2,778 research outputs found

    Adaptive Kernel Methods Using the Balancing Principle

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    The regularization parameter choice is a fundamental problem in supervised learning since the performance of most algorithms crucially depends on the choice of one or more of such parameters. In particular a main theoretical issue regards the amount of prior knowledge on the problem needed to suitably choose the regularization parameter and obtain learning rates. In this paper we present a strategy, the balancing principle, to choose the regularization parameter without knowledge of the regularity of the target function. Such a choice adaptively achieves the best error rate. Our main result applies to regularization algorithms in reproducing kernel Hilbert space with the square loss, though we also study how a similar principle can be used in other situations. As a straightforward corollary we can immediately derive adaptive parameter choice for various kernel methods recently studied. Numerical experiments with the proposed parameter choice rules are also presented

    Protein induced by vitamin K absence or antagonist-II (PIVKA-II) specifically increased in Italian hepatocellular carcinoma patients

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    OBJECTIVE: As a marker for Hepatocellular Carcinoma (HCC), Protein Induced by Vitamin K Absence II (PIVKA-II) seems to be superior to alpha fetoprotein (AFP). To better characterize the role of PIVKA-II, both AFP and PIVKA-II have been measured in Italian patients with diagnosis of HCC compared with patients affected by non-oncological liver pathologies. MATERIALS AND METHODS: Sixty serum samples from patients with HCC, 60 samples from patients with benign liver disease and 60 samples obtained from healthy blood donors were included in the study. PIVKA-II and AFP were measured by LUMIPULSE(®) G1200 (Fujirebio-Europe, Belgium). We considered as PIVKA-II cutoff 70 mAU/ml (mean +3SD) of the values observed in healthy subjects. RESULTS: The evaluation of PIVKA-II showed a positivity of 70% in patients with HCC and 5% in patients with benign diseases (p < 0.0001) whereas high levels of AFP were observed in 55% of HCC patients and in 47% of patients with benign diseases. The combined Receiver Operating Characteristic (ROC) analysis of the two analytes revealed a higher sensitivity (75%) compared to those observed for the individual biomarkers. In conclusion, we demonstrate that as a marker for HCC, PIVKA-II is more specific for HCC and less prone to elevation during chronic liver diseases. CONCLUSIONS: The combination of the two biomarkers, evaluated by the ROC analysis, improved the specificity compared to a single marker. These data suggest that the combined analysis of the two markers could be a useful tool in clinical practice

    Impairment of the autophagic flux in astrocytes intoxicated by trimethyltin

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    Autophagy is a lysosomal catabolic route for protein aggregates and damaged organelles which in different stress conditions, such as starvation, generally improves cell survival. An impairment of this degradation pathway has been reported to occur in many neurodegenerative processes. Trimethyltin (TMT) is a potent neurotoxin present as an environmental contaminant causing tremors, seizures and learning impairment in intoxicated subjects. The present data show that in rat primary astrocytes autophagic vesicles (AVs) appeared after few hours of TMT treatment. The analysis of the autophagic flux in TMT-treated astrocytes was consistent with a block of the late stages of autophagy and was accompanied by a progressive accumulation of the microtubule associated protein light chain 3 (LC3) and of p62/SQSTM1. Interestingly, an increased immunoreactivity for p62/SQSTM1 was also observed in hippocampal astrocytes detected in brain slices of TMT-intoxicated rats. The time-lapse recordings of AVs in EGFP-mCherry-LC3B transfected astrocytes demonstrated a reduced mobility of autophagosomes after TMT exposure respect to control cells. The observed block of the autophagic flux cannot be overcome by known autophagy inducers such as rapamycin or 0.5mM lithium. Although ineffective when used at 0.5mM, lithium at higher concentrations (2mM) was able to protect astrocyte cultures from TMT toxicity. This effect correlated well with its ability to determine the phosphorylation/inactivation of glycogen kinase synthase-3β (GSK-3β)

    Covariant localizations in the torus and the phase observables

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    We describe all the localization observables of a quantum particle in a one-dimensional box in terms of sequences of unit vectors in a Hilbert space. An alternative representation in terms of positive semidefinite complex matrices is furnished and the commutative localizations are singled out. As a consequence, we also get a vector sequence characterization of the covariant phase observables.Comment: 16 pages, no figure, Latex2

    Understanding neural networks with reproducing kernel Banach spaces

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    Characterizing the function spaces corresponding to neural networks can provide a way to understand their properties. In this paper we discuss how the theory of reproducing kernel Banach spaces can be used to tackle this challenge. In particular, we prove a representer theorem for a wide class of reproducing kernel Banach spaces that admit a suitable integral representation and include one hidden layer neural networks of possibly infinite width. Further, we show that, for a suitable class of ReLU activation functions, the norm in the corresponding reproducing kernel Banach space can be characterized in terms of the inverse Radon transform of a bounded real measure, with norm given by the total variation norm of the measure. Our analysis simplifies and extends recent results in [43, 34, 35]

    Procedure Manual for the Pneumology Department of an Argentine university hospital

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    Introducción La redacción de un manual de procedimientos (MP) obliga a racionalizar la actividad diaria, permite hallar imperfecciones, discutir e implementar medidas preventivas y correctivas, y acorta la brecha entre teoría y práctica. Nuestro objetivo es describir las etapas que llevaron a su redacción para un Servicio de Neumonología en un hospital universitario de gestión pública, detallar su estructura y relatar dificultades y perspectivas. Material y métodos Se determinó el organigrama y se establecieron interrelaciones y competencias. Se asignó la redacción de procedimientos según competencia de cada profesional en base a bibliografía, regulaciones, normas de acreditación y experiencia institucional. Los procedimientos fueron vinculados mediante hipertexto y cargados en la red informática. Resultados Ocupa 300 páginas, en 3 secciones: Procedimientos Administrativos, Operativos y de Seguridad, y un anexo. Consta de 57 procedimientos (48 de confección propia, 9 tomados de sociedades científicas). Para estudios específicos que se realizan en el Laboratorio se redactaron procedimientos de novo. Cuando se hallaron disponibles, se utilizaron procedimientos previos, especialmente aquellos referidos a bioseguridad y seguridad ambiental. Discusión: Se dedicó toda una sección a detallar diversas acciones administrativas de uso habitual, detectadas como fuente de conflicto. Dado que cada institución tiene su idiosincrasia administrativa y operativa, creemos que los textos y recomendaciones de sociedades científicas deben ser adaptados y/o modificados para expresar la práctica habitual en cada Servicio. Conclusiones: La información recabada dará lugar a futuras actualizaciones. Esto debe culminar en una mejor atención del paciente, fin último de nuestra Institución.Introduction The writing of a procedure manual (PM) requires streamlining daily activities, allowing to find imperfections, discuss and implement preventive and corrective measures, and decreases the gap between theory and practice. We describe the stages that led to the drafting of a PM for a Pneumology Department at a public university hospital, detailing its structure and reporting problems and prospects. Methods We determined an organization flow chart and established interrelations and personnel skills. The drafting of procedures was assigned according to competence of each staff member, based on literature, regulations, accreditation standards and institutional experience. The procedures were linked by hypertext and loaded into our computer network. Results: It extend over 300 pages in 3 sections: Administrative, Operational and Safety Procedures, and an appendix . It consists of 57 procedures (48 of these are own, while 9 were drawn from scientific societies). Some procedures for specific studies that are performed in our laboratory were written de novo. When available, previous procedures were used, especially those related to biosafety and environmental safety. Discussion: An entire section is devoted to a number of commonly used administrative actions, identified as source for conflict. As each institution has its own administrative and operational idiosyncrasies, we believe that recommendations of scientific societies should not be used verbatim, but must be adapted and/or modified to the usual practice in each department. Conclusions: The gathered information will lead to future updates. All this must lead to better patient care, ultimate goal of our InstitutionFil: Arce, S. C.. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Civale, S. N.. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Rodriguez, M. N.. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: de Vito, Eduardo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin

    Quantum Homodyne Tomography as an Informationally Complete Positive Operator Valued Measure

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    We define a positive operator valued measure EE on [0,2π]×R[0,2\pi]\times R describing the measurement of randomly sampled quadratures in quantum homodyne tomography, and we study its probabilistic properties. Moreover, we give a mathematical analysis of the relation between the description of a state in terms of EE and the description provided by its Wigner transform.Comment: 9 page
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