التحریر چوک
کبری الجامعہ کے علاوہ قاہرہ میں دریائے نیل پر ایک پل اور بھی ہے جس کو ۱۲ اکتوبر پل کہا جاتا ہے ۔مسافر دکتور محمود سے وجہ تسمیہ پوچھی تو اس نے کہا عرب اسرائیل جنگ کی یاد میں یہ پل بنایاگیا ہے ۔اس پل کے کنارے قاہرہ ٹاور ہے جس کی بلندی نے باقی عمارتوں کو ماند کر رکھا ہے ۔ ڈوبتے سورج کی سرمئی روشنی میں قاہرہ کے مینار کی نکھری رنگت نقرئی نظر آنے لگی جس نے اس کی وجاہت اور قد کاٹھ میں بڑھوتری پیدا کر دی تھی ۔
۱۲ اکتوبر پل کے دوسرے کنارے ’’التحریر ‘‘کے نام سے ایک بڑا چوک ہے ۔اس نام سے میری شناسائی چند سال پہلے اس وقت ہوئی جب سابقہ مصری صدر حسنِ مبارک کے طویل دور حکومت کے خلاف ایک تحریک شروع ہوئی ۔تحریک جب احتجاج میں بدلی تو مرکزی حیثیت التحریر چوک کوملی جہاں مصری نوجوانوں نے کئی ہفتوں تک دھرنا دیا اور آخر کار حسن مبارک نے پہلے حکومت چھوڑی اور پھر جیل جانا پڑا ۔سیاست کے ماہرین نے اس تحریک کو ’’عرب بہار ‘‘کا حصہ گردانا جو عرب ملکوں میں مطلق العنان بادشاہوں کے خلاف شروع ہوئی تھی ۔بیسوی صدی کی ساتویں دہائی کے اواخر میں ’’مرگ برشاہ‘‘اور ’’شاہ رفت‘‘کی جو آوزیں تہران کی مرکزی شاہراہوں اور چوکوں میں سنی گئی تھیں۔عرب بادشاہوں کو بھی مطلق العنانی کے خلاف ایسی ہی آوازوں کا سامنا کر نا پڑا ۔اس میں کوئی مبالغہ نہیں کہ انقلاب خواہ کتنا ہی پرانا کیوں نہ ہو جائے اس کی داستان ہمیشہ تازہ رہتی ہے۔ امید اور عمل ،بیداری اور خود شناسی ،جنوں اور لہو کی داستان بھی کبھی پرانی ہو سکتی ہے؟زمانہ اس کو بار بار دہراتا ہے فرق صرف نام ،مقام اور وقت کا ہو تا ہے ۔
Functional magnetic resonance imaging (fMRI) is one of the most powerful neuroimaging modalities due to its high spatio-temporal resolution characteristics. This known modality is applied on mapping the temporal, occipital, frontal cortices of the brain for localizing the neural activities generated due to any visual, physical or mental task or brain diseases or brain disorders. The occipital cortex is composed of middle, left, right, interior and exterior occipital gyrus and is responsible for visional function of human brain. The occipital gyrus reflects the neural image generated in the brain due to any visual activity. In this research paper, four different visual stimuli images of faces, scrambled, scenes and objects along with gap of blank space, forming a long sequence of stimuli observed by two female subjects, are experimented to examine and localize the most contrasting neural image generated in occipital gyrus of the brain. The visual fMRI brain data received from the two subjects is processed through fMRI-SPM12 toolbox based on Matlab software. In order to demonstrate the results statistically, two regressions such as T-contrast and F-contrast vectors are applied on fMRI images to highlight, and to localize the most active neural stimuli activities generated in the occipital gyrus of brain. In the results, it is demonstrated that maximum neural response can be mapped only for face stimulus in the bilateral occipital gyrus of the brain by applying T-contrast vectors regressions as when compared to other stimuli conditions and F-contrast vectors regressions. Further, it is also investigated that, the response of the face stimulus in F-contrast regressions achieved is somehow dispersed and unclear due to the large variances and interlinked communication of other stimuli or induced neural noises generated in entire volume of the brain. Further from the given images, it is also investigated that the most reflecting and contrast area for any visual stimuli (such as face stimulus in this case) is either the middle or bilateral part of occipital gyrus of the human brain as identified through application of T-contrast vectors regressions.
The present research work was aimed to investigate the potential of bismuth sulfide and lead sulphide quantum dots thin films to be employed as n-type and p-type nanomaterials for efficient solar harvesting. Binary and ternary n-type bismuth sulphide and p-type lead sulphide thin films at different dopant concentration levels were deposited by the chemical bath deposition (CBD) and Successive Ionic layer Adsorption Reaction (SILAR) methods, respectively. Nitrate salts were used as cationic precursor, while thioacetamide and sodium sulphide were used as S2- source for deposition of bismuth sulphide and lead sulphide thin films, respectively. The aim of the study was also to improve the optoelectronic properties and reduce the toxicity level of constituent materials particularly, lead sulphide by means of doping. Few earth abundant and environment friendly, bi and tri-valent cations like; Cu2+, Ni2+, Co2+ and Al3+ were used as dopants. Five doped series of Bi2S3 and two series of PbS quantum dots thin films having different dopant content were deposited on microscopic glass slides. CBD and SILAR were found as the suitable and cost effective methods even extendable for the deposition of derivatives of both Bi2S3 and PbS thin films, respectively. Phase composition, optical, electrical, morphological and electronic transport properties were investigated by X-Ray Diffraction, UV-Vis. Spectroscopy, Photoluminescence, Hall Effect Studies, Scanning Electron Microscopy and Atomic Force Microscopy. The film thickness was measured by ellipsometry and was found to be dependent on the composition of bath solutions. Optical parameters i.e. absorption-coefficient, dielectric constants, dispersion and Eurbach energy were investigated. Electronic as well as transport properties including conductivity, type of charge carrier, sheet carrier concentrations and mobility of charges were also studied. The obtained data revealed that all deposited Bi2S3 and PbS quantum dots thin films have direct allowed band gaps energies (Eg). For Bi2S3 thin films, Eg value was 1.6eV which upon dopant addition reduced down to 1.1eV, while in case of PbS quantum dots thin films, Eg was as high up to 2.1eV which was successfully reduced down to 1.8eV. Doping also played a role to enhance the absorption capacity of the materials, especially for Bi2S3 derivatives. In case of Bi2S3 thin films and its derivatives, values of refractive index (n) were found in the range of 2.9 to 1.3 and for extinction co-efficient (k) values were 1.03 to 0.3. While, in case of PbS quantum dots thin films, respective values were in the range of 1.6 to 1.5 and 0.1 to 0.002, respectively. Photoluminescence spectra exhibited by all doped derivatives were also modified with reduced luminescence intensity. Ellipsometry studies revealed the decrease in film thickness for all samples but only in case of Al3+ doped Bi2S3, the thickness increased from 269.99 to 506.04 nm. Structural analysis showed that Bi2S3 conserved its orthorhombic crystal lattice for Ni2+ and Co2+ doped series. While for Cu2+ doped series, emergence of new crystalline phase occurred and for Al+3 doped series, a transition from crystalline to amorphous phase was observed.In case of quantum dots, few other peaks were observed along with PbS cubic phase. Topographical analysis validated the use of most of the synthesized materials in photovoltaic devices due to homogeneous and compact film deposition. Optoelectronic properties suggested that doping is an effective tool to enhance the charge carrier concentration for both the studied materials. All the synthesized binary and ternary materials were studied for fabrication of new heterojunctions in photovoltaic devices. Results showed that efficiency was enhanced from 0.36% to 0.54%, owing to the modification in the characteristic properties of individual n and p layers.