First Experimental Evidence for Chaos-Assisted Tunneling in a Microwave Annular Billiard

We report on first experimental signatures for chaos-assisted tunneling in a two-dimensional annular billiard. Measurements of microwave spectra from a superconducting cavity with high frequency resolution are combined with electromagnetic field distributions experimentally determined from a normal conducting twin cavity with high spatial resolution to resolve eigenmodes with properly identified quantum numbers. Distributions of so-called quasi-doublet splittings serve as basic observables for the tunneling between whispering gallery type modes localized to congruent, but distinct tori which are coupled weakly to irregular eigenstates associated with the chaotic region in phase space.Comment: 5 pages RevTex, 5 low-resolution figures (high-resolution figures: http://linac.ikp.physik.tu-darmstadt.de/heiko/chaospub.html, to be published in Phys. Rev. Let

Regional but not global temperature variability underestimated by climate models at supradecadal timescales

Knowledge of the characteristics of natural climate variability is vital when assessing the range of plausible future climate trajectories in the next decades to centuries. The reliable detection of climate fluctuations on multidecadal to centennial timescales depends on proxy reconstructions and model simulations, as the instrumental record extends back only a few decades in most parts of the world. Systematic comparisons between model-simulated and proxy-based inferences of natural variability, however, often seem contradictory. Locally, simulated temperature variability is consistently smaller on multidecadal and longer timescales than is indicated by proxy-based reconstructions, implying that climate models or proxy interpretations might have deficiencies. In contrast, at global scales, studies found agreement between simulated and proxy reconstructed temperature variations. Here we review the evidence regarding the scale of natural temperature variability during recent millennia. We identify systematic reconstruction deficiencies that may contribute to differing local and global model–proxy agreement but conclude that they are probably insufficient to resolve such discrepancies. Instead, we argue that regional climate variations persisted for longer timescales than climate models simulating past climate states are able to reproduce. This would imply an underestimation of the regional variability on multidecadal and longer timescales and would bias climate projections and attribution studies. Thus, efforts are needed to improve the simulation of natural variability in climate models accompanied by further refining proxy-based inferences of variability.This study was undertaken by members of CVAS and 2k Network, working groups of the Past Global Changes (PAGES) Global Research association. This is a contribution to the SPACE ERC, STACY and PALMOD projects. The SPACE ERC project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 716092). STACY has been funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, project no. 395588486). This work has also been supported by the German Federal Ministry of Education and Research (BMBF), through the PalMod project (subprojects 01LP1926B (O.B.), 01LP1926D (M.C.) and 01LP1926C (B.E., P.S. and N.W.)) from the Research for Sustainability initiative (FONA). B.E. is supported by the Heinrich Böll Foundation. E.M.-C. was supported by the PARAMOUR project, funded by the Fonds de la Recherche Scientifique–FNRS and the FWO under the Excellence of Science (EOS) programme (grant no. O0100718F, EOS ID no. 30454083). A.H. was supported by a Legacy Grant from the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage. B.M. was supported by LINKA20102 and the Spanish Ministry of Science and Innovation project CEX2018‐000794‐S. The work originated from discussions at the CVAS working group of PAGES at a workshop at the Internationales Wissenschaftsforum Heidelberg, which was funded by a Hengstberger Prize. We thank N. Beech, C. Brierley, F. Gonzalez-Rouco and M. MacPartland for comments on earlier drafts of the manuscript. This manuscript uses data provided by the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP and PMIP. We thank the research groups for producing and kindly making their model outputs, measurements and palaeoclimate reconstructions available to us. Editorial assistance, in the form of language editing and correction, was provided by XpertScientific Editing and Consulting Services. We acknowledge support by the Open Access Publication Funds of Alfred-Wegener-Institut Helmholtz Zentrum für Polar- und Meeresforschung.Peer ReviewedPostprint (author's final draft

Decay of Classical Chaotic Systems - the Case of the Bunimovich Stadium

The escape of an ensemble of particles from the Bunimovich stadium via a small hole has been studied numerically. The decay probability starts out exponentially but has an algebraic tail. The weight of the algebraic decay tends to zero for vanishing hole size. This behaviour is explained by the slow transport of the particles close to the marginally stable bouncing ball orbits. It is contrasted with the decay function of the corresponding quantum system.Comment: 16 pages, RevTex, 3 figures are available upon request from [email protected], to be published in Phys.Rev.

Erythritol and xylitol differentially impact brain networks involved in appetite regulation in healthy volunteers

Background: There is a growing consensus that sugar consumption should be reduced and the naturally occurring, low-calorie sweeteners xylitol and erythritol are gaining popularity as substitutes, but their effect on brain circuitry regulating appetite is unknown. Aim: The study’s objective was to examine the effects of the two sweeteners on cerebral blood flow (rCBF) and resting functional connectivity in brain networks involved in appetite regulation, and test whether these effects are related to gut hormone release. Methods: The study was performed as a randomized, double-blind, placebo-controlled, cross-over trial. Twenty volunteers received intragastric (ig) loads of 50g xylitol, 75g erythritol, 75g glucose dissolved in 300mL tap water or 300mL tap water. Resting perfusion and blood oxygenation level-dependent data were acquired to assess rCBF and functional connectivity. Blood samples were collected for determination of CCK, PYY, insulin and glucose. Results: We found: (i) xylitol, but not erythritol, increased rCBF in the hypothalamus, whereas glucose had the opposite effect; (ii) graph analysis of resting functional connectivity revealed a complex pattern of similarities and differences in brain network properties following xylitol, erythritol, and glucose; (iii) erythritol and xylitol induced a rise in CCK and PYY, (iv) erythritol had no and xylitol only minimal effects on glucose and insulin. Conclusion: Xylitol and erythritol have a unique combination of properties: no calories, virtually no effect on glucose and insulin while promoting the release of gut hormones, and impacting appetite-regulating neurocircuitry consisting of both similarities and differences with glucose

Onset of transcription of the aminopeptidase N (leukemia antigen CD 13) gene at the crypt/villus transition zone during rabbit enterocyte differentiation

AbstractThe sequence of a cDNA clone (2.82 kbp) of rabbit intestinal aminopeptidase N (CD 13) is reported. Using the corresponding anti-sense RNA probe, the distribution of aminopeptidase N mRNA along the crypt/villus axis of the rabbit small intestine was studied by in situ hybridization. The aminopeptidase N gene is expressed along the whole length of the villus with a maximum at its base. Expression was not detected in the crypt cells. The distribution of aminopeptidase N mRNA correlates with the presence of active enzyme as monitored by histochemical staining. The results are compatible with onset of transcription of the aminopeptidase N gene at the crypt/villus transition zone during the enterocyte differentiation

Synchronous and proportional deglacial changes in Atlantic meridional overturning and northeast Brazilian precipitation

Changes in heat transport associated with fluctuations in the strength of the Atlantic meridional overturning circulation (AMOC) are widely considered to affect the position of the Intertropical Convergence Zone (ITCZ), but the temporal immediacy of this teleconnection has to date not been resolved. Based on a high-resolution marine sediment sequence over the last deglaciation, we provide evidence for a synchronous and near-linear link between changes in the Atlantic interhemispheric sea surface temperature difference and continental precipitation over northeast Brazil. The tight coupling between AMOC strength, sea surface temperature difference, and precipitation changes over northeast Brazil unambiguously points to a rapid and proportional adjustment of the ITCZ location to past changes in the Atlantic meridional heat transport

Can burglary prevention be low-carbon and effective? Investigating the environmental performance of burglary prevention measures

There has been limited study to date on the environmental impacts of crime prevention measures. We address this shortfall by estimating the carbon footprint associated with the most widely used burglary prevention measures: door locks, window locks, burglar alarms, lighting and CCTV cameras. We compare these footprints with a measure of their effectiveness, the security protection factor, allowing us to identify those measures that are both low-carbon and effective in preventing burglary. Window locks are found to be the most effective and low-carbon measure available individually. Combinations of window locks, door locks, external and indoor lightings are also shown to be effective and low-carbon. Burglar alarms and CCTV do not perform as strongly, with low security against burglary and higher carbon footprints. This information can be used to help inform more sustainable choices of burglary prevention within households as well as for crime prevention product design