Search results for "Viscosity."
showing 10 items of 537 documents
Field effect in the viscosity of magnetic colloids studied by multi-particle collision dynamics
2019
Abstract Colloidal solutions of magnetic nanoparticles are usually employed when the fluidity and magnetic properties are required at the same time, either in technical or biomedical applications. However, when the magnetic size of the nanoparticles is large enough (>12–15 nm) the colloid may form an equilibrium structure with or without the external magnetic field, which can significantly influence its rheology. Using multi-particle collision dynamics we study the internal structure and viscosity of the magnetic colloids at varying magnitudes of the externally applied field. We show a generalized structural behavior across all studied regimes and an appreciable increase of flow resistance …
The Influence of Crystal Size Distributions on the Rheology of Magmas: New Insights From Analog Experiments
2017
This study examines the influence of particle size distributions on the rheology of particle suspensions by using analogue experiments with spherical glass beads in silicone oil as magma equivalent. The analyses of 274 individual particle-bearing suspensions of varying modality (uni-, bi- tri- and tetramodality), as well as of polymodal suspensions with specific defined skewness and variance, are the first data set of its kind and provide important insights in the relationship between the solid particles of a suspension and its rheological behaviour. Since the relationship between the rheology of particle bearing suspensions and its maximum packing fraction ϕm is well established by several…
An expanded model and application of the combined effect of crystal-size distribution and crystal shape on the relative viscosity of magmas
2018
International audience; This study examines the combined effect of crystal-size distributions (CSD) and crystal shape on the rheology of vesicle free magmatic suspensions and provides the first practical application of an empirical model to estimate the relative effect of crystal content and CSD's on the viscosity of magma directly from textural image analysis of natural rock samples in the form of a user-friendly texture-rheology spreadsheet calculator. We extend and apply established relationships between the maximum packing fraction ϕm of a crystal bearing suspension and both its rheological properties and the polydispersity γ of a CSD. By using analogue rotational rheometric experiments…
Coping with the climate: cuticular hydrocarbon acclimation of ants under constant and fluctuating conditions
2018
International audience; Terrestrial arthropods achieve waterproofing by a layer of cuticular hydrocarbons (CHCs). At the same time, CHCs also serve as communication signals. To maintain waterproofing under different climate conditions, insects adjust the chemical composition of their CHC layer, but this may affect the communication via CHCs. The detailed acclimatory changes of CHCs and how these influence their physical properties are still unknown. Here, we studied acclimation in two closely related ant species with distinct CHC profiles, Myrmica rubra and Myrmica ruginodis, in response to constant or fluctuating temperature and humidity regimes. We measured how acclimation affected CHC co…
Communication versus waterproofing: the physics of insect cuticular hydrocarbons
2019
Understanding the evolution of complex traits is among the major challenges in biology. One such trait is the cuticular hydrocarbon (CHC) layer in insects. It protects against desiccation and provides communication signals, especially in social insects. CHC composition is highly diverse within and across species. To understand the adaptive value of this chemical diversity, we must understand how it affects biological functionality. So far, CHCs received ample research attention, but their physical properties were little studied. We argue that these properties determine their biological functionality, and are vital to understand how CHC composition affects their adaptive value. We investigat…
Non-conventional osmotic solutes (honey and glycerol) improve mass transfer and extend shelf life of hot-air dried red carrots: Kinetics, quality, bi…
2020
The effect of solutes (sucrose, honey and glycerol) on mass transfer kinetics, physico-chemical and biological quality, and shelf life of red carrot slices (RCSs) obtained by hot-air drying at 60 degrees C/6-8 h was studied. RCSs were osmosed for 24 h in sucrose (S), sucrose + honey (SH), honey (H) and sucrose + glycerol (SGL) before drying. Honey and glycerol enhanced the water loss (WL) and solute gain (SG), giving higher values for Peleg's model constants (k(1), WL = 6.9 and 6.5, for H and SGL, respectively; k(1), SG = 92.8 and 73.5, for H and SGL, respectively). Decreased viscosity of osmotic solutions corresponded with the solute effect on WL and SG, reaching equilibrium after 16 h. Di…
Artificial Oral Processing of Extruded Pea Flour Snacks
2021
International audience; The structure of extruded pea flour can affect chewing performances. Our objective was to relate the bolus properties (fragmentation, moisture content and viscosity) of chewed extruded pea snacks to their structure. In order to have control over oral physiological parameters, we opted for an in vitro approach using a chewing simulator, the variables of which were the flow rate of artificial salivary fluid and chewing time. The structure of the extruded pea snacks was characterized by its density and protein solubility in dithioerythritol (DTE), which reflected the amount of protein aggregates cross-linked by disulphide bonds. The particle size distribution and median…
Cellulose ether emulsions as fat source in cocoa creams: Thermorheological properties (flow and viscoelasticity)
2019
Flow behaviour and viscoelastic properties at three different temperatures (20, 45 and 70 °C) of cocoa filling creams have been studied. These creams were composed of cocoa, starch, sugar, skimmed milk powder and non-digestible cellulose ether emulsions as fat source. Two types of methylcelluloses, MC, and two types of hydroxypropyl methylcelluloses, HPMC, with different chemical substitution degrees were employed. Results showed important differences in zero shear viscosity and shear thinning character at room temperature, due to the different internal structure revealed by the viscoelastic moduli spectra. Temperature sweeps of storage modulus showed different temperature gelation dependin…
Screening of durum wheat landraces (Triticum turgidum subsp. durum) for the malting suitability
2018
Abstract Durum (T. turgidum subsp. durum) wheat production worldwide is substantially less than that of common wheat (Triticum aestivum) mainly due to the relatively limited end-users. In order to evaluate malting and brewing suitability, sixteen old durum wheat landraces were malted at micro scale. Results show malt quality parameters in the range 78.2–85.9% for the extract, 72.9–80.9% for the fermentability, 3–5 EBC units for the colour, 0.49–0.79% dm for water-extractable arabinoxylans and 0.043–0.059% dm for the β-glucans. Regarding wort viscosity (1.53–1.92 mPa s), we found negative correlation with endo-1,4-β-D-xylanase, positive correlation with endo-β-glucanases and soluble proteins…
Monitoring of rheologic variables during postoperative high-dose brachytherapy for uterine cancer.
2004
Oxygenation of tumor tissue has recently been assed an important prerequisite for the effectiveness of radiotherapy in cervical cancer. Hyperviscosity is a common phenomenon in malignancy and a cause of reduced oxygen transport capacity that would favour tissue hypoxia. Hemorheological variables were serially tested preoperatively, during four cycles of fractionated adjuvant IR192 HDR after loading radiation (HDR-AL) of the vaginal vault (weekly intervals), and 6 months postoperatively in patients with cervical (n=12) and endometrial cancer (n=26). Women who were scheduled for benign tumor surgery served as controls (n=29). Preoperatively, in cervical and endometrial cancer patients, mean …