Early Fall Migration of Sedge Wrens

Johnsgard (1980) lists the Sedge Wren (Cistothorus platensis) as an uncommon spring and fall migrant in eastern Nebraska, and a rare summer resident in eastern Nebraska, mostly east of a line from Knox to Gage counties. Half of the initial spring records occur between 1 and 12 May, with the latest 3 June. Half of the final fal1 records occur between 11 Sept. and 9 Oct., with the earliest 29 July. This paper presents observations of Sedge Wrens during 1987 in southcentral Nebraska, west of the line. I found Sedge Wrens to be local1y common in grassy or marshy areas from late July through at least mid-August, 1987. I recorded Sedge Wrens in Clay, Hall, and Hamilton counties (Table 1). All Wrens counted were singing. Many were unseen because of their reclusive habits, but I saw about half of them either singing from an exposed position near the top of the vegetation or by “swishing” them. The birds at the Taylor Ranch, in northwestern Hall Co., were in a complex of dry short-grass prairie mixed with low spots that had tall (4 to 5 ft.) marsh vegetation. These low spots had dried up earlier in the summer. The Wrens were using the tall vegetation. After finding the 4 birds on 28 July I returned the next day to look for evidence of nesting. I looked for a couple of hours and saw no evidence of anything other than the presence of singing birds, but a more thorough search did reveal at least 12 Sedge Wrens. No Marsh Wrens were using this area

Quantum fluctuation driven first order phase transition in weak ferromagnetic metals

In a local Fermi liquid (LFL), we show that there is a line of weak first order phase transitions between the ferromagnetic and paramagnetic phases due to purely quantum fluctuations. We predict that an instability towards superconductivity is only possible in the ferromagnetic state. At T=0 we find a point on the phase diagram where all three phases meet and we call this a quantum triple point (QTP). A simple application of the Gibbs phase rule shows that only these three phases can meet at the QTP. This provides a natural explanation of the absence of superconductivity at this point coming from the paramagnetic side of the phase diagram, as observed in the recently discovered ferromagnetic superconductor, $UGe_{2}$.Comment: 5 pages, 5 figure

Nesting Ecology of Sedge Wrens in Hall County, Nebraska

The status of the Sedge Wren (Cistothorus platensis) in Nebraska is not well known. Cink (1973) summarized summer records from 1867 to 1971 and described only a few nest records. One nest discovered on 28 August 1902 at Capitol Beach, Lancaster Co., was assumed empty, apparently because of the late date. Bedell (1987) recorded July and August sightings in south central Nebraska and raised the question of whether these birds were migrants or nesting. Sedge Wrens are frequently polygynous (Crawford 1977, Burns 1982) and may exhibit two waves of nesting effort in some areas (Burns 1982). Nest initiation appears to fall into two periods depending on the latitude; one from early May to June in Michigan (Walkinshaw 1935), Minnesota (Burns 1982), North Dakota (stewart 1975), and Wisconsin (Manci and Rusch 1988), and the other beginning in late July through August in Kansas (Cink pers. comm., Williams 1981) and Arkansas (Meanley 1952) in addition to more northern latitudes as cited above. This may explain why Sedge Wrens are often not encountered during typical May and June breeding bird censuses, especially in southern and western portions of their nesting range (Robbins et al. 1986). This paper compares nesting densities on a grazed versus an ungrazed area and describes the nesting phenology of Sedge Wrens during the 1988 nesting season in Hall Co

Physical properties of ferromagnetic-superconducting coexistent system

We studied the nuclear relaxation rate 1/T1 of a ferromagnetic-superconducting system from the mean field model proposed in Ref.14. This model predicts the existence of a set of gapless excitations in the energy spectrum which will affect the properties studied here, such as the density of states and, hence, 1/T1. The study of the temperature variation of 1/T1(for T<Tc) shows that the usual Hebel-Slichter peak exists, but will be reduced because of the dominant role of the gapless fermions and the background magnetic behavior. We have also presented the temperature dependence of ultrasonic attenuation and the frequency dependence of electromagnetic absorption within this model. We are successful in explaining certain experimental results.Comment: 10 Pages, 9 figute

Robustness of a local Fermi Liquid against Ferromagnetism and Phase Separation

We study the properties of Fermi Liquids with the microscopic constraint of a local self-energy. In this case the forward scattering sum-rule imposes strong limitations on the Fermi-Liquid parameters, which rule out any Pomeranchek instabilities. For both attractive and repulsive interactions, ferromagnetism and phase separation are suppressed. Superconductivity is possible in an s-wave channel only. We also study the approach to the metal-insulator transition, and find a Wilson ratio approaching 2. This ratio and other properties of Sr_{1-x}La_xTiO_3 are all consistent with the local Fermi Liquid scenario.Comment: 4 pages (twocolumn format), can compile with or without epsf.sty latex style file -- Postscript files: fig1.ps and fig2.p

Acoustic attenuation probe for fermion superfluidity in ultracold atom gases

Dilute gas Bose-Einstein condensates (BEC's), currently used to cool fermionic atoms in atom traps, can also probe the superfluidity of these fermions. The damping rate of BEC-acoustic excitations (phonon modes), measured in the middle of the trap as a function of the phonon momentum, yields an unambiguous signature of BCS-like superfluidity, provides a measurement of the superfluid gap parameter and gives an estimate of the size of the Cooper-pairs in the BEC-BCS crossover regime. We also predict kinks in the momentum dependence of the damping rate which can reveal detailed information about the fermion quasi-particle dispersion relation.Comment: 4 pages, 2 figures. Revised versio

Low-Temperature Spin Diffusion in a Spin-Polarized Fermi Gas

We present a finite temperature calculation of the transverse spin-diffusion coefficient, $D_\bot$, in a dilute degenerate Fermi gas in the presence of a small external magnetic field, $H$. While the longitudinal diffusion coefficient displays the conventional low-temperature Fermi-liquid behavior, $D_\parallel \propto T^{-2}$, the corresponding results for $D_\bot$ show three separate regimes: (a) $D_\bot \sim H^{-2}$ for $T \ll H$; (b) $D_\bot \sim T^{-2}$, $D_\bot /D_\parallel \neq 1$ for $T \gg H$ and large spin-rotation parameter $\xi \gg 1$, and (c) $D_\bot = D_\parallel \propto T^{-2}$ for $T \gg H$ and $\xi \ll 1$. Our results are qualitatively consistent with the available experimental data in weakly spin-polarized $^3{\rm He}$ and $^3{\rm He} - ^4{\rm He}$ mixtures.Comment: 13 pages, REVTEX, 3 figures available upon request, RU-94-4

Assessing the prevalence of refractive errors and accuracy of vision screening by schoolteachers in Liberia

Background Evidence indicates that school-based vision screening by trained teachers is an effective way of identifying and addressing potential vision problems in schoolchildren. However, inconsistencies have been reported in both the testing methods and accuracy of the screeners. This study assessed the prevalence of refractive errors and accuracy of screening by teachers in Grand Kru County, Liberia. Methods We conducted a retrospective analysis of data from four schools where, in February 2019, children were screened for refractive errors by trained teachers and then re-examined by ophthalmic technicians. One row of five optotypes of the Snellen 6/9 (0.2 logMar) scale (tumbling E chart) was used at a distance of 3 m. The prevalence of visual impairment and associations with sex, age and school were explored. Sensitivity, specificity and predictive values were calculated. Results Data were available for 823 of 1095 eligible children with a mean age of 13.7 y (range 5–18) and male:female ratio of 1:0.8. Poor vision was identified in 24 (2.9%) children with no differences by either sex or age but small differences by school. Screening by teachers had a sensitivity of 0.25 (95% confidence interval [CI] 0.077 to 0.423) and a specificity of 0.996 (95% CI 0.992 to 1.000). Positive and negative predictive values were 0.667 (95% CI 0.359 to 0.975) and 0.978 (95% CI 0.968 to 0.988), respectively. The results were influenced by a high number of misclassifications in one of the four schools. Conclusions Teachers can be trained to conduct vision screening tests on schoolchildren to an acceptable level of accuracy, but strong monitoring and quality assurance systems should be built into screening programmes from the onset. In settings like Liberia, where many children do not attend school regularly, screening programmes should extend to community platforms to reach children out of school