Pro‐oxidant activity of Fe2+ in oxidation of cod phospholipids in liposomes

This work examines how different factors such as temperature, amount of injected Fe²⁺, lipid concentration, pH, concentration of NaCl and concentration of dissolved oxygen influenced the lipid oxidation rate of liposomes made from cod phospholipids. The rate of lipid oxidation was measured by consumption of dissolved oxygen by liposomes in a closed vessel. The rate of oxygen consumption in liposomes was proportional to the concentration of iron and the lipid concentration in the assay mixture. The oxygen consumption rate was dependent on pH, with a maximum observed between pH 4 and 5. The addition of salt (final concentration 0.04–0.8 M) decreased the rate of oxygen consumption. The rate of oxidation was independent of the concentration of dissolved oxygen (in the range of 230–5 μM). The oxygen consumption rate followed Arrhenius kinetics, and the variation in activation energy found (60–87 kJ/moles×K) might be due to variations in the composition of raw materials used in the experiments and different susceptibility to oxidation.     

Water diffusion coefficients during copper electropolishing

Cu electropolishing was studied using a rotating disc electrode in a variety of phosphoric acid-based electrolytes, including several with ethanol and other species added as diluents. Diluents allow a wider range of water concentrations and electrolyte viscosities to be accessed and also reduce the removal rate during Cu electropolishing, simplifying possible application to damascene processing. Transient and steady state currents in the mass transfer limited regime are shown to depend on both the number of water acceptor molecules associated with each dissolving Cu ion and on the effective diffusion coefficient of water. Transient analysis samples the bulk transport properties, whereas steady state analysis integrates them through the diffusion layer. Assuming that the effective diffusion coefficients appropriate to transient and steady state behavior are the same, about one water molecule is associated with each dissolving Cu ion. This analysis yields effective diffusion coefficients for water on the order of 10^–9cm²s^–1. However, the data is also consistent with an assumption that six water molecules are associated with each dissolving Cu ion, but the effective diffusion coefficient appropriate for a Levich analysis is somewhat lower than that in the bulk electrolyte. This analysis yields effective diffusion coefficients for water on the order of 10^–8–10^–7cm²s^–1. The latter interpretation, that six water molecules are associated with each dissolving Cu ion, appears more likely since it provides almost exact agreement with the effective diffusion coefficient reported previously by Vidal and West. In combination with previously published impedance results ruling out a salt film mechanism, the good agreement between the transient and steady state analyses confirm that water is the acceptor species that complexes dissolving Cu ions in phosphoric acid-based electropolishing baths.     

INVESTIGATION OF ASPHALTENE PRECIPITATION AT ELEVATED TEMPERATURE

In order to obtain quantitative data on the asphaltene precipitation induced by the addition of n-alkane (heptane) at temperatures above the normal boiling point of the precipitant, a high temperature/ high pressure filtration apparatus has been constructed. Oil and alkane are mixed at the appropriate temperature and the pressure in closed vessels keeping the mixture at the liquid state. The filtration is performed with a small differential pressure over the filter so as to avoid flashing the mixture. The technique requires a low dead volume in the system to minimize the content of maltenes in the extracted fraction, hence there is no room for stirring. The equipment as well as solutions to some of the problems are presented along with precipitation data from 40 to 200° C The asphaltenes separated are analyzed using FT-ir. The filtrate containing the maltenes was cooled to room temperature and the asphaltenes separating upon cooling was collected and analyzed. The oil and selected maltene fractions and extraction/ cleaning solvents were analyzed using GC     

Mechanical Properties of Single-Crystal α-Si3N4

Single crystals of α-Si₃N₄ several millimeters in diameter and several millimeters long have been grown by chemical vapor deposition. Some of the microstructural and mechanical properties have been evaluated using X-ray diffracometry, optical and transmission electron microscopy, and high-temperature microhardness testing. The crystallographic growth direction determines the quality of the crystals, including the density of internal microcracks and the nature and quantity of special boundaries. The measurement of crack lengths associated with microindentations has shown that cleavage in α-Si₃N₄ is relatively isotropic. Finally, indentation fracture toughness values agree well with theoretical predictions based on recent bond-energy calculations.     

It's the rents,stupid! The political economy of the resource curse

A number of studies suggest that natural resources can have a negative impact on the developing prospects of countries. Empirical results suggest that political economy models of patronage and rent-seeking are central to understanding why such a resource curse arises. In other words, the resource curse is created by certain resource rents leading to dysfunctional behaviour. This article introduces the term impartiality enhancing institutions to structure policy debates by distinguishing conditions under which negative effects of resources can be mitigated. Moreover, it is argued that viewing institutions as an equilibrium outcome has implications for the analysis of institutional change. Policy initiatives that do not promote the impartiality of institutions, nor attend to the underlying interests and incentives keeping a bad institutional equilibrium in place, will not help lift the resource curse.     

The cognitive and linguistic foundations of early reading development: A Norwegian latent variable longitudinal study.

The authors present the results of a 2-year longitudinal study of 228 Norwegian children beginning some 12 months before formal reading instruction began. The relationships between a range of cognitive and linguistic skills (letter knowledge, phoneme manipulation, visual–verbal paired-associate learning, rapid automatized naming (RAN), short-term memory, and verbal and nonverbal ability) were investigated and related to later measures of word recognition in reading. Letter knowledge, phoneme manipulation, and RAN were independent longitudinal predictors of early reading (word recognition) skills in the regular Norwegian orthography. Early reading skills initially appeared well described as a unitary construct that then showed rapid differentiation into correlated subskills (word decoding, orthographic choice, text reading, and nonword reading) that showed very high levels of longitudinal stability. The results are related to current ideas about the cognitive foundations of early reading skills. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Speciation of lead, copper, zinc and antimony in water draining a shooting range—Time dependant metal accumulation and biomarker responses in brown trout (Salmo trutta L.)

The speciation of Pb, Cu, Zn and Sb in a shooting range run-off stream were studied during a period of 23 days. In addition, metal accumulation in gills and liver, red blood cell ALA-D activity, hepatic metallothionine (Cd/Zn-MT) and oxidative stress index (GSSG/ tGSH levels) in brown trout (Salmo trutta L.) exposed to the stream were investigated. Fish, contained in cages, were exposed and sampled after 0, 2, 4, 7, 9, 11 and 23 days of exposure. Trace metals in the water were fractionated in situ according to size (nominal molecular mass) and charge properties. During the experimental period an episode with higher runoff occurred resulting in increased levels of metals in the stream. Pb and Cu were mainly found as high molecular mass species, while Zn and Sb were mostly present as low molecular mass species. Pb, Cu and Sb accumulated on gills, in addition to Al origination from natural sources in the catchment. Pb, Cu and Sb were also detected at elevated concentration in the liver. Blood glucose and plasma Na and Cl levels were significantly altered during the exposure period, and are attributed to elevated concentrations of Pb, Cu and Al. A significant suppression of ALA-D was detected after 11 days. Significant differences were detected in Cd/Zn-MT and oxidative stress (tGSH/GSSG) responses at Day 4. For Pb the results show a clear link between the HMM (high molecular mass) positively charged Pb species, followed by accumulation on gills and liver and a suppression in ALA-D. Thus, high flow episodes can remobilise metals from the catchment, inducing stress to aquatic organisms.     

In Situ Raman Indentation of β-Eucryptite: Characterization of the Pressure-Induced Phase Transformation

A pressure-induced phase transformation in the lithium aluminum silicate β-eucryptite was studied with in situ Raman spectroscopy. Dense β-eucryptite composites were made via powder synthesis followed by sintering. The specimens were then subjected to diamond indentation up to applied contact stresses of about 8 GPa, while collecting Raman spectra. The appearance of a Raman peak (∼520 cm⁻¹) at a contact stress of about 3 GPa likely corresponds to the reversible phase transformation of β-eucryptite to the orthorhombic phase ɛ-eucryptite. Loading and unloading in situ Raman indentation experiments are discussed with regards to this transformation.     

Future threats to agricultural food production posed by environmental degradation,climate change,and animal and plant diseases – a risk analysis in three economic and climate settings

Global food security is one of the most pressing issues for humanity, and agricultural production is critical for achieving this. The existing analyses of specific threats to agricultural food production seldom bring out the contrasts associated with different levels of economic development and different climatic zones. We therefore investigated the same biophysical threats in three modelled types of countries with different economic and climatic conditions. The threats analysed were environmental degradation, climate change and diseases and pests of animals and plants. These threats were analysed with a methodology enabling the associated risks to be compared. The timeframe was 2012–2050 and the analysis was based on three underlying assumptions for 2050: the world population will have increased to 9 billion people, there will be a larger middle class in the world and climate change will be causing more extreme weather events, higher temperatures and altered precipitation. It is suggested that the risks, presented by the biophysical threats analysed, differ among the three modelled types of countries and that climate zone, public stewardship and economic strength are major determinants of these differences. These determinants are far from evenly spread among the world’s major food producers, which implies that diversification of risk monitoring and international assessment of agricultural production is critical for assuring global food security in 2050.     

Review and advances in delta-sigma DAC error estimation based on additive noise modelling

High-resolution and very high resolution data conversion is dominated by the use of delta-sigma modulating converters. Oversampling and noise-shaping is employed to enable a coarsely quantized conversion with high effective resolution. The time-domain output waveform from a delta-sigma modulator is often impossible to predict analytically, therefore modulator design is largely based on high level digital simulations and rule-of-thumb estimation. However, the output waveform also largely determines the distortion caused by analog error sources in the converter. Therefore optimization of the modulator with regards to digital quantization noise might not yield an optimal design when analog errors are included. This paper extends common estimation methods to include analog error sources, with the objective of enabling more global rule-of-thumb optimization.