| 141. |
- Abbas, Zareen, 1962, et al.
(författare)
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Monte Carlo simulation of the dissociation constants of CO2 in 0 to 1 molal sodium chloride between 0 and 25 °C
- 2013
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 150:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Stoichiometric dissociation constants of the carbon dioxide system in NaCl solution between 0 and 1 mol and 0 to 25 °C were estimated by Monte Carlo (MC) simulations, and compared with Pitzer calculations and experimental measurements. The MC simulations used experimentally determined dielectric constants of water at different temperatures, and optimal agreement with the experimental data and Pitzer calculations was achieved by adjusting the ionic radii. This simple procedure resulted in effective ionic radii which were further used to simulate the activity coefficients of salt mixtures. The first and second stoichiometric dissociation constants of carbonic acid in NaCl solution (pK1⁎ and pK2⁎) were estimated from the MC-derived activity coefficients of mixed salts in NaCl. The MC results are in good agreement with the experimental data as well as with the Pitzer calculations. This study shows that Monte Carlo simulations in the temperature and ionic strength range relevant to seawater can provide pK values of the same quality as Pitzer calculations, and constitutes the first step in developing a temperature-dependent MC model for seawater. While MC calculations require greater computing resources, the number of parameters derived by fitting to thermodynamic data is substantially smaller than for Pitzer calculations.
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| 142. |
- Abbas, Zareen, 1962, et al.
(författare)
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Monte Carlo Simulations of Salt Solutions: Exploring the Validity of Primitive Models
- 2009
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 113:17, s. 5905-5916
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Tidskriftsartikel (refereegranskat)abstract
- An extensive series of Monte Carlo (MC) simulations were performed in order to explore the validity of simple primitive models of electrolyte solutions and in particular the effect of ion size asymmetry on the bulk thermodynamic properties of real salt solutions. Ionic activity and osmotic coefficients were calculated for 1:1, 2:1, and 3:1 electrolytes by using the unrestricted primitive model (UPM); i.e., ions are considered as charged hard spheres of different sizes dissolved in a dielectric continuum. Mean ionic activity and osmotic coefficients calculated by the MC simulations were fitted simultaneously to the experimental data by adjusting only the cation radius while keeping the anion radius fixed at its crystallographic value. Ionic radii were further optimized by systematically varying the cation and anion radii at a fixed sum of ionic radii. The success of this approach is found to be highly salt specific. For example, experimental data (mean ionic activity and osmotic coefficients) of salts which are usually considered as dissociated such as HCl, HBr, LiCl, LiBr, LiClO4, and KOH were successfully fitted up to 1.9, 2.5, 1.9, 3, 2.5, and 4.5 M concentrations, respectively. In the case of partially dissociated salts such as NaCl, the successful fits were only obtained in a more restricted concentration range. Consistent sets of the best fitted cation radii were obtained for acids, alkali, and alkaline earth halides. A list of recommended ionic radii is also provided. The reliability of the optimized ionic radii was further tested in simulations of the osmotic coefficients of LiCl−NaCl−KCl salt mixtures. A very good agreement between the simulated and experimental data was obtained up to ionic strength of 4.5 M.
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| 143. |
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| 144. |
- Abbas, Zareen, 1962, et al.
(författare)
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Size-Dependent Surface Charging of Nanoparticles
- 2008
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Ingår i: J of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:15, s. 5715-5723
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Tidskriftsartikel (refereegranskat)abstract
- Experimental interest in the possible curvature dependence of particle charging in electrolyte solutions is subjected to theoretical analysis. The corrected Debye-Hückel theory of surface complexation (CDH-SC) and Monte Carlo (MC) simulation are applied to investigate the dependence of surface charging of metal oxide nanoparticles on their size. Surface charge density versus pH curves for spherical metal oxide nanoparticles in the size range of 1-100 nm are calculated at various concentrations of a background electrolyte. The surface charge density of a nanoparticle is found to be highly size-dependent. As the particle diameter drops to below 10 nm there is considerable increase in the surface charge density as compared with the limiting values seen for particles larger than 20 nm. This increase in the surface charge density is due to the enhanced screening efficiency of the electrolyte solution around small nanoparticles, which is most prominent for particles of diameters less than 5 nm. For example, the surface charge densities calculated for 2 nm particles at 0.1 M concentration are very close to the values obtained for 100 nm particles at 1 M concentration. These predictions of the dependence of surface charge density on particle size by the CDH-SC theory are in very good agreement with the corresponding results obtained by the MC simulations. A shift in the pH value of the point of zero charge toward higher pH values is also seen with a decreasing particle size.
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| 145. |
- Abbas, Zareen, 1962, et al.
(författare)
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Synthesis, characterization and particle size distribution of TiO2 colloidal nanoparticles
- 2011
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 384:1-3, s. 254-261
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles of controlled size, well defined shape, pure phase and of clean surfaces are ideal model systems to investigate surface/interfacial reactions. In this study we have explored the possibility of synthesizing TiO2 nanoparticles in the size range of 7–20 nm under well controlled experimental conditions. A simple method based on the hydrolysis of TiCl4 was used to obtain particles having surfaces free from organics. Stable dispersions of TiO2 nanoparticles of various sizes were obtained by optimizing the reaction/dialysis time and temperature. The synthesized TiO2 particles were found to be predominantly of anatase phase and narrow particle size distributions were obtained. The TiO2 particles were characterized with respect to their phase, size and shape by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Particle size distribution in a colloidal dispersion was obtained by the electrospray scanning mobility particle sizer (ES-SMPS) method and compared with an average particle size determined from dynamic light scattering (DLS). The average particle sizes obtained by the DLS and ES-SMPS methods were in good agreement, while a primary particle size of 4 nm was found in X-ray diffraction irrespective of the particle size in solution. Early stages of the nucleation process were monitored by the ES-SMPS method. These results show that small particles of 4–5 nm are initially formed and it is highly likely that large particles are formed due to aggregation of primary particles.
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| 146. |
- Abbaspoor, Zahra, et al.
(författare)
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Translation and cultural adaptation of the Childbirth Experience Questionnaire (CEQ) in Iran
- 2019
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Ingår i: Iranian Journal of Nursing and Midwifery Research. - 1735-9066 .- 2228-5504. ; 24:4, s. 296-300
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Iranian Journal of Nursing and Midwifery Research Published by Wolters Kluwer - Medknow. A standardized method to measure and quantify women's birth experiences is required to study satisfaction of childbirth care. Therefore, this study aimed to translate and culturally adapt the Childbirth Experience Questionnaire (CEQ) for use in Iran. Materials and Methods: This was a cross-sectional study including 203 women who attended 2 hospitals and 2 health centers and met the inclusion criteria in Ahvaz city, between February 2013 and June 2014. After forward and backward translation of the Swedish CEQ into Persian language, content validity was assessed by an expert panel. Scale reliability (internal consistency and test-retest reliability) was assessed with respect to the psychometric properties of the scale. Results: Minor cultural differences were identified and resolved during the translation process. One item was excluded. The intraclass correlation coefficient ranging from 0.63 to 0.90 was satisfactory. Conclusions: The Persian version of the CEQ appears to be valid and reliable; hence, it can be an effective tool in designing childbirth experience interventions and also childbirth care and education interventions for the promotion of positive childbirth experience in Iranian women.
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| 147. |
- Abbaspour, S., et al.
(författare)
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Real-Time and Offline Evaluation of Myoelectric Pattern Recognition for the Decoding of Hand Movements
- 2021
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 21:16
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Tidskriftsartikel (refereegranskat)abstract
- Pattern recognition algorithms have been widely used to map surface electromyographic signals to target movements as a source for prosthetic control. However, most investigations have been conducted offline by performing the analysis on pre-recorded datasets. While real-time data analysis (i.e., classification when new data becomes available, with limits on latency under 200-300 milliseconds) plays an important role in the control of prosthetics, less knowledge has been gained with respect to real-time performance. Recent literature has underscored the differences between offline classification accuracy, the most common performance metric, and the usability of upper limb prostheses. Therefore, a comparative offline and real-time performance analysis between common algorithms had yet to be performed. In this study, we investigated the offline and real-time performance of nine different classification algorithms, decoding ten individual hand and wrist movements. Surface myoelectric signals were recorded from fifteen able-bodied subjects while performing the ten movements. The offline decoding demonstrated that linear discriminant analysis (LDA) and maximum likelihood estimation (MLE) significantly (p < 0.05) outperformed other classifiers, with an average classification accuracy of above 97%. On the other hand, the real-time investigation revealed that, in addition to the LDA and MLE, multilayer perceptron also outperformed the other algorithms and achieved a classification accuracy and completion rate of above 68% and 69%, respectively.
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| 148. |
- Abbaszadehbanaeiyan, Amin, et al.
(författare)
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Design and fabrication of high-throughput application-specific microfluidic devices for studying single-cell responses to extracellular perturbations
- 2013
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Ingår i: Proc. SPIE 8765, Bio-MEMS and Medical Microdevices, 87650K. ; 8765
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Konferensbidrag (refereegranskat)abstract
- Single cell analysis techniques provide a unique opportunity of determining the intercellular heterogeneity in a cell population, which due to genotype variations and different physiological states of the cells i.e. size, shape and age, cannot be retrieved from averaged cell population values. In order to obtain high-value quantitative data from single-cell experiments it is important to have experimental platforms enabling high-throughput studies. Here, we present a microfluidic chip, which is capable of capturing individual cells in suspension inside separate traps. The device consists of three adjacent microchannels with separate inlets and outlets, laterally connected through the V-shaped traps. Vshaped traps, with openings smaller than the size of a single cell, are fabricated in the middle (main) channel perpendicular to the flow direction. Cells are guided into the wells by streamlines of the flows and are kept still at the bottom of the traps. Cells can then be exposed to extracellular stimuli either in the main or the side channels. Microchannels and traps of different sizes can be fabricated in polydimethylsiloxane (PDMS), offering the possibility of independent studies on cellular responses with different cell types and different extracellular environmental changes. We believe that this versatile high-throughput cell trapping approach will contribute to further development of the current knowledge and information acquired from single-cell studies and provide valuable statistical experimental data required for systems biology. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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| 149. |
- Abbaszadehbanaeiyan, Amin, 1983, et al.
(författare)
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Hydrodynamic Cell Trapping for High Throughput Single-Cell Applications
- 2013
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Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 4:4, s. 414-430
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to conduct complete cell assays under a precisely controlled environment while consuming minor amounts of chemicals and precious drugs have made microfluidics an interesting candidate for quantitative single-cell studies. Here, we present an application-specific microfluidic device, cellcomb, capable of conducting high-throughput single-cell experiments. The system employs pure hydrodynamic forces for easy cell trapping and is readily fabricated in polydimethylsiloxane (PDMS) using soft lithography techniques. The cell-trapping array consists of V-shaped pockets designed to accommodate up to six Saccharomyces cerevisiae (yeast cells) with the average diameter of 4 μm. We used this platform to monitor the impact of flow rate modulation on the arsenite (As(III)) uptake in yeast. Redistribution of a green fluorescent protein (GFP)-tagged version of the heat shock protein Hsp104 was followed over time as read out. Results showed a clear reverse correlation between the arsenite uptake and three different adjusted low = 25 nL min−1, moderate = 50 nL min−1, and high = 100 nL min−1 flow rates. We consider the presented device as the first building block of a future integrated application-specific cell-trapping array that can be used to conduct complete single cell experiments on different cell types.
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| 150. |
- Abbaszadehbanaeiyan, Amin, et al.
(författare)
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Liver-lobule-on-a-chip microfluidic device for long-term maintenance of human hepatocytes
- 2017
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Ingår i: Presented at EMBEC’17 & NBC’17 (conference), 11-15 juni 2017, Tampere, Finland.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The pressing need for in vitro micro-physiological platforms for drug discovery and development has given rise to the emergence of organs-on-a-chip (OOC) microfluidic devices. The possibility of reproducing the native niche of each organ in a dynamic microenvironment offers advantages over current static 2D and 3D cell culture techniques. Constant removal of waste products and metabolites from the culture while providing a continuous flow of growth media is one of the major benefits of dynamic OOC systems. Additionally, physiological flow conditions can be introduced to the system allowing for reproduction of the vasculature parameters of organs in vitro. The liver is the main organ in the body for drug clearance and detoxification. The key role of the liver in the metabolism system of the human body makes it an interesting target organ to mimic in the dynamic OOC systems. Here we present a PDMS-based liver-lobule-on-a-chip microfluidic device designed to reproduce the geometrical as well as convection-diffusion mass transport aspects of the classic liver lobule. We cultured human induced pluripotent stem cell (hiPSC)-derived hepatocytes (CDI) in honeycomb cell culture chambers with involvement of two different extra-cellular matrix (ECM) materials. In the first approach, microfluidic devices were pre-treated with rat-tail collagen I and cell suspension was seeded in the devices afterwards. Cells were seeded in the devices with the supplemented plating medium (RPMI) and culture for 5 days. The medium was changed to the supplemented mainte-nance media (RPMI) thereafter and replaced every other day. In the second approach, we mixed the cell suspension with 20% diluted GeltrexTM (15 mg/ml) in a 1:1 ratio. Cells were seeded in the supplemented plating media (RPMI) and were kept under conditions identical to approach one during the hepatocyte maturation period. After day 5, however, the formulation of maintenance media was changed to supplemented DMEM/F12. Cultures were kept viable and functional for at least three weeks. In both scenarios cells formed 3D tissue-like structures and formation of bile canaliculi network was observed in the devices versus 2D static cultures. The compatibility of the device for drug toxicity applications and multi-cellular in vitro organotype construction is currently under exploration.
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