Analysis and calibration of absorptive images of Bose-Einstein condensate at non-zero temperatures

We describe the method allowing quantitative interpretation of absorptive images of mixtures of BEC and thermal atoms which reduces possible systematic errors associated with evaluation of the contribution of each fraction. By using known temperature dependence of the BEC fraction, the analysis allows precise calibration of the fitting results. The developed method is verified in two different measurements and compares well with theoretical calculations and with measurements performed by another group.Comment: 17 pages, 8 figure

Hemagglutinin Spatial Distribution Shifts in Response to Cholesterol in the Influenza Viral Envelope

AbstractInfluenza virus delivers its genome to the host cytoplasm via a process of membrane fusion mediated by the viral hemagglutinin protein. Optimal fusion likely requires multiple hemagglutinin trimers, so the spatial distribution of hemagglutinin on the viral envelope may influence fusion mechanism. We have previously shown that moderate depletion of cholesterol from the influenza viral envelope accelerates fusion kinetics even though it decreases fusion efficiency, both in a reversible manner. Here, we use electron cryo-microscopy to measure how the hemagglutinin lateral density in the viral envelope changes with cholesterol extraction. We extract this information by measuring the radial distribution function of electron density in >4000 viral images per sample, assigning hemagglutinin density by comparing images with and without anti-HA Fab bound. On average, hemagglutinin trimers move closer together: we estimate that the typical trimer-trimer spacing reduces from 94 to 84 Å when ∼90% of cholesterol is removed from the viral membrane. Upon restoration of viral envelope cholesterol, this spacing once again expands. This finding can qualitatively explain the observed changes to fusion kinetics: contemporary models from single-virus microscopy are that fusion requires the engagement of several hemagglutinin trimers in close proximity. If removing cholesterol increases the lateral density of hemagglutinin, this should result in an increase in the rate of fusion

Strontium optical lattice clocks for practical realization of the metre and secondary representation of the second

We present a system of two independent strontium optical lattice standards probed with a single shared ultra-narrow laser. The absolute frequency of the clocks can be verified by the use of Er:fiber optical frequency comb with the GPS-disciplined Rb frequency standard. We report hertz-level spectroscopy of the clock line and measurements of frequency stability of the two strontium optical lattice clocks.Comment: This is an author-created, un-copyedited version of an article accepted for publication in Meas. Sci. Technol. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi:10.1088/0957-0233/26/7/07520

Fibre-optic delivery of time and frequency to VLBI station

The quality of Very Long Baseline Interferometry (VLBI) radio observations predominantly relies on precise and ultra-stable time and frequency (T&F) standards, usually hydrogen masers (HM), maintained locally at each VLBI station. Here, we present an operational solution in which the VLBI observations are routinely carried out without use of a local HM, but using remote synchronization via a stabilized, long-distance fibre-optic link. The T&F reference signals, traceable to international atomic timescale (TAI), are delivered to the VLBI station from a dedicated timekeeping laboratory. Moreover, we describe a proof-of-concept experiment where the VLBI station is synchronized to a remote strontium optical lattice clock during the observation.Comment: 8 pages, 8 figures, matches the version published in A&A, section Astronomical instrumentatio

Morphological traits can track coral reef responses to the Anthropocene

MD was supported by the John Templeton Foundation (60501) and JM was supported by the Australian Research Council (FT110100609) during the period this research was undertaken.1. Susceptibility to human-driven environmental changes is mediated by species traits. Therefore, identifying traits that predict organism performance, ecosystem function and response to changes in environmental conditions can help forecast how ecosystems are responding to the Anthropocene. 2. Morphology dictates how organisms interact with their environment and other organisms, partially determining the environmental and biological contexts in which they are successful. Morphology is important for autogenic ecosystem engineering organisms, such as reef-building corals, because it determines the shape of the structures they create and by extension the communities they support. 3. Here, we present six morphological traits that capture variation in volume compactness, surface complexity and top-heaviness. With support from the literature, we propose causal links between morphology and a performance–function–response framework. 4. To illustrate these concepts, we combine 3D scanning and coral survey data to predict morphological traits from in situ colonies. We present a case study that examines how assemblage-scale morphological traits have responded to two cyclones and the 2016 mass bleaching event—two phenomena predicted to increase in severity in the Anthropocene—and discuss how these changes may impact ecosystem function. 5. The morphological traits outlined here offer a generalised and hypothesis-driven approach to tracking how reefs respond to the Anthropocene. The ability to predict these traits from field data and the increasing use of photogrammetry makes them readily applicable across broad spatiotemporal scales.PostprintPeer reviewe

Monohydroxylated metabolites of the K2 synthetic cannabinoid JWH-073 retain intermediate to high cannabinoid 1 receptor (CB1R) affinity and exhibit neutral antagonist to partial agonist activity

K2 and several similar purported “incense products” spiked with synthetic cannabinoids are abused as cannabis substitutes. We hypothesized that metabolism of JWH-073, a prevalent cannabinoid found in K2, contributes to toxicity associated with K2 use. Competition receptor binding studies and G-protein activation assays, both performed by employing mouse brain homogenates, were used to determine the affinity and intrinsic activity, respectively, of potential monohydroxylated (M1, M3–M5) and monocarboxylated (M6) metabolites at cannabinoid 1 receptors (CB1Rs). Surprisingly, M1, M4 and M5 retain nanomolar affinity for CB1Rs, while M3 displays micromolar affinity and M6 does not bind to CB1Rs. JWH-073 displays equivalent efficacy to that of the CB1R full agonist CP-55,940, while M1, M3, and M5 act as CB1R partial agonists, and M4 shows little or no intrinsic activity. Further in vitro investigation by Schild analysis revealed that M4 acts as a competitive neutral CB1R antagonist (Kb~40nM). In agreement with in vitro studies, M4 also demonstrates CB1R antagonism in vivo by blunting cannabinoid-induced hypothermia in mice. Interestingly, M4 does not block agonist-mediated responses of other measures in the cannabinoid tetrad (e.g., locomotor suppression, catalepsy or analgesia). Finally, also as predicted by in vitro results, M1 exhibits agonist activity in vivo by inducing significant hypothermia and suppression of locomotor activity in mice. In conclusion, the present study indicates that further work examining the physiological effects of synthetic cannabinoid metabolism is warranted. Such a complex mix of metabolically produced CB1R ligands may contribute to the adverse effect profile of JWH-073-containing products

Thermomechanical Fatigue Behavior of a Silicon Carbide Fiber-Reinforced Calcium Aluminosilicate Composite

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65874/1/j.1151-2916.1993.tb04022.x.pd

Observation of Coherent Elastic Neutrino-Nucleus Scattering

The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross-section is the largest by far of all low-energy neutrino couplings. This mode of interaction provides new opportunities to study neutrino properties, and leads to a miniaturization of detector size, with potential technological applications. We observe this process at a 6.7-sigma confidence level, using a low-background, 14.6-kg CsI[Na] scintillator exposed to the neutrino emissions from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the Standard Model for this process, are observed in high signal-to-background conditions. Improved constraints on non-standard neutrino interactions with quarks are derived from this initial dataset