Heterochiral π-Stacking Dimerization of Helical Secondary Structures with Emerging Supramolecular Chirality.

A specific interface mode type was observed between helical secondary structures, in which a left-handed (M) helix binds specifically to a right-handed (P) helix along the helical axis, leading to the formation of discrete heterochiral helical dimers. Moreover, a concealed supramolecular chirality within the meso-supramolecular dimers was unexpectedly discovered by chiral induction, and was further underpinned by covalent meso-helix structures.

Carboxylic acid isomer-directed synthesis of CdS nanocluster isomers.

Selective synthesis of nanocluster (NC) isomers with tailored structures holds significant importance for enhancing their applications. Here, we develop an effective strategy for the selective synthesis of CdS NC isomers through the judicious choice of a pair of carboxylic acid isomer additives. Specifically, CdS NC-312 and NC-323 (denoted by their UV-vis absorption peak position) could be selectively produced by introducing a conventional mixture of Cd and S precursors, with the addition of 2-methylbutyric acid (2-MA) and 3-methylbutyric acid (3-MA), respectively. The synthesized NC isomers demonstrated a precise isomeric relationship, sharing both the isomeric inorganic core and organic surface. Alternatively, the as-synthesized NCs were interconvertible by re-adding the acid isomers. The density functional theory calculations further support that 2-MA and 3-MA have specific selectivity for producing CdS NC isomers by interfacial tuning. Finally, the generality of this methodology was also evidenced with applications in other CdS NC synthetic systems. This study unveils the intriguing correlation between additive structures and the configuration of NCs, providing a foundation for the selective synthesis of NC isomers.

Single-Stranded Nucleic Acid Transmembrane Molecular Carriers Based on Positively Charged Helical Foldamers.

Transmembrane delivery of biologically active nucleic acids is an important process in cells and has inspired one to develop advanced drug delivery techniques. In this contribution, molecular-level single-stranded nucleic acid transmembrane carriers are reported based on 3.2 nm long Huc's foldamers (AOrnQ3Q3)8 and (mQ3Q2)8 with linearly and helically aligned positive charges, respectively. These two foldamers not only show very strong DNA affinity via electrostatic interactions but also discriminatively bind single-stranded DNA (ss-DNA) and double-stranded DNA (ds-DNA), corroborating the importance of precise charge arrangement in the electrostatic interactions. More importantly, these two foldamers are capable of efficiently transporting ss-DNA across the lipid membranes, and the ss-DNA transport activity of (AOrnQ3Q3)8 with linearly aligned charges is higher than that of (mQ3Q2)8 with helically aligned charges. Thus a type of novel single-stranded nucleic acid transmembrane molecular carriers based on positively charged helical foldamers are introduced. Further, effective and enhanced expression in EGFP-mRNA transfection experiments strongly demonstrates the potential of positively charged foldamers for RNA transmembrane transport and therapy.

Heteroatoms-Doped Mesoporous Carbon Nanosheets with Dual Diffusion Pathways for Highly Efficient Potassium Ion Storage.

The high potassization/depotassization energy barriers and lack of efficient ion diffusion pathways are two serious obstacles for carbon-based materials to achieve satisfactory potassium ion storage performance. Herein, a facile and controllable one-step exfoliation-doping-etching strategy is proposed to construct heteroatoms (N, O, and S)-doped mesoporous few-layer carbon nanosheets (NOS-C). The mixed molten salts of KCl/K2SO4 are innovatively used as the exfoliators, dopants, and etching agents, which enable NOS-C with expanded interlayer spacing and uniformly distributed mesopores with the adjusted electronic structure of surrounding carbon atoms, contributing efficient dual (vertical and horizontal) K-ion diffusion pathways, low potassization/depotassization energy barriers and abundant active sites. Thus, the NOS anodes achieve a high reversible capacity of 516.8 mAh g-1 at 0.05 A g-1, superior rate capability of 202.8 mAh g-1 at 5 A g-1 and excellent long-term cyclic stability, and their practical application potential is demonstrated by the assembled potassium-ion full batteries. Moreover, a surface-interlayer synergetic K+ storage mechanism is revealed by a combined theoretical and experimental approach including in situ EIS, in situ Raman, ex situ XPS, and SEM analysis. The proposed K+ storage mechanism and unique structural engineering provide a new pathway for potassium-ion storage devices and even beyond.

Backscattering properties of randomly oriented hexagonal hollow columns for lidar application.

The study of the optical properties of cirrus clouds is necessary to improve the accuracy of interpreting data from space lidars and ground-based lidar networks. Existing databases of backscattering properties do not include data on hollow columns. In this paper, the backscattering properties of randomly oriented hollow column ice crystal particles in cirrus at wavelengths of 355 nm, 532 nm, and 1064 nm have been investigated. The backscattering cross section (M11), depolarization ratio (δ), lidar ratio (S), and color ratio (χ) of randomly oriented hollow columns with sizes ranging from 10-316.23 µm are calculated within the framework of the physical optical approximation (PO). For the first time, we introduce the concept of modal hollow columns (MHC) suitable for mid-latitude regions, which simplifies the description of hollow ice crystals in nature. It is found that when the mixing proportion of MHC and solid columns (SC) reaches 50%, the mixing ratio can be distinguished by the lidar ratio for a wavelength of 1064 nm and by the χ(1064,532)-δ(532) relation.

Fine mapping of a novel QTL DM9.1 conferring downy mildew resistance in melon.

Downy mildew (DM) is a major foliar disease globally causing great economic loss in melon production. Utilizing disease-resistant cultivars is the most efficient approach for disease control, while discovery of disease-resistant genes is crucial for the success of DM-resistant breeding. To address this problem, two F2 populations were constructed using the DM-resistant accession PI 442177 in this study, and QTLs conferring DM resistance were mapped using linkage map and QTL-seq analysis, respectively. A high-density genetic map with the length of 1096.7 cM and density of 0.7 cM was generated by using the genotyping-by-sequencing data of a F2 population. A major QTL DM9.1 with the phenotypic variance explained proportion of 24.3-37.7% was consistently detected at the early, middle, and late growth stages using the genetic map. QTL-seq analyses on the two F2 populations also validated the presence of DM9.1. Kompetitive Allele-Specific PCR (KASP) assay was further carried out to fine map DM9.1 into 1.0 Mb interval. A KASP marker co-segregating with DM9.1 was successfully developed. These results not only provided valuable information for DM-resistant gene cloning, but also offered useful markers for melon DM-resistant breeding programs.

Parameter Optimization and Development of Mini Infrared Lidar for Atmospheric Three-Dimensional Detection.

In order to conduct more thorough research on the structural characteristics of the atmosphere and the distribution and transmission of atmospheric pollution, the use of remote sensing technology for multi-dimensional detection of the atmosphere is needed. A light-weight, low-volume, low-cost, easy-to-use and low-maintenance mini Infrared Lidar (mIRLidar) sensor is developed for the first time. The model of lidar is established, and the key optical parameters of the mIRLidar are optimized through simulation, in which wavelength of laser, energy of pulse laser, diameter of telescope, field of view (FOV), and bandwidth of filter are included. The volume and weight of the lidar system are effectively reduced through optimizing the structural design and designing a temperature control system to ensure the stable operation of the core components. The mIRLidar system involved a 1064 nm laser (the pulse laser energy 15 µJ, the repetition frequency 5 kHz), a 100 mm aperture telescope (the FOV 1.5 mrad), a 0.5 nm bandwidth of filter and an APD, where the lidar has a volume of 200 mm × 200 mm × 420 mm and weighs about 13.5 kg. It is shown that the lidar can effectively detect three-dimensional distribution and transmission of aerosol and atmospheric pollution within a 5 km detection range, from Horizontal, scanning and navigational atmospheric measurements. It has great potential in the field of meteorological research and environmental monitoring.

Soft 2D Covalent Organic Framework with Compacted Honeycomb Topology.

In this contribution, we report the synthesis of an imine-based soft 2D covalent organic framework (S-COF) with compacted honeycomb topology via inveterately selecting a helically folded ditopic flexible linker and a trigonal building block. In contrast to various topological structures of rigid monomer-based COFs (R-COFs) reported so far, owing to the presence of flexible skeleton S-COF can spontaneously form a compacted and nonporous topological structure via intramolecular π stacking of presupposed honeycomb-like topology. Such S-COFs with a compacted honeycomb topology have neither been proposed theoretically nor been achieved experimentally. The compacted topological structure of 2D S-COF was clearly characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and circular dichroism (CD) measurements. This study opens a new window to the development of S-COFs and will significantly expand the scope of COF materials.

Detecting aerosol backscattering coefficient across the whole troposphere by the sidescattering lidar system with three CCD cameras.

Due to geometric overlap factor, the backscattering lidar is not suitable to detect atmospheric characteristics near the ground. A new sidescattering lidar system consisting of three CCD cameras and one CW laser is developed for the first time to measure the profiles of the backscattering coefficient of atmospheric aerosols across the whole troposphere, which has no detection blind zone near the ground. The aerosol relative phase function was detected by its horizontal CCD channel. The vertical distribution of aerosol backscattering coefficient across the whole troposphere was observed by the other two CCD cameras of vertical channel. The reasons for choosing three CCD cameras and their respective functions are analyzed in detail. Comparative experiments and continuous observations indicate that the new sidescattering lidar system including three CCD cameras is simple in structure and reliable in performance with low cost as well.

New Denoising Method for Lidar Signal by the WT-VMD Joint Algorithm.

Light detection and ranging (LIDAR) is an active remote sensing system. Lidar echo signal is non-linear and non-stationary, which is often accompanied by various noises. In order to filter out the noise and extract valid signal information, a suitable method should be chosen for noise reduction. Some denoising methods are commonly used, such as the wavelet transform (WT), the empirical mode decomposition (EMD), the variational mode decomposition (VMD), and their improved algorithms. In this paper, a new denoising method named the WT-VMD joint algorithm based on the sparrow search algorithm (SSA), for lidar signal is selected by comparative experiment analysis. It is shown that this method is the most suitable one with the maximum signal-to-noise ratio (SNR), the minimum root-mean-square error (RMSE), and a relatively small indicator of smoothness when it is used in three kinds (50, 100, and 1000 pulses) of simulate lidar signals. The SNR is increased by 138.5%, 77.8% and 42.8% and the RMSE is decreased by 81.8%, 72.0% and 68.8% when being used to the three kinds of cumulative signal without pollution. Then, the SNR is increased by 83.3%, 60.4% and 24.0% and the RMSE is decreased by 70.8%, 66.0% and 50.5% when being used to the three kinds of cumulative signal with aerosol and clouds. The WT-VMD joint algorithm based on SSA is used in the denoising process for the actual lidar signal, showing extraordinary denoising effect and will improve the inversion accuracy of the lidar signal.

Lidar backscatter simulation for angular scanning of cirrus clouds with quasi-horizontally oriented ice crystals.

Backscattering properties of ice crystals are numerically investigated in the case of plate-like quasi-horizontally oriented crystals of cirrus clouds. In this case, a vertically oriented lidar detects the specular reflection from the clouds while a lidar with angular scanning allows one to infer the microphysical properties like the transverse shape of the crystals. It is shown that the depolarization ratio as a function of the lidar tilt reveals a step at a lidar tilt of about 30° from the vertical. This step has been observed experimentally. Appearance of this step indicates that the transverse shapes of the plate-like crystals are regular.

Structurally Durable Bimetallic Alloy Anodes Enabled by Compositional Gradients.

Metals such as Sb and Bi are important anode materials for sodium-ion batteries because they feature a large capacity and low reaction potential. However, the accumulation of stress and strain upon sodium storage leads to the formation of cracks and fractures, resulting in electrode failure upon extended cycling. In this work, the design and construction of Bix Sb1-x bimetallic alloy films with a compositional gradient to mitigate the intrinsic structural instability is reported. In the gradient film, the top is rich in Sb, contributing to the capacity, while the bottom is rich in Bi, helping to reduce the stress in the interphase between the film and the substrate. Significantly, this gradient film affords a high reversible capacity of ≈500 mAh g-1 and sustains 82% of the initial capacity after 1000 cycles at 2 C, drastically outperforming the solid-solution counterpart and many recently reported alloy anodes. Such a gradient design can open up the possibilities to engineering high-capacity anode materials that are structurally unstable due to the huge volume variation upon energy storage.

Radar-lidar ratio for ice crystals of cirrus clouds.

Simultaneous measurement of lidar and radar signals returned from the same cirrus clouds is a prospective method for retrieving the cloud microphysics, i.e. size and shape of the ice crystals constituting the clouds. In this study, the ratio of the backscattered signals of lidar and radar called the radar-lidar ratio has been calculated for the first time for typical shapes of ice crystals and wide distribution of the crystals over their sizes. It is shown that it is the lidar-radar ratio that is most sensitive to crystal sizes while the lidar depolarization ratio is most sensitive to crystal shapes.

An Energetic CuS-Cu Battery System Based on CuS Nanosheet Arrays.

The development of low-cost and high-energy aqueous battery technologies is of significance for renewable and stationary energy applications. However, this development has been bottlenecked by poor conductivity, low capacity, and limited cycling stability of existing electrode materials. In this work, we report on an energetic aqueous copper ion system based on CuS nanosheet arrays, taking profit of high conductivity of CuS and efficient charge carrier of copper ions. Electrochemical results reveal a high capacity of 510 mAh g-1, robust rate capability of 497 mAh g-1 at a high rate of 7.5 A g-1, and ultrastable cycling by retaining 91% of the initial capacity over 2500 cycles. The charge-storage mechanism was systematically investigated by ex situ and in situ techniques involving a reversible transition from CuS to Cu7S4 and to Cu2S through the redox of Cu2+/Cu+. Moreover, we demonstrate a hybrid ion battery consisting of CuS positive electrode and Zn negative electrode, which affords an energy and power of 286 Wh kg-1 and 900 W kg-1, respectively, on the basis of both electrodes, exceeding many aqueous battery systems.

Biodegradation of erythromycin by Delftia lacustris RJJ-61 and characterization of its erythromycin esterase.

The residual erythromycin in fermentation waste can pollute the environment and threaten human health. However, there are no effective approaches to remedy this issue. In this study, an erythromycin-degrading bacterium named RJJ-61 was isolated and identified as a strain of Delftia lacustris based on morphological and phylogenetic analyses. The degradation ability of this strain was also evaluated; it could degrade 45.18% of erythromycin at 35°C in 120 h. Furthermore, the key degradation gene ereA was cloned from strain RJJ-61 and expressed in Escherichia coli BL21; the molecular weight of the expressed protein was ~45 kDa. The enzyme activity of EreA was 108.0 mU ml-1 at 35°C and pH 7.0. Finally, the EreA protein was used to degrade erythromycin from mycelial dregs and 50% diluted solution, and the removal rates in them were 41.42% and 69.78%, respectively. In summary, D. lacustris RJJ-61 is a novel erythromycin-degrading strain that has great potential to remove erythromycin pollutants from the environment.

Isolation and identification of a novel erythromycin-degrading fungus, Curvularia sp. RJJ-5, and its degradation pathway.

Erythromycin pollution is an important risk to the ecosystem and human health worldwide. Thus, it is urgent to develop effective approaches to decontaminate erythromycin. In this study, we successfully isolated a novel erythromycin-degrading fungus from an erythromycin-contaminated site. The erythromycin biodegradation characteristics were investigated in mineral salt medium with erythromycin as the sole carbon and energy source. The metabolites of erythromycin degraded by fungus were identified and used to derive the degradation pathway. Based on morphological and phylogenetic analyses, the isolated strain was named Curvularia sp. RJJ-5 (MN759651). Optimal degradation conditions for strain RJJ-5 were 30°C, and pH 6.0 with 100 mg L-1 erythromycin substrate. The strain could degrade 75.69% erythromycin under this condition. The following metabolites were detected: 3-depyranosyloxy erythromycin A, 7,12-dyhydroxy-6-deoxyerythronolide B, 2,4,6,8,10,12-hexamethyl-3,5,6,11,12,13-hexahydroxy-9-ketopentadecanoic acid and cladinose. It was deduced that the erythromycin A was degraded to 3-depyranosyloxy erythromycin A by glycoside hydrolase in the initial reaction. These results imply that Curvularia sp. RJJ-5 is a novel erythromycin-degrading fungus that can hydrolyze erythromycin using a glycoside hydrolase and has great potential for removing erythromycin from mycelial dreg and the contaminated environment.

Isolation and characterization of the novel oil-degrading strain Kosakonia cowanii IUMR B67 and expression of the degradation enzyme.

Oils in food waste can pollute the environment and negatively affect human health. Biodegradation is a promising method for disposing of waste edible oils. In this study, an oil-degrading bacterium was isolated from kitchen waste for efficient degradation of edible oils. Its growth and oil degradation characteristics were investigated in basic salt medium with edible oils as the sole carbon and energy source; the triacylglycerol lipase gene (EC 3.1.1.3) was cloned and expressed in Escherichia coli. A novel oil-degrading bacterium assigned as IUMR B67 was successfully isolated. Morphological and molecular analyses revealed that strain IUMR B67 belongs to Kosakonia cowanii. After 144 h of incubation, the oil degradation rate at 37°C was 95.80%. Optimal conditions for IUMR B67 were recorded at 37°C and 0.1% NaCl with 0.1% ammonium sulfate supplementation. The lipase gene of strain IUMR B67 was determined to be 912 base pairs, and the lipase activity of the expressed protein was 3.02 U/mL, which was significantly higher than the control (P < 0.05). Overall, Kosakonia cowanii IUMR B67 is a novel edible oil-degrading strain that can hydrolyze oil via its lipase activity, which may be useful in the disposal of oils and oily food waste.

Rooting binder-free tin nanoarrays into copper substrate via tin-copper alloying for robust energy storage.

The need for high-energy batteries has driven the development of binder-free electrode architectures. However, the weak bonding between the electrode particles and the current collector cannot withstand the severe volume change of active materials upon battery cycling, which largely limit the large-scale application of such electrodes. Using tin nanoarrays electrochemically deposited on copper substrate as an example, here we demonstrate a strategy of strengthening the connection between electrode and current collector by thermally alloying tin and copper at their interface. The locally formed tin-copper alloys are electron-conductive and meanwhile electrochemically inactive, working as an ideal "glue" robustly bridging tin and copper to survive harsh cycling conditions in sodium ion batteries. The working mechanism of the alloy "glue" is further characterized through a combination of electrochemical impedance spectroscopy, atomic structural analysis and in situ X-ray diffraction, presenting itself as a promising strategy for engineering binder-free electrode with endurable performance.

Extinction matrix for cirrus clouds in the visible and infrared regions.

The extinction matrix for cirrus clouds has been calculated for the visible and infrared regions using the physical optics approximation. The cirrus clouds are modeled as a statistical ensemble of the hexagonal ice plates, distributed over their size and orientations by the gamma and Gaussian laws, respectively. Then, the extinction matrixes as the functions of the incident wavelength, incident direction, crystal size, and crystal orientation are numerically calculated for the first time. It is shown that the off-diagonal elements of the matrix are negligible. Therefore, the extinction in cirrus clouds is described with good accuracy by the scalar exponential law.

Automated Detection of Red Lesions Using Superpixel Multichannel Multifeature.

Red lesions can be regarded as one of the earliest lesions in diabetic retinopathy (DR) and automatic detection of red lesions plays a critical role in diabetic retinopathy diagnosis. In this paper, a novel superpixel Multichannel Multifeature (MCMF) classification approach is proposed for red lesion detection. In this paper, firstly, a new candidate extraction method based on superpixel is proposed. Then, these candidates are characterized by multichannel features, as well as the contextual feature. Next, FDA classifier is introduced to classify the red lesions among the candidates. Finally, a postprocessing technique based on multiscale blood vessels detection is modified for removing nonlesions appearing as red. Experiments on publicly available DiaretDB1 database are conducted to verify the effectiveness of our proposed method.