Nonsmooth nonnegative matrix factorization (nsNMF)

We propose a novel nonnegative matrix factorization model that aims at finding localized, part-based, representations of nonnegative multivariate data items. Unlike the classical nonnegative matrix factorization (NMF) technique, this new model, denoted "nonsmooth nonnegative matrix factorization" (nsNMF), corresponds to the optimization of an unambiguous cost function designed to explicitly represent sparseness, in the form of nonsmoothness, which is controlled by a single parameter. In general, this method produces a set of basis and encoding vectors that are not only capable of representing the original data, but they also extract highly focalized patterns, which generally lend themselves to improved interpretability. The properties of this new method are illustrated with several data sets. Comparisons to previously published methods show that the new nsNMF method has some advantages in keeping faithfulness to the data in the achieving a high degree of sparseness for both the estimated basis and the encoding vectors and in better interpretability of the factors.     

Thermo-Metallurgical Modeling of Nodular Cast Iron Cooling Process

A new numerical model to describe the microstructural evolution of a eutectic nodular cast iron during its cooling is presented. In particular, equiaxial solidification assuming an independent nucleation of austenite and graphite nodules is considered. In this context, the austenite has dendritic growth whereas the graphite grows with a spherical shape. After solidification occurs, the model assumes that the graphite nodules present in the cast iron continue growing since the carbon content in austenite decreases. Once the stable eutectoid temperature is reached, the alloy undergoes the austenite-ferrite transformation. The nucleation of the ferrite takes place at the contour of the spherical graphite nodules where austenite has low carbon concentration. A ferrite shell surrounding the graphite nodules is formed afterward by means of a process governed by carbon diffusion. Then, a ferrite-pearlite competitive transformation occurs when the temperature is below the metastable temperature. This thermo-metallurgical model is discretized and solved by means of the finite element method. The model allows the computation of cooling curves, fraction evolution for each component, and size and distribution of graphite nodules. The present numerical results are compared with experiments using standardized Quick-cup-type cups, and satisfactory numerical predictions of the final microstructure and cooling curves are achieved.     

Linear estimation for discrete-time systems in the presence oftime-correlated disturbances and uncertain observations

This note considers optimum linear recursive estimation for linear discrete-time systems with uncertain observations in cases where state and measurement noises are correlated. The different kinds of estimation problems treated include one-stage prediction and filtering     

A new phase consistency criterion and its application in electron crystallography

In this work, we present the principles and potential advantages of a methodology to assess Fourier components in terms of phase consistency. We define a new phase consistency criterion among sets of spatially translated images based upon a novel conception of the spatial shift property of the Fourier transform. The article shows how this criterion can be used in the alignment stage of the 3D reconstruction process with a two-fold objective: Assessment of the frequency components and robustness in the alignment. In that sense, the article shows and analyzes the results obtained from the application of the new index of quality in the context of projection image alignment. We have focussed our attention on the electron crystallography field, by applying such a phase consistency definition over image reflections. The results that have been obtained show that the new phase-consistency definition may complement the traditional SNR-based index of quality (commonly known as IQ) of reflections. As a consequence, the reliability of the alignment may be improved by discarding those reflections judged as non-reliable according to the phase-consistency criterion.     

Analysis of a hydrogen station roll-out strategy to introduce hydrogen vehicles in Andalusia

The issue of the distribution of a sufficient infrastructure of hydrogen fueling stations to enable meeting of the initial demand and to satisfy the different roll-out scenarios has been addressed by different authors, in different geographies, and with different methods and approaches. In this paper, we use a spatial approach to study the prospect of a sequential roll-out strategy from the present time to 2030 for Andalusia, a region in southern Spain. In every stage, we identify main nodes and clusters by examining in which areas of this region the roll-out of fueling stations should start. Finally, we estimate the number and size of fueling stations for every stage, as well as the investment required for this infrastructure roll-out based on the estimated costs for each type of hydrogen fueling station over the aforesaid time.     

The RepA protein of plasmid RSF1010 is a replicative DNA helicase

The RepA protein of the mobilizable broad host range plasmid RSF1010 has a key function in its replication. RepA is one of the smallest known helicases. The protein forms a homohexamer of 29,896-Da subunits. A variety of methods were used to analyze the quaternary structure of RepA. Gel filtration and cross-linking experiments demonstrated the hexameric structure, which was confirmed by electron microscopy and image reconstruction. These results agree with recent data obtained from RepA crystals diffracting at 3.5-A resolution (R?leke, D., Hoier, H., Bartsch, C., Umbach, P., Scherzinger, E., Lurz, R., and Saenger, W. (1997) Acta Crystallogr. Sec. D 53, 213-216). The RepA helicase has 5' --> 3' polarity. As do most true replicative helicases, RepA prefers a tailed substrate with an unpaired 3'-tail mimicking a replication fork. Optimal unwinding activity was achieved at the remarkably low pH of 5.5. In the presence of Mg2+ (Mn2+) ions, the RepA activity is fueled by ATP, dATP, GTP, and dGTP and less efficiently by CTP and dCTP. UTP and dTTP are poor effectors. Nonhydrolyzable ATP analogues, ADP, and pyrophosphate inhibit the helicase activity, whereas inorganic phosphate does not. The presence of Escherichia coli single-stranded DNA-binding protein stimulates unwinding at physiological pH 2-3-fold, whereas the RSF1010 replicon-specific primase, RepB' protein, has no effect, either in the presence or in the absence of single-stranded DNA-binding protein.     

Oral treatment schedules for onychomycosis: a study of patient preference

BACKGROUND: An improved understanding of patients' attitudes to medication may help promote compliance with oral medications for onychomycosis. This study was performed to assess patients' preference between continuous and intermittent oral treatment schedules for onychomycosis and to determine the reasons underlying the selections made. METHODS: Patients were eligible for inclusion if they had current onychomycosis and were willing to take oral medication for this condition. In a 30-min, face-to-face interview, each patient answered questions about four possible treatment schedules for onychomycosis; regimen 1--continuous (daily regular intake) for 12 weeks; regimen 2--intermittent 1 week/month for 3 months (last week of therapy is week 9); regimen 3--intermittent once weekly for 21 weeks; regimen 4--intermittent 1 week/month for 4 months (last week of therapy is week 13). RESULTS: A total of 102 patients from Germany and Spain participated in the study. When asked to choose between regimens 1, 2, and 3, 46% of patients favored the 9-week intermittent schedule, 42% selected the 12-week continuous schedule, and 12% preferred the 21-week intermittent schedule. The preference for the 9-week intermittent schedule was more notable among younger patients (< 45 years), possibly because they are less used to taking regular medication, and among Spanish patients, an effect that could not be attributed to age because the average age of patients was similar in the participating countries (Germany 47.2 years; Spain 48.0 years). When the patients who preferred regimen 2 were asked to choose between regimens 1, 3, and 4 (both intermittent schedules longer than the continuous schedule), most (57%) favored the shortest treatment schedule (regimen 2). CONCLUSIONS: Overall, patients favored an intermittent schedule lasting 9 weeks. Treatment duration is the critical factor in determining patients' preference for treatment schedules for onychomycosis.     

Glia conditioned medium protects fetal rat midbrain neurones in culture from L-DOPA toxicity

L-DOPA kills dopamine neurones in culture but is the most effective drug for the treatment of Parkinson's disease, where it exhibits no clear toxicity. While glial cells surround and protect neurones in vivo, neurones are usually cultured in vitro in the absence of glia. We treated fetal midbrain rat neurones with L-DOPA, mesencephalic glia conditioned medium (CM) and L-DOPA + CM. L-DOPA reduced the number of tyrosine hydroxylase-positive (TH+) cells and [3H]DA uptake, and increased quinone levels. L-DOPA + CM restored [3H]DA uptake and quinone levels to normal, and increased the number of TH+ cells and terminals to 170% of control. CM greatly increased the number of TH+ cells and [3H]DA uptake. Mesencephalic glia therefore produced soluble factors which are neurotrophic for dopamine neurones, and which protect these neurones from the toxic effects of L-DOPA.     

Information recovery in missing angular data cases: an approach by the convex projections method in three dimensions

We have studied the method of projections on to convex sets (POCS) for the restoration of three-dimensional signals, especially applied for the degraded information obtained in three-dimensional (3-D) reconstructions by electron microscopy due to the limited tilting angular range of the sample that is obtainable in practice. A computer generated specimen has been used as a test object. Several noise levels were added to the specimen, obtaining signal-to-noise ratios (signal power/noise power) of between 12 and 0·5 dB. Different missing data angular regions of 30° and 10° zenithal angle have been considered. Our results illustrate the possibilities of POCS to restore incomplete 3-D data in the absence and the presence of noise, and offer ways for further applications to improve the quality of 3-D reconstructions based on real data.     

Fuzzy sets-based classification of electron microscopy images of biological macromolecules with an application to ribosomal particles

Pattern recognition methods based on the theory of fuzzy sets are tested for their ability to classify electron microscopy images of biological specimens. The concept of fuzzy sets was chosen for its ability to represent classes of objects that are vaguely described from the measured data. A number of partitional clustering algorithms and an extensive set of cluster-validity functionals (some already reported and some newly developed) have been applied to a test-data set and to two real-data sets of images. One of the real-data sets corresponded to images of the Escherichia coli 50S ribosomal subunits depleted of proteins L7/L12 and the other set to images of the E. coli 70S monosome in the range of overlap views. These two latter sets had been previously studied by another clustering methodology. The new results obtained by the application of fuzzy clustering techniques will be compared to those previously obtained and some conclusions about the consistency of these classifications will be drawn from this comparison.