Liquid-Liquid phase separation in concentrated polymer solutions studied by electron microscopy

Depending upon quenching temperature and composition, liquid-liquid phase separation in polymer solutions will occur either by nucleation and growth or by the spinodal decomposition. Both mechanisms occur in the system poly(2,6-dimethyl-1,4-phenylene oxide)-toluene and can be made visible by electronmicroscopy using the freeze-etching method as sample preparation technique

Competitive adsorption of plasma proteins at solid—liquid interfaces

The competitive adsorption of human serum albumin (HSA), human immuno-γ-globulin (HIgG) and human fibrinogen (HFb) onto polystyrene (PS) at 20° C and a pH of 7.35 (phosphate-buffered saline) was studied. Protein adsorption was studied using enzyme immunoassay. The results obtained with the immunoassay were compared with those obtained using radiolabelled proteins. Recent studies revealed that the adsorption behaviour of radiolabelled proteins onto surfaces differs from that of the non-labelled proteins, which may lead to misinterpretation of adsorption data. Differences in the adsorption behaviour of the labelled proteins as compared to non-labelled proteins can possibly be explained by the formation of modified proteins during the labelling procedure as shown by ion-exchange high-performance liquid chromatography (HPLC). The competitive adsorption of HSA, HIgG and HFb onto a PS latex was studied by measuring the depletion of proteins in solution. The decrease in protein concentration in solution was determined by HPLC techniques. A strong preferential adsorption of HFb was observed with maximum adsorption values of 0.6 μg/cm2

Calculation of liquid-liquid phase separation in a ternary system of a polymer in a mixture of a solvent and a nonsolvent

A numerical method for the calculation of the binodal of liquid-liquid phase separation in a ternary system is described. The Flory-Huggins theory for three-component systems is used. Binodals are calculated for polymer/solvent/nonsolvent systems which are used in the preparation of asymmetric ultrafiltration or reverse osmosis membranes: cellulose acetate/solvent/water and polysulfone/solvent/water. The values for the binary interaction parameters are taken from literature sources. The effect of a concentration-dependent solvent/nonsolvent interaction parameter is discussed. Although knowledge of the interaction parameters for all compositions in the ternary system is rather poor, fairly good agreement has been found between calculated and experimentally found miscibility gaps when the solvent/nonsolvent parameter is taken to be concentration dependent and the other parameters, the polymer/solvent and the polymer/nonsolvent interaction parameter, are kept constant

Characterization of new membrane materials by means of fouling experiments Adsorption of bsa on polyetherimide-polyvinylpyrrolidone membranes

The hydrophilicity of polyetherimide-polyvinylpyrrolidone (PEI-PVP) microfiltration membranes can be adjusted by means of a suitable post-treatment. The influence of the nature of the membrane surface on fouling properties was studied using permeation experiments before and after exposure to a protein (BSA) solution and adsorption experiments with 14C labelled BSA. A correlation between the permeation experiments and the radiolabelled BSA adsorption experiments was found. The PVP in the membrane matrix prevents BSA adsorption taking place to a large extent and it appeared that heat-treated PEI-PVP membranes showed the same nonfouling behaviour as, for example, cellulose acetate membranes

Mineralenbolus geiten alleen bij tekorten

Op biologische geitenbedrijven zijn er soms twijfels over de mineralenvoorziening van de geiten. Afwijkende vacht, kromme pootjes en een slechte vruchtbaarheid zouden aanwijzingen kunnen zijn voor tekorten aan mineralen. In de stalperiode 2008/2009 is nagegaan of de bloedwaarden bij de geiten en hun lammeren beïnvloed werden door het toedienen van een mineralenbolus. Bij een ruime dekking van de theoretische behoeftenorm met het rantsoen mag van het toedienen van een bolus alleen effect verwacht worden op de bloedwaarden als de norm en/of de referentiewaarden niet goed gekozen zijn

Vruchtbaarheid in relatie tot produktie en diergezondheid

In dit artikel wordt ingegaan op relaties tussen vruchtbaarheidskengetallen en produktie. Hierbij wordt onderscheid gemaakt tussen verbanden op dier- en bedrijfsniveau

Interpreting predictions of cognition from simulated versus empirical resting state functional connectivity

The relation between structure and function of the brain, and how behavior arises from it, is a central topic of interest in neuroscience. This problem can be formulated in terms of Structural Connectivity (SC) and Functional Connectivity (FC), respectively representing anatomical connections and functional interactions between regions in the brain. Recently, a study by Sarwar and colleagues has demonstrated individualized prediction of FC from SC using machine learning, additionally showing that variation in cognitive performance is explained by simulated FC (sFC) almost as well as by empirical FC (eFC). We investigated how decisions made to predict cognition differ between the models based on eFC and sFC. We predicted cognitive performance with Lasso regression in 100 cross-validation loops from both eFC and sFC separately, using FC between each of the 2278 pairs of regions in the 68-region Desikan-Killiany parcellation as features. We identified relevant predictors of cognition by inspecting permutation importance scores and keeping only features whose importance scores were consistently high across validation loops. 13 eFC features and 21 sFC features survived this procedure. Of these, only one feature overlapped between eFC and sFC. Analyzing overlap between regions corresponding to important features and functional systems known to support cognition revealed no patterns for either eFC or sFC features. In conclusion, we found that while cognition can be predicted from sFC almost as well as from eFC, different features are used in the models, and these features were not found to follow any structure in terms of functional systems. This shows that while machine learning models provide a theoretical upper bound on how accurately function can be predicted from structure, they do not necessarily produce output that can be interpreted in the same way as the data the models were trained on

Eenvoudig boeren met gezonde koeien

Met eenvoudige middelen wordt op het lagekostenbedrijf getracht een goede diergezondheid te realiseren. In dit artikel wordt besproken welke maatregelen op het bedrijf worden genomen in het kader van diergezondheid en het optreden van gezondheidsprobleme

Working memory performance is associated with functional connectivity between the right dlPFC and DMN in glioma patients

Patients with primary brain tumors frequently suffer from cognitive impairments in multiple domains, leading to serious consequences for socio-professional functioning and quality of life. The functional-anatomical basis of these impairments is still poorly understood.The study of correlated BOLD activity in the brain (i.e. functional connectivity) has greatly contributed to our understanding of how brain activity supports cognitive function. In particular, activity observed during the execution of specific tasks can be related to various distributed functional networks, stressing the importance of interactions between remote brain regions. Among these networks, the Default Mode Network (DMN) and the Fronto-Parietal Network (FPN) have consistently been associated with working memory performance.Recently, using task-fMRI in glioma patients, poor performance in a working memory task was associated with less deactivation of the DMN during this task and to a lack of task-evoked changes in the DMN-FPN structure. In this study, we investigated whether these effects are reflected in the resting-state (RS) functional connectivity of the same patient group, i.e. when no task was performed during fMRI. We additionally zoomed in on the part of the FPN located in the dorsolateral Prefrontal Cortex (dlPFC), since this region is believed to be mainly responsible for DMN deactivation.Resting-state functional MRI data were acquired pre-operatively from 45 brain tumor patients (20 low- and 25 high-grade glioma patients). Results of a pre-operative in-scanner N-back working memory fMRI task were used to assess working memory performance.Patient brains were parcellated into ROIs using both the Gordon and Yeo atlas, which have the FPN and DMN network identities readily available. The dlPFC was defined based on masks retrieved from NeuroSynth.To measure DMN-FPN functional connectivity the average Pearson correlation between the activation time series in the regions belonging to the FPN and the DMN was calculated. Functional connectivity between the DMN and the dlPFC was calculated in a similar way.The average correlation between the resting-state fMRI activity in the right dlPFC and in the DMN was negatively associated with working memory performance for both the Gordon atlas (p \\< 0.003) and Yeo atlas (p \\< 0.007). No association was found for the correlation between activity in the left dlPFC and the DMN, nor for the correlation between the activity in the whole FPN and the DMN.Our findings show that working memory performance of glioma patients is related to interactions between networks that can be measured with resting-state fMRI. Furthermore, the results provide further evidence that not only specific brain regions are important for cognitive performance, but that also the interactions between large-scale networks should be considered