Showing papers by "University of Iceland published in 1987"
TL;DR: In this paper, a study was made of 903 fractures, most of which are of postglacial age, on the Reykjanes Peninsula, and they were studied in great detail.
196 citations
TL;DR: Seven members of a new group of rod-shaped hyperthermophilic neutrophilic archaebacteria were isolated from boiling neutral to alkaline solfataric waters from the Azores, Iceland, and Italy, representing a new genus which is named Pyrobaculum (the “fire stick”).
Abstract: Seven members of a new group of rod-shaped hyperthermophilic neutrophilic archaebacteria were isolated from boiling neutral to alkaline solfataric waters from the Azores, Iceland, and Italy. The organisms are strict anaerobes, growing optimally at 100°C. The cells are motile due to peritrichous or bipolar polytrichous flagellation. The isolates grow facultatively chemolithoautotrophically or obligately heterotrophically. Molecular hydrogen or complex organic substances are used as electron donors. During heterotrophic growth, elemental sulfur, thiosulfate, sulfite, l(-)cystine and oxidized glutathione may serve as electron acceptors depending on the individual strain. Elemental sulfur is strictly required as an electron acceptor for autotrophic growth. The G+C content of the DNA is around 46 mol%. The isolates represent a new genus which we have named Pyrobaculum (the “fire stick”). Two species are described: the facultatively autotrophic Pyrobaculum islandicum (DSM 4184), which is the type species, and the obligately heterotrophic Pyrobaculum organotrophum (DSM 4185).
173 citations
TL;DR: The Thingvellir swarm as mentioned in this paper contains about 100 fractures of average orientation N29.3E. The average length of fractures is 620 m, the minimum being 57 m and the maximum 7.7 km.
146 citations
TL;DR: This investigation demonstrates that hereditary cerebral hemorrhage with amyloidosis may be diagnosed by two laboratory methods: immunohistochemical investigation of cystatin C in brain tissue specimens and quantitation of cysteine proteinases in cerebrospinal fluid.
Abstract: Cystatin C, a protein inhibitor of lysosomal cysteine proteinases, was demonstrated by immunohistochemical techniques to be present in the birefringent amyloid deposits of the small arteries in the cerebrum, cerebellum, and leptomeninges of 10 Icelandic individuals with hereditary cerebral hemorrhage with amyloidosis. Specimens from other organs were investigated in one of the patients, and amyloid angiopathy characterized by an immunoreactivity of cystatin C was found in a submandibular lymph node. No immunoreactivity of amyloid fibril protein AA, kappa or lambda immunoglobulin light chain, or prealbumin was observed. Significantly low cerebrospinal fluid concentrations of cystatin C were found in all 9 investigated individuals with hereditary cerebral hemorrhage with amyloidosis. The concentrations of beta 2-microglobulin, albumin, and IgG in the cerebrospinal fluid were within normal limits. Isoelectric focusing showed that cystatin C from the cerebrospinal fluid of 9 patients with hereditary cerebral hemorrhage with amyloidosis had an isoelectric point identical to that of normal individuals. This investigation demonstrates that hereditary cerebral hemorrhage with amyloidosis may be diagnosed by two laboratory methods: immunohistochemical investigation of cystatin C in brain tissue specimens and quantitation of cystatin C in cerebrospinal fluid.
93 citations
TL;DR: In this article, the authors argue that rules of access to sea resources can only be understood in the context of the total socioeconomic system of which they form a part, including its land-based component.
Abstract: By showing that small-scale fishermen practice a number of forms of self-regulation, among them some that many have referred to as “property” at sea, anthropologists have challenged the assumptions of the “tragedy of the commons” model—that unregulated harvesting of a common-property resource is the cause of depletion of sea resources. Some have been inspired by ecological models of territoriality developed to explain the behavior of human foragers. We argue that rules of access to sea resources can only be understood in the context of the total socioeconomic system of which they form a part, including its land-based component. We also suggest that while the concept of ownership does apply to some forms of sea tenure, the extension of the concept to include informal rules of access is obfuscatory. [fishing, ownership, sea tenure, ecology, states]
89 citations
TL;DR: There is significant genetic differentiation between the small benthivorous charr and the other three morphs, and the relative relatedness of morphs based on gene frequency data is only partially concordant with that based on morphology and ecological specialization.
Abstract: The degree of genetic differentiation among four morphs of Arctic charr (small benthivorous, large benthivorous, piscivorous, and planktivorous) from Thingvallavatn, Iceland, was determined electrophoretically. Five of 36 enzyme loci were found to be polymorphic (Est2, Gpi3, Ldh4, Mdh4, 5 and Pgm2). However, only Est2 and Mdh4,5 showed enough variability to permit statistical analysis of divergence among morphs. All four morphs are very closely related; the values of Nei's (D) range from 0.00004 to 0.00126. These morphs are conspecific and do not represent different evolutionary lineages. There is significant genetic differentiation between the small benthivorous charr and the other three morphs. The relative relatedness of morphs based on gene frequency data is only partially concordant with that based on morphology and ecological specialization. The biological significance of this result is unclear because of the limited number of polymorphic loci upon which the genetic analysis is based and the high degree of relatedness among morphs.
70 citations
TL;DR: Habitat use by four morphs of arctic charr,Salvelinus alpinus, was investigated in Thingvallavatn, Iceland, by sampling with pelagic and benthic gill nets and the results are discussed in relation to food supply, competition and predation.
Abstract: Habitat use by four morphs of arctic charr,Salvelinus alpinus, was investigated in Thingvallavatn, Iceland, by sampling with pelagic and benthic gill nets. Sampling was done in May/June and August/September. Greatest abundance of fish was recorded in the littoral and epipelagic zone in early autumn. Catches were low in early summer. The four morphs are partly segregated in habitat. Small (SB-) and large benthivorous (LB-) charr have a more restricted spatial distribution than piscivorous (PI-), and especially planktivorous (PL-) charr. Both benthivorous morphs are mainly found in the littoral zone, and occur in largest numbers in stony shallows at depths between 0 and 10 m. PL-charr usually dominates in numbers in all habitats. PI-charr is most abundant in epibenthic habitats, although numbers are always low. All morphs are caught in higher numbers at night than during the day, but the diurnal activity difference is highest among SB-charr. The habitat use by different morphs is as may be expected from their morphology and diets. Within the population of PL-charr, young and small fish are more abundant on the bottom than in the pelagic zone, and there is a surplus of females in the pelagic zone. Along the benthic profile, young, small and immature PL-charr are more abundant in deep than in shallow waters. The results are discussed in relation to food supply, competition and predation. Possible reasons for the occurrence of four arctic charr morphs are also discussed.
69 citations
TL;DR: In this paper, it was shown that, provided the feeder-reservoir does not participate in the eruption, the volume of individual eruptions from elastic crustal magma chambers in Iceland is less than 0.25 km3.
Abstract: Summary
Provided magma flow in a partially molten layer follows Darcy's law of flow in porous media, it can be demonstrated that magma in the proposed magma layer beneath Iceland flows towards regions of reduced crustal thickness. In these regions, magma accumulates to form partially molten magma reservoirs, which are thus located in the magma layer. These reservoirs either give rise to surface eruptions or feed totally molten shallow magma chambers, located in the crust, that may erupt. It is argued that the melt fraction varies throughout a reservoir, being highest near the top where the reservoir may be totally molten, but that the average is 0.25. It is concluded that for individual eruptions the reservoirs behave, on the whole, as a poroelastic material. It is suggested that formation of crustal magma chambers is facilitated by the occurrence of stress barriers that lead to the formation of thick sills. While liquid, such sills absorb the magma of all dykes that enter them and may evolve into magma chambers. Ideal sites for stress barriers, and thus for magma chambers, are formations where individual layers have different elastic properties, i.e. where the crust behaves as a multilayer. Denoting the bulk volume of the reservoirs by Vb, the volume of the crustal chambers by V, and the volume of lava and dyke material in individual eruptions by Ve, it is found that Vb = 5365Ve and V= 1850Ve. Using the estimated volumes of exposed plutons as a basis, it is found that, provided the feeder-reservoir does not participate in the eruption, the volume of individual eruptions from elastic crustal magma chambers in Iceland is less than 0.25 km3, usually less than 0.1 km3, and that typical central volcano eruptions should be about 0.02 km3. For eruptions of the order of 1 km3 or larger, the reservoirs must supply magma during the eruption. It is concluded that, from the point of view of volume, historical eruptions of typical size could have come from elastic crustal magma chambers.
69 citations
TL;DR: In this paper, it was shown that the quadratic form (1, a) only represents elements in % u a% and such an element a is called divisible by two.
60 citations
50 citations
01 Jan 1987
TL;DR: Visna, the prototype of slow infections, is a menin-goencephalitis of sheep, caused by a retrovirus which belongs to the group of lentiviruses and is related to the recently isolated human virus that causes AIDS.
Abstract: Visna, the prototype of slow infections (Sigurdsson, 1954), is a menin-goencephalitis of sheep, caused by a retrovirus (Petursson et al., 1979) which belongs to the group of lentiviruses and is related to the recently isolated human virus that causes AIDS (Sonigo et al., 1985).
TL;DR: In this article, the authors examined the effect of formation or reopening of caldera fractures on fissure eruptions in Iceland and concluded that formation of fractures has no effect on the magmatic pressure in the chamber and thus does not lead to magma being squeezed out of it.
TL;DR: Although ovarian pregnancy is rare, the observed incidence in the material was nearly five times as high as previously described and women with ectopic pregnancy while using an IUCD appear to be at significantly higher risk of having an ovarian implantation.
Abstract: During 1968 - 82,759 histologically verified ectopic pregnancies occurred in Iceland. Retrospective analysis revealed that 26 of these were ovarian pregnancies. All but three of the ovarian pregnancies occurred in parous women. In 21 cases (80.8%), there was an association with the use of an IUCD at the time of conception. There was a significant difference (p<0.001) between the 10.7% rate of ovarian implantation in ectopic pregnancies in IUCD users and the 0.9% rate in non users. Although ovarian pregnancy is rare, the observed incidence in our material was nearly five times as high as previously described. Women with ectopic pregnancy while using an IUCD appear to be at significantly higher risk of having an ovarian implantation.
TL;DR: Desmosomatids from bathyal and abyssal arctic waters were collected in the Norwegian and Greenland Seas during the NORBI expedition in July-August 1975 and during cruises with R/V Halkon Mosby in March, June, and August 1981, and in January and November 1982.
Abstract: Desmosomatidae from bathyal and abyssal arctic waters were collected in the Norwegian and Greenland Seas during the NORBI expedition in July-August 1975 and in the Norwegian Sea during cruises with R/V Halkon Mosby in March, June, and August 1981, and in January and November 1982. Desmosomatids from the North Polar Sea were sampled during an expedition with the icebreaker Ymer in July 1980. Seven species were found; Whoia dumbshafensis sp. nov., Eugerda arctica sp. nov., Eugerda reticulata (GURJANOVA, 1946), Desmosoma strombergi sp. nov., Eugerdella hessleri JUST, 1980, Cryodesma agnari gen. nov., sp. nov., and Oecidiobranchus nanseni JUST, 1980. W. dumbshafensis, D. strombergi, and E. hessleri were only found in the Norwegian Sea, E. arctica and E. reticulata in the Norwegian Sea and the North Polar Sea, and C. agnari and O. nanseni in the Greenland Sea, the Norwegian Sea, and the North Polar Sea.
TL;DR: Ht-c and Ht-d are isoenzymes with only very minor differences in their structures, and are concluded to be hemorrhagic proteinases from Crotalus atrox venom.
TL;DR: The largest of the 1986 projects was a survey of Iceland that involved ultimately the use of 26 TI4100 receivers by over 30 scientists from nine nations and 20 different universities, institutions, and companies were involved in the effort.
Abstract: For a number of years, geophysicists have followed the development o f the Navigation Satellite Timing and Ranging (NAVSTAR) Global Positioning System (GPS) in anticipation of conducting geodetic surveys of such a size and accuracy [Bossler, 1984] that the detailed monitoring of neotectonic movements on a regional scale will be permitted. During 1986 the technology had considerable application in this field, including studies conducted in California, Mexico, the Caribbean, and New England. The largest of the 1986 projects was a survey of Iceland that involved ultimately the use of 26 TI4100 receivers by over 30 scientists from nine nations. Twenty different universities, institutions, and companies were involved in the effort. This article briefly describes the field campaign and the concurrent data processing
TL;DR: Diabetes is associated with a diminution in fatty acid desaturation, affecting the fatty acid composition of phosphatidyl choline in particular, and these changes may be relevant to development of atherosclerosis and relative resistance to catecholamine-induced cardiac necrosis in diabetes.
TL;DR: In this paper, simultaneous observations of pulsating aurora were carried out in September, 1984, using all-sky TV cameras at a geomagnetically conjugate pair of stations: Syowa Station in Antarctica and Husafell in Iceland.
Abstract: Simultaneous observations of pulsating auroras were carried out in September, 1984, using all-sky TV cameras at a geomagnetically conjugate pair of stations: Syowa Station in Antarctica and Husafell in Iceland. From the data obtained at the two places on 26 September, the following characteristics are found: Spatial configuration of pulsating auroras is very similar in the conjugate regions. In this particular event each pulsating aurora has its counterpart with topologically the same shape in the other hemisphere. However, the timing of the appearance or fade-out of the pulsating auroras depends on the type of aurora. That is, the patchy type of aurora appears nearly simultaneously in both hemispheres, but the expansion type of pulsating aurora, extending from an aurora with much slower variations, is not synchronously observed and often appears almost out of phase between the conjugate regions.
TL;DR: In 1985 dentists in the Lothian Region of Scotland were questioned about their use of prophylactic antibiotics for patients at risk of developing infective endocarditis; results showed a marked change in practice with widespread adoption of the single-dose oral amoxycillin regimen.
Abstract: In 1985 dentists in the Lothian Region of Scotland were questioned about their use of prophylactic antibiotics for patients at risk of developing infective endocarditis. Replies were compared with those obtained from a similar survey in 1981. The results showed a marked change in practice with widespread adoption of the single-dose oral amoxycillin regimen; this was the regimen of choice for 63% of general dental practitioners. For patients allergic to penicillin 76% of practitioners used erythromycin and there was a decline in the use of tetracycline and clindamycin. The adoption of amoxycillin reflects the ease of compliance with a simple single-dose regimen. This change has produced a striking improvement in the timing of prophylactic antibiotic therapy.
TL;DR: A method of precise lake level observations has been tested at lake Myvatn since June 1984 as mentioned in this paper, and twelve observations over a period of 21 months show that this method is useful in detecting relative vertical ground displacements which exceed one millimeter.
TL;DR: In this article, a preliminary analysis of the initial vibrational population distributions and spectroscopic parameters of XeO and KrO has been achieved through a preliminary analyzer of their chemiluminescence spectra.
01 Jan 1987
TL;DR: The phase change instability mechanism induces convection prior to the onset of ordinary buoyancy-driven thermal convection in the two-phase convection as discussed by the authors, which is of major importance in geothermal reservoirs.
Abstract: Geothermal reservoirs are generally more complex than reservoirs of groundwater or petroleum. Physical states of the hydrothermal fluid fall into four categories: vapor-saturated, two-phase boiling, liquid-saturated and supercritical. Liquid-saturated reservoirs and liquid-dominated or vapor-dominated reservoirs of the two-phase boiling type are the most common types exploited so far. There is growing interest in submarine geothermal systems and heat extraction from hot rock or magma bodies, where the hydrothermal fluid circulates at supercritical temperatures and pressures. Meteoric water dominates in continental systems and ocean water in submarine systems. The contribution of magmatic water is small at upper levels in the crust, but may increase as magma bodies are approached. The larger fumarolic fields have magma as a heat source. The rate of heat transfer required to sustain the intense heat output of such fields remains problematic, unless an intimate contact between circulating fluids and hot boundary rock of the magma is maintained over the lifetime of the activity. Convective downward migration of fluid along existing fractures and water penetration by thermal cracking of hot rock are important processes in this respect. Two-phase convection is of major importance in geothermal reservoirs. The phase change instability mechanism induces convection prior to the onset of ordinary buoyancy-driven thermal convection. Mathematical modelling of geothermal systems has greatly advanced the understanding of the dynamic nature of geothermal reservoirs and their response to exploitation.
TL;DR: In the election to the Althingi on 25 April 1987, the established party system in Iceland received its greatest blow so far as discussed by the authors, the four main parties between them managed only three-quarters of the valid votes, the Independence Party and the People's Alliance, both suffered their worst defeats ever.
TL;DR: In this paper, data from two kinds of experiments for extrasensory perception were retrospectively analyzed for possible relationships with local geomagnetic activity (K-index), and ESP scores from 70 Ganzfeld sessions (telepathy-clairvoyance) were found significantly related to the day prior to the experimental sessions (rs = 0.23, n = 70, P < 0.03, one-tailed).
TL;DR: During electrophoresis ESTERASE-5 exists in a dynamic equilibrium between monomers and dimers, an equilibrium that is dependent on the running temperature of the gels, which is a significant determinant of EST-5 electrophoretic mobility.
Abstract: Esterase-5 is one of the most polymorphic loci in Drosophila pseudoobscura. Some variants reportedly produce a dimeric enzyme, while a few produce a monomeric form. This paper reports the finding that during electrophoresis ESTERASE-5 exists in a dynamic equilibrium between monomers and dimers, an equilibrium that is dependent on the running temperature of the gels. This is shown by a series of analytical electrophoresis experiments in which the apparent molecular weights of several variants are determined at four different temperatures. Increasing temperatures result in a linear decrease in the logarithm of apparent molecular weights. Macromolecular interactions thus are a significant determinant of EST-5 electrophoretic mobility.
01 Jan 1987
TL;DR: In this paper, a different model, involving crustal metasomatism, is introduced and discussed, in which the observed chemical variability turns out to be a necessary consequence of the process of crustal accretion and of the geodynamics of Iceland.
Abstract: The geochemistry of Icelandic volcanics, especially as pertains LIL-elements, RE-elements, and isotopes, has in the literature called for explanations involving heterogeneous mantle source. These explanations are shown to be incompatible with the data at hand. A different model, involving crustal metasomatism, is introduced and discussed, in which the observed chemical variability turns out to be a necessary consequence of the process of crustal accretion and of the geodynamics of Iceland. Crustal accretion is confined to volcanic systems that form an array of dike swarms over the plate boundary. Each system evolves independently, through cyclic processes, toward a silicic central volcano with associated extensive hydrothermal alteration, but the overall result of the accretion process is chemically, mineralogically, and seismically layered oceanic crust, capable of yielding different anatectic melts. These melts are the “metasomatic ichors” that primarily cause the variability of Icelandic volcanics. At the surface they are observed as volcanic formations, as discrete components in mixed magmas, and as chemical imprints that have been mistaken for signs of a mantle heterogeneity or mantle metasomatism.