Strong evidence for latitudinal diversity gradient in mosses across the world

Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major groups of organisms.In plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and liverworts.However,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now.Here,we analyze a comprehensive data set including moss species in each band of 20° in latitude worldwide.Our results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World) are considered separately.This result holds when variation in area size among latitudinal bands is taken into account.Pearson's correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern Hemispheres.Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.

单层MoSSe力学性质的分子动力学模拟研究

硫硒化钼(MoSSe)是一种新型二维“双面神”半导体材料,具有丰富的物理、化学、力学与电学性质.本文基于Stillinger-Weber势函数,采用分子动力学模拟方法对不同温度下的完美和含晶界MoSSe单层结构展开详细的力学行为分析.结果表明:完美单层MoSSe结构的力学性能呈现明显的各向异性;在单向拉伸作用下,其杨氏模量、强度极限和极限应变均随温度的升高而降低;当温度低于100 K时,沿锯齿形手性方向受拉伸作用的单层MoSSe结构发生由六环蜂窝相向四方相的相变,新四方相的杨氏模量约为原相结构的1.3倍且强度显著提升;当温度高于100 K时,沿锯齿形手性方向拉伸呈现脆性断裂;含晶界单层MoSSe结构受拉伸作用首先在晶界处产生裂缝,并逐步扩展至整个结构后断裂.锯齿形偏向晶界结构的强度随倾斜角度的增大而降低,扶手椅形偏向晶界结构也呈下降趋势.本研究对基于单层MoSSe的电子器件的强度设计和性能优化具有重要指导意义.

改进MOSSE的小面积滑动指纹图像追踪算法

随着指纹传感器采集的指纹图像趋向于小型化,指纹图像所包含的指纹特征信息越来越少。针对传统模板匹配算法在处理小面积滑动指纹时计算量大、精度不理想、抗干扰能力差等问题,本文提出一种基于MOSSE的改进滑动指纹追踪算法。改进MOSSE算法使用多输入,将灰度特征与HOG特征在响应层加权融合,并引入Fourier-Mellin算法、加汉宁窗用以处理发生旋转的指纹。通过多种算法对小面积指纹进行跟踪的结果进行对比,表明本算法继承了原MOSSE算法的优点,并提高了指纹匹配精度,对正常图像匹配精度为99%,对含噪声图像匹配精度为90.3%,每帧均值计算时间为0.1036 s,保证了指纹追踪的实时性,鲁棒性强,对产生形变和旋转的指纹图像也能进行很好的跟踪。

Establishment of In Vitro Regeneration System of the Atrichum Mosses

In vitro regeneration systems of Atrichum mosses, Atrichurn undulatum (Hedw.) P. Beauv. and A. undulatum var. minus (Hedw.) Par. were established. After one month, soft, friable and green calli were induced successfully from inoculated protonema of Atrichum mosses on MS medium containing glucose (4%) and 6-BA (0.2-2.0 mg/L). The suitable culture medium for the callus induction and regular subculture was MS medium with 1.0-2.0 mg/L 6-BA and 4% glucose. The calli of Atrichum mosses developed into protonema, when it was transferred to phytohormone-free MS medium with 4% glucose. Meanwhile, the calli developed into erect gametophytes through protonema phase on carbohydrate-free Benecke medium.

改进的基于特征融合MOSSE冠脉目标追踪算法

CT血管造影(computed tomography angiography,CTA)作为一种无创、检测精确较高的辅助诊断方法,尚急需能有效消除冠脉目标附近干扰噪声并寻求可全自动快速准确追踪目标的新算法以大幅减轻医生阅片压力、辅助其进行可靠诊断与治疗。提出了一种特征融合的误差最小平方和(minimum output sum of squared error,MOSSE)冠脉目标追踪新算法,通过提取冠脉血管多个特征,将其融合加入现有的MOSSE追踪方法,实现全自动准确快速追踪冠脉目标。使用河北大学附属医院9位患者(5男4女,均龄65岁,其中6位有冠心病史)的CTA数据进行了算法验证,并与文献已报道基于中心线提取和基于区域生长的现有冠脉目标提取算法进行了处理结果对比分析。结果表明,新算法处理追踪一例患者切片数据仅需耗时0.02 s,多个病例的平均准确度达94.30%,性能优于上述现有冠脉目标提取算法,能实现全自动准确高效追踪到形态变化剧烈的冠脉目标,可为冠心病的临床诊治起到更为高效的辅助作用。

真性红细胞增多症并发Mosse综合征1例

患者男,64岁,农民。以'间断腹胀、黑便20+d'入院。患者20+d前出现腹胀、乏力,以进食后加重,伴反酸,无厌油腻食物,无牙龈出血及鼻衄,无黄疸及脂肪泻等表现,但间断出现黑便,为黑色糊状便,每1~2天1次,每次量约100~200ml,无呕血,在当地医院给予内科治疗后,疗效不佳,为求进一步诊治入住我科。既往1年前因'慢性阻塞性肺疾病、消化性溃疡'多次住院治疗。体格检查:T 36.4℃,P 70次/分,R 20次/分,

Strain engineering the D-band center for Janus MoSSe edge: Nitrogen fixation

Nitrogen fixation is one of the most important and challenging process in production of ammonia at ambient temperature. We have first performed density function theory to propose the edge of Janus MoSSe(EJM) monolayer as a potential catalyst for nitrogen reduction reaction. Our results show that the superficial D-band centers play an important role in nitrogen fixation. The strain effects greatly alter the D-band center, and further change the interaction between the adsorbates and the surface of catalysts.Our findings provide a new thought into designing transition-metal chalcogenide catalysts for nitrogen fixation.

Li掺杂单层Janus MoSSe电子结构和光学性质的第一性原理研究

运用第一性原理方法,研究了不同浓度碱金属Li的掺杂对单层Janus MoSSe的电子结构和光学性质的影响。计算结果表明:Li替代掺杂后,其结合能数值均为负值,表明在掺杂过程中释放出能量,Li掺杂Janus MoSSe体系具有良好的稳定性。能带结构分析发现,Li掺杂后能在单层Janus MoSSe禁带中引入杂质能级,从而使它由直接带隙半导体变为间接带隙半导体,并减小了带隙值。其中,当掺杂物质的量分数为6.25%时,Li替代掺杂Se面时的禁带宽度减小更多,其对电子结构的调制效果更好。光学性质研究表明,Li的掺杂能改变该材料可见光区的吸收系数和静态介电常数ε(0)。Li替代掺杂增大了材料的光吸收率,使其对可见光吸收能力有所增强,具有太阳光能量收集或光催化等方面的潜在应用价值。

Early Miocene Mosses from Weichang, North China, and their Environmental Significance

Twenty-seven moss specimens collected from the Guangfayong section （Early Miocene,22.1 Ma） of the Weichang District,North China were investigated in the present study.Based on the morphological and anatomical features of gametophytes,all specimens were found to belong to three species：Leptodictyum riparium,Drepanocladus subtrichophyllus sp.nov.,and Amblystegium varium,all of which belong to the family Amblystegiaceae.The microhabitats and living environments of fossil mosses were also investigated based on comparison with living mosses.The results suggest that these mosses grew primarily at the edges of rivers,streams,and lakes and favored being submerged in streams or lakes in the Weichang District in the Early Miocene.

氢/氟化Janus MoSSe的电子结构和光学性质对比研究

采用第一性原理方法,对比研究了本征、氢/氟化Janus MoSSe电子结构和光学性质的变化。由电子结构分析发现,在氢/氟化后,材料的禁带宽度均减小了,但是氢化对其影响更剧烈。因此,氢化的方法更适合于调节材料的禁带宽度。另外,从光学性质的讨论可知,氢/氟化Janus MoSSe后材料对可见光的吸收均变强;氢化Janus MoSSe对可见光的吸收强于氟化Janus MoSSe;氢/氟化后,材料对紫外光谱的反射率明显降低。因此,氢/氟化方法均可增强Janus MoSSe对可见光的吸收,且减少材料在紫外波段的光反射。研究首次对本征、氢/氟化Janus MoSSe进行了对比,并对其潜在应用进行了预测,具有一定的指导意义。

Early Snowmelt Enhances the Carbon Sequestration of Hummock-Forming Sphagnum Mosses on Boreal Wetlands

Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditions due to global warming may affect the relations between Sphagnum mosses and vascular plants but also the competition among Sphagnum, and thus alter the accumulation of carbon on boreal wetlands. Sphagnum mosses are a plant genus with a favorable ability to grow in low solar irradiance and temperature conditions compared to vascular plants. This may be increasingly beneficial in increased wintertime temperatures and predated snowmelt conditions. To understand particularly the importance of early spring photosynthetic activity and thus the role of the length of growing season on carbon balance, we analyzed the CO2 exchange of Sphagnum mosses with closed chamber technique in two categories of microtopographical habitats, hummocks and lawns, during four seasons 2010-2013 on a raised bog in Central Finland. During CO2 exchange measurements, instantaneous net ecosystem exchange (NEE) and ecosystem respiration (RE) were measured. Our results show that the mean measured seasonal NEE, i.e. the instantaneous net carbon sequestration, of hummocks was generally only slightly higher than the NEE of lawns, but the mean measured seasonal RE of hummocks was clearly and significantly higher than the RE of lawns in every study year. A reason for the observed still higher seasonal carbon sequestration of hummocks than that of lawns besides the slightly higher rate of carbon accumulation was the longer duration of physiologically active growing season. Therefore, hummock-forming Sphagnum mosses exposed firstly from snow cover showed to get the extra time for photosynthesis and thus extra benefit compared to other mire plants. This may be further enhanced by the expansion of hummock-forming Sphagnum moss dominated raised bogs towards northern aapa-mire region due to the global warming.

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.

Discrepancies in Growth Measurement Methods of Mosses: An Example from Two Keystone Species Grown under Increased CO₂and N Supply in a Restored Peatland

Bryophytes dominate northern peatlands. Obtaining reliable measurements of moss-growth and how it may be affected by global changes are therefore important. Several methods have been used to measure moss-growth but it is unclear how comparable they are in different conditions and this uncertainty undermines comparisons among studies. In a field experiment we measured the growth and production of Sphagnum fallax (Sphagnum) and Polytrichum strictum (Polytrichum) using two handling methods, using cut and uncut plants, and three growth-variables, height-growth, length-growth, and mass-growth. We aimed “benchmarking” a combination of six methodological options against exactly the same set of factorial experiments: atmospheric CO2 enrichment and N addition. The two handling methods produced partly different results: in half of the cases, one method revealed a significant treatment effect but the other one did not: significant negative effects on growth were only observed on uncut plants for elevated CO2 and on cut plants for N addition. Furthermore, the correspondence between measurements made with various growth-variables depended on the species and, to a lesser extent, treatments. Sphagnum and Polytrichum growth was inhibited under elevated CO2, and correlated to higher ammonium values. Sphagnum was however less affected than Polytrichum and the height difference between the two species decreased. N addition reduced the P/N ratio and probably induced P-limiting conditions. Sphagnum growth was more inhibited than Polytrichum and the height difference between the two species increased. Our data show that such a problem indeed exists between the cut and uncut handling methods. Not only do the results differ in absolute terms by as much as 82% but also do their comparisons and interpretations depend on the handling method—and thus the interpretation would be biased—in half of the cases. These results call for caution when comparing factorial studies based on different handling methods.

基于感知哈希和MOSSE算法的多国钞票类型快速识别技术研究

提出了用于现金自助设备的钞票类型快速识别技术。该技术通过综合利用图像感知哈希和MOSSE(Minimum Output Sum of Squared Error)算法实现,利用图像感知哈希快速计算机制,初步筛选出可能的钞票类型,再利用MOSSE相关滤波器最终确定钞票类型。

Comparison of Mosses as Bioindicator of Heavy Metal Pollution in Aramoko-Ekiti and Are-Ekiti, Nigeria

The increasing global concern over the public health impacts attributed to environmental pollution led us to investigate and compare the deposition of some heavy metals in mosses from an urban area, Aramoko Ekiti and a rural area, Are Ekiti. Both towns are located in the SouthWest, Nigeria. Moss samples were collected at different sites in the two towns. These samples were then digested in acid and analysed for Cd, Cr, Ni, Pb and Cu, using a flame atomic absorption spectrometer. The results of the study show variations in the concentrations of the heavy metals among the different sites in each town as well as between the two towns. Apart from cd which was suspected to have originated from natural sources in the investigated samples, the relatively higher concentrations of the other metals in Aramoko-Ekiti suggests an important anthropogenic source which we suspect to be automobiles since there are little or no industrial or mining activities within the town. Furthermore, the relatively higher concentrations of the metals exhibited by moss samples collected around locations prone to higher traffic situations in the two towns such as roadsides, filling stations and garages stresses the significance of traffic density in heavy metal pollution of the environment. These places （filling stations and garages） should be sited far away from residential areas. Also, residences should be sited at considerably far distances from major roads. These will prevent the bioaccumulation of the heavy metals in residents. Though, the results show that Aramoko-Ekiti is more polluted with the heavy metals than Are-Ekiti, the concentration of the heavy metals were still within the permissible limits. Given the results of this work and similar ones, there is need to evaluate the pollution status of the environment from time to time especially the urban areas and high traffic areas.

Two-dimensional polarized MoSSe/MoTe2 van der Waals heterostructure: A polarization-tunable optoelectronic material

Two-dimensional (2D) heterostructures have shown great potential in advanced photovoltaics due to their restrained carrier recombination, prolonged exciton lifetime and improved light absorption. Herein, a 2D polarized heterostructure is constructed between Janus MoSSe and MoTe_(2) monolayers and is systematically investigated via first-principles calculations. Electronically, the valence band and conduction band of the MoSSe−MoTe_(2) (MoSeS−MoTe_(2)) are contributed by MoTe_(2) and MoSSe layers, respectively, and its bandgap is 0.71 (0.03) eV. A built-in electric field pointing from MoTe_(2) to MoSSe layers appears at the interface of heterostructures due to the interlayer carrier redistribution. Notably, the band alignment and built-in electric field make it a direct z-scheme heterostructure, benefiting the separation of photogenerated electron-hole pairs. Besides, the electronic structure and interlayer carrier reconstruction can be readily controlled by reversing the electric polarization of the MoSSe layer. Furthermore, the light absorption of the MoSSe/MoTe_(2) heterostructure is also improved in comparison with the separated monolayers. Consequently, in this work, a new z-scheme polarized heterostructure with polarization-controllable optoelectronic properties is designed for highly efficient optoelectronics.

Evaluating the quantum confinement effects modulating exciton and electronic band structures of two-dimensional layered MoSSe films and their photodetection potentials

Emerging two-dimensional ternary transition metal dichalcogenide alloys have attracted much attention for their unique optical and optoelectronic properties,making them ideal candidates for optoelectronic applications.However,a comprehensive understanding of their quantum confinement effects and photoelectronic response characteristics remains crucial for device optimization and performance enhancement.In this study,we employed various spectroscopic techniques to investigate the optical properties and electronic band structures of molybdenum sulfide selenide(MoSSe)films with different layer numbers(4–11 layers).Our results revealed the splitting of Raman modes and shifting of phonon vibrational frequencies with increasing thickness,suggesting that MoSSe has strong interactions within the lattice.The A1g and E2g 1 modes were mainly shifted by internal strain and dielectric screening effect versus thickness,respectively.The redshift phenomenon of A and B excitons with increasing thickness was attributed to the leading effect of quantum confinement on exciton properties and optical band gaps.We observed a strong decrease in the direct bandgap spectral weight in photoluminescence(PL)when the layer number increased from 4 to 5.In addition,we have fabricated MoSSe photodetectors that exhibit a broadband response in the visible wavelength band of 350–800 nm.Furthermore,the observed enhancement in photocurrent and responsivity with increasing film thickness underscored the potential of MoSSebased devices for practical optoelectronic applications.This research contributes to advancing our fundamental understanding of MoSSe materials and paves the way for the design and development of high-performance optoelectronic devices.

基于机器视觉的目标跟踪算法研究

针对遮挡情况下目标跟踪产生漂移的问题,提出一种基于MOSSE和Kalman滤波的目标跟踪算法以改善跟踪效果。算法使用MOSSE滤波器与目标图像的相关性度量来判断遮挡情况。无遮挡时,以MOSSE滤波器为主跟踪器,获取目标位置,更新MOSSE滤波器,并修正Kalman滤波器;遇到遮挡时,将Kalman滤波器设置为主跟踪器,预测目标位置,并保持MOSSE滤波器不变。实验从跟踪速度、精度、成功率等角度进行定性与定量分析,结果表明算法在遮挡情况下,实现目标的快速有效的跟踪。与同类算法比较,能有效改善遮挡情况下的跟踪效果,具有很强的鲁棒性。

Progress in the study of algae and mosses in biological soil crusts

Algae and mosses are not only two of the familiar communities in the process of desert vegetational succession,but also have the highest biomass in biological soil crusts.Meanwhile,being the pioneer plants,algae and mosses are involved in the establishment of biological soil crusts,which have great importance in arid environments and play a major role in desert ecosystems,such as being the indicator of the vegetation type,soil-holding,preventing erosion by water and wind,and sand fixation.This paper reviews the advances in the study of algae and mosses in arid and semi-arid areas.It mainly describes the ecological functions of algae and mosses including their influences on water cycle,circulation of substances,and community succession.In addition,the relationships between algae and mosses are discussed.Finally,some suggestions are proposed for the research orientations of algae and mosses in biological soil crusts.Ecologically,algae and mosses have significant ecological importance in arid areas,especially in those areas where environmental problems are becoming increasingly serious.

Nitrogen and phosphorus translocation of forest floor mosses as affected by a pulse of these nutrients

Aims Mosses are dominant in many ecosystems where nutrients from deposition are one of the main nutrient sources.However,it is difficult to evaluate mosses’role in nutrient cycling without knowledge of how mosses use deposited nutrient inputs.To fill this gap,the present study aims to investigate:(i)how nitrogen(N)and phosphorus(P)concentrations of new-grown segments change along a gradient of N or P amount in a pulse treatment?(ii)how do a pulse of major nutrient(N or P)affect N or P translocation rate along a moss shoot?and(iii)to what extent do N or P translocation rates link to nutrient status of the new-grown segments of mosses?Methods We measured N and P concentrations of segments with different ages in two dominant forest floor mosses,Actinothuidium hookeri and Hylocomium splendens,on 8 days and 1 year after N and P pulse treatment with an in situ experiment in a subalpine fir forest in eastern Tibetan Plateau.Important Findings Both mosses were efficient in taking up nutrients from a pulse of either N or P.Nitrogen and P concentrations of new-grown segments were affected by nutrient pulse treatments.These N and P concentration changes were attributed to the initial N and P concentration of the young segments harvested 8 days after nutrient pulse treatments,suggesting that the captured nutrients were reallocated to the new-grown segments via translocation,which was largely controlled by a source-sink relationship.While no significant relationship was found between N translocation rate and N:P ratio of the new-grown segments,P translocation rate explained 21%-23%of the variance of N:P ratio of the new-grown segments,implying importance of P transport in supporting the new-grown sections.These results suggest that nutrient(N,P)translocation is a key process for mosses to utilize intermittent nutrient supply,and thus make mosses an important nutrient pool of the ecosystem.