Denoising Diffusion Probabilistic Models for Generation of Realistic Fully-Annotated Microscopy Image Data Sets

Recent advances in computer vision have led to significant progress in the generation of realistic image data, with denoising diffusion probabilistic models proving to be a particularly effective method. In this study, we demonstrate that diffusion models can effectively generate fully-annotated microscopy image data sets through an unsupervised and intuitive approach, using rough sketches of desired structures as the starting point. The proposed pipeline helps to reduce the reliance on manual annotations when training deep learning-based segmentation approaches and enables the segmentation of diverse datasets without the need for human annotations. This approach holds great promise in streamlining the data generation process and enabling a more efficient and scalable training of segmentation models, as we show in the example of different practical experiments involving various organisms and cell types.Comment: 9 pages, 2 figure

Automatic detection of cell-cycle stages using recurrent neural networks.

Mitosis is the process by which eukaryotic cells divide to produce two similar daughter cells with identical genetic material. Research into the process of mitosis is therefore of critical importance both for the basic understanding of cell biology and for the clinical approach to manifold pathologies resulting from its malfunctioning, including cancer. In this paper, we propose an approach to study mitotic progression automatically using deep learning. We used neural networks to predict different mitosis stages. We extracted video sequences of cells undergoing division and trained a Recurrent Neural Network (RNN) to extract image features. The use of RNN enabled better extraction of features. The RNN-based approach gave better performance compared to classifier based feature extraction methods which do not use time information. Evaluation of precision, recall, and F-score indicates the superiority of the proposed model compared to the baseline. To study the loss in performance due to confusion between adjacent classes, we plotted the confusion matrix as well. In addition, we visualized the feature space to understand why RNNs are better at classifying the mitosis stages than other classifier models, which indicated the formation of strong clusters for the different classes, clearly confirming the advantage of the proposed RNN-based approach

Thermal Analysis of Building Roofs with Latent Heat Storage for Reduction in Energy Consumption and CO2 Emissions: An Experimental and Numerical Research

In green energy buildings, air conditioning charges can be lowered through careful planning of the building’s envelope. This article investigates several strategically designed phase change material (PCM) roof envelopes for savings on air conditioning prices, CO2 emission abatement, and payback timeframes in hot–arid and warm-temperate climates, taking into account unsteady heat transfer characteristics, cooling, and heating degree–hours. This is accomplished by using six different PCMs–RCC (reinforced cement concrete) roof envelope cases (RCC roof with PCM layer on the outer side, RCC roof with PCM layer on the center (middle), RCC roof with PCM layer on the inside, RCC roof with PCM layers placed on the outside and center, RCC roof with PCM layers placed on the center and inside, and RCC roof with PCM layers placed on the outer side and inside) with three PCMs (FS29 (form stable mixture), HS29 (hydrated salt), and OM29 (organic mixture)). PCM thermophysical characteristics are experimentally measured. The analytical results are experimentally validated. In hot–arid and warm-temperate regions, the layer of PCM installed on the outside of the RCC with HS29 saved the most on air conditioning expenses, at 6.29 and 6.61 $/m2, respectively. They also reported the greatest carbon mitigation of 300.55 kg of CO2/year and 281.58 kg of CO2/year with the faster payback periods. PCM roof envelopes are the most energy-efficient option for green buildings

Quantitative results of synthetic data.

PSNR values presented as boxplots, calculated between real image data and synthetic image data generated from corresponding silver truth and segmentation masks. Those silver truth segmentations are generated with automated approaches and validated to be reliable for training purposes. Whiskers range from the 5th to the 95th quantile, median values are indicated as orange line while mean values are depicted as green triangle and boxes represent the interquartile range. The involved datasets are 3D Caenorhabditis elegans (CE) [19], 2D Mouse Stem Cells (GOWT1) [19], 2D HeLa Cells (HeLa) [19], 3D Nuclei and Membranes of Danio rerio (DRNuc,DRMem) [21], 2D+t mitotic progression in Mouse Stem Cells (HeLa+t) [24] and 2D overlapping cervical cancer cells (Cerv) [39]. Using corresponding sketches and the optimized settings of tstart = 400 and σ = 1, the backward process was used to replicate corresponding image samples and PSNR values were calculated to assess similarity between synthetic and real versions. The Danio rerio multi-channel data and the temporal HeLa data present special cases, which demonstrate limitations of the proposed approach. (PDF)</p

Thermal Analysis of Building Roofs with Latent Heat Storage for Reduction in Energy Consumption and CO2 Emissions: An Experimental and Numerical Research

In green energy buildings, air conditioning charges can be lowered through careful planning of the building’s envelope. This article investigates several strategically designed phase change material (PCM) roof envelopes for savings on air conditioning prices, CO2 emission abatement, and payback timeframes in hot–arid and warm-temperate climates, taking into account unsteady heat transfer characteristics, cooling, and heating degree–hours. This is accomplished by using six different PCMs–RCC (reinforced cement concrete) roof envelope cases (RCC roof with PCM layer on the outer side, RCC roof with PCM layer on the center (middle), RCC roof with PCM layer on the inside, RCC roof with PCM layers placed on the outside and center, RCC roof with PCM layers placed on the center and inside, and RCC roof with PCM layers placed on the outer side and inside) with three PCMs (FS29 (form stable mixture), HS29 (hydrated salt), and OM29 (organic mixture)). PCM thermophysical characteristics are experimentally measured. The analytical results are experimentally validated. In hot–arid and warm-temperate regions, the layer of PCM installed on the outside of the RCC with HS29 saved the most on air conditioning expenses, at 6.29 and 6.61 $/m2, respectively. They also reported the greatest carbon mitigation of 300.55 kg of CO2/year and 281.58 kg of CO2/year with the faster payback periods. PCM roof envelopes are the most energy-efficient option for green buildings

Latent feature representation.

2D feature representations obtained with t-SNE from the latent representation of an autoencoder for real 3D Arabidopsis thaliana image data [18] and corresponding synthetic data generated from sketches of manual annotations. Additionally, feature representations obtained for raw sketches serve as a reference. Since this data set contains large-scale image data, each image stack is partitioned into patches to reduce computational demand. During application, a feature representation for each single patch is obtained and averaged to derive an overall feature description of the entire image stack. Results indicate that the diffusion model learns the average distribution of real image data, since latent representations of synthetic data is enclosed by representations obtained for real image data. Sketch representations form a more distinct cluster, further promoting the realism of synthetic image data. (PDF)</p

Pipeline optimization.

(a) Noisy data created by the forward process from either real images or sketches needs to be sufficiently similar to allow for the generation of realistic image data in the backward process, assessed by histograms. For the backward process, peak signal-to-noise ratio (PSNR) and zero-normalized cross-correlation (ZNCC) are used as metrics, to assess the realism of image data generated from different starting points tstart and sketch blurring factors σ. (b) Overlays of generated image data (red) and annotation masks (green) show how structural correlation is diminishing with increasing tstart in regions of low contrast, while manual annotation inaccuracies even present in regions of high contrast do not appear in simulated data.</p

Special cases of generated image data.

Examples of real image data and corresponding synthetic image data generated from corresponding annotations of overlapping cells [39] (top). Moreover, examples of varying background illumination in C. elegans [19, 20] was generated by adding indications within the sketches (bottom). This demonstrates the intuitive strength of the proposed approach, as more complex scenes of overlapping cells can be realistically generated and position-dependent texture characteristics can be straightforwardly imposed and controlled. (PDF)</p