Jackson Model Research Articles

Simulations of nerve signal propagation in axons

PurposeIn the literature, soliton solutions of the Heimburg–Jackson model have been proposed by Drab et al. (2022), but for the considered models, i.e. Eq.(1) and Eq.(2), the existence of solitons, the dispersion analysis and the pseudospectral method have been studied (Engelbrecht et al., 2006, 2018, 2020; Tamm et al., 2017, 2022; Peets et al., 2013). Therefore, the gap should be filled by this work.Design/methodology/approachWhen nonlinear terms, dissipative terms and forcing terms are ignored, the system (Eq.(2)) reduces to a single, sixth-order partial differential equation (Tamm et al., 2022). In this work, our aim is to propose analytical solutions in the explicit form via ansatz-based method. Therefore, the parameter effects in wave profile will be proposed clearly in figures.FindingsWhile progress has been made in signal propagation in nerves, thanks to many experimental studies and theoretical predictions over the last two centuries, the results obtained in this study may answer new questions that arise.Originality/valueIn the literature, the existence of solitons, dispersion analysis and pseudospectral method have been investigated for the Heimburg-Jackson model (Engelbrecht et al., 2006, 2018, 2020; Tamm et al., 2017, 2022; Peets et al., 2013), and this study fills the gap in soliton solutions. Additionally, when nonlinear terms, dissipative term and forcing terms are ignored, the system (Eq.(2)) reduced to a single equation that is sixth-order partial differential equation (Tamm et al., 2022). In this work, our aim is to propose analytical solutions in the explicit form via ansatz-based method. Therefore, the parameter effects in wave profile will be proposed clearly in figures.

Design and Implementation of a Shipborne Echo Sounder Simulator Based on a Seabed Echo Scattering and Noise Model

The Manila Amendment 2010 to the STCW International Convention has made clear requirements for seafarers to use the navigation simulation system for training. A shipborne echo sounder is an important navigation aid equipment necessary for a ship’s bridge. Proper use of this equipment can effectively prevent ship grounding accidents. Given the lack of research on simulating different seabed substrate echoes within echo sounder simulations, this paper proposes an algorithm for generating echoes and clutter from various seabed substrates, based on the Jackson model and noise model. Using the seabed echo generation algorithm, the bathymetric data and seabed echo under the influence of ship rolling are generated, the seabed echo simulation of the sounder under the influence of four different grazing angles and six different substrates is realized. Clutter images, including random noise, bubble interference, co-frequency interference, and fish school interference, are also simulated. A typical ship echo sounder simulator is designed and developed. The echo sounder simulator developed in this paper has high realism in seabed echoes and clutter simulation, complete functions, and friendly human–computer interaction. The system has been used by college students and crews, with satisfactory results, which can effectively meet the needs of actual training of seafarers.

STRATEGIC PERSONNEL MANAGEMENT MODELS AND THE IMPORTANCE AND NECESSITY OF THEIR REDESIGN TODAY

In the article - "Strategic personnel management models and the importance and necessity of their redesign today" - strategic management models are listed and discussed. Among them are: D. Guest model, Michigan and Harvard models, Armstrong model, Fottler model, Cheveldry model, Shuler and Jackson model. These models were developed in previous centuries. The authors of the article have compared them with their current requirements, in particular with the current needs of companies in this field. Today's needs are to provide managers not with general models of strategic personnel management, but with specific ways of achieving the characteristics that are fixed in these models. In the article, the authors have performed exactly this work on the model of scientist Fottler and have also shown it graphically. Keywords: personnel; strategic management; Models of strategic personnel management.

Experimental and numerical investigation on agglomeration of aluminum during combustion process of aluminized composite propellant

The addition of aluminum particles can effectively improve the energy characteristics of solid composite propellants in propulsion systems. However, these aluminum particles affecting propellant mixture viscosity, ignition delay time, burning time and specific impulse could also lead to undesirable effects. Therefore, it is a general practice that in the early stage of propellant formulation design that the particle size of condensed phase products is optimized/minimized through formulation adjustment to reduce its negative impact on the engine. In practice, it means that a costly manpower and materials are needed to obtain the size distribution of condensed phase products during the combustion process of propellants via experimental tests. Thus, there is a strong industrial need for a reasonable and feasible simulation method of agglomeration process during the combustion process of propellants. In this work, we propose and examine the implementation of molecular dynamics and a random packing algorithm on creating numerically models of aluminized composite propellants. Considering the pyrolysis of ammonium perchlorate (AP) and the combustion process of aluminum, we develop a more accurate agglomeration model basing on the classical Jackson model. Our proposed methods and simulations models are validated by our experimental results. It confirms that the present work provides a prediction tool for simulating and improving the agglomeration process, thus aiming at optimizing solid propellant formula.

Performance of real evapotranspiration products and water yield estimations in Uruguay

Real evapotranspiration (ETR) is a key variable in socio-ecological systems since it is related to the food supply, climate regulation, among others. Additionally, ETR plays a significant role in determining water yield (WY) at the catchment level, which directly impacts water availability for consumption and irrigation. Therefore, it is essential to quantify ETR and WY fluctuations in response to various human pressures to enable comprehensive water planning. In recent decades, remote sensing has become increasingly employed worldwide for hydrological monitoring and estimating ETR. In Uruguay, several approaches have been attempted to quantify ETR. However, there is still a lack of assessments concerning the performance of different products, particularly those using remote sensing. The main objectives of this article were twofold: a) to evaluate the performance of various spatial explicit approaches for estimating real ETR and b) to estimate and analyse the variability in WY derived from the different ETR products for three climatically contrasting years. To achieve these objectives, we utilized four remote sensing ETR products: the Penman–Monteith–Leuning model (PMLv2), the MODIS product, the Simplified Jackson Model based on Landsat images and INTA-SEPA model based on NOAA-AVHRR images. We also employed two water balance models at two scales: national (derived from the National Institute for Agricultural Research of Uruguay, INIA) and micro-watershed level. Our results indicate that MODIS and PMLv2 remote sensing products exhibited better performances compared to the other approaches. These products provided the highest spatial (500 m) and temporal (8 days) resolution, effectively capturing seasonal differences between land-covers. Moreover, they showed positive and strong correlations with annual precipitation and productivity. The discrepancies observed between products have direct implications on the estimation of WY, not only in terms of quantity but also in terms of spatial patterns. Future studies should explore the application of MODIS and PMLv2 ETR estimations for understanding hydrological and ecological processes, conducting climate change research, detecting and mitigating agricultural drought, and managing water resources effectively.

Comment on "Solitons in the Heimburg-Jackson model of sound propagation in lipid bilayers are enabled by dispersion of a stiff membrane" by M. Drab et al.

Comment on "Solitons in the Heimburg-Jackson model of sound propagation in lipid bilayers are enabled by dispersion of a stiff membrane" by M. Drab et al.

Factors in Condensate Product Particle Size During Aluminized Propellant Combustion

The addition of aluminum to propellants positively affects their energy density but also causes problems such as two-phase flow loss, nozzle contamination, wake heat radiation, and condensate particle deposition in the combustion chamber. This paper concentrates on the agglomeration process of aluminum particles and factors in condensed product size during aluminized propellant combustion. The condensed products are divided according to the combustion stage into initial condensed products on the burning surface and final condensed products in the gas stream. The differences in combustion behaviors and size distributions between initial and final condensed products are analyzed in detail. Then, the influence of aluminum content and initial aluminum particle size on the size distribution of the condensed products is studied. It is found that both the initial and final condensed products increase with increasing aluminum content and initial aluminum particle size. A modified Jackson model is presented to estimate the particle size of the propellants’ condensed products. The findings in this paper provide methods for reducing the condensate products of aluminized propellants and provide a basis for applying these propellants and improving their formulation.

Participative Decision Making and Organizational Commitment: The Mediatory Role of Influence and Communication

In a high turnover environment, inculcating organizational commitment among employees is a big challenge. We proposed a theoretical framework explaining how participative decision making affects commitment. For this, we modified the Jackson (1983) model explaining the effect of Participation in Decision Making on communication, and further extend it to Organizational commitment in the perspective of Elele & Fields (2010). The participative decision was measured by employee engagement in decision making (EE), meeting load (ML), and management support (MS). These factors increase, Perceived Influence among employees (PI), Job-related communication (JR), and Personal communication (PC). Moreover, thorough these communication factors, organizational commitment got increase. This is classified as Affective commitment (AC), normative commitment (NC), and continuance commitment (CC). To establish its empirical validity, we conducted a survey based on a close-ended questionnaire, from 200 employees, working in different organizations of Karachi. Data were analyzed using structured equation modeling and confirmatory factor analysis. The result suggested that Job-related communication effectively mediate employee engagement in decision making and both Affective and normative commitment. Similarly, Personal communication and Perceived Influence also mediate the effect of meeting load on continuance and normative commitment respectively. Moreover, management support increases both Perceived Influence and Job-related communication. And lastly, employee engagement has a significant positive effect on Perceived Influence. Overall findings backed our theory and explain the strong effect of Participative decision making on commitment mediated by communication.

Design and field testing of a non-linear single-beam echosounder for multi-frequency seabed characterization

Seabed mapping and characterization are best performed using several frequencies and several angles of incidence. This is often an issue because of the need to employ different sonars, with distinct frequencies but co-located as much as possible to image the same patch of seafloor. This article presents the design, calibration and field testing of a multiple-frequency single-beam echosounder (SBES), mounted on a mechanical pan-and-tilt head. It uses very high transmitting levels to produce non-linear effects and generate harmonics of a 100 kHz fundamental frequency. PZT transducers are used to transmit high acoustic powers and PDVF transducers enable the reception of scattering levels over a very broad frequency band (for the different harmonics). Tank experiments are used to verify effective harmonic generation. The shock distance (at which harmonics are at their maximum level) is measured as 2 m from the transmitter and recommended as the minimum far-field range. Non-linear transmission losses (distinct from linear losses) are calibrated using a full metal sphere 38.1 mm in diameter and of known frequency response, up to ranges commensurate with the depths expected in the field (⩽30 m). The −3 dB beamwidth varies from 5.8° at 100 kHz to 2.8° at 300 kHz. Harmonics are used to resolve phase ambiguities in detecting seabed depths. Backscattering strengths BS are matched to the Generic Seafloor Acoustic Backscatter (GSAB) model to derive the best-fitting parameters. Field validation took place in the Bay of Brest (France) in May 2016, over three different types of seafloor (namely: sandy mud; gravel; gravelly coarse sand with maerl). Additional in situ calibration was used. The echosounder was pointed at angles from 0° (nadir) to 60° by 5° steps. One of the areas surveyed (“Carré Renard”), commonly used for instrument calibration and comparison with other measurements, showed differences <1 dB at 200 kHz. Videos and photographs of the seafloor were used to ground truth interpretations of the BS curves. The results show that these BS curves measured with the echosounder are relevant for seabed classification and characterization. The different shapes and levels of BS when compared to ground truth are coherent with the Jackson model. The main limit of this prototype of echosounder is the signal to noise ratio, in particular for high frequency harmonics (⩾400 kHz). The in situ calibration is unavoidable because of the non-linear parameter variations with water characteristics (temperature, salinity…). Calibrated BS curves from 100 kHz to 300 kHz can be directly compared to other measurements, for example to calibrate other instruments.

SOLITARY TRANSMISSION OF NEURONAL SIGNALS APPROACHED VIA HE'S SEMI INVERSE METHOD

An investigation of neuronal signal transmission is intended in this paper through the establishment of solitary wave solutions for the improved Heimburg Jackson model governing the propagation of the mechanical wave in biomembranes. The computation of soliton solutions is carried out employing He's semi inverse variational principle. The role of nonlinearity and dispersive effects in the solitonic propation is correlated to the role of compressibility, elasticity, and inertia over the neuronal signal transmission in the unilamellar DPPC vesicles at T = 45o. The study reveals that He's semi inverse method is a direct and effective algebraic method to study the experimental features of the nerve pulse in the biomembranes.

Crystal growth in deeply undercooled Ni50Al50: Signature of the ordering sequence at the interface.

Crystal growth of the intermetallic alloy, Ni50Al50, is investigated by molecular dynamics simulations with two different interatomic potentials. The calculated growth rate can be captured by the Wilson-Frenkel or Broughton-Gilmer-Jackson model at small undercoolings but deviates from the theory at deep undercoolings. Failure of the theory is found to be correlated with the dynamic processes that emerged at the interface, but not apparently with the static interface structure. The chemical segregation of Ni and Al atoms occurs before the geometrical ordering upon crystallization at small undercoolings. In contrast, the geometrical ordering precedes the chemical one at deep undercoolings. These two ordering processes show a collapsed time evolution at the crossover temperature consistent with the onset of the theoretical deviation. We rationalize the delayed chemical segregation behavior by the collective atomic motion, which is characterized by the super-Arrhenius transition of the temperature-dependent diffusivity and structural relaxation time at the crossover point.

Modeling and Analysis of the Time-Dependent Contact Behavior of Multiscale Rough Surfaces Subjected to Random Shocks

In complex operational environments, random shocks change the contact behavior of rough surfaces, resulting in time-dependent and uncertain characteristics, which further affect their friction, wear, and lubrication properties. However, in the currently available impact models, only deterministic shocks are considered at surfaces in contact and the evolution of contact behavior over time is ignored, which is detrimental in many engineering applications. Therefore, in the current study, a model based on elastic–plastic deformation and the loading/unloading contact theory is proposed to analyze the time-dependent behavior of contacting asperities; this model is affected by two characteristic parameters of random shocks, viz. shock magnitude and interarrival time. The corresponding contact variables of surfaces were deduced using the multiscale Jackson and Streator model while individual asperities were assumed to be power law hardening materials under stick contact conditions to comply better with physical reality. Furthermore, experimental results on AISI 1045 steel ring contact pairs considering the shock effect were compared with predictions made by the theoretical model; the reasonable difference between the two sets of results illustrates the effectiveness of the current approach. In addition, the impact of the strain hardening exponent, shock properties, and sample size on the time-dependent surface load is discussed. These insights can potentially help in analyzing the time-dependent wear behavior of multiscale rough surfaces.

Numerical study of the solid flow behavior in a rotating drum based on a multiphase CFD model accounting for solid frictional viscosity and wall friction

In continuum-based models, the kinetic theory of granular flow (KTGF) provides a model for calculating solids stresses but has limitations in densely packed regions such as mills, kilns and rotating drums. The Eulerian-Eulerian multiphase model coupled with KTGF is evaluated in the present work. An additional frictional stress models were added, and their suitability evaluated. For the evaluation, a rotating drum at three rotational speeds (20rpm, 42rpm and 65rpm) was analyzed. Compared with Positron Emission Particle Tracking (PEPT) measurement data from literature, Johnson and Jackson's model and Schaeffer's model for the frictional stress both showed a lower angle of repose regardless of the wall boundary condition used. Thus, a new frictional viscosity model based on granular pressure was proposed. By adjusting the specularity coefficient of wall boundary condition, results of the present model agreed well with the PEPT measurements in terms of angle of repose and spatial velocity fields. In addition, considering that the actual Johnson and Jackson model for boundary condition includes two parts, collisional and frictional part, a discussion was made about boundary condition. The results showed that the validation of the proposed frictional viscosity model with experimental results could be completed at different rotational speeds by considering only the collisional part of the boundary condition with different specularity coefficients or only the frictional part of the boundary condition with different angles of friction or both parts with the same specularity coefficient and angle of friction. Nevertheless, when the complete Johnson and Jackson model of boundary condition was applied, the same specularity coefficient and angle of friction are used at different rotational speeds which is more physically meaningful. Moreover, it is found that the frictional contribution has greater influence on dynamic angle of repose than collisional contribution of the boundary condition in the current rotating drum.

Integration of intracellular signaling: Biological analogues of wires, processors and memories organized by a centrosome 3D reference system

BackgroundMyriads of signaling pathways in a single cell function to achieve the highest spatio-temporal integration. Data are accumulating on the role of electromechanical soliton-like waves in signal transduction processes. Theoretical studies strongly suggest feasibility of both classical and quantum computing involving microtubules. AimA theoretical study of the role of the complex composed of the plasma membrane and the microtubule-based cytoskeleton as a system that transmits, stores and processes information. MethodsTheoretical analysis presented here refers to (i) the Penrose–Hameroff theory of consciousness (Orchestrated Objective Reduction; Orch OR), (ii) the description of the centrosome as a reference system for construction of the 3D map of the cell proposed by Regolini, (iii) the Heimburg–Jackson model of the nerve pulse propagation along axons’ lipid bilayer as soliton-like electro-mechanical waves. Results and conclusionThe ideas presented in this paper provide a qualitative model for the decision-making processes in a living cell undergoing a differentiation process. OutlookThis paper paves the way for the real-time live-cell observation of information processing by microtubule-based cytoskeleton and cell fate decision making.

A design-by-treatment interaction model for network meta-analysis and meta-regression with integrated nested Laplace approximations.

Network meta‐analysis (NMA) is gaining popularity for comparing multiple treatments in a single analysis. Generalized linear mixed models provide a unifying framework for NMA, allow us to analyze datasets with dichotomous, continuous or count endpoints, and take into account multiarm trials, potential heterogeneity between trials and network inconsistency. To perform inference within such NMA models, the use of Bayesian methods is often advocated. The standard inference tool is Markov chain Monte Carlo (MCMC), which is computationally expensive and requires convergence diagnostics. A deterministic approach to do fully Bayesian inference for latent Gaussian models can be achieved by integrated nested Laplace approximations (INLA), which is a fast and accurate alternative to MCMC. We show how NMA models fit in the class of latent Gaussian models and how NMA models are implemented using INLA and demonstrate that the estimates obtained by INLA are in close agreement with the ones obtained by MCMC. Specifically, we emphasize the design‐by‐treatment interaction model with random inconsistency parameters (also known as the Jackson model). Also, we have proposed a network meta‐regression model, which is constructed by incorporating trial‐level covariates to the Jackson model to explain possible sources of heterogeneity and/or inconsistency in the network. A publicly available R package, nmaINLA, is developed to automate the INLA implementation of NMA models, which are considered in this paper. Three applications illustrate the use of INLA for a NMA.

Tungsten wires and porous NiAl prepared through directional solidification and selective dissolution

ABSTRACTThe combination of directional solidification and selective dissolution was applied to fabricate tungsten (W) wires and porous NiAl matrix. A NiAl–W pseudobinary eutectic alloy with 1.5 at.% tungsten was directionally solidified in a Bridgman-type oven at 1700°C. Results confirmed that the relationships of the growth rate with the interfibrous spacing and diameter of W fibrous phases in the directionally solidified samples are in accordance with the Jackson and Hunt (J−H) model. Afterward, the NiAl matrix was selectively dissolved in an HCl:H2O2 solution to reveal W wires, which present various three-dimensional (3D) morphologies at different growth rates. The W fibrous phases in the NiAl–W alloy samples were then selectively removed with a mixed etchant of ammonium acetate to form a porous NiAl matrix at a constant potential. Dynamic corrosion curves revealed that etching W from the NiAl matrix was inhibited after 2–3 h. The porous structures of NiAl after removing W phases are linked to the 3D morphologies of W fibrous phases embedded in the NiAl matrix. The aspect ratio of W wires and the structures of porous NiAl can be adjusted by selecting the process parameters of this combined technology.

The Lived Experiences of African American Development Administrators At Public Universities

This study explores the lived career experiences of African American development administrators who work at public higher education institutions, with particular attention to factors of recruitment, engagement, and retention, as well as perceptions of efficacy regarding these efforts. Jerlando Jackson's ERA model is used as the theoretical framework and provides a guide to inquiry. Qualitative interviews with selected participants reveal six primary themes, which have to do with (1) the pipeline into the profession, (2) onboarding and investment, (3) opportunities for career advancement, (4) engagement beyond the institution, (5) career challenges related to personal demographics, and (6) personal considerations and relational/family issues. Recommendations are provided to promote the diversification of the development profession and further the research agenda on this topic.

Numerical prediction of flow characteristics of slush hydrogen in a horizontal pipe

Slush hydrogen has lower temperature, higher density and higher heat capacity than those of liquid hydrogen, and is considered as a potential propellant for novel aerospace rockets with decreased spacecraft size and weight. In this study, an improved three-dimensional numerical model based on Euler–Euler two-fluid model has been built to predict the flow characteristics of slush hydrogen in a horizontal pipe. In this model, an effective viscosity of mixture, which takes the particle shape and size into consideration, is adopted to modify the drag law for interphase momentum exchange, and the wall boundary conditions for the solid phase are based on Johnson–Jackson model which involves the friction and collision between the particle and the wall. The performance of the model has been verified by the comparison between the calculated results and the experimental data from the literatures and considered to be effective for slush hydrogen flow. The improved model is then used to analyze the effects of inlet velocity, solid fraction, particle size on the flow characteristics, including pressure gradient, solid volume fraction distribution and velocity distribution and abundant to predict the flow pattern shift. Moreover, the numerical results indicate that the pressure drops for subcooled liquid hydrogen, under some operating conditions, are greater than those of slush hydrogen, which are presented in some published experimental work.

Evaluation of wall friction models for riser flow

Two different approaches for modelling the particle-wall collisions, the frequently employed Johnson & Jackson model and the recently proposed Schneiderbauer model, were evaluated in a fluidized bed riser by comparing simulation results to experimental data over a range of fluidization velocities and solids fluxes. For the Johnson & Jackson model, it was shown that partial slip settings recommended for denser fluidization conditions (a specularity coefficient in the order of 0.1) failed to predict cluster formation at the walls at higher gas flow rates due to unrealistically large granular temperature generation in the near-wall regions. By reducing wall friction to settings approaching a free-slip condition (specularity coefficient in the order of 0.001), this problem is overcome by eliminating excessive granular temperature generation from over-predicted strain rates at the walls. However, this approach results in an overestimation of the downward velocity of the clusters at the wall in dense cases. Despite this shortcoming, predictions are remarkably accurate for most of the cases. The Schneiderbauer model, with model parameters close to recommended settings, performs similarly well for most of the cases, slightly under-predicting cluster formation at the walls in the dilute cases. Generally, it also predicts more realistic flow behaviour since it prevents dense clusters from falling rapidly at the walls. The Schneiderbauer wall friction model is therefore recommended for use in future studies of risers, since it is able to deliver reasonable results over a wider range of flow conditions than the Johnson and Jackson model, using a single set of friction parameters. Furthermore, it has the benefit of using experimentally measurable quantities as input.

Building Power in a Frontline Community: The Cooperation Jackson Model

Editor: You have spoken about the ethics and values of cooperatives, but your perspective goes well beyond the notion of individual cooperatives. Can you tell me a little bit about the cooperative ...