SR90, strontium shaped-charge critical ionization velocity experiment

In May 1986 an experiment was performed to test Alfven's critical ionization velocity (CIV) effect in free space, using the first high explosive shaped charge with a conical liner of strontium metal. The release, made at 540 km altitude at dawn twilight, was aimed at 48 deg to B. The background electron density was 1.5 x 10(exp 4) cu cm. A faint field-aligned Sr(+) ion streak with tip velocity of 2.6 km/s was observed from two optical sites. Using two calibration methods, it was calculated that between 4.5 x 10(exp 20) and 2 x 10(exp 21) ions were visible. An ionization time constant of 1920 s was calculated for Sr from the solar UV spectrum and ionization cross section which combined with a computer simulation of the injection predicts 1.7 x 10(exp 21) solar UV ions in the low-velocity part of the ion streak. Thus all the observed ions are from solar UV ionization of the slow (less than critical) velocity portion of the neutral jet. The observed neutral Sr velocity distribution and computer simulations indicate that 2 x 10(exp 21) solar UV ions would have been created from the fast (greater than critical) part of the jet. They would have been more diffuse, and were not observed. Using this fact it was estimated that any CIV ions created were less than 10(exp 21). It was concluded that future Sr CIV free space experiments should be conducted below the UV shadow height and in much larger background plasma density

Climate research and open data at Oxford

Climate change is a crucial issue globally. There are many departments and groups across the University of Oxford that focus on fundamental areas of research to help support change and development, with experts in their fields contributing to key discussions, studies, and policy – resulting in a wealth of publications and research outputs. How can Open Access and Open Data be used to support, inform and shape the future? Short lightning presentations will focus on how discovery, access and re-use of research and research data can help to better inform key areas of Climate Research

Ultrafast sodium channel block by dietary fish oil prevents dofetilide-induced ventricular arrhythmias in rabbit hearts

9 pages, 4 figures, 1 table.-- et al.Several epidemiologic and clinical studies show that following myocardial infarction, dietary supplements of omega-3 polyunsaturated fatty acids (omega3FA) reduce sudden death. Animal data show that omega3FA have antiarrhythmic properties, but their mechanisms of action require further elucidation. The effects of omega3FA supplementation were studied in female rabbits to analyze whether their antiarrhythmic effects are due to a reduction of triangulation, reverse use-dependence, instability, and dispersion (TRIaD) of the cardiac action potential (TRIaD as a measure of proarrhythmic effects). In Langendorff-perfused hearts challenged by a selective rapidly activating delayed rectifier potassium current inhibitor that has been shown to exhibit proarrhythmic effects (dofetilide; 1 to 100 nM), omega3FA pretreatment (30 days; n=6) prolonged the plateau phase of the monophasic action potential; did not slow the terminal fast repolarization; reduced the dofetilide-induced prolongation of the action potential duration; reduced dofetilide-induced triangulation; and reduced dofetilide-induced reverse use-dependence, instability of repolarization, and dispersion. Dofetilide reduced excitability in omega3FA-pretreated hearts but not in control hearts. Whereas torsades de pointes (TdP) were observed in five out of six in control hearts, none were observed in omega3FA-pretreated hearts. Docosahexaenoic acid (DHA) inhibited the sodium current with ultrafast kinetics. Dietary omega3FA supplementation markedly reduced dofetilide-induced TRIaD and abolished dofetilide-induced TdP. Ultrafast sodium channel block by DHA may account for the antiarrhythmic protection of the dietary supplements of omega3FA against dofetilide-induced proarrhythmia observed in this animal model.This work was funded by Solvay Pharma, Novartis, Grants CICYT SAF2004-06856 and SAF2007-65868 and Red Temática de Investigación Cooperativa Grant FIS RD06/0014/0006.Peer reviewe

CL study of blue and UV emissions in ß-Ga_2O_3 nanowires grown by thermal evaporation of GaN

We report a cathodoluminescence (CL) study of ß-Ga_2O_3 nanowires grown by thermal evaporation of GaN on Si(100) and Au/Si(00) substrates. Condensation and subsequent oxidation of metallic Ga is suggested as the growth mechanism of ß-Ga_2O_3 nanowires. The ß-Ga_2O_3 nanowires grown on Si(100) show multiple bends or undulations, together with a strong UV emission at 3.31 eV and a weak blue emission centered at 2.8 eV as a band component. The ß-Ga_2O_3 nanowires grown on Au/Si(100) substrates recorded a lower CL intensity of a well-defined blue emission of 2.8 eV. A thermal treatment on these samples produced an increase of the UV emission and quenching of the blue band. Thermal annealing of oxygen vacancies is proposed as the responsible mechanism for the observed behavior of these samples

Patterns of nocturnal rehydration in root tissues of Vaccinium corymbosum L. under severe drought conditions

Although roots in dry soil layers are commonly rehydrated by internal hydraulic redistribution during the nocturnal period, patterns of tissue rehydration are poorly understood. Rates of nocturnal rehydration were examined in roots of different orders in Vaccinium corymbosum L. ‘Bluecrop’ (Northern highbush blueberry) grown in a split-pot system with one set of roots in relatively moist soil and the other set of roots in dry soil. Vaccinium is noted for a highly branched and extremely fine root system. It is hypothesized that nocturnal root tissue rehydration would be slow, especially in the distal root orders because of their greater hydraulic constraints (smaller vessel diameters and fewer number of vessels). Vaccinium root hydraulic properties delayed internal water movement. Even when water was readily available to roots in the wet soil and transpiration was minimal, it took a whole night-time period of 12 h for the distal finest roots (1st to 4th order) under dry soil conditions to reach the same water potentials as fine roots in moist soil (1st to 4th order). Even though roots under dry soil equilibrated with roots in moist soil, the equilibrium point reached before sunrise was about –1.2 MPa, indicating that tissues were not fully rehydrated. Using a single-branch root model, it was estimated that individual roots exhibiting the lowest water potentials in dry soil were 1st order roots (distal finest roots of the root system). However, considered at the branch level, root orders with the highest hydraulic resistances corresponded to the lowest orders of the permanent root system (3rd-, 4th-, and 5th-order roots), thus indicating possible locations of hydraulic safety control in the root system of this species

Lhx6 Delineates a Pathway Mediating Innate Reproductive Behaviors from the Amygdala to the Hypothalamus

In mammals, innate reproductive and defensive behaviors are mediated by anatomically segregated connections between the amygdala and hypothalamus. This anatomic segregation poses the problem of how the brain integrates activity in these circuits when faced with conflicting stimuli eliciting such mutually exclusive behaviors. Using genetically encoded and conventional axonal tracers, we have found that the transcription factor Lhx6 delineates the reproductive branch of this pathway. Other Lhx proteins mark neurons in amygdalar nuclei implicated in defense. We have traced parallel projections from the posterior medial amygdala, activated by reproductive or defensive olfactory stimuli, respectively, to a point of convergence in the ventromedial hypothalamus. The opposite neurotransmitter phenotypes of these convergent projections suggest a “gate control” mechanism for the inhibition of reproductive behaviors by threatening stimuli. Our data therefore identify a potential neural substrate for integrating the influences of conflicting behavioral cues and a transcription factor family that may contribute to the development of this substrate

Pulse calibration and non-adiabatic control of solid-state artificial atoms

Transitions in an artificial atom, driven non-adiabatically through an energy-level avoided crossing, can be controlled by carefully engineering the driving protocol. We have driven a superconducting persistent-current qubit with a large-amplitude, radio-frequency field. By applying a bi-harmonic waveform generated by a digital source, we demonstrate a mapping between the amplitude and phase of the harmonics produced at the source and those received by the device. This allows us to image the actual waveform at the device. This information is used to engineer a desired time dependence, as confirmed by detailed comparison with simulation.Comment: 4.1 pages, 3 figure

Comparative salivary gland transcriptomics of sandfly vectors of visceral leishmaniasis

BACKGROUND: Immune responses to sandfly saliva have been shown to protect animals against Leishmania infection. Yet very little is known about the molecular characteristics of salivary proteins from different sandflies, particularly from vectors transmitting visceral leishmaniasis, the fatal form of the disease. Further knowledge of the repertoire of these salivary proteins will give us insights into the molecular evolution of these proteins and will help us select relevant antigens for the development of a vector based anti-Leishmania vaccine. RESULTS: Two salivary gland cDNA libraries from female sandflies Phlebotomus argentipes and P. perniciosus were constructed, sequenced and proteomic analysis of the salivary proteins was performed. The majority of the sequenced transcripts from the two cDNA libraries coded for secreted proteins. In this analysis we identified transcripts coding for protein families not previously described in sandflies. A comparative sandfly salivary transcriptome analysis was performed by using these two cDNA libraries and two other sandfly salivary gland cDNA libraries from P. ariasi and Lutzomyia longipalpis, also vectors of visceral leishmaniasis. Full-length secreted proteins from each sandfly library were compared using a stand-alone version of BLAST, creating formatted protein databases of each sandfly library. Related groups of proteins from each sandfly species were combined into defined families of proteins. With this comparison, we identified families of salivary proteins common among all of the sandflies studied, proteins to be genus specific and proteins that appear to be species specific. The common proteins included apyrase, yellow-related protein, antigen-5, PpSP15 and PpSP32-related protein, a 33-kDa protein, D7-related protein, a 39- and a 16.1- kDa protein and an endonuclease-like protein. Some of these families contained multiple members, including PPSP15-like, yellow proteins and D7-related proteins suggesting gene expansion in these proteins. CONCLUSION: This comprehensive analysis allows us the identification of genus- specific proteins, species-specific proteins and, more importantly, proteins common among these different sandflies. These results give us insights into the repertoire of salivary proteins that are potential candidates for a vector-based vaccine

Evaluating the utility of camera traps in field studies of predation

Artificial prey techniques—wherein synthetic replicas of real organisms are placed in natural habitats—are widely used to study predation in the field. We investigated the extent to which videography could provide additional information to such studies. As a part of studies on aposematism and mimicry of coral snakes (Micrurus) and their mimics, observational data from 109 artificial snake prey were collected from video-recording camera traps in three locations in the Americas (terra firme forest, Tiputini Biodiversity Station, Ecuador; premontane wet forest, Nahá Reserve, Mexico; longleaf pine forest, Southeastern Coastal Plain, North Carolina, USA). During 1,536 camera days, a total of 268 observations of 20 putative snake predator species were recorded in the vicinity of artificial prey. Predators were observed to detect artificial prey 52 times, but only 21 attacks were recorded. Mammals were the most commonly recorded group of predators near replicas (243) and were responsible for most detections (48) and attacks (20). There was no difference between avian or mammalian predators in their probability of detecting replicas nor in their probability of attacking replicas after detecting them. Bite and beak marks left on clay replicas registered a higher ratio of avian:mammalian attacks than videos registered. Approximately 61.5% of artificial prey monitored with cameras remained undetected by predators throughout the duration of the experiments. Observational data collected from videos could provide more robust inferences on the relative fitness of different prey phenotypes, predator behavior, and the relative contribution of different predator species to selection on prey. However, we estimate that the level of predator activity necessary for the benefit of additional information that videos provide to be worth their financial costs is achieved in fewer than 20% of published artificial prey studies. Although we suggest future predation studies employing artificial prey to consider using videography as a tool to inspire new, more focused inquiry, the investment in camera traps is unlikely to be worth the expense for most artificial prey studies until the cost:benefit ratio decreases