A Methodology for Engineering Collaborative and ad-hoc Mobile Applications using SyD Middleware

Today’s web applications are more collaborative and utilize standard and ubiquitous Internet protocols. We have earlier developed System on Mobile Devices (SyD) middleware to rapidly develop and deploy collaborative applications over heterogeneous and possibly mobile devices hosting web objects. In this paper, we present the software engineering methodology for developing SyD-enabled web applications and illustrate it through a case study on two representative applications: (i) a calendar of meeting application, which is a collaborative application and (ii) a travel application which is an ad-hoc collaborative application. SyD-enabled web objects allow us to create a collaborative application rapidly with limited coding effort. In this case study, the modular software architecture allowed us to hide the inherent heterogeneity among devices, data stores, and networks by presenting a uniform and persistent object view of mobile objects interacting through XML/SOAP requests and responses. The performance results we obtained show that the application scales well as we increase the group size and adapts well within the constraints of mobile devices

Simplified immobilisation method for histidine-tagged enzymes in poly(methyl methacrylate) microfluidic devices

Article in press. Kulsharova, G., New BIOTECHNOLOGY (2017), https://doi.org/10.1016/j.nbt.2017.12.004Poly(methyl methacrylate) (PMMA) microfluidic devices have become promising platforms for a wide range of applications. Here we report a simple method for immobilising histidine-tagged enzymes suitable for PMMA microfluidic devices. The 1-step-immobilisation described is based on the affinity of the His-tag/Ni-NTA interaction and does not require prior amination of the PMMA surface, unlike many existing protocols. We compared it with a 3-step immobilisation protocol involving amination of PMMA and linking NTA via a glutaraldehyde cross-linker. These methods were applied to immobilise transketolase (TK) in PMMA microfluidic devices. Binding efficiency studies showed that about 15% of the supplied TK was bound using the 1-step method and about 26% of the enzyme was bound by the 3-step method. However, the TK-catalysed reaction producing l-erythrulose performed in microfluidic devices showed that specific activity of TK in the device utilising the 1-step immobilisation method was approximately 30% higher than that of its counterpart. Reusability of the microfluidic device produced via the 1-step method was tested for three cycles of enzymatic reaction and at least 85% of the initial productivity was maintained. The device could be operated for up to 40 h in a continuous flow and on average 70% of the initial productivity was maintained. The simplified immobilisation method required fewer chemicals and less time for preparation of the immobilised microfluidic device compared to the 3-step method while achieving higher specific enzyme activity. The method represents a promising approach for the development of immobilised enzymatic microfluidic devices and could potentially be applied to combine protein purification with immobilisation.Peer reviewe

Discovery of Infection Associated Metabolic Markers in Human African Trypanosomiasis

Peer reviewedPublisher PD

Permeability and chemical analysis of aromatic polyamide based membranes exposed to sodium hypochlorite

In this study, a cross-linked aromatic polyamide based reverse osmosis membrane was exposed to variable sodium hypochlorite ageing conditions (free chlorine concentration, solution pH) and the resulting evolutions of membrane surface chemical and structural properties were monitored. Elemental and surface chemical analysis performed using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), showed that chlorine is essentially incorporated on the polyamide layer of a commercially available composite RO membrane, when soaked in chlorine baths, presumably through a two step electrophilic substitution reaction governed by the concentration of hypochlorous acid (HOCl), at pH values above 5. Deconvolution of the FTIR vibrational amide I band experimentally confirmed previous assumptions stated in the literature regarding the weakening of polyamide intermolecular hydrogen bond interactions with the incorporation of chlorine. An increase in the fraction of non associated Cdouble bond; length as m-dashO groups (1680 cm−1) and a decrease of hydrogen bonded Cdouble bond; length as m-dashO groups (1660 cm−1) were observed with an increase in the concentration of the free chlorine active specie. The relative evolution of pure water permeability was assessed during lab-scale filtration of MilliQ water of a membrane before and after exposure to chlorine. Filtration results indicate polyamide conformational order changes, associated with the weakening of polyamide intermolecular H bonds, as observed with the increase in the packing propensity of the membrane, dominant for HOCl doses above 400 ppm h. In addition, water–sodium chloride selectivity capabilities permanently decreased above this HOCl concentration threshold, further suggesting polyamide chain mobility. However, under controlled exposure conditions, i.e., HOCl concentration, operating conditions (applied pressure or permeation flux) can be improved while maintaining similar RO membrane separation performance

When Channel Bonding is Beneficial for Opportunistic Spectrum Access Networks

Transmission over multiple frequency bands combined into one logical channel speeds up data transfer for wireless networks. On the other hand, the allocation of multiple channels to a single user decreases the probability of finding a free logical channel for new connections, which may result in a network-wide throughput loss. While this relationship has been studied experimentally, especially in the WLAN configuration, little is known on how to analytically model such phenomena. With the advent of Opportunistic Spectrum Access (OSA) networks, it is even more important to understand the circumstances in which it is beneficial to bond channels occupied by primary users with dynamic duty cycle patterns. In this paper we propose an analytical framework which allows the investigation of the average channel throughput at the medium access control layer for OSA networks with channel bonding enabled. We show that channel bonding is generally beneficial, though the extent of the benefits depend on the features of the OSA network, including OSA network size and the total number of channels available for bonding. In addition, we show that performance benefits can be realized by adaptively changing the number of bonded channels depending on network conditions. Finally, we evaluate channel bonding considering physical layer constraints, i.e. throughput reduction compared to the theoretical throughput of a single virtual channel due to a transmission power limit for any bonding size.Comment: accepted to IEEE Transactions on Wireless Communication

A Novel Admission Control Model in Cloud Computing

With the rapid development of Cloud computing technologies and wide adopt of Cloud services and applications, QoS provisioning in Clouds becomes an important research topic. In this paper, we propose an admission control mechanism for Cloud computing. In particular we consider the high volume of simultaneous requests for Cloud services and develop admission control for aggregated traffic flows to address this challenge. By employ network calculus, we determine effective bandwidth for aggregate flow, which is used for making admission control decision. In order to improve network resource allocation while achieving Cloud service QoS, we investigate the relationship between effective bandwidth and equivalent capacity. We have also conducted extensive experiments to evaluate performance of the proposed admission control mechanism

On application of least-delay variation problem in ethernet networks using SDN concept

The goal of this paper is to present an application idea of SDN in Smart Grids, particularly, in the area of L2 multicast as defined by IEC 61850-9-2. Authors propose an Integer Linear Formulation (ILP) dealing with a Least-Delay-Variation multicast forwarding problem that has a potential to utilize Ethernet networks in a new way. The proposed ILP formulation is numerically evaluated on random graph topologies and results are compared to a shortest path tree approach that is traditionally a product of Spanning Tree Protocols. Results confirm the correctness of the ILP formulation and illustrate dependency of a solution quality on the selected graph models, especially, in a case of scale-free topologies

Thermal Stability of Distillate Hydrocarbon Fuels

Thermal stability of fuels is expected to become a severe problem in the future due to the anticipated use of broadened specification and alternative fuels. Future fuels will have higher contents of heteroatomic species which are reactive constituents and are known to influence fuel degradation. To study the degradation chemistry of selected model fuels, n-dodecane and n-dodecane plus heteroatoms were aerated by bubbling air through the fuels amd stressed on a modified Jet Fuel Thermal Oxidation Tester facility operating at heater tube temperatures between 200 to 400 C. The resulting samples were fractionated to concentrate the soluble products and then analyzed using gas chromatographic and mass spectrometric techniques to quantify and identify the stable reaction intermediate and product specifically. Heteroatom addition showed that the major soluble products were always the same, with and without heteroatoms, but their distributions varied considerably