Effect of Wetting and Dewetting Dynamics on Atomic Force Microscopy Measurements.

Water bridge dynamics between an atomic force microscopy (AFM) tip and a flat substrate is studied by using a multibody dissipative particle dynamics (MDPD) model. First, the numerical model is validated by comparing the present results of droplet contact angles and liquid bridges with those reported in the literature. Then, the ability of MDPD to capture the meniscus shape and behavior for different operating conditions and geometric parameters is examined for both static and dynamic cases. Hence, several parametric studies and analyses of the AFM tip configuration and its operating conditions are reported. It is found that a critical capillary number of about 0.001 is calculated based on 5% change on the force measurements between the static and dynamic results. It is also demonstrated that the hysteresis behavior in the capillary force exerted on the AFM tip can be successfully predicted by using the MDPD model when the tip approaches or retracts from the substrate. Moreover, there is an excellent agreement in the results of breakup distance for different water bridge volumes between the predictions of the MDPD model and the theory. Also, the hysteresis of capillary force exerted on an AFM tip composed of multibody design is studied. The prediction on the transition of the capillary force vs distance between the AFM tip and the substrate is in good agreement with the experimental results. Therefore, we demonstrate a validated MDPD model which can successfully capture liquid bridge dynamics. This model can be used as a powerful design tool for meniscus manipulation technology, such as dip-pen nanolithography, as well as for studying dynamic, e.g., tapping mode AFM tip, interactions with a liquid bridge.

The erythrocyte differential count in newborn infants.

The three-dimensional shape of erythrocytes is assessed by light microscopy using a simple technique to view glutaraldehyde-fixed erythrocytes. The technique and its standardization is described. Using this method the erythrocytes of adults have been compared to those of full-term and premature infants. In adults, the majority of erythrocytes are bowl-shaped at 37 degrees C and disc-shaped at room temperature. Newborn infants have significantly more bowl-shaped cells as well as significantly more irregularly shaped cells. Erythrocyte differential counts have been performed on a large series of patients to determine the normal range for each cell shape in adults, full-term, and premature infants. It is suggested that the study of erythrocyte morphology in haematologic disease in newborn infants requires three-dimensional assessment and quantitative data of normal values.

The hematology of bacterial infections in premature infants.

A series of premature infants was studied for the presence of bacterial infection. On the basis of clinical evidence and bacteriological studies, they were divided into three groups in which sepsis was considered to be proven, possible, or unlikely. Band neutrophil counts were elevated most frequently in the "sepsis-proven" group and the elevation occurred usually within 24 hours of onset of signs of disease. Qualitative changes in neutrophils (Döhle bodies, toxic granulation, and vacuolization) were more frequent in the sepsis-proven group and, together with the band count, provided valuable techniques for the diagnosis of bacterial infections. Thrombocytopenia occurred frequently in the sepsis-proven group and seemed to result from increased utilization or destruction of platelets rather than failure of production. In such cases, evidence of intravascular coagulation was minimal and it was concluded that thrombocytopenia had resulted from a direct effect of the bacteria or its products on platelets and/or endothelium.