Browsing by Subject "Steady state"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Open Access Dynamic implications of the wealth-leisure nexus(Bilkent University, 2022-06) Skenderaj, ArlindoThis thesis analyses a one-sector optimal growth model in which wealth affects the utility obtained from leisure. We consider that an increase in wealth increases the propensity to consume leisure goods and services and hence affects how the instantaneous utility depends on leisure time. We prove the existence of the optimal path and characterize the dynamics and the properties of equilibria. We provide the conditions under which the model has unique or multiple steady states. The intensity of wealth in the utility obtained from leisure and the output elasticity of physical capital play an important role in the number of steady states and in the monotonicity of the optimal path of physical capital. We find that the optimal path of physical capital is monotonic and converges to the unique steady state, provided that the output elasticity of capital is higher than the intensity of wealth in the utility obtained from leisure.Item Open Access Extended phase diagram of ASEP with two types of particles(Bilkent University, 2010) Yeşil, Ayşe FerhanThe ASEP (Asymmetric Simple Exclusion Process) model system with two types of particles is studied. The system is interesting because it exhibits spontaneous symmetry breaking when parameters controlling the dynamics of the two types of particles of the same system. By using Mean Field approximation its extended phase diagram was obtained for non-symmetric values of entering rates of the two types of particles. The system is understood to be the combination of two decoupled ASEP systems with one type of particle system for the values of equal hopping and exchange rates. (Evans et al.,PR E, 74 208, (1995)) It is understood that for the exchange rates different from the hopping rates the system can no longer be analyzed as combination of two decoupled one particle ASEP. The “tiny phase” first observed by Evans et al, is examined in more detail. It is found that this phase still exists when entering rates are not symmetric. Also, Monte Carlo simulations for certain values of parameters of the system were carried out to determine the particle density profiles. The phase diagram of the system displays unexpectedly rich structure for the relatively simple dynamics.Item Open Access Functionally conserved effects of rapamycin exposure on zebrafish(Spandidos Publications, 2016-03) Sucularli, C.; Shehwana, H.; Kuscu, C.; Dungul, D. C.; Ozdag, H.; Konu, O.Mechanistic target of rapamycin (mTOR) is a conserved serine/threonine kinase important in cell proliferation, growth and protein translation. Rapamycin, a well-known anti-cancer agent and immunosuppressant drug, inhibits mTOR activity in different taxa including zebrafish. In the present study, the effect of rapamycin exposure on the transcriptome of a zebrafish fibroblast cell line, ZF4, was investigated. Microarray analysis demonstrated that rapamycin treatment modulated a large set of genes with varying functions including protein synthesis, assembly of mitochondrial and proteasomal machinery, cell cycle, metabolism and oxidative phosphorylation in ZF4 cells. A mild however, coordinated reduction in the expression of proteasomal and mitochondrial ribosomal subunits was detected, while the expression of numerous ribosomal subunits increased. Meta-analysis of heterogeneous mouse rapamycin microarray datasets enabled the comparison of zebrafish and mouse pathways modulated by rapamycin, using Kyoto Encyclopedia of Genes and Genomes and Gene Ontology pathway analysis. The analyses demonstrated a high degree of functional conservation between zebrafish and mice in response to rapamycin. In addition, rapamycin treatment resulted in a marked dose-dependent reduction in body size and pigmentation in zebrafish embryos. The present study is the first, to the best of our knowledge, to evaluate the conservation of rapamycin-modulated functional pathways between zebrafish and mice, in addition to the dose-dependent growth curves of zebrafish embryos upon rapamycin exposure.Item Open Access Profile-encoding reconstruction for multiple-acquisition balanced steady-state free precession imaging(John Wiley and Sons Inc., 2017) Ilicak, Efe; Senel, Lutfi Kerem; Biyik, Erdem; Çukur, TolgaPurpose: The scan-efficiency in multiple-acquisition balanced steady-state free precession imaging can be maintained by accelerating and reconstructing each phase-cycled acquisition individually, but this strategy ignores correlated structural information among acquisitions. Here, an improved acceleration framework is proposed that jointly processes undersampled data across N phase cycles. Methods: Phase-cycled imaging is cast as a profile-encoding problem, modeling each image as an artifact-free image multiplied with a distinct balanced steady-state free precession profile. A profile-encoding reconstruction (PE-SSFP) is employed to recover missing data by enforcing joint sparsity and total-variation penalties across phase cycles. PE-SSFP is compared with individual compressed-sensing and parallel-imaging (ESPIRiT) reconstructions. Results: In the brain and the knee, PE-SSFP yields improved image quality compared to individual compressed-sensing and other tested methods particularly for higher N values. On average, PE-SSFP improves peak SNR by 3.8 ± 3.0 dB (mean ± s.e. across N = 2–8) and structural similarity by 1.4 ± 1.2% over individual compressed-sensing, and peak SNR by 5.6 ± 0.7 dB and structural similarity by 7.1 ± 0.5% over ESPIRiT. Conclusion: PE-SSFP attains improved image quality and preservation of high-spatial-frequency information at high acceleration factors, compared to conventional reconstructions. PE-SSFP is a promising technique for scan-efficient balanced steady-state free precession imaging with improved reliability against field inhomogeneity. Magn Reson Med 78:1316–1329, 2017.Item Open Access Targeting IRE1 with small molecules counteracts progression of atherosclerosis(National Academy of Sciences, 2017-01) Tufanli, O.; Akillilar, P. T.; Acosta-Alvear, D.; Kocaturk, B.; Onat, U. I.; Hamid, S. M.; Çimen, I.; Walter, P.; Weber, C.; Erbay, E.Metaflammation, an atypical, metabolically induced, chronic lowgrade inflammation, plays an important role in the development of obesity, diabetes, and atherosclerosis. An important primer for metaflammation is the persistent metabolic overloading of the endoplasmic reticulum (ER), leading to its functional impairment. Activation of the unfolded protein response (UPR), a homeostatic regulatory network that responds to ER stress, is a hallmark of all stages of atherosclerotic plaque formation. The most conserved ERresident UPR regulator, the kinase/endoribonuclease inositol-requiring enzyme 1 (IRE1), is activated in lipid-laden macrophages that infiltrate the atherosclerotic lesions. Using RNA sequencing in macrophages, we discovered that IRE1 regulates the expression of many proatherogenic genes, including several important cytokines and chemokines. We show that IRE1 inhibitors uncouple lipid-induced ER stress from inflammasome activation in both mouse and human macrophages. In vivo, these IRE1 inhibitors led to a significant decrease in hyperlipidemia-induced IL-1β and IL-18 production, lowered T-helper type-1 immune responses, and reduced atherosclerotic plaque size without altering the plasma lipid profiles in apolipoprotein E-deficient mice. These results show that pharmacologic modulation of IRE1 counteracts metaflammation and alleviates atherosclerosis.