manufactured Al alloys showed hypoeutectic microstructure that consisted of primary Al (α-Al) dendrite and ultrafine Al–Si eutectic. The effect of heat input on hardness and strain rate sensitivity (SRS) were investigated through nanoindentation. The nanohardness decreased with the increasing heat input, in accordance with the trend of yield strength and microhardness in the previous studies, in which the mechanism was usually explained by the grain growth model and Hall-Petch relationship. This work suggests a distinct mechanism regarding the effect of heat input on nanohardness, which is the enhanced solid solution strengthening produced by lower heat input. In addition, the heat input had little effect on the SRS and activation volume. It is hoped that this study leads to new insights into the understanding of the relation between heat input and nanomechanical properties, and further benefits to improve the targeted mechanical properties and engineering applications of the AM-ed materials.publishedVersio

Quantum key distribution and beyond: introduction

This feature issue presents a collection of recent theoretical and experimental developments in the field of quantum key distribution (QKD) and its extension to other quantum cryptography protocols and devices. It encompasses work on a variety of QKD protocols, including continuous-variable, measurement-device independent, and twin-field QKD, as well as other newly proposed protocols, in platforms ranging from optical fiber through to wireless indoor and satellite links. It covers examples of hacking strategies and their countermeasures as well as applications of machine learning techniques in designing quantum networks. It also includes new developments in efficient superconducting photon-number resolving detectors as well as fast quantum random number generators. Distinctively, this feature issue demonstrates how different expertise in science and engineering can come together to produce an outcome that hopefully takes us one step closer to the wide-scale deployment of quantum communications technologies

Low Iodine Nutrition Knowledge in Chinese Breastfeeding Women despite Adequate Iodine Status

There has been a scarcity of evidence about iodine nutrition knowledge among women during pregnancy and lactation. The aim of this study was to determine women’s iodine knowledge and the relationship between knowledge and iodine status during pregnancy and lactation. Women were recruited from a hospital in the western part of China in the third trimester of pregnancy and followed until the end of the first week of lactation. The women’s iodine status was measured by their urinary iodine concentration (UIC) and an iodine-specific, validated food frequency questionnaire (FFQ). Iodine nutrition knowledge was assessed using an iodine nutrition knowledge questionnaire. A total of 200 women (mean age of 29.0 ± 4.2 years) completed the whole study. The majority of the women did not consume enough iodine during both pregnancy and lactation (231.89 vs. 237.26 µg/day). The overall mean iodine knowledge scores in our sample of women during pregnancy and lactation were 4.77 and 4.87, indicating low iodine knowledge. The use of iodized salt and a higher education level were significantly associated with an increased iodine knowledge score. In conclusion, this study reported poor iodine nutrition knowledge in women, highlighting a public health concern. Therefore, the iodine knowledge of women should be improved, possibly via maternal health campaigns to avoid the consequences of iodine deficiency disorders in newborns.</jats:p