北京市学分银行建设问题研究

为了适应我国建设一个面向全民的终身教育体系,加速职业教育国家学分银行建设,北京市经过两年多的实践探索,产生了一些实践案例。本研究对当前北京市政府推进学分银行建设进行梳理和研究,阐述了北京市学分银行建设的现状,通过研究认为当前在学分银行建设中,存在法律法规不健全,制度保障不到位,平台建设资金投入不足,认证与转换标准体系建设推进缓慢,公民参与率、知晓率低,学分银行公信力低等六个方面主要问题,提出了加快法律法规体系建设,完善学分银行制度保障体系建设,加大平台投入,建设智能化学分银行应用平台,强化学分银行运行标准化体系建设,加强学分银行知晓度和参与度建设,多维度促进学分银行公信力建设的对策建议。

New CFAR target detector for SAR images based on kernel density estimation and mean square error distance

A new constant false alarm rate （CFAR） target detector for synthetic aperture radar （SAR） images is developed. For each pixel under test, both the local probability density function （PDF） of the pixel and the clutter PDF in the reference window are estimated by the non-parametric density estimation. The target detector is defined as the mean square error （MSE） distance between the two PDFs. The CFAR detection in SAR images having multiplicative noise is achieved by adaptive kernel bandwidth proportional to the clutter level. In addition, for obtaining a threshold with respect to a given probability of false alarm （PFA）, an unsupervised null distribution fitting method with outlier rejection is proposed. The effectiveness of the proposed target detector is demonstrated by the experiment result using the RADATSAT-2 SAR image.

Food Supply Values and Their Factors of Three Pond Aquaculture Ecosystems: A Case Study of Shanghai

Studies on food supply values,the basis of eco-service values,and their factors of different pond aquaculture ecosystems are helpful to explain the influences of the inputted factors and their variations among these ecosystems and provide information for stakeholders to adjust their decisions and behaviors to increase their total eco-service values. On the basis of continued records from 2011 to 2012 of 18 ponds of three pond aquaculture ecosystems,namely Litopenaeus vannamei,Macrobrachium nippponensis and carp fresh water pond aquaculture ecosystems in Qingpu,Fengxian,and Jiading,three suburban districts of Shang,this paper analyzed the costs,returns,net food supply values and their regional and temporal fluctuations. The results showed that:(1) the net food supply values of the three ecosystems are 143252. 4,135883. 7,and 52623. 1Yuan /Ha in 2011 correspondently,with the Litopenaeus vannamei pond aquaculture ecosystem(LVPAE) ranking highest and the carp pond aquaculture ecosystem(CPAE) lowest among them,and the trend was same in 2012,but the values decreased than that of 2011 with the rate of 30. 0%( LVPAE),38. 0 %( Macrobrachium nippponensis pond aquaculture ecosystem,MNPAE) and 13. 7 %( CPAE).(2)The dominant factors of the net food supply values of these ecosystems are the produce price and variable costs; fry and feed costs are the main variable factors producing the noticeable difference among the ecosystems.(3) The cost- benefit ratio of per unit product of the CPAE,LVPAE and MNPAE changed from 27. 5%,91. 7%,129. 0% in 2011 to 23. 0%,73. 8% and 63. 8% in 2012,with the CPAE ranked lowest among them in both years.(4) For all the three ecosystems,their net food supply values may not always change in same trends with their net eco-service values,if stakeholders want to keep a balance between these two types of values,MNPAE should be encouraged in these districts.

High-spatial-resolution composition analysis of micro/nanostructures with a nanoscale compositional variation

The composition of materials in a micro-/nano-devices plays a key role in determining their mechanical,physical,and chemical properties.Especially,for devices with a compositional change on nanoscale which can often be achieved by point-by-point direct writing technology using a focused ion beam(FIB),electron beam(EB),or laser beam(LB),but so far,nanoscale composition analysis of a large-area micro/nano structures with a variation composition remains a big challenge in cost,simpleness,and flexibility.Here we present a feasible route to realize large-area composition analysis with nanoscale spatial resolution by using Raman spectroscopy.We experimentally verified the capability of this method by analyzing a complex Sn-SnOx system of a microscale grayscale mask with nanoscale spatial resolution of composition.Further analyses using Auger electron spectroscopy,transmission electron microscopy,and atomic force microscopy indicated the effectiveness and practicality of our method.This work opens up a way to analyze the composition of a large-area complex system at a nanoscale spatial resolution,and the method can be extended to many other material systems.

Architecture of severe fever with thrombocytopenia syndromevirus

Dear Editor,Severe fever with thrombocytopenia syndrome(SFTS)is an acute infectious disease caused by severe fever with thrombocytopenia syndrome virus(SFTSV)and is characterized by rapid onset,high mortality and widespread distribution.The fatality rate can be as high as 10%-30%,which is significantly higher than that of the hemorrhagic fever caused by Hantavirus in the same area(Song et al.,2018).However,no effective treatments or vaccines are available yet,and the underlying pathogenic mechanisms of the virus are poorly understood.

Structures of the portal vertex reveal essential protein-protein interactions for Herpesvirus assembly and maturation

Dear Editor,Herpesviridae is a large family of double-stranded DNA(dsDNA)viruses that cause a variety of human diseases ranging from cold sores and chicken pox to congenital defects,blindness and cancer(Chayavichitsilp et al.,2009;Wang et al.,2018).In the past 70 years,substantial advances in our knowledge of the molecular biology of herpesviruses have led to insights into disease pathogenesis and management.However,the mechanism for capsid assembly that requires the ordered packing of about 4,000 protein subunits into the hexons,pentons and triplexes remains elusive.It is still a puzzle how initially identical subunits adopt both hexameric and pentameric conformations in the capsid and select the correct locations needed to form closed shells of the proper size.Biochemical and genetic studies have shown that the portal is involved in initiation of capsid assembly(Newcomb et al.,2005)and functions akin to a DNA-sensor coupling genome-packaging achieved by a genome-packaging machinery-“terminase complex”(Chen et al.,2020;Yunxiang Yang,2020)with icosahedral capsid maturation(Lokareddy et al.,2017).Structural investigations of the herpesvirus portal have proven challenging due to the small size of this dodecamer,which accounts for less than 1%of the total mass of the capsid protein layer and the technical difficulties involved in resolving non-icosahedral components of such large icosahedral viruses(diameter is∼1,250Å).Efforts of many investigators over two decades have made to reconstruct the cryo-electron microscopy(cryo-EM)structure of herpesvirus portal vertex and more recently near-atomic structures of two herpesvirus(herpes simplex virus type 1(HSV-1)and Kaposi’s sarcoma-associated herpesvirus(KSHV))portal vertices were reported(McElwee et al.,2018;Gong et al.,2019;Liu et al.,2019).

Supramolecular assembly of chloroplast NADH dehydrogenase-like complex with photosystem Ⅰfrom Arabidopsis thaliana

Cyclic electron transport/flow(CET/CEF)in chloroplasts is a regulatory process essential for the optimization of plant photosynthetic efficiency.A crucial CEF pathway is catalyzed by a membrane-embedded NADH dehydrogenase-like(NDH)complex that contains at least 29 protein subunits and associates with photosystem I(PSI)to form the NDH-PSI supercomplex.Here,we report the 3.9Åresolution structure of the Arabidopsis thaliana NDH-PSI(AtNDH-PSI)supercomplex.We constructed structural models for 26 AtNDH subunits,among which 11 are unique to chloroplasts and stabilize the core part of the NDH complex.In the supercomplex,one NDH can bind up to two PSI-light-harvesting complex I(PSI-LHCI)complexes at both sides of its membrane arm.Two minor LHCIs,Lhca5 and Lhca6,each present in one PSI-LHCI,interact with NDH and contribute to supercomplex formation and stabilization.Collectively,our study reveals the structural details of the AtNDH-PSI supercomplex assembly and provides a molecular basis for further investigation of the regulatory mechanism of CEF in plants.

Surface Exciton-Plasmon Polariton Enhanced Light Emission via Integration of Single Semiconductor Nanowires with Metal Nanostructures

The light emission enhancement behavior from single ZnO nanowires integrated with metallic contacts is investigated by micro-photoluminescence measurements.Apart from surface plasmon polaritons at the air/metal interface,the emission of a single ZnO nanowire can be coupled into guided modes of surface exciton-plasmon polaritons(SEPPs).The out-coupling avenues of SEPP guided modes are modeled in the presence of nanostructures,such as corrugation and gratings,on the metal surface.The guided modes of SEPPs in metal-contacted ZnO nanowires are calculated using the effective index method.The enhanced light emission from single semiconductor nanowires shows promise for use in highly efficient nano-emitters and nano-lasers,as well as macroscopic solid state light sources with very high efficiency.

Bending-Induced Conductance Increase in Individual Semiconductor Nanowires and Nanobelts

Reliable ohmic contacts were established in order to study the strain sensitivity of nanowires and nanobelts.Significant conductance increases of up to 113%were observed on bending individual ZnO nanowires or CdS nanobelts.This bending strain-induced conductance enhancement was confirmed by a variety of bending measurements,such as using different manipulating tips(silicon,glass or tungsten)to bend the nanowires or nanobelts,and is explained by bending-induced effective tensile strain based on the principle of the piezoresistance effect.

Low threshold random lasing in dye-doped and strongly disordered chiral liquid crystals

Random lasing was experimentally investigated in pyrromethene 597-doped strongly disordered chiral liquid crystals (CLCs) composed of the nematic liquid crystal SLC1717 and the chiral agent CB15. The concentration of the chiral agent tuned the bandgap, and disordered CLC microdomains were achieved by fast quenching of the mixture from the isotropic to the cholesteric phase. Random lasing and band edge lasing were observed synchronously, and their behavior changed with the spectral location of the bandgap. The emission band for band edge lasing shifted with the change of the bandgap, while the emission band for random lasing remained practically constant. The results show that the threshold for random lasing sharply decreases if the CLC selective reflection band overlaps with the fluorescence peak of the dye molecules and if the band edge coincides at the same time with the excitation wavelength.

Topologically tuned terahertz confinement in a nonlinear photonic chip

Compact terahertz(THz)functional devices are greatly sought after for high-speed wireless communication,biochemical sensing,and non-destructive inspection.However,controlled THz generation,along with transport and detection,has remained a challenge especially for chip-scale devices due to low-coupling efficiency and unavoidable absorption losses.Here,based on the topological protection of electromagnetic waves,we demonstrate nonlinear generation and topologically tuned confinement of THz waves in an engineered lithium niobate chip forming a wedge-shaped Su-Schrieffer-Heeger lattice.Experimentally measured band structures provide direct visualization of the THz localization in the momentum space,while robustness of the confined mode against chiral perturbations is also analyzed and compared for both topologically trivial and nontrivial regimes.Such topological control of THz waves may bring about new possibilities in the realization of THz integrated circuits,promising for advanced photonic applications.