Electrical characteristics of a small active volume (1 cm3) discharge-pumped XeCl laser

Through the use of a PFL (pulse-forming line) of conveniently changeable output impedance Z_O, the electrical characteristics of a small volume-discharge of standard XeCl laser gas mix was studied. The impedance Z_D from a 2×0.5×1(=1) cm³ discharge was found to be about 10. A PFL of very low impedance is therefore rather inefficient in driving the discharge, because of the impedance mismatch and the slower current rise time. The data presented will be useful for the design of excimer lasers of small discharge volume, which find applications in serving as master oscillator or in high repetition rate operation.     

Electromagnetic transition probability from the ground to the first excited 2+ state in138ce

The ratio of the B(E2) values for the 0 ₁ ⁺ → 2 ₁ ⁺ transitions in¹³⁸Ce and¹⁴²Ce was measured by Coulomb excitation with α-particles. From the known value of the transition probability in¹⁴²Ce it results: B(E2,¹³⁸Ce, 0 ₁ ⁺ → 2 ₁ ⁺ =0.45 +/?0.03 e² b ²     

Determination of myo-inositol in a flow-injection system with co-immobilized enzyme reactors and amperometric detection

A selective and sensitive flow-injection system for the determination of myo-inositol (hexahydroxycyclohexane) is described. Inositol dehydrogenase, IDH, lactate dehydrogenase, LDH, and lactate oxidase, LOD, are co-immobilized on porous glass and used in a packed-bed enzyme reactor. myo-Inositol reacts to produce an equivalent amount of hydrogen peroxide, which oxidizes hexacyanoferrate(II) to hexacyanoferrate(III) in a second reactor containing immobilized peroxidase. The hexacyanoferrate(III) is then detected amperometrically at 0 mV vs. SCE in a flow-through detector. The system responds linearly to injected samples of myo-inositol (25 μl) in the concentration range 1–300 μM. The maximum throughput was 90 samples per hour. The IDH/LDH/LOD reactor was stable for at least 5 weeks.     

On finite {1,2,3}-semiaffine planes

In this paper, we investigate {1,2,3}-semiaffine planes. All such planes of order n >51 shall be classified. It turns out that they are embeddable into projective planes of the same order n in the most natural way.Work supported by National Research Project on Strutture Geometriche Combinatoria, loro applicazioni of Italian M.P.I. and G.N.S.A.G.A. of C.N.R.     

Photopyroelectric spectroscopy (P2ES) of electronic defect centers in crystalline n-CdS

The electrical and dielectric properties of mercuric iodide were studied at room temperature under various intensities and colours of light in the frequency range 1 Hz–10 kHz. In the high-frequency region (>40 Hz), the real part of the dielectric constant () is almost constant with frequency (f), colour and intensity of light. At lower frequencies, varies nearly as 1/f and monotonically increases with intensity (I) of the yellow (or green) light, whereas it is almost constant with red light intensity. This behaviour is discussed in the view of the different polarization contributions. The imaginary part of the dielectric constant () was found to vary as 1/f over the frequency range studied. This behaviour was observed whether the crystal was in dark or illuminated implying that the roomtemperature ac dark- or photo-conductivity () is independent of frequency. The observed variation of with intensity of yellow (or green) light was found to follow anI ^1/2 dependence and a weaker dependence for the red light. the red light. The conductivity behaviour is discussed in the view of the current theories.     

Microbial synthesis and characterization of physiochemical properties of polyhydroxyalkanoates (PHAs) produced by bacteria isolated from activated sludge obtained from the municipal wastewater works in Hong Kong

The first objective of this study was the measurement of physical properties of P(3HB-co-3HV) copolymers with different (hydroxybutyrate) HB to (hydroxyvalerate) HV ratios produced by Bacillus cereus (TRY2) isolated from activated sludge. The 3HV PHBV copolymers were 0.05, 22.6, 39.2, 54.1, and 69.1 mol%, respectively. The second objective was to study possible wastewater treatment and production of PHAs at the same time by B. cereus (TRY2) and Pseudomonas spp. (TOB17) (both were isolated from activated sludge), recombinant Bacillus DH5α, and a combination of the above three bacteria. The results were satisfactory; the maximum COD and TOC of the sewage sludge reduced were 53.5% and 67.5%, respectively.     

Half-sandwich titanium(IV) complexes with Kläui's tripod ligand

Treatment of [Ti(O-i-Pr)(2)Cl(2)] with NaL(OEt) (L(OEt)(-) = [CpCo[P(O)(OEt)(2)](3)](-), Cp = eta(5)-C(5)H(5)) afforded [L(OEt)Ti(O-i-Pr)(2)Cl] that reacted with HCl in ether to give [L(OEt)TiCl(3)] (1). The average Ti-O and Ti-Cl distances in 1 are 1.975 and 2.293 A, respectively. Reaction of titanyl sulfate with NaL(OEt) in water followed by addition of HBF(4) afforded [L(OEt)TiF(3)] (2), the Ti-O and Ti-F distances of which are 2.020(2) and 1.792(2) A, respectively. The Zr(IV) analogue [L(OEt)ZrF(3)] (3) was prepared similarly from zirconyl nitrate, NaL(Oet), and HBF(4) in water. The Zr-O and average Zr-F distances in 3 are 2.139(2) and 1.938(2) A, respectively. Treatment of 1 with tetrachlorocatechol (H(2)Cl(4)cat) afforded [L(OEt)Ti(Cl(4)cat)Cl] (4). The average Ti-O(P), Ti-O(C), and Ti-Cl distances in 4 are 1.972, 1.926, and 2.334 A, respectively. Hydrolysis of 4 in the presence of Et(3)N yielded the mu-oxo dimer [(L(OEt))(2)Ti(2)(Cl(4)cat)(2)(mu-O)] (5). The average Ti-O(P), Ti-O(C), and Ti-O(Ti) distances in 5 are 2.027, 1.926, and 1.7977(9) A. Treatment of 1 with 1,1'-binaphthol (BINOLH(2)) in the presence of Et(3)N afforded [(L(OEt))(2)Ti(2)(mu-O)(2)(mu-BINOL)] x 2BINOLH(2) (6.2BINOLH(2)). Complex 1 is capable of catalyzing ring opening of epoxides with Me(3)SiN(3) under solvent-free conditions presumably via a Ti-azide intermediate.     

A Formal Total Synthesis of (+)-Methyl Trachyloban-18-oate and (+)-Methyl 16-Oxo-17-norkauran-18-oate: Regio- and Diastereoselective Preparation of Methyl (13S)-13-Hydroxyisoatisiren-18-oate from (−)-Abietic Acid

A novel preparation of methyl (13S)-13-hydroxyisoatisiren-18-oate ( 4 ), a key-intermediate in a synthesis of (+)-methyl trachyloban-18-oate ((+)- 1 ), from (?)-abietic acid, is described. Since (?)- 1 has been previously converted into (?)-methyl 16-oxo-17-norkauran-18-oate ((?)- 16 ), our preparation of 4 constitutes also a formal total synthesis, from (?)-abietic acid, of (+)- 16 . Key steps in this approach were the allene photoaddition to podocarp-8(14)-en-13-one ( 5 ) and the conversion of the endo-toluene-4-sulfonate 11 into the exo-benzoate 12b .     

Effects of pretreatments and modifiers on electrochemical properties of carbon paste electrodes

The electrochemical properties of carbon paste electrodes (CPEs), including unmodified and modified with protein and polycations, were investigated by impedance spectroscopy (IS) using ferricyanide and ferrocene monocarboxylic acid (FcMA) as redox probes. Various electrochemical pretreatments were applied to the unmodified CPE. The heterogeneous charge transfer rate constant of ferro/ferricyanide couple is enhanced by 2 to 10 times compared with that obtained at untreated electrodes. It was found that for ferricyanide the more suitable pretreatments are successive cyclic voltammetric scans, cathodization and a square wave-like stepping rather than high-potential anodization. However, the pretreatment only exhibits a slight effect on the kinetics of FcMA. At the CPEs containing modifier, the electron transfer rate of the redox couple depends more on the pH of electrolyte solution if ferro/ferricyanide is used. The results can be explained by the differently charged states of the CPEs that were caused by the protonation or deprotonation of the modifiers in various pH solutions and demonstrate the importance of the electrostatic interaction on the kinetics of the highly polar species such as ferricyanide. The different adsorptive behavior of ferricyanide and FcMA is also discussed.     

Modeling and electrokinetic evidences on the processes of the Al(III) sorption continuum in SiO2(s) suspension

Reactions of Al(III) at the interface between SiO2(s) and aqueous solution were characteristically and quantitatively studied using electrophoretic methods and applying a surface complexation/precipitation model (SCM/SPM). The surface and bulk properties of Al(III)/SiO2 suspensions were determined as functions of pH and initial Al(III) concentration. Simulated modeling results indicate that the SCM, accounting for the adsorption mechanism, predicts sorption data for low surface coverage only reasonably well. Al(III) hydrolysis and surface hydroxide precipitation must be invoked as the Al(III) concentration and/or pH progressively increase. Accordingly, the three processes in the Al(III) sorption continuum, from adsorption through hydrolysis to surface precipitation, could be identified by the divergence between the SCM/SPM predictions and the experimental data. SiO2(s) suspensions with low Al(III) concentrations (1 x 10(-4) and 1 x 10(-5) M) exhibit electrophoretic behavior similar to that of a pure SiO2(s) system. In Al(III)/SiO2 systems with high Al concentrations of 1 x 10(-3), 5 x 10(-3) and 1 x 10(-2) M, three charge reversals (CR) are observed, separately representing, in order of increasing pH, the point of zero charge (PZC) on the SiO2 substrate (CR1), the onset of the surface precipitation of Al hydroxide (CR2), and at a high pH, the PZC of the Al(OH)3 coating (CR3). Furthermore, in the 1 x 10(-3) M Al(III)/SiO2(s) system, CR2 is consistent with the modeling results of SCM/SPM and provides evidence that Al(III) forms a surface precipitate on SiO2(s) at pH above 4. SiO2(s) dissolution was slightly inhibited when Al(III) was adsorbed onto the surface of SiO2(s), as compared to the dissolution that occurs in a pure SiO2(s) suspension system. Al hydroxide surface precipitation dramatically reduced the dissolution of SiO2(s) because the Al hydroxide passive film inhibited the corrosion of the SiO2(s) surface by OH- ions.