30 research outputs found
General Adiabatic Evolution with a Gap Condition
We consider the adiabatic regime of two parameters evolution semigroups
generated by linear operators that are analytic in time and satisfy the
following gap condition for all times: the spectrum of the generator consists
in finitely many isolated eigenvalues of finite algebraic multiplicity, away
from the rest of the spectrum. The restriction of the generator to the spectral
subspace corresponding to the distinguished eigenvalues is not assumed to be
diagonalizable. The presence of eigenilpotents in the spectral decomposition of
the generator forbids the evolution to follow the instantaneous eigenprojectors
of the generator in the adiabatic limit. Making use of superadiabatic
renormalization, we construct a different set of time-dependent projectors,
close to the instantaneous eigeprojectors of the generator in the adiabatic
limit, and an approximation of the evolution semigroup which intertwines
exactly between the values of these projectors at the initial and final times.
Hence, the evolution semigroup follows the constructed set of projectors in the
adiabatic regime, modulo error terms we control
Magnetism in AV3Sb5 (Cs, Rb, K): Origin and Consequences for the Strongly Correlated Phases
The V-based kagome systems AV3Sb5 (A = Cs, Rb and K) are unique by virtue of
the intricate interplay of non-trivial electronic structure, topology and
intriguing fermiology, rendering them to be a playground of many mutually
dependent exotic phases like charge-order and superconductivity. Despite
numerous recent studies, the interconnection of magnetism and other complex
collective phenomena in these systems has yet not arrived at any conclusion.
Using first-principles tools, we demonstrate that their electronic structures,
complex fermiologies and phonon dispersions are strongly influenced by the
interplay of dynamic electron correlations, non-trivial spin-polarization and
spin-orbit coupling. An investigation of the first-principles-derived
inter-site magnetic exchanges with the complementary analysis of q-dependence
of the electronic response functions and the electron-phonon coupling indicate
that the system conforms as a frustrated spin-cluster, where the occurrence of
the charge-order phase is intimately related to the mechanism of
electron-phonon coupling, rather than the Fermi-surface nesting.Comment: Accepted in Physical Review Letter
Magnetism in AV3Sb5 (A = Cs, Rb, K): Complex Landscape of the Dynamical Magnetic Textures
We have investigated the dynamical magnetic properties of the V-based kagome
stibnite compounds by combining the ab-initio calculated magnetic parameters of
a spin Hamiltonian like inter-site exchange parameters, magnetocrystalline
anisotropy and site projected magnetic moments, with full-fledged simulations
of atomistic spin-dynamics. Our calculations reveal that in addition to a
ferromagnetic order along the [001] direction, the system hosts a complex
landscape of magnetic configurations comprised of commensurate and
incommensurate spin-spirals along the [010] direction. The presence of such
chiral magnetic textures may be the key to solve the mystery about the origin
of the experimentally observed inherent breaking of the C6 rotational symmetry-
and the time-reversal symmetry.Comment: Accepted In Physical Review
Linked randomised controlled trials of face-to-face and electronic brief intervention methods to prevent alcohol related harm in young people aged 14–17 years presenting to Emergency Departments (SIPS junior)
Background: Alcohol is a major global threat to public health. Although the main burden of chronic alcohol-related disease is in adults, its foundations often lie in adolescence. Alcohol consumption and related harm increase steeply from the age of 12 until 20 years. Several trials focusing upon young people have reported significant positive effects of brief interventions on a range of alcohol consumption outcomes. A recent review of reviews also suggests that electronic brief interventions (eBIs) using internet and smartphone technologies may markedly reduce alcohol consumption compared with minimal or no intervention controls.
Interventions that target non-drinking youth are known to delay the onset of drinking behaviours. Web based alcohol interventions for adolescents also demonstrate significantly greater reductions in consumption and harm among ‘high-risk’ drinkers; however changes in risk status at follow-up for non-drinkers or low-risk
drinkers have not been assessed in controlled trials of brief alcohol interventions
The interplay of local electron correlations and ultrafast spin dynamics in fcc Ni
The complex electronic structure of metallic ferromagnets is determined by a balance between exchange interaction, electron hopping leading to band formation, and local Coulomb repulsion. The interplay between the respective terms of the Hamiltonian is of fundamental interest, since it produces most, if not all, of the exotic phenomena observed in the solid state. By combining high energy and temporal resolution in femtosecond time-resolved X-ray absorption spectroscopy with ab initio time-dependent density functional theory we analyze the electronic structure in fcc Ni on the time scale of these interactions in a pump-probe experiment. We distinguish transient broadening and energy shifts in the absorption spectra, which we demonstrate to be caused by electron repopulation and correlation-induced modifications of the electronic structure, respectively. Importantly, the theoretical description of this experimental result hence requires to take the local Coulomb interaction into account, revealing a temporal interplay between band formation, exchange interaction, and Coulomb repulsion
Transcutaneous flow related variables measured in vivo: the effects of gender
BACKGOUND: The identification of potential sources of error is a crucial step for any new assessment technique. This is the case for transcutaneous variables, such as flow and arterial gases, which have been applied as functional indicators of various aspects of human health. Regarding gender, a particular subject-related determinant, it is often claimed that women present higher transcutaneous oxygen pressure (tcpO(2)) values than men. However, the statistical significance of this finding is still uncertain. METHODS: The haemodynamical-vascular response to a local reactive hyperaemia procedure (the tourniquet cuff manoeuvre) was studied in two previously selected group of volunteers (n = 16; 8 women and 8 men). The effect of gender was assessed under standardised experimental conditions, using the transcutaneous flow-related variables tcpO(2)-tcpCO(2) and Laser-doppler Flowmetry (LDF). RESULTS: Regarding tcpO(2), statistically significant differences between genders were not found, although higher values were consistently found for the gases in the female group. Regarding LDF, high statistically significant differences (p < 0.005) were found, with the men's group presenting the highest values and variability. Other derived parameters used to characterise the vascular response following the cuff-deflation (t-peak) were similar in both groups. CONCLUSIONS: The relative influence of gender was not clearly demonstrated using these experimental conditions. However the gender-related LDF differences suggest that further investigation should be done on this issue. Perhaps in the presence of certain pathological disparities involving peripheral vascular regulation, other relationships may be found between these variables
Etiologies of Associations Between Childhood Sleep and Behavioral Problems in a Large Twin Sample
Objective
To examine the etiologies of covariation of childhood sleep problems and other behavioral/emotional problems in young children.
Method
The parents of more than 6,000 twin pairs provided information on their twins’ anxiety, conduct, and hyperactivity at ages 3, 4, and 7 by completing the Strengths and Difficulties Questionnaire. Information on sleep problems was obtained at age 3/4.
Results
Phenotypic correlations in preschool years between sleep problems and anxiety, conduct, and hyperactivity ranged from 0.17 to 0.22. These correlations were largely due to shared environmental factors (0.72–0.96) and less to heredity (0.05–0.26) and nonshared environment (0.00–0.06). Sleep problems at age 3/4 years predicted at age 7 years anxiety (β = .12, p < .001), conduct problems (β = .09, p < .001), and hyperactivity (β = .07, p < .001), after accounting for stability of these problems. These predictive associations were also mainly mediated by shared environment (0.16–0.91), although genetic (0.02–0.84) and nonshared environmental (−0.03–0.09) factors were also influential.
Conclusions
The modest associations between early sleep problems and later behavioral/emotional problems are largely accounted for by common psychosocial risk factors. Further research on which specific risks may mediate these connections is needed