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Home > Synthesis and Characterization of Mg and Ge Doped Cu0. 5Tl0. 5 Ba2can-1Cuno2n+4-Δ N = 3, 4, 5 Superconductors

Synthesis and Characterization of Mg and Ge Doped Cu0. 5Tl0. 5 Ba2can-1Cuno2n+4-Δ N = 3, 4, 5 Superconductors

Thesis Info

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External Link

Author

Irfan, Muhammad

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2010

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1826

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725377096

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Different series of polycrystalline superconductor, Cu0.5Tl0.5Ba2Ca4-xMgxCu5O14-δ (x = 0, 1, 2 and 3), (Cu0.5Tl0.5)Ba2Ca2Cu3-yGeyO10-d (y = 0, 0.5, 0.75 and 1.0) and (Cu0.5Tl0.5)Ba2Ca3(Cu4-yGey)O12-d (y = 0, 0.3, 0.6 and 0.9) have been synthesized by solid-state reaction method. The structure and physical properties were investigated by powder X-ray diffraction (XRD), resistivity, ac-susceptibility and Fourier transform infrared absorption spectroscopy (FTIR). X-ray diffraction scans of polycrystalline samples of Cu0.5Tl0.5Ba2Ca4-xMgxCu5O14-δ (x = 0, 1, 2 and 3) samples show tetragonal structure following P4/mmm space group. The dominant phase in x = 0 sample is CuTl- 1234 while the remaining all Mg doped samples show the projected CuTl-1245 phase with a small inclusion of impurity phases. It suggests that the presence of Mg plays a very vital role in synthesis of five planar CuTl-1245 compounds. With the partial substitution of Ca with Mg in the samples, the CuO2 planes become uniformly doped due to improved inter-planer coupling which results in the enhancement of Tc (R = 0) as well as the magnitude of diamagnetism. Further superconducting properties of the samples have been enhanced by carrying out annealing experiments in nitrogen air and oxygen atmospheres. The enhanced superconductivity in different annealing environments have been attributed to the optimization of carrier density in the OPs and the IPs. Oxygen annealed samples show the best superconductivity among all, which have been attributed to the optimization of carrier concentration in the CuO2 planes and improved weak link behavior due to the intercalation of the oxygen in the unit cell and at the intra-grain and inter-grain sites. Superconductivity in the Cu0.5Tl0.5Ba2Ca2Mg2Cu5O14-d superconductor has been optimized by varying both time and temperature during the air annealing experiments by attaining Tc ~ 132 K. In (Cu0.5Tl0.5)Ba2Ca2Cu3-yGeyO10-d (y = 0, 0.5, 0.75 and 1.0) samples, synthesized at 860oC, y = 0 and 0.5 show the CuTl-1223 tetragonal phase but y = 0.75 and 1.0 develop CuTl-1234 as the dominant phase. It indicates that the substitution of Ge lowers the synthesis temperature and for single phase sample, temperature less than 860oC seems more plausible. Four planar Ge doped (Cu0.5Tl0.5)Ba2Ca3(Cu4-yGey)O12-d (y = 0, 0.3, 0.6 0.9) superconductors were prepared at 870oC rather than 880oC and investigated for their superconducting properties. X-ray diffraction scans of the samples confirm the CuTl-1234 phase. Increased Ge substitution at the Cu planar sites has been found to suppress the superconducting properties of the samples. Possible causes include the impurity scattering and the carrier depletion due the replacement of Cu2+ ions with Ge4+ ions. The superconductivity has been restored by carrier doping through annealing processes. FTIR analysis has also been conducted and the role Ge in the variations of different phonon modes has been discussed. Also the effect of oxygen annealing on these phonon modes have been observed and analyzed. The fluctuation induced conductivity of Cu0.5Tl0.5Ba2Ca4−xMgxCu5O14−δ (x = 1, 2) and Cu0.5Tl0.5Ba2Ca2Cu2M1O10-d (M =Si, Sn, Ge) superconductor samples has been done. FIC data of the as-prepared Cu0.5Tl0.5Ba2Ca4−xMgxCu5O14−δ (x = 1) sample does not fit with 2D, 3D AL equations, but for x = 2 and the oxygen annealed samples seem to fit well with 2DAL, 3D AL equations with two distinct cross over temperatures. In the samples the interlayer coupling strength J is found to increase with increased Mg content and oxygen post annealing. Higher concentration of Mg seems to lower the anisotropy along the c-axis and thus improves the inter-planer coupling. It results in 2D to 3D cross over of the conductivity and enhancement of the interlayer coupling strength J. The 2D to 3D cross over and higher J values in post annealed samples can be attributed to the change in the carrier concentration in the CuO2 planes, and improved weak link behavior, brought about by the intercalation of the oxygen in the charge reservoir layer. The excess- conductivity data of Cu0.5Tl0.5Ba2Ca2Cu2M1O10-d (M = Si, Sn and Ge) samples also shows two cross over temperatures and three distinct exponents. Si and Sn doped samples with almost same critical temperature have not shown much diversity in different parameters such as room temperature resistivity, transition width, a (rN 0 K) etc. Similarly not much difference is seen in the dimensionality exponents and the corresponding temperature ranges. The Ge doped sample with lower critical temperature has shown different FIC parameters with large transition width. Ge doped sample has shown higher 3D character; in this sample 2D fluctuations are found in very small temperature range. Here a possible link between the confinement of the 2D fluctuations to a narrow temperature window and the lower critical temperature of the Ge doped sample can be conjectured but not claimed.
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15. Al-Hijr/The Rocky Tract

15. Al-Hijr/The Rocky Tract

I/We begin by the Blessed Name of Allah

The Immensely Merciful to all, The Infinitely Compassionate to everyone.

15:01
Alif. Lam. Ra’.
These are Messages of the Divine Book - that is a Clear Qur’an.

15:02
a. The time will come when those who disbelieve now will wish that they were Muslims.

15:03
But leave them alone to feast and enjoy themselves as if it is the only aim of life, and let their wishful hopes distract them.
For they will soon realize the futility of their endeavors.

15:04
a. And WE have never destroyed any settlement or a community for its wrongdoing without its having a known decree beforehand.

15:05
a. No community can either precede its appointed time of doom nor delay it.

15:06
And they say:
‘O you - Muhammad - upon whom this Reminder - the Qur’an – is being sent down as you claim!
We think you are certainly possessed’ and insane.

15:07
a. So ‘why are you not bringing us the angels to testify your truthfulness, if you are of the truthful?’

15:08
However, WE do not send down the angels except with demands of the truth,
and were the angels to appear now with the decision, then they will not be spared.

15:09
Indeed, it is WE WHO are sending down this Reminder – The Qur’an, and
surely, WE will preserve it against any satanic change in its Sacred Arabic Text and its form.

15:10
a. And, certainly, WE did assign the Messengers before you among the earlier communities,

Frequency of depression and anxiety among heart failure patients in a tertiary care hospital of Faisalabad, Pakistan Depression & anxiety among cardiac patients

Heart failure (HF) is a chronic illness with high prevalence and mortality, leading toeconomic burden ofhealth due to prolonged hospital stay and re-admissions. Failure to comprehend the importance of identifying mental illnesses could lead to explanations that why the morbidity and mortality of heart failure patients endure to be very high. Objective: To determine the frequency of anxiety and depression in heart failure patients. Methods: It is a descriptive cross sectional study including 323 CHF patients admitted to the Faisalabad Institute of Cardiology hospital, 250 were males and 73 were females, mean age was 54.1 ± 9.2 years having 70 years as maximum and 25 years as minimum.  Data was collected with the help of HADS questionnaire. Patients were interviewed for assessment of anxiety and depression. Data was analyzed using SPSS version 24. Mean and standard deviation was calculated for quantitative data and for qualitative data frequency and percentageswas calculated. To measure the association of anxiety and depression with age categories and gender, chi square test was used. P values less than and equal to 0.05 were taken as significant. Results: The results showed that 43% subjects had <11 score indicating no anxiety, 57% had >11score indicating anxiety. 45% subjects had<11 score indicating no depression, 55% had >11score indicating depression. Conclusions: The study concluded that frequency of depression and anxiety is high in congestive heart failure patients. Strategies are required to assess and diagnose these mental illnesses to establish early treatment which may foster multidisciplinary health care team approach and interventions that address the psychological burden.

Static and Dynamic Simulation of Heu and Leu Cores of Research Reactors Using Multi-Group and Coupled Space-Time Thermal Hydraulic Approach

Sadaf Waqar, PhD, Department of Physics & Applied Mathematics, PIEAS, June 2008." Static and Dynamic Simulation of HEU and LEU Cores of Research Reactors using Multi- group and Coupled Space-Time Thermal Hydraulic Approach”; Supervisor: Dr. Nasir M. Mirza; Co-Supervisor: Dr. Sikander M. Mirza; Department of Physics & Applied Mathematics, PIEAS, Nilore 45650, Islamabad. A comparative study has been performed for neutronic analysis of HEU and potential LEU cores for the Pakistan Research Reactor-2 (PARR-2) taken as a typical MNSR system. The group constant generation has been carried out using transport theory code WIMS-D4 and a detailed five-group RZ-model has been used in the CITATION code for multigroup diffusion theory analysis. The neutronic analysis of the 90% HEU (reference fuel) and potential LEU alternative fuels: UO2, U3Si2 and U9Mo, has been carried out yielding 11%, 20.7% and 14.25% enrichments with corresponding values of excess reactivity: 4.33, 4.30 and 4.07 mk. These results have been found in good agreement with recently reported Monte Carlo based transport theory calculations. The diffusion theory based calculated values of thermal flux profiles for axial as well as for radial directions have been found to agree well with the corresponding experimental measurements. The UO2 based LEU core has been found having flux spectrum closest to the reference core while U9Mo core has significantly harder flux spectrum at irradiation site. Fuel burn-up study and buildup of actinides and fission products for potential LEU fuels (UO2 and U9Mo) with existing HEU fuel (UAl4-Al, 90% enriched) for a typical Miniature Neutron Source Reactor (MNSR) has been carried out using the WIMSD4 computer program. For the complete burnup, the UAl4-Al, UO2 and U9Mo based systems show a total consumption of 6.89, 6.83 and 6.88 g of Relative to 0.042 g 235 U respectively. 239 Pu produced in case of UAl4-Al HEU core, UO2 and U9Mo based cores have been found to yield 0.793 and 0.799 g respectively indicating much larger values of conversion-ratios and correspondingly high values of fuel utilization factor. The end-of-cycle activity of the HEU core has been found to be 2284 Ci which agrees well with the value found by Khattab [48], where as for UO2 based and U9Mo based LEU cores show 1.8% and 4.8% increase with values of 2326 and 2394 Ci respectively. A two-group, three dimensional diffusion theory based methodology coupled with one-dimensional single-phase heat transfer calculations has been developed for the transient analysis of typical material test reactors (MTRs). This methodology has been implemented in a Fortran based computed program MTRAP3. It uses the CITATION computer program for static neutronic calculations while the group constant generation is performed by employing the WIMS-D/4 code. The MTRAP3 program uses Cranck- Nicolson (CN) based numerical scheme for solution of time dependent neutron diffusion calculations while time-implicit strategy is employed for detailed heat-transfer calculations. The CN-scheme has been found to remain stable for much larger time steps (∆t~10-5 s) as compared with the time-explicit scheme which remains stable for very small time steps only (∆t~10-10 s). For step as well as for ramp reactivity induced transients, the predicted values of core integrated reactor power and core average temperatures has been found to agree well with the corresponding values found by using the PARET computer program. The assembly-wise power profile as found by the MTRAP3 program has been found consistent with the corresponding experimental measurements.