The colored revolution of bioimaging

This paper provides an overview of the main aspects of modern fluorescence microscopy. It covers the principles of fluorescence and highlights the key discoveries in the history of fluorescence microscopy. The paper also discusses the optics of fluorescence microscopes and examines the various types of detectors. It also discusses the signal and image processing challenges in fluorescence microscopy and highlights some of the present developments and future trends in the field.     

Radiative lifetimes of electrons and holes in a thin semiconductor layer

Radiative lifetimes of nondegenerate electrons and holes distributed uniformly in a semiconductor layer either deposited on a substrate or bounded by two dielectric media are calculated. The obtained expression takes into account the radiation reabsorbtion and interference effects and determines the dependences of the radiative lifetimes on the refractive indices of the external media and on the layer thickness.     

Hopping and optical absorption of electrons in nano-porous crystal 12CaO·7Al2O3

Recently it has been discovered that a nano-porous main group oxide 12CaO·7Al₂O₃ (C12A7) can be converted from a wide-gap insulator to a good transparent conductor. Using ab initio modelling we explain good conductivity of this material by very small barriers for hopping of localised electrons between neighbouring positive cages. We show that optical absorption of C12A7 in infrared region and at energies higher than 2.7 eV is due to inter-cage and intra-cage electron transitions, respectively. The proposed mechanisms can be useful in further search for conducting transparent media.     

Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators

 An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence of feedback control gain on the static and dynamic responses of the FGM plates are examined. Received: 13 March 2002 / Accepted: 5 March 2003 The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CityU 1024/01E).     

Microchemical Engineering: Components,Plant Concepts User Acceptance – Part I

Over the last five years, many activities have focused on the unexploited field of carrying out reactions on small scales. Due to the rapid development of new components, this paper deals with recent developments only in a compressed form. An important point is the analysis of possible plant concepts for microreactors and whether these are a sensible option. Due to the enormous difference in size between the microchannels and the fluid periphera of possible components this is not just a technical question. It touches on the microtechnology concept as a whole. The direction in which the field should be developed and which measures can be taken to influence its development are questions that are addressed here with respect to the big industrial interest in microreactors.     

The effect of segment length on some properties of thermoplastic poly(ester–siloxane)s

A series of novel thermoplastic elastomers, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reactions of dimethyl terephthalate and methyl esters of carboxypropyl‐terminated poly(dimethylsiloxane)s (M?_n = 550–2170 g mol^?1) with 1,4‐butanediol. The lengths of both the hard and soft segments were varied while the weight ratio of the hard to soft segments in the reaction mixture was maintained constant (57/43). The molecular structure, composition and molecular weights of the poly(ester–siloxane)s were examined by ¹H NMR spectroscopy. The effectiveness of the incorporation of the methyl‐ester‐terminated poly(dimethylsiloxane)s into the copolymer chains was verified by chloroform extraction. The effect of the segment length on the transition temperatures (T_m and T_g) and the thermal and thermo‐oxidative degradation stability, as well as the degree of crystallinity and hardness properties of the synthesized TPESs, were studied. Copyright © 2003 Society of Chemical Industry     

Mixed oxide supported hydrodesulfurization catalysts—a review

Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al₂O₃ containing mixed oxide supports, TiO₂ containing mixed oxide supports, ZrO₂ containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO₂ containing mixed oxides received maximum attention, especially TiO₂–Al₂O₃ supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication.     

Changes in the gaseous H2S barrier properties of damaged silicate coated nylon 6 films

The damage imposed on SiO _x deposited nylon 6 films as a result of abrasion with a cotton cloth and Gelboflex testing was examined by evaluating the rate at which copper plates, which were enveloped by the damaged films, were corroded by H₂S. Abrasion with a cotton cloth caused some micro-cracking of the SiO _x layer and the permeation rate of H₂S approached that of the uncoated nylon 6 film. Damage to the SiO _x layer by twisting and crushing progressed gradually with the number of Gelboflex test cycles and correspondingly the corrosion rate of the copper plates increased. Comparison of the corrosion rates of the copper plates kept in the pouches made of various commercial films with those obtained for the damaged SiO _x deposited nylon 6 films showed a clear relationship between the H₂ permeation rate of the films and the corrosion rate of the copper plates by H₂S.     

Mathematical Modeling of Thermomechanical Processes under Intense Thermal Effect

Mathematical models of thermomechanical processes which are based on the laws of rational thermodynamics of irreversible processes are treated. Singular features of the unsteady-state behavior of a continuous medium are demonstrated within different models, such as a medium with internal parameters of state, a medium with memory, and a medium of the velocity type.     

Explosive chemistry: Simulating the chemistry of energetic materials at extreme conditions

In this article, we review recent atomistic computational techniques to study the electronic structure aspects and chemistry of energetic materials at high-pressure and/or high temperature. While several mechanisms have been proposed for the initial events of energetic materials at high-pressure, we explore the validity of a proposed shear-induced local metallization via molecular bond bending in the insensitive explosive TATB. We study the effect of high-stress (both uniform and uniaxial) on the electronic energy band-gap and the first chemical event of a prototypical energetic material, that of nitromethane. We also determine chemical reactions rate laws and decomposition mechanisms from a quantum-based molecular dynamics simulation of HMX, a widely used explosive material, at conditions of high density and temperature similar to that encounter under detonation. Finally, we review a new multi-scale computational tool recently developed to model the shock-induced chemistry of energetic materials at the atomistic level, and report its applicability to shocked solid nitromethane. This revised version was published online in June 2006 with corrections to the Cover Date.