467 research outputs found

    Roundtable: Antecedents of 2019: 1949

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    Roundtable: Antecedents of 2019: 1969

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    Recent Decisions

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    Comments on recent decisions by Joseph P. Summers, William J. Luff, Jr., Thomas Kavadas, Jr., Joseph A. Marino, James J. Harrington, Cornelius J. Collins, George P. McAndrews, Richard M. Bies, George A. Pelletier, Jr., Thomas M. Clusserath, and Rocco L. Puntureri

    Integrated optical Mach-Zehnder interferometer as simazine immunoprobe

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    Immunoassay has become a versatile tool in several fields of analytical chemistry. We describe the characterization and the application of different integrated optical channel waveguide Mach-Zehnder interferometers (MZIs) as label-free immunoprobes. The performance of the classical MZI is compared with that of a modified structure which incorporates a 3x3 coupler. Characterization of the devices demonstrates a dramatic improvement gained by using the 3x3 coupler. Two main advantages are achieved by the modified device. First, the possibility of referencing the output signal allows the elimination of signal fluctuations due to coupling and light-source instabilities. An increase of the signal-to-noise ratio by a factor of up to 10 is achieved. Secondly, the phase shift between the three outputs allows unambiguous detection with optimum sensitivity. For the detection of the herbicide simazine, the functional properties of the transducer surface are optimized by an appropriate chemical modification. Using this improved device, a simazine immunoassay has been carried out with a test midpoint of 0.3 ppb and a detection limit of approximately 0.1 ppb. The excellent performance, established manufacturing techniques and the potential for simplification and parallelization make the device attractive for further development

    CD1d expression demarcates CDX4+ hemogenic mesoderm with definitive hematopoietic potential

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    To achieve efficient, reproducible differentiation of human pluripotent stem cells (hPSCs) towards specific hematopoietic cell-types, a comprehensive understanding of the necessary cell signaling and developmental trajectories involved is required. Previous studies have identified the mesodermal progenitors of extra-embryonic-like and intra-embryonic-like hemogenic endothelium (HE), via stage-specific WNT and ACTIVIN/NODAL, with GYPA/GYPB (CD235a/b) expression serving as a positive selection marker for mesoderm harboring exclusively extra-embryonic-like hemogenic potential. However, a positive mesodermal cell-surface marker with exclusively intra-embryonic-like hemogenic potential has not been identified. Recently, we reported that early mesodermal expression of CDX4 critically regulates definitive HE specification, suggesting that CDX4 may act in a cell-autonomous manner during hematopoietic development. To identify CDX4+ mesoderm, we performed single cell (sc)RNAseq on hPSC-derived mesodermal cultures, revealing CDX

    Between overt and covert research: concealment and disclosure in an ethnographic study of commercial hospitality

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    This article examines the ways in which problems of concealment emerged in an ethnographic study of a suburban bar and considers how disclosure of the research aims, the recruitment of informants, and elicitation of information was negotiated throughout the fieldwork. The case study demonstrates how the social context and the relationships with specific informants determined overtness or covertness in the research. It is argued that the existing literature on covert research and covert methods provides an inappropriate frame of reference with which to understand concealment in fieldwork. The article illustrates why concealment is sometimes necessary, and often unavoidable, and concludes that the criticisms leveled against covert methods should not stop the fieldworker from engaging in research that involves covertness

    Secondary user relations in emerging mobile computing environments

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    Mobile technologies are enabling access to information in diverse environ.ments, and are exposing a wider group of individuals to said technology. Therefore, this paper proposes that a wider view of user relations than is usually considered in information systems research is required. Specifically, we examine the potential effects of emerging mobile technologies on end-­‐user relations with a focus on the ‘secondary user’, those who are not intended to interact directly with the technology but are intended consumers of the technology’s output. For illustration, we draw on a study of a U.K. regional Fire and Rescue Service and deconstruct mobile technology use at Fire Service incidents. Our findings provide insights, which suggest that, because of the nature of mobile technologies and their context of use, secondary user relations in such emerging mobile environments are important and need further exploration

    Integrated optical directional coupler sensor for pesticide analysis

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    Integrated optical transducers for the measurement of interactions between biological molecules and the specific detection of chemical and biochemical species are the subject of growing interest. Targeted applications include environmental monitoring, industrial process control and medical diagnostics. Integrated optical devices are capable of delivering the high detection sensitivity achievable through optical techniques in a compact format, and offer the potential for the detection of several analytes simultaneously through the fabrication of multiple transducers on a single chip. Here we describe the use of a new type of integrated optical sensor applied to the detection of low concentrations of the pesticide atrazine in aqueous solution. The transducer is based on a planar waveguide directional coupler structure fabricated by Ag+-Na+ ion-exchange in a low-index glass substrate. This sensor has the advantage of differential outputs, which gives improved signal-to-noise characteristics and offers the potential for the simultaneous measurement of the real and imaginary parts of the refractive indices of bulk or thin-film analytes
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