Probing the formation history of the nuclear star cluster at the Galactic Centre with millisecond pulsars

The origin of the Nuclear Star Cluster in the centre of our Galaxy is still unknown. One possibility is that it formed after the disruption of stellar clusters that spiralled into the Galactic Centre due to dynamical friction. We trace the formation of the Nuclear Star Cluster around the central black hole, using state-of-the-art N-body simulations, and follow the dynamics of the neutron stars born in the clusters. We then estimate the number of Millisecond Pulsars (MSPs) that are released in the Nuclear Star Cluster, during its formation. The assembly and tidal dismemberment of globular clusters lead to a population of MSPs distributed over a radius of about 20 pc, with a peak near 3 pc. No clustering is found on the sub-parsec scale. We simulate the detectability of this population with future radio telescopes like the MeerKAT radio telescope and SKA1, and find that about of order ten MSPs can be observed over this large volume, with a paucity of MSPs within the central parsec. This helps discriminating this scenario from the in-situ formation model for the Nuclear Star Cluster that would predict an over abundance of MSPs closer to the black hole. We then discuss the potential contribution of our MSP population to the gamma-ray excess at the Galactic Centre.Comment: 11 pages, 8 figures, accepted for publication in MNRA

Glycerol confined in zeolitic imidazolate frameworks: The temperature-dependent cooperativity length scale of glassy freezing

In the present work, we employ broadband dielectric spectroscopy to study the molecular dynamics of the prototypical glass former glycerol confined in two microporous zeolitic imidazolate frameworks (ZIF-8 and ZIF-11) with well-defined pore diameters of 1.16 and 1.46 nm, respectively. The spectra reveal information on the modified alpha relaxation of the confined supercooled liquid, whose temperature dependence exhibits clear deviations from the typical super-Arrhenius temperature dependence of the bulk material, depending on temperature and pore size. This allows assigning well-defined cooperativity length scales of molecular motion to certain temperatures above the glass transition. We relate these and previous results on glycerol confined in other host systems to the temperature-dependent length scale deduced from nonlinear dielectric measurements. The combined experimental data can be consistently described by a critical divergence of this correlation length as expected within theoretical approaches assuming that the glass transition is due to an underlying phase transition.Comment: 14 pages, 5 figures + Supplemental Material (4 pages, 6 figures). Final version as accepted for publicatio

Zooarchaeological analysis at 49-RAT-32: historical ecology and maritime subsistence in the late Aleutian period

Thesis (M.A.) University of Alaska Fairbanks, 2020This thesis utilizes a zooarchaeological collection from 49-RAT-32 on Amchitka Island in the Western Aleutians to examine Unangax̂ subsistence strategies, and human/environment interactions from 620 ± 20 to 320 ± 20 years B.P. The materials used for this analysis were recovered from primary and secondary fill overlaying the House 1 floor. Paleoecological records within this region are limited and conflict with each other, but the cool and wet conditions of the Little Ice Age 600-100 years B.P, or C.E. 1350-1850 are believed to be in effect during the deposition of the fill materials. Marine mammal, fish, and sea urchin remains were analyzed to understand subsistence practices, seasonality, and land/seascape use. The relative abundance of the exploited taxa and fork lengths of marine fishes were analyzed to identify potential resource stress and change over time. Atka mackerel dominates the faunal assemblage and Pacific cod are present in very low frequencies, both of which make 49-RAT-32 unique when compared to other Aleutian assemblages. Atka mackerel, Pacific cod, and Irish lords are larger in size than their modern counterparts, with the large size of Pacific cod indicating deep sea fishing practices. The size differentials in Atka mackerel and Irish lords may reflect differences in ocean conditions. This analysis of fauna from 49-RAT-32 does not indicate the presence of human-driven resource depression, in fact, fish sizes were increasing, and diet breadth was shrinking. The opposite pattern from what would be expected if humans were overfishing. The data from this analysis increase our understanding of resource utilization and landscape use during the Late Aleutian Period, and provides baseline information for future studies analyzing changes in fish size over time.University of Alaska Museum of the North Geist FundChapter 1: Introduction. Chapter 2: Background -- 2.1 Physical Environment -- 2.1.1 Setting -- 2.1.2 Physical Geology -- 2.1.3 Climate -- 2.1.4 Oceanography -- 2.2 Ecology -- 2.2.1 Vegetation -- 2.2.2 Marine Mammals -- 2.2.3 Birds -- 2.2.4 Fish -- 2.3 Culture History -- 2.3.1 Region -- 2.3.2 The Unangax̂ -- 2.3.3 Social Organization and Politics -- 2.3.4 Burial Practices -- 2.3.5 Warfare -- 2.3.6 Settlements and Households -- 2.3.7 Material Culture -- 2.3.8 Subsistence -- 2.4 Archaeological Studies & Interpretations in the Aleutians -- 2.4.1 Early Studies & Ideas -- 2.4.2 Population Continuity or Replacement 1000 Years BP? -- 2.4.2 Maritime Economy -- 2.4.3 Archaeology in the Western Aleutians -- 2.4.4 Limiting Factors -- 2.5 Background Summary. Chapter 3: Theoretical Framework -- 3.1 Historical Ecology -- 3.1.1 Background of Historical Ecology -- 3.1.2 Historical Ecology in the Aleutians and Southwest Alaska -- 3.2 Research Questions -- 3.3 Research Goals and Expectations -- 3.3.1 Subsistence Practices -- 3.3.2 Change Over Time and Resource Stress -- 3.4 Non-Human vs. Human Signatures -- 3.4.1 The Effect of Climate Regimes on Marine Resources -- 3.4.2 Human Signatures -- 3.5 Impact on Future Aleutian Studies. Chapter 4: Materials and Methods -- 4.1 Excavation -- 4.1.1 49-RAT-32 Setting -- 4.1.2 Collection and Sampling Methods -- 4.2 Identification Methods and Data Classes -- 4.3 Quantification of Species -- 4.3.1 Number of Identified Species -- 4.3.2 Normalized NISP -- 4.3.3 Minimum Number of Individuals -- 4.3.4 Age Determinations -- 4.4 Fork Length, Meat Weight, and Statistical Measures -- 4.4.1 Estimated Fork Length -- 4.4.2 Meat Weights -- 4.4.3 Statistical Measures -- 4.5 Taphonomy -- 4.6 Summary. Chapter 5: Results -- 5.1 Identified Taxa -- 5.2 Results -- 5.2.1 Analyzed Deposit -- 5.2.2 Recovered Fish -- 5.3 Statistical Measures -- 5.3.1 Changes in Taxonomic Frequency Over Time -- 5.3.2 Fish Lengths -- 5.4 Marine Mammals -- 5.5 Meat Weights -- 5.6 Butchery and Storage -- 5.7 Taphonomy -- 5.8 Interlude to the Discussion. Chapter 6: Discussion -- 6.1 Faunal Analysis and Identification -- 6.1.1 Sample Context -- 6.1.2 Comparative Material -- 6.2 Season(s) of Site Occupation -- 6.3 Exploited Habitats -- 6.3.1 Intertidal and Nearshore -- 6.3.2 Offshore -- 6.4 Fish Exploitation and Variation in Body Size -- 6.4.1 Atka Mackerel Fork Lengths and Frequency -- 6.4.2 Greenling Fork Lengths and Frequency -- 6.4.3 Irish Lords Fork Lengths and Frequency -- 6.4.4 Pacific Cod Fork Lengths and Frequency -- 6.4.5 Rockfish Fork Lengths and Frequency -- 6.4.6 Atka Mackerel Versus Greenlings -- 6.4.7 Summary of Measurements and Abundance -- 6.5 Diet and Meat Weights -- 6.6 Body Part Profiles -- 6.7 Summary -- Chapter 7: Conclusions -- References Cited -- Appendices

Dielectric study on mixtures of ionic liquids

Ionic liquids are promising candidates for electrolytes in energy-storage systems. We demonstrate that mixing two ionic liquids allows to precisely tune their physical properties, like the dc conductivity. Moreover, these mixtures enable the gradual modification of the fragility parameter, which is believed to be a measure of the complexity of the energy landscape in supercooled liquids. The physical origin of this index is still under debate; therefore, mixing ionic liquids can provide further insights. From the chemical point of view, tuning ionic liquids via mixing is an easy and thus an economic way. For this study, we performed detailed investigations by broadband dielectric spectroscopy and differential scanning calorimetry on two mixing series of ionic liquids. One series combines an imidazole based with a pyridine based ionic liquid and the other two different anions in an imidazole based ionic liquid. The analysis of the glass-transition temperatures and the thorough evaluations of the measured dielectric permittivity and conductivity spectra reveal that the dynamics in mixtures of ionic liquids are well defined by the fractions of their parent compounds.Comment: 9 pages, 4 figure

People making deontological judgments in the Trapdoor dilemma are perceived to be more prosocial in economic games than they actually are

Why do people make deontological decisions, although they often lead to overall unfavorable outcomes? One account is receiving considerable attention: deontological judgments may signal commitment to prosociality and thus may increase people’s chances of being selected as social partners–which carries obvious long-term benefits. Here we test this framework by experimentally exploring whether people making deontological judgments are expected to be more prosocial than those making consequentialist judgments and whether they are actually so. In line with previous studies, we identified deontological choices using the Trapdoor dilemma. Using economic games, we take two measures of general prosociality towards strangers: trustworthiness and altruism. Our results procure converging evidence for a perception gap according to which Trapdoor-deontologists are believed to be more trustworthy and more altruistic towards strangers than Trapdoor-consequentialists, but actually they are not so. These results show that deontological judgments are not universal, reliable signals of prosociality

Past warming trend constrains future warming in CMIP6 models

Future global warming estimates have been similar across past assessments, but several climate models of the latest Sixth Coupled Model Intercomparison Project (CMIP6) simulate much stronger warming, apparently inconsistent with past assessments. Here, we show that projected future warming is correlated with the simulated warming trend during recent decades across CMIP5 and CMIP6 models, enabling us to constrain future warming based on consistency with the observed warming. These findings carry important policy-relevant implications: The observationally constrained CMIP6 median warming in high emissions and ambitious mitigation scenarios is over 16 and 14% lower by 2050 compared to the raw CMIP6 median, respectively, and over 14 and 8% lower by 2090, relative to 1995–2014. Observationally constrained CMIP6 warming is consistent with previous assessments based on CMIP5 models, and in an ambitious mitigation scenario, the likely range is consistent with reaching the Paris Agreement target

Creep and fatigue analysis of reinforced concrete structures

A computional procedure for the creep and fatigue analysis of reinforced concrete structures exposed to flexure is presented. The fatigue loading effects are modified into an equivalent creep analysis. The analysis is based on the finite element method employing beam elements. The material behavior of steel, concrete and bond between reinforcement and concrete are described as realisticly as possible. For the reinforcing steel the stress-strain behavior as measured in tests or given in codes is assumed. For the stress-strain behavior of concrete in compression under static loading, the proposal by Park/Pauley is taken. The influence of sustained or fatigue loading is taken into account by using the isochrone σ-ε-relationship valid for t > t o or N > 1 respectively; whereby the creep coefficients for both type of loadings are taken from MC90. For sustained and fatigue loading the isochrone bond stressslip relationship is used. The creep coefficients are taken from MC90. The accuracy of the proposed model is checked by comparing the behavior of some test beams under sustained and fatigue loading with the predictions