Islet amyloid polypeptide (IAPP, or amylin) is one of the major secretory products of β-cells of the pancreatic islets of Langerhans. It is a regulatory peptide with putative function both locally in ...the islets, where it inhibits insulin and glucagon secretion, and at distant targets. It has binding sites in the brain, possibly contributing also to satiety regulation and inhibits gastric emptying. Effects on several other organs have also been described. IAPP was discovered through its ability to aggregate into pancreatic islet amyloid deposits, which are seen particularly in association with type 2 diabetes in humans and with diabetes in a few other mammalian species, especially monkeys and cats. Aggregated IAPP has cytotoxic properties and is believed to be of critical importance for the loss of β-cells in type 2 diabetes and also in pancreatic islets transplanted into individuals with type 1 diabetes. This review deals both with physiological aspects of IAPP and with the pathophysiological role of aggregated forms of IAPP, including mechanisms whereby human IAPP forms toxic aggregates and amyloid fibrils.
Brønsted acid sites on supported Nb- and W-oxides are active and selective for the dehydration of glycerol to form acrolein. Adding oxygen to the feed of glycerol and water improves the stability of ...the catalyst. Display omitted
•Supported W- and Nb-oxides are active for dehydration of glycerol to form acrolein.•Brønsted acid W and Nb sites are selective for acrolein formation.•Deactivation of the catalyst occurs with time on stream.•Addition of oxygen to the feed gives reduced deactivation rate.•With oxygen, W-oxide on TiO2 gives 80% selectivity to acrolein at high conversion.
Hypothetical monolayer loadings of niobium and tungsten oxide supported on alumina, silica, and titania were investigated as catalysts for the dehydration of glycerol to produce acrolein. Besides activity measurements, to have information about the supported structures, the catalysts were characterized by XRD, Raman spectroscopy, XPS, XANES, and FTIR combined with adsorption of pyridine and CO2. Compared with silica showing the presence of crystalline Nb2O5 and WO3, alumina and titania gave better dispersion and formation of hydrated niobate and tungstate species. Deactivation of the catalysts occurred with time on stream. However, the stability was improved considerably by adding oxygen to the feed. A dependence of the selectivity to acrolein on the Brønsted acidity of the catalyst was observed. Under anaerobic conditions, an alumina-supported mixed Nb–W-oxide catalyst gave a selectivity of more than 70% for glycerol conversions above 40%. Even better selectivity was obtained using a catalyst with tungsten oxide supported on titania, which gave 80% selectivity under aerobic conditions at high conversion.
The common swift (Apus apus) is adapted to an aerial lifestyle, where food and nest material are captured in the air. Observations have prompted scientists to hypothesize that swifts stay airborne ...for their entire non-breeding period 1, 2, including migration into sub-Saharan Africa 3–5. It is mainly juvenile common swifts that occasionally roost in trees or buildings before autumn migration when weather is bad 1, 6. In contrast, the North American chimney swift (Chaetura pelagica) and Vaux’s swift (C. vauxi) regularly settle to roost in places like chimneys and buildings during migration and winter 7, 8. Observations of common swifts during the winter months are scarce, and roost sites have never been found in sub-Saharan Africa. In the breeding season, non-breeding individuals usually spend the night airborne 9, whereas adult nesting birds roost in the nest 1. We equipped common swifts with a micro data logger with an accelerometer to record flight activity (years 1–2) and with a light-level sensor for geolocation (year 2). Our data show that swifts are airborne for >99% of the time during their 10-month non-breeding period; some individuals never settled, but occasional events of flight inactivity occurred in most individuals. Apparent flight activity was lower during the daytime than during the nighttime, most likely due to prolonged gliding episodes during the daytime when soaring in thermals. Our data also revealed that twilight ascents, previously observed during the summer 10, occur throughout the year. The results have important implications for understanding physiological adaptations to endure prolonged periods of flight, including the need to sleep while airborne.
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•Common swifts remain airborne for 10 months of their non-breeding period•Dawn and dusk ascents occur throughout the migration and wintering periods•Periodic nocturnal landings of short duration occur in most individuals•A new micro data logger with optimized sampling routines made this research possible
Hedenström et al. show that common swifts almost never land during their 10-month migration and wintering periods. Occasional nightly landings occur in winter, but they are often brief, and accumulated time not flying is less than 1%. These findings provide evidence of a long-standing conjecture about the aerial lifestyle in common swifts.
Every year, billions of seasonal migrants connect continents by transporting nutrients, energy, and pathogens between distant communities and ecosystems. For animals that power their movements by ...endogenous energy stores, the daily energy intake rates strongly influence the speed of migration. If access to food resources varies cyclically over the season, migrants sensitive to changes in daily energy intake rates may adjust timing of migration accordingly. As an effect, individuals adjusting to a common temporal cycle are expected to approach synchrony in foraging and movement. A large-scale periodic pattern, such as the dark-light cycle of the moon, could thus synchronize migrations across animal populations. However, such cyclic effects on the temporal regulation of migration has not been considered. Here, we show the temporal influence of the lunar cycle on the movement activity and migration tactics in a visual hunting nocturnal insectivore and long-distance migrant, the European nightjar, Caprimulgus europeaus. We found that the daily foraging activity more than doubled during moonlit nights, likely driven by an increase in light-dependent fuelling opportunities. This resulted in a clear cyclicity also in the intensity of migratory movements, with occasionally up to 100% of the birds migrating simultaneously following periods of full moon. We conclude that cyclic influences on migrants can act as an important regulator of the progression of individuals and synchronize pulses of migratory populations, with possible downstream effects on associated communities and ecosystems.
The use of accelerometers has become an important part of biologging techniques for large-sized birds with accelerometer data providing information about flight mode, wing-beat pattern, behaviour and ...energy expenditure. Such data show that birds using much energy-saving soaring/gliding flight like frigatebirds and swifts can stay airborne without landing for several months. Successful accelerometer studies have recently been conducted also for free-flying small songbirds during their entire annual cycle. Here we review the principles and possibilities for accelerometer studies in bird migration. We use the first annual actograms (for red-backed shrike
Lanius collurio
) to explore new analyses and insights that become possible with accelerometer data. Actogram data allow precise estimates of numbers of flights, flight durations as well as departure/landing times during the annual cycle. Annual and diurnal rhythms of migratory flights, as well as prolonged nocturnal flights across desert barriers are illustrated. The shifting balance between flight, rest and different intensities of activity throughout the year as revealed by actogram data can be used to analyse exertion levels during different phases of the life cycle. Accelerometer recording of the annual activity patterns of individual birds will open up a new dimension in bird migration research.
Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture ...and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to today's turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%.
Flight activity recorders have recently confirmed that alpine and common swifts spend the majority of their non‐breeding period on the wing, which may last 6–10 months. Here we test the hypothesis ...that the closely related pallid swift, a species with a breeding distribution around the Mediterranean, lead a similar aerial life‐style during its migration and wintering periods. The pallid swift usually lays two clutches in one season and therefore spends more time in the breeding area than the common swift. We successfully tracked four pallid swifts with data loggers that record light for geolocation and acceleration every 5 min to monitor flight activity. The birds wintered south of the Sahel in west Africa from the Ivory Coast to Cameroon. The pallid swifts spent the majority of their non‐breeding time in flight, especially the first two months after leaving the breeding area in autumn, while a few landing events occurred during the winter. The total time grounded was < 1%, similar to that of the common and alpine swifts. The mass specific flight metabolic rate of swifts is similar to the average non‐breeding metabolic rate of a long distance terrestrial migrant, suggesting swifts are not more likely to procure oxidative damage as a consequence of continuous flight than other migrants. The open airspace used by swifts may provide a relatively safe habitat that explain the high survival rate found in swifts.
Recent advances in tracking technology are based on the use of miniature sensors for recording new aspects of individual migratory behaviour. In this study, we have used activity data loggers with ...barometric and temperature sensors to record the flight altitudes as well as ground elevations during stationary periods of migratory songbirds. We tracked one individual of red‐backed shrike and one great reed warbler along their autumn migration from Europe to Africa. Both individuals performed their migration stepwise in travel segments and climbed most metres during the passage across the Mediterranean Sea and the Sahara Desert and least metres during the first flight segment in Europe. The great reed warbler reached its highest flight altitude of 3950 m a.s.l. during the travel segment from Europe to west Africa, while the red‐backed shrike reached 3650 m a.s.l as maximum flight altitude during its travel segment from Sahel to southern Africa. Both individuals used both lowlands and highlands for resting periods along their migrations. Furthermore, temperature decreased with increasing altitude during migratory flights for both individuals, highlighting the potential to determine flight duration from temperature measurements. Finally, we discuss how barometric data could be used to investigate birds’ responses to changes in air pressure as a cue for departures on migratory flights. This new technique, i.e. using a miniature data logger with barometric pressure sensor to estimate flight altitudes and ground elevations, will open up new avenues for research and importantly advance our understanding on how small birds behave during migratory flights.
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