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influence of thyroid volume reduction on absorbed dose in ^(131)i therapy studied by using Geant4 monte Carlo simulation

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Chinese Physics C 2014年第5期38卷 62-68页

作者： Ziaur Rahman Sikander m mirza Waheed Arshed Nasir m mirza Waheed Ahmed Health Physics Division Pakistan Institute of Nuclear Science and Technology Department of Physics and Applied mathematics Pakistan Institute of Engineering and Applied Sciences

A simulation study has been performed to quantify the effect of volume reduction on the thyroid absorbed dose per decay and to investigate the variation of energy deposition per decay due to β- and γ-activity of 131i with volume/mass of thyroid, for water, iCRP- and iCRU-soft tissue taken as thyroid material. A monte Carlo model of the thyroid, in the Geant4 radiation transport simulation toolkit was constructed to compute the β- and γ-absorbed dose in the simulated thyroid phantom for various values of its volume. The effect of the size and shape of the thyroid on energy deposition per decay has also been studied by using spherical, ellipsoidal and cylindrical models for the thyroid and varying its volume in 1-25 cm3 range. The relative differences of Geant4 results for different models with each other and mCNP results lie well below 1.870%. The maximum relative difference among the Geant4 estimated results for water with iCRP and iCRU soft tissues is not more than 0.225%. S-values for ellipsoidal, spherical and cylindrical thyroid models were estimated and the relative difference with published results lies within 3.095%. The absorbed fraction values for beta particles show a good agreement with published values within 2.105% deviation. The Geant4 based simulation results of absorbed fractions for gammas again show a good agreement with the corresponding mCNP and EGS4 results （±6.667%） but have 29.032% higher values than that of miRD calculated values. Consistent with previous studies, the reduction of the thyroid volume is found to have a substantial effect on the absorbed dose. Geant4 simulations confirm dose dependence on the volume/mass of thyroid in agreement with mCNP and EGS4 computed values but are substantially different from miRD8 data. Therefore, inclusion of size/mass dependence is indicated for 131i radiotherapy of the thyroid.

关键词： mean absorbed dose rate Geant4 monte Carlo simulation and 131i therapy

Spatially Adaptive image Restoration Using Fuzzy Punctual Kriging

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Journal of Computer Science & Technology 2007年第4期22卷 580-589页

作者： Anwar m.mirza Asmatullah Chaudhry Badre munir Faculty of Cornputer Science and Engineering Ghulam Ishaq Khan(GIK)Institute of Engineering Science and Technology Topi-23460SwabiPakistan

We present a general formulation based on punctual kriging and fuzzy concepts for image restoration in spatial domain. Gray-level images degraded with Gaussian white noise have been considered. Based on the pixel local neighborhood, fuzzy logic has been employed intelligently to avoid unnecessary estimation of a pixel. The intensity estimation of the selected pixels is then carried out by employing punctual kriging in conjunction with the method of Lagrange multipliers and estimates of local semi-variances. Application of such a hybrid technique performing both selection and intensity estimation of a pixel demonstrates substantial improvement in the image quality as compared to the adaptive Wiener filter and existing fuzzykriging approaches. it has been found that these filters achieve noise reduction without loss of structural detail information, as indicated by their higher structure similarity indices, peak signal to noise ratios and the new variogram based quality measures.

关键词： image restoration fuzzy logic punctual kriging semivariance structure similarity index adaptive spatial filtering

The Klein-Gordon and the Dirac Oscillators in a Noncommutative Space

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Communications in Theoretical Physics 2004年第5X期42卷 664-668页

作者： B.mirza m.mohadesi DepartmentofPhysics IsfahanUniversityofTechnologyIsfahan84154Iran

We study the Dirac and the Klein-Gordon oscillators in a noncommutative space. it is shown that the Klein-Gordon oscillator in a noncommutative space has a similar behaviour to the dynamics ofa particle in a commutative space and in a constant magnetic field. The Dirac oscillator in a noncommutative space has a similar equation to the equation of motion for a relativistic fermion in a commutative space and in a magnetic field, however a new exotic term appears, which implies that a charged fermion in a noncommutative space has an electric dipole moment.

关键词：振荡器非交换几何学兰道问题量子场

Noncommutative Geometry and Classical Orbits of Particles in a Central Force Potential

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Communications in Theoretical Physics 2004年第2X期42卷 183-184页

作者： B.mirza m.Dehghani instituteforStudiesinTheoreticalPhysicsandmathematics P.O.Box5746Tehran19395Iran DepartmentofPhysics IsfahanUniversityofTechnologyIsfahan84154Iran

We investigate the effect of the noncommutative geometry on the classical orbits of particles in a central force potential The relation is implemented through the modified commutation relations [xi,xj] = iθij. Compar... 详细信息

关键词：非交换几何学行星轨道量子万有引力行星物理学莱布尼兹规则哈密顿算符

Shocks and Solitons in Ultradense Degenerate Electron-Positron-ion Plasmas

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Communications in Theoretical Physics 2011年第1期55卷 151-157页

作者： S.A.Khan Arshad m.mirza National Centre for Physics Quaid-i-Azam University Campusand Department of PhysicsCOMSATS Institute of Information Technology Theoretical Plasma Physics Group Department of PhysicsQuaid-i-Azam University

The formation and propagation of shocks and solitons are investigated in an unmagnetized, ultradense plasma containing degenerate Fermi gas of electrons and positrons, and classical ion gas by employing Thomas-Fermi model. For this purpose, a deformed Korteweg-de Vries-Berger （dKdVB） equation is derived using the reductive perturbative technique for cold, adiabatic, and isothermal ions. Localized analytical solutions of dKdVB equation in planar geometry are obtained for dispersion as well as dissipation dominant cases. For nonplanar （cylindrical and spherical） geometry, time varying numerical shock wave solution of dKdVB equation is found. its dispersion dominant case leading to the soliton solution is also discussed. The effect of ion temperature, positron concentration and dissipation is found significant on these nonlinear structures. The relevance of the results to the systems of scientific interest is pointed out.

关键词： degenerate plasma nonplanar geometry shocks solitons

Gravitomagnetic Effects on Collective Plasma Oscillations in Compact Stars

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Communications in Theoretical Physics 2006年第3期45卷 568-572页

作者： Babur m. mirza Hamid Saleem Depaxtment of mathematics Quaid-i-Azam University Islamabaci 45320 Pakistan PiNSTECH Nilore Islamabad Pakistan COmSATS institute of information Technology Islamabad Pakistan

The effects of gravitomagnetic force on plasma oscillations are investigated using the kinetic theory of homogeneous electrically neutral plasma in the absence of external electric or magnetic field. The random phase assumption is employed neglecting the thermal motion of the electrons with respect to a fixed ion background. it is found that the gravitomagnetic force reduces the characteristic frequency of the plasma thus enhancing the refractive index of the medium. The estimates for the predicted effects are given for a typical white dwarf, pulsar, and neutron star.

关键词： gravitomagnetism compact stars plasma osillations

Neurogenesis dynamics in the olfactory bulb:deciphering circuitry organization, function, and adaptive plasticity

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Neural Regeneration Research 2025年第6期20卷 1565-1581页

作者： moawiah m.Naffaa Department of Psychology and Neuroscience Duke UniversityDurhamNCUSA Department of Cell Biology Duke University School of MedicineDurhamNCUSA

Adult neurogenesis persists after birth in the subventricular zone, with new neurons migrating to the granule cell layer and glomerular layers of the olfactory bulb, where they integrate into existing circuitry as inhibitory interneurons. The generation of these new neurons in the olfactory bulb supports both structural and functional plasticity, aiding in circuit remodeling triggered by memory and learning processes. However, the presence of these neurons, coupled with the cellular diversity within the olfactory bulb, presents an ongoing challenge in understanding its network organization and function. moreover,the continuous integration of new neurons in the olfactory bulb plays a pivotal role in regulating olfactory information processing. This adaptive process responds to changes in epithelial composition and contributes to the formation of olfactory memories by modulating cellular connectivity within the olfactory bulb and interacting intricately with higher-order brain regions. The role of adult neurogenesis in olfactory bulb functions remains a topic of debate. Nevertheless, the functionality of the olfactory bulb is intricately linked to the organization of granule cells around mitral and tufted cells. This organizational pattern significantly impacts output, network behavior, and synaptic plasticity, which are crucial for olfactory perception and memory. Additionally, this organization is further shaped by axon terminals originating from cortical and subcortical regions. Despite the crucial role of olfactory bulb in brain functions and behaviors related to olfaction, these complex and highly interconnected processes have not been comprehensively studied as a whole. Therefore, this manuscript aims to discuss our current understanding and explore how neural plasticity and olfactory neurogenesis contribute to enhancing the adaptability of the olfactory system. These mechanisms are thought to support olfactory learning and memory, potentially through increased

关键词： network adaptability neurogenesis neuronal communication olfactory bulb olfactory learning olfactory memory synaptic plasticity

Cosmological Expansion and its Effect on Small Systems

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Communications in Theoretical Physics 2006年第6X期46卷 987-990页

作者： B. mirza m. Zamani-Nasab Department of Physics Isfahan University of Technology (IUT) Isfahan (84156) Iran

in order to study the effect of large scale cosmological expansion on small systems, we assume a Friedmann- Robertson-Walker type coordinate system in presence of a nonzero cosmological constant and derive a non-static Reissner-Nrdstr6m metric. it is an analytic function of r for all values except at r = O, which is singular. By determining the equation of motion in this metric we can estimate how expansion of the universe may affect Pioneer＇s motion. Because the metric does not have any event horizon and so high potential regions are accessible, this may help us in better understanding AGN phenomenon.

关键词： general relativity exact solution

mitochondria–cGAS–STiNG axis is a potential therapeutic target for senescence-dependent inflammaging-associated neurodegeneration

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Neural Regeneration Research 2025年第3期20卷 805-807页

作者： Josém.izquierdo Centro de Biología molecular Severo Ochoa(CBm) Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid(CSIC-UAM)MadridSpain

The word “senescence” comes from the Latin senescens, meaning “to begin to age”, and is characterized by a long-lasting but reversible block in proliferation, resulting from stress-induced cell cycle arrest of pre... 详细信息

关键词： Latin potential lasting