Browsing by Subject "Microscopy"

Now showing 1 - 11 of 11

Open Access
A transformer-based real-time focus detection technique for wide-field interferometric microscopy
(IEEE - Institute of Electrical and Electronics Engineers, 2023-08-28) Polat, Can; Güngör, A.; Yorulmaz, M.; Kızılelma, B.; Çukur, Tolga
Wide-field interferometric microscopy (WIM) has been utilized for visualization of individual biological nanoparticles with high sensitivity. However, the image quality is highly affected by the focusing of the image. Hence, focus detection has been an active research field within the scope of imaging and microscopy. To tackle this issue, we propose a novel convolution and transformer based deep learning technique to detect focus in WIM. The method is compared to other focus detecton techniques and is able to obtain higher precision with less number of parameters. Furthermore, the model achieves real-time focus detection thanks to its low inference time.
Open Access
Air-guided photonic-crystal-fiber pulse-compression delivery of multimegawatt femtosecond laser output for nonlinear-optical imaging and neurosurgery
(AIP Publishing LLC, 2012-03-06) Lanin, A.; Fedotov, I. V.; Sidorov Biryukov, D. S.; Doronina Amitonova, L. V.; Ivashkina, O. I.; Zots, M. A.; Sun, C. K.; Ilday, F. O.; Fedotov, A. B.; Anokhin, K. V.; Zheltikov, A. M.
Large-core hollow photonic- crystal fibers (PCFs) are shown to enable a fiber-format air-guided delivery of ultrashort infrared laser pulses for neurosurgery and nonlinear-optical imaging. With an appropriate dispersion precompensation, an anomalously dispersive 15-mu m-core hollow PCF compresses 510-fs, 1070-nm light pulses to a pulse width of about 110 fs, providing a peak power in excess of 5 MW. The compressed PCF output is employed to induce a local photodisruption of corpus callosum tissues in mouse brain and is used to generate the third harmonic in brain tissues, which is captured by the PCF and delivered to a detector through the PCF cladding.
Open Access
A color and shape based algorithm for segmentation of white blood cells in peripheral blood and bone marrow images
(John Wiley & Sons, Inc., 2014) Arslan, S.; Ozyurek, E.; Gunduz Demir, C.
Computer-based imaging systems are becoming important tools for quantitative assessment of peripheral blood and bone marrow samples to help experts diagnose blood disorders such as acute leukemia. These systems generally initiate a segmentation stage where white blood cells are separated from the background and other nonsalient objects. As the success of such imaging systems mainly depends on the accuracy of this stage, studies attach great importance for developing accurate segmentation algorithms. Although previous studies give promising results for segmentation of sparsely distributed normal white blood cells, only a few of them focus on segmenting touching and overlapping cell clusters, which is usually the case when leukemic cells are present. In this article, we present a new algorithm for segmentation of both normal and leukemic cells in peripheral blood and bone marrow images. In this algorithm, we propose to model color and shape characteristics of white blood cells by defining two transformations and introduce an efficient use of these transformations in a marker-controlled watershed algorithm. Particularly, these domain specific characteristics are used to identify markers and define the marking function of the watershed algorithm as well as to eliminate false white blood cells in a postprocessing step. Working on 650 white blood cells in peripheral blood and bone marrow images, our experiments reveal that the proposed algorithm improves the segmentation performance compared with its counterparts, leading to high accuracies for both sparsely distributed normal white blood cells and dense leukemic cell clusters. © 2014 International Society for Advancement of Cytometry.
Open Access
Evidence for Nonradiative Energy Transfer in Graphene-Oxide-Based Hybrid Structures
(American Chemical Society, 2013-11-13) Yeltik, A.; Kucukayan-Dogu, G.; Guzelturk, B.; Fardindoost, S.; Kelestemur, Y.; Demir, Hilmi Volkan
Solution processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) are promising materials for potential optoelectronic applications. To date, efficiency of the excitation energy transfer into GO and RGO thin layers has not been investigated in terms of donor-acceptor separation distance. In the present work, we study nonradiative energy transfer (NRET) from CdSe/CdS quantum dots into single and/or double layer GO or RGO using time-resolved fluorescence spectroscopy. We observe shorter lifetimes as the separation distance between the QDs and GO or RGO decreases. In accordance with these lifetimes, the rates reveal the presence of two different mechanisms dominating the NRET. Here we show that excitonic NRET is predominant at longer intervals while both excitonic and nonexcitonic NRET exist at shorter distances. In addition, we find the NRET rate behavior to be strongly dependent on the reduction degree of the GO-based layers. We obtain high NRET efficiency levels of similar to 97 and similar to 89% for the closest separation of the QD-RGO pair and the QD-GO pair, respectively. These results indicate that strong NRET from QDs into thin layer GO and RGO makes these solution-processable thin films promising candidates for light harvesting and detection systems.
Open Access
Fabrication of 100 nm pMOSFETS With Hybrid AFW / STM lithography
(IEEE, 1997-06) Soh, H. T.; Wilder, K.; Atalar, Abdullah; Quate, C. F.
Scanning probe lithography (SPL) is an emerging area of research in which the scanning tunneling microscope (STM) or atomic force microscope (AFM) is used to pattern nanometer-scale features. Four factors will dictate the viability of SPL as a patterning technology for the semiconductor industry: 1) resolution, 2) alignment accuracy, 3) reliability, and 4) throughput. We present a new SPL technique-a hybrid between the AFM and STMto address these issues. We demonstrate its capabilities and its compatibility with semiconductor processing by fabricating a pMOSFET with an effective channel length (L,ff) of 100 nm and report the device characteristics.
Open Access
Hybridization of fano and vibrational resonances in surface-enhanced infrared absorption spectroscopy of streptavidin monolayers on metamaterial substrates
(2014) Alici, K. B.
We present spectral hybridization of organic and inorganic resonant materials and related bio-sensing mechanism. We utilized a bound protein (streptavidin) and a Fano-resonant metasurface to illustrate the concept. The technique allows us to investigate the vibrational modes of the streptavidin and how they couple to the underlying metasurface. This optical, label-free, nonperturbative technique is supported by a coupled mode-theory analysis that provides information on the structure and orientation of bound proteins. We can also simultaneously monitor the binding of analytes to the surface through monitoring the shift of the metasurface resonance. All of this data opens up interesting opportunities for applications in biosensing, molecular electronics and proteomics. © 2014 IEEE.
Open Access
Intracavity optical trapping of microscopic particles in a ring-cavity fiber laser
(Nature Publishing Group, 2019-06) Kalantarifard, Fatemeh; Elahi, Parviz; Makey, Ghaith; İlday, F. Ömer; Volpe, Giovanni; Maragò, O. M.
Standard optical tweezers rely on optical forces arising when a focused laser beam interacts with a microscopic particle: scattering forces, pushing the particle along the beam direction, and gradient forces, attracting it towards the high-intensity focal spot. Importantly, the incoming laser beam is not affected by the particle position because the particle is outside the laser cavity. Here, we demonstrate that intracavity nonlinear feedback forces emerge when the particle is placed inside the optical cavity, resulting in orders-of-magnitude higher confinement along the three axes per unit laser intensity on the sample. This scheme allows trapping at very low numerical apertures and reduces the laser intensity to which the particle is exposed by two orders of magnitude compared to a standard 3D optical tweezers. These results are highly relevant for many applications requiring manipulation of samples that are subject to photodamage, such as in biophysics and nanosciences.
Open Access
Penetration depth of the scanning acoustic microscope
(IEEE, 1985-03) Atalar, Abdullah
A definition for the penetration depth of the scanning reflection acoustic microscope is given. With this definition it is possible to calculate the penetration depth of a given lens geometry for a given material. The penetration depth depends on the elastic parameters of the object, the signal-to-noise ratio, and the operation frequency of the acoustic microscope. Calculations show that for high-impedance materials, the penetration depthis limited by the wavelength of the surface waves and hence by frequency. For low-impedance materials the opening angle of the lens can be properly selected to make the longitudinal or shear wave penetration dominant, effectively increasing the penetration well above the wavelength limit of the surface wave.
Open Access
Roadmap on wavefront shaping and deep imaging in complex media
(Institute of Physics, 2022-10) Gigan, Sylvain; Katz, Ori; De Aguiar, Hilton B.; Andresen, Esben Ravn; Aubry, Alexandre; Bertolotti, Jacopo; Bossy, Emmanuel; Bouchet, Dorian; Brake, Joshua; Brasselet, Sophie; Bromberg, Yaron; Cao, Hui; Chaigne, Thomas; Cheng, Zhongtao; Choi, Wonshik; Čižmár, Tomáš; Cui, Meng; Curtis, Vincent R.; Defienne, Hugo; Hofer, Matthias; Horisaki, Ryoichi; Horstmeyer, Roarke; Ji, Na; LaViolette, Aaron K.; Mertz, Jerome; Moser, Christophe; Mosk, Allard P; Pégard, Nicolas C; Piestun, Rafael; Popoff, Sebastien; Phillips, David B.; Psaltis, Demetri; Rahmani, Babak; Rigneault, Hervé; Rotter, Stefan; Tian, Lei; Vellekoop, Ivo M.; Waller, Laura; Wang, Lihong; Weber, Timothy; Xiao, Sheng; Xu, Chris; Yamilov, Alexey; Yang, Changhuei; Yılmaz, Hasan
The last decade has seen the development of a wide set of tools, such as wavefront shaping, computational or fundamental methods, that allow us to understand and control light propagation in a complex medium, such as biological tissues or multimode fibers. A vibrant and diverse community is now working in this field, which has revolutionized the prospect of diffraction-limited imaging at depth in tissues. This roadmap highlights several key aspects of this fast developing field, and some of the challenges and opportunities ahead. © 2022 The Author(s). Published by IOP Publishing Ltd.
Open Access
Room temperature scanning Hall probe microscopy using GaAs/AlGaAs and Bi micro-hall probes
(Elsevier Science B.V., 2002) Sandhu, A.; Masuda, H.; Oral, A.; Yamada, A.; Konagai, M.
A room temperature scanning Hall probe microscope system utilizing GaAs/AlGaAs and bismuth micro-Hall probes was used for magnetic imaging of ferromagnetic domain structures on the surfaces of crystalline thin film garnets and permanent magnets. The Bi micro-Hall probes had dimensions ranging between 0.25 and 2.8μm2 and were fabricated using a combination of optical lithography and focused ion beam milling. The use of bismuth was found to overcome surface depletion effects associated with semiconducting micro-Hall probes. Our experiments demonstrated that Bi is a practical choice of material for fabricating sub-micron sized Hall sensors.
Open Access
Toxicity of lanthanum oxide (La2O3) nanoparticles in aquatic environments
(Royal Society of Chemistry, 2015) Balusamy, B.; Taştan, B. E.; Ergen, S. F.; Uyar, Tamer; Tekinay, T.
This study demonstrates the acute toxicity of lanthanum oxide nanoparticles (La2O3 NP) on two sentinel aquatic species, fresh-water microalgae Chlorella sp. and the crustacean Daphnia magna. The morphology, size and charge of the nanoparticles were systematically studied. The algal growth inhibition assay confirmed absence of toxic effects of La2O3 NP on Chlorella sp., even at higher concentration (1000 mg L-1) after 72 h exposure. Similarly, no significant toxic effects were observed on D. magna at concentrations of 250 mg L-1 or less, and considerable toxic effects were noted in higher concentrations (effective concentration [EC50] 500 mg L-1; lethal dose [LD50] 1000 mg L-1). In addition, attachment of La2O3 NP on aquatic species was demonstrated using microscopy analysis. This study proved to be beneficial in understanding acute toxicity in order to provide environmental protection as part of risk assessment strategies.