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Showing papers by "University of Alcalá published in 1984"


Journal ArticleDOI
TL;DR: In this paper, the authors measured the stress-optical behavior of an elastomeric network of poly(diethylene glycol terephthalate) (PDET) over a wide range of elongation ratios α (up to 5) and temperatures (293-353K).
Abstract: The stress-optical behaviour of an elastomeric network of poly(diethylene glycol terephthalate) (PDET) was measured over a wide range of elongation ratios α (up to 5) and temperatures (293-353K). No evidence of strain -induced crystallization was found;on the contrary, the plot of birefringence versus stress exhibits negative deviations from linearity at values of α over 2.6. Values of the optical configuration parameter Δα of the order of 20 × 10−24cm3 with relative temperature coefficients of -1.1 × 10−3K−1 were found for the unswollen sample. The introduction of tricresylphosphate as diluent roughly doubles the birefringence of the network, presumably because of an increase in intermolecular interactions. Theoretical calculations carried out with the RIS model give values of Δα about one order of magnitude smaller than the experimental ones and temperature coefficients of about 4.1 × 10−3K−1. No reasonable modification of conformational energies or contributions to the anisotropic part of the polarizability tensor would achieve agreement between theory and experiments. The discrepancy between theoretical and experimental results may be qualitatively explained by intermolecular interactions.

28 citations


Journal ArticleDOI
TL;DR: In the last decade, a number of attempts have been made to constrain the precision of the cifras of the information provided by estadisticas comerciales.
Abstract: Las insuficiencias de las estadisticas espanolas de comercio exterior son, hasta fechas relativamente cercanas, evidentes. No existen balanzas comer­ ciales con periodicidad anual hasta 1850 y, para la primera mitad del siglo xix, tan solo se dispone de informacion dispar en once anos '. En el siglo xviii, unicamente la balanza comercial de 1792 y la estimacion incompleta para 1795, publicada por Matilla Tascon, se encuentran disponibles . Por otra parte, la precision de las cifras ofrecidas en las estadisticas existentes ha sido puesta en duda'. En los ultimos anos han sido realizados algunos intentos para establecer la fiabilidad de las estadisticas comerciales. Los estudios de Tortella, Martin Acena, Sanz y Zapata, por un lado, y de Prados de la Escosura. por otro, han permitido cuantificar los sesgos o errores de las senes oficiales de exportaciones e importaciones durante la segunda mitad del si­ glo XIX y primeros anos del siglo xx, y constituyen un timido, pero necesa­ rio, avance hacia la reconstruccio n del comercio exterior de Espana en estos * Estoy muy agradecido a Max HartweU, Patrick O'Brien Pedro Tedde de>rca y Gabriel Tortella'Casares por su estimulo y su critica mientras he reahzado es a .nv«t.ga. cion lavier Cuenca v PetVr Mathias hicieron comentarios muy valiosos para la redaccion cien Javier i^uenca y retcr ™""'" Isabela Ortiz de Soorzano colaboro generosa

24 citations


Journal ArticleDOI
TL;DR: In this article, a new series of cationic areneiridium(I) complexes of formula [Ir(barrelene)(arene)] + or [Ir (barrelenes)(PhNRPh)] + (R= Ph or H) have been synthesized from neutral iridium complexes of the type [IrY(Barrelene)] x (barrellene = Me 3 TFB, Y = Cl or OMe (x = 2), Y = acac (x= 1); barrelene = TFB), Y= OMe(x

23 citations


Journal ArticleDOI
TL;DR: The identification of one chromosome involved in one translocation in ‘Chinese Spring’ x ‘Pané 247’ has been made through heterochromatin bands observed in the chromosomes involved in multivalents.
Abstract: The C-banding pattern of nine meiotic chromosomes of common wheat (Triticum aestivum L.) as described. In F1s of crosses between monosomics of ‘Chinese Spring’ and two Spanish wheat cultivars, univalent chromosomes were used to aid the recognition and analysis of the C-banding pattern for the individual chromosomes. The identification of one chromosome involved in one translocation in ‘Chinese Spring’ x ‘Pane 247’ has been made through heterochromatin bands observed in the chromosomes involved in multivalents.

22 citations


Journal ArticleDOI
TL;DR: In this article, morphological changes affecting the lympho-hemopoietic organs of the anadromous sea lamprey Petromyzon marinus throughout its life span were analyzed.
Abstract: We have analyzed morphological changes affecting the lympho-hemopoietic organs of the anadromous sea lamprey, Petromyzon marinus throughout its life span. For this analysis, ammocoetes (2–4 years), premetamorphosing lampreys (nearly 5 years), metamorphosing lampreys, macrophtalmia stages (young adults) and parasitic adults (nearly 7 years) were used. The principal lympho-hemopoietic organs in the ammocoete are typhlosole, larval opisthonephros and nephros-associated adipose tissue. After metamorphosis, these organs degenerate, and their lympho-hemopoietic tissue is replaced by dense connective tissue. The supraneural body and to a lesser degree, the definitive opisthonephros, are the main blood-forming organs in adult lampreys. During larval life, lympho-hemopoietic cells appear in the branchial area, associated with pharyngeal epithelium. These loci are not morphologically homologous to the thymus gland of jawed vertebrates. These results are discussed, with special emphasis on the importance of cell microenvironments in eluciding changes in different blood-forming loci throughout the life cycle and their significance for the lamprey's immune capacity.

18 citations


Journal ArticleDOI
TL;DR: Differences in the chiasmata frequencies per chromosome arm cannot be explained on the basis of relative arm lengths only and possible effects of arm-to-arm heterochromatic differences on meiotic pairing are discussed.
Abstract: The meiotic identification of nine pairs of chromosomes at metaphase I of meiosis of Triticum aestivum (B genome, 4A and 7A) has been achieved using a Giemsa C-banding technique. As a result, the analysis of the pairing of each chromosome arm in disomic and monosomic intervarietal hybrids between ‘Chinese Spring’ and the Spanish cultivar ‘Pane 247’ could be carried out. Differences in the chiasmata frequencies per chromosome arm cannot be explained on the basis of relative arm lengths only. Possible effects of arm-to-arm heterochromatic differences on meiotic pairing are discussed.

15 citations


Journal ArticleDOI
TL;DR: There is a synthesis of 2,3‐bisphosphoglycerate during the erythropoietic process which parallels the synthesis of haemoglobin in rat bone marrow cells fractionated by density gradient in Percoll.
Abstract: Rat bone marrow cells have been fractionated by density gradient in Percoll. Differential counting of erythroid cells, haemoglobin concentration and bisphosphoglycerate mutase and phosphoglycerate kinase activities have been determined in cellular fractions. As shown by means of a statistical approach, an increase in bisphosphoglycerate mutase activity and a slight decrease in phosphoglycerate kinase activity is found in erythroid cells as their haemoglobin content increases. Our results suggest that there is a synthesis of 2,3-bisphosphoglycerate during the erythropoietic process which parallels the synthesis of haemoglobin.

13 citations


Journal ArticleDOI
TL;DR: In this article, the authors greatly appreciate the financial support received from the Comision Asesora de Investigacion Cientifica y Tecnica (CITECH) in Spain.

12 citations


Journal ArticleDOI
TL;DR: It is concluded that dopamine produced both relaxation of lung parenchymal strip due to direct activation of β‐adrenoceptors and contraction mediated through direct and indirect (catecholamine release) actions at α‐adreceptors.
Abstract: Responses to dopamine were examined in the guinea-pig isolated lung parenchymal strip. Complete cumulative concentration-response curves to dopamine exhibited a biphasic pattern with a small initial contraction at concentrations below 10(-5) M followed by a dose-dependent relaxation at higher concentrations. Phentolamine (10(-5) M) completely abolished the contractile component and enhanced sensitivity and maximal relaxation to dopamine. In the presence of phentolamine, propranolol antagonized the dopamine-induced relaxation (pA2 = 8.54 +/- 0.07). In the presence of propranolol (10(-6) M), dopamine produced a dose-related contraction displaced to the right by phentolamine. Incubation with haloperidol (10(-5) M) did not modify the characteristics of the concentration-response curve to dopamine. Pretreatment with reserpine abolished the contraction to dopamine without affecting its relaxant response. Cocaine significantly increased the pD2 value of dopamine in the presence of propranolol. It is concluded that dopamine produced both relaxation of lung parenchymal strip due to direct activation of beta-adrenoceptors and contraction mediated through direct and indirect (catecholamine release) actions at alpha-adrenoceptors. There is no evidence in favour of the existence of specific dopamine-receptors in this preparation.

11 citations


Journal ArticleDOI
TL;DR: Measurement of specific activities of BPGM and phytase in the two subpopulations present in young chickens showed that these phosphates could be specifically and predominantly formed in these two red cell populations.
Abstract: Two generations of red cells (embryonic and definitive), different types of haemoglobins, and special organic phosphates involved in the control of haemoglobin oxygenation (2:3-bisphosphoglycerate, BPG, and inositol-5-phosphate, IP5), have been found progressively during development of the chick. Levels of both organic phosphates, as well as activities of the enzymes involved in BPG synthesis (2:3-bisphosphoglycerate synthase, BPGM) and IP5 formation (phytase), were studied in the erythrocyte populations from embryo, young and adult chickens. Measurement of specific activities of BPGM and phytase in the two subpopulations present in young chickens showed that these phosphates could be specifically and predominantly formed in these two red cell populations.

11 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that (η 5 -C 5 H 5 ) 2 NbX(PMe 3 ) (X = Cl, Br) gave metallic silver and cationic halide complexes.

Journal ArticleDOI
TL;DR: In this paper, atactic poly(vinyl acetate) was crosslinked by means of benzoyl peroxide and the resulting elastomeric networks were studied in elongation, both unswollen and swollen with triethylbenzene, over the range 0-90°C.
Abstract: Atactic poly(vinyl acetate) prepared in a free-radical polymerization was crosslinked by means of benzoyl peroxide. The resulting elastomeric networks were studied in elongation, both unswollen and swollen with triethylbenzene, over the range 0–90°C. The most important experimental results obtained were values of the network birefringence, which is negative, as was recently also found to be the case for networks of atactic poly(methyl acrylate).Calculations carried out to interpret the birefringence were based on Monte Carlo simulations of the atactic structure, and on the rotational isomeric-state theory of chain configurations. The agreement between theory and experiment was very good, in fact much better than has usually been observed for other polymers studied to date.

Journal ArticleDOI
TL;DR: The kinetics of the hydrolysis of the tris(4,7-diphenyl-1,10-phenanthrolinedisulphonate)iron(II) ion is studied and from the analysis of the kinetic results the rate constants have been determined.
Abstract: The kinetics of the hydrolysis of the tris(4,7-diphenyl-1,10-phenanthrolinedisulphonate)iron(II) ion has been studied. The results are consistent with a consecutive reaction mechanism with a reversible step, and from the analysis of the kinetic results the rate constants have been determined.

Journal ArticleDOI
TL;DR: In addition to the adrenergic component (catecholamine release and direct alpha-adrenoceptor activation) there is an important contribution of other receptor systems such as histamine (guinea-pig) and 5-hydroxytryptamine (rat) to the contractile response to tyramine in lung tissue.

Journal ArticleDOI
TL;DR: In this article, a study has been made on Ziegler-Natta polymerization, under various conditions, using styrene and 2-vinylpyridine as monomers, AlEt 3 -VCl 3 as catalyst system and pyridine, α- and γ-picolines as co-catalyst.

Journal ArticleDOI
TL;DR: In this article, the electrical, birefringence of Dimethyl Terephthalate (DMT) and Poly (Diethylene Glycol Terephate) (PDET) in p-dioxane solutions were measured at 20°C.
Abstract: Electrical, birefringence of Dimethyl Terephthalate (DMT) and Poly (Diethylene Glycol Terephthalate) (PDET) in p-dioxane solutions were measured at 20°C. The results were used to compute molar Kerr constants of both compounds at infinite dilution. The experimental results were 〈mK〉= = 780 and 〈mK〉= -732, both in units of 10−27m5V−2 mol−1, for DMT and PDET respectively. Theoretical analysis of 〈mK〉 of DMT indicates that the inductive effects that prevent the additivity of tensors of benzene and ester groups account for about 12% of the value of 〈mK〉. The tensor obtained for DMT was used, together with literature values of all the non optical parameters, to calculate 〈mK〉/x of PDET according to the RIS model. The concordance between theoretical and experimental results of this magnitude is excellent.

Journal ArticleDOI
TL;DR: The in vivo [1-14C]-acetate incorporation into free and esterified cholesterol in castrated animals decreases as compared with that in normal rats and it does not depend on the age of the animal.
Abstract: 1. Thein vivo [1-14C]acetate incorporation into free and esterified cholesterol in rat ventral prostate depends on the animal developmental process, and it is the highest in the puberty stage. 2. The relationship between free cholesterol and total lipids is 12–14% and that between esterified cholesterol and total lipids is 4–5%, both of the two being maintained during the animal development. 3. The [1-14C]-acetate incorporation into free and esterified cholesterol in castrated animals decreases as compared with that in normal rats and it does not depend on the age of the animal.

Journal ArticleDOI
TL;DR: In this article, the authors measured the stress-optical behavior of an unswollen elastomeric network of poly(3-methyltetrahydrofuran) and found that Δa ranged from 2.4 to 2.8 in units of 10−24 cm3, in the temperature range studied, with a temperature coefficient 3.1 × 10−3 K−1.
Abstract: The stress-optical behavior of an unswollen elastomeric network of poly(3-methyltetrahydrofuran) was measured for elongation ratios a in the range 1.182–1.549, at several temperatures between 20 and 60°C. No evidence of strain-induced crystallization was found; moreover, the dependence of birefringence Δn on true stress f/A was linear in the interval of α investigated. Values of Δa ranged from 2.4 to 2.8 in units of 10−24 cm3, in the temperature range studied, with a temperature coefficient 3.1 × 10−3 K−1. Theoretical calculations carried out with the rotational-isomeric-state model gave values of Δa noticeably smaller than the experimental results; however, a small increase in the backbone valence angles θ improved the theoretical result of Δa without worsening that of the dipole ratio. Analysis of the Δa results seems to corroborate the conclusion obtained through the study of dipole moments concerning the preference for nucleophilic attack on the less hindered α carbon in the monomer. Theoretical and experimental values of the temperature coefficient of Δa were in clear disagreement; a qualitative explanation for this discrepancy is discussed.

Journal ArticleDOI
TL;DR: Aguilar et al. as discussed by the authors present a pequeno estudio en el complicado, and siempre actual, tema de la historia economica andaluza, de las actitudes empresariales ante las posibilidades economicas of la region.
Abstract: Este trabajo pretende ser una aportacion al conocimiento de las vicisitudes de la construccion de una de las lineas ferroviarias andaluzas de trayectoria mas compleja en el siglo xix, completando de esta forma otros trabajos que tratan de la misma, especialmente los de P. Tedde. Se centra, sobre todo, en los aspectos financieros de la construccion y en la pregunta sobre las motivaciones que tuvieron los grupos empresariales andaluces involucrados para interesarse en el negocio. Se integra, pues, este pequeno estudio en el complicado, y siempre actual, tema de la historia economica andaluza, de las actitudes empresariales ante las posibilidades economicas de la region. Profundizar en todo ello ha requerido utilizar una fuente no empleada hasta ahora en los trabajos sobre esta linea, como son los expedientes y documentos sueltos manuscritos de concesion, subvencion y construccion, conservados en el Archivo del Ministerio de Obras Publicas o depositados por este en el Archivo General de la Administracion.

Journal ArticleDOI
TL;DR: In Andalucia, el estudio del sector industrial en el pasado comenzo con un cierto retraso con respecto a otras zonas de Espana, tal vez porque resultaba obvio no preocuparse del tema in una region con tan poco peso especifico del sector secundario en el presente as mentioned in this paper.
Abstract: En Andalucia, el estudio del sector industrial en el pasado comenzo con un cierto retraso con respecto a otras zonas de Espana, tal vez porque resultaba obvio no preocuparse del tema en una region con tan poco peso especifico del sector secundario en el presente. El interes historico, cuando se hacia economico y social, se encerraba hasta los anos sesenta en los temas de la estructura agraria y los movimientos sociales a ella ligados. Sin embargo, asi como Chaunu en 1960 desperto un nuevo interes por el estudio del comercio maritimo en Andalucia, J. Nadal, con sus estudios sobre la industria, dio el segundo paso en la renovacion del panorama investigador en la historia social y economica de la region.

Journal ArticleDOI
TL;DR: In this paper, the authors present an enfoque teorico que pone de relieve that the "eficiencia" and "control" are complementarias.
Abstract: Segun la teoria economica dominante, la teoria neoclasica, la unica razon que explica la introduccion de nuevas tecnicas en el proceso productivo es que estas son mas eficientes o productivas que las conocidas hasta la fecha. Las razones por las que aparecen esas nuevas tecnicas pertenecen a dominios extraeconomicos, es decir, las variables economicas no se consideran un factor relevante en dicha aparicion. Por otra parte, los escritos recientes de algunos autores pertenecientes a la linea de pensamiento marxista, de entre los que destaca Stephen Marglin (1974), parecen haber sostenido que la introduccion de cambios tecnicos, y mas concretamente de la division del trabajo, responde a un deseo por parte de los capitalistas de controlar mejor a sus obreros mas que a razones de eficiencia productiva. En este articulo partimos de un enfoque teorico que pone de relieve que la «eficiencia» y el «control» no son variables contradictorias, sino complementarias. Es decir, puede haber cambios tecnicos que respondan a razones de eficiencia, que llamaremos «fisicos», y cambios tecnicos que correspondan a razones de control, que llamaremos «extractivos». Nuestra critica a la teoria neoclasica no es, por tanto, que sea erronea, sino que solo es parcialmente correcta. El objetivo de este trabajo es poner de relieve, mediante el estudio concreto de una serie de cambios tecnicos ocurridos en una misma planta en un periodo relativamente corto de tiempo, que los cambios extractivos tienen relevancia empirica. El caso analizado es el de la fabrica McCormick, de Chicago, en las dos ultimas decadas del siglo XIX. Por supuesto, seria arriesgado generalizar estos resultados tan concretos. Por ello, esta investigacion debe considerarse unicamente como un ejemplo en el que el marco teorico propuesto resulta validado y como una invitacion a posteriores investigaciones, tal vez menos distantes en el tiempo y, sobre todo, en el espacio, que confirmen o rechacen sus hallazgos.

Journal ArticleDOI
TL;DR: The expansion of the field of Historia Economica in Español durante two ultimas decadas is de sobra conocido el singular auge de los estudios de Historia Económica en Espana.
Abstract: Es de sobra conocido el singular auge de los estudios de Historia Economica en Espana durante las dos ultimas decadas. Los antecedentes de esta expansion se encuentran en los trabajos de autores tales como Hamilton, Vicens Vives y Vilar, por mencionar solo aquellos mas influyentes, aunque sea preciso recordar otros que por su modernidad metodologica debieron recibir mas atencion de la que fueron objeto, como es el caso de los estudios de Sarda. La obra de estos historiadores y economistas fue un acontecimiento hasta cierto punto aislado en el panorama de la disciplina en Espana.

Journal ArticleDOI
TL;DR: Oxygen-dependent SCEs could arise as a consequence of the modification of chromosome replication either directly or due to the formation of oxygen induced alterations of chromosomal DNA during the S phase.
Abstract: SUMMARYThe formation of sister-chromatid exchanges (SCEs) under high oxygen concentrations in the growth medium bubbling with pure oxygen has been studied in the chromosomes of Allium cepa L. meristem cells. The experimental approach included the analysis of SCE yields both in second and third division chromosomes from cells grown in BrdUrd-containing media for different cycles. Our results lead us to conclude that: (1) the ability of oxygen to provoke SCEs appears to be additive for different cycles; (2) under our experimental conditions there is a small synergism between BrdUrd incorporation and oxygen exposure in terms of SCE induction; (3) the action of oxygen in provoking SCEs seems to be restricted to the S period. Thus, oxygen-dependent SCEs could arise as a consequence of the modification of chromosome replication either directly or due to the formation of oxygen induced alterations of chromosomal DNA during the S phase.

Journal ArticleDOI
TL;DR: Results for in vitro experiments, show that increasing concentrations of testosterone and dihydro-testosterone correspond to an increase in the incorporation of labelled acetate into phospholipids and a decrease in the incorporate into triacylglycerols.
Abstract: 1. 1. To obtain information about androgenic hormone actions on the synthesis of lipids from [1- 14 C]acetate in rat ventral prostate, in vitro and in vivo experiments have been carried out. The time course of incorporation of labelled acetate was studied. Also different solubilization media of androgenic hormones was investigated. We have selected Tween-80. 2. 2. Results for in vitro experiments, show that increasing concentrations of testosterone and dihydrotestosterone correspond to an increase in the incorporation of labelled acetate into phospholipids and a decrease in the incorporation into triacylglycerols. 3. 3. In vivo experiments of incorporation of [1- 14 C]acetate have also been carried out and show a similar pattern to the situation found in our in vitro experiments.