A freeze-etch electron microscopic study of liquid propane jet-frozen human erythrocyte membranes

Freeze-etch electron micrographs of haemolysing erythrocytes and isolated erythrocyte membranes frozen using a liquid propane jet-freezer reveal fracture faces very different from those seen after conventional freezing by dipping the specimens into partly solidified Freon 22. Instead of the rather smooth extracellular fracture faces found after conventional specimen freezing, extracellular fracture faces exhibiting large amounts of fibre-like structures are seen after liquid propane jet-freezing of these specimens. No such structures were found in normal red blood cells. When isolated erythrocyte membranes are frozen under conditions favouring spectrin-actin release, freeze-etch micrographs reveal an apparent continuity between the fibrelike structures on the extracellular fracture face and the long fibre-like structures which extend from the protoplasmic surface of the erythrocyte membrane. These results suggest that liquid propane jet-freezing is capable of revealing a structural difference between the membrane of haemolysing and nonhaemolysed red blood cells, and that this difference is related to the fibrous, peripheral proteins of the membrane.     

Numerical collapse analysis of compression members

A brief survey of weld-induced stresses and deflections in steel-plated structures is given. A finite element approach for analyzing stiffened panels is presented. The stiffener formulation accounts for torsional buckling. Yielding is taken into account and, based on the updated Lagrangian formulation, the effect of large deflections is allowed for. By using the so-called volume approach the development of plastic zones can be followed. The non-linear equations are solved using a combined step-iterative procedure.The examples presented comprise an unstiffened rectangular plate under biaxial compression, and two stiffened panels under uniaxial compression. The effect of initial deflections and stresses is considered.     

Software Framework for Parameter Updating and Finite-Element Response Sensitivity Analysis

The finite-element software framework OpenSees is extended with parameter updating and response sensitivity capabilities to support client applications such as reliability, optimization, and system identification. Using software design patterns, member properties, applied loadings, and nodal coordinates can be identified and repeatedly updated in order to create customized finite-element model updating applications. Parameters are identified using a Chain of Responsibility software pattern, where objects in the finite-element model forward a parameterization request to component objects until the request is handled. All messages to identify and update parameters are passed through a Facade that decouples client applications from the finite-element domain of OpenSees. To support response sensitivity analysis, the Strategy design pattern facilitates multiple approaches to evaluate gradients of the structural response, whereas the Visitor pattern ensures that objects in the finite-element domain make the proper contributions to the equations that govern the response sensitivity. Examples demonstrate the software design and the steps taken by representative finite-element model updating and response sensitivity applications.     

Reliability-Based Optimal Design of Electrical Transmission Towers Using Multi-Objective Genetic Algorithms

Abstract:   A hybrid methodology for performing reliability-based structural optimization of three-dimensional trusses is presented. This hybrid methodology links the search and optimization capabilities of multi-objective genetic algorithms (MOGA) with structural performance information provided by finite element reliability analysis. To highlight the strengths of the proposed methodology, a practical example is presented that concerns optimizing the topology, geometry, and member sizes of electrical transmission towers. The weight and reliability index of a tower are defined as the two objectives used by MOGA to perform Pareto ranking of tower designs. The truss deformation and the member stresses are compared to threshold values to assess the reliability of each tower under wind loading. Importance sampling is used for the reliability analysis. Both the wind pressure and the wind direction are considered as random variables in the analysis. The research results presented demonstrate the benefit of implementing MOGA optimization as an integral part of a reliability-based optimization procedure for three-dimensional trusses.     

Integrated and decentralised protection and development of mountain landscapes

This article discusses how new trends for decentralised and integrated protection and local development of mountain landscapes have appeared in recent management practice, and how decentralised protection and management models could contribute to integrated and dynamic local development practice. Case studies performed on two larger protected areas and two regional parks based on local initiatives and agreements show that the two trends are quite visible in Norwegian mountain landscape management, but only to a certain extent. Our suggestions for promoting these trends are to consider: (1) revising the protected area regulations managed by the nature protection authorities to also include local development as a specific purpose; (2) transferring the protected area responsibility to the land use planning authorities; and (3) using regional parks as a framework for integrated and decentralised development within the existing restrictions and possibilities.     

Comparing the climate effect of emissions of short- and long-lived climate agents

Multi-gas climate agreements require a metric by which emissions of gases with different lifetimes and radiative properties can be placed on a common scale. The Kyoto Protocol to the United Nations Framework Convention on Climate Change uses the global warming potential (GWP) as such a metric. The GWP has attracted particular criticism as being inappropriate in the context of climate policy which seeks to restrict warming below a given target, because it gives equal weight to emissions irrespective of the target and the proximity to the target. The use of an alternative metric, the time-dependent global temperature change potential (GTP), is examined for its suitability and the prospects for it including very short-lived species. It retains the transparency and relative ease of use, which are attractive features of the GWP, but explicitly includes a dependence on the target of climate policy. The weighting of emissions using the GTP is found to be significantly dependent on the scenarios of future emissions and the sensitivity of the climate system. This may indicate that the use of any GTP-based weighting in future policymaking would necessitate regular revisions, as the global-mean temperature moves towards a specified target.     

Variation in the response to manipulation of post-mortem glycolysis in beef muscles by low-voltage electrical stimulation and conditioning temperature

The aim of this study was to investigate how manipulation of glycolytic rate by post-mortem processing conditions influences quality of aged beef of two bovine muscles of different physiological character, longissimus dorsi (LD) and adductor (AD). Post-mortem glycolysis was manipulated by low-voltage electrical stimulation (LV-ES) of half carcasses and by chilling rate of the muscles. Multivariate statistical analysis was used to visualise the data, while ANOVA was used to identify significant effects and interactions. As expected there was a significant effect of LV-ES on the pH decline in the first hours post-mortem in both muscles. Moreover, significant effects of LV-ES on WB shear force measured 2 and 8 days after slaughter were observed for LD at both chilling temperatures, while for AD no effect on WB shear force was observed. Furthermore, the results revealed a large individual variation in the response of LV-ES on both pH decline and WB shear force, and this variation did not always correlate for the two responses. Some animals showed no response of LV-ES on pH decline, but still had an improved WB shear force, and vice versa. The results from this study indicate that there probably are other mechanisms than accelerated pH decline and prevention of cold-shortening, by which LV-ES can affect meat tenderness.     

Accuracy of q-space related parameters in MRI: simulations and phantom measurements

The accuracy of q-space measurements was evaluated at a 3.0-T clinical magnetic resonance imaging (MRI) scanner, as compared with a 4.7-T nuclear magnetic resonance (NMR) spectrometer. Measurements were performed using a stimulated-echo pulse-sequence on n-decane as well as on polyethylene glycol (PEG) mixed with different concentrations of water, in order to obtain bi-exponential signal decay curves. The diffusion coefficients as well as the modelled diffusional kurtosis K(fit) were obtained from the signal decay curve, while the full-width at half-maximum (FWHM) and the diffusional kurtosis K were obtained from the displacement distribution. Simulations of restricted diffusion, under conditions similar to those obtainable with a clinical MRI scanner, were carried out assuming various degrees of violation of the short gradient pulse (SGP) condition and of the long diffusion time limit. The results indicated that an MRI system can not be used for quantification of structural sizes less than about 10 microm by means of FWHM since the parameter underestimates the confinements due to violation of the SGP condition. However, FWHM can still be used as an important contrast parameter. The obtained kurtosis values were lower than expected from theory and the results showed that care must be taken when interpreting a kurtosis estimate deviating from zero.     

Comparison of driving simulator performance with real driving after alcohol intake: A randomised,single blind,placebo-controlled,cross-over trial

The purpose of this study was to establish and validate a driving simulator method for assessing drug effects on driving. To achieve this, we used ethanol as a positive control, and examined whether ethanol affects driving performance in the simulator, and whether these effects are consistent with performance during real driving on a test track, also under the influence of ethanol. Twenty healthy male volunteers underwent a total of six driving trials of 1 h duration; three in an instrumented vehicle on a closed-circuit test track that closely resembled rural Norwegian road conditions, and three in the simulator with a driving scenario modelled after the test track. Test subjects were either sober or titrated to blood alcohol concentration (BAC) levels of 0.5 g/L and 0.9 g/L. The study was conducted in a randomised, cross-over, single-blind fashion, using placebo drinks and placebo pills as confounders. The primary outcome measure was standard deviation of lateral position (SDLP; “weaving”). Eighteen test subjects completed all six driving trials, and complete data were acquired from 18 subjects in the simulator and 10 subjects on the test track, respectively. There was a positive dose–response relationship between higher ethanol concentrations and increases in SDLP in both the simulator and on the test track (p < 0.001 for both). In the simulator, this dose–response was evident already after 15 min of driving. SDLP values were higher and showed a larger inter-individual variability in the simulator than on the test track. Most subjects displayed a similar relationship between BAC and SDLP in the simulator and on the test track; however, a few subjects showed striking dissimilarities, with very high SDLP values in the simulator. This may reflect the lack of perceived danger in the simulator, causing reckless driving in a few test subjects. Overall, the results suggest that SDLP in the driving simulator is a sensitive measure of ethanol impaired driving. The comparison with real driving implies relative external validity of the simulator.