Species-specific relationships between water transparency and male coloration within and between two closely related Lake Victoria cichlid species

Environmental variation in signalling conditions affects animal communication traits, with possible consequences for sexual selection and reproductive isolation. Using spectrophotometry, we studied how male coloration within and between populations of two closely related Lake Victoria cichlid species (Pundamilia pundamilia and P. nyererei) covaries with water transparency. Focusing on coloration patches implicated in sexual selection, we predicted that in clear waters, with broad-spectrum light, (1) colours should become more saturated and (2) shift in hue away from the dominant ambient wavelengths, compared to more turbid waters. We found support for these predictions for the red and yellow coloration of P. nyererei but not the blue coloration of P. pundamilia. This may be explained by the species difference in depth distribution, which generates a steeper gradient in visual conditions for P. nyererei compared to P. pundamilia. Alternatively, the importance of male coloration in intraspecific sexual selection may differ between the species. We also found that anal fin spots, that is, the orange spots on male haplochromine anal fins that presumably mimic eggs, covaried with water transparency in a similar way for both species. This is in contrast to the other body regions studied and suggests that, while indeed functioning as signals, these spots may not play a role in species differentiation.</p

Less than 50% sublattice polarization in an insulating S=3/2 kagome' antiferromagnet at low T

We have found weak long range antiferromagnetic order in the quasi-two-dimensional insulating oxide $KCr_3(OD)_6(SO_4)_2$ which contains Cr$^{3+}$ S=3/2 ions on a kagom\'{e} lattice. In a sample with $\approx$ 76% occupancy of the chromium sites the ordered moment is 1.1(3)$\mu_B$ per chromium ion which is only one third of the N\'{e}el value $g\mu_BS=3\mu_B$. The magnetic unit cell equals the chemical unit cell, a situation which is favored by inter-plane interactions. Gapless quantum spin-fluctuations ($\Delta/k_B >$T_N$= 1.6K are the dominant contribution to the spin correlation function,$S(Q,\omega)$ in the ordered phase.Comment: 18 pages, RevTex/Latex, with 6 figure

Habitat-related birdsong divergence: a multi-level study on the influence of territory density and ambient noise in European blackbirds

Song plays an important role in avian communication and acoustic variation is important at both the individual and population level. Habitat-related variation between populations in particular can reflect adaptations to the environment accumulated over generations, but this may not always be the case. In this study, we test whether variation between individuals matches local conditions with respect to noise level and territory density to examine whether short-term flexibility could contribute to song divergence at the population level. We conducted a case study on an urban and forest population of the European blackbird and show divergence at the population level (i.e. across habitats) in blackbird song, anthropogenic noise level and territory density. Unlike in several other species, we found a lack of any correlation at the individual level (i.e. across individuals) between song features and ambient noise. This suggests species-specific causal explanations for noise-dependent song differentiation which are likely associated with variation in song-copying behaviour or feedback constraints related to variable singing styles. On the other hand, we found that at the level of individual territories, temporal features, but not spectral ones, are correlated to territory density and seasonality. This suggests that short-term individual variation can indeed contribute to habitat-dependent divergence at the population level. As this may undermine the potential role for song as a population marker, we conclude that more investigations on individual song flexibility are required for a better understanding of the impact of population-level song divergence on hybridisation and speciation

Transmission Characteristics of Primate Vocalizations: Implications for Acoustic Analyses

Acoustic analyses have become a staple method in field studies of animal vocal communication, with nearly all investigations using computer-based approaches to extract specific features from sounds. Various algorithms can be used to extract acoustic variables that may then be related to variables such as individual identity, context or reproductive state. Habitat structure and recording conditions, however, have strong effects on the acoustic structure of sound signals. The purpose of this study was to identify which acoustic parameters reliably describe features of propagated sounds. We conducted broadcast experiments and examined the influence of habitat type, transmission height, and re-recording distance on the validity (deviation from the original sound) and reliability (variation within identical recording conditions) of acoustic features of different primate call types. Validity and reliability varied independently of each other in relation to habitat, transmission height, and re-recording distance, and depended strongly on the call type. The smallest deviations from the original sounds were obtained by a visually-controlled calculation of the fundamental frequency. Start- and end parameters of a sound were most susceptible to degradation in the environment. Because the recording conditions can have appreciable effects on acoustic parameters, it is advisable to validate the extraction method of acoustic variables from recordings over longer distances before using them in acoustic analyses

Physicochemical Characterization of Tris(5-acetyl-3-thienyl)methane Inclusion Compounds with 1,n-Dichloroalkane Guests (n=1 to 10). A Combined TGA, 13C CP/MAS NMR, Powder X-ray Diffraction and DSC Study

Various physicochemical characterization techniques were used to study tris(5-acetyl-3-thienyl)methane (TATM) inclusion compounds with 1,n-dichloroalkane guests (n=1-10). Thermogravimetric analysis (TGA) experiments allowed us to determine host-guest stoichiometric ratios. We determined that the smallest size guests (n=1-4) form 2H:1G TATM inclusion compounds, the intermediate size guests (n=5 and 6) form 3H:1G TATM inclusion compounds, while the largest size guests (n=8-10) form 4H:1G TATM inclusion compounds. From the multiplicity of the host signals in the <PRE>13</PRE>C CP/MAS NMR spectrum, we were able to determine the number of host molecules in the asymmetric unit of each inclusion compound. For n=1-4, there is 1 TATM molecule in the asymmetric unit, for n=5 and 6, there are 3 TATM molecules in the asymmetric unit, while for n=8-10, there are 2 TATM molecules in the asymmetric unit. Powder X-ray diffraction experiments were conducted to determine if any of the nine guests form isostructural TATM inclusion compounds. Only 1,9-dichlorononane and 1,10-dichlorodecane form isostructural TATM inclusion compounds. This behaviour is compared with isostructuralism among previously studied TATM-alkyl halide guest systems. DSC experiments were performed to determine the relationship between the size of guest and the thermal properties of the inclusion compound. We found a direct relationship between the melting temperature and the heat of fusion. These data are compared to a recent study on urea-carboxylic acid complexes.NRC publication: Ye

Structural Type and Thermal Stability of tris (5-acetyl-3-thienyl) Methane Inclusion Compounds: a co mbined 13C CP/MAS NMR, Powder X-Ray Diffraction and Differential Scanning Calorimeter Study

NRC publication: Ye

The impact of SO2 on post combustion carbon dioxide capture in bed of silica sand through hydrate formation

Hydrate crystallization technology is one of the novel approaches for capturing carbon dioxide from flue gases. The presence of impurities such as SO2, NO2, H2S can influence the CO2 hydrate formation process. In the present work the impact of SO2 on hydrate equilibrium was investigated using the isothermal pressure search method. The hydrate equilibrium shifted to low pressures and high temperatures in the presence of small amount SO2. For example the hydrate formation pressure shifted from 7.7MPa to 7.25MPa at 273.75K. In addition, the presence of SO2 enhanced the initial hydrate formation rate and final moles of gas consumed 16h after the hydrate nucleation. The CO2 and SO2 gases were preferentially incorporated into the hydrate phase. The presence of SO2 helps the thermodynamics and kinetics of the hydrate formation process. Therefore complete removal of this SO2 impurity is not necessary; in fact it aids both thermodynamically and kinetically for hydrate formation, which indeed is a positive factor for the capture and geological sequestration of CO2 in the form of hydrates. The addition of THF reduces the CO2/N2/SO2 hydrate formation conditions (from 7.25MPa to 0.15MPa at 273.75K), which is practically important for reducing high compression costs. Moreover, the presence of THF decreases the hydrate nucleation time but reduces the hydrate formation rate significantly. \ua9 2013.Peer reviewed: YesNRC publication: Ye

Enhanced rate of gas hydrate formation in a fixed bed column filled with sand compared to a stirred vessel

10.1016/j.ces.2011.10.030Chemical Engineering Science681617-623CESC

Insights into the behavior of biological clathrate hydrate inhibitors in aqueous saline solutions

The performance of two antifreeze proteins (AFPs), type I and III (AFP I and III), as kinetic natural gas hydrate inhibitors in saline solutions was evaluated using a high pressure micro differential scanning calorimeter and a high pressure apparatus consisting of two crystallizers. Although AFP I and III were found to prolong crystallization time and reduce initial gas hydrate growth in saline solutions, the growth rate increased when hydrate started to form in the gas phase. Circular dichroism experiments suggested that the saline solution did not perturb AFP I and III structures. However, in the presence of saline, the inhibitory activity of AFP I to prolong induction time decreased while AFP III was more active. As a consequence, we propose that a decrease in hydrophobic forces and the neutralization of ion charges could explain AFP adsorption to the surface of hydrate crystals. Once the hydrate formed, melting was delayed, and consequently hydrate decomposition took longer in the presence of AFPs. We suggest conditions whereby the properties of AFPs could be harnessed for petrochemical recovery and transport. \ua9 2014 American Chemical Society.Peer reviewed: YesNRC publication: Ye