Towards carbon neutrality: A study on China's long-term low-carbon transition pathways and strategies.

As the world's biggest carbon dioxide (CO2) emitter and the largest developing country, China faces daunting challenges to peak its emissions before 2030 and achieve carbon neutrality within 40 years. This study fully considered the carbon-neutrality goal and the temperature rise constraints required by the Paris Agreement, by developing six long-term development scenarios, and conducting a quantitative evaluation on the carbon emissions pathways, energy transformation, technology, policy and investment demand for each scenario. This study combined both bottom-up and top-down methodologies, including simulations and analyses of energy consumption of end-use and power sectors (bottom-up), as well as scenario analysis, investment demand and technology evaluation at the macro level (top-down). This study demonstrates that achieving carbon neutrality before 2060 translates to significant efforts and overwhelming challenges for China. To comply with the target, a high rate of an average annual reduction of CO2 emissions by 9.3% from 2030 to 2050 is a necessity, which requires a huge investment demand. For example, in the 1.5 °C scenario, an investment in energy infrastructure alone equivalent to 2.6% of that year's GDP will be necessary. The technological pathway towards carbon neutrality will rely highly on both conventional emission reduction technologies and breakthrough technologies. China needs to balance a long-term development strategy of lower greenhouse gas emissions that meets both the Paris Agreement and the long-term goals for domestic economic and social development, with a phased implementation for both its five-year and long-term plans.

Simultaneous 3D deconvolution and halo removal for spatial light interference microscopy through a two-edge apodized Wiener filter.

As one of the most sensitive quantitative phase microscopy techniques, spatial light interference microscopy (SLIM) has undergone rapid development in the past decade and has seen wide application in both basic science and clinical studies. However, as with any other traditional microscope, the axial resolution is the worst among the three dimensions. This leads to lower contrast in the thicker regions of cell samples. Another common foe in the phase contrast image is the halo artifact, which can block underlying structures, in particular when high resolution is desired. Current solutions focus on either halo removal or contrast enhancement alone, and thus need two processing steps to create both high contrast and halo-free phase images. Further, raw images often suffer from artifacts that are both bright and slowly varying, dubbed here as cloud-like artifacts. After deconvolution, these cloud-like artifacts often dominate the image and obscure high-frequency information, which is typically of greatest interest. In this paper, we first analyzed the unique characteristics of the phase transfer function associated with SLIM to find the root of the cloud-like artifacts and halo artifacts. Then we designed a two-edge apodized deconvolution scheme as a counter measure. We show that even with a simple Wiener filter, the two-edge apodization (TEA) can effectively improve the contrast while suppressing the halo and cloud-like artifacts. Our algorithm, named TEA-Weiner, is non-iterative and thus can be implemented in real time. For low-contrast structures inside the cell such as the endoplasmic reticulum (ER), where ringing artifacts are more likely, we show that two-edge apodization can be combined with additional constraints such as total variation so that their contrast can be enhanced simultaneously with other bright structures inside the cell. Comparing our method with other state-of-the-art algorithms, our method has two advantages: First, deconvolution and halo removal are accomplished simultaneously; second, the image quality is highest using TEA-Weiner filtering.

Epi-illumination dark-field microscopy enables direct visualization of unlabeled small organisms with high spatial and temporal resolution.

Dark-field microscopy is known to offer both high resolution and direct visualization of thin samples. However, its performance and optimization on thick samples is under-explored and so far, only meso-scale information from whole organisms has been demonstrated. In this work, we carefully investigate the difference between trans- and epi-illumination configurations. Our findings suggest that the epi-illumination configuration is superior in both contrast and fidelity compared to trans-illumination, while having the added advantage of experimental simplicity and an "open top" for experimental intervention. Guided by the theoretical analysis, we constructed an epi-illumination dark-field microscope with measured lateral and axial resolutions of 260 nm and 520 nm, respectively. Subcellular structures in whole organisms were directly visualized without the need for image reconstruction, and further confirmed via simultaneous fluorescence imaging. With an imaging speed of 20 to 50 fps, we visualize fast dynamic processes such as cell division and pharyngeal pumping in Caenorhabditis elegans.

Organelle-specific phase contrast microscopy enables gentle monitoring and analysis of mitochondrial network dynamics.

Mitochondria are delicate organelles that play a key role in cell fate. Current research methods rely on fluorescence labeling that introduces stress due to photobleaching and phototoxicity. Here we propose a new, gentle method to study mitochondrial dynamics, where organelle-specific three-dimensional information is obtained in a label-free manner at high resolution, high specificity, and without detrimental effects associated with staining. A mitochondria cleavage experiment demonstrates that not only do the label-free mitochondria-specific images have the required resolution and precision, but also fairly include all cells and mitochondria in downstream morphological analysis, while fluorescence images omit dim cells and mitochondria. The robustness of the method was tested on samples of different cell lines and on data collected from multiple systems. Thus, we have demonstrated that our method is an attractive alternative to study mitochondrial dynamics, connecting behavior and function in a simpler and more robust way than traditional fluorescence imaging.

Multimodal 3D Printing of Phantoms to Simulate Biological Tissue.

Biomedical optical imaging is playing an important role in diagnosis and treatment of various diseases. However, the accuracy and the reproducibility of an optical imaging device are greatly affected by the performance characteristics of its components, the test environment, and the operations. Therefore, it is necessary to calibrate these devices by traceable phantom standards. However, most of the currently available phantoms are homogeneous phantoms that cannot simulate multimodal and dynamic characteristics of biological tissue. Here, we show the fabrication of heterogeneous tissue-simulating phantoms using a production line integrating a spin coating module, a polyjet module, a fused deposition modeling (FDM) module, and an automatic control framework. The structural information and the optical parameters of a "digital optical phantom" are defined in a prototype file, imported to the production line, and fabricated layer-by-layer with sequential switch between different printing modalities. Technical capability of such a production line is exemplified by the automatic printing of skin-simulating phantoms that comprise the epidermis, dermis, subcutaneous tissue, and an embedded tumor.

Quantitative phase microscopy with enhanced contrast and improved resolution through ultra-oblique illumination (UO-QPM).

Recent developments in phase contrast microscopy have enabled the label-free visualization of certain organelles due to their distinct morphological features, making this method an attractive alternative in the study of cellular dynamics. However tubular structures such as endoplasmic reticulum (ER) networks and complex dynamics such as the fusion and fission of mitochondria, due to their low phase contrast, still need fluorescent labeling to be adequately imaged. In this article, we report a quantitative phase microscope with ultra-oblique illumination that enables us to see those structures and their dynamics with high contrast for the first time without labeling. The imaging capability was validated through comparison to the fluorescence images with the same field-of-view. The high image resolution (~270 nm) was validated using both beads and cellular structures. Furthermore, we were able to record the vibration of ER networks at a frame rate of 250 Hz. We additionally show complex cellular processes such as remodeling of the mitochondria networks through fusion and fission and vesicle transportation along the ER without labels. Our high spatial and temporal resolution allowed us to observe mitochondria "spinning", which has not been reported before, further demonstrating the advantages of the proposed method.