Resting posture drives the evolution of agonistic displays in bats

Agonistic displays are one of the most diverse social behaviors that have important functions in animal's life history. However, their origin and driving factors have largely been unexplored. Here, we evaluated agonistic displays of 71 bat species across 10 families and classified these displays into two categories: (a) boxing displays where a bat attacks its opponent with its wrist and thumb and (b) pushing displays where a bat uses its head or body to hit a rival. We estimated the strength of the phylogenetic signal of the agonistic displays, revealed their origin, and tested the potential evolutionary relationships between agonistic behaviors and body size or resting posture (free hanging vs. contact hanging where the bat is in contact with some surface). We found that agonistic displays were phylogenetically conserved and that boxing displays are the ancestral state. Moreover, we found that bats with a free-hanging resting posture were more likely to exhibit boxing displays than pushing displays. In addition, bats with longer forearms do not have a higher propensity for boxing displays. This study expands our limited knowledge of the evolution of agonistic displays and highlights the importance of resting posture as a driving force in the diversity of agonistic displays.

Acidic Oxygen Evolution Reaction: Fundamental Understanding and Electrocatalysts Design

Water electrolysis driven by "green electricity" is an ideal technology to realize energy conversion and store renewable energy into hydrogen. With the development of proton exchange membrane (PEM), water electrolysis in acidic media suitable for many situations with an outstanding advantage of high gas purity has attracted significant attention. Compared with hydrogen evolution reaction (HER) in water electrolysis, oxygen evolution reaction (OER) is a kinetic sluggish process that needs a higher overpotential. Especially in acidic media, OER process poses higher requirements for the electrocatalysts, such as high efficiency, high stability and low costs. This review focuses on the acidic OER electrocatalysis, reaction mechanisms, and critical parameters used to evaluate performance. Especially the modification strategies applied in the design and construction of new-type electrocatalysts are also summarized. The characteristics of traditional noble metal-based electrocatalysts and the noble metal-free electrocatalysts developed in recent decades are compared and discussed. Finally, the current challenges for the most promising acidic OER electrocatalysts are presented, together with a perspective for future water electrolysis.

The role of cannabinoid receptor 2 in bone remodeling during orthodontic tooth movement

BACKGROUND

The purpose of this study is to explore the effects of CB2 on bone regulation during orthodontic tooth movement.

METHODS

Thirty male mice were allocated into 2 groups (n = 15 in each group): wild type (WT) group and CB2 knockout (CB2-/-) group. Orthodontic tooth movement (OTM) was induced by applying a nickel-titanium coil spring between the maxillary first molar and the central incisors. There are three subgroups within the WT groups (0, 7 and 14 days) and the CB2-/- groups (0, 7 and 14 days). 0-day groups without force application. Tooth displacement, alveolar bone mass and alveolar bone volume were assessed by micro-CT on 0, 7 and 14 days, and the number of osteoclasts was quantified by tartrate-resistant acid phosphatase (TRAP) staining. Moreover, the expression levels of RANKL and OPG in the compression area were measured histomorphometrically.

RESULTS

The WT group exhibited the typical pattern of OTM, characterized by narrowed periodontal space and bone resorption on the compression area. In contrast, the accelerated tooth displacement, increased osteoclast number (P < 0.0001) and bone resorption on the compression area in CB2-/- group. Additionally, the expression of RANKL was significantly upregulated, while OPG showed low levels in the compression area of the CB2 - / - group (P < 0.0001).

CONCLUSIONS

CB2 modulated OTM and bone remodeling through regulating osteoclast activity and RANKL/OPG balance.

Boron Nitride Microspheres via Pyrolysis of Polymerized Precursors

Microspheric BN materials have high application potential because they have better fluidity and dispersion ability to endow hexagonal boron nitride (h-BN) ceramics and h-BN/polymer composites with highly desired performance. In this work, a novel synthetic route to the BN microspheres has been developed by means of a controllable pyrolysis of polymerized spherical precursors. The precursor formation mechanism is proposed to be the F-127-induced self-assembling polymerization of a boric acid-melamine-formaldehyde (MF) colloid. It is found that ammonia-annealing of an air-pyrolysis (700 °C) intermediate causes higher BN phase transformation within final BN microspheres with more uniform diameter distribution compared to those of direct ammonia-pyrolysis of spherical precursors at the same temperatures of 1100 and 1500 °C. After ammonia-annealing and ammonia-pyrolyzed treatment at 1100 and 1500 °C, the obtained BN microspheres have a low specific surface area (SSA) property, but replacing part of melamine with dicyandiamide could increase their SSAs to more than 1000 m²/g. We believe that this new microspherical BN preparation with more facile and controllable operation would be well suited for industrialization.

Role of Autophagy Mediated by AMPK/DDiT4/mTOR Axis in HT22 Cells Under Oxygen and Glucose Deprivation/Reoxygenation

Background: cerebral ischemia/reperfusion (I/R) injury is an important complication of ischemic stroke, and autophagy is one of the mechanisms of it. In this study, we aimed to determine the role and mechanism of autophagy in cerebral I/R injury. Methods: the oxygen and glucose deprivation/reoxygenation (OGD/R) method was used to model cerebral I/R injury in HT22 cells. CCK-8 and LDH were conducted to detect viability and damage of the cells, respectively. Apoptosis was measured by flow cytometry and Tunel staining. Autophagic vesicles of HT22 cells were assessed by transmission electron microscopy. Western blotting analysis was used to examine the protein expression involving AMPK/DDiT4/mTOR axis and autophagy-related proteins. 3-Methyladenine and rapamycin were, respectively, used to inhibit and activate autophagy, compound C and AICAR acted as AMPK inhibitor and activator, respectively, and were used to control the starting link of AMPK/DDiT4/mTOR axis. Results: autophagy was activated in HT22 cells after OGD/R was characterized by an increased number of autophagic vesicles, the expression of Beclin1 and LC3II/LC3I, and a decrease in the expression of P62. Rapamycin could increase the viability, reduce LDH leakage rate, and alleviate cell apoptosis in OGD/R cells by activating autophagy. 3-Methyladenine played an opposite role to rapamycin in OGD/R cells. The expression of DDiT4 and the ratio of p-AMPK/AMPK were increased after OGD/R in HT22 cells. While the ratio of p-mTOR/mTOR was reduced by OGD/R, AICAR effectively increased the number of autophagic vesicles, improved viability, reduced LDH leakage rate, and alleviated apoptosis in HT22 cells which suffered OGD/R. However, the effects of compound C in OGD/R HT22 cells were opposite to that of AICAR. Conclusions: autophagy is activated after OGD/R; autophagy activator rapamycin significantly enhanced the protective effect of autophagy on cells of OGD/R. AMPK/DDiT4/mTOR axis is an important pathway to activate autophagy, and AMPK/DDiT4/mTOR-mediated autophagy significantly alleviates cell damage caused by OGD/R.

Texture and Magnetic Property of Fe-6.5 wt % Si Steel Strip with Cu-Rich Particles Modification

Based on the ordered phase effectively suppressed by rapid solidification technology, the grain refinement concept using Cu is incorporated into the soft magnetic materials. Cu dosage not only could refine the grain size with an average grain size of 8.7 μm but also improve the continuity and consistency of Fe-6.5 wt % Si steel strip. It mainly attributes to the Cu-rich particles precipitating at the grain boundary, nailing the grain boundaries movement and inhibiting the grain growth, and then improving the magnetic properties and mechanical properties. The 1.5 wt % Cu sample exhibits an excellent magnetic property with the saturation magnetization of 236.54 emu/g, which mainly attributes to the strong η, λ, Goss texture formation and the band structure optimization of Si-Cu comodification. Furthermore, the mechanical properties of the steel strip are effectively improved, and the failure plastic deformation of 1.5 wt % Cu steel strip is about 11%. The rapid solidification with Cu-dosage refinement technology also has a remarkable reference on the mechanical properties and magnetic properties modification of other metal materials.

Long-Lived Afterglow from Elemental Sulfur Powder: Synergistic Effects of Impurity and Structure

Elemental sulfur is not traditionally considered as an afterglow material, even though it can be endowed with fluorescence properties through processing it into nanodots. Herein, we discovered that elemental sulfur powder could emit room temperature phosphorescence (RTP) with a lifetime of 3.7 ms. A long-lived (>12 s) afterglow emission at 77 K could also be observed by the naked eye. Detailed investigations suggested that such a special phenomenon was attributed to impurity-related traps coupled with conduction and valence bands. After the sulfur is processed into nanodots, the rigid environment formed by the cross-linking of the surface ligands could stabilize the excited charges from quenching. This results in the promotion of RTP intensity and lifetime to achieve an emission lifetime of 200 ms. These results confirm the unique RTP of elemental sulfur powder, and also suggest the potential of sulfur-based materials as versatile components for the development of RTP materials.

Effects of Substrate Surface Characteristics on the Adhesion Properties of Geopolymer Coatings

Geopolymer is a kind of material with a better ability of high-temperature and corrosion resistance. Poor adhesion could easily lead to problems such as coating cracks, peeling at an early stage, and inability to work with the substrate. The adhesion depends on many factors such as chemical composition of the raw materials, the formulation of the geopolymer, the type of substrate, surface roughness of the substrate, etc. The higher the Si/Al ratio, the greater the shear strength of the coating. This is because geopolymers synthesized with different Si/Al ratios have different phases in the geopolymer binder. Each study uses different multi-parameter combinations selected by itself, which is not uniform and has no universal applicability. As the parameter Ra is determined by the profile centerlines of the substrate surface, it is difficult to get an appropriate value of Ra to represent the roughness of the substrate surface. The parameter-relative area, determined by area scale fractal analysis, can effectively characterize the surface roughness, predict the texture component of bond strength, and establish a connection between which and the bonding performance of the geopolymer coating at a high level of confidence. The bonding strength reduces with the decrease in the value of the relative area. The magnitude of scale employed should be seriously determined when characterizing the surface roughness.

Highly Sensitive Detection of Iron Ions in Aqueous Solutions Using Fluorescent Chitosan Nanoparticles Functionalized by Rhodamine B

Detection of iron ions in aqueous solutions is of significant importance because of their important role in the environment and the human body. Herein, a fluorescent rhodamine B-functionalized chitosan nanoparticles probe is reported for the efficient detection of iron ions. The chitosan nanospheres-rhodamine B (CREN) was prepared by grafting rhodamine B onto the surface of chitosan nanospheres through an amidation reaction. The as-prepared CREN fluorescent probes exhibit high fluorescence intensity under ultraviolet light. When iron ions are added to the CREN solution, they can be coordinated with weak-field ligands such as N and O on the surface of chitosan nanoparticles (CSNP) by a high-spin method. The self-assembly of Fe³⁺ on the surface of the CREN led to the generation of single electrons and the presence of high paramagnetism, resulting in fluorescence quenching. The quenching effect of Fe³⁺ on the CREN fluorescent probe can achieve the efficient detection of Fe³⁺, and the detection limit reaches 10^-5 mol/mL. Moreover, this fluorescence quenching effect of Fe³⁺ on the CREN fluorescent probe is specific, which could not be disturbed by other metal ions and counteranions.

Optical Images of Molecular Vibronic Couplings from Tip-Enhanced Fluorescence Excitation Spectroscopy

Tip-based photoemission spectroscopic techniques have now achieved subnanometer resolution that allows visualization of the chemical structure and even the ground-state vibrational modes of a single molecule. However, the ability to visualize the interplay between electronic and nuclear motions of excited states, i.e., vibronic couplings, is yet to be explored. Herein, we theoretically propose a new technique, namely, tip-enhanced fluorescence excitation (TEFE). TEFE takes advantage of the highly confined plasmonic field and thus can offer a possibility to directly visualize the vibronic effect of a single molecule in real space for arbitrary excited states in a given energy window. Numerical simulations for a single porphine molecule confirm that vibronic couplings originating from Herzberg-Teller (HT) active modes can be visually identified. TEFE further enables high-order vibrational transitions that are normally suppressed in the other plasmon-based processes. Images of the combination vibrational transitions have the same pattern as that of their parental HT active mode's fundamental transition, providing a direct protocol for measurements of the activity of Franck-Condon modes of selected excited states. These findings strongly suggest that TEFE is a powerful strategy to identify the involvement of molecular moieties in the complicated electron-nuclear interactions of the excited states at the single-molecule level.

Characterization of the Fe-6.5wt%Si Strip with Rapid Cooling Coupling Deep Supercooled Solidification

The phase transition law between ordered and disordered phases, second phase reinforcement, microstructure, and mechanical properties were systematically studied in the rapid cooling coupling deep supercooled solidification process through an arc melting furnace, electromagnetic induction heating, and high-speed cooling single-roll technology. The results show that uniform nucleation and grain refinement are promoted under rapid cooling coupling deep supercooled solidification, and the phase transition from the disordered phase (A2) to the ordered phase (B2 and DO₃) is also effectively suppressed. The decreased crystalline grain size and optimized microstructure morphology improved the plasticity and magnetic property. The Fe-6.5wt%Si steel strip at 42 m/s has a good phase composition of Fe (predominant), Fe₂Si, and SiC. The sample showed an equiaxed ferrite crystal structure, and the saturation magnetizations were 302.5 and 356.6 emu/g in the parallel magnetic direction and the vertical magnetic direction, respectively. This phase transition behavior contributed to the exceptional magnetic property of the Fe-6.5wt%Si steel.

Homogeneous Catalysts Based on First-Row Transition-Metals for Electrochemical Water Oxidation

Strategies that enable the renewable production of storable fuels (i. e. hydrogen or hydrocarbons) through electrocatalysis continue to generate interest in the scientific community. Of central importance to this pursuit is obtaining the requisite chemical (H+ ) and electronic (e- ) inputs for fuel-forming reduction reactions, which can be met sustainably by water oxidation catalysis. Further possibility exists to couple these redox transformations to renewable energy sources (i. e. solar), thus creating a carbon neutral solution for long-term energy storage. Nature uses a Mn-Ca cluster for water oxidation catalysis via multiple proton-coupled electron-transfers (PCETs) with a photogenerated bias to perform this process with TOF 100∼300 s-1 . Synthetic molecular catalysts that efficiently perform this conversion commonly utilize rare metals (e. g., Ru, Ir), whose low abundance are associated to higher costs and scalability limitations. Inspired by nature's use of 1st row transition metal (TM) complexes for water oxidation catalysts (WOCs), attempts to use these abundant metals have been intensively explored but met with limited success. The smaller atomic size of 1st row TM ions lowers its ability to accommodate the oxidative equivalents required in the 4e- /4H+ water oxidation catalysis process, unlike noble metal catalysts that perform single-site electrocatalysis at lower overpotentials (η). Overcoming the limitations of 1st row TMs requires developing molecular catalysts that exploit biomimetic phenomena - multiple-metal redox-cooperativity, PCET and second-sphere interactions - to lower the overpotential, preorganize substrates and maintain stability. Thus, the ultimate goal of developing efficient, robust and scalable WOCs remains a challenge. This Review provides a summary of previous research works highlighting 1st row TM-based homogeneous WOCs, catalytic mechanisms, followed by strategies for catalytic activity improvements, before closing with a future outlook for this field.