Understanding the interactions of nanoparticles (NPs) with biological system, especially interactions with cell membranes, is critical for the rational design of nanocarrier agents and drug delivery systems. Here, we have performed coarse-grained molecular dynamics simulations aimed at the effect of hydrophilic/hydrophobic properties of nanoparticles on the interaction with cell membranes (dipalmitoylphosphatidylcholine or DPPC bilayer). Two kinds of nanoparticles (hydrophobic and semihydrophilic) are modeled in the simulation. The results indicate that a hydrophobic nanoparticle can result in the inclusion into the bilayer, whereas a semihydrophilic nanoparticle is only found to adsorb into the membrane. For different system free energy profiles have been calculated to elucidate those phenomena. For the semihydrophilic nanoparticle case, we also discuss the potential substantial energy barrier of particle wrapping, implicating that the endocytosis-like mechanism is an energy-mediated process. The landscapes of the membrane fluctuation in the transitions imply that the deformation of the lipid bilayer induced by the addition of NPs is short-range, and the rearrangement of lipid molecules plays a significant role for morphological variations of NP-containing lipid membrane patches. These results show that the surface hydrophobicity can result in different response mechanisms of NP-biomembrane interactions.

The focus of this study was to investigate the effects of surface charge and surface hydrophobicity on anodic biofilm formation, biofilm community composition, and current generation in bioelectrochemical systems (BESs). Glassy carbon surfaces were modified with -OH, -CH3, -SO3(-), or -N(+)(CH3)3 functional groups by electrochemical reduction of aryl diazonium salts and then used as anodes with poised potential of -0.2 V (vs Ag/AgCl). The average startup times and final current densities for the -N(+)(CH3)3, -OH, -SO3(-), and -CH3, electrodes were (23 d, 0.204 mA/cm(2)), (25.4 d, 0.149 mA/cm(2)), (25.9 d, 0.114 mA/cm(2)), and (37.2 d, 0.048 mA/cm(2)), respectively. Biofilms on different surfaces were analyzed by nonturnover cyclic voltammetry (CV), fluorescence in situ hybridization (FISH), and 16S rRNA gene amplicon pyrosequencing. The results demonstrated that 1) differences in the maximum current output between surface modifications was correlated with biomass quantity, and 2) all biofilms were dominated by Geobacter populations, but the composition of -CH3-associated biofilms differed from those formed on surfaces with different chemical modification. This study shows that anode surface charge and hydrophobicity influences biofilm development and can lead to significant differences in BESs performance. Positively charged and hydrophilic surfaces were more selective to electroactive microbes (e.g. Geobacter) and more conducive for electroactive biofilm formation.

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In this paper, we present a unified approach to study a class of cooperative games arising from inventory centralization. The optimization problems corresponding to the inventory games are formulated as stochastic programs. We observe that the strong duality of stochastic linear programming not only directly leads to a series of recent results concerning the non-emptiness of the cores of such games, but also suggests a way to find an element in the core. The proposed approach is also applied to inventory games with concave ordering cost. In particular, we show that the newsvendor game with concave ordering cost has a non-empty core. Finally, we prove that it is NP-hard to determine whether a given allocation is in the core for the inventory games even in a very simple setting.

A mechanistic understanding of the growth of multiply twinned nanoparticles (MTPs), such as decahedra (Dh) and icosahedra (Ih), is crucial for precisely controlled syntheses and applications. Despite previous successes, no consensus has been reached regarding the multiple competing growth pathways for MTPs proposed thus far, in part due to the lack of information about their nucleation and growth dynamics. Here, we used decahedral and icosahedral gold nanoparticles as a model system in conjunction with in situ liquid cell transmission electron microscopy (LCTEM) to investigate the nucleation and growth dynamics of MTPs in aqueous solution; two growth pathways were successfully identified: (A) nucleation-based layer-by-layer growth from a rounded multiply twinned seed and (B) the successive twinning and growth of tetrahedra. The LCTEM results enabled us to directly and conclusively identify the growth behaviors of intermediate products. The internal strain relaxation mechanisms and growth kinetics differ for the two pathways: in pathway A, a MTP grew by the opening and closing of re-entrant grooves at the twin boundaries, which was not found in pathway B. We also analyzed different MTP growth pathways from an energetic perspective and discussed how the preferred pathway (A or B) is related to factors, such as the initial seed yield and the sizeand morphology-dependent formation of MTPs. Our results contextualize the current understanding of MTP formation mechanisms and provide insightful guidance for the precisely controlled synthesis of MTPs for practical applications.

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Inspired by the self-cleaning superhydrophobic taro leaf, a polystyrene (PS) film with superhydrophobic surface was obtained using a natural taro leaf as template. The water contact angle and the sliding angle of the superhydrophobic PS surface were 158° ± 1.6° and 3°, respectively. The PS surface was still superhydrophobic when contacting with black ink, fresh blood and even viscous glue water. SEM shows that the surface structure comprises many uniform papillae with the diameters ranging from 10 to 15 µm, which is similar to the surface structure of natural taro leaf. Such a special surface morphology may result in the superhydrophobic property.

We study a dynamic pricing problem of a firm facing reference price effects at an aggregate demand level, where demand is more sensitive to gains than losses. We find that even the myopic pricing strategy belongs to one type of discontinuous maps, which can exhibit complex dynamics over time. Our numerical examples show that, in general, the optimal pricing strategies may not admit any simple characterizations and the resulting reference price/price dynamics can be very complicated. We then show for a special case that a cyclic skimming pricing strategy is optimal, and we provide conditions to guarantee the optimality of high-low pricing strategies.