Synchrotron X-Ray-Driven Nitrogen Reduction on an AgCu Thin Film.

Nitrogen (N2 ) is an essential element for life, but kinetically stable N2 in the atmosphere needs to be reduced to biologically available forms as a nutrient for organisms. Abiotic nitrogen fixation is critical to the origin of life on the early Earth, which is due to lightning or mineral-based reduction. Here, synchrotron X-ray-induced silver nitrate formation on a silver copper (AgCu) thin-film is reported. Time-resolved X-ray diffraction measurements show that under intense X-ray exposure, initially formed silver oxides (AgOx) are quickly converted to silver nitrate (AgNO3 ). Interestingly, AgNO3 is first formed in its high-temperature phase with a space group of R3cH, which gradually transforms to the room temperature phase with a space group of Pbca under continuous X-ray irradiation. The result not only provides a new clue about the abiotic nitrogen reduction prior to life but also demonstrates a novel strategy of materials synthesis using synchrotron X-rays.

A medium-range structure motif linking amorphous and crystalline states.

Amorphous materials have no long-range order, but there are ordered structures at short range (2-5 Å), medium range (5-20 Å) and even longer length scales1-5. While regular6,7 and semiregular polyhedra8-10 are often found as short-range ordering in amorphous materials, the nature of medium-range order has remained elusive11-14. Consequently, it is difficult to determine whether there exists any structural link at medium range or longer length scales between the amorphous material and its crystalline counterparts. Moreover, an amorphous material often crystallizes into a phase of different composition15, with very different underlying structural building blocks, further compounding the issue. Here, we capture an intermediate crystalline cubic phase in a Pd-Ni-P amorphous alloy and reveal the structure of the medium-range order, a six-membered tricapped trigonal prism cluster (6M-TTP) with a length scale of 12.5 Å. We find that the 6M-TTP can pack periodically to several tens of nanometres to form the cube phase. Our experimental observations provide evidence of a structural link between the amorphous and crystalline phases in a Pd-Ni-P alloy at the medium-range length scale and suggest that it is the connectivity of the 6M-TTP clusters that distinguishes the crystalline and amorphous phases. These findings will shed light on the structure of amorphous materials at extended length scales beyond that of short-range order.

Spontaneous Strain Buffer Enables Superior Cycling Stability in Single-Crystal Nickel-Rich NCM Cathode.

The capacity degredation in layered Ni-rich LiNixCoyMnzO2 (x ≥ 0.8) cathode largely originated from drastic surface reactions and intergranular cracks in polycrystalline particles. Herein, we report a highly stable single-crystal LiNi0.83Co0.12Mn0.05O2 cathode material, which can deliver a high specific capacity (∼209 mAh g-1 at 0.1 C, 2.8-4.3 V) and meanwhile display excellent cycling stability (>96% retention for 100 cycles and >93% for 200 cycles). By a combination of in situ X-ray diffraction and in situ pair distribution function analysis, an intermediate monoclinic distortion and irregular H3 stack are revealed in the single crystals upon charging-discharging processes. These structural changes might be driven by unique Li-intercalation kinetics in single crystals, which enables an additional strain buffer to reduce the cracks and thereby ensure the high cycling stability.

Stacking Fault Driven Phase Transformation in CrCoNi Medium Entropy Alloy.

Phase transformation is an effective means to increase the ductility of a material. However, even for a commonly observed face-centered-cubic to hexagonal-close-packed (fcc-to-hcp) phase transformation, the underlying mechanisms are far from being settled. In fact, different transformation pathways have been proposed, especially with regard to nucleation of the hcp phase at the nanoscale. In CrCoNi, a so-called medium-entropy alloy, an fcc-to-hcp phase transformation has long been anticipated. Here, we report an in situ loading study with neutron diffraction, which revealed a bulk fcc-to-hcp phase transformation in CrCoNi at 15 K under tensile loading. By correlating deformation characteristics of the fcc phase with the development of the hcp phase, it is shown that the nucleation of the hcp phase was triggered by intrinsic stacking faults. The confirmation of a bulk phase transformation adds to the myriads of deformation mechanisms available in CrCoNi, which together underpin the unusually large ductility at low temperatures.

Nanoscale Structural Evolution and Anomalous Mechanical Response of Nanoglasses by Cryogenic Thermal Cycling.

One of the central themes in the amorphous materials research is to understand the nanoscale structural responses to mechanical and thermal agitations, the decoding of which is expected to provide new insights into the complex amorphous structural-property relationship. For common metallic glasses, their inherent atomic structural inhomogeneities can be rejuvenated and amplified by cryogenic thermal cycling, thus can be decoded from their responses to mechanical and thermal agitations. Here, we reported an anomalous mechanical response of a new kind of metallic glass (nanoglass) with nanoscale interface structures to cryogenic thermal cycling. As compared to those metallic glasses by liquid quenching, the Sc75Fe25 (at. %) nanoglass exhibits a decrease in the Young's modulus but a significant increase in the yield strength after cryogenic cycling treatments. The abnormal mechanical property change can be attributed to the complex atomic rearrangements at the short- and medium- range orders due to the intrinsic nonuniformity of the nanoglass architecture. The present work gives a new route for designing high-performance metallic glassy materials by manipulating their atomic structures and helps for understanding the complex atomic structure-property relationship in amorphous materials.

Tuning the indirect-direct band gap transition in the MoS2-xSex armchair nanotube by diameter modulation.

The application of the reported armchair transition-metal dichalcogenide (MoS2, MoTe2, MoSTe and WS2, etc.) nanotube is hindered for the optoelectronic devices due to the indirect band gap. By using first-principles calculations, the electronic structures of MoS2-xSex single-wall armchair nanotubes with respect to different diameters are investigated. The MoS2 armchair nanotube exhibits an indirect band gap as a function of nanotube diameters from 10 Å to 50 Å, whereas MoSSe and MoSe2 exhibit a surprising diameter-induced indirect-direct band gap crossover at the diameters of 25 Å and 33 Å, respectively. We also find that the optical properties of MoS2-xSex armchair nanotubes are anisotropic and strongly depend on the diameter.

The total number of prelaryngeal and pretracheal lymph node metastases: is it a reliable predictor of contralateral central lymph node metastasis in papillary thyroid carcinoma?

BACKGROUND: Central lymph node (CLN) metastasis in papillary thyroid carcinoma (PTC) is common and being able to predict CLN metastasis helps surgeons determine individualized therapy. However, the relationship between contralateral CLN metastasis and the total number of positive lymph nodes (LNs) in the combined prelaryngeal and pretracheal region remains unclear. This study aimed to investigate whether the total number of positive LNs in the combined prelaryngeal and pretracheal region has clinical significance as a predictor for contralateral CLN metastasis. METHODS: We prospectively enrolled 153 consecutive patients with unifocal PTC >1.0 cm without ultrasonographic evidence of nodal metastasis who underwent total thyroidectomy and prophylactic bilateral CLN dissection from July 2011-May 2013. Patients were divided into three groups according to the total number of positive LNs in the combined prelaryngeal and pretracheal region. RESULTS: Rates of metastasis to ipsilateral and contralateral central compartments in PTC >1.0 cm were 84.3% and 24.2%, respectively. Multivariate analysis showed that ≥3 positive LNs in the combined prelaryngeal and pretracheal region were an independent predictive factor of contralateral CLN metastasis (P < 0.001; odds ratio, 8.585). After a mean follow-up of 24.1 mo, none of these patients had a recurrence in the central or lateral compartment. CONCLUSIONS: Occult metastasis is highly prevalent in the ipsilateral central neck of patients with PTC >1.0 cm, and the total number of prelaryngeal and pretracheal LNs metastases may be a useful indicator to predict contralateral CLN metastasis in patients with unifocal PTC.

Changing the order and ratio of substrate filling reduced CH4 and N2O emissions from the aerated constructed wetlands.

Constructed wetlands (CWs) have been used to enhance pollutant removal by filling several types of material as substrates. However, research on substrate filling order remains still limited, particularly regarding the effects of greenhouse gas (GHG) emissions. In this study, six CWs were constructed using zeolite and ferric­carbon micro-electrolysis (Fe-C) fillers to evaluate the effect of changing the filling order and ratio on pollutant removal, GHGs emissions, and associated microbial structure. The results showed that the order of substrate filling significantly impacted pollutant removal performance on CWs. Specifically, CWs filled with zeolite in the top layer exhibited superior NH4+-N removal compared to those filled in the lower layer. Moreover, the highest NH4+-N removal (95.0 % ± 1.9 %) was observed in CWs with a zeolite to Fe-C volume ratio of 8:2 (CWZe-1). Moreover, zeolite-filled at the top had lower GHGs emissions, with the lowest CH4 (0.22 ± 0.10 mg m-2 h-1) and N2O (167.03 ± 61.40 µg m-2 h-1) fluxes in the CWZe-1. In addition, it is worth noting that N2O is the major contributor to integrated global warming potential (GWP) in the six CWs, accounting for 81.7 %-90.8 %. The upper layer of CWs filled with zeolite exhibited higher abundances of nirK, nirS and nosZ genes. The order in which the substrate was filled affected the microbial community structure and the upper layer of CWs filled with zeolite had higher relative abundance of nitrifying genera (Nitrobacter, Nitrosomonas) and denitrifying genera (Zoogloea, Denitratisoma). Additionally, N2O emission was reduced by approximately 41.2 %-64.4 % when the location of the aeration of the CWs was changed from the bottom to the middle. This study showed that both the order of filling the substrate and the aeration position significantly affected the GHGs emissions from CWs, and that CWs had lower GHGs emissions when zeolites were filled in the upper layer and the aeration position was in the middle.

Deuteration-enhanced neutron contrasts to probe amorphous domain sizes in organic photovoltaic bulk heterojunction films.

An organic photovoltaic bulk heterojunction comprises of a mixture of donor and acceptor materials, forming a semi-crystalline thin film with both crystalline and amorphous domains. Domain sizes critically impact the device performance; however, conventional X-ray scattering techniques cannot detect the contrast between donor and acceptor materials within the amorphous intermixing regions. In this study, we employ neutron scattering and targeted deuteration of acceptor materials to enhance the scattering contrast by nearly one order of magnitude. Remarkably, the PM6:deuterated Y6 system reveals a new length scale, indicating short-range aggregation of Y6 molecules in the amorphous intermixing regions. All-atom molecular dynamics simulations confirm that this short-range aggregation is an inherent morphological advantage of Y6 which effectively assists charge extraction and suppresses charge recombination as shown by capacitance spectroscopy. Our findings uncover the amorphous nanomorphology of organic photovoltaic thin films, providing crucial insights into the morphology-driven device performance.

Uncommon deformation mechanisms during fatigue-crack propagation in nanocrystalline alloys.

The irreversible damage at cracks during the fatigue of crystalline solids is well known. Here we report on in situ high-energy x-ray evidence of reversible fatigue behavior in a nanocrystalline NiFe alloy both in the plastic zone and around the crack tip. In the plastic zone, the deformation is fully recoverable as the crack propagates, and the plastic deformation invokes reversible interactions of dislocation and twinning in the nanograins. But around the crack tip lies a regime with reversible grain lattice reorientation promoted by a change of local stress state. These observations suggest unprecedented fatigue deformation mechanisms in nanostructured systems that are not addressed theoretically.

High-Performance Supramolecular Organogel Adhesives for Antimicrobial Applications in Diverse Conditions.

Supramolecular organogel coatings that can disinfect the deposited microbial pathogens are emerging as an effective vehicle to prevent pathogen transmission. However, the development of anti-pathogen supramolecular adhesives with mechanical robustness and controlled oil inclusion is technically challenging. Here, we report supramolecular adhesives with mechanical integrity and robust interfacial adhesion over a wide range of biogenic antimicrobial oil. Bifunctional monomers are synthesized and assembled into linear polymers with semicrystalline stackings through hierarchical hydrogen bonds, where incorporated bioactive oil could regulate the semicrystalline stackings into nanosized crystalline domains through intermolecular hydrogen bonds. The abundant bonding motifs provided by the supramolecular cross-linked networks could accommodate oil molecules with high inclusion capability and provide more interfacial binding sites with high adhesion strength, and the nanosized crystalline domains could stabilize the organogel network and compensate for the interactions with oil molecules to enhance structural and mechanical stability. In addition, rapid healing, robust adhesion, and antimicrobial and antiviral properties of the resultant organogel coatings are demonstrated. This study paves the way for the development of high-performance antimicrobial supramolecular adhesives with controlled oil inclusion, showing potential applications in soft robotics, tissue engineering, and biomedical devices.

Application of alkali-heated corncobs enhanced nitrogen removal and microbial diversity in constructed wetlands for treating low C/N ratio wastewater.

Lack of carbon source is the main limiting factor in the denitrification of low C/N ratio wastewater in the constructed wetlands (CWs). Agricultural waste has been considered as a supplementary carbon source but research is still limited. To solve this problem, ferric carbon (Fe-C) + zeolite, Fe-C + gravel, and gravel were used as substrates to build CWs in this experiment, aiming to investigate the effects of different carbon sources (rice straw, corncobs, alkali-heated corncobs) on nitrogen removal performance and microbial community structure in CWs for low C/N wastewater. The results demonstrated that the microbial community and effluent nitrogen concentration of CWs were mainly influenced by the carbon source rather than the substrate. Alkali-heated corncobs significantly enhanced the removal of NO2--N, NH4+-N, NO3-N, and TN. Carbon sources addition increased microbial diversity. Alkali-heated corncobs addition significantly increased the abundance of heterotrophic denitrifying bacteria (Proteobacteria and Bacteroidota). Furthermore, alkali-heated corncobs addition increased the copy number of nirS, nosZ, and nirK genes while greenhouse gas fluxes were lower than common corncobs. In summary, alkali-heated corncobs can be considered as an effective carbon source.

Restoration of FMRP expression in adult V1 neurons rescues visual deficits in a mouse model of fragile X syndrome.

Many people affected by fragile X syndrome (FXS) and autism spectrum disorders have sensory processing deficits, such as hypersensitivity to auditory, tactile, and visual stimuli. Like FXS in humans, loss of Fmr1 in rodents also cause sensory, behavioral, and cognitive deficits. However, the neural mechanisms underlying sensory impairment, especially vision impairment, remain unclear. It remains elusive whether the visual processing deficits originate from corrupted inputs, impaired perception in the primary sensory cortex, or altered integration in the higher cortex, and there is no effective treatment. In this study, we used a genetic knockout mouse model (Fmr1KO), in vivo imaging, and behavioral measurements to show that the loss of Fmr1 impaired signal processing in the primary visual cortex (V1). Specifically, Fmr1KO mice showed enhanced responses to low-intensity stimuli but normal responses to high-intensity stimuli. This abnormality was accompanied by enhancements in local network connectivity in V1 microcircuits and increased dendritic complexity of V1 neurons. These effects were ameliorated by the acute application of GABAA receptor activators, which enhanced the activity of inhibitory neurons, or by reintroducing Fmr1 gene expression in knockout V1 neurons in both juvenile and young-adult mice. Overall, V1 plays an important role in the visual abnormalities of Fmr1KO mice and it could be possible to rescue the sensory disturbances in developed FXS and autism patients.

Engineering Atomic-to-Nano Scale Structural Homogeneity towards High Corrosion Resistance of Amorphous Magnesium-Based Alloys.

Magnesium-based amorphous alloys have aroused broad interest in being applied in marine use due to their merits of lightweight and high strength. Yet, the poor corrosion resistance to chloride-containing seawater has hindered their practical applications. Herein, we propose a new strategy to improve the chloride corrosion resistance of amorphous Mg65Cu15Ag10Gd10 alloys by engineering atomic-to-nano scale structural homogeneity, which is implemented by heating the material to the critical temperature of the liquid-liquid transition. By using various electrochemical, microscopic, and spectroscopic characterization methods, we reveal that the liquid-liquid transition can rearrange the local structural units in the amorphous structure, slightly decreasing the alloy structure's homogeneity, accelerate the formation of protective passivation film, and, therefore, increase the corrosion resistance. Our study has demonstrated the strong coupling between an amorphous structure and corrosion behavior, which is available for optimizing corrosion-resistant alloys.

Bridging Structural Inhomogeneity to Functionality: Pair Distribution Function Methods for Functional Materials Development.

The correlation between structure and function lies at the heart of materials science and engineering. Especially, modern functional materials usually contain inhomogeneities at an atomic level, endowing them with interesting properties regarding electrons, phonons, and magnetic moments. Over the past few decades, many of the key developments in functional materials have been driven by the rapid advances in short-range crystallographic techniques. Among them, pair distribution function (PDF) technique, capable of utilizing the entire Bragg and diffuse scattering signals, stands out as a powerful tool for detecting local structure away from average. With the advent of synchrotron X-rays, spallation neutrons, and advanced computing power, the PDF can quantitatively encode a local structure and in turn guide atomic-scale engineering in the functional materials. Here, the PDF investigations in a range of functional materials are reviewed, including ferroelectrics/thermoelectrics, colossal magnetoresistance (CMR) magnets, high-temperature superconductors (HTSC), quantum dots (QDs), nano-catalysts, and energy storage materials, where the links between functions and structural inhomogeneities are prominent. For each application, a brief description of the structure-function coupling will be given, followed by selected cases of PDF investigations. Before that, an overview of the theory, methodology, and unique power of the PDF method will be also presented.

Uncovering the out-of-plane nanomorphology of organic photovoltaic bulk heterojunction by GTSAXS.

The bulk morphology of the active layer of organic solar cells (OSCs) is known to be crucial to the device performance. The thin film device structure breaks the symmetry into the in-plane direction and out-of-plane direction with respect to the substrate, leading to an intrinsic anisotropy in the bulk morphology. However, the characterization of out-of-plane nanomorphology within the active layer remains a grand challenge. Here, we utilized an X-ray scattering technique, Grazing-incident Transmission Small-angle X-ray Scattering (GTSAXS), to uncover this new morphology dimension. This technique was implemented on the model systems based on fullerene derivative (P3HT:PC71BM) and non-fullerene systems (PBDBT:ITIC, PM6:Y6), which demonstrated the successful extraction of the quantitative out-of-plane acceptor domain size of OSC systems. The detected in-plane and out-of-plane domain sizes show strong correlations with the device performance, particularly in terms of exciton dissociation and charge transfer. With the help of GTSAXS, one could obtain a more fundamental perception about the three-dimensional nanomorphology and new angles for morphology control strategies towards highly efficient photovoltaic devices.

Structure modulation driven by cyclic deformation in nanocrystalline NiFe.

Theoretical modeling suggests that the grain size remains unchanged during fatigue crack growth in nanocrystalline metals. Here we demonstrate that a modulated structure is generated in a nanocrystalline Ni-Fe alloy under cyclic deformation. Substantial grain coarsening and loss of growth twins are observed in the path of fatigue cracks, while the grains away from the cracks remain largely unaffected. Statistical analyses suggest that the grain coarsening is realized through the grain lattice rotation and coalescence and the loss of growth twins may be related to the detwinning process near crack tip.