781 research outputs found
Over-Fitting in Model Selection with Gaussian Process Regression
Model selection in Gaussian Process Regression (GPR) seeks to determine the optimal values of the hyper-parameters governing the covariance function, which allows flexible customization of the GP to the problem at hand. An oft-overlooked issue that is often encountered in the model process is over-fitting the model selection criterion, typically the marginal likelihood. The over-fitting in machine learning refers to the fitting of random noise present in the model selection criterion in addition to features improving the generalisation performance of the statistical model. In this paper, we construct several Gaussian process regression models for a range of high-dimensional datasets from the UCI machine learning repository. Afterwards, we compare both MSE on the test dataset and the negative log marginal likelihood (nlZ), used as the model selection criteria, to find whether the problem of overfitting in model selection also affects GPR. We found that the squared exponential covariance function with Automatic Relevance Determination (SEard) is better than other kernels including squared exponential covariance function with isotropic distance measure (SEiso) according to the nLZ, but it is clearly not the best according to MSE on the test data, and this is an indication of over-fitting problem in model selection
NEW CONSTRAINTS on the MOLECULAR GAS in the PROTOTYPICAL HyLIRGs BRI 1202-0725 and BRI 1335-0417
We present Karl G Jansky Very Large Array (VLA) observations of CO(2-1) line
emission and rest-frame 250GHz continuum emission of the Hyper-Luminous IR
Galaxies (HyLIRGs) BRI1202-0725 (z=4.69) and BRI1335-0417 (z=4.41), with an
angular resolution as high as 0.15". Our low order CO observations delineate
the cool molecular gas, the fuel for star formation in the systems, in
unprecedented detail. For BRI1202-0725, line emission is seen from both extreme
starburst galaxies: the quasar host and the optically obscured submm galaxy
(SMG), in addition to one of the Lyman-alpha emitting galaxies in the group.
Line emission from the SMG shows an east-west extension of about 0.6". For
Lyalpha-2, the CO emission is detected at the same velocity as [CII] and [NII],
indicating a total gas mass ~4.0*10^10 solar masses. The CO emission from
BRI1335-0417 peaks at the nominal quasar position, with a prominent northern
extension (~1", a possible tidal feature). The gas depletion timescales are
~10^7 years for the three HyLIRGs, consistent with extreme starbursts, while
that of Lyalpha-2 may be consistent with main sequence galaxies. We interpret
these sources as major star formation episodes in the formation of massive
galaxies and supermassive black holes (SMBHs) via gas rich mergers in the early
Universe.G. C. J. is grateful for support from NRAO through the Grote Reber Doctoral Fellowship Program. R. G. M. acknowledges the UK Science and Technology Facilities Council (STFC). K. O. acknowledges the Kavli Institute Fellowship at the Kavli Institute for Cosmology in the University of Cambridge supported by the Kavli Foundation. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank all those involved in the VLA project for making these observations possible (project code 13A-012).This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by IOP Publishing
Effects of implantation of bone marrow cells on cytokine levels in the ischemic heart tissue. An experimental study
<p>Abstract</p> <p>Background</p> <p>In order to achieve a safe and persistent angiogenic effect, we investigated the potential of bone marrow cells implantation to enhance angiogenesis of ischemic hearts in a rat model, and also we have investigated growth factors accompanying and intermediating the angiogenesis, and the changes occurring in the levels of cytokines and their relations with angiogenesis.</p> <p>Methods</p> <p>30 adult male Wistar albino rats from the same colony were used. After anterior myocardial infarction induced by occlusion of the left anterior descending artery, they were divided into two groups (Group I and Group II). 2 × 10<sup>7 </sup>bone marrow cells suspended in 0.1 ml phosphate-buffered saline solution and 0.1 ml phosphate-buffered saline solution were injected at six points in the infarcted area in Group I and Group II respectively. Changes in the vascular density and, vascular endothelial growth factor, vascular cell adhesion molecule and cytokine levels in the infarcted myocardium after bone marrow cells implantation were examined.</p> <p>Results</p> <p>The implantation assay showed that bone marrow cells induced angiogenesis. Light microscopic analysis of the vascular density in the ischemic area showed that, angiogenesis had been induced to higher in Group I than Group II. Levels of vascular endothelial growth factor, vascular cell adhesion molecule and the inflammatory cytokines such as interleukin-1 and tumor necrosis factor-α in Group I were significantly elevated compared with those in Group II.</p> <p>Conclusion</p> <p>Bone marrow cells implantation induced angiogenesis in a rat ischemic heart model as a result of increase of the levels of vascular endothelial growth factor, vascular cell adhesion molecule, interleukin-1, and tumor necrosis factor-α.</p
Complaint management: comparison between traditional and digital banks and the benefits of using management systems for improvement
Purpose: This paper compares traditional and digital banks in nine categories of complaints and provides insights to improve complaint management performance. Design/methodology/approach: A sample of the major Brazilian banks was defined, with four traditional and four digital banks. The grey relational analysis (GRA) method was applied as an analytical tool to compare the most frequent complaints of traditional and digital banks. The most critical complaints identified were considered to discuss potential improvements in complaint management using quality and service management system concepts. Findings: The GRA method enabled the development of a ranking of nine complaint categories, considering the uncertainty involved in the data and differentiating between traditional and digital banks. The most critical complaint categories, regardless of business model, were “unauthorized charges” and “poor service,” which were ranked first and second in the frequency rankings. Traditional and digital banks differed the most in the complaint category “unfair charge,” ranking third and eighth in the rankings, respectively. Practical implications: Managers from traditional and digital banks can improve complaint management performance by applying ISO 9001 and ISO 20000 concepts such as incident, problem, change, service level, availability, capacity, information technology service continuity and financial management. Social implications: The study's findings can help bank managers improve service levels in the face of technological competition. Improving these organizations is an important factor for developing countries such as Brazil. Originality/value: This paper reveals the differences between two business models regarding complaint management. It also considers a methodological approach to include the uncertainty related to customers' perception and subjectivity inherent to complaints
SOD2 immunoexpression predicts lymph node metastasis in penile cancer
BACKGROUND:
Superoxide dismutase-2 (SOD2) is considered one of the most important antioxidant enzymes that regulate cellular redox state in normal and tumorigenic cells. Overexpression of this enzyme in lung, gastric, colorectal, breast cancer and cervical cancer malignant tumors has been observed. Its relationship with inguinal lymph node metastasis in penile cancer is unknown.
METHODS:
SOD2 protein expression levels were determined by immunohistochemistry in 125 usual type squamous cell carcinomas of the penis from a Brazilian cancer center. The casuistic has been characterized by means of descriptive statistics. An exploratory logistic regression has been proposed to evaluate the independent predictive factors of lymph node metastasis.
RESULTS:
SOD2 expression in more than 50% of cells was observed in 44.8% of primary penile carcinomas of the usual type. This expression pattern was associated with lymph node metastasis both in the uni and multivariate analysis.
CONCLUSIONS:
Our results indicate that SOD2 expression predicts regional lymph node metastasis. The potential clinical implication of this observation warrants further studies.Dr. Lara Termini (FAPESP 2005/57274-9); Dr. Luisa Lina Villa (FAPESP 2008/57889-1 and CNPq 573799/2008-3)
A combined analysis technique for the search for fast magnetic monopoles with the MACRO detector
We describe a search method for fast moving ()
magnetic monopoles using simultaneously the scintillator, streamer tube and
track-etch subdetectors of the MACRO apparatus. The first two subdetectors are
used primarily for the identification of candidates while the track-etch one is
used as the final tool for their rejection or confirmation. Using this
technique, a first sample of more than two years of data has been analyzed
without any evidence of a magnetic monopole. We set a 90% CL upper limit to the
local monopole flux of in the
velocity range and for nucleon decay
catalysis cross section smaller than .Comment: 29 pages (12 figures). Accepted by Astroparticle Physic
Final results of magnetic monopole searches with the MACRO experiment
We present the final results obtained by the MACRO experiment in the search
for GUT magnetic monopoles in the penetrating cosmic radiation, for the range
. Several searches with all the MACRO sub-detectors
(i.e. scintillation counters, limited streamer tubes and nuclear track
detectors) were performed, both in stand alone and combined ways. No candidates
were detected and a 90% Confidence Level (C.L.) upper limit to the local
magnetic monopole flux was set at the level of cm
s sr. This result is the first experimental limit obtained in
direct searches which is well below the Parker bound in the whole range
in which GUT magnetic monopoles are expected.Comment: 12 pages, Latex, 9 figures and 2 Table
Non-standard interactions versus non-unitary lepton flavor mixing at a neutrino factory
The impact of heavy mediators on neutrino oscillations is typically described
by non-standard four-fermion interactions (NSIs) or non-unitarity (NU). We
focus on leptonic dimension-six effective operators which do not produce
charged lepton flavor violation. These operators lead to particular
correlations among neutrino production, propagation, and detection non-standard
effects. We point out that these NSIs and NU phenomenologically lead, in fact,
to very similar effects for a neutrino factory, for completely different
fundamental reasons. We discuss how the parameters and probabilities are
related in this case, and compare the sensitivities. We demonstrate that the
NSIs and NU can, in principle, be distinguished for large enough effects at the
example of non-standard effects in the --sector, which basically
corresponds to differentiating between scalars and fermions as heavy mediators
as leading order effect. However, we find that a near detector at superbeams
could provide very synergistic information, since the correlation between
source and matter NSIs is broken for hadronic neutrino production, while NU is
a fundamental effect present at any experiment.Comment: 32 pages, 5 figures. Final version published in JHEP. v3: Typo in Eq.
(27) correcte
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