RESUMEN
The importance of nitrate and ammonium salts both in the environment and in biological processes cannot be questioned. In this work, using the TIP4P/2005 water model, aqueous solutions of nitrate and ammonium electrolytes are parametrized using scaled charges while keeping a rigid structure and nonpolarizable charge distributions. The models are optimized by systematically testing a set of properties for twelve electrolytes-eight nitrate and four ammonium salts-thus, enlarging the number of potential chemical species encompassed within the Madrid-2019 force field for ions. The capacity of the force field for predicting densities, ion-ion and ion-solvent structures, and transport properties of the solutions comprised by the trial batch of salts was tested and discussed. Both the dependence of the densities with the salt concentration and the solution structure were nicely reproduced by the models in the whole concentration range without any trace of precipitating events and with improved accuracy in comparison with recently reported models, while the agreement of the simulated transport properties with experimental data ranges from good to reasonable, depending on the ion/counterion pair. These scaled charge models might be considered as force fields embodying a reasonable compromise between exactness and general applicability and also as an important step in the development of accurate models for polyatomic ions.
RESUMEN
The interest in the description of the properties of fluids of restricted dimensionality is growing for theoretical and practical reasons. In this work, we have firstly developed an analytical expression for the Helmholtz free energy of the two-dimensional square-well fluid in the Barker-Henderson framework. This equation of state is based on an approximate analytical radial distribution function for d-dimensional hard-sphere fluids (1 ≤ d ≤ 3) and is validated against existing and new simulation results. The so-obtained equation of state is implemented in a discrete perturbation theory able to account for general potential shapes. The prototypical Lennard-Jones and Yukawa fluids are tested in its two-dimensional version against available and new simulation data with semiquantitative agreement.
RESUMEN
This is a report about a case of prenatal diagnosis of critical fetal aortic stenosis with severe mitral valve insufficiency in a 35+6 weeks fetus. Aortic stenosis represents 3% of congenital heart diseases, but its association with mitral regurgitation is quite unusual. Thanks to the latest advances in fetal ultrasonography we can now achieve a more precise diagnosis and we have been able to improve the understanding of its physiopathology. Based on this case we have reviewed the most recent literature about fetal aortic stenosis and mitral valve insufficiency, with the aim of summarizing its main physiopathological features, highlighting the clues and key points for its intrauterine diagnosis, describing its principal complications and summarizing its current treatment options.
Asunto(s)
Estenosis de la Válvula Aórtica/embriología , Corazón Fetal/diagnóstico por imagen , Insuficiencia de la Válvula Mitral/embriología , Ultrasonografía Prenatal/métodos , Adulto , Estenosis de la Válvula Aórtica/complicaciones , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/fisiopatología , Estenosis de la Válvula Aórtica/cirugía , Cateterismo Cardíaco , Cesárea , Ecocardiografía Doppler en Color , Ecocardiografía Doppler de Pulso , Fibroelastosis Endocárdica/diagnóstico por imagen , Fibroelastosis Endocárdica/embriología , Fibroelastosis Endocárdica/cirugía , Femenino , Edad Gestacional , Trasplante de Corazón , Humanos , Recién Nacido , Masculino , Insuficiencia de la Válvula Mitral/diagnóstico por imagen , Insuficiencia de la Válvula Mitral/etiología , Insuficiencia de la Válvula Mitral/cirugía , Polihidramnios , Embarazo , Pronóstico , Reoperación , Stents , Disfunción Ventricular Izquierda/etiologíaRESUMEN
OBJECTIVE: To describe the ultrasound findings, maternal and perinatal variables in cases with a prenatal diagnosis of persistence of right umbilical vein. PATIENTS AND METHODS: A descriptive analysis of cases with prenatal diagnosis of persistence of right umbilical vein in the Fetal Medicine Unit, Department of Obstetrics and Gynecology, Hospital Universitario Severo Ochoa. We described ultrasound findings, maternal and perinatal variables. RESULTS: We explored 9198 fetuses and 6 cases (0.06%) were diagnosis prenatally of persistent right umbilical vein, between 20 and 29 weeks of gestation. The male/female ratio was 1/1. Ductus venosus was presented in all cases. Two fetuses (33%) were proved to have other structural anomalies and their parents opted for termination of the pregnancy. All cases had no chromosomal anomaly associated and after birth, neonatal developments were favorable. CONCLUSION: Based on our results and a literature review, after prenatal diagnosis of persistent right umbilical vein, an exhaustive morphological study, which included a fetal echocardiography, is mandatory in order to rule out other structural malformations. Indication for fetal karyotype study has to be individualized considering persistence right umbilical vein type and other ultrasound findings.
Asunto(s)
Ultrasonografía Prenatal , Venas Umbilicales/anomalías , Venas Umbilicales/diagnóstico por imagen , Estudios Transversales , Femenino , Humanos , Recién Nacido , Masculino , Estudios RetrospectivosRESUMEN
BACKGROUND: Ovarian cysts in fetal abdominal tumors are more frequently diagnosed during pregnancy. Most of the time are usually small, asymptomatic and resolve spontaneously during pregnancy or in early neonatal life. OBJECTIVE: To describe the clinical and ultrasound cases with prenatal diagnosis of ovarian cyst treated in our center between 2002 and 2005. MATERIAL AND METHODS: Descriptive and observational cases of fetal ovarian cyst diagnosedbefore birth. The variables maternal and perinatal most relevant clinical data obtained at diagnosis and after birth. RESULTS: We explored 9.198 fetuses, of which there were 10 cases of ovarian cyst diagnosed between the second and third trimesters of pregnancy. All cases were unilateral andsonographic appearance homogeneous. In four cases there was spontaneous disappearance during the remaining gestational period. In the other six cases, four missing in the first 12 months and only two image persisted more than a year. CONCLUSIONS: Based on our results and in accordance with the literature, the prenatal diagnosis of fetal ovarian cyst is usually associated with a conservative approach with serialultrasound monitoring to rule out rare serious complications. During the neonatal period spontaneous disappearance is often the case and the surgical approach is indicated in cases with suspected persistent or torsion or hemorrhage, with cystectomy as first choice.