1,727,492 research outputs found
Droplet microfluidics based platform technology for continuous chemical sensing
No full textContinuous monitoring of biomarkers such as metabolites and hormones can be extremely useful in understanding physiological processes, for drug development, personalised therapy, and many other applications. In environmental analysis, continuous monitoring can help generate nutrient profiles necessary for identifying short-term events, cyclic variations, thereby has potential in expanding our knowledge of aquatic ecosystems and guiding us in taking appropriate remedial actions. Droplet microfluidics, which is the compartmentalization of liquids into nano-litre droplets, provides advantages such as small volumes of sample and reagents consumption, improved sensitivity and temporal resolution, short analysis time, high throughput and parallelisation compared with conventional laboratory assays. In recent times, continuous measurement of analytes in droplets indicates it as a potential new sensor platform in continuous biochemical analysis resulting in a new class of dataset for dynamics to be captured. The most up-to-date systems however address mostly homogenous, single step “mix-and-read” assays. This thesis presents the technology development of advanced droplet platforms for multiple step assays and autonomous analysis for continuous monitoring. Heterogeneous assays such as enzyme-linked immunosorbent assays (ELISA) are commonly used to measure antibodies, antigens, proteins and glycoproteins in biological samples, and with wide applications in disease diagnostics and treatment. ELISA normally requires multiple assay steps to be carried out with complex laboratory equipment. This thesis presents a miniaturised magnetic bead based platform, where a multitude of assays can be implemented using a versatile droplet generation method. The platform incorporates a phased peristaltic micropump and microfluidic chip for droplet generation, a pair of ‘electromagnetic tweezers’ for manipulation of magnetic beads and a spectrophotometer for colorimetric detection. This platform automates the entire process from sample collection to detection. As a proof-of-concept, the platform was used to carry out a heterogeneous assay and analysis of cortisol, a stress related hormone implicated in many diseases including dementia and Cushing’s syndrome. The prototype device is able to analyse sample containing free bioactive cortisol every 10 seconds and has an initial sample-to-signal time of 10 minutes. It is able to measure in the analytical range of 3.175-100 ng/mL with less variability than the well plate-based assay. Droplet microfluidics based platform technology for continuous chemical sensing W. Bhuiyan 3 Ammonium is one of the most important macronutrients and intermediates of the nitrogen cycle. Increased concentrations of ammonium could lead to nutrient enrichment, oxygen depletion and toxicity to aquatic ecosystems. This thesis reports the first of its kind droplet microfluidics ammonium sensor. The sensor miniaturizes the widely adopted indophenol blue assay and can perform high frequency measurement and long-term monitoring with low sample consumption. The sensor has been implemented for two separate applications, which displays its versatility, with the first measuring ammonium in river water samples. Another application of this sensor prototype has been in a sequential batch bioreactor enriched with PHA accumulating bacteria. The sensor can autonomously collect samples (via filter) from the bioreactor, produce droplet trains, regulate temperature for completion of reaction and provide colorimetric measurements (5 per minute) via an in-line spectrophotometer, thus removing human intervention. The preliminary data obtained over a four-day period demonstrates high resolution monitoring and reveals the fast-feeding behaviour of the bacteria. This kind of monitoring data could lead to feedback-controlled bioprocessing and the development of more efficient bioreactors. This thesis further presents the development of a multiple micropump platform for the robust generation of droplet trains, based on phased droplet generation technology. The multiple micropump platform can generate droplet trains containing different sizes, compositions, and sequences on-demand. This setup does not require any change in pump hardware for different assays, therefore making the platform truly versatile. The 3D printed micropumps are robust with low footprint and the platform can be taken to point of care. Latest design can generate droplets from 120 nL upwards with a coefficient of variation of less than 0.7%. Overall, the developments and research findings in this thesis paves the way for a new generation of droplet microfluidic sensors for continuous monitoring
Impact of western TV channels on viewers of Bangladesh
Full text linkThesis(Master) --KDI School:Master of Public Policy,2007masterpublishedby Md. Jalal abdul Naser Bhuiyan
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Rais Bhuiyan Interview
No full textThis interview is with Rais Bhuiyan, the founder of World Without Hate, who currently lives in Seattle, WA. Rais describes his youth in Bangladesh and his first career in the Bangladeshi military before coming to the US for school. He describes his experience of 9/11, after which he was the victim of Islamophobic gun violence, and then experienced food insecurity and medical debt due to his lack of medical insurance. He shares about his decision to try to save his attacker from death row with the help of Amnesty International and fellow humanitarians. Rais also talks about World Without Hate and its current projects. Content Warning: The following interview contains sensitive material. Please note that the interview includes description of graphic violence and hate crimes. These subjects will be discussed at 21:17 - 26:27 (in the transcript p. 5).Henry Luce FoundationReligious StudiesTranscript created with Otter.ai and edited by project assistant
Tri-tropic-level interactions between herbivorous insects and their natural enemies
No full textThe ultimate objective of crop protection is to achieve high yield. To do so many control measures, including the application of harmful pesticides are used to combat pest problems, but in most cases the role of the plant itself (first trophic level), and that of the parasitoids and predators (third trophic level) are ignored. Natural enemies have a tremendous influence on herbivores (second trophic level). In this project the role of each of these trophic levels was evaluated. Prior mechanical damage to the leaves of tomato (Lycopersicon esculentum) and oilseed rape (Brassica napus) deterred herbivore (Spodoptera littoralis) feeding and affected the distribution of grazing damage between upper and lower leaves of the plants. The percentage leaf area eaten by the larvae of S.littoralis in the wounded leaves of tomato and oilseed rape in the presence of the soil-dwelling insect predator (Pterostichus melanarius) was significantly lower than that of the unwounded leaves in the absence of predators. Rearing of the grain aphid Sitobion avenae on some spring wheat cultivars indicated that their numbers were higher at the early growth stages of the awnless cultivar Alexandria than on the awned cultivar Wembley. The distribution of aphids on different parts of wheat plants differed significantly between cultivar types. The fall-off rates of the grain aphids from the awned cultivars was also significantly higher than that on the awnless cultivars. These fall-off rates increased in the same cultivar when the awns were cut. Natural enemies of the grain aphid (e.g. predators and parasitoids) exerted an important influence in reducing aphid populations in both the laboratory and field experiments. The presence of Coccinella septempunctata and P.melanarius reduced the grain aphid population on different cultivars of wheat.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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