Calculating optimal modulation periods to maximize the peak capacity in two-dimensional HPLC

Theoretical calculations are presented to optimize modulation period for maximum total peak capacity in comprehensive two-dimensional HPLC (2D-HPLC) taking into account the effect of modulation on the apparent peak capacity of the first-dimension (1D) separation. Results indicate that modulation periods are most favorable when they are adjusted to approximately 2.2-4 times the standard deviation of a 1D peak in order to avoid excessively short run times at the second dimension (2D). Data are presented that effective peak capacities of several thousand in 60 min can be expected for practical 2D-HPLC conditions, utilizing 1D gradient elution followed by 2D isocratic elution, that remain at approximately 50-70% of the theoretical maximum peak capacity. This work suggests that lower modulation frequencies and longer 2D separation times than previously proposed are favorable under realistic chromatographic conditions, alleviating some practical problems associated with 2D-HPLC.     

Electrochemical reduction of carbon dioxide to ethylene with high Faradaic efficiency at a Cu electrode in CsOH/methanol

The electrochemical reduction of CO₂ with a Cu electrode in CsOH/methanol-based electrolyte was investigated. The main products from CO₂ were methane, ethylene, ethane, carbon monoxide and formic acid. A maximum Faradaic efficiency of ethylene was 32.3% at −3.5 V vs. Ag/AgCl saturated KCl. The best methane formation efficiency was 8.3% at −4.0 V. The ethylene/methane current efficiency ratio was in the range 2.9–7.9. In the CsOH/methanol, the efficiency of hydrogen formation, being a competitive reaction against CO₂ reduction, was depressed to below 23%.     

Measurement of electric intensity distribution inside human cadaver cochlea for multichannel cochlear implants

We have proposed a Tripolar Electrode Stimulation Method (TESM) which may succeed in narrowing the stimulation region and continuously moving the stimulation site for cochlear implants. The TESM stimulates the auditory nerve array through lymphatic fluid by means of three adjacent electrodes selected from among an electrode array. Currents are emitted from the electrodes on each side and the central electrode receives them. The current received by the latter electrode is equal to the sum of the currents emitted from the electrodes on the two sides. In this paper, the electric intensity profiles produced by the TESM and by monopolar stimulation were measured in a human cadaver cochlea and in a saline solution. We found that in the TESM, the electric intensity profile produced in the human cadaver cochlea was about the same as that in the saline solution. In addition, in the TESM, the electric intensity profile was much sharper than that of monopolar stimulation in the human cadaver cochlea. Furthermore, the nervous excitation region could be localized in a certain range by means of TESM. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 1–9, 1999     

Electrochemical properties of LiPON films made from a mixed powder target of Li3PO4 and Li2O

Lithium phosphorus oxynitride (LiPON) films were prepared by radio frequency magnetron sputtering. In order to control the atomic composition of the films, a mixture of Li₃PO₄ and Li₂O powders was used as the sputtering target. The ionic conductivity of the films showed a maximum (6.4 × 10^− 6 S/cm) when the molar ratio of Li₃PO₄ to Li₂O in the target was 1:2. The films formed from a target not containing Li₂O showed good durability in air at the expense of slightly poorer ionic conductivity. This is probably due to the amount of Li in the film being significantly less which effectively suppressed absorption of CO₂ in air.     

Analysis of Cs-adsorption behavior using a column filled with microcapsule beads of potassium copper hexacyanoferrate

Ash-washing technology is a crucially important technology for removing radioactive Cs from contaminated ash. For that technology, Cs⁺ removal from the ash-washing solution by the adsorbent is necessary. This study was conducted to establish rapid preparation of appropriate adsorption columns for Cs⁺ uptake. A one-site model was not used for analysis because the model cannot accommodate sites with different adsorption speed. Results demonstrated that the adsorption behavior of the column filled with the granules of potassium copper hexacyanoferrate was well reproduced by a two-site adsorption model with parameters chosen through analysis of batch adsorption test results.     

Crystal structure and ferroelectric properties of Ca(Cu3−xMx)Ti4O12 (M = Fe and Ni) ceramics

M-substituted Ca(Cu_3−xM_x)Ti₄O₁₂ (CCMTO) ceramics, where M = Fe and Ni, were synthesized and the influence of M substitutions for Cu on the crystal structure and ferroelectric properties of CCMTO ceramics were investigated in this study. From the variations in the lattice parameters of CCMTO ceramics, the solubility limit of Ni substitution for Cu in CaCu_3−xNi_xTi₄O₁₂ (CCNTO) ceramics was x = 0.2, whereas that of CaCu_3−xFe_xTi₄O₁₂ (CCFTO) ceramics was x = 0.05. The crystal structural analysis of CCMTO ceramics revealed that the single phase of CCMTO ceramics belongs to the I23 non-centrosymmetric space group of I23; as a result, the P_r and E_c values of CCFTO ceramics at x = 0.05 were 1.8 μC/cm² and 40 kV/cm, respectively. The ferroelectric behavior of CCMTO ceramics by the M substitutions for Cu may be related to the displacement of a Ti⁴⁺ cation in the TiO₆ octahedra and tilting of the Ti–O–Ti angle because of the non-centrosymmetric space group.     

Measurement of Liquid Film Thickness by a Fringe Method

A technique was developed and tested to measure the local thickness of a droplet or a liquid film on a surface of an opaque or thick single transparent plate by an interference fringe pattern that was easily formed by reflecting laser lights. Monochromatic epi-illumination through an objective lens of a conventional microscope was provided by a 5 mW or 300 mW laser and a filter to remove the noise caused by laser speckle. The incremental height difference of the liquid layer between neighboring maxima or minima of fringes was evaluated from the wavelength of the laser light and the refractive index of the liquid. Estimation error of a local inclination angle was discussed using ray tracing under parallel illumination approximation. Droplet profiles evaluated from the interferogram that were obtained by the present fringe method agreed well with those by Laser Focus Displacement Meter. Measurement was made to ensure the usefulness of the present technique. It was made clear that the contact angle of a liquid droplet could be obtained precisely and swiftly, even in small size or small contact angle, and that instantaneous three-dimensional profile of a liquid film on a bubble moving in a microchannel could be measured. The fringe method had sufficient potential to obtain more detailed information about three-dimensional characteristics of liquid film in flows such as the generation, breakdown, and growth of waves and the liquid film on a bubble at the beginning of movement.     

An enzyme catalyzing O-prenylation of the glucose moiety of fusicoccin A, a diterpene glucoside produced by the fungus Phomopsis amygdali

Isoprenoids form the largest family of compounds found in nature. Isoprenoids are often attached to other moieties such as aromatic compounds, indoles/tryptophan, and flavonoids. These reactions are catalyzed by three phylogenetically distinct prenyltransferases: soluble aromatic prenyltransferases identified mainly in actinobacteria, soluble indole prenyltransferases mostly in fungi, and membrane‐bound prenyltransferases in various organisms. Fusicoccin A (FC A) is a diterpene glycoside produced by the plant‐pathogenic fungus Phomopsis amygdali and has a unique O‐prenylated glucose moiety. In this study, we identified for the first time, from a genome database of P. amygdali, a gene (papt) encoding a prenyltransferase that reversibly transfers dimethylallyl diphosphate (DMAPP) to the 6′‐hydroxy group of the glucose moiety of FC A to yield an O‐prenylated sugar. An in vitro assay with a recombinant enzyme was also developed. Detailed analyses with recombinant PAPT showed that the enzyme is likely to be a monomer and requires no divalent cations. The optimum pH and temperature were 8.0 and 50 °C, respectively. K_m values were calculated as 0.49±0.037 μM for FC P (a plausible intermediate of FC A biosynthesis) and 8.3±0.63 μM for DMAPP, with a k_cat of 55.3±3.3×10^?3 s. The enzyme did not act on representative substrates of the above‐mentioned three types of prenyltransferase, but showed a weak transfer activity of geranyl diphosphate to FC P.     

Improvement of Electrical Contact Between TE Material and Ni Electrode Interfaces by Application of a Buffer Layer

A single ??-structure thermoelectric (TE) module based on p-type NaCo₂O₄, n-type Mg₂Si, and Ni electrode was fabricated by the spark plasma sintering (SPS) method. The NaCo₂O₄ powder was synthesized by using a metal?Ccitric acid complex decomposition method. Bulk Mg₂Si prepared by melt quenching was ground into a powder and sieved to particle size of 75???m or less. To obtain a sintered body of NaCo₂O₄ or Mg₂Si, the powder was sintered using SPS. Pressed Ni powder or mixed powder consisting of Ni and SrRuO₃ powder was inserted between these materials and the Ni electrode in order to connect them, and electrical power was passed through the electrodes from the SPS equipment. The open-circuit voltage (V _OC) values of a single module in which TE materials were connected to the Ni electrodes by using pressed Ni powder was 82.7?mV, and the maximum output current (I _max) and maximum output power (P _max) were 212.4?mA and 6.65?mW at ??T?=?470?K, respectively. On the other hand, V _OC of a single module in which TE materials and an Ni electrode were connected with a mixed powder (Ni:SrRuO₃?=?6:4 volume fraction) was 109?mV, and I _max and P _max were 4034?mA and 109?mW at ??T?=?500?K, respectively. These results indicate that the resistance at the interface between the TE materials and the Ni electrode can be decreased and the output power can be increased by application of a buffer layer consisting of Ni and SrRuO₃.