Envelope Density Research Articles

Geometallurgical characterisation of Mn ores

ABSTRACT This article details two geometallurgical case studies using classification schemes developed for Mn fine and lump ores. For the first, the relative abundance of 15 material types was compared to chemistry by size fraction. Positive correlations were evident between the proportion of aluminosilicate-bearing ore groups and Al2O3 content, the ratio of Mn oxide/Fe oxide ore groups and the Mn/Fe content, the proportion of cryptomelane-bearing groups and the K2O and BaO contents, and the ratio of hard to moderately hard + friable particles and the K2O + Ba + Na content. For the second, agreement was observed between the types of predominant material types in the two different ores and their mass distributions, major and trace element chemistries. Different material types had clear variances in their envelope and apparent particle densities. These two case studies support the expanded use of particle-based ore classification schemes for the characterisation of Mn ores to better predict their downstream processing performance.

Tuning the Electrical and Solar Thermal Heating Efficiencies of Nanocarbon Aerogels

Nanocarbon aerogels display outstanding electrical and solar thermal heating efficiencies. However, little is known about the relationship between their microstructure and the heating performance. In this study, two different types of carbon nanotube (CNT) aerogels were synthesized via an ice-templating (IT) and emulsion-templating (ET) approach, respectively, which induces a drastic difference in internal microstructures, cross-linking densities, and porosities. These structural differences give rise to substantial efficiency differences in electrical aerogel heating (e.g., 46 °C/W for rET-CNT aerogel, 75 °C/W for rIT-CNT aerogel). Systematic comparison of nanocarbon aerogel microstructure in terms of nanocarbon type, envelope density, and nanocarbon graphiticity shows that the Joule-heating efficiency is highly correlated with the thermal conductivities of the aerogels, where aerogels with lower thermal conductivities exhibit higher Joule-heating efficiencies. This relationship is also observed for solar thermal aerogel heating, with the aerogels of lowest thermal conductivity (rIT-CNT aerogel) exhibiting a 30% higher efficiency in solar water evaporation, compared to rET-CNT aerogels. These results demonstrate that the heating properties of nanocarbon aerogels can be readily tuned and enhanced through structural control alone. The findings provide a new perspective for the design of nanocarbon aerogels for applications that involve electrical or solar thermal heating, such as temperature-dependent separation, sorption, sensing, and catalysis.

Regioselective Functionalization of the Mesoporous Metal-Organic Framework, NU-1000, with Photo-Active Tris-(2,2'-bipyridine)ruthenium(II).

Solvent-assisted ligand incorporation is an excellent method for the post-synthetic functionalization of Zr-based metal–organic frameworks (MOFs), as carboxylate-derivative functionalities readily coordinate to the Zr6 nodes by displacing node-based aqua and terminal hydroxo ligands. In this study, a photocatalytically active ruthenium complex RuII(bpy)2(dcbpy), that is, bis-(2,2′-bipyridine)-(4,4′-dicarboxy-2,2′-bipyridine)ruthenium, was installed in the mono-protonated (carboxylic acid) form within NU-1000 via SALI. Crystallographic information regarding the siting of the ruthenium complex within the MOF pores is obtained by difference envelope density analysis. The ruthenium-functionalized MOF, termed Ru-NU-1000, shows excellent heterogeneous photocatalytic activity for an oxidative amine coupling reaction.

Starch-Based Aerogels Obtained via Solvent-Induced Gelation.

In this work, the ability of several solvents to induce gel formation from amylomaize starch solubilized in dimethyl sulfoxide (DMSO) was investigated. The formed gels were subjected to solvent exchange using ethanol and dried with supercritical carbon dioxide (sc-CO2) to obtain the aerogels. The influence of starch concentration (3–15 wt%) and solvent content (20–80 wt%) on gel formation was also studied. It was demonstrated that the gelation of starch in binary mixtures of solvents can be rationalized by Hansen Solubility Parameters (HSP) revealing a crucial hole of hydrogen bonding for the gel’s strength, which is in agreement with rheological measurements. Only the addition of water or propylene glycol to starch/DMSO solutions resulted in strong gels at a minimum starch and solvent content of 7.5 wt% and 50 wt%, respectively. The resulting aerogels showed comparably high specific surface areas (78–144 m2 g−1) and low envelope densities (0.097–0.203 g cm−3). The results of this work indicate that the HSP parameters could be used as a tool to guide the rational selection of water-free gelation in starch/DMSO systems. In addition, it opens up an attractive opportunity to perform starch gelation in those solvents that are miscible with sc-CO2, avoiding the time-consuming step of solvent exchange.

The abundance of S- and Si-bearing molecules in O-rich circumstellar envelopes of AGB stars.

We aim to determine the abundances of SiO, CS, SiS, SO, and SO2 in a large sample of oxygen-rich asymptotic giant branch (AGB) envelopes covering a wide range of mass loss rates to investigate the potential role that these molecules could play in the formation of dust in these environments. We surveyed a sample of 30 oxygen-rich AGB stars in the λ 2 mm band using the IRAM 30m telescope. We performed excitation and radiative transfer calculations based on the large velocity gradient (LVG) method to model the observed lines of the molecules and to derive their fractional abundances in the observed envelopes. We detected SiO in all 30 targeted envelopes, as well as CS, SiS, SO, and SO2 in 18, 13, 26, and 19 sources, respectively. Remarkably, SiS is not detected in any envelope with a mass loss rate below 10-6 M⊙ yr-1, whereas it is detected in all envelopes with mass loss rates above that threshold. From a comparison with a previous, similar study on C-rich sources, it becomes evident that the fractional abundances of CS and SiS show a marked differentiation between C-rich and O-rich sources, being two orders of magnitude and one order of magnitude more abundant in C-rich sources, respectively, while the fractional abundance of SiO turns out to be insensitive to the C/O ratio. The abundance of SiO in O-rich envelopes behaves similarly to C-rich sources, that is, the denser the envelope the lower its abundance. A similar trend, albeit less clear than for SiO, is observed for SO in O-rich sources. The marked dependence of CS and SiS abundances on the C/O ratio indicates that these two molecules form more efficiently in C- than O-rich envelopes. The decline in the abundance of SiO with increasing envelope density and the tentative one for SO indicate that SiO and possibly SO act as gas-phase precursors of dust in circumstellar envelopes around O-rich AGB stars.

Characterization of Spray Dried Particles Through Microstructural Imaging

Spray drying is commonly used to produce amorphous solid dispersions (ASD) to improve the bioperformance of poorly water-soluble drugs. In this study, imaging techniques such as focused ion beam-scanning electron microscopy (FIB-SEM) and X-ray microcomputed tomography (XRCT) were used to study the microstructure of spray dried (SD) particles. Spray drying at higher outlet temperature (Tout) was found to produce more spherical hollow particles with smooth surface and thinner walls, while more raisin-like particles with thicker walls were generated at lower Tout. For the first time, an artificial intelligence–facilitated XRCT image analysis tool was developed to make quantitative analysis of thousands of particles individually possible. The particle size distribution through XRCT image analysis is generally in line with what is measured by laser diffraction. The image analysis reveals envelope density as a more sensitive physical attribute for process change than conventional bulk/tap density. Further, the tensile strength of SD particle compacts correlates with the particle wall thickness, and this is likely caused by the larger interparticle contact area generated by more deformation of particles with thinner walls. The knowledge gained here can help enable SD particle engineering and drug product with more robust process and optimized performance.

Monolithic resorcinol–formaldehyde alcogels and their corresponding nitrogen-doped activated carbons

Here we report the adaptation of formaldehyde crosslinked phenolic resin-based aerogel and xerogel synthesis to ethanol-based solvent systems. Three specific formulations, namely one resorcinol–formaldehyde (RF) and two resorcinol–melamine–formaldehyde (RMF) systems were studied. As-prepared resins were characterized in terms of envelope and skeletal density. Furthermore, resin samples were pyrolyzed and activated in a CO2 gas atmosphere using a single-step protocol. The corresponding carbon materials featured high surface areas, moderate water uptake capacity and thermal conductivities in the 0.1 W.m−1K−1 range, in line with comparable activated carbons. The amount of formaldehyde in the synthesis of the RMF derived carbons proved to be a critical parameter in terms of both structural features and amount of N dopant in the carbonaceous matrix. Furthermore, a high formaldehyde concentration also has a drastic effect on the pore structure of the corresponding RMF carbons, leading primarily to mesopore formation without almost any macropore formation. Perhaps more importantly, the effect of the ammonia curing catalyst concentration on the material microstructure showed the opposite effect as observed in classical, water-based phenolic resin preparations. The ethanol-based synthesis clearly affects the pore structure of the resulting materials but also opens up the possibility to create inorganic/organic hybrid materials by simple combination with classical alkoxide-based silica sol–gel chemistry.

Metal-Organic-Framework-Supported and -Isolated Ceria Clusters with Mixed Oxidation States.

The formation of oxygen vacancies via reversible transitions between Ce(IV) and Ce(III) plays a crucial role in the propensity of cerium oxide to act as a supporting promoter in oxidative heterogeneous catalysis. An open challenge is, however, preparation of high-porosity, supported arrays of isolated ceria(IV, III) clusters with high porosity. Herein, we report two examples of oxy-Ce(IV, III) clusters supported and spatially isolated on an oxy-zirconium MOF, NU-1000. The clusters are introduced using either of two Ce complexes (precursors): CeIV(tmhd)4 (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionate) or CeIII(iPrCp)3 (iPrCp = tris(isopropyl-cyclopenta-dienyl), via SIM (solvothermal installation in MOFs). The prepared materials are named Ce-l-SIM-NU-1000 and Ce-n-SIM-NU-1000, respectively. X-ray photoelectron spectroscopy characterization shows that the ratio of Ce(III) to Ce(IV) oxidation states can be modulated. Difference envelope density analyses of X-ray scattering show that CexOyHz clusters in Ce-n-SIM-NU-1000 are located between pairs of Zr6 nodes, whereas in Ce-l-SIM-NU-1000, they are sited on MOF linkers throughout the micropores of NU-1000. Cluster size differences were further evaluated by pair function distribution (PDF) analyses of total X-ray scattering reveal that the node sited clusters contain of only a few cerium ions, whereas the linker-sited clusters each contain ∼90 cerium ions. The observed size appears to be defined by the size of NU-1000s triangular pores, that is, cluster formation appears to be pore templated. The Ce-SIM functionalized materials are catalytically active for hydrolysis of DMNP (dimethyl 4-nitrophenyl phosphate), a nerve-agent simulant. Conversion of a small fraction of the Ce(IV) ions in which the presence of small fractions of the cerium(IV) ions in Ce-l-SIM-NU-1000 to cerium(III) significantly enhances catalytic activity-perhaps by labilizing aqua ligands and facilitating simulant binding to the clusters Lewis-basic metal ions. While not explored here, the larger clusters, when partially reduced, are, we believe, candidate catalysts for O2 activation and subsequent selective oxidation of organic substrates.

Vapor-Phase Fabrication and Condensed-Phase Application of a MOF-Node-Supported Iron Thiolate Photocatalyst for Nitrate Conversion to Ammonium

We describe a method for synthesizing a nitrate reduction catalyst within a metal–organic framework (MOF). The MOF NU-1000, a zirconium-based mesoporous material, is exposed by using atomic layer deposition (ALD) to a vaporous iron amidinate coordination complex and subsequently a dodecanethiol ligand to synthesize an iron thiolate cluster grafted on the zirconium oxide nodes. Structural identification of the cluster is conducted through X-ray absorption spectroscopy (XAS) and differential envelope density (DED) analyses. Once submerged in an aqueous solution containing nitrate (30 ppm of N) and irradiated with light, the MOF/iron thiolate cluster assembly can photochemically transform the nitrate to ammonium ions. We suggest that sequential, self-limiting, atomic (metal ion), and molecular (ligand) deposition onto the reactive nodes of chemically and thermally stable MOFs could prove to be a versatile and attractive method for obtaining nature-inspired chemical catalysts.

Enhancing Hepatitis C virus pseudoparticles infectivity through p7NS2 cellular expression

Hepatitis C pseudoparticles (HCVpp) are used to evaluate HCV cell entry while screening for neutralizing antibodies induced upon vaccination or while screening for new antiviral drugs. In this work we explore the stable production of HCVpp aiming to reduce the variability associated with transient productions. The performance of stably produced HCVpp was assessed by evaluating the influence of Human Serum and the impact of CD81 cellular expression on the infectivity of HCVpp. After evaluating the performance of stably produced HCVpp we studied the effect of co-expressing p7NS2 openreading frame (ORF) on HCVpp infectivity. Our data clearly shows an enhanced infectivity of HCVppp7NS2. Even though the exact mechanism was not completely elucidated, the enhanced infectivity of HCVppp7NS2 is neither a result of an increase production of virus particles nor a result from increased envelope density. The inhibitory effect of p7 inhibitory molecules such as rimantadine suggests a direct contribution of p7 ion channel for the enhanced infectivity of HCVppp7NS2 which is coherent with a pH-dependent cell entry mechanism. In conclusion, we report the establishment of a stable production system of HCVpp with enhanced infectivity through the overexpression of p7NS2 ORF contributing to improve HCV entry assessment assays widely used in antiviral drug discovery and vaccine development.

A novel MM algorithm and the mode-sharing method in Bayesian computation for the analysis of general incomplete categorical data

Incomplete categorical data often occur in the fields such as biomedicine, epidemiology, psychology, sports and so on. In this paper, we first introduce a novel minorization–maximization (MM) algorithm to calculate the maximum likelihood estimates (MLEs) of parameters and the posterior modes for the analysis of general incomplete categorical data. Although the data augmentation (DA) algorithm and Gibbs sampling as the corresponding stochastic counterparts of the expectation–maximization (EM) and ECM algorithms are developed very well, up to now, little work has been done on creating stochastic versions to the existing MM algorithms. This is the first paper to propose a mode-sharing method in Bayesian computation for general incomplete categorical data by developing a new acceptance–rejection (AR) algorithm aided with the proposed MM algorithm. The key idea is to construct a class of envelope densities indexed by a working parameter and to identify a specific envelope density which can overcome the four drawbacks associated with the traditional AR algorithm. The proposed mode-sharing based AR algorithm has three significant characteristics: (I) it can automatically establish a family of envelope densities {gλ(⋅): λ∈Sλ} indexed by a working parameter λ, where each member in the family shares mode with the posterior density; (II) with the one-dimensional grid method searching over the finite interval Sλ, it can identify an optimal working parameter λopt by maximizing the theoretical acceptance probability, yielding a best easy-sampling envelope density gλopt(⋅), which is more dispersive than the posterior density; (III) it can obtain the optimal envelope constant copt by using the mode-sharing theorem (indicating that the high-dimensional optimization can be completely avoided) or by using the proposed MM algorithm again. Finally, a toy model and three real data sets are used to illustrate the proposed methodologies.

The application of percolation threshold theory to predict compaction behaviour of pharmaceutical powder blends

Percolation theory provides a statistical model which can be used to predict the behaviour of powder blends based on particle-particle interactions. The aim of this study was to investigate if percolation theory could be used to predict the drug loading concentration of pharmaceutical tablets, and the relative density of a blend, above which tablet tensile strength is reduced, resulting in the production of unsatisfactory products. The model blend studied contained ibuprofen as the API, which exhibits poor flow and compressibility, and microcrystalline cellulose (MCC) as the excipient, which exhibits good flowability and compressibility. Two MCC grades with differing physical properties were investigated, Vivapur® 102 (air streamed dried quality), and Emcocel® 90 (spray dried quality) to test the theory. Blends containing 2.5 to 40% w/w of ibuprofen were compacted at a range of pressures and the values of the powder true density, compaction pressure, tablet envelope density, and tablet tensile strength were used to calculate the percolation thresholds mathematically. The drug loading threshold values predicted with the model (19.08% w/w and 17.76% w/w respectively for Vivapur® 102 and Emcocel® 90) were found to be in good agreement when compared to experimental data and the infinite cluster of drug was visually confirmed on the surface of tablets using Raman imaging. The capability of multivariate analysis to predict the drug loading threshold was also tested. Principal component analysis was unable to identify the threshold, but provided an overview of the changes of the analysed properties as ibuprofen drug loading increased. It was also able to identify differences between blends containing Vivapur® or Emcocel®. In conclusion, percolation theory was able to predict the maximum acceptable drug loading for this binary system of API and excipient. This methodology could be employed for other binary systems to predict maximum drug loading potential without the need for time consuming and expensive tablet production.

Can one determine the density of an individual synthetic macromolecule?

Dendronized polymers (DPs) are large and compact main-chain linear polymers with a cylindrical shape and cross-sectional diameters of up to ∼15 nm. They are therefore considered molecular objects, and it was of interest whether given their experimentally accessible, well-defined dimensions, the density of individual DPs could be determined. We present measurements on individual, deposited DP chains, providing molecular dimensions from scanning and transmission electron microscopy and mass-per-length values from quantitative scanning transmission electron microscopy. These results are compared with density values obtained from small-angle X-ray scattering on annealed bulk specimen and with classical envelope density measurements, obtained using hydrostatic weighing or a density gradient column. The samples investigated comprise a series of DPs with side groups of dendritic generations g = 1-8. The key findings are a very large spread of the density values over all samples and methods, and a consistent increase of densities with g over all methods. While this work highlights the advantages and limitations of the applied methods, it does not provide a conclusive answer to the question of which method(s) to use for the determination of densities of individual molecular objects. We are nevertheless confident that these first attempts to answer this challenging question will stimulate more research into this important aspect of polymer and soft matter science.

Rapidly evolving episodic outflow in IRAS 18113−2503: clues to the ejection mechanism of the fastest water fountain

ABSTRACT Water fountains are evolved stars showing early stages of collimated mass-loss during transition from the asymptotic giant branch, providing valuable insight into the formation of asymmetric planetary nebulae. We report the results of multi-epoch VLBI observations, which determine the spatial and three-dimensional kinematic structure of H2O masers associated with the water fountain IRAS 18113−2503. The masers trace three pairs of high-velocity (∼150–300 km s−1) bipolar bow shocks on a scale of 0${^{\prime\prime}_{.}}$18 (∼2000 au). The expansion velocities of the bow shocks exhibit an exponential decrease as a function of distance from the central star, which can be explained by an episodic, jet-driven outflow decelerating due to drag forces in a circumstellar envelope. Using our model, we estimate an initial ejection velocity ∼840 km s−1, a period for the ejections ∼10 yr, with the youngest being ∼12 yr old, and an average envelope density within the H2O maser region $n_{\text{H}_2}{\approx }10^{6}$ cm−3. We hypothesize that IRAS 18113−2503 hosts a binary central star with a separation of ∼10 au, revealing novel clues about the launching mechanisms of high-velocity collimated outflows in water fountains.

Productivity and biomass characteristics of selected poplar (Populus spp.) cultivars under the climatic conditions of northern Poland

This study aimed to determine the productivity and energy values of 10 poplar cultivars for use as potential fuel sources in Poland. The study was conducted over a seven-year cycle in northern Poland. The cultivars belonged to clones traditionally used for timber production, as well as new clones specific to short-rotation coppice (SRC) practices. Biomass production and biomass properties were measured, including elemental composition, the gross and net calorific values (heating value) of wood, and envelope density. For each cultivar, the synthetic fuel value index (FVI) was calculated. Biomass dry matter (DM) production differed noticeably between cultivars, and it was the highest for traditional cultivars (‘NE-42’ and ‘Fritzi Pauley’, amounting to 8 Mg ha−1 yr−1), and the lowest for new cultivars (DM was one-third that of the cultivars with the highest production). Two traditional cultivars (‘NE-42’ and ‘Fritzi Pauley’) had the highest FVI, representing potential biofuels, whereas two new SRC cultivars (‘AF-8’ and ‘AF-2’) had the lowest indexes. Overall, poplar plantations with short rotations could be considered as a potential additional source of renewable energy in Poland. However, the key factor is selection of appropriate genotypes for the specific climatic conditions. In conclusion, our study demonstrated the importance of testing cultivars under local climatic conditions before using them at a commercial scale.

Planetary Engulfment in the Hertzsprung–Russell Diagram

Abstract Planets accompany most Sun-like stars. The orbits of many are sufficiently close that they will be engulfed when their host stars ascend the giant branch. This Letter compares the power generated by orbital decay of an engulfed planet to the intrinsic stellar luminosity. Orbital decay power is generated by drag on the engulfed companion by the surrounding envelope. As stars ascend the giant branch their envelope density drops and so does the power injected through orbital decay, scaling approximately as . Their luminosity, however, increases along the giant branch. These opposed scalings indicate a crossing, where . We consider the engulfment of planets along isochrones in the Hertzsprung–Russell (H–R) diagram. We find that the conditions for such a crossing occur around (or au) for Jovian planetary companions. The consumption of closer-in giant planets, such as hot Jupiters, leads to , while more distant planets such as warm Jupiters, , lead to minor perturbations of their host stars with . Our results map out the parameter space along the giant branch in the H–R Diagram where interaction with planetary companions leads to significant energetic disturbance of host stars.

Effect of freeze-thaw cycling on grain size of biochar.

Biochar may improve soil hydrology by altering soil porosity, density, hydraulic conductivity, and water-holding capacity. These properties are associated with the grain size distributions of both soil and biochar, and therefore may change as biochar weathers. Here we report how freeze-thaw (F-T) cycling impacts the grain size of pine, mesquite, miscanthus, and sewage waste biochars under two drainage conditions: undrained (all biochars) and a gravity-drained experiment (mesquite biochar only). In the undrained experiment plant biochars showed a decrease in median grain size and a change in grain-size distribution consistent with the flaking off of thin layers from the biochar surface. Biochar grain size distribution changed from unimodal to bimodal, with lower peaks and wider distributions. For plant biochars the median grain size decreased by up to 45.8% and the grain aspect ratio increased by up to 22.4% after 20 F-T cycles. F-T cycling did not change the grain size or aspect ratio of sewage waste biochar. We also observed changes in the skeletal density of biochars (maximum increase of 1.3%), envelope density (maximum decrease of 12.2%), and intraporosity (porosity inside particles, maximum increase of 3.2%). In the drained experiment, mesquite biochar exhibited a decrease of median grain size (up to 4.2%) and no change of aspect ratio after 10 F-T cycles. We also document a positive relationship between grain size decrease and initial water content, suggesting that, biochar properties that increase water content, like high intraporosity and pore connectivity large intrapores, and hydrophilicity, combined with undrained conditions and frequent F-T cycles may increase biochar breakdown. The observed changes in biochar particle size and shape can be expected to alter hydrologic properties, and thus may impact both plant growth and the hydrologic cycle.

Fine-Tuning the Activity of Metal-Organic Framework-Supported Cobalt Catalysts for the Oxidative Dehydrogenation of Propane.

Few-atom cobalt-oxide clusters, when dispersed on a Zr-based metal-organic framework (MOF) NU-1000, have been shown to be active for the oxidative dehydrogenation (ODH) of propane at low temperatures (<230 °C), affording a selective and stable propene production catalyst. In our current work, a series of promoter ions with varying Lewis acidity, including Ni(II), Zn(II), Al(III), Ti(IV) and Mo(VI), are anchored as metal-oxide,hydroxide clusters to NU-1000 followed by Co(II) ion deposition, yielding a series of NU-1000-supported bimetallic-oxo,hydroxo,aqua clusters. Using difference envelope density (DED) analyses, the spatial locations of the promoter ions and catalytic cobalt ions are determined. For all samples, the promoter ions are sited between pairs of Zr6 nodes along the MOF c-axis, whereas the location of the cobalt ions varies with the promoter ions. These NU-1000-supported bimetallic-oxide clusters are active for propane ODH after thermal activation under O2 to open a cobalt coordination site and to oxidize Co(II) to Co(III), as evidenced by operando X-ray absorption spectroscopy at the Co K-edge. In accord with the decreasing Lewis acidity of the promoter ion, catalytic activity increases in the following order: Mo(VI) < Ti(IV) < Al(III) < Zn(II) < Ni(II). The finding is attributed to increasing ease of formation of Co(III)-O• species and stabilization of a cobalt(III)-oxyl/propane transition state as the Lewis acidity of the promoter ions decreases. The results point to an increasing ability to fine-tune the structure-dependent activity of MOF-supported heterogeneous catalysts. Coupled with mechanistic studies-computational or experimental-this ability may translate into informed prediction of improved catalysts for propane ODH and other chemical reactions.

Understanding the effect of carbon in carbon/salt/adhesive electrodes for surface electromyography measurements

Abstarct Dry electrodes that do not require silver and hydrogel might provide the advantages of having very long shelf life and lower cost, compared to the gold standard Ag/AgCl hydrogel electrodes. Recently, we compared novel carbon/salt/adhesive (CSA) electrodes with Ag/AgCl electrodes for surface electromyography (sEMG) signal collection. We found no significant differences in amplitude, but CSA electrodes outperformed Ag/AgCl in response to noise and motion artifacts. However, the carbon component may be redundant, and the salt/adhesive (SA) mixture might be as effective as CSA for such a task. In the SA electrodes, the salt concentration is the only tunable factor. To determine if carbon contribution is necessary for effective sEMG measuring capabilities, we varied the salt concentration in the SA electrodes to 10%, 15%, and 25% and their performance was compared to the functional capabilities of CSA electrodes. Twenty subjects were recruited to collect simultaneous recordings of sEMG signals using CSA and SA electrodes, side-by-side on triceps brachii, tibial anterior muscles, biceps brachii and quadriceps femoris. SA 15% and SA 25% electrodes detected higher amplitude values during contraction in biceps, tibials and quadriceps, compared to CSA. All SA electrodes exhibited high mean correlation with CSA electrodes, on the linear envelopes (≥ 0.887), RMS envelope (≥ 0.87) and power spectrum density (≥ 0.94). SA 15% and SA 25% electrodes performed better in response to noise and were more sensitive to myoelectric activity than CSA electrodes, but CSA electrodes exhibited better response to motion artifacts than SA electrodes. SA 10% electrodes presented high electrode-skin impedance, producing some lower values in sEMG signals during contraction, worse motion corruption and spectral deformation compared to CSA. Results suggest that carbon improves capability to manage motion, but at the expense of more susceptibility to noise corruption. Higher salt concentration reduced motion artifacts and spectral deformation, but reduced the sensitivity to myoelectric signals. In conclusion, SA electrodes, specifically the mixture with 15% salt, provided a better response to myoelectric activity and seem to be the most suitable alternative for sEMG data collection.

Bridging Zirconia Nodes within a Metal-Organic Framework via Catalytic Ni-Hydroxo Clusters to Form Heterobimetallic Nanowires.

Metal-organic frameworks (MOFs), with their well-ordered pore networks and tunable surface chemistries, offer a versatile platform for preparing well-defined nanostructures wherein functionality such as catalysis can be incorporated. Notably, atomic layer deposition (ALD) in MOFs has recently emerged as a versatile approach to functionalize MOF surfaces with a wide variety of catalytic metal-oxo species. Understanding the structure of newly deposited species and how they are tethered within the MOF is critical to understanding how these components couple to govern the active material properties. By combining local and long-range structure probes, including X-ray absorption spectroscopy, pair distribution function analysis, and difference envelope density analysis, with electron microscopy imaging and computational modeling, we resolve the precise atomic structure of metal-oxo species deposited in the MOF NU-1000 through ALD. These analyses demonstrate that deposition of NiOxHy clusters occurs selectively within the smallest pores of NU-1000, between the zirconia nodes, serving to connect these nodes along the c-direction to yield heterobimetallic metal-oxo nanowires. This bridging motif perturbs the NU-1000 framework structure, drawing the zirconia nodes closer together, and also underlies the sintering resistance of these clusters during the hydrogenation of light olefins.