Frequency dependence of the dielectrophoretic separation of single-walled carbon nanotubes

Dielectrophoresis on single-walled carbon nanotubes in surfactant suspensions has been demonstrated to separate metallic from semiconducting tubes by their different electric field-induced polarisabilities. Here we report that the interaction between SWNTs and the surfactant induces a nanotube surface conductance which gives rise to a unique electric field frequency dependence of the dielectrophoretic force acting on semiconducting SWNTs. We observe a surfactant concentration dependent crossover frequency enabling separation of metallic from semiconducting SWNTs at high frequency and deposition of metallic and semiconducting SWNTs at low frequency. Proof for the effectiveness of separation is given by a comparative Raman spectroscopy study on dielectrophoretically deposited tubes excited with two different wavelengths.     

Affective implications of seeking psychological counseling.

Asked 315 undergraduates to evaluate either "a typical person," "a typical person seeking counseling," "a client seeking counseling," or "a patient seeking counseling" on the Personal Attitude Inventory. Ss evaluated a typical person significantly more positively than the other target groups mentioned above. These findings held regardless of the sex of the respondent or whether the respondents had previously sought counseling services. It appears that counselors may need to continue to educate the public to offset the negative stereotypes that seem to be surrounding counseling and those who seek it. (6 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spectroscopy of single- and double-wall carbon nanotubes in different environments

Individual single-wall carbon nanotubes (SWNTs) and double-wall carbon nanotubes (DWNTs) were suspended in water for optical studies using sodium-cholate and other surfactants. We used time-resolved photoluminescence (PL) spectroscopy to study the influence of tube chirality and diameter as well as of the environment on nonradiative decay in small diameter tubes. The studies provide evidence for PL from small diameter core tubes in DWNTs and for a correlation of nonradiative decay with tube diameter and exciton red shift as induced by interaction with the environment.     

Surface Modification of Silicon Anodes for Durable and High?Energy Lithium-Ion Batteries

Carbonaceous materials have dominated lithium-ion battery anodes since their discovery in 1972. Materials and design challenges have prevented the move to silicon-based anodes, despite their significantly higher specific energies. Morphological design motifs have focused on minimizing the structural instabilities that arise during lithium insertion and removal, which are themselves the subject of numerous articles and reviews. This review focuses on surface modification techniques that have been developed to minimize volume expansion, stabilize the surface of silicon against electrical isolation following pulverization, and improve the electronic and ionic conductivities of silicon anodes during operation and cycling.     

Rheological Properties of Hot Melt Pressure Sensitive Adhesives (HMPSAs) Based on Styrene–Isoprene Copolymers,Part 3: Rheological Behavior of Different Block Copolymers With High Diblock Content

The processing and application properties of hot-melt pressure-sensitive adhesives (HMPSA) are governed, to a large extent, by their rheological properties. Coating of the HMPSA is performed at high temperatures in the molten state. At room temperature, the adhesive satisfies the Dahlquist criterion and, consequently, has permanent tack. We have particularly studied the full formulations based on triblock and diblock copolymers, and also those based on newly designed molecules, such as tetrablock or radial copolymers. We have demonstrated in the previous articles of this series that, for these systems, the volume fraction of the free polyisoprene is the most important parameter that drives the tack performances by controlling the level of the secondary elastic plateau modulus observed in the low-frequency range. To improve the end-user properties, we have increased the diblock content in the blends. We describe here the dynamic mechanical properties, at room temperature, of the pure copolymer blends (i.e., without addition of a tackifying resin) and the full HMPSA formulations. We focus particularly in this article on blends that contain a high diblock content. The effect of the morphology of the diblock copolymer on the rheological behavior of the adhesive is discussed in detail. Finally, we propose a model, based on molecular dynamics concepts, which describes the rheological behavior in a very wide range of frequencies for all copolymers and full formulations of the study.     

Purification of CFTR for mass spectrometry analysis: identification of palmitoylation and other post-translational modifications

Post-translational modifications (PTMs) play a crucial role during biogenesis of many transmembrane proteins. Previously, it had not been possible to evaluate PTMs in cystic fibrosis transmembrane conductance regulator (CFTR), the epithelial ion channel responsible for cystic fibrosis, because of difficulty obtaining sufficient amounts of purified protein. We recently used an inducible overexpression strategy to generate recombinant CFTR protein at levels suitable for purification and detailed analysis. Using liquid chromatography (LC) tandem and multiple reaction ion monitoring (MRM) mass spectrometry, we identified specific sites of PTMs, including palmitoylation, phosphorylation, methylation and possible ubiquitination. Many of these covalent CFTR modifications have not been described previously, but are likely to influence key and clinically important molecular processes including protein maturation, gating and the mechanisms underlying certain mutations associated with disease.     

A 5-GHz direct-conversion CMOS transceiver utilizing automatic frequency control for the IEEE 802.11a wireless LAN standard

A fully integrated CMOS direct-conversion 5-GHz transceiver with automatic frequency control is implemented in a 0.18-/spl mu/m digital CMOS process and housed in an LPCC-48 package. This chip, along with a companion baseband chip, provides a complete 802.11a solution The transceiver consumes 150 mW in receive mode and 380 mW in transmit mode while transmitting +15-dBm output power. The receiver achieves a sensitivity of better than -93.7dBm and -73.9dBm for 6 Mb/s and 54 Mb/s, respectively (even using hard-decision decoding). The transceiver achieves a 4-dB receive noise figure and a +23-dBm transmitter saturated output power. The transmitter also achieves a transmit error vector magnitude of -33 dB. The IC occupies a total die area of 11.7 mm/sup 2/ and is packaged in a 48-pin LPCC package. The chip passes better than /spl plusmn/2.5-kV ESD performance. Various integrated self-contained or system-level calibration capabilities allow for high performance and high yield.