Electrical conductivity of hexaiodobenzene and tetrahalo-p-benzoquinone under very high pressures

The electrical resistances of hexaiodobenzene, iodanil, bromanil, and chloranil have been studied under very high pressures. The lowest resistivity at 500 kbar is about 5 Ω-cm for hexaiodobenzene and 5 × 10^?2 Ω-cm for iodanil. This difference may be mainly explained by the charge transfer from iodine to oxygen atoms in the latter compound.     

Effects of transformations in higher order asymptotic expansions

Summary Approximate formulae using a large number of terms of Edgeworth type asymptotic expansions for the distributions of statistics often produce spurious oscillations and give poor fits to the exact distribution functions in parts of the tails. A general method for suppressing these oscillations and evoking more accurate approximations is introduced here. This work was supported in part by Ministry of Education Grant 59530016 and 60530017. The Institute of Statistical Mathematics     

TECHNICAL NOTE

Abstract— –The use of a proximity type 12 µm microchannel plate photomultiplier (Hamamatsu R1564U) is demonstrated for the accurate determination of picosecond lifetimes of xanthione, stiff stilbene, cryptocyanine, pinacyanol chloride, erythrosin and l, l'-diethyl-2,2'-dicarbocyanine iodide in solution at room temperature. Single curve and global analyses with reference convolution give statistically acceptable mono-exponential fits to all obtained decays. The count rate and wavelength dependence of the measured excitation pulse profile are discussed. Matching the count rates of sample and reference is recommended for reliable picosecond lifetime determinations.     

Sample preparation followed by HPLC under harmless 100% aqueous conditions for determination of oxytetracycline in milk and eggs

A simple and hazardous chemical-free method for the high-performance liquid chromatographic determination of oxytetracycline (OTC) residues in milk and eggs has been developed. Sample preparation consists in homogenization with an aqueous solution by means of a handheld ultrasonic homogenizer followed by centrifugal ultrafiltration. HPLC is performed with an isocratic aqueous mobile phase and a photodiode array detector. Average recoveries of OTC (0.05, 0.1, and 0.2 microg mL(-1) for milk; 0.1, 0.2, and 0.4 microg mL(-1) for eggs) were > or =84% with relative standard deviations of < or =2.3%. The total time required for the analysis of one sample and LOQs were <30 min and <0.1 microg mL(-1), respectively. In all the processes, no organic solvents or hazardous reagents were used.     

Automated interpretation of mass spectra of complex mixtures by matching of isotope peak distributions

Mass spectrometry is now firmly established as a powerful technique for the identification and characterization of proteins when used in conjunction with sequence databases. Various approaches involving stable-isotope labeling have been developed for quantitative comparisons between paired samples in proteomic expression analysis by mass spectrometry. However, interpretation of such mass spectra is far from being fully automated, mainly due to the difficulty of analyzing complex patterns resulting from the overlap of multiple peaks arising from the assortment of natural isotopes. In order to facilitate the interpretation of a complex mass spectrum of such a mixture, such as an MS spectrum of a stable-isotope-enriched ion species, we report on the development of a software application, 'Matching' (web accessible), that enables the automatic matching of theoretical isotope envelopes to multiple ion peaks in a raw spectrum. It is particularly useful for resolving the relative abundances of narrow-split paired peaks caused by enrichment with a stable isotope, such as 18O, 13C, 2H, or 15N.     

Preparation and properties of silicon containing polyamides

Silicon containing polyamides were prepared by melt polycondensation method with a 1,3-bis(3-aminopropyl)tetramethyldisiloxane and aliphatic dicarboxylic acids having various numbers of methylene groups. Only one endothermic peak appeared in the DTA curve of the quenched sample for polyamides having an even number of methylene groups in the repeating unit. Two endothermic peaks, however, appeared for the sample kept for a week in dry air at ambient temperature after quenching: the peak at the higher temperature is called peak I; and the peak at the lower one, peak II. By heat treatment at the higher temperature, peak II shifted to a higher temperature and increased its peak area, and peak I decreased its peak area while keeping its temperature unchanged. This behavior suggests the existence of two types of crystalline states. The peak temperature of peak I alternatively decreased with the increase of the number of methylene groups. The Young's modulus and the tensile strength increased with increase of annealing time at ambient temperature. The solubilities in various solvents, the resistance to alkali solution, and the thermal stability were acceptable. Both the permeation coefficient of oxygen (P) and the separation ratio (P/P) increased with the increase of silicon content in the repeating unit.     

Syntheses and electronic properties of the nickel and palladium complexes of the octaethylporphyrin(M1)-(dihexylbithiophene)n-octaethylporphyrin(M2) system [OEP(M1)-(DHBTh)n-OEP(M2)] connected with the diacetylene linkage. A methodology for molecular design of the particular electronic structure

The palladium complexes of highly extended π-electronic conjugation system, octaethylporphyrin(Pd)-(dihexylbithiophene)_n-octaethylporphyrin(Pd) [OEP(Pd)-(DHBTh)_n-OEP(Pd), n=1-6], were synthesized, in which all the chromophores are connected with diacetylene linkage. The unsymmetrical derivatives of OEP(Ni)-DHBTh-OEP(Pd) were also successfully synthesized. Electronic properties of these symmetrical and unsymmetrical complexes were conclusively described, as compared with those of OEP(Ni)-(DHBTh)_n-OEP(Ni). Based on the structure elements, a methodical guiding principle for molecular design of the particular electronic structure will be proposed.     

Development of a comprehensive analytical method for phosphate metabolites in plants by ion chromatography coupled with tandem mass spectrometry

This paper describes the development of a practical method for the analysis of phosphorus compounds with a focus on sugar phosphates from the model higher plant Arabidopsis thaliana by ion chromatography coupled to electrospray ionization tandem mass spectrometry (IC-ESI-MS-MS). After the analytical separation, the potassium hydroxide eluent was converted to water with an anion suppressor allowing the effluent from the IC to be connected to the mass spectrometer directly. In the optimized method, 17 phosphorous compounds (adenosine diphosphate (ADP), fructose 1,6-bisphosphate, fructose 2,6-bisphosphate, fructose 6-phosphate, galactose 1-phosphate, glucose 1-phosphate, glucose 1,6-bisphosphate, glucose 6-phosphate, mannose 6-phosphate, phosphoenol pyrvate, 3-phosphoglyceric acid, ribulose 1,5-bisphosphate, ribulose 5-phosphate, ribose 5-phosphate, sucrose 6-phosophate and uridine 5'-diphosphate-glucose (UDPG)) were determined. The linearity of response for these phosphorous compounds over the concentration range of 0 and 10 microM was better than 0.9993 in all cases. The minimum detection limit was between 0.01 and 2.50 microM for a 25 microL injection, and recovery rates for standard addition to the sample were within the range from 93% to 110%.     

Development of chiral stationary phases consisting of low-molecular-weight cellulose derivatives covalently bonded to silica gel

We prepared chiral supports whose chiral stationary phase (CSP), consisting of a low-molecular-weight cellulose derivative (degree ofpolymerization: 15), is covalently bonded to silica gel. The cellulose used asthe base material of the CSP was pre-hydrolysed with phosphoric acid before thecoupling reaction to unite a reducing terminal in the cellulose and anaminopropyl group on the surface of silanized silica. After substitutinghydroxyl groups in cellulose by using 3,5-dichlorophenyl isocyanate or phenylisocyanate, we tested the CSP thus obtained for its performance in chiralrecognition and found a wide range of chiral discrimination ability. We alsoconfirmed that an elution using strong solvents as a mobile phasecould be achieved, which is difficult for the coated-type CSPs because themobile phase may dissolve the CSP. However, more enantiomeric mixtures showedlarger selectivity factors () when eluted on the coated-type CSPs thanonthe covalently bonded CSPs. A coated-type CSP consisting of thelow-molecular-weight cellulose phenylcarbamate, prepared as a control CSPsample, showed comparable performance with the commercial coated-type column(CHIRALCEL® OC), so the slightly poorer performance ofthe chemically bonded CSPs may be explained by the difficulty of the polymerconsisting of the CSPs in taking an optimal supermolecular structure requiredfor chiral recognition due to the fixation to the silica gel. The lowdegreeof polymerization may have an additional effect.     

Protected amino acids as a nonbonding source of chirality in induction of single-handed screw-sense to helical macromolecular catalysts

Chiral nonbonding interaction with N-protected amino acid methyl esters used as chiral additives in achiral solvents allows dynamic induction of single-handed helical conformation in poly(quinoxaline-2,3-diyl)s (PQX) bearing only achiral substituents. Ac-l-Pro-OMe, for instance, allows induction of energy preference of 0.16 kJ mol⁻¹ per monomer unit for the M-helical structure over the P-helix in t-butyl methyl ether (MTBE). With this new mode of screw-sense induction, homochiral screw-sense has been induced in virtually achiral poly(quinoxaline-2,3-diyl)s 1000-mer containing phosphine pendants (PQXphos). Use of PQXphos as a helically dynamic ligand along with Ac-Pro-OMe (l or d) as a chiral additive in MTBE allowed a highly enantioselective Suzuki–Miyaura coupling reaction with up to 95% enantiomeric excess.

Achiral poly(quinoxaline-2,3-diyl) containing Ar₂P groups undergo dynamic induction of M-helical conformation through nonbonding interaction with protected AA such as Ac-l-Pro-OMe, serving as a chiral ligand in asymmetric cross-coupling with up to 95% ee.