High-performance electronics using dense, perfectly aligned arrays of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWNTs) have many exceptional electronic properties. Realizing the full potential of SWNTs in realistic electronic systems requires a scalable approach to device and circuit integration. We report the use of dense, perfectly aligned arrays of long, perfectly linear SWNTs as an effective thin-film semiconductor suitable for integration into transistors and other classes of electronic devices. The large number of SWNTs enable excellent device-level performance characteristics and good device-to-device uniformity, even with SWNTs that are electronically heterogeneous. Measurements on p- and n-channel transistors that involve as many as approximately 2,100 SWNTs reveal device-level mobilities and scaled transconductances approaching approximately 1,000 cm(2) V(-1) s(-1) and approximately 3,000 S m(-1), respectively, and with current outputs of up to approximately 1 A in devices that use interdigitated electrodes. PMOS and CMOS logic gates and mechanically flexible transistors on plastic provide examples of devices that can be formed with this approach. Collectively, these results may represent a route to large-scale integrated nanotube electronics.     

Screening of Water Dipoles Inside Finite-Length Armchair Carbon Nanotubes

The electronic structure and dielectric screening of finite-length armchair carbon nanotubes are studied with both tight-binding and ab initio methods. Good agreement is found in the band gap oscillation patterns and dielectric constants, which validates the tight-binding method as a reliable and fast approach to describe the screening effect of carbon nanotubes. For an illustration, our method is applied to a system consisting of a short (6,6) nanotube filled with six water molecules. Substantial screening of the water dipoles through the nanotube is observed. This polarization effect should have an important influence on the permeation of water and other biomolecules inside carbon nanotubes.     

Homogeneous Tubular‐Flow Process for Monoolein Preparation

Esterification of fatty acids with glycerol is characterized by negligible solubility of the two liquid phases. The reactions to mono‐, di‐ and triglycerides taking place in the fatty acid phase, are limited by chemical equilibrium. The scope of this study is to investigate in a tubular reactor the conversion of a homogeneous mixture of oleic acid and glycerol in tert‐butanol. The liquid composition in this study was 1 mol of oleic acid, 6 mol of glycerol and 14 mol of tert‐butanol. Experiments were conducted in a tubular reactor at 35 atm over a temperature range of 200–240 °C and residence times of 0.7–17.6 h to determine the kinetics and the chemical equilibrium. The selectivity to monoolein was >95 mol %. A reversible second order reaction fits the data well.     

Morphological Profiling Identifies a Common Mode of Action for Small Molecules with Different Targets

Unbiased morphological profiling of bioactivity, for example, in the cell painting assay (CPA), enables the identification of a small molecule's mode of action based on its similarity to the bioactivity of reference compounds, irrespective of the biological target or chemical similarity. This is particularly important for small molecules with nonprotein targets as these are rather difficult to identify with widely employed target-identification methods. We employed morphological profiling using the CPA to identify compounds that are biosimilar to the iron chelator deferoxamine. Structurally different compounds with different annotated cellular targets provoked a shared physiological response, thereby defining a cluster based on their morphological fingerprints. This cluster is based on a shared mode of action and not on a shared target, that is, cell-cycle modulation in the S or G2 phase. Hierarchical clustering of morphological fingerprints revealed subclusters that are based on the mechanism of action and could be used to predict target-related bioactivity.     

When problem solving is superior to studying worked examples.

Interactions between levels of learner knowledge in a domain and levels of instructional guidance were investigated. Inexperienced mechanical trade apprentices were presented with either a series of worked examples to study or problems to solve. On subsequent tests, inexperienced trainees benefited most from the worked examples condition, with this group performing better with lower ratings of mental load than similar trainees who solved problems. With more experience in the domain, worked examples became redundant and problem solving proved superior. It is suggested that the relative effectiveness of either worked examples or problem solving depends heavily on levels of learner knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classification and analysis of excitations in a coupled finite nanoparticle cylinder-shell lattice

We present a general model for computing an optical response function of a finite shell lattice of semiconducting or metallic nanoparticles. Within a second quantization formalism, a cylindrical shell of induced, coupled dipoles is considered in the presence of an external electric field. Numerical analysis of the eigenmodes and quantum mechanical response function allow us to identify resonator effects due to constructive interferometric interaction of the light to the dipole lattice. Adjusting the wavelength of the external electric field, a coherent resonance excitation is possible for a fixed parameter of the cylinder radius.     

Large-scale analysis of self-disclosure patterns among online social networks users: a Russian context

Online social network services (SNS) provide an unprecedented rich source of information about millions of users worldwide. However, most existing studies of this emerging phenomenon are limited to relatively small data samples, with an emphasis on mostly “western” online communities (such as Facebook and MySpace users in Western countries). To understand the cultural characteristics of users of online social networks, this paper explores the behavioral patterns of more than 16 million users of a popular social network in the Russian segment of the Internet, namely, My.Mail.Ru (also known as “My World” or “Moj Mir” in Russian). Our main goal is to study the self-disclosure patterns of the site users as a function of their age and gender. We compare the findings of our analysis to the previous studies on Western users of SNS and discuss the culturally distinctive aspects. Our study highlights some important cultural differences in usage patterns among Russian users, which call for further studies in SNS in various cultural contexts.     

Correlation between structure characteristics and adsorption properties of regenerated cellulose fibers

We correlate fine structure with the adsorption behavior of new (lyocell) and conventional (viscose, modal) regenerated cellulose fibers. We have studied the molecular structure, the fine structure and, most important of all, the amorphous regions and voids in the system. Differences in adsorption properties of all three-fiber types were determined by using several methods for quantification of water, dye and iodine adsorption. The structural analysis shows that higher molecular weight, a higher degree of crystallinity and a higher molecular orientation are found in lyocell fibers [1]. Our results obtained by several independent methods demonstrate clearly that the adsorption properties of cellulose fibers depend, with the exception of the portion and orientation of amorphous regions, predominantly on the void system (diameter, volume and inner surface of voids) [2]. Electronic Publication