Long‐term monoculture of watermelon results in inhibited growth and decreased crop yields, possibly because of imbalance in microbial ecology caused by accumulation of the pathogen in soil. This ...results in serious problems in the economics of watermelon production. We investigated the build‐up of Fusarium in soil under watermelon cultivation and changes over 3 yr of fallow in a microcosm. We focused on changes in the microbial community of Fusarium‐infected soil, including the diversity of the microfloral species composition, and species abundance. Long‐term monoculture of watermelon leads to changes in microbial diversity and community structure. The microbes most readily cultured from infested soil were suppressed by watermelon wilt pathogen Fusarium oxysporum f. sp. niveum (FON). Of 52 isolated and identified culturable microbes, 83.3% of bacteria, 85.7% of actinomycetes, 31.6% of fungi and 20.0% of Fusarium sp. were inhibited by FON on bioassay plates. Prior to fallowing, infested soil was a transformed ‘fungus‐type’ soil. After 3 yr of fallow, the infested soil had remediated naturally, and soil microbial diversity recovered considerably. Abundance of dominant bacterial populations was increased by 118–177%, actinomycetes, fungi and FON were decreased by 23–32, 33–37 and 50%, respectively. The ratio of bacteria: actnomycetes: fungus: Fusarium sp. in infested soil changed from 24 000:100:4:1 prior to fallow to 57 000:100:3.5:1 after fallowing, nearer to the 560 000:400:8:1 ratio of healthy soil not used for watermelon cultivation. This suggests the ‘fungus‐type’ soil was converting to ‘bacteria‐type’ soil and that disrupted microbial communities in infested soil were restored during fallow.
Our research on adverse effects of lead exposures on physical and neurobehavioral health of children aged 6–12
years in 4 villages, labeled as K, M, L, and X, in rural China, was reported in this ...article. Lead in blood (PbB), urine (PbU), hairs (PbH), and nails (PbN) were measured by graphite furnace atomic absorption spectrometry. Abbreviated Symptom Questionnaire of Conner's instruments and Revised Raven's Standard Progressive Matrices were applied to evaluate childhood attention deficit/hyperactivity disorders (ADHD) and intelligences. Geometric means (SD) of PbB, PbU, PbH and PbN concentrations were 71.2
μg/L (1.56), 11.7
μg/g (1.75), 12.5
μg/g (2.82), and 25.3
μg/g (2.79), respectively. 54 (17.0%) children had PbB levels of ≥
100
μg/L. Boys, the 6–10
years old, and living in village K were 2.11, 2.48, and 9.16 times, respectively, more likely to be poisoned by lead than girls, aged 11–12
years, and residing in X. 18 (5.7%) and 37 (11.7%) subjects had ADHD and mental retardations, respectively. Inverse relationships between intelligences and natural log transformed PbU and PbH levels were observed with respective odds ratios (95%CI) of 1.79 (1.00–3.22) and 1.46 (1.06–2.03) or 1.28 (1.04–1.58) and 1.73 (1.18–2.52) by binary or ordinal logistic regression modeling. ADHD prevalence was different by gender and age of subjects. PbU, PbH, and PbN related to PbB positively with respective correlation coefficients of 0.530, 0.477, and 0.181. Receiver operating characteristic (ROC) curves of the three measurements reveled areas under curves (AUCs) being 0.829, 0.758, and 0.687, respectively. In conclusion, children had moderate levels of lead exposures in this rural area. Intelligence declines were associated with internal lead levels among children. ROC analysis suggests PbU an internal lead indicator close to PbB.
We observe proximity-induced superconductivity in the \textit{in situ} prepared heterostructures constructed by topological insulator Bi\(_{2}\)Te\(_{3}\) thin films and high-temperature cuprate ...superconductors Bi\(_{2}\)Sr\(_{2}\)CaCu\(_{2}\)O\(_{8+\delta}\). The superconducting gap maximum is about 7.6 meV on the surface of Bi\(_{2}\)Te\(_{3}\) thin films with a thickness of two quintuple layers, and the gap value decreases with an increase in the film thickness. Moreover, the quasiparticle interference data show a clear evidence of a twofold symmetric superconducting gap with gap minima along one pair of the principal crystalline axes of Bi\(_{2}\)Te\(_{3}\). This gap form is consistent with the \(\Delta_{4y}\) notation of the topological superconductivity proposed in such systems. Our results provide fruitful information of the possible topological superconductivity induced by the proximity effect in high-temperature superconducting cuprates.
The interplay between charge order and superconductivity remains one of the central themes of research in quantum materials. In the case of cuprates, the coupling between striped charge fluctuations ...and local electromagnetic fields is especially important, as it affects transport properties, coherence and dimensionality of superconducting correlations. Here, we study the emission of coherent terahertz radiation in single-layer cuprates of the La\(_{2-x}\)Ba\(_x\)CuO\(_4\) family, for which this effect is expected to be forbidden by symmetry. We find that emission vanishes for compounds in which the stripes are quasi-static, but is activated when \(c\)-axis inversion symmetry is broken by incommensurate or fluctuating charge stripes, such as in La\(_{1.905}\)Ba\(_{0.095}\)CuO\(_4\) and in La\(_{1.845}\)Ba\(_{0.155}\)CuO\(_4\). In this case, terahertz radiation is emitted by surface Josephson plasmons, which are generally dark modes, but couple to free space electromagnetic radiation because of the stripe modulation.
Although copper oxide high-temperature superconductors constitute a complex and diverse material family, they all share a layered lattice structure. This curious fact prompts the question of whether ...high-temperature superconductivity can exist in an isolated monolayer of copper oxide, and if so, whether the two-dimensional superconductivity and various related phenomena differ from those of their three-dimensional counterparts. The answers may provide insights into the role of dimensionality in high-temperature superconductivity. Here we develop a fabrication process that obtains intrinsic monolayer crystals of the high-temperature superconductor Bi
Sr
CaCu
O
(Bi-2212; here, a monolayer refers to a half unit cell that contains two CuO
planes). The highest superconducting transition temperature of the monolayer is as high as that of optimally doped bulk. The lack of dimensionality effect on the transition temperature defies expectations from the Mermin-Wagner theorem, in contrast to the much-reduced transition temperature in conventional two-dimensional superconductors such as NbSe
. The properties of monolayer Bi-2212 become extremely tunable; our survey of superconductivity, the pseudogap, charge order and the Mott state at various doping concentrations reveals that the phases are indistinguishable from those in the bulk. Monolayer Bi-2212 therefore displays all the fundamental physics of high-temperature superconductivity. Our results establish monolayer copper oxides as a platform for studying high-temperature superconductivity and other strongly correlated phenomena in two dimensions.
Zirconium pentatelluride was recently reported to be a 3D Dirac semimetal, with a single conical band, located at the center of the Brillouin zone. The cone's lack of protection by the lattice ...symmetry immediately sparked vast discussions about the size and topological or trivial nature of a possible gap opening. Here, we report on a combined optical and transport study of ZrTe_{5}, which reveals an alternative view of electronic bands in this material. We conclude that the dispersion is approximately linear only in the a-c plane, while remaining relatively flat and parabolic in the third direction (along the b axis). Therefore, the electronic states in ZrTe_{5} cannot be described using the model of 3D Dirac massless electrons, even when staying at energies well above the band gap 2Δ=6 meV found in our experiments at low temperatures.
Degradation of dimethyl isophthalate (DMI) and dimethyl phthalate ester (DMPE) was investigated using microorganisms isolated from mangrove sediment of Hong Kong Mai Po Nature Reserve. One enrichment ...culture was capable of utilizing DMI as the sole source of carbon and energy, but none of the bacteria in the enrichment culture was capable of degrading DMI alone. In co-culture of two bacteria, degradation was observed proceeding through monomethyl isophthalate (MMI) ester and isophthalic acid (IPA) before the aromatic ring opening. Using DMI as the sole carbon and energy source, Klebsiella oxytoca Sc and Methylobacterium mesophilicum Sr degraded DMI through the biochemical cooperation. The initial hydrolytic reaction of the ester bond was by K. oxytoca Sc and the next step of transformation was by M. mesophilicum Sr, and IPA was degraded by both of them. In another investigation, a novel bacterium, strain MPsc, was isolated for degradation of dimethyl phthalate ester (DMPE) also from the mangrove sediment. On the basis of phenotypic, biochemical and 16S rDNA gene sequence analyses, the strain MPsc should be considered as a new bacterium at the genus level (8% differences). This strain, together with a Rhodococcus zopfii isolated from the same mangrove sediment, was able to degrade DMPE aerobically. The consortium consisting of the two species degraded 450 mg/l DMPE within 3 days as the sole source of carbon and energy, but none of the individual species alone was able to transform DMPE. Furthermore, the biochemical degradation pathway proceeded through monomethyl phthalate (MMP), phthalic acid (PA) and then protocatechuate before aromatic ring cleavage. Our results suggest that degradation of complex organic compounds including DMI and DMPE may be carried out by several members of microorganisms working together in the natural environments.
The unconventional normal-state properties of the cuprates are often discussed in terms of emergent electronic order that onsets below a putative critical doping of xc = 0.19. Charge-density wave ...(CDW) correlations represent one such order; however, experimental evidence for such order generally spans a limited range of doping that falls short of the critical value xc, leading to questions regarding its essential relevance. Here, we use x-ray diffraction to demonstrate that CDW correlations in La2-xSrxCuO4 persist up to a doping of at least x = 0.21. The correlations show strong changes through the superconducting transition, but no obvious discontinuity through xc = 0.19, despite changes in Fermi surface topology and electronic transport at this doping. These results demonstrate the interaction between CDWs and superconductivity even in overdoped cuprates and prompt a reconsideration of the role of CDW correlations in the high-temperature cuprate phase diagram.
PDF
