Surface Modification of Polyethylene with Multi-End-Functional Polyethylene Additives

We have prepared and characterized a series of multifluorocarbon end-functional polyethylene additives, which when blended with polyethylene matrices increase surface hydrophobicity and lipophobicity. Water contact angles of >112° were observed on spin-cast blended film surfaces containing less than 1% fluorocarbon in the bulk, compared to 98° in the absence of any additive. Crystallinity in these films gives rise to surface roughness that is an order of magnitude greater than is typical for amorphous spin-cast films but is too little to give rise to superhydrophobicity. X-ray photoelectron spectroscopy (XPS) confirms the enrichment of the multifluorocarbon additives at the air surface by up to 80 times the bulk concentration. Ion beam analysis was used to quantify the surface excess of the additives as a function of composition, functionality, and molecular weight of either blend component. In some cases, an excess of the additives was also found at the substrate interface, indicating phase separation into self-stratified layers. The combination of neutron reflectometry and ion beam analysis allowed the surface excess to be quantified above and below the melting point of the blended films. In these films, where the melting temperatures of the additive and matrix components are relatively similar (within 15 °C), the surface excess is almost independent of whether the blended film is semicrystalline or molten, suggesting that the additive undergoes cocrystallization with the matrix when the blended films are allowed to cool below the melting point

Late Winter Biogeochemical Conditions Under Sea Ice in the Canadian High Arctic

With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO2) uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO2 measurements during spring, summer or autumn, but there are few data for the winter or winter–spring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (78° 43.11′ N, 104° 47.44′ W) in the Canadian High Arctic. Results show relatively low surface water (1–10 m) nitrate (<1.3 µM) and total inorganic carbon concentrations (mean±SD=2015±5.83 µmol kg−1), total alkalinity (mean±SD=2134±11.09 µmol kg−1) and under-ice pCO2sw (mean±SD=286±17 µatm). These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season

Nanoparticles for Applications in Cellular Imaging

In the following review we discuss several types of nanoparticles (such as TiO2, quantum dots, and gold nanoparticles) and their impact on the ability to image biological components in fixed cells. The review also discusses factors influencing nanoparticle imaging and uptake in live cells in vitro. Due to their unique size-dependent properties nanoparticles offer numerous advantages over traditional dyes and proteins. For example, the photostability, narrow emission peak, and ability to rationally modify both the size and surface chemistry of Quantum Dots allow for simultaneous analyses of multiple targets within the same cell. On the other hand, the surface characteristics of nanometer sized TiO2allow efficient conjugation to nucleic acids which enables their retention in specific subcellular compartments. We discuss cellular uptake mechanisms for the internalization of nanoparticles and studies showing the influence of nanoparticle size and charge and the cell type targeted on nanoparticle uptake. The predominant nanoparticle uptake mechanisms include clathrin-dependent mechanisms, macropinocytosis, and phagocytosis

Electrospinning Superhydrophobic Fibers Using Surface Segregating End-Functionalized Polymer Additives

We describe here a facile route for the in situ modification of the surface properties of fibers produced by electrospinning polystyrene containing small quantities of compatible polymer additives, end-functionalized with 1–3 fluoroalkyl groups. Such additives undergo spontaneous surface segregation during the electrospinning process, resulting in fibers with low surface energy, fluorine-rich, superhydrophobic surfaces. Surface properties were analyzed using static contact angle measurements (with water as the contact fluid) and X-ray photoelectron spectroscopy. We report the effect of a number of parameters on the surface properties of the resulting polystyrene fibers including the molecular weight and concentration of functionalized additive, the number of fluoroalkyl groups, the effect of annealing, and spinning solvent. The majority of the fibers were successfully produced using THF as the spinning solvent and fibers with a contact angle of ∼150° were attainable. However, preliminary investigations using a blend of polystyrene and 4 wt % of such an additive, end-functionalized with 3 C8F17 groups in a mixed solvent of DMF/THF (3:1 v/v), resulted in a mat of fibers with a superhydrophobic surface and a contact angle of 158°

Seasonal azithromycin use in paediatric protracted bacterial bronchitis does not promote antimicrobial resistance but does modulate the nasopharyngeal microbiome

Protracted bacterial bronchitis (PBB) causes chronic wet cough for which seasonal azithromycin is increasingly used to reduce exacerbations. We investigated the impact of seasonal azithromycin on antimicrobial resistance and the nasopharyngeal microbiome. In an observational cohort study, 50 children with PBB were enrolled over two consecutive winters; 25/50 at study entry were designated on clinical grounds to take azithromycin over the winter months and 25/50 were not. Serial nasopharyngeal swabs were collected during the study period (12–20 months) and cultured bacterial isolates were assessed for antimicrobial susceptibility. 16S rRNA-based sequencing was performed on a subset of samples. Irrespective of azithromycin usage, high levels of azithromycin resistance were found; 73% of bacteria from swabs in the azithromycin group vs. 69% in the comparison group. Resistance was predominantly driven by azithromycin-resistant S. pneumoniae, yet these isolates were mostly erythromycin susceptible. Analysis of 16S rRNA-based sequencing revealed a reduction in within-sample diversity in response to azithromycin, but only in samples of children actively taking azithromycin at the time of swab collection. Actively taking azithromycin at the time of swab collection significantly contributed to dissimilarity in bacterial community composition. The discrepancy between laboratory detection of azithromycin and erythromycin resistance in the S. pneumoniae isolates requires further investigation. Seasonal azithromycin for PBB did not promote antimicrobial resistance over the study period, but did perturb the microbiome

Diagnostic monitoring of a changing environment: An alternative UK perspective

Adaptive management of the marine environment requires an understanding of the complex interactions within it. Establishing levels of natural variability within and between marine ecosystems is a necessary prerequisite to this process and requires a monitoring programme which takes account of the issues of time, space and scale. In this paper, we argue that an ecosystem approach to managing the marine environment should take direct account of climate change indicators at a regional level if it is to cope with the unprecedented change expected as a result of human impacts on the earth climate system. We discuss the purpose of environmental monitoring and the importance of maintaining long-term time series. Recommendations are made on the use of these data in conjunction with modern extrapolation and integration tools (e.g. ecosystem models, remote sensing) to provide a diagnostic approach to the management of marine ecosystems, based on adaptive indicators and dynamic baselines

Gorgon CO2 Surface and Near-surface Monitoring

This report is a review of the current status of the various techniques used to monitor the near-surface environment above a GCS (geological CO2 storage) project, with specific reference to Barrow Island. The review covers a range of environments, broadly sub-divided into near-surface atmospheric, soil gas, groundwater and the near-shore and marine environment. For each environment the key parameters likely to be indicative of migrant CO2 (including CO2 directly) are considered. The techniques covered include geochemical, isotopic, geophysical, microbial, marine and near-surface atmospheric. For each technique what parameters are measured, the effectiveness of each, the stage of development, relative cost and footprint and some of the practicalities of implementing such a system on Barrow Island are described. Included in the report is a review of where these technologies are being deployed or researched at different GCS sites around the world. There are few commercial scale GCS projects, the majority are demonstration scale and the monitoring techniques being applied are as much for technology development as leakage detection. One of the major difficulties with a near-surface environmental monitoring system is the need to be able to demonstrate detectability of a small or non-existent signal within an inherently noisy system. There are potentially many ways to detect CO2 or parameters affected by its presence; however, they need to be coupled with a method to quantitatively distinguish them from the background environmental or anthropogenic variability. For each of the technologies reviewed, three common themes emerged. The first is that no single technology is likely to meet all of the monitoring objectives. The need for targeted, high intensity monitoring sites at high risk locations should be coupled with lower resolution, larger scale monitoring at low risk sites. There are technologies that are appropriate for each of these; small scale (centimetre to metres) continuous monitoring, such as soil gas or geochemistry and those more suited to periodic, regional scale characterisation and monitoring such as the airborne geophysical techniques (10's of kilometers). Some of the near-surface ambient techniques may be suitable for intermediate scale monitoring of several kilometers. The second theme is the need for modelling studies supported by field trials and data collection to quantify the effects and therefore the detectability of each parameter that may be affected by CO2. The modelling would be used to identify the areas of high risk or high uncertainty and form the foundation for building the monitoring system. The third theme is the need to collect baseline data at least one year prior to injection beginning. The collection of baseline data is fundamental to building the models and understanding the natural variation of the system, including emission sources. However, the collection of baseline data is a non-trivial exercise, particularly on Barrow Island. Each of the potentially suitable techniques would require further field based studies to determine their most effective instrument set-up and measurement resolution. Finally, the technology associated with GCS near-surface monitoring is evolving rapidly. Instrument sensitivity, data sampling rates, equipment deployability, deployment costs and processing/interpretation methods are undergoing rapid change. The monitoring system deployed on Barrow Island will need to be flexible and adaptable to account for changing conditions and technologies