Cavitation clusters in lipid systems - surface effects, local heating and streamer formation.

Cavitation clusters and streamers are characterised in lipid materials (specifically sunflower oil) and compared to water systems. The lipid systems, which are important in food processing, are studied with high-speed camera imaging, laser scattering and pressure measurements. In these oils, clusters formed at an aged (roughened) tip of the sound source (a piston like emitter, PLE) are shown to collapse with varied periodicity in relation to the drive amplitude employed. A distinct streamer (an area of increased flow emanating from the cavitation cluster) is seen in the lipid media which is collimated directly away from the tip of the PLE source whereas in water the cavitation plume is visually less distinct. The velocity of bubbles in the lipid streamer near the cluster on the order of 10 m s-1. Local heating effects, within the streamer, are detected using a dual thermocouple measurement at extended distances. Viscosity, temperature and the outgassing within the oils are suggested to play a key role in the streamer formation in these systems.

Microsecond resolution of cavitation bubble dynamics using a high-speed electrochemical impedance approach.

A new method to detect the uncompensated resistance, the capacitance and the Faradaic current at an electrode exposed to ultrasonic cavitation is presented. The method enables these parameters to be resolved with a 2 microsecond resolution and relies on the detection of the impedance of an electrode recorded as a function of time with a suitable AC excitation signal (here 500 kHz). Data obtained from an aluminium electrode, held under potentiostatic control, is used to illustrate the technique with particular relevance to the effects of cavitation bubbles generated by ultrasound. Analysis of the data recorded shows that the cavitation bubbles form close to the surface of the electrode and collapse, causing damage to the passive film formed at the aluminium surface. The capacitance, uncompensated resistance and Faradaic signals are used to explore the dynamic processes and show expansion and collapse of bubbles prior to erosion/corrosion. The close proximity of the bubbles to the surface is deduced from the reductions in capacitance and increases in resistance prior to bubble collapse, which is then shown to trigger the onset of a Faradaic signal, thus confirming the erosion/corrosion mechanism previously assumed.

PIK3CA mutations can initiate pancreatic tumorigenesis and are targetable with PI3K inhibitors.

Aberrations in the phosphoinositide 3-kinase (PI3K) signaling pathway have a key role in the pathogenesis of numerous cancers by altering cell growth, metabolism, proliferation and apoptosis. Interest in targeting the PI3K signaling cascade continues, as new agents are being clinically evaluated. PIK3CA mutations result in a constitutively active PI3K and are present in a subset of pancreatic cancers. Here we examine mutant PIK3CA-mediated pancreatic tumorigenesis and the response of PIK3CA mutant pancreatic cancers to dual PI3K/mammalian target of rapamycin (mTOR) inhibition. Two murine models were generated expressing a constitutively active PI3K within the pancreas. An increase in acinar-to-ductal metaplasia and pancreatic intraepithelial neoplasms (PanINs) was identified. In one model these lesions were detected as early as 10 days of age. Invasive pancreatic ductal adenocarcinoma developed in these mice as early as 20 days of age. These cancers were highly sensitive to treatment with dual PI3K/mTOR inhibition. In the second model, PanINs and invasive cancer develop with a greater latency owing to a lesser degree of PI3K pathway activation in this murine model. In addition to PI3K pathway activation, increased ERK1/2 signaling is common in human pancreatic cancers. Phosphorylation of ERK1/2 was also investigated in these models. Phosphorylation of ERK1/2 is demonstrated in the pre-neoplastic lesions and invasive cancers. This activation of ERK1/2 is diminished with dual PI3K/mTOR inhibition. In summary, PIK3CA mutations can initiate pancreatic tumorigenesis and these cancers are particularly sensitive to dual PI3K/mTOR inhibition. Future studies of PI3K pathway inhibitors for patients with PIK3CA mutant pancreatic cancers are warranted.

Segmental dynamics of polymers in nanoscopic confinements, as probed by simulations of polymer/layered-silicate nanocomposites.

In this paper we review molecular modeling investigations of polymer/layered-silicate intercalates, as model systems to explore polymers in nanoscopically confined spaces. The atomic-scale picture, as revealed by computer simulations, is presented in the context of salient results from a wide range of experimental techniques. This approach provides insights into how polymeric segmental dynamics are affected by severe geometric constraints. Focusing on intercalated systems, i.e. polystyrene (PS) in 2 nm wide slit-pores and polyethylene-oxide (PEO) in 1 nm wide slit-pores, a very rich picture for the segmental dynamics is unveiled, despite the topological constraints imposed by the confining solid surfaces. On a local scale, intercalated polymers exhibit a very wide distribution of segmental relaxation times (ranging from ultra-fast to ultra-slow, over a wide range of temperatures). In both cases (PS and PEO), the segmental relaxations originate from the confinement-induced local density variations. Additionally, where there exist special interactions between the polymer and the confining surfaces ( e.g., PEO) more molecular mechanisms are identified.

Learning from living in space.

NASA: The current state of space life sciences knowledge and research is described. Findings about the health of astronauts in space are reviewed and a plea is made by some former astronauts to increase the amount of research being conducted. Longitudinal studies of the long term effects of space travel, especially radiation exposure, are being conducted and have yet to show any ill effects. Current research focuses are discussed, including Neurolab, an upcoming shuttle mission devoted to neurological and vestibular research. Experiment and spacecraft hardware is discussed, as are future directions in research. Partnership with Russian space life sciences investigators is also underway.^ieng