基体分离/MC-ICP-MS测定树皮表层235U/238U同位素比率

分别从日本广岛和京都采集了香樟树(Cinnamomum camphora)树皮样品共12份,用X射线能谱仪研究了树皮表层基体元素组成,并用扫描电镜观察了树皮表层微观形貌.将树皮表层样品进行干灰化法处理后,采用DOWEX(R)1-X8型阴离子交换树脂分离基体元素,然后用多接收器电感耦合等离子体质谱仪(MC-ICP-MS)测定了树皮表层235U/238U同位素比率.研究结果表明:树皮表层主要基体元素为Al,Ca,Fe,K,Mg,Si和C,O,S;采用不同浓度硝酸淋洗DOWEX(R) 1-X8型阴离子交换树脂可实现树皮表层痕量U与基体元素的有效分离.与京都树皮表层相比,广岛树皮表层不仅U含量显著偏高(P=0.012),而且部分样品235U/238U同位素比率亦略高于其自然丰度比.     

Fourth generation CP violation effects on B-->Kpi, phiK, and rhoK in next-to-leading-order perturbative QCD

We study the effect from a sequential fourth generation quark on penguin-dominated two-body nonleptonic B meson decays in the next-to-leading order perturbative QCD formalism. With an enhancement of the color-suppressed tree amplitude and possibility of a new CP phase in the electroweak penguin amplitude, we can account better for A(CP)(B(0)-->K+ pi-)-A(CP)(B+-->K+ pi0). Taking |V(t's)V(t'b)| approximately 0.02 with a phase just below 90 degrees, which is consistent with the b-->sl+ l- rate and the B(s) mixing parameter Deltam(B)(s), we find a downward shift in the mixing-induced CP asymmetries of B(0)-->K(S)(pi 0) and phi(K)(S). The predicted behavior for B(0)-->rho(0)(K)(S) is opposite.     

Random walks on the Bethe lattice

We obtain random walk statistics for a nearest-neighbor (Pólya) walk on a Bethe lattice (infinite Cayley tree) of coordination numberz, and show how a random walk problem for a particular inhomogeneous Bethe lattice may be solved exactly. We question the common assertion that the Bethe lattice is an infinite-dimensional system.Supported in part by the U.S. Department of Energy.     

A tool for real-time acoustic species identification of delphinid whistles

The ability to identify delphinid vocalizations to species in real-time would be an asset during shipboard surveys. An automated system, Real-time Odontocete Call Classification Algorithm (ROCCA), is being developed to allow real-time acoustic species identification in the field. This Matlab-based tool automatically extracts ten variables (beginning, end, minimum and maximum frequencies, duration, slope of the beginning and end sweep, number of inflection points, number of steps, and presence/absence of harmonics) from whistles selected from a real-time scrolling spectrograph (ISHMAEL). It uses classification and regression tree analysis (CART) and discriminant function analysis (DFA) to identify whistles to species. Schools are classified based on running tallies of individual whistle classifications. Overall, 46% of schools were correctly classified for seven species and one genus (Tursiops truncatus, Stenella attenuata, S. longirostris, S. coeruleoalba, Steno bredanensis, Delphinus species, Pseudorca crassidens, and Globicephala macrorhynchus), with correct classification as high as 80% for some species. If classification success can be increased, this tool will provide a method for identifying schools that are difficult to approach and observe, will allow species distribution data to be collected when visual efforts are compromised, and will reduce the time necessary for post-cruise data analysis.     

Bd-->phi KS CP asymmetries as an important probe of supersymmetry

The decay B(d)-->phi K(S) is a special probe of physics beyond the standard model (SM), since it has no SM tree level contribution. Motivated by recent data suggesting a deviation from the SM for its time-dependent CP asymmetry, we examine supersymmetric explanations. Chirality preserving contributions are generically small, unless gluino is relatively light. Higgs contributions are also too small to explain a large asymmetry. Chirality flipping LR and RL gluino contributions actually can provide sizable effects without conflict with all related results. We discuss how various insertions can be distinguished, and argue the needed sizes of mass insertions are reasonable.     

Topologies and Laplacian spectra of a deterministic uniform recursive tree

The uniform recursive tree (URT) is one of the most important models and has been successfully applied to many fields. Here we study exactly the topological characteristics and spectral properties of the Laplacian matrix of a deterministic uniform recursive tree, which is a deterministic version of URT. Firstly, from the perspective of complex networks, we determine the main structural characteristics of the deterministic tree. The obtained vigorous results show that the network has an exponential degree distribution, small average path length, power-law distribution of node betweenness, and positive degree-degree correlations. Then we determine the complete Laplacian spectra (eigenvalues) and their corresponding eigenvectors of the considered graph. Interestingly, all the Laplacian eigenvalues are distinct.     

Photoacoustic investigation of copaiba oil

In this study we demonstrate the usefulness of the Photoacoustic Spectroscopy (PAS) in the investigation of copaiba oil obtained from Copaifera tree, located in a site within Rond?nia State, Amazon region, Brazil. Pure copaiba oil sample was diluted in 98% ethanol providing 10 different samples at volume concentration in the range of 5 to 50% vv. The observed photoacoustic spectral features from pure copaiba oil and the corresponding diluted samples, in the 0.18 to 4.00 μm wavelength region, are discussed in terms of five distinct bands (C, S, L, K, and X bands). Photoacoustic peak intensity was investigated as a function of the copaiba oil concentration in the 5 to 50% v.v.     

Contemporary electrostatics—I: Physical background and applications

This article contains a brief introduction to Newton's early life to put into context the subsequent events in this narrative. It is followed by a summary of accounts of Newton's famous story of his discovery of universal gravitation which was occasioned by the fall of an apple in the year 1665/6. Evidence of Newton's friendship with a prosperous Yorkshire family who planted an apple tree arbour in the early years of the eighteenth century to celebrate his discovery is presented. A considerable amount of new and unpublished pictorial and documentary material is included relating to a particular apple tree which grew in the garden of Woolsthorpe Manor (Newton's birthplace) and which blew down in a storm before the year 1816. Evidence is then presented which describes how this tree was chosen to be the focus of Newton's account. Details of the propagation of the apple tree growing in the garden at Woolsthorpe in the early part of the last century are then discussed, and the results of a dendrochronological study of two of these trees is presented. It is then pointed out that there is considerable evidence to show that the apple tree presently growing at Woolsthorpe and known as 'Newton's apple tree' is in fact the same specimen which was identified in the middle of the eighteenth century and which may now be 350 years old. In conclusion early results from a radiocarbon dating study being carried out at the University of Oxford on core samples from the Woolsthorpe tree lend support to the contention that the present tree is one and the same as that identified as Newton's apple tree more than 200 years ago. Very recently genetic fingerprinting techniques have been used in an attempt to identify from which sources the various 'Newton apple trees' planted throughout the world originate. The tentative result of this work suggests that there are two separate varieties of apple tree in existence which have been accepted as 'the tree'. One may conclude that at least some of the current Newton apple trees have no connection with the original tree at Woolsthorpe Manor.     

动态故障树在主蒸汽管道破裂事故风险评价中的初步应用研究

冗余设计使核电厂系统广泛存在复杂时序失效行为,而基于静态故障树(Static fault tree, SFT)的事故风险评价无法对时序失效行为进行准确模拟。为解决这一问题,本工作提出一种基于事件树+动态故障树(Dynamic Fault Tree, DFT)的事故风险分析框架,并以典型三代压水堆主蒸汽管道破裂事故为例,开展动态事故风险案例分析。首先,建立主蒸汽管道破裂事故的事件树模型以及相关系统的DFT模型;其次,将系统故障树分为DFT模块和SFT模块,并将DFT树模块替换为超级事件参与后续计算;最后,采用割集法计算案例结果,并在相同条件下与传统SFT方法进行对比。案例分析结果表明：(1)相较于SFT方法,所提方法更为贴近系统的真实失效场景;(2)针对文中案例所提方法可以降低相关系统失效概率与部分事故序列的发生频率、有助于释放保守风险。     

Differential response of two Pinus spp. to avian nitrogen input as revealed by nitrogen isotope analysis for tree rings

Temporal variations in N concentration and δ(15)N value of annual tree rings (1 year of time resolution) of two Japanese Black Pine (Pinus thunbergii) and three Japanese Red Pine (Pinus densiflora) trees under current breeding activity of the Great Cormorant (Pharacrocorax carbo) and the Black-tailed Gull (Larus crassirostris), respectively, in central and northeastern Japan were studied. Both species from control sites where no avian input occurs show negative values (δ(15)N = around -4 ‰ to -2 ‰) which are common among higher plants growing under high rainfall regimes. The δ(15)N values of P. densiflora show uniformly positive values several years before and after the breeding event, indicating N translocation that moved the absorbed N of a given growth year to tree rings of the previous year while a clear historical value of soil N dynamics was kept intact in the annual rings of P. thunbergii. Long-term N trends inferred from tree rings must take into account tree species with limited translocation rates that can retain actual N annual acquisition.     

光诱导雄黄矿物同质异象变化的显微成像拉曼散射研究

利用拉曼光谱研究了激光照射诱导雄黄的同质异象变化,这些结果证实了下面的反应：由于As—As键相对较弱,首先As—As键被破坏,有1个S原子加入到As—As键中,形成As—S—As键。此时由As₄S₄(Realgar类型)变化为As₄S₅相,而As₄S₅处于不稳定状态,As₄S₅相变化为 Pararealgar时有1个S原子从As—S—As键中释放出来。释放出来的S原子又加入到另外1个As₄S₄(Realgar)中,引起As₄S₄(Realgar)相变化为As₄S₅,As₄S₅进而分裂为1个S原子和As₄S₄(Pararealgar类型)。照射促进雄黄经由 As₄S₅ 分子被转换成副雄黄。     

Genealogical trees from genetic distances

In a population with haploid reproduction any individual has a single parent in the previous generation. If all genealogical distances among pairs of individuals (generations from the closest common ancestor) are known it is possible to exactly reconstruct their genealogical tree. Unfortunately, in most cases, genealogical distances are unknown and only genetic distances are available. The genetic distance between two individuals is measurable from differences in mtDNA (mitochondrial DNA) since in the case of humans or other complex organisms mtDNA is transmitted in a haploid manner. An analogous distance can be also computed for languages where it may be measured from lexical differences, in this case, nevertheless, haploid reproduction is only a raw approximation. Assuming a constant rate of mutation, these genetic distances are random and proportional only on average to genealogical ones. The reconstruction of the genealogical tree from the available genetic distances is forceful imprecise. In this paper we try to quantify the error one may commit in the reconstruction of the tree for different degrees of randomness. The errors may concern both topology of the tree (the branching hierarchy) and, in case of correct topology, the proportions of the tree (length of various branches).     

Remote Estimation of the Chlorophyll Concentration of Living Trees Using Laser-induced Fluorescence Imaging Lidar

Monthly variation in chlorophyll concentration of living ginko tree leaves 65 m away from a system was remotely estimated by a laser-induced fluorescence imaging lidar. The combination of a pulsed laser and a short-time gated CCD using an image intensifier made it possible to monitor the weak fluorescence signal from the ginko tree leaves as an image. By applying the experimental idea that a ratio of intensity of the chlorophyll fluorescence at 740 nm to that at 685 nm showed a linear correlation to the chlorophyll concentration, the fluorescence image of the ginko tree obtained by the lidar was converted to the chlorophyll concentration distribution image.     

All-optical prefix tree adder with the help of terahertz optical asymmetric demultiplexer

We propose and describe an all-optical prefix tree adder with the help of a terahertz optical asymmetric demultiplexer (TOAD) using a set of optical switches. The prefix tree adder is useful in compound adder implementation. It is preferred over the ripple carry adder and the carry lookahead adder. We also describe the principle and possibilities of the all-optical prefix tree adder. The theoretical model is presented and verified through numerical simulation. The new method promises higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuits of enhanced functionality in which the prefix tree adder is the basic building block.     

Exact Solution of a Generalized ANNNI Model on a Cayley Tree

We consider the Ising model on a rooted Cayley tree of order two with nearest neighbor interactions and competing next nearest neighbor interactions restricted to spins belonging to the same branch of the tree. This model was studied by Vannimenus who found a new modulated phase, in addition to the paramagnetic, ferromagnetic, antiferromagnetic phases and a (+ + - -) periodic phase. Vannimenus’s results are based on an analysis of the recurrence equations (relating the partition function of an n ? generation tree to the partition function of its subsystems containing (n ?1) generations) and most results are obtained numerically. In this paper we analytically study the recurrence equations and obtain some exact results: critical temperatures and curves, number of phases, partition function.     

Potential for assessing long-term dynamics in soil nitrogen availability from variations in delta15N of tree rings

Numerous researchers have used the isotopic signatures of C, H, and O in tree rings to provide a long-term record of changes in the physiological status, climate, or water-source use of trees. The frequently limiting element N is also found in tree rings, and variation in its isotopic signature may provide insight into long-term changes in soil N availability of a site. However, research has suggested that N is readily translocated among tree ring of different years; such infidelity between the isotopic compositions of the N taken up from the soil and the N contained in the ring of that growth year would obscure the long-term N isotopic record. We used a 15-year 15N-tracer study to assess the degree of N translocation among tree rings in ponderosa pine (Pinus ponderosa) trees growing in a young, mixed-conifer plantation. We also measured delta13C and delta15N values in unlabeled trees to assess the degree of their covariance in wood tissue, and to explore the potential for a biological linkage between them. We found that the maximum delta15N values in rings from the labeled trees occurred in the ring formed one-year after the 15N was applied to the roots. The delta15N value of rings from labeled trees declined exponentially and bidirectionally from this maximum peak, toward younger and older rings. The unlabeled trees showed considerable interannual variation in the delta15N values of their rings (up to 3 and 5 per thousand), but these values correlated poorly between trees over time and differed by as much as 6 per thousand. Removal of extractives from the wood reduced their delta15N value, but the change was fairly small and consistent among unlabeled trees. The delta13C and delta15N values of tree rings were correlated over time in only one of the unlabeled trees. Across all trees, both delta13C values of tree rings and annual stem wood production were well correlated with annual precipitation, suggesting that soil water balance is an important environmental factor controlling both net C gain and transpirational water loss at this site. Our results suggest that interannual translocation of N among tree rings is substantial, but may be predictable enough to remove this source of variation from the tree-ring record, potentially allowing the assessment of long-term changes in soil N availability of a site.     

高频电压下交联聚乙烯电缆绝缘中电树枝生长的动力学模型

针对高压交联聚乙烯电缆绝缘试样,在1000—2000Hz 10kV峰值正弦电压下,采用计算机实时显微数字摄像技术进行了电树枝培养实验.基于半结晶绝缘材料中电树枝生长机理和电树枝结构的分形特征,提出了一个在高频范围定量预测电应力驱动下交联聚乙烯电缆绝缘中电树枝生长特性的动力学模型,获得了电树枝生长率方程和从电树枝生长到击穿过程的寿命公式.将该模型预测值与实验中获得的电树枝生长规律实验数据进行比较,其结果有较好的一致性,表明提出的模型化方法可以应用到交联聚乙烯电缆绝缘中电树枝老化规律的定量分析研究中. 关键词： 交联聚乙烯电缆绝缘 电树枝 施压频率 动力学模型     

Minimum Query Set for Decision Tree Construction

A new two-stage method for the construction of a decision tree is developed. The first stage is based on the definition of a minimum query set, which is the smallest set of attribute-value pairs for which any two objects can be distinguished. To obtain this set, an appropriate linear programming model is proposed. The queries from this set are building blocks of the second stage in which we try to find an optimal decision tree using a genetic algorithm. In a series of experiments, we show that for some databases, our approach should be considered as an alternative method to classical ones (CART, C4.5) and other heuristic approaches in terms of classification quality.     

基于时序NDVI与光谱微分变换的森林优势树种识别

基于遥感光谱特征准确识别优势树种类型对于区域林业资源的监测和经营具有重要意义,也是当前亟待解决的重要科学问题。伴随遥感技术的发展,利用时间序列高分影像能够有效获取林分树种不同物候期生长特性及其冠层光谱动态信息,有利于克服区域森林类型精细识别中普遍存在的异物同谱难题。以中国东北地区赤峰市旺业甸国有林场为试验区,采用覆盖完整自然年的共36景高分一号（GF-1）WFV时间序列数据（16 m）,提取包含不同优势树种生长阶段特征的林分冠层光谱归一化植被指数（NDVI）,结合支持向量机（SVM）模型对研究区内5种典型优势树种：油松、落叶松、山杨、白桦和蒙古栎,进行不同时间尺度下（单季相、全季相、逐月和逐旬）的光谱识别研究。同时,分别基于原始时序光谱及其一阶、二阶和三阶微分变换结果,探讨了不同分辨率时序NDVI光谱及其3种微分变换结果对区域森林优势树种的识别效果。结果显示,基于不同尺度的时间序列数据能够获得比不同季节单时相数据更好的树种识别结果（p＜0.05）,其中采用全季相数据的树种总分类精度相比于春、夏和秋不同季节的单季相数据结果,分别提高了7.67%,6.64%和3.6%,表明时间序列影像中所包含的植被物候信息对于区分不同森林树种类型十分重要,同时秋季是采用单时相数据的最佳识别季节（p＜0.05）;在不同时间序列数据中,基于逐旬的NDVI数据显著优于基于逐月和全季相数据的光谱识别结果（p＜0.05）,而基于全季相数据的光谱识别结果最低（p＜0.05）,表明更密集的时序光谱信息有利于区域树种类型识别精度的提升。此外,结合光谱微分变换后的树种识别结果比仅采用原始NDVI时间序列的识别结果精度更高（p＜0.05）,其中基于逐旬和逐月时间分辨率数据的最高识别精度能够达到82.1%和78.74%,分别提升了3.38%和2.95%。研究表明采用基于全年逐旬或逐月尺度的时序光谱数据,并结合相应的微分变换方法,可以有效提高区域尺度优势树种的识别精度,为相关多光谱森林植被精细识别研究提供参考。