Showing papers by "University of Coimbra published in 1975"
TL;DR: An electrometric system was used to measure Ca++ uptake by sarcoplasmic reticulum vesicles and the ultrasensitivity of the method permits to follow changes in Ca++ concentration below 10−6 M.
78 citations
TL;DR: It is proved that no graph in a matroidal family has a vertex of degree two and consequently that no two graphs in such a family are homeomorphic.
31 citations
TL;DR: The results indicate that most of the Ca2+ retained by sarcoplasmic reticulum under conditions of passive uptake is bound to the external side of the membrane.
24 citations
TL;DR: The major-, minor and trace-elements chemistry of Hercynian granitoids and their minerals from the central area of northern Portugal indicates that the composition of the rocks and also of their minerals varies in the comagmatic sequence of granite, aplite and pegmatite.
23 citations
TL;DR: Uranium-helium ages have been determined for a suite of 25 whole-rock basalts from Madeira and Porto Santo islands in the Madeira Archipelago as discussed by the authors.
19 citations
TL;DR: In this paper, the relative efficiencies of tetraphenylbutadiene, p-terphenyl, diphenyl-stilbene, sodium salicylate and p-quaterphenyl were measured.
Abstract: The behaviour of xenon and argon-xenon gas proportional scintillation counters is con sidered. For X-rays, ranges of window area are defined showing competition with semiconductor detectors. Data for primary scintillation of X-rays and alpha particles are included. Relative efficiencies of tetraphenylbutadiene, p-terphenyl, diphenyl-stilbene, sodium salicylate and p-quaterphenyl were measured.
18 citations
TL;DR: The gas proportional scintillation counter (PS counter) as mentioned in this paper enables the localization of tracks of ionizing particles by timing the primary and the secondary scintillations of the PS counter.
14 citations
TL;DR: In this paper, a gas proportional scintillation counter with uniform electric field is described, based on the Frish ionization chamber, and its principle is discussed and the properties experimentally studied using pure argon.
Abstract: A new type of gas proportional scintillation counter with uniform electric field is described. This counter is the scintillation counter analog of the Frish ionization chamber. Its principle is discussed and the properties experimentally studied using pure argon. Energy resolutions of 1.9% were obtained for 8.1 MeV alpha particles. Some results concerning the interpretation of the mechanism of the secondary scintillation are discussed.
13 citations
TL;DR: In this paper, an argon uniform-field gas proportional scintillation counter was used to obtain energy resolutions of 1.6% for 8.1 MeV α-particles.
10 citations
TL;DR: In this article, the construction and method of operation of an all-metal system for K Ar and U-He dating is described in detail, which is capable of handling samples in batches of about 15 g total weight.
9 citations
TL;DR: In this paper, the strong coupling theory of the polaron is derived by simple variational methods (The Hartree-Fock and the Generator Coordinate Methods) based on coherent state-wave functions describing the electron surrounded by a phonon cloud.
TL;DR: It is proved that the wheels share many of these properties with the cycles when regarded as circuits of a matroid defined on the edge set of G.
TL;DR: In this article, the performance of spark chambers is described and discussed, which are designed to visualise the distribution of β-emitting radioactivity on chromatograms, and they lead to ease of construction with good uniformity of sensitivity and stability of operation.
TL;DR: In this paper, the anion radical of the fully aromatic di-Noxide system of azobispyridine N-oxide was prepared and studied by ESR, and the spin densities were calculated at ==================¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Abstract: The anion radical of the fully aromatic di-N-oxide system of azobispyridine N-oxide was prepared and studied by ESR. Utilising computer simulation and CNDO computation the ESR spectrum was interpreted as follows:
Using appropriate equations the spin densities were calculated at
Ths semi-quinoidal nature of the radical suggests a possible use as a spin label.
TL;DR: In this paper, an investigation of the production of initiatory electrons from the cathode surfaces of detectors by field emission effects is described, and the results show that emission rates are high enough to account for a significant proportion of spurious sparks.
20 May 1975
TL;DR: In this article, it was shown that the cluster expansion formalism can also be used as a basis for describing excited states of closed or open-shell systems, and the possibility of using cluster expansion in combination with the generator coordinate method is discussed.