Kinetics of strontium ion adsorption on natural clay samples

Summary The adsorption kinetics of strontium ion was studied on seven natural clay samples with radioactive tracer method. The kinetic curves were determined and the kinetic data were evaluated by forms of first-rate kinetic equations with different terms, generally used for adsorption of ions of low concentration. The adsorption process was reduced to two steps. Film diffusion and participle diffusion were found in the case of five samples. Gel diffusion, film diffusion and participle diffusion were found in the case of the other two samples. The presence of significant amount of cristobalite can explain the gel phase in these two samples. The rate coefficients of steps were calculated from the kinetic curves.     

A possible construction of chemical reaction networks

The chemical reaction networks and the sequence networks represent the pathways of a complex chemical process. In order to study the pathways separately the systematization of the elementary processes included in the possible mechanism is inevitable.This systematization was realized by a special procedure based on linear algebraic methods and enabled us to select the corresponding processes from the possible mechanism. The efficiency of the procedure has been illustrated by its application to the liquid phase oxidation of ethylbenzene and the elementary processes have been selected using a computer program.     

Phosphasila-, phosphagerma-, and phosphaarsaallenes --P=C=E (E = Si,Ge, As) and arsa- and diarsaallenes --As=C=E" (E" = C,As)

The paper reviews the contribution from our group to the studies of heteroallenes. The transient 1,3-phosphasilaallene ArP=C=Si(Ph)Tip (Ar = 2,4,6-tri-tert-butylphenyl, Tip = 2,4,6-triisopropylphenyl) and 1,3-phosphagermaallene ArP=C=GeMes₂ (Mes = 2,4,6-trimethylphenyl) were characterized below –40 °C by NMR spectroscopy and chemical trapping. These compounds dimerize above –40 °C through two routes. With increased steric hindrance on germanium, the phosphagermaallene ArP=C=Ge(Bu^t)Tip was stabilized as monomer at room temperature. 3-Chloro-2-lithio-1,3-phosphasilapropene ArP=C(Li)Si(Cl)CMeR₂ (CMeR₂ = 9-methylfluorenyl) behaves, at least in some cases, as a synthetic equivalent of the functionalizable allene ArP=C=Si(Cl)CMeR₂. Arsaallene ArAs=C=CR₂, phosphaarsaallenes ArP=C=AsAr and ArP=C=AsDmt (Dmt = 2,6-dimesityl-4-methylphenyl), and diarsaallene ArAs=C=AsAr exhibit a higher thermal, air, and moisture stability than the above phosphasilaallenes and phosphagermaallenes. The physicochemical data for the arsaallenes and diarsaallenes, particularly, their X-ray structural parameters, display a bonding system close to allenes. On going down the Periodic table, the stabilization becomes more difficult. For this reason, tin allenic derivatives are very rare and antimony allenic compounds have not yet been isolated.     

Amino acid cluster formation studied by electrospray ionization mass spectrometry

The association properties of natural and non-natural amino acids were studied in detail using electrospray ionization mass spectrometry. The results show a highly diverse cluster formation behavior of amino acids. There are differences regarding the degree of clustering (average cluster size), the presence or absence of one or several 'magic' clusters of special stability and the influence of chirality on cluster stability. Cluster formation does not show a good correlation with simple physico-chemical properties (such as solubility), indicating that it is a specific process and not only a simple aggregation during evaporation/ionization. A systematic study of cluster formation of serine derivatives reveals that all functional groups play a prominent role in the binding of the magic octamer. The results support the idea of the zwitterionic character of the octamer. Electrospray ionization of the side-chain acetylated serine shows the formation of a very stable tetramer with a strong preference for homochirality. The results suggest that Ser8 is made up of two tetramer subunits, held together by hydrogen bonds of the side-chain.     

Kinetics and mechanism of the oxidation of a substituted phenol by a superoxochromium(III) ion

A superoxochromium(III) ion, CraqOO2+, abstracts the hydrogen atom from the hydroxylic group of a substituted, cationic phenol (ArOH), kCrOO = 1.24 M-1 s-1 in acidic aqueous solution at 25 degrees C. The reaction has a large kinetic isotope effect, kArOH/kArOD approximately 12 and produces ArO., which also reacts with CraqOO2+ in a rapid second step, kArO = 1.26 x 10(4) M-1 s-1. The final oxidation product is an o-quinone, which was identified by its behavior on a cation-exchange resin, UV-visible spectrum, and reaction with iodide ions. This work has extended to three the types of element-hydrogen bonds that react with CraqOO2+ about 10(2) times more slowly than with CraqO2+. The mechanistic implications of these findings are discussed.     

A new approach to irreversibility in deep inelastic collisions

We use concepts of statistical mechanics to discuss the irreversible character of the experimental data in deep inelastic collisions. A definition of irreversibility proposed by Ruch permits a unified overview on current theories which describe these reactions. An information theoretical analysis of the data leads to a Fokker-Planck equation for the collective variables (excitation energy, charge and mass). The concept of mixing distance can serve as a quantitative measure to characterize the “approach to equilibrium”. We apply it to the brownian motion as an illustration and also to the phenomenological analysis of deep inelastic scattering data with interesting results.     

Renormalization Conditions and the Sliding Scale in the Implicit Regularization Scheme: A Simple Connection

We describe in detail how a sliding scale is introduced in the renormalization of a QFT according to integer-dimensional implicit regularization scheme. We show that since no regulator needs to be specified at intermediate steps of the calculation, the introduction of a mass scale is a direct consequence of a set of renormalization conditions. As an illustration the one-loop -function for QED and ⁴ theories are derived. They are given in terms of derivatives of appropriately systematized functions (related to definite parts of the amplitudes) with respect to a mass scale . Our formal scheme can be easily generalized for higher loop calculations.     

Internal energy deposition and ion fragmentation in atmospheric-pressure mid-infrared laser ablation electrospray ionization

Mid-infrared laser ablation of water-rich targets at the maximum of the 2.94 μm absorption band is a two-step process initiated by phase explosion followed by recoil pressure induced material ejection. Particulates and/or droplets ejected by this high temperature high pressure process can be ionized for mass spectrometry by charged droplets from an electrospray. In order to gauge the internal energy introduced in this laser ablation electrospray ionization (LAESI?) process, we apply the survival yield method and compare the results with electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI). The results indicate that LAESI yields ions with internal energies indistinguishable from those produced by ESI. This finding is consistent with the recoil pressure induced ejection of low micrometre droplets that does not significantly change the internal energy of solute molecules.