Molecular Gas in the Circumstellar Environment of Unusual Evolved Stars

As low- and intermediate mass stars (with masses up to 8-9 solar masses) age, they experience a series of evolutionary changes which culminate in the removal of nearly their entire envelope through extensive mass loss. The ejected material cools down, which allows for the formation of molecules and the nucleation of dust grains in the circumstellar environment (CSE) of the star. Much about the properties and composition of the gas and dust in these CSEs is not well understood. Here, we study the rich CSEs of two unusual evolved stars by analyzing spectral observations in the infrared and using molecular spectroscopy to determine the chemical and physical properties of the circumstellar gas. We first present the mid-infrared spectrum of the carbon-rich pre-planetary nebula SMP LMC 11. The spectrum is rich in molecular bands of a variety of species, including several polyynes and cyanopolyynes and unusually strong absorption from benzene. We also confirm the presence of propyne. We find that this molecular gas resides in a dense torus around the central object. A detailed comparison with results from chemical models indicates that important chemical pathways to benzene and other carbon-rich molecules are currently missing from the models. Next, we analyze the molecular gas in the mid- and near-infrared spectrum of the peculiar evolved binary HR 4049. This system is known to be surrounded by a long-lived circumbinary disk. We find that the disk is gas-rich, hot, massive and much more radially extended than previously thought. A recent and significant increase in CO2 emission may also point to ongoing processing in the disk. Given the column densities of especially CO2 and H2O in the disk, radiative trapping must be an important ingredient in determining the physical structure of the disk and its resulting spectrum. Such effects may well be important in many other circumstellar environments as well. Finally, we can also estimate the mass of the primary, and conclude that it may be too low for the star to have experienced a ``normal evolutionary path

Antimicrobial activity of copper kaolinite and surfactant modified copper kaolinite against gram positive and gram negative bacteria

The aim of this research was to determine the antimicrobial activity of kaolinite modified with antimicrobial compounds against Gram positive and Gram negative bacteria. Copper kaolinite (Cu-kaolinite) was prepared by loading raw kaolinite with copper nitrate trihydrate (CuNO3) while surfactant modified Cu-kaolinite (SM-Cu-kaolinite) was prepared by adding cationic surfactants hexadecyltrimethyl ammonium (HDTMA) on Cu-Kaolinite. Samples was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyzer. The antimicrobial activity of the samples was tested against Gram negative bacteria (Escherichia coli ATCC 11229 and Pseudomonas aeruginosa ATCC 15442), and Gram positive bacteria (Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 29212) through disc diffusion technique (DDT) and minimum inhibition concentration (MIC). The results showed that the antimicrobial activity of Cu-kaolinite increased after modified with HDTMA due to the synergistic effects of Cu ions and HDTMA molecules on the kaolinite. The antimicrobial activity for surfactant modified Cu-kaolinite was greater for Gram positive bacteria compared to Gram negative bacteria. In conclusion, the attachment of HDTMA on Cu-kaolinite contributed to the enhanced antimicrobial activity against wide spectrum of bacteria (Gram positive and Gram negative bacteria)

A compact and lightweight microstrip antenna array with Wilkinson power divider for X-band application at 9.5 GHz

In this paper, a two-element microstrip antenna array with a compatible 1:2 Wilkinson Power Divider operating at 9.5 GHz for X-band application is presented. The design, simulation and optimization of this work are performed using Computer Simulation Technology (CST) Microwave Studio. The proposed design is shown to exhibit good simulation performances with return loss of -38.21 dB, bandwidth of 493 MHz, and gain of 7.08 dB. Coupled with the antenna array, a 1:2 Wilkinson Power Divider is then designed, simulated and optimized. The simulation result of the power divider exhibits three modes of resonance at 8.0-8.5 GHz, 9.09-10.28 GHz and 11.2-11.5 GHz. The operating frequency at 9.5 GHz resulted an equal power division with insertion loss less than 3.68 dB and less mutual coupling as the isolation factor is at 16.23 dB. The antenna array and Wilkinson Power Divider configuration produced an overall dimension of 83.14 mm 67.34 mm, which realized a portable solution for the parabolic reflector antenna

Psychological and social well-being of the urban poor in Malaysia

Similar to other countries, Malaysia is also affected by the social and economic process of urbanization leading to various concerns, particularly among the urban poor. This conceptual literature review draws on the theoretical framework of absolute poverty, relative poverty, and causal attributions in defining and explaining poverty in urban areas. Psychological and social well-being are known as significant aspects of an individual’s life. Studies conducted internationally and locally have indicated that several factors of psychological well-being such as mental health, financial constraints, and housing vulnerability, contributes to poor psychological well-being of the urban poor. Additionally, previous research has highlighted that the social well-being of urbanites is impacted due to factors such as social exclusion and lack of social support. However, further studies in Malaysia are needed to emphasize different dimensions of individual psychological and social well-being, such as personal growth, autonomy, social contribution, and social coherence

Beam Steering using the Active Element Pattern of Antenna Array

An antenna array is a set of a combination of two or more antennas in order to achieve improved performance over a single antenna. This paper investigates the beam steering technique using the active element pattern of dipole antenna array. The radiation pattern of the array can be obtain by using the active element pattern method multiplies with the array factor. The active element pattern is crucial as the mutual coupling effect is considered, and it will lead to an accurate radiation pattern, especially in determining direction of arrival (DoA) of a signal. A conventional method such as the pattern multiplication method ignores the coupling effect which is essential especially for closely spaced antenna arrays. The comparison between both techniques has been performed for better performance. It is observed that the active element pattern influenced the radiation pattern of antenna arrays, especially at the side lobe level. Then, the beam of the 3x3 dipole antenna array has been steered to an angle of 60° using three techniques; Uniform, Chebyshev and Binomial distribution. All of these are accomplished using CST and Matlab software

Beam steering using the active element pattern of antenna array

An antenna array is a set of a combination of two or more antennas in order to achieve improved performance over a single antenna. This paper investigates the beam steering technique using the active element pattern of dipole antenna array. The radiation pattern of the array can be obtain by using the active element pattern method multiplies with the array factor. The active element pattern is crucial as the mutual coupling effect is considered, and it will lead to an accurate radiation pattern, especially in determining direction of arrival (DoA) of a signal. A conventional method such as the pattern multiplication method ignores the coupling effect which is essential especially for closely spaced antenna arrays. The comparison between both techniques has been performed for better performance. It is observed that the active element pattern influenced the radiation pattern of antenna arrays, especially at the side lobe level. Then, the beam of the 3x3 dipole antenna array has been steered to an angle of 60° using three techniques; Uniform, Chebyshev and Binomial distribution. All of these are accomplished using CST and Matlab softwar

Design and optimize microstrip patch antenna array using the active element pattern technique

Microstrip patch antennas are widely used in modern day communication devices due to their light weight, low cost and ease of fabrication. In this paper, we have designed and fabricated two Microstrip Patch Antennas (slotted-ring and truncated-slotted ring) and array at 2.4 GHz for Wireless Local Area Network (WLAN) applications using Computer Simulation Technology, CST. The antenna design consists of rectangular radiating patch on Rogers RT5880 substrate and is excited by using coaxial probe feeding technique. The truncated-slotted ring has been designed on top of the radiating patch to improve bandwidth. The simulation and measurement results of the both antennas are in close agreement with each other. Due to the good agreement of simulation and measurement results of truncatedslotted ring antenna in comparison with slotted-ring antenna, it has been selected for antenna array design. The simulated and measured S11 of truncated-slotted ring antenna shows -21dB and -15.6 dB at 2.4 GHz respectively. Then, the antenna has been formed into 1x4 array in order to observe its beamforming capability. The proposed antenna array is suitable for 802.11b/g/n Wi-Fi standard which is proposed to be used for IoT