Showing papers by "State University of Campinas published in 1977"
TL;DR: In this paper, the temperature dependence of the phonon and electron contribution to the dielectric constant, e.g., in the c-and α-axes, was determined and compared to the capacitance measurements.
Abstract: Measurements of all A1 and E transverse and longitudinal phonons in BaTiO3 are reported in the temperature range 10 to 132 °C where the crystal is in the tetragonal phase. A least squares fitting of the spectral shapes is done and the resulting temperature dependence of the frequencies, linewidths and coupling parameters is presented. The temperature dependence of the phonon and electron contribution to the dielectric constant, e, in the c- and α-axes is determined and compared to the capacitance measurements. It is found that the dielectric constant discrepancy is highly anisotropic.
291 citations
255 citations
18 Jul 1977
TL;DR: In this paper, it was shown that given a problem, is it more difficult to tell how many solutions the problem has than just deciding whether it has a solution? And in specific cases, the question can be put into a mathematically meaningful form, namely when we can translate "number of solutions" as 'number of distinct accepting computations of a non-deterministic Turing machine' (perhaps with appropriate weights).
Abstract: We examine the following question: ‘Given a problem, is it more difficult to tell how many solutions the problem has than just deciding whether it has a solution?’. We show, that in specific cases, the question can be put into a mathematically meaningful form, namely when we can translate ‘number of solutions’ as ‘number of distinct accepting computations of a nondeterministic Turing machine’ (perhaps with appropriate weights). In this context, as we show, these questions are equivalent to problems about probabilistic machines (in the sense of Gill (9)).
93 citations
TL;DR: It is suggested that glutamate synthase plays a key role in the N nutrition of the maize endosperm providing a means whereby N transported in the form of glutamine is made available for the synthesis of other seed protein amino acids via transaminase reactions.
Abstract: Glutamate synthase activity was demonstrated in the developing endosperm of maize (Zea mays L.). The enzyme shows specificity for glutamine and alpha-ketoglutarate as amino donor and acceptor, respectively. Both NADH and NADPH function as electron donors although lower activities were often, but not always, obtained with NADPH. The apparent K(m) values for glutamine, alpha-ketoglutarate, and NADH were 1.35 mm, 0.57 mm, and 7 mum, respectively.The pattern of activity during endosperm development revealed a well defined peak coinciding with the period of most active N accumulation. Activity in general was related to the rates of accumulation throughout development. Maximum glutamate synthase activity was the order of 56 nmoles of glutamate formed per minute per endosperm compared with a rate of N accumulation of 9.5 nmoles per minute.It is suggested that glutamate synthase plays a key role in the N nutrition of the maize endosperm providing a means whereby N transported in the form of glutamine is made available for the synthesis of other seed protein amino acids via transaminase reactions. Transaminase activity involving glutamate, the product of the glutamate synthase reaction, was also demonstrated.
59 citations
55 citations
49 citations
01 Jun 1977
TL;DR: In this article, the authors study Lorentz spaces with mixed or iterated norms and give an interpolation theorem of the Marcinkiewicz type for weak-type in product space.
Abstract: We study Lorentz spaces, with mixed or iterated norms. The usual Lorentz spaces enable us to clarify the concept of weak-type; the spaces with mixed norms enable us to clarify and to classify four extended notions of weak-type in product space. We give also an interpolation theorem, of the Marcinkiewicz type.
49 citations
TL;DR: In this paper, stability parameters are proposed and evaluated for interface breakdown by coalescence of steps emanating from apexes of cubic crystals, and the influence of interface kinetics is ambiguous; more rapid kinetics decrease the probability of step formation at corners becoming significant, but makes wave and inclusion formation easier when such step formation does occur.
46 citations
46 citations
TL;DR: In this article, the zone-center optical phonons of layer materials GaSe, GaTe, and their solid solutions are studied by means of Raman scattering, revealing an abrupt phase transition from hexagonal to monoclinic structures in the composition range $0.26lxl0.60$.
Abstract: The zone-center optical phonons of layer materials GaSe, GaTe, and their solid solutions are studied by means of Raman scattering. Most of the structure in the hitherto unstudied spectrum of GaTe is identified by following their evolution in the solid solutions and relating them to already known bands in GaSe. Increased layer-layer interaction, as solutions become richer in Te, allow the observation of Davydov splittings. Detailed study of the spectra of $\mathrm{Ga}{\mathrm{Se}}_{1\ensuremath{-}x}{\mathrm{Te}}_{x}$ reveal an abrupt phase transition from hexagonal to monoclinic structures in the composition range $0.26lxl0.60$. Both one- and two-mode behaviors are observed in the phonon bands of the solid solutions.
44 citations
01 Dec 1977
TL;DR: In this paper, the optimal and sub-optimal algorithms for the state filtering problem in discrete time non-linear systems are examined and general conditions are obtained which ensure multimodal character for the a-posteriori densities.
Abstract: This paper examines optimal and sub-optimal algorithms for the state filtering problem in discrete time non-linear systems. The optimal equations of sequential filtering are analyzed and general conditions are obtained which ensure multimodal character for the a-posteriori densities. These analysis is utilized in the discussion of the performance of sub-optimal linearized filters, and suggestions are made for their improvement in critical situations.
TL;DR: In this paper, it was argued that the Gompertz growth function may better meet the features of some growth processes than the logistic growth function, and a method of fitting the GOMpertz growing function under homoscedasticity was described.
Abstract: Both the logistic growth function and the Gompertz growth function are used to describe growth processes. In this paper it is argued that, although the logistic has been more studied, the Gompertz growth function may better meet the features of some growth processes. In order to make possible the comparison between both growth functions when an additive error is assumed, a method of fitting the Gompertz growth function under homoscedasticity is described herein. Two numerical examples and a brief discussion of the results are also provided.
TL;DR: In this article, a cube growing from an infinite quiescent solution was calculated numerically and the total flux was constant over the cube and was considered to be controlled by the concentration at a screw dislocation at the center of each face.
TL;DR: In this article, the authors focus on the imaginary life of Vasil'ēv and emphasize that Vasilev can be considered as a forerunner of non-classical logics constructed for the study of inconsistent non-trivial theories.
Abstract: Publisher Summary This chapter focuses on the imaginary life of Vasil'ēv and emphasizes that Vasil'ēv can be considered as a forerunner of non-classical logics constructed for the study of inconsistent non-trivial theories. According to some of Vasil'ēv insights three propositional calculi (V1, V2, and V3) are constructed, and they are related to propositional calculi of Costa 1974 and of Routley and Heyer 1976. The chapter aims at developing and studying the systems V1, V2, and V3 and presents some results obtained about the corresponding predicate calculi and their extension. A certain formal system is a formalization of a given interpretation of Vasil'ēv imaginary logic. The chapter also presents a summary of Vasil'ēv's ideas that are taken as motivations for the construction of V1, V2, and V3. Opinions of the Russian logic is interpreted in a way that justifies systems as Vasil'ēv propositional calculi. Vasil'ēv's logical system is composed of two parts—that he calls metalogic and ontological basis of logic. Vasil'ēv also tried to show that his imaginary logic with his law of excluded fourth has a classical interpretation, as is the case with the imaginary geometry of Lobachevsky.
TL;DR: Biosystematic analysis incorporating abundant new field data from many parts of the Neotropics has led to an ordered revision of the mimetic ithomiine genera Melinaea and Mechanitis, resulting in fewer clear-cut mimetic associations, more extensive blurring of differentiation patterns, and apparently fewer incipient biological species in this genus.
Abstract: Biosystematic analysis incorporating abundant new field data from many parts of the Neotropics has led to an ordered revision of the mimetic ithomiine genera Melinaea and Mechanitis. The various polytypic species of these general probably served as prime movers for the differentiation of other mimetic butterflies in Quaternary forest refuges. The revisions are presented in the form of supplements to the works of Richard M. Fox on these genera, with analyses based on his divisions. Seven species (or monophyletic species-groups) and sixty-three well-differentiated geographic subspecies (six of these described here for the first time) are recognized in Melinaea. Specimens are illustrated which demonstrate intergradation between refuge-derived subspecies. Five species and fifty-two differentiated subspecies are recognized in Mechanitis, whose members are more abundant and gregarious, more plastic, and apparently more vagile than those of Melinaea, resulting in fewer clear-cut mimetic associations, more extensive blurring of differentiation patterns, and apparently fewer incipient biological species in this genus than in Melinaea.
TL;DR: This paper considers two service stages in tandem with infinite queue capacity in front of each stage with single server who performs the service in both stages by switching from one stage to the other when the number of customers in the active stage reaches the value zero.
Abstract: This paper considers two service stages in tandem with infinite queue capacity in front of each stage. There is a single server who performs the service in both stages by switching from one stage to the other when the number of customers in the active stage reaches the value zero. The arrival process is assumed to be Poisson and the service processes are independent renewal processes. The state probabilities are obtained in the steady-state case. In addition for the steady-state case, the Laplace-Stieltjes transform is obtained for the time a customer waits until the beginning of service in each stage, for the busy period of the server, and for the busy period of each stage.
TL;DR: In this article, the 13 C NMR spectra of some eperuane diterpenes have been recorded and the signals assigned, and the substituent shielding effects in these compounds, in comparison with those observed in other series of diterphenes, are also presented.
TL;DR: Data accumulated from population samples, stomach contents and the behaviour of individuals maintained in aquaria suggest that Astyanax is the principal prey of Probolodus, at least in certain areas of its range.
Abstract: Probolodus heterostomus, one of the scale-eating characoid fishes, is found in the coastal rivers of southeastern Brazil from Espirito Santo to Sao Paulo1–3. The species is usually placed in the subfamily Cheirodontinae2–4 although a taxonomic affinity with the Tetragonopterinae has been suggested1. The latter view was apparently based largely on the morphological similarity of Probolodus with some species of Astyanax and especially A. fasciatus, a member of the Tetragonopterinae. The external similarity between the two species, which are sympatric over the Rio Paraiba drainage, is indeed striking (Fig. 1). But data accumulated from population samples, stomach contents and the behaviour of individuals maintained in aquaria suggest that Astyanax is the principal prey of Probolodus, at least in certain areas of its range. I suggest here that the similarity between these two genera is a form of aggressive mimicry5,6 irrespective of taxonomic affinities.
TL;DR: In the context of locally convex spaces, the authors provides an overview of the concepts of holomorphically bornological spaces and Mackey spaces that are more restricted classes than the corresponding linear ones.
Abstract: Publisher Summary This chapter provides an overview of the fact that in the holomorphic approach the corresponding concepts have been introduced as holomorphically bornological, holomorphically barreled, holomorphically infrabaralled, and holomorphically Mackey spaces that are more restricted classes than the corresponding linear ones. In the linear theory of locally convex spaces, it is classical to study bornological, barreled, infrabarreled, and Mackey spaces. An interesting highlight is the holomorphic Banach-Steinhaus on a Frechet space that contains, as a particular case, the classical linear Banach-Steinhaus theorem on such a space. A holomorphically bornological space is also a bornological space. A semimetrizable space is a holomorphically bornological space. A Silva space is known to be essentially the same thing as the dual of a Frechet-Schwartz space, or FS-space; thus, it is also known as a DFS-space. A Silva space is a holomorphically bornological space. Any inductive limit of bornological spaces is a bornological space.
TL;DR: Hummingbird pollination of Barbacenia flava was observed in the Serra do Cipo, Minas Gerais, Brazil, and experiments indicate that B. flava is probably a predominantly outbreeding species, although it also may be autogamous.
TL;DR: Anomalous leveling of the A 1 (Z ) polaritons of ferroelectric LiTaO 3 was observed below certain wavevectors on approaching the Curie temperature as discussed by the authors.
TL;DR: In this article, the authors present a theory that explains long time delays and internal Q switching in GaAs junction lasers, using only processes known to occur in these lasers: perturbation of refractive index of the active region by injected carriers, joule heating, and gain guiding.
Abstract: In this paper we present a theory that explains long time delays and internal Q switching in GaAs junction lasers, using only processes known to occur in these lasers: perturbation of refractive index of the active region by injected carriers, joule heating, and gain guiding.
TL;DR: In this paper, Raman scattering and luminescence have been observed in coal and the similarity of the results to those of disordered graphite is striking, and the disorder-induced line in graphite was shown to be due to the high phonon density of states at 0 and K points of the Brillouin zone for graphite.
TL;DR: In this article, lower superconducting transition temperatures have been found in amorphous transition metal alloys composed of elements widely separated in the Periodic Table, which differs from data on amorphously alloys consisting of nearest and next nearest neighbors.
TL;DR: In this paper, the cinnamate of grandifloric acid from Mikania oblongifolia has been isolated from the leaves of a single plant, and the results are reported.
TL;DR: Gain spectra in highly photoexcited CdS have been studied in this paper and the results are compatible with the assumption of condensation of the photo-excited carriers into a strongly interacting electron-hole liquid (EHL).
TL;DR: In this article, the temperature dependence of the A1 broad phonon linewidth is discussed and it is shown that it can adequately be accounted for by assuming a simple model where the Ti ions are sitting off the center of the unit cell and tunneling through a double well in the direction of the ferroelectric axis.
TL;DR: In this paper, a method of fabrication of epitaxial layers of GaAs doped with Mn is described, and resistivity and Hall effect measurements are made on various samples in the temperature range 77-300°K.
Abstract: The method of fabrication of epitaxial layers of GaAs doped with Mn is described. Resistivity and Hall effect measurements are made on various samples in the temperature range 77–300°K. The experimental results are used to determine the densities Na, Nd of acceptors and compensating donors, the activation energy Ea of the acceptor level associated with Mn and also the mobility of the carriers. These values are calculated using a model involving the two valence bands carriers. The results obtained confirm that the acceptor doping presents a saturation. They are compared to results previously published. A new value, rather close to unity, is obtained for the distribution coefficient of Mn in the case of low doping.