Re-analysis of the Levanluhta skeletal material : Sex and stature estimation of individuals in an Iron Age water burial in Finland

Levanluhta, an Iron Age water burial site in Finland, and its material consisting of commingled skeletal remains and artifacts, has been studied by several researchers over the past 100 years, resulting in multiple interpretations of the people and the site. Previous skeletal analyses have concluded that the majority of the individuals represented in the remains were females and children and were of relatively short stature, so possibly nutritionally deprived. This study re-analyzed the commingled adult human remains with updated methods. The methods applied in this study to estimate sex and stature were based on more representative European reference samples than the previously applied methods. The methods included morphology, osteometrics, and computed tomography (CT) scans. Our results indicated that depending on the reference data, the majority of the individual adult bones including os coxae (73%, n = 45) and long bones (humerus 83%-89%, n = 52; radius 72%-89%, n = 47; ulna 50%-65%, n = 58; femur 92%-100%, n = 25; tibia 77%-85%, n = 26) were classified as females based on their size and morphology. The cross-sectional bone properties of humerii, femora, and tibiae visualized using CT scanning also supported these findings. However, the cranial morphology did not show as clear female-biased sex ratio as other methods (42% females, 33% males, 24% undetermined, n = 33). In females, the mean stature based on the tibia (155.3 cm, n = 10) was within the range of the coeval European females and did not necessarily indicate nutritional deprivation, which is in line with previously published stable isotope findings from the site. The mean stature based on the tibia suggested that the Levanluhta males were short (164.0 cm, n = 3), but final interpretations were limited due to the small number of male individuals. The current study affirmed that the Levanluhta skeletal assemblage was female biased and gave new insights into interpretation of the stature.Peer reviewe

A topographically controlled tipping point for complete Greenland ice sheet melt

A major impact of anthropogenic climate change is the crossing of tipping points, which may have severe consequences such as the complete mass loss of the Greenland ice sheet (GrIS). At present, the GrIS is losing mass at an accelerated rate, largely due to a steep decrease in its surface mass balance (SMB; the balance between snow accumulation and surface ablation from melt and associated runoff). Previous work on the magnitude and nature of a threshold for GrIS complete melt remains controversial. Here, we explore a potential SMB threshold for complete melt of the GrIS; the impact and interplay of surface melt and glacial isostatic adjustment (GIA) in determining this threshold; and whether the GrIS exhibits characteristics commonly associated with tipping points, such as sensitivity to external forcing. To this end, we force the Community Ice Sheet Model v.2 (CISM2) by cycling different SMB climatologies previously calculated at multiple elevation classes with the Community Earth System Model v.2 (CESM2) in a two-way coupled CESM2–CISM2 transient simulation of the global climate and GrIS under high CO2 forcing. The SMB calculation in CESM2 has been evaluated with contemporary observations and high-resolution modelling and includes an advanced representation of surface melt and snow–firn processes. We find a positive SMB threshold for complete GrIS melt of 230 ± 84 Gt yr−1, corresponding to a 60 % decrease in SMB and to a global mean warming of +3.4 K compared to pre-industrial CESM2–CISM2 simulated values. In our simulations, a small change in the initial SMB forcing (from 255 to 230 Gt yr−1) and global mean warming above pre-industrial levels (from +3.2 to +3.4 K) causes an abrupt change in the GrIS final volume (from 50 % mass to nearly complete deglaciation). This nonlinear behaviour is caused by the SMB–elevation feedback, which responds to changes in surface topography due to surface melt and GIA. The GrIS tips from ∼ 50 % mass towards nearly complete melt when the impact of melt-induced surface lowering outweighs that of GIA-induced bedrock uplift and the (initially positive) SMB becomes and remains negative for at least a few thousand years. We also find that the GrIS tips towards nearly complete melt when the ice margin in the central west unpins from a coastal region with high topography and SMB. We show that if we keep the SMB fixed (i.e. no SMB–elevation feedback) in this relatively confined region, the ice sheet retreat is halted and nearly complete GrIS melt is prevented even though the initial SMB forcing is past the threshold. Based on the minimum GrIS configuration in previous paleo-ice-sheet modelling studies, we suggest that the surface topography in the central west might have played a role in preventing larger GrIS loss during the last interglacial period ∼ 130–115 kyr BP.</p

Metabolism before, during and after anaesthesia in colic and healthy horses

<p>Abstract</p> <p>Background</p> <p>Many colic horses are compromised due to the disease state and from hours of starvation and sometimes long trailer rides. This could influence their muscle energy reserves and affect the horses' ability to recover. The principal aim was to follow metabolic parameter before, during, and up to 7 days after anaesthesia in healthy horses and in horses undergoing abdominal surgery due to colic.</p> <p>Methods</p> <p>20 healthy horses given anaesthesia alone and 20 colic horses subjected to emergency abdominal surgery were anaesthetised for a mean of 228 minutes and 183 minutes respectively. Blood for analysis of haematology, electrolytes, cortisol, creatine kinase (CK), free fatty acids (FFA), glycerol, glucose and lactate was sampled before, during, and up to 7 days after anaesthesia. Arterial and venous blood gases were obtained before, during and up to 8 hours after recovery. Gluteal muscle biopsy specimens for biochemical analysis of muscle metabolites were obtained at start and end of anaesthesia and 1 h and 1 day after recovery.</p> <p>Results</p> <p>Plasma cortisol, FFA, glycerol, glucose, lactate and CK were elevated and serum phosphate and potassium were lower in colic horses before anaesthesia. Muscle adenosine triphosphate (ATP) content was low in several colic horses. Anaesthesia and surgery resulted in a decrease in plasma FFA and glycerol in colic horses whereas levels increased in healthy horses. During anaesthesia muscle and plasma lactate and plasma phosphate increased in both groups. In the colic horses plasma lactate increased further after recovery. Plasma FFA and glycerol increased 8 h after standing in the colic horses. In both groups, plasma concentrations of CK increased and serum phosphate decreased post-anaesthesia. On Day 7 most parameters were not different between groups. Colic horses lost on average 8% of their initial weight. Eleven colic horses completed the study.</p> <p>Conclusion</p> <p>Colic horses entered anaesthesia with altered metabolism and in a negative oxygen balance. Muscle oxygenation was insufficient during anaesthesia in both groups, although to a lesser extent in the healthy horses. The post-anaesthetic period was associated with increased lipolysis and weight loss in the colic horses, indicating a negative energy balance during the first week post-operatively.</p

Attenuated Fatigue in Slow Twitch Skeletal Muscle during Isotonic Exercise in Rats with Chronic Heart Failure

During isometric contractions, slow twitch soleus muscles (SOL) from rats with chronic heart failure (chf) are more fatigable than those of sham animals. However, a muscle normally shortens during activity and fatigue development is highly task dependent. Therefore, we examined the development of skeletal muscle fatigue during shortening (isotonic) contractions in chf and sham-operated rats. Six weeks following coronary artery ligation, infarcted animals were classified as failing (chf) if left ventricle end diastolic pressure was >15mmHg. During isoflurane anaesthesia, SOL with intact blood supply was stimulated (1s on 1s off) at 30Hz for 15 min and allowed to shorten isotonically against a constant afterload. Muscle temperature was maintained at 37°C. In resting muscle, maximum isometric force (Fmax) and the concentrations of ATP and CrP were not different in the two groups. During stimulation, Fmax and the concentrations declined in parallel sham and chf. Fatigue, which was evident as reduced shortening during stimulation, was also not different in the two groups. The isometric force decline was fitted to a bi-exponential decay equation. Both time constants increased transiently and returned to initial values after approximately 200 s of the fatigue protocol. This resulted in a transient rise in baseline tension between stimulations, although this effect which was less prominent in chf than sham. Myosin light chain 2s phosphorylation declined in both groups after 100 s of isotonic contractions, and remained at this level throughout 15 min of stimulation. In spite of higher energy demand during isotonic than isometric contractions, both shortening capacity and rate of isometric force decline were as well or better preserved in fatigued SOL from chf rats than in sham. This observation is in striking contrast to previous reports which have employed isometric contractions to induce fatigue

Interactions and Evolution of the Greenland Ice Sheet Surface Mass Balance with the Global Climate

One of the major consequences of ongoing global warming is the melting of the Greenland ice sheet (GrIS). The GrIS, as the world’s second­ largest freshwater reservoir, has the potential to raise sea levels by 7.4 m (Bamber et al., 2018a,b). Such a sea­ level rise would have a devastating effect on coastal societies, where a large fraction of the world’s population lives. Therefore, constraining the GrIS’ contribution to sea ­level rise is an important and vital task to plan for the future efficiently.Since the 1990s, the GrIS has been losing mass at an accelerated rate (Ender­lin et al., 2014; Bamber et al., 2018a; Shepherd et al., 2019; Oppenheimer et al., 2019). We can separate GrIS mass loss into the contribution from the surface mass balance (SMB) and ice discharge. The SMB is the primary contributor to recent GrIS mass loss (van den Broeke et al., 2016); thus, there is a need for accurate projec­ tions of GrIS SMB, and a thorough understanding of physical processes governing the surface mass loss under global warming. Further, the GrIS also interacts with the climate system (Fyke et al., 2018), highlighting the need for coupled global climate projections.This thesis’ primary targets are to1. Investigate the co­evolution of the GrIS SMB and the global climate under increased greenhouse gases.2. Examine the impact of reduced Arctic sea ice on GrIS SMB 3. Make projections of future GrIS surface melt.This is achieved by using the Community Earth System Model (CESM) version 2.1 (Danabasoglu et al., 2020). CESM2 is a newly developed coupled earth system model that features an online downscaling of the SMB through elevation classes (ECs), advanced snow physics (van Kampenhout et al., 2017), and a prognostic calculation of snow albedo (Flanner and Zender, 2006). Also, the EC simulated SMB is interactive; that is, modification of surface fluxes of mass and energy is communicated to the earth system’s other components.This thesis presents analysis of some of the first simulations of Greenland ice sheet climate and SMB with the newly developed CESM2 and CESM2­CISM2. While many questions regarding the future of the GrIS remain, the results presented here contribute towards a better understanding of the coupled global climate and GrIS SMB evolution, and processes leading GrIS surface mass loss. The first steps towards making computationally efficient and robust projections of GrIS surface melt through machine learning are also taken.Physical and Space Geodes

First Application of Artificial Neural Networks to Estimate 21st Century Greenland Ice Sheet Surface Melt

Future Greenland ice sheet (GrIS) melt projections are limited by the lack of explicit melt calculations within most global climate models and the high computational cost of dynamical downscaling with regional climate models (RCMs). Here, we train artificial neural networks (ANNs) to obtain relationships between quantities consistently available from global climate model simulations and annually integrated GrIS surface melt. To this end, we train the ANNs with model output from the Community Earth System Model 2.1 (CESM2), which features an interactive surface melt calculation based on a downscaled surface energy balance. We find that ANNs compare well with an independent CESM2 simulation and RCM simulations forced by a CMIP6 subset. The ANNs estimate a melt increase for 2,081–2,100 ranging from 414 (Formula presented.) 275 Gt (Formula presented.) (SSP1-2.6) to 1,378 (Formula presented.) 555 Gt (Formula presented.) (SSP5-8.5) for the full CMIP6 suite. The primary source of uncertainty throughout the 21st century is the spread of climate model sensitivity.Physical and Space Geodes

Influence of Arctic sea-ice loss on the Greenland ice sheet climate

The Arctic is the region on Earth that is warming the fastest. At the same time, Arctic sea ice is reducing while the Greenland ice sheet (GrIS) is losing mass at an accelerated pace. Here, we study the seasonal impact of reduced Arctic sea ice on GrIS surface mass balance (SMB), using the Community Earth System Model version 2.1 (CESM2), which features an advanced, interactive calculation of SMB. Addressing the impact of sea-ice reductions on the GrIS SMB from observations is difficult due to the short observational records. Also, signals detected using transient climate simulations may be aliases of other forcings. Here, we analyze dedicated simulations from the Polar Amplification Model Intercomparison Project with reduced Arctic sea ice and compare them with preindustrial sea ice simulations while keeping all other forcings constant. In response to reduced sea ice, the GrIS SMB increases in winter due to increased precipitation, driven by the more humid atmosphere and increasing cyclones. In summer, surface melt increases due to a warmer, more humid atmosphere providing increased energy transfer to the surface through the sensible and latent heat fluxes, which triggers the melt-albedo feedback. Further, warming occurs throughout the entire troposphere over Baffin Bay. This deep warming results in regional enhancement of the 500 hPa geopotential heights over the Baffin Bay and Greenland, increasing blocking and heat advection over the GrIS’ surface. This anomalous circulation pattern has been linked to recent increases in the surface melt of the GrIS.Physical and Space GeodesyGeoscience and Remote Sensin

La résistance au gel des bétons à haute performance

A literature survey of the frost resistance of high-performance concrete (HPC) is presented in this paper. Various aspects of HPC behaviour to frost, such as ice formation, resistance to internal microcracking and scaling, and air entrainment were discussed. The survey clearly indicates that the volume of ice formed in the 0 to −20 °C range is significantly reduced by the low porosity of HPC. This reduction is often accompanied by a significant improvement of the scaling resistance. Some studies even reveal the existence of a critical water/binder ratio below which air entrainment would not be required as a protection against this type of deterioration. However, this critical water/binder ratio would not apply to internal cracking. In many instances, HPC with no air entrainment were resistant to scaling but susceptible to internal microcracking. The behaviour of HPC to frost is discussed from both theoretical and applied points of view. Key words: frost resistance, high-performance concrete, ice formation, internal microcracking, scaling. </jats:p