This article discusses the effect of nanopore size on the emission properties of a porous carbon material with a density of 1.4 g/cm3. Atomistic models of porous carbon materials with different nanopore sizes have been constructed. Numerical experiments were carried out using the density functional method with allowance for periodic boundary conditions. It is established that the work function of a porous carbon material with a density of 1.4 g/cm3 decreases with an increase in the size of nanopores and an increase in the concentration of cesium ions.
The research for the energy stability of columnar graphene was carried out. It has been established that pillared graphene with zigzag carbon nanotubes and mixed chirality of carbon nanotubes (zigzag and armchair) are energy-stable. An obligatory criterion of sorbent is energy stability. Therefore, pillared graphene with chirality of zigzag carbon nanotubes and mixed chirality of carbon nanotubes (zigzag and armchair) can be used as an element base of nanofilters for water desalination.
KEYWORDS: Decision support systems, Surgery, Spine, Pathology, Medicine, Databases, Safety, Information technology, Systems modeling, Picture Archiving and Communication System
Using of Decision Support System (DSS) in medicine affects the improvement of health care quality by means of increasing accuracy and specificity of diagnostics, customization of medical care, decreasing sequelae and terms of patients’ rehabilitation. DSS are using for proving of treatment efficacy and safety and let reduce personnel labour efforts. In this regard developing of DSS requires studying the needs of orthopedic surgeons as key users of such systems. Aim of this study performed at the base of 2 university medical centers in Saratov and Nizhny Novgorod which fulfill about 10% of surgeries in Russia concerning spine-and-pelvic complex pathology) deals with discovering the needs of orthopedic surgeons about desired DSS functionality by means of using the specially designed questionnaire. Results of the study determine following DSS functionality: use of geometric planning and biomechanical modeling before the surgery; surgery fate prognosis at the base of clinical and X-ray success criteria; ability to design the individual implants; integration of DSS with PACS and often using medical informational systems.
The theoretical molecular-mechanical method using the AIREBO energy potential was modernized to study the mechanical properties of porous carbon nanostructures doped with potassium atoms. The selection of coefficients was carried out by solving a minimax problem based on experimental data of the distances between the potassium and carbon atoms. The choice of this particular method for modifying and studying the mechanical properties of nanostructures is due to the necessity of calculating a large number of atoms with minimal time expenditures and with no loss of calculation accuracy. The study of mechanical properties was carried out depending on the size of the nanopores of the porous carbon nanostructure. The modernization consisted in the selection of weighting coefficients to describe the interaction between potassium and carbon atoms. Physical interaction is described by the Lennard-Jones potential. This modernization was performed to study the mechanical properties of carbon nanostructures of doped potassium atoms.
The effect of different concentrations of K+, Na+, Ca2+, Ni2+, Al3+ and Fe3+ ions on surface-active substance monolayer stability has been studied using molecular mechanics method. For numerical calculations, energy potential Amber was used. Arachidic acid was chosen as a surface-active substance for monolayer formation because it is insoluble in water at normal conditions. Energy stability values representing system stability was calculated for different ion concentrations. It is established that the most stable system is formed by trivalent metal ions and that system stability decreases together with ionic charge. For each type of ions, a concentration value corresponding to most optimal stability was found with further increase of ion concentration leading to decrease of stability.
The most important problem of the nowadays is the short of the clear water. We suppose the using of the novel material – the pillared graphene for resolving this problem. The pillared graphene exceeds already used in the sorption the frame carbon materials in the values of the specific surface area. One of the most important specified requirements for sorbent is a mechanical strength. It is known, that mechanical strength heavily depends on the pillared graphene’s geometry: the lengths and the diameter of the carbon nanotubes. In this paper, we have carried out theoretical research of the depending Young’s modulus of the finite size pillared graphene based on the zigzag-CNT on his geometry. The composite, which has the most strength, is recommended for using in the water purification.
Last times carbon nanostructures based on carbon nanotubes and graphene are actively used in different fields of science and technic. Main problem of using these carbon nanostructures in water environment is that carbon nanostructures have a tendency to bond with each other via Van-der-Waals interaction. This issue can be resolved by the appending surface-active materials, such as phospholipids, into composite. We have carried out research on influence of phospholipids on stability of carbon composite. This researching was carried out by the increasing of the number of the phospholipids in the structure. Numerical counts were carried out on minimal structure cell of composite using AMBER energy potential with Berenson thermostat. Its concluded that stable of composite decreases by the increasing of number of the phospholipids.
Preoperative planning systems (PPS) currently are very important for evidence-based medicine promotion in surgery worldwide. Design and development of such systems is the mainstream of health care provision in Russia and let to apply preventive, diagnostic and remedial technologies based on the evidenced effectiveness and safety. PPS allow to reduce planning time, increase its accuracy and to minimize medical malpractice. Modern PPS perform a geometric planning helping surgeon to make the correct decision regarding surgery management. Special PPS designed for vertebral-pelvic complex surgery allow evaluate bone and joint deformation degree, planning simultaneous implants replacement, osteotomy. The evaluation is based on 2D and 3D medical images (if available) studying. The analysis of the most demanded modern PPS (MediCad, TraumaCad, OrthoView and Surgimap) properties shows that all of these products allow to measure a massive number of orthopedic parameters: scoliosis, lordosis, sagittal balance, the angular deviation of the sacrum, the cervico-diaphyseal angle, the Hilgenreiner angle etc. However not all of indicated systems allow to automatically search such parameters as the Reimer index (percentage) and epiphyseal index. Also not all the systems have the detection of calibration devices function and Auto-Hip function. So the aim of this study is to identify and prove the sufficient number of parameters to be evaluated by the surgeon to perform correct geometric preoperative planning in vertebral and pelvic complex surgery.
In nowadays the nanoscale materials are actively used in medicine, based on the properties of adsorption. One of the main problems of this field of medicine is the increase in specific surface of sorbent. We proposed to use carbon composites consisting of an extended in its directions graphene sheet with attached to it by chemical bonds zigzag carbon nanotubes (CNT). This paper presents the results of a theoretical study of the mechanical properties of graphene based on the CNT zigzag depending on the geometric dimensions of the composite (length and diameter of CNTs).
Investigation of conducting properties of ZnS quantum dot by acceding to them the gold atoms were presented. It was found that redistribution of electrons in the quantum dot change after the accession of the gold atoms. When adding gold atoms is observed the change in geometry of structure and the change in the redistribution of the electron density. Search equilibrium configuration of the molecule was carried out by the density of state method with basis b3lyp. The object of research is a symmetrical molecule ZnS.
Porous carbon structures are the greatest interest, since they are actively used in various fields of science and technology. The aim of this work is the investigation of the mechanical strength of the porous carbon structures with a density of 1.4 g/cm3 with different pore sizes and different concentration of oxygen atoms. The investigation of the mechanical properties of porous carbon nanostructures was carried out on three models with different nanopore sizes (0.4-0.8 nm, 0.2 nm - 1.12 nm, 0.7-1.3 nm). The character of the change in the Young's modulus of porous nanostructures as a function of the location of oxygen atoms was established.
KEYWORDS: Image segmentation, Raster graphics, Systems modeling, 3D modeling, Bone, Solid state physics, Algorithms, Image processing algorithms and systems, Algorithm development, Tin
It is developed within a method of the active contours the approach, which is allowing to realize separation of a contour of a object of the image in case of its segmentation. This approach exceeds a parametric method on speed, but also does not concede to it on decision accuracy. The approach is offered within this operation will allow to realize allotment of a contour with high accuracy of the image and quicker than a parametric method of the active contours.
For the first time, the dependence of the bending force on the transverse displacement of atoms in the center of the composite material consisting of graphene and parallel oriented zigzag nanotubes was studied. Mathematical modeling of the action of the needle of the atomic force microscope was carried out using the single-layer armchair carbon nanotube. Armchair nanotubes are convenient for using them as a needle of an atomic force microscope, because their edges are not sharpened (unlike zigzag tubes). Consequently, armchair nanotubes will cause minimal damage upon contact with the investigation object. The geometric parameters of the composite was revealed under the action of the bending force of 6μN.
Perspective materials in adsorption medicine are the composite carbon nanostructures based on carbon nanotubes and graphene because of their unique mechanical properties and because of their ability to attach other types of atoms. The ability to control the pore size in synthesis process is an important feature of this material. The deformation of nanotubes and graphene in the longitudinal direction of the graphene sheet will occur during the filtration of microorganisms by the composite. Investigation the deformation of the composite under tension along the graphene sheet is carried out for the first time in this work by molecular mechanical method based on potential of DFT.
The porous carbon structures (sorbent) with a density of 1.4 g/cm3 are of most interest compared with existing porous carbon structures. This interest can be explained the technology of synthesis such structures. This technology allows to change the pore size in the sorbent leaving a constant concentration of the particles. Investigation of mechanical properties of sorbents allows choosing the synthesis conditions of the sorbent and its parameters so that it was possible to filter the heavy particles moving at high speed. Therefore, the aim of this work is to study the mechanical strength of the porous carbon materials with a density of 1.4 g/cm3 with different pore sizes. The influence of pore size and form of the sorbent on the adsorption capacity were investigated.
At the present time actual task of the modern materials is the creation of biodegradable biocompatible composite materials possessing high strength properties for medical purposes. One of the most promising biomaterials from a position of creation on their basis super strong nanofibres is chitosan. The aim of this work is a theoretical study of the structural features and physico-mechanical properties of biocomposite materials based on chitosan and carbon nanostructures. As matrix nanocomposite we considered various carbon nano-objects, namely carbon nanotubes and graphene. Using the developed original software complex KVAZAR we built atomistic and coarse-grained models of the biocomposite material. To identify regularities of influence of the configuration of the carbon matrix on the mechanical and electronic properties of biocomposite we carried out a series of numerical experiments using a classical algorithm of molecular dynamics and semi-empirical methods. The obtained results allow us to suggest that the generated biocomposite based on chitosan and carbon nanostructures has high stability and strength characteristics. Such materials can be used in biomedicine as a base material for creating of artificial limbs.
The main property of carbon nanotubes that determinates their wide application in electronics is a change of the chirality for ideal structure of a nanotube at implementing of structural Stone-Wales defect (pentagon-heptagon pairs) to its atomic framework. This property allows us to create nanotube-based different electronic devices (diodes, transistors, resistors), similar to traditional silicon devices. Nanotube with incorporated defect can be considered as a metalsemiconductor heterojunction. On the basis of this heterojunction semiconductor elements of very small size can be implemented, less than the current silicon elements. To create devices based on metal-semiconductor heterojunction is necessary to know the mechanisms of formation of the molecular compounds of nanotubes with different chirality. The aim of this work is a theoretical study of the formation of the molecular compounds of nanotubes with different chirality leading to the appearance of the metal-semiconductor heterojunction using molecular modeling methods. The object of investigation is a heterojunction formed by the compound of nanotubes with chirality indices (13,10) and (14, 10). To identify regularities of change in the electronic structure of the compound nanotubes we calculated the density of electronic states (DOS) for the heterojunction, and for each of its constituent chiral tubes. Also, we carried out a numerical evaluation of the reaction enthalpy of formation of the heterojunction. Based on these results it can be concluded that the investigated molecular compounds can be used to create highly sensitive sensors.
Model of terahertz emitter is based on carbon nanotube filled with fullerenes by the molecular-mechanical method. Creating of the conditions for which there was observed a terahertz range of was carried out. It is shown that the emitter has a nanometer size. It was established that the terahertz radiation with a frequency 0.6 THz is observed when there is no electric field, and this frequency can increase by an electric field of 1 * 106 V / cm and the charge fullerene +5 e.
The complete search of controlling mode of motion of phospholipid was held. We found, that single molecule of phospholipid move randomly on graphene layer in both cases: with electric field or without it. And then we used additional charged molecules and changed value of electric field strength to find out how we can control that motion. We found, that motion of phospholipid molecule can be controlled through the using of molecules С60 and electric field with strength 106 V/m.
KEYWORDS: Composites, Graphene, Chemical species, Carbon nanotubes, Carbon, Data modeling, Numerical simulations, Physics, Particles, Chemical elements
The investigation of energy stability of composites based on graphene sheets and carbon nanotubes was investigated. The dependence of enthalpy of formation from geometry parameters, such as length and diameter of nanotubes, distance between nanotubes on graphene sheet, of composites parts, optimal geometry for most energy sustainable composites were found.
At the present time carbon nanostructures are the main functional material for the development of electronic devices of broad applications. One of the most perspective for practical application forms of carbon nanostructures are nanotori. This paper presents results of prediction the stability of toroidal structures using computer modeling methods. The stability of carbon nanotori are determined by scanning of the local stresses map. Obtained results showed that the highest stability is characterized for carbon nanotori (13, 0) formed by the folding of a zigzag carbon nanotube. These nanotori are characterized by the lowest enthalpy of structure formation (101 eV).
In this paper we study the behavior of [2.2.2] cryptand with various metal ions (Na, K, Eu, Fe) inside the armchair carbon nanotube. To identify regularities of behavior for cryptand inside a nanotube we carried out a series of numerical experiments in molecular dynamics using Amber force field at different temperatures and under influence of external electric field. We have established the dependence of the oscillation frequency of the cryptand inside a carbon nanotube. On the basis of the established effect of fluctuations for cryptand inside the nanotube is predicted that such complexes can be used as miniature radiating systems.
In this work, we study the behavioral regularity of fullerene C20 inside the icosahedral outer shell of fullerene C240. The feature of such two-shell fullerenes is that the internal fullerene will move at low temperatures in a certain way: between the potential wells. The aim of this work is to reveal the regularities for motion of small fullerenes in nanospace of large external icosahedral fullerene, including the identification of the spatial configuration for a multi-well potential of interaction between two objects and prediction of possible movement for the internal object between potential wells. For the fullerene C20 it was found twenty potential wells in the direction of the fifth order axes for icosahedron of fullerene C240 cage, thirty towards in the direction of the middle of the ribs and twenty potential wells towards centers of the faces of the icosahedron. The prediction of possible moving for the internal object between potential wells and the regularities of this movement were made based on the relief analysis of the interaction energy surface of fullerenes. The numerical simulation of C20 motion in the field of C240 was carried out to test the prediction of movement. As results of the experiment, it was found that the fullerene C20 is easy to jump between the potential wells even at low temperatures up to 300K. Molecular dynamics simulations confirmed our conclusions about regularities of C20 movement between potential wells. Thus, one can conclude that the analysis of the topology of the energy surface of van der Waals interaction between the components of nanoparticles gives a true predictive picture of the regularities of the internal molecule behavior. Probably, the phenomenon of fullerene C20 movement in a cell of another fullerene can be used in modern technologies, such as determining a local temperature by increase of jumping velocity.
The results of the theoretical and experimental investigations of the emission properties of the partitioned carbon nanotubes are presented in this paper. We have calculated ionization potential and energy gap of the energy spectrum for stable carbon partitioned carbon nanotube (15,15) of the smallest diameter by means of the tight-binding method. Also we have developed the original synthesis technique of the partitioned carbon nanostructures. This synthesis technology provides the high efficiency of the partitioned carbon nanotubes growth. As a result of calculations it was established that the emission properties of the infinite partitioned carbon nanotubes at the increasing of the distance between the bridges are better in comparison to the emission properties of the hollow nanotubes.
In the process of field emission surface of carbon nanotubes is heated, that may lead to the rapid destruction of the emitter based on them. Therefore, the problems of heat reducing and the destruction of carbon nanotubes prevention are important. Experimental study of the thermal conductivity of isolated CNT is time consuming and expensive process, so it is better to use the numerical models to understand the process of heat transfer in carbon nanotubes. In this work the change of the nanotubes thermal conductivity was investigated with increasing length and diameter of the nanotubes and the number of defects Stone-Wales.
The results of theoretical study of bilayer fullerene C60@C540 are presented in this paper. In order to identify regularities of internal fullerene movement in the field of the outer shell retaining potential multiwell potential of C60 and C540 fullerenes interaction was calculated. On the basis of the two-shell fullerene structure topology data and analysis of the fullerenes interaction energy surface relief possible options of C60 tunneling between potential wells are predicted. Compiled forecast is confirmed by the data of numerical experiment.
Different types of carbon nanotube + graphene quantum dot composites were investigated. Stable configuration of
carbon nanotube + graphene quantum dot composites with the van der Waals and the chemical interactions were
established. It was shown that a peapod + graphene quantum dot (GQD) composite is a stable configuration at the
chemical interaction. Investigation of the stability were performed by means of the empirical method based on Brenner's
potential. The ionization potential of the peapod + GQD composite decreases by 0.5% in comparison with the ionization
potential of the hollow nanotubes.
We studied the phospholipid molecule structure, rigidity, rotary mobility and micelle aggregation process using a coarse-grained
(CG) model. It was found that the phospholipid structure can be presented as a spring with a rigidity of 27.68
kN/m. The rotational frequency of such molecule equals to 0.9 GHz at the temperature of 293 K and increases up to 1.2
GHz at 309K. At the constant temperature the micelle aggregation time does not depend on number of interacting
molecules. Along with the temperature increase, the aggregation time decreases. At lower temperatures the assembly
process depends on distance between the adjacent molecules.
Model of terahertz radiation sources was developed in this work. This model based on the nanopeapod: carbon nanotube
(10, 10) with incapsulated chains of the fullerene C60. Simulation of the nanoemitter action was carried out by means of
the molecular-mechanical model. The length of the considered nanotube is equals to 10.3 nm, and radius of this tube is
equals to 1.35 nm. It was found that to generate the radiation in terahertz range it is necessary to apply the external field
with strength of 1⋅106 V / cm to our system. The moving fullerene C60 has a charge of +3е, and the nanotube has a charge
of -3е. It was established that the field emission process from the surface of the nanotube is not observed in this case.
The submitter model of nanoemitter works with a frequency 0.36 THz at a field strength of 1⋅106 V / cm.
The results of quantum-chemical analysis of elastic and strength properties of the bamboo-like tube are presented in this
paper. For the first time the configuration of the thinnest stable bamboo-like tube was established. The bamboo-like
nanotube breaking point is established to be under compression of 11GPa. Configuration of the nanoindentor based on
symmetric and streamlined tip of the tube (15,15), presented in this work, provides perfect interaction between the
nanoindentor tip and the tissue because tip has no sharp protruding pieces.
We report the results of the chitosan dimer study, the mechanism of its interaction with the carbon nanostructures and
also the mechanical properties of the chitosan/graphene, chitosan/nanotube complexes using the density function and
the molecular dynamic methods. It was established that the physical adsorption of the chitosan with graphene is carried
out by the Van der Waals interaction between the hexagonal links of the chitosan with the hexagonal cell of the atomic
grid of graphene and nanotube.
We report the results of quantum mechanical investigations of the atomic structure and deformations of
graphene nanoparticle undergoing axial compression. We applied the tight-binding (TB) method. Our transferable tightbinding
potential correctly reproduced tight-binding changes in the electronic configuration as a function of the local
bonding geometry around each carbon atom. The tight-binding method applied provided the consideration and
calculation of the rehybridization between σ- and π-orbitals. To research nanoribbons using tight-binding potential our
own program was used. We adapted TB method to be able to run the algorithm on a parallel computing machine
(computer cluster).
To simulate axial compression of graphene nanoparticles the atoms on the ends were fixed on the plates. The
plates were moved towards each other to decrease the length at some percent. Plane atomic network undergoing axial
compression became wave-like. The amplitude of wave and its period were not constant and changed along axis. This is
a phase transition. The strain energy collapse occurs at the value of axial compression 0.03-0.04. The strain energy
increased up to the quantity compression 0.03, then collapsed sharply and decreased.
So according to our theoretical investigation, the elasticity of graphene nanoparticles is more than the elasticity
of nanotubes the same width and length. The curvature of the atomic network because of compression will decrease the
reactivity of graphene nanoparticles.
We have calculated the atomic structure and electronic structure of the compression graphene nanopaticle at
each step of strain of axial compression. We have come to the conclusion that the wave-like graphenes adsorbing protein
and nucleic acid are the effective nanosensors and bionanosensors.
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