Activity and Movement Patterns of Polar Bears Inhabiting Consolidated versus Active Pack Ice

We investigated the influence of ice conditions on activity and movement patterns of polar bears in the Canadian-West Greenland Arctic. We used radiotelemetry data gathered over 11 years (1989-99) from 160 adult female polar bears to test for differences in movement and activity of bears inhabiting active ice and consolidated ice. Bears inhabiting active ice moved more than those inhabiting consolidated ice (12 versus 8 km/day), but their activity throughout the year did not differ (bears of both groups were active for 21% of the day). Differences in activity and movement of bears in the two study areas appeared to be related to differences in predominant ice conditions and presumed prey availability. Seals, particularly juveniles, are most plentiful in spring and summer, when polar bears moved more and were most active. During winter, when juvenile seals were less available in consolidated ice areas, bears in that habitat were less active and moved less than bears in active ice areas. Polar bears have evolved flexible patterns of seasonal activity, movements, and facultative den use as adaptations to different sea-ice environments.On a étudié l'influence des conditions de glace sur le régime de l'activité et du déplacement de l'ours polaire dans l'Arctique canadien de l'ouest du Groenland. On s'est servi de données prélevées par radiomesure sur une période de 11 ans (de 1989 à 1999) portant sur 160 ourses polaires adultes afin de déterminer s'il existe des différences dans le déplacement et l'activité des ourses entre celles qui vivent sur la glace mobile et celles qui vivent sur la glace soudée. Les ourses vivant sur la glace mobile se déplaçaient plus que celles vivant sur la glace soudée (12 km/jour contre 8), mais leur activité tout au long de l'année ne différait pas (les ourses des deux groupes étaient actives 21 p. cent de la journée). Les différences dans l'activité et le déplacement des ourses entre les deux zones d'étude semblaient être reliées à des différences dans les conditions de glace prédominantes et dans la disponibilité présumée des proies. L'abondance des phoques, en particulier les jeunes, atteint son maximum au printemps et en été, au moment où les ourses polaires étaient souvent le plus actives et se déplaçaient le plus. Durant l'hiver, quand les phoques juvéniles étaient moins disponibles dans les zones de glace soudée, les ourses vivant dans cet habitat étaient moins actives et se déplaçaient moins que les ourses vivant dans les zones de glace mobile. L'ourse polaire a développé une certaine flexibilité de comportement dans son activité, son déplacement et son utilisation facultative d'une tanière, pour s'adapter à différents environnements de glace de mer

A dynamic perspective on affect and creativity

10.5465/amj.2010.0894Academy of Management Journal562432-45

Structural Transition of Actin Filament in a Cell-Sized Water Droplet with a Phospholipid Membrane

Actin filament, F-actin, is a semiflexible polymer with a negative charge, and is one of the main constituents on cell membranes. To clarify the effect of cross-talk between a phospholipid membrane and actin filaments in cells, we conducted microscopic observations on the structural changes in actin filaments in a cell-sized (several tens of micrometers in diameter) water droplet coated with a phospholipid membrane such as phosphatidylserine (PS; negatively-charged head group) or phosphatidylethanolamine (PE; neutral head group) as a simple model of a living cell membrane. With PS, actin filaments are distributed uniformly in the water phase without adsorption onto the membrane surface between 2 and 6 mM Mg2+, while between 6 and 12 mM Mg2+, actin filaments are adsorbed onto the inner membrane surface. With PE, actin filaments are uniformly adsorbed onto the inner membrane surface between 2 and 12 mM Mg2+. With both PS and PE membranes, at Mg2+ concentrations higher than 12 mM, thick bundles are formed in the bulk water droplet accompanied by the dissolution of actin filaments from the membrane surface. The attraction between actin filaments and membrane is attributable to an increase in the translational entropy of counterions accompanied by the adsorption of actin filaments onto the membrane surface. These results suggest that a microscopic water droplet coated with phospholipid can serve as an easy-to-handle model of cell membranes

A Simulation Methodology for Reliability Analysis in Multi-Core SoCs

Reliability has become a significant challenge for system design in new process technologies. Higher integration levels dramatically increase power densities, which leads to higher temperature and adverse effects on reliability. In this paper, we introduce a simulation methodology to analyze reliability of multi-core SoCs. The proposed simulator is the first to provide system-on-chip level fine-grained reliability analysis. We use our simulation methodology to study the reliability effects of design choices such as thermal packaging and placement, as well as runtime events such as power management policies and workload distributions

Demography and Viability of a Hunted Population of Polar Bears

We estimated demographic parameters and harvest risks for a population of polar bears (Ursus maritimus) inhabiting Baffin Bay, Canada and Greenland, from 1974 to 1997. Our demographic analysis included a detailed assessment of age- and sex-specific survival and recruitment from 1221 marked polar bears, which used information contained within the standing age distribution of captures and mark-recapture analysis performed with Program MARK. Unharvested (natural) survival rates for females (± 1 SE) from mark-recapture analysis were 0.620 ± 0.095 (cubs), 0.938 ± 0.042 (ages 1–4), 0.953 ± 0.020 (ages 5–20), and 0.919 ± 0.046 (ages 21+). Total (harvested) survival rates for females were reduced to 0.600 ± 0.096 (cubs), 0.901 ± 0.045 (ages 1–4), 0.940 ± 0.021 (ages 5–20), and 0.913 ± 0.047 (ages 21+). Mean litter size was 1.59 ± 0.07 cubs, with a mean reproductive interval of 2.5 ± 0.01 years. By age 5, on average 0.88 ± 0.40 of females were producing litters. We estimated the geometric means (± bootstrapped SDs) for population growth rates at stable age distribution as 1.055 ± 0.011 (unharvested) and 1.019 ± 0.015 (harvested). The model-averaged, mark-recapture estimate of mean abundance (± 1 SE) for years 1994–97 was 2074 ± 266 bears, which included 1017 ± 192 females and 1057 ± 124 males. We incorporated demographic parameters and their error terms into a harvest risk analysis designed to consider demographic, process, and sampling uncertainty in generating likelihoods of persistence (i.e., a stochastic, harvest-explicit population viability analysis). Using our estimated harvest of polar bears in Baffin Bay (88 bears/yr), the probability that the population would decline no more than could be recovered in five years was 0.95, suggesting that the current hunt is sustainable.De 1974 à 1997, on a évalué les paramètres démographiques d’une population d’ours polaires (Ursus maritimus) habitant la baie de Baffin (Canada et Groenland), ainsi que les risques associés à leur prélèvement. Notre analyse démographique comprenait un bilan détaillé de la survie et du recrutement par âge et par sexe, bilan mené sur 1221 ours polaires étiquetés et qui faisait appel à l’information contenue dans les limites de la structure d’âge des captures à un moment précis, ainsi que des analyses de marquage-recapture réalisées avec le logiciel MARK. Les taux de survie sans prélèvements (c’est-à-dire naturels) des femelles (± 1 erreur-type) tirés de l’analyse de marquage-recapture étaient les suivants: 0,620 ± 0,095 (oursons), 0,938 ± 0,042 (1–4 ans), 0,953 ± 0,020 (5–20 ans) et 0,919 ± 0,046 (21 ans et plus). Les taux de survie globaux (avec prélèvements) des femelles diminuaient à: 0,600 ± 0,096 (oursons), 0,901 ± 0,045 (1–4 ans), 0,940 ± 0,021 (5–20 ans) et 0,913 ± 0,047 (21 ans et plus). La taille moyenne des portées était de 1,59 ± 0,07 ourson avec des intervalles moyens de reproduction de 2,5 ± 0,01 ans. Arrivées à l’âge de cinq ans, en moyenne 0,88 ± 0,40 des femelles avaient eu des petits. On a évalué que les moyennes géométriques (± écart-type bootstrappé) pour les taux de croissance de la population à la structure d’âge stable étaient de 1,055 ± 0,011 (sans prélèvements) et de 1,019 ± 0,015 (avec prélèvements). La valeur estimée à partir du marquage-recapture, moyennée par le modèle, de l’abondance moyenne (± 1 erreur-type), pour les années allant de 1994 à 1997 était de 2074 ± 266 ours, dont 1017 Å} 192 femelles et 1057 ± 124 mâles. On a intégré les paramètres démographiques et leurs termes d’erreur dans une analyse des risques de prélèvements conçue pour tenir compte des incertitudes démographiques, de processus et d’échantillonnage lors du calcul des probabilités de persistance (c.-à-d. une analyse stochastique de la viabilité de la population qui tient compte des prélèvements). En se basant sur nos prélèvements estimés de l’ours polaire dans la baie de Baffin (88 ours/an), la probabilité que la population ne décline pas plus que ce qu’elle pourrait récupérer en 5 ans était de 0,95, ce qui suggère que la chasse actuelle est durable

Barriers and facilitators for prevention in Danish dental care

Objective: To explore barriers and facilitators to oral disease prevention in Danish dental care from a multi-stakeholder perspective. Methods: Eleven semi-structured focus groups and interviews about Danish oral healthcare were conducted with 27 stakeholders (general public, dental teams, dental policy makers) in Copenhagen. Transcripts were analyzed using deductive thematic analysis independently by KR and HL, supervised by JC and KVC. Results: Seven broad themes were identified, including both barriers and facilitators: Knowledge and attitudes, Education and training, Regulation, Incentivization, Multidisciplinary approach, Access to care and the Dental professional-patient relationship. Whilst all themes were relevant to each group of stakeholders, the salient driver within each theme was different for each group. Conclusions: Stakeholder perspectives on the Danish Oral health care system suggest the following are important features for a preventively focused system: (a) Involving all stakeholders in oral healthcare planning. (b) Securing sufficient and ongoing briefing regarding disease prevention for all stakeholders. (c) Regulatory support and creation of incentives to promote and facilitate implementation of disease prevention. (d) Appropriate prevention for disadvantaged groups within society which may be possible to a higher degree by means of multidisciplinary collaboration. (e) Personal relations between the patient and the professional based on mutual trust

Protein phosphatase 4 controls circadian clock dynamics by modulating CLOCK/BMAL1 activity

In all organisms with circadian clocks, post-translational modifications of clock proteins control the dynamics of circadian rhythms, with phosphorylation playing a dominant role. All major clock proteins are highly phosphorylated, and many kinases have been described to be responsible. In contrast, it is largely unclear whether and to what extent their counterparts, the phosphatases, play an equally crucial role. To investigate this, we performed a systematic RNAi screen in human cells and identified protein phosphatase 4 (PPP4) with its regulatory subunit PPP4R2 as critical components of the circadian system in both mammals an

Hadean geodynamics inferred from time-varying 142Nd/144Nd in the early Earth rock record

Tracking the secular evolution of 142Nd/144Nd anomalies is important towards understanding the crust-mantle dynamics in the early Earth. Excessive scatter in the published data, however, precludes identifying the fine structure of 142Nd/144Nd evolution as the expected variability is on the order of few parts per million. We report ultra-high precision 142Nd/144Nd data for Eoarchean and Palaeoarchean rocks from the Isua Supracrustal Belt (SW Greenland) that show a well-resolved 142Nd/144Nd temporal variability suggesting progressive convective homogenisation of the Hadean Isua depleted mantle. This temporally decreasing 142Nd/144Nd signal provides a direct measure of early mantle dynamics, defining a stirring timescale of <250 Myr consistent with vigorous convective stirring in the early mantle. The 142Nd/144Nd evolution suggests protracted crustal residence times of ~1000-2000 Myr, inconsistent with modern-style plate tectonics in the Archean. In contrast, a stagnant-lid regime punctuated by episodes of mantle overturns accounts for the long life-time estimated here for the Hadean proto-crust

Habitable Zones and UV Habitable Zones around Host Stars

Ultraviolet radiation is a double-edged sword to life. If it is too strong, the terrestrial biological systems will be damaged. And if it is too weak, the synthesis of many biochemical compounds can not go along. We try to obtain the continuous ultraviolet habitable zones, and compare the ultraviolet habitable zones with the habitable zones of host stars. Using the boundary ultraviolet radiation of ultraviolet habitable zone, we calculate the ultraviolet habitable zones of host stars with masses from 0.08 to 4.00 \mo. For the host stars with effective temperatures lower than 4,600 K, the ultraviolet habitable zones are closer than the habitable zones. For the host stars with effective temperatures higher than 7,137 K, the ultraviolet habitable zones are farther than the habitable zones. For hot subdwarf as a host star, the distance of the ultraviolet habitable zone is about ten times more than that of the habitable zone, which is not suitable for life existence.Comment: 5 pages, 3 figure