Investigation of flow and heat transfer phenomena in a channel filled partially or fully with porous medium is of significant interest as it has numerous applications in heat exchangers, crude oil extraction, jet printers, petroleum reservoir, filtration mechanism, magnetic refrigerator, rocket propulsion etc. It is observed that the pressure gradient and temperature difference play vital role in the channel and pipe flows. Also, presence of porous medium has a significant effect on heat transfer phenomenon. Theoretical analysis of such flows is helpful to examine more complex problems related to flow and heat transfer phenomena. A lot of research has been conducted in this direction. However, characteristics of heat transfer in composite channel flows are yet to be explored as a few literature is available on this topic. Keeping this in mind, emphasis has been paid on the steady of flow and heat transfer characteristics in channels partially or fully filled with porous medium. Newtonian and non-Newtonian fluid known as Casson fluid have been considered and the impact of presence of magnetic field, unsteadiness and suction/injection on fluid flow and heat transfer are observed. The considered problems are mathematically modelled using momentum and energy equations. In some particular cases, entropy generation effects are also investigated to measure the energy losses during these processes. Different techniques like numerical and analytical are used to solve partial differential equations which govern heat transfer and flow phenomena. Regular perturbation method is used to solve analytically the governing equations whereas finite difference scheme are employed to obtain the numerical solutions. The validity and accuracy level of the solutions have been determined either by comparing both the solutions or calculating the residual error. The analysis carried out in this dissertation reveals that the presence of porous medium decreases the velocity of the fluid within the pipes or composite channels. Also, it is noticed that the flow and heat transfer strongly depend on the viscosity ratios, magnetic field parameter, thermal conductivity ratios, inclination angle and porosity parameter. Moreover, the Newtonian fluid velocity is higher than the Casson fluid velocity for irregular channel with convective boundary conditions. In case of composite channel, temperature enhancement is more in porous region as compared to clear region. Furthermore, presence of porous medium, magnetic field parameter and viscous dissipation effects are the major factor responsible for entropy generation.
اس وقت دنیا کا سب سے بڑا ریاضی دان ایک ہندوستانی تھا، مسٹر رامانجم کی بابت، جس کے کمالات ریاضیہ کا ذکر آج سے ٹھیک ایک سال قبل معارف میں آچکا ہے، بعض علماء فن کا خیال تھا کہ نیوٹن کے بعد سے دنیا میں اس دماغ کا ریاضی دان نہیں پیدا ہوا ہے اور اس کا تو سب کو اعتراف تھا کہ انھوں نے بعض وہ مسائل حل کردیئے جو پوری ایک صدی سے لاینحل چلے آرہے تھے، سخت افسوس ہے کہ ماہ گذشتہ میں اسی ہستی نے دق میں مبتلا ہوکر دنیا کو اپنے فیض سے ہمیشہ کے لئے محروم کردیا، مرحوم کا سن کل ۳۲ سال کا تھا۔
خوش درخشید ولے دولت مستعجمل بود
(جون ۱۹۲۰ء)
مدراس کے نامور ریاضی دان رامانجم کی خبر وفات کسی پچھلے معارف میں درج ہوچکی ہے، یورپ کے اعلیٰ علمی رسائل مدت تک ان کے ماتم میں سوگوار رہے، اور متعدد ماہرین فن کے قلم نے اس حادثہ عظیم پر علم و فن کی جانب سے فریضۂ تعزیت ادا کیا، کیمبرج یونیورسٹی کے مشہور پروفیسر جی،ایچ، ہارڈی نے سائنٹفک ہفتہ وار نیچر میں جو تعزیت نامہ شائع کیا ہے، اس میں بار بار اس قسم کے فقرہ ملتے ہیں۔ ’’یہ بالکل یقینی ہے کہ مرحوم کی مہندسانہ فضیلت اعلیٰ ترین پایہ کی تھی اور وہ ایک استشنائی قوت فکر و اجتہاد کا شخص تھا‘‘۔ اس کے تقریباً بیس مقالات شائع ہوئے، جنھوں نے زمانۂ جنگ ہی میں تمام دنیائے ریاضیات کو اپنی جانب متوجہ کرلیا‘‘۔ اس کے پیش نظر صرف وہ مسائل تھے، جن تک معدددے چند افراد کی رسائی ہوسکتی ہے‘‘۔ اس کی قوت استنباط بالکل حیرت انگیز تھی، جس کی کوئی نظیر کسی یوروپین ریاضی دان میں...
Darier-Ferrand dermatofibrosarcoma is a rare but not exceptional malignant mesenchymal skin tumor, representing 0.1 % of malignant skin tumors. It is characterized by high recurrence, slow growth and low metastatic potential. Although several clinical cases of an unusual variant of Darier-Ferrand dermatofibrosarcoma have been reported in the literature, localization on the palmar face of the hand is not common. We report a case of Darier and Ferrand dermatofibrosarcoma at the level of the fourth commissure of the palm of the left hand in a 43- year-old young Malagasy adult treated by a large surgical excision with a healthy margin of two centimeters associated with adjuvant chemotherapy with Imatinib.
This study was designed to investigate the role of enriched environment in preventing and/or reducing the neurobehavioral deficits produced after nicotine administration in albino Wistar rats. Equal numbers of rat in two groups were either placed in social environment (control group) or social along with physically enriched environment for four weeks before the administration of nicotine. Exposure to different environmental conditions was followed by the intraperitoneal injection of nicotine at the dose of 0.6 mg/kg for seven consecutive days during which addictive behavior was monitored using conditioned placed preference paradigm. Behavioral responses to locomotor activity, anxiety and retention of short term memory were investigated in control and nicotine injected groups exposed to different environments. Results of this study showed that the rats pre-exposed to physical along with social enrichment exhibited a decrease in drug seeking behavior, hyper locomotion, anxiogenic effects along with improvement of working memory as compared to control and nicotine injected groups that were kept in social environment alone. This behavioral study suggests that the exposure to physical enrichment along with socialization in young age can later reduce the chances of compulsive dependence on nicotine and related neurobehavioral deficits.