21 research outputs found
Monomer-dimer tatami tilings of square regions
We prove that the number of monomer-dimer tilings of an square
grid, with monomers in which no four tiles meet at any point is
, when and have the same parity. In addition, we
present a new proof of the result that there are such tilings with
monomers, which divides the tilings into classes of size . The
sum of these tilings over all monomer counts has the closed form
and, curiously, this is equal to the sum of the squares of
all parts in all compositions of . We also describe two algorithms and a
Gray code ordering for generating the tilings with monomers,
which are both based on our new proof.Comment: Expanded conference proceedings: A. Erickson, M. Schurch, Enumerating
tatami mat arrangements of square grids, in: 22nd International Workshop on
Combinatorial Al- gorithms (IWOCA), volume 7056 of Lecture Notes in Computer
Science (LNCS), Springer Berlin / Heidelberg, 2011, p. 12 pages. More on
Tatami tilings at
http://alejandroerickson.com/joomla/tatami-blog/collected-resource
Statistical models for RNA-seq data derived from a two-condition 48-replicate experiment
High-throughput RNA sequencing (RNA-seq) is now the standard method to
determine differential gene expression. Identifying differentially expressed
genes crucially depends on estimates of read count variability. These estimates
are typically based on statistical models such as the negative binomial
distribution, which is employed by the tools edgeR, DESeq and cuffdiff. Until
now, the validity of these models has usually been tested on either
low-replicate RNA-seq data or simulations. A 48-replicate RNA-seq experiment in
yeast was performed and data tested against theoretical models. The observed
gene read counts were consistent with both log-normal and negative binomial
distributions, while the mean-variance relation followed the line of constant
dispersion parameter of ~0.01. The high-replicate data also allowed for strict
quality control and screening of bad replicates, which can drastically affect
the gene read-count distribution. RNA-seq data have been submitted to ENA
archive with project ID PRJEB5348.Comment: 15 pages 6 figure
How many biological replicates are needed in an RNA-seq experiment and which differential expression tool should you use?
An RNA-seq experiment with 48 biological replicates in each of 2 conditions
was performed to determine the number of biological replicates ()
required, and to identify the most effective statistical analysis tools for
identifying differential gene expression (DGE). When , seven of the nine
tools evaluated give true positive rates (TPR) of only 20 to 40 percent. For
high fold-change genes () the TPR is percent. Two
tools performed poorly; over- or under-predicting the number of differentially
expressed genes. Increasing replication gives a large increase in TPR when
considering all DE genes but only a small increase for high fold-change genes.
Achieving a TPR % across all fold-changes requires . For
future RNA-seq experiments these results suggest , rising to
when identifying DGE irrespective of fold-change is important. For
, superior TPR makes edgeR the leading tool tested. For , minimizing false positives is more important and DESeq outperforms the
other tools.Comment: 21 Pages and 4 Figures in main text. 9 Figures in Supplement attached
to PDF. Revision to correct a minor error in the abstrac
Paired domination in prisms of graphs
The paired domination number of a graph G is the smallest cardinality of a dominating set S of G such that âšSâ© has a perfect matching. The generalized prisms ÏG of G are the graphs obtained by joining the vertices of two disjoint copies of G by |V(G)| independent edges. We provide characterizations of the following three classes of graphs: for all ÏG; ;
The depression of a graph and k-kernels
An edge ordering of a graph G is an injection f : E(G) â R, the set of real numbers. A path in G for which the edge ordering f increases along its edge sequence is called an f-ascent ; an f-ascent is maximal if it is not contained in a longer f-ascent. The depression of G is the smallest integer k such that any edge ordering f has a maximal f-ascent of length at most k. A k-kernel of a graph G is a set of vertices U â V (G) such that for any edge ordering f of G there exists a maximal f-ascent of length at most k which neither starts nor ends in U. Identifying a k-kernel of a graph G enables one to construct an infinite family of graphs from G which have depression at most k. We discuss various results related to the concept of k-kernels, including an improved upper bound for the depression of trees
Wild-type yeast gene read counts from 48 replicate experiment
<p>These data are RNA-seq read counts for 48 biological replicates of wild-type yeast.</p>
<p>The reads were aligned to the Saccharomyces cerevisiae genome with Tophat and gene counts determined with htseq-count. Reference genome and gene annotations were taken from Ensembl.</p>
<p>See the linked papers for more details and the source for the raw data.</p