25 research outputs found
Incomplete devil's staircase in the magnetization curve of SrCu2(BO3)2
We report on NMR and torque measurements on the frustrated
quasi-two-dimensional spin-dimer system SrCu2(BO3)2 in magnetic fields up to 34
T that reveal a sequence of magnetization plateaus at 1/8, 2/15, 1/6, and 1/4
of the saturation and two incommensurate phases below and above the 1/6
plateau. The magnetic structures determined by NMR involve a stripe order of
triplets in all plateaus, suggesting that the incommensurate phases originate
from proliferation of domain walls. We propose that the magnetization process
of SrCu2(BO3)2 is best described as an incomplete devil's staircase.Comment: 21 pages, 9 figures (main: 12 pages, 4 figures/supplemental material:
9 pages, 5 figures
Selection assisted by a BoLA-DR/DQ haplotype against susceptibility to bovine dermatophilosis
Bovine dermatophilosis is a severe skin infection of tropical ruminants inducing a severe loss in productivity and a 15% mortality rate. This disease is caused by the actinomycete bacterium Dermatophilus congolensis associated with the tick Amblyomma variegatum. Currently there are no prospects for a vaccine, and acaricide or antibiotic control is hampered by the development of chemoresistance. Animal breeders have observed that dermatophilosis susceptibility seems to be determined genetically, and we previously identified a BoLA-DRB3-DQB class II haplotype marker for high (R2 = 0.96) susceptibility to the disease. With this marker, we developed a successful eugenic selection procedure for zebu Brahman cattle in Martinique (FWI). Over a period of five years, a marked reduction in disease prevalence, from 0.76 to 0.02 was achieved, and this low level has been maintained over the last two years. The selection procedure, based on a genetic marker system targeting the highly polymorphic BoLA locus, eliminates only those individuals which are at the highest risk of contracting the disease. In the present work, we discuss the properties of this system, including the "heterozygote advantage" and the "frequency dependence" theories, and examine their involvement in the biological mechanisms at the host/pathogen interface. We speculate on the exact role of the MHC molecules in the control of the disease, how the natural selection pressure imposed by the pathogens selectively maintains MHC diversity, and how our results can be practically applied for integrated control of dermatophilosis in developing countries
Intertwining threshold settings, biological data and database knowledge to optimize the selection of differentially expressed genes from microarray.
International audienceBACKGROUND: Many tools used to analyze microarrays in different conditions have been described. However, the integration of deregulated genes within coherent metabolic pathways is lacking. Currently no objective selection criterion based on biological functions exists to determine a threshold demonstrating that a gene is indeed differentially expressed. METHODOLOGY/PRINCIPAL FINDINGS: To improve transcriptomic analysis of microarrays, we propose a new statistical approach that takes into account biological parameters. We present an iterative method to optimise the selection of differentially expressed genes in two experimental conditions. The stringency level of gene selection was associated simultaneously with the p-value of expression variation and the occurrence rate parameter associated with the percentage of donors whose transcriptomic profile is similar. Our method intertwines stringency level settings, biological data and a knowledge database to highlight molecular interactions using networks and pathways. Analysis performed during iterations helped us to select the optimal threshold required for the most pertinent selection of differentially expressed genes. CONCLUSIONS/SIGNIFICANCE: We have applied this approach to the well documented mechanism of human macrophage response to lipopolysaccharide stimulation. We thus verified that our method was able to determine with the highest degree of accuracy the best threshold for selecting genes that are truly differentially expressed
Selection assisted by a BoLA-DR/DQ haplotype against susceptibility to bovine dermatophilosis
Influence of wind loading on root system development and architecture in oak (<em>Quercus robur</em> L.) seedlings
International audienc
Spitzer observations of mutual events in the binary system (617) Patroclus-Menoetius
We report Spitzer observations of the binary Trojan system (617) Patroclus-Menoetius during two mutual events, when respectively one component shadowed and occulted the other. Observing the thermal response to mutual shadowing with spectral ( 8--33 ”m) and temporal resolution allowed us to determine the system's thermal inertia in a uniquely direct way. Furthermore, our analysis provided an accurate determination of the system's size which is methodologically independent of the estimate by Berthier et al. (this session). Our results allow a more reliable estimate of the system's bulk density (the total mass was determined from the system's mutual orbit; Marchis et al., 2006; Berthier et al., this session).
This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This material is partly based upon work supported by the national Aeronautics and Space Administration issue through the Science Mission Directorate Research and Analysis Programs number NNG05GF09G
An Embedded Deep Brain Stimulator for Biphasic Chronic Experiments in Freely Moving Rodents
Selection assisted by a BoLA-DR/DQ haplotype against susceptibility to bovine dermatophilosis
Bovine dermatophilosis is a severe skin infection of tropical
ruminants inducing a severe loss in productivity and a 15% mortality
rate. This disease is caused by the actinomycete bacterium
Dermatophilus congolensis associated with the tick
Amblyomma variegatum. Currently there are no prospects for a
vaccine, and acaricide or antibiotic control is hampered by the
development of chemoresistance. Animal breeders have observed that
dermatophilosis susceptibility seems to be determined genetically, and
we previously identified a BoLA-DRB3-DQB class II haplotype
marker for high (R = 0.96) susceptibility to the
disease. With this marker, we developed a successful eugenic selection
procedure for zebu Brahman cattle in Martinique (FWI). Over a period
of five years, a marked reduction in disease prevalence, from 0.76 to
0.02 was achieved, and this low level has been maintained over the
last two years. The selection procedure, based on a genetic marker
system targeting the highly polymorphic BoLA locus,
eliminates only those individuals which are at the highest risk of
contracting the disease. In the present work, we discuss the
properties of this system, including the âheterozygote advantageâ and
the âfrequency dependenceâ theories, and examine their involvement in
the biological mechanisms at the host/pathogen interface. We speculate
on the exact role of the MHC molecules in the control of the disease,
how the natural selection pressure imposed by the pathogens
selectively maintains MHC diversity, and how our results can be
practically applied for integrated control of dermatophilosis in
developing countries