974 resultados para analytical techniques
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Bioscience subjects require a significant amount of training in laboratory techniques to produce highly skilled science graduates. Many techniques which are currently used in diagnostic, research and industrial laboratories require expensive equipment for single users; examples of which include next generation sequencing, quantitative PCR, mass spectrometry and other analytical techniques. The cost of the machines, reagents and limited access frequently preclude undergraduate students from using such cutting edge techniques. In addition to cost and availability, the time taken for analytical runs on equipment such as High Performance Liquid Chromatography (HPLC) does not necessarily fit with the limitations of timetabling. Understanding the theory underlying these techniques without the accompanying practical classes can be unexciting for students. One alternative from wet laboratory provision is to use virtual simulations of such practical which enable students to see the machines and interact with them to generate data. The Faculty of Science and Technology at the University of Westminster has provided all second and third year undergraduate students with iPads so that these students all have access to a mobile device to assist with learning. We have purchased licences from Labster to access a range of virtual laboratory simulations. These virtual laboratories are fully equipped and require student responses to multiple answer questions in order to progress through the experiment. In a pilot study to look at the feasibility of the Labster virtual laboratory simulations with the iPad devices; second year Biological Science students (n=36) worked through the Labster HPLC simulation on iPads. The virtual HPLC simulation enabled students to optimise the conditions for the separation of drugs. Answers to Multiple choice questions were necessary to progress through the simulation, these focussed on the underlying principles of the HPLC technique. Following the virtual laboratory simulation students went to a real HPLC in the analytical suite in order to separate of asprin, caffeine and paracetamol. In a survey 100% of students (n=36) in this cohort agreed that the Labster virtual simulation had helped them to understand HPLC. In free text responses one student commented that "The terminology is very clear and I enjoyed using Labster very much”. One member of staff commented that “there was a very good knowledge interaction with the virtual practical”.
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Mangroves are diverse group of trees, palms, shrubs, and ferns that share a common ability to live in waterlogged saline soils exposed to regular flooding, and are highly specialised plants which have developed unusual adaptations to the unique environmental conditions. They are sites of accumulation and preservation of both allochthonous and autochthonous organic matter owing to their strategic loction at the interface between land and sea and prevailing reducing environment. They are among the most productive ecosystems and are efficient carbon sinks with most of the carbon stored in sediments.Mangrove ecosystems play a significant role in global carbon cycle and hence the knowledge on the processes controlling the delivery of organic matter to coastal sediments, and how these signatures are preserved in the sediment is a prerequisite for the understanding of biogeochemical cycles. The evaluation of nature and sources of organic matter can be accomplished by the determination of biochemical constituents like carbohydrates, proteins and lipids. When characterised at molecular level, lipids provide valuable information about the sources of organic matter, even though they account only small fraction of organic matter. They are useful for the paleo-environmental reconstruction because of their low reactivity, high preservation potential and high source specificity relative to other organic class of compounds. The application of recent analytical techniques has produced a wealth of useful information but has also indicated the gaps in our knowledge on cycling of organic matter in the coastal ecosystems. The quantity and quality of organic matter preserved in sediments vary depending up on the nature of material delivered to the sediment and on the depositional environment. The input from both autochthonous and allochthonous sources sharpens the complexity of biogeochemistry of mangrove ecosystem and hence bulk sedimentary parameters are not completely successful in evaluating the sources of organic matter in mangrove sediments. An effective tool for the source characterisation of organic matter in coastal ecosystems is biomarker approach. Biomarkers are chemical "signatures" present in environmental samples whose structural information can be linked to its biological precursor. The usefulness of molecular biomarkers depends on high taxonomic specificity, potential for preservation, recalcitrant against geochemical changes, easily analysable in environmental samples and should have a limited number of well-defined sources.
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Nucleic acids play key roles in the storage and processing of genetic information, as well as in the regulation of cellular processes. Consequently, they represent attractive targets for drugs against gene-related diseases. On the other hand, synthetic oligonucleotide analogues have found application as chemotherapeutic agents targeting cellular DNA and RNA. The development of effective nucleic acid-based chemotherapeutic strategies requires adequate analytical techniques capable of providing detailed information about the nucleotide sequences, the presence of structural modifications, the formation of higher-order structures, as well as the interaction of nucleic acids with other cellular components and chemotherapeutic agents. Due to the impressive technical and methodological developments of the past years, tandem mass spectrometry has evolved to one of the most powerful tools supporting research related to nucleic acids. This review covers the literature of the past decade devoted to the tandem mass spectrometric investigation of nucleic acids, with the main focus on the fundamental mechanistic aspects governing the gas-phase dissociation of DNA, RNA, modified oligonucleotide analogues, and their adducts with metal ions. Additionally, recent findings on the elucidation of nucleic acid higher-order structures by tandem mass spectrometry are reviewed.
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The red deer (Cervus elaphus) is currently one of the most widespread and abundant wild ungulates in the Iberian Peninsula and is extremely important both ecologically, as a key species for the functioning of the ecosystems, and economically, as a major game species. In Iberia, red deer populations are subjected to different management systems that may affect the physical condition of the individuals, with further consequences for population dynamics. Studies investigating the effects of management practices and environmental conditions on the performance of red deer are still rare regarding Mediterranean ecosystems. Much of the knowledge concerning the ecology of red deer and the impact of management on its physical condition is based on studies conducted in northern and central regions of Europe, where climatological features and management practices differ from those observed in the Mediterranean areas of Iberia. Studies on a biogeographical scale can provide important insights into the relationships between species and a particular environment and contribute to the development of more targeted and appropriate management practices. The optimisation of sampling procedures and the fine-tuning of pre-existing analytical techniques are also fundamental to a more cost-effective monitoring and, therefore, are of enormous value to wildlife managers. In this context, the main aims of this thesis were: 1) to optimise the procedures used to assess the physical condition of red deer; and 2) to identify relevant management and environmental factors affecting the nutritional condition and stress physiology of red deer in the Mediterranean ecosystems of Iberia, as well as any potential interactions between those factors. Two studies with a methodological focus, presented in the first part of the thesis, demonstrated that the physical condition of red deer can be evaluated more simply, using more cost- and time-effective procedures than those traditionally used: i) it was shown that only one kidney and its associated fat is enough to assess nutritional condition in red deer; and ii) the feasibility of using near infrared spectroscopy to predict the concentrations of stress hormone metabolites was demonstrated using faeces of red deer for the first time. Subsequently, two large-scale observational studies, conducted in representative red deer populations found in Mediterranean Iberia, highlighted the importance of considering seasonal environmental variations and variables related to hunting management practices to better understand the nutritional and physiological ecology of red deer. High population densities had adverse effects on the nutritional condition of the deer and were associated with increased stress levels in natural populations without supplementary feeding. Massive hunting events involving the use of hounds were also identified as a potential source of chronic stress in red deer. The research presented in this thesis has clear implications regarding the management and monitoring of red deer populations in Mediterranean environments and is intended to help wildlife managers to implement more effective monitoring programmes and sustainable management practices.
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In the last thirty years, the emergence and progression of biologging technology has led to great advances in marine predator ecology. Large databases of location and dive observations from biologging devices have been compiled for an increasing number of diving predator species (such as pinnipeds, sea turtles, seabirds and cetaceans), enabling complex questions about animal activity budgets and habitat use to be addressed. Central to answering these questions is our ability to correctly identify and quantify the frequency of essential behaviours, such as foraging. Despite technological advances that have increased the quality and resolution of location and dive data, accurately interpreting behaviour from such data remains a challenge, and analytical methods are only beginning to unlock the full potential of existing datasets. This review evaluates both traditional and emerging methods and presents a starting platform of options for future studies of marine predator foraging ecology, particularly from location and two-dimensional (time-depth) dive data. We outline the different devices and data types available, discuss the limitations and advantages of commonly-used analytical techniques, and highlight key areas for future research. We focus our review on pinnipeds - one of the most studied taxa of marine predators - but offer insights that will be applicable to other air-breathing marine predator tracking studies. We highlight that traditionally-used methods for inferring foraging from location and dive data, such as first-passage time and dive shape analysis, have important caveats and limitations depending on the nature of the data and the research question. We suggest that more holistic statistical techniques, such as state-space models, which can synthesise multiple track, dive and environmental metrics whilst simultaneously accounting for measurement error, offer more robust alternatives. Finally, we identify a need for more research to elucidate the role of physical oceanography, device effects, study animal selection, and developmental stages in predator behaviour and data interpretation.
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Next-generation sequencing of complete genomes has given researchers unprecedented levels of information to study the multifaceted evolutionary changes that have shaped elite plant germplasm. In conjunction with population genetic analytical techniques and detailed online databases, we can more accurately capture the effects of domestication on entire biological pathways of agronomic importance. In this study, we explore the genetic diversity and signatures of selection in all predicted gene models of the storage starch synthesis pathway of Sorghum bicolor, utilizing a diversity panel containing lines categorized as either ‘Landraces’ or ‘Wild and Weedy’ genotypes. Amongst a total of 114 genes involved in starch synthesis, 71 had at least a single signal of purifying selection and 62 a signal of balancing selection and others a mix of both. This included key genes such as STARCH PHOSPHORYLASE 2 (SbPHO2, under balancing selection), PULLULANASE (SbPUL, under balancing selection) and ADP-glucose pyrophosphorylases (SHRUNKEN2, SbSH2 under purifying selection). Effectively, many genes within the primary starch synthesis pathway had a clear reduction in nucleotide diversity between the Landraces and wild and weedy lines indicating that the ancestral effects of domestication are still clearly identifiable. There was evidence of the positional rate variation within the well-characterized primary starch synthesis pathway of sorghum, particularly in the Landraces, whereby low evolutionary rates upstream and high rates downstream in the metabolic pathway were expected. This observation did not extend to the wild and weedy lines or the minor starch synthesis pathways.
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Nos dias de hoje a contaminação dos solos e águas subterrâneas com pesticidas através da agricultura tornou-se um problema. Problema este, considerado ainda maior nas áreas onde o abastecimento de água potável é quase totalmente à base de água subterrânea, causando deste modo risco para a saúde humana devido à exposição directa de possíveis resíduos de pesticidas na água potável. É certo que a persistência dos pesticidas no solo é importante para obter um bom controlo sob as ervas daninhas durante a sua época de crescimento, contudo o uso desses pesticidas contamina não só o solo como as águas superficiais. As questões acerca do uso de pesticidas na actualidade continuarão a persistir, uma vez que existem muitos factores e características inerentes a este processo que necessitam de ser abordadas e mais importante que isso estudadas, como por exemplo a sua degradação e toxicidade. Neste trabalho efectuou-se o encapsulamento de pesticidas em moléculas de β – ciclodextrina (β-CD). O que se pretende com este encapsulamento, é aumentar a hidrofilicidade do pesticida de forma a garantir que este persista o tempo suficiente permitindo um bom controlo das ervas daninhas, tendo sempre em conta as preocupações inerentes ao uso dos pesticidas, como por exemplo a dificuldade de biodegradação. O estudo centrou-se em torno de dois dos pesticidas mais utilizados em Portugal: MCPA e Bentazona. Estes herbicidas foram encapsulados individualmente na β-CD formando assim complexos, mais solúveis e eventualmente mais estáveis quimicamente garantindo uma redução dos efeitos dos pesticidas no meio ambiente. Este estudo foi dividido essencialmente em duas partes: a síntese e caracterização dos complexos pesticida-β-CD e posteriormente a avaliação da estabilidade química em solução aquosa e da solubilidade dos complexos formados. A utilização de diversas técnicas analíticas nomeadamente DSC, FTIR, Espectrofotometria de UV, HPLC e Electroquímica permitiram concluir que o pesticida MCPA encapsula pela acção da β-CD aquando do complexo formado em solução etanólica e numa proporção estequiométrica MCPA:β-CD de 1:2 respectivamente. Obteve-se para as várias soluções estudadas, todas elas com concentrações diferentes de β-CD, uma constante de estabilidade de 102,4. No caso da Bentazona, os resultados preliminares obtidos indiciam claramente a formação de um complexo com a β-CD para o complexo formado em solução etanólica.
Resumo:
Next-generation sequencing of complete genomes has given researchers unprecedented levels of information to study the multifaceted evolutionary changes that have shaped elite plant germplasm. In conjunction with population genetic analytical techniques and detailed online databases, we can more accurately capture the effects of domestication on entire biological pathways of agronomic importance. In this study, we explore the genetic diversity and signatures of selection in all predicted gene models of the storage starch synthesis pathway of Sorghum bicolor, utilizing a diversity panel containing lines categorized as either ‘Landraces’ or ‘Wild and Weedy’ genotypes. Amongst a total of 114 genes involved in starch synthesis, 71 had at least a single signal of purifying selection and 62 a signal of balancing selection and others a mix of both. This included key genes such as STARCH PHOSPHORYLASE 2 (SbPHO2, under balancing selection), PULLULANASE (SbPUL, under balancing selection) and ADP-glucose pyrophosphorylases (SHRUNKEN2, SbSH2 under purifying selection). Effectively, many genes within the primary starch synthesis pathway had a clear reduction in nucleotide diversity between the Landraces and wild and weedy lines indicating that the ancestral effects of domestication are still clearly identifiable. There was evidence of the positional rate variation within the well-characterized primary starch synthesis pathway of sorghum, particularly in the Landraces, whereby low evolutionary rates upstream and high rates downstream in the metabolic pathway were expected. This observation did not extend to the wild and weedy lines or the minor starch synthesis pathways.
Resumo:
O trabalho apresentado nesta tese focou-se no estudo do amido, nomeadamente na avaliação das características físico-químicas, morfológicas, térmicas e reológicas do amido de seis variedades de milho crioulo, preservadas no estado de Santa Catarina (Brasil), com o intuito de contribuir para a valorização e preservação de variedades locais que são cultivadas em sistemas de produção orgânica, também conhecidas como variedades crioulas. Estas sementes são importantes quer para a preservação da biodiversidade quer para os pequenos produtores que as conservam e as produzem fazendo uso de uma agricultura sustentável e independente comercialmente. Para além da caracterização dos amidos crioulos foram também analisadas as alterações que ocorrem nos processos de gelatinização e retrogradação do amido quando realizados na presença de outros biopolímeros, nomeadamente a quitosana e galactomananas. No Capítulo I é apresentada uma breve revisão do conhecimento científico sobre o amido e sobre a quitosana e galactomananas, os outros biopolímeros utilizados. Igualmente é feita uma sucinta abordagem sobre as principais técnicas analíticas que foram utilizadas: reologia fundamental, calorimetria diferencial de varrimento, microscopia eletrónica de varrimento e espectroscopia de infravermelho médio. No capítulo II apresenta-se o isolamento dos amidos das seis variedades de milho crioulo e a sua caracterização junto com um amido comercial usado como modelo de comparação. Os amidos apresentaram genericamente características físicoquímicas semelhantes e o amido extraído das variedades crioulas MT e MPA 01 apresentaram menor temperatura de gelatinização e maior percentagem de retrogradação, respetivamente. Os efeitos da adição da quitosana e de três galactomananas (goma guar, goma de alfarroba e goma cassia) em sistemas mistos com o amido são analisados nos Capítulos III e IV respetivamente. A adição dos biopolímeros aos amidos resultou no aumento das temperaturas de gelatinização, na alteração da retrogradação do amido pelas galactomananas e na alteração das propriedades viscoeláticas dos géis formados. Os dados de infravermelho esclareceram que nos sistemas com quitosana, o amido formou complexos com o ácido acético usado para dissolver a quitosana e que esta por sua vez formou acetato de quitosana. O comportamento durante a gelatinização do amido comercial quando comparado com o amido do milho crioulo MPA na sua interação com as galactomananas é diferenciado.
Resumo:
Evaluation of the quality of the environment is essential for human wellness as pollutants in trace amounts can cause serious health problem. Nitrosamines are a group of compounds that are considered potential carcinogens and can be found in drinking water (as disinfection byproducts), foods, beverages and cosmetics. To monitor the level of these compounds to minimize daily intakes, fast and reliable analytical techniques are required. As these compounds are relatively highly polar, extraction and enrichment from environmental samples (aqueous) are challenging. Also, the trend of analytical techniques toward the reduction of sample size and minimization of organic solvent use demands new methods of analysis. In light of fulfilling these requirements, a new method of online preconcentration tailored to an electrokinetic chromatography is introduced. In this method, electroosmotic flow (EOF) was suppressed to increase the interaction time between analyte and micellar phase, therefore the only force to mobilize the neutral analytes is the interaction of analyte with moving micelles. In absence of EOF, polarity of applied potential was switched (negative or positive) to force (anionic or cationic) micelles to move toward the detector. To avoid the excessive band broadening due to longer analysis time caused by slow moving micelles, auxiliary pressure was introduced to boost the micelle movement toward the detector using an in house designed and built apparatus. Applying the external auxiliary pressure significantly reduced the analysis times without compromising separation efficiency. Parameters, such as type of surfactants, composition of background electrolyte (BGE), type of capillary, matrix effect, organic modifiers, etc., were evaluated in optimization of the method. The enrichment factors for targeted analytes were impressive, particularly; cationic surfactants were shown to be suitable for analysis of nitrosamines due to their ability to act as hydrogen bond donors. Ammonium perfluorooctanoate (APFO) also showed remarkable results in term of peak shapes and number of theoretical plates. It was shown that the separation results were best when a high conductivity sample was paired with a BGE of lower conductivity. Using higher surfactant concentrations (up to 200 mM SDS) than usual (50 mM SDS) for micellar electrokinetic chromatography (MEKC) improved the sweeping. A new method for micro-extraction and enrichment of highly polar neutral analytes (N-Nitrosamines in particular) based on three-phase drop micro-extraction was introduced and its performance studied. In this method, a new device using some easy-to-find components was fabricated and its operation and application demonstrated. Compared to conventional extraction methods (liquid-liquid extraction), consumption of organic solvents and operation times were significantly lower.
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Reverse osmosis (RO) brine produced at a full-scale coal seam gas (CSG) water treatment facility was characterized with spectroscopic and other analytical techniques. A number of potential scalants including silica, calcium, magnesium, sulphates and carbonates, all of which were present in dissolved and non-dissolved forms, were characterized. The presence of spherical particles with a size range of 10-1000nm and aggregates of 1-10 microns was confirmed by transmission electron microscopy (TEM). Those particulates contained the following metals in decreasing order: K, Si, Sr, Ca, B, Ba, Mg, P, and S. Characterization showed that nearly one-third of the total silicon in the brine was present in the particulates. Further, analysis of the RO brine suggested supersaturation and precipitation of metal carbonates and sulphates during the RO process should take place and could be responsible for subsequently capturing silica in the solid phase. However, the precipitation of crystalline carbonates and sulphates are complex. X-ray diffraction analysis did not confirm the presence of common calcium carbonates or sulphates but instead showed the presence of a suite of complex minerals, to which amorphous silica and/or silica rich compounds could have adhered. A filtration study showed that majority of the siliceous particles were less than 220nm in size, but could still be potentially captured using a low molecular weight ultrafiltration membrane. © 2015 Elsevier Ltd.
Resumo:
A popularidade das séries televisivas que abordam as Ciências Forenses (CSI 1 Mentes Criminosas, Casos Arquivados...) permite construir actividades que envolvem os alunos numa exploração científica de modo a que dominem os conceitos e apreciem a natureza da Ciência. Estes recursos educativos aplicam uma abordagem Ciência Tecnologia-Sociedade -Pensamento Crítico (CTS-PC) e podem ser explorados segundo uma metodologia de Aprendizagem Baseada na Resolução de Problemas (ABRP). Neste trabalho são propostas actividades laboratoriais, a decorrer no contexto formal das aulas da disciplina de Física e Química A (FQ·A), utilizando sensores e a calculadora gráfica. Num contexto não-formal, e baseadas nas técnicas analíticas utilizadas em Ciências Forenses, foram desenvolvidas actividades para um Clube de Ciência ou Laboratórios Abertos, complementadas por um blogue (CSI-Mafra). Estes recursos foram posteriormente partilhados com outros professores de Física e Química, numa acção de formação, proposta pela autora, e cujo objectivo principal foi a diversificação das estratégias de ensino e aprendizagem. O entusiasmo dos alunos na realização das tarefas propostas e os resultados nos questionários de grau de satisfação e de opinião, aplicados a alunos e professores, sugere que as actividades desenvolvidas podem contribuir na motivação dos alunos para o estudo da Física e da Química e promover a literacia científica da comunidade escolar. ABSTRACT; The high popularity between teenagers of the television series that have Forensic Sciences and Criminal lnvestigations as central theme, such as CSI, Dexter, Criminal Minds and Cold Case, can be used to develop learning activities that involves the students into a scientific exploration which aim is leading the students to learn Chemistry and Physics with pleasure, motivation and curiosity. The educational resources developed in this thesis make use of the strategy Science-Technology-Society-Critical Thinking (STS-CP) and can be exploited according the teaching methodology Problem Based Learning (PBL). ln this work we propose a number of laboratory activities that can be used on the classes of the High School course Physic and Chemistry A (FQ-A) and a different set of activities to be used in a non-formal teaching environment, which are based on the analytical techniques used in Forensic Sciences. The non-formal activities were developed as part of the activities of a Science Club and complemented with an interactive blog. The teaching resources developed by us were also used in a professional training course to physics and chemistry teachers aimed to teach how to introduce new teaching learning strategies. The enthusiasm of the students shown during the activities and the extremely positive results of the questionnaires, applied to students and teachers after the activities, clearly indicates that the learning resources developed in this thesis contribute to the student's motivation to learn Physic and Chemistry and to promote the scientific Iiteracy of the scholar community.
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The sediments of Bear Creek near Baltimore, Maryland demonstrate substantial toxicity to benthic organisms, and contain a complex mixture of organic and inorganic contaminants. The present study maps the spatial extent and depth profile of toxicity and contamination in Bear Creek, and explores correlations between heavy metals, organic contaminants, and toxic responses. Two novel analytical techniques – handheld XRF and an antibody-based PAH biosensor – were applied to samples from the site to quantify total metals and total PAHs in sediments. By comprehensively assessing toxicity in Bear Creek, the present study provides data to inform future risk assessments and management decisions relating for the site, while demonstrating the benefits of applying joint biological assays and chemical assessment methods to sediments with complex contaminant mixtures.
Resumo:
Background: Analytical techniques such as methylation-sensitive amplification polymorphism and high-performance liquid chromatography were used to detect variation in DNA methylation of mature Chrysanthemum leaves during the floral transition induced by short-day (SD) treatment. Results: For both early- and late-flowering cultivars, the time from the date of planting to the appearance of the capitulum bud and early blooming were significantly shorter than those of the control. The capitulum development of the early-flowering cultivar was significantly accelerated compared to the control, unlike the late-flowering cultivar. The DNA methylation percentage of leaves was significantly altered during flower development. For the early-flowering cultivar, DNA methylation was 42.2–51.3% before the capitulum bud appeared and 30.5–44.5% after. The respective DNA methylation percentages for the late-flowering cultivar were 43.5–56% and 37.2–44.9%. Conclusions: The DNA methylation percentage of Chrysanthemum leaves decreased significantly during floral development. The decline in DNA methylation was elevated in the early-flowering cultivar compared with the late-flowering cultivar.
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The growing concern with the solid residues management, observed in the last decade, due to its huge amount and impact, has motivated the search for recycling processes, where these residues can be reprocessed to generate new products, enlarging the cycle of materials and energy which are present. Among the polymeric residues, there is poly (ethylene terephthalate) (PET). PET is used in food packaging, preferably in the bottling of carbonated beverages. The reintegration of post-consumer PET in half can be considered a productive action mitigation of environmental impacts caused by these wastes and it is done through the preparation of several different products at the origin, i.e. food packaging, with recycling rates increasing to each year. This work focused on the development and characterization mechanical, thermal, thermo-mechanical, dynamic mechanical thermal and morphology of the pure recycled PET and recycled PET composites with glass flakes in the weight fraction of 5%, 10% and 20% processed in a single screw extruder, using the following analytical techniques: thermogravimetry (TG), differential scanning calorimetry (DSC), tensile, Izod impact, Rockwell hardness, Vicat softening temperature, melt flow rate, burn rate, dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). The results of thermal analysis and mechanical properties leading to a positive evaluation, because in the thermograms the addition of glass flakes showed increasing behavior in the initial temperatures of thermal decomposition and melting crystalline, Furthermore was observed growing behavior in the mechanical performance of polymer composites, whose morphological structure was observed by SEM, verifying a good distribution of glass flakes, showing difference orientation in the center and in the surface layer of test body of composites with 10 and 20% of glass flakes. The results of DMTA Tg values of the composites obtained from the peak of tan ä showed little reductions due to poor interfacial adhesion between PET and recycled glass flakes.