Preparation of Film Based on Polyvinyl Alcohol Modified by Alkaline Starch and Lignin Fiber

This study presents an easily prepared film based on alkaline starch-polyvinyl alcohol hybrid and lignin fiber as an additive(SPL film).The SPL film was prepared under acidic conditions through a polycondensation reaction of PVA and a mixture incorporating alkaline starch and lignin fiber from agriculture or forest source.The examination using scanning electron microscopy(SEM)showed that the surface of SPL film was smooth and the lignin fiber had good compatibility within the film hybrid.Electrospray ionization mass spectroscopy(ESI-MS)and fourier transform infrared(FTIR)investigations indicated that alkaline starch and lignin fiber reacted with PVA under acidic conditions and that–CH_(2)–O–groups were involved in the cross-linking of the SPL system.In addition,the SPL film exhibited only 4%light transmittance,which effectively reduces the ultraviolet and visible light(UV-Vis)penetration,along with good performance when exposed to thermal degradation,in which the mass loss reached around 60%at 400℃.More-over,the SPL film acquired excellent tensile strength,which is much higher than that of PVA-lignin(PL)composite film.

A chromosome-scale genome assembly of a diploid alfalfa,the progenitor of autotetraploid alfalfa

Alfalfa(Medicago sativa L.)is one of the most important and widely cultivated forage crops.It is commonly used as a vegetable and medicinal herb because of its excellent nutritional quality and significant economic value.Based on Illumina,Nanopore and Hi-C data,we assembled a chromosome-scale assembly of Medicago sativa spp.caerulea(voucher PI464715),the direct diploid progenitor of autotetraploid alfalfa.The assembled genome comprises 793.2 Mb of genomic sequence and 47,202 annotated protein-coding genes.The contig N50 length is 3.86 Mb.This genome is almost twofold larger and contains more annotated protein-coding genes than that of its close relative,Medicago truncatula(420 Mb and 44,623 genes).The more expanded gene families compared with those in M.truncatula and the expansion of repetitive elements rather than whole-genome duplication(i.e.,the two species share the ancestral Papilionoideae whole-genome duplication event)may have contributed to the large genome size of M.sativa spp.caerulea.Comparative and evolutionary analyses revealed that M.sativa spp.caerulea diverged from M.truncatula~5.2 million years ago,and the chromosomal fissions and fusions detected between the two genomes occurred during the divergence of the two species.In addition,we identified 489 resistance(R)genes and 82 and 85 candidate genes involved in the lignin and cellulose biosynthesis pathways,respectively.The near-complete and accurate diploid alfalfa reference genome obtained herein serves as an important complement to the recently assembled autotetraploid alfalfa genome and will provide valuable genomic resources for investigating the genomic architecture of autotetraploid alfalfa as well as for improving breeding strategies in alfalfa.

Reactions with Criegee intermediates are the dominant gas-phase sink for formyl fluoride in the atmosphere

Atmospheric oxidation processes are of central importance in atmospheric climate models.It is often considered that volatile organic molecules are mainly removed by hydroxyl radical;however,the kinetics of some reactions of hydroxyl radical with volatile organic molecules are slow.Here we report rate constants for rapid reactions of formyl fluoride with Criegee intermediates.These rate constants are calculated by dual-level multistructural canonical variational transition state theory with small-curvature tunneling(DL-MS-CVT/SCT).The treatment contains beyond-CCSD(T)electronic structure calculations for transition state theory,and it employs validated density functional input for multistructural canonical variational transition state theory with small-curvature tunneling and for variable-reaction-coordinate variational transition state theory.We find that the M11-L density functional has higher accuracy than CCSD(T)/CBS for the HC(O)F+CH2OO and HC(O)F+anti-CH_(3)CHOO reactions.We find significant negative temperature dependence in the ratios of the rate constants for HC(O)F+CH2OO/anti-CH_(3)CHOO to the rate constant for HC(O)F+OH.We also find that different Criegee intermediates have different rate-determining-steps in their reactions with formyl fluoride,and we find that the dominant gas-phase removal mechanism for HC(O)F in the atmosphere is the reaction with CH2OO and/or anti-CH_(3)CHOO Criegee intermediates.

Self-synchronized temporal-spectral characterization system for revealing ultrafast fiber laser dynamics

Due to the electronic bottleneck limited real-time measurement speed of common temporal-spectral detection and the particle-like nature of optical soliton enabled nonrepeatable transient behaviors, capturing the ultrafast laser pulses with unknown times of arrival and synchronously characterizing their temporal-spectral dynamic evolution is still a challenge. Here, using the Raman soliton frequency shift based temporal magnifier and dispersive Fourier transform based spectral analyzer, we demonstrate a self-synchronized, ultrafast temporal-spectral characterization system with a resolution of 160 fs and 0.05 nm, and a recording length above milliseconds. The synchronized nonlinear process makes it possible to image full-filled temporal sub-picosecond pulse trains regardless of their arrival times and without extra pump lasers and photoelectric conversion devices. To demonstrate the significance of this improvement, a buildup dynamic process of a soliton laser with a complex breakup and collisions of multisolitons is visually displayed in the spectral and temporal domains. The soliton dynamic evolution processes observed by our characterization system are in one-to-one correspondence with the numerical simulation results. We believe this work provides a new multidimensional technique to break the electronic bottleneck to gain additional insight into the dynamics of ultrafast lasers and nonlinear science.

Single-shot measurement of wavelength-resolved state of polarization dynamics in ultrafast lasers using dispersed division-of-amplitude

Characterization of the state of polarization(SOP)of ultrafast laser emission is relevant in several application fields such as field manipulation,pulse shaping,testing of sample characteristics,and biomedical imaging.Nevertheless,since high-speed detection and wavelength-resolved measurements cannot be simultaneously achieved by commercial polarization analyzers,single-shot measurements of the wavelength-resolved SOP of ultrafast laser pulses have rarely been reported.Here,we propose a method for single-shot,wavelength-resolved SOP measurements that exploits the method of division-of-amplitude under far-field transformation.A large accumulated chromatic dispersion is utilized to time-stretch the laser pulses via dispersive Fourier transform,so that spectral information is mapped into a temporal waveform.By calibrating our test matrix with different wavelengths,wavelength-resolved SOP measurements are achieved,based on the division-of-amplitude approach,combined with high-speed opto-electronic processing.As a proof-of-concept demonstration,we reveal the complex wavelength-dependent SOP dynamics in the build-up of dissipative solitons.The experimental results show that the dissipative soliton exhibits far more complex wavelength-related polarization dynamics,which are not shown in single-shot spectrum measurement.Our method paves the way for single-shot measurement and intelligent control of ultrafast lasers with wavelength-resolved SOP structures,which could promote further investigations of polarization-related optical signal processing techniques,such as pulse shaping and hyperspectral polarization imaging.