Rational Passivation of Sulfur Vacancy Defects in Two-Dimensional Transition Metal Dichalcogenides.

Structural defects vary the optoelectronic properties of monolayer transition metal dichalcogenides, leading to concerted efforts to control defect type and density via materials growth or postgrowth passivation. Here, we explore a simple chemical treatment that allows on-off switching of low-lying, defect-localized exciton states, leading to tunable emission properties. Using steady-state and ultrafast optical spectroscopy, supported by ab initio calculations, we show that passivation of sulfur vacancy defects, which act as exciton traps in monolayer MoS2 and WS2, allows for controllable and improved mobilities and an increase in photoluminescence up to 275-fold, more than twice the value achieved by other chemical treatments. Our findings suggest a route for simple and rational defect engineering strategies for tunable and switchable electronic and excitonic properties through passivation

Rational Passivation of Sulfur Vacancy Defects in Two-Dimensional Transition Metal Dichalcogenides.

Structural defects vary the optoelectronic properties of monolayer transition metal dichalcogenides, leading to concerted efforts to control defect type and density via materials growth or postgrowth passivation. Here, we explore a simple chemical treatment that allows on-off switching of low-lying, defect-localized exciton states, leading to tunable emission properties. Using steady-state and ultrafast optical spectroscopy, supported by ab initio calculations, we show that passivation of sulfur vacancy defects, which act as exciton traps in monolayer MoS2 and WS2, allows for controllable and improved mobilities and an increase in photoluminescence up to 275-fold, more than twice the value achieved by other chemical treatments. Our findings suggest a route for simple and rational defect engineering strategies for tunable and switchable electronic and excitonic properties through passivation

A prospective cohort study of school-going children investigating reproductive and neurobehavioral health effects due to environmental pesticide exposure in the Western Cape, South Africa: study protocol

Abstract Background Research on reproductive health effects on children from low-level, long-term exposure to pesticides currently used in the agricultural industry is limited and those on neurobehavioral effects have produced conflicting evidence. We aim at investigating the association between pesticide exposure on the reproductive health and neurobehavior of children in South Africa, by including potential relevant co-exposures from the use of electronic media and maternal alcohol consumption. Methods The design entails a prospective cohort study with a follow-up duration of 2 years starting in 2017, including 1000 school going children between the ages of 9 to 16 years old. Children are enrolled with equal distribution in sex and residence on farms and non-farms in three different agricultural areas (mainly apple, table grapes and wheat farming systems) in the Western Cape, South Africa. The neurobehavior primary health outcome of cognitive functioning was measured through the iPad-based CAmbridge Neuropsychological Test Automated Battery (CANTAB) including domains for attention, memory, and processing speed. The reproductive health outcomes include testicular size in boys and breast size in girls assessed in a physical examination, and blood samples to detect hormone levels and anthropometric measurements. Information on pesticide exposure, co-exposures and relevant confounders are obtained through structured questionnaire interviews with the children and their guardians. Environmental occurrence of pesticides will be determined while using a structured interview with farm owners and review of spraying records and collection of passive water and air samples in all three areas. Pesticide metabolites will be analysed in urine and hair samples collected from the study subjects every 4 months starting at baseline. Discussion The inclusion of three different agricultural areas will yield a wide range of pesticide exposure situations. The prospective longitudinal design is a further strength of this study to evaluate the reproductive and neurobehavioural effects of different pesticides on children. This research will inform relevant policies and regulatory bodies to improve the health, safety and learning environments for children and families in agricultural settings

Evolutionary Pathways of the Pandemic Influenza A (H1N1) 2009 in the UK

The emergence of the influenza (H1N1) 2009 virus provided a unique opportunity to study the evolution of a pandemic virus following its introduction into the human population. Virological and clinical surveillance in the UK were comprehensive during the first and second waves of the pandemic in 2009, with extensive laboratory confirmation of infection allowing a detailed sampling of representative circulating viruses. We sequenced the complete coding region of the haemagglutinin (HA) segment of 685 H1N1 pandemic viruses selected without bias during two waves of pandemic in the UK (April-December 2009). Phylogenetic analysis showed that although temporal accumulation of amino acid changes was observed in the HA sequences, the overall diversity was less than that typically seen for seasonal influenza A H1N1 or H3N2. There was co-circulation of multiple variants as characterised by signature amino acid changes in the HA. A specific substitution (S203T) became predominant both in UK and global isolates. No antigenic drift occurred during 2009 as viruses with greater than four-fold reduction in their haemagglutination inhibition (HI) titre (“low reactors”) were detected in a low proportion (3%) and occurred sporadically. Although some limited antigenic divergence in viruses with four-fold reduction in HI titre might be related to the presence of 203T, additional studies are needed to test this hypothesis

Towards an Ecosystem-of-Learning for Architectural Education: Reflecting on a network of six pedagogical clusters

This research is situated in the context of our collective exploration of a new ecosystem-of-learning approach for architectural education, as a catalyst for change. To move online architectural education beyond emergency remote teaching requires a total reset of current thinking and practices. In this essay, we propose a complex network of six new pedagogical clusters, namely Anthropo-Pedagogy, Catalytic Pedagogy, Synergic Pedagogy, Co-generative Pedagogy, Spatio-temporal Pedagogy, and Meta-morphic Pedagogy. We approached our research using an iterative and reflective narrative inquiry method. Examining the development of these complex pedagogical clusters, we highlight the most significant potential contributions towards a responsive, resilient, and replicable ecosystem-of-learning approach for architectural education

Pedagogy through an ecosystem-of-learning lens: Reflecting on a network of six pedagogical clusters

In this presentation, we propose learning as an ecosystem comprising a complex network of six new pedagogical clusters. These pedagogical clusters include Anthropy Pedagogy, Catalytic Pedagogy, Synergic Pedagogy, Co-generative Pedagogy, Spatio-temporal Pedagogy, and Meta-morphic Pedagogy. This research is situated in the context of our collective exploration of a new ecosystem-of-learning for architectural education, in our respective contexts, namely South Africa, Uganda, United Kingdom and Australia. This ecosystem is framed as a catalyst for change following the experience of the COVID-19 pandemic. To move online architectural education beyond emergency remote teaching, requires a total reset of current thinking and practices. We approached our research using an iterative and reflective narrative inquiry method. Examining the development of these complex pedagogical clusters, we highlight the most promising potential contributions towards a responsive, resilient, and replicable ecosystem-of-learning approach for architectural education.This presentation is based on a paper published in the journal, Charrette, 7(1), pp.15-40 (2021).<br/

Fiber optic biosensing for allergen and pathogen screening in food

Fiber optic biosensing for allergen and pathogen screening in food F. Delport, K. Knez, I. Arghir, N. Marien, D. Spasic, S. Vermeir, J. Lammertyn Point-of-care (POC) diagnostic tests for allergen analysis are expected to deliver fast and sensitive detection of DNA and/or protein targets. However, nowadays, detection of molecular targets alone, without their quantification and/or identification is often insufficient1,2. Although, different assays have been developed to meet these requirements, including quantitative PCR (qPCR)3 followed by high resolution melting analysis as well as ligation assays4, most of them are still largely incompatible with the concept of POC testing due to their cost or complexity. Furthermore, antibody sandwich assays, such as ELISA and lateral flow tests, are the industry standard, but lack kinetics and they need multiple handling steps and another detection setup. In this work, we present the fiber optic (FO) SPR sensor as a flexible platform for multiplex, real-time monitoring of DNA amplification and detection of single nucleotide polymorphisms (SNPs) in a single sample. Furthermore, we report for the first time the selection of aptamers against one of the most important peanut allergens, Ara h1 and the comparison to the antibody based detection (Figure 1). Three approaches of an immunoassay to detect Ara h1 peanut allergens in chocolate candy bars were compared; a label-free assay, a secondary antibody sandwich assay and a nanobead enhanced assay (Figure 1A)5. Although label-free detection is the most convenient, our results illustrate that functionalized nanobeads can offer a refined solution to improve the fiber SPR detection limit. By applying magnetite nanoparticles as a secondary label, the detection limit of the SPR bioassay for Ara h1 was improved by two orders of magnitude from 9 to 0.09 g/mL (Figure 1B). The SPR fibers could be regenerated easily and one fiber could be reused for up to 35 times without loss of sensitivity. The results were benchmarked against a commercially available polyclonal ELISA kit with an excellent correlation, but a longer linear dynamic range. In addition, with the SPR fiber we could measure the samples twice as fast as compared to the fastest ELISA protocol. Several Ara h1 DNA aptamers were selected using capillary electrophoresis (CE)-SELEX6. The selected aptamers specifically recognized Ara h1 and did not significantly bind with other proteins, including another peanut allergen Ara h2. Furthermore, the selected aptamer was used for bioassay development on the FO-SPR biosensor platform for detecting Ara h1 protein in both buffer and food matrix samples demonstrating its real potential for the development of novel, more accurate aptamer-based biosensors. Figure 1. (A) overview of the Ara h1 immunoassay strategies on the fiber optic SPR biosensor. (B) Comparison of the three presented immunoassays on the fiber optic SPR sensor for different Ara h1 concentrations. The error bars indicate standard deviations (n = 3). The aforementioned FO-SPR set-up (Figure 2A) has been used for monitoring the DNA melting profile by implementing DNA functionalized gold nanoparticles (Au NP) as labels (Figure 2B), which allowed discriminating SNPs at high resolution7,8. However, to realize simultaneous quantification and cycle-to-cycle identification of the reaction products, the FO-SPR melting assay was combined either with the PCR or with ligase chain reaction (LCR). The FO-SPR LCR assay amplifies DNA in exponential manner through multiple ligation cycles that progress through 3 succeeding phases: hybridization, ligation and melting phase (Figure 2C). The detection limit of the FO-SPR melting assay was drastically improved using the LCR, whereas capacity for SNP detection was preserved (Figure 2 D,E). Furthermore, to achieve detection of multiple targets within the same sample, FO-SPR melting assay was combined with solution phase PCR using two sets of hybridization probes. The DNA targets in this study were used to discriminate Mycobacterium bovis from Mycobacterium avium subsp. Paratuberculosis. These two bacteria, which are frequently encountered in life stock, were used in a proof-of-concept study that showed the capacity of FO-SPR melting assay for multiplex DNA detection (Figure 2F), thereby further emphasizing the potential of this platform in POC test development. Figure 2. (A) Schematic representation of the FO-SPR setup with all components. (B) Schematic representation of a FO-SPR melting assay (top panel) with DNA target (1) and DNA probes immobilized on the FO-SPR sensor (2) and on Au NP (3). Gene probes hybridize at the FO surface, and are subsequently melted off by a gradual increase of the temperature, resulting in the FO-SPR sensorgram (bottom panel). (C) Schematic overview of the FO-SPR LCR: (1) Different components of the reaction. (2) LCR reaction where the forward and reverse probes are ligated only in the presence of the target sequence, resulting in an exponential amplification during multiple cycles. (3) The forward LCR product can, during the LCR reaction, form a complex with two complementary probes immobilized on the FO-SPR sensor and on Au NPs, allowing real-time monitoring of the reaction. (D) The derived calibration curve with Ct values from the FO-SPR LCR, spans 7 orders of magnitude for DNA concentrations. (E) Obtained signals for WT and MM target DNA using FO-SPR LCR assay (right panel). (F) FO-SPR multiplex PCR, which allows resolving the melting point of the two targets. 1. E. M. Cornett, E. A. Campbell, G. Gulenay, E. Peterson, N. Bhaskar and D. M. Kolpashchikov, Angew Chem Int Ed Engl, 2012, 51, 9075-9077. 2. C. J. Murray and J. A. Salomon, Proceedings of the National Academy of Sciences of the United States of America, 1998, 95, 13881-13886. 3. J. C. Cheng, C. L. Huang, C. C. Lin, C. C. Chen, Y. C. Chang, S. S. Chang and C. P. Tseng, Clinical chemistry, 2006, 52, 1997-2004. 4. S. Sando, H. Abe and E. T. Kool, Journal of the American Chemical Society, 2004, 126, 1081-1087. 5. Pollet, J., Delport, F., Janssen, K., Tran, T., Wouters, J., Verbiest, T., Lammertyn, J., Talanta, 2011, 83, 1436-1441. 6. D. T Tran, K. Knez, K. P. Janssen, J. Pollet, D. Spasic, J. Lammertyn, Biosensors & bioelectronics, 2012, 43, 245-251. 7. J, Pollet, K. Janssen, K. Knez, J.Lammertyn, Small, 2011, 7, 1003-1006 8. K. Knez, K. Janssen, D. Spasic, P. Declerck, L. Vanysacker, C. Denis, T. Tran, J. Lammertyn, Analytical Chemistry,2013, 85, 1734-1742.status: accepte

Farm residence and reproductive health among boys in rural South Africa.

BACKGROUND: Few studies have investigated reproductive health effects of contemporary agricultural pesticides in boys. OBJECTIVES: To determine the association between pesticide exposure and reproductive health of boys. METHODS: We conducted a cross-sectional study in rural South Africa of boys living on and off farms. The study included a questionnaire (demographics, general and reproductive health, phyto-estrogen intake, residential history, pesticide exposures, exposures during pregnancy); and a physical examination that included sexual maturity development ratings; testicular volume; height, weight, body mass index; and sex hormone concentrations. RESULTS: Among the 269 boys recruited into the study, 177 (65.8%) were categorized as farm (high pesticide exposures) and 98 (34.2%) as non-farm residents (lower pesticide exposures). Median ages of the two groups were 11.3 vs 12.0 years, respectively (