Showing papers by "Instituto Politécnico Nacional published in 1980"
01 Jan 1980
TL;DR: In this paper, a geometrical approach to the nonlinear solvable equations, based on the study of the "groups of motion" of special infinite-dimensional manifolds called "symplectic Kahler manifolds", is suggested.
Abstract: A geometrical approach to the nonlinear solvable equations, based on the study of the “groups of motion” of special infinite-dimensional manifolds called “symplectic Kahler manifolds”, is suggested. This approach is constructive, tensorial and simple in its ideas. It allows to recover the equations obtained through the socalled AKNS approach, together with some other examples. It leads to conjecture a possible “integrability condition” for infinite-dimensional systems, and to hope to be able to give a geometrical explanation of the so-called “spectral transform method”.
161 citations
127 citations
TL;DR: The product synthesized by the chitosome subunits was characterized by X-ray diffractometry ad alpha-chitin and was by the criterion indistinfuishable from chitin made by preparations of undissociated chitOSomes and often exhibited a needle-like appearance.
62 citations
TL;DR: The first two examples of naturally occurring C -glucosyl-α-hydroxydihydrochalcones have been isolated from Eysenhardtia polystachya, a Mexica
40 citations
TL;DR: In this paper, a tracer method was used to evaluate the wetted areas of a catalyst and the static hold-up values as determined by fitting the liquid RTDF with the PE model.
39 citations
TL;DR: This paper examines in particular how the determination of the appropriate sequence of diagnostic tests that have to be performed on the patient can be optimised by the use of a decision table, in which the medical knowledge is shown.
Abstract: In this paper we discuss a simple model for an interactive consultation system for medical applications. That system was developed to provide consultative advice on diagnosis of arthritis, but it could be easily applied to a different class of diseases. We examine in particular how the determination of the appropriate sequence of diagnostic tests that have to be performed on the patient can be optimised by the use of a decision table, in which the medical knowledge is shown. We begin with a review of features which were seen to be essential to a consultation system for medical applications and we suggest how these requirements imply program design criteria. This is followed by a formal explanation of the proposed model and its fundamental assumptions. The last part of the paper is then devoted to a report of our experience with the experimental computer system.
30 citations
TL;DR: In this paper, a real-time Kalman predictor is derived from the model, namely a recursive relationship which, at the beginning of each time step, supplies the "best" forecast of future flow-rate on the basis of current rainfall and flowrate measurements.
28 citations
TL;DR: The first heptanuclear mixed carbonyl cluster, the anion [NiRh6(CO)16]2− has been prepared by redox condensation of [Rh6CO)15] 2− with [Ni6CO12] 2 − or Ni(CO4)4.
26 citations
TL;DR: In this paper, the points in the vibrational infra-red and/or Raman spectrum at which a tight, (200) type, fold should show absorptions and scattering are predicted.
25 citations
TL;DR: In this paper, the authors investigated the wear mechanisms of polymeric composites and found that they are similar to delamination wear but homogeneous polymers wear by continuous deformation favored by thermal softening or melting.
24 citations
TL;DR: Three new sesquiterpenes, furanether A, furosardonin A and sardonialactone A (7-hydroxyblennin A), together with lactaral, vellerolactone, and cerevisterol, were isolated from Russula sardonia.
01 Jan 1980
TL;DR: The modeling of a reaction unit in which the absorption of a gas is associated with a liquid-phase catalytic reaction is a difficult problem in which both chemical and fluodynamic factors are involved as mentioned in this paper.
Abstract: The modeling of a reaction unit in which the absorption of a gas is associated with a liquid-phase catalytic reaction is a difficult problem in which both chemical and fluodynamic factors are involved. Many excellent reviews in which the chemical details of the liquid-phase catalytic processes and the engineering implications of the gas-liquid reactions are separately discussed are available.
TL;DR: In this article, a general optimal method for the measurement of viscoelastic constants of nematic liquid crystals by light scattering is given, and the experimental results are given which show the validity of the theory.
Abstract: A general optimal method for the measurement of viscoelastic constants of nematic liquid crystals by light scattering is given. It is shown that, under suitable scattering conditions, several causes of error, like the multiple-scattering effect, the light scattering by crystal defects and the necessity of changing the liquid-crystal alignment in some type of measurements can be removed. The theory allows us to relate the experimental results obtained in such optimal conditions with all the viscoelastic constants characterizing the nematic liquid crystal. Some experimental results are given which show the validity of the theory. They also extend the range of spectral power density measurements of the scattered light down to very low frequency (0.1 Hz) by the use of an oblique-incidence scattering geometry.
01 Jul 1980
TL;DR: The pattern trajectory approach appears to offer advantages in the analysis of complex nonstationary data sets where conventional time series techniques are insufficient and time-dependent clustering provides a means to identify a composite source model.
Abstract: Multivariate data sets with dependency between observations are described using a feature space representation. The resulting ordered set of points in feature space is termed the pattern trajectory. A set of descriptors of the pattern trajectory has been developed. Time-dependent clusters and transition segments form the basic structural description from which both lower level properties, e.g., cluster position, cluster dispersion, transition rate, and higher level properties, e.g., rebound, periodicity, finite state model, may be derived. Two algorithms have been developed for time-dependent cluster analysis. The time-weighted minimum spanning tree (TWMST) algorithm utilizes a composite space-time distance measure and creates clusters by cutting the longest tree branches. The time-dependent Isodata (TD-ISODATA) algorithm utilizes a global clustering to initiate the segmentation into timedependent cluster cores and transition segments. Examples of the applica tion of these algorithms to nonstationary neuronal spike train data and to simulated animal migration data are described. The pattern trajectory approach appears to offer advantages in the analysis of complex nonstationary data sets where conventional time series techniques are insufficient. Time-dependent clustering provides a means to identify a composite source model.
TL;DR: In this paper, the average contour length of the loops within the bundles of intramolecular clusters (bundles) is calculated and the average number of stems per bundle is of order 10 at moderate undercoolings.
Abstract: Polymer crystallization is assumed to be controlled by an equilibrium distribution of intramolecular clusters (“bundles”), insofar as it consists of their aggregation to the side surface of the crystallites. The average contour length of the loops within the bundles dictates the lamellar thickness. Each bundle contains at least three packed stems; unlike previous assumptions their length is considered to be variable and it is shown that their statistical weight *** like ((exp(-E/kBT)-exp(-E/kBT°)), where E is the (negative) packing energy and T° is the melting or dissolution temperature. Adopting two different models having opposite limitations in terms of the configurational enumeration of the bundles, the calculated thickness of polyethylene crystals at different temperatures is in reasonable agreement with observation. The average number of stems per bundle is of order 10 at moderate undercoolings, in rough agreement with neutron diffraction experiments on solution-grown crystals. The same mod...
TL;DR: A new metabolite, 3,6-dimethyl-4,10-dihydroxy-2-oxaspiro[4.5]dec-7-en-1,9-dione (1a ), was isolated from a strain of Mycosphaerella rosigena grown on potato-agar medium as discussed by the authors.
Journal Article•
TL;DR: In this article, the reaction of [IrCl(C8H14)2]2 with AgOCOCOCF3 in CH2Cl2 affords a mixture of iridium trifluoroacetates, when treated with CF3COOH and arenes are converted into cations of general formula [Ir(arene)L2]+ (L = cyclooctene, L 2 = 1,5-C 8H12).
TL;DR: In this paper, a new metal telluromolybdate MgTeMoO 6 was obtained in the case of Mg; its structure belongs to the orthorhombic system with unit-cell dimensions a = 5.262A, b =5.028 A, c = 8.880 A.
TL;DR: In this paper, the vibrational intensities of solid n-decane were predicted using the first members of the series in the gas phase and higher terms in the solid phase.
TL;DR: The positive and negative ion mass spectra of three secondary metabolites of Aspergillus Wentii Wehmer, namely 15-acetoxy hexadecyl, 15-oxohexadecyl- and 15-hydroxyhexadeylcitraconic anhydrides are reported and discussed.
Abstract: The positive and negative ion mass spectra of three secondary metabolites of Aspergillus Wentii Wehmer, namely 15-acetoxyhexadecyl-, 15-oxohexadecyl- and 15-hydroxyhexadecylcitraconic anhydrides are reported and discussed. The positive ion mass spectra, which have been studied in detail by exact mass measurements and metastable ion detection using a defocusing method, show very weak molecular ions and complex fragmentation pathways, strongly influenced by the group on C-15. However, the negative ion mass spectra show very abundant molecular ions and little fragmentation, with the negative charge mainly retained by the anhydride moiety. The behaviour of both positive and negative ions is in agreement with the charge localization concept, on the grounds of ionization energy and electron affinity considerations. Positive and negative ion mass spectra are largely complementary, thus increasing their analytical value.
TL;DR: In this article, the synthesis of N-benzoyl-L -ristosamine from natural tartaric acid through the intermediacy of the δ- xylo and γ- ribo lactones was reported.
TL;DR: Titanium(III) chloride promotes reductive decyanation of 4-CN and 2-CN-pyridine as mentioned in this paper, and the role of complex forming agents is discussed.
Journal Article•
TL;DR: In this article, a new sesquiterpene blennin D (2-hydroxyblennin A) was isolated and its structure elucidated together with the stereochemistry of the already known BLENIN A.