Showing papers by "University of Iceland published in 1988"

The Glacial History of Iceland During the Past Three Million Years

Abstract: Iceland is built up of volcanic rocks with sedimentary interbeds, which have been piled up continuously since Miocene times. In the Pleistocene rock series, sediments of fluvial, lacustrine, marine and glacial origin and soils are very common and frequently thick. A sudden climatic deterioration took place at about 3 Ma BP. The Pliocene lusitanic marine fauna was replaced by a boreal fauna. Conifers and deciduous forest vanished and the flora became similar to the present one. From 3 to 2 Ma BP, inland ice caps were common during cold spells. From then on ice sheets reaching down to sea level have covered most of the country at least 12 times during glacials.

Formation of collapse calderas

Abstract: Collapse calderas are common in many volcanic regions, but the mechanics of their formation is not well understood. I propose that collapse calderas may form as a result of the growth of associated shallow magma chambers. Excess magmatic pressure in a shallow chamber gives rise to tensile stresses at the surface, but the location and magnitude of the maximum tensile stress depend on the shape of and depth ( d ) to the top of the chamber. This model indicates that penny-shaped chambers, i.e., sill-like chambers of circular horizontal cross sections, are most likely to initiate collapse calderas. For such a chamber with horizontal radius a , the higher the a/d (radius/depth) ratio, the greater the probability of forming a collapse caldera.

The Skipper Effect in the Icelandic Herring Fishery

Abstract: The centrality of the skipper to the economic and social organization of fishing is based on the assumption that he plays an important role in fishing success. This crucial assumption has recently been hotly debated in the social science literature in various contexts. In this study an attempt is made to estimate the role of the skipper in fishing success. The study is based on data from the Icelandic summer herring fishery from the years 1959, 1960 and 1961. The analysis of the data shows a correlation ranging from .59 to .70 for the skippers' catches between fishing seasons. When relevant variables—size of boat and time spent fishing—are controlled for, correlation for skippers' catches between seasons remains high (Beta = .52 and .53). Further, analysis of case histories of individual skippers and other qualitative evidence support the view that the skipper plays a central role in fishing success. Finally, results are discussed in the context of current social science debate around the folk belief in t...

Studies on the mechanism of hemorrhage production by five proteolytic hemorrhagic toxins from Crotalus atrox venom.

Abstract: The sites and relative rates of peptide bond hydrolysis of the oxidized B chain of bovine insulin by two hemorrhagic proteinases, Ht-a and Ht-b, isolated from the venom of the Western Diamondback Rattlesnake, Crotalus atrox, were investigated. The results were compared with previous results on the digestion of the same substrate by the C. atrox hemorrhagic proteinases Ht-c, d, and e. Both toxins, Ht-a and Ht-b, were found to cleave the His5-Leu6, His10-Leu11, Ala14-Leu15, and Tyr16-Leu17 bonds of the oxidized insulin B chain. In addition, Ht-a cleaves the Asn3-Gln4 bond, whereas Ht-b cleaves the Gly23-Phe24 bond. The cleavage specificity of Ht-b on the insulin B chain is identical to that of the weakly hemorrhagic isoenzymes Ht-c and Ht-d. Hemorrhagic proteinase Ht-a cleaves the Ala14-Leu15 bond most rapidly, having a turnover number of 12.6 min-1 which was approximately twice as fast as the Tyr16-Leu17 bond turnover of cleavage. Hemorrhagic proteinase Ht-b, on the other hand, cleaves the Tyr16-Leu17 bond fastest, having a turnover number of 61.3 min-1. The Ala14-Leu15 bond is the peptide bond cleaved the second fastest by Ht-b, with a turnover number of 48.2 min-1. The five hemorrhagic toxins from Crotalus atrox venom were also examined for their capability to hydrolyse basement membrane preparations, and the identities of the digested proteins comprising the basement membrane were determined. From the results it is concluded that all five hemorrhagic toxins cleave laminin and the component of the basement membrane referred to as band a.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumours in Iceland 10. Malignant tumours of the female breast

Abstract: The Icelandic Cancer Registry has records of 1,720 cases of malignant tumours of the female breast diagnosed in 1,659 patients in the 30-year period 1955 — 1984. Of these, 1,658 tumours were invasive. Sufficient histological material existed for 1,666 malignant tumours to make it possible to classify them according to the criteria published by the WHO. The most frequent histological type was Ductal carcinoma: 1,064 neoplasms, or 64%. Second in frequency was Lobular carcinoma: 175 neoplasms, or 10%; third was Mucinous carcinoma: 115 neoplasms, or 7%; and fourth in frequency was Medullary carcinoma: 69 neoplasms, or 4%. The incidence of carcinoma of the breast increased by 74% from 37.0 per 100,000 per annum in 1955 — 59 to 64.4 per 100,000 in 1980 — 84. This increase in incidence affected all morphological types, but Lobular and Muci IOUS more than Ductal and Medullary. The survival times have improved with time. Unilateral tumours were 710 in the right and 837 in the left breast. Both breasts were involved 167 times (106 patients), and in 6 patients the side was not recorded. A second primary was more likely to develop when the first one was in the right breast. This study of malignant tumours of the breast is the tenth in a series of investigations into histological classification of tumours occurring in Iceland.

Role of phosphoinositides in the regulation of endothelial prostacyclin production.

Abstract: To elucidate the role of the phosphoinositide signal transduction system in endothelial endothelial prostacyclin production, endothelial cells from human umbilical veins previously labelled with 3H-inositol were incubated with thrombin or histamine. Water-soluble inositol phosphates were separated on anion exchange columns. Both agonists evoked transient bursts of inositol phosphate production with inositol trisphosphate peaking at 15 seconds in histamine-stimulated cells and at 60 seconds in thrombin-stimulated cells. The inositol phosphate production was closely linked to prostacyclin production. After stimulation, there was concurrent desensitization to prostacyclin production and formation of inositol phosphates. Arachidonic acid and the Ca2+-ionophore A23187 did not affect inositol phosphate production in concentrations sufficient to increase prostacyclin production 20-fold, and they did not affect desensitization to a subsequent thrombin stimulation. The phorbol ester 12-o-tetradecanoyl phorbol 13-acetate, a stimulator of protein kinase C, inhibited thrombin-induced generation of inositol phosphates, enhanced A23187-mediated prostacyclin production, and had complex effects on thrombin-mediated prostacyclin production, but had no effect on its production from extrinsic arachidonic acid. The current data suggest that production of inositol phosphates is a link in receptor stimulation of endothelial cells to produce prostacyclin and that associated activation of protein kinase C affects both the generation of second messengers and the release of arachidonic acid.

Density, length distribution, and diet of age-0 arctic charrSalvelinus alpinus in the surf zone of Thingvallavatn, Iceland

Abstract: Population densities of age-0 arctic chaff in the surf zone averaged 1.83 and 4.70 fish m-2 in August 1984 and June 1985, respectively. Length variation of the littoral fish was low in early summer, increasing in late summer and autumn. Newly emerged charr, ∼ 20 mm long, appeared in the stony shallow water zone during both May and June. From length variation and variation in mouth position of the young charr, it is concluded that at least two of the four chaff morphs in the lake are present in the surf zone during spring and summer. In August, some of the larger age-0 charr had moved out from the surf zone, into the pelagic and the deeper epibenthic waters. The food of young littoral charr was dominated by large chironomid larvae (instar 3 and 4) and pupae

Familial and sporadic breast cancer cases in Iceland: A comparison related to ABO blood groups and risk of bilateral breast cancer

Abstract: This study was aimed at determining whether the familial clustering often observed in breast cancer is associated with genetic factors. We compared familial and sporadic breast cancer cases with respect to ABO blood group distribution and the risk of bilateral disease, using the data from the Icelandic Cancer Registry which contains genealogical information for about 30% of the breast cancer cases diagnosed in Iceland since 1911. Cases were classified as familial if at least one first-degree relative had breast cancer. Using this criterion, we identified 184 familial cases and 572 sporadic cases. The familial cases had a 2-fold higher prevalence of blood group B than did the sporadic cases, and the frequency of this blood group in non-affected relatives of cases was significantly reduced. Familial cases were about 2.7 times more likely to suffer from bilateral breast cancer than were the sporadic patients. These results support the presence of a genetic factor in the etiology of familial breast cancer.

Vibrational relaxation of KrF* and XeCl* by rare gases

Abstract: A steady-state, chemiluminescence technique has been used to measure effective rate constants for vibrational relaxation as a function of vibrational level for KrF* in collisions with He, Ne, and Ar and XeCl* with Ar. The effective rate constants reported include contributions to relaxation due to intersystem crossing between theB andC states, in addition to direct relaxation within theB state. The relevance of these results to the understanding of previous measurements in KrF and XeCl lasers is discussed.

Bathyal and abyssal Asellota (Crustacea, Isopoda) from the Norwegian, Greenland, and North Polar Seas)

Abstract: Asellote isopods were collected from bathyal and abyssal depths; in the Norwegian and Greenland Seas during the NORBI Expedition in July-August 1975; from the Norwegian Sea during cruises with R.V. Hakon Mosby in March, June, and August 1981, and in January and November 1982; and from the North Polar Sea during the Ymer Expedition in July 1980. Two species new to science were collected: Ilyarachna torleivi sp. nov. and Paramunnopsis justi sp. nov. In addition seventeen other species were found: Ianthopsis pulchra (HANSEN, 1916), Haploniscus bicuspis (G.O. SARS, 1877), H. ingolfi WOLFF, 1962, Munna acanthifera HANSEN, 1916, M. hanseni STAPPERS, 1911, Pleurogonium intermedium HANSEN, 1916, Pleurogonium sp. ?, Nannoniscoides angulatus HANSEN, 1916, Nannoniscus reticulatus HANSEN, 1916, N. profundus SVAVARSSON, 1982, Exiliniscus hanseni (JUST, 1970), Macrostylis subinermis HANSEN, 1916, Ilyarachna hirticeps G.O. SARS, 1870, I. bergendali OHLIN, 1901, I. dubia HANSEN, 1916, Echinozone arctica HANSEN, ...

The Concentration of Blood Glucose, Urea, Calcium and Magnesium in Milking Dairy Cows

Abstract: Summary Blood samples from 362 milking Icelandic dairy cows were sampled over a 3 year period. The cows came from 9 herds in 2 areas in Iceland, the north (area 1) and the south (area 2). The cows were kept in tie-stalls and fed hay, silage and concentrates 2–4 times a day during winter but grazed on pasture during summer and received concentrates twice daily. The total of 963 samples were collected and analysed for glucose, urea, calcium, magnesium and ketone bodies. The effects of year, season, area, herd and age were studied. The overall means and standard deviations for the blood constituents were in agreement with the findings of other authors. The effects of year were significant for all the blood constituents. The effect of season was also significant for all constituents except Mg. The effect of area was significant for urea and Mg but not for glucose and Ca. The differences between herds were significant only for Mg in area 1, but for glucose urea and Mg in area 2. Glucose, Ca and Mg were negatively correlated with age, although the correlation coefficients were small, r = – 0.18, – 0.23 and – 0.24, respectively. Cows with clinical ketosis (and blood ketone concentrations > 10 mmol/l) had significantly lower glucose and Ca values than healthy cows (P < 0.001 and 0.01, respectively). The glucose values were significantly correlated with urea (r = – 0.09, P < 0.001), Ca (r = 0.12, P < 0.001) and Mg (r = 0.09, P < 0.01). Urea was significantly correlated with Mg (r = 0.09, P < 0.01) and Ca was correlated with Mg (r = 0.10, P < 0.001). Zusammenfassung Blutkonzentrationen von Glucose, Harnstoff, Calcium und Magnesium bei laktierenden Milchkuhen Bei 362 laktierenden Islandischen Milchkuhen wurden 3 Jahre lang Blutproben entnommen. Die Kuhe gehorten zu 9 Herden, die in 2 Gebieten von Island, namlich im Norden (Gebiet 1) und Suden (Gebiet 2) gehalten wurden. Die Kuhe waren im Winter im Anbindestall untergebracht und erhielten 2–4mal taglich Heu, Silage und Kraftfutter. Wahrend des Sommers befanden sie sich auf der Weide. Insgesamt wurden 963 Blutproben entnommen und auf Glucose, Harnstoff, Calcium, Magnesium und Ketonkorper untersucht. Es wurde der Einflus des Jahres, der Saison, des Gebiets, der Herde und des Alters untersucht. Die Gesamtmittelwerte, Standardabweichungen der Blutwerte stimmten mit Befunden anderer Autoren uberein. Der Einflus des Jahres war bei allen Blutwerten signifikant. Das gleiche gilt, mit Ausnahme des Mg, fur die Saison. Der Einflus des Gebiets war fur Harnstoff und Mg signifikant, nicht jedoch fur Glucose und Ca. Die Unterschiede zwischen den Herden waren im Gebiet 1 nur fur Mg signifikant, im Gebiet 2 jedoch fur Glucose, Harnstoff und Mg. Glucose, Ca und Mg waren mit dem Alter negativ korreliert, wenn auch die Korrelationskoeffizienten gering waren (r = –0,18, –0,23 bzw. –0,24). Kuhe mit Ketose (und Blut-Ketonkorper-Konzentrationen > 10 mmol/l) wiesen signifikant niedrigere Glucose- und Ca-Werte auf als gesunde Kuhe (p < 0,001 bzw. 0,01). Die Glucosewerte waren mit den Harnstoff- (r = –0,09, p < 0,001), Ca- (r = 0,12, p < 0,001) und Mg- (r = 0,09, p < 0,01) Werten korreliert. Die Harnstoffwerte waren signifikant mit den Mg-Werten (r = 0,09, p < 0,01), und die Ca-Werte signifikant mit den Mg-Werten korreliert (r = 0,10, p < 0,001).

Gastric cancer after gastrectomy.

Abstract: Inhabitants of Iceland who had undergone gastric resection for non-malignant diseases between 1930 and 1974 were identified and followed up at the Icelandic Cancer Registry in order to evaluate the risk of gastric cancer subsequent to gastric resection. There were 1,214 males and 581 females, contributing 30,792 person/years. The results show an overall 1.16-fold, not significant, increase in the relative risk for gastric cancer. In the first 15 years after operation the risk was decreased, 0.49, 95% confidence interval (CI) 0.24-0.90, but from 15 years or more following operation, the risk was 2.17, 95% CI 1.46-3.10. We conclude that for these subjects the risk is not significantly increased. Patients surviving 15 years or more after operation have an increased risk (p less than 0.001), but they do not contribute substantially to the number of gastric cancer patients in Iceland.

Equality and Educational Opportunity in Iceland

Abstract: Thorlindsson, T. 1988. Equality and Educational Opportunity in Iceland. Scandinavian Journal of Educational Research 32, 9‐22. This paper analyses educational mobility and educational opportunity in Reykjavik, Iceland, in the light of educational reform. The analysis focuses on the one hand on the issue of the openness of the educational system and the issue of equality of educational access on the other. The results show that the upper levels of the educational system are relatively open to individuals of diverse origin and thus do not indicate the formation of a university educated elite. The lowest educational strata, however, is characterized by closure and a high degree of self‐recruitment. Furthermore, the results show that educational opportunities are not equally distributed in terms of parents' education. These results are discussed in the context of the growing educational expansion and the egalitarian beliefs of the Icelanders. It is pointed out, among other things, that the two issues...

Periungual hyperpigmentation mimicking Hutchinson's sign associated with minocycline administration.

Abstract: . An assessment of the occurrence rate of periungual hyperpigmentation with subungual melanoma (Hutchinson's sign) and periungual hyperpigmentation with other subungual lesions has not been published, although periungual hyperpigmentation with a pigmented streak or other pigmented lesion of the nail has been considered pathognomonic for subungual melanoma for a century. We report a case of minocycline hyperpigmentation presenting as a longitudinal pigmented streak of the nail associated with periungual hyperpigmentation. These pigmentary changes could be mistaken for Hutchinson's sign. J Dermatol Surg Oncol 1988; 14:1011–1013.

State observers and state-feedback controllers for a class of non-linear systems

Abstract: A design methodology for observers and controllers for a class of single-input, single-output non-linear systems is developed. A non-linear observer form is defined, and a corresponding observer using non-linear observer gains is specified. The resulting error dynamics, which are non-linear, are asymptotically stable for a proper choice of those gains and bounded inputs and outputs. A non-linear controller form is defined and a corresponding controller, which results in linear closed-loop dynamics with arbitrary eigenvalue placement, is devised. Transformations from the class of interest to the defined forms are derived. In the observer case, the transformation to the observer form and the non-linear entries in the state matrix of that form can be determined separately, leading to a system of linear partial-differential equations—a major simplification. In the controller case, a simple, well-known system of linear partial-differential equations is obtained. The efficacy of the developed methodology is sho...

Orthopantomographic examination of the edentulous mouth.

Abstract: Orthopantomograms from 250 persons, edentulous in one or both jaws, were examined with the aim to assess the frequency and location of significant radiographic abnormalities. The most frequent findings were retained roots and teeth, disclosed in 11.1% and 4.9% of the subjects, respectively. The findings were compared with the results of previous surveys and the various radiographic methods used in the examination of edentulous jaws discussed. The results of this and previous studies demonstrates (1) the necessity of a routine radiographic examination of the jaws of every patient before construction of a single denture or complete dentures, and (2) the need for a better extraction technique together with more universal use of radiographs before and after extraction.

The relationship between blood and fertility parameters in post partum dairy cows.

Abstract: The onset of post partum ovarian activity, the number of artificial inseminations (AI) and the time of conception were monitored in 412 Icelandic dairy cows during a period of 3 years. Blood was sampled from the animals at various times after calving and the serum concentration of glucoce, urea, calcium (Ca) and magnesium (Mg) measured. A significant positive correlation was found between the levels of glucose, urea and Ca and the number of days from calving. A significant negative correlation was found between the level of urea and the time of first post partum ovulation. A significant positive correlation was found between the level of glucose and the time of conception. No correlation was found between the blood parameters and the number of AI per animal, the length of first post partum ovarian cycle or the ammount of progesterone found during that cycle. A distinct, although not statistically significant, tendency towards a negative correlation between the level of glucose and the time of first post partum ovulation was found. Our results show that the levels of glucose and urea shortly after parturition do indicate the time of onset of post partum ovarian cyclicity. Our findings indicate that low blood glucose and urea values early post partum lead to subclinical or clinical ketosis which can considerably delay the onset of ovarian activity.

Distribution of Cystatin C Amyloid Deposits in the Icelandic Patients with Hereditary Cystatin C Amyloid Angiopathy

Abstract: Cystatin C, a basic microprotein inhibitor of lysosomal proteinases is a precursor of the amyloid fibril deposition in patients with hereditary cystatin C amyloid angiopathy (HCCAA) in Iceland. Cystatin C amyloid deposits were demonstrated immunohistochemically in the following areas. Firstly within the CNS in practically all arteries and arterioles throughout the CNS. Massive cystatin C amyloid was also present in interstitial tissue of the basal ganglia and the hippocampus, especially perivascularly. Spinal pia mater showed positive immuno-staining in all cases as did frequently the arachnoid and arachnoid granulations. Secondly, outside the CNS cystatin C amyloid deposits were demonstrated in the walls of small arteries in all lymphnodes investigated independent of localization in the body. Amyloid material was also detected in the inter-lobular connective tissue of the submandibular salivary gland. These findings suggest that the diagnosis of HCCAA can now be supported by two laboratory methods: Estimation of cystatin C in the cerebrospinal fluid and immunohistochemical study of lymphnode biopsies.