The effect of using water containing micro‐nano bubbles (WMNB) without adding any admixtures and normal water (NW) on the mechanical properties of cement mortar and concrete samples were investigated. Four various water to cement ratios equal to 0.6, 0.5, 0.4, and 0.35 (ranging from conventional concrete to high strength concrete), and three different curing ages of 7, 28, and 90 days were considered. The experimental results showed that the initial and final setting time of cement paste, the flow of hydraulic cement mortar and the slump of concrete samples made with WMNB were lower than that of made with NW. However, the compressive strength of cement mortar in using WMNB indicated an increase up to 16 and 7% in at 7 and 28 days, respectively. We also concluded that the optimum percentage of water to cement ratio was 0.35, which in that ratio the compressive strength enhancement of concrete made of WMNB reached the peak of 6, 18.3, and 16.3% at 7, 28, and 90 days age, respectively. Whereas increasing water to cement ratio, resulted in reducing the compressive strength of concrete. Besides, the high‐resolution scanning electron microscopy images with Energy Dispersive X‐Ray analysis were briefly conducted to explore the morphological change.

Background:In the developing countries, Tuberculosis is one of leading causes of morbidity and mortality. The detection and identification of Mycobacterium tuberculosis is considered a great challenge for clinical microbiologists. Albeit Ziehl-Neelsen (ZN) smear is being a rapid diagnostic tool for TB, the culture on Lowenstein Jensen (LJ) medium is considered the golden diagnostic tool for TB in the developing countries.Objectives: To evaluate the validity and reliability of ZN smear of acid-fast bacilli compared to the culture on LJ medium. Patients and methods:The retrospective analytic comparative cross-sectional study included patients visiting TB OPD clinic at NCDC, including transferred patients from other healthcare facilities and hospitals. A total of 2783 specimen of suspected pulmonary TB cases were processed for both direct smear and culture. The direct smears were stained with ZN method (1% Carbolfuchsin, 3% Hydrochloric acid Ethanol and 0.1% methylene blue). Specimens were observed under 100-x oil immersion lens, whilst cultures were inoculated on LJ medium after digestion and decontamination of the clinical specimens.Results: Of total 2783 study subjects, 203 (7.29%) were smear positive while 327 (11.74%) were culture positive. Out of 203 smear positive pulmonary cases, 154 (47.094%) were found to be positive on LJ culture. A total of 2407 pulmonary cases were negative on the smear and LJ culture for Mycobacterium tuberculosis.Conclusion: This preliminary study indicated the low sensitivity of sputum smear direct microscopy for early diagnosis of TB, while culture on LJ remains the golden standard modality.