Friedel oscillations responsible for stacking fault of adatoms: The case of Mg(0001) and Be(0001)

We perform a first-principles study of Mg adatom and adislands on the Mg(0001) surface, and Be adatom on Be(0001), to obtain further insights into the previously reported energetic preference of the fcc faulty stacking of Mg monomers on Mg(0001). We first provide a viewpoint on how Friedel oscillations influence ionic relaxation on these surfaces. Our three-dimensional charge-density analysis demonstrates that Friedel oscillations have maxima which are more spatially localized than what one-dimensional average density or two-dimensional cross sectional plots could possibly inform: The well-known charge-density enhancement around the topmost surface layer of Mg(0001) is strongly localized at its fcc hollow sites. The charge accumulation at this site explains the energetically preferred stacking fault of the Mg monomer, dimer and trimer. Yet, larger islands prefer the normal hcp stacking. Surprisingly, the mechanism by which the fcc site becomes energetically more favorable is not that of enhancing the surface-adatom bonds but rather those between surface atoms. To confirm our conclusions, we analyze the stacking of Be adatom on Be(0001) - a surface also largely influenced by Friedel oscillations. We find, in fact, a much stronger effect: The charge enhancement at the fcc site is even larger and, consequently, the stacking-fault energy favoring the fcc site is quite large, 44 meV.Comment: Submitted to Physical Review

Convergence of strain energy release rate components for edge-delaminated composite laminates

Strain energy release rates for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial strain was studied. The individual components of the strain energy release rates did not show convergence as the delamination tip elements were made smaller. In contrast, the total strain energy release rate converged and remained unchanged as the delamination tip elements were made smaller and agreed with that calculated using a classical laminated plate theory. The studies of the near field solutions for a delamination at an interface between two dissimilar isotropic or orthotropic plates showed that the imaginary part of the singularity is the cause of the nonconvergent behavior of the individual components. To evaluate the accuracy of the results, an 8-ply laminate with the delamination modeled in a thin resin layer, that exists between the -35 and 90 plies, was analyzed. Because the delamination exists in a homogeneous isotropic material, the oscillatory component of the singularity vanishes

Effect of misfit dislocation on surface diffusion

We apply molecular dynamics and molecular static methods to study the effect of misfit dislocations on adatom diffusion in close proximity to the dislocation core in heteroepitaxial systems, using many-body interaction potentials. Our system consists of several layers (three-seven) of Cu on top of a Ni(111) substrate. The misfit dislocations are created with the core located at the interface between the Cu film and the Ni substrate, using the repulsive biased potential method described earlier. We find that presence of the defect under the surface strongly affects the adatom trajectory, creating anisotropy in atomic diffusion, independent of the thickness of the Cu film. We also calculate the potential energy surface available to the adatom and compare the energy barriers for adatom diffusion in the proximity of the core region and on the defect-free surface

Development of a collaborative model of low back pain: report from the 2017 NASS consensus meeting

Low back pain (LBP) is a multifactorial problem with complex interactions among many biological, psychological and social factors. It is difficult to fully appreciate this complexity because the knowledge necessary to do so is distributed over many areas of expertise that span the biopsychosocial domains.This study describes the collaborative modeling process, undertaken among a group of participants with diverse expertise in LBP, to build a model to enhance understanding and communicate the complexity of the LBP problem.The study involved generating individual models that represented participants' understanding of the LBP problem using fuzzy cognitive mapping (FCM), and 4 subsequent phases of consultation and consensus with the participants to characterize and refine the interpretation of the FCMs.The phases consisted of: proposal of Categories for clustering of model Components; preliminary evaluation of structure, composition and focal areas of participant's FCMs; refinement of Categories and Components with consensus meeting; generation of final structure and composition of individual participant's FCMs. Descriptive statistics were applied to the structural and composition metrics of individual FCMs to aid interpretation.From 38 invited contributors, 29 (76%) agreed to participate. They represented 9 disciplines and 8 countries. Participants' models included 729 Components, with an average of 25 (SD = 7) per model. After the final FCM refinement process (Components from separate FCMs that used similar terms were combined, and Components from an FCM that included multiple terms were separated), there were 147 Components allocated to ten Categories. Although individual models varied in their structure and composition, a common opinion emerged that psychological factors are particularly important in the presentation of LBP. Collectively, Components allocated to the "Psychology" Category were the most central in almost half (14/29) of the individual models.The collaborative modeling process outlined in this paper provides a foundation upon which to build a greater understanding and to communicate the complexity of the LBP problem. The next step is to aggregate individual FCMs into a metamodel and begin disentangling the interactions among its Components. This will lead to an improved understanding of the complexity of LBP, and hopefully to improved outcomes for those suffering from this condition

Tallo: A global tree allometry and crown architecture database.

This is the final version. Available from Wiley via the DOI in this record. Data capturing multiple axes of tree size and shape, such as a tree's stem diameter, height and crown size, underpin a wide range of ecological research-from developing and testing theory on forest structure and dynamics, to estimating forest carbon stocks and their uncertainties, and integrating remote sensing imagery into forest monitoring programmes. However, these data can be surprisingly hard to come by, particularly for certain regions of the world and for specific taxonomic groups, posing a real barrier to progress in these fields. To overcome this challenge, we developed the Tallo database, a collection of 498,838 georeferenced and taxonomically standardized records of individual trees for which stem diameter, height and/or crown radius have been measured. These data were collected at 61,856 globally distributed sites, spanning all major forested and non-forested biomes. The majority of trees in the database are identified to species (88%), and collectively Tallo includes data for 5163 species distributed across 1453 genera and 187 plant families. The database is publicly archived under a CC-BY 4.0 licence and can be access from: https://doi.org/10.5281/zenodo.6637599. To demonstrate its value, here we present three case studies that highlight how the Tallo database can be used to address a range of theoretical and applied questions in ecology-from testing the predictions of metabolic scaling theory, to exploring the limits of tree allometric plasticity along environmental gradients and modelling global variation in maximum attainable tree height. In doing so, we provide a key resource for field ecologists, remote sensing researchers and the modelling community working together to better understand the role that trees play in regulating the terrestrial carbon cycle.Natural Environment Research Council (NERC)Natural Environment Research Council (NERC); Ministry of Education, Youth and Sports of the Czech RepublicFAPEMIGUniversidad Nacional Autónoma de MéxicoUniversidad Nacional Autónoma de MéxicoConsejo Nacional de Ciencia y TecnologíaSwedish Energy AgencyUKRIFederal Ministry of Education and ResearchNational Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Science FoundationNational Science FoundationInternational Foundation for ScienceP3FACDynAfForNanjing Forestry UniversityJiangsu Science and Technology Special ProjectHebei UniversityAgence Nationale de la RechercheAgence Nationale de la RechercheAgua Salud ProjectU.S. Department of EnergyCAPE

Webometrics benefitting from web mining? An investigation of methods and applications of two research fields

Webometrics and web mining are two fields where research is focused on quantitative analyses of the web. This literature review outlines definitions of the fields, and then focuses on their methods and applications. It also discusses the potential of closer contact and collaboration between them. A key difference between the fields is that webometrics has focused on exploratory studies, whereas web mining has been dominated by studies focusing on development of methods and algorithms. Differences in type of data can also be seen, with webometrics more focused on analyses of the structure of the web and web mining more focused on web content and usage, even though both fields have been embracing the possibilities of user generated content. It is concluded that research problems where big data is needed can benefit from collaboration between webometricians, with their tradition of exploratory studies, and web miners, with their tradition of developing methods and algorithms

COVID-19: Rental housing and homelessness impacts in Australia

Confounding most predictions, by far the most significant housing impact of the pandemic in Australia has been the house price boom that took off in late 2020; stimulated by Government measures to boost private market demand, this has compounded longstanding unaffordability, inequality and indebtednessLess reported has been the rapid escalation in rent inflation from mid-2020, with annual national increases accelerating to over 8% by Q3 2021 – the fastest rate of increase for well over a decade, and far ahead of wage growth (at 1.7%); rents in regional Australia meanwhile surged by a remarkable 12.4% in the year to August 2021Damaging impacts of recent trends on rental affordability in regional Australia are confirmed by detailed figures for non-metropolitan Victoria showing the proportion of tenancies affordable to low-income tenants declining from 41% to 33% in the year to Q2 2021The key causes of recent regional rent inflation are likely to lie in new demand hitting markets where there is currently unusually low turnover in existing rental properties and new properties entering the rental sector – measured by new tenancy bonds lodged, private rental supply fell by 6% in 2020-21 in regional NSW and by 15% in regional VictoriaAfter the extraordinary rental policy responses of 2020 – eviction moratoriums, rent variation and rent relief schemes – similar actions in reaction to 2021 lockdowns were comparatively light. Whereas in 2020 all states and territories implemented eviction moratoriums, in 2021 only half imposed similar restrictions during Delta outbreaks – and notably the jurisdiction most affected, Victoria, enacted no second moratorium.The few published data indicate the incompleteness of the moratoriums: almost 3,000 South Australian tenancies were subject to eviction proceedings during the moratorium in 2020, and almost 4,600 tenancies were subject to termination proceedings in New South Wales in the first 10 weeks of its 2021 ‘stay at home’ lockdown.Most of the 2020 rent relief schemes were undersubscribed, reflecting the significance of federal income support programs, lack of engagement in rent negotiations and the weak delivery of relief through rebates on land tax (from which most landlords are already exempt).In both the boarding house sector, and in international student support, there are highly knowledgeable workers engaged directly with persons in need; their capacity could be enhanced and leveraged to inform support strategies for each sector.During 2020 at least 12,073 rough sleepers benefited from COVID-19 Emergency Accommodation (EA) programs staged by NSW, South Australia, Queensland, and Victoria, although in the first two of these, there has been no significant follow-through in terms of expanding permanent social and affordable housing provisionBy 2022 EA placements and move-on housing programs in NSW and Victoria alone will have facilitated safe, secure and supported accommodation pathways for around 3,500 former rough sleepers with complex needs; at least partially relieving the growing backlog of chronic rough sleepers built up over previous years.Unlike Victoria, the NSW Government has resisted calls for stimulus investment to significantly expand permanent social housing provision; as a result, longer term housing pathways for assisted former rough sleepers assisted in the state will be at the expense of others in severe housing need.In 2020 and 2021 four state governments announced significant self-funded social housing construction programs as a component of post-pandemic stimulus investment; these add up to nearly $10 billion to be invested over the next few years.In all, state/territory governments plan to construct over 23,000 social housing units over the three years from 2021-22; a threefold increase on national social housebuilding rates during the late 2010s, and comparable in scale to the Rudd Government’s post-GFC Social Housing Initiative (2009-12).The scale of planned development in Victoria, Queensland and Tasmania, will (at least temporarily) reverse historically declining representation of social housing in these states; in other jurisdictions a continuing contraction in the sector’s share of all dwellings is in prospect, with NSW’s social housing set to fall below 4% of total occupied stock within 10 years (for reference, the OECD average is 7.1%).While both remarkable and badly needed, Australia’s recent social housing construction revival is not only patchy across the country, but also unsustainable without a reversal in current Australian Government policy eschewing additional financial support to enable social housing growth (whether via public or community housing)

The Role Of Van Der Waals Interaction In The Tilted Binding Of Amine Molecules To The Au(111) Surface

We present the results of ab initio electronic structure calculations for the adsorption characteristics of three amine molecules on Au(111), which show that the inclusion of vanderWaals interactions between the isolated molecule and the surface leads in general to good agreement with experimental data on the binding energies. Each molecule, however, adsorbs with a small tilt angle (between 5 and 9°). For the specific case of 1,4-diaminobenzene (BDA) our calculations reproduce the larger tilt angle (close to 24°) measured by photoemission experiments, when intermolecular (vanderWaals) interactions (for about 8% coverage) are included. These results point not only to the important contribution of vanderWaals interactions to moleculesurface binding energy, but also that of intermolecular interactions, often considered secondary to that between the molecule and the surface, in determining the adsorption geometry and pattern formation. © 2012 IOP Publishing Ltd

Selection of support system for urban deep excavations: A case study in Ahvaz geology

Today, the increased need for construction in congested urban areas has necessitated construction of tall and massive structures. In these cases, design engineers have the option of excavation and digging of undisturbed and fresh spaces under the ground. Due to the presence of urban structures and public facilities adjacent to the excavation sites, which in some cases are highly important, the use of a support system with good and safe performance that can prevent probable losses is essential. Therefore, various support systems can be proposed for stabilizing the excavations and their surroundings. Nevertheless, selecting an appropriate support system in urban areas that can increase the stability of excavations has been a long-time challenge for design engineers. Due to the variable geotechnical conditions in these areas, which occasionally cause extensive changes between soil layers within a close distance, the stress-deformation field is very complicated and extended, making it difficult to select and design a proper and safe support system. Therefore, in this study, after investigating different excavation methods in urban areas and comparing conventional and widely used methods in these areas, an appropriate and safe support system was proposed for excavation in urban areas depending on construction, structural and economic conditions. The behavior of a controlled excavation using the proposed support system in Ahvaz city which possesses variable and complex geotechnical properties, was investigated, and the displacement values during the construction and the progress of the excavation were examined and assessed. For a more precise investigation of the support system behavior, the performance of the support system was compared with other systems utilized in other projects in Ahvaz city. The obtained results indicated that application of a rigid system would have the best performance. Keywords: Ahvaz Soil, Supporting Systems, Deep Excavation, Urban Are