1,716 research outputs found
Well-Posedness and averaging of NLS with time-periodic dispersion management
We consider the Cauchy problem for dispersion managed nonlinear Schroedinger
equations, where the dispersion map is assumed to be periodic and piecewise
constant in time. We establish local and global well-posedness results and the
possibility of finite time blow-up. In addition, we shall study the scaling
limit of fast dispersion management and establish convergence to an effective
model with averaged dispersion.Comment: 15 pages; Minor modifications, some extra references and explanations
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Readers of the m6A epitranscriptomic code
International audienceN6-methyl adenosine (m6A) is the most prevalent and evolutionarily conserved, modification of polymerase II transcribed RNAs. By post-transcriptionally controlling patterns of gene expression, m6A deposition is crucial for organism reproduction, development and likely stress responses. m6A mostly mediates its effect by recruiting reader proteins that either directly accommodate the modified residue in a hydrophobic pocket formed by their YTH domain, or otherwise have their affinity positively influenced by the presence of m6A. We firstly describe here the evolutionary history, and review known molecular and physiological roles of eukaryote YTH readers. In the second part, we present non YTH-proteins whose roles as m6A readers largely remain to be explored. The diversity and multiplicity of m6A readers together with the possibility to regulate their expression and function in response to various cues, offers a multitude of possible combinations to rapidly and finely tune gene expression patterns and hence cellular plasticity
Sodium polymer electrolytes composed of sulfonated polysulfone and macromolecular/molecular solvents for Na-batteries
Polysulfone acidic ionomers have been extensively used as Fuel Cell membranes, mainly because of their mechanical, thermal, chemical and electrochemical stability as well as their excellent film-forming capability. This contribution deals with the development of blends based on polysulfone-sodium sulfonate and macromolecular/molecular solvents, consisting of poly(oxyethylene), POE, and propylene carbonate, PC, respectively. The objectives were to take advantage of both the thermomechanical performances and the macromolecular polyanions provided by the polysulfone ionomer. Combining POE/PC solvents, didn't allow obtaining sufficient blend's conductivities. Nevertheless, the addition of very low amounts of sodium perchlorate led to appreciable conductivities.This work has been supported by Projects funded by the regional government (Comunidad de Madrid through MATERYENER3CM S2013/MIT-2753), the Spanish Government, MICINN (MAT2016-78362-C4-3-R) and FundaciĂłn Iberdrola España for the Energy and Environment Research Grants 2016. J-Y Sanchez acknowledges the CONEX Programme, funding received from Universidad Carlos III de Madrid, the European Unionâs Seventh Framework Programme for research, technological development and demonstration (Grant
agreement nÂș 600371), Spanish Ministry of Economy and Competitiveness (COFUND2013-40258) and Banco Santander
Development of sodium hybrid quasi-solid electrolytes based on porous NASICON and ionic liquids
Lithium-ion batteries are currently the alternative of choice to overcome the increasing demand of energy. However, besides the scarcity of lithium and limited geolocation, it is believed that such batteries have already reached their maximum maturity. Sodium batteries emerge as an alternative to produce the new, so called, post-lithium batteries. In this study, we explore (i) the effect of sodium content and sintering temperature in solid electrolytes based in NASICON-type compounds and (ii) the use of two methodologies to obtain porous NASICON samples: application of natural substances and organic materials as pore-formers and freeze casting. The main purpose is the attainment of hybrid quasi-solid state electrolytes, with enhanced room temperature conductivity, based on porous ceramic electrolyte layers infiltrated with ionic liquids. Using this approach, porous samples with different microstructure and porous morphology and distribution were achieved, providing an enhancement in conductivity (ranging from 0.45 to 0.96âmS cmâ1 at 30â°C) of one order of magnitude for infiltrated samples respect to pore-free samples. According to these results the porous NASICON might be considered as a functional macroporous inorganic separator that can act as a Na+ reservoir.The authors would like to thank the Agencia Española de InvestigaciĂłn /Fondo Europeo de Desarrollo Regional (FEDER/UE) for funding the projects PID2019-106662RBC43. This work has also been supported by Comunidad de Madrid (Spain) - multiannual agreement with UC3M ("Excelencia para el Profesorado Universitario" - EPUC3M04) - Fifth regional research plan 2016-2020
Nanocrystalline cellulose reinforced poly(ethylene oxide) electrolytes for lithium-metal batteries with excellent cycling stability
Polyethylene oxide (PEO) based polymer electrolytes are still the state of the art for commercial lithium-metal batteries (LMBs) despite their remaining challenges such as the limited ionic conductivity at ambient temperature. Accordingly, the realization of thin electrolyte membranes and, thus, higher conductance is even more important, but this requires a sufficiently high mechanical strength. Herein, the incorporation of nanocrystalline cellulose into PEO-based electrolyte membranes is investigated with a specific focus on the electrochemical properties and the compatibility with lithium-metal and LiFePO-based electrodes. The excellent cycling stability of symmetric Li||Li cells, including the complete stripping of lithium from one electrode to the other, and Li||LiFePO cells renders this approach very promising for eventually yielding thin high-performance electrolyte membranes for LMBs
The La-related protein 1-specific domain repurposes HEAT-like repeats to directly bind a 5âČTOP sequence
La-related protein 1 (LARP1) regulates the stability of many mRNAs. These include 5âČTOPs, mTOR-kinase responsive mRNAs with pyrimidine-rich 5âČ UTRs, which encode ribosomal proteins and translation factors. We determined that the highly conserved LARP1-specific C-terminal DM15 region of human LARP1 directly binds a 5âČTOP sequence. The crystal structure of this DM15 region refined to 1.86 Ă
resolution has three structurally related and evolutionarily conserved helix-turn-helix modules within each monomer. These motifs resemble HEAT repeats, ubiquitous helical protein-binding structures, but their sequences are inconsistent with consensus sequences of known HEAT modules, suggesting this structure has been repurposed for RNA interactions. A putative mTORC1-recognition sequence sits within a flexible loop C-terminal to these repeats. We also present modelling of pyrimidine-rich single-stranded RNA onto the highly conserved surface of the DM15 region. These studies lay the foundation necessary for proceeding toward a structural mechanism by which LARP1 links mTOR signaling to ribosome biogenesis
Challenges and barriers to optimising sedation in intensive care: a qualitative study in eight Scottish intensive care units
Objectives: Various strategies to promote light sedation are highly recommended in recent guidelines, as deep sedation is associated with suboptimum patient outcomes. Yet, the challenges met by clinicians in delivering high-quality analgosedation is rarely addressed. As part of the evaluation of a cluster-randomised quality improvement trial in eight Scottish intensive care units (ICUs), we aimed to understand the challenges to optimising sedation in the Scottish ICU settings prior to the trial. This article reports on the findings.Design: A qualitative exploratory design: We conducted focus groups (FG) with clinicians during the preintervention period.Setting and participants: Eight Scottish ICUs. Nurses, physiotherapists and doctors working in each ICU volunteered to participate. FG were recorded and verbatim transcribed and inserted in NVivo V.10 for analysis. Qualitative thematic analysis was undertaken to develop emergent themes from the patterns identified in relation to sedation practice. Ethical approval was secured by Scotland A Research ethics committee.Results: Three themes emerged from the inductive analysis: (a) a recent shift in sedation practice, (b) uncertainty in decision-making and (c) system-level factors including the ICU environment, organisational factors and educational gaps. Clinicians were challenged daily to manage agitated or difficult-to-sedate patients in the era of a progressive mantra of âjust sedate lessâ imposed by the painâagitationâdelirium guidelines.Conclusions: The current implementation of guidelines does not support behaviour change strategies to allow a patient-focused approach to sedation management, which obstructs optimum sedationâanalgesia management. Recognition of the various challenges when mandating less sedation needs to be considered and novel sedationâanalgesia strategies should allow a system-level approach to improve sedationâanalgesia quality
Electromagnetic form factors in the J/\psi mass region: The case in favor of additional resonances
Using the results of our recent analysis of e^+e^- annihilation, we plot the
curves for the diagonal and transition form factors of light hadrons in the
time-like region up to the production threshold of an open charm quantum
number. The comparison with existing data on the decays of J/\psi into such
hadrons shows that some new resonance structures may be present in the mass
range between 2 GeVand the J/\psi mass. Searching them may help in a better
understanding of the mass spectrum in both the simple and a more sophisticated
quark models, and in revealing the details of the three-gluon mechanism of the
OZI rule breaking in K\bar K channel.Comment: Formulas are added, typo is corrected, the text is rearranged.
Replaced to match the version accepted in Phys Rev
Interplay between Conductivity, Matrix Relaxations and Composition of Ca-Polyoxyethylene Polymer Electrolytes
This article also appears in: In Memoriam: Prof. Jean-Michel SavĂ©ant.In this report, the conductivity mechanism of Ca2+-ion in polyoxyethylene (POE) solid polymer electrolytes (SPEs) for calcium secondary batteries is investigated by broadband electrical spectroscopy studies. SPEs are obtained by dissolving into the POE hosting matrix three different calcium salts: CaTf2, Ca(TFSI)2 and CaI2. The investigation of the electric response of the synthetized SPEs reveals the presence in materials of two polarization phenomena and two dielectric relaxation events. It is demonstrated that the nature of the anion (i.âe., steric hindrance, charge density and ability to act as coordination ligand) and the density of âdynamic crosslinksâ of SPEs is fundamental in the establishment of ion-ion/ion-polymer interactions. The long-range charge migration processes occurring along the two revealed percolation pathways of the electrolytes are generally coupled with the polymer host dynamics and depend on the temperature and the anion nature. This study offers the needed tools for understanding Ca2+ conduction in POE-based electrolytes.This work has been supported by the European Unionâs Horizon 2020 research and innovation programme under grant agreement No 829145(FETOPEN-VIDICAT).V. Di Notothanks the University CarlosIII of Madrid for the âCatedras de Excelencia UC3M-Santanderâ (Chairof Excellence UC3M-Santander)
Advances in antibiotic therapy in the critically ill
Infections occur frequently in critically ill patients and their management can be challenging for various reasons, including delayed diagnosis, difficulties identifying causative microorganisms, and the high prevalence of antibiotic-resistant strains. In this review, we briefly discuss the importance of early infection diagnosis, before considering in more detail some of the key issues related to antibiotic management in these patients, including controversies surrounding use of combination or monotherapy, duration of therapy, and de-escalation. Antibiotic pharmacodynamics and pharmacokinetics, notably volumes of distribution and clearance, can be altered by critical illness and can influence dosing regimens. Dosing decisions in different subgroups of patients, e.g., the obese, are also covered. We also briefly consider ventilator-associated pneumonia and the role of inhaled antibiotics. Finally, we mention antibiotics that are currently being developed and show promise for the future
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