1,061 research outputs found
Iron under Earth's core conditions: Liquid-state thermodynamics and high-pressure melting curve
{\em Ab initio} techniques based on density functional theory in the
projector-augmented-wave implementation are used to calculate the free energy
and a range of other thermodynamic properties of liquid iron at high pressures
and temperatures relevant to the Earth's core. The {\em ab initio} free energy
is obtained by using thermodynamic integration to calculate the change of free
energy on going from a simple reference system to the {\em ab initio} system,
with thermal averages computed by {\em ab initio} molecular dynamics
simulation. The reference system consists of the inverse-power pair-potential
model used in previous work. The liquid-state free energy is combined with the
free energy of hexagonal close packed Fe calculated earlier using identical
{\em ab initio} techniques to obtain the melting curve and volume and entropy
of melting. Comparisons of the calculated melting properties with experimental
measurement and with other recent {\em ab initio} predictions are presented.
Experiment-theory comparisons are also presented for the pressures at which the
solid and liquid Hugoniot curves cross the melting line, and the sound speed
and Gr\"{u}neisen parameter along the Hugoniot. Additional comparisons are made
with a commonly used equation of state for high-pressure/high-temperature Fe
based on experimental data.Comment: 16 pages including 6 figures and 5 table
Photon-assisted tunneling in a Fe8 Single-Molecule Magnet
The low temperature spin dynamics of a Fe8 Single-Molecule Magnet was studied
under circularly polarized electromagnetic radiation allowing us to establish
clearly photon-assisted tunneling. This effect, while linear at low power,
becomes highly non-linear above a relatively low power threshold. This
non-linearity is attributed to the nature of the coupling of the sample to the
thermostat.These results are of great importance if such systems are to be used
as quantum computers.Comment: 4 pages, 4 figure
Qualidade de Vida e Atitudes dos Idosos Face à Velhice
A problemática do envelhecimento tem assumido, nos últimos anos, uma
crescente importância na consciência coletiva da população, tornando-se cada vez mais importante compreender a população idosa e a sua realidade.
Posto isto, foi realizado um estudo quantitativo e correlacional, que teve como
objectivo avaliar a qualidade de vida e atitudes face à velhice de idosos, bem como a
relação entre estas e as variáveis sociodemográficas e familiares.
Foram inquiridos 100 idosos, com mais de 65 anos e sem deficit cognitivo . Para
a recolha de dados utilizou-se uma entrevista estruturada, constituída dados
sóciodemográficos do idoso, WHOQOL-AGE (Caballero, Miret, Power, Chatterji,
Tobiasz-Adamczyk, Koskinen, Leonardi, Olaya, Haro &Ayuso-Mateos, 2013) e o AAQ
( Laidlaw, Power, Schmidt and the WHOQOL-OLD Group, 2007).
Dos resultados destacamos os seguintes: A amostra é constituída por 52% de
idosos do sexo masculino tendo uma média de idades de 74,7 (DP=6,8). È no fator
Perdas Psicossociais e no Desenvolvimento Psicológico que os idosos têm uma melhor
atitude face ao envelhecimento. É no item “Tem dinheiro suficiente para satisfazer as
suas necessidades?” que os idosos apresentam uma menor qualidade de vida.
Não ter doença diagnosticada e ser do sexo masculino permitem ter melhores
atitudes face ao envelhecimento.
A Qualidade de Vida está relacionada com a idade, com o estado de saúde e com
a intensidade de preocupação da família. Constatou-se que os idosos que não estão
institucionalizados apresentam uma melhor qualidade de vida e uma melhor atitude face à velhice. Quem não precisa de ajudas técnicas para se movimentar apresenta uma melhor qualidade de vida.
Diferenças nas atitudes face ao envelhecimento consoante a residência onde
habita são significativas nas mudanças físicas e no desenvolvimento psicológico sendo
que os idosos que não vivem em lares têm uma atitude mais positiva em ambos os
fatores. / Over the past few years the issue of aging has played a growing importance in the population`s collective consciousness becoming increasingly important to
understand the elderly population and this reality.
Therefore a quantitative correlational study was performed to assess the quality
of life of seniors and their attitudes towards old age, and the relationship between these
and the socio-demographic and family factors.
100 seniors with more than 65 years and without cognitive deficit were
surveyed. For data collection we used a structured interview consisting of sociodemographic data of the elderly, WHOQOL-AGE (Caballero Miret Power Chatterji
Tobiasz-Adamczyk Koskinen Leonardi Olaya Ayuso-Mateos & Haro 2013) and AAQ
(Laidlaw Power Schmidt and the WHOQOL-OLD Group 2007).
We highlight: The sample is composed of 52% of males with a mean age of 74.7
(SD = 6.8). It is in the factor Psychosocial Losses and Psychological Development that
elderly people have a better attitude towards aging. It is in the item "Do you have
enough money to meet your needs?" that seniors show less quality of life.
Not having illness and being male allows having better attitudes towards aging.
Quality of Life is related to age, health condition and the intensity of family
concerns. It was observed that the elderly who are not institutionalized have a better
quality of life and a better attitude towards old age. Who does not need assistive devices to move around has a better quality of life.
Differences in attitudes towards aging, according to residency, are significant in
physical changes and psychological development, thus verifying that elderly who do not
live in nursing homes have a more positive attitude in both factors
Primordial He4 Abundance Constrains the Possible Time Variation of the Higgs Vacuum Expectation Value
We constrain the possible time variation of the Higgs vacuum expectation
value () by recent results on the primordial abundance (). For
that, we use an analytic approach which enables us to take important issues
into consideration, that have been ignored by previous works, like the
-dependence of the relevant cross sections of deuterium production and
photodisintegration, including the full Klein- Nishina cross section.
Furthermore, we take a non-equilibrium Ansatz for the freeze-out concentration
of neutrons and protons and incorporate the latest results on the neutron
decay. Finally, we approximate the key-parameters of the primordial
production (the mean lifetime of the free neutron and the binding energy of the
deuteron) by terms of (where denotes the present theoretical
estimate). Eventually, we derive the relation and the most stringent
limit on a possible time variation of is given by: .Comment: Accepted for publication in IJT
Scalar field "mini--MACHOs": a new explanation for galactic dark matter
We examine the possibility that galactic halos are collisionless ensembles of
scalar field ``massive compact halo objects'' (MACHOs). Using mass constraints
from MACHO microlensing and from theoretical arguments on halos made up of
massive black holes, as well as demanding also that scalar MACHO ensambles of
all scales do not exhibit gravothermal instability (as required by consistency
with observations of LSB galaxies), we obtain the range: m\alt 10^{-7}
M_\odot or 30 M_\odot\alt m\alt 100 M_\odot. The rather narrow mass range of
large MACHOs seems to indicate that the ensambles we are suggesting should be
probably made up of scalar MACHOs in the low mass range (``mini--MACHOs''). The
proposed model allows one to consider a non--baryonic and non--thermal
fundamental nature of dark matter, while at the same time keeping the same
phenomenology of the CDM paradigm.Comment: 5 pages, 1 eps figure. RevTex 4 style. To appear in Physical Review
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
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