53 research outputs found
Perinatal grief following neonatal comfort care for lethal fetal condition
BACKGROUND: The objective of the study was to assess perinatal grief experienced after continuing pregnancy and comfort care in women diagnosed with lethal fetal condition compared with termination of pregnancy for fetal anomaly (TOPFA).
METHODS: This was a retrospective observational study which included women who chose to continue their pregnancy after the diagnosis of lethal fetal condition with comfort care support at birth at the Prenatal Diagnosis Center of Rennes Hospital from January 2007 to January 2017. Women were matched with controls who underwent TOPFA for the same type of fetal anomaly, gestational age at diagnosis and year. Women were evaluated by a questionnaire including the Perinatal Grief Scale.
RESULTS: There were 28 patients in the continuing pregnancy group matched with 56 patients in the TOPFA group. Interval between fetal loss and completion of questionnaire was 6±3 years. Perinatal grief score was similar at 61±22 vs 58±18 (p = 0.729) in the continuing pregnancy and TOPFA groups, respectively. Women in the TOPFA group expressed more guilt. The cesarean-section rate in the continuing pregnancy group was 25% .
CONCLUSION: Perinatal grief experienced by women opting for continuing pregnancy and comfort care after diagnosis of a potentially lethal fetal anomaly is not more severe than for those choosing TOPFA
Nucleation of Al3Zr and Al3Sc in aluminum alloys: from kinetic Monte Carlo simulations to classical theory
Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and
Al3Sc which for low supersaturations of the solid solution have the L12
structure. The aim of the present study is to model at an atomic scale this
kinetics of precipitation and to build a mesoscopic model based on classical
nucleation theory so as to extend the field of supersaturations and annealing
times that can be simulated. We use some ab-initio calculations and
experimental data to fit an Ising model describing thermodynamics of the Al-Zr
and Al-Sc systems. Kinetic behavior is described by means of an atom-vacancy
exchange mechanism. This allows us to simulate with a kinetic Monte Carlo
algorithm kinetics of precipitation of Al3Zr and Al3Sc. These kinetics are then
used to test the classical nucleation theory. In this purpose, we deduce from
our atomic model an isotropic interface free energy which is consistent with
the one deduced from experimental kinetics and a nucleation free energy. We
test di erent mean-field approximations (Bragg-Williams approximation as well
as Cluster Variation Method) for these parameters. The classical nucleation
theory is coherent with the kinetic Monte Carlo simulations only when CVM is
used: it manages to reproduce the cluster size distribution in the metastable
solid solution and its evolution as well as the steady-state nucleation rate.
We also find that the capillary approximation used in the classical nucleation
theory works surprisingly well when compared to a direct calculation of the
free energy of formation for small L12 clusters.Comment: submitted to Physical Review B (2004
Statistical Derivation of Basic Equations of Diffusional Kinetics in Alloys with Application to the Description of Diffusion of Carbon in Austenite
Basic equations of diffusional kinetics in alloys are statistically derived
using the master equation approach. To describe diffusional transformations in
substitution alloys, we derive the "quasi-equilibrium" kinetic equation which
generalizes its earlier versions by taking into account possible "interaction
renormalization" effects. For the interstitial alloys Me-X, we derive the
explicit expression for the diffusivity D of an interstitial atom X which
notably differs from those used in previous phenomenological treatments. This
microscopic expression for D is applied to describe the diffusion of carbon in
austenite basing on some simple models of carbon-carbon interaction. The
results obtained enable us to make certain conclusions about the real form of
these interactions, and about the scale of the "transition state entropy" for
diffusion of carbon in austenite.Comment: 26 pages, 5 postscript figures, LaTe
Study of Damage Propagation at the Interface Localization-Delocalization Transition of the Confined Ising Model
The propagation of damage in a confined magnetic Ising film, with short range
competing magnetic fields () acting at opposite walls, is studied by means
of Monte Carlo simulations. Due to the presence of the fields, the film
undergoes a wetting transition at a well defined critical temperature .
In fact, the competing fields causes the occurrence of an interface between
magnetic domains of different orientation. For ) such
interface is bounded (unbounded) to the walls, while right at the
interface is essentially located at the center of the film.
It is found that the spatio-temporal spreading of the damage becomes
considerably enhanced by the presence of the interface, which act as a
''catalyst'' of the damage causing an enhancement of the total damaged area.
The critical points for damage spreading are evaluated by extrapolation to the
thermodynamic limit using a finite-size scaling approach. Furthermore, the
wetting transition effectively shifts the location of the damage spreading
critical points, as compared with the well known critical temperature of the
order-disorder transition characteristic of the Ising model. Such a critical
points are found to be placed within the non-wet phase.Comment: 22 pages, 13 figures include
The ANTENATAL multicentre study to predict postnatal renal outcome in fetuses with posterior urethral valves: objectives and design
Abstract
Background
Posterior urethral valves (PUV) account for 17% of paediatric end-stage renal disease. A major issue in the management of PUV is prenatal prediction of postnatal renal function. Fetal ultrasound and fetal urine biochemistry are currently employed for this prediction, but clearly lack precision. We previously developed a fetal urine peptide signature that predicted in utero with high precision postnatal renal function in fetuses with PUV. We describe here the objectives and design of the prospective international multicentre ANTENATAL (multicentre validation of a fetal urine peptidome-based classifier to predict postnatal renal function in posterior urethral valves) study, set up to validate this fetal urine peptide signature.
Methods
Participants will be PUV pregnancies enrolled from 2017 to 2021 and followed up until 2023 in >30 European centres endorsed and supported by European reference networks for rare urological disorders (ERN eUROGEN) and rare kidney diseases (ERN ERKNet). The endpoint will be renal/patient survival at 2 years postnatally. Assuming α = 0.05, 1–β = 0.8 and a mean prevalence of severe renal outcome in PUV individuals of 0.35, 400 patients need to be enrolled to validate the previously reported sensitivity and specificity of the peptide signature.
Results
In this largest multicentre study of antenatally detected PUV, we anticipate bringing a novel tool to the clinic. Based on urinary peptides and potentially amended in the future with additional omics traits, this tool will be able to precisely quantify postnatal renal survival in PUV pregnancies. The main limitation of the employed approach is the need for specialized equipment.
Conclusions
Accurate risk assessment in the prenatal period should strongly improve the management of fetuses with PUV
Méthodes atomiques et élasticité
La connaissance du diagramme de phase d’un alliage est essentielle lorsqu’on élabore un
matériau à la recherche de propriétés spécifiques (tenue mécanique, résistance à la
chaleur, à l’oxydation, propriétés électriques, magnétiques, etc.). Il est important de
connaître la stabilité des différentes phases qui peuvent se développer dans le système et
de caractĂ©riser les possibles transformations entre elles. Pour cela, une description Ă
l’échelle atomique basée sur des calculs de structure électronique et de physique
statistique est nécessaire. Les modèles utilisés dans le cadre de ces calculs dépendent de
la nature des matériaux étudiés ainsi que du degré de complexité des mécanismes physiques
qui s’y développent. Au-delà de la stabilité des phases, il est aussi intéressant de
connaître l’évolution de la microstructure de l’alliage en fonction du temps, de la
température et de la concentration. Dans cet exposé, nous regarderons particulièrement les
effets de la différence de taille des atomes (effets élastiques) sur la forme de
diagrammes de phases d’alliages métalliques massifs et confinés présentant des
transformations de phase du type « démixtion » et de type « ordre-désordre ». L’effet de
la compétition entre effets chimiques et effets élastiques sera aussi analysé. Deux
méthodes numériques à l’échelle atomique sont particulièrement intéressantes pour ce type
d’étude : l’approche Monte Carlo avec déplacements et la méthode des fonctions de Green
sur réseau (« Lattice statics »). La première est une méthode en principe exacte. Elle
permet d’aller au delà de l’élasticité linéaire lorsque les différences de taille sont
importantes et permet, en principe, de reproduire d’éventuelles pertes de cohérence. La
deuxième méthode se situe dans le cadre de l’élasticité linéaire et intègre les effets
élastiques sous la forme d’interactions effectives (à longue portée) sur réseau. Ainsi,
seuls des diagrammes de phases et des microstructures cohérents peuvent être étudiés. Son
avantage réside dans la possibilité de traiter des volumes de simulation beaucoup plus
importants que dans le cas des simulations Monte Carlo avec déplacements. En utilisant ces
deux méthodes, nous illustrerons et analyserons l’effet de l’élasticité sur des
microstructures d’alliages binaires
Effect of saddle point anisotropy of point defects on their absorption by dislocations and cavities
International audienceDeveloping predictive models for the microstructure evolution of materials requires an accurate description of the point defects fluxes to the different sinks, such as dislocations, grain boundaries and cavities. This work aims at improving the evaluation of sink strengths of dislocations and cavities using object kinetic Monte-Carlo simulations parametrized with density functional theory calculations. The present accurate description of point defects migration enables quantitative assessment of the influence of the point defects anisotropy at saddle point. The results in aluminum show that the anisotropy at saddle point has a large influence on sink strengths. In particular, this anisotropy leads to the cavity being a biased sink. These results are explained by the analysis of the point defect trajectories to the sinks, which are shown to be strongly affected by the saddle point anisotropy
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