149 research outputs found
Highly sensitive detection of Campylobacter spp. In chicken meat using a silica nanoparticle enhanced dot blot DNA biosensor
No full textPaper-based DNA biosensors are powerful tools in point-of-care diagnostics since they are affordable, portable, user-friendly, rapid and robust. However, their sensitivity is not always as high as required to enable DNA quantification. To improve the response of standard dot blots, we have applied a new enhancement strategy that increases the sensitivity of assays based on the use of biotinylated silica-nanoparticles (biotin-Si-NPs). After immobilization of a genomic Campylobacter DNA onto a paper membrane, and addition of a biotinylated-DNA detection probe, hybridization was evidenced using streptavidin-conjugated to horseradish peroxidase (HRP) in the presence of luminol and H2O2. Replacement of the single biotin by the biotin-Si-NPs boosted on average a 30 fold chemiluminescent read-out of the biosensor. Characterization of biotin-Si-NPs onto a paper with immobilized DNA was done using a scanning electron microscope. A limit of detection of 3 pg/μL of DNA, similar to the available qPCR kits, is achieved, but it is cheaper, easier and avoids inhibition of DNA polymerase by molecules from the food matrices. We demonstrated that the new dot blot coupled to biotin-Si-NPs successfully detected Campylobacter from naturally contaminated chicken meat, without needing a PCR step. Hence, such an enhanced dot blot paves the path to the development of a portable and multiplex paper based platform for point-of-care screening of chicken carcasses for Campylobacter
Static and dynamic aspects of coupling between creep behavior and oxidation on MC2 single crystal superalloy at 1150 °C
Get PDFCreep tests were performed on thin wall specimens made of MC2 single crystal superalloy at 1150 °C and under controlled atmosphere. The results highlight the deleterious oxidation effect on creep properties. The assumption that oxidation leads to a non-load-bearing affected zone is insufficient to explain the difference in creep rate that was noticed between tests performed under synthetic air and under hydrogenated argon, and cannot explain the decrease of the strain rate during the tests that were carried out with a change of atmosphere from synthetic air to hydrogenated argon. On the other hand, these experimental results are consistent with vacancy injection due to partial cationic oxidation, which accelerates the creep rate by promoting creep mechanisms controlled by diffusion. The anionic protective alumina scale formed under hydrogenated argon prevents this vacancy flux
The Debate on Influencing Doctors’ Decisions: Are Drug Characteristics the Missing Link?
Get PDFDecision-making by physicians on patients’ treatment has come under increased public scrutiny. In fact, there is a fair amount of debate on the effects of marketing actions of pharmaceutical firms toward physicians and their impact on physician prescription behavior. While some scholars find a strong and positive influence of marketing actions, some find only moderate effects, and others even find negative effects. Debate is also mounting on the role of other influencers (such as patient requests) in physician decision-making, both on prescriptions and sample-dispensing. The authors argue that one factor that may tip the balance in this debate is the role of drug characteristics, such as a drug’s effectiveness and a drug’s side effects. Using a unique data set, they show that marketing efforts – operationalized as detailing and symposium meetings of firms to physicians – and patient requests do affect physician decision-making differentially across brands. Moreover they find that the responsiveness of physicians’ decision-making to marketing efforts and patient requests depends upon the drug’s effectiveness and side effects. The paper presents clear guidelines for public policy and managerial practice and envisions that the study of the role of drug characteristics – such as effectiveness and side effects – may lead to valuable insights in this surging public debate.public policy;side effects;sampling;Physician decision-making;drug effectiveness;drug prescription;marketing efforts;patient requests;pharmaceuticals;sample-dispensing
Universal Domains for Sequential Computation
No full textThis work was also published as a Rice University thesis/dissertation: http://hdl.handle.net/1911/16836Classical recursion theory asserts that all conventional programming languages are equally expressive because they can define all partial recursive functions over the natural numbers. However, most real programming languages support some form of higher-order data such as potentially infinite streams, lazy trees, and functions. Since these objects do not have finite canonical representations, computations over these objects cannot be accurately modeled as ordinary computations over the natural numbers. In my thesis, I develop a theory of higher order computability based on a new formulation of domain theory. This new formulation interprets elements of any data domain as lazy trees. Like classical domain theory, it provides a universal domain T and a universal language KL. A rich class of domains called observably sequential domains can be specified in T with functions definable in KL. Such an embedding of a data domain enables the operations on the domain to be defined in the universal language. Unlike embeddings in classical domain theory, embeddings in T retain enough computational information to separate terminating and non-terminating computations. An important practical consequence of this embedding is the fact that the definitions of program operations are effective, implying that denotational language definitions expressed in this framework are effective interpreters
Universal domains for sequential computation
No full textClassical recursion theory asserts that all conventional programming languages are equally expressive because they can define all partial recursive functions over the natural numbers. However, most real programming languages support some form of higher-order data such as potentially infinite streams, lazy trees, and functions. Since these objects do not have finite canonical representations, computations over these objects cannot be accurately modeled as ordinary computations over the natural numbers.
In my thesis, I develop a theory of higher order computability based on a new formulation of domain theory. This new formulation interprets elements of any data domain as lazy trees. Like classical domain theory, it provides a universal domain T and a universal language KL. A rich class of domains called observably sequential domains can be specified in T with functions definable in KL. Such an embedding of a data domain enables the operations on the domain to be defined in the universal language. Unlike embeddings in classical domain theory, embeddings in T retain enough computational information to separate terminating and non-terminating computations. An important practical consequence of this embedding is the fact that the definitions of program operations are effective, implying that denotational language definitions expressed in this framework are effective interpreters
Changes in microbial profile during traditional idli batter fermentation: Isolation and identification of predominant lactic acid bacteria
No full textAmino acids responsible for the novel progesterone C-21 hydroxylase activity in a chimera of cytochrome P-450 2C2/2C1
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Reason: ETDs are only available to UIUC Users without author permissionA hybrid cytochrome P450, C2MstC1, with 306 amino terminal P450 2C2 amino acids and 184 carboxy-terminal P450 2C1 amino acids acquires a novel progesterone C-21 hydroxylase activity which is absent in the parent enzymes. Extension of P450 2C2 sequence to residue 383 (C2StyC1), reduced progesterone hydroxylase activity to 5% of that of C2MstC1, while further extension to residue 411 (C2BalC1), increased activity back to about 30%. Only 28 carboxy-terminal amino acids from P450 2C1 (C2HincC1) were required for activity 40% of that of C2MstC1. In C2StyC1, substitution of P450 2C1 amino acids at positions 368, 369, and 374 increased progesterone hydroxylase activity greater than that in C2MstC1. In C2BalC1 however, additional substitutions of P450 2C1 amino acids at positions 386 and 388 were required to obtain activities greater than that of C2MstC1. These results suggest that an interaction occurs between residues 368, 369 or 374 and residues 386 or 388 which affects the binding of progesterone or its accessibility to the active site of the enzyme. These five changes confer progesterone hydroxylase activity to P450 2C2 but only about 10% of that of C2MstC1. Mutational analysis of the 28 carboxy-terminal amino acids of P450 2C2 revealed that valine 473 was an additional requirement for an increase in the progesterone C-21 hydroxylase activity, comparable to that of C2MstC1. In contrast to the progesterone hydroxylase activity, the lauric acid hydroxylase activities of all chimeras and mutant cytochromes P450 differed by 2-fold or less demonstrating that the changes in progesterone activities reflected altered interactions with the substrate rather than general effects on enzyme activity or expression of functional protein. An exception was the valine 477 glycine mutation, in which activity for both substrates was reduced and the regiospecificity of hydroxylation was altered. Molecular modeling of the substrate binding pockets of P450 2C2 and its mutant consisting of P450 2C1 residues at the above mentioned positions, based on the three dimensional structure of the bacterial cytochrome P450cam suggest that the P450 2C1 amino acids facilitate progesterone binding by providing a larger, more hydrophobic substrate binding pocket and/or through interactions with the heme.Made available in DSpace on 2011-05-07T12:43:56Z (GMT). No. of bitstreams: 2
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Study of bare, sintered, coated and inverted opals for photonic band gap properties at visible wavelengths
No full textWe have performed calculations using the Transfer Matrix method to study the photonic, band gap properties of bare opals of different diameters, different thicknesses, sintered opals with filling fractions varying between 0.74 and 1.00, partial and complete coating with semiconducting GaN and lastly, inverted opals. Two prominent directions [100] and [111] have been analyzed. Sintering improves the gap and shifts the energy range of its occurrence, while partial coating gives a better bandgap than complete coating. Inverted opals with semiconductor background shows a gap with transmission decreasing to much lower values, as expected due to an improvement in dielectric contrast
Helicobacter pylori resists phagocytosis by macrophages: quantitative assessment by confocal microscopy and fluorescence-activated cell sorting
Get PDFExpeditious microwave-assisted synthesis and bio-evaluation of novel bis (trifluoromethyl) phenyl-triazole-pyridine hybrid analogues by the click chemistry approach
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