Study of cryogenic fluid mixing techniques. Volume 1 - Large-scale experimental mixing investigations and liquid-oxygen mixer design Final report

Large-scale experimental liquid hydrogen mixing and liquid oxygen mixer desig

Study of cryogenic fluid mixing techniques. Volume 2 - Large-scale mixing data Final report, Jul. 1969 - Jul. 1970

Basic mixing data and dimensionless correlations for 52 tests in large-scale stratified mixing tank for cryogenic rocket propellant

Rapid synaptic vesicle endocytosis in cone photoreceptors of salamander retina.

Following synaptic vesicle exocytosis, neurons retrieve the fused membrane by a process of endocytosis to provide a supply of vesicles for subsequent release and maintain the presynaptic active zone. Rod and cone photoreceptors use a specialized structure called the synaptic ribbon that enables them to sustain high rates of neurotransmitter release. They must also employ mechanisms of synaptic vesicle endocytosis capable of keeping up with release. While much is known about endocytosis at another retinal ribbon synapse, that of the goldfish Mb1 bipolar cell, less is known about endocytosis in photoreceptors. We used capacitance recording techniques to measure vesicle membrane fusion and retrieval in photoreceptors from salamander retinal slices. We found that application of brief depolarizing steps (\u3c100 \u3ems) to cones evoked exocytosis followed by rapid endocytosis with a time constant ∼250 ms. In some cases, the capacitance trace overshot the baseline, indicating excess endocytosis. Calcium had no effect on the time constant, but enhanced excess endocytosis resulting in a faster rate of membrane retrieval. Surprisingly, endocytosis was unaffected by blockers of dynamin, suggesting that cone endocytosis is dynamin independent. This contrasts with synaptic vesicle endocytosis in rods, which was inhibited by the dynamin inhibitor dynasore and GTPγS introduced through the patch pipette, suggesting that the two photoreceptor types employ distinct pathways for vesicle retrieval. The fast kinetics of synaptic vesicle endocytosis in photoreceptors likely enables these cells to maintain a high rate of transmitter release, allowing them to faithfully signal changes in illumination to second-order neurons

A study of cryogenic propellant mixing techniques. Volume 1 - Mixer design and experimental investigations Final report, Jul. 1967 - Sep. 1968

Mixer design and experimental tank study for cryogenic propellants, with applications for manned Mars missio

Ca2+ Diffusion through Endoplasmic Reticulum Supports Elevated Intraterminal Ca2+ Levels Needed to Sustain Synaptic Release from Rods in Darkness.

UNLABELLED: In addition to vesicle release at synaptic ribbons, rod photoreceptors are capable of substantial slow release at non-ribbon release sites triggered by Ca(2+)-induced Ca(2+) release (CICR) from intracellular stores. To maintain CICR as rods remain depolarized in darkness, we hypothesized that Ca(2+) released into the cytoplasm from terminal endoplasmic reticulum (ER) can be replenished continuously by ions diffusing within the ER from the soma. We measured [Ca(2+)] changes in cytoplasm and ER of rods from Ambystoma tigrinum retina using various dyes. ER [Ca(2+)] changes were measured by loading ER with fluo-5N and then washing dye from the cytoplasm with a dye-free patch pipette solution. Small dye molecules diffused within ER between soma and terminal showing a single continuous ER compartment. Depolarization of rods to -40 mV depleted Ca(2+) from terminal ER, followed by a decline in somatic ER [Ca(2+)]. Local activation of ryanodine receptors in terminals with a spatially confined puff of ryanodine caused a decline in terminal ER [Ca(2+)], followed by a secondary decrease in somatic ER. Localized photolytic uncaging of Ca(2+) from o-nitrophenyl-EGTA in somatic ER caused an abrupt Ca(2+) increase in somatic ER, followed by a slower Ca(2+) increase in terminal ER. These data suggest that, during maintained depolarization, a soma-to-terminal [Ca(2+)] gradient develops within the ER that promotes diffusion of Ca(2+) ions to resupply intraterminal ER Ca(2+) stores and thus sustain CICR-mediated synaptic release. The ability of Ca(2+) to move freely through the ER may also promote bidirectional communication of Ca(2+) changes between soma and terminal. SIGNIFICANCE STATEMENT: Vertebrate rod and cone photoreceptors both release vesicles at synaptic ribbons, but rods also exhibit substantial slow release at non-ribbon sites triggered by Ca(2+)-induced Ca(2+) release (CICR). Blocking CICR inhibits \u3e50% of release from rods in darkness. How do rods maintain sufficiently high [Ca(2+)] in terminal endoplasmic reticulum (ER) to support sustained CICR-driven synaptic transmission? We show that maintained depolarization creates a [Ca(2+)] gradient within the rod ER lumen that promotes soma-to-terminal diffusion of Ca(2+) to replenish intraterminal ER stores. This mechanism allows CICR-triggered synaptic release to be sustained indefinitely while rods remain depolarized in darkness. Free diffusion of Ca(2+) within the ER may also communicate synaptic Ca(2+) changes back to the soma to influence other critical cell processes

Influence of Normal Daytime Fat Deposition on Laboratory Measurements of Torpor Use in Territorial versus Nonterritorial Hummingbirds

Fat deposition and torpor use in hummingbirds exhibiting distinct foraging styles should vary. We predicted that dominant territorial hummingbirds will use torpor less than subordinate nonterritorial species because unrestricted access to energy by territory owners allows for fat storage. Entry into torpor was monitored using open-flow respirometry on hummingbirds allowed to accumulate fat normally during the day. Fat accumulation was measured by solvent fat extraction. Territorial blue-throated hummingbirds (Lampornis clemenciae) had the highest fat accumulation and used torpor only 17% of the time. Fat storage by L. clemenciae averaged 26% of lean dry mass (LDM) in 1995 and 18% in 1996, similar to that measured for other nonmigratory birds. Fat storage by magnificent hummingbirds (Eugenes fulgens; trapliner) and black-chinned hummingbirds (Archilochus alexandri; nectar robber) averaged 19% and 16% of LDM, respectively, and they used torpor frequently (64% and 92% of the time, respectively). All species initiated torpor if total body fat dropped below 10% of LDM, indicating the existence of a torpor threshold. The ability of L. clemenciae to store enough fat to support nighttime metabolism is likely an important benefit of territoriality. Likewise, frequent torpor use by subordinates suggests that natural restrictions to energy intake can impact their energy budget, necessitating energy conservation by use of torpor

On undirected trips, satisfaction, and well-being: Evidence from Flanders (Belgium)

Despite having the potential to improve subjective well-being, satisfaction with undirected travel, or travel for its own sake (e.g. taking a walk, bike ride, or joy ride), has not yet been empirically investigated. Using mean-comparison and generalized linear regression models, this study analyzes 1579 undirected trips made by 852 respondents to a survey in Flanders, Belgium during the COVID-19 pandemic lockdown (18 March – 4 May 2020). Undirected travel was found to be longer in duration and more satisfying than results from directed trips in previous literature, with an indication that higher levels of physical activity are important to satisfaction. Undirected travel satisfaction was found to have a clear positive relationship to well-being. As these trips are often active and were found to imply a positive utility of travel, understanding them can be important to policy goals regarding health, sustainability, and improving individual well-being

Evolutions in undirected travel (satisfaction) during the COVID-19 pandemic

The COVID-19 pandemic illustrated that undirected travel (UT), or trips taken for their own sake, can partly compensate for a reduction in destination-based trips due to governmental regulations. Consequently, UT (in general, but particularly during the pandemic) may be especially satisfying and therefore important to subjective well-being. However, through the course of the pandemic, changes in UT were anticipated as individuals adapted to a ‘new normal’. This research – conducted in Flanders, Belgium – first investigates whether the characteristics of and satisfaction with UT persisted after one year into the pandemic (April 2020 to May 2021) using longitudinal panel data from two waves (n = 332). Results of paired sample t-tests indicate that UT satisfaction increased though duration of trips decreased, and results of the Sign test indicate that the frequency of UT generally decreased. Second, this research investigates characteristics of individuals with different UT behavior. Six profiles of UT behavior were identified based on starting or stopping UT, increasing or decreasing UT, maintaining UT frequency, or not participating in UT. Chi2 tests identified differences among profiles based on wave 1 UT frequency, most recent trip mode, socio-demographic, and household characteristics. Results indicate that participation in UT might motivate future UT, one to three UT trips per week is a maintainable frequency, UT might be important to those with smaller living spaces and those living with children or other adults, and suggest that attention should be paid to mobility equity, including how and for whom systems are planned. These findings are important to understanding the effects of long-term governmental regulations in response to the COVID-19 pandemic on travel behavior, and how investigating UT might help to challenge and reimagine traditional mobility systems post-pandemic

A framework for the prospective analysis of super-diversity coming from high levels of immigration

Background Pressures to keep immigration rates at relatively high levels are likely to persist in most developed countries. At the same time, immigrant cohorts are becoming more and more diverse, leading host societies to become increasingly heterogeneous across multiple dimensions. For scholars who study demographic or socio-economic behaviours, the need to account for ethnocultural “super-diversity” brings new challenges and complications. Objective The main objective of this paper is to present a framework for the prospective analysis of super-diversity in several high immigration countries. Methods We developed microsimulation models that simultaneously project several population-dimensions for Canada, the United States and countries of the European Union, with the aim of studying the consequences of alternate future population and migration trends. Results The paper presents the projected progression of three indicators of diversity for Canada, the USA and the EU28: percentage of foreign-born population, percentage of the population using a non-official language at home and percentage of non-Christians under the reference scenario. Results from alternative scenarios show the potential impact of modifying the composition of migrant cohorts. The paper also examines the projected changes in the labour force for each region by education level and language. Finally, the paper proposes a new longitudinal indicator that counts the number of years lived as active and inactive over the life course for foreign- and native-born cohorts. Contribution The microsimulation models provide much more informative results than more traditional cohort-component or multi-state models to study the future effects of ethnocultural super-diversity on high immigration countries