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There are few measurements of barium sulfate (BaSO4) solubility in water above 373 K available in the literature. BaSO4 solubility data at water saturation pressure are scare. The pressure dependence on BaSO4 solubility has not previously been comprehensively reported for the pressure range 100–350 bar. In this work, an experimental apparatus was designed and built to measure BaSO4 solubility in aqueous solutions under high-pressure (HP), high-temperature (HT) conditions. The solubility of BaSO4 was experimentally determined in pure water over the temperature range from T = (323.1 to 440.1) K and pressures ranging from p = (1 to 350) bar. Most of the measurements were done at water saturation pressure: six data points were done above the saturation pressure (323.1–373.1 K) and 10 experiments were conducted at water saturation (373.1–440.1 K). The reliability of the extended UNIQUAC model and results generated in this work was demonstrated by comparing with the scrutinized experimental data reported in the literature. The model gives a very good agreement with BaSO4 equilibrium solubility data, demonstrating the reliability of the extended UNIQUAC model. The accuracy of the model at high temperature and saturated pressure due to data insufficiencies is discussed.

OBJECTIVE: To study the incidence and analyze risk factors to neonatal periventricular-intraventricular hemorrhage; to suggest a working protocol for diagnosis in newborns at risk.METHODS: This is a cohort prospective study including 120 out of 129 children weighing less than 2000g born from May 18 th, 1994 to May 17 th,1995 at the Hospital das Clínicas da UFMG. The study group comprised 39 newborns with the ultrasound diagnosis of periventricular-intraventricular hemorrhage; the control group comprised 81 newborns who although submitted to the same evaluation protocol did not show any echographic signs of hemorrhage. The ultrasound examinations were all done by the same researcher who was not aware of the clinical history or the neurologic and laboratory examinations. The hemorrhage was classified according to Papilés criteria: grade I (13%); grade II (7%); grade III (9%) and grade IV (3%).RESULTS: Low gestational age, low birth weight, masculine sex, vaginal delivery, and neonatal sepsis were significantly associated (p0.05) with periventricular-intraventricular hemorrhage in univariate analysis. Apgar score in the first or fifth minute and Battagliás and Lubchenkós classification for the weight in relation to gestational age were not predisposing factors to the hemorrhage. Low gestational age (p = 0.002), vaginal delivery (p = 0.037), and masculine sex (p = 0.016) kept statistical significance after multivariate adjustment. Birth weight may substitute for gestational age in the multivariate model because they are highly associated. The best cutoff point to screen for periventricular-intraventricular hemorrhage was 1750 g instead of the traditionally adopted point of 1500 g. CONCLUSIONS: The incidence of neonatal periventricular-intraventricular hemorrhage was similar to those reported by other studies. Low gestational age or low birth weight, vaginal delivery and masculine sex were the most important risk factors to the hemorrhage. The screening cutoff point of 1750 g seems to be more adequate than the commonly used birth weight of 1500 g.

OBJECTIVE: To evaluate the efficacy of the clinical neurologic examination, hematocrit and glycemia in the diagnosis of periventricular-intraventricular hemorrhage in the newborn weighing less than 2000g considering the neurosonography as the gold standard.METHODS: This is a cohort prospective study from May 18th, 1994 to May 17th, 1995 carried out at the Hospital das Clinicas da UFMG. The study group comprised 38 newborns with the ultrasound diagnosis of periventricular-intraventricular hemorrhage; the control group comprised 81 newborns who although submitted to the same evaluation protocol did not show any echographic signs of hemorrhage. The ultrasound examinations were all done by the same researcher who was not aware of the clinical history or the neurologic and laboratory examinations.RESULTS: Clinical neurologic alterations, mainly generalized hypotonia, were found to be associated with hemorrhage (p = 0.009), but there was a confounding effect due to the gestational age of the newborn. The predictive values of a positive or negative test were only 45% and 79%, respectively, which is clearly unreliable for the diagnosis of the hemorrhage. Hematocrit and glycemia were not clinically relevant either.CONCLUSIONS: The clinical neurologic examination is not reliable to indicate periventricular-intraventricular hemorrhage in the newborn. Newborns at risk should be routinely screened by neurosonography.