Gold in graphene: in-plane adsorption and diffusion

We study the bonding and diffusion of Au in graphene vacancies using density-functional theory. Energetics show that Au adsorbs preferably to double vacancies, steadily in-plane with graphene. All diffusion barriers for the complex of Au in double vacancy are above 4 eV, whereas the barriers for larger vacancies are below 2 eV. Our results support the main results of a recent experiment [Gan et al., Small 4, 587 (2008)], but suggest that the observed diffusion mechanism is not thermally activated, but radiation-enhanced.Comment: 3 pages, 3 figure

Conductance through atomic point contacts between fcc(100) electrodes of gold

Electrical conductance through various nanocontacts between gold electrodes is studied by using the density functional theory, scalar-relativistic pseudopotentials, generalized gradient approximation for the exchange-correlation energy and the recursion-transfer-matrix method along with channel decomposition. The nanocontact is modeled with pyramidal fcc(100) tips and 1 to 5 gold atoms between the tips. Upon elongation of the contact by adding gold atoms between the tips, the conductance at Fermi energy E_F evolves from G ~ 3 G_0 to G ~ 1 G_0 (G_0 = 2e/h^2). Formation of a true one-atom point contact, with G ~ 1 G_0 and only one open channel, requires at least one atom with coordination number 2 in the wire. Tips that share a common vertex atom or tips with touching vertex atoms have three partially open conductance channels at E_F, and the symmetries of the channels are governed by the wave functions of the tips. The long 5-atom contact develops conductance oscillations and conductance gaps in the studied energy range -3 < E-E_F < 5 eV, which reflects oscillations in the local density of electron states in the 5-atom linear "gold molecule" between the electrodes, and a weak coupling of this "molecule" to the tips

Prevalence of tail biting in pigs and associations to carcass condemnations - a Finnish pilot study

The aim of this study was to investigate the prevalence of tail biting in Finland and the relationship between tail biting and carcass condemnation

Unexplained limits on species distributions: how important is climate in defining species’ range edges?

The study of species’ range margins has a long history of academic interest, but is of particular relevance today due to its applications in modelling species range shifts induced by climate change, and predicting the spread of invasive species. Climate has long been assumed to structure species’ ranges over broad scales, but this consensus has recently been challenged by work on non-climatic factors, such as dispersal, biotic interactions and gene flow. It remains unclear how and where non-climatic factors can structure species’ ranges, and to what extent species’ ranges will consistently match sets of climatic conditions. In this thesis I investigate what can lead to a species underfilling its climatic niche (when a species fails to colonise all climatically suitable areas), or expanding its climatic niche (when a species is able to colonise new types of climate). I find evidence that several non-climatic factors can slow or prevent non-native species colonising all climatically suitable areas in their naturalised regions, including dispersal, fragmentation of climatically suitable areas and the area of introduction. I also find that species will readily spread into new precipitation regimes with which they have not been previously associated. This suggests that species ranges can be constrained by non-climatic factors in the wettest part of their native range, and these constraints are frequently lifted in their naturalised range. I find evidence that species range limits set by temperature, in particular temperature maxima and minima, are more conserved and species will rarely expand into new thermal regimes. I also find evidence that species have different phenotypic responses to temperature across their range. Together these results indicate that a species’ current range frequently does not indicate its overall climatic tolerance, particularly in relation to precipitation, hence predictions that rely on associations between occurrence and environmental variables will frequently be flawed. Future work should consider a systematic way of detecting and including non-climatic factors that constrain the edges of species’ ranges

Formation and propagation of great salinity anomalies

North Atlantic/Arctic ocean and sea ice variability for the period 1948–2001 is studied using a global Ocean General Circulation Model coupled to a dynamic/thermodynamic sea ice model forced by daily NCEP/NCAR reanalysis data [Kalnay et al., 1996]. Variability of Arctic sea ice properties is analysed, in particular the formation and propagation of sea ice thickness anomalies that are communicated via Fram Strait into the North Atlantic. These export events led to the Great Salinity Anomalies (GSA) of the 1970s, 1980s and 1990s in the Labrador Sea (LS). All GSAs were found to be remotely excited in the Arctic, rather than by local atmospheric forcing over the LS. Sea ice and fresh water exports through the Canadian Archipelago (CAA) are found to be only of minor importance, except for the 1990s GSA. Part of the anomalies are tracked to the Newfoundland Basin, where they enter the North Atlantic Current. The experiments indicate only a minor impact of a single GSA event on the strength of the North Atlantic Thermohaline Circulation (THC)

Results of Russian geomagnetic observatories in the 19th century: magnetic activity, 1841&ndash;1862

Hourly (spot readings) magnetic data (H- and D-components) were digitized from Russian yearbook tables for the years 1850–1862 from four observatories. The pdf pictures for digitization were taken by a normal digital camera. The database obtained consists of about 900 000 single data points. The time series of hourly magnetic values reveal slow secular variations (declination only) as well as transient and regular geomagnetic variations of external origin. The quality and homogeneity of the data is satisfactory. Daily Ak-indices were calculated using the index algorithm that has been earlier applied to 19th century data from Helsinki (Finland) as well as modern magnetic observatory recordings. The activity index series derived from the Russian data is consistent with earlier activity index series for 1850–1862. The digitized index data series derived in this study was extended back to 1841 by including magnetic <I>C</I>9 activity index data available from a Russian observatory (St. Petersburg). Magnetic data rescued here is well suitable for various reconstructions for studies of the long-term variation of the space weather in the 19th century

Comparison of Raman spectra and vibrational density of states between graphene nanoribbons with different edges

Vibrational properties of graphene nanoribbons are examined with density functional based tight-binding method and non-resonant bond polarization theory. We show that the recently discovered reconstructed zigzag edge can be identified from the emergence of high-energy vibrational mode due to strong triple bonds at the edges. This mode is visible also in the Raman spectrum. Total vibrational density of states of the reconstructed zigzag edge is observed to resemble the vibrational density of states of armchair, rather than zigzag, graphene nanoribbon. Edge-related vibrational states increase in energy which corroborates increased ridigity of the reconstructed zigzag edge.Comment: 4 pages, 4 figure

Supported magnetic nanoclusters: Softlanding of Pd clusters on a MgO surface

Low-energy deposition of neutral Pd_N clusters (N=2-7 and 13) on a MgO(001) surface F-center (FC) was studied by spin-density-functional molecular dynamics simulations. The incident clusters are steered by an attractive "funnel" created by the FC, resulting in adsorption of the cluster, with one of its atoms bonded atop of the FC. The deposited Pd_2-Pd_6 clusters retain their gas-phase structures, while for N>6 surface-commensurate isomers are energetically more favorable. Adsorbed clusters with N > 3 are found to remain magnetic at the surface.Comment: 5 pages, 2 figs, Phys.Rev.Lett., accepte

Increased interleukin-6 and C-reactive protein levels after instrumented lumbar spine fusion in older patients

Purpose: Interleukin 6 (IL-6) and the acute phase C-reactive protein (CRP) blood concentrations after lumbar spine fusion may be affected by age. The purpose of this prospective observational study was to assess postoperative serum levels of pro-inflammatory IL-6 and CRP after instrumented lumbar spine fusion surgery. We hypothesized that older patients would have increased levels of IL-6 and CRP after surgery. Methods: IL-6 and high-sensitive CRP biochemical marker levels were measured before instrumented spinal fusion, and postoperatively at 1 and 3 days, 6 weeks, and 3 months. The 49 patients in this sample were divided into two groups: age 60 years (n = 26). Results: Acute changes in IL-6 high-sensitivity and CRP from preoperative levels to postoperative day (POD) 1 increased with age. Mean (95% CI) difference between the age-groups in changes of IL-6 at PODs 1 and 3 was 45 pg/ml (10-83, p = 0.014) and 20 pg/ml (5-36, p = 0.021), respectively. Mean (95% CI) difference between groups in changes of CRP at PODs 1 and 3 was 9.6 mg/l (-3.5 to 22.7, p = 0.47) and 24.8 mg/l (-17 to 67, p = 0.33), respectively. Both groups had decreased IL-6 and CRP levels at 6 weeks after surgery compared to the preoperative level. Conclusions: Elevation of IL-6 and CRP is stronger in patients over 60 years old after instrumented lumbar spinal fusion. The CRP and IL-6 are sensitive markers for acute postoperative inflammation. Even high acute CRP values do not necessarily indicate postoperative infection.Peer reviewe

Electronic-structure-induced deformations of liquid metal clusters

Ab initio molecular dynamics is used to study deformations of sodium clusters at temperatures $500\cdots 1100$ K. Open-shell Na$_{14}$ cluster has two shape isomers, prolate and oblate, in the liquid state. The deformation is stabilized by opening a gap at the Fermi level. The closed-shell Na$_8$ remains magic also at the liquid state.Comment: REVTex, 11 pages, no figures, figures (2) available upon request (e-mail to hakkinen at jyfl.jyu.fi), submitted to Phys. Rev.