5,101 research outputs found
Distributions associated with general runs and patterns in hidden Markov models
This paper gives a method for computing distributions associated with
patterns in the state sequence of a hidden Markov model, conditional on
observing all or part of the observation sequence. Probabilities are computed
for very general classes of patterns (competing patterns and generalized later
patterns), and thus, the theory includes as special cases results for a large
class of problems that have wide application. The unobserved state sequence is
assumed to be Markovian with a general order of dependence. An auxiliary Markov
chain is associated with the state sequence and is used to simplify the
computations. Two examples are given to illustrate the use of the methodology.
Whereas the first application is more to illustrate the basic steps in applying
the theory, the second is a more detailed application to DNA sequences, and
shows that the methods can be adapted to include restrictions related to
biological knowledge.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS125 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Determination of the strange-quark mass from QCD pseudoscalar sum rules
A new determination of the strange-quark mass is discussed, based on the
two-point function involving the axial-vector current divergences. This Green
function is known in perturbative QCD up to order O(alpha_s^3), and up to
dimension-six in the non-perturbative domain. The hadronic spectral function is
parametrized in terms of the kaon pole, followed by its two radial excitations,
and normalized at threshold according to conventional chiral-symmetry. The
result of a Laplace transform QCD sum rule analysis of this two-point function
is: m_s(1 GeV^2) = 155 pm 25 MeV.Comment: Invited talk given by CAD at QCD98, Montpellier, July 1998. To appear
in Nucl.Phys.B Proc.Suppl. Latex File. Four (double column) page
Recommended from our members
Quantifying Physical Activity in Young Children Using a Three-Dimensional Camera
The purpose of this study was to determine the feasibility and validity of using three-dimensional (3D) video data and computer vision to estimate physical activity intensities in young children. Families with children (2–5-years-old) were invited to participate in semi-structured 20-minute play sessions that included a range of indoor play activities. During the play session, children’s physical activity (PA) was recorded using a 3D camera. PA video data were analyzed via direct observation, and 3D PA video data were processed and converted into triaxial PA accelerations using computer vision. PA video data from children (n = 10) were analyzed using direct observation as the ground truth, and the Receiver Operating Characteristic Area Under the Curve (AUC) was calculated in order to determine the classification accuracy of a Classification and Regression Tree (CART) algorithm for estimating PA intensity from video data. A CART algorithm accurately estimated the proportion of time that children spent sedentary (AUC = 0.89) in light PA (AUC = 0.87) and moderate-vigorous PA (AUC = 0.92) during the play session, and there were no significant differences (p \u3e 0.05) between the directly observed and CART-determined proportions of time spent in each activity intensity. A computer vision algorithm and 3D camera can be used to estimate the proportion of time that children spend in all activity intensities indoors
Pulmonary capillary haemangiomatosis - An unusual cause of hypoxia.
We describe the case of a 58-year-old man who presented with progressive dyspnoea on exertion and severe exertional hypoxia. There was a paucity of radiological findings, mild pulmonary hypertension, and no demonstrable anatomical shunt. Post mortem examination of lung tissue suggested a diagnosis of pulmonary capillary haemangiomatosis. The case is unusual in displaying few radiological findings. We postulate that the severe hypoxia was due to shunting through the abnormal capillary proliferations
Assessing the performance of MODIS NDVI and EVI for seasonal crop yield forecasting at the ecodistrict scale
Crop yield forecasting plays a vital role in coping with the challenges of the impacts of climate change on agriculture. Improvements in the timeliness and accuracy
of yield forecasting by incorporating near real-time remote sensing data and the use of sophisticated statistical methods can improve our capacity to respond effectively to
these challenges. The objectives of this study were (i) to investigate the use of derived vegetation indices for the yield forecasting of spring wheat (Triticum aestivum L.) from the Moderate resolution Imaging Spectroradiometer (MODIS) at the ecodistrict scale across Western Canada with the Integrated Canadian Crop Yield Forecaster (ICCYF); and (ii) to compare the ICCYF-model based forecasts and their accuracy across two spatial scales-the ecodistrict and Census Agricultural Region (CAR), namely in CAR with previously reported ICCYF weak performance. Ecodistricts are areas with distinct climate, soil, landscape and ecological aspects, whereas CARs are census-based/statistically-delineated areas. Agroclimate variables combined respectively with MODIS-NDVI and MODIS-EVI indices
were used as inputs for the in-season yield forecasting of spring wheat during the 2000–2010 period. Regression models were built based on a procedure of a leave-one-year-out. The
results showed that both agroclimate + MODIS-NDVI and agroclimate + MODIS-EVI performed equally well predicting spring wheat yield at the ECD scale. The mean absolute
error percentages (MAPE) of the models selected from both the two data sets ranged from 2% to 33% over the study period. The model efficiency index (MEI) varied
between -1.1 and 0.99 and -1.8 and 0.99, respectively for the agroclimate + MODIS-NDVI and agroclimate + MODIS-EVI data sets. Moreover, significant improvement in forecasting
skill (with decreasing MAPE of 40% and 5 times increasing MEI, on average) was obtained at the finer, ecodistrict spatial scale, compared to the coarser CAR scale. Forecast models need to consider the distribution of extreme values of predictor variables to improve the selection of remote sensing indices. Our findings indicate that statistical-based forecasting error could be significantly reduced by making use of MODIS-EVI and NDVI indices at
different times in the crop growing season and within different sub-regions
Strong Decays of Strange Quarkonia
In this paper we evaluate strong decay amplitudes and partial widths of
strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give
numerical results for all energetically allowed open-flavor two-body decay
modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and
1F multiplets, comprising strong decays of a total of 43 resonances into 525
two-body modes, with 891 numerically evaluated amplitudes. This set of
resonances includes all strange qqbar states with allowed strong decays
expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic
quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical
results for all amplitudes present in each decay mode. We also discuss the
status of the associated experimental candidates, and note which states and
decay modes would be especially interesting for future experimental study at
hadronic, e+e- and photoproduction facilities. These results should also be
useful in distinguishing conventional quark model mesons from exotica such as
glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table
Comment on evidence for new interference phenomena in the decay D+ -> K- pi+ mu+ nu
The experimental determination of low energy pi K scattering phase shifts
would assist in determining scattering lengths as well as low energy constants
of chiral perturbation theory for which sum rules have been constructed. The
FOCUS collaboration has presented evidence for interference pheomena from their
analysis of D_l4 decays based on decay amplitudes suitable for a cascade decay
D -> K* -> K pi. We point out that if the well-known full five body kinematics
are taken into account, pi K scattering phases may be extracted. We also point
out that other distributions considered in the context of K_l4 decays can be
applied to charm meson decays to provide constraints on violation of |Delta
I|=1/2 rule and T-violation.Comment: 9 pages, plain latex; version with minor changes compared to v1 on
lepton masses effects, sign error eliminated, clarifying remarks added, one
additional ref.; version to appear in Phys. Lett.
Evaluation of 172 candidate polymorphisms for association with oligozoospermia or azoospermia in a large cohort of men of European descent
Spin-Parity Analysis of the Centrally produced KsKs system at 800 GeV
Results are presented of the spin-parity analysis on a sample of centrally
produced mesons in the reaction (p p -> p_{slow} K_s K_s p_{fast}) with 800 GeV
protons on liquid hydrogen. The spin-parity analysis in the mass region between
threshold and 1.58 GeV/c^2 shows that the (K_s K_s) system is produced mainly
in S-wave. The f_0(1500) is clearly observed in this region. Above 1.58 GeV/c^2
two solutions are possible, one with mainly S-wave and another with mainly
D-wave. This ambiguity prevents a unique determination of the spin of the
f_J(1710) meson.Comment: 6 pages, including 6 figures. LaTex, uses 'espcrc2.sty'. To appear in
LEAP'96 proceeding
Towards modelling language innovation acceptance in online social networks
Language change and innovation is constant in online and offline communication, and has led to new words entering people’s lexicon and even entering modern day dictionaries, with recent additions of ‘e-cig’ and ‘vape’. However the manual work required to identify these ‘innovations’ is both time consuming and subjective. In this work we demonstrate how such innovations in language can be identified across two different OSN’s (Online Social Networks) through the operationalisation of known language acceptance models that incorporate relatively simplistic statistical tests. From grounding our work in language theory, we identified three statistical tests that can be applied, variation in; frequency, form and meaning; each showing different success rates across the two networks (Geo-bound Twitter sample and a sample of Reddit). These tests were also applied to different community levels within the two networks allow- ing for different innovations to be identified across different community structures over the two networks, for instance: identifying regional variation across Twitter, and variation across groupings of Subreddits, where identified example in- novations included ‘casualidad’ and ‘cym’
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