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Descriptor systems can describe algebraic constraints and impulsive behaviour of systems and hence represent more general and broad category of complex dynamical systems. The impulsive behaviour of descriptor systems must be eliminated as it can cause degradation and saturation in performance or even can damage the system. To eliminate impulsive modes using discrete-time controllers, discrete-time models of descriptor systems are required. This paper deals with this problem and proposes a novel discretization technique for regular descriptor systems with impulsive mode when the input is applied through a zero-order-hold device. Using the Kronecker canonical form, the system model is decomposed into exponential, static and impulsive modes. Exact discrete-time models of exponential and static modes are obtained but an approximate discrete-time model for impulsive mode is proposed using limiting value functions because exact discretization is not possible as digital devices cannot realize infinite magnitude in zero time. An upper bound on error introduced by discretization is also derived. In addition, a simulation example is presented to show the efficacy of the proposed technique. [ABSTRACT FROM AUTHOR]

Not only is the reuse of wastewater, particularly for irrigation purposes, an increasingly common practice in developing countries, it is also encouraged by many governments and official entities. Although exposure to wastewater has noteworthy hazardous effects on human health and the environment, this is poorly understood by farmers who reuse wastewater for crop production. Using household-level survey data of 321 respondents, this study investigates the effects of wastewater reuse on farmers' perceived health risks and the determinants of farmers' reuse of wastewater for vegetable production in Punjab, Pakistan. A Zero-Inflated Poisson (ZIP) regression model shows that wastewater irrigation has a significant positive effect (P < 0.05) on farmers' perceived health risks. Farmers using wastewater have relatively little knowledge of its negative effects on human health compared to their counterparts using freshwater. Around 85% and 80% of farmers who used wastewater state that water scarcity and decreased production costs were the key reasons why they use wastewater for vegetable production, respectively. A logit regression model indicates that farmer age, household size, irrigation experience, income, access to institutional credit, awareness of health risks, access to canal water, ownership of tube well, and perceived health risks are the key determinants of wastewater reuse. The findings of this study and subsequent recommendations may guide policymakers in educating and updating farmers' knowledge about the hazardous effects of wastewater through frequent training and workshops. Installation of plants for wastewater treatment by collecting a pollution premium from farmers seems to be a viable option for sustainable agricultural development. • Effects of wastewater reuse on perceived health risks of farmers were examined. • Wastewater reuse had a significant positive effect on farmers' perceived health risks. • Illness rates were higher among farmers who used wastewater than their fresh water using counterparts. • Farmers reused wastewater for a variety of reasons, including water scarcity, lower production costs, and increased crop yields. • Increased farmer awareness and knowledge may aid in reducing wastewater reuse. [ABSTRACT FROM AUTHOR]

The present study describes synthesis of amino-decorated mesoporous silica nanoparticles (MSNs) for sustained delivery and enhanced bioavailability of sofosbuvir. Sofosbuvir is active against hepatitis C virus and pharmaceutically classified as class III drug according to biopharmaceutics classification system (BCS). MSNs were synthesized using modified sol-gel method and the surface was decorated with amino functionalization. Drug loaded MSNs were also grafted with polyvinyl alcohol in order to compare it with the amino-decorated MSNs for sustained drug release. The prepared MSNs were extensively characterized and the optimized formulation was toxicologically and pharmacokinetically evaluated. The functionalized MSNs of 196 nm size entrapped 29.13% sofosbuvir in the pores, which was also confirmed by the decrease in surface area, pore volume and pore size. The drug-loaded amino-decorated MSNs revealed an improved thermal stability as confirmed by thermal analysis. Amino-decorated MSNs exhibited Fickian diffusion controlled sofosbuvir release as compared with non-functionalized and PVA grafted MSNs. Amino-decorated MSNs were deemed safe to use in Sprague-Dawley rats after 14-days exposure as confirmed by the toxicological studies. More interestingly, we achieved a 2-fold higher bioavailability of sofosbuvir in Sprague-Dawley rats in comparison with sofosbuvir alone, and the T max was delayed 3-times indicating a sustained release of sofosbuvir. Image, graphical abstract [ABSTRACT FROM AUTHOR]

This work presents an analysis of a two-dimensional model of a liquid chromatographic column. Constant flow rates and linear adsorption isotherms are assumed. Different sets of boundary conditions are considered, including injections through inner and outer regions of the column inlet cross section. The finite Hankel transform technique in combination with the Laplace transform method is applied to solve the model equations. The developed analytical solutions illustrate the influence and quantify the magnitude of the solute transport in the radial direction. Comparing Dirichlet and Danckwerts boundary conditions, the predicted elution profiles differ significantly for large axial dispersion coefficients. For further analysis of the solute transport behavior, the temporal moments up to the fourth order are derived from the Laplace-transformed solutions. The analytical solutions for the concentration profiles and the moments are in good agreement with the numerical solutions of a high resolution flux limiting finite volume scheme. Results of different case studies are presented and discussed covering a wide range of mass transfer characteristics. The derived analytical solutions provide useful tools to quantify jointly occurring longitudinal and radial dispersion effects. [ABSTRACT FROM AUTHOR]

In this work the catalytic activity of cobalt based MOF and its composites with graphene oxide (GO) towards electrochemical oxidation of methanol is studied. Co-MOF-71 and its GO composites were prepared by hydrothermal method and characterized by X-ray diffraction, XPS, scanning electron microscopy and FTIR. XRD patterns revealed incorporation of GO without disturbing the crystal structure. The synthesized catalysts were tested for their electrocatalytic activity for methanol oxidation reaction (MOR) in alkaline medium. The electrochemical parameters measured with modified GCE represent the effect of graphene oxide on methanol oxidation reaction catalysed by Co-MOF-71. Co-MOF-71/GO composite showed excellent peak current density (29.1 mA/cm 2 ) at lower potential (0.1 V) and scan rate of 50 mV/s. The enhanced electrochemical activity and stability is attributed to the synergetic effect of the MOF and the GO substrate for methanol oxidation. [ABSTRACT FROM AUTHOR]

Pakistan is among the naturally gifted countries that are rich in conventional and renewable energy resources. Despite the massive potential of energy resources, Pakistan is still an energy deficient country and have to import petroleum products to barely accomplish its energy demand. Geothermal energy is still one of the unexplored energy resources for electric power generation in Pakistan. Pakistan can overcome the energy shortage to a significant level by harnessing renewable energy resources, such as, geothermal energy. Majority of the geothermal hot springs and mud volcanoes exists within the seismic belt of Pakistan. Therefore, the country has viable geothermal energy manifestations. Several hot springs in Gilgit and Hunza region are originated due to the collision of Indian Plate with Eurasian Plate. Similarly, various geothermal reservoirs exist in Northeast to Southeast narrow belt along Indus basin margin. The survey discusses the current energy crisis in Pakistan and addresses the role of geothermal energy for the economic development of Pakistan. We served the manifestation and geographies of geologically active zones of Pakistan, like fault lines, plate tectonics, belt, and tectonic thrust, cleanest, base load, reliable, renewable, and sustainable geothermal energy resources. In our work, the hot springs and mud volcanoes of geologically active areas in maps are enlisted in Tables with potential features. The schemes used for extraction of geothermal energy for electric power generation are also investigated. The global electric power production from geothermal energy is visualized and discussed. Moreover, the suitable moderate temperature Binary Cycle Geothermal Power Plant for electric power generation in Pakistan is also described in detail. Furthermore, geothermal plants are experimentally summarized in different case studies. Finally the performance of geothermal and conventional thermal plants is critically analysed. [ABSTRACT FROM AUTHOR]

Climate change may influence crop income negatively or positively. To address this, present study is an attempt to quantify the impacts of climate change on net income from crop farming in Bangladesh using Ricardian method. For estimating the relationship between net crop income and climatic parameters, farm household and climate data were collected from the selected agro-ecological zones (AEZs) in Bangladesh. The results revealed that net crop income is sensitive to climate, particularly to seasonal temperature. Temperature rise was found to be positively influencing net crop income in AEZs having adequate irrigation facilities. Marginal impact estimates suggest that increase in temperature and rainfall will lead to increase in net income from crop farming in Bangladesh. However, the impacts will vary significantly across cropping seasons and space (studied AEZs). Using selected AOGCM scenarios, the study predicts that net crop incomes are expected to increase in the future. The empirical findings underscore the need for policy makers to take agro-ecological zones specific effects of climate change into consideration when formulating and implementing the adaptation strategies in Bangladesh. • Analyzes economic impacts of climate change on crop farming in Bangladesh. • Net crop income in Bangladesh is more sensitive to temperature than rainfall. • Increasing temperature and rainfall would cause an increase in crop income. AOGCMs predict positive future impacts on net crop income. • Irrigation is a key adaptation measure to offset climate impacts and to maintain and boost income from crop farming. • Underscores the importance of agro-ecological zones (AEZs) specific adaptation policy. [ABSTRACT FROM AUTHOR]