Euler--Chern Correspondence via Topological Superconductivity

The Fermi sea topology is characterized by the Euler characteristics $\chi_F$. In this paper, we examine how $\chi_F$ of the metallic state is inhereted by the topological invariant of the superconducting state. We establish a correspondence between the Euler characteristic and the Chern number $C$ of $p$-wave topological superconductors without time-reversal symmetry in two dimensions. By rewriting the pairing potential $\Delta_{\bf k}=\Delta_1-i\Delta_2$ as a vector field ${\bf u}=(\Delta_1,\Delta_2)$, we found that $\chi_F=C$ when ${\bf u}$ and fermion velocity ${\bf v}$ can be smoothly deformed to be parallel or antiparallel on each Fermi surface. We also discuss a similar correspondence between Euler characteristic and 3D winding number of time-reversal-invariant $p$-wave topological superconductors in three dimensions.Comment: 6 pages, 3 figur

Cyclosporine Biosynthesis in Tolypocladium inflatum Benefits Fungal Adaptation to the Environment

The cycloundecapeptide cyclosporin A (CsA) was first isolated from the insect-pathogenic fungus Tolypocladium inflatum for its antifungal activity and later developed as an immunosuppressant drug. However, the full biosynthetic mechanism of CsA remains unknown and has puzzled researchers for decades. In this study, the biosynthetic gene cluster is suggested to include 12 genes encoding enzymes, including the nonribosomal peptide synthetase (NRPS) (SimA) responsible for assembling the 11 amino acid substrates of cyclosporine and a polyketide synthase (PKS) (SimG) to mediate the production of the unusual amino acid (4R)-4-[(E)-2butenyl]-4-methyl-L-threonine (Bmt). Individual deletion of 10 genes, isolation of intermediates, and substrate feeding experiments show that Bmt is biosynthesized by three enzymes, including SimG, SimI, and SimJ. The substrate D-alanine is catalyzed from L-alanine by alanine racemase SimB. Gene cluster transcription is regulated by a putative basic leucine zipper (bZIP)-type protein encoded by the cluster gene SimL. We also found that the cluster cyclophilin (SimC) and transporter (SimD) genes contribute to the tolerance of CsA in the CsA-producing fungus. We also found that cyclosporine production could enable the fungus to outcompete other fungi during cocultivation tests. Deletion of the CsA biosynthetic genes also impaired fungal virulence against insect hosts. Taking all the data together, in addition to proposing a biosynthetic pathway of cyclosporines, the results of this study suggest that CsA produced by this fungus might play important ecological roles in fungal environment interactions. IMPORTANCE The cyclopeptide cyclosporin A was first isolated from the filamentous fungus Tolypocladium inflatum showing antifungal activity and was later developed as an immunosuppressant drug. We report the biosynthetic mechanism of cyclosporines that are mediated by a cluster of genes encoding NRPS and PKS controlled by a bZIP-type transcriptional regulator. The two unusual amino acids Bmt and D-Ala are produced by the PKS pathway and alanine racemase, respectively. The cyclophilin and transporter genes jointly contribute to fungal self-protection against cyclosporines. Cyclosporine confers on T. inflatum the abilities to outcompete other fungi in competitive interactions and to facilitate fungal infection of insect hosts, which therefore benefits fungal adaptations to different environments

Evolution of Urban Spatial Clusters in China: A Graph-Based Method Using Nighttime Light Data

An urban spatial cluster (USC) describes one or more geographic agglomerations and the linkages among cities. USCs are conventionally delineated based on predefined administrative boundaries of cities, without considering the dynamic and evolving nature of the spatial extent of USCs. This study uses Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light (NTL) satellite images to quantitatively detect and characterize the evolution of USCs. We propose a dynamic minimum spanning tree (DMST) and a subgraph partitioning method to identify the evolving USCs over time, which considers both the spatial proximity of urban built-up areas and their affiliations with USCs at the previous snapshot. China is selected as a case study for its rapid urbanization process and the cluster-based economic development strategy. Four DMSTs are generated for China using the urban built-up areas extracted from DMSP/OLS NTL satellite images collected in 2000, 2004, 2008, and 2012. Each DMST is partitioned into various subtrees and the urban built-up areas connected by the same subtree are identified as a potential USC. By inspecting the evolution of USCs over time, three different types of USCs are obtained, including newly emerging, single-core, and multicore clusters. Using the rank-size distribution, we find that large-sized USCs have greater development than medium- and small-sized USCs. A clear directionality and heterogeneity are observed in the expansions of the ten largest USCs. Our study provides further insight for the understanding of urban system and its spatial structures, and assists policymakers in their planning practices at national and regional scales

Gene Expression Profiling for Diagnosis of Triple-Negative Breast Cancer: A Multicenter, Retrospective Cohort Study

Background: Triple-negative breast cancer (TNBC) accounts for 12–20% of all breast cancers. Diagnosis of TNBC is sometimes quite difficult based on morphological assessment and immunohistochemistry alone, particularly in the metastatic setting with no prior history of breast cancer.Methods: Molecular profiling is a promising diagnostic approach that has the potential to provide an objective classification of metastatic tumors with unknown primary. In this study, performance of a novel 90-gene expression signature for determination of the site of tumor origin was evaluated in 115 TNBC samples. For each specimen, expression profiles of the 90 tumor-specific genes were analyzed, and similarity scores were obtained for each of the 21 tumor types on the test panel. Predicted tumor type was compared to the reference diagnosis to calculate accuracy. Furthermore, rank product analysis was performed to identify genes that were differentially expressed between TNBC and other tumor types.Results: Analysis of the 90-gene expression signature resulted in an overall 97.4% (112/115, 95% CI: 0.92–0.99) agreement with the reference diagnosis. Among all specimens, the signature correctly classified 97.6% of TNBC from the primary site (41/42) and lymph node metastasis (41/42) and 96.8% of distant metastatic tumors (30/31). Furthermore, a list of genes, including AZGP1, KRT19, and PIGR, was identified as differentially expressed between TNBC and other tumor types, suggesting their potential use as discriminatory markers.Conclusion: Our results demonstrate excellent performance of a 90-gene expression signature for identification of tumor origin in a cohort of both primary and metastatic TNBC samples. These findings show promise for use of this novel molecular assay to aid in differential diagnosis of TNBC, particularly in the metastatic setting

Seasonal Dynamics in Forest Soil Seed Banks along an Elevational Gradient in the Rocky Mountainous Area of North China

Although exploring soil seed bank characteristics and dynamics is conducive to plant diversity protection and restoration, few investigations have been undertaken in the rocky mountainous area of North China. To address this research gap, qualitative and quantitative changes in soil seed bank characteristics over different seasons and elevations as well as potential causes for differences were examined, using data from 25 secondary forest communities in the Songshan area of Beijing, China. Nonmetric multidimensional scaling (NMDS) was used to test the similarity of the composition of the seed bank and the understory vegetation during different seasons. In addition, the structural equation model (SEM) was used to explore the direct and indirect effects on seed bank density. The results indicate that abundance and species richness decreased with elevation, with seed density reaching its maximum and minimum levels in April and July at all elevation levels, respectively. In terms of species composition, the understory vegetation was significantly different from the seed bank, and the proportion of herbaceous plants species in the seed bank was higher. Soil total nitrogen, available phosphorus and available potassium all changed with elevation, directly or indirectly affecting seed bank density. The application of seed banks present in topsoil from the rocky mountainous area of North China can be potentially used for ecological restoration. It is important, however, to consider the elevation and the season related to the removal of the topsoil to achieve optimal effects

Grafting Onto Artemisia annua Improves Drought Tolerance in Chrysanthemum by Enhancing Photosynthetic Capacity

Drought stress drastically influences the yield and quality of chrysanthemums, and thus grafting has been widely used to improve tolerance to biotic and abiotic stresses. To explore the mechanisms underlying improvements in drought resistance afforded by grafting, we investigated the changes in growth, gas exchange, ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) expression and activity, sugar components, and the relative expression of photosynthesis-related genes of chrysanthemum (Chrysanthemum morifolium Ramat. ‘Hangbaiju’) plants grafted onto Artemisia annua rootstocks under drought stress by withholding water for 6 d. The results revealed that the growth declines in the grafted chrysanthemums were relatively lower than those of the non-grafted plants under drought stress, and net photosynthetic rate, stomatal conductance, water use efficiency, and transpiration rate in the non-grafted chrysanthemums were significantly decreased. Moreover, the intercellular CO2 concentrations were significantly increased compared with the grafted plants at 5 and 6 d following drought stress. The grafted plants exhibited higher relative expression of the CmrbcL, CmrbcS, CmpsaB, and Cmcab genes, as well as higher Rubisco activity and chlorophyll content under the drought treatment. Sugar accumulation also increased under drought stress, particularly in the non-grafted plants. This result suggested that non-grafted chrysanthemums were less able to resist dehydration, and repressed the genes encoding the expression of photosynthetic components. In conclusion, using A. annua rootstock could alleviate drought stress in chrysanthemums by improving gas exchange capacity and maintaining CmrbcL, CmrbcS, Cmcab, and CmpsaB gene expression, thereby increasing Rubisco activity and improving photosynthetic performance. Keywords: artemisia annua, chrysanthemum, grafting, drought stress, sugar components, photosynthetic capacit

Tryptamine accumulation caused by deletion of MrMao-1 in Metarhizium genome significantly enhances insecticidal virulence.

Metarhizium is a group of insect-pathogenic fungi that can produce insecticidal metabolites, such as destruxins. Interestingly, the acridid-specific fungus Metarhizium acridum (MAC) can kill locusts faster than the generalist fungus Metarhizium robertsii (MAA) even without destruxin. However, the underlying mechanisms of different pathogenesis between host-generalist and host-specialist fungi remain unknown. This study compared transcriptomes and metabolite profiles to analyze the difference in responsiveness of locusts to MAA and MAC infections. Results confirmed that the detoxification and tryptamine catabolic pathways were significantly enriched in locusts after MAC infection compared with MAA infection and that high levels of tryptamine could kill locusts. Furthermore, tryptamine was found to be capable of activating the aryl hydrocarbon receptor of locusts (LmAhR) to produce damaging effects by inducing reactive oxygen species production and immune suppression. Therefore, reducing LmAhR expression by RNAi or inhibitor (SR1) attenuates the lethal effects of tryptamine on locusts. In addition, MAA, not MAC, possessed the monoamine oxidase (Mao) genes in tryptamine catabolism. Hence, deleting MrMao-1 could increase the virulence of generalist MAA on locusts and other insects. Therefore, our study provides a rather feasible way to design novel mycoinsecticides by deleting a gene instead of introducing any exogenous gene or domain

Analysis of Changes in Herbaceous Peony Growth and Soil Microbial Diversity in Different Growing and Replanting Years Based on High-Throughput Sequencing

The herbaceous peony (Paeonia lactiflora Pall.), a perennial herbaceous flower, can grows continuously for approximately 10 years. However, a replanting problem can occur during division propagation which reduces the land use rate and restricts the development of the herbaceous peony industry. We investigated microbial community changes and soil chemical properties in herbaceous peony soils during different growing and replanting years. The results indicated that the flowering rate, plant height, stem diameter, and leaf area of replanted herbaceous peony were lower, and decreased gradually with increasing replanting years. Compared with the soil after replanting herbaceous peony for one year, soil pH, nutrient contents (AN, AP, AK, and OM), enzyme activities (Inv, Ure, Pho, and Cat), diversity and richness of fungal and bacterial communities decreased after replanting for five years. Long-term replanting increased the relative abundance of harmful soil microorganisms (e.g., Gibberella), and reduced that of beneficial microorganisms (e.g., Bacillus). Overall, after the long-term replanting of herbaceous peony, the soil environment deteriorated, and the soil microbial community structure changed, resulting in the imbalance of soil microecology, damaging the normal growth of herbaceous peony

Analysis of Changes in Herbaceous Peony Growth and Soil Microbial Diversity in Different Growing and Replanting Years Based on High-Throughput Sequencing

The herbaceous peony (Paeonia lactiflora Pall.), a perennial herbaceous flower, can grows continuously for approximately 10 years. However, a replanting problem can occur during division propagation which reduces the land use rate and restricts the development of the herbaceous peony industry. We investigated microbial community changes and soil chemical properties in herbaceous peony soils during different growing and replanting years. The results indicated that the flowering rate, plant height, stem diameter, and leaf area of replanted herbaceous peony were lower, and decreased gradually with increasing replanting years. Compared with the soil after replanting herbaceous peony for one year, soil pH, nutrient contents (AN, AP, AK, and OM), enzyme activities (Inv, Ure, Pho, and Cat), diversity and richness of fungal and bacterial communities decreased after replanting for five years. Long-term replanting increased the relative abundance of harmful soil microorganisms (e.g., Gibberella), and reduced that of beneficial microorganisms (e.g., Bacillus). Overall, after the long-term replanting of herbaceous peony, the soil environment deteriorated, and the soil microbial community structure changed, resulting in the imbalance of soil microecology, damaging the normal growth of herbaceous peony

NPP-VIIRS DNB Daily Data in Natural Disaster Assessment: Evidence from Selected Case Studies

Whereas monthly and annual nighttime light (NTL) composite datasets are being increasingly used to estimate socioeconomic status, use of the National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS) Day/Night Band (DNB) daily data has been limited for detecting and assessing the impact of short-term disastrous events. This study explores the application of daily NPP-VIIRS DNB data in assessing the impact of three types of natural disasters: earthquakes, floods, and storms. Daily DNB images one month prior to and 10 days after a disastrous event were collected and a Percent of Normal Light (PNL) image was produced as the ratio of the mean DNB radiance of the pre- and post-disaster images. Areas with a PNL value lower than one were considered as being affected by the event. The results were compared with the damaged proxy map and the flood proxy map generated using synthetic aperture radar data as well as the reported power outage rates. Our analyses show that overall NPP-VIIRS DNB daily data are useful for detecting damages and power outages caused by earthquake, storm, and flood events. Cloud coverage was identified as a major limitation in using the DNB daily data; rescue activities, traffic, and socioeconomic status of the areas also affect the use of DNB daily data in assessing the impact of natural disasters. Our findings offer new insight into the use of the daily DNB data and provide a practical guide for researchers and practitioners who may consider using such data in different situations or regions