Chiral separation membranes from modified polysulfone having myrtenal-derived terpenoid side groups

Novel polymeric materials, having a chiral environment, were obtained by the reaction of lithiated polysulfone with chiral terpenoid myrtenal. The resulting polymers gave self-standing durable membranes. Molecularly imprinted membranes were prepared from the novel myrtenal-containing polysulfones by the presence of print molecules during the membrane preparation process. The d-isomer imprinted membrane showed d-isomer adsorption and diffusivity selectivity, and vice versa. As a result, the d-isomer imprinted membrane transported the d-isomer in preference to the l-isomer, and vice versa. The control non-imprinted membrane also showed permselectivity toward racemic glutamic acid mixtures. The expression of permselectivity for the molecularly imprinted membranes was synergistically due to adsorption and diffusivity selectivity.     

Thiacalix[4]arenetetrasulfonate as specific pre-column chelating reagent for nickel(II) ion in kinetic differentiation mode high-performance liquid chromatography

Thiacalix[4]arenetetrasulfonate (TCAS) has been examined as a pre-column chelating reagent for the determination of trace metal ions by kinetic differentiation mode (KD) ion-pair reversed-phase high-performance liquid chromatography (HPLC) with spectrophotometric detection. Among 14 kinds of common metal ions tested here, viz. Al(III), Ca(II), Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Hg(II), Mg(II), Mn(II), Ni(II), Pb(II), V(V), and Zn(II) ion, only Ni(II) ion was detected as the TCAS chelate in the HPLC separation stage in spite of TCAS forming the chelates with various metal ions except for Al(III), Ca(II), and Mg(II) at the pre-column chelation stage. The undetected metal-TCAS chelates seemed to be dissociated on an HPLC column where no added TCAS was present in the mobile phase because of their kinetic unstability. The calibration graph for Ni(II) ion gave a wide linear dynamic range (40-20,000 nM) with the very low detection limit (DL) (3σ base-line fluctuation) to be 5.4 nM (0.32 ng ml⁻¹). The practical applicability of the KD-HPLC method with TCAS was demonstrated with the determination of trace Ni in coal fly ash.     

An Oblivious Routing Algorithm for Two-Dimensional Meshes of Constant Queue-Size

This paper shows an important exception to the common perception that three-dimensional meshes are more powerful than two-dimensional ones. Let N be the total number of processors. Then permutation routing over three-dimensional mesh computers needs Θ(N^2/3) steps while it takes Θ(N^1/2) steps over two-dimensional ones under the following conditions: (1) The path of each packet must be determined solely by its initial position and destination, i.e., the algorithm must be oblivious. (2) Each path must be “elementary,” i.e., it must be shortest and as straight as possible. Thus the conditions, under which, somewhat surprisingly, three-dimensional meshes are significantly less powerful than two-dimensional ones for the fundamental network operation, are quite reasonable in practice.     

Residual-stress analysis of an epoxy plate subjected to rapid cooling on both surfaces

This paper presents theoretical and experimental methods of finding the residual stress in an epoxy plate subjected to rapid cooling on both surfaces. The theoretical residual-stress distributions in a plate are calculated by using the fundamental equations based on the linear viscoelastic theory. The specimens in the experiment are subjected to rapid cooling. The residual stresses are measured by the layer-removal method. The theoretical and experimental results are compared and discussed.