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4D-STEM, in which the 2D diffraction plane is captured for each 2D scan position in the scanning transmission electron microscope (STEM) using a pixelated detector, is complementing, and increasingly replacing existing imaging approaches. However, at present the speed of those detectors, although having drastically improved in the recent years, is still 100 to 1,000 times slower than the current PMT technology operators are used to. Regrettably, this means environmental scanning-distortion often limits the overall performance of the recorded 4D data. Here, we present an extension of existing STEM distortion correction techniques for the treatment of 4D data series. Although applicable to 4D data in general, we use electron ptychography and electric-field mapping as model cases and demonstrate an improvement in spatial fidelity, signal-to-noise ratio (SNR), phase precision, and spatial resolution.
In patients who require enteric tube-feeding the osmolality of the formulas is assumed to play an important role. There is the dilemma that osmolality increases as the digestibility of formulas is enhanced by means of degradation of the nutrients. Hitherto there have been no reports of whether there are differences in nutrient absorption and water fluxes between iso-osmotic polymeric and hyperosmotic oligomeric diets. We therefore investigated absorption of nutrients and net fluxes of water during perfusion of a 1·5 m jejunal segment with oligomeric, polymeric and commercial oligopeptide diets either in the absence of pancreatic juice or with concomitant infusion of pancreatic enzymes. In the absence of pancreatic juice the absorption rates of the polymeric diet and the commercial oligopeptide diets reached 58·0 and 84·5 % respectively of that of a completely-hydrolysed hyperosmotic oligomeric diet. The concomitant infusion of pancreatic enzymes with the polymeric and oligopeptide diets significantly increased the absorption rates of nutrients and energy. The highest absorption rate of energy occurred with the commercial formula Survimed® (Fresenius, Bad Homburg, Germany), probably due to an optimal composition of the macronutrients. The increase in absorption due to the degradation of nutrients by pancreatic enzymes was associated with an increase in net water secretion and flow-rate, reaching similar values to those with the hyperosmotic oligomeric diet. It may be concluded that iso-osmotic oligopeptide formulas require further pancreatic hydrolysis for optimum absorption. In patients with normal pancreatic secretion, oligopeptide formulas have no advantage over polymeric diets. In patients with reduced pancreatic secretion, either completely-hydrolysed hyperosmotic oligomeric diets or polymeric diets supplemented with pancreatic enzymes are appropriate.
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