Mister Butterfly

https://digitalcommons.library.umaine.edu/mmb-vp/3286/thumbnail.jp

The Lovelight In Your Eyes

https://digitalcommons.library.umaine.edu/mmb-vp/4644/thumbnail.jp

Determining Ages of APOGEE Giants with Known Distances

We present a sample of local red giant stars observed using the New Mexico State University 1 m telescope with the APOGEE spectrograph, for which we estimate stellar ages and the age distribution from the high-resolution spectroscopic stellar parameters and accurate distance measurements from Hipparcos. The high-resolution (R ~ 23,000), near infrared (H-band, 1.5-1.7 micron) APOGEE spectra provide measurements of the stellar atmospheric parameters (temperature, surface gravity, [M/H], and [alpha/M]). Due to the smaller uncertainties in surface gravity possible with high-resolution spectra and accurate Hipparcos distance measurements, we are able to calculate the stellar masses to within 40%. For red giants, the relatively rapid evolution of stars up the red giant branch allows the age to be constrained based on the mass. We examine methods of estimating age using both the mass-age relation directly and a Bayesian isochrone matching of measured parameters, assuming a constant star formation history (SFH). To improve the prior on the SFH, we use a hierarchical modeling approach to constrain the parameters of a model SFH from the age probability distribution functions of the data. The results of an alpha dependent Gaussian SFH model shows a clear relation between age and [alpha/M] at all ages. Using this SFH model as the prior for an empirical Bayesian analysis, we construct a full age probability distribution function and determine ages for individual stars. The age-metallicity relation is flat, with a slight decrease in [M/H] at the oldest ages and a ~ 0.5 dex spread in metallicity. For stars with ages < 1 Gyr we find a smaller spread, consistent with radial migration having a smaller effect on these young stars than on the older stars.Comment: 14 page, 18 figures, accepted to ApJ with minor revisions, full electronic table of data available upon publicatio

Land cover influence on catchment scale subsurface water storage investigated by multiple methods:Implications for UK Natural Flood Management

Study region: United Kingdom (UK). Study Focus: ‘Natural flood management’ (NFM) schemes manipulating land use and other catchment features to control runoff are increasingly promoted across the UK. Catchment water storage and mixing processes influence runoff, but our understanding of the effects of land cover change on these processes is still limited. This study combined hydrometric, isotopic and geochemical measurements to investigate land cover versus potential topographic, soil and geological controls. It compared storage-discharge dynamics in nine nested catchments within a 67 km2 managed upland catchment in southern Scotland. Storage and mixing dynamics were characterised from hydrometric data using recession analysis and from isotopic data using mean transit time and young water fraction estimates. To give information on water sources, groundwater fraction was estimated from end member mixing analysis based on acid neutralising capacity.New hydrological insights: The analysis showed low but variable sub-catchment scale dynamic storage (16–200 mm), mean transit times (134–370 days) and groundwater fractions (0.20–0.52 of annual stream runoff). Soil hydraulic conductivity was most significantly positively correlated with storage and mixing measures, whilst percentage forest cover was inversely correlated. Any effects of forest cover on increasing catchment infiltration and storage are masked by soil hydraulic properties even in the most responsive catchments. This highlights the importance of understanding dominant controls on catchment storage when using tree planting as a flood management strategy

Natural flood management, lag time and catchment scale:Results from an empirical nested catchment study

Natural flood management (NFM) techniques attract much interest in flood risk management science, not least because their effectiveness remains subject to considerable uncertainty, particularly at larger catchment and event scales. This derives from a paucity of empirical studies which can offer either longitudinal or comparison data sets in which changes can be observed. The Eddleston catchment study, with 13 stream gauges operated continuously over 9 years, is based on both longitudinal and comparison data sets. Two years of baseline monitoring have been followed by 7 years of further monitoring after a range of NFM interventions across the 69 km2 catchment. This study has examined changes in lag as an index of hydrological response which avoids dependence on potentially significant uncertainties in flow data. Headwater catchments up to 26 km2 showed significant delays in lag of 2.6–7.3 hr in catchments provided with leaky wood structures, on‐line ponds and riparian planting, while larger catchments downstream and those treated with riparian planting alone did not. Two control catchments failed to show any such changes. The findings provide important evidence of the catchment scale at which NFM can be effective and suggest that effects may increase with event magnitude

The impact of across-slope forest strips on hillslope subsurface hydrological dynamics

Forest cover has a significant effect on hillslope hydrological processes through its influence on the water balance and flow paths. However, knowledge of how spatial patterns of forest plots control hillslope hydrological dynamics is still poor. The aim of this study was to examine the impact of an across-slope forest strip on sub-surface soil moisture and groundwater dynamics, to give insights into how the structure and orientation of forest cover influences hillslope hydrology. Soil moisture and groundwater dynamics were compared on two transects spanning the same elevation on a 9° hillslope in a temperate UK upland catchment. One transect was located on improved grassland; the other was also on improved grassland but included a 14 m wide strip of 27-year-old mixed forest. Sub-surface moisture dynamics were investigated upslope, underneath and downslope of the forest over 2 years at seasonal and rainfall event timescales. Continuous data from point-based soil moisture sensors and piezometers installed at 0.15, 0.6 and 2.5 m depth were combined with seasonal (~bi-monthly) time-lapse electrical resistivity tomography (ERT) surveys. Significant differences were identified in sub-surface moisture dynamics underneath the forest strip over seasonal timescales: drying of the forest soils was greater, and extended deeper and for longer into the autumn compared to the adjacent grassland soils. Water table levels were also persistently lower in the forest and the forest soils responded less frequently to rainfall events. Downslope of the forest, soil moisture dynamics were similar to those in other grassland areas and no significant differences were observed beyond 15 m downslope, suggesting minimal impact of the forest at shallow depths downslope. Groundwater levels were lower downslope of the forest compared to other grassland areas, but during the wettest conditions there was evidence of upslope-downslope water table connectivity beneath the forest. The results indicate that forest strips in this environment provide only limited additional sub-surface storage of rainfall inputs in flood events after dry conditions in this temperate catchment setting

Universal bounds for positive matrix semigroups

Version of record at https://doi.org/10.4064/sm8421-3-2016We show that any compact semigroup of positive n×n matrices is similar (via a positive diagonal similarity) to a semigroup bounded by n√. We give examples to show this bound is best possible. We also consider the effect of additional conditions on the semigroup and obtain improved bounds in some cases.First author’s research was supported by Colby College Natural Sciences Division Grant. The other authors’ research was supported by NSERC (Canada) Discovery Grants

Standard versus short stem cemented Exeter^® when used for primary total hip arthroplasty:a survivorship analysis

Aims: The aims were to compare the survival of the cemented standard (150 mm) with the short (DDH [35.5 mm offset or less], number 1 short stem [125 mm options of 37.5 mm, 44 mm, 50 mm offset] and revision [44/00/125]) Exeter ® V40 femoral stems when used for primary total hip arthroplasty (THA). Methods: Patients were retrospectively identified from an arthroplasty database. A total of 664 short stem Exeter ® variants were identified, of which 229 were DDH stems, 208 number 1 stems and 227 revision stems were implanted between 2011 and 2020. A control group of 698 standard Exeter ® stems used for THA was set up, and were followed up for a minimum of 10 years follow-up (implanted 2011). All-cause survival was assessed for THA and for the stem only. Adjusted analysis was undertaken for age, sex and ASA grade. Results: The median survival time for the short stems varied according to design: DDH had a survival time of 6.7 years, number 1 stems 4.1 years, and revision stems 7.2 years. Subjects in the short stem group (n = 664) were significantly younger (mean difference 5.1, P &lt; 0.001) and were more likely to be female (odds ratio 1.89, 95% CI 1.50 to 2.39, P &lt; 0.001), compared to the standard group. There were no differences in THA (P = 0.26) or stem (P = 0.35) survival at 5 years (adjusted THA: 98.3% vs. 97.2%; stem 98.7% vs. 97.8%) or 10 years (adjusted THA 97.0% vs. 96.0 %; stem 96.7% vs. 96.2%) between standard and short stem groups, respectively. At 5 years no differences were found in THA (DDH: 96.7%, number 1 97.5%, revision 97.3%, standard 98.6%) or stem (DDH: 97.6%, number 1 99.0%, revision 97.3%, standard 98.2%) survival between/among the different short stems or when compared to the standard group. Conclusion: The Exeter ® short stems offer equivocal survival when compared to the standard stem at 5- to 10-year follow-up, which does not seem to be influenced by the short stem design.</p

Critical Currents of Ideal Quantum Hall Superfluids

Filling factor $\nu=1$ bilayer electron systems in the quantum Hall regime have an excitonic-condensate superfluid ground state when the layer separation $d$ is less than a critical value $d_c$. On a quantum Hall plateau current injected and removed through one of the two layers drives a dissipationless edge current that carries parallel currents, and a dissipationless bulk supercurrent that carries opposing currents in the two layers. In this paper we discuss the theory of finite supercurrent bilayer states, both in the presence and in the absence of symmetry breaking inter-layer hybridization. Solutions to the microscopic mean-field equations exist at all condensate phase winding rates for zero and sufficiently weak hybridization strengths. We find, however, that collective instabilities occur when the supercurrent exceeds a critical value determined primarily by a competition between direct and exchange inter-layer Coulomb interactions. The critical current is estimated using a local stability criterion and varies as $(d_c-d)^{1/2}$ when $d$ approaches $d_c$ from below. For large inter-layer hybridization, we find that the critical current is limited by a soliton instability of microscopic origin.Comment: 18 RevTeX pgs, 21 eps figure

Hilbert space operators with compatible off-diagonal corners

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.jfa.2018.04.002 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Given a complex, separable Hilbert space H, we characterize those operators for which ‖PT(I−P)‖=‖(I−P)TP‖ for all orthogonal projections P on H. When H is finite-dimensional, we also obtain a complete characterization of those operators for which rank(I−P)TP=rankPT(I−P) for all orthogonal projections P. When H is infinite-dimensional, we show that any operator with the latter property is normal, and its spectrum is contained in either a line or a circle in the complex plane.Natural Sciences and Engineering Research Council of Canad