Management of abnormal invasive placenta in a low- and medium-resource setting.

The purpose of this review is to describe the panorama of placenta accreta spectrum (PAS) disorder management in low- and middle-income countries, providing information that allows for the improvement of maternal and perinatal outcomes in the management of this pathology. This spectrum of disorders is associated with implications of high morbidity and mortality, both maternal and perinatal, which is why clinical practice guidelines based on management are produced in settings where there is a wide range of available resources. This situation often contrasts with what the reality is in low-resource countries. Prenatal diagnosis of placental accreta is essential to carry out adequate surgical planning in centres where multidisciplinary teams are in place, which improve results and reduce complications. These ideal scenarios should be developed in countries with more significant difficulties in the availability of human and technological resources, through teamwork in the different hospital centres and the adequate transfer of patients at higher risk to centres with the best interdisciplinary management skills.

Theoretical prediction of crystallization kinetics of a supercooled Lennard-Jones fluid.

The first order curvature correction to the crystal-liquid interfacial free energy is calculated using a theoretical model based on the interfacial excess thermodynamic properties. The correction parameter (δ), which is analogous to the Tolman length at a liquid-vapor interface, is found to be 0.48 ± 0.05 for a Lennard-Jones (LJ) fluid. We show that this curvature correction is crucial in predicting the nucleation barrier when the size of the crystal nucleus is small. The thermodynamic driving force (Δµ) corresponding to available simulated nucleation conditions is also calculated by combining the simulated data with a classical density functional theory. In this paper, we show that the classical nucleation theory is capable of predicting the nucleation barrier with excellent agreement to the simulated results when the curvature correction to the interfacial free energy is accounted for.

Solid-liquid interface free energies of pure bcc metals and B2 phases.

The solid-liquid interface (SLI) free energy was determined from molecular dynamics (MD) simulation for several body centered cubic (bcc) metals and B2 metallic compounds (space group: Pm3̄m; prototype: CsCl). In order to include a bcc metal with a low melting temperature in our study, a semi-empirical potential was developed for Na. Two additional synthetic "Na" potentials were also developed to explore the effect of liquid structure and latent heat on the SLI free energy. The obtained MD data were compared with the empirical Turnbull, Laird, and Ewing relations. All three relations are found to predict the general trend observed in the MD data for bcc metals obtained within the present study. However, only the Laird and Ewing relations are able to predict the trend obtained within the sequence of "Na" potentials. The Laird relation provides the best prediction for our MD data and other MD data for bcc metals taken from the literature. Overall, the Laird relation also agrees well with our B2 data but requires a proportionality constant that is substantially different from the bcc case. It also fails to explain a considerable difference between the SLI free energies of some B2 phases which have nearly the same melting temperature. In contrast, this difference is satisfactorily described by the Ewing relation. Moreover, the Ewing relation obtained from the bcc dataset also provides a reasonable description of the B2 data.

Free Energy Calculations of Crystalline Hard Sphere Complexes Using Density Functional Theory.

Recently developed fundamental measure density functional theory (FMT) is used to study binary hard sphere (HS) complexes in crystalline phases. By comparing the excess free energy, pressure, and phase diagram, we show that the fundamental measure functional yields good agreements to the available simulation results of AB, AB2, and AB13 crystals. Furthermore, we use this functional to study the HS models of five binary crystals, Cu5Zr(C15b), Cu51Zr14(ß), Cu10Zr7(ϕ), CuZr(B2), and CuZr2(C11b), which are observed in the Cu-Zr system. The FMT functional gives a well-behaved minimum for most of the hard sphere crystal complexes in the two-dimensional Gaussian parameter space, namely a crystalline phase. However, the current version of FMT functional (White Bear) fails to give a stable minimum for the structure Cu10Zr7(ϕ). We argue that the observed solid phases for the HS models of the Cu-Zr system are true thermodynamic stable phases and can be used as a reference system in perturbation calculations.

Theoretical calculation of the melting curve of Cu-Zr binary alloys.

Helmholtz free energies of the dominant binary crystalline solids found in the Cu-Zr system at high temperatures close to the melting curve are calculated. Our theoretical approach combines fundamental measure density functional theory (applied to the hard-sphere reference system) and a perturbative approach to include the attractive interactions. The studied crystalline solids are Cu(fcc), Cu_{51}Zr_{14}(ß), CuZr(B2), CuZr_{2}(C11b), Zr(hcp), and Zr(bcc). The calculated Helmholtz free energies of crystalline solids are in good agreement with results from molecular-dynamics (MD) simulations. Using the same perturbation approach, the liquid phase free energies are calculated as a function of composition and temperature, from which the melting curve of the entire composition range of this system can be obtained. Phase diagrams are determined in this way for two leading embedded atom method potentials, and the results are compared with experimental data. Theoretical melting temperatures are compared both with experimental values and with values obtained directly from MD simulations at several compositions.