Ermakov Systems with Multiplicative Noise

Using the Euler-Maruyama numerical method, we present calculations of the Ermakov-Lewis invariant and the dynamic, geometric, and total phases for several cases of stochastic parametric oscillators, including the simplest case of the stochastic harmonic oscillator. The results are compared with the corresponding numerical noiseless cases to evaluate the effect of the noise. Besides, the noiseless cases are analytic and their analytic solutions are briefly presented. The Ermakov-Lewis invariant is not affected by the multiplicative noise in the three particular examples presented in this work, whereas there is a shift effect in the case of the phasesComment: 12 pages, 4 figures, 22 reference

Compressive mechanical cracking of pili (Canarium ovatum Engl.) nuts: Concept and mechanism design

A mechanical pili nut cracker that used gradual compression for cracking was proposed and developed. This was a deviation from the traditional practice of applying impact for cracking pili nuts. The cracking unit of the machine accomplishes gradual compression by a rotating assembly of discs and compression bars travelling along an arrangement of cam rails. The cracker’s performance was established using pili nuts at different moisture levels.  The tests followed a single-factor three-level experiment where the response variables included cracking capacity, cracking efficiency, cracking recovery, whole kernel recovery, kernel damage, kernel losses and purity of output. The machine performed satisfactorily using nuts dried for three days after depulping (moisture content wet basis = 11.6%). At this moisture level, the machine showed consistent and satisfactory performance in terms of cracking capacity (25 kernels min-1), cracking efficiency (74.0%), cracking recovery (62.6%) and whole kernel recovery (84.3%). Modifications were recommended to further reduce kernel damage (30.6%) and kernel losses (37.4%) and to improve the purity of output (46.8%). It was successfully demonstrated that gradual compression can be used for cracking pili nuts. It is recommended that the operating characteristics of the machine should be optimized to improve its performance.  Furthermore, a dedicated feeding assembly and a more suitable separation method should be explored to further enhance the performance of the cracker

Respiratory infection by Corynebacterium striatum: Epidemiological and clinical determinants

© 2014 The Authors. The increasing prevalence of advanced chronic respiratory disease, with frequent exposure to broad-spectrum antibiotics for repeated and prolonged hospitalizations, favours the emergence of nosocomial respiratory infection by Gram-positive bacteria, such as outbreaks of Corynebacterium striatum. There is little evidence about patterns of respiratory infection, transmission and adaptive ability of this pathogen. Seventy-two C. striatum isolates from 51 advanced respiratory patients, mainly chronic obstructive pulmonary disease, were studied during 38 months. Patients were 74.8 ± 8.6 years old and 81.9% were men, who had required an average of 2.2 hospitalizations and 63.5 days in the hospital in the previous year. Of 49 isolates from 42 patients we were able to identify 12 clones by multilocus sequence analysis (MLSA), nine phenotypic variants and 22 antibiotic susceptibility patterns, and we determined their clinical and epidemiological determinants. MLSA allows identification of the existence of nosocomial outbreaks by transmission of the same or different clones, the persistence of the same clone in the environment or in patient airways for months. The study showed the high variability and adaptive capacity of the isolates, the antibiotic multidrug-resistance in all of them, and their contribution to a high morbidity and mortality (41%) during the study period.This work was supported by the General Board for Research, Technological Development and Innovation of the Department of Finance and Innovation of the Autonomous Community of the Balearic Islands (Direcció General de Recerca, Desenvolupament Tecnològic i Innovació, de la Conselleria d'Hisenda i Innovació, de la Comunitat Autònoma de les Illes Balears). This work was supported also by funding from Spanish MINECO through Consolider CSD2009-00006. Margarita Gomila was supported by a postdoctoral contract from the University of the Balearic Islands, with funds from the Spanish Ministry of Education, Culture and Sports through the International Excellence Campus ProgrammePeer Reviewe

Identification and diversity of multiresistant Corynebacterium striatum clinical isolates by MALDI-TOF mass spectrometry and by a multigene sequencing approach

<p>Abstract</p> <p>Background</p> <p>The genus <it>Corynebacterium </it>is composed of Gram-positive bacteria that are widely distributed throughout the environment; these bacteria are also part of the normal microbiota of human skin and mucous membranes. Multiple studies have shown that species of this genus, including <it>C. striatum</it>, become pathogenic to humans under special conditions. Our aim was to determine the characteristics of clinical multiresistant strains of <it>C. striatum </it>that were isolated in our geographical region, to determine their diversity, and to compare them with the type strain and with related species. We studied fifty-two strains of <it>C. striatum </it>isolated from different hospitals from Mallorca, Spain, mainly from the Hospital Joan March in Bunyola, Mallorca. Most of the strains were isolated from sputum cultures of respiratory samples from patients with chronic obstructive pulmonary disease. To gain further insight into the genetic diversity of the strains, we analysed several housekeeping genes and other genes associated with antibiotic resistance. Strains were also characterised phenotypically by their antibiotic resistance profiles and by MALDI-TOF mass spectrometry analysis.</p> <p>Results</p> <p>The ITS1 region, <it>gyrA </it>and <it>rpoB </it>were chosen as the appropriate genes in the <it>C. striatum </it>genome to study the genetic diversity of <it>C. striatum </it>species and to discriminate between strains. After analysing these three genes, four sequence types (ST2, ST4, ST1 and ST11) were found to be the most abundant. Splits tree analysis of the strains demonstrated that these clinical isolates did not share any alleles with the type strain of the species. Recombination was detected within all of the <it>C. striatum </it>isolates, and different clonal populations were detected within the samples.</p> <p>Conclusions</p> <p>Our results demonstrate that the isolates were best identified using gene-based molecular methods; using these methods, the isolated strains were determined to be different from the type strain of <it>C. striatum</it>. The ITS1 region and the <it>gyrA </it>and <it>rpoB </it>genes were selected because of their variability and were the most useful tools for discriminating between strains. The phenotype and antibiotype characteristics of the strains did not seem suitable for typing purposes. MALDI-TOF mass spectrometry can be a useful method for identifying and discriminating between <it>C. striatum </it>strains.</p

Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction

Citation: Marquez-Miranda, V., Araya-Duran, I., Camarada, M. B., Comer, J., Valencia-Gallegos, J. A., & Gonzalez-Nilo, F. D. (2016). Self-Assembly of Amphiphilic Dendrimers: The Role of Generation and Alkyl Chain Length in siRNA Interaction. Scientific Reports, 6, 15. https://doi.org/10.1038/srep29436An ideal nucleic-acid transfection system should combine the physical and chemical characteristics of cationic lipids and linear polymers to decrease cytotoxicity and uptake limitations. Previous research described new types of carriers termed amphiphilic dendrimers (ADs), which are based on polyamidoamine dendrimers (PAMAM). These ADs display the cell membrane affinity advantage of lipids and preserve the high affinity for DNA possessed by cationic dendrimers. These lipid/dendrimer hybrids consist of a low-generation, hydrophilic dendron (G2, G1, or G0) bonded to a hydrophobic tail. The G2-18C AD was reported to be an efficient siRNA vector with significant gene silencing. However, shorter tail ADs (G2-15C and G2-13C) and lower generation (G0 and G1) dendrimers failed as transfection carriers. To date, the self-assembly phenomenon of this class of amphiphilic dendrimers has not been molecularly explored using molecular simulation methods. To gain insight into these systems, the present study used coarse-grained molecular dynamics simulations to describe how ADs are able to self-assemble into an aggregate, and, specifically, how tail length and generation play a key role in this event. Finally, explanations are given for the better efficiency of G2/18-C as gene carrier in terms of binding of siRNA. This knowledge could be relevant for the design of novel, safer ADs with well-optimized affinity for siRNA

Nitrogen Fertilization Has a Stronger Effect on Soil Nitrogen-Fixing Bacterial Communities than Elevated Atmospheric CO2

Biological nitrogen fixation is the primary supply of N to most ecosystems, yet there is considerable uncertainty about how N-fixing bacteria will respond to global change factors such as increasing atmospheric CO2 and N deposition. Using the nifH gene as a molecular marker, we studied how the community structure of N-fixing soil bacteria from temperate pine, aspen, and sweet gum stands and a brackish tidal marsh responded to multiyear elevated CO2 conditions. We also examined how N availability, specifically, N fertilization, interacted with elevated CO2 to affect these communities in the temperate pine forest. Based on data from Sanger sequencing and quantitative PCR, the soil nifH composition in the three forest systems was dominated by species in the Geobacteraceae and, to a lesser extent, Alphaproteobacteria. The N-fixing-bacterial-community structure was subtly altered after 10 or more years of elevated atmospheric CO2, and the observed shifts differed in each biome. In the pine forest, N fertilization had a stronger effect on nifH community structure than elevated CO2 and suppressed the diversity and abundance of N-fixing bacteria under elevated atmospheric CO2 conditions. These results indicate that N-fixing bacteria have complex, interacting responses that will be important for understanding ecosystem productivity in a changing climate