Theory of Dispersed Fixed-Delay Interferometry for Radial Velocity Exoplanet Searches

The dispersed fixed-delay interferometer (DFDI) represents a new instrument concept for high-precision radial velocity (RV) surveys for extrasolar planets. A combination of Michelson interferometer and medium-resolution spectrograph, it has the potential for performing multi-object surveys, where most previous RV techniques have been limited to observing only one target at a time. Because of the large sample of extrasolar planets needed to better understand planetary formation, evolution, and prevalence, this new technique represents a logical next step in instrumentation for RV extrasolar planet searches, and has been proven with the single-object Exoplanet Tracker (ET) at Kitt Peak National Observatory, and the multi-object W. M. Keck/MARVELS Exoplanet Tracker at Apache Point Observatory. The development of the ET instruments has necessitated fleshing out a detailed understanding of the physical principles of the DFDI technique. Here we summarize the fundamental theoretical material needed to understand the technique and provide an overview of the physics underlying the instrument's working. We also derive some useful analytical formulae that can be used to estimate the level of various sources of error generic to the technique, such as photon shot noise when using a fiducial reference spectrum, contamination by secondary spectra (e.g., crowded sources, spectroscopic binaries, or moonlight contamination), residual interferometer comb, and reference cross-talk error. Following this, we show that the use of a traditional gas absorption fiducial reference with a DFDI can incur significant systematic errors that must be taken into account at the precision levels required to detect extrasolar planets.Comment: 58 pages, 11 figures, 1 table, 3 appendices. Accepted for publication in ApJS. Minor typographical corrections; update to acknowledgment

Fundamental Performance of a Dispersed Fixed Delay Interferometer In Searching For Planets Around M Dwarfs

We present a new method to calculate fundamental Doppler measurement limits with a dispersed fixed-delay interferometer (DFDI) in the near infrared wavelength region for searching for exoplanets around M dwarfs in the coming decade. It is based on calculating the Q factor, a measure of flux-normalized Doppler sensitivity in the fringing spectra created with DFDI. We calculate the Q factor as a function of spectral resolution R, stellar projected rotational velocity V sini, stellar effective temperature T_eff and optical path difference (OPD) of the interferometer. We also compare the DFDI Q factor to that for the popular cross-dispersed echelle spectrograph method (the direct echelle (DE) method). Given the IR Doppler measurement is likely to be detector-limited for a while, we introduce new merit functions, which is directly related to photon-limited RV uncertainty, to evaluate Doppler performance with the DFDI and DE methods. We find that DFDI has strength in wavelength coverage and multi-object capability over the DE for a limited detector resource. We simulate the performance of the InfraRed Exoplanet Tracker (IRET) based on the DFDI design, being considered for the next generation IR Doppler measurements. The predicted photon-limited RV uncertainty suggests that IRET is capable of detecting Earth-like exoplanets in habitable zone around nearby bright M dwarfs if they exist. A new method is developed to quantitatively estimate the influence of telluric lines on RV uncertainty. Our study shows that photon-limited RV uncertainty can be reached if 99% of the strength of telluric lines can be removed from the measured stellar spectra. At low to moderate levels of telluric line strength removal (50% to 90%), the optimal RV uncertainty is typically a factor of 2-3 times larger than photon-limited RV uncertainty.Comment: 43 pages, 20 figures, 6 tables. Accepted by Ap

Microbiological and health related perspectives of geophagia: An overview

Geophagia, which refers to the deliberate eating of soil, is considered to be a deviant eating disorder, a sequel to poverty and famine but could also be observed in the absence of hunger and in both scenarios may be associated with high degree of mortality and morbidity. The phenomenon has been reported to be common among pregnant women, lactating women, school children and people with psychiatric disorders. The microbiology of soil shows a broad diversity and functionality of soil microflora which impact variously on soil and its consumption. Soil microbes contribute immensely to the quality of soil and even determine soil types. Geophagia may be beneficial or harmful. Beneficial aspects include the use of kaolin to treat diarrhea, gastritis, colitis, enhancement of bioactivities and maintenance of normal intestinal flora by commensal flora found in soil. Clay or soil containing special constituents are valuable oral and topical antimicrobials as well as adsorbents of toxins. Microbiological underpinnings of geophagia include the ingestion of eggs of parasitic worms such as Ascaris lumbricoides, Trichuris trichiura with the health consequences. Highly toxigenic bacteria such as Clostridium perfringens, Clostridium tetani, Clostridium botulinum, the causative agents of gas gangrene, tetanus and botulism and other human pathogens may be ingested. It has also been postulated that indirect consumption of soil may pose serious health problems. For example, nitrate run-off and leaching from soil into water bodies may lead to eutrophication and colonization by toxic cyanobacteria with ripple medical effects such as gastroenteritis. Some general health implications of geophagia include association with iron deficiency and anemia, intestinal obstruction, constipation, peritonitis, dental damage, eclampsia, iron deficiency and even mortality. The interplay of factors involved in geophagia, though varied, intricate and researched may not have been fully elucidated. Further concerted efforts aimed at multidisciplinary research are warranted so as to address gaps in the corpus of knowledge on the important subject.Keywords: Geohelminths, geophagia, health, microorganisms, soilAfrican Journal of Biotechnology Vol. 9(19), pp. 5784-5791, 10 May, 201

Interaction-induced mode switching in steady-state microlasers

We demonstrate that due to strong modal interactions through cross-gain saturation, the onset of a new lasing mode can switch off an existing mode via a negative power slope. In this process of interaction-induced mode switching (IMS) the two involved modes maintain their identities, i.e. they do not change their spatial field patterns or lasing frequencies. For a fixed pump profile, a simple analytic criterion for the occurrence of IMS is given in terms of their self- and cross-interaction coefficients and non-interacting thresholds, which is verified for the example of a two-dimensional microdisk laser. When the spatial pump profile is varied as the pump power is increased, IMS can be induced even when it would not occur with a fixed pump profile, as we show for two coupled laser cavities. Our findings apply to steady-state lasing and are hence different from dynamical mode switching or hopping. IMS may have potential applications in robust and flexible all-optical switching.Comment: 14 pages, 5 figure

First High Contrast Imaging Using a Gaussian Aperture Pupil Mask

Placing a pupil mask with a gaussian aperture into the optical train of current telescopes represents a way to attain high contrast imaging that potentially improves contrast by orders of magnitude compared to current techniques. We present here the first observations ever using a gaussian aperture pupil mask (GAPM) on the Penn State near-IR Imager and Spectrograph (PIRIS) at the Mt. Wilson 100$^{\prime\prime}$ telescope. Two nearby stars were observed, $\epsilon$ Eridani and $\mu$ Her A. A faint companion was detected around $\mu$ Her A, confirming it as a proper motion companion. Furthermore, the observed H and K magnitudes of the companion were used to constrain its nature. No companions or faint structure were observed for $\epsilon$ Eridani. We found that our observations with the GAPM achieved contrast levels similar to our coronographic images, without blocking light from the central star. The mask's performance also nearly reached sensitivities reported for other ground based adaptive optics coronographs and deep HST images, but did not reach theoretically predicted contrast levels. We outline ways that could improve the performance of the GAPM by an order of magnitude or more.Comment: 8 pages, 4 figures, accepted by ApJ letter

Activity and social interactions in a wideranging specialist scavenger, the Tasmanian devil (Sarcophilus harrisii), revealed by animalborne video collars

Observing animals directly in the field provides the most accurate understanding of animal behaviour and resource selection. However, making prolonged observation of undisturbed animals is difficult or impossible for many species. To overcome this problem for the Tasmanian devil (Sarcophilus harrisii), a cryptic and nocturnal carnivore, we developed animal-borne video collars to investigate activity patterns, foraging behaviour and social interactions. We collected 173 hours of footage from 13 individual devils between 2013 and 2017. Devils were active mostly at night, and resting was the most common behaviour in all diel periods. Devils spent more time scavenging than hunting and exhibited opportunistic and flexible foraging behaviours. Scavenging occurred mostly in natural vegetation but also in anthropogenic vegetation and linear features (roads and fence lines). Scavenging frequency was inversely incremental with size e.g. small carcasses were scavenged most frequently. Agonistic interactions with conspecifics occurred most often when devils were traveling but also occurred over carcasses or dens. Interactions generally involved vocalisations and brief chases without physical contact. Our results highlight the importance of devils as a scavenger in the Tasmanian ecosystem, not just of large carcasses for which devils are well known but in cleaning up small items of carrion in the bush. Our results also show the complex nature of intraspecific interactions, revealing greater detail on the context in which interactions occur. In addition, this study demonstrates the benefits of using animal-borne imaging in quantifying behaviour of elusive, nocturnal carnivores not previously seen using conventional field methods

Gas Explosions in Partially Filled, Large Twin Enclosures Connected with an Open Door and Having Variable Vent Sizes on Both Compartments

Accidental gas explosions are a recognised hazard in process industries but they are also common in residential buildings. Whilst process plants have specifically designed vent reliefs to limit the enclosure damage, in homes a similar effect is achieved due to the presence of doors and windows whose failure often protects the building. There are empirically based correlations for predicting overpressure and for vent sizing, however these are limited in application to simple enclosures. In practice, enclosures have interconnected spaces which would potentially increase the flame acceleration considerably. In this paper we present the results of full scale natural gas layer tests in a twin chamber, which consisted of two 22 m3 enclosures connected by an open doorway. Layered natural gas/air mixtures of 8, 10 and 12% by volume, were ignited at the rear of one of the chambers. Explosion relief was provided by vent openings of 2.48, 1.49 or 0.74 m2 on the far walls of both chambers. With tests with equal large vents on each of the chambers, the dominant influence was the external explosion. The maximum overpressure was produced by tests involving a 12% natural gas concentration. The use of a smaller vent in the adjoining enclosure had a significant effect on the maximum overpressure and the mechanism of the explosion development. However, altering the size from 1.49 m2 to 0.74 m2 had little overall effect. This was largely due to the greater generation of turbulence and the venting process which predominantly occurred via the doorway and through the ignition-chamber vent opening. The use of a smaller vent in the ignition enclosure also altered the manner in which the explosion developed. A venting driven ‘jetting’ expanding flame, propagated into the adjoining enclosure and towards the far vent opening, generating the dominant pressure peak in these type of tests

Scalable numerical approach for the steady-state ab initio laser theory

We present an efficient and flexible method for solving the non-linear lasing equations of the steady-state ab initio laser theory. Our strategy is to solve the underlying system of partial differential equations directly, without the need of setting up a parametrized basis of constant flux states. We validate this approach in one-dimensional as well as in cylindrical systems, and demonstrate its scalability to full-vector three-dimensional calculations in photonic-crystal slabs. Our method paves the way for efficient and accurate simulations of lasing structures which were previously inaccessible.Comment: 17 pages, 8 figure

MEMS Based Tracking Devices for Measuring Distribution Hazards on the Product and Package

This paper introduces two microelectromechanical systems (MEMS) based working data logger prototypes and the cloud based data analysis system that were trademarked and patented as Pak-TrackTM-I and Pak-TrackTM-II. The Pak-TrackTM-I is designed to wirelessly record and report information in real time about individually packaged products during transit. The system allows the user to immediately view the data with a Global Positioning System (GPS) location via a secured website or Android tablet or smart phone. The Pak-TrackTM-II is a standalone device that stores all measurements on internal memory without communicating over a network. The cloud based server and website analyzes and displays the data collected to further study the effects that transportation and handling had on the product and package. The lab obtained data are within expected limits for the purpose of validation. Two field tests were conducted, testing the configuration and setup of the sensors, real time monitoring, display, and analysis. Finally, the collected vibration data was sent to Matlab to generate the PSD chart for validating the FFT algorithm used in the system

HOW E-COMMERCE IS CHANGING THE FACILITY MANAGEMENT PRACTICES OF BUILDING OWNERS

"The corporate Ford of 2010 will look more like Cisco, a company that manufactures very little.” "Direct-to-the-assembly-line ordering will enable Ford to custom configure cars much the way that Dell custom configures computers.” --Forbes, July 17, 2000 The above quotation is an indication of how information technology is changing even old-line manufacturing organizations. The research reported in this paper was motivated by our desire to better understand how information technology and, in particular, the recent phenomenon of e-commerce, was influencing the design and construction industry. Since trends in the building industry are often determined by the desires and programs initiated by large building owners, we decided to focus our research on facility management organizations in Fortune-500 companies