Reverse atom transfer radical polymerization of stearyl methacrylate using 2,2′‐azobisisobutyronitrile as the initiator

The living/controlled radical polymerization of stearyl methacrylate was carried out with a conventional radical initiator (2,2′‐azobisisobutyronitrile) in N,N‐dimethylformamide in the presence of a 2,2′‐bipyridine complex of hexakis(N,N‐dimethylformamide)iron(III) perchlorate. The polymerization mechanism was thought to proceed through a reverse atom transfer radical polymerization. The molecular weights of resulting poly(stearyl methacrylate) increased with conversion, and the resulting molecular weight distributions were quite narrow. The rates of polymerization exhibited first‐order kinetics with respect to the monomer. A probable reaction mechanism for the polymerization system is postulated to explain the observed results. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1236–1245, 2002     

Nanoscale Ⅲ-V on Si-based junctionless tunnel transistor for EHF band applications

A single gate Ⅲ-V junctionless tunnel field effect transistor (SG-JLTFET) has been reported which shows excellent dc characteristics at low power supply operation. This device has a thin uniformly n-type doped channel of GaSb i.e. gallium antimonide which is grown epitaxially over silicon substrate. The DC performance parameters such as I_ON, I_ON/I_OFF, average and point subthreshold slope as well as device parameters for analog applications viz. transconductance g_m, transconductance generation efficiency g_m/I_D, various capacitances and the unity gain frequency f_T are studied using a device simulator. Along with examining its endurance to short channel effects, the performances are also compared with a Silicon Dual Gate Junctionless Tunnel FET (DG-JLTFET). The DC and small signal analog performance reflects that GaSb SG-JLTFET has immense purview for extreme high-frequency and low-power applications.     

Labelling Proteins with Carbon Nanodots

We present efficient labelling of several proteins with orange‐emissive carbon dots. N‐Hydroxysuccinimide was used to activate the carboxyl groups of carbon dots, which subsequently reacted with the lysine groups present on the protein. Labelling was confirmed by UV absorption spectroscopy, PAGE and fluorescence correlation spectroscopy. Protein‐conjugated carbon dots showed an enhancement in fluorescence lifetime and intensity owing to reduced intramolecular dynamic fluctuations. Single‐molecule fluorescence measurements showed reduced fluorescence fluctuations and higher photon budget after protein tagging. Our study opens up opportunities to use carbon dots as highly precise biolabelling probes.     

Attractor selection in a modulated laser and in the Lorenz circuit

By tuning a control parameter, a chaotic system can either display two or more attractors (generalized multistability) or exhibit an interior crisis, whereby a chaotic attractor suddenly expands to include the region of an unstable orbit (bursting regime).Recently, control of multistability and bursting have been experimentally proved in a modulated class B laser by means of a feedback method. In a bistable regime, the method relies on the knowledge of the frequency components of the two attractors. Near an interior crisis, the method requires retrieval of the unstable orbit colliding with the chaotic attractor.We also show that a suitable parameter modulation is able to control bistability in the Lorenz system. We observe that, for every given modulation frequency, the chaotic attractor is destroyed under a boundary crisis. The threshold control amplitude depends on the control frequency and the location of the operating point in the bistable regime. Beyond the boundary crisis, the system remains in the steady state even if the control is switched off, demonstrating control of bistability.     

Motion Panoramas

In this paper we describe a method for analysing video sequences and for representing them as mosaics or panoramas. Previous work on video mosaicking essentially concentrated on static scenes. We generalize these approaches to the case of a rotating camera observing both static and moving objects where the static portions of the scene are not necessarily dominant, as it has been often hypothesized in the past. We start by describing a robust technique for accurately aligning a large number of video frames under unknown camera rotations and camera settings. The alignment technique combines a feature‐based method (initialization and refinement) with rough motion segmentation followed by a colour‐based direct method (final adjustment). This precise frame‐to‐frame alignment allows the dynamic building of a background representation as well as an efficient segmentation of each image such that moving regions of arbitrary shape and size are aligned with the static background. Thus a motion panorama visualizes both dynamic and static scene elements in a geometrically consistent way. Extensive experiments applied to archived videos of track‐and‐field events validate the approach. Copyright © 2004 John Wiley & Sons, Ltd.     

A feasibility study of steam-jet refrigeration

In this paper a feasibility study of steam-jet refrigeration is conducted. First and second law analyses as well as the economics of a steam-jet refrigeration system are presented. Thermodynamic parameters investigated include the coefficient of performance (COP), refrigerating effect, condenser heat rejection, motive steam requirements, second law efficiency, and system irreversibility. Economic parameters investigated include equipment costs, space needs, power requirements, and installed and operational costs. © 1998 John Wiley & Sons, Ltd.     

Polymerization of methyl methacrylate by charge-transfer mechanism with 2,2′-bipyridine and iron (III) complex

Polymerization of methyl methacrylate (MMA) by the charge-transfer complex formed by the interaction of 2,2′-bipyridine (bpy), MMA, and carbon tetrachloride (CCl₄) was studied in dimethylsulfoxide (DMSO) at 60°C. The rate of polymerization (R_p) is sensitive to the [CCl₄] at low concentration of CCl₄, but at a higher concentration it is practically independent of [CCl₄]. R_p is proportional to [MMA]^1.45±0.04 and [bpy]^0.52±0.04 when [CCl₄] > [bpy], and the average rate constant, k, at 60°C for the polymerization of MMA was 7.14 ± 0.40 × 10⁻⁶ L mol⁻¹s⁻¹. Kinetic studies showed that the polymerization proceeds through free radical intermediates. This article also reports the polymerization of MMA initiated by bpy and CCl₄ and accelerated by Lewis acid, hexakis (dimethylsulfoxide)iron(III) perchlorate [Fe(DMSO)₆](ClO₄)₃ at 60°C. The glass transition temperature and molecular weights of the samples were investigated by using differential scanning calorimetry and gel permeation chromatography techniques, respectively. Probable reaction mechanisms are proposed to explain the observed results. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2097–2103, 1997     

Estimation of heat source model parameters for twin-wire submerged arc welding

Heat source models are mathematical expressions that represent the generation term in the fundamental heat transfer equation. Investigators have successfully demonstrated different heat source models for single-wire welding. The present investigation estimates the double ellipsoidal heat source model parameters for twin-wire application. The heat source model parameters have been estimated for varying set of welding conditions. It has been found that the heat source model parameters for twin-wire welding are different from the single-wire welding. Moreover, the heat source model parameters also depend upon process parameters. Effects of welding current, electrode polarity and wire diameter on the size of heat source model have been presented. Flux consumption is also found to play a significant role in deciding the heat source model parameters.     

Thickness dependent electronic structure of ultra-thin tetrahedral amorphous carbon (ta-C) films

Microstructural properties of ultrathin (1-10 nm) tetrahedral amorphous carbon (ta-C) films are investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, X-ray Photoelectron Spectroscopy, Raman spectroscopy and Atomic Force Microscopy (AFM). The CK-edge NEXAFS spectra of 1 nm ta-C films provided evidence of surface defects (C―H bonds) which rapidly diminish with increasing film thickness. A critical thickness for stabilization of largely sp³ matrix structure distorted by sp² sites is observed via the change of π*C═C peak behavior. Meanwhile, an increase in the film thickness promotes an enhancement in sp³ content, the film roughness remains nearly constant as probed by spectroscopic techniques and AFM, respectively. The effect of thickness on local bonding states of ultrathin ta-C films proves to be the limiting factor for their potential use in magnetic and optical storage devices.