Effect of ageing on phase evolution and mechanical properties of a high tungsten super-duplex stainless steel

Peer reviewedPostprin

Dynamic modelling to predict the likelihood of plant species persisting in fragmented landscapes in the face of climate change

Many species are threatened by global climate change, but plants are particularly vulnerable because, as sessile organisms, they are unable to move to areas with more suitable conditions as the climate changes. Instead they must rely on their seeds dispersing far and often to keep pace with a changing climate. This problem is exacerbated by the fragmentation of natural landscapes by clearing for agricultural or urban development, or similarly by a species requirement for particular soil types or topography. Models can help predict how different species will be affected by climate change. Most previous modelling work on predicting the persistence of plant and other species under climate change has been static, regression style modelling, known as climate envelope modelling. This has focussed on predicting where suitable environments for a species will likely occur under possible future climatic conditions, based on the species’ distribution under current conditions. While the existence of suitable environments in a new climate is a necessary condition for a species’ persistence, for sessile organisms such as plants, the ability of a species to move and colonise these suitable environments is also likely to be a major limitation. There is therefore a need for models that account for the dynamic processes involved in plant species’ migration and colonisation in changing climates. This paper presents such a dynamic model, called PPunCC (Plant Persistence under Climate Change). We describe how the PPunCC model represents the important factors and processes likely to affect a plant species’ capacity to migrate across a landscape fast enough to keep pace with a changing climate, such as the rate of climate change, the degree of landscape fragmentation, and the plant species’ life history, seed production, dispersal, and establishment. We also discuss how the model could be used to inform management decisions regarding adaptation options such as assisted migration or the creation of large-scale corridors that increase the connectivity of fragmented landscapes in order to help species migrate naturally and find suitable environments in new climates

Precise bounds on the Higgs boson mass

We study the renormalization group evolution of the Higgs quartic coupling $\lambda_{H}$ and the Higgs mass $m_{H}$ in the Standard Model. The one loop equation for $\lambda_{H}$ is non linear and it is of the Riccati type which we numerically and analytically solve in the energy range $[m_{t},E_{GU}]$ where $m_{t}$ is the mass of the top quark and $E_{GU}=10^{14}$ GeV. We find that depending on the value of $\lambda_{H}(m_{t})$ the solution for $\lambda_{H}(E)$ may have singularities or zeros and become negative in the former energy range so the ultra violet cut off of the standard model should be below the energy where the zero or singularity of $\lambda_{H}$ occurs. We find that for $0.369\leq\lambda_{H}(m_{t})\leq0.613$ the Standard Model is valid in the whole range $[m_{t},E_{GU}]$. We consider two cases of the Higgs mass relation to the parameters of the standard model: (a) the effective potential method and (b) the tree level mass relations. The limits for $\lambda_{H}(m_{t})$ correspond to the following Higgs mass relation $150\leq m_{H}\lessapprox 193$ GeV. We also plot the dependence of the ultra violet cut off on the value of the Higgs mass. We analyze the evolution of the vacuum expectation value of the Higgs field and show that it depends on the value of the Higgs mass. The pattern of the energy behavior of the VEV is different for the cases (a) and (b). The behavior of $\lambda_{H}(E)$, $m_{H}(E)$ and $v(E)$ indicates the existence of a phase transition in the standard model. For the effective potential this phase transition occurs at the mass range $m_{H}\approx 180$ GeV and for the tree level mass relations at $m_{H}\approx 168$ GeV.Comment: 14 pages, 7 figures. Expanded the discussion of the Higgs mass relation between the parameters of the Standard Model. Included the method of the Higgs effective potentia

Estimating the effects of Bose-Einstein correlations on the W mass measurement at LEP2

The influence of Bose-Einstein correlations on the determination of the mass of the W boson in e+e- -> WW -> 4jet events at LEP2 energies is studied, using a global event weighting method. We find that it is possible to keep the systematic error on the W mass from this source below 20 MeV, if suitable precautions are taken in the experimental analysis.Comment: 12 pages including 3 .eps figures. Paper revised to correct for a software bug which overestimated heavy quark contributio

Photosynthesis at an extreme end of the leaf trait spectrum: how does it relate to high leaf dry mass per area and associated structural parameters?

Leaf dry mass per area (LMA) is a composite parameter relating to a suite of structural traits that have the potential to influence photosynthesis. However, the extent to which each of these traits contributes to variation in LMA and photosynthetic rates is not well understood, especially at the high end of the LMA spectrum. In this study, the genus Banksia (Proteaceae) was chosen as a model group, and key structural traits such as LMA, leaf thickness, and density were measured in 49 species. Based on the leaf trait variation obtained, a subset of 18 species displaying a wide range in LMA of 134–507 g m−2 was selected for analyses of relationships between leaf structural and photosynthetic characteristics. High LMA was associated with more structural tissue, lower mass-based chlorophyll and nitrogen concentrations, and therefore lower mass-based photosynthesis. In contrast, area-based photosynthesis did not correlate with LMA, despite mesophyll volume per area increasing with increases in LMA. Photosynthetic rate per unit mesophyll volume declined with increasing LMA, which is possibly associated with structural limitations and, to a lesser extent, with lower nitrogen allocation. Mesophyll cell wall thickness significantly increased with LMA, which would contribute to lower mesophyll conductance at high LMA. Photosynthetic nitrogen use efficiency and the nitrogen allocation to Rubisco and thylakoids tended to decrease at high LMA. The interplay between anatomy and physiology renders area-based photosynthesis independent of LMA in Banksia species

Three Methods of Determining Hardness of Increment Core Segments

Three methods were devised to measure the hardness of small wood samples: a sanding test, a diamond point indentation test, and a saw blade tooth deformity test. Based on step-wise multiple regression analysis with 19 and with five important independent variables, the sanding test was best, followed by the indentation test. The saw blade test gave poor results and was discarded. The order of important independent variables among the four plots analyzed individually showed a nearly perfect relationship with the sanding test, but no consistent order of the variables among plots for the indentation test. Again this indicated that the sanding test was best