Resonant inelastic x-ray scattering at the limit of subfemtosecond natural lifetime

We present measurements of the resonant inelastic x-ray scattering (RIXS) spectra of the CH(3)I molecule in the hard-x-ray region near the iodine L(2) and L(3) absorption edges. We show that dispersive RIXS spectral features that were recognized as a fingerprint of dissociative molecular states can be interpreted in terms of ultrashort natural lifetime of ～200 attoseconds in the case of the iodine L-shell core-hole. Our results demonstrate the capacity of the RIXS technique to reveal subtle dynamical effects in molecules with sensitivity to nuclear rearrangement on a subfemtosecond time scale.     

Hydrogenated amorphous silicon nanostructures: novel structure�Creactivity relationships for cyclization and ring opening in the gas phase

The effects of the reactive center connectivity and internal rotations on the reactivity of hydrogenated silicon nanostructures toward cyclization and ring opening pathways have been investigated. Rate coefficients for 25 cyclization and ring opening reactions for hydrides containing up to eight silicon atoms have been calculated using G3//B3LYP. The overall reactions exhibit two elementary steps. Overcoming the first barrier results in the formation of a hydrogen-bridged cyclic intermediate from a substituted silylene. Passing over the second barrier converts this intermediate into a cyclic silicon hydride. The rate-determining step varied according to the ring size formed and the temperature. Assuming a rate-determining step, values for the single-event Arrhenius pre-exponential factor, $ \tilde{A}$ , and the activation energy, E _a, were calculated from G3//B3LYP rate coefficients corrected for internal rotations, and a group additivity scheme was developed to predict $ \tilde{A}$ and E _a. The values predicted by group additivity are more accurate than structure?Creactivity relationships currently used in the literature, which rely on a representative $ \tilde{A}$ value for each reaction class and the Evans-Polanyi correlation to predict E _a. Internal rotation corrections played a prominent role in cyclization pathways, impacting $ \tilde{A}$ values for larger ring formation reactions more strongly than any variations in the connectivity of the reactive center.     

Les sections secrètes des tores simples dans l'espace euclidienR 3 telles que Kuiper les dévoile à Hirzebruch

Sans résuméDédié à Friedrich Hirzebruch     

Bemerkung zur Arbeit L. D. Mahajans „Eine Theorie der Erscheinung von flüssigen Tropfen“ usw

Ohne Zusammenfassung L. D. Mahajan, Kolloid-Z.65, 20 (1933).     

Dairy aroma compounds recovery by pervaporation

Original pervaporation experiments with two dairy aroma compounds diluted in model aqueous solutions through GFT silicalite-filled silicone composite membrane and GKSS PEBA homogeneous membrane (0.1 m² effective area) were carried out on a pilot-plant. A systematic approach was done, studying the influence of various operating parameters (feed temperature and permeate pressure). The permeabilities of the membranes were calculated for each permeant, based on the estimation of the driving force as a fugacities difference. The pervaporation membranes tested showed a good selectivity for the extraction of methylthiobutanoate (hydrophobic molecule with cheese fragrance) at high dilution rate. However, these membranes proved to be less selective for the recovery of diacetyl (hydrophilic butter aroma). For this component, the coupling of pervaporation and two-stage condensation improved significantly the selectivity of the whole process. The thermodynamic properties in the liquid feed (real dairy media) as well as in the permeate (vapour-liquid equilibria at low pressure) have to be well known in order to optimize the recovery of the aroma compounds     

Lead determination in wine by potentiometric stripping analysis

Summary Computerized potentiometric stripping analysis (PSA) was used for lead determination in wine samples. In this method sample preparation before determination is limited to dilution with an appropriate supporting electrolyte (0.5 mol/l HCl and 40 mg/l Hg²⁺). Due to the very high sensitivity, the time needed for one determination can be reduced to 2 min. The method was tested by lead determination in different wines, different concentration ranges and in one European interlaboratory comparison organized by BCR. Using PSA it is possible to simultaneously determine cadmium, lead and copper in wine. For other elements such as Bi, Tl, Hg, Sn, As, Zn the determination procedures are under development. The PSA equipment is available on the market, small in size, relatively cheap and it does not require any special installation such as gas or cooling water.     

Real time task scheduling allowing fuzzy due dates

The paper deals with periodical task scheduling. The tasks are described by fuzzy due dates and fuzzy execution times. The goal of scheduling is to find an optimal assignment of priorities such that the satisfaction associated with due dates and execution times be minimized. The paper shows how the rules associated with task priorities improve the optimal assignment search.