Distribution and Abundance of Micronekton and Macrozooplankton in the NW Weddell Sea: Relation to a Spring Ice-Edge Bloom

Micronekton and macrozooplankton were collected during the austral spring of 1993 in the NW Weddell Sea. Sampling was done in three areas of the marginal ice zone: pack ice, ice edge, and open water, to examine the short-term effects of the spring phytoplankton bloom on the distribution and abundance of dominant fish and invertebrate species. Significant differences were observed for several common species, including Salpa thompsoni, Euphausia superba, Electrona antarctica, Gymnoscopelus braueri, and G. opisthopterus. Increased abundance seaward of the pack ice for these species is attributed to elevated phytoplankton and zooplankton biomass at the ice edge and in the open water areas. Distribution of the hyperiid amphipods, Cyllopus lucasii and Vibilia stebbingi mirrored that of S. thompsoni. No distributional trends between the areas were observed for Thysanoessa macrura, the amphipods Cyphocaris richardi and Primno macropa, the decapod shrimp Pasiphaea scotiae, the scyphomedusae Atolla wyvilli and Periphylla periphylla, and chaetognaths, indicating a trophic independence from the ice-edge bloom for these species. Lower occurrence of the mesopelagic fish Bathylagus antarcticus and Cyclothone microdon under the ice suggested that trophic repercussions of the spring bloom can also extend to deeper living species

Thermal Conductivity and Chiral Critical Point in Heavy Ion Collisions

Background: Quantum Chromodynamics is expected to have a phase transition in the same static universality class as the 3D Ising model and the liquid-gas phase transition. The properties of the equation of state, the transport coefficients, and especially the location of the critical point are under intense theoretical investigation. Some experiments are underway, and many more are planned, at high energy heavy ion accelerators. Purpose: Develop a model of the thermal conductivity, which diverges at the critical point, and use it to study the impact of hydrodynamic fluctuations on observables in high energy heavy ion collisions. Methods: We apply mode coupling theory, together with a previously developed model of the free energy that incorporates the critical exponents and amplitudes, to construct a model of the thermal conductivity in the vicinity of the critical point. The effect of the thermal conductivity on correlation functions in heavy ion collisions is studied in a boost invariant hydrodynamic model via fluctuations, or noise. Results: We find that the closer a thermodynamic trajectory comes to the critical point the greater is the magnitude of the fluctuations in thermodynamic variables and in the 2-particle correlation functions in momentum space. Conclusions: It may be possible to discern the existence of a critical point, its location, and thermodynamic and transport properties near to it in heavy ion collisions using the methods developed here.Comment: 36 pages, 8 figures. Version published in Phys.Rev.C86, 054911 (2012). It contains some minor improvements with respect to v1: further clarifications, small changes on figures and two extra reference

Mitochondrial energetics of benthic and pelagic Antarctic teleosts.

Antarctic fauna are highly adapted to the frigid waters of the Southern Ocean. This study describes the in vitro temperature sensitivity of oxygen consumption rates measured in liver mitochondria from the pelagic notothenioid Pleuragramma antarcticum between 5 and 35 C. Oxygen fluxes were measured after the addition of millimolar levels of pyruvate, malate, succinate and glutamate (state II, LEAK) and saturating levels of ADP [state III, oxidative phosphorylation (OXPHOS)]. State III respiration significantly decreased above 18.7 C. A comparison of the oxidative capacities among P. antarcticum and other notothenioids showed significant differences in state III respiration, where benthic species exhibited about 50 % lower rates than P. antarcticum . In addition, state III respiration rates normalized per milligram of mitochondrial protein of P. antarcticum were up to eight times higher than state III rates reported in the literature for other notothenioids. The comparatively high respiration rates measured in this study may be explained by our approach, which engaged both complexes I and II under conditions of oxidative phosphorylation. State III rates of independently activated complexes I and II were found to range from 42 to 100 % of rates obtained when both complexes were activated simultaneously in the same species. The remarkable tolerance of P. antarcticum OXPHOS toward warmer temperatures was unexpected for an Antarctic stenotherm and may indicate that thermal sensitivity of their mitochondria is not the driving force behind their stenothermy

Determinants of Childhood Zoonotic Enteric Infections in a Semirural Community of Quito, Ecuador.

Domestic animals in the household environment have the potential to affect a child's carriage of zoonotic enteric pathogens and risk of diarrhea. This study examines the risk factors associated with pediatric diarrhea and carriage of zoonotic enteric pathogens among children living in communities where smallholder livestock production is prevalent. We conducted an observational study of children younger than 5 years that included the analysis of child (n = 306) and animal (n = 480) fecal samples for Campylobacter spp., atypical enteropathogenic Escherichia coli, Shiga toxin-producing E. coli, Salmonella spp., Yersinia spp., Cryptosporidium parvum, and Giardia lamblia. Among these seven pathogens, Giardia was the most commonly identified pathogen among children and animals in the same household, most of which was found in child-dog pairs. Campylobacter spp. was also relatively common within households, particularly among child-chicken and child-guinea pig pairs. We used multivariable Poisson regression models to assess risk factors associated with a child being positive for at least one zoonotic enteric pathogen or having diarrhea during the last week. Children who interacted with domestic animals-a behavior reported by nearly three-quarters of households owning animals-were at an increased risk of colonization with at least one zoonotic enteric pathogen (prevalence ratio [PR] = 1.56, 95% CI: 1.00-2.42). The risk of diarrhea in the last seven days was elevated but not statistically significant (PR = 2.27, CI: 0.91, 5.67). Interventions that aim to reduce pediatric exposures to enteric pathogens will likely need to be incorporated with approaches that remove animal fecal contamination from the domestic environment and encourage behavior change aimed at reducing children's contact with animal feces through diverse exposure pathways

The US Southern Ocean Global Ocean Ecosystems Dynamics Program

The article presents information on the U.S. Southern Ocean Global Ocean Ecosystem Dynamics program (US SO GLOBEC). It was aimed at understanding the environmental and biological factors that contribute to enhanced Antarctic krill growth, reproduction, recruitment and survivorship, as well as the interactions between Antarctic krill and its predators and competitors. The highlights of US SO GLOBEC research are also discussed

Perilesional edema in radiation necrosis reflects axonal degeneration

BACKGROUND: Recently, we characterized a Gamma Knife® radiation necrosis mouse model with various magnetic resonance imaging (MRI) protocols to identify biomarkers useful in differentiation from tumors. Though the irradiation was focal to one hemisphere, a contralateral injury was observed that appeared to be localized in the white matter only. Interestingly, this injury was identifiable in T2-weighted images, apparent diffusion coefficient (ADC), and magnetization transfer ratio (MTR) maps, but not on post-contrast T1-weighted images. This observation of edema independent of vascular changes is akin to the perilesional edema seen in clinical radiation necrosis. FINDINGS: The pathology underlying the observed white-matter MRI changes was explored by performing immunohistochemistry for healthy axons and myelin. The presence of both healthy axons and myelin was reduced in the contralateral white-matter lesion. CONCLUSIONS: Based on our immunohistochemical findings, the contralateral white-matter injury is most likely due to axonal degeneration

The Architecture of the GW Ori Young Triple Star System and Its Disk: Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses

We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the pre-main sequence hierarchical triple star system GW Ori. A forward-modeling of the ${}^{13}$CO and C${}^{18}$O $J$=2-1 transitions permits a measurement of the total stellar mass in this system, $5.29 \pm 0.09\,M_\odot$, and the circum-triple disk inclination, $137.6 \pm 2.0^\circ$. Optical spectra spanning a 35 year period were used to derive new radial velocities and, coupled with a spectroscopic disentangling technique, revealed that the A and B components of GW Ori form a double-lined spectroscopic binary with a $241.50\pm0.05$ day period; a tertiary companion orbits that inner pair with a $4218\pm50$ day period. Combining the results from the ALMA data and the optical spectra with three epochs of astrometry in the literature, we constrain the individual stellar masses in the system ($M_\mathrm{A} \approx 2.7\,M_\odot$, $M_\mathrm{B} \approx 1.7\,M_\odot$, $M_\mathrm{C} \approx 0.9\,M_\odot$) and find strong evidence that at least one (and likely both) stellar orbital planes are misaligned with the disk plane by as much as $45^\circ$. A $V$-band light curve spanning 30 years reveals several new $\sim$30 day eclipse events 0.1-0.7~mag in depth and a 0.2 mag sinusoidal oscillation that is clearly phased with the AB-C orbital period. Taken together, these features suggest that the A-B pair may be partially obscured by material in the inner disk as the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude that stellar evolutionary models are consistent with our measurements of the masses and basic photospheric properties if the GW Ori system is $\sim$1 Myr old.Comment: 26 pages, 15 figures, accepted to Ap

Radiative properties of aerosols in Saharan dust outbreaks using ground-based and satellite data: applications to radiative forcing

We report on measurements of atmospheric transmission (ATT) and aerosol optical depth (AODT) made at three wavelengths (368, 500, and 778 nm) with a spectroradiometer placed on Tenerife (28.5°N, 16.3°W), Canary Islands. Using the National Oceanic and Atmospheric Administration (NOAA) advanced very high resolution radiometer (AVHRR) channel 1, we also measured the aerosol optical depth (AODS) and albedo over a region of the North Atlantic Ocean extending from 15°–35°N to 12°–25°W. We observe large changes in ATT and AODT when dust outbreaks pass over this region. Using all these data, we derive the asymmetry factor (g), the single-scattering albedo (ω), and the local mean AODT and we compute the direct radiative forcing ΔF attributable to mineral dust. The local radiative forcing obtained is over the ocean ΔF = −9.7 W/m2 and for the land ΔF = −4.5 W/m2 with an error of ±25%. Extending these results to global-scale averages, we obtain values of ΔF of −1.22 W/m2 over the ocean and −0.57 W/m2 over land. The forcings attributable to dust are comparable in magnitude to those reported in the literature for anthropogenic sulphate and for biomass burning aerosols.We wish to thank the Gobierno Autónomo de Canarias for its financial support by contract 4/95, the Comisi6n Interministerial de Ciencia y Tecnologia (CICYT) by contract CLI97- 0453, and the University of La Laguna by contract 1802260003. A portion of this work was carried out as part of the Atmosphere/Ocean Chemistry Experiment (AEROCE) and supported by the National Science Foundation grants ATM-9414808, ATM-9414812, and ATM- 9414846

Robust Network Stability of Mosquitoes and Human Pathogens of Medical Importance

Background: The exact number of mosquito species relevant to human health is unknown, posing challenges in understanding the scope and breadth of vector–pathogen relationships, and how resilient mosquito vector–pathogen networks are to targeted eradication of vectors. Methods: We performed an extensive literature survey to determine the associations between mosquito species and their associated pathogens of human medical importance. For each vector–pathogen association, we then determined the strength of the associations (i.e., natural infection, lab infection, lab dissemination, lab transmission, known vector). A network analysis was used to identify relationships among all pathogens and vectors. Finally, we examined how elimination of either random or targeted species affected the extinction of pathogens. Results: We found that 88 of 3578 mosquito species (2.5%) are known vectors for 78 human disease-causing pathogens; however, an additional 243 species (6.8%) were identified as potential or likely vectors, bringing the total of all mosquitos implicated in human disease to 331 (9.3%). Network analysis revealed that known vectors and pathogens were compartmentalized, with the removal of six vectors being enough to break the network (i.e., cause a pathogen to have no vector). However, the presence of potential or likely vectors greatly increased redundancies in the network, requiring more than 41 vectors to be eliminated before breaking the network. Conclusion: Although \u3c 10% of mosquitoes are involved in transmitting pathogens that cause human disease, our findings point to inherent robustness in global mosquito vector–pathogen networks

Discovery and Validation of Kepler-452b: A 1.6-Re Super Earth Exoplanet in the Habitable Zone of a G2 Star

We report on the discovery and validation of Kepler-452b, a transiting planet identified by a search through the 4 years of data collected by NASA's Kepler Mission. This possibly rocky 1.63$^{+0.23}_{-0.20}$ R$_\oplus$ planet orbits its G2 host star every 384.843$^{+0.007}_{0.012}$ days, the longest orbital period for a small (R$_p$ < 2 R$_\oplus$) transiting exoplanet to date. The likelihood that this planet has a rocky composition lies between 49% and 62%. The star has an effective temperature of 5757$\pm$85 K and a log g of 4.32$\pm$0.09. At a mean orbital separation of 1.046$^{+0.019}_{-0.015}$ AU, this small planet is well within the optimistic habitable zone of its star (recent Venus/early Mars), experiencing only 10% more flux than Earth receives from the Sun today, and slightly outside the conservative habitable zone (runaway greenhouse/maximum greenhouse). The star is slightly larger and older than the Sun, with a present radius of 1.11$^{+0.15}_{-0.09}$ R$_\odot$ and an estimated age of 6 Gyr. Thus, Kepler-452b has likely always been in the habitable zone and should remain there for another 3 Gyr.Comment: 19 pages, 16 figure