scholarly journals Dynamics of the generator with three circuits in the feedback loop. Multistability formation and transition to chaos

2021 ◽  
Vol 21 (1) ◽  
pp. 21-28
Author(s):  
Oleg V. Astakhov ◽  
◽  
Sergey V. Astakhov ◽  
Natalia S. Fadeeva ◽  
Vladimir V. Astakhov ◽  
...  
Keyword(s):  
Feedback Loop ◽  
Van Der Pol Oscillator ◽  
Phase Portraits ◽  
Nonlinear Phenomena ◽  
Oscillatory Circuit ◽  
Oscillating Systems ◽  
Urgent Task ◽  
Wide Range ◽  
Before And After ◽  
Mechanisms Of Formation

Background and Objectives: Studying the dynamical mechanisms of the emergence of nonlinear phenomena that are characteristic for multimode self-oscillating systems consisting of interacting oscillators and an ensemble of passive oscillators or representing active nonlinear systems with complex feedback channels is an important urgent task. The simplest example of a self-oscillating system with a complex feedback is the well-known classical van der Pol oscillator with an additional linear oscillatory circuit included in the feedback channel. We investigate the behavior of the multimode system increasing the number of oscillatory circuits in the oscillator’s feedback loop. The research in this paper can help to better understand the mechanisms of multistability formation in infinite-dimensional self-oscillating systems such as a generator with delayed feedback and a generator with distributed feedback. Materials and Methods: The system equations were derived for the electronic scheme of the self-oscillating system. To describe the existing dynamic modes by numerical simulation methods, the projections of the phase portraits and the Poincare sections were obtained. To study the mechanisms of formation of multistable states, the bifurcation analysis methods were used. Results: It was found that the mechanism underlying the multistability formation is based on a sequence of two supercritical Andronov – Hopf bifurcations and a subcritical Neymark – Saker bifurcation. Therefore, the multistability emerges as a result of gaining stability by the unstable limit set that existed before the multistability appears. Conclusion: The discovered mechanism of multistability formation opens up wide possibilities for managing the multistability, which are inaccessible for systems in which the multistability is realized through tangential bifurcations. In contrast to the tangential bifurcation, the subcritical Neymark – Sacker bifurcation assumes the existence of a limit cycle both before and after the bifurcation. Thus, it is possible to use a wide range of methods and tools to stabilize saddle limit cycles in order to control the boundaries of the multistability region in the space of control parameters of the system.

NONLINEAR DYNAMICS OF CELL CYCLES WITH STOCHASTIC MATHEMATICAL MODELS

2009 ◽  
Vol 17 (03) ◽  
pp. 425-460 ◽  
Author(s):  
RODERICK V. N. MELNIK ◽  
XILIN WEI ◽  
GABRIEL MORENO–HAGELSIEB
Keyword(s):  
Nonlinear Dynamics ◽  
Cell Cycle ◽  
Regulatory Networks ◽  
Deterministic Model ◽  
Phase Portraits ◽  
Nonlinear Phenomena ◽  
Cellular Dynamics ◽  
Cell Cycles ◽  
Special Events ◽  
Wide Range

Cell cycles are fundamental components of all living organisms and their systematic studies extend our knowledge about the interconnection between regulatory, metabolic, and signaling networks, and therefore open new opportunities for our ultimate efficient control of cellular processes for disease treatments, as well as for a wide variety of biomedical and biotechnological applications. In the study of cell cycles, nonlinear phenomena play a paramount role, in particular in those cases where the cellular dynamics is in the focus of attention. Quantification of this dynamics is a challenging task due to a wide range of parameters that require estimations and the presence of many stochastic effects. Based on the originally deterministic model, in this paper we develop a hierarchy of models that allow us to describe the nonlinear dynamics accounting for special events of cell cycles. First, we develop a model that takes into account fluctuations of relative concentrations of proteins during special events of cell cycles. Such fluctuations are induced by varying rates of relative concentrations of proteins and/or by relative concentrations of proteins themselves. As such fluctuations may be responsible for qualitative changes in the cell, we develop a new model that accounts for the effect of cellular dynamics on the cell cycle. Finally, we analyze numerically nonlinear effects in the cell cycle by constructing phase portraits based on the newly developed model and carry out a parametric sensitivity analysis in order to identify parameters for an efficient cell cycle control. The results of computational experiments demonstrate that the metabolic events in gene regulatory networks can qualitatively influence the dynamics of the cell cycle.

Perioperative Skin Conditioning for Patients With Skin of Color

2021 ◽  
pp. 074880682198989
Author(s):  
Alix Ferdinand ◽  
Suzan Obagi
Keyword(s):  
Treatment Regimen ◽  
Skin Care ◽  
Practical Approach ◽  
Postoperative Phase ◽  
Upward Trend ◽  
Wide Range ◽  
Before And After

The interest in cosmetic procedures for patients with skin of color is on an upward trend. Globally, dyschromia and hyperpigmentation remain the most common disorders for which patients seek treatment. The goals of a perioperative skin conditioning program include allowing a broad range of patients to be treated regardless of skin phototypes, maximizing results, and reducing risk of complications such as post-inflammatory hyperpigmentation and managing post-inflammatory hyperpigmentation if it occurs. The purpose of this article is to highlight common pigmentation concerns among patients with skin of color, the topical agents used to combat these concerns, and a practical approach to creating an effective yet straightforward topical skin care regimen that can be used across a wide range of patient skin phototypes. Before and after photos of patients with a variety of pigmentation concerns are presented along with a description of the treatment regimen used to improve their conditions and to get their skin to a safer state prior to performing any office-based procedures. By understanding the main concerns of patients with skin of color, one can use a simple and effective skincare regimen to allow these patients to be more safely treated. An effective skincare regimen both prepares the skin prior to procedures and postoperatively to help minimize dyschromias in the postoperative phase.

scholarly journals Changes in Cellular Regulatory Factors before and after Decompression of Odontogenic Keratocysts

2020 ◽  
Vol 10 (1) ◽  
pp. 30
Author(s):  
Slmaro Park ◽  
Han-Sung Jung ◽  
Young-Soo Jung ◽  
Woong Nam ◽  
Jung Yul Cha ◽  
...  
Keyword(s):  
Recurrence Rate ◽  
Biological Behavior ◽  
Nuclear Antigen ◽  
Epithelial Cyst ◽  
Ki 67 ◽  
Proliferation Markers ◽  
Odontogenic Keratocysts ◽  
Wide Range ◽  
Before And After ◽  
Cyst Lining

Decompression followed by enucleation, which is one of the treatments used for odontogenic keratocysts (OKCs), is frequently used in OKC lesions of large sizes. This method offers the advantage of minimizing the possibility of sensory impairment without creating a wide-range bone defect; moreover, the recurrence rate can be significantly lower than following simple enucleation. This study aimed to assess the changes in histology and expression of proliferation markers in OKCs before and after decompression treatment. A total of 38 OKC tissue samples from 19 patients who had undergone decompression therapy were examined morphologically and immunohistochemically to observe changes in proliferative activity before and after decompression. The markers used for immunohistochemistry (IHC) staining were Bcl-2, epidermal growth factor receptor (EGFR), Ki-67, P53, PCNA, and SMO. The immunohistochemistry positivity of the 6 markers was scored by using software ImageJ, version 1.49, by quantifying the intensity and internal density of IHC-stained epithelium. The values of Bcl-2, Ki-67, P53, proliferating cell nuclear antigen (PCNA), and SMO in OKCs before and after decompression showed no significant change. No correlation between clinical shrinkage and morphologic changes or expression of proliferation and growth markers could be found. There was no statistical evidence that decompression treatment reduces potentially aggressive behavior of OKC within the epithelial cyst lining itself. This might indicate that decompression does not change the biological behavior of the epithelial cyst lining or the recurrence rate.

Recycling to Soils: a Sustainable Way of Sludge Disposal and its Practice in China

2011 ◽  
Vol 183-185 ◽  
pp. 1417-1422 ◽  
Author(s):  
Xiang Sheng Cao ◽  
Xue Jing Meng ◽  
Xue Zheng Meng
Keyword(s):  
Sewage Treatment ◽  
Land Application ◽  
Sludge Treatment ◽  
Sewage Treatment Plants ◽  
Sludge Disposal ◽  
Successful Case ◽  
Urgent Task ◽  
Before And After ◽  
Treatment And Disposal ◽  
Disposal Problem

With the booming construction of sewage treatment plants aiming at environmental protection, China has to face an emerging urgent task to address the sludge treatment and disposal problem. However there is a big controversy in China about the sludge treatment and disposal strategies. Some scientists suggest incinerating, while others insist on landfilling. In this paper, from the perspective of sustainable development and cyclic economy, a detailed analysis of nutrients cycle mainly related to nitrogen and phosphate before and after industrialization was made and a view that sludge should go back to soils to re-establish a sound nutrients cycle was put forward. Then the feasibility for sludge recycle to soils was discussed and some land application methods for sludge were introduced. At last, a successful case of producing compounded fertilizer from dewatered sludge in Northeast China was described in detail.

Nonlinear Dynamics of an Imperfect Microbeam Under an Axial Load and Electric Excitation

2011 ◽  
Author(s):  
Laura Ruzziconi ◽  
Mohammad I. Younis ◽  
Stefano Lenci
Keyword(s):  
Nonlinear Dynamics ◽  
Microelectromechanical Systems ◽  
Complex Dynamics ◽  
Nonlinear Behavior ◽  
Single Mode ◽  
Phase Portraits ◽  
Nonlinear Phenomena ◽  
Theoretical Point ◽  
Initial Shape ◽  
Electric Excitation

This study is motivated by the growing attention, both from a practical and a theoretical point of view, toward the nonlinear behavior of microelectromechanical systems (MEMS). We analyze the nonlinear dynamics of an imperfect microbeam under an axial force and electric excitation. The imperfection of the microbeam, typically due to microfabrication processes, is simulated assuming the microbeam to be of a shallow arched initial shape. The device has a bistable static behavior. The aim is that of illustrating the nonlinear phenomena, which arise due to the coupling of mechanical and electrical nonlinearities, and discussing their usefulness for the engineering design of the microstructure. We derive a single-mode-reduced-order model by combining the classical Galerkin technique and the Pade´ approximation. Despite its apparent simplicity, this model is able to capture the main features of the complex dynamics of the device. Extensive numerical simulations are performed using frequency response diagrams, attractor-basins phase portraits, and frequency-dynamic voltage behavior charts. We investigate the overall scenario, up to the inevitable escape, obtaining the theoretical boundaries of appearance and disappearance of the main attractors. The main features of the nonlinear dynamics are discussed, stressing their existence and their practical relevance. We focus on the coexistence of robust attractors, which leads to a considerable versatility of behavior. This is a very attractive feature in MEMS applications. The ranges of coexistence are analyzed in detail, remarkably at high values of the dynamic excitation, where the penetration of the escape (dynamic pull-in) inside the double well may prevent the safe jump between the attractors.

Space Modeling of Problem Solving Strategies of “Prisoner's Dilemma”

2021 ◽  
pp. 99-116
Author(s):  
D.J. Balanev ◽  
Keyword(s):  
Neural Networks ◽  
Social Identity ◽  
Identity Formation ◽  
Social Factors ◽  
Prisoner's Dilemma ◽  
Prisoner’S Dilemma ◽  
Real People ◽  
Space Modeling ◽  
Wide Range ◽  
Before And After

An iterated version of the game "Prisoner's Dilemma" is used as a model of cooperation largely due to the wide range of strategies that the subjects can use. The problem of the effec-tiveness of strategies for solving the Iterated Prisoner's Dilemma (IPD) is most often considered from the point of view of information models, where strategies do not take into account the relationship that arise when real people play. Some of these strategies are obvious, others depend upon social context. In our paper, we use one of the promising directions in the development of studying IPD strategies – the use of artificial neural networks. We use neural networks as a modeling tool and as a part of game environment. The main goal of our work is to build an information model that predicts the behavior of an individual person as well as group of people in the situation of solving of social dilemma. It takes into account social relationship, including those caused by experimental influence, gender differences, and individual differences in the strategy for solving cognitive tasks. The model demonstrates the transition of individual actions into socially determined behavior. Evaluation of the effect of socialization associated with the procedure of the game provides additional information about the effectiveness and characteristics of the experimental impact.The paper defines the minimum unit of analysis of the IPD player's strategy in a group, the identity with which can be considered as a variable. It discusses the influence of the experi-mentally formed group identity on the change of preferred strategies in social dilemmas. We use the possibilities of neural networks as means of categorizing the results of the prisoner's iterative dilemma in terms of the strategy applied by the player, as well as social factors. We define the patterns of changes in the IPD player's strategy before and after socialization are determined. The paper discusses the questions of real player's inclination to use IPD solution strategies in their pure form or to use the same strategy before and after experimental inter-ventions related to social identity formation. It is shown that experimentally induced socialization can be considered as a mechanism for increasing the degree of certainty in the choice of strategies when solving IPD task. It is found out that the models based on neural networks turn out to be more efficient after experi-mentally evoked social identity in a group of 6 people; and the models based on neural net-works are least effective in the case of predicting a subject's belonging to a gender group. When solving IPD problems by real people, it turns out to be possible to talk about generalized strategies that take into account not only the evolutionary properties of «pure» strategies, but also reflect various social factors.

Model Child Care Health Policies

2013 ◽  
Author(s):  
Keyword(s):  
Child Care ◽  
Early Education ◽  
Health And Safety ◽  
Large Family ◽  
Health Policies ◽  
After School ◽  
Wide Range ◽  
Before And After ◽  
Care Health ◽  
Child Care Facilities

Significantly revised and updated, the new Model Child Care Health Policies, 5th Edition is a must-have tool to foster adoption and implemenation of best practices for health and safety in group care settings for young children. These settings include early care and education as well as before and after school child care programs. These model policies are intended to ease the burden of writing site-specific health and safety policies from scratch. They cover a wide range of aspects of operation of early education and child care programs. Child care programs of any type can use Model Child Care Health Policies by selecting relevant issues for their operation and modifying the wording to make selected policies appropriate to the specific settings. These settings include early education and child care centers, small and large family child care homes, part day-programs for ill children, facilities that serve children with special needs, school-age child care facilities, and drop-in facilities. The model policies can be adapted for public, private, Head Start, and tuition-funded facilities. All of the most commonly covered health and safety topics the National Association of Child Care Resource and Referral Agencies found in state regulations are included in this guide.

Peak calf blood flow estimates are higher with Dohn than with Whitney plethysmograph

1996 ◽  
Vol 81 (3) ◽  
pp. 1418-1422 ◽  
Author(s):  
D. N. Proctor ◽  
J. R. Halliwill ◽  
P. H. Shen ◽  
N. E. Vlahakis ◽  
M. J. Joyner
Keyword(s):  
Blood Flow ◽  
Reactive Hyperemia ◽  
Arterial Occlusion ◽  
Venous Occlusion ◽  
Calf Blood Flow ◽  
Absolute Flow ◽  
Wide Range ◽  
Before And After ◽  
The Mean ◽  
Highly Correlated

Estimates of calf blood flow with venous occlusion plethysmography vary widely between studies, perhaps due to the use of different plethysmographs. Consequently, we compared calf blood flow estimates at rest and during reactive hyperemia in eight healthy subjects (four men and four women) with two commonly used plethysmographs: the mercury-in-silastic (Whitney) strain gauge and Dohn air-filled cuff. To minimize technical variability, flow estimates were compared with a Whitney gauge and a Dohn cuff on opposite calves before and after 10 min of bilateral femoral arterial occlusion. To account for any differences between limbs, a second trial was conducted in which the plethysmographs were switched. Resting flows did not differ between the plethysmographs (P = 0.096), but a trend toward lower values with the Whitney was apparent. Peak flows averaged 37% lower with the Whitney (27.8 +/- 2.8 ml.dl-1.min-1) than with the Dohn plethysmograph (44.4 +/- 2.8 ml.dl-1.min-1; P < 0.05). Peak flow expressed as a multiple above baseline was also lower with the Whitney (10-fold) than with the Dohn plethysmograph (14.5-fold; P = 0.02). Across all flows at rest and during reactive hyperemia, estimates were highly correlated between the plethysmographs in all subjects (r2 = 0.96-0.99). However, the mean slope for the Whitney-Dohn relationship was only 60 +/- 2%, indicating that over a wide range of flows the Whitney gauge estimate was 40% lower than that for the Dohn cuff. These results demonstrate that the same qualitative results can be obtained with either plethysmograph but that absolute flow values will generally be lower with Whitney gauges.

scholarly journals Efficient Removal of Methyl Orange and Rhodamine-B Dyes with Low Cost Banana Peel Activated Carbon

2020 ◽  
Vol 32 (5) ◽  
pp. 1121-1127
Author(s):  
Mahesh Kumar Gupta ◽  
P.K. Tandon ◽  
Neelam Shukla ◽  
Harendra Singh ◽  
Shalini Srivastava
Keyword(s):  
Activated Carbon ◽  
Methyl Orange ◽  
Rhodamine B ◽  
Low Cost ◽  
Banana Peel ◽  
Duration Of Treatment ◽  
Wide Range ◽  
Before And After ◽  
Efficient Adsorbent ◽  
Solution Changes

Acid activated carbon obtained from cheap, non-toxic and locally available banana peel was used as a low cost and efficient adsorbent for the removal of dyes methyl orange and rhodamine-B from the aqueous solution. Changes in the resulting material before and after activation and after treatment were studied by different techniques, such as SEM-EDX, XRD, FTIR measurements. Effects of duration of treatment, amount of banana peel activated carbon, pH, and initial methyl orange and rhodamine-B concentration, on the removal of dye were studied to get optimum conditions for maximum dye removal. Removal efficiency of the activated ash remains almost constant in a wide range of pH from 2.5 to 5.6. In 75 min at room temperature removal of 98.5 % methyl orange (anionic) and 99.0 % rhodamine-B (cationic) dyes with 0.1 g and 0.125 g, respectively was obtained from the contaminated water having 10 ppm dye concentration.

scholarly journals Comparative methodological studies of L-asparaginase encapsulation into erythrocytes

2018 ◽  
Vol 13 (3) ◽  
pp. 91-101
Author(s):  
D. V. Borsakova ◽  
M. E. Plakhotnik ◽  
L. D. Koleva ◽  
E. A. Bovt ◽  
Yu. G. Alexandrovich ◽  
...  
Keyword(s):  
Lymphoblastic Leukemia ◽  
Comparative Investigation ◽  
Hypertonic Solution ◽  
Clinical Use ◽  
Hematological Indices ◽  
Healthy Donors ◽  
Wide Range ◽  
Before And After ◽  
Hypotonic Buffer ◽  
Flow Dialysis

Background. L-asparaginase is an enzyme, widely used in the therapy of acute lymphoblastic leukemia in children and adults, but its use is limited due to a wide range of side effects and anaphylactic reactions. L-asparaginase loaded into erythrocytes can solve these problems. This enzyme is protected from the immune system and plasma proteases due to erythrocyte membrane, but continues to work inside the cell because its membrane is permeable to L-asparagine. Thus, the half-life of the drug increases and anaphylactic reactions reduce. The encapsulation of L-asparaginase into erythrocytes can be performed by various osmotic methods. Each of them is characterized by the amount of encapsulated enzyme, the cell yield, as well as by the quality indices of the survived erythrocytes. An important parameter of each method is the possibility to provide sterility of this dosage form for the clinical use.The aim of the study was the comparing of three osmotic methods of L-asparaginase encapsulation into erythrocytes (hypo-osmotic lysis, dialysis and flow dialysis) to select the most promising method for clinical use.Materials and methods. A suspension of erythrocytes of healthy donors (hematocrit 60–70%) was mixed with L-asparaginase from E. сoli. The procedures of hypotonic reversible lysis, dialysis in dialysis bags, or flow dialysis using pediatric dialyzers were performed. The physiological osmolality was restored in suspensions after the procedure by the addition of a hypertonic solution, and they were incubated for 30 min at 37 °C. Then the cells were washed in isotonic phosphate-buffered saline with pH 7.4. Activity of L-asparaginase, volume, hematocrit, hematological indices and osmotic cell fragility of erythrocytes were measured in the suspensions of erythrocytes before and after the enzyme encapsulation procedure.Results. An optimal osmolality of the hypotonic buffer for each method was selected and was equal to 90–110 mOsm/kg. The yields of encapsulation were 4.2 ± 2.0, 6.0 ± 2.3 and 16.2 ± 2.2 % for hypotonic lysis, dialysis and flow dialysis, respectively. The hematological indices of the obtained erythrocyte-carriers differed from the corresponding parameters of the initial erythrocytes, but did not differ significantly for different methods.Conclusion. Comparative investigation of mentioned above parameters allowed choosing the method of flow dialysis as the most promising for clinical use.

Sign in / Sign up

Export Citation Format

Share Document