Effect of ring-shaped clusters on magnetic hyperthermia: modelling approach

2021 ◽  
Vol 379 (2205) ◽  
pp. 20200316
Author(s):  
Ali F. Abu-Bakr ◽  
Andrey Yu. Zubarev
Keyword(s):  
Composite System ◽  
Magnetic Interaction ◽  
Magnetic Hyperthermia ◽  
Theme Issue ◽  
Host Medium ◽  
Closed Ring ◽  
Heterogeneous Structures ◽  
Kinetics Of ◽  
Debye Equation ◽  
Modelling Approach

Experiments demonstrate that magnetic nanoparticles, embedded in a tissue, very often form heterogeneous structures of various shapes and topologies. These structures (clusters) can significantly affect macroscopical properties of the composite system, in part its ability to generate heat under an alternating magnetic field (so-called magnetic hyperthermia). If the energy of magnetic interaction between the particles significantly exceeds the thermal energy of the system, the particles can form the closed ring-shaped clusters. In this work, we propose a relatively simple model of the heat production by the particles united in the ‘ring’ and immobilized in a host medium. Mathematically, this model is based on the phenomenological Debye equation of kinetics of the particles remagnetization. Magnetic interaction between all particles in the cluster is taken into account. Our results show that the appearance of the clusters can significantly decrease the thermal effect. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.

scholarly journals On the theory of magnetic hyperthermia: clusterization of nanoparticles

2020 ◽  
Vol 378 (2171) ◽  
pp. 20190251 ◽  
Author(s):  
Ali F. Abu-Bakr ◽  
Andrey Yu. Zubarev
Keyword(s):  
Mathematical Modelling ◽  
Magnetic Anisotropy ◽  
Heat Production ◽  
Theoretical Study ◽  
Magnetic Hyperthermia ◽  
Strong Anisotropy ◽  
Theme Issue ◽  
Weak Anisotropy ◽  
Host Medium ◽  
Ferromagnetic Particles

Experiments show that clusters consisting of nano-sized ferromagnetic particles strongly affect the intensity of heat production during magnetic hyperthermia. In this paper, a theoretical study and mathematical modelling of the heat production by clusters of single-domain ferromagnetic particles, immobilized in a host medium, are presented. Two situations of strong and weak magnetic anisotropy of the particles are considered. Our results show that, in the case of strong anisotropy, the clusterization weakens the thermal effect, whereas in the case of weak anisotropy it enhances it. This article is part of the theme issue ‘Patterns in soft and biological matters'.

Structural analysis of calcium reactive hydride composite for solid state hydrogen storage

2014 ◽  
Vol 47 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Fahim Karimi ◽  
P. Klaus Pranzas ◽  
Armin Hoell ◽  
Ulla Vainio ◽  
Edmund Welter ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Composite System ◽  
Structural Investigation ◽  
Sorption Kinetics ◽  
Hydrogen Storage Material ◽  
X Ray ◽  
X Ray Scattering ◽  
Diffusion Paths ◽  
X Ray Absorption ◽  
Kinetics Of

Owing to a theoretical hydrogen storage capacity of 10.5 wt% H2, Ca(BH4)2+MgH2, the so-called calcium reactive hydride composite (Ca-RHC), has a great potential as a hydrogen storage material. However, its dehydrogenation temperature (∼623 K) is too high for any mobile applications. By addition of 10 mol% of NbF5into Ca(BH4)2+MgH2, a decrease of the dehydrogenation onset temperature by ∼120 K is observed. In order to understand the reasons behind this desorption temperature decrement two sets of samples [Ca(BH4)2+MgH2and Ca(BH4)2+MgH2+0.1NbF5] in different hydrogenation states, were prepared. The structural investigation of the above mentioned sets of samples by means of volumetric measurements, anomalous small-angle X-ray scattering (ASAXS) and X-ray absorption spectroscopy (XAS) is reported here. The XAS results show that after the milling procedure NbB2is formed and remains stable upon further de/rehydrogenation cycling. The results of Nb ASAXS point to nanometric spherical NbB2particles distributed in the hydride matrix, with a mean diameter of ∼10 nm. Results from Ca ASAXS indicate Ca-containing nanostructures in the Ca-RHC+0.1NbF5samples to be ∼50% finer compared to those without additive. Thus, a higher reaction surface area and shorter diffusion paths for the constituents are concluded to be important contributions to the catalytic effect of an NbF5additive on the hydrogen sorption kinetics of the Ca(BH4)2+MgH2composite system.

A kinetic model for magnetostriction of a ferrogel with physical networking

2021 ◽  
Vol 379 (2205) ◽  
pp. 20200315 ◽  
Author(s):  
A. P. Safronov ◽  
A. Yu. Zubarev ◽  
E. A. Mikhnevich ◽  
E. V. Rusinova
Keyword(s):  
Magnetic Particles ◽  
Guar Gum ◽  
Loss Modulus ◽  
Liquid Droplet ◽  
Mechanical Analysis ◽  
Strontium Hexaferrite ◽  
Theme Issue ◽  
Natural Polysaccharide ◽  
Order Of Magnitude ◽  
Kinetics Of

Kinetics of magnetostriction of ferrogel with physical networking based on natural polysaccharide guar gum with embedded strontium hexaferrite magnetic particles were studied in the uniform magnetic field 420 mT. An ellipsoidal sample was elongated by 37% along the applied field and contracted by 15% in the transverse direction, while its volume was kept constant. The characteristic time of magnetostriction was 440 s. Dynamic mechanical analysis in an oscillatory mode showed that the deformation of ferrogel is mostly elastic rather than viscous. Its storage modulus was almost constant in a frequency range of 0.1–100 Hz and by at least an order of magnitude larger than the loss modulus. Meanwhile, a developed theoretical model based on the elasto-viscous behaviour of the ferrogel failed to estimate correctly the experimental value of its magnetostriction. Calculated values of the elongation of ferrogel in the field were several orders of magnitude lower than those observed in the experiment for the ferrogel with physical networking. Consistency between the experiment and the theory was achieved using the alternative consideration based on the deformation of a liquid droplet of ferrofluid. The applicability of such an approach was discussed concerning structural relaxation properties of the ferrogel with physical networking. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.

A dynamic scaffolding mechanism for rhodopsin and transducin interaction in vertebrate vision

2011 ◽  
Vol 440 (2) ◽  
pp. 263-271 ◽  
Author(s):  
Daniele Dell'Orco ◽  
Karl-Wilhelm Koch
Keyword(s):  
Supramolecular Organization ◽  
Coupling Mechanism ◽  
Free Diffusion ◽  
Cone Cells ◽  
Light Stimuli ◽  
Systems Modelling ◽  
Monomeric Proteins ◽  
Kinetics Of ◽  
Phototransduction Cascade ◽  
Modelling Approach

The early steps in vertebrate vision require fast interactions between Rh (rhodopsin) and Gt (transducin), which are classically described by a collisional coupling mechanism driven by the free diffusion of monomeric proteins on the disc membranes of rod and cone cells. Recent findings, however, point to a very low mobility for Rh and support a substantially different supramolecular organization. Moreover, Rh–Gt interactions seem to possibly occur even prior to light stimuli, which is also difficult to reconcile with the classical scenario. We investigated the kinetics of interaction between native Rh and Gt in different conditions by surface plasmon resonance and analysed the results in the general physiological context by employing a holistic systems modelling approach. The results from the present study point to a mechanism that is intermediate between pure collisional coupling and physical scaffolding. Such a ‘dynamic scaffolding’, in which prevalently dimeric Rh and Gt interact in the dark by forming transient complexes (~25% of Gt is precoupled to Rh), does not slow down the phototransduction cascade, but is compatible with the observed photoresponses on a broad scale of light stimuli. We conclude that Rh molecules and Rh–Gt complexes can both absorb photons and trigger the visual cascade.

Numerical Modelling of the Tensile Behaviour of BFRCM Strips

2019 ◽  
Vol 817 ◽  
pp. 15-22 ◽  
Author(s):  
Alessia Monaco ◽  
Jennifer D'Anna ◽  
Maria Concetta Oddo ◽  
Giovanni Minafò ◽  
Lidia La Mendola
Keyword(s):  
Composite System ◽  
Numerical Models ◽  
Tensile Behaviour ◽  
Basalt Fibre ◽  
Cementitious Matrix ◽  
Levels Of Detail ◽  
Number Of Layers ◽  
Natural Composite ◽  
Different Levels ◽  
Modelling Approach

This paper aims at investigating the tensile behaviour of basalt fibres on cementitious matrix for the strengthening of masonry structures. The use of Basalt Fibre Reinforced Cementitious Matrix (BFRCM) is favourably considered by the scientific community because it represents a natural composite material with high compatibility with stone and masonry substrate. The study is developed through the generation of Finite Element (FE) models capable of reproducing the tensile behaviour of BFRCM strips with different number of layers of grid. For the scope, the micro-modelling approach is adopted assuming different levels of detail for the simulation of the interface constitutive behaviour. Fibre and substrate are modelled separately and the interface between the two components is simulated by introducing numerical contact properties for reproducing the perfect bond condition, on one hand, and the cohesive tangential slip, on the other hand. The damage of the composite system is investigated using proper damage numerical models at the interface.

scholarly journals Effect of internal chain-like structures on magnetic hyperthermia in non-liquid media

2019 ◽  
Vol 377 (2143) ◽  
pp. 20180213 ◽  
Author(s):  
Andrey Yu. Zubarev
Keyword(s):  
Theoretical Study ◽  
Linear Chain ◽  
Particle Diameter ◽  
Magnetic Hyperthermia ◽  
Heating Time ◽  
Theme Issue ◽  
Magnetic Medium ◽  
Internal Structures ◽  
Magnetite Particles ◽  
Process Observation

This paper deals with a theoretical study of the effect of chain-like aggregates on magnetic hyperthermia in systems of single-domain ferromagnetic particles immobilized in a non-magnetic medium. We assume that the particles form linear chain-like aggregates and the characteristic time of the Néel remagnetization is much longer than the time of medium heating (time of process observation). This is applicable to magnetite particles when the particle diameter exceeds 20–25 nm. Our results show that the appearance of the chains significantly decreases the intensity of heat production. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

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