Kernel formula approach to the universal Whitham hierarchy

Based on the kernel formula proposed by Carroll and Kodama, we derive the dispersionless Hirota equations of the universal Whitham hierarchy. We also verify the associativity equations in this hierarchy from the dispersionless Hirota equations and give a realization of the associative algebra with the structure constants expressed in terms of residue formulas.     

Effect of oxygen addition on the hydrogen production from ethanol steam reforming in a Pd–Ag membrane reactor

In this communication, a porous stainless steel (PSS) tube was electrolessly plated into Pd–Ag membrane reactor which was used for separating hydrogen produced in an ethanol steam reforming reaction with the addition of oxygen, which has not been reported before. Palladium and silver were deposited on porous stainless steel tube via the sequential electroless plating procedure with an overall film thickness of 20 μm and Pd/Ag weight ratio of 78/22. Ethanol–water mixture (n_water/n_ethanol = 1 or 3) and oxygen (n_oxygen/n_ethanol = 0.2 or 0.7) were fed concurrently into the membrane reactor packed with MDC-3. The reaction temperatures were set at 593–723 K and the pressures 3–10 atm. The effect of oxygen addition plays a vital role on the ethanol steam reforming reaction, especially for the Pd–Ag membrane reactor in which a higher flux of hydrogen is required. If oxygen in the feed is not sufficient, it would be possible that steam reforming reaction prevails. Inversely, high O₂ addition will shift the reaction scenario to be partial oxidation dominating, and selectivity of CO₂ increases with increasing oxygen feed. At high pressure, autothermal reaction of ethanol would be easily reached.     

Negative electrorheological responses of micro-polar fluids in the finite spin viscosity small spin velocity limit. I. Couette flow geometries

Negative electrorheological responses induced by micro-particle electrorotation in two-dimensional Couette flow geometries are analyzed by a set of continuum modeling field equations originating from anti-symmetric/couple stress theories in the finite spin viscosity small spin velocity (FSV) limit. Analytical solutions are obtained for the first time to express the spin velocity, linear velocity, and effective viscosity in terms of the electric field strength, driving shear rate, boundary condition selection parameter, and spin viscosity. Good agreement is achieved between the FSV theoretical predictions presented herein and the experimental measurements reported in recent literature for the effective viscosity for low driving shear rates.     

Diffusioosmotic micropolar liquid flows in parallel plate microchannels subject to boundary slip

Meccanica - Analytical solutions to the microrotation, linear velocity, and volume flow rate are developed for electrokinetic diffusioosmotic flows of micropolar liquids in slit microchannel...     

Novel flavonoids of Thelypteris torresiana

In our continuing research on cytotoxic components from the Formosan pteridophyte Thelypteris torresiana (GAUD.) ALSTONONE, two new compounds, a novel flavonoid, flavotorresin (1), and a flavonoid diglycoside, multiflorin C (2), along with five known compounds, were isolated. The structural elucidation was established on the basis of spectroscopic data analysis. The possible biosynthetic pathway of the flavonoids from this fern is summarized.     

Longicalycinin A, a new cytotoxic cyclic peptide from Dianthus superbus var. longicalycinus (MAXIM.) WILL

A new cyclic peptide, longicalycinin A (1), and six known compounds, vaccaroside A, dianoside A, dianoside G, 3-(4-hydroxy-3-methoxy-phenyl)propionic acid methyl ester, p-hydroxybenzoic acid, and p-hydroxybenzaldehyde were isolated from the MeOH extract of Dianthus superbus var. longicalycinus. The amino acid sequences of 1 was elucidated as cyclo(Gly(1)-Phe(2)-Tyr(3)-Pro(4)-Phe(5)-) on the basis of ESI tandem mass fragmentation analysis, chemical evidence, and extensive 2D NMR methods. Furthermore, compound 1 showed cytotoxicity to Hep G2 cancer cell line.     

The zone-refine driven growth of jellyfish-like core-shell nanowires

Thermal evaporation of a Sn-silica mixture produces core-shell nanowires assembled into jellyfish-like structures. The growth mechanism involves zone-refine driven phase separation at the solid-liquid interface. The materials emit blue and red lights; the luminescence centers are discussed and verified.     

Metallic Nanocrystallites-Coated Piezoelectric Quartz for Applications in Gas Sensing

This article reports the gas-sensing capability of nanocrystalline (NC) transition metal-coated piezoelectric quartz crystal (PQC). NC transition metal particles of Pd and Ag with particles size of 10–15 nm, while Pt and Au are 20–25 nm are used. The NC particles deposited on the quartz substrate adsorbs gaseous pollutants, thereby increasing the weight of the quartz substrate and decreasing its vibration frequency. We have found that transition metals, Pd, Pt, Au, and Ag in particular, show good sensitivity for NH₃-detection; the maximum frequency change occurs at 150°C for Pd and Pt and at 100°C for Au and Ag. The NC Pd- and NC Pt-coated PQC also show good sensitivity for CO₂-detection at 150°C. Likewise, the NC Au-coated PQC shows very good sensitivity for NO₂-detection but at a higher temperature (180^°C). The frequency change as a function of the pollutant gas concentration ( f-curve) follows the Langmuir adsorption isotherm (unimolecular adsorption) except in the case of NC Pd-coated PQC under NH₃ and NC Au-coated PQC under NO₂. The f-curve for the NC Pd-coated PQC is convex with respect to the NH₃ concentration axis. The f-curve for the NC Au-coated PQC is convex in the low NO₂ concentration region, and concave in the high NO₂ concentration region. Both curves indicate multi-molecular adsorption, Type III and Type V adsorption, respectively. Therefore, the good sensitivity and stability of these gas sensors can be attributed to physical adsorption of the pollutant gases as a result of van der Waals attraction.     

Passive solute separation in AC electroosmosis including surface charge-coupled hydrodynamic slip effects

Separation of electrically neutral, mutually noninteracting passive solutes via AC electroosmotic slit channel flows is investigated for general asymmetric wall surface zeta potentials and apparent hydrodynamic slip lengths. We consider the nontrivial coupling between the surface potentials (or charge densities) and the apparent slip lengths, and focus our attention on the occurrence of a so called “crossover phenomenon” for separating out the slow diffusers when both slow and fast diffusers are present. Results show that regardless of the potential-slip coupling, wider bandwidths become available for crossover phenomenon to occur when the electroosmotic velocity gradient (magnitude) is greater. Contrarily, plug-like velocity profiles inhibit crossover phenomenon, and the potential-slip parametric combinations leading to such profiles can be easily identified by the conditions for minimal transport enhancement reported in recent literature. When separating out the slow diffuser or crossover phenomenon is desired, we recommend incorporating significant asymmetry in the surface potential and apparent slip boundary conditions such that the operating frequency and flow oscillation amplitude may be lowered to more practical values. Our results also agree with and strengthen the physical picture for explaining crossover phenomenon in macroscopic pressure-driven oscillatory flows.     

Negative electrorheological responses of micro-polar fluids in the finite spin viscosity small spin velocity limit. II. Poiseuille flow geometries

Analytical solutions to the continuum spin and linear velocities as well as the two-dimensional volume flow rate are solved and presented for negative electrorheological Poiseuille flows induced by internal micro-particle Quincke electrorotation using continuum anti-symmetric/couple stress theories with finite spin viscosities and small spin velocities. Theoretical predictions on the volume flow rate and linear velocity profile obtained from the continuum finite spin viscosity small spin velocity theory presented herein agree very well with the experimental measurements in the parametric regime of low or small driving pressure gradients as reported in current literature.