Search results for: electrons concentration

Authors: N. Kekelidze, B. Kvirkvelia, E. Khutsishvili, T. Qamushadze, D. Kekelidze, R. Kobaidze, Z. Chubinishvili, N. Qobulashvili, G. Kekelidze

Abstract:

On the basis of InAs, InP and their InP_xAs_1-x solid solutions, the technologies were developed and materials were created where the electron concentration and optical and thermoelectric properties do not change under the irradiation with Ф = 2∙10¹⁸ n/cm² fluences of fast neutrons high-energy electrons (50 MeV, Ф = 6·10¹⁷ e/cm²) and 3 MeV electrons with fluence Ф = 3∙10¹⁸ e/cm². The problem of obtaining such material has been solved, in which under hard irradiation the mobility of the electrons does not decrease, but increases. This material is characterized by high thermal stability up to T = 700 °C. The complex process of defects formation has been analyzed and shown that, despite of hard irradiation, the essential properties of investigated materials are mainly determined by point type defects.

Keywords: InAs, InP, solid solutions, irradiation

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Authors: Maurizio Dapor, Isabel Abril, Pablo de Vera, Rafael Garcia-Molina

Abstract:

The ionization yield of ion tracks in polymers and bio-molecular systems reaches a maximum, known as the Bragg peak, close to the end of the ion trajectories. Along the path of the ions through the materials, many electrons are generated, which produce a cascade of further ionizations and, consequently, a shower of secondary electrons. Among these, very low energy secondary electrons can produce damage in the biomolecules by dissociative electron attachment. This work deals with the calculation of the energy distribution of electrons produced by protons in a sample of polymethylmethacrylate (PMMA), a material that is used as a phantom for living tissues in hadron therapy. PMMA is also of relevance for microelectronics in CMOS technologies and as a photoresist mask in electron beam lithography. We present a Monte Carlo code that, starting from a realistic description of the energy distribution of the electrons ejected by protons moving through PMMA, simulates the entire cascade of generated secondary electrons. By following in detail the motion of all these electrons, we find the radial distribution of the energy that they deposit in PMMA for several initial proton energies characteristic of the Bragg peak.

Keywords: Monte Carlo method, secondary electrons, energetic ions, ion-beam cancer therapy, ionization cross section, polymethylmethacrylate, proton beams, secondary electrons, radial energy distribution

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Authors: Djemai Bara, Mohamed Faouzi Mahboub, Djamila Bennaceur-Doumaz

Abstract:

In this work, the role of the preformed plasma created on the front face of a target, irradiated by a high intensity short pulse laser, in the framework of ion acceleration process, modeled by Target Normal Sheath Acceleration (TNSA) mechanism, is studied. This plasma is composed of cold ions governed by fluid equations and non-thermal & trapped with densities represented by a "Cairns-Gurevich" equation. The self-similar solution of the equations shows that electronic trapping and the presence of non-thermal electrons in the pre-plasma are both responsible in ion acceleration as long as the proportion of energetic electrons is not too high. In the case where the majority of electrons are energetic, the electrons are accelerated directly by the ponderomotive force of the laser without the intermediate of an accelerating plasma wave.

Keywords: Cairns-Gurevich Equation, ion acceleration, plasma expansion, pre-plasma

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Authors: Valentina V. Zhurikhina, Mihail I. Petrov, Alexandra A. Rtischeva, Mark Dussauze, Thierry Cardinal, Andrey A. Lipovskii

Abstract:

Polarization of glass, often referred to as thermal poling, is a well-known method to modify the glass physical and chemical properties, that manifest themselves in loosing central symmetry of the medium, glass structure and refractive index modification. The usage of the poling for second optical harmonic generation, fabrication of optical waveguides and electrooptic modulators was also reported. Nevertheless, the detailed description of the poling of glasses, containing multiple charge carriers is still under discussion. In particular, the role of possible migration of electrons in the space charge formation usually remains out of the question. In this work, we performed the numerical simulation of thermal poling of a silicate glass, containing Na, K, Mg, and Ca. We took into consideration the contribution of electrons in the polarization process. The possible explanation of migration of electrons can be the break of non-bridging oxygen bonds. It was found, that the modeled depth of the space charge region is about 10 times higher if the migration of the negative charges is taken under consideration. The simulated profiles of cations, participating in the polarization process, are in a good agreement with the experimental data, obtained by glow discharge spectroscopy.

Keywords: glass poling, charge transport, modeling, concentration profiles

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Authors: M. Sikoń, E. Bidzińska

Abstract:

An attempt to apply EPR (Electron Paramagnetic Resonance) spectroscopy to experimental analysis of the mechanical state of the loaded material is considered in this work. Theory concerns the participation of electrons in transfer of mechanical action. The model of measurement is shown by applying classical mechanics and quantum mechanics. Theoretical analysis is verified using EPR spectroscopy twice, once for the free spacemen and once for the mechanical loaded spacemen. Positive results in the form of different spectra for free and loaded materials are used to describe the mechanical state in continuum based on statistical mechanics. Perturbation of the optical electrons in the field of the mechanical interactions inspires us to propose new optical properties of the materials with mechanical stresses.

Keywords: Cosserat medium, EPR spectroscopy, optical active electrons, optical activity

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Authors: Nodar Kekelidze, David Kekelidze, Elza Khutsishvili, Bela Kvirkvelia

Abstract:

The semiconductor devices are irreplaceable elements for investigations in Space (artificial Earth satellite, interplanetary space craft, probes, rockets) and for investigation of elementary particles on accelerators, for atomic power stations, nuclear reactors, robots operating on heavily radiation contaminated territories (Chernobyl, Fukushima). Unfortunately, the most important parameters of semiconductors dramatically worsen under irradiation. So creation of radiation-resistant semiconductor materials for opto and microelectronic devices is actual problem, as well as investigation of complicated processes developed in irradiated solid states. Homogeneous single crystals of InP-InAs solid solutions were grown with zone melting method. There has been studied the dependence of the optical absorption coefficient vs photon energy near fundamental absorption edge. This dependence changes dramatically with irradiation. The experiments were performed on InP, InAs and InP-InAs solid solutions before and after irradiation with electrons and fast neutrons. The investigations of optical properties were carried out on infrared spectrophotometer in temperature range of 10K-300K and 1mkm-50mkm spectral area. Radiation fluencies of fast neutrons was equal to 2·1018neutron/cm2 and electrons with 3MeV, 50MeV up to fluxes of 6·1017electron/cm2. Under irradiation, there has been revealed the exponential type of the dependence of the optical absorption coefficient vs photon energy with energy deficiency. The indicated phenomenon takes place at high and low temperatures as well at impurity different concentration and practically in all cases of irradiation by various energy electrons and fast neutrons. We have developed the common mechanism of this phenomenon for unirradiated materials and implemented the quantitative calculations of distinctive parameter; this is in a satisfactory agreement with experimental data. For the irradiated crystals picture get complicated. In the work, the corresponding analysis is carried out. It has been shown, that in the case of InP, irradiated with electrons (Ф=1·1017el/cm2), the curve of optical absorption is shifted to lower energies. This is caused by appearance of the tails of density of states in forbidden band due to local fluctuations of ionized impurity (defect) concentration. Situation is more complicated in the case of InAs and for solid solutions with composition near to InAs when besides noticeable phenomenon there takes place Burstein effect caused by increase of electrons concentration as a result of irradiation. We have shown, that in certain conditions it is possible the prevalence of Burstein effect. This causes the opposite effect: the shift of the optical absorption edge to higher energies. So in given solid solutions there take place two different opposite directed processes. By selection of solid solutions composition and doping impurity we obtained such InP-InAs, solid solution in which under radiation mutual compensation of optical absorption curves displacement occurs. Obtained result let create on the base of InP-InAs, solid solution radiation-resistant optical materials. Conclusion: It was established the nature of optical absorption near fundamental edge in semiconductor materials and it was created radiation-resistant optical material.

Keywords: InAs-InP, electrons concentration, irradiation, solid solutions

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Authors: Abid Ali Abid

Abstract:

One-dimensional (1-D) particle-in-cell (PIC) electrostatic simulations are carried out to investigate the electrostatic waves, whose constituents are hot, cold and beam electrons in the background of motionless positive ions. In fact, the electrostatic modes excited are electron acoustic waves, beam driven waves as well as Langmuir waves. It is assessed that the relevant plasma parameters, for example, hot electron temperature, beam electron drift speed, and the electron beam density significantly modify the electrostatics wave's profiles. In the nonlinear stage, the wave-particle interaction becomes more evident and the waves have obtained its saturation level. Consequently, electrons become trapped in the waves and trapping vortices are clearly formed. Because of this trapping vortices and mixing of the electrons in phase space, finally, lead to electrons thermalization. It is observed that for the high-density value of the beam-electron, the solitary waves having a bipolar form of the electric field. These solitons are the nonlinear Brenstein-Greene and Kruskal wave mode that attributes the trapping of electrons potential well of phase-space hole. These examinations revealed that electrostatic waves have been exited in beam-plasma model and producing waves having broad-frequency ranges, which may clarify the broadband electrostatic noise (BEN) spectrum studied in the auroral zone.

Keywords: electron acoustic waves, trapping of cold electron, Langmuir waves, particle-in cell simulation

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Authors: Aouina Nabila Yasmina, Zine El Abidine Chaoui

Abstract:

Recently, understanding the interactions of electrons with the DNA molecule and its components has attracted considerable interest because DNA is the main site damaged by ionizing radiation. The interactions of radiation with DNA induce a variety of molecular damage such as single-strand breaks, double-strand breaks, basic damage, cross-links between proteins and DNA, and others, or the formation of free radicals, which, by chemical reactions with DNA, can also lead to breakage of the strand. One factor that can contribute significantly to these processes is the effect of water hydration on the formation and reaction of radiation induced by these radicals in and / or around DNA. B-DNA requires about 30% by weight of water to maintain its native conformation in the crystalline state. The transformation depends on various factors such as sequence, ion composition, concentration and water activity. Partial dehydration converts it to DNA-A. The present study shows the results of theoretical calculations for positrons and electrons elastic scattering with DNA medium and water over a broad energy range from 10 eV to 100 keV. Indeed, electron elastic cross sections and elastic mean free paths are calculated using a corrected form of the independent atom method, taking into account the geometry of the biomolecule (SCAR macro). Moreover, the elastic scattering of electrons and positrons by atoms of the biomolecule was evaluated by means of relativistic (Dirac) partial wave analysis. Our calculated results are compared with theoretical data available in the literature in the absence of experimental data, in particular for positron. As a central result, our electron elastic cross sections are in good agreement with existing theoretical data in the range of 10 eV to 1 keV.

Keywords: elastic cross scrion, elastic mean free path, scar macro method, electron collision

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Authors: Dilesh Indorkar

Abstract:

The aromatic, six membered ring containing three nitrogen atoms are known as triazines. Three triazines are theoretically possible, 1,3,5-triazine, 1,2,4-triazine and 1,2,3-triazine[1]. The 1,3,5-triazines are amongst the oldest known organic compounds. Originally they were called the symmetric triazines. Usuelly abbreviated to s- or sys triazines. The numbering follows the usual convention of beginning at the hetero atom as shown for the parent compound 1,3,5-triazine (I). The triazine rings, each contain 6 pi electrons which fill three bonding molecular orbital there are also three pairs of non bonding electrons in each molecule which are responsible for basic properties of the compounds.

Keywords: s-triazine, thiazoline, isoxazoline, benzoxazine heterocyclic

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Authors: R. Ondarza-Rovira, T. J. M. Boyd

Abstract:

Intense femtosecond laser light incident on over-critical density plasmas has shown to emit a prolific number of high-order harmonics of the driver frequency, with spectra characterized by power-law decays Pm ~ m-p, where m denotes the harmonic order and p the spectral decay index. When the laser pulse is p-polarized, plasma effects do modify the harmonic spectrum, weakening the so-called universal decay with p=8/3 to p=5/3, or below. In this work, appeal is made to a single particle radiation model in support of the predictions from particle-in-cell (PIC) simulations. Using this numerical technique we further show that the emission radiated by electrons -that are relativistically accelerated by the laser field inside the plasma, after being expelled into vacuum, the so-called Brunel electrons is characterized not only by the plasma line but also by ultraviolet harmonic orders described by the 5/3 decay index. Results obtained from these simulations suggest that for ultra-relativistic light intensities, the spectral decay index is further reduced, with p now in the range 2/3 ≤ p ≤ 4/3. This reduction is indicative of a transition from the regime where Brunel-induced plasma radiation influences the spectrum to one dominated by bremsstrahlung emission from the Brunel electrons.

Keywords: ultra-relativistic, laser-plasma interactions, high-order harmonic emission, radiation, spectrum

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Authors: Hoang Van Ngoc, Nguyen Vu Nhan, Nguyen Quang Bau

Abstract:

The light-effect in cylindrical quantum wire with an infinite potential for the case of electrons, optical phonon scattering, is studied based on the quantum kinetic equation. The density of the direct current in a cylindrical quantum wire by a linearly polarized electromagnetic wave, a DC electric field, and an intense laser field is calculated. Analytic expressions for the density of the direct current are studied as a function of the frequency of the laser radiation field, the frequency of the linearly polarized electromagnetic wave, the temperature of system, and the size of quantum wire. The density of the direct current in cylindrical quantum wire with an infinite potential for the case of electrons – optical phonon scattering is nonlinearly dependent on the frequency of the linearly polarized electromagnetic wave. The analytic expressions are numerically evaluated and plotted for a specific quantum wire, GaAs/GaAsAl.

Keywords: the light–effect, cylindrical quantum wire with an infinite potential, the density of the direct current, electrons-optical phonon scattering

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Authors: Sang-Wook Han, In-Hui Hwang, Zhenlan Jin, Chang-In Park

Abstract:

We used temperature-dependent X-Ray absorption fine structure (XAFS) measurements to examine the local structural properties around vanadium atoms at the V K edge from VO₂ films. A direct comparison of simultaneously-measured resistance and XAFS from the VO₂ films showed that the thermally-driven structural phase transition (SPT) occurred prior to the metal-insulator transition (MIT) during heating, whereas these changed simultaneously during cooling. XAFS revealed a significant increase in the Debye-Waller factors of the V-O and V-V pairs in the {111} direction of the R-phase VO₂ due to the phonons of the V-V arrays along the direction in a metallic phase. A substantial amount of structural disorder existing on the V-V pairs along the c-axis in both M₁ and R phases indicates the structural instability of V-V arrays in the axis. The anomalous structural disorder observed on all atomic sites at the SPT prevents the migration of the V 3d¹ electrons, resulting in a Mott insulator in the M₂-phase VO₂. The anomalous structural disorder, particularly, at vanadium sites, effectively affects the migration of metallic electrons, resulting in the Mott insulating properties in M₂ phase and a non-congruence of the SPT, MIT, and local density of state. The thermally-induced phonons in the {111} direction assist the delocalization of the V 3d¹ electrons in the R phase VO₂ and the electrons likely migrate via the V-V array in the {111} direction as well as the V-V dimerization along the c-axis. This study clarifies that the tetragonal symmetry is essentially important for the metallic phase in VO₂.

Keywords: metal-insulator transition, XAFS, VO₂, structural-phase transition

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Authors: Sara Arafeh, Kovriguine Evguine

Abstract:

Cytochromes P450 are enzymes that require a supply of electrons to catalyze the synthesis of steroid hormones, fatty acids, and prostaglandin hormone. Cytochrome P450 Oxidoreductase (CYPOR), a membrane bound enzyme, provides these electrons in its open conformation. CYPOR has two cytosolic domains (FAD domain and FMN domain) and an N-terminal in the membrane. In its open conformation, electrons flow from NADPH, FAD, and finally to FMN where cytochrome P450 picks up these electrons. In the closed conformation, cytochrome P450 does not bind to the FMN domain to take the electrons. It was found that when the cytosolic domains are isolated, CYPOR could not bind to cytochrome P450. This suggested that the membrane environment is important for CYPOR function. This project takes the initiative to better understand the dynamics of CYPOR in its full length. Here, we determine the distance between specific sites in the FAD and FMN binding domains in CYPOR by Forster Resonance Energy Transfer (FRET) and Ultrafast TA spectroscopy with and without NADPH. The approach to determine these distances will rely on labeling these sites with red and infrared fluorophores. Mimic membrane attachment is done by inserting CYPOR in lipid nanodiscs. By determining the distances between the donor-acceptor sites in these domains, we can observe the open/closed conformations upon reducing CYPOR in the presence and absence of cytochrome P450. Such study is important to better understand CYPOR mechanism of action in various endosomal membranes including hepatic CYPOR which is vital in plasma cholesterol homeostasis. By investigating the conformational cycles of CYPOR, we can synthesize drugs that would be more efficient in affecting the steroid hormonal levels and metabolism of toxins catalyzed by Cytochrome P450.

Keywords: conformational cycle of CYPOR, cytochrome P450, cytochrome P450 oxidoreductase, FAD domain, FMN domain, FRET, Ultrafast TA Spectroscopy

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Authors: Rosangliana Chawngthu, Ramkumar K. Thapa

Abstract:

A model calculation of photoassisted field emission current (PFEC) by using transfer Hamiltonian method will be present here. When the photon energy is incident on the surface of the metals, such that the energy of a photon is usually less than the work function of the metal under investigation. The incident radiation photo excites the electrons to a final state which lies below the vacuum level; the electrons are confined within the metal surface. A strong static electric field is then applied to the surface of the metal which causes the photoexcited electrons to tunnel through the surface potential barrier into the vacuum region and constitutes the considerable current called photoassisted field emission current. The incident radiation is usually a laser beam, causes the transition of electrons from the initial state to the final state and the matrix element for this transition will be written. For the calculation of PFEC, transfer Hamiltonian method is used. The initial state wavefunction is calculated by using Kronig-Penney potential model. The effect of the matrix element will also be studied. An appropriate dielectric model for the surface region of the metal will be used for the evaluation of vector potential. FORTRAN programme is used for the calculation of PFEC. The results will be checked with experimental data and the theoretical results.

Keywords: photoassisted field emission, transfer Hamiltonian, vector potential, wavefunction

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Authors: Tobias Schnabel

Abstract:

Naphthalene and naphthalene similar compounds are a common problem in the indoor air of buildings from the 1960s and 1970s in Germany. Often tar containing roof felt was used under the concrete floor to prevent humidity to come through the floor. This tar containing roof felt has high concentrations of PAH (Polycyclic aromatic hydrocarbon) and naphthalene. Naphthalene easily evaporates and contaminates the indoor air. Especially after renovations and energetically modernization of the buildings, the naphthalene concentration rises because no forced air exchange can happen. Because of this problem, it is often necessary to change the floors after renovation of the buildings. The MFPA Weimar (Material research and testing facility) developed in cooperation a project with LEJ GmbH and Reichmann Gebäudetechnik GmbH. It is a technical solution for the disintegration of naphthalene in naphthalene, similar compounds in indoor air with photocatalytic reforming. Photocatalytic systems produce active oxygen species (hydroxyl radicals) through trading semiconductors on a wavelength of their bandgap. The light energy separates the charges in the semiconductor and produces free electrons in the line tape and defect electrons. The defect electrons can react with hydroxide ions to hydroxyl radicals. The produced hydroxyl radicals are a strong oxidation agent, and can oxidate organic matter to carbon dioxide and water. During the research, new titanium oxide catalysator surface coatings were developed. This coating technology allows the production of very porous titan oxide layer on temperature stable carrier materials. The porosity allows the naphthalene to get easily absorbed by the surface coating, what accelerates the reaction of the heterogeneous photocatalysis. The photocatalytic reaction is induced by high power and high efficient UV-A (ultra violet light) Leds with a wavelength of 365nm. Various tests in emission chambers and on the reformer itself show that a reduction of naphthalene in important concentrations between 2 and 250 µg/m³ is possible. The disintegration rate was at least 80%. To reduce the concentration of naphthalene from 30 µg/m³ to a level below 5 µg/m³ in a usual 50 ² classroom, an energy of 6 kWh is needed. The benefits of the photocatalytic indoor air treatment are that every organic compound in the air can be disintegrated and reduced. The use of new photocatalytic materials in combination with highly efficient UV leds make a safe and energy efficient reduction of organic compounds in indoor air possible. At the moment the air cleaning systems take the step from prototype stage into the usage in real buildings.

Keywords: naphthalene, titandioxide, indoor air, photocatalysis

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Authors: Sandeep Kumar, Naveen Gupta

Abstract:

Terahertz (THz) generation has been investigated by beating two cosh-Gaussian laser beams of the same amplitude but different wavenumbers and frequencies through rippled collisionless plasma. The ponderomotive force is operative which is induced due to the intensity gradient of the laser beam over the cross-section area of the wavefront. The electrons evacuate towards a low-intensity regime, which modifies the dielectric function of the medium and results in cross focusing of cosh-Gaussian laser beams. The evolution of spot size of laser beams has been studied by solving nonlinear Schrodinger wave equation (NLSE) with variational technique. The laser beams impart oscillations to electrons which are enhanced with ripple density. The nonlinear oscillatory motion of electrons gives rise to a nonlinear current density driving THz radiation. It has been observed that the periodicity of the ripple density helps to enhance the THz radiation.

Keywords: rippled collisionless plasma, cosh-gaussian laser beam, ponderomotive force, variational technique, nonlinear current density

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Authors: Yuan Yan

Abstract:

Interlayer interactions or hybridization in van der Waals (vdW) heterostructures of two-dimensional (2D) materials significantly influence their physical characteristics, including layer-dependent electronic and vibrational structures, magic-angle superconductivity, interlayer antiferromagnetism, and interlayer excitons. These interactions are sensitive to a set of interdependent and externally tunable parameters. To fully exploit the potential of these materials, it is crucial to understand the physical origins of interlayer interaction and hybridization. Traditional theories often attribute these interactions to the sharing of electrons via p orbital lone pairs or π electrons, based on the octet rule, which posits that p electrons are the primary occupants of the outermost atomic shells, except in hydrogen. However, our study challenges this prevailing belief. Through geometry-based analysis, we conducted a high-throughput screening of the Materials Project database and identified 1,623 layered materials. By examining the atomic structure and bonding characteristics of surface atoms, we demonstrate that s-orbital lone pairs can also drive interlayer interactions in two-dimensional materials. Using density functional theory, we further analyzed charge distribution and electronic localization. The crystal field and inert pair effect induce a Stark-like phenomenon, leading to energy level splitting and the formation of directional electron clouds. This allows these electrons to directly participate in the hybridization of interlayer wavefunctions without forming chemical bonds. it findings expand the understanding of interlayer interactions, revealing new mechanisms that govern these properties and providing a theoretical foundation for manipulating interlayer phenomena in 2D materials.

Keywords: interlayer interaction, nanomaterials, 2D materials, van der waals, heterostructures

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Authors: Intissar Benrhouma, Marta Victoria, Ignacio Anton, Bechir Chaouachi

Abstract:

Concentrating photovoltaic systems CPV use optical elements, such as Fresnel lenses, to concentrate solar intensity. The concentrated solar energy is delivered to the solar cell from 20 to 100 W/cm². Some of this energy is converted to electricity, while the rest must be disposed of as a residual heat. Solar cells cooling should be a necessary part of CPV modeling because these systems allowed increasing the power received by the cell. This high power can rise the electrons’ potential causing the heating of the cell, which reduces the global module’s efficiency. This work consists of modeling a concentrating photovoltaic module with and without a cooling system. We have established a theoretical model based on energy balances carried out on a photovoltaic module using solar radiation concentration cells. Subsequently, we developed a calculation program on Matlab which allowed us to simulate the functioning of this module. The obtained results show that the addition of a cooling system to the module improves greatly the performance of our CPV system.

Keywords: solar energy, photovoltaic, concentration, cooling, performance improvement

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Authors: Ioan Rusu

Abstract:

Let us consider that the entire universe is composed of a single hydrogen atom within which the electron is moving around the proton. In this case, according to classical theories of physics, radiation and photons, respectively, should be absorbed by the electron. Depending on the number of photons absorbed, the electron radius of rotation around the proton is established. Until now, the principle of photon absorption by electrons and the electron transition to a new energy level, namely to a higher radius of rotation around the proton, is not clarified in physics. This paper aims to demonstrate that photons have mass and negative electrostatic charge similar to electrons but infinitely smaller. The experiments which demonstrate this theory are simple: thermal expansion, photoelectric effect and thermonuclear reaction.

Keywords: electrostatic, electron, photon, proton, radiation

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Authors: Nguyen Quang Bau, Nguyen Thu Huong, Dang Thi Thanh Thuy

Abstract:

The analytic expression for the Hall Coefficient (HC) caused by the confined electrons in the presence of a strong electromagnetic wave (EMW) including the effect of phonon confinement in rectangular quantum wires (RQWs) is calculated by using the quantum kinetic equation for electrons in the case of electron - optical phonon scattering. It is because the expression of the HC for the confined phonon case contains indexes m, m’ which are specific to the phonon confinement. The expression in a RQW is different from that for the case of unconfined phonons in a RQW or in 2D. The results are numerically calculated and discussed for a GaAs/GaAsAl RQW. The numerical results show that HC in a RQW can have both negative and positive values. This is different from the case of the absence of EMW and the case presence of EMW including the effect of phonon unconfinement in a RQW. These results are also compared with those in the case of unconfined phonons in a RQW and confined phonons in a quantum well. The conductivity in the case of confined phonon has more resonance peaks compared with that in case of unconfined phonons in a RQW. This new property is the same in quantum well. All results are compared with the case of unconfined phonons to see differences.

Keywords: Hall coefficient, rectangular quantum wires, electron-optical phonon interaction, quantum kinetic equation, confined phonons

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Authors: Sanjit Kumar Paul, A. A. Mamun, M. R. Amin

Abstract:

The Linear propagation of the dust-acoustic wave in a dusty plasma consisting of Boltzmann distributed electrons and ions and mobile charge fluctuating positive dust grains has been investigated by employing the reductive perturbation method. It has been shown that the dust charge fluctuation is a source of dissipation and its responsible for the formation of the dust-acoustic waves in such a dusty plasma. The basic features of such dust-acoustic waves have been identified. It has been proposed to design a new laboratory experiment which will be able to identify the basic features of the dust-acoustic waves predicted in this theoretical investigation.

Keywords: dust acoustic waves, dusty plasma, Boltzmann distributed electrons, charge fluctuation

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Authors: Jing Hu, Xiaoping Ouyang

Abstract:

We develop an optical readout gas chamber based on avalanche-induced scintillation for energetic charged particles track. The gas chamber is equipped with a Single Anode Wires (SAW) structure to produce intensive electric field when the measured particles are of low yield or even single. In the presence of an intensive electric field around the single anode, primary electrons, resulting from the incident charged particles when depositing the energy along the track, accelerate to the anode effectively and rapidly. For scintillation gasses, this avalanche of electrons induces multiplying photons comparing with the primary scintillation excited directly from particle energy loss. The electric field distribution for different shape of the SAW structure is analyzed, and finally, an optimal one is used to study the optical readout performance. Using CF4 gas and its mixture with the noble gas, the results indicate that the optical readout characteristics of the chamber are attractive for imaging. Moreover, images of particles track including single particle track from 5.485MeV alpha particles are successfully acquired. The track resolution is quite well for the reason that the electrons undergo less diffusion in the intensive electric field. With the simple and ingenious design, the optical readout gas chamber has a high sensitivity. Since neutrons can be converted to charged particles when scattering, this optical readout gas chamber can be applied to neutron measurement for dark matter, fusion research, and others.

Keywords: optical readout, gas chamber, charged particle track, avalanche-induced scintillation, neutron measurement

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Authors: Natarajan Tirupattur Srinivasan

Abstract:

Quantum mechanics( QM) and (special) relativity (SR) have indeed revolutionized the very thinking of physicists, and the spectacular successes achieved over a century due to these two theories are mind-boggling. However, there is still a strong disquiet among some physicists. While the mathematical structure of these two theories has been established beyond any doubt, their physical interpretations are still being contested by many. Even after a hundred years of their existence, we cannot answer a very simple question, “What is an electron”? Physicists are struggling even now to come to grips with the different interpretations of quantum mechanics with all their ramifications. However, it is indeed strange that the (special) relativity theory of Einstein enjoys many orders of magnitude of “acceptance”, though both theories have their own stocks of weirdness in the results, like time dilation, mass increase with velocity, the collapse of the wave function, quantum jump, tunnelling, etc. Here, in this paper, it would be shown that by postulating an intrinsic internal motion to these enigmatic electrons, one can build a fairly consistent picture of reality, revealing a very simple picture of nature. This is also evidenced by Schrodinger’s ‘Zitterbewegung’ motion, about which so much has been written. This leads to a helical trajectory of electrons when they move in a laboratory frame. It will be shown that the helix is a three-dimensional wave having all the characteristics of our familiar 2D wave. Again, the helix, being a geodesic on an imaginary cylinder, supports ‘quantization’, and its representation is just the complex exponentials matching with the wave function of quantum mechanics. By postulating the instantaneous velocity of the electrons to be always ‘c’, the velocity of light, the entire relativity comes alive, and we can interpret the ‘time dilation’, ‘mass increase with velocity’, etc., in a very simple way. Thus, this model unifies both QM and SR without the need for a counterintuitive postulate of Einstein about the constancy of the velocity of light for all inertial observers. After all, if the motion of an inertial frame cannot affect the velocity of light, the converse that this constant also cannot affect the events in the frame must be true. But entire relativity is about how ‘c’ affects time, length, mass, etc., in different frames.

Keywords: quantum reconstruction, special theory of relativity, quantum mechanics, zitterbewegung, complex wave function, helix, geodesic, Schrodinger’s wave equations

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Authors: K. Thiel, P. Patrikainen, C. Nagy, D. Fitzpatrick, E.-M. Aro, P. Kallio

Abstract:

Photosynthetic cyanobacteria have been recognized as potential future biotechnological hosts for the direct conversion of CO₂ into chemicals of interest using sunlight as the solar energy source. However, in order to develop commercially viable systems, the flux of electrons from the photosynthetic light reactions towards specified target chemicals must be significantly improved. The objective of the study was to investigate whether the autotrophic production efficiency of specified end-metabolites can be improved in engineered cyanobacterial cells by rescuing excited electrons that are normally lost to molecular oxygen due to the cyanobacterial flavodiiron protein Flv1/3. Natively Flv1/3 dissipates excess electrons in the photosynthetic electron transfer chain by directing them to molecular oxygen in Mehler-like reaction to protect photosystem I. To evaluate the effect of flavodiiron inactivation on autotrophic production efficiency in the cyanobacterial host Synechocystis sp. PCC 6803 (Synechocystis), sucrose was selected as the quantitative reporter and a representative of a potential end-product of interest. The concept is based on the native property of Synechocystis to produce sucrose as an intracellular osmoprotectant when exposed to high external ion concentrations, in combination with the introduction of a heterologous sucrose permease (CscB from Escherichia coli), which transports the sucrose out from the cell. In addition, cell growth, photosynthetic gas fluxes using membrane inlet mass spectrometry and endogenous storage compounds were analysed to illustrate the consequent effects of flv deletion on pathway flux distributions. The results indicate that a significant proportion of the electrons can be lost to molecular oxygen via Flv1/3 even when the cells are grown under high CO₂ and that the inactivation of flavodiiron activity can enhance the photosynthetic electron flux towards optionally available sinks. The flux distribution is dependent on the light conditions and the genetic context of the Δflv mutants, and favors the production of either sucrose or one of the two storage compounds, glycogen or polyhydroxybutyrate. As a conclusion, elimination of the native Flv1/3 reaction and concomitant introduction of an engineered product pathway as an alternative sink for excited electrons could enhance the photosynthetic electron flux towards the target endproduct without compromising the fitness of the host.

Keywords: cyanobacterial engineering, flavodiiron proteins, redirecting electron flux, sucrose

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Authors: Sivapan Choo-In

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The main objective of this study was investigate particulate matter concentration on main and secondary roadside in urban area. And studied on the concentration of some heavy metal including lead (Pb), zinc (Zn), copper (Cu) and cadmium (Cd) in particulate matter in Bangkok area. The averaged particle concentration for main roadside are higher than secondary roadside. The particulate matter less than 10 micron concentration contribute the majority of the Total Suspended Particulate for main road and zinc concentration were higher than copper and lead for both site.

Keywords: air pollution, air quality, polution, monitoring

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Authors: Anchal Gupta

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Amid the escalating digitalization and deployment of cross-border technological solutions, a significant portion of the industry and regulatory bodies have begun to pose queries concerning the formulation, computation, and contemplation of concentration risk. In the financial sector, well-established parameters exist for gauging the concentration of a portfolio and similar elements. However, a unified framework appears to be absent, which could guide industry and regulators pertaining to non-financial concentration risk. This paper introduces a framework, constructed on the foundation of multiple regulations where regulators are advocating for licensed corporations to evaluate their concentration risk. The lacuna lies in the fact that, while regulators delineate what constitutes concentration risk, unlike other domains, no guidelines are provided that could assist firms. This frequently results in ambiguity and individual corporate interpretation, which, from a risk management standpoint, is less than ideal.

Keywords: concentration risk, non-financial risk, government regulation, financial regulation, non-market risk, MAS, DORA, EDSP, SFC

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Authors: Dake Xiong, Ben Hankamer, Ian Ross

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The most urgent challenge of our time is to replace the depleting resources of fossil fuels by sustainable environmentally friendly alternatives. Hydrogen is a promising CO2-neutral fuel for a more sustainable future especially when produced photo-biologically. Hydrogen can be photosynthetically produced in unicellular green alga like Chlamydomonas reinhardtii, catalysed by the inducible highly active and bidirectional [FeFe]-hydrogenase enzymes (HydA). However, evolutionary and physiological constraints severely restrict the hydrogen yield of algae for industrial scale-up, mainly due to its competition among other metabolic pathways on photosynthetic electrons. Among them, a major challenge to be resolved is the inferior competitiveness of hydrogen production (catalysed by HydA) with NADPH production (catalysed by ferredoxin-NADP+-reductase (FNR)), which is essential for cell growth and takes up ~95% of photosynthetic electrons. In this work, the in vivo hydrogen production efficiency of mutants with ferredoxin-hydrogenase (Fd*-HydA1*) fusion protein construct, where the electron donor ferredoxin (Fd*) is fused to HydA1* and expressed in the model organism C. reinhardtii was investigated. Once Fd*-HydA1* fusion gene is expressed in algal cells, the fusion enzyme is able to draw the redistributed photosynthetic electrons and use them for efficient hydrogen production. From preliminary data, mutants with Fd*-HydA1* transgene showed a ~2-fold increase in the photosynthetic hydrogen production rate compared with its parental strain, which only possesses the native HydA in vivo. Therefore, a solid method of having more efficient hydrogen production in microalgae can be achieved through the expression of the synthetic enzymes.

Keywords: Chlamydomonas reinhardtii, ferredoxin, fusion protein, hydrogen production, hydrogenase

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Authors: Yin Rui, Yin Ming, Wang Yang

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For a rotational reference frame of the theory of special relativity, the critical radius is defined as the distance from the axis to the point where the tangential velocity is equal to the speed of light, and the critical cylinder as the set of all points separated from the axis by this critical radius. Based on these terms, two relativistic effects of rotation are discovered: (i) the tangential velocity in the region of Outside Critical Cylinder (OCC) is not superluminal due to the existence of space-time exchange; (ii) some of the physical quantities of the rotational body have an opposite mathematic sign at OCC versus those at Inside Critical Cylinder (ICC), which is termed as the Critical Cylindrical Effect (CCE). The laboratory experiments demonstrate that the repulsive force exerted on an anion by electrons will change to an attractive force by the electrons in precession while the anion is at OCC of the precession. Thirty-six screenshots from four experimental videos are provided. Theoretical proofs for both space-time exchange and CCE are then presented. The CCEs of field force are also discussed.

Keywords: critical radius, critical cylindrical effect, special relativity, space-time exchange

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Authors: S. K. Jain, M. K. Mishra

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Oblique propagation of ion-acoustic solitons in magnetized electron-positron-ion (EPI) plasma with warm adiabatic ions and isothermal electrons has been studied. Korteweg-de Vries (KdV) equation using reductive perturbation method has been derived for the system, which admits an obliquely propagating soliton solution. It is found that for the selected set of parameter values, the system supports only compressive solitons. Investigations reveal that an increase in positron concentration diminishes the amplitude as well as the width of the soliton. It is also found that the temperature ratio of electron to positron (γ) affects the amplitude of the solitary wave. An external magnetic field do not affect the amplitude of ion-acoustic solitons, but obliqueness angle (θ), the angle between wave vector and magnetic field affects the amplitude. The amplitude of the ion-acoustic solitons increases with increase in angle of obliqueness. Magnetization and obliqueness drastically affect the width of the soliton. An increase in ionic temperature decreases the amplitude and width. For the fixed set of parameters, profiles have been drawn to study the combined effect with variation of two parameters on the characteristics of the ion-acoustic solitons (i.e., amplitude and width). The result may be applicable to plasma in the laboratory as well as in the magnetospheric region of the earth.

Keywords: ion-acoustic solitons, Korteweg-de Vries (KdV) equation, magnetized electron-positron-ion (EPI) plasma, reductive perturbation method

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Authors: Jie Yin, Jun Zhang

Abstract:

Measuring the growth performance and critical supersaturation of particle group have a high reference value for constructing a supersaturated water vapor environment that can improve the removal efficiency of the high-concentration particle group. The critical supersaturation and the variation of the growth performance with supersaturation for high-concentration particles were measured by a flow cloud chamber. Findings suggest that the influence of particle concentration on the growth performance will reduce with the increase of supersaturation. Reducing residence time and increasing particle concentration have similar effects on the growth performance of the high-concentration particle group. Increasing particle concentration and shortening residence time will increase the critical supersaturation of the particle group. The critical supersaturation required to activate a high-concentration particle group is lower than that of the single-particle when the minimum particle size in the particle group is the same as that of a single particle.

Keywords: sub-micron particles, heterogeneous condensation, critical supersaturation, nucleation

Procedia PDF Downloads 154