Subjects: Biology >> Botany >> Applied botany submitted time 2024-05-15 Cooperative journals: 《广西植物》
Abstract： Rock outcrop is a typical feature of karst ecosystem, on which there are complex microhabitats and various colonized plants, but the relationship between these plants and microhabitats is not clear. Taking a tropical seasonal humid forest in Xishuangbanna as the research object in this study, we measured the morphological characteristics and external environmental factors of 586 microhabitats on rock outcrops surface. All colonized vascular species on these microhabitats were identified and counted. Then, Pearson correlation analysis and redundancy analysis (RDA) were used to reveal the relationship between microhabitats (including morphological characteristics and environmental factors) and vascular plants richness. The results were as follows: (1) In tropical karst forest, the microhabitat characteristic such as soil depth [(4.92±4.00)] cm and area [(532.28±1 575.10) cm2] have great variability. (2) A total of 1 518 individuals of 90 species belonging to 82 genera and 44 families were recorded in all microhabitats, and karst preferent species that dominants on limestone accounted for 35.6%. (3) The area size and soil depth of microhabitat can explain more than 70% of species composition and colonized plants richness in RDA model. (4) The species-area relationship between the richness of the colonized plants and the area of rock outcrops microhabitats shows an obvious exponential decay. In conclusion, microhabitats on rock outcrops in the tropical karst forest is highly heterogeneous, the area size and soil depth are the key factors affecting plant colonization, and the species-area relationship dominates the species richness pattern on rock outcrops microhabitats.
Subjects: Biology >> Botany >> Applied botany submitted time 2024-05-15 Cooperative journals: 《广西植物》
Abstract： The updated List of National Key Protected Wild Plants (LNKPWP) was released by 1National Forestry and Grassland Administration and Ministry of Agriculture and Rural Affairs of China in September 2021. By integrating literature search, herbarium record, field investigation and expert consultation, we compiled the updated list, investigated the geographic map, research progresses, threatened status, and protection status of National Key Protected Wild Plants (NKPWP) in Hubei Province. The results were as follows: (1) There are 155 species on the LNKPWP in Hubei Province, of which 11 species belong to Category I and the remaining 144 species belong to Category II. (2) Geographic distribution of NKPWP in Hubei Province is uneven and concentrated in west and southwest areas, with Shennongjia and Lichuan have the greatest numbers of NKPWP. (3) The most studied species are the species with economic value, flagship species and regional representative species. In addition, more than a third of the species (55 species) were almost unstudied. The research of NKPWP in Hubei Province focused on genetic diversity, genetic structure, future distribution prediction under global change conditions, and phylogeography. (4) According to the “China Red List of Biodiversity-Higher Plants Volume”, the NKPWP in Hubei Province contain 9 critically endangered species, 30 endangered species, 41 vulnerable species and 19 near-threatened species. The main threatened factors are direct mining or logging, habitat degradation or loss, and species intrinsic factors. (5) Until now, 137 species(88%) of NKPWP in Hubei Province are wholly or partially located in protected areas, and the remaining 18 species (12%) are completely located outside protected areas. At present, 93 species of NKPWP have been introduced and cultivated in Hubei Province, while the other 62 species have not been recorded under ex situ conservation. In addition, very few species have been reintroduced into the wild. (6) At present, although the distribution ranges of seven wild plants in Hubei Province (five of which are endemic to Hubei) are limited and they are negatively affected by internal causes and human interference, they have not been included in the LNKPWP. In addition, this study points out the knowledge gaps in the research and protection of NKPWP in Hubei Province, and puts forward specific research suggestions and protection strategies.
Subjects: Biology >> Botany >> Applied botany submitted time 2024-05-15 Cooperative journals: 《广西植物》
Abstract： Based on the 25 ha karst forest big plot in Gulinqing, Yunnan, through sample-plot investigation, specimen collection and identification, floristic analysis, Jaccard similarity coefficient and PCA, we explored its floristic characteristics and the status of the Gulinqing big plot in Yunnnan and the geographical relationships among Gulinqing in Yunnan, Bubeng in Yunnan, and Nonggang in Guangxi, China. The results were as follows: (1) There were about 78 families, 238 genera, and 406 species（including infraspecies taxa and excluding woody vines）of woody plants with DBH≥ 1cm. (2) In the plot, the families with two–five species and with one species were dominant and accounted for 37.18% and 34.62% of the total number of families, respectively, while the genera with two–four species and with one species were also dominant and accounted for 30.25% and 65.13% of the total number of genera, respectively. (3) Through analysis of the areal-types of families and genera, it was found that it had been divided into 9 areal-types and 7 variations at the family level, and the proportion of families was the highest at Pantropic, accounting for 50.77%, and the ratio of tropical flora to temperate flora (R/T) was 4.42; there were 11 areal-types at the genera level, mainly composed of Tropical Asian, Pantropic, Old World Tropics, 33.47%, 18.22%, and 13.98% respectively, and with R/T of the genera was 10.25. (4) The composition of Gulinqing, Bubeng and Nonggang big plots showed that Gulinqing and Bubeng had the highest similarity in family and genera level at Jaccard similarity coefficient (0.674 and 0.395, respectively), and Bubeng and Nonggang with the smallest Jaccard similarity coefficient (0.575 and 0.297, respectively). (5) PCA principal component analysis of the floristic spectrum had similar result of the Jaccard similarity coefficient above in the level of genera, but different one at the level of families, e.g. a higher geographical connection between Gulinqing and Nonggang. In summary, this plot has a high diversity of families and genera, significant tropical characteristics, ancient floristic characteristics, obvious transitional status and extensive flora connections. However, there is an inconsistent geographical connection among Gulinqing, Bubeng and Nonggang from the composition and floristic spectrum.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-01
Hua Leiming
Lu Fei
Su Jun
Shen Yangping
Jin Shilun
Yang Guochun
Li Zhihong
Guo Bing
Liu Longxiang
Cao Xiguang
Abstract： The 𝛽-Oslo experimental method provides an important investigative tool for examining the properties of radioactive nuclides in highly excited states and exploring the nucleosynthesis process for elements ranging from iron to uranium. This paper introduces a novel data processing technique designed to eliminate the impact of 𝛽-decay electrons on the detection of nuclear 𝛾 de-excitation within 𝛽-Oslo experiments, accurately unfolding the observed 𝛾-ray spectra. Utilizing a comprehensive detector response function matrix for 𝛾 rays and decay electrons, this method combines column-pivotal elimination and iterative step-by-step inverse solution approaches to determine the true incident 𝛾 spectrum. The reliability and validity of the proposed method have been substantiated through extensive simulations and inverse calculations.
Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： Mountain grassland are an essential component of pasture resources in the Xinjiang UygurAutonomous Region. However, mountain grassland are highly vulnerable to human-associated disturbance andclimate change. The responses of the mountain grassland plant community characteristics and diversity todifferent grazing managements in Barkol County, Xinjiang, are still unclear. In this study, three different grazingmanagement treatments were set up in 2012 to investigate the response patterns of the plant communitycharacteristics, diversity, and the relationship between the diversity and the aboveground biomass in the mountaingrasslands. The three grazing management blocks were M0, M1, and M2, which represented the permanentgrazing prohibition, winter grazing, and year-round grazing management, respectively. During the peak growingseasons of 2013, 2017, and 2022, the data regarding the number of species, height, coverage, density, andaboveground plant biomass were collected for further analysis. The results indicated that the different grazingmanagements had no significant impacts on the importance value of the dominant species, such as Stipa glareosa.However, the importance values of the nondominant species such as Neotrinia splendens and Achnatheruminebrians (Hance) Keng increased under winter and year- round grazing. As grazing intensity increased, plantheight, coverage, density, aboveground biomass, and their response ratios declined significantly (P<0.05). Therewere no significant differences in the Shannon- Wiener diversity, Simpson dominance, and Pielou evennessindices in M0, M1, and M2. In contrast, the Margalef richness index elevated markedly (P<0.05), indicating thatgrazing provided more survival resources helpful for other species. In the permanent grazing prohibition block,the aboveground biomass was negatively correlated with the Simpson dominance, Shannon-Wiener diversity, andPielou evenness indices. In the winter grazing block, aboveground biomass was negatively correlated with theMargalef richness index. Overall, the importance value of the dominant species showed no remarkabledifferences under varying grazing management, and its dominance remained unchanged. Except for the Margalefrichness index, the other diversity indices were not significantly influenced by grazing. Winter and year- roundgrazing enhanced the vital value of unpalatable species, altering the composition of forage, which was notconducive to future animal husbandry development. In summary, as the enclosure time increased, permanentgrazing prohibition was beneficial for restoring degraded grasslands, improving community characteristic values,improving grassland productivity, and maintaining community stability to a certain extent. Grazing would affectresource redistribution in the ecosystem, releasing ecological niches for more species, but year-round grazing ledto intensified grassland degradation because of overgrazing pressure.
Subjects: Biology >> Botany >> Applied botany submitted time 2023-12-24 Cooperative journals: 《广西植物》
Abstract： The seeds are invariably exposed to high temperature conditions since global warming frequently causes abnormally high temperatures. This study used intermediate Citrus maxima ‘Mansailong’ seeds as the research material, heated the seeds at different developmental stages, and simultaneously detected changes in seed morphology, contents of soluble and heat-stable proteins, and cellular ultrastructure in order to investigate the physiological basis of high-temperature tolerance in seeds. The results were as follows: (1) The seed moisture content dramatically dropped between 23 and 49 WAF (weeks after flowering), whereas the percentage of DW/FW and fresh weight increased significantly. All of these indicators began to change quickly from 31 WAF and stabilized around 41 WAF. (2) At 29 WAF, the seeds acquired full seedling formation ability and a preliminary tolerance to high temperatures; from there, the high-temperature tolerance gradually grew and improved quickly between 37 and 49 WAF. The improvement in high-temperature tolerance was accompanied by a steady increase in the contents of soluble and heat-stable protein in seeds, from 23 to 49 WAF. The results of the correlation analysis showed a substantial positive correlation between the accumulation of heat-stable and soluble proteins and the ability of seeds to tolerate high temperatures. (3) Ultrastructural observation showed that the number of mitochondria progressively dropped as the seed developed, the volume of the embryonic axis cells gradually decreased, and the number of lipid bodies in the cells gradually rose and their arrangement became more and more regular. In addition, the vacuoles enlarge at the same time, and at a later stage, they were packed with black floccules. In conclusion, the Citrus maxima ‘Mansailong’ seeds reached physiological maturity at 41 WAF without any noticeable maturation drying; the ability to withstand high temperatures was acquired during seed development and was further enhanced until a later stage; changes in cellural ultrastructure and an increase in soluble and heat-stable protein contents of the seeds were essential in helping the seeds develop their high-temperature tolerance.
Subjects: Biology >> Botany >> Applied botany submitted time 2023-12-24 Cooperative journals: 《广西植物》
LUO Yahuang
MA Liangliang
GAO Lianming
WANG Xinjie
ZHAO Wei
YANG Xingliang
MA Shaobin
SHI Xiaochun
LIU Jie
Abstract： A better understanding of the spatiotemporal dynamics of species composition and biodiversity provides significant insights into the distribution patterns of biodiversity and the prediction of biodiversity fate in a global change context. However, how species and phylogenetic diversity change along elevational gradient with temporal scale in mountain ecosystems is largely unknown. In this study, we used census data (2004, 2008 and 2013) of an elevational transect (elevational range 960-2 878 m) covering eastern and western slopes of Gaoligong Mountains, SW China, to investigate the spatiotemporal dynamics of forest arbor layer (DBH≥5 cm) species diversity and phylogenetic diversity. The results were as follows: (1) Species diversity was humpshaped along the elevational gradient, while the phylogenetic diversity increased with increasing elevation. Clustering phylogenetic structure was observed at low elevations, and overdispersed or random structure was detected at high elevations. (2) Overall, temporal species and phylogenetic beta diversity analysis showed no significant difference among these three investigation time points. However, we found a higher clustering of phylogenetic structure along the temporal scale. (3) Spatial beta diversity showed that there was a significant loss of species at low elevations (960-1 381 m) on the eastern slope, where the vegetation has been disturbed or completely converted into farmland. The main lost species including Terminalia chebula, Quercus acutissima,Pistacia weinmanniifolia, Hovenia acerba and Ilex wattii. In contrast, the change in the western slope is mild at low elevations, only observing species abundance increasing, which include Cyclobalanopsis oxyodon, Symplocos chinensis, and Taiwania cryptomerioides. Therefore, we speculate that the change in species and phylogenetic diversity of the arbor layer of subtropical evergreen broadleaf forest may be related to succession process and climatic change in middle and high elevations, while the communities at low elevations were seriously impacted by human activities in the Gaoligong Mountains. The results will deepen the understanding of the mechanisms of plant community dynamics in the Gaoligong Mountains and provide new insights to guide precise conservation strategies in the region.
Subjects: Biology >> Ecology submitted time 2023-08-26 Cooperative journals: 《干旱区研究》
Abstract： To investigate the response of plant community distribution to topography and soil factors in the premountaindesert grassland of Baicheng County on the southern piedmont of Tianshan Mountain, we selected atypical area for investigation. We used the dominance method and canonical correspondence analysis (CCA) tostudy the relationship between plant community distribution and topography and soil factors in the mountaindesert grassland. We observed differences in the species diversity of shrub and herb layers between survey samplesites. Specifically, the Shannon-Wiener index, Pielou index, and Simpson index on the eastern slope showed moreshrubs than herbs; while on the western and northern slopes, these indexes showed more herbs than shrubs. Theresults of CCA show that topographic factors influenced plant community diversity in the order of slopeorientation > slope gradient > slope position; and soil factors influenced plant community diversity in the order ofsoil moisture in the 30-100 cm soil layer > total soil porosity (STP) > soil moisture in the 0-30 cm soil layer(SMC-1). Topography and soil factors had certain screening effects on the formation of plant communities. Soilmoisture in the 30-100 cm soil layer and slope orientation were the key factors affecting the distribution of plantcommunities in the pre- mountain desert grassland of Baicheng County on the southern piedmont of TianshanMountain.
Subjects: Biology >> Ecology submitted time 2023-08-26 Cooperative journals: 《干旱区研究》
Abstract： Carbon sequestration is among the main functions of terrestrial ecosystem services, and the carbonsequestration capacity of terrestrial ecosystems directly affects global carbon emissions and climate changeprocesses. Human activities directly influence land use and cover change, consequently affecting the carbonsequestration function of ecosystems. The terrestrial ecosystem services in dry and cold regions are morevulnerable and significantly impacted by human activities. Therefore, utilizing land use data from the Irtysh RiverBasin in the Altai Mountains from 2000 to 2020, the InVEST model was used to estimate and analyze the spatialdistribution of carbon stocks in the basin during different periods. Subsequently, the influence of human activitieson the spatial distribution of carbon stocks was discussed. The results show the following: (1) The main land usetypes in the basin are woodland, grassland, and unused land, and the land use pattern changed significantly from2000 to 2020. Cultivated land, urban and rural land, industrial and mining land, and residential land expandedcontinuously, increasing by 2619.35 km2 and 186.68 km2, respectively. Grassland and water areas initiallydecreased and then expanded, increasing by 4725.13 km2 and 33.47 km2, respectively. Meanwhile, forest land andunused land decreased continuously by 2328.88 km2 and 5237.76 km2, respectively. (2) During this period, thespatial distribution pattern of carbon stocks in the basin was similar and showed a zonal distribution. High-valueareas were distributed in high- altitude regions where grassland and woodland were clustered, while low- valueareas were distributed in low-altitude regions where unused land was clustered. In 2000, 2005, 2010, 2015, 2020the total carbon storage in the basin was 641.60 Tg, 645.78 Tg, 646.83 Tg, 650.28 Tg, and 665.91 Tg,respectively , with an annual growth rate of 0.95%, showing an upward trend. (3) The areas in the basin wherecarbon storage decreased or increased showed a spot- like distribution. Furthermore, carbon storage reductionmainly occurred through the conversion of grassland to unused land and cultivated land, with an average annualreduction of 58.81 Tg. The increase in carbon storage primarily resulted from the conversion of unused land intocultivated land and grassland, with an average annual increase of 64.82 Tg. From 2000 to 2020, the netsequestration of carbon storage exceeded the net release, indicating an increasing carbon sequestration capacity inthe Irtysh River Basin. Overall, the reclamation of land and grass due to human activities is the main reason forthe increase in carbon storage in the basin. However, it is necessary to coordinate the development and utilizationof water and soil resources, as this will guarantee not only an increased carbon sink but also the preservation ofthe carrying capacity of water and soil resources, ultimately achieving sustainable economic development in theIrtysh River Basin. The results of this study will help to promote the carbon cycle of the basin and the carbonsequestration capacity of the ecosystem, as well as provide a scientific basis for the establishment andmanagement of the basin carbon pool.
Subjects: Geosciences >> Hydrology submitted time 2023-08-25 Cooperative journals: 《干旱区研究》
Abstract： Understanding the dynamic process of evapotranspiration and its causes is crucial for water resourcestability, ecological and environmental security, and agricultural water resource management in arid Central Asia.Evapotranspiration is the connection between the water-energy-carbon cycle. This study used the Priestley-Taylordiurnal land surface temperature range (PT- DTsR) model to calculate and analyze the spatial and temporalvariability of evapotranspiration in arid Central Asia from 2000 to 2019. It also used the Lindeman- Merenda-Gold method to quantitatively evaluate the absolute contributions of various drivers to each component ofevapotranspiration. By weighing each component’s contribution to the change in evapotranspiration, thecontribution of each driver to evapotranspiration was assessed. According to the findings, evapotranspirationincreased in dry Central Asia at a rate of 1.45 mm per year, and its pattern indicates that it increased in the eastand decreased in the west. The changes in transpiration, evaporation, and interception were 2.46 mm·a-1, -1.03mm·a- 1, and 0.02 mm·a- 1, respectively. These three trends contributed 70.09%, 29.34%, and 0.57%, to thechange in evapotranspiration. With an absolute contribution of 28.16%, Normalized Difference Vegetation Index(NDVI) is the key driver of evapotranspiration fluctuations in arid Central Asia.
Subjects: Biology >> Botany >> Applied botany submitted time 2023-08-04 Cooperative journals: 《广西植物》
Abstract： The decline in seedling growth of Malania oleifera as the age increases is often observed in the absence of host plants. A better knowledge of nutrient dynamics in terms of concentration and distribution patterns in different parts of the declining seedlings can provide valuable information for evaluating seedling growth vigor and offer scientific guidance for rational fertilization in M. oleifera nurseries. In this study, the concentrations of N, P, and K were comparatively analyzed in various organs of unattached M. oleifera seedlings grown for half a year, two years, and three years. Additionally, the starch content and distribution patterns in the roots and stems of seedlings with different vigor levels were qualitatively assessed by staining cross-sections. The results were as follows: (1) As the growth vigor of M. oleifera seedlings declined, the concentrations of N, P, and K in most organs decreased, except for a significant increase in K concentration in lateral roots. The leaf N/P ratios of the declining seedlings became increasingly imbalanced, indicating different nutrient deficiency types among the seedlings with varying decline degrees. Unattached M. oleifera seedlings grown for half a year were primarily limited by insufficient N supply (with an average N/P ratio of 11.33) and subsequently by P limitation after two years (average N/P ratio 17.81). The leaf N/P ratio of unattached M. oleifera seedlings grown for three years was remarkably imbalanced (with an average value of 52.46). As the growth vigor of unattached three-year seedlings is considerably low, they are deemed unsuitable for afforestation. (2) A decrease in starch content was observed in declining seedlings, as evidenced by the reduced staining intensity of cross-sections. After three years, the starch content of unattached M. oleifera seedlings was found to have decreased to an extremely low level. Significant differences in starch content were observed at various locations, including the connecting point of the stems and roots, the basal swelling top of the root, the main root, and lateral roots, among seedlings with different degrees of decline. These findings suggest that starch content levels can serve as crucial criteria for evaluating the growth vigor of seedlings. Specifically, lateral roots were identified as optimal sampling materials for assessing seedling growth vigor through a minimally invasive method.
Subjects: Biology >> Botany >> Applied botany submitted time 2023-07-13 Cooperative journals: 《广西植物》
Abstract： Paphiopedilum parishii is a rare and endangered species with few localities and fragmented populations found in China, Myanmar, Thailand and Lao. Environmental changes and over-harvesting have led to a decrease in its wild populations. It is important to protect endangered species' genetic diversity since it provides the species with the ability to adapt and survive. However, little is known about the genetic information of this species. This study aims to detect intraspecific variation and develop polymorphic genetic markers of P. parishii. The complete chloroplast genome of four individuals of wild P. parishii was obtained by sequencing, assembling and annotating, then compared with the existing genomic data of two individuals available from GenBank to detect the intraspecific variation. Further, simple sequence repeats (SSRs), single nucleotide polymorphisms (SNPs), and insertions and deletions (InDels) were identified. The results were as follows: (1) The four new sequencing chloroplast genomes were quadripartite, with a length between 154 403 bp and 154 809 bp, with 129 genes (78 protein coding genes, 39 tRNAs, 8rRNAs and 4 pseudogenes). (2) As a result of comparison of six individuals, 103-107 SSR loci were identified in the chloroplast genome of six individuals of P. parishii, and 21SSRs were polymorphic. And 60 long repeats were found, including 17-21 forward repeats, 18-29 reverse repeats, 9-16 palindromic repeats, and 4-9 complement repeats. (3) In addition, a total of 10 SNPs and 60 InDels were uncovered across the plastome. Three of the non-synonymous mutations caused amino acid changes in functional domains. 19 InDels might be selected for possible chloroplast DNA markers to determine intraspecific variation. (4) The value of nucleotide diversity (Pi) was calculated ranging from 0-0.006 32 suggesting sequences with low variation. Hyper-polymorphic regions, e.g. intergenic spacers rps3-rpl22, trnL-UAC-rpl32, rpoB-trnC-GCA and ycf4 gene were identified as potential barcoding regions. (5) The phylogenetic analyses based on the complete chloroplast genome supported three lineages in Paphiopedilum, and 6 individuals of P. parishii form a monophyletic group. SSRs, long repeats, InDels, SNPs and nucleotide sequences showed sufficient intraspecific genetic variation in P. parishii. The molecular markers developed here will contribute to further evolutionary studies and conservation of P. parishii.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-01-17 Cooperative journals: 《天文研究与技术》
Abstract： The purpose of this design is to realize the digital temperature control of the hydrogen maser. Is based on the basic principle of temperature detection and control design of a two-stage temperature control system (including the hydrogen maser inside the furnace and the furnace), the temperature control system is mainly composed of bridge circuit, analog-to-digital conversion circuit, temperature calculation and PID (proportional integral differential) control system, PWM (pulse width modulation) output circuit, heating wire. When the ambient temperature fluctuates from 21℃ to 25℃, the digital temperature control system achieves the temperature stability of 0.002℃, which proves the feasibility of the digital board to control the temperature of the hydrogen maser.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-11-22 Cooperative journals: 《天文研究与技术》
Abstract： Timekeeping atomic clocks mainly include hydrogen masers and cesium atomic clocks. In order to further explore the time-scale performance of different types of timekeeping atomic clocks, this paper carried out a study on the hydrogen maser and the hydrogen-cesium combined time scale . Firstly, the hydrogen maser was classified according to the d bulletin issued by BIPM. According to the classification results, the atomic time-scale theory is used to calculate the hydrogen maser time scale, and the analysis results are given. Then the time scales of cesium clocks are calculated and two different time scales of hydrogen-cesium combined ensembles are analyzed and explored. The results show that the time-scale fluctuation range of the hydrogen maserensemble based on the small frequency drift is smaller, and the stability is better than the time scale of the hydrogen maserensemble based on the larger frequency drift. The time scale stability of the hydrogen-cesium combination is better than the total cesium clock, and the result of different hydrogen-cesium combination time scale clocks are similar.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-11-01 Cooperative journals: 《天文研究与技术》
Abstract： Time-frequency data resources are important national information resources. The design of the time-frequency data platform relies on the time-frequency data generated by the daily operation of the National Time Service Center, the bulletin issued by Bureau International Des Poids et Mesures (BIPM) and International Earth Rotation and Reference Systems Service(IERS).The data platform can provide abundant data resources for the research of time-keeping technology. This paper first introduces the construction of the time-frequency data platform, and then uses the local time-keeping system comparison and long-distance link comparison data collected by the data platform to carry out time-keeping technology research, including the evaluation of the state of the atomic clock, and the analysis of the abnormal jump of the atomic clock. For different types of clock keeping, analyze and compare the performance indicators of atomic clocks such as fluctuation and stability, and conduct clock error prediction research based on the ARIMA model. The research contents of those different aspects can provide important reference for the continuous and reliable operation of the time-keeping system.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-10-17 Cooperative journals: 《天文研究与技术》
Abstract： In order to reduce the relative change rate of the transition frequency of the hydrogen masers caused by the inhomogeneous C field, two designs of C field components, three-segment solenoids and four sets of coils, are proposed. Using the high-order expansion of the magnetic field on the axis, the ampere-turn ratio and the solenoid spacing were calculated when the three-segment solenoid with L=0.05-0.5 constructed a uniform magnetic field. The finite element analysis of the magnetic field is carried out with L=0.2-0.45, and the magnetic field non-uniformity distribution with different widths is given. Among them, the maximum non-uniformity with L=0.45 in the storage bubble area is 0.105%, and the corresponding relative change rate of transition frequency is1.02×10-13 . Using the same method, the ampere-turn ratio and spacing between coils when four or five sets of coils construct a uniform magnetic field are calculated, and the finite element simulation of the magnetic field in the coil is carried out, and the non-uniformity distribution is given. The maximum non-uniformity of the magnetic field in the storage bubble region in the four sets of coils is 0.066%, and the corresponding transition frequency relative change rate is 6.42×10-14
Subjects: Biology >> Botany >> Applied botany submitted time 2022-07-05 Cooperative journals: 《广西植物》
Abstract： The restoration and reconstruction of mangrove wetland ecosystems is one of the key research fields in ecological restoration in the coastal zones of South China. How to optimize the assembly of mangrove species is the priority to be concerned in the restoration and transformation of mangrove forest community. In order to reveal the physiological and ecological strategies to light conditions of mangrove plant species and provide theoretical guidance for optimal assembly of mangrove community structure, the characteristics of leaf total soluble protein content and activities of five antioxidant enzymes in seedlings of eight mangrove plant species (Sonneratia apetala, Kandelia candel, Bruguiera gymnorrhiza, Aegiceras corniculatum, Acanthus ilicifolius, Acrostichum aureum, Heritiera littoralis and Hibiscus tiliaceus) under different light intensities (100%, 45%, 30%, and 10% of natural sunlight) were studied using shading control experiment. The results were as follows: (1) Low light intensities had little impact on the leaf total soluble protein content of Bruguiera gymnorrhiza, Acanthus ilicifolius and Acrostichum aureum, whereas the other five species showed a decreasing trend in the leaf soluble protein content with the decline in light intensity. (2) The activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in the leaves of Bruguiera gymnorrhiza, Acanthus ilicifolius and Acrostichum aureum in 10% of natural light intensity were not significantly from control, while the other five mangrove species showed a decreasing trend in activities of all the five antioxidant enzymes. In conclusion, our results indicate that Bruguiera gymnorrhiza, Acanthus ilicifolius and Acrostichum aureum are suitable for planting under the forest with high canopy density, while Sonneratia apetala, Kandelia candel, Aegiceras corniculatum, Heritiera littoralis, Hibiscus tiliaceus are suitable to be planted under forest with lower canopy density or planted as upper layer tree species in mangrove.
Subjects: Biology >> Botany >> Applied botany submitted time 2022-07-05 Cooperative journals: 《广西植物》
Abstract： The circadian clock is a conservative endogenous regulatory mechanism that stimulates and maintains the rhythmic expression of plant physiological characteristics. The PRR proteins are critical components of the circadian clock central oscillator and regulate a variety of life processes such as seed germination and flowering. Anthocyanins are plant secondary metabolites, which play an important role in plant growth, reproduction and stress responses. In this study, we took Arabidopsis thaliana as the research object and explored the function and mechanism of circadian clock PRR proteins in the control of anthocyanin biosynthesis. The results were as follows: (1) The accumulation of anthocyanins and the expression of some anthocyanin synthesis-related genes were significantly reduced in PRR genes single mutant and multiple mutant seedlings. (2) In the seedlings with overexpression of PRR5, the accumulation of anthocyanin and the expression of some anthocyanin synthesis-related genes were significantly increased. (3) The results of the protein-protein interaction experiment showed that PRR5 protein can interact with MYB75, MYB90, MYB113 and TT8 to form protein complexes. (4) Results of genetic analysis showed that PRR5 promoted anthocyanin synthesis in A. thaliana seedlings was the MYB family anthocyanin regulatory proteins dependent. In conclusion, the circadian clock PRR protein may promote the synthesis and accumulation of anthocyanins in A. thaliana seedlings through the interaction of PRR5 protein with MYB75, TT8.
Subjects: Biology >> Botany >> Applied botany submitted time 2022-03-18 Cooperative journals: 《广西植物》
Abstract： As a traditional Dai medicine, “Dai-Bai-Jie” is a kind of antidote, and its source plant was firstly recorded as Dregea sinensis. Currently, the source plant has been corrected as Marsdenia tenacissima. In order to further clarify the source plants of “Dai-Bai-Jie”, we carried out an integrated analysis of the source plants of “Dai-Bai-Jie” and its related species in this study. Our key results were as follows: (1) Phylogenetic relationship of Marsdenia and other species of Marsdenieae using three DNA fragments (psbD-trnT, trnL-trnF, ITS) showed that all “Dai-Bai-Jie” samples were supported as monophyletic with the sample of M. tenacissima, and were sister to M. cavaleriei; (2) Comparative analyses of morphological characters with type specimen proved that morphological characters of the “Dai-Bai-Jie” samples were consistent with those of the type specimen of M. tenacissima and obviously different from those of M. cavaleriei. In this study, the source plant of “Dai-Bai-Jie” was identified as the species M. tenacissima. Meanwhile, it is easy to discriminate from M. cavaleriei in the leaf and floral characters. According to both morphological and molecular evidence, it has been confirmed that the source plant of “Dai-Bai-Jie” was M. tenacissima that can be used for rapid and accurate authentication of medicinal herbs in the market, and also benefit for the development and utilization of the “Dai-bai-jie” medicine in future.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-01-14 Cooperative journals: 《天文研究与技术》
Abstract：甚长基线干涉测量（VLBI）通过相位校准（PCAL）信号来校准链路时延。但现有系统的PCAL信号只能获取链路时延的相对变化。而面对UT1精准测量、台站钟差补偿、维护诊断和提升未来深空探测精度等需求，天线链路的绝对时延定标至关重要。在天线链路中，由于存在变频器等器件，绝对时延测量较为困难。本文利用梳状谱相位随频率线性变化的特点，提出了一种不需要参考变频器，采用PCAL信号定标绝对链路群时延的方法。同时，本文设计了一款用于台站快速诊断和绝对时延定标的轻量级PCAL提取软件，该软件目前已在实际调试工作中应用。
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