Potential Perturbation Research Articles

Airborne particulate matters induce thrombopoiesis from megakaryocytes through regulating mitochondrial oxidative phosphorylation

BackgroundAlthough airborne fine particulate matter (PM) pollution has been demonstrated as an independent risk factor for pulmonary and cardiovascular diseases, their currently-available toxicological data is still far from sufficient to explain the cause-and-effect. Platelets can regulate a variety of physiological and pathological processes, and the epidemiological study has indicated a positive association between PM exposure and the increased number of circulative platelets. As one of the target organs for PM pollution, the lung has been found to be involved in the storage of platelet progenitor cells (i.e. megakaryocytes) and thrombopoiesis. Whether PM exposure influences thrombopoiesis or not is thus explored in the present study by investigating the differentiation of megakaryocytes upon PM treatment.ResultsThe results showed that PM exposure promoted the thrombopoiesis in an exposure concentration-dependent manner. PM exposure induced the megakaryocytic maturation and development by causing cell morphological changes, occurrence of DNA ploidy, and alteration in the expressions of biomarkers for platelet formation. The proteomics assay demonstrated that the main metabolic pathway regulating PM-incurred alteration of megakaryocytic maturation and thrombopoiesis was the mitochondrial oxidative phosphorylation (OXPHOS) process. Furthermore, airborne PM sample promoted-thrombopoiesis from megakaryocytes was related to particle size, but independent of sampling filters.ConclusionThe findings for the first time unveil the potential perturbation of haze exposure in thrombopoiesis from megakaryocytes by regulating mitochondrial OXPHOS. The substantial evidence on haze particle-incurred hematotoxicity obtained herein provided new insights for assessing the hazardous health risks from PM pollution.

Responses of Halo Occupation Distributions: a new ingredient in the halo model & the impact on galaxy bias

Halo occupation distribution (HOD) models describe the number of galaxies that reside in different haloes, and are widely used in galaxy-halo connection studies using the halo model (HM). Here, we introduce and study HOD response functions R \U0001d4aa g that describe the response of the HODs to long-wavelength perturbations \U0001d4aa. The linear galaxy bias parameters b \U0001d4aa g are a weighted version of b \U0001d4aa h + R \U0001d4aa g , where b \U0001d4aa h is the halo bias, but the contribution from R \U0001d4aa g is routinely ignored in the literature. We investigate the impact of this by measuring the R \U0001d4aa g in separate universe simulations of the IllustrisTNG model for three types of perturbations: total matter perturbations, \U0001d4aa = δ h ; baryon-CDM compensated isocurvature perturbations, \U0001d4aa = σ; and potential perturbations with local primordial non-Gaussianity, \U0001d4aa ∝ f NLϕ. Our main takeaway message is that the R \U0001d4aa g are not negligible in general and their size should be estimated on a case-by-case basis. For stellar-mass selected galaxies, the responses R \U0001d4aa g and R σ g are sizeable and cannot be neglected in HM calculations of the bias parameters b ϕ g and b σ g ; this is relevant to constrain inflation using galaxies. On the other hand, we do not detect a strong impact of the HOD response R 1 g on the linear galaxy bias b 1 g . These results can be explained by the impact that the perturbations \U0001d4aa have on stellar-to-total-mass relations. We also look into the impact on the bias of the gas distribution and find similar conclusions. We show that a single extra parameter describing the overall amplitude of R \U0001d4aa g recovers the measured b \U0001d4aa g well, which indicates that R \U0001d4aa g can be easily added to HM/HOD studies as a new ingredient.

Perturbation of Urbanization to Earth's Surface Energy Balance

AbstractUrbanization, one of the most dramatic forms of land conversion, modifies local climatic environments and threatens human life and health. Here we use the space‐for‐time approach combined with satellite data to quantify the potential perturbation of surface energy balance and land surface temperature (LST) caused by urbanization at global scale. We estimate that collectively +2.4°C, +0.9°C, and +1.7°C potential changes for annual daytime, nighttime, and mean LST could be triggered when land surface converted from natural area to urban use, due primarily to the decline of latent heat during months from April to October (−23.9–−3.2 W m−2), and the reduced sensible heat and ground heat storage in other months (−5.2–−2.4 W m−2). Urbanization perturbation to surface energy balance and temperature exhibit conspicuous spatial heterogeneity (i.e., varying with latitude and climate zones) and temporal asymmetries (i.e., diurnal and seasonal: strong in summer daytime and weak in winter nighttime). These spatial‐temporal variations are interrelated closely with local background climate‐vegetation regimes, as indicated by strong correlations between urbanization perturbation to surface biophysical effects and precipitation, temperature, vegetation index across regions and months. Our findings provide empirical evidence that biophysical mechanisms of urbanization need to be considered in predicting future trajectories of climate change and local susceptibility of surface energy balance should be accounted for when evaluating urbanization effects and mitigating urban heat.

How real are liquid groundstates? Ultra-fast crystal growth and the susceptibility of energy minima in liquids

We calculate the degree to which the final structure of the local groundstate in a liquid is a function of the strength of a perturbing potential applied during energy minimization. This structural susceptibility is shown to correlate well with the observed tendency of the liquid adjacent to a crystal interface to exhibit a crystalline groundstate, a feature that has been strongly linked to the observation of ultra-fast crystal growth in pure metals and ionic melts. It is shown that the structural susceptibility increases dramatically as the interaction potential between atoms is softened.

Capacitive Hysteresis Effects in Ionic Liquids: 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate on Polycrystalline Gold Electrode

Ionic liquids (ILs) add complexity to electrochemical interfaces that cannot be adequately treated with traditional double layer models. We present a series of carefully controlled capacitance measurements to optimize the collection of reproducible and uniform capacitance-potential datasets. We quantitatively evaluate analysis methods on the experimentally observed capacitance of l-ethyl-3-methylimidazolium trifluoromethauesulfonate [Emim][TFO] IL at the gold-IL interface. The major outcomes of our work are to identify how experimental data collection methods affect capacitive hysteresis, and to suggest a systematic approach to collect reproducible capacitance data for IL systems. We evaluate different potential scan directions, examine varying potential sweep rates, and capacitance collection methods. We find that faster scan rates can mitigate the capacitive hysteresis between the anodic and cathodic scans for a particular collection technique. However, faster scan rates also result in more variation between the collection techniques. We also find that decreasing the effective potential sweep rate reduces hysteresis between different collection techniques when other factors are held constant. It is crucial for researchers to consistently report the direction of the potential sweep and the effective rate of potential sweep. Our data suggest that using slower effective potential perturbation rates would reduce discrepancies in capacitance data collected from different laboratories under different experimental conditions.

Cryo-EM structure of amyloid fibrils formed by the entire low complexity domain of TDP-43

Amyotrophic lateral sclerosis and several other neurodegenerative diseases are associated with brain deposits of amyloid-like aggregates formed by the C-terminal fragments of TDP-43 that contain the low complexity domain of the protein. Here, we report the cryo-EM structure of amyloid formed from the entire TDP-43 low complexity domain in vitro at pH 4. This structure reveals single protofilament fibrils containing a large (139-residue), tightly packed core. While the C-terminal part of this core region is largely planar and characterized by a small proportion of hydrophobic amino acids, the N-terminal region contains numerous hydrophobic residues and has a non-planar backbone conformation, resulting in rugged surfaces of fibril ends. The structural features found in these fibrils differ from those previously found for fibrils generated from short protein fragments. The present atomic model for TDP-43 LCD fibrils provides insight into potential structural perturbations caused by phosphorylation and disease-related mutations.

Tidal constraints on the low-viscosity zone of the Moon

In this paper, the effect on the tidal response of the low-viscosity zone in the deep interior of the Moon is investigated based on hypothetical temperature profiles. The tidal parameters are computed numerically to demonstrate their dependence on the low-viscosity zone and frequency. One of the calculated parameters is the tidal quality factor, to which energy dissipation is inversely proportional. The other parameters are the tidal Love numbers, which are normalized magnitudes of displacement and potential perturbation of tidal deformation. Unlike earlier considerations, the viscosity structure of the low-viscosity zone is no longer assumed to be fully uniform but linked with several temperature profiles such as a thermal boundary layer model or a convective layer model. The calculations show that the latest observational ranges of the frequency-dependent quality factors can be satisfied only by the convective layer model with some viscosity value for the middle layer but not by the thermal boundary layer model for any structure. The approximate viscosity solution is estimated to be 3 × 1016 Pa s. If considering also the observational ranges of the Love numbers together with those of the quality factors, the solution of the outer radius of the low-viscosity zone is approximately either 560 or 580 km. These solutions are almost identical to those based on the previous model where the low-viscosity zone has uniform viscosity. It is concluded that the thermal state of the bottom layer of the lunar mantle is predicted to be mainly controlled by local convection, and possibly maintained by the energy balance between convective cooling and tidal heating, as previously suggested.

Repeated exposure to tripping like perturbations elicits more precise control and lower toe clearance of the swinging foot during steady walking.

Controlling minimum toe clearance (MTC) is considered an important factor in preventing tripping. In the current study, we investigated modifications of neuro-muscular control underlying toe clearance during steady locomotion induced by repeated exposure to tripping-like perturbations of the right swing foot. Fourteen healthy young adults (mean age 26.4±3.1years) participated in the study. The experimental protocol consisted of three identical trials, each involving three phases: steady walking (baseline), perturbation, and steady walking (post-perturbation). During the perturbation, participants experienced 30 tripping-like perturbations at unexpected timing delivered by a custom-made mechatronic perturbation device. The temporal parameters (cadence and stance phase%), mean, and standard deviation of MTC were computed across approximately 90 strides collected during both baseline and post-perturbation phases, for all trials. The effects of trial (three levels), phase (two levels: baseline and post-perturbation) and foot (two levels: right and left) on the outcome variables were analyzed using a three-way repeated measures analysis of variance. The results revealed that exposure to repeated trip-like perturbations modified MTC toward more precise control and lower toe clearance of the swinging foot, which appeared to reflect both the expectation of potential forthcoming perturbations and a quicker compensatory response in cases of a lack of balance. Moreover, locomotion control enabled subjects to maintain symmetric rhythmic features during post-perturbation steady walking. Finally, the effects of exposure to perturbation quickly disappeared among consecutive trials.

Mechanistic link between CaM-RyR2 interactions and the genesis of cardiac arrhythmia

In this study, we develop a computational model of the interaction between ryanodine receptor type 2 (RyR2) and calmodulin (CaM) to explore the mechanistic link between CaM-RyR2 interactions and cardiac arrhythmia. Our starting point is a biophysically based computational model of CaM binding to a single RyR2 subunit, which reproduces single-channel RyR2 measurements in lipid bilayers. We then integrate this CaM-RyR2 model into a spatially distributed whole-cell model of Ca cycling, which is used to investigate the relationship between CaM and Ca cycling homeostasis. We show that a reduction in CaM concentration leads to a substantial increase in the rate of spontaneous Ca sparks, and this induces a marked reduction in sarcoplasmic reticulum Ca load during steady-state pacing. Also, we show that a reduction in CaM modifies the RyR2 open probability, which makes the cell more prone to Ca wave propagation. These results indicate that aberrant Ca cycling activity during pacing is determined by the interplay between sarcoplasmic reticulum load reduction and the threshold for Ca wave propagation. Based on these results, we show that when CaM is reduced, Ca waves can occur in a cell and induce action potential perturbations that are arrhythmogenic. Thus, this study outlines a novel, to our knowledge, mechanistic link between CaM-RyR2 binding kinetics and the induction of arrhythmias in the heart.

Investigation on responses and wave climbing of a ship in large waves using a fully nonlinear boundary element method

In this study, a fully nonlinear method, in the time domain, is used to simulate ship motion caused by large waves, and the problem of wave climbing along the freeboard in large waves is studied. The method is based on a three-dimensional potential flow theory. Further, the nonlinear free surface condition is adopted, the incident potential and disturbance potential are separated from each other, and the problem of determining the disturbance potential is established. In order to consider the nonlinearity of the body surface, the wetted surface area of the hull is continuously updated with time and extended along the tangential direction of the uppermost grid when the free liquid level exceeds the height of the hull deck. In addition, an artificial damping layer is provided to eliminate the reflection of waves at the outflow boundary. Under the fully nonlinear boundary conditions, the perturbation potential is solved by the Rankine source boundary element method. Introducing auxiliary functions solves the coupling problem between motion and load in the process of solving rigid body motion equations. After the solution is completed, it is updated to the next time step using the Runge-Kutta 4th order method. In this study, the convergence of the computational grid of the numerical model is firstly verified. Then, the motion and load responses of a zero-speed ship in the regular wave of unit wave amplitude using this method are examined and compared with the linear method. The latter verifies the accuracy of this method in the linear field. Afterwards, in order to investigate the superiority of the fully nonlinear method when the nonlinear phenomenon is strong, the motion and load of the ship in the large amplitute wave are simulated and the influence of the nonlinear phenomenon is analyzed. Finally, the phenomenon of wave climbing generated in high waves is analyzed, and the relationship between wave and water heights is evaluated.

Generalized gravity-gradient mitigation scheme

A major challenge in high-precision light-pulse atom interferometric experiments such as in tests of the weak equivalence principle is the uncontrollable dependency of the phase on initial velocity and position of the atoms in the presence of inhomogeneous gravitational fields. To overcome this limitation, mitigation strategies have been proposed, however, valid only for harmonic potentials or only for small branch separations in more general situations. Here we provide a mitigation formula for anharmonic perturbation potentials including local gravitational effects that vary on length scales much smaller than the spatial extent probed by the atoms and originate, e.g., from buildings that surround the experiment. Furthermore, our results are applicable to general interferometer geometries with arbitrary branch separation and allow for compensation of Coriolis effects in rotating reference frames.

Alchemical transformations for concerted hydration free energy estimation with explicit solvation.

We present a family of alchemical perturbation potentials that enable the calculation of hydration free energies of small- to medium-sized molecules in a single concerted alchemical coupling step instead of the commonly used sequence of two distinct coupling steps for Lennard-Jones and electrostatic interactions. The perturbation potentials we employ are non-linear functions of the solute-solvent interaction energy designed to focus sampling near entropic bottlenecks along the alchemical pathway. We present a general framework to optimize the parameters of alchemical perturbation potentials of this kind. The optimization procedure is based on the λ-function formalism and the maximum-likelihood parameter estimation procedure we developed earlier to avoid the occurrence of multi-modal distributions of the coupling energy along the alchemical path. A novel soft-core function applied to the overall solute-solvent interaction energy rather than individual interatomic pair potentials critical for this result is also presented. Because it does not require modifications of core force and energy routines, the soft-core formulation can be easily deployed in molecular dynamics simulation codes. We illustrate the method by applying it to the estimation of the hydration free energy in water droplets of compounds of varying size and complexity. In each case, we show that convergence of the hydration free energy is achieved rapidly. This work paves the way for the ongoing development of more streamlined algorithms to estimate free energies of molecular binding with explicit solvation.

Quantum Behavior of a Classical Particle Subject to a Random Force

We give a partial answer to the question whether the Schrodinger equation can be derived from the Newtonian mechanics of a particle in a potential subject to a random force. We show that the fluctuations around the classical motion of a one dimensional harmonic oscillator subject to a random force can be described by the Schrodinger equation for a period of time depending on the frequency and the energy of the oscillator. We achieve this by deriving the postulates of Nelson's stochastic formulation of quantum mechanics for a random force depending on a small parameter. We show that the same result applies to small potential perturbations around the harmonic oscillator as long as the total potential preserves the periodicity of motion with a small shift in frequency. We also show that the noise spectrum can be chosen to obtain the result for all oscillator frequencies for fixed mass. We discuss heuristics to generalize the result for a particle in one dimension in a potential where the motion can be described using action-angle variables.

Isoform-specific upregulation of FynT kinase expression is associated with tauopathy and glial activation in Alzheimer's disease and Lewy body dementias.

Cumulative data suggest the involvement of Fyn tyrosine kinase in Alzheimer's disease (AD). Previously, our group has shown increased immunoreactivities of the FynT isoform in AD neocortex (with no change in the alternatively spliced FynB isoform) which associated with neurofibrillary degeneration and reactive astrogliosis. Since both the aforementioned neuropathological features are also variably found in Lewy Body dementias (LBD), we investigated potential perturbations of Fyn expression in the post‐mortem neocortex of patients with AD, as well as those diagnosed as having one of the two main subgroups of LBD: Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB). We found selective upregulation of FynT expression in AD, PDD, and DLB which also correlated with cognitive impairment. Furthermore, increased FynT expression correlated with hallmark neuropathological lesions, soluble β‐amyloid, and phosphorylated tau, as well as markers of microglia and astrocyte activation. In line with the human post‐mortem studies, cortical FynT expression in aged mice transgenic for human P301S tau was upregulated and further correlated with accumulation of aggregated phosphorylated tau as well as with microglial and astrocytic markers. Our findings provide further evidence for the involvement of FynT in neurodegenerative dementias, likely via effects on tauopathy and neuroinflammation.

Essential Self-Adjointness of Perturbed Biharmonic Operators via Conformally Transformed Metrics

We give sufficient conditions for the essential self-adjointness of perturbed biharmonic operators acting on sections of a Hermitian vector bundle over a Riemannian manifold with additional assumptions, such as lower semi-bounded Ricci curvature or bounded sectional curvature. In the case of lower semi-bounded Ricci curvature, we formulate our results in terms of the completeness of the metric that is conformal to the original one, via a conformal factor that depends on a minorant of the perturbing potential V. In the bounded sectional curvature situation, we are able to relax the growth condition on the minorant of V imposed in an earlier article. In this context, our growth condition on the minorant of V is consistent with the literature on the self-adjointness of perturbed biharmonic operators on \(\mathbb {R}^{n}\).

Spectral theory of first-order systems: From crystals to Dirac operators

Let [Formula: see text] be a constant coefficient first-order partial differential system, where the matrices [Formula: see text] are Hermitian. It is assumed that the homogeneous part is strongly propagative. In the non-homogeneous case it is assumed that the operator is isotropic. The spectral theory of such systems and their potential perturbations is expounded, and a Limiting Absorption Principle is obtained up to thresholds. Special attention is given to a detailed study of the Dirac and Maxwell operators. The estimates of the spectral derivative near the thresholds are based on detailed trace estimates on the slowness surfaces. Two applications of these estimates are presented: Global spacetime estimates of the associated evolution unitary groups, that are also commonly viewed as decay estimates. In particular, the Dirac and Maxwell systems are explicitly treated. The finiteness of the eigenvalues (in the spectral gap) of the perturbed Dirac operator is studied, under suitable decay assumptions on the potential perturbation.

Budget analysis of mesoscale available potential energy in a heavy rainfall event over the eastern Tibetan Plateau: 青藏高原东部暴雨的中尺度有效位能收支分析

Using model simulated data, the distribution characteristics, genesis, and impacts on precipitation of available potential energy (APE) are analyzed for a heavy rainfall event that took place over the eastern Tibetan Plateau during 10–11 July 2018. Results show that APE was mainly distributed below 4 km and within 8–14 km. The APE distribution in the upper level had a better correspondence with precipitation. Northwestern cold advection and evaporation of falling raindrops were primary factors leading to positive anomalies of APE in the lower level, while positive anomalies of APE in the upper level were caused by a combination of thermal disturbances driven by latent heat and potential temperature perturbations resulting from the orography of the Tibetan Plateau. Budget analysis of APE indicated that APE fluxes and conversion between APE and kinetic energy (KE) were the main source and sink terms. Meridional fluxes of APE and conversion of KE to APE fed the dissipation of APE in the lower level. Vertical motion enhanced by conversion of APE to KE in the upper level was the major factor that promoted precipitation evolution. A positive feedback between APE and vertical motion in the upper level generated a powerful correlation between them. Conversion of KE to APE lasted longer in the lower level, which weakened vertical motion; whereas, northwestern cold advection brought an enhanced trend to the APE, resulting in a weak correlation between APE and vertical motion.摘要针对2018年7月10-11日青藏高原东部一次暴雨过程, 利用模式模拟资料分析了有效位能分布特征,成因及其对降水发展演变的影响.结果表明, 有效位能主要分布在对流层低层4km以下和高层8-14km, 高层有效位能和降水有更好的对应性西北冷平流和降水粒子下落的蒸发作用是低层有效位能高值中心的主要成因, 而降水过程释放潜热带来的热力扰动叠加高原大地形造成的位温扰动是导致高层有效位能高值的主要原因.有效位能收支分析表明, 有效位能的通量输送项以及与动能间的转换项是主要源汇项.低层有效位能的经向通量输送和动能向有效位能的转化补给了有效位能的耗散;高层有效位能向垂直动能转化增强垂直运动是促进降水发展演变的主要因素.高层有效位能与垂直运动之间的正反馈过程使得两者相关性较强;低层较长时间内均存在垂直动能向有效位能的转化, 削弱了垂直运动, 而西北冷平流使得低层有效位能有增强的趋势, 因此二者相关性较弱.

Role of substrate strain to tune energy bands–Seebeck relationship in semiconductor heterostructures

In doped semiconductors and metals, the Seebeck coefficient or thermopower decreases monotonically with increasing carrier concentration in agreement with the Pisarenko relation. Here, we establish a fundamental mechanism to modulate and increase the thermopower of silicon (Si)/germanium (Ge) heterostructures beyond this relation, induced by the substrate strain. We illustrate the complex relationship between the lattice strain and the modulated thermopower by investigating the electronic structure and cross-plane transport properties of substrate strained [001] Si/Ge superlattices (SLs) with two independent theoretical modeling approaches: first-principles density functional theory and the analytical Krönig–Penny model in combination with the semi-classical Boltzmann transport equation. Our analysis shows that the SL bands, formed due to the cubic structural symmetry, combined with the potential perturbation and the intervalley mixing effects, are highly tunable with epitaxial substrate strain. The strain tuned energy band shifts lead to modulated thermopowers, with a peak approximately fivefold Seebeck enhancement in strained [001] Si/Ge SLs in the high-doping regime. As a consequence, the power factor of a 2.8% substrate strained SL shows a ≈1.8-fold improvement over bulk Si at high carrier concentrations, ≈12×1020cm−3. It is expected that the fundamental understanding discussed here, regarding the complex effect of lattice strain to control energy bands of heterostructures, will help to exploit strain engineering strategies on a class of future technology-enabling materials, such as novel Si/Ge heterostructures as well as layered materials, including van der Waals heterostructures.

Determination and perturbation of the electronic potentials of solid catalysts for innovative catalysis.

Concerns about energy and the environment are motivating a reexamination of catalytic processes, aiming to achieve more efficient and improved catalysis compatible with sustainability. Designing an active site for such heterogeneous catalytic processes remains a challenge leading to a next level breakthrough. Herein, we discuss a fundamental aspect of heterogeneous catalysis: the chemical potential of electrons in solid catalysts during thermal catalysis, which directly reflects the consequent catalytic reaction rate. The use of electrochemical tools during thermal catalysis allows for the quantitative determination of the ill-defined chemical potentials of solids in operando, whereby the potential–rate relationship can be established. Furthermore, the electrochemical means can also introduce the direct perturbation of catalyst potentials, in turn, perturbing the coverage of adsorbates functioning as poison, promoters, or reactants. We collect selected publications on these aspects, and provide a viewpoint bridging the fields of thermal- and electro-catalysis.

Guaranteed distributed machine learning: Privacy-preserving empirical risk minimization.

Distributed learning over data from sensor-based networks has been adopted to collaboratively train models on these sensitive data without privacy leakages. We present a distributed learning framework that involves the integration of secure multi-party computation and differential privacy. In our differential privacy method, we explore the potential of output perturbation and gradient perturbation and also progress with the cutting-edge methods of both techniques in the distributed learning domain. In our proposed multi-scheme output perturbation algorithm (MS-OP), data owners combine their local classifiers within a secure multi-party computation and later inject an appreciable amount of statistical noise into the model before they are revealed. In our Adaptive Iterative gradient perturbation (MS-GP) method, data providers collaboratively train a global model. During each iteration, the data owners aggregate their locally trained models within the secure multi-party domain. Since the conversion of differentially private algorithms are often naive, we improve on the method by a meticulous calibration of the privacy budget for each iteration. As the parameters of the model approach the optimal values, gradients are decreased and therefore require accurate measurement. We, therefore, add a fundamental line-search capability to enable our MS-GP algorithm to decide exactly when a more accurate measurement of the gradient is indispensable. Validation of our models on three (3) real-world datasets shows that our algorithm possesses a sustainable competitive advantage over the existing cutting-edge privacy-preserving requirements in the distributed setting.