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The results from a new numerical method for simulating the strength and fracture locations of small glass specimens subjected to double ring bending are compared with experimental data. The method implements the weakest-link principle while assuming the existence of Griffith flaws. A Weibull distribution for the strength is simulated based on a single population of Pareto distributed crack sizes. The effect of using different fracture criteria is investigated. An alternative distribution is simulated based on two populations of flaws. This distribution models the apparent bimodality in the empirical data set. The numerical method is dependent on a representation of the surface flaws condition in glass. As new techniques become available for examining the surface characteristics, this numerical method is promising as a means for modelling the strength better than current methods do.

The main challenge in predicting structure-borne sound in wood buildings is to accurately model the vibration transmission between the source and the receiving room. Large variations in model parameters make it difficult to predict absolute vibration levels and to make conclusions regarding the relative effects of different designs. A step towards establishing reliable models is to investigate the possibilities and limitations of using deterministic methods, which requires correlations between simulations and measurements. In this paper, we present a multi-level model correlation approach for low-frequency vibration transmission in wood buildings. We apply the proposed approach to a scaled-size experimental structure representing a part of a two-storey wood building, and we evaluate the results for frequencies up to 100 Hz. We perform correlations between simulations and measurements four different levels: structural components (viz. beams and boards), planar structures (viz. floor, ceiling and walls), room structures and the complete structure. The results indicate that the dynamic behaviour of the experimental structure was to a great extent captured by the developed model. Based on the observations made in the multi-level correlations, we discuss important model parameters and propose modelling guidelines. We conclude that it is possible to employ deterministic methods in order to simulate the low-frequency vibration transmission in wood buildings provided that measurement data for calibration purposes are available. The developed numerical model can be used as a reference model for investigations on the effects of variations and uncertainties in the modelling.

Experimental data on the strength of new annealed float glass tested in an ambient environment was collected. A comparison was made between four standard distributions, the normal, lognormal, Gumbel and Weibull, with respect to the performance in modelling the strength. The Weibull distribution outperformed the normal and lognormal distributions when the data contained edge only failure origins. When the data was selected to contain surface only failure origins it is indicated that the extreme value distributions performed poorly. The Weibull model is known to have a basis in a failure-mechanism concept based on the weakest-link principle. The Gumbel distribution can also be derived from failure-based mechanics and be associated with certain types of flaw size distribution. The Weibull model, however, is a better choice for a failure model of glass edge strength compared to the normal and lognormal distributions and at least as good as a Gumbel distribution. The surface strength is complicated to model and none of the standard distributions which were examined are capable of producing a proper model. The sample size also has a profound impact on the performance of the surface strength models.

Dynamic substructuring is often employed to reduce the size of numerical models for structural dynamic analysis. In this paper, we discuss how elastomeric vibration isolators can be modelled within the framework of dynamic substructuring in order to obtain accurate and efficient reduced order models. For several reasons, it is beneficial to divide a structure containing elastomeric isolators into substructures at the interfaces between elastomers and surrounding parts of the structure. Therefore, we consider the elastomeric isolators as reduced coupling elements in the connections of substructure models. The coupling elements are established by reducing the number of degrees of freedom of 3D finite element models of elastomers. The main purpose of the studies presented in the paper is to evaluate the performance of different reduction method when applied to elastomer models. In addition, the effects of modelling features such as rotational coupling and frequency-dependent material properties of elastomeric isolators are investigated. A model of a wooden building structure with elastomeric isolators is used as an example case, considering steady-state dynamic analysis in the low-frequency range. The results and discussions presented in the paper provide guidance for reduced order modelling of elastomeric isolators in dynamic substructuring.

Population growth and urbanization results in densified cities, where new buildings are being built closer to existing vibration sources, and new transportation systems are constructed closer to existing buildings. Potential disturbing vibrations are one issue to consider in planning urban environments and densification of cities. Vibrations can be annoying for humans but also for sensitive equipment in, for example, hospitals. In determining the risk for disturbing vibrations, the distance between the source and the receiver, the ground properties, and type and size of the building are governing factors. In the paper, a study is presented aiming at investigating the influence of various parameters of the building’s structural design on vibration levels in the structure caused by ground surface loads, e.g. traffic. Parameters studied are related to the type of construction material (if it would be a light or heavy structure), and to the slab thickness. The study is limited to the structural response at frequencies near the first resonance frequency of the soil. The finite element method is employed for discretizing the building structure that is coupled to a semi-analytical model considering a layered ground.

To account for dynamic cross-coupling of structures via the soil, a computational model must be accurate enough to provide the correct overall behaviour of the scattered wave field. However, simplicity is also important when a model should be used for design purposes, especially in the early design stages and feasibility studies. The paper addresses the accuracy of simple models in which an array of structures is simplified into blocks placed on the ground surface or embedded within the soil. Comparisons are made between models that account or do not account, in a proper manner, for the inertia and embedment of the structures. Especially, the limitations of simplified models are discussed regarding their capability to quantify the insertion loss accurately. (Less)

Vibration disturbances in buildings may stem from ambient sources, such as motorway traffic, or from internal sources such as people walking inside the building. Vibrations can exceed requirements for sensitive equipment or cause annoyance to humans and therefore the vibrations may need to be reduced. Vibrations from both external and internal sources can be reduced by modifying the properties of concrete slabs and of the soil underneath. Soil can be improved by being mixed with a binder material in order to increase its stiffness. In this study, parametric finite element analyses were conducted on the achieved vibration reduction on a slab on soil from improving the properties of a concrete slab on soil or of the soil underneath. The size, elastic modulus, and depth of the stabilised soil were found to markedly affect the level of reduction obtained. The soil stabilisation at a vibration-sensitive facility was used as an example case, where the developed finite element model was calibrated to green-field measurements carried out on-site. Frequency spectra of both road traffic loads and internal pedestrian loads were considered in the model. The calibrated finite element model predicted reductions of almost 60% for the road traffic and 80% for the pedestrian load.

Reduction in traffic-induced ground vibrations by the use of barriers is investigated. The traffic load characteristics were measured for motorway traffic. The effects of parameters on various types of barriers were examined by the use of a finite element model that was calibrated to green-field measurements. The model involved a layered soil and bedrock. The depth of a trench and the elastic modulus of a solid back-fill material were found to be the most important parameters to consider. In investigation of the effects of infiltration of water into an open trench, a coupled finite element formulation of the water and the soil was applied. Infiltration of water was found to decrease the achieved reduction. At long distances from the vibration source, of around 500 m and longer, amplification in vibration level can be seen when a trench has been installed. It was also found, at long distances, that the motion of the ground surface follows the motion of the bedrock.

A method for form finding with dynamic relaxation and Non-Uniform Rational B-Splines (NURBS) based isogeometric membrane elements has been implemented and studied regarding the influence of the discretization and element shape on the form finding. The procedure allows for rapid form finding since NURBS describe the curved geometry well and it is shown that the form-finding can be performed using a coarse mesh. However, to minimize the bending strain energy a fine mesh is needed. Using smaller elements is more advantageous than increasing the degree of the basis functions, keeping the number of integration points few and converging at a lesser number of iterations. Using isogeometric analysis (IGA) simplifies further studies since the form-found shape can be exactly represented with a shell element formulation. The method is suitable to be used in computer aided design environments such as Rhinoceros 3D during design stages, where the form finding can be evaluated together with other studies in a design context.

In the paper, the effect of modeling strategies regarding the dynamic behavior of a railway slab track on a layered half-space is studied. The track is modeled with various degrees of accuracy through the use of either beam theory, shell finite elements or solid finite elements. The underlying soil response is included through a dynamic stiffness, obtained via the Green’s function for a horizontally layered visco-elastic half-space in the frequency–wavenumber domain. The effect of different assumptions regarding the track cross-section behavior and the track–soil interface conditions on the resulting free-field vibrations are studied for a harmonic load moving along the track. First, only the out-of-plane displacements of the slab–soil interface are coupled, i.e. only the vertical contact pressure is accounted for. Secondly, the effect of coupling the slab–soil in-plane displacements on the free-field vibrations is studied. It is found that the in-plane slab–soil coupling significantly affects the vertical vibration in the free-field. It is also found that a beam model of the track yields accurate response levels compared to a solid continuum model in the case of a thick slab, whereas considerable differences are obtained for a thin slab.

In the design of vibration-sensitive structures, large three-dimensional numerical models are frequently used, those occasionally being too large to be simulated in a practical manner. More specifically, the analyses of vibrating complex water-pipe systems require efficient model order reduction strategies. In the paper, a numerical procedure for model order reduction of a water-pipe system housed in a vibration-sensitive research facility is presented. The finite element model employed includes a water-pipe system where fluid–structure interaction effects are accounted for. The reduced model is developed using component mode synthesis and a reduction of the interface degrees of freedom, enabling time-efficient dynamic analyses. The model was proven to be time-efficient and to generate output of high accuracy.

Determining the dynamic behaviour of lightweight buildings by means of finite element analyses requires models representing the geometry involved in great detail, resulting in systems having many millions of degrees of freedom. It is, therefore, important to avoid unnecessarily detailed models by carefully considering what is essential to include in the models and the level of details required for describing the phenomena of interest accurately. In the study presented here, it was investigated whether or not air and insulation in cavities of multi-storey wood buildings affect the transmission of low-frequency structural vibrations. It was concluded, by means of numerical studies, that including air and insulation in cavities, modelled as acoustic media, affects the transmission from a floor to the underlying ceiling and surrounding walls. (C) 2014 Elsevier Ltd. All rights reserved. (Less)

A reduced finite element model for determining the maximum principal stress of a glass pane subjected to dynamic impact load is developed and compared to a full dynamic finite element model. The reduced model is based on the Rayleigh-Ritz method. The Ritz vectors used are determined by simple static load-cases. The model is applicable to centrically and eccentrically applied impact and to glass of various support conditions. It is demonstrated that the model performs well for various types of supported glass panes and impact applied at different locations on the glass pane. The applicability to small or medium sized glass panes is shown through a parametric investigation in which the results are compared to linear and nonlinear finite element solutions. For large glass panes, especially at smaller glass thickness, geometric nonlinear effects must be considered in the analysis. An outline of how to expand the model to include nonlinear geometric effects is given. Finally, it is shown that the reduced model performs excellently in the modeling of a standard laminated glass balustrade with clamp fixings. Apparently, the model is very well suited for strength design of commonly used glass structures.

Reduction in traffic-induced ground vibrations by the use of shaped landscapes is investigated here by shaping the landscape surrounding a high-tech facility, using the landscape thus produced as a wave obstacle. The effects of the geometric parameters of a shaped landscape were examined in parametric studies. An architectural landscape design was also investigated in terms of its effectiveness in reducing traffic-induced ground vibrations. Finite element models, analysed in the frequency domain, were employed. The models involve a layer of soil and the underlying bedrock. It was found that anywhere from an appreciable reduction to an appreciable amplification of the vibrations produced can occur, depending upon the geometric parameters of the shaped landscape involved. The most effective shape was found for a topography that acted as a waveguide that reduced the level of vibration by approximately 35%.

An existing, recently developed solid-shell finite element is proposed for efficient and accurate modeling of laminated glass structures. The element is applied to one test example treating a thin laminated glass structure subjected to biaxial bending and the performance concerning accuracy and efficiency is compared with standard three-dimensional solid elements. Further examples illustrate how the element could be applied in the modeling of laminated glass structures with bolted and adhesive joints. For these examples, experimental data for relevant quantities are provided as a comparison. It is concluded that the element is an excellent candidate for the modeling of laminated glass.

Many cities experience an increasing population leading to a need for urban densification. In these cities, unused land close to railways will have to be developed with new residential and office buildings. The infrastructural demand will also increase, resulting in heavily trafficked roads and railways close to where people work and live. Annoyance from traffic-induced vibrations and noise is expected to be a growing issue. To predict the level of vibration and noise in buildings caused by railway and road traffic, calculation models are needed.In the present paper, a simplified prediction model is briefly described. This prediction model is based on the assumption that the ground and railway embankment can be described in an axisymmetric model, to provide the transfer functions between the track and the free-field. In the paper, the error that arise by assuming axisymmetric response is studied by comparing the response in a three-dimensional finite-element model. Transfer functions at several positions in the free-field are compared.

in Undetermined general method for determining stress concentration factors for laminated glass balustrades with two plus two bolt fixings with variable positions is developed. It is demonstrated how the stress concentration factors can be presented graphically in design charts and representative charts are displayed for the case of a more specific bolt-fixed balustrade type. In general, the use of simple formulas and design charts allows the maximum principal stresses of the balustrade to be determined for any relevant combination of variable geometry parameters involved.

Construction of high speed railway lines has been an increasing trend in recent years. Countries like Denmark and Sweden plan to expand and upgrade their railways to accommodate high-speed traffic. To benefit from the full potential of the reduced commuting times, these lines must pass through densely populated urban areas with the collateral effect of increased noise and vibrations levels. This paper aims to quantify the vibrations levels in the area surrounding an elevated railway line built as a multi-span bridge structure. The proposed model employs finite-element analysis to model the bridge structure, including a multi-degree-of-freedom vehicle model and accounting for the track unevenness via a nonlinear contact model. The foundations are implemented as rigid footings resting on the ground surface, while the soil is modelled utilizing Green’s function for a horizontally layered half-space. The paper analyses the effects of structure-soil-structure interaction on the dynamic behaviour of the surrounding soil surface. The effects of different soil stratification and material properties as well as different train speeds are assessed. Finally, the drawbacks of simplifying the numerical model, in order to reduce the complexity of the calculations, are determined.

Vibration of machinery and construction work are major sources of noise and vibration pollution in the urban environment. The frequencies dominating the vibration, and the distances over which it spreads via the ground, depend on the source. However, soil stratification and foundation type have a significant influence. Thus, in order to achieve fair accuracy in the prediction of ground vibration caused by sources vibrating on a foundation, accurate models of the ground and foundation may be required. However, for assessment of vibration in the design phase, simple models may be preferred. The paper provides a parameter study regarding the influence of soil stratification and foundation type on the ground vibration at different distances away from the source. Especially, vibration levels caused by sources placed on surface footings and piles are compared, employing a three-dimensional numerical model. Piles of different length are included in order to analyze the differences that can be expected regarding shaft-bearing and end-bearing piles. The paper provides insight into the significance of modelling the correct foundation structure and soil stratification and discusses the differences related to vibration near a source and at longer distances away from the source. Based on this, guidelines for model simplifications are given.

Lightweight buildings are sensitive to low-frequency vibrations, making it difficult to construct them in such a way that noise and disturbing vibrations are kept at an acceptable level. In the design of vibration reduction measures, it is desirable to have computational models for predicting the effects of structural modifications. Validations of the models to experimental data have to be performed to ensure reliable predictions. The experimental studies are simplified if full-scale models can be scaled down in size. In the paper, methods for designing scaled experimental models of building structures are discussed. An example, the scaling of a wooden building structure, is presented.

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) conducted in real time is a powerful tool for measuring messenger RNA (mRNA) levels in biological samples. Multiplex PCR is defined as the simultaneous amplification of two or more DNA (cDNA) targets in a single reaction vessel and may be carried out only using uniquely labeled probes for each target. Up to four genes can be detected in a multiplex 5' nuclease assay when using the appropriate instrument and the right combination of fluorophores. One of the more important advantages of multiplexing is a reduced sample requirement, which is especially important when sample material is scarce. Additional benefits are saving time on reaction setup and lower cost compared to singleplex reactions. Although multiplexing has several advantages over singleplex qRT-PCR, limited work has been done to show its feasibility. Few publications on four-color multiplex qRT-PCR have been reported, and to our knowledge no work has been done to explore the assay's limitations. In this paper, we report the first in-depth analysis of a four-gene multiplex qRT-PCR. To achieve a better understanding of the potential limitations of the qRT-PCR assay, we used in vitro transcribed RNA derived from four human genes. To emulate gene expression experiments, we developed a model system in which the in vitro transcripts were spiked with plant total RNA. This model allowed us to develop an artificial system closely resembling differential gene expression levels varying up to a million fold. We identified a single "universal" reaction condition that enabled optimal amplification in real time of up to four genes over a wide range of template concentrations. This study shows that multiplexing is a feasible approach applicable to most qRT-PCR assays performed with total RNA, independent of the expression levels of the genes under scrutiny.

In order to reduce the vibration transmission in multi-storey wood buildings, it is common to insert viscoelastic elastomer materials between parts of the buildings. The studies presented here investigate to which extent different design choices for the elastomer layers affect the isolation of low-frequency vibrations (0–100 Hz). A finite element model of two storeys of a multi-storey wood building, involving blocks of elastomer material in between the storeys, was used to perform numerical investigations. Parametric studies were carried out, considering different properties of the elastomer material and different placements of the elastomer blocks. Considering the transmission from the floor of the upper storey to the underlying ceiling, the material properties of the elastomer material were found to affect the vibration levels appreciably. A too stiff elastomer material can result in an amplification of the vibration levels in the ceiling for certain frequencies, whilst a less stiff material, in general, reduces the vibration transmission. The placement of the elastomer blocks was varied by shifting the position of the blocks while maintaining their centre-to-centre distance, resulting in a small effect on the vibration levels.

in Undetermined This paper presents a numerical study on the reduction of vibrations in the ground. The influence of landscape shaping to reduce vibration levels induced by traffic is investi-gated by means of the finite element method with dynamic analyses. Both two-dimensional as well as three-dimensional finite element models are employed for the investigations. A har-monic point force is applied where the force is scaled to represent the frequency dependent traffic load. Finally, the vibration reduction effect is evaluated by comparing RMS-values at a number of different evaluation points. It is concluded from the analyses that the two-dimensional and three-dimensional models correlates fairly well. The performance of a hill is increased if it is preceded by a valley but when applying more valleys than hills, amplification may occur. When using continuous hills instead of a checkered pattern, the hills seem to cap-ture and guide waves in the direction of the hill. Locally this could reduce vibrations of sig-nificant importance. Applying the constraints given within the numerical example, vibration reductions of approximately 20 % could be seen. (Less)

The mechanical behaviour of wood was studied from a micro up to a macro level. Wood is a cellular material possessing a high degree of anisotropy. Like other cellular solids, it often exhibits a highly nonlinear stress–strain behaviour. In the present study the mechanical properties of the cellular structure of wood are characterized and modelled, the irregular cell shape, the anisotropic layered structure of the cell walls and the periodic variations in density being taken into account. The continuum properties were derived by use of a homogenization procedure and the finite element method. Stiffness and shrinkage properties determined by this procedure are presented and are compared with measured data. The constitutive properties thus determined at various structural levels can be used in numerical simulations of the behaviour of wood in different industrially related areas. One such area is that of the refining process in mechanical pulp manufacture. Simulations of the deformation and fracturing of wood specimens loaded under conditions similar to those found in the refining process are presented. The numerical and experimental results obtained are compared.

All attempts to identify ornithine decarboxylase in the human pathogen Trypanosoma cruzi have failed. The parasites have instead been assumed to depend on putrescine uptake and S-adenosylmethionine decarboxylase (AdoMetDC) for their synthesis of the polyamines spermidine and spermine. We have now identified the gene encoding AdoMetDC in T. cruzi by PCR cloning, with degenerate primers corresponding to conserved amino acid sequences in AdoMetDC proteins of other trypanosomatids. The amplified DNA fragment was used as a probe to isolate the complete AdoMetDC gene from a T. cruzi genomic library. The AdoMetDC gene was located on chromosomes with a size of approx. 1.4 Mbp, and contained a coding region of 1110 bp, specifying a sequence of 370 amino acid residues. The protein showed a sequence identity of only 25% with human AdoMetDC, the major differences being additional amino acids present in the terminal regions of the T. cruzi enzyme. As expected, a higher sequence identity (68–72%) was found in comparison with trypanosomatid AdoMetDCs. When the coding region was expressed in Escherichia coli, the recombinant protein underwent autocatalytic cleavage, generating a 33–34 kDa α subunit and a 9 kDa β subunit. The encoded protein catalysed the decarboxylation of AdoMet (Km 0.21 mM) and was stimulated by putrescine but inhibited by the polyamines, weakly by spermidine and strongly by spermine. Methylglyoxal-bis(guanylhydrazone) (MGBG), a potent inhibitor of human AdoMetDC, was a poor inhibitor of the T. cruzi enzyme. This differential sensitivity to MGBG suggests that the two enzymes are sufficiently different to warrant the search for compounds that might interfere with the progression of Chagas' disease by selectively inhibiting T. cruzi AdoMetDC. The nucleotide sequence data reported will appear in DDBJ, EMBL and GenBank Nucleotide Sequence Databases under the accession number (BankIt151525) AF032907.

In the present study, different model order reduction methods were compared in terms of their effects on the dynamic characteristics of individual building components. A wide variety of methods were employed in two numerical examples, both being models of wooden floor structures, in order to draw conclusions regarding their relative efficiency when applied to models of such structures. It was observed that a comparison of the methods requires the reduced models to be exposed to realistic boundary conditions, free–free eigenvalue analyses being insufficient for evaluating the accuracy of the reduced models when employed in an assembly of substructures.

Transmitted vibrations from water-pipe systems, involving supports standing on a concrete slab and the underlying ground, are investigated here. The effects of varying parameters of the supports, such as location, their elastic modulus and their cross-section, on the level of vibrations transmitted by the water-pipe system are analysed in order to minimise vibrations transmitted to sensitive parts in a facility. A finite element model involving use of both finite and infinite elements was employed for analyses in the frequency domain where account was taken of both fluid-structure interaction and soil-structure interaction. It was concluded from the analyses performed that the parameters of the supports had an appreciable effect on the vibration level in the facility.

Accurately modelling the dynamic behaviour of multi-storey buildings in wood requires the geometry involved to be represented in great detail, resulting in systems having many millions of degrees of freedom. Consequently, there is a need for model order reduction and the methodology of substructure modelling is employed here to create reduced models for analysis of low-frequency vibrations. The full finite element model of a building is divided into substructures which are reduced in size before being assembled to form the global model. The efficiency of the reduced models is strongly dependent on the number of degrees of freedom at the interface surfaces of the substructures, why it may be necessary to perform interface reduction of some sort. Multi-storey buildings in wood are often constructed with elastomer layers separating the structural components, these offering a natural choice of dividing the buildings into substructures. In this paper, the methodology of introducing a condensation node is adopted for employing interface reduction at the interfaces between the elastomer layers and the structural components in wood. Different methods of coupling the condensation node to the interface surfaces were compared in a test model consisting of a floor–ceiling structure in wood, where the floor and the ceiling are separated by elastomer blocks. It was concluded that a rigid coupling is the most appropriate choice for the interface surfaces of the elastomer blocks, while a distributed coupling provides the most accurate results for the interface surfaces of the floor and the ceiling.

The degradation of ornithine decarboxylase (ODC) is mediated by antizyme, a protein regulated by the end-products of ODC activity, the polyamines. High levels of polyamines induce a +1 ribosomal frameshift in the translation of the rat antizyme message leading to the expression of a full-length protein. We have studied whether the regulation of antizyme expression occurs only at the level of translation or whether polyamine levels also affect the transcription of the antizyme gene. Thus, we have cloned and sequenced the mouse homologues of the rat ODC-antizyme gene and cDNA. Northern blot analysis shows that although high concentrations of polyamines do not affect the steady-state levels of antizyme message in L1210 leukemia cells, polyamine depletion using 2-(difluoromethyl)ornithine [Orn(F2Me)] leads to a marked decrease in mRNA levels. Results of transient transfections of luciferase-reporter-gene constructs driven by antizyme promoter fragments in untreated and Orn(F2Me)-treated Balb/C 3T3 cells indicate that the transcription of the antizyme gene is altered upon polyamine depletion. The amount of antizyme protein on Western blots was also altered by polyamine depletion and addition, and the polysomal distribution of antizyme message suggests a general translational increase of the message when polyamine concentrations are high. These results indicate a role for polyamines in the transcriptional and translational regulation of ornithine decarboxylase antizyme.

Normally, in pulp wood chipping, the chips desired are thinner and have less fiber damage than those currently being produced. However, experiments to develop chippers are rather laborious, so there is a need for a mathematical model to complement the experiments. A two-dimensional finite element model was developed in order to be able to predict chip thickness and chip damage, the model incorporated a fictitious crack model and elasto-plastic material properties. The sensitivity of the model to changes in material data was controlled, and the results of the calculations were compared to experimental observations reported in the literature. Finally, the influences of the geometry of the cutting knife and of the friction between knife and wood were calculated. The general impression of the modelled chip formation was that the results of the finite element model were in reasonable agreement with experimental observations and that the model yields qualitative results that are trustworthy. The calculations indicate that there is a strong interaction - which greatly influences chip formation - between the knife angle and the coefficient of friction between the knife and the wood. The results suggest that a chipper knife should have a small knife angle complemented with a bevel, and should have a small coefficient of friction to wood.

A genomic clone for a mouse S-adenosylmethionine decarboxylase (AdoMetDC) gene was isolated from a cosmid library. Surprisingly, the gene proved to be intronless. With the exception of three base substitutions (changing 2 amino acids in the deduced protein), the 1002-nucleotide sequence of the open reading frame was identical to that of mouse AdoMetDC cDNA. Moreover, the gene contained a poly(dA) tract at the 3' end and was flanked by 13-base pair direct repeats. Our findings suggest that this gene has arisen by retroposition, in which a fully processed AdoMetDC mRNA has been reverse transcribed into a DNA copy and inserted into the genome. By polymerase chain reaction, we positively identified the intronless gene in the mouse genome, and, by primer extension analysis, we proved the gene to be functional. Thus, its transcripts were found in many cell lines and tissues of the mouse and were particularly abundant in the liver. When the open reading frame of the intronless gene was expressed in Escherichia coli HT551, a strain with no AdoMetDC activity, it was found to encode a 38-kDa protein, corresponding to AdoMetDC proenzyme. Although the change of methionine 70 to isoleucine was close to the cleavage site at serine 68, this protein underwent proenzyme processing, generating a 31-kDa alpha subunit and an 8-kDa beta subunit. Importantly, the protein encoded by the intronless gene was functional, i.e. it catalyzed the decarboxylation of S-adenosylmethionine, and its specific activity was comparable with that of recombinant human AdoMetDC purified according to the same procedure.

In multi-storey buildings, the use of lightweight material has many advantages. The low weight, the low energy consumption and the sustainability of the material are some attractive benefits from using lightweight materials. Compared with heavier structures i.e. concrete the challenge in constructing a building compliant with building codes vis-a-vis the propagation of sound and vibrations within the structure is a challenge. Focusing on junctions in a multi-storey lightweight buildings, a modular finite element model is developed to be used for analyses of vibration transmission in lightweight buildings subjected to different types of loads.

Noise is a nuisance in the built environment, and to avoid undesirable transmission of sound and vibration within a building, its vibro-acoustic performance must be addressed in the design phase. For heavy structures, a reliable assessment of the sound pressure levels can be made by statistical energy analysis—especially at high frequencies. However, for lightweight buildings a numerical approach, e.g. the finite-element method, must be applied. A problem in this regard is the computational complexity. Even at low frequencies, many degrees of freedom are required in a model accounting for all possible paths for transmission of sound in a building—in particular when finite elements are employed for the air. This paper examines whether a rigorous model of the acoustic field in each room is necessary in order to obtain accurate estimates of the sound pressure, or if a simpler approach may be adopted. Five different cases are compared: A model that only includes the structure, a model with semi-infinite elements to account for radiation from the structure into the air, a model introducing finite elements for the acoustic field, a model with dissipation of sound inside the room, and finally a model with sound absorption on the surfaces of walls, floors and ceilings.

Migration of bovine neutrophils towards endotoxin, recombinant bovine interleukin-1 beta (rBoIL-1 beta), recombinant human tumor necrosis factor-alpha (rhTNF-alpha), platelet-activating factor (PAF), complement factor C5a, leukotriene B4 (LTB4), and recombinant human interleukin-8 (rhIL-8) was studied in vivo, using the teat cistern model, and in vitro using the modified Boyden chamber method. Infusion of endotoxin, rBoIL-1 beta, rhTNF-alpha, PAF, or C5a into the teat cistern induced significant accumulation of leukocytes, mainly neutrophils, during the sampling period. Endotoxin was, on a molar basis, the most potent inducer of cell accumulation in vivo, followed by rBoIL-1 beta, while C5a, PAF and rhTNF-alpha were less potent. No significant cell accumulation was observed after infusion of LTB4 or rhIL-8. A significant migration of cells into the teat cistern was first observed 2 h after the infusion of endotoxin or rBoIL-1 beta, the rBoIL-1 beta-induced response started somewhat earlier. The first significant cell accumulation after infusion of PAF or C5a was observed already 1.5 h post infusion. The largest numbers of cells were reached 2.5-4.5 h after the infusion of endotoxin, rBoIL-1 beta, rhTNF-alpha, PAF or C5a. In vitro, significant migration of bovine blood neutrophils was observed towards C5a or rhIL-8, and to a lower extent towards LTB4, while no chemotactic response to endotoxin, rBoIL-1 beta, rhTNF-alpha, and PAF was observed. Possible roles of the different substances as inducers of neutrophil migration into the bovine teat are discussed.

This chapter focuses on moisture-induced deformations in three-layered cross-laminated timber with a symmetrical build-up, where the fibre direction of the middle layer is oriented perpendicular to that of the outer layers. Dimensional stability, i.e. the ability to resist warping, is of main interest for the application of such wood panels. The cross lamination of the layers is advantageous to warping. The moisture-induced expansion/contraction of each single layer is partly restrained by the adjacent layers. The free swelling and shrinkage of adjacent layers differ approximately by a factor of 10 (radial/longitudinal) to 20 (tangential/longitudinal). As a consequence of this difference, stresses and even cracks may occur. In large-scale panels warping was observed. This reduces the serviceability in the practice. Due to a climate gradient considerable distortions (warp) in the form of cup and twist may occur. Models to calculate the moisture and stress fields are provided and validated to experimental tests.

Holzforschung, 63 (3), ISSN:0018-3830, ISSN:1437-434X

A fracture mechanics model for analysis of crack initiation and propagation in wood is defined and applied. The model has the advantage of being simple, yet it enables reasonably general and accurate analysis commonly associated with more complex models. The present applied calculations are made by means of the finite element method and relate to progressive cleavage fracture along grain. The calculations concern a tapered double cantilever beam specimen and an end-notched beam. Comparisons are made of experimental test results. The fracture properties of the wood are modelled by means of a very thin linear elastic layer located along the crack propagation path. The properties of the layer are such that the strength and fracture energy of the wood are represented correctly. This makes a single linear elastic calculation sufficient for strength prediction. Both crack development and pre-existing cracks can be analyzed. Both material strength and fracture energy and stiffness are taken into account, their relative influence on structural strength being different for different elements. The fracture layer is in the finite element context represented by joint elements. Propagation of a crack can be analyzed either by a series of elastic calculations corresponding to different crack lengths or by use of a finite element code for non-linear analysis. The computational results include sensitivity analysis with respect to the influence of the various material parameters on structural strength.

Flight feather moult in small passerines is realized in several ways. Some species moult once after breeding or once on their wintering grounds; others even moult twice. The adaptive significance of this diversity is still largely unknown. We compared the resistance to mechanical fatigue of flight feathers from the chiffchaffPhylloscopus collybita, a migratory species moulting once on its breeding grounds, with feathers from the willow warblerPhylloscopus trochilus, a migratory species moulting in both its breeding and wintering grounds. We found that flight feathers of willow warblers, which have a shaft with a comparatively large diameter, become fatigued much faster than feathers of chiffchaffs under an artificial cyclic bending regime. We propose that willow warblers may strengthen their flight feathers by increasing the diameter of the shaft, which may lead to a more rapid accumulation of damage in willow warblers than in chiffchaffs.

S-Adenosylmethionine decarboxylase (AdoMetDC) is a key enzyme in the biosynthesis of polyamines. We have previously identified a mouse AdoMetDC gene that exhibits the hallmarks of a retroposon; that is, it has no introns, is flanked by direct repeats, and has a poly(dA) tract at its 3′-end. This gene, termed Amd-2, is not a processed pseudogene; rather, it is transcribed in a variety of mouse tissues and encodes a functional enzyme. In the current report, we present the sequence of a 6.7-kb genomic segment of the Amd-2 locus. Several sequences of interest, including an intercisternal A particle (IAP) element, a transposon-related sequence, and several expressed sequence tags (ESTs), were found within or near Amd-2. We also show, through analysis of an interspecific backcross, that Amd-2 is located on Chr 12, tightly linked to the gene (Odc) that encodes ornithine decarboxylase, another key enzyme in polyamine synthesis. Finally, we show that Amd-2 is present among several divergent species of the genus Mus. Thus, the integration event that generated Amd-2 may have occurred early during Mus evolution.

The inflammatory response, as measured by the accumulation of leukocytes and ovine serum albumin, induced by interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), interleukin-beta (IL-8), and granulocyte-macrophage colony stimulating factor (GM-CSF) was studied in lactating ovine udders, and in test cisterns of dry ewes after surgical closure of the passage between the teat and udder cisterns. In the lactating udders, IL-1 beta and TNF-alpha, but not IL-8 and GM-CSF, induced significant accumulation of cells. In the teat cisterns, all four cytokines IL-1 beta, TNF-alpha, IL-8, and GM-CSF induced significant cell accumulation. IL-1 beta was the most potent cytokine. A slight increase in serum albumin, paralleling the changes in leukocyte numbers, was observed after infusion of IL-1 beta and, to some extent, TNF-alpha. The cell accumulation induced by IL-1 beta or TNF-alpha was dose and time dependent in lactating udders, and time-dependent in teat cisterns. The cell numbers were considerably higher in lactating udders than in teat cisterns after infusion with IL-1 beta. The first influx of cells was observed earlier, and the cell numbers peaked earlier in the teat cisterns than in the lactating udders. IL-8 and GM-CSF induced dose and time dependent cell accumulation in teat cisterns only. The differences between lactating udders and teat cisterns may be attributable to the differences in tissue area involved and the number of receptors available, or to dilution of cytokines in milk, or to presence of inhibitory factors. Differences between cytokines in their inflammatory effects may be explained by their modes of action. IL-1 beta and TNF-alpha have a wide range of cellular functions enabling them to induce a more prominent response than IL-8 and GM-CSF. Furthermore, receptors for IL-1 beta and TNF-alpha are present on a larger number of cell types. Finally, the results indicated that the teat cisterns, being the port of entry for udder infections, as well as the lactating udders are capable of a diversified inflammatory response which is important in the defence against udder infections.

Urban densification is a way of accommodating population growth. Land adjacent to railways is used for constructing residences and other buildings, and new tramway systems are planned. Under these circumstances, nearby buildings will be exposed to vibrations and noise that may become a nuisance for the residents. It is necessary, even at an early stage of planning, to assess the extent of the vibrations and state requirements for the building in order to avoid costly changes at later stages. Ground vibration induced by railway traffic is studied in the paper. The aim is to develop a strategy for predicting vibrations in nearby buildings in an early stage of the building process. The strategy is based on that there is a fairly good knowledge of the properties of the ground and that some on-site vibration measurements are made. By combining these with finite-element analysis, the vibration level in typical buildings can be predicted. Design of building foundations and structural design can then be addressed. Field vibration measurements along railway tracks as well as at built-up areas have been carried out. Conclusions from the measurements and numerical simulation s are discussed to establish a strategy for predicting railway-induced vibrations.

To predict ground-borne vibration levels caused by railway traffic, models for estimating the load from the vibration source, as well as the vibration transmission through the ground, are needed. In the present paper, a finite element formulation in a frame of reference following the moving load, is used for modeling a railway slab track. The response of the underlying soil is represented through a dynamic stiffness matrix, obtained via the Green’s function for a horizontally layered visco-elastic half-space in a moving frame of reference in the frequency–wavenumber domain. The track can be modeled as continuously connected beams, but the use of plate elements allows for more general stress and displacement distributions in the transverse direction of the slab to be resolved. Here, the free-field response due to a harmonic load moving along a slab track, is evaluated and compared using different modeling strategies for the slab. (Less)