195 research outputs found
DNA methyltransferase-3-dependent nonrandom template segregation in differentiating embryonic stem cells.
Asymmetry of cell fate is one fundamental property of stem cells, in which one daughter cell self-renews, whereas the other differentiates. Evidence of nonrandom template segregation (NRTS) of chromosomes during asymmetric cell divisions in phylogenetically divergent organisms, such as plants, fungi, and mammals, has already been shown. However, before this current work, asymmetric inheritance of chromatids has never been demonstrated in differentiating embryonic stem cells (ESCs), and its molecular mechanism has remained unknown. Our results unambiguously demonstrate NRTS in asymmetrically dividing, differentiating human and mouse ESCs. Moreover, we show that NRTS is dependent on DNA methylation and on Dnmt3 (DNA methyltransferase-3), indicating a molecular mechanism that regulates this phenomenon. Furthermore, our data support the hypothesis that retention of chromatids with the old template DNA preserves the epigenetic memory of cell fate, whereas localization of new DNA strands and de novo DNA methyltransferase to the lineage-destined daughter cell facilitates epigenetic adaptation to a new cell fate
Charged particle detection performances of CMOS pixel sensors produced in a 0.18 um process with a high resistivity epitaxial layer
The apparatus of the ALICE experiment at CERN will be upgraded in 2017/18
during the second long shutdown of the LHC (LS2). A major motivation for this
upgrade is to extend the physics reach for charmed and beauty particles down to
low transverse momenta. This requires a substantial improvement of the spatial
resolution and the data rate capability of the ALICE Inner Tracking System
(ITS). To achieve this goal, the new ITS will be equipped with 50 um thin CMOS
Pixel Sensors (CPS) covering either the 3 innermost layers or all the 7 layers
of the detector. The CPS being developed for the ITS upgrade at IPHC
(Strasbourg) is derived from the MIMOSA 28 sensor realised for the STAR-PXL at
RHIC in a 0.35 um CMOS process. In order to satisfy the ITS upgrade
requirements in terms of readout speed and radiation tolerance, a CMOS process
with a reduced feature size and a high resistivity epitaxial layer should be
exploited. In this respect, the charged particle detection performance and
radiation hardness of the TowerJazz 0.18 um CMOS process were studied with the
help of the first prototype chip MIMOSA 32. The beam tests performed with
negative pions of 120 GeV/c at the CERN-SPS allowed to measure a
signal-to-noise ratio (SNR) for the non-irradiated chip in the range between 22
and 32 depending on the pixel design. The chip irradiated with the combined
dose of 1 MRad and 10^13 n_eq/cm^2 was observed to yield a SNR ranging between
11 and 23 for coolant temperatures varying from 15 C to 30 C. These SNR values
were measured to result in particle detection efficiencies above 99.5% and 98%
before and after irradiation respectively. These satisfactory results allow to
validate the TowerJazz 0.18 um CMOS process for the ALICE ITS upgrade.Comment: (v2) Added hyper-links; (v3) A typo correcte
Oxytocin is an age-specific circulating hormone that is necessary for muscle maintenance and regeneration.
The regenerative capacity of skeletal muscle declines with age. Previous studies suggest that this process can be reversed by exposure to young circulation; however, systemic age-specific factors responsible for this phenomenon are largely unknown. Here we report that oxytocin--a hormone best known for its role in lactation, parturition and social behaviours--is required for proper muscle tissue regeneration and homeostasis, and that plasma levels of oxytocin decline with age. Inhibition of oxytocin signalling in young animals reduces muscle regeneration, whereas systemic administration of oxytocin rapidly improves muscle regeneration by enhancing aged muscle stem cell activation/proliferation through activation of the MAPK/ERK signalling pathway. We further show that the genetic lack of oxytocin does not cause a developmental defect in muscle but instead leads to premature sarcopenia. Considering that oxytocin is an FDA-approved drug, this work reveals a potential novel and safe way to combat or prevent skeletal muscle ageing
Interaction between caesium iodide particles and gaseous boric acid in a flowing system through a thermal gradient tube (1030 Kâ450 K) and analysis with ASTEC/SOPHAEROS
International audienceThe present work aimed at studying the interaction between caesium iodide particles and gaseous boric acidthrough a Thermal Gradient Tube (TGT) from 1023 K to 453 K under Ar/H2O. Particles size range of transportedparticles was measured by ELPI and the fraction of gaseous compounds by ICP-MS and UVâvisible spectroscopy.Reaction between the two compounds was deduced by measuring a significant fraction of gaseous iodine at theoutlet of the facility, representing more than 80% of the total iodine sampled at the outlet. The reaction rate wasshown to be lower when the flow rate inside the facility was increased. Analysis with SOPHAEROS module ofASTEC code was performed. The ASTEC fission products models allowed performing the evaluation of theexperimentally observed results for the analysis of the transport of pure compounds. However, the heterogeneousinteraction between the caesium iodide particles and the gaseous boric acid was not reproduced, as the modelsare not taken into account in the version v2.1_1_6 of the ASTEC/SOPHAEROS module. The next step would be toidentify the mechanism of the reaction by comparing the results with other studies and to determine the reactionrates. Then, a first development in SOPHAEROS would be to implement such phenomena
Development of CMOS pixel sensors for tracking and vertexing in high energy physics experiments
CMOS pixel sensors (CPS) represent a novel technological approach to building
charged particle detectors. CMOS processes allow to integrate a sensing volume
and readout electronics in a single silicon die allowing to build sensors with
a small pixel pitch () and low material budget () per layer. These characteristics make CPS an attractive option for
vertexing and tracking systems of high energy physics experiments. Moreover,
thanks to the mass production industrial CMOS processes used for the
manufacturing of CPS the fabrication construction cost can be significantly
reduced in comparison to more standard semiconductor technologies. However, the
attainable performance level of the CPS in terms of radiation hardness and
readout speed is mostly determined by the fabrication parameters of the CMOS
processes available on the market rather than by the CPS intrinsic potential.
The permanent evolution of commercial CMOS processes towards smaller feature
sizes and high resistivity epitaxial layers leads to the better radiation
hardness and allows the implementation of accelerated readout circuits. The
TowerJazz CMOS process being one of the most relevant examples
recently became of interest for several future detector projects. The most
imminent of these project is an upgrade of the Inner Tracking System (ITS) of
the ALICE detector at LHC. It will be followed by the Micro-Vertex Detector
(MVD) of the CBM experiment at FAIR. Other experiments like ILD consider CPS as
one of the viable options for flavour tagging and tracking sub-systems
Survey of ICIC Techniques in LTE Networks under Various Mobile Environment Parameters
International audienc
Gut Pathology and Responses to the Microsporidium Nosema ceranae in the Honey Bee Apis mellifera
The microsporidium Nosema ceranae is a newly prevalent parasite of the European honey bee (Apis mellifera). Although this parasite is presently spreading across the world into its novel host, the mechanisms by it which affects the bees and how bees respond are not well understood. We therefore performed an extensive characterization of the parasite effects at the molecular level by using genetic and biochemical tools. The transcriptome modifications at the midgut level were characterized seven days post-infection with tiling microarrays. Then we tested the bee midgut response to infection by measuring activity of antioxidant and detoxification enzymes (superoxide dismutases, glutathione peroxidases, glutathione reductase, and glutathione-S-transferase). At the gene-expression level, the bee midgut responded to N. ceranae infection by an increase in oxidative stress concurrent with the generation of antioxidant enzymes, defense and protective response specifically observed in the gut of mammals and insects. However, at the enzymatic level, the protective response was not confirmed, with only glutathione-S-transferase exhibiting a higher activity in infected bees. The oxidative stress was associated with a higher transcription of sugar transporter in the gut. Finally, a dramatic effect of the microsporidia infection was the inhibition of genes involved in the homeostasis and renewal of intestinal tissues (Wnt signaling pathway), a phenomenon that was confirmed at the histological level. This tissue degeneration and prevention of gut epithelium renewal may explain early bee death. In conclusion, our integrated approach not only gives new insights into the pathological effects of N. ceranae and the bee gut response, but also demonstrate that the honey bee gut is an interesting model system for studying host defense responses
Oscillatory behavior of Pd-Au catalysts in toluene total oxidation
In this work, the activity of bimetallic Pd-Au doped hierarchically structured titania catalysts has been investigated in the total oxidation of toluene. In earlier works, doping titania with group Vb metal oxides ensured an increased catalytic performance in the elimination of VOC molecules. A synergy between gold and palladium loaded at the surface of titania supports provided better performances in VOC oxidation reactions. Therefore, the main focus in this work was to investigate the durability of the prepared catalysts under long time-on-stream periods. Vanadium-doped catalysts showed a stable activity throughout the whole 110 h test, whereas, surprisingly, niobium-doped catalysts presented a cycle-like activity while nevertheless maintaining a high performance in toluene elimination. Operando Diffuse Reflectance Infrared Fourrier Transform spectroscopy (DRIFT) experiments revealed that variations in the presence of OH radicals and the presence of carbonaceous compounds adsorbed at the surface of spent catalysts varies with the occurrence of oscillations. X-ray Photoelectron Spectroscopy (XPS) results show that interactions between the material and the active phase provided extra amounts of mobile oxygen species and participated in easing the reduction of palladium. An enhanced redox reaction scheme is thus obtained and allows the occurrence of the cyclic-like performance of the catalyst
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