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A new phenylalkanoid, undecyl (E)-8-(4-hydroxy-3-methoxyphenyl)-6- oxooct-7-enoate (1) was isolated from the rhizomes of Alpinia galangal (Zingiberaceae). The structure of the new phenylalkanoid was elucidated by chemical and physical evidence.

The present study utilizes a modified Poisson–Boltzmann (MPB) equation to take into account ion-size (steric) effect and then performs a series of simulations to investigate the ionic transport phenomenon within two nanofluidic devices, namely a nanoslit and a nanotube. The results show that at all electrolyte concentrations, the streaming conductance increases when the ion-size effect is taken into account, particularly under conditions of high surface charge density. The net charge density is amplified by the ion-size effect for both nanogeometries as well. The enhancement in the streaming conductance is particularly pronounced in the nanotube since the net charge density has higher value by the geometry effect of the nanotube. The maximum ratio of net charge density () is 1.55 near the surface of nanotube. In addition, it is shown that for both configurations, the contribution of electroosmotic flow to the electrical conductance increases when the finite ion size is taken into account.

When the channel size approaches the thickness of the charged layer (typically, ∼10–100 nm), the resulting molecular and non-equilibrium effects are markedly different from those observed in larger channels and have a significant effect on the transport behavior of solutes and solvents. As a result, the problem of modeling fluidic behavior at the nanoscale has attracted increasing interest in recent years. This review introduces the fundamental theories and principles associated with electrokinetic transport and molecular dynamics modeling, and discusses various applications of nanofluidic devices in the physics, mechanics, and chemistry fields.

Numerical simulations based on the full Poisson–Nernst–Planck (PNP) equations are performed to investigate the reverse electrodialysis (RED) in negatively charged conical nanopores. The simulations consider three different salts (i.e., KCl, NaCl and LiCl) and examine the effects of the concentration gradient, surface charge density and diffusion coefficient on the current–voltage characteristics and energy conversion efficiency of the RED system. When diffusion takes place from the base side to the tip side, the transference number of counter-ion (t+) can be enhanced due to an addition in the EDL overlap near the tip side. It results in the higher energy conversion efficiency of RED than the salt ion diffusion from the tip side to the base side, i.e., the RED performance of the conical nanopore is dependent on the direction of salt concentration gradient. In addition, the results show that the conversion efficiency increases as the diffusion coefficient of the positive ions (D+) approaches that of the negative ions (D−). For D+ < D−, the diffusion current and diffusion potential in negatively charged conical nanopores show negative on the current–voltage characteristics and the conversion efficiency increases as the concentration gradient is increased at small surface charge density. Finally, the calculated maximum power conversion efficiency reaches 45%.

In order to enhance the performance of the direct methanol fuel cell (DMFC), the product of CO2 bubble has to be efficiently removed from the anode channel during the electrochemical reaction. In this study, the materials of Polymethyl Methacrylate (PMMA) with hydrophilic property and polydimethylsiloxane (PDMS) with hydrophobic property are used to form the anode cannel. The channel is fabricated through a microelectromechanical system (MEMS) manufacture process of the DMFCs. In addition, some particles with high hydrophobic properties are added into the PDMS materials in order to further reduce the hydro-resistance in the anode channel. The performance of the DMFCs is investigated under the influence of operation conditions, including operation temperature, flow rate, and methanol concentration. It is found that the performance of the DMFC, which is made of PDMS with high hydrophobic particles, can be greatly enhanced and the hydrophobic property of the particles can be unaffected by different operation conditions.

Cinnamoum reticulatum Hayata (Lauraceae) is an indigenous tree species in Taiwan. In this study, we further isolated the two flavonoids compounds kaempferol-3-O-(2",4"-di-E-p-coumaroyl)-α-L-rhamnopyranoside (1) and kaempferol-3-O-(3",4"-di-E-p-coumaroyl)-α-L-rhamnopyranoside (2) from the leaves and stems of C. reticulatum Hayate. The phytochemical characteristics, antioxidant and cytotoxic activities of the two compounds were evaluated. Kaempferol-3-O-(2",4"-di-E-p-coumaroyl)-α-L-rhamnopyranoside (1) and kaempferol-3-O-(3",4"-di-E-p-coumaroyl)-α- L-rhamnopyranoside (2) have antiproliferation activity in lung cancer cell line (A549 and NCI-H460) and breast cancer cell line (MCF-7 and MDA-MB-231). However, (1) displays better antioxidantactivity than (2). Our results showed that the two flavonoidsfrom C. reticulatum might have good potential for further development as chemoprevention or antioxidant remedies.

A numerical investigation is performed into the characteristics of an electro-osmotic pump consisting of a negatively charged conical nanopore. It is shown that the dependence of the flow rectification effect on the bias direction is the reverse of that of the ion current rectification effect. Moreover, the nozzle mode (i.e., the bias is applied from the base side of the nanopore to the tip side) has a higher flow rate compared to the diffuser mode (i.e., the bias is applied from the tip side of the nanopore to the base side). The results showed that the ion-concentration polarization effect occurred inside the conical nanopore, resulting in surface conduction dominating in the ionic current. The ions inside the nanopore are depleted and enriched under the nozzle mode and the diffuser mode, respectively. As a result, the electro-osmotic pump yields a greater pumping pressure, flow rate, and energy conversion efficiency when operating in the nozzle mode. In addition, we also investigated the flow rate rectification behavior for the conical nanopore. The best flow rate rectification factor in this work is 2.06 for an electrolyte concentration of ${10}^{\ensuremath{-}3}\phantom{\rule{0.16em}{0ex}}M$.

When a concentrated salt solution and a diluted salt solution are separated by an ion-selective membrane, cations and anions would diffuse at different rates depending on the ion selectivity of the membrane. The difference of positive and negative charges at both ends of the membrane would produce a potential, called the diffusion potential. Thus, electrical energy can be converted from the diffusion potential through reverse electrodialysis. This study demonstrated the fabrication of an energy conversion microchip using the standard micro-electromechanical technique, and utilizing Nafion junction as connecting membrane, which was fabricated by a surface patterned process. Through different salinity gradient of potassium chloride solutions, we experimentally investigated the diffusion potential and power generation from the microchip, and the highest value measured was 135 mV and 339 pW, respectively. Furthermore, when the electrolyte was in pH value of 3.8, 5.6, 10.3, the system exhibited best performance at pH value of 10.3; whereas, pH value of 3.8 yielded the worst.

In this paper, a series of numerical simulations was performed to investigate the pumping performance of electro-osmotic micropumps containing electrode arrays patterned on the upper and lower sides of a microchannel. The simulations have been analyzed with a linear electro-osmotic model based upon the Debye-Huckel theory of the double layer. The potential drop across the diffuse layer is assumed to be less than 25 mV (k(B)T/e), and there is a linear response between the surface charge and the voltage drop across the double layer. The double layer is not resolved but is lumped into effective parameters that are imported from the Debye-Huckel and Stern layers. We examined the effects of the relative positioning of the electrodes in the opposing arrays (i.e., symmetrical or staggered), and the phase lag and the angular frequency of the alternating current (ac) signals applied to the electrodes within the two arrays. A critical height of the microchannel was observed, below which the interactions of the applied electrical potentials on the walls became significant. The optimum pumping effect was obtained when the electrode arrays were symmetrical to one another around the centerline of the channel and were activated by ac potentials with a 0° phase shift. The corresponding angular frequency of the maximum pumping velocity for different phase shifts of the applied ac signals was also determined. Overall, the simulation results presented in this paper provide a useful insight into the optimal design parameters and operating conditions for micropumps containing two arrays of microelectrodes on the microchannel walls.

Reticumanone (1), a new chromanone, isolated from the leaves of Cinnamomum reticulatum Hay (Lauraceae), has been characterized as (S*)-2,7,8-trihydroxychroman-4-one, by means of spectroscopic methods.