Higher absorbed solar radiation partly offset the negative effects of water stress on the photosynthesis of Amazon forests during the 2015 drought

Amazon forests play an important role in the global carbon cycle and Earth\u27s climate. The vulnerability of Amazon forests to drought remains highly controversial. Here we examine the impacts of the 2015 drought on the photosynthesis of Amazon forests to understand how solar radiation and precipitation jointly control forest photosynthesis during the severe drought. We use a variety of gridded vegetation and climate datasets, including solar-induced chlorophyll fluorescence (SIF), photosynthetic active radiation (PAR), the fraction of absorbed PAR (APAR), leaf area index (LAI), precipitation, soil moisture, cloud cover, and vapor pressure deficit (VPD) in our analysis. Satellite-derived SIF observations provide a direct diagnosis of plant photosynthesis from space. The decomposition of SIF to SIF yield (SIFyield) and APAR (the product of PAR and fPAR) reveals the relative effects of precipitation and solar radiation on photosynthesis. We found that the drought significantly reduced SIFyield, the emitted SIF per photon absorbed. The higher APAR resulting from lower cloud cover and higher LAI partly offset the negative effects of water stress on the photosynthesis of Amazon forests, leading to a smaller reduction in SIF than in SIFyield and precipitation. We further found that SIFyield anomalies were more sensitive to precipitation and VPD anomalies in the southern regions of the Amazon than in the central and northern regions. Our findings shed light on the relative and combined effects of precipitation and solar radiation on photosynthesis, and can improve our understanding of the responses of Amazon forests to drought

Study of a sociable molecule: Mapping the binding interfaces of the cell division regulator MipZ in Caulobacter crescentus

In most bacteria, cell division requires assembly of FtsZ, the tubulin homologue, into a ring-like structure, the so-called Z-ring. The Z-ring acts as a scaffold for the cell division machinery and marks the future division site. To precisely localize the Z-ring, bacteria have evolved different regulatory mechanisms. In the model organism Caulobacter crescentus, Z-ring positioning depends on a P-loop ATPase, MipZ. MipZ forms bipolar gradients within the cell and acts as an inhibitor of FtsZ polymerization, thereby restricting assembly of the Z-ring to the midcell region. Gradient formation is driven by the alternation of MipZ between a monomeric and dimeric state with distinct interaction patterns and diffusion rates. This alternation results in a dynamic localization cycle, in which MipZ continuously oscillates between non-specific chromosomal DNA and the polarly localized ParB protein. In this study, we investigated the function of MipZ by mapping its interaction interfaces with FtsZ, ParB and DNA. We systematically exchanged surface-exposed residues using alanine-scanning mutagenesis. Analyzing the subcellular distribution of the mutant proteins as well as their ability to support division site placement, we identified four clusters of residues that are important for MipZ activity. Two of them are likely responsible for contacting FtsZ and chromosomal DNA, respectively, whereas the other two appear to be involved in the interaction with ParB. Notably, the DNA-binding and FtsZ-binding interfaces of MipZ comprise residues from both monomeric subunits and are located on opposite sides of the dimer. This result is consistent with the previous finding that the regulatory effect of MipZ is specific for its dimeric form and that only the dimeric form contacts DNA and FtsZ. We also found that the DNA-binding region mainly consists of positively charged arginine and lysine residues. In vivo and in vitro studies showed that mutation of these residues impairs the DNA-binding activity of MipZ to different extents; moreover, mutation of R194 and R198 abolished the MipZ-DNA interaction. These results provide the first detailed analysis of the interaction determinants of MipZ and deepen our knowledge of the molecular mechanism underlying the function of this intriguing cell division regulator

Geodesic Distance Function Learning via Heat Flow on Vector Fields

Learning a distance function or metric on a given data manifold is of great importance in machine learning and pattern recognition. Many of the previous works first embed the manifold to Euclidean space and then learn the distance function. However, such a scheme might not faithfully preserve the distance function if the original manifold is not Euclidean. Note that the distance function on a manifold can always be well-defined. In this paper, we propose to learn the distance function directly on the manifold without embedding. We first provide a theoretical characterization of the distance function by its gradient field. Based on our theoretical analysis, we propose to first learn the gradient field of the distance function and then learn the distance function itself. Specifically, we set the gradient field of a local distance function as an initial vector field. Then we transport it to the whole manifold via heat flow on vector fields. Finally, the geodesic distance function can be obtained by requiring its gradient field to be close to the normalized vector field. Experimental results on both synthetic and real data demonstrate the effectiveness of our proposed algorithm

Effects of particle size and content of RDX on burning stability of RDX-based propellants

Abstract Particle size and content of RDX are the two main factors that affect the burning stability of RDX-based propellants. However, these effects and the corresponding mechanisms are still controversial. In this work, we investigated the physicochemical processes during burning and the corresponding mechanisms through the technologies of structure compactness analysis on the base of voidage measurement and theoretical interfacial area estimation, apparent burning rate measurement using closed vessel (CV) and extinguished burning surface characterization relying on interrupted closed vessel (ICV) and scanning electron microscope (SEM). The results indicate that the voidage increased with the increase of RDX content and particle size due to the increasing interfacial area and increasing interface gap size, respectively. The apparent burning rate increased with the increase of RDX particle size because of the decreasing RDX specific surface area on the burning surface, which could decrease the heat absorbing rates of the melting and evaporation processes of RDX in the condensed phase. Similarly, the apparent burning rate decreased with the increase of RDX content at pressures lower than around 55 MPa due to the increasing RDX specific surface area. Whereas, an opposite trend could be observed at pressures higher than around 55 MPa, which was attributed to the increasing heat feedback from the gas phase as the result of the increasing propellant energy. For propellants containing very coarse RDX particles, such as 97.8 and 199.4 μm average size, the apparent burning rate increased stably with a flat extinguished surface at pressures lower than around 30 MPa, while increased sharply above around 30 MPa with the extinguished surface becoming more and more rugged as the pressure increased. In addition, the turning degree of u-p curve increased with the increase of coarse RDX content and particle size, and could be reduced by improving the structure compactness

Hybrid ceramics-based cancer theranostics

Cancer is a major threat to human lives. Early detection and precisely targeted therapy/therapies for cancer is the most effective way to reduce the difficulties (e.g., side effects, low survival rate, etc.) in treating cancer. To enable effective cancer detection and treatment, ceramic biomaterials have been intensively and extensively investigated owing to their good biocompatibility, high bioactivity, suitable biodegradability and other distinctive properties that are required for medical devices in oncology. Through hybridization with other materials and loading of imaging agents and therapeutic agents, nanobioceramics can form multifunctional nanodevices to simultaneously provide diagnostic and therapeutic functions for cancer patients, and these nanodevices are known as hybrid ceramics-based cancer theranostics. In this review, the recent developments of hybrid ceramics-based cancer theranostics, which include the key aspects such as their preparation, biological evaluation and applications, are summarized and discussed. The challenges and future perspectives for the clinical translation of hybrid ceramics-based cancer theranostics are also discussed. It is believed that the potential of hybrid ceramic nanoparticles as cancer theranostics is high and that the future of these theranostics is bright despite the difficulties along the way for their clinical translation

Metric Subregularity for Subsmooth Generalized Constraint Equations in Banach Spaces

This paper is devoted to metric subregularity of a kind of generalized constraint equations. In particular, in terms of coderivatives and normal cones, we provide some necessary and sufficient conditions for subsmooth generalized constraint equations to be metrically subregular and strongly metrically subregular in general Banach spaces and Asplund spaces, respectively

Metric Subregularity for Subsmooth Generalized Constraint Equations in Banach Spaces

This paper is devoted to metric subregularity of a kind of generalized constraint equations. In particular, in terms of coderivatives and normal cones, we provide some necessary and sufficient conditions for subsmooth generalized constraint equations to be metrically subregular and strongly metrically subregular in general Banach spaces and Asplund spaces, respectively

Evaluation of segment convergence and settlement of subway shield tunnel in water-rich complex stratum

Based on the shield tunnel construction of the left line of Guowei road station-Qingshan lake west station of Nanchang metro line 3, the study focuses on the adverse effects of tunnel segment convergence and settlement deformation of vault and arch bottom on shield construction in the process of shield tunnel construction in water-rich complex stratum. The time-space curves of segment convergence and settlement value on typical monitoring sections are drawn, their variation laws are analyzed, and the deformation values of monitoring data are analyzed and tested. Based on the analysis results, the qualitative and quantitative evaluation of the overall or local deformation state of each monitoring object of tunnel segment is carried out. The results show that the cumulative deformation of each typical monitoring section is lower than the warning value, and the tunnel segment has a systematic offset in the horizontal and vertical directions of the clearance