Partial least squares regression as a tool to predict fluoropolymer surface modification by dielectric barrier discharge in a corona process configuration in a nitrogen-organic gaseous precursor environment

A dielectric barrier discharge in a corona process configuration is used to treat the surface of fluoropolymers in a nitrogen−organic precursor environment. The surface chemistry, thickness, and water contact angle of the deposited coatings are measured and used to build up an output matrix to be correlated with an input matrix built using electrical parameters of the discharge, the gas mixture chemical composition, and spectroscopic parameters measured in both the infrared and ultraviolet−visible emission spectral regions. A partial least-squares regression (PLSR) model enables determining the most important plasma parameters to drive the coating physicochemical characteristics. From the PLSR model, it is determined that the plasma electrical parameters drive the surface modification process, at the expense of other plasma characteristics such as gas flow, gaseous precursor concentration, nitrogen vibrational temperature, and the level of gaseous precursor conversion within the plasma

Optical emission spectroscopy as a process-monitoring tool in plasma enhanced chemical vapor deposition of amorphous carbon coatings - multivariate statistical modelling

Production of Diamond-Like Carbon (DLC) nanocoatings using plasma enhanced chemical vapor deposition is studied by Optical Emission Spectroscopy (OES) as a plasma diagnostic technique. The objective of the current research is to establish a predictive model of DLC properties using a multivariate analysis method. This model is based on OES data instead of process parameters, which are reactor dependent and accordingly, their effect on the plasma deposition process may vary from one reactor to another. The predictive potential of OES is evaluated using partial least square regression (PLSR) analysis. The results show that OES derived data are capable of replacing some process parameters to predict the DLC properties. The perspective of PLSR modelling and OES application for the development and monitoring of a structurally graded DLC coating is also discussed

Correlation between the plasma characteristics and the surface ‎chemistry of plasma-treated polymers through partial least ‎squares analysis

We investigated the effect of various plasma parameters (relative density of atomic N and H, plasma temperature, and vibrational temperature) and process conditions (pressure and H2/(N2 + H2) ratio) on the chemical composition of modified poly(tetrafluoroethylene) (PTFE). The plasma parameters were measured by means of near-infrared (NIR) and UV-visible emission spectroscopy with and without actinometry. The process conditions of the N2-H2 microwave discharges were set at various pressures ranging from 100 to 2000 mTorr and H2/(N2+H2) gas mixture ratios between 0 and 0.4. The surface chemical composition of the modified polymers was determined by X-ray photoelectron spectroscopy (XPS). A mathematical model was constructed using the partial least-squares regression algorithm to correlate the plasma information (process condition and plasma parameters as determined by emission spectroscopy) with the modified surface characteristics. To construct the model, a set of data input variables containing process conditions and plasma parameters were generated, as well as a response matrix containing the surface composition of the polymer. This model was used to predict the composition of PTFE surfaces subjected to N2-H2 plasma treatment. Contrary to what is generally accepted in the literature, the present data demonstrate that hydrogen is not directly involved in the defluorination of the surface but rather produces atomic nitrogen and/or NH radicals that are shown to be at the origin of fluorine atom removal from the polymer surface. The results show that process conditions alone do not suffice in predicting the surface chemical composition and that the plasma characteristics, which cannot be easily correlated with these conditions, should be considered. Process optimization and control would benefit from plasma diagnostics, particularly infrared emission spectroscopy

Defining what constitutes a reliable dataset to test for hybridization and introgression in marine zooplankton: Comment on Choquet et al. 2020 “No evidence for hybridization between Calanus finmarchicus and C. glacialis in a subarctic area of sympatry”

The article ‘No evidence for hybridization between Calanus finmarchicus and C. glacialis in a subarctic area of sympatry’ (Choquet et al. 2020) concludes that “no evidence supports a potential for hybridization between C. finmarchicus and C. glacialis”. We argue that the InDel markers used by Choquet et al. (2020) may have limited capacity to detect admixed genotypes between C. finmarchicus and C. glacialis due to an inappropriate choice of reference sample for each species during the marker development. We first review terms and concepts used in genetic classification using reference samples and describe problems associated with the selection of genetic markers in the context of possible hybridization. We reanalyze InDel genotypes provided with Choquet et al. (2017) and identified an admixed individual. We then contrast methods used by Choquet et al. (2017) and Parent et al. (2012) and explain how Parent et al. (2012) developed microsatellite markers capable of discriminating admixed genotypes from parental species. In this comment, we have identified a major issue that must be considered when selecting reference samples in the context of testing for possible hybridization.publishedVersio

Diet of St. Lawrence Estuary Beluga (Delphinapterus leucas) in a changing ecosystem

Ecosystems and community structure fluctuate over time as a result of natural and anthropogenic factors that may affect prey availability and population dynamics. Most of what we know about St. Lawrence Estuary (SLE) Beluga (Delphinapterus leucas) diet comes from stomach contents collected 80 years ago mainly from a hunting site that Beluga no longer use. How reflective these data are of Beluga diet at other sites and at the current time is unknown. In the context of the recent population decline, general information of prey species alone may help identify useful conservation actions for potentially important prey or habitats. Here, we examined the diet of SLE Beluga using digestive tracts collected from carcasses recovered over the past 30 years, in the context of historical diet data and recent changes in the St. Lawrence ecosystem. We showed they have a varied diet composed of fish and invertebrates generally <30 cm in length, and that adult males and females differ in their summer diet in a way that is consistent with the sex segregation observed in this population. Our results also indicate that polychaete worms, squid, and cod are still among the most prevalent prey, and that species such as redfish (Sebastes spp.) might be important prey items. This study shows that Beluga diet has changed since the 1930s, and that prey from digestive tracts identified to species are valuable for making comparisons to the past, and for improving applications of molecular analyses, such as stable isotopes and fatty acids

Toward High-Performance Coatings for Biomedical Devices: Study on Plasma-Deposited Fluorocarbon Films and Ageing in PBS

High performance coatings tailored to medical devices represent a recognised approach to modulate surface properties. Plasma-deposited fluorocarbon films have been proposed as a potential stent coating. Previous studies have shown promising adhesion properties: the 35 nm-thick film sustained plastic deformation up to 25% such as induced during the clinical implantation. In this study, the compositional and morphological changes of plasma-deposited fluorocarbon films were examined during ageing in a pseudo-physiological medium, a phosphate buffer solution (PBS), by angle-resolved XPS, FT-IR data and AFM images. The evolution of the ageing process is discussed: defluorination and crosslinking yielded an oxidized protective top layer onto the films, which showed further degradation

Defining what constitutes a reliable dataset to test for hybridization and introgression in marine zooplankton: Comment on Choquet et al. 2020 “No evidence for hybridization between Calanus finmarchicus and C. glacialis in a subarctic area of sympatry”

The article ‘No evidence for hybridization between Calanus finmarchicus and C. glacialis in a subarctic area of sympatry’ (Choquet et al. 2020) concludes that “no evidence supports a potential for hybridization between C. finmarchicus and C. glacialis”. We argue that the InDel markers used by Choquet et al. (2020) may have limited capacity to detect admixed genotypes between C. finmarchicus and C. glacialis due to an inappropriate choice of reference sample for each species during the marker development. We first review terms and concepts used in genetic classification using reference samples and describe problems associated with the selection of genetic markers in the context of possible hybridization. We reanalyze InDel genotypes provided with Choquet et al. (2017) and identified an admixed individual. We then contrast methods used by Choquet et al. (2017) and Parent et al. (2012) and explain how Parent et al. (2012) developed microsatellite markers capable of discriminating admixed genotypes from parental species. In this comment, we have identified a major issue that must be considered when selecting reference samples in the context of testing for possible hybridization