Single Peak Behavior Research Articles

Two for tau: Automated model discovery reveals two-stage tau aggregation dynamics in Alzheimer’s disease

Alzheimer’s disease is a neurodegenerative disorder characterized by the presence of amyloid-β plaques and the accumulation of misfolded tau proteins and neurofibrillary tangles in the brain. A thorough understanding of the local accumulation of tau is critical to develop effective therapeutic strategies. Tau pathology has traditionally been described using reaction–diffusion models, which succeed in capturing the global spread, but fail to accurately describe the local aggregation dynamics. Current mathematical models enforce a single-peak behavior in tau aggregation, which does not align well with clinical observations. Here we identify a more accurate description of tau aggregation that reflects the complex patterns observed in patients. We propose an innovative approach that uses constitutive neural networks to autonomously discover bell-shaped aggregation functions with multiple peaks from clinical positron emission tomography (PET) data of misfolded tau protein. Our method reveals previously overlooked two-stage aggregation dynamics by uncovering a two-term ordinary differential equation that links the local accumulation rate to the tau concentration. When trained on data from amyloid-β positive and negative subjects, the neural network clearly distinguishes between both groups and uncovers a more subtle relationship between amyloid-β and tau than previously postulated. In line with the amyloid-tau dual pathway hypothesis, our results show that the presence of toxic amyloid-β influences the accumulation of tau, particularly in the earlier disease stages. We expect that our approach to autonomously discover the accumulation dynamics of pathological proteins will improve simulations of tau dynamics in Alzheimer’s disease and provide new insights into disease progression.Significance StatementIn Alzheimer’s disease, understanding the local dynamics of tau protein aggregation is crucial for developing effective treatments. Traditional models for tau protein dynamics use reaction-diffusion models that fail to accurately capture these local patterns. Our study introduces a novel approach that leverages constitutive neural networks to autonomously discover the complex, multi-peak aggregation dynamics from clinical PET data. This method reveals a previously overlooked two-stage tau accumulation process and a nuanced relationship between amyloid-β and tau. By distinguishing between amyloid-β positive and negative subjects, our model supports the amyloid-tau dual pathway hypothesis and offers novel insights into tau protein aggregation that have the potent to advance our understanding of Alzheimer’s disease progression.

Improved light-cone harmonic oscillator model for the ϕ -meson longitudinal leading-twist light-cone distribution amplitude and its effects to Ds+→ϕℓ+νℓ

In the present paper, we study the properties of ϕ-meson longitudinal leading-twist light-cone distribution amplitude ϕ2;ϕ∥(x,μ) by starting from a light-cone harmonic oscillator model for its wave function. To fix the input parameters, we derive the first ten order ξ moments of ϕ2;ϕ∥(x,μ) by using the QCD sum rules approach under the background field theory. The curves of ϕ2;ϕ∥(x,μ=2 GeV) tend to be a single-peak behavior, which is consistent with the latest lattice QCD result. To show how the twist-3 light-cone distribution amplitudes (LCDAs) affect the results, we consider two scenarios for the ϕ-meson chiral twist-3 LCDAs ϕ3;ϕ⊥(x) and ψ3;ϕ⊥(x), i.e., the ones using the Wandzura-Wilczek approximation with ϕ2;ϕ∥(x,μ) (S1) and the ones using self-consistent conformal expansion with second-order Gegenbauer moments a2;ϕ2 in this work (S2). As an application, we derive the Ds+→ϕ transition form factors (TFFs) by using the QCD light-cone sum rules. The TFFs at large recoil point for those two scenarios are given separately. As for the two TFF ratios γV and γ2, we obtain γV(S1)=1.755−0.005+0.008, γ2(S1)=0.852−0.133+0.135, γV(S2)=1.723−0.021+0.023, and γ2(S2)=0.785−0.104+0.100. After extrapolating those TFFs to the physically allowable region, we then obtain the transverse, longitudinal, and total decay widths for semileptonic decay Ds+→ϕℓ+νℓ. Then the branching fractions are B(S1)(Ds+→ϕe+νe)=(2.347−0.191+0.342)×10−3, B(S1)(Ds+→ϕμ+νμ)=(2.330−0.190+0.341)×10−3, B(S2)(Ds+→ϕe+νe)=(2.367−0.132+0.256)×10−3, and B(S2)(Ds+→ϕμ+νμ)=(2.349−0.132+0.255)×10−3, which show good agreement with the data issued by the BESIII, CLEO, and Collaborations. We finally calculate Ds+→ϕℓ+νℓ polarization and asymmetry parameters, which can be measured and tested in future experiments. Published by the American Physical Society 2024

Fluid resonance in narrow gaps formed by three-box system with sharp and round edge profiles under irregular wave actions

Fluid resonance within narrow gaps in multiple-box systems with sharp and round edge profiles under irregular wave actions are investigated by using a viscous fluid flow solver based on OpenFOAM® package. In difference to the two-peak behavior under regular wave actions, the variation of free surface amplitudes in narrow gaps with incident spectral peak frequencies show the single-peak behavior, including the sharp and round edge profiles. Spectral analysis indicates that the wave spectrums of fluid oscillations in narrow gaps mainly around the first- and/or second-order resonant frequencies. The second-order fluid resonance is easier to be aroused for round edge profiles than that for sharp edge profiles. Furthermore, the statistical and histogram results indicate the significant periods are always around the resonant frequencies; while the corresponding standard deviations approach to cover the region between two resonant frequencies. The above results confirm that the wave responses in narrow gaps mainly oscillate with two resonant frequencies under irregular wave actions.

Characterization of hot workability of a Cu containing high strength low alloy steel using processing map

Hot workability of an experimental Cu containing martensitic high strength low alloy (HSLA) steel was characterized by conducting isothermal hot compression tests at different temperatures (900–1100 °C) and strain rates (0.0003–1 s−1). Flow curves exhibits predominantly single peak behaviour at temperatures for a strain rate > 0.01 s−1. At temperature > 950 °C and for low strain rates of 0.0003 and/or 0.001 s−1, multiple peaks characterised by oscillations in flow stress was observed. The strain rate sensitivity (m), temperature sensitivity (S) of the material was calculated and the processing map was developed to identify optimum condition for thermo-mechanical processing. The material exhibits three suitable processing windows in temperature – strain rate space viz., (1) 1050–1100 °C; 0.1–0.01 s−1 (2) 980–1020 °C; 0.1–1 s−1 and (3) 980–1020 °C; 0.001–0.0003 s−1. The microstructure of the material deformed under all the above mentioned processing conditions exhibited defect free equiaxed dynamically recrystallized grains with an average grain size of 30–40 μm. Any or combination of these processing conditions can be used by the industry for designing suitable forging process (roughing, finishing etc.) based on the infrastructure available. Further, using Avrami approach, the effect of strain, strain rate and temperature on the kinetics of dynamic recrystallization (DRX) was also evaluated. The results obtained are presented and discussed.

Magnetoimpedance effect in electrodeposited NiFe/Cu wire using trisodium citrate additive in plating bath

Magnetoimpedance (MI) and magnetic properties of the electroplated NiFe/Cu thin films with a steadily rising concentration of trisodium citrate (TSC) additive in the plating bath is systematically examined in a wide frequency range of 10 kHz–8 MHz. The addition of TSC to the plating bath reduces the crystalline size and coercivity of the NiFe film, resulting in increased magnetic softness and MI ratio. The grain refining action of TSC additive is responsible for the random distribution of magnetic anisotropy axis in individual tiny crystallite which enhance circumferential permeability of deposited film and its MI ratio. The optimum concentration of TSC additive is found to be 40 g/l and sample electrodeposited at that TSC concentration boosts the MI ratio to 113% as compared to 28% when no TSC is used. When the film is deposited without any additive, a typical double peak behavior of the MI response curve is exhibited at higher frequency. This feature is eradicated with slightest inclusion of TSC additive in the electrodeposition bath which is an indication that inclusion of trisodium citrate weakens the circumferential anisotropy in plated film. Based on the analytical formulation of circumferential permeability the results of MI measurements are mapped with the theoretical framework, and the circumferential permeability of the NiFe magnetic film is reconstructed by curve fitting. Through the investigation of the fitting parameters, it is found that the addition of TSC to the bath completely annihilates the circumferential anisotropy found in as deposited permalloy film which is responsible for the transition from double to single peak behavior of MI response at higher frequencies.

Carbon-coated iron nanopowder as a sintering aid for water-atomized iron powder

The paper examines the influence of carbon coating on iron nanopowder used as a sintering aid for water-atomized iron powder. Iron nanopowder without such a coating was used as a reference sintering aid to isolate the influence of the carbon coating. Both nanopowder variants were characterised using XPS and HRTEM. The results showed a core–shell structure for both variants. The iron nanopowder is covered by a 3–4 nm thick iron oxide layer, while the carbon-coated iron nanopowder is encapsulated with several nanometric carbon layers. Thermogravimetry conducted in a pure hydrogen environment shows a multipeak behaviour for the carbon-coated iron nanopowder, while a single peak behaviour is observed for the iron nanopowder. Two types of micro/nanobimodal powders were obtained by mixing the nanopowder with water-atomized iron powder. Improved linear shrinkage was observed during sintering when the carbon-coated iron nanopowder was added. This can be explained by the reduction in surface diffusion in the nanopowder caused by the carbon coating, which allows the nanopowder to sinter at higher temperatures and improves densification. Carbon and oxygen analysis, density measurements, optical microscopy and JMatPro calculations were also performed.

Effect of dopants on magnetic and magnetoimpedance properties of rapidly solidified FeCoBM (M = Al, Cu and Si) ribbons

In this work magnetic properties, magnetoimpedance (MI) and field sensitivity (η) of rapidly solidified (Fe0.7Co0.3)80B19M1 (M = B, Al, Si & Cu) ribbons have been investigated in the frequency range 0.5 – 13 MHz. Present study shows replacement of boron (B) by a nonmagnetic element (Al, Si or Cu) can alter the thermal stability, soft magnetic and magnetoimpedance properties of the (Fe0.7Co0.3)80B20 ribbons. It is found that saturation magnetization reaches the largest value for Cu-containing sample and the smallest value for Al-containing sample. The MI studies show maximum MI ratios 30% at 5 MHz, 23% at 7 MHz, 26% at 3 MHz and 39% at 4 MHz for M = B, Al, Si & Cu respectively. Variation of MI with external magnetic field shows single peak behavior of Al-content ribbon over the entire frequency range, whereas for all other samples single peak converted to double peak at higher frequency, which indicates existence of stronger longitudinal magnetic anisotropy in Al-containing ribbon. The MI variation with magnetization, M and damping constant, α is also validated through numerical simulations using standard electrodynamics models. Present study reveals that the variations of MI response are associated with formation of soft magnetic phase and development of anisotropy with replacement of B by an additional element.

Exchange bias training effect in IrMn-layer/ferromagnetic-ribbon heterostructures probed with magnetoimpedance

The exchange-bias training effect in IrMn-layer/ferromagnetic-ribbon heterostructure is studied by performing magnetoimpedance (MI) measurements. Asymmetric, hysteretic and single peak behavior of the MI response and a shift in the MI peak to zero fields accompanied by 52% increase in MI has been detected as the signature of the exchange bias (EB) and training effect (TE), respectively. Also, during the consecutive filed sweep of MI response, both EB field and the degree of asymmetry of MI decrease that is another reason for existence of TE in our sample. The analysis of the magneto-optical Kerr effect (MOKE) and MI behavior establish that Hoffmann s model (Phys. Rev. Lett. 93, 097203 (2004)) is a good description of our experimental data, due to the existence of a strong single cycle TE in our IrMn-layer/ferromagnetic-ribbon system.

Modeling the flow behavior of AISI 321 austenitic stainless steel using a simple combined phenomenological method

In the present study, the hot flow curves of AISI 321 austenitic stainless steel were obtained by performing compression tests in the temperature range of 1050–1200°C and strain rates in the range of 0.01–1 s−1. All the flow curves showed single peak behavior which indicates the occurrence of dynamic recrystallization. The combination of the Cingara and Ebrahimi methods was used for mathematical modeling of the obtained flow curves. The Cingara phenomenological method was used to predict the flow stress value at the strains lower than the peak strain and Ebrahimi method was employed for higher strains. Results of the study showed that this simple combined phenomenological method can be used for precise prediction of the flow stress of AISI 321 steel during the occurrence of dynamic recrystallization.

Electron Backscattered Diffraction Study of Microstructural Evolution During Isothermal Deformation of High-N Mn18Cr18 Alloy

In order to understand the dynamic recrystallization (DRX) mechanism of Mn18Cr18N austenitic stainless steel during hot deformation, the investigation of microstructure evolution is significant. Isothermal compression tests were conducted on a Gleeble-3500 thermomechanical simulator in the temperature range of 950 °C to 1150 °C and strain rate range between 0.001 and 1 s−1. Optical microscopy (OM) and electron backscattered diffraction (EBSD) were employed to study the resultant microstructures. More grain boundary information of hot-deformed specimens was provided by EBSD. It was found that the fraction of low-angle grain boundaries (LAGBs) increases with the decrease of deformation temperature or the increase of strain rate and can be expressed as a function of the Zener–Hollomon parameter. DRX easily occurs at the high deformation temperature and low strain rate. From the flow stress curves, the occurrence of single peak behavior and multiple transient steady-state (MTSS) behavior illustrated the existence of different DRX mechanisms. The EBSD analysis indicated that both continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) existed during hot deformation. For the low fraction of 10 to 15 deg misorientation, CDRX is the minor DRX mechanism while DDRX is the major DRX mechanism for the studied steel.

Formation of asymmetric giant magnetoimpedance in amorphous ferromagnetic wires by micro magnets

Asymmetric giant magnetoimpedance (AGMI) was created using two micro magnets placed at 1 cm away from the ends of amorphous ferromagnetic non-magnetostrictive (Fe0.06Co0.94)72.5Si12.5B15 wire. At low frequencies, single-peak behaviour of the AGMI was observed, and the AGMI curves exhibited two-peak behaviour within high-frequency range. The asymmetry in the magnetization curves of amorphous wire with two micro magnets having the same orientation was found, the maximum of the GMI ratio at positive field region decreases from 515% to 356%, and the peak value at negative field region decreases from 513% to 261% at 1 MHz driving current frequency. A linear change in the AGMI curves was obtained, which could be of importance for magnetic sensor applications. Experimental results were qualitatively explained in the framework of a model for the AGMI response in amorphous wire taking into account effects of bias field induced by micro magnets.

Influence of particle size on crystallization and relaxation behavior of Ge20Se4Te76 glass for infrared optics

Influence of particle size on relaxation and crystallization behavior of the Ge20Se4Te76 chalcogenide glass was studied by differential scanning calorimetry (DSC). The structural relaxation kinetics was described by means of the Tool–Narayaswamy–Moynihan (TNM) model; it was found that the structural relaxation processes are not influenced by powder particle size or by the mechanically induced defects and heterogeneities originating from the grinding procedures — the evaluated TNM parameters were constant for all tested powders. On the other hand, the crystallization kinetics of the Ge20Se4Te76 glass was found to be significantly influenced by the powder size. While the coarser powders exhibited a single-peak behavior corresponding to the nucleation-growth Johnson–Mehl–Avrami (JMA) kinetics, the crystallization of finest powders proceeded in two distinct steps. XRD analysis identified the two DSC signals as crystallization of hexagonal Te and rhombohedral GeTe, indicating that large amounts of mechanically induced defects accelerate the Te precipitation. Regarding the overall thermal characterization, the evaluated glass-stability criteria have shown that although the studied chalcogenide glass is a very good glass-former, its stability largely depends on the sample form.

B → ρ transition form factors and the ρ-meson transverse leading-twist distribution amplitude

The QCD light-cone sum rules (LCSR) provide an effective way for dealing with heavy-to-light transition form factors (TFFs), in which the non-perturbative dynamics are parameterized into the light-meson’s light-cone distribution amplitudes (LCDAs). By taking the chiral correlator as the starting point, we derive new LCSRs for TFFs up to twist-4 accuracy. In those LCSRs, the twist-2 transverse LCDA provides dominant contribution, while the twist-3 and twist-4 contributions are δ2-suppressed (). Thus, they provide good platforms for testing behavior. For the purpose, we suggest a WH-model for , in which a single parameter dominantly controls its longitudinal distribution. When setting , varies from the single-peak behavior to the double-humped behavior. We present a detailed comparison of the LCSR estimation for TFFs with those predicted by pQCD and lattice QCD calculations. The TFFs become smaller with the increment of and a larger is not allowed by lattice QCD predictions. By using the extrapolated TFFs, we further predict the Cabibbo–Kobayashi–Maskawa (CKM)-matrix element with the help of two semi-leptonic decays. The predicted increases with the increment of , i.e. we have for and for . If treating the BABAR prediction on as a criteria, we observe that should be within the region of [−0.20, +0.10], which indicates that the ρ-meson LCDA prefers a single-peak behavior rather than a double-humped behavior.

Magnetoimpedance Effects in Electrodeposited NiFe Nanowire Array

In this work, NiFe nanowires were grown in highly ordered porous anodic alumina oxide templates by dc electrodeposition at a pH value of 2.6. Scanning electron microscopy showed that wires have diameters of about 250 310 nm and length 25 30 μm. The energy dispersive X-ray analysis showed that the composition of the nanowires is Ni65Fe35. Electrical contacts were made on both sides of the nanowire array and their magnetoimpedance properties were investigated. All the magnetoimpedance curves showed single peak behavior due to the high shape anisotropy. The maximum magnetoimpedance change at the 79 MHz driving current frequency was ≈ 1.45%.

Magnetoimpedance effects in a CoNiFe nanowire array

This report describes the growth of CoNiFe nanowires into highly ordered porous anodic alumina oxide (AAO) templates by DC electrodeposition at a pH value of 2.6. Scanning electron microscopy (SEM) observations revealed that the wires have diameters of approximately 270–290nm and a length of 25μm. The energy dispersive X-ray (EDX) analysis indicated that the composition of the nanowires is Co12Ni64Fe24. Electrical contacts were created on both sides of the nanowire array, and their magnetoimpedance (MI) properties were investigated. The impedance value was initially 1.2ohm at low frequency and increased to approximately 1000ohm for a 33-MHz driving current frequency under no applied magnetic field. All the MI curves exhibited single peak behaviour due to the high shape anisotropy. The maximum MI change at the 33-MHz driving current frequency was 2.72%. The maximum resistance change was 5.4% at 33MHz.

EBSD study of a hot deformed austenitic stainless steel

The microstructural evolution of a 304 H austenitic stainless steel subjected to hot compression was studied by the electron backscattered diffraction (EBSD) technique. Detailed data about the boundaries, coincidence site lattice (CSL) relationships and grain size were acquired from the orientation imaging microscopy (OIM) maps. It was found that twins play an important role in the nucleation and growth of dynamic recrystallization (DRX) during hot deformation. Moreover, the conventional discontinuous DRX (DDRX) was found to be in charge of grain refinement reached under the testing conditions studied. Furthermore, the recrystallized fraction (X) was determined from the grain average misorientation (GAM) distribution based on the threshold value of 1.55°. The frequency of high angle boundaries showed a direct relationship with X. A time exponent of 1.11 was determined from Avrami analysis, which was related to the observed single-peak behavior in the stress–strain flow curves.

Ca2+ Dynamics in Apoptosis: Real-Time Data and Mathematical Modeling

The time-dependent behavior of Ca2+ in statistically significant number of live apoptotic cells in the same population is measured for the first time (along with behavior of other apoptosis markers phosphatidyl serine and caspase-3/7). The Ca2+ dynamics shows predominantly a single peak behavior at the early stage but also multiple peak behavior in a small fraction of the cells. These data enable for the first time mathematical modeling of the Ca2+ dynamics in apoptosis. Towards this end we propose a physical model motivated by the role of cytochrome c binding to the IP3R in the endoplasmic reticulum membrane thereby enhancing the probability of Ca2+ release as demonstrated by Boehing et al. (Nat Cell Biol, 2003, 5, 1051). The IP3R opening probability under the influence of cytochrome c is modeled as a modification of the probability in its absence in non-apoptotic cells (Mak et al. PNAS, 1998, 95, 15821). Coupled ordinary differential equations for the dynamics of Ca2+ and cytochrome c are formulated and solved for the behavior under nonapoptotic and apoptotic conditions. The results are qualitatively consistent with the overall observed dynamics of Ca2+, including the appearance of multiple peak behavior for certain ranges of the parameter space. The detailed analysis of the model indicates that the binding of cytochrome c to IP3R is the main source of cytosolic Ca2+ elevation in apoptosis while the active pumps on the plasma membrane provide the sink for the elevated cytosolic Ca2+ to return near the base level. The experimentally measured Ca2+ dynamics exhibit a significant cell-to-cell variation inherent to the stochastic nature of the underlying biochemical processes. Such variations are manifest in the modeling in terms of the uncertainites of the initial conditions in different cells upon the intiation of the apoptotic stress.

Effect of tensile stress on magnetoimpedance properties of CoNiFe/Cu wire

A Co20.5Ni40.5Fe39 magnetic film was electrodeposited onto a copper wire 50 µm in diameter. The magnetoimpedance (MI) effect, (ΔZ/Z)H(%) = ((Z(H) − Zmax)/Zmax) × 100, was measured in the Co20.5Ni40.5Fe39/Cu composite wire under varying tensile stresses up to 30 MPa. The results showed that large MI and stress impedance (SI) effects can be observed in the Co20.5Ni40.5Fe39/Cu composite wire. The MI curve at zero tensile stress shows a small split peak in the low-field region. With increasing applied tensile stress, single-peak behaviour of the MI effect is observed. The magnitude of the MI and SI effects decreases with increasing tensile stress, σ. The peak values of (ΔZ/Z)H(%) for the sample decrease from 265% at σ = 0 to 39% at σ = 30 MPa at 40 kHz ac driving-current frequency. The impedance of a sample under the effect of 25 MPa tensile stress at 40 kHz ac driving-current frequency showed variations of about 146%. It was also found that the frequency value, f*, where the maximum MI effect was observed as a function of driving-current frequency, increases with increasing tensile stress.

Acoustic emission in the fcc-fct martensitic transition ofFe68.8Pd31.2

An experimental study of acoustic emission (AE) in a single crystal and in a polycrystalline sample of ${\text{Fe}}_{68.8}{\text{Pd}}_{31.2}$ is presented. The samples are studied in a temperature range that is known to include not only a martensitic transition (MT) but also premartensitic effects and strong lattice-parameter variations below the transition. AE activity is compared to calorimetric and magnetic-susceptibility measurements. AE has only been detected during the martensitic transition. The kinetics of the MT for the single crystal exhibits a series of reproducible peaks of activity. This structured activity is not observed for the polycrystal, which shows a single-peak behavior. Despite these differences the AE measurements reveal that the martensitic transitions in both samples start at the same temperature. Results are also compatible with a negligible hysteresis at the transition. The statistics of the amplitude, energy, and duration of AE signals is analyzed in detail and characterized by power-law exponents. For the single crystal the exponents are coincident for heating and cooling ramps and are independent of the rate. For the polycrystalline sample, the exponents are different for heating and cooling.

Influence of torsion and tensile stress on magnetoimpedance effect in Fe-rich amorphous microwires at high frequencies

In this work, we study the magnetoimpedance response under tensile and torsional stress of Fe 76B 13Si 11 glass-coated amorphous microwires (with the metallic nucleus diameter of 17 μm) prepared by Taylor–Ulitovski method. The impedance was evaluated using a Network Analyser in the frequency range of 10–500 MHz. In order to induce a helical magnetic anisotropy that modifies the magnetic domain structure and the magnetic response of the sample, the torsion stresses have been applied. The effect of such torsion on giant magnetoimpedance (GMI) has been studied in a Fe-rich amorphous microwire as a function of the driving current frequency. Unusual behaviour of the GMI with torsion has been observed up to 500 MHz: at this frequency, the change from double-peak to single-peak behaviour has been observed. It could be ascribed to changes on domain structures and surface anisotropy induced by applied torsion. For this frequency range, an abrupt decrease of the impedance with torsion has been observed. We have also studied the tensile-induced changes of GMI effect in a Fe-rich amorphous microwire. The GMI effect increases with applied tensile stress and with the frequency of AC current. Observed dependences could be attributed to the change of the overall magnetic anisotropy under applied torsion.