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Öğe Analysis of Acoustic Signals of Footsteps from the Piezoelectric Sensor(2023) Çiftçi, Bilge Çiğdem; Kaya, Gamze; Kurt, MustafaSome materials can change their electrical polarization under the influence of a mechanical stress due to the piezoelectric effect. This stress-induced change in polarization produces a potential difference across the material. For this reason, the piezoelectric material generates an electrical signal when it is subjected to a pressure from acoustic energy. In this study, analysis of acoustic signals of footsteps from the piezoe-lectric sensor, especially for human footsteps, have been studied by considering the analytical relationship between the electrical signal generated from the sensor and the acoustic signal that provides the effect. We analyzed the acoustic signal data by assuming that the electrical output voltage of the piezoelectric sensor completely coincides with the frequency of the acoustic signals. The original signal was pre-processed using filtering systems and analyzed by the fast Fourier transform and power spectral density methods to extract descriptive spectral features of the signal. This preliminary study proposed a method as a sensor based piezoelectric security system to detect the acoustic signals that can indicate possible dangers to the safety of people or property. The source of the acoustic signal can be determined by matching it with the existing database using machine learning algorithms like face recognition systems for future goals.Öğe Control of Femtosecond Filamentation by Revivals of Nonadiabatic Molecular Alignment(IEEE, 2017) Kaya, Necati; Kaya, Gamze; Boran, Yakup; Kolomenskii, Alexandre A.; Amani, Mahmood; Schuessler, Hans A.[Anstract Not Available]Öğe Control of laser-induced nonadiabatic molecular alignment in dissipative media(Tubitak Scientific & Technological Research Council Turkey, 2018) Kaya, GamzeLaser-induced nonadiabatic alignment in nitrogen and mixtures of nitrogen with Ar gas was investigated using the ultrafast optical Kerr effect in the collinear pump-probe setup. We find that dissipative media produce desired alignment characteristics in distinct manners to decoherence and to population relaxation. The results show that the intense laser alignment can be used as a control tool of molecular dynamics in dissipative environments.Öğe Controlled formation of femtosecond laser-induced filaments in water(Springer, 2020) Kaya, GamzeControlled formation of femtosecond laser-induced filaments in water was introduced and demonstrated experimentally, based on the transverse spatial phase change in the initial femtosecond laser pulse. Single or multi-filament formations were controlled and organized by switching on and off through a computer-controlled transverse spatial phase mask on a liquid crystal Spatial Light Modulator (SLM). We introduced a pi phase step on SLM, which distributed laser intensity non-uniformly and in certain locations peak intensity exceeded the critical threshold, and filaments were formed in the peaks of the intensity. The setup with controllable phase shift on SLM may have great flexibility and convenience in controls of filament formation.Öğe Design of a New Ultra-sensitive Methane Sensor Based On Optical Approaches that Utilize Laser Diodes(Old City Publishing, 2021) Keskin, Alpgiray; Kaya, Necati; Kaya, GamzeWe design a new ultra-sensitive optical methane sensor by combining such optical approaches as appropriate use of absorption bands of methane by HITRAN database in the near-infrared (NIR) region, effective absorption path length in circular multi-pass optical cell, a wavelength modulation, and noise suppression with dual beam configuration. The design offers a compact and portable optical sensor for methane gas measurements in real time and high sensitivity. In the design, one can select different laser diode source to expand the selectivity labels for the interest many other trace gases. This is inexpensive and simpler experimental design without complexity of laser frequency locking and phase stabilization. It can find wide applications in many fields such as physical, environmental, and atmospheric research as well as physics, analytical chemistry, biology, medical diagnosis and process technology.Öğe Diffractive multifocal lenses by computer-generated holograms(SPIE (Society of Photo-optical Instrumentation Engineers), 2021) Kaya, Necati; Kaya, Gamze; Strohaber, James; Zhou, Junfeng; Kolomenskii, Alexandre A.; Schuessler, Hans A.The dynamics of rotational wave packets of laser-aligned linear molecules were studied with femtosecond laser-driven strong-field ionization (SFI). The dynamics were observed as a function of the delay between a femtosecond probe pulse and a linearly polarized aligning pump pulse. The induced nonadiabatic molecular alignment was directly monitored by the total SFI yield. The measured revival signatures were compared to the calculated degree of molecular alignment taking into account the effects of electronic structure and symmetry of the molecules. By fitting the calculated alignment parameter to the measured experimental data, we also determined the molecular rotational constants of N2, CO, O2, and C2H2 gas molecules.Öğe Diffractive multifocal lenses by computer-generated holograms(SPIE, 2021) Kaya, Necati; Kaya, Gamze; Strohaber, James; Zhou, Junfeng; Kolomenskii, Alexandre A.; Schuessler, Hans A.Diffractive lenses are optical elements commonly used in many applications owing to their simple and compact design. A multifocal diffractive lens enables the simultaneous focusing of an incident laser beam on several positions along the optical axis. The distances between the focal points and the energy densities in the foci can be changed by varying grating parameters, i.e., the modulation depth and the grating period. This requires grating structures that have to be fabricated for each targeted optical arrangement. Even though some methods for designing diffractive lenses with variable focal positions are available, they do not provide real-time control over the energy distribution and focal locations of the foci. We aimed to develop coaxial or multiaxial multifocus diffractive lenses with computer-generated holograms. The focal distances and energy densities in the foci can be dynamically controlled by programmable holographic codes. The generated holographic lenses can be used for imaging with dynamic repositioning of created images fast and easily. Such a holographic diffractive lens can withstand a highly intense laser radiation, so it can be used in nonlinear optics experiments and can be employed for high harmonic generation, pump-probe experiments, optical tweezers, filamentation, and other applications. © 2021 Society of Photo-Optical Instrumentation Engineers (SPIE).Öğe Dynamic Control of Airy Beams Using Real-Time Phase-Amplitude Encoding on a Spatial Light Modulator(Mdpi, 2024) Keskin, Alpgiray; Kaya, Gamze; Kaya, Necati; Strohaber, James; Kolomenskii, Alexandre A.; Schuessler, Hans A.Airy beams showing curved paths have found extensive applications in fields such as optical trapping, biomedical analysis, and material processing. Despite their utility, dynamic control of Airy beams poses a significant challenge. This work investigates the experimental realization of dynamic steering of Airy beams by utilizing computer-generated holograms with phase-amplitude encoding on a phase-only spatial light modulator (SLM). We successfully generated and controlled Airy beams by imposing dynamic phase masks that manipulated both the phase and amplitude of the field, which sets our approach apart from conventional methods with only phase manipulation. By directly encoding in situ such a hologram and transferring it to an SLM, we are able to control the initial position and rotational orientation of Airy beams without relying on mechanical movement or traditional optical setups involving lenses and apertures. Generating Airy beams in any initial position and rotational direction is anticipated to significantly impact applications such as optical trapping, optical communication, and biomedical imaging by providing a flexible platform for dynamic Airy beam manipulation.Öğe Field-free molecular alignment of carbon dioxide molecules measured with above-threshold ionization yields(Canadian Science Publishing, 2020) Kaya, GamzeWe present measurements of above-threshold ionization (ATI) of CO2 in a pump-probe experiment where the pump pulse creates a rotational wave packet and the linearly polarized probe pulse generates the ATI spectrum as a function of the pump-probe delay time, which sweeps over the revival time of field-free alignment and its quarter fractions. The observed alignment signals, which are the electron yields of ATI by a probe pulse as a function of a delay between the pump and probe pulse, are compared with the calculated alignment parameter << cos(2) theta >>. The results are explained by nuclear spin statistics and the wave packet evolution of the CO2 molecule in terms of the highest occupied molecular orbital.Öğe In-situ measurement of aligning intensity and rotational temperature in field-free molecular alignment via white light generation(Elsevier GmbH, 2021) Kaya, Necati; Kaya, Gamze; Boran, Yakup; Kolomenski, Alexandre; Schuessler, Hans A.We determine the aligning intensity and rotational temperature in field-free molecular alignment measured via white light signal. Relying on temporal dependencies of the time-resolved alignment signature obtained via white-light generation by femtosecond laser pulses in N2 molecules, we derived the aligning pump intensity and rotational temperature using the occurrence times of the local alignment and anti-alignment around the half and full revivals. Results proved that the aligning intensity and rotational temperature can be obtained simultaneously by any two reverse local alignment extrema in the evolution of field-free molecular alignment.Öğe Prevalence, antibiotic and pulsed-field gel electrophoresis patterns of Staphylococcus aureus small-colony variants in cystic fibrosis patients(SEAMEO TROPMED Network, 2016) Pakasticali, Nagehan; Kaya, Gamze; Senel, Unal; Kipritci, Oner; Tamay, Zeynep; Guler, Nermin; Nazik, HasanStaphylococcus aureus is the most common pathogen isolated from respiratory tract samples in cystic fibrosis (CF) cases. Rate of infection with S. aureus small-colony variants (SCVs) also is increasing in CF patients. In this study, we aimed to determine the prevalence, antibiotic susceptibility and genotypic property of S. aureus SCVs in respiratory tract samples of CF patients admitted to Istanbul Faculty of Medicine Hospital, Turkey. Among 305 respiratory tract samples from 84 CF patients, normal S. aureus isolates were present in 71% of the CF patients and S. aureus SCVs in 21%. The highest antibiotic resistance was against penicillin (82%) followed by clarithromycin (21%) in S. aureus SCVs, while resistance to levofloxacin was low (2%) in normal S. aureus isolates but was 16% in S. aureus SCVs. No mecA and mecC were detected. The S. aureus strains constituted 24 different genotypes based on pulsed field gel-electrophoresis assay. The possible existence of S. aureus SCVs that are more resistant to antibiotis than normal S. aureus should be taken into considerstion when treating CF patients for this pernicious bacterial infection. © 2017, SEAMEO TROPMED Network. All Rights Reserved.Öğe PREVALENCE, ANTIBIOTIC AND PULSED-FIELD GEL ELECTROPHORESIS PATTERNS OF STAPHYLOCOCCUS AUREUS SMALL-COLONY VARIANTS IN CYSTIC FIBROSIS PATIENTS(Southeast Asian Ministers Educ Organization, 2016) Pakasticali, Nagehan; Kaya, Gamze; Senel, Unal; Kipritci, Oner; Tamay, Zeynep; Guler, Nermin; Nazik, HasanStaphylococcus aureus is the most common pathogen isolated from respiratory tract samples in cystic fibrosis (CF) cases. Rate of infection with S. aureus small-colony variants (SCVs) also is increasing in CF patients. In this study, we aimed to determine the prevalence, antibiotic susceptibility and genotypic property of S. aureus SCVs in respiratory tract samples of CF patients admitted to Istanbul Faculty of Medicine Hospital, Turkey. Among 305 respiratory tract samples from 84 CF patients, normal S. aureus isolates were present in 71% of the CF patients and S. aureus SCVs in 21%. The highest antibiotic resistance was against penicillin (82%) followed by clarithromycin (21%) in S. aureus SCVs, while resistance to levofloxacin was low (2%) in normal S. aureus isolates but was 16% in S. aureus SCVs. No mecA and mecC were detected. The S. aureus strains constituted 24 different genotypes based on pulsed field gel-electrophoresis assay. The possible existence of S. aureus SCVs that are more resistant to antibiotis than normal S. aureus should be taken into considerstion when treating CF patients for this pernicious bacterial infection.Öğe Türkiye-Afganistan Siyasi İlişkileri (1921- 2021): Yüzyılı Aşan Özel, Siyasi, Güvenlik ve Kültürel Bağlar(İstanbul Medeniyet Üniversitesi, 2020) Kaya, Gamze; Elik, SüleymanAfganistan, tarih boyunca imparatorlukların battığı ve büyük güçlerin hezimete uğratıldığı bir coğrafyadır. Son iki yüzyılda da Büyük Britanya, Sovyetler Birliği ve Amerika aynı kaderi yaşamıştır. Türkiye’nin Afganistan ile yüzyılı aşan ilişkisi büyük güçlerin istilalarına rağmen çok özel bir düzlemde devam etmiştir. Pakistan ile Afganistan, Türkiye’nin Yeniden Asya Girişimi’nin Orta Asya Türk coğrafyasının stratejik derinliği ve parçası olarak düşünülür. Çin, Rusya ve Hindistan arasında kilit bir jeopolitik öneme sahip olan iki Müslüman ülke Kuşak Yol Projesi’nin ana geçiş güzergâhı olan Kalpgah’la bütünleşmektedir. Türkiye’nin dini ve kültürel bağlarından beslenen yumuşak güç unsurları Afgan toplumunun temel ihtiyaçları olan eğitim, sağlık ve alt yapı hizmetlerini sunma imkânı sağlamaktadır. Bu durum Taliban’ın Kabil’de yönetimi almasına rağmen devam etmektedir. Çalışmada Türkiye’nin Afganistan’a hangi bağlamda yaklaştığı, tarihten günümüze kadar Afganistan'daki iç dinamiklerin ilişkilere etkisi, Soğuk Savaş ve sonrası bölgesel ve küresel meselelerin iki ülke ilişkilerine nasıl yansıdığı sorularına cevap aranmıştır. Çalışmanın temel tespiti yüzyılı aşan tarihi süreç içerisinde her iki ülkenin iç ve dış konjonktüründeki değişimlere rağmen ilişkilerinin kopmadığı, kendine has istisnai ve her zaman özel bir ilişki türünün var olduğudur. Diğer tespit ise jeopolitik rekabette Türkiye'ye stratejik fayda sağlama potansiyeline sahip olduğudur. Türkiye Afganistan ilişkilerinin tarihi gelişimi ve gelecekte ne yönde şekillenebileceği ortaya konulmaya çalışılmıştır
