Chlamydiae are strict intracellular pathogens residing within a specialised membrane-bound compartment called the inclusion. Therefore, each infected cell can, be considered as a single entity where bacteria form a community within the inclusion. It remains unclear as to how the population of bacteria within the inclusion influences individual bacterium. The life cycle of Chlamydia involves transitioning between the invasive elementary bodies (EBs) and replicative reticulate bodies (RBs). We have used cryo-soft X-ray tomography to observe individual inclusions, an approach that combines 40 nm spatial resolution and large volume imaging (up to 16 µm). Using semi-automated segmentation pipeline, we considered each inclusion as an individual bacterial niche. Within each inclusion, we identifyed and classified different forms of the bacteria and confirmed the recent finding that RBs have a variety of volumes (small, large and abnormal). We demonstrate that the proportions of these different RB forms depend on the bacterial concentration in the inclusion. We conclude that each inclusion operates as an autonomous community that influences the characteristics of individual bacteria within the inclusion.
Understanding the structure of chromatin in chromosomes during normal and diseased state of cells is still one of the key challenges in structural biology. Using DAPI staining alone together with Fluorescence lifetime imaging (FLIM), the environment of chromatin in chromosomes can be explored. Fluorescence lifetime can be used to probe the environment of a fluorophore such as energy transfer, pH and viscosity. Multicolor FISH (M-FISH) is a technique that allows individual chromosome identification, classification as well as assessment of the entire genome. Here we describe a combined approach using DAPI as a DNA environment sensor together with FLIM and M-FISH to understand the nanometer structure of all 46 chromosomes in the nucleus covering the entire human genome at the single cell level. Upon DAPI binding to DNA minor groove followed by fluorescence lifetime measurement and imaging by multiphoton excitation, structural differences in the chromosomes can be studied and observed. This manuscript provides a blow by blow account of the protocol required to perform M-FISH-FLIM of whole chromosomes.
Synchrotron high-energy X-ray diffraction computed tomography has been employed to investigate, for the first time, commercial cylindrical Li-ion batteries electrochemically cycled over the two cycling rates of C/2 and C/20. This technique yields maps of the crystalline components and chemical species as a cross-section of the cell with high spatiotemporal resolution (550 × 550 images with 20 × 20 × 3 µm3 voxel size in ca. 1 h). The recently developed Direct Least-Squares Reconstruction algorithm is used to overcome the well-known parallax problem and led to accurate lattice parameter maps for the device cathode. Chemical heterogeneities are revealed at both electrodes and are attributed to uneven Li and current distributions in the cells. It is shown that this technique has the potential to become an invaluable diagnostic tool for real-world commercial batteries and for their characterization under operating conditions, leading to unique insights into “real” battery degradation mechanisms as they occur.
In this paper, a systematic investigation is carried out to test micro-SORS capability to non-destructively characterize a system where an agent diffuses into a turbid matrix with potential applications in heritage science and elsewhere. Defocusing micro-SORS experiments were performed on two specially designed sets of samples with controlled characteristics. Three parameters have been considered, namely penetration depth, concentration of the agent and its profile within the matrix. A relative agent/matrix Raman intensity decay rate is observed when the microscope objective is moved away from the sample surface, and the slope of this ratio trend was found to correlate with the penetration depth of the agent involved in the diffusion process. In situations where the concentration profile is known, different penetration depths of the agent can be discriminated from each other using the slope of the normalized agent/matrix Raman intensity decay rate. This outcome opens prospects for non-destructively monitoring the efficacy of conservation treatments, based on the penetration depth of the products as well as it provides an analytical tool for other applications where the penetration of an agent into a diffusely scattering matrix is involved such as drug perfusion through skin, pharmaceutical tablet dissolution process and numerous others.
In spite of many years of research, the physical phenomena leading to the evolution of compacted graphite (CG) during solidification is still not fully understood. In particular, it is unknown how highly branched CG aggregates form and evolve in the semi-solid, and how local microstructural variations at micrometer length scale affect this growth process. We present here the first time-resolved synchrotron tomography combined with a bespoke high-temperature environmental cell that allows direct observation of the evolution of CG and relates this dynamic process to the local surrounding microstructures in a cast iron sample during repeated melting and solidification. Distinct processes are identified for the formation of CG involving the nucleation, growth, development of branches and interconnection of graphite particles, ultimately evolving into highly branched graphite aggregates with large sizes and low sphericities. CG is found to nucleate with a spheroidal or a plate-like shape, developing branches induced by high carbon concentration, e.g. thin melt channels. Additionally, CG grows much faster than spheroidal graphite during subsequent cooling in solid state. The direct visualization of the dynamic solidification process provides unprecedented new insights into formation mechanisms of CG and correlating factors such as local microstructural variations, and guides the development of CG iron solidification models.
The top-performing perovskite solar cells (efficiency > 20%) generally rely on the use of a nanocrystal TiO2 electron transport layer (ETL). However, the efficacies and stability of the current stereotypically prepared TiO2 ETLs employing commercially available TiO2 nanocrystal paste are far from their maximum values. As revealed herein, the long-hidden reason for this discrepancy is that acidic protons (∼0.11 wt %) always remain in TiO2 ETLs after high-temperature sintering due to the decomposition of the organic proton solvent (mostly alcohol). These protons readily lead to the formation of Ti–H species upon light irradiation, which act to block the electron transfer at the perovskite/TiO2 interface. Affront this challenge, we introduced a simple deprotonation protocol by adding a small amount of strong proton acceptors (sodium ethoxide or NaOH) into the common TiO2 nanocrystal paste precursor and replicated the high-temperature sintering process, which wiped out nearly all protons in TiO2 ETLs during the sintering process. The use of deprotonated TiO2 ETLs not only promotes the PCE of both MAPbI3-based and FA0.85MA0.15PbI2.55Br0.45-based devices over 20% but also significantly improves the long-term photostability of the target devices upon 1000 h of continuous operation.
Liquids, glasses, and amorphous materials are ubiquitous in the Earth sciences and are intrinsic to a plethora of geological processes, ranging from volcanic activity, deep Earth melting events, metasomatic processes, frictional melting (pseudotachylites), lighting strikes (fulgurites), impact melting (tektites), hydrothermal activity, aqueous solution geochemistry, and the formation of dense high-pressure structures. However, liquids and glassy materials lack the long-range order that characterizes crystalline materials, and studies of their structure require a different approach to that of conventional crystallography. The pair distribution function is the neutron diffraction technique used to characterize liquid and amorphous states. When combined with atomistic models, neutron diffraction techniques can determine the properties and behavior of disordered structures.
Carbon capture and utilization (CCU) represent a promising strategy to reduce CO2 emissions and promote a sustainable economy. We report an integrated CCU (ICCU) process by integrating CO2 capture with reverse water gas shift reaction by applying simple and low-cost CaO as both sorbent and catalyst. By switching the feeding gas from CO2 source to H2 isothermally, up to 75% of captured CO2 was 100% converted into CO at 600-700 °C and the cycle performance of CaO was significantly improved under ICCU condition. In addition, the simulation confirms the significant economic advantage compared to similar traditional processes. The work could dramatically reduce the cost of materials and simplify CCU processes to advance the development and deployment of carbon neutrality technologies.
Many soft tissues, such as the intervertebral disc (IVD), have a hierarchical fibrous composite structure which suffers from regional damage. We hypothesise that clinical injury patterns in these tissues occur in localised regions where there is an integrated requirement for both marked compliance and significant load transfer. Here we used synchrotron computed tomography (sCT) to resolve collagen fibre bundles (~5μm width) in 3D throughout an intact native rat lumbar IVD under increasing compressive load. Using intact samples meant that tissue boundaries (such as endplate-disc or nucleus-annulus) and residual strain were preserved; this is vital for characterising both the inherent structure and structural changes upon loading in tissue regions functioning in a near-native environment. Nano-scale displacement measurements along >10,000 individual fibres were tracked, and fibre orientation, curvature and strain changes were compared between the failure-prone posterior-lateral region and the more robust anterior region. These methods can be widely applied to other soft tissues, to identify fibre structures which cause tissue regions to be more susceptible to injury and degeneration. Our results demonstrate for the first time that highly-localised changes in fibre orientation, curvature and strain indicate differences in regional strain transfer and mechanical function (e.g. tissue compliance), correlating directly with locations clinically at risk of damage. This included decreased fibre reorientation at higher loads, specific tissue morphology which reduced capacity for flexibility and high strain at the disc-endplate boundary.