7 research outputs found
Advances in Modeling of Scanning Charged-Particle-Microscopy Images
Modeling artificial scanning electron microscope (SEM) and scanning ion
microscope images has recently become important. This is because of the need to
provide repeatable images with a priori determined parameters. Modeled
artificial images are highly useful in the evaluation of new imaging and
metrological techniques, like image-sharpness calculation, or drift-corrected
image composition (DCIC). Originally, the NIST-developed artificial image
generator was designed only to produce the SEM images of gold-on-carbon
resolution sample for image-sharpness evaluation. Since then, the new improved
version of the software was written in C++ programming language and is in the
Public Domain. The current version of the software can generate arbitrary
samples, any drift function, and many other features. This work describes
scanning in charged-particle microscopes, which is applied both in the
artificial image generator and the DCIC technique. As an example, the
performance of the DCIC technique is demonstrated.Comment: 9 pages, 6 figure
Static optical sorting in a laser interference field
We present a unique technique for optical sorting of heterogeneous suspensions of microparticles, which does not require the flow of the immersion medium. The method employs the size-dependent response of suspended dielectric particles to the optical field of three intersecting beams that form a fringelike interference pattern. We experimentally demonstrate sorting of a polydisperse suspension of polystyrene beads of diameters 1, 2, and 5.2 mu m and living yeast cells. (c) 2008 American Institute of Physics.</p
Handling and storage of human body fluids for analysis of extracellular vesicles
Because procedures of handling and storage of body fluids affect numbers and composition of extracellular vesicles (EVs), standardization is important to ensure reliable and comparable measurements of EVs in a clinical environment. We aimed to develop standard protocols for handling and storage of human body fluids for EV analysis. Conditions such as centrifugation, single freeze–thaw cycle, effect of time delay between blood collection and plasma preparation and storage were investigated. Plasma is the most commonly studied body fluid in EV research. We mainly focused on EVs originating from platelets and erythrocytes and investigated the behaviour of these 2 types of EVs independently as well as in plasma samples of healthy subjects. EVs in urine and saliva were also studied for comparison. All samples were analysed simultaneously before and after freeze–thawing by resistive pulse sensing, nanoparticle tracking analysis, conventional flow cytometry (FCM) and transmission (scanning) electron microscopy. Our main finding is that the effect of centrifugation markedly depends on the cellular origin of EVs. Whereas erythrocyte EVs remain present as single EVs after centrifugation, platelet EVs form aggregates, which affect their measured concentration in plasma. Single erythrocyte and platelet EVs are present mainly in the range of 100–200 nm, far below the lower limit of what can be measured by conventional FCM. Furthermore, the effects of single freeze–thaw cycle, time delay between blood collection and plasma preparation up to 1 hour and storage up to 1 year are insignificant (p>0.05) on the measured concentration and diameter of EVs from erythrocyte and platelet concentrates and EVs in plasma, urine and saliva. In conclusion, in standard protocols for EV studies, centrifugation to isolate EVs from collected body fluids should be avoided. Freezing and storage of collected body fluids, albeit their insignificant effects, should be performed identically for comparative EV studies and to create reliable biorepositories