Dielectric properties of Sr3CuNb2O9 perovskite ceramics

The dielectric constant ? and loss tangent tanδ of Sr₃CuNb₂O₉ perovskite ceramics prepared by solid-state reactions have been measured at temperatures from 300 to 900 K and frequencies from 25 to 1 × 10⁶ Hz. The results demonstrate that the samples slowly cooled from the temperature of the final, high-temperature firing (1200°C) have relatively low permittivity (? ? 10) and dielectric losses (tanδ ? 0.005 at 1 kHz) at room temperature, with no strong dielectric dispersion and no prominent maxima in the temperature dependences of their permittivity and dielectric loss. The ceramics quenched from 1300°C exhibit a pronounced Debye-type low-frequency relaxation and strong dielectric dispersion in conjunction with high permittivity ? ? 2000 at low frequencies and/or high temperatures. The observed dielectric anomalies in the Sr₃CuNb₂O₉ ceramics can be understood in terms of Maxwell-Wagner relaxation at dielectric inhomogeneities associated with the quenching-induced difference in oxygen-vacancy concentration between the grain bulk and surface layer.     

Naturally occurring contamination in the Mancos Shale

Some uranium mill tailings disposal cells were constructed on dark-gray shale of the Upper Cretaceous Mancos Shale. Shale of this formation contains contaminants similar to those in mill tailings. To establish the contributions derived from the Mancos, we sampled 51 locations in Colorado, New Mexico, and Utah. Many of the groundwater samples were saline with nitrate, selenium, and uranium concentrations commonly exceeding 250,?000, 1000, and 200 μg/L, respectively. Higher concentrations were limited to groundwater associated with shale beds, but were not correlated with geographic area, stratigraphic position, or source of water. The elevated concentrations suggest that naturally occurring contamination should be considered when evaluating groundwater cleanup levels. At several locations, seep water was yellow or red, caused in part by dissolved organic carbon concentrations up to 280 mg/L. Most seeps had (234)U to (238)U activity ratios greater than 2, indicating preferential leaching of (234)U. Seeps were slightly enriched in (18)O relative to the meteoric water line, indicating limited evaporation. Conceptually, major ion chemical reactions are dominated by calcite dissolution following proton release from pyrite oxidation and subsequent exchange by calcium for sodium residing on clay mineral exchange sites. Contaminants are likely released from organic matter and mineral surfaces during weathering.     

Loline alkaloids in tall fescue hay and seed and their relationship to summer fescue toxicosis in cattle

In three trials, young Holstein steers housed in restraint type crates in a controlled environment room were fed tall fescue hay or seed diets to determine the ability of the diets to produce signs of summer syndrome. Trial 1 examined the effects of dehydration and extended storage of G1-307 fescue compared to alfalfa on dairy steers. Calves fed G1-307 fescue had lower daily feed intake, higher rectal temperatures and respiration rates, and lost 13.4 kg more body weight during the experimental period as compared to those fed alfalfa hay. In trial 2, benomyl (a systemic fungicide) was used to eliminate the fungus Epichloe typhina from treated G1-307 fescue plants. Steers fed the treated G1-307 fescue progeny had higher daily intakes, lower rectal temperature, lower respiration rates, and lost less body weight over the trial period as compared with those fed untreated G1-307 fescue. Kenhy tall fescue seeds with and without analyzable N-acetyl and N-formyl loline alkaloids and a control diet were fed in trial 3. Steers fed the seed with the loline alkaloids had reduced intake, higher rectal temperatures, and lost 10.9 kg more body weight over the trial period than steers fed seed that did not contain loline alkaloids.     

烟草转化株烟碱含量对其向降烟碱转化程度的影响

在烟株生长早期鉴别转化株,需要对转化株的烟碱转化进行诱导以使转化性状充分表达,但同一基因型材料在不同生长条件下经诱导产生的烟碱转化程度存在较大差异。本试验旨在探讨转化株的烟碱基础含量对诱导后烟碱转化程度的影响。结果表明由于打顶和增施氮肥造成烟碱基础含量增高可显著降低诱导后的烟碱转化程度。在温室条件下,通过调节氮肥施用量获得具有不同烟碱含量的植株,以白肋烟TN90的高转化品系为材料的试验表明,当烟碱基础含量超过2.0%时,烟碱向降烟碱转化不完全,随着烟碱含量的增高,烟碱转化百分率几乎呈线形下降。采用由高转化系和非转化系杂交的F1植株为材料进行试验,发现烟碱转化百分率随烟碱含量下降的趋势更加明显。采用低转化株的自交分离后代进行试验,发现在低施氮水平下对转化株进行诱导和鉴别的有效性高于在高施氮条件下对转化株的诱导和鉴别。因此,使烟株维持较低的烟碱水平有利于转化株特别是低转化株的有效鉴别。      

Metal Residues in Farm-Raised Channel Catfish, Rainbow Trout, and Red Swamp Crayfish from the Southern U.S.

ABSTRACT: Farm-raised channel catfish (Ictalurus punctatus), rainbow trout (Oncorhynchus mykiss), and red swamp crayfish (Procambarus clarkii) were collected from production and processing sites across the southern U.S. and analyzed for barium, cadmium, copper, chromium, silver, lead, arsenic, selenium, and mercury. Average metal residues were much lower than recommended safety limits. Residues of barium, copper, and mercury were slightly higher in crayfish than catfish or trout. Selenium was higher in crayfish and trout than catfish, and lead was higher in catfish and trout than crayfish. Residues of mercury in all samples were much lower than the FDA's Action Limit (1 ppm) for mercury in the edible tissue of fish.     

Sublethal concentrations of mercury in river otters: monitoring environmental contamination

Hair, muscle, and liver mercury concentrations were determined in river otter (Lutra canadensis) carcasses collected from the lower coastal plain and piedmont of Georgia. Mean muscle and hair mercury concentrations were greater (P < 0.001) in otters from the lower coastal plain (4.42 and 24.25 mg/kg wet wt, respectively) compared to otters from the piedmont (1.48 and 15.24 mg/kg, respectively). Liver tissue from lower coastal plain otters averaged 7.53 mg/kg mercury. Mean fetus brain and muscle mercury concentrations were 1.03 and 1.58 mg/kg wet wt, respectively, and fetal muscle mercury concentrations were correlated (r = 0.92) with maternal muscle mercury concentrations. Comparison of mercury concentrations found in Georgia otters to those associated with adverse effects in otter and mink (Mustela vison), indicate sublethal contamination with concentrations in some individuals approaching that observed in experimentally dosed individuals that developed clinical signs of mercurialism. Mercury concentrations in fish from the lower coastal plain approached or exceeded concentrations demonstrated to be toxic to experimentally dosed otters.     

Land-Use Planning’s Role in Urban Forest Strategies: Recent Local Government Approaches in Australia

Many urban development processes, supported by land-use planning, negatively impact urban trees. Urban forest strategies are one approach local governments take to protect and increase urban trees. We evaluate connections between urban forest strategies and land-use planning to achieve tree cover on private property, through a review of 18 Australian local government strategies. We highlight the importance of state-level policies for local land-use planning, and conclude that if state-level land-use planning is to aid the protection and enhancement of urban trees, more active engagement with and explicit links to urban forest strategies at both local and state levels is needed.     

Toward a conceptualization of the family's adaptation to a member's head injury: A critique of developmental stage models.

Developmental stage models proposed to conceptualize the family's adaptation to a head-injured member are critiqued. In general, hypotheses about stages have not been subjected to empirical investigation. Due to conceptual problems in the models, the stages do not meet the criteria of legitimate explanatory constructs. In their present form, stages proposed by different models are, at best, of heuristic value. It is argued that principles from S. Minuchin's (1974) structural family therapy model may be integrated with the stage model approach in a manner that helps resolve some conceptual problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decreased type II/type I TGF-beta receptor ratio in cells derived from human atherosclerotic lesions. Conversion from an antiproliferative to profibrotic response to TGF-beta1

Atherosclerosis and postangioplasty restenosis may result from abnormal wound healing. The present studies report that normal human smooth muscle cells are growth inhibited by TGF-beta1, a potent wound healing agent, and show little induction of collagen synthesis to TGF-beta1, yet cells grown from human vascular lesions are growth stimulated by TGF-beta1 and markedly increase collagen synthesis. Both cell types increase plasminogen activator inhibitor-1 production, switch actin phenotypes in response to TGF-beta1, and produce similar levels of TGF-beta activity. Membrane cross-linking of 125I-TGF-beta1 indicates that normal human smooth muscle cells express type I, II, and III receptors. The type II receptor is strikingly decreased in lesion cells, with little change in the type I or III receptors. RT-PCR confirmed that the type II TGF-beta1 receptor mRNA is reduced in lesion cells. Transfection of the type II receptor into lesion cells restores the growth inhibitory response to TGF-beta1, implying that signaling remains responsive. Because TGF-beta1 is overexpressed in fibroproliferative vascular lesions, receptor-variant cells would be allowed to grow in a slow, but uncontrolled fashion, while overproducing extracellular matrix components. This TGF-beta1 receptor dysfunction may be relevant for atherosclerosis, restenosis and related fibroproliferative diseases.     

Laboratory animal allergy

Since the second World War, excess mortality of males has been steadily growing in Poland. The aim of this paper was to analyze the basic relationships between excess male mortality and some social and economic factors, with special reference to both age and place of residence. Data published in Demographic Yearbooks and included in reports produced by the Government Population Council were used in the analysis. The excess male mortality is expressed in terms of male/female mortality ratio, and also in terms of the difference between the average female and male life expectancy. In the early 1990s the general male mortality rate in Poland was by 23% higher than the general female mortality rate, whereas in males at younger working age (20-44 years) mortality was three times higher, and in the older age (45-64 years) groups 2.7 times higher than the female mortality. Compared with the majority of European countries, Poland is characterised by high rates of excess male mortality, which points to a deteriorated health status of the population. At present, excess mortality of the working age males is much higher than in the 1960s and 1970s. Our analysis of the 1960-1994 trends revealed that the highest excess male mortality occurs in the 20-24 age group. Although recently a falling trend has been observed in the infant, juvenile and post working age groups, a continuous increase is noted in the working age population of Poland. Causes of death were also included in our analysis. Among circulatory diseases, the highest excess mortality was due to acute myocardial infarction (the risk of death from this disease was 8 times higher for males than for females). Accidents, injuries and poisoning constitute another leading group of causes responsible for excess mortality (6/1 male/female death risk ratio). The excess male mortality rates are higher in the rural than in the urban areas. The excess male mortality was also reflected in the indices of average life expectancy. In 1995, the average life expectancy was 67.6 years for males and 76.4 years for females. Thus, in Poland males live 8.6 years shorter than females on average. Increased excess mortality among the working age males, a considerable difference between male and female average life expectancy, disturbed demographic male/female balance, these are at least some of the reasons why further in depth studies of excess male mortality in Poland should continue.