Showing papers by "University of Iceland published in 1980"

Subsidence events in the Krafla area, North Iceland, 1975-1979

Abstract: In the inflation-deflation sequence of the Krafla magma chamber since its beginning in 1975, 12 deflation or subsidence events have been identified until May, 1979. The tilt and distance measurements relating to these subsidence events are discussed in some detail. All of these subsidence events are associated with horizontal magma flow along the N-S trending fissure zone, which goes through the central part of the Krafla caldera, to form a dike 3 to 5 m wide, 80 km long, and 1.0 to 2.5 km high from the bottom to the top. The total volume of magma, which flowed out of the Krafla magma chamber during these 12 events, is estimated as 481 x 106 m3 , whereof 407 x 106 m 3 are estimated to have flowed northwards, 72 x 106 m3 southwards and about 2 x 106 m 3 came to the surface as basaltic lava.

Petrology of hybrid intermediate and silicic rocks from Öræfajökull, southeast Iceland

Abstract: Intermediate and acid volcanic rocks from the Oraefajokull central volcano, southeast Iceland, are hybrids with calc-alkaline affinity. These rocks are characterized by basic xenocrysts of olivine, plagioclase, and clinopyroxene set in a glassy matrix. Linear variation curves for a number of major and trace elements show that the rocks are mixing products of basic and silicic members of the main series of the volcano. It is concluded that this mixing results from contamination of silicic melts by basaltic and gabbroic xenoliths.

Cellular calcium as a determinant of action potential duration in rabbit myocardium.

Abstract: It has been suggested that the amount of calcium in the myocardial cell determines force production as well as the duration of the action potential. We have examined two factors proposed to determine the action potential duration: (1) the inotropic state of the muscle and (2) the preceding stimulation interval. The experiments were performed on isolated papillary muscles from rabbits. The preparations were stimulated to contrast isometrically at a temperature of 37 degrees C and intracellular recordings of action potentials were made. An increased inotropic state produced either by raised external calcium concentration or by increased stimulation frequency was associated with shortened action potentials, confirming factor (1) above. The dependence of the action potential duration on the preceding stimulation interval (factor (2) above) disappeared over a wide range of intervals when the preparation was exposed to 4 microM D600. The action potential duration was, however, still dependent on the preceding stimulation interval when the extracellular calcium concentration had been lowered from 2.0 mM to 1.0 and 0.5 mM respectively. The results are discussed in terms of a model which postulates an inverse relationship between the amount of calcium in a membrane compartment and the action potential duration.

Mapping of the supP (Su6+) Amber Suppressor Gene in Escherichia coli

Abstract: The supP (Su6+) amber suppressor gene has been mapped on the clockwise side of the valS locus near min 95 on the Escherichia coli chromosome.

Nonlinear Stochastic Analysis Of Compliant Platforms

Abstract: This paper deals with nonlinear stochastic analysis of compliant deepwater platforms subjected to wave action. The structure selected to exemplify this study is a guyed tower of the EXXON type. The response of the platform is predicted applying a simplified finite element model. The nonlinear effects considered are geometrical nonlinearities due to the cable system and nonlinear flow-induced forces due to the drag term in the modified Morison equation. In the evaluation of the wave forces due account is taken of the real geometry of the structural system. The structural response is evaluated applying two basically different approaches, i.e. the stochastic linearization method and a new iterative approach. This iterative approach, which may be used to predict non-Gaussian behaviour, is found generally more efficient than the stochastic linearization method and methods based on Monte-Carlo simulation and appears to be more sound than the perturbation method. Approximate extremes of the deck displacement, tower stresses and cable forces are estimated emphasizing the importance of the non-Gaussian characteristics of the structural response. The dynamic performance of the platform is discussed with respect to the relative influence of the spectral composition of the ocean waves, the softening of the cable system, the dissipative damping forces and the deck mass. The human response to the deck motion is also investigated.

Prevalence of mental disorders. A 5‐year follow‐up study with questionnaires

Abstract: In order to estimate the prevalence of mental disorders in the general population by commonly used health questionnaires it is necessary to add some questions related to alcohol abuse. Even if this is done, the estimates are probably too low as the group not responding to questionnaires probably contains a larger proportion of mentally ill persons. In a 3.7% random sample of the population in Iceland aged 20–49 years the prevalence of mental disorders was estimated at approximately 20% by a health questionnaire with questions relating to alcohol abuse being added. The prevalence rate was highest in the youngest age group. The respondents in this sample have been approached again after a period of five years and asked to answer the same questionnaire. The overall prevalence rate was this time found to be similar, but slightly lower, while the prevalence rate in the youngest age group was significantly lower. The remission rate among the respondents in the follow-up was 8.5% while the incidence over the five years was found to be 6.7%.

Chemical Stimuli: Role in the Behavior of Fishes

Abstract: Chemoreception plays a major role in important areas of fish behavior such as feeding, migration, spawning, care of young, schooling and defence. Chemosensory adaptations to a variety of environmental conditions exist. These are mainly adaptations of receptor sites or of central processing systems rather than morphological changes of the chemosensory organs. It is not my intention to present a complete review of the literature on chemical sensation in fish, but rather to discuss briefly the properties of chemical stimuli in water, and to point out the importance of certain chemicals in fish behavior.

Direct HIG test for rubella antibodies.

Abstract: A modification of the haemolysis-in-gel test for rubella is described. This involves using, instead of sera, whole blood samples taken from the earlobe and placed directly onto the test plates without any pretreatment. A comparison was made between this method and the HI test. Samples from 461 individuals were tested by both methods. The results of these two tests were in good agreement. No false negatives or false positives were observed by the direct HIG test. The direct HIG test is particularly well suited for screening large groups for rubella antibodies in connection with a vaccination program.

Low temperature photoconductivity in arsenic-chalcogenide glasses

Abstract: Measurements are presented on photoconductivity, at different levels of illumination, in several AsSe alloys, at temperatures down to about 100°K. These results, as well as earlier results from the litterature, are presented in a form different from and mathematically simpler than, the hitherto conventional form. The complementary nature of photoconductivity and photoluminescence is discussed and a common parameter is found.