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Purpose Size-specific dose estimates (SSDEs) are the latest focus of interest among medical physicists studying radiation dose to the patient in computed tomography (CT). This study aims to make conversions from CTDIvol to SSDE and investigate the relationship between mean SSDE (SSDE) and central SSDE (SSDEcenter) values for pediatric patients of different age groups undergoing chest, abdomen, and pelvis scans. Methods In this retrospective study, we examined 105 consecutive pediatric CT exams of chest, abdomen, and pelvis (CAP) classified in 3 separate groups according to age: 0-5 years, 6-10 years, and 11-16 years. A MATLAB program was developed to determine SSDE values for each patient along 6 subregions: chest, abdomen, pelvis, chest and abdomen, abdomen and pelvis, and CAP. SSDE values derived over the slice at the center of each scan range (SSDEcenter) were also recorded. SSDE and corresponding SSDEcenter results were compared for each age group. Results Root mean square differences (RMSD) between SSDE and SSDEcenter values ranged between 0.13 mGy and 2.1 mGy through all groups and subregions, corresponding to 1.2% and 11%, respectively. Conclusion In pediatric CT exams involving CAP region, CTDIvol and the water equivalent diameter at the middle of the scan range can be used to provide a reasonable estimate of mean SSDE with an RMSD of 11% at most.

The behavior of beta particles under the magnetic field was investigated both theoretically and experimentally based on the assumption of reducing the damage to the normal tissues created by using magnetic field in radionuclide therapy.A water-filled spherical medium and a beta particle source was formed by using Geant4 simulation software for the theoretical study. After applying a homogenous magnetic field, the volume of points at which the particles interact with the medium was calculated by determining particle range. The range of beta particles was examined using yttrium-90 source and Gafchromic films for the experimental study. The setup was kept in normal room conditions and in the magnetic resonance imaging device. Then the irradiated films were analyzed by creating isodose curves.With the increase of the magnetic field, the number of hits at the center was increased, but the number of hits at the outer boundaries decreased inversely proportional to the strength of the magnetic field. The change perpendicular to the magnetic field was greater as compared to the change parallel to the magnetic field. The volume of hits of beta particles got smaller with the increase of the magnetic field.When magnetic field is increased, the decrease in the number of interactions at the outer boundaries became more pronounced in the perpendicular direction to the magnetic field. The effect of magnetic field was more apparent for higher energy beta particles than lower energy particles.Amaç: Beta yayan radyoizotoplarla yapılan kanser tedavilerinde manyetik alan kullanılarak normal dokularda oluşan zararın azaltılmasının mümkün olabileceği varsayımı ile beta parçacıklarının manyetik alandaki davranışları teorik ve deneysel olarak araştırıldı. Yöntem: Teorik çalışmada, Geant4 programında içi su dolu küresel bir ortam oluşturuldu ve merkezine beta parçacığı kaynağı yerleştirildi. Homojen bir manyetik alan uygulanarak parçacıkların ortamla etkileştikleri noktaların hacmi, parçacıklarının menzilleri belirlenerek hesaplandı. Deneysel çalışmada, beta parçacıklarının menzili itriyum-90 kaynağı ve Gafkromik film kullanılarak incelendi. Düzenek normal oda koşullarında ve manyetik rezonans görüntüleme cihazında bekletildi. Işınlanan filmler izodoz eğrileri oluşturularak analiz edildi. Bulgular: Manyetik alan artmasıyla beraber merkezde etkileşim sayısında artma olduğu, merkezin dışında ise etkileşim sayısının manyetik alanla ters orantılı olarak azaldığı görüldü. Manyetik alana dik yöndeki değişim manyetik alana paralel yöndekine göre daha fazla idi. Manyetik alanın artmasıyla beta parçacıklarının etkileştiği hacim küçülmekte idi. Sonuç: Manyetik alan arttıkça, manyetik alana dik yönlerde merkezin dışındaki alanlarda etkileşim sayısındaki azalım daha belirgin olmaktadır. Manyetik alan etkisinin düşük enerjililere oranla yüksek enerjili beta parçacıklarında daha belirgin olduğu görülmüştür.

WOS: 000271864200007, Valence band structure with spin-orbit (SO) coupling of GaAs/Ga1-xAlxAs square quantum well (SQW) under the electric field by a calculation procedure based on a finite element method (FEM) is investigated using the multiband effective mass theory ((k) over right arrow . (p) over right arrow method). The validity of the method is confirmed with the results of D. Ahn, S. L. Chuang and Y. C. Chang (J. Appl. Phys. 64 (1998) 4056), who calculated valence band structure, using axial approximation for Luttinger-Kohn Hamiltonian and finite difference method. Our results demonstrated that SO coupling and electric field have significant effects on the valence band structure., T. R. Prime Ministry State Planning Organization [DPT-120220], The authors would like to thank the T. R. Prime Ministry State Planning Organization for financial support (project No. DPT-120220).

In this work, the effects of an off-center attractive Gaussian impurity on the ground-state energy and spin properties of parabolic quantum-dot lithium are investigated with Configuration Interaction Method. Phase transition between spin-1/2 and spin-3/2 states of the system is obtained for various strengths of the impurity potential and the electron-electron interaction. Charge densities of the system are studied in different interaction regimes. Numerical results reveal that the gap between two spin states is increased by the impurity which consequently yields to the suppression of the polarization. (C) 2015 Elsevier B.V. All rights reserved.

State-selective differential cross sections for single-electron capture processes in very slow collisions of Arq+ (q = 4–6) ions with neon (Ne) have been studied experimentally at laboratory impact energies between 0.4 and 4 qeV/amu and scattering angles between 0 ° and 8 ° by means of the translational energy-gain spectroscopy technique. The translational energy spectra show that the dominant reaction channels are due to capture into excited states of the projectile product Ar(q−1)+. However, at very low energies, other channels due to transfer excitation processes are found to open at large scattering angles. The energy-gain spectra are interpreted qualitatively in terms of the reaction windows, which are calculated using the single-crossing Landau-Zener model and the extended version of the classical over-the-barrier model. The energy dependence of cross sections for single-electron capture by Arq+ (q = 4–8) ions from Ne are also measured and found to be nearly constant with changing impact energy, but increase with an increase in the projectile charge state. The data are also compared with available measurements and theoretical calculations. Copyright © 1999 John Wiley & Sons, Ltd.

IntroductionVolumecomputed tomography dose index(CTDIvol) does not contain any dose information regarding the patient size. Size specific dose estimates (SSDE) give more reliable results accounting for the patient size as well. This parameter uses CTDIvol and size dependent conversion factors (fDw) which are calculated by means of water equivalent diameter (Dw) of the patient cross section in every slice of image.PurposeTo develop software to automatically calculate SSDE and to assess the impact of variations in Dw along the z axis on SSDE for CT examinations of the torso in pediatric patients.Materials and methods55 consecutive CT exams of the combined chest, abdomen and pelvis (CAP) have been examined. SSDE has been calculated for 6 hypothetical scan ranges: chest alone, abdomen alone, pelvis alone, chest and abdomen, abdomen and pelvis, and CAP. Two methods were used in mean SSDE approach: (1) mean SSDE over each scan range; (2) SSDE value at the middle of the scan range.ResultsFor scan ranges 1 to 6, the average of the difference in maximal and minimal Dw accross patients was 3.7, 3.8, 2.6, 4.1, 4.4 and 4.5 cm. The mean SSDE values calculated using methods (1) and (2) were highly compatible, with root mean square differences of 0.4, 0.5, 0.3, 1.0, 1.5 and 0.7mGy or 3%, 4%, 2%, 7%, 10%, 5%.ConclusionUsing the mean CTDIvol and the water equivalent diameter at the middle of the scan range provides a reasonable estimation of patient dose in pediatric exams.

In this work we solve thermo-hydrodynamical equations considering a two dimensional electron system in the integer quantum Hall regime, to calculate the spatial distribution of the local electron temperature. We start from the self-consistently calculated electrostatic and electrochemical potentials in equilibrium. Next, by imposing an external current, we investigate the variations of the electron temperature in the linear-response regime. Here a local relation between the electron density and conductivity tensor elements is assumed. Following the Ohm's law we obtain local current densities and by implementing the results of the thermo-hydrodynamical theory, calculate the local electron temperature. We observe that the local electron temperature strongly depends on the formation of compressible and incompressible strips., Comment: 10 pages, 4 figures

We calculated the total energy of a semiconductor quantum dot formed in gate and etching defined devices. A 3D Poisson equation is solved self-consistently to obtain the electron density and potential profile. The total energies of electrons in the quantum dots with two different sizes are calculated with three different approximations by using the density and potential obtained from self-consistent procedure. In our calculation we used a recently developed energy functional called "orbital-free energy functional", Thomas-Fermi approximation and standard local-density approximation within density functional theory. The comparison of these methods reveals the efficacy of the used newly developed orbital-free energy functional which facilitates the calculation of Hartree integral for treatment of electron-electron interaction. (C) 2011 Elsevier B.V. All rights reserved.

In this study the electronic eigenstructure of an exciton in a parabolic quantum dot (QD) has been calculated with a high accuracy by using Finite element method (FEM). We have converted the coordinates of electronlight-hole system to relative and center of mass coordinate, then placed the Spherical Harmonics into Schrödinger equation analytically and obtained the Schrödinger equation which depends only on the radial variable. Finally we used FEM with only radial variable in order to get the accurate numerical results. We also showed first 21 energy level spectra of exciton depending on confinement and Coulomb interaction parameters. © 2011 World Scientific Publishing Company., Cumhuriyet Üniversitesi TBAG 105T492, TBAG 107T012, TBAG-108T015, The authors acknowledge the support of the Cumhuriyet University, National MOVPE Crystal Growth and Characterization Laboratory, Turkey, DPT-K 120, TUBITAK Grants TBAG 105T492, TBAG 107T012, and TBAG-108T015., Do?an, Ü.; Physics Department, Dokuz Eylül University, Izmir, 35160, Turkey; email: umit.dogan@deu.edu.tr

WOS: 000289155800009, A study of variational wave functions for calculation of the ground-state energies of excitons confined in a two-dimensional (2D) disc-like and three-dimensional (3D) spherical parabolic GaAs quantum dots (QDs) is presented. We have used four variational trial wave functions constructed as the harmonic-oscillator basis multiplied by different correlation functions. The proposed correlation function formed by including linear expansion in terms of Hylleraas-like coordinates to the Jastrow factor is able to capture nearly exactly the ground-state energies of 31) excitons, and it properly account for the results of 2D excitons. Quantum Monte Carlo techniques combined with the proposed wave function are a powerful tool for studying excitons in parabolic QDs., Cumhuriyet University; National MOVPE Crystal Growth and Characterization Laboratory, Turkey [DPT-K 120]; TUBITAK [TBAG 105T492, TBAG 107T012, TBAG-10ST015], The authors acknowledge the support of the Cumhuriyet University, National MOVPE Crystal Growth and Characterization Laboratory, Turkey, DPT-K 120, TUBITAK Grants TBAG 105T492, TBAG 107T012, and TBAG-10ST015.

WOS: 000264290900048, In this work, the effects of quantum confinement on the ground state energy of a correlated electron-hole pair in a spherical and in a disc-like quantum dot have been investigated as a function of quantum dot size. Under parabolic confinement potential and within effective mass approximation Ritz's variational method is applied to Hylleraas-like trial wavefunction. An efficient method for reducing the main effort of the calculation of terms like r(ch)(k) exp (-lambda r(eh)) is introduced. The main contribution of the present work is the introduction of integral transforms which provide the calculation of expectation value of energy and the related matrix elements to be done analytically over single-particle coordinates instead of Hylleraas coordinates.

WOS: 000268802300062, In this work, we propose an efficient method of reducing the computational effort of variational calculation with a Hylleraas-like trial wavefunction. The method consists of introducing integra transforms for the terms as r(12)(k) exp (-lambda r(12)) which provide the calculation of the expectation value of energy and the relevant matrix elements to be done analytically over single-electron coordinates instead of Hylleraas coordinates. we have used this method to calculate the ground state energy of a two-electron system in a spherical dot and a disk-like quantum dot separately. Under parabolic confinement potential and within effective mass approximation size and shape effects of quantum dots on the ground state energy of two electrons have been investigated. The calculation shows that our results even with a small number of basis states are in good agreement with previous theoretical results., Cumhuriyet University; National MOVPE Crystal Growth and Characterization Laboratory, Turkey [DPT-K 120]; TUBITAK [TBAG 105T492, TBAG 107T012, TBAG-108T015], Project supported by the Cumhuriyet University, National MOVPE Crystal Growth and Characterization Laboratory, Turkey, DPT-K 120, TUBITAK (Grant Nos TBAG 105T492, TBAG 107T012, and TBAG-108T015).

State-selective, non-dissociative electron capture processes by very slow nitrogen dications from atoms (He, Ne and Ar) and molecules (D 2 , N 2 and O 2 ) has been studied experimentally at impact energies of 28 eV by means of ion translational energy spectrometry and theoretically by means of ab initio configuration interaction calculations of the potential energy curves involved in the electron capture process. Information is obtained on the principal quantal states involved in the incoming and outgoing channels; indications are obtained that the electron capture occurs primarily into electronically-excited states of N 2 + and that the dynamics may involve non-Franck-Condon routes.

Doubly differential cross sections, in energy and angle, for state-selective single-electron capture by Ne3+, Ne4+ ions from Ne, and Ne6+ ions from He have been measured at laboratory impact energies between 60 and 600 eV and scattering angles between 0 degrees and 5 degrees. The measurements show that the angular distributions of the reaction channels with large energy-gain values are shifted towards larger scattering angles as would be expected. The energy-gain spectra are interpreted qualitatively in terms of the reaction window, which are calculated using the single-crossing Landau-Zener model.

The title compound, C16H17NO2, was found to crystallize in the triclinic space group P1. The unit cell parameters are: a = 8.279(1)A, b = 14.843(2)A, c = 5.959(1)A, α = 97.02(1)°, β = 102.75(1)°, γ = 100.52(1)°; Z = 2. The molecule is not planar. The ethoxy group is almost coplanar with the ethoxyphenyl ring, the hydroxy group and the central moiety of the molecule are almost in the hydroxyphenyl ring plane. The dihedral angle between the two planes is 65.4(1)°. The crystal structure is stabilized by weak intermolecular interactions of the C-H···O type.

Double differential cross sections for state-selective single-electron capture processes in Ar6+-He collisions have been measured at laboratory energies between 75 and 900 eV and scattering angles between 0 and 8 degrees. At the lowest energy, the zero-angle spectrum shows capture into Ar5+(4p) to be the most important channel. However,as the scattering angle is increased, a second peak appears at angles greater than or equal to 2 degrees and becomes more pronounced relative to the 4p capture channel. The energy spectra are interpreted qualitatively in terms of the reaction windows, which are calculated using the single-crossing Landau-Zener model Total and differential cross sections are also measured and compared with available measurements and calculations.