6,286 research outputs found
On the RKKY range function of a one dimensional non interacting electron gas
We show that the pitfalls encountered in earlier calculations of the RKKY
range function for a non interacting one dimensional electron gas at zero
temperature can be unraveled and successfully dealt with through a proper
handling of the impurity potential.Comment: to appear in Phys. Re
Persistent left superior vena cava in cardiac congenital surgery
La persistance d'une veine cave supérieure gauche (VCSG) est une entité relativement fréquente dans le cadre des malformations cardiaques congénitales. Le but de cette étude est d'analyser à quel moment le diagnostic de la persistance de la VCSG est effectué, à quel moment le diagnostic des éventuelles anomalies du sinus coronarien associées est effectué, et de l'impact global de la persistance d'une VCSG sur la mortalité et la morbidité des patients après chirurgie cardiaque pour une malformation cardiaque congénitale.
Analyse rétrospective d'une cohorte d'enfants ayant subi une chirurgie cardiaque avec circulation extracorporelle pour une malformation cardiaque congénitale. Trois-cent septante et un patients ont été inclus dans l'étude avec un âge médian de 2.75 ans (IQR 0.65-6.63). Parmi eux, 47 patients présentaient une persistance de la VCSG (12.7%), et cette persistance de la VCSG a été identifiée par échocardiographie dans le cadre du bilan préopératoire chez 39 patients (83%).
Trois patients (6.4%) présentant une persistance de la VCSG, ont développé après chirurgie cardiaque, une obstruction significative de la voie d'entrée du ventricule gauche qui a aboutit à un débit cardiaque anormal ou à une hypertension pulmonaire secondaire. Chez huit patients (17%), la persistance de la VCSG, était associée à un défaut partiel ou total de fermeture du sinus coronarien et dans deux cas (4%) à une atrésie de l'ostium du sinus coronarien. La durée de la ventilation mécanique était plus courte de façon significative dans le groupe contrôle (1.2 vs. 3.0 jours, p = 0.004), tandis que la durée de séjour aux soins intensifs ne différait pas. La mortalité était significativement moins élevée dans le groupe contrôle que dans le groupe de patient avec persistance de la VCSG (2.5 vs. 10.6 %, p = 0.004).
Les résultats de cette étude montrent que la persistance de la VCSG en association avec une malformation cardiaque congénitale augmente le risque de mortalité chez les enfants qui subissent une chirurgie cardiaque avec circulation extracorporelle. La mise en évidence d'une persistance de la VCSG et des anomalies associées, s'impose pour éviter des complications pendant et après une chirurgie cardiaque
The scaling limit of the energy correlations in non integrable Ising models
We obtain an explicit expression for the multipoint energy correlations of a
non solvable two-dimensional Ising models with nearest neighbor ferromagnetic
interactions plus a weak finite range interaction of strength , in a
scaling limit in which we send the lattice spacing to zero and the temperature
to the critical one. Our analysis is based on an exact mapping of the model
into an interacting lattice fermionic theory, which generalizes the one
originally used by Schultz, Mattis and Lieb for the nearest neighbor Ising
model. The interacting model is then analyzed by a multiscale method first
proposed by Pinson and Spencer. If the lattice spacing is finite, then the
correlations cannot be computed in closed form: rather, they are expressed in
terms of infinite, convergent, power series in . In the scaling limit,
these infinite expansions radically simplify and reduce to the limiting energy
correlations of the integrable Ising model, up to a finite renormalization of
the parameters. Explicit bounds on the speed of convergence to the scaling
limit are derived.Comment: 75 pages, 11 figure
Response properties of III-V dilute magnetic semiconductors: interplay of disorder, dynamical electron-electron interactions and band-structure effects
A theory of the electronic response in spin and charge disordered media is
developed with the particular aim to describe III-V dilute magnetic
semiconductors like GaMnAs. The theory combines a detailed k.p description of
the valence band, in which the itinerant carriers are assumed to reside, with
first-principles calculations of disorder contributions using an
equation-of-motion approach for the current response function. A fully dynamic
treatment of electron-electron interaction is achieved by means of
time-dependent density functional theory. It is found that collective
excitations within the valence band significantly increase the carrier
relaxation rate by providing effective channels for momentum relaxation. This
modification of the relaxation rate, however, only has a minor impact on the
infrared optical conductivity in GaMnAs, which is mostly determined by the
details of the valence band structure and found to be in agreement with
experiment.Comment: 15 pages, 9 figure
DEVELOPMENT OF METHODS FOR THE DETERMINATION OF THE HIGH TEMPERATURE THERMAL DIFFUSIVITY OF DC. EUR 337.e
Neutrinoless Double Beta Decay, the Inverted Hierarchy and Precision Determination of theta(12)
Ruling out the inverted neutrino hierarchy with neutrinoless double beta
decay experiments is possible if a limit on the effective mass below the
minimal theoretically possible value is reached. We stress that this lower
limit depends strongly on the value of the solar neutrino mixing angle: it
introduces an uncertainty of a factor of 2 within its current 3 sigma range. If
an experiment is not background-free, a factor of two in effective mass
corresponds to a combined factor of 16 improvement for the experimental
parameters running time, detector mass, background level and energy resolution.
Therefore, a more precise determination of theta(12) is crucial for the
interpretation of experimental results and the evaluation of the potential and
requirements for future experiments. We give the required half-lifes to exclude
(and touch) the inverted hierarchy regime for all double beta decay isotopes
with a Q-value above 2 MeV. The nuclear matrix elements from 6 different groups
and, if available, their errors are used and compared. We carefully put the
calculations on equal footing in what regards various convention issues. We
also use our compilation of matrix elements to give the reachable values of the
effective mass for a given half-life value.Comment: 26 pages, 6 figures. v2: error corrected (misprint in paper we took a
value from), slightly modifying the result
Enhanced carrier scattering rates in dilute magnetic semiconductors with correlated impurities
In III-V dilute magnetic semiconductors (DMSs) such as GaMnAs,
the impurity positions tend to be correlated, which can drastically affect the
electronic transport properties of these materials. Within the memory function
formalism we have derived a general expression for the current relaxation
kernel in spin and charge disordered media and have calculated spin and charge
scattering rates in the weak-disorder limit. Using a simple model for magnetic
impurity clustering, we find a significant enhancement of the charge
scattering. The enhancement is sensitive to cluster parameters and may be
controllable through post-growth annealing.Comment: 4 pages, 3 figure
Genetics of human longevity within an eco-evolutionary nature-nurture framework
Human longevity is a complex trait, and to disentangle its basis has a great theoretical and practical consequences for biomedicine. The genetics of human longevity is still poorly understood despite several investigations that used different strategies and protocols. Here, we argue that such rather disappointing harvest is largely because of the extraordinary complexity of the longevity phenotype in humans. The capability to reach the extreme decades of human lifespan seems to be the result of an intriguing mixture of gene-environment interactions. Accordingly, the genetics of human longevity is here described as a highly context-dependent phenomenon, within a new integrated, ecological, and evolutionary perspective, and is presented as a dynamic process, both historically and individually. The available literature has been scrutinized within this perspective, paying particular attention to factors (sex, individual biography, family, population ancestry, social structure, economic status, and education, among others) that have been relatively neglected. The strength and limitations of the most powerful and used tools, such as genome-wide association study and whole-genome sequencing, have been discussed, focusing on prominently emerged genes and regions, such as apolipoprotein E, Forkhead box O3, interleukin 6, insulin-like growth factor-1, chromosome 9p21, 5q33.3, and somatic mutations among others. The major results of this approach suggest that (1) the genetics of longevity is highly population specific; (2) small-effect alleles, pleiotropy, and the complex allele timing likely play a major role; (3) genetic risk factors are age specific and need to be integrated in the light of the geroscience perspective; (4) a close relationship between genetics of longevity and genetics of age-related diseases (especially cardiovascular diseases) do exist. Finally, the urgent need of a global approach to the largely unexplored interactions between the 3 genetics of human body, that is, nuclear, mitochondrial, and microbiomes, is stressed. We surmise that the comprehensive approach here presented will help in increasing the above-mentioned harvest
Electron corrected Lorentz forces in solids and molecules in magnetic field
We describe the effective Lorentz forces on the ions of a generic insulating
system in an magnetic field, in the context of Born-Oppenheimer ab-initio
molecular dynamics. The force on each ion includes an important contribution of
electronic origin, which depends explicitly on the velocity of all other ions.
It is formulated in terms of a Berry curvature, in a form directly suitable for
future first principles classical dynamics simulations based {\it e.g.,} on
density functional methods. As a preliminary analytical demonstration we
present the dynamics of an H molecule in a field of intermediate strength,
approximately describing the electrons through Slater's variational
wavefunction.Comment: 5 pages, 2 figures; to appear in Phys. Rev.
Response by Giuliani et al to Letter Regarding Article, "genetics of Human Longevity Within an Eco-Evolutionary Nature-Nurture Framework"
Comment on Genetics of Human Longevity Within an Eco-Evolutionary Nature-Nurture Framework. [Circ Res. 2018]
Letter by Morris Regarding Article, "Genetics of Human Longevity Within an Eco-Evolutionary Nature-Nurture Framework". [Circ Res. 2019
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