Biometrical modelling in genetics: are complex traits too complex?

The field of traditional biometrical genetics uses mixed-effects models to quantify the influence of genetic and environmental factors on a biological trait, based essentially on estimating within-family trait correlations. Such analyses provide a useful preview of what may be discovered with the emerging full-scale genotyping strategies. However, biometrical analyses require unrealistically large sample sizes to obtain a reasonable precision, particularly for dichotomous traits. In addition, it may be very difficult to separate genetic and environmental effects because environmental correlations are poorly understood. We illustrate these and other difficulties using population-based cousins and nuclear family data for birth weight, collected from the Medical Birth Registry of Norway.     

Probabilistic capacity models and seismic fragility estimates for RC columns subject to corrosion

In this paper, probabilistic drift and shear force capacity models are developed for corroding reinforced concrete (RC) columns. The developments represent a merger between a probabilistic model for chloride-induced corrosion, a time-dependent corrosion rate, and previously developed probabilistic models for drift and shear force capacity of pristine (undamaged) RC columns. Fragility estimates are obtained for an example corroding column by applying the developed models at given shear and drift demands. Model uncertainties in both the capacity and corrosion models are considered in the fragility estimation, in addition to uncertainties in environmental conditions, material properties, and structural geometry. Sensitivity analyses of the corroding RC column are carried out to identify the parameters to which the reliability of the example column is most sensitive. The developed models consider different combinations of chloride exposure condition, environmental oxygen availability, water-to-cement ratios, and curing conditions. They are applicable to both existing and new RC columns and may be employed for the prediction of service-life and life-cycle cost analysis of RC structures.     

The quantum confined Stark effect in silicon nanocrystals

The quantum confined Stark effect (QCSE) in Si nanocrystals embedded in a SiO(2) matrix is demonstrated by photoluminescence (PL) spectroscopy at room and cryogenic temperatures. It is shown that the PL peak position shifts to higher wavelengths with increasing applied electric field, which is expected from carrier polarization within the quantum dots. It is observed that the effect is more pronounced at lower temperatures due to the improved carrier localization at the lowest energy states of the quantum dots. Experimental results are shown to be in good agreement with phenomenological model developed for the QCSE model.     

Water transport in ion exchange membranes

Water transport across ion exchange membranes has been studied experimentally. Water transference numbers were obtained from streaming potential measurements for cation and anion exchange membranes. At low salt concentration the water transference number reaches a limiting value which for the cation exchange membranes seems to be closely correlated with the cation—water friction in infinite dilute solutions.The observed water transference number for a given anion exchange membrane does not seem to be much dependent on the type of coion even at concentrations where the membrane is no longer perfectly permselective.     

Influence of the olfactory sense upon smolt transformation in salmonid fishes

The effect of olfactory deprivation on the process of smolt transformation in Atlantic salmon (Salmo salar L.) was investigated. Salmon parr were rendered anosmic by heat-cauterizing in November, and, together with controls, size, purine deposition (silvering), and mortality were monitored throughout spring in individuals within sibling groups. In May the fish were exposed to seawater (3.2% salinity) to determine levels of smoking in anosmic fish compared with control fish. Olfactory deprivation was found to induce a negative effect on survival in both anosmic fish as well as controls when reared within the same rearing tank. A 54% survival was metered in anosmic fish as opposed to only 26% survival in control fish during the experimental period. The low survival rates observed are suggested to result from abnormal behavior in anosmic fish due to lack of proper olfactory stimuli. Within each strain, the anosmic fish were found shorter and displayed less-silvering than their control fish at the end of the experimental period. Further, since control fish could withstand salinity exposure longer than anosmic fish, smolting is suggested to have been retarded among the anosmic fish. Olfactory influence on smolt transformation may be caused by conspecific pheromones secreted for the purpose of mediating effects of life-history patterns in salmonid fishes.     

Mixed-oxide (MOX) fuel performance benchmarks

Within the framework of the OECD/NEA Expert Group on Reactor-based Plutonium disposition (TFRPD), fuel modeling code benchmarks for MOX fuel were initiated. This paper summarizes the calculation results provided by the contributors for the first two fuel performance benchmark problems. A limited sensitivity study of the effect of the rod power uncertainty on code predictions of fuel centerline temperature and fuel pin pressure also was performed and is included in the paper.     

On the use of risk acceptance criteria in the offshore oil and gas industry

Risk acceptance criteria, as upper limits of acceptable risks, have been used for offshore activities on the Norwegian Continental Shelf for more than 20 years. The common thinking has been that risk analyses and assessments cannot be conducted in a meaningful way without the use of such criteria. The ALARP principle also applies, but the risk acceptance criteria have played a more active role in the assessment processes than seen for example in the UK. Recently there has, however, been a discussion about the suitability of risk acceptance criteria to assess and control risks. The purpose of this paper is to contribute to this discussion by presenting and discussing a risk analysis regime that is not based on the use of risk acceptance criteria at all. We believe that we can do better if cost-effectiveness (in a wide sense) is the ruling thinking rather than adoption of pre-defined risk acceptance limits. This means a closer resemblance with the ALARP principle as adopted in the UK and other countries, but is not a direct application of this practice. Also the building blocks of the common way of applying the ALARP principle are reviewed. The Norwegian offshore oil and gas industry is the starting point, but the discussion is to large extent general.     

Uncertainties in smart grids behavior and modeling: What are the risks and vulnerabilities? How to analyze them?

This paper looks into the future world of smart grids from a rather different perspective than usual: that of uncertainties and the related risks and vulnerabilities. An analysis of the foreseen constituents of smart grids and of the technological, operational, economical and policy-driven challenges is carried out to identify and characterize the related uncertainties and associated risks and vulnerabilities. The focus is on the challenges posed to the representation and treatment of uncertainties in the performance assessment of such systems, given their complexity and high-level of integration of novel technologies. A general framework of analysis is proposed.     

Higher order structure of short immunostimulatory oligonucleotides studied by atomic force microscopy

Immunostimulatory CpG-DNA activates the innate immune system by binding to Toll-like receptor 9. Structurally different CpG-containing oligonucleotides trigger a different type of immune response while activating the same receptor. We therefore investigated the higher order structure of two different classes of immunostimulatory CpG-DNA. Class A, which contains a partly self-complementary sequence and poly-G ends, forms duplexes and nanoparticles in salt solution, while class B, which does not contain these features and is purely linear, does not form a duplex or nanoparticles. Results obtained here by high-resolution atomic force microscopy of classes A and B CpG-DNA, reflect these differences in secondary structure. Detailed structural analysis of the atomic force microscopy topographs is presented for two different sample preparation methods.     

On risk assessment in the petroleum activities on the Norwegian and UK continental shelves

This article discusses some key principles and tools of safety management, with focus on risk analyses, risk interpretation, risk acceptance criteria and risk communication, as well as emergency preparedness. The starting point for the discussion is the experience from the activity on the Norwegian and UK continental shelves, and the implementation of new safety regulations in particular.