Parameters Electron Density Research Articles

Ultra-low concentration protein detection based on phenylalanine-Pd/SWCNT as a high sensitivity nanoreceptor.

Pd doped single-walled carbon nanotubes as an enhanced physical transducer with phenylalanine amino acid can be efficiently used as a biocompatible nanoreceptor to detect proteins. DFT/B3LYP was used to calculate the optimized geometries, energies and electron density parameters to determine the stability and reactivity of the nanoreceptor. Among different adsorbed configurations of phenylalanine, the amine and carboxylic acid sites have higher adsorption energies and more stable complexes. With direct strong chemical adsorption of phenylalanine amino acid onto the Pd doped single-walled carbon nanotube, the free active carboxylic acid group of the amino acid can react with free amine groups on the surface of the proteins. More over the π–π stacking interaction between the free aromatic ring of adsorbed phenylalanine amino acid onto the functionalized single-walled carbon nanotube and the aromatic rings of the proteins also contributes to the intelligent detection of proteins. Frontier molecular orbital and molecular electrostatic potential (MPE) surface studies have been employed to investigate the active sites of the nanoreceptor. The effects of different solvents on the structural and electronic properties were investigated. Finally, in order to investigate biological function of the biosensor, docking studies were performed.

Synthesis and characterization of lead borate glasses comprising cement kiln dust and Bi2O3 for radiation shielding protection

The low cost and high efficient radiation shielding materials are necessary to protect the human being from the exceedingly used harmful nuclear radiations. The cement kiln dust (CKD) is the largest waste stream from cement plants that harm the environment. In this study, new glasses containing moderate contents of CKD for radiation shielding had been synthesized by the melt quenching technique. The synthesized glasses had the chemical formula (25−x)PbO–32CKD–40B2O3–3BaO– xBi2O3 (0 ≤ x ≤ 25 mol%). NaI (Tl) scintillation detector and pulse-echo techniques were used to investigate the radiation shielding and the mechanical features of the investigated samples. The mass attenuation coefficient (μm), half-value layer (HVL), tenth value layer (TVL), mean free path (mfp), radiation protection efficiency (RPE), effective atomic number (Zeff) and effective electron density (Nel) parameters for glass samples have been determined experimentally. The G-P fitting method was used to calculate the exposure (EBF) and energy absorption buildup factor (EABF) for the prepared glass samples in the photon energy range of 0.015–15 MeV up to 40 mfp. The specific absorbed fraction of the energy (SAFE), the relative dose distribution (RDD) and the neutron shielding parameters have been computed. Moreover, the elastic moduli of the investigated glasses were determined by considering the measured values of the ultrasonic velocities at 5 MHz and the density. The investigated glasses are considered as a promising candidate for radiation application.

Superconductivity in Cu Co-Doped SrxBi2Se3 Single Crystals.

In this study, we grew Cu co-doped single crystals of a topological superconductor candidate SrBiSe, and studied their structural and transport properties. We reveal that the addition of even as small an amount of Cu co-dopant as 0.6 atomic %, completely suppresses superconductivity in SrBiSe. Critical temperature (∼2.7 K) is rather robust with respect to co-doping. We show that Cu systematically increases the electron density and lattice parameters a and c. Our results demonstrate that superconductivity in SrBiSe-based materials is induced by significantly lower Sr doping level than commonly accepted , and it strongly depends on the specific arrangement of Sr atoms in the host matrix. The critical temperature in superconductive Sr-doped BiSe is shown to be insensitive to carrier density.

Conclusive Research Design and Development of the Effect of Linear Deformation on Some Debye Properties of Metals

This Work, Debye Temperature And Debye Frequency Of Metals Were Computed And Studied Using Quantum Einstein Theory. The Electron Density Parameters Of Strained Metals Is Obtained And Used In The Computation.. The Results Obtained Revealed That There Is Agreement Between The Computed And Experimental Values Of Debye Temperature And Debye Frequency. This Shows That The Model Can Be Used To Study Debye Properties Of Metals. The Debye Temperature And Debye Frequency Obtained Are More Concentrated In The High Density Limit. This Revealed That Debye Temperature And Debye Frequency Of Metals Depend On The Electronic Concentration. Also, The Experimental Value Of Debye Temperature And Debye Frequency Is Higher Than The Computed Value, This Is Because Of Some Factor Which Debye Temperature And Debye Frequency Relied On That The Theory Failed To Account For. Debye Temperature And Debye Frequency Of Metals Reduces As Strain Increase. This Shows That As Strain Increase, Space Between Lattice Atom Increase Which Reduces Strength Of Electron Interaction And There-By Forces Debye Temperature, Debye Frequency To Decrease As Deformation Increase. This Behavior Of Metals Reveal That Debye Temperature And Debye Frequency Is Greatly Affected By Deformation.

Nuclear radiation shielding and mechanical properties of colemanite mineral doped concretes

ABSTRACTThe present research focused on the investigation of photon and fast neutron shielding parameters of colemanite mineral doped and undoped concretes. The fabricated concretes have been exposed to gamma rays at 59.5 and 81 keV energies and the measurements have been carried out with NaI(Tl) detector. The parameters of effective atomic number (Zeff) and electron density (Nel) have been determined experimentally and theoretically. The exposure buildup factor (EBF) and energy absorption buildup factor (EBF) have been computed utilizing the Geometric progression (G–P) fitting method. In addition to the photon shielding parameters, the macroscopic effective removal cross-section calculations for fast neutron (ΣR) were performed. As a result, it was observed that the concretes doped with colemanite mineral are not very effective in gamma radiation shielding. On the contrary, it was observed that concretes with colemanite were more effective in shielding fast neutrons and the fast neutron removal cross-section values increased with increasing colemanite concentration in the concrete. Additionally, compressive strength values (MPa) of concretes were tested using ALFA TESTING (B001-PC) 200 tons capacity device.

Integrated operation of steady-state long-pulse H-mode in Experimental Advanced Superconducting Tokamak

Recent Experimental Advanced Superconducting Tokamak (EAST) experiments have successfully demonstrated a long-pulse steady-state scenario with improved plasma performance through integrated operation since the last IAEA FEC in 2016. A discharge with a duration over 100 s using pure radio frequency (RF) power heating and current drive has been obtained with the required characteristics for future long-pulse tokamak reactors such as good energy confinement quality (H98y2 ~ 1.1) with electron internal transport barrier inside ρ < 0.4, small ELMs (frequency ~100–200 Hz), and good control of impurity and heat exhaust with the tungsten divertor. The optimization of X-point, plasma shape, the outer gap and local gas puffing near the low hybrid wave (LHW) antenna were integrated with global parameters of BT and line-averaged electron density for higher current drive efficiency of LHW and on-axis deposition of electron cyclotron heating in the long-pulse operation. More recently, a high βP RF-only discharge (βP ~ 1.9 and βN ~ 1.5, /nGW ~ 0.80, f bs ~ 45% at q95 ~ 6.8) was successfully maintained over 24 s with improved hardware capabilities, demonstrating performance levels needed for the China Fusion Engineering Test Reactor steady-state operation. A higher energy confinement is observed at higher βP and with favorable toroidal field direction. Towards the next goal (⩾400 s long-pulse H-mode operations with ~50% bootstrap current fraction) on EAST, an integrated control of the current density profile, pressure profile and radiated divertor will be addressed in the near future.

Central ion cyclotron emission in the DIII-D tokamak

Collective ion cyclotron emission (ICE) at the ion cyclotron frequency and its harmonics is a potential passive diagnostic of the fast-ion distribution in fusion reactors. ICE is observed in most plasmas in the DIII-D tokamak and is most strongly excited by the fast ions from neutral beam injection. The conventional outboard-edge ICE is detected in H-mode plasmas. However, weaker centrally-localized ICE is measured in L-mode plasmas, including those with negative triangularity shapes. Similar ICE spectra are found with both ICE diagnostics systems, the dedicated magnetic probes and the instrumented antenna straps. Many differences in the behavior of this central ICE are generated by varying the deuterium beam injection angle into deuterium plasmas. The co-current ‘near-perpendicular’ beam excites the most central ICE from the co-current beams, with this emission detected from the fundamental to the fifth ICE harmonic. However, the counter-current ‘near-tangential’ beam destabilizes the highest amounts of centrally-localized ICE. This emission is spectrally broader than that driven by the co-current beams and is observed up to its seventh ICE harmonic. The central ICE excited by this co-current beam correlated strongly on the local electron density and related parameters (plasma current and neutron rate) and increased with deeper fast-ion loss boundaries towards the magnetic axis. This was also the case with second harmonic ICE driven by the counter-current beam but not with its stronger third harmonic emission. The central ICE harmonics destabilized by both beams are observed to have different temporal dynamics. The central ICE amplitude responds rapidly to transient MHD events; it dropped and recovered in less than a millisecond at each sawtooth event. ICE frequency splitting is triggered by both the co-current and counter-current ‘near-tangential’ beams. The data presented in this paper provide opportunities to test and validate models of excitation of ICE by energetic ions.

Reflection, transmission, and absorption of circularly polarized electromagnetic waves in a moving collisional magnetized plasma slab with inhomogeneous collision frequency and density

In this paper, microwave propagation through an inhomogeneous drifting collisional magnetized plasma slab is theoretically analyzed. The electron density and collision frequency have sinusoidal distribution. The electromagnetic wave has right-handed circular polarization and normally incident on the plasma surface. The reflectance, transmittance, and absorbance coefficients of this inhomogeneous plasma have been calculated by dividing the total slab into several sub-slabs so that electron density and collisional frequency parameters are considered constant in every sub-slab. Here the external magnetic field is uniform and its direction is along the inhomogeneity and perpendicular to surfaces of the plasma slab. Moreover, the plasma layer is moving with a non-relativistic constant velocity along the external magnetic field. The effects of frequency of the incident wave, cyclotron frequency, collision frequency, and velocity of the slab on the transmission, absorption, and reflection of the electromagnetic wave from the plasma layer are simulated. Results show that in this inhomogeneous magnetized plasma slab, reflection and absorption of the wave can be controlled by the external magnetic field and collision frequency. In low collision frequencies, the plasma slab behaves like an opaque or transparent medium when the frequency of the incident wave is lower or higher than the plasma frequency, respectively, whereas by increasing the collisional effects, the transmission of the high-frequency electromagnetic wave decreases and the significant part of the wave energy is absorbed by the plasma medium. Furthermore, the electromagnetic wave transmitted from this inhomogeneous slab can almost be vanished by adjusting the strength of the external magnetic field.

Plasmas Computed with ATMED CR of the 3rd Non-LTE Code Comparison Workshop Database

In this paper, there are presented some results calculated with ATMED CR of the 3rd Non-LTE Code Comparison Workshop held in December 2003, when this software didn’t exist, having been released in 2017. NLTE population kinetics codes were tested of steady-state cases for C, Al, Ar, Ge, Xe and Au plasmas selected for detailed comparisons. The scope of the meeting consisted of analyzing steady-state dense plasma cases of carbon, low temperature plasmas of aluminium and argon, X-ray laser experiments of germanium also with imposing a Planckian radiation field, medium- and high-Z multicharged ions of hot “experiment-related” plasmas of xenon, using real electron temperature and density parameters inferred from electronic and ionic Thomson scattering spectra and finally plasmas of gold. Being motivated by germanium X-ray laser experiments, the time history of electronic temperature Te and density Ne for a temporal dependent case is provided in Workshop NLTE-3. The calculation with ATMED CR has been carried out to t = 1.975 ns considering the non-uniform time grid along with the corresponding values of Te and Ne presented, being the initial condition LTE at low temperature. &#x0D; The results for plasma properties can be considered as relatively precise and optimal, being checked fundamentally the high sensitivity of calculations to changes in regime, local thermodynamic equilibrium (LTE) or non-LTE (NLTE), electronic and radiation temperatures, electronic density and the percentage of hot electrons. Frequency resolved and mean opacities are also displayed computed with ATMED CR using UTA (Unresolved Transition Array) or Mixed UTA formalisms.

Determination of the Signal Fluctuation Threshold of the Temperature‐Ion Composition Ambiguity Problem Using Monte Carlo Simulations

AbstractUnambiguously estimating the plasma parameters of the ionosphere at altitudes between 130 and 300 km presents a problem for the incoherent scatter radar (ISR). At these ranges, ISR is unable to distinguish between different mixtures of molecular ions (NO+ and O2+) and atomic oxygen ions (O+). Common solutions to this problem are either to employ empirical or theoretical models of the ionosphere or to add a priori known plasma parameter information obtained from the plasma line of the ISR spectrum. Studies have demonstrated that plasma parameters can be unambiguously estimated in almost noiseless scenarios, not commonly feasible during routine monitoring. In this study, we define a theoretical framework to quantify the ambiguity problem and determine the maximum signal fluctuation levels of the ISR signal to unambiguously estimate plasma parameters. We conduct Monte Carlo simulations for different plasma parameters to evaluate the estimation performance of the most commonly used nonlinear least squares optimization algorithm. Results are shown as probability curves of valid convergence and correct estimation. We use simulations to quantify the estimation error when using ionospheric models as initial conditions of the optimization algorithm. We also determine the contribution to the estimation process of different combinations of parameters known from the plasma line, the particular contribution of each plasma parameter, and the effect of increasing the level of uncertainty of the parameters known a priori. Results suggest that knowing a priori both electron density and electron temperature parameters allows an unambiguous estimation even at high fluctuation levels.

Assessing seismo-ionospheric disturbances using Vanuatu and Honshu earthquakes of March 25, 2007, employing DEMETER and GPS data

The signals of detection of electromagnetic emissions transmitted from earthquake regions (DEMETER), plasma ion analyser, instrument Sonde de Langmuir sensors, global positioning system and total electron content (TEC) were used to decipher variations of electron and ion density in the neighbourhoods of twin seismic events. These events took place on March 25, 2007, at Vanuatu and Honshu (Japan). Investigations through statistical analysis revealed that ionospheric plasma parameters of electron density and ion density were disturbed on both sets of data on the 6th and 4th days before the Honshu earthquake in Japan, during quiet geomagnetic period. However, for the Vanuatu earthquake, all detected irregularities from DEMETER data occurred during geomagnetic storm. Nevertheless, TEC anomaly showed unusual variations exactly two weeks before the seismic activity on quiet geomagnetic day. The disturbance storm time and planetarische Kennziffer indices were engaged in isolating pre-earthquake irregularities from other irregularities associated with geomagnetic actions.

Passive Radar Jamming: A Novel Method Using Time-Varying Plasma

Based on the resonance absorption effect of plasma, a novel time-varying plasma passive jamming method against one dimensional range profile of radar detection is proposed in this paper. The jamming mechanism of time-varying plasma structure is presented and verified. Based on the transmission line analogy, an instantaneous method is developed to calculate the radar time domain echo and the pulse compression of a target coated by the time-varying plasma. Then, the distortions of radar waveform and spectrum are numerically calculated. Finally, the jamming effect of the time-varying plasma on the one-dimensional range profile of a target is studied systematically for different regulating amplitude and frequency of electron density, radar bandwidth and pulse width parameters. The range profile result indicates that single radar target coating by time-varying plasma structure will generate cloaking effects and produce two or more false radar targets, and the distance between real and false target as well as reduction of echo intensity are related to the radar and regulating plasma parameters. The results show that this jamming method could have a great impact on the one-dimensional range profile, and the results could provide many useful reference to radar countermeasure.

Solving the enigma of weak fluorine contacts in the solid state: a periodic DFT study of fluorinated organic crystals.

The nature and strength of weak interactions with organic fluorine in the solid state are revealed by periodic density functional theory (periodic DFT) calculations coupled with experimental data on the structure and sublimation thermodynamics of crystalline organofluorine compounds. To minimize other intermolecular interactions, several sets of crystals of perfluorinated and partially fluorinated organic molecules are considered. This allows us to establish the theoretical levels providing an adequate description of the metric and electron-density parameters of the C–F⋯F–C interactions and the sublimation enthalpy of crystalline perfluorinated compounds. A detailed comparison of the C–F⋯F–C and C–H⋯F–C interactions is performed using the relaxed molecular geometry in the studied crystals. The change in the crystalline packing of aromatic compounds during their partial fluorination points to the structure-directing role of C–H⋯F–C interactions due to the dominant electrostatic contribution to these contacts. C–H⋯F–C and C–H⋯O interactions are found to be identical in nature and comparable in energy. The factors that determine the contribution of these interactions to the crystal packing are revealed. The reliability of the results is confirmed by considering the superposition of the electrostatic potential and electron density gradient fields in the area of the investigated intermolecular interactions.

Structure and electrostatic properties of the pyrimethamine-3,5-dihydroxybenzoic acid cocrystal in water solvent studied using transferred electron-density parameters.

Pyrimethamine is an antimalarial drug. The cocrystal salt form of pyrimethamine with 3,5-dihydroxybenzoic acid in water solvent has been synthesized, namely 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium 3,5-dihydroxybenzoate hemihydrate, C12H14ClN4+·C7H5O4-·0.5H2O. X-ray diffraction data were collected at room temperature. Refinement of the crystal structure was carried out using the classical Independent Atom Model (IAM), while the electrostatic properties were studied by transferring electron-density parameters from an electron-density database. The Cl atom was refined anharmonically. The results of both refinement methods were compared. Topological analyses were carried out using Bader's theory of Atoms in Molecules (AIM). The three-dimensional Hirshfeld surface analysis and the two-dimensional fingerprint maps of individual molecules revealed that the crystal structures are dominated by H...O/O...H and H...H contacts. Other close contacts are also present, including weak C...H/H...C contacts. Charge transfer between the pyrimethamine and 3,5-dihydroxybenzoic acid molecules results in a molecular assembly based on strong intermolecular hydrogen bonds. This is further validated by the calculation of the electrostatic potential based on transferred electron-density parameters. The current work proves the significance of the transferability principle in studying the electron-density-derived properties of molecules in cases where high-resolution diffraction data at low temperature are not available.

Experimental and theoretical study on the formation of hybrid discharge structure in a compact rf-driven negative hydrogen ion source

This study reports on an experimental and theoretical investigation of the formation of a hybrid discharge structure in a compact rf-driven negative hydrogen ion source. This structure suggests deposition of dc power in the expanding plasma region of the source, leading to a continuous axial increase of the plasma potential which is needed to drive the volume-produced negative hydrogen ions towards the extraction system. The dc power deposition is established by means of applying a bias that is higher than the plasma bulk potential at the first electrode of the extraction system. The 2D fluid-plasma model employed reveals the spatial distribution of the main plasma parameters of electron density, electron temperature and plasma potential, and it describes the mechanism of dc power deposition when the plasma electrode is biased. Optical emission spectroscopy is applied for diagnostics of the three regions of the source: rf power deposition, plasma expansion/dc power deposition, and extraction. The experimental results are not only for the electron ensemble (electron density and temperature), but also for that of the positive ions (ion densities) and neutrals (atomic and molecular temperatures and densities). The theory and experiment show good agreement, confirming the presence of the hybrid discharge structure.

The use of satellite beacon TEC data from GRBR campaign-based observations for ionosphere tomography over West Java Indonesia

The experiment of ionospheric tomographic reconstruction using satellite beacon TEC data from two or more adjacent GRBR observation stations following equatorial latitude and longitude have been conducted on campaign-based observation in Sumedang, Pameungpeuk and Indramayu West Java on 2016 and 2017. The reconstruction technique utilized is a simple algebraic reconstruction technique (ART). The result obtained is the ionosphere electron density distribution along the longitude of 108 degrees East over the area of West Java and Indonesia. The ionosphere electron density parameters obtained from the IRI-2012 Model were used as the initiation to construct ionospheric tomographic reconstruction. The validation performed by correlating foF2 from the ionospheric tomographic reconstruction with foF2 obtained from ionosonde observation at Sumedang station, one of the GRBR observation sites shows that corresponded to the correlation coefficient value of 0.8665, with a bias frequency of 1.386 MHz, whereas the correlation with the maximum electron density value obtained from the IRI-2016 model gives a correlation coefficient value of 0.8958. a bias frequency of 1.386 MHz, whereas the correlation with the maximum electron density value obtained from the IRI-2016 model gives a correlation coefficient value of 0.8958.

Instantaneous polarization statistic property of EM waves incident on time-varying reentry plasma

An analytical method is proposed in this paper to study the effect of time-varying reentry plasma sheath on the instantaneous polarization statistic property of electromagnetic (EM) waves. Based on the disturbance property of the hypersonic fluid, the spatial-temporal model of the time-varying reentry plasma sheath is established. An analytical technique referred to as transmission line analogy is developed to calculate the instantaneous transmission coefficient of EM wave propagation in time-varying plasma. Then, the instantaneous polarization statistic theory of EM wave propagation in the time-varying plasma sheath is developed. Taking the S-band telemetry right hand circularly polarized wave as an example, effects of incident angle and plasma parameters, including the electron density and the collision frequency on the EM wave's polarization statistic property are studied systematically. Statistical results indicate that the lower the collision frequency and the larger the electron density and incident angle is, the worse the deterioration of the polarization property is. Meanwhile, in conditions of critical parameters of certain electron density, collision frequency, and incident angle, the transmitted waves have both the right and left hand polarization mode, and the polarization mode will reverse. The calculation results could provide useful information for adaptive polarization receiving of the spacecraft's reentry communication.

Biotransformation, spectroscopic investigation, crystal structure and electrostatic properties of 3,7α-dihydroxyestra-1,3,5(10)-trien-17-one monohydrate studied using transferred electron-density parameters.

The biologically transformed product of estradiol valerate, namely 3,7α-dihydroxyestra-1,3,5(10)-trien-17-one monohydrate, C18H22O3·H2O, has been investigated using UV-Vis, IR, 1H and 13C NMR spectroscopic techniques, as well as by mass spectrometric analysis. Its crystal structure was determined using single-crystal X-ray diffraction based on data collected at 100 K. The structure was refined using the independent atom model (IAM) and the transferred electron-density parameters from the ELMAM2 database. The structure is stabilized by a network of hydrogen bonds and van der Waals interactions. The topology of the hydrogen bonds has been analyzed by the Bader theory of `Atoms in Molecules' framework. The molecular electrostatic potential for the transferred multipolar atom model reveals an asymmetric character of the charge distribution across the molecule due to a substantial charge delocalization within the molecule. The molecular dipole moment was also calculated, which shows that the molecule has a strongly polar character.

Fitting electron density as a physically sound basis for the development of interatomic potentials of complex alloys

The development of new interatomic potentials to model metallic systems is a difficult task, due in part to the dependence between the parameters that describe the electron density and the short-range interactions. Parameter search methods are prone to false convergence. To solve this problem, we have developed a methodology for obtaining the electron density parameters independently of the short-range interactions, so that physically sound parameters can be obtained to describe the electron density, after which the short-range parameters can be fitted, thus reducing the complexity of the process and yielding better interatomic potentials. With the new method we can develop self-consistent, accurate force fields, using solely calculations, without the need to fit to experimental data. Density functional theory calculations are used to compute the observables with which the potential is fit. We applied the method to a Ni-based Inconel 625 superalloy (IN625), modelled here as Ni, Cr, Mo and Fe solid solution alloys. The capability of the force fields developed using this new method is validated, by comparing the structural and thermo-elastic properties predicted with the force fields, with the corresponding experimental data, both for single crystals and polycrystalline alloys.

Electrostatic properties of the pyrimethamine–2,4-dihydroxybenzoic acid cocrystal in methanol studied using transferred electron-density parameters

The crystal structure of the cocrystal salt form of the antimalarial drug pyrimethamine with 2,4-dihydroxybenzoic acid in methanol [systematic name: 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium 2,4-dihydroxybenzoate methanol monosolvate, C12H14ClN4+·C7H5O4-·CH3OH] has been studied using X-ray diffraction data collected at room temperature. The crystal structure was refined using the classical Independent Atom Model (IAM) and the Multipolar Atom Model by transferring electron-density parameters from the ELMAM2 database. The Cl atom was refined anharmonically. The results of both refinement methods have been compared. The intermolecular interactions have been characterized on the basis of Hirshfeld surface analysis and topological analysis using Bader's theory of Atoms in Molecules. The results show that the molecular assembly is built primarily on the basis of charge transfer between 2,4-dihydroxybenzoic acid and pyrimethamine, which results in strong intermolecular hydrogen bonds. This fact is further validated by the calculation of the electrostatic potential based on transferred electron-density parameters.