Medición de frecuencias de resonancia, factor de pérdida y módulo de Young dinámico de varillas empotradas

En este trabajo se estudian teórica y experimentalmente las vibraciones forzadas de varillas rígidas y flexibles empotradas en un extremo. Las experiencias que se analizan, además de ilustrar el fenómeno de resonancia en una estructura diferente del clásico oscilador masa-resorte, permiten medir el módulo de Young del material. En el caso de la varilla flexible es fácil visualizar también el segundo y el tercer modo normal de vibración, lo cual nos permite comparar la forma que adopta la varilla, cuando vibra en sus diferentes modos, con las predicciones teóricas. En particular se pueden observar los "cuasi-nodos" (o nodos con pequeña amplitud) que se deben al flujo de energía a través de los mismos para compensar las pérdidas

A normative chart for cognitive development in a genetically selected population

Certain pathogenic genetic variants impact neurodevelopment and cause deviations from typical cognitive trajectories. Understanding variant-specific cognitive trajectories is clinically important for informed monitoring and identifying patients at risk for comorbid conditions. Here, we demonstrate a variant-specific normative chart for cognitive development for individuals with 22q11.2 deletion syndrome (22q11DS). We used IQ data from 1365 individuals with 22q11DS to construct variant-specific normative charts for cognitive development (Full Scale, Verbal, and Performance IQ). This allowed us to calculate Z-scores for each IQ datapoint. Then, we calculated the change between first and last available IQ assessments (delta Z-IQ-scores) for each individual with longitudinal IQ data (n = 708). We subsequently investigated whether using the variant-specific IQ-Z-scores would decrease required sample size to detect an effect with schizophrenia risk, as compared to standard IQ-scores. The mean Z-IQ-scores for FSIQ, VIQ, and PIQ were close to 0, indicating that participants had IQ-scores as predicted by the normative chart. The mean delta-Z-IQ-scores were equally close to 0, demonstrating a good fit of the normative chart and indicating that, as a group, individuals with 22q11DS show a decline in IQ-scores as they grow into adulthood. Using variant-specific IQ-Z-scores resulted in 30% decrease of required sample size, as compared to the standard IQ-based approach, to detect the association between IQ-decline and schizophrenia (p < 0.01). Our findings suggest that using variant-specific normative IQ data significantly reduces required sample size in a research context, and may facilitate a more clinically informative interpretation of IQ data. This approach allows identification of individuals that deviate from their expected, variant-specific, trajectory. This group may be at increased risk for comorbid conditions, such as schizophrenia in the case of 22q11DS