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field flow fractionation

Yue Wu, Liangfan Zhu, Yun Luo
The blood pump has become a possible solution to heart diseases. For the prevention of device failure and hemocompatibility problems, a rotary pump with suspended bearing is a preferred solution. In our previous work, a novel injection suspension method has been introduced to levitate the rotor. The suspension method is totally passive. This study aims to apply this suspension method to a double-suction pump, and the property of the pump was investigated using computational fluid dynamics (CFD) methods. The flow field of the pump is simulated based on the SST k-ω turbulent model...
July 26, 2017: Artificial Organs
Georg Krebs, Thomas Becker, Martina Gastl
Cereal-based beverages contain a complex mixture of various polymeric macromolecules including polysaccharides, peptides, and polyphenols. The molar mass of polymers and their degradation products affect different technological and especially sensory parameters of beverages. Asymmetrical flow field-flow fractionation (AF4) coupled with multi-angle light scattering (MALS) and refractive index detection (dRI) or UV detection (UV) is a technique for structure and molar mass distribution analysis of macromolecules commonly used for pure compound solutions...
July 22, 2017: Analytical and Bioanalytical Chemistry
Alba María Martínez-Pérez, Xosé Antón Álvarez-Salgado, Javier Arístegui, Mar Nieto-Cid
Despite of the major role ascribed to marine dissolved organic matter (DOM) in the global carbon cycle, the reactivity of this pool in the dark ocean is still poorly understood. Present hypotheses, posed within the size-reactivity continuum (SRC) and the microbial carbon pump (MCP) conceptual frameworks, need further empirical support. Here, we provide field evidence of the soundness of the SRC model. We sampled the high salinity core-of-flow of the Levantine Intermediate Water along its westward route through the entire Mediterranean Sea...
July 18, 2017: Scientific Reports
Guilaume Greyling, Harald Pasch
Multidetector thermal field-flow fractionation (ThFFF) is shown to be a versatile characterisation platform that can be used to characterise hydrophilic polymers in a variety of organic and aqueous solutions with various ionic strengths. It is demonstrated that ThFFF fractionates isotactic and syndiotactic poly(methacrylic acid) (PMAA) as well as poly(2-vinyl pyridine) (P2VP) and poly(4-vinyl pyridine) (P4VP) according to microstructure in organic solvents and that the ionic strength of the mobile phase has no influence on the retention behaviour of the polymers...
July 8, 2017: Journal of Chromatography. A
Tasawar Hayat, Farwa Haider, Taseer Muhammad, Ahmed Alsaedi
Here we are concerned with the Darcy-Forchheimer three-dimensional flow of carbon nanotubes in a rotating frame. Flow is generated by stretching of the surface. Xue model is adopted for nanofluid transport mechanism. Results for single wall carbon nanotubes (SWCNTs) and multi wall carbon nanotubes are achieved and compared. Flow saturating porous space obeys Darcy-Forchheimer expression. Boundary layer approximations are invoked to simplify governing partial differential system. Optimal homotopy analysis method (OHAM) is utilized for solutions of governing model...
2017: PloS One
Arash Naseri, Sana Shaghaghian, Omid Abouali, Goodarz Ahmadi
In the present study, unsteady airflow patterns and particle deposition in healthy human upper airways were simulated. A realistic 3-D computational model of the upper airways including the vestibule to the end of the trachea was developed using a series of CT scan images of a healthy human. Unsteady simulations of the inhaled and exhaled airflow fields in the upper airway passages were performed by solving the Navier-Stokes and continuity equations for low breathing rates corresponding to low and moderate activities...
July 1, 2017: Respiratory Physiology & Neurobiology
Chad W Cuss, Iain Grant-Weaver, William Shotyk
The smallest colloids exert a disproportionately large influence on colloidal systems owing to their greater surface area; however, the challenges of working in the smaller size range have limited most field-flow fractionation-ICPMS analyses to sizes > ca. 1 kDa. We discuss considerations and present solutions for overcoming these challenges, including high pressures associated with using the 300-Da membrane, calibration in this small size range, accounting for drifting LODs and separation conditions during membrane aging, and optimizing the compromise between resolution and recovery...
July 14, 2017: Analytical Chemistry
Dmitriy A Kara, Vera A Borzova, Kira A Markossian, Sergey Yu Kleymenov, Boris I Kurganov
When studying the anti-aggregation activity of chemical chaperones, a kinetic regime of the aggregation process for selected test systems should be established. To elucidate the mechanism of suppression of protein aggregation by polyamines (putrescine, spermidine) and arginine, we used a test system based on dithiothreitol (DTT)-induced aggregation of bovine serum albumin (BSA) at 45°C (0.1M Na-phosphate buffer, pH 7.0; [DTT]=2mM). The rate-limiting stage of DTT-induced aggregation of BSA under the studied conditions is that of unfolding of the protein molecule...
June 23, 2017: International Journal of Biological Macromolecules
Wenhao Wang, Min Chen, Laodong Guo, Wen-Xiong Wang
The Jiulong River estuary, located in the southeastern China, suffered from metal pollution due to industrial effluent releases. Mixing of effluent and estuarine water may have significantly affected the size distribution of trace metals and their environmental fate. In the present study, colloidal size distribution of organic matter and selected metals were quantified using asymmetric flow field-flow fractionation (AF4) and ICP-MS. We demonstrated a dominance of dissolved metals in the 1-10kDa fraction, and metals such as Cu, Zn, Ni, Co, Pb, Cd and Mn were mostly regulated by terrestrial fulvic acid...
June 19, 2017: Science of the Total Environment
Vera A Borzova, Kira A Markossian, Sergey Yu Kleymenov, Boris I Kurganov
Chemical chaperones including arginine and its derivatives are widely used by biochemists working on the design of agents, which are able to efficiently suppress protein aggregation. To elucidate the mechanisms of anti-aggregation activity of chemical chaperones, methods based on registration of the increment in light scattering intensity must be supplemented with methods for direct detection of the portion of aggregated protein (γagg). For this purpose asymmetric flow field-flow fractionation was used in the present work...
June 21, 2017: Scientific Reports
Andres A Aguirre-Pablo, Meshal K Alarfaj, Er Qiang Li, J F Hernández-Sánchez, Sigurdur T Thoroddsen
We demonstrate the viability of using four low-cost smartphone cameras to perform Tomographic PIV. We use colored shadows to imprint two or three different time-steps on the same image. The back-lighting is accomplished with three sets of differently-colored pulsed LEDs. Each set of Red, Green & Blue LEDs is shone on a diffuser screen facing each of the cameras. We thereby record the RGB-colored shadows of opaque suspended particles, rather than the conventionally used scattered light. We subsequently separate the RGB color channels, to represent the separate times, with preprocessing to minimize noise and cross-talk...
June 16, 2017: Scientific Reports
Diego Gella, Diego Maza, Iker Zuriguel
We experimentally analyze the effect that particle size has on the mass flow rate of a quasi two-dimensional silo discharged by gravity. In a previous work, Janda et al. [Phys. Rev. Lett. 108, 248001 (2012)PRLTAO0031-900710.1103/PhysRevLett.108.248001] introduced a new expression for the mass flow rate based on a detailed experimental analysis of the flow for 1-mm diameter beads. Here, we aim to extend these results by using particles of larger sizes and a variable that was not explicitly included in the proposed expression...
May 2017: Physical Review. E
Upenyu L Muza, Guilaume Greyling, Harald Pasch
Micelles prepared from amphiphilic block copolymers (ABCs) have found numerous applications in pharmaceutical, electronics, environmental, cosmetics, and hygiene industries. These micelles, whether in the pure or mixed micelle form, often exist as multiple morphologies (spherical, cylindrical, worm, or vesicular) in equilibrium with each other. However, none of the current column-based fractionation techniques or any microscopic technique are capable of a successful separation, identification, and quantitation of these complex self-assemblies with regards to morphology, size, molar mass, and chemical composition in one experiment...
June 22, 2017: Analytical Chemistry
Minseong Kim, Hui-Suk Yun, Geun Hyung Kim
Nano/microfibrous structure can induce high cellular activities because of the topological similarity of the extracellular matrix, and thus, are widely used in various tissue regenerative materials. However, the fabrication of a bioceramic (high weight percent)-based 3D microfibrous structure is extremely difficult because of the low process-ability of bioceramics. In addition, three-dimensional (3D) microfibrous structure can induce more realistic cellular behavior when compared to that of 2D fibrous structure...
June 9, 2017: Scientific Reports
Nick Petford, Seyed Mirhadizadeh
The McMurdo Dry Valleys magmatic system, Antarctica, provides a world-class example of pervasive lateral magma flow on a continental scale. The lowermost intrusion (Basement Sill) offers detailed sections through the now frozen particle microstructure of a congested magma slurry. We simulated the flow regime in two and three dimensions using numerical models built on a finite-element mesh derived from field data. The model captures the flow behaviour of the Basement Sill magma over a viscosity range of 1-10(4) Pa s where the higher end (greater than or equal to 10(2) Pa s) corresponds to a magmatic slurry with crystal fractions varying between 30 and 70%...
May 2017: Royal Society Open Science
C Hamngren Blomqvist, T Gebäck, A Altskär, A-M Hermansson, S Gustafsson, N Lorén, E Olsson
We have used Electron Tomography (ET) to reveal the detailed three-dimensional structure of particulate hydrogels, a material category common in e.g. controlled release, food science, battery and biomedical applications. A full understanding of the transport properties of these gels requires knowledge about the pore structure and in particular the interconnectivity in three dimensions, since the transport takes the path of lowest resistance. The image series for ET were recorded using High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM)...
September 2017: Micron: the International Research and Review Journal for Microscopy
Marta Garcia-Cortes, Emma Sotelo González, María T Fernández-Argüelles, Jorge Ruiz Encinar, José M Costa-Fernández, Alfredo Sanz-Medel
Colloidal Mn(2+)-doped ZnS quantum dots (QDs) were synthesized, surface modified, and thoroughly characterized using a pool of complementary techniques. Cap exchange of the native l-cysteine coating of the QDs with dihydrolipoic acid (DHLA) ligands is proposed as a strategy to produce nanocrystals with a strong phosphorescent-type emission and improved aqueous stability. Moreover, such a stable DHLA coating can facilitate further bioconjugation of these QDs to biomolecules using established reagents such as cross-linker molecules...
June 12, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Karel Folens, Gijs Du Laing
Certain specialty elements are indispensable in modern technologies for their particular properties. Yet, potential risks associated to the release of these elements at any stage, remains unknown. Therefore, the dispersion of indium (In), thallium (Tl), tantalum (Ta) and niobium (Nb) in the aquatic environment of the Scheldt estuary (Flanders, Belgium) was studied. Maximum concentrations in intertidal sediments of 101 ± 15 μg kg(-1) for In, 481 ± 37 μg kg(-1) for Tl, 88 ± 19 μg kg(-1) for Ta and 1162 ± 4 μg kg(-1) for Nb appeared on the sampling location closest to the river mouth, i...
May 17, 2017: Chemosphere
Pollyanna Álvaro Spósito, Ana Lia Mazzeti, Caroline de Oliveira Faria, Julio A Urbina, Gwenaelle Pound-Lana, Maria Terezinha Bahia, Vanessa Furtado Mosqueira
Self-emulsifying drug delivery systems (SEDDSs) are lipid-based anhydrous formulations composed of an isotropic mixture of oil, surfactant, and cosurfactants usually presented in gelatin capsules. Ravuconazole (Biopharmaceutics Classification System [BCS] Class II) is a poorly water-soluble drug, and a SEDDS type IIIA was designed to deliver it in a predissolved state, improving dissolution in gastrointestinal fluids. After emulsification, the droplets had mean hydrodynamic diameters <250 nm, zeta potential values in the range of -45 mV to -57 mV, and showed no signs of ravuconazole precipitation...
2017: International Journal of Nanomedicine
Daysi Perez-Rea, Claudia Zielke, Lars Nilsson
Starch and hence, amylopectin is an important biomacromolecule in both the human diet as well as in technical applications. Therefore, accurate and reliable analytical methods for its characterization are needed. A suitable method for analyzing macromolecules with ultra-high molar mass, branched structure and high polydispersity is asymmetric flow field-flow fractionation (AF4) in combination with multiangle light scattering (MALS) detection. In this paper we illustrate how co-elution of low quantities of very large analytes in AF4 may cause disturbances in the MALS data which, in turn, causes an overestimation of the size...
May 12, 2017: Journal of Chromatography. A
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