A simple relation (v-lnB) (u-lnx)=c was recognized betweenx as dbh (or individual basal area) andB as the cumulative basal area abovex, for various stands of warm-temperate rain forests of Yakushima Island, southern Japan (v, u andc, parameters). The model parameters explained a difference in the pattern of stand development between secondary succession
after clear-felling and gap regeneration within primary forests. 相似文献
Knowledge of the spatial distribution of stored product insects may reduce the dependency on chemicals for control of these insects. Biological control, for instance, could be improved based on such knowledge. In this paper we describe the three-dimensional spatial oviposition pattern of Callosobruchus maculatus in stored cowpea. Individual C. maculatus females oviposited in clusters of 70±15 (SD) eggs. These clusters were variable in shape. In any cluster 90 to 95% of the eggs fitted into a volume of 19.1±3.5 cm3. The egg density was highest (0.6 eggs bean–1) at the center of a cluster and decreased towards the periphery. A statistically significant relationship existed between the number of eggs n in a cluster and the cluster volume, V(cm3): V=11.5+0.11n. We also investigated the spatial egg distribution of beetles which emerged from egg clusters such as those produced by individual females. Their oviposition was not confined to one specific area but was scattered throughout the bean mass. A point pattern analysis showed that the density of the `parent' cluster had no effect on the spatial egg pattern. These results give insight into the foraging environment which the egg parasitoid Uscana lariophaga, a promising candidate for biological control of C. maculatus, is facing. We argue that the probability p of encountering at least one other bean with eggs after a parasitization is a function of the number n of beans that are visited: p=1–0.42 (0.37)(n–1). 相似文献
In the study of spatial patterns, the statistic I' = (n — 1)s2/x was commonly used. In this paper, we found that x — s2 has an approximated normal distribution with zero mean if the xi's (i = 1 to n) are independent identically distributed Poisson variables. Based on this conclusion, the hypothesis that a point pattern is completely random can be tested directly. And a method for the test of spatial patterns was proposed which can be sued as an alternative to the Chi-square based dispersion index test. 相似文献
A recombinant Helicoverpa armigera nucleopolyhedrovirus (HearNPV) expressing the insect‐selective neurotoxin (RjAa17f) from Cuban scorpion Rhopalurus junceus was constructed by replacing the UDP‐glucosyltransferase gene (egt) using λ‐red homologous recombination system. Another egt deleted control HearNPV was constructed in a similar way by inserting egfp gene into the egt locus. One‐step viral growth curve and viral DNA replication curve analysis confirmed that the recombination did not affect the viral growth and DNA replication in host cells. There is no discernable difference in occlusion‐body morphogenesis between RjAa17f‐HearNPV, Egfp‐HearNPV and HZ8‐HearNPV, which was confirmed by transmission electron microscopy analysis. However, the insecticidal activity of RjAa17f‐HearNPV is enhanced against the third instar H. armigera larvae according to the bioassay on virulence comparison. There is a dramatic reduction (56.9%) in median lethal dose (LD50) and also a reduction (13.4%) in median survival time (ST50) for the recombinant RjAa17f‐HearNPV compared to the HZ8‐HearNPV, but only a 27.5% reduction in LD50 and 10.1% reduction in ST50 value when Egfp‐HearNPV is compared with HZ8‐HearNPV. The daily diet consumption analysis showed that the RjAa17f‐HearNPV was able to inhibit the infected larvae feeding compared with the egt minus HearNPV. These results demonstrated that this novel recombinant RjAa17f‐HearNPV could improve the insecticidal effect against its host insects and RjAa17f could be a considerable candidate for other recombinant baculovirus constructions. 相似文献
The estimator ?0(x) of the regression r(x) = E (Y | × = x) from measured points (xi, yi), i = 1(1) n, of a continuous two-dimensional random variable (X, Y) with unknown continuous density function f(x, y) and with moments up to the second order can be made with the help of a density estimation f?0(x, y) (see e.g. SCHMERLING and PEIL, 1980). Here f?0(x, y) still contains free parameters (so-called band-width-parameters), the values of which have to be optimally fixed in the concrete case. This fixing can be done by using a modification of the maximum-likelihood principle including jackknife techniques. The parameter values can be also found from the estimators for r(x). Here the cross-validation principle can be applied. Some numerical aspects of these possibilities for optimally fixing the bandwidth-parameter are discussed by means of examples. If ?0(x) is used as a smoothing operator for time series the optimal choice of the parameter values is dependent on the purpose of application of the smoothed time series. The fixing will then be done by considering the so-called filter-characteristic of ?C0(x). 相似文献
We study the discrete model for cooperation as expressed through the dynamics of the family of noninvertible planar maps (x, y) (x exp(r(1 – x) + sy), y exp(r(1 – y) + sx)), with parameters r, s > 0. We prove that the map is proper in the open positive quadrant and describe its various stretching and folding actions. We determine conditions for a Hopf bifurcation — probably one of a cascade of double, quadruple, ... limit cycles, as a curve is followed in parameter space. For r > s an approximating version of the map is dissipative and permanent in the positive quadrant. We include the results of an extensive computer simulation, including a bifurcation diagram (y vs. r, with s fixed) through which is cut a number of x–y phase-plane plots; (an r–y curve penetrates each plot like a thread through cards). These indicate a complex dynamical evolution for cooperation, from stable cycle to strange attractor. A general conclusion is that the benefit of cooperation can be relatively high average values at the cost of oscillations of high amplitude. 相似文献
Let X1:n, X2:n, X3:n…, Xn:n be the order statistics of n independent random variables with the common (absolutely continuous strictly increasing) distribution function F. The main results given in this article are:
1 For any fixed r and two distinct numbers s1 and s2 (1<r<s1<s2≦n) the distributions of Vi and Wi (defined in (1.11) and (1.12) are identical for i = 1,2 iff F(x) is WEIBULL (1.2).
2 The statistics D1 and D2 (as in (1.8) and (1.9)) are independent iff F(x) is WEIBULL (1.2).
3 The statistics Ui (1≦j≦n?1) and Xi:n (i ≦ j) are independent iff F(x) is WEIBULL (1.2).
4 Let X, X1, X2, …, Xk be random variables such that
These conditions are necessary and sufficient for F(x) to be WEIBULL . 相似文献
A continuous time discrete state cumulative damage process {X(t), t ≥ 0} is considered, based on a non‐homogeneous Poisson hit‐count process and discrete distribution of damage per hit, which can be negative binomial, Neyman type A, Polya‐Aeppli or Lagrangian Poisson. Intensity functions considered for the Poisson process comprise a flexible three‐parameter family. The survival function is S(t) = P(X(t) ≤ L) where L is fixed. Individual variation is accounted for within the construction for the initial damage distribution {P(X(0) = x) | x = 0, 1, …,}. This distribution has an essential cut‐off before x = L and the distribution of L – X(0) may be considered a tolerance distribution. A multivariate extension appropriate for the randomized complete block design is developed by constructing dependence in the initial damage distributions. Our multivariate model is applied (via maximum likelihood) to litter‐matched tumorigenesis data for rats. The litter effect accounts for 5.9 percent of the variance of the individual effect. Cumulative damage hazard functions are compared to nonparametric hazard functions and to hazard functions obtained from the PVF‐Weibull frailty model. The cumulative damage model has greater dimensionality for interpretation compared to other models, owing principally to the intensity function part of the model. 相似文献
Cold atmospheric‐pressure plasmas have become of increasing importance in sterilization processes especially with the growing prevalence of multi‐resistant bacteria. Albeit the potential for technological application is obvious, much less is known about the molecular mechanisms underlying bacterial inactivation. X‐jet technology separates plasma‐generated reactive particles and photons, thus allowing the investigation of their individual and joint effects on DNA. Raman spectroscopy shows that particles and photons cause different modifications in DNA single and double strands. The treatment with the combination of particles and photons does not only result in cumulative, but in synergistic effects. Profilometry confirms that etching is a minor contributor to the observed DNA damage in vitro.
Schematics of DNA oligomer treatment with cold atmospheric‐pressure plasma. 相似文献
Following our established theoretical model to deal with the second-harmonic generation (SHG) excited by a linearly polarized
focused beam in type I collagen, in this paper, we further quantitatively characterize the differences between SHG emissions
in type I collagen excited by collimated and focused beams. The effects of the linear polarization angle (α) and the fibril polarity characterized by the hyperpolarizability ratio ρ on SHG emission has been compared under collimated and focused beam excitation, respectively. In particular, SHG emission
components along the i axis ( I2w,i )\left( {I_{2\omega {,}i} } \right) (i = x,y,z), the induced SHG emission deviation angle γij, and the detected SHG signals (I2ω,ij) in the ij plane by rotating the applied polarizer angle φij have been investigated (i = x, x, y; j = y, z, z). Results show that under our simulation model, SHG emission in the xy plane, such as I2ω,x ,I2ω,y ,γxy and I2ω,xy varying as polarization angle (α) under collimated and focused light, presents no significant difference. The reverse of the fibril polarity has induced great
impact on I2ω,x ,γxy and I2ω,xy in both collimated and focused light. I2ω,x and γxy show similarity, but I2ω,xy at α = 30° demonstrates a slight difference in focused light to that in collimated light. Under focused light, the reverse of
fibril polarity causes obvious changes of the collected SHG intensity I2ω,xz and I2ω,yz at a special polarization angle α = 60° and γxz, γyz along α. 相似文献
For spherical particles randomly dispersed in the space of a specimen the estimators of the parameters of the space structure from the measurements obtained from extraction replicas are given. First an arbitrary form of the probability density function f(x) of the diameter X and then the generalized RAYLEIGH and lognormal distributions of X are considered. Unbiased estimators of the space parameters and of parameters of these distributions are found. The variances of these estimators are given and unbiased estimators of these variances are determined. 相似文献
The CAUCHY-PEXIDER functional equation H (x±y)=F(x) G(y) is generalized to the form H ((xc±yc)1/c) = F(x) G(y), c≠0, assuming the function H(x) possesses a measurable majorant on a set of positive measure. The result is used to obtain a characterization of WEIBULL distribution. This functional equation is generalized to functions of vector variables. 相似文献
Optical properties (μa, μs and g) of certain human tissue types such as skin and blood have been very well investigated. However until today, for internal body organs such as the esophagus they are not well characterized. For ex‐vivo measurements “Inverse Adding Doubling” (IAD) and Inverse Monte‐Carlo‐Simulation (IMCS) are state of the art. Both methods need the measurement of the collimated transmission. Current methods lack a proper way of measuring the collimated transmission. Hence, this measurement of the g‐factor has a systematic error. Therefore, for the measurement of the collimated transmission, a new approach has been developed and evaluated with intralipid. Finally, the optical properties of mucosa, sub mucosa, muscularis and adventitia of pig esophagus tissue are calculated with IAD. The results are promising and in agreement with published literature.
In metapopulations, individual patch contribution (source or sink) is typically calculated as a patch growth rate (the intrinsic lambda, I) dependent only upon local demographics. We demonstrate that when dispersal is explicitly included in the model, the growth rates for all patches calculated in an analogous manner (the observed lambda, O) equilibrate to the overall metapopulation growth rate and thus no longer serve as a useful reflection of the demographic and dispersive characteristics of a given patch. In these situations we suggest an alternative method of estimating patch contribution (the contribution lambda, C) in which a patch is decremented for losses that occur within it and credited for gains that occur anywhere in the metapopulation because of it. We compare values of I, O, and C for individual patches in discrete-time density-independent metapopulation models of two organisms with very different life histories, mayflies with adult dispersal, and reef fish with larval dispersal. Results confirm that when dispersal is included only C clearly indicates the contribution of a particular patch. I–C comparisons indicate that inclusion of dispersal in the mayfly model was only important if connectivity patterns were random or directional. In the reef fish model, however, results were very different when dispersal was included and there were many cases of patches being misidentified (e.g., as a source when it was really a sink) depending upon the metric used (I or C). Our results demonstrate the importance of including dispersal in metapopulation models when considering the contribution of individual patches. 相似文献
A biological microbeam for precisely positioned single-ion/single cell irradiation is built in the Institute of Modern Physics
in Fudan University, Shanghai, China, based on the tandem accelerator (2 × 3MV) in the laboratory. In this paper, the developing
progress of the FUDAN microbeam is reported, including the newly constructed beam line, the microbeam collimator, the ion
detection system, and the cell-imaging and targeting systems. Statistical models are proposed for evaluating the spatial resolution
and dosage precision of the microbeam. By taking the collimated ions as a Gaussian beam, the spatial resolution can be evaluated
by the full width at half maximum of the 2-D Gaussian distribution, which is determined by fitting the proportions of peripheral
pits outside specific radii in the pit clusters etched on ion track detectors to a 2-D Gaussian distribution. In the preset
hitting of defined ion number, by taking the real delivered number of ions as an independent identically distributed random
variable (iidrv), according to the Law of Large Numbers and Central Limit Theorem, the expected value μ and standard deviation
σ of the real delivered ion number in a preset N-ion hitting can be determined by approaching the normal distribution of N (μ, σ2/n) with the proportions of the mean counts of pits in multiple pit clusters on ion track detectors. By the values of μ, σ and additional assumptions, statistical dosage precision evaluations can be made on the preset hitting. From the linear fit
curve of μ(N) and the power function fit curve of σ(N) on different preset ion numbers, characteristic factors k, b, A, p can be extracted for a precision evaluation independent of the specific preset ion number. 相似文献
A new experimental framework for the characterization of defects in semiconductors is demonstrated. Through the direct, energy‐resolved correlation of three analytical techniques spanning six orders of magnitude in spatial resolution, a critical mid‐bandgap electronic trap level (EV + 0.56 eV) within Ag0.2Cu0.8In1?xGaxSe2 is traced to its nanoscale physical location and chemical source. This is achieved through a stepwise, site‐specific correlated characterization workflow consisting of device‐scale (≈1 mm2) deep level transient spectroscopy (DLTS) to survey the traps present, scanning probe–based DLTS (scanning‐DLTS) for mesoscale‐resolved (hundreds of nanometers) mapping of the target trap state's spatial distribution, and scanning transmission electron microscope based electron energy‐loss spectroscopy (STEM‐EELS) and X‐ray energy‐dispersive spectroscopy for nanoscale energy‐, structure, and chemical‐resolved investigation of the defect source. This first demonstration of the direct observation of sub‐bandgap defect levels via STEM‐EELS, combined with the DLTS methods, provides strong evidence that the long‐suspected CuIn/Ga substitutional defects are indeed the most likely source of the EV + 0.56 eV trap state and serves as a key example of this approach for the fundamental identification of defects within semiconductors, in general. 相似文献
Rather than simply acting as a photographic camera capturing two‐dimensional (x, y) intensity images or a spectrometer acquiring spectra (λ), a hyperspectral imager measures entire three‐dimensional (x, y, λ) datacubes for multivariate analysis, providing structural, molecular, and functional information about biological cells or tissue with unprecedented detail. Such data also gives clinical insights for disease diagnosis and treatment. We summarize the principles underpinning this technology, highlight its practical implementation, and discuss its recent applications at microscopic to macroscopic scales.
Datacube acquisition strategies in hyperspectral imaging x, y, spatial coordinates; λ, wavelength. 相似文献
Connections among species-abundance (i-mi), species-frequency (i-Fi), and species-sample size (Sn-n) relationships were examined on the basis of the mapping data of a natural forest in Thailand. The spatial distribution of
individual trees without any discrimination of species was nearly random. Provided that the spatial distribution of each species
was random, thei-mi and thei-Fi relationship was reconstructed from each other in terms of the total number of species (S) and the total number of individuals (N) in the data. The number of species (Sn) in a subsample consisting ofn individuals was then obtained from thei-Firelationship. Logarithm ofSn increased with logn and showed a convex curve through the origin. The values of diversity indices based onN andS(orn andSn) were affected by sample size. These trends were further examined on the basis of 944 data sets of biotic communities and
three mathematical models of anS-N relationship. The properties of species-area relation were discussed in the light of these results. 相似文献