TY - JOUR AB - We consider a class of polaron models, including the Fröhlich model, at zero total momentum, and show that at sufficiently weak coupling there are no excited eigenvalues below the essential spectrum. AU - Seiringer, Robert ID - 14662 IS - 3 JF - Journal of Spectral Theory SN - 1664-039X TI - Absence of excited eigenvalues for Fröhlich type polaron models at weak coupling VL - 13 ER - TY - JOUR AB - In order to demonstrate the stability of newly proposed iridium-based Ir2Cr(In,Sn) and IrRhCr(In,Sn) heusler alloys, we present ab-initio analysis of these alloys by examining various properties to prove their stability. The stability of these alloys can be inferred from different cohesive and formation energies as well as positive phonon frequencies. Their electronic structure results indicate that they are semi-metals in nature. The magnetic moments are computed using the Slater-Pauling formula and exhibit a high value, with the Cr atom contributing the most in all alloys. Mulliken’s charge analysis results show that our alloys contain a range of linkages, mainly ionic and covalent ones. The ductility and mechanical stability of these alloys are confirmed by elastic constants viz. Poisson’s ratio, Pugh’s ratio, and many different types of elastic moduli. AU - Gupta, Shyam Lal AU - Singh, Saurabh AU - Kumar, Sumit AU - Anupam, Unknown AU - Thakur, Samjeet Singh AU - Kumar, Ashish AU - Panwar, Sanjay AU - Diwaker, D. ID - 14652 JF - Physica B: Condensed Matter SN - 0921-4526 TI - Ab-initio stability of Iridium based newly proposed full and quaternary heusler alloys VL - 674 ER - TY - JOUR AB - Sleep plays a key role in preserving brain function, keeping the brain network in a state that ensures optimal computational capabilities. Empirical evidence indicates that such a state is consistent with criticality, where scale-free neuronal avalanches emerge. However, the relationship between sleep, emergent avalanches, and criticality remains poorly understood. Here we fully characterize the critical behavior of avalanches during sleep, and study their relationship with the sleep macro- and micro-architecture, in particular the cyclic alternating pattern (CAP). We show that avalanche size and duration distributions exhibit robust power laws with exponents approximately equal to −3/2 e −2, respectively. Importantly, we find that sizes scale as a power law of the durations, and that all critical exponents for neuronal avalanches obey robust scaling relations, which are consistent with the mean-field directed percolation universality class. Our analysis demonstrates that avalanche dynamics depends on the position within the NREM-REM cycles, with the avalanche density increasing in the descending phases and decreasing in the ascending phases of sleep cycles. Moreover, we show that, within NREM sleep, avalanche occurrence correlates with CAP activation phases, particularly A1, which are the expression of slow wave sleep propensity and have been proposed to be beneficial for cognitive processes. The results suggest that neuronal avalanches, and thus tuning to criticality, actively contribute to sleep development and play a role in preserving network function. Such findings, alongside characterization of the universality class for avalanches, open new avenues to the investigation of functional role of criticality during sleep with potential clinical application.Significance statementWe fully characterize the critical behavior of neuronal avalanches during sleep, and show that avalanches follow precise scaling laws that are consistent with the mean-field directed percolation universality class. The analysis provides first evidence of a functional relationship between avalanche occurrence, slow-wave sleep dynamics, sleep stage transitions and occurrence of CAP phase A during NREM sleep. Because CAP is considered one of the major guardians of NREM sleep that allows the brain to dynamically react to external perturbation and contributes to the cognitive consolidation processes occurring in sleep, our observations suggest that neuronal avalanches at criticality are associated with flexible response to external inputs and to cognitive processes, a key assumption of the critical brain hypothesis. AU - Scarpetta, Silvia AU - Morrisi, Niccolò AU - Mutti, Carlotta AU - Azzi, Nicoletta AU - Trippi, Irene AU - Ciliento, Rosario AU - Apicella, Ilenia AU - Messuti, Giovanni AU - Angiolelli, Marianna AU - Lombardi, Fabrizio AU - Parrino, Liborio AU - Vaudano, Anna Elisabetta ID - 12487 IS - 10 JF - iScience TI - Criticality of neuronal avalanches in human sleep and their relationship with sleep macro- and micro-architecture VL - 26 ER - TY - JOUR AB - Background: Fighting disease while fighting rivals exposes males to constraints and tradeoffs during male-male competition. We here tested how both the stage and intensity of infection with the fungal pathogen Metarhizium robertsii interfered with fighting success in Cardiocondyla obscurior ant males. Males of this species have evolved long lifespans during which they can gain many matings with the young queens of the colony, if successful in male-male competition. Since male fights occur inside the colony, the outcome of male-male competition can further be biased by interference of the colony’s worker force. Results: We found that severe, but not yet mild, infection strongly impaired male fighting success. In late-stage infection, this could be attributed to worker aggression directed towards the infected rather than the healthy male and an already very high male morbidity even in the absence of fighting. Shortly after pathogen exposure, however, male mortality was particularly increased during combat. Since these males mounted a strong immune response, their reduced fighting success suggests a trade-off between immune investment and competitive ability already early in the infection. Even if the males themselves showed no difference in the number of attacks they raised against their healthy rivals across infection stages and levels, severely infected males were thus losing in male-male competition from an early stage of infection on. Conclusions: Males of the ant C. obscurior have evolved high immune investment, triggering an effective immune response very fast after fungal exposure. This allows them to cope with mild pathogen exposures without cost to their success in male-male competition, and hence to gain multiple mating opportunities with the emerging virgin queens of the colony. Under severe infection, however, they are weak fighters and rarely survive a combat already at early infection when raising an immune response, as well as at progressed infection, when they are morbid and preferentially targeted by worker aggression. Workers thereby remove males that pose a future disease threat by biasing male-male competition. Our study thus revealed a novel social immunity mechanism how social insect workers protect the colony against disease risk. AU - Metzler, Sina AU - Kirchner, Jessica AU - Grasse, Anna V AU - Cremer, Sylvia ID - 12696 JF - BMC Ecology and Evolution SN - 2730-7182 TI - Trade-offs between immunity and competitive ability in fighting ant males VL - 23 ER - TY - JOUR AB - Understanding the response of Himalayan glaciers to global warming is vital because of their role as a water source for the Asian subcontinent. However, great uncertainties still exist on the climate drivers of past and present glacier changes across scales. Here, we analyse continuous hourly climate station data from a glacierized elevation (Pyramid station, Mount Everest) since 1994 together with other ground observations and climate reanalysis. We show that a decrease in maximum air temperature and precipitation occurred during the last three decades at Pyramid in response to global warming. Reanalysis data suggest a broader occurrence of this effect in the glacierized areas of the Himalaya. We hypothesize that the counterintuitive cooling is caused by enhanced sensible heat exchange and the associated increase in glacier katabatic wind, which draws cool air downward from higher elevations. The stronger katabatic winds have also lowered the elevation of local wind convergence, thereby diminishing precipitation in glacial areas and negatively affecting glacier mass balance. This local cooling may have partially preserved glaciers from melting and could help protect the periglacial environment. AU - Salerno, Franco AU - Guyennon, Nicolas AU - Yang, Kun AU - Shaw, Thomas AU - Lin, Changgui AU - Colombo, Nicola AU - Romano, Emanuele AU - Gruber, Stephan AU - Bolch, Tobias AU - Alessandri, Andrea AU - Cristofanelli, Paolo AU - Putero, Davide AU - Diolaiuti, Guglielmina AU - Tartari, Gianni AU - Verza, Gianpietro AU - Thakuri, Sudeep AU - Balsamo, Gianpaolo AU - Miles, Evan S. AU - Pellicciotti, Francesca ID - 14659 JF - Nature Geoscience SN - 1752-0894 TI - Local cooling and drying induced by Himalayan glaciers under global warming VL - 16 ER -