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Eggshell damages lead to economic losses in the egg production industry and are a threat to human health. We examined 49-wk-old Rhode Island White hens (Gallus gallus) that laid eggs having shells with significantly different strengths and thicknesses. We used HiSeq 2000 (Illumina) sequencing to characterize the chicken transcriptome and whole genome to identify the key genes and genetic mutations associated with eggshell calcification. We identified a total of 14,234 genes expressed in the chicken uterus, representing 89% of all annotated chicken genes. A total of 889 differentially expressed genes were identified by comparing low eggshell strength (LES) and normal eggshell strength (NES) genomes. The DEGs are enriched in calcification-related processes, including calcium ion transport and calcium signaling pathways as reveled by gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis. Some important matrix proteins, such as OC-116, LTF and SPP1, were also expressed differentially between two groups. A total of 3,671,919 single-nucleotide polymorphisms (SNPs) and 508,035 Indels were detected in protein coding genes by whole-genome re-sequencing, including 1775 non-synonymous variations and 19 frame-shift Indels in DEGs. SNPs and Indels found in this study could be further investigated for eggshell traits. This is the first report to integrate the transcriptome and genome re-sequencing to target the genetic variations which decreased the eggshell qualities. These findings further advance our understanding of eggshell calcification in the chicken uterus.

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The keeper electrode was believed to be beneficial for improving the hollow cathode performance. However, this paper shows that it can also be hazardous to the discharge if not treated properly. Interactions between the extracted electron beam and the keeper electrode were revealed in an experiment regarding the hollow cathode discharge in the magnetic field environment. It was found that when the electron beam was wider than the keeper orifice, non-negligible electron current was irreversibly lost on the cold keeper wall, inferring from the escalated floating potential of the keeper with respect to the cathode potential. This loss triggered the high-amplitude ionization oscillations in the cathode plume that were highly coherent with the potential fluctuations of keeper itself. The magnetic field that was parallel to the cathode axis could restrict electron diffusion onto the keeper surface and greatly restrain the triggering. Based on the discovered triggering mechanism, several suggestions regarding the cathode design and thruster-cathode coupling were given.