On the Magnitude of Dark Energy Voids and Overdensities

We investigate the clustering of dark energy within matter overdensities and voids. In particular, we derive an analytical expression for the dark energy density perturbations, which is valid both in the linear, quasi-linear and fully non-linear regime of structure formation. We also investigate the possibility of detecting such dark energy clustering through the ISW effect. In the case of uncoupled quintessence models, if the mass of the field is of order the Hubble scale today or smaller, dark energy fluctuations are always small compared to the matter density contrast. Even when the matter perturbations enter the non-linear regime, the dark energy perturbations remain linear. We find that virialised clusters and voids correspond to local overdensities in dark energy, with \delta_{\phi}/(1+w) \sim \Oo(10^{-5}) for voids, \delta_{\phi}/(1+w) \sim \Oo(10^{-4}) for super-voids and \delta_{\phi}/(1+w) \sim \Oo(10^{-5}) for a typical virialised cluster. If voids with radii of $100-300 {\rm Mpc}$ exist within the visible Universe then $\delta_{\phi}$ may be as large as $10^{-3}(1+w)$. Linear overdensities of matter and super-clusters generally correspond to local voids in dark energy; for a typical super-cluster: \delta_{\phi}/(1+w) \sim \Oo(-10^{-5}). The approach taken in this work could be straightforwardly extended to study the clustering of more general dark energy models.Comment: 20 pages, 14 figures. Accepted by the Astrophys.

Structural investigations of phosphorus-nitrogen compounds. 7. Relationships between physical properties, electron densities, reaction mechanisms and hydrogen-bonding motifs of N3P3Cl(6-n)(NHBut)(n) derivatives

A series of compounds of the N3P3Cl(6-n)(NHBut)n family (where n = 0, 1, 2, 4 and 6) are presented and their molecular parameters are related to trends in physical properties, which provides insight into a potential reaction mechanism for nucleophilic substitution. The crystal structures of N3P3Cl5(NHBut) and N3P3Cl2(NHBut)4 have been determined at 120K and those of N3P3Cl6 and N3P3Cl4(NHBut)2 have been re-determined at 120K. These are compared with the known structure of N3P3(NHBut)6 studied at 150K. Trends in molecular parameters (phosphazene ring, P-Cl & P-N(HBut) distances, PCl2 angles and endo- and exo-cyclic phosphazene ring parameters) across the series are observed. Hydrogen-bonding motifs are identified, characterised and compared. Both the molecular and hydrogen bonding parameters are related to the electron distribution in bonds and the derived basicities of the cyclophosphazene series of compounds. These findings provide evidence for a proposed mechanism for nucleophilic substitution at a phosphorus site bearing a PCl(NHBut) moiety

Shaped nozzles for cryogenic buffer gas beam sources

Cryogenic buffer gas beams are important sources of cold molecules. In this work we explore the use of a converging-diverging nozzle with a buffer-gas beam. We find that, under appropriate circumstances, the use of a nozzle can produce a beam with improved collimation, lower transverse temperatures, and higher fluxes per solid angle

The thermodynamics of prediction

A system responding to a stochastic driving signal can be interpreted as computing, by means of its dynamics, an implicit model of the environmental variables. The system's state retains information about past environmental fluctuations, and a fraction of this information is predictive of future ones. The remaining nonpredictive information reflects model complexity that does not improve predictive power, and thus represents the ineffectiveness of the model. We expose the fundamental equivalence between this model inefficiency and thermodynamic inefficiency, measured by dissipation. Our results hold arbitrarily far from thermodynamic equilibrium and are applicable to a wide range of systems, including biomolecular machines. They highlight a profound connection between the effective use of information and efficient thermodynamic operation: any system constructed to keep memory about its environment and to operate with maximal energetic efficiency has to be predictive.Comment: 5 pages, 1 figur

[Reliability of Commercial Tests for Hepatitis C Virus].

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The 2015 Fillmore Earthquake Swarm and Possible Crustal Deformation Mechanisms near the Bottom of the Eastern Ventura Basin, California

The 2015 Fillmore swarm occurred about 6 km west of the city of Fillmore in Ventura, California, and was located beneath the eastern part of the actively subsiding Ventura basin at depths from 11.8 to 13.8 km, similar to two previous swarms in the area. Template‐matching event detection showed that it started on 5 July 2015 at 2:21 UTC with an M ∼1.0 earthquake. The swarm exhibited unusual episodic spatial and temporal migrations and unusual diversity in the nodal planes of the focal mechanisms as compared to the simple hypocenter‐defined plane. It was also noteworthy because it consisted of >1400 events of M ≥ 0.0, with M 2.8 being the largest event. We suggest that fluids released by metamorphic dehydration processes, migration of fluids along a detachment zone, and cascading asperity failures caused this prolific earthquake swarm, but other mechanisms (such as simple mainshock–aftershock stress triggering or a regional aseismic creep event) are less likely. Dilatant strengthening may be a mechanism that causes the temporal decay of the swarm as pore‐pressure drop increased the effective normal stress, and counteracted the instability driving the swarm

Standard-Level Herbivory in an Old-Growth Conifer Forest Canopy

Herbivory is an important ecological process in forest canopies but is difficult to measure, especially for whole stands. We used the Wind River Canopy Crane in Washington State to access 101 randomly-located sample points throughout the forest canopy. This provided a relatively quick and convenient way to estimate herbivory for a whole stand. The overall level of herbivory was estimated at 1.6% of leaf area. The distribution was strongly skewed to the lower canopy where broad-leafed species experienced higher levels of herbivory. Herbivory averaged 0.3% in conifers and 13.5% in broad-leafed species. Fully half of the sample points had no detectable herbivory. Herbivory in this old-growth conifer forest is among the lowest levels published for forests around the globe and may reflect the general levels of herbivory in temperate coniferous forests during nonoutbreak conditions. Our whole-stand estimate is the first attempt at measuring herbivory for an entire forest stand in the Pacific Northwest

Streaming Motions Towards the Supermassive Black Hole in NGC 1097

We have used GMOS-IFU and high resolution HST-ACS observations to map, in unprecedented detail, the gas velocity field and structure within the 0.7 kpc circumnuclear ring of the SBb LINER/Seyfert 1 galaxy NGC 1097. We find clear evidence of radial streaming motions associated with spiral structures leading to the unresolved (<3.5 parsecs) nucleus, which we interpret as part of the fueling chain by which gas is transported to the nuclear starburst and supermassive black hole.Comment: 4 pages, 3 figures using emulateapj. Accepted for publication in Astrophysical Journal Letters. Download high-resolution version from http://www.astro.uu.se/~kambiz/DOC/paper-N1097.pd