On the fate of the phantom dark energy universe in semiclassical gravity II: Scalar phantom fields

Quantum corrections coming from massless fields conformally coupled with gravity are studied, in order to see if they can lead to avoidance of the annoying Big Rip singularity which shows up in a flat Friedmann-Robertson-Walker universe filled with dark energy and modeled by a scalar phantom field. The dynamics of the model are discussed for all values of the two parameters, named $\alpha>0$ and $\beta<0$, corresponding to the regularization process. The new results are compared with the ones obtained in \cite{hae11} previously, where dark energy was modeled by means of a phantom fluid with equation of state $P=\omega\rho$, with $\omega<-1$

Sudden singularities in semiclassical gravity

It has been claimed in a recent paper \cite{bbfhd12} that sudden singularities will survive in semiclassical gravity. This issue is here carefully reviewed, pointing out that such conclusion, even if valid under some specific conditions, does not stand in other cases. An explicit example is studied in detail to support our statement, stemming from these other situations, that quantum effects may in fact drastically modify the behavior of sudden singularities.Comment: Accepted for publication in PR

Development of green/red-absorbing chromophores based on a coumarin scaffold that are useful as caging groups

We report the design, synthesis and spectroscopic characterization of a series of pushpull chromophores based on a novel coumarin scaffold in which the carbonyl of the lactone function of the original coumarin dyes has been replaced by the cyano(4- nitrophenyl)methylene moiety. The skeleton of the compounds was synthesized by condensation of a thiocoumarin precursor with the corresponding arylacetonitrile derivatives, and their photophysical properties were fine-tuned through the incorporation of electron-withdrawing groups (EWG) like nitro and cyano at the phenyl ring, leading to absorption in the green to red region. Although fluorescence emission was weakened or even cancelled upon introduction of two or three strong EWGs, it is noticeable the emission of the mononitro-containing coumarin derivatives in the red region upon excitation with green light, as well as their significant large Stokes' shifts. The new coumarin derivatives can be useful as photocleavable protecting groups, as demonstrated through the synthesis and characterization of a series of coumarin-based photocages of benzoic acid. Preliminary photolysis studies with green light have demonstrated that the structure of the coumarin chromophore influences on the rate of the uncaging process, opening the way to exploiting these new coumarin scaffolds as caging groups removable with visible light

X chromosome inactivation does not necessarily determine the severity of the phenotype in Rett syndrome patients

WOS: 000481590200024PubMed ID: 31427717Rett syndrome (RTT) is a severe neurological disorder usually caused by mutations in the MECP2 gene. Since the MECP2 gene is located on the X chromosome, X chromosome inactivation (XCI) could play a role in the wide range of phenotypic variation of RTT patients; however, classical methylation-based protocols to evaluate XCI could not determine whether the preferentially inactivated X chromosome carried the mutant or the wild-type allele. Therefore, we developed an allele-specific methylation-based assay to evaluate methylation at the loci of several recurrent MECP2 mutations. We analyzed the XCI patterns in the blood of 174 RTT patients, but we did not find a clear correlation between XCI and the clinical presentation. We also compared XCI in blood and brain cortex samples of two patients and found differences between XCI patterns in these tissues. However, RTT mainly being a neurological disease complicates the establishment of a correlation between the XCI in blood and the clinical presentation of the patients. Furthermore, we analyzed MECP2 transcript levels and found differences from the expected levels according to XCI. Many factors other than XCI could affect the RTT phenotype, which in combination could influence the clinical presentation of RTT patients to a greater extent than slight variations in the XCI pattern.Spanish Ministry of Health (Instituto de Salud Carlos III/FEDER) [PI15/01159]; Crowdfunding program PRECIPITA, from the Spanish Ministry of Health (Fundacion Espanola para la Ciencia y la Tecnologia); Catalan Association for Rett Syndrome; Fondobiorett; Mi Princesa RettWe thank all patients and their families who contributed to this study. The work was supported by grants from the Spanish Ministry of Health (Instituto de Salud Carlos III/FEDER, PI15/01159); Crowdfunding program PRECIPITA, from the Spanish Ministry of Health (Fundacion Espanola para la Ciencia y la Tecnologia); the Catalan Association for Rett Syndrome; Fondobiorett and Mi Princesa Rett