Reaction Kinetics in the Production of Pd Nanoparticles in Reverse Microemulsions. Effect on Particle Size

In the synthesis of metallic nanoparticles in microemulsions, we hypothesized that particle size is mainly controlled by the reaction rate. Thus, the changes observed on the particle sizes as reaction conditions, such as concentrations, temperature, type of surfactant used, etc., are varied should not be correlated directly to the modification of those conditions but indirectly to the changes they produce on the reaction rates. By means of time resolved UV-vis spectroscopy, we measured the reaction rates in the production of Pd nanoparticles inside microemulsions at different reactant concentrations, keeping all the other parameters constant. The measured reaction rates were then correlated with the particle sizes measured by transmission electron microscopy (TEM). We found that nanoparticle size increases linearly as the reaction rates increases, independently of the actual reactant concentrations. We proposed that the kinetics is controlled mainly by the diffusion of the reducing agent through the surfactant monolayer covering the microemulsion membrane. With this model, we predicted that particle size should depend indirectly, via the reaction kinetics, on the micelle radius (v0 ~ r^-3), the water volume (v0~vw^3) and the total microemulsion volume (v0~vT^-3), and temperature (Arrhenius). Some of these predictions were explored in this article

The catalytic mechanism of steroidogenic cytochromes P450 from all-atom simulations: Entwinement with membrane environment, redox partners, and post-transcriptional regulation

Cytochromes P450 (CYP450s) promote the biosynthesis of steroid hormones with major impact on the onset of diseases such as breast and prostate cancers. By merging distinct functions into the same catalytic scaffold, steroidogenic CYP450s enhance complex chemical transformations with extreme efficiency and selectivity. Mammalian CYP450s and their redox partners are membrane-anchored proteins, dynamically associating to form functional machineries. Mounting evidence signifies that environmental factors are strictly intertwined with CYP450s catalysis. Atomic-level simulations have the potential to provide insights into the catalytic mechanism of steroidogenic CYP450s and on its regulation by environmental factors, furnishing information often inaccessible to experimental means. In this review, after an introduction of computational methods commonly employed to tackle these systems, we report the current knowledge on three steroidogenic CYP450s\u2014CYP11A1, CYP17A1, and CYP19A1\u2014endowed with multiple catalytic functions and critically involved in cancer onset. In particular, besides discussing their catalytic mechanisms, we highlight how the membrane environment contributes to (i) regulate ligand channeling through these enzymes, (ii) modulate their interactions with specific protein partners, (iii) mediate post-transcriptional regulation induced by phosphorylation. The results presented set the basis for developing novel therapeutic strategies aimed at fighting diseases originating from steroid metabolism dysfunction

XPySom: High-performance self-organizing maps

In this paper, we introduce XPySom, a new open-source Python implementation of the well-known Self-Organizing Maps (SOM) technique. It is designed to achieve high performance on a single node, exploiting widely available Python libraries for vector processing on multi-core CPUs and GP-GPUs. We present results from an extensive experimental evaluation of XPySom in comparison to widely used open-source SOM implementations, showing that it outperforms the other available alternatives. Indeed, our experimentation carried out using the Extended MNIST open data set shows a speed-up of about 7x and 100x when compared to the best open-source multi-core implementations we could find with multi-core and GP-GPU acceleration, respectively, achieving the same accuracy levels in terms of quantization error

Machine learning methods for generating high dimensional discrete datasets

The development of platforms and techniques for emerging Big Data and Machine Learning applications requires the availability of real-life datasets. A possible solution is to synthesize datasets that reflect patterns of real ones using a two-step approach: first, a real dataset X is analyzed to derive relevant patterns Z and, then, to use such patterns for reconstructing a new dataset X ' that preserves the main characteristics of X. This survey explores two possible approaches: (1) Constraint-based generation and (2) probabilistic generative modeling. The former is devised using inverse mining (IFM) techniques, and consists of generating a dataset satisfying given support constraints on the itemsets of an input set, that are typically the frequent ones. By contrast, for the latter approach, recent developments in probabilistic generative modeling (PGM) are explored that model the generation as a sampling process from a parametric distribution, typically encoded as neural network. The two approaches are compared by providing an overview of their instantiations for the case of discrete data and discussing their pros and cons. This article is categorized under: Fundamental Concepts of Data and Knowledge > Big Data Mining Technologies > Machine Learning Algorithmic Development > Structure Discover

A deep learning approach for detecting security attacks on blockchain

In these last years, Blockchain technologies have been widely used in several application fields to improve data privacy and trustworthiness and security of systems. Although the blockchain is a powerful tool, it is not immune to cyber attacks: for instance, recently (January 2019) a successful 51% attack on Ethereum Classic has revealed security vulnerabilities of its platform. Under a statistical perspective, attacks can be seen as an anomalous observation, with a strong deviation from the regular behavior. Machine Learning is a science whose goal is to learn insights, patterns and outliers within large data repositories; hence, it can be exploit for blockchain attack detection. In this work, we define an anomaly detection system based on a encoder-decoder deep learning model, that is trained exploiting aggregate information extracted by monitoring blockchain activities. Experiments on complete historical logs of Ethereum Classic network prove the capability of the our model to effectively detect the publicly reported attacks. To the best of our knowledge, our approach is the first one that provides a comprehensive and feasible solution to monitor the security of blockchain transactions

Larga batalla de un paciente con sida y tuberculosis recurrente: ¿reinfección o reactivación?

The advent of Mycobacterium tuberculosis strain genotyping has allowed differentiation between disease relapse and exogenous re-infection. We report here a remarkable case of multiply recurrent tuberculosis in a patient living with HIV. Between 1995 and 2009, a young HIV-infected intravenous drug user, who was reluctant to comply with anti-retroviral treatment, underwent at least five tuberculosis episodes caused by three distinct M. tuberculosis strains sharply differentiated by drug susceptibility profile, genotype and infectious source. Eventually, the patient died during a relapse of tuberculosis due to a notorious multidrug-resistant outbreak-strain, which infected him during a prolonged hospitalization in the epicentre of such outbreak. Whether recurrent tuberculosis is due to a new infection or to reactivation of a previous one is a century-long controversial question. In our patient, both conditions alternated throughout his 15 years of living with HIV. Cases such as this might not be exceptional in certain underprivileged suburban areas of Argentina and should raise concern over three pending issues in tuberculosis control policies, namely secondary preventive therapy, institutional infection control and patient follow-up throughout the health network system.La genotipificación de aislamientos clínicos de Mycobacterium tuberculosis permite diferenciar entre recaída y reinfección exógena. Presentamos un notable caso de tuberculosis recurrente asociado a sida. Entre 1995 y 2009, un usuario de drogas ilegales por vía endovenosa, con infección por el VIH pero reacio al tratamiento antirretroviral, sufrió cinco episodios de tuberculosis causados por tres cepas de M. tuberculosis. Las cepas se diferenciaron por los genotipos, los perfiles de sensibilidad a antibióticos y las fuentes de infección. El paciente murió de tuberculosis por una cepa multirresistente, responsable de un extenso brote en Argentina, que lo infectó durante una prolongada internación en el hospital que fue el epicentro de dicho brote. La controversia sobre el origen de la tuberculosis recurrente –reinfección o reactivación– lleva ya un siglo y continúa vigente. En el caso que aquí se describe, las dos situaciones se alternaron a lo largo de los 15 años de lucha contra el sida que atravesó este paciente. Esta situación puede no ser excepcional en áreas suburbanas desfavorecidas de Argentina, y pone en evidencia tres temas insuficientemente atendidos en nuestro medio: el tratamiento preventivo de la tuberculosis secundaria, el control de su transmisión en hospitales y cárceles, y el seguimiento de los pacientes a través del sistema de salud.Fil: Reniero, A.. Hospital Municipal de San Isidro; ArgentinaFil: Beltrán, M.. Hospital Municipal de San Isidro; ArgentinaFil: de Kantor, I. N.. PAHO/WHO consultant; ArgentinaFil: Ritacco, Gloria Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; Argentin

Larga batalla de un paciente con sida y tuberculosis recurrente: ¿reinfección o reactivación?

The advent of Mycobacterium tuberculosis strain genotyping has allowed differentiation between disease relapse and exogenous re-infection. We report here a remarkable case of multiply recurrent tuberculosis in a patient living with HIV. Between 1995 and 2009, a young HIV-infected intravenous drug user, who was reluctant to comply with anti-retroviral treatment, underwent at least five tuberculosis episodes caused by three distinct M. tuberculosis strains sharply differentiated by drug susceptibility profile, genotype and infectious source. Eventually, the patient died during a relapse of tuberculosis due to a notorious multidrug-resistant outbreak-strain, which infected him during a prolonged hospitalization in the epicentre of such outbreak. Whether recurrent tuberculosis is due to a new infection or to reactivation of a previous one is a century-long controversial question. In our patient, both conditions alternated throughout his 15 years of living with HIV. Cases such as this might not be exceptional in certain underprivileged suburban areas of Argentina and should raise concern over three pending issues in tuberculosis control policies, namely secondary preventive therapy, institutional infection control and patient follow-up throughout the health network system.La genotipificación de aislamientos clínicos de Mycobacterium tuberculosis permite diferenciar entre recaída y reinfección exógena. Presentamos un notable caso de tuberculosis recurrente asociado a sida. Entre 1995 y 2009, un usuario de drogas ilegales por vía endovenosa, con infección por el VIH pero reacio al tratamiento antirretroviral, sufrió cinco episodios de tuberculosis causados por tres cepas de M. tuberculosis. Las cepas se diferenciaron por los genotipos, los perfiles de sensibilidad a antibióticos y las fuentes de infección. El paciente murió de tuberculosis por una cepa multirresistente, responsable de un extenso brote en Argentina, que lo infectó durante una prolongada internación en el hospital que fue el epicentro de dicho brote. La controversia sobre el origen de la tuberculosis recurrente –reinfección o reactivación– lleva ya un siglo y continúa vigente. En el caso que aquí se describe, las dos situaciones se alternaron a lo largo de los 15 años de lucha contra el sida que atravesó este paciente. Esta situación puede no ser excepcional en áreas suburbanas desfavorecidas de Argentina, y pone en evidencia tres temas insuficientemente atendidos en nuestro medio: el tratamiento preventivo de la tuberculosis secundaria, el control de su transmisión en hospitales y cárceles, y el seguimiento de los pacientes a través del sistema de salud.Fil: Reniero, A.. Hospital Municipal de San Isidro; ArgentinaFil: Beltrán, M.. Hospital Municipal de San Isidro; ArgentinaFil: de Kantor, I. N.. PAHO/WHO consultant; ArgentinaFil: Ritacco, Gloria Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; Argentin