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Synthesis of Fine Managnetic Particles and Study of the Micro Structure and Stability With Temperature

Thesis Info

Author

Ghulm Mustafa

Supervisor

Muhammad Anwar

Institute

Allama Iqbal Open University

Institute Type

Public

City

Islamabad

Country

Pakistan

Thesis Completing Year

2007

Thesis Completion Status

Completed

Page

94.;

Subject

Physics

Language

English

Other

Call No: 538.4 GHS; Publisher: Aiou

Added

2021-02-17 19:49:13

Modified

2023-01-06 19:20:37

ARI ID

1676710527986

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اشفاق احمد

اشفاق احمدرجحان ساز شخصیت
پیدائش:
معروف دانشور، ادیب، ڈرامہ نگار، تجزیہ نگار، سفر نامہ نگار اور براڈ کاسٹر جناب اشفاق احمد خان بھارت کے شہر ہوشیار پور کے ایک چھوٹے سے گاؤں خان پور میں ڈاکٹر محمد خان کے گھر 22 اگست 1925ء کو بروز پیر پیدا ہوئے۔
تعلیم:
اشفاق احمد کی پیدائش کے بعد اْن کے والد ڈاکٹر محمد خان کا تبادلہ خان پور سے فیروز پور ہو گیا۔ اشفاق احمد نے اپنی تعلیمی زندگی کا آغاز اسی گاؤں فیروز پورسے کیا۔ اور فیروز پور کے ایک قصبہ مکستر سے میٹرک کا امتحان پاس کیا۔اشفاق احمد نے ایف۔ اے کا امتحان بھی اسی قصبہ فیروز پور کے ایک کالج ‘‘رام سکھ داس ’’ سے پاس کیا۔ اس کے علاوہ بی۔اے کا امتحان امتیازی نمبروں کے ساتھ فیروز پور کے ‘‘آر، ایس،ڈی ‘‘RSDکالج سے پاس کپا۔
پاکستان ہجرت:
قیام پاکستان کے بعد اشفاق احمد اپنے خاندان کے ہمراہ فیروز پور (بھارت) سے ہجرت کر کے پاکستان آ گئے۔ پاکستان آنے کے بعد اشفاق احمد نے گورنمنٹ کالج لاہور کے ‘‘شعبہ اردو ’’ میں داخلہ لیا۔یہاں معروف اساتذہ سے علم حاصل کیا۔اْس زمانے میں بانو قدسیہ نے بھی ایم۔ اے اردو میں داخلہ لیا۔ یہ وہ دور تھا جب اورینٹل کالج پنجاب یونیورسٹی میں اردو کی کلاسیں ابھی شروع نہیں ہوئی تھیں۔
شادی:
جن دنوں اشفاق احمد گورنمنٹ کالج لاہور میں ایم۔ اے اردو کے طالب علم تھے۔ بانو قدسیہ ان کی ہم جماعت تھی۔ ذہنی ہم آہنگی دونوں کو اس قدر قریب لے آئی کہ دونوں نے شادی کا فیصلہ کیا۔ان کے والد ایک غیر پٹھان لڑکی کو بہو بنانے کے حق میں نہ تھے۔جس کی وجہ سے شادی کے بعد ان کو مجبوراً اپنا گھر چھوڑنا پڑا۔
تصانیف:
اشفاق احمد کی تصانیف میں افسانے، ناول، ٹی وی ڈرامے، ریڈیائی ڈرامے، فیچر اور سفر نامے شامل...

الإمام الطحاوي و منهجه في كتابه مشكل الآثار

Qur’an and prophetic traditions (Hadith) are the fundamental sources of Islam. Muslims believe that Qur’an is the word of God (Allah). Hadith (Prophet’s Sayings, actions and silent approvals and disapprovals for something) likewise is based on divine revelation. Qur’an affirms also this view: (God says) Your Companion (Muhammad) has neither gone astray nor has erred. Nor does He speak of (his own) desire. It is only a Revelation revealed. Al-Qur’an (53: 2-4). Allah Almighty Himself took the responsibility to guard His word (the Qur’an): (He says: ) verily, We, it is We Who have sent down the Dhikr (i.e. The Qur’an) and surely, We will got it (from corruption). (Al-Qur’an: 15: 9) on the contrary the responsibility to guard the prophetic traditions (Hadith) was put on the shoulders on the Muslim Ūmmah. The scholars of Islam (ʽulāmʼs) try their utmost to collect and save the Prophetic traditions and guard it from any alteration. To achieve this purpose, they introduced different hadith sciences to distinguished between the true and the fabricated hadith. The authentic Sunnah is contained within the vast body of Hadith literature. Different scholars have compiled the books which contain a large numbers of Ahadith, one of them is ʼimam Taḥāwi. In this article we will discuss the ʼimam Taḥāwi approach towards “Ahadith” in his book Mushkil ul Āathʼar.

Black Holes: Quartic Quasi-Topological Gravity and Greybody Factor

We have constructed a complete set of quartic curvature theories of gravity. Under the restriction of spherical symmetry, the field equations of each of these theories reduce to the total derivative of a single metric function. In the case of four dimensions, we found that there are six generalized quasi-topological theories which have non-trivial contribution and these are given in equations (2.25)-(2.28) and (2.34). The equations of motion of these theories are in the form of total derivative of a polynomial of single metric function f(r) and its first two derivatives. In the case of dimensions five and higher, theories constructed here break up into the following categories: 1. Quartic Lovelock gravity: the explicit form of the Lagrangian for this class is given by the eight dimensional Euler density X8. An interesting aspect of theories of this class is that the equations of motion are always of second order. Furthermore, if we impose the restriction of spherical symmetry, the equation of motion will be unique and in the form of a total derivative of a single metric function. 2. Six quasi-topological theories, with Lagrangians given by equations (2.19) and (2.20). One of these, given in equation (2.19), is already known [61]; the remaining five given in equation (2.20) are new. For all these theories, in a general background, the equations of motion will be different and are of fourth order. On the other hand, if we impose the condition of spherical symmetry, the equations of motion are of second order and contributions of each of six Lagrangians coincide. This is due to the fact that the Lagrangians are equivalent up to the terms which vanish for spherically symmetric metrics. 3. Four generalized quasi-topological theories are found whose Lagrangians are given by equations (2.25)-(2.28). For this quartet, if we impose the condition of spherical symmetry, field equation will be same and in the form of a total derivative of a polynomial of single metric function f and its first and second derivatives. 4. The Lagrangians for six theories, whose field equations vanish when one sets N as constant, are given by equation (2.24). For situations where the stress-energy tensor has Ttt 6= Trr, there will be two non-trivial field equations that determine N and f. We have presented a generalized charged anti-de Sitter black hole solution for cubic quasitopological gravity and also elaborated its thermodynamic aspect. Furthermore, we have derived the analytic expression of greybody factor for non-minimally coupled scalar fields from Reissner-Nordström-de Sitter black hole in low energy approximation. This expression is valid for general, partial modes. For coupling to scalar curvature, which can be regarded as mass or charge terms, greybody factor tend to zero in low frequency regime, irrespective of the values of the coupling parameter. Non-zero greybody factor in low frequency regime means that there is non-zero Hawking emission rate of Hawking radiations. The matching technique is used in deriving formula for greybody factor. The significance of the results is elaborated by giving formulae of differential rate of energy and generalized absorption cross section from the greybody factor. The results of the present study reduce to those of Ref. [101] in appropriate limiting case, i.e., if we put charge Q = 0, we recover the previously reported results. The effective potential and greybody factor are also analyzed graphically. We observe that the height of gravitational barrier increases with the increase of ξ, the coupling parameter, whereas in the absence of the coupling parameter, it is decreased by increasing the values of the cosmological constant. Also, from the plots of greybody factor, it is observed that an increase in the value of the coupling parameter decreases the greybody factor. This is due to the fact that non-minimal coupling plays the role of effective mass and hence suppresses the greybody factor. In the previous chapter, we have presented a study of the greybody factor for a scalar field which are coupled to the Einstein tensor in the background of a charged black string, considering low energy approximation. We demonstrated that the greybody factor depends on the coupling between Einstein tensor and scalar field. It is observed that the presence of coupling enhances the greybody factor of the scalar field in the black string spacetime. Furthermore, for weaker coupling, greybody factor decreases with increase in charge of black string. In the second case, we discussed this work without considering coupling of scalar field and the Einstein tensor. It is trivial from results that the later case reduces to the result of former in absence of coupling constant. In the case of three-dimensional topological black holes [90, 120] like the charged BTZ (Bañados , Teitelboim, Zanelli) black holes, we find the propagation of scalar fields with non-minimal coupling to gravity obeys the Universality theorem. This means that under the restrictions of zero angular-momentum, low energy regime, massless/chargeless scalar field and minimal coupling, the greybody factor approaches to a constant value. However, Universality theorem does not hold for zero angular-momentum if any of the above restrictions is relaxed. We have thus explored theories in several aspects. Consideration of linearized spectrum of these theories revealed that on a constant curvature background, it is only the massless graviton that is propagated by these theories. We also have found the explicit forms of field equations of these theories in general spacetime dimension d which are valid for spherical symmetric background. Also, explicit form of black hole entropy in general spacetime dimension is presented. The consequence of this particular result is very interesting; for the case of black brane solutions, it modifies the usual Bekenstein-Hawking area law. It was observed previously that this aspect was not seen before for theories like Lovelock and quasi-topological gravities. Therefore, holographic consideration of these generalized quasi-topological theories may have interesting implications. Furthermore, we have found four dimensional asymptotic, flat, black solutions for these theories. This solution revealed that it is characterized only by mass, implying that it does not give rise to higher derivative “hair”. We have presented perturbative and numerical solutions, but interestingly, thermodynamics can be studied analytically. In this regard, we found that first law of black hole thermodynamics holds. We presented black brane solutions of these theories in general d dimensions. Expected thermodynamic relations for a CFT (without chemical potential) are satisfied by these solutions, living in one dimension less. We also found the peculiar thermodynamical behaviour of these black brane solutions which is in contrast to the corresponding black brane solutions in Lovelock and quasi-topological gravities. For this reason, this result may have interesting consequences in holographic studies. This class of theories (which has now been constructed to cubic [8, 65] and quartic order) provides interesting generalizations of Einstein’s gravity that are non-trivial in four (and higher) dimensions. This contrasts with previous constructions of Lovelock and quasi-topological gravities, which vanish on four dimensional (spherically symmetric) metrics. The generalized quasitopological terms can be thought of as the theories which have many of the interesting properties observed for Einsteinian cubic gravity [65] in four dimensions [7, 81], but in higher dimensions and/or to higher orders in the curvature. These theories necessarily [66] propagate only a massless, transverse graviton on a constant curvature spacetime. Furthermore, they admit black hole solutions which are characterized only by their mass. The thermodynamics of the black holes can be studied exactly, despite the lack of an exact, analytic solution to the field equations. Construction of these theories has opened many problems which deserve further study. These problems include further investigations of the properties of four and higher dimensional black hole solutions in these theories. Also, as we know that the Birkhoff theorem holds for Lovelock and quasi-topological gravities [71, 72, 121]; it would be interesting to see whether this is the case for these theories. More interestingly, these theories seem well-suited for holographic study and therefore can serve as a good toy model in such investigations. A study in the context of holography could better shed further light on the stability of the solutions of these theories and the allowed values of coupling constants, and may reveal novel features in the case of black brane solutions of the theory. An ambitious undertaking would be to elucidate the general structure of the Lagrangians in this class of theories. This has been long known in the case of Lovelock gravity [5] but remains an open problem in the (generalized) quasi-topological cases." xml:lang="en_US