Suppression of zero order diffraction from the reconstructed images in digital holography

The numerically reconstructed images in digital holography contain two undesirable features. After reconstruction, the zero order diffraction as well as the complex conjugate image will be present in pictures and drastically reduce their qualities. Practical applications of digital holography in the context of characterization and measuring the physical properties of objects require the suppression of these two features, before starting the reconstruction phase. In this work, using the required mathematical functions for suppressing the zero order diffraction and by transforming them to their discrete form, numerical filters for passing over the CCD images have been constructed. After passing these filters over the experimentally recorded CCD images, the reconstruction phase has been completed applying the discrete Fresnel transform. Carefully investigating the quality of various reconstructed images, we came to the conclusion that if a filter covers a smaller neighborhood of the recorded CCD images, it will have a better performance in suppressing the zero order diffraction. Among the used filters in this work, a 3×3 average filter showed the best performance in suppressing the zero order diffraction from the reconstructed images

Large Optical Nonlinearity of the Activated Carbon Nanoparticles Prepared by Laser Ablation

Carbon nanoparticles (CNPs) with high porosity and great optical features can be used as a luminescent material. One year later, the same group investigated the NLO properties CNPs and boron-doped CNPs by 532 nm and 1064 nm laser excitations to uncover the underlying physical mechanisms in their NLO response. Hence, a facile approach, laser ablation technique, was employed for carbon nanoparticles (CNPs) synthesis from suspended activated carbon (AC). Morphological properties of the prepared CNPs were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). UV-Vis and fluorescence (FL) spectra were used to optical properties investigation of CNPs. The size distribution of nanoparticles was evaluated using dynamic light scattering (DLS). The nonlinear optical (NLO) coefficients of the synthesized CNPs were determined by the Z-scan method. As a result, strong reverse saturable absorption and self-defocusing effects were observed at the excitation wavelength of 442 nm laser irradiation. These effects were ascribed to the presence of delocalized π-electrons in AC CNPs. To the best of our knowledge, this is the first study investigating the NLO properties of the AC CNPs

Evaluation of Tuberculosis Situation in Economic Cooperation Countries in 2009; Achievement and Gaps toward Millennium Development Goals

Background : Evaluating the tuberculosis (TB) status of the Economic Cooperation Organization (ECO) member countries relation to goal 6-c of the third millennium, which includes that TB incidence, prevalence, and death rates should be halved by 2015, compared with their level in 1990. Methods : In 2009, we have critically reviewed the countries′ Millennium Development Goals (MDGs) reports and extracted the data from the surveillance system and published and unpublished data. The main stakeholders, from both governmental and international organizations in the country have been visited and interviewed by the research team as part of the data validation process. Results : The TB incidence is very heterogeneous among ECO countries, which differ from 21.7 in Iran to 230.7 per 100,000 in Tajikistan. TB incidence (per 100,000) is more than 100 in six countries and is from 50 to 100 in two countries and is less than 30 in two countries. Only in two countries the crude death rate (CDR) is higher than 70%. In seven countries the death rate is higher than 10 per 100,000. Two countries are among the 20 top world countries with the highest tuberculosis burden. Conclusion : There are some signs and signals indicating the bad condition of an ECO member including: incidence of more than 50 per 100000, CDR of less than 70%, death rate more than 10 per 100,000, and rating two member countries among 20 top countries with the highest burden in the world. Iran and Turkey could achieve MDGs by 2015, but if other countries do not prepare urgent intervention programs, they will not be able to fulfill the goals