Zero-inflated distributions are common in statistical problems where there is interest in testing homogeneity of two or more independent groups. Often, the underlying distribution that has an inflated number of zero-v...Zero-inflated distributions are common in statistical problems where there is interest in testing homogeneity of two or more independent groups. Often, the underlying distribution that has an inflated number of zero-valued observations is asymmetric, and its functional form may not be known or easily characterized. In this case, comparisons of the groups in terms of their respective percentiles may be appropriate as these estimates are nonparametric and more robust to outliers and other irregularities. The median test is often used to compare distributions with similar but asymmetric shapes but may be uninformative when there are excess zeros or dissimilar shapes. For zero-inflated distributions, it is useful to compare the distributions with respect to their proportion of zeros, coupled with the comparison of percentile profiles for the observed non-zero values. A simple chi-square test for simultaneous testing of these two components is proposed, applicable to both continuous and discrete data. Results of simulation studies are reported to summarize empirical power under several scenarios. We give recommendations for the minimum sample size which is necessary to achieve suitable test performance in specific examples.展开更多
Let I be the set of all infinitely divisible random variables with finite second moments,I_(0)={X∈I;Var(X)>0},P_(I)=inf_(x∈I)P{|X-E[X]|≤√Var(X)}and P_(I_(0))=inf P{|X-E[X]|<√Var(X)}.Firstly,we prove that P_...Let I be the set of all infinitely divisible random variables with finite second moments,I_(0)={X∈I;Var(X)>0},P_(I)=inf_(x∈I)P{|X-E[X]|≤√Var(X)}and P_(I_(0))=inf P{|X-E[X]|<√Var(X)}.Firstly,we prove that P_(I)≥P_(I_(0))>0.Secondly,we find_(x∈I_(0))the exact values of inf P{|X-E[X]|≤√Var(X)}and inf P{|X-E[X]|<√Var(X)}for the cases that J is the set of all geometric random variables,symmetric geometric random variables,Poisson random variables and symmetric Poisson random variables,respectively.As a consequence,we obtain that P_(I)≤e^(-1)^(∞)∑_(k=0)1/2^(2k)(k!)^(2)≈0.46576 and P_(I_(0))≤e^(-1)≈0.36788.展开更多
The distributions of light and nitrogen within a plant's canopy reflect the growth adaptation of crops to the environment and are conducive to improving the carbon assimilation ability.So can the yield in crop pro...The distributions of light and nitrogen within a plant's canopy reflect the growth adaptation of crops to the environment and are conducive to improving the carbon assimilation ability.So can the yield in crop production be maximized by improving the light and nitrogen distributions without adding any additional inputs?In this study,the effects of different nitrogen application rates and planting densities on the canopy light and nitrogen distributions of two highyielding maize cultivars(XY335 and DH618)and the regulatory effects of canopy physiological characteristics on radiation use efficiency(RUE)and yield were studied based on high-yield field experiments in Qitai,Xinjiang Uygur Autonomous Region,China,during 2019 and 2020.The results showed that the distribution of photosynthetically active photon flux density(PPFD)in the maize canopy decreased from top to bottom,while the vertical distribution of specific leaf nitrogen(SLN)initially increased and then decreased from top to bottom in the canopy.When SLN began to decrease,the PPDF values of XY335 and DH618 were 0.5 and 0.3,respectively,corresponding to 40.6 and49.3%of the total leaf area index(LAI).Nitrogen extinction coefficient(K_(N))/light extinction coefficient(K_(L))ratio in the middle and lower canopy of XY335(0.32)was 0.08 higher than that of DH618(0.24).The yield and RUE of XY335(17.2 t ha^(-1)and 1.8g MJ^(-1))were 7.0%(1.1 t ha^(-1))and 13.7%(0.2 g MJ^(-1))higher than those of DH618(16.1 t ha^(-1)and 1.6 g MJ^(-1)).Therefore,better light conditions(where the proportion of LAI in the upper and middle canopy was small)improved the light distribution when SLN started to decline,thus helping to mobilize the nitrogen distribution and maintain a high K_(N)and K_(N)/K_(L)ratio.In addition,K_(N)/K_(L)was a key parameter for yield improvement when the maize nutrient requirements were met at 360 kg N ha^(-1).At this level,an appropriately optimized high planting density could promote nitrogen utilization and produce higher yields and greater efficiency.The results of this study will be important for achieving high maize yields and the high efficiency cultivation and breeding of maize in the future.展开更多
The Chinese tree shrew has gained prominence as a model organism due to its phylogenetic proximity to primates,offering distinct advantages over traditional rodent models in biomedical research.However,the neuroanatom...The Chinese tree shrew has gained prominence as a model organism due to its phylogenetic proximity to primates,offering distinct advantages over traditional rodent models in biomedical research.However,the neuroanatomy of this species remains insufficiently defined,limiting its utility in neurophysiological and neuropathological studies.In this study,immunofluorescence microscopy was employed to comprehensively map the distribution of three calciumbinding proteins,parvalbumin,calbindin D-28k,and calretinin,across the tree shrew cerebrum.Serial brain sections in sagittal,coronal,and horizontal planes from 12 individuals generated a dataset of 3638 cellular-resolution images.This dataset,accessible via Science Data Bank(https://doi.org/10.57760/sciencedb.23471),provides detailed region-and laminar-selective distributions of calcium-binding proteins valuable for the cyto-and chemoarchitectural characterization of the tree shrew cerebrum.This resource will not only advance our understanding of brain organization and facilitate basic and translational neuroscience research in tree shrews but also enhance comparative and evolutionary analyses across species.展开更多
A double-moment cloud microphysics scheme requires an assumption for cloud droplet size distributions(DSDs).However,since observations of cloud DSDs are limited,default values for shape parameters and cloud condensati...A double-moment cloud microphysics scheme requires an assumption for cloud droplet size distributions(DSDs).However,since observations of cloud DSDs are limited,default values for shape parameters and cloud condensation nuclei activation parameters are often used in numerical simulations.In this study,the effects of cloud DSDs on numerical simulations of warm stratiform precipitation around Tokyo are investigated using the Japan Meteorological Agency's non-hydrostatic model,which incorporates a double-moment cloud microphysics scheme.Simulations using the default cloud DSD showed higher cloud droplet number concentrations and lower radar reflectivity than observed data,suggesting that the default cloud DSD is too narrow.Simulations with a cloud DSD based on in situ cloud observations corrected these errors.In addition,observation-based cloud DSDs affected rainfall amounts through the autoconversion rate of cloud water and improved the threat scores.These results suggest that realistic cloud DSDs should be provided for double-moment cloud microphysics schemes in scientific studies.展开更多
Geochemical surveys are essential for understanding the spatial distribution of ore-forming elements.However,these surveys often involve compositional data,the weight concentrations,which do not meet the requirements ...Geochemical surveys are essential for understanding the spatial distribution of ore-forming elements.However,these surveys often involve compositional data,the weight concentrations,which do not meet the requirements of statistical methods due to the closure effect.In this study,we applied an integrated approach combining compositional data,multifractal,and multivariate statistical analyses to identify the nonlinear complexity of the spatial distributions of elemental concentrations in the Er’renshan ore field.Initially,the raw concentrations were transformed into log-ratios following the principles of composition data theory to alleviate the impact of the closure effect.Multifractal analysis was then conducted to characterise the nonlinear complexity of the concentration distributions.Furthermore,principal component analysis(PCA)and factor analysis(FA)were applied to identify spurious correlations and the potential factors controlling the distribution patterns.The results demonstrate that:a)the raw data are biased,while the log-ratio data are unbiased and more reliable;b)the spatial distributions of elemental concentrations exhibit nonlinear complexity;and c)the elemental distribution in the study area is largely controlled by structural factors.展开更多
Using the ERA5 wave reanalysis,the distributions and trends of global available wave energy storage during 1980−2019 are analyzed.The results show that the available wave energy storage is not only related to total wa...Using the ERA5 wave reanalysis,the distributions and trends of global available wave energy storage during 1980−2019 are analyzed.The results show that the available wave energy storage is not only related to total wave energy storage but is also affected by the local available wave probability.Different distributions and trends between the available wave energy and total wave energy storage are observed.Larger values of total wave energy storage are concentrated in the high-latitude westerlies zone,whereas available wave energy storage exhibits greater concentration in the middle-low latitude regions.In each basin,there is a notable upward trend in both total wave energy storage and available wave energy storage.However,the northern Hemisphere(NH)exhibits an increasing trend in available wave probability,whereas the southern Hemisphere(SH)experiences a decreasing trend.This divergence contributes to the spatial distributions of available wave energy storage becoming increasingly uniform.These trends in wave energy are primarily influenced by changes in significant wave height.Although the increasing trend of significant wave height across all frequency ranges induces the growth of total wave energy storage,only the increasing of wave heights falling in 1.3−4 m can cause the growth of available wave energy storage.The consistent increasing rates of wave height under different mean levels contribute to the divergent trends in available wave probability.展开更多
The characteristics of summertime raindrop size distribution(DSD) and associated relations in the semi-arid region over the Inner Mongolian Plateau(IMP) were investigated,utilizing five-year continuous observations by...The characteristics of summertime raindrop size distribution(DSD) and associated relations in the semi-arid region over the Inner Mongolian Plateau(IMP) were investigated,utilizing five-year continuous observations by a PARSIVEL2disdrometer in East Ujimqin County(EUC),China.It is found that only 7.94% of the 15 664 one-min precipitation samples meet classification criteria as convective rain(CR),but its contribution to the total rainfall amount is 63.87%.Notably,40.72% of the rainfall comes from large-sized raindrops(D> 3 mm),despite the fact that large-sized raindrops account for only 1.73% of the CR total number concentration.Further results show that the mean value of mass-weighted mean diameters(Dm) is larger(2.43 mm) and generalized intercepts(lgN_(W)) is lower(3.19) in CR,aligning with a "continentallike" cluster,which is mainly influenced by the joint impact of in-cloud ice-based processes and the below-cloud environmental background.Also,the empirical relationships of shape-slope(μ-Λ),radar reflectivity-rain rate(Z-R),and rainfall kinetic energy(KE_(time)-Rand KE_(time)-Z) are localized.To quantitatively analyze the impact of DSD parameters on kinetic energy estimation,power-law KE_(time)-R and KE_(time)-Z relationships are derived based on the normalized gamma distribution.N_(W)takes precedence over μ in affecting variabilities of multiplicative coefficients,especially for KE_(time)-R relationship where the multiplicative coefficient is proportional to N_(W)^(-0.287).It should be noted that although the proportion of CR occurring throughout the summer is small,raindrops with lower N_(W) and larger Dmwill generate higher KE_(time),which will bring a higher potential risk of soil erosion in semi-arid regions over IMP.展开更多
The Yarlung Tsangpo River(YTR),located in the Himalayan orogenic belt,is renowned for its deep gorges and complex tectonic features,as well as its reputation as a landslide-prone region.However,less is known about the...The Yarlung Tsangpo River(YTR),located in the Himalayan orogenic belt,is renowned for its deep gorges and complex tectonic features,as well as its reputation as a landslide-prone region.However,less is known about the distribution of landslides across the entire river basin.To address this gap in knowledge,this study first established a comprehensive landslide inventory across the entire basin using remote sensing mapping and multiple field investigations.Then,a systematic analysis of the spatial and size distributions was conducted.The results indicated that the YTR basin features at least 2390 landslides with areas exceeding 104 m2,spanning a total area and volume of 1087.6 km^(2) and 48.4 km^(3),respectively.These landslides can be classified into eight types,and rockslides are the most common(53.1%).Their distributions are highly asymmetric,with the following notable patterns:(1)the Tsangpo suture zone(53.4%)contains a greater number of landslides than other tectonic units;(2)the landslide size is influenced by the relief and elevation conditions,with positive relationships observed between the local relief and landslide area,as well as between the elevation range and landslide area;and(3)the landslide distribution is not significantly correlated with rainfall,and seasonally frozen ground is associated with a greater concentration of landslides.Alternating slate and shale groups in the Tsangpo suture zone may be the factors responding to landslide concentration.A total of 20.6%of landslide-blocked rivers were observed,with some forming river knickpoints.Due to the limited data,spatial and size analyses are perhaps immature,and further systematic analysis remains necessary.展开更多
Empirical estimates of power and Type I error can be misleading if a statistical test does not perform at the stated rejection level under the null hypothesis. We employed the permutation test to control the empirical...Empirical estimates of power and Type I error can be misleading if a statistical test does not perform at the stated rejection level under the null hypothesis. We employed the permutation test to control the empirical type I errors for zero-inflated exponential distributions. The simulation results indicated that the permutation test can be used effectively to control the type I errors near the nominal level even the sample sizes are small based on four statistical tests. Our results attest to the permutation test being a valuable adjunct to the current statistical methods for comparing distributions with underlying zero-inflated data structures.展开更多
In this paper,we consider testing the hypothesis concerning the means of two independent semicontinuous distributions whose observations are zero-inflated,characterized by a sizable number of zeros and positive observ...In this paper,we consider testing the hypothesis concerning the means of two independent semicontinuous distributions whose observations are zero-inflated,characterized by a sizable number of zeros and positive observations from a continuous distribution.The continuous parts of the two semicontinuous distributions are assumed to follow a density ratio model.A new two-part test is developed for this kind of data.The proposed test takes the sum of one test for equality of proportions of zero values and one conditional test for the continuous distribution.The test is proved to follow a 2 distribution with two degrees of freedom.Simulation studies show that the proposed test controls the type I error rates at the desired level,and is competitive to,and most of the time more powerful than two popular tests.A real data example from a dietary intervention study is used to illustrate the usefulness of the proposed test.展开更多
Purpose:To analyze the diversity of citation distributions to publications in different research topics to investigate the accuracy of size-independent,rank-based indicators.The top percentile-based indicators are the...Purpose:To analyze the diversity of citation distributions to publications in different research topics to investigate the accuracy of size-independent,rank-based indicators.The top percentile-based indicators are the most common indicators of this type,and the evaluations of Japan are the most evident misjudgments.Design/methodology/approach:The distributions of citations to publications from countries and journals in several research topics were analyzed along with the corresponding global publications using histograms with logarithmic binning,double rank plots,and normal probability plots of log-transformed numbers of citations.Findings:Size-independent,top percentile-based indicators are accurate when the global ranks of local publications fit a power law,but deviations in the least cited papers are frequent in countries and occur in all journals with high impact factors.In these cases,a single indicator is misleading.Comparisons of the proportions of uncited papers are the best way to predict these deviations.Research limitations:This study is fundamentally analytical,and its results describe mathematical facts that are self-evident.Practical implications:Respectable institutions,such as the OECD,the European Commission,and the U.S.National Science Board,produce research country rankings and individual evaluations using size-independent percentile indicators that are misleading in many countries.These misleading evaluations should be discontinued because they can cause confusion among research policymakers and lead to incorrect research policies.Originality/value:Studies linking the lower tail of citation distribution,including uncited papers,to percentile research indicators have not been performed previously.The present results demonstrate that studies of this type are necessary to find reliable procedures for research assessments.展开更多
The vast majority of in vitro studies have demonstrated that PINK1 phosphorylates Parkin to work together in mitophagy to protect against neuronal degeneration.However,it remains largely unclear how PINK1 and Parkin a...The vast majority of in vitro studies have demonstrated that PINK1 phosphorylates Parkin to work together in mitophagy to protect against neuronal degeneration.However,it remains largely unclear how PINK1 and Parkin are expressed in mammalian brains.This has been difficult to address because of the intrinsically low levels of PINK1 and undetectable levels of phosphorylated Parkin in small animals.Understanding this issue is critical for elucidating the in vivo roles of PINK1 and Parkin.Recently,we showed that the PINK1 kinase is selectively expressed as a truncated form(PINK1–55)in the primate brain.In the present study,we used multiple antibodies,including our recently developed monoclonal anti-PINK1,to validate the selective expression of PINK1 in the primate brain.We found that PINK1 was stably expressed in the monkey brain at postnatal and adulthood stages,which is consistent with the findings that depleting PINK1 can cause neuronal loss in developing and adult monkey brains.PINK1 was enriched in the membrane-bound fractionations,whereas Parkin was soluble with a distinguishable distribution.Immunofluorescent double staining experiments showed that PINK1 and Parkin did not colocalize under physiological conditions in cultured monkey astrocytes,though they did colocalize on mitochondria when the cells were exposed to mitochondrial stress.These findings suggest that PINK1 and Parkin may have distinct roles beyond their well-known function in mitophagy during mitochondrial damage.展开更多
There are two weaknesses in current researches into human casualty of ship collision.One is that the range of injuries or fatalities is restricted to the maximum number of casualties in a particular sample,which may n...There are two weaknesses in current researches into human casualty of ship collision.One is that the range of injuries or fatalities is restricted to the maximum number of casualties in a particular sample,which may not cover all the possible numbers of casualties in the future.International Maritime Organization(IMO)employed the injured or dead percentage of all the persons on board to represent casualties,but it only provided several discrete values to quantify human losses in different scenarios.The other is that the assumption that the distributions of the injuries or fatalities follow certain distribution,such as negative binomial and Poisson distributions is left to be statistically tested.Firstly,this study considers casualty rate,including injury and fatality rates,as random variables;the interval of the variables are from 0 to 1.Then,the distributions of the variables are investigated using historical data.From historical data,we can find that there are many zeros.Zeroinflated models are proved to be effective in processing data with inflated zeros.Furthermore,the probability density of the variables decreases rapidly as the casualty rate becomes larger.Thus,zero-inflated exponential distribution is assumed to fit the data.The parameters of zero-inflated exponential distribution are calibrated by maximum likelihood estimation(MLE)method.Finally,the assumption is tested by chi-square test.The zeroinflated exponential distribution can be used to generate human losses as a part of consequences in the simulation of ship collision risk.展开更多
Exploring the vertical variation in volatile organic compounds(VOCs)in background regions can provide infor-mation on the spatial distribution of pollutants,providing a scientific basis for atmospheric pollution preve...Exploring the vertical variation in volatile organic compounds(VOCs)in background regions can provide infor-mation on the spatial distribution of pollutants,providing a scientific basis for atmospheric pollution prevention and control strategies.From 15 August to 5 September 2023,at the Southeast Tibet Mountain Comprehensive Environmental Observation Station(SETS),a tethered balloon was used to sample VOCs every 100 m from the ground to 1000 m.A total of 403 air bag samples were collected,and 39 vertical profiles of VOCs were obtained.Ninety-two VOC species were detected.The VOC concentration at the SETS did not change significantly verti-cally,and the average VOC concentration was 11.1±2.4 ppbv.The main components were alkanes(51.4%),alkenes(18.7%),and halohydrocarbons(18.1%).There was no obvious diurnal change in VOCs and no signif-icant difference between the different layers.When the surface VOC concentration was less than 10 ppbv,the concentrations,components,and sources of VOCs were evenly distributed vertically,and the main sources of VOCs at different heights were vehicle exhaust and background.When the surface VOC concentration exceeded 10 ppbv,the VOC concentration gradually decreased with height.The proportion of alkanes in surface VOCs in-creased,and the source was mainly vehicle exhaust.This study confirmed that VOCs are vertically homogeneous in the background of the Tibetan Plateau,emphasizing the importance of vehicle emissions as a potential source of VOCs.展开更多
Background: In Sub-Saharan Africa, pre-eclampsia remains a major health problem contributing to high rates of maternal mortality. Despite this condition having adverse effects on maternal and child health, its prevale...Background: In Sub-Saharan Africa, pre-eclampsia remains a major health problem contributing to high rates of maternal mortality. Despite this condition having adverse effects on maternal and child health, its prevalence and associated risk factors are still significant, especially in developing countries including Ghana. This study aimed to assess the prevalence and demographic distributions associated with pre-eclampsia among pregnant women at the Ho Teaching Hospital. Methods: A facility-based retrospective study was conducted by reviewing available data or hospital records of pregnant mothers admitted to the labor and maternity wards from January 2018 to December 2020. All pregnant women who were diagnosed with pre-eclampsia within this period were included in the study. The data were collected using a structured checklist. Results: 5609 data on pregnant women from 2018 to 2020 were recorded. Out of the 5609 data recorded, 314 pre-eclampsia cases were recorded giving an overall prevalence of 5.6%. The yearly prevalence for 2018, 2019, and 2020 were 4.6%, 5.6%, and 6.6%, respectively. The most recorded pre-eclampsia cases were seen among women within the age group of 18 - 24 years. The data showed that 112 (35.7%) of the pregnant women who had pre-eclampsia were nulliparous. Pre-eclampsia-associated maternal and fetal complications were;preterm delivery 221 (70.4%), intrauterine fetal death 62 (19.7%), eclampsia 9 (2.9%), HELLP syndrome 5 (1.6%) and maternal death 17 (5.4%). Associated factors of pre-eclampsia were parity, level of education, and occupation (p ≤ 0.05). Conclusion: The findings of this study showed a rising trend in the incidence of pre-eclampsia over the years at the Ho Teaching Hospital. Parity, level of education, and occupation were found to be associated with developing pre-eclampsia.展开更多
Sea salt aerosols play a critical role in regulating the global climate through their interactions with solar radiation.The size distribution of these particles is crucial in determining their bulk optical properties....Sea salt aerosols play a critical role in regulating the global climate through their interactions with solar radiation.The size distribution of these particles is crucial in determining their bulk optical properties.In this study,we analyzed in situ measured size distributions of sea salt aerosols from four field campaigns and used multi-mode lognormal size distributions to fit the data.We employed super-spheroids and coated super-spheroids to account for the particles’non-sphericity,inhomogeneity,and hysteresis effect during the deliquescence and crystallization processes.To compute the singlescattering properties of sea salt aerosols,we used the state-of-the-art invariant imbedding T-matrix method,which allows us to obtain accurate optical properties for sea salt aerosols with a maximum volume-equivalent diameter of 12μm at a wavelength of 532 nm.Our results demonstrated that the particle models developed in this study were successful in replicating both the measured depolarization and lidar ratios at various relative humidity(RH)levels.Importantly,we observed that large-size particles with diameters larger than 4μm had a substantial impact on the optical properties of sea salt aerosols,which has not been accounted for in previous studies.Specifically,excluding particles with diameters larger than 4μm led to underestimating the scattering and backscattering coefficients by 27%−38%and 43%−60%,respectively,for the ACE-Asia field campaign.Additionally,the depolarization ratios were underestimated by 0.15 within the 50%−70%RH range.These findings emphasize the necessity of considering large particle sizes for optical modeling of sea salt aerosols.展开更多
In the present work, we are interested in studying the joint distributions of pairs of the monthly maxima of the pollutants used by the environmental authorities in Mexico City to classify the air quality in the metro...In the present work, we are interested in studying the joint distributions of pairs of the monthly maxima of the pollutants used by the environmental authorities in Mexico City to classify the air quality in the metropolitan area. In order to obtain the joint distributions a copula will be considered. Since we are analyzing the monthly maxima, the extreme value distributions of Weibull and Fréchet are taken into account. Using these two distributions as marginal distributions in the copula a Bayesian inference was made in order to estimate the parameters of both distributions and also the association parameters appearing in the copula model. The pollutants taken into account are ozone, nitrogen dioxide, sulphur dioxide, carbon monoxide, and particulate matter with diameters smaller than 10 and 2.5 microns obtained from the Mexico City monitoring network. The estimation was performed by taking samples of the parameters generated through a Markov chain Monte Carlo algorithm implemented using the software OpenBugs. Once the algorithm is implemented it is applied to the pairs of pollutants where one of the coordinates of the pair is ozone and the other varies on the set of the remaining pollutants. Depending on the pollutant and the region where they were collected, different results were obtained. Hence, in some cases we have that the best model is that where we have a Fréchet distribution as the marginal distribution for the measurements of both pollutants and in others the most suitable model is the one assuming a Fréchet for ozone and a Weibull for the other pollutant. Results show that, in the present case, the estimated association parameter is a good representation to the correlation parameters between the pair of pollutants analyzed. Additionally, it is a straightforward task to obtain these correlation parameters from the corresponding association parameters.展开更多
Molecular-frame photoelectron momentum distributions(MF-PMDs)have been studied for imaging molecular structures.We investigate the MF-PMDs of CO_(2)molecules exposed to circularly polarized(CP)attosecond laser pulses ...Molecular-frame photoelectron momentum distributions(MF-PMDs)have been studied for imaging molecular structures.We investigate the MF-PMDs of CO_(2)molecules exposed to circularly polarized(CP)attosecond laser pulses bysolving the time-dependent Schrodinger equations based on the single-active-electron approximation frames.Results showthat high-frequency photons lead to photoelectron diffraction patterns,indicating molecular orbitals.These diffractionpatterns can be illustrated by the ultrafast photoionization models.However,for the driving pulses with 30 nm,a deviationbetween MF-PMDs and theoretically predicted results of the ultrafast photoionization models is produced because theCoulomb effect strongly influences the molecular photoionization.Meanwhile,the MF-PMDs rotate in the same directionas the helicity of driving laser pulses.Our results also demonstrate that the MF-PMDs in a CP laser pulse are the superpositionof those in the parallel and perpendicular linearly polarized cases.The simulations efficiently visualize molecularorbital geometries and structures by ultrafast photoelectron imaging.Furthermore,we determine the contribution of HOMOand HOMO-1 orbitals to ionization by varying the relative phase and the ratio of these two orbitals.展开更多
Background: The signal-to-noise ratio (SNR) is recognized as an index of measurements reproducibility. We derive the maximum likelihood estimators of SNR and discuss confidence interval construction on the difference ...Background: The signal-to-noise ratio (SNR) is recognized as an index of measurements reproducibility. We derive the maximum likelihood estimators of SNR and discuss confidence interval construction on the difference between two correlated SNRs when the readings are from bivariate normal and bivariate lognormal distribution. We use the Pearsons system of curves to approximate the difference between the two estimates and use the bootstrap methods to validate the approximate distributions of the statistic of interest. Methods: The paper uses the delta method to find the first four central moments, and hence the skewness and kurtosis which are important in the determination of the parameters of the Pearsons distribution. Results: The approach is illustrated in two examples;one from veterinary microbiology and food safety data and the other on data from clinical medicine. We derived the four central moments of the target statistics, together with the bootstrap method to evaluate the parameters of Pearsons distribution. The fitted Pearsons curves of Types I and II were recommended based on the available data. The R-codes are also provided to be readily used by the readers.展开更多
文摘Zero-inflated distributions are common in statistical problems where there is interest in testing homogeneity of two or more independent groups. Often, the underlying distribution that has an inflated number of zero-valued observations is asymmetric, and its functional form may not be known or easily characterized. In this case, comparisons of the groups in terms of their respective percentiles may be appropriate as these estimates are nonparametric and more robust to outliers and other irregularities. The median test is often used to compare distributions with similar but asymmetric shapes but may be uninformative when there are excess zeros or dissimilar shapes. For zero-inflated distributions, it is useful to compare the distributions with respect to their proportion of zeros, coupled with the comparison of percentile profiles for the observed non-zero values. A simple chi-square test for simultaneous testing of these two components is proposed, applicable to both continuous and discrete data. Results of simulation studies are reported to summarize empirical power under several scenarios. We give recommendations for the minimum sample size which is necessary to achieve suitable test performance in specific examples.
基金supported by the National Natural Science Foundation of China(12161029,12171335)the National Natural Science Foundation of Hainan Province(121RC149)+1 种基金the Science Development Project of Sichuan University(2020SCUNL201)the Natural Sciences and Engineering Research Council of Canada(4394-2018).
文摘Let I be the set of all infinitely divisible random variables with finite second moments,I_(0)={X∈I;Var(X)>0},P_(I)=inf_(x∈I)P{|X-E[X]|≤√Var(X)}and P_(I_(0))=inf P{|X-E[X]|<√Var(X)}.Firstly,we prove that P_(I)≥P_(I_(0))>0.Secondly,we find_(x∈I_(0))the exact values of inf P{|X-E[X]|≤√Var(X)}and inf P{|X-E[X]|<√Var(X)}for the cases that J is the set of all geometric random variables,symmetric geometric random variables,Poisson random variables and symmetric Poisson random variables,respectively.As a consequence,we obtain that P_(I)≤e^(-1)^(∞)∑_(k=0)1/2^(2k)(k!)^(2)≈0.46576 and P_(I_(0))≤e^(-1)≈0.36788.
基金supported by the National Natural Science Foundation of China(32172118)the National Key Research and Development Program of China(2016YFD0300110 and 2016YFD0300101)+1 种基金the Basic Scientific Research Fund of Chinese Academy of Agricultural Sciences,China(S2022ZD05)the Agricultural Science and Technology Innovation Program,China(CAAS-ZDRW202004)。
文摘The distributions of light and nitrogen within a plant's canopy reflect the growth adaptation of crops to the environment and are conducive to improving the carbon assimilation ability.So can the yield in crop production be maximized by improving the light and nitrogen distributions without adding any additional inputs?In this study,the effects of different nitrogen application rates and planting densities on the canopy light and nitrogen distributions of two highyielding maize cultivars(XY335 and DH618)and the regulatory effects of canopy physiological characteristics on radiation use efficiency(RUE)and yield were studied based on high-yield field experiments in Qitai,Xinjiang Uygur Autonomous Region,China,during 2019 and 2020.The results showed that the distribution of photosynthetically active photon flux density(PPFD)in the maize canopy decreased from top to bottom,while the vertical distribution of specific leaf nitrogen(SLN)initially increased and then decreased from top to bottom in the canopy.When SLN began to decrease,the PPDF values of XY335 and DH618 were 0.5 and 0.3,respectively,corresponding to 40.6 and49.3%of the total leaf area index(LAI).Nitrogen extinction coefficient(K_(N))/light extinction coefficient(K_(L))ratio in the middle and lower canopy of XY335(0.32)was 0.08 higher than that of DH618(0.24).The yield and RUE of XY335(17.2 t ha^(-1)and 1.8g MJ^(-1))were 7.0%(1.1 t ha^(-1))and 13.7%(0.2 g MJ^(-1))higher than those of DH618(16.1 t ha^(-1)and 1.6 g MJ^(-1)).Therefore,better light conditions(where the proportion of LAI in the upper and middle canopy was small)improved the light distribution when SLN started to decline,thus helping to mobilize the nitrogen distribution and maintain a high K_(N)and K_(N)/K_(L)ratio.In addition,K_(N)/K_(L)was a key parameter for yield improvement when the maize nutrient requirements were met at 360 kg N ha^(-1).At this level,an appropriately optimized high planting density could promote nitrogen utilization and produce higher yields and greater efficiency.The results of this study will be important for achieving high maize yields and the high efficiency cultivation and breeding of maize in the future.
基金supported by the Science and Technology Innovation(STI)2030-Major Projects(2022ZD0205000 to L.L.)CAS“Light of West China”Program(xbzg-zdsys-202404 to L.L.)+1 种基金Yunnan Revitalization Talent Support Program Yunling Scholar Project(to L.L.)Yunnan Fundamental Research Projects(202305AH340006,202301AS070060 to L.L.,202401AT070206 to X.C.)。
文摘The Chinese tree shrew has gained prominence as a model organism due to its phylogenetic proximity to primates,offering distinct advantages over traditional rodent models in biomedical research.However,the neuroanatomy of this species remains insufficiently defined,limiting its utility in neurophysiological and neuropathological studies.In this study,immunofluorescence microscopy was employed to comprehensively map the distribution of three calciumbinding proteins,parvalbumin,calbindin D-28k,and calretinin,across the tree shrew cerebrum.Serial brain sections in sagittal,coronal,and horizontal planes from 12 individuals generated a dataset of 3638 cellular-resolution images.This dataset,accessible via Science Data Bank(https://doi.org/10.57760/sciencedb.23471),provides detailed region-and laminar-selective distributions of calcium-binding proteins valuable for the cyto-and chemoarchitectural characterization of the tree shrew cerebrum.This resource will not only advance our understanding of brain organization and facilitate basic and translational neuroscience research in tree shrews but also enhance comparative and evolutionary analyses across species.
基金supported by Grants in Aid from the Japan Society for the Promotion of Science(JSPS)KAKENHI[grant numbers JP21H01163 and JP23H00149].
文摘A double-moment cloud microphysics scheme requires an assumption for cloud droplet size distributions(DSDs).However,since observations of cloud DSDs are limited,default values for shape parameters and cloud condensation nuclei activation parameters are often used in numerical simulations.In this study,the effects of cloud DSDs on numerical simulations of warm stratiform precipitation around Tokyo are investigated using the Japan Meteorological Agency's non-hydrostatic model,which incorporates a double-moment cloud microphysics scheme.Simulations using the default cloud DSD showed higher cloud droplet number concentrations and lower radar reflectivity than observed data,suggesting that the default cloud DSD is too narrow.Simulations with a cloud DSD based on in situ cloud observations corrected these errors.In addition,observation-based cloud DSDs affected rainfall amounts through the autoconversion rate of cloud water and improved the threat scores.These results suggest that realistic cloud DSDs should be provided for double-moment cloud microphysics schemes in scientific studies.
基金supported by the Doctoral Research Start-up Fund,East China University of Technology(DHBK2019313)the Open Research Fund Program of Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring(Central South University),the Ministry of Education(2020YSJS10)+1 种基金the Open Research Fund Program of Shandong Provincial Engineering Laboratory of Application and Development of Big Data for Deep Gold Exploration(SDK202224)the Basic Scientific Research Fund of the Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences(AS2022P03).
文摘Geochemical surveys are essential for understanding the spatial distribution of ore-forming elements.However,these surveys often involve compositional data,the weight concentrations,which do not meet the requirements of statistical methods due to the closure effect.In this study,we applied an integrated approach combining compositional data,multifractal,and multivariate statistical analyses to identify the nonlinear complexity of the spatial distributions of elemental concentrations in the Er’renshan ore field.Initially,the raw concentrations were transformed into log-ratios following the principles of composition data theory to alleviate the impact of the closure effect.Multifractal analysis was then conducted to characterise the nonlinear complexity of the concentration distributions.Furthermore,principal component analysis(PCA)and factor analysis(FA)were applied to identify spurious correlations and the potential factors controlling the distribution patterns.The results demonstrate that:a)the raw data are biased,while the log-ratio data are unbiased and more reliable;b)the spatial distributions of elemental concentrations exhibit nonlinear complexity;and c)the elemental distribution in the study area is largely controlled by structural factors.
基金The National Key R&D Program of China under contract No.2023YFE0126300the National Natural Science Foundation of China under contract No.41930538the Open Fund of China Meteorological Administration Hydro-Meteorology Key Laboratory,Hohai University,under contract No.23SWQXM049.
文摘Using the ERA5 wave reanalysis,the distributions and trends of global available wave energy storage during 1980−2019 are analyzed.The results show that the available wave energy storage is not only related to total wave energy storage but is also affected by the local available wave probability.Different distributions and trends between the available wave energy and total wave energy storage are observed.Larger values of total wave energy storage are concentrated in the high-latitude westerlies zone,whereas available wave energy storage exhibits greater concentration in the middle-low latitude regions.In each basin,there is a notable upward trend in both total wave energy storage and available wave energy storage.However,the northern Hemisphere(NH)exhibits an increasing trend in available wave probability,whereas the southern Hemisphere(SH)experiences a decreasing trend.This divergence contributes to the spatial distributions of available wave energy storage becoming increasingly uniform.These trends in wave energy are primarily influenced by changes in significant wave height.Although the increasing trend of significant wave height across all frequency ranges induces the growth of total wave energy storage,only the increasing of wave heights falling in 1.3−4 m can cause the growth of available wave energy storage.The consistent increasing rates of wave height under different mean levels contribute to the divergent trends in available wave probability.
基金supported by the National Natural Science Foundation of China(Grant Nos.42325503,42075063,42075066,and 42021004)the Hubei Provincial Natural Science Foundation and the Meteorological Innovation and Development Project of China(Grant No.2023AFD096)the Beijige Foundation of NJIAS(Grant No.BJG202304).
文摘The characteristics of summertime raindrop size distribution(DSD) and associated relations in the semi-arid region over the Inner Mongolian Plateau(IMP) were investigated,utilizing five-year continuous observations by a PARSIVEL2disdrometer in East Ujimqin County(EUC),China.It is found that only 7.94% of the 15 664 one-min precipitation samples meet classification criteria as convective rain(CR),but its contribution to the total rainfall amount is 63.87%.Notably,40.72% of the rainfall comes from large-sized raindrops(D> 3 mm),despite the fact that large-sized raindrops account for only 1.73% of the CR total number concentration.Further results show that the mean value of mass-weighted mean diameters(Dm) is larger(2.43 mm) and generalized intercepts(lgN_(W)) is lower(3.19) in CR,aligning with a "continentallike" cluster,which is mainly influenced by the joint impact of in-cloud ice-based processes and the below-cloud environmental background.Also,the empirical relationships of shape-slope(μ-Λ),radar reflectivity-rain rate(Z-R),and rainfall kinetic energy(KE_(time)-Rand KE_(time)-Z) are localized.To quantitatively analyze the impact of DSD parameters on kinetic energy estimation,power-law KE_(time)-R and KE_(time)-Z relationships are derived based on the normalized gamma distribution.N_(W)takes precedence over μ in affecting variabilities of multiplicative coefficients,especially for KE_(time)-R relationship where the multiplicative coefficient is proportional to N_(W)^(-0.287).It should be noted that although the proportion of CR occurring throughout the summer is small,raindrops with lower N_(W) and larger Dmwill generate higher KE_(time),which will bring a higher potential risk of soil erosion in semi-arid regions over IMP.
基金supported by the National Key R&D Program of China(Grant No.2023YFC3008300)the Science and Technology Research Program of the Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,Chinese Academy of Sciences(Grant No.IMHE-ZYTS-03 and IMHE-ZDRW-03).
文摘The Yarlung Tsangpo River(YTR),located in the Himalayan orogenic belt,is renowned for its deep gorges and complex tectonic features,as well as its reputation as a landslide-prone region.However,less is known about the distribution of landslides across the entire river basin.To address this gap in knowledge,this study first established a comprehensive landslide inventory across the entire basin using remote sensing mapping and multiple field investigations.Then,a systematic analysis of the spatial and size distributions was conducted.The results indicated that the YTR basin features at least 2390 landslides with areas exceeding 104 m2,spanning a total area and volume of 1087.6 km^(2) and 48.4 km^(3),respectively.These landslides can be classified into eight types,and rockslides are the most common(53.1%).Their distributions are highly asymmetric,with the following notable patterns:(1)the Tsangpo suture zone(53.4%)contains a greater number of landslides than other tectonic units;(2)the landslide size is influenced by the relief and elevation conditions,with positive relationships observed between the local relief and landslide area,as well as between the elevation range and landslide area;and(3)the landslide distribution is not significantly correlated with rainfall,and seasonally frozen ground is associated with a greater concentration of landslides.Alternating slate and shale groups in the Tsangpo suture zone may be the factors responding to landslide concentration.A total of 20.6%of landslide-blocked rivers were observed,with some forming river knickpoints.Due to the limited data,spatial and size analyses are perhaps immature,and further systematic analysis remains necessary.
文摘Empirical estimates of power and Type I error can be misleading if a statistical test does not perform at the stated rejection level under the null hypothesis. We employed the permutation test to control the empirical type I errors for zero-inflated exponential distributions. The simulation results indicated that the permutation test can be used effectively to control the type I errors near the nominal level even the sample sizes are small based on four statistical tests. Our results attest to the permutation test being a valuable adjunct to the current statistical methods for comparing distributions with underlying zero-inflated data structures.
基金Supported by the National Natural Science Foundation of China(No.11971433)the First Class Discipline of Zhejiang-A(Zhejiang Gongshang University-Statistics)the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
文摘In this paper,we consider testing the hypothesis concerning the means of two independent semicontinuous distributions whose observations are zero-inflated,characterized by a sizable number of zeros and positive observations from a continuous distribution.The continuous parts of the two semicontinuous distributions are assumed to follow a density ratio model.A new two-part test is developed for this kind of data.The proposed test takes the sum of one test for equality of proportions of zero values and one conditional test for the continuous distribution.The test is proved to follow a 2 distribution with two degrees of freedom.Simulation studies show that the proposed test controls the type I error rates at the desired level,and is competitive to,and most of the time more powerful than two popular tests.A real data example from a dietary intervention study is used to illustrate the usefulness of the proposed test.
文摘Purpose:To analyze the diversity of citation distributions to publications in different research topics to investigate the accuracy of size-independent,rank-based indicators.The top percentile-based indicators are the most common indicators of this type,and the evaluations of Japan are the most evident misjudgments.Design/methodology/approach:The distributions of citations to publications from countries and journals in several research topics were analyzed along with the corresponding global publications using histograms with logarithmic binning,double rank plots,and normal probability plots of log-transformed numbers of citations.Findings:Size-independent,top percentile-based indicators are accurate when the global ranks of local publications fit a power law,but deviations in the least cited papers are frequent in countries and occur in all journals with high impact factors.In these cases,a single indicator is misleading.Comparisons of the proportions of uncited papers are the best way to predict these deviations.Research limitations:This study is fundamentally analytical,and its results describe mathematical facts that are self-evident.Practical implications:Respectable institutions,such as the OECD,the European Commission,and the U.S.National Science Board,produce research country rankings and individual evaluations using size-independent percentile indicators that are misleading in many countries.These misleading evaluations should be discontinued because they can cause confusion among research policymakers and lead to incorrect research policies.Originality/value:Studies linking the lower tail of citation distribution,including uncited papers,to percentile research indicators have not been performed previously.The present results demonstrate that studies of this type are necessary to find reliable procedures for research assessments.
基金supported by the National Natural Science Foundation of China,Nos.32070534(to WY),32370567(to WY),82371874(to XL),81830032(to XL),82071421(to SL)Key Field Research and Development Program of Guangdong Province,No.2018B030337001(to XL)+2 种基金Guangzhou Key Research Program on Brain Science,No.202007030008(to XL)Department of Science and Technology of Guangdong Province,Nos.2021ZT09Y007,2020B121201006(to XL)Guangdong Basic and Applied Basic Research Foundation,Nos.2022A1515012301(to WY),2023B1515020031(to WY).
文摘The vast majority of in vitro studies have demonstrated that PINK1 phosphorylates Parkin to work together in mitophagy to protect against neuronal degeneration.However,it remains largely unclear how PINK1 and Parkin are expressed in mammalian brains.This has been difficult to address because of the intrinsically low levels of PINK1 and undetectable levels of phosphorylated Parkin in small animals.Understanding this issue is critical for elucidating the in vivo roles of PINK1 and Parkin.Recently,we showed that the PINK1 kinase is selectively expressed as a truncated form(PINK1–55)in the primate brain.In the present study,we used multiple antibodies,including our recently developed monoclonal anti-PINK1,to validate the selective expression of PINK1 in the primate brain.We found that PINK1 was stably expressed in the monkey brain at postnatal and adulthood stages,which is consistent with the findings that depleting PINK1 can cause neuronal loss in developing and adult monkey brains.PINK1 was enriched in the membrane-bound fractionations,whereas Parkin was soluble with a distinguishable distribution.Immunofluorescent double staining experiments showed that PINK1 and Parkin did not colocalize under physiological conditions in cultured monkey astrocytes,though they did colocalize on mitochondria when the cells were exposed to mitochondrial stress.These findings suggest that PINK1 and Parkin may have distinct roles beyond their well-known function in mitophagy during mitochondrial damage.
基金the Liberal Arts and Social Sciences Foundation of Ministry of Education in China(No.19YJCGJW003)
文摘There are two weaknesses in current researches into human casualty of ship collision.One is that the range of injuries or fatalities is restricted to the maximum number of casualties in a particular sample,which may not cover all the possible numbers of casualties in the future.International Maritime Organization(IMO)employed the injured or dead percentage of all the persons on board to represent casualties,but it only provided several discrete values to quantify human losses in different scenarios.The other is that the assumption that the distributions of the injuries or fatalities follow certain distribution,such as negative binomial and Poisson distributions is left to be statistically tested.Firstly,this study considers casualty rate,including injury and fatality rates,as random variables;the interval of the variables are from 0 to 1.Then,the distributions of the variables are investigated using historical data.From historical data,we can find that there are many zeros.Zeroinflated models are proved to be effective in processing data with inflated zeros.Furthermore,the probability density of the variables decreases rapidly as the casualty rate becomes larger.Thus,zero-inflated exponential distribution is assumed to fit the data.The parameters of zero-inflated exponential distribution are calibrated by maximum likelihood estimation(MLE)method.Finally,the assumption is tested by chi-square test.The zeroinflated exponential distribution can be used to generate human losses as a part of consequences in the simulation of ship collision risk.
基金supported by the second Tibetan Plateau Scientific Expedition and Research Program[No.2019QZKK0604]the National Natural Science Foundation of China[Nos.42177081 and 42171450]the Youth Cross Team Scientific Research Project of the Chinese Academy of Sciences[No.JCTD-2021–10]。
文摘Exploring the vertical variation in volatile organic compounds(VOCs)in background regions can provide infor-mation on the spatial distribution of pollutants,providing a scientific basis for atmospheric pollution prevention and control strategies.From 15 August to 5 September 2023,at the Southeast Tibet Mountain Comprehensive Environmental Observation Station(SETS),a tethered balloon was used to sample VOCs every 100 m from the ground to 1000 m.A total of 403 air bag samples were collected,and 39 vertical profiles of VOCs were obtained.Ninety-two VOC species were detected.The VOC concentration at the SETS did not change significantly verti-cally,and the average VOC concentration was 11.1±2.4 ppbv.The main components were alkanes(51.4%),alkenes(18.7%),and halohydrocarbons(18.1%).There was no obvious diurnal change in VOCs and no signif-icant difference between the different layers.When the surface VOC concentration was less than 10 ppbv,the concentrations,components,and sources of VOCs were evenly distributed vertically,and the main sources of VOCs at different heights were vehicle exhaust and background.When the surface VOC concentration exceeded 10 ppbv,the VOC concentration gradually decreased with height.The proportion of alkanes in surface VOCs in-creased,and the source was mainly vehicle exhaust.This study confirmed that VOCs are vertically homogeneous in the background of the Tibetan Plateau,emphasizing the importance of vehicle emissions as a potential source of VOCs.
文摘Background: In Sub-Saharan Africa, pre-eclampsia remains a major health problem contributing to high rates of maternal mortality. Despite this condition having adverse effects on maternal and child health, its prevalence and associated risk factors are still significant, especially in developing countries including Ghana. This study aimed to assess the prevalence and demographic distributions associated with pre-eclampsia among pregnant women at the Ho Teaching Hospital. Methods: A facility-based retrospective study was conducted by reviewing available data or hospital records of pregnant mothers admitted to the labor and maternity wards from January 2018 to December 2020. All pregnant women who were diagnosed with pre-eclampsia within this period were included in the study. The data were collected using a structured checklist. Results: 5609 data on pregnant women from 2018 to 2020 were recorded. Out of the 5609 data recorded, 314 pre-eclampsia cases were recorded giving an overall prevalence of 5.6%. The yearly prevalence for 2018, 2019, and 2020 were 4.6%, 5.6%, and 6.6%, respectively. The most recorded pre-eclampsia cases were seen among women within the age group of 18 - 24 years. The data showed that 112 (35.7%) of the pregnant women who had pre-eclampsia were nulliparous. Pre-eclampsia-associated maternal and fetal complications were;preterm delivery 221 (70.4%), intrauterine fetal death 62 (19.7%), eclampsia 9 (2.9%), HELLP syndrome 5 (1.6%) and maternal death 17 (5.4%). Associated factors of pre-eclampsia were parity, level of education, and occupation (p ≤ 0.05). Conclusion: The findings of this study showed a rising trend in the incidence of pre-eclampsia over the years at the Ho Teaching Hospital. Parity, level of education, and occupation were found to be associated with developing pre-eclampsia.
基金supported by the National Natural Science Foundation of China(Grant Nos.42022038,and 42090030).
文摘Sea salt aerosols play a critical role in regulating the global climate through their interactions with solar radiation.The size distribution of these particles is crucial in determining their bulk optical properties.In this study,we analyzed in situ measured size distributions of sea salt aerosols from four field campaigns and used multi-mode lognormal size distributions to fit the data.We employed super-spheroids and coated super-spheroids to account for the particles’non-sphericity,inhomogeneity,and hysteresis effect during the deliquescence and crystallization processes.To compute the singlescattering properties of sea salt aerosols,we used the state-of-the-art invariant imbedding T-matrix method,which allows us to obtain accurate optical properties for sea salt aerosols with a maximum volume-equivalent diameter of 12μm at a wavelength of 532 nm.Our results demonstrated that the particle models developed in this study were successful in replicating both the measured depolarization and lidar ratios at various relative humidity(RH)levels.Importantly,we observed that large-size particles with diameters larger than 4μm had a substantial impact on the optical properties of sea salt aerosols,which has not been accounted for in previous studies.Specifically,excluding particles with diameters larger than 4μm led to underestimating the scattering and backscattering coefficients by 27%−38%and 43%−60%,respectively,for the ACE-Asia field campaign.Additionally,the depolarization ratios were underestimated by 0.15 within the 50%−70%RH range.These findings emphasize the necessity of considering large particle sizes for optical modeling of sea salt aerosols.
文摘In the present work, we are interested in studying the joint distributions of pairs of the monthly maxima of the pollutants used by the environmental authorities in Mexico City to classify the air quality in the metropolitan area. In order to obtain the joint distributions a copula will be considered. Since we are analyzing the monthly maxima, the extreme value distributions of Weibull and Fréchet are taken into account. Using these two distributions as marginal distributions in the copula a Bayesian inference was made in order to estimate the parameters of both distributions and also the association parameters appearing in the copula model. The pollutants taken into account are ozone, nitrogen dioxide, sulphur dioxide, carbon monoxide, and particulate matter with diameters smaller than 10 and 2.5 microns obtained from the Mexico City monitoring network. The estimation was performed by taking samples of the parameters generated through a Markov chain Monte Carlo algorithm implemented using the software OpenBugs. Once the algorithm is implemented it is applied to the pairs of pollutants where one of the coordinates of the pair is ozone and the other varies on the set of the remaining pollutants. Depending on the pollutant and the region where they were collected, different results were obtained. Hence, in some cases we have that the best model is that where we have a Fréchet distribution as the marginal distribution for the measurements of both pollutants and in others the most suitable model is the one assuming a Fréchet for ozone and a Weibull for the other pollutant. Results show that, in the present case, the estimated association parameter is a good representation to the correlation parameters between the pair of pollutants analyzed. Additionally, it is a straightforward task to obtain these correlation parameters from the corresponding association parameters.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974007,12074146,12074142,61575077,12374265,11947243,91850114,and 11774131)the Natural Science Foundation of Jilin Province of China(Grant No.20220101016JC).
文摘Molecular-frame photoelectron momentum distributions(MF-PMDs)have been studied for imaging molecular structures.We investigate the MF-PMDs of CO_(2)molecules exposed to circularly polarized(CP)attosecond laser pulses bysolving the time-dependent Schrodinger equations based on the single-active-electron approximation frames.Results showthat high-frequency photons lead to photoelectron diffraction patterns,indicating molecular orbitals.These diffractionpatterns can be illustrated by the ultrafast photoionization models.However,for the driving pulses with 30 nm,a deviationbetween MF-PMDs and theoretically predicted results of the ultrafast photoionization models is produced because theCoulomb effect strongly influences the molecular photoionization.Meanwhile,the MF-PMDs rotate in the same directionas the helicity of driving laser pulses.Our results also demonstrate that the MF-PMDs in a CP laser pulse are the superpositionof those in the parallel and perpendicular linearly polarized cases.The simulations efficiently visualize molecularorbital geometries and structures by ultrafast photoelectron imaging.Furthermore,we determine the contribution of HOMOand HOMO-1 orbitals to ionization by varying the relative phase and the ratio of these two orbitals.
文摘Background: The signal-to-noise ratio (SNR) is recognized as an index of measurements reproducibility. We derive the maximum likelihood estimators of SNR and discuss confidence interval construction on the difference between two correlated SNRs when the readings are from bivariate normal and bivariate lognormal distribution. We use the Pearsons system of curves to approximate the difference between the two estimates and use the bootstrap methods to validate the approximate distributions of the statistic of interest. Methods: The paper uses the delta method to find the first four central moments, and hence the skewness and kurtosis which are important in the determination of the parameters of the Pearsons distribution. Results: The approach is illustrated in two examples;one from veterinary microbiology and food safety data and the other on data from clinical medicine. We derived the four central moments of the target statistics, together with the bootstrap method to evaluate the parameters of Pearsons distribution. The fitted Pearsons curves of Types I and II were recommended based on the available data. The R-codes are also provided to be readily used by the readers.
