Promising Techniques (promising + techniques)

Distribution by Scientific Domains

Selected Abstracts

Metastable zone determination of lipid systems: Ultrasound velocity versus optical back-reflectance measurements

Kesarin Chaleepa
Abstract The metastable zone width (MZW) of a multi-component system as influenced by the process parameters cooling rate, agitation speed, and additive concentration was determined via ultrasound velocity measurements. The results were compared with those obtained by optical back-reflectance measurements (ORM) using coconut oil as a model substance. Increasing the cooling rate led to the shift of the nucleation point to lower temperatures. This tendency was better visualized by the ultrasonic curves while a significant disturbance of the ORM signal could be observed. Agitation led to an increase of the nucleation temperature and hence a narrower metastable zone. The influence of an additive on the MZW was found to strongly depend on its concentration. The MZW detected by the ultrasound technique was narrower compared to that obtained by the ORM method, indicating the faster response to the phase transition of the ultrasound technique. Another advantage of the ultrasound technique was the in situ evaluation of the experimental data, while ORM needed a linear fitting to estimate the saturation temperature. Furthermore, ultrasound velocity measurements are based on density determination of the medium whereas the ORM sensor is able to detect only particles that are located within the measuring zone and possess a well-defined size. Practical applications: MZW is one of the most important parameters that determine the characteristics of crystalline products. However, a proper technique that can be used in MZW detection in fat systems has rarely been reported, due to the difficulties in dealing with natural fats. The findings of this study can greatly help those who are involved in the field of fat crystallization from both the academic and the practical point of view. This is due to the fact that new and promising techniques for the online and in situ determination of the MZW of fats, with high accuracy, and reproducibility, under most process conditions, were clarified in this work. The readers can easily follow the procedure developed in this paper. Also information about the influence of process parameters and additives on the MZW is included. [source]

Optimised spreading code redistribution PAPR reduction technique for MC-CDMA systems

Lin Yang
Multicarrier code division multiple access (MC-CDMA) is one of the most promising techniques considered for future broadband mobile services. However, the high peak to average power ratio (PAPR) problem associated with MC-CDMA systems can significantly degrade the power efficiency at the transmitter. This paper proposes an efficient PAPR reduction technique for the downlink of MC-CDMA systems. It regards the order of the CDMA spreading codes as an extra degree of freedom and exploits it to effectively reduce the PAPR of the signal. The proposed technique requires only slight modification to the MC-CDMA base station and negligible complexity to the mobile terminals. Both lightly loaded and fully loaded systems are examined when using the orthogonal sets of Walsh,Hadamard (WH) and Golay complementary sequences (CSs). It will be demonstrated that the proposed technique achieves significant PAPR reduction with low system complexity at both transmitter and receiver. Copyright 2009 John Wiley & Sons, Ltd. [source]

Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applications

Direct measurement of lung volume, i.e. functional residual capacity (FRC) has been recommended for monitoring during mechanical ventilation. Mostly due to technical reasons, FRC measurements have not become a routine monitoring tool, but promising techniques have been presented. We performed a literature search of studies with the key words ,functional residual capacity' or ,end expiratory lung volume' and summarize the physiology and patho-physiology of FRC measurements in ventilated patients, describe the existing techniques for bedside measurement, and provide an overview of the clinical questions that can be addressed using an FRC assessment. The wash-in or wash-out of a tracer gas in a multiple breath maneuver seems to be best applicable at bedside, and promising techniques for nitrogen or oxygen wash-in/wash-out with reasonable accuracy and repeatability have been presented. Studies in ventilated patients demonstrate that FRC can easily be measured at bedside during various clinical settings, including positive end-expiratory pressure optimization, endotracheal suctioning, prone position, and the weaning from mechanical ventilation. Alveolar derecruitment can easily be monitored and improvements of FRC without changes of the ventilatory setting could indicate alveolar recruitment. FRC seems to be insensitive to over-inflation of already inflated alveoli. Growing evidence suggests that FRC measurements, in combination with other parameters such as arterial oxygenation and respiratory compliance, could provide important information on the pulmonary situation in critically ill patients. Further studies are needed to define the exact role of FRC in monitoring and perhaps guiding mechanical ventilation. [source]

Approaches to combat with confounding by indication in observational studies of intended drug effects

Alex D. McMahon
Abstract There has been a resurgence of controversy about the usefulness of observational data to study the efficacy of drugs. Nearly every week a researcher makes some criticism of clinical trials or justifies observational research into intended effects, with other researchers offering a contradictory viewpoint. Literature reviews are not useful in this regard because the contradictory studies will not usually be carried out. Some methods are discussed which may have potential utility in the study of intended effects. There may be a marginal role for statistical techniques such as propensity scores and confounder scores. More promising techniques may include ecological analyses, restriction of subjects and blinded prospective review. Because it is currently unknown when the observational study of drug efficacy is possible, we should arguably always carry out a study of the determinants of prescribing first, and possibly consider using the various techniques that are outlined in this article. Copyright 2003 John Wiley & Sons, Ltd. [source]

Fabricating three-dimensional polymeric photonic structures by multi-beam interference lithography,

Jun Hyuk Moon
Abstract The fabrication of true three-dimensional (3D) microstructures both rapidly and economically over a large area with negligible defects is attractive for a wide range of applications. In particular, multi-beam interference lithography is one of the promising techniques that can mass-produce polymeric 3D photonic crystals defect-free over a large area. This review discusses the relationship between beam geometry and the symmetry of the interference patterns, the lithographic process, and various types of photoresist systems, including thick films of negative-tone and positive-tone photoresists, organic-inorganic hybrids, hydrogels, and holographic polymer-dispersed liquid crystals. Copyright 2006 John Wiley & Sons, Ltd. [source]

Non-thermal bacterial inactivation with dense CO2

S. Spilimbergo
Abstract The use of CO2 under pressure (dense CO2) is one of the most promising techniques to achieve cold pasteurization and/or sterilization of liquid and solid materials, and is likely to replace or partially substitute currently and widely applied thermal processes. Although the ability of CO2 to inactivate microorganisms has been known since the 1950's, only within the last 15 years it has received special attention, and the scientific and economic interest towards practical applications is presently growing more and more. Here we collect and discuss the relevant current knowledge about the potentials of dense CO2 as a non-thermal technology in the field of microbial inactivation. We summarize the state of the art, including definitions, description of the equipment, relevant applications, in both simple suspensions and complex media, for the treatment of a wide range of microorganisms in both liquid and solid substrates. Finally, we also summarize and discuss the different hypotheses about the mechanisms of inactivation 2003 Wiley Periodicals, Inc. Biotechnol Bioeng84: 627,638, 2003. [source]