7,465 research outputs found
Analyzing Temperature Effects on Mortality Within the R Environment: The Constrained Segmented Distributed Lag Parameterization
Here we present and discuss the R package modTempEff including a set of functions aimed at modelling temperature effects on mortality with time series data. The functions fit a particular log linear model which allows to capture the two main features of mortality- temperature relationships: nonlinearity and distributed lag effect. Penalized splines and segmented regression constitute the core of the modelling framework. We briefly review the model and illustrate the functions throughout a simulated dataset.
On the occurrence and detectability of Bose-Einstein condensation in helium white dwarfs
It has been recently proposed that helium white dwarfs may provide promising
conditions for the occurrence of the Bose-Einstein condensation. The argument
supporting this expectation is that in some conditions attained in the core of
these objects, the typical De Broglie wavelength associated with helium nuclei
is of the order of the mean distance between neighboring nuclei. In these
conditions the system should depart from classical behavior showing quantum
effects. As helium nuclei are bosons, they are expected to condense.
In order to explore the possibility of detecting the Bose-Einstein
condensation in the evolution of helium white dwarfs we have computed a set of
models for a variety of stellar masses and values of the condensation
temperature. We do not perform a detailed treatment of the condensation process
but mimic it by suppressing the nuclei contribution to the equation of state by
applying an adequate function. As the cooling of white dwarfs depends on
average properties of the whole stellar interior, this procedure should be
suitable for exploring the departure of the cooling process from that predicted
by the standard treatment.
We find that the Bose-Einstein condensation has noticeable, but not dramatic
effects on the cooling process only for the most massive white dwarfs
compatible with a helium dominated interior (\approx 0.50 M_\odot) and very low
luminosities (say, Log(L/L_\odot) < -4.0). These facts lead us to conclude that
it seems extremely difficult to find observable signals of the Bose-Einstein
condensation.
Recently, it has been suggested that the population of helium white dwarfs
detected in the globular cluster NGC 6397 is a good candidate for detecting
signals of the Bose-Einstein condensation. We find that these stars have masses
too low and are too bright to have an already condensed interior.Comment: 13 pages, 3 figures, 2 tables, accepted for publication in the
Journal of Cosmology and Astroparticle Physics (JCAP
Adhesive contact of model randomly rough rubber surfaces
We study experimentally and theoretically the equilibrium adhesive contact
between a smooth glass lens and a rough rubber surface textured with spherical
microasperities with controlled height and spatial distributions. Measurements
of the real contact area versus load are performed under compression by
imaging the light transmitted at the microcontacts. is found to be
non-linear and to strongly depend on the standard deviation of the asperity
height distribution. Experimental results are discussed in the light of a
discrete version of Fuller and Tabor's (FT) original model (\textit{Proceedings
of the Royal Society A} \textbf{345} (1975) 327), which allows to take into
account the elastic coupling arising from both microasperities interactions and
curvature of the glass lens. Our experimental data on microcontact size
distributions are well captured by our discrete extended model. We show that
the elastic coupling arising from the lens curvature has a significant
contribution to the relationship. Our discrete model also clearly shows
that the adhesion-induced effect on remains significant even for
vanishingly small pull-off forces. Last, at the local asperity length scale,
our measurements show that the pressure dependence of the microcontacts density
can be simply described by the original FT model
An evolutionary model for the gamma-ray system PSR J1311-3430 and its companion
The most recent member of the millisecond pulsar with very low-mass
companions and short orbital periods class, PSR J1311-3430 (Pletsch et al.
2012) is a remarkable object in various senses. Besides being the first
discovered in gamma-rays, its measured features include the very low or absent
hydrogen content. We show in this Letter that this important piece of
information leads to a very restricted range of initial periods for a given
donor mass. For that purpose, we calculate in detail the evolution of the
binary system self-consistently, including mass transfer and evaporation,
finding the features of the new evolutionary path leading to the observed
configuration. It is also important to remark that the detailed evolutionary
history of the system naturally leads to a high final pulsar mass, as it seems
to be demanded by observations.Comment: 5 pages, 5 figures, 1 table. Accepted for publication in MNRAS
Letter
The Quasi-Roche lobe overflow state in the evolution of Close Binary Systems containing a radio pulsar
We study the evolution of close binary systems formed by a normal (solar
composition), intermediate mass donor star together with a neutron star. We
consider models including irradiation feedback and evaporation. These
non-standard ingredients deeply modify the mass transfer stages of these
binaries. While models that neglect irradiation feedback undergo continuous,
long standing mass transfer episodes, models including these effect suffer a
number cycles of mass transfer and detachment. During mass transfer the systems
should reveal themselves as low-mass X-ray binaries (LMXBs), whereas when
detached they behave as a binary radio pulsars. We show that at these stages
irradiated models are in a Roche lobe overflow (RLOF) state or in a quasi-RLOF
state. Quasi-RLOF stars have a radius slightly smaller than its Roche lobe.
Remarkably, these conditions are attained for orbital period and donor mass
values in the range corresponding to a family of binary radio pulsars known as
"redbacks". Thus, redback companions should be quasi-RLOF stars. We show that
the characteristics of the redback system PSR J1723-2837 are accounted for by
these models.
In each mass transfer cycle these systems should switch from LMXB to binary
radio pulsar states with a timescale of \sim million years. However, there is
recent and fast growing evidence of systems switching on far shorter, human
timescales. This should be related to instabilities in the accretion disc
surrounding the neutron star and/or radio ejection, still to be included in the
model having the quasi-RLOF state as a general condition.Comment: 27 pages, 7 figures. Accepted for publication in The Astrophysical
Journa
Microstructure and chemical composition of Roman orichalcum coins emitted after the monetary reform of Augustus (23 B.C.)
A collection of ancient Roman orichalcum coins, i.e., a copper-zinc alloy, minted under the reigns from Caesar to Domitianus, have been characterised using scanning electron microscopy (SEM-EDS) and electron microprobe analysis (EMPA). We studied, for the first time, coins emitted by Romans after the reforms of Augustus (23 B.C.) and Nero (63-64 A.D). These coins, consisting of asses, sestertii, dupondii and semisses, were analysed using non- and invasive analyses, aiming to explore microstructure, corrosive process and to acquire quantitative chemical analysis. The results revealed that the coins are characterized by porous external layers, which are affected by dezincification and decuprification processes. As pictured by the X-ray maps, the elemental distribution of Cu and Zn shows patterns of depletion that in some cases penetrate in deep up to 1 mm. The composition of the un-corroded nucleus is a Cu-Zn alloy containing up to 30% of Zn, typical of coins produced via cementation process
Vulnerability and Protection of Critical Infrastructures
Critical infrastructure networks are a key ingredient of modern society. We
discuss a general method to spot the critical components of a critical
infrastructure network, i.e. the nodes and the links fundamental to the perfect
functioning of the network. Such nodes, and not the most connected ones, are
the targets to protect from terrorist attacks. The method, used as an
improvement analysis, can also help to better shape a planned expansion of the
network.Comment: 4 pages, 1 figure, 3 table
The Limits of Permissible Judicial Campaign Speech in New York
(Excerpt)
In December 2018, New Yorkâs Advisory Committee on Judicial Ethics (âACJEâ), which I proudly served on for ten years, issued Opinion 17-28, concerning an inquiry by a judicial candidate as to whether he or she could respond to a candidate questionnaire prepared by the New York State Right to Life Committee (âRTL questionnaireâ). In the RTL questionnaire, the candidate is asked a series of questions concerning the candidateâs personal beliefs on abortion, the beginning of life, Roe v. Wade, the definition of personhood, the New York and United States Constitutions, and so on. Each question asking for the candidateâs personal beliefs is preceded by a prefatory acknowledgment of âthe judicial obligation to follow binding precedents of higher courts and applicable constitutional and statutory provisions, to honor stare decisis, and to decide any future case based on the law and facts of that case.â
Concluding that the RTL questionnaire, âwhen viewed as a whole, is clearly designed to elicit a series of implied pledges, promises, and commitments, touching on a wide variety of closely interrelated issues that may come before judges at every level of the judiciaryâ and that âa candidateâs impartialityâ could â âreasonably be questionedâ in a wide variety of cases . . . if he/she agreed to the bold-faced statements on the questionnaire,â the candidate was advised to decline responding to it. As I strongly disagree with the ACJEâs opinion, I write this Article to express my personal views on the subject. Let me emphasize that this Article reflects my attempt to engage in a reasoned analysis of an admittedly difficult topic which, in my opinion, has not been sufficiently explored or discussed by academics, ethics committees, or judges since the Supreme Court of the United States decided Republican Party of Minnesota v. White (occasionally abbreviated herein as âWhiteâ)
Group Theoretical Quantum Tomography
The paper is devoted to the mathematical foundation of the quantum tomography
using the theory of square-integrable representations of unimodular Lie groups.Comment: 13 pages, no figure, Latex2e. Submitted to J.Math.Phy
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