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Bashir Mohi Ud Din Bhat,Jehangir Rashid Dar,Pratima Sen 한국탄소학회 2016 Carbon Letters Vol.17 No.-
This paper addresses the effect of dopants on the electronic properties of zigzag (8, 0) semiconducting single walled carbon nanotubes (SWCNTs), using extended H?ckel theory combined with nonequilibrium Green’s function formalism. Through appropriate dopant concentrations, the electronic properties of SWCNTs can be modified. Within this context, we present our ongoing investigation on (8, 0) SWCNTs doped with nitrogen. Quantum confinement effects on the electronic properties of the SWCNTs have also been investigated. The obtained results reveal that the electronic properties of SWCNTs are strongly dependent on the dopant concentration and modification of electronic structures by hydrogen confinement.
Stock Prices and Exchange Rate Nexus in Pakistan: An Empirical Investigation Using MGARCH-DCC Model
Tabassam RASHID,Malik Fahim BASHIR 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.5
The study examines stock prices (LOGKSE) and exchange rate (LOGPK)-Pakistani Rupee vis-à-vis US Dollar- interactions in Pakistan. This study employs a multivariate VAR-GARCH model using monthly data from January 2012 to October 2020. The results of the Johansen cointegration test show that there is no relationship between Foreign Exchange Market and Stock Market in the long run. In the short-run, stock exchange returns are affected slightly negatively by the changes in the foreign exchange market, but the foreign exchange market does not seem to be affected by the ups and downs of the stock exchange. The VAR model and Granger Causality show that both markets are strongly influenced by their own lagged values rather than by the lagged values of one another and show weak or no correlation between the two markets. Volatility persistence is observed in both the stock and foreign exchange markets, implying that shocks and past period volatility are major drivers of future volatility in both markets. Thus greater uncertainties today will induce panic and consequently generate higher volatility in the future period. This phenomenon has been observed many times on Pakistan Stock Exchange especially. The results have important implications for local international investors in portfolio diversification decisions and risk hedging strategies.
“Bottom-up” Approach for ImplementingNano/microstructure Using Biological andChemical Interactions
구윤모,이상우,장우진,Rashid Bashir 한국생물공학회 2007 Biotechnology and Bioprocess Engineering Vol.12 No.3
The “Bottom-up” approach for implementing nano/microstructure using biological self-assembled systems has been investigated with tremendous interest by many researchers in the field of medical diagnostics, material synthesis, and nano/microelectronics. As a result, the techniques for achieving these systems have been extensively explored in recent years. The developed or developing techniques are based on many interdisciplinary areas such as biology, chemistry, physics, electrical engineering, mechanical engineering, and so on. In this paper, we review the fundamentals behind the self-assembly concepts and describe the state of art in the biological and chemical self-assembled systems for the implementation of nano/microstructures. These structures described in the paper can be applied to the implementation of hybrid biosensors, biochip, novel bio-mimetic materials, and nano/microelectronic devices.
"Bottom-up" Approach for Implementing Nano/microstructure Using Biological and Chemical Interactions
Lee, Sang-Woo,Chang, Woo-Jin,Bashir, Rashid,Koo, Yoon-Mo Korean Society for Biotechnology and Bioengineerin 2007 Biotechnology and Bioprocess Engineering Vol.12 No.3
The "Bottom-up" approach for implementing nano/microstructure using biological self-assembled systems has been investigated with tremendous interest by many researchers in the field of medical diagnostics, material synthesis, and nano/microelectronics. As a result, the techniques for achieving these systems have been extensively explored in recent years. The developed or developing techniques are based on many interdisciplinary areas such as biology, chemistry, physics, electrical engineering, mechanical engineering, and so on. In this paper, we review the fundamentals behind the self-assembly concepts and describe the state of art in the biological and chemical self-assembled systems for the implementation of nano/microstructures. These structures described in the paper can be applied to the implementation of hybrid biosensors, biochip, novel bio-mimetic materials, and nano/microelectronic devices.
Park, In Soo,Eom, Kilho,Son, Jongsang,Chang, Woo-Jin,Park, Kidong,Kwon, Taeyun,Yoon, Dae Sung,Bashir, Rashid,Lee, Sang Woo American Chemical Society 2012 ACS NANO Vol.6 No.10
<P>The simultaneous investigation of a large number of events with different types of intermolecular interactions, from nonequilibrium high-force pulling assays to quasi-equilibrium unbinding events in the same environment, can be very important for fully understanding intermolecular bond-rupture mechanisms. Here, we describe a novel dielectrophoretic force spectroscopy technique that utilizes microsized beads as multifunctional probes for parallel measurement of intermolecular forces with an extremely wide range of force rate (10<SUP>–4</SUP> to 10<SUP>4</SUP> pN/s) inside a microfluidic device. In our experiments, various forces, which broadly form the basis of all molecular interactions, were measured across a range of force loading rates by multifunctional probes of various diameters with a throughput of over 600 events per mm<SUP>2</SUP>, simultaneously and in the same environment. Furthermore, the individual bond-rupture forces, the parameters for the characterization of entire energy landscapes, and the effective stiffness of the force spectroscopy were determined on the basis of the measured results. This method of determining intermolecular forces could be very useful for the precise and simultaneous examination of various molecular interactions, as it can be easily and cost-effectively implemented within a microfluidic device for a range of applications including immunoassays, molecular mechanics, chemical and biological screening, and mechanobiology.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-10/nn302202t/production/images/medium/nn-2012-02202t_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn302202t'>ACS Electronic Supporting Info</A></P>
‘Living cantilever arrays’ for characterization of mass of single live cells in fluids
Park, Kidong,Jang, Jaesung,Irimia, Daniel,Sturgis, Jennifer,Lee, James,Robinson, J. Paul,Toner, Mehmet,Bashir, Rashid Royal Society of Chemistry 2008 Lab on a chip Vol.8 No.7
<P>The size of a cell is a fundamental physiological property and is closely regulated by various environmental and genetic factors. Optical or confocal microscopy can be used to measure the dimensions of adherent cells, and Coulter counter or flow cytometry (forward scattering light intensity) can be used to estimate the volume of single cells in a flow. Although these methods could be used to obtain the mass of single live cells, no method suitable for directly measuring the mass of single adherent cells without detaching them from the surface is currently available. We report the design, fabrication, and testing of ‘living cantilever arrays’, an approach to measure the mass of single adherent live cells in fluid using silicon cantilever mass sensor. HeLa cells were injected into microfluidic channels with a linear array of functionalized silicon cantilevers and the cells were subsequently captured on the cantilevers with positive dielectrophoresis. The captured cells were then cultured on the cantilevers in a microfluidic environment and the resonant frequencies of the cantilevers were measured. The mass of a single HeLa cell was extracted from the resonance frequency shift of the cantilever and was found to be close to the mass value calculated from the cell density from the literature and the cell volume obtained from confocal microscopy. This approach can provide a new method for mass measurement of a single adherent cell in its physiological condition in a non-invasive manner, as well as optical observations of the same cell. We believe this technology would be very valuable for single cell time-course studies of adherent live cells.</P> <P>Graphic Abstract</P><P>A single HeLa cell was captured and cultured on a silicon cantilever and then its mass was measured by monitoring the change in resonant frequency of the cantilever. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b803601b'> </P>
Yang, Liju,Banada, Padmapriya P.,Chatni, Mohammad R.,Seop Lim, Kwan,Bhunia, Arun K.,Ladisch, Michael,Bashir, Rashid Royal Society of Chemistry 2006 Lab on a chip Vol.6 No.7
<P>In this study, we demonstrated a micro-fluidic system with multiple functions, including concentration of bacteria using dielectrophoresis (DEP) and selective capture using antibody recognition, resulting in a high capture efficiency of bacterial cells. The device consisted of an array of oxide covered interdigitated electrodes on a flat silicon substrate and a ∼16 µm high and ∼260 µm wide micro-channel within a PDMS cover. For selective capture of <I>Listeria monocytogenes</I> from the samples, the channel surface was functionalized with a biotinylated BSA–streptavidin–biotinylated monoclonal antibody sandwich structure. Positive DEP (at 20 V<SUB>pp</SUB> and 1 MHz) was used to concentrate bacterial cells from the fluid flow. DEP could collect ∼90% of the cells in a continuous flow at a flow rate of 0.2 µl min<SUP>−1</SUP> into the micro-channel with concentration factors between 10<SUP>2</SUP>–10<SUP>3</SUP>, in sample volumes of 5–20 µl. A high flow rate of 0.6 µl min<SUP>−1</SUP> reduced the DEP capture efficiency to ∼65%. Positive DEP attracts cells to the edges of the electrodes where the field gradient is the highest. Cells concentrated by DEP were captured by the antibodies immobilized on the channel surface with efficiencies of 18 to 27% with bacterial cell numbers ranging from 10<SUP>1</SUP> to 10<SUP>3</SUP> cells. It was found that DEP operation in our experiments did not cause any irreversible damage to bacterial cells in terms of cell viability. In addition, increased antigen expression (antigens to C11E9 monoclonal antibody) on cell membranes was observed following the exposure to DEP.</P> <P>Graphic Abstract</P><P>Bacterial cells were concentrated by positive dielectrophoresis. Target cells were selectively captured by specific antibodies immobilized on the channel surface. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b607061m'> </P>
Lee, Min Kyung,Rich, Max H.,Shkumatov, Artem,Jeong, Jae Hyun,Boppart, Marni D.,Bashir, Rashid,Gillette, Martha U.,Lee, Jonghwi,Kong, Hyunjoon Wiley (John WileySons) 2015 Advanced Healthcare Materials Vol.4 No.2
<P>This study demonstrates that a new method to align microparticles releasing bioactive molecules in microchannels of a hydrogel allows the guiding of growth direction and spacing of vascular networks.</P>
Park, In Soo,Kwak, Tae Joon,Lee, Gyudo,Son, Myeonggu,Choi, Jeong Woo,Choi, Seungyeop,Nam, Kihwan,Lee, Sei-Young,Chang, Woo-Jin,Eom, Kilho,Yoon, Dae Sung,Lee, Sangyoup,Bashir, Rashid,Lee, Sang Woo American Chemical Society 2016 ACS NANO Vol.10 No.4
<P>The direct quantification of weak intermolecular binding interactions is very important for many applications in biology and medicine. Techniques that can be used to investigate such interactions under a controlled environment, while varying different parameters such as loading rate, pulling direction, rupture event measurements, and the use of different functionalized probes, are still lacking. Herein, we demonstrate a biaxial dielectrophoresis force spectroscopy (BDFS) method that can be used to investigate weak unbinding events in a high-throughput manner under controlled environments and by varying the pulling direction (i.e., transverse and/or vertical axes) as well as the loading rate. With the BDFS system, we can quantitatively analyze binding interactions related to hydrogen bonding or ionic attractions between functionalized microbeads and a surface within a microfluidic device. Our BDFS system allowed for the characterization of the number of bonds involved in an interaction, bond affinity, kinetic rates, and energy barrier heights and widths from different regimes of the energy landscape.</P>