Potential Perturbation Research Articles

Regeneration of Lithium-ion battery impedance using a novel machine learning framework and minimal empirical data

The use of Electrochemical Impedance Spectroscopy on rechargeable Lithium-ion battery characterization is an extensively recognized non-destructive procedure for both in-situ and ex-situ analyses. In an impedance measurement for a rechargeable battery, the oscillating current with an accompanying phase angle is the response for a potential perturbation. The proper evaluation of phase angle as a crucial impedance parameter, provides critical understanding of the status of the battery. Although fast and simple, impedance data is difficult to interpret. Using a novel data-centric Machine Learning framework (co-modeling) we demonstrate how to impute experimental data quickly, precisely, and inexpensively that agrees with wholly experimentally generated data. In particular, we predict the phase angle with 99.9% accuracy by training the minimal empirical impedance data. This approach demonstrates a potentially burgeoning field of Machine Learning experimental data imputation and the consequence of faster diagnostic and study of batteries.

First and Second-Order Energy Eigenvalues of One-Dimensional Quantum Harmonic and Anharmonic Oscillator with Linear, Quadratic, Cubic and Polynomial Perturbation Potential

This work is aimed at obtaining the energy eigenvalues for one-dimensional quantum harmonic and anharmonic oscillators perturbed by linear, quadratic, cubic and polynomial potentials. To obtain the solutions of the energy eigenvalues, we employed the time-independent perturbation theory to calculate the first and the second-order energy correction, which we used to obtain the complete generalised energy eigenvalues of the quantum harmonic oscillators with linear, quadratic, cubic and polynomial perturbation potential of the same unperturbed Hamiltonian (H).

Time-Resolved APXPS with Chemical Potential Perturbations: Recent Developments at the MAX IV Laboratory

Time-Resolved APXPS with Chemical Potential Perturbations: Recent Developments at the MAX IV Laboratory

Abstract 461: Antiphospholipid Antibodies In Covid-19 Convalescent Plasma

Background: Although convalescent plasma has historically yielded significant benefits in the treatment of infectious diseases, numerous clinical trials have not shown a consistent benefit in treating either moderately or severely ill COVID-19 patients with plasma from convalescent patients. We previously reported increased levels of antiphospholipid antibodies (aPL) in acutely ill COVID patients, with high aPL titers correlating with more neutrophil extracellular traps (NETs) and poorer patient outcomes. We hypothesized that persistence of potentially deleterious autoantibodies in previously hospitalized, convalescent plasma donors may activate immune cells and add context for the lack of clinical efficacy in COVID. Methods: 116 samples of convalescent plasma from donors previously hospitalized with COVID were obtained from Vitalant. Antibody titers (IgG, IgM, IgA) of anti-2-glycoprotein 1 (a2GP1) and anti-cardiolipin (aCL) and anti-phosphatidylserine/prothrombin (IgG, IgM) were quantified. NET formation by healthy human neutrophils treated with convalescent plasma was evaluated in vitro. Results: High aPL titers >40 U/mL) were observed in 10/116 (8.6%) convalescent samples, and 6/10 were positive for either IgG or IgM aCL. The aPL positivity rate exceeded the expected background population rate of ~3%. Six of 116 convalescent samples increased NET-associated MPO activity in purified, primary neutrophils from healthy donors compared with control plasma (mean increase of 23% +/- 11, p<0.01), where only 2 of these were aPL-positive samples. Conclusion: aPL were elevated in a larger proportion of surveyed convalescent plasma samples than reported in the healthy population. aPL positivity did not correlate with purified neutrophil activation, suggesting aPL in donor plasma does not have a direct, activating effect on healthy neutrophils. Considering the complex interactions among circulating blood cells, ongoing experiments are examining the impact of convalescent plasma on platelet and endothelial cell function to further elucidate potential autoantibody-mediated vascular perturbations. The results of these studies will be important in informing the vascular implications and safety of convalescent plasma in COVID.

Tumor micro-environment targeted collagenase-modified albumin nanoparticles for improved drug delivery

Gemcitabine is a deoxycytidine analogue used as an adjunct therapy in the treatment of various solid tumors. The therapeutic efficacy of this drug is compromised because of its short circulation half-life (∼17 min), fast metabolic degradation and dose dependent adverse effects. Also, there are various barriers in the tumor microenvironment which limit the drug delivery to the solid tumor. Keeping these aspects into consideration, in the present investigation, protease (collagenase) coated gemcitabine-loaded human serum albumin (HSA) nanoparticles (CG-HSANPs) were prepared to improve the drug delivery to the solid tumor compared with uncoated gemcitabine-loaded HSA nanoparticles (G-HSANPs). The desolvation technique was used to develop nanocarriers, which were evaluated for physicochemical properties such as average particle diameter, surface charge, morphology, drug loading and in vitro drug release. The average particle diameter of G-HSANPs and CG-HSANPs was found to be 160.5 ± 4.1 and 181.7 ± 2.54 nm, respectively. The morphology of nanocarrier was investigated by transmission electron microscopy (TEM) and the nanoparticles were also evaluated using differential scanning calorimetry (DSC). The in vitro antiproliferative activity showed comparable cytotoxicity of CG-HSANPs, G-HSANPs and native drug. The fluorescence microscopy showed uptake of collagenase coated HSA nanoparticles (C-HSANPs) and uncoated HSA nanoparticles (HSANPs) in MiaPaCa-2 cells and there was higher nuclear fragmentation, generation of reactive oxygen species and perturbation in mitochondrial membrane potential of CG-HSANPs compared to the native drug. Further, C-HSANPs exhibited improved tumor spheroid penetration as compare to HSANPs. The present study demonstrated the potential of CG-HSANPs as a carrier for improved drug delivery.

Theory-agnostic reconstruction of potential and couplings from quasinormal modes

In this work, we use a parametrized theory-agnostic approach that connects the observation of black hole quasi-normal modes with the underlying perturbation equations, with the goal of reconstructing the potential and the coupling functions appearing in the latter. The fundamental quasi-normal mode frequency and its first two overtones are modeled through a second order expansion in the deviations from general relativity, which are assumed to be small but otherwise generic. By using a principal component analysis, we demonstrate that percent-level measurements of the fundamental mode and its overtones can be used to constrain the effective potential of tensor perturbations and the coupling functions between tensor modes and ones of different helicity, without assuming an underlying theory. We also apply our theory-agnostic reconstruction framework to analyze simulated quasi-normal mode data produced within specific theories extending general relativity, such as Chern-Simons gravity.

A new model for thermally induced redistributions of free carriers in centrosymmetric flexoelectric semiconductor beams

A new model is developed for thermally induced redistributions of free carriers in flexoelectric semiconductor beams using a thermoflexotronic theory. This theory, which accounts for flexotronic, strain gradient and temperature effects, is first proposed using the theory of flexoelectric semiconductors, thermoelasticity and strain gradient elasticity. The new beam model is then formulated by applying the thermoflexotronic theory and Bernoulli-Euler kinematic relations, which simultaneously incorporates the flexoelectric, temperature and semiconducting effects and provides all the governing equations and boundary conditions, unlike existing models. To illustrate the new model, the concentration perturbation in a simply supported beam induced by temperature changes in the transverse and axial directions respectively is analytically determined. For the former, the deformed shape and redistribution of free carriers in the beam are analytically obtained and graphically displayed, and the charge accumulation formula capturing the thermoflexotronic effect is analytically derived. For the latter, the axial displacement, electric potential and concentration perturbation of free carriers are analytically determined and graphically illustrated. It reveals that the distribution of the electric potential and redistribution of free carriers can be tailored by controlling the mode and amplitude of the prescribed temperature change.

2D distributions of potential and density mean-values and oscillations in the ECRH and NBI plasmas at the TJ-II stellarator

2D plasma potential ϕ distribution was measured in the electron cyclotron resonance heating (ECRH) and neutral beam injection (NBI) plasmas of the TJ-II stellarator with the heavy ion beam probe for the whole radial range and wide area of the poloidal angle, and supported by Langmuir probe data at the edge. The whole operation domain for the on-axis ECRH was explored ( = 0.45–0.8 ×1019 m−3, P EC = 220–470 kW), in addition, NBI plasmas with = 0.9–1.3 × 1019 m−3 and P NBI = 510 kW were studied. In ECRH plasmas the density ramp-up is accompanied by the evolution of the potential from the bell-like to the Mexican hat profile, while the density profiles were flat or slightly hollow. The potential has the positive peak at the centre, and LFS-HFS (low field—high field sides) and up-down symmetry. Equipotential lines are consistent with vacuum magnetic flux surfaces. In the high-density NBI scenario, the ϕ profile was fully negative with a minimum up to −300 V at the centre, while at low-density ECRH plasma, ϕ has a maximum up to +0.9 kV at the centre. Fluctuations of potential and density are stronger in low-density scenarios and not poloidally symmetric. At the mid-radius (area of the maximum density), root mean square (RMS) of fluctuations were up to ϕ ∼ 15 V at LFS vs ∼20 V at HFS; RMS n e ∼ 2% at LFS vs ∼3% at HFS. In the NBI plasmas with the density rise, the asymmetry decreases and finally vanishing at = 1.2 × 1019 m−3. 2D distribution of the NBI-induced Alfvén eigenmodes (AEs) shows asymmetric ballooning structure: contrary to broadband turbulence, AE-associated potential perturbation dominates in the LFS with a factor up to 1.7 respect to the HFS. The electrostatic mode, excited in ECRH plasmas by suprathermal electrons also shows asymmetric structures: density perturbation dominates in the top-bottom direction compared to LFS-HFS direction.

The primitive model in classical density functional theory: beyond the standard mean-field approximation

The primitive model describes ions by point charges with an additional hard-core interaction. In classical density-functional theory (DFT) the mean-field electrostatic contribution can be obtained from the first order of a functional perturbation of the pair potential for an uncharged reference system of hard spheres. This mean-field electrostatic term particularly contributes at particle separations that are forbidden due to hard-core overlap. In this work we modify the mean-field contribution such that the pair potential is constant for distances smaller than the contact distance of the ions. We motivate our modification by the underlying splitting of the potential, which is similar to the splitting of the Weeks–Chandler–Andersen potential and leads to higher-order terms in the respective expansion of the functional around the reference system. The resulting formalism involves weighted densities similar to the ones found in fundamental measure theory. To test our modifications, we analyze and compare density profiles, direct and total correlation functions, and the thermodynamic consistency of the functional via a widely established sum rule and the virial pressure formula for our modified functional, for established functionals, and for data from computer simulations. We found that our modifications clearly show improvements compared to the standard mean-field functional, especially when predicting layering effects and direct correlation functions in high concentration scenarios; for the latter we also find improved consistency when calculated via different thermodynamic routes. In conclusion, we demonstrate how modifications toward higher order corrections beyond mean-field functionals can be made and how they perform, by this providing a basis for systematic future improvements in classical DFT for the description of electrostatic interactions.

Mitochondrial complex IV defects induce metabolic and signaling perturbations that expose potential vulnerabilities in HCT116 cells.

Mutations in genes encoding cytochrome c oxidase (mitochondrial complex IV) subunits and assembly factors [e.g., synthesis of cytochrome c oxidase 2 (SCO2)] are linked to severe metabolic syndromes. Notwithstanding that SCO2 is under transcriptional control of tumor suppressor p53, the role of mitochondrial complex IV dysfunction in cancer metabolism remains obscure. Herein, we demonstrate that the loss of SCO2 in HCT116 colorectal cancer cells leads to significant metabolic and signaling perturbations. Specifically, abrogation of SCO2 increased NAD+ regenerating reactions and decreased glucose oxidation through citric acid cycle while enhancing pyruvate carboxylation. This was accompanied by a reduction in amino acid levels and the accumulation of lipid droplets. In addition, SCO2 loss resulted in hyperactivation of the insulin‐like growth factor 1 receptor (IGF1R)/AKT axis with paradoxical downregulation of mTOR signaling, which was accompanied by increased AMP‐activated kinase activity. Accordingly, abrogation of SCO2 expression appears to increase the sensitivity of cells to IGF1R and AKT, but not mTOR inhibitors. Finally, the loss of SCO2 was associated with reduced proliferation and enhanced migration of HCT116 cells. Collectively, herein we describe potential adaptive signaling and metabolic perturbations triggered by mitochondrial complex IV dysfunction.

Ketogenic Diet Consumption Inhibited Mitochondrial One-Carbon Metabolism.

Given the popularity of ketogenic diets, their potential long-term consequences deserve to be more carefully monitored. Mitochondrially derived formate has a critical role in mammalian one-carbon (1C) metabolism and development. The glycine cleavage system (GCS) accounts for another substantial source for mitochondrially derived 1C units. Objective: We investigated how the ketogenic state modulates mitochondrial formate generation and partitioning of 1C metabolic fluxes. Design: HepG2 cells treated with physiological doses (1 mM and 10 mM) of β-hydroxybutyrate (βHB) were utilized as the in vitro ketogenic model. Eight-week male C57BL/6JNarl mice received either a medium-chain fatty-acid-enriched ketogenic diet (MCT-KD) or a control diet AIN 93M for 8 weeks. Stable isotopic labeling experiments were conducted. Results and Conclusions: MCT-KD is effective in weight and fat loss. Deoxythymidine (dTMP) synthesis from the mitochondrial GCS-derived formate was significantly suppressed by βHB and consumption of MCT-KD. Consistently, plasma formate concentrations, as well as the metabolic fluxes from serine and glycine, were suppressed by MCT-KD. MCT-KD also decreased the fractional contribution of mitochondrially derived formate in methionine synthesis from serine. With the worldwide application, people and medical professionals should be more aware of the potential metabolic perturbations when practicing a long-term ketogenic diet.

On the nonlinear perturbations of self-adjoint operators

Abstract Using elements of the theory of linear operators in Hilbert spaces and monotonicity tools we obtain the existence and uniqueness results for a wide class of nonlinear problems driven by the equation T x = N ( x ) Tx=N\left(x) , where T T is a self-adjoint operator in a real Hilbert space ℋ {\mathcal{ {\mathcal H} }} and N N is a nonlinear perturbation. Both potential and nonpotential perturbations are considered. This approach is an extension of the results known for elliptic operators.

A Pseudomonas aeruginosa PQS quorum-sensing system inhibitor with anti-staphylococcal activity sensitizes polymicrobial biofilms to tobramycin

SummaryAs single- and mixed-species biofilms, Staphylococcus aureus and Pseudomonas aeruginosa cause difficult-to-eradicate chronic infections. In P. aeruginosa, pseudomonas quinolone (PQS)-dependent quorum sensing regulates virulence and biofilm development that can be attenuated via antagonists targeting the transcriptional regulator PqsR (MvfR). Here, we exploited a quinazolinone (QZN) library including PqsR agonists and antagonists for their activity against S. aureus alone, when co-cultured with P. aeruginosa, and in combination with the aminoglycoside tobramycin. The PqsR inhibitor, QZN 34 killed planktonic Gram-positives but not Gram-negatives. QZN 34 prevented S. aureus biofilm formation, severely damaged established S. aureus biofilms, and perturbed P. aeruginosa biofilm development. Although P. aeruginosa protected S. aureus from tobramycin in mixed biofilms, the combination of aminoglycoside antibiotic with QZN 34 eradicated the mixed-species biofilm. The mechanism of action of QZN 34 toward Gram-positive bacteria is shown to involve membrane perturbation and dissipation of transmembrane potential.

Hydrodynamic Relaxation in a Strongly Interacting Fermi Gas.

We measure the free decay of a spatially periodic density profile in a normal fluid strongly interacting Fermi gas, which is confined in a box potential. This spatial profile is initially created in thermal equilibrium by a perturbing potential. After the perturbation is abruptly extinguished, the dominant spatial Fourier component exhibits an exponentially decaying (thermally diffusive) mode and a decaying oscillatory (first sound) mode, enabling independent measurement of the thermal conductivity and the shear viscosity directly from the time-dependent evolution.

Cosmological perturbation theory in f(Q,T) gravity

We developed the cosmological linear theory of perturbations for f(Q,T) gravity, which is an extension of symmetric teleparallel gravity, with Q the non-metricity and T the trace of the stress-energy tensor. By considering an ansatz of f(Q,T) = f 1(Q)+f 2(T), which has been broadly studied in the literature and the coincident gauge where the connection vanishes, we got equations consistent with f(Q) gravity when fT = 0. In the case of the tensor perturbations, the propagation of gravitational waves was found to be identical to f(Q), as expected. For scalar perturbations, outside the limit fT = 0, we got that the coupling between Q and T in the Lagrangian produces a coupling between the perturbation of the density and the pressure. This coupling is preserved when considering the weak coupling limit between Q and T. On the other hand, in the strong coupling limit with a generic function of the form f 2(T) = αT + β T 2, the perturbative equations are heavily driven by the f 2(T) derivatives when β ≠ 0. However, when β = 0, the perturbative equations are identical to the weak coupling limit even though this case is a non-minimally coupling one. The presence of T in the Lagrangian breaks the equation of the conservation of energy, which in turn breaks the standard ρ' + 3\U0001d4d7 (ρ+p) = 0 relation. We also derived a coupled system of differential equations between δ, the density contrast and v in the \U0001d4d7 ≪ k limit and with negligible time derivative of the scalar perturbation potentials, which will be useful in future studies to see whether this class of theories constitute a good alternative to dark matter. These results might also enable to test f(Q,T) gravity with CMB and standard siren data that will help to determine if these models can reduce the Hubble constant tension and if they can constitute an alternative to the ΛCDM model.

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 reac-tive 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 as-trocyte 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 evi-dence for the involvement of FynT in neurodegenerative dementias, likely via effects on tauopathy and neuroinflammation.

The effects of changes in diversity on phytoplankton community metabolism

ABSTRACT Changes in composition of phytoplankton communities cause drastic changes in functioning of aquatic ecosystems. In this study, we hypothesized that the shifts in composition of the phytoplankton community of Lake Kinneret induced notable shifts in the relationship between primary production and decomposition of organic matter in the lake ecosystem. To test this, we created an approach based on a statistical analysis of long-term dynamics of diversity indices and their relationships with potential perturbations: changes in lake water level, nutrient loads, and annual average epilimnetic temperature. Biodiversity of the algal community was estimated using Simpson’s Diversity Index and community-weighted mean trait value (functional diversity index). Specific community respiration and photosynthesis assimilation number were considered as the functional traits characterizing the role of phytoplankton in cycling organic matter. The observed temporal trends in the diversity indices provided estimates of the shift in the biotic community from large, relatively faster aerobic decomposing and slower photosynthesizing producers towards slower aerobic decomposing and faster photosynthesizing producers. These trends were confirmed by the results of direct determination of community respiration and (indirectly) by the reduced microbial activity in the epilimnetic waters of the lake.

Overstability of plasma slow electron holes

Sufficient conditions are found on the ion velocity distribution $f_i$ and potential amplitude for stability of steady electron holes moving at slow speeds, coinciding with the bulk of $f_i$ . Fully establishing stability requires calculation of the ion response to shift potential perturbations having an entire range of oscillatory frequencies, because under some conditions real frequencies intermediate between the ion and electron responses prove to be unstable even when the extremes are not. The mechanism of this overstability is explained and calculated in detail. Electron holes of peak potential $\psi$ less than approximately 0.01 times the background temperature ( $\psi \lesssim 0.01T_0/e$ ) avoid the oscillatory instability entirely. For them, the necessary condition that there be a local minimum in $f_i$ in which the hole resides is also sufficient, unless the magnetic field $B$ is low enough to permit the transverse instability having finite wavenumber $k$ perpendicular to $B$ .

Perturbed distribution functions with accurate action estimates for the Galactic disc

In the Gaia era, understanding the effects of the perturbations of the Galactic disc is of major importance in the context of dynamical modelling. In this theoretical paper we extend previous work in which, making use of the epicyclic approximation, the linearized Boltzmann equation had been used to explicitly compute, away from resonances, the perturbed distribution function of a Galactic thin-disc population in the presence of a non-axisymmetric perturbation of constant amplitude. Here we improve this theoretical framework in two distinct ways in the new code that we present. First, we use better estimates for the action-angle variables away from quasi-circular orbits, computed from the AGAMA software, and we present an efficient routine to numerically re-express any perturbing potential in these coordinates with a typical accuracy at the per cent level. The use of more accurate action estimates allows us to identify resonances such as the outer 1:1 bar resonance at higher azimuthal velocities than the outer Lindblad resonance, and to extend our previous theoretical results well above the Galactic plane, where we explicitly show how they differ from the epicyclic approximation. In particular, the displacement of resonances in velocity space as a function of height can in principle constrain the 3D structure of the Galactic potential. Second, we allow the perturbation to be time dependent, thereby allowing us to model the effect of transient spiral arms or a growing bar. The theoretical framework and tools presented here will be useful for a thorough analytical dynamical modelling of the complex velocity distribution of disc stars as measured by past and upcoming Gaia data releases.

Fluorinated graphene nanomaterial causes potential mechanical perturbations to a biomembrane.

Fluorinated graphene (F-GRA) has attracted great interest in biomedical applications. In this context, the direct interaction between F-GRA and various biomolecules is a vital process guiding the bio-function of this nanomaterial. Nevertheless, information regarding the interaction of F-GRA with biomolecules is scarce, particularly at the molecular level. In this study, using an in silico approach, we investigate the adsorption of F-GRA to a phospholipid bilayer to evaluate the potential effect of the nanomaterial to a biomembrane and its mechanism. Our results indicate that F-GRA can either slightly insert into the membrane or parallelly adhere on the membrane surface, different from the complete insertion of graphene. Detailed analysis confirms that the electrostatic forces dominantly mediate the adsorption process. F-GRA in its parallel binding pattern causes a partial enlargement in the membrane thickness via the disruption of the lipids' order parameters, indicating a mild mechanical influence to the membrane structure. Although the potential mechanical perturbation of F-GRA to membrane is detected, this impact is much weaker than graphene. These findings suggest the potentially weak physical perturbations of F-GRA to the cellular membrane, which may establish the basis for the future biomedical applications of this material after proper surface coating.