Semi-Asynchronous Federated Edge Learning Mechanism via Over-the-air Computation

Over-the-air Computation (AirComp) has been demonstrated as an effective transmission scheme to boost the efficiency of federated edge learning (FEEL). However, existing FEEL systems with AirComp scheme often employ traditional synchronous aggregation mechanisms for local model aggregation in each global round, which suffer from the stragglers issues. In this paper, we propose a semi-asynchronous aggregation FEEL mechanism with AirComp scheme (PAOTA) to improve the training efficiency of the FEEL system in the case of significant heterogeneity in data and devices. Taking the staleness and divergence of model updates from edge devices into consideration, we minimize the convergence upper bound of the FEEL global model by adjusting the uplink transmit power of edge devices at each aggregation period. The simulation results demonstrate that our proposed algorithm achieves convergence performance close to that of the ideal Local SGD. Furthermore, with the same target accuracy, the training time required for PAOTA is less than that of the ideal Local SGD and the synchronous FEEL algorithm via AirComp

Asynchronous Federated Learning with Incentive Mechanism Based on Contract Theory

To address the challenges posed by the heterogeneity inherent in federated learning (FL) and to attract high-quality clients, various incentive mechanisms have been employed. However, existing incentive mechanisms are typically utilized in conventional synchronous aggregation, resulting in significant straggler issues. In this study, we propose a novel asynchronous FL framework that integrates an incentive mechanism based on contract theory. Within the incentive mechanism, we strive to maximize the utility of the task publisher by adaptively adjusting clients' local model training epochs, taking into account factors such as time delay and test accuracy. In the asynchronous scheme, considering client quality, we devise aggregation weights and an access control algorithm to facilitate asynchronous aggregation. Through experiments conducted on the MNIST dataset, the simulation results demonstrate that the test accuracy achieved by our framework is 3.12% and 5.84% higher than that achieved by FedAvg and FedProx without any attacks, respectively. The framework exhibits a 1.35% accuracy improvement over the ideal Local SGD under attacks. Furthermore, aiming for the same target accuracy, our framework demands notably less computation time than both FedAvg and FedProx

Follow-up of patients with COVID-19 by the Delta variant after hospital discharge in Guangzhou, Guandong, China

The B.1.617.2 (Delta) variant of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has contributed to a new increment in cases across the globe. We conducted a prospective follow-up of COVID-19 cases to explore the recurrence and potential propagation risk of the Delta variant and discuss potential explanations for the infection recurrence. A prospective, non-interventional follow-up of discharged patients who had SARS-CoV-2 infections by the Delta variant in Guangdong, China, from May 2021 to June 2021 was conducted. The subjects were asked to complete a physical health examination and undergo nucleic acid testing and antibody detection for the laboratory diagnosis of COVID-19. In total, 20.33% (25/123) of patients exhibited recurrent positive results after discharge. All patients with infection recurrence were asymptomatic and showed no abnormalities in the pulmonary computed tomography. The time from discharge to the recurrent positive testing was usually between 1-33 days, with a mean time of 9.36 days. The cycle threshold from the real-time polymerase chain reaction assay that detected the recurrence of positivity ranged from 27.48 to 39.00, with an average of 35.30. The proportion of vaccination in the non-recurrent group was higher than that in the recurrently positive group (26% vs. 4%; χ2 = 7.902; P < 0.05). Two months after discharge, the most common symptom was hair loss and 59.6% of patients had no long-term symptoms at all. It is possible for the Delta variant SARS-CoV-2 patients after discharge to show recurrent positive results of nucleic acid detection; however, there is a low risk of continuous community transmission. Both, the physical and mental quality of life of discharged patients were significantly affected. Our results suggest that it makes sense to implement mass vaccination against the Delta variant of SARS-CoV-2

Growth, Mechanical, Thermal and Spectral Properties of Cr3+∶MgMoO4 Crystal

This paper reports the growth, mechanical, thermal and spectral properties of Cr3+∶MgMoO4 crystals. The Cr3+∶MgMoO4 crystals with dimensions up to 30 mm×18 mm×14 mm were obtained by TSSG method. The absorption cross-sections of 4A2→4T1 and 4A2→4T2 transitions are 12.94×10−20 cm2 at 493 nm and 7.89×10−20 cm2 at 705 nm for E//Ng, respectively. The Cr3+∶MgMoO4 crystal shows broad band emission extending from 750 nm to 1300 nm with peak at about 705 nm. The emission cross-section with FWHM of 188 nm is 119.88×10−20 cm2 at 963 nm for E//Ng. The investigated results showed that the Cr3+∶MgMoO4 crystal may be regarded as a potential tunable laser gain medium

Growth, spectroscopy and first laser operation of monoclinic Ho3+ :MgWO4 crystal

A monoclinic 0.86 at.% Ho3+:MgWO4 crystal is grown by the Top-Seeded-Solution Growth method. Its spectroscopic properties are studied with polarized light for E || a, b, c. The Ho3+ ion transition probabilities are determined within the modified Judd-Ofelt theory (mJ-O) accounting for the configuration interaction. The intensity parameters are Ω2 = 21.09, Ω4 = 4.42, Ω6 = 2.28 [10–20 cm2] and α= 0.053 [10-4cm]. The calculated radiative lifetime of the 5I7 state is 6.18 ms. The Stark splitting of the 5I7 and 5I8 multiplets is determined with low-temperature spectroscopy. The absorption, stimulated-emission (SE) and gain cross-sections for the 5I8↔5I7 transition are derived. Ho3+ :MgWO4 features a large Stark splitting of the ground-state (380 cm-1), high maximumσSE of 1.82 × 10–20 cm2 at 2.083μm, broad gain spectra and high luminescence quantum yield making it suitable for efficient continuous-wave and mode-locked lasers at∼2.1μm. First laser operation of Ho3+:MgWO4 crystal is demonstrated at 2.104μm reaching a slope efficiency of 72%

Trends and age-period-cohort effect on incidence of hepatitis B from 2008 to 2022 in Guangzhou, China

Abstract Hepatitis B virus (HBV) infection is highly prevalent in Guangzhou, China. This study aimed to examine the long-term trend of HB incidence from 2008 to 2022 and the independent impacts of age, period, and cohort on the trends. HBV data were collected from the China Information System for Disease Control and Prevention. Joinpoint regression was utilized to examine temporal trends, and an age-period-cohort model was employed to estimate the effects of age, period, and cohort. A total of 327,585 HBV cases were included in this study. The incidence of chronic and acute HB showed a decreasing trend in Guangzhou over the past 15 years, with an average annual percent change of − 4.31% and − 16.87%, respectively. Age, period, and cohort all exerted significant effects. The incidence of HB was higher in males than in females and non-central areas compared to central areas. Age groups of 0–4 years and 15–24 years were identified as high-risk groups. The period relative risks for chronic HB incidence decreased initially and then stabilized. Cohorts born later had lower risks. Chronic HB incidences remain high in Guangzhou, especially among males, younger individuals, and residents of non-central areas. More efforts are still needed to achieve hepatitis elimination targets

Seroprevalence of Diphtheria and Tetanus Immunoglobulin G among the General Health Population in Guangzhou, China

A seroepidemiological study was conducted in 2018 to assess diphtheria and tetanus antibodies in Guangzhou, China. Diphtheria and tetanus antibody concentrations were measured with an enzyme-linked immunosorbent assay. A total of 715 subjects were enrolled in the study. The overall diphtheria and tetanus toxoid IgG-specific antibody levels were 0.126 IU/mL (95% CI: 0.115, 0.137) and 0.210 IU/mL (95% CI: 0.185, 0.240), respectively; the overall positivity rate was 61.82% (95% CI: 58.14, 65.39) and 71.61% (95% CI: 68.3, 74.92), respectively. The diphtheria and tetanus antibody concentration was decreased by age and increased by doses. The geometric mean concentrations and positivity rate of diphtheria and tetanus antibodies were lowest and below the essential protection level in people over 14 years of age. Compared to children and adolescents, middle-aged people and the aged are at much higher risk of infection with Corynebacterium diphtheriae and Clostridium tetani. The current diphtheria and tetanus immunization schedule does not provide persistent protection after childhood. There is an urgent need to adjust the current immunization schedule

Positive effects of COVID-19 control measures on influenza prevention

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has now become a pandemic threat to the whole world. At the same time, influenza virus has been active, with influenza virus and SARS-CoV-2 sharing the same transmission routes. This article aims to alert clinicians of the presence of co-infection with these two viruses and to describe the effect of the measures taken to fight COVID-19 on influenza prevention and control