Transport Fluctuations Research Articles

Sedimentary grain-size record of Holocene runoff fluctuations in the Lake Lugu watershed, SE Tibetan Plateau

Changes in moisture conditions or precipitation in the SE Tibetan Plateau during the Holocene have been studied using various environmental archives and proxies. However, due to different interpretations of the proxies and records, the pattern of Holocene precipitation/moisture variations in the region remains unclear. A lake-sediment-based reconstruction of runoff variations, which can directly and sensitively reflect changes in precipitation, provides the opportunity to reconstruct the evolution of moisture conditions in the SE Tibetan Plateau during the Holocene. In this study, we used a well-dated sediment core (LGH2) from Lake Lugu, a deep alpine lake charged mainly by precipitation on the lake surface and by runoff from the watershed, to reconstruct variations in runoff during the Holocene. In addition, 70 lake surface sediment samples were collected to examine the spatial variation of grain size. Endmember modeling analysis of the grain-size data was used to characterize the processes of sediment transport and runoff fluctuations. The carbonate content of core LGH2 shows that the lake level was generally high during 11,600–3100 cal years BP, and that the lake basin was closed after 3100 cal years BP and semi-closed since 90 cal years BP. Grain-size endmember EM 3, which represents the runoff input clastic materials, is used to reconstruct runoff fluctuations in the Lake Lugu watershed. The record indicates a gradual increase in runoff during 11,600–9000 cal years BP, stable and high runoff during 9000–2000 cal years BP, and weak runoff and a low lake level since 2000 cal years BP. Our reconstruction of runoff fluctuations tracks changes in regional temperature and tropical SSTs rather than in boreal summer insolation. This finding supports the hypothesis that increasing tropical SSTs strengthened ITCZ convection which enhanced the flux of water vapour from the ocean to the air, and hence the moisture supplies to SW China.

Self-equilibration theorem in quantum-point contacts of interacting electrons: Time-dependent quantum fluctuations of tunnel transport beyond the Levitov–Lesovik scattering approach

Equilibration to the steady state for a wide class of Luttinger liquid ballistic weakly linked tunnel contacts is extensively studied. Quantum fluctuations of tunnel current are considered in all orders in tunnel coupling and out of the equilibrium in the time domain. Especially, two important mathematical statements: Self-equilibration (SE-)theorem and Self-equilibration (SE-)lemma on the exact re-exponentiation of thermal average from the Keldysh-contour-ordered evolution operator for arbitrary weakly linked Luttinger liquid tunnel contact are proven. Demonstrated proof of SE-theorem and SE-lemma represents first evidence of a novel emergent phenomenon of ”self-equilibration” in the dynamics of quantum fluctuations of electron transport through ballistic tunnel junctions. This phenomenon and all related real-time full counting statistics are shown to be much more general as compared to the usual Levitov–Lesovik scattering approach for the non-interacting electrons, though SE-theorem also contains known results obtained within the Levitov–Lesovik scattering approach as corresponding limiting case for lowest order cumulants at g=1. As the result, corresponding differential equation of ”self-equilibration” for time-dependent Keldysh partition function of tunnel contact is derived and explained. It is shown that proven SE-theorem can be considered also as the dynamical version of well-known Jarzynski equality for the tunnel electron transport out of the equilibrium. As the result, for arbitrary weakly linked tunnel junction model of interest the exact time-dependent cumulant generating functional is derived being valid at arbitrary electron–electron repulsion in the Luttinger liquid leads of the junction, arbitrary temperature and arbitrary bias voltage. Respective general formula in its long-time asymptote turns into a non-perturbative Luttinger liquid generalization of the Levitov–Lesovik type of detailed balance formula for cumulant generating function. As the consequence of obtained results, a universal character of self-equilibration of tunnel current in one-dimensional weakly linked tunnel junctions is revealed and studied on the level of non-equilibrium Fano factor. As well, a new measure of disequilibrium in such systems – the ”steady flow” rate – is also introduced and discussed.

Surmounting potential barriers: Hydrodynamic memory hedges against thermal fluctuations in particle transport.

Recently, trapped-particle experiments have probed the instantaneous velocity of Brownian motion revealing that, at early times, hydrodynamic history forces dominate Stokes damping. In these experiments, nonuniform particle motion is well described by the Basset-Boussinesq-Oseen (BBO) equation, which captures the unsteady Basset history force at a low Reynolds number. Building off of these results, earlier we showed that, at low temperature, BBO particles could exploit fluid inertia in order to overcome potential barriers (generically modeled as a tilted washboard), while its Langevin counter-part could not. Here, we explore the behavior of neutrally buoyant BBO particles at finite temperature for moderate Stokes damping. Remarkably, we find that the transport of particles injected into a bumpy potential with sufficiently high barriers can be completely quenched at intermediate temperatures, whereas itinerancy may be possible above and below that temperature window. This effect is present for both Langevin and BBO dynamics, though these occur over drastically different temperature ranges. Furthermore, hydrodynamic memory mitigates these effects by sustaining initial particle momentum, even in the difficult intermediate temperature regime.

Anisotropy fluctuation and correlation in central α -clustered C12+Au197 collisions

In the framework of a multi-phase transport model, fluctuation and correlation of the azimuthal anisotropies in $^{12}$C+$^{197}$Au collisions at $\sqrt{S_{NN}}$ = 200 GeV are explored. Properties of the initial eccentricity and final harmonic flow fluctuation resulted from $^{12}$C+$^{197}$Au collisions with Woods-Saxon configuration and triangular $\alpha$-clustering configurations of $^{12}$C are investigated via scaled variance, skewness and kurtosis. Comparisons are made between results from $\alpha$-clustered configurations and Woods-Saxon configuration. The triangular flow fluctuation is found to have particular sensitivity in distinguishing triangular $\alpha$-clustering structure of $^{12}$C. Furthermore, correlations between initial eccentricities and final flow harmonics are studied with strong multiplicity dependence observed for the correlation functions.

Pending recovery in the strength of the meridional overturning circulation at 26° N

Abstract. The strength of the Atlantic meridional overturning circulation (AMOC) at 26∘ N has now been continuously measured by the RAPID array over the period April 2004–September 2018. This record provides unique insight into the variability of the large-scale ocean circulation, previously only measured by sporadic snapshots of basin-wide transport from hydrographic sections. The continuous measurements have unveiled striking variability on timescales of days to a decade, driven largely by wind forcing, contrasting with previous expectations about a slowly varying buoyancy-forced large-scale ocean circulation. However, these measurements were primarily observed during a warm state of the Atlantic multidecadal variability (AMV) which has been steadily declining since a peak in 2008–2010. In 2013–2015, a period of strong buoyancy forcing by the atmosphere drove intense water-mass transformation in the subpolar North Atlantic and provides a unique opportunity to investigate the response of the large-scale ocean circulation to buoyancy forcing. Modelling studies suggest that the AMOC in the subtropics responds to such events with an increase in overturning transport, after a lag of 3–9 years. At 45∘ N, observations suggest that the AMOC may already be increasing. Examining 26∘ N, we find that the AMOC is no longer weakening, though the recent transport is not above the long-term mean. Extending the record backwards in time at 26∘ N with ocean reanalysis from GloSea5, the transport fluctuations at 26∘ N are consistent with a 0- to 2-year lag from those at 45∘ N, albeit with lower magnitude. Given the short span of time and anticipated delays in the signal from the subpolar to subtropical gyres, it is not yet possible to determine whether the subtropical AMOC strength is recovering nor how the AMOC at 26∘ N responds to intense buoyancy forcing.

Effect of interlayer tunneling barrier on carrier transport and fluctuation in multilayer ReS2

Multilayer rhenium disulfide (ReS2) has recently attracted significant attention because of the decoupled van der Waals interaction between its adjacent layers that leads to a much higher interlayer resistivity than that in other layered materials. Although the carrier transport in multilayer materials is well described by the interlayer resistance and Thomas–Fermi charge screening length (λ) in theoretical resistor network models, the understanding of the effect of electric field-dependent interlayer tunneling barrier (Eint) on current fluctuation in two-dimensional (2D) multilayer materials is limited. Herein, we report the effects of Eint on carrier transport and charge fluctuation in multilayer ReS2. The electrostatic back-gate (VBG)- and drain bias (VD)-dependent Eint causes channel migration along the c-axis in 2D multilayer systems and consequently results in two plateaus in the transconductance curve, thereby allowing us to determine the top and bottom carrier mobilities of multilayer ReS2 separately. Furthermore, the strong correlation between Eint and the Coulomb scattering parameter in multilayer ReS2 is elucidated via low-frequency noise spectroscopy. The results of our study provide a clear insight into the origins of carrier transport and current fluctuation in 2D multilayer devices.

Invariant density of intermittent nonlinear maps descriptive of coherent quantum transport through disorderless lattices

Weakly chaotic attractors of an intermittent map defined on the complex unit circle arise in an analogy with a recurrence relation of the scattering matrix associated with wave transport through locally periodic structures of consecutive sizes. It is demonstrated that the fixed-point solution (infinite iteration time or scattering structure size) of the relation corresponds to an average of the scattering matrix over a set, or “ensemble”, of systems of all sizes. This ergodic property implies the analyticity of the scattering matrix S and the existence of its “ensemble” average 〈S〉, called the optical S-matrix. We find that the invariant density of the map that governs the sample-to-sample fluctuations of coherent transport is given by the Poisson kernel of potential theory, and consequently the distribution of S is uniquely determined by 〈S〉 which depends only on the transport properties of a single scattering cell. The theoretical distribution, closely related to the Cauchy distribution, shows perfect agreement with numerical results for a chain of delta potentials. A consequence of our findings is the a priori knowledge of 〈S〉 without the customary resort to experimental data.

Noise and full counting statistics of a Cooper pair splitter

We investigate theoretically the noise and the full counting statistics of electrons that are emitted from a superconductor into two spatially separated quantum dots by the splitting of Cooper pairs and further on collected in two normal-state electrodes. With negatively-biased drain electrodes and a large superconducting gap, the dynamics of the Cooper pair splitter can be described by a Markovian quantum master equation. Using techniques from full counting statistics, we evaluate the electrical currents, their noise power spectra, and the power-power correlations in the output leads. The current fluctuations can be attributed to the competition between Cooper pair splitting and elastic cotunneling between the quantum dots via the superconductor. In one regime, these processes can be clearly distinguished in the cross-correlation spectrum with peaks and dips appearing at characteristic frequencies associated with elastic cotunneling and Cooper pair splitting, respectively. We corroborate this interpretation by analyzing the charge transport fluctuations in the time domain, specifically by investigating the $g^{(2)}$-function of the output currents. Our work identifies several experimental signatures of the fundamental transport processes involved in Cooper pair splitting and provides specific means to quantify their relative strengths. As such, our results may help guide and interpret future experiments on current fluctuations in Cooper pair splitters.

Electron Transfer Mechanism at the Oil/Water Interface Revealed by Multidimensional Free Energy Calculations.

The electron transfer (ET) reaction of ferrocene and ferricyanide at the water-dichloromethane interface, a typical liquid-liquid ET in electrochemistry, was intensively investigated with a three-dimensional free energy surface that fully describes the transport, association, and solvent fluctuation in the ET processes. The calculated free energy surface provides the comprehensive picture of the ET mechanism at the liquid-liquid interface. The present calculation revealed the heterogeneous route of ET that takes place over the interface, rather than the homogeneous one. The present conclusion is found to be consistent with previous results of electrochemical experiments by careful re-examination of the analysis.

Joint Stochastic Bedload Transport and Bed Elevation Model: Variance Regulation and Power Law Rests

We describe the joint dynamics of bedload transport and bed elevation changes with a stochastic population model, and we analyze (1) the dependence of bedload flux statistics on local bed elevations and (2) resting time distributions for sediment undergoing burial in the fluctuating sedimentary bed. The model involves entrainment and deposition in a control volume characterized by elevation‐dependent rates, and it exhibits a statistical regulation effect, whereby bed aggradation suppresses the variance of the bedload flux while degradation enhances it. This variance regulation effect is contingent on collective entrainment, whereby moving grains destabilize stationary grains in a positive feedback. When collective entrainment is turned off,bedload transport fluctuations become independent of the bed elevation. Return times from above in the bed elevation time series provide heavy‐tailed power law distributions of resting times with tail behavior characterized by the mean erosion rate and the active layer depth. These results imply bedload statistics measurements on relatively short timescales can be strongly biased by bed elevation changes when collective entrainment occurs, and they support the growing consensus that sediment burial generates heavy‐tailed sediment resting times that ultimately generate anomalous bedload diffusion.

Current-Resistance Effects Inducing Nonlinear Fluctuation Mechanisms in Granular Aluminum Oxide Nanowires.

The unusual superconducting properties of granular aluminum oxide have been recently investigated for application in quantum circuits. However, the intrinsic irregular structure of this material requires a good understanding of the transport mechanisms and, in particular, the effect of disorder, especially when patterned at the nanoscale level. In view of these aspects, electric transport and voltage fluctuations have been investigated on thin-film based granular aluminum oxide nanowires, in the normal state and at temperatures between 8 and 300 K. The nonlinear resistivity and two-level tunneling fluctuators have been observed. Regarding the nature of the noise processes, the experimental findings give a clear indication in favor of a dynamic random resistor network model, rather than the possible existence of a local ordering of magnetic origin. The identification of the charge carrier fluctuations in the normal state of granular aluminum oxide nanowires is very useful for improving the fabrication process and, therefore, reducing the possible sources of decoherence in the superconducting state, where quantum technologies that are based on these nanostructures should work.

The influence of transport vibrations on the condition of Russian cultural heritage objects

This article is devoted to the negative impact of transport vibrations on the condition of historical and cultural monuments. The causes of the occurrence of transport fluctuations and the consequences of their impact were considered. The authors proposed a classification of the negative impact of transport on monuments, ways to reduce of the negative impact were given, as well as the regions of Russian Federation that are the most susceptible to such impact were analyzed.

Hierarchical quantum master equation approach to current fluctuations in nonequilibrium charge transport through nanosystems

We present a hierarchical quantum master equation (HQME) approach, which allows the numerically exact evaluation of higher-order current cumulants in the framework of full counting statistics for nonequilibrium charge transport in nanosystems. The novel methodology is exemplarily applied to a model of vibrationally coupled electron transport in a molecular nanojunction. We investigate the influence of cotunneling on avalanche-like transport, in particular in the nonresonant transport regime, where we find that inelastic cotunneling acts as trigger process for resonant avalanches. In this regime, we also demonstrate that the correction to the elastic noise upon opening of the inelastic transport channel is strongly affected by the nonequilibrium excitation of the vibration as well as the polaron shift.

Dynamic Comfort Inside the Building under Microseismic Influence from the Movement of Vehicles

Vibration and it’s high background bring a danger to human health. According to the intensity of fluctuations in the urban environment transport, especially trams, trains, including metro bring the greatest impact on human. This article investigates the reaction of high-rise building on microseismic influence of the motion of the external transport. There are determined the minimum reserves of dynamic comfort for different frequencies of impacts, as well as potentially dangerous average frequencies for the studied building. A comparison of the results of the calculation of the building using explicit and implicit schemes of integration of the equations of motion is made. Conclusions about the feasibility of using implicit integration schemes for solving problems of this type are made.

Transport fluctuations in integrable models out of equilibrium

We propose exact results for the full counting statistics, or the scaled cumulant generating function, pertaining to the transfer of arbitrary conserved quantities across an interface in homogeneous integrable models out of equilibrium. We do this by combining insights from generalised hydrodynamics with a theory of large deviations in ballistic transport. The results are applicable to a wide variety of physical systems, including the Lieb-Liniger gas and the Heisenberg chain. We confirm the predictions in non-equilibrium steady states obtained by the partitioning protocol, by comparing with Monte Carlo simulations of this protocol in the classical hard rod gas. We verify numerically that the exact results obey the correct non-equilibrium fluctuation relations with the appropriate initial conditions.

Water Price Calculations in Concept Of Environmental Service: A Case in Cimanuk Watershed

Cimanuk Watershed is one of the important water sources in West Java Province. The damage that occurred in Cimanuk watershed affected the sustainability of water supply in West Java. The administrative area of ​​Cimanuk watershed extends to 4 regencies, namely Garut Regency, Sumedang Regency, Majalengka Regency, and Indramayu Regency. The Cimanuk River itself has a length of ± 338 km which can supply water needs of 2.2 billion m3 every year with the main utilization for irrigation in agricultural areas. Forest areas in the upper Cimanuk watershed affect the continuity of the hydrological, erosion and sedimentation process. Changes in the upstream area in terms of land use and forest exploitation that do not consider environmental aspects can damage the entire watershed ecosystem, causing fluctuations in water flow, sediment transport, and material dissolved in the water flow system. Given the reciprocal relationship in the concept of watershed management, the implementation of the Payment Environmental Services or PES mechanism is important, where water is one of components that deserves be consideration. The economic valuation of water quantified as water prices is also a fundamental reason for the importance of PES studies. Water prices based on scientific calculations, both qualitative and quantitative, determine the feasibility value that will be given from the downstream community upstream as conservation actors to support the concept of fair environmental services. Quantitative analysis is carried out in the form of valuations involving several methods, namely the Contingent Valuation Method, Value of Marginal Product Water, and Full Cost Pricing. The price of water can be used as an indicator of the cost of forest environmental services as a water provider as well as improving market mechanisms. This paper concludes the mechanism of payment for environmental services (PES) through water pricing policies can be an alternative source of funding to improve the condition of a watershed

Lyapunov Exponents of Two Stochastic Lorenz 63 Systems

Two different types of perturbations of the Lorenz 63 dynamical system for Rayleigh–Bénard convection by multiplicative noise—called stochastic advection by Lie transport (SALT) noise and fluctuation–dissipation (FD) noise—are found to produce qualitatively different effects, possibly because the total phase-space volume contraction rates are different. In the process of making this comparison between effects of SALT and FD noise on the Lorenz 63 system, a stochastic version of a robust deterministic numerical algorithm for obtaining the individual numerical Lyapunov exponents was developed. With this stochastic version of the algorithm, the value of the sum of the Lyapunov exponents for the FD noise was found to differ significantly from the value of the deterministic Lorenz 63 system, whereas the SALT noise preserves the Lorenz 63 value with high accuracy. The Lagrangian averaged version of the SALT equations (LA SALT) is found to yield a closed deterministic subsystem for the expected solutions which is isomorphic to the original Lorenz 63 dynamical system. The solutions of the closed chaotic subsystem, in turn, drive a linear stochastic system for the fluctuations of the LA SALT solutions around their expected values.

Fluctuating-time and full counting statistics for quantum transport in a system with internal telegraphic noise

Many molecular junctions display stochastic telegraphic switching between two distinct current values, which is therefore an important source of fluctuations in nanoscale quantum transport. We investigate electronic fluctuations arising via Markovian master equations; identifying regions of non-renewal behavior due to telegraphic switching. Non-renewal behavior is characterized by the emergence of correlations between successive first-passage times of detection in one of the leads. Our method of including telegraphic switching is general for any source-molecule-drain setup, but we consider three specific cases. In the first, we model stochastic transitions between an Anderson impurity with and without an applied magnetic field $B$. The last two scenarios couple the electronic level to a single vibrational mode via the Holstein model. We then stochastically switch between two vibrational conformations, with different electron-phonon coupling and vibrational frequency, which corresponds to different molecular conformations. Finally, we model the molecule attaching and detaching from an electrode by switching between two different molecule-electrode coupling strengths. We find, for all three cases, that including the telegraph process in the master equation induces relatively strong positive correlations, with Pearson coefficient $p \approx 0.5$, between successive first-passage times. These correlations only appear, however, when there is telegraphic switching between two significantly different transport scenarios, and we show that it arises from the underlying physics of the model. We also find that, in order for correlations to appear, the switching rate $\nu$ must be much smaller than the rate of electron transfer $\gamma$.

Fluctuations in Ballistic Transport from Euler Hydrodynamics

We propose a general formalism, within large-deviation theory, giving access to the exact statistics of fluctuations of ballistically transported conserved quantities in homogeneous, stationary states. The formalism is expected to apply to any system with an Euler hydrodynamic description, classical or quantum, integrable or not, in or out of equilibrium. We express the exact scaled cumulant generating function (or full counting statistics) for any (quasi-)local conserved quantity in terms of the flux Jacobian. We show that the “extended fluctuation relations” of Bernard and Doyon follow from the linearity of the hydrodynamic equations, forming a marker of “freeness” much like the absence of hydrodynamic diffusion does. We show how an extension of the formalism gives exact exponential behaviours of spatio-temporal two-point functions of twist fields, with applications to order-parameter dynamical correlations in arbitrary homogeneous, stationary state. We explain in what situations the large-deviation principle at the basis of the results fail, and discuss how this connects with nonlinear fluctuating hydrodynamics. Applying the formalism to conformal hydrodynamics, we evaluate the exact cumulants of energy transport in quantum critical systems of arbitrary dimension at low but nonzero temperatures, observing a phase transition for Lorentz boosts at the sound velocity.

Effect of Temperature Fluctuation and Transport Time on Complete Blood Count Parameters

Abstract Introduction Reliable specimen collection and transport are fundamental to obtain high-quality test results in the hematology laboratory. Recognizing the effect of fluctuations in transport and storage conditions, time, and temperatures on the integrity of specimens and quality of results may help define the optimal transport and storage parameters. We designed an IRB-approved quality improvement study to investigate the effects of temperature fluctuation and duration of storage on blood parameters. Methods Ten volunteers donated blood for the study. All samples were deidentified and volunteers were blinded to the results without any review of their charts. Eight EDTA vials were collected from each volunteer and were immediately stored in heating blocks/refrigerators/freezers at selected temperatures including 0°C, 2 to 8°C, 25°C, 30°C, 35°C, 40°C, 45°C and at room temperature (21°C). Blood parameters were then measured using sysmex XN series at 0, 8, 12, 24, and 48 hours and values were analyzed. Results We observed that total white cell count, Hb, MCH, and platelets were stable for 12 hours at 2 to 35°C. RBCs and MPV were stable for 12 hours at 2 to 30°C, whereas blood parameters including Hct, RDW, MCV, and MCHC were stable up until 12 hours at room temperature but not at higher temperatures. All parameters were stable at 2 to 8°C even up to 48 hours. Conclusion It is preferable to perform CBC on blood specimens as soon as they are received. However, our data suggest that most of the blood parameters are stable for at least 12 hours at room temperature. The integrity of specimens and consequently the quality of the results deteriorate above 35°C and when stored longer than 24 hours; 2 to 8°C is the optimal temperature range for specimen transport, especially if delays in analysis are anticipated.