scholarly journals Controling Switching between Birhythmic States in a New Conductance-based Bursting Neuronal Model

2021 ◽  
Author(s):  
Innocent TAGNE NKOUNGA ◽  
Francois Marie MOUKAM KAKMENI ◽  
Baba Issa CAMARA ◽  
R. YAMAPI
Keyword(s):  
Control Parameter ◽  
Three Dimensional ◽  
Harmonic Balance Method ◽  
Neuronal Model ◽  
Slow Variable ◽  
Neuron System ◽  
And Control ◽  
Adaptation Variable ◽  
Good Agreement

Abstract A birhythmic conductance-based neuronal model with fast and slow variables is proposed to generate and control the coexistence of two different attracting modes in amplitudes and frequencies. However, periodic bursting, chaotic spiking and bursting haven’t been clearly observed there. The control of bistability is investigated in a three-dimensional birhythmic conductance-based neuronal model. We consider slow processes in neuron materialized by an adaptation variable coupled to system in the presence of an externalinusoidal current applied. By using the harmonic balance method, we obtain the frequency-response curve in which membrane potential resonance with his corresponding frequency are control by varying a specific parameter. At the resonance frequency, bifurcation and lyapunov exponent diagrams versus a control parameter are obtained. They reveal, a coexistence of two different complex attractors namely periodic and chaotic spiking, periodic and chaotic bursting. By using the control parameter as the slow variable, the system can switch from bistable to monostable behavior. This is done by destroying subthreshold (small) oscillation of the neuron. The role of adaptation variable in neuron system is then to filtered many existing electrical processes and permit to adapt the system by the multiple transitions states in the chosen electrical mode. A fairly good agreement is observed between analytical and numerical results.

A theoretical and experimental investigation into the vibration response of a flexible rotor and squeeze-film damper assembly

2001 ◽  
Vol 215 (10) ◽  
pp. 1251-1269 ◽  
Author(s):  
C-C Siew ◽  
M Hill ◽  
R Holmes ◽  
M Brennan
Keyword(s):  
Harmonic Balance ◽  
Three Dimensional ◽  
Harmonic Balance Method ◽  
Vibration Response ◽  
Mode Shapes ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Linear Vibration ◽  
Squeeze Film Damper ◽  
Good Agreement

This paper presents two efficient methods to calculate the unbalance vibration response of a flexible rotor provided with a squeeze-film damper (SFD) with retainer springs. Both methods are iterative and combine the harmonic balance and receptance approaches. The first method, called the modified iteration method (MIM), is suitable for predicting the three-dimensional mode shapes of a concentric SFD-rotor system. The second method, called the modified harmonic balance method (MHBM), is developed to calculate the non-linear vibration response of a flexible shaft provided with either a concentric or eccentric SFD. The system is also investigated experimentally under different conditions. The predictions computed by these methods are compared with experimental measurements and reasonably good agreement is obtained.

On the Role of Characterization in the Design of Interfaces in Nanoscale Materials Technology

2004 ◽  
Vol 10 (3) ◽  
pp. 324-335 ◽  
Author(s):  
S.P. Ringer ◽  
K.R. Ratinac
Keyword(s):  
Three Dimensional ◽  
Atom Probe ◽  
Turbine Rotor ◽  
Clay Nanocomposites ◽  
Multimodal Approach ◽  
Transmission Electron ◽  
Different Types ◽  
And Control

This work reviews recent research on the design and control of interfaces in engineering nanomaterials. Four case studies are presented that demonstrate the power of a multimodal approach to the characterization of different types of interfaces. We have used a combination of conventional, high resolution, and analytical transmission electron microscopy, microbeam electron diffraction, and three-dimensional atom probe to study polymer–clay nanocomposites, turbine rotor steels used for power generation, multicomponent aluminum alloys, and nanocrystalline magnetic materials.

scholarly journals DNA sequence encodes the position of DNA supercoils

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Sung Hyun Kim ◽  
Mahipal Ganji ◽  
Eugene Kim ◽  
Jaco van der Torre ◽  
Elio Abbondanzieri ◽  
...  
Keyword(s):  
Dna Sequence ◽  
Structural Information ◽  
Three Dimensional ◽  
Decisive Role ◽  
Chromosomal Dna ◽  
Dna Structures ◽  
Cellular Processes ◽  
Specific Sequences ◽  
Good Agreement

The three-dimensional organization of DNA is increasingly understood to play a decisive role in vital cellular processes. Many studies focus on the role of DNA-packaging proteins, crowding, and confinement in arranging chromatin, but structural information might also be directly encoded in bare DNA itself. Here, we visualize plectonemes (extended intertwined DNA structures formed upon supercoiling) on individual DNA molecules. Remarkably, our experiments show that the DNA sequence directly encodes the structure of supercoiled DNA by pinning plectonemes at specific sequences. We develop a physical model that predicts that sequence-dependent intrinsic curvature is the key determinant of pinning strength and demonstrate this simple model provides very good agreement with the data. Analysis of several prokaryotic genomes indicates that plectonemes localize directly upstream of promoters, which we experimentally confirm for selected promotor sequences. Our findings reveal a hidden code in the genome that helps to spatially organize the chromosomal DNA.

The Parametric Analysis of the Threshold Value Judging Mechanism in MEMS Safety and Arming Device

2015 ◽  
Vol 645-646 ◽  
pp. 968-971
Author(s):  
Fu Fu Wang ◽  
Wen Zhong Lou ◽  
Fang Yi Liu ◽  
Da Kui Wang ◽  
Ming Rong Zhang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Threshold Value ◽  
Element Model ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Long Distance ◽  
And Control ◽  
The Mathematical Model ◽  
The Finite Element Model

In this paper, a mechanical MEMS S&A device has been proposed. The size of the device is 10mm×13mm×0.5mm. The role of the threshold value judging mechanism is to determine the environment suffered by centrifugal force and control the sub-centrifugal slider not movement under the threshold, so as to effectively guarantee the time of long-distance arming. Through establishing the three-dimensional model of threshold value judging mechanism, establishing the force and the parameters of locking-releasing mechanism, deriving the mathematical model according to the rigid dynamic mechanics theory and establishing the finite element model by using ANSYS/LS-DYNA, appropriate threshold value judging mechanism is designed to meet two items, one item is the deformation of threshold value rod is not enough to release sub-centrifugal slider when the speed is less than 60000r/min; the other item is deformation of threshold value rod can release sub-centrifugal slider when the speed is more than 60000r/min.

Evaluation and control of the in-plane stiffness of timber floors for the performance-based retrofit of URM buildings

2009 ◽  
Vol 42 (3) ◽  
pp. 204-221 ◽  
Author(s):  
Anna Brignola ◽  
Stefano Pampanin ◽  
Stefano Podestà
Keyword(s):  
Seismic Response ◽  
Three Dimensional ◽  
Internal Force ◽  
Design Guidelines ◽  
Reinforced Masonry ◽  
Performance Based Assessment ◽  
Flexible Diaphragm ◽  
Open Question ◽  
And Control

The seismic response of existing un-reinforced masonry (URM) buildings is strongly dependent on the characteristics of wooden floors and, in particular, on their in-plane stiffness and on the quality of connection between the floors and the URM elements. It is generally well-recognized that an adequate in-plane-stiffness and proper connections can significantly improve the three-dimensional response of these buildings, obtaining a better distribution and transfer of forces to the lateral load resisting walls. However, the extensive damage observed during past earthquakes on URM buildings of different types have highlighted serious shortcomings in typical retrofit interventions adopted in the past and based on stiffening the diaphragm. Recent numerical investigations have also confirmed that increasing the stiffness of the diaphragm is not necessarily going to lead to an improved response, but could actually result to detrimental effects. The evaluation of the in-plane stiffness of timber floors in their as-built and retrofitted configuration is still an open question and a delicate issue, with design guidelines and previous research results providing incomplete and sometimes controversial suggestions to practicing engineers involved in the assessment and/or retrofit of these type of structures. In this contribution, the role of the in-plane stiffness of timber floors in the seismic response of URM buildings is critically discussed, based on the relatively limited available experimental and numerical evidences. A framework for a performance-based assessment and retrofit strategy of URM buildings, capable of accounting for the effects of a flexible diaphragm on the response prior to and after the retrofit intervention, is then proposed. By controlling the in-plane stiffness of the diaphragm, adopting a specific strengthening (or weakening) intervention, the displacements, accelerations and internal force demands can be maintained within targeted levels. This will protect undesired local mechanisms and aim for a more appropriate hierarchy of strength within the whole system.

scholarly journals The role of surface adhesion on the macroscopic wrinkling of biofilms

2021 ◽  
Author(s):  
Steffen Geisel ◽  
Eleonora Secchi ◽  
Jan Vermant
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Bacterial Biofilm ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Microfluidic Channels ◽  
Channel Networks ◽  
Biofilm Growth ◽  
And Control

Biofilms, bacterial communities of cells encased by a self-produced matrix, exhibit a variety of three-dimensional structures. Specifically, channel networks formed within the bulk of the biofilm have been identified to play an important role in the colonies viability by promoting the transport of nutrients and chemicals. Here, we study channel formation and focus on the role of the adhesion of the biofilm matrix to the substrate in Pseudomonas aeruginosa biofilms grown under constant flow in microfluidic channels. We perform phase contrast and confocal laser scanning microscopy to examine the development of the biofilm structure as a function of the substrates surface energy. The formation of the wrinkles and folds is triggered by a mechanical buckling instability, controlled by biofilm growth rate and the film's adhesion to the substrate. The three-dimensional folding gives rise to hollow channels that rapidly increase the overall volume occupied by the biofilm and facilitate bacterial movement inside them. The experiments and analysis on mechanical instabilities for the relevant case of a bacterial biofilm grown during flow enable us to predict and control the biofilm morphology.

scholarly journals A physical description of the adhesion and aggregation of platelets

2017 ◽  
Vol 4 (4) ◽  
pp. 170219 ◽  
Author(s):  
Bastien Chopard ◽  
Daniel Ribeiro de Sousa ◽  
Jonas Lätt ◽  
Lampros Mountrakis ◽  
Frank Dubois ◽  
...  
Keyword(s):  
Effective Diffusion ◽  
Three Dimensional ◽  
Physical Description ◽  
A Value ◽  
Platelet Aggregate ◽  
The Impact ◽  
Aggregation Of Platelets ◽  
Good Agreement

The early stages of clot formation in blood vessels involve platelet adhesion–aggregation. Although these mechanisms have been extensively studied, gaps in their understanding still persist. We have performed detailed in vitro experiments, using the well-known Impact-R device, and developed a numerical model to better describe and understand this phenomenon. Unlike previous studies, we took into account the differential role of pre-activated and non-activated platelets, as well as the three-dimensional nature of the aggregation process. Our investigation reveals that blood albumin is a major parameter limiting platelet aggregate formation in our experiment. Simulations are in very good agreement with observations and provide quantitative estimates of the adhesion and aggregation rates that are hard to measure experimentally. They also provide a value of the effective diffusion of platelets in blood subject to the shear rate produced by the Impact-R.

scholarly journals Electro-fluid dynamics of aqueous humor production: simulations and new directions

2016 ◽  
Vol 1 (2) ◽  
pp. 48-58
Author(s):  
Aurelio Giancarlo Mauri ◽  
Lorenzo Sala ◽  
Paolo Airoldi ◽  
Giovanni Novielli ◽  
Riccardo Sacco ◽  
...  
Keyword(s):  
Aqueous Humor ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Active Secretion ◽  
Sodium Potassium ◽  
Transepithelial Potential ◽  
Aqueous Humor Flow ◽  
New Directions ◽  
Good Agreement

Purpose: to theoretically investigate the role of bicarbonate ion (HCO−3 ) on the nonpigmented transepithelial potential dierence Vm, the sodium potassium pump (Na/K) and the active secretion of aqueous humor.Methods: a three-dimensional mathematical model is proposed to isolate the roles of HCO−3 and Na+, which are diicult to investigate experimentally. The model combines the velocity-extended Poisson-Nernst-Planck equations to describe ion electrodiusion and the Stokes equations to describe aqueous humor flow into the basolateral space adjacent to the nonpigmented ephitelial cells.Results: Computations showthat Vm is close to baseline experimental measurements (on monkeys) in the range [−2.7,−2.3]mVonly if HCO−3 is included in the simulation. The model is also capable of reproducing the flow of Na+ exiting the cell and the flow of K+ entering the cell, in accordance with the physiology of the Na/K pump. The simulated Na/K ratio is 1.53, which is in very good agreement with the theoretical value of 1.5.Conclusion: Model simulations suggest that HCO−3 inhibition may prevent physiologically correct baseline values of the nonpigmented transepithelial potential difference and Na/K ATPase function. This may provide useful indication in the design of medications that decrease the active secretion of aqueous humor, and supports the advantage of using mathematical models as a noninvasive complement of animal models.

scholarly journals The Role of the Thoracic Spine during Breathing in Osteogenesis Imperfecta: A Combined Traditional Morphometry and 3D Geometric Morphometrics Research

Osteology ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 1-10
Author(s):  
José María González-Ruiz ◽  
Carlos A. Palancar ◽  
Federico Mata Escolano ◽  
Susanna Llido ◽  
Isabel Torres-Sanchez ◽  
...  
Keyword(s):  
Geometric Morphometrics ◽  
Thoracic Spine ◽  
Three Dimensional ◽  
Secondary Effects ◽  
Respiratory Problems ◽  
Spine Shape ◽  
Computed Tomography Scans ◽  
And Control ◽  
Shape Data

OsteogenesisImperfecta (OI) is a rare disease with respiratory problems, which are usually attributed to the secondary effects of scoliosis and rib fractures and to severe restrictive pulmonary disease. Conventional morphometry has already been studied in OI patients but three-dimensional geometric morphometrics (3D GMM) has never been used to assess how the thoracic spine shape changes during maximal breathing. A total of 6 adult subjects with OI type III and 16 healthy controls underwent a spirometric study and two computed tomography scans in maximal inspiration and expiration. Shape data by means of 3D GMM and Cobb angle values of scoliosis and kyphosis were obtained and their relationship with spirometric values was analysed using regressions and mean shape comparisons. No differences in kyphosis (p = 0.285) and scoliosis Cobb values (p = 0.407) were found between inspiration and expiration in OI patients. The 3D GMM analysis revealed significant shape differences between OI and control subjects (p < 0.001) that were related to the inspiration (p = 0.030) and not to the expiration (p = 0.079). Nevertheless, no significant relation was found between thoracic spine shape, scoliosis, kyphosis and breathing outcomes in both OI patients and controls. There were thoracic spine shape differences during maximal breathing between OI patients and controls that were mainly related to the inspiration.

Morphogenesis of a New Human Herpes-Type Virus Isolate (Sasha Virus)

1973 ◽  
Vol 31 ◽  
pp. 592-593
Author(s):  
R. F. Zeigel ◽  
W. Munyon
Keyword(s):  
Virus Isolate ◽  
Calf Serum ◽  
Uranyl Acetate ◽  
Human Herpes ◽  
Human Embryonic Lung ◽  
Human Herpes Virus ◽  
Intracytoplasmic Inclusions ◽  
Hel Cells ◽  
And Control

In continuing studies on the role of viruses in biochemical transformation, Dr. Munyon has succeeded in isolating a highly infectious human herpes virus. Fluids of buccal pustular lesions from Sasha Munyon (10 mo. old) uiere introduced into monolayer sheets of human embryonic lung (HEL) cell cultures propagated in Eagles’ medium containing 5% calf serum. After 18 hours the cells exhibited a dramatic C.P.E. (intranuclear vacuoles, peripheral patching of chromatin, intracytoplasmic inclusions). Control HEL cells failed to reflect similar changes. Infected and control HEL cells were scraped from plastic flasks at 18 hrs. of incubation and centrifuged at 1200 × g for 15 min. Resultant cell packs uiere fixed in Dalton's chrome osmium, and post-fixed in aqueous uranyl acetate. Figure 1 illustrates typical hexagonal herpes-type nucleocapsids within the intranuclear virogenic regions. The nucleocapsids are approximately 100 nm in diameter. Nuclear membrane “translocation” (budding) uias observed.

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