Search results for " Lower"
showing 10 items of 378 documents
A Motzkin filter in the Tamari lattice
2015
The Tamari lattice of order n can be defined on the set T n of binary trees endowed with the partial order relation induced by the well-known rotation transformation. In this paper, we restrict our attention to the subset M n of Motzkin trees. This set appears as a filter of the Tamari lattice. We prove that its diameter is 2 n - 5 and that its radius is n - 2 . Enumeration results are given for join and meet irreducible elements, minimal elements and coverings. The set M n endowed with an order relation based on a restricted rotation is then isomorphic to a ranked join-semilattice recently defined in Baril and Pallo (2014). As a consequence, we deduce an upper bound for the rotation distan…
On Ekeland's variational principle in partial metric spaces
2015
In this paper, lower semi-continuous functions are used to extend Ekeland's variational principle to the class of parti al metric spaces. As consequences of our results, we obtain some fixed p oint theorems of Caristi and Clarke types.
Structure formation during an early period of matter domination
2014
In this work we show that modifying the thermal history of the Universe by including an early period of matter domination can lead to the formation of astronomical objects. However, the survival of these objects can only be possible if the dominating matter decays to a daughter particle which is not only almost degenerate with the parent particle but also has an open annihilation channel. This requirement translates in an upper bound for the coupling of such a channel and makes the early structure formation viable.
Tectono-stratigraphic evolution of a basin generated by transpression: the case of the Early Pliocene Lascari Basin (northern Sicily)
2011
Integrated stratigraphy and structural analysis carried out in the Madonie Mts. (Northern Sicily) is aimed to the description of a syn-sedimentary tectonic event, recorded in a small infra-pliocene basin restricted to the Lascari Syncline core. The onset and evolution of the basin was driven by transpressive tectonics, generating a lens-shaped, deep and narrow tectonic depression, bounded by steep and high, tectonically controlled slopes, also reflected in the present-day topography of the area. During the genesis of the basin, the tectonic control interferes with a dramatic sea level oscillation during the Messinian-Early Pliocene time interval. In this paper, the syn-tectonic deposits of …
Alignment-free sequence comparison using absent words
2018
Sequence comparison is a prerequisite to virtually all comparative genomic analyses. It is often realised by sequence alignment techniques, which are computationally expensive. This has led to increased research into alignment-free techniques, which are based on measures referring to the composition of sequences in terms of their constituent patterns. These measures, such as $q$-gram distance, are usually computed in time linear with respect to the length of the sequences. In this paper, we focus on the complementary idea: how two sequences can be efficiently compared based on information that does not occur in the sequences. A word is an {\em absent word} of some sequence if it does not oc…
Failure of topological rigidity results for the measure contraction property
2014
We give two examples of metric measure spaces satisfying the measure contraction property MCP(K,N) but having different topological dimensions at different regions of the space. The first one satisfies MCP(0,3) and contains a subset isometric to $\mathbb{R}$, but does not topologically split. The second space satisfies MCP(2,3) and has diameter $\pi$, which is the maximal possible diameter for a space satisfying MCP(N-1,N), but is not a topological spherical suspension. The latter example gives an answer to a question by Ohta.
Numerical approach for signal delay in general distributed networks
2003
The authors consider a general network with telegraph equations modelling distributed elements and having, additionally, nonlinear capacitors. A global asymptotic exponential stability of the solution is given. A simple computable upper bound of the delay time is given. Numerical examples illustrate the usefulness of the results. >
Effects of pneumatic dilation and myotomy on esophageal function and morphology in patients with achalasia.
2005
Only two treatment modalities–pneumatic dilation and Heller myotomy–promise long-term relief from dysphagia and regurgitation in patients with achalasia. The objective of this study was to determine whether both options differ in their effects on esophageal function, morphology, and improvement in symptoms. Eighty-nine patients diagnosed with achalasia between January 1980 and December 2002 at a single center were enrolled in this study. Sixty-four patients underwent pneumatic dilation and 25 Heller myotomy in combination with an anterior semifundoplication (Dor procedure). Clinical evaluation (Eckardt-Score), esophageal manometry, and barium swallow were performed before and within 6 mont…
Conical upper density theorems and porosity of measures
2008
Abstract We study how measures with finite lower density are distributed around ( n − m ) -planes in small balls in R n . We also discuss relations between conical upper density theorems and porosity. Our results may be applied to a large collection of Hausdorff and packing type measures.
Nearly tight bounds on the learnability of evolution
2002
Evolution is often modeled as a stochastic process which modifies DNA. One of the most popular and successful such processes are the Cavender-Farris (CF) trees, which are represented as edge weighted trees. The Phylogeny Construction Problem is that of, given /spl kappa/ samples drawn from a CF tree, output a CF tree which is close to the original. Each CF tree naturally defines a random variable, and the gold standard for reconstructing such trees is the maximum likelihood estimator of this variable. This approach is notoriously computationally expensive. We show that a very simple algorithm, which is a variant on one of the most popular algorithms used by practitioners, converges on the t…