Map Reconstruction of radio observations with Conditional Invertible Neural Networks

In radio astronomy, the challenge of reconstructing a sky map from time ordered data (TOD) is known as an inverse problem. Standard map-making techniques and gridding algorithms are commonly employed to address this problem, each offering its own benefits such as producing minimum-variance maps. However, these approaches also carry limitations such as computational inefficiency and numerical instability in map-making and the inability to remove beam effects in grid-based methods. To overcome these challenges, this study proposes a novel solution through the use of the conditional invertible neural network (cINN) for efficient sky map reconstruction. With the aid of forward modeling, where the simulated TODs are generated from a given sky model with a specific observation, the trained neural network can produce accurate reconstructed sky maps. Using the five-hundred-meter aperture spherical radio telescope (FAST) as an example, cINN demonstrates remarkable performance in map reconstruction from simulated TODs, achieving a mean squared error of $2.29\pm 2.14 \times 10^{-4}~\rm K^2$, a structural similarity index of $0.968\pm0.002$, and a peak signal-to-noise ratio of $26.13\pm5.22$ at the $1\sigma$ level. Furthermore, by sampling in the latent space of cINN, the reconstruction errors for each pixel can be accurately quantified.Comment: Accepted for publication in Research in Astronomy and Astrophysics (RAA); 20 pages, 10 figure

Mapping and candidate-gene screening of the novel Turnip mosaic virus resistance gene retr02 in Chinese cabbage (Brassica rapa L.)

The extreme resistance to Turnip mosaic virus observed in the Chinese cabbage (Brassica rapa) line, BP8407, is monogenic and recessive. Bulked segregant analysis was carried out to identify simple sequence repeat and Indel markers linked to this recessive resistance gene, termed recessive Turnip mosaic virus resistance 02 (retr02). Mapping of PCR-specific Indel markers on 239 individuals of a BP8407 × Ji Zao Chun F 2 population, located this resistance gene to a 0.9-cM interval between two Indel markers (BrID10694 and BrID101309) and in scaffold000060 or scaffold000104 on chromosome A04 of the B. rapa genome. Eleven eukaryotic initiation factor 4E (eIF4E) and 14 eukaryotic initiation factor 4G (eIF4G) genes are predicted in the B. rapa genome. A candidate gene, Bra035393 on scaffold000104, was predicted within the mapped resistance locus. The gene encodes the eIF(iso)4E protein. Bra035393 was sequenced in BP8407 and Ji Zao Chun. A polymorphism (A/G) was found in exon 3 between BP8407 and Ji Zao Chun. This gene was analysed in four resistant and three susceptible lines. A correlation was observed between the amino acid substitution (Gly/Asp) in the eIF(iso)4E protein and resistance/susceptibility. eIF(iso)4E has been shown previously to interact with the TuMV genome-linked protein, VPg

Investigation and development of power-generating building material systems based on air-cathode microbial fuel cell using Geobacter sulfurreducens

The increasing environmental pollution, carbon emissions, and limited fossil fuel reserves necessitate the gradual replacement of fossil fuels with sustainable and renewable green energy sources. However, current green energy sources have specific requirements for their application, such as solar energy requiring sufficient sunlight and wind energy requiring sufficient wind without negative impacts on the environment. Hydrogen fuel cells are also gradually being utilized as a clean energy source. As a means of power generation, the key factor in fuel cells is the catalytic effect on the reaction. In nature, there exists a group of electrochemically active microorganisms that are widely distributed in soil and wastewater. They act as natural catalysts in fuel cells. Although these microbial fuel cells have seen significant improvements in power generation in recent years, their application has not been widely promoted due to cost. Concrete is the most widely used building material in the world. Its low raw material cost, high compressive strength, and simple production process make it an attractive and easily applicable material in the field of construction and building. If mineral materials can be used to make fuel cells, the manufacturing cost would be greatly reduced, which would greatly benefit the development of fuel cells. In order to use mineral materials as electrodes for fuel cells, they must have a low enough electrical resistance. This PhD research is based on the theory of percolation and studies two types of building materials, Portland cement and geopolymer, from a microstructural perspective. By comparing their differences in microstructure and the changes in electrical conductivity of their mixes in dry and wet conditions, it is found that when the volume fraction of conductive fillers exceeds its percolation threshold, the overall electrical conductivity of the composite is no longer related to its water content. In other words, the conductive mechanism in the mix is mainly in the form of electronic conduction, and the ionic conduction in the solution has little impact on the electrical conductivity of the mix. The geopolymer, due to their excellent microstructure, make it possible for direct electronic transitions of conductive fillers. Therefore, graphite-geopolymer composite have better electronic conductivity than graphite-portland cement composite at the same graphite content. To study the conductive mechanism of geopolymer and graphite mixture more in-depth, a Monte Carlo method was employed to simulate the percolation threshold of the mixture. The model, based on the HYMOSTRUC3D framework, is a three-dimensional model that considers the particle size distribution, and it can accurately describe the spatial distribution and interactions of different particles. By introducing the concept of effective volume fraction, the influence of pores on the mixture was eliminated. The effective medium model simulated the relationship between the overall electrical conductivity and graphite effective volume fraction, which was consistent with experimental data. The microstructural properties of geopolymers make it possible to create high-performance electrical conductive materials using low-cost graphite particles. The porous structure of this mixture also provides necessary growth space for microorganisms, leading to the formation of more biofilm. In order to verify the feasibility of this mineral-based electrode as a microbial fuel cell, a single-strain Geobacter sulfurreducens culture was used to cultivate a dual-chamber microbial fuel cell. During the one-week testing period, the microbial fuel cell with the graphite geopolymer anode had a peak operating current density of 155.9 A·s/cm² even higher than the operating current density of 144.5 A·s/cm² with graphite as the electrode. This research also explored the feasibility of large-scale application of microbial fuel cells using the mineral-based electrode. The study found that the mineral-based electrode can be used to power a green LED light, and by connecting 224 soil-based microbial fuel cells in series and parallel, and creating a control board for energy collection, it was possible to power a lighting system in a bike shed. The Ph.D. thesis demonstrates the feasibility of using mineral-based materials as electrodes in microbial fuel cells and explains the conductive mechanism in the composite. Due to its superior electrical conductivity, the mineral-based material can also be used in other types of fuel cells and even rechargeable batteries

Sky reconstruction for the Tianlai cylinder array

In this paper, we apply our sky map reconstruction method for transit type interferometers to the Tianlai cylinder array. The method is based on the spherical harmonic decomposition, and can be applied to cylindrical array as well as dish arrays and we can compute the instrument response, synthesised beam, transfer function and the noise power spectrum. We consider cylinder arrays with feed spacing larger than half wavelength, and as expected, we find that the arrays with regular spacing have grating lobes which produce spurious images in the reconstructed maps. We show that this problem can be overcome, using arrays with different feed spacing on each cylinder. We present the reconstructed maps, and study the performance in terms of noise power spectrum, transfer function and beams for both regular and irregular feed spacing configurations.Comment: 15 pages, 12 figures, accepted by RA

Data Processing Pipeline For Tianlai Experiment

The Tianlai project is a 21cm intensity mapping experiment aimed at detecting dark energy by measuring the baryon acoustic oscillation (BAO) features in the large scale structure power spectrum. This experiment provides an opportunity to test the data processing methods for cosmological 21cm signal extraction, which is still a great challenge in current radio astronomy research. The 21cm signal is much weaker than the foregrounds and easily affected by the imperfections in the instrumental responses. Furthermore, processing the large volumes of interferometer data poses a practical challenge. We have developed a data processing pipeline software called {\tt tlpipe} to process the drift scan survey data from the Tianlai experiment. It performs offline data processing tasks such as radio frequency interference (RFI) flagging, array calibration, binning, and map-making, etc. It also includes utility functions needed for the data analysis, such as data selection, transformation, visualization and others. A number of new algorithms are implemented, for example the eigenvector decomposition method for array calibration and the Tikhonov regularization for $m$-mode analysis. In this paper we describe the design and implementation of the {\tt tlpipe} and illustrate its functions with some analysis of real data. Finally, we outline directions for future development of this publicly code.Comment: 13 pages, 5 figures, accepted for publication on Astronomy and Computin

The Tianlai Cylinder Pathfinder array: System functions and basic performance analysis

The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the post-reionization Universe, with the ultimate aim of mapping the large scale structure and measuring cosmological parameters such as the dark energy equation of state. Each of its three parallel cylinder reflectors is oriented in the north-south direction, and the array has a large field of view. As the Earth rotates, the northern sky is observed by drift scanning. The array is located in Hongliuxia, a radio-quiet site in Xinjiang, and saw its first light in September 2016. In this first data analysis paper for the Tianlai cylinder array, we discuss the sub-system qualification tests, and present basic system performance obtained from preliminary analysis of the commissioning observations during 2016-2018. We show typical interferometric visibility data, from which we derive the actual beam profile in the east-west direction and the frequency band-pass response. We describe also the calibration process to determine the complex gains for the array elements, either using bright astronomical point sources, or an artificial on site calibrator source, and discuss the instrument response stability, crucial for transit interferometry. Based on this analysis, we find a system temperature of about 90 K, and we also estimate the sensitivity of the array

Kostengünstige VR-Plattform zur Visualisierung und Begehung von komplexen 3D-Modellen

Die Nutzung von Simulationen und 3D-Modellen steigern nachweislich das Verständnis und erhöhen den Lerneffekt. Eine Anwendung immersiver virtueller Räume zur Darstellung von komplexen oder schwerzugänglichen Fachinhalten ist somit anzustreben. Mit der entwickelten VR-Plattform ist dies über eine webbasierte Anwendung auf jedem internetfähigen Gerät möglich. Durch die Anbindung von WebVR wird virtuelle Realität für das Smartphone, aber auch eine 3D-Ansicht ohne Immersion für Tablets oder Computer möglich. Ein unkomplizierter und kostengünstiger Zugang zu immersiven 3D-Modellen ist dadurch umgesetzt worden. Eine Anwendung für einen gemeinschaftlichen Exkursraum mit hilfreichen Werkzeugen zur Darstellung und Manipulation von 3D-Modellen ist entwickelt worden. Unterschiedliche Nutzergruppen ermöglichen verschiedene Interaktionsrechte, wodurch Führungsrollen durch das Geschehen und Modelle leiten können

Electrical conductivity of geopolymer-graphite composites: Percolation, mesostructure and analytical modeling

International audienc

Analysis of small RNA changes in different Brassica napus synthetic allopolyploids

Allopolyploidy is an evolutionary and mechanisticaly intriguing process involving the reconciliation of two or more sets of diverged genomes and regulatory interactions, resulting in new phenotypes. In this study, we explored the small RNA changes of eight F2 synthetic B. napus using small RNA sequencing. We found that a part of miRNAs and siRNAs were non-additively expressed in the synthesized B. napus allotetraploid. Differentially expressed miRNAs and siRNAs differed among eight F2 individuals, and the differential expression of miR159 and miR172 was consistent with that of flowering time trait. The GO enrichment analysis of differential expression miRNA target genes found that most of them were concentrated in ATP-related pathways, which might be a potential regulatory process contributing to heterosis. In addition, the number of siRNAs present in the offspring was significantly higher than that of the parent, and the number of high parents was significantly higher than the number of low parents. The results have shown that the differential expression of miRNA lays the foundation for explaining the trait separation phenomenon, and the significant increase of siRNA alleviates the shock of the newly synthesized allopolyploidy. It provides a new perspective between small RNA changes and trait separation in the early stages of allopolyploid polyploid formation