Monte Carlo study of coaxially gated CNTFETs: capacitive effects and dynamic performance

Carbon Nanotube (CNT) appears as a promising candidate to shrink field-effect transistors (FET) to the nanometer scale. Extensive experimental works have been performed recently to develop the appropriate technology and to explore DC characteristics of carbon nanotube field effect transistor (CNTFET). In this work, we present results of Monte Carlo simulation of a coaxially gated CNTFET including electron-phonon scattering. Our purpose is to present the intrinsic transport properties of such material through the evaluation of electron mean-free-path. To highlight the potential of high performance level of CNTFET, we then perform a study of DC characteristics and of the impact of capacitive effects. Finally, we compare the performance of CNTFET with that of Si nanowire MOSFET.Comment: 15 pages, 14 figures, final version to be published in C. R. Acad. Sci. Pari

Regulation of caspase-3 processing by cIAP2 controls the switch between pro-inflammatory activation and cell death in microglia.

Cell Death and Disease is an open-access journal published by Nature Publishing Group. This work is licensed under a Creative Commons Attribution 4.0 International Licence. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons licence, users will need to obtain permission from the licence holder to reproduce the material.The activation of microglia, resident immune cells of the central nervous system, and inflammation-mediated neurotoxicity are typical features of neurodegenerative diseases, for example, Alzheimer's and Parkinson's diseases. An unexpected role of caspase-3, commonly known to have executioner role for apoptosis, was uncovered in the microglia activation process. A central question emerging from this finding is what prevents caspase-3 during the microglia activation from killing those cells? Caspase-3 activation occurs as a two-step process, where the zymogen is first cleaved by upstream caspases, such as caspase-8, to form intermediate, yet still active, p19/p12 complex; thereafter, autocatalytic processing generates the fully mature p17/p12 form of the enzyme. Here, we show that the induction of cellular inhibitor of apoptosis protein 2 (cIAP2) expression upon microglia activation prevents the conversion of caspase-3 p19 subunit to p17 subunit and is responsible for restraining caspase-3 in terms of activity and subcellular localization. We demonstrate that counteracting the repressive effect of cIAP2 on caspase-3 activation, using small interfering RNA targeting cIAP2 or a SMAC mimetic such as the BV6 compound, reduced the pro-inflammatory activation of microglia cells and promoted their death. We propose that the different caspase-3 functions in microglia, and potentially other cell types, reside in the active caspase-3 complexes formed. These results also could indicate cIAP2 as a possible therapeutic target to modulate microglia pro-inflammatory activation and associated neurotoxicity observed in neurodegenerative disorders

Microwave Transport in Metallic Single-Walled Carbon Nanotubes

The dynamical conductance of electrically contacted single-walled carbon nanotubes is measured from dc to 10 GHz as a function of source-drain voltage in both the low-field and high-field limits. The ac conductance of the nanotube itself is found to be equal to the dc conductance over the frequency range studied for tubes in both the ballistic and diffusive limit. This clearly demonstrates that nanotubes can carry high-frequency currents at least as well as dc currents over a wide range of operating conditions. Although a detailed theoretical explanation is still lacking, we present a phenomenological model of the ac impedance of a carbon nanotube in the presence of scattering that is consistent with these results.Comment: Added reference

Low-frequency Current Fluctuations in Individual Semiconducting Single-Wall Carbon Nanotubes

We present a systematic study on low-frequency current fluctuations of nano-devices consisting of one single semiconducting nanotube, which exhibit significant 1/f-type noise. By examining devices with different switching mechanisms, carrier types (electrons vs. holes), and channel lengths, we show that the 1/f fluctuation level in semiconducting nanotubes is correlated to the total number of transport carriers present in the system. However, the 1/f noise level per carrier is not larger than that of most bulk conventional semiconductors, e.g. Si. The pronounced noise level observed in nanotube devices simply reflects on the small number of carriers involved in transport. These results not only provide the basis to quantify the noise behavior in a one-dimensional transport system, but also suggest a valuable way to characterize low-dimensional nanostructures based on the 1/f fluctuation phenomenon

Electronic Devices Based on Purified Carbon Nanotubes Grown By High Pressure Decomposition of Carbon Monoxide

The excellent properties of transistors, wires, and sensors made from single-walled carbon nanotubes (SWNTs) make them promising candidates for use in advanced nanoelectronic systems. Gas-phase growth procedures such as the high pressure decomposition of carbon monoxide (HiPCO) method yield large quantities of small diameter semiconducting SWNTs, which are ideal for use in nanoelectronic circuits. As-grown HiPCO material, however, commonly contains a large fraction of carbonaceous impurities that degrade properties of SWNT devices. Here we demonstrate a purification, deposition, and fabrication process that yields devices consisting of metallic and semiconducting nanotubes with electronic characteristics vastly superior to those of circuits made from raw HiPCO. Source-drain current measurements on the circuits as a function of temperature and backgate voltage are used to quantify the energy gap of semiconducting nanotubes in a field effect transistor geometry. This work demonstrates significant progress towards the goal of producing complex integrated circuits from bulk-grown SWNT material.Comment: 6 pages, 4 figures, to appear in Nature Material

Defining sustainable transport in rural tourism: experiences from the New Forest

Transport policy agendas have long sought to bring about more sustainable transport at tourism destinations. While there are examples of successes, it remains unclear what inroads have been made towards creating a sustainable transport future. Policy directions have evolved over a number of years and in many tourism destination contexts it is far from clear what a desirable transport future looks like. When translated to implementation, the aims of initiatives can be unclear and baseline measures inconsistent, making success difficult to judge. This paper analyses how sustainable travel has been implemented in practice at a destination level. The focus is rural tourism and data are derived from a specific case, the New Forest National Park, UK, where a wide range of transport initiatives have been implemented since the Park’s designation in 2005. The study adopts a social practice theory perspective. Data are derived from a visitor survey, interviews and observations. It finds there is scope to improve sustainable transport provision at destinations through understanding visitor practices, but limited scope to influence meanings associated with visitor travel and travel skills. Policy meets the needs of some visitors more than others

Electrical properties of 0.4 cm long single-walled carbon nanotubes

Centimeter scale aligned carbon nanotube arrays are grown from nanoparticle metal catalyst pads. We find the nanotubes grow both with and against the wind. A metal underlayer provides in-situ electrical contact to these long nanotubes with no post growth processing needed. Using the electrically contacted nanotubes, we study electrical transport of 0.4 cm long nanotubes. The source drain I-V curves are quantitatively described by a classical, diffusive model. Our measurements show that the outstanding transport properties of nanotubes can be extended to the cm scale and open the door to large scale integrated nanotube circuits with macroscopic dimensions.Comment: 17 pages, 9 figure

A Conductometric Indium Oxide Semiconducting Nanoparticle Enzymatic Biosensor Array

We report a conductometric nanoparticle biosensor array to address the significant variation of electrical property in nanomaterial biosensors due to the random network nature of nanoparticle thin-film. Indium oxide and silica nanoparticles (SNP) are assembled selectively on the multi-site channel area of the resistors using layer-by-layer self-assembly. To demonstrate enzymatic biosensing capability, glucose oxidase is immobilized on the SNP layer for glucose detection. The packaged sensor chip onto a ceramic pin grid array is tested using syringe pump driven feed and multi-channel I–V measurement system. It is successfully demonstrated that glucose is detected in many different sensing sites within a chip, leading to concentration dependent currents. The sensitivity has been found to be dependent on the channel length of the resistor, 4–12 nA/mM for channel lengths of 5–20 μm, while the apparent Michaelis-Menten constant is 20 mM. By using sensor array, analytical data could be obtained with a single step of sample solution feeding. This work sheds light on the applicability of the developed nanoparticle microsensor array to multi-analyte sensors, novel bioassay platforms, and sensing components in a lab-on-a-chip