Ultralong coherence times in the purely electronic zero-phonon line emission of single molecules

We report the observation of ultralong coherence times in the purely electronic zero-phonon line emission of single terrylenediimide molecules at 1.4 K. Vibronic excitation and spectrally resolved detection with a scanning Fabry-Perot spectrum analyzer were used to measure a linewidth of 65 MHz. This is within a factor of 1.6 of the transform limit. It therefore indicates that single molecule emission may be suited for applications in linear optics quantum computation. Additionally it is shown that high resolution spectra taken with the spectrum analyzer allow for the investigation of fast spectral dynamics in the emission of a single molecule.Comment: to appear in Applied Physics Letter

Android Kötücül Yazılım Tespit Sistemleri İncelemesi

Akıllı telefonların hayatımıza girmesiyle birlikte akıllı telefonları kullanan kullanıcı sayısı her geçen gün artarak devam etmektedir. Akıllı telefonların fazla talep görmesindeki neden, insanların bir cihazla istedikleri işleri tek dokunuşla kolaylıkla yapabilmesidir. International Data Corporation (IDC) firmasının 2016 2. çeyrek raporuna göre; akıllı telefon pazarında Android %87.6 gibi çok yüksek bir paya sahiptir [1]. Android'in akıllı telefon kullanan kullanıcılar arasında popüler olması ile birlikte açık kaynaklı bir yapıya sahip olması ve markete uygulama yüklenirken detaylı olarak kötücül yazılım incelenmesi yapılmadığından dolayı Android platformu kötü niyetli kişilerin bir numaralı hedefi haline gelmiştir. Android market ve diğer alternatif Android marketlerde kötü niyetli uygulamaların sayısı her geçen gün artmaktadır. G Data'nın 2015 1. Çeyrek raporuna göre; kötücül yazılımların %50.3 finansal amaçlıdır [2]. Finansal amaçlı olmasındaki neden Avrupa kıtasındaki kullanıcıların %41'nin banka işlemlerini akıllı telefonlarını kullanarak yapmasıdır [2]. Bu yüzden Android marketlerde bulunan uygulamaların kötücül olup olmadığını tespit etmek için etkin kötücül yazılım tespiti yapan sistemlere ihtiyaç vardır. Bu çerçevede bu çalışmada kötücül yazılım tespit sistemleri anlatılmıştır

A Deep Learning Model for Automated Segmentation of Fluorescence Cell images

Deep learning techniques bring together key advantages in biomedical image segmentation. They speed up the process, increase the reproducibility, and reduce the workload in segmentation and classification. Deep learning techniques can be used for analysing cell concentration, cell viability, as well as the size and form of each cell. In this study, we develop a deep learning model for automated segmentation of fluorescence cell images, and apply it to fluorescence images recorded with a home-built epi-fluorescence microscope. A deep neural network model based on U-Net architecture was built using a publicly available dataset of cell nuclei images [1]. A model accuracy of 97.3% was reached at the end of model training. Fluorescence cell images acquired with our home-built microscope were then segmented using the developed model. 141 of 151 cells in 5 images were successfully segmented, revealing a segmentation success rate of 93.4%. This deep learning model can be extended to the analysis of different cell types and cell viability

Examination of a New Defense Mechanism: Honeywords

Past experiences show us that password breach is still one of the main methods of attackers to obtain personal or sensitive user data. Basically, assuming they have access to list of hashed passwords, they apply guessing attacks, i.e., attempt to guess a password by trying a large number of possibilities. We certainly need to change our way of thinking and use a novel and creative approach in order to protect our passwords. In fact, there are already novel attempts to provide password protection. The Honeywords system of Juels and Rivest is one of them which provides a detection mechanism for password breaches. Roughly speaking, they propose a method for password-based authentication systems where fake passwords, i.e., "honeywords" are added into a password file, in order to detect impersonation. Their solution includes an auxiliary secure server called "honeychecker" which can distinguish a user's real password among her honeywords and immediately sets off an alarm whenever a honeyword is used. However, they also pointed out that their system needs to be improved in various ways by highlighting some open problems. In this paper, after revisiting the security of their proposal, we specifically focus on and aim to solve a highlighted open problem, i.e., active attacks where the adversary modifies the code running on either the login server or the honeychecker

Examination of a New Defense Mechanism: Honeywords

It has become much easier to crack a password hash with the advancements in the graphicalprocessing unit (GPU) technology. An adversary can recover a user’s password using brute-force attack on password hash. Once the password has been recovered no server can detect any illegitimate user authentication (if there is no extra mechanism used). In this context, recently, Juels and Rivest published a paper for improving the security of hashed passwords. Roughly speaking, they propose an approach for user authentication, in which some false passwords, i.e., “honeywords” are added into a password file, in order to detect impersonation. Their solution includes an auxiliary secure server called “honeychecker” which can distinguish a user’s real password among her honeywords and immediately sets off an alarm whenever a honeyword is used. In this paper, we analyze the security of the proposal, provide some possible improvements which are easy to implement and introduce an enhanced model as a solution to an open problem

Thermal tuning of spectral emission from optically trapped liquid-crystal droplet resonators

Surfactant-stabilized emulsion droplets of liquid crystals (LCs) suspended in water and labeled with a fluorescent dye form active, anisotropic optofluidic microresonators. These microresonators can host whispering gallery modes (WGMs), high-quality morphology-dependent optical resonances that are supported due to the contrast of refractive index between the LC droplets and the surrounding aqueous medium. In addition, owing to the refractive index contrast, such LC emulsion droplets can be stably trapped in three dimensions using optical tweezers, enabling long-term investigation of their spectral characteristics. We explore various combinations of fluorescently dyed LC droplets and host liquid-surfactant systems and show that the WGM emission spectra of optical resonators based on optically trapped LC emulsion droplets can be largely and (almost) reversibly tuned by controlled changes of the ambient temperature. Depending on the actual range of temperature modulation and LC phase of the studied droplet, thermally induced effects can either lead to phase transitions in the LC droplets or cause modifications of their refractive index profile without changing their LC phase. Our results indicate feasibility of this approach for creating miniature thermally tunable sources of coherent light that can be manipulated and stabilized by optical forces

Examination of the criteria affecting Industry 4.0 with structural equation model and a pilot study

Günümüzde teknoloji ve üretim ortamı sürekli gelişmektedir. İşletmeler bu rekabet ortamında ayakta kalabilmek için yenilikleri takip etmek zorundadır. Endüstri 4.0 ya da diğer bir adıyla dördüncü sanayi devriminin temel amacı bilişim teknolojileri ve endüstriyi bir araya getirmektir. Endüstri 4.0, birbirleri ile haberleşebilen, veri alışverişi yapabilen sistemler arası bütünleşmeyi içeren, ileri otomasyon seviyesi ile veri analizini yaparak, üretimdeki makine ve teçhizata ait tüm verilerin, üretimin eş zamanlı yapılabilmesi için bir bulut sisteminde depolanması olarak özetlenebilir. Endüstri 4.0, üretimde esnekliğin arttırılmasına ve daha yüksek verimliliğin sağlanmasına olanak sağlar. Bu çalışmada, işletmelerin Endüstri 4.0 seviyesini etkileyen kriterler belirlenmiş ve kriter etkilerinin Endüstri 4.0 seviyesine etkisinin analizi için yapısal eşitlik modeli (YEM) kullanılmıştır. Modelde teknoloji, strateji, müşteriler, liderlik, devlet politikası, kültür, süreçler ve çalışanlar olmak üzere 8 kriter kullanılmıştır. Gerçekleştirilen uygulama ile Endüstri 4.0 seviyesine etki eden en önemli üç kriterin sırasıyla 1,00 faktör yükü ile strateji, 0,97 faktör yükü ile kültür ve 0,90 faktör yükü ile süreçler olduğu görülmektedir. Çalışmada elde edilen bulguların işletmelerin Endüstri 4.0 hedefine ulaşmaları konusundaki eksik ve geliştirilebilir yönlerini görmeleri konusunda yardımcı olması hedeflenmektedir.Nowadays, technology and production environment is constantly developing. Companies have to follow innovations in order to survive in this competitive environment. The main purpose of Industry 4.0 or the fourth industrial revolution is to bring information technology and industry together. Industry 4.0 can be summarized as the storage of all data related to the machinery and equipment in production in a cloud system so that the production can be performed simultaneously by analyzing the data with the advanced automation level, which can communicate with each other and can exchange these data. Industry 4.0 enables increased flexibility in production and in productivity. In this study, the criteria affecting the Industry 4.0 level were determined and the structural equation model (SEM) was used to analyze the impact of the criterion effects on the Industry 4.0 level. 8 criteria were used in the model: technology, strategy, customers, leadership, government policy, culture, processes and employees. The most important three factors affecting the Industry 4.0 level are strategy with 1.00 factor load, culture with 0.97 factor load and processes with 0.90 factor load. It is aimed that the findings obtained in the study will help the companies to see their deficiencies and improvements in reaching the goal of Industry 4.0

An LED-Based Structured Illumination Microscope Using A Digital Micromirror Device And GPU Accelerated Image Reconstruction

When combined with computational approaches, fluorescence imaging becomes one of the most powerful tools in biomedical research. It is possible to achieve resolution figures beyond the diffraction limit, and improve the performance and flexibility of high-resolution imaging systems with techniques such as structured illumination microscopy (SIM) reconstruction. In this study, the hardware and software implementation of an LED-based superresolution imaging system using SIM employing GPU accelerated parallel image reconstruction is presented. The sample is illuminated with two-dimensional sinusoidal patterns with various orientations and lateral phase shifts generated using a digital micromirror device (DMD). SIM reconstruction is carried out in frequency space using parallel CUDA kernel functions. Furthermore, a general purpose toolbox for the parallel image reconstruction algorithm and an infrastructure that allows all users to perform parallel operations on images without developing any CUDA kernel code is presented. The developed image reconstruction algorithm was run separately on a CPU and a GPU. Two different SIM reconstruction algorithms have been developed for the CPU as mono-thread CPU algorithm and multi-thread OpenMP CPU algorithm. SIM reconstruction of 1024 × 1024 px images was achieved in 1.49 s using GPU computation, indicating an enhancement by *28 and *20 in computation time when compared with mono-thread CPU computation and multi-thread OpenMP CPU computation, respectively

Fabrication and Characterization of Large Numerical Aperture, High-Resolution Optical Fiber Bundles Based on High-Contrast Pairs of Soft Glasses for Fluorescence Imaging

Fabrication and characterization of flexible optical fiber bundles (FBs) with inhouse synthesized high-index and low-index thermally matched glasses are presented. The FBs composed of around 15000 single-core fibers with pixel sizes between 1.1 and 10 μm are fabricated using the stack-and-draw technique from sets of thermally matched zirconiumsilicate ZR3, borosilicate SK222, sodium-silicate K209, and F2 glasses. With high refractive index contrast pair of glasses ZR3/SK222 and K209/F2, FBs with numerical apertures (NAs) of 0.53 and 0.59 are obtained, respectively. Among the studied glass materials, ZR3, SK222, and K209 are in-house synthesized, while F2 is commercially acquired. Seven different FBs with varying pixel sizes and bundle diameters are characterized. Brightfield imaging of a micro-ruler and a Convallaria majalis sample and fluorescence imaging of a dye-stained paper tissue and a cirrhotic mice liver tissue are demonstrated using these FBs, demonstrating their good potential for microendoscopic imaging. Brightfield and fluorescence imaging performance of the studied FBs are compared. For both sets of glass compositions, good imaging performance is observed for FBs, with core diameter and core-to-core distance values larger than 1.6 μm and 2.3 μm, respectively. FBs fabricated with K209/F2 glass pairs revealed better performance in fluorescence imaging due to their higher NA of 0.59