Pulmonary acini exhibit complex changes during postnatal rat lung development

Pulmonary acini represent the functional gas-exchanging units of the lung. Due to technical limitations, individual acini cannot be identified on microscopic lung sections. To overcome these limitations, we imaged the right lower lobes of instillation-fixed rat lungs from postnatal days P4, P10, P21, and P60 at the TOMCAT beamline of the Swiss Light Source synchrotron facility at a voxel size of 1.48 μm. Individual acini were segmented from the three-dimensional data by closing the airways at the transition from conducting to gas exchanging airways. For a subset of acini (N = 268), we followed the acinar development by stereologically assessing their volume and their number of alveoli. We found that the mean volume of the acini increases 23 times during the observed time-frame. The coefficients of variation dropped from 1.26 to 0.49 and the difference between the mean volumes of the fraction of the 20% smallest to the 20% largest acini decreased from a factor of 27.26 (day 4) to a factor of 4.07 (day 60), i.e. shows a smaller dispersion at later time points. The acinar volumes show a large variation early in lung development and homogenize during maturation of the lung by reducing their size distribution by a factor of 7 until adulthood. The homogenization of the acinar sizes hints at an optimization of the gas-exchange region in the lungs of adult animals and that acini of different size are not evenly distributed in the lungs. This likely leads to more homogeneous ventilation at later stages in lung development.

Kinetics of 1- and 2-methylallyl + O2 reaction, investigated by photoionisation using synchrotron radiation

The reaction kinetics of the isomers of the methylallyl radical with molecular oxygen has been studied in a flow tube reactor at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source storage ring.

Time-of-arrival detection for time-resolved scanning transmission X-ray microscopy imaging

A setup for time-resolved scanning transmission X-ray microscopy imaging is presented, which allows for an increase in the temporal resolution without the requirement of operating the synchrotron light source with low-α optics through the measurement of the time-of-arrival of the X-ray photons. Measurements of two filling patterns in hybrid mode of the Swiss Light Source are presented as a first proof-of-principle and benchmark for the performances of this new setup. From these measurements, a temporal resolution on the order of 20–30 ps could be determined.

The TELL automatic sample changer for macromolecular crystallography

In this paper, the design and functionalities of the high-throughput TELL sample exchange system for macromolecular crystallography is presented. TELL was developed at the Paul Scherrer Institute with a focus on speed, storage capacity and reliability to serve the three macromolecular crystallography beamlines of the Swiss Light Source, as well as the SwissMX instrument at SwissFEL.

Chemical-mechanical-hydraulic coupling in deforming, dehydrating halite-gypsum rocks - implications for basal detachments in thin-skinned tectonics

<p>Long-distance transport along weak basal detachments in thin-skinned tectonics is often accomplished by rheologically weak evaporites. This weakness can be attributed to  the behavior of gypsum and/or halite. While the former dehydrates and the released fluid reduces the effective stress in the system, the latter is known to be extremely weak at the corresponding conditions. Separately, both minerals and their behavior under tectonic loading have been studied in great detail. However, these studies on single minerals are limited in that natural detachments are often not monomineralic and are clearly affected by interdependencies between different mineral species. In evaporitic sequences, two key couplings that can be expected are: 1) the sensitivity of the dehydration reaction to the pore fluid pressure versus the notoriously low permeability of rock salt (a potentially negative feedback), and 2) the exposure of halite to undersaturated water released from the gypsum dehydration reaction, versus the response of the dehydration reaction to lower water activity due to dissolved salt species (a potentially positive feedback). </p><p>Here we present insights from experiments that used time-resolved (4D) synchrotron tomographic microscopy and our x-ray transparent triaxial deformation rig Mjølnir to document the evolution of layered gypsum-halite samples that were simultaneously deformed and dehydrated. Our data, which were acquired at the TOMCAT beamline at the Swiss Light Source, allow us to visualise chemical-hydraulic-mechanical feedbacks on the grain scale, and quantify the microscale evolution of transport properties. In this contribution, we show that gypsum dehydration affects the capacity of the halite layers to retain the liberated fluids. The reaction itself generates the pore fluid pressure to create permeability in the salt layers through hydraulic fracturing. Dissolved salt significantly accelerates the reaction, and the evolving interconnected porosity facilitates the transport and precipitation of solutes, which contributes to the rheological complexity. These insights have, potentially significant, repercussions on the long-standing assumption about the significance of the gypsum dehydration on thrust fault formation within evaporitic sequences.</p>

Pulmonary acini exhibit complex changes during postnatal rat lung development

Pulmonary acini represent the functional gas-exchanging units of the lung. Due to technical limitations, individual acini cannot be identified on microscopic lung sections. To overcome these limitations, we imaged the right lower lobes of instillation-fixed rat lungs from postnatal days P4, P10, P21, and P60 at the TOMCAT beamline of the Swiss Light Source synchrotron facility at a voxel size of l.48μm. Individual acini were segmented from the three-dimensional data by closing the airways at the transition from conducting to gas exchanging airways. For a subset of acini (N=268), we followed the acinar development by stereologically assessing their volume and their number of alveoli. We found that the mean volume of the acini increases 23 times during the observed timeframe. The coefficients of variation dropped from 1.26 to 0.49 and the difference between the mean volumes of the fraction of the 20 % smallest to the 20 % largest acini decreased from a factor of 27.26 (day 4) to a factor of 4.07 (day 60), i.e. shows a smaller dispersion at later time points. The acinar volumes show a very large variation early in lung development and homogenize during maturation of the lung by reducing their size distribution by a factor of 7 until adulthood. The homogenization of the acinar sizes hints at an optimization of the gas-exchange region in the lungs of adult animals and that acini of different size are not evenly distributed in the lungs. This likely leads to more homogeneous ventilation at later stages in lung development.