Transient effects on microchannel electrokinetic filtering with an ion-permselective membrane

The electrokinetics and hydrodynamics in a hybrid microfluidic/nanofluidic pore network configuration and its effect on the concentration enrichment of charged analytes are described. A hydrogel microplug, photopolymerized in a microfluidic channel, with negative surface charge serves as a nanoporous membrane and dictates the electrokinetic behavior within the adjoining microchannel compartments. The nanoporous hydrogel with a mean pore size on the order of the electrical double layer thickness imparts ion-permselectivity (cation-selectivity) to the migration of ionic species which, under the influence of an applied electrical field, drives concentration polarization in bulk solution near the interfaces between the two microchannel compartments and the hydrogel-based nanopores. The concentration enrichment efficiency for charged analytes depends on this concentration polarization, which strongly affects the distribution of local electrical field strength. In addition, electroosmotic flow in the device plays a critical role in determining the location of the analyte enrichment zone. A theoretical model and simulations are presented to explain the interplay of concentration polarization and electroosmotic flow with respect to the observed concentration enrichment of negatively charged analytes at the cathodic hydrogel plug-microchannel solution interface.     

A SEMI-EMPIRICAL APPROACH TO OPTIMISE THE QUANTITY OF DRYING AIDS REQUIRED TO SPRAY DRY SUGAR-RICH FOODS

ABSTRACT

A semi-empirical linear equation has been developed to optimise the amount of maltodextrin additive (DE 6) required to successfully spray dry a sugar-rich product on the basis of its composition. Based on spray drying experiments, drying index values for individual sugars (sucrose, glucose, fructose) and citric acid were determined, and using these index values an equation for model mixtures of these components was established. This equation has been tested with two sugar-rich natural products, pineapple juice and honey. The relationship was found to be valid for these products.     

The Ultralight Steel Auto Body program completes phase I

The UltraLight Steel Auto Body program was initiated by the American Iron and Steel Institute and the International Iron and Steel Institute. The purpose of the program is to demonstrate the advantages of steel for reducing the weight of the automotive body-in-white. The holistic design approach—considering the body structure, materials, manufacturing methods, and engineering analysis together—has yielded a design for a body-in-white that is about 25 percent lighter than a typical vehicle produced at present, with improved structural performance. The materials and manufacturing processes required for the design are either in use or “near-reach” technologies.     

TV requirements for manipulation in space

An analytical and experimental study was conducted to specify a video system for remote manipulation in space. An operator function analysis identified two basic characteristics, work volume and element relationship, which define 4 manipulation tasks chosen for examination. A visual function analysis developed a set of elemental scene parameters which grouped the visual dimensions into major areas of influence. Simulation testing was conducted with a 4 degree-of-freedom motion frame which allowed an operator to perform the manipulation tasks. Four video systems were included in the simulation testing: a black and white and a color monoscopic system, a stereoscopic system, and a black and white 2-view system. A sequential experimental plan first provided an overall analysis of the effects of tasks, scene parameters and video systems. This was followed by a detailed experimental examination of the critical dimensions identified in the first experiment. Results are discussed in terms of a recommended TV system.     

Reactions and Reactivity in Self‐Assembled Monolayers

Self‐assembled monolayers (SAMs) are excellent models for studying interfacial reactions. Here monolayer chemistry is reviewed, focusing on the features that have no analogues in solution chemistry. The growth of surface‐attached polymers, intrafilm reactions, chemistry, photochemistry and reactivity issues are all discussed.     

Phenomenology in Absentia: Dennett's Philosophy of Mind.

Daniel Dennett's philosophical abolition of mind is examined with reference to its methodology, intent, philosophic origins, and internal consistency. His treatment of the contents of perception and introspection is shown to be derivative from realist reductionist misinterpretations of physics, physiology, and phenomenology of perception. In order to rectify inconsistencies of that realistic paradigm devolved from psycho-neural identity theory of mid-twentieth century, Dennett radicalizes its logic and redefines even veridical phenomenology of exteroception to be "illusory." This measure in extremis still does not save the appearances of his predecessors, nevertheless, for Dennett tacitly presupposes the existence of veridical phenomenology in his very treatment of non-veridical sensory phenomena that he uses to argue analogically from, to thereby suggest the plausibility of a parallel illusoriness of veridical phenomena of perception and introspection. This inhering inconsistency renders unsound Dennett's radical extension of the logic of identity theory, and ironically shows up the persistence of mental phenomenology that extant reductionism appears so desirous to argumentively eliminate. Nonetheless there is much to be learned from such an analysis of Dennett's purported elimination of mental contents, for a generalization of our critique throws light on the occult assumptions underlying realism and reductionism since early identity theory and its variants, and upon the possible viability of that programme as a whole. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Clean intermittent catheterization for home management in children with myelomeningocele

Sixty-two children with myelomeningocele and neurogenic bladders have been managed with clean intermittent catheterization (CIC) at home for periods of 6 to 42 months. Abnormal upper urinary tracts improved or stabilized in 83 per cent of the children. There was no renal deterioration in children who began with normal upper tracts while on CIC. Bacteruria was common, but clinically not a problem, unless ureterovesical reflux was present. Urinary control was improved in 66 per cent of the children. CIC is an effective and safe method to regularly empty the urinary bladder and is an alternative to supravesical urinary diversion in many children with neurogenic bladders.     

Parallel fabrication of RNA microarrays by mechanical transfer from a DNA master

A new method for fabrication of RNA microarrays is described. The approach involves cohybridization of a short, biotinylated DNA oligonucleotide and an RNA probe sequence to DNA templates spotted onto a master array. Next, the short DNA sequence and the RNA probe are linked using a T4 DNA ligase. Finally, a poly(dimethylsiloxane) (PDMS) monolith modified on the surface with streptavidin is brought into conformal contact with the master array. This results in binding of the biotinylated DNA/RNA oligonucleotides to the PDMS surface. When the two substrates are mechanically separated, the DNA/RNA oligonucleotides transfer to the PDMS replica, and the DNA oligonucleotides remaining on the master array are ready to template another RNA replica array. This sequence can be repeated for at least 18 cycles using a single master array. RNA arrays consisting of up to three different oligonucleotide sequences and consisting of up to 2500 individual approximately 70 microm spots have been prepared.     

Simultaneous determination of the size and surface charge of individual nanoparticles using a carbon nanotube-based Coulter counter

A resistive-pulse Coulter counter based on a membrane containing a single multiwall carbon nanotube (MWNT) channel was used to simultaneously determine the size and surface charge of carboxy-terminated polystyrene nanoparticles. The membrane was prepared from an epoxy section containing a MWNT channel mounted on a poly(dimethylsiloxane) (PDMS) support structure. The PDMS support reduced the background noise level by a factor of > 20 compared to the Si/Si3N4 support structure used in our previous study. The lower noise level makes it possible to accurately measure the height and width of resistive-pulse signals resulting from transport of individual particles through the MWNT channel. Particle sizes, calculated from current pulse heights, were comparable to those determined by transmission electron microscope (TEM). The width of the current pulses is a measure of the nanoparticle transport time, and it permits calculation of the electrokinetic surface charge. Different types of polystyrene nanoparticles having nearly the same size, but different electrokinetic surface charge, could be resolved on the basis of the difference in their transport time.