2,903 research outputs found
4D gravity on a brane from bulk higher-curvature terms
We study a gravity model where a tensionful codimension-one three-brane is
embedded on a bulk with infinite transverse length. We find that 4D gravity is
induced on the brane already at the classical level if we include
higher-curvature (Gauss-Bonnet) terms in the bulk. Consistency conditions
appear to require a negative brane tension as well as a negative coupling for
the higher-curvature terms.Comment: 10 pages, no figures; a minor change in wording (to appear in MPLA
Fragile to strong crossover coupled to liquid-liquid transition in hydrophobic solutions
Using discrete molecular dynamics simulations we study the relation between
the thermodynamic and diffusive behaviors of a primitive model of aqueous
solutions of hydrophobic solutes consisting of hard spheres in the Jagla
particles solvent, close to the liquid-liquid critical point of the solvent. We
find that the fragile-to-strong dynamic transition in the diffusive behavior is
always coupled to the low-density/high-density liquid transition. Above the
liquid-liquid critical pressure, the diffusivity crossover occurs at the Widom
line, the line along which the thermodynamic response functions show maxima.
Below the liquid-liquid critical pressure, the diffusivity crossover occurs
when the limit of mechanical stability lines are crossed, as indicated by the
hysteresis observed when going from high to low temperature and vice versa.
These findings show that the strong connection between dynamics and
thermodynamics found in bulk water persists in hydrophobic solutions for
concentrations from low to moderate, indicating that experiments measuring the
relaxation time in aqueous solutions represent a viable route for solving the
open questions in the field of supercooled water.Comment: 6 pages, 4 figures. Accepted for publication on Physical Review
Effect of hydrophobic solutes on the liquid-liquid critical point
Jagla ramp particles, interacting through a ramp potential with two
characteristic length scales, are known to show in their bulk phase
thermodynamic and dynamic anomalies, similar to what is found in water. Jagla
particles also exhibit a line of phase transitions separating a low density
liquid phase and a high density liquid phase, terminating in a liquid-liquid
critical point in a region of the phase diagram that can be studied by
simulations. Employing molecular dynamics computer simulations, we study the
thermodynamics and the dynamics of solutions of hard spheres (HS) in a solvent
formed by Jagla ramp particles. We consider the cases of HS mole fraction x =
0.10, 0.15 and 0.20, and also the case x = 0.50 (a 1:1 mixture of HS and Jagla
particles). We find a liquid-liquid critical point, up to the highest HS mole
fraction; its position shifts to higher pressures and lower temperatures upon
increasing x. We also find that the diffusion coefficient anomalies appear to
be preserved for all the mole fractions studied.Comment: 8 pages, 7 figures, 1 table. In press (Phys. Rev. E
The comprehensive environmental management model in post-Covid19 era
To restrict the adverse impact of Green House Gas there is a need of rapid action for transformation of the current situation to achieve the targets mentioned by the United Nations Programme. The coronavirus crisis generated additional challenges but also generated a provision for companies to develop a sustainable model in the recovery period by incorporating the non-financial aspect of green environment in their business model. In this paper, we identify some of the main problems of the existing projects related to Green House Gas control and propose the Dragon Value System with a potentiality of overcoming the drawbacks of the existing models. We find a comprehensive environmental management model that will be opportunity driven, based on certain financial assets associated with wide spectrum of stakeholders and applicable by company of any size. The findings of the paper will contribute to the academic literature related to environmental management and SDG 7. The proposed model will assist the investors to identify a comprehensive model to invest and could generate new public-private partnership to apply highly beneficial and comprehensive environmental management model
Robustness of a bisimulation-type faster-than preorder
TACS is an extension of CCS where upper time bounds for delays can be
specified. Luettgen and Vogler defined three variants of bismulation-type
faster-than relations and showed that they all three lead to the same preorder,
demonstrating the robustness of their approach. In the present paper, the
operational semantics of TACS is extended; it is shown that two of the variants
still give the same preorder as before, underlining robustness. An explanation
is given why this result fails for the third variant. It is also shown that
another variant, which mixes old and new operational semantics, can lead to
smaller relations that prove the same preorder.Comment: Express Worksho
On the definition of parallel independence in the algebraic approaches to graph transformation
Parallel independence between transformation steps is a basic and well-understood notion of the algebraic approaches to graph transformation, and typically guarantees that the two steps can be applied in any order obtaining the same resulting graph, up to isomorphism. The concept has been redefined for several algebraic approaches as variations of a classical “algebraic” condition, requiring that each matching morphism factorizes through the context graphs of the other transformation step. However, looking at some classical papers on the double-pushout approach, one finds that the original definition of parallel independence was formulated in set-theoretical terms, requiring that the intersection of the images of the two left-hand sides in the host graph is contained in the intersection of the two interface graphs. The relationship between this definition and the standard algebraic one is discussed in this position paper, both in the case of left-linear and non-left-linear rules
Retiolites angustidens Elles & Wood, 1908 (Graptholitina) from the Silurian of Mt. Cocco (Carnic Alps, Italy)
Retiolites angustidens, trovato in un blocco isolato di calcare a Orthoceras nell’area di Monte Cocco in
associazione con Monograptus cf. priodon, viene qui descritto e figugurato per la prima volta nelle Alpi Carniche: in precedenza
la sua presenza, infatti, era stata segnalata, ma mai documentata. Dato che tutti i graptoliti rinvenuti hanno un limitato valore
stratigrafico, l’età precisa dell’associazione studiata è attribuita alla Biozona a Pterospathodus am. amorphognathoides (Llandovery
sup.) in base ai conodonti.Retiolites angustidens is described and figured for the first time from the Carnic Alps, from a loose block collected
from Mt. Cocco area. ! e association includes also Monograptus cf. priodon: this species, in fact, was previously reported,
but never documented, from this area. Since all the graptolites found have a limited stratigraphic value, the precise age of
the studied association is determined by conodonts as belonging to the latest Llandovery (Pterospathodus am. amorphognathoides
conodont Zone)
Smooth tensionful higher-codimensional brane worlds with bulk and brane form fields
Completely regular tensionful codimension-n brane world solutions are
discussed, where the core of the brane is chosen to be a thin codimension-(n-1)
shell in an infinite volume flat bulk, and an Einstein-Hilbert term localized
on the brane is included (Dvali-Gabadadze-Porrati models). In order to support
such localized sources we enrich the vacuum structure of the brane by the
inclusion of localized form fields. We find that phenomenological constraints
on the size of the internal core seem to impose an upper bound to the brane
tension. Finite transverse-volume smooth solutions are also discussed.Comment: 1+14 pages, 2 figures; section 2.3 improved, typos corrected and
references added. Published versio
Retrieval of SO2 from thermal infrared satellite measurements: correction procedures for the effects of volcanic ash
The simultaneous presence of SO2 and ash in
a volcanic plume can lead to a significant error in the SO2
column abundance retrieval when multispectral Thermal InfraRed
(TIR) data are used. The ash particles within the
plume with effective radii from 1 to 10ÎĽm reduce the Top Of
Atmosphere (TOA) radiance in the entire TIR spectral range,
including the channels used for SO2 retrieval. The net effect
is a significant SO2 overestimation.
In this work the interference of ash is discussed and two
correction procedures for satellite SO2 volcanic plume retrieval
in the TIR spectral range are developed to achieve an
higher computational speed and a better accuracy.
The ash correction can be applied when the sensor spectral
range includes the 7.3 and/or 8.7ÎĽm SO2 absorption bands,
and the split window bands centered around 11 and 12ÎĽm
required for ash retrieval. This allows the possibility of simultaneous
estimation of both volcanic SO2 and ash in the
same data set. The proposed ash correction procedures have
been applied to the Moderate Resolution Imaging Spectroradiometer
(MODIS) and the Spin Enhanced Visible and Infrared
Imager (SEVIRI) measurements. Data collected during
the 24 November 2006 Mt. Etna eruption have been used
to illustrate the technique. The SO2 and ash estimation is carried
out by using a best weighted least squares fit method and
the Brightness Temperature Difference (BTD) procedures,
respectively. The simulated TOA radiance Look-Up Table
(LUT) needed for the SO2 column abundance and the ash
retrievals have been computed using the MODTRAN 4 Radiative
Transfer Model.
The results show the importance of the ash correction on
SO2 retrievals at 8.7ÎĽm, where the corrected SO2 column abundance values are less than 50% of the uncorrected values.
The ash correction on SO2 retrieval at 7.3ÎĽm is much
less important and only significant for low SO2 column abundances.
Results also show that the simplified and faster
correction procedure underestimates the ash correction compared
with the more time consuming but more accurate correction
procedure. Such underestimation is greater for instruments
having better ground pixel resolution, i.e. greater for
MODIS than for SEVIRI
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