Showing papers by "University of Arkansas published in 1988"

Bulk superconductivity at 120 K in the Tl-Ca/Ba-Cu-O system

Abstract: The discovery of 30-K superconductivity in the La–Ba–Cu–O system1 and 90-K superconductivity in the Y–Ba–Cu–O system2 stimulated a worldwide search for even higher-temperature superconductors. Unfortunately, most of the higher-temperature transitions reported in the past year have proved to be unstable, irreproducible, or not due to bulk superconductivity3–7. Recently, we and co-workers8,9 reported superconductivity above 90 K in a new Tl–Ba–Cu–O system, and pointed out that elemental substitutions in this system may lead to even higher-temperature superconductivity. Here we report stable and reproducible bulk superconductivity with an onset at 120 K and zero resistance above 100 K in the Tl–Ca/Ba–Cu–O system. This transition temperature is much higher than those observed for typical rare-earth-containing superconductors, and the onset temperatures are comparable to that in the Bi–Ca/Sr–Cu–O system, as reported in refs 10 and 11 (received after submission of this paper).

Superconductivity in the rare-earth-free Tl–Ba–Cu–O system above liquid-nitrogen temperature

Abstract: The initial discovery by Bednorz and Muller1 of 35-K superconductivity in the La-Ba-Cu-O system has stimulated worldwide activity in searching for higher-temperature superconductors. Elemental substitution has proved to be most effective in raising transition temperature. Substitution of Sr for Ba has produced 40-K superconductivity2–5and substitution of Y for La has produced a new high-temperature superconductor with transition temperature above liquid-nitrogen temperature6. A class of superconducting compounds of the form RBa2Cu307-x has been explored by further substitutions of other rare earths (Y is considered in the rare-earth [RI category here) for Y7-13. To date, a rare earth, an alkaline earth, copper and oxygen have been required for all high-temperature superconductors14,15. (Zhanget al 14reported 90-K superconductivity in the Th-Ba-Pb(Zr)-Cu-O system. Panetal15reported 50-K superconductivity in the Y-Ba-Ag-O system. As Th is a member of the actinide series which belongs to the same Group 3B in the periodic table as the lanthanide series and Ag belongs to the same Group 1B as Cu, high-temperature supercon-ductors are still thought to be closed in the Group 3B—Group 2A-Group 1B—oxygen system. ) Only partial substitutions ha. e led to superconductors, but with no significant rise of transition tem-perature (the only exception is 40-K superconductivity in La2CuO4-x , refs 16, 17). Here we report superconductivity in the rare-earth-free TI-Ba-Cu-O system. We have obsened sharp drops of resistance starting above 90 K with zero resistance at 81 K in this system. Magnetic measurements have confirmed that these sharp drops of resistance in the TI-Ba-Cu-O samples origi-nate from superconductivity. The samples are stable in air for at least two months, and their preparation is easily reproduced.

Psychological and behavioral correlates of family violence in child witnesses and victims.

Abstract: Abused and nonabused child witnesses to parental violence temporarily residing in a battered women's shelter were compared to children from a similar economic background on measures of self-esteem, anxiety, depression, and behavior problems, using mothers' and self-reports. Results indicated significantly more distress in the abused-witness children than in the comparison group, with nonabused witness children's scores falling between the two. Age of child and types of violence were mediating factors. Implications of the findings are discussed.

100-K superconducting phases in the Tl-Ca-Ba-Cu-O system.

Abstract: Two superconducting phases, ${\mathrm{Tl}}_{2}$${\mathrm{Ca}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{10+\mathrm{\ensuremath{\delta}}}$ (2223) and ${\mathrm{Tl}}_{2}$${\mathrm{Ca}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{2}$${)}_{8+\mathrm{\ensuremath{\delta}}}$ (2122), both with onset ${\mathrm{T}}_{\mathrm{c}}$ near 120 K and zero resistivity at 100 K, have been isolated from samples in the Tl-Ca-Ba-Cu-O system. The new 2223 superconductor has a 5.40\ifmmode\times\else\texttimes\fi{}5.40\ifmmode\times\else\texttimes\fi{}36.25-A${\mathrm{\r{}}}^{3}$ pseudotetragonal unit cell. The 2122 superconductor, which appears to be structurally related to ${\mathrm{Bi}}_{2}$${\mathrm{CaSr}}_{2}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$, has a 5.44\ifmmode\times\else\texttimes\fi{}5.44\ifmmode\times\else\texttimes\fi{}29.55-A${\mathrm{\r{}}}^{3}$ pseudotetragonal subcell. The 2223 phase is probably related to 2122 by the addition of extra calcium and copper layers.

Superconductivity at 90 K in the Tl-Ba-Cu-O system.

Abstract: Stable and reproducible superconductivity has been unambiguously observed in a new Tl-Ba-Cu-O system containing no group-IIIB elements. Resistance in these rare-earth--free oxides starts to drop sharply above 90 K and reaches zero at 81 K. Meissner flux expulsion and diamagnetic shielding show bulk superconductivity. Further substitutions of elements for this system may lead to even higher-temperature superconductors.

Confirmatory factor analysis of the interpersonal support evaluation list

Abstract: Cohen and Hoberman (1983) designed the Interpersonal Support Evaluation List (ISEL) to measure the perceived availability of four relatively independent social support resources and thus to provide tests of stress-buffering hypotheses. The utility of the ISEL for such tests requires evidence that it actually measures distinct functional support dimensions. A confirmatory factor analysis of the ISEL for 133 college students showed that a four-factor model provided a reasonable fit to the data, but the large correlations among the four factors were strongly suggestive of a general, second-order social support factor. However, scoring the ISEL as a unidimensional measure only would result in the loss of unique information contained in the four subscales. Researchers should therefore follow Cohen and Hoberman's procedure of analyzing ISEL subscale scores and the total score.

North Carolina climate changes reconstructed from tree rings: a.d. 372 to 1985.

Abstract: Millennium-old bald cypres trees (Taxodium distichum [(L.) Rich.] have ben used to develop a 1614-year reconstruction of the June Palmer drought severity index for North Carolina. This proxy paleoclimatic record indicates that the growing season climate of North Carolina has undergone many changes between significantly different regimes of drought and wetness that persist for approximately 30 years. Alternating wet and dry regimes were particularly well developed during the Medieval Warm Epoch (A.D. 1000 to 1300). The record June droughts in 1985 and 1986 and the preceding three decades of much wetter than average conditions both appear to have been rare climatic events, equaled only five times each since A.D. 372.

The effect of Acremonium coenophialum on the growth and nematode infestation of tall fescue

Abstract: The presence of the endophytic fungusAcremonium coenophialum Morgan-Jones et Gams in tall fescue (Festuca arundinacea Schreb.) induces toxicity when this grass is grazed by cattle; however, there is evidence that removing the endophyte reduces the stand vigor and longevity of fescue. A field trial was conducted to determine the effects of water supply and the presence of the endophytic fungus on plant growth, drought tolerance, and soil nematode populations in ‘Kentucky 31’ tall fescue. The design included two factors, level of endophyte infection (0 and 75%) and irrigation regime (none, low, and high). Where water deficits occurred, herbage yield and leaf area were lower, and percentage dead tissue and canopy minus air temperature were greater in endophyte-free compared with endophyte-infected fescue. Soil populations ofPratylenchus scribneri andTylenchorhynchus acutus were substantially higher in the noninfected than in the endophyte-infected plots. The endophyte apparently confers drought tolerance to Kentucky 31 tall fescue, and this effect may be at least partially mediated through enhanced resistance to soil-borne nematodes.

Ego involvement and leisure behavior: a conceptual specification.

Abstract: Numerous theories have been advanced to explain the social psychological attachments between individuals and leisure pursuits. Unfortunately, many of the theories overlap in meaning. Most lack the ...

Texas drought history reconstructed and analyzed from 1698 to 1980

Abstract: A selected group of nine climate-sensitive tree-ring chronologies from old post oak trees are used to reconstruct the June Palmer Drought Severity Index (PDSI) from 1698 to 1980 for two large regions in northern and southern Texas. Analysis of tree growth and monthly climate variables indicate that the June PDSI is the most robust climate signal evident in these chronologies, and principal component analysis (PCA) reveals a north-south geographic pattern in the relationships between the regional tree-ring time series. Serially random amplitude series from the first two significant eigenvectors of tree growth, which explain 65% of the total variance in the tree-ring data, were entered into stepwise multiple regression as predictors of regionally averaged June PDSI in north and south Texas for the common interval 1931–80. The regression models explain 59% and 60% of the variance in north and south Texas June PDSI, respectively, and both reconstructions are well verified against independent June PDS...

Single-atom cavity-enhanced absorption. I. Photon statistics in the bad-cavity limit

Abstract: The photon statistics of the transmitted light from a driven cavity containing a single resonant two-level atom are studied in the bad-cavity limit. For weak driving fields, the second-order intensity correlation function shows novel nonclassical behavior due to the interference of the driving field and forward reradiation from the atom. This behavior is related to squeezing in the cavity transmission. A physical interpretation is given in terms of the reduced quantum state of the coupled atom-field system following photodetection. >

An analysis of consumer loyalty to municipal recreation programs

Abstract: This study of participant loyalty to selected municipal recreation programs emerged from the consumer behavior literature on brand loyalty, applying the concept to a service‐oriented leisure agency. Using a two‐dimensional measure of loyalty, incorporating both a behavioral or repeat purchasing dimension and an attitudinal or commitment dimension, this study found that participants exhibited a high degree of repeat purchasing and only a moderate level of commitment to agency programs. Loyalty segmentation results demonstrated that loyal patrons were more likely to be older and have more agency experience than less loyal participants. Applications of the study to program marketing and to future research are discussed.

Biological production of alcohols from coal through indirect liquefaction

Abstract: A bacterial culture has been isolated from animal waste that is capable of converting CO in synthesis gas to ethanol and acetate. The culture requires a yeast extract level of approximately.01 g/L, and the conversion is enhanced by agitation. The culture produces a higher yield of ethanol and ratio of ethanol to acetate when BESA and excess yeast extract are removed from the media. An ethanol concentration of 4.3 g/L has been obtained in batch screening experiments. The culture has been purified by successive dilution and tentatively identified as a member of theClostridium species. Further experimentation is required for positive identification.

Valuing Forecast Characteristics in a Dynamic Agricultural Production System

Abstract: A dynamic programming model of east-central Illinois corn production is utilized to determine the value of seasonal climate forecasts. Results indicate that the value of climate forecasts is sensitive to economic conditions as well as forecast characteristics. A trade-off between forecast accuracy and lead time exists. A less accurate forecast received earlier in the production process may be more valuable than a more accurate forecast received later. Additional characteristics evaluated include forecast periods of greatest importance, prior knowledge assumptions, and interactions between forecasting adjacent periods.

Resonant Mie scattering from a layered sphere

Abstract: The theory of Aden and Kerker is used to compute the resonant response of large layered spheres to an incident linearly polarized plane wave. Cases considered include hollow spheres and those with transparent and absorbing cores whose diameters range from zero up to that of the particle. Both core and layer resonances are studied. The results are presented as partial wave amplitudes, energy densities, and scattered light intensities for a typical resonant mode, TE39.

Superconductivity in the Tl-Sr-Ca-Cu-O system

Abstract: Superconductivity at 20 K has been unambiguously observed in the Tl-Sr-Ca-Cu-O system. Superconductivity at 70 K was also observed in the same system. These observations may provide a new insight into the mechanism of oxide superconductivity.

Bulk superconductivity in Tl2CaBa2Cu2O8+δ up to 120 K

Abstract: Recently, Sheng and Hermann1 reported the achievement of zero resistance at >100 K in the system Tl–Ca–Ba–Cu–O (TCBCO). Two superconducting phases were immediately identified2 as Tl2CaBa2Cu2O8+δ (2122) and Tl2Ca2Ba2Cu3O10+δ (2223). Here we confirm that zero resistance is achievable above 100 K in 2122–TCBCO synthesized by a fast solid-state reaction, and report a small positive pressure dependence of the transition temperature, as in Bi2CaSr2Cu2O8+δ3.

Chronology of the differentiation of cotton (Gossypium hirsutum L.) fiber cells.

Abstract: Cotton fibers are single elongated cells that develop from epidermal cells of the ovule. The chronology of fiber differentiation was investigated using cultured ovules. Epidermal cells differentiate into fiber cells approx. 3 d before anthesis. When ovules were cultured on a defined medium, fiber growth could be initiated on ovules any time between 2 d preanthesis and the time of anthesis by adding indole-3-acetic acid and gibberellic acid to the medium. In the absence of phytohormones, fibers did not grow, and when ovules between 2 d preanthesis and anthesis were cultured without hormones past the day of anthesis and hormones then added, most ovules failed to produce fibers. The results define the timing of fiber differentiation from epidermal cells, and also define a window of time when differentiated cells are capable of further development. During this window, fiber cells are latent awaiting appropriate stimulation which in the intact plant is apparently associated with anthesis.