Theoretical Investigations on Enhancement of Nonlinear Optical Properties of Alkali and Alkaline Earth Metal Doped X12Y12 Nanocages Materials with nonlinear optical response find applications in laser physics, optical fibers, optical computing, optical data handling, optical wave guides and gyroscopes, optical limiters, sensors and scanners. A number of strategies have appeared in the literature to design high performance nonlinear optical materials. A few well studied strategies are bond length alternation (BLA), synthesis of octupolar molecules, molecules with diradical character electrides, and alkalides. A relatively less explored strategy is doping of organic and inorganic systems with alkali metals. Doping with alkali metal generates diffuse excess electrons which reduce the transition energies for crucial excitations. The present research aims at exploring the potential of alkali and alkaline earth metal doping on the nonlinear optical response of X12Y12 nanocages. The objective of this study is not only to find the best nano-cage for doping but also to compare alkali metal with alkaline earth metal doping (substitutional and exohedral). Prior to this study, the literature illustrated only exohedral doping of alkali metal on Al12N12 nano-cage. In this study, Al12N12, B12N12, Al12P12 and B12P12 nanocages were studied. The stabilities of exohedral and substitutional doped nanocages are evaluated through adsorption and cohesive energies, respectively. The exohedral complexes of alkali metal are quite stable as reflected from their adsorption energies; however, certain alkaline earth metal doped systems have negligible adsorption energies. Cohesive energies of substitutional doped nanocages were less than the undoped system. Regardless of the doping mode, the HOMO-LUMO gaps are reduced significantly. The H-L gaps are reduced up to 74% of the original value. The maximum change in H-L gap is observed for Ca@PtopAl12P12 where the gap is reduced to 74.4% of the pristine AlP nanocage. The decrease in H-L gap also reduced the energies for crucial excitation which leads to significantly higher hyperpolarizabilities. The hyperpolarizabilities of the doped nanocages generally range from 1.3×102 au to 7.9×105 au which are several orders of magnitude higher than the values for pristine nanocages. Two level model is also applied to rationalize the obtained hyperpolarizabilities of certain doped systems. The trends of xi hyperpolarizabilities from two level method agree with the hyperpolarizability values from DFT calculations. 2nd hyperpolarizability values, which are real measure of practical application of a system are evaluated through βvec, are also remarkably high and in the same order as first hyperpolarizabilities. The participation of diffuse excess electrons in boosting nonlinear optical response of these doped systems is confirmed through analysis of partial densities of states. The results offer new insight into structure property relationship of inorganic fullerenes in designing new high performance nonlinear optical materials.
هدفت الدراسة للتعرف على المعايير المهنية للإدارة والقيادة المدرسية في بعض الدول الأفريقية وإمكانية الإفادة منها بسلطنة عمان، واتبعت الدراسة المنهج الوصفي، كما استخدمت نظرية تحليل المضمون في تحليل الوثائق في جمع البيانات والمعلومات. وتوصلت الدراسة إلى مجموعة من النتائج أهمها: أن معايير الإدارة والقيادة المدرسية في سلطنة عمان تركز على تناول المؤشرات دون تفسير شامل ومُتكامل لتلك المعايير، وأن مؤشرات كل معيار محدودة وقليلة للغاية ولا تٌلبي طموحات تطوير القيادة المدرسية في سلطنة عُمان في ضوء خططها المُستقبلية، وأنها بحاجة إلى معايير مستقلة في المعارف والمهارات والاتجاهات المهنية، كما أنها بحاجة إلى التركيز على المُصطلحات والمفاهيم التربوية والإدارية المُعاصرة مثل: التخطيط الاستراتيجي، والشراكات المجتمعية، وتكنولوجيا المعلومات والاتصالات، ومجتمعات التعلم المهنية، وأخلاقيات مهنة الإدارة المدرسي
The challenges accompanying socio-ecological and demographic transformations in the urban areas necessitate for coordinated efforts to ensure urban ecological resilience. Trans-disciplinary analytical construct of urban eco-system services (UES) empowers the policy makers and urban planners to synchronize the orientations of human impacts and resilience of ecological resources in urban areas. The current study provides a systematic overview about the research orientations, approaches and techniques used in the recent studies regarding UES. The study examined: what types of evaluation methods were adopted in the recent UES research? What is their spatial and temporal pattern? What types of UES were focused and environmental components relied upon for the assessment? To address these questions, 116 relevant publications were scrutinized by using a set of assessment criteria. The findings indicated a lesser focus in research towards UES in developing countries as compared to the volume and increasing share of their urban population. The study also establishes that an overwhelming proportion of the UES research was carried out in the industrialized countries of the northern hemisphere but rather skewed towards studying regulatory eco-system services. The recommendations for improving the relevancy of contemporary research for stakeholders were made. The present study deciphers the impacts of urban planning and role of socio-economic determinants on the perception about urban vegetation. The residents inhabiting the planned (Islamabad) and the semi-planned (Rawalpindi) urban centres were the study population. Both urban areas, lying in close proximity, face rapid transformations in LULC due to urbanization. Despite their closeness, such variants as discrepancies in the standards of urban-planning and socio-economic characteristics of inhabitants make them apt study-sites. The inhabitants’ perception was tapped regarding the importance of urban vegetation, temporal and spatial changes and their impacts. The majority concurred to its efficacy, a substantial proportion observed transformations in it over time while a reasonable number perceived these changes as negative and unwelcome. Such socio-economic determinants as location, education, gender, ownership status of residence and income of respondents were studied, deploying Statistical analyses (KW). Responses varied, with location and income weighing-in more heavily. Pairwise comparison (WRST) further vindicated the results. Urbanization is sure to tarnish the environmental sustainability of both cities. Synchronized efforts from all stakeholders are a must. LULC changes transform everything. They test the resilience of natural environment making their study imperative.Such advanced tools as remote sensing (RS) and geographic information system (GIS) were deployed and assessments made by developing codes in the Google earth engine (GEE). The current investigation used Islamabad and Rawalpindi as contextual settings. These physically close cities are distanced by contradictory policies and management frameworks rendering them as perfect locales for research. Temporal quantitative fluctuations in the selected LULC were observed and shrinkages and expansions noticed according to the varying human needs. Population-growth and migration have, primarily, triggered these transformations. The intrusion of private conglomerates for their business gains, made urbanization unruly.The study reveals how organized land-management policies succeeded in Islamabad and compromised policies failed in Rawalpindi. Effective legislation and compelling implementation are indispensable for sustained urban growth. Urbanization is proving stressful for the supply-demand budget of eco-system Services (ESS) and a real challenge of the present times. It is accelerating in Pakistan and demands enhanced focus on ESS research. Keeping in view the contextual constraints, the land cover-based Matrix Model was relied upon. It linked the LULC types of the study area for assessments of supply and demand potential of ESS by integrating expertbased judgments. The findings established that the built up areas are the principal consumer and ecological resources as producers of ESS in the study context. The degeneration in the performances of ecological infrastructure is more acute in Rawalpindi as compared to Islamabad. The observed variations are rooted in the differences in the socio-demographic aspects planning and management.The findings confirmed that the matrix model is a pragmatic option for assessing the supply-demand potentials of ESS in developing regions.