Versailles Project on Advanced Materials and Standards interlaboratory study on intensity calibration for x-ray photoelectron spectroscopy instruments using low-density polyethylene

We report the results of a Versailles Project on Advanced Materials and Standards interlaboratory study on the intensity scale calibration of x-ray photoelectron spectrometers using low-density polyethylene (LDPE) as an alternative material to gold, silver, and copper. An improved set of LDPE reference spectra, corrected for different instrument geometries using a quartz-monochromated Al Kα x-ray source, was developed using data provided by participants in this study. Using these new reference spectra, a transmission function was calculated for each dataset that participants provided. When compared to a similar calibration procedure using the NPL reference spectra for gold, the LDPE intensity calibration method achieves an absolute offset of ∼3.0% and a systematic deviation of ±6.5% on average across all participants. For spectra recorded at high pass energies (≥90 eV), values of absolute offset and systematic deviation are ∼5.8% and ±5.7%, respectively, whereas for spectra collected at lower pass energies (<90 eV), values of absolute offset and systematic deviation are ∼4.9% and ±8.8%, respectively; low pass energy spectra perform worse than the global average, in terms of systematic deviations, due to diminished count rates and signal-to-noise ratio. Differences in absolute offset are attributed to the surface roughness of the LDPE induced by sample preparation. We further assess the usability of LDPE as a secondary reference material and comment on its performance in the presence of issues such as variable dark noise, x-ray warm up times, inaccuracy at low count rates, and underlying spectrometer problems. In response to participant feedback and the results of the study, we provide an updated LDPE intensity calibration protocol to address the issues highlighted in the interlaboratory study. We also comment on the lack of implementation of a consistent and traceable intensity calibration method across the community of x-ray photoelectron spectroscopy (XPS) users and, therefore, propose a route to achieving this with the assistance of instrument manufacturers, metrology laboratories, and experts leading to an international standard for XPS intensity scale calibration

Procesamiento digital de imágenes usando wavelets

Cada vez tiene mayor importancia en la ingeniería el procesado de señales digitales, puesto que es una ciencia que se entrelaza con una gran cantidad de ciencias y puesto que posee grandes características como lo son su alta flexibilidad de diseño, su capacidad de programación y de cambiar esta para obtener mejores resultados en un procesado real, además de que se cuenta con dispositivos digitales de alta velocidad y con un costo mucho mas barato que dispositivos electrónicos análogos o incluso mecánicos, esta ciencia se ha convertido en un pilar fundamental de otras ciencias en cuanto se refiere al tratamiento y representación de las señales

Electrónica y Telecomunicaciones

Cada vez tiene mayor importancia en la ingeniería el procesado de señales digitales, puesto que es una ciencia que se entrelaza con una gran cantidad de ciencias y puesto que posee grandes características como lo son su alta flexibilidad de diseño, su capacidad de programación y de cambiar esta para obtener mejores resultados en un procesado real, además de que se cuenta con dispositivos digitales de alta velocidad y con un costo mucho mas barato que dispositivos electrónicos análogos o incluso mecánicos, esta ciencia se ha convertido en un pilar fundamental de otras ciencias en cuanto se refiere al tratamiento y representación de las señales

Luminescent Properties of Silicon Nanocrystals:Spin on Glass Hybrid Materials

The photoluminescence characteristics of films consisting of Si nanocrystals either coated with or embedded into Spin on Glass (SOG) were studied. Si nanocrystals showing red or blue luminescence when suspended in alcohol solution were obtained from porous silicon films. These were then either deposited in Si substrates and coated with SOG, or mixed in an SOG solution that was later spun on Si substrates. Both types of films were thermally annealed at 1100 °C for three hours in N2 atmosphere. Transmission electron microscopy measurements showed a mean diameter of 2.5 nm for the Si nanocrystals, as well as the presence of polycrystalline Si nanoagglomerates. These results were confirmed by X-ray diffraction studies, which revealed the (111), (220) and (311) Bragg peaks in Si nanocrystals. Fourier transform infrared spectroscopy studies showed that the coated films present higher chemical reactivity, promoting the formation of non-stoichiometric SiO2, while the embedded films behave as a stoichiometric SiO2 after the thermal annealing. The PL (photoluminescence) characterization showed that both embedded and coated films present emission dominated by the Quantum Confinement Effect before undergoing any thermal treatment. After annealing, the spectra were found to be modified only in the case of the coated films, due to the formation of defects in the nanocrystals/SiO2 interface

Plant growth-promoting rhizobacteria associated with avocado display antagonistic activity against <i>Phytophthora cinnamomi</i> through volatile emissions

<div><p>Rhizobacteria associated with crops constitute an important source of potentially beneficial microorganisms with plant growth promoting activity or antagonistic effects against phytopathogens. In this study, we evaluated the plant growth promoting activity of 11 bacterial isolates that were obtained from the rhizosphere of healthy avocado trees and from that of avocado trees having survived root rot infestations. Seven bacterial isolates, belonging to the genera <i>Bacillus</i>, <i>Pseudomonas</i> and <i>Arthrobacter</i>, promoted <i>in vitro</i> growth of <i>Arabidopsis thaliana</i>. These isolates were then tested for antagonistic activity against <i>Phytophthora cinnamomi</i>, in direct dual culture assays. Two of those rhizobacterial isolates, obtained from symptomatic-declining trees, displayed antagonistic activity. Isolate A8a, which is closely related to <i>Bacillus acidiceler</i>, was also able to inhibit <i>P</i>. <i>cinnamomi</i> growth <i>in vitro</i> by 76% through the production of volatile compounds. Solid phase microextraction (SPME) and analysis by gas chromatography coupled with mass spectrometry (GC-MS) allowed to tentatively identify the main volatiles emitted by isolate A8a as 2,3,5-trimethylpyrazine, 6,10-dimethyl-5,9-undecadien-2-one and 3-amino-1,3-oxazolidin-2-one. These volatile compounds have been reported to show antifungal activity when produced by other bacterial isolates. These results confirm the significance of rhizobacteria and suggest that these bacteria could be used for biocontrol of soil borne oomycetes through their volatiles emissions.</p></div

Co-cultivation of <i>Arabidopsis thaliana</i> seedlings with rhizobacterial isolates from symptomatic-declining avocado trees.

<p>Representative photographs of Arabidopsis Col-0 seedlings transferred to non-inoculated (Control) fresh media, or inoculated with rhizobacterial isolates at 2.5 cm (long distance) and 1 cm (close distance) from root tip. Primary root length (b), lateral root number (c) and fresh weight accumulation (d) were the developmental parameters analyzed. Data values represent the mean of 30 seedlings ± SE per treatment; different letters in graphs indicate significant differences (<i>P</i> < 0.05).</p

Antagonical activity of isolate A8a, phylogenetically close to <i>Bacillus acidiceler</i>, against <i>Phytophthora cinnamomi</i>.

<p>Disks of <i>P</i>. <i>cinnamomi</i> mycelium were grown on agar PDA-containing plates. Radial growth was monitored for 11 days in non-inoculated conditions (a). Confrontation with <i>B</i>. <i>acidiceler</i> was performed by directly co-cultivating mycelial disks with bacterial inoculum, at a distance of 2 cm (b), or indirectly, growing them on the opposite halves of the same Petri dish (c). Assays were carried out by triplicate. Representative plates were photographed at day 5 and 11 after inoculation (dai). At 7 dai, the inhibition percentage of mycelial radial growth by direct (light gray bars) or indirect (dark gray bars) antagonism was analyzed (d); hyphal deformations induced by indirect inoculation were visually analyzed by stereoscopic observations at 7 dai (e). Values shown in (d) represent the mean of three replicates ± SD; asterisks indicate significant inhibition (<i>P</i> ≤ 0.05).</p

Maximum-Likelihood tree of partially sequenced 16S rRNA genes.

<p>Bold letters indicate rhizobacterial isolates that were obtained in this study. Values above nodes are bootstrap values obtained from 1000 replicates.</p

Direct antagonism assays of avocado rhizobacteria against <i>Phytophthora cinnamomi</i>.

<p>Mycelial growth was measured at fifth day after dual culture.</p

Molecular identification of avocado rhizobacteria with plant growth promoting activity by 16S rRNA sequencing.

<p>Taxonomic assignment was determined with the rdp classifier tool. Sequence closest matches were based on the NCBI database “16S ribosomal RNA sequences (Bacteria and Archaea)”.</p