Parasite-mediated host behavioural modifications: Gyrodactylus turnbulli infected Trinidadian guppies increase contact rates with uninfected conspecifics

While group formation provides antipredatory defences, increases foraging efficiency and mating opportunities, it can be counterintuitive by promoting disease transmission amongst social hosts. Upon introduction of a pathogen, uninfected individuals often modify their social preferences to reduce infection risk. Infected hosts also exhibit behavioural changes, for example, removing themselves from a group to prevent an epidemic. Conversely, here we show how Trinidadian guppies infected with a directly transmitted ectoparasite, Gyrodactylus turnbulli, significantly increase their contact rates with uninfected conspecifics. As uninfected fish never perform this behaviour, this is suggestive of a parasite-mediated behavioural response of infected hosts, presumably to offload their parasites. In the early stages of infection, however, such behavioural modifications are ineffective in alleviating parasite burdens. Additionally, we show that fish exposed to G. turnbulli infections for a second time, spent less time associating than those exposed to parasites for the first time. We speculate that individuals build and retain an infection cue repertoire, enabling them to rapidly recognize and avoid infectious conspecifics. This study highlights the importance of considering host behavioural modifications when investigating disease transmission dynamics

BALLET: Balloon Locomotion for Extreme Terrain

This report documents the work performed in our investigation into the BALLET (Balloon Locomotion for Extreme Terrain) concept. We focused on four areas in this Phase I effort. They were 1) identifying the science targets and objectives with the corresponding requisite instrumentation and operational capabilities that could be achieved with a BALLET mission, 2) developing an architecture for the deployment and operation of this concept for a future mission to a planetary body, 3) analyzing a parametric physical model of BALLET under the environmental conditions of Mars, Titan and Earth to determine its feasibility, and 4) developing and demonstrating coordinated control of the BALLET mobility system to enable locomotion over rugged terrain. The results of our investigations in these focus areas are documented in the following sections. A paper summarizing the preliminary results from this study has been accepted for publication and presentation at the 2019 IEEE Aerospace Conference [Nayar, 2019]

γ‐ray diagnostics of α slowing in inertial confinement fusion targets

For large inertial confinement fusion deuterium-tritium targets, a way to diagnose alpha slowing might be via capture reaction gamma rays. Calculations are presented for two such methods: one uses the alpha+T direct capture gamma rays, the other is based on a series of resonant alpha-capture reactions. For small targets (rhoR less-than-or-equal-to 0.02 g/cm2), the total alpha+T gamma-ray yield relative to the DT neutron yield is temperature independent and proportional to the rhoR value. For large targets (rhoR greater-than-or-equal-to 0.2 g/cm2), this quantity becomes temperature dependent and rhoR independent. Some experimental aspects are discussed

Substituent Effects on the Electronic Spectroscopy of Tryptophan Derivatives in Jet Expansions

Electronic excitation spectra of seven tryptophan derivatives entrained in a supersonic expansion have been recorded using both resonantly enhanced two-photon ionization and laser induced fluorescence. Two derivatives, tryptophan amide and tryptophan methyl amide, were found to have substantial low frequency vibrational progressions in their excitation spectra, yet in both compounds this behavior was apparent in only one conformer. Other derivatives did not display as much vibronic activity. Conformers which had vibrational progressions were found to emit in a broad band far to the red of excitation. All other conformers were found to fluoresce most strongly in resonance with excitation. The presence of low frequency vibrational activity and red shifted fluorescence correlates well with the ability of the derivative to form an intramolecular hydrogen bond between the amine and the carboxylic acid. Backbone conformers that contain an intramolecular hydrogen bond are expected to have large dipole moments, which may strongly perturb the electronic structure of the indole chromophore. © 1990 American Institute of Physics

Water Pump Development for the EVA PLSS

This paper describes the effort by the Texas Engineering Experiment Station (TEES) and Honeywell for NASA to design, fabricate, and test a preflight prototype pump for use in the Extravehicular activity (EVA) portable life support subsystem (PLSS). Major design decisions were driven by the need to reduce the pump s mass, power, and volume compared to the existing PLSS pump. In addition, the pump will accommodate a much wider range of abnormal conditions than the existing pump, including vapor/gas bubbles and increased pressure drop when employed to cool two suits simultaneously. A positive displacement, external gear type pump was selected because it offers the most compact and highest efficiency solution over the required range of flow rates and pressure drops. An additional benefit of selecting a gear pump design is that it is self priming and capable of ingesting noncondensable gas without becoming "air locked." The chosen pump design consists of a 28 V DC, brushless, sealless, permanent magnet motor driven, external gear pump that utilizes a Honeywell development that eliminates the need for magnetic coupling. Although the planned flight unit will use a sensorless motor with custom designed controller, the preflight prototype to be provided for this project incorporates Hall effect sensors, allowing an interface with a readily available commercial motor controller. This design approach reduced the cost of this project and gives NASA more flexibility in future PLSS laboratory testing. The pump design was based on existing Honeywell designs, but incorporated features specifically for the PLSS application, including all of the key features of the flight pump. Testing at TEES will simulate the vacuum environment in which the flight pump will operate. Testing will verify that the pump meets design requirements for range of flow rates, pressure rise, power consumption, working fluid temperature, operating time, and restart capability. Pump testing is currently scheduled for March, 2009, after which the pump will be delivered to NASA for further testing

GenerAges : Generations as They Age

GenerAges examines the history and culture of the 20th century that shaped the lives of Americans age 65 and older today, with a special focus on the generations coming of age in the 1920s (centenarians), ‘40s (the Greatest Generation) and ‘60s (Age of Aquarius). The lengthy work is full of statistics and information regarding what was then the technological revolution of the early 20th century as well as the cultural revolution of the 1960s and early 1970s that ushered in a new era of civil rights and women’s liberation and equality. While this study emphasizes the enormous amount of technological, social and cultural change over the past century, it also stresses a certain commonality found among generations in their quest for peace and prosperity, and that “each will be on the cutting edge of fashion, technology and modern conveniences; and each will recede into history with relative rapidity, appearing amusingly antiquated in the process.

Estimation of liquidus temperatures in silicate glasses

Two models for estimating liquidus temperature from composition are presented and compared with thermodynamically calculated temperature as well as primary phase. Α simple polynomial model is given for high silica glasses, while a model covering a wide composition range and several primary phase fields is more complex. Thermodynamic calculations generally give too high liquidus temperatures in the devitrite field and too low in the primary field for Na2O · 2 CaO · 3 SiO2. In the wollastonite field the values are scattered, but in general too high

Getting into hot water:sick guppies frequent warmer thermal conditions

Ectotherms depend on the environmental temperature for thermoregulation and exploit thermal regimes that optimise physiological functioning. They may also frequent warmer conditions to up-regulate their immune response against parasite infection and/or impede parasite development. This adaptive response, known as ‘behavioural fever’, has been documented in various taxa including insects, reptiles and fish, but only in response to endoparasite infections. Here, a choice chamber experiment was used to investigate the thermal preferences of a tropical freshwater fish, the Trinidadian guppy (Poecilia reticulata), when infected with a common helminth ectoparasite Gyrodactylus turnbulli, in female-only and mixed-sex shoals. The temperature tolerance of G. turnbulli was also investigated by monitoring parasite population trajectories on guppies maintained at a continuous 18, 24 or 32 °C. Regardless of shoal composition, infected fish frequented the 32 °C choice chamber more often than when uninfected, significantly increasing their mean temperature preference. Parasites maintained continuously at 32 °C decreased to extinction within 3 days, whereas mean parasite abundance increased on hosts incubated at 18 and 24 °C. We show for the first time that gyrodactylid-infected fish have a preference for warmer waters and speculate that sick fish exploit the upper thermal tolerances of their parasites to self medicate