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Showing papers by "University of Iceland published in 1992"


Journal ArticleDOI
TL;DR: Tephrochronological dating of postglacial volcanism in the Dyngjufjoll volcanic complex, a major spreading center in the Icelandic Rift Zone, indicates a high production rate in the millennia following deglaciation as compared to the present low productivity.
Abstract: Tephrochronological dating of postglacial volcanism in the Dyngjufjoll volcanic complex, a major spreading center in the Icelandic Rift Zone, indicates a high production rate in the millennia following deglaciation as compared to the present low productivity. The visible and implied evidence indicates that lava production in the period 10 000–4500 bp was at least 20 to 30 times higher than that in the period after 2900 bp but the results are biased towards lower values for lava volumes during the earlier age periods since multiple lava layers are buried beneath younger flows. The higher production rate during the earlier period coincides with the disappearance of glaciers of the last glaciation. Decreasing lithostatic pressure as the glacier melts and vigorous crustal movements caused by rapid isostatic rebound may trigger intense volcanism until a new pressure equilibrium has been established.

191 citations


Journal ArticleDOI
TL;DR: In this article, a positive linear relation between maximum throw and length of the Holocene faults was found, which can be explained by a similar relation between fault length and width, where the width (depth) must be the smallest (controlling) dimension of many faults.
Abstract: The divergent plate boundary in Iceland is characterized by 40–80 km long and 5–10 km wide swarms of tension fractures (∼102 m long) and normal faults (∼103 m long). The upper part of the crust is mainly composed of lava flows, with abundant columnar joints that are mostly perpendicular to the lava contacts. The lava flows are horizontal at the surface of the rift zone but become tilted at the rate of 1° for every 150 m depth in the crust. At the surface of the rift zone the joints are vertical and parallel to the vertical principal stress. Because of tilting of the lava pile, the columnar joints become oblique to this stress, hence becoming potential shear fractures, and form echelon sets at greater depths in the crust. Theoretical considerations suggest that normal faults start to nucleate on sets of en echelon columnar joints and/or large-scale tension fractures at crustal depths of 0.5–1.5 km. The width (depth) must be the smallest (controlling) dimension of many faults. Nevertheless, there is a positive linear relation (r = 0.91) between maximum throw and length of the Holocene faults. If the faults grow as self-similar structures, the throw-length relationship can be explained by a similar relation between fault length and width.

164 citations


Journal ArticleDOI
TL;DR: It is concluded that panretinal photocoagulation improves the oxygen supply to the inner retina and thereby minimizes the influence of retinal ischemia in diabetic retinopathy.

143 citations


Journal ArticleDOI
TL;DR: In this paper, it is shown that glass shards can retain their overall chemical integrity on at least a four millennial time-scale in contrasting depositional environments in Iceland and Scotland, and that an acid digestion process, the most practical method for extracting tephra from peat, does not significantly bias the results of major element analysis by electron microprobe.
Abstract: This paper tests two assumptions fundamental to the use of fine-grained silicic tephras from Iceland for creating chronological frameworks in northwest Europe. It is shown firstly, that glass shards can retain their overall chemical integrity on at least a four millennial time-scale in contrasting depositional environments in Iceland and Scotland, and secondly, that an acid digestion process, the most practical method for extracting tephra from peat, does not significantly bias the results of major element analysis by electron microprobe. The implication is that there is great potential and an appropriate method for developing both the resolution and the spatial coverage of chronologies based on silicic Icelandic tephras in northwest Europe.

141 citations


Journal ArticleDOI
TL;DR: The eruption of the Hekla volcano in South Iceland on 17 January 1991, and came to an end on 11 March, produced mainly andesitic lava with an estimated volume of 0.15 km3.
Abstract: The eruption that started in the Hekla volcano in South Iceland on 17 January 1991, and came to an end on 11 March, produced mainly andesitic lava. This lava covers 23 km2 and has an estimated volume of 0.15 km3. This is the third eruption in only 20 years, whereas the average repose period since 1104 is 55 years. Earthquakes, as well as a strain pulse recorded by borehole strainmeters, occurred less than half an hour before the start of the eruption. The initial plinian phase was very short-lived, producing a total of only 0.02 km3 of tephra. The eruption cloud attained 11.5 km in height in only 10 min, but it became detached from the volcano a few hours later. Several fissures were active during the first day of the eruption, including a part of the summit fissure. By the second day, however, the activity was already essentially limited to that segment of the principal fissure where the main crater subsequently formed. The average effusion rate during the first two days of the eruption was about 800 m3 s−1. After this peak, the effusion rate declined rapidly to 10–20 m3 s−1, then more slowly to 1 m3 s−1, and remained at 1–12 m3 s−1 until the end of the eruption. Site observations near the main crater suggest that the intensity of the volcanic tremor varied directly with the force of the eruption. A notable rise in the fluorine concentration of riverwater in the vicinity of the eruptive fissures occurred on the 5th day of the eruption, but it levelled off on the 6th day and then remained essentially constant. The volume and initial silica content of the lava and tephra, the explosivity and effusion rate during the earliest stage of the eruption, as well as the magnitude attained by the associated earthquakes, support earlier suggestions that these parameters are positively related to the length of the preceeding repose period. The chemical difference between the eruptive material of Hekla itself and the lavas erupted in its vicinity can be explained in terms of a density-stratified magma reservoir located at the bottom of the crust. We propose that the shape of this reservoir, its location at the west margin of a propagating rift, and its association with a crustal weakness, all contribute to the high eruption frequency of Hekla.

132 citations


Journal ArticleDOI
06 Aug 1992-Nature
TL;DR: In this paper, the authors reported the observation of a strain transient at the divergent (spreading) plate boundary in Iceland, and used a simple one-dimensional model with a thin elastic layer overlying a viscous layer, which yields a stress diffusivity of 1.1 a±0.3 m2s−1.
Abstract: INTERACTION of the elastic lithosphere with the underlying anelastic asthenosphere causes strain to propagate along the Earth's surface in a diffusion-like manner following tectonism at plate boundaries. This process transfers stress between adjacent tectonic segments and influences the temporal tectonic pattern along a plate boundary. Observations of such strain transients have been rare, and have hitherto been confined to strike-slip and underthrusting plate boundaries1. Here we report the observation of a strain transient at the divergent (spreading) plate boundary in Iceland. A Global Positioning System survey undertaken a decade after an episode of dyke intrusion accompanying several metres of crustal spreading reveals a spatially varying strain field with the expected diffusion-pulse shape and an amplitude three times greater than the 5.7 cm that would be expected from the average spreading rate2. A simple one-dimensional model with a thin elastic layer overlying a viscous layer fits the data well and yields a stress diffusivity of 1.1 a±0.3 m2s−1. Combined with struc-tural information from magnetotelluric measurements, this implies a viscosity of 0.3−2 × 1019 Pa s—a value comparable to that derived for Iceland from post-glacial rebound23, but low compared with estimates for mantle viscosity obtained elsewhere3.

121 citations


Journal ArticleDOI
TL;DR: The results suggest that carnocin UI49 belongs to the class of bacteriocins termed lantibiotics, and the sequence of the first seven amino acid residues was determined to be N-Gly-Ser-Glu-Ile-Gln-Pro-Arg.
Abstract: A bacteriocin-producing Carnobacterium sp. was isolated from fish. The bacteriocin, termed carnocin UI49, was purified to homogeneity by a four-step purification procedure, including hydrophobic interaction chromatography and reverse-phase chromatography. Carnocin UI49 has a bactericidal mode of action. It was shown to be heat tolerant and stable between pH 2 and 8. At pH above 8, carnocin UI49 was rapidly inactivated. Amino acid analysis revealed a composition of about 35 to 37 amino acids in addition to an unidentified peak which migrates at the position of lanthionine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis suggests a molecular weight of about 4,500 to 5,000. Mass spectrometry gave a molecular weight of 4,635, which is about 1,000 larger than that calculated from the amino acid analysis data. Performic acid oxidation of carnocin UI49, followed by amino acid hydrolysis, revealed the presence of cysteic acid. The sequence of the first seven amino acid residues was determined to be N-Gly-Ser-Glu-Ile-Gln-Pro-Arg. After the seventh amino acid, carnocin UI49 was not available for further Edman degradation. The results suggest that carnocin UI49 belongs to the class of bacteriocins termed lantibiotics.

116 citations


Journal ArticleDOI
TL;DR: A facultative psychrotrophic lactic acid bacterium isolated from fresh fish was identified as Carnobacterium piscicola on the basis of carbohydrate utilization, G + C content and 16S RNA analysis and has a bactericidic mode of action which results in lysis of sensitive cells.
Abstract: A facultative psychrotrophic lactic acid bacterium isolated from fresh fish was identified as Carnobacterium piscicola on the basis of carbohydrate utilization, G + C content and 16S RNA analysis. Its bacteriocin, designated carnocin UI49, is produced during the mid-exponential phase of growth at temperatures between 15 degrees C and 34 degrees C. Carnocin UI49 is active against a large number of closely-related lactic acid bacteria including carnobacteria, lactobacilli, pediococci and lactococci. Furthermore, the bacteriocin has a bactericidic mode of action which results in lysis of sensitive cells. Maximum bactericidal activity is observed at 34 degrees C with a decrease in activity down to 15 degrees C where it is completely abolished.

103 citations


Journal ArticleDOI
TL;DR: The feeding performance of two morphs of a trophically polymorphic fish, the arctic charr Salvelinus alpinus, feeding on zooplankton, was studied in the laboratory and suggests that benthic morphs are phenotypically inferior at using the pelagic food niche.
Abstract: The feeding performance of two morphs of a trophically polymorphic fish, the arctic charr Salvelinus alpinus, feeding on zooplankton, was studied in the laboratory. Limnetic morphs, with a fusiform body, terminal mouth, short pectoral fins, and relatively long and dense gill rakers, fed at significantly higher rates on Daphnia and Cyclops than did benthic morphs. The benthic morphs were characterized by a chunky body form, subterminal mouth, long pectoral fins, and relatively short and spaced-out gill rakers. The limnetic morphs attacked the prey at significantly higher rates and were more successful in capture. Benthic morphs were more reluctant to start feeding on zooplankton and reaction time was longer than in limnetic morphs. In the absence as well as presence of zooplankton food, the position of the two morphs in the aquaria differed markedly. The results agree with dietary differences found in field-collected fish. The limnetic morphs consume zooplankton, whereas benthic morphs specialize on Lymnaea gastropods. The results suggest that benthic morphs are phenotypically inferior at using the pelagic food niche. This implies that the current role of competitive or predatory interactions in segregating the morphs may be minor.

99 citations


Journal ArticleDOI
TL;DR: In this article, gas samples from seventeen high-temperature and twenty-two lowtemperature geothermal systems have been analyzed for chemistry and 3 He 4 He ratios, showing a consistent regional pattern: 14-19 times the atmospheric ratio in the southwest, 8-11 RA in the north, and 17-26 A in central Iceland.

96 citations


Journal ArticleDOI
TL;DR: The T cell repertoire in MS includes, besides myelin basic protein, proteolipid protein and myelin oligodendrocyte glycoprotein, also MAG and, in addition, measles and mumps virus.

Journal ArticleDOI
TL;DR: In this paper, the integrative and physiological effects of sport participation were investigated using data from a national survey of Icelandic adolescents, focusing on mental health and health related behavior, and the study showed more benefit from club sport than informal group sport, and, in turn, individual sport.
Abstract: The integrative and physiological effects of sport participation are investigated using data from a national survey of Icelandic adolescents. Focusing on mental health and health related behavior, the study shows more benefit from club sport than informal group sport, and, in turn, individual sport. As the physiological perspective suggests, beneficial effects are largely due to strenuousness of exercise. However, findings also suggest that club sport has an integrative effect when predicting positive aspects of mental health, an effect limited to urban communities, as comports with social integration theory. The idea that participation in organized social life prevents deviance and malfunctioning has been central in sociological thought ever since Durkheim. He maintains that cohesive and structured social groups provide collective ideas, sentiments, and rituals that prevent vulnerable individuals from psychological distress and suicide. Two factors obtain this preventive effect in Durkheim's view. First, an integrated society has social control mechanisms that constrain individuals and intervene if they attempt the wrong line of action ([1897] 1951, p. 209). An integrated society controls its members not only externally but also internally, since, "fashioning us in its image, [it] fills us with religious, political and moral beliefs that control our actions" (p. 212). Second, in integrated society members provide mutual "moral support" by sharing ideas and feelings and strengthening each other when exhausted (p. 210). Consequently, individuals in a state of "egoism," without sufficient control and support from others, experience considerable strain in that they lack purpose in life, lose the courage to live, and become hopeless and depressed (pp. 210, 214). In this way, Durkeim views social integration, in the form of social control and support, as a provoking agent directly affecting distress, suicide, and other social problems.

Journal ArticleDOI
TL;DR: In this article, the authors measured the surface deflation volume of Hekla volcano during the 1991 eruption of the volcano and found that it was associated with the presence of GPS control points close to the volcano.
Abstract: Between January 17 and March 11, 1991, 0.15 km3 of lava erupted initially from several radial fissures and subsequently from a single fissure on the SE flank of Hekla volcano, Iceland. Hekla is surrounded by an array of control points measured in 1989 using GPS geodesy and re-measured after the eruption. These measurements indicate that the eruption was associated with a surface deflation volume of centered on Hekla . The depth to the magma reservoir is km, poorly constrained due to the absence of GPS control points close to the volcano.

Journal ArticleDOI
TL;DR: In this paper, the lake level of Lake Langisjor at the SW edge of the Vatnajokull ice cap is estimated to have a tilt of 0.26 +/- 0.06 microrad/yr in the years of 1959-1991.
Abstract: Measurements of the lake level of Lake Langisjor at the SW edge of the Vatnajokull ice cap indicate a tilt of 0.26 +/- 0.06 microrad/yr away from the ice cap in the years of 1959-1991. The tilt is too large to be explained as an elastic Earth response to ice retreat this century, or to be caused by change in the gravitational pull of the ice cap, but it can be explained by sub-lithospheric viscous adjustment. Regional subsidence in historical times in SE Iceland can similarly be attributed to viscous adjustment resulting from the increased load of Vatnajokull during the Little Ice Age. The inferred sublithospheric viscosity is 1 x 10 exp 18 - 5 x 10 exp 19 Pa s.

Journal ArticleDOI
TL;DR: In this paper, the interactions between several commonly used preservatives, i.e. benzalkonium chloride, chlorhexidine gluconate, chlorobutanol, methylparaben and propylparabens, and 2-hydroxypropyl-β-cyclodextrin were investigated.
Abstract: The interactions between several commonly used preservatives, i.e. benzalkonium chloride, chlorhexidine gluconate, chlorobutanol, methylparaben and propylparaben, and 2-hydroxypropyl-β-cyclodextrin were investigated. The interactions were shown to be twofold. Firstly, the preservative molecules can displace the drug molecules from the cyclodextrin cavity, thus, reducing the solubilizing effects of the cyclodextrin. Secondly, the antimicrobial activity of the preservatives were reduced by formation of preservative-cyclodextrin inclusion complexes. The magnitude of the interactions were dependent on the degree of complexation.

01 Jan 1992
TL;DR: In this article, copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.
Abstract: General rights Unless other specific re-use rights are stated the following general rights apply: Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal

Journal ArticleDOI
TL;DR: It is shown rigorously that there are five regions as Z→∞ B >Z 3 .
Abstract: The ground-state energy of an atom of nuclear charge Ze and in a magnetic field B is evaluated exactly in the asymptotic regime Z\ensuremath{\rightarrow}\ensuremath{\infty}. We show rigorously that there are five regions as Z\ensuremath{\rightarrow}\ensuremath{\infty}: B\ensuremath{\ll}${\mathit{Z}}^{4/3}$, B\ensuremath{\approxeq}${\mathit{Z}}^{4/3}$, ${\mathit{Z}}^{4/3}$\ensuremath{\ll}B\ensuremath{\ll}${\mathit{Z}}^{3}$, B\ensuremath{\approxeq}${\mathit{Z}}^{3}$, B\ensuremath{\gg}${\mathit{Z}}^{3}$. Different regions have different physics and different asymptotic therories. Regions 1,2,3,5 are described exactly by a simple density-functional theory, but only in regions 1,2,3 is it of the semiclassical Thomas-Fermi form. Region 4 cannot be described exactly by any simple density-functonal theory; surprisingly, it can be described by a simple density matrix functonal theory.


Journal ArticleDOI
TL;DR: In this article, the Tertiary Reykjadalur central volcano in West Iceland, there is a remarkable change in strike, dip, thickness and percentage of sheets at a distance of about 9 km from the centre of the volcano.

Journal ArticleDOI
TL;DR: Analyses of published sequence variation of cod from Norway and Newfoundland showed that the extensive continuity of intraspecific phylogeny of cod in Iceland extends from Norway to Newfoundland and possibly to larger areas of the Atlantic.
Abstract: Restriction analysis of mitochondrial DNA was used to study genetic variation and geographic population structure of Atlantic cod from localities around Iceland. Gene phylogenies were constructed and geographic locations superimposed on these. The variation was not localized. Estimated gene flow was large. Thus, Atlantic cod in Iceland belong to a single genetic population. Analyses of published sequence variation of cod from Norway and Newfoundland showed that the extensive continuity of intraspecific phylogeny of cod in Iceland, which is very similar to other marine organisms with a similar life history, extends from Norway to Newfoundland and possibly to larger areas of the Atlantic.

Journal ArticleDOI
TL;DR: A number of cyclodextrins were examined as to their ability to stabilize doxorubicin in solution and to enhance the rate of its dissolution as mentioned in this paper, and the results showed that the modified Cyclodextrin is innocuous even when given in large doses parenterally.

Journal ArticleDOI
TL;DR: In this paper, a general discussion of the Thomas-Fermi (TF) and Thomas Fermi-Dirac (TFD) approximations for the ground state properties of matter in a magnetic field taking all Landau levels into account is presented.

Book ChapterDOI
01 Jan 1992
TL;DR: In this paper, tin oxide sensors are used to measure volatile aroma compounds of fish to evaluate fish freshness, and the results have been encouraging but further tests have to be made under normal storage conditions.
Abstract: In this project tin oxide sensors are used to measure volatile aroma compounds of fish to evaluate fish freshness. Spoilage of fish kept in ice occurs because of microbial action on the flesh. Aroma changes during spoilage of fish are well recognized and organoleptic tests have traditionally been used to evaluate fish freshness. There is, however, a demand for methods to objectively measure fish aroma quality. Gas chromatography (GC) has been used to measure volatile compounds of fish, as these provide a means to define the chemical basis of seafood aromas, but GC is not suitable for high speed on-line applications. In the work reported here, a few aroma compounds that are produced during spoilage of fish were selected and the response of tin oxide sensors to them was measured. The response of the sensors to fish odours was also measured, initially by letting the fish deteriorate at room temperature, but later also under normal storage conditions in ice. Comparison was made with sensory evaluation and methods based on chemical and physical tests. So far the results have been encouraging but further tests have to be made under normal storage conditions.

Journal ArticleDOI
TL;DR: The prevalence rate of latent thyroid carcinoma in each sex does not follow the frequency distribution of clinical disease, being 7.5% in males and 5.1% in females, and suggesting that promoting factors might be of particular importance where incidence and mortality rates are high.
Abstract: The annual incidence rate of thyroid carcinoma in Iceland is high, 4.4 pr. 100,000 men, and 11.7 pr. 100,000 women, as published by the Icelandic Cancer Registry for the period 1955-1984. This rate is more than twice that in the other Nordic countries and one of the highest incidence rates reported anywhere. This led us to investigate the prevalence rate of latent thyroid carcinoma in Iceland. We serially sectioned and examined thyroid glands from 201 consecutive forensic autopsies. Altogether, sixteen carcinomas were identified in fourteen glands: fourteen papillary, one follicular and one medullary carcinoma. We conclude that the prevalence rate of latent thyroid carcinoma in each sex does not follow the frequency distribution of clinical disease, being 7.5% in males and 5.1% in females. Comparisons between populations show the same lack of consistency. Further, most, but not all, latent carcinomas of the thyroid gland are of the papillary type. These findings suggest that promoting factors might be of particular importance where incidence and mortality rates are high, but further research is needed into the role of host resistance.


Journal ArticleDOI
TL;DR: Smokers had fewer remaining teeth and were more often edentulous than ex-smokers, smoking time not considered, who again suffered more tooth loss than those who had never smoked.
Abstract: A random sample of 1023 people 52-79 yr of age out of a group participating in a longitudinal study at the Heart Preventive Clinic of the Icelandic Heart Association in Reykjavik, Iceland, was examined. The examination was carried out in 1985-7. The results on the number of remaining teeth and total edentulousness were compared to information regarding smoking habits and social status. Total edentulousness was more common among women. Total and partial edentulousness was more frequent in the lower "employment" classes while no statistical difference was found for smoking in this respect. This, however, did not affect the significance of tobacco smoking as a factor in the loss of teeth. In general smokers had fewer remaining teeth and were more often edentulous than ex-smokers, smoking time not considered, who again suffered more tooth loss than those who had never smoked. Therefore it is concluded that tobacco smoking may be a major single independent risk factor in the loss of teeth.

Journal ArticleDOI
TL;DR: The present study shows that the lipid fraction of infant formulas is not only a source of nutrients but also a sources of antiviral and antibacterial activity following incubation with lipases.
Abstract: Six infant formulas in which triglycerides varied in the proportions of their constituent medium-chain saturated and long-chain unsaturated fatty acids were incubated with either pancreatic lipase, pancreatic lipase plus colipase, bile salt-stimulated lipase, or lipoprotein lipase and then measured for antiviral and antibacterial activity. Herpes simplex virus-1 (HSV-1) was inactivated following all incubations, with the exception of lipoprotein lipase, with one of three infant formulas with a coconut/soy blend (formula 5). After incubation of each formula with pancreatic lipase plus colipase, dilutions of these mixtures by as much as 100–250 fold still inactivated HSV-1. Lipase-treated formulas inactivated the gram-positive bacterium Staphylococcus epidermidis but were ineffective against gram-negative Escherichia coli and Salmonella enteritidis. The present study shows that the lipid fraction of infant formulas is not only a source of nutrients but also a source of antiviral and antibacterial activity following incubation with lipases.

Journal ArticleDOI
TL;DR: The correlation of the number of CD8-positive cells in the CSF with the severity of lesions and the reversed ratio of CD4/CD8- positive Cells in the diffusely infiltrated neuroparenchyma indicates that the CD8 -positive T lymphocyte may be an important effector cell in the induction of CNS lesions.

Journal ArticleDOI
TL;DR: All tested nerve types were baroreceptor dependent and there were no significant differences between the slopes relating nerve activity inhibition to increase in blood pressure (infusion of phenylephrine).
Abstract: Carlsson, S., Skarphedinsson, J. O., Delle, M., Hoffman, P. & Thoren, P. 1992. Reflex changes in post- and preganglionic sympathetic nerve activity and postganglionic sympathetic renal nerve activity upon arterial baroreceptor activation and during severe haemorrhage in the rat. Acta Physiol Scand144, 317–323. Received 19 August 1991, accepted 18 November 1991. ISSN 0001–6772. Department of Physiology, University of Goteborg, Sweden and Department of Physiology, University of Iceland, Reykjavik, Iceland. The aim of the study was to compare pre- (pre-aSNA) and postganglionic adrenal sympathetic nerve activity (post-aSNA) and postganglionic renal sympathetic nerve activity (rSNA) in rats during arterial baroreceptor activation and haemorrhage. Adrenal multifibre nerve activity was recorded in chloralose-anaesthetized Wistar rats. To test for pre-aSNA or post-aSNA in adrenal nerves, a ganglionic blocker, trimethaphan (10 mg kg-1), was administered i.v. If the nerve activity in the adrenal nerve decreased or increased the nerve was considered to contain predominantly post-or preganglionic fibres, respectively. In contrast, the renal nerves exhibit an almost pure postganglionic activity. Baroreceptor activity was tested by activation of baroreceptors, with an a-receptor agonist, phenylephrine, which was slowly infused (0.5–2 mUg kg-1 min-l), and to deactivate the baroreceptors the rats were bled down to 50 mmHg for 8 min. The experiments showed that all tested nerve types were baroreceptor dependent. There were no significant differences between the slopes relating nerve activity inhibition to increase in blood pressure (infusion of phenylephrine). During maximal inhibition there was a difference between the rSNA and pre-aSNA, 87 ± 4%, n=6, and 68±6%, n = 10 (P < 0.01) of the control value, respectively. The maximal inhibition of post-aSNA was 80 ± 3%, n=7, of the control value. During haemorrhage there was a difference between the nerve populations. Pre-aSNA responded with a marked increase within 1.5 rnin (159 ± 29% of control, n= 7) and was then maintained at that level until retransfusion. Post-aSNA responded with i transient increase, reaching 158 ± 19% of control after 1.5min but then decreased slowly during the next 3 min, reaching a value of 89 8 76 at 7.5 rnin of haemorrhage. Finally, rSNA (n = 7) responded with an initial increase (peak value 1.5 min 138 ± 16%) followed by an inhibition to a minimum of 74±12% of control. Our conclusion is that the postganglionic adrenal nerves respond in a similar way to postganglionic renal nerves during baroreceptor activation and also show the same pattern of response during haemorrhage. This might indicate that postganglionic fibres to the adrenal gland and postganglionic renal fibres to the kidney have the same target structures, i.e. blood vessels. and postganglionic adrenal fibres might therefore be of importance in adrenal blood flow regulation.

Journal ArticleDOI
TL;DR: In this paper, the authors consider the problem of finding a local net of von Neumann algebras corresponding to a given Wightman field in terms of strengthened versions of the usual positivity property.
Abstract: The subject of the paper is an old problem of the general theory of quantized fields: When can the unbounded operators of a Wightman field theory be associated with local algebras of bounded operators in the sense of Haag? The paper reviews and extends previous work on this question, stressing its connections with a noncommutive generalization of the classical Hamburger moment problem. Necessary and sufficient conditions for the existence of a local net of von Neumann algebras corresponding to a given Wightman field are formulated in terms of strengthened versions of the usual positivity property of Wightman functionals. The possibility that the local net has to be defined in an enlarged Hilbert space cannot be ruled out in general. Under additional hypotheses, e.g., if the field operators obey certain energy bounds, such an extension of the Hilbert space is not necessary, however. In these cases a fairly simple condition for the existence of a local net can be given involving the concept of “central positivity” introduced by Powers. The analysis presented here applies to translationally covariant fields with an arbitrary number of components, whereas Lorentz covariance is not needed. The paper contains also a brief discussion of an approach to noncommutative moment problems due to Dubois-Violette, and concludes with some remarks on modular theory for algebras of unbounded operators.