Development of a low-cost multi-camera star tracker for small satellites

This thesis presents a novel small satellite star tracker that uses an array of low-cost, off the shelf imaging sensors to achieve high accuracy attitude determination performance. The theoretical analysis of improvements in star detectability achieved by stacking images from multiple cameras is presented. An image processing algorithm is developed to combine images from multiple cameras with arbitrary focal lengths, principal point offsets, distortions, and misalignments. The star tracker also implements other algorithms including the region growing algorithm, the intensity weighted centroid algorithm, the geometric voting algorithm for star identification, and the singular value decomposition algorithm for attitude determination. A star tracker software simulator is used to test the algorithms by generating star images with sensor noises, lens defocusing, and lens distortion. A hardware prototype is being assembled for eventual night sky testing to verify simulated performance levels. Star tracker flight hardware is being developed in the Laboratory for Advanced Space Systems at Illinois (LASSI) at the University of Illinois at Urbana Champaign for future CubeSat missions

Investigation into and Analysis on Middle School English Teachers’ Competencies

For teachers’ competence, there is no uniform standard in domestic and foreign academic circles. Foreign scholars think that the personality of the teacher can do the performance of competence while domestic scholars believe that the professional values of the teachers, that is, personal qualities, professional ethics can be competent. The domestic and foreign scholars all agree that: the definition of teachers' competence should include the professional knowledge and professional skills related to the implementation of the successful teaching. Through questionnaire survey and interview, this paper makes a research on English teachers’ conception and language skills---the core competency of middle school English teachers in Shaanxi Province. It is found that there are some disparities of English teachers’ conception and language skills from the requirements of the new curriculum standards. Based on the reason analysis of disparities, the following suggestions are put forward: study the new curriculum standards seriously, strengthen the studies on education and teaching theories, strengthen the guidance on teaching practice and encourage the teachers to reflect on their teaching methods

Development of a Low-Cost Multi-Camera Star Tracker for Small Satellites

This paper presents a novel small satellite star tracker that uses multiple low-cost cameras to achieve viable attitude determination performance. The theoretical analysis of the star detectability improvement by stacking images from multiple cameras is presented. An image processing algorithm is developed to combine images from multiple cameras with various focal lengths, principal point offsets, distortions, and misalignments. The star tracker also implements other algorithms including the region growing algorithm, the intensity weighted centroid algorithm, the geometric voting algorithm for star identification, and the singular value decomposition algorithm for attitude determination. A star tracker software simulator is used to test the algorithms by generating star images with sensor noises, lens defocusing, and lens distortion. A hardware prototype is assembled, and preliminary night sky testing was conducted to verify the feasibility of the selected hardware. The flight hardware for the star tracker is being developed in the Laboratory for Advanced Space Systems at Illinois (LASSI) at the University of Illinois at Urbana Champaign for future CubeSat missions

Virus contamination and infectivity in beach environment: Focus on sand and stranded material

To assess the exposure of beachgoers to viruses, a study on seawater, sand, and beach-stranded material was carried out, searching for human viruses, fecal indicator organisms, and total fungi. Moreover, for the first time, the genome persistence and infectivity of two model viruses was studied in laboratory-spiked sand and seawater samples during a one-week experiment. Viral genome was detected in 13.6 % of the environmental samples, but it was not infectious (Human Adenovirus – HAdV, and enterovirus). Norovirus and SARS-CoV-2 were not detected. The most contaminated samples were from sand and close to riverine discharges. In lab-scale experiments, the infectivity of HAdV5 decreased by ~1.5-Log10 in a week, the one of Human Coronavirus-229E disappeared in <3 h in sand. The genome of both viruses persisted throughout the experiment. Our results confirm viral contamination of the beach and suggest HAdV as an index pathogen for beach monitoring and quantitative risk assessment

Sodium Fluoride Arrests Renal G2/M Phase Cell-Cycle Progression by Activating ATM-Chk2-P53/Cdc25C Signaling Pathway in Mice

Background/Aims: Excessive fluoride intake can induce cytotoxicity, DNA damage and cell-cycle changes in many tissues and organs, including the kidney. However, the underlying molecular mechanisms of fluoride-induced renal cell-cycle changes are not well understood at present. In this study, we used a mouse model to investigate how sodium fluoride (NaF) induces cell-cycle changes in renal cells. Methods: Two hundred forty ICR mice were randomly assigned to four equal groups for intragastric administration of NaF (0, 12, 24 and 48 mg/kg body weight/day) for 42 days. Kidneys were taken to measure changes of the cell-cycle at 21 and 42 days of the experiment, using flow cytometry, quantitative real-time polymerase chain reaction (qRT-PCR) and western blot methods. Results: NaF, at more than 12 mg/kg body weight, induced G2/M phase cell-cycle arrest in the renal cells, which was supported by the finding of significantly increased percentages of renal cells in the G2/M phase. We found also that G2/M phase cell-cycle arrest was accompanied by up-regulation of p-ATM, p-Chk2, p-p53, p-Cdc25C, p-CDK1, p21, and Gadd45a protein expression levels; up-regulation of ATM, Chk2, p53, p21, and Gadd45a mRNA expression levels; down-regulation of CyclinB1, mdm2, PCNA protein expression levels; and down-regulation of CyclinB1, CDK1, Cdc25C, mdm2, and PCNA mRNA expression levels. Conclusion: In this mouse model, NaF, at more than 12 mg/ kg, induced G2/M phase cell-cycle arrest by activating the ATM-Chk2-p53/Cdc25C signaling pathway, which inhibits the proliferation of renal cells and development of the kidney. Activation of the ATM-Chk2-p53/Cdc25C signaling pathway is the mechanism of NaF-induced renal G2/M phase cell-cycle arrest in this model

Organic Pollutants Associated with Plastic Debris in Marine Environment: A Systematic Review of Analytical Methods, Occurrence, and Characteristics

Plastic pollution has become one of the most serious environmental problems, and microplastics (MPs, particles < 5 mm size) may behave as a vehicle of organic pollutants, causing detrimental effects to the environment. Studies on MP-sorbed organic pollutants lack methodological standardization, resulting in a low comparability and replicability. In this work, we reviewed 40 field studies of MP-sorbed organic contaminants using PRISMA guidelines for acquiring information on sampling and analytical protocols. The papers were also scored for their reliability on the basis of 7 criteria, from 0 (minimum) to 21 (maximum). Our results showed a great heterogeneity of the methods used for the sample collection, MPs extraction, and instruments for chemicals’ identification. Measures for cross-contamination control during MPs analysis were strictly applied only in 13% of the studies, indicating a need for quality control in MPs-related research. The most frequently detected MP-sorbed chemicals were polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs). Most of the studies showed a good reliability (>75% of the total score), with 32 papers scoring 16 or higher. On the basis of the collected information, a standardizable protocol for the detection of MPs and MP-sorbed chemicals has been suggested for improving the reliability of MPs monitoring studies

Figures 55-61 from: Zhao C, Zhang H, Tong X (2018) A revision of Chinese Psalidothrips Priesner (Thysanoptera, Phlaeothripidae), with the descriptions of five new species. ZooKeys 746: 25-50. https://doi.org/10.3897/zookeys.746.22882

An initial checklist of mayflies (Ephemeroptera) of Iran is compiled based on critical review of available literature data, complemented with new data from 38 localities of Gilan and Ardabil provinces. At present, altogether only 46 species and 25 genera are known from Iran, 18 species are reported as new to Iran in this study. Some previously published data are critically evaluated and doubtful taxa are excluded from the list. Basic analysis of the distribution and biogeography of recorded species is given. Procloeon (Pseudocentroptilum) caspicum Sroka, sp. n. is described based on mature larva and egg. Critical differential diagnostic characters distinguishing the species from related taxa are discussed in detail

The Assessment of Urban Ecological Environment in Watershed Scale

AbstractUrban ecological environment is closely related to the harmonious development of the region. The interaction between ecological environment of the city and the watershed where it locates is less considered in current study. In this paper, making use of multi-source data with remote sensing data as the main data source and according to the “Technical Standard for Evaluation of Ecological Environment” (HJ192-2015) promulgated by Ministry of Environment Protection, we accomplished the quality assessment of ecological environment of Yanhe watershed in 250m × 250m pixel unit with synthetical index method. Based on this, we also combined demographic data, DEM data of Yanhe watershed to analyze the interaction between urban ecological environment and ecological environment status of the entire watershed. The results showed that: 1) The ecological environment quality levels of urban areas in Yanhe watershed were mainly “poor” and “worse”, and the farther from the urban area, the better quality level of ecological environment in general, which indicated the existence of the city exerted stress on the ecological environment; 2) The ecological environment of the city at higher altitude was in poorer condition, indicating that the distribution of the topography of the watershed had a certain impact on the ecological environment of the city; 3) By comparing the distribution of the ecological environment quality of different cities in the watershed, the more concentrated population density of the city, the greater scope of the poorer ecological environment, indicating that human activities had great influences on the urban ecological environment. We can conclude that it is necessary to consider the interaction between urban ecological environment and watershed ecological environment where the city locates, so as to provide new ideas for the construction and protection of the ecological environment of the city