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The study of synthetic biology focusing on biosensor systems has resulted from a growing interest in developing customized biological devices with desired cellular functions. Recently, biosensors have been used for a variety of medical applications such as disease diagnosis, prevention, rehabilitation, patient health monitoring, and human health management. Meanwhile, the ability to track biomarkers based on biosensors allows researchers and medical practitioners to provide patients with individualized treatment regimens and health management. Biosensors that respond to electrochemical, optical, thermal, piezoelectric and magnetic signals have been developed and utilized for various disease therapies and biomedical applications. This study reviews recent developments in biosensor-based therapeutic tools by sensing diverse biomarkers in many diseases (e.g. cancer, infections, metabolic diseases), such as physical biomarkers (e.g. pressure, temperature) and chemical biomarkers (e.g. dissolved oxygen, glucose). Additionally, we highlight the challenges and problems of biosensor-based therapeutics and possible solutions for biosensor engineering thereof. Current biosensors enable for coarsely programable personal treatment and health management, however, new sensors with optimized dose-response functions, for example, fast response and tight-control performances, could significantly boost versatile uses in medical treatment in the coming future. [ABSTRACT FROM AUTHOR]

Certain high-Tc cuprate superconductors, which naturally realize a stack of Josephson junctions, thus can be used to generate electromagnetic waves in the terahertz region. A plate-like single crystal with 104 junctions without cavity resonance was proposed to achieve strong radiation. For this purpose, it is required to synchronize the Josephson plasma oscillation in all junctions. In this work, we propose to use two stacks of junctions shunted in parallel to achieve synchronization. The two stacks are mutually synchronized in the whole IV curve, and there is a phase shift between the plasma oscillation in the two stacks. The phase shift is nonzero when the number of junctions in different stacks is the same, while it can be arbitrary when the number of junctions is different. This phase shift can be tuned continuously by applying a magnetic field when all the junctions are connected by superconducting wires. [ABSTRACT FROM AUTHOR]

We study the dynamics of skyrmions in a metallic chiral magnet. First, we show that skyrmions can be created dynamically by destabilizing the ferromagnetic background state through a spin polarized current. We then treat skyrmions as rigid particles and derive the corresponding equation of motion. The dynamics of skyrmions is dominated by the Magnus force, which accounts for the weak pinning of skyrmions observed in experiments. Finally, we discuss the quantum motion of skyrmions. [ABSTRACT FROM AUTHOR]

Left-handed materials usually are realized in artificial subwavelength structures. Here, we show that some anisotropic superconductors such as Bi2Sr2CaCu2O8+δ; YBa2CuxOy,and La2-xSrxCuO4,are intrinsic left-handed materials. The condition is that the plasma frequency in the c axis, ωc, and in the ab plane, ωab, and the operating angular frequency, ω, satisfy ωc < ω < ωab. In addition, ω should be smaller than the superconducting energy gap to sustain superconductivity. We study the reflection and transmission of electromagnetic waves and reveal negative refraction and the backward wave with the phase velocity opposite to the direction of energy flux propagation. We also discuss possible approaches for improvement, making these properties feasible for experimental validation. Being intrinsic left-hand materials, the anisotropic superconductors are promising for applications in functional electromagnetic devices in the terahertz frequency band. [ABSTRACT FROM AUTHOR]

Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) is an autosomal recessive disorder resulting from biallelic mutations of the SLC25A13 gene. Due to the lack of well-recognized clinical or biochemical diagnostic criteria, the definitive diagnosis of this disease relies on the genetic analysis of SLC25A13 at present. As novel large deletion/insertion mutations of the SLC25A13 gene are difficult to detect using routine DNA analytic approaches, the timely diagnosis of patients with these types of mutations remains a challenge. The present study aimed to examine SLC25A13 mutations in an infant with a suspected diagnosis of NICCD. DNA was extracted from blood samples, and SLC25A13 mutations were examined by screening for high-frequency mutations and Sanger sequencing. Reverse transcription-polymerase chain reaction and cDNA cloning analyses were then performed using peripheral blood lymphocytes (PBLs) to identify the obscure mutation. The results demonstrated that the infant was heterozygous for a paternally-inherited mutation, c.851_854del4, and a maternally-inherited large deletion, c.1019_1177+893del, which has not been reported previously. A positive diagnosis of NICCD was made, and the infant responded favorably to a galactose-free and medium-chain triglyceride-enriched formula. The present study confirmed the effectiveness of this formula in NICCD therapy, enriched the SLC25A13 mutational spectrum and supported the feasibility of cDNA cloning analysis using PBLs as a molecular tool for facilitating the identification of large SLC25A13 deletions. [ABSTRACT FROM AUTHOR]

We study the equilibrium and dynamical properties of skyrmions in thin films of chiral magnets with oblique magnetic field. The shape of an individual skyrmion is noncircular and the skyrmion density decreases with the tilt angle from the normal of films. As a result, the interaction between two skyrmions depends on the relative angle between them in addition to their separation. The triangular lattice of skyrmions under a perpendicular magnetic field is distorted into a centered rectangular lattice for a tilted magnetic field. For a low skyrmion density, skyrmions form a chainlike structure. The dynamical response of the noncircular skyrmions depends on the direction of external currents. [ABSTRACT FROM AUTHOR]

Skyrmions are topological spin defects which have been observed in chiral magnets and other materials including some multiferroics in recent years. The typical size of a skyrmion varies in the range 5–100 nm with thousands of spins in it and a characteristic energy scale of 1 meV per layer. They can also be viewed as emergent mesoscopic particles which can be moved or manipulated by electrical current, temperature gradient, electric and magnetic field, thus rendering them useful for a variety of applications including information storage. In particular, the current needed to move a skyrmion is five to six orders of magnitude smaller than that needed for moving magnetic domain walls and vortices, therefore making them promising candidates for spintronics. [ABSTRACT FROM PUBLISHER]

A model cascade is usually created before constructing a practical isotope separation cascade as the target for approximating a practical cascade. The Q-cascade is a widely used model cascade for continuous profiles in separating multi-component isotope mixtures. The optimization of a Q-cascade with specified concentrations for a target component in the product and waste flows can be conveniently performed by adjusting the mass number (M*) of a virtual component. In previous studies, the M* parameter was treated as identical throughout the entire cascade. This paper proposes further optimization of a Q-cascade by splitting the cascade into segments and allowing each segment to take a different value for M*. An example is presented for separating Cd isotopes; the numerical results demonstrated that segmented Q-cascades achieved better separation performance than traditional Q-cascades. [ABSTRACT FROM AUTHOR]

We study the equilibrium phase diagram of ultrathin chiral magnets with easy-plane anisotropy A. The vast triangular skyrmion lattice phase that is stabilized by an external magnetic Held evolves continuously as a function of increasing A into a regime in which nearest-neighbor skyrmions start overlapping with each other. This overlap leads to a continuous reduction of the skyrmion number from its quantized value Q = 1 and to the emergence of antivortices at the center of the triangles formed by nearest-neighbor skyrmions. The antivortices also carry a small "skyrmion number" QA ⪡ 1 that grows as a function of increasing A. The system undergoes a first order phase transition into a square vortex-antivortex lattice at a critical value of A. Finally, a canted ferromagnetic state becomes stable through another first order transition for a large enough anisotropy A. Interestingly enough, this first order transition is accompanied by metastable meron solutions. [ABSTRACT FROM AUTHOR]

Lars Onsager and Richard Feynman envisaged that the three-dimensional (3D) superfluid-to-normal λ transition in 4He occurs through the proliferation of vortices. This process should hold for every phase transition in the same universality class. The role of topological defects in symmetry-breaking phase transitions has become a prime topic in cosmology and high-temperature superconductivity, even though direct imaging of these defects is challenging. Here we show that the U(1) continuous symmetry that emerges at the ferroelectric critical point of multiferroic hexagonal manganites leads to a similar proliferation of vortices. Moreover, the disorder field (vortices) is coupled to an emergent U(1) gauge field, which becomes massive by means of the Higgs mechanism when vortices condense (span the whole system) on heating above the ferroelectric transition temperature. Direct imaging of the vortex network in hexagonal manganites offers unique experimental access to this dual description of the ferroelectric transition, while enabling tests of the Kibble-Zurek mechanism. [ABSTRACT FROM AUTHOR]

A numerical method is presented for cascade analysis and design for multi-component isotope separations. A fun-damental issue of interest in cascade analysis and design is the solution of the nonlinear algebraic equation system. This system describes the mass conservation and the separation property of a cascade, which provides the hydraulic state and the component distributions in the cascade. Analytical solutions for the system are only available in a few special cases. Numerical methods are preferred for many of the complicated separation situations; however, the solution process in a numerical method is carried out through iterations and is very sensitive to initial values, which often leads to the failure of the method. Continuation techniques satisfactorily resolve the problem of sen-sitivity. This paper presents computer algorithms in detail to show how the techniques were implemented in order to tackle the problems in constructing different cascades. Various cascades were employed as test problems, includ-ing the well-known matched-R cascade, the quasi-ideal cascade, the less-known matched-X cascade and a newly invented pseudo-binary cascade. Numerical experiments on these cascades demonstrated that these cascades are readily solved with the required properties and that the proposed method is a powerful technique for analyzing and designing isotope separation cascades. [ABSTRACT FROM AUTHOR]

It is important to know the decoherence mechanism of a qubit based on Josephson junctions. At low temperatures, as quasiparticle concentration becomes exponentially small, one needs to consider energy transfer from tunneling electrons to other degrees of freedom tofind dissipation in Josephson junctions and decoherence in qubits. Here we discuss the energy transfer to two-level systems, i.e., the transitions between two different configurations of ions inside an insulating layer separated by a potential barrier. We derive a general equation of motion for the phase difference between two superconducting electrodes and we find a retarded dissipation term due to electromagnetic mechanism and also contribution due to electron tunneling mechanism. Using the equation of motion we calculate the decay of Rabi oscillations and frequency shift in qubits due to the presence of the two-level systems. In the long-time limit our results coincide with those obtained by Martinis et al. [ABSTRACT FROM AUTHOR]

Objectives To clarify the time-course changes in left ventricular myocardial deformation using velocity vector imaging and to provide insights into our understanding of the cardiac pathophysiology in diabetes mellitus. Methods Thirty New Zealand white rabbits were randomly divided into either the control group (n = 10) or the diabetes mellitus (DM) group (induced with STZ, n = 20). For the myocardial deformation studies, echocardiography and syngo-vector velocity imaging (VVI) were performed at baseline and after 2, 4, 8, and 12 weeks in all of the rabbits. The left ventricular (LV) global longitudinal and circumferential strain and strain rate were measured. For histomorphological study of the heart structure, 2 of the STZ-induced rabbits were killed at 2, 4, 8, and 12 weeks. Routine hematoxylin and eosin staining was performed. Results At 2 weeks, the global longitudinal strain (GLS), systolic strain rate (GLSRs), and diastolic strain rate (GLSRd) were significantly lower in the DM group compared with the control group (-18.16% versus -24.00%, -1.86 s-1 versus -2.49 s-1, 1.93 s-1 versus 2.42 s-1, respectively, P < 0.05), while, compared with the control group, the global circumferential strain (GCS), systolic strain rate (GCSRs), and diastolic strain rate (GCSRd) in the DM group were significantly decreased (-12.77% versus -23.31%, -1.31 s-1 versus -2.20 s-1, 1.41 s-1 versus 2.15 s-1, respectively, P < 0.05) at 8 weeks. With the progression of untreated diabetes, the histoanatomical alterations intensified gradually beginning at 2 weeks. Conclusions The progressive impairments in LV myocardial deformation and structure occurred early in diabetic rabbits with normal LV ejection fraction (EF), FS, and E/A. VVI could be used to evaluate subtle cardiac dysfunction in the early phase of DM. [ABSTRACT FROM AUTHOR]

We introduce a minimal spin model for describing the magnetic properties of CuCrCO2. Our Monte Carlo simulations of this model reveal a rich magnetic-field-induced phase diagram, which explains the measured field dependence of the electric polarization. The sequence of phase transitions between different multiferroic states arises from a subtle interplay between spatial and spin anisotropy, magnetic frustration, and thermal fluctuations. Our calculations are compared to new measurements up to 92 T. [ABSTRACT FROM AUTHOR]

We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications. [ABSTRACT FROM AUTHOR]

We study the triangular lattice Ising model with a finite number of vertically stacked layers and demonstrate a low temperature reentrance of two Berezinskii-Kosterlitz-Thouless transitions, which results in an extended disordered regime down to T = 0. Numerical results are complemented with the derivation of an effective low-temperature dimer theory. Contrary to order by disorder, we present a new scenario for fluctuation-induced ordering in frustrated spin systems. While short-range spin-spin correlations are enhanced by fluctuations, quasi-long-range ordering is precluded at low enough temperatures by proliferation of topological defects. [ABSTRACT FROM AUTHOR]

A spin texture called skyrmion has been recently observed in certain chiral magnets without inversion symmetry. The observed skyrmions are extended objects with typical linear sizes of 10 to 100 nm that contain 103 to 105 spins and can be deformed in response to external perturbations. Weak deformations are characterized by internal modes, which are localized around the skyrmion center. Knowledge of internal modes is crucial to assess the stability and rigidity of these topological textures. Here, we compute the internal modes of a skyrmion in a ferromagnetic background state by numerical diagonalization of the dynamical matrix. We find several internal modes below the magnon continuum, such as the mode corresponding to the translational motion and different kinds of breathing modes. The number of internal modes is larger for lower magnetic fields. Indeed, several modes become gapless in the low-field region indicating that the single skyrmion solution becomes unstable, although a skyrmion lattice remains thermodynamically stable. On the other hand, only three internal modes exist at high fields and the skyrmion texture remains locally stable even when the ferromagnetic state becomes thermodynamically stable. We also show that the presence of out-of-plane easy-axis anisotropy stabilizes the single skyrmion solution. Finally, we discuss the effects of damping and possible experimental observations of these internal modes. [ABSTRACT FROM AUTHOR]

We derive the effective heat current density operator for the strong-coupling regime of Mott insulators. Similarly to the case of the electric current density, the leading contribution to this effective operator is proportional to the local scalar spin chirality Xjkl = Sj . (Sj × Sk). This common form of the effective heat and electric current density operators leads to a novel cross response in Mott insulators. A heat current induces a distribution of orbital magnetic moments in systems containing loops of an odd number of hopping terms. The relative orientation of the orbital moments depends on the particular lattice of magnetic ions. This subtle effect arises from the symmetries that the heat and electric currents have in common. [ABSTRACT FROM AUTHOR]

Abstract: Using mesa array fabricated at the top of Bi2Sr2CaCu2O8 single crystal was demonstrated recently as a promising route to enhance the radiation power generated by the Josephson oscillations in mesas. We study the synchronization in such an array via the plasma waves in the base crystal. First, we analyze plasma oscillations inside the base crystal generated by the synchronized mesa array and the associated dissipation. We then solve the dynamic equation for the superconducting phase numerically to find conditions for synchronization and to check the stability of the synchronized state. We find that the mesas are synchronized when the cavity resonance of mesas matches with that of the base crystal. An optimal configuration of the mesa arrays is also obtained. [Copyright &y& Elsevier]

A topological excitation called skyrmion has been observed experimentally in chiral magnets without spatial inversion symmetry. The dynamics of a skyrmion is equivalent to an electron moving in a strong magnetic field. As a skyrmion involves large number of spins, it is not clear whether there exist observable quantum effects. In this work, we study the quantum dynamics of a skyrmion in a pinning potential. Without a pinning potential, the skyrmion performs cyclotron motion due to the strong emergent magnetic field originating from the Berry phase of spins, and all skyrmions occupy the lowest Landau level. Their wave functions are strongly localized in a region with radius less than 1 Å when no driving force is applied. Thus in most circumstances, the quantum effects of a skyrmion are weak. In the presence of a pinning potential, the lowest Landau level for skyrmions is split into quantized levels, characterized by the orbital moments. The transition between quantized levels can be observed experimentally by microwave absorption measurements in low temperature region. The quantum effects are more prominent for a skyrmion with a small size, which can be realized in magnets with a large Dzyaloshinskii-Moriya interaction. [ABSTRACT FROM AUTHOR]

A skyrmion in a nanosized disk of a chiral magnet can be used as a bit of information. To this end, it is desirable to control the creation and removal of a skyrmion only by currents without using external magnetic fields. Here, we propose to create a skyrmion by applying a current pulse to a nanodisk. The skyrmion can be removed from the disk by applying a dc current. We show that the dynamics of the created skyrmion can lead to a rectification effect, in which a dc voltage is generated by the motion of skyrmion in the presence of an ac current. [ABSTRACT FROM AUTHOR]

The powerful terahertz emission from intrinsic Josephson junctions in high-Tc cuprate superconductors has been detected recently. The synchronization of different junctions is enhanced by excitation of the geometrical cavity resonance. A key characteristic of the radiation is its linewidth. In this work, we study the intrinsic linewidth of the radiation near the internal cavity resonance. Surprisingly, this problem was never considered before, neither for a single Josephson junction nor for a stack of the intrinsic Josephson junctions realized in cuprate superconductors. The linewidth appears due to the slow phase diffusion, which is determined by the dissipation and amplitude of the noise. We found that both these parameters are resonantly enhanced when the cavity mode is excited but enhancement of the dissipation dominates leading to the net suppression of diffusion and dramatic narrowing of the linewidth. The line shape changes from Lorentzian to Gaussian when either the Josephson frequency is shifted away from the, resonance or the temperature is increased. [ABSTRACT FROM AUTHOR]

Recently spin textures called skyrmions have been discovered in certain chiral magnetic materials without spatial inversion symmetry, and they have attracted enormous attention due to their promising application in spintronics since only a low applied current is necessary to drive their motion. When a conduction electron moves around the skyrmion, its spin is fully polarized by the spin texture and acquires a quantized phase; thus, the skyrmion yields an emergent electrodynamics that in turn determines skyrmion motion and gives rise to a finite Hall angle. As topological excitations, skyrmions behave as particles. In this paper we derive the equation of motion for skyrmions as rigid point particles from a microscopic continuum model and obtain the short-range interaction between skyrmions and the interaction between skyrmions and defects. Skyrmions also experience a Magnus force perpendicular to their velocity due to the underlying emergent electromagnetic field. We validate the equation of motion by studying the depinning transition using both the particle and the continuum models. By using the particle description, we explain the recent experimental observations of the rotation of a skyrmion lattice in the presence of a temperature gradient. We also predict quantum and thermal creep motion of skyrmions in the pinning potential. [ABSTRACT FROM AUTHOR]

We study the dynamics of Skyrmions in chiral magnets in the presence of a spin polarized current. The motion of Skyrmions in the ferromagnetic background excites spin waves and contributes to additional damping. At a large current, the spin wave spectrum becomes gapless and Skyrmions are created dynamically from the ferromagnetic state. At an even higher current, these Skyrmions are strongly deformed due to the damping and become unstable at a threshold current, leading to a chiral liquid. We show how Skyrmions can be created by increasing the current in the magnetic spiral state. We then construct a dynamic phase diagram for a chiral magnet with a current. The instability transitions between different states can be observed as experimentally clear signatures in the transport measurements, such as jumps and hysteresis. [ABSTRACT FROM AUTHOR]

The fabrication of high-quality thin superconducting films is essential for single-photon detectors. Their device performance is crucially affected by their material parameters, thus requiring reliable and nondestructive characterization methods after the fabrication and patterning processes. Important material parameters to know are the resistivity, superconducting transition temperature, relaxation time of quasiparticles, and uniformity of patterned wires. In this work, we characterize micropatterned thin NbN films by using transport measurements in magnetic fields. We show that from the instability of vortex motion at high currents in the flux-flow state of the / V characteristic, the inelastic lifetime of quasiparticles can be determined to be about 2 ns. Additionally, from the depinning transition of vortices at low currents, as a function of magnetic field, the size distribution of grains can be extracted. This size distribution is found to be in agreement with the film morphology obtained from scanning electron microscopy and high-resolution transmission electron microscopy images. [ABSTRACT FROM AUTHOR]

Multiband superconductors support the excitation of vortices with fractional quantum flux, known as fractional vortices. In the ground state, the fractional vortices in different bands bond together to form a composite vortex with the standard flux quantum Φ0; thus it is difficult to stabilize the fractional vortices. Here we show that fractional vortex lattices can be stabilized in multiband superconductors with a periodic pinning array at the half-matching field of the composite system, when full matching of the fractionalized vortices occurs. In the presence of a high current, the fractional vortices in different bands decouple and move at different velocities. When the current is turned off suddenly, the fractional vortices in different bands may be trapped at different pinning sites. This system also exhibits rich dynamic behavior, and for fractional vortices in two-band superconductors we find phases where the vortices in one band are pinned and the vortices in the other band are moving. These different phases can be observed in transport measurements and produce a new type of self-induced Shapiro steps that can arise under the application of only a dc drive. [ABSTRACT FROM AUTHOR]

In multiband superconductors, each superconducting condensate supports vortices with fractional quantum flux. In the ground state, vortices in different bands are spatially bounded together to form a composite vortex, carrying one quantum flux (I)~. Here we predict dissociation of the composite vortices lattice in the flux flow state due to the disparity of the vortex viscosity and flux of the vortex in different bands. For a small driving current, composite vortices start to deform, but the constituting vortices in different bands move with the same velocity. For a large current, composite vortices dissociate and vortices in different bands move with different velocities. The dissociation transition shows up as an increase of flux flow resistivity. In the dissociated phase, Shapiro steps are developed when an ac current is superimposed with a dc current. [ABSTRACT FROM AUTHOR]

In order to enhance the radiation power in the terahertz band based on intrinsic Josephson junctions of Bi2Sr2CaCu2O8+δ single crystal, we investigate a long cylindrical sample embedded in a dielectric material. Tuning the dielectric constant, the radiation power has a maximum which is achieved when it equals the dissipation caused by the Josephson plasma. This yields the optimal dielectric constant of the wrapping material in terms of the properties of a BSCCO single crystal. The maximal radiation power is found proportional to the product of the critical superconducting current squared and the typical normal resistance, which offers a guideline for choosing superconductors as a source of strong radiation. [ABSTRACT FROM AUTHOR]

We demonstrate that there is a long-range vortex-vortex attraction in ferromagnetic superconductors due to polarization of the magnetic moments. Vortex clusters are then stabilized in the ground state for low vortex densities. The motion of vortex clusters driven by the Lorentz force excites magnons. This regime becomes unstable at a threshold velocity above which domain walls are generated for slow relaxation of the magnetic moments and the vortex configuration becomes modulated. This dynamics of vortices and magnetic moments can be probed by transport measurements. [ABSTRACT FROM AUTHOR]

We propose to use a superconductor-magnet multilayer structure to achieve high critical current density by invoking the polaronic mechanism of pinning. The magnetic layers should have large magnetic susceptibility to enhance the coupling between the vortices and magnetization in those layers. The relaxation of die magnetization should be slow. When the velocity of vortices is low, they are dressed by nonuniform magnetization and move as polarons. In mis case, the viscosity of vortices, which is proportional to the magnetic relaxation time, is enhanced significantly. As the velocity increases, the polarons dissociate and the viscosity drops to me usual Bardeen-Stephen value, resulting in a jump in the I-V curve. Experimentally the jump shows up as a depinning transition and the corresponding current at the jump is the depinning current. For Nb and an appropriate magnet multilayer structure, we estimate the critical current density Jc ~ 109 A/m² at magnetic field B ≈ 1 T. [ABSTRACT FROM AUTHOR]

Strong terahertz radiation from the mesa structure of a Bi²Sr²CaCu²O8+δ single crystal has been observed recently, where the mesa intrinsically forms a cavity. For a thick mesa of a large number of junctions, there are many cavity modes with different wave vectors along the c axis corresponding to almost the same bias voltages. The mechanism responsible for exciting the uniform mode which radiates coherent terahertz waves in experiments is unknown. In this paper, we show that the in-plane dissipation selects the uniform mode. For perturbations with nonzero wave numbers along the c axis, the in-plane dissipations are significantly enhanced, which prevents the excitation of corresponding cavity modes. Our analytical results are confirmed by numerical simulations. [ABSTRACT FROM AUTHOR]

In borocarbide ErNi2B2C, the phase transition to the commensurate spin density wave at 2.3 K leaves 1 /20 part of Ising-like Er spins practically free. Vortices polarize these spins nonuniformly and repolarize them when moving. At a low spin relaxation rate and at low bias currents, vortices carrying magnetic polarization clouds become polaronlike and their velocities are determined by the effective drag coefficient, which is significantly bigger than the Bardeen-Stephen (BS) one. As current increases, at a critical current Jc vortices release polarization clouds and the velocity as well as the voltage in the I-V characteristics jump to values corresponding to the BS drag coefficient. The nonuniform components of the magnetic field and magnetization drop as velocity increases, resulting in weaker polarization and discontinuous dynamic dissociation depinning transition. As current decreases, on the way back, vortices are retrapped by polarization clouds at the current Jr < Jc. [ABSTRACT FROM AUTHOR]

The working principle of magnetic force microscopy and scanning SQUID microscopy is introducing a magnetic source near a superconductor and measuring the magnetic field distribution near the superconductor, from which one can obtain the penetration depth. We investigate the magnetic field distribution near the surface of a magnetic superconductor when a magnetic source is placed close to the superconductor, which can be used to extract both the penetration depth &lgr;L and magnetic susceptibility X by magnetic force microscopy or scanning SQUID microscopy. When the magnetic moments are parallel to the surface, one extracts &lgr;L/√l -- 4&pgr;X. When the moments are perpendicular to the surface, one obtains &lgr;L. By changing the orientation of the crystal, one thus is able to extract both X and &lgr;L. [ABSTRACT FROM AUTHOR]

In this work, we investigate the Josephson effect between a two-band superconductor either with the s++ (two energy gaps have the same sign and are fully gapped) pairing symmetry or j± (two energy gaps have n phase difference and are fully gapped) pairing symmetry and a conventional s-wave superconductor. The ground state, critical current, plasma modes, flux-flow dynamics, response to external ac electric field, and possible soliton solutions are investigated. For junctions with the charge neutrality breaking, we find a new plasma mode for junctions, which gives rise to new resonance peaks in the Josephson flux-flow region. Because of the frustrated interaction injunctions with s± pairing symmetry, time-reversal symmetry (TRS) can be broken if the frustration is optimized. In the TRS broken (TRSB) state, there is a nontrivial phase difference between the two Josephson tunneling channels, which results in a nontrivial interference. Furthermore, we find a massless plasma mode at the TRSB transition for junctions with the charge neutrality breaking. In the TRSB state, a spontaneous magnetic flux appears where there is a spatial inhomogeneity in the Josephson coupling, thus providing a possible smoking-gun evidence for the underlying pairing symmetry. [ABSTRACT FROM AUTHOR]

The Josephson-like interband couplings in multi-band superconductivity exhibit degenerate energy minima, which support states with kinks in phase of superconductivity. When the interband couplings in systems of three or more components are frustrated, the time-reversal symmetry (TRS) can be broken, which generates another type of phase kink between the two time-reversal symmetry breaking (TRSB) pair states. In this work, we focus on these novel states of phase kinks, and investigate their stability, similarity, differences and physical consequences. The main results can be summarized as follows: (i) we find a new type of phase slip when the kink becomes unstable. (ii) In the kink region, TRS is broken and spontaneous magnetic fields are induced. (iii) In superconductors with TRSB, composite topological excitations associated with variations of both the superconductivity phase and amplitude can be created by local perturbations or due to proximity effect between normal metals. [ABSTRACT FROM AUTHOR]

The Leggett mode associated with out-of-phase oscillations of the superconducting phase in multiband superconductors usually is heavy due to interband coupling, which makes its excitation and detection difficult. We report on the existence of a massless Leggett mode in three-band superconductors with time-reversal-symmetry breaking. The mass of this Leggett mode is small close to the time-reversal-symmetry-breaking transition and vanishes at the transition point, and thus locates within the smallest superconducting energy gap, which makes it stable and detectable, e.g., by means of the Raman spectroscopy. The thermodynamic consequences of this massless mode and possible realization in iron-based superconductors are also discussed. [ABSTRACT FROM AUTHOR]

A single vortex overcoming the surface barrier in a mesoscopic superconductor with lateral dimensions of several coherence lengths and thickness of several nanometers provides an ideal platform to study thermal activation of a single vortex. In the presence of thermal fluctuations, there is nonzero probability for vortex penetration into or exclusion from the superconductor even when the surface barrier does not vanish. We consider the thermal activation of a single vortex in a mesoscopic superconducting disk of circular shape. To obtain statistics for the penetration and exclusion magnetic fields, slow and periodic magnetic fields are applied to the superconductor. We calculate the distribution of the penetration and exclusion fields from the thermal activation rate. This distribution can also be measured experimentally, which allows for a quantitative comparison. [ABSTRACT FROM AUTHOR]

We propose to measure the spectrum of magnetic excitation in magnetic materials using the motion of a vortex lattice driven by both ac and dc currents in superconductors. When the motion of a vortex lattice is resonant with the oscillation of magnetic moments, the voltage decreases at a given current. From transport measurement, one can obtain the frequency of the magnetic excitation with the wave number determined by the vortex-lattice constant. By changing the lattice constant through applied magnetic fields, one can obtain the spectrum of the magnetic excitation up to a wave vector of order 10 nm-1. [ABSTRACT FROM AUTHOR]

We investigate the behavior of vortices of multicomponent superconductivity with intercomponent coupling, realized in MgB2 and Fe-based superconductors, within the framework of Ginzburg-Landau (GL) theory in terms of numerical calculations of the time-dependent GL equations and the variational method. It is revealed that close to the critical point of the composite system the intercomponent coupling makes the system behave as a single component superconductivity. However, when the bare mean-field critical points of the two components coincide with each other, and furthermore the interband coupling disappears at the same temperature, interesting phenomena occur as follows. Vortices interact attractively at large separation and repulsively at short distance in certain parameter space. Because of the nonmonotonic interaction profile, phase separations between vortex clusters of triangular order and the Meissner state take place, which indicates a first-order phase transition associated with the penetration of the magnetic field into a superconductor sample. Phase diagrams of vortex states are then constructed with the associated magnetization curve. It is found that the system shares some features of both type-I and -II superconductors. [ABSTRACT FROM AUTHOR]

The possibility of estimating the minimum total flow in a cascade with concentrations of a target component given in the product and waste flows by means of a model match abundance ratio cascade (MARC) is studied. The parameters required to describe MARC characteristics are the total number of separation stages, the feed flow location, and the M* parameter, which is equal to a half-sum of mass numbers of the target and the supporting components. Specific research carried out independently in two scientific labs in China and Russia has demonstrated that the integral parameters of the MARC, optimized by the M* parameter, are very close to that of the optimum by the minimum total flow cascade found by means of numerical optimization. The calculation is performed for separation of krypton isotopes when the end component 78Kr and the intermediate component 83Kr are considered to be the targets. It paves the way to use the optimized MARC parameters for two purposes: first, for fast and easy evaluation of the real cascade parameters and second, as an initial guess in its further direct numerical optimization, thereby allowing significant savings in computation time. [ABSTRACT FROM AUTHOR]

A new family of dynamic states are found in a stack of inductively coupled intrinsic Josephson junctions in the absence of an external magnetic field. In this state, (2 m l+1) π phase kinks with integers m l’s stack along the c axis and lock neighboring junctions together. A significant part of the dc power is pumped into plasma oscillations via kinks at the cavity resonances. The plasma oscillation is uniform along the c axis with the frequency satisfying the ac Josephson relation. Thus this state supports strong terahertz radiation and seems to be compatible with the recent experimental observations. [ABSTRACT FROM AUTHOR]

In isotope separation pulse cascades are non-conventional and transient processes take place at each stage and in the whole cascade. A numerical method is developed to study the transient process of reaching steady state and applied to square pulse cascades to identify the majors of influence. Without feed and withdrawals, the main factors influencing the transient process are the cascade length and the ratio of the centrifuge holdup to the pipe holdup. With feed and withdrawals, the factors influencing the transient process include the feed, the centrifuge holdup, the pipe holdup, and the cascade length. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To assess the feasibility and utility of high-resolution three-dimensional magnetic resonance angiography (3D MRA) and contrast-enhanced 3D spoiled gradient-recalled imaging (3D SPGRI) for the purpose of visualization of neurovascular contact in trigeminal neuralgia (TN) patients. Methods: Forty-five patients (25 males, 20 females; age range, 23–82 years; and mean age, 55.67±18.23 years) with unilateral typical TN and 36 control subjects (21 males, 15 females; age range, 25–85 years; mean age, 57.53±19.25 years) underwent high-resolution 3D MRA and contrast-enhanced 3D SPGRI assessment. The images were reviewed by two experienced neuroradiologists who were blinded to the clinical details. The imaging results were compared with the operative findings in all the patients; additionally, the degree of neurovascular contact was compared between the two groups based on MR imaging. Results: In 45 patients with unilateral typical TN, the use of 3D MRA in conjunction with the contrast-enhanced 3D SPGRI identified neurovascular contact in 40 of the 42 symptomatic nerves; the contact was verified surgically. Based on the surgical findings, the sensitivity and specificity of MR imaging were 95.20% and 100%, respectively. Based on MRI, the compressing vessel (artery, vein) was correctly identified in 32 of the 39 cases verified by microvascular decompression. There was good agreement (K =0.77; 95% confidence interval, 0.54–0.99) between the position (medial, lateral, superior, and inferior) of the compressing vessel relative to the trigeminal nerve as defined by MR imaging and the surgical findings. The rates of vascular contact with the trigeminal nerve as observed on MRI were 31.94%, 48.89%, and 88.9% in the control subjects, asymptomatic, and symptomatic side of patients, respectively. Conclusion: The combined use of high-resolution 3D MRA and contrast-enhanced 3D SPGRI is an extremely sensitive and specific technique for demonstrating vascular contact with the trigeminal nerve in TN patients. [Copyright &y& Elsevier]

The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered alloy of highly dissimilar elements (large Ce and small Al atoms) by compressing the Ce3Al intermetallic compound >15 GPa or the Ce3AI metallic glass >25 GPa. Synchrotron X-ray diffraction, Ce L3-edge absorption spectroscopy, and ab initio calculations revealed that the pressure-induced Kondo volume collapse and 4f electron delocalization of Ce reduced the differences between Ce and Al and brought them within the Hume-Rothery (HR) limit for substitutional alloying. The alloy re- mained after complete release of pressure, which was also accompanied by the transformation of Ce back to its ambient 4f electron localized state and reversal of the Kondo volume collapse, resulting in a non-HR alloy at ambient conditions. [ABSTRACT FROM AUTHOR]

Objective: To assess the left ventricular (LV) longitudinal systolic and diastolic function in patients with dilated cardiomyopathy (DCM) by syngo Velocity Vector Imaging (VVI). Methods: Digital dynamic images of 30 DCM patients and 30 healthy subjects were collected; then the longitudinal velocity, strain, and strain rate were measured in systolic early and late diastolic periods, and the time to peak systolic velocity, strain, and strain rate were measured and recorded. The parameters of the two groups were compared. Results: All of the parameters of the DCM were significantly lower than those of the normal group (P < 0.05–0.01), except that the parameter of late diastolic strain was not different between the two groups (P > 0.05). Conclusions: VVI is a novel noninvasive tool to assess quantitatively and objectively LV regional systolic and diastolic function in patients with DCM; it provides another useful modality for evaluating cardiac function. [ABSTRACT FROM AUTHOR]

A nonconventional gas centrifuge cascade, called the NFSW(no feed and single withdrawal) cascade, is studied in the separation of middle components by means of numerical simulation. The cascade has no feed and only a single withdrawal at either end of the cascade, different from conventional cascades, which usually have two withdrawals at the two ends of the cascade and one feed in between. The material to be separated is loaded in a reservoir at either end, and the desired component is enriched in either the reservoir or the withdrawal at the other end. The effects of the unit separation factor(equivalently, the cascade length) and the ratio of the upstreaming flow rate to the withdrawal rate are investigated on separation. The separation performance is evaluated in terms of the material recovery and the operation time efficiency, and is compared with those of the corresponding conventional cascades and another type of nonconventional cascade, the SW(single withdrawal) cascade. It is found that the NFSW cascade is superior to the conventional cascade and comparable in the material recovery with, but advantageous in the operation time efficiency over the SW cascade. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluated the elastic characteristics of the pulmonary trunk and distal branches in fetuses diagnosed with tetralogy of Fallot (TOF) using Doppler echocardiography. Methods: Data on 42 fetuses diagnosed with TOF and 84 gestational age-matched normal fetuses were prospectively collected from the Second Xiangya Hospital of Central South University between August 2022 and January 2023. The severity of TOF was classified into three categories based on the z-score of the pulmonary annulus diameter: mild (z-score =-2), moderate (-40.05). Conclusion: Fetuses diagnosed with TOF exhibited increased vascular stiffness in the MPA and reduced stiffness in the distal pulmonary artery (PA). Larger-scale follow-up studies are required to elucidate the relationships between these changes in vascular stiffness and PA development in patients with TOF. [ABSTRACT FROM AUTHOR]

In recent years, there has been an intense search for materials realizing the Kitaev quantum spin liquid model. A number of edge-shared compounds with strong spin-orbit coupling, such as RuCl3 and iridates, have been proposed to realize this model. Nevertheless, an effective spin Hamiltonian derived from the microscopic model relevant to these compounds generally contains terms that are antagonistic toward the quantum spin liquid. This is consistent with the fact that the zero magnetic field ground state of these materials is generally magnetically ordered. It is a pressing issue to identify protocols to drive the system to the limit of the Kitaev quantum spin model. In this work, we propose Floquet engineering of these Kitaev quantum magnets by coupling materials to a circularly polarized laser. We demonstrate that all the magnetic interactions can be tuned in situ by the amplitude and frequency of the laser, hence providing a route to stabilize the Kitaev quantum spin liquid phase. Kitaev materials are prime candidates to study quantum spin liquids but despite many known examples it is still a challenge to realize systems that have a total absence of magnetic ordering. Here, the authors propose Floquet engineering and the use of light-matter interactions to achieve a Kitaev quantum spin liquid phase. [ABSTRACT FROM AUTHOR]

It is observed experimentally that the sign of the Hall resistance can be flipped by a dc electric current in the twisted bilayer graphene (TBG) at 3/4 filling of the fourfold degenerate conduction flat bands. The experiment implies a switching of the valley polarization (VP) and topology in TBG. Here we present a theory on the current-induced switching of VP and topology. The presence of current in the bulk causes the redistribution of electron occupation in bands near the Fermi energy, which then deforms and shifts the band dispersion due to the Coulomb interaction. Above a critical current, the original occupied and empty bands can be swapped, resulting in the switching of VP and topology. [ABSTRACT FROM AUTHOR]

The d-wave superconductor CeCoIn5 has been proposed as a strong candidate for supporting the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state near the low-temperature boundary of its upper critical field. Neutron diffraction, however, finds spin-density-wave (SDW) order in this part of the phase diagram for field in the a-b plane, and evidence for the SDW disappears as the applied field is rotated toward the tetragonal c axis. It is important to understand the interplay between the SDW and a possible FFLO state in CeCoIn5, as the mere existence of an SDW does not necessarily exclude an FFLO state. Here, based on a model constructed on the basis of available experiments, we show that an FFLO state competes with an SDW phase. The SDW state in CeCoIn5 is stabilized when the field is directed close to the a-b plane. When the field is rotated toward the c axis, the FFLO state emerges, and the SDW phase disappears. In the FFLO state, the nodal planes with extra quasiparticles (where the superconducting order parameter is zero) are perpendicular to the field, and in the SDW phase, the quasiparticle density of states is reduced. We test this model prediction by measuring heat transported by normal quasiparticles in the superconducting state. As a function of field, we observe a reduction of thermal conductivity for field close to the a-b plane and an enhancement of thermal conductivity when field is close to the c axis, consistent with theoretical expectations. Our modeling and experiments, therefore, indicate the existence of the FFLO state when field is parallel to the c axis. [ABSTRACT FROM AUTHOR]