Sufficiency of the number of segregating sites in the limit under finite-sites mutation

We show that the number of segregating sites is a sufficient statistic for the scaled mutation parameter (θ) in the limit as the number of sites tends to infinity and there is free recombination between sites. We assume that the mutation parameter at each site tends to zero such than the total mutation parameter (θ) is constant in the limit. Our results show that Watterson’s estimator is the maximum likelihood estimator in this case, but that it estimates a composite parameter which is different for different mutation models. Some of our results hold when recombination is limited, because Watterson’s estimator is an unbiased, method-of-moments estimator regardless of the recombination rate. The quantity it estimates depends on the details of how mutations occur at each site.     

The zero-sum assumption in neutral biodiversity theory

The neutral theory of biodiversity as put forward by Hubbell in his 2001 monograph has received much criticism for its unrealistic simplifying assumptions. These are the assumptions of functional equivalence among different species (neutrality), the assumption of point mutation speciation, and the assumption that resources are continuously saturated, such that constant resource availability implies constant community size (zero-sum assumption). Here we focus on the zero-sum assumption. We present a general theory for calculating the probability of observing a particular species-abundance distribution (sampling formula) and show that zero-sum and non-zero-sum formulations of neutral theory have exactly the same sampling formula when the community is in equilibrium. Moreover, for the non-zero-sum community the sampling formula has this same form, even out of equilibrium. Therefore, the term "zero-sum multinomial (ZSM)" to describe species abundance patterns, as coined by Hubbell [2001. The Unified Neutral Theory of Biodiversity and Biogeography, Princeton University Press, Princeton, NJ], is not really appropriate, as it also applies to non-zero-sum communities. Instead we propose the term "dispersal-limited multinomial (DLM)", thus making explicit one of the most important contributions of neutral community theory, the emphasis on dispersal limitation as a dominant factor in determining species abundances.     

Effects of reduced irradiance on leaf morphology,photosynthetic capacity,and fruit yield in olive (<Emphasis Type="Italic">Olea europaea</Emphasis> L.)

One-year-old olive trees (cv. Koroneiki) were grown in plastic containers of 50 000 cm³ under full daylight and 30, 60, and 90 % shade for two years. The effects of shade on leaf morphology and anatomy, including stomatal density and chloroplast structure, net photosynthetic rate (P _N), stomatal conductance (g _s), and fruit yield were studied. Shade reduced leaf thickness due to the presence of only 1–2 palisade layers and reduced the length of palisade cells and spongy parenchyma. The number of thylakoids in grana as well as in stroma increased as shade increased, while the number of plastoglobuli decreased in proportion to the reduced photosynthetically active radiation (PAR). The higher the level of shade, the lower the stomatal and trichome density, leaf mass per area (ALM), g _s, and P _N. Shade of 30, 60, and 90 % reduced stomatal density by 7, 16, and 27 %, respectively, while the corresponding reduction in P _N was 21, 35, and 67 %. In contrast, chlorophyll a+b per fresh mass, and leaf width, length, and particularly area increased under the same shade levels (by 16, 33, and 81 % in leaf area). P _N reduction was due both to a decrease in PAR and to the morphological changes in leaves. The effect of shade was more severe on fruit yield per tree (32, 67, and 84 %) than on P _N indicating an effect on bud differentiation and fruit set. The olive tree adapts well to shade compared with other fruit trees by a small reduction in stomatal and trichome density, palisade parenchyma, and a significant increase in leaf area.     

热消散法(TDP)在5种竹子蒸腾耗水测定中的适用性评价

为评价热消散法在竹子蒸腾耗水测定中的适用性,利用室内离体竹段注水变压法结合野外整株容器称重法对Granier 公式进行了验证和系数校正,同时观察了5 种竹子(毛竹Phyllostachys edulis、粉单竹Bambusa chungii、青皮竹B. textilis、茶秆竹Arundinaria amabilis、龙头竹B. vulgaris)的茎秆维管束结构。结果表明,茎秆维管束分布不均,维管束发育程度从竹壁外向内逐渐成熟,输水能力也逐渐增强。液流密度(F_d)和液流指数(K)呈幂函数关系,相关系数R²>0.83,说明热消散探针方法能较好地估算竹类的液流密度。用整株容器称重法对推导出的液流密度公式进行校正,校正后的液流密度公式与原始Granier 公式中各系数均不同,尤其是α 值。分别采用校正前后公式计算的竹子日蒸腾量差异显著,尤其是一天中液流高峰时段(午间)的差异最大。因此,只要对热消散探针方法准确验证、校正Granier 原始公式系数,TDP 技术是估计竹类植物水分利用的一种适宜方法。     

三种控释肥在赤红壤中的氧化亚氮排放

采用静态箱收集和对比法,研究了无作物种植条件下包膜与否对高氮、均衡及高钾3种氮磷钾配比复合肥在华南赤红壤发育的菜园土中氧化亚氮(N2O)排放情况.结果表明:肥料氮磷钾配比不同,N2O排放量差异显著,3种类型复合肥N2O累积排放量表现为均衡型≥高氮型＞高钾型;同一类型复合肥,包膜控释能显著降低N2O排放量,包膜控释高氮、均衡及高钾型复合肥N2O排放总量分别为不包膜复合肥N2O排放量的34.4％、30.5％和89.3％;与不包膜相比,复合肥包膜能降低肥料在土壤中的N2O日排放通量,滞后和削减N2O排放高峰,减少土壤氮素损失以及由N2O排放造成的全球增温潜势.     

Procedural Steps in Human Risk Assessment for Contaminated Sites: An Italian Case-Study Application with the ARA-CoSSSLs Approach

Within the increased attention to the absolute risk assessment for potentially contaminated sites at the Italian level, the definable ARA-CoS_SSLs modeling approach for human health protection was recently derived with predominant reference to the USEPA SSLs procedure. The basic aim of the ARA-CoS_SSLs applications regards the possible technical-scientific improvement and better understanding of significant aspects in carrying out the human risk assessment at a given site. Particularly, the final reliability of the human risk assessment depends on the scientific plausibility of the procedural steps implemented during the elaboration of the available site investigation and information data. In this perspective, this article deals with the procedural elaboration steps conceived and implemented for the ARA-CoS_SSLs case-study application at a potentially contaminated subarea of a major Italian priority industrial site. Specific indications and aspects are addressed in the paper on the following procedural steps: (1) the usefulness of selection criteria for contaminants of concern; (2) the consideration of the possible soil gas loss (during drilling and/or sampling and/or analytical operations) for a reliable definition of subsurface representative concentrations for organic contaminants; (3) the geostatistical definition of the site areal extent, with a proposed conservative scenario in case of sparse spatial concentration data.     

Force-extension formula for the worm-like chain model from a variational principle

Stiff polymers, such as single-stranded DNA, unstructured RNA and cellulose, are all basically extremely long rods with relatively short repeating monomers. The simplest model for describing such stiff polymers is called the freely jointed chain model, which treats a molecule as a chain of perfectly rigid subunits of orientationally independent statistical segments, joined together by perfectly flexible hinges. A more realistic model that incorporates the entropic elasticity of a molecule, called the worm-like chain model, has been proposed by assuming that each monomer resists the bending force. Some force-extension formulae for the worm-like chain model have been previously found in terms of interpolation and numerical solutions resulting from statistical mechanics. In this paper, however, we adopt a variational principle to seek the minimum energy configuration of a stretched molecule by incorporating all the possible orientations of each monomer under thermal equilibrium, i.e., constant temperature. We determine a force-extension formula for the worm-like chain model analytically. We find that our formula suggests new terms such as the free energy and the cut-off force of a molecule, which define a clear transition from the entropic regime to the enthalpic regime and the fracture of the molecule, respectively. In addition, we predict two possible phase changes for a stretched molecule, i.e., from a super-helix to a soliton and then from a soliton to a vertical twisted line. We show theoretically that a molecule must undergo at least one phase change before it is fully stretched into its total contour length. This new formula is used to fit recent experimental data and shows a good agreement with some current literature that uses a statistical approach. Finally, an instability analysis is adopted to investigate the sensitivity of the new formula subject to small changes in temperature.     

Bioavailability of zinc and its binding to casein in milks and formulas

Differences in zinc bioavailability among milk and formulas may be attributed to binding of zinc to various ligands. We determined the distribution of zinc and protein at different pHs and zinc and calcium concentrations. We used radiolabelled cow's milk, human milk, whey-predominant (WPF) and casein-predominant (CPF) infant formula. Lowering the pH changed zinc and protein distribution: zinc shifted from pellet (casein) to whey in cow's milk, from fat to whey in human milk and from fat and pellet to whey in formulas. Protein shifted from whey to pellet in human milk and from whey and pellet to fat in formulas. Increasing zinc and calcium concentrations shifted protein and zinc from pellet to whey for cow's milk and from whey and pellet to fat for the formulas. Protein distribution was not affected by calcium or zinc addition in human milk or CPF, while zinc shifted from whey to fat in human milk and from fat and pellet to whey in CPF. Zinc and calcium binding to isolated bovine or human casein increased with pH. At 500 mg/L of zinc, bovine casein bound 32.0 +/- 1.8 and human casein 10.0 +/- 0.9 mg zinc/g protein. At 500 mg/L of calcium, calcium was preferentially bound over zinc. Adding calcium and zinc resulted in 32.0 +/- 1.8 mg zinc/g bound to bovine casein and 17.0 +/- 0.8 mg zinc/g to human casein, while calcium binding was low. Suckling rat pups dosed with 65Zn labelled infant diets were killed and individual tissues were gamma counted. Lower zinc bioavailability was found for bovine milk at pH = 4.0 (%65Zn in liver = 18.7+1.4) when compared to WPF (22.8 +/- 1.6) or human milk (26.9 +/- 0.8). Lowering the pH further decreased zinc bioavailability from human milk, but not from cow's milk or WPF. Knowledge of the compounds binding minerals and trace elements in infant formulas is essential for optimizing zinc bioavailability.     

鳄梨油在化妆品中的应用及配方

本文对鳄梨油的化学成分、生物活性及美容化妆品配方进行概述。