Bab el-Gasus in context: different approaches of the dynamics and interpretation of coffin/sarcophagus evolution in Ancient Egypt

Middle Eastern Studie

Layer effects on the magnetic textures in magnets with local inversion asymmetry

Magnets with broken local inversion symmetries are interesting candidates for chiral magnetic textures such as skyrmions and spin spirals. The property of these magnets is that each subsequent layer can possess a different Dzyaloshniskii-Moriya interaction (DMI) originating from the local inversion symmetry breaking. Given that new candidates of such systems are emerging, with the Van der Waals crystals and magnetic multilayer systems, it is interesting to investigate how the chiral magnetic textures depend on the number of layers and the coupling between them. In this article, we model the magnetic layers with a classical Heisenberg spin model, where the sign of the DMI alternates for each consecutive layer. We use Monte Carlo simulations to examine chiral magnetic textures and show that the pitch of magnetic spirals is influenced by the interlayer coupling and the number of layers. We observe even-odd effects in the number of layers, where we observe a suppression of the spin spirals for even layer numbers. We give an explanation for our findings by proposing a net DMI in systems with strongly coupled layers. Our results can be used to determine the DMI in systems with a known number of layers, and for new technologies based on the tunability of the spiral wave length.Comment: 8 pages, 8 figures and 2 table

Spectroscopic study of the morphology development of closed-cell polyurethane foam using bio-based malonic acid as chain extender

In this study the advantages of using bio-based multi-functional malonic acid salt as chain extender in preparing closed cell polyurethane foams is demonstrated. We found that the presence of malonic acid salt can alter the reaction kinetics, segmental mobility and hence the relative kinetics of polyurethane and polyurea formation. By analyzing the infrared active vibrations, it is demonstrated that the formation of urethane and urea linkages is accelerated at the initial stage of reaction, resulting in enhanced viscosity build-up attributed to the catalytic activity of the triethylamine complexed with malonic acid. The relative kinetics in formation of different morphological features thus can be used to control the cell opening process. These results, combining information on polymerization kinetics, gas evolution and phase separation, illustrate the capability of using malonic acid salt as the chain extender to manipulate polyurethane foam morphology and its potential application in polyurethane closed cell foam systems

Structural transitions of skyrmion lattices in synthetic antiferromagnets

Thin magnetic films with Dzyaloshinskii-Moriya interactions are known to host skyrmion crystals, which typically have a hexagonal lattice structure. We investigate skyrmion-lattice configurations in synthetic antiferromagnets, i.e., a bilayer of thin magnetic films that is coupled antiferromagnetically. By means of Monte-Carlo simulations, we find that by tuning the interlayer coupling the skyrmion lattice structure can be tuned from square to hexagonal. We give a simple interpretation for the existence of this transition based on the fact that for synthetic antiferromagnetic coupling the skyrmions in different layers repel each other and form each others' dual lattice. Our findings may be useful to experimentally switch between two lattice configurations to, for example, modify spin-wave propagation

CO2 exchange and carbon balance in two grassland sites on eutrophic drained peat soils.

In this study we investigated the role of intensive and extensive dairy farm practices on CO₂ exchange and the carbon balance of peatlands by means of eddy covariance (EC) measurements. Year long EC measurements were made in two adjacent farm sites on peat soil in the western part of the Netherlands. One site (Stein) is a new meadow bird reserve and is managed predominantly by mowing in June and August. The second site (Oukoop) is an intensive dairy farm. Maximum photosynthetic uptake of the grass sward (range 2 to 34 mu mol CO₂ m(-2) s(-1)) showed a close and similar linear relationship with Leaf Area Index (LAI; range 1 to 5) except in maturing hay meadows, where maximum photosynthetic uptake did not increase further. Apparent quantum yield varied between 0.02 and 0.08 (mean 0.045) mu mol CO₂ mu mol(-1) photons at both sites and was significantly correlated with LAI during the growth season. Ecosystem Respiration at 10 degrees C (R-10) calculated from the year round data set was 3.35 mu mol CO₂ m(-2) s(-1) at Stein and 3.69 mu mol CO₂ m(-2) s(-1) at Oukoop. Both sites were a source of carbon in winter and a sink during summer with net ecosystem exchange varying between 50 to 100 mmol CO₂ m(-2) d(-1) in winter to below -400 mmol CO₂ m(-2) d(-1) in summer. Periodically, both sites became a source after mowing. Net annual ecosystem exchange (NEE) for Stein was -5.7 g C m(-2) a(-1) and for Oukoop 133.9 g C m(-2) a(-1). When biomass removal, manure applications and estimates of methane emissions ware taken into account, both eutrophic peat meadows are a strong source for C around 420 g C m(-2) a(-1)

A school-based intervention to reduce overweight and inactivity in children aged 6–12 years: study design of a randomized controlled trial

Background Effective interventions to prevent overweight and obesity in children are urgently needed especially in inner-city neighbourhoods where prevalence of overweight and inactivity among primary school children is high. A school based intervention was developed aiming at the reduction of overweight and inactivity in these children by addressing both behavioural and environmental determinants. Methods/design The main components of the intervention (Lekker Fit!) are the re-establishment of a professional physical education teacher; three (instead of two) PE classes per week; additional sport and play activities outside school hours; fitness testing; classroom education on healthy nutrition, active living and healthy lifestyle choices; and the involvement of parents. The effectiveness of the intervention is evaluated through a cluster randomized controlled trial in 20 primary schools among grades 3 through 8 (6–12 year olds). Primary outcome measures are BMI, waist circumference and fitness. Secondary outcome measures are assessed in a subgroup of grade 6–8 pupils (9–12 year olds) through classroom questionnaires and constitute of nutrition and physical activity behaviours and behavioural determinants. Multilevel regression analyses are used to study differences in outcomes between children in the intervention schools and in control schools, taking clustering of children within schools into account. Discussion Hypotheses are that the intervention results in a lower prevalence of children being overweight and an improved mean fitness score, in comparison with a control group where the intervention is not implemented. The results of our study will contribute to the discussion on the role of physical education and physical activity in the school curriculum. Trial registration [ISRCTN84383524

Naproxen affects multiple organs in fish but is still an environmentally better alternative to diclofenac

The presence of diclofenac in the aquatic environment and the risks for aquatic wildlife, especially fish, have been raised in several studies. One way to manage risks without enforcing improved wastewater treatment would be to substitute diclofenac (when suitable from a clinical perspective) with another non-steroidal anti-inflammatory drug (NSAID) associated with less environmental risk. While there are many ecotoxicity-studies of different NSAIDs, they vary extensively in set-up, species studied, endpoints and reporting format, making direct comparisons difficult. We previously published a comprehensive study on the effects of diclofenac in the three-spined stickleback (Gasterosteus aculeatus). Our present aim was to generate relevant effect data for another NSAID (naproxen) using a very similar setup, which also allowed direct comparisons with diclofenac regarding hazards and risks. Sticklebacks were therefore exposed to naproxen in flow-through systems for 27 days. Triplicate aquaria with 20 fish per aquarium were used for each concentration (0, 18, 70, 299 or 1232 mu g/L). We investigated bioconcentration, hepatic gene expression, jaw lesions, kidney and liver histology. On day 21, mortalities in the highest exposure concentration group unexpectedly reached >= 25 % in all three replicate aquaria, leading us to terminate and sample that group the same day. On the last day (day 27), the mortality was also significantly increased in the second highest exposure concentration group. Increased renal hematopoietic hyperplasia was observed in fish exposed to 299 and 1232 mu g/L. This represents considerably higher concentrations than those expected in surface waters as a result of naproxen use. Such effects were observed already at 4.6 mu g/L in the experiment with diclofenac (lowest tested concentration). Similar to the responses to diclofenac, a concentration-dependent increase in both relative hepatic gene expression of c7 (complement component 7) and jaw lesions were observed, again at concentrations considerably higher than expected in surface waters. Naproxen bioconcentrated less than diclofenac, in line with the observed effect data. An analysis of recent sales data and reported concentrations in treated sewage effluent in Sweden suggest that despite higher dosages used for naproxen, a complete substitution would only be expected to double naproxen emissions. In summary, naproxen and diclofenac produce highly similar effects in fish but the environmental hazards and risks are clearly lower for naproxen. Hence, if there are concerns for environmental risks to fish with diclofenac, a substitution would be advisable when naproxen presents an adequate alternative from a clinical point-of-view