Increase of magnetic hyperthermia efficiency due to optimal size of particles: theoretical and experimental results

For decades now, conventional sinusoidal signals have been exclusively used in magnetic hyperthermia as the only alternating magnetic field waveform to excite magnetic nanoparticles. However, there are no theoretical nor experimental reasons that prevent the use of different waveforms. The only justifiable motive behind using the sinusoidal signal is its availability and the facility to produce it. Following the development of a configurable alternating magnetic field generator, we aim to study the effect of various waveforms on the heat production effectiveness of magnetic nanoparticles, seeking to prove that signals with more significant slope values, such as the trapezoidal and almost-square signals, allow the nanoparticles to reach higher efficiency in heat generation. Furthermore, we seek to point out that the nanoparticle power dissipation is dependent on the waveform’s slope and not only the frequency, magnetic field intensity and the nanoparticle size. The experimental results showed a remarkably higher heat production performance of the nanoparticles when exposed to trapezoidal and almost-square signals than conventional sinusoidal signals. We conclude that the nanoparticles respond better to the trapezoidal and almost-square signals. On the other hand, the experimental results were used to calculate the normalized power dissipation value and prove its dependency on the slope. However, adjustments are necessary to the coil before proceeding with in vitro and in vivo studies to handle the magnetic fields required.

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Variable formation control of multiple robots via VRc and formation switching to accommodate large heading changes by leader robot

Advances in Mechanical Engineering ◽

10.1177/1687814019857339 ◽

2019 ◽

Vol 11 (6) ◽

pp. 168781401985733

Author(s):

Sung-Gil Wee ◽

Yanyan Dai ◽

Tae Hun Kang ◽

Suk-Gyu Lee

Keyword(s):

Real Time ◽

Collision Avoidance ◽

Formation Control ◽

Experimental Results ◽

Optimal Size ◽

Multiple Robots ◽

Flexible Control ◽

Formation Pattern ◽

Multi Robot

This article describes a novel multi-robot formation control based on a switching technique that allows follower robots to maintain formation when the leader robot’s direction changes rapidly or unexpectedly. The formation pattern is determined using Virtual Robot’s Center of the multi-robot formation. To avoid collision, the formation of robots reformed in optimal size by estimating the distance between the robot and an obstacle in real time. When the leader robot suddenly changes its direction, waypoints of follower robots are switched and the formation is quickly reconstructed. This prevents follower robots from colliding with each other and reduces their radius of movement and allows them to follow the leader robot at higher speed. The proposed method which is inherently a flexible control of multi-robot formation guarantees collision avoidance and prevents sudden changes in waypoints of the system by gradually changing its size. The validity of the proposed method is demonstrated via simulation and experimental results.

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Laser Ignition of Metalized Solid Propellants

Energetic Materials Research, Applications, and New Technologies - Advances in Chemical and Materials Engineering ◽

10.4018/978-1-5225-2903-3.ch004 ◽

2018 ◽

pp. 79-99

Author(s):

Igor G. Assovskiy

Keyword(s):

Laser Pulse ◽

Energetic Material ◽

Critical Density ◽

Thermal Relaxation ◽

Resonant Interaction ◽

Maximum Temperature ◽

Optimal Size ◽

Solid Propellants ◽

Metallic Particles ◽

Size Of Particles

This Chapter presents a theoretical analysis of radiation interaction with a semi-transparent metalized energetic material. Main regularities of the laser pulse interaction with metalized compositions are considered within the framework of non-resonant interaction of radiation with matter. The large variety of metalized composite propellants with different properties of the components, their ratio and dispersion can be divided into two classes, depending on the ratio of the laser irradiation's characteristic time (tr) and the thermal relaxation time of the propellant characteristic cell containing one metal particle (tm). Analysis of the role of metallic particles shape shows that in the case of spherical metal particles, duration of the laser pulse corresponds to the optimal size of particles, heated to a maximum temperature. In the case of flat metallic particles and constant pulse duration, the critical radiation flux and the critical density of ignition energy significantly decrease with decreasing thickness of the particle.

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Optimal Size of Nanoparticles for Magnetic Hyperthermia: A Combined Theoretical and Experimental Study

Advanced Functional Materials ◽

10.1002/adfm.201101243 ◽

2011 ◽

Vol 21 (23) ◽

pp. 4573-4581 ◽

Cited By ~ 227

Author(s):

Boubker Mehdaoui ◽

Anca Meffre ◽

Julian Carrey ◽

Sébastien Lachaize ◽

Lise-Marie Lacroix ◽

...

Keyword(s):

Experimental Study ◽

Magnetic Hyperthermia ◽

Optimal Size

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Diagnostics of Gold Laser Plasmas

International Astronomical Union Colloquium ◽

10.1017/s0252921100108085 ◽

1988 ◽

Vol 102 ◽

pp. 357-360

Author(s):

J.C. Gauthier ◽

J.P. Geindre ◽

P. Monier ◽

C. Chenais-Popovics ◽

N. Tragin ◽

...

Keyword(s):

Experimental Results ◽

Pure Gold ◽

Electronic Temperature ◽

X Ray ◽

Laser Plasmas ◽

Collisional Radiative Model ◽

Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

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Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100051967 ◽

1974 ◽

Vol 32 ◽

pp. 390-391

Author(s):

Y. Harada ◽

T. Goto ◽

H. Koike ◽

T. Someya

Keyword(s):

Field Emission ◽

Phase Contrast ◽

Image Formation ◽

Fresnel Diffraction ◽

Experimental Results ◽

Electron Gun ◽

Scanning Microscopy ◽

Emission Electron ◽

Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

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A new dissociation mode for dislocations in silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108878 ◽

1978 ◽

Vol 36 (1) ◽

pp. 346-347

Author(s):

A. Ourmazd ◽

G.R. Booker ◽

C.J. Humphreys

Keyword(s):

Detailed Examination ◽

Experimental Results ◽

Dislocation Network ◽

Weak Beam ◽

Phosphorus Doped

A (111) phosphorus-doped Si specimen, thinned to give a TEM foil of thickness ∼ 150nm, contained a dislocation network lying on the (111) plane. The dislocation lines were along the three <211> directions and their total Burgers vectors,ḇt, were of the type , each dislocation being of edge character. TEM examination under proper weak-beam conditions seemed initially to show the standard contrast behaviour for such dislocations, indicating some dislocation segments were undissociated (contrast A), while other segments were dissociated to give two Shockley partials separated by approximately 6nm (contrast B) . A more detailed examination, however, revealed that some segments exhibited a third and anomalous contrast behaviour (contrast C), interpreted here as being due to a new dissociation not previously reported. Experimental results obtained for a dislocation along [211] with for the six <220> type reflections using (g,5g) weak-beam conditions are summarised in the table below, together with the relevant values.

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Detection of viruses by electron microscopy: Increased sensitivity by direct micro-ultracentrifugation of samples

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128821 ◽

1987 ◽

Vol 45 ◽

pp. 908-909

Author(s):

Alain R. Trudel ◽

M. Trudel

Keyword(s):

Electron Microscopy ◽

Fold Increase ◽

Observation Time ◽

Clinical Samples ◽

Maximum Speed ◽

Viral Particles ◽

Structural Details ◽

Latex Spheres ◽

Increased Sensitivity ◽

Size Of Particles

AirfugeR (Beckman) direct ultracentrifugation of viral samples on electron microscopy grids offers a rapid way to concentrate viral particles or subunits and facilitate their detection and study. Using the A-100 fixed angle rotor (30°) with a K factor of 19 at maximum speed (95 000 rpm), samples up to 240 μl can be prepared for electron microscopy observation in a few minutes: observation time is decreased and structural details are highlighted. Using latex spheres to calculate the increase in sensitivity compared to the inverted drop procedure, we obtained a 10 to 40 fold increase in sensitivity depending on the size of particles. This technique also permits quantification of viral particles in samples if an aliquot is mixed with latex spheres of known concentration.Direct ultracentrifugation for electron microscopy can be performed on laboratory samples such as gradient or column fractions, infected cell supernatant, or on clinical samples such as urine, tears, cephalo-rachidian liquid, etc..

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