Polyamide from lactams by reactive rotational molding via anionic ring-opening polymerization: Optimization of processing parameters

A reactive rotational molding (RRM) process was developed to obtain a PA6 by activated anionic ring-opening polymerization of epsilon-caprolactam (APA6). Sodium caprolactamate (C10) and caprolactam magnesium bromide (C1) were employed as catalysts, and difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20) was used as an activator. The kinetics of the anionic polymerization of !-caprolactam into polyamide 6 was monitored through dynamic rheology and differential scanning calorimetry measurements. The effect of the processing parameters, such as the polymerization temperature, different catalyst/activator combinations and concentrations, on the kinetics of polymerization is discussed. A temperature of 150°C was demonstrated to be the most appropriate. It was also found that crystallization may occur during PA6 polymerization and that the combination C1/C20 was well suited as it permitted a suitable induction time. Isoviscosity curves were drawn in order to determine the available processing window for RRM. The properties of the obtained APA6 were compared with those of a conventionally rotomolded PA6. Results pointed at lower cycle times and increased tensile properties at weak deformation

A quantum approach to Laplace operators

In this paper, a theory of stochastic processes generated by quantum extensions of Laplacians is developed. Representations of the associated heat semigroups are discussed by means of suitable time shifts. In particular the quantum Brownian motion associated to the Levy-Laplacian is obtained as the usual Volterra-Gross Laplacian using the Cesaro Hilbert space as initial space of our process as well as multiplicity space of the associated white noise

Short-Term Forecasting of GDP Using Large Monthly Datasets: A Pseudo Real-Time Forecast Evaluation Exercise

This paper evaluates different models for the short-term forecasting of real GDP growth in ten selected European countries and the euro area as a whole. Purely quarterly models are compared with models designed to exploit early releases of monthly indicators for the nowcast and forecast of quarterly GDP growth. Amongst the latter, we consider small bridge equations and forecast equations in which the bridging between monthly and quarterly data is achieved through a regression on factors extracted from large monthly datasets. The forecasting exercise is performed in a simulated real-time context, which takes account of publication lags in the individual series. In general, we find that models that exploit monthly information outperform models that use purely quarterly data and, amongst the former, factor models perform best.Bridge models, Dynamic factor models, real-time data flow model

Short-term forecasting of GDP using large monthly datasets: a pseudo real-time forecast evaluation exercise.

This paper evaluates different models for the short-term forecasting of real GDP growth in ten selected European countries and the euro area as a whole. Purely quarterly models are compared with models designed to exploit early releases of monthly indicators for the nowcast and forecast of quarterly GDP growth. Amongst the latter, we consider small bridge equations and forecast equations in which the bridging between monthly and quarterly data is achieved through a regression on factors extracted from large monthly datasets. The forecasting exercise is performed in a simulated real-time context, which takes account of publication lags in the individual series. In general, we find that models that exploit monthly information outperform models that use purely quarterly data and, amongst the former, factor models perform best.Bridge models ; Dynamic factor models ; real-time data flow.

Low energy measurement of the 7Be(p,gamma)8B cross section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let

Study of the two nucleophilic attack modes AC and ACl the reaction between triethylphosphite and tetrachloromethane: DFT Analysis.

The objective of our work was to theoretical study by the quantum method DFT/B3LYP/6-311G(d,p) of the reaction of tetrachloromethane (CCl4) with triethylphosphite (P(OEt)3). For the prediction of regioselectivity, several quantum approaches have been developed, namely molecular orbital frontier theory (MFO), Transition State Theory (TST), and reactivity descriptors derived from the conceptual DFT. The results obtained in this work show that triethylphosphite is defined as a nucleophile while tetrachloromethane behaves as an electrophile. The nucleophilic attack of the phosphorus atom of P(OEt)3 is preferably on the chlorine of the tetrachloromethane instead of carbon and the reaction is polar and regioselective

Characterization Theorems for Differential Operators on White Noise Spaces

We characterize through their action on stochastic exponentials the class of white noise operators which are derivations with respect to both the point-wise and Wick products. We define the class of second order differential operators and second order Wick differential operators and we characterize the white noise operators belonging to both classes. We find that the intersection of these two classes, in the first and second order cases, is identified by a skewness condition on the coefficients of the differential operator. Our technique relies on simple algebraic properties of commutators and on the Gaussian structure of our white noise space. Our approach is suitable to study differential operators of any orde

Theoretical study of the regioselectivity of the reaction between tetrachloromethane and trivalent phosphorus derivatives using the DFT B3LYP/6-31G(d) method

In this study we used the DFT B3LYP/6-31G(d) method to determine certain thermodynamic properties, transition states, energies of the highest occupied and lowest unoccupied molecular orbits (HOMO and LUMO respectively), the difference between the two (εLUMO – εHOMO), global indices and chemical potentials of the reaction between tetrachloromethane and the following trivalent phosphorus derivatives: P(OEt)3, (NEt2)P(OEt)2 , (NEt2)2P(OEt) and (NEt2)3P. Our results show that the trivalent phosphorus derivatives behave as nucleophiles, while tetrachloromethane behaves as an electrophile. The nucleophilic attack takes place preferentially at the chlorine atom of the tetrachloromethane rather than at the carbon atom. The reaction is exothermic and regioselective, and the reaction mechanism is controlled by charge transfer. These results are comparable to those obtained experimentally.

Quantum Laplacians on generalized operators on Boson Fock Space

By adapting the white noise theory, the quantum analogues of the (classical) Gross Laplacian and L´evy Laplacian, so called the quantum Gross Laplacian and quantum L´evy Laplacian, respectively, are introduced as the Laplacians acting on the spaces of generalized operators. Then the integral representations of the quantum Laplacians in terms of quantum white noise derivatives are studied. Correspondences of the classical Laplacians and quantum Laplacians are studied. The solutions of heat equations associated with the quantum Laplacians are obtained from a normal-ordered white noise differential equation

Localization and composition of seed oils of Crithmum maritimum L. (Apiaceae)

The use of some halophytes for rehabilitation of salt affected area has been reported. Crithmum maritimum L. halophyte and apiaceae can tolerate high levels of salt. Their seed was endospermic and had a suitable size for oil extraction. The aim of this report is to localize the lipids in the seed and determine their oils composition. The results showed that the lipids were accumulated in endosperm tissue as oil globoids. The percentage of oils was 44.4% dry weight basis. The C. maritimum L. seed oil was rich with oleic acid (78.6%), low level of palmitic acid (4.8%) and non negligible amount of linoleic acid (15.4%). This composition is similar to olive oil and canola oil. These results confirmed the good quality of C. maritimum L. seed oils.Keys word: Halophytes; Crithmum maritimum L.; seed oils