Indirect Dissociative Recombination of LiH+^+ Molecules Fueled by Complex Resonance Manifolds

The LiH$^{+}$ molecule is prototypical of the indirect dissociative recombination (DR) process, in which a colliding electron destroys the molecule through Rydberg capture pathways. This Letter develops the first quantitative test of the Siegert state multichannel quantum defect theory description of indirect DR for a diatomic molecular ion. The R-matrix approach is adopted to calculate ab-initio quantum defects, functions of the internuclear distance that characterize both Rydberg states and the zero-energy collisions of electrons with LiH$^{+}$ ions. The calculated DR rate coefficient agrees accurately with recent experimental data (S. Krohn et al, Phys. Rev. Lett. 86, 4005). We identify the doorways to fast indirect DR as complex resonance manifolds, which couple closed channels having both high and low principal quantum numbers. This sheds new light on the competition between direct and indirect DR pathways, and suggests the reason why previous theory underestimated the DR rate by an order of magnitude.Comment: Submitted to PR

Improved growth and morphological plasticity of <i>Haloferax volcanii</i>.

Some microbes display pleomorphism, showing variable cell shapes in a single culture, whereas others differentiate to adapt to changed environmental conditions. The pleomorphic archaeon Haloferax volcanii commonly forms discoid-shaped ('plate') cells in culture, but may also be present as rods, and can develop into motile rods in soft agar, or longer filaments in certain biofilms. Here we report improvement of H. volcanii growth in both semi-defined and complex media by supplementing with eight trace element micronutrients. With these supplemented media, transient development of plate cells into uniformly shaped rods was clearly observed during the early log phase of growth; cells then reverted to plates for the late log and stationary phases. In media prepared with high-purity water and reagents, without supplemental trace elements, rods and other complex elongated morphologies ('pleomorphic rods') were observed at all growth stages of the culture; the highly elongated cells sometimes displayed a substantial tubule at one or less frequently both poles, as well as unusual tapered and highly curved forms. Polar tubules were observed forming by initial mid-cell narrowing or tubulation, causing a dumbbell-like shape, followed by cell division towards one end. Formation of the uniform early log-phase rods, as well as the pleomorphic rods and tubules were dependent on the function of the tubulin-like cytoskeletal protein, CetZ1. Our results reveal the remarkable morphological plasticity of H. volcanii cells in response to multiple culture conditions, and should facilitate the use of this species in further studies of archaeal biology

The BAHAMAS project: Effects of dynamical dark energy on large-scale structure

In this work we consider the impact of spatially-uniform but time-varying dark energy (or `dynamical dark energy', DDE) on large-scale structure in a spatially flat universe, using large cosmological hydrodynamical simulations that form part of the BAHAMAS project. As DDE changes the expansion history of the universe, it impacts the growth of structure. We explore variations in DDE that are constrained to be consistent with the cosmic microwave background. We find that DDE can affect the clustering of matter and haloes at the ~10% level (suppressing it for so-called `freezing' models, while enhancing it for `thawing' models), which should be distinguishable with upcoming large-scale structure surveys. DDE cosmologies can also enhance or suppress the halo mass function (with respect to LCDM) over a wide range of halo masses. The internal properties of haloes are minimally affected by changes in DDE, however. Finally, we show that the impact of baryons and associated feedback processes is largely independent of the change in cosmology and that these processes can be modelled separately to typically better than a few percent accurac

Presynaptic actions of 4-Aminopyridine and γ-aminobutyric acid on rat sympathetic ganglia in vitro

Responses to bath-applications of 4-aminopyridine (4-AP) and -aminobutyric acid (GABA) were recorded intracellularly from neurones in the rat isolated superior cervical ganglion. 4-aminopyridine (0.1–1.0 mmol/l) usually induced spontaneous action potentials and excitatory postsynaptic potentials (EPSPs), which were blocked by hexamethonium. Membrane potential was unchanged; spike duration was slightly increased. Vagus nerve B-and C-fibre potentials were prolonged. In 4-AP solution (0.1–0.3 mmol/l), GABA (0.1 mmol/l), 3-aminopropanesulphonic acid or muscimol evoked bursts of spikes and EPSPs in addition to a neuronal depolarization. These bursts, which were not elicited by glycine, glutamate, taurine or (±)-baclofen, were completely antagonised by hexamethonium, tetrodotoxin or bicuculline methochloride. It is concluded that: (a) 4-AP has a potent presynaptic action on sympathetic ganglia; (b) presynaptic actions of GABA can be recorded postsynaptically in the presence of 4-AP; and (c) the presynaptic GABA-receptors revealed in this condition are similar to those on the postsynaptic membrane

Apneusis responding to buspirone in multiple sclerosis

Apneusis is a disturbance of respiratory rhythm characterized by severely prolonged inspiratory effort, and is caused by bilateral lesions in the dorsal pons. In humans it is most commonly caused by pontine infarction and has rarely been reported in multiple sclerosis (MS). Here we report on a patient with MS who developed episodic apneusis which responded to treatment with buspirone, a serotonin type 1A receptor agonist

Intrinsic alignments of the extended radio continuum emission of galaxies in the EAGLE simulations

We present measurements of the intrinsic alignments (IAs) of the star-forming gas of galaxies in the EAGLE simulations. Radio continuum imaging of this gas enables cosmic shear measurements complementary to optical surveys. We measure the orientation of star-forming gas with respect to the direction to, and orientation of, neighbouring galaxies. Star-forming gas exhibits a preferentially radial orientation-direction alignment that is a decreasing function of galaxy pair separation, but remains significant to $\gtrsim 1$ Mpc at $z=0$. The alignment is qualitatively similar to that exhibited by the stars, but is weaker at fixed separation. Pairs of galaxies hosted by more massive subhaloes exhibit stronger alignment at fixed separation, but the strong alignment of close pairs is dominated by ${\sim}L^\star$ galaxies and their satellites. At fixed comoving separation, the radial alignment is stronger at higher redshift. The orientation-orientation alignment is consistent with random at all separations, despite subhaloes exhibiting preferential parallel minor axis alignment. The weaker IA of star-forming gas than for stars stems from the former's tendency to be less well aligned with the dark matter structure of galaxies than the latter, and implies that the systematic uncertainty due to IA may be less severe in radio continuum weak lensing surveys than in optical counterparts. Alignment models equating the orientation of star-forming gas discs to that of stellar discs or the DM structure of host subhaloes will therefore overestimate the impact of IAs on radio continuum cosmic shear measurements

Variation in quality of acute stroke care by day and time of admission: prospective cohort study of weekday and weekend centralised hyperacute stroke unit care and non-centralised services.

OBJECTIVE: To investigate variations in quality of acute stroke care and outcomes by day and time of admission in London hyperacute stroke units compared with the rest of England. DESIGN: Prospective cohort study using anonymised patient-level data from the Sentinel Stroke National Audit Programme. SETTING: Acute stroke services in London hyperacute stroke units and the rest of England. PARTICIPANTS: 68 239 patients with a primary diagnosis of stroke admitted between January and December 2014. INTERVENTIONS: Hub-and-spoke model for care of suspected acute stroke patients in London with performance standards designed to deliver uniform access to high-quality hyperacute stroke unit care across the week. MAIN OUTCOME MEASURES: 16 indicators of quality of acute stroke care, mortality at 3 days after admission to the hospital, disability at the end of the inpatient spell, length of stay. RESULTS: There was no variation in quality of care by day and time of admission to the hospital across the week in terms of stroke nursing assessment, brain scanning and thrombolysis in London hyperacute stroke units, nor was there variation in 3-day mortality or disability at hospital discharge (all p values>0.05). Other quality of care measures significantly varied by day and time of admission across the week in London (all p values0.05). CONCLUSIONS: The London hyperacute stroke unit model achieved performance standards for 'front door' stroke care across the week. The same benefits were not achieved by other models of care in the rest of England. There was no weekend effect for mortality in London or the rest of the England. Other aspects of care were not constant across the week in London hyperacute stroke units, indicating some performance standards were perceived to be more important than others

Quenching of satellite galaxies of Milky Way analogues: reconciling theory and observations

The vast majority of low-mass satellite galaxies around the Milky Way and M31 appear virtually devoid of cool gas and show no signs of recent or ongoing star formation. Cosmological simulations demonstrate that such quenching is expected and is due to the harsh environmental conditions that satellites face when joining the Local Group (LG). However, recent observations of Milky Way analogues in the SAGA survey present a very different picture, showing the majority of observed satellites to be actively forming stars, calling into question the realism of current simulations and the typicality of the LG. Here we use the ARTEMIS suite of high-resolution cosmological hydrodynamical simulations to carry out a careful comparison with observations of dwarf satellites in the LG, SAGA, and the Local Volume (LV) survey. We show that differences between SAGA and the LG and LV surveys, as well as between SAGA and the ARTEMIS simulations, can be strongly reduced by considering differences in the host mass distributions and (more importantly) observational selection effects, specifically that low-mass satellites which have only recently been accreted are more likely to be star-forming, have a higher optical surface brightness, and are therefore more likely to be included in the SAGA survey. This picture is confirmed using data from the deeper LV survey, which shows pronounced quenching at low masses, in accordance with the predictions of LCDM-based simulations

What does it take to provide clinical interventions with temporal consistency? A qualitative study of London hyperacute stroke units.

OBJECTIVES: Seven-day working in hospitals is a current priority of international health research and policy. Previous research has shown variability in delivering evidence-based clinical interventions across different times of day and week. We aimed to identify factors influencing such variations in London hyperacute stroke units (HASUs). DESIGN: Interview and observation study to explain patterns of variation in delivery and outcomes of care described in a quantitative partner paper (Melnychuk et al). SETTING: Eight HASUs in London. PARTICIPANTS: We interviewed HASU staff (n=76), including doctors, nurses, therapists and administrators. We also conducted non-participant observations of delivery of care at different times of the day and week (n=45; ~102 hours). We analysed the data for thematic content relating to the ability of staff to provide evidence-based interventions consistently at different times of the day and week. RESULTS: Staff were able to deliver 'front door' interventions consistently by taking on additional responsibilities out of hours (eg, deciding eligibility for thrombolysis); creating continuities between day and night (through, eg, governance processes and staggering rotas); building trusting relationships with, eg, Radiology and Emergency Departments and staff prioritisation of 'front door' interventions. Variations by time of day resulted from reduced staffing in HASUs and elsewhere in hospitals in the evenings and at the weekend. Variations by day of week (eg, weekend effect) resulted from lack of therapy input and difficulties repatriating patients at weekends, and associated increases in pressure on Fridays and Mondays. CONCLUSIONS: Evidence-based service standards can facilitate 7-day working in acute stroke services. Standards should ensure that the capacity and capabilities required for 'front door' interventions are available 24/7, while other services, for example, therapies are available every day of the week. The impact of standards is influenced by interdependencies between HASUs, other hospital services and social services

Testing extensions to LCDM on small scales with forthcoming cosmic shear surveys

We investigate the constraining power of forthcoming Stage-IV weak lensing surveys (Euclid, LSST, and NGRST) for extensions to the LCDM model on small scales, via their impact on the cosmic shear power spectrum. We use high-resolution cosmological simulations to calculate how warm dark matter (WDM), self-interacting dark matter (SIDM) and a running of the spectral index affect the non-linear matter power spectrum, P(k), as a function of scale and redshift. We evaluate the cosmological constraining power using synthetic weak lensing observations derived from these power spectra and that take into account the anticipated source densities, shape noise and cosmic variance errors of upcoming surveys. We show that upcoming Stage-IV surveys will be able to place useful, independent constraints on both WDM models (ruling out models with a particle mass of 10 cm^2 g^-1) through their effects on the small-scale cosmic shear power spectrum. Similarly, they will be able to strongly constrain cosmologies with a running spectral index. Finally, we explore the error associated with the cosmic shear cross-spectrum between tomographic bins, finding that it can be significantly affected by Poisson noise (the standard assumption is that the Poisson noise cancels between tomographic bins). We provide a new analytic form for the error on the cross-spectrum which accurately captures this effect