Fitting Parameters Research Articles

Fitness-based growth of directed networks with hierarchy

Abstract Growing attention has been brought to the fact that many real directed networks exhibit hierarchy and directionality as measured through techniques like Trophic Analysis and non-normality. We propose a simple growing network model where the probability of connecting to a node is defined by a preferential attachment mechanism based on degree and the difference in fitness between nodes. 
In particular, we show how mechanisms such as degree-based preferential attachment and node fitness interactions can lead to the emergence of the spectrum of hierarchy and directionality observed in real networks. In this work, we study various features of this model relating to network hierarchy, as measured by Trophic Analysis. This includes (I) how preferential attachment can lead to network hierarchy, (II) how scale-free degree distributions and network hierarchy can coexist, (III) the correlation between node fitness and trophic level, (IV) how the fitness parameters can predict trophic incoherence and how the trophic level difference distribution compares to the fitness difference distribution, (V) the relationship between trophic level and degree imbalance and the unique role of nodes at the ends of the fitness hierarchy and (VI) how fitness interactions and degree-based preferential attachment can interplay to generate networks of varying coherence and degree distribution. We also provide an example of the intuition this work enables in the analysis of a real historical network. This work provides insight into simple mechanisms which can give rise to hierarchy in directed networks and quantifies the usefulness and limitations of using Trophic Analysis as an analysis tool for real networks.

Neutrino halo profiles: HR-DEMNUni simulation analysis

Using the high-resolution HR-DEMNUni simulations, we computed neutrino profiles within virialized dark matter haloes. These new high-resolution simulations allowed us to revisit fitting formulas proposed in the literature and provided updated fitting parameters that extend to less massive haloes and lower neutrino masses than previously in the literature, in accordance with new cosmological limits. The trend we observe for low neutrino masses is that, for dark matter halo masses below ∼ 4 × 1014 h -1 M ⊙, the presence of the core becomes weaker and the profile over the whole radius is closer to a simple power law. We also characterised the neutrino density profile dependence on the solid angle within clustered structures: a forward-backward asymmetry larger than 10% was found when comparing the density profiles from neutrinos along the direction of motion of cold dark matter particles within the same halo. In addition, we looked for neutrino wakes around halo centres produced by the peculiar motion of the halo itself. Our results suggest that the wakes effect is present in haloes with masses greater than 3 × 1014 h -1 M ⊙ where a mean displacement of 0.06h -1Mpc was found.

Experimental investigation and statistical analysis of the microwave drying process on the physical properties of Y2O3–Al2O3–ZrO2 composite ceramic powder

Y2O3–Al2O3–ZrO2 composite ceramic powders are an important structural and functional material. The agglomeration problem in the ceramic powder drying process must be resolved to prepare high-quality ceramic powder, and choosing the right drying techniques can significantly lessen ceramic powder agglomeration. Y2O3–Al2O3–ZrO2 ceramic powder was dried using microwave drying. The drying kinetics of the powders were examined with their initial mass, moisture content, and microwave power. As microwave power, beginning moisture content, and initial mass rose, the average drying rate also increased, according to the experimental data. To better characterize the microwave drying process, the drying data were fitted and analyzed using four thin-layer drying kinetic models, namely Quadratic Model, Modified Page, Wang and Singh, and Two-term exponential. The outcomes demonstrate the good fitting effect of the Modified Page model and the compliance of the fitting parameters with the law. The samples before and after drying were characterized by Fourier transform infrared spectroscopy. Calculating the diffusion coefficient by Fick's second law shows that the effective diffusion coefficient of Y2O3–Al2O3–ZrO2 composite ceramic powder is 5.6 × 10−11 m2/s when the initial moisture content is 5%, the microwave heating power is 560 W, and the initial mass is 25 g. The activation energy for microwave drying of Y2O3–Al2O3–ZrO2 ceramic powders was calculated to be 22.83 W/g according to the Arrhenius formula. This paper aims to provide a theoretical basis and rich experimental data for the study of microwave drying of Y2O3–Al2O3–ZrO2 composite ceramic powder.

Health-Related Physical Fitness and Biochemical Parameters in Overweight Older People during Social Isolation Imposed by the COVID-19 Pandemic: A Longitudinal and Observational Study.

With COVID-19, evidence indicates that the elderly will have worse biochemical markers related to health in social isolation. The objective was to analyze the impacts on physical fitness and biochemical parameters of older adults' health during COVID-19 social isolation. Quantitative, longitudinal, and observational study was conducted between 2020, 2021, and 2022. Thirty-three older adults of both sexes were evaluated. A sociodemographic questionnaire, biomarkers, and health-related physical fitness were used. Significant differences were observed for the sum of maximum isometric right and left handgrip strength, with a reduction in 2022 (p = 0.009); getting up and walking (p < 0.001), reduction in 2021 and 2022 (p < 0.05); elbow flexion and extension (p = 0.004), reduction in 2021 (p = 0.006); and sitting and standing (p = 0.002), reduction in 2022 (p = 0.003) and peak oxygen consumption (p < 0.001), reduction in 2021 and 2022 (p < 0.05). Differences were observed in fasting blood glucose (p < 0.001), with increase in 2021 and 2022 (p < 0.05), triglycerides (p < 0.001), with increase in 2021 and 2022 (p < 0.05), triglyceride-glucose index (p < 0.001), with increase in 2021 and 2022 (p < 0.05), triglyceride-glucose index with waist circumference (p < 0.001), with increase in 2021 (p < 0.001); and triglyceride-glucose index with body mass index (p < 0.001), with increase in 2021 (p < 0.001). However, no differences were observed between anthropometric and body composition (p > 0.05). Conclusions: Older people had changes in biochemical and physical fitness parameters related to health during the social isolation of the COVID-19 pandemic.

Effect of Circuit Training and Interval Training on Health Related Physical Fitness of Physical Education Professional Students

Abstract: The purpose of this study was to know the effect of circuit training and interval training on health related physical fitness of physical education professional students. Ninety boys belonging to B.P.Ed class of Govt. College of physical Education, Bhubaneswar age ranging between 22 to 25 years acted as subjects and assigned to three groups (two experimental and one control group) with 30 students each. The two experimental groups were Circuit Training and Interval Training groups. Health related physical fitness parameters such as Abdominal Muscle Strength (Sit Up), Flexibility (Sit and Reach), Cardiovascular Endurance (1 Mile Run), and Body Fat % (Triceps and Sub-Scapular Skin fold) were measured before and after training. All the experimental Groups (Circuit training and Interval training) was administered with the selected exercises, thrice in a week for a duration of 8 weeks under direct supervision of the research scholars. The analysis of data revealed that the three experimental groups, showed significant gains in performance of health related physical fitness after administration of training for duration of 8 weeks. The control group did not show any significant increase in the performance

Total, Between-, and Within-Item Attribute Person Fit Analysis Using Mokken Scaling Techniques: An Exploratory Nonparametric Approach to Person Fit

The purpose of this study was to consider how researchers can incorporate item attributes into nonparametric person fit analysis for the purpose of providing additional insight into person fit beyond what is available using typical total-scale person fit approaches. Inspired by parametric person fit statistics that consider patterns of residuals at the total-scale, between-item-attribute, and within-item-attribute levels, we proposed simple adaptations to standard Mokken Scale Analysis (MSA) person fit analysis techniques to reflect these three levels of person fit analysis. We demonstrated the technique using a secondary analysis of survey data related to learning motivation and considered how the results may be interpreted in an affective assessment context. We used a simple exploratory simulation study to consider the techniques under a wider range of conditions. Overall, the results suggested that it is possible to incorporate item attributes into MSA person fit analysis at the total-scale, between-item-attribute, and within-item attribute levels, and that each set of analyses provides a unique perspective on person fit.

Association of Hand Grip Strength and Physical Fitness Parameters in Middle-Aged and Older Korean Men.

The purpose of this study was to assess whether hand grip strength (HGS) could be an effective indicator to estimate other physical fitness parameters in middle-aged and older men using large population data. Data for this study were obtained from the National Fitness Center operated by the Korea Institute of Sport Science (n = 429 572). The following were excluded from this study: women aged 44 years or younger (n = 238 257), repeated measurement data (n = 130 466), and errors or missing data (n = 6 497). The final sample included 54 352 participants (27 878 middle-aged and 26 474 older-aged). The highest overall physical fitness grade among participants was 5.6% (4.7%, middle-aged men; 6.6%, older men), the lowest was 52.1% (59.0%, middle-aged men, 43.9%, older men). HGS was positively correlated with flexibility (r = 0.183, P < .001), muscular endurance (r = 0.354, P < .001), and power (r = 0.463, P < .001) in middle-aged men. In older men, flexibility (r = 0.227, P < .001) and 30SCS (r = 0.385, P < .001) were positively correlated; Timed Up and Go (r = -0.405, P < .001) and F8W (r = -0.433, P < .001) were negatively correlated. All physical fitness parameters were significantly higher in participants with normal HGS than those with low HGS. Our finding suggests that HGS is a predictive method for physical fitness variables and a useful biomarker for global public health.

Study on the Effect of Silica–Manganese Slag Mixing on the Deterioration Resistance of Concrete under the Action of Salt Freezing

The use of silico-manganese slag as a substitute for cement in the preparation of concrete will not only reduce pollution in the atmosphere and on land due to solid waste but also reduce the cost of concrete. To explore this possibility, silico-manganese slag concrete was prepared by using silico-manganese slag as an auxiliary cementitious material instead of ordinary silicate cement. The mechanical properties of the silico-manganese slag concrete were investigated by means of slump and cubic compressive strength tests. The rates of mass loss and strength loss of silico-manganese slag concrete were tested after 25, 50, and 75 cycles. The effect of the silica–manganese slag admixture on the microfine structure and properties of concrete was also investigated using scanning electron microscopy (SEM). Finally, the damage to the silica–manganese slag concrete after numerous salt freezing cycles was predicted using the Weibull model. The maximum enhancement of slump and compressive strength by silica–manganese slag was 17.64% and 11.85%, respectively. The minimum loss of compressive strength after 75 cycles was 9.954%, which was 34.96% lower than that of the basic group. An analysis of the data showed that the optimal substitution rate of silica–manganese slag is 10%. It was observed by means of electron microscope scanning that the matrix structure was denser and had less connected pores and that the most complete hydration reaction occurred with a 10% replacement of silica–manganese slag, where an increase in the number of bladed tobermorite and flocculated C-S-H gels was observed to form a three-dimensional reticulated skeleton structure. We decided to use strength damage as a variable, and the two-parameter Weibull theory was chosen to model the damage. The final comparison of the fitted data with the measured data revealed that the model has a good fitting effect, with a fitting parameter above 0.916. This model can be applied in real-world projects and provides a favorable basis for the study of damage to silica–manganese slag concrete under the action of salt freezing.

Galactic dynamics in the presence of scalaron: a perspective from f(R) gravity

We consider f(R) modified gravity theory incorporating the chameleon mechanism to address galactic dynamics. By employing the metric formalism and utilizing a conformal transformation, we simplify the field equations and describe the extra degree of freedom f R via a scalar field (scalaron) with chameleonic behavior. A recently proposed f(R) model is analyzed to illustrate this behavior effectively. Subsequently, the rotational velocity equation including the scalaron’s contribution is derived for a test particle in a static, spherically symmetric spacetime. Then we generate rotation curves and fit them to observational data of thirty seven galaxies using two fitting parameters, M 0 and r c , the total mass and core radius of a galaxy respectively.

First joint X-ray solar microflare observations with NuSTAR and Solar Orbiter/STIX

Abstract We present the first joint spectral and imaging analysis of hard X-ray (HXR) emission from 3 microflares observed by the Nuclear Spectroscopic Telescope ARray (NuSTAR) and Solar Orbiter/Spectrometer/Telescope for Imaging X-rays (STIX). We studied 5 joint spectra from GOES A7, B1 and B6 class microflares from active region AR12765 on 2020 June 6 and 7. As these events are very bright for NuSTAR, resulting in extremely low (&amp;lt;1%) livetime, we introduce a pile-up correction method. All five joint spectra were fitted with an isothermal model finding temperatures in the 9–11 MK range. Furthermore, three joint spectra required an additional non-thermal thick-target model finding non-thermal powers of 1025–1026 erg s−1. All the fit parameters were within the ranges expected for HXR microflares. The fit results give a relative scaling of STIX and NuSTAR mostly between 6-28% (one outlier at 52%) suggesting each instrument are well calibrated. In addition to spectral analysis, we performed joint HXR imaging of the June 6 and one of the June 7 microflares. In NuSTAR’s field of view (FOV), we observed two separate non-thermal sources connected by an elongated thermal source during the June 6 microflares. In STIX’s FOV (44○ W with respect to NuSTAR), we imaged thermal emission from the hot flare loops which when reprojected to an Earth viewpoint matches the thermal sources seen with NuSTAR and in the hotter EUV channels with the Solar Dynamic Observatory’s Atmospheric Imaging Assembly.

Missing-Mass Measurement of the 12C(K-, K+) Reaction at 1.8 GeV/c with the Superconducting Kaon Spectrometer

Abstract We performed a measurement of the inclusive missing-mass spectrum of the $^{12}$C$(K^-, K^+)$ reaction at an incident beam momentum of 1.8 GeV/c. This measurement was carried out by using the Superconducting Kaon Spectrometer (SKS) and the K1.8 beamline spectrometer at the Hadron Experimental Facility in J-PARC. From the missing-mass of the $^{12}$C$(K^-, K^+)$ reaction, the binding energy of a $\Xi ^-$ hyperon in a core $^{11}$B nucleus, $B_{\Xi ^-}$, can be calculated. Our experimental setup yielded a good energy resolution of 8.2 MeV (full width at half maximum), which allowed us to observe significant enhancements in the proximity of the $^{12}_{\Xi }$Be production threshold region. In order to extract information from the missing-mass spectrum, we employed several fitting parameters assumptions. A good agreement with the spectrum shape was obtained by adding two Gaussian functions, with the constant experimental resolution for the $\Xi$-hypernuclear states, to the background distribution. The peak positions were obtained to be $B_{\Xi ^-} = 8.9 \pm 1.4$ (stat.) $^{+3.8}_{-3.1}$ (syst.) MeV and $B_{\Xi ^-} = -2.4 \pm 1.3$ (stat.) $^{+2.8}_{-1.2}$ (syst.) MeV. Another model assumption, one Breit–Wigner function with $B_{\Xi ^-} = -2.7 \pm 2.2$ (stat.) $^{+0.5}_{-0.7}$ (syst.) MeV and $\Gamma = 4.1 \pm 2.1$ (stat.) $^{+1.2}_{-0.7}$ (syst.) MeV, also yielded a similar $\chi ^2$ value.

A New Critical Plane Multiaxial Fatigue Criterion with an Exponent to Account for High Mean Stress Effect

The mean stress effect remains a critical aspect in multiaxial fatigue analysis. This work presents a new criterion that, based on the classical Findley criterion, applies a material-dependent exponent to the mean normal stress term and includes the ultimate tensile stress as a fitting parameter. This way of considering the non-linear effect of the mean stress, with a material-dependent rather than a fixed exponent, is totally innovative among the multiaxial fatigue criteria found in the literature. In order to verify its accuracy, the new criterion has been checked against an extended version of the Papuga database of multiaxial experimental tests with 485 results, and compared with the criteria by Findley, Robert, and Papuga. The new criterion provides outstanding results for pure uniaxial cases, with multiaxial performance similar to the Robert criterion with a smaller range of error and a conservative trend, even surpassing the popular Papuga method in several relevant loading scenarios. These features enhance the applicability and versatility of the criterion for its use in the fatigue design of structural components.

Experimental study on characterization of resilient modulus and prediction model of saline aeolian sand

The dynamic resilience characteristics of aeolian sand subgrade are influenced by salt content and water content, exhibiting significant stress dependence and anisotropy. The resilient modulus(MR) of aeolian sand represents the stress-strain nonlinearity under cyclic loading, serving as an important parameter for the design of aeolian sand subgrade in desert areas. In order to investigate the variation of MR of aeolian sand subgrade with salt content and water content under traffic loading, as well as the MR characteristics under these conditions, three types of aeolian sand samples with varying water content and four sulphate contents were prepared. The variation of MR of aeolian sand under different confining pressures and deviator stress levels, as well as the influences of water content and salt content, was studied through indoor dynamic triaxial testing. Based on the pattern of the fitting parameters of the benchmark model, a prediction model suitable for the MR of aeolian sand was constructed. The results indicate a rise in aeolian sand's MR with increasing deviator stress and confining pressure, with confining pressure having a more significant impact than deviator stress. With the increase in water content, the MR of aeolian sand decreases nonlinearly, and with the increase in salt content, it exhibits a wave-shaped trend of "increasing-decreasing-increasing," which is related to the dissolution state of sodium sulfate in the soil. Based on the experimental results, a prediction model of the MR of aeolian sand was established, derived from the benchmark model, which can reflect the influence of salt content and water content on the MR, introducing them as variables within the model.

Addressing type Ia supernova color variability with a linear spectral template

Type Ia Supernovae (SNeIa) provided the first evidence of an accelerated expansion of the universe and remain a valuable probe to cosmology. They are deemed standardizable candles due to the observed correlations between their luminosity and photometric quantities. This characteristic can be exploited to estimate cosmological distances after accounting for the observed variations. There is however a remaining dispersion unaccounted for in the current state-of-the-art standardization methods. In an attempt to explore this issue, we propose a simple linear 3-component rest-frame flux description for a light-curve fitter. Since SNIa intrinsic color index variations are expected to be time-dependent, our description builds upon the mathematical expression of the well-known Spectral Adaptive Light Curve Template 2 (SALT2) for rest-frame flux, whilst we drop the exponential factor and add an extra model component with time and wavelength dependencies. The model components are obtained by performing either Principal Component Analysis (PCA) or Factor Analysis (FA) onto a representative training set. The constraining power of the model dubbed Pure Expansion Template for Supernovae (PETS) is evaluated and we found compatible results with SALT2 for Ωm0 and ΩΛ0 within 68% uncertainty between the two models, with PETS’ fit parameters exhibiting non-negligible linear correlations with SALT2’ parameters. For both PCA and FA model versions we verified that the first component mainly describes color index variations, proving it is a dominant effect on SNIa spectra. The model nuisance parameter which multiplies the color index variation-like fit parameter shows evolution with redshift in an initial binned cosmology analysis. This behavior can be due to selection effects and should be further investigated with higher redshift SNeIa samples. Overall, our model shows promise, as there are still a few aspects to be refined; however, it still falls short in reducing the unaccounted dispersion.

Assessing the effects of drainage and forest structure on presence and absence of fledglings of boreal grouse

Anthropogenic factors threaten biodiversity of natural habitats globally, including boreal forest habitats of culturally important game species, such as grouse. Forestry and intense draining of wetlands have resulted in landscape fragmentation of the peatlands and the forests in terms of their structure (a mosaic of differently managed small stands), and the loss and alteration of natural grouse habitats, which impacts on fitness parameters are still partly unexamined. We used grouse brood location data from the Finnish wildlife triangle censuses from 2017 to 2020 to study how forest structure and drainage affect breeding success of four grouse species. We calculated environmental characteristics (forest and landscape structure, peatlands and their drainage status) around individual brood observations with different buffer sizes and used them to explain brood size variation and the probability of complete failure (female with no brood). While the most important buffer zones differed by species, brood sizes were generally linked to habitats that offer shelter and food. Black grouse brood size increased when the proportions of deciduous trees and xeric heath forests increased. Hazel grouse broods were largest in spruce-dominated mires and herb-rich forests. Willow grouse brood size decreased with increasing proportion of poorer barren heath forest habitat. Capercaillie brood size decreased as a function of drainage ditch length. In Capercaillie and Black grouse, females without broods were overrepresented (zero-inflation), and the zero excess was related to habitats that differed from those of brooded females. These results suggest that forest management methods and peatland drainage can have a negative effect on offspring production of boreal grouse species. Restoration of natural peatlands and less invasive management such continuous cover forestry should enhance environmental conditions for grouse.

Physics-informed neural network for creep-fatigue life prediction of Inconel 617 and interpretation of influencing factors

Providing a comprehensive assessment of the creep-fatigue life of critical structures in nuclear power facilities is important for structural integrity and performance requirements during service. The data-driven modeling method can set aside traditional mechanical theory and use experimental data to drive creep-fatigue performance modeling directly, avoiding complex parameter fitting. A sufficiently robust purely data-driven model must be supported by a large amount of training data, which means significant time and financial costs. To address these issues, a physics-informed neural network (PINN) is proposed in this work to predict the creep-fatigue life of Inconel 617 at high temperatures, where the physical constraints are introduced to enhance the physical fundamentals. The prediction results show that introduced physical constraints promote the stability of prediction performance and analysis based on the strength of physical constraints provides valuable guidance for creep-fatigue modeling to select the suitable architecture for building PINN. The SHapley Additive exPlanations (SHAP) method and dependency analysis are utilized to reveal the intrinsic mechanism of the properties and structure of PINN.

End-Member Mixing Model for Methane Carbon Isotope Fractionation During Shale Gas Desorption and Its Application.

Unlike conventional natural gas reservoirs, shale gas development involves systematic changes in methane carbon isotopes that cannot be effectively described by existing isotope fractionation models and mechanisms. Therefore, based on fundamental theories such as Rayleigh fractionation, mass transfer flow, and mass conservation, this study established isotopic fractionation equations for methane in adsorbed and free gas. By considering adsorbed and free gases as two end-members and using an isotope mixing model, a fractionation model for methane carbon isotopes during shale gas desorption was constructed. This model quantifies the isotopic fractionation effects during shale gas desorption and elucidates the mechanism of methane carbon isotope fractionation. Using on-site desorbed gas content and isotope data, parameter fitting and model calculations were conducted to characterize methane carbon isotope variations throughout the process of shale core field desorption. The results show a pattern of "initially negative and then turning positive," consistent with those of physical simulation experiments. It was clarified that differences in mixing the two end-members and isotopic fractionation play key roles in the variation of methane carbon isotopic composition in shale gas. By applying the methane carbon isotope fractionation model, the contribution of adsorbed gas during shale gas production was explored. It was found that in the early stage of development, the adsorbed gas in Well JY 1 was negligible. After nearly seven years of development, the contribution of adsorbed gas in the later stage has only reached nearly 15%, indicating that the production contribution of adsorbed gas is still less than 0.3 million cubic feet per day. The open flow of Well JY 6-2 is more conducive to the production of adsorbed gas, but the production capacity is still mainly contributed by free gas, indicating that the shale gas production capacity in the later stage in the Jiaoshiba gas field is still primarily dominated by free gas.

Plasma, Urinary, Erythrocyte and Platelet Zinc Concentrations in Soccer Players.

Essential trace minerals are vital for general human health and athletic performance. Zinc (Zn) plays critical roles in several biochemical processes in exercise physiology, especially during intense physical exercise. This research aimed to analyze erythrocyte, platelet, plasma and urine Zn concentrations among men's and female soccer players over a sports season. A total of 22 male soccer players (20.61 ± 2.66 years; 71.50 ± 5.93 kg) and 24 female soccer players (23.37 ± 3.95 years; 59.58 ± 7.17 kg) participated in this longitudinal quasi-experimental study. Three assessments were carried out over the season: 1st evaluation: first week of training (August); 2nd assessment: middle of the season, between the end of the first and second round (January) and 3rd assessment: last week of training (May/June). In all evaluations extracellular (plasma and urine) and intracellular (erythrocytes and platelets) Zn concentrations were determined, as well as physical fitness and several blood parameters. Inductively coupled plasma mass spectrometry was used to measure Zn concentrations. Plasma and urinary concentrations were higher among male soccer players (p < 0.05) while erythrocyte and platelet Zn concentrations were higher in the female soccer players (p < 0.05). Additionally, variations in urinary and platelet Zn concentrations were observed over the season. The differences could be related to muscle mass, muscle damage or the specific sport's physical demands.

Modelling white matter microstructure using diffusion OGSE MRI: Model and analysis choices

Alterations in white matter (WM) microstructure of the central nervous system have been shown to be pathophysiological presentations of various neurodegenerative disorders. Current methods for measuring such WM features require ex vivo tissue samples analyzed using electron microscopy. Magnetic Resonance Imaging (MRI) diffusion-weighted pulse sequences provide a non-invasive tool for estimating such microstructural features in vivo. The current project investigated the use of two methods of analysis, including the ROI-based (Region of Interest, RBA) and voxel-based analysis (VBA), as well as four mathematical models of WM microstructure, including the ActiveAx Frequency-Independent Extra-Axonal Diffusion (AAI), ActiveAx Frequency-Dependent Extra-Axonal Diffusion (AAD), AxCaliber Frequency-Independent Extra-Axonal Diffusion (ACI), and AxCaliber Frequency-Dependent Extra-Axonal Diffusion (ACD) models. Two mice samples imaged at 7 T and 15.2 T were analyzed. Both the AAI and AAD models provide a single value for each of the fit parameters, including mean effective axon diameter AxD¯, packing fraction fin, intra-cellular and Din and extra-cellular Dex diffusion coefficients, as well as the frequency dependence of Dex, βex for the AAD model. The ACI and ACD models provide this, in addition to a distribution of axon diameters for a chosen ROI. VBA extends this, providing a parameter value for each voxel within the selected ROI, at the cost of increased computational load and analysis time. Overall, RBA-ACD and VBA-AAD were found to be optimal for parameter fitting to physically relevant values in a reasonable time frame. A full comparison of each combination of RBA and VBA with AAI, AAD, ACI, and ACD is provided to give the reader sufficient information to make an informed decision of which model is best for their own experiments.

Impedimetric detection of chloride ions using two symmetric Ag/AgCl electrodes

The suitability of Ag/AgCl electrodes for specific detection of chloride ions in aqueous gels is investigated. In contrast to potentiometric sensors, we use an impedimetric approach and avoid the need for a separate reference electrode through a symmetric two-electrode configuration. As such, electrochemical impedance spectroscopy is employed to characterise the response of the Ag/AgCl electrodes in contact with gels at various hydration levels containing different types as well as concentrations of salt. In order to extract quantitative information related to e.g. the ion concentration and mobility from the impedance spectra, an equivalent circuit model is fitted to the data. Here, we develop a simple equivalent circuit model related to the physical parameters of the system, which can be reduced to a modified Randles circuit with only few circuit elements. Importantly, even though the equivalent circuit model contains the same elements as a Randles circuit, their physical origin is different. Systematic variations of ion mobility, ion concentration, and type of ions allow us to evaluate the relationship between those physical properties and the resulting fitting parameters of the modified Randles circuit. This finally enables us to determine chloride concentrations in complex liquids, containing other salts and long chain molecules.