In this study, a combination of spectral and fixed point methods is used to solve an optimal control problem for a model of tumour growth. The growth of tumour is modelled using three first-order hyperbolic equations describing the evolution of cells and two second-order parabolic equations describing the diffusion of nutrient and drug concentration. In the optimal control problem, four control variables are employed to control the concentration of nutrient and drug on the boundary and inside the tumour. Since the problem is nonlinear, applying the fixed point method, in each step of iteration, the problem is changed to a linear one and the parabolic equations are solved using the spectral method. The convergence and stability of method are proven. Some examples are considered to illustrate the efficiency of method. Finally, some figures are provided to reflect the effects of control on the densities of tumourcells. 相似文献
Myocardial infarction is remains the leading cause of death in developed countries. Recent data show that the composition of the extracellular matrix might differ despite similar heart function and infarction sizes. Because collagen is the main component of the extracellular matrix, we hypothesized that changes in inflammatory cell recruitment influence the synthesis of different collagen subtypes in myofibroblasts, thus changing the composition of the scar. We found that neutrophils sustain the proliferation of fibroblasts, remodeling, differentiation, migration and inflammation, predominantly by IL-1 and PPARγ pathways (n = 3). They also significantly inhibit the mRNA expression of fibrillar collagen, maintaining a reduced stiffness in isolated myofibroblasts (n = 4–5). Reducing the neutrophil infiltration in CCR1−/− resulted in increased mRNA expression of collagen 11, moderate expression of collagen 19 and low expression of collagen 13 and 26 in the scar 4 weeks post infarction compared with other groups (n = 3). Mononuclear cells increased the synthesis of all collagen subtypes and upregulated the NF-kB, angiotensin II and PPARδ pathways (n = 3). They increased the synthesis of collagen subtypes 1, 3, 5, 16 and 23 but reduced the expression of collagens 5 and 16 (n = 3). CCR2−/− scar tissue showed higher levels of collagen 13 (n = 3), in association with a significant reduction in stiffness (n = 4–5). Upregulation of the inflammation-related genes in myofibroblasts mostly modulated the fibrillar collagen subtypes, with less effect on the FACIT, network-forming and globular subtypes (n = 3). The upregulation of proliferation and differentiation genes in myofibroblasts seemed to be associated only with the fibrillar collagen subtype, whereas angiogenesis-related genes are associated with fibrillar, network-forming and multiplexin subtypes. In conclusion, although we intend for our findings to deepen the understanding of the mechanism of healing after myocardial infarction and scar formation, the process of collagen synthesis is highly complex, and further intensive investigation is needed to put together all the missing puzzle pieces in this still incipient knowledge process. 相似文献
In this paper, employing a fixed point-collocation method, we solve an optimal control problem for a model of tumor growth with drug application. This model is a free boundary problem and consists of five time-dependent partial differential equations including three different first-order hyperbolic equations describing the evolution of cells and two second-order parabolic equations describing the diffusion of nutrient and drug concentration. In the mentioned optimal control problem, the concentration of nutrient and drug is controlled using some control variables in order to destroy the tumor cells. In this study, applying the fixed point method, we construct a sequence converging to the solution of the optimal control problem. In each step of the fixed point iteration, the problem changes to a linear one and the parabolic equations are solved using the collocation method. The stability of the method is also proved. Some examples are considered to illustrate the efficiency of method. 相似文献
A patient-friendly delivery system to release human growth hormone (hGH) is very desirable. In situ forming implant systems (ISIs) can provide a long acting and effective protein delivery. In these systems, solvents and additives play major roles in drug release. In this study, four groups of PLGA-based ISIs containing hGH were prepared in N-methyl-2-pyrrolidone (NMP) and poly(ethylene glycol) dimethyl ether (PEG-DME) as solvents with and without tris(hydroxymethyl) aminomethane (Tris) as stabilizer. Several analyses were used to investigate the implants, which include release profile, viscosity, contact angle, gel permeation chromatography (GPC), scanning electron microscopy (SEM), hGH and IGF-1 serum measurements and histopathology. In in vitro release experiments, the hGH cumulative release from PEG-DME system was twice that from NMP system during 14 days, and hGH release was tripled in the presence of Tris. With the addition of Tris to the ISIs containing PEG-DME, the water penetration, interconnectivity of pores and inner channels, surface pores and hydrophilicity were increased. Moreover, the effect of Tris on the hGH stabilization synergized its positive effects and increased the hGH final cumulative release. Results of the ISIs containing PEG-DME and Tris injection in rabbits demonstrated a reduced tissue inflammation. Moreover, the 14-days serum levels of the hGH and IGF-1 of this system in recipient rabbits were comparable to those of the commercial daily injection samples.
Silicon - In this study, by using of density functional theory calculations, the oxidation of methylene on surface of Tin-doped boron nitride nanocage via Langmuir Hinshelwood and Eley Rideal... 相似文献