Luminescence dating of sediments from Underhoull and Lund, Unst, Shetland

This report concerns optically stimulated luminescence (OSL) investigations of sediments from the the foreshore at Burga Sands, Underhoull, and a dune section at Lund, in south-west Unst (Shetland). Samples were collected in February 2016 to establish the timing of sand accumulation, adding to an expanding set of dated sand blows in the Northern Isles and Scotland. The resulting chronologies define the local environmental record of sand movements in the vicinity of Underhoull and Lund, with their adjacent Norse longhouses and chapel. The sediment stratigraphies on the foreshore of Burga Sands were explored through four profiles, comprising the natural accumulations adjacent to two noosts (profiles 1 and 2), and the substrate sequences immediately beneath the noosts (P3&4). The dune section at Lund was explored in a single profile (P5). This report describes the progression from fieldwork and sampling, through initial luminescence screening measurements made with the portable OSL reader (on 45 samples), to subsequent calibrated analysis in the laboratory, first, to characterise the OSL and IRSL signals from each sample, then by targeted quantitative OSL dating on a further set of 10 samples. The ‘field profiles’ provided the first indication that the substrate stratigraphies at Underhoull, extend from the late glacial period to the modern day. The maxima and dynamic ranges in signal intensities for the sequences beneath the noosts, suggest that the construction and modification of these structures were temporally distinct. For the Lund section, the range in signal intensities through these sediments, indicate a shorter chronology, which was confirmed by subsequent characterisation of the profiling samples in the laboratory. The following chronology was obtained for the Underhoull section: 1) onset of sand activity, as recorded in the sedimentary archives of profiles 1 and 2, at 3.22 ± 0.29 ka (1210 ± 290BC; SUTL2861) and 1.99 ± 0.15 ka (AD30 ± 150; SUTL2863) 2) modification and re-build of the first noost at 0.48 ± 0.06 ka (AD1540 ± 60; SUTL2866) 3) construction of the second noost at 0.81 ± 0.07 ka (AD1210 ± 70; SUTL2867) 4) continued sand movements into the early 20th century AD (0.12 ± 0.06 ka; AD1900 ± 60; SUTL2862), with arguably heightened activity at the onset of the Little Ice Age (0.64 ± 0.10 ka; AD 1380 ± 60; SUTL2866). For the Lund dune section, the sediment chronology spans from the early 14th century AD through to the early 18th century AD (0.70 ± 0.05 ka; SUTL2868, through 0.52 ± 0.04 ka; SUTL2869, to 0.31 ± 0.02 ka; SUTL2870), corresponding with the onset and waning stages of the Little Ice Age. The chronology presented here is consistent with an emerging regional framework of sand movements in the Northern Isles and Scotland, with activity in the Neolithic, Early and Late Bronze Ages, the Iron Age, the Viking/Medieval period, and Little Ice Age. The Underhoull section dated here provides a broad chronology for sand blow and, importantly, places sediments underneath two noosts into the late Norse/ Mediaeval period. The dune section dates a high resolution local record within the last 700 years. Opportunities to extend the high resolution palaeoenvironmental record were identified in the adjacent land and dune-scape, and especially in the palaeo-loch landward of the Lund section, which has received sand in the past

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Determinants of mortality in non-neutropenic ICU patients with candidaemia

Introduction: Candidaemia in critically-ill intensive care unit (ICU) patients is associated with high crude mortality. Determinants of mortality – particularly those amenable to potential modification – are incompletely defined. Methods: A nationwide prospective clinical and microbiological cohort study of all episodes of ICU-acquired candidaemia occurring in non-neutropenic adults was undertaken in Australian ICUs between 2001 and 2004. Multivariate Cox regression analyses were performed to determine independently significant variables associated with mortality. Results: 183 episodes of ICU-acquired candidaemia occurred in 183 patients during the study period. Of the 179 with microbiological data, Candida albicans accounted for 111 (62%) episodes and Candida glabrata, 32 (18%). Outcome data were available for 173: crude hospital mortality at 30 days was 56%. Host factors (older age, ICU admission diagnosis, mechanical ventilation and ICU admission diagnosis) and failure to receive systemic antifungal therapy were significantly associated with mortality on multivariate analysis. Among the subset who received initial fluconazole therapy (n = 93), the crude mortality was 52%. Host factors (increasing age and haemodialysis receipt), but not organism- (Candida species, fluconazole MIC), pharmacokinetic- (fluconazole dose, time to initiation), or pharmacodynamic-related parameters (fluconazole dose:MIC ratio) were associated with mortality. Process of care measures advocated in recent guidelines were implemented inconsistently: follow-up blood cultures were obtained in 68% of patients, central venous catheters removed within five days in 80% and ophthalmological examination performed in 36%. Conclusions: Crude mortality remains high in Australian ICU patients with candidaemia and is overwhelmingly related to host factors but not treatment variables (the time to initiation of antifungals or fluconazole pharmacokinetic and pharmacodynamic factors). The role and timing of early antifungal intervention in critically-ill ICU patients requires further investigation.Deborah J.E. Marriott, E. Geoffrey Playford, Sharon Chen, Monica Slavin, Quoc Nguyen, David Ellis and Tania C. Sorrell for the Australian Candidaemia Stud

Reprioritization of liver export protein synthesis in patients with decompensated alcoholic liver disease

Background: Decompensated alcoholic liver disease is associated with abnormalities in protein synthesis. The relationship of this to reprioritisation of hepatic export proteins and markers of the systemic inflammatory response is unclear. We examined the longitudinal relationship between albumin and fibrinogen synthetic rates and disease severity in decompensated alcoholic liver cirrhosis. Patients and Methods: Hepatic protein synthetic rates were measured in patients with decompensated Childs grade B or C alcohol-related cirrhosis using a validated technique, based on incorporation of deuterated phenylalanine into the plasma pool of albumin and fibrinogen. As a measure of liver export protein reprioritisation, we calculated the fibrinogen and albumin synthetic rates and the Acute Phase Protein Quotient (APPQ; the ratio of these rates). Serum CRP and fibrin D-Dimer were recorded. Measurements were at baseline and on clinical recovery at 4-6 weeks. Results: 17 patients were studied. All patients had hypoalbuminaemia with elevated median C-reactive protein (CRP), D-dimer, bilirubin and prothrombin times. Median albumin and fibrinogen synthetic rates were reduced resulting in marginally increased APPQ. On follow up (n=10), there was reduction in Child-Pugh score (p<0.01), plasma concentrations of Fibrin D-dimer (p<0.01), CRP (p<0.01), bilirubin (p<0.01) and prothrombin time (p<0.01). Plasma albumin concentrations increased (p<0.01) and synthetic rates of both albumin (p<0.05) and fibrinogen (p<0.10) increased marginally such that median APPQ remained similar. Conclusion: Patients with decompensated alcohol-related cirrhosis had low albumin and fibrinogen synthetic rates and raised CRP indicative of systemic inflammation. On recovery, albumin synthetic rate increased and CRP levels fell, although albumin and fibrinogen synthetic rates remained below normal. Further studies assessing the interaction between protein synthesis and systemic inflammation in chronic liver disease are indicated