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Search Results: 1 - 10 of 195275 matches for " G. Selva-Vera "
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Motor speed predicts stability of cognitive deficits in both schizophrenic and bipolar I patients at one-year follow-up
J. Salazar-Fraile,V. Balanzá-Martínez,G. Selva-Vera,A. Martínez-Aran
The European Journal of Psychiatry , 2009,
Abstract: Background: We examined whether motor speed assessed by the finger tapping test predicts generalized and specific stable deficits because of a common pathogenic process in bipolar and schizophrenic patients. Methods: One hundred and two patients underwent a battery of neuropsychological tests. Patients with a score of less than one standard deviation from their siblings', sample in two assessments with an interval of one year were defined as suffering from stable deficits because of a common pathogenic process. In addition to univariate analyses, factor analyses, ordinal logistic regression, and multiple linear regressions were used. A general score was also calculated. Results: No differences were found between schizophrenic and bipolar patients in the deficits of verbal fluency, shift reasoning ability and executive attention. Schizophrenic patients had greater persistent cognitive deficit because of a common pathogenic factor in the verbal memory dimension than bipolar patients. Motor speed predicted the specific deficits of verbal fluency, shift reasoning, executive attention and the general deficit of both bipolar I and schizophrenic patients. Bipolar patients suffered a lesser specific deficit in the verbal memory dimension than schizophrenic patients did, this domain not being predicted by motor speed. Motor speed predicted the generalized deficit and the specific dimensions in which schizophrenic and bipolar patients showed no differences. Conclusions: These results suggest the presence of general and specific stable cognitive deficits because of a common pathogenic factor related to psychomotor slowness. Motor speed seems to be suitable endophenocognitype for schizophrenia and bipolar disorder.
Motor speed predicts stability of cognitive deficits in both schizophrenic and bipolar I patients at one-year follow-up
Salazar-Fraile,J.; Balanzá-Martínez,V.; Selva-Vera,G.; Martínez-Aran,A.; Sánchez-Moreno,J.; Rubio,C.; Vieta,E.; Gómez-Beneyto,M.; Tabarés-Seisdedos,R.;
The European Journal of Psychiatry , 2009, DOI: 10.4321/S0213-61632009000300007
Abstract: background: we examined whether motor speed assessed by the finger tapping test predicts generalized and specific stable deficits because of a common pathogenic process in bipolar and schizophrenic patients. methods: one hundred and two patients underwent a battery of neuropsychological tests. patients with a score of less than one standard deviation from their siblings', sample in two assessments with an interval of one year were defined as suffering from stable deficits because of a common pathogenic process. in addition to univariate analyses, factor analyses, ordinal logistic regression, and multiple linear regressions were used. a general score was also calculated. results: no differences were found between schizophrenic and bipolar patients in the deficits of verbal fluency, shift reasoning ability and executive attention. schizophrenic patients had greater persistent cognitive deficit because of a common pathogenic factor in the verbal memory dimension than bipolar patients. motor speed predicted the specific deficits of verbal fluency, shift reasoning, executive attention and the general deficit of both bipolar i and schizophrenic patients. bipolar patients suffered a lesser specific deficit in the verbal memory dimension than schizophrenic patients did, this domain not being predicted by motor speed. motor speed predicted the generalized deficit and the specific dimensions in which schizophrenic and bipolar patients showed no differences. conclusions: these results suggest the presence of general and specific stable cognitive deficits because of a common pathogenic factor related to psychomotor slowness. motor speed seems to be suitable endophenocognitype for schizophrenia and bipolar disorder.
The switch from conventional to atypical antipsychotic treatment should not be based exclusively on the presence of cognitive deficits. A pilot study in individuals with schizophrenia
Gabriel Selva-Vera, Vicent Balanzá-Martínez, José Salazar-Fraile, José Sánchez-Moreno, Anabel Martinez-Aran, Patricia Correa, Eduard Vieta, Rafael Tabarés-Seisdedos
BMC Psychiatry , 2010, DOI: 10.1186/1471-244x-10-47
Abstract: In this naturalistic study, we used a comprehensive neuropsychological battery of tests to assess a sample of schizophrenia patients taking either conventional (n = 13) or novel antipsychotics (n = 26) at baseline and at two years after.Continuous antipsychotic treatment regardless of class was associated with improvement on verbal fluency, executive functions, and visual and verbal memory. Patients taking atypical antipsychotics did not show greater cognitive enhancement over two years than patients taking conventional antipsychotics.Although long-term antipsychotic treatment slightly improved cognitive function, the switch from conventional to atypical antipsychotic treatment should not be based exclusively on the presence of these cognitive deficits.Cognitive disturbances are a core feature of schizophrenia and have been extensively studied in recent years [1]. Cognitive impairment is present before the onset of the illness [2] and is also found in healthy relatives of patients, although to a lesser degree [3]. In addition, this feature is not exclusively secondary to psychiatric symptoms or medication [4]. Cognitive impairment is a better predictor of future functional outcomes compared with positive symptoms [5-7].The positive action of conventional antipsychotics drugs (APDs) on cognition is considered mild or moderate [8] and is limited to certain cognitive domains such as sustained attention [9,10].Regarding novel antipsychotics, this supposed cognitive enhancement would be mediated by their capability to raise the level of dopamine and acetylcholine in prefrontal regions [11]. However, their different affinity for brain receptors may result in different procognitive profiles of each class of antipsychotics. Many studies support a cognitive enhancement of the different atypical antipsychotics: quetiapine and olanzapine [12], quetiapine and risperidone [13], ziprasidone and olanzapine [14]; olanzapine, quetiapine, and risperidone [15], risperidone and quetiap
QUESTIONING AN “ICON OF CHANGE”: THE NURUOSMANIYE COMPLEX AND THE WRITING OF OTTOMAN ARCHITECTURAL HISTORY
Selva SUMAN
Middle East Technical University Journal of the Faculty of Architecture , 2011,
Abstract:
Efficient Sampling of Band-limited Signals from Sine Wave Crossings
J. Selva
Mathematics , 2010,
Abstract: This correspondence presents an efficient method for reconstructing a band-limited signal in the discrete domain from its crossings with a sine wave. The method makes it possible to design A/D converters that only deliver the crossing timings, which are then used to interpolate the input signal at arbitrary instants. Potentially, it may allow for reductions in power consumption and complexity in these converters. The reconstruction in the discrete domain is based on a recently-proposed modification of the Lagrange interpolator, which is readily implementable with linear complexity and efficiently, given that it re-uses known schemes for variable fractional-delay (VFD) filters. As a spin-off, the method allows one to perform spectral analysis from sine wave crossings with the complexity of the FFT. Finally, the results in the correspondence are validated in several numerical examples.
FFT Interpolation from Nonuniform Samples Lying in a Regular Grid
J. Selva
Mathematics , 2014,
Abstract: This paper presents a method to interpolate a periodic band-limited signal from its samples lying at nonuniform positions in a regular grid, which is based on the FFT and has the same complexity order as this last algorithm. This kind of interpolation is usually termed "the missing samples problem" in the literature, and there exists a wide variety of iterative and direct methods for its solution. The one presented in this paper is a direct method that exploits the properties of the so-called erasure polynomial, and it provides a significant improvement on the most efficient method in the literature, which seems to be the burst error recovery (BER) technique of Marvasti's et al. The numerical stability and complexity of the method are evaluated numerically and compared with the pseudo-inverse and BER solutions.
Signal Estimation from Nonuniform Samples with RMS Error Bound -- Application to OFDM Channel Estimation
J. Selva
Mathematics , 2014,
Abstract: We present a channel spectral estimator for OFDM signals containing pilot carriers, assuming a known delay spread or a bound on this parameter. The estimator is based on modeling the channel's spectrum as a band-limited function, instead of as the discrete Fourier transform of a tapped delay line (TDL). Its main advantage is its immunity to the truncation mismatch in usual TDL models (Gibbs phenomenon). In order to assess the estimator, we compare it with the well-known TDL maximum likelihood (ML) estimator in terms of root-mean-square (RMS) error. The main result is that the proposed estimator improves on the ML estimator significantly, whenever the average spectral sampling rate is above the channel's delay spread. The improvement increases with the spectral oversampling ratio.
Regularized sampling of multiband signals
J. Selva
Mathematics , 2010, DOI: 10.1109/TSP.2010.2057248
Abstract: This paper presents a regularized sampling method for multiband signals, that makes it possible to approach the Landau limit, while keeping the sensitivity to noise at a low level. The method is based on band-limited windowing, followed by trigonometric approximation in consecutive time intervals. The key point is that the trigonometric approximation "inherits" the multiband property, that is, its coefficients are formed by bursts of non-zero elements corresponding to the multiband components. It is shown that this method can be well combined with the recently proposed synchronous multi-rate sampling (SMRS) scheme, given that the resulting linear system is sparse and formed by ones and zeroes. The proposed method allows one to trade sampling efficiency for noise sensitivity, and is specially well suited for bounded signals with unbounded energy like those in communications, navigation, audio systems, etc. Besides, it is also applicable to finite energy signals and periodic band-limited signals (trigonometric polynomials). The paper includes a subspace method for blindly estimating the support of the multiband signal as well as its components, and the results are validated through several numerical examples.
Efficient Maximum Likelihood Estimation of a 2-D Complex Sinusoidal Based on Barycentric Interpolation
J. Selva
Mathematics , 2011,
Abstract: This paper presents an efficient method to compute the maximum likelihood (ML) estimation of the parameters of a complex 2-D sinusoidal, with the complexity order of the FFT. The method is based on an accurate barycentric formula for interpolating band-limited signals, and on the fact that the ML cost function can be viewed as a signal of this type, if the time and frequency variables are switched. The method consists in first computing the DFT of the data samples, and then locating the maximum of the cost function by means of Newton's algorithm. The fact is that the complexity of the latter step is small and independent of the data size, since it makes use of the barycentric formula for obtaining the values of the cost function and its derivatives. Thus, the total complexity order is that of the FFT. The method is validated in a numerical example.
Evaluation of hexahydrated magnesium chloride (Bischofite) performance as a chemical stabilizer of granular road surfaces
Thenoux, G.,Vera, S.
Materiales de Construccion , 2002,
Abstract: Hexahydrated Magnesium Chloride or Bischofite is a salt. It has different properties that enable it to be useful as a chemical stabilizer of granular road surfaces: its capacity of absorbing and retaining humidity from its surrounding environment, increases water surface tension and decreases its vapor pressure. The objective of this research was to evaluate Bischofite performance as a chemical stabilizer of granular road surfaces. Research was based on laboratory tests and the evaluation of test road sections of granular road surfaces stabilized with Bischofite in arid and semi-arid zones of Chile. In general, the field trial results have been more conclusive than the laboratory tests. The use of Bischofite creates a stable granular road surface, reduces potholes, corrugations, erosion and dust emissions, and improves the riding quality. El Cloruro de Magnesio Hexahidratado o Bischofita es una sal. ésta posee diversas propiedades que permiten su uso potencial como estabilizador químico de capas de rodadura granulares: capacidad de absorber y retener la humedad del ambiente circundante, incrementa la tensión superficial del agua y reduce la presión de vapor del agua. La investigación tuvo el propósito de evaluar la efectividad de la Bischofita como estabilizador químico de caminos no pavimentados, y se basa en resultados de ensayos de laboratorio y la evaluación de tramos de prueba de capas de rodadura estabilizadas con Bischofita en zonas áridas y semi-áridas de Chile. En general, los resultados de terreno han sido más significativos que los de laboratorio, observándose que la adición de Bischofita permite obtener una capa de rodadura estable, reduce la formación de baches, corrugaciones, pérdida de áridos y emisiones de polvo, y mejora la calidad de rodadura.
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