Mechanostereochemistry and the mechanical bond

Barin, Gokhan,Forgan, Ross S.,Stoddart, J. Fraser The Royal Society 2012 Proceedings, Mathematical, physical, and engineeri Vol.468 No.2146

<P> The chemistry of mechanically interlocked molecules (MIMs), in which two or more covalently linked components are held together by <I>mechanical bonds</I> , has led to the coining of the term <I>mechanostereochemistry</I> to describe a new field of chemistry that embraces many aspects of MIMs, including their syntheses, properties, topologies where relevant and functions where operative. During the rapid development and emergence of the field, the synthesis of MIMs has witnessed the forsaking of the early and grossly inefficient statistical approaches for template-directed protocols, aided and abetted by molecular recognition processes and the tenets of self-assembly. The resounding success of these synthetic protocols, based on templation, has facilitated the design and construction of artificial molecular switches and machines, resulting more and more in the creation of integrated functional systems. This review highlights (i) the range of template-directed synthetic methods being used currently in the preparation of MIMs; (ii) the syntheses of topologically complex knots and links in the form of stable molecular compounds; and (iii) the incorporation of bistable MIMs into many different device settings associated with surfaces, nanoparticles and solid-state materials in response to the needs of particular applications that are perceived to be fair game for mechanostereochemistry. </P>

A Modular Decomposition Model for Software Project Scheduling

Kim, Kiseong,Nag, Barin N. 한국경영과학회 1993 韓國經營科學會誌 Vol.18 No.3

The high level of activity in the development and maintenance of computer software makes the scheduling of software projects an important factor in reducing operating costs and increasing competitiveness. Software activity is labor intensive. Scheduling management of hours of software work is complicated by the interdependencies between the segments of work, and the uncertainties of the work itself. This paper discusses issues of scheduling in software engineering management, and presents a modular decomposition model for software project scheduling, tasking advantage of the facility for decomposition of a software project into relatively independent work segment modules. Modular decomposition makes it possible to treat scheduling as clustering and sequencing in the context of integer programming. A heuristic algorithm for the model is presented with some computational experiments.

UV-Assisted Room-Temperature Gas Sensing by HfO2 Thin Films

Irmak Karaduman,Ozlem Barin,Selim Acar 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.11

This research paper presents a detailed study of the influence of annealing temperature and UV irradiation on the sensitivity to NO2 of HfO2 thin films that can be used for the development of metal-oxide gas sensors. The HfO2 thin films were grown with a 3.3-nm thickness by using atomic layer deposition (ALD) and were annealed at different temperatures. The HfO2 thin films were characterized by using an atomic force microscope (AFM). The roughnesses of thin films were seen to have been affected by the annealing treatment. The effects of annealing temperature, as well as the operating temperature, on the response and the recovery characteristics of the HfO2 film were investigated. The results showed that both the annealing temperature and the operating temperature had significant effects on the sensing characteristics. Also, at room-temperature operation, the sensitivity of HfO2 thin films to 5 ppm of NO2 gas in air was investigated under UV irradiation. UV irradiation not only increased the response but also reduced the response and the recovery times during the gas-sensing measurements.

High hopes: can molecular electronics realise its potential?

Coskun, Ali,Spruell, Jason M.,Barin, Gokhan,Dichtel, William R.,Flood, Amar H.,Botros, Youssry Y.,Stoddart, J. Fraser The Royal Society of Chemistry 2012 Chemical Society reviews Vol.41 No.14

<P>Manipulating and controlling the self-organisation of small collections of molecules, as an alternative to investigating individual molecules, has motivated researchers bent on processing and storing information in molecular electronic devices (MEDs). Although numerous ingenious examples of single-molecule devices have provided fundamental insights into their molecular electronic properties, MEDs incorporating hundreds to thousands of molecules trapped between wires in two-dimensional arrays within crossbar architectures offer a glimmer of hope for molecular memory applications. In this critical review, we focus attention on the collective behaviour of switchable mechanically interlocked molecules (MIMs)—specifically, bistable rotaxanes and catenanes—which exhibit reset lifetimes between their ON and OFF states ranging from seconds in solution to hours in crossbar devices. When these switchable MIMs are introduced into high viscosity polymer matrices, or self-assembled as monolayers onto metal surfaces, both in the form of nanoparticles and flat electrodes, or organised as tightly packed islands of hundreds and thousands of molecules sandwiched between two electrodes, the thermodynamics which characterise their switching remain approximately constant while the kinetics associated with their reset follow an intuitively predictable trend—that is, fast when they are free in solution and sluggish when they are constrained within closely packed monolayers. The importance of seamless interactions and constant feedback between the makers, the measurers and the modellers in establishing the structure-property relationships in these integrated functioning systems cannot be stressed enough as rationalising the many different factors that impact device performance becomes more and more demanding. The choice of electrodes, as well as the self-organised superstructures of the monolayers of switchable MIMs employed in the molecular switch tunnel junctions (MSTJs) associated with the crossbars of these MEDs, have a profound influence on device operation and performance. It is now clear, after much investigation, that a distinction should be drawn between two types of switching that can be elicited from MSTJs. One affords small ON/OFF ratios and is a direct consequence of the switching in bistable MIMs that leads to a relatively small remnant molecular signature—an activated chemical process. The other leads to a very much larger signature and ON/OFF ratios resulting from physical or chemical changes in the electrodes themselves. Control experiments with various compounds, including degenerate catenanes and free dumbbells, which cannot and do not switch, are crucial in establishing the authenticity of the small ON/OFF ratios and remnant molecular signatures produced by bistable MIMs. Moreover, experiments conducted on monolayers in MSTJs of molecules designed to switch and molecules designed not to switch have been probed directly by spectroscopic and other means in support of MEDs that store information through switching collections of bistable MIMs contained in arrays of MSTJs. In the quest for the next generation of MEDs, it is likely that monolayers of bistable MIMs will be replaced by robust crystalline extended structures wherein the switchable components, derived from bistable MIMs, are organised precisely in a periodic manner.</P> <P>Graphic Abstract</P><P>There is a world of difference between a molecular electronic device which switches at high (blue) rather than at low (red) bias. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cs35053j'> </P>

Feasibility study of a non invasive Cardiac Rhythm Management System

Peter Leijdekkers,Valerie Gay,Edward Barin 동국대학교 정보융합기술원 2009 International Journal of Assistive Robotics and Sy Vol.10 No.4

This paper discusses the trial results of a personalised Cardiac Rhythm Management (CRM) system using a smart phone (PDA) and a wireless ECG sensor. The system is used in a trial to record and diagnose abnormal cardiac arrhythmias. This novel approach uses standard mobile phones, off-the-shelf ECG sensors and personalised feedback to the patient when compared to a conventional clinical Holter and event monitor systems. The preliminary results are discussed of an ongoing trial conducted with the Royal North Shore Hospital in Sydney Australia. The results indicate the viability of the system for commercial purposes.

Measurement of the ground-state distributions in bistable mechanically interlocked molecules using slow scan rate cyclic voltammetry

Fahrenbach, A.C.,Barnes, J.C.,Li, H.,Benitez, D.,Basuray, A.N.,Fang, L.,Sue, C.-H.,Barin, G.,Dey, S.K.,Goddard, W.A. National Academy of Sciences 2011 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.108 No.51