Briquet M.,Catholic University of Leuven |
Briquet M.,Fund for Scientific Research |
Korhonen H.,European Southern Observatory |
Gonzalez J.F.,Institute Ciencias Astronomicas |
And 2 more authors.
Astronomy and Astrophysics | Year: 2010
Aims: We gathered about 100 high-resolution spectra of three typical HgMn (mercury-manganese) stars, HD11753, HD53244, and HD221507, to search for slowly pulsating B-like pulsations and surface inhomogeneous distribution of various chemical elements. Methods: Classical frequency analysis methods were used to detect line profile variability and to determine the variation period. Doppler imaging reconstruction was performed to obtain abundance maps of chemical elements on the stellar surface. Results: For HD11753, which is the star with the most pronounced variability, distinct spectral line profile changes were detected for Ti, Sr, Y, Zr, and Hg, whereas for HD53244 and HD221507 the most variable line profiles belong to the elements Hg and Y, respectively. We derived rotation periods for all three stars from the variations of radial velocities and equivalent widths of spectral lines belonging to inhomogeneously distributed elements: Prot (HD11753) = 9.54 d, Prot (HD53244) = 6.16 d, and Prot (HD221507) = 1.93 d. For HD11753 the Doppler imaging technique was applied to derive the distribution of the most variable elements Ti, Sr, and Y using two datasets separated by ∼65 days. Results of Doppler imaging reconstruction revealed noticeable changes in the surface distributions of Ti II, Sr II, and Y II between the datasets, indicating the hitherto not well understood physical processes in stars with radiative envelopes that cause a rather fast dynamical chemical spot evolution. © 2010 ESO.
Boulanger N.,University of Mons |
Boulanger N.,Fund for Scientific Research |
Cook P.P.,King's College London |
Ponomarev D.,University of Mons
Journal of High Energy Physics | Year: 2012
In a spacetime of dimension n, the dual graviton is characterised by a Young diagram with two columns, the first of length n - 3 and the second of length one. In this paper we perform the off-shell dualisation relating the dual graviton to the double-dual graviton, displaying the precise off-shell field content and gauge invariances. We then show that one can further perform infinitely many off-shell dualities, reformulating linearised gravity in an infinite number of equivalent actions. The actions require supplementary mixed-symmetry fields which are contained within the generalised Kac-Moody algebra E 11 and are associated with null and imaginary roots. © SISSA 2012.
News Article | December 1, 2016
Even gut microbes have a routine. Like clockwork, they start their day in one part of the intestinal lining, move a few micrometers to the left, maybe the right, and then return to their original position. New research in mice now reveals that the regular timing of these small movements can influence a host animal's circadian rhythms by exposing gut tissue to different microbes and their metabolites as the day goes by. Disruption of this dance can affect the host. The study appears December 1 in Cell. "This research highlights how interconnected the behavior is between prokaryotes and eukaryotes, between mammalian organisms and the microbes that live inside them," says Eran Elinav, an immunologist at the Weizmann Institute of Science, who led the work with co-senior author Eran Segal, a computational biologist also at the Weizmann. "These groups interact with and are affected by each other in a way that can't be separated." The new study had three major findings: Previous work by Elinav and Segal revealed that our biological clocks work in tandem with the biological clocks in our microbiota and that disrupting sleep-wake patterns and feeding times in mice induced changes in the microbiome in the gut. "Circadian rhythms are a way of adapting to changes in light and dark, metabolic changes, and the timing of when we eat," says Segal. "Other studies have shown the importance of the microbiome in metabolism and its effect on health and disease. Now, we've shown for the first time how circadian rhythms in the microbiota have an effect on circadian rhythms in the host." The investigators say their work has potential implications for human health in two important ways. First of all, because drugs ranging from acetaminophen to chemotherapy are metabolized in the liver, understanding -- and potentially being able to manipulate -- the circadian rhythms of our microbiota could affect how and when medications are administered. Second, understanding more about this relationship could help to eventually intervene in health problems like obesity and metabolic syndrome, which are more common in people whose circadian rhythms are frequently disrupted due to shift work or jet lag. "What we learned from this study is that there's a very tight interconnectivity between the microbiome and the host. We should think of it now as one supraorganism that can't be separated," Segal says. "We have to fully integrate our thinking with regard to any substance that we consume." This research was primarily funded by Yael and Rami Ungar, Israel; Leona M. and Harry B. Helmsley Charitable Trust; the Gurwin Family Fund for Scientific Research; Crown Endowment Fund for Immunological Research; estate of Jack Gitlitz; estate of Lydia Hershkovich; the Benoziyo Endowment Fund for the Advancement of Science; Adelis Foundation; John L. and Vera Schwartz, Pacific Palisades; Alan Markovitz, Canada; Cynthia Adelson, Canada; CNRS (Centre National de la Recherche Scientifique); estate of Samuel and Alwyn J. Weber; Mr. and Mrs. Donald L. Schwarz, Sherman Oaks; grants funded by the European Research Council; the German-Israel Binational foundation; the Israel Science Foundation; the Minerva Foundation; the Rising Tide foundation; the Alon Foundation scholar award; the Rina Gudinski Career Development Chair; and the Canadian Institute For Advanced Research (CIFAR). Cell (@CellCellPress), the flagship journal of Cell Press, is a bimonthly journal that publishes findings of unusual significance in any area of experimental biology, including but not limited to cell biology, molecular biology, neuroscience, immunology, virology and microbiology, cancer, human genetics, systems biology, signaling, and disease mechanisms and therapeutics. Visit: http://www. . To receive Cell Press media alerts, contact email@example.com.
News Article | December 5, 2016
Combination drug treatments have become successful at long-term control of HIV infection, but the goal of totally wiping out the virus and curing patients has so far been stymied by HIV's ability to hide out in cells and become dormant for long periods of time. Now a new study on HIV's close cousin, simian immunodeficiency virus (SIV), in macaques finds that a proposed curative strategy could backfire and make things worse if the virus is in fact lurking in the brain. One of the proposed curative strategies for HIV, known as "shock and kill," first uses so-called latency-reversing agents to wake up dormant viruses in the body, making them vulnerable to the patient's immune system. The idea is that this, in combination with antiretroviral medicines, would wipe out the majority of infected cells. But based on a study of macaques with SIV, a group of researchers warns in a report published in the January 2 issue of the journal AIDS that such a strategy could cause potentially harmful brain inflammation. "The potential for the brain to harbor significant HIV reservoirs that could pose a danger if activated hasn't received much attention in the HIV eradication field," says Janice Clements, Ph.D., professor of molecular and comparative pathobiology at the Johns Hopkins University School of Medicine. "Our study sounds a major cautionary note about the potential for unintended consequences of the shock-and-kill treatment strategy." HIV research efforts have long focused on prevention and developing antiretroviral therapies that keep the virus in check without eradicating it, essentially transforming HIV into a manageable chronic condition, says Lucio Gama, Ph.D., assistant professor of molecular and comparative pathobiology at Johns Hopkins and the lead author of the new study. Then, in 2009, a group in Berlin reported it had cured a man of HIV by giving him a bone marrow transplant from a donor whose genetics conferred natural resistance to the virus. This galvanized federal funding of new research projects aimed at finding a more broadly applicable "AIDS cure," Gama says. He and Clements are part of that pursuit as members of the Collaboratory of AIDS Researchers for Eradication. One cure strategy being pursued is to find a medication that would "wake up" virus in the reservoirs, forcing it to reveal itself. But Gama says that could be problematic if HIV reservoirs exist in the brain, and investigators already had some evidence that they do: the many cases of AIDS dementia that developed before the current antiretroviral cocktail treatment was developed. "Research had also shown that HIV can infect monocytes in the blood, which we know cross into the brain," he says. But no studies had definitively answered whether significant reservoirs of latent HIV in patients under long-term therapy could be sustained in the brain -- in part because, in autopsies, it is unclear whether virus detected in the brain comes from brain cells themselves or surrounding blood. For the new study, Clements, Gama and their collaborators treated three pig-tailed macaque monkeys infected with SIV with antiretrovirals for more than a year. Then the researchers gave two of the macaques ingenol-B, a latency-reversing agents thought to "wake up" the virus. "We didn't really see any significant effect," Gama says, "So we coupled ingenol-B with another latency-reversing agent, vorinostat, which is used in some cancer treatments to make cancer cells more vulnerable to the immune system." The macaques also continued their course of antiretrovirals throughout the experiment. After a 10-day course of the combined treatment, one of the macaques remained healthy, while the other developed symptoms of encephalitis, or brain inflammation, Gama says, and blood tests revealed an active SIV infection. When the animal's illness worsened, the researchers humanely killed it and carefully removed the blood from its body so that blood sources of the virus would not muddle their examination of the brain. Testing revealed SIV was still present in the brain, but only in one of the regions analyzed: the occipital cortex, which processes visual information. The affected area was so small that "we almost missed it," he says. Gama cautions that the results of their study on macaques with SIV may not apply to humans with HIV. It's also possible, he says, that the encephalitis was transient and could have resolved by itself. Still, he says, the results signal a need for extra caution in exploring ways to flush out HIV reservoirs and eradicate the virus from the body. Other authors on the paper are Celina M. Abreu, Erin N. Shirk, Sarah L. Price, Ming Li, Greg M. Laird, Kelly A. Metcalf Pate and Robert F. Siliciano of The Johns Hopkins University; Stephen W. Wietgrefe and Ashley T. Haase of the University of Minnesota; Shelby L. O'Connor of the University of Wisconsin; Luiz Pianowski of Kyolab in Brazil; Carine van Lint of the Université Libre de Bruxelles in Belgium; and the LRA-SIV Study Group. Research reported in this publication was supported by the National Institute of Mental Health (grant number P01MH070306-01), the National Institute of Allergy and Infectious Disease (grant number U19A1076113), the National Institutes of Health's Office of the Director (grant numbers P40OD013117 and P51OD011106), the Research Facilities Improvement Program (grant numbers RR15459-01 and RR020141-01), the France Recherche Nord & Sud Sida-HIV Hépatites, the Belgian Fund for Scientific Research (FRS-FNRS Belgium), the Fondation Roi Baudouin, the NEAT program and the Wallo on Region (the Excellence Program Cibles).
Acke B.,Catholic University of Leuven |
Acke B.,Fund for Scientific Research
EAS Publications Series | Year: 2011
I give an overview of the recent scientific results based on observations of PAH emission from circumstellar disks around young stars. The stellar radiation field plays a key role in the excitation and destruction of the PAH molecules in the disk. The detection rate of PAH emission in disks is optimal for stars of spectral type A. Around stars of similar temperature, the disk structure determines the PAH emission strength: disks with a flared geometry produce stronger PAH emission than flattened disks. The spectral properties of the emission features, indicative of the chemistry of the emitting hydrocarbons, is closely linked to the central star radiation field. The main PAH features shift to redder wavelengths with decreasing stellar effective temperature. This trend has been interpreted as an indication for a higher aliphatic/aromatic ratio of the hydrocarbon mixture around cool stars with respect to hot stars. An alternative explanation may be a more significant contribution to the infrared emission of very small grains around cooler stars. © EAS, EDP Sciences 2011.
Guns M.,Catholic University of Louvain |
Guns M.,Fund for Scientific Research |
Vanacker V.,Catholic University of Louvain
Environmental Earth Sciences | Year: 2013
Tropical mountain regions are prone to landslide hazards. Given the current land pressure with increasing occupation of steep uplands, landslide hazards are expected to increase in the near future. Understanding the factors that control landslide hazards is therefore essential. Rare event logistic regression allows us to perform a robust detection of landslide controlling factors. This technique is here applied to the tropical Andes to evaluate the impact of dynamic land cover changes on landslide occurrences. Land cover change trajectories (i.e. dynamic evolution of land cover through time) were specifically included in the probabilistic landslide analysis. While natural physical processes such as slope undercutting by rivers and failure of oversteepened slopes are important in this tropical mountainous site, landslides are increasingly associated with human activities. The data show that land cover trajectories are associated with landslide patterns. In this humid mountainous site, forest degradation does not lead to a measurable increase in landslide occurrence. However, few years after forests are converted to pastures, a rapid decline of slope stability is observed. Land cover conversion from forest to pasture permanently reduces slope stability. It is assumed that major changes in soil properties and hydrology induced by the vegetation conversion play a role in accelerating landslide hazards. © 2013 Springer-Verlag Berlin Heidelberg.
Bastin C.,University of Liège |
Bastin C.,Fund for Scientific Research |
Salmon E.,University of Liège
European Journal of Clinical Nutrition | Year: 2014
Lifestyle modification offers a promising way of preventing or delaying Alzheimer's disease (AD). In particular, nutritional interventions can contribute to decrease the risk of dementia. The efficacy of such interventions should be assessed in individuals thought to be prone to AD. It is therefore necessary to identify markers that may help detecting AD as early as possible. This review will focus on subtle neuropsychological changes that may already exist in the predementia phase, and that could point to individuals at risk of dementia. Episodic memory decline appears consistently as the earliest sign of incipient typical AD. An episodic memory test that ensures deep encoding of information and assesses retrieval with free as well as cued recall appears as a useful tool to detect patients at an early stage of AD. Beyond the memory domain, category verbal fluency has been shown to decline early and to predict progression to AD. Moreover, in line with current diagnosis criteria for prodromal AD, combining neuropsychological scores and neuroimaging data allows a better discrimination of future AD patients than neuroimaging or neuropsychological data alone. Altogether, the detection of cognitive changes that are predictive of the typical form of probable AD already in the predementia stage points to at risk people who are the best target for therapeutic interventions, such as nutrition or physical exercise counseling or dietary interventions. © 2014 Macmillan Publishers Limited.
Demoulin A.,University of Liège |
Demoulin A.,Fund for Scientific Research
Geophysical Research Letters | Year: 2012
Despite constant progress in numerical and field studies of landscape evolution, time evolution is still poorly constrained in many uplifted areas where low denudation rates prevent the use of low temperature thermochronology, especially outside high relief mountainous areas. Here, I show that regional statistics of the landscape metric R involving hypsometric integrals at three nested levels of a catchment are able to isolate the time effect on landscape geometry during the latter's transient response to a tectonic perturbation. Analysis of 210 catchments from 9 regions of known uplift age worldwide shows that the regionally characteristic, R-derived S R index is in inverse power law relation with the time elapsed since a base level lowering. Suggesting a response time of ∼5 My, this finding has important implications for quantifying the rate of landform evolution and determining whether a landscape has reached steady-state form. © 2012. American Geophysical Union. All Rights Reserved.
Guns M.,Catholic University of Louvain |
Guns M.,Fund for Scientific Research |
Vanacker V.,Catholic University of Louvain
Natural Hazards and Earth System Science | Year: 2012
Statistical analysis of natural hazards needs particular attention, as most of these phenomena are rare events. This study shows that the ordinary rare event logistic regression, as it is now commonly used in geomorphologic studies, does not always lead to a robust detection of controlling factors, as the results can be strongly sample-dependent. In this paper, we introduce some concepts of Monte Carlo simulations in rare event logistic regression. This technique, so-called rare event logistic regression with replications, combines the strength of probabilistic and statistical methods, and allows overcoming some of the limitations of previous developments through robust variable selection. This technique was here developed for the analyses of landslide controlling factors, but the concept is widely applicable for statistical analyses of natural hazards. © 2012 Author(s). CC Attribution 3.0 License.
News Article | April 20, 2016
The Acknowledgements of this Letter should have included the following sentence: “This work was also supported in part by the University of Antwerp (TOP BOF 29069 to A.J.); the Fund for Scientific Research-Flanders (grant number G078414N to A.J.); the Association Belge contre les Maladies Neuromusculaire (to A.J.); the Association Française contre les Myopaties (grant number 16197 to A.J.).