University College for Women

About: University College for Women is a education organization based out in Hyderabad, India. It is known for research contribution in the topics: Catalysis & Ion. The organization has 242 authors who have published 260 publications receiving 2334 citations.

An investigation on the influence of support type for Ni catalysed vapour phase hydrogenation of aqueous levulinic acid to γ-valerolactone

Abstract: Ni (20 wt%) supported on SiO2, γ-Al2O3 and ZrO2 catalysts was examined for hydrogenation of aqueous levulinic acid (LA) to γ-valerolactone (GVL) at 270 °C and ambient pressure. The band intensities of Bronsted (BAS: 1540 cm−1) and Lewis acid sites (LAS: 1450 cm−1) estimated by pyridine adsorbed DRIFT spectra revealed a lower ratio of BAS/LAS over the Ni/SiO2 catalyst than over the Ni/ZrO2 and Ni/γ-Al2O3 catalysts. The rate of angelica lactone (AL) formation was lower than the rate of AL hydrogenation over the Ni/SiO2 catalyst. The poisoning and regeneration of the Ni/SiO2 catalyst using pyridine and 2,6-dimethylpyridine demonstrated that Lewis acid sites influenced the conversion of LA to AL and subsequent hydrogenation of AL to GVL occurred on surface Ni sites. In contrast, Bronsted acid sites were responsible for the ring opening of GVL to valeric acid (VA). Kinetic data emphasized that the hydrogenation activity and product distribution were dependent on the type of acid site, and the Ni sites in close proximity to Bronsted acid sites are prone to hydrogenolysis of GVL to valeric acid and hydrocarbons.

Bandwidth Aggregation-Aware Dynamic QoS Negotiation for Real-Time Video Streaming in Next-Generation Wireless Networks

Abstract: In next generation wireless networks, Internet service providers (ISPs) are expected to offer services through several wireless technologies (e.g., WLAN, 3G, WiFi, and WiMAX). Thus, mobile computers equipped with multiple interfaces will be able to maintain simultaneous connections with different networks and increase their data communication rates by aggregating the bandwidth available at these networks. To guarantee quality-of-service (QoS) for these applications, this paper proposes a dynamic QoS negotiation scheme that allows users to dynamically negotiate the service levels required for their traffic and to reach them through one or more wireless interfaces. Such bandwidth aggregation (BAG) scheme implies transmission of data belonging to a single application via multiple paths with different characteristics, which may result in an out-of-order delivery of data packets to the receiver and introduce additional delays for packets reordering. The proposed QoS negotiation system aims to ensure the continuity of QoS perceived by mobile users while they are on the move between different access points, and also, a fair use of the network resources. The performance of the proposed dynamic QoS negotiation system is investigated and compared against other schemes. The obtained results demonstrate the outstanding performance of the proposed scheme as it enhances the scalability of the system and minimizes the reordering delay and the associated packet loss rate.

Antimicrobial compounds produced by probiotic Lactobacillus brevis isolated from dairy products

Abstract: A total of 38 lactic acid bacteria, belonging to Lactobacillus, isolated from 24 samples of traditional Egyptian dairy products, were screened for antimicrobial activity against different Gram-positive and Gram-negative bacteria. A strain of Lactobacillus brevis showed the best inhibitory activity when tested by well diffusion assay. The antibacterial activity was pronounced between early logarithmic and early stationary phases. The strain produced a heat-stable antimicrobial compound showing no reduction in activity after heat treatment from 60 to 100°C for 15 and 30 min. Since it was inactivated by proteolytic enzymes, it is considered to be proteinaceous in nature and, therefore, referred to as a bacteriocin-like substance. This compound was also active over a wide pH range (pH 2–6). The antimicrobial compound was partially purified by 40% ammonium sulfate precipitation. Lactobacillus brevis was tested for its in vitro antibiotics susceptibility, tolerance to bile salts, resistance to low pH values, acidifying activity, proteolytic activity, and haemolytic activity. The results showed the potential of L. brevis strain as a probiotic culture, and hence it can be utilized in the manufacturing of pharmaceuticals and dietary supplements.