The main predictor of outcome at 6 months post-operatively in all eleven domains was the pre-intervention score of each domain. Presence of social support, absence of low back pain and higher baseline SF-36 mental health score were related to the improvement in the health-related quality of life post-operatively.

Cumene solutions of asphaltenes (8 g/L) were treated with p-nitrophenol (PNP) and a precipitated solid was collected after 3 days. For the asphaltene samples examined, between 48 and 70% of the sample could be precipitated by this treatment. PNP, known to form chargetransfer complexes with aromatic compounds, probably forms this type of compounds with asphaltenes, leading to precipitation. The sample precipitated was dissolved in chloroform, and the PNP was removed by extraction with aqueous sodium hydroxide. Although the initial asphaltene sample has the usual high solubility in toluene (higher than 50 g/L, room temperature), the precipitated asphaltene sample obtained in this way (A 1 ), has a very low solubility in toluene (≈90 mg/L, room temperature). These results show that asphaltenes are a mixture of compounds with vast differences in solubility and suggest that their solutions in aromatic solvents are constituted by a colloidal phase, formed by the low-soluble fraction A 1 dispersed by a soluble asphaltene fraction A 2 .

76 RESUMENComposición química de las semillas de Sacha Inchi (Plukenetia volubilis L.) y características de su fracción lipídica.Semillas de Sacha inchi (Plukenetia volubilis L.) de Colombia fueron analizadas en su composición química. Las semillas de Sacha inchi (SIO) fueron ricas en aceite (41.4%) y proteína (24.7%). Los principales minerales presentes en las SIS fueron potasio (5563.5 ppm), magnesio (3210 ppm) y calcio (2406 ppm). El análisis de ácidos grasos reveló que los ácidos a-linolénico (50.8%) y linoleico (33.4%) fueron los principales ácidos grasos presentes en el aceite de Sacha inchi (SIO). El fraccionamiento del SIO, realizado por extracción en fase sólida, produjo principalmente lípidos neutros (97.2%), y bajas cantidades de ácidos grasos libres (1.2%) y fosfolípidos (0.8%). Las propiedades fisicoquímicas del aceite incluyen: índice de saponificación 185.2; índice de yodo 193.1; densidad 0.9187 g/cm 3 , índice de refracción 1.4791 y viscosidad 35.4 mPa.s. Los perfiles de fusión del SIO se caracterizaron por la presencia de un ancho pico endotérmico con una entalpía de fusión de 23.2 J/g. Los resultados indican que el Sacha inchi es una importante nueva especie con aplicaciones en las industrias de alimentos y farmacéutica. PALABRAS CLAVE: Ácidos grasos -DSC -Perfiles de fusión -Plukenetia volubilis -Propiedades de aceites -Sacha Inchi. SUMMARY