319 research outputs found
Surface doping in T6/ PDI-8CN2 Heterostructures investigated by transport and photoemission measurements
In this paper, we discuss the surface doping in sexithiophene (T6) organic
field-effect transistors by PDI-8CN2. We show that an accumulation
heterojunction is formed at the interface between the organic semiconductors
and that the consequent band bending in T6 caused by PDI-8CN2 deposition can be
addressed as the cause of the surface doping in T6 transistors. Several
evidences of this phenomenon have been furnished both by electrical transport
and photoemission measurements, namely the increase in the conductivity, the
shift of the threshold voltage and the shift of the T6 HOMO peak towards higher
binding energies.Comment: 5 pages, 5 figure
The binding of glucosylceramidase to glucosylceramide is promoted by its activator protein
AbstractA protein activator of glucosylceramidase (EC 3.2.1.45) has been previously identified by us in human placenta [(1985) Biochim. Biophys. Acta 836, 157–166]. In the present paper we report that its function in vitro is to stimulate the binding of the enzyme to its substrate, glucosylceramide. After the purification step which frees the enzyme of most of its activator protein (octyl-Sepharose 4B chromatography), the capacity of glucosylceramidase to bind to the glucosylceramide micelles is dramatically decreased. The addition of the activator protein to the purified enzyme restores this binding
Fast Likelihood-Based Change Point Detection
Change point detection plays a fundamental role in many real-world applications, where the goal is to analyze and monitor the behaviour of a data stream. In this paper, we study change detection in binary streams. To this end, we use a likelihood ratio between two models as a measure for indicating change. The first model is a single bernoulli variable while the second model divides the stored data in two segments, and models each segment with its own bernoulli variable. Finding the optimal split can be done in O(n) time, where n is the number of entries since the last change point. This is too expensive for large n. To combat this we propose an approximation scheme that yields (1 - epsilon) approximation in O(epsilon(-1) log(2) n) time. The speed-up consists of several steps: First we reduce the number of possible candidates by adopting a known result from segmentation problems. We then show that for fixed bernoulli parameters we can find the optimal change point in logarithmic time. Finally, we show how to construct a candidate list of size O(epsilon(-1) log n) formodel parameters. We demonstrate empirically the approximation quality and the running time of our algorithm, showing that we can gain a significant speed-up with a minimal average loss in optimality.Peer reviewe
Dynamic hierarchies in temporal directed networks
The outcome of interactions in many real-world systems can be often explained
by a hierarchy between the participants. Discovering hierarchy from a given
directed network can be formulated as follows: partition vertices into levels
such that, ideally, there are only forward edges, that is, edges from upper
levels to lower levels. In practice, the ideal case is impossible, so instead
we minimize some penalty function on the backward edges. One practical option
for such a penalty is agony, where the penalty depends on the severity of the
violation. In this paper we extend the definition of agony to temporal
networks. In this setup we are given a directed network with time stamped
edges, and we allow the rank assignment to vary over time. We propose 2
strategies for controlling the variation of individual ranks. In our first
variant, we penalize the fluctuation of the rankings over time by adding a
penalty directly to the optimization function. In our second variant we allow
the rank change at most once. We show that the first variant can be solved
exactly in polynomial time while the second variant is NP-hard, and in fact
inapproximable. However, we develop an iterative method, where we first fix the
change point and optimize the ranks, and then fix the ranks and optimize the
change points, and reiterate until convergence. We show empirically that the
algorithms are reasonably fast in practice, and that the obtained rankings are
sensible
Genome-scaled phylogeny of Saccharomyces cerevisiae from spontaneous must fermentations
Modern winemakers commonly inoculate selected S. cerevisiae strains in must to obtain controlled fermentations and reproducible products. However, wine has been produced for thousands of years using spontaneous fermentations from wild strains, a practice that is experiencing a revival among small wine producers. Despite the widespread usage of such strains in the past, there is much to know about their ecology, evolution and functional potential. For example, the reciprocal affinities of these strains within the S. cerevisiae phylogeny have yet to be discovered, as well as the degree of their biodiversity and their impact on wine terroir. To fill this knowledge gap, we aim at characterising at strain level the S. cerevisiae present in spontaneously fermented musts sampled across Italy. We set up a protocol based on polyphenols-removing prewashes, followed by whole-genome shotgun sequencing at a depth of 5Gb of DNA per sample. We performed both an assembly-free analysis to reconstruct the strain-level phylogeny of S. cerevisiae strains using the species-specific-marker based StrainPhlAn, and the reconstruction of Metagenome-Assembled Genomes of these strains for downstream functional analyses. To plan conservation acts in a scenario of continuous climate change, we aim at isolating and maintaining strains of interest. We will present preliminary results from the analysis of spontaneous musts sampled at different fermenting stages
Clinical, biochemical and molecular characterization of prosaposin deficiency
Prosaposin (PSAP) deficiency is an ultra-rare, fatal infantile lysosomal storage disorder (LSD) caused by variants in the PSAP gene, with 7 subjects reported so far. Here, we provide the clinical, biochemical and molecular characterization of two additional PSAP deficiency cases. Lysoplex, a targeted resequencing approach was utilized to identify the variant in the first patient, while quantification of plasma lysosphingolipids (lysoSLs), assessed by liquid chromatography mass spectrometry (LC-MS/MS) and brain magnetic resonance imaging (MRI), followed by Sanger sequencing allowed to attain diagnosis in the second case. Functional studies were carried out on patients' fibroblast lines to explore the functional impact of variants. The two patients were homozygous for two different truncating PSAP mutations (c.895G>T, p.Glu299*; c.834_835delGA, p.Glu278Aspfs*27). Both variants led to a complete lack of processed transcript. LC-MS/MS and brain MRI analyses consistently provided a distinctive profile in the two children. Quantification of specific plasma lysoSLs revealed elevated levels of globotriaosylsphingosine (lysoGb3) and glucosylsphingosine (GlSph), and accumulation of autophagosomes, due to a decreased autophagic flux, was observed. This report documents the successfully use of plasma lysoSLs profiling in the PSAP deficiency diagnosis, as a reliable and informative tool to obtain a preliminary information in infantile cases with complex traits displaying severe neurological signs and visceral involvement.Prosaposin (PSAP) deficiency is an ultra-rare, fatal infantile lysosomal storage disorder (LSD) caused by variants in the PSAP gene, with seven subjects reported so far. Here, we provide the clinical, biochemical and molecular characterization of two additional PSAP deficiency cases. Lysoplex, a targeted resequencing approach was utilized to identify the variant in the first patient, while quantification of plasma lysosphingolipids (lysoSLs), assessed by liquid chromatography mass spectrometry (LC-MS/MS) and brain magnetic resonance imaging (MRI), followed by Sanger sequencing allowed to attain diagnosis in the second case. Functional studies were carried out on patients' fibroblast lines to explore the functional impact of variants. The two patients were homozygous for two different truncating PSAP mutations (c.895G>T, p.Glu299*; c.834_835delGA, p.Glu278Aspfs*27). Both variants led to a complete lack of processed transcript. LC-MS/MS and brain MRI analyses consistently provided a distinctive profile in the two children. Quantification of specific plasma lysoSLs revealed elevated levels of globotriaosylsphingosine (LysoGb3) and glucosylsphingosine (GlSph), and accumulation of autophagosomes, due to a decreased autophagic flux, was observed. This report documents the successful use of plasma lysoSLs profiling in the PSAP deficiency diagnosis, as a reliable and informative tool to obtain a preliminary information in infantile cases with complex traits displaying severe neurological signs and visceral involvement
Synthesis of single layer graphene on Cu(111) by C-60 supersonic molecular beam epitaxy
We acknowledge funding from the EU under the FP7th grant agreement 604391 (Graphene Flagship), from FBK via the CMM Director grant “SuperCar”, and PRIN project DESCARTES (no. 2010BNZ3F2), MIUR, Italy. N. M. P. is supported by ERC StG Ideas 2011 BIHSNAM (no. 279985), ERC PoC 2013-1 REPLICA2 (no. 619448), and by ERC PoC 2013-2 KNOTOUGH (no. 632277). S. T., N. M. P. and G. G. are also supported by the Provincia Autonoma di Trento (“Graphene nanocomposites”, no. S116/2012-242637 and reg. delib. no. 2266). G. G. and S. T. acknowledge support by INFN through the “Supercalcolo” agreement with FBK. S. T. gratefully acknowledges the Institute for Advanced Studies in Bologna for supporting his ISA fellowship
Shallow whole-genome sequencing of Aedes japonicus and Aedes koreicus from Italy and an updated picture of their evolution based on mitogenomics and barcoding
Aedes japonicus and Aedes koreicus are two invasive mosquitoes native to East Asia that are quickly establishing in temperate regions of Europe. Both species are vectors of arboviruses, but we currently lack a clear understanding of their evolution. Here, we present new short-read, shallow genome sequencing of A. japonicus and A. koreicus individuals from northern Italy, which we used for downstream phylogenetic and barcode analyses. We explored associated microbial DNA and found high occurrences of Delftia bacteria in both samples, but neither Asaia nor Wolbachia. We then assembled complete mitogenomes and used these data to infer divergence times estimating the split of A. japonicus from A. koreicus in the Oligocene, which was more recent than that previously reported using mitochondrial markers. We recover a younger age for most other nodes within Aedini and other Culicidae. COI barcoding and phylogenetic analyses indicate that A. japonicus yaeyamensis, A. japonicus amamiensis, and the two A. koreicus sampled from Europe should be considered as separate species within a monophyletic species complex. Our studies further clarify the evolution of A. japonicus and A. koreicus, and indicate the need to obtain whole-genome data from putative species in order to disentangle their complex patterns of evolution
Choroidal vascularity map in unilateral central serous chorioretinopathy: A comparison with fellow and healthy eyes
Background: To map the choroidal vascularity index and compare two eyes in patients with unilateral central serous chorioretinopathy (CSCR). Methods: This was a retrospective, observa-tional study performed in patients with unilateral CSCR. Choroidal thickness (CT) and Choroidal vascularity index (CVI) were measured and mapped in various zones according to the early treatment diabetic retinopathy (ETDRS) grid. Results: A total of 20 CSCR patients (20 study and 20 fellow eyes) were included in the study. Outer nasal region CT was seen to be significantly lower than central CT (p = 0.042) and inner nasal CT (p = 0.007); outer ring CT was significantly less than central (p = 0.04) and inner ring (p = 0.01) CT in CSCR eyes. On potting all the CVI values against the corresponding CT values, a positive correlation was seen in CSCR eyes (r = 0.54, p < 0.01), which was slightly weaker in fellow eyes (r = 0.3, p < 0.01) and a negative correlation was seen in healthy eyes (r = −0.262, p < 0.01). Conclusions: Correlation between CVI and CT was altered in CSCR eyes as compared to fellow and normal eyes with increasing CVI towards the center of the macula and superiorly in CSCR eyes
A novel combined experimental and multiscale theoretical approach to unravel the structure of SiC/SiOx core/shell nanowires for their optimal design
In this work we propose a realistic model of nanometer-thick SiC/SiOxcore/shell nanowires (NWs) using a combined first-principles and experimental approach. SiC/SiOxcore/shell NWs were first synthesised by a low-cost carbothermal method and their chemical-physical experimental analysis was accomplished by recording X-ray absorption near-edge spectra. In particular, the K-edge absorption lineshapes of C, O, and Si are used to validate our computational model of the SiC/SiOxcore/shell NW architectures, obtained by a multiscale approach, including molecular dynamics, tight-binding and density functional simulations. Moreover, we present ab initio calculations of the electronic structure of hydrogenated SiC and SiC/SiOxcore/shell NWs, studying the modification induced by several different substitutional defects and impurities into both the surface and the interfacial region between the SiC core and the SiOxshell. We find that on the one hand the electron quantum confinement results in a broadening of the band gap, while hydroxyl surface terminations decrease it. This computational investigation shows that our model of SiC/SiOxcore/shell NWs is capable to deliver an accurate interpretation of the recorded X-ray absorption near-edge spectra and proves to be a valuable tool towards the optimal design and application of these nanosystems in actual devices
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