Measurement of mass force field driving water refilling of cuttage.

Cuttage is a common plant cultivation method, and the key to its survival is the restoration of water refilling, which remains unclear up to now. We report 3D dynamic imaging of water refilling of cuttage without resorting to any contrast agent. Hydrodynamics of the refilled water flow over time reveals the existence of a unit mass force field with a gradient along the refilling direction, which means that cutting plants also have a gradient force field to drive the recovery of water refilling, as predicted by Cohesion-Tension theory in normal plants. We found that force fields of different functional regions are isolated and independently distributed, which is conducive to ensure the safety of water transmission. At the same time, we also found that there is a so-called "inchworm effect" in the mass force field, which contributes to the force transfer inside the cutting through local force accumulation. Results of this paper demonstrate that the developed method for the measurement of mass force field in-vivo is applicable to help decipher the mechanism of plant water refilling.

Extraction of cellulose nanofibrils from pine sawdust by integrated chemical pretreatment.

Reducing energy consumption is major challenge in the industrialization of chemical pretreatments for the extraction of cellulose nanofibrils (CNF). In this study, an integrated chemical pretreatment with alkaline/acid-chlorite/TEMPO-oxidant was used for the nano-fibrillation of CNF from pine sawdust (WS). The alkaline and acid-chlorite pretreatments effectively eliminated the non-cellulosic components present in WS, resulting in the delamination of individual cell layers and swelling of the internal structures within the cellulose fiber bundles and cellulose microfibrils that form these layers. The spacing between CNF within the cellulose microfibrils increased from 3.7 nm to 5.5 nm. These loosely packed hierarchical structures facilitated the penetration of the reagent, which led to an increase in the specific surface area during the TEMPO-oxidant reaction and consequently accelerated the reaction rate. The WS was pretreated in a very dilute solution (1 % NaOH and 0.5 % NaClO2) under mild conditions (70 °C for 1 h), which resulted in a significant reduction of the TEMPO reaction time (from 3 h to 30 min) and a lower consumption of the reaction reagent (one fourth of the amount consumed compared to the direct oxidation of WS to achieve the same degree of cellulose nano-fibrillation).

Dynamic X-ray speckle-tracking imaging with high-accuracy phase retrieval based on deep learning.

Speckle-tracking X-ray imaging is an attractive candidate for dynamic X-ray imaging owing to its flexible setup and simultaneous yields of phase, transmission and scattering images. However, traditional speckle-tracking imaging methods suffer from phase distortion at locations with abrupt changes in density, which is always the case for real samples, limiting the applications of the speckle-tracking X-ray imaging method. In this paper, we report a deep-learning based method which can achieve dynamic X-ray speckle-tracking imaging with high-accuracy phase retrieval. The calibration results of a phantom show that the profile of the retrieved phase is highly consistent with the theoretical one. Experiments of polyurethane foaming demonstrated that the proposed method revealed the evolution of the complicated microstructure of the bubbles accurately. The proposed method is a promising solution for dynamic X-ray imaging with high-accuracy phase retrieval, and has extensive applications in metrology and quantitative analysis of dynamics in material science, physics, chemistry and biomedicine.

Full-field hard X-ray nano-tomography at SSRF.

An in-house designed transmission X-ray microscopy (TXM) instrument has been developed and commissioned at beamline BL18B of the Shanghai Synchrotron Radiation Facility (SSRF). BL18B is a hard (5-14 keV) X-ray bending-magnet beamline recently built with sub-20 nm spatial resolution in TXM. There are two kinds of resolution mode: one based on using a high-resolution-based scintillator-lens-coupled camera, and the other on using a medium-resolution-based X-ray sCMOS camera. Here, a demonstration of full-field hard X-ray nano-tomography for high-Z material samples (e.g. Au particles, battery particles) and low-Z material samples (e.g. SiO2 powders) is presented for both resolution modes. Sub-50 nm to 100 nm resolution in three dimensions (3D) has been achieved. These results represent the ability of 3D non-destructive characterization with nano-scale spatial resolution for scientific applications in many research fields.

Inhibiting weld cracking in high-strength aluminium alloys.

Cracking from a fine equiaxed zone (FQZ), often just tens of microns across, plagues the welding of 7000 series aluminum alloys. Using a multiscale correlative methodology, from the millimeter scale to the nanoscale, we shed light on the strengthening mechanisms and the resulting intergranular failure at the FQZ. We show that intergranular AlCuMg phases give rise to cracking by micro-void nucleation and subsequent link-up due to the plastic incompatibility between the hard phases and soft (low precipitate density) grain interiors in the FQZ. To mitigate this, we propose a hybrid welding strategy exploiting laser beam oscillation and a pulsed magnetic field. This achieves a wavy and interrupted FQZ along with a higher precipitate density, thereby considerably increasing tensile strength over conventionally hybrid welded butt joints, and even friction stir welds.

Redefinition to bilayer osmotic pump tablets as subterranean river system within mini-earth via three-dimensional structure mechanism.

Defining and visualizing the three-dimensional (3D) structures of pharmaceuticals provides a new and important tool to elucidate the phenomenal behavior and underlying mechanisms of drug delivery systems. The mechanism of drug release from complex structured dosage forms, such as bilayer osmotic pump tablets, has not been investigated widely for most solid 3D structures. In this study, bilayer osmotic pump tablets undergoing dissolution, as well as after dissolution in a desiccated solid state were examined, and visualized by synchrotron radiation micro-computed tomography (SR-µCT). In situ formed 3D structures at different in vitro drug release states were characterized comprehensively. A distinct movement pattern of NaCl crystals from the push layer to the drug layer was observed, beneath the semi-permeable coating in the desiccated tablet samples. The 3D structures at different dissolution time revealed that the pushing upsurge in the bilayer osmotic pump tablet was directed via peripheral "roadways". Typically, different regions of the osmotic front, infiltration region, and dormant region were classified in the push layer during the dissolution of drug from tablet samples. According to the observed 3D microstructures, a "subterranean river model" for the drug release mechanism has been defined to explain the drug release mechanism.

Bridging the structure gap between pellets in artificial dissolution media and in gastro-intestinal tract in rats.

Changes in structure of oral solid dosage forms (OSDF) elementally determine the drug release and its therapeutic effects. In this research, synchrotron radiation X-ray micro-computed tomography was utilized to visualize the 3D structure of enteric coated pellets recovered from the gastrointestinal tract of rats. The structures of pellets in solid state and in vitro compendium media were measured. Pellets in vivo underwent morphological and structural changes which differed significantly from those in vitro compendium media. Thus, optimizations of the dissolution media were performed to mimic the appropriate in vivo conditions by introducing pepsin and glass microspheres in media. The sphericity, pellet volume, pore volume and porosity of the in vivo esomeprazole magnesium pellets in stomach for 2 h were recorded 0.47, 1.55 × 108 µm3, 0.44 × 108 µm3 and 27.6%, respectively. After adding pepsin and glass microspheres, the above parameters in vitro reached to 0.44, 1.64 × 108 µm3, 0.38 × 108 µm3 and 23.0%, respectively. Omeprazole magnesium pellets behaved similarly. The structural features of pellets between in vitro media and in vivo condition were bridged successfully in terms of 3D structures to ensure better design, characterization and quality control of advanced OSDF.

Real-time X-ray imaging of mouse cerebral microvessels in vivo using a pixel temporal averaging method.

Rodents are used extensively as animal models for the preclinical investigation of microvascular-related diseases. However, motion artifacts in currently available imaging methods preclude real-time observation of microvessels in vivo. In this paper, a pixel temporal averaging (PTA) method that enables real-time imaging of microvessels in the mouse brain in vivo is described. Experiments using live mice demonstrated that PTA efficiently eliminated motion artifacts and random noise, resulting in significant improvements in contrast-to-noise ratio. The time needed for image reconstruction using PTA with a normal computer was 250 ms, highlighting the capability of the PTA method for real-time angiography. In addition, experiments with less than one-quarter of photon flux in conventional angiography verified that motion artifacts and random noise were suppressed and microvessels were successfully identified using PTA, whereas conventional temporal subtraction and averaging methods were ineffective. Experiments performed with an X-ray tube verified that the PTA method could also be successfully applied to microvessel imaging of the mouse brain using a laboratory X-ray source. In conclusion, the proposed PTA method may facilitate the real-time investigation of cerebral microvascular-related diseases using small animal models.

Sensitive imaging of intact microvessels in vivo with synchrotron radiation.

Early stages of diseases, including stroke, hypertension, angiogenesis of tumours, spinal cord injuries, etc., are closely associated with the lesions of microvasculature. Rodent models of human vascular diseases are extensively used for the preclinical investigation of the disease evolution and therapy with synchrotron radiation. Therefore, non-invasive and in vivo X-ray imaging with high sensitivity and clarity is desperately needed to visualize the microvessels in live-animal models. Contrast agent is essential for the in vivo X-ray imaging of vessels and angiomatous tissue. Because of the non-rigid motion of adjacent tissues, the short circulation time and the intermittent flow of contrast agents in vessels, it is a great challenge for the traditional X-ray imaging methods to achieve well defined images of microvessels in vivo. In this article, move contrast X-ray imaging (MCXI) based on high-brightness synchrotron radiation is developed to overcome the intrinsic defects in conventional methods. Experiments with live rodents demonstrate the practicability of the MCXI method for sensitive and intact imaging of microvessels in vivo.

Dynamic structure model of polyelectrolyte complex based controlled-release matrix tablets visualized by synchrotron radiation micro-computed tomography.

Hydrophilic matrix tablets are the most commonly used dosage forms to fabricate oral controlled-release systems. It is highly desirable to design delivery system with novel mechanism to achieve sustained drug release through a simplified preparation process. The chitosan-anionic polymers based matrix tablets is assumed to produce self-assembly in the gastrointestinal tract, then transferring into film-coated tablets from original matrix type. But its dynamic behavior during dissolution process and the on-going internal microstructural changes during drug release were still in the dark. In this study, by using synchrotron radiation X-ray micro-tomography (SR-µCT) with phase contrast imaging, the micro-structure characteristics of chitosan-λ-carrageenan (CS-λ-CG) matrix based tablets during the dissolution were successfully elucidated for the first time. The qualitative and quantitative analyses of intensity distribution distinguished a hydrated CS-λ-CG layer from a solid core. Visualization based on 3D models provided quantitative details on the micro-structural characteristics of hydration dynamics. After CS-λ-CG matrix tablets were immersed in simulated gastric fluid (SGF) pH 1.2 medium for 0.5-2.0 h, the hydrated layer transformed into a gel layer and a solid swollen layer. The erosion front, swelling front, and solvent penetration front were also defined from the distinguishable micro-structures. More importantly, once the matrix tablet was transferred from SGF to the simulated intestinal fluid (SIF) pH 6.8 medium, a new layer with the enhanced strength and compactness in comparison to common gels was formed on the surface of tablets. The temporal and spatial variation of 3D models further provided direct evidence for this cross-linking behavior, the new layer was composed of CS-λ-CG polyelectrolyte complexes (PEC) which subsequently dominated release mechanisms. In summary, the phase contrast SR-µCT technique was utilized to investigate the hydration dynamics of CS-λ-CG matrix tablets which was supposed to provide a novel drug release mechanism. Based on the structure feature obtained from the high contrast image, different hydration region was distinguished and the cross-linked film was identified and visualized directly for the first time.

Comprehensive characterization of TSV etching performance with phase-contrast X-ray microtomography.

Comprehensive evaluation of through-silicon via (TSV) reliability often requires deterministic and 3D descriptions of local morphological and statistical features of via formation with the Bosch process. Here, a highly sensitive phase-contrast X-ray microtomography approach is presented based on recorrection of abnormal projections, which provides comprehensive and quantitative characterization of TSV etching performance. The key idea is to replace the abnormal projections at specific angles in principles of linear interpolation of neighboring projections, and to distinguish the interface between silicon and air by using phase-retrieval algorithms. It is demonstrated that such a scheme achieves high accuracy in obtaining the etch profile based on the 3D microstructure of the vias, including diameter, bottom curvature radius, depth and sidewall angle. More importantly, the 3D profile error of the via sidewall and the consistency of parameters among all the vias are achieved and analyzed statistically. The datasets in the results and the 3D microstructure can be applied directly to a reference and model for further finite element analysis. This method is general and has potentially broad applications in 3D integrated circuits.

Synchrotron Radiation-Based Three-Dimensional Visualization of Angioarchitectural Remodeling in Hippocampus of Epileptic Rats.

Characterizing the three-dimensional (3D) morphological alterations of microvessels under both normal and seizure conditions is crucial for a better understanding of epilepsy. However, conventional imaging techniques cannot detect microvessels on micron/sub-micron scales without angiography. In this study, synchrotron radiation (SR)-based X-ray in-line phase-contrast imaging (ILPCI) and quantitative 3D characterization were used to acquire high-resolution, high-contrast images of rat brain tissue under both normal and seizure conditions. The number of blood microvessels was markedly increased on days 1 and 14, but decreased on day 60 after seizures. The surface area, diameter distribution, mean tortuosity, and number of bifurcations and network segments also showed similar trends. These pathological changes were confirmed by histological tests. Thus, SR-based ILPCI provides systematic and detailed views of cerebrovascular anatomy at the micron level without using contrast-enhancing agents. This holds considerable promise for better diagnosis and understanding of the pathogenesis and development of epilepsy.

High-efficiency fast X-ray imaging detector development at SSRF.

Indirect X-ray imaging detectors consisting of scintillator screens, long-working-distance microscope lenses and scientific high-speed complementary metal-oxide semiconductor (CMOS) cameras are usually used to realize fast X-ray imaging with white-beam synchrotron radiation. However, the detector efficiency is limited by the coupling efficiency of the long-working-distance microscope lenses, which is only about 5%. A long-working-distance microscope lenses system with a large numerical aperture (NA) is designed to increase the coupling efficiency. It offers an NA of 0.5 at 8× magnification. The Mitutoyo long-working-distance microscope lenses system offers an NA of 0.21 at 7.5× magnification. Compared with the Mitutoyo system, the developed long-working-distance microscope lenses system offers about twice the NA and four times the coupling efficiency. In the indirect X-ray imaging detector, a 50 µm-thick LuAG:Ce scintillator matching with the NA, and a high-speed visible-light CMOS FastCAM SAZ Photron camera are used. Test results show that the detector realized fast X-ray imaging with a frame rate of 100000 frames s-1 and fast X-ray microtomography with a temporal sampling rate up to 25 Hz (25 tomograms s-1).

Synchrotron radiation micro-tomography for high-resolution neurovascular network morphology investigation.

There has been increasing interest in using high-resolution micro-tomography to investigate the morphology of neurovascular networks in the central nervous system, which remain difficult to characterize due to their microscopic size as well as their delicate and complex 3D structure. Synchrotron radiation X-ray imaging, which has emerged as a cutting-edge imaging technology with a high spatial resolution, provides a novel platform for the non-destructive imaging of microvasculature networks at a sub-micrometre scale. When coupled with computed tomography, this technique allows the characterization of the 3D morphology of vasculature. The current review focuses on recent progress in developing synchrotron radiation methodology and its application in probing neurovascular networks, especially the pathological changes associated with vascular abnormalities in various model systems. Furthermore, this tool represents a powerful imaging modality that improves our understanding of the complex biological interactions between vascular function and neuronal activity in both physiological and pathological states.

Magnetic-Sensitive Nanoparticle Self-Assembled Superhydrophobic Biopolymer-Coated Slow-Release Fertilizer: Fabrication, Enhanced Performance, and Mechanism.

Although commercialized slow-release fertilizers coated with petrochemical polymers have revolutionarily promoted agricultural production, more research should be devoted to developing superhydrophobic biopolymer coatings with superb slow-release ability from sustainable and ecofriendly biomaterials. To inform the development of the superhydrophobic biopolymer-coated slow-release fertilizers (SBSF), the slow-release mechanism of SBSF needs to be clarified. Here, the SBSF with superior slow-release performance, water tolerance, and good feasibility for large-scale production was self-assembly fabricated using a simple, solvent-free process. The superhydrophobic surfaces of SBSF with uniformly dispersed Fe3O4 superhydrophobic magnetic-sensitive nanoparticles (SMNs) were self-assembly constructed with the spontaneous migration of Fe3O4 SMNs toward the outermost surface of the liquid coating materials ( i.e., pig fat based polyol and polymethylene polyphenylene isocyanate in a mass ratio 1.2:1) in a magnetic field during the reaction-curing process. The results revealed that SBSF showed longer slow-release longevity (more than 100 days) than those of unmodified biopolymer-coated slow-release fertilizers and excellent durable properties under various external environment conditions. The governing slow-release mechanism of SBSF was clarified by directly observing the atmosphere cushion on the superhydrophobic biopolymer coating using the synchrotron radiation-based X-ray phase-contrast imaging technique. Liquid water only contacts the top of the bulges of the solid surface (10.9%), and air pockets are trapped underneath the liquid (89.1%). The atmosphere cushion allows the slow diffusion of water vapor into the internal urea core of SBSF, which can decrease the nutrient release and enhance the slow-release ability. This self-assembly synthesis of SBSF through the magnetic interaction provides a strategy to fabricate not only ecofriendly biobased slow-release fertilizers but also other superhydrophobic materials for various applications.

A substitute variety for agronomically and medicinally important Serenoa repens (saw palmetto).

Serenoa repens (saw palmetto) berries are one of the most consumed medicinal herbs in the United States and the wild green variety is used in the initial therapy of benign prostatic hyperplasia (BPH), globally. Use of saw palmetto is approved by the German Commission E, and several clinical trials are underway for evaluation of its efficacy. Exploitation of its habitats and over foraging imperil this plant, which only grows in the wild. This is the first study, to propose the use of the S. repens forma glauca (silver variety) as a qualitative substitute for the wild variety, to support its conservation. We compared tissue microstructures and lipid and water distribution through spatial imaging and examined metabolite distribution of three tissue domains and whole berries. This combined approach of 3D imaging and metabolomics provides a new strategy for studying phenotypic traits and metabolite synthesis of closely related plant varieties.

Investigation of inner ear anatomy in mouse using X-ray phase contrast tomography.

A thorough understanding of inner ear anatomy is important for investigators. However, investigation of the mouse inner ear is difficult due to the limitations of imaging techniques. X-ray phase contrast tomography increases contrast 100-1,000 times compared with conventional X-ray imaging. This study aimed to investigate inner ear anatomy in a fresh post-mortem mouse using X-ray phase contrast tomography and to provide a comprehensive atlas of microstructures with less tissue deformation. All experiments were performed in accordance with our institution's guidelines on the care and use of laboratory animals. A fresh mouse cadaver was scanned immediately after sacrifice using an inline phase contrast tomography system. Slice images were reconstructed using a filtered back-projection (FBP) algorithm. Standardized axial and coronal planes were adjusted with a multi-planar reconstruction method. Some three-dimensional (3D) objects were reconstructed by surface rendering. The characteristic features of microstructures, including otoconia masses of the saccular and utricular maculae, superior and inferior macula cribrosae, single canal, modiolus, and osseous spiral lamina, were described in detail. Spatial positions and relationships of the vestibular structures were exhibited in 3D views. This study investigated mouse inner ear anatomy and provided a standardized presentation of microstructures. In particular, otoconia masses were visualized in their natural status without contrast for the first time. The comprehensive anatomy atlas presented in this study provides an excellent reference for morphology studies of the inner ear.

Structural and topological nature of plasticity in sheared granular materials.

Upon mechanical loading, granular materials yield and undergo plastic deformation. The nature of plastic deformation is essential for the development of the macroscopic constitutive models and the understanding of shear band formation. However, we still do not fully understand the microscopic nature of plastic deformation in disordered granular materials. Here we used synchrotron X-ray tomography technique to track the structural evolutions of three-dimensional granular materials under shear. We establish that highly distorted coplanar tetrahedra are the structural defects responsible for microscopic plasticity in disordered granular packings. The elementary plastic events occur through flip events which correspond to a neighbor switching process among these coplanar tetrahedra (or equivalently as the rotation motion of 4-ring disclinations). These events are discrete in space and possess specific orientations with the principal stress direction.

Material distributions and functional structures in probiotic microcapsules.

Smart microstructure design of dosage forms such as microcapsules that protect the microorganism, can improve probiotics survival from gastric pH challenges and prolong their shelf life. In this study, synchrotron radiation X-ray microcomputed tomography (SR-µCT) was applied to quantitatively reveal the material distributions and functional structures of bifidobacterium and lactobacillus microcapsules. The shell layer, middle protective layer, and the microorganisms as particles in the center layer were extracted and visualized. All the microorganisms were encapsulated by the shell completely, which prevents them from being destroyed by external environments. However, the non-uniform thickness of the shell and typical defects in the microcapsules were observed. The quantitative analysis and characterization of internal microstructures provide evidence of the need for further improvement in formulations and processing technologies for the structured system to deliver living microorganisms.

Improving the efficiency of small-angle x-ray scattering computed tomography using the OSEM algorithm.

Small-angle x-ray scattering computed tomography (SAXS-CT) is a nondestructive method for the nanostructure analysis of heterogeneous materials. However, the limits of a long data acquisition time and vast amounts of data prevent SAXS-CT from becoming a routine experimental method in the applications of synchrotron radiation. In this study, the ordered subsets expectation maximization (OSEM) algorithm is introduced to improve the efficiency of SAXS-CT. To demonstrate the practicability of this method, a systematic simulation and experiments were carried out. The simulation results on a numerical phantom show that the OSEM-based SAXS-CT can effectively eliminate streaking artifacts and improve the efficiency of data acquisition by at least 3 times compared with the filter backprojection algorithm. By compromising the reconstruction speed and image quality, the optimal reconstruction parameters are also given for the image reconstruction in the OSEM-based SAXS-CT experiments. An experiment on a bamboo sample verified the validity of the proposed method with limited projection data. A further experiment on polyethylene demonstrated that the OSEM-based SAXS-CT is able to reveal the local nanoscale information about the crystalline structure and distributional difference inside the sample. In conclusion, the OSEM-based SAXS-CT can significantly improve experimental efficiency, which may promote SAXS-CT becoming a conventional method.