37 research outputs found
Interacting New Agegraphic Dark Energy in a Cyclic Universe
The main goal of this work is investigation of NADE in the cyclic universe
scenario. Since, cyclic universe is explained by a phantom phase (),
it is shown when there is no interaction between matter and dark energy, ADE
and NADE do not produce a phantom phase, then can not describe cyclic universe.
Therefore, we study interacting models of ADE and NADE in the modified
Friedmann equation. We find out that, in the high energy regime, which it is a
necessary part of cyclic universe evolution, only NADE can describe this
phantom phase era for cyclic universe. Considering deceleration parameter tells
us that the universe has a deceleration phase after an acceleration phase, and
NADE is able to produce a cyclic universe. Also it is found valuable to study
generalized second law of thermodynamics. Since the loop quantum correction is
taken account in high energy regime, it may not be suitable to use standard
treatment of thermodynamics, so we turn our attention to the result of
\citep{29}, which the authors have studied thermodynamics in loop quantum
gravity, and we show that which condition can satisfy generalized second law of
thermodynamics.Comment: 8 pages, 3 figure
Dark Energy and Gravity
I review the problem of dark energy focusing on the cosmological constant as
the candidate and discuss its implications for the nature of gravity. Part 1
briefly overviews the currently popular `concordance cosmology' and summarises
the evidence for dark energy. It also provides the observational and
theoretical arguments in favour of the cosmological constant as the candidate
and emphasises why no other approach really solves the conceptual problems
usually attributed to the cosmological constant. Part 2 describes some of the
approaches to understand the nature of the cosmological constant and attempts
to extract the key ingredients which must be present in any viable solution. I
argue that (i)the cosmological constant problem cannot be satisfactorily solved
until gravitational action is made invariant under the shift of the matter
lagrangian by a constant and (ii) this cannot happen if the metric is the
dynamical variable. Hence the cosmological constant problem essentially has to
do with our (mis)understanding of the nature of gravity. Part 3 discusses an
alternative perspective on gravity in which the action is explicitly invariant
under the above transformation. Extremizing this action leads to an equation
determining the background geometry which gives Einstein's theory at the lowest
order with Lanczos-Lovelock type corrections. (Condensed abstract).Comment: Invited Review for a special Gen.Rel.Grav. issue on Dark Energy,
edited by G.F.R.Ellis, R.Maartens and H.Nicolai; revtex; 22 pages; 2 figure
Use of chromatin remodeling ATPases as RNAi targets for parental control of western corn rootworm (Diabrotica virgifera virgifera) and Neotropical brown stink bug (Euschistus heros)
An Observational Overview of Solar Flares
We present an overview of solar flares and associated phenomena, drawing upon
a wide range of observational data primarily from the RHESSI era. Following an
introductory discussion and overview of the status of observational
capabilities, the article is split into topical sections which deal with
different areas of flare phenomena (footpoints and ribbons, coronal sources,
relationship to coronal mass ejections) and their interconnections. We also
discuss flare soft X-ray spectroscopy and the energetics of the process. The
emphasis is to describe the observations from multiple points of view, while
bearing in mind the models that link them to each other and to theory. The
present theoretical and observational understanding of solar flares is far from
complete, so we conclude with a brief discussion of models, and a list of
missing but important observations.Comment: This is an article for a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
Macrosocial determinants of population health in the context of globalization
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55738/1/florey_globalization_2007.pd
Free-field blast parameter errors from Cartesian cell representations of bursting sphere-type charges
The bursting sphere model is a simple approach to the numerical simulation of blast from charge detonation. It involves initializing a group of computational cells at high pressure with the correct blast energy to represent the charge volume. In this paper, a programme of numerical simulations of charge detonations in free-field air using the bursting sphere approach will be performed. This is done to investigate the errors in important blast parameters like peak overpressure and impulse that arise due to deviation of the charge shape from an ideal spherical profile when the charge is represented by a Cartesian mesh. This study will also include an assessment of the quality of error estimation for this problem based on grid refinement studies
Médecine d'urgence [Emergency medicine: updates 2012].
We review some of the most influential papers from 2012 in the different aspects of emergency medicine, such as prehospital medicine, resuscitation, early diagnosis and timely ED discharge and treatment. In particular, intramuscular benzodiazepines have been shown to be efficient in prehospital status epilepticus, epinephrines usefulness in cardiopulmonary resuscitation has been challenged, colloids have been shown to be deleterious in the treatment of severe sepsis and septic shock, the time window for thrombolysis in acute stroke will probably be extended, acute pyelonephritis treatment duration can be decreased, new D-dimers thresholds for older patients may prevent further diagnosis tests, and hs-Troponin may allow earlier discharge of low coronary risk patients