Multivariate Analysis of Rotifers Community from Safari Zoo Lake Lahore, Pakistan

Rotifers are zooplanktons that react more sharply to the environmental changes. Objective: To better understand the community composition of rotifers in Safari Zoo Lake, Lahore, PakistanMethods: wecollected 16 water samples on monthly basis, dividing lake into four major sites: northern, southern, eastern, and western sites. Each of these was further subdivided into four locations, for a total of 16 sampling sites. A total 23 rotifer species were recorded from the lake with Brachionus calyciflorus having maximum abundance. A species abundance curve was plotted between months and number of species of rotifers indicating their lowest and highest abundance through the study period. Results: A Cluster Analysis yielded three main groups of closely related species including species like Brachionus quadridentatus, Synchaeta stylata and Brachionus calyciflorusetc. We used a Principal Component Analysis (I and II) to study variation in the rotifer community on a seasonal basis and among sampling sites. A biplot of Principal Component Analysis (PCA I) reflected the relationship of rotifers with the months. Some of the species showed a positive positive relationship, while others showed negative one. PCA II was plotted between months and physico-chemical parameters showing their negative and positive relations. Conclusions: We conclude that a lesser replacement of fresh water, increased density of waterfowl, reptilia and solid waste left overduring boating has resulted in eutrophication of lake leading to overall low diversity of rotifers observed

Reflect Arrays for High Gain Applications

This research work focuses on design and analysis of low-cost, single-layer broadband reflectarrays for X-band applications. Traditionally, parabolic reflectors and phased arrays were introduced to obtain the high gain. The disadvantages associated with traditional antenna types include: narrow bandwidth, high fabrication cost and complex feed networks. Recently, reflectarray antennas have been developed to overcome the disadvantages associated with parabolic reflectors and phased arrays. High gain reflectarray antennas are typically employed in radars, satellite communication and direct broadcasting applications. Four different type of delay-lines integrated reflectarray elements which include: single circular delay-line, pair of circular delay-lines, quad-meander and T-shape delay-lines are designed to obtain a broad linear phase range, high gain and good aperture efficiency. The reflectarray unit element performance is investigated in terms of phase range, Transverse Electric (TE) and Transverse Magnetic (TM) modes and far-field radiation patterns. The reflectarray unit element is analyzed by using circuit model technique and equivalent circuit results are verified through High Frequency Structure Simulator (HFSS™). The circuit model technique replaces the lengthy full-wave simulation of FEM method. This method provides fast and accurate calculation of electromagnetic parameters i.e. magnitude and phase range. The unit element shape and configurations are used to extract the lumped parameters and reflection characteristics. The reflectarray antenna system contains a feed horn antenna and an arrangement of phase shifting array elements. A hybrid Finite Element Boundary Integral (FEBI) method is used for electromagnetic modeling of reflectarray antenna system. The FEBI method provides accurate electromagnetic analysis of complex and medium-to-large sized structures. The reflectarray far-field radiation characteristics are obtained by using the hybrid FEBI method. The reflectarray antenna system model comprises of feed horn antenna and array of phase shifting elements. The feed horn antenna and array elements are designed separately. The effect of the incident angle, feed-to-diameter ratio and transmission modes can easily be considered in the FEBI based system simulations. The proposed reflectarray prototypes are fabricated and measured on a low-cost FR-4 substrate. The reflectarray antenna measurements are made in anechoic chamber. A gain of more than 20 dBi is realized for the proposed reflectarray configurations. The simulated and measured cross polarizations and side-lobe-levels are below -20 dB in all design configurations. More importantly, simulated results are in good agreement with the measured results.