Improved Stretchable and Sensitive Fe Nanowire-Based Strain Sensor by Optimizing Areal Density of Nanowire Network.

Flexible strain sensors, when considering high sensitivity and a large strain range, have become a key requirement for current robotic applications. However, it is still a thorny issue to take both factors into consideration at the same time. Here, we report a sandwich-structured strain sensor based on Fe nanowires (Fe NWs) that has a high GF (37-53) while taking into account a large strain range (15-57.5%), low hysteresis (2.45%), stability, and low cost with an areal density of Fe NWs of 4.4 mg/cm2. Additionally, the relationship between the contact point of the conductive network, the output resistance, and the areal density of the sensing unit is analyzed. Microscopically, the contact points of the conductive network directly affect the sensor output resistance distribution, thereby affecting the gauge factor (GF) of the sensor. Macroscopically, the areal density and the output resistivity of the strain sensor have the opposite percolation theory, which affects its linearity performance. At the same time, there is a positive correlation between the areal density and the contact point: when the stretching amount is constant, it theoretically shows that the areal density affects the GF. When the areal density reaches this percolation threshold range, the sensing performance is the best. This will lay the foundation for rapid applications in wearable robots.

High-Areal Density Single-Atoms/Metal Oxide Nanosheets: A Micro-Gas Blasting Synthesis and Superior Catalytic Properties.

The two-dimensional nanosheets are conducive to not only endow opened surfaces for loading active metal atoms but also boost the mass transfer for the heterogeneous reactions. The challenge is how to load and stabilize single-atoms on nanosheets in high-areal densities. This work reports an efficient micro-gas blasting (MGB) strategy to access versatile noble metal single-atoms/metal oxide nanosheets, including Ir1 /CoOx , Pd1 /CeO2 , etc. Especially for Pt/CeO2 nanosheets (Pt1 /CeO2 -S), the Pt loading is increased to 15 at%. The Pt1 /CeO2 -S catalysts from MGB are revealed to possess superior reactivity and tolerance in the model reaction of water-gas shift (WGS). The Pt1 /CeO2 -S catalyst exhibit 2-3 times reactivity that of their thicker counterpart, single-atom Pt1 /CeO2 microspheric catalyst. Moreover, the single-atom sites in Pt1 /CeO2 -S (1-10 %) catalysts are stable in a harsh WGS reaction condition of 10 % CO. This work thus paves a way to access the practical single-atom catalysts.

Energy dispersive x-ray spectroscopy for nanostructured thin film density evaluation.

In this paper, we report on two fast and non-destructive methods for nanostructured film density evaluation based on a combination of energy dispersive x-ray spectroscopy for areal density measurement and scanning electron microscopy (SEM) for thickness evaluation. These techniques have been applied to films with density ranging from the density of a solid down to a few [Formula: see text], with different compositions and morphologies. The high resolution of an electron microprobe has been exploited to characterize non-uniform films both at the macroscopic scale and at the microscopic scale.

Designing lightweight neutron absorbing composites using a comprehensive absorber areal density metric.

Efforts to lightweight neutron absorbing composites are limited by incomplete understandings of the interaction between absorbing particles and their matrices. In this study, analytical models and a more physically representative simulation evaluated the penalty to neutron absorbing performance due to neutron channeling between large absorbing particles. Models and simulation agreed that B4C particles smaller than 100µm and especially those smaller than 10µm did not cause excessive neutron channeling. A more comprehensive neutron absorbing composite design metric - boron-10 equivalent areal density, which considers the particle size penalty and the matrix contribution to absorptivity - was introduced and used to estimate lightweighting via matrix substitution. Calculations using this new metric showed that a non-absorbing Mg matrix reduced mass by up to 35% over Al, constrained by the difference in mass density, while an absorbing Mg-Li matrix reduced mass by up to 60%, exceeding the difference in mass densities alone. Measurement of apparent absorber areal density through two experimental techniques - foil activation and direct counting - validated estimated absorber areal density as a neutron absorbing composite design metric. This updated understanding of the particle size penalty, newly introduced design metric, and experimental validation demonstrate a path to lightweight neutron absorbing composites.

Cytoarchitecture, myeloarchitecture, and parcellation of the chimpanzee inferior parietal lobe.

The parietal lobe is a region of especially pronounced change in human brain evolution. Based on comparative neuroanatomical studies, the inferior parietal lobe (IPL) has been shown to be disproportionately larger in humans relative to chimpanzees and macaques. However, it remains unclear whether the underlying histological architecture of IPL cortical areas displays human-specific organization. Chimpanzees are among the closest living relatives of humans, making them an ideal comparative species to investigate potential evolutionary changes in the IPL. We parcellated the chimpanzee IPL using cytoarchitecture and myeloarchitecture, in combination with quantitative comparison of cellular features between the identified cortical areas. Four major areas on the lateral convexity of the chimpanzee IPL (PF, PFG, PG, OPT) and two opercular areas (PFOP, PGOP) were identified, similar to what has been observed in macaques. Analysis of the quantitative profiles of cytoarchitecture showed that cell profile density was significantly different in a combination of layers III, IV, and V between bordering cortical areas, and that the density profiles of these six areas supports their classification as distinct. The similarity to macaque IPL cytoarchitecture suggests that chimpanzees share homologous IPL areas. In comparison, human rostral IPL is reported to differ in its anatomical organization and to contain additional subdivisions, such as areas PFt and PFm. These changes in human brain evolution might have been important as tool making capacities became more complex.

X-ray fluorescence spectroscopy (XRF) for metallome analysis of herbarium specimens.

BACKGROUND: "Herbarium X-ray Fluorescence (XRF) Ionomics" is a new quantitative approach for extracting the elemental concentrations from herbarium specimens using handheld XRF devices. These instruments are principally designed for dense sample material of infinite thickness (such as rock or soil powder), and their built-in algorithms and factory calibrations perform poorly on the thin dry plant leaves encountered in herbaria. While empirical calibrations have been used for 'correcting' measured XRF values post hoc, this approach has major shortcomings. As such, a universal independent data analysis pipeline permitting full control and transparency throughout the quantification process is highly desirable. Here we have developed such a pipeline based on Dynamic Analysis as implemented in the GeoPIXE package, employing a Fundamental Parameters approach requiring only a description of the measurement hardware and derivation of the sample areal density, based on a universal standard. RESULTS: The new pipeline was tested on potassium, calcium, manganese, iron, cobalt, nickel, and zinc concentrations in dry plant leaves. The Dynamic Analysis method can correct for complex X-ray interactions and performs better than both the built-in instrument algorithms and the empirical calibration approach. The new pipeline is also able to identify and quantify elements that are not detected and reported by the device built-in algorithms and provides good estimates of elemental concentrations where empirical calibrations are not straightforward. CONCLUSIONS: The new pipeline for processing XRF data of herbarium specimens has a greater accuracy and is more robust than the device built-in algorithms and empirical calibrations. It also gives access to all elements detected in the XRF spectrum. The new analysis pipeline has made Herbarium XRF approach even more powerful to study the metallome of existing plant collections.

Measuring the areal density of nanomaterials by electron energy-loss spectroscopy.

Thickness measurements of nanomaterials are usually performed using transmission electron microscopy (TEM) techniques such as convergent beam electron diffraction (CBED) patterns analysis and the log-ratio method based on electron energy-loss spectroscopy (EELS) spectrum. However, it is challenging to obtain both the thickness and elemental information, especially in non-crystalline materials or for very thin samples. In this work, we establish a series of procedures to calculate the areal density of the material by directly measuring the inelastic scattering probability in a thin sample. Core-loss EELS are fit with a quantitative model to extract atomic areal density. Knowledge of one of the parameters (volume density or sample thickness) allows a measurement of the other. The absolute error between the known thicknesses and those measured was less than 4% using two-dimensional materials with a well-defined thickness as test samples, which is much better than the log-ratio method for very thin samples. One promising advantage of this method is the thickness/areal density determination in mixed phase/element systems. We use Ag-Co bimetallic triangles and black rutile as examples to calculate the thickness map in mixture systems in different cases. We also demonstrate this technique can be applied to measure the argon gas density in spherical cavities. This allows a temperature vs pressure curve to be obtained and illustrates the unique capability of this technique.

Uniform Distribution of Alloying/Dealloying Stress for High Structural Stability of an Al Anode in High-Areal-Density Lithium-Ion Batteries.

Aluminum (Al) is one of the most attractive anode materials for lithium-ion batteries (LIBs) due to its high theoretical specific capacity, excellent conductivity, abundance, and especially low cost. However, the large volume expansion, originating from the uneven alloying/dealloying reactions in the charge/discharge process, causes structural stress and electrode pulverization, which has long hindered its practical application, especially when assembled with a high-areal-density cathode. Here, an inactive (Cu) and active (Al) co-deposition strategy is reported to homogeneously distribute the alloying sites and disperse the stress of volume expansion, which is beneficial to obtain the structural stability of the Al anode. Owing to the homogeneous reaction and uniform distribution of stress during the charge/discharge process, the assembled full battery (LiFePO4 cathode with a high areal density of ≈7.4 mg cm-2 ) with the Cu-Al@Al anode, achieves a high capacity retention of ≈88% over 200 cycles, suggesting the feasibility of the interfacial design to optimize the structural stability of alloying metal anodes for high-performance LIBs.