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Local controllability of models of combined anticancer therapy with delays in control
No full textWe present sufficient conditions of local controllability for a class of models of treatment response to combined anticancer therapies which include delays in control strategies. The combined therapy is understood as combination of direct anticancer strategy e.g. chemotherapy and indirect modality (in this case antiangiogenic therapy). Controllability of the models in the form of semilinear second order dynamic systems with delays in control enables to answer the questions of realizability of different objectives of multimodal therapy in the presence of PK/PD effects. We compare results for the models without delays and conditions for relative local controllability of models with delays. © EDP Sciences, 2014
Evolutionary dynamics of cancer cell populations under immune selection pressure and optimal control of chemotherapy
No full textIncreasing experimental evidence suggests that epigenetic and microenvironmental factors play a key role in cancer progression. In this respect, it is now generally recognized that the immune system can act as an additional selective pressure, which modulates tumor development and leads, through cancer immunoediting, to the selection for resistance to immune effector mechanisms. This may have serious implications for the design of effective anti-cancer protocols. Motivated by these considerations, we present a mathematical model for the dynamics of cancer and immune cells under the effects of chemotherapy and immunity-boosters. Tumor cells are modeled as a population structured by a continuous phenotypic trait, that is related to the level of resistance to receptor-induced cell death triggered by effector lymphocytes. The level of resistance can vary over time due to the effects of epigenetic modifications. In the asymptotic regime of small epimutations, we highlight the ability of the model to reproduce cancer immunoediting. In an optimal control framework, we tackle the problem of designing effective anti-cancer protocols. The results obtained suggest that chemotherapeutic drugs characterized by high cytotoxic effects can be useful for treating tumors of large size. On the other hand, less cytotoxic chemotherapy in combination with immunity-boosters can be effective against tumors of smaller size. Taken together, these results support the development of therapeutic protocols relying on combinations of less cytotoxic agents and immune-boosters to fight cancer in the early stages. © EDP Sciences, 2014
A Semiparametric Estimation for Regression Functions in the Partially Linear Autoregressive Time Series Model
Get PDFIn this paper, a semiparametric method is proposed for estimating regression function in the partially linear autoregressive time series model . Here, we consider a combination of parametric forms and nonlinear functions, in which the errors are independent. Semiparametric and nonparametric curve estimation provides a useful tool for exploring and understanding the structure of a nonlinear time series data set to make for a more efficient study in the partially linear autoregressive model. The unknown parameters are estimated using the conditional nonlinear least squares method, and the nonparametric adjustment is also estimated by defining and minimizing the local L2 -fitting criterion with respect to the nonparametric adjustment and, with smooth-kernel method , these estimates are corrected. Then, the autoregression function estimators, which can be calculated with the sample and simulation data , are obtained. In this case , some strong and weak consistency and simulated results for the semiparametric estimation in this model are presented . The root mean square error and the average square error criterions are also applied to verify the efficiency of the suggested model
Solution of the SIR models of epidemics using MSGDTM
Get PDFStochastic compartmental (e.g., SIR) models have proven useful for studying the epidemics of childhood diseases while taking into account the variability of the epidemic dynamics. Here, we use the multi-step generalized differential transform method (MSGDTM) to approximate the numerical solution of the SIR model and numerical simulations are presented graphically
Molybdopterin biosynthesis: Trapping of intermediates for the MoaA-catalyzed reaction using 2′-deoxyGTP and 2′-chloroGTP as substrate analogues.
No full textMoaA is a radical S-adenosylmethionine (AdoMet) enzyme that catalyzes a complex rearrangement of guanosine-5\u27-triphosphate (GTP) in the first step of molybdopterin biosynthesis. In this paper, we provide additional characterization of the MoaA reaction product, describe the use of 2′-chloroGTP to trap the GTP C3′ radical, generated by hydrogen atom transfer to the 5′-deoxyadenosyl radical, and the use of 2′-deoxyGTP to block a late step in the reaction sequence. These probes, coupled with the previously reported trapping of an intermediate in which C3′ of the ribose is linked to C8 of the purine, allow us to propose a plausible mechanism for the MoaA-catalyzed reaction. © 2014 American Chemical Society
Modelling the Dynamics of a Renewable Resource under Harvesting with Taxation as a Control Variable
Get PDFThe present paper describes a model of resource biomass and population with a non-linear catch rate function on resource biomass. The harvesting effort is assumed to be a dynamical variable. Tax on per unit harvested resource biomass is used as a tool to control exploitation of the resource. Pontryagin’s Maximum Principle is used to find the optimal control to maintain the resource biomass and population at an optimal level. A numerical simulation is also carried out to support the analytical results
A Characterization of Skew Normal Distribution by Truncated Moment
Get PDFA probability distribution can be characterized through various methods. This paper discusses a new characterization of skew normal distribution by truncated moment. It is hoped that the findings of the paper will be useful for researchers in different fields of applied science
Effect of Slip Condition on Coup le Stress Fluid Flow in a Channel with Mild Stenosis in the Presence of Uniform Magnetic Field
Get PDFThe s teady flow of an incompressible couple stress fluid in a two dimensional uniform channel with stenosis under the influence of a magnetic field has been investigated. Assuming the stenosis to be mild, the flow equations have been analy tically solved using the slip condition and expressions for the resistance to flow and wall shear stress have been derived. The effects of various parameters on these flow variables have been studied. It is found that the resistance to flow as well as the wall shear stress increase with the height of the stenosis and decrease with the couple stress and magnetic parameters. The effects of other parameters on resistance to flow and the wall shear stress have been considered
Growth Patterns of Ethnic Groups in Bexar County With Dynamic Leslie Models
Get PDFThe purpose of this study is to modify the Leslie model with a dynamic matrix for better population projections in Bexar County, where UIW is located and the authors reside. A dynamic matrix was used to improve the static Leslie model used in the previous study since human population growth is dynamic and complex. The matrix was constructed with functions that modeled the birth rates and survival rates. This allowed the rates to change from year to year. The population projections using the dynamic matrix were compared to the real population data and the static matrix. The researcher concluded that the dynamic matrix produced good population projections for the ethnic groups in Bexar County when compared with actual census data. Some preliminary projections were also made for the election cycles in the immediate and mid-range future
Domination Integrity of Some Path Related Graphs
Get PDFThe stability of a communication network is one of the important parameters for network designers and users. A communication network can be considered to be highly vulnerable if the destruction of a few elements cause large damage and only few members are able to communicate. In a communication network several vulnerability measures like binding number, toughness, scattering number, integrity, tenacity, edge tenacity and rupture degree are used to determine the resistance of network to the disruption after the failure of certain nodes (vertices) or communication links (edges). Domination theory also provides a model to measure the vulnerability of a graph network. The domination integrity of a simple connected graph is one such measure. Here we determine the domination integrity of square graph of path as well as the graphs obtained by composition (lexicographic product) of two paths