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field flow fractionation

Laurent Chevillard
Motivated by the modeling of the temporal structure of the velocity field in a highly turbulent flow, we propose and study a linear stochastic differential equation that involves the ingredients of an Ornstein-Uhlenbeck process, supplemented by a fractional Gaussian noise, of parameter H, regularized over a (small) time scale ε>0. A peculiar correlation between these two plays a key role in the establishment of the statistical properties of its solution. We show that this solution reaches a stationary regime, which marginals, including variance and increment variance, remain bounded when ε→0...
September 2017: Physical Review. E
Tamal Roy, Kai Szuttor, Jens Smiatek, Christian Holm, Steffen Hardt
We study the stretching of a surface-tethered polyelectrolyte confined between parallel surfaces under the application of a dc electric field. We explore the influence of the electric-field strength, the length of the polyelectrolyte, and the degree of confinement on the conformation of the polyelectrolyte by single-molecule experiments and coarse-grained coupled lattice-Boltzmann molecular-dynamics simulations. The fractional extension of the polyelectrolyte is found to be a universal function of the product of the applied electric field and the molecular contour length, which is explained by simple scaling arguments...
September 2017: Physical Review. E
Haiou Qu, Jiang Wang, Yong Wu, Jiwen Zheng, Yellela S R Krishnaiah, Mohammad Absar, Stephanie Choi, Muhammad Ashraf, Celia N Cruz, Xiaoming Xu
Commonly used characterization techniques such as cryogenic-transmission electron microscopy (cryo-TEM) and batch-mode dynamic light scattering (DLS) are either time consuming or unable to offer high resolution to discern the poly-dispersity of complex drug products like cyclosporine ophthalmic emulsions. Here, a size-based separation and characterization method for globule size distribution using an asymmetric flow field flow fractionation (AF4) is reported for comparative assessment of cyclosporine ophthalmic emulsion drug products (model formulation) with a wide size span and poly-dispersity...
January 13, 2018: International Journal of Pharmaceutics
Rafael Pinilla, Leise Riber, Søren J Sørensen
The study of horizontal gene transfer (HGT) in microbial communities has been revolutionized by significant advances in cultivation-independent methods based on fluorescence reporter gene technologies. Recently, the combination of these novel approaches with flow cytometry has presented itself as one of the most powerful tools to study the spread of mobile genetic elements (MGEs) in the environment. However, the use of fluorescent markers like green fluorescent protein (GFP) and mCherry is limited by environmental constraints that affect the correct maturation of their fluorophores, such as oxygen availability and pH levels...
January 12, 2018: Applied and Environmental Microbiology
Arnab Mukherjee, Vincent A Hackley
Cellulose nanocrystals (CNCs) are renewable, naturally derived polymeric nanomaterials receiving substantial attention for a wide range of potential applications. The recent availability of high quality reference materials will facilitate the development and validation of measurement methods needed to advance the scientific and commercial use of CNCs. In the present study, we demonstrate an optimized method to fractionate CNCs with narrow size dispersion based on asymmetrical-flow field-flow fractionation (AF4) coupled with on-line multi-angle light scattering (MALS), dynamic light scattering (DLS), and differential refractometry (dRI)...
January 11, 2018: Analyst
Aniuska Becerra-Artiles, Tessa Santoro, Lawrence J Stern
BACKGROUND: Human herpesvirus 6 (HHV-6A and HHV-6B) infection of cell cultures can be measured by different methods, including immunofluorescence microscopy, flow cytometry, or quantification of virus DNA by qPCR. These methods are reliable and sensitive but require long processing times and can be costly. Another method used in the field relies on the identification of enlarged cells in the culture; this method requires little sample processing and is relatively fast. However, visual inspection of cell cultures can be subjective and it can be difficult to establish clear criteria to decide if a cell is enlarged...
January 5, 2018: Virology Journal
Dajun Sun, Rodney Rouse, Vikram Patel, Yong Wu, Jiwen Zheng, Alokita Karmakar, Anil K Patri, Priyanka Chitranshi, David Keire, Jia Ma, Wenlei Jiang
The objective of this study was to evaluate physicochemical equivalence between brand (i.e., Ferrlecit) and generic sodium ferric gluconate (SFG) in sucrose injection by conducting a series of comparative in vitro characterizations using advanced analytical techniques. The elemental iron and carbon content, thermal properties, viscosity, particle size, zeta potential, sedimentation coefficient, and molecular weight were determined. There was no noticeable difference between brand and generic SFG in sucrose injection for the above physical parameters evaluated, except for the sedimentation coefficient determined by sedimentation velocity analytical ultracentrifugation (SV-AUC) and molecular weight by asymmetric field flow fractionation-multi-angle light scattering (AFFF-MALS)...
January 5, 2018: Nanomaterials
Teerawat Panyabut, Natnicha Sirirat, Atitaya Siripinyanond
Electrothermal atomic absorption spectrometry (ETAAS) was applied to investigate the atomization behaviors of gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) in order to relate with particle size information. At various atomization temperatures from 1400 °C to 2200 °C, the time-dependent atomic absorption peak profiles of AuNPs and AgNPs with varying sizes from 5 nm to 100 nm were examined. With increasing particle size, the maximum absorbance was observed at the longer time. The time at maximum absorbance was found to linearly increase with increasing particle size, suggesting that ETAAS can be applied to provide the size information of nanoparticles...
February 13, 2018: Analytica Chimica Acta
Malte Renz, Christian Wunder
Photoactivatable fluorescent proteins (PA-FPs) have been widely used to assess the dynamics of cell biological processes. In addition, PA-FPs enabled single-molecule based super-resolution imaging (photoactivated localization microscopy) and thereby provided unprecedented structural insight. For the lack of tools, however, the fraction of PA-FPs that is, actually being switched on to fluoresce, that is, the photoactivation efficiency, has been difficult to assess. Uncertainty about photoactivation efficiency has hampered an understanding of the absolute amount of PA-FPs, that is, being examined...
December 29, 2017: Cytometry. Part A: the Journal of the International Society for Analytical Cytology
Francisco A H Fonseca, Maria Cristina Izar, Ieda M L Maugeri, Otavio Berwanger, Lucas P Damiani, Ibraim M Pinto, Gilberto Szarf, Carolina N França, Henrique T Bianco, Flavio T Moreira, Adriano Caixeta, Claudia M R Alves, Aline Soriano Lopes, Aline Klassen, Marina F M Tavares, Henrique A Fonseca, Antonio C C Carvalho
BACKGROUND: Early reperfusion of the occluded coronary artery during acute myocardial infarction is considered crucial for reduction of infarcted mass and recovery of ventricular function. Effective microcirculation and the balance between protective and harmful lymphocytes may have roles in reperfusion injury and may affect final ventricular remodeling. METHODS/DESIGN: BATTLE-AMI is an open-label, randomized trial comparing the effects of four therapeutic strategies (rosuvastatin/ticagrelor, rosuvastatin/clopidogrel, simvastatin plus ezetimibe/ticagrelor, or simvastatin plus ezetimibe/clopidogrel) on infarcted mass and left ventricular ejection fraction (LVEF) (blinded endpoints) in patients with ST-segment elevation myocardial infarction submitted to fibrinolytic therapy before coronary angiogram (pharmacoinvasive strategy)...
December 19, 2017: Trials
Claudia Zielke, Catalina Fuentes, Lennart Piculell, Lars Nilsson
Most polymers generally have complex characteristics. Analysis and understanding of these characteristics is crucial as they, for instance, influence functionality. Separation and analysis of samples of polymers, biopolymers in particular, is challenging since they often display broad distributions in size, structure and molar mass (M) and/or a tendency to form aggregates. Only few analytical techniques are suitable for the task. AF4-MALS-dRI is highly suited for the task, but the analysis can nevertheless be especially challenging for heterogeneous mixtures of polymers that exhibit wide size distributions or aggregation...
December 13, 2017: Journal of Chromatography. A
Hans Bolinsson, Yi Lu, Stephen Hall, Lars Nilsson, Andreas Håkansson
This study suggests a novel method for determination of the channel height in asymmetrical flow field-flow fractionation (AF4), which can be used for calibration of the channel for hydrodynamic radius determinations. The novel method uses an oil-in-water nanoemulsion together with multi angle light scattering (MALS) and elution theory to determine channel height from an AF4 experiment. The method is validated using two orthogonal methods; first, by using standard particle elution experiments and, secondly, by imaging an assembled and carrier liquid filled channel by x-ray computed tomography (XCT)...
December 12, 2017: Journal of Chromatography. A
Guilaume Greyling, Harald Pasch
Charged block copolymer self-assemblies, such as charged micelles, have attracted much attention as versatile drug delivery systems due to their readily tunable characteristics such as size and surface charge. However, current column-based analytical techniques are not suitable to fractionate and comprehensively characterize charged micelles in terms of size, molar mass, chemical composition and morphology. Multidetector thermal field-flow fractionation (ThFFF) is shown to be a unique characterization platform that can be used to characterize charged micelles in terms of size, molar mass, chemical composition and morphology in aqueous mobile phases with various ionic strengths and pH...
December 5, 2017: Journal of Chromatography. A
Anke Urbansky, Pelle Ohlsson, Andreas Lenshof, Fabio Garofalo, Stefan Scheding, Thomas Laurell
Effective separation methods for fractionating blood components are needed for numerous diagnostic and research applications. This paper presents the use of acoustophoresis, an ultrasound based microfluidic separation technology, for label-free, gentle and continuous separation of mononuclear cells (MNCs) from diluted whole blood. Red blood cells (RBCs) and MNCs behave similar in an acoustic standing wave field, compromising acoustic separation of MNC from RBC in standard buffer systems. However, by optimizing the buffer conditions and thereby changing the acoustophoretic mobility of the cells, we were able to enrich MNCs relative to RBCs by a factor of 2,800 with MNC recoveries up to 88%...
December 7, 2017: Scientific Reports
Pierre Bohec, Jérémie Gachelin, Véronique Ollivier, Thibaut Mutin, Xavier Télot, Benoît Ho-Tin-Noé, Sandra Sanfilippo
Purity, limited platelet activation, and preservation of platelet function are important stakes of preparation of platelet concentrates (PC) for clinical use. In fact, contaminating red blood cells and leukocytes, as well as activated and/or poorly functional platelets in PC, represents a risk of poor efficiency and adverse side effects during platelet transfusion. Therefore, optimization of preparation and storage of PC is still an active field of research. Shear-induced platelet activation is an unwanted side effect of the hard-spin (up to 5000g) step of centrifugation-based methods currently used in blood banks to prepare PC from whole blood samples...
December 6, 2017: Platelets
Apostolos Kiaos, Ioannis Tziatzios, Stavros Hadjimiltiades, Charalambos Karvounis, Theodoros D Karamitsos
INTRODUCTION: The purpose of this study was to investigate the accuracy of qualitative stress perfusion cardiac magnetic resonance (CMR) to diagnose ischemia-causing lesions according to different definitions of significant coronary artery disease (CAD), and magnetic field strength. METHODS: We searched PubMed, Web of Science, and the Cochrane Library for studies evaluating diagnostic performance of qualitative stress perfusion CMR for diagnosis of CAD versus coronary angiography or fractional flow reserve (FFR) from inception to 10 September 2017...
November 24, 2017: International Journal of Cardiology
Hongpyo Lee, Yoonho Nam, Ho-Joon Lee, Jung-Jiin Hsu, Roland G Henry, Dong-Hyun Kim
Myelin water fraction (MWF) mapping with a multi-echo gradient echo (mGRE) sequence using complex-value based model fitting approach was recently described, in which the phase of the data plays an important role in the accuracy of the fitting results. Thus, influences coming from the undesirable phase components need to be reduced. Targeted for improved MWF mapping, methods to combat these phase related issues which include offset correction, main magnetic field (B0) inhomogeneity related correction, and flow compensation have been developed...
November 27, 2017: NeuroImage
A A Colbourne, T W Blythe, R Barua, S Lovett, J Mitchell, A J Sederman, L F Gladden
Nuclear magnetic resonance rheology (Rheo-NMR) is a valuable tool for studying the transport of suspended non-colloidal particles, important in many commercial processes. The Rheo-NMR imaging technique directly and quantitatively measures fluid displacement as a function of radial position. However, the high field magnets typically used in these experiments are unsuitable for the industrial environment and significantly hinder the measurement of shear stress. We introduce a low field Rheo-NMR instrument (1H resonance frequency of 10...
November 21, 2017: Journal of Magnetic Resonance
Jaeyeong Choi, Seungho Lee, Javier A Linares-Pastén, Lars Nilsson
In this work, asymmetrical flow field-flow fractionation (AF4) coupled with UV/Vis, multi-angle light scattering (MALS), and differential refractive index (dRI) detectors (AF4-UV-MALS-dRI) was employed for analysis of glutamate decarboxylase (LbGadB) from Lactobacillus brevis (L. brevis). AF4 provided molecular weight (MW) (or size)-based separation of dimer, hexamer, and aggregates of LbGadB. The effect of pH on oligomerization of LbGadB was investigated, and then AF4 results were compared to those from molecular modeling...
November 22, 2017: Analytical and Bioanalytical Chemistry
Giuseppe Giannini, Anna Alekseeva, Annamaria Naggi, Laura Salvini, Lorenzo Tei, Rita De Santis
AvidinOX, the oxidized derivative of Avidin, is a chemically modified glycoprotein, being currently under clinical investigation for targeted delivery of radioactive biotin to inoperable tumors. AvidinOX is produced by 4-hydroxyazobenzene-2-carboxylic acid (HABA)-assisted sodium periodate oxidation of Avidin. The peculiar property of the periodate-generated glycol-split carbohydrate moieties to form Schiff's bases with amino groups of the tissue proteins allows to achieve a tissue half-life of 2 weeks compared to 2 h of native Avidin...
November 22, 2017: Analytical and Bioanalytical Chemistry
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