2,238 research outputs found
Predictive value of noninvasive measures of atherosclerosis for incident myocardial infarction: the Rotterdam Study.
BACKGROUND: Several noninvasive methods are available to investigate the
severity of extracoronary atherosclerotic disease. No population-based
study has yet examined whether differences exist between these measures
with regard to their predictive value for myocardial infarction (MI) or
whether a given measure of atherosclerosis has predictive value
independently of the other measures. METHODS AND RESULTS: At the baseline
(1990-1993) examination of the Rotterdam Study, a population-based cohort
study among subjects age > or =55 years, carotid plaques and intima-media
thickness (IMT) were measured by ultrasound, abdominal aortic
atherosclerosis by x-ray, and lower-extremity atherosclerosis by
computation of the ankle-arm index. In the present study, 6389 subjects
were included; 258 cases of incident MI occurred before January 1, 2000.
All 4 measures of atherosclerosis were good predictors of MI independently
of traditional cardiovascular risk factors. Hazard ratios were equally
high for carotid plaques (1.83 [1.27 to 2.62], severe versus no
atherosclerosis), carotid IMT (1.95 [1.19 to 3.19]), and aortic
atherosclerosis (1.94 [1.30 to 2.90]) and slightly lower for
lower-extremity atherosclerosis (1.59 [1.05 to 2.39]), although
differences were small. The hazard ratio for MI for subjects with severe
atherosclerosis according to a composite atherosclerosis score was 2.77
(1.70 to 4.52) compared with subjects with no atherosclerosis. The
predictive value of MI for a given measure of atherosclerosis was
independent of the other atherosclerosis measures. CONCLUSIONS:
Noninvasive measures of extracoronary atherosclerosis are strong
predictors of MI. The relatively crude measures directly assessing plaques
in the carotid artery and abdominal aorta predict MI equally well as the
more precisely measured carotid IMT
A model of mother tongue-based bilingual education in Vietnam: Achievements and lessons learnt
This articlesummarizes findings from the implementation of the mother tongue-based bilingual education model
and the tracer study on the students who participated in the mother tongue-based bilingual education program at preschool and primary schools and transitioned to higher levels of education in the framework of the UNICEFfunded
"Learning for children" project. The research team would like to thank UNICEF Viet Nam,the Vietnam
National Institute of Educational Sciences, Departments of Education and Training of Lao Cai, Gia Lai and Tra
Vinh provinces, and educational managers, teachers and students in the three provinces for their support and
cooperation.Education practices in ethnic minority areas in Vietnam with regional and ethnic differences influence
its educational development. In particular, the language difference is a factor because the language
used in teaching and learning is Vietnamese, not the mother tongue. Therefore, the mother tonguebased
bilingual education model was developed to provide quick and convenient access to
Vietnamese (the nationâs official language) and knowledge for students in ethnic minority areas. Its
approach is to use the ethnic studentsâ mother tongues as the initial foundation in their first schooling
years. The outstanding results of the successfully tested model have contributed to the improvement
of the quality of ethnic minority education in Vietnam
Higgs for Graviton: Simple and Elegant Solution
A Higgs mechanism for gravity is presented, where four scalars with global
Lorentz symmetry are employed. We show that in the broken symmetry phase a
graviton absorbs all scalars and become massive spin 2 particle with five
degrees of freedom. The resulting theory is unitary and free of ghosts.Comment: 8 pages, References added. The decoupling of ghost state is analyzed
in detail
Cement composites reinforced with surface modified coir fibers
An experimental investigation of coir mesh reinforced mortar (CMRM) is conducted using nonwoven coir mesh matting. The main parameters in this study are the fiber volume fraction (number of mesh layers) and fiber surface treatment with a wetting agent. The composites are subjected to the four-point bending test. The short-term mechanical properties of CMRM are discussed. Scanning electron micrograph analysis is used to observe the fiber—matrix interfacial characteristics. The results indicate that the addition of coir mesh to mortar significantly improves the composite post-cracking flexural stress, toughness, ductility, and toughness index, compared to plain mortar materials. The Albatex © FFC wetting agent (2-ethylhexanol) can effectively improve water absorption of coir fiber and enhance the fiber—matrix bonding strength. These coir mesh reinforced composites may be useful in civil engineering applications.<br /
Imaging spontaneous currents in superconducting arrays of pi-junctions
Superconductors separated by a thin tunneling barrier exhibit the Josephson
effect that allows charge transport at zero voltage, typically with no phase
shift between the superconductors in the lowest energy state. Recently,
Josephson junctions with ground state phase shifts of pi proposed by theory
three decades ago have been demonstrated. In superconducting loops,
pi-junctions cause spontaneous circulation of persistent currents in zero
magnetic field, analogous to spin-1/2 systems. Here we image the spontaneous
zero-field currents in superconducting networks of temperature-controlled
pi-junctions with weakly ferromagnetic barriers using a scanning SQUID
microscope. We find an onset of spontaneous supercurrents at the 0-pi
transition temperature of the junctions Tpi = 3 K. We image the currents in
non-uniformly frustrated arrays consisting of cells with even and odd numbers
of pi-junctions. Such arrays are attractive model systems for studying the
exotic phases of the 2D XY-model and achieving scalable adiabatic quantum
computers.Comment: Pre-referee version. Accepted to Nature Physic
Massive Gravity: Exorcising the Ghost
We consider Higgs massive gravity [1,2] and investigate whether a nonlinear
ghost in this theory can be avoided. We show that although the theory
considered in [10,11] is ghost free in the decoupling limit, the ghost
nevertheless reappears in the fourth order away from the decoupling limit. We
also demonstrate that there is no direct relation between the value of the
Vainshtein scale and the existence of nonlinear ghost. We discuss how massive
gravity should be modified to avoid the appearance of the ghost.Comment: 16 page
Twinning superlattices in indium phosphide nanowires
Here, we show that we control the crystal structure of indium phosphide (InP)
nanowires by impurity dopants. We have found that zinc decreases the activation
barrier for 2D nucleation growth of zinc-blende InP and therefore promotes the
InP nanowires to crystallise in the zinc blende, instead of the commonly found
wurtzite crystal structure. More importantly, we demonstrate that we can, by
controlling the crystal structure, induce twinning superlattices with
long-range order in InP nanowires. We can tune the spacing of the superlattices
by the wire diameter and the zinc concentration and present a model based on
the cross-sectional shape of the zinc-blende InP nanowires to quantitatively
explain the formation of the periodic twinning.Comment: 18 pages, 4 figure
On Non-Linear Actions for Massive Gravity
In this work we present a systematic construction of the potentially
ghost-free non-linear massive gravity actions. The most general action can be
regarded as a 2-parameter deformation of a minimal massive action. Further
extensions vanish in 4 dimensions. The general mass term is constructed in
terms of a "deformed" determinant from which this property can clearly be seen.
In addition, our formulation identifies non-dynamical terms that appear in
previous constructions and which do not contribute to the equations of motion.
We elaborate on the formal structure of these theories as well as some of their
implications.Comment: v3: 22 pages, minor comments added, version to appear in JHE
Considering the Case for Biodiversity Cycles: Reexamining the Evidence for Periodicity in the Fossil Record
Medvedev and Melott (2007) have suggested that periodicity in fossil
biodiversity may be induced by cosmic rays which vary as the Solar System
oscillates normal to the galactic disk. We re-examine the evidence for a 62
million year (Myr) periodicity in biodiversity throughout the Phanerozoic
history of animal life reported by Rohde & Mueller (2005), as well as related
questions of periodicity in origination and extinction. We find that the signal
is robust against variations in methods of analysis, and is based on
fluctuations in the Paleozoic and a substantial part of the Mesozoic.
Examination of origination and extinction is somewhat ambiguous, with results
depending upon procedure. Origination and extinction intensity as defined by RM
may be affected by an artifact at 27 Myr in the duration of stratigraphic
intervals. Nevertheless, when a procedure free of this artifact is implemented,
the 27 Myr periodicity appears in origination, suggesting that the artifact may
ultimately be based on a signal in the data. A 62 Myr feature appears in
extinction, when this same procedure is used. We conclude that evidence for a
periodicity at 62 Myr is robust, and evidence for periodicity at approximately
27 Myr is also present, albeit more ambiguous.Comment: Minor modifications to reflect final published versio
Nonlinear Dynamics of 3D Massive Gravity
We explore the nonlinear classical dynamics of the three-dimensional theory
of "New Massive Gravity" proposed by Bergshoeff, Hohm and Townsend. We find
that the theory passes remarkably highly nontrivial consistency checks at the
nonlinear level. In particular, we show that: (1) In the decoupling limit of
the theory, the interactions of the helicity-0 mode are described by a single
cubic term -- the so-called cubic Galileon -- previously found in the context
of the DGP model and in certain 4D massive gravities. (2) The conformal mode of
the metric coincides with the helicity-0 mode in the decoupling limit. Away
from this limit the nonlinear dynamics of the former is described by a certain
generalization of Galileon interactions, which like the Galileons themselves
have a well-posed Cauchy problem. (3) We give a non-perturbative argument based
on the presence of additional symmetries that the full theory does not lead to
any extra degrees of freedom, suggesting that a 3D analog of the 4D
Boulware-Deser ghost is not present in this theory. Last but not least, we
generalize "New Massive Gravity" and construct a class of 3D cubic order
massive models that retain the above properties.Comment: 21 page
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