Sound propagation over uneven ground and irregular topography

The acoustic impedance of the surface coverings used in the laboratory experiments on sound diffraction by topographical ridges was determined. The model, which was developed, takes into account full wave effects and the possibility of surface waves and predicts the sound pressure level at the receiver location relative to what would be expected if the flat surface were not present. The sound pressure level can be regarded as a function of frequency, sound speed in air, heights of source and receiver, and horizontal distance from source to receiver, as well as the real and imaginary parts of the surface impedance

The InfraRed Imaging Spectrograph (IRIS) for TMT: photometric precision and ghost analysis

The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT) that will be used to sample the corrected adaptive optics field by NFIRAOS with a near-infrared (0.8 - 2.4 $\mu$m) imaging camera and Integral Field Spectrograph (IFS). In order to understand the science case specifications of the IRIS instrument, we use the IRIS data simulator to characterize photometric precision and accuracy of the IRIS imager. We present the results of investigation into the effects of potential ghosting in the IRIS optical design. Each source in the IRIS imager field of view results in ghost images on the detector from IRIS's wedge filters, entrance window, and Atmospheric Dispersion Corrector (ADC) prism. We incorporated each of these ghosts into the IRIS simulator by simulating an appropriate magnitude point source at a specified pixel distance, and for the case of the extended ghosts redistributing flux evenly over the area specified by IRIS's optical design. We simulate the ghosting impact on the photometric capabilities, and found that ghosts generally contribute negligible effects on the flux counts for point sources except for extreme cases where ghosts coalign with a star of $\Delta$m$>$2 fainter than the ghost source. Lastly, we explore the photometric precision and accuracy for single sources and crowded field photometry on the IRIS imager.Comment: SPIE 2018, 14 pages, 14 figures, 4 tables, Proceedings of SPIE 10702-373, Ground-based and Airborne Instrumentation for Astronomy VII, 10702A7 (16 July 2018

Validation of the Work Observation Method By Activity Timing (WOMBAT) method of conducting time-motion observations in critical care settings: an observational study

<p>Abstract</p> <p>Background</p> <p>Electronic documentation handling may facilitate information flows in health care settings to support better coordination of care among Health Care Providers (HCPs), but evidence is limited. Methods that accurately depict changes to the workflows of HCPs are needed to assess whether the introduction of a Critical Care clinical Information System (CCIS) to two Intensive Care Units (ICUs) represents a positive step for patient care. To evaluate a previously described method of quantifying amounts of time spent and interruptions encountered by HCPs working in two ICUs.</p> <p>Methods</p> <p>Observers used PDAs running the Work Observation Method By Activity Timing (WOMBAT) software to record the tasks performed by HCPs in advance of the introduction of a Critical Care clinical Information System (CCIS) to quantify amounts of time spent on tasks and interruptions encountered by HCPs in ICUs.</p> <p>Results</p> <p>We report the percentages of time spent on each task category, and the rates of interruptions observed for physicians, nurses, respiratory therapists, and unit clerks. Compared with previously published data from Australian hospital wards, interdisciplinary information sharing and communication in ICUs explain higher proportions of time spent on professional communication and documentation by nurses and physicians, as well as more frequent interruptions which are often followed by professional communication tasks.</p> <p>Conclusions</p> <p>Critical care workloads include requirements for timely information sharing and communication and explain the differences we observed between the two datasets. The data presented here further validate the WOMBAT method, and support plans to compare workflows before and after the introduction of electronic documentation methods in ICUs.</p

The VANDELS survey: the ionizing properties of star-forming galaxies at 3≤z≤53 \leq z \leq 5 using deep rest-frame ultraviolet spectroscopy

To better understand the ionizing properties of galaxies in the EoR, we investigate deep, rest-frame ultraviolet (UV) spectra of $\simeq 500$ star-forming galaxies at $3 \leq z \leq 5$ selected from the public ESO-VANDELS spectroscopic survey. The absolute ionizing photon escape fraction ($f_{\rm esc}^{\rm abs}$) is derived by combining absorption line measurements with estimates of the UV attenuation. The ionizing production efficiency ($\xi_{ion}$) is calculated by fitting the far-UV (FUV) stellar continuum of the VANDELS galaxies. We find that the $f_{\rm esc}^{\rm abs}$ and $\xi_{ion}$ parameters increase towards low-mass, blue UV-continuum slopes and strong Ly$\alpha$ emitting galaxies, and both are just slightly higher-than-average for the UV-faintest galaxies in the sample. Potential Lyman Continuum Emitters (LCEs) and selected Lyman Alpha Emitters (LAEs) show systematically higher $\xi_{ion}$ ($\log \xi_{ion}$ (Hz\erg) $\approx 25.38, 25.41$) than non-LCEs and non-LAEs ($\log \xi_{ion}$ (Hz\erg) $\approx 25.18, 25.14$) at similar UV magnitudes. This indicates very young underlying stellar populations ($\approx 10~{\rm Myr}$) at relatively low metallicities ($\approx 0.2~{\rm Z_{\odot}}$). The FUV non-ionizing spectra of potential LCEs is characterized by very blue UV slopes ($\leq -2$), enhanced Ly$\alpha$ emission ($\leq -25$A), strong UV nebular lines (e.g., high CIV1550/CIII]1908 $\geq 0.75$ ratios), and weak absorption lines ($\leq 1$A). The latter suggests the existence of low gas-column-density channels in the interstellar medium which enables the escape of ionizing photons. By comparing our VANDELS results against other surveys in the literature, our findings imply that the ionizing budget in the EoR was likely dominated by UV-faint, low-mass and dustless galaxies.Comment: 25 pages, 18 figures, 2 tables; submitted to MNRA

The InfraRed Imaging Spectrograph (IRIS) for TMT: photometric characterization of anisoplanatic PSFs and testing of PSF-Reconstruction via AIROPA

The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT) that will be used to sample the corrected adaptive optics field by the Narrow-Field Infrared Adaptive Optics System (NFIRAOS) with a near-infrared (0.8 - 2.4 µm) imaging camera and integral field spectrograph. To better understand IRIS science specifications we use the IRIS data simulator to characterize relative photometric precision and accuracy across the IRIS imaging camera 34”x34” field of view. Because the Point Spread Function (PSF) varies due to the effects of anisoplanatism, we use the Anisoplanatic and Instrumental Reconstruction of Off-axis PSFs for AO (AIROPA) software package to conduct photometric measurements on simulated frames using PSF-fitting as the PSF varies in single-source, binary, and crowded field use cases. We report photometric performance of the imaging camera as a function of the instrumental noise properties including dark current and read noise. Using the same methods, we conduct comparisons of photometric performance with reconstructed PSFs, in order to test the veracity of the current PSF-Reconstruction algorithms for IRIS/TMT

The InfraRed Imaging Spectrograph (IRIS) for TMT: photometric characterization of anisoplanatic PSFs and testing of PSF-Reconstruction via AIROPA

The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT) that will be used to sample the corrected adaptive optics field by the Narrow-Field Infrared Adaptive Optics System (NFIRAOS) with a near-infrared (0.8 - 2.4 µm) imaging camera and integral field spectrograph. To better understand IRIS science specifications we use the IRIS data simulator to characterize relative photometric precision and accuracy across the IRIS imaging camera 34”x34” field of view. Because the Point Spread Function (PSF) varies due to the effects of anisoplanatism, we use the Anisoplanatic and Instrumental Reconstruction of Off-axis PSFs for AO (AIROPA) software package to conduct photometric measurements on simulated frames using PSF-fitting as the PSF varies in single-source, binary, and crowded field use cases. We report photometric performance of the imaging camera as a function of the instrumental noise properties including dark current and read noise. Using the same methods, we conduct comparisons of photometric performance with reconstructed PSFs, in order to test the veracity of the current PSF-Reconstruction algorithms for IRIS/TMT

Generalized dipole polarizabilities and the spatial structure of hadrons

We present a phenomenological discussion of spin-independent, generalized dipole polarizabilities of hadrons entering the virtual Compton scattering process gamma* h -> gamma h. We introduce a new method of obtaining a tensor basis with appropriate Lorentz-invariant amplitudes which are free from kinematical singularities and constraints. We then motivate a gauge-invariant separation into a generalized Born term containing ground-state properties only, and a residual contribution describing the model-dependent internal structure. The generalized dipole polarizabilities are defined in terms of Lorentz-invariant residual amplitudes. Particular emphasis is laid on a physical interpretation of these quantities as characterizing the spatial distributions of the induced electric polarization and magnetization of hadrons. It is argued that three dipole polarizabilities, namely the longitudinal electric alpha_L(q^2), the transverse electric alpha_T(q^2), and the magnetic beta(q^2) ones are required in order to fully reconstruct local polarizations induced by soft external fields in a hadron. One of these polarizabilities, alpha_T(q^2), describes an effect of higher order in the soft final-photon momentum q'. We argue that the associated spatial distributions obtained via the Fourier transforms in the Breit frame are meaningful even for such a light particle as the pion. The spatial distributions are determined at large distances r ~ 1/m_pi for pions, kaons, and octet baryons by use of ChPT.Comment: 41 pages, 5 figures, RevTex fil

The Infrared Imaging Spectrograph (IRIS) for TMT: advancing the data reduction system

Infrared Imaging Spectrograph (IRIS) is the first light instrument for the Thirty Meter Telescope (TMT) that consists of a near-infrared (0.84 to 2.4 micron) imager and integral field spectrograph (IFS) which operates at the diffraction-limit utilizing the Narrow-Field Infrared Adaptive Optics System (NFIRAOS). The imager will have a 34 arcsec x 34 arcsec field of view with 4 milliarcsecond (mas) pixels. The IFS consists of a lenslet array and slicer, enabling four plate scales from 4 mas to 50 mas, multiple gratings and filters, which in turn will operate hundreds of individual modes. IRIS, operating in concert with NFIRAOS will pose many challenges for the data reduction system (DRS). Here we present the updated design of the real-time and post-processing DRS. The DRS will support two modes of operation of IRIS: (1) writing the raw readouts sent from the detectors and performing the sampling on all of the readouts for a given exposure to create a raw science frame; and (2) reduction of data from the imager, lenslet array and slicer IFS. IRIS is planning to save the raw readouts for a given exposure to enable sophisticated processing capabilities to the end users, such as the ability to remove individual poor seeing readouts to improve signal-to-noise, or from advanced knowledge of the point spread function (PSF). The readout processor (ROP) is a key part of the IRIS DRS design for writing and sampling of the raw readouts into a raw science frame, which will be passed to the TMT data archive. We discuss the use of sub-arrays on the imager detectors for saturation/persistence mitigation, on-detector guide windows, and fast readout science cases (< 1 second).Comment: 14 pages, 5 figures, 6 tables, Proceeding 10707-112 of the SPIE Astronomical Telescopes + Instrumentation 201

The Infrared Imaging Spectrograph (IRIS) for TMT: final design development of the data reduction system

IRIS (Infrared Imaging Spectrograph) is the near-infrared (0.84 to 2.4 micron) diffraction-limited imager and Integral Field Spectrograph (IFS) designed for the Thirty Meter Telescope (TMT) and the Narrow-Field Infrared Adaptive Optics System ( NFIRAOS ). The imager will have a 34 arcsec x 34 arcsec field of view with 4 milliarcseconds (mas) pixels. The IFS consists of a lenslet array and slicer, enabling four plate scales from 4 mas to 50 mas, with multiple gratings and filters. We will report the progress on the development of the IRIS Data Reduction System ( DRS ) in the final design phase. The IRIS DRS is being developed in Python with the software architecture based on the James Webb Space Telescope science calibration pipeline. We are developing a library of algorithms as individual Python classes that can be configured independently and bundled into pipelines. We will interface this with the observatory software to run online during observations and we will release the package publicly for scientists to develop custom analyses. It also includes a C library for readout processing to be used for both in real-time processing (e.g., up-the-ramp, MCDS) as well the ability for astronomers to use for offline reduction. Lastly, we will also discuss the development of the IRIS simulation packages that simulate raw spectra and image readout-data from the Hawaii-4RG detectors, which helps in developing reduction algorithms during this design phase