19 research outputs found
Dark Matter Annihilation around Intermediate Mass Black Holes: an update
The formation and evolution of Black Holes inevitably affects the
distribution of dark and baryonic matter in the neighborhood of the Black Hole.
These effects may be particularly relevant around Supermassive and Intermediate
Mass Black Holes (IMBHs), the formation of which can lead to large Dark Matter
overdensities, called {\em spikes} and {\em mini-spikes} respectively. Despite
being larger and more dense, spikes evolve at the very centers of galactic
halos, in regions where numerous dynamical effects tend to destroy them.
Mini-spikes may be more likely to survive, and they have been proposed as
worthwhile targets for indirect Dark Matter searches. We review here the
formation scenarios and the prospects for detection of mini-spikes, and we
present new estimates for the abundances of mini-spikes to illustrate the
sensitivity of such predictions to cosmological parameters and uncertainties
regarding the astrophysics of Black Hole formation at high redshift. We also
connect the IMBHs scenario to the recent measurements of cosmic-ray electron
and positron spectra by the PAMELA, ATIC, H.E.S.S., and Fermi collaborations.Comment: 12 pages, 7 figures. Invited contribution to NJP Focus Issue on "Dark
Matter and Particle Physics
Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing
No abstract available
Sleep is required to consolidate odor memory and remodel olfactory synapses
Animals with complex nervous systems demand sleep for memory consolidation and synaptic remodeling. Here, we show that, although the Caenorhabditis elegans nervous system has a limited number of neurons, sleep is necessary for both processes. In addition, it is unclear if, in any system, sleep collaborates with experience to alter synapses between specific neurons and whether this ultimately affects behavior. C. elegans neurons have defined connections and well-described contributions to behavior. We show that spaced odor-training and post-training sleep induce long-term memory. Memory consolidation, but not acquisition, requires a pair of interneurons, the AIYs, which play a role in odor-seeking behavior. In worms that consolidate memory, both sleep and odor conditioning are required to diminish inhibitory synaptic connections between the AWC chemosensory neurons and the AIYs. Thus, we demonstrate in a living organism that sleep is required for events immediately after training that drive memory consolidation and alter synaptic structures
Aqueous alteration processes in Jezero crater, Marsâimplications for organic geochemistry
The Perseverance rover landed in Jezero crater, Mars, in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep-ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, which probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks and are preserved in minerals related to both aqueous environments
Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry
Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase
Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTICâHF: baseline characteristics and comparison with contemporary clinical trials
Aims:
The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTICâHF) trial. Here we describe the baseline characteristics of participants in GALACTICâHF and how these compare with other contemporary trials.
Methods and Results:
Adults with established HFrEF, New York Heart Association functional class (NYHA)ââ„âII, EF â€35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokineticâguided dosing: 25, 37.5 or 50âmg bid). 8256 patients [male (79%), nonâwhite (22%), mean age 65âyears] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NTâproBNP 1971âpg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTICâHF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressureâ<â100âmmHg (n = 1127), estimated glomerular filtration rate <â30âmL/min/1.73 m2 (n = 528), and treated with sacubitrilâvalsartan at baseline (n = 1594).
Conclusions:
GALACTICâHF enrolled a wellâtreated, highârisk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation
TriclinicâCubic Phase Transition and Negative Expansion in the Actinide IV (Th, U, Np, Pu) Diphosphates
International audienceThe AnP2O7 diphosphates (An = Th, U, Np, Pu) have been synthesized by various routes depending on the stability of the AnIV cation and its suitability for the unusual octahedral environment. Synchrotron and X-ray diffraction, thermal analysis, Raman spectroscopy, and 31P nuclear magnetic resonance reveal them as a new family of diphosphates which probably includes the recently studied CeP2O7. Although they adopt at high temperature the same cubic archetypal cell as the other known MP2O7 diphosphates, they differ by a very faint triclinic distortion at room temperature that results from an ordering of the P2O7 units, as shown using high-resolution synchrotron diffraction for UP2O7. The uncommon triclinicâcubic phase transition is first order, and its temperature is very sensitive to the ionic radius of AnIV. The conflicting effects which control the thermal variations of the PâOâP angle are responsible for a strong expansion of the cell followed by a contraction at higher temperature. This inversion of expansion occurs at a temperature significantly higher than the phase transition, at variance with the parent compounds with smaller MIV cations in which the two phenomena coincide. As shown by various approaches, the PâObâP linkage remains bent in the cubic form
Structural distortions in the high-pressure polar phases of ammonium metal formates
The high-pressure behaviour of ammonium metal formates has been investigated using high-pressure single-crystal X-ray diffraction on ammonium iron and nickel formates, and neutron powder diffraction on ammonium zinc formate in the pressure range of 0â2.3 GPa. A structural phase transition in the pressure range of 0.4â1.4 GPa, depending on the metal cation, is observed for all three ammonium metal formates. The hexagonal-to-monoclinic high-pressure transition gives rise to characteristic sixfold twinning based on the single-crystal diffraction data. Structure solution of the single-crystal data and refinement of the neutron powder diffraction characterise the pressure-induced distortions of the metal formate frameworks. The pressure dependence of the principal axes shows significantly larger anisotropic compressibilities in the high-pressure monoclinic phase (K = 48 TPa, K = â7 TPa) compared to the ambient hexagonal phase (K = 16 TPa, K = â2 TPa), and can be related to the symmetry-breaking distortions that cause deformation of the honeycomb motifs in the metal formate framework. While high-pressure Raman spectroscopy suggests that the ammonium cations remain dynamically disordered upon the phase transition, the pressure-induced distortions in the metal formate framework cause polar displacements in the ammonium cations. The magnitude of polarisation in the high-pressure phase of ammonium zinc formate was calculated based upon the offset of the ammonium cation relative to the anionic zinc formate framework, showing an enhanced polarisation of Ps ⌠4 ÎŒC cm at the transition, which then decreases with increasing pressure
TriclinicâCubic Phase Transition and Negative Expansion in the Actinide IV (Th, U, Np, Pu) Diphosphates
The <i>An</i>P<sub>2</sub>O<sub>7</sub> diphosphates
(<i>An</i> = Th, U, Np, Pu) have been synthesized by various
routes depending on the stability of the <i>An</i><sup>IV</sup> cation and its suitability for the unusual octahedral environment.
Synchrotron and X-ray diffraction, thermal analysis, Raman spectroscopy,
and <sup>31</sup>P nuclear magnetic resonance reveal them as a new
family of diphosphates which probably includes the recently studied
CeP<sub>2</sub>O<sub>7</sub>. Although they adopt at high temperature
the same cubic archetypal cell as the other known MP<sub>2</sub>O<sub>7</sub> diphosphates, they differ by a very faint triclinic distortion
at room temperature that results from an ordering of the P<sub>2</sub>O<sub>7</sub> units, as shown using high-resolution synchrotron diffraction
for UP<sub>2</sub>O<sub>7</sub>. The uncommon triclinicâcubic
phase transition is first order, and its temperature is very sensitive
to the ionic radius of <i>An</i><sup>IV</sup>. The conflicting
effects which control the thermal variations of the PâOâP
angle are responsible for a strong expansion of the cell followed
by a contraction at higher temperature. This inversion of expansion
occurs at a temperature significantly higher than the phase transition,
at variance with the parent compounds with smaller M<sup>IV</sup> cations
in which the two phenomena coincide. As shown by various approaches,
the PâO<sub>b</sub>âP linkage remains bent in the cubic
form