Characterization of wettability effects on pressure drop of two-phase flow in microchannel

The Characterization of the effects of surface wettability and geometry on pressure drop of slug flow in isothermal horizontal microchannels is investigated for circular and square channels with hydraulic diameter (D _h ) of 700 μm. Flow visualization is employed to characterize the bubble in slug flow established in microchannels of various surface wettabilities. Pressure drop increases with decrease in surface wettability, while the channel geometry influences slug frequency. It is observed that the gas–liquid contact line in advancing and receding interfaces of bubble change with surface wettability in slug flows. Flow resistance, where capillary force is important, is estimated using Laplace–Young equation considering the change of dynamic contact angles of bubble. The experimental study also demonstrates that the liquid film presence elucidates the pressure drop variation of slug flows at various surface wettabilities due to diminishing capillary effect.     

'Illusional' nano-size effect due to artifacts of in-plane conductivity measurements of ultra-thin films

The nano-size effect, which indicates a drastic increase in conductivity in solid electrolyte materials of nano-scale microstructures, has drawn substantial attention in various research fields including in the field of solid oxide fuel cells (SOFCs). However, especially in the cases of the conductivity of ultra-thin films measured in an in-plane configuration, it is highly possible that the 'apparent' conductivity increase originates from electrical current flowing through other conduction paths than the thin film. As a systematic study to interrogate those measurement artifacts, we report various sources of electrical current leaks regarding in-plane conductivity measurements, specifically insulators in the measurement set-up. We have observed a 'great conductivity increase' up to an order of magnitude at a very thin thickness of a single layer yttria-stabilized zirconia (YSZ) film in a set-up with an intentional artifact current flow source. Here we propose that the nano-size effect, reported to appear in ultra-thin single layer YSZ, can be a result of misinterpretation.     

Theoretical study of formamide decomposition pathways

The chemical transformations of formamide (NH(2)CHO), a molecule of prebiotic interest as a precursor for biomolecules, are investigated using methods of electronic structure computations and Rice-Rampserger-Kassel-Marcus (RRKM) theory. Specifically, quantum chemical calculations applying the coupled-cluster theory CCSD(T), whose energies are extrapolated to the complete basis set limit (CBS), are carried out to construct the [CH(3)NO] potential energy surface. RRKM theory is then used to systematically examine decomposition channels leading to the formation of small molecules including CO, NH(3), H(2)O, HCN, HNC, H(2), HNCO, and HOCN. The energy barriers for the decarboxylation, dehydrogenation, and dehydration processes are found to be in the range of 73-78 kcal/mol. H(2) loss is predicted to be a one-step process although a two-step process is competitive. CO elimination is found to prefer a two-step pathway involving the carbene isomer NH(2)CHO (aminohydroxymethylene) as an intermediate. This CO-elimination channel is also favored over the one-step H(2) loss, in agreement with experiment. The H(2)O loss is a multistep process passing through a formimic acid conformer, which subsequently undergoes a rate-limiting dehydration. The dehydration appears to be particularly favored in the low-temperature regime. The new feature identifies aminohydroxymethylene as a transient but crucial intermediate in the decarboxylation of formamide.     

Comparative study of codon substitution patterns in foot-and-mouth disease virus (serotype O)

We compared genetic variations in the VP1 gene of foot-and-mouth disease viruses (FMDVs) isolated since 2000 from various region of the world. We analyzed relative synonymous codon usage (RSCU) and phylogenetic relationship between geographical regions, and calculated the genetic substitution patterns between Korean isolate and those from other countries. We calculated the ratios of synonymously substituted codons (SSC) to all observed substitutions and developed a new analytical parameter, EMC (the ratio of exact matching codons within each synonymous substitution group) to investigate more detailed substitution patterns within each synonymous codon group. We observed that FMDVs showed distinct RSCU patterns according to phylogenetic relationships in the same serotype (serotype O). Moreover, while the SSC and EMC values of FMDVs decreased according to phylogenetic distance, G + C composition at the third codon position was strictly conserved. Although there was little variation among the SSC values of 18 amino acids, more dynamic differences were observed in EMC values. The EMC values of 4- and 6-fold degenerate amino acids showed significantly lower values while most 2-fold degenerate amino acids showed no significant difference. Our findings suggest that different EMC patterns among the 18 amino acids might be an important factor in determining the direction of evolution in FMDV.     

Enhanced Raman spectrum of lawsone on Ag surface: vibrational analyses, frequency shifts, and molecular geometry

The surface-enhanced Raman spectrum of lawsone, a well known natural dye, has been investigated. Activation with KNO(3) or Na(2)SO(4) solution was necessary to enhance the Raman signal, whereas addition of NaCl solution depletes the effects. In the enhanced Raman spectrum, the strong double-bond stretching bands are most distinctive and show large red shifts from those in the infrared and FT-Raman spectra. The observed strong double-bond stretching bands reflect lawsone coordinated perpendicular to the Ag surface. DFT computations have been carried out for the plausible configurations of lawsone coordinated to an adatom on the Ag surface. Lawsone coordinated to an Ag(+) adatom with H(+) released best reproduces the observed vibrational characteristics.     

CR singular images of generic submanifolds under holomorphic maps

The purpose of this paper is to organize some results on the local geometry of CR singular real-analytic manifolds that are images of CR manifolds via a CR map that is a diffeomorphism onto its image. We find a necessary (sufficient in dimension 2) condition for the diffeomorphism to extend to a finite holomorphic map. The multiplicity of this map is a biholomorphic invariant that is precisely the Moser invariant of the image, when it is a Bishop surface with vanishing Bishop invariant. In higher dimensions, we study Levi-flat CR singular images and we prove that the set of CR singular points must be large, and in the case of codimension 2, necessarily Levi-flat or complex. We also show that there exist real-analytic CR functions on such images that satisfy the tangential CR conditions at the singular points, yet fail to extend to holomorphic functions in a neighborhood. We provide many examples to illustrate the phenomena that arise.     

Studies on the E7 liquid crystal orientations confined to perfluorinated carboxylic acid‐treated cylindrical cavities of Anodisc membranes by FTIR spectroscopy

The orientation of E7 liquid crystal (LC) confined within 200 nm diameter cylindrical cavities of Anodisc membranes are investigated by FTIR dichroism techniques. The cavity walls of the confining pores were chemically modified with different length perfluorinated carboxylic acids (PCAs, C _n F_2n+1COOH, n = 3, 4, 5, 6) at 1, 3 and 5 mM concentrations. From the FTIR spectra of PCA‐treated alumina Anodsic membranes, we found salt formation between the –COOH group of the PCAs and the Anodisc membranes. From the FTIR spectra of LC‐filled Anodisc membranes, we found an abrupt alignment direction change, from parallel to perpendicular, of the LC molecules along the long axis of the cavities between n = 4 and n = 5 for the 1 mM concentration of PCA. However, for the 5 mM concentration of PCA, the parallel‐to‐perpendicular alignment direction of LC molecules changed between n = 3 and n = 4. These LC orientation changes for PCA‐treated Anodisc membranes occurred at shorter length than for hydrocarbon carboxylic acid (HCA, C _n H_2n+1COOH)‐treated Anodisc membranes. This change may be caused by the lower surface energy of the –(CF₂) _n CF₃ chain of PCA than that of the –(CH₂) _n CH₃ chain of HCA.     

First Total Synthesis of Cytotoxic Diarylheptanoids,Galeon, and Pterocarine

The first total synthesis of cytotoxic diphenyl ether‐type diarylheptanoids, galeon and pterocarine, was described in which the Ullmann reaction was employed at the final step for the diaryl ether formation of key intermediate, 1‐(3‐bromo‐4‐benzyloxyphenyl)‐7‐(4‐hydroxy‐3‐methoxyphenyl)heptan‐3‐one, assembled by a series of cross‐aldol condensation from 3‐methoxy‐4‐benzyloxybenzaldehyde.     

Efficient Solid/Liquid Phase-Transfer Catalytic Diazo Transfer Synthesis

A simple and efficient solid/liquid phase-transfer catalytic diazo transfer reaction for the synthesis of diazocarbonyl, diazophosphonyl, and diazophosphinyl compounds is reported.     

Dibromomethane as One‐Carbon Source in Organic Synthesis: Formal Total Synthesis of (±)‐Nephrosteranic Acid

A diastereoselective formal total synthesis of (±)‐nephrosteranic acid (10) is described. The key step is to introduce the α‐methylene group by the ozonolysis of monosubstituted alkenes followed by reaction with a preheated mixture of CH₂Br₂–Et₂NH. The α‐methyl group of compound 10 was formed from the reduction of the corresponding α‐methylene precursor.