Review of the transition From smouldering to flaming combustion in wildfires

Wildfires are uncontrolled combustion events occurring in the natural environment (forest, grassland, or peatland). The frequency and size of these fires are expected to increase globally due to changes in climate, land use, and population movements, posing a significant threat to people, property, resources, and the environment. Wildfires can be broadly divided into two types: smouldering (heterogeneous combustion) and flaming (homogeneous combustion). Both are important in wildfires, and despite being fundamentally different, one can lead to the other. The smouldering-to-flaming (StF) transition is a quick initiation of homogeneous gas-phase ignition preceded by smouldering combustion, and is considered a threat because the following sudden increase in spread rate, power, and hazard. StF transition needs sufficient oxygen supply, heat generation, and pyrolysis gases. The unpredictable nature of the StF transition, both temporally and spatially, poses a challenge in wildfire prevention and mitigation. For example, a flaming fire may rekindle through the StF transition of an undetected smouldering fire or glowing embers. The current understanding of the mechanisms leading to the transition is poor and mostly limited to experiments with samples smaller than 1.2 m. Broadly, the literature has identified the two variables that govern this transition, i.e., oxygen supply and heat flux. Wind has competing effects by increasing the oxygen supply, but simultaneously increasing cooling. The permeability of a fuel and its ability to remain consolidated during burning has also been found to influence the transition. Permeability controls oxygen penetration into the fuel, and consolidation allows the formation of internal pores where StF can take place. Considering the high complexity of the StF transition problem, more studies are needed on different types of fuel, especially on wildland fuels because most studied materials are synthetic polymers. This paper synthesises the research, presents the various StF transition characteristics already in the literature, and identifies specific topics in need of further research

Establishment of Hyperspectral Prediction Model of Water Content in Anshan-Type Magnetite

The high water content of iron ore will reduce its machinability, which is not conducive to the smooth progress of mineral processing, sintering, smelting and tailings treatment. Therefore, it is very important to control the water content of iron ore reasonably for improving mining production efficiency, reducing energy consumption and reducing waste of raw materials. However, due to the complexity of iron ore composition and properties, traditional detection techniques (such as loss on drying method and resistance method) have shortcomings in sensitivity and accuracy. Three kinds of Anshan-type magnetite from a certain area in Tangshan, Hebei Province, were selected to test hyperspectral data under different water contents (0−40.0%). Using S-G smoothing filtering (S-G), multivariate scattering correction (MSC), standard normal transformation (SNV), second derivative (SD), reciprocal logarithm (LR) and continuum removal (CR) to preprocess the data, the spectral characteristics and their correlation with water content were analyzed. In order to further improve the prediction ability of the model, the competitive adaptive reweighting method (CARS) was used to optimize the characteristic band, and a prediction model was established by combining random forest regression (RFR), least squares support vector regression (LSSVR) and particle swarm optimization least squares support vector regression (PSO-LSSVR). The prediction effects of different magnetite water content models were compared, and finally the best model was selected to improve the accuracy of water content detection in mineral processing and smelting. The results show that: (1) when the water content of Anshan-type magnetite samples with different particle sizes changes, the change trend of their spectral curves is generally consistent, and the reflectivity is negatively correlated with the water content, it shows obvious absorption characteristics around 990nm, 1440nm and 1920nm; the Pearson correlation coefficient (r) of spectral data pretreated by MSC and SNV can reach −0.950(412nm) and −0.964 (421nm), respectively. (2) Among the three models, the PSO-LSSVR model is the most stable, and the SNV-CARS-LSSVR model with granularity of 0.3−0.5mm and the MSC-CARS-PSO-LSSVR model with granularity of 0.5−2mm are preferred. The prediction set determination coefficients (R2) of the models are 0.778 and 0.789, and the root mean square error (RMSE) were 5.45% and 5.41%, respectively. Compared with previous studies, a more stable water content prediction model of Anshan magnetite was constructed by combining data preprocessing, CARS feature screening and nonlinear regression algorithm, which provides higher precision support for water content detection in mining production

Cooperative wrapping of nanoparticles of various sizes and shapes by lipid membranes

Understanding the interaction between nanoparticles (NPs) and cell membranes is crucial for the design of NP-based drug delivery systems and for the assessment of the risks exerted by the NPs. Recent experimental and theoretical studies have shown that cell membranes can mediate attraction between NPs and form tubular structures to wrap multiple NPs. However, the cooperative wrapping process is still not well understood, and the shape effect of NPs is not considered. In this article, we use large-scale coarse-grained molecular dynamics (CGMD) simulations to study the cooperative wrapping of NPs when a varying number of NPs adhered to the membrane. Spherical, prolate and oblate NPs of different sizes are considered in this study. We find that, in addition to tubular structures, the membrane can form a pocket-like and a handle-like structure to wrap multiple NPs depending on the size and shape of the NPs. Furthermore, we find that NPs can mediate membrane hemifusion or fusion during this process. Our findings provide new insights into the interaction of NPs with the cell membrane.National Natural Science Foundation of China [41173113, 41473122]; Hundred Talents Program of Chinese Academy of SciencesSCI(E)ARTICLE264644-46521

Inflammation switches the chemoattractant requirements for naive lymphocyte entry into lymph nodes.

Sustained lymphocyte migration from blood into lymph nodes (LNs) is important for immune responses. The CC-chemokine receptor-7 (CCR7) ligand CCL21 is required for LN entry but is downregulated during inflammation, and it has been unclear how recruitment is maintained. Here, we show that the oxysterol biosynthetic enzyme cholesterol-25-hydroxylase (Ch25h) is upregulated in LN high endothelial venules during viral infection. Lymphocytes become dependent on oxysterols, generated through a transcellular endothelial-fibroblast metabolic pathway, and the receptor EBI2 for inflamed LN entry. Additionally, Langerhans cells are an oxysterol source. Ch25h is also expressed in inflamed peripheral endothelium, and EBI2 mediates B cell recruitment in a tumor model. Finally, we demonstrate that LN CCL19 is critical in lymphocyte recruitment during inflammation. Thus, our work explains how naive precursor trafficking is sustained in responding LNs, identifies a role for oxysterols in cell recruitment into inflamed tissues, and establishes a logic for the CCR7 two-ligand system

MDM2 Degradation as a Novel and Efficacious Cancer Therapy

p53 is a prominent tumor suppressor which plays a crucial role in controlling cancer development by inhibiting cell proliferation and promoting cell death. p53 is frequently inactivated in over 50% of human cancers mainly through loss-of-function mutation, gain-of-function mutations, deletion, or increased interactions with its negative regulators. The E3 ubiquitin ligase Murine Double Minute 2 (MDM2) is the most important negative regulator of p53 tumor suppressor which works by targeting it for ubiquitination and proteasomal degradation. Amplification or overexpression of the MDM2 gene occurs in many human cancers and contributes to tumor development and progression. Targeting MDM2 to restore p53 function is an attractive therapeutic strategy against human cancers harboring wild-type TP53. Currently, numerous drugs inhibiting the MDM2-p53 interaction and reactivating p53 pathway have been created and entered different stages of clinical trials, such as RG7112 (Roche, Phase I), MI-773 (Sanofi, Phase I), DS-3032b (Daiichi Sankyo, Phase I) and AMG 232 (Amgen, Phase I/II). However, these MDM2 inhibitors exert limited efficacy possibly due to the feedback upregulation of MDM2 mediated by activated p53, which can lead to inadequate p53 induction. Targeting protein degradation by proteolysis targeting chimeras (PROTACs) has become a promising therapeutic strategy for treatment of human diseases. Recently, we have designed a series of small-molecule PROTAC MDM2 degraders by attaching a small-molecule MDM2 inhibitor to phthalimide. The phthalimide moiety interacts with cereblon, its target protein and recruits the CUL4-DDB1-RBX1-CRBN (also known as CRL4CRBN) E3 ubiquitin ligase complex to promote ubiquitination and proteasomal degradation of MDM2. Our studies demonstrate that the MDM2 degraders robustly activate wild-type p53 by inducing rapid degradation of MDM2. This leads to strong apoptosis in leukemia cell lines through MDM2, cereblon and cullin-RING E3 ligases (CRLs) and a proteasome-dependent mechanism. More importantly, the MDM2 degraders show great efficacy in inducing complete tumor regression in human leukemia xenograft mouse models and they significantly improve survival in a disseminated human leukemia mouse model at well-tolerated dose-schedules. There is therefore a strong preclinical rationale to develop MDM2 degraders as the basis of a novel therapy for human acute leukemias. To explore the structure-activity relationships (SAR) of MDM2 degraders, we slightly modified the MDM2 inhibitor portion, retaining its binding with MDM2, and synthesized a new series of putative MDM2 degraders. Unexpectedly, these new conjugate compounds exhibited however extremely potent antitumor activity independent of MDM2 and p53, suggesting a completely different mechanism of action (MOA). Upon mass spectrometric analysis, we identified the potential cellular target of these new compounds as a translation terminating protein GSPT1. Further investigation confirmed significant depletion of GSPT1 induced by these new conjugate analogues through engagement of the CRL4CRBN E3 complex. Additional investigation into the specific structural basis for the GSPT1 recruitment by these phthalimide conjugates is therefore important and presents the options of either avoiding it when designing phthalimide conjugate degraders or taking advantage of their therapeutic possibilities.PHDPharmacologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/153501/1/jiulingy_1.pd

Investigation on the structure and the oxidation activity of the solid carbon produced from catalytic decomposition of methane

The structure and the oxidation activity of the solid carbon produced from catalytic decomposition of methane at different temperatures were investigated using TEM, XRD, Raman and TPO techniques. The results show that the graphitization degree of the solid carbon is increased with decomposition reaction temperature. The addition of ethylene or acetylene to methane can change the growth way of the solid carbon and decrease their graphitization degree. The average oxidation temperature of the solid carbon has a close relationship with the corresponding graphitization degree. The addition of ethylene or acetylene to methane can decrease the average oxidation temperature of the solid carbon. © 2009 Elsevier Ltd. All rights reserved