A P-stable exponentially-fitted method for the numerical integration of the Schrödinger equation

In this paper we present a P-stable exponentially-fitted four-step method for the numerical integration of the radial Schrödinger equation. More specifically we present a method than satisfies the property of P-stability and also integrates exactly any linear combination of the functions {1, x, exp( ± w x), x exp( ± w x), x ²exp( ± w x)}. We tested the efficiency of our newly developed scheme against well known methods, with excellent results. The numerical illustration showed that our method is considerably more efficient compared to well‐known methods used for the numerical integration of resonance problem of the radial Schrödinger equation.     

Statistical mechanics approach to inhomogeneous van der Waals fluids

A general methodology is proposed to formulate density functional approximation (DFA) for inhomogeneous van der Waals fluids. The present methodology needs as input only a hard sphere DFA, second order direct correlation function (DCF) and pressure of coexistence bulk fluid, and therefore can be applicable to both supercitical and subcritical temperature regions. As illustrating example, the present report combines a recently proposed hard sphere “Formally exact truncated non-uniform excess Helmholtz free energy density functional approximation” with the present methodology, and applies the resultant DFA to calculate density profile of the inhomogeneous Lennard-Jones (LJ) fluid in coexistence with a bulk LJ fluid being situated at “dangerous” regions, i.e. the coexistence bulk state is near the critical temperature or the gas-liquid coexistence line. The theoretical predictions are in very good agreement with the recent simulation results, it is concluded that the present DFA is a globally excellent one. A discussion is given why the present methodology can lead to so excellent DFA.     

A century of fish growth in relation to climate change,population dynamics and exploitation

Marine ecosystems, particularly in high‐latitude regions such as the Arctic, have been significantly affected by human activities and contributions to climate change. Evaluating how fish populations responded to past changes in their environment is helpful for evaluating their future patterns, but is often hindered by the lack of long‐term biological data available. Using otolith increments of Northeast Arctic cod (Gadus morhua) as a proxy for individual growth, we developed a century‐scale biochronology (1924–2014) based on the measurements of 3,894 fish, which revealed significant variations in cod growth over the last 91 years. We combined mixed‐effect modeling and path analysis to relate these growth variations to selected climate, population and fishing‐related factors. Cod growth was negatively related to cod population size and positively related to capelin population size, one of the most important prey items. This suggests that density‐dependent effects are the main source of growth variability due to competition for resources and cannibalism. Growth was also positively correlated with warming sea temperatures but negatively correlated with the Atlantic Multidecadal Oscillation, suggesting contrasting effects of climate warming at different spatial scales. Fishing pressure had a significant but weak negative direct impact on growth. Additionally, path analysis revealed that the selected growth factors were interrelated. Capelin biomass was positively related to sea temperature and negatively influenced by herring biomass, while cod biomass was mainly driven by fishing mortality. Together, these results give a better understanding of how multiple interacting factors have shaped cod growth throughout a century, both directly and indirectly.     

Determinants of soil organic carbon sequestration and its contribution to ecosystem carbon sinks of planted forests

The area of forest established through afforestation/reforestation has been increasing on a global scale, which is particularly important as these planted forests attenuate climate change by sequestering carbon. However, the determinants of soil organic carbon (SOC) sequestration and their contribution to the ecosystem carbon sink of planted forests remain uncertain. By using globally distributed data extracted from 154 peer‐reviewed publications and a total of 355 sampling points, we investigated above‐ground biomass carbon (ABC) sequestration and SOC sequestration across three different climatic zones (tropical, warm temperate, and cold temperate) through correlation analysis, regression models, and structural equation modeling (SEM). We found that the proportion of SOC sequestration in the ecosystem C sequestration averaged 14.1% globally, being the highest (27.0%) in the warm temperate and the lowest (10.7%) in the tropical climatic zones. The proportion was mainly affected by latitude. The sink rate of ABC (R_ABC) in tropical climates (2.48 Mg C ha^?1 year^?1) and the sink rate of SOC (R_SOC) in warm temperate climates (0.96 Mg C ha^?1 year^?1) were higher than other climatic zones. The main determinants of R_SOC were the number of frost‐free days, latitude, mean annual precipitation (MAP), and SOC density (SOCD) at the initial observation; however, these variables depended on the climatic zone. According to the SEM, frost‐free period, mean annual temperature (MAT) and MAP are the dominant driving factors affecting R_SOC in Chinese plantations. MAT has a positive effect on R_SOC, and global warming may increase R_SOC of temperate plantations in China. Our findings highlight the determinants of SOC sequestration and quantitatively reveal the substantial global contribution of SOC sequestration to ecosystem carbon sink provided by planted forests. Our results help managers identify and control key factors to increase carbon sequestration in forest ecosystems.     

Refining the role of phenology in regulating gross ecosystem productivity across European peatlands

The role of plant phenology as a regulator for gross ecosystem productivity (GEP) in peatlands is empirically not well constrained. This is because proxies to track vegetation development with daily coverage at the ecosystem scale have only recently become available and the lack of such data has hampered the disentangling of biotic and abiotic effects. This study aimed at unraveling the mechanisms that regulate the seasonal variation in GEP across a network of eight European peatlands. Therefore, we described phenology with canopy greenness derived from digital repeat photography and disentangled the effects of radiation, temperature and phenology on GEP with commonality analysis and structural equation modeling. The resulting relational network could not only delineate direct effects but also accounted for possible effect combinations such as interdependencies (mediation) and interactions (moderation). We found that peatland GEP was controlled by the same mechanisms across all sites: phenology constituted a key predictor for the seasonal variation in GEP and further acted as a distinct mediator for temperature and radiation effects on GEP. In particular, the effect of air temperature on GEP was fully mediated through phenology, implying that direct temperature effects representing the thermoregulation of photosynthesis were negligible. The tight coupling between temperature, phenology and GEP applied especially to high latitude and high altitude peatlands and during phenological transition phases. Our study highlights the importance of phenological effects when evaluating the future response of peatland GEP to climate change. Climate change will affect peatland GEP especially through changing temperature patterns during plant phenologically sensitive phases in high latitude and high altitude regions.     

Egg morphology of Swift Terns in South Africa

Morphology of Swift Tern Thalasseus bergii bergii eggs was examined on Robben Island, South Africa. A recently formed colony was found abandoned en masse, probably following human disturbance, and 146 freshly laid eggs were collected. The mean±SD nest density was 7±2.5 nests m?2 and 3% of nests contained two eggs. Eggs ranged in shape from oval to pyriform and displayed black markings (blotched, streaked, scrawled or speckled) overlaying the eggs’ colour. The mean length and width of a sample of 105 eggs was 62.2?mm (56.3–66.9?mm) and 42.3?mm (39.8–45.3?mm), respectively. All collected eggs were weighed and the mean mass was 57.9±3.72?g. Estimated volume of eggs was calculated to be 56.3±3.74 cm3. This is the first report of mass measurements obtained from freshly laid eggs Swift Tern eggs and provides insight on egg morphology, for which knowledge is limited for this species.     

Detoxification of sulfur mustard by enzyme-catalyzed oxidation using chloroperoxidase

One of the most interesting methods for the detoxification of sulfur mustard is enzyme-catalyzed oxidation. This study examined the oxidative destruction of a sulfur mustard by the enzyme chloroperoxidase (EC 1.11.1.10). Chloroperoxidase (CPO) belongs to a group of enzymes that catalyze the oxidation of various organic compounds by peroxide in the presence of a halide ion. The enzymatic oxidation reaction is affected by several factors: pH, presence or absence of chloride ion, temperature, the concentrations of hydrogen peroxide and enzyme and aqueous solubility of the substrate. The optimum reaction conditions were determined by analyzing the effects of all factors, and the following conditions were selected: solvent, Britton–Robinson buffer (pH = 3) with tert-butanol (70:30 v/v); CPO concentration, 16 U/mL; hydrogen peroxide concentration, 40 mmol/L; sodium chloride concentration, 20 mmol/L. Under these reaction conditions, the rate constant for the reaction is 0.006 s⁻¹. The Michaelis constant, a measure of the affinity of an enzyme for a particular substrate, is 1.87 × 10⁻³ M for this system. The Michaelis constant for enzymes with a high affinity for their substrate is in the range of 10⁻⁵ to 10⁻⁴ M, so this value indicates that CPO does not have a very high affinity for sulfur mustard.     

The effect of perceived cultural and material threats on ethnic preferences in immigration attitudes

This paper shows that cultural and material threats exist side by side, serving different psychological functions, and that they manifest in differential attitudes towards immigrants from different ethnic or racial origins. While culturally threatened individuals prefer immigrants akin to themselves, as opposed to those from different races and cultures, the materially threatened prefer immigrants who are different from themselves who can be expected not to compete for the same resources. We test our hypotheses using multilevel structural equation modelling, based on data from twenty countries in the 2002 wave of the European Social Survey. The disaggregation of these two types of perceived threat reveals responsiveness to the race of immigrants that is otherwise masked by pooling the two threat dimensions.     

Light requirements of Australian tropical vs. cool-temperate rainforest tree species show different relationships with seedling growth and functional traits

Background and Aims

A trade-off between shade tolerance and growth in high light is thought to underlie the temporal dynamics of humid forests. On the other hand, it has been suggested that tree species sorting on temperature gradients involves a trade-off between growth rate and cold resistance. Little is known about how these two major trade-offs interact.

Methods

Seedlings of Australian tropical and cool-temperate rainforest trees were grown in glasshouse environments to compare growth versus shade-tolerance trade-offs in these two assemblages. Biomass distribution, photosynthetic capacity and vessel diameters were measured in order to examine the functional correlates of species differences in light requirements and growth rate. Species light requirements were assessed by field estimation of the light compensation point for stem growth.

Results

Light-demanding and shade-tolerant tropical species differed markedly in relative growth rates (RGR), but this trend was less evident among temperate species. This pattern was paralleled by biomass distribution data: specific leaf area (SLA) and leaf area ratio (LAR) of tropical species were significantly positively correlated with compensation points, but not those of cool-temperate species. The relatively slow growth and small SLA and LAR of Tasmanian light-demanders were associated with narrow vessels and low potential sapwood conductivity.

Conclusions

The conservative xylem traits, small LAR and modest RGR of Tasmanian light-demanders are consistent with selection for resistance to freeze–thaw embolism, at the expense of growth rate. Whereas competition for light favours rapid growth in light-demanding trees native to environments with warm, frost-free growing seasons, frost resistance may be an equally important determinant of the fitness of light-demanders in cool-temperate rainforest, as seedlings establishing in large openings are exposed to sub-zero temperatures that can occur throughout most of the year.