Showing papers by "Instituto Politécnico Nacional published in 1968"
350 citations
TL;DR: In this paper, the authors collected all the possible experimental, theoretical and empirical evidence which may support the assignment of biphenyl-d 0 and biphexyl- d 10, compared with the experimental data collected from a new set of experiments as well as from what is available in the literature.
102 citations
TL;DR: In this paper, a modified Urey-Bradley Force Field and a simplified Valence Force Field have been refined through a least square technique on the fundamental frequencies of biphenyl-d0, d10 and d11.
78 citations
77 citations
TL;DR: The natural chromenes d,l -cannabichromene, franklinone, alloevodionol, evodionols methyl ether and the trimethy ether of flemingin C were synthesized by cyclodehydrogenation of the corresponding isoprenylphenols with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) or via the chromanes and dehydrogenation with DDQ.
68 citations
TL;DR: The existence of liver receptors informing the CNS about some variable connected with glucose metabolism was postulated and caused the disappearance of both the anorexia and the initial hypoglycemic phase.
67 citations
45 citations
TL;DR: The data tend to favor the existence of two separate electron-transport chains in these photosynthetic bacteria, which are blocked by substances which inhibit light-induced formation of ATP.
42 citations
39 citations
TL;DR: In this article, four new chalcones, Flemingins A, B and C (I, II, III) and homoflemingin (IV) have been isolated from the dichloroethylene extract of the drug Wars, obtained from the seeds of Flemingia rhodocarpa Baker.
33 citations
TL;DR: In this article, it was shown that, both for a four-and three-level laser, one can get as much power at the second harmonic wavelength as that which can be obtained at the laser wavelength.
Abstract: The optimum coupling for intracavity second harmonic generation has been theoretically studied. It has been shown that, both for a four- and three-level laser, one can get as much power at the second harmonic wavelength as that which can be obtained at the laser wavelength. It is also shown that, for both cases, an optimum value for lw/w_{0} exists, where l is the nonlinear crystal length, and w and w 0 are the spot sizes of the laser beam, respectively, in the laser material and in the nonlinear crystal.
TL;DR: The arterial blood glucose of cats anesthetized with pentobarbital sodium was found to be higher than the portal blood glucose, which agrees with the hypothesis that liver has glucoreceptors which intervene in the control of blood glucose and food-intake.
TL;DR: In this paper, the problem of redundant coordinates in the harmonic approximation is discussed and it is shown that, as long as only small vibrations are considered, the possible redundancy relations among the coordinates are always linear, and the constant K which is usually called intramolecular tension does not enter the equations of motion in the case of small vibrations.
TL;DR: In this article, the static and dynamic behavior of a single-mode 4-level solid-state laser has been studied both theoretically and experimentally, where the usual rate equations are modified in order to take into account the spatial variation of the inverted population due to the cavity field.
Abstract: The static and dynamic behavior of a single-mode 4-level solid-state laser has been studied both theoretically and experimentally. In the theoretical section, the usual rate equations are modified in order to take into account the spatial variation of the inverted population due to the cavity field. These theoretical results have been verified with the help of a CW Nd-YAG laser. The experimental results on the output power and on the transient behavior are in good agreement with the theory within the accuracy of the experimental results (∼ 15 percent).
TL;DR: The sequence of reactions described in this article confirms that perezinone (IIb) is a quinone methide related to the 2H-naphtho [1,8-bc] furan system.
TL;DR: The white cardboards used attracted in most cases a preponderant majority of flies in the open air but not so when placed versus yellow, whereas black is preferred to gray and to white and to all hues in the indoor tests.
Abstract: The results of experiments in the open air with houseflies settling on surfaces (cardboards) of light and dark shades and of various colours differed from those in laboratory tests. Whereas black is preferred to gray and to white and to all hues in the indoor tests, the white cardboards we used attracted in most cases a preponderant majority of flies in the open air but not so when placed versus yellow.
It is assumed that the attraction of the white cardboard is due to the reflection of the “near ultraviolet” of sunlight. Ultraviolet reflection of a more moderate degree by gray, blue and yellow cardboards could be only one of various factors which cooperate in rendering the respective colour attractive in the open air. Red was quite frequently preferred both in indoor and outdoor tests. Blue was the least frequented colour in indoor and brown in outdoor tests.
Zusammenfassung
GEGENSATZLICHE REIZBEANTWORTUNG VON MUSCA DOMESTICA IN DER WAHL VON HELLEN BZW. DUNKLEN TONUNGEN UND FARBEN
Die Fliegen wurden in Laboratoriumsversuchen in einen zylinderformigen, 80 cm weiten und 35 cm hohen, aus durchsichtiger Plastik hergestellten Behalter gesetzt. Der Boden und die Wand waren in sechs Sektoren eingeteilt, die abwechselnd mit Kartons zwei verschiedener Farben belegt wurden.
In Freilandversuchen (im Hof einer grossen Milchviehwirtschaft) wurden dieselben farbigen Kartons benutzt. Ein Paar verschiedenfarbiger Bogen, die mit einer Zuckerlosung bestrichen waren, wurde auf den Boden an Orten ausgelegt, wo sich Fliegen in grosser Menge angesammelt hatten.
In den Laboratoriumsversuchen liesen sich 75% der Fliegen auf Schwarz und 25% auf Weiss nieder. In der Wahl gegenuber den funf chromatischen Farben (Rot, Braun, Gelb, Grun und Blau) bevorzugten zwischen 63% und 68% der Fliegen die schwarze Unterlage. In Versuchen, in denen die funf genannten Farben unter sich verglichen wurden, wurde Rot stets bevorzugt und Blau niemals; Braun, Gelb und Grun wurden in verschiedenem Mase gewahlt je nach der Kombination, in der sie sich befanden.
Die Bevorzugung von Schwarz spricht fur die Auffassung, das in geschlossenen Raumen im allgemeinen die dunkleren Farben bevorzugt werden, doch zeigt die Wahl der farbigen Flachen, das, wenn man die Helligkeitswerte derselben in Betracht zieht, der Farbe an sich (dem Chroma) eine wichtige Rolle bei der Auswahl zukommt.
In den Freilandversuchen wurde Gelb von 77%–93% der Fliegen gegenuber Weis, Grau und Schwarz bevorzugt und von 81%–95% gegenuber den funf andern Farben. Ausserdem wurden folgende Bevorzugungen festgestellt: Rot gegenuber Blau, Grau, Schwarz und Braun; Weis gegenuber Grun, Grau, Schwarz und Braun, Blau gegenuber Weis, Grau, Schwarz und Braun; Grun gegenuber Blau, Schwarz und Braun; Grau gegenuber Schwarz und Braun; Schwarz gegenuber Braun. Farbpaare mit annahernd gleicher Verteilung der Fliegen waren Rot und Grun, Rot und Weis, und Grun und Grau, Die am wenigsten besuchte Farbe war Braun.
Ein Vergleich der Ergebnisse der Freilandversuche mit denen der Laboratoriumsexperimente zeigt keine Ubereinstimmung. Am auffalligsten ist die Verschiedenheit in der Wahl von Schwarz und Weis. Im Gegensatz zu den 75% der Fliegen auf Schwarz im Laboratorium, liessen sich im Freien 80% auf Weis nieder. Da keine Beeinflussung der Wahl durch Warme, Feuchtigkeit, Wind, Licht oder Schatten festgestellt werden konnte, vermuten wir, das im Freien die starke Reflektion des im Sonnenlicht vorhandenen Ultraviolett das weise Papier fur die Fliegen anziehend macht, fur das (von Professor Autrum in Munchen) eine Reflektion von 40%–80% der Wellenlangen zwischen 320 und 380 mμ gemessen wurde.
Wenn wir fur die verschiedene Wahl von Schwarz und Weis im Plastikkafig des Laboratoriums einerseits und im Freiland andererseits eine Erklarung geben konnen, so fehlt uns eine solche fur das verschiedene Verhalten der Fliegen gegenuber den Farben. Eine sehr masige Reflektion von Ultraviolett seitens der blauen, gelben und grauen Kartons kann bestenfalls nur einer von mehreren Faktoren sein, die zusammenwirken, um die betreffenden Farben im Freiland anziehend zu machen.
TL;DR: In this paper, absolute cross-sections and isomeric cross-section ratios were measured for the following reactions in which the 69Zn and69Zn averaged m ≥ 0.
Abstract: Absolute cross-sections and isomeric cross-section ratios were measured for the following reactions in which the69Zn and69Zn
m
,71Zn and71Zn
m
isomeric pairs are produced:69Ga(n, p),71Ga(n, p),72Ge(n, α) and74Ge(n, α). These experimental values are interpreted in terms of the spin dependence of the nuclear level density. Isomeric ratios were compared with calculations based on different nuclear models. Calculations with a shifted Fermi gas model require a moment of inertia smaller than the rigid body; in general a reasonable fit is obtained with independent-pairing and superconductor models.
TL;DR: Uptake of the monosaccharides d-glucose and d-mannose by Nocardia asteroides and N. brasiliensis is dependent on the presence of an adequate phosphate concentration in the environment.
Abstract: Uptake of the monosaccharides d-glucose and d-mannose by Nocardia asteroides and N. brasiliensis is dependent on the presence of an adequate phosphate concentration in the environment. When phosphate is replaced by solutions of sodium chloride or potassium chloride of identical ionic strength, there is no sugar uptake. In the presence of iso-osmolar concentrations of sodium arsenate, there is, however, sugar uptake activation. When nonmetabolizable 3-O-methyl d-glucose is used, most of the sugar taken up can be shown to be in the cell at a concentration never exceeding that of the external medium. Phosphate, or arsenate, seems to be essential for the actual migration of the sugar through the cell envelope. The transport of the nonmetabolizable 3-O-methyl glucose also requires phosphate, and the transport seems to be of a type that does not require energy.
TL;DR: In this article, a general method for setting up the dynamical matrix of a polymer chain containing a random distribution of folds is proposed, and Vibrational frequency spectra are calculated using the negative eigenvalues theorem for randomly folded simple zig-zag chains.
TL;DR: In this article, the free mean-square lengths of polypropylenes with various types and degrees of tacticity are discussed in detail, in particular, the chain distributions of d and I units, coresponding to the models taken into consideration, are closely represented by the MARKOFFian law.
Abstract: It is shown here how the theory proposed in the preceding paper may be applied to the conformational analysis of atactic polymers as well as of oligomers in solution. The calculation of the free mean-square lengths of polypropylenes with various types and degrees of tacticity is discussed in detail. In particular, the chain distributions of d and I units, coresponding to the models taken into consideration, are closely represented by the MARKOFFian law. The agreement between our results and those obtained by FLORY et al. through Monte-Carlo calculations is substantially good. The reasons why the configurational defects in nearly isotactic poly-α-olefins should be more closely represented by the (… dddlddd …) sequences than by the (… dddlll …) ones proposed by FLORY, avidenced.
Es wird gezeigt, wie die in der vorstehenden Arbeit vorgeschlagene Theorie fur die Konformationsanalyse von ataktischen Polymeren und von Oligomeren in Losung angewandt werden kann. Die Berechnung des mittleren Fadenendenabstand-Quadratesbeiverschiedener Art und verschiedenem Grad der Taktizitat wird im einzelnen diskutiert. Insbesondere wird die Verteilung der d- und I-Einheiten in der Kette, die den in Betracht gezogenen Modellen entspricht, durch das MARKOFF-Gesetz gut wiedergegeben. Die Ubereinstimmung zwischen unseren und den von FLORY und Mitarb. durch eine Monte-Carlo-Berechnung erhaltenen Ergebnissen ist im wesentlichen gut. Es wird gezeigt, weshalb die Fehler in der Konfiguration von quasi-isotaktischen Poly-α-olefinen besser durch (… dddlddd …)- als durch die von FLORY vorgeschlagenen (… dddlll …)-Sequenzen dargestellt werden konnen.
TL;DR: In this paper, the effect of scatterer thickness on Mott-scattering asymmetry is theoretically treated in the case of large thicknesses; the theory suggested in the present paper is an extension of Wegener' theory valid in the limit of small thicknesses.
Abstract: The effect of scatterer thickness on Mott-scattering asymmetry is theoretically treated in the case of large thicknesses; the theory suggested in the present paper is an extension of Wegener’ theory valid in the limit of small thicknesses. The results of numerical calculations based on the theory are compared with the results of the measurements by Brosiet al. On this basis, a heuristic extension of the theory is suggested.
TL;DR: It is shown that prodigiosin obtained in less drastic conditions is conjugated with a protein thereby giving a soluble form, the function of which is unknown.
Abstract: PRODIGIOSIN—the red pigment produced by S. marcescens—is a linear tripyrrole which has been studied by many workers. Previously the prodigiosin has been isolated by drastic methods—such as extraction by ethanol, chloroform, acetone and alkali. In this report, we show that prodigiosin obtained in less drastic conditions is conjugated with a protein thereby giving a soluble form, the function of which is unknown.
TL;DR: In this article, the annihilation of positrons in substances of unsymmetrical valence type such as fluorite was investigated and it was found that the lifetimes are nearly equal to those observed in alkali halides having the same anion.
TL;DR: In this article, the elastic incoherent multiple scattering angular distributions of fast electrons have been calculated, in the case of low mean numbers of scatterings and in the small-angle approximation.
Abstract: The elastic incoherent multiple scattering angular distributions of fast electrons have been calculated, in the case of low mean numbers of scatterings and in the small-angle approximation The target atom is described with the Thomas-Fermi model and the single scattering cross-section is calculated as suggested recently by Zeitler and Olsen Results are given in the form of a universal function of the mean number of scatterings and of a suitable reduced angular variable
TL;DR: This communication describes an analog circuit for the on-line estimation of running averages, variances, covariances, and correlation coefficient of neural population responses that is inexpensive when compared with an equivalent digital system.
Abstract: This communication describes an analog circuit for the on-line estimation of running averages, variances, covariances, and correlation coefficient of neural population responses. It requires operational amplifiers, multipliers, pulse generators, and pen recorders, and is inexpensive when compared with an equivalent digital system.