A frost decay exposure index for porous,mineral building materials

The disintegrative process of freezing and thawing of porous, mineral materials represents a significant challenge in the design and construction of building enclosures. In this paper, we present a simple method for assessing the relative potential of a climate to accelerate frost decay based on multi-year records of daily air temperatures and rainfall, with special emphasis on masonry. Distributions of 4-day rainfall prior to days with freezing events provide quantitative information on the geographically dependant frost decay risk in porous, mineral building materials in a given climate. Data from 168 weather stations in Norway are analysed, using weather data from the reference 30-year period 1961–1990.     

Integrated tool for risk assessment in agricultural management of soil erosion and losses of phosphorus and nitrogen

In recent years, increased attention has been focused on models for risk assessment of source areas in agricultural landscapes. Among the simplest of such models are index tools, which have been developed particularly for phosphorus (P) and to some extent nitrogen (N). However, only a few studies have considered the development of an integrated management strategy that includes erosion and losses of both P and N. Accordingly, the major objective of this study was to initiate the development of an integrated risk assessment tool, consisting of indices for erosion, P and N. The strategy used to create the integrated tool was based on the assumption that all input data at field scale should be readily available either from ordinary agricultural statistics or from the farmer. The results from using the indices in a pilot case study catchment illustrated that losses of P and N had often different critical source areas. The P index was highest for fields with manure application and/or high soil P status or with autumn ploughing, and the N index was highest for fields with excessive N application. The integrated risk was greatest for areas with manure application and some areas with a high erosion risk in combination with high nutrient application rate. Additionally, four different management options were assessed: (1) reduced fertilisation, (2) catch crops, (3) autumn ploughing, and (4) no autumn ploughing. The results verified that reduced nutrient application and stubble during autumn and winter led to the largest decrease in index values, and it was also apparent that management changes in high-risk areas had the greatest impact on the indices. Overall, our findings indicate that the present integrated risk assessment tool with readily available input data can be used to rank farm fields according to risk of soil erosion and losses of P and N.     

Uncertainty in hydroelectric power supply

This paper discusses the dimensioning and capacity utilization of a hydroelectric power system when uncertainty in supply and demand is taken explicity into consideration. It is shown how the optimal sales of firm power depend on properties of the long-term and short-term demand curves. A long-run marginal cost criterion is derived, which shows that the long-run marginal cost should be equal to the expected price in the short-term market. Uncertainties in supply as well as demand will, under reasonable assumptions, reinforce each other with respect to their implications for the excess capacity in the hydro power system.     

On the distance of stabilizer quantum codes from <Emphasis Type="Italic">J</Emphasis>-affine variety codes

Self-orthogonal J-affine variety codes have been successfully used to obtain quantum stabilizer codes with excellent parameters. In a previous paper we gave formulae for the dimension of this family of quantum codes, but no bound for the minimum distance was given. In this work, we show how to derive quantum stabilizer codes with designed minimum distance from J-affine variety codes and their subfield-subcodes. Moreover, this allows us to obtain new quantum codes, some of them either with better parameters, or with larger distances than the previously known codes.     

Experiments on bioassay sensitivity in the study of allelopathy

The purpose of these experiments was to study the effects of various experimental procedures and conditions on bioassay sensitivity in allelopathic studies. The following factors were considered: bioassay methods, choice of test species, the effect of osmotic potential on germination and growth of the test species, growth in dark or in light and the effect of concentrating the extracts in vacuo. Extracts from rape and rye were used in the studies to act as allelopathic agents. Ryegrass appeared as the most sensitive test species when grown horizontally on quartz sand, while radish was the most sensitive test species when grown on filter paper in transparent boxes at a 45° angle. Root length was the most sensitive growth variable measured. Percent germination appeared a more sensitive measure than the speed of germination index, S, when germinated seeds were counted after one and two days for radish and ryegrass, respectively. A rise in the osmotic potential affected germination more than root length, and radish appeared more sensitive to a rise in osmotic potential than ryegrass. A confounding of germination and root length inhibition may therefore, give misleading results.     

Biological Properties of Iron Oxide Nanoparticles for Cellular and Molecular Magnetic Resonance Imaging

Superparamagnetic iron-oxide particles (SPIO) are used in different ways as contrast agents for magnetic resonance imaging (MRI): Particles with high nonspecific uptake are required for unspecific labeling of phagocytic cells whereas those that target specific molecules need to have very low unspecific cellular uptake. We compared iron-oxide particles with different core materials (magnetite, maghemite), different coatings (none, dextran, carboxydextran, polystyrene) and different hydrodynamic diameters (20–850 nm) for internalization kinetics, release of internalized particles, toxicity, localization of particles and ability to generate contrast in MRI. Particle uptake was investigated with U118 glioma cells und human umbilical vein endothelial cells (HUVEC), which exhibit different phagocytic properties. In both cell types, the contrast agents Resovist, B102, non-coated Fe₃O₄ particles and microspheres were better internalized than dextran-coated Nanomag particles. SPIO uptake into the cells increased with particle/iron concentrations. Maximum intracellular accumulation of iron particles was observed between 24 h to 36 h of exposure. Most particles were retained in the cells for at least two weeks, were deeply internalized, and only few remained adsorbed at the cell surface. Internalized particles clustered in the cytosol of the cells. Furthermore, all particles showed a low toxicity. By MRI, monolayers consisting of 5000 Resovist-labeled cells could easily be visualized. Thus, for unspecific cell labeling, Resovist and microspheres show the highest potential, whereas Nanomag particles are promising contrast agents for target-specific labeling.     

Positional specificity of gastric hydrolysis of long-chain n−3 polyunsaturated fatty acids of seal milk triglycerides

Long-chain n−3 polyunsaturated fatty acids (n−3 PUFA) of marine oils are important dietary components for both infants and adults, and are incorporated into milks following maternal dietary intake. However, little is known about the hydrolysis of these PUFA from milk triglycerides (TG) by lipases in suckling young. Seals, like humans, possess gastric lipase; however, the milk lipids of seals and sea lions are almost devoid of the readily hydrolyzable medium-chain fatty acids, and are characterized by a large percentage (10–30%) of n−3 PUFA. Gastric hydrolysis of milk lipids was studiedin vivo in suckling pups of three species (the California sea lion, the harp seal and the hooded seal) in order to elucidate the actions and specificity of gastric lipases on milk TG in relation to fatty acid composition and TG structure. Regardless of milk fat content (31–61% fat) or extent of gastric hydrolysis (10–56%), the same fatty acids were preferentially released in all three species, as determined by their relative enrichment in the free fatty acid (FFA) fraction. In addition to 16∶1 and 18∶0, these were the PUFA of 18 carbons and longer, except for 22∶6n−3. Levels of 20∶5n−3 were most notably enriched in FFA, at up to five times that found in the TG. Although 22∶6n−3 was apparently also released from the TG (reduced in the diglyceride), it was also notably reduced in FFA. Positional analysis of milk TG based on the products of Grignard hydrolysis revealed that these PUFA, including 22∶6n−3, were preferentially esterified at the α-position of the TG, and that the fatty acids not released during gastric hydrolysis were located at thesn-2 position. The extreme reduction of 22∶6n−3 and enrichment of 20∶5n−3 in FFA is discussed. Results from this study are consistent with reports that gastric lipase acts stereo-specifically to release fatty acids at the α-positions (sn−3,sn−1). We conclude that the n−3 PUFA in milk are efficiently hydrolyzed by gastric lipase and that this has important implications for digestion of milks enriched in PUFA by neonates in general. Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April 1990; part of this work is from the doctoral dissertation by S.J.I., University of Maryland, 1988.     

Solid state sintering of nano-crystalline indium tin oxide

The sintering of single phase nano-crystalline In₂O₃ and ITO (In_1.9Sn_0.1O_3.05) powders is reported and discussed with particular focus on the underlying mass transport mechanisms. The mass transport in the initial stage of sintering was surface diffusion, resulting in necking and coarsening, and grain boundary diffusion, accompanied by grain growth. Lattice diffusion caused significant densification at higher temperatures, leading to densities higher than 95%. The onset of densification and the maximum densification rate were shifted significantly to higher temperatures for ITO compared to In₂O₃. The reduced sintering rate of ITO was related to the higher valence state of Sn⁴⁺ relative to In³⁺, and due to precipitation of SnO₂(s). The volatile sub-oxides In₂O(g) and SnO(g) caused significant weight losses at high temperatures, particularly in the case of ITO and inert conditions. The sintering at intermediate temperatures is discussed with focus on heat treatment of ITO thin films.     

Diatom frustules as a biomaterial: effects of chemical treatment on organic material removal and mechanical properties in cleaned frustules from two <Emphasis Type="Italic">Coscinodiscus</Emphasis> species

The three-dimensional structure of silica diatom frustules offers a great potential as nanoporous material for several nanotechnological applications, but the starting point for these applications is the ability to obtain clean frustules with sufficient mechanical strength and intact structure. Here, frustules from the diatoms Coscinodiscus centralis Ehrenberg and Coscinodiscus wailesii Gran et Angst are characterized with respect to their structural integrity, content of residual organic biomaterial and their mechanical properties after two cleaning methods using either hydrogen peroxide as oxidizing agent or a combination of a surfactant (sodium dodecyl sulphate) and a complexing agent. Fluorescence microscopy and energy dispersive spectroscopy (SEM/EDS) analysis revealed clear differences regarding the amount of organic residual within the frustules depending on the cleaning process, with little organic material left after the oxidizing method. This method, however, induced a partial cracking of the frustules suggesting an embrittlement due to the cleaning. Nanoindentation confirmed this and showed that the oxidizing method resulted in more brittle frustules compared to the surfactant/complexing method. More efficient cleaning of organic biomaterial may result in more fragile frustules, and the choice of cleaning method must be based on the planned application.