A new method for the voltammetric determination of molybdenum(VI) using carbon paste electrodes modified in situ with cetyltrimethylammonium bromide

Molybdenum(VI) is determined by anodic stripping voltammetry using a carbon paste electrode modified in situ with cetyltrimethylammonium bromide (CTAB). The preconcentration of molybdenum is performed by adsorption and reduction of ion-pairs of cetyltrimethylammonium and molybdenum(VI) oxalate at a potential of −0.4 V vs. the saturated calomel electrode (SCE). The supporting electrolyte contains 0.01 M oxalic acid and 0.075 mM CTAB. Differential pulse anodic stripping voltammetry exploiting the reoxidation signal is used for the determination of trace levels of molybdenum(VI). Linearity between current and concentration exists for a range of 0.5–500 μg 1⁻¹ Mo with proper preconcentration times; the limit of detection (calculated as 3σ) is 0.04 μg 1⁻¹ with an accumulation period of 10 min.     

Thermal-, pressure-, and light-induced spin transition in novel cyanide-bridged FeII-AgI bimetallic compounds with three-dimensional interpenetrating double structures (FeIILx[Ag(CN)2]2).G

Low-spin, high-spin and spin-transition behaviours have been observed for the doubly interpenetrating three-dimensional bimetallic compounds (FeII(pz)[Ag(CN)2]2).pz (pz = pyrazine), (FeII(4,4'-bipy)2[Ag(CN)2]2) (4,4'-bipy = 4,4'-bipyridine), and (FeII(bpe)2[Ag(CN)2]2) (bpe = bispyridylethylene), respectively. The single crystals of the bpe derivative undergo a spin transition with a large hysteresis loop at about 95 K. After several warming and cooling cycles, the single crystals become a microcrystalline powder with 50% spin transition. Influence of pressure--as well as light-induced excited spin-state trapping (LIESST) on the thermal 50% spin transition of the microcrystalline sample has also been investigated. Thermal spin-transition behaviour has also been induced at pressures higher than 1 bar for the 4,4'-bipy derivative. Both the 4,4'-bipy and bpe derivatives show strong pressure dependence of the spin state at 300 K.     

Non-analytic functional calculi in several variables

Generalizing a result of [1] and [2], we show that every-scalar system (see Def. 3) is decomposable (in the sense of [6], [7]). By means of this fact and by some results on decomposable n-tuples (contained in [6] and [7]) we prove the theorem of support and (in the case of an inverse closed admissible algebra) the spectral mapping theorem for-functional calculi in several variables (see Def. 3). In the case of a single operator we obtain a simplification of the definition of an-spectral function (in the sense of [5], Def. 3.1.3).     

The coherent K L 0 C → K S 0 C regeneration at high energies

New experimental results on the coherentK _L ⁰ C K _S ⁰ C regeneration in the momentum range 10p30 GeV/c are presented. For the quantity (f ₀–¯f ₀/k (where f₀ and¯f ₀ are theKC and¯K ⁰C forward scattering amplitudes andk is the wave number) we have obtained: arg (f ₀–¯f ₀)/k=–126±14 and ¦(f ₀–¯f ₀/k¦ p ^{–0.62±0.14} These results are well described by a simple Regge pole model including only the (-trajectory exchange in thet-channel with the intercept (0) close to 0.4.Presented at the IV International Symposium on High Energy and Elementary Particle Physics, Warszaw, September 1975.     

On sums of two coprimek-th powers

Under the assumption of the Riemann Hypothesis, an asymptotic formula with a sharp error term is established for _{nx k} (n), where _k (n) denotes the number of ways to writen as a sum of twok-th powers of coprime positive integers (k3).     

On an asymmetric divisor problem with congruence conditions

For fixed positive integersab, natural numbersl ₁k ₁,l ₂k ₂ andn, denote withd _a,b (l ₁,k ₁;l ₂,k ₂;n) the number of all (,)N² with ^{a b} =n,l ₁(modk ₁),l ₂(modk ₂). In the present paper we establish asymptotic formulas for the Dirichlet summatory function ofd _a,b (l ₁,k ₁;l ₂,k ₂;n) with both upper and lower estimates of the error term, all of them uniform in the moduli.     

Enhancement of the effectiveness of electroporation-augmented cutaneous DNA vaccination by a particulate adjuvant

DNA vaccines are attracting increased attention due to multiple advantages over conventional vaccines. Attempts to improve these vaccines focus on enhancing DNA delivery and employing novel immunoadjuvants. Electroporation (EP) has emerged as an effective method for delivering DNA vaccines, significantly enhancing humoral and cellular responses. To further improve EP-augmented DNA vaccination, we used micron-size gold particles as a particulate adjuvant. DNA is not bound, or adsorbed, to the particles. Gold particles were coinjected intradermally with plasmid DNA encoding the hepatitis B virus surface antigen (HBsAg) into mice, both in the absence and presence of noninvasive EP. The particles enhanced the percentage of responding animals, and shortened the time for reaching maximal antibody titers by 2 weeks. Subtyping of the produced antibodies revealed a predominantly Th1-like response which did not change significantly with the absence or presence of particles. The particles likely function as an attractant for antigen-presenting cells (APCs), and probably do not affect EP or antigen expression to a significant extent. We conclude that micron-size gold particles injected intradermally together with DNA followed by EP give rise to an accelerated, potent immune response with a strong cellular component. This method may become important for the development of fast-acting therapeutic and prophylactic vaccines.     

Asymmetric radical additions using chiral 1,3-dioxolane-4-ones

Moderate facial selectivities are observed in additions of alkyl radicals to the chiral (c,d) olefin (2S)-2-tert-butyl-5-ethoxycarbonylmethylene-1,3-dioxolane-4-one 1. The following hydrogen abstraction from tributylstannane proceeds with excellent asymmetric stereocontrol, leading to two of four possible diastereoisomers with high diastereomeric excesses. Additions of chiral radicals obtained from (2R,5R)-5-alkyl-5-bromo-1,3-dioxolane-4-ones to ethyl acrylate show high asymmetric 1,3-induction.     

Untersuchung der Thermolysereaktion von Malonsäuremonoarylestern

Thermolysis of malonic acid monoaryl esters gives rise to the formation of a steady-state equilibrium with diaryl malonates and free malonic acid, the latter being decarboxylated to form acetic acid. The yields of diaryl malonates are lowered by a concurrent reaction, namely the decarboxylation of the monoesters, giving aryl acetates and CO₂.

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H. Junek, E. Ziegler, U. Herzog undH. Kroboth, Synthesis1976, 332.