Attempts to find a molecular theory for which the high-frequency dynamic viscosity is less than the solvent viscosity

It has been found that for some dilute polymer solutions the dynamic viscosity at very high frequencies is less than the zero-shear-rate solvent viscosity. Such an effect cannot be explained by the usual kinetic theories using bead-spring-rod models. Here we examine several modifications of the kinetic theories that might be expected to explain the experimental facts.This paper is dedicated to Prof. Hanswalter Giesekus on the occasion of his retirement as Editor of Rheologica Acta.     

Insulating state in open quantum dots and quantum dot arrays

We describe the observation of novel localization in mesoscopic quantum dots and quantum dot arrays, which are realized in high mobility GaAs/AlGaAs heterojunctions using the split‐gate technique. With a sufficient gate voltage applied to form the devices, their resistance diverges as the temperature is lowered below a degree Kelvin, behavior which we attribute to localization. Evidence for the localization is found over the entire range of gate voltage for which the dots are defined, persisting to conductances higher than 50e²/h.     

Reveal for Salmonella test system.

The Reveal for Salmonella (RSS) test system is a presumptive qualitative test that detects the presence of Salmonella organisms in foods within 21 h total testing time, allowing the user to release negative products 24 h earlier than when using other rapid test kits. Foods are enriched with a proprietary resuscitation medium called Revive and then selectively enriched with either Selenite Cystine or Rappaport-Vassiliadis selective media. The enriched culture is used to inoculate the RSS detection device, which initiates a lateral flow through a reagent zone containing anti-Salmonella antibodies conjugated to colloidal gold particles that capture antigens present in the culture. The antigen-antibody complex migrates farther and is captured by an additional anti-Salmonella antibody, causing the colloidal gold to precipitate and form a visual line, indicating a positive result. A procedural control line also will form regardless of the presence of Salmonella organisms to indicate the test is working properly. Existing AOAC Official Methods for Salmonella organisms require a 48 h enrichment before testing. Hence, a food product has to be held before release, adding extra cost to the company and the consumer. The RSS test system was evaluated by quantitative spiking studies. Although AOAC encourages inclusion of naturally contaminated foods, almost all microbiological AOAC validation studies have been performed with artificially contaminated foods for absolute control over the study. The RSS test system is designed to test many food types for Salmonella organisms and has a limit of detection of 5-10 colony-forming units (cfu)/25 g with a false-negative rate of < 1% and a false-positive rate of < 5.0%. It showed an 81% overall agreement with the traditional procedure of the U.S. Department of Agriculture's Food Safety Inspection Service.     

Large-amplitude oscillatory shear flow from the corotational Maxwell model

Using the single relaxation time corotational Maxwell fluid, we derive explicit analytical expressions for the first, third, and fifth harmonics of the alternating shear stress response in large-amplitude oscillatory shear (LAOS). We also derive corresponding expressions for the zeroth, second, and fourth harmonics of both the first and second normal stress differences. These harmonics are found to depend upon just two dimensionless groups: the Deborah and Weissenberg numbers, each of which causes non-Newtonian behavior. The form of the solution for the corotational Maxwell model in LAOS matches the forms of the analytical solutions for two molecular models for dilute solutions and one for concentrated solutions or melts. We also derive an analytical solution for the corotational Maxwell model after startup of LAOS. For this we find that both small and large amplitude cases approach a periodic limit cycle (alternance) at the same rate for both the shear stress response and for the normal stress differences. For molten high density polyethylene that is lightly filled with carbon black, we find good quantitative agreement with measured LAOS behavior when our analytical solution is superposed for multiple relaxation times.     

Scientific and technical data sharing: a trading perspective

It is arguably a precept that the open sharing of data maximises the scientific utility of the research that generated that data. Indeed, progress depends on individual scientists being able to build on the results produced by others. The means to facilitate sharing undoubtedly exist, but various studies have identified reluctance among researchers to share information with their peers, at least until the professional priorities of the original researchers have been accommodated. With a view to encouraging less inhibited collaboration, we appraise the processes of data exchange from the perspective of a trading environment and consider how data exchanges might promote (or perhaps hinder) collaboration in data-rich scientific research disciplines and how such an exchange might be set up. We suggest an exchange with trusted brokers (akin to the commodity markets) as a way to overcome the challenges of the current environment. We conclude by encouraging the scientific and technical community to debate the merits of a trading perspective on data sharing and exchange.     

High throughput ion implantation systems in western electric

Within Western Electric, a number of high throughput systems have been developed to meet the differing needs of high voltage and low voltage ion implantation applications. The PR-500 is a general purpose 500 kV machine which provides typical target currents of 0.5 ma of the common dopants and throughputs of 100 75-mm wafers/hour. The PR-200 is a 200 kV machine with typical target currents of 2.5 ma P, As, and Sb, and 1.0 ma B, and wafer throughputs of 150/hour. The PR-30 is a 30 kV single-species machine which can perform predeposition implants at rates of up to 450 wafers/hour. Typical PR-30 target currents are 5 ma P, As, and Sb. and 1.5 ma B. Each of these systems makes use of a common family of high current ion sources, and a rotating disk mechanical scanning system which permits a minimum implant time for 1 % uniformity of two seconds per wafer.     

Single-electron tunneling in silicon-on-insulator nano-wire transistors

The gate bias dependent evolution of the Coulomb oscillations in a silicon-on-insulator nano-wire transistor is reported. Transport data obtained for a wide range of front- and back-gate bias strongly suggest that multiple quantum dots (QDs) with different potential depths are formed in the nano-wire channel. Our data can be clearly interpreted as arising from the turning on or off of one of these QDs as the back-gate bias is varied. Quantitative calculation based on the model of single-electron tunneling through two parallel QDs is in reasonable agreement with the measured data in the back-gate bias range where the third dot is not activated.