The use of thin marble and limestone for facade cladding has increased substantially during the last five decades. The durability of such thin slabs (often only 30 mm thick) has been assumed to be satisfactory based on centuries of successful use as a structural building stone. Nevertheless, all over the world, the long-term deformation and strength loss of some claddings have led to concerns about its safe and durable use. The detailed assessment of marble and limestone within TEAM (see also www.sp.se/building/team), is used to develop a hypothesis for the observed deterioration and to develop remedial actions. This paper considers the influence of rock and mineral properties on the behaviour of marble claddings. A selection of results is presented, illustrating the influence of properties like mineralogy, grain size and boundaries, preferred orientation and pore structure. Of the intrinsic parameters, the interlocking of the grains and the lattice preferred orientation seem to be very important influencing factors. The final evaluation of the results will be presented in 2005.
The use of thin marble and limestone panels for facade cladding has increased substantially during the last five decades. The durability of such thin slabs (often only 30 mm thick) has been assumed to be satisfactory based on centuries of successful use as a structural building stone. Nevertheless, all over the world, the long-term deformation and strength loss of some cladding panels have led to concerns about its safe and durable use. The detailed assessment of marble and limestone within the TEAM-project (see also www.sp.se/building/team), is used to develop a hypothesis for the observed deterioration and to develop remedial actions. This paper presents test methods for the bowing and expansion potential of marble. The method is discussed and the relevance of the test exposures is demonstrated by comparisons with on-site observations on marble cladding. A number of results are presented, illustrating the influence of the temperature cycles, the humidity and the stonetype on the bowing and expansion.
Natursten är ett av de äldsta byggnadsmaterial vi har. Nu ökar importen av billig utomeuropeisk natursten, med egenskaper vi inte alltid känner till. Stenen kan ha svårt att klara svensk vinter. Det blir allt knivigare att välja. Granit är inte längre synonymt med beständig sten.
Sustainability is not only a matter of choosing durable stone types for a specific application. It is also about theenergy consumed during the production, transportation and placing of the stone. It is also about dimensioningand shaping of the stone properly for the actual construction and the stone together with other materials in theconstruction. This contribution deals with the latter and is a case study on a failed paving construction.Stone paving is the collective expression for the use of stone slabs, setts and kerbs for exterior paving purposes.There are three European product standards in force; EN 1341, 1342 and 1343 respectively. These standardsdescribe e.g. how to denominate the products, the allowed dimensional tolerances and which technical propertiesto validate. There is little or no information on the actual usage of these products. Such information has generallyto be elaborated by each country.The standard way of construction for pavements is non-bonded laying of elements in crushed sand/splitmixtures. Under special loads and cleaning requirements this traditional, unbound construction method easily failsand a bound construction is needed. The structural integrity of an unbound pavement construction is maintainedon the basis of friction and mechanical interlock. Energy from traffic loading enters the structure via the surfacecourse, some of this energy is dissipated within the surface course itself and some is transmitted into the beddingcourse and thereafter the supporting base layers beneath. There are two structural elements in the surface course,the setts and the jointing medium. The jointing medium has physical properties which are important to consider,such as stiffness modulus, resistance to shear et al, which crucially affect the manner in which the pavementresponds to applied loads.Sufficient friction between the various components is crucial but is not generated and mechanical interlock notexercised without movement of the component parts of the structural model. The unbound paving is not a rigidconstruction and the various parts of this structural model must be mobilised in order that friction is generated.The paving is therefore also heavily dependant upon the unseen surface finishing of the setts (and slabs). In orderto adequately generate friction between the paving element and both bedding and jointing materials the unseensurfaces have to be rough, preferably a cleft or riven surface, to function properly.There are two distinct categories of setts, shallow setts and full setts, each requiring a different approach:Shallow setts are those having depth less than width.Specifying shallow setts makes a more economical use of the raw material used in their manufacture but thepavement construction requires to designed more carefully and there is an upper limit to the level of traffic whichcan be carried. A concrete base must be provided when specifying shallow setts.Full setts are those having depth not less than width.For many centuries the "golden rule" was that setts must be at least as deep as they are wide. The heavier thetraffic loading, the deeper the sett in relation to its width. Before the advent of concrete and mortar, when jointing,bedding and supporting base were all unbound, this rule was very necessary. Even with the development of highperformance mortars and reinforced concrete for a base, we need to use full setts when the traffic loading exceedsa given maximum.The deeper the sett in relation to its width, the more the strength of the pavement is taken by the joints between thesetts. So, with deep, full setts we can sometimes lay over an unbound or a bituminous base, even for heavy traffic.As can be seen, these simple rules given above depend on proper definition of the traffic loads. i.e. numberof vehicles per day and the weight of them. When the general rules are not followed the stones start to move inan uncontrolled manner. Some cases and one in particular will be detailed in this presentation. The case studiesdemonstrate the importance of the necessary knowledge needed to build a paving that can cope with the dynamicand static traffic loads. In addition, it shows the problem that may arise due to a poorly defined border betweensetts and slabs.
The use of natural stone as facade cladding has been shown to have much lower life cycle costs and they are more environmentally friendly than comparable products of concrete, glass, and steel. Promoting the use of natural stone has therefore a great positive impact on the environment. However, the number of occurrences of bowing and expansion of marble and limestone panels has led to increased maintenance costs, significant safety risk, and negative publicity. The lack of knowledge of a solution to the problem of bowing marble has a large negative effect on the entire stone trade. In response, short-sighted and less durable construction solutions are used as an alternative, adding to the decreasing export figures and numbers of employees within the stone sector. The TEAM _TEAM_TEsting and Assessment of Marble and limestone_ project addresses a problem with marble types, from several European countries, that display bowing on facades in both cold and warm climates. There is, therefore a need to develop harmonized European standards for differentiating between marble that is susceptible to bowing and marble that is not. Resolution No. 013, in May 1999 taken by the European Committee for Standardization _CEN_, Technical Committee _TC_ 246 Natural Stone states the urgent needs “to develop a direct test method of the bowing risk for marble cladding products.” Thus, the project addresses the mandate for external wall coverings and the safety of panels. This paper serves to give a comprehensive overview of the main findings in the project. The main objectives were: • To understand and explain the mechanisms of the expansion and loss of strength, probably the most important phenomena leading to degradation of marble and limestone clad facades. • To prevent the use of deleterious marble and limestone by introducing drafts for European standards. • To develop a concept for assessment of facades, including a monitoring system in order to predict strength development and improve safety and reliability. • To analyze if surface coating and impregnation could prevent or diminish the degradation. • To address quality control aspects in order to optimize the production conditions. The TEAM project consortium, representing nine EU _European union_ countries, comprised sixteen partners representing stone producers and trade associations, testing laboratories, standardization and certification bodies, consultants, building owners and caretakers and producers of fixing and repair systems. A state-of-the-art report has been written and is based on an extensive compilation of more than 400 papers on marble and limestone deterioration dating from the late 1800s to 2006. A survey of about 200 buildings has given a clear picture of the extent of the problem in geographical, geological, and climatological terms. Detailed case studies of six buildings have resulted in a methodology for assessment of facades including monitoring system and risk assessment. Research both in the laboratory and the field were performed on a large number of different stone types from different countries and used in different climates. This gave the explanation of degradation mechanisms and led to the determination of the critical influencing factors. Two tests methods, including precision statements: one for bowing _1_ and one for thermal and moisture irreversible expansion have been prepared for submission to CEN TC 246. Repair techniques based on the use of surface coating and impregnation systems has been tested at laboratory and in the field. Positive side effects including increased durability and easier cleaning have been observed. Guidelines for production and product control have been proposed, and an instruction for stone sampling and description has been developed.
Natural stone has been used for centuries as building material. In historical time it was mainly used as load bearing elements, but within the past 50 years a new processing technique has made it commercially feasible to produce and use thin façade cladding. Unfortunately, a number of marble facades on buildings in both Europe and elsewhere have had serious problems with deterioration of the stone material. The TEAM _TEAM _ TEsting and Assessment of Marble and limestone_ project consortium represents nine European countries and comprises 16 partners, representing stone producers and trade associations, testing laboratories, standardization and certificate bodies, consultants, building owners and caretakers and producers of fixing and repair systems. The project had a budget of approximately 5 million dollars and was partly funded by the European Commission under the contract no. G5RD-CT-2000-00233. Two of the main objectives in the TEAM project were: — To understand and explain the mechanisms of the expansion, bowing, and loss of strength leading to degradation of marble and limestone clad facades. —To prevent the use of deleterious marble and limestone by introducing a draft for new European standards. This paper presents some of the important conclusions drawn from a literature review carried out within the TEAM project—and was based on an extensive review of literature on marble and limestone deterioration dating from the late 1800s to 2006 and the results of the TEAM project. The comprehensive information from more than 70 selected literature references is reviewed and discussed in order to describe the present knowledge on the causes and mechanisms responsible for the bowing and strength loss of thin marble cladding. In the following, the literature and TEAM findings are grouped under a number of headings proposed to explain observations. Thus, the information from the literature is compared and supplemented with the results from the TEAM project in order to present a good overview of the existing, most relevant, knowledge in the field. The literature review reveals that only few researchers have examined the durability problem from a broad perspective. In addition, no conclusive answer about the mechanisms and influencing factors can be given. The TEAM project has made it possible to identify several of the key influencing factors in marble degradation, the relative importance of various factors, and to gain a deeper understanding of the mechanisms involved.
As a step towards the introduction of the new European product standard SS-EN 13450 for Railway track ballast in Sweden, SP was given the commission to make a survey of older test results and compare testing of selected materials with test methods in accordance with the old and the new regulations/standards. Test results for the past 10 years, from most Swedish producers, were collected, evaluated and compared with the old and new requirements. 10 aggregates were chosen for a detailed study of almost all properties specified in the new standard. The outcome is a recommendation for properties to be declared and categories to be used in the new Swedish standard. The most difficult part is how to deal with conformity criteria since no such are given in EN 13450! It is not stated whether the categories shall be interpreted as absolute values or if they can be used to compare with e.g. characteristic values, mean values … It has also to be defined in a special document how old test results can be used for the conformity assessment. The following properties will be used in Sweden: Petrographic composition, Particle size distribution, Los Angeles Value, micro-Deval, Shape index, Water absorption and density. Depending on the value of the water absorption, a frost resistance test will also be required. For basalts of unknown origin, a “Sonnenbrand test” will most likely be required. Key words: Railway ballast, Standards, Aggregates, European standard, Swedish norms
A medial surface (MS) analysis of the rhombohedral infinite periodic minimal surface family rPD is presented. The rPD family of bicontinuous surfaces has been suggested as a pathway for transitions between its two cubic members, the P and the D surface, in mesophases in liquid-crystalline self-assembly. The MS is a representation of a labyrinth as a centered 2D skeleton. By providing a definition of a pointwise channel diameter, the MS allows for an analysis of homogeneity of such surfaces including chain stretching frustration. For the rPD surface, variations of this channel diameter are locally minimal for the D surface, and a horizontal inflection point for the P surface. This may have implications for the phase stability of the corresponding liquid-crystalline mesophases. The MS can be further reduced to a 1D line graph. For the rPD surface, this graph contains curved edges and cannot be deduced from symmetry considerations alone
This paper presents a packaging approach for inertial sensors using wire bonding technology. The die is mounted exclusively by bond wires on the front- and backside to the package. Conventional single-side die attach to substrates, such as gluing, is abandoned. The approach is characterized by its novel and symmetric die attach concept as well as its simplicity of applying a standard wire bonding process. The wire bond attachment facilitates significant reduction of thermally induced mechanical stresses. The attachment concept is characterized in terms of attachment stiffness and potential die resonances using Laser Doppler Vibrometry (LDV). White-light interferometry is used to investigate stress related warping that is induced by the die attachment process.
Climate change mitigation trade-offs between increasing harvests to exploit substitution effects versus accumulating forest carbon sequestration complicate recommendations for climate beneficial forest management. Here, a time dynamic assessment ascertains climate change mitigation potential from different rotation forest management alternatives across three Swedish regions integrating the forest decision support system Heureka RegWise with a wood product model using life cycle assessment data. The objective is to increase understanding on the climate effects of varying the forest management. Across all regions, prolonging rotations by 20% leads on average to the largest additional net climate benefit until 2050 in both, saved emissions and temperature cooling, while decreasing harvests by 20% leads to the cumulatively largest net climate benefits past 2050. In contrast, increasing harvests or decreasing the rotation period accordingly provokes temporally alternating net emissions, or slight net emission, respectively, regardless of a changing market displacement factor. However, future forest calamities might compromise potential additional temperature cooling from forests, while substitution effects, despite probable prospective decreases, require additional thorough and time explicit assessments, to provide more robust policy consultation. © 2022, The Author(s).
Multi-family housing construction (MFHC) with wood instead of concrete as frame material results in lower greenhouse gas emissions. Hence, substituting wood for concrete in MFHC in Sweden until 2030, and onwards to 2070, could be a promising climate change mitigation option. But to what extent, and how would it impact Sweden’s forests? Here we assess climate and biodiversity implications - in terms of the area of old forest - of a completely wood-based future MFHC in Sweden. The wood required is assumed to be exclusively sourced as additional fellings in Swedish forests, thus carbon leakage from wood imports as well as displacement of other wood uses can be disregarded. Different types of timber frame systems and the role of varying future dwelling sizes are considered. We find that the wood needed for a complete substitution of concrete would result in very minor increases in harvests. We further register slight net additional climate change mitigation, irrespective of the wood construction system. There is a small tradeoff between climate change mitigation and biodiversity, as the area of old forest reduces slightly. The largest climate benefit, and lowest impact on Swedish forests, is provided when using timber-light frame combined with reduced dwelling size. © 2023 The Authors
Comets are composed of dust and frozen gases. The ices are mixed with the refractory material either as an icy conglomerate, or as an aggregate of pre-solar grains (grains that existed prior to the formation of the Solar System), mantled by an ice layer. The presence of water-ice grains in periodic comets is now well established. Modelling of infrared spectra obtained about ten kilometres from the nucleus of comet Hartley 2 suggests that larger dust particles are being physically decoupled from fine-grained water-ice particles that may be aggregates, which supports the icy-conglomerate model. It is known that comets build up crusts of dust that are subsequently shed as they approach perihelion. Micrometre-sized interplanetary dust particles collected in the Earth's stratosphere and certain micrometeorites are assumed to be of cometary origin. Here we report that grains collected from the Jupiter-family comet 67P/Churyumov-Gerasimenko come from a dusty crust that quenches the material outflow activity at the comet surface. The larger grains (exceeding 50 micrometres across) are fluffy (with porosity over 50 per cent), and many shattered when collected on the target plate, suggesting that they are agglomerates of entities in the size range of interplanetary dust particles. Their surfaces are generally rich in sodium, which explains the high sodium abundance in cometary meteoroids. The particles collected to date therefore probably represent parent material of interplanetary dust particles. This argues against comet dust being composed of a silicate core mantled by organic refractory material and then by a mixture of water-dominated ices. At its previous recurrence (orbital period 6.5 years), the comet's dust production doubled when it was between 2.7 and 2.5 astronomical units from the Sun, indicating that this was when the nucleus shed its mantle. Once the mantle is shed, unprocessed material starts to supply the developing coma, radically changing its dust component, which then also contains icy grains, as detected during encounters with other comets closer to the Sun.
Aluminium, gallium, and indium are group 13 metals with similar chemical and physical properties. While aluminium is one of the most abundant elements in the Earth's crust, gallium and indium are present only in trace amounts. However, the increased use of the latter metals in novel technologies may result in increased human and environmental exposure. There is mounting evidence that these metals are toxic, but the underlying mechanisms remain poorly understood. Likewise, little is known about how cells protect themselves from these metals. Aluminium, gallium, and indium are relatively insoluble at neutral pH, and here we show that they precipitate in yeast culture medium at acidic pH as metal-phosphate species. Despite this, the dissolved metal concentrations are sufficient to induce toxicity in the yeast Saccharomyces cerevisiae. By chemical-genomic profiling of the S. cerevisiae gene deletion collection, we identified genes that maintain growth in the presence of the three metals. We found both shared and metal-specific genes that confer resistance. The shared gene products included functions related to calcium metabolism and Ire1/Hac1-mediated protection. Metal-specific gene products included functions in vesicle-mediated transport and autophagy for aluminium, protein folding and phospholipid metabolism for gallium, and chorismate metabolic processes for indium. Many of the identified yeast genes have human orthologues involved in disease processes. Thus, similar protective mechanisms may act in yeast and humans. The protective functions identified in this study provide a basis for further investigations into toxicity and resistance mechanisms in yeast, plants, and humans. © 2023 The Author(s).
We investigate the properties of the magnetocapacitance and dissipation factor of epitaxial graphene Hall bars with different electrode configurations to gain insight into the underlying physical mechanisms. The dependence of magnetocapacitance and dissipation factor on the magnetic field shows how the screening ability of the two-dimensional electron gas (2DEG) changes at the transition from the nonquantized to the quantized state. Both magnetocapacitance and dissipation factor exhibit a characteristic and correlated voltage dependence, which is attributed to the alternating contraction and expansion of the nonscreening 2DEG regions due to the alternating local electric field. Two regimes with seemingly different voltage dependencies are explained as the limiting cases of weak and strong electric fields of the same general voltage dependence. Electric fields in the plane of the 2DEG are found to cause about three orders of magnitude more ac dissipation than perpendicular electric fields. This strong directionality is attributed to the fact that the electrons are mobile in the plane of the 2DEG but are confined in the third dimension. In the quantized state, not only the screening edge of the 2DEG but also compressible puddles embedded in the bulk cause ac dissipation, as follows from the measured frequency dependence. Finally, characteristic parameters like the width of the screening edge, the threshold voltage, and the charging time of the compressible puddles are determined. .
For optimal safety a dive computer should be easy to use and the displayed information easy to understand. The present study examines the usability of dive computers and potential technologies to enhance safety. It should be noted that even if the ease of use of a dive computer is increased to an extent where it is intuitive to use, this does not release the diver from the recommendation to read the dive computer manual to safely dive with it. For the present work, 47 dive computer models by 14 manufacturers were purchased and the manuals of another three were studied. Function selection was noted for each model. Where selection required a combination of long and short pushes, or more than one button, it was considered necessary to read the instruction manual merely to modify settings in the dive computer. The mean number of buttons, switches or contacts per dive computer was 3.3 (SD 1.1, range 1–7). Twelve models (24%) did not have multiple functions per button, one model (2%) had a single multi-function and 36 models (72%) had multiple multi-functions per button. Accessing these functions required short or long push combinations. In 41 out of 50 (82%) of the dive computer models, the user interface was not intuitive. The majority of popular dive computers employ combinations of long and short pushes to access multiple functions, requiring training and mnemonic effort to operate the device. They are not intuitive, and scope exists to improve the usability and safety of dive computers. Possibilities are described including touch screens, a wheel to replace traditional buttons and near field communications (NFC).