Pre-impoundment Limnological Study of the Strawberry River in Northeastern Arkansas

A study of pre-impoundment limnological characteristics of the Strawberry River was made from August, 1967 to June, 1968. Two collecting stations were established, one upstream which would not be inundated and a lower station which would be inundated when impoundment was complete. The Strawberry River was characterized by high alkalinity and pH, low carbon dioxide and turbidity, and adequate oxygen values. Plankton was characterized by limited numbers of Staurastrum, Gomphonema, and Rotatoria. Pool-riffle communities were ill-defined. Chironomidae, Oligochaeta and Ephemeroptera were dominant pool macroinvertebrates among 13 taxa collected. Of the 20 taxa collected in riffles Trichoptera, Ephemeroptera, Simuliidae and Chironomidae were the most numerous. Longitudinal zonation was characterized by an increase in species and numbers of pool benthic macroinvertebrates from headwater to downstream areas. Numerical standing crop was recorded for pools on 8 June 1968 and riffles on 30 September 1967. A total of 1979 fishes constituting 49 species were taken in this study. Station I and II pools yielded 242 and 185 fishes/ha respectively, Dorosoma cepedianum and Moxostoma erythrurum being the dominant forms. The substantial populations of Dorosoma cepedianum seemingly are supported by debris and allochthonous materials and not on the sparse plankton present. Station I and II riffles yielded 2896 and 1108 fishes/ha respectively, Etheostoma caeruleum and Percina caprodes being most numerous. Longitudinal zonation was characterized by decrease in number/ha and species present from headwater to downstream areas

The Aquatic Macroinvertebrates of the White River National Wildlife Refuge

The primary purpose of this study was to survey the diversity of the aquatic macroinvertebrates of the White River National Wildlife Refuge (WRNWR). Determining relative abundance and distributional and seasonal patterns were secondary objectives. No comprehensive investigations of the WRNWR aquatic macroinvertebrates had been conducted previously, and it was hypothesized that this relatively undisturbed area may serve as a refugium. Further, this study provides base line data by which management programs can be composed. Thirty sampling stations were established within the WRNWR. Samples were collected from north to south at a basic rate of five stations per month. Revisit collections were made during the subsequent six month period, providing a total of 60 samples. Each station was sampled on each occasion for 1.4 man hours with a Turtox Indestructible dip net, and specimens were preserved in 70% ethanol. Three black light samples were taken to augment the species list. Of the 15,083 organisms collected, 80.4% were insects while 6.4% were decapod crustaceans, 5.2% were molluscs, 4.5% were isopods and 2.1% were amphipods. Number of taxa collected per station ranged from 8-36, while numerical standing crop ranged from 8-600. Shannon-Wiener diversity values ranged from 1.056-4.717. The most complex aquatic macroinvertebrate communities were found, in general, in the southeastern portion of the refuge. Great diversity here and at a few other stations was correlated with minimal disturbance by human activity. Parts of the WRNWR apparently function as a refugium. Four of the ten leach species collected, and an uncommon beetle, Suphis, were new state records

Effects of thinking-aloud pair problem solving on the troubleshooting performance of undergraduate students in a power technology course

A randomized post-test-only experimental design with a counter-balanced internal replication was used to determine the effects of thinking-aloud pair problem solving (TAPPS) on the troubleshooting performance of college students in a power technology course. The experimental results were stable across two troubleshooting tasks. Students who participated in the pair problem solving groups were significantly more successful (p ≤ .05) at troubleshooting engine faults than were students in the control groups. Among students who successfully completed the troubleshooting tasks across both groups, there were no significant differences in time required for completion. These findings indicate that the use of pair problem solving may be an important step in the development of metacognitive skills among students in technological troubleshootin

Competing Quantum Orderings in Cuprate Superconductors: A Minimal Model

We present a minimal model for cuprate superconductors. At the unrestricted mean-field level, the model produces homogeneous superconductivity at large doping, striped superconductivity in the underdoped regime and various antiferromagnetic phases at low doping and for high temperatures. On the underdoped side, the superconductor is intrinsically inhomogeneous and global phase coherence is achieved through Josephson-like coupling of the superconducting stripes. The model is applied to calculate experimentally measurable ARPES spectra.Comment: 5 pages, 4 eps included figure

Effects of atomic short-range order on the properties of perovskite alloys in their morphotropic phase boundary

The effects of atomic short-range order on the properties of Pb(Zr_{1-x}Ti_x)O_3 alloy in its morphotropic phase boundary (MPB) are predicted by combining first-principles-based methods and annealing techniques. Clustering is found to lead to a compositional expansion of this boundary, while the association of unlike atoms yields a contraction of this region. Atomic short-range order can thus drastically affect properties of perovskite alloys in their MPB, by inducing phase transitions. Microscopic mechanisms responsible for these effects are revealed and discussed.Comment: 4 pages, with 2 postscript figures embedded. Uses REVTEX4 and graphicx macro

Discovery of excess O I absorption towards the z = 6.42 QSO SDSS J1148+5251

We present a search for O I in the spectra of nine 4.9 < z_qso < 6.4 QSOs taken with Keck/HIRES. We detect six systems with N(O I) > 10^13.7 cm^{-2} in the redshift intervals where O I 1302 falls redward of the Ly-alpha forest. Four of these lie towards SDSS J1148+5251 (z_qso = 6.42). This imbalance is unlikely to arise from variations in sensitivity among our data or from a statistical fluctuation. The excess O I occurs over a redshift interval that also contains transmission in Ly-alpha and Ly-beta. Therefore, if these O I systems represent pockets of neutral gas, then they must occur within or near regions of the IGM that are highly ionized. In contrast, no O I is detected towards SDSS J1030+0524 (z_qso = 6.30), whose spectrum shows complete absorption in Ly-alpha and Ly-beta over \Delta z ~ 0.2. Assuming no ionization corrections, we measure mean abundance ratios = -0.04 +/- 0.06, = -0.31 +/- 0.09, and = -0.34 +/- 0.07 (2 sigma), which are consistent with enrichment dominated by Type II supernovae. The O/Si ratio limits the fraction of silicon in these systems contributed by metal-free very massive stars to < 30%, a result which is insensitive to ionization corrections. The ionic comoving mass densities along the z_qso > 6.2 sightlines, including only the detected systems, are \Omega(O I) = (7.0 +/- 0.6) * 10^{-8}, \Omega(Si II) = (9.6 +/- 0.9) * 10^{-9}, and \Omega(C II) = (1.5 +/- 0.2) * 10^{-8}.Comment: Submitted to ApJ, with changes to reflect referee's comment