Variation in size of living articulated brachiopods with latitude and depth

Geographical variations in animal characters are one of the main subjects for study in macroecology. Variation with latitude has received special interest. Articulated brachiopods are possibly the commonest macrofossil with large variations in size of taxa through the fossil record. Here, we investigate trends in size of the 3 main orders of articulated brachiopod with latitude and depth. Data were insufficient to identify patterns in Thecideida (a micromorph taxon only recorded from low latitudes). Rhynchonellida had no clear trends in size with latitude or depth. Terebratulida exhibited hemispheric differences in size relations, with increasing length of species towards the pole in the south and no significant trend in the north. Tropical species were small (<20 mm length between 10°N and 10°S), and the largest species were found between 30° and 60° latitude in both hemispheres. There were no articulated brachiopods recorded from the high arctic, and support for a continuous trend in size with latitude was small or absent. In Terebratulida, there was a significant decrease in species length with depth of 1.7 mm per 100 m depth increase. These trends could be explained by competition for space and reduced availability of habitat with progressive depth beyond the continental shelf

Latitudinal and depth gradients in marine predation pressure

There is a general paradigm that marine predation pressure increases towards the tropics and decreases with depth. However, data demonstrating global trends are generally lacking. Rhynchonelliform brachiopods inhabit all the oceans and often survive shell-crushing predator attacks. We investigate shell repair in brachiopods across a range of Southern Hemisphere and tropical Northern Hemisphere latitudes and depths

A Flaring Megamaser in Mrk 348

We report new observations of the H2O megamaser in the Seyfert 2 galaxy Mrk 348. Following our initial detection in 2000 March using the Effelsberg 100 m telescope, re-analysis of previous data on this source indicates that the maser was present but only marginally detectable in late 1997. Monitoring through late 2000 shows that the maser has again decreased to its original level. The H2O line is redshifted by ~130 km/s with respect to the systemic velocity, is extremely broad, with a FWHM of 130 km/s, and has no detectable high velocity components within 1500 km/s on either side of the strong line. Followup VLBA observations show that the maser emission emanates entirely from a region >0.25 pc in extent, toward the base of the radio jet.Comment: 4 pages, 2 figures, to appear in Cosmic Masers: from Protostars to Black Holes, IAU 206, Eds. V. Migenes et al., ASP Conference Serie

Redshifts and Neutral Hydrogen Observations of Compact Symmetric Objects in the COINS Sample

Compact Symmetric Objects (CSOs) are young radio galaxies whose jet axes lie close to the plane of the sky, and whose appearance is therefore not dominated by relativistic beaming effects. The small linear sizes of CSOs make them valuable for studies of both the evolution of radio galaxies and testing unified schemes for active galactic nuclei (AGN). A parsec-scale region of gas surrounding the central engine is predicted by both accretion and obscuration scenarios. Working surfaces, or ``hot spots,'' and the radio jets of CSOs are close enough to the central engines that this circumnuclear gas can be seen in absorption. The CSOs Observed in the Northern Sky (COINS) sample is comprised of 52 CSO candidates identified in three VLBI surveys. Of these, 27 have now been confirmed as CSOs. Optical redshifts are available in the literature for 28 of the CSO candidates, and HI absorption has been detected toward four. We present new optical spectroscopic redshifts for three of the candidates and summarize the current status of optical identifications. We further report on the discovery of HI in absorption towards the CSO J1816+3457 and summarize the results of neutral hydrogen absorption studies of the sources in this sample.Comment: 12 pages, Accepted for publication in Ap

On the Prospects for Laser Cooling of TlF

We measure the upper state lifetime and two ratios of vibrational branching fractions f_{v'v} on the B^{3}\Pi_{1}(v') - X^{1}\Sigma^{+}(v) transition of TlF. We find the B state lifetime to be 99(9) ns. We also determine that the off-diagonal vibrational decays are highly suppressed: f_{01}/f_{00} < 2x10^{-4} and f_{02}/f_{00} = 1.10(6)%, in excellent agreement with their predicted values of f_{01}/f_{00} < 8x10^{-4} and f_{02}/f_{00} = 1.0(2)% based on Franck-Condon factors calculated using Morse and RKR potentials. The implications of these results for the possible laser cooling of TlF and fundamental symmetries experiments are discussed.Comment: 5 pages, 2 figure

Obscuration of the Parsec Scale Jets in the Compact Symmetric Object 1946+708

We present results of VLA and VLBA observations of the 1.420 GHz neutral hydrogen absorption associated with the Compact Symmetric Object 1946+708 (z=0.101). We find significant structure in the gas on parsec scales. The peak column density in the HI (N_HI~2.2x10^23 cm^-2 (T_s/8000K)) occurs toward the center of activity of the source, as does the highest velocity dispersion (FWHM~350 \kms). In addition, we find that the continuum spectra of the various radio components associated with these jets strongly indicate free-free absorption. This effect is particularly pronounced toward the core and inner components of the receding jet, suggesting the presence of a screen local to the source, perhaps part of an obscuring torus.Comment: revised version, some text added, 1 figure changed; accepted to Astrophysical Journal, 22 page LaTeX document includes 8 postscript figure

Ocean acidification does not impact shell growth or repair of the Antarctic brachiopod Liothyrella uva (Broderip, 1833)

Marine calcifiers are amongst the most vulnerable organisms to ocean acidification due to reduction in the availability of carbonate ions for skeletal/shell deposition. However, there are limited long-term studies on the possible impacts of increased pCO2 on these taxa. A 7 month CO2 perturbation experiment was performed on one of the most calcium carbonate dependent species, the Antarctic brachiopod Liothyrella uva, which inhabits the Southern Ocean where carbonate ion saturation levels are amongst the lowest on Earth. The effects of the predicted environmental conditions in 2050 and 2100 on the growth rate and ability to repair shell in L.uva were tested with four treatments; a low temperature control (0°C, pH7.98), a pH control (2°C, pH8.05), mid-century scenario (2°C, pH7.75) and end-century scenario (2°C, pH7.54). Environmental change impacts on shell repair are rarely studied, but here repair was not affected by either acidified conditions or temperature. Growth rate was also not impacted by low pH. Elevated temperature did, however, increase growth rates. The ability of L.uva to continue, and even increase shell production in warmer and acidified seawater suggests that this species can acclimate to these combined stressors and generate suitable conditions for shell growth at the site of calcification.Emma Cross is supported by the NERC PhD Studentship (NE/T/A/2011).This is the accepted manuscript. The final version is available at http://www.sciencedirect.com/science/article/pii/S0022098114002743

New Limits on Local Lorentz Invariance in Mercury and Cesium

We report new bounds on Local Lorentz Invariance (LLI) violation in Cs and Hg. The limits are obtained through the observation of the the spin- precession frequencies of 199Hg and 133Cs atoms in their ground states as a function of the orientation of an applied magnetic field with respect to the fixed stars. We measure the amplitudes of the dipole couplings to a preferred direction in the equatorial plane to be 19(11) nHz for Hg and 9(5) microHz for Cs. The upper bounds established here improve upon previous bounds by about a factor of four. The improvement is primarily due to mounting the apparatus on a rotating table. New bounds are established on several terms in the standard model extension including the first bounds on the spin-couplings of the neutron and proton to the z direction, <7e-30 GeV and <7e-29 GeV, respectively.Comment: 17 pages, 6 figure