Xianjun Zhang

Mitochondria regenerate adenosine triphosphate (ATP) through oxidative phosphorylation. This process is carried out by five membrane-bound complexes collectively known as the respiratory chain, working in concert to transfer electrons and pump protons. The precise organization of these complexes in native cells is debated. We used in situ cryo–electron tomography to visualize the native structures and organization of several major mitochondrial complexes in Chlamydomonas reinhardtii cells. ATP synthases and respiratory complexes segregate into curved and flat crista membrane domains, respectively. Respiratory complexes I, III, and IV assemble into a respirasome supercomplex, from which we determined a native 5-angstrom (Å) resolution structure showing binding of electron carrier cytochrome c . Combined with single-particle cryo–electron microscopy at 2.4-Å resolution, we model how the respiratory complexes organize inside native mitochondria.

In situ cryo-electron tomography (cryo-ET) has emerged as the method of choice to investigate structures of biomolecules in their native context. However, challenges remain in the efficient production of large-scale cryo-ET datasets, as well as the community sharing of this information-rich data. Here, we applied a cryogenic plasma-based focused ion beam (cryo-PFIB) instrument for high-throughput milling of the green alga Chlamydomonas reinhardtii , a useful model organism for in situ visualization of numerous fundamental cellular processes. Combining cryo-PFIB sample preparation with recent advances in cryo-ET data acquisition and processing, we generated a dataset of 1829 reconstructed and annotated tomograms, which we provide as a community resource to drive method development and inspire biological discovery. To assay the quality of this dataset, we performed subtomogram averaging (STA) of both soluble and membrane-bound complexes ranging in size from >3 MDa to ∼200 kDa, including 80S ribosomes, Rubisco, nucleosomes, microtubules, clathrin, photosystem II, and mitochondrial ATP synthase. The majority of these density maps reached sub-nanometer resolution, demonstrating the potential of this C. reinhardtii dataset, as well as the promise of modern cryo-ET workflows and open data sharing towards visual proteomics.

EMPIAR, the Electron Microscopy Public Image Archive centered at EMBL-EBI, is a public resource for raw electron microscopy images related to EMDB, contains micrographs, particle sets and tilt-series.

The aim of this study was to establish a prediction model for 30-day deaths of cirrhotic patients in intensive care unit. A case-control study involving 1840 patients was conducted in the Medical Information Mart of the Intensive Care Database III version 1.4. The logistic regression with L1 regularization was used to screen out the variables. The 30-day in-hospital death was used as the dependent variable and the selected variables were used as the independent variable to build a random forest model. The performance of the model was validated by the internal validation. The variables screened by logistic regression analysis were the age, heart rate, respiratory rate, systolic blood pressure, diastolic blood pressure, Oxygen saturation, white blood cells, platelets, red cell distribution width, glucose, blood urea nitrogen, bicarbonate, total bilirubin, hematocrit, alanine transaminase, aspartate transaminase, bilirubin, Simplified Acute Physiology Score II and Sequential Organ Failure Assessment. The areas under the curve of the random forest model based on these variables was 0.908, and the performance of this model were internally validated with an areas under the curve of 0.801. The random forest model displayed that Simplified Acute Physiology Score, Sequential Organ Failure Assessment, blood urea nitrogen, total bilirubin and bilirubin were more important predictors for the 30-day death of cirrhotic patients in intensive care unit. A prediction model for death of cirrhotic patients was developed based on a random forest analysis, providing a tool to evaluate the patients with a high risk of 30-day in-hospital deaths to help clinician make preventive intervention to decrease the mortality.

Subcellular maps of β cells reveal the coordinated reorganization of organelles during insulin secretion.

Multiple distinct tomograms of a single β cell enable investigation of the architecture of insulin vesicle neighborhoods.

The 4H SiliconCarbide metal semiconductor field effect transistor (4H-SiC MESFET) with a buffer layer between the gate and channel (BG) is optimized and a new stair-stepping buffer-gate structure (SBG) is proposed for improving the breakdown characteristics. The terminal technology of breakdown point transfer (BPT) is applied in 4H-SiC SBG-MESFET in order to scatter the electric field lines and transfer the breakdown point. The breakdown mechanism is further investigated by simulating the surface electric field distribution and electrostatic potential contours. The results show that the breakdown voltage is increased from 120 V to 180 V, improved by the rate of 50% while the current density has hardly deteriorated, and thus the current density is improved from 9.35 W/mm to 13.2 W/mm in comparison with BG structure.

Current density and breakdown voltage of step-buffer 4H-SiC metal semiconductor field effect transistor (4H-SiC MESFET) are simulated by using ISE-TCAD. Simulated results show that current density of the step-buffer structure is higher than that of the conventional structure at the same gate bias, 800 mA/mm and 600 mA/mm at Vgs=-4V, respectively. The breakdown happened in the gate corner close to the drain since there crowds most electric field line and the breakdown voltage of the step-buffer 4H-SiC MESFET is 140V, 40 per cent higher than that of the conventional 4H-SiC MESFET because there is a more dispersive electric field distribution. So, the step-buffer 4H-SiC MESFET has better power performance, when compared with the conventional structure.

Electrification of rural areas has always been a challenge. In addition, large livestock farms such as dairy farms, also face environmental problems due to inappropriate treatment of animal wastes. Therefore, improvement of the electrical system in farms vis-a-vis efficient waste management is of great importance to industry. In this paper, a combined cooling, heating, and power (CCHP) microgrid model was built to improve system efficiency of energy utilization and lessen environmental problems caused by animal wastes based on multi-objective optimization. In this proposed model, the animal manure is used to produce biogas, which is used to feed internal combustion engines (ICEs), gas boilers, and absorption chillers. The generated electricity would offset that would otherwise be bought from main grids. PV generation is introduced to further increase the renewable fraction of energy contents. The electrical storage is also included to balance power demand and power supply. To increase system efficiency of energy utilization, coolant water from ICEs, plus their exhaust, could be utilized based on the thermal storage modeled, by inclusion of absorption refrigerator and heat exchanger. The final goal is to maximize energy output from distributed energy resources (DERs) and meanwhile minimize daily system operating cost. Extra electricity generated beyond the load demand could be used to charge battery storage. In this way, system energy cost is reduced with energy system improvement and reconfiguration, and surrounding environmental problems due to animal wastes are also lessened.