Browsing by Subject "Light scattering"

Now showing 1 - 12 of 12

Open Access
Development of an experimental image processing tool and flow-cytometry based electromagnetic scattering analysis for medical diagnosis of red blood cell pathology
(2020-08) Göktaş, Polat
The morphological, biophysical and biochemical properties of biological cells are critical markers for many fields, including life sciences, medical diagnosis, etc. Label-free, high-throughput classification and detection of cellular information at the single-cell level are invaluable for medical diagnostics. In particular, an efficient algorithm for image analytics plays an important role in biomedical research and in vitro diagnostics with grow importance for healthcare. Morphological/biophysical alterations in single biological cells have been associated with hematologic diseases, such as sickle cell disease. Anemia, which has multiple causes, such as iron deficiency, chronic blood loss and hemolysis, is a prevalent health problem affecting an estimated two billion people or 30% of the world’s population. The ability to measure hemoglobin concentration in anemic patients continuously has significant potential to facilitate hemoglobin monitoring, improve the detection of acute anemia, and avoid the complications and expense. Currently, a major challenge in many clinical laboratories, quantification of cellular information at the single-cell level requires complex laboratory sample preparation and data analysis procedures. Here, we demonstrate that the combination of a novel incubation procedure with rapid gas exchange, image-based flow cytometry (IFC) and a computational cell morphology framework, based on the boundary integral equation method (with the use of Muller Boundary Integral Equation Method) is presented to improve the accuracy of classification of red blood cells (RBCs) subtypes (including normal, intermediate and sickled RBCs) as they appear in time under low oxygen. In this dissertation, the results of the following numerical simulations and experiments are presented: We have investigated the changes in time to follow the rate of sickling with IFC as cells undergo deoxygenation. We have proposed a new shape quantification feature criteria as a Sickle Index parameter obtained from a user-defined custom mask in the IFC data to provide better identification of “true” normal, intermediate and sickle cell region boundaries in IFC. Especially, the main merit of the study lies in showing for the first time that the light scattering analysis based on boundary shape structures is correlated with the measured side scattering (SSC-A) pattern realized by IFC to provide the refractive index distribution for each RBC subtypes. Moreover, we applied different ionic strengths and osmolarity conditions to control the ratio of Discocyte/Stomatocyte/Echinocyte (D/S/E) subtypes in murine RBCs. Analysis of samples were performed using conventional and image-based flow cytometry (FC). The predicted cellular information showed good agreement with the expected results of our experimental data extracted from bright-field and dark-field images in IFC. The rich information on the predicted scattering pattern makes our angle-resolved light scattering technique for the purpose of the automatic RBC morphological profile in conventional FC, and discover RBC subpopulation target areas for the label-free analysis of conventional FC data. With this approach, we are able to notably reduce the data analysis procedure to identify RBC subtypes from a cell population in a given experiment through IFC or conventional FC with an angle-resolved light scattering method. Our approach could lead to replacing current manual protocols in the clinical procedure to avoid complex laboratory processes, and manual gating analysis and fluorescent stains in light microscopy or FCs. This study shows that our method has the potential to be used robust and objective characterization, and follow-up care of anemia status, and to provide a rapid action for the conditions that would lead to chronic anemia condition causing to a reduced lifespan, organ damage or painful crisis, and will be useful for the evaluation of anti-sickling agents which are currently proposed or are in clinical trials.
Open Access
Effects of laser ablated silver nanoparticles on Lemna minor
(Elsevier, 2014) Üçüncü, E.; Özkan, A. D.; Kurşungöz, C.; Ülger, Z. E.; Ölmez, T. T.; Tekinay, T.; Ortaç, B.; Tunca E.
Open Access
Engineering particle trajectories in microfluidic flows using speckle light fields
(SPIE, 2014) Volpe, G.; Volpe, Giovanni; Gigan, S.
Optical tweezers have been widely used in physics, chemistry and biology to manipulate and trap microscopic and nanoscopic objects. Current optical trapping techniques rely on carefully engineered setups to manipulate nanoscopic and microscopic objects at the focus of a laser beam. Since the quality of the trapping is strongly dependent on the focus quality, these systems have to be very carefully aligned and optimized, thus limiting their practical applicability in complex environments. One major challenge for current optical manipulation techniques is the light scattering occurring in optically complex media, such as biological tissues, turbid liquids and rough surfaces, which give rise to apparently random light fields known as speckles. Here, we discuss an experimental implementation to perform optical manipulation based on speckles. In particular, we show how to take advantage of the statistical properties of speckle patterns in order to realize a setup based on a multimode optical fiber to perform basic optical manipulation tasks such as trapping, guiding and sorting. We anticipate that the simplicity of these "speckle optical tweezers" will greatly broaden the perspectives of optical manipulation for real-life applications. © 2014 SPIE.
Open Access
Enhanced light scattering with energy downshifting using 16 nm indium nitride nanoparticles for improved thin-film a-Si N-i-P solar cells
(Electrochemical Society Inc., 2015-05) Chowdhury F.I.; İslam, K.; Alkış, Sabri; Ortaç, Bülend; Alevli, Mustafa; Dietz, N.; Okyay, Ali Kemal; Nayfeh, A.
In this work the effect of Indium nitride (InN) nanoparticles (NPs) on the performance of a-Si: H solar cells has been investigated. The average Jsc of InN NPs coated cells was found 6.76 mA/cm2 which is 16.69% higher than the average Jsc of the reference cell which was 5.79 mA/cm2. Average efficiency of InN NPs coated cells showed 14.16% increase from 3.32% to 3.79%. Peak EQE has increased from 44.8% at 500 nm to 51.67% at 510 nm and peak IQE has increased from 51.70% at 510 nm to 68.38% at 500 nm for InN NPs coated cell. Further study shows that EQE change is larger between 510 nm-700 nm compared to IQE change indicting a surface scattering mechanism that reduces the reflectivity. However, between 400 nm-510 nm IQE change is larger than EQE change which indicates that energy downshifting mechanism is dominating. So overall performance enhancement can be attributed to the scattering and photoluminescence properties of InN NPs that enhances absorption inside a-Si: H solar cells. © The Electrochemical Society.
Open Access
Image-Based flow cytometry and angle-resolved light scattering to define the sickling process
(International Society for Advancement of Cytometry, 2019) Göktaş, Polat; Sukharevsky, I.; Larkin, S.; Kuypers, F.; Yalçın, Ö.; Ayhan, Altıntaş
Red blood cells (RBCs) from sickle cell patients exposed to a low oxygen tension reveal highly heterogeneous cell morphologies due to the polymerization of sickle hemoglobin (HbS). We show that angle‐resolved light scattering approach with the use of image‐based flow cytometry provides reliable quantitative data to define the change in morphology of large populations of RBCs from sickle cell patients when the cells are exposed for different times to low oxygen. We characterize the RBC morphological profile by means of a set of morphological and physical parameters, which includes cell shape, size, and orientation. These parameters define the cell as discocyte, sickle, elongated, as well as irregularly or abnormal RBC shaped cells, including echinocytes, holly‐leaf, and granular structures. In contrast to microscopy, quick assessment of large numbers of cells provides statistically relevant information of the dynamic process of RBC sickling in time. The use of this approach facilitates the understanding of the processes that define the propensity of sickle blood samples to change their shape, and the ensuing vaso‐occlusive events in the circulation of the patients. Moreover, it assists in the evaluation of treatments that include the use of anti‐sickling agents, gene therapy‐based hemoglobin modifications, as well as other approaches to improve the quality of life of sickle cell patients. © 2019 International Society for Advancement of Cytometry
Open Access
Influence of gold-silica nanoparticles on the performance of small-molecule bulk heterojunction solar cells
(Elsevier BV * North-Holland, 2015) Xu, X.; Kyaw, A. K. K.; Peng, B.; Xiong, Q.; Demir, Hilmi Volkan; Wang Y.; Wong, T. K. S.; Sun, X. W.
Light trapping by gold (Au)-silica nanospheres and nanorods embedded in the active layer of small-molecule (SM) organic solar cell has been systematically compared. Nanorod significantly outperforms nanosphere because of more light scattering and higher quality factor for localized surface plasmon resonance (LSPR) triggered by nanorods. The optimum concentration of nanorod was characterized by charge carrier transport and morphology of the active layers. At optimum nanorod concentration, almost no change in the morphology of the active layer reveals that LSPR and scattering effects rather than the morphology are mainly responsible for the enhanced power conversion efficiency. In addition, the preliminary lifetime studies of the SM solar cells with and without Au-silica nanorods were conducted by measuring the current density-voltage characteristics over 20 days. The results show that plasmonic device with nanorods has no adverse impact on the device stability
Open Access
Large flat plate models in the physical optics method for RCS calculations
(IEEE, 2004-09) Altıntaş, Ayhan; Çelik, Aslıhan
The calculation of Radar Cross Section (RCS) of arbitrarily large perfectly conducting body is presented. The body is modelled as triangular meshes of any size by the help of graphical tools. For the calculation of scattered field, Physical Optics(PO) surface integral is analytically evaluated over each of the triangular meshes. Due to the analytical integration, there is no limitation on the size of the triangles.
Open Access
Novel one-step synthesis of silica nanoparticles from sugarbeet bagasse by laser ablation and their effects on the growth of freshwater algae culture
(Elsevier, 2014) San, N. O.; Kurşungöz, C.; Tümtaş, Y.; Yaşa, Ö.; Ortac, B.; Tekinay, T.
Scientific research involving nanotechnology has grown exponentially and has led to the development of engineered nanoparticles (NPs). Silica NPs have been used in numerous scientific and technological applications over the past decade, necessitating the development of efficient methods for their synthesis. Recent studies have explored the potential of laser ablation as a convenient way to prepare metal and oxide NPs. Due to its high silica content, low cost, and widespread availability, sugarbeet bagasse is highly suitable as a raw material for producing silica NPs via laser ablation. In this study, two different NP production methods were investigated: laser ablation and NaOH treatment. We developed a novel, one-step method to produce silica NPs from sugarbeet bagasse using laser ablation, and we characterized the silica NPs using environmental scanning electron microscopy (ESEM), energy dispersive spectrometry (EDS), dynamic light scattering (DLS), transmission electron microscopy (TEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. EDS analysis and XPS confirmed the presence of silica NPs. The NPs produced by laser ablation were smaller (38-190 nm) than those produced by NaOH treatment (531-825 nm). Finally, we demonstrated positive effects of silica NPs produced from laser ablation on the growth of microalgae, and thus, our novel method may be beneficial as an environmentally friendly procedure to produce NPs.
Open Access
Numerically exact analysis of a two-dimensional variable-resistivity reflector fed by a complex-point source
(Institute of Electrical and Electronics Engineers, 1997-11) Nosich, A. I.; Yurchenko, V. B.; Altintaş, A.
Accurate numerical analysis of a two-dimensional (2-D) variable-resistivity reflector has been carried out by the method of regularization based on the analytical inversion of the corresponding static problem. The complex source-point model has been used to account for the directivity of the feeder and both the H- and E-polarization cases are considered. Far-field radiation patterns, directivity, and total radiative power have been computed for reflectors of uniform and nonuniform complex resistivities. The concept of edge loading for the control and improvement of antenna characteristics is confirmed by this numerically rigorous technique.
Open Access
Simulating a wavelength-size 2-D lens with an accurate numerical method
(IEEE, 2001) Boriskin, A. V.; Nosich, A. I.; Altıntaş, Ayhan
The effect of a localized light source directivity improvement due to an arbitrarily shaped dielectric cylinder taken as a 2-D model of a dielectric lens is studied. The source is simulated by the field of a complex source-point (CSP). An efficient algorithm for the solution of 2-D problem of wave scattering by a smooth dielectric cylinder is developed, based on the concept of analytical regularization. The basic properties of the algorithm are studied. Numerical results for the accuracy of the algorithm and sample far-field characteristics such as the total radiated power, directivity and radiation patterns for various lens parameters are presented.
Open Access
Spectrally accelerated biconjugate gradient stabilized method for scattering from and propagation over electrically large inhomogeneous geometries
(John Wiley & Sons, 2005) Babaoglu, B.; Altintas, A.; Ertürk, V. B.
Scattering from and propagation over rough-terrain profiles, as well as reentrant surfaces are investigated using an integral equation (IE)-based spectrally accelerated biconjugate gradient stabilized (SA-BiCGSTAB) method, with a storage requirement and a computational cost of O(N) per iteration, where N is the surface unknowns in the discretized IE. Numerical results in the form of current and path loss are presented and compared with previously published as well as measured results in order to assess the accuracy and efficiency of this method.
Open Access
Towards multimaterial multifunctional fibres that see, hear, sense and communicate
(Nature Publishing Group, 2007) Abouraddy, A. F.; Bayındır, Mehmet; Benoit, G.; Hart, S. D.; Kuriki, K.; Orf, N.; Shapira, O.; Sorin, F.; Temelkuran, B.; Fink, Y.
Virtually all electronic and optoelectronic devices necessitate a challenging assembly of conducting, semiconducting and insulating materials into specific geometries with low-scattering interfaces and microscopic feature dimensions. A variety of wafer-based processing approaches have been developed to address these requirements, which although successful are at the same time inherently restricted by the wafer size, its planar geometry and the complexity associated with sequential high-precision processing steps. In contrast, optical-fibre drawing from a macroscopic preformed rod is simpler and yields extended lengths of uniform fibres. Recently, a new family of fibres composed of conductors, semiconductors and insulators has emerged. These fibres share the basic device attributes of their traditional electronic and optoelectronic counterparts, yet are fabricated using conventional preform-based fibre-processing methods, yielding kilometres of functional fibre devices. Two complementary approaches towards realizing sophisticated functions are explored: on the single-fibre level, the integration of a multiplicity of functional components into one fibre, and on the multiple-fibre level, the assembly of large-scale two- and three-dimensional geometric constructs made of many fibres. When applied together these two approaches pave the way to multifunctional fabric systems. © 2007 Nature Publishing Group.