Study of fullerenes via their symmetry groups

In this paper, we compute the automorphism group of some infinite classes of fullerene graphs and then we compute their symmetric Szeged index which is a new topological index based on the automorphism group.     

Theoretical study on possible usage of difluoromethylene fullerenes as electron-transport materials

The usefulness of the difluoromethylene fullerenes C₆₀(CF₂)_n(n = 1, 2) materials for the organic devices is theoretically discussed, comparing with C₆₀, about the following three points: electron transport in the material, electron injection from the electrode into the material, and thin-film formation of the material. Concerning the thin-film formation, dipole moments are calculated. Frontier orbital energies and adiabatic electron affinities are discussed in connection with the electron injection from the electrode into the material. Additionally, the inter-molecular electron transport is discussed from the viewpoint of the reorganization energy based on the Marcus theory. These results indicate the usage of some C₆₀(CF₂)_n isomers as the useful electron-transport materials.     

Comparative analysis of two methods for synthesis of fullerenes at different helium pressures

Abstract

The results of the effect of helium pressure in the chamber on the amount and composition of the produced fullerenes (C₆₀, C₇₀, etc.) synthesized in the arc plasma with graphite electrodes are presented. The findings obtained when the arc is powered by a direct (DC) and alternating (AC) currents of low frequency were compared in the same chamber with the electrodes located at the same angle to each other. These two methods are drastically different. The complete conversion of graphite into fullerene soot in AC occurs, but a part of the graphite is converted into a cathode deposit that does not contain fullerenes in DC, the relative amount of which increases when decreasing the helium pressure in the chamber. The highest fullerene content in fullerene soot of 10.2?wt.% is produced at a pressure of 127.5?kPa in AC arc, but in DC arc, the highest content of fullerenes in fullerene soot of 8.3?wt.% is produced at a pressure of 33.3?kPa.     

Controlled synthesis of fullerenes and endohedral metallofullerenes in high frequency arc discharge

The article presents the high-frequency arc discharge setup operating in helium atmosphere and applicable for the syntheses of carbon condensate with different dispersion and structure, along with fullerenes and endohedral metallofullerenes. It also highlights how the change of helium pressure in chamber can control the amount and composition of products in carbon condensate. The setup can be applied for the purposes of analysis, for instance in order to obtain information about the process of fullerenes and endohedral met-allofullerenes formation. Also, the fact that the yield of higher fullerenes is increasing with the pressure rise, whereas the yield of endohedral metallofullerenes is decreasing suggests different formation mechanisms.     

Synthesis evaluation of nitrogen atom encapsulated fullerenes by optical emission spectra in nitrogen plasmas

The nitrogen atom encapsulated fullerene (N@C₆₀) with relatively high yield has been synthesized by a plasma irradiation method. We have examined the relationship between optical emission spectra of a radio frequency (RF) discharge nitrogen plasma and the synthesis yield of N@C₆₀. As a consequence, the increasing amount of nitrogen molecule ions (N₂⁺) impinging on the sublimated fullerenes are found to enhance the synthesis of N@C₆₀. Furthermore, it is clarified that there is an optimum condition of the nitrogen plasma for the high-yield synthesis of N@C₆₀, which is generated under lower gas pressure and is irradiated to the larger amount of fullerenes.     

Facile and scalable synthesis of a highly hydroxylated water-soluble fullerenol as a single nanoparticle

A water-soluble polyhydroxylated fullerene, i.e. a fullerenol, with 44 hydroxyl groups and 8 secondary bound water molecules, C₆₀(OH)₄₄·8H₂O (estimated average structure), has been synthesized in a facile one step reaction from pristine C₆₀ by hydroxylation with hydrogen peroxide in the presence of a phase-transfer catalyst, tetra-n-butylammonium hydroxide (TBAH), under organic/aqueous bilayer conditions. The fullerenol exhibited high water solubility, up to 64.9 mg/mL, under neutral (pH = 7) conditions. Dynamic light-scattering (DLS) analysis showed a narrow particle size distribution, of 1–2 nm, indicating that the fullerenol had high dispersion properties in water. The results of particle size analyses, which both focused on a single nanoregion and were conducted using a novel induced grating (IG) method and a scanning probe microscope (SPM), were consistent with the DLS results. A plausible reaction mechanism, which includes fullerene oxide intermediates detected by liquid chromatography-mass spectrometry (LC-MS), has been proposed.     

An explorative study of the relationship between lifestyle and driving behaviour among young drivers

The high accident risk among young drivers is a well-known and well-documented fact in most countries, including Denmark. Lifestyle has proven to be related to driving behaviour as well as accident risk among young drivers. However, the underlying process through which the relationship between the lifestyle and the driving behaviour is established is not yet fully understood. Using focus group interviews divided by sex and education this study explores the psychosocial function of driving as well as the process through which a relationship between lifestyle and driving behaviour is established. Twenty-nine young drivers living in the Copenhagen area participated in the study. Data were analysed using a modified version of the Editing Analysis Style.     

He Ion Bombardment of C70 Fullerene: An FT-IR and Raman Study

C₇₀ fullerene films deposited on a silicon substrate have been bombarded with He⁺ ions at 30 keV at room temperature in vacuum. The structural changes undergone by C₇₀ have been followed by both FT-IR and Raman spectroscopy. The results have been compared to the behavior of C₆₀ fullerene and discussed in an astrochemical context. The main conclusion is that C₇₀, contrary to C₆₀, does not form oligomers at low radiation dose but it is directly and gradually degraded to amorphous carbon (carbon black).     

The Effect of Formulation on Radioiodide Thyroid Uptake in the Hyperthyroid Cat

This investigation was designed to compare in vitro dissolution profiles from sodium iodide capsules with radioiodide thyroid uptake in hyperthyroid cats using sodium iodide capsules prepared with a formulation exhibiting a complete release of radioiodide (I-123) in vitro and a formulation with an incomplete release of radioiodide. In vitro dissolution profiles for I-123 sodium iodide capsules with two different formulations were determined using the USP XXIII dissolution test. The two formulations studied in vitro were sodium phosphate dibasic powder with 1% magnesium stearate and calcium phosphate dibasic powder with 3% magnesium stearate. By 20 min after initiation of the dissolution test, over 95% of the I-123 was released from capsules of sodium phosphate dibasic powder. The capsules of calcium phosphate dibasic powder reached 75% at 65 min, with no further release occurring thereafter. There was a statistically significant difference in the dissolution profiles of the two formulations. The thyroid uptake of I-123 from capsules exhibiting complete release and incomplete release of radioiodide was determined in hyperthyroid cats. At 4 hr, the mean percentage thyroid uptake value for sodium phosphate dibasic powder with 1% magnesium stearate (complete release formulation) was 12.0% compared to 9.4% for calcium phosphate dibasic powder with 3% magnesium stearate (incomplete release formulation); at 24 hr, the values were 34.4% compared to 23.7%. The data suggest that the incomplete dissolution profile observed in vitro may correlate with a reduction in the bioavailability of the radioiodide in vivo. However, using the Wilcoxon signed rank test, statistically significant differences did not occur between the complete release formulation and incomplete release formulation at either 4 hr or 24 hr (p >. 05). The results of the in vivo study with five hyperthyroid cats were not conclusive due to the variability in response between individual cats.     

Development of modified release diltiazem HCl tablets using composite index to identify optimal formulation

This article reports the preparation of tartaric acid treated ispaghula husk powder for the development of modified release tablets of diltiazem HCl by adopting direct compression technique and a 3² full factorial design. The modified ispaghula husk powder showed superior swelling and gelling as compared to untreated powder. Addition of compaction augmenting agent such as dicalcium phosphate was found to be essential for obtaining tablets with adequate crushing strength. In order to improve the crushing strength of diltiazem HCl tablets, to modulate drug release pattern, and to obtain similarity of dissolution profiles in distilled water and simulated gastric fluid (pH 1.2), modified guar gum was used along with modified ispaghula husk powder and tartaric acid. A novel composite index, which considers a positive or a negative deviation from an ideal value, was calculated considering percentage drug release in 60, 300, and 540 min as dependent variables for the selection of a most appropriate batch. Polynomial equation and contour plots are presented. The concept of similarity factor (f₂) was used to prove similarity of dissolution in water and simulated gastric fluid (pH 1.2).     

Analysis of Distance-Based Topological Polynomials Associated with Zero-Divisor Graphs

Chemical compounds are modeled as graphs. The atoms of molecules represent the graph vertices while chemical bonds between the atoms express the edges. The topological indices representing the molecular graph corresponds to the different chemical properties of compounds. Let be are two positive integers, and be the zero-divisor graph of the commutative ring . In this article some direct questions have been answered that can be utilized latterly in different applications. This study starts with simple computations, leading to a quite complex ring theoretic problems to prove certain properties. The theory of finite commutative rings is useful due to its different applications in the fields of advanced mechanics, communication theory, cryptography, combinatorics, algorithms analysis, and engineering. In this paper we determine the distance-based topological polynomials and indices of the zero-divisor graph of the commutative ring (for as prime numbers) with the help of graphical structure analysis. The study outcomes help in understanding the fundamental relation between ring-theoretic and graph-theoretic properties of a zero-divisor graph .     

An automatic formulation of inverse free second moment method for algebraic systems

In systems with probabilistic uncertainties, an estimation of reliability requires at least the first two moments. In this paper, we focus on probabilistic analysis of linear systems. The important tasks in this analysis are the formulation and the automation of the moment equations. The main objective of the formulation is to provide at least means and variances of the output variables with at least a second-order accuracy. The objective of the automation is to reduce the storage and computational complexities required for implementing (automating) those formulations. This paper extends the recent work done to calculate the first two moments of a set of random algebraic linear equations by developing a stamping procedure to facilitate its automation. The new method has an additional advantage of being able to solve problems when the mean matrix of a system is singular. Lastly, from storage and computational complexities and accuracy point of view, a comparison between the new method and another recently developed first order second moment method is made with numerical examples.     

Equivalent geometric transformations for spin and orbital angular momentum of light

We consider the analogous geometric transformations for spin and orbital angular momentum states of light. Spin angular momentum is manifested as polarization and its possible transformations are typified by those introduced by waveplates and the rotation associated with optical activity. Orbital angular momentum is associated with the mode structure of the beam and, while the action of a waveplate is similar to that of a mode converter, the equivalent analogue of optical activity is not obvious. We reason that the equivalent is a rotation of the transmitted image. We consider the extent to which an image orientation of this type might be achieved by a coherent fibre bundle, twisted around its central axis. The possibility of equivalents to the Kerr, Pockels and Faraday electro-optic effects for orbital angular momentum is raised.     

Neutron bombardment of C60 and C70 fullerenes: A spectroscopic and calorimetric study

C₆₀ and C₇₀ fullerenes were neutron-bombarded to an integral dose of 3.28×10¹⁶ n cm^?2. After the neutron treatment the trichloromethane soluble fraction was determined spectrophotometrically and C₆₀ insoluble fraction was found at 3.8% while the insoluble fraction of C₇₀ 17.9%. The formation of the CHCl₃ insoluble fraction is due to polymerization and incipient amorphization of the neutron-bombarded fullerenes where C₇₀ appears more sensitive to radiation damage than C₆₀. Raman spectroscopy was used for the characterization of the irradiated fullerenes as well as electron spin resonance (ESR) and electronic absorption spectroscopy on solid samples. Differential scanning calorimetry (DSC) to 630°C was employed for the determination of the Wigner energy of the neutron-damaged fullerenes. The results are consistent with a higher level of radiation damage reached by C₇₀ in comparison to C₆₀ at the same neutron dose.     

An investigation of the electrical transport properties of graphene-oxide thin films

The electrical transport properties of graphene-oxide (GO) thin films were investigated. The GO was synthesized by a modified Hummers method and was characterized by X-ray diffraction and UV-visible spectroscopy. The thin film of GO was made on a Si/SiO₂ substrate by drop-casting. The surface morphology of the GO film was analyzed by using scanning electron microscopy and atomic force microscopy techniques. Temperature dependent resistance and current-voltage measurements were studied using four-terminal method at various temperatures (120, 150, 175, 200, 250 and 300 K) and their charge transport followed the 3D variable range hopping mechanism which was well supported by Raman spectra analysis. The presence of various functional groups in GO were identified by using high resolution X-ray photo electron (XPS) and Fourier transform infra red (FT-IR) spectroscopic techniques. Graphene-oxide thin film field effect transistor devices show p-type semiconducting behavior with a hole mobility of 0.25 cm² V⁻¹ s⁻¹ and 0.59 cm² V⁻¹ s⁻¹ when measured in air and vacuum respectively.     

An alternative time-domain index for condition monitoring of rolling element bearings—A comparison study

Statistical moments have been widely used for detection and diagnosis of rolling element bearing damage. Among them, Kurtosis and Honarvar third moment S_r are the major parameters. In this paper a new statistical moment, from the viewpoint of Rényi entropy, is derived, which is shown to be as effective as kurtosis and S_r. Comprehensive comparisons of kurtosis, S_r and this moment are performed, and the results from simulations and experiments show the new moment has a better overall performance than kurtosis and S_r. On the one hand, this moment behaves much like kurtosis but is less susceptible to spurious vibrations, which is considered to be one of the main shortcomings of higher statistical moments including kurtosis. On the other hand, from the viewpoint of sensitivity to incipient faults, which is the major drawback of lower statistical moments including S_r, the new moment is superior to S_r. Moreover, the sensitivity of this new moment to changes of bearing speed and load is also less than kurtosis and is close to that of S_r.     

Development and study of new hybrid semiconducting systems involving Cd chalcogenide thin films coated by a fullerene derivative

New hybrid organic-inorganic semiconducting systems have been developed exhibiting an interesting photoconductive behavior. The inorganic part consists of a thin film of CdSe or CdTe prepared by an electrodeposition technique. On the other hand, the organic layer, comprising of N-methyl[60]fulleropyrrolidine, is applied onto the as-plated inorganic surface by deposition from a toluene solution, followed by a mild heat treatment. The products obtained were fully characterized with XRD and SEM-EDAX techniques and their photoelectric behavior was studied using a PhotoElectrochemical Cell (PEC). An attenuation of the n- and correspondingly a reinforcement of the p-character of the inorganic semiconductors were concluded, after the deposition of the organic layer, due to the electron acceptor behavior of the fullerene moiety.     

Functionalization of mesoporous MCM-41 for the delivery of curcumin as an anti-inflammatory therapy

In this study, mesoporous silica nanoparticles (MSNs) composed of MCM-41 were synthesized and modified with amine groups (i.e., NH₂) to form NH_2/MCM-41, which was loaded with curcumin (CUR) to form CUR@NH₂/MCM-41 to create an efficient carriers in drug delivery systems (DDSs). The three samples (i.e., pure MCM-41, NH₂/MCM-41, and CUR@NH₂/MCM-41) were characterized using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transition electron microscopy (TEM), and a thermogravimetric analyzer (TGA). The study investigated the effect of the carrier dose, CUR concentration, pH, and contact time on the drug loading efficiency (DLE%) by adsorption. The best DLE% for MCM-41 and NH₂/MCM-41 was found to be 15.78 and 80%, respectively. This data demonstrated that the Langmuir isotherm had a greater correlation coefficient (R²) of 0.9840 for MCM-41 and 0.9666 for NH₂/MCM-41 than the Freundlich and Temkin isotherm models. A pseudo-second-order kinetic model seems to fit well with R² = 0.9741 for MCM-41 and R² = 0.9977 for NH₂/MCM-41. A phosphate buffer solution (PBS) with a pH of 7.4 was utilized to study CUR release behavior. As a result, the full release after 72 h was found to have a maximum of 74.1% and 29.95% for pure MCM-41 and NH₂/MCM-41, respectively. The first-order, Weibull, Hixson-Crowell, Korsmeyer-Peppas, and Higuchi kinetic release models were applied to releasing CUR from CUR@MCM-41 and CUR@NH₂/MCM-41. The Weibull kinetic model fit well, with R² = 0.944 and 0.96912 for pure MCM-41 and NH₂/MCM-41, respectively.