Equilibrium model for CO2 absorption in an aqueous solution of 2-amino-2-methyl-1-propanol

A semi-empirical gas-liquid equilibrium model for the absorption of CO₂ in aqueous 3M AMP (2-amino-2-methyl-1-propanol) is presented. It applies to high CO₂ loadings (y > 0.5) in the temperature range between 20 and 50 °C, and is based on experimental solubility and pH determinations. For a given amine concentration, it yields the equilibrium partial pressure of CO₂ as a function of only two variables: the CO₂ loading and temperature. The model correlates the expressions for the chemical equilibria involved as follows: p = m y × 10^x, where p is the equilibrium partial pressure, x = logK - pH, m is the amine molarity, y the CO₂ loading, and K is a parameter involving Henry's law constant, H, and the first dissociation constant, K₁, of carbonic acid. pH is found to depend on both temperature and CO₂ loading while logK depends only on the CO₂ loadIng. Correlations for pH and logK are presented. The model fits own data for 3M AMP very well as well as the equilibrium data found in recent literature.     

DYFRAM: dynamic fragmentation and replica management in distributed database systems

In distributed database systems, tables are frequently fragmented and replicated over a number of sites in order to reduce network communication costs. How to fragment, when to replicate and how to allocate the fragments to the sites are challenging problems that has previously been solved either by static fragmentation, replication and allocation, or based on a priori query analysis. Many emerging applications of distributed database systems generate very dynamic workloads with frequent changes in access patterns from different sites. In such contexts, continuous refragmentation and reallocation can significantly improve performance. In this paper we present DYFRAM, a decentralized approach for dynamic table fragmentation and allocation in distributed database systems based on observation of the access patterns of sites to tables. The approach performs fragmentation, replication, and reallocation based on recent access history, aiming at maximizing the number of local accesses compared to accesses from remote sites. We show through simulations and experiments on the DASCOSA distributed database system that the approach significantly reduces communication costs for typical access patterns, thus demonstrating the feasibility of our approach.     

Screening of biomarkers in rat urine using LC/electrospray ionization-MS and two-way data analysis

Biofluids, like urine, form very complex matrixes containing a large number of potential biomarkers, that is, changes of endogenous metabolites in response to xenobiotic exposure. This paper describes a fast and sensitive method of screening biomarkers in rat urine. Biomarkers for phospholipidosis, induced by an antidepressant drug, were studied. Urine samples from rats exposed to citalopram were analyzed using solid-phase extraction (SPE) and liquid chromatography mass spectrometry (LC/MS) analysis detecting negative ions. A fast iterative method, called Gentle, was used for the automatic curve resolution, and metabolic fingerprints were obtained. After peak alignment principal component analysis (PCA) was performed for pattern recognition, PCA loadings were studied as a means of discovering potential biomarkers. In this study a number of potential biomarkers of phospholipidosis in rats are discussed. They are reported by their retention time and base peak, as their identification is not within the scope of the study. In addition to the fact that it was possible to differentiate control samples from dosed samples, the data were very easy to interpret, and signals from xenobiotic-related substances were easily removed without affecting the endogenous compounds. The proposed method is a complement or an alternative to NMR for metabolomic applications.     

Science, Social Networks and Spillovers

Although prior empirical research has established an association between science and the widespread diffusion of knowledge, the exact mechanism(s) through which science catalyses information flow remains somewhat ambiguous. This paper investigates whether the knowledge diffusion associated with science-based innovation stems from the norm of openness and incentives for publication, or whether scientists maintain more extensive and dispersed social networks that facilitate the dissemination of tacit knowledge. Our analysis supports the first mechanism: we track the movement of knowledge with patent citations, and find that science-based innovations diffuse more rapidly and widely, even after controlling for the underlying social networks of researchers as measured using information on prior collaborations. We also find that publication and social networks act as substitutes in the diffusion of knowledge.     

A New Design Concept for High-Performance Fading Channel Simulators Using Set Partitioning

In this paper, we introduce a new technique for the design of high-performance Rayleigh fading channel simulators. The proposed design method uses set partitioning – a technique, which plays a key role in the design of trellis-coded modulation schemes. We show how set partitioning can be used to design multiple uncorrelated fading waveforms enabling the simulation of Rayleigh fading channels. For the important case of isotropic scattering, we show that the sample average of the generated waveforms results in a deterministic process, the autocorrelation function (ACF) of which tends to the zeroth-order Bessel function of the first kind as the number of sample functions increases. The proposed procedure is completely deterministic. The comparison with a stochastic procedure using Monte Carlo techniques will be made. A study of the performance shows clearly that the new technique using set partitioning outperforms by far existing Monte Carlo methods.     

Recolonization by heterotrophic bacteria after UV irradiation or ozonation of seawater; a simulation of ballast water treatment

Transport of ballast water with ships represents a risk for introduction of foreign species. If ballast water is treated during uptake, there will be a recolonization of the ballast water by heterotrophic bacteria during transport. We investigated survival and succession of heterotrophic bacteria after disinfection of seawater in the laboratory, representing a model system of ballast water treatment and transport. The seawater was exposed to ultraviolet (UV) irradiation, ozone (2 doses) or no treatment, incubated for 16 days and examined with culture-dependent and -independent methods. The number of colony-forming units (CFU) was reduced below the detection level after disinfection with UV and high ozone dose (700 mV), and 1% of the initial level for the low ozone dose (400 mV). After less than 3 days, the CFU was back or above the starting point for the control, UV and low ozone treatment, whereas it took slightly more than 6 days for the high ozone treatment. Disinfection increased substrate availability and reduced cell densities. Lack of competition and predation induced the recolonization by opportunistic bacteria (r-strategists), with significant increase in bacterial numbers and a low diversity (based on DGGE band pattern). All cultures stabilized after the initial recolonization phase (except Oz700) where competition due to crowding and nutrient limitation favoured bacteria with high substrate affinity (K-strategists), resulting in higher species richness and diversity (based on DGGE band pattern). The bacterial community was significantly altered qualitatively and quantitatively and may have a higher potential as invaders in the recipient depending on disinfection method and the time of release. These results have implications for the treatment strategy used for ballast water.     

Modeling the longitudinal variation of sawn timber grades in Norway spruce (Picea abies (L.) Karst.)

Grades derived from visual assessments of sawn timber are determined by the worst part of each piece. Since grade varies longitudinally in timber, grade yield will decrease if the average length of timber increases. The variation in grade is caused by longitudinal variation in knot properties and other features as they appear on the sawn surface taken into account during grading. The objective of this study is to describe and analyze this variation in Picea abies. The study consisting of 768 boards for which all features that could lead to downgrading were recorded noting position, type and size. Based on this information, all boards were graded according to appearance by Nordic Timber, and strength by INSTA 142. Logistic regression models of grade as a function of position in the stem were developed, and the dependence between responses was taken into consideration by using General Estimating Equations (GEE). The models showed a decreasing trend in grade from the butt end toward the top end of the trees, and the effect was more pronounced in strength grading than in appearance grading. Models with binomial response and different correlation structures were tested, and it was shown that both independent and autoregressive correlation structures could be used. This suggests that a multinomial ordinal logistic regression with a GEE-approach with an independent correlation structure is appropriate for modeling grade in this study.     

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 Fe(3)O(4) 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.     

Mastitis and the shape of the lactation curve in Norwegian dairy cows

An investigation of the shape of the lactation curve and the mastitis incidence was conducted to identify whether management interventions of the lactation curve constitute a potential for reducing incidence of mastitis at herd level. Lactation curves were estimated to describe the variation of daily milk yield during the 305-d lactation period in Norwegian Red cows. Associations between mastitis incidence at herd level and lactation curve characteristics such as production level at onset of lactation, magnitude and time of peak milk yield, and increase and decrease of milk yield rates were studied. Data from 250,303 lactations occurring during 2005 and 2006 from 14,766 herds were obtained from the Norwegian Dairy Herd Recording System. Besides veterinary treatments, the records included information on monthly test-day milk yields. The shapes of the lactation curves at herd level were parameterized using a modified Wilmink model in two separate mixed model analyses. In the first analysis a subset of lactations with no records of veterinary treatments was used. Lactation curves from herds with high (>0·31 cases/305-d lactation) and low (<0·07 cases/305-d lactation) herd mastitis incidence rate were parameterized and compared for three separate strata of parity. The result showed that high herd mastitis incidence rate was associated with a low intercept (P<0·05), a steep slope before peak milk yield (P<0·01) and a rapid decline after peak milk yield (P<0·01). In the second analysis a subset of high-yielding lactations with veterinary treatments of mastitis only and lactations with no records of veterinary treatment were compared. This was done to investigate whether the findings at herd level were also reflected at cow level. These results showed that lactation curves from lactations with mastitis cases were associated with a steep slope before peak milk yield (P<0·05) in second and later parities and a rapid decline after peak milk yield (P<0·01) in all three parity groups.