Induction heating of planetary interiors in white dwarf systems

Context. White dwarfs are the last evolutionary stage for the majority of main-sequence stars. With nuclear burning having ceased, these stars are slowly cooling. There is observational evidence indicating that planetary remnants, and possibly even planets, orbit a considerable fraction of the known white dwarf population. These objects are interesting targets for transit observations due to their large planet-to-star radius ratio. Especially interesting is the possible outgassing from such objects and their eventual observational prospects. Aims. Here, we investigate whether electromagnetic induction heating can drive additional volcanic outgassing from small planetary remnants orbiting white dwarfs. This mechanism can be important for such bodies in addition to tidal heating due to the extremely strong magnetic fields of some white dwarfs and close orbital distances of planets to their host stars. Methods. We calculated the heating and related magmatic effects for a Moon-sized body around a magnetized white dwarf using an analytical model for induction heating and a numerical model for interior processes. We also calculated induction heating inside asteroid-sized bodies. Results. We show that induction heating can melt the mantle of a Moon-sized object within a geologically short time and contribute to desiccation of small asteroids on extremely tight orbits. These findings can have important implications for the evolution of rocky bodies orbiting white dwarfs and the potential detection of their outgassing

Spatial and temporal overlaps between leopards (Panthera pardus) and their competitors in the African large predator guild

Understanding the mechanisms facilitating coexistence within species assemblages is a key consideration for conservation as intact assemblages are necessary for maintaining full ecosystem function. The African large predator guild represents one of the few remaining functionally intact large predator assemblages on Earth, and as such, represents a unique study system to understand competitive interactions. Yet, relatively little is known of the coexistence mechanisms between some of its intermediately sized members, particularly leopards (Panthera pardus). Here, we use overlapping spatio‐temporal activity and GPS data on lions (Panthera leo), leopards, African wild dogs (Lycaon pictus) and cheetahs (Acinonyx jubatus) to examine spatial interactions and temporal partitioning between leopards and other guild members in northern Botswana. We found that at the population level, male leopard space use and activity patterns were largely unaffected by intraguild competitors. Leopards showed minimal movement coherence with competitors (avoidance or attraction) when moving through areas of home ranges shared with intraguild species. Moreover, we found evidence to support the hypothesis that guild species’ activity patterns are primarily driven by light availability rather than predator avoidance. Our results suggest predator avoidance has a limited impact on broad‐scale leopard spatio‐temporal niches, with aspects of the leopards’ ecology and life history likely facilitating its ability to thrive in close proximity to competitors. Considered alongside other studies, our results suggest that landscape‐level approaches to conservation may be suitable for aiding leopard conservation

Biomechanics of predator–prey arms race in lion, zebra, cheetah and impala

The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator–prey pairs, lion–zebra and cheetah–impala, in their natural savannah habitat in Botswana. We show that although cheetahs and impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator–prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate

Nuclear survivin expression is a positive prognostic factor in taxane-platinum-treated ovarian cancer patients

<p>Abstract</p> <p>Background</p> <p>Survivin is an inhibitor of apoptosis and a regulator of mitotic progression. TP53 protein is a negative transcriptional regulator of survivin. The aim of our study was to evaluate the clinical significance of survivin expression in advanced stages ovarian cancer with respect to the TP53 status.</p> <p>Methods</p> <p>Survivin and TP53 expression was evaluated immunohistochemically in 435 archival samples of ovarian carcinomas (244 patients were treated with platinum/cyclophosphamide-PC/PAC; 191-with taxane-platinum (TP) agents). Univariate and multivariate statistical analyses were performed in patients groups divided according to the administered chemotherapeutic regimen, and in subgroups with and without TP53 accumulation (TP53+ and TP53-, respectively).</p> <p>Results</p> <p>Nuclear and cytoplasmic survivin expression was observed in 92% and 74% of the carcinomas, respectively. In patients treated with TP, high nuclear survivin expression decreased the risk of disease recurrence and death, and increased the probability of high platinum sensitivity (p < 0.01), but only in the TP53(+) group, and not in the TP53(-) group.</p> <p>Conclusions</p> <p>It appears that TP53 status determines the clinical importance of nuclear survivin expression in taxane-platinum treated ovarian cancer patients.</p

Dynamics of direct inter-pack encounters in endangered African wild dogs

Aggressive encounters may have important life history consequences due to the potential for injury and death, disease transmission, dispersal opportunities or exclusion from key areas of the home range. Despite this, little is known of their detailed dynamics, mainly due to the difficulties of directly observing encounters in detail. Here, we describe detailed spatial dynamics of inter-pack encounters in African wild dogs (Lycaon pictus), using data from custom-built high-resolution GPS collars in 11 free-ranging packs. On average, each pack encountered another pack approximately every 7 weeks and met each neighbour twice each year. Surprisingly, intruders were more likely to win encounters (winning 78.6% of encounters by remaining closer to the site in the short term). However, intruders did tend to move farther than residents toward their own range core in the short-term (1 h) post-encounter, and if this were used to indicate losing an encounter, then the majority (73.3%) of encounters were won by residents. Surprisingly, relative pack size had little effect on encounter outcome, and injuries were rare (<15% of encounters). These results highlight the difficulty of remotely scoring encounters involving mobile participants away from static defendable food resources. Although inter-pack range overlap was reduced following an encounter, encounter outcome did not seem to drive this, as both packs shifted their ranges post-encounter. Our results indicate that inter-pack encounters may be lower risk than previously suggested and do not appear to influence long-term movement and ranging

A Critical Tryptophan and Ca2+ in Activation and Catalysis of TPPI, the Enzyme Deficient in Classic Late-Infantile Neuronal Ceroid Lipofuscinosis

Tripeptidyl aminopeptidase I (TPPI) is a crucial lysosomal enzyme that is deficient in the fatal neurodegenerative disorder called classic late-infantile neuronal ceroid lipofuscinosis (LINCL). It is involved in the catabolism of proteins in the lysosomes. Recent X-ray crystallographic studies have provided insights into the structural/functional aspects of TPPI catalysis, and indicated presence of an octahedrally coordinated Ca(2+).Purified precursor and mature TPPI were used to study inhibition by NBS and EDTA using biochemical and immunological approaches. Site-directed mutagenesis with confocal imaging technique identified a critical W residue in TPPI activity, and the processing of precursor into mature enzyme.NBS is a potent inhibitor of the purified TPPI. In mammalian TPPI, W542 is critical for tripeptidyl peptidase activity as well as autocatalysis. Transfection studies have indicated that mutants of the TPPI that harbor residues other than W at position 542 have delayed processing, and are retained in the ER rather than transported to lysosomes. EDTA inhibits the autocatalytic processing of the precursor TPPI.We propose that W542 and Ca(2+) are critical for maintaining the proper tertiary structure of the precursor proprotein as well as the mature TPPI. Additionally, Ca(2+) is necessary for the autocatalytic processing of the precursor protein into the mature TPPI. We have identified NBS as a potent TPPI inhibitor, which led in delineating a critical role for W542 residue. Studies with such compounds will prove valuable in identifying the critical residues in the TPPI catalysis and its structure-function analysis

Spatio-temporal factors impacting encounter occurrences between leopards and other large African predators

Encounters between individuals can have implications for a range of processes, including 24 disease transmission, information transfer, and competition. For large carnivores, 25 difficulties in directly observing individuals and historical hardware limitations of GPS 26 collars mean that relatively little is known of the spatio-temporal factors contributing to 27 encounters. The African large predator guild represents one of the few remaining 28 functionally intact guilds of large carnivores on the globe and so represents a unique 29 study system for understanding competitor interactions. We explored the drivers of male 30 leopard (Panthera pardus) encounters with lions (Panthera leo), African wild dogs (Lycaon 31 pictus) and cheetahs (Acinonyx jubatus) in the context of habitat characteristics and 32 temporal activity overlaps. Using high resolution (five minute GPS fixes) data from 48 33 large African carnivores from 2012 to 2018, we quantified encounter occurrences 34 between male leopards and other guild species and related these to habitat type (open vs 35 closed), activity overlaps, and moonlight levels. Leopards met wild dogs 4.56 ± 1.15 36 (standard error), lions 3.11 ± 0.56, and cheetahs 2.27 ± 0.73 times per month. All species 37 instigated encounters, but leopard instigated encounters with dominant competitors 38 appeared to reflect imperfect information on risk, primarily occurring within habitats with 39 limited visibility. Moreover, encounters peaked during periods of high temporal overlap, 40 suggesting that, although previous research indicates temporal activity patterns may not 41 be driven by predator avoidance, temporal overlap has implications for competitor 42 dynamics. Our results show how habitat characteristics and niche overlaps contribute to 43 encounters between competitors and provide an example of how niche shifts within 44 competitor assemblages can impact competition between species

Isotopic Resolution of Fission Fragments from 238U+12C Transfer and Fusion Reactions

Expérience GANILInternational audienceRecent results from an experiment at GANIL, performed to investigate the main properties of fission-fragment yields and energy distributions in different fissioning nuclei as a function of the excitation energy, in a neutron-rich region of actinides, are presented. Transfer reactions in inverse kinematics between a 238U beam and a 12C target produced different actinides, within a range of excitation energy below 30 MeV. These fissioning nuclei are identified by detecting the target-like recoil, and their kinetic and excitation energy are determined from the reconstruction of the transfer reaction. The large-acceptance spectrometer VAMOS was used to identify the mass, atomic number and charge state of the fission fragments in flight. As a result, the characteristics of the fission-fragment isotopic distributions of a variety of neutron-rich actinides are observed for the first time over the complete range of fission fragments

Study of 124^{124}Sn+136^{136}Xe fusion-evaporation: analysis of a rare-event experiment

7 pages, 4 figuresFusion-evaporation in the $^{124}$Sn+$^{136}$Xe system is studied using a high intensity xenon beam provided by the Ganil accelerator and the LISE3 wien filter for the selection of the products. Due to the mass symmetry of the entrance system, the rejection of the beam by the spectrometer was of the order of $5times10^8$. We have thus performed a detailed statistical analysis to estimate random events and to infer the fusion-evaporation cross sections. No signicant decay events were detected and upper limit cross sections of 172~pb, 87~pb and 235~pb were deduced for the synthesis of $^{257}$Rf, $^{258}$Rf and $^{259}$Rf, respectively