Browsing by Author "Saglam, M."

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Open Access
A critical look at quantum diffusion and some of its interesting aspects
(Springer, 2007) Mukhopadhyay, S.; Saglam, M.; Chatterjee, A.
A fresh and critical look has been given to the long-time behaviour of the quantum diffusion problem and a marginally more accurate solution has been obtained as compared to the one reported in the recent literature. Attempt has also been made to bring out a few interesting generic features of this problem which may have important bearing on real systems in the quantum domain.
Open Access
The effects of respiratory muscle training on resting-state brain activity and thoracic mobility in healthy subjects: A randomized controlled trial
(2022-06-28) Karli-Oguz, Kader; Dasgin, Hacer; Vardar-Yagli, N.; Saglam, M.
Background: Although inspiratory muscle training (IMT) is an effective intervention for improving breath perception, brain mechanisms have not been studied yet. Purpose: To examine the effects of IMT on insula and default mode network (DMN) using resting-state functional MRI (RS-fMRI). Study Type: Prospective. Population: A total of 26 healthy participants were randomly assigned to two groups as IMT group (n = 14) and sham IMT groups (n = 12). Field Strength/Sequence: A 3-T, three-dimensional T2* gradient-echo echo planar imaging sequence for RS-fMRI was obtained. Assessment: The intervention group received IMT at 60% and sham group received at 15% of maximal inspiratory pressure (MIP) for 8 weeks. Pulmonary and respiratory muscle function, and breathing patterns were measured. Groups underwent RS-fMRI before and after the treatment. Statistical Tests: Statistical tests were two-tailed P < 0.05 was considered statistically significant. Student’s test was used to compare the groups. One-sample t-test for each group was used to reveal pattern of functional connectivity. A statistical threshold of P < 0.001 uncorrected value was set at voxel level. We used False discovery rate (FDR)-corrected P < 0.05 cluster level. Results: The IMT group showed more prominent alterations in insula and DMN connectivity than sham group. The MIP was significantly different after IMT. Respiratory rate (P = 0.344), inspiratory time (P = 0.222), expiratory time (P = 1.000), and inspiratory time/total breath time (P = 0.572) of respiratory patterns showed no significant change after IMT. All DMN components showed decreased, while insula showed increased activation significantly. Data Conclusion: Differences in brain activity and connectivity may reflect improved ventilatory perception with IMT with a possible role in regulating breathing pattern by processing interoceptive signals. Evidence Level: 2 Technical Efficacy: Stage 4
Open Access
Polaronic effects in a gaussian quantum dot
(Elsevier, 2008) Yanar, S.; Sevim, A.; Boyacioglu, B.; Saglam, M.; Mukhopadhyaya, S.; Chatterjee, A.
The problem of an electron interacting with longitudinal-optical (LO) phonons is investigated in an N-dimensional quantum dot with symmetric Gaussian confinement in all directions using the Rayleigh-Schrödinger perturbation theory, a variant of the canonical transformation method of Lee-Low-Pines, and the sophisticated apparatus of the Feynman-Haken path-integral technique for the entire range of the coupling parameters and the results for N = 2 and N = 3 are obtained as special cases. It is shown that the polaronic effects are quite significant for small dots with deep confining potential well and the parabolic potential is only a poor approximation of the Gaussian confinement. The Feynman-Haken path-integral technique in general gives a good upper bound to the ground state energy for all values of the system parameters and therefore is used as a benchmark for comparison between different methods. It is shown that the perturbation theory yields for the ground state polaron self-energy a simple closed-form analytic expression containing only Gamma functions and in the weak-coupling regime it provides the lowest energy because of an efficient partitioning of the Gaussian potential and the subsequent use of a mean-field kind of treatment. The polarization potential, the polaron radius and the number of virtual phonons in the polaron cloud are obtained using the Lee-Low-Pines-Huybrechts method and their variations with respect to different parameters of the system are discussed.
Open Access
Quantum size effect on the phonon-induced Zeeman splitting in a GaAs quantum dot with Gaussian and parabolic confining potentials
(Elsevier B.V., 2008) Mukhopadhyaya, S.; Boyacioglu, B.; Saglam, M.; Chatterjee, A.
The Zeeman splitting of the ground and the first excited level of a Gaussian GaAs quantum dot is studied in the presence of electron-longitudinal-optical (LO)-phonon interaction incorporating the spin of the electron and is compared with the case of a parabolic dot. It is shown that the Zeeman splitting is suppressed because of the polaronic interaction and becomes strongly size dependent, but the parabolic confinement overestimates this Zeeman suppression. It is also shown that although the energy levels are split because of the spin-field interaction, the cyclotron frequencies and the Zeeman lines are independent of the electron spin in the dipole transition. © 2008 Elsevier B.V. All rights reserved.