223 research outputs found
Exact ground states of a staggered supersymmetric model for lattice fermions
We study a supersymmetric model for strongly interacting lattice fermions in
the presence of a staggering parameter. The staggering is introduced as a
tunable parameter in the manifestly supersymmetric Hamiltonian. We obtain
analytic expressions for the ground states in the limit of small and large
staggering for the model on the class of doubly decorated lattices. On this
type of lattice there are two ground states, each with a different density. In
one limit we find these ground states to be a simple Wigner crystal and a
valence bond solid (VBS) state. In the other limit we find two types of quantum
liquids. As a special case, we investigate the quantum liquid state on the one
dimensional chain in detail. It is characterized by a massless kink that
separates two types of order.Comment: 21 pages, 6 figures, v2: largely rewritten version with more emphasis
on physical interpretatio
The Alcuin number of a graph and its connections to the vertex cover number
We consider a planning problem that generalizes Alcuin's river crossing problem to scenarios with arbitrary conflict graphs. This generalization leads to the so-called Alcuin number of the underlying conflict graph. We derive a variety of combinatorial, structural, algorithmical, and complexity theoretical results around the Alcuin number. Our technical main result is an NP-certificate for the Alcuin number. It turns out that the Alcuin number of a graph is closely related to the size of a minimum vertex cover in the graph, and we unravel several surprising connections between these two graph parameters. We provide hardness results and a fixed parameter tractability result for computing the Alcuin number. Furthermore we demonstrate that the Alcuin number of chordal graphs, bipartite graphs, and planar graphs is substantially easier to analyze than the Alcuin number of general graphs
Supplementary data for the article: Marković, J. M.; Trišović, N. P.; Tóth-Katona, T.; Milčić, M. K.; Marinković, A. D.; Zhang, C.; Jákli, A. J.; Fodor-Csorba, K. A Structure-Property Relationship Study of Bent-Core Mesogens with Pyridine as the Central Unit. New Journal of Chemistry 2014, 38 (4), 1751–1760. https://doi.org/10.1039/c3nj01430d
Supplementary material for: [https://doi.org/10.1039/c3nj01430d]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1518
Supersymmetric lattice fermions on the triangular lattice: superfrustration and criticality
We study a model for itinerant, strongly interacting fermions where a
judicious tuning of the interactions leads to a supersymmetric Hamiltonian. On
the triangular lattice this model is known to exhibit a property called
superfrustration, which is characterized by an extensive ground state entropy.
Using a combination of numerical and analytical methods we study various ladder
geometries obtained by imposing doubly periodic boundary conditions on the
triangular lattice. We compare our results to various bounds on the ground
state degeneracy obtained in the literature. For all systems we find that the
number of ground states grows exponentially with system size. For two of the
models that we study we obtain the exact number of ground states by solving the
cohomology problem. For one of these, we find that via a sequence of mappings
the entire spectrum can be understood. It exhibits a gapped phase at 1/4
filling and a gapless phase at 1/6 filling and phase separation at intermediate
fillings. The gapless phase separates into an exponential number of sectors,
where the continuum limit of each sector is described by a superconformal field
theory.Comment: 50 pages, 12 figures, 2 appendice
Comparative analysis of IL6 and IL6 receptor gene polymorphisms in mastocytosis
Mastocytosis is a rare disease with reported high interleukin-6 (IL6) levels influencing disease severity. The present study investigated polymorphisms within the genes that encode IL6 and its receptor (IL6R) in relation to mastocytosis development in a case-control design. Analysis of the IL6R Asp358Ala polymorphism showed that carriers of the AA genotype had a 2.5-fold lower risk for mastocytosis than those with the AC or CC genotypes. No association with mastocytosis was found for the IL6-174G/C polymorphism, however, it may influence the effect of IL6R polymorphism. To the best of our knowledge this is the first study analysing IL6/IL6R polymorphisms in mastocytosis
Asteroseismology of the Beta Cephei star 12 (DD) Lacertae: photometric observations, pulsational frequency analysis and mode identification
We report a multisite photometric campaign for the Beta Cephei star 12
Lacertae. 750 hours of high-quality differential photoelectric Stromgren,
Johnson and Geneva time-series photometry were obtained with 9 telescopes
during 190 nights. Our frequency analysis results in the detection of 23
sinusoidal signals in the light curves. Eleven of those correspond to
independent pulsation modes, and the remainder are combination frequencies. We
find some slow aperiodic variability such as that seemingly present in several
Beta Cephei stars. We perform mode identification from our colour photometry,
derive the spherical degree l for the five strongest modes unambiguously and
provide constraints on l for the weaker modes. We find a mixture of modes of 0
<= l <= 4. In particular, we prove that the previously suspected rotationally
split triplet within the modes of 12 Lac consists of modes of different l;
their equal frequency splitting must thus be accidental.
One of the periodic signals we detected in the light curves is argued to be a
linearly stable mode excited to visible amplitude by nonlinear mode coupling
via a 2:1 resonance. We also find a low-frequency signal in the light
variations whose physical nature is unclear; it could be a parent or daughter
mode resonantly coupled. The remaining combination frequencies are consistent
with simple light-curve distortions.
The range of excited pulsation frequencies of 12 Lac may be sufficiently
large that it cannot be reproduced by standard models. We suspect that the star
has a larger metal abundance in the pulsational driving zone, a hypothesis also
capable of explaining the presence of Beta Cephei stars in the LMC.Comment: 12 pages, 7 figures, MNRAS, in pres
Supplementary data for the article: Marković, J. M.; Trišović, N. P.; Tóth-Katona, T.; Milčić, M. K.; Marinković, A. D.; Zhang, C.; Jákli, A. J.; Fodor-Csorba, K. A Structure-Property Relationship Study of Bent-Core Mesogens with Pyridine as the Central Unit. New Journal of Chemistry 2014, 38 (4), 1751–1760. https://doi.org/10.1039/c3nj01430d
Supplementary material for: [https://doi.org/10.1039/c3nj01430d]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1518
Mutually exclusive sense–antisense transcription at FLC facilitates environmentally induced gene repression
Antisense transcription through genic regions is pervasive in most genomes; however, its functional significance is still unclear. We are studying the role of antisense transcripts (COOLAIR) in the cold-induced, epigenetic silencing of Arabidopsis FLOWERING LOCUS C (FLC), a regulator of the transition to reproduction. Here we use single-molecule RNA FISH to address the mechanistic relationship of FLC and COOLAIR transcription at the cellular level. We demonstrate that while sense and antisense transcripts can co-occur in the same cell they are mutually exclusive at individual loci. Cold strongly upregulates COOLAIR transcription in an increased number of cells and through the mutually exclusive relationship facilitates shutdown of sense FLC transcription in cis. COOLAIR transcripts form dense clouds at each locus, acting to influence FLC transcription through changed H3K36me3 dynamics. These results may have general implications for other loci showing both sense and antisense transcription
Distinct Effects of p19 RNA Silencing Suppressor on Small RNA Mediated Pathways in Plants
RNA silencing is one of the main defense mechanisms employed by plants to fight viruses. In change, viruses have evolved silencing suppressor proteins to neutralize antiviral silencing. Since the endogenous and antiviral functions of RNA silencing pathway rely on common components, it was suggested that viral suppressors interfere with endogenous silencing pathway contributing to viral symptom development. In this work, we aimed to understand the effects of the tombusviral p19 suppressor on endogenous and antiviral silencing during genuine virus infection. We showed that ectopically expressed p19 sequesters endogenous small RNAs (sRNAs) in the absence, but not in the presence of virus infection. Our presented data question the generalized model in which the sequestration of endogenous sRNAs by the viral suppressor contributes to the viral symptom development. We further showed that p19 preferentially binds the perfectly paired ds-viral small interfering RNAs (vsiRNAs) but does not select based on their sequence or the type of the 5’ nucleotide. Finally, co-immunoprecipitation of sRNAs with AGO1 or AGO2 from virus-infected plants revealed that p19 specifically impairs vsiRNA loading into AGO1 but not AGO2. Our findings, coupled with the fact that p19-expressing wild type Cymbidium ringspot virus (CymRSV) overcomes the Nicotiana benthamiana silencing based defense killing the host, suggest that AGO1 is the main effector of antiviral silencing in this host-virus combination
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