Experimental and computational investigation of turbulent mixing in microscale reactors

Flash Nanoprecipitation (FNP) is a promising technique for mass production of nanoparticles for use in various areas. Mixing time is such a crucial factor that it affects the particle size distribution as well as the particle morphology. Turbulent mixing in microscale nanoprecipitation reactors, i.e., the planar conned impinging-jet reactor (CIJR) and the multi-inlet vortex reactor (MIVR), is therefore investigated by means of numerical simulations as well as experimental flow visualization methods. In the process of studying, the computational fluid dynamics (CFD) models are validated by comparing simulation results with experimental data. One of the experimental visualization techniques developed in this work uses the phenolphthalein as the tracer that characterizes the acid-base neutralization reaction. Mixing is qualitatively and, by applying a special image processing technique, also quantitatively evaluated. Coherent flow structures are also analyzed through spatial correlation and POD. For the MIVR, the microscopic particle velocimetry (micro-PIV or microPIV) is first employed to measure the velocity field. Results from Reynolds-averaged Navier-Stokes (RANS) simulations and large eddy simulations (LES) are compared to the micro-PIV results. Comparisons show LES is more suitable for simulating flow field in these reactors. In addition, another experimental method developed in this work is also applied to the MIVR, which couples the confocal laser scanning microscopy (CLSM) and the microscopic laser induced fluorescence (micro-LIF). More detailed and quantitatively accurate data are obtained for the CFD model validation. Passive scalar mixing and reactive mixing experiments are both accomplished to quantify the mixing at the maroscale and microscale respectively

Confocal imaging of laminar and turbulent mixing in a microscale multi-inlet vortex nanoprecipitation reactor

Mass production of functional nanoparticles may be realized through flash nanoprecipiation in microscale reactors such as the multi-inlet vortex reactor (MIVR). A comprehensive understanding of mixing in the MIVR is required for process control and reactor design. Mixing in the MIVR is studied using a technique coupling laser induced fluorescence with confocal laser scanning microscopy. It is shown to provide meaningful qualitative and statistical data of the scalar field for analysis and comparison with numerical simulations. Data were collected for four flow rates, showing that mixing is incomplete even at the highest flow rate

A unified mechanism for intron and exon definition and back-splicing.

The molecular mechanisms of exon definition and back-splicing are fundamental unanswered questions in pre-mRNA splicing. Here we report cryo-electron microscopy structures of the yeast spliceosomal E complex assembled on introns, providing a view of the earliest event in the splicing cycle that commits pre-mRNAs to splicing. The E complex architecture suggests that the same spliceosome can assemble across an exon, and that it either remodels to span an intron for canonical linear splicing (typically on short exons) or catalyses back-splicing to generate circular RNA (on long exons). The model is supported by our experiments, which show that an E complex assembled on the middle exon of yeast EFM5 or HMRA1 can be chased into circular RNA when the exon is sufficiently long. This simple model unifies intron definition, exon definition, and back-splicing through the same spliceosome in all eukaryotes and should inspire experiments in many other systems to understand the mechanism and regulation of these processes

Discovery of Unique Lanthionine Synthetases Reveals New Mechanistic and Evolutionary Insights

Identification of a new class of lanthionine synthetases provides insight into the mechanism and evolution of cyclic peptide biosynthesis

The structural and optical properties of GaSb/InGaAs type-II quantum dots grown on InP (100) substrate

We have investigated the structural and optical properties of type-II GaSb/InGaAs quantum dots [QDs] grown on InP (100) substrate by molecular beam epitaxy. Rectangular-shaped GaSb QDs were well developed and no nanodash-like structures which could be easily found in the InAs/InP QD system were formed. Low-temperature photoluminescence spectra show there are two peaks centered at 0.75eV and 0.76ev. The low-energy peak blueshifted with increasing excitation power is identified as the indirect transition from the InGaAs conduction band to the GaSb hole level (type-II), and the high-energy peak is identified as the direct transition (type-I) of GaSb QDs. This material system shows a promising application on quantum-dot infrared detectors and quantum-dot field-effect transistor

Effect of Tanshinone IIA on gut microbiome in diabetes-induced cognitive impairment

Diabetes-induced cognitive impairment (DCI) presents a major public health risk among the aging population. Previous clinical attempts on known therapeutic targets for DCI, such as depleted insulin secretion, insulin resistance, and hyperglycaemia have delivered poor patient outcomes. However, recent evidence has demonstrated that the gut microbiome plays an important role in DCI by modulating cognitive function through the gut–brain crosstalk. The bioactive compound tanshinone IIA (TAN) has shown to improve cognitive and memory function in diabetes mellitus models, though the pharmacological actions are not fully understood. This study aims to investigate the effect and underlying mechanism of TAN in attenuating DCI in relation to regulating the gut microbiome. Metagenomic sequencing analyses were performed on a group of control rats, rats with diabetes induced by a high-fat/high-glucose diet (HFD) and streptozotocin (STZ) (model group) and TAN-treated diabetic rats (TAN group). Cognitive and memory function were assessed by the Morris water maze test, histopathological assessment of brain tissues, and immunoblotting of neurological biomarkers. The fasting blood glucose (FBG) level was monitored throughout the experiments. The levels of serum lipopolysaccharide (LPS) and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunoassays to reflect the circulatory inflammation level. The morphology of the colon barrier was observed by histopathological staining. Our study confirmed that TAN reduced the FBG level and improved the cognitive and memory function against HFD- and STZ-induced diabetes. TAN protected the endothelial tight junction in the hippocampus and colon, regulated neuronal biomarkers, and lowered the serum levels of LPS and TNF-α. TAN corrected the reduced abundance of Bacteroidetes in diabetic rats. At the species level, TAN regulated the abundance of B. dorei, Lachnoclostridium sp. YL32 and Clostridiodes difficile. TAN modulated the lipid metabolism and biosynthesis of fatty acids in related pathways as the main functional components. TAN significantly restored the reduced levels of isobutyric acid and butyric acid. Our results supported the use of TAN as a promising therapeutic agent for DCI, in which the underlying mechanism may be associated with gut microbiome regulation