Abstract-We define an opportunistic network as one type of challenged networks where network contacts are intermittent or where link performance is highly variable or extreme. In such a network, there does not exist a complete path from source to destination for most of the time. In addition, the path can be highly unstable and may change or break quickly. Therefore, in order to make communication possible in an opportunistic network, the intermediate nodes may take custody of data during the blackout and forward it when the connectivity resumes. In this paper, we discuss some research challenges in an opportunistic network.

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Environmental stressors like pathogens and toxins may depress the animal immune system through invasion of the gastrointestinal tract (GIT) tract, where they may impair performance and production, as well as lead to increased mortality rates. Therefore, protection of the GIT tract and improving animal health are top priorities in animal production. Being natural-sourced materials, phytochemicals are potential feed additives possessing multiple functions, including: anti-inflammatory, anti-fungal, anti-viral and antioxidative properties. This paper focuses on immunity-related physiological parameters regulated by phytochemicals, such as carvacrol, cinnamaldehyde, curcumin, and thymol; many studies have proven that these phytochemicals can improve animal performance and production. On the molecular level, the impact of inflammatory gene expression on underlying mechanisms was also examined, as were the effects of environmental stimuli and phytochemicals in initiating nuclear factor kappa B and mitogen-activated protein kinases signaling pathways and improving health conditions.

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SUMMARYThis paper presents a new observer-based sub-optimal digital tracker for the continuous-time system with input and state time delays. We directly convert the continuous-time input-state delayed system into an equivalent discrete-time input-state delayed model and its extended discrete-time delay-free model. In addition, we directly discretize the linear quadratic performance index specified in the continuoustime domain into an equivalent decoupled discrete-time performance index using the newly developed extended delay-free model. As a consequence, the well-developed discrete-time optimal control theory for discrete-time delay-free system can be applied to determine the optimal digital tracker for the continuous-time input-state delayed system. When the states of the continuous-time input-state delayed system are not available for measurements, we develop a sub-optimal digital observer for the original continuous-time input-state delayed system using the state-matching digital redesign technique and the digital-to-analog model conversion technique. As a result, the proposed observer-based linear quadratic digital tracker is able to make the output of the digitally controlled continuous-time input-state delayed system sub-optimally track the desired reference signals. An illustrative example is presented to demonstrate the effectiveness of the proposed design methodology.