Application of silver nitrate colorimetric method to non-steady-state diffusion test

NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick and simple method to measure the penetration depth of chloride by spraying 0.1 mol/L silver nitrate solution. The objective of this work is to study the possibility of the use of colorimetric method in the calculation of non-steady-state diffusion coefficient. Twelve concrete mixtures with different supplementary cementitious materials and water-to-cement ratios of 0.35, 0.48 and 0.6 were used for study. According to NT build 443, the concrete specimens were immersed in 165 g/L NaC1 （2.8 mol/L） solution for 42 d. Both water-soluble （convert to free chloride） chloride and acid-soluble chloride at different layers of specimens were measured. The results show that the mean value of free chloride concentration at the color change boundary Cd was 0.306 mol/L. The surface free chloride concentration cs was obtained by profile fitting method, which was 40% lower than the chloride concentration of exposure solution after an immersion period of 42 d. Chloride diffusion coefficients obtained by the colorimetric method was not well correlated with those obtained by profile fitting method.

A revisit to staining reagents for neuronal tissues

In the early days of deciphering the injured neuronal tissues led to the realization that contrast is necessary to discern the parts of the recovering tissues from the damaged ones.Early attempts relied on available(and often naturally occurring)staining substances.Incidentally,the active ingredients of most of them were small molecules.With the advent of time,the knowledge of chemistry helped identify compounds and conditions for staining.The staining reagents were even found to enhance the visibility of the organelles.Silver impregnation identification of Golgi bodies was discovered in owl optic nerve.Staining reagents since the late 1800s were widely used across all disciplines and for nerve tissue and became a key contributor to advancement in nerve-related research.The use of these reagents provided insight into the organization of the neuronal tissues and helped distinguish nerve degeneration from regeneration.The neuronal staining reagents have played a fundamental role in the clinical research facilitating the identification of biological mechanisms underlying eye and neuropsychiatric diseases.We found a lack of systematic description of all staining reagents,whether they had been used historically or currently used.There is a lack of readily available information for optimal staining of different neuronal tissues for a given purpose.We present here a grouping of the reagents based on their target location:(I)the central nervous system(CNS),(II)the peripheral nervous system(PNS),or(III)both.The biochemical reactions of most of the staining reagents is based on acidic or basic pH and specific reaction partners such as organelle or biomolecules that exists within the given tissue type.We present here a summary of the chemical composition,optimal staining condition,use for given neuronal tissue and,where possible,historic usage.Several biomolecules such as lipids and metabolites lack specific antibodies.Despite being non-specific the reagents enhance contrast and provide corroboration about the microenvironment.In future,these reagents in combination with emerging techniques such as imaging mass spectrometry and kinetic histochemistry will validate or expand our understanding of localization of molecules within tissues or cells that are important for ophthalmology and vision science.

Preparation and characterization of hollow carambola-shaped silver sulfide microspheres using a microwave-assisted template-free method

A simple and convenient method, free of template, has been proposed to synthesize hollow carambolashaped Ag2 S microspheres with Ag NO3, thiourea（TU）, Na Cl and diethanolamine as reagents using a microwave-assisted method, at low temperatures of below 100 ℃. Powder X-ray diffraction（XRD）,scanning electron microscopy（FESEM） and high resolution transmission electron microscopy（HRTEM）were employed to characterize the morphology and composition of those microspheres. The results indicated that the hollow carambola-shaped silver sulfide microspheres（with high purity and homogeneous morphology） were prepared by an Ostwald ripening process. A possible formation mechanism of hollow carambola-shaped Ag2 S microspheres was proposed.