A Comprehensive Survey on Orbital Edge Computing: Systems, Applications, and Algorithms

The number of satellites, especially those operating in low-earth orbit (LEO), is exploding in recent years. Additionally, the use of COTS hardware into those satellites enables a new paradigm of computing: orbital edge computing (OEC). OEC entails more technically advanced steps compared to single-satellite computing. This feature allows for vast design spaces with multiple parameters, rendering several novel approaches feasible. The mobility of LEO satellites in the network and limited resources of communication, computation, and storage make it challenging to design an appropriate scheduling algorithm for specific tasks in comparison to traditional ground-based edge computing. This article comprehensively surveys the significant areas of focus in orbital edge computing, which include protocol optimization, mobility management, and resource allocation. This article provides the first comprehensive survey of OEC. Previous survey papers have only concentrated on ground-based edge computing or the integration of space and ground technologies. This article presents a review of recent research from 2000 to 2023 on orbital edge computing that covers network design, computation offloading, resource allocation, performance analysis, and optimization. Moreover, having discussed several related works, both technological challenges and future directions are highlighted in the field.Comment: 18 pages, 9 figures and 5 table

Trajectories of the Hippocampal Subfields Atrophy in the Alzheimer’s Disease: A Structural Imaging Study

BackgroundThe hippocampus and hippocampal subfields have been found to be diversely affected in Alzheimer’s Disease (AD) and early stages of Alzheimer’s disease by neuroimaging studies. However, our knowledge is still lacking about the trajectories of the hippocampus and hippocampal subfields atrophy with the progression of Alzheimer’s disease.ObjectiveTo identify which subfields of the hippocampus differ in the trajectories of Alzheimer’s disease by magnetic resonance imaging (MRI) and to determine whether individual differences on memory could be explained by structural volumes of hippocampal subfields.MethodsFour groups of participants including 41 AD patients, 43 amnestic mild cognitive impairment (aMCI) patients, 35 subjective cognitive decline (SCD) patients and 42 normal controls (NC) received their structural MRI brain scans. Structural MR images were processed by the FreeSurfer 6.0 image analysis suite to extract the hippocampus and its subfields. Furthermore, we investigated relationships between hippocampal subfield volumes and memory test variables (AVLT-immediate recall, AVLT-delayed recall, AVLT-recognition) and the regression model analyses were controlled for age, gender, education and eTIV.ResultsCA1, subiculum, presubiculum, molecular layer and fimbria showed the trend toward significant volume reduction among four groups with the progression of Alzheimer’s disease. Volume of left subiculum was most strongly and actively correlated with performance across AVLT measures.ConclusionThe trend changes in the hippocampus subfields and further illustrates that SCD is the preclinical stage of AD earlier than aMCI. Future studies should aim to associate the atrophy of the hippocampal subfields in SCD with possible conversion to aMCI or AD with longitudinal design

Towards Client Selection in Satellite Federated Learning

Large-scale low Earth orbit (LEO) remote satellite constellations have become a brand new, massive source of space data. Federated learning (FL) is considered a promising distributed machine learning technology that can communicate optimally using these data. However, when applying FL in satellite networks, it is necessary to consider the unique challenges brought by satellite networks, which include satellite communication, computational ability, and the interaction relationship between clients and servers. This study focuses on the siting of parameter servers (PSs), whether terrestrial or extraterrestrial, and explores the challenges of implementing a satellite federated learning (SFL) algorithm equipped with client selection (CS). We proposed an index called “client affinity” to measure the contribution of the client to the global model, and a CS algorithm was designed in this way. A series of experiments have indicated the advantage of our SFL paradigm—that satellites function as the PS—and the availability of our CS algorithm. Our method can halve the convergence time of both FedSat and FedSpace, and improve the precision of the models by up to 80%

Role of trehalose in MPTP-induced injury of SH-SY5Y cells and its mechanism

Objective: To establish a Parkinson's disease (PD) cell model of human neuroblastoma cells (SH-SY5Y) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and to explore the possible mechanism of trehalose in PD. Methods: SH-SY5Y cells were cultured and divided into four groups: control group, trehalose group, MPTP group and trehalose +MPTP group.The trehalose was detected with MTT assay for its effect of on the viability of injured SH-SY5Y cells. The lactate dehydrogenase (LDH) was detected by kit for its level in culture medium. The ROS was assessed by DCFH-DA for its average level in cells. Besides, Hoechst 33342 staining was used to detect apoptosis. The endoplasmic reticulum stress (ERS) related proteins GRP78, IRE1, PERK and ATF6 were also detected by Western blot for its expression levels. Results: The survival rate of MPTP group decreased significantly and the levels of LDH and ROS increased compared with the control group. In addition, the survival rate of cells in trehalose +MPTP group increased significantly and the levels of LDH and ROS decreased compared with MPTP group. The expressions of GRP78, IRE1, p- IRE1, PERK, p- PERK and ATF6 in MPTP group increased, but decreased in trehalose +MPTP group compared with the control group. Conclusion: Trehalose has a significant protective effect on MPTP-induced SH-SY5Y cells injury, and its mechanism may be related to the effect of trehalose on oxidative stress by inhibiting ER stress response.</jats:p

Nitrous Oxide Poisoning Complicated by Syringomyelia: a Case Report

Abstract Background: Nitrous oxide is a colorless, aromatic, inert organic gas with low toxicity and is currently abused in many recreational areas.Nitrous oxide abuse can lead to vitamin B12 deficiency, which can lead to neurological damage such as spinal neuropathy and peripheral neuropathy. Its abuse has not been associated with syringomyelia.Case presentation: We described the case of a 21-year-old young girl who presented with progressive weakness in both legs and numbness in four limbs after excessive recreational inhalation of nitrous oxide and her imaging findings were considered syringomyelia.Conclusion: Nitrous oxide abuse may be associated with syringomyelia, and that patients with nitrous oxide abuse should be further performed cervical and thoracic MRI to determine whether they have syringomyelia and give timely treatment.</jats:p