ABSTRACT
The polymer-to-ceramic transformation kinetics of two widely employed ceramic precursors, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (TTCS) and polyureamethylvinylsilazane (CERASET), have been investigated using coupled thermogravimetry and mass spectrometry (TG-MS), Raman, XRD and FTIR. The thermally induced decomposition of the pre-ceramic polymer is the critical step in the synthesis of polymer derived ceramics (PDCs) and accurate kinetic modeling is key to attaining a complete understanding of the underlying process and to attempt any behavior predictions. However, obtaining a precise kinetic description of processes of such complexity, consisting of several largely overlapping physico-chemical processes comprising the cleavage of the starting polymeric network and the release of organic moieties, is extremely difficult. Here, by using the evolved gases detected by MS as a guide it has been possible to determine the number of steps that compose the overall process, which was subsequently resolved using a semiempirical deconvolution method based on the Frasier-Suzuki function. Such a function is more appropriate that the more usual Gaussian or Lorentzian functions since it takes into account the intrinsic asymmetry of kinetic curves. Then, the kinetic parameters of each constituent step were independently determined using both model-free and model-fitting procedures, and it was found that the processes obey mostly diffusion models which can be attributed to the diffusion of the released gases through the solid matrix. The validity of the obtained kinetic parameters was tested not only by the successful reconstruction of the original experimental curves, but also by predicting the kinetic curves of the overall processes yielded by different thermal schedules and by a mixed TTCS-CERASET precursor.
ABSTRACT
Los embarazos cervicales son una rara forma de embarazo ectópico. El diagnóstico se establece por ecografía, hallazgos analíticos o en estudio histopatológico. Presentamos un caso clínico de una paciente con hemorragia genital que requirió histerectomía para control del sangrado resultando un embarazo ectópico cervical. La pronta identificación de un embarazo ectópico cervical puede ayudar a mejorar la morbilidad y mortalidad de las pacientes (AU)
Cervical pregnancies are a rare form of ectopic pregnancy. Diagnosis is established by ultrasound, biochemical findings and histopathology. We report the case of a patient with hemorrhage, requiring hysterectomy to control the bleeding. Early identification of a cervical ectopic pregnancy can help to prevent significant morbidity and mortality in patients seeking emergency care (AU)
Subject(s)
Humans , Female , Adult , Pregnancy , Pregnancy, Ectopic/complications , Pregnancy, Ectopic/surgery , Pregnancy Complications/diagnosis , Pregnancy Complications/surgery , Hysterectomy/methods , Diagnosis, Differential , Abdominal Pain/complications , Abdominal Pain/diagnosis , Pregnancy Trimester, First/physiology , Echocardiography, Doppler/trends , Echocardiography, Doppler , Hemorrhage/complicationsABSTRACT
La deficiencia de piruvato cinasa es una causa rara de anemia hemolítica. Durante el embarazo, se ha tratado casos graves de esta deficiencia con transfusiones profilácticas de concentrados de hematíes para mantener unos valores de hemoglobina entre 7 y 8 g/dl. Caso clínico. Se descubrió un caso de anemia hemolítica secundaria a déficit de piruvato cinasa durante el primer embarazo de una mujer de 32 años. La anemia se trató con transfusiones de concentrados de hematíes, y en la segunda gestación fue necesario un mayor número de ellas para mantener los valores de hemoglobina por encima de 7 g/dl. En ambos casos, los recién nacidos tuvieron pesos en el percentil adecuado para su edad gestacional. Conclusiones. Este tipo de anemia es raro, y en ocasiones se descubre en situaciones especiales, como embarazo, infección o estrés (AU)
Pyruvate kinase deficiency is a rare cause of hemolytic anemia. During pregnancy, severe cases have traditionally been treated with prophylactic blood transfusions to maintain the hemoglobin concentration above arbitrary thresholds of 7-8 g/dL. Case report. A case of hemolytic anemia due to pyruvate kinase deficiency was discovered during the first pregnancy of a 32-year-old woman. The anemia was treated with blood transfusions. In a second pregnancy, the patient required a greater number of transfusions to keep the hemoglobin concentration above 7 g/dL. Both newborns were healthy and had adequate birth weight for gestational age. Conclusions. This kind of anemia is rare and sometimes occurs in special situations such as pregnancy, infection, or stress (AU)
