Counter-current chromatographic separation of nucleic acid constituents with a hydrophilic solvent system

Nucleic acid constituents such as nucleobases, nucleosides and nucleotides were separated by counter-current chromatography using type J coil planet centrifuge. The separation was performed with a hydrophilic solvent system composed of 1-propanol/800 mM potassium phosphate buffer (pH 7.4) (1:1, v/v) by eluting the lower aqueous phase at a flow-rate of 0.5 ml/min. Eight selected nucleic acid constituents (4.0 mg, 0.5 mg of each), uridine monophosphate (UMP), adenosine monophosphate (AMP), deoxyadenosine monophosphate (dAMP), uridine, urasile, deoxy uridine, adenosine and adenine were well resolved within 160 min.     

A low-cost method for determination of calcium carbonate in cement by membraneless vaporization with capacitively coupled contactless conductivity detection

This work presents a flow analysis method for direct quantitation of calcium carbonate in cement without pretreatment of the sample. The method is based on online vaporization of CO₂ gas following acidification of the sample inside a small chamber that has a flow of acceptor solution passing around it. Solubilization of the CO₂ gas into the acceptor stream changes the conductivity of the acceptor solution causing an increase of signal at the capacitively coupled contactless conductivity detection (C⁴D) placed at the outlet of the vaporization chamber. This chamber is an adaption from previous work reported on ‘membraneless vaporization’ (MBL-VP).The method can be used in the quality control of production of mixed cement. These cement materials usually have calcium carbonate contents at high concentration range (e.g., 33-99% (w/w) CaCO₃). Analysis of samples by this method is direct and convenient as it requires no sample pretreatment. The method is low-cost with satisfactory accuracy and acceptable precision.     

Dissolved oxygen in the bottom water of the Sea of Japan as a sensitive alarm for global climate change

The Sea of Japan, a semi-closed marginal sea (greatest depth ∼3700 m) in the northwestern-most Pacific Ocean, has an independent, deep convection system, which is driven by the formation and the sinking of cool, saline surface water towards the bottom in severe winters. Continuous measurement of dissolved oxygen using highly precise versions of the Winkler titration method has revealed 8-10% decreases in the bottom concentration of oxygen (O₂) over the past 30 years. The temporal decrease in O₂ means an imbalance between the supply of O₂ from the surface and the in situ consumption of O₂ in decomposing organic matter, suggesting that the change in the deep convection pattern of the Sea of Japan is probably caused by global climate change to reduce winter cooling of surface seawater.     

Decidability of the representation extension property for finite semigroups

We prove that the decision problem of whether or not a finite semigroup has the representation extension property is decidable.