The successive reduction of data subsets: A new method for estimating parameters of thermodynamic models

The successive reduction method allows the fitting of models to large sets of data using microcomputers of moderate memory size. It relies on the assumption that the information brought by a set of data is summarized by the maximum likelihood parameters and their inverse variance—covariance matrix. The parameters are estimated from the last data subset, taking account of the information brought by the former ones. The successive reduction method is compared with the classical 'global' method. They give exactly the same results for linear models. With a non-linear model, equivalent results are obtained when this model is consistent with the data. Applications are presented, relating to parameter estimation for generalized equations of state, to vapour—liquid equilibrium and excess enthalpy data reduction using the NRTL and UNIQUAC models.     

Hybrid Systems and Hybrid Computation 1st Part: Hybrid Systems

In the first part of this paper we will give a short historical survey of the field of hybrid systems, a precise definition of a hybrid system and some comments on the definition. In a second paper (Hybrid systems and hybrid computation – 2nd part: Hybrid computation) we will concentrate on a particular aspect of the theory closely related to scientific computation, that we have called hybrid computation.     

Cytotoxic triterpenoid saponins from the roots of Cephalaria gigantea

Three new oleanane-type saponins, giganteosides L (1), M (2) and N (3) along with eight known ones were isolated from the roots of Cephalaria gigantea. Their structures were established as 3-O-[beta-D-galactopyranosyl-(1-->2)-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl]-oleanolic acid, 3-O-[beta-D-galactopyranosyl-(1-->2)-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl]-hederagenin, 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl]-hederagenin, respectively, by means of spectroscopic methods (1D and 2D NMR, HR-ESI-MS). Cytotoxic activity of monodesmosides was investigated in vitro using three cancer cell lines, namely, human non pigmented melanoma MEL-5 and human leukemia HL-60. Giganteosides D (4) and E (5) showed antiproliferative effect on human cell lines with IC(50) values in the range 3.15-7.5 microM.     

Epoxyesters p‐menthaniques et pinaniques en milieu basique – Parfum de noix de coco

Base‐Induced Reactions of p ‐ Menthane‐ and Pinane‐Derived Epoxyesters – Coconut Fragrance The base‐induced isomerization of p‐menthane‐ and pinane‐derived epoxy esters was studied. The reaction is dependent on the structure of the terpene compound, the nature of the base, and experimental conditions. Among all the new synthesized compounds, one, 6a , emits a very strong fragrance of coconut. In the structure of this tricyclic lactone, the presence of a methyl substituent is essential.     

Even Cycles in Graphs with Many Odd Cycles

It will be shown that if G is a graph of order n which contains a triangle, a cycle of length n or n−1 and at least cn odd cycles of different lengths for some positive constant c, then there exists some positive constant k=k(c) such that G contains at least kn ^1/6 even cycles of different lengths. Other results on the number of even cycle lengths which appear in graphs with many different odd length cycles will be given. Received: October 15, 1997     

Experimental evaluation of the measurement of isotope ratios by time of flight mass spectrometry with laser ablation

Time of flight mass spectrometry (TOF-MS) in combination with laser ablation (LA) applied for low isotope composition measurements is limited by energy and spatial dispersion of ions, spatial charge density, and some other factors. In order to reduce these factors that make the extraction of the plasma ions difficult, we used a second laser to create ions by non-isotope-selective photoionization of neutral particles. The photoionization was carried out in uranium vapor beam by the third harmonic of a pulsed Nd:YAG laser. This work presents the results of tentative experiments to estimate the characteristics of the LA-TOF-MS method with non-selective photoionization.