103 research outputs found
Linear And Nonlinear Arabesques: A Study Of Closed Chains Of Negative 2-Element Circuits
In this paper we consider a family of dynamical systems that we call
"arabesques", defined as closed chains of 2-element negative circuits. An
-dimensional arabesque system has 2-element circuits, but in addition,
it displays by construction, two -element circuits which are both positive
vs one positive and one negative, depending on the parity (even or odd) of the
dimension . In view of the absence of diagonal terms in their Jacobian
matrices, all these dynamical systems are conservative and consequently, they
can not possess any attractor. First, we analyze a linear variant of them which
we call "arabesque 0" or for short "A0". For increasing dimensions, the
trajectories are increasingly complex open tori. Next, we inserted a single
cubic nonlinearity that does not affect the signs of its circuits (that we call
"arabesque 1" or for short "A1"). These systems have three steady states,
whatever the dimension is, in agreement with the order of the nonlinearity. All
three are unstable, as there can not be any attractor in their state-space. The
3D variant (that we call for short "A1\_3D") has been analyzed in some detail
and found to display a complex mixed set of quasi-periodic and chaotic
trajectories. Inserting cubic nonlinearities (one per equation) in the same
way as above, we generate systems "A2\_D". A2\_3D behaves essentially as
A1\_3D, in agreement with the fact that the signs of the circuits remain
identical. A2\_4D, as well as other arabesque systems with even dimension, has
two positive -circuits and nine steady states. Finally, we investigate and
compare the complex dynamics of this family of systems in terms of their
symmetries.Comment: 22 pages, 12 figures, accepted for publication at Int. J. Bif. Chao
Reference Distribution Functions for Magnetically Confined Plasmas from the Minimum Entropy Production Theorem and the MaxEnt Principle, subject to the Scale-Invariant Restrictions
We derive the expression of the reference distribution function for
magnetically confined plasmas far from the thermodynamic equilibrium. The local
equilibrium state is fixed by imposing the minimum entropy production theorem
and the maximum entropy (MaxEnt) principle, subject to scale invariance
restrictions. After a short time, the plasma reaches a state close to the local
equilibrium. This state is referred to as the reference state. The aim of this
letter is to determine the reference distribution function (RDF) when the local
equilibrium state is defined by the above mentioned principles. We prove that
the RDF is the stationary solution of a generic family of stochastic processes
corresponding to an universal Landau-type equation with white parametric noise.
As an example of application, we consider a simple, fully ionized, magnetically
confined plasmas, with auxiliary Ohmic heating. The free parameters are linked
to the transport coefficients of the magnetically confined plasmas, by the
kinetic theory.Comment: 9 pages and 6 figures. arXiv admin note: substantial text overlap
with arXiv:1305.592
Effects of Surface Geology on Seismic Ground Motion Deduced from Ambient-Noise Measurements in the Town of Avellino, Irpinia Region (Italy)
The effects of surface geology on ground motion
provide an important tool in seismic hazard studies. It is well
known that the presence of soft sediments can cause amplification
of the ground motion at the surface, particularly when there is a
sharp impedance contrast at shallow depth. The town of Avellino is
located in an area characterised by high seismicity in Italy, about
30 km from the epicentre of the 23 November 1980, Irpinia
earthquake (M = 6.9). No earthquake recordings are available in
the area. The local geology is characterised by strong heterogeneity,
with impedance contrasts at depth. We present the results
from seismic noise measurements carried out in the urban area of
Avellino to evaluate the effects of local geology on the seismic
ground motion. We computed the horizontal-to-vertical (H/V)
noise spectral ratios at 16 selected sites in this urban area for which
drilling data are available within the first 40 m of depth. A Rayleigh
wave inversion technique using the peak frequencies of the
noise H/V spectral ratios is then presented for estimating Vs
models, assuming that the thicknesses of the shallow soil layers are
known. The results show a good correspondence between experimental
and theoretical peak frequencies, which are interpreted in
terms of sediment resonance. For one site, which is characterised
by a broad peak in the horizontal-to-vertical spectral-ratio curve,
simple one-dimensional modelling is not representative of the
resonance effects. Consistent variations in peak amplitudes are seen
among the sites. A site classification based on shear-wave velocity
characteristics, in terms of Vs30, cannot explain these data. The
differences observed are better correlated to the impedance contrast
between the sediments and basement. A more detailed investigation
of the physical parameters of the subsoil structure, together with
earthquake data, are desirable for future research, to confirm these
data in terms of site response
Distribution, sources and ecological risk assessment of polycyclic aromatic hydrocarbons in water and sediments from Tiber River and estuary, Italy
The concentration, source and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in the Tiber River and its environmental impact on the Tyrrhenian Sea (Central Mediterranean Sea) were estimated. The 16 priority PAHs were determined in the water dissolved phase (DP), suspended particulate matter (SPM) and sediments collected from 21 sites in four different seasons. Total concentrations of PAHs ranged from 10.3 to 951.6ngL-1 and from 36.2 to 545.6ngg-1 in water (sum of DP and SPM) and in sediment samples, respectively. The compositions of PAHs showed that 2- to 4-ring PAHs were abundant in DP, 4- to 6-ring PAHs were predominant in SPM samples, and 4- to 5-ring PAHs were abundant in sediments. The diagnostic ratio analysis indicated that the PAHs mainly had a pyrolytic source. The toxic equivalent concentration of carcinogenic PAHs was 45.3ngTEQg-1, suggesting low carcinogenic risk for Tiber River. Total PAHs loads into the sea were calculated in about 3161.7kgyear-1 showing that this river is one of the main contribution sources of these contaminants to the Tyrrhenian Sea
Estimates of Tiber River organophosphate pesticide loads to the Tyrrhenian Sea and ecological risk
The organophosphate pesticides pollution in the Tiber River and its environmental impact on the Tyrrhenian Sea (Central Mediterranean Sea) were estimated. Eight selected organophosphate pesticides (diazinon, dimethoate, malathion, chlorpyrifos, pirimiphos-methyl, fenitrothion, methidathion, tolclofos-methyl) were determined in the water dissolved phase, suspended particulate matter and sediment samples collected from 21 sites in different seasons. Total organophosphate pesticides concentrations ranged from 0.40 to 224.48 ng L-1 in water (as the sum of the water dissolved phase and suspended particulate matter) and from 1.42 to 68.46 ng g(-1) in sediment samples. Contaminant discharges of organophosphate pesticides into the sea were calculated in about 545.36 kg year(-1) showing that this river should be consider as one of the main contribution sources of organophosphate pesticides to the Tyrrhenian Sea. In relation to the eco-toxicological assessment, the concentrations of most OPPs in the water and sediments from the Tiber River and its estuary were lower than guideline values
Polychlorinated biphenyls and organochlorine pesticides in water and sediment from Volturno River, Southern Italy: occurrence, distribution and risk assessment
Abstract
Background
To assess the Volturno River pollution and its environmental impact on the Tyrrhenian Sea (Central Mediterranean Sea) caused by Polychlorinated biphenyls (PCBs) and Organochlorine pesticides (OCPs), 32 PCBs and aldrin, α-BHC, β-BHC, δ-BHC, γ-BHC (lindane), 4,4′- DDD, 4,4′-DDE, 4,4′-DDT, dieldrin, endosulfan I, endosulfan II, endosulfan sulphate, endrin, heptachlor, heptachlor epoxide (isomer B) and methoxychlor have been selected and were analyzed in three different phases: dissolved phase (DP), suspended particulate matter (SPM) and sediments. PCBs and OCPs were extracted using an SPE column for the DP and glass fiber filter for SPM and sediment samples. Cleaned extracts were analyzed by gas chromatography with electron capture detector (ECD) and mass spectrometry (MS) detector for PCBs and OCPs, respectively.
Results
Pollutants discharges of PCBs and OCPs into the sea were calculated in about 106.9 kg year−1 (87.1 kg year−1 of PCBs and 19.7 kg year−1 of OCPs), showing that this river could be a major source of PCBs and OCPs pollution to the Central Mediterranean Sea. Total concentrations of PCBs ranged from 4.1 to 48.0 ng L−1 in water (sum of DP and SPM) and from 4.3 to 64.3 ng g−1 in sediment samples. The concentrations of total organochlorine pesticides (OCPs) obtained in water (sum of DP and SPM) ranged from 0.93 to 8.66 ng L−1 and from 0.52 to 9.89 ng g−1 in sediment samples. Principal component analysis shows that all PCB compounds are more likely to come from surface runoff than an atmospheric deposition.
Conclusion
The data show that higher levels of PCBs and OCPs were found in sediment samples than in DP and SPM samples, which are an indication of no fresh inputs of these compounds. Based on our results, unintentionally produced PCBs by industrial processes (and other processes) were considered to be the main sources of PCBs in Volturno River and Estuary sediments. Considering the Sediment Quality Guidelines (SQGs), the Ecological Risk Index (ERI), the Risk Quotient (RQ) and the USEPA Environmental Quality Standards (EQS), the Volturno River and its Estuary would be considered an area in which the integrity is possibly at risk
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