51 research outputs found

    The Solution Growth of Copper Nanowires and Nanotubes is Driven by Screw Dislocations

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    Copper (Cu) nanowires (NWs) are inexpensive conducting nanomaterials intensively explored for transparent conducting electrodes and other applications. However, the mechanism for solution growth of Cu NWs remains elusive so far. Here we show that the one-dimensional anisotropic growth of Cu NWs and nanotubes (NTs) in solution is driven by axial screw dislocations. All three types of evidence for dislocation-driven growth have been conclusively observed using transmission electron microscopy (TEM) techniques: rigorous two-beam TEM analysis that conclusively characterizes the dislocations in the NWs to be pure screw dislocations along ⟹110⟩ direction, twist contour analysis that confirms the presence of Eshelby twist associated with the dislocation, and the observation of spontaneously formed hollow NTs. The reduction–oxidation (redox) electrochemical reaction forming the Cu NWs presents new chemistry for controlling supersaturation to promote dislocation-driven NW growth. Using this understanding to intentionally manipulate the supersaturation, we have further improved the NW growth by using a continuous flow reactor to yield longer Cu NWs under much milder chemical conditions. The rational synthesis of Cu NWs with control over size and geometry will facilitate their applications

    Changes in crop mix and the effects on agricultural carbon emissions in China

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    Changes in crop mix significantly affect the carbon emissions from cropping systems, thus underscoring their importance in achieving sustainable agriculture development. This article aims to offer new insights into the relationship between crop mix changes and carbon emissions from cropping systems. Based on provincial statistical data on crop production, this study analyzed the spatiotemporal dynamics of crop mix and the subsequent effect on the carbon emissions from cropping systems in China from 2005 to 2020. The crop-mix type identification rules, emission-factor approach, and grey incidence analysis were applied. The results showed clear changes in crop mix and obvious transitions from grain crops to cash crops in southern provinces. Among crops, the abundance of maize, vegetables, and melons increased remarkably. Besides, the carbon emission intensity (CI) from cropping systems generally showed an upward trend in most provinces, with a spatial pattern of gradual decrease from southeast to northwest. The changes in CI were most closely correlated with rice, maize, vegetables, and melon, with coefficients of 0.808, 0.773, 0.814, and 0.792, respectively. Additionally, the growth of maize and vegetables ratios played a significant role in the CI increases in most provinces. To optimize crop cultivation and mitigate carbon emissions, possible strategies including rational crop production layout, land transfer, and clean production technologies were proposed.</p

    Comparison of specific activities of AccGSTO1 and other GSTO.

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    <p>Specific activity shown in ÎŒmol/min/mg. ND, not detectable. “_”indicated not determined. C38A, P39A and Y40A are mutants for bmGSTO.</p

    SNP Identification by Transcriptome Sequencing and Candidate Gene-Based Association Analysis for Heat Tolerance in the Bay Scallop <i>Argopecten irradians</i>

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    <div><p>The northern bay scallop <i>Argopecten irradians irradians</i> (Lamarck) and the southern bay scallop <i>Argopecten irradians concentricus</i> (Say) were introduced into China in the 1980s and 1990s, and are now major aquaculture molluscs in China. Here, we report the transcriptome sequencing of the two subspecies and the subsequent association analysis on candidate gene on the trait of heat tolerance. In total, RNA from six tissues of 67 and 42 individuals of northern and southern bay scallops, respectively, were used and 55.5 and 34.9 million raw reads were generated, respectively. There were 82,267 unigenes produced in total, of which 32,595 were annotated. Altogether, 32,206 and 23,312 high-quality SNPs were identified for northern and southern bay scallops, respectively. For case-control analysis, two intercrossed populations were heat stress treated, and both heat-susceptible and heat-resistant individuals were collected. According to annotation and SNP allele frequency analysis, 476 unigenes were selected, and 399 pairs of primers were designed. Genotyping was conducted using the high-resolution melting method, and Fisher’s exact test was performed for allele frequency comparison between the heat-susceptible and heat-resistant groups. SNP all-53308-760 T/C showed a significant difference in allele frequency between the heat-susceptible and heat-resistant groups. Notably, considerable difference in allele frequency at this locus was also observed between the sequenced natural populations. These results suggest that SNP all-53308-760 T/C may be related to the heat tolerance of the bay scallop. Moreover, quantitative expression analysis revealed that the expression level of all-53308 was negatively correlated with heat tolerance of the bay scallop.</p></div

    The detection of the MDA content at different temperatures.

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    <p>In all experiments, foragers at 34°C were used as the controls. The effects of temperature-induced oxidative stress on the MDA concentration (nmol mg<sup>−1</sup> protein) in foragers. The vertical bars represent the mean ± S.E.M. (n = 3).</p

    Characterization and Mutational Analysis of Omega-Class GST (<i>GSTO1</i>) from <i>Apis cerana cerana</i>, a Gene Involved in Response to Oxidative Stress

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    <div><p>The Omega-class of GSTs (GSTOs) is a class of cytosolic GSTs that have specific structural and functional characteristics that differ from those of other GST groups. In this study, we demonstrated the involvement of the <i>GSTO1</i> gene from <i>A. cerana cerana</i> in the oxidative stress response and further investigated the effects of three cysteine residues of GSTO1 protein on this response. Real-time quantitative PCR (qPCR) showed that <i>AccGSTO1</i> was highly expressed in larvae and foragers, primarily in the midgut, epidermis, and flight muscles. The <i>AccGSTO1</i> mRNA was significantly induced by cold and heat at 1 h and 3 h. The TBA (2-Thiobarbituric acid) method indicated that cold or heat resulted in MDA accumulation, but silencing of <i>AccGSTO1</i> by RNAi in honeybees increased the concentration of MDA. RNAi also increased the temperature sensitivity of honeybees and markedly reduced their survival. Disc diffusion assay indicated that overexpression of AccGSTO1 in <i>E. coli</i> caused the resistance to long-term oxidative stress. Furthermore, AccGSTO1 was active in an <i>in vitro</i> DNA protection assay. Mutations in Cys-28, Cys-70, and Cys-124 affected the catalytic activity and antioxidant activity of AccGSTO1. The predicted three-dimensional structure of AccGSTO1 was also influenced by the replacement of these cysteine residues. These findings suggest that <i>AccGSTO1</i> plays a protective role in the response to oxidative stress.</p></div

    The expression profile of <i>AccGSTO1</i> determined using qPCR.

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    <p>(A) <i>AccGSTO1</i> mRNA expression at different developmental stages. Total RNA was isolated from larvae (L3-third instars, L4-fourth instars, and L5-fifth instars), pupae (Pw-white eyes pupae, Pp-pink eyes pupae, and Pb-brown eyes pupae), and adults (Em-newly emerged bees, Nu-nurse bees, Fo-foragers, Oa-old bees, and De-dead bees). (B) The tissue distribution of <i>AccGSTO1</i> expression. Total RNA was extracted from dissected brain (Br), epidermis (EP), flight muscle (Fm), midgut (Mi), and mandibular gland (Mg) tissues of foragers. (C) Expression of <i>AccGSTO1</i> after different temperature treatments (4°C, 15°C, 25°C, 34°C, and 43°C). Samples were collected at 0.5, 1, 3, 5, and 7 h. Bees at 34°C were used as a control. The vertical bars represent the mean ± S.E.M. (n = 3). The different letters above the columns indicate significant differences (P<0.05) according to Duncan's multiple range test performed using SAS version 9.1 software.</p

    Sequence analysis of the AccGSTO1.

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    <p>(A) Alignment of AccGSTO1 with the Omega-class GSTs from <i>Apis florea</i> (AfGSTO1), <i>Bombyx mori</i> (BmGSTO1), <i>Homo sapiens</i> (HsGSTO1), <i>Megachile rotundata</i> (MrGSTO1) and <i>Nasonia vitripennis</i> (NvGSTO1). Identical amino acids are shaded in black and similar amino acids are shown in gray. The putative secondary structures are displayed, and the H-site regions are boxed. The Cys residues in AccGSTO1 are marked by asterisks. The intron/exon junctions are indicated by triangles. (B) Phylogenetic relationships among GSTO1 and other GST families. Six main groups are shown. Acc: <i>Apis cerana cerana</i>; Af: <i>Apis florea</i>; Am: <i>Apis mellifera</i>; Bm: <i>Bombyx mori</i>; Bt: <i>Bombus terrestris</i>; Dm: <i>Drosophila melanogaster</i>; Hs: <i>Homo sapiens</i>; Mm: <i>Mus musculus</i>; Mr: <i>Megachile rotundata</i>; Nv: <i>Nasonia vitripennis</i>. (C) Comparison between the genomic structures of <i>AccGSTO1</i> and <i>AccGSTO2</i>. The translational initiation codons (ATG) and termination codons (TAA) are marked with dots and asterisks, respectively.</p
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