Experimental evidence of solitary wave interaction in Hertzian chains

We study experimentally the interaction between two solitary waves that approach one to another in a linear chain of spheres interacting via the Hertz potential. When these counter propagating waves collide, they cross each other and a phase shift respect to the noninteracting waves is introduced, as a result of the nonlinear interaction potential. This observation is well reproduced by our numerical simulations and it is shown to be independent of viscoelastic dissipation at the beads contact. In addition, when the collision of equal amplitude and synchronized counter propagating waves takes place, we observe that two secondary solitary waves emerge from the interacting region. The amplitude of secondary solitary waves is proportional to the amplitude of incident waves. However, secondary solitary waves are stronger when the collision occurs at the middle contact in chains with even number of beads. Although numerical simulations correctly predict the existence of these waves, experiments show that their respective amplitude are significantly larger than predicted. We attribute this discrepancy to the rolling friction at the beads contacts during solitary wave propagation

Patterns of protein carbonylation during Medicago truncatula seed maturation

Seeds mainly acquire their physiological quality during maturation, whereas oxidative conditions reign within cells triggering protein carbonylation. To better understand the role of this protein modification in legume seeds, we compared by proteomics patterns of carbonylated proteins in maturing seeds of Medicago truncatula naturally desiccated or prematurely dried, a treatment known to impair seed quality acquisition. In both cases, protein carbonylation increased in these seeds, accompanying water removal. We identified several proteins whose extent of carbonylation varied when comparing natural desiccation and premature drying and that could therefore be responsible for the impairment of seed quality acquisition or expression. In particular, we focused on PM34, a protein specific to seeds exhibiting a high sensitivity to carbonylation and of which function in dicotyledons was not known before. PM34 proved to have a cellulase activity presumably associated with cell elongation, a process required for germination and subsequent seedling growth. We discuss the possibility that PM34 (abundance or redox state) could be used to assess crop seed quality

Gravitational waves from spinning eccentric binaries

This paper is to introduce a new software called CBwaves which provides a fast and accurate computational tool to determine the gravitational waveforms yielded by generic spinning binaries of neutron stars and/or black holes on eccentric orbits. This is done within the post-Newtonian (PN) framework by integrating the equations of motion and the spin precession equations while the radiation field is determined by a simultaneous evaluation of the analytic waveforms. In applying CBwaves various physically interesting scenarios have been investigated. In particular, we have studied the appropriateness of the adiabatic approximation, and justified that the energy balance relation is indeed insensitive to the specific form of the applied radiation reaction term. By studying eccentric binary systems it is demonstrated that circular template banks are very ineffective in identifying binaries even if they possess tiny residual orbital eccentricity. In addition, by investigating the validity of the energy balance relation we show that, on contrary to the general expectations, the post-Newtonian approximation should not be applied once the post-Newtonian parameter gets beyond the critical value $\sim 0.08-0.1$. Finally, by studying the early phase of the gravitational waves emitted by strongly eccentric binary systems---which could be formed e.g. in various many-body interactions in the galactic halo---we have found that they possess very specific characteristics which may be used to identify these type of binary systems.Comment: 37 pages, 18 figures, submitted to Class. Quantum Gra

Defining functional DNA elements in the human genome

With the completion of the human genome sequence, attention turned to identifying and annotating its functional DNA elements. As a complement to genetic and comparative genomics approaches, the Encyclopedia of DNA Elements Project was launched to contribute maps of RNA transcripts, transcriptional regulator binding sites, and chromatin states in many cell types. The resulting genome-wide data reveal sites of biochemical activity with high positional resolution and cell type specificity that facilitate studies of gene regulation and interpretation of noncoding variants associated with human disease. However, the biochemically active regions cover a much larger fraction of the genome than do evolutionarily conserved regions, raising the question of whether nonconserved but biochemically active regions are truly functional. Here, we review the strengths and limitations of biochemical, evolutionary, and genetic approaches for defining functional DNA segments, potential sources for the observed differences in estimated genomic coverage, and the biological implications of these discrepancies. We also analyze the relationship between signal intensity, genomic coverage, and evolutionary conservation. Our results reinforce the principle that each approach provides complementary information and that we need to use combinations of all three to elucidate genome function in human biology and disease

Proteomics and Posttranslational Proteomics of Seed Dormancy and Germination

The seed is the dispersal unit of plants and must survive the vagaries of the environment. It is the object of intense genetic and genomic studies because processes related to seed quality affect crop yield and the seed itself provides food for humans and animals. Presently, the general aim of postgenomics analyses is to understand the complex biochemical and molecular processes underlying seed quality, longevity, dormancy, and vigor. Due to advances in functional genomics, the recent past years have seen a tremendous progress in our understanding of several aspects of seed development and germination. Here, we describe the proteomics protocols (from protein extraction to mass spectrometry) that can be used to investigate several aspects of seed physiology, including germination and its hormonal regulation, dormancy release, and seed longevity. These techniques can be applied to the study of both model plants (such as Arabidopsis) and crops

Production and characterization of natural rubber-Ca/P blends for biomedical purposes

This study presents the development of natural rubber-Ca/P blends, as promising candidates for biomedical purposes. The specific objectivewas the incorporation of Ca/P into a natural rubber polymericmatrix. Ca/P crystalline phaseswere synthesized by the sol-gel method and the polymeric matrices were produced using natural rubber extracted from latex of the Hevea brasiliensis. The shape and size of natural rubber particles present in the NR membrane, as well as, the way the Ca/P powder grains aggregate in the polymeric matrix were investigated, giving information about the interactions between the Ca/P and the natural rubber particles. Confocal fluorescence scanning microscopy measurements allowed us to propose a structure where the Ca/P grains are surrounded by natural rubber particles. This structure may mediate Ca2+ release for tissue regeneration. The systeminvestigated may open new horizons for development of a bandage which provides the controlled-release of biomaterials.CNPq (555100/2010-3)CAPES (PNPD/2583/2011)INCT/INEONanoBiome

fMRI changes over time and reproducibility in unmedicated subjects at high genetic risk of schizophrenia

Background. Functional brain abnormalities have been repeatedly demonstrated in schizophrenia but there is little data concerning their progression. For such studies to have credibility it is first important to establish the reproducibility of functional imaging techniques. The current study aimed to examine these factors in healthy controls and in unmedicated subjects at high genetic risk of the disorder: (i) to examine the reproducibility of task-related activation patterns, (ii) to determine if there were any progressive functional changes in high-risk subjects versus controls reflecting inheritance of the schizophrenic trait, and (iii) to examine changes over time in relation to fluctuating positive psychotic symptoms (i.e. state effects). Method. Subjects were scanned performing the Hayling sentence completion test on two occasions 18 months apart. Changes in activation were examined in controls and high-risk subjects (n=16, n=63). Reproducibility was assessed for controls and high-risk subjects who remained asymptomatic at both time points (n=16, n=32). Results. Intra-class correlation values indicated good agreement between scanning sessions. No significant differences over time were seen between the high-risk and control group; however, comparison of high-risk subjects who developed symptoms versus those who remained asymptomatic revealed activation increases in the left middle temporal gyrus (p = 0.026). Conclusions. The current results suggest that functional changes over time occur in the lateral temporal cortex as high genetic risk subjects become symptomatic, further, they indicate the usefulness of functional imaging tools for investigating progressive changes associated with state and trait effects in schizophrenia

Analyse des remaniements du protéome associés à la levée de dormance d’une graine imbibée

National audienc

Time interval between self-expandable metal stent placement or creation of a decompressing stoma and elective resection of left-sided obstructive colon cancer

Background The optimal timing of resection after decompression of left-sided obstructive colon cancer is unknown. Revised expert-based guideline recommendations have shifted from an interval of 5-10 days to approximately 2 weeks following self-expandable metal stent (SEMS) placement, and recommendations after decompressing stoma are lacking. We aimed to evaluate the recommended bridging intervals after SEMS and explore the timing of resection after decompressing stoma. Methods This nationwide study included patients registered between 2009 and 2016 in the prospective, mandatory Dutch ColoRectal Audit. Additional data were collected through patient records in 75 hospitals. Only patients who underwent either SEMS placement or decompressing stoma as a bridge to surgery were selected. Technical SEMS failure and unsuccessful decompression within 48 hours were exclusion criteria. Results 510 patients were included (182 SEMS, 328 decompressing stoma). Median bridging interval was 23 days (interquartile range [IQR] 13-31) for SEMS and 36 days (IQR 22-65) for decompressing stoma. Following SEMS placement, no significant differences in post-resection complications, hospital stay, or laparoscopic resections were observed with resection after 11-17 days compared with 5-10 days. Of SEMS-related complications, 48% occurred in patients operated on beyond 17 days. Compared with resection within 14 days, an interval of 14-28 days following decompressing stoma resulted in significantly more laparoscopic resections, more primary anastomoses, and shorter hospital stays. No impact of bridging interval on mortality, disease-free survival, or overall survival was demonstrated. Conclusions Based on an overview of the data with balancing of surgical outcomes and timing of adverse events, a bridging interval of approximately 2 weeks seems appropriate after SEMS placement, while waiting 2-4 weeks after decompressing stoma further optimizes surgical conditions for laparoscopic resection with restoration of bowel continuity