Modulation of pair bonding in female prairie voles (Microtus ochrogaster) by corticosterone.

Glucocorticoid levels in animals may respond to and influence the development of social attachments. This hypothesis was tested in prairie voles (Microtus ochrogaster), monogamous rodents that form long-term heterosexual pair bonds. In socially naive female prairie voles, cohabitation with an unfamiliar male resulted in a dramatic decline in serum corticosterone levels. When corticosterone levels were reduced via adrenalectomy, females developed partner preferences after 1 h of cohabitation, while sham-operated and untreated females required 3 h or more of nonsexual cohabitation to establish a partner preference. In adrenalectomized and intact females, exogenous injections of corticosterone, given prior to social exposure, prevented the development of preferences for the cohabitating male. Although corticosterone inhibited the development of partner preferences, it did not interfere with the expression of previously established social preferences. These results suggest that social stimuli can modulate adrenal activity and that adrenal activity, in turn, is capable of influencing the formation of adult social preferences in female prairie voles. The involvement of the adrenal axis in the formation of partner preferences and the subsequent development of pair bonds provides a mechanism through which environmental and social factors may influence social organization in this species.

Drought and grazing combined: Contrasting shifts in plant interactions at species pair and community level

The combined effects of drought stress and grazing pressure on shaping plant–plant interactions are still poorly understood, while this combination is common in arid ecosystems. In this study we assessed the relative effect of grazing pressure and slope aspect (drought stress) on vegetation cover and soil functioning in semi-arid Mediterranean grassland–shrublands in southeastern Spain. Moreover, we linked these two stress factors to plant co-occurrence patterns at species-pair and community levels, by performing C-score analyses. Vegetation cover and soil functioning decreased with higher grazing pressure and more south-facing (drier) slopes. At the community level, plants at south-facing slopes were negatively associated at no grazing but positively associated at low grazing pressure and randomly associated at high grazing pressure. At north-facing slopes, grazing did not result in a shift in the direction of the association. In contrast, analysis of pairwise species co-occurrence patterns showed that the dominant species Stipa tenacissima and Anthyllis cytisoides shifted from excluding each other to co-occurring with increasing grazing pressure at north-facing slopes. Our findings highlight that for improved understanding of plant interactions along stress gradients, interactions between species pairs and interactions at the community level should be assessed, as these may reveal contrasting results.

Mercury determination in urine samples by gold nanostructured screen-printed carbon electrodes after vortex-assisted ionic liquid dispersive liquid–liquid microextraction

A novel approach is presented to determine mercury in urine samples, employing vortex-assisted ionic liquid dispersive liquid–liquid microextraction and microvolume back-extraction to prepare samples, and screen-printed electrodes modified with gold nanoparticles for voltammetric analysis. Mercury was extracted directly from non-digested urine samples in a water-immiscible ionic liquid, being back-extracted into an acidic aqueous solution. Subsequently, it was determined using gold nanoparticle-modified screen-printed electrodes. Under optimized microextraction conditions, standard addition calibration was applied to urine samples containing 5, 10 and 15 μg L−1 of mercury. Standard addition calibration curves using standards between 0 and 20 μg L−1 gave a high level of linearity with correlation coefficients ranging from 0.990 to 0.999 (N = 5). The limit of detection was empirical and statistically evaluated, obtaining values that ranged from 0.5 to 1.5 μg L−1, and from 1.1 to 1.3 μg L−1, respectively, which are significantly lower than the threshold level established by the World Health Organization for normal mercury content in urine (i.e., 10–20 μg L−1). A certified reference material (REC-8848/Level II) was analyzed to assess method accuracy finding 87% and 3 μg L−1 as the recovery (trueness) and standard deviation values, respectively. Finally, the method was used to analyze spiked urine samples, obtaining good agreement between spiked and found concentrations (recovery ranged from 97 to 100%).

Three particle effects in the pair distribution function for He [superscript 4] gas,

"Supported in part by the Atomic Energy Commission."

Path integral calculation of the three-particle direct and exchange contributions to the pair distribution function and of the third virial coefficient for He4 gas /

Thesis--Illinois.

Pair of Doors Carved in the 'Beveled Style'

Wood, Iraq, Abbasid; 7 ft. 3 3/4 in.x 17 ft. 5 27/32 in.x 1 1/2 in. (left); 7 ft. 2 1/2 in.x 1 ft. 8 15/64 in.x 1 1/2 in. (right); teak

Villa of Agrippa Postumus, Egyptianizing scene and a pair of swans: detail

Boscotrecase, Italy; fresco on lime plaster

The motion of turbulent vortex-pairs in homogeneous and density stratified media /

Photocopy of microfilm. Springfield, Va. : National Technical Information Service, [1979]

Mémoires et souvenirs d'un pair de france-- .

Vols. 3-4 have imprint: Paris, E. Guyot, 1830.

Memoires du Marechal de Berwik, duc et pair de France et generalissime des armées de sa majesté : tome second

Mode of access: Internet.

[Le liure de la toute belle sans pair qui est la Vierge Marie]

Mode of access: Internet.

Mémoires du Maréchal de Berwik, Duc et Pair de France, et Généralissime des Armées de Sa Majesté : tome premier.

ICCU,

Souvenirs intimes et notes du Baron Mounier, secrétaire de Napoléon ler, pair de France, directeur général de la police;

Editor's name, comte d'Hérisson, at head of title.

Pair of Eyes

Sculpture, Techniques, Greek; 1 1/2 in.x 2 1/64 in.; marble, frit, quartz, obisidan and bronze