4,164 research outputs found
Combinatorics of patience sorting piles
Despite having been introduced in 1962 by C.L. Mallows, the combinatorial
algorithm Patience Sorting is only now beginning to receive significant
attention due to such recent deep results as the Baik-Deift-Johansson Theorem
that connect it to fields including Probabilistic Combinatorics and Random
Matrix Theory.
The aim of this work is to develop some of the more basic combinatorics of
the Patience Sorting Algorithm. In particular, we exploit the similarities
between Patience Sorting and the Schensted Insertion Algorithm in order to do
things that include defining an analog of the Knuth relations and extending
Patience Sorting to a bijection between permutations and certain pairs of set
partitions. As an application of these constructions we characterize and
enumerate the set S_n(3-\bar{1}-42) of permutations that avoid the generalized
permutation pattern 2-31 unless it is part of the generalized pattern 3-1-42.Comment: 19 pages, LaTeX; uses pstricks; view PS, not DVI; use dvips + ps2pdf,
not dvi2pdf; part of FPSAC'05 proceedings; v3: final journal version, revised
Section 3.
A Geometric Form for the Extended Patience Sorting Algorithm
Patience Sorting is a combinatorial algorithm that can be viewed as an
iterated, non-recursive form of the Schensted Insertion Algorithm. In recent
work the authors extended Patience Sorting to a full bijection between the
symmetric group and certain pairs of combinatorial objects (called pile
configurations) that are most naturally defined in terms of generalized
permutation pattern and barred pattern avoidance. This Extended Patience
Sorting Algorithm is very similar to the Robinson-Schensted-Knuth (or RSK)
Correspondence, which is itself built from repeated application of the
Schensted Insertion Algorithm.
In this work we introduce a geometric form for the Extended Patience Sorting
Algorithm that is in some sense a natural dual algorithm to G. Viennot's
celebrated Geometric RSK Algorithm. Unlike Geometric RSK, though, the lattice
paths coming from Patience Sorting are allowed to intersect. We thus also give
a characterization for the intersections of these lattice paths in terms of the
pile configurations associated with a given permutation under the Extended
Patience Sorting Algorithm.Comment: 14 pages, LaTeX, uses pstricks; v2: major revision after section 3;
to be published in Adv. Appl. Mat
Identification of and correction for publication bias
Some empirical results are more likely to be published than others. Such
selective publication leads to biased estimates and distorted inference. This
paper proposes two approaches for identifying the conditional probability of
publication as a function of a study's results, the first based on systematic
replication studies and the second based on meta-studies. For known conditional
publication probabilities, we propose median-unbiased estimators and associated
confidence sets that correct for selective publication. We apply our methods to
recent large-scale replication studies in experimental economics and
psychology, and to meta-studies of the effects of minimum wages and de-worming
programs
A critical analysis of urban regeneration programmes in Europe
Urban regeneration is informed and driven by the causes and effects of globalization, climate change, the global economic crisis, and lifestyle changes. In Europe, there is currently a pressing demand to redevelop brownfields areas, inner-city heritage sites, post-conflict and post-disaster areas, and large-housing estates. Housing regeneration strategies range from large-scale to micro-scale interventions that lead to a complete change to the physical
features of neighbourhoods and the life of their residents.
This paper presents activities and cases studied in the OIKONET Erasmus Lifelong Learning Project, by highlighting that regeneration is an important issue driving the production of
contemporary housing in Europe. The presented review is part of wider research and pedagogical work aimed at identifying significant conceptual, contextual and policy changes
affecting housing regeneration demand. Examples of urban regeneration programmes on different urban areas in selected European countries, i.e. the UK, Hungary, Serbia, Slovakia
and Russia are examined. As a result of the comparison between the cases analysed, some conclusions can be drawn to inform future research and set up pedagogical programmes to
be carried out within the OIKONET project
Unbiased Instrumental Variables Estimation Under Known First-Stage Sign
We derive mean-unbiased estimators for the structural parameter in
instrumental variables models with a single endogenous regressor where the sign
of one or more first stage coefficients is known. In the case with a single
instrument, there is a unique non-randomized unbiased estimator based on the
reduced-form and first-stage regression estimates. For cases with multiple
instruments we propose a class of unbiased estimators and show that an
estimator within this class is efficient when the instruments are strong. We
show numerically that unbiasedness does not come at a cost of increased
dispersion in models with a single instrument: in this case the unbiased
estimator is less dispersed than the 2SLS estimator. Our finite-sample results
apply to normal models with known variance for the reduced-form errors, and
imply analogous results under weak instrument asymptotics with an unknown error
distribution
Measurement of Pressure-Expansion Behaviour Required in Infant Airway Stents Using Digital Image Correlation (DIC) in Rabbit Trachea
INTRODUCTION: Airway stents are used during treatment of tracheal deformities in infants. However, complications including post implantation stent migration occur [1], resulting from too low stent radial stiffness, which causes permanent stent collapse. This collapse is partially controlled by the mechanical properties of the trachea. However, the mechanical behaviour of the human trachea is poorly understood [2]. A clearer understanding of this relationship should improve the long term performance of infant airway stents.
Rabbit tracheas provide an appropriate model for neonates due to the similarities in size and shape [3]. Digital image correlation (DIC) compares the displacement of a random speckled pattern on the surface of a sample before and during deformation to compute mechanical strains [5]. The aim of this study was to determine the pressure-expansion characteristics of full length rabbit trachea using DIC and thereby predict the required mechanical properties for an infant airway stent.
MATERIALS AND METHODS: Specimen preparation: Tracheas from New Zealand White rabbits (lengths 42.1±5.3mm, n=20), aged 13-16 weeks were dissected within 3hrs of sacrifice and immediately immersed in phosphate buffered saline and frozen. Prior to testing, samples were thawed and a random speckled pattern was produced on the surface of the trachea (Fig1A) using black ink (Higgins Black Magic, Water Proof Ink) superimposed on a white background (SupaDec Spray Paint). A balloon dilatation catheter (Ultrathin Diamond, Boston Scientific) connected to an inflation pump (Basix COMPAK Inflation syringe) was inserted through the tracheal cavity.
DIC and loading regime: A Vic3D digital image correlation device (Rutherford Appleton Laboratory – really?? This is the supplier NOT the manufacturer) was used to record displacement vectors during tracheal expansion. Two high resolution cameras mounted onto a tripod were positioned so that the frontal surface of the trachea was visible to both cameras simultaneously, allowing 3D surface strain measurements. The balloon pressure was increased in increments of 0.2 atm (20kPa) while tracheal expansion was recorded.
RESULTS: Axial/longitudinal strain (xx) for applied pressures of 0.2-1.0 atm increased from 0.0053- 0.01115 (Fig1b). DIC showed that deformation of the trachea by balloon dilatation was characterised by uneven expansion with higher Axial/longitudinal strain (yy) occurring distal to the balloon compared with the central zone of the trachea (Fig2). The tracheal expansion modulus at low strains was calculated to be 9.08MPa.
Conclusions the DIC technique has the potential to provide accurate assessment of infant airway mechanics and prediction of pressure expansion properties required in paediatric tracheal stents
Valid Two-Step Identification-Robust Confidence Sets for GMM
In models with potentially weak identification, researchers often decide whether to report a robust confidence set based on an initial assessment of model identification. Two-step procedures of this sort can generate large coverage distortions for reported confidence sets, and existing procedures for controlling these distortions are quite limited. This paper introduces a generally applicable approach to detecting weak identification and constructing two-step confidence sets in GMM. This approach controls coverage distortions under weak identification and indicates strong identification, with probability tending to 1 when the model is well identified
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Therapy of cancer by insect cells containing recombinant baculovirus encoding genes
Provided are compositions and methods of use for insect cells comprising baculovirus encoding non-surface expressed proteins and peptides. The claimed invention particularly relates to compositions comprising insect cells containing baculovirus that express cytokines. Such compositions may be administered by, for example, direct intratumoral injection into tumors in mammals, resulting in tumor reduction or recission. Another aspect of the claimed invention concerns methods of promoting resistance to the reoccurence of tumors in mammals who have undergone such tumor recission. In a specific aspect of the claimed invention, the mammals are human subjects presenting with various forms of cancer.Board of Regents, University of Texas Syste
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