Material Limitations on the Detection Limit in Refractometry

We discuss the detection limit for refractometric sensors relying on high-Q optical cavities and show that the ultimate classical detection limit is given by min{Dn} > eta with n+i*eta being the complex refractive index of the material under refractometric investigation. Taking finite Q factors and filling fractions into account, the detection limit declines. As an example we discuss the fundamental limits of silicon-based high-Q resonators, such as photonic crystal resonators, for sensing in a bio-liquid environment, such as a water buffer. In the transparency window of silicon the detection limit becomes almost independent on the filling fraction, while in the visible, the detection limit depends strongly on the filling fraction because silicon absorbs strongly.Comment: Published in Special Issue "Laser Spectroscopy and Sensing", Edited by Prof. M.W. Sigris

An Examination of the Application of FAIR Data Principles to Institutional Research Management Data

Defined by Wilkinson, M D, et al. 2016 in “The FAIR Guiding Principles for scientific data mmanagement and stewardship” the FAIR data principles propose a framework to enable the findability, accessibility, interoperability, and reusability of scholarly data. But are there lessons which could be learned from this and applied to data arising from institutional research administrative processes? Institutional data suffers from the same sorts of problems the FAIR principles were designed to overcome. In a large institution it can be difficult to know what data exists and how to locate it, difficult to access it and have it in a form which means it caninteract with other data without needing a great deal of manual intervention, which leads to barriers when wanting to reuse it. This lightning talk examines some of the issues we might experience when applying FAIR data principles to institutional data, with an emphasis on research management data, who’s currently applying these principles and what we may need to do to adopt them within the University of Edinburgh

Spatially resolved detection of crystallized water ice in a TTauri object

We search for frozen water and its processing around young stellar objects (YSOs of class I/II). We try to detect potential, regional differences in water ice evolution within YSOs, which is relevant to understanding the chemical structure of the progenitors of protoplanetary systems and the evolution of solid materials. Water plays an important role as a reaction bed for rich chemistry and is an indispensable requirement for life as known on Earth. We present our analysis of NAOS-CONICA/VLT spectroscopy of water ice at 3um for the TTauri star YLW 16A in the rho-Ophiuchi molecular cloud. We obtained spectra for different regions of the circumstellar environment. The observed absorption profiles are deconvolved with the mass extinction profiles of amorphous and crystallized ice measured in laboratory. We take into account both absorption and scattering by ice grains. Water ice in YLW 16A is detected with optical depths of between tau=1.8 and tau=2.5. The profiles that are measured can be fitted predominantly by the extinction profiles of small grains (0.1um - 0.3um) with a small contribution from large grains (<10%). However, an unambiguous trace of grain growth cannot be found. We detected crystallized water ice spectra that have their origin in different regions of the circumstellar environment of the TTauri star YLW 16A. The crystallinity increases in the upper layers of the circumstellar disk, while only amorphous grains exist in the bipolar envelope. As in studies of silicate grains in TTauri objects, the higher crystallinity in the upper layers of the outer disk regions implies that water ice crystallizes and remains crystallized close to the disk atmosphere where water ice is shielded against hard irradiation.Comment: 17 pages, 13 figures, 4 tables; accepted by Astronomy and Astrophysic

Magnetic Nanoparticles in the Interstellar Medium: Emission Spectrum and Polarization

The presence of ferromagnetic or ferrimagnetic nanoparticles in the interstellar medium would give rise to magnetic dipole radiation at microwave and submm frequencies. Such grains may account for the strong mm-wavelength emission observed from a number of low-metallicity galaxies, including the Small Magellanic Cloud. We show how to calculate the absorption and scattering cross sections for such grains, with particular attention to metallic Fe, magnetite Fe3O4, and maghemite gamma-Fe2O3, all potentially present in the interstellar medium. The rate of Davis-Greenstein alignment by magnetic dissipation is also estimated. We determine the temperature of free-flying magnetic grains heated by starlight and we calculate the polarization of the magnetic dipole emission from both free-fliers and inclusions. For inclusions, the magnetic dipole emission is expected to be polarized orthogonally relative to the normal electric dipole radiation. Finally, we present self-consistent dielectric functions for metallic Fe, magnetite Fe3O4, and maghemite gamma-Fe2O3, enabling calculation of absorption and scattering cross sections from microwave to X-ray wavelengths.Comment: submitted to Ap.J. Fig. 10 has been corrected. Minor changes to the discussion in section 10.2.

HOW TO DISTINGUISH BETWEEN CLOUDY MINI-NEPTUNES AND WATER/VOLATILE-DOMINATED SUPER-EARTHS

One of the most profound questions about the newly discovered class of low-density super-Earths is whether these exoplanets are predominately H2-dominated mini-Neptunes or volatile-rich worlds with gas envelopes dominated by H2O, CO2, CO, CH4, or N2. Transit observations of the super-Earth GJ 1214b rule out cloud-free H2-dominated scenarios, but are not able to determine whether the lack of deep spectral features is due to high-altitude clouds or the presence of a high mean molecular mass atmosphere. Here, we demonstrate that one can unambiguously distinguish between cloudy mini-Neptunes and volatile-dominated worlds based on wing steepness and relative depths of absorption features in moderate-resolution near-infrared transmission spectra (R ~ 100). In a numerical retrieval study, we show for GJ 1214b that an unambiguous distinction between a cloudy H2-dominated atmosphere and cloud-free H2O atmosphere will be possible if the uncertainties in the spectral transit depth measurements can be reduced by a factor of ~3 compared to the published Hubble Space Telescope Wide-Field Camera 3 and Very Large Telescope transit observations by Berta et al. and Bean et al. We argue that the required precision for the distinction may be achievable with currently available instrumentation by stacking 10-15 repeated transit observations. We provide a scaling law that scales our quantitative results to other transiting super-Earths and Neptunes such as HD 97658b, 55 Cnc e, GJ 3470b and GJ 436b. The analysis in this work is performed using an improved version of our Bayesian atmospheric retrieval framework. The new framework not only constrains the gas composition and cloud/haze parameters, but also determines our confidence in having detected molecules and cloud/haze species through Bayesian model comparison. Using the Bayesian tool, we demonstrate quantitatively that the subtle transit depth variation in the Berta et al. data is not sufficient to claim the detection of water absorption

The effect of herbicides, pesticides, and fertilizers on the optical properties of water

A reflectometer accessory for a spectrophotometer was designed and constructed in our laboratory. Using distilled water as the reflectance standard, the reflectometer was used to measure relative specular reflectance of 0.5M aqueous solutions of K2SO4 and NH4H2PO4 in the 2-12m wavelength region and for 1M (NH2)2CO in the 2-20m wavelength region for infrared radiant flux incident at about 70 degrees and linearly polarized perpendicular to the plane of incidence. Absolute reflectances of the solutions were computed for 70 degrees angle of incidence by using the relative reflectance measurements, one of the Fresnel equations, and the optical constants of water. The optical constants of the aqueous solutions were then computed by applying a Kramers-Kronig phase-shift dispersion analysis to the absolute reflectance spectra. The report provides a description of the instrumentation and the experimental procedures for making the measurements. The relative reflectances, absolute reflectances, and optical constants are presented in graphical form in the text and are tabulated in Appendix I. Spectral signatures characteristic of the solutes are discussed in the text. In addition, further investigations of the optical constants of distilled water were made in that they are related to the investigations of aqueous solutions. The work on distilled water was accomplished in cooperation with Dr. Dudley Williams at Kansas State University. A reprint describing the work is presented in Appendix I.Project # A-030-MO Agreement # 14-31-0001-302

Dogslife: A web-based longitudinal study of Labrador Retriever health in the UK

<p>Abstract</p> <p>Background</p> <p>Dogslife is the first large-scale internet-based longitudinal study of canine health. The study has been designed to examine how environmental and genetic factors influence the health and development of a birth cohort of UK-based pedigree Labrador Retrievers.</p> <p>Results</p> <p>In the first 12 months of the study 1,407 Kennel Club (KC) registered eligible dogs were recruited, at a mean age of 119 days of age (SD 69 days, range 3 days – 504 days). Recruitment rates varied depending upon the study team’s ability to contact owners. Where owners authorised the provision of contact details 8.4% of dogs were recruited compared to 1.3% where no direct contact was possible. The proportion of dogs recruited was higher for owners who transferred the registration of their puppy from the breeder to themselves with the KC, and for owners who were sent an e-mail or postcard requesting participation in the project. Compliance with monthly updates was highly variable. For the 280 dogs that were aged 400 days or more on the 30^th June 2011, we estimated between 39% and 45% of owners were still actively involved in the project. Initial evaluation suggests that the cohort is representative of the general population of the KC registered Labrador Retrievers eligible to enrol with the project. Clinical signs of illnesses were reported in 44.3% of Labrador Retrievers registered with Dogslife (median age of first illness 138 days), although only 44.1% of these resulted in a veterinary presentation (median age 316 days).</p> <p>Conclusions</p> <p>The web-based platform has enabled the recruitment of a representative population of KC registered Labrador Retrievers, providing the first large-scale longitudinal population-based study of dog health. The use of multiple different methods (e-mail, post and telephone) of contact with dog owners was essential to maximise recruitment and retention of the cohort.</p