2,368 research outputs found
Carbon nanoparticles in lateral flow methods to detect genes encoding virulence factors of Shiga toxin-producing Escherichia coli
No full textThe use of carbon nanoparticles is shown for the detection and identification of different Shiga toxin-producing Escherichia coli virulence factors (vt1, vt2, eae and ehxA) and a 16S control (specific for E. coli) based on the use of lateral flow strips (nucleic acid lateral flow immunoassay, NALFIA). Prior to the detection with NALFIA, a rapid amplification method with tagged primers was applied. In the evaluation of the optimised NALFIA strips, no cross-reactivity was found for any of the antibodies used. The limit of detection was higher than for quantitative PCR (q-PCR), in most cases between 10 4 and 10 5 colony forming units/mL or 0.1-0.9 ng/¿L DNA. NALFIA strips were applied to 48 isolates from cattle faeces, and results were compared to those achieved by q-PCR. E. coli virulence factors identified by NALFIA were in very good agreement with those observed in q-PCR, showing in most cases sensitivity and specificity values of 1.0 and an almost perfect agreement between both methods (kappa coefficient larger than 0.9). The results demonstrate that the screening method developed is reliable, cost-effective and user-friendly, and that the procedure is fast as the total time required is <1 h, which includes amplification. © 2010 The Author(s).This work was partially supported by the Generalitat Valenciana (BEST/2009/026), the Universidad Politecnica de Valencia (PAID-00-09-2837), and by the Dutch Ministry of Agriculture, Nature and Food Quality (KennisBasis 6 programme). The authors would like to thank Dr. Eva Moller Nielsen at the Danish Veterinary Institute (Copenhagen, Denmark) for providing E. coli control strains and Dr. Lutz Geue (Friedrich-Loeffler-Institut, Wusterhausen, Germany) and Dr. Dorte Dopfer (School of Veterinary Medicine, University of Wisconsin, Madison, WI, USA) for field isolates.Noguera Murray, PS.; Posthuma-Trumpie, G.; Van Tuil, M.; Van Der Wal, F.; De Boer, A.; Moers, A.; Van Amerongen, A. (2011). Carbon nanoparticles in lateral flow methods to detect genes encoding virulence factors of Shiga toxin-producing Escherichia coli. 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Lateral flow (immuno)assay: its strengths, weaknesses, opportunities and threats. A literature survey
No full textLateral flow (immuno)assays are currently used for qualitative, semiquantitative and to some extent quantitative monitoring in resource-poor or non-laboratory environments. Applications include tests on pathogens, drugs, hormones and metabolites in biomedical, phytosanitary, veterinary, feed/food and environmental settings. We describe principles of current formats, applications, limitations and perspectives for quantitative monitoring. We illustrate the potentials and limitations of analysis with lateral flow (immuno)assays using a literature survey and a SWOT analysis (acronym for 'strengths, weaknesses, opportunities, threats'). Articles referred to in this survey were searched for on MEDLINE, Scopus and in references of reviewed papers. Search terms included 'immunochromatography', 'sol particle immunoassay', 'lateral flow immunoassay' and 'dipstick assay'
Toward a dry reagent immunoassay of progesterone in bovine milk
No full textThis thesis is aimed at the development of a dry reagent immunoassay of progesterone in cow's milk. Progesterone is a steroid hormone and regulates ovulation in female mammals. The concentration of progesterone in blood and in milk is in accordance with the reproductive cycle of the individual female. When items related to reproduction need to be addressed, an assay of progesterone is often the method of choice. In the dairy industry, progesterone tests in bovine milk are used as a non-invasive method for determination of the reproductive status of the cow. To minimize user handling, the format of a dry reagent assay is chosen. This format can be automated, gives results fast, and investments and disposables are low-cost. These requirements are obligatory as preferably these test are performed at every milking.
The Greece of the Greeks: By G.A. Perdicaris, A.M. Late Consul of the United Stats at Athens, in two volumes. New-York: Paine and Burgess, 1845.
No full textIntroduction: (introductory) by the authorDedication: by the author to those who are interested in the Fate of GreecePagination: PP21+293P, PP8+300P+1PPVolumes: 2Edition:1stText Genre:Prose / Journa
Lateral flow assays
No full textA simple version of immunochemical-based methods is the Lateral Flow Assay (LFA). It is a dry chemistry technique (reagents are included); the fluid from the sample runs through a porous membrane (often nitrocellulose) by capillary force. Typically the membrane is cut as a strip of 0.5*5 cm. In most cases, coloured colloidal nanoparticles serve as a label. The method is very user-friendly, as only the liquid sample has to be added. Results are available within 5-15 minutes and after evaluation of the signal by visual inspection, a desktop scanner with image analysis software, or a dedicated reader, the used strips can be discarded. With respect to the specificity, sensitivity and efficiency the technology is heavily dependent on the recognition of the analyte by the corresponding antibody. Lateral flow assays are mainly used for qualitative or semi-quantitative detection of (un)wanted substances in the biomatrix or the environment. The technology requires a minimum of resources and skills of the operator. Many applications already reached the market. We will address here a bit of history and the general principle of the technique, and critical parameters influencing the performance of the assay. Amongst those are the material of the membrane, the sample pad, the conjugate pad and the absorbent pad, properties of currently used labels, formats of the tests and properties of good recognition elements. Processing of the results will be discussed as well
Lateral flow assays
No full textA simple version of immunochemical-based methods is the Lateral Flow Assay (LFA). It is a dry chemistry technique (reagents are included); the fluid from the sample runs through a porous membrane (often nitrocellulose) by capillary force. Typically the membrane is cut as a strip of 0.5*5 cm. In most cases, coloured colloidal nanoparticles serve as a label. The method is very user-friendly, as only the liquid sample has to be added. Results are available within 5-15 minutes and after evaluation of the signal by visual inspection, a desktop scanner with image analysis software, or a dedicated reader, the used strips can be discarded. With respect to the specificity, sensitivity and efficiency the technology is heavily dependent on the recognition of the analyte by the corresponding antibody. Lateral flow assays are mainly used for qualitative or semi-quantitative detection of (un)wanted substances in the biomatrix or the environment. The technology requires a minimum of resources and skills of the operator. Many applications already reached the market. We will address here a bit of history and the general principle of the technique, and critical parameters influencing the performance of the assay. Amongst those are the material of the membrane, the sample pad, the conjugate pad and the absorbent pad, properties of currently used labels, formats of the tests and properties of good recognition elements. Processing of the results will be discussed as well
Ultraslow microdialysis and microfiltration for in-line, on-line and off-line monitoring
No full textIn medicine and biotechnology, close monitoring of molecular processes might assist to optimise therapeutic interventions and production of biochemicals, respectively. Here, we summarize the current status of two automatic and continuous sampling technologies, microdialysis and microfiltration, which facilitate both in vivo and in vitro monitoring of nearly any analyte, because they can be combined easily with many analytical techniques. Conventional microdialysis and microfiltration, which require collecting relatively large samples, are however often impractical and semi-quantitative; hence, we focus on ultraslow sampling to circumvent such limitations. Ultraslow microdialysis and microfiltration already have been used successfully for quantitative pharmacokinetics, glucose metabolism (e.g. of the brain), cytokines and proteomics (e.g. tumour secretomes), both in vivo and in vitro
Automatic sign language recognition inspired by human sign perception
No full textAutomatic sign language recognition is a relatively new field of research (since ca. 1990). Its objectives are to automatically analyze sign language utterances. There are several issues within the research area that merit investigation: how to capture the utterances (cameras, magnetic sensors, instrumented gloves), how to extract interesting information from the captured data, and how to classify signs or sentences automatically using the extracted information. These issues are of an immediate and basic nature, and must be solved before any automatic recognition of sign language can be achieved. But other issues, pertaining to the nature of sign language and human recognition, are no less interesting: which elements of a sign are important for the meaning of an utterance? How do consecutive signs influence one another? Why are certain types of variation unimportant while others change the meaning of the sign? Automatic sign language recognition has, until recently, mostly focused on the first set of issues. In this thesis, we attempt to integrate knowledge about sign languages and human sign recognition into the automatic sign recognition process. Research on the (psycho)linguistics of sign languages is itself quite young (since ca. 1960), and many questions as yet unanswered. For this reason, we conduct our own studies of human sign language recognition. The knowledge gained from these experiments is applied in an existing automatic sign language recognition system. The thesis is divided into two parts: the first part describes the experiments conducted with human signers, the second part describes experiments investigating the possibilities of integrating such knowledge in the automatic recognizer. This recognizer is meant to be used in an interactive environment for young children to practice sign language vocabulary. For this reason, it is vision-based (which is unobtrusive), and only handles isolated signs. The experiments in part I of the thesis investigate the information content of various sign elements: fragments of a sign in time (chapter 2), and the sign aspects handshape and hand orientation (chapter 3). In time, the central phase of a sign is the most informative one, equally informative to the entire sign. Recognition based on other phases is also possible to a certain extent, and the transition from the preparation phase to the central phase appears to be a salient moment. As for the aspects, the aspect handshape proves more useful for recognition than hand orientation. Chapter 4 gives an overview of the human recognition research and discusses possibilities for application. In part II, the possibilities of utilizing the results of part I in the recognition system are investigated. Chapter 5 describes the addition of the handshape feature to the system (which chapter 3 showed to be the most interesting feature to add). Adding handshape gives a small improvement in the recognition performance. In chapter 6, the salience of the sign fragments used in chapter 2 for the automatic recognizer is investigated. The central phase proves to be the most informative one, as it was for human signers. Chapter 7 describes experiments in which a small set of frames is used to represent a sign. The results show a deterioration in recognition performance. Strict demands on the correctness of the remaining frames are probably partly responsible for the performance decrease. In conclusion, we can say that applying human knowledge in automatic sign language recognition is a complex task. Conclusions about human sign recognition do not necessarily hold for the automatic recognizer as well. The most important obstacles for utilizing information successfully seem to be: 1) data acquisition: computer vision is not as accomplished as human observers in capturing the complex, dynamic hand and face motions that form sign language. This means that information that is present in a sign movement for a human being may not be (correctly) observed by an automatic vision analysis system. Thus, the data that humans work with is not necessarily identical to the data the recognizer works with, and this may cause techniques that are successful for human signers to fail in the automatic system. And 2) differences in basic system architecture. Research into human sign recognition is still ongoing, there is no clear model of human sign recognition yet. This makes it more difficult to translate observations from human sign recognition to the automatic recognizer: human signers may use techniques that are not compatible with the current architecture of the recognizer. For example: human signers may process aspects independently. If the recognition system processes all data as a single stream, then such a technique cannot be implemented. A more thorough understanding of human sign recognition, more sophisticated computer vision techniques, and a close co-operation between the fields of automatic sign language recognition and human sign perception, seems the best way to overcome these obstacles.MediamaticsElectrical Engineering, Mathematics and Computer Scienc
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