Combinatorial materials research applied to the development of new surface coatings IV. A high-throughput bacterial biofilm retention and retraction assay for screening fouling-release performance of coatings

Abstract

A high-throughput bacterial biofilm retention screening method has been augmented to facilitate the rapid analysis and down-selection of fouling-release coatings for identification of promising candidates. Coatings were cast in modified 24-well tissue culture plates and inoculated with the marine bacterium Cytophaga lytica for attachment and biofilm growth. Biofilms retained after rinsing with deionised water were dried at ambient laboratory conditions. During the drying process, retained biofilms retracted through a surface de-wetting phenomenon on the hydrophobic silicone surfaces. The retracted biofilms were stained with crystal violet, imaged, and analysed for percentage coverage. Two sets of experimental fouling-release coatings were analysed with the high-throughput biofilm retention and retraction assay (HTBRRA). The first set consisted of a series of model polysiloxane coatings that were systematically varied with respect to ratios of low and high MW silanol-terminated PDMS, level of cross-linker, and amount of silicone oil. The second set consisted of cross-linked PDMS-polyurethane coatings varied with respect to the MW of the PDMS and end group functionality. For the model polysiloxane coatings, HTBRRA results were compared to data obtained from field immersion testing at the Indian River Lagoon at the Florida Institute of Technology. The percentage coverage calculations of retracted biofilms correlated well to barnacle adhesion strength in the field (R² = 0.82) and accurately identified the best and poorest performing coating compositions. For the cross-linked PDMS-polyurethane coatings, the HTBRRA results were compared to combinatorial pseudobarnacle pull-off adhesion data and good agreement in performance was observed. Details of the developed assay and its implications in the rapid discovery of new fouling-release coatings are discussed.     

Enhanced adhesion and chemoattraction of zoospores of the fouling alga enteromorpha to some foul‐release silicone elastomers

Significantly higher numbers of zoospores of the fouling, green alga Enteromorpha adhered to silicone elastomers cured by dibutyltin dilaurate (DBTDL) than to identical polymers cured by dibutyltin diacetate (DBTDA). Enhanced zoospore adhesion was shown to be due to the presence of DBTDL and the effect was concentration‐dependent. Further experiments revealed that enhanced zoospore adhesion also occurred to glass coverslips coated with lauric acid (C₁₂) and other saturated fatty acids. The possibility that fatty acids may act as chemical cues (chemoattractants), guiding motile zoospores to the substratum for settlement in the natural environment is discussed. Settlement of other fouling organisms to DBTDL‐cured silicone elastomers is currently being investigated.     

Sources of Thought Two 19th-century Chronobiologists: Thomas Laycock and Edward Smith

This article describes the works of two 19th-century chronobiologists. Thomas Laycock (1812-1876), who held the Chair of Medicine in Edinburgh from 1855-1876, published a series of seven articles in Lancet, all dedicated to periodicities in “vital phenomena.” Laycock considered the understanding of periodicities essential for the advancement of the treatment of diseases. Edward Smith (1818-1874) was a pioneer in experimental chronobiology. In his 1861 book entitled: Health and disease as influenced by daily, seasonal and other cyclical changes in the human, Smith summarized a large number of experiments in which he investigated the occurrence of periodicities in pulse rate, urine flow, urea excretion, and respiration. From his experimental results and those of others, Smith drew practical conclusions regarding patients' care, the timing of drug administration, and the design of night work.     

Using an Activity to Simulate the Dangers of Multitasking with Technology while Walking

People are increasingly trying to multitask while walking. Text messaging while walking is a significant area for concern. The number of text messages sent is expected to be more than 8 trillion in 2012. Texting is becoming so commonplace that people use this technology while engaged in other activities. The dangers of multitasking have hit the streets as people are becoming involved in more accidents while walking as they text on mobile phones. This simulation activity measures a student's ability to multitask by texting and walking. The activity simulates walking in the real world and is best suited for middle school students. Additional activities, after completing the simulation, will challenge middle school students to learn more about multitasking globally through scientific inquiry researched on the Internet. The students will use language arts skills to generate a report or presentation to share with classmates. Their findings will give the entire class a cultural perspective on accident statistical comparisons between different countries.     

Ecology and the War on Hunger

This interdisciplinary activity promotes science, technology, and language arts and is well suited for upper elementary grade students. In the activity, students' research about a teacher-assigned weather phenomenon facilitates their study of the weather. When they have completed their research, students word process a paper summarizing their findings and generate graphical representations of a weather phenomenon using Microsoft Paint software. The paper and the computer-generated graphical representation measure learning and provide insight into the level of student understanding that other assessment tools, such as quizzes, tests, and questioning techniques, do not provide.     

Domesticating Islam: exploring academic knowledge production on Islam and Muslims in European societies

The attacks on the Twin Towers in New York in September 2001 and subsequent events not only ignited a ‘war on terror’, but also marked a crucial change in the policies on integration of migrants of Islamic background in Europe. Most countries departed from integration policies based on some sort of recognition of cultural diversity and emphasized national culture as the only legitimate format for citizenship. The result is a strengthening of a frame of governance with the aim to regulate Islamic practices and to mould outlooks, institutional settings and legal arrangements into the nation-state format. This has been referred to as the ‘domestication of Islam’. One of the consequences is the narrowing down of research agendas and academic knowledge production. In this article I explore this process and address important fields of study that tend to be neglected in the study of Islam in Europe.     

Negotiating British Muslim belonging: a qualitative longitudinal study

British Muslims are often viewed as holding values incompatible with Britishness, regarded with suspicion and sometimes subjected to gendered forms of racism. Research projects have found that identifiably Muslim women face everyday microaggressions, yet little is known about how they negotiate both this and their identities over time. This article addresses this gap by reporting the results of qualitative longitudinal research that explores the narratives of two young British Muslim women over a seven-year period. The women were first interviewed when they were single undergraduates in 2010 and followed up as married young professionals in 2017. On both occasions they were negotiating their identities and sense of belonging in a climate of heightened scrutiny of Muslims. The paper examines their reflections on: “fitting in” with Britishness, their religious identities and the complexity of belonging. Methodologically, it contributes to qualitative longitudinal narrative research.     

Good student questions in inquiry learning

Acquisition of scientific reasoning is one of the big challenges in education. A popular educational strategy advocated for acquiring deep knowledge is inquiry-based learning, which is driven by emerging ‘good questions’. This study will address the question: ‘Which design features allow learners to refine questions while preserving student ownership of the inquiry process?’ This design-based research has been conducted over several years with advanced high-school biology classes. The results confirm the central role of question elaboration as an interactive process that leads from vague to complex and adequate. To make this happen, the inquiry process must extend over a long time, learners and teachers should share a knowledge improvement goal, and text produced by students should be structured by question–answer pairs addressing a single concept using authentic resources. Further features are discussion with peers, teacher feedback with respect to answer elaboration and conceptual differentiation, and finally, teacher guidance that should fade out in successive inquiry cycles to ensure student responsibility.     

A Comparison of Ship-Recycling Legislation Between Chinese Law and the 2009 Hong Kong Convention

This article discusses the Chinese legal framework in relation to ship recycling and suggests that the various legislation, standards, and opinions provide disorderly and nosystematic regulation. A uniform law specifically regulating the ship-recycling industry should be adopted by China, with a single competent authority empowered to supervise ship-recycling activities, that will effectively implement the 2009 Hong Kong International Convention for the Safe and Environmentally Sound Recycling of Ships.     

Research Ethics and Intellectual Disability: Broadening the Debates

This article examines the ethical issues surrounding the inclusion of people with intellectual disabilities as research subjects. It explores subject selection, competence, risk and benefits, and authority through three tensions that emerge when considering these concepts in the context of the Disability Rights Movement and critical disability scholarship. These tensions are defined as the double dangers of inclusion and exclusion; the challenges of defining competence and risk in terms of individuals vs. groups; and the conflicts that arise when pursuing the dual goals of amelioration and elimination of disabilities. Though these tensions are not resolved, they underscore the importance of researchers engaging with critical disability perspectives in order to navigate these complex ethical questions.