6 results on '"Mehdizadeh, A. R."'
Search Results
2. Lovelock thin-shell wormholes.
- Author
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Dehghani, M. H. and Mehdizadeh, M. R.
- Subjects
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WORMHOLES (Physics) , *GRAVITY , *NUCLEAR energy , *ASTROPHYSICS , *SYMMETRY (Physics) , *PRESSURE , *SURFACE energy , *ENERGY density - Abstract
We construct the asymptotically fiat charged thin-shell wormholes of Lovelock gravity in seven dimensions by a cut-and-paste technique and apply the generalized junction conditions in order to calculate the energy-momentum tensor of these wormholes on the shell. We find that for negative second-order and positive third-order Lovelock coefficients, there are thin-shell wormholes that respect the weak energy condition. In this case, the amount of normal matter decreases as the third-order Lovelock coefficient increases. For positive second- and third-order Lovelock coefficients, the weak energy condition is violated and the amount of exotic matter decreases as the charge increases. Finally, we perform a linear stability analysis against a symmetry-preserving perturbation and find that the wormholes are stable, provided the derivative of surface pressure density with respect to surface energy density is negative and the throat radius is chosen suitably. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
3. Cosmological wormholes in Lovelock gravity.
- Author
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Mehdizadeh, M. R. and Riazi, N.
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WORMHOLES (Physics) , *GRAVITY , *INFLATIONARY universe , *PARAMETER estimation , *ASTROPHYSICS , *NUCLEAR energy - Abstract
We present dynamic wormhole solutions in the framework of Lovelock gravity with compact extra dimensions. Calculations are done in D = 7, although they can be extended to an arbitrary number of extra dimensions. It is shown that as the wormhole inflates with the three-dimensional space, the extra dimensions deflate to very small, yet nonvanishing scales. The weak energy condition is shown to hold for certain ranges of the free parameters, everywhere, down to the throat of the wormhole. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
4. Photothermal cancer therapy by gold-ferrite nanocomposite and near-infrared laser in animal model.
- Author
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Heidari, M., Sattarahmady, N., Azarpira, N., Heli, H., Mehdizadeh, A., Zare, T., and Mehdizadeh, A R
- Subjects
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PHOTOTHERMAL effect , *CANCER treatment , *FERRITES , *GOLD nanoparticles , *NEAR infrared radiation , *ANIMAL models in research , *MELANOMA treatment , *THERAPEUTIC nanotechnology , *NONIONIZING radiation , *ANIMAL experimentation , *BIOLOGICAL models , *CELL lines , *COMBINED modality therapy , *GOLD , *IRON compounds , *MEDICAL lasers , *MELANOMA , *MICE , *NANOPARTICLES , *NANOTECHNOLOGY , *THERAPEUTICS - Abstract
Surface plasmon resonance effect of gold nanostructures makes them good candidates for photothermal therapy (PTT) application. Herein, gold-ferrite nanocomposite (GFNC) was synthesized and characterized as a photothermal agent in PTT. The aim of this study was to investigate the effect of GFNC upon laser irradiation on treatment of cancer in mice bearing melanoma cancer. Thirty mice received 1.5 × 10(6) B16/F10 cells subcutaneously. After 1 week, the mice bearing solid tumor were divided into four groups: control group (without any treatment), laser group (received laser irradiation without GFNC injection), GFNC group (only received intratumorally GFNC), and GFNC + laser group (received intratumorally GFNC upon laser irradiation). In GFNC + laser group, 200 μL of fluid, 1.3 × 10(-7) mol L(-1) gold nanoparticles, was injected intratumorally and immediately the site of tumor was exposed to continuous wave diode laser beam (808 nm, 1.6 W cm(-2)) for 15 min. All mice but four were euthanized 24 h after treatment to compare the necrotic surface area histologically by using measuring graticule. Statistical analyses revealed significant differences in necrosis extent for GFNC + laser group, compared to other groups. Four subjects (control group and GFNC + laser group, two mice each) were kept for longitudinal study. Histological analyses and tumor volume measurements of the four subjects indicated that tumor in GFNC + laser group was controlled appropriately. It was concluded that combining an 808-nm laser at a power density of 1.6 W cm(-2) with GFNC has a destruction effect in melanoma cancer cells in an animal model. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
5. Increased Radioresistance to Lethal Doses of Gamma Rays in Mice and Rats After Exposure to Microwave Radiation Emitted by a GSM Mobile Phone Simulator.
- Author
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Mortazavi, S M J, Mosleh-Shirazi, M A, Tavassoli, A R, Taheri, M, Mehdizadeh, A R, Namazi, S A S, Jamali, A, Ghalandari, R, Bonyadi, S, Haghani, M, and Shafie, M
- Subjects
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DRUG dosage , *GAMMA rays , *LABORATORY mice , *MICROWAVES , *CELL phones , *RADIATION doses , *DOSE-response relationship in biochemistry - Abstract
The aim of this study was to investigate the effect of pre-irradiation with microwaves on the induction of radioadaptive response. In the 1st phase of the study, 110 male mice were divided into 8 groups. The animals in these groups were exposed/sham-exposed to microwave, low dose rate gamma or both for 5 days. On day six, the animals were exposed to a lethal dose (LD). In the 2nd phase, 30 male rats were divided into 2 groups of 15 animals. The 1st group received microwave exposure. The 2nd group (controls) received the same LD but there was no treatment before the LD. On day 5, all animals were whole-body irradiated with the LD. Statistically significant differences between the survival rate of the mice only exposed to lethal dose of gamma radiation before irradiation with a lethal dose of gamma radiation with those of the animals pre-exposed to either microwave (p=0.02), low dose rate gamma (p=0.001) or both of these physical adapting doses (p=0.003) were observed. Likewise, a statistically significant difference between survival rates of the rats in control and test groups was observed. Altogether, these experiments showed that exposure to microwave radiation may induce a significant survival adaptive response. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
6. Black holes in (quartic) quasitopological gravity.
- Author
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Dehghani, M. H., Bazrafshan, A., Mann, R. B., Mehdizadeh, M. R., Ghanaatian, M., and Vahidinia, M. H.
- Subjects
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BLACK holes , *GRAVITY , *QUARTIC fields , *SYMMETRY (Physics) , *THERMODYNAMICS , *ENTROPY , *CURVATURE cosmology - Abstract
We construct quartic quasitopological gravity, a theory of gravity containing terms quartic in the curvature that yields second-order differential equations in the spherically symmetric case. Up to a term proportional to the quartic term in Lovelock gravity we find a unique solution for this quartic case, valid in any dimensionality larger than 4 except 8. This case is the highest degree of curvature coupling for which explicit black hole solutions can be constructed, and we obtain and analyze the various black hole solutions that emerge from the field equations in (n + 1) dimensions. We discuss the thermodynamics of these black holes and compute their entropy as a function of the horizon radius. We then make some general remarks about K-th order quasitopological gravity, and point out that the basic structure of the solutions will be the same in any dimensionality for general K apart from particular cases. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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