7,959 research outputs found
Kinematic fingerprint of core-collapsed globular clusters
Dynamical evolution drives globular clusters toward core collapse, which
strongly shapes their internal properties. Diagnostics of core collapse have so
far been based on photometry only, namely on the study of the concentration of
the density profiles. Here we present a new method to robustly identify
core-collapsed clusters based on the study of their stellar kinematics. We
introduce the \textit{kinematic concentration} parameter, , the ratio
between the global and local degree of energy equipartition reached by a
cluster, and show through extensive direct -body simulations that clusters
approaching core collapse and in the post-core collapse phase are strictly
characterized by . The kinematic concentration provides a suitable
diagnostic to identify core-collapsed clusters, independent from any other
previous methods based on photometry. We also explore the effects of incomplete
radial and stellar mass coverage on the calculation of and find that our
method can be applied to state-of-art kinematic datasets.Comment: Accepted for publication in MNRAS Lette
SBV Regularity for Genuinely Nonlinear, Strictly Hyperbolic Systems of Conservation Laws in one space dimension
We prove that if is the entropy
solution to a strictly hyperbolic system of conservation laws with
genuinely nonlinear characteristic fields then up to a
countable set of times the function is in
, i.e. its distributional derivative is a measure with no
Cantorian part.
The proof is based on the decomposition of into waves belonging to
the characteristic families and the balance
of the continuous/jump part of the measures in regions bounded by
characteristics. To this aim, a new interaction measure \mu_{i,\jump} is
introduced, controlling the creation of atoms in the measure .
The main argument of the proof is that for all where the Cantorian part
of is not 0, either the Glimm functional has a downward jump, or there is
a cancellation of waves or the measure is positive
A Framework to Assess Social Indicators in a Circular Economy Perspective
The thriving circular economy is expected to contribute to all three dimensions of sustainable development: environmental, economic, and social. This paper aims to propose a framework to assess social indicators to support circular business models. To validate the framework, we conducted a case study in a medium-size Italian footwear luxury industry, using the Value Focused Thinking-VFT. This approach was used to define proper social indicators to measure the perception of the company's managers related to the level of incorporation of social dilemmas in the company. We collect data through interviews, documental analysis and direct observation from October/2019 until August/2020 and apply a questionnaire in 2020/2021. The novelty of this paper lies in the proposition of a framework to assess the social indicators in broad categories, capable of covering all supply chains: Corporation, Community; Consumers; Suppliers; Human Rights and Human Resources. Another novelty is related to the analysis of indicators in terms of strategic, tactical, and operational levels, similarly to the idea of a Balanced Scorecard, which was allowed by applying the VFT approach
Quadratic interaction functional for general systems of conservation laws
For the Glimm scheme approximation u_\e to the solution of the system of conservation laws in one space dimension
\begin{equation*}
u_t + f(u)_x = 0, \qquad u(0,x) = u_0(x) \in \R^n,
\end{equation*}
with initial data with small total variation, we prove a quadratic (w.r.t. \TV(u_0)) interaction estimate, which has been used in the literature for stability and convergence results. No assumptions on the structure of the flux are made (apart smoothness), and this estimate is the natural extension of the Glimm type interaction estimate for genuinely nonlinear systems.
More precisely we obtain the following results:
\begin{itemize}
\item a new analysis of the interaction estimates of simple waves;
\item a Lagrangian representation of the derivative of the solution, i.e. a map which follows the trajectory of each wave from its creation to its cancellation;
\item the introduction of the characteristic interval and partition for couples of waves, representing the common history of the two waves;
\item a new functional controlling the variation in speed of the waves w.r.t. time.
\end{itemize}
This last functional is the natural extension of the Glimm functional for genuinely nonlinear systems.
The main result is that the distribution is a measure with total mass \leq \const \TV(u_0)^2
SBV regularity of Systems of Conservation Laws and Hamilton-Jacobi Equation
We review the SBV regularity for solutions to hyperbolic systems of conservation laws and Hamilton-Jacobi equations. We give an overview of the techniques involved in the proof, and a collection of related problems concludes the paper
Physiological Responses to Acute Silver Exposure in the Freshwater Crayfish (\u3cem\u3eCambarus diogenes diogenes\u3c/em\u3e)—A Model Invertebrate?
Adult crayfish (Cambarus diogenes diogenes) exposed to 8.41 ± 0.17 μg silver/L (19.4% as Ag+) in moderately hard freshwater under flow-through conditions for 96 h exhibited ionoregulatory disturbance, elevated metabolic ammonia (Tamm) production and substantial silver accumulation in the gills, hemolymph, and hepatopancreas. The ionoregulatory disturbance included both a generally reduced unidirectional Na1 influx and an increased unidirectional Na+ efflux, leading to a substantial net loss of Na+ from the silver-exposed crayfish. The Na+ uptake in silver-exposed crayfish differed overall from controls, while the increased Na+ efflux recovered to control values 48 h into the 96 h of exposure. The general inhibition of Na+ uptake could be explained by a reduced sodium/potassium-adenosine triphosphatase (Na/K-ATPase) activity in terminally obtained gill samples from the silver exposed crayfish. The silver-induced effect on Na+ uptake and loss translated to reduced hemolymph Na+ concentrations but not significantly reduced hemolymph Cl- concentrations. Hemolymph Tamm and Tamm efflux both increased in silver-exposed crayfish, indicating an increased metabolic Tamm production. The present study demonstrates that the toxic mechanism of waterborne silver exposure in freshwater crayfish resembles that of freshwater teleost fish. The crayfish might therefore be a useful model system for extending current environmental regulatory strategies, currently based on teleost fish, to invertebrates
The unusual 2006 dwarf nova outburst of GK Perseii
The 2006 outburst of GK Perseii differed significantly at optical and
ultraviolet wavelengths from typical outbursts of this object. We present
multi-wavelength (X-ray, UV and optical) Swift and AAVSO data, giving
unprecedented broad-band coverage of the outburst, allowing us to follow the
evolution of the longer-than-normal 2006 outburst across these wavelengths. In
the optical and UV we see a triple-peaked morphology with maximum brightness
~1.5 magnitudes lower than in previous years. In contrast, the peak hard X-ray
flux is the same as in previous outbursts. We resolve this dichotomy by
demonstrating that the hard X-ray flux only accounts for a small fraction of
the total energy liberated during accretion, and interpret the optical/UV
outburst profile as arising from a series of heating and cooling waves
traversing the disc, caused by its variable density profile.Comment: 9 pages, 7 figures, accepted for publication in MNRA
The boundary Riemann solver coming from the real vanishing viscosity approximation
We study a family of initial boundary value problems associated to mixed
hyperbolic-parabolic systems:
v^{\epsilon} _t + A (v^{\epsilon}, \epsilon v^{\epsilon}_x ) v^{\epsilon}_x =
\epsilon B (v^{\epsilon} ) v^{\epsilon}_{xx}
The conservative case is, in particular, included in the previous
formulation.
We suppose that the solutions to these problems converge to a
unique limit. Also, it is assumed smallness of the total variation and other
technical hypotheses and it is provided a complete characterization of the
limit.
The most interesting points are the following two.
First, the boundary characteristic case is considered, i.e. one eigenvalue of
can be .
Second, we take into account the possibility that is not invertible. To
deal with this case, we take as hypotheses conditions that were introduced by
Kawashima and Shizuta relying on physically meaningful examples. We also
introduce a new condition of block linear degeneracy. We prove that, if it is
not satisfied, then pathological behaviours may occur.Comment: 84 pages, 6 figures. Text changes in Sections 1 and 3.2.3. Added
Section 3.1.2. Minor changes in other section
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