Effective Relaxation Time Research Articles

Heterogeneous interactions and polymer entropy decide organization and dynamics of chromatin domains

Chromatin is known to be organized into multiple domains of varying sizes and compaction. While these domains are often imagined as static structures, they are highly dynamic and show cell-to-cell variability. Since processes such as gene regulation and DNA replication occur in the context of these domains, it is important to understand their organization, fluctuation, and dynamics. To simulate chromatin domains, one requires knowledge of interaction strengths among chromatin segments. Here, we derive interaction-strength parameters from experimentally known contact maps and use them to predict chromatin organization and dynamics. Taking two domains on the human chromosome as examples, we investigate its three-dimensional organization, size/shape fluctuations, and dynamics of different segments within a domain, accounting for hydrodynamic effects. Considering different cell types, we quantify changes in interaction strengths and chromatin shape fluctuations in different epigenetic states. Perturbing the interaction strengths systematically, we further investigate how epigenetic-like changes can alter the spatio-temporal nature of the domains. Our results show that heterogeneous weak interactions are crucial in determining the organization of the domains. Computing effective stiffness and relaxation times, we investigate how perturbations in interactions affect the solid- and liquid-like nature of chromatin domains. Quantifying dynamics of chromatin segments within a domain, we show how the competition between polymer entropy and interaction energy influence the timescales of loop formation and maintenance of stable loops.

Effective mass of high-mobility In2O3 -based transparent conductive oxides fabricated by solid-phase crystallization

Polycrystalline ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$ films, which are solid-phase crystallized (spc) from amorphous films doped with hydrogen (H) and transition metals (TMs), exhibit remarkably high mobilities $(100--160\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1})$; moreover, their specific resistance is equivalent to $2--3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ or less, even when the carrier density is reduced to one-fifth $(1--4\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})$ that of conventional transparent conductive oxide (TCO) films. The high mobility and low carrier density significantly reduce free-carrier absorption, and the transparent region of the TCO films extends across the visible and near-infrared regions. In this study, we experimentally demonstrate that spc-${\mathrm{In}}_{2}{\mathrm{O}}_{3}$:H and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$:TM,H films with an impurity concentration of less than a few at. % exhibit superior mobility compared to that of optimized ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$:Sn,H films $(\ensuremath{\sim}70\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1})$ with similar Sn and close-carrier concentrations. Photoelectron spectroscopy measurements revealed that the electronic state of the spc films, including the valence of TM impurities, changed with varying In/O ratios of the amorphous films. Furthermore, the In, O, TM, and H compositions in the amorphous films were found to be critical for effective activation of ${\mathrm{TM}}_{\mathrm{In}}^{+}$, ${\mathrm{H}}_{\mathrm{O}}^{+}$, and ${{\mathrm{H}}_{\mathrm{i}}}^{+}$ donors after crystallization. To determine the origin of the high electron mobility, the effective mass and relaxation time of electrons in these films were evaluated by spectroscopic ellipsometry. The results showed that the high mobility could be primarily attributed to the long relaxation time instead of the small effective mass. Additionally, the dispersion of conduction bands near the Fermi energy was found to be almost independent of the type of metallic impurity (Sn, H, Ce, Zr, and W) for the investigated impurity concentrations. Moreover, the increase in relaxation time by H and TM doping was examined.

Parametric generation of spin waves in nanoscaled magnonic conduits

The research feld of magnonics proposes a low-energy wave-logic computation technology based on spin waves to complement the established CMOS technology and provide a basis for emerging unconventional computation architectures. However, magnetic damping is a limiting factor for all-magnonic logic circuits and multi-device networks, ultimately rendering mechanisms to effciently manipulate and amplify spin waves a necessity. In this regard, parallel pumping is a versatile tool since it allows to selectively generate and amplify spin waves. While extensively studied in microscopic systems, nano-scaled systems are lacking investigation to assess the feasibility and potential future use of parallel pumping in magnonics. Here, we investigate a longitudinally magnetized 100 nm-wide magnonic nano-conduit using space and time-resolved micro-focused Brillouin-light-scattering spectroscopy. Employing parallel pumping to generate spin waves, we observe that the non-resonant excitation of dipolar spin waves is favored over the resonant excitation of short wavelength exchange spin waves. In addition, we utilize this technique to access the effective spin-wave relaxation time of an individual nano-conduit, observing a large relaxation time up to (115.0 +- 7.6) ns. Despite the significant decrease of the pumping effciency in the investigated nano-conduit, a reasonably small threshold is found rendering parallel pumping feasible on the nano-scale.

A lattice Boltzmann simulation on the gas flow in fractal organic matter of shale gas reservoirs

The gas flow in the organic matter with multiple flow regimes is critical to the shale gas production from shale gas reservoirs, but simultaneously simulating the full flow regimes of shale gas in the nanopores of the fractal shale organic matter is still unavailable. This paper presents a modified lattice Boltzmann model with effective relaxation time to simulate the shale gas micro-flow behaviors in fractal organic matter for permeability prediction. Firstly, some fractal shale organic matters are reconstructed by the quartet structure generation set (QSGS) algorithm, and the structural parameters such as fractal dimension, lacunarity and average pore diameter are calculated to characterize the complexity of the fractal shale organic matter. Secondly, effective viscosity and Knudsen layer are introduced into the effective relaxation time to formulate a modified lattice Boltzmann model. Thirdly, this modified lattice Boltzmann model is verified by comparing with the theoretical permeability models for the gas flow in the body centered cubic (BCC) arrays. Finally, a series of gas flow simulations in reconstructed fractal shale organic matter are conducted to explore the effects of structure parameters on permeability. Numerical simulations show that the modified lattice Boltzmann model can simulate the full gas flow regimes and predict the permeability of the fractal shale organic matter. The logarithm of permeability is negatively linearly correlated with fractal dimension and positively linearly correlated with lacunarity of the shale organic matter. This permeability exponentially increases with the increase of average pore diameter and a power law is observed between the fractal dimension and average pore diameter of these fractal shale organic matters. The anisotropic structures have great impacts on the directional permeability of shale organic matter. The permeability kx in the horizontal direction increases first and then decreases with the increase of anisotropic ratio (AR) and reaches the peak when AR is about 20. The permeability ky in the vertical direction monotonically decreases with the increase of AR.

The SiPb monolayer with high thermoelectric performance at room temperature

The SiPb monolayer with low lattice thermal conductivity and high dimensionless figure of merit (ZT) is identified by the first-principles calculations. The geometrical configuration is optimized, and the stabilities are confirmed with phonon dispersion and ab initio molecular dynamics simulation. The effective mass, mobility, and relaxation time are calculated by using the deformation theory. Based on the semiclassical Boltzmann transport theory and the band alignment by the Heyd-Scuseria-Ernzerhof hybrid functional, the Seebeck coefficient, electrical conductivity, power factor, and electron thermal conductivity relative to the carrier and temperature are obtained, while the ZT dependent on temperature is envaulted with the bipolar effect. The obtained ZT of 0.666/0.907 in the x/y-direction at 310 K supports the SiPb monolayer as a very promising application in implantable bioelectronics and wearable electronics.

A novel MRI-based quantitative water content atlas of the human brain

The measurement of quantitative, tissue-specific MR properties, e.g., water content, longitudinal relaxation time (T1) and effective transverse relaxation time (T2⁎), using quantitative MRI at a clinical field strength (1.5 T to 3T) is a well-explored topic. However, none of the commonly used standard brain atlases, such as MNI or JHU, provide quantitative information. Within the framework of quantitative MRI of the brain, this work reports on the development of the first quantitative brain atlas for tissue water content at 3T. A methodology to create this quantitative atlas of in vivo brain water content based on healthy volunteers is presented, and preliminary, practical examples of its potential applications are also shown.Established methods for the fast and reliable measurement of the absolute water content were used to achieve high precision and accuracy. Water content and T2⁎ were mapped based on two different methods: an intermediate-TR, two-point method and a long-TR, single-scan method. Twenty healthy subjects (age 25.3 ± 2.5 years) were examined with these quantitative imaging protocols. The images were normalised to MNI stereotactic coordinates, and water content atlases of healthy volunteers were created for each method and compared. Regions-of-interest were generated with the help of a standard MNI template, and water content values averaged across the ROIs were compared to water content values from the literature.Finally, in order to demonstrate the strength of quantitative MRI, water content maps from patients with pathological changes in the brain due to stroke, tumour (glioblastoma) and multiple sclerosis were voxel-wise compared to the healthy brain.The water content atlases were largely independent of the method used to acquire the individual water maps. Global grey matter and white matter water content values between the methods agreed with each other to within 0.5 %. The feasibility of detecting abnormal water content in the brains of patients based on comparison to a healthy brain water content atlas was demonstrated.In summary, the first quantitative water content brain atlas in vivo has been developed, and a voxel-wise assessment of pathology-related changes in the brain water content has been performed. These results suggest that qMRI, in combination with a water content atlas, allows for a quantitative interpretation of changes due to disease and could be used for disease monitoring.

Modified LB model for simulation of gas flow in shale pore systems by introducing end effects and local effective mean free path

Natural gas flow in shale pore systems determines the accumulation and production of shale gas. Under the conditions of reservoir, gas flow in such shale pores is significantly different from that in conventional reservoirs. Studies of gas flow under such conditions are usually limited to simple pore models with tube/slit geometries or bundle of tubes/slits, which constructs important theoretical basis, however, cannot represent the pore networks of shales. For directly simulating gas flow in complex media, we proposed a modified microscale lattice Boltzmann (MM-LB) model, in which the local effective mean free path (MFP) at any location of the pore system with complex geometry corrected by a custom two-dimensional (2D) eight-direction wall function was considered to capture the effective relaxation time for each lattice node in LB model. What's more, to consider slip velocity at solid boundaries, a combined bounce-back specular-reflection (BSR) scheme was adopted. The MM-LB model was firstly validated in 2D pore systems with simple slit/channel geometries and complex geometries (square and triangular cylinder flows) and in a 3D Sierpinski carpet, where good agreements with linearized Boltzmann solutions, molecular dynamics (MD) simulation and the direct simulation BGK (DSBGK) method results were found. Using the MM-LB model, we quantified the end effect on gas flow through pore throat and found that the end effect is caused by not only the streaming bending but also the variance of MFP (i.e., viscosity) throughout the pore throat. Finally, we applied this model to simulate shale gas flow in three digital reconstructions of kerogen pore systems and compared the results of apparent permeability prediction with Klinkenberg model and Beskok-Karniadakis (B–K) model. It is showed that the apparent permeability of gas flow in shales decreases with the decrease of temperature or the increase of pressure, and the pressure has a greater effect than temperature. For similar pore structures, the apparent permeability increases with the width of pore body and pore throat, especially the pore throat, which dominates the overall flow velocity of the entire flow field. According to the comparison and analysis of the results of MM-LB model with Klinkenberg and B–K model, it can be inferred that permeability prediction based on models of tube/slit (or bundle of tube/slit) pores misestimate the apparent permeability due to ignoring the connectivity and the end effect, especially for the conditions of lower pressures and nanoscale pore spaces.

First principle investigation on 2D beryllium chalcogenides for thermoelectric and optical applications

This article reports a detailed investigation of structural, electronic, thermoelectric and optical properties of square lattice beryllium chalcogenides (s-BeX; X = O, S, Se and Te) for the first time. Phonon dispersion analysis is carried out to determine the dynamical stability of the s-BeX compounds, whereas all the s-BeX compounds are found to be energetically and dynamically stable. The electronic properties are studied in terms of electronic band structures and partial density of states of s-BeX compounds. The BeO compound shows an indirect bandgap, while other chalcogenides, viz. BeS, BeSe and BeTe appear to be direct semiconductor materials. The effective mass, mobility and relaxation time for the electron and hole from the band structure of s-BeX are also studied to gain more insight into these considered materials. The thermoelectric properties of the entire s-BeX series are investigated for an extensive temperature range as 50–800 K in terms of thermal conductivity (κ), electrical conductivity (σ), Seebeck coefficient (S) and figure of merit (ZT). The thermoelectric merit of s-BeX compounds is also compared to the zinc-blende and hexagonal-monolayer phases of beryllium chalcogenides, which indicates that the thermoelectric potential of BeX compounds depends on their structural phases. The optical properties such as dielectric function ϵ(ω), refraction index n(ω), reflectivity R(ω), absorption spectra I(ω) and extinction index k(ω) of s-BeX are also investigated in the presence of parallel and perpendicular field polarizations. The present work reveals s-BeO, zb-BeSe and h-BeTe as the best thermoelectric materials in their respective series. Also, these compounds are mainly UV-active and therefore can possibly be applicable as UV-photodetectors and UV protectant materials.

Pseudo single domain NiZn-γFe2O3 colloidal superparamagnetic nanoparticles for MRI-guided hyperthermia application

Magnetic resonance imaging (MRI)-guided magnetic nanofluid hyperthermia (MNFH) is highly desirable in cancer treatment because it can allow for diagnosis, therapeutics, and prognosis simultaneously. However, the application of currently developed iron-oxide based superparamagnetic nanoparticles (IOSPNPs) for an MRI-guided MNFH agent is technically limited by the low AC heat induction power at the physiologically tolerable range of AC magnetic field (H AC,safe), and the low transverse r 2-relaxivity responsible for the insufficient heating of cancers, and the low resolution of contrast imaging, respectively. Here, pseudo single domain colloidal Ni x Zn1−x –γFe2O3 (x = 0.6) superparamagnetic nanoparticle (NiZn-γFe2O3 PSD-SPNP) physically and theoretically designed at the H AC,safe, specifically by the applied frequency, is proposed for a highly enhanced MRI-guided MNFH agent application. The NiZn-γFe2O3 PSD-SPNP showed the superparamagnetic characteristics, significantly enhanced AC heat induction performance (ILP = 6.3 nHm2 kg−1), highly improved saturation magnetization (M s = 97 emu g−1 Fe, 3.55 × 105 A m−1) and r 2-relaxivity (r 2 = 396 mM−1 s−1) that are desirable for highly efficient MRI-guided MNFH agent applications. According to the analyzed results, the remarkably enhanced effective relaxation time constant and its dependent out-of-phase magnetic susceptibility, as well as the DC/AC magnetic softness optimized by the PSD-SPNP at the H AC,safe were revealed as the main physical reason for the significance. All the fundamental in vitro and in vivo experimental results demonstrated that the physically designed NiZn-γFe2O3 PSD-SPNP is bio-technically feasible for a highly efficient MRI-guided MNFH agent for future cancer nanomedicine.

Numerical evaluation of the ferrofluid behaviour under the influence of three-dimensional non-uniform magnetic field

Ferrofluids have always been the centre of interest for a broad range of applications where the flow manipulation is achieved using different types of magnetic fields. In the present work, a Finite Volume Method based numerical study is performed to investigate the ferrofluid behaviour in the laminar flow regime using the complete set of Ferrohydrodynamics equations. Four distinct single layer finite solenoids of different Ls/Ds (length to diameter ratio) are considered to replicate a 3D (three-dimensional) non-uniform magnetic field, and a twofold validation is also reported to authenticate the generated field distributions. Moreover, a magnetic field dependent viscosity model is used to take into account the variation of ferrofluid viscosity in the presence of a non-uniform magnetic field. To accommodate the varying particle size distribution of ferrofluid, an effective relaxation time constant is used that can accurately predict the magnetization using Debye relaxation mechanism. The obtained flow characteristics are then further discussed and compared along with the case of stationary ferrofluid for all solenoid configurations. New insights about the flow structures are provided using the λ2 criteria of vortex identification technique and the critical point theory analysis. It is observed that each solenoid arrangement have a distinct magnetic field distribution which leads to the occurrence of unique vortex structures and fluid deformations. Also, different flow trajectories are noticed within the fluid domain owing to the peculiar distribution of Kelvin force density. Results from the present work have direct implications in all ferrofluid based momentum transport devices and can be effectively used to further improve our understanding about their performances.

Metastable states, relaxation and failure mechanisms in condensed matter with defects

The article is concerned with experimental studies of anomalous momentum transfer mechanisms in condensed matter exhibiting multiple defect-induced gaped momentum states. The performed experiments revealed the relationship between the metastable states, the specific critical phenomena in condensed matter with defects, the structural-scaling transitions, and the mechanisms of structural relaxation disclosing viscosity anomalies in solids and liquids due to the strong interactions between the structure constituents. The possibility of these mechanisms under intensive loading including turbulence was substantiated in Naimark (1998), Naimark (1997), Naimark (2004). The established regularities of criticality in the behavior of condensed matter with mesoscopic defects made it possible to study the thermodynamics and kinetics of the nonlinear liquid and solid systems exhibiting the metastable states, and to provide an explanation of the anomalous mechanisms of momentum transfer in systems with "strong interaction." Anomalous momentum transfer mechanisms are associated with the subjection of the dynamics of condensed matter to the established types of collective modes in ensembles of defects (breathers, autosolitons, dissipative blow-up structures) manifesting the character of self-similar solutions. The subordination of dynamics to collective modes is accompanied by a sharp increase in the effective relaxation times and absorption anomalies. The theoretical results are confirmed by the experimental data on the formation of self-similar (quasi-plastic) fronts in liquids and the attainment of viscosity asymptotics due to initiation of fracture waves under shock-wave loading of fused quartz (Naimark (2003), Naimark (2010)).

Anisotropic photoconductivity excited in a semiconductor by two-frequency optical radiation

Anisotropic photoconductivity at a difference frequency, excited in a semiconductor by linearly polarized two-frequency optical radiation, is considered. The anisotropy of the photoconductivity arises due to the optical alignment of photoexcited electrons momenta and dependence of their effective mass and momentum relaxation time on energy. It is shown that the contribution of the anisotropic photoconductivity to the photocurrent at the difference frequency lying in the terahertz frequency range can be comparable with that of the isotropic photoconductivity. This effect can manifest itself in photoconductive antennae, devices used to generate terahertz radiation. Keywords: Anisotropic photoconductivity, photomixing, terahertz radiation, photoconductive antenna.

Анизотропная фотопроводимость, возбуждаемая в полупроводнике двухчастотным оптическим излучением

Anisotropic photoconductivity at a difference frequency, excited in a semiconductor by linearly polarized two-frequency optical radiation, is considered. The anisotropy of the photoconductivity arises due to the optical alignment of photoexcited electrons momenta and dependence of their effective mass and momentum relaxation time on energy. It is shown that the contribution of the anisotropic photoconductivity to the photocurrent at the difference frequency lying in the terahertz frequency range can be comparable with that of the isotropic photoconductivity. This effect can manifest itself in photoconductive antennaе – devices used to generate terahertz radiation.

Dresselhaus spin-orbit interaction in the p -AlGaAs/GaAs/AlGaAs structure with a square quantum well: Surface acoustic wave study

The effect of spin-orbit interaction was studied in a high-quality $p$-AlGaAs/GaAs/AlGaAs structure with a square quantum well using acoustic methods. The structure grown on a GaAs (100) substrate was symmetrically doped with carbon on both sides of the quantum well. Shubnikov-de Haas-type oscillations of the ac conductance of two-dimensional holes were measured. At a low magnetic field $B <$2 T conductance oscillations undergo beating induced by a spin-orbit interaction. Analysis of the beating character made it possible to separate the conductance contributions from the two heavy holes subbands split by the spin-orbit interaction. For each of the subbands the values of the effective masses and quantum relaxation times have been determined, and then the energy of the spin-orbit interaction was obtained. The quantum well profile, as well as the small magnitude of the spin-orbit interaction, allowed us to conclude that the spin-orbit splitting is governed by the Dresselhaus mechanism.

Structural, vibrational, electronic, elastic and thermoelectric properties of monolayer alkali halide compounds from first principles investigation

A detailed analysis of structural, vibrational, electronic, elastic and thermoelectric properties for sixteen hexagonal monolayers which belongs to family of group I-VII compounds (alkali halides) are performed with first-principles calculations using density functional theory (DFT) and semi-classical-Boltzmann transport equations (BTE). The thermoelectric properties of monolayer alkali halides is reported for the first time. The frequency dependent phonon dispersion relations indicate the dynamical stability of all the considered group I-VII hexagonal monolayers, namely, MX (M=Li, Na, K, Rb and XF, Cl, Br, I) in their planner structure. Along with phonon dispersion relations, we also investigated their mechanical stability by calculating elastic properties. The obtained elastic parameters and polar diagrams of Young’s modulus and Poisson’s ratio confirms mechanical stability of all the considered systems. All the monolayers alkali halides are found to possess wide indirect energy bandgaps ranging between 3.91 and 6.74 eV, which indicates that these compounds are active in the UV region of electromagnetic spectra. In order to gain more insight on I-VII MX compounds, we also obtained their effective mass, deformation potential, relaxation time and mobility for electron and holes along armchair and zigzag directions. Finally, we computed the thermoelectric properties for all considered hexagonal monolayers (MX) with respect to temperature. The investigated thermoelectric properties include electrical conductivity (σ), thermal conductivity (k), Seebeck coefficients (S) and figure of merit (ZT). Among all the MX hexagonal monolayers, LiI, KBr, KI and RbCl observed to exhibits outstanding thermoelectric properties for a wide range of temperature (200–800 K). The present investigation certainly reports the merits of I-VII MX monolayers as possible materials for future thermoelectric devices.

Detecting Dye-Contaminated Vegetables Using Low-Field NMR Relaxometry.

Dyeing vegetables with harmful compounds has become an alarming public health issue over the past few years. Excessive consumption of these dyed vegetables can cause severe health hazards, including cancer. Copper sulfate, malachite green, and Sudan red are some of the non-food-grade dyes widely used on vegetables by untrusted entities in the food supply chain to make them look fresh and vibrant. In this study, the presence and quantity of dye-based adulteration in vegetables are determined by applying 1H-nuclear magnetic resonance (NMR) relaxometry. The proposed technique was validated by treating some vegetables in-house with different dyes and then soaking them in various solvents. The resulting solutions were collected and analyzed using NMR relaxometry. Specifically, the effective transverse relaxation time constant, T2,eff, of each solution was estimated using a Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence. Finally, the estimated time constants (i.e., measured signatures) were compared with a library of existing T2,eff data to detect and quantify the presence of unwanted dyes. The latter consists of data-driven models of transverse decay times for various concentrations of each water-soluble dye. The time required to analyze each sample using the proposed approach is dye-dependent but typically no longer than a few minutes. The analysis results can be used to generate warning flags if the detected dye concentrations violate widely accepted standards for food dyes. The proposed low-cost detection approach can be used in various stages of a produce supply chain, including consumer household.

Numerical Transport Process of Splitting Kinetic Schemes in the Navier–Stokes–Fourier Limit

The Boltzmann equation is the fundamental governing equation in rarefied gas dynamics. Due to the complexity of Boltzmann collision term, operator splitting treatment is commonly adopted, where the Boltzmann equation is split into a convection equation for particles' free transport and an ordinary differential equation for particles' collision. However, this split treatment will introduce numerical error proportional to the time step, which may contaminate the physical solution in the near continuum regime. Therefore, for a multiscale kinetic method, the asymptotic preserving property to obtain the Navier–Stokes–Fourier (NSF) solution in the hydrodynamic limit is very important. In this paper, we analyse the effective relaxation time from different evolution processes of several kinetic schemes and investigate their capabilities to recover the NSF solution. The general requirement on a splitting kinetic method for the NSF solution has been presented. Numerical validation has been carried out, which shows good agreement with the theoretical analysis.

High magnetic fluid hyperthermia efficiency in copper ferrite nanoparticles prepared by solvothermal and hydrothermal methods

CuFe2O4 magnetic nanoparticles (MNPs) of two different morphologies and high magnetic heating efficiency are prepared using hydrothermal (CF) and solvothermal (CFPG) methods. Temperature dependent magnetization measurements indicate the presence of superparamagnetic phase at room temperature. The saturation magnetization for CFPG MNPs (~32.7 emu/g) is found to be ~ 31% higher than the CF MNPs, which is due to nearly collinear Neel type alignment of the magnetic moments in the tetrahedral and octahedral sites with a low Yafet-Kittel angle of ~ 5.980 and lower thickness of the magnetically disordered shell, which are confirmed from the cation distributions, non-zero spin canting angles and sub-spectral area analyses using low temperature (~5 K) in-field (~5 T) Mössbauer spectroscopy. The maximum specific absorption rate for CFPG MNPs is found to be ~ 192 ± 7 W/g, which is significantly higher than the previously reported values for copper ferrite MNPs. The high heating efficiency of CFPG MNPs is attributed to the near-resonant relaxation dynamics (ωτ ~ 1, where ω and τ indicate the angular frequency of the applied field and effective relaxation time, respectively). Heating efficiency is found to decrease with increasing sample concentration due to an enhancement in dipolar interactions, which is found to be in agreement with the quasi-static calculations. In vitro cytotoxicity studies indicate good bio-compatibility of the CFPG MNPs against human colon epithelial cells (HT-29) due to the presence of polyethylene glycol coating. The observed high heating efficiency along with negligible room temperature coercivity and superior bio-compatibility indicate the suitability of the solvothermally synthesized CuFe2O4 MNPs for magnetic fluid hyperthermia.

A Colossal Enhancement of Thermoelectric Performance of Monolayer SbAs Using Strain Engineering

The effect of uniaxial strain on the thermoelectric (TE) conversion efficiency of puckered monolayer arsenic antimonide (SbAs) is explored based on the density function and Boltzmann transport equation (BTE) theories. The lattice thermal conductivity (κl) can be sharply lowered through tensile strain. Taking a + 3.25% tensile strain as an example, κl along the armchair (AC) direction at 300 K decreases almost three times than that without a strain, which is ascribed to the low phonon group velocity, large Grüneisen parameter, and high three‐phonon scattering phase space. The carrier effective mass decreases in imposing tensile strain monolayer SbAs and slightly suppresses the Seebeck coefficient; however, the electrical conductivity is improved due to the small effective mass and long relaxation time. Thus, power factor increases by 3.4 times under a + 3.25% tensile at cm−2 compared with a SbAs monolayer without strain. Thereafter, the figure of merit in an n‐type SbAs monolayer with a tensile strain of +3.25% is eight times as large as that in SbAs without strain at 300 K along the AC direction. Furthermore, the maximum TE figure of merit is 1.85 for an n‐type SbAs monolayer with +3.25% strain at 800 K. This study paves a way toward improving the TE performance through strain engineering in the TE field.

Screening Metal-Organic Frameworks for Separation of Binary Solvent Mixtures by Compact NMR Relaxometry.

Metal–organic frameworks (MOFs) have great potential as an efficient alternative to current separation and purification procedures of a large variety of solvent mixtures—a critical process in many applications. Due to the huge number of existing MOFs, it is of key importance to identify high-throughput analytical tools, which can be used for their screening and performance ranking. In this context, the present work introduces a simple, fast, and inexpensive approach by compact low-field proton nuclear magnetic resonance (NMR) relaxometry to investigate the efficiency of MOF materials for the separation of a binary solvent mixture. The mass proportions of two solvents within a particular solvent mixture can be quantified before and after separation with the help of a priori established correlation curves relating the effective transverse relaxation times T2eff and the mass proportions of the two solvents. The new method is applied to test the separation efficiency of powdered UiO-66(Zr) for various solvent mixtures, including linear and cyclic alkanes and benzene derivate, under static conditions at room temperature. Its reliability is demonstrated by comparison with results from 1H liquid-state NMR spectroscopy.