A non-polynomial gravity formulation for Loop Quantum Cosmology bounce

Recently the so-called mimetic gravity approach has been used to obtain corrections to Friedmann equation of General Relativity similar to the ones present in loop quantum cosmology. In this paper, we propose an alternative way to derive this modified Friedmann equation via the so-called non-polynomial gravity approach, which consists in adding geometric non-polynomial higher derivative terms to Hilbert-Einstein action, which are nonetheless polynomials and lead to second order differential equation in Friedmann-Lema\^itre-Robertson-Walker spacetimes. Our explicit action turns out to be a realization of the Helling proposal of effective action with infinite number of terms. The model is investigated also in presence of non vanishing cosmological constant and a new exact bounce solution is found and studied.Comment: 7 pages, minor modifications, references added, accepted versio

Novel solution processable dielectrics for organic and graphene transistors

In this thesis we report the development of a range of high-performance thin-film transistors utilising different solution processable organic dielectrics grown at temperatures compatible with inexpensive substrate materials such as plastic. Firstly, we study the dielectric properties and application of a novel low-k fluoropolymer dielectric, named Hyflon AD (Solvay). The orthogonal nature of the Hyflon formulation, to most conventional organic semiconductors, allows fabrication of top-gate transistors with optimised semiconductor/dielectric interface. When used as the gate dielectric in organic transistors, this transparent and highly water-repellent polymer yields high-performance devices with excellent operating stability. In the case of top-gate organic transistors, hole and electron mobility values close to or higher than 1 cm2/Vs, are obtained. These results suggest that Hyflon AD is a promising candidate for use as dielectric in organic and potentially hybrid electronics. By taking advantage of the non-reactive nature of the Hyflon AD dielectric, the p-doping process of an organic blend semiconductor using a molybdenum based organometallic complex as the molecular dopant, has also been investigated for the first time. Although the much promising properties of Hyflon AD were demonstrated, the resulting transistors need, however, to be operated at high voltages typically in the range of 50-100 V. The latter results to a high power consumption by the discrete transistors as well as the resulting integrated circuits. Therefore, reduction in the operating voltage of these devices is crucial for the implementation of the technology in portable battery-operated devices. Our approach towards the development of low-voltage organic transistors and circuits explored in this work focused on the use of self-assembled monolayer (SAM) organics as ultra-thin gate dielectrics. Only few nanometres thick (2-5 nm), these SAM dielectrics are highly insulating and yield high geometrical capacitances in the range 0.5 - 1 μF/cm2. The latter has enabled the design and development of organic transistors with operating voltages down to a few volts. Using these SAM nanodielectrics high performance transistors with ambipolar transport characteristics have also been realised and combined to form low-voltage integrated circuits for the first time. In the final part of this thesis the potential of Hyflon AD and SAM dielectrics for application in the emerging area of graphene electronics, has been explored. To this end we have employed chemical vapour deposited (CVD) graphene layers that can be processed from solution onto the surface of the organic dielectric (Hyflon AD, SAM). By careful engineering of the graphene/dielectric interface we were able to demonstrate transistors with improved operating characteristics that include; high charge carrier mobility (~1400 cm2/Vs), hysteresis free operation, negligible unintentional doping and improved reliability as compared to bare SiO2 based devices. Importantly, the use of SAM nanodielectrics has enabled the demonstration of low voltage (<|1.5| V) graphene transistors that have been processed from solution at low temperature onto flexible plastic substrates. Graphene transistors with tuneable doping characteristics were also demonstrated by taking advantage of the SAM’s flexible chemistry and more specifically the type of the chemical SAM end-group employed. Overall, the work described in this thesis represents a significant step towards flexible carbon-based electronics where large-volume and low-temperature processing are required

Extracellular proteases and their inhibitors ingenetic diseases of the central nervous system

Cumulative evidence has shown that a delicate balance between serine proteases and their inhibitors is crucial for normal functioning of several biological pathways. The importance of proteases and their inhibitors is well documented in several human diseases. Among them, the best documented are hemophilia B, a genetic deficiency of the serine protease coagulation factor IX and serpinophathies. Alpha-1-antitrypsin deficiency (MIM 107400), is associated with early-onset emphysema and liver disease, while hereditary angioedema (HANE; MIM 106100) is caused by mutations in the C1 inhibitor, a serpin involved in the regulation of the complement cascade. Recently, two human genetic diseases of the central nervous system have been related to mutations in components of extracellular proteolytic systems. Here, we review the recent advances in this fiel

Universal Code Equivalent of a Yeast Mitochondrial lntron Reading Frame Is Expressed into E. coli as a Specific Double Strand Endonuclease

International audienceThe intron of the mitochondrial21S rRNA gene of Sac-charomyces cerevisiae (rl intron) possesses a 235 codon long internal open reading frame (rl ORF) whose translation product determines the duplicative transposition of that intron during crosses between intron-plus strains (omega+) and intron-minus ones (omega-). Using site-directed mutagenesis, we have constructed a universal code equivalent of the rl ORF that, under appropriate promoter control, allows the overexpression in E. coli of a protein identical to the mitochondrial intron encoded "transposase". This protein exhibits a double strand endonuclease activity specific for the omega-site. This finding demonstrates , for the first time, the enzymatic activity of an intron encoded protein whose function is to promote the spreading of that intron by generating double strand breaks at a specific sequence within a gene

Ультрадисперсные порошки на основе железа как катализаторы синтеза жидких углеводородов из СО и Н[2]

International audienceTo date, uniparental disomy (UPD) with phenotypic relevance is described for different chromosomes and it is likely that additional as yet unidentified UPD phenotypes exist. Due to technical difficulties and limitations of time and resources, molecular analyses for UPD using microsatellite markers are only performed in cases with specific phenotypic features. In this study, we carried out a whole genome UPD screening based on a microarray genotyping technique. Six patients with the diagnosis of both complete or segmental UPD including Prader-Willi syndrome (PWS; matUPD15), Angelman syndrome (AS; patUPD15), Silver-Russell syndrome (SRS; matUPD7), Beckwith-Wiedemann syndrome (BWS; patUPD11p), pseudohypoparathyroidism (PHP; patUPD20q) and a rare chromosomal rearrangement (patUPD2p, matUPD2q), were genotyped using the GeneChip Human Mapping 10K Array. Our results demonstrate the presence of UPD in the patients with high efficiency and reveal clues about the mechanisms of UPD formation. We thus conclude that array based SNP genotyping is a fast, cost-effective, and reliable approach for whole genome UPD screening

Utility of whole exome sequencing for the early diagnosis of pediatric-onset cerebellar atrophy associated with developmental delay in an inbred population

International audienceAbstractBackgroundCerebellar atrophy and developmental delay are commonly associated features in large numbers of genetic diseases that frequently also include epilepsy. These defects are highly heterogeneous on both the genetic and clinical levels. Patients with these signs also typically present with non-specific neuroimaging results that can help prioritize further investigation but don’t suggest a specific molecular diagnosis.MethodsTo genetically explore a cohort of 18 Egyptian families with undiagnosed cerebellar atrophy identified on MRI, we sequenced probands and some non-affected family members via high-coverage whole exome sequencing (WES; >97 % of the exome covered at least by 30x). Patients were mostly from consanguineous families, either sporadic or multiplex. We analyzed WES data and filtered variants according to dominant and recessive inheritance models.ResultsWe successfully identified disease-causing mutations in half of the families screened (9/18). These mutations are located in seven different genes, PLA2G6 being the gene most frequently mutated (n = 3). We also identified a recurrent de novo mutation in the KIF1A gene and a molybdenum cofactor deficiency caused by the loss of the start codon in the MOCS2A open-reading frame in a mildly affected subject.ConclusionsThis study illustrates the necessity of screening for dominant mutations in WES data from consanguineous families. Our identification of a patient with a mild and improving phenotype carrying a previously characterized severe loss of function mutation also broadens the clinical spectrum associated with molybdenum cofactor deficiency