Measurements of the complex permittivity and permeability of solids at high electromagnetic field greater than 10 kV/m pose a significant challenge to RF connectors and input amplifiers of the ...measurement equipment. Specifically, difficulties arise in measuring materials with high imaginary permittivity or low impedance, which act as short circuits, either exceeding the measurement equipment damage threshold or that of the material under test, and/or inducing an unacceptable signal-to-noise in the collected data. In this work, we report the development of a new measurement technique where we introduce an outer air-gap between the material under test and the conductor of a coax airline. The introduced air-gap reduces the effective conductivity of the sample, mitigating damage to the materials under test and allowing for high power measurement. This study compares the ability of air-gap correction methods to recover the complex permittivity and permeability to within 10% of the value measured without an air-gap introduced.
Majorana zero-modes-a type of localized quasiparticle-hold great promise for topological quantum computing. Tunnelling spectroscopy in electrical transport is the primary tool for identifying the ...presence of Majorana zero-modes, for instance as a zero-bias peak in differential conductance. The height of the Majorana zero-bias peak is predicted to be quantized at the universal conductance value of 2e
/h at zero temperature (where e is the charge of an electron and h is the Planck constant), as a direct consequence of the famous Majorana symmetry in which a particle is its own antiparticle. The Majorana symmetry protects the quantization against disorder, interactions and variations in the tunnel coupling. Previous experiments, however, have mostly shown zero-bias peaks much smaller than 2e
/h, with a recent observation of a peak height close to 2e
/h. Here we report a quantized conductance plateau at 2e
/h in the zero-bias conductance measured in indium antimonide semiconductor nanowires covered with an aluminium superconducting shell. The height of our zero-bias peak remains constant despite changing parameters such as the magnetic field and tunnel coupling, indicating that it is a quantized conductance plateau. We distinguish this quantized Majorana peak from possible non-Majorana origins by investigating its robustness to electric and magnetic fields as well as its temperature dependence. The observation of a quantized conductance plateau strongly supports the existence of Majorana zero-modes in the system, consequently paving the way for future braiding experiments that could lead to topological quantum computing.
Electroporation or electropermeabilization is a technique that enables transient increase in the cell membrane permeability by exposing cells to pulsed electric field. However, the molecular ...mechanisms of the long-lived cell membrane permeability, which persists on the minutes time scale after the pulse treatment, remain elusive. Experimental studies have suggested that lipid peroxidation could present a mechanism of this prolonged membrane permeabilization. In this study we make the first important step in quantifying the possible contribution of lipid peroxidation to electropermeabilization. We use free energy calculations to quantify the permeability and conductance of bilayers, containing an increasing percentage of hydroperoxide lipid derivatives, to sodium and chloride ions. We then compare our calculations to experimental measurements on electropermeabilized cells. Our results show that the permeability and conductance increase dramatically by several orders of magnitude in peroxidized bilayers. Yet this increase is not sufficient to reasonably account for the entire range of experimental measurements. Nevertheless, lipid peroxidation might be considered an important mechanism of prolonged membrane permeabilization, if exposure of cells to high voltage electric pulses leads to secondary lipid peroxidation products. Our analysis calls for experimental studies, which will determine the type and amount of lipid peroxidation products in electropermeabilized cell membranes.
•Na and Cl ions permeability of peroxidized lipid bilayers is investigated using Unified Free Energy Dynamics simulations.•The contribution of lipid peroxidation to electropermeabilization is quantitatively assessed.•High amounts of peroxidized lipids increase the bilayers permeability and conductance by several orders of magnitude.•Hydroperoxide lipid derivatives are not permeable enough to account for the measured electropermeabilization of cells.
•Synthesis of new hydrazone complexes which fully characterized by all possible techniques.•IR, 1H NMR, TGA, CHN, SEM, XRD, ESR, UV-Vis and magnetism were the tools basically used.•The biological ...tests were executed in-vitro towards bacteria and ctDNA-degradation.•Conductometric study was performed for copper sulfate in its bulk or nano-sized also under several conditions.
A series of new hydrazone complexes were prepared and perfectly elucidated to be 1:1 molar ratio with Cd(II) complex, while 1:2 (M:L) with Co(II), Ni(II) and Cu(II) complexes. The bidentate form of bonding was proposed for all complexes, either in octahedral or square-planer geometry with the Ni(II) complex. The UV-Vis spectral data as well as the magnetism of complexes (except Cd(II) one) suggested the geometry of complexes around the central atoms as well as the ligand field parameters (10Dq, B & β). In addition, the spin Hamiltonian parameters attribute to S = 1/2 and I = 3/2, were calculated for Cu(II) complex according to its ESR spectrum. XRD and SEM analyses were performed for selected complexes and the particle size of Ni(II) complex appeared in nan-scale. The DFT approach was used to optimize the ligand and its complexes under valence double-zeta polarized basis set and the correlation-consistent basis set. The ligand exhibited favorable characteristic for O(11) and O(12) atoms as orientation, nucleophilicity and charges, which help their priority in coordination. Genotoxicity of H2PHNH ligand and its Cd(II), Cu(II), and Ni(II) complexes degraded ctDNA into two distinct bands. Conductometric analysis for copper sulfate was performed in its bulk or nano-sized as well as in absence or presence of H2PHNH ligand. Using Fuoss-Hsia-Fernández-Prini (FHFP) equation, the molar conductance (Λm), the limiting molar conductance (Λo), Onsager slope (S), Walden product (Λo ηo), ion-pair interaction constant (KA), degree of dissociation (α), and activity coefficient (γ±) were calculated. The obtained data were elaborately discriminated according to the state of CuSO4 used (bulk & nano-sized) also in absence or presence of the ligand. Moreover, the thermodynamic parameters as well as the molar ratio of the formed complexes, were estimated in all systems studied. Finally, in bulk or nano-sized CuSO4 in presence of H2PHNH complexes, the formation constants and Gibbs free energies obey this order: Kf(1:2) > Kf (1:1) M:L.
•We designed and realized a set of four custom tuning forks.•We investigated the Quartz tuning forks (QTFs) electrical performance.•We determined the dependence of QTFs main physical parameters on ...their dimensions.•We identified in quality factor and conductance the figures of merit for sensing.•We provided guidelines to design tuning forks for photoacoustic spectroscopy.
We report a detailed experimental and theoretical analysis of the influence of quartz tuning fork (QTF) dimensions on the main physical parameters controlling the QTF performance, namely, the quality factor Q, the resonance frequency, the fork stiffness, the spring constant, and the electrical resistance. Two different gold contact patterns were also compared. As a general trend, the QTF performance in terms of Q and electrical conductance values improves at increasing both the crystal thickness T and prong thickness w, while decreasing the prongs length Lp. However, since the QTF resonance frequency f0 is proportional to T/Lp2, a trade-off should be found in order to keep f0<40kHz, i.e., well below the typical values of non-radiative relaxation rate of a targeted gas absorption lines.
Asymmetric membranes and asymmetric pores are broad classes of objects, the role of which is steadily growing in academia and industry. During the last two decades, asymmetric (often called ...“conical”) track-etched nanopores have attracted increasing attention from the scientific community due to their great potential for accomplishing useful functions in nanofluidic devices. A great body of knowledge has been gained on the electrical and electroosmotic properties of track-etched asymmetric nanopores in electrolyte solutions. Less attention has been paid to the pore geometry, and practically no attempts have been made to explore their osmotic and hydraulic properties. The present study fills this gap by examining the interrelations between the electrical, osmotic, hydraulic and structural characteristics of an asymmetrically etched ion-track nanopore. Several consecutive phases of pore evolution are identified. In the last phase, the highly asymmetric membrane resembles a porous 2D material. The temporal dependences of the two counter-fluxes – the diffusional flux of the etchant and the volume flux of stopping media - are elucidated and analyzed in light of their effect on the nanopore configuration. The osmotic reflection coefficients of highly asymmetric pores are estimated under etching conditions and in diluted electrolyte solutions. Our results allow a new level of understanding of the phenomena underlying the development of an ion-track nanopore and pave the way for the controlled fabrication of a variety of nanopores of different shapes using one and the same principle of an asymmetric chemical treatment.
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•Asymmetric etching of ion-track single- and multipore membranes is investigated.•Ionic conductance, osmotic, and structural properties of the membranes are studied.•Several consecutive phases of nanopore evolution during etching are identified.•In the last phase, the highly asymmetric membrane resembles a porous 2D material.•Roles of diffusion and osmotic flow in controlling the pore geometry are elucidated.
SiC nanowires with different lengths were prepared, and the effect of nanowire length on their dielectric permittivity and microwave absorption properties were investigated. The results reveal that ...SiC nanowires with longer length can improve the electrical conductivity of microwave absorbing materials. This may be attributed to the fact that longer nanowires are more easily to interconnect with each other, which facilitates the construction of a more complete electrical conduction network in the matrix. Cole-Cole curves also indicate that with increasing nanowire length, the dominant loss mechanism of SiC nanowires is changed from polarization loss to conductance loss. Therefore, the conductivity-dependent dielectric permittivity and microwave absorbing ability of SiC nanowires were significantly improved with the increase in the nanowire lengths.
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•SiC nanowires with different nanowire lengths were prepared.•Dielectric permittivity and microwave absorption properties were investigated.•Longer SiC nanowires exhibit higher permittivity and microwave absorption ability.•Longer SiC nanowires are much easier to form a complete conduction loss network.•With increasing nanowire length, the conduction loss dominates absorption ability.
The low thermoelectric figure of merit, ZT, is severely limiting the wide practical applications of thermoelectric materials. In this research theoretical calculations were performed on Ni ...substituted cobalt oxide (Co3O4) semiconductor materials to identify the qualitative trend of thermoelectric properties due to substitutions. Ni substitutions were made in the tetrahedral sites of 56 atom Co3O4 super cell. With the increasing Ni substitution, the band gap near the Fermi region started to close, from 0.337 eV for pure Co3O4 to 0 eV with Ni+2 substitutions in the tetrahedral sites of Co3O4, thereby showing an increasing metallic behavior which is also evident from the electrical conductance calculations. To calculate band structure, Seebeck coefficient, electrical conductance and thermal conductance due to electrons, first principles based density functional theory, DFT, combined with non-equilibrium Green's function method for two-probe systems were used. To calculate the lattice thermal conductance, reverse non-equilibrium molecular dynamics was used. The calculated Seebeck coefficients were 720 μV/K for pure Co3O4 and decreased exponentially to 35 μV/K for Co2NiO4, where the qualitative trend aligned very well with the available experimental data for Ni substituted cobalt oxide materials. These calculated properties assisted in calculating the theoretical thermoelectric figure of merit, and to qualitatively assess the effect of doping on the overall performance. Improved thermoelectric properties such as low thermal conductance and high Seebeck coefficient for low Nickel substitutions (12.5% of tetrahedral sites represented with Ni0·125Co2·875O4), was observed which yielded a 10-fold increase in thermoelectric figure of merit, ZT, in comparison to pure Co3O4 at 300 K. Additionally, the effect of Nickel substitutions on the p-type behavior was presented and discussed in this research article.
•Dilute doping increased the thermoelectric performance by 10 folds.•P-type behavior with Ni substitution reported in experimental research was observed here also.•The trend of experimentally reported Seebeck coefficient was observed.•Usage of new and efficient Force Field Calculations were employed in this research and the results matched well with experimental data.
Background. Radiation therapy (RT) is one of the main methods of treating cancer, including breast cancer (BC). This is one of the most knowledge-intensive medical industries, which is based on the ...latest advances in radiobiology, chemistry, radiation physics, engineering and others. Effective PT involves the use of fairly high doses of radiation, which is what determines the success of comprehensive treatment, in particular the increase in the number of patients who survived 5 years or more. In turn, the increase in survival after a course of combination treatment leads to an increase in the absolute number of patients with adverse treatment outcomes, including radiation-related complications (RC).
The aim of the work was to characterize the changes in the skin electrical conductance in patients with breast cancer and an increased risk of RC.
Materials and methods. The study was conducted on the basis of the clinic of the Grigoriev Institute of Medical Radiology and Oncology of NAMS of Ukraine. To study the skin electrical conductance, 16 patients with BC with an increased risk of RC were selected, with a mean age of 53.8 ± 3.7 (95% CI: 46.6–61.0) years. Studies of tissue electrical conductance were performed using the device "Electrodermatometer", measuring the indicators: modulus of complex impedance, impedance angle, complex impedance, and electrical capacity.
Results and discussion. The study showed that in patients with BC and increased risk of RC, there was a decrease in the complex impedance of tissues at the study points during RT. The modulus of complex impedance at the mitral area decreased by only 6.8% (p > 0.05), while at the aortic, pulmonic and tricuspid areas, this figure was significantly (p < 0.05) decreased by 27.0%; 26.2% and 33.0%, respectively, relative to the initial indicators for RT. It was found that the most pronounced changes in the skin electrical conductance in patients with BC at risk of RC were observed at the projection points of the tricuspid and pulmonic areas, where these indicators were significantly (p < 0.05) increased by 41.1% and 34.2% relative to the baseline and equaled 9.8 ± 0.89 pF and 9.8 ± 0.88 pF, respectively.
Conclusions. In patients with breast cancer at risk of RC, there was a statistically significant decrease (p < 0.05) in the value of the modulus of complex impedance by an average of 23.3% and a statistically significant increase (p < 0.05) in the tissue electrical conductance by an average of 29.8% relative to the baseline during radiation therapy.
Diamond and graphene are carbon allotropes with starkly different physical characteristics. Their combination into graphene-on-diamond heterostructures could benefit from the complementary properties ...of both components. Graphitization of single-crystalline diamond surfaces is a promising synthesis route, but a clear understanding of the growth of graphene or graphite from solid carbon sources is so far missing. Using aberration-corrected transmission electron microscopy, Raman spectroscopy, and electrical transport measurements, we provide detailed insight in the mechanisms of structural changes of nickel-catalyzed graphitization of diamond. We propose competing atomistic processes occurring at contact sites of diamond and Ni, depending on diamond surface terminations. One-dimensional etching process dominates on (111) diamond surfaces that remain almost atomically flat during graphitization. Two-dimensional etching of (110) and (100) diamond surfaces results in Ni drilling into the diamond substrate. Our findings also provide evidence on the reaction rates of the catalysis. The most reactive diamond surface in the (100) orientation is covered with the largest amount of well-crystallized graphite, whereas the (111) surface shows the highest stability against catalytic etching. In the latter case, only a thin disordered graphite layer is formed, yielding the lowest electric conductance. By clarifying these etching mechanisms, our results can improve the synthesis of graphene-on-diamond heterostructures.
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