RESUMEN
The efficient measurement of the threshold and slope of the psychometric function (PF) is an important objective in psychoacoustics. This paper proposes a procedure that combines a Bayesian estimate of the PF with either a look one-ahead or a look two-ahead method of selecting the next stimulus presentation. The procedure differs from previously proposed algorithms in two respects: (i) it does not require the range of possible PF parameters to be specified in advance and (ii) the sequence of probe signal-to-noise ratios optimizes the threshold and slope estimates at a performance level, Ï, that can be chosen by the experimenter. Simulation results show that the proposed procedure is robust and that the estimates of both threshold and slope have a consistently low bias. Over a wide range of listener PF parameters, the root-mean-square errors after 50 trials were â¼1.2 dB in threshold and 0.14 in log-slope. It was found that the performance differences between the look one-ahead and look two-ahead methods were negligible and that an entropy-based criterion for selecting the next stimulus was preferred to a variance-based criterion.
Asunto(s)
Psicoacústica , Percepción del Habla , Prueba del Umbral de Recepción del Habla/métodos , Estimulación Acústica , Algoritmos , Teorema de Bayes , Simulación por Computador , Humanos , Método de Montecarlo , Inteligibilidad del HablaRESUMEN
A de novo tandem inverted duplication of 10p was diagnosed in a 17-week fetus. The appearance of GTG banded preparations and the results of fluorescence in situ hybridization (FISH) studies are consistent with duplication of the entire arm, including the telomere. The FISH studies also demonstrated the presence of chromosome 10 alphoid repeats at the junction between the inverted segment and the long arm, consistent with the presence of the entire long arm of the abnormal chromosome. Therefore, this is a case of pure trisomy 10p without an associated deficiency of any other chromosome segment. A comparison of the phenotype associated with pure trisomy 10p and trisomy associated with a duplication/deficiency state documented a higher frequency (of borderline significance) of clubfoot and high-arched/cleft palate in the cases of pure trisomy. The frequency of palatal anomalies was observed to be significantly higher in the cases where the breakpoint of the trisomic segment is in the most proximal band (10p11). However, other clinical manifestations were observed inconsistently, even in the cases with pure, nearly complete trisomy 10p. Therefore, a clearly defined trisomy 10p clinical syndrome could not be documented in this study.
Asunto(s)
Cromosomas Humanos Par 10 , Fisura del Paladar/genética , Pie Equinovaro/genética , Feto/anomalías , Trisomía , Adulto , Amniocentesis , Femenino , Humanos , Hibridación Fluorescente in Situ , Cariotipificación , EmbarazoRESUMEN
OBJECTIVE: Pregnancy-induced hypertension is believed to be a disorder of the vascular endothelium, possibly focused in the placenta. Markers such as cellular fibronectin appear early in patients in whom pregnancy-induced hypertension develops. We hypothesized that patients with elevated second-trimester levels of human chorionic gonadotropin would have an increased risk for pregnancy-induced hypertension. STUDY DESIGN: We conducted a cohort study, using a database of patients undergoing second-trimester serum screening for Down syndrome and who were delivered at our institution between January 1990 and August 1991. We included all 180 women with human chorionic gonadotropin levels > or = 2.0 multiples of the median. A sequential sample of 369 women with levels < 2.0 multiples of the median served as the referent group. Standard American College of Obstetricians and Gynecologists definitions of pregnancy-induced hypertension and proteinuria were used. RESULTS: Patients with elevated human chorionic gonadotropin levels were at increased risk for pregnancy-induced hypertension (risk ratio 1.7, 95% confidence interval 1.2 to 2.4) and proteinuric pregnancy-induced hypertension (risk ratio 5.1, 95% confidence interval 1.6 to 16.2). Adjusting for potential confounding factors did not alter these associations. CONCLUSIONS: Patients with elevated human chorionic gonadotropin appear to be at higher risk of pregnancy-induced hypertension and proteinuric pregnancy-induced hypertension. Second-trimester human chorionic gonadotropin levels should be further investigated as a potential marker for pregnancy-induced hypertension.