Determination of interaction parameters in aqueous two-phase systems

U radu je prikazan postupak modeliranja ravnoteže u vodenom dvofaznom sustavu voda – polietilenglikol – (NH4)2SO4 pri atmosferskom tlaku i temperaturi 25 °C. Na temelju literaturnih podataka istražena je primjenjivost modela koeficijenta aktivnosti NRTL modificiranog prema Wu i suradnicima, modificiranog Pitzerovog virijalnog modela te empirijskog modela dobivenog kombiniranjem Merchukove jednadžbe za opis binodalne krivulje s Othmer-Tobiasovim izrazom za nagib veznih linija. Posebna pažnja usmjerena je na odabir i primjenu optimizacijskih algoritama – rješenje genetskog algoritma korišteno je kao inicijacija za egzaktne optimizacijske algoritme: algoritam po Nelder-Meadu, odnosno po Levenberg-Marquardtu. Uz postojanje odstupanja modela od eksperimentalnih podataka, modificirani Pitzerov virijalni model pokazao se prikladnijim za opis ravnoteže kapljevina-kapljevina od modificiranog modela NRTL . Modificirani Pitzerov virijalni model pokazao se prikladniji i prilikom predviđanja ravnoteže sustava ovisno o molekulskoj masi polimera. Empirijski model eksperimentalne podatke opisuje točnije od teorijskih modela, ali za razliku od njih nema mogućnost predviđanja faznog ponašanja u uvjetima koji se razlikuju od onih pri kojima su prikupljeni eksperimentalni podaci.This thesis presents the procedure of modelling liquid-liquid equilibrium in the aqueous two-phase system water – polyethylene glycol – (NH4)2SO4 at atmospheric pressure and temperature of 25 °C. Based on literature data, the applicability of NRTL activity coefficient model modified by Wu and collaborators, modified Pitzer virial model and empirical model formed by combining Merchuk expresion for binodal curve and Othmer-Tobias tie line correlation were tested. Special attention was paid to choosing and applying optimisation algorithms – the solution of genetic algorithm was used as an initiation for exact optimisation algorithms of Nelder-Mead's and Levenberg-Marquardt. Considering the difference between calculated and experimental data, modified Pitzer virial model appeared to be more suitable for describing liquid-liquid equilibrium than modified NRTL model. Modified Pitzer virial model also appeared to be more suitable for predicting the equilibrium of the systems dependence on polymer molecular weight. Empirical model describes the experimental data more acurately than teoretical models but lacks the ability to predict the phase behaviour in conditions different than the ones used in the experiments

Determination of interaction parameters in aqueous two-phase systems

U radu je prikazan postupak modeliranja ravnoteže u vodenom dvofaznom sustavu voda – polietilenglikol – (NH4)2SO4 pri atmosferskom tlaku i temperaturi 25 °C. Na temelju literaturnih podataka istražena je primjenjivost modela koeficijenta aktivnosti NRTL modificiranog prema Wu i suradnicima, modificiranog Pitzerovog virijalnog modela te empirijskog modela dobivenog kombiniranjem Merchukove jednadžbe za opis binodalne krivulje s Othmer-Tobiasovim izrazom za nagib veznih linija. Posebna pažnja usmjerena je na odabir i primjenu optimizacijskih algoritama – rješenje genetskog algoritma korišteno je kao inicijacija za egzaktne optimizacijske algoritme: algoritam po Nelder-Meadu, odnosno po Levenberg-Marquardtu. Uz postojanje odstupanja modela od eksperimentalnih podataka, modificirani Pitzerov virijalni model pokazao se prikladnijim za opis ravnoteže kapljevina-kapljevina od modificiranog modela NRTL . Modificirani Pitzerov virijalni model pokazao se prikladniji i prilikom predviđanja ravnoteže sustava ovisno o molekulskoj masi polimera. Empirijski model eksperimentalne podatke opisuje točnije od teorijskih modela, ali za razliku od njih nema mogućnost predviđanja faznog ponašanja u uvjetima koji se razlikuju od onih pri kojima su prikupljeni eksperimentalni podaci.This thesis presents the procedure of modelling liquid-liquid equilibrium in the aqueous two-phase system water – polyethylene glycol – (NH4)2SO4 at atmospheric pressure and temperature of 25 °C. Based on literature data, the applicability of NRTL activity coefficient model modified by Wu and collaborators, modified Pitzer virial model and empirical model formed by combining Merchuk expresion for binodal curve and Othmer-Tobias tie line correlation were tested. Special attention was paid to choosing and applying optimisation algorithms – the solution of genetic algorithm was used as an initiation for exact optimisation algorithms of Nelder-Mead's and Levenberg-Marquardt. Considering the difference between calculated and experimental data, modified Pitzer virial model appeared to be more suitable for describing liquid-liquid equilibrium than modified NRTL model. Modified Pitzer virial model also appeared to be more suitable for predicting the equilibrium of the systems dependence on polymer molecular weight. Empirical model describes the experimental data more acurately than teoretical models but lacks the ability to predict the phase behaviour in conditions different than the ones used in the experiments

Determination of interaction parameters in aqueous two-phase systems

U radu je prikazan postupak modeliranja ravnoteže u vodenom dvofaznom sustavu voda – polietilenglikol – (NH4)2SO4 pri atmosferskom tlaku i temperaturi 25 °C. Na temelju literaturnih podataka istražena je primjenjivost modela koeficijenta aktivnosti NRTL modificiranog prema Wu i suradnicima, modificiranog Pitzerovog virijalnog modela te empirijskog modela dobivenog kombiniranjem Merchukove jednadžbe za opis binodalne krivulje s Othmer-Tobiasovim izrazom za nagib veznih linija. Posebna pažnja usmjerena je na odabir i primjenu optimizacijskih algoritama – rješenje genetskog algoritma korišteno je kao inicijacija za egzaktne optimizacijske algoritme: algoritam po Nelder-Meadu, odnosno po Levenberg-Marquardtu. Uz postojanje odstupanja modela od eksperimentalnih podataka, modificirani Pitzerov virijalni model pokazao se prikladnijim za opis ravnoteže kapljevina-kapljevina od modificiranog modela NRTL . Modificirani Pitzerov virijalni model pokazao se prikladniji i prilikom predviđanja ravnoteže sustava ovisno o molekulskoj masi polimera. Empirijski model eksperimentalne podatke opisuje točnije od teorijskih modela, ali za razliku od njih nema mogućnost predviđanja faznog ponašanja u uvjetima koji se razlikuju od onih pri kojima su prikupljeni eksperimentalni podaci.This thesis presents the procedure of modelling liquid-liquid equilibrium in the aqueous two-phase system water – polyethylene glycol – (NH4)2SO4 at atmospheric pressure and temperature of 25 °C. Based on literature data, the applicability of NRTL activity coefficient model modified by Wu and collaborators, modified Pitzer virial model and empirical model formed by combining Merchuk expresion for binodal curve and Othmer-Tobias tie line correlation were tested. Special attention was paid to choosing and applying optimisation algorithms – the solution of genetic algorithm was used as an initiation for exact optimisation algorithms of Nelder-Mead's and Levenberg-Marquardt. Considering the difference between calculated and experimental data, modified Pitzer virial model appeared to be more suitable for describing liquid-liquid equilibrium than modified NRTL model. Modified Pitzer virial model also appeared to be more suitable for predicting the equilibrium of the systems dependence on polymer molecular weight. Empirical model describes the experimental data more acurately than teoretical models but lacks the ability to predict the phase behaviour in conditions different than the ones used in the experiments

A quadratic programming algorithm for deriving efficient farm plans in a risk setting

The main focus was on developing an algorithm and supporting computer programs for use by extension personel to counsel farm managers on problems of enterprise choice. Investigation was initiated from the complete certainty viewpoint of linear programming. Upon introducing uncertainty, ramifications of changing expected income, variance and the correlation coefficient between enterprises were explored. This was extended to develop a quadratic programming algorithm which resulted in complete algebraic specification of the efficiency frontier through integration of the Lagrangian multipliers. The Von Neuman-Morgenstern utility analysis framework was posed for selecting the best alternative but dismissed as being cumbersome for practical application. A probability of loss function which places confidence intervals about the income level of each alternative was used since it is more amenable for application by extension workers. Data requirements were found to be no more difficult to satisfy in the quadratic programming model than in the presently used linear programming models. The triangular probability distribution was used in obtaining subjective estimates for the mean and variance of prices and yields. Subjective methods for deriving covariances between incomes from farm enterprises were discarded as being difficult to administer and subject to inconsistencies. A regional correlation matrix was used from which specific covariance estimates for individual decision problems were computed. Seven cases were studied as a test of the computer programs and the algorithm. Four of these cases were submitted from actual farm situations by an extension agent. Output from the computer provided each farmer with a report containing the composition of every efficient plan, the pattern of resource use, the shadow prices of limiting resources and confidence statements about achieving certain levels of gross margin. The report was presented in tabular form, in graphic form and as a set of algebraic equations. Although no extensive test of acceptance by farm decision makers was made, results with the four cases studied appeared encouraging

Preparation of chitosan-copper complex microspheres modified by bioactive glass

The aim of this work was to prepare composite microspheres with high sphericity and narrow size distribution based on chitosan-copper complex and bioactive glass (bioglass). The influence of the bioactive glass content on the size and morphology of chitosan-copper complex microspheres was investigated. The electrohydrodynamic atomization process was used to produce highly spherical particles of narrow size distribution and with defined surface morphology. The addition of bioglass particles caused the surface changes, from smooth to wrinkled surface by increasing the bioglass quantity. The size of the obtained microspheres was estimated to be between 40 and 100 μm, depending on the bioglass content

Community Psychology Coverage in Introduction to Psychology Textbooks

The field of Community Psychology is approximately 50 years old, and it has become an active and invigorating source of ideas (e.g., prevention, ecological theory, sense of community, empowerment, participatory-based research, providing care to marginalized populations, etc.) for the overall field of Psychology. However, many undergraduates have never heard of this discipline in part because introductory Psychology textbooks are not providing adequate coverage of this field. The current study examined 53 introductory Psychology textbooks, published between 2010 and 2016, for their coverage of the field of Community Psychology. Findings indicated that only 17% of these textbooks contained an adequate representation of the discipline of Community Psychology. The lack of adequate coverage of this field in most introductory Psychology textbooks has significant implications for attracting undergraduates to this content area. Fifty percent of the textbook authors responded to an email that provided them information regarding the current study, and many indicated that new versions of their textbooks could include information from the field of Community Psychology.  This positive response suggests that many authors are willing to better represent the field of Community Psychology in their introductory Psychology textbooks.&nbsp

Community Psychology Coverage in Introduction to Psychology Textbooks

The field of Community Psychology is approximately 50 years old, and it has become an active and invigorating source of ideas (e.g., prevention, ecological theory, sense of community, empowerment, participatory-based research, providing care to marginalized populations, etc.) for the overall field of Psychology. However, many undergraduates have never heard of this discipline in part because introductory Psychology textbooks are not providing adequate coverage of this field. The current study examined 53 introductory Psychology textbooks, published between 2010 and 2016, for their coverage of the field of Community Psychology. Findings indicated that only 17% of these textbooks contained an adequate representation of the discipline of Community Psychology. The lack of adequate coverage of this field in most introductory Psychology textbooks has significant implications for attracting undergraduates to this content area. Fifty percent of the textbook authors responded to an email that provided them information regarding the current study, and many indicated that new versions of their textbooks could include information from the field of Community Psychology.  This positive response suggests that many authors are willing to better represent the field of Community Psychology in their introductory Psychology textbooks.&nbsp

PCL-Coated Multi-Substituted Calcium Phosphate Bone Scaffolds with Enhanced Properties

[EN] Ionic substitutions within the hydroxyapatite lattice are a widely used approach to mimic the chemical composition of the bone mineral. In this work, Sr-substituted and Mg- and Sr-co-substituted calcium phosphate (CaP) scaffolds, with various levels of strontium and magnesium substitution, were prepared using the hydrothermal method at 200 degrees C. Calcium carbonate skeletons of cuttlefish bone, ammonium dihydrogenphosphate (NH4H2PO4), strontium nitrate (Sr(NO3)(2)), and magnesium perchlorate (Mg(ClO4)(2)) were used as reagents. Materials were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Whole powder pattern decomposition refinements of XRD data indicated that increased magnesium content in the Mg- and Sr-co-substituted scaffolds was related to an increased proportion of the whitlockite (WH) phase in the biphasic hydroxyapatite (HAp)/WH scaffolds. In addition, refinements indicate that Sr2+ ions have replaced Ca2+ sites in the WH phase. Furthermore, PCL-coated Mg-substituted and Sr- and Mg-co-substituted scaffolds, with the HAp:WH wt. ratio of 90:10 were prepared by vacuum impregnation. Results of compression tests showed a positive impact of the WH phase and PCL coating on the mechanical properties of scaffolds. Human mesenchymal stem cells (hMSCs) were cultured on composite scaffolds in an osteogenic medium for 21 days. Immunohistochemical staining showed that Mg-Sr-CaP/PCL scaffold exhibited higher expression of collagen type I than the Mg-CaP/PCL scaffold, indicating the positive effect of Sr2+ ions on the differentiation of hMSCs, in concordance with histology results. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis confirmed an early stage of osteogenic differentiation.This research was funded by the Croatian Science Foundation (project IP-2014-09-3752) and the European Structural and Investments Funds (grant KK.01.1.1.07.0014.). The authors thank Inga Urli, Faculty of Science, University of Zagreb for providing Hek293 and hMSC cells. Compression experiments were carried out at the Centre for Biomaterials and Tissue Engineering (CBIT), Universitat Politecnica de Valencia, Valencia, Spain under the PID2019-106000RB-C21/AEI/10.13039/501100011033 project. The authors would like to thank Jorge Mas-Estelles for his generous assistance.Bauer, L.; Antunovic, M.; Gallego-Ferrer, G.; Ivankovic, M.; Ivankovic, H. (2021). PCL-Coated Multi-Substituted Calcium Phosphate Bone Scaffolds with Enhanced Properties. Materials. 14(16):1-19. https://doi.org/10.3390/ma14164403S119141

Single‐Molecule Manipulation in Zero‐Mode Waveguides

The mechanobiology of receptor–ligand interactions and force‐induced enzymatic turnover can be revealed by simultaneous measurements of force response and fluorescence. Investigations at physiologically relevant high labeled substrate concentrations require total internal reflection fluorescence microscopy or zero mode waveguides (ZMWs), which are difficult to combine with atomic force microscopy (AFM). A fully automatized workflow is established to manipulate single molecules inside ZMWs autonomously with noninvasive cantilever tip localization. A protein model system comprising a receptor–ligand pair of streptavidin blocked with a biotin‐tagged ligand is introduced. The ligand is pulled out of streptavidin by an AFM cantilever leaving the receptor vacant for reoccupation by freely diffusing fluorescently labeled biotin, which can be detected in single‐molecule fluorescence concurrently to study rebinding rates. This work illustrates the potential of the seamless fusion of these two powerful single‐molecule techniques