Spatial variability of snow chemistry in western Dronning Maud Land, Antarctica

During the austral summer of 1993-94 a number of 1-2 m deep snow pits were sampled in connection with firn-coring in western Dronning Maud Land, Antarctica. The traverse went from 800 to about 3000 m a.s.l. upon the high-altitude plateau. Profiles of cations (Na+, K+, Mg2+, Ca2+), anions (Cl−, NO3-, SO4 2- , CH3SO3 −) and stable oxygen isotopes (δ18O) from 11 snow pils are presented here. Close to the coast 2 m of snow accumulates in about 2-3 years, whilst at sites on the high-altitude plateau 2 m of snow accumulates in 10—14 years. The spatial variation in ion concentrations shows that the ions can be divided into two groups, one with sea-salt elements and methane sulfonate and the other with nitrate and sulfate. For the sca-salt elements and methane sulfonate the concentrations decrease with increasing altitude and increasing distance from the coast, as well as with decreasing temperature and decreasing accumulation rate. For nitrate and sulfate the concentrations are constant or increase with respect to these parameters. This pattern suggests that the sources for sca-salt elements and methane sulfonate are local, whereas the sources for nitrate and sulfate are a mixture of local and long-range transport

La representación de la memoria histórica en el espacio del museo

The present essay offers a reflection on the role of museum spaces in society as political actors and as builders of the historical memory of the armed conflict in Colombia. It examines the function of art as a tool for resistance and the symbolic reparation of the victims, as well as the concepts of representation derived from the exhibition contexts of the agents within this problematic and the challenges and strategies that these contexts imply.El presente ensayo ofrece una reflexión sobre el papel de los espacios museísticos en la sociedad como actores políticos y como constructores de la memoria histórica del conflicto armado en Colombia. Examina la función del arte como herramienta de resistencia y la reparación simbólica de las víctimas, así como los conceptos de representación derivados de los contextos expositivos de los agentes dentro de esta problemática y los desafíos y estrategias que implican estos contextos

Factors associated with deep sternal wound infection after open-heart surgery in a Danish registry

Objective: To conduct a comprehensive multivariate analysis of variables associated with deep sternal wound infection, after open-heart surgery via median sternotomy. Method: A retrospective cohort of all adult patients, who underwent open-heart surgery at Odense University Hospital between 01‐01-2000 and 31-12-2020 was extracted from the West Danish Heart Registry. Data were analyzed using maximum likelihood logistic regression. Results: A total of 15,424 patients underwent open-heart surgery and 244 developed a deep sternal wound infection, equivalent to 1,58 %. After data review 11,182 entries were included in the final analysis, of which 189 developed DSWI, equivalent to 1,69 %. Multivariate analysis found the following variables to be associated with the development of deep sternal wound infection (odds ratios and 95%confidens intervals in parentheses): Known arrhythmia (1.70; 1.16–2.44), Left Ventricular Ejection Fraction (1.66; 1.02–2.58), Body Mass Index 25–30 (1.66; 1.12–2.52), Body Mass Index 30–35 (2.35; 1.50–3.71), Body Mass Index 35–40 (3.61; 2.01–6.33), Body Mass Index 40+ (3.70; 1.03–10.20), Age 60–69 (1.64; 1.04–2.67), Age 70–79 (1.95; 1.23–3.19), Chronic Obstructive Pulmonary Disease (1.77; 1.21–2.54), Reoperation (1.63; 1.06–2.45), Blood transfusion in surgery (1.09; 1.01–1.17), Blood transfusion in intensive care unit (1.03; 1.01–1.06), Known peripheral atherosclerosis (1.82; 1.25–2.61), Current smoking (1.69; 1.20–2.35), Duration of intubation (1.33; 1.12–1.57). Conclusion: Increased risk of deep sternal wound infection after open-heart surgery is a multifactorial problem, while some variables are unchangeable others are not. Focus should be on optimizing the condition of the patient prior to surgery e.g. weight loss and smoking. But also factors surrounding the patient e.g. preventing blood loss and minimizing intubation time.</p

Two-hundred-year Record of Biogenic Sulfur in a South Greenland Ice Core (20D)

The concentration of methanesulfonic acid (MSA) was determined in a shallow south central Greenland ice core(20D). This study provides a high-resolution record of the DMS-derived biogenic sulfur in Greenland precipitation over the past 200 years. The mean concentration of MSA is 3.30 ppb(σ = 2.38 ppb,n = 1134). The general trend of MSA is an increase from 3.01 to 4.10 ppb between 1767 and 1900, followed by a steady decrease to 2.34 ppb at the present time. This trend is in marked contrast to that of non-sea-salt sulfate (nss SO42-), which increases dramatically after 1900 due to the input of anthropogenic sulfur. The MSA fraction ((MSA/(MSA+ nss SO42-))* 100) ranges from a mean of 15% in preindustrial ice to less than 5% in recent ice. These MSA fraction suggest that approximately 5 to 40% of the sulfur in recent Greenland ice is of biological origin. It is suggested that there is a significant low-latitude component to the biogenic sulfur in the core and that variations in the MSA fraction reflect changes in the relative strengths of low- and high-latitude inputs. The data shown o evidence for a strong dependence of dimethyl sulfide(DMS) emissions on sea surface temperature during the last century. There is also no indication that the yield of MSA from DMS oxidation has been altered by increased NOx levels over the North Atlantic during this period

Technical innovations and optimizations for intermediate ice-core drilling operations

The British Antarctic Survey, in collaboration with Laboratoire de Glaciologie et Géophysique de l’Environnement, has in recent years successfully drilled to bedrock on three remote sites around the Antarctic Peninsula. Based on the experience from the multi-season project at Berkner Island (948m depth, 2002–05) we optimized the drill set-up to better suit two subsequent single-season projects at James Ross Island (363m depth, 2008) and Fletcher Promontory (654m depth, 2012). The adaptations, as well as the reasons for them, are discussed in detail and include a drill tent set-up without a trench; drilling without a borehole casing with a relatively low fluid column height; and using a shorter drill. These optimizations were aimed at reducing cargo loads and installation time while maintaining good core quality, productivity and a safe working environment. In addition, we introduce a number of innovations, ranging from a new lightweight cable tensioning device and drill-head design to core storage and protection trays. To minimize the environmental impact, all the drill fluid was successfully recovered at both sites and we describe and evaluate this operation

Spatial Variability of Snow Chemistry in Western Dronning Maud Land, Antarctica

During the austral summer of 1993-94 a number of 1-2 m deep snow pits were sampled in connection with firn-coring in western Dronning Maud Land, Antarctica. The traverse went from 800 to about 3000 m a.s.l. upon the high-altitude plateau. Profiles of cations (Na+, K+, Mg2+, Ca2+), anions (CI-, NO3-, SO42-, CH3SO3-) and stable oxygen isotopes (δ18O) from II snow pits are presented here. Close to the coast 2 m of snow accumulates in about 2-3 years, whilst at sites on the high-altitude plateau 2 m of snow accumulates in 10-14 years. The spatial variation in ion concentrations shows that the ions can be divided into two groups, one with sea-salt elements and methane sulfonate and the other with nitrate and sulfate. For the sea-salt elements and methane sulfonate the concentrations decrease with increasing altitude and increasing distance from the coast, as well as with decreasing temperature and decreasing accumulation rate. For nitrate and sulfate the concentrations are constant or increase with respect to these parameters. This pattern suggests that the sources for sea-salt elements and methane sulfonate are local, whereas the sources for nitrate and sulfate are a mixture of local and long-range transport

Oxygen isotope composition of surface snow collected along the traverse route from Zhongshan Station toward Dome A, Antarctica

Oxygen isotope composition of surface snow sampled in the austral summer of 1998/1999 along the traverse route from Zhongshan Station toward Dome A, Antarctica is measured with the conventional mass spectrometer technique. The results of measurement show that oxygen isotope composition of surface snow varies in a wide range from -22.51‰ to -50.67‰, and has a tendency that isotopic values gradually decrease with increase of distance from Zhongshan Station and altitude. Linear regression analysis indicates that there exists good correlation between oxygen isotope composition of surface snow and distance from Zhongshan Station, altitude and/or latitude, which actually reflects the close relation between stable isotope composition and air temperature

RADIX: a minimal-resources rapid-access drilling system

Determining the expected age at a potential ice-core drilling site on a polar ice sheet generally depends on a combination of information from remote-sensing methods, estimates of current accumulation and modelling. This poses irreducible uncertainties in retrieving an undisturbed ice core of the desired age. Although recently perfected radar techniques will improve the picture of the ice sheet below future drilling sites, rapid prospective drillings could further increase the success of deep drilling projects. Here we design and explore a drilling system for a minimum-size rapid-access hole. The advantages of a small hole are the low demand for drilling fluid, low overall weight of the equipment, fast installing and de-installing and low costs. We show that, in theory, drilling of a 20mm hole to a depth of 3000m is possible in ~4 days. First concepts have been realized and verified in the field. Both the drill cuttings and the hole itself can be used to characterize the properties of the ice sheet and its potential to provide a trustworthy palaeo-record. A candidate drilling site could be explored in ~2 weeks, which would enable the characterization of several sites in one summer season