Use of the ultrasonic cavitation in wool dyeing process: Effect of the dye-bath temperature.

The present work aims to study the effect of the liquid temperature on the performance of ultrasounds (US) in a dyeing process. The approach was both theoretical and experimental. In the theoretical part the simplified model of a single bubble implosion is used to demonstrate that the "maximum implosion pressure" calculated with the well known Rayleigh-Plesset equation for a single bubble can be correlated with the cavitation intensity experimentally measured with an Ultrasonic Energy Meter (by PPB Megasonics). In particular the model was used to study the influence of the fluid temperature on the cavitation intensity. The "relative" theoretical data calculated from the implosion pressure were satisfactorily correlated with the experimental ones and evidence a zone, between 50 and 60°C, were the cavitation intensity is almost constant and still sufficiently high. Hence an experimental part of wool dyeing was carried out both to validate the previous results and to verify the dyeing quality at low temperatures (40-70°C) in presence of US. A prototype dyeing equipment able to treat textile samples with US system of 600W power, was used. The dyeing performances in the presence and absence of US were verified by measuring ΔE (colour variation), Re,% (reflectance percentage), K/S (colour strength) and colour fastness. The US tests performed in the temperature range of 40-70°C were compared with the conventional wool dyeing at 98°C. The obtained results show that a temperature close to 60°C should be chosen as the recommended US dyeing condition, being a compromise between the cavitation intensity and the kinetics which rules the dyestuff diffusion within the fibres.

Mapping of cavitational activity in a pilot plant dyeing equipment.

A large number of papers of the literature quote dyeing intensification based on the application of ultrasound (US) in the dyeing liquor. Mass transfer mechanisms are described and quantified, nevertheless these experimental results in general refer to small laboratory apparatuses with a capacity of a few hundred millilitres and extremely high volumetric energy intensity. With the strategy of overcoming the scale-up inaccuracy consequent to the technological application of ultrasounds, a dyeing pilot-plant prototype of suitable liquor capacity (about 40 L) and properly simulating several liquor to textile hydraulic relationships was designed by including US transducers with different geometries. Optimal dyeing may be obtained by optimising the distance between transducer and textile material, the liquid height being a non-negligible operating parameter. Hence, mapping the cavitation energy in the machinery is expected to provide basic data on the intensity and distribution of the ultrasonic field in the aqueous liquor. A flat ultrasonic transducer (absorbed electrical power of 600 W), equipped with eight devices emitting at 25 kHz, was mounted horizontally at the equipment bottom. Considering industrial scale dyeing, liquor and textile substrate are reciprocally displaced to achieve a uniform colouration. In this technology a non uniform US field could affect the dyeing evenness to a large extent; hence, mapping the cavitation energy distribution in the machinery is expected to provide fundamental data and define optimal operating conditions. Local values of the cavitation intensity were recorded by using a carefully calibrated Ultrasonic Energy Meter, which is able to measure the power per unit surface generated by the cavitation implosion of bubbles. More than 200 measurements were recorded to define the map at each horizontal plane positioned at a different distance from the US transducer; tap water was heated at the same temperature used for dyeing tests (60°C). Different liquid flow rates were tested to investigate the effect of the hydrodynamics characterising the equipment. The mapping of the cavitation intensity in the pilot-plant machinery was performed to achieve with the following goals: (a) to evaluate the influence of turbulence on the cavitation intensity, and (b) to determine the optimal distance from the ultrasound device at which a fabric should be positioned, this parameter being a compromise between the cavitation intensity (higher next to the transducer) and the US field uniformity (achieved at some distance from this device). By carrying out dyeing tests of wool fabrics in the prototype unit, consistent results were confirmed by comparison with the mapping of cavitation intensity.

Avaliaçäo da composiçäo corporal em gestantes de termo / Assessment of body composition in pregnant women at term

A gravidez acompanha-se de modificaçoes fisiológicas bem conhecidas nos compartimentos hídricos e energéticos maternos, que se somam a hipertrofias orgânicas e ao aparecimento de um bloco feto-placentario. Conseqüentemente, a composiçao corporal sofre alteraçoes, porém poucos estudos têm documentado tal fenomeno. O advento da bioimpedância favoreceu a obtençao das informaçoes desejadas de forma pratica e segura. Objetivos. Foram os propósitos deste trabalho: registrar as principais variaveis antropométricas numa populaçao de gestantes de termo; determinar as medidas de composiçao corpórea pela bioimpedância; comparar esses achados com os primeiros, assim como com outras metodologias relatadas na literatura. Métodos. A populaçao consistiu de 30 gestantes de termo admitidas no período pré-parto, sem complicaçoes, sofrimento fetal ou gravidez múltipla, e submetidas às seguintes mensuraçoes: Antropometria - Peso, altura, índice de massa corporal, prega cutânea do tríceps, circunferência muscular do braço; Bioimpedância - Gordura corporal, massa magra, agua total, agua intra e extracelular, terceiro espaço e relaçao sódio/potassio permut vel. Resultados. Observaram-se valores de peso corporal e índice de massa corporal aumentados, porém inteiramente compatíveis com a situaçao fisiológica das gestantes. A agua corpórea total situava-se na mesma faixa percentual de mulheres nao-gravidas, tal como ja suspeitado por outros autores, porém com indícios de expansao do extracelular e formaçao de terceiro espaço. A massa gorda elevou-se, porém, também em proporçoes nao muito diferentes do relatado anteriormente em levantamentos antropométricos. Conclusoes. Nas condiçoes do presente trabalho, em que uma equaçao de bioimpedância para uso geral foi aplicada, o método demonstrou resultados compatíveis com as informaçoes clínicas disponíveis, as verificaçoes antropométricas e os registros de outros investigadores. Conclui-se que a impedância bioelétrica é um procedimento de avaliaçao promissor na gravidez, justificando estudos ulteriores com esta metodologia.

[Assessment of body composition in pregnant women at term]. / Avaliação da composição corporal em gestantes de termo.

BACKGROUND: Pregnancy is associated with well-known physiologic changes of maternal fluid and energy compartments, along with organ hypertrophies and the appearance of fetal and placental tissues. As a consequence, body composition is modified, but this phenomenon has not been well documented. The advent of bioimpedance has contributed to the documentation of the desired information in a safe and practical way. AIMS: The aims of this study were: To register the principal anthropometric variables in a population of pregnant women at term; To determine body composition by bioimpedance analysis; To compare these findings with the former results, as well as with other assessment procedures reported in the literature. PATIENTS AND METHOD: The population consisted of 30 pregnant women at term admitted for delivery, without complications, fetal distress or multiple pregnancy, and submitted to the following measurements: Anthropometry--Weight, height, body mass index, triceps skinfold, arm muscle circumference; Bioimpedance analysis--Body fat, lean body mass, total water, intra and extra-cellular water, third space, and exchangeable Na/K ratio. RESULTS: Body weight and body mass index were increased but within the expected values for these patients. Total body water was similar to results in non-pregnant women when expressed as percentage, in accordance with other studies, but with a trend toward increase in the extracellular compartment and presence of third space fluid. Body fat was elevated, but the proportions were not much different from previous anthropometric surveys. CONCLUSIONS: In the conditions of this investigation, in which a bioimpedance equation for general use was employed, the method indicated results that were consistent with the clinical course, anthropometric documentation, and the findings of other groups. It is concluded that bioimpedance analysis compares favorably with other assessment procedures in pregnancy, and further studies with this method should be undertaken.