3,322 research outputs found
The presumption of sociality: Social learning in diverse contexts in brown-headed cowbirds (Molothrus ater).
Data are presented on social and vocal learning in cowbirds (Molothrus ater) housed in large aviaries and given more degrees of freedom than in conventional experimental studies. The studies show that social and vocal outcomes are facultative responses to social contexts. Several findings are reviewed: First, cowbirds quickly self-organize into groups by age and sex; second, opportunities to interact across age and sex do exist and affect courtship competence; third, female cowbirds organize themselves differently in the presence and absence of male competition; and fourth, young, naive cowbirds show rapid and differential sensitivity to group dynamics. Taken as a whole, the data show that social Umwelten are dynamic, developmental ecologies. Solitude is a human presumption. Every quiet step is thunder to beetle life underfoot, a tug of impalpable thread on the web pulling the mate to mate and predator to prey, a beginning or an end. Every choice is a new beginning for the chosen.-Barbara Kingsolver, Prodigal Summer Terra firma provides humans with sure footing but sometimes narrow thinking about the sensory world of other inhabitants. The air-ground complex is one of myriad environments, many neithe
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Conformational modulation of sequence recognition in synthetic macromolecules
The different triplet sequences in high molecular weight aromatic copolyimides comprising pyromellitimide units ("I") flanked by either ether-ketone ("K") or ether-sulfone residues ("S") show different binding strengths for pyrene-based tweezer-molecules. Such molecules bind primarily to the diimide unit through complementary π-π-stacking and hydrogen bonding. However, as shown by the magnitudes of 1H NMR complexation shifts and tweezer-polymer binding constants, the triplet "SIS" binds tweezer-molecules more strongly than "KIS" which in turn bind such molecules more strongly than "KIK". Computational models for tweezer-polymer binding, together with single-crystal X-ray analyses of tweezer-complexes with macrocyclic ether-imides, reveal that the variations in binding strength between the different triplet sequences arise from the different conformational preferences of aromatic rings at diarylketone and diarylsulfone linkages. These preferences determine whether or not chain-folding and secondary π−π-stacking occurs between the arms of the tweezermolecule and the 4,4'-biphenylene units which flank the central diimide residue
Projected climate-induced faunal change in the western hemisphere
Climate change is predicted to be one of the greatest drivers of ecological change in the coming century. Increases in temperature over the last century have clearly been linked to shifts in species distributions. Given the magnitude of projected future climatic changes, we can expect even larger range shifts in the coming century. These changes will, in turn, alter ecological communities and the functioning of ecosystems. Despite the seriousness of predicted climate change, the uncertainty in climate-change projections makes it difficult for conservation managers and planners to proactively respond to climate stresses. To address one aspect of this uncertainty, we identified predictions of faunal change for which a high level of consensus was exhibited by different climate models. Specifically, we assessed the potential effects of 30 coupled atmosphere–ocean general circulation model (AOGCM) future-climate simulations on the geographic ranges of 2954 species of birds, mammals, and amphibians in the Western Hemisphere. Eighty percent of the climate projections based on a relatively low greenhouse-gas emissions scenario result in the local loss of at least 10% of the vertebrate fauna over much of North and South America. The largest changes in fauna are predicted for the tundra, Central America, and the Andes Mountains where, assuming no dispersal constraints, specific areas are likely to experience over 90% turnover, so that faunal distributions in the future will bear little resemblance to those of today
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Synthesis, x-ray structure and anion binding properties of a cryptand-like hybrid calixpyrrole
The novel cryptand in/out-3, containing two tripyrrolemethane units briged by three 1,3- diisopropylidenbenzene arms was readily synthesized by a convergent three-step synthesis. It binds fluoride by inclusion with excellent selectivity with respect to a number of other tested anions. The structure of the free receptor and that of its fluoride complex were investigated in solution by NMR spectroscopy. The solid state X-ray structure of the free cryptand 3 was also determined
Synthesis and Characterization of Two Novel Zinc(II) Complexes with Ciprofloxacin. Crystal Structure of [C17H19N3O3F]2 ⋅ [ZnCl4] ⋅ 2H2O
The complexation of ZnII ions with quinolone in aqueous solution depends mainly upon pH. To investigate the pH dependence of the complexation between ZnII and the quinolone derivative Ciprofloxacin (abbreviation cfH), UV-Vis spectroscopy was used. The crystal structure of the compound [C17H19N3O3F]2 ⋅ [ZnCl4] ⋅ 2H2O (compound I) was determined by X-ray diffraction, which showed the structure to be ionic, consisting of a tetrachlorozincate(II) dianion and two protonated, monocationic Ciprofloxacin molecules. Compound II ([Zn(cf)2] ⋅ 3H2O) was obtained as microcrystals from an aqueous solution of Ciprofloxacin hydrochloride and zine sulphate adjusted to pH = 8 by the addition of sodium hydroxide. Both complexes were characterized by elemental analysis, mass speetrometry, TG analysis and IR spectroscopy. From the analysis of these results we have proposed a probable mode of bonding for the complexation of ZnII to Ciprofloxacin in compound II
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Shoot yield drives phosphorus use efficiency in Brassica oleracea and correlates with root architecture traits
The environmental and financial costs of using inorganic phosphate fertilizers to maintain crop yield and quality are high. Breeding crops that acquire and use phosphorus (P) more efficiently could reduce these costs. The variation in shoot P concentration (shoot-P) and various measures of P use efficiency (PUE) were quantified among 355 Brassica oleracea L. accessions, 74 current commercial cultivars, and 90 doubled haploid (DH) mapping lines from a reference genetic mapping population. Accessions were grown at two or more external P concentrations in glasshouse experiments; commercial and DH accessions were also grown in replicated field experiments. Within the substantial species-wide diversity observed for shoot-P and various measures of PUE in B. oleracea, current commercial cultivars have greater PUE than would be expected by chance. This may be a consequence of breeding for increased yield, which is a significant component of most measures of PUE, or early establishment. Root development and architecture correlate with PUE; in particular, lateral root number, length, and growth rate. Significant quantitative trait loci associated with shoot-P and PUE occur on chromosomes C3 and C7. These data provide information to initiate breeding programmes to improve PUE in B. oleracea
Brain Specificity of Diffuse Optical Imaging: Improvements from Superficial Signal Regression and Tomography
Functional near infrared spectroscopy (fNIRS) is a portable monitor of cerebral hemodynamics with wide clinical potential. However, in fNIRS, the vascular signal from the brain is often obscured by vascular signals present in the scalp and skull. In this paper, we evaluate two methods for improving in vivo data from adult human subjects through the use of high-density diffuse optical tomography (DOT). First, we test whether we can extend superficial regression methods (which utilize the multiple source–detector pair separations) from sparse optode arrays to application with DOT imaging arrays. In order to accomplish this goal, we modify the method to remove physiological artifacts from deeper sampling channels using an average of shallow measurements. Second, DOT provides three-dimensional image reconstructions and should explicitly separate different tissue layers. We test whether DOT's depth-sectioning can completely remove superficial physiological artifacts. Herein, we assess improvements in signal quality and reproducibility due to these methods using a well-characterized visual paradigm and our high-density DOT system. Both approaches remove noise from the data, resulting in cleaner imaging and more consistent hemodynamic responses. Additionally, the two methods act synergistically, with greater improvements when the approaches are used together
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Soil Microbial Networks Shift Across a High-Elevation Successional Gradient.
While it is well established that microbial composition and diversity shift along environmental gradients, how interactions among microbes change is poorly understood. Here, we tested how community structure and species interactions among diverse groups of soil microbes (bacteria, fungi, non-fungal eukaryotes) change across a fundamental ecological gradient, succession. Our study system is a high-elevation alpine ecosystem that exhibits variability in successional stage due to topography and harsh environmental conditions. We used hierarchical Bayesian joint distribution modeling to remove the influence of environmental covariates on species distributions and generated interaction networks using the residual species-to-species variance-covariance matrix. We hypothesized that as ecological succession proceeds, diversity will increase, species composition will change, and soil microbial networks will become more complex. As expected, we found that diversity of most taxonomic groups increased over succession, and species composition changed considerably. Interestingly, and contrary to our hypothesis, interaction networks became less complex over succession (fewer interactions per taxon). Interactions between photosynthetic microbes and any other organism became less frequent over the gradient, whereas interactions between plants or soil microfauna and any other organism were more abundant in late succession. Results demonstrate that patterns in diversity and composition do not necessarily relate to patterns in network complexity and suggest that network analyses provide new insight into the ecology of highly diverse, microscopic communities
Yttrium-Catalyzed Amine–Silane Dehydrocoupling: Extended Reaction Scope with a Phosphorus-Based Ligand
The
scope of the catalytic dehydrocoupling of primary and secondary
amines with phenylsilanes has been investigated using [Y{N(SiMe<sub>3</sub>)<sub>2</sub>}<sub>3</sub>] and a four-coordinate analogue
bearing a cyclometalated phosphonium methylide ligand. Inclusion of
the phosphorus-based ligand on yttrium results in increased substrate
scope in comparison to the tris(amide) analogue. While reversible
C–H bond activation of the cyclometalated ligand was observed
in stoichiometric experiments, D-labeling experiments and DFT calculations
suggest that reversible ligand activation is not involved in silazane
formation under catalytic conditions. We suggest that the extended
reaction scope with the four-coordinate yttrium phosphonium methylide
complex relative to the three-coordinate yttrium (tris)amide complex
is a result of differences in the ease of amine inhibition of catalysis
Comparison of geomechanical deformation induced by megatonne-scale CO2 storage at Sleipner, Weyburn, and In Salah
Geological storage of CO2 that has been captured at large, point source emitters represents a key potential method for reduction of anthropogenic greenhouse gas emissions. However, this technology will only be viable if it can be guaranteed that injected CO2 will remain trapped in the subsurface for thousands of years or more. A significant issue for storage security is the geomechanical response of the reservoir. Concerns have been raised that geomechanical deformation induced by CO2 injection will create or reactivate fracture networks in the sealing caprocks, providing a pathway for CO2 leakage. In this paper, we examine three large-scale sites where CO2 is injected at rates of ∼1 megatonne/y or more: Sleipner, Weyburn, and In Salah. We compare and contrast the observed geomechanical behavior of each site, with particular focus on the risks to storage security posed by geomechanical deformation. At Sleipner, the large, high-permeability storage aquifer has experienced little pore pressure increase over 15 y of injection, implying little possibility of geomechanical deformation. At Weyburn, 45 y of oil production has depleted pore pressures before increases associated with CO2 injection. The long history of the field has led to complicated, sometimes nonintuitive geomechanical deformation. At In Salah, injection into the water leg of a gas reservoir has increased pore pressures, leading to uplift and substantial microseismic activity. The differences in the geomechanical responses of these sites emphasize the need for systematic geomechanical appraisal before injection in any potential storage sit
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