Researcher: Tanısalı, Gökhan
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Tanısalı, Gökhan
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Publication Metadata only 21 fs Cr:LiSAF laser mode locked with a single-walled carbon nanotube saturable absorber(Optical Soc Amer, 2019) Bae, Ji Eun; Rotermund, Fabian; Demirbaş, Ümit; N/A; N/A; N/A; Department of Physics; Tanısalı, Gökhan; Toker, Işınsu Baylam; Taşçı, Mısra; Sennaroğlu, Alphan; PhD Student; PhD Student; Undergraduate Student; Faculty Member; Department of Physics; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; School of Medicine; College of Sciences; N/A; N/A; N/A; 23851We report the shortest femtosecond pulses directly generated from a solid-state laser that is mode locked by using a single-walled carbon nanotube saturable absorber (SWCNT-SA). In the experiments, we used a 660 nm diode-pumped, low-threshold extended-cavity Cr:LiSAF laser operating around 850 nm with a repetition rate of 47.9 MHz. The SWCNT-SA mode-locked Cr:LiSAF laser produced 21 fs pulses with a time-bandwidth product of 0.56 by using only 210 mW of pump power. Pump-probe spectroscopy measurements showed that the SWCNT-SA exhibited saturable absorption with slow and fast decay times of 2.7 ps and 0.4 ps. The single-pass modulation depth and saturation fluence of the SWCNT-SA were further determined as 0.3% and 45 mu J/cm(2) at the pump wavelength of 850 nm.Publication Metadata only Generation of 23-fs pulses at 850 nm from a carbon nanotube mode-locked solid-state laser(Optical Society of America (OSA), 2019) Bae, Ji Eun; Rotermund, Fabian; Demirbaş, Ümit; N/A; N/A; N/A; Department of Physics; Tanısalı, Gökhan; Toker, Işınsu Baylam; Canbaz, Ferda; Sennaroğlu, Alphan; PhD Student; PhD Student; PhD Student; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 23851We report, to the best of our knowledge, direct generation of the shortest pulses from a single-walled carbon nanotube mode-locked solid-state laser with a Cr:LiSAF gain medium, yielding 23-fs, nearly transform-limited pulses at 850 nm.Publication Open Access Near-physiological-temperature serial crystallography reveals conformations of SARS-CoV-2 main protease active site for improved drug repurposing(Elsevier, 2021) Durdağı, Serdar; Doğan, Berna; Avşar, Timuçin; Erol, İsmail; Çalış, Şeyma; Orhan, Müge D.; Aksoydan, Busecan; Şahin, Kader; Oktay, Lalehan; Tolu, İlayda; Olkan, Alpsu; Erdemoğlu, Ece; Yefanov, Oleksandr M.; Dao, E. Han; Hayes, Brandon; Liang, Mengning; Seaberg, Matthew H.; Hunter, Mark S.; Batyuk, Alex; Mariani, Valerio; Su, Zhen; Poitevin, Frederic; Yoon, Chun Hong; Kupitz, Christopher; Sierra, Raymond G.; Snell, Edward H.; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; N/A; Demirci, Hasan; Dağ, Çağdaş; Büyükdağ, Cengizhan; Ertem, Fatma Betül; Yıldırım, Günseli; Destan, Ebru; Güven, Ömür; Ayan, Esra; Yüksel, Büşra; Göcenler, Oktay; Can, Özgür; Özabrahamyan, Serena; Tanısalı, Gökhan; Faculty Member; Faculty Member; Undergraduate Student; PhD Student; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Koç Üniversitesi İş Bankası Enfeksiyon Hastalıkları Uygulama ve Araştırma Merkezi (EHAM) / Koç University İşbank Center for Infectious Diseases (KU-IS CID); College of Sciences; Graduate School of Sciences and Engineering; School of Nursing; 307350; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/AThe COVID-19 pandemic has resulted in 198 million reported infections and more than 4 million deaths as of July 2021 (covid19.who.int). Research to identify effective therapies for COVID-19 includes: (1) designing a vaccine as future protection; (2) de novo drug discovery; and (3) identifying existing drugs to repurpose them as effective and immediate treatments. To assist in drug repurposing and design, we determine two apo structures of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease at ambient temperature by serial femtosecond X-ray crystallography. We employ detailed molecular simulations of selected known main protease inhibitors with the structures and compare binding modes and energies. The combined structural and molecular modeling studies not only reveal the dynamics of small molecules targeting the main protease but also provide invaluable opportunities for drug repurposing and structure-based drug design strategies against SARS-CoV-2.Publication Open Access Effectiveness of different types of masks in aerosol dispersion in SARS-CoV-2 infection(Elsevier, 2021) Sözak, A.; Bulut, A. S.; Sander, T. Z.; Department of Molecular Biology and Genetics; Department of Industrial Engineering; N/A; Tanısalı, Gökhan; Doğan, Özlem; Dağ, Çağdaş; Gönen, Mehmet; Can, Füsun; Demirci, Hasan; Ergönül, Önder; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Industrial Engineering; Koç Üniversitesi İş Bankası Enfeksiyon Hastalıkları Uygulama ve Araştırma Merkezi (EHAM) / Koç University İşbank Center for Infectious Diseases (KU-IS CID); College of Sciences; College of Engineering; Graduate School of Sciences and Engineering; School of Medicine; N/A; 170418; N/A; 237468; 103165; 307350; 110398Objective: to compare the effectiveness of different mask types in limiting the dispersal of coughed air. Method: the Schlieren method with a single curved mirror was used in this study. Coughed air has a slightly higher temperature than ambient air, which generates a refractive index gradient. A curved mirror with a radius of curvature of 10 m and a diameter of 60 cm was used. The spread of the cough wavefront was investigated among five subjects wearing: (1) no mask; (2) a single surgical mask; (3) a double surgical mask; (4) a cloth mask; (5) a valveless N95 mask; and (6) a valved N95 mask. Results: all mask types reduced the size of the contaminated region significantly. The percentage reduction in the cross-sectional area of the contaminated region for the same mask types on different subjects revealed by normalized data suggests that the fit of a mask plays an important role. Conclusions: no significant difference in the spread of coughed air was found between the use of a single surgical mask or a double surgical mask. Cloth masks may be effective, depending on the quality of the cloth. Valved N95 masks exclusively protect the user. The fit of a mask is an important factor to minimize the contaminated region.