186 research outputs found
Free energy for parameterized Polyakov loops in SU(2) and SU(3) lattice gauge theory
We present a study of the free energy of parameterized Polyakov loops P in
SU(2) and SU(3) lattice gauge theory as a function of the parameters that
characterize P. We explore temperatures below and above the deconfinement
transition, and for our highest temperatures T > 5 T_c we compare the free
energy to perturbative results.Comment: Minor changes. Final version to appear in JHE
Compression Behavior of Single-layer Graphene
Central to most applications involving monolayer graphene is its mechanical
response under various stress states. To date most of the work reported is of
theoretical nature and refers to tension and compression loading of model
graphene. Most of the experimental work is indeed limited to bending of single
flakes in air and the stretching of flakes up to typically ~1% using plastic
substrates. Recently we have shown that by employing a cantilever beam we can
subject single graphene into various degrees of axial compression. Here we
extend this work much further by measuring in detail both stress uptake and
compression buckling strain in single flakes of different geometries. In all
cases the mechanical response is monitored by simultaneous Raman measurements
through the shift of either the G or 2D phonons of graphene. In spite of the
infinitely small thickness of the monolayers, the results show that graphene
embedded in plastic beams exhibit remarkable compression buckling strains. For
large length (l)-to-width (w) ratios (> 0.2) the buckling strain is of the
order of -0.5% to -0.6%. However, for l/w <0.2 no failure is observed for
strains even higher than -1%. Calculations based on classical Euler analysis
show that the buckling strain enhancement provided by the polymer lateral
support is more than six orders of magnitude compared to suspended graphene in
air
Posterior Association Networks and Functional Modules Inferred from Rich Phenotypes of Gene Perturbations
Combinatorial gene perturbations provide rich information for a systematic exploration of genetic interactions. Despite successful applications to bacteria and yeast, the scalability of this approach remains a major challenge for higher organisms such as humans. Here, we report a novel experimental and computational framework to efficiently address this challenge by limiting the ‘search space’ for important genetic interactions. We propose to integrate rich phenotypes of multiple single gene perturbations to robustly predict functional modules, which can subsequently be subjected to further experimental investigations such as combinatorial gene silencing. We present posterior association networks (PANs) to predict functional interactions between genes estimated using a Bayesian mixture modelling approach. The major advantage of this approach over conventional hypothesis tests is that prior knowledge can be incorporated to enhance predictive power. We demonstrate in a simulation study and on biological data, that integrating complementary information greatly improves prediction accuracy. To search for significant modules, we perform hierarchical clustering with multiscale bootstrap resampling. We demonstrate the power of the proposed methodologies in applications to Ewing's sarcoma and human adult stem cells using publicly available and custom generated data, respectively. In the former application, we identify a gene module including many confirmed and highly promising therapeutic targets. Genes in the module are also significantly overrepresented in signalling pathways that are known to be critical for proliferation of Ewing's sarcoma cells. In the latter application, we predict a functional network of chromatin factors controlling epidermal stem cell fate. Further examinations using ChIP-seq, ChIP-qPCR and RT-qPCR reveal that the basis of their genetic interactions may arise from transcriptional cross regulation. A Bioconductor package implementing PAN is freely available online at http://bioconductor.org/packages/release/bioc/html/PANR.html
Reducing the development gaps between regions in Poland with the use of European Union funds
The paper evaluates the processes of regional income convergence in Poland. This new research approach involves an attempt to assess the process of convergence from the point of view of development gaps. Six key development gaps were considered in the region of Eastern Poland, which is a singular case, significantly different from other regions. A dynamic panel data model was applied to investigate the impact of EU funds on the progress made towards closing these development gaps. Among the analysed development gaps, only the structural gap was not reduced in the period 2004–2015. Studies have also revealed the different impact of structural funds on each category of development gaps (a positive impact on reducing the regional transport accessibility gap and the investment gap, but negative – on reducing the innovation gap). Research has suggested the need for a change in the structure of using EU funds in the period 2014–2020 to favour stronger support for entrepreneurship and the creation of new jobs. Greater stimulation of the economic structure of peripheral regions has been proposed as the prerequisite for the future reduction in the discrepancies between regions and for the intensification of convergence.
First published online 2 April 201
Organic nanofibers embedding stimuli-responsive threaded molecular components
While most of the studies on molecular machines have been performed in
solution, interfacing these supramolecular systems with solid-state
nanostructures and materials is very important in view of their utilization in
sensing components working by chemical and photonic actuation. Host polymeric
materials, and particularly polymer nanofibers, enable the manipulation of the
functional molecules constituting molecular machines, and provide a way to
induce and control the supramolecular organization. Here, we present
electrospun nanocomposites embedding a self-assembling rotaxane-type system
that is responsive to both optical (UV-visible light) and chemical (acid/base)
stimuli. The system includes a molecular axle comprised of a dibenzylammonium
recognition site and two azobenzene end groups, and a dibenzo[24]crown-8
molecular ring. The dethreading and rethreading of the molecular components in
nanofibers induced by exposure to base and acid vapors, as well as the
photoisomerization of the azobenzene end groups, occur in a similar manner to
what observed in solution. Importantly, however, the nanoscale mechanical
function following external chemical stimuli induces a measurable variation of
the macroscopic mechanical properties of nanofibers aligned in arrays, whose
Young's modulus is significantly enhanced upon dethreading of the axles from
the rings. These composite nanosystems show therefore great potential for
application in chemical sensors, photonic actuators and environmentally
responsive materials.Comment: 39 pages, 16 figure
Detection and Characterization of Wolbachia Infections in Natural Populations of Aphids: Is the Hidden Diversity Fully Unraveled?
Aphids are a serious threat to agriculture, despite being a rather small group of insects. The about 4,000 species worldwide engage in highly interesting and complex relationships with their microbial fauna. One of the key symbionts in arthropods is Wolbachia, an α-Proteobacterium implicated in many important biological processes and believed to be a potential tool for biological control. Aphids were thought not to harbour Wolbachia; however, current data suggest that its presence in aphids has been missed, probably due to the low titre of the infection and/or to the high divergence of the Wolbachia strains of aphids. The goal of the present study is to map the Wolbachia infection status of natural aphids populations, along with the characterization of the detected Wolbachia strains. Out of 425 samples from Spain, Portugal, Greece, Israel and Iran, 37 were found to be infected. Our results, based mainly on 16S rRNA gene sequencing, indicate the presence of two new Wolbachia supergroups prevailing in aphids, along with some strains belonging either to supergroup B or to supergroup A
Dependence of Polymer Thin Film Adhesion Energy on Cohesive Interactions between Chains
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