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Background: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are cost-effective procedures that decrease pain and improve health-related quality of life for patients with advanced symptomatic arthritis, including rheumatoid arthritis (RA). Patients with RA have a longer length of stay (LOS) after THA or TKA than patients with osteoarthritis, yet the factors contributing to LOS have not been investigated. Purpose: We sought to identify the factors contributing to LOS for patients with RA undergoing THA and TKA at a single tertiary care orthopedic specialty hospital. Methods: We retrospectively reviewed data from a prospectively collected cohort of 252 RA patients undergoing either THA or TKA. Demographics, RA characteristics, medications, serologies, and disease activity were collected preoperatively. Linear regression was performed to explore the relationship between LOS (log-transformed) and possible predictors. A multivariate model was constructed through backward selection using significant predictors from a univariate analysis. Results: Of the 252 patients with RA, 83% were women; they had a median disease duration of 14 years and moderate disease activity at the time of arthroplasty. We had LOS data on 240 (95%) of the cases. The mean LOS was 3.4 ± 1.5 days. The multivariate analysis revealed a longer LOS for RA patients who underwent TKA versus THA, were women versus men, required a blood transfusion, and took preoperative opioids. Conclusion: Our retrospective study found that increased postoperative LOS in RA patients undergoing THA or TKA was associated with factors both non-modifiable (type of surgery, sex) and modifiable (postoperative blood transfusion, preoperative opioid use). These findings suggest that preoperative optimization of the patient with RA might focus on improving anemia and reducing opioid use in efforts to shorten LOS. More rigorous study is warranted.

Background Patients with rheumatoid arthritis (RA) receive transfusions more often than patients with osteoarthritis following lower extremity total joint arthroplasty (TJA), but mitigating factors are not described. Tranexamic acid (TXA) is widely used to reduce blood loss in patients undergoing TJA, but its effect on transfusion rates in patients with RA has not been studied. Methods We retrospectively reviewed data from a prospectively collected cohort of patients with RA undergoing TJA. Disease activity measured by Clinical Disease Activity Index, patient-reported outcome measures, and serologies was obtained. Baseline characteristics were summarized and compared. Transfusion requirements and TXA usage were obtained from chart review. Logistic regression was used to determine factors associated with transfusion in RA patients undergoing TJA. Results The cohort included 252 patients, mostly women with longstanding RA and end-stage arthritis requiring TJA. In multivariate analysis, 1 g/dL decrease in baseline hemoglobin (odds ratio [OR] = 0.394, 95% confidence interval [CI] [0.232, 0.669], P = .001), 1-minute increase in surgical duration (OR = 1.022, 95% CI [1.008, 1.037], P = .003), and 1-point increase in Clinical Disease Activity Index (OR = 1.079, 95% CI [1.001, 1.162]) were associated with increased risk of transfusion. TXA use was not associated with decreased risk of postoperative transfusion. Conclusions Preoperative health optimization should include assessment and treatment of anemia in RA patients before TJA, as preoperative hemoglobin level is the main risk factor for postoperative transfusion. Increased disease activity and increased surgical time were independent risk factors for postoperative transfusion but are less modifiable. While TXA did not decrease transfusion risk in this population, a prospective trial is needed to confirm this. Level of Evidence IV.

Background The purpose of this study was to identify reasons for revision of total hip arthroplasty (THA) in patients who underwent primary THA at or before the age of 35 years. We hypothesized that the reasons for revision in younger patients would be different from the general older population of patients undergoing THA because of the differences in diagnoses, complexity of deformities, and differences in activity level. Methods Data for 108 hips in 82 patients who underwent primary THA at our institution before the age of 35 years from 1982-2007 and subsequently underwent revision THA were reviewed. Operative reports and clinic notes were reviewed to determine baseline characteristics, reason for revision, timing of revision, and components revised. Results The mean age at index surgery was 25.4 years, and mean time from index to revision surgery was 10.1 years. The most common preoperative diagnoses included avascular necrosis, juvenile idiopathic arthritis, developmental dysplasia of the hip, and posttraumatic arthritis. The most common reasons for revision were acetabular loosening (30.1%), femoral loosening (23.7%), and polyethylene wear (24.7%). 8.3% of patients underwent primary THA with highly cross-linked polyethylene, while the remainder of the patients underwent THA when conventional polyethylene was used. There was no statistically significant association between which component(s) were revised and initial fixation (ie cemented or uncemented prosthesis) (P = .26). Conclusion Causes of revision in this population appear to differ from the general THA population. In young patients, acetabular loosening, femur loosening, and polyethylene wear were the most common causes of revision. Instability and infection were less common compared with literature reports of causes of revision in older patients. Findings in this study may be useful in counseling young patients undergoing THA, though results were likely influenced by the use of conventional rather than highly cross-linked polyethylene in this cohort.

Using the combination of high resolution core level spectroscopy and density functional theory we present adetailed spectroscopic study for all clean and hydrogen covered phases of Ir(100). The results are complementedby an investigation of the hydrogen desorption process from various phases using temperature programmeddesorption spectroscopy and scanning tunneling microscopy. In total, all experimentally determined core levelshifts match very well with those predicted by density functional theory based on established structural models.In particular, we find for the (bridge site) adsorption on the unreconstructed 1×1 phase that the initial core levelshift of surface Ir atoms is altered by +0.17 eV for each Ir–H bond formed. In the submonolayer regime we findevidence for island formation at low temperatures. For the H-induced deconstructed 5×1-H phase we identifyfour different surface core level shifts with two of them being degenerate. Finally, for the reconstructed 5×1-hexphase also four surface components are identified, which undergo a rather rigid core level shift of +0.15 eV uponhydrogen adsorption suggesting a similarly homogeneous charge transfer to all Ir surface atoms.Thermodesorption experiments for the 5×1-H phase reveal two different binding states for hydrogenindependent of the total coverage. We conclude that the surface always separates into patches of fully covereddeconstructed and uncovered reconstructed phases. We could also show by tunneling microscopy that with thedesorption of the last hydrogen atom from the deconstructed unit cell the surface instantaneously reverts intothe reconstructed state. Eventually, we could determine the saturation coverage upon molecular adsorption forall phases to be θmax = 1.0 ML1×1−H , θ = 0.8 ML max5×1−H , and θ ≥ 1.0 ML max5×1−hex−H . (Less)

Decomposing leaf litter is a large supply of energy and nutrients for soil microorganisms. How long decaying leaves continue to fuel anaerobic microbial activity in wetland ecosystems is poorly understood. Here, we compare leaf litter from 15 tree species with different growth forms (angiosperms and gymnosperms, deciduous, and longer life span), using litterbags positioned for up to 4 years in a forested peatland in New York State. Periodically, we incubated partially decayed residue per species with fresh soil to assess its ability to fuel microbial methane (CH4) production and concomitant anaerobic carbon dioxide (CO2) production. Decay rates varied by leaf type: deciduous angiosperm > evergreen gymnosperm > deciduous gymnosperm. Decay rates were slower in leaf litter with a large concentration of lignin. Soil with residue of leaves decomposed for 338 days had greater rates of CH4 production (5.8 µmol g−1 dry mass d−1) than less decomposed (

Background Increased mortality in chronic rheumatic diseases is mostly attributed to cardiovascular events (CVE). Assessment of endothelial dysfunction can help to identify patients at risk for major CVE. Studies have shown that the underlying endothelial dysfunction in rheumatoid arthritis is closely associated with inflammation. Only limited information is available whether the blockade of TNFα can restore endothelial function. Objectives To investigate parameters of endothelial function bevor and after initiation of immunosuppressive therapie (anti-TNF-therapy or methotrexate) in patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) or ankylosing spondylitis in an open-label, prospective study. Methods Patients with active RA, PsA or SpA were eligible for inclusion with active disease and when new treatment with sDMARD (methotrexate) or bDMARD (anti-TNF-therapy) was started. Study visits were performed at baseline, at 3 and at 12 months. Clinical disease activity and inflammation marker were obtained. Systemic Coronary Risc Evaluation (SCORE) and measurement of intima media thickness (IMT) were performed to assess baseline cardiovascular (CV) risk. Endothelial function was measured as arterial dilatation (artFID), arterial constriction (artFIC) and venous dilatation (venFID) in response to flicker light by dynamic vessel analysis (DVA; IMEDOS) and by peripheral arterial tonometry (EndoPAT) as reactive hyperemia index (RHI). For the primary endpoint, we analysed the endothelial function before and during treatment (month 12). Secondary endpoints were ACR20/50 response for RA and PsA and ASAS20 response for SpA. A comparison was made for changes in endothelial function in responder and non-responder to immunosuppressive treatment. Results 62 patients (37 RA, 13 PsA, 14 SpA) were included (mean age 51.3±14.9 years, 46.8% females). The mean ten-year risk of fatal cardiovascular disease (SCORE) was estimated with 2.2% (95%CI: 1.5–3.0). Mean IMT was 0.59±0.13 mm. Treatment was initiated with etanercept (n=21), certolizumab (n=10), infliximab (n=2), adalimumab (n=13), golimumab (n=4) or methotrexat (n=12). Response to treatment after 3 (n=57) and 12 months (n=32) measured by ACR20/50 (RA and PsA) and ASAS20 (SpA) was found in 33.3/16.7% and 57.2% (month 3) and 29.2/20.8% and 50.0% (month 12). ArtFID increased (3.1%±2.8% to 4.0±3.2%; p Conclusions Our data indicate, that patients with active RA, PsA or SpA are at risk for cardiovascular events. Immunosuppressive treatment can improve endothelial function at retinal arteries but has no effect on reactive hyperemia index at peripheral arteries. The effect of immunosuppressive treatment on parameters of endothelial function was not different in responders or non-responders and did not depend on whether the patients were treated with anti-TNF-therapy or methotrexate. Acknowledgements The study was funded be a grant from Pfizer Pharma GmbH (WS 1541087). Disclosure of Interest None declared

This corrects the article DOI: 10.1103/PhysRevLett.117.046101.

The complex coacervation of natural polyelectrolytes and their applications in delivery systems are the focus of this chapter. There are various applications of complex coacervates, especially in controlled delivery systems and mostly in the form of either micro/nanocapsules/beads or stimuli-responsive membranes. The main principle of microencapsulation is the ability of the coacervates to form a coating around sensitive materials (e.g., drug particle or an oil droplet containing flavors), and it has widely been investigated in the literature. Membranes made of complex coacervation of natural polyelectrolytes can be effectively utilized for the stimuli-responsive controlled delivery of drugs. Complex coacervation constitutes a promising route for the preparation of a wide variety of tools such as capsules and membranes used in controlled delivery systems. Therefore, we can expect many new and innovative controlled delivery applications making use of different complex coacervation systems in the near future.

ZusammenfassungAuf Basis der Analyse sexualisierter Gewalt durch Pastoren in der Nordelbischen evangelischen- lutherischen Kirche (Nordkirche) werden spezifische Wahrnehmungsblockaden in der evangelischen Kirche beschrieben. Es wird besonderes Augenmerk auf den Zusammenhang zwischen psychischer und sexualisierter Gewalt sowie auf die Bedeutung grenzverletzender Selbsterfahrungsübungen gelegt. Bisher ist der Aspekt der sexualisierten Gewalt gegen Jungerwachsene in der Diskussion über sexualisierte Gewalt in Institutionen zu wenig berücksichtigt worden. Bei der Untersuchung der Fälle sexualisierter Gewalt durch Pastoren in der Nordkirche hat sich gezeigt, dass ihnen eine hohe Bedeutung zukommen kann und sie zu massiven Folgeproblemen führen können. Der Umgang mit den Betroffenen und die Aufarbeitung der Fälle in der Nordkirche werden kritisch beleuchtet.

We report on the self-organized growth of monatomic transition-metal oxide chains of ($3\ifmmode\times\else\texttimes\fi{}1$) periodicity and unusual $M{\mathrm{O}}_{2}$ stoichiometry ($M=\mathrm{Ni}$, Co, Fe, Mn) on Ir(100). We analyze their structural and magnetic properties by means of quantitative LEED, STM, and density functional theory (DFT) calculations. LEED analyses reveal a fascinating common atomic structure in which the transition-metal atoms sit above a missing-row structure of the surface and are coupled to the substrate only via oxygen atoms. This structure is confirmed by DFT calculations with structural parameters deviating by less than 1.7 pm. The DFT calculations predict that the ${\mathrm{NiO}}_{2}$ chains are nonmagnetic, ${\mathrm{CoO}}_{2}$ chains are ferromagnetic, while ${\mathrm{FeO}}_{2}$ and ${\mathrm{MnO}}_{2}$ are antiferromagnetic. All structures show only weak magnetic interchain coupling. Further, we demonstrate the growth of oxide chains of binary alloys of Co and Ni or Fe on Ir(100), which allows us to produce well-controlled ensembles of ferromagnetic chains of different lengths separated by nonmagnetic or antiferromagnetic segments.

Malus sylvestris (L.) Mill. is the only indigenous wild apple species in Europe and recognized as rare and endangered species. An important prerequisite for the preservation of M. sylvestris is the identification of ‘true type’ M. sylvestris individuals because hybrids with cultivated apple could be also occurred. In this study variations among 625 putative M. sylvestris trees originated in the East Ore Mountains were evaluated with 20 selected morphological traits. The importance of these traits concerning the differentiation of ‘true type’ and hybrids of M. sylvestris were determined by statistical analysis. The results demonstrated a strong correlation of individual traits and those contributing mostly to variation of M. sylvestris were detected by the Principal Component Analysis. The relationship of 284 M. sylvestris, 18 M. × domestica, M. floribunda 821 and M. robusta 5 individuals were calculated based on the morphological data and presented in a dendrogram. The individuals grouped in two main clusters and 68 hybrids of M. sylvestris were identified. The main result of the morphological data of these hybrids indicates that the grouping is mainly based on the flower and leaf pubescence and less on the fruit size.

In response to a recent Surface Science Editorial (2010) [1] and accompanying Prospective article [2], we propose that the community of surface scientists and nanoscientists select a common data format for reporting experimental data and atomic coordinates, and have it accepted by relevant journals.

As a structurally rather flexible surface Ir(1 0 0) can be prepared with different structural phases. The clean and stable phase, Ir(1 0 0)-(5 × 1)-hex, exhibits a quasi-hexagonal top layer arranged in 5-fold periodicity on the square substrate. Also, a hydrogen stabilized phase, Ir(1 0 0)-(5 × 1)-H, with Ir wires of single atomic width and again 5-fold periodicity residing on (1 0 0) layers below can be prepared as well as a bulk-like terminated but metastable phase, Ir(1 0 0)-(1 × 1). The (5 × 1) reconstructed phases offer linear adsorption channels of nanosized width, so that by deposition of other metals linear nanostructures can be formed by self-organisation in a bottom-up process. This is demonstrated for the deposition of the transition metals Fe, Co and Ni which, on the flat (1 0 0) surface, would be under considerable tensile strain of the order of 8–9%. We show that the accompanying stress leads to the formation of stair-rod dislocations by which the stress is relaxed. Calculations using density functional theory (DFT) reveal for the ( 1 × 1 ) phase as substrate that these dislocations appear at a coverage of about 3–4 monolayers and are either pinned by surface defects or by further adatoms which decorate them. On the (5 × 1)-H phase this pinning appears with long-range order. So, by the Ir wires at the interface the developing nanostructures including the dislocations can be structurally accessed by experiment, here with crystallographic precision by quantitative low-energy electron diffraction (LEED). Moreover, scanning tunneling microscopy (STM) reveals both the morphology of the nanostructured films and their buckling with atomic resolution.

The adsorption structure of hydrogen on ultrathin epitaxial nickel films in pseudomorphic arrangement on the unreconstructed Ir(100) surface is investigated by quantitative low-energy electron diffraction (LEED). This is highly interesting in the light of the fact that on Ni(100) adsorption is in hollow sites whilst on unreconstructed Ir(100) it is exclusively in bridge sites. On Ni films thicker than 1 monolayer (ML) the adsorption is in 4-fold coordinated hollow sites as it is on Ni(100). This is in spite of the considerable tensile strain of the Ni film (+8.9%) and is interpreted by the dominance of ensemble effects in the hydrogen bonding. In contrast, on the 1 ML Ni film on Ir(100), with iridium atoms being nearest neighbours to nickel atoms, there is occupation of both bridge and hollow sites of the nickel layer – a clear indication for the presence of ligand effects.

The evolution and structure of graphene layers on 4H-SiC(0001) and the corresponding interface are investigated by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The surface is characterized by the so-called (6p3£6p3)R30± reconstruction, whose structural properties are still unclear but at the same time are crucial for the controlled growth of homogeneous high-quality large-terrace graphene surfaces. We analyse the properties of three phases in this reconstruction with periodicities (6p3£6p3)R30±, (6£6) and (5£5). Their LEED intensities strongly depend on the surface preparation procedure applied. The graphitization process imprints distinct features in the STM images as well as in the LEED spectra. An easy and practicable determination of the number of graphene layers is outlined by means of LEED intensities.

We analyze the joint evolution of an ecological character and of dispersal distance in asexual and sexual populations inhabiting an environmental gradient. Several interesting phenomena resulting from the evolutionary interplay of these characters are revealed. First, asexual and sexual populations exhibit two analogous evolutionary regimes, in which either speciation in the ecological character occurs in conjunction with evolution of short-range dispersal, or dispersal distance remains high and speciation does not occur. Second, transitions between these two regimes qualitatively differ between asexual and sexual populations, with the former showing speciation with long-range dispersal and the latter showing no speciation with short-range dispersal. Third, a phenotypic gradient following the environmental gradient occurs only in the last case, i.e., for non-speciating sexual populations evolving towards short-range dispersal. Fourth, the transition between the evolutionary regimes of long-range dispersal with no speciation and short-range dispersal with speciation is typically abrupt, mediated by a positive feedback between incipient speciation and the evolution of short-range dispersal. Fifth, even though the model of sexual evolution analyzed here does not permit assortative mating preferences, speciation occurs for a surprisingly wide range of conditions. This illustrates that dispersal evolution is a powerful alternative to preference evolution in enabling spatially distributed sexual populations to respond to frequency-dependent disruptive selection.

Human appropriation of net primary production (HANPP), the aggregate impact of land use on biomass available each year in ecosystems, is a prominent measure of the human domination of the biosphere. We present a comprehensive assessment of global HANPP based on vegetation modeling, agricultural and forestry statistics, and geographical information systems data on land use, land cover, and soil degradation that localizes human impact on ecosystems. We found an aggregate global HANPP value of 15.6 Pg C/yr or 23.8% of potential net primary productivity, of which 53% was contributed by harvest, 40% by land-use-induced productivity changes, and 7% by human-induced fires. This is a remarkable impact on the biosphere caused by just one species. We present maps quantifying human-induced changes in trophic energy flows in ecosystems that illustrate spatial patterns in the human domination of ecosystems, thus emphasizing land use as a pervasive factor of global importance. Land use transforms earth's terrestrial surface, resulting in changes in biogeochemical cycles and in the ability of ecosystems to deliver services critical to human well being. The results suggest that large-scale schemes to substitute biomass for fossil fuels should be viewed cautiously because massive additional pressures on ecosystems might result from increased biomass harvest.

Dispersal functions are an important tool for integrating dispersal into complex models of population and metapopulation dynamics. Most approaches in the literature are very simple, with the dispersal functions containing only one or two parameters which summarise all the effects of movement behaviour as for example different movement patterns or different perceptual abilities. The summarising nature of these parameters makes assessing the effect of one particular behavioural aspect difficult. We present a way of integrating movement behavioural parameters into a particular dispersal function in a simple way. Using a spatial individual-based simulation model for simulating different movement behaviours, we derive fitting functions for the functional relationship between the parameters of the dispersal function and several details of movement behaviour. This is done for three different movement patterns (loops, Archimedean spirals, random walk). Additionally, we provide measures which characterise the shape of the dispersal function and are interpretable in terms of landscape connectivity. This allows an ecological interpretation of the relationships found.

Diffractive scattering of $\gamma^* p \to X + N$, where $N$ is either a proton or a nucleonic system with $M_N~, Comment: 45 pages, including 16 figures

Simulation models that describe autonomous individual organisms (individual based models, IBM) or agents (agent-based models, ABM) have become a widely used tool, not only in ecology, but also in many other disciplines dealing with complex systems made up of autonomous entities. However, there is no standard protocol for describing such simulation models, which can make them difficult to understand and to duplicate. This paper presents a proposed standard protocol, ODD, for describing IBMs and ABMs, developed and tested by 28 modellers who cover a wide range of fields within ecology. This protocol consists of three blocks (Overview, Design concepts, and Details), which are subdivided into seven elements: Purpose, State variables and scales, Process overview and scheduling, Design concepts, Initialization, Input, and Submodels. We explain which aspects of a model should be described in each element, and we present an example to illustrate the protocol in use. In addition, 19 examples are available in an Online Appendix. We consider ODD as a first step for establishing a more detailed common format of the description of IBMs and ABMs. Once initiated, the protocol will hopefully evolve as it becomes used by a sufficiently large proportion of modellers.

The search strategies dispersers employ to search for new habitat patches affect individuals’ search success and subsequently landscape connectivity and metapopulation viability. Some evidence indicates that individuals within the same species may display a variety of behavioural patch searching strategies rather than one species-specific strategy. This may result from landscape heterogeneity. We modelled the evolution of individual patch searching strategies in different landscapes. Specifically, we analysed whether evolution can favour different, co-existing, behavioural search strategies within one population and to what extent this coexistence of multiple strategies was dependent on landscape configuration. Using an individual-based simulation model, we studied the evolution of patch searching strategies in three different landscape configurations: uniform, random and clumped. We found that landscape configuration strongly influenced the evolved search strategy. In uniform landscapes, one fixed search strategy evolved for the entire spatially structured population, while in random and clumped landscapes, a set of different search strategies emerged. The coexistence of several search strategies also strongly depended on the dispersal mortality. We show that our result can affect landscape connectivity and metapopulation dynamics.

Animal response to landscape heterogeneity directs dispersal and affects connectivity between populations. Topographical heterogeneity is a major source of landscape heterogeneity, which is rarely studied in the contexts of movement, dispersal, or connectivity. The current study aims at characterizing and quantifying the impacts of topography on landscape connectivity. We focus on ‘hilltopping’ behavior in butterflies, a dispersal-like behavior where males and virgin females ascend to mountain summits and mate there. Our approach integrates three elements: an individual-based model for simulating animal movements across topographically heterogeneous landscapes; a formula for the accessibility of patches in homogenous landscapes; and a graphical analysis of the plots of the simulation-based vs. the formula-based accessibility values. We characterize the functional relationship between accessibility values and landscape structure (referred to as ‘accessibility patterns’) and analyze the influence of two factors: the intensity of the individuals’ response to topography, and the level of topographical noise. We show that, despite the diversity of topographical landscapes, animal response to topography results in the formation of two, quantifiable accessibility patterns. We term them ‘effectively homogeneous’ and ‘effectively channeled’. The latter, in which individuals move toward a single summit, prevails over a wide range of behavioral and spatial parameters. Therefore, ‘channeled’ accessibilities may occur in a variety of landscapes and contexts. Our work provides novel tools for understanding and predicting accessibility patterns in heterogeneous landscapes. These tools are essential for linking movement behavior, movement patterns and connectivity. We also present new insights into the practical value of ecologically scaled landscape indices.

Metapopulation models are frequently used for analysing species–landscape interactions and their effect on structure and dynamic of populations in fragmented landscapes. They especially support a better understanding of the viability of metapopulations. In such models, the processes determining metapopulation viability are often modelled in a simple way. Animals’ dispersal between habitat fragments is mostly taken into account by using a simple dispersal function that assumes the underlying process of dispersal to be random movement. Species-specific dispersal behaviour such as a systematic search for habitat patches is likely to influence the viability of a metapopulation. Using a model for metapopulation viability analysis, we investigate whether such specific dispersal behaviour affects the predictions of ranking orders among alternative landscape configurations rated regarding their ability to carry viable metapopulations. To incorporate dispersal behaviour in the model, we use a submodel for the colonisation rates which allows different movement patterns to be considered (uncorrelated random walk, correlated random walk with various degrees of correlation, and loops). For each movement pattern, the landscape order is determined by comparing the resulting mean metapopulation lifetime Tm of different landscape configurations. Results show that landscape orders can change considerably between different movement patterns. We analyse whether and under what circumstances dispersal behaviour influences the ranking orders of landscapes. We find that the ‘competition between patches for migrants’ – i.e. the fact that dispersers immigrating into one patch are not longer available as colonisers for other patches – is an important factor driving the change in landscape ranks. The implications of our results for metapopulation modelling, planning and conservation are discussed.

Dispersal has been shown to be a key determinant of spatially structured populations. One crucial aspect is predicting patch accessibility: the probability rij of a certain patch j being reached by individuals starting at another patch i. Patch accessibility rij depends on both the landscape structure and the individuals’ dispersal behaviour. To investigate the effects of these factors on rij, we developed a simulation model focusing on animal dispersal. Our model analyses show that there is an important intrinsic effect of the interplay between landscape structure and dispersal behaviour on patch accessibility: the competition between patches for migrants. We derive a formula for patch accessibility. This formula is very simple because it just takes distances into account: not only the distance between start patch and target patch, but also between the start patch and all the other patches in the landscape. Despite its simplicity, the formula is able to cover effects such as the competition for migrants. The formula was found to have high predictive power for a variety of movement behaviours (random walk with various degrees of correlation, Archimedean spirals and loops) in any given landscape. The formula can be interpreted as a generic function for patch accessibility for further population dynamics analyses. It also delivers insights into the consequences of dispersal in fragmented landscapes.

The stable (5 × 1) surface reconstruction of Ir(1 0 0) is shown to restructure upon exposure to hydrogen as observed and determined by STM and quantitative LEED. The new phase, Ir(1 0 0)-(5 × 1)-H, consists of defect-free Ir nanowires of up to micrometre length with their lateral order depending sensitively on the details of preparation. The Ir wires can be decorated by Fe on both their sides, so that Fe–Ir–Fe sandwich nanowires are formed. The space between the Ir wires can also be filled completely equivalent to the formation of a Fe4Ir surface alloy. It is speculated how this lateral nanostructuring may be combined with one vertical to the surface.

Ir(100) is well known to exhibit a (5×1) periodic surface reconstruction denoted as (5×1)-hex. The atoms of the outermost layer are quasi-hexagonally arranged rather than being of quadratic order as the layers below and in the bulk. Accordingly, an excess of 20% of atoms is accommodated in the top layer and the surface is buckled with atomic rows protruding from the surface. It is shown by the combined application of atomically resolved scanning tunnelling microscopy (STM) and quantitative low-energy electron diffraction (LEED) that hydrogen adsorption at sufficiently high temperature induces the surface to restructure. The new phase, (5×1)-H, develops by the extraction of surface protruding and close packed atomic Ir wires from the hexagonal layer. The remaining atoms of the latter reassume quadratic order and the wires expelled reside on this layer. The extraction of the Ir wires proceeds in a zip-like process and starts preferentially at surface defects, in particular at step edges or domain boundaries. The wires’ lateral periodicity normal to their spatial orientation is again 5-fold, but only on average. The precise lateral arrangement depends sensitively on the details of preparation, in particular the amount of hydrogen exposure and the sample’s temperature during, or temperature treatment after, exposure.

The power of the combined application of quantitative low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) is demonstrated for several examples. It is shown that the STM image in most cases provides the key to the applicable structural model type. Such an initial guess is needed by LEED to start a structural search in which the model parameters are varied so that the complete crystallographic structure is obtained. The input from STM is invaluable when a large number of different model types have to be tested or, even more, in cases where the scientist lacks the imagination to think of the correct model type. If a structural misinterpretation of the STM image puts LEED on the wrong track, then the method becomes aware of that by the best fit achieved being unsatisfying. In this sense, the combination of STM and quantitative LEED is almost ideal and provides new power for the access of complex structures.

The basal surfaces of hexagonal SiC exhibit a large variety of surface reconstructions that develop under a similarly rich variety of sample preparations. A subset of these surface phases, which have been investigated in structural detail using scanning tunnelling microscopy and quantitative low-energy electron diffraction, is described and shown to offer the scope to be used for the formation of SiC-based semiconductor devices. The phases discussed are the (3 × 3) and reconstructions for the (0001) surfaces of 4H- and 6H-SiC and the oxygen-uptake-driven reconstructions of these polytypes for both the (0001) and the (000) surface orientations. We show that the (3 × 3) reconstruction corresponds to a highly passivated surface that facilitates hexagonal single-crystal growth, while suitable preparation of the reconstruction favours a switch to cubic growth and hence to the formation of a heterojunction. The reconstructions promise to form defect-free interfaces to insulating silicon oxide films, which is important for device applications.

It is shown by scanning tunnelling microscopy (STM) that the Ir(100) surface can be used as a template to form other nanostructures after it has restructured upon exposure to hydrogen. Extremely long and defect-free Ir nanowires produced in the restructuring process can be decorated by, e.g., Fe so that FeIrFe nanochains develop as sandwiches of atomically thin Fe and Ir wires. Laterally they recur with 1.36 nm periodicity on average, i.e. two atomic rows are missing between two sandwiches. By additional deposition of Fe this space can be filled so that the vacancy spaced {FeIrFe} lateral superlattice transforms to a {Fe4Ir} superlattice. Their crystallography is determined by quantitative low-energy electron diffraction (LEED).

We present a combined experimental and theoretical investigation of the interface between a B2-type FeSi film and Si(111). Using an ultra-thin B2-FeSi film grown on Si(111), the interface is still reached by electrons, so quantitative low-energy electron diffraction (LEED) could be applied to determine the bonding geometry experimentally. As a result, the local configuration at the shallow buried interface is characterized by near-substrate Fe atoms being 8-fold coordinated to Si atoms and by the silicide unit cell being rotated by 180° with respect to the Si unit cell (B8 configuration). The interface energetics were explored by total-energy calculations using density functional theory (DFT). The B8-type interface proves to be the most stable one, consistent with the experimental findings. The atomic geometries obtained experimentally (LEED) and theoretically (DFT) agree within the limits of errors. Additionally, the calculations explain the stabilization of the B2 phase, which is unstable as bulk material: the analysis of the elastic behaviour reveals a reversed energy hierarchy of B2 and the bulk stable B20 phase when epitaxial growth on Si(111) is enforced.

The stoichiometries and geometric structures formed by the segregation of C, Al and S on a Fe(100) surface have been investigated by Auger electron spectroscopy and quantitative low-energy electron diffraction (LEED). Step-wise annealing of a sputtered surface with increasing annealing temperature reveals the successive segregation of C, Al and S. According to quantitative LEED analyses, each segregand forms a distinct c(2 × 2) long-range ordered structure. Also, each segregand removes the preceding one from the surface entirely, i.e. segregation in the Fe(100)–(C, Al, S) system is purely competitive with no ordered co-segregation regimes involving two or even three elements. The c(2 × 2) phases of segregated carbon and sulfur consist of elemental surface adlayers with the adatoms residing in four-fold symmetric hollow sites of the iron substrate. This is in contrast to segregated Al which, according to an earlier analysis, forms a c(2 × 2)-symmetric surface alloy layer with iron. In all cases there is some chemical disorder within subsurface layers with Fe atoms substituted by Al. The bond lengths between the segregated adatoms and iron neighbours are close to the sum of the covalent radii of the elements involved whereby carbon appears to be five-fold coordinated, in contrast to four-fold coordinated sulfur.

We present a new investigation of the metastable 1 × 1 and reconstructed 5 × 1 phases of Ir(100) using quantitative low-energy electron diffraction and scanning tunnelling microscopy. It is shown that the 5 × 1 reconstruction of Ir(100) extends up to the fourth layer into the surface. This structural information is retrieved by the use of electron energies up to 600 eV which simultaneously provides an unusually broad database of more than 10.000 eV. Together with an excellent quality of the theory–experiment fit equivalent to an R-factor of RP = 0.144 this allows for rather small error limits of the as many as 17 structural parameters describing the four-layer reconstructed surface. Similar features hold for the 1 × 1 phase which is analysed in parallel. In addition, we present a systematic investigation of the influence of the electron energy range applied and of the allowed depth of reconstruction on the accuracy of the analysis. It appears that for the case of Ir(100)-5 × 1 the structural parameters describing the top two layers are largely independent from the consideration of the reconstruction of deeper layers.

We report that the quality of atomic images reconstructed directly within the framework of holographic low energy electron diffraction can suffer from considerable atomic displacements. These are due to serious disturbances of the holographic object wave which exist when the object owns the same translational symmetry as the arrangement of beam splitters, for example when the latter induce a substrate reconstruction. We propose and test an iterative procedure for reducing these disturbances by a hybrid combination of the holographic reconstruction and some data fitting procedure. A reliable atomic image results after only a few iteration steps.