The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber optic sensors for space-based nuclear power applications. The purpose of the highneutron fluence testing was to demonstrate the survivability of fiber Bragg grating (FBG) sensors in a fission reactor environment. 520 FBGs were installed in the Ford reactor at the University of Michigan. The reactor was operated for 1012 effective full power hours resulting in a maximum neutron fluence of approximately 5x10 19 n/cm 2 , and a maximum gamma dose of 2x10 3 MGy gamma. This work is significant in that, to the knowledge of the authors, the exposure levels obtained are approximately 1000 times higher than for any previously published experiment. Four different fiber compositions were evaluated. An 87% survival rate was observed for fiber Bragg gratings located at the fuel centerline. Optical Frequency Domain Reflectometry (OFDR), originally developed at the NASA Langley Research Center, can be used to interrogate several thousand low-reflectivity FBG strain and/or temperature sensors along a single optical fiber. A key advantage of the OFDR sensor technology for space nuclear power is the extremely low mass of the sensor, which consists of only a silica fiber 125µm in diameter. The sensors produced using this technology will fill applications in nuclear power for current reactor plants, emerging Generation-IV reactors, and for space nuclear power. The reported research was conducted by Luna Innovations and was funded through a Small Business Innovative Research (SBIR) contract with the NASA Glenn Research Center.

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A general mathematical model that describes the temporal behavior of a real‐time isothermal process used for nucleic acid amplification is derived. A monotonically‐increasing fluorescence signal s(t) generated and measured during the amplification reaction can be modeled in the form of a logistic function of time that is completely described by three parameters (k, t50, and Smax), which may be readily estimated from experimentally acquired s(t) data. Experimental data obtained from a real‐time loop‐mediated isothermal amplification (LAMP) assay for the infectious pathogen Erwinia amylovora (E. amylovora) are used to illustrate and validate the mathematical model. Implementation of such a modeling approach can allow for the extraction of quantitative information from real‐time LAMP data through parameter estimation techniques; this is demonstrated experimentally using real‐time amplification data acquired using the real‐time E. amylovora assay.

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Measurement of the laser beam diameter is essential for estimation of the beam divergence, in optical disks, and metrology application utilizing laser sensors. While the rectangular (Ronchi) ruling of a particular period (L) is capable of estimating the beam radius (ro) for ro/L ranging from between 0.2 and 1.2, triangular and sinusoid gratings1 extend the range to a much smaller radius compared to the grating period. The upper limit of the beam diameter measurement has recently been improved by formulation of an aperiodic ruling.2 However, because of the rectangular (discontinuous) nature of the grating, the lower values of the beam radius cannot be measured. In this work, we propose a novel grating with periodic logarithmic transmission characteristics that are capable of extending the range to both higher and lower values of the beam radius. Our proposed logarithmic periodic grating provides a linear variation of k for ro/L between 0 to 1.2. Using two or more gratings it is possible to extend the beam radius on a truly continuous scale. Gratings of such characteristics can be fabricated by contact screen method.