The 3D nanoimaging beamline at SSRF

Full-field transmission X-ray microscopy(TXM)is a powerful non-destructive three-dimensional(3D)imaging method with a nanoscale spatial resolution that has been used in most synchrotron facilities worldwide.An in-house-designed TXM system was constructed at the BL18B 3D nanoimaging beamline at the Shanghai Synchrotron Radiation Facility.The beamline operates from 5 to 14 keV and enables 20 nm spatial resolution imaging.The characterization details of the beamline are described in this paper.The performances in terms of spatial resolution,nano-CT,and nano-spectral imaging of the TXM beamline are also presented in this article.

The new X-ray imaging and biomedical application beamline BL13HB at SSRF

A new X-ray imaging and biomedical application beamline(BL13HB)has been implemented at the Shanghai Radiation Synchrotron Facility(SSRF)as an upgrade to the old X-ray imaging and biomedical application beamline(BL13W1).This is part of the Phase II construction project of the SSRF.The BL13HB is dedicated to 2D and 3D static and dynamic X-ray imaging,with a field of view of up to 48.5 mm×5.2 mm and spatial resolution as high as 0.8μm.A super-bending magnet is used as the X-ray source in BL13HB,which has a maximum magnetic field of 2.293 T.The energy range of monochromatic X-ray photons from a double-multiplayer monochromator was 8–40 keV,and the white beam mode was provided on the beamline for dynamic X-ray imaging and dynamic X-ray micro-CT.While maintaining the previous experimental setup of BL13W1,new equipment was added to the beamline experimental station.The beamline is equipped with different sets of X-ray imaging detectors for several experimental methods such as micro-CT,dynamic micro-CT,and pair distribution function.The experimental station of BL13HB is designed specifically for various in situ dynamic experiments,and BL13HB has been open to users since June 2021.

Methodology development and application of X-ray imaging beamline at SSRF

This paper introduces some latest developments regarding the X-ray imaging methodology and applications of the X-ray imaging and biomedical application beamline(BL13W1)at Shanghai Synchrotron Radiation Facility in the past 5 years.The photon energy range of the beamline is 8–72.5 keV.Several sets of X-ray imaging detectors with different pixel sizes(0.19–24 lm)are used to realize X-ray microcomputed tomography(X-ray micro-CT)and X-ray in-line phase-contrast imaging.To satisfy the requirements of user experiments,new X-ray imaging methods and image processing techniques are developed.In vivo dynamic micro-CT experiments with living insects are performed in 0.5 s(sampling rate of 2 Hz,2 tomograms/s)with a monochromatic beam from a wiggler source and in 40 ms(sampling rate of 25 Hz,25 tomograms/s)with a white beam from a bending magnet source.A new X-ray imaging method known as move contrast X-ray imaging is proposed,with which blood flow and moving tissues in raw images can be distinguished according to their moving frequencies in the time domain.Furthermore,X-ray speckle-tracking imaging with twice exposures to eliminate the edge enhancement effect is developed.A high-precision quantification method is realized to measure complex three-dimensional blood vessels obtained via X-ray micro-CT.X-ray imaging methods such as three-dimensional X-ray diffraction microscopy,small-angle X-ray scattering CT,and X-ray fluorescence CT are developed,in which the X-ray micro-CT imaging method is combined with other contrast mechanisms such as diffraction,scattering,and fluorescence contrasts respectively.Moreover,an X-ray nano-CT experiment is performed with a 100 nm spatial resolution.Typical user experimental results from the fields of material science,biomedicine,paleontology,physics,chemistry,and environmental science obtained on the beamline are provided.

Nanofabrication of 50 nm zone plates through e-beam lithography with local proximity effect correction for x-ray imaging

High resolution Fresnel zone plates for nanoscale three-dimensional imaging of materials by both soft and hard x-rays are increasingly needed by the broad applications in nanoscience and nanotechnology.When the outmost zone-width is shrinking down to 50 nm or even below,patterning the zone plates with high aspect ratio by electron beam lithography still remains a challenge because of the proximity effect.The uneven charge distribution in the exposed resist is still frequently observed even after standard proximity effect correction(PEC),because of the large variety in the line width.This work develops a new strategy,nicknamed as local proximity effect correction(LPEC),efficiently modifying the deposited energy over the whole zone plate on the top of proximity effect correction.By this way,50 nm zone plates with the aspect ratio from 4:1 up to 15:1 and the duty cycle close to 0.5 have been fabricated.Their imaging capability in soft(1.3 keV)and hard(9 keV)x-ray,respectively,has been demonstrated in Shanghai Synchrotron Radiation Facility(SSRF)with the resolution of 50 nm.The local proximity effect correction developed in this work should also be generally significant for the generation of zone plates with high resolutions beyond 50 nm.

X-ray fluorescence microtomography based on polycapillary- focused X-rays from laboratory source

X-ray fluorescence microtomography(μXFCT)is a nondestructive analytical technique and has been widely used to nondestructively detect and quantify the elemental composition and distributions in samples. Usually, synchrotron radiation X-rays are used for μXFCT, due to its high flux density. In this paper, a laboratory-sourcebased μXFCT system was developed, in which a polycapillary lens is employed to focus the X-ray beam and improve the flux density. The maximum likelihood expectation maximization algorithm was used to reconstruct the computed tomography slices at a limited number of projections. The experimental results demonstrated that the developed system could reveal the elemental distribution inside the test sample, with an elemental sensitivity of 1000 ppm.

Calibrating the linearity between grayscale and element content for X-ray KES imaging of alloys

Doped elements in alloys significantly impact their performance.Conventional methods usually sputter the surface material of the sample,or their performance is limited to the surface of alloys owing to their poor penetration ability.The X-ray K-edge subtraction(KES)method exhibits great potential for the nondestructive in situ detection of element contents in alloys.However,the signal of doped elements usually deteriorates because of the strong absorption of the principal component and scattering of crystal grains.This in turn prevents the extensive application of X-ray KES imaging to alloys.In this study,methods were developed to calibrate the linearity between the grayscale of the KES image and element content.The methods were aimed at the sensitive analysis of elements in alloys.Furthermore,experiments with phantoms and alloys demonstrated that,after elaborate calibration,X-ray KES imaging is capable of nondestructive and sensitive analysis of doped elements in alloys.

Characterization of full-length transcriptome and mechanisms ofsugar accumulation in Annona squamosa fruit

Annona squamosa is a multipurpose fruit tree employed in nutritional,medicinal,and industrial fields.Its fruit is significantly enriched in sugars,making it an excellent species to study sugar accumulation in fruit.However,the scarcity of genomic resources hinders genetic studies in this species.This study aimed at generating large-scale genomic resources in A.squamosa and deciphering the molecular basis of its high sugar content.Herein,we sequenced and characterized the full-length transcriptome of A.squamosa fruit using PacBio Iso-seq.In addition,we analyzed the changes in sugar content over five fruit growth and ripening stages,and we applied RNA-sequencing technology to investigate the changes in gene expression related to sugar accumulation.A total of 783,647 circular consensus sequences were generated,from which we obtained 48,209 high-quality,full-length transcripts.Additionally,1,838 transcription factors and 1,768 long non-coding RNAs were detected.Furthermore,we identified 10,400 alternative splicing events from 2,541 unigenes having on average 2–4 isoforms.A total of 15,061 simple sequence repeat(SSR)motifs were discovered and up to three primer pairs were designed for each SSR locus.Sugars mainly accumulate during the ripening stage in A.squamosa.Most of the genes involved in sugar transport and metabolism in the fruit were progressively repressed overgrowth and ripening stages.However,sucrose phosphate synthase involved in sucrose synthesis and more importantly,isoamylase,alpha-amylase,beta-amylase,4-alphaglucanotransferase genes involved in starch degradation displayed positive correlations with sugar accumulation in fruit.Overall,we provide here a high-quality,full-length transcriptome assembly which will facilitate gene discovery and molecular breeding of A.squamosa.We found that starch degradation during fruit ripening was the main channel for sugar accumulation in A.squamosa fruit,and the key genes positively linked to sugar accumulation could be further studied to identify targets for controlling sugar content in A.squamosa fruit.

La掺杂的TiO_(2)纳米棒在常温常压下可促进电催化的N_(2)转化为NH_(3)

氨在化肥、染料、药品和炸药的制造中起着重要作用。目前,传统的Haber-Bosch工艺主要用于NH_(3)的大规模工业化生产,在苛刻的反应条件(300-500℃,150-300 atm)下不可避免地伴随着温室气体的过量排放.因此,必须寻求一种绿色并且可持续的方法来生产NH_(3).电化学还原N_(2)(NRR)已成为在环境条件下将N_(2)连续固定NH_(3)的一种有吸引力的替代方法.由于稳定的N≡N具有较强的偶极矩并与析氢反应存在激烈竞争,因此需要高效的NRR催化剂.TiO_(2)是典型的n型半导体,被认为是一种很有前途的NRR电催化剂.最近的研究表明,La2O3对N_(2)还原电催化也具有活性,然而镧金属的稀土性质限制了其大规模应用.本文研究发现镧可以作为一种有效的掺杂剂提高TiO_(2)的NRR活性.通过水热法制备了镧掺杂的TiO_(2)纳米棒(La-TiO_(2)).透射电子显微镜结果表明,原始TiO_(2)与La-TiO_(2)在形貌上都是纳米棒,镧的引入对其形貌并没有显著影响.选区电子衍射证实了La-TiO_(2)纳米棒的高结晶度和四边形单晶结构.电子自旋共振分析结果表明La-TiO_(2)纳米棒中存在氧空位.La-TiO_(2)的线性扫描伏安曲线结果表明,在N?饱和电解液中的电流密度明显大于在Ar饱和电解液中,说明NRR的发生.为了进一步证实这一假设,在五个不同电位下分别进行了一系列的计时电流测试,结果表明,连续电解2h后在-0.70V时,NH_(3)产率最高,达23.06μg h^(-1) mg_(Cat)^(-1),并且法拉第效率也最大,达14.54%.此外,电解2 h后,没有检测到副产物表明La-TiO_(2)催化剂对NHj合成具有良好的选择性.本文还比较了La-TiO_(2)/CP,TiO_(2)/CP和CP的NRR电催化性能,结果表明,La-TiO_(2)/CP的NH_(3)产率最高,说明La的引入提高了La-TiO_(2)的NRR活性.La-TiO_(2)/CP通过在-0.70V下连续6次循环测试以及连续48 h电解测试证实La-TiO_(2)对NRR电催化具有良好的电化学稳定性.通过对La-O_(v)构型进行密度泛函理论计算,重点研究*N_(2)+H^(+)+e^(-)→*NNH的反应步骤,由于*N_(2)加氢的自由能垒较低,La-TiO_(2)更容易激活N_(2)分子,计算了La-TiO_(2)和纯TiO_(2)上*NNH中间体的电荷密度差异,*NNH与La-TiO_(2)之间存在更多的电荷转移.采用N-N键的积分晶体轨道哈密顿布居(ICOHP)分析出La-TiO_(2)的ICOHP负值较小(-16.67 vs.-19.93),说明N-N键的活化更多.

Autophagy-associated long non-coding RNA signature for lung adenocarcinoma

Background:Autophagy-associated long non-coding RNAs(aalncRNAs)take an important position in the tumorigeness of lung cancer,but current researches have not systematically investigated autophagy-associated lncRNAs in lung adenocarcinoma(LUAD).Methods:In this research,RNA-sequences of LUAD patients were downloaded from the TCGA and autophagy-associated genes were obtained from the GSEA website.The Pearson's test was conducted to find the correlation between autophagy-associated lncRNAs and autophagy-associated genes.AalncRNAs with prognostic significance were identified by using Cox and LASSO regression analysis in R,gradually.Risk score model was built to estimate prognosis-associated lncRNAs.Results:A risk score model was established according to the expressions of 7 aalncRNAs(RP11-102K13.5,RP11-1029J19.4,LINC00942,KLHL7-AS1,AC092198.1,C20orf197,LINC01116),and low-risk group was found to have a better prognosis(P<0.001).Next,single gene expression survival analysis show that 4 out of these lncRNAs were significantly associated with the survival of patients.In addition,the AUC value of model reached 0.724,demonstrating the good predictive ability of the model.Conclusion:These aalncRNAs in LUAD might possibly offered biological markers for the diagnosis and therapy of lung adenocarcinoma.

CoFe-LDH nanowire arrays on graphite felt: A high-performance oxygen evolution electrocatalyst in alkaline media

Developing non-noble-metal oxygen evolution reaction(OER) electrocatalysts with high performance is critical to electrocatalytic water splitting. In this work, we fabricated Co Fe-layered double hydroxide(LDH) nanowire arrays on graphite felt(Co Fe-LDH/GF) via a hydrothermal method. The Co Fe-LDH/GF, as a robust integrated 3 D OER anode, exhibits excellent catalytic activity with the need of low overpotential of 252 and 285 mV to drive current densities of 10 and 100 mA/cm^(2) in 1.0 mol/L KOH, respectively. In addition, it also maintains electrochemical durability for at least 24 h. This work would open up avenues for the development of GF like attractive catalyst supports for oxygen evolution applications.

Megapixel X-ray ghost imaging with a binned detector in the object arm

At present,reconstruction of megapixel and high-fidelity images with few measurements is a major challenge for X-ray ghost imaging(XGI).The available strategies require massive measurements and reconstruct low-fidelity images of less than 300 × 300 pixels.Inspired by the concept of synthetic aperture radar,synthetic aperture XGI(SAXGI)integrated with compressive sensing is proposed to solve this problem with a binned detector in the object arm.Experimental results demonstrated that SAXGI can accurately reconstruct the 1200 × 1200 pixels image of a binary sample of tangled strands of tungsten fiber from 660 measurements.Accordingly,SAXGI is a promising solution for the practical application of XGI.

Remote sensing detection and verification of disappeared reservoirs along the Grand Canal of China

Digital Earth is an information-rich expression of the real Earth and is a new way of understanding the Earth in the twenty-first century.Archeology has found great potentialities in Digital Earth,strongly increasing its development and its interdisciplinary experimentations.With the rapid development of remote sensing,the importance of applying Earth observation technology to archeological research has caught a great amount of attention worldwide.The objective of this study is to apply Radarsat-1 and Landsat imagery,historical maps,and aerial photographs in the detection and verification of disappeared reservoirs built 500 years ago as part of the Grand Canal of China.The results of the study show that the potential sites present distinct variations in soil moisture,biomass,and biological vigor,characterized by weak backscattering in Radarsat imagery;high vegetation indices in Landsat imagery;and distinct anomalies in a Landsat principle components image.Historical maps and aerial photographs also verified the existence of the sites of disappeared reservoirs.Since the sites have so far not been extensively explored,the results should represent a significant contribution to the understanding of the Grand Canal of China and its auxiliary facilities.

Light output improvement of GaN-based light-emitting diodes grown on Si (111) by a via-thin-film structure

This work reports the fabrication of via-thin-film light-emitting diode （via-TF-LED） to improve the light output power （LOP） of blue/white GaN-based LEDs grown on Si （111） substrates. The as-fabricated via-TF-LEDs were featured with a roughened n-GaN surface and the p-GaN surface bonded to a wafer carrier with a silver-based reflective electrode, together with an array of embedded n-type via pillar metal contact from the p-GaN surface etched through the multiple-quantum-wells （MQWs） into the n-GaN layer. When operated at 350 mA, the via-TF- LED gave an enhanced blue LOP by 7.8% and over 3.5 times as compared to the vertical thin-film LED （TF-LED） and the conventional lateral structure LED （LS-LED）. After covering with yellow phosphor that converts some blue photons into yellow light, the via-TF-LED emitted an enhanced white luminous flux by 13.5% and over 5 times, as compared with the white TF-LED and the white LS-LED, respectively. The significant LOP improve- ment of the via-TF-LED was attributed to the elimination of light absorption by the Si （111） epitaxial substrate and the finger-like n-electrodes on the roughened emitting surface.

A general White–Box strategy for designing thermoelectric cooling system

Thermoelectric cooling(TEC)is critically important in thermal management of laser modules or chips and potentially for personalized thermoregulation.The formulae for efficiency in standard textbooks can only describe the performance of a TEC module with ideal thermal conditions,that is,fixed terminal temperatures,but are unable to deal with a real TEC system where heat transfer at its interfaces with the heat source and sink are finite and with thermal resistances.Here,we define the TEC system-level performance indices,that is,the maximum cooling power,temperature difference,and coefficient of performance,by introducing a set of explicit formulae.The external heat transfer conditions are taken into account as dimensionless thermal resistance parameters.With these formulae,the TEC system performances are evaluated elegantly with errors well within±5%over broad operating conditions.We further optimize the cooling power and the coefficient of performance in practical scenarios and establish a general White–Box design procedure for TEC systems,which enables a transparent design process and straightforward analysis of performance bottlenecks.A set of cooling experiments are performed to validate the analytical model and to illustrate the dependence of system design on realistic thermal conditions.By choosing the suitable TEC module parameter under given external heat transfer conditions,the cooling power can be improved by more than 100%.This work sheds some light on the integral design of TEC systems for broad applications to take full advantage of the advanced thermoelectric materials in the cooling field.