Tem and Cathodoluminescence investigations of CdS grown by different techniques

This work presents the results of an investigation of cadmium sulphide with various characterisation techniques such as TEM- Cathodoluminescence, SEM, XRD, PL and optical transmittance. A model based on a convolution method is proposed to predict CL signal emission. It was assumed that the CL can originate from electron and X-ray sources. Measurement of CL signal and noise over a wide range of magnifications showed that signal-to-noise is too low when STEM is operating at higher magnifications than 3000 times. This may lead to some extent to some CL imaging limitations. The origin of this phenomenon is discussed. A study of the suitability of a combined transmission electron microscope (ТЕМ) / Cathodoluminescence (CL) imaging and spectroscopy apparatus for investigations of CdS is presented. Photoluminescence (PL) was used to evaluate the effect of the Ar+ and I+ ion beam thinning used in ТЕМ specimen preparation of CdS: a minor increase in yellow emission (594 nm) resulted. However, excitation of luminescence spectra m the ТЕМ had a quenching effect on red luminescence (734 nm), this being considered due to the high excitation density compared to that in PL. Significant electron beam damage to the CdS single crystal could be avoided by using scanning transmission electron microscope (STEM) illumination in preference to the conventional ТЕМ mode. Dislocation images were correlated with contrast in the STEM-CL imaging mode. The potential of the apparatus to make further direct correlations of CL images with diffraction contrast ТЕМ imaging was assessed using the Rose visibility criterion. Finally, optical and structural properties of thin films CdS grown by chemical bath deposition and metal organic chemical deposition were investigated. For both growth methods, ТЕМ diffraction pattern confirm that the crystallographic structure of CdS was hexagonal, with a strong selected (002) orientation. It was found that either air annealing or CdCI(_2) treatment on CBD CdS increased modestly the grain size of 6 nm. While for MOCVD CdS, the growth temperature and the II/VI play an important role in obtaining large grain. Hence, sample grown at 330 c with a II/VI of 0.78 revealed a better crystalline quality due to the presence of the excitonic bound centred around 2.55 eV and exhibited the largest grains of about 97 nm

Post - prandial rise of microvesicles in peripheral blood of healthy human donors

<p>Abstract</p> <p>Background</p> <p>Microvesicles isolated from body fluids are membrane - enclosed fragments of cell interior which carry information on the status of the organism. It is yet unclear how metabolism affects the number and composition of microvesicles in isolates from the peripheral blood.</p> <p>Aim</p> <p>To study the post - prandial effect on microvesicles in isolates from the peripheral blood of 21 healthy donors, in relation to blood cholesterol and blood glucose concentrations.</p> <p>Results</p> <p>The average number of microvesicles in the isolates increased 5 hours post - prandially by 52%; the increase was statistically significant (p = 0.01) with the power P = 0.68, while the average total blood cholesterol concentration, average low density lipoprotein cholesterol concentration (LDL-C) and average high density lipoprotein cholesterol concentration (HDL-C) all remained within 2% of their fasting values. We found an 11% increase in triglycerides (p = 0.12) and a 6% decrease in blood glucose (p < 0.01, P = 0.74). The post - prandial number of microvesicles negatively correlated with the post - fasting total cholesterol concentration (r = - 0.46, p = 0.035) while the difference in the number of microvesicles in the isolates between post - prandial and post - fasting states negatively correlated with the respective difference in blood glucose concentration (r = - 0.39, p = 0.05).</p> <p>Conclusions</p> <p>In a population of healthy human subjects the number of microvesicles in isolates from peripheral blood increased in the post - prandial state. The increase in the number of microvesicles was affected by the fasting concentration of cholesterol and correlated with the decrease in blood glucose.</p

Scanning electron microscopy as a new tool for diagnostic pathology and cell biology

Scanning electron microscopy (SEM) use in the biomedical sciences has traditionally been used for characterisation of cell and tissue surface topography. This paper demonstrates the utility of high-resolution scanning electron microscopy (HRSEM) to diagnostic pathology and cell biology ultrastructural examinations. New SEM applications based on the production of transmission electron microscopy-like (TEM-like) images are now possible with the recent introduction of new technologies such as low kV scanning transmission electron microscopy (STEM) detectors, automated scan generators and high-resolution column configurations capable of sub-nanometre resolution. Typical specimen types traditionally imaged by TEM have been examined including renal, lung, prostate and brain tissues. The specimen preparation workflow was unchanged from that routinely used to prepare TEM tissue, apart from replacing copper grids for section mounting with a silicon substrate. These instruments feature a small footprint with little in the way of ancillary equipment, such as water chillers, and are more cost-effective than traditional TEM columns. Also, a new generation of benchtop SEMs have recently become available and have also been assessed for its utility in the tissue pathology and cell biology settings

The Condensation of Water on Adsorbed Viruses.

The wetting and dewetting behavior of biological nanostructures and to a greater degree single molecules is not well-known even though their contact with water is the basis for all biology. Here, we show that environmental electron microscopy (EM) can be applied as a means of imaging the condensation of water onto viruses. We captured the formation of submicrometer water droplets and filaments on single viral particles by environmental EM and by environmental transmission EM. The condensate structures are compatible with capillary condensation between adsorbed virus particles and with known droplet shapes on patterned surfaces. Our results confirm that such droplets exist down to <50 nm. The viruses preserved their shape after a condensation/evaporation cycle as expected from their stability in air and water. Moreover we developed procedures that overcome problems of beam damage and of resolving structures with a low atomic number

The Condensation of Water on Adsorbed Viruses

The wetting and dewetting behavior of biological nanostructures and to a greater degree single molecules is not well-known even though their contact with water is the basis for all biology. Here, we show that environmental electron microscopy (EM) can be applied as a means of imaging the condensation of water onto viruses. We captured the formation of submicrometer water droplets and filaments on single viral particles by environmental EM and by environmental transmission EM. The condensate structures are compatible with capillary condensation between adsorbed virus particles and with known droplet shapes on patterned surfaces. Our results confirm that such droplets exist down t