Detection of recurrent or persistent nasopharyngeal carcinomas after radiotherapy with 18-fluoro-2-deoxyglucose positron emission tomography and comparison with computed tomography

PURPOSE: The effectiveness of positron emission tomography (PET) with 1 8-fluoro-2-deoxyglucose (FDG) for detecting suspected recurrence of nasopharyngeal carcinomas (NPC) was evaluated and compared with computed tomography (CT). PATIENTS AND METHODS: FDG-PET studies were performed on 36 NPC patients 4 months after radiotherapy. The images were interpreted visually and quantitatively by calculating standardized uptake values (SUVs). RESULTS: The sensitivity, specificity, and accuracy of visually interpreted FDG-PET images, for differentiation of recurrent or persistent NPC from benign lesions, were 100%, 96%, and 97%, respectively. Cases with recurrent or persistent NPC (1.6 to 5.8) had significantly higher SUVs than cases with benign lesions (0.8 to 1.5). The sensitivity, specificity, and accuracy of CT for detecting recurrent or persistent NPC were 72%, 88%, and 83%, respectively. CONCLUSION: FDG-PET is a better tool than CT for the detection of recurrent or persistent NPC. Either visual interpretation or SUV can be used to differentiate benign lesions from recurrent or persistent NPC.     

Will the self-tuning approach work for general cost criteria?

We expose a fundamental limitation of the self-tuning procedure for adaptive control of linear stochastic systems. Specifically, if the cost criterion measuring the performance of the unknown system is anything other than a minimum (output) variance criterion, then the procedure of estimating the unknown parameters of the linear system and then applying a control input which is optimal for the given cost criterion and the parameter estimates, will not self-tune to the optimal control law. Since our arguments are based on the analysis of an ordinary differential equation of Ljung, and since we do not, in our general context, have a proof that this O.D.E. represents the asymptotic behaviour of the system, further work is needed. An exception to the above situation is the class of systems with a large enough delay, for which self-tuning to the optimal, and indeed, convergence to the true parameters, cannot be ruled out.     

Surface tension driven and 3-D vortex enhanced rapid mixing microchamber

This paper proposes a novel passive micromixer design for mixing enhancement by forming a large three-dimensional (3-D) flow vortex in a counterflow microfluidic system. The counterflow fluids are self-driven by surface tension to perform mixing in an open chamber. The chamber design consists of two rectangular bars to house the chamber and to form two opening inlets from opposite directions. The best design is selected from various versions of mixing chambers. The mixing effectiveness is tremendously increased by folds of contacting surface between two fluids induced and enhanced due to the stretching of two fluid contacting interfaces by the formation of a 3-D large size vortex structure inside the mixing chamber itself with unaccountable numbers of fluid layers. Both numerical simulations and experiments are performed and compared to identify the design parameters for maximum utilization in this microfluidic system, such as the length of rectangular bar, microchannel wall height, and mixing chamber size. Compared to traditional micromixers operated by two-dimensional (2-D) vortex, this passive mixer can greatly enhance mixing efficiency and reduce mixing time by tenfold from around 10 s to less than 10 ms by 3-D effective chaotic flow structures in a more compact size. This mixing chamber is also suitable for an H-shape digital fluidic system for parallel mixing process in different mixing ratio simultaneously as a lab-on-a-chip system.     

Modeling and analysis of nonlinear guideway for double-ball bar (DBB) measurement and diagnosis

The purpose of this paper is to study nonlinear geometric errors in multi-axis machine tools. A general mathematical model for guideway systems that can be applied to high-precision machine tools such as CNC lathes is introduced. Using this model, most nonlinear error sources in the guideway systems can be diagnosed by measuring the contouring error using a double-ball bar (DBB). Diagnostic software has been developed to identify system parameters based on the least-squares estimation method. Inputting two or three contouring errors pattern data into this software enables parameters to be identified quickly, based on the nonlinear model.     

High throughput micro droplet generator array controlled by two-dimensional dynamic virtual walls

A chamber-free two-dimensional-array micro droplet generator has been realized by precise time-delayed control of micro bubble arrays as virtual chamber walls. Droplets can be ejected out by the bubbles around the ejection site in specific configuration of excitation, thus replacing physical chamber walls for pressure preservation. The micro droplet generator array was fabricated by heater lithography and direct nozzle formation on a laminated SU-8 dry film without any solid chamber wall among heaters. The nozzle density of this compact droplet generator can be five to ten times higher than that of commercial inkjet printheads in one-dimensional formats. The volume and initial speed of the generated droplets was 3.6–5.7 pL and 14–15 m/s, respectively, meeting the standard of commercial printheads. The micro droplet generator is free of satellite droplets due to the precise meniscus control. The analyzed data shows the meniscus undergoes a “push–pull–push” progress which effectively cuts the liquid column short. The refilling time of the innovative micro droplet generator was estimated to be 0.296 μs from the simplified chamber model, and it was one-tenth of the commercial printheads. In addition, the frequency response was estimated to be higher than 20 kHz by observing the meniscus fluctuation condition. Finally, a 3 × 5 heater array was used to generate two droplets simultaneously, which shows that the crosstalk problem can be eliminated by precise time-delayed control. An interlacing operation was also proposed to address the large array control algorithm. To summarize, a 330-dpi monolithic micro droplet generator prototype has been proposed for high speed and large 2D format printing.     

Plasma surface modification of graphene oxide nanosheets for the synthesis of GO/PES nanocomposite ultrafiltration membrane for enhanced oily separation

In this study, two different monomers, namely hexafluorobutyl acrylate (HFBA) and diethylaminoethyl methacrylate (DEAEMA) were individually used to modify graphene oxide (GO) nanosheets via environmentally friendly plasma enhanced chemical vapor deposition (PECVD) method. The results from instrumental analyses confirmed the successful deposition of respective functional material onto the nanomaterials. Modified GOs were used as the nano-fillers to develop composite polyethersulfone (PES) ultrafiltration (UF) membrane with improved surface properties for oily solution treatment. All the developed membranes were characterized with a series of analytical instruments to support the findings of membrane filtration performance. The results indicated that the membrane incorporated with DEAEMA-GOs (coated with hydrophilic polymer) could achieve better results in terms of oil rejection, antifouling resistance and water recovery rate than the membrane incorporated with HFBA-GOs (coated with hydrophobic polymer). This is due to the reduced agglomeration between modified GOs as well as better interaction of hydrophilic-coated GOs with polymer membrane. Compared to the pure water flux of the membrane incorporated with unmodified GO, the membrane incorporated with DEAEMA-GO achieve approximately 85% higher value with oil removal rate remained almost unchanged (98.94% rejection).     

Computer simulation of enhanced output from bifacial photovoltaic modules

A bifacial photovoltaic module can collect not only the light falling directly on its front but also light incident on its rear after reflection from natural surroundings, called the albedo reflection, and light scattered from the sky itself. the benefits of such bifacial response are analysed by modifying a standard computer photovoltaic simulation software package (PVFORM version 3.3). Results obtained from computer simulation and field experiments show that, without any special features, there is about a 20% increase in the total annual energy generated by a bifacial panel compared to a monofacial panel. There are also summer peaks caused by the morning and evening light falling directly on the rear side of the panel. This means that the bifacial panel allows extended operation during summer. There is also a slightly smaller reduction in relative output power for the bifacial module on cloudy days.