Inhomogeneity Length Research Articles

Electron cyclotron resonance during plasma initiation

Electron-cyclotron resonance heating (ECRH) is the main heating mechanism in the Wendelstein 7-X (W7-X) stellarator. Although second-harmonic ECRH (X2) has been used routinely for plasma startup, startup at third harmonic (X3) is known to be much more difficult. In this work, we investigate the energy gain of particles during nonlinear wave–particle interaction for conditions relevant to second- and third-harmonic startups in W7-X. We take into account both the beam and the ambient magnetic field inhomogeneities. The latter is shown to significantly increase the mean energy gain resulting from a single wave–particle resonant interaction. In W7-X-like conditions, the improvement in maximum gained energy is up to 4 times the analogous uniform magnetic field case. However, this improvement is not enough to ensure X3 startup. The optimal magnetic field inhomogeneity length scale for average energy gain and start up in W7-X-like conditions is found to be in the range of $1$ to $3\ {\rm km}^{-1}$ . A possibility of using multiple beams with neighbouring resonances is also considered. A considerable enhancement of the energy gain is demonstrated.

The effect of collisions on the rayleigh-taylor instability in magnetized quantum plasma

Rayleigh-Taylor instability occurs at the interface between light and heavy fluids whenever the heavier fluid is accelerated by the light one. An important issue is the stability conditions of these systems. Various parameters such as density difference between two fluids, density inhomogeneity length, magnetic field, viscosity, collision can affect the stabilization or destabilization of the system. So far, some of these factors have been investigated in the fields of classical and quantum physics. This process has also been studied in both linear and nonlinear states. Here we consider a collisional magnetic inhomogeneous quantum plasma. For the inhomogeneity profile of density as an exponential function, we calculated the second ordinary equation for the disturbed velocity. Since the differential equation does not have an analytical solution, we have calculated the growth rate curve using numerical methods and obtained the disturbed velocity profile in the discontinuity. Then the effects of different parameters such as collision, magnetic field, quantum effects, and density difference of two fluids on the system stabilization are studied. The various branches of the instability growth rate curve and its relationship with the turbulent velocity profile in discontinuity are also discussed.

Light-Reconfiguring Inhomogeneous Soft Helical Pitch with Fatigue Resistance and Reversibility.

Active engineering and modulation of optical spectra in a remote and fully reversible light is urgently desired in photonics, chemistry, and materials. However, the real-time regulation of multiple optical information such as wavelength, bandwidth, reflectance, and polarization is still a longstanding issue due to the lack of an appropriate photoresponsive candidate. Herein, we propose an additional "degree-of-freedom (DOF)" in a photo-modulated soft helix, and build up an unprecedented inhomogeneous helical pitch length with light-reconfiguring property, fatigue resistance, and reversibility. For the working model, the intrinsic chiral photoswitch LBC5 is employed as an actuator to modulate the helical pitch length, which is proportional to the irradiation intensity, and the unique broadband absorbance photo-modulator BTA-C5 is incorporated as an attenuator of the transmitted light to decrease its intensity along the sample thickness, therefore successfully adding another controlled DOF on the pitch length distribution (i.e., homogeneous or inhomogeneous) apart from the common soft helix with only a single DOF on the pitch length. The absorbance photo-modulator BTA-C5 with a unique variable broadband absorption enables the light to reconfigure the helical pitch from homogeneous to inhomogeneous, thereby achieving the robust fatigue-resistance establishment of reversible spectral programming. The established light-reconfigurable inhomogeneous helical pitch with the photoresponsive modulator BTA-C5 can provide a breakthrough to control absorbance and chirality, especially for dynamically broadening and narrowing the bandwidth on demand, and further enable the ever-desired broadband NIR circularly polarized luminescence (CPL) with a high dissymmetry factor glum of up to 1.88. The cutting-edge photoswitchable inhomogeneous soft helical pitch provides access to multi-freedom control in soft materials, optics, biophotonics, and other relevant fields.

Genome-Wide Study of Colocalization between Genomic Stretches: A Method and Applications to the Regulation of Gene Expression.

Simple SummaryAddressing a large number of genomic problems requires the comparison of genetic and epigenetic features distributed over the genome (genome tracks). The mutual arrangement of these features determines basic molecular mechanisms related to the dynamics of the genome architecture and gene expression. The analysis of data on the genome tracks stored in numerous databases cannot be performed without suitable bioinformatic tools. A package, the Genome Track Colocalization Analyzer, developed by the authors, is intended for the study of colocalization effects between stretch–stretch and stretch–point genome tracks.In this paper, we describe a method for the study of colocalization effects between stretch–stretch and stretch–point genome tracks based on a set of indices varying within the (–1, +1) interval. The indices combine the distances between the centers of neighboring stretches and their lengths. The extreme boundaries of the interval correspond to the complete colocalization of the genome tracks or its complete absence. We also obtained the relevant criteria of statistical significance for such indices using the complete permutation test. The method is robust with respect to strongly inhomogeneous positioning and length distribution of the genome tracks. On the basis of this approach, we created command-line software, the Genome Track Colocalization Analyzer. The software was tested, compared with other available packages, and applied to particular problems related to gene expression. The package, Genome Track Colocalization Analyzer (GTCA), is freely available to the users. GTCA complements our previous software, the Genome Track Analyzer, intended for the search for pairwise correlations between point-like genome tracks (also freely available). The corresponding details are provided in Data Availability Statement at the end of the text.

Correlating the Annealing Temperature Dependence of the Structural Inhomogeneity and the Diffusion in Zr-Ti-Cu-Ni-Be Glassy System

The relation between the annealing temperature dependence of the structural inhomogeneity and the diffusion coefficient in a metallic glass forming system Zr-Ti-Cu-Ni-Be is studied by using reported experimental data. It is shown that the diffusion coefficient increases with the increase of the correlation length of the structural inhomogeneity. Interestingly, the result found resembles the behavior known in superionic glasses. A discussion on the found relationship is given by exploiting the model for the superionic glasses proposed by the author. Based on the model, an inhomogeneity dependent diffusivity maximum is predicted.

Comparison of fibers from hop rich biogas digestate with natural fibers as raw material for composites

ABSTARCT Fibrous material extracted from biogas digestate is investigated as a possible raw material for composites. Digestate is a by-product of every biogas plant and consists mostly of water, undegraded plant biomass, and minerals. On the other hand, natural fibers and fibrous by-products are increasingly used as fiber component, especially in short-fiber reinforced plastics. The fibrous solid fraction of biogas digestate can be another alternative fiber source. The properties are decisive to determine the suitability of raw materials. Information on the length and constituents of woody and various non-woody plants can be found in the literature. In the study presented, fibrous solids obtained from digestate with a high content of hop vines are investigated. Fiber length and cell wall matter content are analyzed to characterize the digestate. The results are compared with classical plant fibers. It turns out that the investigated fibrous solids from digestate have a very inhomogeneous length distribution. The equalization can be achieved through an additional process step. The proportion of cell wall matter is comparable to that of woody plants and various non-woody plants. The fibers extracted from hop digestate can be regarded as an ecological and favorable alternative to wood fibers in composite materials.

Detection of bias inhomogeneity in Josephson junctions by switching current distributions

We demonstrate the double-peaked switching current distributions of a long Josephson junction from the zero to the finite voltage state in the case of asymmetrical bias feed profile. The considered asymmetry stands to be a natural feature of YBCO junctions fabricated on bicrystal substrates. We argue that such a picture is associated with the formation of solitons at the opposite junction edges for slightly different bias currents, arisen due to asymmetry. System parameters such as junction length, noise intensity and character of bias feed inhomogeneity leading to atypical distribution of switching currents are discussed.

Delamination analysis of multilayered beams exhibiting creep under torsion

A delamination analysis of a multilayered inhomogeneous beam structure under linear creep is developed. A viscoelastic model that consists of an arbitrary number of linear springs and linear dashpots is used. The cross-section of the beam is a circle. The beam is made of concentric longitudinal layers. Each layer is continuously inhomogeneous in thickness and length directions. Therefore, the shear moduli and the coefficients of viscosity of the viscoelastic model are distributed continuously along the thickness and length of each layer. Two concentric delamination cracks are located arbitrary between layers. The beam is loaded in torsion. Time-dependent solutions to the strain energy release rate for the two delaminations are derived by using the time-dependent strain energy in the beam. The strain energy release rates are derived also by the compliance method for verification. The variation of the strain energy release rate with time due to creep is evaluated. The effects of material inhomogeneity, external loading and delamination length on the strain energy release rate are investigated.

Gulf Stream Mean and Eddy Kinetic Energy: Three‐Dimensional Estimates From Underwater Glider Observations

AbstractThe strong, meandering, and eddy‐shedding Gulf Stream is a large oceanic reservoir of both mean and eddy kinetic energy in the northwestern Atlantic. Since 2015, underwater gliders equipped with Doppler current profilers have collected over 20,000 absolute velocity profiles in and near the Gulf Stream along the US East Coast. Those observations are used to make three‐dimensional estimates of mean and eddy kinetic energy, substantially expanding the geographic coverage of prior estimates of subsurface kinetic energy in the Gulf Stream. Glider observations are combined via weighted least squares fitting with anisotropic and inhomogeneous length scales to reflect both circulation and sampling density; this averaging technique can be applied to other quantities measured by the gliders. Mean and eddy kinetic energy decay approximately exponentially away from the surface. Vertical decay scales are longest within the high‐speed core of the Gulf Stream and somewhat shorter on the flanks of the Gulf Stream.

Verification of abrupt and gradual shifts in Iranian precipitation and temperature data with statistical methods and stations metadata.

Climate time series may exhibit abrupt or gradual shift, due to non-climatic changes (e.g., the station relocation) or actual climate change of a region. This study presented a step-by-step methodology for detecting the climatic and non-climatic changes in annual precipitation ([Formula: see text]) and maximum ([Formula: see text]) and minimum ([Formula: see text]) air temperature data related to 37 weather stations across Iran, using the statistical methods and stations metadata. All data cover the common period of 1961-2014. Abrupt changes in climate data were detected using the non-parametric Pettitt test and the piecewise linear regression model, the gradual changes using the non-parametric Mann-Kendall (MK) test, and the magnitude of trends using the Sen's slope estimator. In addition, a two-sample t-test was used to consider whether means of the climate data have been significantly changed in the presence of change points recorded in stations metadata. Results indicated overall increasing trends in [Formula: see text] and[Formula: see text], with more increasing rate for [Formula: see text]. In case of precipitation, most stations indicated non-significant decreasing/increasing trends while six of them showed significant decreasing trends. The detected breaking points, mainly in [Formula: see text] were concurrent with the years of change in the original locations of 6 out of 37 stations. It was specified that the unreliable stations' data intensified the trend orientation and magnitude of climatic variables compared to the reliable ones. In addition, increasing rates in [Formula: see text] and [Formula: see text] (decreasing rate in[Formula: see text]) for the stations located in the urban areas were larger (smaller) than those in the non-urban areas. This research revealed the necessity of metadata for accurate interpretation of results obtained from the statistical methods. The study suggests to the Iranian climate researchers to employ with caution a homogeneous length of series rather than total inhomogeneous length of series.

Determining a technique for transmitting measuring data on the spatial positioning of the piercing head in small-size installations during controlled soil piercing

For laying of underground utility systems in urban conditions by the method of horizontally directed soil piercing, small-sized units are designed. Such units should have measurement systems for determining the spatial position of the piercing head. In known systems, the surface layer of the soil is used as a data transmission line for transmitting measurement information. This method of transmitting information signals in urban conditions is not very acceptable. Ground-based objects reflect electromagnetic radiation of the head transmitter which leads to distortion of the directional diagram of the emitter and complicates the reliable reception of measurement information. It was proposed to use an autonomous measuring system with an operating frequency of 5 GHz based on Wi-Fi technologies and an unconventional method of transmitting measurement information using hollow steel bars in the piercing unit itself. This transmission line has periodic discontinuities because of the bar design. These discontinuities accumulate as the piercing head advances. For the basic vibration type Н 11 , more accurate analytical expressions were obtained for calculating the power transfer coefficient of the measurement signal in such non-uniform lines. It was shown that inhomogeneity of the transmission line in comparison with its surface resistance does not significantly affect the transmission coefficient. For example, damping in the line increased by 1.2 dB with the maximum length of inhomogeneity of 5 mm and the total length of jointed bars of 50 m. It has been theoretically proven that the range of soil piercing with reliable signal reception can be up to 50 meters. The proposed method for transmitting information signals makes it possible to reduce the transmitter power, ensure noise immunity of the measuring system, and reliable reception of the measuring information throughout the entire piercing path

Electron glass effects in amorphous NbSi films

We report on non equilibrium field effect in insulating amorphous NbSi thin films having different Nb contents and thicknesses. The hallmark of an electron glass, namely the logarithmic growth of a memory dip in conductance versus gate voltage curves, is observed in all the films after a cooling from room temperature to 4.2~K. A very rich phenomenology is demonstrated. While the memory dip width is found to strongly vary with the film parameters, as was also observed in amorphous indium oxide films, screening lengths and temperature dependence of the dynamics are closer to what is observed in granular Al films. Our results demonstrate that the differentiation between continuous and discontinuous systems is not relevant to understand the discrepancies reported between various systems in the electron glass features. We suggest instead that they are not of fundamental nature and stem from differences in the protocols used and in the electrical inhomogeneity length scales within each material.

Impact of the Fiber Length Distribution on Porous Sponges Originating from Short Electrospun Fibers Made from Polymer Yarn

AbstractUltralight highly porous sponges made of short electrospun polymer fibers have gained significant attention for a variety of applications. According to the established procedures, short electrospun fibers are obtained by cutting or homogenization of electrospun fibers in suspension, which yield fibers with inhomogeneous fiber length. The role of the fiber length distribution and the fiber length in the mechanical compressibility of the sponges is unknown. Therefore, as a model study, sponges made from suspensions of short electrospun poly(acrylonitrile) (PAN) fibers with controlled fiber length distribution are investigated, and the role of the fiber length distribution in the compressibility of the sponges is analyzed quantitatively. These sponges are also compared to the ones prepared by established procedure as a benchmark. It is found that the compression stress and modulus of ultralight sponges with monodisperse short fibers are respectively 32% and 45% higher than that made with polydisperse short fibers. The study also shows that sponges made from longer fibers have higher modulus in comparison to the sponges made from shorter fibers.

Spatial Distribution of Random Velocity Inhomogeneities in the Southern Aegean From Inversion of S Wave Peak Delay Times

AbstractThe southern Aegean is characterized by an ongoing process of oceanic subduction. In this study, 1,718 intermediate depth (>35 km) events recorded in the southern Aegean are used to calculate the peak delay times (tp). The tp are measured as the time difference between S wave onset and the peak of the S wave envelope in 2‐to 4‐, 4‐ to 8‐, 8‐ to 16‐, and 16‐ to 32‐Hz bands. The tp are also inverted to estimate the scattering parameters (κ and εparam) and power spectral density function (P (m)) at large wave numbers (m = 15 km−1 or ml) of the medium modeled as von Kármán type. κ controls frequency dependence of scattering while P (ml) represents the scattering strength in high frequencies for ɑml >> 1 (ɑ = correlation length of inhomogeneities). High P (ml) with low κ across Peloponnese in 0‐ to 20‐km depth may result from intermixing of oceanic material with continental rocks at different levels with a possibility of fluid activity and salt diapirism in northwest Peloponnese. Moderate P (ml) in 0‐ to 60‐km depth across Crete is likely due to a combination of factors including past megathrust earthquakes, sediment underplating, and flow of metamorphosed material in a subduction channel. Cyclades shows low κ in 0‐ to 40‐km depth, indicative of inhomogeneities produced by metamorphic core complexes. Very low κ in 60‐ to 80‐km depth is consistent with the location of mantle magma reservoir in the back‐arc region. Our results suggest that a significant portion of total S wave attenuation (Qs−1) in eastern Cyclades for 20‐ to 80‐km depth may be due to scattering losses.

Formation of a Wave Structure on the Surface of a Graphene Film

A wavy structure of the surface of graphene nanoparticles on a hydrocarbon substrate has been obtained. It has been shown that the wavy surface is the manifestation of the Kelvin-Helmholtz instability at the interface between liquid paraffin and graphene suspension with the inhomogeneity length λ = 250 nm. The manifestation of such wavy structures is due primarily to van der Waals forces.

Inference of magnetic field strength and density from damped transverse coronal waves

A classic application of coronal seismology uses transverse oscillations of waveguides to obtain estimates of the magnetic field strength. The procedure requires information on the density of the structures. Often it ignores the damping of the oscillations. We computed marginal posteriors for parameters such as the waveguide density, the density contrast, the transverse inhomogeneity length scale, and the magnetic field strength under the assumption that the oscillations can be modelled as standing magnetohydrodynamic (MHD) kink modes damped by resonant absorption. Our results show that the magnetic field strength can be properly inferred, even if the densities inside and outside the structure are largely unknown. Incorporating observational estimates of plasma density further constrains the obtained posteriors. The amount of information that is included a priori for the density and the density contrast influences their corresponding posteriors, but very little the inferred magnetic field strength. The decision to include or leave out the information on the damping and the damping timescales has a minimal impact on the obtained magnetic field strength. In contrast to the classic method, which provides numerical estimates with error bars or possible ranges of variation for the magnetic field strength, Bayesian methods offer the full distribution of plausibility over the considered range of possible values. The methods applied to available datasets of observed transverse loop oscillations can be extended to prominence fine structures or chromospheric spicules, and implemented to propagating waves in addition to standing oscillations.

A Lagrangian formulation of metamaterial homogenization

Many metamaterials may be well described as multi-scale systems where the large scale is represented by the wavelength and the small scales are represented by inhomogeneity lengths. The effective material properties of a metamaterial of this sort may be derived by considering the averaged behavior of material elements that are considered “infinitesimal” relative to the wavelength but is on the order of the inhomogeneity lengths. The averaging of the small-scale features enables a straightforward process to describe the metamaterial mechanics in terms of a Lagrangian formalism, and the macroscopic constitutive equations may be obtained by deriving the Euler-Lagrange equations for the macroscopic field quantities. This energetic approach to homogenization may be used to estimate both linear and nonlinear material properties. This talk describes this homogenization method for one-dimensional systems and compares the resulting effective material properties with other homogenization methods.

Досвід розроблення та використання засобів інформаційних технологій на підставі метал-діелектричних структур та плазмового розряду

Наведено результати аналізу принципів побудови та прикладів застосування сучасних засобів інформаційних технологій на базі метал-діелектричних структур. Виявлено, що стрімкий розвиток сучасних засобів інформаційних технологій зумовлений використанням фізичних властивостей поверхневих плазмонів і поверхневих плазмон-поляритонів. Оцінено вплив модуляції поверхневого імпедансу метал-діелектричних структур на форму просторового розподілу поля. Виявлено, що в засобах передавання електромагнітної енергії ефективно використовується гофрована металева структура в ролі штучного діелектрика для сповільнення рухомої поверхневої хвилі. З'ясовано, що технологія збудження поверхневих плазмонів за геометрією Кретчмана дотепер широко вживана в засобах інфокомунікацій. Встановлено, що вагому роль у розвитку сучасних випромінювальних засобів інформаційних технологій відіграє використання високоіонізованого газу як компонента структури, здатної поширювати поверхневі плазмон-поляритони. Виявлено низку переваг засобів інформаційних технологій на базі плазмового розряду, які зумовлені фізичними особливостями плазми. Досліджено сучасні інформаційно-комп'ютерні технології модельних досліджень електродинамічних параметрів випромінювальних засобів. на підстаі здійсненого аналізу запропоновано використання ребристо-стержневих структур на базі плазмового розряду в ролі засобів передавання електромагнітної енергії.

Marginal stability, characteristic frequencies, and growth rates of gradient drift modes in partially magnetized plasmas with finite electron temperature

The detailed analysis of stability of azimuthal oscillations in partially magnetized plasmas with crossed electric and magnetic fields is presented. The instabilities are driven by the transverse electron current which, in general, is due to a combination of E×B and electron diamagnetic drifts. Marginal stability boundary is determined for a wide range of the equilibrium plasma parameters. It is shown that in some regimes near the instability threshold, only the low-frequency long-wavelength oscillations are unstable, while the short-wavelength high-frequency modes are stabilized by the finite Larmor radius effects. Without such stabilization, the high-frequency modes have much larger growth rates and dominate. A new regime of the instability driven exclusively by the magnetic field gradient is identified. Such instability takes place in the region of the weak electric field and for relatively large gradients of plasma density (ρs/ln>1, where ρs is the ion-sound Larmor radius and ln is the scale length of plasma density inhomogeneity).

Lattice, Charge, and Spin Phase Inhomogeneity in Complex-Striped Quantum Matter

The Superstripes 2016 conference, held on June 23-29, 2016 in the island of Ischia in Italy celebrated the 20th anniversary of this series of conferences. For 20 years structural, electronic, and magnetic phase inhomogeneities in quantum matter have been the scientific focus for a growing physics community interested in complexity in quantum matter. It has been the meeting point for different scientific communities facing the challenging project to unveil the complex space and time landscapes in quantum matter. The interesting spatial inhomogeneity length scale of multiple coexisting phase ranges from atomic to mesoscopic and the time fluctuations are spread over multiple time scales. The response of these materials changes using different experimental techniques with different spatial and time resolution probing different aspects of the quantum complexity.