54 research outputs found
Passerine Birds Breeding under Chronic Noise Experience Reduced Fitness
Background
Fitness in birds has been shown to be negatively associated with anthropogenic noise, but the underlying mechanisms remain obscure. It is however crucial to understand the mechanisms of how urban noise impinges on fitness to obtain a better understanding of the role of chronic noise in urban ecology. Here, we examine three hypotheses on how noise might reduce reproductive output in passerine birds: (H1) by impairing mate choice, (H2) by reducing territory quality and (H3) by impeding chick development.
Methodology/Principal Findings
We used long-term data from an island population of house sparrows, Passer domesticus, in which we can precisely estimate fitness. We found that nests in an area affected by the noise from large generators produced fewer young, of lower body mass, and fewer recruits, even when we corrected statistically for parental genetic quality using a cross-fostering set-up, supporting H3. Also, individual females provided their young with food less often when they bred in the noisy area compared to breeding attempts by the same females elsewhere. Furthermore, we show that females reacted flexibly to increased noise levels by adjusting their provisioning rate in the short term, which suggests that noise may be a causal factor that reduces reproductive output. We rejected H1 and H2 because nestbox occupancy, parental body mass, age and reproductive investment did not differ significantly between noisy and quiet areas.
Conclusions/Significance
Our results suggest a previously undescribed mechanism to explain how environmental noise can reduce fitness in passerine birds: by acoustically masking parentâoffspring communication. More importantly, using a cross-fostering set-up, our results demonstrate that birds breeding in a noisy environment experience significant fitness costs. Chronic noise is omnipresent around human habitation and may produces similar fitness consequences in a wide range of urban bird species
The internal structure of poly(methyl methacrylate) latexes in nonpolar solvents
Hypothesis: Poly(methyl methacrylate) (PMMA) latexes in nonpolar solvents are an excellent model system to understand phenomena in low dielectric media, and understanding their internal structure is critical to characterizing their performance in both fundamental studies of colloidal interactions and in potential industrial applications. Both the PMMA cores and the poly(12-hydroxystearic acid) (PHSA) shells of the latexes are known to be penetrable by solvent and small molecules, but the relevance of this for the properties of these particles is unknown.
Experiments: These particles can be prepared in a broad range of sizes, and two PMMA latexes dispersed in n-dodecane (76 and 685 nm in diameter) were studied using techniques appropriate to their size. Small-angle scattering (using both neutrons and X-rays) was used to study the small latexes, and analytical centrifugation was used to study the large latexes. These studies enabled the calculation of the core densities and the amount of solvent in the stabilizer shells for both latexes. Both have consequences on interpreting measurements using these latexes.
Findings: The PHSA shells are highly solvated (âź85% solvent by volume), as expected for effective steric stabilizers. However, the PHSA chains do contribute to the intensity of neutron scattering measurements on concentrated dispersions and cannot be ignored. The PMMA cores have a slightly lower density than PMMA homopolymer, which shows that only a small free volume is required to allow small molecules to penetrate into the cores. Interestingly, the observations are essentially the same, regardless of the size of the particle; these are general features of these polymer latexes. Despite the latexes being used as a model physical system, the internal chemical structure is complex and must be fully considered when characterizing them
Adam Smith's 'Optimistic Deism', the Invisible Hand of Providence, and the Unhappiness of Nations
This article questions Adam Smithâs commitment to the notion of a beneficent Deity, or âall-perfect Being,â whose purpose is to promote the âreal happinessâ of humankind. It is argued that Smith conceals his true position in The Theory of Moral Sentiments by emphasizing the deceptive âlove of systemâ (the fascination with well-crafted contrivances) as the main spur to material acquisitiveness; by using the empty formulation that âall the different ranks of life are nearly upon a levelâ without specifying which level they are ânearly uponâ; and by introducing a contented beggar, who, with his identity as Diogenes the Cynic cloaked in anonymity, could be tendentiously misconstrued as a representative of the poor and lowly. It is concluded that Smithâs commitment to what I call âoptimistic deismâ must be regarded as deeply suspect and more probably nonexistent, and that as far as âreal happinessâ is concerned his position was one of pessimism of almost Cynic proportions, albeit a pessimism partially obscured by a veiled reference to the greatest Cynic of them all.</jats:p
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