1,523 research outputs found
The thermodynamics and roughening of solid-solid interfaces
The dynamics of sharp interfaces separating two non-hydrostatically stressed
solids is analyzed using the idea that the rate of mass transport across the
interface is proportional to the thermodynamic potential difference across the
interface. The solids are allowed to exchange mass by transforming one solid
into the other, thermodynamic relations for the transformation of a mass
element are derived and a linear stability analysis of the interface is carried
out. The stability is shown to depend on the order of the phase transition
occurring at the interface. Numerical simulations are performed in the
non-linear regime to investigate the evolution and roughening of the interface.
It is shown that even small contrasts in the referential densities of the
solids may lead to the formation of finger like structures aligned with the
principal direction of the far field stress.Comment: (24 pages, 8 figures; V2: added figures, text revisions
Measurement Of Positron Annihilation Line Shapes With A Ge(Li) Detector
We observed that the annihilation radiation photopeak in a Ge(Li) detector is considerably broader than that of a γ ray of the same energy. It seems reasonable to assume that the increased width is the result of the Doppler broadening of the annihilation photopeak, i.e., the longitudinal Doppler shift of the radiations is measured, while the transverse shift is measured in the usual angular-correlation experiments. By using a computer stripping program to remove the distortion produced by the finite energy resolution of our detector, we obtain momentum distributions in agreement with those which have been published. Only one detector is necessary for these measurements, and all momentum channels are detected at once. However, the detector energy resolution severely limits the momentum resolution. Arguments are presented which indicate that no very large improvement in Ge(Li) detector resolution can be expected. © 1968 The American Physical Society
Scale Free Cluster Distributions from Conserving Merging-Fragmentation Processes
We propose a dynamical scheme for the combined processes of fragmentation and
merging as a model system for cluster dynamics in nature and society displaying
scale invariant properties. The clusters merge and fragment with rates
proportional to their sizes, conserving the total mass. The total number of
clusters grows continuously but the full time-dependent distribution can be
rescaled over at least 15 decades onto a universal curve which we derive
analytically. This curve includes a scale free solution with a scaling exponent
of -3/2 for the cluster sizes.Comment: 4 pages, 3 figure
Comparing the temperatures of galaxy clusters from hydro-N-body simulations to Chandra and XMM-Newton observations
Theoretical studies of the physical processes guiding the formation and
evolution of galaxies and galaxy clusters in the X-ray are mainly based on the
results of numerical hydrodynamical N-body simulations, which in turn are often
directly compared to X-ray observations. Although trivial in principle, these
comparisons are not always simple. We demonstrate that the projected
spectroscopic temperature of thermally complex clusters obtained from X-ray
observations is always lower than the emission-weighed temperature, which is
widely used in the analysis of numerical simulations. We show that this
temperature bias is mainly related to the fact that the emission-weighted
temperature does not reflect the actual spectral properties of the observed
source. This has important implications for the study of thermal structures in
clusters, especially when strong temperature gradients, like shock fronts, are
present. Because of this bias, in real observations shock fronts appear much
weaker than what is predicted by emission-weighted temperature maps, and may
even not be detected. This may explain why, although numerical simulations
predict that shock fronts are a quite common feature in clusters of galaxies,
to date there are very few observations of objects in which they are clearly
seen. To fix this problem we propose a new formula, the spectroscopic-like
temperature function, and show that, for temperature larger than 3 keV, it
approximates the spectroscopic temperature better than few per cent, making
simulations more directly comparable to observations.Comment: Submitted for publication in MNRAS; 15 pages, 10 color figures and 13
BW figures,mn2e.cls. High resolution figures available here:
http://people.roma2.infn.it/~mazzotta/preprints/mazzotta.pd
Practical operation strategies for pumped hydroelectric energy storage (PHES) utilising electricity price arbitrage
Taxonomy and evolutionary relationships within species of section Rimosae (Inocybe) based on ITS, LSU and mtSSU sequence data
The present study aimed at elucidating the structure of Inocybe subg. Inosperma sect. Rimosae but included also representatives from subg. Mallocybe and the genus Auritella. Phylogenetic relationships were inferred using ITS, LSU and mtSSU sequence data. The analyses recovered the ingroup as a monophyletic, strongly supported clade. The results indicate that recognizing Auritella on the genus level renders Inocybe paraphyletic. The species traditionally placed in sect. Rimosae were found to be distributed over two strongly supported clades, Maculata and Rimosae s.s. The Maculata clade clusters with sect. Cervicolores and the two represent subg. Inosperma in a strict sense. Rimosae s.s. emerges as an independent, supported clade well separated from Inosperma s.s. Twenty-one terminal groups were correlated with morphologically distinct species. In addition several taxa on single branches and minor less supported clades were recovered. A key to the identified species of the Maculata and Rimosae s.s. clades which occur in Northwest Europe is provided
Microalbuminuria, Preeclampsia, and Preterm Delivery in Pregnant Women With Type 1 Diabetes: Results from a nationwide Danish study
2-Methyl-3-{2-nitro-1-[2-(prop-2-yn-1-yloxy)phenyl]ethyl}-1H-indole
In the title compound, C20H18N2O3, the indole unit is essentially planar, with a maximum deviation of 0.0197 (18) Å for the N atom and forms a dihedral angle of 78.09 (9)° with the propyne-subsituted phenyl ring. The propyne group is almost linear, the C—C C angle being 176.5 (2)°, and is also in the flagpole position on the O atom. In the crystal, molecules are linked via N—H⋯O and C—H⋯O intermolecular hydrogen bonds involving the nitro-group O atoms as acceptors
Weak-Lensing Halo Numbers and Dark-Matter Profiles
Integral measures of weak gravitational lensing by dark-matter haloes, like
the aperture mass, are sensitive to different physical halo properties
dependent on the halo mass density profile. For isothermal profiles, the
relation between aperture mass and virial mass is steeper than for haloes with
the universal NFW profile. Consequently, the halo mass range probed by the
aperture mass is much wider for NFW than for isothermal haloes. We use recent
modifications to the Press-Schechter mass function in CDM models normalised to
the local abundance of rich clusters, to predict the properties of the halo
sample expected to be accessible with the aperture mass technique. While ~10
haloes should be detected per square degree if the haloes have NFW profiles,
their number density is lower by approximately an order of magnitude if they
have isothermal profiles. These results depend only very mildly on the
cosmological background model. We conclude that counts of haloes with a
significant weak-lensing signal are a powerful discriminator between different
dark-matter profiles.Comment: submitted to A&
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