Feeding, Respiration and Excretion of the Copepod Calanus hyperboreus from Baffin Bay, Including Waters Contaminated by Oil Seeps

Metabolic processes in eastern arctic copepods Calanus hyperboreus were analyzed during the post-bloom period (August-September). Mixed adult and subadult copepods were collected from 12 stations in Baffin Bay (Davis Strait to Lancaster Sound) by trawling from 0-300 m. Measurements were made of clearance rate, O2-consumption and NH3 excretion. The cruise track included 6 stations in oil-seep contaminated waters of Scott Inlet and Buchan Gulf. Physiological parameters for populations of C. hyperboreus from the latter stations were compared with those from non-seep stations. Mean O2 consumption rates (0.309 - 0.907 µl O2 / mg dry wt / h) for all stations were similar to those described for Antarctic calanoid species but were higher than reported for more northern arctic waters. Mean ammonia excretion rates (0.023 - 0.071 µg N / mg dry wt / h) were somewhat lower than reported for comparable Antarctic species and were similar to values from other eastern arctic studies. O:N ratios for 11 of the 12 stations occupied ranged between 8.4 and 22.1, indicative of protein-based metabolism. The single exception was a High Arctic station with O:N ratio 43.6. Clearance rates were low to nonexistant for all stations. Most of the non-feeding values came from the Scott Inlet-Buchan Gulf region of western Baffin Bay. At those stations in this region a strong negative correlation (P<.01) exists between clearance rate and hydrocarbon contamination. This suggests that in the oil-seep region of Baffin Bay feeding may be suppressed in Calanus hyperboreus by low concentrations of petroleum hydrocarbons derived from sub-sea seepage.Key words: zooplankton, Calanus hyperboreus, Arctic, metabolism, oil seep, petroleum, hydrocarbons, oil pollutionMots clés: zooplancton, Calanus hyperboreus, Arctique, métabolisme, suitements de pétrole, pétrole, hydrocarbures, pollution par les hydrocarbure

Cross-modal individual recognition in wild African lions

Individual recognition is considered to have been fundamental in the evolution of complex social systems and is thought to be a widespread ability throughout the animal kingdom. Although robust evidence for individual recognition remains limited, recent experimental paradigms that examine cross-modal processing have demonstrated individual recognition in a range of captive non-human animals. It is now highly relevant to test whether cross-modal individual recognition exists within wild populations and thus examine how it is employed during natural social interactions. We address this question by testing audio–visual cross-modal individual recognition in wild African lions (Panthera leo) using an expectancy-violation paradigm. When presented with a scenario where the playback of a loud-call (roaring) broadcast from behind a visual block is incongruent with the conspecific previously seen there, subjects responded more strongly than during the congruent scenario where the call and individual matched. These findings suggest that lions are capable of audio–visual cross-modal individual recognition and provide a useful method for studying this ability in wild populations

Resistance to dislodgement: habitat and size-specific differences in morphology and tenacity in an intertidal snail

The authors quantified 1) shell size (defined as the maximum projected surface area, MPSA); 2) shell shape; 3) foot area; 4) maximum force to dislodge a snail in shear; and 5) tenacity (force per foot area required to dislodge) of the herbivorous Littorina obtusata. Wave-exposed snails were smaller (lower average MPSA), and were shorter and had larger foot area and greater dislodgement force than did protected snails of similar MPSA. The greater dislodgement force at the exposed site was due to larger foot area, not to greater tenacity. -from Author

Square-wave switching in vertical-cavity surface-emitting lasers with polarization-rotated optical feedback: Experiments and simulations

We study experimentally the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated (PR) optical feedback, such that the natural lasing polarization of a VCSEL is rotated by 90 deg and then is reinjected into the laser. We observe noisy, square-wave-like polarization switchings with periodicity slightly longer than twice the delay time, which degrade to (or alternate with) bursts of irregular oscillations. We present results of simulations that are in good agreement with the observations. The simulations demonstrate that close to threshold the regular switching is very sensitive to noise, while well above threshold is less affected by the noise strength. The frequency splitting between the two polarizations plays a key role in the switching regularity, and we identify wide parameter regions where deterministic and robust switching can be observed.Postprint (published version

The Inherent Tracer Fingerprint of Captured CO2.

Carbon capture and storage (CCS) is the only currently available technology that can directly reduce anthropogenic CO2 emissions arising from fossil fuel combustion. Monitoring and verification of CO2 stored in geological reservoirs will be a regulatory requirement and so the development of reliable monitoring techniques is essential. The isotopic and trace gas composition - the inherent fingerprint - of captured CO2 streams is a potentially powerful, low cost geochemical technique for tracking the fate of injected gas in CCS projects; carbon and oxygen isotopes, in particular, have been used as geochemical tracers in a number of pilot CO2 storage sites, and noble gases are known to be powerful tracers of natural CO2 migration. However, the inherent tracer fingerprint in captured CO2 streams has yet to be robustly investigated and documented and key questions remain, including how consistent is the fingerprint, what controls it, and will it be retained en route to and within the storage reservoir? Here we present the first systematic measurements of the carbon and oxygen isotopes and the trace noble gas composition of anthropogenic CO2 captured from combustion power stations and fertiliser plants. The analysed CO2 is derived from coal, biomass and natural gas feedstocks, using amine capture, oxyfuel and gasification processes, from six different CO2 capture plants spanning four different countries. We find that δ13C values are primarily controlled by the δ13C of the feedstock while δ18O values are predominantly similar to atmospheric O2. Noble gases are of low concentration and exhibit relative element abundances different to expected reservoir baselines and air, with isotopic compositions that are similar to air or fractionated air. The use of inherent tracers for monitoring and verification was provisionally assessed by analysing CO2 samples produced from two field storage sites after CO2 injection. These experiments at Otway, Australia, and Aquistore, Canada, highlight the need for reliable baseline data. Noble gas data indicates noble gas stripping of the formation water and entrainment of Kr and Xe from an earlier injection experiment at Otway, and inheritance of a distinctive crustal radiogenic noble gas fingerprint at Aquistore. This fingerprint can be used to identify unplanned migration of the CO2 to the shallow subsurface or surface

Rose of the Underworld

Photograph of Lynn Cantor; Illustration of woman sitting on padded bench playing lute with Oriental ornaments in backgroundhttps://scholarsjunction.msstate.edu/cht-sheet-music/12499/thumbnail.jp

Preferential Paths of Air-water Two-phase Flow in Porous Structures with Special Consideration of Channel Thickness Effects.

Accurate understanding and predicting the flow paths of immiscible two-phase flow in rocky porous structures are of critical importance for the evaluation of oil or gas recovery and prediction of rock slides caused by gas-liquid flow. A 2D phase field model was established for compressible air-water two-phase flow in heterogenous porous structures. The dynamic characteristics of air-water two-phase interface and preferential paths in porous structures were simulated. The factors affecting the path selection of two-phase flow in porous structures were analyzed. Transparent physical models of complex porous structures were prepared using 3D printing technology. Tracer dye was used to visually observe the flow characteristics and path selection in air-water two-phase displacement experiments. The experimental observations agree with the numerical results used to validate the accuracy of phase field model. The effects of channel thickness on the air-water two-phase flow behavior and paths in porous structures were also analyzed. The results indicate that thick channels can induce secondary air flow paths due to the increase in flow resistance; consequently, the flow distribution is different from that in narrow channels. This study provides a new reference for quantitatively analyzing multi-phase flow and predicting the preferential paths of immiscible fluids in porous structures

Constant regulation for stable CD8 T-cell functional avidity and its possible implications for cancer immunotherapy.

The functional avidity (FA) of cytotoxic CD8 T cells impacts strongly on their functional capabilities and correlates with protection from infection and cancer. FA depends on TCR affinity, downstream signaling strength, and TCR affinity-independent parameters of the immune synapse, such as costimulatory and inhibitory receptors. The functional impact of coreceptors on FA remains to be fully elucidated. Despite its importance, FA is infrequently assessed and incompletely understood. There is currently no consensus as to whether FA can be enhanced by optimized vaccine dose or boosting schedule. Recent findings suggest that FA is remarkably stable in vivo, possibly due to continued signaling modulation of critical receptors in the immune synapse. In this review, we provide an overview of the current knowledge and hypothesize that in vivo, codominant T cells constantly "equalize" their FA for similar function. We present a new model of constant FA regulation, and discuss practical implications for T-cell-based cancer immunotherapy