close packing
Recently Published Documents


TOTAL DOCUMENTS

576
(FIVE YEARS 93)

H-INDEX

52
(FIVE YEARS 4)

2022 ◽  
Vol 52 (1) ◽  
pp. 48-55
Author(s):  
O A Zyuryukina ◽  
M E Shvachkina ◽  
V I Kochubey ◽  
Yu P Sinichkin ◽  
D A Yakovlev

Abstract Using optical coherence tomography, the scattering coefficients of collagen bundles are estimated at different levels of tissue hydration. We test the validity of a simple theoretical model of dehydration changes in the optical characteristics of a collagen bundle, which is considered as a system of parallel cylinders that model the collagen fibrils forming the bundle. The characteristics of scattering by individual scatterers are calculated using the Mie theory. To take into account the cooperative effects caused by the close packing of the scatterers, use is made of the standard packing function for a system of identical cylinders. The theoretical model also relies on a certain empirical law of changes in the hydration level of fibrils with a change in the water content in the tissue, which predetermines changes in the diameter and refractive index of fibrils during dehydration and rehydration of the tissue. It is shown that the theoretical estimates obtained using this model are in good agreement with the experimental data, which makes it possible to consider this model as reliable.


2021 ◽  
Vol 55 (11) ◽  
pp. 115301
Author(s):  
Ayesha Sharif ◽  
Nazar Farid ◽  
Mingqing Wang ◽  
Rajani K Vijayaraghavan ◽  
Kwang-Leong Choy ◽  
...  

Abstract It is challenging to crystalize a thin film of higher melting temperature when deposited on a substrate with comparatively lower melting point. Trading such disparities in thermal properties between a thin film and its substrate can significantly impede material processing. We report a novel solid-state crystallization process for annealing of high melting point molybdenum thin films. A systematic investigation of laser induced annealing from single pulse to high pulse overlapping is reported upon scanning at fluences lower than the threshold required for the damage/ablation of molybdenum thin films. The approach allows better control of the grain size by changing the applied laser fluence. Atomic force microscopy surface morphology and x-ray diffraction (XRD) analysis reveal significant improvements in the average polycrystalline grain size after laser annealing; the sheet resistance was reduced by 19% of the initial value measured by a Four-point probe system. XRD confirms the enlargement of the single crystal grain size. No melting was evident, although a change in the close packing, shape and size of nanoscale polycrystalline grains is observed. Ultrashort laser induced crystallinity greatly enhances the electrical properties; Hall measurements reinforced that the overall carrier concentration increases after scanning at different laser fluences. The proposed method, based on the aggregation and subsequent growth of polycrystalline and single crystal-grains, leading to enhanced crystallization, has potential to be applicable in thin film processing industry for their wide applications.


2021 ◽  
Author(s):  
◽  
Riyad Mahmud-Mistry Mucadam

<p>Marginopora sp. is an eukaryotic large benthic foraminifera that biomineralises a high magnesium calcitic test (shell) in which dinoflagellate symbionts are stored. The discoidal test has a complex architecture; a very large cellular organism expends considerable energy to assemble and maintain a complex shell. What does the organism realise from this architecture? What are the elemental features of the architecture? Researchers have studied the test’s microstructures and chemical composition; its functional value has been suggested but an endeavour to pinpoint any particular value can be extremely complicated in a biological structure, i.e. an intractable problem is presented. Form is related to and often determines the adaptive functional value of biological structures; an enhanced understanding of form precedes and informs an understanding of function. This work increases an understanding of the form and functional value of the complex architecture of the test. Particularly, it adds to existing knowledge by: extending to a nanoscale a detailed characterization of the microstructures of the test, revealing calcium carbonate nanostructures and their associations to form crystals; conceptualising and applying a hierarchical arrangement of the microstructures across nano-macro dimensions of scale; visualising in three dimensions (3D) the microstructures of the test through ontogeny to reveal anisotropy and symmetry in the morphology of microstructures and in the test; and discovering and interpreting structural patterns that were previously not visible. Based upon these findings, the architecture and microstructures of the test; properties of biomineralised structures such as bone and echinoderm skeletons; structural arrangement of adequate models; and predominantly the mechanical adaptive value of the test are correlated. This thesis advances ideas and suggestions for research, design and practical applications of the structural principles abstracted from these findings and interpretations towards a biomimetic design of structures and processes. A combination of advanced microscopy techniques at higher resolutions and magnifications than previously used in the research of the test were used to evaluate pristine specimens of the test of Marginopora sp. Data and images obtained by the use of high resolution and cryo-scanning electron microscopy, transmission electron microscopy, polarising microscopy and, X-ray micro computed tomography (X-ray MCT) of several specimens representing different ontogenic stages were analysed. Especially, the applicability of X-ray MCT as a technique was tested for the quantitative and qualitative analysis of 3D features of the test. Visualisation and statistical techniques used in network analysis were applied to the data obtained by X-ray MCT. A materials sciences approach was adopted towards interpreting the nano-macro scale structural features of the test. In lieu of a protracted and difficult experimental approach a method used in the field of artificial intelligence was adopted to find models that could adequately point to the adaptive value of the architecture of the test. Results obtained using this approach indicated that the adaptive values are self-assembly in a phyllotactic pattern that allows an effective mechanical flexural response using a minimum of materials; close-packing of a particular pore volume; and that enables large surface areas and transmission of light through a 3D biconcave disc.</p>


2021 ◽  
Author(s):  
◽  
Riyad Mahmud-Mistry Mucadam

<p>Marginopora sp. is an eukaryotic large benthic foraminifera that biomineralises a high magnesium calcitic test (shell) in which dinoflagellate symbionts are stored. The discoidal test has a complex architecture; a very large cellular organism expends considerable energy to assemble and maintain a complex shell. What does the organism realise from this architecture? What are the elemental features of the architecture? Researchers have studied the test’s microstructures and chemical composition; its functional value has been suggested but an endeavour to pinpoint any particular value can be extremely complicated in a biological structure, i.e. an intractable problem is presented. Form is related to and often determines the adaptive functional value of biological structures; an enhanced understanding of form precedes and informs an understanding of function. This work increases an understanding of the form and functional value of the complex architecture of the test. Particularly, it adds to existing knowledge by: extending to a nanoscale a detailed characterization of the microstructures of the test, revealing calcium carbonate nanostructures and their associations to form crystals; conceptualising and applying a hierarchical arrangement of the microstructures across nano-macro dimensions of scale; visualising in three dimensions (3D) the microstructures of the test through ontogeny to reveal anisotropy and symmetry in the morphology of microstructures and in the test; and discovering and interpreting structural patterns that were previously not visible. Based upon these findings, the architecture and microstructures of the test; properties of biomineralised structures such as bone and echinoderm skeletons; structural arrangement of adequate models; and predominantly the mechanical adaptive value of the test are correlated. This thesis advances ideas and suggestions for research, design and practical applications of the structural principles abstracted from these findings and interpretations towards a biomimetic design of structures and processes. A combination of advanced microscopy techniques at higher resolutions and magnifications than previously used in the research of the test were used to evaluate pristine specimens of the test of Marginopora sp. Data and images obtained by the use of high resolution and cryo-scanning electron microscopy, transmission electron microscopy, polarising microscopy and, X-ray micro computed tomography (X-ray MCT) of several specimens representing different ontogenic stages were analysed. Especially, the applicability of X-ray MCT as a technique was tested for the quantitative and qualitative analysis of 3D features of the test. Visualisation and statistical techniques used in network analysis were applied to the data obtained by X-ray MCT. A materials sciences approach was adopted towards interpreting the nano-macro scale structural features of the test. In lieu of a protracted and difficult experimental approach a method used in the field of artificial intelligence was adopted to find models that could adequately point to the adaptive value of the architecture of the test. Results obtained using this approach indicated that the adaptive values are self-assembly in a phyllotactic pattern that allows an effective mechanical flexural response using a minimum of materials; close-packing of a particular pore volume; and that enables large surface areas and transmission of light through a 3D biconcave disc.</p>


2021 ◽  
Author(s):  
Pavel Makarov ◽  
Vladimir Ustyugov ◽  
Leonid Kotov ◽  
Sergey V. Nekipelov ◽  
Viktor Sivkov

An algorithm for the numerical simulation of the propagation of electromagnetic waves in randomly inhomogeneous magnetic media by the FDTD method has been developed. The formulated algorithm is suitable for analyzing the main timing characteristics, as well as identifying the features of the propagation of various types of signals in both time-independent and time-dependent layered randomly inhomogeneous media. The simulation of the propagation of the sine pulse, sine signal and square wave in time-independent magnetic randomly inhomogeneous media with a various levels of phase contrast of two types - with a “diffuse” distribution of inhomogeneities and their “close packing” is carried out. The influence of the concentration of magnetic granules and the type of their distribution on the characteristics of the transmitted and reflected signals is revealed.


2021 ◽  
Author(s):  
Pavel Makarov ◽  
Vladimir Ustyugov ◽  
Leonid Kotov ◽  
Sergey V. Nekipelov ◽  
Viktor Sivkov

An algorithm for the numerical simulation of the propagation of electromagnetic waves in randomly inhomogeneous magnetic media by the FDTD method has been developed. The formulated algorithm is suitable for analyzing the main timing characteristics, as well as identifying the features of the propagation of various types of signals in both time-independent and time-dependent layered randomly inhomogeneous media. The simulation of the propagation of the sine pulse, sine signal and square wave in time-independent magnetic randomly inhomogeneous media with a various levels of phase contrast of two types - with a “diffuse” distribution of inhomogeneities and their “close packing” is carried out. The influence of the concentration of magnetic granules and the type of their distribution on the characteristics of the transmitted and reflected signals is revealed.


2021 ◽  
Author(s):  
Pavel Makarov ◽  
Vladimir Ustyugov ◽  
Leonid Kotov ◽  
Sergey V. Nekipelov ◽  
Viktor Sivkov

An algorithm for the numerical simulation of the propagation of electromagnetic waves in randomly inhomogeneous magnetic media by the FDTD method has been developed. The formulated algorithm is suitable for analyzing the main timing characteristics, as well as identifying the features of the propagation of various types of signals in both time-independent and time-dependent layered randomly inhomogeneous media. The simulation of the propagation of the sine pulse, sine signal and square wave in time-independent magnetic randomly inhomogeneous media with a various levels of phase contrast of two types - with a “diffuse” distribution of inhomogeneities and their “close packing” is carried out. The influence of the concentration of magnetic granules and the type of their distribution on the characteristics of the transmitted and reflected signals is revealed.


2021 ◽  
Vol 928 ◽  
Author(s):  
Clare R. Rees-Zimmerman ◽  
Alexander F. Routh

This research is motivated by the desire to control the solids distribution during the drying of a film containing particles of two different sizes. A variety of particle arrangements in dried films has been seen experimentally, including a thin layer of small particles at the top surface. However, it is not fully understood why this would occur. This work formulates and solves a colloidal hydrodynamics model for (i) diffusion alone and (ii) diffusion plus excluded volume diffusiophoresis, to determine their relative importance in affecting the particle arrangement. The methodology followed is to derive partial differential equations (PDEs) describing the motion of two components in a drying film. The diffusive fluxes are predicted by generalising the Stokes–Einstein diffusion coefficient, with the dispersion compressibility used to produce equations valid up until close packing. A further set of novel equations incorporating diffusiophoresis is derived. The diffusiophoretic mechanism investigated in this work is the small particles being excluded from a volume around the large particles. The resulting PDEs are scaled and solved numerically using a finite volume method. The model includes the chemical potentials of the particles, allowing for incorporation of any interaction term. The relative magnitudes of the fluxes of the differently sized particles are compared using scaling arguments and via numerical results. The diffusion results, without any inter-particle interactions, predict stratification of large particles to the top surface. Addition of excluded volume diffusiophoresis introduces a downwards flux on the large particles, that can result in small-on-top stratification, thus providing a potential explanation of the experimental observations.


Sign in / Sign up

Export Citation Format

Share Document