The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Myung-hwan Whangbo - One of the best experts on this subject based on the ideXlab platform.
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Study of scanning tunneling microscopy images and probable relaxations of the SrTiO3(100) surface by electronic structure calculations
Surface Science, 1997Co-Authors: Dong Kyun Seo, J. Ren, K. Perdue, Myung-hwan WhangboAbstract:Abstract Partial electron Density Plots were calculated for a model SrTiO 3 (100) surface with √5 × √5 ordered oxygen vacancy to examine why the bright spots of the scanning tunneling microscopy (STM) images of SrTiO 3 (100) observed in ultrahigh vacuum (UHV) correspond to the oxygen vacancy sites. Possible dependence of the image on the polarity and magnitude of the bias voltage was also discussed on the basis of partial electron Density Plot calculations. Our study strongly suggests that the UHV STM imaging involves the lowest-lying d-block level of every two Ti 3+ centers adjacent to an oxygen vacancy, the tip-sample distance involved in the UHV STM experiments is substantially larger than that involved in typical ambient-condition STM imaging, and the Ti 4+ and Ti 3+ sites of SrTiO 3 (100) are reconstructed.
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Study of the origin of superstructure patterns in the scanning tunneling images of perylene-3,4,9,10-tetracarboxylic-dianhydride on graphite by electronic structure calculations
Surface Science, 1997Co-Authors: Dong Kyun Seo, J. Ren, Myung-hwan WhangboAbstract:Partial electron Density Plots were calculated for various arrangements of perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) molecules on graphite to understand why scanning tunneling microscopy (STM) images of PTCDA on graphite exhibit superstructure contrast variations. In agreement with experiment, the contrast of the partial electron Density Plot depends strongly on the orientation and position of PTCDA on graphite. This observation originates from the fact that the overlap between the orbitals of the adsorbate and substrate is strongly affected by their relative arrangement. The HOMO or LUMO Density of an adsorbate molecule can be inadequate in interpreting STM images of adsorbate molecules.
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Interpreting STM and AFM Images
Advanced Materials, 1994Co-Authors: Sergei Magonov, Myung-hwan WhangboAbstract:The necessity for a rational interpretation of scanning tunneling microscopy (STM) and atomic force microscopy (AFM) images is demonstrated by our recent STM/AFM studies of layered transition-metal chalcogenides, layered transition-metal halides, organic conducting salts, and alkanes adsorbed on graphite. To a first approximation, the STM image of a surface is described by the partial Density Plot ρ(r0, ef) of the surface, and the AFM image by the total Density Plot ρ(r0). The contribution of an atom to the ρ(r0, ef) Plot increases with decreasing distance to the tip and with increasing electronic contribution to the energy levels around the Fermi level. Since the atoms that protrude more do not necessarily make greater contributions to the energy levels near the Fermi level, it is difficult to achieve a rational interpretation of STM images unless appropriate partial Density Plots are calculated. For a variety of layered compounds, the STM and AFM images are well simulated by the ρ(r0, ef) and ρ(r0) Plots calculated by the extended Huckel tight-binding electronic band structure method. Partial and total Density Plot calculations provide not only a basis for a rational interpretation of ideal STM and AFM images but also a step toward systematic studies of how tip–surface interactions and tunneling conditions affect the images.
A.-f. A. Mentis - One of the best experts on this subject based on the ideXlab platform.
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Antiviral susceptibility profile of influenza A viruses; keep an eye on immunocompromised patients under prolonged treatment
European Journal of Clinical Microbiology & Infectious Diseases, 2017Co-Authors: A. Kossyvakis, A Meijer, A.-f. A. Mentis, K. Tryfinopoulou, V. Pogka, A. Kalliaropoulos, E. Antalis, T. Lytras, S. Tsiodras, P. KarakitsosAbstract:There was an increase in severe and fatal influenza cases in Greece during the 2011–2015 post-pandemic period. To investigate causality, we determined neuraminidase (NA) inhibitor susceptibility and resistance-conferring NA and hemagglutinin (HA) mutations in circulating influenza type A viruses during the pandemic (2009–2010) and post-pandemic periods in Greece. One hundred thirty-four influenza A(H1N1)pdm09 and 95 influenza A(H3N2) viruses submitted to the National Influenza Reference Laboratory of Southern Greece were tested for susceptibility to oseltamivir and zanamivir. Antiviral resistance was assessed by neuraminidase sequence analysis, as well as the fluorescence-based 50 % inhibitory concentration (IC_50) method. Five influenza A(H1N1)pdm09 viruses (2.2 %) showed significantly reduced inhibition by oseltamivir (average IC_50 300.60nM vs. 1.19nM) by Gaussian kernel Density Plot analysis. These viruses were isolated from immunocompromised patients and harbored the H275Y oseltamivir resistance-conferring NA substitution. All A(H1N1)pdm09 viruses were zanamivir-susceptible, and all A(H3N2) viruses were susceptible to both drugs. Oseltamivir-resistant viruses did not form a distinct cluster by phylogenetic analysis. Permissive mutations were detected in immunogenic and non immunogenic NA regions of both oseltamivir- resistant and susceptible viruses in the post-pandemic seasons. Several amino acid substitutions in the HA1 domain of the HA gene of post-pandemic viruses were identified. This study indicated low resistance to NAIs among tested influenza viruses. Antiviral resistance emerged only in immunocompromised patients under long-term oseltamivir treatment. Sequential sample testing in this vulnerable group of patients is recommended to characterise resistance or reinfection and viral evolution.
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NAIPlot: An opensource web tool to visualize neuraminidase inhibitor (NAI) phenotypic susceptibility results using kernel Density Plots.
Antiviral Research, 2016Co-Authors: T. Lytras, A. Kossyvakis, A.-f. A. MentisAbstract:The results of neuraminidase inhibitor (NAI) enzyme inhibition assays are commonly expressed as 50% inhibitory concentration (IC50) fold-change values and presented graphically in box Plots (box-and-whisker Plots). An alternative and more informative type of graph is the kernel Density Plot, which we propose should be the preferred one for this purpose. In this paper we discuss the limitations of box Plots and the advantages of the kernel Density Plot, and we present NAIPlot, an opensource web application that allows convenient creation of Density Plots specifically for visualizing the results of NAI enzyme inhibition assays, as well as for general purposes.
A. Kossyvakis - One of the best experts on this subject based on the ideXlab platform.
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Antiviral susceptibility profile of influenza A viruses; keep an eye on immunocompromised patients under prolonged treatment
European Journal of Clinical Microbiology & Infectious Diseases, 2017Co-Authors: A. Kossyvakis, A Meijer, A.-f. A. Mentis, K. Tryfinopoulou, V. Pogka, A. Kalliaropoulos, E. Antalis, T. Lytras, S. Tsiodras, P. KarakitsosAbstract:There was an increase in severe and fatal influenza cases in Greece during the 2011–2015 post-pandemic period. To investigate causality, we determined neuraminidase (NA) inhibitor susceptibility and resistance-conferring NA and hemagglutinin (HA) mutations in circulating influenza type A viruses during the pandemic (2009–2010) and post-pandemic periods in Greece. One hundred thirty-four influenza A(H1N1)pdm09 and 95 influenza A(H3N2) viruses submitted to the National Influenza Reference Laboratory of Southern Greece were tested for susceptibility to oseltamivir and zanamivir. Antiviral resistance was assessed by neuraminidase sequence analysis, as well as the fluorescence-based 50 % inhibitory concentration (IC_50) method. Five influenza A(H1N1)pdm09 viruses (2.2 %) showed significantly reduced inhibition by oseltamivir (average IC_50 300.60nM vs. 1.19nM) by Gaussian kernel Density Plot analysis. These viruses were isolated from immunocompromised patients and harbored the H275Y oseltamivir resistance-conferring NA substitution. All A(H1N1)pdm09 viruses were zanamivir-susceptible, and all A(H3N2) viruses were susceptible to both drugs. Oseltamivir-resistant viruses did not form a distinct cluster by phylogenetic analysis. Permissive mutations were detected in immunogenic and non immunogenic NA regions of both oseltamivir- resistant and susceptible viruses in the post-pandemic seasons. Several amino acid substitutions in the HA1 domain of the HA gene of post-pandemic viruses were identified. This study indicated low resistance to NAIs among tested influenza viruses. Antiviral resistance emerged only in immunocompromised patients under long-term oseltamivir treatment. Sequential sample testing in this vulnerable group of patients is recommended to characterise resistance or reinfection and viral evolution.
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NAIPlot: An opensource web tool to visualize neuraminidase inhibitor (NAI) phenotypic susceptibility results using kernel Density Plots.
Antiviral Research, 2016Co-Authors: T. Lytras, A. Kossyvakis, A.-f. A. MentisAbstract:The results of neuraminidase inhibitor (NAI) enzyme inhibition assays are commonly expressed as 50% inhibitory concentration (IC50) fold-change values and presented graphically in box Plots (box-and-whisker Plots). An alternative and more informative type of graph is the kernel Density Plot, which we propose should be the preferred one for this purpose. In this paper we discuss the limitations of box Plots and the advantages of the kernel Density Plot, and we present NAIPlot, an opensource web application that allows convenient creation of Density Plots specifically for visualizing the results of NAI enzyme inhibition assays, as well as for general purposes.
T. Lytras - One of the best experts on this subject based on the ideXlab platform.
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Antiviral susceptibility profile of influenza A viruses; keep an eye on immunocompromised patients under prolonged treatment
European Journal of Clinical Microbiology & Infectious Diseases, 2017Co-Authors: A. Kossyvakis, A Meijer, A.-f. A. Mentis, K. Tryfinopoulou, V. Pogka, A. Kalliaropoulos, E. Antalis, T. Lytras, S. Tsiodras, P. KarakitsosAbstract:There was an increase in severe and fatal influenza cases in Greece during the 2011–2015 post-pandemic period. To investigate causality, we determined neuraminidase (NA) inhibitor susceptibility and resistance-conferring NA and hemagglutinin (HA) mutations in circulating influenza type A viruses during the pandemic (2009–2010) and post-pandemic periods in Greece. One hundred thirty-four influenza A(H1N1)pdm09 and 95 influenza A(H3N2) viruses submitted to the National Influenza Reference Laboratory of Southern Greece were tested for susceptibility to oseltamivir and zanamivir. Antiviral resistance was assessed by neuraminidase sequence analysis, as well as the fluorescence-based 50 % inhibitory concentration (IC_50) method. Five influenza A(H1N1)pdm09 viruses (2.2 %) showed significantly reduced inhibition by oseltamivir (average IC_50 300.60nM vs. 1.19nM) by Gaussian kernel Density Plot analysis. These viruses were isolated from immunocompromised patients and harbored the H275Y oseltamivir resistance-conferring NA substitution. All A(H1N1)pdm09 viruses were zanamivir-susceptible, and all A(H3N2) viruses were susceptible to both drugs. Oseltamivir-resistant viruses did not form a distinct cluster by phylogenetic analysis. Permissive mutations were detected in immunogenic and non immunogenic NA regions of both oseltamivir- resistant and susceptible viruses in the post-pandemic seasons. Several amino acid substitutions in the HA1 domain of the HA gene of post-pandemic viruses were identified. This study indicated low resistance to NAIs among tested influenza viruses. Antiviral resistance emerged only in immunocompromised patients under long-term oseltamivir treatment. Sequential sample testing in this vulnerable group of patients is recommended to characterise resistance or reinfection and viral evolution.
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NAIPlot: An opensource web tool to visualize neuraminidase inhibitor (NAI) phenotypic susceptibility results using kernel Density Plots.
Antiviral Research, 2016Co-Authors: T. Lytras, A. Kossyvakis, A.-f. A. MentisAbstract:The results of neuraminidase inhibitor (NAI) enzyme inhibition assays are commonly expressed as 50% inhibitory concentration (IC50) fold-change values and presented graphically in box Plots (box-and-whisker Plots). An alternative and more informative type of graph is the kernel Density Plot, which we propose should be the preferred one for this purpose. In this paper we discuss the limitations of box Plots and the advantages of the kernel Density Plot, and we present NAIPlot, an opensource web application that allows convenient creation of Density Plots specifically for visualizing the results of NAI enzyme inhibition assays, as well as for general purposes.
Jurandir Nadal - One of the best experts on this subject based on the ideXlab platform.
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Effects of maximal oxygen uptake test and prolonged cycle ergometer exercise on sway Density Plot of postural control
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009Co-Authors: Roger G. T. Mello, Liliam F. Oliveira, Jurandir NadalAbstract:This work aims at testing the influence of the maximal oxygen uptake test and prolonged cycle ergometer exercise on sway Density Plot (SDP) parameters of postural control. Sixteen healthy male subjects were submitted to stabilometric tests with eye open and closed, before and after two different exercises. The maximal oxygen uptake test caused decrease of the mean duration of peaks in SDP, decreasing the stability level, without modify the rates of central and muscular torque controls. Conversely, 60 min exercise increased the mean time interval between two consecutive peaks in SDP, thus decreasing the control rate but not changing the stability level. Visual privation had a greater effect on body sway than these exercises, which were applied to muscles that are not the main actuators in body sway control. Concluding, the changes in postural control are dependent on the intensity and duration of exercise.