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Quartile: search.filters.quartile.Q1Subject: search.filters.subject.Applied physics

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Now showing 1 - 10 of 24
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    An electrochemical gelation method for patterning conductive PEDOT:PSS hydrogels
    (2019) Feig, Vivian Rachel; Tran, Helen; Lee, Minah; Liu, Kathy; Huang, Zhuojun; Mackanic, David G.; Bao, Zhenan; Department of Mechanical Engineering; Beker, Levent; Faculty Member; Department of Mechanical Engineering; College of Engineering; 308798
    Due to their high water content and macroscopic connectivity, hydrogels made from the conducting polymer PEDOT:PSS are a promising platform from which to fabricate a wide range of porous conductive materials that are increasingly of interest in applications as varied as bioelectronics, regen-erative medicine, and energy storage. Despite the promising properties of PEDOT:PSS-based porous materials, the ability to pattern PEDOT:PSS hydrogels is still required to enable their integration with multifunctional and multichannel electronic devices. In this work, a novel electrochemical gelation (“electrogelation”) method is presented for rapidly patterning PEDOT:PSS hydrogels on any conductive template, including curved and 3D surfaces. High spatial resolution is achieved through use of a sacrificial metal layer to generate the hydrogel pattern, thereby enabling high-performance conducting hydrogels and aerogels with desirable material properties to be introduced into increasingly complex device architectures
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    PublicationOpen Access
    Correcting for electrostatic cutoffs in free energy simulations: toward consistency between simulations with different cutoffs
    (American Institute of Physics (AIP) Publishing, 1998) McCammon, J. Andrew; Department of Physics; Reşat, Haluk; Faculty Member; Department of Physics; College of Sciences
    The use of electrostatic cutoffs in calculations of free energy differences by molecular simulations introduces errors. Even though both solute-solvent and solvent-solvent cutoffs are known to create discrepancies, past efforts have mostly been directed toward correcting for the solute-solvent cutoffs. In this work, an approach based on the generalized reaction field formalism is developed to correct for the solvent-solvent cutoff errors as well. It is shown using a series of simulations that when the cutoff lengths are significantly smaller than the half unit cell size, and the solute-solvent cutoff is not much larger than the solvent-solvent cutoff, the new algorithm is able to yield better agreement among simulations employing different truncation lengths.
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    PublicationOpen Access
    Correcting for solvent-solvent electrostatic cutoffs considerably improves the ion-pair potential of mean force
    (American Institute of Physics (AIP) Publishing, 1999) Department of Physics; Reşat, Haluk; Faculty Member; Department of Physics; College of Sciences
    A recently developed algorithm based on the continuum treatment of the solvent molecules beyond the electrostatic cutoff sphere is applied to the potential of mean force results between sodium and chloride ions to study the effects of the solute-solvent and solvent-solvent cutoff errors. The results show that although the solute-solvent correction improves the thermodynamic results slightly, physically realistic results are obtained only when the solvent-solvent correction is applied. This further supports past findings that proper treatment of solvent-solvent interactions is as important as that of the solute interactions, and should not be ignored.
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    Electrical conduction and NO 2 gas sensing properties of ZnO nanorods
    (Elsevier, 2014) Sahin, Yasin; Öztürk, Sadullah; Kosemen, Arif; Erkovan, Mustafa; Öztürk, Zafer Ziya; Department of Electrical and Electronics Engineering; Kılınç, Necmettin; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; 59959
    Thermally stimulated current (TSC), photoresponse and gas sensing properties of zinc oxide (ZnO) nanorods were investigated depending on heating rates, illumination and dark aging times with using sandwich type electrode system. Vertically aligned ZnO nanorods were grown on indium tin oxide (ITO) coated glass substrate by hydrothermal process. TSC measurements were performed at different heating rates under constant potential. Photoresponse and gas sensing properties were investigated in dry air ambient at 200 degrees C. For gas sensing measurements, ZnO nanorods were exposed to NO2 (100 ppb to 1 ppm) in dark and illuminated conditions and the resulting resistance transient was recorded. It was found from dark electrical measurements that the dependence of the dc conductivity on temperature followed Mott's variable range hopping (VRH) model. In addition, response time and recovery times of ZnO nanorods to NO2 gas decreased by exposing to white light.
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    End-to-end deep multi-modal physiological authentication with smartbands
    (IEEE-Inst Electrical Electronics Engineers Inc, 2021) Ekiz, Deniz; Dardağan, Yağmur Ceren; Aydar, Furkan; Köse, Rukiye Dilruba; Ersoy, Cem; N/A; Can, Yekta Said; Researcher; College of Social Sciences and Humanities; N/A
    The number of fitness tracker users increases every day. Most of the applications require authentication to protect privacy-preserving operations. Biometrics such as face images have been used widely as login tokens, but they have privacy issues. Moreover, occlusions like face masks used for COVID may reduce their effectiveness. Smartbands can track heart rate, movements, and electrodermal activities. They have been widely used for health-related applications. The use of smartbands for authentication is in the exploratory stage. Physiological signals gathered from smartbands may be used to create a multi-modal and multi-sensor authentication system. The popularity of smartbands enables us to deploy new applications without a need to buy additional hardware. In this study, we explore the multi-modal physiological biometrics with end-to-end deep learning and feature-based traditional systems. We collected multi-modal physiological data of 80 people for five days using modern smartbands. We applied a deep learning approach to the multi-modal physiological data and used feature-based traditional machine learning classifiers. The CNN-LSTM model achieved a 9.31% equal error rate and outperformed other models in terms of authentication performance.
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    Engineered sulfated polysaccharides for biomedical applications
    (Wiley-V C H Verlag Gmbh, 2021) Arlov, Oystein; Rutsche, Dominic; Korayem, Maryam Asadi; Zenobi-Wong, Marcy; N/A; Öztürk, Ece; Faculty Member; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); School of Medicine; 326940
    Sulfated polysaccharides are ubiquitous in living systems and have central roles in biological functions such as organism development, cell proliferation and differentiation, cellular communication, tissue homeostasis, and host defense. Engineered sulfated polysaccharides (ESPs) are structural derivatives not found in nature but generated through chemical and enzymatic modification of natural polysaccharides, as well as chemically synthesized oligo- and polysaccharides. ESPs exhibit novel and augmented biological properties compared with their unmodified counterparts, mainly through facilitating interactions with other macromolecules. These interactions are closely linked to their sulfation patterns and backbone structures, providing a means to fine-tune biological properties and characterize structural-functional relationships by employing well-characterized polysaccharides and strategies for regioselective modification. The following review provides a comprehensive overview of the synthesis and characterization of ESPs and of their biological properties. Through the pioneering research presented here, key emerging application areas for ESPs, which can lead to novel breakthroughs in biomedical research and clinical treatments, are highlighted.
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    Enhanced hydrogen evolution via in situ generated 2D black phosphorous nanocomposites at the liquid/liquid interfaces
    (Elsevier, 2022) Aslan, Emre; Yanalak, Gizem; Patır, İmren Hatay; Department of Chemistry; Department of Chemistry; Eroğlu, Zafer; Metin, Önder; Researcher; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; College of Sciences; N/A; 46962
    The mimicry of bio-membrane with a liquid/liquid interface between two immiscible electrolyte solutions is intrinsically defect-free to study catalysis of energy conversion reactions i.e., CO2 reduction, oxygen reduction, and hydrogen evolution. Herein, we report the in-situ generation of electrodeposited black phosphorous (BP) based nanocomposites at the liquid/liquid interface for the first time and their catalysis in hydrogen evolution reaction (HER). The catalytic HER activities of these catalysts have been investigated electrochemically and also chemically by two-phase reactions. The BP/MoSx, BP/Cu, and BP/Pt nanocomposites were formed by reducing the catalyst precursors such as (NH4)(2)MoS4, (NH4)(2)PtCl4, and CuCl2 salts, respectively on the BP nanosheets by decamethylferrocene (DMFc) electron donor during the catalytic HER. The electrodeposited nanocomposites were collected from the interface and characterized by using advanced analytical techniques. Among them, the BP/MoSx nanocomposites showed the highest HER activity with a reaction rate constant of 0.202 min(-1) was about 230- and 7-times greater than the ones obtained by non-catalytic reaction and the free-MoSx catalyst. Moreover, the nucleation of the catalysts and the HER mechanisms were also explained in detail. The BP/MoSx also showed higher HER activity compared to that of carbon nanotubes CNTMoSx and reduced graphene oxide rGOMoS(x) nanocomposites.
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    Erratum to: exciton recycling via InP quantum dot funnels for luminescent solar concentrators
    (Tsinghua University) Ow-Yang, Cleva W.; N/A; N/A; N/A; N/A; Department of Physics; Department of Electrical and Electronics Engineering; Jalali, Houman Bahmani; Sadeghi, Sadra; Toker, Işınsu Baylam; Han, Mertcan; Sennaroğlu, Alphan; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Physics; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; N/A; N/A; 23851; 130295
    The article "Exciton recycling via InP quantum dot funnels for luminescent solar concentrators" written by Houman Bahmani Jalali(1),, Sadra Sadeghi(2),, Isinsu Baylam(3,4), Mertcan Han(5), Cleva W. Ow-Yang(6), Alphan Sennaroğlu(3,4), and Sedat Nizamoğlu(1,2,5) (x2709;), was originally published Online First without Open Access. After publication online first, the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to (c) The Author(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The original article has been corrected.
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    Frequency domain spectroscopy in rare-earth-doped gain media
    (Institute of Electrical and Electronics Engineers (IEEE), 2018) Callahan, Patrick; Li, Nanxi; Bradley, Jonathan D. B.; Singh, Neetesh; Ruocco, Alfonso; Kolodziejski, Leslie A.; Ippen, Erich P.; Watts, Michael R.; Department of Electrical and Electronics Engineering; Mağden, Emir Salih; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 276368
    Many spectroscopic techniques today rely on time-resolved measurements under short excitation pulses. Instead of using a chopped pump excitation, or ultrafast optical pulses, we expand on and apply the previously developed set of frequency domain methods to analyze the population level dynamics in rare-earth-doped media. By identifying the full frequency response of the gain medium, this method can accurately yield excited state lifetimes and can also be used to estimate transition cross-sections. The accuracy of the frequency domain methods are verified with Er3+- and Tm3+-doped fibers, and an Al2O3: Tm3+ waveguide, recovering similar results as reported by time-resolved techniques. The complete frequency domain model presented here can be used in characterization of novel optical gainmedia, and can provide insights into population dynamics in solid state amplifiers and lasers.
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    PublicationOpen Access
    Ionic dimers in He droplets: interaction potentials for Li-2(+)-He,Na-2(+)-He, and K-2(+)-He and stability of the smaller clusters
    (American Institute of Physics (AIP) Publishing, 2006) Bodo, E.; Yurtsever, M.; Gianturco, F. A.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129
    We present post Hartree-Fock calculations of the potential energy surfaces (PESs) for the ground electronic states of the three alkali dimer ions Li-2(+), Na-2(+), and K-2(+) interacting with neutral helium. The calculations were carried out for the frozen molecular equilibrium geometries and for an extensive range of the remaining two Jacobi coordinates, R and theta, for which a total of about 1000 points is generated for each surface. The corresponding raw data were then fitted numerically to produce analytic expressions for the three PESs, which were in turn employed to evaluate the bound states of the three trimers for their J=0 configurations: The final spatial features of such bound states are also discussed in detail. The possible behavior of additional systems with more helium atoms surrounding the ionic dopants is gleaned from further calculations on the structural stability of aggregates with up to six He atoms. The validity of a sum-of-potential approximation to yield realistic total energies of the smaller cluster is briefly discussed vis-a-vis the results from many-body calculations.