Temporal heterogeneity in climatic responses of four tree species in the Altai Mountains, northwest China

In the context of ongoing climate change,rela-tionships between tree growth and climate present uncertain-ties,which limits the predictions of future forest dynamics.Northwest China is a region undergoing notable warming and increased precipitation;how forests in this region will respond to climate change has not been fully understood.We used dendrochronological methods to examine the rela-tionship between climate and the radial growth of four tree species in a riparian forest habitat in Altai region:European aspen(Populus tremula),bitter poplar(Populus laurifolia),Swedish birch(Betula pendula),and Siberian spruce(Picea obovata).The results reveal that European aspen was insen-sitive to climate changes.In contrast,bitter poplar showed a positive response to elevated temperatures and negative to increased moisture during the growing season.Swedish birch and Siberian spruce were adversely affected by higher temperatures but benefited from increased precipitation.A moving correlation analysis suggested that,against a back-drop of continuous warming,growth patterns of these spe-cies will diverge:European aspen will require close moni-toring,bitter poplar may likely to show accelerated growth,and the growth of Swedish birch and Siberian spruce may be inhibited,leading to a decline.These findings offer insight into the future dynamics of riparian forests under changing climate.

Fabrication and Optical Properties of Silicon Nanowires Arrays by Electroless Ag-catalyzed Etching

In order to realize ultralow surface reflectance and broadband antireflection effects which common pyramidal textures and antireflection coatings can't achieve in photovoltaic industry,we used low-cost and easy-made Ag-catalyzed etching techniques to synthesize silicon nanowires(Si NWs) arrays on the substrate of single-crystalline silicon.The dense vertically-aligned Si NWs arrays are fabricated by local oxidation and selective dissolution of Si in etching solution containing Ag catalyst.The Si NWs arrays with 3 μm in depth make reflectance reduce to less than 3% in the range of 400 to 1000 nm while reflectance gradually reached the optimum value with the increasing of etching time.The antireflection of Si NWs arrays are based on indexgraded mechanism:Si NWs arrays on a subwavelength scale strongly scatter incident light and have graded refractive index that enhance the incidence of light in usable wavelength range.However,surface recombination of Si NWs arrays are deteriorated due to numerous dangling bonds and residual Ag particles.

Convenient design of anti-wetting nano-Al/WO_(3)metastable intermolecular composites(MICs)with an enhanced exothermic life-span

For solving the dilemma of the short exothermic life-span of WO_(3)based metastable interstitial composites(MICs)with extensive application prospect,this paper has firstly designed the promising antiwetting Al/WO_(3)MICs via electrophoresis assembly of nano-Al and WO_(3)particles fabricated by hydrothermal synthesis method,followed by the subsequent fluorination treatment.A combination of X ray diffraction(XRD),field emission scanning electron microscope(FESEM),energy dispersive X-ray spectroscopy(EDX),and Fourier transform infrared spectroscopy(FT-IR)techniques were utilized in order to characterize the crystal structure,microstructure,and elemental composition distribution of target films after different natural exposure tests.The product with uniform distribution and high purity possesses a high contact angle of~170°and a minute sliding angle of~1°,and displays the outstanding anti-wetting property using droplets with different surface tensions.It also shows great moisture stability in high relative-humidity circumstances after one year of the natural exposure experiment.Notably,the heat output of a fresh sample can reach up to 2.3 kJ/g and retain 96%after the whole exposure test,showing outstanding thermo-stability for at least one year.This work further proposed the mechanism of antiwetting Al/WO_(3)MICs considering the variation tendency of their DSC curve,providing a valuable theoretical reference for designing other self-protected MICs with a long exothermic life-span applied in wide fields of national defense,military industry,etc.

Optical second-harmonic generation of Janus MoSSe monolayer

The transition metal dichalcogenides(TMD)monolayers have shown strong second-harmonic generation(SHG)ow-ing to their lack of inversion symmetry.These ultrathin layers then serve as the frequency converters that can be intergraded on a chip.Here,taking MoSSe as an example,we report the first detailed experimental study of the SHG of Janus TMD monolayer,in which the transition metal layer is sandwiched by the two distinct chalcogen layers.It is shown that the SHG effectively arises from an in-plane second-harmonic polarization under paraxial focusing and detection.Based on this,the orientation-resolved SHG spectroscopy is realized to readily determine the zigzag and armchair axes of the Janus crystal with an accuracy better than±0.6°.Moreover,the SHG intensity is wavelength-dependent and can be greatly enhanced(~60 times)when the two-photon transition is resonant with the C-exciton state.Our findings uncover the SHG properties of Janus MoSSe monolayer,therefore lay the basis for its integrated frequency-doubling applications.

Characterization and performance of Pt/SBA-15 for low-temperature SCR of NO by C_3H_6

Pt supported on mesoporous silica SBA-15 was investigated as a catalyst for low temperature selective catalytic reduction（SCR） of NO by C 3 H 6 in the presence of excess oxygen.The prepared catalysts were characterized by means of XRD,BET surface area,TEM,NO-TPD,NO/C 3 H 6-TPO,NH 3-TPD,XPS and 27 Al MAS NMR.The effects of Pt loading amount,O 2 /C 3 H 6 concentration,and incorporation of Al into SBA-15 have been studied.It was found that the removal efficiency increased significantly after Pt loading,but an optimal loading amount was observed.In particular,under an atmosphere of 150 ppm NO,150 ppm C 3 H 6,and 18 vol.% O 2,0.5% Pt/SBA-15 showed remarkably high catalytic performance giving 80.1% NOx reduction and 87.04% C 3 H 6 conversion simultaneously at 140°C.The enhanced SCR activity of Pt/SBA-15 is associated with its outstanding oxidation activities of NO to NO 2 and C 3 H 6 to CO 2 in low temperature range.The research results also suggested that higher concentration of O 2 and higher concentration of C 3 H 6 favored NO removal.The incorporation of Al into SBA-15 improved catalytic performance,which could be ascribed to the enhancement of catalyst surface acidity caused by tetrahedrally coordinated AlO 4.Moreover,the catalysts could be easily reused and possessed good stability.

Perovskite quantum dot lasers

Owing to the excellent properties of perovskite quantum dots(QDs),such as an easy synthesis process,high photoluminescence quantum yields,high defect tolerance,and tunable bandgap with different elements,laser actions have been widely conducted.Over the past few years,several approaches have been used for successfully creating perovskite QD lasers.In this review,we summarize the progress of perovskite QD lasers from the aspects of laser theory,characteristics and applications of QD lasers,advantages of perovskite materials for lasers,factors influencing the QD laser threshold,two-photon pumped QD lasers,and perovskite QD laser stability.At the same time,aiming at existing problems,possible solutions and prospects are presented.

Cavity engineering of two-dimensional perovskites and inherent light-matter interaction

Two-dimensional(2D)perovskites are hybrid layered materials in which the inorganic lattice of an octahedron is sandwiched by organic layers.They behave as a quantum-well structure exhibiting large exciton binding energy and high emission efficiency,which is excellent for photonic applications.Hence,the cavity modulation and cavity devices of 2D perovskites are widely investigated.In this review,we summarize the rich photophysics,synthetic methods of different cavity structures,and the cavity-based applications of 2D perovskites.We highlight the strong exciton–photon coupling and photonic lasing obtained in different cavity structures.In addition,functional optoelectronic devices using cavity structures of 2D perovskites are also reviewed.

Space-confined and substrate-directed synthesis of transition-metal dichalcogenide nanostructures with tunable dimensionality

Atomically thin transition-metal dichalcogenide(TMDC) nanostructures are predicted to exhibit novel physical properties that make them attractive candidates for the fabrication of electronic and optoelectronic devices. However, TMDCs tend to grow in the form of two-dimensional nanoplates(NPs) rather than one-dimensional nanoribbons(NRs) due to their native layered structure. Herein, we have developed a space-confined and substrate-directed chemical vapor deposition strategy for the controllable synthesis of WS2, WSe2, MoSe2, MoS2, WS2(1-x)Se2x NPs and NRs. TMDC NRs with lengths ranging from several micrometers to 100 μm have been obtained and the widths of TMDC NRs can be effectively tuned.Moreover, we found that TMDC NRs show different growth behaviors on van der Waals(vdW) and nonvd W substrates. The micro-nano structures, optical and electronic properties of synthesized TMDC NRs have been systematically investigated. This approach provides a general strategy for controllable synthesis of TMDC NRs, which makes these materials easily accessible as functional building blocks for novel optoelectronic devices.

An on-Si directional second harmonic generation amplifier for MoS2/WS2 heterostructure

Transition metal dichalcogenides(TMD)heterostructure is widely applied for second harmonic generation(SHG)and holds great promises for laser source,nonlinear switch,and optical logic gate.However,for atomically thin TMD heterostructures,low SHG conversion efficiency would occur due to reduction of light-matter interaction length and lack of phase matching.Herein,we demonstrated a facile directional SHG amplifier formed by MoS2/WS2 monolayer heterostructures suspended on a holey SiO_(2)/Si substrate.The SHG enhancement factor reaches more than two orders of magnitude in a wide spectral range from 355 to 470 nm,and the radiation angle is reduced from 38°to 19°indicating higher coherence and better emission directionality.The giant SHG enhancement and directional emission are attributed to the great excitation and emission field concentration induced by a self-formed vertical Fabry-Pérot microcavity.Our discovery gives helpful insights for the development of two-dimensional(2D)nonlinear optical devices.

上海市宝山区未签约中青年居民对家庭医生签约服务需求状况的分析

目的分析上海市宝山区未签约中青年居民对家庭医生签约服务的需求状况。方法本研究为横断面调查。2021年6月,按照分层随机抽样方法在上海市宝山区抽取18~60岁居民进行线上问卷调查,评估702名未签约中青年居民对五类签约服务(电子健康档案建立、更新与查询,日常检测项目,健康促进,诊疗便利,居家服务)需求程度,进一步分析对不同签约服务需求程度的影响因素。结果五类签约服务中,未签约中青年对“诊疗便利”[3.8(3.0,5.0)]和“居家服务”[4.0(3.0,5.0)]的服务需求相对最高,对“电子健康档案建立、更新与查询”[3.0(2.0,5.0)]和“健康促进”[3.0(2.0,5.0)]的服务需求相对较低。不同性别、年龄、学历、户籍以及家庭月收入的人群对五类签约服务项目的需求差异均有统计学意义(均P<0.05)。不同医保类型的青年居民对除“电子健康档案建立、更新与查询”外四类签约服务的需求差异有统计学意义(均P<0.05)。Logistic回归显示,女性(OR=1.83,P<0.001)、高学历(OR=4.81,P=0.019)、上海户籍(OR=1.80,P=0.004)对“诊疗便利”的需求更高。女性(OR=1.68,P=0.001)、高学历(OR=4.56,P=0.023)对“居家服务”需求更高。结论上海市宝山区未签约中青年居民的签约服务需求存在差异,但“便捷性服务”为普遍签约关注点。可针对未签约中青年不同特征,提供契合其需求的多元化签约服务。

Few-layered organic single-crystalline heterojunctions for high-performance phototransistors

Photogating and electrical gating are key physical mechanisms in organic phototransistors(OPTs).However,most OPTs are based on thick and polycrystalline films,which leads to substantially low efficiency of both photogating and electrical gating and thus reduced photoresponse.Herein,high-performance OPTs based on few-layered organic single-crystalline heterojunctions are proposed and the obstacle of thick and polycrystalline films for photodetection is overcome.Because of the molecular scale thickness of the type I organic single-crystalline heterojunctions in OPTs,both photogating and electrical gating are highly efficient.By synergy of efficient photogating and electrical gating,key figures of merit of OPTs reach the highest among those based on planar heterojunctions so far as we know.The production of few-layered organic single-crystalline heterojunctions will provide a new type of advanced materials for various applications.

Carrier mobility tuning of MoS_(2) by strain engineering in CVD growth process

Strain engineering is proposed to be an effective technology to tune the properties of two-dimensional(2D)transition metal dichalcogenides(TMDCs).Conventional strain engineering techniques(e.g.,mechanical bending,heating)cannot conserve strain due to their dependence on external action,which thereby limits the application in electronics.In addition,the theoretically predicted strain-induced tuning of electrical performance of TMDCs has not been experimentally proved yet.Here,a facile but effective approach is proposed to retain and tune the biaxial tensile strain in monolayer MoS_(2) by adjusting the process of the chemical vapor deposition(CVD).To prove the feasibility of this method,the strain formation model of CVD grown MoS_(2) is proposed which is supported by the calculated strain dependence of band gap via the density functional theory(DFT).Next,the electrical properties tuning of strained monolayer MoS_(2) is demonstrated in experiment,where the carrier mobility of MoS_(2) was increased by two orders(~0.15 to~23 cm^(2)·V^(−1)·s^(−1)).The proposed pathway of strain preservation and regulation will open up the optics application of strain engineering and the fabrication of high performance electronic devices in 2D materials.

Low-temperature selective catalytic reduction of NO with NH_(3) based on MnO_(x)-CeO_(x)/ACFN

MnO_(x)-CeO_(x)/ACFN were prepared by the impregnation method and used as catalyst for selective catalytic reduction of NO with NH_(3) at 80℃-150℃.The catalyst was characterized by N_(2)-BET,scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR).The fraction of the mesopore and the oxygen functional groups on the surface of activated carbon fiber(ACF)increased after the treatment with nitric acid,which was favorable to improve the catalytic activities of MnO_(x)-CeO_(x)/ACFN.The experimental results show that the conversion of NO is nearly 100%in the range 100℃-150℃under the optimal preparation conditions of MnO_(x)-CeO_(x)/ACFN.In addition,the effects of a series of performance parameters,including initial NH3 concentration,NO concentration and O_(2) concentration,on the conversion of NO were studied.

Estimation of fine root production, mortality and turnover with Minirhizotron in Larix gmelinii and Fraxinus mandshurica plantations

Fine root turnover is a major pathway for carbon and nutrient cycling in forest ecosystems.However,to estimate fine root turnover,it is important to first understand the fine root dynamic processes associated with soil resource availability and climate factors.The objectives of this study were:(1)to examine patterns of fine root production and mortality in different seasons and soil depths in the Larix gmelinii and Fraxinus mandshurica plantations,(2)to analyze the correlation of fine root production and mortality with environmental factors such as air temperature,precipitation,soil temperature and available nitrogen,and(3)to estimate fine root turnover.We installed 36 Minirhizotron tubes in six monospecific plots of each species in September 2003 in the Mao’ershan Experimental Forest Station.Minirhizotron sampling was conducted every two weeks from April 2004 to April 2005.We calculated the average fine root length,annual fine root length production and mortality using image data of Minirhizotrons,and estimated fine root turnover using three approaches.Results show that the average growth rate and mortality rate in L.melinii were markedly smaller than in F.mandshurica,and were highest in the surface soil and lowest at the bottom among all the four soil layers.The annual fine root production and mortality in F.mandshurica were significantly higher than in L.gmelinii.The fine root production in spring and summer accounted for 41.7% and 39.7% of the total annual production in F.mandshurica and 24.0% and 51.2% in L.gmelinii.The majority of fine root mortality occurred in spring and summer for F.mandshurica and in summer and autumn for L.gmelinii.The turnover rate was 3.1 a^(-1) for L.gmelinii and 2.7 a^(-1) for F.mandshurica.Multiple regression analysis indicates that climate and soil resource factors together could explain 80% of the variations of the fine root seasonal growth and 95%of the seasonal mortality.In conclusion,fine root production and mortality in L.gmelinii and F.mandshurica have different patterns in different seasons and at different soil depths.Air temperature,precipitation,soil temperature and soil available nitrogen integratively control the dynamics of fine root production,mortality and turnover in both species.

Evaluation and prospect of scientific research capacity ranking for community healthcare centres in China

The National Health and Family Planning Commission of the People's Republic of China has proposed to improve the medical capacity of general practitioners and the establishment of general practice in recent health reform.For the first time,the ability to conduct scientific research was included in this reform,which demands community healthcare centres(CHCs)to strengthen their research capacity.The evaluation of community scientific research capacity has become an important endeavour to promote the implementation of research in CHCs.Since 2016,our research team has been working on an evaluation system and has published the scientific research capacity ranking for the top 100 CHCs in China.The latest released ranking of scientific research capacities of China CHCs has aroused great attention in the country.