A phenology-based vegetation index for improving ratoon rice mapping using harmonized Landsat and Sentinel-2 data

Ratoon rice,which refers to a second harvest of rice obtained from the regenerated tillers originating from the stubble of the first harvested crop,plays an important role in both food security and agroecology while requiring minimal agricultural inputs.However,accurately identifying ratoon rice crops is challenging due to the similarity of its spectral features with other rice cropping systems(e.g.,double rice).Moreover,images with a high spatiotemporal resolution are essential since ratoon rice is generally cultivated in fragmented croplands within regions that frequently exhibit cloudy and rainy weather.In this study,taking Qichun County in Hubei Province,China as an example,we developed a new phenology-based ratoon rice vegetation index(PRVI)for the purpose of ratoon rice mapping at a 30 m spatial resolution using a robust time series generated from Harmonized Landsat and Sentinel-2(HLS)images.The PRVI that incorporated the red,near-infrared,and shortwave infrared 1 bands was developed based on the analysis of spectro-phenological separability and feature selection.Based on actual field samples,the performance of the PRVI for ratoon rice mapping was carefully evaluated by comparing it to several vegetation indices,including normalized difference vegetation index(NDVI),enhanced vegetation index(EVI)and land surface water index(LSWI).The results suggested that the PRVI could sufficiently capture the specific characteristics of ratoon rice,leading to a favorable separability between ratoon rice and other land cover types.Furthermore,the PRVI showed the best performance for identifying ratoon rice in the phenological phases characterized by grain filling and harvesting to tillering of the ratoon crop(GHS-TS2),indicating that only several images are required to obtain an accurate ratoon rice map.Finally,the PRVI performed better than NDVI,EVI,LSWI and their combination at the GHS-TS2 stages,with producer's accuracy and user's accuracy of 92.22 and 89.30%,respectively.These results demonstrate that the proposed PRVI based on HLS data can effectively identify ratoon rice in fragmented croplands at crucial phenological stages,which is promising for identifying the earliest timing of ratoon rice planting and can provide a fundamental dataset for crop management activities.

A Novel Millimeter-Wave Channel Measurement Platform for 6G Intelligent Railway Scenarios

This paper presented a novel millimeterwave channel measurement platform for the 6G intelligent railway.This platform used phased array antenna with 64 elements and can support instant bandwidth up to 1 GHz.Combined with improved multi-tone sounding signals,the platform can enhance dynamic measurement capability in high-speed railway scenarios.We performed calibration works about frequency flatness,frequency offset and proved platform reliability with channel emulator based closed-loop verification.We also carried out field trials in high-speed railway carriage scenarios.Based on measurement results,we extracted channel characteristic parameters of path loss,power delay profile and delay spread to further verify the field measurement performance of the platform.

Antimicrobial Chlorinated Carbazole Alkaloids from the Sponge-Associated Actinomycete Streptomyces diacarni LHW51701

Four new chlorinated carbazole alkaloids,chlocarbazomycins(CCBs)A-D,were isolated from sponge associated bacterium Streptomyces diacarni LHW51701.Their structures were elucidated via spectroscopic techniques(including HRESIMS,ID&2D NMR),and X-ray crystallographic analysis.Structurally,the 4-chloro coupled with 3-methoxyl substituents in the tricycle nucleus of CCBs A-D and the A/-methoxyl group of CCB-D are rare in naturally occurred tricyclic carbazole alkaloids.Moreover,CCBs A-D do not bear the typical Cl poro-alkyl and C2 meto-methyl side chains of bacterial tricycle carbazoles,suggesting a novel mechanism of aromatic ring formation in biosynthesis.The biological evaluation showed that CCB-C possessed inhibitory activities against pathogenic microorganisms including methicillin-resistant Staphylococcus aureus(MRSA),Mycobacterium smegmatis,Bacillus mycoides,and Candida albicans.

Diterpenoid UDP-Glycosyltransferases from Chinese Sweet Tea and Ashitaba Complete the Biosynthesis of Rubusoside

Dear Editor,Diterpenoids are important molecules that play significant roles in many biological processes. In plants, acyclic diterpene phytol is a representative side chain of chlorophyll, and tetracyclic diterpene gibberellins ubiquitously serve as plant hormones regulating growth and development. Decoration of diterpene core struc-tures by oxidation and glycosylation are usually key steps to confer final bioactivity of diterpenoid compounds. In contrast to the extensively studied oxidases involved in gibberellin biosyn- thesis, diterpenoid-related glycosyltransferases have been scarcely documented, possibly due to the relative rarity of diter- pene glycosides in the plant kingdom. Only a few UDP-dependent glycosyltransferases （UGTs） have been characterized to participate in diterpene glycoside biosynthesis （Richman et al., 2005; Nagatoshi et al., 2012）.

Hydrocyanation of Unsaturated Imines Using Potassium Hexacyanoferrate(Ⅱ) as a Cyanide Source

An efficient method for the hydrocyanation of unsaturated imines to synthesizeβ,γ-unsaturatedα-aminonitriles by a one-pot two-step procedure using potassium hexacyanoferrate(Ⅱ)as a cyanide source and benzoyl chloride as a promoter under catalyst-free condition is described.The advantages of this protocol are the use of a nontoxic,nonvolatile and inexpensive cyanating agent,no use of transition metal catalysts,high yield and simple work-up procedure.