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Fabrication & Thermophysical Studies of Hexa Ferrites

Thesis Info

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Author

Ghulam Asghar

Supervisor

Muhammad Anis-Ur-Rehman

Program

PhD

Institute

COMSATS University Islamabad

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2011

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1671

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726180673

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Strontium hexaferrite nano material with nominal composition SrFe12O19 is prepared by wet chemical methods. The effect of variation in synthesis parameters such as molar ratio of cations (Fe/Sr), volume rate of addition of precipitating agent and the pH of the solution on the phase purity and particle size is studied to optimize them for the synthesis by co- precipitation method. The effect of molar ratio of cations (Fe/Sr) on phase purity is studied by using X-ray diffraction (XRD) patterns. It is observed from indexed XRD patterns that molar ratio of cations does not affect the phase purity of strontium hexaferrites as there is no impurity peak present in any sample and all patterns are almost similar. The effect of volume rate of addition of precipitating agent on phase purity and surface morphology are analyzed by using XRD diffraction patterns and scanning electron micrographs (SEM). The indexed XRD patterns show that the increase in the volume rate of addition of precipitating agent improves the phase purity and SEM micrographs show that the size of the particles also decrease with the increase in the volume rate of addition of precipitating agent. The effect of pH variation on structural and electrical properties of strontium hexaferrite is analyzed by using X-ray diffractometer, scanning electron microscope, temperature dependent dc resistivity measurement system and precision component analyzer. Indexed XRD patterns show that the secondary phases are decreased with the increase in pH of the solution and single phase strontium hexaferrite is obtained for pH=13. The pH of the solution also imparts a significant effect on structural morphology of prepared hexaferrite samples. The SEM micrographs with varying pH samples clearly indicate that most of the particles are of hexagonal shape. It can also be seen that the particle size and their distribution also decrease with the increase in the pH of the solution. The dc resistivity is also increased by increasing pH and this may be due to increase in the grain boundaries. The composition SrFe12-xCrxO19 (X=0.0, 0.2, 0.4, 0.6, 0.8) is prepared in order to increase the coercivity of strontium hexaferrites. Results obtained indicate that Cr doping causes the formation of secondary phases. It is also observed that for X ≤ 0.6, both dielectric constant and coercivity is increased while saturation magnetization is decreased. The increase in coercivity was due to variation in particle size and impurity phases which acted as pinning centers. The decrease in saturation magnetization is because of the replacement of cation (Fe3+) having high magnetic moment (5μB) on octahedral sites with cation (Cr3+) having smaller magnetic moment (3μB). Another composition SrFe12-2xCrxZnxO19 with (X=0.0, 0.2, 0.4, 0.6, 0.8) is prepared with co-precipitation method in order to reduce the dielectric loss tangent. The results show that Cr-Zn doping causes increase in the particle size and decrease in dielectric loss tangent and make the strontium hexaferrite useful for high frequency applications. The hysteresis loops of the Cr-Zn doped samples reveal that both coercivity and saturation magnetization is decreased with increase in doping concentration. The same composition SrFe12-2xCrxZnxO19 with x=0.0, 0.2, 0.4, 0.6, 0.8 is synthesized with WOWS sol- gel method (WOWS stands for Without Water and Surfactants; a new simplified sol-gel method developed in our lab). The structural and dielectric measurements results obtained from the samples prepared with WOWS sol-gel method are better than the results obtained from the same composition prepared with co-precipitation. In some cases, the materials with high loss as well as high dielectric constant may be desired in applications such as electromagnetic (EM) wave absorbing coatings. To achieve these properties, reduction of oxygen from sintered SrFe12O19 is made. This treatment resulted in the increase in the concentration of Fe2+ ions and free iron atoms and hence in the increase in both dielectric constant and dielectric loss and making the material useful for microwave absorption.
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ڈاکٹر حفیظ سید

ڈاکٹر حفیظ سید مرحوم
افسوس ہے کہ ہماری علمی بزم کی ایک پرانی یادگار ڈاکٹر حفیظ سید مرحوم نے گزشتہ مہینہ انتقال کیا ان کی پوری زندگی تعلیمی اور علمی مشاغل میں گزری اور آخر میں الٰہ آباد یونیورسٹی کی اردو کی پروفیسری سے ریٹائرڈ ہوئے تھے، وہ مشہور صاحب قلم تھے اردو، انگریزی دونوں زبانوں میں سیکڑوں مضامین، ان کی یادگار ہیں مستقل کتابوں میں مشہور دکنی شاعر قاضی محمود بحری کا کلیات تصحیح و ترتیب کے جملہ لوازم کے ساتھ مرتب کرکے شائع کیا تھا، ان کو تصوف اور روحانیات سے خاص دلچسپی تھی، اس ذوق میں انھوں نے مختلف مذاہب کے روحانی مرکزوں اور ان کی روحانی شخصیتوں سے بھی استفادہ کیا تھا مگر آخر میں اپنے اصلی مرکز کی طرف لوٹ آئے تھے اور اسی پر ان کا خاتمہ ہوا، مرحوم علامہ شبلی کے صحبت یافتہ اور ارکان دارالمصنفین کے پرانے رفقاء میں تھے، اس لیے دارالمصنفین سے ان کو دیرینہ مخلصانہ تعلق تھا، اس کی مجلس عاملہ اور مجلس انتظامیہ کے رکن بھی تھے، ادھر کئی سال سے فالج میں مبتلا تھے، گذشتہ مہینہ آنکھ کھلوانے کے لیے سیتاپور گئے تھے، وہیں دفعتہ انتقال کیا اور الٰہ آباد میں تجہیزوتکفین ہوئی۔ اللھم اغفرْلہٗ وَ ارْحمَہٗ۔ (شاہ معین الدین ندوی، جنوری ۱۹۶۲ء)

 

ابن ہمام اور ان کی کتاب فتح القدیر کا تعارف و منہج

Fath ul Qadeer is one of the most comprehensive and well organized works in the Hanafi School of thought. Full name of this book is Fath ul Qadeer Lel ‘Aajez el Faqeer. It is a commentary and illustration of Hedaya, the most popular and authentic book in Islamic jurisprudence and in Islamic schools of thought. It is compendium of Islamic knowledge with a discussion on various subjects that are from various types of fiqh and Usool-e-fiqh. Author, Ibn e Hamam used a critical explanation of words from lexical to technical, their grammatical analysis, connection on the basis of grammatical and syntax regulations and illustration of differences between synonyms. The methodology of this book is unique as it provide unprejudiced and impartial in analysis of various topics under discussion and the rational and logical arguments given by the author in support of his view make this book a significant work and a remarkable milestone in fiqh collections. The paper concludes with a comprehensive analysis of the aspects dealt with in terms of methodology and its characteristics.

Genetic Analysis of Cervical Cancer in Pakistani Women

Uterine cervical cancer is one of the leading causes of morbidity and mortality amongst the gynecological cancers worldwide, especially in underdeveloped countries. In Pakistan, it ranks the 3rd largest cancer killer of women after breast and oral cavity. It is the 2nd most common cancer among Pakistani women aged between 15-44 years of age. According to Information Centre on HPV and Cancer (ICO), in Pakistan, approximately 5,233 women are diagnosed with cervical cancer every year and approximately 2,876 die of this lethal disease. Several risk factors have been associated with pathogenesis of cervical cancer. Genital infection with high risk types of human papillomavirus (HPV) especially 16 and 18, is the most important risk factor in pathogenesis of cervical cancer. Among women with HPV infection, risk factors for cervical cancer include high parity (>7), long-term use of oral contraceptives (>5 years), active and passive smoking, exposure to ionizing radiation, and co-infection with Human Immunodeficiency Virus (HIV). Other risk factors for cervical cancer include history of genital warts, lack of circumcision and non-use of condoms in the male sexual partner, thus emphasizing the venereal nature of disease and pointing to HR HPV as an important agent. Multiple number of female sexual partners, number of female prostitutes as sexual partners, and detection of HPV DNA in husbands/male sexual partners are significant markers of exposure to HPV to a woman during her sexual relationship. HPV can also spread from one person to another during skin-to-skin contact. HPV infection precedes the development of cervical cancer and that persistent infection with HPV is a necessary factor for the development and progression of pre-cancerous cervical lesions to high grade cancer. Cervical cancer starts in the cells of mucosal lining of the cervix. Transitional zone of cervix is the most common site of cervical cancer and it is most susceptible to the tumorigenicity of HR HPV. The major histopathologic types of cervical cancers are squamous cell carcinoma and adenocarcinoma which constitute about 85% and 10-12% of all cases of cervical cancer, respectively. The squamous cell carcinoma arises in the squamocolumnar junction between the ectocervical squamous epithelium and the endocervical columnar epithelium and is preceded by a long phase of cervical intraepithelial neoplasia (CIN1, CIN2 and CIN3). The adenocarcinoma originates from glandular precursor lesions of the endocervical mucosa. Cancer of uterine cervix develops as a result of multiple genetic alterations that cause malignant transformation of cervical cells. Inactivation of tumor suppressor gene is a key event in cervical carcinogenesis. P53 is one of the most important tumor suppressor genes in the genome, and its mutations are found in approximately 50% of human cancers. Infection with human papillomavirus (HPV) is a critical event for the development of uterine cervical cancer. The pathogenesis of cervical cancer is thought to occur through a multistep process involving HPV infection in more than 95% of the cases. The viral proteins E6/E7 of HPV functionally interfere with cell cycle control by inactivating tumor suppressor gene p53 and the retinoblastoma protein. The complex binding between the p53 protein, and the E6 protein from the human papilloma virus may result in the disturbance of the growth-inhibitory effect of wildtype p53 which results in uncontrolled cell proliferation and malignant transformation. Present study was aimed to find out the frequency of mutation of p53 gene in Pakistani women which might be important in the origin or progression of cervical carcinoma. Secondly to find out the frequency of human papillomavirus infection in cervical cancer patients and correlate its association with p53 gene mutation in Pakistani population. Another aim was to study ultrastructural changes in cervical cancer cells under transmission electron microscope. For this study, 83 samples of cervical cancer were collected. All patients were females with age range from 19-70 years. Formalin fixed paraffin embedded tissue blocks were used. Out of 83 cervical cancer specimens, seventy four (89.16%) were of squamous cell carcinoma type and 9 (10.84%) were of adenocarcinoma type. DNA isolation was done by using Qiagen spin column method followed by PCR amplification. SSCP (single stranded conformation polymorphism) was done to detect mutant samples. Exons 4, 5, 6, 7 and 8 of p53 gene were studied for mutation. Mutations were confirmed by DNA sequencing. PCR of all samples was done to find out the E6 and E7 oncoproteins of human papillomavirus type 16 and 18. It was found that, 63 (75.9%) were HPV16 positive and only 2 cases (2.4%) were HPV18 positive. Among eighteen cases (21.68%), HPV16/18 were not identified. Two positive cases for HPV18 were of adenocarcinoma type and out of sixty three, HPV16 positive cases, seven were adenocarcinoma and 55 were of squamous cell variety. The frequency of mutation of p53 gene was calculated by using SPSS 21.0 software. It was found that in 59% of cervical cancer cases, p53 gene was mutated. One of the noteworthy observations in present study was that out of mutated samples, exon 4 of p53 gene was mutated in 40.8% of the cases. Exon 5, 6, and 7 were mutated in 16.32% cases each and exon 8 was mutated in only 10% of cases. Seven patients (14.28%) with p53 gene mutation were of age more than 60 years. Age of fourteen patients with p53 gene mutation (28.57%) ranged between 46 to 60 years of age. Twenty eight (57.14%) patients with p53 gene mutation were below 45 years of age. When further explored, it was found that among patients having adenocarcinoma 7 (77.8%) were of age above 45 years while among squamous cell carcinoma (SCC), 45(60.8%) had age below 45 years. This difference was significant with p-value (0.026). Association of cancer type with age, HPV 16/18 status, and p53 gene mutation was noted. It was found that the cases with HPV16/18 infection along with p53 mutation were significantly higher among age group younger than 45 years (p value 0.038), most common in patients with histological grade-II cervical cancer and mostly in squamous cell carcinoma type. It was also noted that out of a total 49 cases with p53 gene mutation, 44 (89.8%) were of squamous cell carcinoma type and only 5 (10.2%) were of adenocarcinoma variety with p value 0.05 which was statistically significant. For ultrastructural analysis of cervical cancer cells, fresh tissues were used for transmission electron microscopy (TEM). Ultrastructure of cervical squamous cell carcinoma cells showed that the nuclear/ cytoplasmic ratio was highly disturbed. Many of the nuclei showed marked irregularity of contour due to deep clefts and infoldings of the nuclear membrane. There was increased density of chromatin in nuclei either in form of clumps adherent to inner side of nuclear membrane or scattered throughout the nuclei. In most of the cervical cancer cells, nucleoli were multiple and hypertrophied and in some cells, meshbasket appearance of nucleoli can be appreciated. In cytoplasm of cells from squamous cell carcinoma of cervix, tonofilaments were noted in perinuclear area. Increased number of cytoplasmic vacuoles were also seen in cervical neoplastic cells. Cervical cancer is the only cancer that is almost completely preventable by safe, simple and inexpensive methods. Cervical cancer screening methods include periodic pap smears, visual inspection of cervix with acetic acid and Lugol’s iodine, and HPV genotyping. Immunizations against human papillomavirus (HPV) types 16 and 18 have the potential to prevent significant number of cervical cancer cases. Recognition of important precursor lesions may play an important role in cervical cancer prevention. It has been reported that p53 gene mutation and HPV 16/18 infection present in precancerous conditions of cervix. Future of cancer prevention depends on early detection and eradication of latent precancerous stage. The greater knowledge of the molecular etiology of cancer will contribute to disease screening strategies, diagnosis, staging of the disease and therapy." xml:lang="en_US