Antimicrobial, Mechanical, and Moisture Barrier Properties of Low pH Whey Protein-based Edible Films Containing p-Aminobenzoic or Sorbic Acids

ABSTRACT: Low pH (5.2) whey protein isolate-based edible films containing p-aminobenzoic acid (PABA) or sorbic acid (SA) were developed and assessed for inhibition of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium DT104 in a disc diffusion assay. Water vapor permeability (WVP), tensile strength (TS), and percent elongation (%E) were also determined. Using 1.5% PABA and SA, average inhibition zone diameters were 21.8, 14.6, 13.9, and 26.7, 10.5, 9.7 mm for L. monocytogenes, E. coli O157:H7, and S. Typhimurium DT104, respectively. Three strains of S. Typhimurium DT104 were resistant to 0.5% SA. Addition of PABA and SA increased %E, but decreased TS. WVP was not affected by 0.5% and 0.75% SA; however, PABA increased WVP.     

A Real-Time and Reliable Transport (RT)$^{2}$ Protocol for Wireless Sensor and Actor Networks

Wireless sensor and actor networks (WSANs) are characterized by the collective effort of heterogeneous nodes called sensors and actors. Sensor nodes collect information about the physical world, while actor nodes take action decisions and perform appropriate actions upon the environment. The collaborative operation of sensors and actors brings significant advantages over traditional sensing, including improved accuracy, larger coverage area and timely actions upon the sensed phenomena. However, to realize these potential gains, there is a need for an efficient transport layer protocol that can address the unique communication challenges introduced by the coexistence of sensors and actors. In this paper, a real-time and reliable transport (RT) protocol is presented for WSANs. The objective of the (RT) protocol is to reliably and collaboratively transport event features from the sensor field to the actor nodes with minimum energy dissipation and to timely react to sensor information with a right action. In this respect, the (RT) protocol simultaneously addresses congestion control and timely event transport reliability objectives in WSANs. To the best of our knowledge, this is the first research effort focusing on real-time and reliable transport protocol for WSANs. Performance evaluations via simulation experiments show that the (RT) protocol achieves high performance in terms of reliable event detection, communication latency and energy consumption in WSANs.     

UV curable sulfonated hybrid materials and their performance as proton exchange membranes

In this study 2-acrylamido-2-methylpropanesulfonic acid (AMPS) containing UV curable nanocomposite membranes were prepared by using the sol–gel method. Tetraethylorthosilicate (TEOS), and 3-(methacryloyloxy)propyl trimethoxysilane (MAPTMS) were used, respectively as an inorganic precursor and coupling agent. Cross linking agents such as poly(ethylene glycol diacrylate) (PEGMA) and ethylene glycol dimethacrylate (EGDMA) were used to arrange the mechanical and physical properties of the resulting hybrid membrane. The hybrid formulation polymerized under UV irradiation and the gel percentage, water uptake of the membranes were calculated. The polymerization conversion of the organic part was investigated by using photo-differential scanning calorimetry (photo-DSC). The thermal and mechanical properties of the membranes indicated good stability. The morphological structure of membranes was investigated by scanning electron microscopy (SEM). In addition proton conductivity and methanol selectivity measurements were performed. The proton conductivity of the AMPS20–SOLGEL30 nanocomposite membrane is about 0.138 S cm^?1 at 50 °C. Selectivity toward methanol for the same membrane is very low with a selectivity factor of α = 0.032, which satisfies the requirements for DMFC applications.     

Predicting stripping and moisture induced damage of asphalt concrete prepared with polymer modified bitumen and hydrated lime

Many highway agencies have been experiencing premature failures that decrease the performance and service life of pavements. One of the major causes of premature pavement failure is the moisture damage of the asphalt concrete layer. Many variables affect the amount of water damage in the asphalt concrete layer such as the type of aggregate, bitumen, mixture design and construction, level of traffic, environment, and the additive properties that are introduced to the bitumen, aggregate or bitumen–aggregate mixture.This study is aimed to determine the effect of additives such as hydrated lime as well as elastomeric (SBS) and plastomeric (EVA) polymer modified bitumen (PMB) on the stripping potential and moisture susceptibility characteristics of hot mix asphalt (HMA) containing different types of aggregate (basalt–limestone aggregate mixture and limestone aggregate). The stripping properties and moisture susceptibility characteristics of the samples have been evaluated by means of captured images and the Nicholson stripping test (ASTM D 1664) as well as the modified Lottman test (AASHTO T 283), respectively.The results indicated that hydrated lime addition and polymer modification increased the resistance of asphalt mixtures to the detrimental effect of water. Moreover, it was found out that samples prepared with SBS PMB exhibited more resistance to water damage compared to samples prepared with EVA PMB.     

Rate-dependent deformation of Sn–3.5Ag lead-free solder

Compression experiments on bulk Sn-3.5Ag lead-free solder specimens have been carried out to help formulate the material constitutive behaviour of this alloy using the concept of an evolving internal stress. Tests covered the temperature range 0–125 °C and fixed strain rates between 3 × 10⁻⁷–3 × 10⁻³ s⁻¹. Flow behaviour was found to be compatible with that for a deforming a tin-rich matrix (stress exponent n = 7, activation energy Q = 46.7 kJ/mol) in which the external applied stress is reduced by an internal back stress due to the presence of precipitate phase particles. Stress–strain curves have been satisfactorily modelled using rate equations incorporating linear hardening and diffusion-controlled recovery. Comparison with supplementary tension and creep experiments, and with data from other researchers, indicates that inconsistencies in reported flow behaviour is most likely to be due to variations in initial microstructure rather than the nature of the applied loading.     

Damping behavior of 6061Al/Gr metal matrix composites

The damping behavior of graphite particulate-reinforced 6061A1 alloy metal matrix composites (MMCs) processed by spray atomization and codeposition is studied. Four spray deposition experiments are made, yielding materials with graphite volume fractions of 0, 0.05, 0.07, and 0.10. A dynamic mechanical thermal analyzer is used to measure the damping capacity and elastic modulus at 0.1, 1, and 10 Hz over the temperature range of 30 °C to 250 °C. The damping capacity of the materials is shown to increase with increasing volume fraction of graphite. Hot extrusion of the spray-deposited MMCs is shown to further increase the damping capacity. The elastic moduli of the spray-deposited MMCs are reduced with the addition of graphite but are improved by hot extrusion. At low temperatures (below 150 °C), the high damping capacity of the MMCs is attributed primarily to thermal expansion mismatch-induced dislocations and the high intrinsic damping of graphite. At high temperatures (above approximately 200 °C), the damping capacity is attributed to Al/graphite interface viscosity, preferred orientation of the graphite, and the presence of dislocations.     

The effects of exploration strategies and communication models on the performance of cooperative exploration

Exploration with mobile robots is utilized in a wide range of applications including search and rescue missions, planetary exploration, homeland security, surveillance, and reconnaissance. Cooperative exploration offers the potential of exploring an unknown zone more quickly and robustly than single-robot case. However, coordinating multiple robots is a challenging task due to heterogeneous processing and communication requirements, and the complexities of exploration algorithms. This paper presents a comparison of different cooperative exploration strategies, such as frontier-based exploration, market-driven exploration, and role-based exploration, based on their exploration performances and processing time requirements. To show the effect of CPU power on the processing time of the exploration algorithms, two notebooks and a netbook with different specifications have been extensively used. Comparative simulation results of our own application developed in Java show that the processing time requirements are consistent with the computational complexities of the exploration strategies. The results we obtained are consistent with the CPU power tests of independent organizations, and show that higher processing power reduces processing time accordingly.     

Developing centrifugal spun thermally cross-linked gelatin based fibrous biomats for antibacterial wound dressing applications

Fibrous materials obtained from natural polymers, such as gelatin, have been used in medical applications due to their biocompatibility and biodegradability. Herein, free-standing durable fibrous gelatin biomats with antibacterial activity were developed via a simple, low cost and fast production route, centrifugal spinning, and subsequent thermal crosslinking. After a series of preliminary experiments, droplet−/bead-free porous biomats with fine fibers, 3.41 ± 1.8 μm in diameter, were fabricated. Subsequently, antimicrobial biomats were produced by adding AgNO₃ into the production solution. X-ray diffractometer and energy dispersive X-ray results showed Ag NPs existing as AgCl in the biomats, which could be attributed to chemical reaction between the Ag NPs and residual Cl in the impure gelatin. Later, both the neat-gelatin and Ag-gelatin biomats were thermally crosslinked at 170°C to gain stability against water. Although the Ag addition reduced ultimate tensile strength by half, from 881 to 495 kPa, the crosslinked biomats were robust enough to be used for wound dressing applications. They were also found to be highly breathable, with the air permeability of 256 and 81.2 mm/s, respectively. The biomats showed antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria. The results show that the free-standing fibrous-gelatin-based biomats produced is applicable for wound dressing applications.