3,038 research outputs found
Building trainable taggers in a web-based, UIMA-supported NLP workbench
Argo is a web-based NLP and text mining workbench with a convenient graphical user interface for designing and executing processing workflows of various complexity. The workbench is intended for specialists and nontechnical audiences alike, and provides the ever expanding library of analytics compliant with the Unstructured Information Management Architecture, a widely adopted interoperability framework. We explore the flexibility of this framework by demonstrating workflows involving three processing components capable of performing self-contained machine learning-based tagging. The three components are responsible for the three distinct tasks of 1) generating observations or features, 2) training a statistical model based on the generated features, and 3) tagging unlabelled data with the model. The learning and tagging components are based on an implementation of conditional random fields (CRF); whereas the feature generation component is an analytic capable of extending basic token information to a comprehensive set of features. Users define the features of their choice directly from Argo’s graphical interface, without resorting to programming (a commonly used approach to feature engineering). The experimental results performed on two tagging tasks, chunking and named entity recognition, showed that a tagger with a generic set of features built in Argo is capable of competing with taskspecific solutions.
Jet Correlations of Identified Particles in PHENIX
Azimuthal two particle correlations at intermediate with one of the
particles identified have been measured at PHENIX. Trigger () baryons and mesons show little significant difference in the number of
associated particles () independent of centrality. For
inclusive hadron triggers with , associated
fragmentation particles with show a higher baryon to
meson ratio on the away side.Comment: talk given at Quark Matter 2004, 4 pages 4 figur
Dihadron Correlation in Jets Produced in Heavy-Ion Collisions
The difference between the structures of jets produced in heavy-ion and
hadronic collisions can best be exhibited in the correlations between particles
within those jets. We study the dihadron correlations in jets in the framework
of parton recombination. Two types of triggers, and proton, are
considered. It is shown that the recombination of thermal and shower partons
makes the most important contribution to the spectra of the associated
particles at intermediate . In collisions the only significant
contribution arises from shower-shower recombination, which is negligible in
heavy-ion collisions. Moments of the associated-particle distributions are
calculated to provide simple summary of the jet structures for easy comparison
with experiments.Comment: 24 pages in Latex + 5 figure
Jet quenching in relativistic heavy ion collisions
Parton propagation in dense nuclear matter results in elastic, inelastic and
coherent multiple soft scattering with the in-medium color charges. Such
scattering leads to calculable modifications of the hadron production cross
section that is evaluated in the framework of the perturbative QCD
factorization approach. Final state medium-induced gluon bremsstrahlung is
arguably the most efficient way of suppressing large transverse momentum
particle production in nucleus-nucleus collisions. The observed hadronic
attenuation, known as jet quenching, can be related to the properties of the
medium, such as density and temperature, and carries valuable information about
the early stages of heavy ion reactions. Non-Abelian energy loss in the
quark-gluon plasma can be studied in much greater detail through the
modification of the two particle back-to-back correlations. Perturbative
calculations give good description of the redistribution of the lost energy in
lower transverse momentum particles and predict significant increase of the
correlation width of away-side di-hadrons. In contrast, energy loss in cold
nuclear matter was found to be small but for large values of Feynman-x is
expected to complement the dynamical higher twist shadowing in experimentally
observable forward rapidity hadron suppression.Comment: Invited plenary talk at the V-th international conference on the
physics and astrophysics of the quark-gluon plasma. 8 pages, 4 figure
The foreign exchange market: return distributions, multifractality, anomalous multifractality and Epps effect
We present a systematic study of various statistical characteristics of
high-frequency returns from the foreign exchange market. This study is based on
six exchange rates forming two triangles: EUR-GBP-USD and GBP-CHF-JPY. It is
shown that the exchange rate return fluctuations for all the pairs considered
are well described by the nonextensive statistics in terms of q-Gaussians.
There exist some small quantitative variations in the nonextensivity
q-parameter values for different exchange rates and this can be related to the
importance of a given exchange rate in the world's currency trade. Temporal
correlations organize the series of returns such that they develop the
multifractal characteristics for all the exchange rates with a varying degree
of symmetry of the singularity spectrum f(alpha) however. The most symmetric
spectrum is identified for the GBP/USD. We also form time series of triangular
residual returns and find that the distributions of their fluctuations develop
disproportionately heavier tails as compared to small fluctuations which
excludes description in terms of q-Gaussians. The multifractal characteristics
for these residual returns reveal such anomalous properties like negative
singularity exponents and even negative singularity spectra. Such anomalous
multifractal measures have so far been considered in the literature in
connection with the diffusion limited aggregation and with turbulence. We find
that market inefficiency on short time scales leads to the occurrence of the
Epps effect on much longer time scales. Although the currency market is much
more liquid than the stock markets and it has much larger transaction
frequency, the building-up of correlations takes up to several hours - time
that does not differ much from what is observed in the stock markets. This may
suggest that non-synchronicity of transactions is not the unique source of the
observed effect
Quantitative features of multifractal subtleties in time series
Based on the Multifractal Detrended Fluctuation Analysis (MFDFA) and on the
Wavelet Transform Modulus Maxima (WTMM) methods we investigate the origin of
multifractality in the time series. Series fluctuating according to a qGaussian
distribution, both uncorrelated and correlated in time, are used. For the
uncorrelated series at the border (q=5/3) between the Gaussian and the Levy
basins of attraction asymptotically we find a phase-like transition between
monofractal and bifractal characteristics. This indicates that these may solely
be the specific nonlinear temporal correlations that organize the series into a
genuine multifractal hierarchy. For analyzing various features of
multifractality due to such correlations, we use the model series generated
from the binomial cascade as well as empirical series. Then, within the
temporal ranges of well developed power-law correlations we find a fast
convergence in all multifractal measures. Besides of its practical significance
this fact may reflect another manifestation of a conjectured q-generalized
Central Limit Theorem
Ockham’s Razor for a Retinal Lesion and Acromegaly and Breaking the Vicious Circle
Acromegaly due to ectopic secretion of growth hormone-releasing hormone (GHRH) is rare. Treatment consists of surgical removal of the primary tumor, cytostatic therapy, “cold” or radioactive somatostatin analogue treatment, and medical therapy for acromegaly, if needed. A 53 year-old female had an ocular lesion noted on a routine optician visit, originally considered to be an ocular melanoma. She had a bronchial carcinoid successfully removed 22 years previously. She had acromegalic features with an enlarged pituitary gland on magnetic resonance imaging and, additionally, metastatic lesions in her bones, liver, and thyroid gland. Elevated GHRH levels (>250× upper limit of normal) suggested a metastatic lung neuroendocrine tumor secreting GHRH. Cold and radioactive somatostatin analogue therapy reduced both GHRH and insulin-like growth factor 1 (IGF-1) levels, but normalization of the biochemical markers of acromegaly was only achieved after pegvisomant was introduced. Complete control of IGF-1 was achieved, and this may have hindered the growth of the metastatic lesions as well, as the patient remains well 13 years after the diagnosis of metastatic disease and 35 years after the original lung operation. A gradual rise in prolactin levels over last 4 years was noted, which is likely due to the prolonged effect of GHRH on prolactin-secreting cells. The diagnosis of this case applied the law of parsimony from the Ockham’s razor principle. We consider that breaking the vicious circle of IGF-1 feeding the metastatic tumor was key for the long-term outcome of this case
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