Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun

Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency's Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10(-10) to 10(-7) kilograms, and 48 grains of mass 10(-5) to 10(-2) kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 +/- 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails.

Concentrations of PBDE and BDE congeners in adipose tissue of East Greenland polar bears (Ursus maritimus)

Polybrominated diphenyl ethers (PBDEs) were analysed in adipose tissue from 92 East Greenland polar bears (Ursus maritimus) sampled during 1999-2001. Mean SumPBDE concentrations were 70 ng/g lipid weight (lw) (range: 22-192 ng/g lw) and showed no relationship with age or sex. Of the 32 analysed PBDE congeners; BDE47, BDE153, BDE99 and BDE100 dominated, and comprised 99.6% of the SumPBDE concentration. The SumPBDE concentration had a highly significant correlation with SumPCB, SumCHL, dieldrin, HCB and SumHCH concentrations. We found a seasonal pattern of median SumPBDE concentration with 1.2 to 1.8 times higher concentrations in March to July than the rest of the year. The seasonal variation also provides a clue to the seasonal exposure, bio-availability, toxic exposure and degradation. We suggest that future geographical PBDE data comparisons may not need corrections for sex or age, but such data sets should be corrected for seasonal variability, using the presented correctional trigonometric regression.

(Table 1) Cortisol concentration in hair of East Greenland polar bears (Ursus maritimus)

To demonstrate the ability to assess long-term hypothalamic-pituitary-adrenocortical (HPA) axis activity in polar bears (Ursus maritimus), a pilot study was conducted in which cortisol concentration was analyzed in hair from 7 female (3-19 years) and 10 male (6-19 years) East Greenland polar bears sampled in 1994-2006. The hair was chosen as matrix as it is non-invasive, seasonally harmonized, and has been validated as an index of long-term changes in cortisol levels. The samples were categorized according to contamination: eight were clean (2 females, 6 males), 5 had been contaminated with bear blood (2 F, 3 M), and 4 with bear fat (3 F, 1 M). There was no significant difference in cortisol concentration between the three categories after external contamination was removed. However, contaminated hair samples should be cleaned before cortisol determination. Average hair cortisol concentration was 8.90 pg/mg (range: 5.5 to 16.4 pg/mg). There was no significant correlation between cortisol concentration and age (p = 0.81) or sampling year (p = 0.11). However, females had higher mean cortisol concentration than males (females mean: 11.0 pg/mg, males: 7.3 pg/mg; p = 0.01). The study showed that polar bear hair contains measurable amounts of cortisol and that cortisol in hair may be used in studies of long-term stress in polar bears.

(Table 1) Lipid content and organohalogen contaminant concentration in captive sledge dogs (Canis familiaris) and wild female polar bears (Ursus maritimus) from Greenland

The limited knowledge and/or the inability to control physiological condition parameters that influence the fate of organohalogen contaminants (OHCs) has been the foremost confounding aspect in monitoring programs and health risk assessments of wild top predators in the Arctic such as the polar bear (Ursus maritimus). In the present comparative study, we used a potential surrogate Canoidea species for the East Greenland polar bear, the captive sledge dog (Canis familiaris), to investigate some factors that may influence the bioaccumulation and biotransformation of major chlorinated and brominated OHCs in adipose tissue and blood (plasma) of control (fed commercial pork fat) and exposed (fed West Greenland minke whale (Balaenoptera acutorostrata) blubber) adult female sledge dogs. Furthermore, we compared the patterns and concentrations of OHCs and their known or suggested hydroxylated (OH) metabolites (e.g., OH-PCBs) in sledge dogs with those in adipose tissue and blood (plasma) of East Greenland adult female polar bears, and blubber of their main prey species, the ringed seal (Pusa hispida). The two-year feeding regime conducted with sledge dogs led to marked differences in overall adipose tissue (and plasma) OHC residue accumulation between the control and exposed groups. Characteristic prey-to-predator OHC bioaccumulation dynamics for major PCB and PBDE congeners (patterns and concentrations) and biotransformation capacity with respect to PCB metabolite formation and OH-PCB retention distinguished, to some extent, captive sledge dogs and wild polar bears. Based on the present findings, we conclude that the use of surrogate species in toxicological investigations for species in the Canoidea family should be done with great caution, although they remain essential in the context of contaminants research with sensitive arctic top carnivore species such as the polar bear.

Política y militarismo : Sun Tzu y Engels

Los acontecimientos revolucionarios de 1848 fueron decisivos en los desarrollos conceptuales posteriores. La guerra, y la violencia, ocuparon un lugar central en el estudio detallado de sus reglas. Este trabajo intenta presentar algunos puntos nodales que intentan avanzar en la respuesta a esta pregunta: ¿Cabe la analogía de la guerra con la lucha de clases? En este sentido el trabajo se limita a señalar los ejes de este debate sobre la base de una relectura de dos clásicos. Sun Tzu y su Arte de la guerra, y varios textos de Engels. La hipótesis sostenida en el trabajo es que la lucha de clases, como momento político, encierra la posibilidad de la guerra sólo como un momento del antagonismo. El conocimiento de esas reglas potencia la capacidad de resolver de manera victoriosa el enfrentamiento, pero no es su contenido. Fijar el antagonismo como guerra es hacer de la lucha un militarismo que soslaya la construcción de una fuerza capaz de dar ese enfrentamiento directo. Intentaré mostrar cómo este debate señala puntos relevantes para entender las líneas políticas a finales de los sesenta en la Argentina

Política y militarismo : Sun Tzu y Engels

Los acontecimientos revolucionarios de 1848 fueron decisivos en los desarrollos conceptuales posteriores. La guerra, y la violencia, ocuparon un lugar central en el estudio detallado de sus reglas. Este trabajo intenta presentar algunos puntos nodales que intentan avanzar en la respuesta a esta pregunta: ¿Cabe la analogía de la guerra con la lucha de clases? En este sentido el trabajo se limita a señalar los ejes de este debate sobre la base de una relectura de dos clásicos. Sun Tzu y su Arte de la guerra, y varios textos de Engels. La hipótesis sostenida en el trabajo es que la lucha de clases, como momento político, encierra la posibilidad de la guerra sólo como un momento del antagonismo. El conocimiento de esas reglas potencia la capacidad de resolver de manera victoriosa el enfrentamiento, pero no es su contenido. Fijar el antagonismo como guerra es hacer de la lucha un militarismo que soslaya la construcción de una fuerza capaz de dar ese enfrentamiento directo. Intentaré mostrar cómo este debate señala puntos relevantes para entender las líneas políticas a finales de los sesenta en la Argentina

Política y militarismo : Sun Tzu y Engels

Los acontecimientos revolucionarios de 1848 fueron decisivos en los desarrollos conceptuales posteriores. La guerra, y la violencia, ocuparon un lugar central en el estudio detallado de sus reglas. Este trabajo intenta presentar algunos puntos nodales que intentan avanzar en la respuesta a esta pregunta: ¿Cabe la analogía de la guerra con la lucha de clases? En este sentido el trabajo se limita a señalar los ejes de este debate sobre la base de una relectura de dos clásicos. Sun Tzu y su Arte de la guerra, y varios textos de Engels. La hipótesis sostenida en el trabajo es que la lucha de clases, como momento político, encierra la posibilidad de la guerra sólo como un momento del antagonismo. El conocimiento de esas reglas potencia la capacidad de resolver de manera victoriosa el enfrentamiento, pero no es su contenido. Fijar el antagonismo como guerra es hacer de la lucha un militarismo que soslaya la construcción de una fuerza capaz de dar ese enfrentamiento directo. Intentaré mostrar cómo este debate señala puntos relevantes para entender las líneas políticas a finales de los sesenta en la Argentina

Rates of seropositivity for Toxoplasma gondii antibodies in polar bears and marine mammals around Svalbard

Little is known about the prevalence of the parasite Toxoplasma gondii in the arctic marine food chain of Svalbard, Norway. In this study, plasma samples were analyzed for T. gondii antibodies using a direct agglutination test. Antibody prevalence was 45.6% among polar bears (Ursus maritimus), 18.7% among ringed seals (Pusa hispida) and 66.7% among adult bearded seals (Erignathus barbatus) from Svalbard, but no sign of antibodies were found in bearded seal pups, harbour seals (Phoca vitulina), white whales (Delphinapterus leucas) or narwhals (Monodon monoceros) from the same area. Prevalence was significantly higher in male polar bears (52.3%) compared with females (39.3%), likely due to dietary differences between the sexes. Compared to an earlier study, T. gondii prevalence in polar bears has doubled in the past decade. Consistently, an earlier study on ringed seals did not detect T. gondii. The high recent prevalence in polar bears, ringed seals and bearded seals could be caused by an increase in the number or survivorship of oocysts being transported via the North Atlantic Current to Svalbard from southern latitudes. Warmer water temperatures have led to influxes of temperate marine invertebrate filter-feeders that could be vectors for oocysts and warmer water is also likely to favour higher survivorship of oocycts. However, a more diverse than normal array of migratory birds in the Archipelago recently, as well as a marked increase in cruise-ship and other human traffic are also potential sources of T. gondii.