Design and testing of a 3D printed propulsion system for small satellites

textA cold gas propulsion system for small spacecraft orbital maneuvers was developed by the University of Texas at Austin's Texas Spacecraft Laboratory. The thruster will allow the Prox-1 spacecraft, developed by the Georgia Institute of Technology, to conduct small scale maneuvers in Earth orbit. 3D printing was used to create a geometrically complex design at a low cost, and allowed the thruster to make efficient use of the available volume. The system was equipped with an onboard microcontroller that provides precise timing for firings, and can collect data from various sensors to send to the flight computer. The testing of this thruster focused on determining the level of thrust available and the specific impulse of the system. The thrust was found to be considerably higher during short pulses (2 milliseconds) than during long pulses (10 milliseconds), from 50±16 mN to 35±2.4 mN, respectively. The specific impulse was found to be 55.4±17.7 seconds, which is sufficient to provide the Prox-1 thruster with a required velocity change of 15 m/s. A testing unit of the thruster was assembled and delivered in January of 2015, and the flight unit is scheduled for delivery in summer of 2015.Aerospace Engineerin

Is nursing student personality important for considering a rural career?

Purpose: Identifying and measuring personality traits assists to understanding professional career choices, however, what impact personality traits have on nursing student rural career choice remains absent. The purpose of this paper is to identify personality traits among nursing students that may be predictive of pursuing a rural career. Design/methodology/approach: A cross-sectional design was used to examine the importance Bachelor of Nursing students place on undertaking rural careers. All nursing students (n=1,982) studying a three-year bachelor’s degree were invited to complete a questionnaire examining personality traits and rural practice intentions. Findings: Students who saw themselves working rurally after graduation had higher levels of conscientiousness than those who wanted metropolitan careers. Students with higher levels of agreeableness or open-mindedness were more likely to consider rural practice when individual community factors were carefully considered. Finally, students with higher levels of neuroticism were less likely to consider rural practice as a future career pathway. Research limitations/implications: The cohort had high numbers of student from rural and regional settings, which may limit the ability to generalise the findings. In addition, student respondents of the survey may not be representative of the whole student cohort given the low response rate. Originality/value: Key personality traits are identifying factors that contribute to nursing student decision making regarding rural practice. Students who displayed higher levels of agreeableness and conscientiousness and open-mindedness have traits that are most likely to impact the consideration of rural practice across their nursing career, which gives additional insight into targeted recruitment strategies. © 2019, Emerald Publishing Limited

The Mountain Caribou in Managed Forests Program: Integrating forestry and habitat management in British Columbia

Caribou in southeastern and east central British Columbia generally use old-growth forests rather than clearcuts or immature stands. During winter, they subsist on arboreal lichens, which are most abundant in old growth. The Mountain Caribou in Managed Forests program was initiated to adress the question: can forest stands be managed, through silvicultural systems and habitat enhancement techniques, to provide both timber and caribou habitat? The program includes radiotelemetry, habitat capability mapping, habitat management trials, and development of an integrated strategy. The management trials are aimed at maintaining arboreal lichens and other key habitat attributes in managed stands. The strategy development component involves wildlife biologists and foresters in developing and implementing solutions to logging-caribou conflicts

In vivo function of the murid herpesvirus-4 ribonucleotide reductase small subunit

The difficulty of eliminating herpesvirus carriage makes host entry a key target for infection control. However, its viral requirements are poorly defined. Murid herpesvirus-4 (MuHV-4) can potentially provide insights into gammaherpesvirus host entry. Upper respiratory tract infection requires the MuHV-4 thymidine kinase (TK) and ribonucleotide reductase large subunit (RNR-L), suggesting a need for increased nucleotide production. However, both TK and RNR-L are likely to be multifunctional. We therefore tested further the importance of nucleotide production by disrupting the MuHV-4 ribonucleotide reductase small subunit (RNR-S). This caused a similar attenuation to RNR-L disruption: despite reduced intra-host spread, invasive inoculations still established infection, whereas a non-invasive upper respiratory tract inoculation did so only at high dose. Histological analysis showed that RNR-S−, RNR-L− and TK− viruses all infected cells in the olfactory neuroepithelium but unlike wild-type virus then failed to spread. Thus captured host nucleotide metabolism enzymes, up to now defined mainly as important for alphaherpesvirus reactivation in neurons, also have a key role in gammaherpesvirus host entry. This seemed to reflect a requirement for lytic replication to occur in a terminally differentiated cell before a viable pool of latent genomes could be established

Hippocampal-dependent appetitive control is impaired by experimental exposure to a Western-style diet

Animals fed a Western-style diet (WS-diet) demonstrate rapid impairments in hippocampal function and poorer appetitive control. We examined if this also occurs in humans. One-hundred and ten healthy lean adults were randomised to either a 1-week WS-diet intervention or a habitual-diet control group. Measures of hippocampal dependent learning and memory (HDLM) and of appetitive control were obtained pre- and post-intervention. HDLM was retested at 3-weeks follow-up. Relative to controls, HDLM performance declined in the WS-diet group (d=0.43), but was not different at follow-up. Appetitive control also declined in the WS-diet group (d=0.47) and this was strongly correlated with HDLM decline (d=1.01). These findings demonstrate that a WS-diet can rapidly impair appetitive control in humans - an effect that could promote overeating in consumers of a WS-diet. The study also suggests a functional role for the hippocampus in appetitive control and provides new evidence for the adverse neurocognitive effects of a WS-diet

In vivo imaging of murid herpesvirus-4 infection

Luciferase-based imaging allows a global view of microbial pathogenesis. We applied this technique to gammaherpesvirus infection by inserting a luciferase expression cassette into the genome of murine herpesvirus-4 (MuHV-4). The recombinant virus strongly expressed luciferase in lytically infected cells without significant attenuation. We used it to compare different routes of virus inoculation. After intranasal infection of anaesthetized mice, luciferase was expressed in the nose and lungs for 7–10 days and in lymphoid tissue, most consistently the superficial cervical lymph nodes, for up to 30 days. Gastrointestinal infection was not observed. Intraperitoneal infection was very different to intranasal, with strong luciferase expression in the liver, kidneys, intestines, reproductive tract and spleen, but none in the nose or lungs. The nose has not previously been identified as a site of MuHV-4 infection. After intranasal infection of non-anaesthetized mice, it was the only site of non-lymphoid luciferase expression. Nevertheless, lymphoid colonization and persistence were still established, even at low inoculation doses. In contrast, virus delivered orally was very poorly infectious. Inoculation route therefore had a major impact on pathogenesis. Low dose intranasal infection without anaesthesia seems most likely to mimic natural transmission, and may therefore be particularly informative about normal viral gene functions

The Cognitive Control of Eating and Body Weight: It’s More Than What You “Think”

Over the past decade, a great deal of research has established the importance of cognitive processes in the control of energy intake and body weight. The present paper begins by identifying several of these cognitive processes. We then summarize evidence from human and nonhuman animal models, which shows how excess intake of obesity-promoting Western diet (WD) may have deleterious effects on these cognitive control processes. Findings that these effects may be manifested as early-life deficits in cognitive functioning and may also be associated with the emergence of serious late-life cognitive impairment are described. Consistent with these possibilities, we review evidence, obtained primarily from rodent models, that consuming a WD is associated with the emergence of pathophysiologies in the hippocampus, an important brain substrate for learning, memory, and cognition. The implications of this research for mechanism are discussed within the context of a “vicious-cycle model,” which describes how eating a WD could impair hippocampal function, producing cognitive deficits that promote increased WD intake and body weight gain, which could contribute to further hippocampal dysfunction, cognitive decline, and excess eating and weight gain

Prey Records for the Eastern Indigo Snake (Drymarchon couperi)

Prey items for the federally protected Eastern Indigo Snake (Drymarchon couperi) were compiled from published and gray literature, field observations, necropsies, dissection of museum specimens, and personal communications from reliable sources. One hundred and eighty-six records were obtained for 48 different prey species. Anurans, Gopher Tortoises, snakes, and rodents comprised ca. 85% of the prey items. Most records (n = 143) that mentioned size were from adult indigos; 17 were from juveniles. Prey records were collected from 1940-2008 and were available for all months of the year. These data confirm that Eastern Indigo Snakes eat a wide assortment of prey of varying sizes. This strategy allows D. couperi to potentially forage successfully in many different types of habitats and under fluctuating environmental conditions, a valuable trait for a top-level predator that requires a large home range

Self-assembly in dilute mixtures of non-ionic and anionic surfactants and rhamnolipid biosurfactant

The self-assembly of dilute aqueous solutions of a ternary surfactant mixture and rhamnolipid biosurfactant/surfactant mixtures has been studied by small angle neutron scattering. In the ternary surfactant mixture of octaethylene glycol monododecyl ether, C12E8, sodium dodecyl 6-benzene sulfonate, LAS, and sodium dioxyethylene monododecyl sulfate, SLES, small globular interacting micelles are observed over the entire composition and concentration range studied. The modelling of the scattering data strongly supports the assumption that the micelle compositions are close to the solution compositions. In the 5-component rhamnolipid/surfactant mixture of the mono-rhamnose, R1, di-rhamnose, R2, rhamnolipids with C12E8/LAS/SLES, globular micelles are observed over much of the concentration and composition range studied. However, for solutions relatively rich in rhamnolipid and LAS, lamellar/micellar coexistence is observed. The transition from globular to more planar structures arises from a synergistic packing in the 5 component mixture. It is not observed in the individual components nor in the ternary C12E8/LAS/SLES mixture at these relatively low concentrations. The results provide an insight into how synergistic packing effects can occur in the solution self-assembly of complex multi-component surfactant mixtures, and give rise to an unexpected evolution in the phase behaviour