A Molecular Dynamics Study of the Cellulose-Graphene Oxide Nanocomposites: The Interface Effects

Cellulose has gained increasing attention due to its abundance and renewability. Obtained through a strong acid hydrolysis treatment of cellulose microfibrils, cellulose nanocrystals (CNCs) stand out among all hierarchical cellulose structures with appealing mechanical and optical properties that have been utilized as a reinforcing nanomaterial for the advanced material design. The cellulose nanocrystal graphene oxide (CNC-GO) nanocomposite film has been developed and successfully applied in portable and bendable sensing optoelectronics, energy storage and electromagnetic pulse protection devices. New material phenomena have been observed through experimental characterizations, but they lack fundamental understanding due to the experimental limitations in nanoscale. Therefore, a systematic and theoretical study at atomic level is desired to address the key factors responsible for the associated material properties of the CNC-GO nanocomposite, especially at its interface. We adopt molecular dynamics (MD) simulation techniques to investigate the role of the hydrogen bonds in the CNC-GO interface interaction with respect to the CNC slab orientation, the CNC slab thickness, the GO oxidation type, and the water content at the interface. The objective is to understand the role of hydrogen bonds at the CNC-GO interface in CNC morphological variations and the mechanical property enhancement. We systematically investigate (1) the crystallography of the CNC-GO nanocomposites and their lattice parameter variations for the suppression of (200) facet in the X-ray diffraction (XRD) spectrum; (2) the hydrogen bond formation, types and distributions of the CNC due to the CNC-GO interface interaction; and (3) the mechanical property variations due to the interface hydrogen bonding of the CNC-GO nanocomposites. Through systematic molecular dynamics simulations of a set of simplified CNC-GO sandwich structures, the mechanism behind local (200) facet manipulation, as well as the global morphological variations, can be elucidated. It will shed light on the correlations between interface types and mechanical loading responses along with the interface water molecules for the mechanical performance enhancement. This research provides an understanding of intrinsically manipulating the CNC-GO interface and potentially engineering the cellulose based nanocomposite materials and mechanical properties for future advanced materials development

Cellular signalling of adrenomedullin regulating endothelial barrier function and granulocyte extravasation

Background: Disturbed endothelial barrier function is a hallmark of inflammation. Effusion of protein rich plasma fluid leading to edema formation and overshooting transmigration of leukocytes contribute to severe organ dysfunction under conditions of generalized inflammation, e.g. acute lung injury and sepsis. The peptide hormone Adrenomedullin (ADM) and its receptor (CRLR/RAMP2/3) constitute an important signaling system for the protection of endothelial barrier function. Although elevation of cAMP in endothelial cells was identified as signaling pathway of ADM responsible for barrier protection, it was speculated that other mechanisms are involved and precise intracellular signaling routes have not been explored, yet. Main findings and conclusions: ADM was confirmed to be a strong stabilizer of the endothelial barrier function in vitro, preventing and reversing hyperpermeability independent of the inflammatory stimulus (as determined by electrical impedance and FITC-dextran permeability measurements after stimulation with thrombin, TNFα, histamine, VEGF). Moreover, it was shown for the first time that ADM inhibited TNFα-induced granulocyte transmigration which was solely due to effects of ADM on endothelial cells. These in vitro-findings could be translated to animal models of vascular permeability and inflammation: ADM dose-dependently reduced vascular permeability in the skin of mice and rats (Miles assay; stimulus histamine). In a murine lipopolysaccharide (LPS)-induced lung injury model, ADM reduced lung edema and leukocyte extravasation. In endothelial cells, barrier protection could solely be reduced to cAMP signaling via the protein kinase A (PKA) and Epac-Rap1 pathways (dose response comparison with Forskolin). Dissection of the downstream cascade by means of cAMP analogs, specific for PKA and Epac-Rap1 signaling (benz-cAMP and “007”, respectively), demonstrated that both pathways are with respect to their efficacy equally involved in effects on permeability probably addressing independent effector mechanisms as suggested by enhanced efficacy of combination of both. Consistently, both pathway activators prevented vascular hyper-permeability in vivo. PKA activation and inhibition of MLC phosphorylation downstream of ADM diminish stimulus induced actin stressfiber formation and contraction of endothelial cells thus counteracting intercellular gap formation and hyperpermeability. Most notably, also effects independent of the contractile apparatus were demonstrated: ADM stabilized barrier function even in the absence of a functional actin cytosceletton after treatment with Cytochalasin D and knockdown of cortactin. ADM induced stabilization of VE-cadherin at the cell borders and increased the amount of detectable VE-cadherin/VE-PTP complex which is important for the regular function of VE-cadherin. In contrast, granulocyte transmigration was only reduced by PKA activation and ADM effects were lost after knockdown of cortactin. In line with this finding, a PKA inhibitor abolished the effect of ADM. As PKA activation reduces myosin light chain phosphorylation these data collectively link leukocyte extravasation to the contractile apparatus of the endothelial cell. As “007” was fully active with respect to TNFα induced hyperpermeability but had no effect with respect to granulocyte transmigration, endothelial hyperpermeability per se is not a prerequisite for granulocyte transmigration

A Mutual Information Based Sequence Distance For Vertebrate Phylogeny Using Complete Mitochondrial Genomes

Traditional sequence distances require alignment. A new mutual information based sequence distance without alignment is defined in this paper. This distance is based on compositional vectors of DNA sequences or protein sequences from complete genomes. First we establish the mathematical foundation of this distance. Then this distance is applied to analyze the phylogenetic relationship of 64 vertebrates using complete mitochondrial genomes. The phylogenetic tree shows that the mitochondrial genomes are separated into three major groups. One group corresponds to mammals; one group corresponds to fish; and the last one is Archosauria (including birds and reptiles). The structure of the tree based on our new distance is roughly in agreement in topology with the current known phylogenies of vertebrates

Occupancy Estimation in Smart Building using Hybrid CO2/Light Wireless Sensor Network

Smart building, which delivers useful services to residents at lowest cost and maximum comfort, has gained increasing attention in recent years. A variety of emerging information technologies have been adopted in modern buildings, such as wireless sensor networks, internet of things, big data analytics, deep machine learning, etc. Most people agree that a smart building should be energy efficient, and consequently, much more affordable to building owners. Building operation accounts for major portion of energy consumption in the United States. HVAC (heating, ventilating, and air conditioning) equipment is a particularly expensive and energy consuming of building operation. As a result, the concept of “demand-driven HVAC control” is currently a growing research topic for smart buildings. In this work, we investigated the issue of building occupancy estimation by using a wireless CO2 sensor network. The concentration level of indoor CO2 is a good indicator of the number of room occupants, while protecting the personal privacy of building residents. Once indoor CO2 level is observed, HVAC equipment is aware of the number of room occupants. HVAC equipment can adjust its operation parameters to fit demands of these occupants. Thus, the desired quality of service is guaranteed with minimum energy dissipation. Excessive running of HVAC fans or pumps will be eliminated to conserve energy. Hence, the energy efficiency of smart building is improved significantly and the building operation becomes more intelligent. The wireless sensor network was selected for this study, because it is tiny, cost effective, non-intrusive, easy to install and flexible to configure. In this work, we integrated CO2 and light senors with a wireless sensor platform from Texas Instruments. Compare with existing occupancy detection methods, our proposed hybrid scheme achieves higher accuracy, while keeping low cost and non-intrusiveness. Experimental results in an office environment show full functionality and validate benefits. This study paves the way for future research, where a wireless CO2 sensor network is connected with HVAC systems to realize fine-grained, energy efficient smart building

A Complexity Indicator for 4D Flight Trajectories Based on Conflict Probability

In this paper, a complexity indicator for 4D flight trajectories is developed based on conflict probability. A 4D trajectory is modeled as piecewise linear segments connected by waypoints. The position of each aircraft is modeled as a 2D Gaussian random variable and an approximation of the conflict probability between two aircraft is deduced analytically over each segment. Based on such conflict probability, a complexity indicator is constructed for the whole trajectory. Numerical examples show that the proposed complexity indicator is able to reflect the complexity of 4D trajectories perceived by air traffic controllers