Isa Navruz

Integrated rapid-diagnostic-test reader platform on a cellphone

We demonstrate a cellphone-based rapid-diagnostic-test (RDT) reader platform that can work with various lateral flow immuno-chromatographic assays and similar tests to sense the presence of a target analyte in a sample. This compact and cost-effective digital RDT reader, weighing only ~65 g, mechanically attaches to the existing camera unit of a cellphone, where various types of RDTs can be inserted to be imaged in reflection or transmission modes under light-emitting diode (LED)-based illumination. Captured raw images of these tests are then digitally processed (within less than 0.2 s per image) through a smart application running on the cellphone for validation of the RDT, as well as for automated reading of its diagnostic result. The same smart application then transmits the resulting data, together with the RDT images and other related information (e.g., demographic data), to a central server, which presents the diagnostic results on a world map through geo-tagging. This dynamic spatio-temporal map of various RDT results can then be viewed and shared using internet browsers or through the same cellphone application. We tested this platform using malaria, tuberculosis (TB) and HIV RDTs by installing it on both Android-based smartphones and an iPhone. Providing real-time spatio-temporal statistics for the prevalence of various infectious diseases, this smart RDT reader platform running on cellphones might assist healthcare professionals and policymakers to track emerging epidemics worldwide and help epidemic preparedness.

Smart-phone based computational microscopy using multi-frame contact imaging on a fiber-optic array.

We demonstrate a cellphone based contact microscopy platform, termed Contact Scope, which can image highly dense or connected samples in transmission mode. Weighing approximately 76 grams, this portable and compact microscope is installed on the existing camera unit of a cellphone using an opto-mechanical add-on, where planar samples of interest are placed in contact with the top facet of a tapered fiber-optic array. This glass-based tapered fiber array has ~9 fold higher density of fiber optic cables on its top facet compared to the bottom one and is illuminated by an incoherent light source, e.g., a simple light-emitting-diode (LED). The transmitted light pattern through the object is then sampled by this array of fiber optic cables, delivering a transmission image of the sample onto the other side of the taper, with ~3× magnification in each direction. This magnified image of the object, located at the bottom facet of the fiber array, is then projected onto the CMOS image sensor of the cellphone using two lenses. While keeping the sample and the cellphone camera at a fixed position, the fiber-optic array is then manually rotated with discrete angular increments of e.g., 1-2 degrees. At each angular position of the fiber-optic array, contact images are captured using the cellphone camera, creating a sequence of transmission images for the same sample. These multi-frame images are digitally fused together based on a shift-and-add algorithm through a custom-developed Android application running on the smart-phone, providing the final microscopic image of the sample, visualized through the screen of the phone. This final computation step improves the resolution and also removes spatial artefacts that arise due to non-uniform sampling of the transmission intensity at the fiber optic array surface. We validated the performance of this cellphone based Contact Scope by imaging resolution test charts and blood smears.

Optimization of Phase Shifted Long-Period Fiber Gratings for Multiband Rejection Filters

A new approach for designing multiband rejection filters is proposed based on the optimization of a periodically phase-shifted long period fiber grating (LPG). The validity of the method is demonstrated by performing simulations for the typical cases. It is shown that using the proposed synthesis method, spectral position, and bandwidth of the each reflection band can be controlled by varying the grating length and the phase shifting period. In addition, a desired number of rejection bands within the transmission spectrum can be generated using a phase-shifted LPG with an optimized phase shifting series. Furthermore, a number of unwanted rejection bands can easily be removed from the transmission spectrum by optimizing the phase shifting series.

DESIGN OF A CHIRPED FIBER BRAGG GRATING FOR USE IN WIDEBAND DISPERSION COMPENSATION

A wideband chirped fiber Bragg grating (FBG) dispersion compensator operating in C band is designed theoretically by numerically solving the coupled mode equations. The power reflectivity spectrum and dispersion characteristics of the chirped fiber Bragg gratings are analysed. In order to achieve wideband dispersion compensation with a low insertion loss, grating length, average refractive index change, apodization profile and chirp parameter of the grating should be precisely optimized. The chirped FBG designs achieved in this study have resulted in a negative dispersion of 4.95 ps/nm for a grating length of L = 10 mm and a negative dispersion of 9.76 ps/nm for a grating length of L = 20 mm with 16 nm bandwidth at around 1550 nm.

Smart rapid diagnostics test reader running on a cell-phone for real-time mapping of epidemics

Rapid diagnostics tests (e.g., immuno-chromatographic assays and other lateral-flow tests) offer significant advantages over conventional approaches (i.e., clinical examination and advanced medical tests) for the surveillance of infectious diseases especially in the remote parts of the world. In order to provide an integrated platform for automated digital reading and real-time mapping of rapid diagnostics tests (RDTs), we developed a universal RDT reader running on a cell-phone that can automatically digitize and evaluate various diagnostics test results. A custom-developed cell-phone application automatically processes raw transmission and reflection RDT images that are digitally acquired using a compact and cost-effective hardware attachment to generate semi-quantitative test evaluation reports. The same cell-phone application also connects this RDT reader to a central database/server that stores and displays RDT evaluation reports, mapping infectious diseases in real-time. Powered by the cell-phone battery or two AAA batteries, RDT reader attachment utilizes simple off-the-shelf components (e.g., multiple diffused light-emitting diode (LED) arrays and a plano-convex lens) and can be customized to fit on different cell-phone devices (i.e., iPhone and Android phones) without any major changes on its design. Providing spatio-temporal statistics for the prevalence of various infectious diseases, this integrated RDT reader platform can be especially useful to support epidemiological studies to fight against global health related problems. Here, we review our recent progress on this cellphone based RDT reader platform and discuss its potential use toward real-time mapping of various diseases globally.

A comparison on the new electronic attack techniques against pulse compression radars

In this study, the mathematical models of Smeared and Chopping/Interleaving Spectrum techniques, which are recent electronic attack techniques against the pulse compression radars, are presented. Then, matched filter outputs are compared by means of a simulator. Moreover, the effect of the weighting filter in the radar receiver is also analyzed.

Optimization based synthesis methods to design multi-channel sampled fiber Bragg gratings with phase-shift

In this paper, two synthesis methods are proposed for designing multi-channel sampled gratings with phase-shifts. The first synthesis method uses non-equally separated ¿-phase shifts and the second uses variable but equally separated phase shifts in sampling period of fiber grating. In both methods, the Fourier transform derived from the phase shifts is related with the reflection spectrum of the fiber Bragg grating. It is demonstrated that a reflection spectrum with desired number of channels can be easily synthesised using a general optimization method. Besides, a comparison is given between these two methods according to the target reflection spectrum.

The effects of frequency and altitude on radar performance with surface ducting

It is possible to see different ducting statistics in the different seas and oceans around the World. The performance of air traffic and sea surface surveillance radars, which is established on the sea shores, are affected especially from ducting over huge water masses. Two important parameters determine the variability of radar performance depending on ducting. They are altitude and frequency of the radar. In this work, the effects of frequency and altitude on radar performance are analysed.

OPTİK HABERLEŞME SİSTEMLERİNDE DİSPERSİYON KOMPANZASYONUNDA OPTİK IZGARA TABANLI ÇÖZÜMLER

Fiberoptik haberlesme sistemlerinin iletim hizini ve mesafesini etkileyen en onemli sinirlayici faktor “ dispersiyon ”dur. Dispersiyon, optik darbenin iletim boyunca yayilmasidir. Iletim hizi ve mesafesi arttikca, dispersiyon sistemin performansini bozucu yonde daha da cok etkiler. Yapilan bu calismada dispersiyonu telafi etmek icin bir optik eleman olan fiber izgaralari onerilmistir. Fiber izgaralarinin modellemesi yapilarak guc yansiticiligi, zaman gecikmesi ve dispersiyon karakteristikleri analiz edilmistir. Elde edilen sonuclardan, apodize edilmis civiltili izgaranin dispersiyonu telafi etmek icin iyi bir yaklasim saglayabilecegi sonucuna varilmistir