Nuclear Background Research Articles

Mechanisms Maintaining Mitochondrial DNA Polymorphisms: The Role of Mito-Nuclear Interactions, Sex-Specific Selection, and Genotype-by-Environment Interactions in Drosophila subobscura.

Experimental mito-nuclear introgression lines (MNILs) were established by backcrossing isofemale lines of D. subobscura originating from the same populations. MNILs were subjected to a series of life-history experiments designed to test the fitness of the bearers of different combinations of two main mtDNA haplotypes on their own nuclear background, as well as on the background of the opposite haplotype. By having 11 replicas of the four mito-nuclear combinations, we could test not only the adaptive significance of the differences between the two main haplotypes but also the influence of additional variation present within each of the 11 combinations on fitness. Testing the fitness of individuals of both sexes enabled us to examine if sex-specific selection has a role in maintaining the frequencies of the two mtDNA haplotypes in nature. Conducting the fitness assays on two different temperatures enabled us to test whether different temperatures favor specific mtDNA haplotypes or mito-nuclear genotypes and consequently promote stable sympatric mtDNA variation. The results show weak signature of genotype-by-environment interactions, and no sex-specific selection regarding differences between the two main haplotypes. However, individual models across different life-history components showed these two mechanisms at play in promoting mtDNA variability present in specific mito-nuclear crosses. Our models show that mito-nuclear interactions are, in fact, more important as units of selection.

Genomic evidence for hybridization, mitochondrial capture and cryptic invasions in the Chinese mitten crab Eriocheir sinensis (Crustacea: Decapoda: Brachyura: Varunidae)

Enhanced genetic diversity arising from interspecific hybridisation and from multiple introductions from different source populations has played a major role in the evolution of invasive traits in introduced populations. Across Europe, mitochondrial haplotypes associated with the Japanese mitten crab Eriocheir japonica have been discovered in populations of the Chinese mitten crab Eriocheir sinensis, one of Europe’s highest priority aquatic invasive non-native species, suggesting a possible cryptic invasion of a second Eriocheir species. Analysis of the nuclear genomes of mitten crabs from one of these populations based on single nucleotide polymorphisms (SNPs) obtained through genotyping by sequencing, combined with landmark analysis of carapace morphology indicates that the crabs resemble E. sinensis in their morphology and nuclear genomic background, regardless of whether they carry an E. sinensis or E. japonica mitochondrial haplotype. This suggests interspecific introgression of mitochondrial DNA originating in the Japanese mitten crab Eriocheir japonica at some point in the population’s history, either in its native range or following introduction to Europe. A discrete cluster of SNP genotypes is associated with the E. japonica mitochondrial haplotype in samples from 2015 but not from 2020, suggesting an intraspecific cryptic invasion of genetically distinct mitten crabs into a previously established population, followed by interbreeding. Genetically diverse and novel hybrid biological invaders require particularly careful monitoring since they are likely to display enhanced evolutionary potential, with their life cycles and ecology possibly diverging from that of ancestral populations in their native range. In addition, mitochondrial environmental DNA and DNA barcoding of mitochondrial markers are increasingly relied upon to detect and identify aquatic non-native species. The potential for mitochondrial introgression between species to confuse these methods must be considered.

Cytoplasmic Male Sterility declines in the presence of resistant nuclear backgrounds

Cytoplasmic Male Sterility declines in the presence of resistant nuclear backgrounds

Exploring mitonuclear interactions in the regulation of cell physiology: Insights from interspecies cybrids.

Exploring mitonuclear interactions in the regulation of cell physiology: Insights from interspecies cybrids.

Development of the Incompatible Insect Technique targeting Aedes albopictus: introgression of a wild nuclear background restores the performance of males artificially infected with Wolbachia.

The bacterium Wolbachia pipientis is increasingly studied for its potential use in controlling insect vectors or pests due to its ability to induce Cytoplasmic Incompatibility (CI). CI can be exploited by establishing an opportunistic Wolbachia infection in a targeted insect species through trans-infection and then releasing the infected males into the environment as sterilizing agents. Several host life history traits (LHT) have been reported to be negatively affected by artificial Wolbachia infection. Wolbachia is often considered the causative agent of these detrimental effects, and the importance of the host's genetic origins in the outcome of trans-infection is generally overlooked. In this study, we investigated the impact of host genetic background using an Aedes albopictus line recently trans-infected with wPip from the Culex pipiens mosquito, which exhibited some fitness costs. We measured several LHTs including fecundity, egg hatch rate, and male mating competitiveness in the incompatible line after four rounds of introgression aiming at restoring genetic diversity in the nuclear genome. Our results show that introgression with a wild genetic background restored most fitness traits and conferred mating competitiveness comparable to that of wild males. Finally, we show that introgression leads to faster and stronger population suppression under laboratory conditions. Overall, our data support that the host genome plays a decisive role in determining the fitness of Wolbachia-infected incompatible males.IMPORTANCEThe bacterium Wolbachia pipientis is increasingly used to control insect vectors and pests through the Incompatible Insect Technique (IIT) inducing a form of conditional sterility when a Wolbachia-infected male mates with an uninfected or differently infected female. Wolbachia artificial trans-infection has been repeatedly reported to affect mosquitoes LHTs, which may in turn compromise the efficiency of IIT. Using a tiger mosquito (Aedes albopictus) line recently trans-infected with a Wolbachia strain from Culex pipiens and displaying reduced fitness, we show that restoring genetic diversity through introgression significantly mitigated the fitness costs associated with Wolbachia trans-infection. This was further demonstrated through experimental population suppression, showing that introgression is required to achieve mosquito population suppression under laboratory conditions. These findings are significant for the implementation of IIT programs, as an increase in female fecundity and male performance improves mass rearing productivity as well as the sterilizing capacity of released males.

<b>Prevalence and obstetrics factors associated with postpartum depression in a Tertiary Care Centre, South India</b>

Background: Postpartum depression is a serious issue affecting society as a whole. While it typically subsides in most women, it can persist in some cases. This condition is particularly concerning because of its effects on the mother, her long-term relationships, and the family. Of special concern is its impact on the mother-infant relationship, which can, in turn, influence infant development. Methods: This hospital-based cross-sectional study was conducted during 2019–2020 covering a population of 355 postpartum women in postnatal clinics. In addition to the structured interview schedule, The Edinburgh Postnatal Depression Scale was used to evaluate the extent of depression. Logistic regression was used to evaluate the independent effects of various socio-clinical variables. Results: The prevalence rate of postnatal depression was 23.0%. Statistically significant risk factors included maternal age >25 years, lower socioeconomic status, nuclear family background, conception through assisted reproductive technology, and history of abortion. Conclusion: The prevalence of Postpartum depression was high in the study population. There were multiple factors associated with its development, which required early screening and intervention. Recommendation: Special counseling sessions and health promotion activities at the institutional level can mitigate postnatal depression.

Cytologic hallmarks and differential diagnosis of papillary thyroid carcinoma subtypes.

Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy, characterized by a range of subtypes that differ in their cytologic features, clinical behavior, and prognosis. Accurate cytologic evaluation of PTC using fine-needle aspiration is essential but can be challenging due to the morphologic diversity among subtypes. This review focuses on the distinct cytologic characteristics of various PTC subtypes, including the classic type, follicular variant, tall cell, columnar cell, hobnail, diffuse sclerosing, Warthin-like, solid/trabecular, and oncocytic PTCs. Each subtype demonstrates unique nuclear features, architectural patterns, and background elements essential for diagnosis and differentiation from other thyroid lesions. Recognizing these distinct cytologic patterns is essential for identifying aggressive subtypes like tall cell, hobnail, and columnar cell PTCs, which have a higher risk of recurrence, metastasis, and poorer clinical outcomes. Additionally, rare subtypes such as diffuse sclerosing and Warthin-like PTCs present unique cytologic profiles that must be carefully interpreted to avoid diagnostic errors. The review also highlights the cytologic indicators of lymph node metastasis and high-grade features, such as differentiated high-grade thyroid carcinoma. The integration of molecular testing can further refine subtype diagnosis by identifying specific genetic mutations. A thorough understanding of these subtype-specific cytologic features and molecular profiles is vital for accurate diagnosis, risk stratification, and personalized management of PTC patients. Future improvements in diagnostic techniques and standardization are needed to enhance cytologic evaluation and clinical decision-making in thyroid cancer.

Mitochondrial Genome Instability in W303-SK1 Yeast Cytoplasmic Hybrids.

Unlike most animals, some fungi, including baker's yeast, inherit mitochondrial DNA (mtDNA) from both parents. When haploid yeast cells fuse, they form a heteroplasmic zygote, whose offspring retain one or the other variant of mtDNA. Meanwhile, some mutant mtDNA (rho-), with large deletions in the nucleotide sequence, can displace wild-type (rho+) mtDNA. Consequently, offspring of zygotes with such rho- mtDNA predominantly carry the mutant variant. This phenomenon is called suppressivity. In this study, we investigated how the suppressivity of rho- mtDNA depends on the mitochondrial and nuclear genomes of the rho+ strain during crossing. Comparing two diverged laboratory strains, SK1 and W303, we measured suppressivity in crosses with four rho- strains. One rho- strain showed significantly higher suppressivity when crossed with SK1 than with W303. We then created cytoplasmic hybrids by swapping mtDNAs between these strains. Surprisingly, we found that the mtDNA of the rho+ strain, rather than its nuclear DNA, determines high suppressivity in crosses of SK1 rho+ with the rho- strain. Additionally, mtDNA replacement reduced respiration rate and growth rate on non-fermentable substrates while increasing the likelihood of functional mtDNA loss. Our data demonstrate that a mutant mtDNA variant's ability to displace another mitochondrial DNA variant in a heteroplasmic cell depends more on mtDNA sequences than on the biochemical and structural context created by the nuclear genome background.

A naturally occurring mitochondrial genome variant confers broad protection from infection in Drosophila.

The role of mitochondria in immunity is increasingly recognized, but it is unclear how variation in mitochondrial DNA (mtDNA) contributes to variable infection outcomes. To quantify the effect of mtDNA variation on humoral and cell-mediated innate immune responses, we utilized a panel of fruit fly Drosophila melanogaster cytoplasmic hybrids (cybrids), where unique mtDNAs (mitotypes) were introgressed into a controlled isogenic nuclear background. We observed substantial heterogeneity in infection outcomes within the cybrid panel upon bacterial, viral and parasitoid infections, driven by the mitotype. One of the mitotypes, mtKSA2, protected against bacterial, parasitoid, and to a lesser extent, viral infections. Enhanced survival was not a result of improved bacterial clearance, suggesting mtKSA2 confers increased disease tolerance. Transcriptome sequencing showed that the mtKSA2 mitotype had an upregulation of genes related to mitochondrial respiration and phagocytosis in uninfected flies. Upon infection, mtKSA2 flies exhibited infection type and duration specific transcriptomic changes. Furthermore, uninfected mtKSA2 larvae showed immune activation of hemocytes (immune cells), increased hemocyte numbers and ROS production, and enhanced encapsulation response against parasitoid wasp eggs and larvae. Our results show that mtDNA variation acts as an immunomodulatory factor in both humoral and cell-mediated innate immunity and that specific mitotypes can provide broad protection against infections.

Mitochondrial background can explain variable costs of immune deployment.

Organismal health and survival depend on the ability to mount an effective immune response against infection. Yet immune defence may be energy-demanding, resulting in fitness costs if investment in immune function deprives other physiological processes of resources. While evidence of costly immunity resulting in reduced longevity and reproduction is common, the role of energy-producing mitochondria on the magnitude of these costs is unknown. Here, we employed Drosophila melanogaster cybrid lines, where several mitochondrial genotypes (mitotypes) were introgressed onto a single nuclear genetic background, to explicitly test the role of mitochondrial variation on the costs of immune stimulation. We exposed female flies carrying one of nine distinct mitotypes to either a benign, heat-killed bacterial pathogen (stimulating immune deployment while avoiding pathology) or to a sterile control and measured lifespan, fecundity, and locomotor activity. We observed mitotype-specific costs of immune stimulation and identified a positive genetic correlation in immune-stimulated flies between lifespan and the proportion of time cybrids spent moving while alive. Our results suggests that costs of immunity are highly variable depending on the mitochondrial genome, adding to a growing body of work highlighting the important role of mitochondrial variation in host-pathogen interactions.

Dissecting the sequential evolution of a selfish mitochondrial genome in Caenorhabditis elegans

Mitochondrial genomes exist in a nested hierarchy of populations where mitochondrial variants are subject to genetic drift and selection at each level of organization, sometimes engendering conflict between different levels of selection, and between the nuclear and mitochondrial genomes. Deletion mutants in the Caenorhabditis elegans mitochondrial genome can reach high intracellular frequencies despite strongly detrimental effects on fitness. During a mutation accumulation (MA) experiment in C. elegans, a 499 bp deletion in ctb-1 rose to 90% frequency within cells while significantly reducing fitness. During the experiment, the deletion-bearing mtDNA acquired three additional mutations in nd5, namely two single insertion frameshift mutations in a homopolymeric run, and a base substitution. Despite an additional fitness cost of these secondary mutations, all deletion-bearing molecules contained the nd5 mutations at the termination of the MA experiment. The presence of mutant mtDNA was associated with increased mtDNA copy-number. Variation in mtDNA copy-number was greater in the MA lines than in a wildtype nuclear background, including a severe reduction in copy-number at one generational timepoint. Evolutionary replay experiments using different generations of the MA experiment as starting points suggests that two of the secondary mutations contribute to the proliferation of the original ctb-1 deletion by unknown mechanisms.

Novel Mito-Nuclear Combinations Facilitate the Global Invasion of a Major Agricultural Crop Pest.

A fundamental understanding of the underlying mechanisms involved in biological invasions is crucial to developing effective risk assessment and control measures against invasive species. The fall armyworm (FAW), Spodoptera frugiperda, is a highly invasive pest that has rapidly spread from its native Americas into much of the Eastern Hemisphere, with a highly homogeneous nuclear genetic background. However, the exact mechanism behind its rapid introduction and propagation remains unclear. Here, a systematic investigation is conducted into the population dynamics of FAW in China from 2019 to 2021 and found that FAW individuals carrying "rice" mitochondria (FAW-mR) are more prevalent (>98%) than that with "corn" mitochondria (FAW-mC) at the initial stage of the invasion and in newly-occupied non-overwintering areas. Further fitness experiments show that the two hybrid-strains of FAW exhibit different adaptions in the new environment in China, and this may have been facilitated by amino acid changes in mitochondrial-encoded proteins. FAW-mR used increases energy metabolism, faster wing-beat frequencies, and lower wing loadings to drive greater flight performance and subsequent rapid colonization of new habitats. In contrast, FAW-mC individuals adapt with more relaxed mitochondria and shuttle energetics into maternal investment, observed as faster development rate and higher fecundity. The presence of two different mitochondria types within FAW has the potential to significantly expand the range of damage and enhance competitive advantage. Overall, the study describes a novel invasion mechanism displayed by the FAW population that facilitates its expansion and establishment in new environments.

Species-specific variation in mitochondrial genome tandem repeat polymorphisms in hares (Lepus spp., Lagomorpha, Leporidae) provides insight into their evolution

The non-coding regions of the mitochondrial DNAs (mtDNAs) of hares, rabbits, and pikas (Lagomorpha) contain short (∼20 bp) and long (130–160 bp) tandem repeats, absent in related mammalian orders. In the presented study, we provide in-depth analysis for mountain hare (Lepus timidus) and brown hare (L. europaeus) mtDNA non-coding regions, together with a species- and population-level analysis of tandem repeat variation. Mountain hare short tandem repeats (SRs) as well as other analyzed hare species consist of two conserved 10 bp motifs, with only brown hares exhibiting a single, more variable motif. Long tandem repeats (LRs) also differ in sequence and copy number between species. Mountain hares have four to seven LRs, median value five, while brown hares exhibit five to nine LRs, median value six. Interestingly, introgressed mountain hare mtDNA in brown hares obtained an intermediate LR length distribution, with median copy number being the same as with conspecific brown hare mtDNA. In contrast, transfer of brown hare mtDNA into cultured mtDNA-less mountain hare cells maintained the original LR number, whereas the reciprocal transfer caused copy number instability, suggesting that cellular environment rather than the nuclear genomic background plays a role in the LR maintenance. Due to their dynamic nature and separation from other known conserved sequence elements on the non-coding region of hare mitochondrial genomes, the tandem repeat elements likely to represent signatures of ancient genetic rearrangements. clarifying the nature and dynamics of these rearrangements may shed light on the possible role of NCR repeated elements in mitochondria and in species evolution.

Differential Expression of Restorer Gene on Different Nuclear Background with Maldandi cytoplasm in Sorghum (Sorghum bicolor (L.) Moench)

To investigate the expression of restorer gene on different nuclear background an experiment was carried out using six iso-plasmic male sterile lines with maldandi cytoplasm, and each having different nuclear background. These lines were hybridized with a strong and stable restorer to generate six iso-plasmic hybrids at Main Agricultural Research Station (MARS), UAS Dharwad during rabi -2020-21. These hybrids were then evaluated for pollen fertility and seed set percentage during rabi -2021-22. The results found that, pollen fertility percentage of six iso-plasmic hybrids ranged from 69.82 per cent for ICSA 88004 A4 (M) × DSMR 8 to 92.42 per cent for M31-2A (M) × DSMR 8. Similarly, for seed set percentage M31-2A (M) × DSMR 8 and ICSA 88004 A4 (M) × DSMR 8 exhibited highest (85.17 per cent) and lowest (61.19 per cent), respectively. All the six iso-plasmic hybrids had varied expression for pollen fertility and seed set percentage which suggests that the restorer gene expressed differentially in different nuclear genome of female parent. The probable reasons for variation in fertility restoration behaviour are, abundance of inhibitors in the female parent or variation in the expressivity of restorer gene or influence of minor or modifier genes in the restorer parent or interaction between nuclear genes of both the parents.

Mitochondrial background can explain variable costs of immune deployment.

Organismal health and survival depend on the ability to mount an effective immune response against infection. Yet immune defence may be energy-demanding, resulting in fitness costs if investment in immune function deprives other physiological processes of resources. While evidence of costly immunity resulting in reduced longevity and reproduction is common, the role of energy-producing mitochondria on the magnitude of these costs is unknown. Here we employed Drosophila melanogaster cybrid lines, where several mitochondrial genotypes (mitotypes) were introgressed onto a single nuclear genetic background, to explicitly test the role of mitochondrial variation on the costs of immune stimulation. We exposed female flies carrying one of nine distinct mitotypes to either a benign, heat-killed bacterial pathogen (stimulating immune deployment while avoiding pathology) or a sterile control and measured lifespan, fecundity, and locomotor activity. We observed mitotype-specific costs of immune stimulation and identified a positive genetic correlation between life span and the proportion of time cybrids spent moving while alive. Our results suggest that costs of immunity are highly variable depending on the mitochondrial genome, adding to a growing body of work highlighting the important role of mitochondrial variation in host-pathogen interactions.

A Single Nucleotide Polymorphism Unique to the Galanthum-CMS of Onion

Different sources of cytoplasmic male sterility (CMS) are used to produce hybrid onion seed. The most commonly used source of CMS in onion is S cytoplasm (S-CMS), and male fertility is restored by a dominant allele at the nuclear male-fertility restoration locus (Ms). Male-sterile plants possess S cytoplasm and have the homozygous recessive genotype at Ms; seed propagation of male-sterile plants is possible by crossing with a male-fertile maintainer plant or inbred possessing normal (N) male-fertile cytoplasm and the homozygous recessive at the Ms locus (N msms). Some commercially important onion populations possess S-CMS and high frequencies of the dominant Ms allele, eliminating the possibility to develop maintainer lines. An alloplasmic source of CMS (Gal-CMS) was developed by backcrossing the cytoplasm of Allium galanthum into the nuclear background of onion. The advantage of Gal-CMS is that the dominant allele at Ms does not restore male fertility, making this source of CMS useful for the development of male-sterile lines from populations possessing S cytoplasm and dominant allele(s) at Ms. In this research, a single nucleotide polymorphism unique to the cytoplasms of A. galanthum and Gal-CMS was identified, useful to distinguish Gal-CMS from other onion cytoplasms.

Paternal leakage of plastids rescues inter-lineage hybrids in Silene nutans.

Organelle genomes are usually maternally inherited in angiosperms. However, biparental inheritance has been observed, especially in hybrids resulting from crosses between divergent genetic lineages. When it concerns the plastid genome, this exceptional mode of inheritance might rescue inter-lineage hybrids suffering from plastid-nuclear incompatibilities. Genetically differentiated lineages of Silene nutans exhibit strong postzygotic isolation owing to plastid-nuclear incompatibilities, highlighted by inter-lineage hybrid chlorosis and mortality. Surviving hybrids can exhibit variegated leaves, which might indicate paternal leakage of the plastid genome. We tested whether the surviving hybrids inherited the paternal plastid genome and survived thanks to paternal leakage. We characterized the leaf phenotype (fully green, variegated or white) of 504 surviving inter-lineage hybrids obtained from a reciprocal cross experiment among populations of four genetic lineages (W1, W2, W3 and E1) of S. nutans from Western Europe and genotyped 560 leaf samples (both green and white leaves for variegated hybrids) using six lineage-specific plastid single nucleotide polymorphisms. A high proportion of the surviving hybrids (≤98 %) inherited the paternal plastid genome, indicating paternal leakage. The level of paternal leakage depended on cross type and cross direction. The E1 and W2 lineages as maternal lineages led to the highest hybrid mortality and to the highest paternal leakage from W1 and W3 lineages in the few surviving hybrids. This was consistent with E1 and W2 lineages, which contained the most divergent plastid genomes. When W3 was the mother, more hybrids survived, and no paternal leakage was detected. By providing a plastid genome potentially more compatible with the hybrid nuclear background, paternal leakage has the potential to rescue inter-lineage hybrids from plastid-nuclear incompatibilities. This phenomenon might slow down the speciation process, provided hybrid survival and reproduction can occur in the wild.

Nuclear Spin-Depleted, Isotopically Enriched 70 Ge/28 Si70 Ge Quantum Wells.

The p-symmetry of the hole wavefunction is associated with a weaker hyperfine interaction, which makes hole spin qubits attractive candidates to implement quantum processors. However, recent studies demonstrate that hole qubits are still very sensitive to nuclear spin bath, thus highlighting the need for nuclear spin-free germanium (Ge) qubits to suppress this decoherence channel. Herein, this work demonstrates the epitaxial growth of 73 Ge- and 29 Si-depleted, isotopically enriched 70 Ge/silicon-germanium (SiGe) quantum wells. The growth is achieved by reduced pressure chemical vapor deposition using isotopically purified monogermane 70 GeH4 and monosilane 28 SiH4 with an isotopic purity higher than 99.9% and 99.99%, respectively. The quantum wells consist of a series of 70 Ge/SiGe heterostructures grown on Si wafers. The isotopic purity is investigated using atom probe tomography (APT) following an analytical procedure addressing the discrepancies caused by the overlap of isotope peaks in mass spectra. The nuclear spin background is found to be sensitive to the growth conditions with the lowest concentration of 73 Ge and 29 Si is below 0.01% in the Ge well and SiGe barriers. The measured average distance between nuclear spins reaches 3-4 nm in 70 Ge/28 Si70 Ge, which is an order of magnitude larger than in natural Ge/SiGe heterostructures.The spread of the hole wavefunction and the residual nuclear spin background in APT voluminals comparable to the size of realistic quantum dots are also discussed.

Birth Order Determining the Perception of Parenting Style among Female Adolescents in Relation to their Family Type

The study of parenting style and practices initially focused on their influence on young children, but eventually revealed their long-term implications on an individual's lifetime, particularly during the crucial and transitional period of adolescence. The process of parenting is unique to each individual and varies for each child within a family. This variation may be influenced by birth order, since parents tend to behave different to each child. This is because each person's individuality plays a role in the interpersonal interactions they develop. The objective of this study is to examine the influence of birth order (first, middle, and last) on adolescent girls’ perception of their parents’ style of parenting, in both joint and nuclear family environments, in a comparative manner. The experiment encompasses a cohort of 100 female adolescent students, typically ranging in age from 16 to 19 years, who have exactly two siblings. The data collection instrument utilized was the Parenting Style Scale developed by Madhu Gupta and Dimple Mehtani (2017). Additionally, a self-designed questionnaire was used to gather demographic information from the participants, including age, birth order, family type, and other relevant factors. The findings indicated that eldest daughters perceived their parents as employing a democratic/authoritative parenting style, while middle-born daughters perceived their parents as employing an autocratic/authoritarian approach. On the other hand, youngest daughters perceived their parents as adopting a permissive parenting style. No significant disparity was observed in the perception of parenting styles among female adolescents from nuclear and joint family backgrounds simultaneously.

Data Augmentation of X-ray Images for Automatic Cargo Inspection of Nuclear Items.

As part of establishing a management system to prevent the illegal transfer of nuclear items, automatic nuclear item detection technology is required during customs clearance. However, it is challenging to acquire X-ray images of major nuclear items (e.g., nuclear fuel and gas centrifuges) loaded in cargo with which to train a cargo inspection model. In this work, we propose a new means of data augmentation to alleviate the lack of X-ray training data. The proposed augmentation method generates synthetic X-ray images for the training of semantic segmentation models combining the X-ray images of nuclear items and X-ray cargo background images. To evaluate the effectiveness of the proposed data augmentation technique, we trained representative semantic segmentation models and performed extensive experiments to assess its quantitative and qualitative performance capabilities. Our findings show that multiple item insertions to respond to actual X-ray cargo inspection situations and the resulting occlusion expressions significantly affect the performance of the segmentation models. We believe that this augmentation research will enhance automatic cargo inspections to prevent the illegal transfer of nuclear items at airports and ports.