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Abstract We propose a general classification of all the modes of a given thermoacoustic system into two sets: one of acoustic origin and one of intrinsic thermoacoustic (ITA) origin. To do this, the definition of intrinsic modes, traditionally based on anechoic boundary conditions, is reformulated in terms of the gain n of the Flame Transfer Function (FTF). As a consequence of this classification, we show how theoretical results for the estimation of all thermoacoustic modes can be derived in the limit n → 0, for both axial and annular combustors, independent of the acoustic boundary conditions. Starting from this limit and using standard continuation methods while increasing n, all the eigenvalues of interest in a given domain in the frequency space can be identified. We also discuss how thermoacoustic modes of acoustic and ITA origin can interact, and in some cases coalesce generating exceptional points (EPs). Although all EPs found have negative growth rates, in their vicinity thermoacoustic eigenmodes have very large sensitivities and exhibit strong mode veering. We demonstrate how, in some cases, mode veering is responsible for the occurrence of thermoacoustic instabilities, and propose a numerical method to identify EPs. All the theoretical results are numerically verified using two generic thermoacoustic configurations.

<p>To understand how global warming can be kept well-below 2°C and even 1.5°C, climate policy uses scenarios that describe how society could transform in order to reduce its greenhouse gas emissions. Such scenario are typically created with integrated assessment models that include a representation of the economy, and the energy, land-use, and industrial system. However, current climate change scenarios have a key weakness in that they typically focus on reaching specific climate goals in 2100 only. <br><br>This choice results in risky pathways that delay action and seemingly inevitably rely on large quantities of carbon-dioxide removal after mid-century. Here we propose a framework that more closely reflects the intentions of the UN Paris Agreement. It focusses on reaching a peak in global warming with either stabilisation or reversal thereafter. This approach provides a critical extension of the widely used Shared Socioecononomic Pathways (SSP) framework and reveals a more diverse picture: an inevitable transition period of aggressive near-term climate action to reach carbon neutrality can be followed by a variety of long-term states. It allows policymakers to explicitly consider near-term climate strategies in the context of intergenerational equity and long-term sustainability.</p>

It has been shown recently that the overpotential originating from ionic conduction of alkali-ions through the inner dense solid-electrolyte interphase (SEI) is strongly non-linear. An empirical equation was proposed to merge the measured resistances from both galvanostatic cycling (GS) and electrochemical impedance spectroscopy (EIS) at 25$^{\circ}$C. Here, this analysis is extended to the full temperature range of batteries from -40$^{\circ}$C to +80$^{\circ}$C for Li, Na, K and Rb-metal electrodes in carbonate electrolytes. Two different transport mechanisms are found. The first one conducts alkali-ions at all measured temperatures. The second transport mechanism conducts ions for all seven measured Li-ion electrolytes and one out of four Na-ion electrolytes, however, only above a certain critical temperature $T_C$. At $T_C$ a phase transition is observed switching-off the more efficient transport mechanism and leaving only the general ion conduction mechanism. The associated overpotentials increase rapidly below $T_C$ depending on alkali-ion, salt and solvent and become a limiting factor during galvanostatic operation of all Li-ion electrolytes at low temperature. In general, the current analysis merges the SEI resistances measured by EIS ranging from 26 $��$cm$^2$ for the best Li up to 292 M$��$cm$^2$ for Rb electrodes to its galvanostatic response over seven orders of magnitude. The determined critical temperatures are between 0-25$^{\circ}$C for the tested Li and above 50$^{\circ}$C for Na electrolytes. 10 pages, 7 figures, file includes Suppl Info, http://jes.ecsdl.org/content/165/2/A323

Gyrfalcon (Falco rusticolus) is the largest falcon in the world. It inhabits a wide range of climate zones in the Northern Hemisphere, from boreal forests in the south of its range to the arid polar deserts of the High Arctic. In Greenland, because of the harsh, remote environments in which gyrfalcons live, research related to the contemporary and pre-modern periods has been limited to the north-west, central west and central east coasts, with no specific investigations being conducted for the north-east. Here, we report the first pre-modern record of a gyrfalcon in north-east Greenland, located at 80.4°N in Kronprins Christian Land. Skin tissue from a decaying gyrfalcon’s body was radiocarbon dated to 769–944 CE (common era) using a terrestrial-only calibration curve, and 1182–1456 CE using a marine-only calibration curve. Since the gyrfalcon has a mixed terrestrial/marine diet, the actual age can be said to belong between these two groups. This limited data, therefore places the presence of the gyrfalcon in north-east Greenland during a period of prolonged elevated temperatures and climate stress associated with the Medieval Climate Anomaly. Whether the gyrfalcon was part of a larger population or a straggler, and whether the species survived the whole of the Medieval Climate Anomaly in north-east Greenland, is unknown. Polar Research, 38 ISSN:0800-0395 ISSN:1751-8369

ABSTRACT Although a whole arsenal of mechanisms are potentially involved in metabolic regulation, it is largely uncertain when, under which conditions, and to which extent a particular mechanism actually controls network fluxes and thus cellular physiology. Based on 13 C flux analysis of Escherichia coli mutants, we elucidated the relevance of global transcriptional regulation by ArcA, ArcB, Cra, CreB, CreC, Crp, Cya, Fnr, Hns, Mlc, OmpR, and UspA on aerobic glucose catabolism in glucose-limited chemostat cultures at a growth rate of 0.1 h −1 . The by far most relevant control mechanism was cyclic AMP (cAMP)-dependent catabolite repression as the inducer of the phosphoenolpyruvate (PEP)-glyoxylate cycle and thus low tricarboxylic acid cycle fluxes. While all other mutants and the reference E. coli strain exhibited high glyoxylate shunt and PEP carboxykinase fluxes, and thus high PEP-glyoxylate cycle flux, this cycle was essentially abolished in both the Crp and Cya mutants, which lack the cAMP-cAMP receptor protein complex. Most other mutations were phenotypically silent, and only the Cra and Hns mutants exhibited slightly altered flux distributions through PEP carboxykinase and the tricarboxylic acid cycle, respectively. The Cra effect on PEP carboxykinase was probably the consequence of a specific control mechanism, while the Hns effect appears to be unspecific. For central metabolism, the available data thus suggest that a single transcriptional regulation process exerts the dominant control under a given condition and this control is highly specific for a single pathway or cycle within the network.

The winter tourism industry is facing considerable challenges with climate change; it is increasingly responding with investments in snowmaking facilities. We present a study on 3 tourism destinations in the Swiss Alps that addressed resource consumption of snowmaking, snow reliability, and future snowmaking potential in a warmer climate. The energy consumption of snowmaking in the ski resorts was in the lower range of what could be expected from literature values. It comprised ∼0.5% of the respective municipality's energy consumption and was moderate compared with other tourism-related activities. Water consumption, however, was in the higher range with regard to what was expected from literature values and was also high compared with other water uses (eg 36% compared with drinking water consumption in one community). Natural snow cover was partly critical for winter sports at low elevations at ∼1200 masl, but uncritical at higher elevations above 2000 masl. Snow cover will become even more critical in a warmer climate but will probably still be sufficient above 2000 masl until 2050. Snowmaking may become critical at lower elevations in the early months of the season (November and December) due to warmer temperatures that can be expected in the coming decades. But, at higher elevations, the potential for snowmaking will probably remain sufficient. Our study provides straightforward and feasible approaches to assess resource consumption and snow cover. Careful consideration of resource consumption and snow cover can foster technical and economical advances as well as more sustainable development in mountains regions. Snow production can represent a valuable adaptation strategy at high-altitude destinations. However, given the increasing economic competition and the changing climate, it will be crucial to use specific regional strengths to provide high-quality winter and summer tourism activities. Mountain Research and Development, 31 (3) ISSN:0276-4741 ISSN:1994-7151