A turbidimetric method for colloid titrations

Positive colloid solutions can be titrated with the polyanion potassium polyvinylsulfate with toluidine blue as indicator, but negative colloid solutions must be treated with an excess of the polycation polydiallyldimethylammonium chloride which is backtitrated with potassium polyvinylsulfate. By turbidimetry however, positive or negative colloid solutions can be directly titrated with, respectively, the polyanionic or polycationic titrant. Two methods, the construction and differential methods, can be used. The latter method is particularly useful when a flocculent precipitate appears during the titration.     

Extraction—spectrophotometric determination of boron with 2,6-dihydroxybenzoic acid and 4-(4-diethyl-aminophenylazo)-n-methylpyridinium iodide,with application to steels

The sensitive and selective method reported is based on the reaction of boric acid with 2,6-dihydroxybenzoic acid in acidic aqueous solution to form a 1:2 complex anion which can be extracted into chloroform as an ion-pair with 4-(4-diethylaminophenylazo)-N-methylpyridinium ion. The ion-pair formed by the excess of reagents and co-extracted into chloroform, is removed by washing the organic phase with phosphate buffer solution (pH 7.0) and 0.025 M sulfuric acid solution. The absorbance of azo dye in chloroform is measured at 570 nm. Calibration graphs are linear in the range 0–1.5 × 10^-5 M of boron. The molar absorptivity is 6.6 × 10⁴ l mol^-1 cm^-1 and the absorbance of the reagent blank is 0.030. The method was applied to the determination of boron at the 0.001% level in steels.     

Fluorimetric determination of nitrate in natural waters with 3-amino-1,5-naphthalenedisulphonic acid in a flow-injection system

A rapid, sensitive and precise flow-injection method for the determination of nitrate in natural waters is presented. Nitrate is first reduced in a copperized cadmium column to nitrite, which reacts with 3-amino-1,5-naphthalenedisulphonic acid to form the azoic acid. This acid forms a fluorescent salt in alkaline medium. The injecton rate is about 30 h^?1, the relative standard deviation for 10 injections of 2 × 10^?5 M nitrate is 0.8%, and the detection limit (S/N = 3)_is 1 × 10^?8 M nitrate.     

Generation of flat power-envelope terahertz-wide modulation sidebands from a continuous-wave laser based on an external electro-optic phase modulator

Flat power-envelope terahertz-wide modulation sidebands are generated by only electro-optic phase modulation of continuous-wave laser light. Generation and power equalization of widespread sidebands are realized simultaneously by spatial distribution of the modulation index within a laser beam cross section by use of simple domain-engineering processes in LiTaO3 electro-optic crystal. Generation of 46 sidebands spaced by 16.25 GHz within a -3-dB bandwidth (over a 1-THz span for a +/- 3-dB bandwidth) is demonstrated.     

Analysis of sound absorption by periodic structures using a hybrid-boundary element/mode expansion method

An improved hybrid method is proposed for analyzing sound scattering by a periodic structure. Part of the scattered field formulated with the mode expansion method is combined with other components of the field formulated with the boundary integration method in one period of the structure. Structures treated by this method can have arbitrary periodic forms made of locally reactive boundaries and porous materials. The oblique incident absorption coefficient of the structure is obtained simply from the reflection factor calculated for each elemental wave of the scattered field. The accuracy of the method is demonstrated by the agreement between calculated and measured values of the normal absorption coefficient of some test structures.     

Densities against temperature of 17 organic liquids and of solid 2,2-dimethylpropane

Densities against temperature of liquids under their equilibrium vapor pressures are reported for three fluoromethanes, three aromatic hydrocarbons, four olefins, bicyclo[2,2,2]octane. 2-methyltetrahydrofuran, and {0.786(1,4-c-C₆H₈) + 0.214C₆H₆}. The volume change on melting 2,2-dimethylpropane at the triple-point temperature is 9.6 per cent. A density parameter for n-pentane by Das and coworkers (J. Chem. Eng. Data1977, 22, 3) has been corrected.     

Liquid chromatographic separation of proteins derivatized with a fluorogenic reagent at cysteinyl residues on a non-porous column for differential proteomics analysis

A wide-pore (30 nm) reversed-phase column (Intrada WP-RP, particle size 3 μm) was recently utilized for protein separation in differential proteomics analysis with fluorogenic derivatization-liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS), and exerted a tremendous effect on finding biomarkers (e.g., for breast cancer). Further high-performance separation is required for highly complex protein mixtures. A recently prepared non-porous small-particle reversed-phase column (Presto FF-C18, particle size: 2 μm) was expected to more effectively separate derivatized protein mixtures than the wide-pore column. A preliminary experiment demonstrated that the peak capacity of the former was threefold greater than that of the latter in gradient elution of a fluorogenic derivatized model peptide, calcitonin. The FD-LC-MS/MS method with a non-porous column was then optimized and applied to separate liver mitochondrial proteins that were not efficiently separated with the wide-pore column. As a result, high-performance separation of mitochondrial proteins was accomplished, and differential proteomics analysis of liver mitochondrial proteins in a hepatitis-infected mouse model was achieved using the FD-LC-MS/MS method with the non-porous column. This result suggests the non-porous small-particle column as a replacement for the wide-pore column for differential proteomics analysis in the FD-LC-MS/MS method.     

Electrochemical Polymerization of Dithienylbenzene and Dithienylpyridine

1,4-Bis(2-thienyl)benzene (T14B), 2,5-bis(2-thienyl)pyridine (T25P), and 2,6-bis(2-thienyl)pyridine (T26P) were electrochemically polymerized. The conductivity of poly-T14B, poly-T25P, and poly-T26P was 1.7 × 10^?1, 2.6 × 10^?8, and 1.2 × 10^?7 S/cm, respectively. A poly-T26P film has a very even surface and is composed of fibrils growing on a thin, dense layer. Infrared spectra showed the monomer units to be linked through the 5,5′-positions of the thiophene rings. On electrochemical oxidation, poly-T26P became a quaternary ammonium salt. Visible/near-infrared spectra of poly-T14B showed that bipolaron states were formed. The conductivities of poly-T25P and poly-T26P rose to about 10^?2 S/cm by iodine doping, irrespective of the bonding sites of pyridine.     

Towards the optimality of Feistel ciphers with substitution-permutation functions

We explore the optimality of balanced Feistel ciphers with SP-type F-functions with respect to their resistance against differential and linear cryptanalysis. Instantiations of Feistel ciphers with the wide class of (SP) \(^u\) and (SP) \(^u\) S F-functions are considered: one F-function can contain an arbitrary number of S-box layers interleaved with linear diffusion. For the matrices with maximum diffusion, it is proven that SPS and SPSP F-functions are optimal in terms of the proportion of active S-boxes in all S-boxes—a common efficiency metric for substitution-permutation ciphers. Interestingly, one SP-layer in the F-function is not enough to attain optimality whereas taking more than two S-box layers does not increase the efficiency either.