Reservoirs and radiocarbon: ¹⁴C dating problems in Myvatnssveit, Northern Iceland

This paper examines 2 potential sources of the radiocarbon offset between human and terrestrial mammal (horse) bones recovered from Norse (~AD 870–1000) pagan graves in Mývatnssveit, north Iceland. These are the marine and freshwater 14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine 14C reservoir effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusk shell) at 2 archaeological sites in Mývatnssveit and 1 site on the north Icelandic coast. These produced 3 new ΔR values for the north coast of Iceland, indicating a ΔR of 106 ± 10 14C yr at AD 868–985, and of 144 ± 28 14C yr at AD 1280–1400. These values are statistically comparable and give an overall weighted mean ΔR of 111 ± 10 14C yr. The freshwater reservoir effect was similarly quantified using freshwater fish bones from a site in Mývatnssveit. These show an offset of between 1285 and 1830 14C yr, where the fish are depleted in 14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2 into the groundwater and subsequently into Lake Mývatn. We conclude the following: i) some of the Norse inhabitants of Mývatnssveit incorporated non-terrestrial resources into their diet that may be identified from the stable isotope composition of their bone collagen; ii) the MRE off the north Icelandic coast during the Norse period fits a spatial gradient of wider North Atlantic MRE values with increasing values to the northwest; and iii) it is important to consider the effect that geothermal activity could have on the 14C activity of samples influenced by groundwater at Icelandic archaeological sites

Individual risk assessment and information technology to optimise screening frequency for diabetic retinopathy.

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field.AIMS/HYPOTHESIS: The aim of this study was to reduce the frequency of diabetic eye-screening visits, while maintaining safety, by using information technology and individualised risk assessment to determine screening intervals. METHODS: A mathematical algorithm was created based on epidemiological data on risk factors for diabetic retinopathy. Through a website, www.risk.is , the algorithm receives clinical data, including type and duration of diabetes, HbA(1c) or mean blood glucose, blood pressure and the presence and grade of retinopathy. These data are used to calculate risk for sight-threatening retinopathy for each individual's worse eye over time. A risk margin is defined and the algorithm recommends the screening interval for each patient with standardised risk of developing sight-threatening retinopathy (STR) within the screening interval. We set the risk margin so that the same number of patients develop STR within the screening interval with either fixed annual screening or our individualised screening system. The database for diabetic retinopathy at the Department of Ophthalmology, Aarhus University Hospital, Denmark, was used to empirically test the efficacy of the algorithm. Clinical data exist for 5,199 patients for 20 years and this allows testing of the algorithm in a prospective manner. RESULTS: In the Danish diabetes database, the algorithm recommends screening intervals ranging from 6 to 60 months with a mean of 29 months. This is 59% fewer visits than with fixed annual screening. This amounts to 41 annual visits per 100 patients. CONCLUSION: Information technology based on epidemiological data may facilitate individualised determination of screening intervals for diabetic eye disease. Empirical testing suggests that this approach may be less expensive than conventional annual screening, while not compromising safety. The algorithm determines individual risk and the screening interval is individually determined based on each person's risk profile. The algorithm has potential to save on healthcare resources and patients' working hours by reducing the number of screening visits for an ever increasing number of diabetic patients in the world

A Severe Throat Infection - Case Report

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenWe report a case of Lemierre?s syndrome or, human necrobacillosis, in a 33 year old icelandic male. A severe clinical picture, fulfilling all the criteria for this syndrome, is described. With antibiotic therapy, and critical care, the outcome was successful. A brief overview of infections due to Fusobacterium necro phorum, with special emphasis on Lemierre?s syndrome, is presented. Etiology, clinical symptoms, treatment and prognosis of this syndrome are dis cussed. We believe this to be the first case of human necrobacillosis to be reported in Iceland.Sjúkrasaga Þrjátíu og þriggja ára gamall bóndi, áður hraust­ur, kom á bráðamóttöku Fjórðungssjúkrahússins á Akureyri (FSA). Hann hafði veikst sex dögum áður með háum hita, miklum slappleika og verkjum aftan í hálsi. Hann var alveg rúmfastur, kastaði mikið upp en var ekki með niðurgang. Allan tímann var hann með óstöðv­andi hiksta. Kona hans tók eftir að hann var móður og svaf illa. Hann mældist með hita um 40° C og fór að lokum til heilsugæslulæknis sem sá að hann var gulur og fárveikur og sendi hann á bráðamóttöku FSA. Við komu á FSA var hann fárveikur (septískur), lá á bekk, vakandi og áttaður, mjög þvoglumæltur, og skalf mikið. Blóðþrýstingur var 140/85 mmHg liggj­andi og 128/64 mmHg sitjandi. Púls 119/mín, reglu­legur. Öndunartíðni 36/mín. Hiti 39,8°C í enda­þarmi. Hann var gulur á húð og í augnhvítu. Mikil þreifi­eymsli voru í hnakka og aftan á hálsi en ekki hnakkastífleiki. Hann var mjög þurr á vörum, með blóð­skorpur í munni og brúnleita, að því er virt­ist, fláka af yfirborðsdrepi á tungu. Hann var mjög bólginn í koki. Fíngert brak heyrðist yfir hægra lunga. Við hjartahlustun heyrðust eðlilegir hjartatónar og slagbilsóhljóð (systólískt). Kviður var aumur undir hægri rifjaboga en engar líffærastækkanir né aðrar fyrirferðaraukningar fundust. Hann var með kylfufingur (talið vera meðfætt) og flísablæðingar sáust undir nöglum. Nöglin á hægri stórutá var inngróin og talsvert sár og bólguholdgun (granulation) umhverfis en ekki merki um bráða sýkingu. Maðurinn var að nálgast sýkingalost án augljósrar orsakar

The role of inertia for the rotation of a nearly spherical particle in a general linear flow

We analyse the angular dynamics of a neutrally buoyant nearly spherical particle immersed in a steady general linear flow. The hydrodynamic torque acting on the particle is obtained by means of a reciprocal theorem, regular perturbation theory exploiting the small eccentricity of the nearly spherical particle, and assuming that inertial effects are small, but finite.Comment: 7 pages, 1 figur

Direct calculation of the spin stiffness on square, triangular and cubic lattices using the coupled cluster method

We present a method for the direct calculation of the spin stiffness by means of the coupled cluster method. For the spin-half Heisenberg antiferromagnet on the square, the triangular and the cubic lattices we calculate the stiffness in high orders of approximation. For the square and the cubic lattices our results are in very good agreement with the best results available in the literature. For the triangular lattice our result is more precise than any other result obtained so far by other approximate method.Comment: 5 pages, 2 figure

Temporal and spatial variations in freshwater 14C reservoir effects: Lake Myvatn, Northern Iceland

Lake Mývatn is an interior highland lake in northern Iceland that forms a unique ecosystem of international scientific importance and is surrounded by a landscape rich in archaeological and palaeoenvironmental sites. A significant Freshwater 14C Reservoir Effect (FRE) has been identified in carbon from the lake at some Norse (c.870-1000 AD) archaeological sites in the wider region (Mývatnssveit). Previous AMS measurements indicated this FRE was ~1500-1900 14C years. Here we present the results of a study using stable isotope and 14C measurements to quantify the Mývatn FRE for both the Norse and modern periods. This work has identified a temporally variable FRE that is greatly in excess of previous assessments. New, paired samples of contemporaneous bone from terrestrial herbivores and omnivores (including humans) from Norse sites demonstrate at least some omnivore diets incorporated sufficient freshwater resources to result in a herbivore-omnivore age offset of up to 400 14C yrs. Modern samples of benthic detritus, aquatic plants, zooplankton, invertebrates and freshwater fish indicate an FRE in excess of 5000 14C yrs in some species. Likely geothermal mechanisms for this large FRE are discussed, along with implications for both chronological reconstruction and integrated investigation of stable and radioactive isotop

Dimer Expansion Study of the Bilayer Square Lattice Frustrated Quantum Heisenberg Antiferromagnet

The ground state of the square lattice bilayer quantum antiferromagnet with nearest ($J_1$) and next-nearest ($J_2$) neighbour intralayer interaction is studied by means of the dimer expansion method up to the 6-th order in the interlayer exchange coupling $J_3$. The phase boundary between the spin-gap phase and the magnetically ordered phase is determined from the poles of the biased Pad\'e approximants for the susceptibility and the inverse energy gap assuming the universality class of the 3-dimensional classical Heisenberg model. For weak frustration, the critical interlayer coupling decreases linearly with $\alpha (= J_2/J_1)$. The spin-gap phase persists down to $J_3=0$ (single layer limit) for 0.45 \simleq \alpha \simleq 0.65. The crossover of the short range order within the disordered phase is also discussed.Comment: 4 pages, 6 figures, One reference adde

Meissner effect in honeycomb arrays of multi-walled carbon nanotubes

We report Meissner effect for type-II superconductors with a maximum Tc of 19 K, which is the highest value among those in new-carbon related superconductors, found in the honeycomb arrays of multi-walled CNTs (MWNTs). Drastic reduction of ferromagnetic catalyst and efficient growth of MWNTs by deoxidization of catalyst make the finding possible. The weak magnetic anisotropy, superconductive coherence length (- 7 nm), and disappearance of the Meissner effect after dissolving array structure indicate that the graphite structure of an MWNT and those intertube coupling in the honeycomb array are dominant factors for the mechanism.Comment: 6 page