Laser-Accelerated proton beams as diagnostics for cultural heritage

This paper introduces the first use of laser-generated proton beams as diagnostic for materials of interest in the domain of Cultural Heritage. Using laser-accelerated protons, as generated by interaction of a high-power short-pulse laser with a solid target, we can produce proton-induced X-ray emission spectroscopies (PIXE). By correctly tuning the proton flux on the sample, we are able to perform the PIXE in a single shot without provoking more damage to the sample than conventional methodologies. We verify this by experimentally irradiating materials of interest in the Cultural Heritage with laser-accelerated protons and measuring the PIXE emission. The morphological and chemical analysis of the sample before and after irradiation are compared in order to assess the damage provoked to the artifact. Montecarlo simulations confirm that the temperature in the sample stays safely below the melting point. Compared to conventional diagnostic methodologies, laser-driven PIXE has the advantage of being potentially quicker and more efficien

Neogene fluvial deposits along the south-west coast of South Africa understanding the palaeoclimate through proxies

Branched glycerol dialkyl glycerol tetraether (GDGTs) membrane lipids have been used as a new proxy for the reconstruction of terrestrial palaeoclimates. These biomarkers (or molecular ‗fossils‘) in conjunction with palynology, have been effective in the novel analysis of Miocene organic-rich sediments from three South African west coast sites at Rondeberg, Noordhoek and Langebaanweg. Lastly, a Quaternary south coast site at Rietvlei, South Africa, was also studied to further elucidate the extent of use of this new proxy. The fluvial peat and organic-rich deposits of the Elandsfontyn Formation (Sandveld Group) were investigated at Noordhoek, Langebaanweg and Rondeberg to provide new evidence for the climate and vegetation patterns during Miocene in this region. Drill-core and quarry samples from all four sites were freeze-dried, powered, and prepared for biogeochemical and palynological analyses. The methylation index of branched tetraethers (MBT) and cyclisation ratio of branched tetraethers (CBT) proxies were used to calculate the mean annual air temperature (MAAT) and pH values of the organic-rich horizons at time of deposition. The Branched versus isoprenoid index of tetraethers (BIT) was used to assess the relative contributions of marine archaeal and terrestrial bacterial tetraethers, and thereby assess the validity of the MBT, CBT and calculated palaeoenvironmental factors. The results presented in this thesis suggest that the use of the MBT/CBT proxy has significant potential in southern Africa, and may complement previously attempted palaeoclimatic and palaeoecological studies of Neogene-aged South African sediments. This type of research has the capacity to provide palaeoenvironmental information where other proxies may be absent. Results indicate that all sites yielded branched tetraether membrane lipids with the exception of Rondeberg, where GDGTs were below detection as a result of poor preservation conditions. Palynological investigation confirmed proxy derived temperatures. Furthermore palynomorph analyses supplemented earlier studies of the Noordhoek site and were piloted for the Rondeberg site, reaffirming alternating sequences of tropical and subtropical palynofloras. The MAATs, likewise, show variability and pronounced trends through time at the Langebaanweg and Noordhoek sites, generally corresponding with the variation and diversity of the pollen population. The terrestrial MAAT results appear to compliment Southern Hemisphere sea level changes associated with Antarctic glaciations. Additionally, this data shows a pattern similar to the Southern and Northern Hemisphere marine isotope records of relative fluctuations in the global climate and sea level change from the early to middle Miocene. The application of these past climate change indicators have been proved to be useful in the reconstruction of South Africa Miocene palaeoclimates, and may aid in understanding the consequences of climate change in the Cape region

Position of the Triassic-Jurassic boundary in South Africa and Lesotho : a multidisciplinary approach aimed at improving the chronostratigraphy and biostratigraphy of the Elliot Formation, Stormberg Group

The continental red bed succession of the main Karoo Basin in South Africa and Lesotho, the Elliot Formation (Stormberg Group, Karoo Supergroup), is a significant stratigraphic unit for the regional and global understanding of the Late Triassic - Early Jurassic evolution of terrestrial vertebrate faunas, however, the temporal resolution of its biostratigraphy is inadequate for detailed regional and global correlations. The main aim of this dissertation is to build a more comprehensive chronostratigraphic framework of the Late Triassic - Early Jurassic Elliot Formation by combining and constraining its biostratigraphy with new results obtained using magnetostratigraphic techniques. This dissertation presents magnetostratigraphic data from ten measured stratigraphic sections in the Elliot Formation across the main Karoo Basin in South Africa and Lesotho

The sauropodomorph biostratigraphy of the ElliotFormation of southern Africa: Tracking the evolution ofSauropodomorpha across the Triassic–Jurassic boundary

The latest Triassic is notable for coinciding with the dramatic decline of many previously dominant groups, followed by the rapid radiation of Dinosauria in the Early Jurassic. Among the most common terrestrial vertebrates from this time, sauropodomorph dinosaurs provide an important insight into the changing dynamics of the biota across the Triassic–Jurassic boundary. The Elliot Formation of South Africa and Lesotho preserves the richest assemblage of sauropodomorphs known from this age, and is a key index assemblage for biostratigraphic correlations with other similarly-aged global terrestrial deposits. Past assessments of Elliot Formation biostratigraphy were hampered by an overly simplistic biozonation scheme which divided it into a lower “Euskelosaurus” Range Zone and an upper Massospondylus Range Zone. Here we revise the zonation of the Elliot Formation by: (i) synthesizing the last three decades’ worth of fossil discoveries, taxonomic revision, and lithostratigraphic investigation; and (ii) systematically reappraising the stratigraphic provenance of important fossil locations. We then use our revised stratigraphic information in conjunction with phylogenetic character data to assess morphological disparity between Late Triassic and Early Jurassic sauropodomorph taxa. Our results demonstrate that the Early Jurassic upper Elliot Formation is considerably more taxonomically and morphologically diverse than previously thought. In contrast, the sauropodomorph fauna of the Late Triassic lower Elliot Formation remains relatively poorly understood due to the pervasive incompleteness of many key specimens, as well as the relative homogeneity of their diagnostic character suites. Our metrics indicate that both Elliot Formation and global sauropodomorph assemblages had greater morphological disparity within the Early Jurassic than the Late Triassic. This result is discussed in the context of changing palaeoclimatic conditions, as well as macroevolutionary events associated with the end-Triassic extinction

Cerebral microbleed distribution following cardiac surgery can mimic cerebral amyloid angiopathy.

BACKGROUND AND AIMS: Having anecdotally noted a high frequency of lobar-restricted cerebral microbleeds (CMBs) mimicking cerebral amyloid angiopathy (CAA) in patients with previous cardiac surgery (especially valve replacement) presenting to our transient ischaemic attack (TIA) clinic, we set out to objectively determine the frequency and distribution of microbleeds in this population. METHODS: We performed a retrospective comparative cohort study in consecutive patients presenting to two TIA clinics with either: (1) previous coronary artery bypass grafting (CABG) (n=41); (2) previous valve replacement (n=41) or (3) probable CAA (n=41), as per the Modified Boston Criteria, without prior cardiac surgery. Microbleed number and distribution was determined and compared. RESULTS: At least one lobar-restricted microbleed was found in the majority of cardiac surgery patients (65%) and 32/82 (39%) met diagnostic criteria for CAA. Valve replacement patients had a higher microbleed prevalence (90 vs 51%, p<0.01) and lobar-restricted microbleed count (2.6±2.7 vs 1.0±1.4, p<0.01) than post-CABG patients; lobar-restricted microbleed count in both groups was substantially less than in CAA patients (15.5±20.4, p<0.01). In postcardiac surgery patients, subcortical white matter (SWM) microbleeds were proportionally more frequent compared with CAA patients. Receiver operator curve analysis of a 'location-based' ratio (calculated as SWM/SWM+strictly-cortical CMBs), revealed an optimal ratio of 0.45 in distinguishing cardiac surgery-associated microbleeds from CAA (sensitivity 0.56, specificity 0.93, area under the curve 0.71). CONCLUSION: Lobar-restricted microbleeds are common in patients with past cardiac surgery, however a higher proportion of these CMBs involve the SWM than in patients with CAA

Feasibility of a Mitral Annuloplasty With the Capability for Peri- and Postoperative Adjustment

Abstract Surgical repair with implantation of a mitral annuloplasty ring is the gold standard treatment for mitral regurgitation. However, outcomes are variable and recurrent mitral regurgitation is not uncommon. A REshapeable Mitral Annuloplasty DevIce (REMADI) is proposed, which consists of a fully encapsulated low melting temperature alloy. The alloy is solid and rigid at body temperature and provides traction force to shape the annulus. When heated using a noncontact method, the alloy melts and the REMADI becomes malleable. The REMADI is engaged with the mitral valve annulus using anchors which automatically deploy upon contact. A passive beating porcine heart model was used to demonstrate the feasibility of the REMADI device, which was deployed, engaged, and used to reduce the diameter of the mitral valve annulus.Armstrong Trus

Quantifying the Shift Toward Transcatheter Aortic Valve Replacement in Low-Risk Patients: A Meta-Analysis.

BACKGROUND: In recent years, use of transcatheter aortic valve replacement has expanded to include patients at intermediate- and low-risk cohorts. We sought to determine disease prevalence and treatment distribution including transcatheter aortic valve replacement eligibility in low-risk patients across 37 advanced economies. METHODS AND RESULTS: Four systematic searches were conducted across MEDLINE, EMBASE, and the Cochrane database for studies evaluating disease prevalence, severity, decision making, and survival in patients with aortic stenosis. Estimates of disease prevalence and treatment eligibility were calculated using stochastic simulation and population data for the 37 countries comprising the International Monetary Fund's advanced economies index. Fifty-six studies comprising 42 965 patients were included across 5 domains: prevalence, severity, symptom status, treatment modality, and outcome. The pooled prevalence in the general population aged 60 to 74 years and >75 years was 2.8% (95% confidence interval [CI], 1.4%-4.1%) and 13.1% (95% CI, 8.2%-17.9%), respectively-corresponding to an estimated 16.1 million (95% CI, 12.2-20.3) people in 37 advanced economies. Of these, an estimated 3.2 million (95% CI, 2.2-4.4) patients have severe aortic stenosis with 1.9 million (95% CI, 1.3-2.6) eligible for surgical aortic valve replacement. There are ≈485 230 (95% CI, 284 550-66 7350) high-risk/inoperable patients, 152 690 (95% CI, 73 410-263 000) intermediate-risk patients, and 378 890 (95% CI, 205 130-610 210) low-risk patients eligible for transcatheter aortic valve replacement. CONCLUSIONS: With a prevalence of 4.5%, an estimated 16.1 million people aged ≥60 years across 37 advanced economies have aortic stenosis. Of these, there are ≈1.9 million patients eligible for surgical aortic valve replacement and 1.0 million patients eligible for transcatheter aortic valve replacement.British Heart Foundation Translational Award TG/15/4/31891 (Drs De Sciscio, Brubert, and Moggridge) and British Heart Foundation Special Project Grant SP/15/5/31548 (Drs Serrani, Stasiak, and Moggridge)

Swimming and related traces of a Late Triassic freshwater community from the lower Elliot Formation, South Africa

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