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Delay/disruption-tolerant networking (DTN) is a networking technology conceived to manage opportunistic connections with no consistent end-to-end link connectivity which is common in both terrestrial and space communication environments. DTN is recognized as a baseline technology for implementing deep-space networks. Considered as the primary transport protocol of DTN in space, Licklider transmission protocol (LTP) is expected to provide reliable data delivery service in a challenging networking environment regardless of presence of random link disruptions and/or extremely long propagation delays. The National Aeronautics and Space Administration (NASA) has implemented the use of DTN protocols on the International Space Station (ISS) for data delivery to the earth ground station. However, little work has been done in studying the performance of LTP for reliable data/file delivery in such a communication environment, especially in presence of link disruption. There is a lack of a solid performance evaluation of LTP for its use in the space station communications. In this paper, an analytical framework is presented to evaluate the performance of LTP for reliable file delivery between the space station and the ground stations with a focus on the effect of link disruption, which may occur either over the downlink or over the uplink. The effect of data loss due to channel error is also integrated. Realistic data block transmission experiments using a PC-based experimental infrastructure are conducted to validate the analytical models.

Delay/disruption-tolerant networking (DTN) is widely recognized as a key internetworking technology for implementing a space system of systems (SoS). Aimed at being the main data transport protocol of DTN, Licklider transmission protocol (LTP) is expected to provide reliable data transmission service in a challenging space SoS networking environment regardless of random link disruptions. In this article, a study of LTP in deep-space communication networks in presence of link disruptions is presented. An analytical framework is developed for the effect of multiple random link disruptions on LTP's reliable data delivery in deep-space networks. The study indicates that the models accurately predict the transmission performance of LTP over a deep-space communication channel in presence of multiple link disruptions. A threshold interval value, obtained from the analytical modeling results, is proposed as a means of determining the reducibility of two successive link disruptions to a single disruption; that threshold value is verified by the experiments.

Designed as the primary transport protocol of delay/disruption-tolerant networking (DTN) in space, Licklider Transmission Protocol (LTP) is expected to provide reliable data delivery service in a challenging networking environment regardless of presence of random link disruptions and/or extremely long propagation delays. The NASA has implemented the use of DTN protocol on the International Space Station for data delivery to the earth ground station. However, there is a lack of a performance evaluation of LTP for its use in the space station communications, especially in presence of link disruption. In this article, a study using a PC-based experimental infrastructure is presented in evaluating the performance of LTP for reliable data delivery from the space station to the ground stations. Realistic experiment results are presented with a focus on the effect of link disruption occurred either over the downlink or over the uplink. The effect of data loss due to channel error is also investigated.

The antimicrobial action of porous CuO microspheres (μCuO), Ag nanoparticles (nAg), and bimetallic porous CuO microspheres decorated with Ag nanoparticles (μCuO/nAg) was evaluated against surrogate microorganisms representative of pathogens commonly implicated in foodborne and healthcare-associated human infections. This work addressed the Gram-negative bacteria E. coli(Escherichia coliO157:H7-GFP B6-914), Salmonella(Salmonella enterica serovar enteritidisphage-type PT21), and the Gram-positive bacteria Listeria(Listeria innocua), as well as environmental microorganisms derived from local river water. Compared to particles composed only of CuO or Ag, the bimetallic porous μCuO/nAg particle exhibits enhanced antimicrobial efficacy. The antimicrobial action of bimetallic porous μCuO/nAg particles is dose-dependent, with 50 μg/mL particle concentration completely inhibiting the growth of both the Gram-negative (Salmonella) and the Gram-positive (Listeria) bacteria after 6 h. To assess the mechanism of antimicrobial action, the changes in surface morphologies of bacteria treated with the particles were observed using scanning electron microscopy. In the case of the Gram-negative bacteria, the bacterial cell membrane is damaged, likely due to the release of metal ions from the particles; however, particle-induced cell membrane damage is not observed for Gram-positive bacteria. Collectively, results from this work shed further light on possible mechanisms of antimicrobial action of micro-/nanoparticles and highlight the potential for bimetallic particle-based inhibition of microbial infections.